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Human Physiology/The Urinary System

Introduction
The Urinary System is a group of organs in the body concerned with filtering out excess fluid and other substances from the bloodstream. The substances are filtered out from the body in the form of urine. Urine is a liquid produced by the kidneys, collected in the bladder and excreted through the urethra. Urine is used to extract excess minerals or vitamins as well as blood corpuscles from the body. The Urinary organs include the kidneys, ureters, bladder, and urethra. The Urinary system works with the other systems of the body to help maintain homeostasis. The kidneys are the main organs of homeostasis because they maintain the acid base balance and the water salt balance of the blood.

Functions of the Urinary System
One of the major functions of the Urinary system is the process of excretion. Excretion is the process of eliminating, from an organism, waste products of metabolism and other materials that are of no use. The urinary system maintains an appropriate fluid volume by regulating the amount of water that is excreted in the urine. Other aspects of its function include regulating the concentrations of various electrolytes in the body fluids and maintaining normal pH of the blood. Several body organs carry out excretion, but the kidneys are the most important excretory organ. The primary function of the kidneys is to maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism. They do this by separating urea, mineral salts, toxins, and other waste products from the blood. They also do the job of conserving water, salts, and electrolytes. At least one kidney must function properly for life to be maintained. Six important roles of the kidneys are:

Regulation of plasma ionic composition. Ions such as sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphates are regulated by the amount that the kidney excretes.

Regulation of plasma osmolarity. The kidneys regulate osmolarity because they have direct control over how many ions and how much water a person excretes.

Regulation of plasma volume. Your kidneys are so important they even have an effect on your blood pressure. The kidneys control plasma volume by controlling how much water a person excretes. The plasma volume has a direct effect on the total blood volume, which has a direct effect on your blood pressure. Salt(NaCl)will cause osmosis to happen; the diffusion of water into the blood.

Regulation of plasma hydrogen ion concentration (pH). The kidneys partner up with the lungs and they together control the pH. The kidneys have a major role because they control the amount of bicarbonate excreted or held onto. The kidneys help maintain the blood Ph mainly by excreting hydrogen ions and reabsorbing bicarbonate ions as needed.

Removal of metabolic waste products and foreign substances from the plasma. One of the most important things the kidneys excrete is nitrogenous waste. As the liver breaks down amino acids it also releases ammonia. The liver then quickly combines that ammonia with carbon dioxide, creating urea which is the primary nitrogenous end product of metabolism in humans. The liver turns the ammonia into urea because it is much less toxic. We can also excrete some ammonia, creatinine and uric acid. The creatinine comes from the metabolic breakdown of creatine phospate (a high-energy phosphate in muscles). Uric acid comes from the break down of nucleotides. Uric acid is insoluble and too much uric acid in the blood will build up and form crystals that can collect in the joints and cause gout.

Secretion of Hormones The endocrine system has assistance from the kidney's when releasing hormones. Renin is released by the kidneys. Renin leads to the secretion of aldosterone which is released from the adrenal cortex. Aldosterone promotes the kidneys to reabsorb the sodium (Na+) ions. The kidneys also secrete erythropoietin when the blood doesn't have the capacity to carry oxygen. Erythropoietin stimulates red blood cell production. The Vitamin D from the skin is also activated with help from the kidneys. Calcium (Ca+) absorption from the digestive tract is promoted by vitamin D.

CC: Chapter Check: Name the role of the kidneys and how they work?

Kidneys And Their Structure

The kidneys are a pair of bean shaped, brown organs about the size of your fist.It measures 10-12 cm long. They are covered by the renal capsule, which is a tough capsule of fibrous connective tissue. Adhering to the surface of each kidney is two layers of fat to help cushion them. There is a concaved side of the kidney that has a depression where a renal artery enters, and a renal vein and a ureter exit the kidney. The kidneys are located at the rear wall of the abdominal cavity just above the waistline, and are protected by the ribcage. They are considered retroperitoneal, which means they lie behind the peritoneum. There are three major regions of the kidney, renal cortex, renal medulla and the renal pelvis. The outer, granulated layer is the renal cortex. The cortex stretches down in between a radially striated inner layer. The inner radially striated layer is the renal medulla. This contains pyramid shaped tissue called the renal pyramids, separated by renal columns. The ureters are continuous with the renal pelvis and is the very center of the kidney.

Renal Vein
The renal veins are veins that drain the kidney. They connect the kidney to the inferior vena cava. Because the inferior vena cava is on the right half of the body, the left renal vein is generally the longer of the two. Unlike the right renal vein, the left renal vein often receives the left gonadal vein (left testicular vein in males, left ovarian vein in females). It frequently receives the left suprarenal vein as well.

Renal Artery
The renal arteries normally arise off the abdominal aorta and supply the kidneys with blood. The arterial supply of the kidneys are variable and there may be one or more renal arteries supplying each kidney. Due to the position of the aorta, the inferior vena cava and the kidneys in the body, the right renal artery is normally longer than the left renal artery. The right renal artery normally crosses posteriorly to the inferior vena cava. The renal arteries carry a large portion of the total blood flow to the kidneys. Up to a third of the total cardiac output can pass through the renal arteries to be filtered by the kidneys.

Ureters
The ureters are two tubes that drain urine from the kidneys to the bladder. Each ureter is a muscular tube about 10 inches (25 cm) long. Muscles in the walls of the ureters send the urine in small spurts into the bladder, (a collapsible sac found on the forward part of the cavity of the bony pelvis that allows temporary storage of urine). After the urine enters the bladder from the ureters, small folds in the bladder mucosa act like valves preventing backward flow of the urine. The outlet of the bladder is controlled by a sphincter muscle. A full bladder stimulates sensory nerves in the bladder wall that relax the sphincter and allow release of the urine. However, relaxation of the sphincter is also in part a learned response under voluntary control. The released urine enters the urethra.

Urinary Bladder
The urinary bladder is a hollow, muscular and distendible or elastic organ that sits on the pelvic floor (superior to the prostate in males). On its anterior border lies the pubic symphysis and, on its posterior border, the vagina (in females) and rectum (in males). The urinary bladder can hold approximately 17 to 18 ounces (500 to 530 ml) of urine, however the desire to micturate is usually experienced when it contains about 150 to 200 ml. When the bladder fills with urine (about half full), stretch receptors send nerve impulses to the spinal cord, which then sends a reflex nerve impulse back to the sphincter (muscular valve) at the neck of the bladder, causing it to relax and allow the flow of urine into the urethra. The Internal urethral sphincter is involuntary. The ureters enter the bladder diagonally from its dorsolateral floor in an area called the trigone. The trigone is a triangular shaped area on the postero-inferior wall of the bladder. The urethra exits at the lowest point of the triangle of the trigone. The urine in the bladder also helps regulate body temperature. A bladder when operating normally empties completely upon a complete discharge, otherwise it is a sign that its elasticity is compromised, when it becomes completely void of fluid, it may cause a chilling sensation due to the rapid change of body temperature.

Urethra

The urethra is a muscular tube that connects the bladder with the outside of the body. The function of the urethra is to remove urine from the body. It measures about 1.5 inches (3.8 cm) in a woman but up to 8 inches (20 cm) in a man. Because the urethra is so much shorter in a woman it makes it much easier for a woman to get harmful bacteria in her bladder this is commonly called a bladder infection or a UTI. The most common bacteria of a UTI is E-coli from the large intestines that have been excreted in fecal matter. Female urethra

In the human female, the urethra is about 1-2 inches long and opens in the vulva between the clitoris and the vaginal opening.

Men have a longer urethra than women. This means that women tend to be more susceptible to infections of the bladder (cystitis) and the urinary tract.

Male urethra

In the human male, the urethra is about 8 inches long and opens at the end of the head of the  penis.

The length of a male's urethra, and the fact it contains a number of bends, makes catheterisation more difficult.

The urethral sphincter is a collective name for the muscles used to control the flow of urine from the urinary bladder. These muscles surround the urethra, so that when they contract, the urethra is closed.

 * There are two distinct areas of muscle: the internal sphincter, at the bladder neck and
 * the external, or distal, sphincter.

Human males have much stronger sphincter muscles than females, meaning that they can retain a large amount of urine for twice as long, as much as 800mL, i.e. "hold it".

Nephrons
A nephron is the basic structural and functional unit of the kidney. The name nephron comes from the Greek word (nephros) meaning kidney. Its chief function is to regulate water and soluble substances by filtering the blood, reabsorbing what is needed and excreting the rest as urine. Nephrons eliminate wastes from the body, regulate blood volume and pressure, control levels of electrolytes and metabolites, and regulate blood pH. Its functions are vital to life and are regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone. Each nephron has its own supply of blood from two capillary regions from the renal artery. Each nephron is composed of an initial filtering component (the renal corpuscle) and a tubule specialized for reabsorption and secretion (the renal tubule). The renal corpuscle filters out large solutes from the blood, delivering water and small solutes to the renal tubule for modification.

Glomerulus
The glomerulus is a capillary tuft that receives its blood supply from an afferent arteriole of the renal circulation. The glomerular blood pressure provides the driving force for fluid and solutes to be filtered out of the blood and into the space made by Bowman's capsule. The remainder of the blood not filtered into the glomerulus passes into the narrower efferent arteriole. It then moves into the vasa recta, which are collecting capillaries intertwined with the convoluted tubules through the interstitial space, where the reabsorbed substances will also enter. This then combines with efferent venules from other nephrons into the renal vein, and rejoins with the main bloodstream.

Afferent/Efferent Arterioles

The afferent arteriole supplies blood to the glomerulus. A group of specialized cells known as juxtaglomerular cells are located around the afferent arteriole where it enters the renal corpuscle. The efferent arteriole drains the glomerulus. Between the two arterioles lies specialized cells called the macula densa. The juxtaglomerular cells and the macula densa collectively form the juxtaglomerular apparatus. It is in the juxtaglomerular apparatus cells that the enzyme renin is formed and stored. Renin is released in response to decreased blood pressure in the afferent arterioles, decreased sodium chloride in the distal convoluted tubule and sympathetic nerve stimulation of receptors (beta-adrenic) on the juxtaglomerular cells. Renin is needed to form Angiotensin I and Angiotensin II which stimulate the secretion of aldosterone by the adrenal cortex.

Glomerular Capsule or Bowman's Capsule
Bowman's capsule (also called the glomerular capsule) surrounds the glomerulus and is composed of visceral (simple squamous epithelial cells) (inner) and parietal (simple squamous epithelial cells) (outer) layers. The visceral layer lies just beneath the thickened glomerular basement membrane and is made of podocytes which send foot processes over the length of the glomerulus. Foot processes interdigitate with one another forming filtration slits that, in contrast to those in the glomeruluar endothelium, are spanned by diaphragms. The size of the filtration slits restricts the passage of large molecules (e.g., albumin) and cells (e.g., red blood cells and platelets). In addition, foot processes have a negatively-charged coat (glycocalyx) that limits the filtration of negatively-charged molecules, such as albumin. This action is called electrostatic repulsion.

The parietal layer of Bowman's capsule is lined by a single layer of squamous epithelium. Between the visceral and parietal layers is Bowman's space, into which the filtrate enters after passing through the podocytes' filtration slits. It is here that smooth muscle cells and macrophages lie between the capillaries and provide support for them. Unlike the visceral layer, the parietal layer does not function in filtration. Rather, the filtration barrier is formed by three components: the diaphragms of the filtration slits, the thick glomerular basement membrane, and the glycocalyx secreted by podocytes. 99% of glomerular filtrate will ultimately be reabsorbed.

The process of filtration of the blood in the Bowman's capsule is ultrafiltration (or glomerular filtration), and the normal rate of filtration is 125 ml/min, equivalent to ten times the blood volume daily. Measuring the glomerular filtration rate (GFR) is a diagnostic test of kidney function. A decreased GFR may be a sign of renal failure. Conditions that can affect GFR include: arterial pressure, afferent arteriole constriction, efferent arteriole constriction, plasma protein concentration and colloid osmotic pressure.

Any proteins that are roughly 30 kilodaltons or under can pass freely through the membrane. Although, there is some extra hindrance for negatively charged molecules due to the negative charge of the basement membrane and the podocytes. Any small molecules such as water, glucose, salt (NaCl), amino acids, and urea pass freely into Bowman's space, but cells, platelets and large proteins do not. As a result, the filtrate leaving the Bowman's capsule is very similar to blood plasma in composition as it passes into the proximal convoluted tubule. Together, the glomerulus and Bowman's capsule are called the renal corpuscle.

Proximal Convoluted Tubule (PCT)
The proximal tubule can be anatomically divided into two segments: the proximal convoluted tubule and the proximal straight tubule. The proximal convoluted tubule can be divided further into S1 and S2 segments based on the histological appearance of it's cells. Following this naming convention, the proximal straight tubule is commonly called the S3 segment. The proximal convoluted tubule has one layer of cuboidal cells in the lumen. This is the only place in the nephron that contains cuboidal cells. These cells are covered with millions of microvilli. The microvilli serve to increase surface area for reabsorption.

Fluid in the filtrate entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries, including approximately two-thirds of the filtered salt and water and all filtered organic solutes (primarily glucose and amino acids). This is driven by sodium transport from the lumen into the blood by the Na+/K+ ATPase in the basolateral membrane of the epithelial cells. Much of the mass movement of water and solutes occurs in between the cells through the tight junctions, which in this case are not selective.

The solutes are absorbed isotonically, in that the osmotic potential of the fluid leaving the proximal tubule is the same as that of the initial glomerular filtrate. However, glucose, amino acids, inorganic phosphate, and some other solutes are reabsorbed via secondary active transport through cotransport channels driven by the sodium gradient out of the nephron.

Loop of the Nephron or Loop of Henle

The loop of Henle (sometimes known as the nephron loop) is a U-shaped tube that consists of a descending limb and ascending limb. It begins in the cortex, receiving filtrate from the proximal convoluted tubule, extends into the medulla, and then returns to the cortex to empty into the distal convoluted tubule. Its primary role is to concentrate the salt in the interstitium, the tissue surrounding the loop.

 * Descending limb:Its descending limb is permeable to water but completely impermeable to salt, and thus only indirectly contributes to the concentration of the interstitium. As the filtrate descends deeper into the hypertonic interstitium of the renal medulla, water flows freely out of the descending limb by osmosis until the tonicity of the filtrate and interstitium equilibrate. Longer descending limbs allow more time for water to flow out of the filtrate, so longer limbs make the filtrate more hypertonic than shorter limbs.

 * Ascending limb:Unlike the descending limb, the ascending limb of Henle's loop is impermeable to water, a critical feature of the countercurrent exchange mechanism employed by the loop. The ascending limb actively pumps sodium out of the filtrate, generating the hypertonic interstitium that drives countercurrent exchange. In passing through the ascending limb, the filtrate grows hypotonic since it has lost much of its sodium content. This hypotonic filtrate is passed to the distal convoluted tubule in the renal cortex.

Distal Convoluted Tubule (DCT)
The distal convoluted tubule is similar to the proximal convoluted tubule in structure and function. Cells lining the tubule have numerous mitochondria, enabling active transport to take place by the energy supplied by ATP. Much of the ion transport taking place in the distal convoluted tubule is regulated by the endocrine system. In the presence of parathyroid hormone, the distal convoluted tubule reabsorbs more calcium and excretes more phosphate. When aldosterone is present, more sodium is reabsorbed and more potassium excreted. Atrial natriuretic peptide causes the distal convoluted tubule to excrete more sodium. In addition, the tubule also secretes hydrogen and ammonium to regulate pH. After traveling the length of the distal convoluted tubule, only 3% of water remains, and the remaining salt content is negligible. 97.9% of the water in the glomerular filtrate enters the convoluted tubules and collecting ducts by osmosis.

Collecting ducts
Each distal convoluted tubule delivers its filtrate to a system of collecting ducts, the first segment of which is the connecting tubule. The collecting duct system begins in the renal cortex and extends deep into the medulla. As the urine travels down the collecting duct system, it passes by the medullary interstitium which has a high sodium concentration as a result of the loop of Henle's countercurrent multiplier system. Though the collecting duct is normally impermeable to water, it becomes permeable in the presence of antidiuretic hormone (ADH). As much as three-fourths of the water from urine can be reabsorbed as it leaves the collecting duct by osmosis. Thus the levels of ADH determine whether urine will be concentrated or dilute. Dehydration results in an increase in ADH, while water sufficiency results in low ADH allowing for diluted urine. Lower portions of the collecting duct are also permeable to urea, allowing some of it to enter the medulla of the kidney, thus maintaining its high ion concentration (which is very important for the nephron).

Urine leaves the medullary collecting ducts through the renal papilla, emptying into the renal calyces, the renal pelvis, and finally into the bladder via the ureter. Because it has a different embryonic origin than the rest of the nephron (the collecting duct is from endoderm whereas the nephron is from mesoderm), the collecting duct is usually not considered a part of the nephron proper.

Renal Hormones

1. Vitamin D- Becomes metabolically active in the kidney. Patients with renal disease have symptoms of disturbed calcium and phosphate balance.

2. Erythropoietin- Released by the kidneys in response to decreased tissue oxygen levels (hypoxia).

3. Natriuretic Hormone- Released from cardiocyte granules located in the right atria of the heart in response to increased atrial stretch. It inhibits ADH secretions which can contribute to the loss of sodium and water.

Formation of Urine
Urine is formed in three steps: Filtration, Reabsorption, and Secretion.

Filtration
Blood enters the afferent arteriole and flows into the glomerulus. Blood in the glomerulus has both filterable blood components and non-filterable blood components. Filterable blood components move toward the inside of the glomerulus while non-filterable blood components bypass the filtration process by exiting through the efferent arteriole. Filterable Blood components will then take a plasma like form called glomerular filtrate. A few of the filterable blood components are water, nitrogenous waste, nutrients and salts (ions). Nonfilterable blood components include formed elements such as blood cells and platelets along with plasma proteins. The glomerular filtrate is not the same consistency as urine, as much of it is reabsorbed into the blood as the filtrate passes through the tubules of the nephron.

Reabsorption
Within the peritubular capillary network, molecules and ions are reabsorbed back into the blood. Sodium Chloride reabsorbed into the system increases the osmolarity of blood in comparison to the glomerular filtrate. This reabsorption process allows water (H2O) to pass from the glomerular filtrate back into the circulatory system.

Glucose and various amino acids also are reabsorbed into the circulatory system. These nutrients have carrier molecules that claim the glomerular molecule and release it back into the circulatory system. If all of the carrier molecules are used up, excess glucose or amino acids are set free into the urine. A complication of diabetes is the inability of the body to reabsorb glucose. If too much glucose appears in the glomerular filtrate it increases the osmolarity of the filtrate, causing water to be released into the urine rather than reabsorbed by the circulatory system. Frequent urination and unexplained thirst are warning signs of diabetes, due to water not being reabsorbed.

Glomerular filtrate has now been separated into two forms: Reabsorbed Filtrate and Non-reabsorbed Filtrate. Non-reabsorbed filtrate is now known as tubular fluid as it passes through the collecting duct to be processed into urine.

Secretion
Some substances are removed from blood through the peritubular capillary network into the distal convoluted tubule or collecting duct. These substances are Hydrogen ions, creatinine, and drugs. Urine is a collection of substances that have not been reabsorbed during glomerular filtration or tubular reabsorbtion.

Maintaining Water-Salt Balance
It is the job of the kidneys to maintain the water-salt balance of the blood. They also maintain blood volume as well as blood pressure. Simple examples of ways that this balance can be changed include ingestion of water, dehydration, blood loss and salt ingestion.

Reabsorption of water
Direct control of water excretion in the kidneys is exercised by the anti-diuretic hormone (ADH), released by the posterior lobe of the pituitary gland. ADH causes the insertion of water channels into the membranes of cells lining the collecting ducts, allowing water reabsorption to occur. Without ADH, little water is reabsorbed in the collecting ducts and dilute urine is excreted. There are several factors that influence the secretion of ADH. The first of these happen when the blood plasma gets too concentrated. When this occurs, special receptors in the hypothalamus release ADH. When blood pressure falls, stretch receptors in the aorta and carotid arteries stimulate ADH secretion to increase volume of the blood.

Reabsorption of Salt
The Kidneys also regulate the salt balance in the blood by controlling the excretion and the reabsorption of various ions. As noted above, ADH plays a role in increasing water reabsorption in the kidneys, thus helping to dilute bodily fluids. The kidneys also have a regulated mechanism for reabsorbing sodium in the distal nephron. This mechanism is controlled by aldosterone, a steroid hormone produced by the adrenal cortex. Aldosterone promotes the excretion of potassium ions and the reabsorption of sodium ions. The release of Aldosterone is initiated by the kidneys. The juxtaglomerular apparatus is a renal structure consisting of the macula densa, mesangial cells, and juxtaglomerular cells. Juxtaglomerular cells (JG cells, also known as granular cells) are the site of renin secretion. Renin is an enzyme that converts angiotensinogen (a large plasma protein produced by the liver) into Angiotensin I and eventually into Angiotensin II which stimulates the adrenal cortex to produce aldosterone. The reabsorption of sodium ions is followed by the reapsorption of water. This causes blood pressure as well as blood volume to increase.

Atrial natriuretic hormone (ANH) is released by the atria of the heart when cardiac cells are stretched due to increased blood volume. ANH inhibits the secretion of renin by the juxtaglomerular apparatus and the secretion of the aldosterone by the adrenal cortex. This promotes the excretion of sodium. When sodium is excreted so is water. This causes blood pressure and volume to decrease.

Hypernatremia
An increase in plasma sodium levels above normal is hypernatremia. Sodium is the primary solute in the extracellular fluid. Sodium levels have a major role in osmolarity regulation. For excitable cells the electrochemical gradient for sodium across the plasma membrane is critical for life. Water retention and an increased blood pressure usually are signs of hypernatremia. If the plasma sodium levels are below normal it is called hyponatremia. Signs of this are low plasma volume and hypotension.

Diuretics
A diuretic (colloquially called a water pill) is any drug that elevates the rate of bodily urine excretion (diuresis). Diuretics also decrease the extracellular fluid (ECF) volume, and are primarily used to produce a negative extracellular fluid balance. Caffeine, cranberry juice and alcohol are all weak diuretics. In medicine, diuretics are used to treat heart failure, liver cirrhosis, hypertension and certain kidney diseases. Diuretics alleviate the symptoms of these diseases by causing sodium and water loss through the urine. As urine is produced by the kidney, sodium and water – which cause edema related to the disease – move into the blood to replace the volume lost as urine, thereby reducing the pathological edema. Some diuretics, such as acetazolamide, help to make the urine more alkaline and are helpful in increasing excretion of substances such as aspirin in cases of overdose or poisoning. The antihypertensive actions of some diuretics (thiazides and loop diuretics in particular) are independent of their diuretic effect. That is, the reduction in blood pressure is not due to decreased blood volume resulting from increased urine production, but occurs through other mechanisms and at lower doses than that required to produce diuresis. Indapamide was specifically designed with this is mind, and has a larger therapeutic window for hypertension (without pronounced diuresis) than most other diuretics. Chemically, diuretics are a diverse group of compounds that either stimulate or inhibit various hormones that naturally occur in the body to regulate urine production by the kidneys. Alcohol produces diuresis through modulation of the vasopressin system.

Diseases of the Kidney
Diabetic nephropathy (nephropatia diabetica), also known as Kimmelstiel-Wilson syndrome and intercapillary glomerulonephritis, is a progressive kidney disease caused by angiopathy of capillaries in the kidney glomeruli. It is characterized by nodular glomerulosclerosis. It is due to longstanding diabetes mellitus, and is a prime cause for dialysis in many Western countries. In medicine, hematuria (or "haematuria") is the presence of blood in the urine. It is a sign of a large number of diseases of the kidneys and the urinary tract, ranging from trivial to lethal.

Kidney stones, also known as nephrolithiases, urolithiases or renal calculi, are solid accretions (crystals) of dissolved minerals in urine found inside the kidneys or ureters. They vary in size from as small as a grain of sand to as large as a golf ball. Kidney stones typically leave the body in the urine stream; if they grow relatively large before passing (on the order of millimeters), obstruction of a ureter and distention with urine can cause severe pain most commonly felt in the flank, lower abdomen and groin. Kidney stones are unrelated to gallstones.

Case Study I was 34 weeks pregnant when I noticed blood in my urine. I immediately went to my OBGYN where I was told that I had a bladder infection and given an antibiotic. The next morning I experienced the most intense pain. I was rushed to the ER where I was told that I had kidney stones. The doctors explained that there was nothing they could do as long as I was pregnant. The next 3 weeks of my life were filled with intense pain and multiple painkillers. After I delivered my baby, CAT scans were done and I was informed that I had 6 kidney stones. It took three more weeks for me to pass all of the stones the largest measuring 5 mm. The stones were tested and I was informed that my body had been building up calcium due to my pregnancy and this was the cause of the kidney stones. I continued to have kidney pain for 6 months after passing the stones. I now live my life on a low calcium diet and the hope that my body will not develop more kidney stones.

Pyelonephritis When an infection of the renal pelvis and calices, called pyelitis, spreads to involve the rest of the kidney as well, the result is pyelonephritis. It usually results from the spread of fecal bacterium Escherichia coli from the anal region superiorly through the urinary tract. In severe cases, the kidney swells and scars, abscesses form, and the renal pelvis fills with pus. Left untreated, the infected kidney may be severely damaged, but administration of antibiotics usually achieve a total cure.

glomerulonephritis Inflammation of the glomerular can be caused by immunologic abnormalities, drugs or toxins, vascular disorders, and systemic diseases. Glomerulonephritis can be acute, chronic or progressive. Two major changes in the urine are distinctive of glomerulonephritis: hematuria and proteinuria with albumin as the major protein. There is also a decrease in urine as there is a decrease in GFR (glomerular filtration rate). Renal failure is associated with oliguria (less than 400 ml of urine output per day).

Renal Failure Uremia is a syndrome of renal failure and includes elevated blood urea and creatinine levels. Acute renal failure can be reversed if diagnosed early. Acute renal failure can be caused by severe hypotension or severe glomerular disease. Diagnostic tests include BUN and plasma creatinine level tests. It is considered to be chronic renal failure if the decline of renal function to less than 25%.

Diabetes Insipidus
This is caused by the deficiency of or decrease of ADH. The person with (DI) has the inability to concentrate their urine in water restriction, in turn they will void up 3 to 20 liters/day. There are two forms of (DI), neurogenic, and nephrogenic. In nephrogenic (DI) the kidneys do not respond to ADH. Usually the nephrogenic (DI) is characterized by the impairment of the urine concentrating capability of the kidney along with concentration of water. The cause may be a genetic trait, electrolyte disorder, or side effect of drugs such as lithium. In the neurogenic (DI), it is usually caused by head injury near the hypophysisal tract.

Urinary tract infections (UTI's)
The second most common type of bacterial infections seen by health care providers is UTI's. Out of all the bacterias that colonize and cause urinary tract infections the big gun is Escherichia coli. In the hospital indwelling catheters and straight catheterizing predispose the opportunity for urinary tract infections. In females there are three stages in life that predispose urinary tract infections, that is menarche, manipulation between intercourse, and menopause. However, a small percentage of men and children will get urinary tract infections. In men it is usually due to the prostate gland growth which usually occurs in older age men. In children it can occur 3% to 5% in girls and 1% in boys, uncircumcised boys it is more common than circumcised ones to have a urinary tract infection, in girls it may be the result of onset of toilet training, some predispositions for getting urinary tract infection include family history and  urinary tract anomalies. In neonates urinary tract infections is most common when bacteremia is present.

Dialysis and Kidney Transplant

Generally, humans can live normally with just one kidney. Only when the amount of functioning kidney tissue is greatly diminished will renal failure develop. If renal function is impaired, various forms of medications are used, while others are contraindicated. Provided that treatment is begun early, it may be possible to reverse chronic kidney failure due to diabetes or high blood pressure. If creatinine clearance (a measure of renal function) has fallen very low ("end-stage renal failure"), or if the renal dysfunction leads to severe symptoms, dialysis is commenced. Dialysis is a medical procedure, performed in various different forms, where the blood is filtered outside of the body.

Kidney transplantation is the only cure for end stage renal failure; dialysis, is a supportive treatment; a form of "buying time" to bridge the inevitable wait for a suitable organ.

The first successful kidney transplant was announced on March 4, 1954 at Peter Bent Brigham Hospital in Boston. The surgery was performed by Dr. Joseph E. Murray, who was awarded the Nobel Prize in Medicine in 1990 for this feat.

There are two types of kidney transplants: living donor transplant and a cadaveric (dead donor) transplant. When a kidney from a living donor, usually a blood relative, is transplanted into the patient's body, the donor's blood group and tissue type must be judged compatible with the patient's, and extensive medical tests are done to determine the health of the donor. Before a cadaveric donor's organs can be transplanted, a series of medical tests have to be done to determine if the organs are healthy. Also, in some countries, the family of the donor must give its consent for the organ donation. In both cases, the recipient of the new organ needs to take drugs to suppress their immune system to help prevent their body from rejecting the new kidney.

Review Questions

 * Answers for these questions can be found here

1. While reading a blood test I notice a high level of creatinine, I could assume from this that
 * A) There is a possibility of a UTI
 * B) There is a possibility of diabetes
 * C) There is a possibility of kidney failure
 * D) There is nothing wrong, this is normal

2. Direct control of water excretion in the kidneys is controlled by
 * A) Anti-diuretic hormone
 * B) The medulla oblongata
 * C) Blood plasma
 * D) Sodium amounts in the blood

3. Nephrons
 * A) Eliminate wastes from the body
 * B) Regulate blood volume and pressure
 * C) Control levels of electrolytes and metabolites
 * D) Regulate blood pH
 * E) All of the above

4. If I am dehydrated, my body will increase
 * A) ATP
 * B) ADP
 * C) Diluted urine
 * D) ADH

5. Which part of the nephron removes water, ions and nutrients from the blood?
 * A ) vasa recta
 * B ) loop of henle
 * C ) proximal convoluted tubule
 * D ) peritubular capillaries
 * E ) glomerulus

6. Kidneys have a direct effect on which of the following
 * A ) Blood pressure
 * B ) How much water a person excretes
 * C ) Total blood volume
 * D ) pH
 * E ) all of the above

7. Why do substances in the glomerulus enter the Bowman's capsule?
 * A ) the magnetic charge of the Bowman's capsule attracts the substances
 * B ) the substances are actively transported into the Bowman's capsule
 * C ) blood pressure of the glomerulus is so great that most substances in blood move into capsule
 * D ) little green men force it in with their ray guns

8. What happens in tubular excretion?
 * A ) urine bonds are formed between the wastes
 * B ) wastes are diffused from the tubule
 * C ) wastes move into the distal convoluted tubule from the blood
 * D ) blood pressure forces wastes away from the kidney

9. The countercurrent exchange system includes_________and_________.
 * A ) glomerulus and macula densa
 * B ) proximal convoluted tubule and distal convoluted tubule
 * C ) loop of  Henle and collecting tubule
 * D ) afferent arteriole and efferent arteriole
 * E ) ureters and bladder

10. The function of the loop of the nephron in the process of urine formation is:
 * A ) reabsorption of water
 * B ) production of filtrate
 * C ) reabsorption of solutes
 * D ) secretion of solutes

11. Name the six important roles of the kidneys.

Glossary
Antidiuretic: lessening or decreasing of urine production or an agent that decreases the release of urine.

Catheterisation: a catheter is a tube that can be inserted into a body cavity, duct or vessel. Catheters thereby allow drainage or injection of fluids or access by surgical instruments. The process of inserting a catheter is catheterisation. In most uses a catheter is a thin, flexible tube: a "soft" catheter; in some uses, it is a larger, solid tube: a "hard" catheter.

Dehydration: condition resulting from excessive loss of body fluid.

Diabetes: a general term for a disease characterized by the beginning stages and onset of renal failure. It is derived from the Greek word diabaínein, that literally means "passing through," or "siphon", a reference to one of diabetes' major symptoms—excessive urine production.

Diuresis: secretion and passage of large amounts of urine.

Diuretic: increasing of urine production, or an agent that increases the production of urine.

Erythropoietin: hormone that stimulates stem cells in the bone marrow to produce red blood cells

Fibrous Capsule: the kidney's loose connective tissue

Glomerulus: capillary tuft that receives its blood supply from an afferent arteriole of the renal circulation.

Gluconeogenesis: the cycle of producing a glucose form fat or protein; preformed by the kidney in times of long fasting, initially gluconeogenesis is preformed by the liver

Juxtaglomerular (JG) cells: Renin-secreting cells that are in contact with the macula densa and the afferent arterioles of the renal nephron.

Juxtaglomerular apparatus (JGA): A site of juxtaglomerular cells connecting with the macula densa where renin is secreted and sensor for control of secretion of golmerular filtration rate.

Loop of Henle/ Nephron Loop: u-shaped tube that consists of a descending limb and ascending limb; primary role is to concentrate the salt in the interstitium, the tissue surrounding the loop

Medullary Pyramids or Renal Pyramids: the cone shaped masses in the kidney

Micturition: another name for excretions

Nephron: basic structural and functional unit of the kidney; chief function is to regulate water and soluble substances by filtering the blood, reabsorbing what is needed and excreting the rest as urine

Podocytes: filtration membrane, in the visceral layer of the bowman's capsule

Renal Calculi: kidney stones, solid crystals of dissolved minerals in urine found inside the kidneys

Renal Cortex: outer portion of the kidney

Renal Lobe: each pyramid together with the associated overlying cortex

Renal Pelvis: a central space, or cavity that transmits urine to the urinary bladder via the ureter

Renin: hormone released by the Juxtaglomerular (JG) cells of the kidneys when blood pressure falls

TURP: transurethral resection of the prostate. During TURP, an instrument is inserted up the urethra to remove the section of the prostate that is blocking urine flow. This is most commonly caused by benign prostatic hyperplasia (BPH). A TURP usually requires hospitalization and is done using a general or spinal anesthetic. It is now the most common surgery used to remove part of an enlarged prostate.

Urethra: a muscular tube that connects the bladder with the outside of the body

Ureters: two tubes that drain urine from the kidneys to the bladder

Urine: liquid produced by the kidneys, collected in the bladder and excreted through the urethra

Urinary Bladder: a hollow, muscular and distensible or elastic organ that sits on the pelvic floor

Urinary System: a group of organs in the body concerned with filtering out excess fluid and other substances from the bloodstream

title: Human Physiology/The Urinary System


text:
C Programming/Pointers and arrays

A pointer is a value that designates the address (i.e., the location in memory), of some value. Pointers are variables that hold a memory location.

There are four fundamental things you need to know about pointers:
 * How to declare them (with the address operator ' ': )
 * How to assign to them
 * How to reference the value to which the pointer points (known as dereferencing, by using the dereferencing operator ' ': )
 * How they relate to arrays (the vast majority of arrays in C are simple lists, also called "1 dimensional arrays", but we will briefly cover multi-dimensional arrays with some pointers in a later chapter).

Pointers can reference any data type, even functions. We'll also discuss the relationship of pointers with text strings and the more advanced concept of function pointers.

Declaring pointers
Consider the following snippet of code which declares two pointers:

Lines 1-4 define a structure. Line 8 declares a variable that points to an int, and line 9 declares a variable that points to something with structure MyStruct. So to declare a variable as something that points to some type, rather than contains some type, the asterisk is placed before the variable name.

In the following, line 1 declares  as a pointer to a long and   as a long and not a pointer to a long. In line 2,  is declared as a pointer to a pointer to an int.

Pointer types are often used as parameters to function calls. The following shows how to declare a function which uses a pointer as an argument. Since C passes function arguments by value, in order to allow a function to modify a value from the calling routine, a pointer to the value must be passed. Pointers to structures are also used as function arguments even when nothing in the struct will be modified in the function. This is done to avoid copying the complete contents of the structure onto the stack. More about pointers as function arguments later.

Assigning values to pointers
So far we've discussed how to declare pointers. The process of assigning values to pointers is next. To assign the address of a variable to a pointer, the  or 'address of' operator is used.

Here, pPointer will now reference myInt and pKeyboard will reference dvorak.

Pointers can also be assigned to reference dynamically allocated memory. The malloc and calloc functions are often used to do this.

The malloc function returns a pointer to dynamically allocated memory (or NULL if unsuccessful). The size of this memory will be appropriately sized to contain the MyStruct structure.

The following is an example showing one pointer being assigned to another and of a pointer being assigned a return value from a function.

When returning a pointer from a function, do not return a pointer that points to a value that is local to the function or that is a pointer to a function argument. Pointers to local variables become invalid when the function exits. In the above function, the value returned points to a static variable. Returning a pointer to dynamically allocated memory is also valid.

Pointer dereferencing
To access a value to which a pointer points, the  operator is used. Another operator, the  operator is used in conjunction with pointers to structures. Here's a short example.

The expression  is entirely equivalent to. They both access the  element of the structure pointed to by. There is one more way of dereferencing a pointer, which will be discussed in the following section.

When dereferencing a pointer that points to an invalid memory location, an error often occurs which results in the program terminating. The error is often reported as a segmentation error. A common cause of this is failure to initialize a pointer before trying to dereference it. C is known for giving you just enough rope to hang yourself, and pointer dereferencing is a prime example. You are quite free to write code that accesses memory outside that which you have explicitly requested from the system. And many times, that memory may appear as available to your program due to the vagaries of system memory allocation. However, even if 99 executions allow your program to run without fault, that 100th execution may be the time when your "memory pilfering" is caught by the system and the program fails. Be careful to ensure that your pointer offsets are within the bounds of allocated memory!

The declaration  is used to declare a pointer of some nonspecified type. You can assign a value to a void pointer, but you must cast the variable to point to some specified type before you can dereference it. Pointer arithmetic is also not valid with  pointers.

Pointers and Arrays
Up to now, we've carefully been avoiding discussing arrays in the context of pointers. The interaction of pointers and arrays can be confusing but here are two fundamental statements about it:

The first case often is seen to occur when an array is passed as an argument to a function. The function declares the parameter as a pointer, but the actual argument may be the name of an array. The second case often occurs when accessing dynamically allocated memory.
 * A variable declared as an array of some type acts as a pointer to that type. When used by itself, it points to the first element of the array.
 * A pointer can be indexed like an array name.

Let's look at examples of each. In the following code, the call to  effectively allocates an array of struct MyStruct items.

Pointers and array names can pretty much be used interchangeably; however, there are exceptions. You cannot assign a new pointer value to an array name. The array name will always point to the first element of the array. In the function, you could however assign a new value to workingArray, as it is just a pointer to the first element of workingArray. It is also valid for a function to return a pointer to one of the array elements from an array passed as an argument to a function. A function should never return a pointer to a local variable, even though the compiler will probably not complain.

When declaring parameters to functions, declaring an array variable without a size is equivalent to declaring a pointer. Often this is done to emphasize the fact that the pointer variable will be used in a manner equivalent to an array.

Now we're ready to discuss pointer arithmetic. You can add and subtract integer values to/from pointers. If myArray is declared to be some type of array, the expression, where j is an integer, is equivalent to. For instance, in the above example where we had the expression, we could have written that as   or more simply.

Note that for addition and subtraction of integers and pointers, the value of the pointer is not adjusted by the integer amount, but is adjusted by the amount multiplied by the size of the type to which the pointer refers in bytes. (For example,  can be thought of as  .)

One pointer may also be subtracted from another, provided they point to elements of the same array (or the position just beyond the end of the array). If you have a pointer that points to an element of an array, the index of the element is the result when the array name is subtracted from the pointer. Here's an example.

You may be wondering how pointers and multidimensional arrays interact. Let's look at this a bit in detail. Suppose A is declared as a two dimensional array of floats and that pf is declared a pointer to a float. If pf is initialized to point to A[0][0], then *(pf+1) is equivalent to A[0][1] and *(pf+D2) is equivalent to A[1][0]. The elements of the array are stored in row-major order.

Let's look at a slightly different problem. We want to have a two dimensional array, but we don't need to have all the rows the same length. What we do is declare an array of pointers. The second line below declares A as an array of pointers. Each pointer points to a float. Here's some applicable code:

We also note here something curious about array indexing. Suppose  is an array and   is an integer value. The expression  is equivalent to. The first is equivalent to, and the second is equivalent to. These turn out to be the same, since the addition is commutative.

Pointers can be used with pre-increment or post-decrement, which is sometimes done within a loop, as in the following example. The increment and decrement applies to the pointer, not to the object to which the pointer refers. In other words,  is equivalent to.

Pointers in Function Arguments
Often we need to invoke a function with an argument that is itself a pointer. In many instances, the variable is itself a parameter for the current function and may be a pointer to some type of structure. The ampersand ( ) character is not needed in this circumstance to obtain a pointer value, as the variable is itself a pointer. In the example below, the variable, a pointer, is a parameter to function  , and is passed as an argument to.

The second parameter to  is an int. Since in function,   is a pointer to an int, the pointer must first be dereferenced using the * operator, hence the second argument in the call is. The third parameter to function  is a pointer to a long. Since  is itself a pointer to a long, no ampersand is needed when it is used as the third argument to the function.

Pointers and Text Strings
Historically, text strings in C have been implemented as arrays of characters, with the last byte in the string being a zero, or the null character '\0'. Most C implementations come with a standard library of functions for manipulating strings. Many of the more commonly used functions expect the strings to be null terminated strings of characters. To use these functions requires the inclusion of the standard C header file "string.h".

A statically declared, initialized string would look similar to the following:

The variable  can be viewed as an array of 21 characters. There is an implied null character ('\0') tacked on to the end of the string after the 'd' as the 21st item in the array. You can also initialize the individual characters of the array as follows:

An initialized array of strings would typically be done as follows:

The initialization of an especially long string can be split across lines of source code as follows.

The library functions that are used with strings are discussed in a later chapter.

Pointers to Functions
C also allows you to create pointers to functions. Pointers to functions syntax can get rather messy. As an example of this, consider the following functions:

Declaring a typedef to a function pointer generally clarifies the code. Here's an example that uses a function pointer, and a void * pointer to implement what's known as a callback. The  function invokes a caller supplied function   with caller data. Note that  really doesn't know anything about what   refers to.

Some versions of C may not require an ampersand preceding the  argument in the   call. Some implementations may require specifically casting the argument to the  type, even though the function signature exacly matches that of the typedef.

Function pointers can be useful for implementing a form of polymorphism in C. First one declares a structure having as elements function pointers for the various operations to that can be specified polymorphically. A second base object structure containing a pointer to the previous structure is also declared. A class is defined by extending the second structure with the data specific for the class, and static variable of the type of the first structure, containing the addresses of the functions that are associated with the class. This type of polymorphism is used in the standard library when file I/O functions are called.

A similar mechanism can also be used for implementing a state machine in C. A structure is defined which contains function pointers for handling events that may occur within state, and for functions to be invoked upon entry to and exit from the state. An instance of this structure corresponds to a state. Each state is initialized with pointers to functions appropriate for the state. The current state of the state machine is in effect a pointer to one of these states. Changing the value of the current state pointer effectively changes the current state. When some event occurs, the appropriate function is called through a function pointer in the current state.

Practical use of function pointers in C
Function pointers are mainly used to reduce the complexity of switch statement. Example with switch statement:

Without using a switch statement:

Function pointers may be used to create a struct member function: Use to implement this pointer (following code must be placed in library).

Examples of pointer constructs
Below are some example constructs which may aid in creating your pointer.

sizeof
The sizeof operator is often used to refer to the size of a static array declared earlier in the same function.

To find the end of an array (example from Buffer overflow):

To iterate over every element of an array, use

Note that the  operator only works on things defined earlier in the same function. The compiler replaces it with some fixed constant number. In this case, the  was declared as an array of 10 char's earlier in the same function, and the compiler replaces   with the number 10 at compile time (equivalent to us hard-coding 10 into the code in place of  ). The information about the length of  is not actually stored anywhere in memory (unless we keep track of it separately) and cannot be programmatically obtained at run time from the array/pointer itself.

Often a function needs to know the size of an array it was given -- an array defined in some other function. For example,

Unfortunately, (in C and C++) the length of the array cannot be obtained from an array passed in at run time, because (as mentioned above) the size of an array is not stored anywhere. The compiler always replaces sizeof with a constant. This sum routine needs to handle more than just one constant length of an array.

There are some common ways to work around this fact:
 * Write the function to require, for each array parameter, a "length" parameter (which has type "size_t"). (Typically we use sizeof at the point where this function is called).
 * Use of a convention, such as a null-terminated string to mark the end of the array.
 * Instead of passing raw arrays, pass a structure that includes the length of the array (such as ".length") as well as the array (or a pointer to the first element); similar to the  or   classes in C++.

It's worth mentioning that sizeof operator has two variations: sizeof (type) (for instance: sizeof (int) or sizeof (struct some_structure)) and sizeof expression (for instance: sizeof some_variable.some_field or sizeof 1).

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: C Programming/Pointers and arrays


text:
File:Bioeconomics fig1.png

Figure showing a logistic growth equation

Converted from a GIF uploaded by ArneEide.

title: File:Bioeconomics fig1.png


text: Template:Spam

title: Template:Spam


text:
User talk:216.206.6.56

Here is the printable version you were looking for. Guanaco 22:32, 9 Jun 2004 (UTC)

title: User talk:216.206.6.56


text:
Hindi/Speaking and Writing

Example of Hindi writing:

मनमोहन सिंह मंत्रिमंडल में मंत्रालयों का बटवारा पूरा हो गया है। कपिल सिब्बल को मानव संसाधन विकास और आनंद शर्मा को वाणिज्य एवं उद्योग विभाग दिया गया है।

Hindi consists of 11 vowels, 40 consonants, and two sound modifiers.

The Hindi syllabary is ordered according to how the sounds are created in the mouth.

Vowels
First are the vowels, which, with one exception, come in pairs:

अ आ इ ई उ ऊ ए ऐ ओ औ अं अः

Using the International Alphabet of Sanskrit Transliteration (IAST), these vowels would be represented thus:

a ā i ī u ū ṛ e ai o au

 * अ (a) is pronounced as a default vowel, similar to a schwa.
 * आ (ā) is like the vowel a in father.
 * इ (i) is like the vowel in tin.
 * ई (ī) is like the vowel in see.
 * उ (u) is like the vowel in book.
 * ऊ (ū) is like the vowel in tool.
 * ए (e) is like the vowel in May except there is no diphthong.
 * ऐ (ai) is one of the only two diphthong vowels in Hindi, and pronounced differently depending on regional accent. Often it is pronounced like the vowel in hat.
 * ओ (o) is like the vowel in hole.
 * औ (au) is the other diphthong vowel, also with varying pronunciation. It is often pronounced like the vowel in saw or awe.
 * ऋ (rri) It is pronounced like the vowel sound in brittle.

All vowels in Hindi have two forms: Their standalone form and their mātrā form. The mātrā form modifies consonants. Here are the eleven vowels paired with the syllable क (k):

 * Note that there is no mātrā form for the first vowel, अ -- a. This is because all Hindi consonants, unless part of a conjunct (see below), or they appear at the end of a word, automatically contain this vowel. So, the letter क is pronounced ka.

Regular Consonants
There are 25 regular consonants (consonants that stop air from moving out of the mouth) in Hindi, and they are organized into groups (vargas) of five. The vargas are ordered according to where the tongue is in the mouth. Each successive varga refers to a successively forward position of the tongue. The vargas are ordered and named thus (with an example of a corresponding consonant):

 * Velar (k)
 * Palatal (j)
 * Retroflex (English t)
 * Dental (Spanish t)
 * Labial (p)

The five consonants in each group are ordered thus:

 * unaspirated, unvoiced
 * aspirated, unvoiced
 * unaspirated, voiced
 * aspirated, voiced
 * nasal

The difference between voiced and unvoiced consonants is as simple for an English speaker to understand as understanding the difference between the consonants "k" and "g" or "j" and "ch." However, aspiration is a distinction foreign to most English speakers. To understand the difference, do this simple exercise:

Hold your palm about an inch in front of your mouth. Say the word "pit." Notice that your hand will likely feel a short burst of air coming from your mouth. Now say the word "spit" and notice that there is little or no burst of air. Now attempt to say "pit" again, this time without letting the burst of air happen.

Here are the five vargas of regular consonants, followed by their corresponding IAST characters:

Notes:

 * The nasal consonants in the first two vargas are almost never found written alone; they are usually conjuncted (more on conjuncts later) with another consonant in their corresponding vargas, as the other nasal consonants often are.

 * The consonants in the first two vargas, as well as the last, are pronounced exactly as they are in English. In other words, a Hindi k sounds like an English "k" (without aspiration).

 * The consonant written 'c' can be confusing; it is pronounced like the first sound in the word chair but without aspiration. The consonant ch is virtually indistinguishable from c to the untrained English speaker, but is indeed a different letter.

 * The English consonants "t" and "d" fall somewhere in between the Hindi consonants t and d, and ṭ and ḍ. They are closer to the latter (retroflex), so when Hindi speakers say or speak English words containing t or d, they almost always use the retroflex version. To achieve these sounds, curl the tongue back and touch the tip to the roof of the mouth.

 * The dental consonants are pronounced exactly like the "t" and "d" in Spanish, with the tongue touching the back of the upper teeth.

 * Voiced, aspirated consonants (gh, bh, etc.) are by far the hardest sounds for the English speaker to learn how to make; however, with some practice they are not overly difficult.

Semivowels
There are four semivowels in Hindi:

य र ल व

y r l w (v)

 * y is very similar to its corresponding English sound.
 * r, like most non-English "r" sounds, is flipped, but not rolled.
 * l is the same as the English "l".
 * w (v) has a somewhat flexible pronunciation, depending on context and regional dialects. Sometimes it is pronounced like the English "w" (as in the word swami), and other times it is closer to the English "v". It is often pronounced somewhere in between the two sounds.

Sibilants
There are three sibilants:

श ष स

ś ṣ s

 * ś is the same as "sh" in English.
 * ṣ is also similar to "sh" in English, and though it is technically pronounced farther back in the mouth, functionally there is very little or no difference between the two in spoken Hindi.
 * s is the same as "s" in English.

Fricative
There is one fricative consonant:

ह

h

 * h is pronounced the same as "h" in English.

Modified Consonants
There are many sounds found in Hindi that do not directly correspond to any Devanagari letter:

 * क़ (q) is pronounced farther back in the throat than क. For example, the Arabic word Qu'ran begins with this letter.

 * ग़ (ġ) is pronounced in the back of the throat, similar to the French "r."

 * ख़ ( kh ) is pronounced like "ch" in German words like Bach or Reich.

 * ज़ (z) is the same as the English "z."

 * ड़ (ṛ) is difficult to describe, except by example. The Hindi word गाड़ी (gaṛī) sounds very much like "gardee." Notice that the character used to denote this character is the same as denotes ऋ . The only way to tell the difference is context; if ṛ is followed by a consonant, it corresponds to ऋ (example: ऋषि -- ṛṣi or "Rishi"). If it is followed by a vowel or falls at the end of a word, is is most likely ड़.

 * ढ़ (ṛh) is the aspirated version of ड़.

 * फ़ is the same as the English sound "f."

Sound Modifiers
The anusvara is notated with a small dot above the corresponding letter. In IAST, it is notated ṃ. It can have two different effects:

 * In mid-word, when it appears before a consonant, it has the same effect as if that consonant's corresponding nasal consonant were placed right before it. For example, if placed before the "k" sound in the English word "buck," it would make the word change to "bunk." Hindi example: संग -- saṃga (group, association) -- is often transliterated as sanga.

 * Placed at the end of a word (after a vowel with no further consonants), it simply nasalizes the vowel, often sounding as if the English "ng" (as in "song") had been placed at the end of the word, though lightly.

Hindi examples: में -- meṃ (in).

The candrabindu (meaning "moon dot") is very similar to the anusvara and is notated with a dot and a small crescent (see below). When placed above a vowel, the vowel becomes nasalized.

Hindi example: महँगा -- mahaṃgā (meaning "expensive").

The visarga is notated with what looks like an English colon. It is transliterated with ḥ. It is only found at the end of words, and only found on Sanskrit loan words. It has the effect of adding a h as well as a lighter version of the preceding vowel. For example, नमः is pronounced namaha, with the last a having as little emphasis as possible.

The halant is a small diagonal line which indicates that the default vowel अ -- a is not to be pronounced. It only appears at the end of words. In Hindi, however, this symbol is almost never seen, as, unlike Sanskrit, the default vowel is almost never pronounced on the final consonants of words. Example: नाम् -- nām (name).

Conjuncts
Very often, two or more consonants are combined.

title: Hindi/Speaking and Writing


text:
Hindi/Core grammar

This page is part of the Hindi course.

Word order
The word order in Hindi/Urdu is:
 * The adjective is before the noun
 * The verb is always at the end of the phrase
 * Similar to Classical Latin and Greek in structure

Hindi: N1 A1 N2 postp1 N3 postp2 N4 cmkr3 LtV1 LtV2 VectorVerb AuxBe

English: N1 Verb prep3 N4 prep2 N3 prep1 A1 N2

The word order can change to put emphasis on a part of the sentence.

So to say My friend's pretty mother cooks food very well, Mere dost ki khoobsurat ma khana aachese banathi. Translated word for word, this is ''My friend of pretty mother food well cooks."

Simple way to order words in a sentence: Adjective subject object verb adverbs

Sentence components

 * case markers and compound post-positions mark the various arguments given to a verb
 * many predicates are so-called light verb expressions, consisting of several words followed by a vector verb. The most common of these vectors are the verbs karnā (to do) and honā (to be or, to happen).

Case markers

 * ne - marks the subject or topic (but only in the past perfective tense for transitive verbs)
 * ka/ke/ki - marks the genitive
 * ko - marks the accusative or dative, although occasionally this is the subject
 * se - typically means "from" or "by", also marks the passive agent
 * mein, par - locative "in", "at"

Subjects, objects, and destinations are sometimes not marked at all.

Compound post-positions
Most English prepositions (which don't otherwise translate with a case marker) will translate with a ke/ki followed by a noun. It is useful to think of the ke/ki paired with these particular nouns as being a compound post-position.

e.g. - "Anyone" + "ke khilaf" means "against" + "Anyone"

title: Hindi/Core grammar


text:
User talk:24.31.174.141

Hello, I noticed all your wonderful improvements on the Existentialist page.

Thank you for getting me straight about Soren and of course the EXISTENTIALIST stage.

Thanks for your suggestions about modern Existentialist authors.

And thank you for correcting my spelling mistakes.

EuropracBHIT 02:12, 10 Jun 2004 (UTC)

title: User talk:24.31.174.141


text:
User talk:168.212.239.2

Romeo and Juliet, Act 2?, Scene 2
Hello 168.212.239.2,

I saw your edits (2-18.25 and 18.27 UTC) on the balcony scene of Romeo and Juliet.

I compared them to KPJas's original.

I was not aware that Shakespeare characters broke out into 21st-century teen-speak.

I do know that Elizabethian plays are often bawdy, but not to the extent that a stage direction would show 'below the waist'.

I will delete your edits accordingly.

Thank you,

EuropracBHIT 02:28, 10 Jun 2004 (UTC)

title: User talk:168.212.239.2


text:
Talk:GTK+ By Example

I have just started working on writing the first programing chapter in this book (yay 4 years in and it has been started :D) and hope I can encourage you to help edit this book, just click at the top of a page, don't worry if you make a mistake it can be undone.

I think I made the front page look a bit prettier, don't you, don't tell anyone but, I totally stole it from Algorithms --Gnepets (talk) 15:36, 4 July 2009 (UTC)

Orphaned page
GTK+ By Example/Environment/Command Line Compilation is not linked to by this book. Please mark it with if it is no longer needed, link to it, or merge it into a page and mark it with. -- Adrignola talk contribs 17:29, 2 August 2009 (UTC)

title: Talk:GTK+ By Example


text:
User talk:68.79.170.99

Dear 68.79.170.99,

Here is what people do when they track your IP address (and have exhausted the powers given them by the Wiki form):

They go to a site like DNS-Stuff.com.

They look at the address.

They report abuse to the abuse e-mail.

They are most careful to find out who you are and where you live.

Your ISP will almost certainly take you off it's a serious charge and there is enough evidence. You may be under civil or criminal charges.

Even though what you may do is not illegal, it most certainly is unethical and immoral.

Glad to see the boys (and girls!) who play American Army have a sense of honour regarding these matters.

Thank you EuropracBHIT 04:14, 10 Jun 2004 (UTC)

title: User talk:68.79.170.99


text:
Cookbook:Bulgur Burgers

| Vegetarian cuisine | Sandwiches

A bulgur burger is a tasty vegetarian patty for use in sandwiches.

Ingredients

 * 3 cups water
 * 2 cloves garlic
 * 1 ½ cups bulghur
 * 2 tablespoons vegetable oil
 * ½ cup scallions, chopped
 * ½ cup carrots, grated
 * ¼ cup fresh parsley, chopped
 * ¼ cup tahini
 * 2 tablespoons tomato paste
 * 2 tablespoons soy sauce
 * 1 teaspoon Dijon mustard
 * 1 dash ground black pepper

Procedure

 * 1) Bring the water to a boil.
 * 2) While it is heating, use a heavy pan or skillet to sauté the garlic and bulghur in the oil on medium-high heat for 2 minutes, stirring frequently.
 * 3) Add the boiling water to the skillet. Return to a boil, cover, and reduce heat to low.
 * 4) Simmer for 15 to 20 minutes, until all of the water is absorbed and the bulghur is soft but still chewy.
 * 5) When the bulghur is ready, stir in the scallions, carrots, parsley, tahini, tomato paste, soy sauce, mustard, and pepper. With moistened hands, form the bulghur mixture into 6 to 8 burgers.
 * 6) Cook the patties in a lightly-oiled heavy skillet on medium-low heat for about 10 minutes, flipping the burgers once when the outside is crunchy, or bake on an oiled baking sheet for 20 minutes at 375 °F (190 °C).

Notes, tips, and variations

 * For a different flavour and more protein, add 1 cup of mashed cooked chickpeas to the cooked bulghur along with the other ingredients, before forming the burgers.

title: Cookbook:Bulgur Burgers


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Cookbook talk:Bulgur Burgers

This module uses text originaly published in the Wikipedia article Bulgher burger. The authors of the text that was copied are included below:

* (cur) (last) 11:12, 15 Nov 2003 Guaka (bb is...) * (cur) (last) 11:11, 15 Nov 2003 Guaka (edit) * (cur) (last) 21:04, 30 Aug 2003 Error m (Links) * (cur) (last) 14:46, 20 Jul 2003 Michael Hardy * (cur) (last) 14:01, 20 Jul 2003 65.95.169.53

title: Cookbook talk:Bulgur Burgers


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Talk:Intelligence Intensification/General Tips For Practicing

I don't get the Info-Ecosystem, how does it connects to the book? I think it is very unrelated.

please tell me what you think, especialy the one who added it.

 * It seems to me there are some good ideas in the section but much is undefined. I've read quite a lot of college mathematics and much of it doesn't make sense to me (even as a metaphor). The author is welcomed to give some concrete practical examples. Maybe we are only seeing the tip of the iceberg? You must know the whole iceberg in order to make sense of the tip, and most readers don't. --DanielJanzon 10:01, 11 Jun 2004 (UTC)

 * For instance: Be mindful that multiplication with zero is zero. Fine. This might be interpreted as "the effort of copying information to k new pieces of the same information is zero", which in turn might be interpreted as "it's free to give away a digital picture to everyone who wants it". But what has that to do with increasing the intelligence? Are you refering to the intelligence on a larger scale, the intelligence of humanity? Maybe that should be more clearly stated. Maybe it should be placed in another section like Systems engineering or something like that. --DanielJanzon 10:20, 11 Jun 2004 (UTC)

 * And what is meant by exponentiating information? Of course exp(0) = 1 if 0 is a number, matrix or something else we have a theory for, but what is the definition of exp(x) where x is information? Information is not a clearly defined word. If we had a preciese mathematical definition of the word, we could make a digital filter filtering out information from a random source. That would clearly be amazing. Observe that Shannon's definition of information is not what we usually mean by information. --DanielJanzon 10:20, 11 Jun 2004 (UTC)


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Talk:Learning the vi Editor/Basic tasks

Hi. I think an explanation of how vi views a text file would greatly help users grok how the different modes/commands fit. Briefly:

 * A file contains lines of text
 * A line of text contains words
 * Words contain characters

Commands are executed based on one of the above three modes.

66.84.146.64 MarkK

title: Talk:Learning the vi Editor/Basic tasks


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Kinematics/Linear Motion

Problems

 * 1. A man fires a rock out of a slingshot directly upward. The rock has an initial velocity of 15 m/s. How long will it take for the rock to return to the level he fired it at?

 * 5 It takes a man ten seconds to ride down an escalator. It takes the same man 15 seconds to walk back up the escalator against its motion. How long will it take the man to walk down the escalator at the same rate he was walking before?

Prerequisite: Calculus
 * 24. Starting with the definitions of velocity and acceleration derive the kinematics equation for constant acceleration x = x0 + v0t + (1/2) at^2.

 * 25. A cockroach starts 1 cm away from a wall. It starts running in a line directly away from the wall with a velocity of 1 cm/s, acceleration of 1 cm/s^2, jerk (d^3 x/dt^3) of 1 cm/s^3, d^4 x/dt^4 of 1 cm/s^4, and so on. How far is the cockroach from the wall after one second?

Solutions
1. 3 s. Use the kinematics equation y = y0 + v0t + 1/2 at^2. Let the rock's initial height y be 0. Plugging the values into the equation yields 0 = 15t - (1/2) 10t^2. Factoring and solving for t yields solutions of 0 s and 3 s. Hence it takes the rock 3 s to return to its original height.

24. The quickest solution is to write the Taylor series for x, this yields the solution immediately. Another route to the solution is to solve the differential equation by separating the variables.

25. e cm. The Taylor series for positions is x = x0 + v0 t + (1/2!) a0 t^2 + (1/3!) j0 t^3 + ... . Since x0, v0, a0, ... are all equal to one and t, t^2, t^3, ... are all equal to one, you have the following series: x = 1 + 1 + 1/2 + 1/6 + ... . This is a series that sums to e, thus the cockroach travels e cm after one second.

title: Kinematics/Linear Motion


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General Mechanics/The Continuum Limit

Introduction
In principle, we could use the methods described so far to predict the behavior of matter by simply keeping track of each atom.

In practice, this is not a useful approach. Instead, we treat matter as a continuum.

In this section we will see how this is done, and how it leads us back to waves.

For an example, we will consider a set of N+1 identical springs and masses, arranged as in the previous section, with spring 0 attached to the wall, and mass N free.

We are interested in what happens for large N, the continuum limit.

The system has three other parameters; the spring constant k, the particle mass Δm, and the spring rest spacing Δa, where variable names have been chosen for future convenience. These can be combined with N to give a similar set of parameters for the system.

Suppose all the masses are displaced by d from rest, with total displacement D=dN of the system end, then the total potential energy is kNd2/2 = kD2/(2N), so

 * The system's spring constant is K=k/N
 * The system mass is m=ΔmN
 * The system rest length is a=ΔaN

If, as we increase N we change the other three parameters to keep K, m, and a constant then in the large N limit this discrete system will look like a spring with mass continuously distributed along its length.

For coordinates, we will use the displacements of each mass, xn. For large N the displacement will vary approximately continuously with distance. We can regard it as a continuous function, x, with

 * $$x(n\Delta a)=x_n \,$$

The kinetic energy of the system is then simply

 * $$T=\frac{1}{2} \Delta m \sum_0^N \dot{x}_n^2 $$

The total potential energy is similarly

 * $$V=\frac{1}{2}k x_0^2 + \frac{1}{2}k \sum_1^N (x_n-x_{n-1})^2 $$

From this we may deduce the equations of motion in two different ways.

Equations of motion: First approach
If we take the large N limit first, these sums become integrals.

 * $$\begin{matrix}

T & = & \frac{m}{2a}\sum_0^N \dot{x}_n^2 \Delta a \\ \lim_{N \rarr \infty} T & = & \frac{m}{2a} \int_0^a \dot{x}^2 ds \end{matrix}$$

where s is the distance from the wall, and

 * $$\begin{matrix}

V & = & \frac{1}{2}k x_0^2 + \frac{1}{2}k \sum_0^{N-1} (x_n-x_{n+1})^2 \\ & = & \frac{1}{2}k x_0^2 + \frac{1}{2}K \sum \left( \frac{ x(n\Delta a+\Delta a)- x(n\Delta a)}{\Delta a} \right)^2 a \Delta a\\ \lim_{N \rarr \infty} V & = & \frac{1}{2}k x(0)^2 + \frac{1}{2}Ka \int \left( \frac{dx}{ds} \right)^2 ds \end{matrix}$$

Since the springs always remain attached to the wall, x(0)=0.

The integrand for T is the product of the density and the square of the velocity, just as we might naively expect. Simalarly, V is the integral of the potential energy of a infinitesimal spring over the length of the system.

Using the Lagrangian will let us get equations of motion from these integrals.

It is

 * $$\begin{matrix}

L & = & \frac{m}{2a} \int_0^a \dot{x}^2 ds - \frac{1}{2}Ka\int_0^a \left( \frac{dx}{ds} \right)^2 ds \\ & = & \frac{m}{2a} \int_0^a (\dot{x}^2 - \frac{Ka^2}{m} x^{\prime 2}) ds\\ \end{matrix}$$

The action of the system is

 * $$\int L dt = \int \int \mathcal{L}(\dot{x},x^\prime) dx dt \quad

\mbox{ where } \mathcal{L}=\frac{m}{2a}(\dot{x}^2 - \frac{Ka^2}{m} x^{\prime 2}) $$

Here, we are integrating over both space and time, rather than just space, but this is still very similar in form to the action for a single particle.

We can expect that the principle of least action will lead us to the natural extension of Lagrange's equations to this action,

 * $$\frac{d}{ds}\frac{\partial \mathcal{L}}{\partial x^\prime}+

\frac{d}{dt}\frac{\partial \mathcal{L}}{\partial \dot{x}} = \frac{\partial \mathcal{L}}{\partial x} $$

This equation can be proven, using the calculus of variations. Using it for this particular Lagrangian gives

 * $$\frac{\partial^2 x}{\partial t^2} - \frac{Ka^2}{m}\frac{\partial^2 x}{\partial s^2} = 0$$

This is a partial differential equation. We will not be discussing its solution in detail, but we will see that it describes waves.

First, though, we will confirm that these equations are the same as we get if we find the equations of motion first, then take the large N limit.

Equations of motion: Second approach
First, we will look at the potential energy to see how it depends on the displacements.

$$\begin{matrix} V & = & \frac{1}{2}k x_0^2 + \frac{1}{2}k \sum_0^{N-1} (x_n-x_{n+1})^2 \\ & = & \frac{1}{2}k \left( x_0^2 \cdots (x_{n-1}-x_n)^2 + (x_n-x_{n+1})^2 \cdots (x_N-x_{N-1})^2 \right) \\ & = & \frac{1}{2}k \left( 2x_0^2 -2x_0 x_1 \cdots -2x_n x_{n+1} + 2x^2_n -2x_n x_{n+1} \cdots x^2_N - 2x_N x_{N-1} \right) \\ & = & \frac{1}{2}k \left( 2x_0^2 -2x_0 x_1 \cdots 2x_n (x_n-x_{n+1}-x_{n-1}) \cdots x^2_N - 2x_N x_{N-1} \right) \\ \end{matrix}$$

Notice that we need to treat the displacements of the first and last masses differently from the other coordinates, because the dependence of the Langragian on them is different.

The kinetic energy is symmetric in the coordinates,

 * $$T=\frac{1}{2} \Delta m \sum_0^N \dot{x}_n^2$$

Using Lagrange's equations, we get that, for x0

 * $$\Delta m \ddot{x}_0 + 2k x_0 = k x_1,$$

for xN,

 * $$\Delta m \ddot{x}_N + k x_N = k x_{N-1},$$

and, for all the other xn

 * $$\Delta m \ddot{x}_n + 2k x_n = k (x_{n+1}+x_{n-1}),$$

We can replace k and Δm by the limiting values K and m using

 * $$\frac{k}{\Delta m} = \frac{K a^2}{m \Delta a^2} $$

giving us

 * $$\begin{matrix}

\ddot{x}_0 & = & \frac{K a^2}{m} \frac{x_1-2x_0}{\Delta a^2}\\ \ddot{x}_n & = & \frac{K a^2}{m} \frac{x_{n-1}+x_{n+1}-2x_n}{\Delta a^2}\\ \ddot{x}_N & = & \frac{K a^2}{m} \frac{x_{N-1}-x_N}{\Delta a^2} \end{matrix}$$

Looking at the general structure of the right hand side, we see difference between the displacement at nearby points divided by the distance between those points, so we expect that in the limit we will get differentials with respect to s, the distance from the wall.

As N tends to infinity both x0 and x1 tend to x(0), which is always zero, so the equation of motion for x0 is always true.

In the continuum limit, the equation for xN becomes

 * $$ \ddot{x}(a) = -\frac{K a^2}{m} \frac{1}{\Delta a} \frac{dx}{ds} $$

Since Δa tends to zero, for this to be true we must have x'=0 at a.

For the other displacements,

 * $$\begin{matrix}

\lim_{\Delta a \rarr 0} \frac{x_{n-1}+x_{n+1}-2x_n}{\Delta a^2} & = & \lim_{\Delta a \rarr 0} & \frac{1}{\Delta a} \left( \frac{x_{n+1}-x_n}{\Delta a} - \frac{x_n-x_{n-1}}{\Delta a} \right) \\ & = & \lim_{\Delta a \rarr 0} & \frac{x^\prime((n+1)\Delta a)-x^\prime(n\Delta a)}{\Delta a} \\ & = & \left. \frac{d^2 x}{ds^2} \right|_{x=a} & \\ \end{matrix}$$

so we get the equation

 * $$\frac{\partial^2 x}{\partial t^2} - \frac{Ka^2}{m}\frac{\partial^2 x}{\partial s^2} = 0$$

just as with the other approach.

Waves
It is intuitively obvious that if we flick one of the masses in this system, vibrations will propagate down the springs, like waves, so we look for solutions of that form.

A generic travelling wave is

 * $$x = A \sin (\omega t - \kappa x + \alpha) \,$$

Substituting this informed guess into the equation gives

 * $$ -A \omega^2 \sin (\omega t - \kappa x + \alpha) =

-\frac{Ka^2}{m} \kappa^2 \sin (\omega t - \kappa x + \alpha) $$

so this wave is a solution provide the frequency and wavenumber are related by

 * $$ \omega^2 = \frac{Ka^2}{m} \kappa^2 $$

The speed of these waves, c, is

 * $$c = \frac{d\omega}{d\kappa} = \pm \sqrt{\frac{Ka^2}{m}}$$

Thus, we've gone from Newton's laws to waves.

We can do the same starting with a three-dimensional array of particles, and deduce the equations for longitudinal and transverse waves in a solid. Everything we said about waves earlier will be true for these systems.

This particular system has two boundary conditions: the displacement is zero at the wall, and a local extrema at the free end. This is typical of all such problems.

When we take account of the boundary conditions we find that the correct solutions is a combination of standing waves, of the form

 * $$x = A_m \sin \left( \frac{2b+1}{2}\frac{\pi s}{a} \right)

\sin \left( \sqrt{\frac{Ka^2}{m}}\frac{2b+1}{2}\frac{\pi}{a}t +\alpha_m \right) $$

where b is any integer.

If we also knew the initial displacement we could use Fourier series to obtain the exact solution for all time.

In practice, N is typically large but finite, so the continuum limit is only approximately true. Allowing for this would give us a power series in 1/N, describing small corrections to the approximation. These corrections can produce interesting effects, including solutions, but we will not calculate them here.

The continuum limit also fails for small wavelengths, comparable with the particle spacing.

Fields
In the continuum limit, the spring is described by a variable which is a function of both position and time. Variable such as this are commonly referred to as fields.

At first sight, classical fields look quite different to classical particles. In one case position is the dependent variable; in the other, it is an independent variable. However, as the above calculations suggest, fields and particles have an underlying unity, if we take a Lagrangian approach.

We can deal with both using essentially the same mathematical techniques, extracting information about both the field and the particles in that field from the same source.

E.g., once we know the Lagrangian for electromagnetism, we can deduce both the partial differential equations for the EM fields, and the forces on charged particles in those fields, from it. We will see precisely how later, when we come to study electromagnetism.

In the example above, the field Lagrangian was the continuum limit of a Lagrangian for the discrete system. It did not have to be. We can investigate the fields described by any Lagrangian we like, whether or not there is an underlying mechanical system.

So far, we've looked at waves and movement under Newton's law, and seen how the study of movement can lead us back to waves. Next, we will look at special relativity, and see how Einstein's insights affect all this.

title: General Mechanics/The Continuum Limit


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User talk:Evelien~enwikibooks

Talk about me? OK, why not?

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title: User talk:Evelien~enwikibooks


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Physics Exercises/Kinematics in One Dimension

Kinematics in one dimension involves motion where the position can be represented by a single number. Motion in other directions (if any) are ignored. For solving kinematics problems without calculus, use of following equations is necessary (these can be derived using calculus):

$$\begin{align} v_f &= a t + v_i \\ x_f &= (1/2) a t^2 + v_i t + x_i \\ v_f^2 &= v_i^2 + 2 a s \end{align}$$.

Without Calculus

 * 1) A man fires a rock out of a slingshot directly upward. The rock has an initial velocity of 15 m/s. How long will it take for the rock to return to the level he fired it at?
 * 2) It takes a man 10 seconds to ride down an escalator. It takes the same man 15 s to walk back up the escalator against its motion.  How long will it take the man to walk down the escalator at the same rate he was walking before?
 * 3) A man riding a bicycle at a speed of 25 km/h passes a parked car. When the bicycle is 100 m ahead of the car, the car starts. The car instantly accelerates to a speed of 50 km/h, and subsequently maintains that speed. Find out when and where the car passes the bicycle, using both a graphical method and an arithmetical method.
 * 4) Cinderella leaves the ball at quarter to twelve in a coach travelling at a speed of 12 mph. Five minutes later the prince also leaves the ball following her. Calculate the speed at which the prince reaches her just as the clock strikes twelve.
 * 5) Two sporty snails are having a race. Because one of them is a famous sprinter, the other is given a head start of 1.0 meters. 15 minutes after the start of the race the sprinter catches up with the slower one. The sprinter was creeping at a speed of 60 cm/min. Calculate the speed of the slower snail.
 * 6) Miss Anna Litical wants to meet a friend living 150 miles away. She starts at 8:30 with an average speed of 50 mph. Her friend starts 30 minutes later travelling at a speed of 35 mph. When and where do they meet?

With Calculus

 * 1) Starting with the definitions of velocity and acceleration, derive the kinematics equation for constant acceleration x = x0 + v0t + (1/2) a t2.
 * 2) A cockroach starts 1 cm away from a wall. It starts running in a line directly away from the wall with a velocity of 1 cm/s, acceleration of 1 cm/s^2, jerk (d3x/dt3) of 1 cm/s3, d4x/dt4 of 1 cm/s^4, and so on.  How far is the cockroach from the wall after 1 s?


text:
Physics Exercises/Kinematics in 2-3 Dimensions

Kinematics in 2 or 3 dimensions is essentially the same as ../Kinematics in One Dimension/ with an extra step added: one must separate the motion into 2 or 3 perpendicular directions (for each problem, one particular choice of axes is better than others) and solve motion in each direction separately as it is done in ../Kinematics in One Dimension/.

Without Calculus

 * 1) A cannon (assumed to be at ground level) is fired off a flat surface at an angle θ above the horizontal with an initial speed of $$v_0$$. Assume no air resistance.
 * 2) What is the initial horizontal component of the velocity?
 * 3) What is the initial vertical component of the velocity?
 * 4) What is the horizontal component of the velocity at the highest point of the trajectory?
 * 5) What is the vertical component of the velocity at that point?
 * 6) What is the horizontal component of the velocity when the projectile lands?
 * 7) What is the vertical component of the velocity when it lands?
 * 8) A woman walks north at 3 km/h on a boat that is moving east at 4 km/h.
 * 9) With respect to the shore, how fast is the woman moving?
 * 10) With respect to the shore, at what angle from the north is she moving?

With Calculus

 * 1) Just for this problem, assume t is a unitless quantity measuring time. A cockroach has a velocity $$v = \sin(t)~\hat{x} + e^t~\hat{y}$$. The cockroach starts at the origin. Derive an expression for
 * 2) the speed of the cockroach as a function of time,
 * 3) the position of the cockroach as a function of time,
 * 4) the acceleration of the cockroach as a function of time.


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Civ/Sid Meier's Alpha Centauri/Citizens

Doctor

 * Psych: 2

Empath
Replaces Doctor
 * Prerequisite: Centauri Meditation
 * Economy: 2
 * Psych: 2

Engineer
Replaces Technician
 * Prerequisite: Fusion Power
 * Economy: 3
 * Labs: 2

Librarian

 * Prerequisite: Planetary Networks
 * Labs: 3

Technician

 * Economy: 3

Thinker
Replaces Librarian
 * Prerequisite: Mind/Machine Interface
 * Psych: 1
 * Labs: 3

Transcend
Replaces Empath and Thinker
 * Prerequisite: Secrets of Alpha Centauri
 * Economy: 2
 * Psych: 2
 * Labs: 4

title: Civ/Sid Meier's Alpha Centauri/Citizens


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User:Moolsan~enwikibooks/Testbench

Testseite

title: User:Moolsan~enwikibooks/Testbench


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General Chemistry/The Quantum Atom

The Quantum Numbers
These four numbers are used to describe the location of an electron in an atom.

Principal Quantum Number (n)
Determines the shell the electron is in. The shell is the main component that determines the energy of the electron (higher n corresponds to higher energy), as well as size of the orbital, corresponding to maximum nuclear distance (higher n means further possible distance from the nucleus). The row that an element is placed on the periodic table tells how many shells there will be. Helium (n = 1), neon (n = 2), argon (n = 3), etc. Note that the shells will have different numbers, as described by the table above; for example, argon will contain the $$n = 1$$, $$n = 2$$,  and $$n = 3$$ subshells, for that total of 3.

Angular Momentum Quantum Number (l)
Also known as azimuthal quantum number. Determines the subshell the electron is in. Each subshell has a unique shape and a letter name. The s orbital is shaped like a sphere and occurs when l = 0. The p orbitals (there are three) are shaped like teardrops and occur when l = 1. The d orbitals (there are five) occur when l = 2. The f orbitals (there are seven) occur when l = 3. (By the way, when l = 4, the orbitals are "g orbitals", but they (and the l = 5 "h orbitals") can safely be ignored in general chemistry.). The numbers of the subshells in each shell can be calculated using the principal quantum number like so. $$l = 0, 1,...(n-2), (n-1).$$ For example, in the $$n = 2$$ shell, the subshells are an $$l = 0$$ subshell, and 3 $$l = 1$$ subshells. You will learn how to determine the number of orbitals for each subshells in the next section.

This number also gives information as to what the angular node of an orbital is. A node is defined as a point on a standing wave where the wave has minimal amplitude. When applied to chemistry this is the point of zero-displacement and thus where no electrons are found. In turn angular node means the planar or conical surface in which no electrons are found or where there is no electron density. The models shown on this page show the most simple representations of these orbitals and their nodes. More accurate, but more complex depictions are not necessary for the scope of this book.

Here are pictures of the orbitals. Keep in mind that they do not show the actual path of the electrons, due to the Heisenberg Uncertainty Principle. Instead, they show the volume where the electron is most likely to occur, i.e. the is largest. The two colors represent two signs (phases) of the (the choice is arbitrary). Each of the depicted orbitals is a superposition of two opposite m quantum numbers (see below).

Magnetic Quantum Number (ml)
Magnetic quantum number determines the orbital in which the electron lies. The number of orbitals in each subshell can be calculated like so: $$m$$$l$$$ = -l, -(l- 1),...,-1,0,1,...(l - 1), l$$. ml determines how rapidly the complex phase increases around the z-axis. Without magnetic field, these orbitals all have the same energy, they are degenerate and can be combined into different shapes and spatial orientations. The orbitals in a subshell with degeneracy are called degenerate orbitals. This simply means that the orbitals in each p subshell all have the same energy level. The difference in shapes as well as orientation of higher $$l$$ subshells is not important during general chemistry, and the orbitals in the same higher $$l$$ subshells are still degenerate regardless of shape differences.

Spin Quantum Number (ms)
Does not determines the spin on the electron. +½ corresponds to the up arrow in an electron configuration box. If there is only one electron in an orbital (one arrow in one box), then it is always considered +½. The second arrow, or down arrow, is considered -½. Every orbital can contain one "spin up" electron, and one "spin down" electron.

Some Examples
Let's examine the quantum numbers of electrons from a magnesium atom, 12Mg. Remember that each list of numbers corresponds to (n, l, ml, ms).

The Periodic Table
Notice a pattern on the periodic table. Different areas, or blocks, have different types of electrons. The two columns on the left make the s-block. The six columns on the right make the p-block. The large area in the middle (transition metals) makes the d-block. The bottom portion makes the f-block (Lanthanides and Actinides). Each row introduces a new shell (aka energy level). Basically, the row tells you how many shells of electrons there will be, and the column tells you which subshells will occur (and which shells they occur in). The value of ml can be determined by some of the rules we will learn in the next chapter. The value of ms doesn't really matter as long as there are no repeating values in the same orbital.

title: General Chemistry/The Quantum Atom


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Japanese/Vocabulary/Dates

This is a list of Japanese vocabulary for dates. It includes months, days, weeks and ect.

Days of the week

 * Days may be abbreviated, for example, 金曜 or 金 (Fri)

title: Japanese/Vocabulary/Dates


text: Japanese/Vocabulary/Time

title: Japanese/Vocabulary/Time