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In Chinese belief, the asterism consisting of Altair, β Aquilae and γ Aquilae is known as Hé Gǔ (; lit. "river drum"). The Chinese name for Altair is thus Hé Gǔ èr (; lit. "river drum two", meaning the "second star of the drum at the river"). However, Altair is better known by its other names: Qiān Niú Xīng ( / ) or Ni... | Altair | Wikipedia | 428 | 3078 | https://en.wikipedia.org/wiki/Altair | Physical sciences | Notable stars | Astronomy |
In analytic geometry, an asymptote () of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the x or y coordinates tends to infinity. In projective geometry and related contexts, an asymptote of a curve is a line which is tangent to the curve at a point at infinity... | Asymptote | Wikipedia | 401 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
The idea that a curve may come arbitrarily close to a line without actually becoming the same may seem to counter everyday experience. The representations of a line and a curve as marks on a piece of paper or as pixels on a computer screen have a positive width. So if they were to be extended far enough they would seem... | Asymptote | Wikipedia | 413 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
Asymptotes of functions
The asymptotes most commonly encountered in the study of calculus are of curves of the form . These can be computed using limits and classified into horizontal, vertical and oblique asymptotes depending on their orientation. Horizontal asymptotes are horizontal lines that the graph of the functi... | Asymptote | Wikipedia | 508 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
The derivative of is the function
.
For the sequence of points
for
that approaches both from the left and from the right, the values are constantly . Therefore, both one-sided limits of at can be neither nor . Hence doesn't have a vertical asymptote at .
Horizontal asymptotes
Horizontal asymptotes are hor... | Asymptote | Wikipedia | 506 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
The oblique asymptote, for the function f(x), will be given by the equation y = mx + n. The value for m is computed first and is given by
where a is either or depending on the case being studied. It is good practice to treat the two cases separately. If this limit doesn't exist then there is no oblique asymptote in ... | Asymptote | Wikipedia | 474 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
shown to the right. As the value of x increases, f approaches the asymptote y = x. This is because the other term, 1/(x+1), approaches 0.
If the degree of the numerator is more than 1 larger than the degree of the denominator, and the denominator does not divide the numerator, there will be a nonzero remainder that g... | Asymptote | Wikipedia | 432 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
For example, the upper right branch of the curve y = 1/x can be defined parametrically as x = t, y = 1/t (where t > 0). First, x → ∞ as t → ∞ and the distance from the curve to the x-axis is 1/t which approaches 0 as t → ∞. Therefore, the x-axis is an asymptote of the curve. Also, y → ∞ as t → 0 from the right, and the... | Asymptote | Wikipedia | 468 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
Let be a parametric plane curve, in coordinates A(t) = (x(t),y(t)), and B be another (unparameterized) curve. Suppose, as before, that the curve A tends to infinity. The curve B is a curvilinear asymptote of A if the shortest distance from the point A(t) to a point on B tends to zero as t → b. Sometimes B is simply r... | Asymptote | Wikipedia | 475 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
is an asymptote if and are not both zero. If and , there is no asymptote, but the curve has a branch that looks like a branch of parabola. Such a branch is called a , even when it does not have any parabola that is a curvilinear asymptote. If the curve has a singular point at infinity which may have several asympt... | Asymptote | Wikipedia | 382 | 3107 | https://en.wikipedia.org/wiki/Asymptote | Mathematics | Mathematical analysis | null |
Arithmetic is an elementary branch of mathematics that studies numerical operations like addition, subtraction, multiplication, and division. In a wider sense, it also includes exponentiation, extraction of roots, and taking logarithms.
Arithmetic systems can be distinguished based on the type of numbers they operate ... | Arithmetic | Wikipedia | 448 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Definition, etymology, and related fields
Arithmetic is the fundamental branch of mathematics that studies numbers and their operations. In particular, it deals with numerical calculations using the arithmetic operations of addition, subtraction, multiplication, and division. In a wider sense, it also includes exponen... | Arithmetic | Wikipedia | 458 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Based on how natural and whole numbers are used, they can be distinguished into cardinal and ordinal numbers. Cardinal numbers, like one, two, and three, are numbers that express the quantity of objects. They answer the question "how many?". Ordinal numbers, such as first, second, and third, indicate order or placement... | Arithmetic | Wikipedia | 465 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
The simplest non-positional system is the unary numeral system. It relies on one symbol for the number 1. All higher numbers are written by repeating this symbol. For example, the number 7 can be represented by repeating the symbol for 1 seven times. This system makes it cumbersome to write large numbers, which is why ... | Arithmetic | Wikipedia | 495 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Arithmetic operations are ways of combining, transforming, or manipulating numbers. They are functions that have numbers both as input and output. The most important operations in arithmetic are addition, subtraction, multiplication, and division. Further operations include exponentiation, extraction of roots, and loga... | Arithmetic | Wikipedia | 472 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Subtraction is the inverse of addition. In it, one number, known as the subtrahend, is taken away from another, known as the minuend. The result of this operation is called the difference. The symbol of subtraction is . Examples are and . Subtraction is often treated as a special case of addition: instead of subtracti... | Arithmetic | Wikipedia | 472 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Roots are a special type of exponentiation using a fractional exponent. For example, the square root of a number is the same as raising the number to the power of and the cube root of a number is the same as raising the number to the power of . Examples are and .
Logarithm is the inverse of exponentiation. The logar... | Arithmetic | Wikipedia | 352 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
For operations on numbers with more than one digit, different techniques can be employed to calculate the result by using several one-digit operations in a row. For example, in the method addition with carries, the two numbers are written one above the other. Starting from the rightmost digit, each pair of digits is ad... | Arithmetic | Wikipedia | 413 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Integer arithmetic is not closed under division. This means that when dividing one integer by another integer, the result is not always an integer. For instance, 7 divided by 2 is not a whole number but 3.5. One way to ensure that the result is an integer is to round the result to a whole number. However, this method l... | Arithmetic | Wikipedia | 279 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Number theory studies the structure and properties of integers as well as the relations and laws between them. Some of the main branches of modern number theory include elementary number theory, analytic number theory, algebraic number theory, and geometric number theory. Elementary number theory studies aspects of int... | Arithmetic | Wikipedia | 398 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Rational number arithmetic
Rational number arithmetic is the branch of arithmetic that deals with the manipulation of numbers that can be expressed as a ratio of two integers. Most arithmetic operations on rational numbers can be calculated by performing a series of integer arithmetic operations on the numerators and ... | Arithmetic | Wikipedia | 417 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
The decimal fraction notation is a special way of representing rational numbers whose denominator is a power of 10. For instance, the rational numbers , , and are written as 0.1, 3.71, and 0.0044 in the decimal fraction notation. Modified versions of integer calculation methods like addition with carry and long multip... | Arithmetic | Wikipedia | 468 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
In science and engineering, numbers represent estimates of physical quantities derived from measurement or modeling. Unlike mathematically exact numbers such as or scientifically relevant numerical data are inherently inexact, involving some measurement uncertainty. One basic way to express the degree of certainty ab... | Arithmetic | Wikipedia | 436 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
More sophisticated methods of dealing with uncertain values include interval arithmetic and affine arithmetic. Interval arithmetic describes operations on intervals. Intervals can be used to represent a range of values if one does not know the precise magnitude, for example, because of measurement errors. Interval arit... | Arithmetic | Wikipedia | 349 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
A common method employed by computers to approximate real number arithmetic is called floating-point arithmetic. It represents real numbers similar to the scientific notation through three numbers: a significand, a base, and an exponent. The precision of the significand is limited by the number of bits allocated to rep... | Arithmetic | Wikipedia | 478 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Tally marks are a simple system based on external tools other than the body. This system relies on mark making, such as strokes drawn on a surface or notches carved into a wooden stick, to keep track of quantities. Some forms of tally marks arrange the strokes in groups of five to make them easier to read.
The abacus ... | Arithmetic | Wikipedia | 490 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Arithmetic systems can be classified based on the numeral system they rely on. For instance, decimal arithmetic describes arithmetic operations in the decimal system. Other examples are binary arithmetic, octal arithmetic, and hexadecimal arithmetic.
Compound unit arithmetic describes arithmetic operations performed o... | Arithmetic | Wikipedia | 473 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Various axiomatizations of arithmetic rely on set theory. They cover natural numbers but can also be extended to integers, rational numbers, and real numbers. Each natural number is represented by a unique set. 0 is usually defined as the empty set . Each subsequent number can be defined as the union of the previous nu... | Arithmetic | Wikipedia | 349 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
It was not until the emergence of ancient civilizations that a more complex and structured approach to arithmetic began to evolve, starting around 3000 BCE. This became necessary because of the increased need to keep track of stored items, manage land ownership, and arrange exchanges. All the major ancient civilization... | Arithmetic | Wikipedia | 474 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Indian mathematicians also developed the positional decimal system used today, in particular the concept of a zero digit instead of empty or missing positions. For example, a detailed treatment of its operations was provided by Aryabhata around the turn of the 6th century CE. The Indian decimal system was further refin... | Arithmetic | Wikipedia | 482 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
Later stages focus on a more abstract understanding and introduce the students to different types of numbers, such as negative numbers, fractions, real numbers, and complex numbers. They further cover more advanced numerical operations, like exponentiation, extraction of roots, and logarithm. They also show how arithme... | Arithmetic | Wikipedia | 495 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
The traditionally dominant view in the epistemology of arithmetic is that arithmetic truths are knowable a priori. This means that they can be known by thinking alone without the need to rely on sensory experience. Some proponents of this view state that arithmetic knowledge is innate while others claim that there is s... | Arithmetic | Wikipedia | 336 | 3118 | https://en.wikipedia.org/wiki/Arithmetic | Mathematics | Mathematics | null |
In number theory, an arithmetic, arithmetical, or number-theoretic function is generally any function f(n) whose domain is the positive integers and whose range is a subset of the complex numbers. Hardy & Wright include in their definition the requirement that an arithmetical function "expresses some arithmetical prope... | Arithmetic function | Wikipedia | 458 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
Ω(n), ω(n), νp(n) – prime power decomposition
The fundamental theorem of arithmetic states that any positive integer n can be represented uniquely as a product of powers of primes: where p1 < p2 < ... < pk are primes and the aj are positive integers. (1 is given by the empty product.)
It is often convenient to writ... | Arithmetic function | Wikipedia | 509 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
This implies that μ(1) = 1. (Because Ω(1) = ω(1) = 0.)
τ(n) – Ramanujan tau function
τ(n), the Ramanujan tau function, is defined by its generating function identity:
Although it is hard to say exactly what "arithmetical property of n" it "expresses", (τ(n) is (2π)−12 times the nth Fourier coefficient in the q-expan... | Arithmetic function | Wikipedia | 499 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
νp(n) – p-adic valuation of an integer n
For a fixed prime p, νp(n), defined above as the exponent of the largest power of p dividing n, is completely additive.
Logarithmic derivative
, where is the arithmetic derivative.
Neither multiplicative nor additive
π(x), Π(x), ϑ(x), ψ(x) – prime-counting functions
These... | Arithmetic function | Wikipedia | 472 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
For powers of odd primes and for 2 and 4, λ(n) is equal to the Euler totient function of n; for powers of 2 greater than 4 it is equal to one half of the Euler totient function of n:
and for general n it is the least common multiple of λ of each of the prime power factors of n:
h(n) – class number
h(n), the class nu... | Arithmetic function | Wikipedia | 501 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
as x tends to infinity. The example above shows that d(n) has the average order log(n).
Dirichlet convolution
Given an arithmetic function a(n), let Fa(s), for complex s, be the function defined by the corresponding Dirichlet series (where it converges):
Fa(s) is called a generating function of a(n). The simplest s... | Arithmetic function | Wikipedia | 454 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
That is, if n is odd, is the sum of the kth powers of the divisors of n, that is, and if n is even it is the sum of the kth powers of the even divisors of n minus the sum of the kth powers of the odd divisors of n.
Adopt the convention that Ramanujan's if x is not an integer.
Divisor sum convolutions
Her... | Arithmetic function | Wikipedia | 508 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
This has been generalized by a number of mathematicians. For example,
B. Sury
N. Rao where a1, a2, ..., as are integers, gcd(a1, a2, ..., as, n) = 1.
László Fejes Tóth where m1 and m2 are odd, m = lcm(m1, m2).
In fact, if f is any arithmetical function
where stands for Dirichlet convolution.
Miscellaneous
Le... | Arithmetic function | Wikipedia | 219 | 3170 | https://en.wikipedia.org/wiki/Arithmetic%20function | Mathematics | Functions: General | null |
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from “ogonori” and “tengusa”. As found in nature, agar is a mixture of two components, the linear polysaccharide agarose and a heterogeneous mixture of smaller molecul... | Agar | Wikipedia | 374 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Macroalgae have been used widely as food by coastal cultures, especially in Southeast Asia. In the Philippines, Gracilaria, known as gulaman (also guraman, gar-garao, or gulaman dagat, among other names) in Tagalog, have been harvested and used as food for centuries, eaten both fresh or sun-dried and turned into jellie... | Agar | Wikipedia | 510 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Agar was first subjected to chemical analysis in 1859 by the French chemist Anselme Payen, who had obtained agar from the marine algae Gelidium corneum.
Beginning in the late 19th century, agar began to be used as a solid medium for growing various microbes. Agar was first described for use in microbiology in 1882 by ... | Agar | Wikipedia | 432 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Physical properties
Agar exhibits a phenomenon known as hysteresis whereby, when mixed with water, it solidifies and forms a gel below about , which is called the gel point, and melts above , which is the melting point. Hysteresis is the property of having a difference between the gel point and melting point temperatu... | Agar | Wikipedia | 325 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Asian culinary
One use of agar in Japanese cuisine is in anmitsu, a dessert made of small cubes of agar jelly and served in a bowl with various fruits or other ingredients. It is also the main ingredient in mizu yōkan, another popular Japanese food. In Philippine cuisine, it is used to make the jelly bars in the vario... | Agar | Wikipedia | 473 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
An agar plate or Petri dish is used to provide a growth medium using a mix of agar and other nutrients in which microorganisms, including bacteria and fungi, can be cultured and observed under the microscope. Agar is indigestible for many organisms so that microbial growth does not affect the gel used and it remains st... | Agar | Wikipedia | 471 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Other fastidious organisms may require the addition of different biological fluids such as horse or sheep blood, serum, egg yolk, and so on. Agar plates can also be selective, and can be used to promote the growth of bacteria of interest while inhibiting others. A variety of chemicals may be added to create an environm... | Agar | Wikipedia | 423 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Another setup commonly used for measuring chemotaxis and chemokinesis utilizes the under-agarose cell migration assay, whereby a layer of agarose gel is placed between a cell population and a chemoattractant. As a concentration gradient develops from the diffusion of the chemoattractant into the gel, various cell popul... | Agar | Wikipedia | 488 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Other uses
Agar is used:
As an impression material in dentistry.
As a medium to precisely orient the tissue specimen and secure it by agar pre-embedding (especially useful for small endoscopy biopsy specimens) for histopathology processing
To make salt bridges and gel plugs for use in electrochemistry.
In formicar... | Agar | Wikipedia | 242 | 3262 | https://en.wikipedia.org/wiki/Agar | Biology and health sciences | Carbohydrates | Biology |
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average. The more acid... | Acid rain | Wikipedia | 498 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Acid rain was first systematically studied in Europe in the 1960s and in the United States and Canada in the following decade.
In Europe
The corrosive effect of polluted, acidic city air on limestone and marble was noted in the 17th century by John Evelyn, who remarked upon the poor condition of the Arundel marbles.
... | Acid rain | Wikipedia | 456 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
In 1980, the US Congress passed an Acid Deposition Act. This Act established an 18-year assessment and research program under the direction of the National Acidic Precipitation Assessment Program (NAPAP). NAPAP enlarged a network of monitoring sites to determine how acidic precipitation was, seeking to determine long-t... | Acid rain | Wikipedia | 483 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
In 1991, the US National Acid Precipitation Assessment Program (NAPAP) provided its first assessment of acid rain in the United States. It reported that 5% of New England Lakes were acidic, with sulfates being the most common problem. They noted that 2% of the lakes could no longer support Brook Trout, and 6% of the la... | Acid rain | Wikipedia | 507 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
In 2007 the EPA estimated that by 2010, the overall costs of complying with the program for businesses and consumers would be $1 billion to $2 billion a year, only one-fourth of what was initially predicted. Forbes says: "In 2010, by which time the cap and trade system had been augmented by the George W. Bush administr... | Acid rain | Wikipedia | 330 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
In the 1970s and 80s, acid rain was a major topic of research at the Experimental Lakes Area (ELA) in Northwestern Ontario, Canada. Researchers added sulfuric acid to whole lakes in controlled ecosystem experiments to simulate the effects of acid rain. Because its remote conditions allowed for whole-ecosystem experimen... | Acid rain | Wikipedia | 457 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Natural phenomena
The principal natural phenomena that contribute acid-producing gases to the atmosphere are emissions from volcanoes. Thus, for example, fumaroles from the Laguna Caliente crater of Poás Volcano create extremely high amounts of acid rain and fog, with acidity as high as a pH of 2, clearing an area of a... | Acid rain | Wikipedia | 490 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Chemical process
Combustion of fuels and smelting of some ores produce sulfur dioxide and nitric oxides. They are converted into sulfuric acid and nitric acid.
In the gas phase sulfur dioxide is oxidized to sulfuric acid:
Nitrogen dioxide reacts with hydroxyl radicals to form nitric acid:
NO2 + OH· → HNO3
The detail... | Acid rain | Wikipedia | 435 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
However, the extent to which acid rain contributes directly or indirectly via runoff from the catchment to lake and river acidity (i.e., depending on characteristics of the surrounding watershed) is variable. The United States Environmental Protection Agency's (EPA) website states: "Of the lakes and streams surveyed, a... | Acid rain | Wikipedia | 285 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Impacts of acidic water and soil acidification on plants could be minor or in most cases major. Most minor cases which do not result in fatality of plant life can be attributed to the plants being less susceptible to acidic conditions and/or the acid rain being less potent. However, even in minor cases, the plant will ... | Acid rain | Wikipedia | 445 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Plants are capable of adapting to acid rain. On Jinyun Mountain, Chongqing, plant species were seen adapting to new environmental conditions. The affects on the species ranged from being beneficial to detrimental. With natural rainfall or mild acid rainfall, the biochemical and physiological characteristics of plant se... | Acid rain | Wikipedia | 444 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Acid rain has a much less harmful effect on oceans on a global scale, but it creates an amplified impact in the shallower waters of coastal waters. Acid rain can cause the ocean's pH to fall, known as ocean acidification, making it more difficult for different coastal species to create their exoskeletons that they need... | Acid rain | Wikipedia | 413 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Sulfur Trioxide Effects
The effects of sulfur trioxide and sulfuric acid are similar because they both produce sulfuric acid when they come into touch with the wet surfaces of your skin or respiratory system. The amount of SO3 breath through the mouth is larger than the amount of SO3 breath through the nose. When huma... | Acid rain | Wikipedia | 474 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Acid rain can damage buildings, historic monuments, and statues, especially those made of rocks, such as limestone and marble, that contain large amounts of calcium carbonate. Acids in the rain react with the calcium compounds in the stones to create gypsum, which then flakes off.
CaCO3 (s) + H2SO4 (aq) CaSO4 (s) + C... | Acid rain | Wikipedia | 464 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
International treaties on the long-range transport of atmospheric pollutants have been agreed upon by western countries for some time now. Beginning in 1979, European countries convened in order to ratify general principles discussed during the UNECE Convention. The purpose was to combat Long-Range Transboundary Air Po... | Acid rain | Wikipedia | 501 | 3263 | https://en.wikipedia.org/wiki/Acid%20rain | Physical sciences | Precipitation | null |
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally 66% copper and 34% zinc. In use since prehistoric times, it is a substitutional alloy: atoms of th... | Brass | Wikipedia | 500 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Today, almost 90% of all brass alloys are recycled. Because brass is not ferromagnetic, ferrous scrap can be separated from it by passing the scrap near a powerful magnet. Brass scrap is melted and recast into billets that are extruded into the desired form and size. The general softness of brass means that it can ofte... | Brass | Wikipedia | 404 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Lead content
To enhance the machinability of brass, lead is often added in concentrations of about 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting. The pattern the globules form on the su... | Brass | Wikipedia | 482 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
"Red brasses", a family of alloys with high copper proportion and generally less than 15% zinc, are more resistant to zinc loss. One of the metals called "red brass" is 85% copper, 5% tin, 5% lead, and 5% zinc. Copper alloy C23000, which is also known as "red brass", contains 84–86% copper, 0.05% each iron and lead, wi... | Brass | Wikipedia | 360 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Other wind instruments may be constructed of brass or other metals, and indeed most modern student-model flutes and piccolos are made of some variety of brass, usually a cupronickel alloy similar to nickel silver (also known as German silver). Clarinets, especially low clarinets such as the contrabass and subcontrabass... | Brass | Wikipedia | 508 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
The bactericidal properties of brass have been observed for centuries, particularly in marine environments where it prevents biofouling. Depending upon the type and concentration of pathogens and the medium they are in, brass kills these microorganisms within a few minutes to hours of contact.
A large number of indepe... | Brass | Wikipedia | 450 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Early copper-zinc alloys
In West Asia and the Eastern Mediterranean early copper-zinc alloys are now known in small numbers from a number of 3rd millennium BC sites in the Aegean, Iraq, the United Arab Emirates, Kalmykia, Turkmenistan and Georgia and from 2nd millennium BC sites in western India, Uzbekistan, Iran, Syri... | Brass | Wikipedia | 404 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
During the later part of first millennium BC the use of brass spread across a wide geographical area from Britain and Spain in the west to Iran, and India in the east. This seems to have been encouraged by exports and influence from the Middle East and eastern Mediterranean where deliberate production of brass from met... | Brass | Wikipedia | 485 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Brass made during the early Roman period seems to have varied between 20% and 28% wt zinc. The high content of zinc in coinage and brass objects declined after the first century AD and it has been suggested that this reflects zinc loss during recycling and thus an interruption in the production of new brass. However it... | Brass | Wikipedia | 289 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
These places would remain important centres of brass making throughout the Middle Ages period, especially Dinant. Brass objects are still collectively known as dinanderie in French. The baptismal font at St Bartholomew's Church, Liège in modern Belgium (before 1117) is an outstanding masterpiece of Romanesque brass cas... | Brass | Wikipedia | 459 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
In Europe a similar liquid process in open-topped crucibles took place which was probably less efficient than the Roman process and the use of the term tutty by Albertus Magnus in the 13th century suggests influence from Islamic technology. The 12th century German monk Theophilus described how preheated crucibles were ... | Brass | Wikipedia | 402 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Renaissance and post-medieval Europe
The Renaissance saw important changes to both the theory and practice of brassmaking in Europe. By the 15th century there is evidence for the renewed use of lidded cementation crucibles at Zwickau in Germany. These large crucibles were capable of producing c.20 kg of brass. There ar... | Brass | Wikipedia | 253 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Eventually it was discovered that metallic zinc could be alloyed with copper to make brass, a process known as speltering, and by 1657 the German chemist Johann Glauber had recognized that calamine was "nothing else but unmeltable zinc" and that zinc was a "half ripe metal". However some earlier high zinc, low iron bra... | Brass | Wikipedia | 311 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
In 1738 Nehemiah's son William Champion patented a technique for the first industrial scale distillation of metallic zinc known as distillation per descencum or "the English process". This local zinc was used in speltering and allowed greater control over the zinc content of brass and the production of high-zinc copper... | Brass | Wikipedia | 212 | 3292 | https://en.wikipedia.org/wiki/Brass | Physical sciences | Specific alloys | null |
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the M... | Brackish water | Wikipedia | 327 | 3336 | https://en.wikipedia.org/wiki/Brackish%20water | Physical sciences | Water: General | Earth science |
The River Thames flowing through London is a classic river estuary. The town of Teddington a few miles west of London marks the boundary between the tidal and non-tidal parts of the Thames, although it is still considered a freshwater river about as far east as Battersea insofar as the average salinity is very low and ... | Brackish water | Wikipedia | 467 | 3336 | https://en.wikipedia.org/wiki/Brackish%20water | Physical sciences | Water: General | Earth science |
Another important brackish water habitat is the mangrove swamp or mangal. Many, though not all, mangrove swamps fringe estuaries and lagoons where the salinity changes with each tide. Among the most specialised residents of mangrove forests are mudskippers, fish that forage for food on land, and archer fish, perch-like... | Brackish water | Wikipedia | 458 | 3336 | https://en.wikipedia.org/wiki/Brackish%20water | Physical sciences | Water: General | Earth science |
The Caspian Sea is the world's largest lake and contains brackish water with a salinity about one-third that of normal seawater. The Caspian is famous for its peculiar animal fauna, including one of the few non-marine seals (the Caspian seal) and the great sturgeons, a major source of caviar.
Hudson Bay is a brackish ... | Brackish water | Wikipedia | 423 | 3336 | https://en.wikipedia.org/wiki/Brackish%20water | Physical sciences | Water: General | Earth science |
The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as either , but other representations such as true/false, yes/no, on/off, or +/−... | Bit | Wikipedia | 500 | 3364 | https://en.wikipedia.org/wiki/Bit | Physical sciences | Data | null |
Ralph Hartley suggested the use of a logarithmic measure of information in 1928. Claude E. Shannon first used the word "bit" in his seminal 1948 paper "A Mathematical Theory of Communication". He attributed its origin to John W. Tukey, who had written a Bell Labs memo on 9 January 1947 in which he contracted "binary in... | Bit | Wikipedia | 429 | 3364 | https://en.wikipedia.org/wiki/Bit | Physical sciences | Data | null |
In the 1950s and 1960s, these methods were largely supplanted by magnetic storage devices such as magnetic-core memory, magnetic tapes, drums, and disks, where a bit was represented by the polarity of magnetization of a certain area of a ferromagnetic film, or by a change in polarity from one direction to the other. Th... | Bit | Wikipedia | 488 | 3364 | https://en.wikipedia.org/wiki/Bit | Physical sciences | Data | null |
Confusingly, the storage capacity of a directly-addressable memory device, such as a DRAM chip, or an assemblage of such chips on a memory module, is specified as a binary multiple -- using the ambiguous prefix G rather than the IEC recommended Gi prefix. For example, a DRAM chip that is specified (and advertised) as ... | Bit | Wikipedia | 472 | 3364 | https://en.wikipedia.org/wiki/Bit | Physical sciences | Data | null |
The International System of Units defines a series of decimal prefixes for multiples of standardized units which are commonly also used with the bit and the byte. The prefixes kilo (103) through yotta (1024) increment by multiples of one thousand, and the corresponding units are the kilobit (kbit) through the yottabit ... | Bit | Wikipedia | 78 | 3364 | https://en.wikipedia.org/wiki/Bit | Physical sciences | Data | null |
The byte is a unit of digital information that most commonly consists of eight bits. 1 byte (B) = 8 bits (bit). Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures. To disam... | Byte | Wikipedia | 508 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
Etymology and history
The term byte was coined by Werner Buchholz in June 1956, during the early design phase for the IBM Stretch computer, which had addressing to the bit and variable field length (VFL) instructions with a byte size encoded in the instruction. It is a deliberate respelling of bite to avoid accidenta... | Byte | Wikipedia | 491 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
In Volume 1 of The Art of Computer Programming (first published in 1968), Donald Knuth uses byte in his hypothetical MIX computer to denote a unit which "contains an unspecified amount of information ... capable of holding at least 64 distinct values ... at most 100 distinct values. On a binary computer a byte must the... | Byte | Wikipedia | 485 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
The lowercase letter o for octet is defined as the symbol for octet in IEC 80000-13 and is commonly used in languages such as French and Romanian, and is also combined with metric prefixes for multiples, for example ko and Mo.
Multiple-byte units
More than one system exists to define unit multiples based on the byte... | Byte | Wikipedia | 429 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
This definition is most commonly used for data-rate units in computer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of most storage media, particularly hard drives, flash-based storage, and DVDs. Operating systems that use this definition include macOS, iOS, Ubuntu, and Debi... | Byte | Wikipedia | 458 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
Various computer vendors have coined terms for data of various sizes, sometimes with different sizes for the same term even within a single vendor. These terms include double word, half word, long word, quad word, slab, superword and syllable. There are also informal terms. e.g., half byte and nybble for 4 bits, octal ... | Byte | Wikipedia | 464 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
Modern standard definitions
The IEC adopted the IUPAC proposal and published the standard in January 1999. The IEC prefixes are part of the International System of Quantities. The IEC further specified that the kilobyte should only be used to refer to bytes.
Lawsuits over definition
Lawsuits arising from alleged co... | Byte | Wikipedia | 485 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
In data transmission systems, the byte is used as a contiguous sequence of bits in a serial data stream, representing the smallest distinguished unit of data. For asynchronous communication a full transmission unit usually additionally includes a start bit, 1 or 2 stop bits, and possibly a parity bit, and thus its size... | Byte | Wikipedia | 99 | 3365 | https://en.wikipedia.org/wiki/Byte | Physical sciences | Data | null |
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorp... | Boron nitride | Wikipedia | 317 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry |
Hexagonal form (h-BN)
The most stable crystalline form is the hexagonal one, also called h-BN, α-BN, g-BN, graphitic boron nitride and "white graphene". Hexagonal boron nitride (point group = D3h; space group = P63/mmc) has a layered structure similar to graphite. Within each layer, boron and nitrogen atoms are bound ... | Boron nitride | Wikipedia | 439 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry |
Wurtzite form (w-BN)
The wurtzite form of boron nitride (w-BN; point group = C6v; space group = P63mc) has the same structure as lonsdaleite, a rare hexagonal polymorph of carbon. As in the cubic form, the boron and nitrogen atoms are grouped into tetrahedra. In the wurtzite form, the boron and nitrogen atoms are grou... | Boron nitride | Wikipedia | 479 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry |
Boron nitride can be doped p-type with beryllium and n-type with boron, sulfur, silicon or if co-doped with carbon and nitrogen. Both hexagonal and cubic BN are wide-gap semiconductors with a band-gap energy corresponding to the UV region. If voltage is applied to h-BN or c-BN, then it emits UV light in the range 215–2... | Boron nitride | Wikipedia | 473 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry |
Mechanical properties
BN nanosheets consist of hexagonal boron nitride (h-BN). They are stable up to 800°C in air. The structure of monolayer BN is similar to that of graphene, which has exceptional strength, a high-temperature lubricant, and a substrate in electronic devices.
The anisotropy of Young's modulus and Po... | Boron nitride | Wikipedia | 505 | 3370 | https://en.wikipedia.org/wiki/Boron%20nitride | Physical sciences | Ceramic compounds | Chemistry |
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