The History of Computers :: Technology Technological Computers Essays

The History of Computers The idea of a machine that would make man’s calculations easier, faster, and more accurate is no new notion. The Abacus, â€Å"Napier’s rods†, the â€Å"Calculating Clock†, and the â€Å"Stepped Reckoner† are a few examples of early computer ideas In the more recent history of the computer, we can see how computers have morphed (or dwarfed) from clunky, million-dollar machines into the compact and convenient parts of our everyday lives (Computer Science Student Resource Website, 2003, â€Å"Evolution of Computers: From Stone to Silicon†, Section 1). The Academic Press Dictionary of Science and Technology informs us that John von Neumann’s name is most well-known among the potential â€Å"founders† of the first computer, but to whom the credit belongs can be debated†¦von Neumann wrote a memorandum explaining the ENIAC, and thus his name is recorded (Academic Press, 2002, Section 2, â€Å"Historical Perspective†). The ENIAC (the Electronic Numerical Integrator and Calculator) was developed by J. Preper Eckert and John Mauchly of the Moore School of the University of Pennsylvania in the mid-1940s. The credit for this â€Å"invention† is â€Å"shady† because Mauchly reportedly visited John Atanasoff before building the ENIAC. Atanasoff and his graduate student Berry built the Atanasoff/Berry Computer in the early 1940s at Iowa State University. At any rate, von Neumann’s name is the most well-known and thus settles the issue! The model von Neumann came up with for the basic computer structure is still today, with modifications for speed and size, the foundation for many computers (Academic Press, 2002, Section 1, p. 527). The Academic Press Dictionary states that von Neumann’s report was so well-received because it had incredible â€Å"focus on the logical principles and organization of the computer rather than on the electrical and electronic technology required for its implementation† (p. 527). As â€Å"Evolution: From Stone to Silicon† reports, the first computers were mechanical and used vacuum tubes. These tubes needed to be replaced constantly (Computer Science Student Resource Website, 2003, Section 3). The EDVAC (Electronic Discrete Variable Computer) invented in 1952 used magnetic tape, a revolution from the mess of wires that needed to be moved and replaced to run new programs.

Blood pressure Essay

Blood pressure (BP), sometimes referred to as arterial blood pressure, is the pressureexerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, â€Å"blood pressure† usually refers to thearterial pressure of the systemic circulation. During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.[1] The blood pressure in the circulation is principally due to the pumping action of the heart.[2] Differences in mean blood pressure are responsible for blood flow from one location to another in the circulation. The rate of mean blood flow depends on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as the circulating blood moves away from the heart through arteries and capillaries due to viscous losses of energy. Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries and arterioles.[3] Gravity affects blood pressure via hydrostatic forces (e.g., during standing) and valves in veins, breathing, and pumping from contraction of skeletal muscles also influence blood pressure in veins.[2] The measurement blood pressure without further specification usually refers to the systemic arterial pressure measured at a person’s upper arm and is a measure of the pressure in the brachial artery, major artery in the upper arm. A person’s blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimetres of mercury (mmHg), for example 120/80. The table on the right shows the classification of blood pressure adopted by the American Heart Association for adults who are 18 years and older.[4] It assumes the values are a result of averaging blood pressure readings measured at two or more visits to the doctor.[6][7] In the UK, blood pressures are usually categorised into three groups: low (90/60 or lower), high (140/90 or higher), and normal (values above 90/60 and below 130/80).[8][9] Normal range of blood pressure While average values for arterial pressure could be computed for any given population, there is often a large variation from person to person; arterial pressure also varies in individuals from moment to moment. Additionally, the average of any given population may have a questionable correlation with its general health; thus the relevance of such average values is equally questionable. However, in a study of 100 human subjects with no known history of hypertension, an average blood pressure of 112/64 mmHg was found,[10] which are currently classified as desirable or â€Å"normal† values. Normal values fluctuate through the 24-hour cycle, with highest readings in the afternoons and lowest readings at night.[11][12] Various factors, such as age and sex influence average values, influence a person’s average blood pressure and variations. In children, the normal ranges are lower than for adults and depend on height.[13] As adults age, systolic pressure tends to rise and diastolic tends to fall.[14] In the elderly, blood pressure tends to be above the normal adult range,[15] largely because of reduced flexibility of the arteries. Also, an individual’s blood pressure varies with exercise, emotional reactions, sleep, digestion and time of day. Differences between left and right arm blood pressure measurements tend to be random and average to nearly zero if enough measurements are taken. However, in a small percentage of cases there is a consistent difference greater than 10 mmHg which may need further investigation, e.g. for obstructive arterial disease.[16][17] The risk of cardiovascular disease increases progressively above 115/75 mmHg.[18] In the past, hypertension was only diagnosed if secondary signs of high arterial pressure were present, along with a prolonged high systolic pressure reading over several visits. Regarding hypotension, in practice blood pressure is considered too low only if noticeable symptoms are present.[5] Clinical trials demonstrate that people who maintain arterial pressures at the low end of these pressure ranges have much better long term cardiovascular health. The principal medical debate concerns the aggressiveness and relative value of methods used to lower pressures into this range for those who do not maintain such pressure on their own. Elevations, more commonly seen in older people, though often considered normal, are associated with increased morbidity and mortality. Physiology There are many physical factors that influence arterial pressure. Each of these may in turn be influenced by physiological factors, such as diet, exercise, disease, drugs or alcohol, stress, obesity, and so-forth.[20] Some physical factors are: †¢ Volume of fluid or blood volume, the amount of blood that is present in the body. The more blood present in the body, the higher the rate of blood return to the heart and the resulting cardiac output. There is some relationship between dietary salt intake and increased blood volume, potentially resulting in higher arterial pressure, though this varies with the individual and is highly dependent on autonomic nervous system response and the renin-angiotensin system.[21][22][23] †¢ Resistance. In the circulatory system, this is the resistance of the blood vessels. The higher the resistance, the higher the arterial pressure upstream from the resistance to blood flow. Resistance is related to vessel radius (the larger the radius, the lower the resistance), vessel length (the longer the vessel, the higher the resistance), blood viscosity, as well as the smoothness of the blood vessel walls. Smoothness is reduced by the build up of fatty deposits on the arterial walls. Substances called vasoconstrictors can reduce the size of blood vessels, thereby increasing blood pressure. Vasodilators (such as nitroglycerin) increase the size of blood vessels, thereby decreasing arterial pressure. Resistance, and its relation to volumetric flow rate (Q) and pressure difference between the two ends of a vessel are described by Poiseuille’s Law. †¢ Viscosity, or thickness of the fluid. If the blood gets thicker, the result is an increase in arterial pressure. Certain medical conditionscan change the viscosity of the blood. For instance, anemia (low red blood cell concentration), reduces viscosity, whereas increased red blood cell concentration increases viscosity. It had been thought that aspirin and related â€Å"blood thinner† drugs decreased the viscosity of blood, but instead studies found[24] that they act by reducing the tendency of the blood to clot. In practice, each individual’s autonomic nervous system responds to and regulates all these interacting factors so that, although the above issues are important, the actual arterial pressure response of a given individual varies widely because of both split-second and slow-moving responses of the nervous system and end organs. These responses are very effective in changing the variables and resulting blood pressure from moment to moment. Moreover, blood pressure is the result of cardiac output increased by peripheral resistance: blood pressure = cardiac output Xperipheral resistance. As a result, an abnormal change in blood pressure is often an indication of a problem affecting the heart’s output, the blood vessels’ resistance, or both. Thus, knowing the patient’s blood pressure is critical to assess any pathology related to output and resistance. Mean arterial pressure The mean arterial pressure (MAP) is the average over a cardiac cycle and is determined by the cardiac output (CO), systemic vascular resistance (SVR), and central venous pressure (CVP),[25] Curve of the arterial pressure during one cardiac cycle The up and down fluctuation of the arterial pressure results from the pulsatile nature of thecardiac output, i.e. the heartbeat. The pulse pressure is determined by the interaction of thestroke volume of the heart, compliance (ability to expand) of the aorta, and the resistance to flow in the arterial tree. By expanding under pressure, the aorta absorbs some of the force of the blood surge from the heart during a heartbeat. In this way, the pulse pressure is reduced from what it would be if the aorta wasn’t compliant.[26] The loss of arterial compliance that occurs with aging explains the elevated pulse pressures found in elderly patients. The pulse pressure can be simply calculated from the difference of the measured systolic and diastolic pressures,[26] Arm–leg gradient The arm–leg (blood pressure) gradient is the difference between the blood pressure measured in the arms and that measured in the legs. It is normally less than 10 mmHg,[27] but may be increased in e.g. coarctation of the aorta.[27] Vascular resistance The larger arteries, including all large enough to see without magnification, are conduits with low vascular resistance (assuming no advanced atherosclerotic changes) with high flow rates that generate only small drops in pressure. The smaller arteries and arterioles have higher resistance, and confer the main drop in blood pressure along the circulatory system. Vascular pressure wave Modern physiology developed the concept of the vascular pressure wave (VPW). This wave is created by the heart during the systoleand originates in the ascending aorta. Much faster than the stream of blood itself, it is then transported through the vessel walls to the peripheral arteries. There the pressure wave can be palpated as the peripheral pulse. As the wave is reflected at the peripheral veins, it runs back in a centripetal fashion. When the reflected wave meets the next outbound pressure wave, the pressure inside the vessel rises higher than the pressure in the aorta. This concept explains why the arterial pressure inside the peripheral arteries of the legs and arms is higher than the arterial pressure in the aorta,[28][29][30] and in turn for the higher pressures seen at the ankle compared to the arm with normal ankle brachial pressure index values. Regulation The endogenous regulation of arterial pressure is not completely understood, but the following mechanisms of regulating arterial pressure have been well-characterized: †¢ Baroreceptor reflex: Baroreceptors in the high pressure receptor zones detect changes in arterial pressure. These baroreceptors send signals ultimately to the medulla of the brain stem, specifically to the Rostral ventrolateral medulla (RVLM). The medulla, by way of the autonomic nervous system, adjusts the mean arterial pressure by altering both the force and speed of the heart’s contractions, as well as the total peripheral resistance. The most important arterial baroreceptors are located in the left and rightcarotid sinuses and in the aortic arch.[31] †¢ Renin-angiotensin system (RAS): This system is generally known for its long-term adjustment of arterial pressure. This system allows the kidney to compensate for loss in blood volume or drops in arterial pressure by activating an endogenous vasoconstrictorknown as angiotensin II. †¢ Aldosterone release: This steroid hormone is released from the adrenal cortex in response to angiotensin II or high serum potassiumlevels. Aldosterone stimulates sodium retention and potassium excretion by the kidneys. Since sodium is the main ion that determines the amount of fluid in the blood vessels by osmosis, aldosterone will increase fluid retention, and indirectly, arterial pressure. †¢ Baroreceptors in low pressure receptor zones (mainly in the venae cavae and the pulmonary veins, and in the atria) result in feedback by regulating the secretion of antidiuretic hormone (ADH/Vasopressin), renin and aldosterone. The resultant increase inblood volume results an increased cardiac output by the Frank–Starling law of the heart, in turn increasing arterial blood pressure. These different mechanisms are not necessarily independent of each other, as indicated by the link between the RAS and aldosterone release. Currently, the RAS is targeted pharmacologically by ACE inhibitors and angiotensin II receptor antagonists. The aldosterone system is directly targeted by spironolactone, an aldosterone antagonist. The fluid retention may be targeted by diuretics; the antihypertensive effect of diuretics is due to its effect on blood volume. Generally, the baroreceptor reflex is not targeted in hypertensionbecause if blocked, individuals may suffer from orthostatic hypotension and fainting. Measurement A medical student checking blood pressure using a sphygmomanometer and stethoscope. Arterial pressure is most commonly measured via a sphygmomanometer, which historically used the height of a column of mercury to reflect the circulating pressure.[32] Blood pressure values are generally reported in millimetres of mercury (mmHg), though aneroid and electronic devices do not use mercury. For each heartbeat, blood pressure varies between systolic and diastolic pressures. Systolic pressure is peak pressure in the arteries, which occurs near the end of the cardiac cyclewhen the ventricles are contracting. Diastolic pressure is minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood. An example of normal measured values for a resting, healthy adult human is 120 mmHgsystolic and 80 mmHg diastolic (written as 120/80 mmHg, and spoken [in the US and UK] as â€Å"one-twenty over eighty†). Systolic and diastolic arterial blood pressures are not static but undergo natural variations from one heartbeat to another and throughout the day (in a circadian rhythm). They also change in response to stress, nutritional factors, drugs, disease, exercise, and momentarily from standing up. Sometimes the variations are large. Hypertension refers to arterial pressure being abnormally high, as opposed to hypotension, when it is abnormally low. Along with body temperature, respiratory rate, and pulse rate, blood pressure is one of the four main vital signs routinely monitored by medical professionals and healthcare providers.[33] Measuring pressure invasively, by penetrating the arterial wall to take the measurement, is much less common and usually restricted to a hospital setting. Noninvasive The noninvasive auscultatory and oscillometric measurements are simpler and quicker than invasive measurements, require less expertise, have virtually no complications, are less unpleasant and less painful for the patient. However, noninvasive methods may yield somewhat lower accuracy and small systematic differences in numerical results. Noninvasive measurement methods are more commonly used for routine examinations and monitoring. [edit]Palpation A minimum systolic value can be roughly estimated by palpation, most often used in emergency situations, but should be used with caution.[34] It has been estimated that, using 50% percentiles, carotid, femoral and radial pulses are present in patients with a systolic blood pressure > 70 mmHg, carotid and femoral pulses alone in patients with systolic blood pressure of > 50 mmHg, and only a carotid pulse in patients with a systolic blood pressure of > 40 mmHg.[34] A more accurate value of systolic blood pressure can be obtained with a sphygmomanometer and palpating the radial pulse.[35] The diastolic blood pressure cannot be estimated by this method.[36] The American Heart Association recommends that palpation be used to get an estimate before using the auscultatory method. Auscultatory Auscultatory method aneroid sphygmomanometer with stethoscope Mercury manometer The auscultatory method (from the Latin word for â€Å"listening†) uses a stethoscope and asphygmomanometer. This comprises an inflatable (Riva-Rocci) cuff placed around the upperarm at roughly the same vertical height as the heart, attached to a mercury or aneroidmanometer. The mercury manometer, considered the gold standard, measures the height of a column of mercury, giving an absolute result without need for calibration and, consequently, not subject to the errors and drift of calibration which affect other methods. The use of mercury manometers is often required in clinical trials and for the clinical measurement of hypertension in high-risk patients, such as pregnant women. A cuff of appropriate size is fitted smoothly and snugly, then inflated manually by repeatedly squeezing a rubber bulb until the artery is completely occluded. Listening with the stethoscope to the brachial artery at the elbow, the examiner slowly releases the pressure in the cuff. When blood just starts to flow in the artery, the turbulent flow creates a â€Å"whooshing† or pounding (first Korotkoff sound). The pressure at which this sound is first heard is the systolic blood pressure. The cuff pressure is further released until no sound can be heard (fifth Korotkoff sound), at the diastolic arterial pressure. The auscultatory method is the predominant method of clinical measurement.[37] Oscillometric The oscillometric method was first demonstrated in 1876 and involves the observation of oscillations in the sphygmomanometer cuff pressure[38] which are caused by the oscillations of blood flow, i.e., the pulse.[39] The electronic version of this method is sometimes used in long-term measurements and general practice. It uses a sphygmomanometer cuff, like the auscultatory method, but with an electronic pressure sensor (transducer) to observe cuff pressure oscillations, electronics to automatically interpret them, and automatic inflation and deflation of the cuff. The pressure sensor should be calibrated periodically to maintain accuracy. Oscillometric measurement requires less skill than the auscultatory technique and may be suitable for use by untrained staff and for automated patient home monitoring. The cuff is inflated to a pressure initially in excess of the systolic arterial pressure and then reduced to below diastolic pressure over a period of about 30 seconds. When blood flow is nil (cuff pressure exceeding systolic pressure) or unimpeded (cuff pressure below diastolic pressure), cuff pressure will be essentially constant. It is essential that the cuff size is correct: undersized cuffs may yield too high a pressure; oversized cuffs yield too low a pressure. When blood flow is present, but restricted, the cuff pressure, which is monitored by the pressure sensor, will vary periodically in synchrony with the cyclic expansion and contraction of the brachial artery, i.e., it will oscillate. The values of systolic and diastolic pressure are computed, not actually measured from the raw data, using an algorithm; the computed results are displayed. Oscillometric monitors may produce inaccurate readings in patients with heart and circulation problems, which include arterial sclerosis, arrhythmia, preeclampsia, pulsus alternans, and pulsus paradoxus. In practice the different methods do not give identical results; an algorithm and experimentally obtained coefficients are used to adjust the oscillometric results to give readings which match the auscultatory results as well as possible. Some equipment uses computer-aided analysis of the instantaneous arterial pressure waveform to determine the systolic, mean, and diastolic points. Since many oscillometric devices have not been validated, caution must be given as most are not suitable in clinical and acute care settings. The term NIBP, for non-invasive blood pressure, is often used to describe oscillometric monitoring equipment. Continuous noninvasive techniques (CNAP) Continuous Noninvasive Arterial Pressure (CNAP) is the method of measuring arterial blood pressure in real-time without any interruptions and without cannulating the human body. CNAP combines the advantages of the following two clinical â€Å"gold standards†: it measures blood pressure continuously in real-time like the invasive arterial catheter system and it is noninvasive like the standard upper arm sphygmomanometer. Latest developments in this field show promising results in terms of accuracy, ease of use and clinical acceptance. Non-occlusive techniques: the Pulse Wave Velocity (PWV) principle Since the 90s a novel family of techniques based on the so-called Pulse wave velocity (PWV) principle have been developed. These techniques rely on the fact that the velocity at which an arterial pressure pulse travels along the arterial tree depends, among others, on the underlying blood pressure.[40] Accordingly, after a calibration maneuver, these techniques provide indirect estimates of blood pressure by translating PWV values into blood pressure values.[41] The main advantage of these techniques is that it is possible to measure PWV values of a subject continuously (beat-by-beat), without medical supervision, and without the need of inflating brachial cuffs. PWV-based techniques are still in the research domain and are not adapted to clinical settings. White-coat hypertension For some patients, blood pressure measurements taken in a doctor’s office may not correctly characterize their typical blood pressure.[42] In up to 25% of patients, the office measurement is higher than their typical blood pressure. This type of error is calledwhite-coat hypertension (WCH) and can result from anxiety related to an examination by a health care professional.[43] The misdiagnosis of hypertension for these patients can result in needless and possibly harmful medication. WCH can be reduced (but not eliminated) with automated blood pressure measurements over 15 to 20 minutes in a quiet part of the office or clinic.[44] Debate continues regarding the significance of this effect.[citation needed] Some reactive patients will react to many other stimuli throughout their daily lives and require treatment. In some cases a lower blood pressure reading occurs at the doctor’s office.[45] Home monitoring Ambulatory blood pressure devices that take readings every half hour throughout the day and night have been used for identifying and mitigating measurement problems like white-coat hypertension. Except for sleep, home monitoring could be used for these purposes instead of ambulatory blood pressure monitoring.[46] Home monitoring may be used to improve hypertension management and to monitor the effects of lifestyle changes and medication related to blood pressure.[6] Compared to ambulatory blood pressure measurements, home monitoring has been found to be an effective and lower cost alternative,[46][47][48] but ambulatory monitoring is more accurate than both clinic and home monitoring in diagnosing hypertension. Ambulatory monitoring is recommended for most patients before the start of antihypertensive drugs.[49] Aside from the white-coat effect, blood pressure readings outside of a clinical setting are usually slightly lower in the majority of people. The studies that looked into the risks from hypertension and the benefits of lowering blood pressure in affected patients were based on readings in a clinical environment. When measuring blood pressure, an accurate reading requires that one not drink coffee, smoke cigarettes, or engage in strenuous exercise for 30 minutes before taking the reading. A full bladder may have a small effect on blood pressure readings; if the urge to urinate arises, one should do so before the reading. For 5 minutes before the reading, one should sit upright in a chair with one’s feet flat on the floor and with limbs uncrossed. The blood pressure cuff should always be against bare skin, as readings taken over a shirt sleeve are less accurate. During the reading, the arm that is used should be relaxed and kept at heart level, for example by resting it on a table.[50] Since blood pressure varies throughout the day, measurements intended to monitor changes over longer time frames should be taken at the same time of day to ensure that the readings are comparable. Suitable times are: †¢ immediately after awakening (before washing/dressing and taking breakfast/drink), while the body is still resting, †¢ immediately after finishing work. Automatic self-contained blood pressure monitors are available at reasonable prices, some of which are capable of Korotkoff’s measurement in addition to oscillometric methods, enabling irregular heartbeat patients to accurately measure their blood pressure at home. Invasive Arterial blood pressure (BP) is most accurately measured invasively through an arterial line. Invasive arterial pressure measurement with intravascular cannulae involves direct measurement of arterial pressure by placing a cannula needle in an artery (usually radial, femoral,dorsalis pedis or brachial). The cannula must be connected to a sterile, fluid-filled system, which is connected to an electronic pressure transducer. The advantage of this system is that pressure is constantly monitored beat-by-beat, and a waveform (a graph of pressure against time) can be displayed. This invasive technique is regularly employed in human and veterinary intensive care medicine, anesthesiology, and for research purposes. Cannulation for invasive vascular pressure monitoring is infrequently associated with complications such as thrombosis, infection, andbleeding. Patients with invasive arterial monitoring require very close supervision, as there is a danger of severe bleeding if the line becomes disconnected. It is generally reserved for patients where rapid variations in arterial pressure are anticipated. Invasive vascular pressure monitors are pressure monitoring systems designed to acquire pressure information for display and processing. There are a variety of invasive vascular pressure monitors for trauma, critical care, and operating room applications. These include single pressure, dual pressure, and multi-parameter (i.e. pressure / temperature). The monitors can be used for measurement and follow-up of arterial, central venous, pulmonary arterial, left atrial, right atrial, femoral arterial, umbilical venous, umbilical arterial, and intracranial pressures. Fetal blood pressure Further information: Fetal circulation#Blood pressure In pregnancy, it is the fetal heart and not the mother’s heart that builds up the fetal blood pressure to drive its blood through the fetal circulation. The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation, and increases to approximately 45 mmHg at 40 weeks of gestation.[51] The average blood pressure for full-term infants: Systolic 65–95 mm Hg Diastolic 30–60 mm Hg[52] Blood pressure is the measurement of force that is applied to the walls of the blood vessels as the heart pumps blood throughout the body.[53] The human circulatory system is 400,000 miles long, and the magnitude of blood pressure is not uniform in all the blood vessels in the human body. The blood pressure is determined by the diameter, flexibility and the amount of blood being pumped through the blood vessel.[53] Blood pressure is also affected by other factors including exercise, stress level, diet and sleep. The average normal blood pressure in the brachial artery, which is the next direct artery from the aorta after the subclavian artery, is 120mmHg/80mmHg. Blood pressure readings are measured in millimeters of mercury (mmHg) using sphygmomanometer. Two pressures are measured and recorded namely as systolic and diastolic pressures. Systolic pressure reading is the first reading, which represents the maximum exerted pressure on the vessels when the heart contracts, while the diastolic pressure, the second reading, represents the minimum pressure in the vessels when the heart relaxes.[54] Other major arteries have similar levels of blood pressure recordings indicating very low disparities among major arteries. The innominate artery, the average reading is 110/70mmHg, the right subclavian artery averages 120/80 and the abdominal aorta is 110/70mmHg.[55] The relatively uniform pressure in the arteries indicate that these blood vessels act as a pressure reservoir for fluids that are transported within them. Pressure drops gradually as blood flows from the major arteries, through the arterioles, the capillaries until blood is pushed up back into the heart via the venules, the veins through the vena cava with the help of the muscles. At any given pressure drop, the flow rate is determined by the resistance to the blood flow. In the arteries, with the absence of diseases, there is very little or no resistance to blood. The vessel diameter is the most principal determinant to control resistance. Compared to other smaller vessels in the body, the artery has a much bigger diameter (4mm), therefore the resistance is low.[55] In addition, flow rate (Q) is also the product of the cross-sectional area of the vessel and the average velocity (Q = AV). Flow rate is directly proportional to the pressure drop in a tube or in this case a vessel. ∆P ÃŽ ± Q. The relationship is further described by Poisseulle’s equation ∆P = 8 µlQ/Ï€r4.[56] As evident in the Poisseulle’s equation, although flow rate is proportional to the pressure drop, there are other factors of blood vessels that contribute towards the difference in pressure drop in bifurcations of blood vessels. These include viscosity, length of the vessel, and radius of the vessel. Factors that determine the flow’s resistance as described by Poiseuille’s relationship: †¢ ∆P: pressure drop/gradient †¢  µ: viscosity †¢ l: length of tube. In the case of vessels with infinitely long lengths, l is replaced with diameter of the vessel. †¢ Q: flow rate of the blood in the vessel †¢ r: radius of the vessel Assuming steady, laminar flow in the vessel, the blood vessels behavior is similar to that of a pipe. For instance if p1 and p2 are pressures are at the ends of the tube, the pressure drop/gradient is:[57] In the arterioles blood pressure is lower than in the major arteries. This is due to bifurcations, which cause a drop in pressure. The more bifurcations, the higher the total cross-sectional area, therefore the pressure across the surface drops. This is why the arterioles have the highest pressure-drop. The pressure drop of the arterioles is the product of flow rate and resistance: ∆P=Q xresistance. The high resistance observed in the arterioles, which factor largely in the ∆P is a result of a smaller radius of about 30  µm.[58] The smaller the radius of a tube, the larger the resistance to fluid flow. Immediately following the arterioles are the capillaries. Following the logic obvserved in the arterioles, we expect the blood pressure to be lower in the capillaries compared to the arterioles. Since pressure is a function of force per unit area, (P = F/A), the larger the surface area, the lesser the pressure when an external force acts on it. Though the radii of the capillaries are very small, the network of capillaries have the largest surface area in the vascular network. They are known to have the largest surface area (485mm) in the human vascular network. The larger the total cross-sectional area, the lower the mean velocity as well as the pressure.[55] Reynold’s number also affects the blood flow in capillaries. Due to its smaller radius and lowest velocity compared to other vessels, the Reynold’s number at the capillaries is very low, resulting in laminar instead of turbulent flow.[59] The Reynold’s number (denoted NR or Re) is a relationship that helps determine the behavior of a fluid in a tube, in this case blood in the vessel. The equation for this dimensionless relationship is written as:[56] †¢ Ï : density of the blood †¢ v: mean velocity of the blood †¢ L: characteristic dimension of the vessel, in this case diameter †¢ ÃŽ ¼: viscosity of blood The Reynold’s number is directly proportional to the velocity and diameter of the tube. Note that NR is directly proportional to the mean velocity as well as the diameter. A Reynold’s number of less than 2300 is laminar fluid flow, which is characterized by constant flow motion, whereas a value of over 4000, is represented as turbulent flow. Turbulent flow is characterized as chaotic and irregular flow.[56] Disorders Disregulation disorders of blood pressure control include high blood pressure, blood pressure that is too low, and blood pressure that shows excessive or maladaptive fluctuation. High Main article: Hypertension Overview of main complications of persistent high blood pressure. Arterial hypertension can be an indicator of other problems and may have long-term adverse effects. Sometimes it can be an acute problem, for examplehypertensive emergency. All levels of arterial pressure put mechanical stress on the arterial walls. Higher pressures increase heart workload and progression of unhealthy tissue growth (atheroma) that develops within the walls of arteries. The higher the pressure, the more stress that is present and the more atheroma tend to progress and the heart muscle tends to thicken, enlarge and become weaker over time. Persistent hypertension is one of the risk factors for strokes, heart attacks,heart failure and arterial aneurysms, and is the leading cause of chronic renal failure. Even moderate elevation of arterial pressure leads to shortened life expectancy. At severely high pressures, mean arterial pressures 50% or more above average, a person can expect to live no more than a few years unless appropriately treated.[60] In the past, most attention was paid to diastolic pressure; but nowadays it is recognised that both high systolic pressure and high pulse pressure (the numerical difference between systolic and diastolic pressures) are also risk factors. In some cases, it appears that a decrease in excessive diastolic pressure can actually increase risk, due probably to the increased difference between systolic and diastolic pressures (see the article on pulse pressure). If systolic blood pressure is elevated (>140) with a normal diastolic blood pressure (

An Early Childhood Education Professional - 1004 Words

Autobiography On November 1st, 1995, the Palm Beach Post published a front page story about Bill Clinton’s latest remarks in a Whitehouse press conference. However, what the Palm Beach Post didn’t publish, and consequently what most of the county didn’t see that morning, was the fact that I was born. As an individual and an educator, in the next five years, I aspire to have been at my school and in my long term classroom for at least 3 years, have a developed and well practice filing system of observations and assessment records, a fool proof method for grading, a knack for detailed and daily lesson planning, as well as having an established parent conferencing style. Competency Goal #1 On my personal path to becoming an Early†¦show more content†¦Likewise, it is self-evident that we desperately need the research of those who are advancing this field of knowledge. After all, educators who are well informed are well prepared to do the task of teaching. Competency Goal #2 In the course of establishing a developmentally appropriate classroom for learning with healthy and respected students, there are several things I will and must do. In chief, there will be two things that I will have the utmost concern for in my future classroom: child safety and respectful behavior. Within the pursuit of a healthy environment, it is clear that the well-being of students comes as a tangent to having their attention for learning. On this token, establishing a healthy classroom must be systemically established by systematic rules. For example, it will be an immediate priority to search for, remove, and replace when possible materials in my classroom that are sharp, easily swallowable, too heavy, too disruptive, and/or too toxic for children to exercise necessary caution around. Similarly, maintaining classroom cleanliness is another key goal. As for the risks, children that are in messy classrooms risk slips and falls around untidied, areas as well a s unnecessary exposure to germs. To avoid this, I will be sure to inspect the classroom at the beginning and end of the day for tidiness, while also having a liberal supply of soap and water. For the purpose of establishingShow MoreRelatedProfessional Development in Early Childhood Education Essay1320 Words   |  6 Pages teacher professionals are individuals who play the key and an active role in their early childhood development are teacher professionals who have a passion and a genuine desire to help them learn, grow and succeed in their education. 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My Experience At The United States Congress - 725 Words

Guide to Comp I John Beckley, the first librarian of the United States Congress, once said, â€Å"Most people don’t plan to fail; they fail to plan.† I have found this to be true in many areas of life, including my college classes. Having almost completed my first semester of Composition I, I have realized that college presents a new arena of life, and therefore demands thoughtful planning, planning made necessary by new found freedom. Freedom is a relative term in college; it is experienced in and out of the classroom, in both creativity and time management. With new found freedoms that college brings, comes heightened responsibility to prioritize and plan for classroom success. I will share specifically about my experience in Composition I. Since success begins with planning, I’ll start there. In my previous English classes, teachers encouraged my ability to â€Å"create† thoughtful essays, and focused more on the elements of voice and less on the structure of writing. This encouragement allowed my perception of my writing ability to be inflated as I entered college. Perhaps you too see yourself as a good writer. Don’t let this perception keep you from embracing the opportunity to increase your writing ability. The fallacy of my perception that I had already arrived as a writer was brought home when I received a fifty-nine on my second essay! Following my normal writing process, I began writing every good idea that presented itself without any forethought to planning orShow MoreRelatedThe National Trust For Historic Preservation Essay700 Words   |  3 Pagesbe referred to in the future as NTHP in this paper), the concept is reflected in their decision to break away from government funding. Beca use Congress had designated them as a trust, they had a large portion of their budget in their hands, about a fifth. When budgeting constraints began to be too close for comfort, the NTHP was done dealing with Congress. 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Irish Emigration Essay Example For Students

Irish Emigration Essay 14 The substantial increase in emigration during and after the famine is certainly note-worthy; however it is important to look at other factors influencing the increase in and pattern of emigration during the 19th Century. An international trend of migration was under way, primarily as a result of European colonialism. The British government, in an effort to settle her colonies actively encouraged emigration. Subsidised emigration to Australasia and Canada is a prime example of this. Subsidised emigration had the effect of making emigration a genuine option to those who would have otherwise been unable to afford it, and influenced the pattern of Irish emigration by encouraging settlement in certain places. Another factor that emerged which encouraged emigration was the improvement of transport technology. The development of steam powered ships, and better ship design, cut down the length of the journeys that migrants undertook, and made emigration increasingly feasible. The first steam packet linked Belfast with Glasgow in 1818, and it was only a short while longer for ferry services to run from Dublin and cork to Liverpool, the main port for trans-Atlantic crossings. The commercialisation of the transport industry was also to play a role. Competing companies drove down the cost of transport, not only making the trips more affordable, but the possibility of a return trip home more plausible. 15 Thus quicker and cheaper transport opportunities were available for emigrants. Furthermore, the pull factors overseas, and push factors in Ireland were inherent even before the famine. The growth of population, the decline of domestic industry, the commercialisation of agriculture, and proto-industrialisation all served as push factors. In particular, the commercialisation of agriculture witnessed the increasing conversion of arable land to pasture, which led to growing dependence on the potato for subsistence; an increased rate of farm consolidation, which added many smallholders and cottiers to the ranks of landless labourers; and the application of new farming techniques, which made agriculture less labour intensive and contributed to under employment and unemployment. 16 The predominant pull factor can certainly be considered the increased desire for material well-being, which was seen as a relatively remote possibility if one were to stay in Ireland. Much Irish emigration resulted from the prospect of relatively well paid employment in the industrialised economies of Britain and America. Furthermore, America had the additional attraction of being free from British rule. 17 Emigration was clearly well under way before the famine, however, the mass exodus of impoverished and starving Irish during the years of the famine was unprecedented, and devastated population growth, with massive social, economic, and psychological consequences on Irish life for years following the famine. Nevertheless, it was the quantity, rather than the fundamental pattern of emigration that was changing. The change in Irish attitudes was where the real transformation took place. Before the famine emigration was seen by many as the path to exile. 18 This is sometimes evidenced by the fact the in the Gaelic language there is no corresponding word to describe the idea of emigration (choosing to leave ones homeland for another) the closest word being exile. The largely agrarian nature of Ireland also encouraged a strong sense of bond to the land amongst many Irish, and consequently saw them reluctant to leave. Thus Irish attitudes to emigration were largely negative. The Great famine certainly saw a marked change in these attitudes; emigration became a welcome and necessary escape route. 19 Emigration success stories of wealth and prestige over shadowed the stories of continued poverty, hardship and discrimination suffered by migrants. Even the horrifying stories of death on the coffin ships did little to discourage the new found fascination with emigration. 20 It became an expected part of life, like marriage for many Irish. One consequence of this was that married Irish couples were able to maintain high levels of fertility (in contrast to the rest of Europe), because they might reasonably presume that children who were unable to find work in Ireland could simply leave. .uca5bd54b630511d0537072e4880dacf0 , .uca5bd54b630511d0537072e4880dacf0 .postImageUrl , .uca5bd54b630511d0537072e4880dacf0 .centered-text-area { min-height: 80px; position: relative; } .uca5bd54b630511d0537072e4880dacf0 , .uca5bd54b630511d0537072e4880dacf0:hover , .uca5bd54b630511d0537072e4880dacf0:visited , .uca5bd54b630511d0537072e4880dacf0:active { border:0!important; } .uca5bd54b630511d0537072e4880dacf0 .clearfix:after { content: ""; display: table; clear: both; } .uca5bd54b630511d0537072e4880dacf0 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .uca5bd54b630511d0537072e4880dacf0:active , .uca5bd54b630511d0537072e4880dacf0:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .uca5bd54b630511d0537072e4880dacf0 .centered-text-area { width: 100%; position: relative ; } .uca5bd54b630511d0537072e4880dacf0 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .uca5bd54b630511d0537072e4880dacf0 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .uca5bd54b630511d0537072e4880dacf0 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .uca5bd54b630511d0537072e4880dacf0:hover .ctaButton { background-color: #34495E!important; } .uca5bd54b630511d0537072e4880dacf0 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .uca5bd54b630511d0537072e4880dacf0 .uca5bd54b630511d0537072e4880dacf0-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .uca5bd54b630511d0537072e4880dacf0:after { content: ""; display: block; clear: both; } READ: Agony And The Ecstacy Essay21 Emigration effectively provided a safety valve for the Irish population. 22 David Fitzpatrick argues that attitudes towards emigration had changed so much by the 1860s, that those who failed to leave Ireland were often stigmatised as indolent incapable of deformed. 23 Janet Nolan, in discussing Irish womens emigration, further disbands the notion of exile by describing it as an unprecedented opportunity, rather than a forced expulsion. 24 The change in Irish attitudes towards emigration as a result of the famine certainly opened up the way for emigration to increase. With its less negative connotations, and perhaps even positive connotations, emigration became a more viable option for those facing hardship in Ireland, and hoping for a chance of betterment elsewhere. Perhaps it even became a palliative drug to which Irish society had grown dangerously addicted. 25 Whether this quote is an exaggeration or not, the fact remains that the attitudes towards emigration by the Irish had certainly changed by the end of the 19th Century, overwhelmingly as a consequence of the famine. Emigration has played a hugely important role in Irish history. It is a tradition that was well underway before the Great Famine, and so to call the famine a fundamental transformation in the pattern of Irish emigration is to well overstate the case. The famine did cause an unprecedented increase in emigration, and the mass emigration of Irish fleeing starvation and poverty left gaping holes in a ravaged society and had lasting consequences for Ireland. Despite this, it was more a matter of building on existing frameworks, than a transformation of emigration patterns. Further, changing conditions, internationally as well as locally, should also be considered when discussing the perpetuating levels of emigration. European colonialism which sponsored emigration, technological advancement and the commercialisation of transport allowed the potential pre-famine push and pull factors to play themselves out. It was Irish attitudes towards emigration that saw the greatest change, perhaps even transformation as a result of the famine. Emigration was no longer viewed as exile, a last resort for the destitute, but a real and desirable alternative to life in Ireland. This transformation in attitudes encouraged the continued emigration of Irish after the Great Famine along the same patterns of emigration that had been laid out in the early 19th Century. Moreover, it was one of the contributing factors which led to what is certainly the most remarkable aspect of Irish history in the 19th Century; the fact that Ireland lost nearly half her population as a result of emigration. 26 1 Alvin Jackson, Ireland: 1798-1998, Oxford, 1999, p. 82. 2 Roger Swift, The historiography of the Irish in nineteenth-century Britain, in Patrick OSullivan (ed. ), The Irish in the new communities, London, 1992, p. 53. 3 Tim Pat Coogan, Wherever Green is worn: The story of the Irish Diaspora, London, 2000, p. xiii. 4 ibid. , p. xi. 5 Ibid. , p. xii. 6 Jackson, p. 83. 7 ibid,. p. 83. 8Christine Kinealy, The Great Irish Famine: Impact, Ideology and rebellion, Basingstoke, p. 32. 9 ibid. , p. 32. 10 Coogan, p. xii. 11 Jackson, p. 69. 12 Coogan, p. xii. 13 Roger Swift, p. 54. 14 Jackson, p. 83. 15 Roger Swift, p. 54. 16ibid. , p. 53. 17ibid. , p. 54. 18 Jackson, p. 83. 19 Jackson, p. 83. 20 Christine Kinealy, p. 58-9. 21 David Fitzpatrick, Irish Emigration in the later Nineteenth Century, Irish Historical Studies XXII, September, 1980, p. 127. 22 ibid. , p. 127. 23ibid. , p. 126. 24 Janet A. Nolan, Ourselves Alone: Womens emigration from Ireland 1885-1920, Kentucky, 1989, p. 85. 25David Fitzpatrick, p. 127.

Margaret Bourke-White Essays - Margaret Bourke-White,

Margaret Bourke-White Margaret Bourke-White was born on June 14th, 1904, in the Bronx, New York. Her father, Joseph White, was an inventor and engineer, and her mother, Minnie Bourke, was forward thinking woman, especially for the early 1900's. When Margaret was very young, the family moved to a rural suburb in New Jersey, so that Joseph could be closer to his job. Margaret, along with her sister Ruth, were taught from an early age by their mother. Her mother was strict in monitoring their outside influences, limiting everything from fried foods to funny papers. When Margaret was eight, her father took her inside a foundry to watch the manufacture of printing presses. While in the foundry, she saw some molten iron poured. This event filled Margaret with joy, and this memory would be burned in her mind for years to come. Joseph White's chief recreation activity suited his scientific mind; her was an amateur photographer. The White's home was filled with his photographs. If something interested Margaret's father, it also interested her. She pretended as a girl to take photographs with an empty cigar box. Although she claimed that she never took a photograph until after her father's death. Her cousin Florence remembers her helping her father to develop prints in his bathtub. In 1917, her father suffered a stroke. By 1919, he had recovered enough for the family to take a trip to Niagara Falls and Canada. While there, she began to make notes on his photographs, and helped him set up shots on several occasions. In 1921, she began college at Rutgers, then moved to the University of Michigan, then to Cornell University, from which she graduated in 1927. As a freshman at Michigan, she began taking pictures for the yearbook, and within a year was offered the seat of photography editor. Instead of taking the position, she married a engineering graduate student, Everett Chapman, and abandoned photography to pursue married life. When the marriage fell apart two years later, she moved to Cornell, where she again took up photography. After she graduated in 1927, she moved to Cleveland, where her family was living, to start her career with a portfolio full of architecture pictures she had taken while at Cornell. She called upon several architects who were Cornell alumni for jobs. After the success of her first job, she founded the Bourke-White studio in her one room apartment. Then, money she made from shooting elegant home and gardens by day was spent on photographing steel mills at night and on the weekends. The circulation of her portfolio brought her to the attention of Cleveland's biggest industrial tycoons. After a few failures, she was successful at capturing the Otis Steel mill. From this, she made enough money to move her studio to the Terminal Tower skyscraper. In the spring of 1929, she received a telegram from Henry R. Luce, a publisher who was planning a new weekly magazine called Time. Luce invited her to come to New York so they could meet, and so Bourke-White could see what Time was to accomplish. She was unimpressed, but Luce and his editor Parker Lloyd- Smith were also planning a new business magazine that would make use of dramatic industrial photographs. This was perfect for Bourke-White. She accepted their offer as a staff photographer. In July 1929, the decision was made to publish the magazine, called Fortune. Bourke-White began working on stories for the premier issue, eight months away. The first lead story was to feature Swift & Co., a hog processing plant. She worked with Lloyd-Smith until he became too sick from the stench to continue. After Bourke-White was finished photographing the hogs, she left most of her camera equipment to be burned. Her documentation of this was a step in the development of the photo essay, and Bourke-White's style. In 1930, Russia was in the midst of an industrial and cultural revolution. It's doors were all but closed to westerners, especially photographers. Bourke-White was attracted to Russia, but her editors at Fortune doubted that she would gain access. They instead sent her to Germany to photograph the emerging industry there. She decided that she would go on her own, and after