Conventional Shopping vs Online Shopping Essay

On-Line Shopping Vs Traditional Shopping The approach of the Internet has had an effect in our lives in a wide range of ways, for example, in the way wherein we convey, tease, date, and above all, how we shop. While even in the ongoing past the idea of whether sometime one would have the option to purchase an Armani outfit wearing nightgown while taking care of the necessities of several little children would have appeared to be a stunning thought, on account of the expanding modernity of the innovation of the 21st century, for all intents and purposes everything is essentially conceivable, and shopping from the solace of one’s home has become a piece of most people’s day by day lives. When retailing on the web began, at some point in the center to the late 1990s, it offered ascend to the discussion which is as yet progressing, about online versus customary shopping. What's more, despite the fact that strip malls are as yet being swarmed by customers, similarly as they do on the Internet, the inquiry despite e verything remains †Whether web based shopping will overcome all, or if conventional shopping will endure this expanding invasion of e-shopping? So as to contemplate this, let’s inspect a couple of advantages and disadvantages of online versus customary shopping: Points of interest of Online Shopping Web has upset the manner in which we do our Shopping. Due to the various Advantages and Benefits of Shopping Online an ever increasing number of individuals nowadays incline toward Online Shopping over customary shopping. Given underneath are my Top 10 Reasons for Buying Online. 1. Comfort: The accommodation of this technique for shopping is the best favorable position loved by numerous individuals. What other place would one be able to do shopping even a 12 PM wearing his/her night suit? one don't need to hold up in a line or hold up till the shop associate is prepared to support him/her with buys. One can do shopping in minutes regardless of whether one is occupied separated from sparing time and keeping away from swarms. Online shops offer us the chance to shop 24 x 7 and furthermore reward us with a ‘no pollution’ shopping. There is no better spot to purchase data items like digital books. Following the installment is caused one to can download the data. Also, downloadable things bought online wipe out the requirement for any sort of material products whatsoever. 2. Better Prices: Another thing which intrigues most clients is the modest arrangements and better costs they get from online stores since items come to them direct from the maker o r dealer without mediators included. Numerous online shops offer markdown coupons and discounts. Aside from this, the Online Store is possibly required to gather deals charge on the off chance that they have a physical area in our state regardless of whether we purchase from a store over the world. 3. Assortment: The decisions one can get for items are stunning. Understand more: Essay About Advantages and Disadvantages of Online Shopping One can get a few brands and items from various merchants at one spot. You can get in on the most recent global patterns without burning through cash on airfare. At the point when you shop on the web, you can shop from retailers in different pieces of the nation or even the world without being restricted by geographic territory. These stores offer a far more prominent choice of hues and sizes than you will discover locally. Aside from that, what number occasions have it happened that you go through your cash arriving at a nearby shop just to find that the item you need is unavailable? Some online shops have an arrangement to acknowledge orders without stock and boat it across to you when the stock opens up. You additionally have the alternative of taking your business to another online store where the item is accessible. 4. Send Gifts: Online Shopping makes sending endowments to family members and companions simple, regardless of any place they remain. Presently there is no need of c oming up with separation a rationalization for not sending a present on events like Birthday, Wedding Anniversary, Marriage, Valentine’s Day, Mother’s Day and so forth. 5. Less Expenses: Many occasions when we settle on customary shopping we will in general spend significantly more than the necessary shopping costs on things like eating out, voyaging, indiscreet shopping and so on 6. Correlation of Prices: Online shops make examination and exploration of items and costs conceivable. Online stores likewise enable you to impart data and audits to different customers who have firsthand involvement in an item or retailer. 7. Groups: Many clients might want to evade the groups when they do the shopping. Particularly during Festivals and Special occasions the groups can truly give a cerebral pain. Groups constrain us to do a rushed shopping more often than not. Groups likewise make an issue with regards to finding a leaving place close by where you need to shop and returning to your vehicle later stacked with shopping packs. 8. Enthusiastic Shopping: Many occasions when we go out on Shopping we wind up purchasing things which we don't require in light of the retailers up selling aptitudes. Once in a while we even trade off on our decisions in view of the absence of decisions in those shops. 9. Purchasing Old or unused Stuff at low costs: Online Shops make it feasible for us to purchase old or unused stuff at absolute bottom costs. On the off chance that we need to purchase collectibles there is no preferred alternatives over online stores. 10. Cautious Purchases: Some things are better done in security. Online shops are likewise best for tactful buys like grown-up toys, provocative unmentionables, etc. Online Shops empower me to buy under pieces of clothing and unmentionables without the humiliation that there are a few people watching me and my decisions. Impediments of web based shopping The fever of web based shopping has gotten fundamentally in the most recent decade and online dealers are relied upon to improve a lot of buys for a considerable length of time to come. There is no uncertainty that one can discover extraordinary arrangements on the web thus a wide range of brands which may not be even accessible in customary stores, in any event, shopping centers. In spite of all the publicity, there are sure inconveniences of web based shopping. 1. One Do Not Physically See The Items: Normally when we shop from an ordinary store, we can see the thing and in any event outwardly examine that it looks fine. You can choose a shading, estimate and can even address a sales rep to explain questions with respect to a thing. The greatest weakness of internet shopping is we don't genuinely observe the thing till it shows up. May be you have seen it in the close by shopping center yet there is a likelihood that the specific piece you have requested might be flawed. Distortion or misconception of things purchased online is a typical issue. Typically the photograph of things you see online are far superior to once you have the thing before you 2. Trust that The Items Will Arrive: Once one put in you request the cat-and-mouse game beginnings. One needs to hang tight for a couple of days for the thing to show up which can be very disappointing. Most specialists accept that we are generally amped up for your â€Å"buy† in the initial not many days, so when your thing shows up you will doubtlessly be less energized then getting the thing on same day you made the installment 3. Odds Of Mishandling While Shipping/Delivery Risks: What if the thing you are expecting never shows up, you will be lost in a progression of calls to the dealer and the dispatch organization. Imagine a scenario in which you are not at home during the hour of conveyance and the dispatch organization leaves the bundle on your entryway and a bystander chooses to take it. Imagine a scenario in which the delivery organization broke your stuff and you understand it in the wake of opening it when the dispatch man has left. The merchant may guarantee that you broke it. 4. Delivery Charges: Only a couple of locales offer free transportation, some others w ill send for nothing just if your all out price tag surpasses a specific sum. Delivery expense is frequently a major demoralization for online customers. 5. Returning Merchandise: Even if the vender consents to reclaim the imperfect product, you frequently need to take care of the expense of delivery it. Also you need to call and persuade the individuals with respect to the explanation of your arrival. Some great destinations do have brilliant merchandise exchange, however not every person. 6. Online Security: Making installments online is typically sheltered however not generally. There might be locales which are not make sure about or don't encode your own Visa information, so if a programmer breaks in their framework, your own information can be undermined. 7. Danger Of Online Fraud: Some individuals imagine selling things at an exceptionally modest cost and regularly send you a low quality, opened or restored thing, in different cases the webpage may close down out of the blue, leaving part of clients who may have just paid for the thing however didn't get anything. Shopping on the web can likewise take you to phishing destination s which need to swindle you. 8. Timezone Difference: In nations like USA there are different time regions and the client assistance hours of the internet shopping website might be unique in relation to your time region, making it hard for you to connect with a human when you need assistance. 9. Deals Tax: Although a web based shopping webpage may not charge you a business charge during the buy, you are lawfully obliged to pay charges when you record yearly duties (accepting you live in an available state). The vast majority can get by, however if there should be an occurrence of an investigation not paying deals charge on online buys may turn into an issue. 10. A Dull Shopping Experience: Many clients appreciate heading off to a shopping center or simply the close by bazaar and appreciate the vibe and feel increasingly social among others. Web based shopping can be exhausting for some and cause you to feel like a maverick. 11. Restocking Fee: Most online stores have a restocking charge, uniquely on electronic th ings. Things that you purchase in a store, can be opened inside the store before a partner after buy, and if there is a conspicuous deformity you can return/trade it without paying a restocking charge which is as a rule between 10 to 20 percent. 12. Spyware On Your Computer: Having an infection or a spyware isn't the dealers issue however there is a danger of your own information/Mastercard data, to be taken right from your own PC. 13. Information on Operating A Computer: Older individuals specifically

Expansion Essay Essay

There were two presidents that did a lot for our nation in the region of development. These two presidents are Thomas Jefferson and James K. Polk. Despite the fact that they had totally various strategies on extension and remote undertakings, them two immensely extended the nation. Jefferson was a devotee to the Monroe Doctrine which essentially said we will mind our own busi ness. He was additionally a firm adherent to a severe translation of the constitution. He didn't look to tremendously grow our nation and whenever the open door introduced itself he made some hard memories settling on the correct choice. The United States was encircled by European claimed regions: England had Canada, Spain had Florida, and France had Louisiana. Dreading a potential war Jefferson fortified the military particularly by Louisiana. This demonstration terrified Napoleon, he was in a war with England and didn’t even need the Louisiana Territory, so dreading a war with the U.S. what's more, requ iring cash for his war with England he offered to sell the entire Louisi ana Territory to us for inexpensively. Jefferson not certain if the constitution supported the demonstration of settling on this buy battled with the choice. He chose he didn’t have a lot of a decision and acknowledged Napoleons offer. Then again, James K. Polk was a firm adherent to Manifest Destiny, which was the conviction that the United States was foreordained to control all of North America. At the point when Polk ran in the 1844 political race his crusade trademark was 54-40 or battle. Despite the fact that he never understood that limit he got much more in various pieces of the nation. After Texas revolted from Mexico Polk was anything but difficult to persuade that the U.S. should step in and take Texas from Mexico. In spite of the fact that he needed Texas he felt that the best prize would be California. After Mexico over and again declined Polk’s offers to purchase Mexico and California Polk sent a military to the Rio Grande. This activity prompted the Mexican War. Polk pushed and pushed for Texas and California which after thirteen thousand American lives and fifty thousand Mexican lives were lost he got his property. Both of these presidents extended the region of our nation an immensely. Jefferson’s arrangements on development kept us out of war and multiplied the size of our nation with extraordinary land that would be truly necessary in coming years. Polk didn’t keep us out of war yet he got us a ton. He picked up the United States a large portion of a million sections of land of prime land. Texas was a magnificent maker of cotton and different yields, while Califor nia was bounteous in gold causing the gold rush where a huge number of men would travel west to California looking for gold. In spite of the fact that Polk and Jefferson had practically inverse strategies, in the zone of development, the two of them air conditioning quired much land for the United States. Jefferson, the adherent to the Monroe Doctrine, and Polk the devotee to Manifest Destiny, presumably would not have concurred with one another yet both did a ton of useful for our nation.

How Psychologists Define Attention

How Psychologists Define Attention Theories Cognitive Psychology Print How Psychologists Define Attention By Kendra Cherry facebook twitter Kendra Cherry, MS, is an author, educational consultant, and speaker focused on helping students learn about psychology. Learn about our editorial policy Kendra Cherry Medically reviewed by Medically reviewed by Steven Gans, MD on January 17, 2016 Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital. Learn about our Medical Review Board Steven Gans, MD Updated on April 25, 2019 Plume Creative / Digital Vision / Getty Images More in Theories Cognitive Psychology Behavioral Psychology Developmental Psychology Personality Psychology Social Psychology Biological Psychology Psychosocial Psychology Attention is a concept studied in cognitive psychology that refers to how we actively process specific information in our environment. As you are reading this, there are numerous sights, sounds, and sensations going on around youâ€"the pressure of your feet against the floor, the sight of the street out of a nearby window, the soft warmth of your shirt, the memory of a conversation you had earlier with a friend. All of these sights, sounds, and sensations vie for our attention, but it turns out that our attentional resources are not limitless. How do we manage to experience all of these sensations and still focus on just one element of our environment? How do we effectively manage the resources we have available in order to make sense of the world around us? Attention as Defined by Philosopher William James According to eminent psychologist and philosopher William James, attention is the taking possession by the mind, in clear and vivid form, of one out of what may seem several simultaneously possible objects or trains of thought. …It implies withdrawal from some things in order to deal effectively with others.â€"The Principles of Psychology, 1890?? Understanding Attention Think of attention as a highlighter. As you read through a section of text in a book, the highlighted section stands out, causing you to focus your interest in that area. But attention is not just about centering your focus on one particular thing; it also involves ignoring a great deal of competing for information and stimuli. Attention allows you to tune out information, sensations, and perceptions that are not relevant at the moment and instead focus your energy on the information thats important.? Not only does our attentional system allow us to focus on something specific in our environment while tuning out irrelevant details, but it also affects our perception of the stimuli surrounding us. In some cases, our attention might be focused on a particular thing, causing us to ignore other things. In some instances, focusing our attention on a primary target might result in not perceiving the second target at all. In other words, by focusing our attention on something in the environment, we sometimes miss other things that are right in front of us. You can probably immediately think of a situation where you were so focused on a task that you neglected to notice someone walking in the room or talking to you. Since your attentional resources were so focused on one thing, you neglected something else. Key Points About Attention In order to understand how attention works and how it affects your perception and experience of the world, its essential to remember a few important points about how attention works, including: Attention is limited. There has been a tremendous amount of research looking at exactly how many things we can attend to and for how long. Key variables that impact our ability to stay on task include how interested we are in the stimulus and how many distractors we experience and attention is limited in terms of both capacity and duration. The illusion that attention is limitless has led many people to practice multitasking. Research published in 2018 has pointed out how multitasking seldom works well because our attention is, in reality, limited.??Attention is selective.  Since attention is a limited resource, we have to be selective about what we decide to focus on. Not only must we focus our attention on a specific item in our environment, but we must also filter out an enormous number of other items. We must be selective in what we attend to, a process that often occurs so quickly that we dont even notice that we have ignored certain stimuli in favor of others.Attention is a bas ic part of the cognitive system.  Attention is a basic component of our biology, present even at birth. Our orienting reflexes help us determine which events in our environment need to be attended to, a process that aids in our ability to survive. Newborns attend to environmental stimuli such as loud noises. A touch against the cheek triggers the rooting reflex, causing the infant to turn his or her head to nurse and receive nourishment. These orienting reflexes continue to benefit us throughout life. The honk of a horn might alert us about an oncoming car. The blaring noise of a smoke alarm might warn you that the casserole you put in the oven is burning. All of these stimuli grab our attention and inspire us to respond to our environment. Attention Research for Greater Understanding of ADHD For the most part, our ability to focus our attention on one thing while blocking out competing distractors seems automatic. Yet the ability of people to selectively focus their attention on a specific subject while dismissing others is very complex. Looking at attention in this way isnt just academic. Research published in 2017 says that neural circuitry (pathways in the brain) related to attention are intricately related to conditions such as attention-deficit/hyperactivity disorder (ADHD) and achieving a greater understanding of this process holds promise for better treatments for those coping with this condition down the line.??

Modern Architecture in Japan and India - 1532 Words

In any well-developed region and national culture there are periods of rejection of the past and periods of revival. These periods are often reflected through architecture as architects, developers, engineers, lay people and even the national governments seek to reflect history with the inclusion of modernity, meaning modern buildings with elements of tradition as well as all the modern amenities sought by users. In an architectural sense much of the focus is on theory within the academy, while the actual development of a great deal of architecture is not produced by university trained architects. There are few better national examples than Japan and India as they seek through laws and standards as well as architectural artistic vision to reinvent the visions of the past with modern buildings that meet modern needs including infrastructural needs to express safety, convenience and ergonomics but do not deny regionalism. The greatest challenge for both India and Japan in the modern world of architecture is to define what is regional and what is modern and make it fit in a global architectural vision, without framing a loss of national identity as a natural outgrowth. In both India and Japan the architectural industry including not just university trained architects relying heavily on theory and international trends but on lay designers who often make up the bulk of national designers and builders, struggle with the marriage of international views and standards inShow MoreRelatedHow Did Ancient Greece Influence Western Civilization951 Words   |  4 Pagesmath, architecture, philosophy, sports, and drama. Without the ancient Greeks, the modern world would not be the same. Men such as Socrates, Plato, and Aristotle changed the way we look at philosophy. The Athenians created the first known democracy, setting the stage for future governments. 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Keleigh Mallory. Ms. Katie Schwartz. En140-11. 29 April

Keleigh Mallory Ms. Katie Schwartz EN140-11 29 April 2017 As people we have all come across a point where we have faced a problem. Problems are always happening to us, whether we want them to or not. We have all thought, Why can t they just give me a break? Giving you a break would make their day easier, which will never happen, so you should always look forward to facing some sort of problem. Everyone faces different problems, so it may be hard for someone else to realize that you are having this problem. Sometimes discussing your problems can help better the situation. Whenever I have a problem I usually call and talk to my parents, and they tell me to always look at the more positive things. An example, my dad always says, â€Å"You’re†¦show more content†¦I think my mom kind of got tired of me asking, â€Å"Can I please have my phone back,† but she really didn’t make it known. Even taking away my electronic devices didn’t seem to help me sleep any better. I still had hard times falling asleep. My mom would sometimes come in my room and say, â€Å"You are still awake, you went to bed a whole hour ago.† I would always respond, â€Å"I just can’t go to sleep, I don’t know why.† This happened about every school night, so eventually she gave in. She knew that electronics was not the problem here, so I went from starting the year off going to sleep without my phone, to finishing the year with it. Sometimes it is just hard for anyone to go to sleep, but others believe this is only certain when your smart phone is involved. I think that where you sleep plays an important role. If you sleep on a hard mattress, or even a sleep sofa, sleeping becomes harder. â€Å"The bedroom environment can have a significant influence on sleep quality and quantity. Several variables combine to make up the sleep environment, including light, noise, and temperature. By being attuned to factors in your sleep environment that put you at ease, and eliminating those that may c ause stress or distraction, you can set yourself up for the best possible sleep.† â€Å"In this book, Harvard Business School professor Leslie Perlow reveals how you can

Vampire Academy Chapter 18 Free Essays

string(24) " be that big of a deal\." EIGHTEEN I WOKE UP STARING AT the boring white ceiling of the clinic. A filtered light – soothing to Moroi patients – shone down on me. I felt strange, kind of disoriented, but I didn’t hurt. We will write a custom essay sample on Vampire Academy Chapter 18 or any similar topic only for you Order Now â€Å"Rose.† The voice was like silk on my skin. Gentle. Rich. Turning my head, I met Dimitri’s dark eyes. He sat in a chair beside the bed I lay on, his shoulder-length brown hair hanging forward and framing his face. â€Å"Hey,† I said, my voice coming out as a croak. â€Å"How do you feel?† â€Å"Weird. Kind of groggy.† â€Å"Dr. Olendzki gave you something for the pain – you seemed pretty bad when we brought you in.† â€Å"I don’t remember that†¦How long have I been out?† â€Å"A few hours.† â€Å"Must have been strong. Must still be strong.† Some of the details came back. The bench. My ankle getting caught. I couldn’t remember much after that. Feeling hot and cold and then hot again. Tentatively, I tried moving the toes on my healthy foot. â€Å"I don’t hurt at all.† He shook his head. â€Å"No. Because you weren’t seriously injured.† The sound of my ankle cracking came back to me. â€Å"Are you sure? I remember†¦the way it bent. No. Something must be broken.† I manage to sit up, so I could look at my ankle. â€Å"Or at least sprained.† He moved forward to stop me. â€Å"Be careful. Your ankle might be fine, but you’re probably still a little out of it.† I carefully shifted to the edge of the bed and looked down. My jeans were rolled up. The ankle looked a little red, but I had no bruises or serious marks. â€Å"God, I got lucky. If I’d hurt it, it would have put me out of practice for a while.† Smiling, he returned to his chair. â€Å"I know. You kept telling me that while I was carrying you. You were very upset.† â€Å"You†¦you carried me here?† â€Å"After we broke the bench apart and freed your foot.† Man. I’d missed out on a lot. The only thing better than imagining Dimitri carrying me in his arms was imagining him shirtless while carrying me in his arms. Then the reality of the situation hit me. â€Å"I was taken down by a bench,† I groaned. â€Å"What?† â€Å"I survived the whole day guarding Lissa, and you guys said I did a good job. Then, I get back here and meet my downfall in the form of a bench.† Ugh. â€Å"Do you know how embarrassing it is? And all those guys saw, too.† â€Å"It wasn’t your fault,† he said. â€Å"No one knew the bench was rotted. It looked fine.† â€Å"Still. I should have just stuck to the sidewalk like a normal person. The other novices are going to give me shit when I get back.† His lips held back a smile. â€Å"Maybe presents will cheer you up.† I sat up straighter. â€Å"Presents?† The smile escaped, and he handed me a small box with a piece of paper. â€Å"This is from Prince Victor.† Surprised that Victor would have given me anything, I read the note. It was just a few lines, hastily scrawled in pen. Rose – I’m very happy to see you didn’t suffer any serious injuries from your fall. Truly, it is a miracle. You lead a charmed life, and Vasilisa is lucky to have you. â€Å"That’s nice of him,† I said, opening the box. Then I saw what was inside. â€Å"Whoa. Very nice.† It was the rose necklace, the one Lissa had wanted to get me but couldn’t afford. I held it up, looping its chain over my hand so the glittering, diamond-covered rose hung free. â€Å"This is pretty extreme for a get-well present,† I noted, recalling the price. â€Å"He actually bought it in honor of you doing so well on your first day as an official guardian. He saw you and Lissa looking at it.† â€Å"Wow.† It was all I could say. â€Å"I don’t think I did that good of a job.† â€Å"I do.† Grinning, I placed the necklace back in the box and set it on a nearby table. â€Å"You did say ? ®presents,’ right? Like more than one?† He laughed outright, and the sound wrapped around me like a caress. God, I loved the sound of his laugh. â€Å"This is from me.† He handed me a small, plain bag. Puzzled and excited, I opened it up. Lip gloss, the kind I liked. I’d complained to him a number of times how I was running out, but I’d never thought he was paying attention. â€Å"How’d you manage to buy this? I saw you the whole time at the mall.† â€Å"Guardian secrets.† â€Å"What’s this for? For my first day?† â€Å"No,† he said simply. â€Å"Because I thought it would make you happy.† Without even thinking about it, I leaned forward and hugged him. â€Å"Thank you.† Judging from his stiff posture, I’d clearly caught him by surprise. And yeah†¦I’d actually caught myself by surprise, too. But he relaxed a few moments later, and when he reached around and rested his hands on my lower back, I thought I was going to die. â€Å"I’m glad you’re better,† he said. His mouth sounded like it was almost in my hair, just above my ear. â€Å"When I saw you fall†¦Ã¢â‚¬  â€Å"You thought, ? ®Wow, she’s a loser.’ â€Å" â€Å"That’s not what I thought.† He pulled back slightly, so he could see me better, but we didn’t say anything. His eyes were so dark and deep that I wanted to dive right in. Staring at them made me feel warm all over, like they had flames inside. Slowly, carefully, those long fingers of his reached out and traced the edge of my cheekbone, moving up the side of my face. At the first touch of his skin on mine, I shivered. He wound a lock of my hair around one finger, just like he had in the gym. Swallowing, I dragged my eyes up from his lips. I’d been contemplating what it’d be like to kiss him. The thought both excited and scared me, which was stupid. I’d kissed a lot of guys and never thought much about it. No reason another one – even an older one – should be that big of a deal. You read "Vampire Academy Chapter 18" in category "Essay examples" Yet the thought of him closing the distance and bringing his lips to mine made the world start spinning. A soft knock sounded at the door, and I hastily leaned back. Dr. Olendzki stuck her head in. â€Å"I thought I heard you talking. How do you feel?† She walked over and made me lie back down. Touching and bending my ankle, she assessed it for damage and finally shook her head when finished. â€Å"You’re lucky. With all the noise you made coming in here, I thought your foot had been amputated. Must have just been shock.† She stepped back. â€Å"I’d feel better if you sat out from your normal trainings tomorrow, but otherwise, you’re good to go.† I breathed a sigh of relief. I didn’t remember my hysteria – and was actually kind of embarrassed that I’d thrown such a fit – but I had been right about the problems this would have caused me if I’d broken or sprained it. I couldn’t afford to lose any time here; I needed to take my trials and graduate in the spring. Dr. Olendzki gave me the okay to go and then left the room. Dimitri walked over to another chair and brought me my shoes and coat. Looking at him, I felt a warm flush sweep me as I recalled what had happened before the doctor had entered. He watched as I slipped one of the shoes on. â€Å"You have a guardian angel.† â€Å"I don’t believe in angels,† I told him. â€Å"I believe in what I can do for myself.† â€Å"Well then, you have an amazing body.† I glanced up at him with a questioning look. â€Å"For healing, I mean. I heard about the accident†¦Ã¢â‚¬  He didn’t specify which accident it was, but it could be only one. Talking about it normally bothered me, but with him, I felt I could say anything. â€Å"Everyone said I shouldn’t have survived,† I explained. â€Å"Because of where I sat and the way the car hit the tree. Lissa was really the only one in a secure spot. She and I walked away with only a few scratches.† â€Å"And you don’t believe in angels or miracles.† â€Å"Nope. I – â€Å" Truly, it is a miracle. You lead a charmed life†¦. And just like that, a million thoughts came slamming into my head. Maybe†¦maybe I had a guardian angel after all†¦ Dimitri immediately noticed the shift in my feelings. â€Å"What’s wrong?† Reaching out with my mind, I tried to expand the bond and shake off the lingering effects of the pain medication. Some more of Lissa’s feelings came through to me. Anxious. Upset. â€Å"Where’s Lissa? Was she here?† â€Å"I don’t know where she is. She wouldn’t leave your side while I brought you in. She stayed right next the bed, right up until the doctor came in. You calmed down when she sat next to you.† I closed my eyes and felt like I might faint. I had calmed down when Lissa sat next to me because she’d taken the pain away. She’d healed me†¦ Just as she had the night of the accident. It all made sense now. I shouldn’t have survived. Everyone had said so. Who knew what kind of injuries I’d actually suffered? Internal bleeding. Broken bones. It didn’t matter because Lissa had fixed it, just like she’d fixed everything else. That was why she’d been leaning over me when I woke up. It was also probably why she’d passed out when they took her to the hospital. She’d been exhausted for days afterward. And that was when her depression had begun. It had seemed like a normal reaction after losing her family, but now I wondered if there was more to it, if healing me had played a role. Opening my mind again, I reached out to her, needing to find her. If she’d healed me, there was no telling what shape she could be in now. Her moods and magic were linked, and this had been a pretty intense show of magic. The drug was almost gone from my system, and like that, I snapped into her. It was almost easy now. A tidal wave of emotions hit me, worse than when her nightmares engulfed me. I’d never felt such intensity from her before. She sat in the chapel’s attic, crying. She didn’t entirely know why she was crying either. She felt happy and relieved that I’d been unharmed, that she’d been able to heal me. At the same time, she felt weak in both body and mind. She burned inside, like she’d lost part of herself. She worried I’d be mad because she’d used her powers. She dreaded going through another school day tomorrow, pretending she liked being with a crowd who had no other interests aside from spending their families’ money and making fun of those less beautiful and less popular. She didn’t want to go to the dance with Aaron and see him watch her so adoringly – and feel him touching her – when she felt only friendship for him. Most of these were all normal concerns, but they hit her hard, harder than they would an ordinary person, I thought. She couldn’t sort through them or figure out how to fix them. â€Å"You okay?† She looked up and brushed the hair away from where it stuck to her wet cheeks. Christian stood in the entrance to the attic. She hadn’t even heard him come up the stairs. She’d been too lost in her own grief. A flicker of both longing and anger sparked within her. â€Å"I’m fine,† she snapped. Sniffling, she tried to stop her tears, not wanting him to see her weak. Leaning against the wall, he crossed his arms and wore an unreadable expression. â€Å"Do†¦do you want to talk?† â€Å"Oh†¦Ã¢â‚¬  She laughed harshly. â€Å"You want to talk now? After I tried so many times – â€Å" â€Å"I didn’t want that! That was Rose – â€Å" He cut himself off and I flinched. I was totally busted. Lissa stood up and strode toward him. â€Å"What about Rose?† â€Å"Nothing.† His mask of indifference slipped back into place. â€Å"Forget it.† â€Å"What about Rose?† She stepped closer. Even through her anger, she still felt that inexplicable attraction to him. And then she understood. â€Å"She made you, didn’t she? She told you to stop talking to me?† He stared stonily ahead. â€Å"It was probably for the best. I would have just messed things up for you. You wouldn’t be where you are now.† â€Å"What’s that supposed to mean?† â€Å"What do you think it means? God. People live or die at your command now, Your Highness.† â€Å"You’re being kind of melodramatic.† â€Å"Am I? All day, I hear people talking about what you’re doing and what you’re thinking and what you’re wearing. Whether you’ll approve. Who you like. Who you hate. They’re your puppets.† â€Å"It’s not like that. Besides, I had to do it. To get back at Mia†¦Ã¢â‚¬  Rolling his eyes, he looked away from her. â€Å"You don’t even know what you’re getting back at her for.† Lissa’s anger flared. â€Å"She set up Jesse and Ralf to say those things about Rose! I couldn’t let her get away with that.† â€Å"Rose is tough. She would have gotten over it.† â€Å"You didn’t see her,† she replied obstinately. â€Å"She was crying.† â€Å"So? People cry. You’re crying.† â€Å"Not Rose.† He turned back to her, a dark smile curling his lips. â€Å"I’ve never seen anything like you two. Always so worried about each other. I get her thing – some kind of weird guardian hang-up – but you’re just the same.† â€Å"She’s my friend.† â€Å"I guess it’s that simple. I wouldn’t know.† He sighed, momentarily thoughtful, then snapped back to sarcastic mode. â€Å"Anyway. Mia. So you got back at her over what she did to Rose. But you’re missing the point. Why did she do it?† Lissa frowned. â€Å"Because she was jealous about me and Aaron – â€Å" â€Å"More to it than that, Princess. What did she have to be jealous about? She already had him. She didn’t need to attack you to drive that home. She could have just made a big show of being all over him. Sort of like you are now,† he added wryly. â€Å"Okay. What else is there, then? Why did she want to ruin my life? I never did anything to her – before all this, I mean.† He leaned forward, crystal-blue eyes boring into hers. â€Å"You’re right. You didn’t – but your brother did.† Lissa pulled away from him. â€Å"You don’t know anything about my brother.† â€Å"I know he screwed Mia over. Literally.† â€Å"Stop it, stop lying.† â€Å"I’m not. Swear to God or whoever else you want to believe in. I used to talk to Mia now and then, back when she was a freshman. She wasn’t very popular, but she was smart. Still is. She used to work on a lot of committees with royals – dances and stuff. I don’t know all of it. But she got to know your brother on one of those, and they sort of got together.† â€Å"They did not. I would have known. Andre would have told me.† â€Å"Nope. He didn’t tell anyone. He told her not to either. He convinced her it should be some kind of romantic secret when really, he just didn’t want any of his friends to find out he was getting naked with a non-royal freshman.† â€Å"If Mia told you that, she was making it up,† exclaimed Lissa. â€Å"Yeah, well, I don’t think she was making it up when I saw her crying. He got tired of her after a few weeks and dumped her. Told her she was too young and that he couldn’t really get serious with someone who wasn’t from a good family. From what I understand, he wasn’t even nice about it either – didn’t even bother with the ? ®let’s be friends’ stuff.† Lissa pushed herself into Christian’s face. â€Å"You didn’t even know Andre! He would never have done that.† â€Å"You didn’t know him. I’m sure he was nice to his baby sister; I’m sure he loved you. But in school, with his friends, he was just as much of a jerk as the rest of the royals. I saw him because I see everything. Easy when no one notices you.† She held back a sob, unsure whether to believe him or not. â€Å"So this is why Mia hates me?† â€Å"Yup. She hates you because of him. That, and because you’re royal and she’s insecure around all royals, which is why she worked so hard to claw up the ranks and be their friend. I think it’s a coincidence that she ended up with your ex-boyfriend, but now that you’re back, that probably made it worse. Between stealing him and spreading those stories about her parents, you guys really picked the best ways to make her suffer. Nice work.† The smallest pang of guilt lurched inside of her. â€Å"I still think you’re lying.† â€Å"I’m a lot of things, but I’m not a liar. That’s your department. And Rose’s.† â€Å"We don’t – â€Å" â€Å"Exaggerate stories about people’s families? Say that you hate me? Pretend to be friends with people you think are stupid? Date a guy you don’t like?† â€Å"I like him.† â€Å"Like or like?† â€Å"Oh, there’s a difference?† â€Å"Yes. Like is when you date a big, blond moron and laugh at his stupid jokes.† Then, out of nowhere, he leaned forward and kissed her. It was hot and fast and furious, an outpouring of the rage and passion and longing that Christian always kept locked inside of him. Lissa had never been kissed like that, and I felt her respond to it, respond to him – how he made her feel so much more alive than Aaron or anyone else could. Christian pulled back from the kiss but still kept his face next to hers. â€Å"That’s what you do with someone you like.† Lissa’s heart pounded with both anger and desire. â€Å"Well, I don’t like or like you. And I think you and Mia are both lying about Andre. Aaron would never make up anything like that.† â€Å"That’s because Aaron doesn’t say anything that requires words of more than one syllable.† She pulled away. â€Å"Get out. Get away from me.† He looked around comically. â€Å"You can’t throw me out. We both signed the lease.† â€Å"Get. Out!† she yelled. â€Å"I hate you!† He bowed. â€Å"Anything you want, Your Highness.† With a final dark look, he left the attic. Lissa sank to her knees, letting out the tears she’d held back from him. I could barely make sense out of all the things hurting her. God only knew things upset me – like the Jesse incident – but they didn’t attack me in the same way. They swirled within her, beating at her brain. The stories about Andre. Mia’s hate. Christian’s kiss. Healing me. This, I realized, was what real depression felt like. What madness felt like. Overcome, drowning in her own pain, Lissa made the only decision she could. The only thing she could do to channel all of these emotions. She opened up her purse and found the tiny razor blade she always carried†¦ Sickened, yet unable to break away, I felt as she cut her left arm, making perfectly even marks, watching as the blood flowed across her white skin. As always, she avoided veins, but her cuts were deeper this time. The cutting stung horribly, yet in doing it, she was able to focus on the physical pain, distract herself from the mental anguish so that she could feel like she was in control. Drops of blood splattered onto the dusty floor, and her world began spinning. Seeing her own blood intrigued her. She had taken blood from others her entire life. Me. The feeders. Now, here it was, leaking out. With a nervous giggle, she decided it was funny. Maybe by letting it out, she was giving it back to those she’d stolen it from. Or maybe she was wasting it, wasting the sacred Dragomir blood that everyone obsessed over. I’d forced my way into her head, and now I couldn’t get out. Her emotions had ensnared me now – they were too strong and too powerful. But I had to escape – I knew it with every ounce of my being. I had to stop her. She was too weak from the healing to lose this much blood. It was time to tell someone. Breaking out at last, I found myself back in the clinic. Dimitri’s hands were on me, gently shaking me as he said my name over and over in an effort to get my attention. Dr. Olendzki stood beside him, face dark and concerned. I stared at Dimitri, truly seeing how much he worried and cared about me. Christian had told me to get help, to go to someone I trusted about Lissa. I’d ignored the advice because I didn’t trust anyone except her. But looking at Dimitri now, feeling that sense of understanding we shared, I knew that I did trust someone else. I felt my voice crack as I spoke. â€Å"I know where she is. Lissa. We have to help her.† How to cite Vampire Academy Chapter 18, Essay examples

Corporate Financial Accounting ActivEX Limited

Question: Discuss about the Corporate Financial Accounting : ActivEX Limited. Answer: Introduction: The chosen company is ActivEX Limited is based on Brisbane and is listed with the Australian Securities Exchange. The company focuses on acquisition, delineation and identification of the projects dealing with mineral resources with the help of active exploration. Portfolio of the ActivEX Limited is widespread ranging from 1 granted lease of mining and 33 granted permissions for explorations along with one application of prospecting licence (Lemus 2016). The license covers more than 2881 km in Queensland and in various regions of Western Australia. Moreover, these licensed areas are quite potential terrain that are embedded with copper and gold mineralisation in the northern and southeast regions of Queensland along with the Cloncurry district situated in the northwest area of Queensland (Lund 2015). ActivEX Limited also possesses an active potash project located in the Western Australia in this project the compny is investigating the most efficient way of percolating processes for extracting and producing the by-products of potash. Role of the CFO of ActivEX Limited: There are mainly five principles that usher the Chief Financial Officer towards the success path. These principles are, It is quintessential for a CFO to become an active member of the senior management team of the company and at the same time be an effective leader. Keeping a balance between the responsibilities associated with the business partnership and stewardship. Playing an important role in navigating and integrating the organization. The Chief Financial Officer should be an effective leader of the functions associated with the finance and accounting activities within the organization. CFO is responsible for bringing about qualities in the role of the organization. These five responsibilities taken together determine a framework in which the Chief Financial Officer of an organization is working. However, the CFO of ActivEX Limited does follow this framework and has efficiently placed the company in a very good position in the competitive market (Diehl 2016). However, in this particular section the study will focus on the three main key responsibilities of the Chief Financial Officer of ActivEX Limited. These responsibilities are stated and explained one by one below, Active participation in the leadership team: The leadership teams in the service organizations may adopt different forms with the different combinations of executives and non-executive members, these leadership teams sometimes also include representatives who are elected by the employees of the organization (Cowell 2013). More specifically these leadership teams are responsible for determining the strategic framework of the organization, implementation of the designed strategy and evaluating the strategies as well. Nowadays it has become a mandate that each and every company should possess a CFO who will report directly to the permanent secretary of the company (Lowies 2012). Furthermore, there are a number of structures which are in effective operation. As per these structures the leadership team sometimes may include the governing body, senior management officials along with the key management committee of the concerned organization and the Chief Financial Officer acts as the key leader within this group (Cui et al. 2015). In the case of the selected organization this framework followed exactly. The Chief Financial Officer in ActivEX Limited plays a significantly important role in directing, governing and advising regarding the financial matters of the entire company as a whole. In order to fulfil these responsibilities efficiently the Chief Financial Officer has access and communication with all the governing members and documents both as an individual and in association with the other people (Baez 2014). It is also quite important that the Chief Financial officer ascertain an effective professional working relationship with the chief members of the governing body built based on mutual trust and respect for each other. It is also quite evident that in this case the Chief Financial Officer works intimately and closely with each of the governors and it is quite necessary. For instance it is necessary for the Chief Financial Officer to work with the finance or the audit committee closely otherwise there will be lack of information (Priest et al. 2016). In the case of ActivEX the multi disciplinary characteristics of the highly designated management teams equips the Chief Financial Officer with the opportunity to contribute valuable inputs form their part in order to form various important strategic decision as a premier member of the team. The Chief Financial Officer also ensures that the strategies adopted by the organization should be delivered with the help of an prearranged financial strategy (Sun et al. 2013). Within the higher management team the Chief Financial Officer is responsible for the following responsibilities, Establishing him or herself as a chief corporate player in order to ensure that the decisions taken will ass value to the prospects of the company as well as contribute in establishing competitive advantage (Menike and Prabath 2014). The Chief Financial Officer will also add value to the process of corporate decision making by imposing challenges, encouraging and evaluating the proposals that will help the organization to achieve its aims and objectives effectively and efficiently (Menike and Prabath 2014). The CFO is also responsible for assisting the effective decision making process absed on available information and thereby bringing out the value of those decisions within the organization as well. Chief Financial Officer of ActivEX Limited is also responsible for supporting the superior management team of the organization by providing the appropriate financial decisions. Henceforth the Chief Financial Officer of the organization is responsible for maintaining the team and establishing proper communication with the organization. Therefore, without the CGO it is nearly impossible to establish a proper decision making framework and implementing appropriate strategies (Menike and Prabath 2014). Designing and implementation of the organizational strategies: During the past few years ActivEX Limited has faced various issues because of the rapid changes which are taking place in the market structure as well as in the structure of competition. The government with the help of the funding bodies has required implementing gains in the level of efficiency, and this in turn have imposed sufficient financial pressure over the organization as well (Casault et al. 2014). It is also quite evident that there are increasing competition among the manufacturing firms in terms of cost and pricing of the products. Partnering with the other organizations as well as cooperating with them will help the organization to achieve further success in future. However, in this case the company wish to operate in the way it is operating right now, that is without partnering with any other organization (Oricchio 2012). As a Chief Financial Officer of ActivEX Limited the focus should be on designing the strategic planning entirely based on the external landscape of the organization, the demand and drivers of cost associated with the organization. Financial decisions actually translate the aims and objectives of the organization in a very common language and therefore the Chief Financial Officer shares the development of strategic framework and its implementation responsibilities with the entire leadership team. The Chief Financial Officer also ensures that the members of the superior leadership teams are well equipped with the financial capabilities so that they are able to discharge their duty as well as their role (Oricchio 2012) The Chief Financial Officer of ActivEX Limited promotes and encourages continuous developments of the organizations so that the institution can deliver its products and service at the highest level. At the same time the prior concern of the Chief Financial Officer will be investigating the processes and controlling the organization and therefore, the CFO is proactive in management of risk and change associated with the organization (Van Gelderen and Monk 2015). Moreover, as the esteemed member of the superior leadership teams the Chief Financial Officer behaves in a way that is consistent with the values and objectives of the organization. Helping with the resources along with delivering the objectives: Presently there is an emerging trend among the Chief Financial Officers to hold different types of responsibilities beyond financial activities. This may include managing the change programmes or leading the other services framework. However, these help an individual to develop him or herself as an efficient corporate personnel but it is not compromised with the financial roles of the Chief Financial Officer (Mouelhi and Saint-Pierre 2013). Overburdening the Chief Financial Officer with increasing responsibilities will definitely result in very inefficient financial outcomes for the organization. Financing of the organization is a very complex and highly controlled phenomenon and therefore the Chief Financial Officer of ActivEX Limited contributes their technical expertise and the interpretation. Hence the CFO of the organization will also be responsible to maintain a balance between the interests of the company and the public at the same time the organization will also take into account the legislative frameworks of the country which are relevant in this regard. Therefore, from the discussion above the roles and responsibilities of the CFO of ActivEX Limited have been understood and it has helped to gain a broader knowledge about the entire topic. The three main responsibilities of the Chief Financial Officer of ActivEX Limited has helped the organization to grow in the market effectively. Following these regulations and meeting the requirements will also help the organization to grow further and flourish in near future (Jamshidi and Jonsson 2016). The Efficient Market Hypothesis: The efficient market hypothesis which is also known as Random Walk Theory is a proposition it states that the present stock prices do reflect all the available information regarding the value of the firm and it also states that there is no way in which a firm can earn excess profits by using this information. This hypothesis deals with the most excite g and fundamental issues relevant to finance that is how prices in the stock market changes and how those changes are taking place (Zahedi and Rounaghi 2015). There are a number of investors who always search for the assets which are undervalued and which are expected to raise their values in near future to be very specific those assets which re expected to increase its value more than the other assets. Most of the investors including the investment managers as well think that they are able to select those securities which will outperform the market (Zahedi and Rounaghi 2015). These officials generally use various forecasting and valuation tools and techniques in order to make their investment decisions. According to the Efficient Market Hypothesis none of these procedures are effective in determining the value and therefore no one will be able to outperform the market (Mouelhi and Saint-Pierre 2013). However, there are no other theories in the context of economics and finance that generate a more passionate discussion between the proponents and the challengers. Therefore, according to the Efficient Market Hypothesis there are no one who will be able to earn profit by predicting the future price. The assumption that investors will not be able to outperform the market however, it has been observed that a number of investors have outperformed the market. Hence, it can be said that when a personnel is not able to outperform the market that is if the Efficient Market Hypothesis is not true then the pension fund manager will definitely select a portfolio with a pin. However, Efficient Market Hypothesis does not imply that the investors will not be able to outperform the market (Zahedi and Rounaghi 2015). It is a widely known fact that constant arrival of information makes price fluctuate. Therefore, sometimes it becomes possible for the investors to predict the price when the arrival of information affects the price of the stock that the investor is holding. Therefore, this is the reason behind the fact that the pension fund managers do not buy a portfolio with a pin (Jamshidi and Jonsson 2016). Now, in order to conclude it can be said that the study have effectively answered the two questions and therefore by answering these questions the student has become able to gain a substantial knowledge about the financial instruments and the responsibilities of the Chief Financial Officer of ActivEX Limited. Reference List: Baez, L., 2014. Prosecutorial Discretion Advised: Analyzing the Proper Role of Economic Consequences as a Factor in Federal Prosecutorial Decisions Not to Seek Criminal Charges.Dartmouth LJ,12, p.1. Casault, S., Groen, A.J. and Linton, J.D., 2014. Improving value assessment of high-risk, high-reward biotechnology research: the role of thick tails.New biotechnology,31(2), pp.172-178. Cowell, F., 2013. Risk Management. InRisk-Based Investment Management in Practice(pp. 47-64). Palgrave Macmillan UK. Cui, J., Jo, H. and Li, Y., 2015. Corporate Social Responsibility and Insider Trading.Journal of Business Ethics,130(4), pp.869-887. Diehl, K.A., 2016. How Sour Is the Apple Inc.? What the Rest of the World Can Learn about Financial Reporting from Apple's Less Than Exemplary Role Modeling.Global Virtue Ethics Review,7(2), p.166. Jamshidi, P. and Jonsson, V., 2016. En eventstudie om svenska marknadsreaktioner p tillknnagivanden av CEO-och CFO-avgngar. Lemus, E., 2016. 3-The Implication of 14 Critical Aspects Evaluating the Relationship between EMH and IFRS.ICL Journal, p.46. Lowies, G.A., 2012.The role of behavioural aspects in investment decision-making by listed property fund managers in South Africa(Doctoral dissertation, University of Pretoria). Lund, T., 2015. Information Asymmetries and Insider Trading in Swedish Share Repurchasing Firms: A comparison between CEOs and CFOs. Menike, M.G.P.D. and Prabath, U.S., 2014. The Impact of Accounting Variables on Stock Price: Evidence from the Colombo Stock Exchange, Sri Lanka.International Journal of Business and Management,9(5), p.125. Mouelhi, C. and Saint-Pierre, J., 2013. The Most Relevant Value Creation Indicator Under Competitive Dynamics of the Firm.Available at SSRN 2266050. Oricchio, G., 2012. The Efficient-market Hypothesis (EMH) and Financial Crisis. InCorporate Management in a Knowledge-Based Economy(pp. 155-168). Palgrave Macmillan UK. Priest, W.W., Bleiberg, S.D. and Welhoelter, M.A., 2016.Winning at Active Management: The Essential Roles of Culture, Philosophy, and Technology. John Wiley Sons. Sun, J., Ju, X.F., Peng, Y.M. and Chang, Y., 2013. Managers' Power and Earnings Manipulating Preference.Advances in Information Sciences and Service Sciences,5(1), p.796. Van Gelderen, E. and Monk, A.H., 2015. Knowledge Management in Asset Management.Available at SSRN 2642467. Zahedi, J. and Rounaghi, M.M., 2015. Application of artificial neural network models and principal component analysis method in predicting stock prices on Tehran Stock Exchange.Physica A: Statistical Mechanics and its Applications,438, pp.178-187.

Havisham Essay free essay sample

Discuss how effectively the poet presents nature or time in this way. Carol Ann Duffys Havisham is a monologue spoken by Charles Dickenss character Miss Havisham from Great Expectations. Jilted by her scheming fiance, Havisham continues to wear her wedding dress and sits amid the remains of her wedding breakfast for the rest of her life, whilst she plots revenge on all men. She hates he spinster state, which suggests Duffys choice of name for the poem, and suggests at the themes of loss, breakdown, jealousy and revenge. This essay will explore how time is presented as a destructive force and how effectively Duffy make use of it through various poetic techniques. Through Duffys use of imagery, the destructive force of time begins to be revelled to the reader. Havisham has become so filled with hatred for men, after what her fiance did to her she wants to take revenge: Prayed for it so hard Ive dark green pebbles for eyes, opes on the back of my hands I could strangle with. We will write a custom essay sample on Havisham Essay or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page She tells us that she has prayed so hard for it (with her eyes closed and her hands together) that her eyes have shrunk and hardened and her hands have sinews strong enough to strangle with, which fits her murderous revenge. Readers who know Dickens novel might think about Miss Havishams ward Estelle at this point whose natural mother, Molly, has strangled a rival and has unusually strong hands. This brings forward the image of hardness and cruelty, as Havisham has become trapped with obsession: thinking, praying and waiting for her fiance. The green has connotations of her envy and jealousy and reflects her thoughts and treatment of married women. Her eyes being like pebbles has connotations of a resistance and stone, and also suggests that Havishams eyes are stone cold and heart has turned to a hard stone, that no longer feels any emotion. This shows how time has not only aged her but has also left her broken and seeking a revenge that will never come. Through Duffys use of imagery, we begin to get a deepened sense of understanding towards Havishams situation, but also how time is eading to her breakdown and beginning to destroy her. Duffys use of word choice and sound, the destructive force of time is further revealed to the reader. Havisham has never changed out of her wedding dress and spends her days in bed, sc reaming at the walls which surround her, I stink and remember. Whole days/in bed cawing Nooooo at the wall. Havisham is aware of her own smell, not just the stink of her unwashed body, but also of the stench of the terrible things that have happened to her. She stays in bed and screams in denial. The setting of her bed portrays how time has destroyed her as she has become so weak she cannot get out of bed. The word choice of cawing gives the impression Duffy is comparing the noise Havisham is making to the noise a crow makes, suggesting Havishams cries are annoying yet constant similar to that of a crow. It could also be suggested that if a male crow leaves or dies, the female will never take another mate, suggesting Havishams spinster state and creates a reason behind her jealousy and revenge. The word choice of Nooooo emphasises Havishams grief and despair and how she cannot express her anger and bitterness through proper words. Duffys use of sound and word choice illustrates how time has destroyed Havishams ability to function properly, leading to her physical breakdown. Through Duffys use of word choice we understand how time has led to Havishams mental breakdown and has destroyed her mind. Duffys uses an image to highlight Havishams confused feelings Loves/ hate behind a white veil; a red balloon bursting/ in my face. The enjambment of love emphasises that that love has been personified and that the hate belongs to love. Love enjoys hurting her with the description of the balloon being an oxymoron, as balloons are supposed to be fun but this comes as a shock, ready to spoil her happiness. The red balloon symbolises how fragile love and the heart is and how easily it can burst. The white veil symbolises her wedding and her wedding dress which she is still wearing, and how she is trying to hang onto her fiance. The final line of the poem brings together Duffys ideas of time as a destructive force as Havisham has become a broken Dont think its just the heart that b-b-b-breaks. This sums up the poem, telling us that more than he heart is broken. The very last word comes out in a stutter, showing us her sadness but at the same time her emotional breakdown. This highlights how as time has gone on, she has become more and more broken and damaged, and the poems structure reflects this, and is quite broken apart, which shows her mental state at the time. Through Duffys use of word choice we see how time has been used as a destructive force and has therefore led to Havishams emotional and mental breakdown. To conclude, Havisham becomes weakened physically, emotionally and mentally by time portrayed as a destructive force through Carol Ann Duffys use of word choice, imagery and sound . This poem teaches us about emotional and mental breakdown as well as the nature of loneliness and revenge and it encourages us to think about what we would do, if in a similar situation. Havisham Essay free essay sample Discuss how effectively the poet presents nature or time in this way. Carol Ann Duffys Havisham is a monologue spoken by Charles Dickenss character Miss Havisham from Great Expectations. Jilted by her scheming fiance, Havisham continues to wear her wedding dress and sits amid the remains of her wedding breakfast for the rest of her life, whilst she plots revenge on all men. She hates he spinster state, which suggests Duffys choice of name for the poem, and suggests at the themes of loss, breakdown, jealousy and revenge. This essay will explore how time is presented as a destructive force and how effectively Duffy make use of it through various poetic techniques. Through Duffys use of imagery, the destructive force of time begins to be revelled to the reader. Havisham has become so filled with hatred for men, after what her fiance did to her she wants to take revenge: Prayed for it so hard Ive dark green pebbles for eyes, opes on the back of my hands I could strangle with. We will write a custom essay sample on Havisham Essay or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page She tells us that she has prayed so hard for it (with her eyes closed and her hands together) that her eyes have shrunk and hardened and her hands have sinews strong enough to strangle with, which fits her murderous revenge. Readers who know Dickens novel might think about Miss Havishams ward Estelle at this point whose natural mother, Molly, has strangled a rival and has unusually strong hands. This brings forward the image of hardness and cruelty, as Havisham has become trapped with obsession: thinking, praying and waiting for her fiance. The green has connotations of her envy and jealousy and reflects her thoughts and treatment of married women. Her eyes being like pebbles has connotations of a resistance and stone, and also suggests that Havishams eyes are stone cold and heart has turned to a hard stone, that no longer feels any emotion. This shows how time has not only aged her but has also left her broken and seeking a revenge that will never come. Through Duffys use of imagery, we begin to get a deepened sense of understanding towards Havishams situation, but also how time is eading to her breakdown and beginning to destroy her. Duffys use of word choice and sound, the destructive force of time is further revealed to the reader. Havisham has never changed out of her wedding dress and spends her days in bed, sc reaming at the walls which surround her, I stink and remember. Whole days/in bed cawing Nooooo at the wall. Havisham is aware of her own smell, not just the stink of her unwashed body, but also of the sten ch of the terrible things that have happened to her. She stays in bed and screams in denial. The setting of her bed portrays how time has destroyed her as she has become so weak she cannot get out of bed. The word choice of cawing gives the impression Duffy is comparing the noise Havisham is making to the noise a crow makes, suggesting Havishams cries are annoying yet constant similar to that of a crow. It could also be suggested that if a male crow leaves or dies, the female will never take another mate, suggesting Havishams spinster state and creates a reason behind her jealousy and revenge. The word choice of Nooooo emphasises Havishams grief and despair and how she cannot express her anger and bitterness through proper words. Duffys use of sound and word choice illustrates how time has destroyed Havishams ability to function properly, leading to her physical breakdown. Through Duffys use of word choice we understand how time has led to Havishams mental breakdown and has destroyed her mind. Duffys uses an image to highlight Havishams confused feelings Loves/ hate behind a white veil; a red balloon bursting/ in my face. The enjambment of love emphasises that that love has been personified and that the hate belongs to love. Love enjoys hurting her with the description of the balloon being an oxymoron, as balloons are supposed to be fun but this comes as a shock, ready to spoil her happiness. The red balloon symbolises how fragile love and the heart is and how easily it can burst. The white veil symbolises her wedding and her wedding dress which she is still wearing, and how she is trying to hang onto her fiance. The final line of the poem brings together Duffys ideas of time as a destructive force as Havisham has become a broken Dont think its just the heart that b-b-b-breaks. This sums up the poem, telling us that more than he heart is broken. The very last word comes out in a stutter, showing us her sadness but at the same time her emotional breakdown. This highlights how as time has gone on, she has become more and more broken and damaged, and the poems structure reflects this, and is quite broken apart, which shows her mental state at the time. Through Duffys use of word choice we see how time has been used as a destructive force and has therefore led to Havishams emotional and mental breakdown. To conclude, Havisham becomes weakened physically, emotionally and mentally by time portrayed as a destructive force through Carol Ann Duffys use of word choice, imagery and sound . This poem teaches us about emotional and mental breakdown as well as the nature of loneliness and revenge and it encourages us to think about what we would do, if in a similar situation.

Jews and the State essays

Jews and the State essays Since the birth of Christ, the relationship among Jews and Christians and the state has radically shifted from one end of the spectrum to the other. Since its inception, Christianity had been the religion coping with intolerance from the Jews and the state, yet as time progressed the attitude toward Jewry turned for the worse. As more Christian rulers came into power, laws and regulations turned against those Jews who had once turned against those supporting Christ. Not until after the medieval ages did the states position on Jews begin to loosen up again. This is not to say that time would heal all problems. In truth, time simply brought a change. Social and economic structure developed over the centuries, and some restrictions on Jews were abandoned while still others were just being formed. Treatment of the Jews varied greatly from region to region. The Age of Enlightenment would bring changes that would finally have a long-standing impact on the Jewish community. The Middle Ages began poorly for the Jews of Europe. In the early fourth century, it was inconceivable to separate church and state. In fact, religion played an important role in the government until well after the Reformation. Constantine, the first Roman Emperor to limit the rights of the Jews in the Holy Roman Empire, disallowed any Jews from becoming missionaries for their faith or displaying any form of anger against Christians (Marcus 3). Twenty years later, Constantius forbade marriage between Jewish men and Christian women, and that law was later expanded to deny all marriages between Christians and Jews. In addition, Jews were no longer allowed to possess slaves. In 439, Theodosius II allowed only Christians to hold any public office that would give honor (4). Theodosius did, however, allow Jews to hold offices that were known to lead to financial decline. In addition, as an attempt to prevent Christians from converting to Judaism, Theo...

CIPD DIPLOMA 1 Essay Example | Topics and Well Written Essays - 1500 words

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The Place to Work in the Bank Essay Example | Topics and Well Written Essays - 500 words

The Place to Work in the Bank - Essay Example For this to happen, you need to put your best foot forward and we would expect you to adhere to the rules and regulations that govern the professional conduct here. The working hours are fixed, though, you may come in a bit late with the prior permission of your manager. Do remember to inform your manager in advance so that the customers do not have to wait at the counter or in your office. You have to ensure that you abide by the timings and if you have put in extra hours, you can claim overtime for it. Note that overtime does not apply to the managerial cadre. Your attire must be professional and it must not be flippant or causal. Men are expected to wear ties and optionally a jacket or a suit. Women are expected to dress professionally in business suits. No jeans or sneakers are allowed on all days. On some Fridays that are specially designated, you may come in casual attire. These days would be intimated to you in advance and most of the time there would be some fun and frolic along with celebrations of special occasions in the office. You are not allowed to have food or drinks at your work seat. There are designated cafeterias for these. You are expected to be civil with the customers and put up with minor irritants in their behavior towards you. However, you may raise the issue with your manager if you feel that a particular customer is behaving badly with you.

On the Implant Communication and MAC Protocols for a WBAN

On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to On the Implant Communication and MAC Protocols for a WBAN On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to