Microeconomics Math Problem Example | Topics and Well Written Essays - 500 words

Microeconomics - Math Problem Example For example, if the company decides not to fly, it will still incur the fixed costs as they are not related to the output. It will only save the variable costs. In this situation there's no revenue as firm's planes are lying idle. In this situation the firm will still have to pay its insurance and incur depreciation incurring a loss of $4000. However, if it flies between the two cities it makes a loss of only $2000. Hence, it is better for the company to fly between the two cities. However, if it keeps on making losses and they extend to the long-run, then it is better for the firm to shut-off its operations and invest its capital in an industry, where it could make a normal profit. b) At the product price of $28, the production will fall to 5 units. At his point the firm will be making a loss of = 140 - 175 = ($35). Despite the loss, the firm will continue to produce as it covering its variable costs. c) At the product price of $22, there will be no production at all. Looking at the data, the firm will try to equate its price with MR and the resulting output according to this should be 2 units. However, the revenue gained from this will be only $44, whereas the average costs will be $75, as a result the firm will not produce at all as its revenue is less than average costs and it will only increase the loss if the firm decides to go with the production. S

The Case for Animal Rights by Tom Reagan Essay Example | Topics and Well Written Essays - 750 words

The Case for Animal Rights by Tom Reagan - Essay Example Animal rights violators have argued that not all living things have equal rights and that humans are superior to the others. They state that human beings have the rights while the other living things, especially animals, have rights only in the right view of the human being responsible. Reagan accounts for the need to have animal rights on the following arguments and sets of theories. First, the violators base their argument on the contractions theory, where the human beings are said to have signed a voluntary contract to ensure rights on themselves and close persons. The rights also cover what the human beings have sentimental value, and what interests them in the society only. Reagan argues that this does not adequately cover the rights of animals in the society from the actions of human beings. He states that in case the animal in question does not have any relevance or value to the human being, then he/she is not morally obligated to uphold or enforce the rights of the animal (Re agan, 1989). The second argument is considered as the cruelty-kindness theory that states that every human being has the duty to be kind to all the animals in the world, whether they have sentimental value or not; we also have an indirect duty not to be cruel to the animals in the world whatsoever. ...The same theory also argues for the statement ‘the end justifies the means’; moreover, Reagan uses the rights view to contradict these statements by egalitarians, by stating that the end does not justify the means, in the upholding animal rights. Reagan’s criticism is valid in light of clearly rational arguments and analysis on some other theories on animal rights. He seeks to bring balance between the animal’s rights and human rights in the world. The sense of belief that animals have no feelings and humans have no moral obligations towards them is clearly misplaced. There needs to be a balance between actions to animals and the results, in that animals are living things too and have emotions and rights that we need to uphold in society, if we are to be rational.

A Piece of Peace Essay Example for Free

A Piece of Peace Essay The terrorist attacks on September 11th affected more than just the lives of those in people who were the direct victims of the attacks. An entire nation was victimized and the whole nation grieved for those who suffered in New York City. As the attacks occurred I sat in my high school English class and while the teacher taught I day dreamed. It was a typical Tuesday morning and to be truthful I did not ever hear her the first time she explained the tragic events that had taken place just moments ago. I heard the word â€Å"terrorists† and the fragments of statements like â€Å"hundreds died this morning when†. Then, I could only hear my heart beat in my ears. I watched my teacher turn on the TV. She flipped through several stations. I dont remember what I saw but I can remember what I heard. It was the sound of people crying. Over the next few months, as a nation, we followed the story as did the world. I can remember President Bush attempting to comfort the United States and telling us America would be going to war for reasons that werent clear to me then and certainly arent clear to me now. Somewhere between the night of September 10th, when I was plotting how I was going to avoid school the next morning and the night of September 11th, I grew up. When I look back on that time in my life I am left with a single haunting thought It is the pursuit of peace which leads to destruction. Even today, years after the terrorist attacks, people still talk about how that day changed everything. I agree, in some ways. It changed me and I became something new. It changed my family. It changed how American view other Americans and how we view the rest of the world. Americans have since the birth of the nation believed that their way was the best way. Americans were shocked to find out that people hated them enough to want to kill them. September 11th forced Americas to reflect on the military, social, and political actions of America and how they effected people of other countries. Perhaps Americans are not always in the right. For example, President Bush I gave weapons to the Afghan people to win a war against Russia. When the Afghan people defeated the Russian, Afghanistan was completely destroy. American promised them they will help rebuild but they did not. That is why the terrorist were able to come into the country and making a terrorist breeding ground. I dont think that September 11th effects the way Americans conduct their lives daily. People who say it does are feeling the pressure of guilt. Society says we must not forget, and as Americans say we wont. As a nation the citizens learned that there is a fine line between terrorist and freedom fighter- we are just afraid to admit it and seem unamerican. Those men who ran planes into building, killed Americans and killed themselves wanted only one thing peace. They wanted freedom from the western world and choose to die. Just as we wanted independence from England centuries ago. In looking for peace they destroyed lives, families, and shook the protected ground the United States sat on. It made the country stronger but not smarter. I am anxious over the global discord and the cultural ignorance that seems to grow between the United States and the rest of the world. The problems in Iraq foretell and may spark future clashes with a number of civilizations in the future. Just recently I drove home from work and I flipped through different radio stations. I caught the end of Bob Dylans â€Å"The Times They Are A-Changing†. Its funny because that is my moms favorite song and I had forgotten it existed. I still can hear her sing, â€Å"Come gather round people Wherever you roam / And admit that the waters Around you have grown /For the times they are a-changin†, while she tinkered around in the kitchen way before anyone else got up. I dont know that I ever really listened to the words before. Dylan knew and my mom knew things I was just beginning to. Dylan and my mom knew â€Å"theres a battle outside And it is ragin† and September 11th did shake our â€Å"windows† and rattled our â€Å"walls†. As a nation its citizens have no right to â€Å"criticize What we [you] cant understand† and our â€Å" sons and [y]our daughters Are beyond our [your] command† (Dylan). Our soldiers fight a war for reasons no one really knows for America that would rather criticize them then help in country that does not seem to want peace. Dylan sings about the injustice in war and that we should not be afraid to speak our minds: Come writers and critics Who prophesize with your pen And keep your eyes wide The chance wont come again And dont speak too soon For the wheels still in spin And theres no tellin who That its namin. For the loser now Will be later to win For the times they are a-changin. (Dylan) Bush wants peace but for his own reasons and through those reasons American soldiers are dying, and so are the Iraqi people. It is ironic that while those terrorists die nobly but ur soldiers die in such a cruel way. McKay writes in his poem, â€Å"If We Must Die,† that people should not die for nothing or by doing nothing. That death is inevitable, especially in war, but all people must fight for the things we want in this world and hold on to life and liberty as long as we can: O kinsmen we must meet the common foe! Though far outnumbered let us show us brave, And for their thousand blows deal one deathblow! What though before us lies the open grave? Like men well face the murderous, cowardly pack, Pressed to the wall, dying, but fighting back! (Claude McKay) In the summer of 2001 I was lying in my hammock and I could see a butterfly in my backyard. I remember as a child learning that caterpillars itch and go into cocoons to find peace from that. Change in a way is a form of destruction. To be able to be someone new people have to give up their old selves and move past who they used to bee. When a child develops into an adult, he must give up his toys, his childhood beliefs like believing in Santa Claus. His childhood fantasies must be destroyed if he is to move on. In the years that followed September 11th I could feel myself â€Å"adapt to my new surroundings† (White Line 2). White, through the use of nature explores the scary nature of change: I have to shed my skin again Adapt to my new surroundings become another version of myself. The change within me does not happen overnight but through the evolution of my life (White) I was filled with Americans sense of patriotism and unity. The new American was like â€Å"the first fish that grew tiny legs† (White Line 8). Christine Whites poem, â€Å"Molting† reminded me that it was not just me that grew up, the United States did too. Whites point of view is that change is not a bad thing and is inevitable. Nearly every person around the country joined together as one united entity to pay tribute and homage to all the fallen heroes. There was a sense of harmony and peace. In way I think America, even those the terrorist attacks were tragic, knew that such an event was needed if we were going to â€Å"shed our [my] skin† (White Line 1) and become a stronger nation. As time goes by and my bad memories fade I remember America in its full glory. Watching the cumulative effect of humanity shining through the fire and smoke. I remember how many people spoke about the importance of peace and understanding. I wonder if there can be peace if Americans are divide both support and protest our soldiers in Iraq. The war over there caused a war here between Americans. It is the protesters protest protesters on both sides of the issues – each wanting peace in their own way. People who do not want our soldiers fighting in Iraq believe that they would be peace if America stopped butting into everyones business. People who are for the war in Iraq believe peace will only come after the destruction of all terrorists. In the end these protesters (on both sides) are destroying the morale and lives of people fighting in the Iraq war and are disgracing the memories of those that died. The price of peace is extremely high especially because Americans do not know if we can ever have it. I do know that â€Å"The line it is drawn The curse it is cast / The slow one now Will later be fast / As the present now Will later be past† (Dylan). I do know that America must hold her ground against the terrorists. Americans will not be tyrannized and forced to live like cowards. Even when we face â€Å"the murderous, cowardly pack, Pressed to the wall, dying, but fighting back! † (McKay Line 14). The American fight for freedom and peace has also managed to destroy our economy. Oil prices increased, the value of the American dollar decreased, and the stock market bottomed out. When Clinton was President the stock market was well over 10,000 after 9/11 it drop well under 8000. President Bush spent the Clinton Surplus on military, and it is just now in 2006 that the stock has become stabilized. I think that our economy will emerge from this disaster and become strong once again like it was before the attacks. In the pursuit of peace and destruction, people in Americans have finally understood their place in society and were back â€Å"in the sun† (White Line 10). Not as a not as a bystanders but an active and willing participants. Americans realize that there needs to be a great deal of change and those changes have started. American citizens encourage our â€Å"senators, congressmen Please heed the call / Dont stand in the doorway Dont block up the hall† (Dylan). And governmental officials are making changes. I think our nation needs to help a new generation of people realize that aftermath of that day when humans lives were lost and Americas unique humanity and independence was demonstrated. This generations hearts were opened and turned around in the wake of airplane crashes. On September 11, 2001 many people lost their lives because men were seeking their own personal peace. Daily our soldiers are destroyed one by one for the goal of peace. The American economy struggles because of the war for peace against terrorism. Americans fight Americans over whether we should be in Iraq or not which tears apart soldiers pride. Before that Tuesday in September, I never thought about life and death. I never considered the consequences of war and the denial of freedoms. Now that I am older, I realize that September 11, 2001 was not just pivotal point for me but America itself. Not since Pearl Harbor had the United States been unexpectedly attacked on its own land. Just as families pulled together so did the United States as a whole. As a nation we cried together and we healed together. To actually witness the attacks was life changing but to be part of the healing process was life affirming.

Effect of Homeopathic Treatment on Insomnia

Effect of Homeopathic Treatment on Insomnia CHAPTER ONE INTRODUCTION Introduction Insomnia is a major health concern particularly when individuals develop dependency and problematic withdrawal symptoms related to conventional prescription drugs. Approximately 27% of the adult male population and 31% of the adult female population in South Africa suffer from insomnia (Strangers et al., 2012). Insomnia disorder is characterized by one or more of the following: difficulty falling asleep, difficulty maintaining sleep, early morning waking, and non-refreshing sleep (South African Association of Sleep Medicine, n.d.). Current conventional treatment for insomnia includes psychological and drug therapies. Conventional medication for insomnia is limited and has its drawbacks (Moch, 2011). While continued research and development is ongoing to broaden the clinical evidence on the use of homeopathic remedies in the treatment of insomnia to further establish its benefits, current information suggests that the effect of individualised homeopathic treatment has not been researc hed to date in females with insomnia disorder. Aim of the Study The aim of this study was to determine the effect of individualised homeopathic treatment on insomnia disorder in females using detailed case studies and the Insomnia Severity Index. Null Hypothesis It is anticipated that the individualised homeopathic remedy will not be effective in the treatment of insomnia disorder in females. Hypothesis It is anticipated that the individualised homeopathic remedy will be effective in the treatment of insomnia disorder in females. Importance of the Problem CHAPTER TWO LITERATURE REVIEW 2.1 Sleep Sleep can be defined as a state of reversible unconsciousness in which the brain becomes less responsive to external stimuli (Schupp Hanning, 2003). Although the amount of sleep a person needs varies, most individuals need an average of six to eight hours of sleep a night in order to feel refreshed (Attele et al., 2000). Numerous physiological processes are regulated during sleep and therefore it is a universal need that is essential for well-being (Moch, 2011). 2.2 The Physiology of Sleep Normal sleep is divided into two distinctive states: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep, which can be differentiated by an electroencephalogram (EEG) (Schupp Hanning, 2003). Normal sleep begins with NREM sleep and progresses through deeper NREM stages, before the first episode of REM sleep occurs about 80 to 100 minutes later. Thereafter, a sleep cycle, which is the alternation of periods of NREM and REM sleep, lasts approximately 90 minutes and recurs 3 to 7 times per night. NREM sleep is more prominent and deeper than REM sleep during the first half of the night; NREM constitutes the main sleep activity. NREM sleep is shallow during the second half of the night, and the proportion of REM sleep gradually increases during each subsequent sleep cycle (Carlstedt, 2010). Figure 2.1 shows EEG graphs of these sleep stages. 2.2.1 NREM Sleep NREM sleep appears as wakefulness-maintaining mechanisms decline. NREM sleep is divided into 4 stages (Lee-Chiong, 2006): Stage 1: an individual first enters stage 1. The EEG is difficult to distinguish from the waking EEG of a drowsy person, theta wave activity occurs, and heart rate and muscle tension begin to decrease. During this early stage of sleep an occasional muscle jerk, usually of an arm or leg, referred to as myoclonus may be experienced. This experience is often accompanied by a brief visual image, such as tripping or falling (Freberg, 2009). Stage 2: after 10 to 15 minutes in stage 1, the individual enters stage 2 NREM sleep. The EEG shows sleep spindles and K-complexes, which reflect the brain’s effort to maintain sleep while monitoring the external environment. Heart rate and muscle tension further reduce. During this stage the individual is able to sleep through familiar stimuli, but wakes in response to unfamiliar stimuli (Freberg, 2009). Stage 3 and 4: after approximately 15 minutes in stage 2, the individual enters stage 3 and stage 4 NREM sleep, also referred to as slow-wave sleep. In both stages, the EEG shows delta wave activity, however, stage 3 differs from stage 4 in the sense that a greater proportion of stage 4 consists of delta waves. During these stages heart rate, blood pressure and core temperature are at their lowest levels. Awakening the individual during these stages is difficult and disorientating (Freberg, 2009). 2.2.2 REM Sleep REM sleep is also referred to as paradoxical sleep because while the EEG resembles the waking EEG, it is accompanied by reduced skeletal muscle tone of stage 3 and stage 4 NREM sleep, except in the eye where rapid eye movements (saccadic eye movements) occur. These saccadic eye movements are small, fast, jerky movements, which bring the eye from one visual fixation point to another and may be associated with watching the visual images of dreams (Sanoop et al., 2012). Despite the apparently alert EEG it is more difficult to awaken an individual from REM sleep than it is to awaken them from slow-wave sleep. In addition, there is an increase in blood pressure, heart rate and respiratory rate, as well as increased blood flow to the genitals. Control of core temperature is poor during this state of sleep (Wagner Silber, 2004). During REM sleep the EEG becomes desynchronised and low voltage fast activity is seen, PGO (ponto-geniculo-occipital) spikes also appear, which is characteristic o f REM sleep (Sanoop et al., 2012). SLEEP STAGES ON AN EEG Figure 2.1 Different Stages of Sleep as seen on an EEG (Source: J. A. Horne. (1998). Why We Sleep: The Functions of Sleep in Humans and Other Animals. Oxford Uni. Press, England) 2.3 The Function of Sleep There are 3 theories accredited to the function of sleep: Energy conservation theory: according to this theory, energy expenditure that has occurred during waking hours recovers during sleep (OrthoApnea, 2012). Two mechanisms explain how sleep is able to conserve energy. First, sleep reduces energy expenditure by indirectly reducing activity; this mechanism is also active when individuals are awake, but inactive. Secondly, sleep reduces energy expenditure below that achieved by quiet wakefulness by causing a change in physiology (Kryger et al., 2011). Findings that endothermic mammals, including humans, reduce their core temperature and metabolic rate during sleep to support the waking demands support this theory (Kothare Kotagal, 2011). Restorative theory: this theory suggests that the function of sleep is to restore physiological and biochemical processes that have been depleted during waking hours. Indirect evidence supports this presumption: There is an increased release of growth hormone by the pituitary gland following sleep onset Endogenous anabolic steroids are released during specific stages of sleep There is an increased rate of bone growth, as well as increased mitosis of lymphocytes during sleep During sleep, genes involved in brain protein synthesis, myelin formation, synaptic vesicle turnover, lipid metabolism, and membrane maintenance are unregulated (Kothare Kotagal, 2011). Learning and memory theory: this theory proposes that sleep is necessary for brain plasticity, which is essential in the processes of learning and memory. Several studies have shown that sleep improves learning and memory without task repetition, which suggests that information processing and long-term memory consolidation are enhanced during sleep (Kothare Kotagal, 2011). 2.4 Insomnia 2.4.1 Definition and Description of Insomnia Insomnia is defined as the inability to obtain an adequate duration or quality of sleep (National Sleep Foundation, n.d.). It is characterized by one or more of the following: difficulty falling asleep, difficulty maintaining sleep, early morning waking, and non-refreshing sleep (South African Association of Sleep Medicine, n.d.). Insomnia occurs despite an adequate time and opportunity for sleep and results in impairment in daytime functioning (World Health Organisation, 2009). 2.4.2 Incidence, Epidemiology and Demographics of Insomnia Insomnia is the most common sleep disorder and the second most common overall complaint reported in primary healthcare settings (Attarian, 2004), with approximately 30% of the general adult population in South Africa occasionally suffering from insomnia. Insomnia is present in around 50% of individuals treated in a clinical setting and about 10% of these individuals suffer from persistent insomnia. Although insomnia affects individuals of almost every demographic, complaints of insomnia increase with age, and women are more affected than men (Truter, 2008). 2.4.3 Insomnia in Females Epidemiological studies comparing the prevalence of insomnia between the genders all report a higher prevalence amongst females. Studies have shown that there is an increased prevalence of insomnia amongst younger females, even in adolescent girls, compared to their age-matched male counterparts. One of the most common perimenopausal symptoms in women aged between 35 and 55 is insomnia (Grewal Doghramji, 2010). Biological differences in sex hormones may contribute to the gender difference in insomnia. For some women, insomnia may arise secondary to menstrual symptoms e.g. headaches, bloating, cramping and breast tenderness. Sleep disturbances during menstrual periods are associated with alterations in progesterone, prolactin and melatonin levels. Melatonin modulation by sex hormones may cause dysregulation of sleep-wake mechanisms (Soares, 2005). Insomnia occurs in approximately half of all menopausal women and may be directly associated with the presence of hot flushes. Nocturnal hot flushes may cause repeated awakenings throughout the night. Menopausal women experiencing hot flushes report more frequent awakenings, inefficient sleep, and poor quality sleep, compared with those who do not experience hot flushes. Temperature-regulating and sleep-regulating centers in the brain may be disturbed by changes in hypothalamic-pituitary-ovarian hormone levels that occur during menopause, resulting in hot flushes and insomnia (Soares, 2005). In addition, increased levels of psychological distress have also been postulated as potential contributors to insomnia in women; including social changes, stress associated with the â€Å"empty nest† syndrome, nursing aging parents or family members, separation from life partners due to divorce or death (Soares, 2005). 2.4.4 Classification of Insomnia Insomnia may be situational (acute), persistent, or recurrent. Situational insomnia lasts for a few days up to a few weeks and is usually caused by life events or rapid changes in environment or sleep schedules. Once the precipitating event subsides, the insomnia usually resolves. In some individuals, insomnia may persist for a long period of time after the initiating event, possibly due to conditioning and heightened arousal; conditioned arousal may then persist and lead to persistent insomnia. However, in some individuals, insomnia may have an insidious onset where no identifiable cause can be found. Insomnia may also be episodic, with recurrent episodes of sleep difficulties occurring during stressful events (American Psychiatric Association, 2013). According to the DSM-V (Diagnostic and Statistical Manual of Mental Disorders, fifth edition), insomnia disorder is classified as: A predominant complaint of dissatisfaction with sleep quantity or quality, associated with one (or more) of the following symptoms: difficulty initiating sleep; difficulty maintaining sleep, characterized by frequent awakenings or problems returning to sleep after awakenings; and/or early-morning awakening with inability to return to sleep The sleep disturbance causes clinically significant distress or impairment in social, occupational, educational, academic, behavioural, or other important areas of functioning. The sleep difficulty occurs at least 3 nights per week. The sleep difficulty is present for at least 3 months. The sleep difficulty occurs despite adequate opportunity for sleep. The insomnia is not better explained by and does not occur exclusively during the course of another sleep-wake disorder (e.g., narcolepsy, a breathing-related sleep disorder, a circadian rhythm sleep-wake disorder, a parasomnia). The insomnia is not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication). Coexisting mental disorders and medical conditions do not adequately explain the predominant complaint of insomnia (American Psychiatric Association, 2013). 2.4.5 Signs and Symptoms of Insomnia Symptoms and signs of insomnia include lying awake for extended periods of time before being able to fall asleep, waking up several times during the night (sleeping for short periods of time), waking up early in the morning with an inability to fall back to sleep and/or waking up in the morning feeling unrefreshed or tired (NIH, 2011). 2.4.6 Predisposing, Precipitating and Perpetuating Factors of Insomnia Factors that predispose an individual to insomnia include: genetics, personality traits, psychologic arousal (eg. anxiety, agitation, and heightened vigilance), and time of day sleep-wake preference (Lee-Chiong, 2008). One theory is that physiological hyperarousal may be a predisposing factor for insomnia; research has shown that individuals with insomnia disorder have an increased metabolic rate, increased secretion of ACTH, increased beta activity in the EEG, a more rapid increase in heart rate in response to stress, and increased daytime alertness despite having a shorter sleeping period. Another predisposing factor for insomnia may be a decreased homeostatic drive for sleep; research has shown that patients with insomnia disorder do not have the same increase in slow-wave sleep following sleep deprivation that is seen in those without insomnia. A decreased sleep drive would make it more difficult to initiate and maintain sleep under baseline as well as sleep-deprived conditions ( Lee-Chiong, 2006). Insomnia is a symptom with numerous and diverse aetiologies, and in a large percentage of the population more than one cause may be present; these include: stressful life events such as conflicts in the workplace, marital distress, or final examinations; a change of usual habits; sudden changes in sleep-wake schedules caused by jet lag or changes in work shifts; environmental disturbances such as excessive noise or light in the bedroom; medication use or medication withdrawal; substance abuse; and chronic medical or psychiatric conditions. Examples of chronic medical conditions include: any condition associated with pain, respiratory or cardiac diseases associated with paroxysmal nocturnal dyspnoea, renal failure, hyperthyroidism, and neurodegenerative diseases (Lee-Chiong, 2006). Perpetuating factors are cognitive and behavioural changes that occur after an individual has had insomnia for a period of time. Cognitive changes that occur include preoccupation with sleep during the day, as well as a fear of not being able to sleep and fear of daytime impairment. This leads to tension at bedtime, and upon waking up during the night. Behavioural changes include keeping irregular sleep-wake schedules, taking naps during the day, staying in bed in an attempt to gain more sleep, and engaging in stimulating activities during the night. Individuals often make these changes in response to their insomnia, in an attempt to get more sleep; however, while these changes may relieve insomnia in the short-term, they promote insomnia in the long-term (Lee-Chiong, 2006). 2.4.7 Consequences of Insomnia Insomnia may result in feelings of fatigue and sleepiness. A number of individuals complain of mood disturbances and cognitive difficulties such as irritability, mild anxiety and depression; they may also complain of poor memory and concentration, and difficulty performing complex mental tasks. Because of the irritability and fatigue that is associated with insomnia, interpersonal difficulties may result; on the other hand, interpersonal difficulties may be the cause of insomnia. Insomnia may result in restriction of daytime activities, such as work, exercise and social events. This lack of regular daytime activity may in turn contribute to insomnia. In addition to these, insomnia may exacerbate symptomatology of co-morbid disease, and may herald the onset of mood disturbances (Schutte-Rodin et al., 2008). 2.5 Measurements used to asses Insomnia 2.5.1 The Insomnia Severity Index The Insomnia Severity Index is a 7-item questionnaire that provides a global measure of an individual’s perceived insomnia severity based on the following indicators: difficulty falling asleep, difficulty staying asleep, and early morning awakenings; satisfaction with sleep; degree of impairment with daytime functioning; degree to which impairments are noticeable; and distress or concern with insomnia. Each item is rated on a 5 point Likert scale, and the total score ranges from 0-28. The ISI has good internal consistency and test-retest reliability. It has proven to be sensitive to therapeutic changes in several treatment studies of insomnia. This instrument can be used to evaluate the initial severity of insomnia, as well as the clinical significance of improvements achieved during the treatment of insomnia (Edinger Carney, n.d.) 2.6 Treatment of Insomnia 2.6.1 Pharmacological Treatment

Light Emitting Diode | Dissertation

Light Emitting Diode | Dissertation Introduction Alight-emitting diode(LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across thevisible, ultraviolet and infrared wavelengths, with very high brightness. When a light-emitting diodeis forward biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is calledelectroluminescenceand thecolorof the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is often small in area (less than 1mm2), and integrated optical components may be used to shape its radiation pattern.LEDs present manyadvantagesover incandescent light sources includinglower energy consumption, longerlifetime, improved robustness, smaller size, faster switching, and greater durability and reliability. LEDs powerful enough for room lighting are relatively expensive and require more precise current andheat managementthan compactfluorescent lampsources of comparable output. Light-emitting diodes are used in applications as diverse as replacements foraviation lighting,automotive lighting(particularly brake lamps, turn signals and indicators) as well as intraffic signals. The compact size, the possibility of narrow bandwidth, switching speed, and extreme reliability of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are also useful in advanced communications technology.InfraredLEDs are also used in theremote controlunits of many commercial products including televisions, DVD players, and other domestic appliances. History Discoveries and early devices Green electroluminescence from a point contact on a crystal ofSiCrecreatesH. J. Rounds original experiment from 1907. Electroluminescenceas a phenomenon was discovered in 1907 by the British experimenterH. J. RoundofMarconi Labs, using a crystal ofsilicon carbideand acats-whisker detector.RussianOleg Vladimirovich Losevreported on the creation of a first LED in 1927.His research was distributed in Russian, German and British scientific journals, but no practical use was made of the discovery for several decades. Rubin Braunstein of theRadio Corporation of Americareported on infrared emission fromgallium arsenide(GaAs) and other semiconductor alloys in 1955.Braunstein observed infrared emission generated by simple diode structures usinggallium antimonide(GaSb), GaAs,indium phosphide(InP), andsilicon-germanium(SiGe) alloys at room temperature and at 77kelvin. In 1961, American experimenters Robert Biard and Gary Pittman working atTexas Instruments,found that GaAs emitted infrared radiation when electric current was applied and received the patent for the infrared LED. The first practical visible-spectrum (red) LED was developed in 1962 byNick Holonyak Jr., while working atGeneral Electric Company.Holonyak is seen as the father of the light-emitting diode.M. George Craford,a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972. In 1976, T.P. Pearsall created the first high-brightness, high efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths. Until 1968, visible and infrared LEDs were extremely costly, on the order of US $200 per unit, and so had little practical use.TheMonsanto Companywas the first organization to mass-produce visible LEDs, using gallium arsenide phosphide in 1968 to produce red LEDs suitable for indicators. Hewlett Packard(HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. The technology proved to have major uses for alphanumeric displays and was integrated into HPs early handheld calculators. In the 1970s commercially successful LED devices at fewer than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with theplanar processinvented by Dr. Jean Hoerni atFairchild Semiconductor.The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions. These methods continue to be u sed by LED producers. History Of LEDs and LED Technology Light Emitting Diode (LED) Light Emitting Diode (LED) is essentially a PN junction semiconductor diode that emits a monochromatic (single color) light when operated in a forward biased direction. The basic structure of an LED consists of the die or light emitting semiconductor material, a lead frame where the die is actually placed, and the encapsulation epoxy which surrounds and protects the die (Figure 1). The first commercially usable LEDs were developed in the 1960s by combining three primary elements: gallium, arsenic and phosphorus (GaAsP) to obtain a 655nm red light source. Although the luminous intensity was very low with brightness levels of approximately 1-10mcd @ 20mA, they still found use in a variety of applications, primarily as indicators. Following GaAsP, GaP, or gallium phosphide, red LEDs were developed. These devices were found to exhibit very high quantum efficiencies, however, they played only a minor role in the growth of new applications for LEDs. This was due to two reasons: First, the 700nm wavelength emission is in a spectral region where the sensitivity level of the human eye is very low (Figure 2) and therefore, it does not appear to be very bright even though the efficiency is high (the human eye is most responsive to yellow-green light). Second, this high efficiency is only achieved at low currents. As the current increases, the efficiency decreases. This pr oves to be a disadvantage to users such as outdoor message sign manufacturers who typically multiplex their LEDs at high currents to achieve brightness levels similar to that of DC continuous operation. As a result, GaP red LEDs are currently used in only a limited number of applications. As LED technology progressed through the 1970s, additional colors and wavelengths became available. The most common materials were GaP green and red, GaAsP orange or high efficiency red and GaAsP yellow, all of which are still used today (Table3). The trend towards more practical applications was also beginning to develop. LEDs were found in such products as calculators, digital watches and test equipment. Although the reliability of LEDs has always been superior to that of incandescent, neon etc., the failure rate of early devices was much higher than current technology now achieves. This was due in part to the actual component assembly that was primarily manual in nature. Individual operators performed such tasks as dispensing epoxy, placing the die into position, and mixing epoxy all by hand. This resulted in defects such as epoxy slop which caused VF (forward voltage) and VR (reverse voltage) leakage or even shorting of the PN junction. In addition, the growth methods and materia ls used were not as refined as they are today. High numbers of defects in the crystal, substrate and epitaxial layers resulted in reduced efficiency and shorter device lifetimes. Gallium Aluminum Arsenide It wasnt until the 1980s when a new material, GaAlAs (gallium aluminum arsenide) was developed, that a rapid growth in the use ofLEDsbegan to occur. GaAlAs technology provided superior performance over previously availableLEDs. The brightness was over 10 times greater than standardLEDsdue to increased efficiency and multi-layer, heterojunction type structures. The voltage required for operation was lower resulting in a total power savings. TheLEDscould also be easily pulsed or multiplexed. This allowed their use in variable message and outdoor signs.LEDswere also designed into such applications as bar code scanners, fiber optic data transmission systems, and medical equipment. Although this was a major breakthrough inLEDtechnology, there were still significant drawbacks to GaAlAs material. First, it was only available in a red 660nm wavelength. Second, the light output degradation of GaAlAs is greater than that of standard technology. It has long been a misconception withLEDsthat lig ht output will decrease by 50% after 100,000 hours of operation. In fact, some GaAlAsLEDsmay decrease by 50% after only 50,000 -70,000 hours of operation. This is especially true in high temperature and/or high humidity environments. Also during this time, yellow, green and orange saw only a minor improvement in brightness and efficiency which was primarily due to improvements in crystal growth and optics design. The basic structure of the material remained relatively unchanged. To overcome these difficult issues new technology was needed.LEDdesigners turned to laser diode technology for solutions. In parallel with the rapid developments inLEDtechnology, laser diode technology had also been making progress. In the late 1980s laser diodes with output in the visible spectrum began to be commercially produced for applications such as bar code readers, measurement and alignment systems and next generation storage systems.LEDdesigners looked to using similar techniques to produce high brightness and high reliabilityLEDs. This led to the development of InGaAlP (Indium Gallium Aluminum Phosphide) visibleLEDs. The use of InGaAlP as the luminescent material allowed flexibility in the design ofLEDoutput color simply by adjusting the size of the energy band gap. Thus, green, yellow, orange and redLEDsall could be produced using the same basic technology. Additionally, light output degradation of InGaAlP material is significantly improved even at elevated temperature an d humidity. Current Developments of LED Technology InGaAlPLEDstook a further leap in brightness with a new development by Toshiba, a leading manufacturer ofLEDs. Toshiba, using the MOCVD (Metal Oxide Chemical Vapor Deposition) growth process, was able to produce a device structure that reflected 90% or more of the generated light traveling from the active layer to the substrate back as useful light output (Figure 4). This allowed for an almost two-fold increase in theLEDluminance over conventional devices.LEDperformance was further improved by introducing a current blocking layer into theLEDstructure (Figure 5). This blocking layer essentially channels the current through the device to achieve better device efficiency. As a result of these developments, much of the growth forLEDsin the 1990s will be concentrated in three main areas: The first is in traffic control devices such as stop lights, pedestrian signals, barricade lights and road hazard signs. The second is in variable message signs such as the one located in Times Square New York which displays commodities, news and other information. The third concentration would be in automotive applications. The visibleLEDhas come a long way since its introduction almost 30 years ago and has yet to show any signs of slowing down. A BlueLED, which has only recently become available in production quantities, will result in an entire generation of new applications. BlueLEDsbecause of their high photon energies (>2.5eV) and relatively low eye sensitivity have always been difficult to manufacture. In addition the technology necessary to fabricate theseLEDsis very different and far less advanced than standardLEDmaterials. The blueLEDsavailable today consist of GaN (gallium nitride) and SiC (silicon carbide) construction with brightness levels in excess of 1000mcd @ 20mA for GaN devices. Since blue is one of the primary colors, (the other two being red and green), full color solid stateLEDsigns, TVs etc. will soon become commercially available. Full colorLEDsigns have already been manufactured on a small prototype basis, however, due to the high price of blueLEDs, it is still not practical on a large scale. Other applications for blueLEDsinclude medical diagnostic equipment and photolithography. LED Colors It is also possible to produce other colors using the same basic GaN technology and growth processes. For example, a high brightness green (approximately 500nm)LEDhas been developed that is currently being evaluated for use as a replacement to the green bulb in traffic lights. Other colors including purple and white are also possible. With the recent introduction of blueLEDs, it is now possible to produce white by selectively combining the proper combination of red, green and blue light. This process however, requires sophisticated software and hardware design to implement. In addition, the brightness level is low and the overall light output of each RGB die being used degrades at a different rate resulting in an eventual color unbalance. Another approach being taken to achieve white light output, is to use a phosphor layer (Yttrium Aluminum Garnet) on the surface of a blueLED. In summary,LEDshave gone from infancy to adolescence and are experiencing some of the most rapid market growth of their lifetime. By using InGaAlP material with MOCVD as the growth process, combined with efficient delivery of generated light and efficient use of injected current, some of the brightest, most efficient and most reliableLEDsare now available. This technology together with other novelLEDstructures will ensure wide application ofLEDs. New developments in the blue spectrum and on white light output will also guarantee the continued increase in applications of these economical light sources. Practical use The first commercial LEDs were commonly used as replacements forincandescentandneonindicator lamps, and inseven-segment displays,first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches (see list ofsignal uses). These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors grew widely available and also appeared in appliances and equipment. As LED materials technology grew more advanced, light output rose, while maintaining efficiency and reliability at acceptable levels. The invention and development of the high power white light LED led to use for illumination, which is fast replacing incandescent and fluorescent lighting. (see list ofillumination applications). Most LEDs were made in the ve ry common 5mm T1Â ¾ and 3mm T1 packages, but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability,so more complex packages have been adapted for efficient heat dissipation. Packages for state-of-the-arthigh power LEDsbear little resemblance to early LEDs. Continuing development The first high-brightness blue LED was demonstrated byShuji NakamuraofNichia Corporationand was based onInGaNborrowing on critical developments inGaNnucleation on sapphire substrates and the demonstration of p-type doping of GaN which were developed byIsamu Akasakiand H. Amano inNagoya. In 1995,Alberto Barbieriat theCardiff UniversityLaboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and demonstrated a very impressive result by using a transparent contact made ofindium tin oxide(ITO) on (AlGaInP/GaAs) LED. The existence of blue LEDs and high efficiency LEDs quickly led to the development of the firstwhite LED, which employed aY3Al5O12:Ce, or YAG, phosphor coating to mix yellow (down-converted) light with blue to produce light that appears white. Nakamura was awarded the 2006Millennium Technology Prizefor his invention. The development of LED technology has caused their efficiency and light output torise exponentially, with a doubling occurring about every 36 months since the 1960s, in a way similar toMoores law. The advances are generally attributed to the parallel development of other semiconductor technologies and advances in optics and material science. This trend is normally calledHaitzs Lawafter Dr. Roland Haitz. In February 2008, 300lumensof visible light per wattluminous efficacy(not per electrical watt) and warm-light emission was achieved by usingnanocrystals. In 2009, a process for growing gallium nitride (GaN) LEDs on silicon has been reported.Epitaxycosts could be reduced by up to 90% using six-inch silicon wafers instead of two-inch sapphire wafers. Illustration of Haitzs Law. Light output per LED as a function of production year, note the logarithmic scale on the vertical axis Technology Physics The LED consists of a chip of semiconducting materialdopedwith impurities to create ap-n junction. As in other diodes, current flows easily from the p-side, oranode, to the n-side, orcathode, but not in the reverse direction. Charge-carriers—electronsandholes—flow into the junction fromelectrodeswith different voltages. When an electron meets a hole, it falls into a lowerenergy level, and releasesenergyin the form of a photon. Thewavelengthof the light emitted, and thus its color depends on theband gapenergy of the materials forming thep-n junction. Insiliconor germaniumdiodes, the electrons and holes recombine by anon-radiative transitionwhich produces no optical emission, because these are indirect band gapmaterials. The materials used for the LED have adirect band gapwith energies corresponding to near-infrared, visible or near-ultraviolet light. LED development began with infrared and red devices made withgallium arsenide. Advances inmaterials sciencehave enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors. LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also usesapphiresubstrate. Most materials used for LED production have very highrefractive indices. This means that much light will be reflected back into the material at the material/air surface interface. Thus,light extraction in LEDsis an important aspect of LED production, subject to much research and development. The inner workings of an LED I-V diagram for adiode. An LED will begin to emit light when the on-voltageis exceeded. Typical on voltages are 2-3volts. Refractive Index Idealized example of light emission cones in a semiconductor, for a single point-source emission zone. The left illustration is for a fully translucent wafer, while the right illustration shows the half-cones formed when the bottom layer is fully opaque. The light is actually emitted equally in all directions from the point-source, so the areas between the cones shows the large amount of trapped light energy that is wasted as heat. The light emission cones of a real LED wafer are far more complex than a single point-source light emission. Typically the light emission zone is a 2D plane between the wafers. Across this 2D plane, there is effectively a separate set of emission cones for every atom. Drawing the billions of overlapping cones is impossible, so this is a simplified diagram showing the extents of all the emission cones combined. The larger side cones are clipped to show the interior features and reduce image complexity; they would extend to the opposite edges of the 2D emission plane. Bare uncoated semiconductors such assiliconexhibit a very highrefractive indexrelative to open air, which prevents passage of photons at sharp angles relative to the air-contacting surface of the semiconductor. This property affects both the light-emission efficiency of LEDs as well as the light-absorption efficiency ofphotovoltaic cells. The refractive index of silicon is 4.24, while air is 1.00002926. Generally a flat-surfaced uncoated LED semiconductor chip will only emit light perpendicular to the semiconductors surface, and a few degrees to the side, in a cone shape referred to as thelight cone,cone of light,or theescape cone.The maximumangle of incidenceis referred to as thecritical angle. When this angle is exceeded photons no longer penetrate the semiconductor, but are instead reflected both internally inside the semiconductor crystal, and externally off the surface of the crystal as if it were amirror. Internal reflectionscan escape through other crystalline faces, if the incidence angle is low enough and the crystal is sufficiently transparent to not re-absorb the photon emission. But for a simple square LED with 90-degree angled surfaces on all sides, the faces all act as equal angle mirrors. In this case the light cannot escape and is lost as waste heat in the crystal. A convoluted chip surface with angledfacetssimilar to a jewel orfresnel lenscan increase light output by allowing light to be emitted perpendicular to the chip surface while far to the sides of the photon emission point. The ideal shape of a semiconductor with maximum light output would be amicrospherewith the photon emission occurring at the exact center, with electrodes penetrating to the center to contact at the emission point. All light rays emanating from the center would be perpendicular to the entire surface of the sphere, resulting in no internal reflections. A hemispherical semiconductor would also work, with the flat back-surface serving as a mirror to back-scattered photons. Transition coatings Many LED semiconductor chips arepottedin clear or colored molded plastic shells. The plastic shell has three purposes: 1. Mounting the semiconductor chip in devices is easier to accomplish. 2. The tiny fragile electrical wiring is physically supported and protected from damage 3. The plastic acts as a refractive intermediary between the relatively high-index semiconductor and low-index open air. The third feature helps to boost the light emission from the semiconductor by acting as a diffusing lens, allowing light to be emitted at a much higher angle of incidence from the light cone, than the bare chip is able to emit alone. Efficiency and operational parameters Typical indicator LEDs are designed to operate with no more than 30-60mWof electrical power. Around 1999,Philips Lumiledsintroduced power LEDs capable of continuous use at oneW. These LEDs used much larger semiconductor die sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow for heat removal from the LED die. One of the key advantages of LED-based lighting is its high efficacy,[dubious-discuss]as measured by its light output per unit power input. White LEDs quickly matched and overtook the efficacy of standard incandescent lighting systems. In 2002, Lumileds made five-watt LEDs available with aluminous efficacyof 18-22 lumens per watt (lm/W). For comparison, a conventional 60-100 Wincandescent light bulbemits around 15 lm/W, and standardfluorescent lightsemit up to 100 lm/W. A recurring problem is that efficacy falls sharply with rising current. This effect is known asdroopand effectively limits the light output of a given LED, raising heating more than light output for higher current. In September 2003, a new type of blue LED was demonstrated by the companyCree Inc.to provide 24mW at 20milliamperes(mA). This produced a commercially packaged white light giving 65 lm/W at 20 mA, becoming the brightest white LED commercially available at the time, and more than four times as efficient as standard incandescents. In 2006, they demonstrated a prototype with a record white LED luminous efficacy of 131 lm/W at 20 mA. Also,Seoul Semiconductorplans for 135 lm/W by 2007 and 145 lm/W by 2008,which would be nearing an order of magnitude improvement over standard incandescents and better than even standard fluorescents.Nichia Corporationhas developed a white LED with luminous efficacy of 150 lm/W at a forward current of 20 mA. Practical general lighting needs high-power LEDs, of one watt or more. Typical operating currents for such devices begin at 350 mA. Note that these efficiencies are for the LED chip only, held at low temperature in a lab. Lighting works at higher temperature and with drive circuit losses, so efficiencies are much lower.United States Department of Energy(DOE) testing of commercial LED lamps designed to replace incandescent lamps orCFLsshowed that average efficacy was still about 46 lm/W in 2009 (tested performance ranged from 17lm/W to 79lm/W). Cree issued a press release on February 3, 2010 about a laboratory prototype LED achieving 208 lumens per watt at room temperature. The correlatedcolor temperaturewas reported to be 4579K. Lifetime and failure Main article:List of LED failure modes Solid state devices such as LEDs are subject to very limitedwear and tearif operated at low currents and at low temperatures. Many of the LEDs made in the 1970s and 1980s are still in service today. Typical lifetimes quoted are 25,000 to 100,000 hours but heat and current settings can extend or shorten this time significantly. The most common symptom of LED (anddiode laser) failure is the gradual lowering of light output and loss of efficiency. Sudden failures, although rare, can occur as well. Early red LEDs were notable for their short lifetime. With the development of high-power LEDs the devices are subjected to higherjunction temperaturesand higher current densities than traditional devices. This causes stress on the material and may cause early light-output degradation. To quantitatively classify lifetime in a standardized manner it has been suggested to use the terms L75 and L50 which is the time it will take a given LED to reach 75% and 50% light output respectively. Like other lighting devices, LED performance is temperature dependent. Most manufacturers published ratings of LEDs are for an operating temperature of 25Â °C. LEDs used outdoors, such as traffic signals or in-pavement signal lights, and that are utilized in climates where the temperature within the luminaire gets very hot, could result in low signal intensities or even failure. LED light output actually rises at colder temperatures (leveling off depending on type at around −30C). Consequently, LED technology may be a good replacement in uses such as supermarket freezer lightingand will last longer than other technologies. Because LEDs emit less heat than incandescent bulbs, they are an energy-efficient technology for uses such as freezers. However, because they emit little heat, ice and snow may build up on the LED luminaire in colder climates.This lack of waste heat generation has been observed to cause sometimes significant problems with street traffic signals and airport runway lighting in snow-prone areas, although some research has been done to try to develop heat sink technologies to transfer heat to other areas of the luminaire. Ultraviolet and blue LEDs BlueLEDs. Blue LEDs are based on the wideband gapsemiconductors GaN (gallium nitride) andInGaN(indium gallium nitride). They can be added to existing red and green LEDs to produce the impression of white light, though white LEDs today rarely use this principle. The first blue LEDs were made in 1971 by Jacques Pankove (inventor of the gallium nitride LED) atRCA Laboratories.These devices had too little light output to be of much practical use. In August of 1989, Cree Inc. introduced the first commercially available blue LED.In the late 1980s, key breakthroughs in GaNepitaxialgrowth andp-typedoping ushered in the modern era of GaN-based optoelectronic devices. Building upon this foundation, in 1993 high brightness blue LEDs were demonstrated. By the late 1990s, blue LEDs had become widely available. They have an active region consisting of one or more InGaNquantum wellssandwiched between thicker layers of GaN, called cladding layers. By varying the relative InN-GaN fraction in the InGaN quantum wells, the light emission can be varied from violet to amber. AlGaNaluminium gallium nitrideof varying AlN fraction can be used to manufacture the cladding and quantum well layers for ultraviolet LEDs, but these devices have not yet reached the level of efficiency and technological maturity of the InGaN-GaN blue/green devices. If the active quantum well layers are GaN, instead of alloyed InGaN or AlGaN, the device will emit near-ultraviolet light with wavelengths around 350-370nm. Green LEDs manufactured from the InGaN-GaN system are far more efficient and brighter than green LEDs produced with non-nitride material systems. With nitrides containing aluminium, most oftenAlGaNandAlGaInN, even shorter wavelengths are achievable. Ultraviolet LEDs in a range of wavelengths are becoming available on the market. Near-UV emitters at wavelengths around 375-395nm are already cheap and often encountered, for example, asblack lightlamp replacements for inspection of anti-counterfeitingUV watermarks in some documents and paper currencies. Shorter wavelength diodes, while substantially more expensive, are commercially available for wavelengths down to 247nm.As the photosensitivity of microorganisms approximately matches the absorption spectrum ofDNA, with a peak at about 260nm, UV LED emitting at 250-270nm are to be expected in prospective disinfection and sterilization devices. Recent research has shown that commercially available UVA LEDs (365nm) are already effective disinfection and sterilization devices. Deep-UV wavelengths were obtained in laboratories usingaluminium nitride(210nm),boron nitride(215nm)anddiamond(235nm). White light There are two primary ways of producing high intensity white-light using LEDs. One is to use individual LEDs that emit threeprimary colors—red, green, and blue—and then mix all the colors to form white light. The other is to use a phosphor material to convert monochromatic light from a blue or UV LED to broad-spectrum white light, much in the same way a fluorescent light bulb works. Due tometamerism, it is possible to have quite different spectra that appear white. RGB systems Combined spectral curves for blue, yellow-green, and high brightness red solid-state semiconductor LEDs.FWHMspectral bandwidth is approximately 24-27 nm for all three colors. White lightcan be formed by mixing differently colored lights, the most common method is to usered, green and blue(RGB). Hence the

Educating Rita Essay -- Educating Rita Humor Social Class Essays

Educating Rita Educating Rita is a humorous play giving out a very strong message, which is telling the reader to never give up in life and keep striving for what you are aiming for. In this play we have a 26 year old woman called Rita whom is a mature woman, seeking an education, as she didn't take the opportunity to learn when she was an amateur student, because of the environment she lived in and the fact she didn't want to learn due to her popularity and her working class culture. In reflection, Rita has come to realise how the law expectations surrounding her and her working class culture held her back from her real potential. She wants to change now and break this cycle. Frank, the other main character, is a teacher at the university where she has applied to do her course. He is around his 50's and is Rita's tutor. He is a lazy man, bored and frustrated by his life he too does not feel like he belongs anywhere. Frank does not like his job very much, he does not have any respect for himself at all. The play is staged in one room and only 2 people are taking the major role in the play. This is quite unusual for a play this long. Throughout the play, there are only two characters: this is known as a two-hander. Other characters are only mentioned in the play, but in the film have been cast as parts. It worked well for the film, but I think it lost the closeness which plays such an important part in the theatre. Some people would find this to be tedious, but I think it adds to the intensity and intimacy between the audience and the characters. Frank is a very important to Rita’s transformation. The relation ship between frank and Rita at the beginning of the play is not strong, Frank doesn't re... ...ing to take ten years off you†, it looked like rita was going to kiss Frank but she goes to him, ges out a scissor and starts cutting up his hair, this is one of the humerous parts. This would symbolise another chance for Frank and Rita, a new life for the both of them. I think this play is one of the best plays I have ever read. At te beginning, I had found out that this play only contained 2 characters, this made me think that this play would be not very interesting, but I was surprised. This had an excellent storyline which gave out strong messages which is basically ‘not to give up in life’, for example Rita had sacrificed a lot for her edcucation, this showed how dedicated she was. This play is presented in different styles, like sometimes this play can be humerous but most of the time it is serious. I think this way, keeps the reader interested.

Letters Home :: Creative Writing Essays

Letters Home The vid screen is dark and ominous, as if it holds secrets that is not for the likes of men to know. John Poldeck, a middle aged, balding man of forty-eight steps forward toward screen and console to activate the beast, this oracle of silicon, plastic, and glass. Today John is hoping for word of his son Kirk, of whom nothing had been heard of since he left for UNDF Marine Corps training at Camp Lejune, South Carolina, a beacon for the phony tough and crazy brave looking for ill conceived adventure and glory. At least that was John’s opinion on the matter. As a mid level market analyst for the transnational ABSCOM John was used to battles fought with market shares, balance sheets, and stock options. For the forty years since the birth of the revamped United Nations war and the conductors of war, the military, had been a dying business. John could still remember the eager look on Kirk’s face when his son had uttered words like, duty, honor, patriotism, words which seemed as alien to John as the worlds the UN exploratory fleet claimed to have found. â€Å"For Christ’s sake John will you turn on the damn console? What the hell is wrong with you today?† John glanced at June, his wife of twenty years and counting. Her dark skinned face was a sharp contrast to his pale complexion, and anger, tinged with concern for her son, clouded and darkened her visage even more. He looked at his wife without comprehension. â€Å"What?† June sighed, and then in a kinder tone, â€Å"The console John. I know you’ve been angry ever since Kirk left for the Marines, hell you’ve been mad ever since he first brought up enlisting. A fool’s errand you called it. Perhaps you’re right. All I know is that he might have sent us a letter today.† A fool’s errand. I remember when I said that John thought. That had been a nasty episode, one of many that had occurred during one of the endless fights he had had with Kirk over this business of enlisting. Try how he might he could never convince his son that business was where the opportunities were. Kirk had then coldly informed his father of his contempt for the Transnationals that now ran everything on Earth, including the UN, and his contempt for anybody connected to them.