Current Concept And Machanisms In The Pathogenesis Of Atherosclerosis Essay Example

Current Concept And Machanisms In The Pathogenesis Of Atherosclerosis Paper Atherosclerosis is the leading cause of death and disability in the developed world. Despite our familiarity with the disease, some of its fundamental characteristics remain poorly recognized and understood. Although many generalized or systemic risk factors predispose to its development, atherosclerosis affects various regions of the circulation preferentially and yields distinct clinical manifestations depending on the particular circulatory bed affected. Atherosclerosis of the coronary arteries commonly causes myocardial infarction and angina pectoris. Atherosclerosis of the arteries supplying the central nervous system frequently provokes strokes and transient cerebral ischemia. In the peripheral circulation, atherosclerosis causes intermittent claudication and gangrene and can jeopardize limb viability. Involvement of the splanchnic circulation can cause mesenteric ischemia. Atherosclerosis can affect the kidneys either directly (e. g. , renal artery stenosis) or as a frequent site of atheroembolic disease. Even with in a given arterial bed, atherosclerosis tends to occur focally, typically in certain predisposed regions. In the coronary circulation, for example, the proximal left anterior descending coronary artery exhibits a particular predilection for developing atherosclerotic occlusive disease. Likewise atherosclerosis preferentially affects the proximal portions of the renal arteries and in the extracranial circulation to the brain, the carotid bifurcation. We will write a custom essay sample on Current Concept And Machanisms In The Pathogenesis Of Atherosclerosis specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Current Concept And Machanisms In The Pathogenesis Of Atherosclerosis specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Current Concept And Machanisms In The Pathogenesis Of Atherosclerosis specifically for you FOR ONLY $16.38 $13.9/page Hire Writer Indeed, atherosclerosis lesions often form at branching points of arteries, regions of disturbed blood flow. Not all manifestations of atherosclerosis result from stenotic, occlusive disease. Ectasia and development of aneurismal disease, for example, frequently occur in the aorta. The mechanisms that underlie this discontinuous anatomic distribution of atherosclerosis remain uncertain. (Rodney A. White, White A. , Ramadan Shaafi, White A. White, 1989) Atherosclerosis manifests itself focally not only in space, as just described, but in time as well. Atherogenesis in humans typically occurs over a period of many years, usually many decades. Growth of atherosclerotic plaques probably does not occur in a smooth linear fashion, but rather discontinuously, with periods of relative quiescence punctuated by periods of rapid evolution. After a generally prolonged silent period, atherosclerosis may become clinically manifest. The clinical expressions of atherosclerosis may be chronic, as in the development of stable, effort-induced angina pectoris or of predictable and reproducible intermittent claudication. Alternatively, a much more dramatic acute clinical event such as myocardial infarction, a cerebrovascular accident, or sudden cardiac death may first herald the presence of atherosclerosis. Other individuals may never experience clinical manifestations of arterial disease despite the presence of widespread atherosclerosis demonstrated post mortem. INITIATION OF ATHEROSCLEROSIS FATTY STREAK FORMATION An integrated view of experimental results in animal and study of human atherosclerosis suggests that the fatty streak represents the initial lesion of atherosclerosis. The formation of these early lesions of atherosclerosis most often seems to arise from focal increases in the content of lipo-protein within regions of the intima. These accumulations of lipoprotein particles may not result simply from an increased permeability or leakiness of the over lining endothelium. Rather this lipoprotein may collect in the intima of arteries because they bind to constituent of the extracellular matrix, increasing the residence time of the lipid- rich particles within the arterial wall. Lipoproteins that accumulate in the extra cellular space of the intima of arteries often associate with proteoglycan molecules of the arterial extracellular matrix, an interaction that may promote the retention of lipoproteins by binding them and slowing their egress from the intima. (James S. C. Gilchrist, Paramjit S. (EDT) Tappia, Thomas (EDT) Netticadan, 2003) Lipoprotein particles in the extracellular space of the intima particularly those born to matrix macromolecules, may undergo chemical modification. Accumulating evidence supports a pathogenic role for such modifications of lipoproteins in atherogenesis. Two types of such alterations in lipoproteins bear particular interest in the context of understanding how risk factors actually promote atherogenesis: oxidation and nonenzymatic glycation. Lipoprotein Oxidation Lipoprotein sequested from plasma antioxidants in the extracellular space of the intima become susceptible to oxidative modification. Oxidatively modified low density lipoprotein (LDL), rather than being defined homogerous entity, actually comprises a variable and incompletely defined mixture. Both the lipid and protein moieties of these particles cab participate in oxidative modification. Modifications of the lipids may include formation of hydroperoxides, lysophospholipids, oxysterols, and aldehydic breakdown products of fatty acids. Modifications of the apoprotein moieties may include breaks in the peptide backbone as well as derivatization of certain amino acid residues. A more recently recognized modification may result from local hypochlorous acid production by inflammatory cells within the plaques, giving rise to chlorinated species such as chlorotyrosyl moieties. Considerable evidence supports the presence of such oxidation products in atherosclerotic lesions. Nonenzymatic Glycation In diabetic patients with sustained hyperglycemia, nonenzymatic glycation of apolipoproteins and other arterial proteins likely occurs that may alter their function and propensity to accelerate atherogenesis. A good deal of experimental work suggests that both oxidatively modified and glycated lipoproteins or their constituents can contribute to many of the subsequent cellular events of lesion development. LEUKOCYTE RECRUITMENT After the accumulation of extracellular lipids, recruitment of leukocyte occurs as a second step in the formation of the fatty streak. The white blood cells types typically found in the evolving atheroma include primarily cells of the mononuclear lineage; monocytes and lymphocytes. A number of adhesion molecules or receptor for leukocyte expressed on the surface of the arterial endothelial cell likely participitate in the recruitment of leukocyte to the nascent fatty streak. Constituent of oxidatively modified LDL can augment expression of leukocyte adhesion molecule. This example of illustrate how the accumulation of lipoprotein in the arterial intima may link mechanistically with leukocyte recruitment and subsequent events in the lesion formation. (Pierre-Jean Touboul, J. R. Crouse, 1997) Laminar shear forces such as those encountered in most regions of normal artery can also suppress of the expression of leukocyte adhesion, example branch points often have disturbed laminar flow. Ordered laminar shear of normal blood flow augments the production of nitric oxide by endothelial cells. This molecule in addition to its vasodilator properties can act at the low levels constitutively produced by arterial endothelium as a local anti-inflammatory autacoid, for example limiting local adhesion molecule expression. These examples indicate how hemodynamic forces may influence the cellular that underlie atherosclerotic lesion initiation and provide a potential explanation for the local distribution of atherosclerotic lesions at certain sites predetermined by altered flow pattern. Once adherent to the surface of the surface of the arterial endothelial cell via interaction with adhesion receptors, the monocytes and lymphocytes penetrates the endothelial layer and take out residence in the intima in addition to products of modified lipoprotein, cytokines can regulate the expression of adhesion molecules involved in the leukocyte recruitment. For example, the cytokines interlukin one (IL-1) or tumor necrosis factor alpha (TNF-alpha) induce or augment the expression of leukocyte adhesion molecules on endothelial cells. Because modified lipoprotein can induce cytokines release from vascular wall cells, this pathway may provide an additional link between accumulation and modification of lipoprotein and leukocyte recruitment. The directed migration of leukocyte into the arterial wall may also result from the action of modified lipoprotein. For example, oxidized LDL may promote the chemotaxis of leukocyte. Also, oxidatively modified lipoprotein can elicit the production by vascular wall cells of chemoattractant cytokines such as monocytes chemoattractant protein-1. (Frank Kessel, Patricia L. Rosenfield, Norman B. Anderson, 2003) FOAM CELL FORMATION Once resident within the intima the mononuclear phagocyte differentiate into macrophages and transform into lipid-laden foam cells. The conversion of mononuclear phagocytes into foam cells requires the uptake of lipoprotein particles by receptomediated endocytosis. One might suppose that the well recognized classical receptor for LDL mediated the lipid uptake. Patients or animals lacking effective LDL receptors due to genetic alterations however have abundant arterial lesions and extraarterial xanthomata rich in macrophage derived foam cells. Also the exogenous cholesterol suppresses expression of the LDL receptor, such that under hypercholesterolemic conditions the level of this cell surface receptor for LDL decreased. Candidates for alternative receptors that can mediate lipid-loading of foam cells include a growing number of macrophage scavenger receptors, which preferentially endocytose modified lipoproteins and other receptors for oxidized LDL or beta-VLDL (very low density lipoprotein) a type of lipoprotein commonly encountered in certain hypercholerterolemic states. By ingesting lipids from the extracellular space the mononuclear phagocytes bearing such scavenger receptors may remove lipoproteins from the developing lesion. Some lipid loaded macrophages may leave the artery wall, functioning to clear lipid from the artery. Lipid accumulation and hence propensity to form atheroma, ensues if the amount of lipid entering the artery wall exceeds that exported by mononuclear phagocytes or other pathways. Macrophages may thus play a vital role in the dynamic economy of lipid accumulation in the arterial wall during atherogenesis. Some lipid laden foam cells within the expanding intimal lesion perish. Some foam cells may die as a result of programmed cell death known as apoptosis. This death of mononuclear phagocytes results in formation of the lipid rich center often called necrotic core, of more complicated atherosclerotic plaques. (Shari R. Waldstein, Merrill E Elias, 2001) Macrophages taking up modified lipoproteins much like intrinsic vascular wall cells may elaborate cytokines and growth factors that can further signal some of the cellular events in lesion complication. A number of growth factors or cytokines elaborated by mononuclear phagocytes can stimulate smooth-muscle cell proliferation and production of extracellular matrix, which accumulates in atherosclerotic plaques. Cytokines found in the plaque including IL-1 or TNF – alpha can induce local production of growth factors such as forms of platelet derived growth factor (PDGF), fibroblast growth factor and others that may contribute to plaque evolution and complication. Other cytokines, notably interferon gamma (IFN-gamma) derived from activated T cells within lesions can inhibit smooth muscle proliferation and synthesis of interstitial forms of collagen. These examples illustrate how atherogenesis likely depends on a complex balance between mediators that can promote lesion formation and other pathways that can mitigate the atherogenic process. (Aron Wolfe Siegman, Timothy W. Smith, 1994) FACTORS THAT MODULATE INHIBITATION OF ATHEROMA Elaboration of small molecules by activated mononuclear phagocytes and vascular wall cells in the evolving lesion may also modulate atherogenesis. Notably reactive oxygen species can modulate growth of smooth muscle cells, activate inflammatory gene expression via the nuclear factor kappa beta (NFk beta) transcriptional control system and annihilate NO radicals, decreasing the effect of this endogenous vasodilator. However macrophage in the lesion may be activated to express the inducible form of the enzyme that can synthesize NO, known as inducible NO synthase. This high capacity form of the enzyme can produce relatively large, potentially cytotoxic amounts of No radicals. While at the low concentrations of NO produced by the constitutive NO synthase in endothelial cells, this radical may produce beneficial effects; when overproduced by activated phagocytes, however it may prove deleterious. Export by phagocytes may constitute one response to local lipid overload in the evolving lesion. Another mechanism, reverse cholesterol transport mediated by high density lipoproteins (HDL), may provide an independent pathway for lipid removal from atheroma. This transfer of cholesterol from the cell to HDL particle involves specialized cell surface molecules such as the ATP binding cassette transporter (ABCA1) (the gene mutated in tangier disease, a condition characterized by very low HDL levels) and a family of scavenger receptors (the B family). Such reverse cholesterol transport explains part of HDL’s antiatherogenic action. (Richard O. Cannon, Julio A. Panza, 1999) Although clear evidence supports lipoprotein disorder as predisposing factors for atheroma formation, other etiologies may contribute to or modulate atherogenesis. For example hypertension constitutes an independent risk factor for coronary events. Male gender and the postmenopausal state also augment the risk of developing coronary artery disease. Premenopausal women have increased HDL levels compared to age matched men. However a favorable lipoprotein pattern only partially accounts for the protection against atherosclerosis conferred by the premenopausal state. Although laboratory studies suggest that estrogens have direct beneficial effects on the arterial wall, clinical trials have not shown that estrogen replacement therapy prevents recurrent myocardial infarction in postmenopausal women. Indeed treatment with a combination of estrogen and progesterone appears to augment cardiovascular events in women with or without prior myocardial infarction. (Susan Wilansky, James T. Willerson, 2002) Diabetes mellitus aggravates atherogenesis. In addition to the well known microvascular complications of diabetes, macrovascular disease such as atherosclerosis causes a great deal of excess mortality in the diabetic population. Diabetes associated dyslipidemias strongly promote atherogenesis. In particular the constellation of insulin resistance, high triglycerides and low HDL often in association with the central adiposity and hypertension frequently seen in type 2 diabetic patients, seems to accelerate atherogenesis potently. As noted above hyperglycemia may promote the nonenzymatic glycation of LDL, LDL modified in this manner, like oxidatively modified LDL, may signal many of the initial events in atherogenesis. Triglyceriderich lipoprotein particles often elevated in poorly controlled diabetic patients also accentuate atherogenesis. Lp(a) (often pronounced lipoprotein little a to distinguish it from apolipoprotein AI and others found in HDL) provides a potential link between hemostasis and blood lipids. The Lp(a) particle consists of an apoprotein (a) molecule bound by a sulfhydryl link to the apolipoprotein B moiety of an LDL particle. Apoprotein (a) has homology with plasminogen and may inhibit fibrinolysis by competing with plasminogen. Other risk factors for atherosclerosis related to blood clotting include elevated levels of fibrinogen or of the inhibitor of fibrinolysis, plasminogen – activator inhibitor 1 (PAI-1). Another nonlipid risk factor for coronary events, elevated levels of homocysteine, may act by promoting thrombosis, although the pathophysiology of this association is uncertain at present. Although individuals with marked elevations of Lp(a) or homocysteine do appear to have heightened risk of coronary thrombosis, in the population at large these factors show a much weaker correlation with vascular events than LDL, HDL, or the global inflammatory marker C-reactive protein (CRP). (Philip M. McCabe, Neil Schneiderman, Tiffany Field, A. Rodney Wellens, 2002) The relationship between tobacco use and atherosclerosis also remains poorly understood. The rapid reduction in risk for cardiac events after cessation of cigarette smoking implies that tobacco may promote thrombosis or some other determinant of plaque stability as well as contribute to the evolution of the atherosclerotic lesion itself. For example tobacco smokers have elevated fibrinogen levels a variable associated with increased atherosclerosis and acute cardiovascular events. INFLAMMATION In other situations, antecedent inflammatory states may predispose toward atherosclerosis. For example Kawasaki disease in childhood may promote developments of vascular lesions in the arteries of adults. Infectious agents continue to be proposed as instigators or potentiators of atherogenesis. However in humans atherogenic role for vital or microbial pathogens remains speculative. In some patients immune or autoimmune reactions may contribute to atherogenesis. In the particular example of the accelerated form of coronary arteriopathy that plagues heart transplant recipients, immunologic factors may contribute importantly to the pathogenesis. (James Shepherd, Sheperd and Gaw, Allan Gaw, 2001) Known monogenic defects in lipoprotein metabolism account for only a fraction of the familial risk for coronary artery disease. Thus other as yet undefined and perhaps multiple genetic factors may contribute to coronary risk. Mechanisms of disease susceptibility involving the arterial wall might account for some of the genetic predisposition to atherosclerosis unexplained by lipoprotein disorders. Application of molecular genetic techniques may identify new polymorphisms linked to coronary risk and may eventually shed light on new pathophysiologic mechanisms. For example some data suggest a link between certain alleles of the genes encoding angiotensin converting enzyme, the cytokine lymphotoxin, or PAI-1 with increased risk of myocardial infarction. Application of genomic technologies may aid identification of modifier genes that modulate individual responses to established risk factors. Large studies currently in progress should clarify these and other potential genetic factors that influence atherosclerosis. REFERENCES: Aron Wolfe Siegman, Timothy W. Smith, 1994. Anger, Hostility, and the Heart; Lawrence Erlbaum Associates Frank Kessel, Patricia L. Rosenfield, Norman B. Anderson, 2003. Expanding the Boundaries of Health and Social Science: Case Studies in Interdisciplinary Innovation; Oxford University Press James Shepherd, Sheperd and Gaw, Allan Gaw, 2001. Lipids and Atherosclerosis; Taylor Francis James S. C. Gilchrist, Paramjit S. (EDT) Tappia, Thomas (EDT) Netticadan, 2003. Biochemistry of Diabetes and Atherosclerosis; Springer Philip M. McCabe, Neil Schneiderman, Tiffany Field, A. Rodney Wellens, 2002. Stress, Coping, and Cardiovascular Disease; Lawrence Erlbaum Associates Pierre-Jean Touboul, J. R. Crouse, 1997. Intima-Media Thickness and Atherosclerosis: Predicting the Risk? ; Taylor Francis Richard O. Cannon, Julio A. Panza, 1999. Endothelium, Nitric Oxide, and Atherosclerosis: From Basic Mechanisms to Clinical Implications; Blackwell Publishing Rodney A. White, White A. , Ramadan Shaafi, White A. White, 1989. Atherosclerosis and Arteriosclerosis: human pathology and experimental animal methods and models; CRC Press Shari R. Waldstein, Merrill E Elias, 2001. Neuropsychology of Cardiovascular Disease; Lawrence Erlbaum Associates Susan Wilansky, James T. Willerson, 2002. Heart Disease in Women; Churchill Livingstone

Criminal Prosecution of Managers as a Weapon against Corporate Crime essays

Criminal Prosecution of Managers as a Weapon against Corporate Crime essays Which laws are broken in the current cases at issue' Recently, a number of headline-grabbing cases, such as the accounting fraud that existed at the Enron Corporation, have highlighted the role of management at various corporations and in the financial industry, in the commission of corporate crime. The role of accountants and the major corporate accounting firms, as well as the chief financial advisors of corporations and the management personnel whom may or may not be aware of illegal accounting activities, are now under strict scrutiny by the SEC. The Securities and Exchange Commission has attempted to become more vigilant in policing and prosecuting illegal activities in recent years. (Asarita, 2002). It is illegal for companies to release fraudulent or even misleading information regarding their company's performance. (Chartier, 2002) However, to a certain extent, these companies state that their managerial, non-accounting staff must trust' what the expert accountants sayafter all, that's why the accountants are considered the experts. However, it is also alleged that managers can pressure their accountants to release fraudulent information, which is illegal. But it is difficult to prove that managers or CEOs knew that this information was fraudulent, or pressured accountants to do so after the fact. Often, the pressure process is so subtle, the SEC has difficulty knowing who knew when, and who said what. Thus, a legal Gordian knot results that is Last year, the number of accounting fraud cases investigated by the Securities and Exchange Commission jumped forty-one percent, according to agency data, resulting in tens of millions of dollars in fines upon the offending companies to settle the charges. This jump is largely attributed, not simply to more creative forensic accounting techniques in discovering illegal accounting meas...

Legal Reasoning and Writing Essay Example | Topics and Well Written Essays - 500 words

Legal Reasoning and Writing - Essay Example ublic’s interest and recognizes states’ legislative authority that the courts would uphold based on the precedent that the case of Jacobson v Massachusetts’ (1905) set. Facts to the case identify an epidemic, viral gastroenteritis, in the nation, which is also significant in the capital of South Caledonia. There has been a series of the viral infection that affects groups such as people in schools, apartment complexes, and has been reported in large emergency shelters. Viral gastroenteritis causes fever, abdominal pain, nausea, vomiting, and diarrhea, and affects people by limiting their ability to go to work when they are sick or by forcing people to stay at home to take care of the infection’s victims. There are however only few cases of hospitalization and two reported fatalities. A vaccine was developed a year ago and the FDA approved it for its proven effectiveness and limited adverse effects that is only realized as a sore at the point of injection. State Legislature of South Caledonia then passed a law requiring all people to receive vaccination with a fine of $ 750 for non-compliance unless a person receives state approval for exempt ion. Even though Mr. Russell does not qualify for exemption under the statute, he does not wish to apply for exemption and does not want to receive vaccination. Instead, he wishes to sue the state for protection of his liberty. The constitution, statutes, and case laws are some of the sources of law for guiding judicial decisions and the case of Jacobson v Massachusetts (1905) offers a basis for interpreting conflicting provisions of the constitution and the statute of South Caledonia. While the constitution provides for protection of individuals rights and liberty, Fourteenth Amendment, it also restricts such rights based on rights of other citizens, the Ninth Amendment, and grants states legislative power (Schultz, 2009). The facts of the Jacobson v Massachusetts’ case in which Jacobson declined to receive

Compare and contrast the processes of democratisation in [country X] Essay

Compare and contrast the processes of democratisation in [country X] and [country Y] - Essay Example emocratization was initiated in both the countries soon after and the cessation of Latvia from the Soviet Union and the voluntary change in the Bulgarian monopolistic Communist party’s ideology. Now, after almost twenty years of the democratic process, both the countries are part of the European Union, a fact indicative of their progress and success in making social and political changes. The current paper aims to analyze the process of democratization in the two countries, Latvia and Bulgaria, and to compare and contrast them on their achievements towards the same. The theoretical frameworks employed by scholars in studying the process of democratization largely fall into two categories. The first approach, called the functionalist approach, proposes that the process of democracy is brought about as a result of economic or cultural development or ushered in simply by the changing times and modernization. Another approach, called the genetic view, that is employed in studying the process of democratization is to assess the involvement of political thinkers and leaders who have contributed in bringing about a change in political thought and practice. (Vanhanen and Pridham, 1994). The present paper aims to combine both the functional as well as the genetic approach in studying and comparing the process of democratization in two Eastern European nations – Latvia and Bulgaria. In order to compare and contrast the process of democratization in the Latvia and Bulgaria, it is necessary to study the historical factors that were responsible for the process to set in as well as understand the structural changes, the social and political struggles and changes that led to the evolution of a democratic electoral system in the two countries. Democratization in the Eastern European nations was influenced by both external and internal factors. (Vanhanen and Pridham, 1994). The external factors like the reforms already started in the Soviet Union by Gorbachev and the

Central Concerns in John Thompsons Political Scandal Essay

Central Concerns in John Thompsons Political Scandal - Essay Example This is because there was no perception of accountability to the public in many societies in the past. Moreover the dissemination of scandals far and wide, and as frequently as is possible, is made possible by the development of a plethora of media now available. This has resulted in lots of unearthing of covert actions of people in power. There are some people who look at the media coverage of scandals as a form of entertainment available to the people. However many consider the role of media as that of vigilant watch dog that unearths the wrongs in society and brings remedial action and plugs in all loopholes that encourage public figures to circumvent regulations and act in their private interest. Many recent books have come out on this subject and John Thompson's book, Political Scandal has made a significant contribution to the ongoing debate on the subject by an analysis of public scandals as churned out by the media and its effect on accountability of high ranking public figures, the effect of this on the erosion of credibility associated with their office and a host of other illuminating aspects of the problem. Thompson considers political scandals as violations of prescribed process and transgressions of regulations, which have been incorporated, in the democratic system as a measure to avoid misuse or check the deviation to unilateral action by a person who has a public responsibility. After the media has gained such significance as tools that can form the attitudes of people and influence the way they cast the vote, there has been a conscious attempt to throw the weight of the media in competitive politics. Thomson sees the reputation of the individual politician as the key asset that will determine his edge over his opponent in the process of election. The media is on the look out for transgressions committed by an individual as a matter of priority in its reporting due to various reasons. While some media report these transgressions merely to enhance their readership or viewer ship others may be committed to their role as watchdog Page 3 in a healthy democracy. In addition to this, in competitive politics, the motive may be to tarnish the reputation of the opponent by constant bombardment of the opponent by targeting weakest points. In this tendency Thompson sees the dangers of dragging political non-issues related to the personal conduct of public figures into vortex of media reporting. In many democracies, including some of the old and celebrated ones, the narrow-minded struggle for power heavily draws on the repertoire of sex scandals real or concocted to deal a deathblow to the reputation of the other. The mud slinging campaigns and personal vituperation that appear so blatantly in the media, Thompson, warns will undermine the social trust of the democratic system (p.251). The exposure of political scandals if undertaken responsibly, Thompson believes, can strengthen the democratic institutions. What he calls power scandals are those that contravene or seek to circumvent the rules, laws and established procedures that govern the exercise of political power (P.196). In a democratic set up power is to be exercised openly and the role of the media as a watchdog makes the exercise of the power an openly done task and hence accountable. However Thompson does not think

The Design of a Voltmeter-Ammeter Using PIC Microcontroller

The Design of a Voltmeter-Ammeter Using PIC Microcontroller In electrical or electronic engineering, the voltmeter and ammeter are important devices and are used to measure current and voltage. These devices are very important as they give you an understanding of what is happening in an electrical or electronic circuit. Without these devices we wouldnt be able to determine numerical values of voltage and current therefore we wouldnt have the ability to solve electrical problems. The main objective of this project is to gain experience with the design process covering all aspects of the design process. Two software packages will be used to orchestrate the design process of the circuit and complete build of the project. These packages are OrCAD PCB Editor and Auto-Cad Inventor. This will entail everything from the designing and building of the circuit, using the software package OrCAD PCB Editor the design process will begin designing the circuit by applying all the necessary components for the Volt-Ammeter. The circuit will be built using a PIC microcontroller with a built in LCD screen which will illuminate the voltage and current readings. The second stage will be using the design package AutoCAD Inventor. This is a design software that is used to design the casing of the product with all the specifications needed to give the product the compact finish needed to complete the product before presenting it to the customer. A volt-ammeter is the project designed for Napier University so the students can benefit from an easy to use product having the ability to test, measure and do calculations when measuring voltage and current. The finished product must have certain specifications which will make the device portable, easy to use and compact and also making the device durable so the students can use the device safely without encountering any problems or difficulties. The budget for the project has to be under  £40 per unit so the university can benefit from the finished designed product. 1.2.1 Functionality Electrical measurement devices are used to digitally calculate electrical quantities. Two of the more common quantities are voltage and current. A volt-ammeter is perfect as an addition to any electronic projects like battery chargers or power supplies where it is a necessity to monitor current and voltage consumption. Regarding this project, a PIC16F876A microcontroller will be used to interface the LCD screen. 1.2.2 Engineering requirements The volt-ammeter device will be designed to measure an output voltage ranging from  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   0-70v/0-500V with a resolution of 100mV which will be carrying a current between 0-10A with a resolution of 10mA. The volt-ammeter will have a step up and step down button for added calibration to make it possible to measure voltages over 70V and to measure current over 10A. A PIC 16F876A microcontroller will be used in the volt-ammeter. The microcontroller will have a built in analogue to digital controller with a blue/green illuminated LCD display. Voltage Supply 6V-30V Voltage Input 0-70V / 0-500V Voltage Resolution 100 mV Current Consumption 100mA LCD Backlight Current Input 0-10A (or more) Current Resolution mA Figure 1- performance table 1.2.3 Additional Specifications Because the Volt-Ammeter is designed with very few External components it will be made possible to meet the specifications fitting all the components onto a small PCB making it possible for the finished product to be a very handy and portable meter. The meter will be able to produce readings that are accurate, this is due to the calibrated software that is built in and additionally the 1%metal film resistors. There is only one supply voltage needed and this can be acquired by using any mains power supply. The completed meter will only consume 10mA from the backlight of the LCD screen when switched on and 3mA when not in use. When the 10 Ohm resistor is disconnected the backlight of the LCD display will be switched off   Ã‚   Figure 2 external components 1.2.5 Casing Specifications The casing needs to be compact so it can be hand held for ease of use. Compact with all wires concealed to illustrate a safe finished product. Waterproof for protection from electrocution and to prevent damage to components. Additional fittings for PCB placement. LCD Screen placement on front of casing. (central) CMOS FLASH-based 8-bit microcontroller. Performance speed of 200 Nano Seconds. Flash Program Memory. Program Memory 14 KB. 368 RAM Bytes. 2 x 8-bit, 1 x 16-bit Timers. Analogue to Digital Converter- 5 channel, 10-bit. 2 Comparators. Temperature Range -40 to 125 degrees Celsius. Figure 3 PIC Microcontroller 2.1.1 Voltmeter when measuring voltage between two points in an electrical or electronic circuit a certain device must be used. This device is a voltmeter and is intended to measure either direct current (DC) or alternating current (AC). There are two types of voltmeter, these devices are either analogue voltmeters or digital voltmeters. The analogue meter has a current meter in series with a high resistance. This high resistance is needed otherwise the circuit being tested will be disturbed due to a significant amount of current being drawn. A digital voltmeter displays numerical values; these values can range of 1000v to 3000v and can increase in powers of 10. 2.1.2 Ammeter An ammeter is the instrument needed to measure electrical current that flows through a circuit. The ampere or amp is the unit of measure for current. Conclusion The writing and design of this project has been made possible due to the applied theories and practical skills that I have learnt and administered in integrated circuit design. The knowledge I have gained has given me the skills to produce design and construct operating systems that are capable of performing practical tasks. Because of these skills it has given me the confidence to write design and produce this project which is titled The Design of a Volt-Ammeter using PIC microcontroller. http://pic-microcontroller.com/voltmeter-ammeter-using-pic-microcontroller/ http://www.microchip.com/wwwproducts/en/PIC16F876A http://whatis.techtarget.com/definition/voltmeter http://study.com/academy/lesson/what-is-an-ammeter-definition-function-quiz.html

James Dickey All American Poet Essay -- essays papers

James Dickey All American Poet James Dickey was an American Poet whose life has been very diverse, and in his poetry that diversity is shown. He has a lifestyle that most poets do not get to experience. He has lived in many states and countries. That gives me the reason to think that his poetry resembles this life’s diversity. James Lafayette Dickey, III was born in the town of Atlanta, Georgia on February 2, 1923. His parents were Maibelle and Eugene Dickey. He went to Ed S. Cook Elementary School and North Fulton High School as a kid, both of which are in Atlanta. He was athletic as a child. He played football and track, but his football career led him to a scholarship at the University of Clemson, in Clemson, South Carolina. But, before he went off to college he spent one year at the Darlington School in Rome, Georgia for one year in preparation for a college. He didn’t last longer than a year in Clemson though because he enlisted into the Army Air Corps. He served in WWII as a flight radar observer and navigator. After serving in the army he went to school at Vanderbilt University in Tennessee. He went there on the G. I. Bill. After graduating from Vanderbilt with a M. A. in English, he started to teach. He taught first at the Rice Institute in Houston, Texas. His time there was cut short because he was recalled to duty in Korea as flight training instructor. But as soon as he was discharged from the Corps he returned to teach again at Rice University. He taught at Rice until 1954 when he left to go to Europe on the Sewanee Review fellowship. After returning to the U.S. he joined the English Department at the University of Florida. He did not stay there long because he resigned after a dispute after he h... ...veryone else. He wakes up every day ready to crow his symbol to bring on that day. In the poem he is ready to protect all the female chickens, from another cock that could be in there house. He is ready to battle to the death for what he thinks is his. In this poem he uses ridicule, when he is talking about the old man in a terminal ward, and he also uses connotations. Some example of connotations are when he uses words like; enraged, sullenly, savagery, unappeased and terminal. The life of James Dickey was very diverse and involved many different people. His poetry showed this diversity in many ways too. He has over 2,000 poems, all of which have different genres and different places they have came from. Some of which could have been from past jobs, and others could have been from his past places of residence. That is why he was a very popular poet for his time.