Crying Souls in The Slave Dancer :: Slave Dancer Essays

Crying Souls in The Slave Dancer It all began in the cold month of January, 1840, in a town familiar to many; New Orleans. Fog laid a heavy blanket on the streets and alleyways of the city. Rain steadily engulfed the seaside locality, and the sound of drunken riverboat men and the slaves celebrating their terrible festivities surrounded the area. New Orleans was the location where Jessie Bollier lived, and 'tis the place where he was captured on that dark January evening. Jessie then found himself aboard The Moonlight, the slaver with its towering sails and masts, cabins and storage space under the deck. For these were places where Jessie had to 'dance the slaves' and where the captain and crew would spend many weeks living in fear of the slaves, of each other, and of getting caught. The story then briefly took the ship's crew and captain to Whydah in the Bight of Benin, the rugged coasts of Africa, where the multitudes of slaves were captured and mistreated. They then made their way across the Atlantic once again to land in the Gulf of Mexico. The Moonlight was anchored there and stayed because it was here where the ship submerged. Two passengers then washed up to the shores of Mississippi where Jessie and Ras meet Daniel, their soon to be friend. Finally, the story concludes in the place it began...the clamoring streets of New Orleans. The Slave Dancer is written in first person point of view, through Jessie's eyes, and projects a depressing, melancholy mood. It is the tragic song of the slaves. The hero of the story is the thirteen year old boy, Jessie Bollier. "He's a fearful runt," comments Captain Cawthorne. He is brought on board the slaver to make the slaves dance, to keep them healthy. Jessie innocent and does not fully understand his purpose. "My life h ad turned upside down. My friend was a man who pressganged me. I disliked the man who befriended me." Jessie does not realize what is going on within him. He does not realize that these men, these women, and children are slaves...are owned. He does not perceive the cruel treatment of the slaves, but does not know why. Jessie himself puts it best, "My stomach rebelled." The antagonist is surprisingly Jessie, but after the voyage. He went through many changes after the excursion. "At first, I made a promise to myself: I would do nothing that was connected with the use of slaves.

National Issues in Election 2008

The five most important issues of Election 2008 (in no particular order) are:1.  Ã‚  Ã‚  Ã‚  Ã‚   The economy: How will the United States correct the recession and what can be done to protect Americans from a recession in the future?2.  Ã‚  Ã‚  Ã‚  Ã‚   The war in Iraq: How will America extract itself from Iraq? Can America extract itself from Iraq?3.  Ã‚  Ã‚  Ã‚  Ã‚   Immigration: Immigrants, primarily in the form of unskilled workers from Mexico, are arriving in the United States in unprecedented numbers. There are now over 10 million unauthorized immigrants living in the United States (Passel, 2005, pp.   4-5).   How will America address the problem of illegal immigration and the need for guest workers?4.  Ã‚  Ã‚  Ã‚  Ã‚   Education: American high school students ranked 25th out of 30 nations in recent comparisons of math and science skills (Glod, 2007). Many American students graduate from high school without being able to read, and many others drop out of school alto gether. How can America fix its broken educational system?5.  Ã‚  Ã‚  Ã‚  Ã‚   Energy policy: Rising oil prices have underscored America's dependency on foreign oil, raising economic concerns and concerns about security. Energy is also closely related to the environment. Can the United States find sustainable and affordable sources of environmentally friendly energy?What should be the government's role in solving these problems? The answer depends on your political perspective.The economy Political Left: America's economic problems are the result of the natural tendency of corporations to put their own interests ahead of what is best for the country. This problem can be solved if the government did a better job of regulating businesses and financial institutions.Political Right: Recessions are part of a natural cycle of economic activity, as the economy makes necessary corrections. Economic problems can be solved by encouraging investment through lower tax rates, less government i ntrusion, and the creation of new markets for goods and services. In a capitalistic economy, jobs are created by businesses, not by governments.Political Center: Some government regulation of business practices is necessary to protect American jobs and incomes. Government and private business must work together to create jobs for American workers.The War Political Left: Can't we all just get along? International disputes are best handled through diplomatic means. America should withdraw as quickly as possible from Iraq and should avoid similar conflicts with other nations in the future.Political Right: The Homeland must be defended! Backing down sends the wrong message to terrorists and to our allies. America must be strong if we are to be respected.Political Center: War is a necessary evil, but should not be a first response. America should conclude its business in Iraq as quickly as possible, and then leave. Other nations should know that America has the capacity and will to prote ct itself, but will do so only if necessary.Immigration Political Left: America is a nation of immigrants. Rejecting immigrants now is hypocritical and racist. Immigrants should have the same rights as anyone else in the country and should not live in fear of being deported.   Government should make it easier for immigrants to be documented.Political Right: The Right seems to be divided on this issue. On one hand, conservatives want the cheap labor that is provided by undocumented workers. On the other hand, conservatives fear that immigration is changing the culture and – let's be honest – the complexion of the United States. The Right argues that immigrants are taking jobs away from Americans, yet they continue to employ undocumented immigrants to do jobs that Americans will not do. These conflicts probably explain why the Right has such a hard time articulating any type of coherent policy on immigration and cannot seem to decide what the role of government should be on this issue.Political Center: Immigrants, a.k.a., guest workers, are an important part of the American economy; however, once they come to the United States, immigrants need to learn English and make show proper respect for American culture. This is the United States, not the Estados Unidos. It is the responsibility of government to help assimilate immigrates and to ensure that no terrorists cross the border masquerading as a guest worker.Education The Right: Government should not have a monopoly on education. American students are failing because schools have no motivation to improve. Privatizing education would create competition and improve the quality of schools.The Left: Schools are failing because they are underfunded. It is the role of government to invest in the future of this country, which includes investing in schools.The Center: Public schools deserve public support. The role of government is to provide funding for public education. In cases where schools are failin g to teach, it is the role of government to ensure that every child has opportunity to learn, which may mean sending some children to private schools.Energy policy The Left: Green is good! It is the role of government to regulate and, if necessary, control energy production and distribution. Extreme Left would probably advocate for public ownership of all energy companies.The Right: Energy production reflects consumer demands. When people want greener fuels, companies will provide them. Government should support research on energy sources, but it is not the place of government to control prices or distribution of gasoline and other energy sources.The Center: Government should allow free markets for gasoline and other energy sources, but should intervene when profits reach extortion levels and people cannot afford to buy gasoline. Government should support research on alternative fuels.ReferenceGlod, M. (2007). U.S. Teens Trail Peers Around World on Math-Science Test. Washington Post (December 5, 2007), p. A07. Retrieved April 10, 2008, from http://www.washingtonpost.com/wp-dyn/content/article/2007/12/04/AR2007120400730.htmlPassel, J.   (2005).   Unauthorized Migrants: Numbers and Characteristics.   Background Briefing Prepared for Task Force on Immigration and America's Future.   Washington, D.C.: Pew Hispanic Center.   Retrieved April 1, 2008, from http://www.pewtrusts.org/uploadedFiles/wwwpewtrustsorg/Reports/Hispanics_in_America/PHC_immigrants_0605.pdf

Explain the Biological Mechanisms by Which Stress Can Induce Depressive Behaviour

Explain the biological mechanisms by which stress can induce depressive behaviour. Introduction Depressive behaviour is a core feature of several major psychological disorders, most obviously major depression (MD) and depressive episodes of bipolar depression (BP). Depression is also frequently found to be co-morbid with psychotic disorders such as schizophrenia and with anxiety-related disorders (e. g. social phobia or OCD). Depression is the biggest major risk factor for self-harm and suicide, thus posing a real clinical problem to try to understand and reverse the mechanisms involved.Traditional anti-depressant treatment has only shown a modest benefit to placebos in treating the disorder; therefore, more effective drugs that target the right biological mechanisms are imminently needed. The majority of experimental research in the area has used rodents to test medication and model known psychopathological aspects of depression in humans, such as learned helplessness, cognitive def icits and increased co-morbidity with anxiety-related behaviours. There are many factors that may explain why some people (around 16% of the population) will experience a depressive episode in their lifetime and others won’t.Genetic vulnerability and epigenetic changes, psychosocial support, socioeconomic status or even climate-related factors all have to be considered in considering the right treatment for individual cases. Whilst the causal link between many of these and the onset of depression is somewhat inconclusive, the strong association between chronic mild stress (CMS) and depressive behaviour is now a huge area of research, resulting in the stress-induced model of depression.Even where there is evidence for the role of genes in depression, such as allele variants for the 5-HTT promoter region, it is shown to vary as a function of exposure to stressful life events. The mechanisms by which environmental stressors can lead to depressive behaviour have been explored tho roughly, with a strong focus on the role of the Hypothalamus-Pituitary-Adrenal (HPA) axis and its dysfunction in depression. The consequent rise in levels of the glucocorticoid hormone cortisol, following HPA activation, has been shown to become chronic increased in depressed patients.This is thought to be due to the development of glucocorticoid resistance, whereby high levels of cortisol are present in the bloodstream and peripheral tissue but negative feedback to shut down the HPA axis no longer works. Due to the numerous roles of cortisol within the body, several biological processes may be affected as a consequence of CMS that may lead to depressive behaviour. Direct and indirect effects of HPA dysfunction include changes in immune response, neuronal damage, decreased rates of neurogenesis and the serotonin pathways.These processes tend to interact and exacerbate one another; therefore, understanding each proposed biological mechanism of stress-induced depression and their impa ct upon each other is likely to lead to a better treatment outcome. Acute Stress and the HPA Axis The experience of acute mild stress is a normal and adaptive process, triggered by an environmental ‘stressor’ deemed to be potentially harmful. From an evolutionary perspective, this serves to protect the individual from danger via activation of the sympathetic nervous system, preparing the individual for ‘fight or flight’ mode.Stress, as well as input from the amygdala, hippocampus and midbrain, directly activates the ‘stress response’ via the Hypothalamic-Pituitary-Adrenal (HPA) axis. The first immediate response is the release of corticotrophin releasing hormone (CRH) from the hypothalamus, which travels to the pituitary where it binds to CRH Receptor 1 (CRHR1). CRH can also act directly on other brain regions, e. g. the amygdala at this early stage. CRH1 activation stimulates the release of adrenocorticotrophin release hormone (ACTH), which tr avels via the bloodstream to the kidneys, stimulating the delayed release of the glucocorticoid (steroid) cortisol.Cortisol acts throughout the body in all cells, via binding to cytoplasmic glucocorticoid and mineralocorticoid receptors (GR and MR) (see Figure 1). Figure 1: Cortisol can pass through the cell membrane due to its lipophillic properties. Binding of cortisol to the GR complex in the cytoplasm causes dissociation of GR from the complex, resulting in an active GR monomer. Two GRs then dimerise to form a GR dimer. This can act as a transcription factor in itself by attaching to Glucocorticoid Binding Elements (GBE), or it can interact with other Hormone Binding Elements and transcription factors to initiate gene transcription. http://jimlund. org/blog/? m=200910] A rise in cortisol levels, alongside CRH, leads to adaptive changes in behaviour, cognition and immune function. Importantly, this rise is followed by a negative feedback loop of cortisol and CRH acting upon its o wn receptors (NC3R1 and CHR2, respectively) to shut down the HPA axis once the ‘threat’ has been resolved. This homeostatic mechanism terminates the production of any more CRH and therefore brings cortisol levels back to baseline (pre-stressor), vital for returning the individual back to a normal ‘resting’ state.It is this negative feedback mechanism which has been shown to be disrupted in patients with depression. Chronic Stress and Glucocorticoid Resistance In a situation of CMS, the prolonged activation of the HPA axis leads to abnormally elevated cortisol levels. However, chronically elevated cortisol can be dangerous, due to its role in suppressing the immune system and increasing vulnerability to infection. It is possible that in order to counteract the constant influx of circulating cortisol causing potentially unwanted downstream effects, GRs in lymphocytes become unresponsive or resistant to glucocorticoids.This dysfunction of GRs is typically seen in depressed patients and has been shown numerous times using the dexamethasone suppression test (DST). Dexamethasone (a synthetic glucocorticoid) mimics cortisol by binding to GRs and shutting down HPA activity in healthy controls. Therefore, dexamethasone-treated individuals have almost no detectable cortisol over the course of the following day. On the other hand, in depressed patients, the DST doesn’t show any significant repression of HPA activity.Whilst they already show significantly higher overall levels of cortisol, they also show reduced suppression of dexamethasone during the DST. This shows that the GRs are unresponsive to glucocorticoids, leading to the typical feature of glucocorticoid resistance in depressed patients. The Inflammation/Cytokine Hypothesis Glucocorticoid resistance has important implications for immune system function. Under normal acute stress, cortisol suppresses lymphocytes in peripheral tissue from producing pro-inflammatory cytokines by act ivating intracellular GRs and leading to transcription of downstream regulatory genes.Key targets of GR-mediated transcription related to immune function include the upregulation of anti-inflammatory genes annexin-1, IL-10 and I? B? (inhibits NF-? B) and down-regulation of pro-inflammatory cytokine genes, such as IL1-6, 9, 11-13, 16-18 and TNF-?. However, glucocorticoid resistance following chronic stress can mean that lymphocytes stop responding to cortisol, so there is an increase in the proliferation of leukocytes and production of pro-inflammatory cytokines.The proposed mechanism for how these peripherally-generated cytokines are able to affect the central nervous system (CNS) involves several pathways. These cytokines (IL-1? , TNF-? and IL-6) cannot typically diffuse across the blood-brain-barrier, but they can enter the CNS in regions of high BBB permeability or be actively transported across the BBB by endothelial cell transporters. Additionally, without crossing the BBB, cyt okines are able to activate endothelial cells to produce soluble factors (e. g.PG-E2) to indirectly activate neurons, as well as activating certain afferent neurons (e. g. the vagus nerve) that carry information to the CNS about the inflammation. In these ways, peripheral inflammation can cause typical changes in the CNS and ‘sickness behaviour’ seen in depressed patients: lethargy, anhedonia, reduced locomotor activity and sleep and weight disturbances. Support for this proposed mechanism comes from findings that clinically depressed patients show an abnormally high production of pro-inflammatory cytokines (IL-1? IL-6 and TNF-? ), cytokine-based immunotherapy often causes depression in cancer or hepatitis C patients and cytokine administration causes depressive behaviour in animal models. Reversal of this depressive behaviour can be seen by administration of anti-depressants, which target and reduce the inflammatory response in both patients and animal models. In a sim ilar fashion, anti-inflammatories such as cyclooxygenase (COX)-2 inhibitors or omega-3 have strong anti-depressant effects on behaviour. Inflammation-Induced NeurodegenerationAnother approach to modelling stress-induced depression has focused on the controversial findings of clinically depressed patients show changes in volume of structural brain regions, including the hippocampus, amygdala, anterior cingulated, prefrontal cortex and basal ganglia. The mechanisms by which some brain regions, in particular the hippocampus as implicated in stress-induced depression, might decrease in volume appear to be a combination of both neurodegeneration (increased apoptosis of neurons) and a decrease in adult neurogenesis in the subgranular zone of the dentate gyrus (DG).Stress-induced HPA hyper-activity may explain the atrophy seen in some brain regions of clinically depressed patients. Glucocorticoids stimulate the breakdown of tissue into glucose for the quick release of energy; therefore, ch ronically increased levels may result in brain tissue loss in regions where cortisol acts, such as the hippocampus. Furthermore, the link between stress, inflammation and an increase in oxidative stress may also explain a large portion of the neurodegeneration apparent in depression.Inflammation has been shown to increase oxidation and the fact that the CNS has no proper defence against oxidative damage makes it very vulnerable to oxidative stress (OS). This has been demonstrated as a key feature in neurodegenerative diseases and depression, implicating a causal role of stress-induced inflammation in triggering degeneration. The damage caused by OS can lead to mitochondrial dysfunction, which can lead to further intracellular build up of damaging oxidised proteins.The only way for cells to cope in this situation is to activate programmed cell death (apoptosis), or in less controlled circumstances, necrosis can occur, leading to a decline in cell numbers and lateral effects on the ne ural network. This mechanism of oxidative stress-induced neurodegeneration can be slowed down and treated by the application of antioxidant enzymes, which serve a neuro-protective role. These enzymes eradicate free radical oxidising particles and also suppress pro-inflammatory cytokine action.A further damaging feature seen in neurodegeneration and depression is nitrosative stress (NS), which may contribute to neurotoxicity and therefore cell death. An increase in the production of cortisol after acute stress will temporarily cause a suppression of neurogenesis in the DG. Neurogenesis in the DG has been demonstrated to be vital for healthy cognition and memory, impacting mood, the sleep-wake cycle and appetite; all affected in depression. Therefore, CMS leads to prolonged suppression of neurogenesis and may explain the behavioural outcomes typical of depression.The decrease in neurogenesis following exposure to stress may possibly involve the neurotrophin Brain Derived Neurotrophic Factor (BDNF), shown to be greatly reduced in regions that also show a decrease in neurogenesis and related to brain regions typically affected in depression. Animal models exposed to CMS show decreased neurogenesis and BDNF levels in overlapping brain regions and elicit depressive behaviours associated with dysfunction of these regions. Furthermore, anti-depressant treatment that successfully increases BDNF levels also leads to recovery from depressive behavioural symptoms.However, the causation here is not clear; whether the BDNF levels dropping are a result of other stress-induced mechanisms or whether it is partly the cause of the behaviour. Some evidence suggests that anti-depressants can work independently of BDNF restoration. Hagen and colleagues set out to control for possible variables such as age, time of cortisol readings and overall brain volume. Whilst there has been no robust evidence for a link between baseline cortisol levels and hippocampal volume, this study did fi nd that hippocampal volume was negatively correlated with length of depressive episode pre-hospitalisation.Furthermore, better responsiveness (lowering of cortisol levels) after treatment was predicted by greater hippocampal volume (relative to overall brain volume). b) antineurogenic effects and reduced brain-derived neurotrophic factor (BDNF) levels; and c) apoptosis with reduced levels of Bcl-2 and BAG1 (Bcl-2 associated athanogene 1), and increased levels of caspase-3. Stress-induced inflammation, e. g. increased IL-1? , but not reduced neurogenesis, is sufficient to cause depression. Antidepressants a) reduce peripheral and central inflammatory pathways by decreasing IL-1? TNF? and IL-6 levels; b) stimulate neuronal differentiation, synaptic plasticity, axonal growth and regeneration through stimulatory effects on the expression of different neurotrophic factors, e. g. trkB, the receptor for brain-derived neurotrophic factor; and c) attenuate apoptotic pathways by activating Bc l-2 and Bcl-xl proteins, and suppressing caspase-3. It is concluded that external stressors may provoke depression-like behaviours through activation of inflammatory, oxidative, apoptotic and antineurogenic mechanisms.The clinical efficacy of antidepressants may be ascribed to their ability to reverse these different pathways. Neuronal damage and apoptosis Activation of the Kynurenine Pathway (KP) 5-HT Accumulated evidence indicates a role of the hippocampal 5-hydroxy-tryptamine (5-HT) and neuropeptide Y (NPY) in the response to stress and modulation of depression, but it is unclear whether and how the hippocampal 5-HT and NPY systems make contributions to chronic unpredicted mild stress (CUMS)-induced depression.Here we observed that rats receiving a variety of chronic unpredictable mild stressors for 3 weeks showed a variety of depression-like behavioral changes, including a significant reduction in body weight, sucrose preference, and locomotion, rearing and grooming in open fiel d test, and a significant increase in immobility time in forced swimming test. These CUMS-induced behavioral changes were suppressed or blocked by intra-hippocampal injection of 5-HT (31. 25 microg/microl) or NPY (10 microg/microl). These data suggest a critical role of reduced hippocampal 5-HT and NPY neurotransmission in CUMS-induced depression.

Engine powered by liquid hydrogen

Wide Range of Flammability:In comparing with all other fuels, Hydrogen has a really broad scope of flammability. Hence, Hydrogen can be combusted in an internal burning engine over a broad scope of fuel-air mixtures. One of the important advantages of this is that Hydrogen fuel can run a really thin mixture. A thin mixture is one in which the sum of fuel is less than the theoretical, stoichiometric or chemically ideal sum needed for burning with a given sum of air. This is why it is reasonably easy to acquire an engine to get down on H. In general, fuel economic system is greater and the burning reaction is more complete when a vehicle is run on a thin mixture. Besides, the concluding burning temperature is lower hence cut downing the sum of pollutants, such as N oxides, emitted in the fumes. However, there is a bound to how thin the engine can be run, as thin operation can significantly cut down the power end product due to a decrease in the volumetric heating value of the air/fuel mixtureLow Ignition Energy:Ignition energy is the energy needed to light a fuel. Hydrogen has really low ignition energy. The sum of energy needed to light H is about one order of magnitude less than that required for gasolene. The feature of low Ignition energy enables hydrogen engines to light thin mixtures and besides ensures prompt ignition. Unfortunately, the low ignition energy besides carries the hazard that hot gases and hot musca volitanss on the cylinder can function as beginnings of ignition and hence making jobs such as premature ignition and flashback. Preventing the above mentioned jobs is one of the jobs associated with runing an engine on H. The broad flammability scope of H agencies that about any mixture can be ignited by a hot topographic point.Small Quenching Distance:Hydrogen has a little extinction distance, even smaller than that of gasolene. Hence, it ‘s more hard to slake a H fire than a gasolene fire. The inclination for blowback additions as a consequence of smaller extinction distance, since the fire from a hydrogen-air mixture more readily passes a about closed consumption valve, than a hydrocarbon-air fire.High Auto-Ignition Temperature:Hydrogen has a comparatively high auto-ignition temperature. This characteristic is of import because the hydrogen-air mixture has to be compressed and the refore plays an of import function in finding the compaction ratio that an engine can utilize, since the temperature rise during compaction is related to the compaction ratio. The temperature should non transcend the auto-ignition temperature, as this would do a premature ignition. Hence, the absolute concluding temperature controls the compaction ratio. The high car ignition temperature of H allows larger compaction ratios to be used in a H engine than in a hydrocarbon engine. On the other manus, H is hard to light in a compaction ignition or Diesel constellation, because the temperatures needed for those types of ignition are comparatively high.High Flame SpeedHydrogen has high fire velocity at stoichiometric ratios. Under these conditions, the H fire velocity is about an order of magnitude higher ( faster ) than that of gasolene. This means that H engines can more closely approach the thermodynamically ideal engine rhythm. At leaner mixtures, nevertheless, the fire speed decreases significantly.High DiffusivityHydrogen has really high diffusivity. This ability to scatter in air is well greater than gasolene and is advantageous for two chief grounds. Fir st, it facilitates the formation of a unvarying mixture of fuel and air. Second, if a H leak develops, the H disperses quickly. Therefore, insecure conditions can either be avoided or minimized.Low DensityHydrogen has really low denseness. This consequences in two jobs when used in an internal burning engine. First, a really big volume is necessary to hive away adequate H to give a vehicle an equal drive scope. Second, the energy denseness of a hydrogen-air mixture, and therefore the power end product, is reduced.Fuel Delivery SystemsHydrogen fuel bringing system can be broken down into three chief types:Cardinal injection ( or â€Å"carburetted† )Port injectionDirect injectionCentral and port fuel bringing systems injection forms the fuel-air mixture during the intake shot. In the instance of cardinal injection or a carburetor, the injection is at the recess of the air intake manifold. In the instance of port injection, it is injected at the recess port. Direct cylinder inje ction is more technologically sophisticated and involves organizing the fuel-air mixture inside the burning cylinder after the air consumption valve has closed.Cardinal Injection or Carburetted Systems:The simplest method of presenting fuel to a H engine is by manner of a carburetor or cardinal injection system. This system has advantages for a H engine. First, cardinal injection does non necessitate the H supply force per unit area to be every bit high as for other methods. Second, cardinal injection or carburetors are used on gasolene engines, doing it easy to change over a standard gasolene engine to hydrogen or a gasoline/hydrogen engine. The disadvantage of cardinal injection is that it is more susceptible to irregular burning due to pre-ignition and back fire. The greater sum of hydrogen/air mixture within the consumption manifold compounds the effects of pre-ignition.Port Injection SystemsThe port injection fuel bringing system injects fuel straight into the consumption manifold at each consumption port, instead than pulling fuel in at a cardinal point. Typically, the H is injected into the manifold after the beginning of the consumption shot. At this point conditions are much less terrible and the chance for premature ignition is reduced. In port injection, the air is injected individually at the beginning of the consumption shot to thin the hot residuary gases and cool any hot musca volitanss. Since less gas ( H or air ) is in the manifold at any one clip, any pre-ignition is less terrible. The recess supply force per unit area for port injection tends to be higher than for carburetted or cardinal injection syste ms, but less than for direct injection systems. The changeless volume injection ( CVI ) system uses a mechanical cam-operated device to clip the injection of the H to each cylinder. The CVI block is shown on the far right of the exposure with four fuel lines go outing on left side of the block ( one fuel line for each cylinder ) . The electronic fuel injection ( EFI ) system meters the H to each cylinder. This system uses single electronic fuel injectors ( solenoid valves ) for each cylinder and pumped to a common fuel rail located down the Centre of the consumption manifold. Whereas the CVI system uses changeless injection timing and variable fuel rail force per unit area, the EFI system uses variable injection timing and changeless fuel rail force per unit area.Direct Injection SystemsMore sophisticated H engines use direct injection into the burning cylinder during the compaction shot. In direct injection, the consumption valve is closed when the fuel is injected, wholly avoiding premature ignition during the intake shot. Consequently the engine can non backlash into the consumption manifold. The power end product of a direct injected H engine is 20 % more than for a gasolene engine and 42 % more than a H engine utilizing a carburetor. While direct injection solves the job of pre-ignition in the consumption manifold, it does non needfully forestall pre ignition within the burning chamber. In add-on, due to the reduced commixture clip of the air and fuel in a direct injection engine, the air/fuel mixture can be non-homogenous. Surveies have suggested this can take to higher NOx emanations than the non-direct injection systems. Direct injection systems require a higher fuel rail force per unit area than the other.Thermal DilutionPre-ignition conditions can be curbed utilizing thermic dilution techniques such as fumes gas recirculation ( EGR ) or H2O injection. As the name implies, an EGR system re-circulates a part of the fumes gases back into the consumption manifold. The debut of exhaust gases helps to cut down the temperature of hot musca volitanss, cut downing the possibility of pre-ignition. Additionally, re-circulating fumes gases cut down the peak burning temperature, which reduces NOx emanations. Typically a 25 to 30 % recirculation of fumes gas is effectual in extinguishing blo wback. On the other manus, the power end product of the engine is reduced when utilizing EGR. The presence of exhaust gases reduces the sum of fuel mixture that can be drawn into the burning chamber. Another technique for thermally thining the fuel mixture is the injection of H2O. Injecting H2O into the H watercourse prior to blending with air has produced better consequences than shooting it into the hydrogen-air mixture within the consumption manifold. A possible job with this type of system is that H2O can acquire assorted with the oil, so care must be taken to guarantee that seals do non leak.Engine DesignThe most effectual agencies of commanding pre-ignition and knock is to re-design the engine for H usage, specifically the burning chamber and the chilling system. A discoid burning chamber ( with a level Piston and chamber ceiling ) can be used to cut down turbulency within the chamber. The disc form helps bring forth low radial and digressive speed constituents and does non magnify recess whirl during compaction. Since unburned hydrocarbons are non a concern in H engines, a big bore-to-stroke ratio can be used with this engine. To suit the wider scope of fire velocities tha t occur over a greater scope of equality ratios, two flicker stoppers are needed. The chilling system must be designed to supply unvarying flow to all locations that need chilling. Extra steps to diminish the chance of pre ignition are the usage of two little exhaust valves as opposed to a individual big one, and the development of an effectual scavenging system, that is, a agency of displacing exhaust gas from the burning chamber with fresh air.Ignition SystemsDue to hydrogen ‘s low ignition energy bound, lighting H is easy and gasoline ignition systems can be used. At really thin air/fuel ratios ( 130:1 to 180:1 ) the fire speed is reduced well and the usage of a double flicker stopper system is preferred. Ignition systems that use a waste flicker system should non be used for H engines. These systems energize the flicker each clip the Piston is at top dead Centre whether or non the Piston is on the compaction stroke or on its exhaust shot. For gasolene engines, waste flicke r systems work good and are less expensive than other systems. For H engines, the waste flickers are a beginning of pre-ignition. Spark stopper for a H engine should hold a cold evaluation and have non-platinum tips. A cold-rated stopper is one that transfers heat from the stopper tip to the cylinder caput quicker than a hot-rated flicker stopper. This means the opportunities of the flicker stopper tip lighting the air/fuel charge is reduced. Hot rated spark stoppers are designed to keep a certain sum of heat so that C sedimentations do non roll up. Since H does non incorporate C, hot-rated flicker stoppers do non function a utile map. Platinum-tip flicker stopper should besides be avoided since Pt is a accelerator, doing H to oxidise with air.Crankcase Ventilation:Crankcase airing is even more of import for H engines than for gasolene engines. As with gasolene engines, un-burnt fuel can ooze by the Piston rings and enter the crankcase. Since H has a lower energy ignition bound than gasolene, any un-burnt H come ining the crankcase has a greater opportunity of lighting. Hydrogen should be prevented from roll uping through airing. Ignition within the crankcase can be merely a startling noise or consequence in engine fire. When H ignites within the crankcase, a sudden force per unit area rise occurs. To alleviate this force per unit area, a force per unit area alleviation valve must be installed on the valve screen. Exhaust gases can besides ooze by the Piston rings into the crankcase. Since H fumes is H2O vapor, H2O can distill in the crankcase when proper airing is non provided. The commixture of H2O into the crankcase oil reduces its lubrication ability, ensuing in a higher grade of engine wear.Emissions:The burning of H with O green goodss H2O as its lone merchandise: 2H2 + O2 = 2H2O The burning of H with air nevertheless can besides bring forth oxides of N ( NOx ) : H2 + O2 + N2 = H2O + N2 + NOx The oxides of N are created due to the high temperatures generated within the burning chamber during burning. This high temperature causes some of the N in the air to unite with the O in the air. The sum of NOx formed depends on:The air/fuel ratioThe engine compaction ratioThe engine velocityThe ignition timingWhether thermic dilution is utilisedIn add-on to oxides of N, hints of C monoxide and C dioxide can be present in the fumes gas, due to ooze oil combustion in the burning chamber. Depending on the status of the engine ( combustion of oil ) and the operating scheme used ( a rich versus thin air/fuel ratio ) , a H engine can bring forth from about zero emanations ( every bit low as a few ppm ) to high NOx and important C monoxide emanations. Power End product: The theoretical maximal power end product from a H engine depends on the air/fuel ratio and fuel injection method used. As mentioned in above, the stoichiometric air/fuel ratio for H is 34:1. At this air/fuel ratio, H will displace 29 % of the burning chamber go forthing merely 71 % for the air. As a consequence, the energy content of this mixture will be less than it would be if the fuel were gasolene ( since gasolene is a liquid, it merely occupies a really little volume of the burning chamber, and therefore allows more air to enter ) . Since both the carburetted and larboard injection methods mix the fuel and air prior to it come ining the burning chamber, these systems limit the maximal theoretical power gettable to about 85 % of that of gasolene engines. For direct injection systems, which mix the fuel with the air after the consumption valve has closed ( and therefore the burning chamber has 100 % air ) , the maximal end product of the engine can be about 15 % higher than that for gasolene engines. Therefore, depending on how the fuel is metered, the maximal end product for a H engine can be either 15 % higher or 15 % less than that of gasolene if a stoichiometric air/fuel ratio is used. However, at a stoichiometric air/fuel ratio, the burning temperature is really high and as a consequence it will organize a big sum of N oxides ( NOx ) , which is a criteria pollutant. Since one of the grounds for utilizing H is low exhaust emanations, H engines are non usually designed to run at a stoichiometric air/fuel ratio. Typically hydrogen engines are designed to utilize approximately twice every bit much air as theoretically required for complete burning. At this air/fuel ratio, the formation of NOx is reduced to near nothing. Unfortunately, this besides reduces the power end product to about half that of a likewise sized gasolene engine. To do up for the power loss, H engines are normally larger than gasolene engines, and/or are equipped with turbochargers or superchargers.Hydrogen Gas Mixtures:Hydrogen can be used well in internal burning engines as an linear to a hydrocarbon fuel. Hydrogen is most normally assorted with high force per unit area natural gas for this intent since both gases can be stored in the same armored combat vehicle. If H is blended with other fuels, it normally has to be stored individually and assorted in the gaseous province instantly before ignition. In general, it is impractical to utilize H in concurrence with other fuels that besides require bulky storage systems, such as propane. Gaseous H can non be stored in the same vas as a liquid fuel. Hydrogen ‘s low denseness will do it to stay on top of the liquid and non blend. Furthermore, liquid fuels are stored at comparatively low force per unit areas so that really small H could be added to the vas. Liquid H can non be stored in the same vas as other fuels. Hydrogen ‘s low boiling point will stop dead other fuels ensuing in fuel â€Å"ice† . Hydrogen can be used in concurrence with compact liquid fuels such as gasolene, intoxicant or Diesel provided each are stored individually. In these applications, the fuel armored combat vehicles can be formed to suit into fresh infinites on the vehicle. Existing vehicles of this type tend to run utilizing one fuel or the other but non both at the same clip. One advantage of this scheme is that the vehicle can go on to run if H is unavailable. Hydrogen can non be used straight in a Diesel ( or â€Å"compression ignition† ) engine since H ‘s car ignition temperature is excessively high ( this is besides true of natural gas ) . Therefore, diesel engines must be outfitted with spark stoppers or utilize a little sum of Diesel fuel to light the gas ( known as pilot ignition ) . Although pilot ignition techniques have been developed for usage with natural gas, no 1 is presently making this with H. One commercially available gas mixture known as Hythane contains 20 % H and 80 % natural gas. At this ratio, no alterations are required to a natural gas engine, and surveies have shown that emanations are reduced by more than 20 % . Mixtures of more than 20 % H with natural gas can cut down emanations further but some engine alterations are required. Thin operation of any internal burning engine is advantageous in footings of oxides of nitrogen emanations and fuel economic system. For hydrocarbon engines, thin operation besides leads to take down emanations of C monoxide and unburned hydrocarbons. As more O is available than required to burn the fuel, the extra O oxidizes more C monoxide into C dioxide, a less harmful emanation. The extra O besides helps to finish the burning, diminishing the sum of unburned hydrocarbons. As with H, the drawback of thin operation with hydrocarbon fuels is a decreased power end product. Thin operation of hydrocarbon engines has extra drawbacks. Thin mixtures are difficult to light, despite the mixture being above the LFL of the fuel. This consequence in dud, which increases unburned hydrocarbon emanations, reduces public presentation and wastes fuel. Another disadvantage is the decreased transition efficiency of 3-way catalytic convertors, ensuing in more harmful emanations. To some extent, blending H with other hydrocarbon fuels reduces all of these drawbacks. Hydrogen ‘s low ignition energy bound and high firing velocity makes the hydrogen/hydrocarbon mixture easier to light, cut downing dud and thereby bettering emanations, public presentation and fuel economic system. Sing power end product, H augments the mixture ‘s energy denseness at thin mixtures by increasing the hydrogen-to-carbon ratio, and thereby improves torsion at wide-open throttle conditions.Current Status:A few car makers have been making some work in the development of hydrogen-powered vehicles ( Ford has late announced that they have developed a â€Å"production ready† hydrogen-powered vehicle utilizing an ICE and BMW has completed a universe circuit exposing a twelve or so hydrogen-powered 750i vehicles ) . However, it is non likely that any hydrogen-powered vehicles will be available to the populace until there is an equal re-fuelling substructure and trained tech nicians to mend and keep these vehicles. Like current gasoline-powered vehicles, the design of each H powered vehicle will most likely vary from maker to maker and theoretical account to pattern. One theoretical account may be simple in design and operation, for illustration, a thin combustion fuel metering scheme utilizing no emanation control systems such as EGR, catalytic convertor, evaporate fuel case shot, etc. Another theoretical account may be really sophisticated in design and operation, for illustration, utilizing an EGR fuel metering scheme with a catalytic convertor, multiple flicker stoppers, etc. Until such clip that a H substructure exists, hydrogen/natural gas fuel blends provide a logical passage to to the full hydrogen-powered vehicles. These vehicles can run on either fuel, depending on handiness

Proposal of Dissertation Essay Example | Topics and Well Written Essays - 1000 words

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Solar Panel Battery Charger 6-12V - Research Paper Example The comparator compares the voltage from the battery and acts as a switch for the voltage regulator circuit. Finally, the battery voltage checker checks the voltage of the battery (as it received from the panel) to determine if the battery needs to charge more. The circuit is designed to be simple, efficient and reliable by using easily available field replaceable parts. It uses a 12V, 5W solar panel rated from 100 milliamps to 1A and a lead acid or other rechargeable battery that is rated from 500 milliamp hours to 40 amp hours of capacity. This circuit regulates the voltage flow from the photovoltaic panel to the lead acid battery. It can produce currents up to 150mA. When external pass transistors are added to this circuit, output currents can reach up to 10A. The maximum input voltage to this circuit is 40V (LM723, 2004) with an output voltage adjustable between 2V and 37V. This circuit consists of a series regulator, LM723. ... Figure 11 and Figure 12 are the connection diagram and the datasheet circuit (Voltage regulator, 2012) as below: Figure 11: Connection Diagram Figure 12: Datasheet Circuit The basic building blocks of LM723 are: 1 The Reference Voltage Amplifier 2 The Error Amplifier 3 The Series Pass Transistor. The equivalent circuit of LM723 (LM723/LM723C Voltage Regulator, 1994) is shown in Figure 13 as below: Figure 13: Equivalent circuit of LM723. The main components used in the voltage regulator circuit are (Table 1): Table 1: Main components of the voltage regulator circuit Quantity Component Value 1 LM723 - 1 R1 4.87k ? 1 R2 7.15k ? 2 Transistor 2N3055 1 Diode 1N4007 1 VR 10k ? 1 C1 0.1?F 1 C2 500PF Calculations: Following are the calculations for design and operation of the circuit: Output voltage- Vout = Vref x ((R1+R2)/R2) Where R1= 4.87K, R2= 7.15K and Vref= 7.35V from the datasheet. Vout= 7.35 x ((4.87 + 7.15)/7.15) = 12.36V. Figure 14: Output voltage. Current- The current is establishe d from the Darlington transistor pair in the regulator circuit (Q1 and Q2 in Figure 10). Q1 and Q2 (2N3055) are silicon, Epitaxial-Base Planar NPN transistor mounted in a Jedec TO-3 metal case (Charger Circuit for 6V or 12V Car Battery, 2012) and are recommended for use in power switching circuits, series and shunt regulators, output stages and high fidelity amplifiers. Figure 15 shows the Darlington transistor pair: Figure 15: Darlington transistor pair used in voltage regulator circuit. In this circuit, a voltage of 0.7V is applied to the base (B) of the first transistor (TR1) to switch it on. A current of 300 milliamps passes through the first transistor from the collector (C) to the Emitter (E). The emitter of TR1 is connected to the second

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Legal Environment Surrounding Sale and Purchase of Goods - Essay Example According to Crose & Miller (2011), in any legal undertaking it is good to understand about what is legally right and what is legally wrong in any kind of legal issue. Therefore, it is advisable that Winston understand where his rights were infringed and where he might have failed during contract signing so that he can lay out a base for his legal arguments. This would enhance his chances of winning the case and thus enabling him to obtain compensation. As a plaintiff in this case he also need to understand the courts that will be involved if the case reaches litigation stage and the procedures involved in this stage so that he can prepare adequately. This paper plays a very significant role in explaining these issues and thus it would be of great assistance to Winston. Any kind of legal environment or undertaking is influenced by various factors. According to Meiners et al (2011), some of the factors that influence the legal environment are the needs and demands of the business comm unity, consumers, and the government. In this paper, we start by explaining the issues surrounding these factors. These issues are like the difference between express and implied terms, sales of goods act, difference between consumer and non-consumer sales, and process and procedures involved in the litigation stage of a case. ... These terms are rigid and cannot change to implied term whatever the case that interpret them. They also do not have further categories and we cannot have very many of them in a contract. However, each contract must have several of those terms clearly understood by both parties before signing. All other terms found in a contract, which are not express term, are regarded as implied terms. Unlike the express terms, these terms are subdivided to those implied primarily by factual circumstances of the agreements and those implied primarily by the law (Klass 2010). Also unlike the express terms, the terms implied by the factual circumstances of the agreement can change to express terms depending on the situation that interpret them. They are also found in larger number in any form of a contract. However, these two terms have one similarity, which is that they have to be included in any form of a contract and each party must read and understand them before signing the contract. According t o Klass (2010), when interpreting a contract, a court gives more priorities to express terms as compared to implied terms. This is merely because of their characteristics and their ability to explain the contract and the situation in which the contract was made. The express terms can also reveal some of the factors that made either of the parties to sign the contract. Therefore when signing any form of a contract one should be very careful with the express terms because they can play a very great part in making a case ruled to your advantage in case of any dispute arising from the contract. Sales of goods act The sales of goods act deals mainly with the sales contract