Robotic Surgery Disposal Essay Example for Free

Robotic Surgery Disposal Essay What is the Environmental Collateral Effects of Minimally Robotic Surgery? Two small studies have looked specifically at differences in communication between laparoscopic and robotic surgery. Both studies found a significant increase in oral communication between the surgeon and the rest of the team in robotic surgery, particularly in relation to the orientation and localization of organs and the manipulation of instruments, with the effect found to be more pronounced in teams that have less experience in robotic surgery. If use of robotic surgery interferes with standard practices of coordination among the OT team, the achievement of seamless, efficient, and timely teamwork may be hampered. It is important to understand any change in communication patterns because of the well-documented relationship between communication and patient safety, with failures in communication and teamwork being identified as key factors in adverse events in the OT. Communication and teamwork around robotic surgery are likely to be influenced by processes associated with the introduction of robotic surgery, such as training and changes in team structure, but equally the integration of robotic surgery in surgical practice may be dependent on the extent to which it is consistent with existing practices for coordination. How is Robotic Surgery Disposal conducted? For robotic surgery to provide the most benefit for patients, it is first necessary to understand the organizational and social factors that support the successful integration of robotic surgery, by which we mean that it becomes embedded into surgical practice, being used routinely and successfully for surgical operations where it offers advantages to the patient. It is also necessary to understand the impacts of robotic surgery on communication, teamwork, and decision making in the OT and how OT teams manage those impacts. Robotic-assisted surgery has evolved over the past two decades with constantly improving technology, assisting surgeons in multiple subspecialty disciplines. Patient positioning requirements can cause significant physiologic effects and may result in many complications. Good communication among team members and knowledge of the nuances of robotic surgery have the potential to improve patient outcomes, increase efficiency,  and reduce surgical and anesthetic comp lications. Robotic surgeries of long duration are associated with both increased risks to patients as well as distinct challenges for care providers As robotic surgery is increasingly utilized, operations with long surgical times may become more common due to increased case complexity and surgeons overcoming the learning curve.

Concepts of Islamic Marriage

Concepts of Islamic Marriage 1.0 Introduction. The Muslims do not see the house as a static entity. As the environment for the generation of life, it is itself a living and dynamic entity. Hence waala talk of the need to continually build up the house. This task needs a man and woman in order to be accomplished. As a Waala saying goes, it needs a man and a woman to build a house, For whilst the man digs the soil the woman provides the water without which he cannot make the motar for the building. Here again, we see how, in a nuanced way, the waala refer both to the sexual division of labor in the putting up of a physical house and the cooperation of the sexes in the generation of children within the social house. In this way, I have the double reference to the house as a physical and social entity. Through these statements, Waala acknowledge the importance of marriage. However they do not see marriage as establishing a household. Waala believe that the House has already been setup by the forebears. It is a task of the descendants to keep the house in existence. Marriage is thus a necessary means of keeping the house a lived through history. Hence a young man is said to take a wife (depogaa) into his house whilst a young girl homes a houseband (kulisira). Girls are destined to marry outside their own patriling into another persons house and thus educated to help build their husbands houses even if they are never considered full members in it. Infact, the remaining members of their own patriclan are expected to be responsible and respectable ambassadors of their own families within their husbands own. Throughout the world and through out history there have been, and still are, a variety of matrimonial systems each of which is the fruit of inventiveness and adaptation to local cir cumstances. The Islamic marriage system is one of them, it has its peculiarities and specific characteristics, carved out by tradition. For the Muslims, marriage is the union of a man and a woman, having in mind the reciprocal services of domestic life and the procreation of children, this union is made possible through the mutual agreement between the kinship group of the man and the woman. Therefore, marriage is not just the affairs of the man and the woman, for the bond that unites them as husband and wife unites at the same time their two lineage groups. Man alone is incomplete and more so the woman, they are like two halves of a Calabash which have to be reunited to have a whole Calabash. The complete human being is the couple (man and woman) and it has been like that since the beginning. For the two, it is the accession to their true maturity especially if their union results in an offspring; Marriage is the fine threshold to cross on earth in the growth through childhood. Celibacy always conserves something if childish immaturity in the eyes of the society. The relation husband-wife is therefore constitutive of the human being and marriage which creates this relation is thus greatly varied. 1.2 Backgrounds to the study Islam recognizes values of sex and advocates marriage. Islam does not believe in celibacy. The prophet of Islam has said marriage is my sunnah (that is recommended action of the prophet) and whoever does not follow my sunnah is not true follower (Ibn Haiah Basum Nilah) All has commanded the Muslims to marry. (Quran 24:33) in Islam, marriage is considered as one of the essential element of adulthood in Islamic context. And marriage is also considered as an essentially a contract. In Islam, both Muslim men and women must satisfy certain conditions before one can go into marriage. The conditions include: There must be a clear proposal There must be a clear acceptance There must be at least the competent. After satisfying the about conditions, the marriage must be witness by the competent persons from both the mans family and the womens family. Respectively. It is necessary to exclude illicit sex and to safeguard legitimacy of progeny. It is recommended that marriage should be widely publicized. The heart of marriage is the marriage gift, little or more, by the bridegroom to the bride. Dowry or marriage gift by bridegroom to the bribe is a symbolic expression of the grooms cognizance of the economic responsibilities of marriage and of his readiness to assume all responsibilities subsequent to marriage Dowry is not any price paid either to wife or family of the wife. Dowry should be estimated according to the circumstances with emphasis on moderation. The prophet (S. A. W.) is reported to have said that the most blessed marriage is that which is least costly and most easy. Marriage is usually a group affair and the ceremony involves, besides the couple and their immediate relations distant kinsfolk, neighbors and friends. Nor is their involvement limited to the ceremony. It is necessary during the preliminary negotiations which culminate in the ceremony. That is why it is said that Ghanaian marriage is between families and not individuals. This view has added significance because in our extended system, the interest of the relatives in the marriage means that the two families have become affirnal real kin of the two sides. Nukunya (2003). According to G. E. kpiebaya the word Bride price instead of the usual word dowry for a reason. The word dowry is often used to refer to the practice among many Africans peoples of giving some goods in exchange for a wife, but strictly speaking, dowry is the money, or the property a woman brings to her husband at marriage. In Africa, in general, it is the boy, not the girl who brings money, property and services to the girls family. In my candle opinion, the Bride price or Bride health is the consideration (thus the benefit to the bridegroom. The consideration paid by the bride should be within the limit of the bride and should be recommended by Islam advocates and confined within the teachings of Islam. The importance of the dowry (bride price, bride health) can not be overemphaised. The bride price is never seen traditionally as payment for the girl, but as an indemnity to the family (kpiebaya), payment of the dowry (bride price, bride health) is a symbolic of the marriage procedure and finally legalize the marriage contract. Once the bride price has been paid by the bride, it confers sexual rights on both parties. Since lslam discourage celibacy. Payments of the dowry also legitimize the unborn children and also the dowry serves as a stabiser to the marriage for once the girls people have receiued it they are not readily prepared to retune it should a breakdown occur. It is therefore in their interest to maintain the marriage (G. E. kpiebaaya). Walimah is a food reception which follows the consummation of the marriage, to make it public. It is offered by the parents of the married couple, by their friends, or by the newly married couple themselves. Friends, relatives, and neighbors are usually invited. This food reception should be within the means of the couple and recommended by lslam. The companion Anas reported that the prophet (S. A. W. ) Saw a trace of yellow on Abd Ar Bahaman /bn Awf, and asked: what is this? He answered: l got married. The prophet (S.A.W.) said: may Allah make it a blessing for you. Make a Walimah, even with only sheep.(Al-Bukhari,Muslim,Al-Tirmizi,Abu Dawood and Malik) . In human life, every human being good through three (3) importance stages in life and each of these stages is marked with celebration and other financial commitment. The stages include: Out- adoring ceremony. Adulthood and marriage ceremony. Death and funeral ceremony. The celebration of these activities should not bring any hardship to those performing them. Recently, the Islamic marriage institution has turn in to a financial institution where Muslims barrow with collateral security and save with a very hard sting conditions. Those Muslims who has not gotten the said collateral security cannot borrow from the Islamic marriage institution. In conclusion marriage is a religious right for Muslim brothers and sisters and this has been recommended by the messenger of Allah (S.A.W.) and His Companions. Emphasis is placed on the affordability of the Dowry (Bride pride). 1.3 Statement of the problem Allah created men and women so that they can provide company to one another, have one another, procreate children and live in peace and tranquility to the commandments of Allah and the directions of His messenger. Nature has so arranged that man and woman are attracted toward each other. This natural attraction binds them together and leads them to live a common life and form a family. This natural tendency or the instinct of sex, like any other instinct, should be guided to the right direction so that it may be utilized in the service of humanity. In the wake of keen desire to established conjugal relations between them selves, man and woman enter into a contract known as marriage or matrimonial contract. This contract has great importance in human life, for it unites the existence of two persons in many ways. It lays the foundation of the life of a human infant and deeply influences his body, life, thought and future actions. That is why a marriage contract is regarded a sacred by various nations and enough attention has been paid in different legal systems to the question connected with it. Islam has also attached great importance to the question of marriage in its social system. In the holy Quran and the sayings of the holy prophet and the imams we find that marriage has been greatly encouraged. The holy prophet has been reported to have said No institution of island is liked by Allah more than that of marriage. Despite the numerous importance marriage in Islamic context. Individual Muslims have tend it into money ventures making it very difficult for afford this huge sum of money to go into marriage. The introduction of new concepts into the Islamic marriage has created difficulties for those who can afford and stand the test of time. The concept include:, showing of identical clothes, hiring of canopies, expensive dowry, hiring of record dance (stero) and among others is an indication that new concepts have been added to the in stilton of marriage besides its traditional concepts due to individual perusal interest. This practices and concepts currently introduced into the Islamic marriage have undermined the integrity of Islam as a religion. I there for urged every meaning, concerned and patriotic Muslim to stand elementally against these practices.. Mr. Daud Baaba Adidas delivered a paper on Islamic marriage, radio progress current affairs. 1.4 Research question (s) Main research question What are the impacts of the commercialization of marriage on Islamic marriage? Sub-question: How is Islamic marriage contracted? What are the essential requirements of Islamic marriage? Are there changes to the essential requirements of Islamic marriage? What are the impacts of these changes on Islamic marriage? 1.5 Research objective (s) Main research objective To assess the impact of commercialization of marriage on Islamic marriage Sub-objectives To identify the procedure of Islamic marriage To identify the requirements of Islamic marriage To determine the changes in procedure and requirements of Islamic marriage overtime. To assess the impact of these changes and Islamic marriage. 1.6 PURPOSE OF THE RESEARCH This research is intended to examine the factors or Circumstances that led the commercialization of the Islamic marriage which currently made very difficult for Young Mushin boys and girls to go into marriage as prescribed by the Holy Book (Quran). The findings the research will be made available to the Islamic Communities and other interested bodies and institutions. CHAPTER TWO 2.0 Literature review This chapter will consist of two (2) Termantic areas. Thus theoretical Framework which comprise previous literature undertook by prominent scholars, journals textbooks both published and non-published on: The procedure on Islamic marriage The requirements of Islamic marriage The changes in procedure and requirement of Islamic marriage The impact of the recent changes in procedure and requirement on Islamic marriage. The second phase of this chapter is the conceptual framework of the procedures and requirements of Islamic marriage. Chapter Three Methodology 3.0 Introduction This chapter deals with the description of the study design; study Area, Population sampling method, sampling Size. Data Collection Approach, interview. and questionnaire 3.1 Study design The research design will follow the following pattern, the topic or title, introduction, Background, problem analysis or statement of the problem, the research question, the research objective , Literature Review, Methodology, Findings and discussion of sub-objectives, conclusion, Recommendations and References. Ha win C (1989), Research Design strategies and choices in the design of social research. Pathways Analysis (Dietz) 3.2 Study Area: WA municipality especially WA township where the practice of the commercialization of marriage on the Islamic Institution is the most affected area. Wa Municipal is one of the nine (9) Districts in the Upper West Region. 3.3 Secondary Data The researcher intended to collect data from the following sources; papers delivered by prominent Islamic scholars, Islamic scholars who have researched into Islamic marriage, Articles publications and son on. 3.4 Population The population of the research will be the Muslim community in Wa Township and it environs. 3.5 Sampling Method; Two main sampling method or technique would be adopted thus; stratified random sampling and purposive sampling procedure Stratified random sampling: In stratified sampling, the sampler divides the population into homogeneous unites. That is to say, if the sampler has any reason to believe that the population has many dissimilar elements or individuals, 3.6 Sample Size The sample size is the number of respondents the researcher will be dealing within the population. Two hundred (200) respondents is targeted 3.7 Data Collection Approach; The researcher intended to use one main methods which include; and questionnaire. The research findings will be both qualitative and quantitative 3.8Questionnaires Formal questions will be framed and written down for the respondents to provide the answers. As a method for data collection, questionnaire is and efficient way to collect statistically quantifiable information. The researcher intended to use an open- ended question. Open-ended questions give flexibility in answering questions. Respondents can express themselves as fully as they wish. The researcher intended to administer one hundred and fifty (150) questionnaires. Network Analysis ( Long 1989, Cees Lewis 1990, Villareal 1990) PROPOSED BUDGET Component Quantity Unit price Totals A-4 Sheet Five (5) 45.00 22.50 Type setting and photocopy of questionnaire One hundred and fifty GHÂÂ ¢7 for type setting (a) 10p per photo copy (a) 100 questionnaires 1050 Field Assistance Four (4) 50.00 200.00 Digital Camera for research purpose One 1 350.00 350.00 Final typesetting of thesis work One 1 200.00 200.00 Photo copy of thesis work Five (5) 20.00 100.00 Type setting of Interviews questions Fifty (50) GHÂÂ ¢7 for the setting 70 Allowance for secretary One 1 50.00 50.00 Photocopy of interview questions Fifty 70Gp for 50 3.50 Traveling Transport for researcher Five (5) gallons of petrol 5.30 26.50 Miscellaneous 174.00 TOTALS 2,246.50 Note: This Budget is subject to amendment and review depending on the prices of component at the time of the thesis writing PROPOSED TIME AND COMPLETION OF THESIS Activity Time frame Gathering of Data December 2010 January 2010 Analysis of data February March 2010 Write up of final thesis 1stApril 2010 30thApril 2010 Submission of thesis to the faculty 1stMay 2010 31stMay 2010

Stars and Black Holes Essay -- essays research papers

Below you will read research on stars and black holes. Black holes are stars whose core has been crushed by gravity. In the text to follow you will see how a star forms, read about its life and how it becomes a black hole. Stars are composed of hydrogen gas and dust. Stars owe their existence to the force of gravity. Stars are created from the thinly spread atoms of dust and gas that swirl throughout space. The atoms clump together into dense clouds that eventually collapse under their own gravity. Other forces counteract the gravity. The dust and cloud grows steadily hotter until a nuclear furnace ignites creating a bright shining star. (Couper H. & Henbest N., 1996). Stars are born when particles of hydrogen, helium and dust combine and collapse, shrinking and falling into itself making the cloud hotter. Tiny protons bump into each other and bounce away at high speeds stick together when it is hot enough. Four protons form a particle of helium gas. Two protons fuse together becoming neutrons. Matter that is released from this fusion turns into energy streaming outward from the core creating nuclear fusion. Once the inward and outward forces are equal it reaches its final size and shines, becoming a star. The length of the hydrogen burning stage depends on the stars weight. A star with 15 times the weight of the sun uses up all its hydrogen in less than 10 million years. (Darling D., 1985) The farthest star in the most distant galaxy is more than ten billion light years away. The kind of star a star becomes depends on how much gas and dust the protostar manages to pack into itself as it forms. The more mass a star collects the hotter and brighter it becomes. (Gallant R ., 2000). Three major star types are red dwarfs, yellow dwarfs and blue giants. Red dwarfs are the dimmest and have the longest life span that is about a trillion years. Red dwarfs become black dwarfs when they exhaust their hydrogen and fuel. Yellow dwarf stars have shorter life spans because they burn their hydrogen fuel faster. As fuel runs low they swell up into a red giant, then release planetary nebula, then shrink into white dwarfs and finally cool as black dwarfs. The massive blue giants have the shortest life span as they’ll swell up into supergiants, explode as a supernova and end up as either a neutron star or black hole. (Gallant R ., 2000). A norm... ...un is a ball of gas. It is 8 and one third light years away and 93 million miles away. The suns diameter is 865,000 miles. The sun is about 5 billion years old. (Darling D., 1985). The sun appears as a large disk. At the top of the sun you can see two huge gas eruptions called prominences. These prominences leap out hundreds of thousands of miles. They have hair like spikes that are surges of hot gas called spicules. The mottled effect is caused by cells of hot gases welling up from beneath the surface, cooling and appearing darker than the surrounding gases. (Gallant R ., 2000). Therefore, the sun, stars and black holes coexist with one another in the solar system along with other matter in the galaxy. The sun is a star. Black holes are collapsed stars. Each does not exist without the other. References Couper H. & Henbest N. (1996). Black Holes. New York, NY: DK Publishing Inc. Darling D. (1985). The Stars from birth to black hole. Minneapolis, Minnesota: Dillon Press Inc. Gallant R . (2000). The life stories of Stars. Tarrytown, New York: Benchmark Books Sipiera P. (1997). Black Holes. Canada: Children’s Press, Grolier Publishing Co. Inc

Depressed Teenagers in Today’s Society Essay -- Psychology Depression

Depressed Teenagers in Today’s Society Being depressed includes many feelings, and they can range from simply being fed up with the world to actually wanting to take one’s own life. I have been depressed before, but I have never wanted to commit suicide. I want to know why teenagers would become so depressed that they would even consider taking their lives. I want to answer the commonly asked questions about teenage depression. Why are teenagers today so depressed? Why do they feel like there is no way out for them except death? What causes teens to feel like there is no way out of their feelings of worthlessness? Does society have a negative impact on teenagers which leads to depression? I want to learn the answers to these questions. I want to discover how to help these teenagers who feel so lost in the world. Being a teenager myself, I realize that there is a lot of stress to be perfect. Although perfect is something that does not exist, it is something that so many teenagers feel the desire to striv e for. I have teenage friends who I feel have been distant lately. I fear that they may be suffering from something serious, something like depression. I too have been a victim of depression, and I know that times can get hard. I also realize that if people do not get help they are giving up on themselves. People can not always fix what it is wrong in their lives. I wish that there were programs which teenagers could attend in order to learn more about what they can do in times when they are depressed. Teenagers need to know that someone is there for them. With suicide rates climbing into the thousands, depression is being seen as a number one cause. In order to help teenagers people need to start at the s... ...en, and Kimberly Kirberger, eds. Chicken Soup For The Teenage Soul. Florida: Health Communications, Inc, 1997. Cohen-Sandler, Roni, Ph.D. â€Å"Do you need a therapist?† Seventeen Dec. 2004: 95. Cytryn, Leon M.D., and Donald McKnew M.D. Growing Up Sad. 1996. Washington: Norton & Company, 1999. Depression in Teenagers. November 2003. Hearts and Minds Network. 8 November 2004 . Kolk, Bessel A., Alexander C. McFarlane, and Lars Weisaeth. Traumatic Stress. 1996. New York: Guildford Press, 2000. McEwen, Bruce, and Elizabeth Norton Lasley. The End of Stress As We Know It. 2000. Washington: Joseph Henry Press, 2002. Pipher, Mary Ph.D. Saving the Selves of Adolescent Girls. New York: Balantin, 1996. Wallenstein, Gene Ph.D., Mind, Stress, and Emotions. 1999. Boston: Common Wealth Press, 2003.

Essay on the Religious Right and The Handmaids Tale :: Handmaids Tale Essays

The Religious Right and The Handmaid's Tale The Handmaid's Tale by Margaret Atwood is set in the near future in the Republic of Gilead, formerly the United States. A religious extremist right-wing movement assassinated the president and congress and took complete control of the government. The constitution was suspended and liberties revoked. Women found themselves completely subordinated in the new regime, generally assigned to the legal care of a male "guardian." Offred, the main character of the story, was fortunate in many ways. Because she was still fertile, she was not branded an "Unwoman" and sent to the "Colonies," where thousands of individuals deemed undesirable by the government were sent to toil in toxic plants and agricultural camps. Instead, her fate was to become a "handmaid." Birthrates were declining in the republic, so a fertile female became a prized commodity. Since Offred had been divorced prior to the revolution, the religious leaders controlling the government saw fit to take her from her second husband and child and assign her to a "guardian," a high ranking male. Her sole purpose in life with the guardian was to become pregnant. Once a month an insemination ceremony would take place, during which the guardian would attempt to impregnate Offred while his wife read passages from the bible to them. All three remained clothed and there was no passion involved. In the course of her life as a handmaid, Offred discovers more about Gilead. Her secondary duty (after getting pregnant) was to go into town each day and purchase food. She gradually makes contact with another handmaid, Ofglen, who introduces her to the underground movement against the republic. She eventually becomes involved in a number of illegal activities, and eventually is forced to try and escape. The Handmaid's Tale is really about the role of women in society. If it were possible to eliminate women from Gilead, it seems that the republic would have done so. Instead, they are reduced into doing the one thing for which Gilead can find no substitute -- producing children. They are so reduced that they cannot even feel passion or enjoy sex. Infertile women have it even worse; they are not considered to be women at all, and are deported or killed. The message is that women are needed to continue humanity but that they are to have no other role in the society that they allow to exist. Essay on the Religious Right and The Handmaid's Tale :: Handmaid's Tale Essays The Religious Right and The Handmaid's Tale The Handmaid's Tale by Margaret Atwood is set in the near future in the Republic of Gilead, formerly the United States. A religious extremist right-wing movement assassinated the president and congress and took complete control of the government. The constitution was suspended and liberties revoked. Women found themselves completely subordinated in the new regime, generally assigned to the legal care of a male "guardian." Offred, the main character of the story, was fortunate in many ways. Because she was still fertile, she was not branded an "Unwoman" and sent to the "Colonies," where thousands of individuals deemed undesirable by the government were sent to toil in toxic plants and agricultural camps. Instead, her fate was to become a "handmaid." Birthrates were declining in the republic, so a fertile female became a prized commodity. Since Offred had been divorced prior to the revolution, the religious leaders controlling the government saw fit to take her from her second husband and child and assign her to a "guardian," a high ranking male. Her sole purpose in life with the guardian was to become pregnant. Once a month an insemination ceremony would take place, during which the guardian would attempt to impregnate Offred while his wife read passages from the bible to them. All three remained clothed and there was no passion involved. In the course of her life as a handmaid, Offred discovers more about Gilead. Her secondary duty (after getting pregnant) was to go into town each day and purchase food. She gradually makes contact with another handmaid, Ofglen, who introduces her to the underground movement against the republic. She eventually becomes involved in a number of illegal activities, and eventually is forced to try and escape. The Handmaid's Tale is really about the role of women in society. If it were possible to eliminate women from Gilead, it seems that the republic would have done so. Instead, they are reduced into doing the one thing for which Gilead can find no substitute -- producing children. They are so reduced that they cannot even feel passion or enjoy sex. Infertile women have it even worse; they are not considered to be women at all, and are deported or killed. The message is that women are needed to continue humanity but that they are to have no other role in the society that they allow to exist.

Computer Networks Essay

I. Internet and layered protocol architecture: Q1. (5 points) In the layered protocol architecture the transport layer functionality includes congestion control and error recovery (e.g., retransmission). One suggested that this functionality should be done strictly at the end points (i.e., at the hosts) without aid from the network. Do you agree? Why? Elaborate showing the design trade-offs. Answer: (5 points) In general, error recovery (e.g., re-transmission) is specific to application needs. Some applications require 100% packet recovery, even with delays and jitters (such as TCP-based applications, http, ftp and telnet traffic). Other applications may be tolerant to loss but less tolerant to delays and jitter, such as voice applications. Re-transmissions and packet recovery add to the jitters and the delays and hence may not be desirable for realtime or voice applications. Hence it is not a good idea, in general, to include error recovery at the network layer (that is not aware of application needs) and it is better to implement such functionality at the transport layer end-to-end. In cases of lossy channels in the network (such as X.25 in the early networking days, or wireless links) it may be desirable to reduce the bit error rates on those links by including error recovery at the end points of those links. [In general, most links nowadays have very low BER, and for wireless links the MAC (such as IEEE 802.11) layer provides Ack’ed delivery]. For congestion control, a similar argument may be given. That is, congestion reaction may be application specific and is better implemented end-to-end. Congestion notification, on the other hand, may provide useful information to the end points to react appropriately. Since losses in the network may be due to congestion or other factors, a signal from the network to the end point may help distinguish congestion errors from other errors. Only congestion errors should trigger ‘back off’ or rate cut at the end points. So, network assistance in congestion notification may help in some scenarios. [extra: In other scenarios network assistance may prevent synchronization effects of congestion control, e.g., RED, or may prevent/isolate misbehavior, e.g., WFQ.]. Q2. (5 points) What advantage does a circuit-switched network have over a packetswitched network? How can it establish such advantage? Answer: A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for the duration of a call. Most packet-switched networks today (including the Internet) cannot make any end-to-end guarantees for bandwidth. Circuit-switched networks use admission control, and reserve a circuit (in TDM it is done in the form of an assigned time slot per source that no other source can use). The allocated resources are never exceeded. Q3. (10 points) What are the advantages and disadvantages of having a layered protocol architecture for the Internet? (mention at least 3 advantages and 2 disadvantages) Answer: Is it true that the change in any of the layers does not affect the other layers? (support your answer/arguments with examples) Advantages: Allows an explicit structure to identify relationships between various pieces of the complex Internet structure, by providing a reference model for discussion. Provides a modular design that facilitates maintenance, updating/upgrading of protocols and implementations (by various vendors) at the various layers of the stack. Supports a flexible framework for future advances and inventions (such as mobile or sensor networks). Disadvantages: overhead of headers, redundancy of functions (sometimes not needed) [such as reliability as the transport layer and the link layer, or routing at the network layer and some link layer protocols (such as ATM)] It is true in many cases that the change in one layer does not affect the change in the other layers, but not always. Examples of change that did not affect the other layers: change from FDDI to token ring, to Ethernet at the MAC layer. Examples of change that affected other layers: wireless vs. wired (performance of TCP and routing degraded drastically). Introduction of 802.11 for wireless and ad hoc networks (a change in the physical and MAC layers), does affect in a major way routing at the network layer and the transport layers. In that case, many of the protocols needed re-design. Q4. (10 total points) Design parameters: In order to be able to analyze performance of the Internet protocols a researcher needs to model some parameters, such as number of nodes in the network, in addition to many other parameters. a. Discuss 4 different main parameters one would need to model in order to evaluate the performance of Internet protocols. [Elaborate on the definition of these parameters and their dynamics] b. Discuss 2 more parameters for mobile wireless networks [these two parameters are not needed for the wired Internet] Answer: a. Traffic model temporal and spatial (packet arrival processes, session/flow arrival processes, spatial distribution of traffic (src-dst) pair distribution across the topology), topology/connectivity model, node failure model, membership dynamics (for multicast) spatio-temporal models. [Any reasonable 4 parameters are ok, with 1.5 points per parameter] b. For mobile wireless networks there is a need to model ‘mobility’ (spatio-temporal), and wireless channel dynamics/loss/bandwidth since it changes with time much more drastically than the wired Internet (in which virtually the max bandwidth of a channel/link is static) [Any 2 reasonable parameters are ok, with 2 points per parameter] II. Statistical multiplexing and queuing theory Note: You may want to make use of the following equations: M/D/1: queuing delay ; Ts is service time & Ï  is link utilization M/D/1: average queue length or buffer occupancy M/M/1: queuing delay , buffer occupancy: Q5. (8 points) Consider two queuing systems, serving packets with lengths that have exponential distribution, and the packet arrival process is Poisson. The first queuing system (system I) has a single queue and a single server, and hence the packet arrival rate is X, and the server speed is Y. The second queuing system (system II) has two queues and two servers, and hence the packet arrival rate is X/2, and the server speed is Y/2. Derive a relation between the delays in each of these systems. What conclusion can you make? Answer: (8 points) We use the M/M/1 queue (because the question states Poisson arrival and exponentially distributed service time). For the first system (I): Tq=Ts/(1-Ï )=1/M(1-ÃŽ »/M)=1/Y(1-X/Y), For the second system (II): Tq=2/Y(1-X/Y)=2Tq (of system I) That is, using ‘1’ queuing system performs better than using ‘2’ queues with half of the arrival rate and half of the output link capacity. Q6. (5 points) In an Internet experiment it was noted that the queuing performance of the switches/routers was worse than expected. One designer suggested increasing the buffer size in the routers drastically to withstand any possible burst of data. Argue for or against this suggestion, and justify your position. A6. Increasing the buffer size allows switches to store more packets (which may reduce loss). However, it does not alleviate the congestion. If this was the only cure proposed, then we expect the queues to build up, increasing the buffer occupancy, and increasing the delays. If the build up persists (due to lack of congestion control for example) the queues shall incur losses and extended delays. Delays may lead re-transmission timers to expire (for reliable protocols, such as TCP) leading to re-transmissions. Also, the TTL value in the header of each packet is reduced based on time (and hop count). So, many of the TTLs may expire leading to the discard of packets. So, in ge neral, only increasing the buffer sizes does not help improve the queuing performance. Q7. (7 points) Describe the network design trade-off introduced by using statistical multiplexing and define and describe a metric that captures this trade-off. A7. (7 points: 3.5 for the link between stat muxing and congestion and 3.5 for the trade off metric (network power) and its description). Statistical multiplexing allows the network to admit flows with aggregate capacity exceeding the network capacity (even if momentarily). This leads to the need for buffering and the ‘store and forward’ model. Subsequently, queuing delays and build up may be experienced as the load on the network is increased. Two major design goals of the network is to provide maximum throughput (or goodput) with least (or min) delay. However, these two goals are conflicting. In order to increase the throughput, the congestion increases and so does the delay. In order to reduce the queuing delays then we need to reduce the load on the network and hence the goodput of the flows would decrease. This is the throughput-delay trade off in network design. One metric that captures both measures is the network power=Tput/Delay, as the Tput increases, so does the network power, and when the delay decreases the network power increases. Q8. (8 points) Flows in the Internet vary widely in their characteristics. Someone suggested that in order to be fair to the various heterogeneous flows then we need the different flows to experience the same delay at the different queues. Argue for or against this suggestion. A8. (8 points: 4 points for the constant ratio and the link to the fluid flow model, 4 points for the unfairnes/greed description) In order to provide the same delay for the various flows we need to maintain the rate/capacity ratio constant (this is based on the fluid flow model we introduced in class). Hence, if the different flows arrive at various rates, then the capacity allocation should reflect such variation. The allocation leading to same delays would favor (i.e., allocate more capacity to) flows with higher rates at the expense of flows with low rates. This strategy encourages greed in the network and cannot achieve fairness, where the existence of high rate (large) flows in the network would adversely affect low rate (small) flows in the network by increasing the overall delay experienced by all the flows. Q9. (12 total points) Consider a network that uses statistical multiplexing. The network has ‘N’ number of ON/OFF sources, each sending at a rate of R packets per second when ON. All the sources are multiplexed through a single output link. The capacity of the output link is ‘M’. – A. (3 points) What is the condition on N, R and M in order to stabilize this network? – When the number of sources to be supported is increased from R to 10R, there were two suggestions to modify the network: Suggestion I is to replicate the above system 10 times. That is, create 10 links, each with capacity of ‘M’ handling R sources. – Suggestion II is to replace the link with another link of capacity ’10 M’ B. (9 points) Which suggestion do you support and why? [Argue giving expressions for the delay/buffer performance of each system. Give both the advantages and disadvantages of each case] Answer: ÃŽ ±=ÃŽ »Ã  A. (3 points) The conditions for a stable network are N.R. ÃŽ ± < M, N.R > M, where ÃŽ ± is the fraction of the time the sources are ON (on average) If ‘N.R. ÃŽ ± > M’, then this leads to constant build up of the queue with no change of recovering from congestion (and draining the queue), which would lead to unstable system. B. (9 points) Write down the equations, M/D/1: queuing delay ; Ts is service time & Ï  is link utilization M/D/1: average queue length or buffer occupancy M/M/1: queuing delay , buffer occupancy: The buffer occupancy depends on Ï  only. If Ï  is the same (i.e., the load on the queue server is the same) then the buffer occupancy is the same, Ï  = ÃŽ ». Ts = ÃŽ ±. N. R / M Increasing the bandwidth of the link to 10M means that we can get the same average buffer occupancy in the two systems. In system I we would need 10 times the buffer size as in system II, so system II is advantageous in that sense. (more sharing and statistical multiplexing) In addition, the queuing delay will be decreased drastically (by a factor of 10) where Tq=Ts. f(Ï ) (6 points for the above argument) (3 points) On the other hand the std deviation/fluctuation around the average in the queue size will be higher since it is shared by more number of flows, and hence the jitter will be relatively higher. III. Application layer and related issues Q10. (5 points) (Stateful vs. Stateless) Discuss one advantage and one disadvantage of having a ‘stateful’ protocol for applications. Advantage: The protocol can now maintain state about (i.e., remembers) users preferences (e.g., shopping preferences as in browser cookies), Disadvantage: when failure occurs the state needs to be reconciled (more complexity and overhead than stateless) [other correct and reasonable answers are accepted] Q11. (5 point) (Web Caching) Describe how Web caching can reduce the delay in receiving a requested object. Will Web caching reduce the delay for all objects requested by a user or for only some of the objects? Why? Ans. Web caching can bring the desired content â€Å"closer† to the user, perhaps to the same LAN to which the user’s host is connected. Web caching can reduce the delay for all objects, even objects that are not cached, since caching reduces the traffic on links. Q12. (1 0 points) Discuss three different architectures of the peer-to-peer applications. Give examples of real applications for each architecture and discuss the advantages and disadvantages of each architecture. Ans. 1. Centralized directory of resources/files, as in Napster. Advantage is that search for resources is simple with min overhead (just ask the centralized server). The disadvantages are: single point of failure, performance bottleneck and target of lawsuit. 2. Fully distributed, non-centralized architecture, as in Gnutella, where all peers and edges form a ‘flat’ overlay (without hierarchy). Advantages: robustness to failure, no performance bottleneck and no target for lawsuit. Disadvantages is that search is more involved and incurs high overhead with query flooding. 3. Hierarchical overlay, with some nodes acting as super nodes (or cluster heads), or nodes forming loose neighborhoods (sometimes referred to as loose hierarchy, as in BitTorrent). Advantages, robust (no single point of failure), avoids flooding to search for resources during queries. Disadvantages, needs to keep track of at least some nodes using the ‘Tracker’ server. In general, this architecture attempts to combine the best of the 2 other architectures. Q13. (7.5 points) Push vs. Pull: A. Give examples of a push protocol and a pull protocol B. Mention three factors one should consider when designing pull/push protocols, discuss how these factors would affect your decision as a protocol designer (give example scenarios to illustrate). Answer: A. An example of a push protocol is: http. An example of a pull protocol: SMTP B. The factors affecting the performance of a pull/push protocol include (but are not limited to): 1. access pattern: how often is this object cached and how often is it accessed (example: a push mechanism for a very popular video that is pushed closer to a large population that is going to frequently watch it, would be better than a pull mechanism), 2. delay: what is the delay to obtain the object, and 3. object dynamics: how often/soon does the information in the object expires (example: in a sensor network where the information sensed is constantly changing, but is queried once in a while would be better ‘not’ to push it, but to pull it when needed only). Q14. (7.5 points) We refer to the problem of getting users to know about each other, whether it is peers in a p2p network or senders and receivers in a multicast group, as the â€Å"rendezvous problem†. What are possible solutions to solve the rendezvous problem in p2p networks (discuss three different alternatives and compare/contrast them. Answer: The possible solutions for the rendezvous problem include: 1. Using a centralized server: advantages: simple to search, little communication overhead. Disadvantages: single-point-of-failure (not robust), bottleneck, doesn’t scale well 2. Using a search technique for discovery, perhaps using a variant of a flood (or scoped-flood) or expanding-ring search mechanism. Advantages: avoids single-point-of-failure and bottlenecks. Disadvantages: may be complex, incurs high communication overhead and may incur delays during the search. 3. hybrid (or hierarchy): where some information (e.g., pointers to potential bootstrap neighbors, or pointers to some resources) are kept at a centralized (or replicated) server or super-nodes, then the actual communication is peer-topeer. Advantage: if designed carefully can avoid single-point-of-failure, bottlenecks, and achieve reasonable overhead and delay. Disadvantage: need to build and maintain the hierarchy (can trigger costly re-configuration control overhead in case of highly dynamic networks and unstable super-nodes).

Cells: The Building Blocks of Life Essay

Cells are the basic building blocks of life. For cells to survive and function normally, fluids and electrolytes must keep a harmonious balance. The human body is composed of approximately 60% electrolyte-containing water, in which it is the kidneys’ job to regulate. Any loss of water should be matched with a consumption of water on a daily basis to ensure cells receive a constant balance of fluids. Water from our bodies comes from foods and liquids. Water loss is mostly through urine and is also lost in sweat, respiratory tract and feces. The kidneys produce large amounts of urine when water intake is high to maintain a balance. When our bodies lose water the kidneys will retain water which produce small amounts of concentrated urine. Life cannot exist without electrolytes. http://www.medicalnewstoday.com/articles/153188.php All higher forms of life cannot exist without electrolytes Charged particles in bodily fluids and blood known as electrolytes transmit electrical impulses for the functioning of the muscles, nerves and heart. Positively and negatively charged particles should be equal. http://www.nlm.nih.gov/medlineplus/ency/article/002350.htm Electrolytes are minerals in your blood and other body fluids that carry an electric charge. Electrolytes are charged particles in body fluids that help transmit electrical impulses for the proper functioning of the heart, nerves and muscles. The number of positively charged particles and negatively charged particles is supposed to be equal. An upset of this balance can result in life-threatening conditions Read more: http://www.livestrong.com/article/274601-how-the-body-maintains-fluid-electrolyte-balance/#ixzz21lBz0L7E