PHYSICS AND CHEMISTRY: Avogadro constant

In chemistry and physics, the Avogadro constant (symbols: L, N_A) is defined as the number of constituent particles (usually atoms ormolecules) per mole of a given substance, where the mole (abbreviation: mol) is one of the seven base units in the International System of Units(SI). The Avogadro constant has dimensions of reciprocal mol and its value is equal to 6.02214129(27)×10²³ mol⁻¹. The constant happens to be quite close to an integer power of two, specifically only about 0.37% less than 2^79 mol⁻¹, making the latter a useful approximation in nuclear physics when considering chain reaction growth rates.

Previous definitions of chemical quantity involved Avogadro's number, a historical term closely related to the Avogadro constant but defined differently: Avogadro's number was initially defined by Jean Baptiste Perrin as the number of atoms in one gram-molecule of hydrogen. It was later redefined as the number of atoms in 12 grams of the isotope carbon-12 and still later generalized to relate amounts of a substance to their molecular weight. For instance, to a first approximation, 1 gram of hydrogen, which has a mass number of 1 (atomic number 1), has6.022×10²³ hydrogen atoms. Similarly, 12 grams of carbon 12, with the mass number of 12 (atomic number 6), has the same number of carbon atoms, 6.022×10²³. Avogadro's number is a dimensionless quantity and has the numerical value of the Avogadro constant given in base units.

The Avogadro constant is fundamental to understanding both the makeup of molecules and their interactions and combinations. For instance, since one atom of oxygen will combine with two atoms of hydrogen to create one molecule of water (H₂O), one can similarly see that one mol of oxygen (6.022×10²³ of O atoms) will combine with two mol of hydrogen (2 × 6.022×10²³ of H atoms) to make one mol of H₂O.

Revisions in the base set of SI units necessitated redefinitions of the concepts of chemical quantity and so Avogadro's number, and its definition, was deprecated in favor of the Avogadro constant and its definition. Changes in the SI units are proposed that will precisely fix the value of the constant to exactly 6.02214X×10²³ when it is expressed in the unit mol⁻¹ (see New SI definitions, in which an "X" at the end of a number means one or more final digits yet to be agreed upon).

SOCIAL SCIENCES: TERTIARY SECTOR.

The service sector consists of the "soft" parts of the economy, i.e. activities where people offer their knowledge and time to improve productivity, performance, potential, and sustainability, what is termed affective labor. The basic characteristic of this sector is the production of services instead of end products. Services (also known as "intangible goods") include attention, advice, access, experience, and discussion. The production of information is generally also regarded as a service, but some economists now attribute it to a fourth sector, the quaternary sector.

The tertiary sector of industry involves the provision of services to other businesses as well as final consumers. Services may involve the transport, distribution and sale of goods from producer to a consumer, as may happen in wholesaling and retailing, or may involve the provision of a service, such as in pest control or entertainment. The goods may be transformed in the process of providing the service, as happens in the restaurant industry. However, the focus is on people interacting with people and serving the customer rather than transforming physical goods.

For the last 100 years, there has been a substantial shift from the primary and secondary sectors to the tertiary sector in industrialised countries. This shift is called tertiarisation.Western world, and is also the fastest-growing sector.

 The tertiary sector is now the largest sector of the economy in the

In examining the growth of the service sector in the early Nineties, the globalist Kenichi Ohmae noted that:

"In the United States 70 percent of the workforce works in the service sector; in Japan, 60 percent, and in Taiwan, 50 percent. These are not necessarily busboys and live-in maids. Many of them are in the professional category. They are earning as much as manufacturing workers, and often more.

TECHNOLOGIES: MAGNETISM

Magnetism is a class of physical phenomena that includes forces exerted by magnets on other magnets. It has its origin in electric currents and the fundamental magnetic moments of elementary particles. These give rise to a magnetic field that acts on other currents and moments. All materials are influenced to some extent by a magnetic field. The strongest effect is on permanent magnets, which have persistent magnetic moments caused by ferromagnetism. Most materials do not have permanent moments. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a much more complex relationship with an applied magnetic field (spin glass behavior and antiferromagnetism). Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminium, gases, and plastic. Pure oxygen exhibits magnetic properties when cooled to a liquid state.

The magnetic state (or phase) of a material depends on temperature (and other variables such as pressure and the applied magnetic field) so that a material may exhibit more than one form of magnetism depending on its temperature, etc.

HISTORY: Steve Jobs

Steven Paul "Steve" Jobs  February 24, 1955 – October 5, 2011  was an American entrepreneur, marketer, and inventor, who was the co-founder, chairman, and CEO of Apple Inc. Through Apple, he is widely recognized as a charismatic pioneer of the personal computer revolution and for his influential career in the computer and consumer electronics fields, transforming "one industry after another, from computers and smartphones to music and movies". Jobs also co-founded and served as chief executive of Pixar Animation Studios; he became a member of the board of directors of The Walt Disney Company in 2006, when Disney acquired Pixar. Jobs was among the first to see the commercial potential of Xerox PARC's mouse-driven graphical user interface, which led to the creation of the Apple Lisa and, a year later, the Macintosh. He also played a role in introLaserWriter, one of the first widely available laser printers, to the market.

ducing the

After a power struggle with the board of directors in 1985, Jobs left Apple and founded NeXT, a computer platform development company specializing in the higher-education and business markets. In 1986, he acquired the computer graphics division of Lucasfilm, which was spun off as Pixar.^[ He was credited in Toy Story (1995) as an executive producer. He served as CEO and majority shareholder until Disney's purchase of Pixar in 2006. In 1996, after Apple had failed to deliver its operating system, Copland, Gil Amelio turned to NeXT Computer, and the NeXTSTEP platform became the foundation for the Mac OS X. Jobs returned to Apple as an advisor, and took control of the company as an interim CEO. Jobs brought Apple from near bankruptcy to profitability by 1998.

As the new CEO of the company, Jobs oversaw the development of the iMac, iTunes, iPod, iPhone, and iPad, and on the services side, the company's Apple Retail Stores, iTunes Store and the App Store. The success of these products and services provided several years of stable financial returns, and propelled Apple to become the world's most valuable publicly traded company in 2011. The reinvigoration of the company is regarded by many commentators as one of the greatest turnarounds in business history.

In 2003, Jobs was diagnosed with a pancreas neuroendocrine tumor. Though it was initially treated, he reported a hormone imbalance, underwent a liver transplant in 2009, and appeared progressively thinner as his health declined. On medical leave for most of 2011, Jobs resigned in August that year, and was elected Chairman of the Board. He died of respiratory arrest related to the tumor on October 5, 2011.

Jobs received a number of honors and public recognition for his influence in the technology and music industries. He has been referred to as "legendary", a "futurist" and a "visionary", and has been described as the "Father of the Digital Revolution", a "master of innovation", "the master evangelist of the digital age" and a "design perfectionist".

HISTORY: Nelson Mandela

Nelson Rolihlahla Mandela  18 July 1918 – 5 December 2013) was a South African anti-apartheid revolutionary, politician, and philanthropist who served as President of South Africa from 1994 to 1999. He was South Africa's first black chief executive, and the first elected in a fully representative democratic election. His government focused on dismantling the legacy of apartheid through tackling institutionalised racism, poverty and inequality, and fostering racial reconciliation. Politically an African nationalist and democratic socialist, he served as President of the African National Congress (ANC) from 1991 to 1997. Internationally, Mandela was Secretary General of the Non-Aligned Movement from 1998 to 1999.

A Xhosa born to the Thembu royal family, Mandela attended the Fort Hare University and the University of Witwatersrand, where he studied law. Living in Johannesburg, he became involved in anti-colonial politics, joining the ANC and becoming a founding member of its Youth League. After the South African National Party came to power in 1948, he rose to prominence in the ANC's 1952 Defiance Campaign, was appointed superintendent of the organisation's Transvaal chapter and presided over the 1955 Congress of the People. Working as a lawyer, he was repeatedly arrested for seditious activities and, with the ANC leadership, was unsuccessfully prosecuted in the Treason Trial from 1956 to 1961. Influenced by Marxism, he secretly joined the South African Communist Party(SACP) and sat on its Central Committee. Although initially committed to non-violent protest, in association with the SACP he co-founded the militant Umkhonto we Sizwe (MK) in 1961, leading a sabotage campaign against the apartheid government. In 1962, he was arrested, convicted of conspiracy to overthrow the state, and sentenced to life imprisonment in the Rivonia Trial.

Mandela served 27 years in prison, initially on Robben Island, and later in Pollsmoor Prison and Victor Verster Prison. An international campaign lobbied for his release. He was released in 1990, during a time of escalating civil strife. Mandela joined negotiations with President F. W. de Klerk to abolish apartheid and establish multiracial elections in 1994, in which he led the ANC to victory and became South Africa's first black president. He published his autobiography in 1995. During his tenure in the Government of National Unity he invited other political parties to join the cabinet, and promulgated a new constitution. He also created the Truth and Reconciliation Commission to investigate past human rights abuses. While continuing the former government's liberal economic policy, his administration also introduced measures to encourage land reform, combat poverty, and expand healthcare services. Internationally, he acted as mediator between Libya and the United Kingdom in the Pan Am Flight 103 bombing trial, and oversawmilitary intervention in Lesotho. He declined to run for a second term, and was succeeded by his deputy, Thabo Mbeki. Mandela became an elder statesman, focusing on charitable work in combating poverty and HIV/AIDS through the Nelson Mandela Foundation.

Mandela was a controversial figure for much of his life. Denounced as a communist terrorist by critics,^[5][6] he nevertheless gained international acclaim for his activism, having received more than 250 honours, including the 1993 Nobel Peace Prize, the USPresidential Medal of Freedom, and the Soviet Order of Lenin. He is held in deep respect within South Africa, where he is often referred to by his Xhosa clan name, Madiba, or as Tata ("Father"); he is often described as "the father of the nation".

                                               

MATHS: GRAPHS

 In mathematics, and more specifically in graph theory, a graph is a representation of a set of objects where some pairs of objects are connected by links. The interconnected objects are represented by mathematical abstractions called vertices, and the links that connect some pairs of vertices are called edges. Typically, a graph is depicted in diagrammatic form as a set of dots for the vertices, joined by lines or curves for the edges. Graphs are one of the objects of study in discrete mathematics.

The edges may be directed or undirected. For example, if the vertices represent people at a party, and there is an edge between two people if they shake hands, then this is an undirected graph, because if person A shook hands with person B, then person B also shook hands with person A. In contrast, if there is an edge from person A to person B when person A knows of person B, then this graph is directed, because knowledge of someone is not necessarily a symmetric relation (that is, one person knowing another person does not necessarily imply the reverse; for example, many fans may know of a celebrity, but the celebrity is unlikely to know of all their fans). This latter type of graph is called a directed graph and the edges are called directed edges or arcs.

Vertices are also called nodes or points, and edges are also called arcs or lines. Graphs are the basic subject studied by graph theory. The word "graph" was first used in this sense by J.J. Sylvester in 1878.

Technology: Machines.

A machine is a tool containing one or more parts that uses energy to perform an intended action. Machines are usually powered by mechanical, chemical, thermal, or electrical means, and are often motorized. Historically, a power tool also required moving parts to classify as a machine. However, the advent of electronics technology has led to the development of power tools without moving parts that are considered machines.

A simple machine is a device that simply transforms the direction or magnitude of a force, but a large number of more complex machines exist. Examples include vehicles, electronic systems, molecular machines, computers, television, and radio.

EXAMPLE OF A MACHINE.

SOCIAL SCIENCES: Secondary Sector Activities.

This sector generally takes the output of the primary sector and manufactures finished goods. These products are then either exported or sold to domestic consumers and to places where they are suitable for use by other businesses. This sector is often divided into light industry and heavy industry. Many of these industries consume large amounts of energy and require factories and machinery to convert the raw materials into goods and products. They also produce waste materials and waste heat that may pose environmental problems or cause pollution.


How do secondary activities work.

BIOLOGY: Nutrition

Nutrition is the selection of foods and preparation of foods, and their ingestion to be assimilated by the body. By practicing a healthy diet, many of the known health issues can be avoided. The diet of an organism is what it eats, which is largely determined by the perceivedpalatability of foods.

Dietitians are health professionals who specialize in human nutrition, meal planning, economics, and preparation. They are trained to provide safe, evidence-based dietary advice and management to individuals (in health and disease), as well as to institutions. Clinicalnutritionists are health professionals who focus more specifically on the role of nutrition in chronic disease, including possible prevention or remediation by addressing nutritional deficiencies before resorting to drugs. Government regulation of the use of this professional title is less universal than for "dietician."

A poor diet may have an injurious impact on health, causing deficiency diseases such as scurvy and kwashiorkor; health-threatening conditions like obesity and metabolic syndrome;and such common chronic systemic diseases as cardiovascular disease,diabetes, and osteoporosis.

MATHS: SYSTEMS OF ECUATIONS.

A EXAMPLE OF A SYSTEM GRAPH.

In mathematics, a system of linear equations (or linear system) is a collection of linear equations involving the same set of variables. For example,

is a system of three equations in the three variables x, y, z. A solution to a linear system is an assignment of numbers to the variables such that all the equations are simultaneously satisfied. A solution to the system above is given by

since it makes all three equations valid.^[1] The word "system" indicates that the equations are to be considered collectively, rather than individually.

In mathematics, the theory of linear systems is the basis and a fundamental part of linear algebra, a subject which is used in most parts of modern mathematics. Computational algorithms for finding the solutions are an important part of numerical linear algebra, and play a prominent role inengineering, physics, chemistry, computer science, and economics. A system of non-linear equations can often be approximated by a linear system (see linearization), a helpful technique when making a mathematical model or computer simulation of a relatively complex system.

Very often, the coefficients of the equations are real or complex numbers and the solutions are searched in the same set of numbers, but the theory and the algorithms apply for coefficients and solutions in any field. For solutions in an integral domain like the ring of the integers, or in other algebraic structures, other theories have been developed, see Linear equation over a ring. Integer linear programming is a collection of method for finding the "best" integer solution (when there are many). Gröbner basis theory provides algorithms when coefficients and unknowns arepolynomials. Also tropical geometry is an example of linear algebra in a more exotic structure.

Physics and Chemistry: The Gamma Rays (Y)

Gamma radiation, also known as gamma rays, and denoted by the Greek letter γ, refers to electromagnetic radiation of extremely high frequency and therefore high energy per photon. Gamma rays are ionizing radiation, and are thus biologically hazardous. They are classically produced by the decay from high energy states of atomic nuclei (gamma decay), but are also created by other processes. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Villard's radiation was named "gamma rays" by Ernest Rutherford in 1903.

Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes, and secondary radiation from atmospheric interactions with cosmic ray particles. Rare terrestrial natural sources produce gamma rays that are not of a nuclear origin, such as lightning strikesand terrestrial gamma-ray flashes. Additionally, gamma rays are also produced by a number of astronomical processes in which very high-energy electrons are produced, that in turn cause secondary gamma rays via bremsstrahlung, inverse Compton scattering and synchrotron radiation. However, a large fraction of such astronomical gamma rays are screened by Earth's atmosphere and can only be detected by spacecraft.

Gamma rays typically have frequencies above 10 exahertz (or >1019 Hz), and therefore have energies above 100 keV and wavelengths less than 10picometers (less than the diameter of an atom). However, this is not a hard and fast definition, but rather only a rule-of-thumb description for natural processes. Gamma rays from radioactive decay are defined as gamma rays no matter what their energy, so that there is no lower limit to gamma energy derived from radioactive decay. Gamma decay commonly produces energies of a few hundred keV, and almost always less than 10 MeV. In astronomy, gamma rays are defined by their energy, and no production process need be specified. The energies of gamma rays from astronomical sources range over 10 TeV, at a level far too large to result from radioactive decay.  A notable example is extremely powerful bursts of high-energy radiation normally referred to as long duration gamma-ray bursts, which produce gamma rays by a mechanism not compatible with radioactive decay. These bursts of gamma rays, thought to be due to the collapse of stars called Hypernovae, are the most powerful events so far discovered in the cosmos.

MATHS: ECUATIONS

ECUATIONS:

In mathematics, an equation is a formula of the form A = B, where A and B are expressions that may contain one or several variables calledunknowns, and "=" denotes the equality binary relation. Although written in the form of proposition, an equation is not a statement that is either true or false, but a problem consisting of finding the values, called solutions, that, when substituted for the unknowns, yield equal values of the expressions Aand B. For example, 2 is the unique solution of the equation x + 2 = 4, in which the unknown is x. Historically, equations arose from the mathematical discipline of algebra, but later become ubiquitous. "Equations" should not be confused with "identities", which are presented with the same notation but have a different meaning: for example 2 + 2 = 4 and x + y = y + x are identities (which implies they are necessarily true) in arithmetic, and do not constitute a values-finding problem, even when variables are present as in the latter example.

The term "equation" may also refer to a relation between some variables that is presented as the equality of some expressions written in terms of those variables' values. For example theequation of the unit circle is x² + y² = 1, which means that a point belongs to the circle if and only if its coordinates are related by this equation. Most physical laws are expressed by equations. One of the most famous ones is Einstein's equation E = mc².

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PHYSICS AND CHEMISTRY: ATOMS

ATOMS

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electron. Theatomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other by chemical bonds based on the same force, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.
Chemical atoms, which in science now carry the simple name of "atom," are minuscule objects with diameters of a few tenths of ananometer and tiny masses proportional to the volume implied by these dimensions. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.94% of an atom's mass is concentrated in the nucleus,with protons and neutrons having roughly equal mass. Each element has at least one isotope with an unstable nucleus that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus. Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emittingphotons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties. The principles of quantum mechanics have been successfully used to model the observed properties of the atom.