Analysis of Wants by Grace Paley

Analysis of 'Wants' by Grace Paley Wants by American writer Grace Paley (1922 - 2007) is the opening story from the authors 1974 collection, Enormous Changes at the Last Minute. It later appeared in her 1994 The Collected Stories, and it has been widely anthologized. At about 800 words, the story could be considered a work of flash fiction. You can read it for free at Biblioklept. Plot Sitting on the steps of the neighborhood library, the narrator sees her ex-husband. He follows her into the library, where she returns two Edith Wharton books she has had for eighteen years and pays the fine. As the ex-spouses discuss their different perspectives on their marriage and its failure, the narrator checks out the same two novels she has just returned. The ex-husband announces that he will probably buy a sailboat.  He tells her, I always wanted a sailboat. [†¦] But you didnt want anything. After they separate, his remark bothers her more and more. She reflects that she doesnt want things, like a sailboat, but she does want to be a particular kind of person and to have particular kinds of relationships. At the end of the story, she returns the two books to the library. Passage of Time As the narrator returns the long-overdue library books, she marvels that she doesnt understand how time passes. Her ex-husband complains that she never invited the Bertrams to dinner, and in her response to him, her sense of time collapses completely. Paley writes: Thats possible, I said. But really, if you remember: first, my father was sick that Friday, then the children were born, then I had those Tuesday-night meetings, then the war began. We didnt seem to know them anymore. Her perspective starts at the level of a single day and one small social engagement, but it quickly sweeps out to a period of years and momentous events like the births of her children and the commencement of war. When she frames it this way, keeping library books for eighteen years seems like the blink of an eye. The Wants in Wants The ex-husband gloats that he is finally getting the sailboat he always wanted, and he complains that the narrator didnt want anything. He tells her, [A]s for you, its too late. Youll always want nothing. The sting of this comment only increases after the ex-husband has left and the narrator is left to ponder it. But what she realizes is that she does want something, but the things she wants look nothing like sailboats. She says: I want, for instance, to be a different person. I want to be the woman who brings these two books back in two weeks. I want to be the effective citizen who changes the school system and addresses the Board of Estimate on the troubles of this dear urban center.  [†¦] I wanted to have been married forever to one person, my ex-husband or my present one. What she wants is largely intangible, and much of it is unattainable. But while it may be comical to wish to be a different person, there is still hope that she can develop some attributes of the different person she wishes to be. The Down Payment Once the narrator has paid her fine, she immediately regains the goodwill of the librarian. She is forgiven her past faults in exactly the same measure that her ex-husband refuses to forgive her. In short, the librarian accepts her as a different person. The narrator could, if she wanted, repeat the exact same mistake of keeping the exact same books for another eighteen years. After all, she doesnt understand how time passes. When she checks out the identical books, she appears to be repeating all her same patterns. But its also possible that shes giving herself a second chance to get things right. She may have been on her way to being a different person long before her ex-husbands issued his scathing assessment of her. She notes that this morning - the same morning she took the books back to the library - she saw that the little sycamores the city had dreamily planted a couple of years before the kids were born had come that day to the prime of their lives. She saw time passing; she decided to do something different. Returning library books is, of course, mostly symbolic. Its a bit easier than, for instance, becoming an effective citizen. But just as the ex-husband has put a down payment on the sailboat - the thing he wants - the narrators returning the library books is a down payment on becoming the sort of person she wants to be.

Strategies for Acing a Multiple Choice Test

Strategies for Acing a Multiple Choice Test We all have to study and take a multiple choice test at some point in our lives. Since these tests are so prevalent, its important to have a few strategies under our belts when we sit for the exams. Read below, because these multiple choice test tips are sure to help you get the score you need on whatever exam youre taking next. Multiple Choice Strategies Read the question while covering up the answer choices. Come up with an answer in your head, and then check to see if it’s one of the choices listed. Use a process of elimination to get rid of as many wrong choices as you can before answering a question. Wrong answers are often easier to find. Look for extremes like never only or â€Å"always. Look for opposites like a substitution of –1 for 1. Look for similarities like conjunctive for subjunctive. Those could be distractors.Physically cross off wrong answer choices so you are not tempted to go back at the end of the test and change your answer. Why? You will read more about trusting your gut in a minute.Read ALL the choices. The right answer may be the one you keep skipping. Many students, in an attempt to move quickly through the test, tend to skim answer choices instead of reading them thoroughly. Do not make that mistake!Cross off any answer that does not fit grammatically with the question on your multiple choice test. If the test blank is looking for a singular noun, for instance, then any question choice displaying a plural noun will be incorrect. If you struggle t o figure it out, then plug the answer choices into the problem to see if it works.   Take an educated guess if there is no guessing penalty like there used to be on the SAT. You will always get the answer wrong by skipping it. You at least have a shot if you answer the question.Look for wordy answers. Unless you’re taking a standardized test, the correct answer is often the choice with the most information. Teachers often have to put as much info down as possible to make sure the answer choice can’t be disputed.Remember that you’re looking for the best answer. Often, more than one answer choice will be technically correct on a  multiple choice test. So, you have to choose which one fits best  with the stem and in the context of the reading passage or test.Use your test booklet or scratch paper. It often helps to write as your work, so write down formulas and equations, solve math problems, outline, paraphrase and underline to help you read. Use the scratch paper to help you work things out logically.Pace yourself. If you get stuck on a questi on, circle it and move on. Come back at the end of the test so you don’t waste precious time on something you may not get right anyway. Trust your gut. Definitely go back through your test to make sure you’ve answered everything, but keep your answers the same unless you’ve discovered new information in a later part of the test to disprove your answer. Click the link for more details about this strategy!

The Real Meaning of the Type of Animal Caregiving Research Paper

The Real Meaning of the Type of Animal Caregiving - Research Paper Example Animal rights advocates have been campaigning for the proper treatment and care of every being other than man. One of the most popular advocacies is the crusade against the use of fur as a wardrobe that well-known fashion models have been supporting. It is also known all over that dog-fighting is highly discouraged. There are a lot of animal rights to enumerate. But as people become aware of the animals’ privileges are they also conscious of proper veterinary care for these beings? Veterinary care is sort of mind, not just the animals’ welfare, but their health in particular. Understanding the term and its etymology will help us understand the real meaning of this type of animal caregiving. Merriam-Webster Online Dictionary (â€Å"Veterinary†) states that the term veterinary derives from a Latin word veterinarians that pertains to beasts of burden. It is similar to the Latin veter- and fetus that is related to the practice or the knowledge in â€Å"prevention, c ure, or alleviation of disease and injury in animals, especially domestic animals.† The people who practice such skill and knowledge are called veterinarians. They also carry the title of â€Å"doctor.† But veterinarians are often regarded with lesser professional esteem compared to the physicians of human beings. Hence, few have developed an interest in this field. But why is veterinary care important? Apart from rabies, there are already a number of deadly animal diseases known to the world, one of which is avian influenza. These diseases can also be fatal when transmitted to humans.

A rhetorical analysis of an argumentative article of your choosing Essay

A rhetorical analysis of an argumentative article of your choosing - Essay Example The article on gun laws was viewed almost by everyone in the world and especially the United States citizens. This was as a result of the Colorado cinema shooting fiasco. The authors’ argument is generally based on the perfect implementation of gun laws in the United States and the rest of the word. This finally will enhance the respect of the sanctity of human life. This paper tries to bring out an argumentative nature of the gun law article. This was because of various opinions from different individuals after the Colorado cinema shooting. According to these composed writers, in 2007, a total number of twelve thousand six hundred and thirty two people in the United States succumbed to firearms related injuries. Another 48676 were admitted to hospitals for gunshot wounds (Bellesiles 28). These two writers are of the opinion that; the restriction gun laws or even relaxing them will reduce the death toll thru shooting which has been a contentious issue in America. These intelle cts on law furthermore argue that proponents of tighter gun laws will definitely do away with these vital and risky weapons falling on wrong hands. These wrong hands in their argumentative article may include criminals, addicted drug users or even the mentally ill individuals (Carter 180). The two with no doubt believe that drug users are majorly the result of the senseless shooting in the public social settings. The gun laws article also criticises the age individuals should be allowed to acquire guns. In the United States, the bare minimum age to hold a gun legally is eighteen years old. This to some extent is not appropriate for these young individuals are not mature for an efficient and effective decision-making (Ramage 98). This according to these two researchers cum writers, in most cases, has also resulted into premature exchange of words and shooting senselessly by the young individuals in the United States. These two writers also believe it is not only in the United States where gun laws are very weak, but this extends to several parts of the world. In a country like South Korea, these prolific writers believe and thus argue that homicide cases related to guns are far less compared to the United States due to strict gun laws which they as well understand is the father of democracy. These examples of fundamentally different states in thefield of gun laws prove that restricting gun laws will actually benefit the populace. These writers, on the other hand, argue that restricting gun laws is more beneficial. Through the restriction of gun laws, the articles firmly believe and argues that day-to-day senseless shooting is curbed totally. Private gun dealers who sell guns ignore critical regulation to those who purchase the guns hence about 85percent of all guns used in crimes unrecovered by law enforcers are linked to them. All these private party sales allow almost everybody to put a stockpile of weapons (Spitzer 238). This as well greatly undermines the g overnment efforts to control the illegal firearms in the country. A private party gun sale is completely unwarranted. This makes the private party gun sales comparable to over the counter purchase of home effects. There are those who argue and believe that relaxing gun laws would create a safer state. Gun advocates and gun manufacturers strongly argue that more guns equals’ tighter security as every gun holder can act as a police. An example is where a criminal or terrorist who pulls out an assault automatic rifle to start

The reassessment of security issues and their impacts on Adventure Essay

The reassessment of security issues and their impacts on Adventure Works business processes - Essay Example In order to promote business on the web requires certain security measures and a fail / safe network environment. After reviewing, the factors that may disrupt organization services are identified below: No Security Policy Defined No Protection of critical Assets on the network No proper data backup policy Moreover, some critical issues or weaknesses that may influence an organization’s business operations need to be addressed on an urgent basis. The top rated issues are: {Security Issue No 1}: No data backup policy defined {Security Issue No 2}: No Disaster recovery plan defined {Security Issue No 3}: No Support for Server requiring 100% uptime {Security Issue No 4}: No IP surveillance for critical server {Security Issue No 5}: In sufficient security for LAN It is vital for Adventure Works to overcome these issues as soon as possible, as these vulnerabilities will directly affect the business operations of the organization. Creating Security Policy As there is no security pol icy defined currently for Adventure Works, the new security policy will illustrate the implementation procedures of security controls that are identified by analyzing the current network and business practices. {Security Issue No 1}: As the organization is maintaining Entity Resource Planning and Customer Relationship Management Server that are considered as core servers may face loss of data or server crash that may result in halting the services. Adventure Works is dependent on these servers, as these servers process most of the paperless work, creating a backup on a regular basis is essential. Recommendation: In order to incorporate a mirror of these servers, disk-mirroring techniques using RAID is recommended. As RAID will synchronize the data on two servers simultaneously, if any one of the server stops responding, the other service will be triggered to ‘primary operation’ mode. {Security Issue No 2}: As one of the branches of Adventure Works is in Mexico, there is a possibility of an earthquake. The impact of earthquake may create disrupt the overall operation of an organization’s network, as well as loss of data. Recommendation: Relocating the instance of critical server data on a different location may be a better choice. In that case, if an earthquake affects Adventure Works network seriously, the data can be extracted from the second location. {Security Issue No 3}: As the core servers of Adventure Works are CRM and ERP, there is a requirement of making their availability 24/7. Moreover, an alternate connectivity is also required that may make them operational if the primary network access is not available due to some issues in a switch. Recommendation: in order to ensure stable power supply, a Power over Ethernet technology is recommended. A comprehensive definition is available in network dictionary, which states as â€Å"Power over Ethernet (PoE) technology describes any system to transmit electrical power, along with data, to remote devices over standard twisted-pair cables in an Ethernet network. This technology is useful for powering IP telephones, wireless LAN access points, webcams, Ethernet hubs, computers, and other appliances where it would be inconvenient or infeasible to supply power separately.† Moreover, the network engineer can rout a dedicated alternate network connection for making the server operational. {Security Issue

Applications of Semiconductor lasers

Applications of Semiconductor lasers Abstract- Semiconductor lasers have the potential to meet the demands of next generation high speed optical network applications and also have great impact on various other technology domains. Its low cost, easy wavelength tune ability, low power consumption and pure output make it ideal for optical communication applications. This paper is a review of the merits, demerits, current applications, commercial availability and future directions of semiconductor lasers in optical communication. Comparative analysis of these semiconductor lasers with respect to various parameters also been conducted. Keywords: Semiconductor lasers, Fabry-Perot laser, Distributed feedback (DFB) laser, External Cavity Diode Lasers (ECDL), Multi Quantum Well (MQW) laser, Vertical Cavity Surface Emitting Lasers (VCSEL) i.Introduction The semiconductor lasers were discovered in 1962 by Robert Hall and his team members [1, 2]. With the advent of this technology patents and articles started to publish on this technology but at that time this technology was not mature enough to realize the dreams of the scientists, engineers and physicist. But with advancement in the field and the enabling technologies soon made it possible to produce inexpensive commercially available semiconductor laser. The invention of semiconductor lasers not only revolutionizes the optical communication but it has many applications in other domains also. Semiconductor lasers are one of the popular optical communication light source for data transmission. They are supposed to be the laser of the future, because of their compactness in size, easy integration, more output power, optical pumps for solid-state lasers (primary light source i.e laser diode pumps another solid state lasers) and their rapid improvement. Semiconductor lasers are essentially diodes which produces coherent light through the process of stimulated emission. They uses semiconductor as a gain medium. The gain medium is pumped by an external source, which is electrical in nature in case of semiconductor lasers [3]. As they are basically p-n junctions, so they are compact and can be fabricated on large scale by the use of advance semiconductor IC technology. Semiconductor lasers are very efficient in converting electrical power into optical power [10]. In section.II basic types of semiconductor lasers are described in terms of their basic working procedure, advantages, disadvantages, commercial availability future directions and applications. Section.III produces the comparison of semiconductor lasers with respect to various parameters and section.IV contains the conclusion. II. Types of semiconductor lasers Following are the basic types of semiconductor lasers Fabry Perot (FP) Lasers Distributed Feedback (DFB) lasers Multi Quantum Well (MQW) laser External Cavity Diode Lasers (ECDL) Vertical Cavity Surface Emitting Lasers (VCSEL) A. Fabry-Perot (FP) lasers In FP lasers, mirrors create the right condition for the lasing to occur. Resonate cavity is formed when two mirrors are put in front of each other. The bouncing of light will take place between these two mirrors, the distance between these two mirrors are adjusted in such a way that this distance is the integral multiple of half wavelength, only is such scenario light will reinforce itself. Wavelengths that are not resonant they undergo destructive interference and deflect. One of the two mirrors is fully reflective and the second mirror allows very small amount of light to pass through [4]. Figure.1.a: Fabry Perot Laser conceptual structure, Ref: [4] Figure.1.b: Fabry Perot Laser structure, Ref: www.scholar.lib.vt.edu A.1. Advantages FP laser gives comb of (Amplified Spontaneous Emission) ASE peak uniform in frequency [5]. FP laser can be used for transmission of data with multimode optical fiber [6]. FP laser also have uniform intensity over Erbium Doped Fiber Amplifier (EDFA) [5]. Perfect for optical links where long term power and wavelength stability is required. A.2. Disadvantages High dispersion in high speed and long transmission system because the spectral width can span as much as 5 nm [6]. At 2.5Gbps and higher the wavelength center of FP laser goes out of wavelength tolerance. Not suitable for long distances. With the improvement in VCSELs technology, applications of 1310 nm and 1550 nm applications are moving from FP laser to VCSEL. A.3. Future directions and Applications Increase in bandwidth up to 15 GHz (the running value) by reducing low frequency roll off parasitic effects of bias circuits by injection locking [7]. FP lasers can generate single longitudinal mode laser [8]. FP lasers external optical modulator for optical access network [9]. Spectral width of FP laser allows transmission to distances of 40 Km at 1.7 Gbps.[5] FP offers Corse wavelength division multiplexing (CWDM) with channels at 1.3ÃŽÂ ¼m and 1.5ÃŽÂ ¼m simultaneously on a single fiber [5]. FP lasers offer benefits in LAN that use one wavelength per fiber [6]. FP laser can be used as multi wavelength source of Amplified Spontaneous Emission (ASE) for spectrum sliced [5]. The 1550 nm FP laser can support Synchronous Optical Network (SONET) [6]. A.4. Commercial availability of FP lasers Multiple Application Platform (MAP) FP laser [9] is FP laser source with key features like single mode or multi mode output, internal modulation, LAN extensions for instrumentation (LXI) compliant etc. This device has weight of almost of half kilo gram is capable of operating on different optical fibers such as Flexcorà ¢Ã¢â‚¬Å¾Ã‚ ¢ and SMF-28 [10] with operational temperature range of 10à ¢Ã‚ Ã‚ °C to 40à ¢Ã‚ Ã‚ °C. This product is commercially available. B. Distributed feedback (DFB) lasers In FP laser there is feedback of light from the mirrors, this light feedback can be provided in distributed manner by series of closely spaced mirrors/reflectors (means there is a periodic variation in the width of the cavity). There is a corrugated section in the cavity; the incident light passes through section causes series of reflections. If the corrugation period is the integral multiple of half wavelength (Bragg condition) the resulting transmitted wave will add in phase. This mechanism suppresses other longitudinal modes and allow only single longitudinal mode whose wavelength is equal to twice the corrugation period. [11] Figure.2. DFB laser structure [4] B.1. Advantages DFB lasers provides better wavelength stability than cleaved end face laser [12] The line width of DFB is less than that of reflective end face lasers [12]. Low chirp [13] Better wavelength selectivity. DFB laser is used in high performance system because of its narrow spectral output width [6]. B.2. Disadvantages The amplitude of the standing wave is fixed because of gratings Emitted wavelength near threshold current cant be controlled [14] Wavelength chirp is associated with the spatial burning of the carrier holes. Some values of rare facet phase give unacceptable performance. B.3.Future directions and applications of Distributed feedback (DFB) lasers All optical flip-flop is one of the building block for fast optical packet switching as it temporary stores the header information while the payload is routed to the correct output port. Single distributed feedback (DFB) laser diode based, all optical flip flop can be used to serve this purpose. Experimental results shows that DFB lasers can provide optical memory in an economical way and at the same time shows fast switching of optical packets (as low as 45 ps can be achieved). Using DFB lasers as an all optical flip flop 40 Gbps can be switched. [15] Used in DWDM system where tune ability of signals are required. Used in the sensing of extreme narrow line width of the signal. B.4. Commercial availability of Distributed Feedback laser The production of Quantum dot pure Green laser [16] is possible by using DFB laser technology. DFB laser gives high reliability for optical communication to form quantum dot crystal with a wavelength of 1064nm [16]. There is significant amount of reduction in power consumption for converting 1064nm quantum dot laser from electricity to light by the use of DFB laser. C. Multi Quantum well (MQW) lasers In Quantum well lasers the active region is very narrow which causes quantum confinement to occur. The wavelength which emits is dependent on the width of the active region rather than the band gap. This feature gives shorter wavelength than conventional lasers [17]. Figure.3. Cavity structure of MQW laser [4] C.1. Advantages Enhanced gain due to quantum well structure and gain co-efficient is usually 3 times or more than single layer FP laser [13] Produce shorter oscillation wavelength Smaller linewidth enhancement factor (ÃŽÂ ±), at larger linewidth enhancement factor the laser instability is enhanced [13]. Small optical losses Better confinement of laser actions because of multiple active regions. Low threshold current High modulation speed Low temperature dependency C.2. Disadvantages The internal structure of MQW laser is designed such that it is more susceptible to back reflections. C.3. Future directions and Applications Modulating retro reflector combines optical retro reflector and optical modulator (MQW lasers). Strained quantum well technology can become the core technology for high performance semiconductor device by expanding the flexibility of band engineering [18]. Optical repeaters, as it gives saturated output power to about 3dBm. C.4.Commercial availability of MQW lasers SANYO GaAlAs index guided laser diodes with MQW structure, these are infrared powerful lasers source [19] of maximum power up to 200mW and wavelength range of 782nm to 830nm is commercially available. SONY GaAlAs index guided laser diodes with MQW structure; these are infrared powerful lasers source [19] gives optical power range from 90mW up to 60W. This huge optical output power gives high brightness. D. External Cavity Diode Lasers (ECDL) ECDL can also be used to achieve the single longitudinal mode wavelength. ECDL is a semiconductor based laser with one end of the laser diode has anti reflective coating and laser resonator is completed with collimating mirror and external mirror. As they are tunable lasers so for wavelength selection they use diffraction gratings. End mirror contains collimating lens and diffraction grating. The anti reflective coated end of the diode gets feedback from the diffracted beam. Tuning of the emitted wavelength is done through the rotation of the diffracting grating. There is some more variation for this setup. [11, 20] Figure.4. EDCL setup Ref: www.clu-in.org D.1.Advantages Side mode suppression ratio (SMSR) is better than -40 dB and has narrow intrinsic line width Pulse repetition rate can easily be selected [21] Filter can be inserted for the fixing of emission wavelength in mode locked diode laser [21] etc. D.2. Disadvantages The direction of output beam changes by rotating the diffraction grating which not suitable for many optical communication applications. In fixed direction of the output beam, the zero order reflection of the beam bounced by the mirror is lost. D.3.Future directions and applications Tunable continuous wave THz radiation can be generated by the use of dual mode ECDL from 250 MHz to several THz [22] Without mode hopping wavelength tuning over 40 nm around 1550 nm is expected by new configuration of EDCL with all dielectric thin film Fabry Perot filters. [23] Atomic clock: ECDL is used in the optical system of the atomic clock; it is used for the cooling and the detection of clock transition. [24] Mode locked ECDL are mostly used in optical communication (DWDM) for data transmission. [21] Testing and measurement in optical fiber communication Non-linear frequency conversion. D.4. Commercial availability of ECDL TEC-100 and TEC-120 [25] External cavity diode Littrow laser system gives optical output power up to 200mW and running range (mod-hop free) up to 30GHz. DLX-100 [26] External cavity tunable diode gives output power up to 1W and mod-hop free tuning up to 15GHz. E. Vertical Cavity Surface Emitting Lasers (VCSEL) VCSEL achieves single longitudinal mode operation in different manner. The active region is placed between two highly reflective surfaces/mirrors. These two reflective surfaces have alternated high and low refractive index. The reflectivity of the surfaces is between 99.5-99.9% that is why light oscillates perpendicularly through the layers and emits from the top or the bottom of the device. [27] E.1. Advantages It has high wavelength stability It is less sensitive to temperature (can operate reliably up to 80 à ¢Ã‚ Ã‚ °C) Less refrigeration is required for VCSEL as it operation do not emit much heat. It provides high powered per unit area ( up to 1200W/cm2) It emits circular beam as a transmitter which leads to small optical loss. Figure.5. VCSEL structure [4] E.2. Disadvantages Because of high mirror reflectivity in the VCSEL internal structure lowers the optical output power. They emit low output power (in mW) because of their small active medium volume. InP based VCSEL suffers from having low conduction band offset, low conduction band offset means low confinements of electron which results improper temperature stability of active material gain. To produce longer wavelength in VCSEL, mechanism of double fusion is used. This mechanism increases the cost as it is complicated procedure [28]. E.2. Future directions and applications of Vertical External Cavity Surface-Emitting Laser (VECSEL) [20, 32] There is an issue of optical power supply for Si-photonics transceiver which are being developed for high density optical interconnect on parallel processors can ideally solved by VECSEL as the emits in 1330 nm and 1550 nm. [29] High speed modulation up to 25 Gb/sec can be achieved by using VCSEL at low current of 7.4 KA/cm2. [30] Fast modulation frequency (in GHz) made its use in optical fiber communication as transmitter Ideal for local and metro area networks as they produce low output power. Threshold less laser [31] etcà ¢Ã¢â€š ¬Ã‚ ¦ E.3. Commercial availability of (VCSEL) VCSEL technology has flourished and gives wide range of products with ultra low noise, narrow line width, high optical output power (up to 1kW) and high speed modulation (speed >5GHz) [27]. For high optical output power up to 1KW, a module for cooling of this system is used and fiber is pigtailed for high brightness VCSEL array. VCSELs are commercially available in blue, green and UV lasers [27]. iii. Comparison of semiconductor lasers In this section DFB, ECDL, MQW and VCSEL are compared with respect to different parameters and their suitability as optical transmitter in different optical networks. Parameters Tuning agent Output power ( in dBm) Tuning speed Modulation speed Lasers DFB Temperature 13 Slow (m-sec) Fast (multi-GHz) MQW Quantum confined stark effect ~7 Fast( Fast(multi-GHz) VCSEL MEMs Optically pumped 6 Electrically pumped -3 Fast(ÃŽÂ ¼-sec) Fast ( few GHz) ECDL Peizo transducer ~13 Slow(m-sec) Slow ( Table.1: Comparison of semiconductor lasers Table.1 shows relative analysis of semiconductor lasers. Each semiconductor laser has got competitive advantage with respect to different parameter. Table.2 gives a comprehensive view of the semiconductor lasers and their application in a specific network type as an optical transmitter. Semiconductor Laser Network type FP laser Short to medium range (Local Metro) Networks DFB Laser Long haul network MWQ Laser Short to medium range (Local Metro) Networks ECDL Long haul network VCSEL Short to medium range (Local Metro) Networks Table.2: Semiconductor lasers with their network type support Lasers Max spectral output width FP 5 nm VCSEL 0.5 nm DFB 0.1 nm Table.3: Spectral width comparison of short range lasers Spectral output width measure the range of the wavelengths produce by a laser. From table.3 it is evident that DFB laser has the narrowest spectral output width, which makes DFB laser the best choice for high performance short range optical transmission systems. iv. Conclusion This paper gives a review on the semiconductor lasers, their working, applications, commercial availability and future directions. Relative analysis of these lasers shows that they have competitive advantage in one or other laser parameters and this analysis also shows that which semiconductor laser is appropriate to which type of optical network. Semiconductor lasers have wide applications in optical fiber communication. Lots of exciting research is going on in this field and there is still room of improvements.

Gambling and the Brain Essay -- Biology Essays Research Papers

Gambling and the Brain Why do gamblers bet more after they just lost a hand? Why do investors throw good money after bad? Why do people believe that a string of losses makes a win more likely? Why do so many people say that they will win their money back in the next hand? Is part of the appeal of gambling its unpredictability? Or do we just look at it as a way to "get rich quick"? The answer to these questions may lie in the science of the brain. Some studies indicate that gamblers bet more after a loss because they are induced to fix an error. Their brains are telling them they've made a mistake and that they need to correct it (1). These studies could possibly explain other risky acts. If you ask many people why gamble, their response is "it is like a drug" (5). Compulsive gambling is a behavior which may rely on brain circuits that evolved to help animals assess rewards important to their survival. Researchers have found that those same circuits are used by the human brain to assess social rewards. They found that the brain systems that detect and evaluate such rewards generally operate outside of conscious awareness. The study said that much of what happens in the brain goes outside of conscious awareness. There are automatic brain circuits which affect activities such as gambling (2). However, this challenges prior notions which say that people make conscious choices about their everyday decision making. If people can get themselves to work unconsciously, how does the brain really know what it must pay conscious attention to? Also, how did evolution create a brain which makes such distinctions? Experiments performed on animals and humans are showing that the brain has evolved to shape itself according to what it e... ...times.com/ 3)Gambling has drug-like effect on brain,USA Today Newspaper article http://www.usatoday.com/news/health/2001-05-24-gambling.htm 4)Gambling—Like Food and Drugs—Produces Feelings of Reward in the Brain , Scientific American http://www.sciam.com/missing.cfm 5)You Bet Gambling Is Addictive , Business Week Online http://www.businessweek.com/bwdaily/dnflash/may2001/nf20010531_176.htm 6)The Good, the Bad, and the Anterior Cingulate, Science Journal, Science Magazine http://www.sciencemag.org/cgi/content/full/295/5563/2193a?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Gambling&searchid=1017881463081_295&stored_search=&FIRSTINDEX=0&fdate=3/1/2002&tdate=3/31/2002 7)The Medial Frontal Cortex and the Rapid Processing of Monetary Gains and Losses, Science Journal, Science Magazine http://www.sciencemag.org/cgi/content/full/295/5563/2279