Camel milk
Camel's milk has supported Bedouin and pastoral cultures since the domestication of camels millennia ago. Herders may for periods survive on the milk when taking the camels on long distances to graze in desert and arid environments. Camel dairy farming is an alternative to cow dairy farming in dry regions of the world where cow farming consumes large amounts of water and electricity to power air-conditioned halls and cooling sprinkler systems. Camel farming, by using a native species well-adapted to arid regions, may facilitate reversal of desertification by UNESCO. Camel milk can be found in supermarkets in the UK, UAE, Saudi Arabia and the United States. Camel milk has enough nutrients to sustain a person through the day. In many countries, camel milk is given to babies suffering from malnutrition. Compared to cow milk fat, buffalo milk fat and ewe milk fat, camel milk fat contains fewer short-chained fatty acids, but the same long-chained fatty acids can be found. Camel milk has more protein than cow's milk.
Cholesterol in camel milk is lower than goat milk. Camel milk has a high mineral content and immunoglobin content. Camel milk is 10 times higher in iron, it is high in unsaturated fatty acids and B vitamins but lower in vitamin A and B2. The composition of camel milk depends of the camel species. Bactrian milk has a higher fat content than dromedary milk. Camel milk is lower in lactose than cow's milk. However, levels of potassium, iron, manganese and zinc are higher than in cow's milk. Camel milk is still a subsistence product, but production in camel milk dairies is a growing industry. Camel milk in India has been used by raika and other desert communities, it finds its presence in the ancient Indian medicinal texts of Ayurveda; the National Research Centre on Camel in Bikaner, India is a national camel research institute which has participated in research projects on the therapeutic values of camel milk in autism, diabetes, TB, etc. The United States has an imported population of 5,000 camels.
The cost of producing a quart of camel's milk is higher than that of producing a quart of cow's milk. In the United States, female camels are rare, their thirteen-month gestation period must conclude in a live birth followed by suckling, else the female camel will stop producing milk. Unlike a dairy cow, parted from her calf when it is born and gives milk for six to nine months, a camel can share her milk with the farmer and her calf for twelve to eighteen months. Pakistani and Afghani camels are supposed to produce the highest yields of milk, up to 30 litres per day; the Bactrian camel produces 5 litres per day and the dromedary produces an average of 20 litres per day. Intensive breeding of cows has created animals that can produce 40 litres per day in ideal conditions. Camels, with their ability to go 21 days without drinking water, produce milk when feeding on low-quality fodder, are a sustainable option for food security in difficult environments. Cheese from camel milk is more difficult to make than cheese from the milk of other dairy animals.
It does not coagulate and bovine rennet fails to coagulate the milk effectively. In camel herding communities camel milk cheeses use spontaneous fermentation, or lactic fermentation to achieve a sour curd. In camel farms in Sudan, the Rashaida tribe use this method to store surplus milk in the rainy season, pulverising the dried curds and adding water for consumption in the dry season. In Mongolia camel milk is consumed as a product at various stages of the curd-making process. Recent advances in cheese making technology have made it possible to coagulate camel milk with a vegetable rennet and camel rennet. A European-style cheese was created through collaboration between Mauritanian camel milk dairy Tiviski, the FAO, professor J. P. Ramet of the École Nationale Supérieure d'Agronomie et des Industries Alimentaires. Curdling was produced by the addition of vegetable rennet. Caravane, the subsequently produced cheese is a product of Tiviski, sold in supermarkets in Nouakchott. EU restrictions prevent this product from being sold in the EU.
Difficulties with the cold chain and economy of scale prevent the camel cheese from being sold in the US. The Technology of Making Cheese from Camel Milk Animal Production and Health Paper Issued by FAO, United Nations. Camels and Camel Milk. Report Issued by FAO, United Nations
Otto Frederick Hunziker
Otto Frederick Hunziker was a pioneer in the American and international dairy industry, as both an educator and a technical innovator. Hunziker was born and raised in Switzerland, emigrated to the U. S. and studied at Cornell University. He started and developed the dairy program at Purdue University when such programs were at their infancy. At this same time, Hunziker was involved with the development of the American Dairy Science Association and the standardization and improvement of many dairy tests and processes. Hunziker wrote several of the leading dairy processing texts. After leaving Purdue University, Hunziker managed research and operations at a large, national condensary, continued to drive ADSA's standardization and publishing efforts, represented the U. S. at international dairy congresses, facilitated dairy industry improvements across the globe. Otto Frederick Hunziker was born in Zürich, Switzerland, on 25 December 1873 to Karl Otto and Luise Hunziker. Otto's siblings were Karl Rudolf, Barbara Luise, Marie Julie.
Hunziker spent many early years in Goldbach, where his father was a pastor and member of the canton parliament. Otto attended the two-year course of studies at Strickhof Agricultural College in Zürich, graduating at age 19. In 1893, Otto Frederick Hunziker emigrated to the United States. During this time period, significant new development in dairy processing technology was occurring on both sides of the Atlantic Ocean. In 1890, Stephen Babcock published specifications for the Babcock test for milk fat content. In 1892, Dr. Niklaus Gerber acquired a Swiss patent on the Gerber method for analyzing fat content in milk. Dr. Gerber was based in Zürich, had studied at the University of Zürich, worked for two years at the Swiss-American Milk Company in Little Falls, New York. Hunziker would spend a substantial amount of time improving these analytic methods. In the United States, Hunziker worked for two years as a laborer on a dairy farm near Attleboro, Massachusetts. To improve his English and commercial skills, he studied at Bryant and Stratton Business College, Rhode Island in 1896.
He returned to Switzerland in 1898 before returning to receive a B. S. Agriculture in 1900 and M. S. A. in 1901 from Cornell University. He served as an assistant in charge of dairy bacteriology at Cornell University until 1902, when he equipped and operated a dairy manufacturing research laboratory for the Scranton Condensed Milk Company in Ellicottville, New York. Otto Frederick married Florence Belle Burne on 10 April 1905 in Portville, Cattaraugus County, New York. In 1905 Hunziker accepted a position at Purdue University in West Lafayette, Indiana as head of Purdue's Dairy Department. Dairy departments were new at American colleges. Hunziker led Purdue's dairy department through significant growth. In the summer of 1906, Hunziker was among 18 teachers and investigators meeting at the University of Illinois, Urbana, to found what was known as National Association of Dairy Instructors and Investigators. From 1910 to 1926, Hunziker chaired ADSA's Committee on Official Methods of Testing Milk and Cream for Butterfat.
In 1911, this committee met in Washington, D. C. with the U. S. Bureau of Dairying, the U. S. Bureau of Standards and manufacturers of glassware. Standard specifications for Babcock glassware were published as a result of this meeting. Hunziker pursued numerous improvements to the testing methodology, which improved the quality and safety of dairy products. Hunziker was the third president of ADSA from 1910 through 1911. During Hunziker's presidency, ADSA also: created a national score card for scoring dairies. Apart from application of improved pedagogy and scientific methodology, Hunziker oversaw planning and construction of Smith Hall, the building which thereafter housed Purdue's dairy manufacturing group, extension service, creamery. While at Purdue, he published over 50 bulletins and scientific treatises addressing dairy farm and plant problems. In 1917, Hunziker left Purdue to manage manufacturing and research at the Blue Valley Creamery Company in Chicago, Illinois. Hunziker wrote dairy articles and textbooks used throughout the world, developed dairy curricula, advocated for dairy laws, developed standard testing methodology.
In particular, Hunziker authored The Butter Industry, Prepared for Factory and Laboratory, a well-known text in the industry that enjoyed at least three editions. A book that Hunziker self-published in 1914, "Condensed Milk and Milk Powder: Prepared for the Use of Milk Condenseries, Dairy Students and Pure Food Departments", was republished in a seventh edition in October 2007 by Cartwright Press. According to one book review: "The popularity of this book may be judged by the fact that this is the fourth edition, the three previous editions having long since been exhausted; the book is the most important contribution on the condensed milk powder industry. It should be in the library of the teacher, the student or factory man interested in any phase of the
Powdered milk
Powdered milk or dried milk is a manufactured dairy product made by evaporating milk to dryness. One purpose of drying milk is to preserve it. Another purpose is to reduce its bulk for economy of transportation. Powdered milk and dairy products include such items as dry whole milk, nonfat dry milk, dry buttermilk, dry whey products and dry dairy blends. Many dairy products exported conform to standards laid out in Codex Alimentarius. Many forms of milk powder are traded on exchanges. Powdered milk is used for food and health, in biotechnology. While Marco Polo wrote of Mongolian Tatar troops in the time of Kublai Khan who carried sun-dried skimmed milk as "a kind of paste", the first modern production process for dried milk was invented by the Russian doctor Osip Krichevsky in 1802; the first commercial production of dried milk was organized by the Russian chemist M. Dirchoff in 1832. In 1855, T. S. Grimwade took a patent on a dried milk procedure, though a William Newton had patented a vacuum drying process as early as 1837.
In modern times, powdered milk is made by spray drying nonfat skimmed milk, whole milk, buttermilk or whey. Pasteurized milk is first concentrated in an evaporator to 50 percent milk solids; the resulting concentrated milk is sprayed into a heated chamber where the water instantly evaporates, leaving fine particles of powdered milk solids. Alternatively, the milk can be dried by drum drying. Milk is applied as a thin film to the surface of a heated drum, the dried milk solids are scraped off. However, powdered milk made this way tends to have a cooked flavour, due to caramelization caused by greater heat exposure. Another process is freeze drying; the drying method and the heat treatment of the milk as it is processed alters the properties of the milk powder, such as its solubility in cold water, its flavour, its bulk density. Powdered milk is used in the manufacture of infant formula, confectionery such as chocolate and caramel candy, in recipes for baked goods where adding liquid milk would render the product too thin.
Powdered milk is widely used in various sweets such as the famous Indian milk balls known as gulab jamun and a popular Indian sweet delicacy known as chum chum. Many no-cook recipes that use nut butters use powdered milk to prevent the nut butter from turning liquid by absorbing the oil. Powdered milk is a common item in UN food aid supplies, fallout shelters and wherever fresh milk is not a viable option, it is used in many developing countries because of reduced transport and storage costs. Like other dry foods, it is considered nonperishable, is favored by survivalists and others requiring nonperishable, easy-to-prepare food; because of its resemblance to cocaine and other drugs, powdered milk is sometimes used in filmmaking as a non-toxic prop that may be insufflated. The weight of nonfat dry milk to use is about 10% of the water weight. Alternatively, when measuring by volume rather than weight, one cup of potable fluid milk from powdered milk requires one cup of potable water and one-third cup of powdered milk.
Milk powders contain all twenty-one standard amino acids, the building blocks of proteins, are high in soluble vitamins and minerals. According to USAID, the typical average amounts of major nutrients in the unreconstituted nonfat dry milk are 36% protein, 52% carbohydrates, calcium 1.3%, potassium 1.8%. Whole milk powder, on the other hand, contains on average 25-27% protein, 36-38% carbohydrates, 26-40% fat, 5-7% ash. In Canada, powdered milk must contain added vitamin D in an amount such that a reasonable daily intake of the milk will provide between 300 to 400 International Units of vitamin D. However, inappropriate storage conditions such as high relative humidity and high ambient temperature can degrade the nutritive value of milk powder. Commercial milk powders are reported to contain oxysterols in higher amounts than in fresh milk. Oxysterols are derivatives of cholesterol that are produced either by enzymes; some free radicals-derived oxysterols have been suspected of being initiators of atherosclerotic plaques.
For comparison, powdered eggs contain more oxysterols, up to 200 μg/g. European production of milk powder is estimated around 800,000 tons of which the main volume is exported in bulk packing or consumer packs. Brands on the market include "Nido", from the company Nestlé, "Incolac" from the company Milcobel, "Dutch Lady" from FrieslandCampina. In the 2008 Chinese milk scandal, melamine adulterant was found in Sanlu infant formula, added to fool tests into reporting higher protein content. Thousands became ill, some children died, after consuming the product. In August 2013, China temporarily suspended all milk powder imports from New Zealand, after a scare where botulism-causing bacteria was falsely detected in several batches of New Zealand-produced whey protein concentrate; as a result of the product recall, the New Zealand dollar slipped based on expected losses in sales from this single commodity. Fat-free powdered milk is used as a saturating agent to block nonspecific binding sites on supports like blotting membranes, preventing binding of further detection reagents and subsequent background.
It may be
Soured milk
Soured milk denotes a range of food products produced by the acidification of milk. Acidification, which gives the milk a tart taste, is achieved either through bacterial fermentation or through the addition of an acid, such as lemon juice or vinegar; the acid causes milk to coagulate and thicken, inhibiting the growth of harmful bacteria and improving the product's shelf life. Soured milk, produced by bacterial fermentation is more called fermented milk or cultured milk. Traditionally, soured milk was fresh milk, left to ferment and sour by keeping it in a warm place for a day near a stove. Modern commercial soured milk may differ from milk. Soured milk, produced by the addition of an acid, with or without the addition of microbial organisms, is more called acidified milk. In the United States, acids used to manufacture acidified milk include acetic acid, adipic acid, citric acid, fumaric acid, glucono-delta-lactone, hydrochloric acid, lactic acid, malic acid, phosphoric acid, succinic acid, tartaric acid.
Soured milk is made at home or is sold and consumed in Europe in Eastern Europe, all over the countries of the former Yugoslavia, Greece, Finland and Scandinavia. It is made at home or sold in supermarkets and consumed in the Great Lakes region of Somalia and Eastern Africa, it is a traditional food of the Bantu people of Southern Africa. Since the 1970s, some producers have used chemical acidification in place of biological agents. Raw milk that has not gone sour is sometimes referred to as "sweet milk", because it contains the sugar lactose. Fermentation converts the lactose to lactic acid. Before the invention of refrigeration, raw milk became sour before it could be consumed, various recipes incorporate such leftover milk as an ingredient. Sour milk produced by fermentation differs in flavor from that produced by acidification, because the acids added in commercial manufacture have different flavors from lactic acid, because fermentation can introduce new flavors. Modern food safety standards mean.
Buttermilk is a common modern substitute for soured milk. Sour milk cheese
Water buffalo
The water buffalo or domestic water buffalo is a large bovid originating in the Indian subcontinent, Southeast Asia, China. Today, it is found in Europe, North America, South America and some African countries; the wild water buffalo native to Southeast Asia is considered a different species, but most represents the ancestor of the domestic water buffalo. Two extant types of domestic water buffalo are recognized based on morphological and behavioural criteria – the river buffalo of the Indian subcontinent and further west to the Balkans and Italy, the swamp buffalo, found from Assam in the west through Southeast Asia to the Yangtze valley of China in the east; the origins of the domestic water buffalo types are debated, although results of a phylogenetic study indicate that the swamp type may have originated in China and was domesticated about 4,000 years ago, while the river type may have originated in India and was domesticated about 5,000 years ago. Water buffalo were traded from the Indus Valley Civilisation to Mesopotamia, in modern Iraq, 2500 BC by the Meluhhas.
The seal of a scribe employed by an Akkadian king shows the sacrifice of water buffalo. At least 130 million domestic water buffalo exist, more people depend on them than on any other domestic animal, they are suitable for tilling rice fields, their milk is richer in fat and protein than that of dairy cattle. A large feral population became established in northern Australia in the late 19th century, there are smaller feral herds in Papua New Guinea and northeastern Argentina. Feral herds are present in New Britain, New Ireland, Irian Jaya, Guyana, Suriname and Uruguay; the skin of river buffalo is black. Swamp buffalo become slate blue later. Albinoids are present in some populations. River buffalo have comparatively longer faces, smaller girths, bigger limbs than swamp buffalo, their dorsal ridges extend further taper off more gradually. Their horns grow downward and backward curve upward in a spiral. Swamp buffalo are stockily built; the forehead is flat, the eyes prominent, the face short, the muzzle wide.
The neck is comparatively long, the withers and croup are prominent. A dorsal ridge ends abruptly just before the end of the chest, their horns grow outward, curve in a semicircle, but always remain more or less on the plane of the forehead. The tail is short, reaching only to the hocks. Height at withers is 129–133 cm for males, 120–127 cm for females, they range in weight from 300–550 kg, but weights of over 1,000 kg have been observed. Tedong bonga is a black pied buffalo featuring a unique black and white colouration, favoured by the Toraja of Sulawesi; the swamp buffalo has 48 chromosomes. The two types do not interbreed, but fertile offspring can occur. Buffalo-cattle hybrids have not been observed to occur, but the embryos of such hybrids reach maturity in laboratory experiments, albeit at lower rates than non-hybrids; the rumen of the water buffalo has important differences from that of other ruminants. It contains a larger population of bacteria the cellulolytic bacteria, lower protozoa, higher fungi zoospores.
In addition, higher rumen ammonia nitrogen and higher pH have been found as compared to those in cattle. River buffalo prefer deep water. Swamp buffalo prefer to wallow in mudholes. During wallowing, they acquire a thick coating of mud. Both are well adapted to a hot and humid climate with temperatures ranging from 0 °C in the winter to 30 °C and greater in the summer. Water availability is important in hot climates, since they need wallows, rivers, or splashing water to assist in thermoregulation; some breeds are adapted to saline sandy terrain. Water buffalo thrive on many aquatic plants. During floods, they will graze submerged, raising their heads above the water and carrying quantities of edible plants. Water buffalo eat reeds, Arundo donax, a kind of Cyperaceae, Eichhornia crassipes, Juncaceae; some of these plants are of great value to local peoples. Others, such as E. crassipes, are a major problem in some tropical valleys and water buffalo may help to keep waterways clear. Green fodders are used for intensive milk production and for fattening.
Many fodder crops are chaffed, or pulped. Fodders include alfalfa, the leaves, stems or trimmings of banana, Mangelwurzel, Leucaena leucocephala and kenaf, oats, peanut, soybean, sugarcane and turnips. Citrus pulp and pineapple wastes have been fed safely to buffalo. In Egypt, whole sun-dried dates are fed to milk buffalo up to 25% of the standard feed mixture. Swamp buffalo become reproductive at an older age than river breeds. Young males in Egypt and Pakistan are first mated at about 3.0–3.5 years of age, but in Italy they may be used as early as 2 years of age. Successful mating behaviour may continue until the animal is 12 years or older. A good river male can impregnate 100 females in a year. A strong seasonal influence on mating occurs. Heat stress reduces libido. Although buffalo are polyoestrous, their reproductive efficiency shows wide variation throughout the year. Buffalo cows exhibit a distinct seasonal change in displaying oestrus, conception rate, calving rate; the age at first oestrus of heifers varies between breeds from 13–33 months, but mating at the first oestrus is infertile and deferred unti
Precipitation (chemistry)
Precipitation is the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the'precipitate'; the chemical that causes the solid to form is called the'precipitant'. Without sufficient force of gravity to bring the solid particles together, the precipitate remains in suspension. After sedimentation when using a centrifuge to press it into a compact mass, the precipitate may be referred to as a'pellet'. Precipitation can be used as a medium; the precipitate-free liquid remaining above the solid is called the'supernate' or'supernatant'. Powders derived from precipitation have historically been known as'flowers'; when the solid appears in the form of cellulose fibers which have been through chemical processing, the process is referred to as regeneration. Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction. If silver nitrate solution is poured into a solution of sodium chloride, a chemical reaction occurs forming a white precipitate of silver chloride.
When potassium iodide solution reacts with lead nitrate solution, a yellow precipitate of lead iodide is formed. Precipitation may occur. Precipitation may occur from a supersaturated solution. In solids, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to e.g. rapid quenching or ion implantation, the temperature is high enough that diffusion can lead to segregation into precipitates. Precipitation in solids is used to synthesize nanoclusters. An important stage of the precipitation process is the onset of nucleation; the creation of a hypothetical solid particle includes the formation of an interface, which requires some energy based on the relative surface energy of the solid and the solution. If this energy is not available, no suitable nucleation surface is available, supersaturation occurs. Precipitation reactions can be used for making pigments, removing salts from water in water treatment, in classical qualitative inorganic analysis.
Precipitation is useful to isolate the products of a reaction during workup. Ideally, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates. An example of this would be the synthesis of porphyrins in refluxing propionic acid. By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, are collected by filtration: Precipitation may occur when an antisolvent is added, drastically reducing the solubility of the desired product. Thereafter, the precipitate may be separated by filtration, decanting, or centrifugation. An example would be the synthesis of chromic tetraphenylporphyrin chloride: water is added to the DMF reaction solution, the product precipitates. Precipitation is useful in purifying products: crude bmim-Cl is taken up in acetonitrile, dropped into ethyl acetate, where it precipitates. Another important application of an antisolvent is in ethanol precipitation of DNA. In metallurgy, precipitation from a solid solution is a useful way to strengthen alloys.
An example of a precipitation reaction: Aqueous silver nitrate is added to a solution containing potassium chloride, the precipitation of a white solid, silver chloride, is observed. AgNO 3 + KCl ⟶ AgCl ↓ + KNO 3 The silver chloride has formed a solid, observed as a precipitate; this reaction can be written emphasizing the dissociated ions in a combined solution. This is known as the ionic equation. Ag + + NO 3 − + K + + Cl − ⟶ AgCl ↓ + K + + NO 3 − A final way to represent a precipitate reaction is known as a net ionic reaction. Many compounds containing metal ions produce precipitates with distinctive colors; the following are typical colors for various metals. However, many of these compounds can produce colors different from those listed. Other compounds form white precipitates. Precipitate formation is useful in the detection of the type of cation in a salt. To do this, an alkali first reacts with the unknown salt to produce a precipitate, the hydroxide of the unknown salt. To identify the cation, the color of the precipitate and its solubility in excess are noted.
Similar processes are used in sequence – for example, a barium nitrate solution will react with sulfate ions to form a solid barium sulfate precipitate, indicating that it is that sulfate ions are present. Digestion, or precipitate ageing, happens when a freshly formed precipitate is left at a higher temperature, in the solution from which it precipitates, it results in bigger particles. The physico-chemical process underlying digestion is called Ostwald ripening. Coprecipitation Salting in Salting out Effervescence Zumdahl, Steven S.. Chemical Principles. New York: Houghton Mifflin. ISBN 0-618-37206-7. Precipitation reactions of certain cations Digestion Instruments A Thesis on pattern formation in precipitation reactions
Viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity can be conceptualized as quantifying the frictional force that arises between adjacent layers of fluid that are in relative motion. For instance, when a fluid is forced through a tube, it flows more near the tube's axis than near its walls. In such a case, experiments show; this is because a force is required to overcome the friction between the layers of the fluid which are in relative motion: the strength of this force is proportional to the viscosity. A fluid that has no resistance to shear stress is known as an inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, the second law of thermodynamics requires all fluids to have positive viscosity. A fluid with a high viscosity, such as pitch, may appear to be a solid; the word "viscosity" is derived from the Latin "viscum", meaning mistletoe and a viscous glue made from mistletoe berries.
In materials science and engineering, one is interested in understanding the forces, or stresses, involved in the deformation of a material. For instance, if the material were a simple spring, the answer would be given by Hooke's law, which says that the force experienced by a spring is proportional to the distance displaced from equilibrium. Stresses which can be attributed to the deformation of a material from some rest state are called elastic stresses. In other materials, stresses are present which can be attributed to the rate of change of the deformation over time; these are called. For instance, in a fluid such as water the stresses which arise from shearing the fluid do not depend on the distance the fluid has been sheared. Viscosity is the material property which relates the viscous stresses in a material to the rate of change of a deformation. Although it applies to general flows, it is easy to visualize and define in a simple shearing flow, such as a planar Couette flow. In the Couette flow, a fluid is trapped between two infinitely large plates, one fixed and one in parallel motion at constant speed u.
If the speed of the top plate is low enough in steady state the fluid particles move parallel to it, their speed varies from 0 at the bottom to u at the top. Each layer of fluid moves faster than the one just below it, friction between them gives rise to a force resisting their relative motion. In particular, the fluid applies on the top plate a force in the direction opposite to its motion, an equal but opposite force on the bottom plate. An external force is therefore required in order to keep the top plate moving at constant speed. In many fluids, the flow velocity is observed to vary linearly from zero at the bottom to u at the top. Moreover, the magnitude F of the force acting on the top plate is found to be proportional to the speed u and the area A of each plate, inversely proportional to their separation y: F = μ A u y; the proportionality factor μ is the viscosity of the fluid, with units of Pa ⋅ s. The ratio u / y is called the rate of shear deformation or shear velocity, is the derivative of the fluid speed in the direction perpendicular to the plates.
If the velocity does not vary linearly with y the appropriate generalization is τ = μ ∂ u ∂ y, where τ = F / A, ∂ u / ∂ y is the local shear velocity. This expression is referred to as Newton's law of viscosity. In shearing flows with planar symmetry, it is what defines μ, it is a special case of the general definition of viscosity, which can be expressed in coordinate-free form. Use of the Greek letter mu for the viscosity is common among mechanical and chemical engineers, as well as physicists. However, the Greek letter eta is used by chemists and the IUPAC; the viscosity μ is sometimes referred to as the shear viscosity. However, at least one author discourages the use of this terminology, noting that μ can appear in nonshearing flows in addition to shearing flows. In general terms, the viscous stresses in a fluid are defined as those resulting from the relative velocity of different fluid particles; as such, the viscous stresses. If the velocity gradients are small to a first approximation the v
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