Noise types.

Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.

Thermal noise.

Johnson–Nyquist noise (more often thermal noise) is unavoidable, and generated by the random thermal motion of charge carriers (usually electrons), inside an electrical conductor, which happens regardless of any applied voltage.  Thermal noise is approximately white, meaning that its power spectral density is nearly equal throughout the frequency spectrum. The amplitude of the signal has very nearly a Gaussian probability density function. A communication system affected by thermal noise is often modelled as an additive white Gaussian noise (AWGN) channel.

Shot noise.

Shot noise in electronic devices results from unavoidable random statistical fluctuations of the electric current when the charge carriers (such as electrons) traverse a gap. If electrons flow across a barrier, then they have discrete arrival times. Those discrete arrivals exhibit shot noise. Typically, the barrier in a diode is used. Shot noise is similar to the noise created by rain falling on a tin roof. The flow of rain may be relatively constant, but the individual raindrops arrive discretely.  The root-mean-square value of the shot noise current "i" is given by the Schottky formula.  where "I" is the DC current, "q" is the charge of an electron, and Δ"B" is the bandwidth in hertz. The Schottky formula assumes independent arrivals.  Vacuum tubes exhibit shot noise because the electrons randomly leave the cathode and arrive at the anode (plate). A tube may not exhibit the full shot noise effect: the presence of a space charge tends to smooth out the arrival times (and thus reduce the randomness of the current). Pentodes and screen-grid tetrodes exhibit more noise than triodes because the cathode current splits randomly between the screen grid and the anode.  Conductors and resistors typically do not exhibit shot noise because the electrons thermalize and move diffusively within the material; the electrons do not have discrete arrival times. Shot noise has been demonstrated in mesoscopic resistors when the size of the resistive element becomes shorter than the electron–phonon scattering length.

Flicker noise.

Flicker noise, also known as 1/"f" noise, is a signal or process with a frequency spectrum that falls off steadily into the higher frequencies, with a pink spectrum. It occurs in almost all electronic devices and results from a variety of effects.

Burst noise.

Burst noise consists of sudden step-like transitions between two or more discrete voltage or current levels, as high as several hundred microvolts, at random and unpredictable times. Each shift in offset voltage or current lasts for several milliseconds to seconds. It is also known a "popcorn noise" for the popping or crackling sounds it produces in audio circuits.

Transit-time noise.

If the time taken by the electrons to travel from emitter to collector in a transistor becomes comparable to the period of the signal being amplified, that is, at frequencies above VHF and beyond, the transit-time effect takes place and noise input impedance of the transistor decreases. From the frequency at which this effect becomes significant, it increases with frequency and quickly dominates other sources of noise.

Coupled noise.

While noise may be generated in the electronic circuit itself, additional noise energy can be coupled into a circuit from the external environment, by inductive coupling or capacitive coupling, or through the antenna of a radio receiver.

Mitigation.

In many cases noise found on a signal in a circuit is unwanted. There are many different noise reduction techniques that can reduce the noise picked up by a circuit.

Quantification.

The noise level in an electronic system is typically measured as an electrical power "N" in watts or dBm, a root mean square (RMS) voltage (identical to the noise standard deviation) in volts, dBμV or a mean squared error (MSE) in volts squared. Noise may also be characterized by its probability distribution and noise spectral density "N"("f") in watts per hertz.  A noise signal is typically considered as a linear addition to a useful information signal. Typical signal quality measures involving noise are signal-to-noise ratio (SNR or "S"/"N"), signal-to-quantization noise ratio (SQNR) in analog-to-digital conversion and compression, peak signal-to-noise ratio (PSNR) in image and video coding, "E"/"N" in digital transmission, carrier to noise ratio (CNR) before the detector in carrier-modulated systems, and noise figure in cascaded amplifiers.  Noise is a random process, characterized by stochastic properties such as its variance, distribution, and spectral density. The spectral distribution of noise can vary with frequency, so its power density is measured in watts per hertz (W/Hz). Since the power in a resistive element is proportional to the square of the voltage across it, noise voltage (density) can be described by taking the square root of the noise power density, resulting in volts per root hertz (formula_2). Integrated circuit devices, such as operational amplifiers commonly quote equivalent input noise level in these terms (at room temperature).  Noise power is measured in watts or decibels (dB) relative to a standard power, usually indicated by adding a suffix after dB. Examples of electrical noise-level measurement units are dBu, dBm0, dBrn, dBrnC, and dBrn("f" − "f"), dBrn(144-line).  Telecommunication systems strive to increase the ratio of signal level to noise level in order to effectively transfer data. Noise in telecommunication systems is a product of both internal and external sources to the system.  In a carrier-modulated passband analog communication system, a certain carrier-to-noise ratio (CNR) at the radio receiver input would result in a certain signal-to-noise ratio in the detected message signal. In a digital communications system, a certain "E"/"N" (normalized signal-to-noise ratio) would result in a certain bit error rate.

Dither.

If the noise source is correlated with the signal, such as in the case of quantisation error, the intentional introduction of additional noise, called dither, can reduce overall noise in the bandwidth of interest. This technique allows retrieval of signals below the nominal detection threshold of an instrument. This is an example of stochastic resonance.

In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects.


Form.

The standard form of a limerick is a stanza of five lines, with the first, second and fifth rhyming with one another and having three feet of three syllables each; and the shorter third and fourth lines also rhyming with each other, but having only two feet of three syllables. The third and fourth lines are usually anapaestic. The first, second and third are usually either anapaests or amphibrachs.  The first line traditionally introduces a person and a place, with the place appearing at the end of the first line and establishing the rhyme scheme for the second and fifth lines. In early limericks, the last line was often essentially a repeat of the first line, although this is no longer customary.  Within the genre, ordinary speech stress is often distorted in the first line, and may be regarded as a feature of the form: "There "was" a young "man" from the "coast";" "There "once" was a "girl" from De"troit"..." Legman takes this as a convention whereby prosody is violated simultaneously with propriety. Exploitation of geographical names, especially exotic ones, is also common, and has been seen as invoking memories of geography lessons in order to subvert the decorum taught in the schoolroom; Legman finds that the exchange of limericks is almost exclusive to comparatively well-educated males, women figuring in limericks almost exclusively as "villains or victims". The most prized limericks incorporate a kind of twist, which may be revealed in the final line or lie in the way the rhymes are often intentionally tortured, or both. Many limericks show some form of internal rhyme, alliteration or assonance, or some element of word play. Verses in limerick form are sometimes combined with a refrain to form a limerick song, a traditional humorous drinking song often with obscene verses.  David Abercrombie, a phonetician, takes a different view of the limerick, and one which seems to accord better with the form. It is this: Lines one, two, and five have three feet, that is to say three stressed syllables, while lines three and four have two stressed syllables. The number and placement of the unstressed syllables is rather flexible. There is at least one unstressed syllable between the stresses but there may be more – as long as there are not so many as to make it impossible to keep the equal spacing of the stresses.

Etymology.

The origin of the name "limerick" for this type of poem is debated. The name is generally taken to be a reference to the City or County of Limerick in Ireland sometimes particularly to the Maigue Poets, and may derive from an earlier form of nonsense verse parlour game that traditionally included a refrain that included "Will [or won't] you come (up) to Limerick?"  Although the "New English Dictionary" records the first usage in England in 1898 and in the United States in 1902, in recent years several earlier examples have been documented, the earliest being an 1880 reference, in a Saint John, New Brunswick newspaper, to an apparently well-known tune,

Edward Lear.

The limerick form was popularized by Edward Lear in his first "Book of Nonsense" (1846) and a later work, "More Nonsense, Pictures, Rhymes, Botany, etc". (1872). Lear wrote 212 limericks, mostly considered nonsense literature. It was customary at the time for limericks to accompany an absurd illustration of the same subject, and for the final line of the limerick to be a variant of the first line ending in the same word, but with slight differences that create a nonsensical, circular effect. The humour is not in the "punch line" ending but rather in the tension between meaning and its lack.  The following is an example of one of Edward Lear's limericks. Lear's limericks were often typeset in three or four lines, according to the space available under the accompanying picture.

Variations.

The limerick form is so well known that it has been parodied in many ways. The following example is of unknown origin: Other parodies deliberately break the rhyme scheme, like the following example, attributed to W.S. Gilbert: Comedian John Clarke has also parodied Lear's style: The British wordplay and recreational mathematics expert Leigh Mercer (1893–1977) devised the following mathematical limerick: formula_1 This is read as follows:  Limerick bibliographies:

A limerick () is a form of verse, usually humorous and frequently rude, in five-line, predominantly meter with a strict rhyme scheme of AABBA, in which the first, second and fifth line rhyme, while the third and fourth lines are shorter and share a different rhyme. The following example is a limerick of unknown origin: The form appeared in England in the early years of the 18th century. It was popularized by Edward Lear in the 19th century, although he did not use the term. Gershon Legman, who compiled the largest and most scholarly anthology, held that the true limerick as a folk form is always obscene, and cites similar opinions by Arnold Bennett and George Bernard Shaw, describing the clean limerick as a "periodic fad and object of magazine contests, rarely rising above mediocrity". From a folkloric point of view, the form is essentially transgressive; violation of taboo is part of its function.


Names.

The internationally known name of the river is based on the Russian name "Обь" ("Obʹ" ). Possibly from Proto-Indo-Iranian "*Hā́p-", "river, water" (compare Vedic "áp-", Persian "āb", Tajik "ob", and Pashto "obə", "water"). Katz (1990) proposes Komi "ob" 'river' as the immediate source of derivation for the Russian name. Katz's proposal of a common Finno-Ugric root, loaned early on from a pre-Indo-Iranian source related to Sanskrit "ambhas-" 'water' is deemed improbable by Rédei (1992), who prefers to analyze this as a later loan from a descendant of the non-nasal root form "*Hā́p-".  The Ob is known to the Khanty people as the "As" (the source of the name "Ostyak"), "Yag", "Kolta" and "Yema"; to the Nenets people as the "Kolta" or "Kuay"; and to the Siberian Tatars as the "Umar" or "Omass".

Geography.

The Ob forms southwest of Biysk in Altai Krai at the confluence of the Biya and Katun rivers. Both these streams have their origin in the Altay Mountains, the Biya issuing from Lake Teletskoye, the Katun, long, bursting out of a glacier on Mount Byelukha.  The Ob's entire main course is within Russia, though its tributaries extend into Kazakhstan, China and Mongolia. The river splits into more than one arm, especially after joining the large Irtysh tributary at about 69° E. (Originating in China, the Irtysh is actually longer than the Ob from source to the point of their confluence.) From the source of the Irtysh to the mouth of the Ob, the river flow is the longest in Russia at 4,248 kilometers (2,640 mi). Other noteworthy tributaries are: from the east, the Tom, Chulym, Ket, Tym and Vakh rivers; and, from the west and south, the Vasyugan, Irtysh (with the Ishim and Tobol rivers), and Severnaya Sosva.  The Ob zigzags west and north until it reaches 55° N, where it curves round to the northwest, and again north, wheeling finally eastwards into the Gulf of Ob, a bay of the Kara Sea, separating the Yamal Peninsula from the Gyda Peninsula.  The combined Ob-Irtysh system, the fourth-longest river system of Asia (after Yenisei, and China's Yangzi and Yellow rivers), is long, and the area of its basin. The river basin of the Ob consists mostly of steppe, taiga, swamps, tundra, and semi-desert topography. The floodplains of the Ob are characterized by many tributaries and lakes. The Ob is ice-bound at southern Barnaul from early in November to near the end of April, and at northern Salekhard, above its mouth, from the end of October to the beginning of June. The Ob River crosses several climatic zones. The upper Ob valley, in the south, grows grapes, melons and watermelons, whereas the lower reaches of the Ob are Arctic tundra. The most comfortable climate for the rest on the Ob are Biysk, Barnaul, and Novosibirsk.

Human use.

The Ob provides irrigation, drinking water, hydroelectric energy, and fishing (the river hosts more than 50 species of fish). There are several hydroelectric power plants along the Ob river, the largest being Novosibirskaya GES rated at 460 MW.  The navigable waters within the Ob basin reach a total length of. The importance of navigation in the Ob basin for transportation was particularly great before the completion of the Trans-Siberian Railway, since, despite the general south-to-north direction of the flow of Ob and most of its tributaries, the width of the Ob basin provided for (somewhat indirect) transportation in the east–west direction as well. Until the early 20th century, a particularly important western river-port was Tyumen, located on the Tura, a tributary of the Tobol. Reached by an extension of the Yekaterinburg-Perm railway in 1885, and thus obtaining a rail link to the Kama and Volga rivers in the heart of Russia, Tyumen became an important railhead for some years until the railway extended further east. In the eastern reaches of the Ob basin, Tomsk on the Tom functioned as an important terminus.  Tyumen had its first steamboat in 1836, and steamboats have navigated the middle reaches of the Ob since 1845. The first steamboat on the Ob, Nikita Myasnikov's "Osnova", was launched in 1844; the early starts were difficult, and it was not until 1857 that steamboat shipping started developing in the Ob system in a serious way. Steamboats started operating on the Yenisei in 1863, on the Lena and Amur in the 1870s. In 1916 there were 49 steamers on the Ob; 10 on the Yenisei.  In an attempt to extend the Ob navigable system even further, a system of canals, utilizing the Ket, long in all, was built in the late 19th-century to connect the Ob with the Yenisei, but soon abandoned as being uncompetitive with the railway.  The Trans-Siberian Railway, once completed, provided for more direct, year-round transportation in the east–west direction. But the Ob river-system still remained important for connecting the huge expanses of Tyumen Oblast and Tomsk Oblast with the major cities along the Trans-Siberian route, such as Novosibirsk or Omsk. In the second half of the 20th century, construction of rail links to Labytnangi, Tobolsk, and the oil and gas cities of Surgut, and Nizhnevartovsk provided more railheads, but did not diminish the importance of the waterways for reaching places still not served by the rail.  A dam built near Novosibirsk in 1956 created the then-largest artificial lake in Siberia, called Novosibirsk Reservoir.  From the 1960s through 1980s, Soviet engineers and administrators contemplated a gigantic project to divert some of the waters of Ob and Irtysh to Kazakhstan and the Soviet Central Asian republics, replenishing the Aral Sea as well. The project never left the drawing board, abandoned in 1986 for economic and environmental considerations.

Pollution.

In its early years of operation, the Mayak plant released vast quantities of radioactively contaminated water into several small lakes near the plant. These lakes drain into the Techa, whose waters ultimately flow into the Ob near the end of its path.

Tributaries.

The Irtysh is the major tributary of the Ob. The larger tributaries along its course are: In addition, the Nadym and the Pur River flow into the Gulf of Ob and the Taz into the Taz Estuary, a side arm of the Gulf of Ob.

Cities.

Cities along the river include:

Bridges.

From a confluence to a source:

The Ob (), also Ob', is a major river in western Siberia, Russia, and is the world's seventh-longest river. It forms at the confluence of the rivers Biya and Katun which have their origins in the Altay Mountains. It is the westernmost of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Yenisei and the Lena).


History.

By 1908, the process of alpha decay was known to consist of the ejection of helium nuclei from the decaying atom; however, as with cluster decay, alpha decay is not typically categorized as a process of fission.  The first nuclear fission process discovered was fission induced by neutrons. Because cosmic rays produce some neutrons, it was difficult to distinguish between induced and spontaneous events. Cosmic rays can be reliably shielded by a thick layer of rock or water. Spontaneous fission was identified in 1940 by Soviet physicists Georgy Flyorov and Konstantin Petrzhak by their observations of uranium in the Moscow Metro Dinamo station, underground.  Cluster decay was shown to be a superasymmetric spontaneous fission process.

Feasibility.

Elemental.

Spontaneous fission is feasible over practical observation times only for atomic masses of 232 amu or more. These are elements at least as heavy as thorium-232 – which has a half-life somewhat longer than the age of the universe. Th, U, and U are primordial nuclides and have left evidence of undergoing spontaneous fission in their minerals.  The known elements most susceptible to spontaneous fission are the synthetic high-atomic-number actinides and transactinides with atomic numbers from 100 onwards.  For naturally occurring thorium-232, uranium-235, and uranium-238, spontaneous fission does occur rarely, but in the vast majority of the radioactive decay of these atoms, alpha decay or beta decay occurs instead. Hence, the spontaneous fission of these isotopes is usually negligible, except in using the exact branching ratios when finding the radioactivity of a sample of these elements.

Mathematical.

The liquid drop model predicts approximately that spontaneous fission can occur in a time short enough to be observed by present methods when  where "Z" is the atomic number and A is the mass number (e.g., for uranium-235). However, all known nuclides which undergo spontaneous fission as their main decay mode do not reach this value of 47, as the liquid drop model is not very accurate for the heaviest known nuclei due to strong shell effects.

Spontaneous fission rates.

In practice, will invariably contain a certain amount of due to the tendency of to absorb an additional neutron during production.'s high rate of spontaneous fission events makes it an undesirable contaminant. Weapons-grade plutonium contains no more than 7.0%.  The rarely used gun-type atomic bomb has a critical insertion time of about one millisecond, and the probability of a fission during this time interval should be small. Therefore, only is suitable. Almost all nuclear bombs use some kind of implosion method.  Spontaneous fission can occur much more rapidly when the nucleus of an atom undergoes superdeformation.

Poisson process.

Spontaneous fission gives much the same result as induced nuclear fission. However, like other forms of radioactive decay, it occurs due to quantum tunneling, without the atom having been struck by a neutron or other particle as in induced nuclear fission. Spontaneous fissions release neutrons as all fissions do, so if a critical mass is present, a spontaneous fission can initiate a self-sustaining chain reaction. Radioisotopes for which spontaneous fission is not negligible can be used as neutron sources. For example, californium-252 (half-life 2.645 years, SF branch ratio about 3.1 percent) can be used for this purpose. The neutrons released can be used to inspect airline luggage for hidden explosives, to gauge the moisture content of soil in highway and building construction, or to measure the moisture of materials stored in silos, for example.  As long as the spontaneous fission gives a negligible reduction of the number of nuclei that can undergo such fission, this process can be approximated closely as a Poisson process. In this situation, for short time intervals the probability of a spontaneous fission is directly proportional to the length of time.  The spontaneous fission of uranium-238 and uranium-235 does leave trails of damage in the crystal structure of uranium-containing minerals when the fission fragments recoil through them. These trails, or "fission tracks", are the foundation of the radiometric dating method called fission track dating.

Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56; spontaneous breakdown into smaller nuclei and a few isolated nuclear particles becomes possible at greater atomic mass numbers.


Etymology.

Medieval German chronicler Adam of Bremen in the latter part of the 11th century AD was the first writer to use the term Baltic in its modern sense to mean the sea of that name. Before him were various ancient places names, such as Balcia, meaning a supposed island in the Baltic Sea.  It should not be surprising that Adam, a speaker of German, might connect "Balt-" with "Belt", a word he was familiar with. However, linguistics has since established that Balt means "white". Many Baltic words contain the stem balt-, "white", which may also refer to shallow bodies of water including marshes.  In Germanic languages there was some form of "East Sea" until after about 1600, when maps in English labeled it the "Baltic Sea". By 1840, the German nobles of the Governorate of Livonia adopted the term "Balts" to distinguish themselves from Germans of Germany. They spoke an exclusive dialect, Baltic German. For many, that was the “Baltic language” until 1919.  In 1845, Georg Heinrich Ferdinand Nesselmann proposed a distinct language group for Latvian, Lithuanian and Old Prussian—Baltic. The term became prevalent after Latvia and Lithuania gained independence in 1918. Up until the early 20th century, either “Latvian” or “Lithuanian” could be used to mean the entire language family.

History.

Origins.

The Balts or Baltic peoples, defined as speakers of one of the Baltic languages, a branch of the Indo-European language family, are descended from a group of Indo-European tribes who settled the area between the lower Vistula and southeast shore of the Baltic Sea and upper Daugava and Dnieper rivers. Because the thousands of lakes and swamps in this area contributed to the Balts' geographical isolation, the Baltic languages retain a number of conservative or archaic features.  Some of the major authorities on Balts, such as Kazimieras Būga, Max Vasmer, Vladimir Toporov and Oleg Trubachyov, in conducting etymological studies of eastern European river names, were able to identify in certain regions names of specifically Baltic provenance, which most likely indicate where the Balts lived in prehistoric times. This information is summarized and synthesized by Marija Gimbutas in "The Balts" (1963) to obtain a likely proto-Baltic homeland. Its borders are approximately: from a line on the Pomeranian coast eastward to include or nearly include the present-day sites of Berlin, Warsaw, Kiev, and Kursk, northward through Moscow to the River Berzha, westward in an irregular line to the coast of the Gulf of Riga, north of Riga.

Proto-history.

The area of Baltic habitation shrank due to assimilation by other groups, and invasions. According to one of the theories which has gained considerable traction over the years, one of the western Baltic tribes, the Galindians, Galindae, or Goliad, migrated to the area around modern day Moscow, Russia around the 4th century AD.  Over time the Balts became differentiated into Western and Eastern Balts. In the 5th century AD parts of the eastern Baltic coast began to be settled by the ancestors of the Western Balts: Brus/Prūsa ("Old Prussians"), Sudovians/Jotvingians, Scalvians, Nadruvians, and Curonians. The Eastern Balts, including the hypothesised Dniepr Balts, were living in modern-day Belarus, Ukraine and Russia.  Germanic peoples lived to the west of the Baltic homelands; by the first century AD, the Goths had stabilized their kingdom from the mouth of the Vistula, south to Dacia. As Roman domination collapsed in the first half of the first millennium CE in Northern and Eastern Europe, large migrations of the Balts occurred — first, the Galindae or Galindians towards the east, and later, Eastern Balts towards the west. In the seventh century, Slavic tribes from the Volga regions appeared. By the 13th and 14th centuries, they reached the general area that the present-day Balts and Belarusians inhabit. Many other Eastern and Southern Balts either assimilated with other Balts, or Slavs in the 4th–7th centuries and were gradually slavicized.

Middle Ages.

In the 12th and the 13th centuries, internal struggles, as well as invasions by Ruthenians and Poles and later the expansion of the Teutonic Order resulted in an almost complete annihilation of the Galindians, Curonians, and Yotvingians. Gradually Old Prussians became Germanized or some Lithuanized during period from the 15th to the 17th centuries, especially after the Reformation in Prussia. The cultures of the Lithuanians and Latgalians/Latvians survived and became the ancestors of the populations of the modern countries of Latvia and Lithuania.  Old Prussian was closely related to the other extinct Western Baltic languages, Curonian, Galindian and Sudovian. It is more distantly related to the surviving Eastern Baltic languages, Lithuanian and Latvian. Compare the Prussian word "seme" ("zemē"), the Latvian "zeme", the Lithuanian "žemė" ("land" in English).

Culture.

The Balts originally practiced Baltic religion. They were gradually Christianized as a result of the Northern Crusades of the Middle Ages. Baltic peoples such as the Latvians, Lithuanians and Old Prussians had their distinct mythologies. The Lithuanians have close historic ties to Poland, and many of them are therefore Roman Catholic. The Latvians have close historic ties of Northern Germany and Scandinavia, and many of them are therefore Lutherans. Irreligion is widespread. In recent times, the Baltic religion has been revived in Baltic neopaganism.

Genetics.

Recent genetic research show that the eastern Baltic in the Mesolithic was inhabited primarily by Western Hunter-Gatherers (WHGs). Their paternal haplogroups were mostly types of I2a and R1b, while their maternal haplogroups were mostly types of U5, U4 and U2. These people carried a high frequency of the derived HERC2 allele which codes for light eye color.  During the Neolithic, increasing admixture from Eastern Hunter-Gatherers (EHGs) is detected. The paternal haplogroups of EHGs was mostly types of R1b and R1a, while their maternal haplogroups appears to have been almost exclusively types of U5, U4, and U2. Baltic hunter-gatherers still displayed a slightly larger amount of WHG ancestry than Scandinavian Hunter-Gatherers (SHGs). WHG ancestry in the Baltic was particularly high among hunter-gatherers in Latvia and Lithuania. Unlike other parts of Europe, the hunter-gatherers of the eastern Baltic do not appear to have mixed much with Early European Farmers (EEFs) arriving from Anatolia.  The rise of the Corded Ware culture in the eastern Baltic in the Chalcolithic and Bronze Age is accompanied by a significant infusion of steppe ancestry and EEF ancestry into the eastern Baltic gene pool. In the aftermath of the Corded Ware expansion, local hunter-gatherer ancestry experienced a resurgence. Haplogroup N did not appear in the eastern Baltic until the late Bronze Age, perhaps as part of a westward migration of Uralic peoples.  Modern Balts have a lower amount of EEF ancestry, and a higher amount of WHG ancestry, than any other population in Europe.

List of Baltic peoples.

Modern Baltic peoples

The Balts or Baltic people (, ) are a group of Indo-European peoples primarily characterized as speakers of the Baltic languages.


Life and career.

Lortzing was born in Berlin to Johann Gottlieb and Charlotte Sophie Lortzing. They had abandoned their leather shop and travelled through Germany as itinerant actors, founding the Berlin theatre company "Urania", and turning their amateur passion into a profession. The young Lortzing's first stage appearance was at the age of 12, entertaining the audience with comic poems during the interval in the "Kornhaus" at the Freiburg Münster. From 1817, the Lortzing family were part of Josef Derossi ensemble in the Rhineland, treading the boards at Bonn, Düsseldorf, Barmen and Aachen. Albert Lortzing became an audience favourite, playing the roles of a youthful lover, a country boy and bon vivant, sometimes also singing small tenor or baritone roles.  On 30 January 1824 he married the actress Rosina Regine Ahles, with whom he subsequently had 11 children. The couple belonged to the Hoftheater (court theatre) in Detmold from late 1826, which toured to Münster and Osnabrück. Lortzing joined the Freemasons, a popular refuge for artists in Metternich's police state. Lortzing composed an oratorio in Detmold, "Die Himmelfahrt Christi" ("Christ's Ascension"), which premiered in Münster, and predictably earned a rebuke for the young composer from the Münster regional governor, who claimed that Lortzing was "a composer of no renown".  Lortzing composed the music for Christian Dietrich Grabbe's Don Juan und Faust, playing the role of Don Juan himself, with his wife as Donna Anna. Lortzing received a glowing report from an anonymous reviewer in a Frankfurt paper, who also mistakenly praised Lortzing for the text "by this brilliant poet". Grabbe, the real poet, was outraged, although the review did bring good publicity for the piece. On 3 November 1833 the young Lortzings gave their debut at the Leipziger Stadttheater. Lortzing's parents had been members of this ensemble since 1832, under Friedrich Sebald Ringelhardt. Here, Lortzing became a member of the artists' club ""Tunnel unter der Pleisse"" ("Tunnel under the Pleiße"), and in 1834 he became a member of the Leipzig Freemasons lodge ""Balduin zur Linde"" ("Balduin to the Linden Tree"). Lortzing was much loved in the Leipzig ensemble, particularly when acting in Johann Nestroy's comedies. However, his tendency to improvise and to deviate from the script attracted the attention of the theatrical police.  His first comic opera, "Zar und Zimmermann", had a tough time with the Leipzig censors. It premiered in Leipzig on 22 December 1837. Lortzing himself sang the role of Peter Iwanow, but it did not make a major breakthrough until its Berlin performances in 1839, where it was much praised.  In 1844, Lortzing became Kapellmeister of the Leipzig Stadttheater. After a quarrel with management, he was dismissed in April 1845 due to his "rheumatic troubles". The repeated protests of the public got him reinstated, but he was soon dismissed again after another argument. In an open letter, signed by almost everyone in the ensemble, he made a plea against the measures taken by the city government.  Between 1846 and 1848, Lortzing worked as Kapellmeister at the Theater an der Wien in Vienna. At the behest of the Freedom Movement, he wrote text and music in 1848 for his political opera "Regina", named after his wife. This work concerned both labour struggles and fear of suicide. His last full-length opera was an 1849 fairy-tale satire of the Prussian military state called "Rolands Knappen" ("Roland's Squire"), featuring the repeated line "And this is supposed to be a world order?" (""Und das soll eine Weltordnung sein?"")  In 1848 he lost his appointment and had to return to work as a touring actor to support his large family. He worked at Gera and Lüneburg, among other cities. Finally in 1850, he became the Kapellmeister in Berlin at the newly opened Friedrich-Wilhelmstädtisches Theater.  Lortzing also wrote music for masonic rituals.  On 20 January 1851, the night his musical comedy "Die Opernprobe" premiered in Frankfurt, Lortzing suffered a stroke at his home in Berlin and died without medical treatment on the morning of the following day, under huge stress and deeply in debt. A number of luminaries from the musical world were present at his funeral, including Giacomo Meyerbeer, Heinrich Dorn, Wilhelm Taubert and Carl Friedrich Rungenhagen. Lortzing's theatrical colleagues decorated his coffin with black, red and gold, a combination forbidden after 1848. A public benefit was then later held for his already impoverished family.

Works.

His first singspiel, "Ali Pascha von Janina", appeared in 1824, but his fame as a musician rests chiefly upon the two operas "Zar und Zimmermann" (1837) and "Der Wildschütz" (1842).  "Zar und Zimmermann" was received with very little enthusiasm by the public of Leipzig. However, at subsequent performances in Berlin there was a much more positive reaction. The opera soon appeared on all the stages of Germany, and today is regarded as one of the masterpieces of German comic opera. It was translated into English, French, Swedish, Danish, Dutch, Bohemian, Hungarian and Russian. The story is based around Tsar Peter I 'The Great' of Russia, who travelled to Germany, Holland and England disguised as a carpenter in order to gain first-hand technical knowledge he believed necessary for his country's economic progress, such as modern shipbuilding.  "Der Wildschütz" was based on a comedy by August von Kotzebue, and was a satire on the unintelligent and exaggerated admiration for the highest beauty in art expressed by the bourgeois gentilhomme.  Of his other operas, "Der Pole und sein Kind", produced shortly after the Polish insurrection of 1831, and "Undine" (1845) are notable.  Lortzing was popular in Berlin and after his death, a memorial statue was erected in the Tiergarten in Berlin.

Gustav Albert Lortzing (23 October 1801 – 21 January 1851) was a German composer, actor and singer. He is considered to be the main representative of the German "Spieloper", a form similar to the French "opéra comique", which grew out of the "Singspiel".


Design and use.

Traditional Advent calendars feature the manger scene, Saint Nicholas and winter weather, while others range in theme, from sports to technology. They come in a multitude of forms, from a simple paper calendar with flaps covering each of the days to fabric pockets on a background scene to painted wooden boxes with cubby holes for small items.  Many Advent calendars take the form of a large rectangular card with "windows", one for each day of December leading up to and including Christmas Eve (December 24) or Christmas Day (December 25). Consecutive doors are opened every day leading up to Christmas, beginning on the start of the Advent season for that year, or in the case of reusable Advent calendars, on December 1. Often the doors are distributed across the calendar in no particular order. The calendar windows open to reveal an image, a poem, a portion of a story (such as the story of the Nativity of Jesus), or a small gift, such as a toy or a chocolate item. Often, each window has a Bible verse and Christian prayer printed on it, which Christians incorporate as part of their daily Advent devotions. Advent calendars may also have puzzles and games printed on their reverse side.  The long-established British magazine "Country Life" incorporates an Advent calendar—which it describes as "our famous Advent calendar"— in its cover for the final issue of November.  There are many variations of Advent calendar, including social media Advent calendars, and string up reusable Advent calendars. Many towns have created living advent calendars. Some Advent calendars even eschew traditional Christmas motifs and themes, focusing only on Jesus as the central character of the Christmas story.

The Nordic Julekalender/Julkalender.

In Denmark, Finland, Iceland, Norway and Sweden there is also a tradition of having a so-called "Julekalender" (Swedish: "Julkalender", Finnish: "Joulukalenteri", Icelandic: "Jóladagatal"; the local word for a Yule—or Christmas—calendar, even though it actually is an Advent calendar) in the form of a television or radio show, starting on December 1 and ending on Christmas Eve (December 24).  Such a show first aired on radio in 1957 in the form of the Swedish radio series "Barnens adventskalender"; the first televised show of the genre aired in 1960 in the form of the Swedish program "Titteliture". The first "julekalender" aired in Denmark was "Historier fra hele verden" in 1962. The televised "julkalender" or "julekalendar" has now extended into the other Nordic countries; in Finland, for example, the show is called "Joulukalenteri".  Over the years, there have been several kinds of "julekalender"; some are directed at children, some at both children and adults, and some directed at adults alone. There is a "Julkalender" radio show in Sweden, which airs in the days leading up to Christmas. A classic example of a "julekalender" enjoyed by children (as well as adults, if purely for nostalgic reasons) is the 1979 Norwegian television show "Jul i Skomakergata"; another is the 1990 Icelandic television show "Á baðkari til Betlehem".

An Advent calendar is a special calendar used to count the days of Advent in anticipation of Christmas. Since the date of the First Sunday of Advent varies, falling between November 27 and December 3 inclusive, many Advent calendars, especially those that are reusable, often begin on December 1, although those that are produced for a specific year often include the last few days of November that are part of the liturgical season. The Advent calendar was first used by German Lutherans in the 19th and 20th centuries.


Name.

The origins of the name "Adriatic" are linked to the Etruscan settlement of Adria, which probably derives its name from the Illyrian "adur" meaning water or sea. In classical antiquity, the sea was known as "Mare Adriaticum" ("Mare Hadriaticum", also sometimes simplified to "Adria") or, less frequently, as "Mare Superum", "[the] upper sea". The two terms were not synonymous, however. "Mare Adriaticum" generally corresponds to the Adriatic Sea's extent, spanning from the Gulf of Venice to the Strait of Otranto. That boundary became more consistently defined by Roman authors – early Greek sources place the boundary between the Adriatic and Ionian seas at various places ranging from adjacent to the Gulf of Venice to the southern tip of the Peloponnese, eastern shores of Sicily and western shores of Crete. "Mare Superum" on the other hand normally encompassed both the modern Adriatic Sea and the sea off the Apennine peninsula's southern coast, as far as the Strait of Sicily. Another name used in the period was "Mare Dalmaticum", applied to waters off the coast of Dalmatia or Illyricum.  The names for the sea in the languages of the surrounding countries include ; ; ; – "Adriatikí thálassa"; ; ;, Јадранско море; ;. In Serbo-Croatian and Slovene, the sea is often referred to as simply "Jadran".

Geography.

The Adriatic Sea is a semi-enclosed sea, bordered in the southwest by the Apennine or Italian Peninsula, in the northwest by the Italian regions of Veneto and Friuli-Venezia Giulia, and in the northeast by Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, and Albania—the Balkan peninsula. In the southeast, the Adriatic Sea connects to the Ionian Sea at the wide Strait of Otranto. The International Hydrographic Organization (IHO) defines the boundary between the Adriatic and the Ionian seas as a line running from the Butrinto River's mouth (latitude 39°44'N) in Albania to the Karagol Cape in Corfu, through this island to the Kephali Cape (these two capes are in latitude 39°45'N), and on to the Santa Maria di Leuca Cape (latitude 39°48'N). It extends from the northwest to the southeast and is wide. It covers and has a volume of. The Adriatic extends northwest from 40° to 45°47' north, representing the Mediterranean's northernmost portion. The sea is geographically divided into the Northern Adriatic, Central (or Middle) Adriatic, and Southern Adriatic. The Adriatic Sea drainage basin encompasses, yielding a land–sea ratio of 1.8. The drainage basin's mean elevation is above sea level, with a mean slope of 12.1°. Major rivers discharging into the Adriatic include the Po, Soča, Krka, Neretva, Drin, Bojana, and Vjosë. In the late 19th century, Austria-Hungary established a geodetic network with an elevation benchmark using the average Adriatic Sea level at the Sartorio pier in Trieste, Italy. The benchmark was subsequently retained by Austria, adopted by Yugoslavia, and retained by the states that emerged after its dissolution. In 2016, Slovenia adopted a new elevation benchmark referring to the upgraded tide gauge station in the coastal town of Koper.

Oil and gas.

Natural gas is produced through several projects, including a joint venture of the Eni and INA companies that operates two platforms—one is in Croatian waters and draws gas from six wells, and the other (which started operating in 2010) is located in Italian waters. The Adriatic gas fields were discovered in the 1970s, but their development commenced in 1996. In 2008, INA produced 14.58 million BOE per day of gas. About 100 offshore platforms are located in the Emilia-Romagna region, along with 17 in the Northern Adriatic. Eni estimated its concessions in the Adriatic Sea to hold at least of natural gas, adding that they may even reach. INA estimates, however, are 50% lower than those supplied by Eni. Oil was discovered in the Northern Adriatic at a depth of approximately ; the discovery was assessed as not viable because of its location, depth and quality. These gas and oil reserves are part of the Po basin Province of Northern Italy and the Northern Mediterranean Sea.  In the 2000s, investigation works aimed at discovering gas and oil reserves in the Middle and Southern Adriatic basins intensified, and by the decade's end, oil and natural gas reserves were discovered southeast of the Bari, Brindisi—Rovesti and Giove oil discoveries. Surveys indicate reserves of 3 billion barrels of oil in place and of gas in place. The discovery was followed by further surveys off the Croatian coast. In January 2012, INA commenced prospecting for oil off Dubrovnik, marking the resumption of oil exploration along the eastern Adriatic coast after surveys commenced in the late 1980s around the island of Brač were cancelled because of Yugoslavia's breakup and war in Croatia. Montenegro is also expected to look for oil off its coast. As of January 2012, only 200 exploration wells had been sunk off the Croatian coast, with all but 30 in the Northern Adriatic basin.

The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkans. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to the northwest and the Po Valley. The countries with coasts on the Adriatic are Albania, Bosnia and Herzegovina, Croatia, Italy, Montenegro and Slovenia. The Adriatic contains over 1,300 islands, mostly located along the Croatian part of its eastern coast. It is divided into three basins, the northern being the shallowest and the southern being the deepest, with a maximum depth of. The Otranto Sill, an underwater ridge, is located at the border between the Adriatic and Ionian Seas. The prevailing currents flow counterclockwise from the Strait of Otranto, along the eastern coast and back to the strait along the western (Italian) coast. Tidal movements in the Adriatic are slight, although larger amplitudes are known to occur occasionally. The Adriatic's salinity is lower than the Mediterranean's because the Adriatic collects a third of the fresh water flowing into the Mediterranean, acting as a dilution basin. The surface water temperatures generally range from in summer to in winter, significantly moderating the Adriatic Basin's climate.


Biography and work.

Family and beginnings.

Gottfried Benn was born in a Lutheran country parsonage, a few hours from Berlin, the son and grandson of pastors in Mansfeld, now part of Putlitz in the district of Prignitz, Brandenburg. He was educated in Sellin in the Neumark and Frankfurt an der Oder. To please his father, he studied theology at the University of Marburg and military medicine at the Kaiser Wilhelm Academy in Berlin. After being laid off as a military doctor in 1912, Benn turned to pathology, where he dissected over 200 bodies between October 1912 and November 1913 in Berlin. Many of his literary works reflect on his time as a pathologist.  In the summer of 1912, Benn started a romantic relationship with the Jewish poet Else Lasker-Schüler.  Gottfried Benn began his literary career as a poet when he published a booklet titled "Morgue and other Poems" in 1912, containing expressionist poems dealing with physical decay of flesh, with blood, cancer, and death — for example No III — "Cycle":  Poems like this "were received by critics and public with shock, dismay, even revulsion." In 1913 a second volume of poems came out, titled "Sons. New Poems".  Benn's poetry projects an introverted nihilism, that is, an existentialist outlook that views artistic expression as the only purposeful action. In his early poems Benn used his medical experience, often using medical terminology, to portray humanity morbidly as just another species of disease-ridden animal.

World War I and Weimar Republic.

After the outbreak of World War I he enlisted in 1914, and spent a brief period on the Belgian front, then served as a military doctor in Brussels. Benn attended the trial and execution of Nurse Edith Cavell. He also worked as a physician in an army brothel. After the war, he returned to Berlin and practiced as a dermatologist and venereal disease specialist. During the 1920s, he had a close relationship with Jewish poet Else Lasker-Schüler who addressed love poems to him. This bond to her is the subject of the film "Mein Herz-niemandem" (1997) by Helma Sanders-Brahms.

During the Third Reich.

Hostile to the Weimar Republic, and rejecting Marxism and Americanism, Benn, like many Germans, was upset with ongoing economic and political instability, and sympathized for a short period with the Nazis as a revolutionary force. He hoped that National Socialism would exalt his aesthetics and that expressionism would become the official art of Germany, as Futurism had in Italy. Benn was elected to the poetry section of the Prussian Academy in 1932 and appointed head of that section in February 1933. In May, he defended the new regime in a radio broadcast, saying "the German workers are better off than ever before." He later signed the "Gelöbnis treuester Gefolgschaft", that is, the "vow of most faithful allegiance" to Adolf Hitler.  The cultural policy of the new State didn't turn out the way he hoped, and in June Hans Friederich Blunck replaced Benn as head of the Academy's poetry section. Appalled by the Night of the Long Knives, Benn turned away from the Nazis. He lived quietly, refraining from public criticism of the Nazi Party, but wrote that the bad conditions of the system "gave me the latter punch" and stated in a letter that the developments presented a "dreadful tragedy!" He decided to perform "the aristocratic form of emigration" and joined the Wehrmacht in 1935, where he found many officers sympathetic to his disapproval of the régime. In May 1936 the SS magazine "Das Schwarze Korps" attacked his expressionist and experimental poetry as degenerate, Jewish, and homosexual. In the summer of 1937, Wolfgang Willrich, a member of the SS, lampooned Benn in his book "Säuberung des Kunsttempels"; Heinrich Himmler, however, stepped in to reprimand Willrich and defended Benn on the grounds of his good record since 1933 (his earlier artistic output being irrelevant). In 1938 the Reichsschrifttumskammer (the National Socialist authors' association) banned Benn from further writing.

After the war.

During World War II, Benn was posted to garrisons in eastern Germany where he wrote poems and essays. After the war, his work was banned by the Allies because of his initial support for Hitler. In 1951 he was awarded the Georg Büchner Prize. He died of cancer in West Berlin in 1956, and was buried in Waldfriedhof Dahlem, Berlin.

Reception.

Benn had a great influence on German poetry immediately before World War I (as an expressionist), as well as after World War II (as the 'Static' poet).

Gottfried Benn (2 May 1886 – 7 July 1956) was a German poet, essayist, and physician. He was nominated for the Nobel Prize in Literature five times.


Etymology.

The coining of the term "qubit" is attributed to Benjamin Schumacher. In the acknowledgments of his 1995 paper, Schumacher states that the term "qubit" was created in jest during a conversation with William Wootters. The paper describes a way of compressing states emitted by a quantum source of information so that they require fewer physical resources to store. This procedure is now known as Schumacher compression.

Bit versus qubit.

A binary digit, characterized as 0 and 1, is used to represent information in classical computers. A binary digit can represent up to one bit of Shannon information, where a bit is the basic unit of information. However, in this article, the word bit is synonymous with binary digit.  In classical computer technologies, a "processed" bit is implemented by one of two levels of low DC voltage, and whilst switching from one of these two levels to the other, a so-called forbidden zone must be passed as fast as possible, as electrical voltage cannot change from one level to another "instantaneously".  There are two possible outcomes for the measurement of a qubit—usually taken to have the value "0" and "1", like a bit or binary digit. However, whereas the state of a bit can only be either 0 or 1, the general state of a qubit according to quantum mechanics can be a coherent superposition of both. Moreover, whereas a measurement of a classical bit would not disturb its state, a measurement of a qubit would destroy its coherence and irrevocably disturb the superposition state. It is possible to fully encode one bit in one qubit. However, a qubit can hold more information, e.g. up to two bits using superdense coding.  For a system of "n" components, a complete description of its state in classical physics requires only "n" bits, whereas in quantum physics it requires 2−1 complex numbers.

Standard representation.

In quantum mechanics, the general quantum state of a qubit can be represented by a linear superposition of its two orthonormal basis states (or basis vectors). These vectors are usually denoted as formula_1 and formula_2. They are written in the conventional Dirac—or "bra–ket"—notation; the formula_3 and formula_4 are pronounced "ket 0" and "ket 1", respectively. These two orthonormal basis states, <math>\

Qubit storage.

In a paper entitled "Solid-state quantum memory using the P nuclear spin", published in the October 23, 2008, issue of the journal "Nature", a team of scientists from the U.K. and U.S. reported the first relatively long (1.75 seconds) and coherent transfer of a superposition state in an electron spin "processing" qubit to a nuclear spin "memory" qubit. This event can be considered the first relatively consistent quantum data storage, a vital step towards the development of quantum computing. Recently, a modification of similar systems (using charged rather than neutral donors) has dramatically extended this time, to 3 hours at very low temperatures and 39 minutes at room temperature. Room temperature preparation of a qubit based on electron spins instead of nuclear spin was also demonstrated by a team of scientists from Switzerland and Australia.

In quantum computing, a qubit () or quantum bit (sometimes qbit) is the basic unit of quantum information—the quantum version of the classical binary bit physically realized with a two-state device. A qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include: the spin of the electron in which the two levels can be taken as spin up and spin down; or the polarization of a single photon in which the two states can be taken to be the vertical polarization and the horizontal polarization. In a classical system, a bit would have to be in one state or the other. However, quantum mechanics allows the qubit to be in a coherent superposition of both states simultaneously, a property which is fundamental to quantum mechanics and quantum computing.


Etymology.

The name "feldspar" derives from the German "Feldspat", a compound of the words "Feld" ("field") and "Spat" ("flake"). "Spat" had long been used as the word for "a rock easily cleaved into flakes"; "Feldspat" was introduced in the 18th century as a more specific term, referring perhaps to its common occurrence in rocks found in fields (Urban Brückmann, 1783) or to its occurrence as "fields" within granite and other minerals (René-Just Haüy, 1804). The change from "Spat" to "-spar" was influenced by the English word "spar", meaning a non-opaque mineral with good cleavage. "Feldspathic" refers to materials that contain feldspar. The alternate spelling, "felspar", has fallen out of use. The term 'felsic', meaning light colored minerals such as quartz and feldspars, is an acronymic word derived from "fel"dspar and "sil"ica, unrelated to the redundant spelling 'felspar'.

Compositions.

This group of minerals consists of tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers:  Solid solutions between K-feldspar and albite are called "alkali feldspar". Solid solutions between albite and anorthite are called "plagioclase", or more properly "plagioclase feldspar". Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the Earth. Albite is considered both a plagioclase and alkali feldspar.

Alkali feldspars.

Alkali feldspars are grouped into two types: those containing potassium in combination with sodium, aluminum, or silicon; and those where potassium is replaced by barium. The first of these include:  Potassium and sodium feldspars are not perfectly miscible in the melt at low temperatures, therefore intermediate compositions of the alkali feldspars occur only in higher temperature environments. Sanidine is stable at the highest temperatures, and microcline at the lowest. Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye. Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.  In addition, peristerite is the name given to feldspar containing approximately equal amounts of intergrown alkali feldspar and plagioclase.

Barium feldspars.

Barium feldspars are also considered alkali feldspars. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure.  The barium feldspars are monoclinic and include the following:

Plagioclase feldspars.

The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses):  Intermediate compositions of plagioclase feldspar also may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colors visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae known as Bøggild intergrowth. The specific gravity in the plagioclase series increases from albite (2.62) to anorthite (2.72–2.75).

Weathering.

Chemical weathering of feldspars results in the formation of clay minerals such as illite and kaolinite.

Production and uses.

About 20 million tonnes of feldspar were produced in 2010, mostly by three countries: Italy (4.7 Mt), Turkey (4.5 Mt), and China (2 Mt).  Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion. In ceramics, the alkalis in feldspar (calcium oxide, potassium oxide, and sodium oxide) act as a flux, lowering the melting temperature of a mixture. Fluxes melt at an early stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fiber. Ceramics (including electrical insulators, sanitaryware, pottery, tableware, and tile) and other uses, such as fillers, accounted for the remainder.  Bon Ami, which had a mine near Little Switzerland, North Carolina, used feldspar as an abrasive in its cleaners. The Little Switzerland Business Association says the McKinney Mine was the largest feldspar mine in the world, and North Carolina was the largest producer. Feldspar had been discarded in the process of mining mica until William Dibbell sent a premium quality product to the Ohio company Golding and Sons around 1910.  In earth sciences and archaeology, feldspars are used for potassium-argon dating, argon-argon dating, and luminescence dating.  In October 2012, the Mars Curiosity rover analyzed a rock that turned out to have a high feldspar content.

Feldspars (KAlSiO – NaAlSiO – CaAlSiO) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight.


Overview.

A lattice system is a class of lattices with the same set of lattice point groups, which are subgroups of the arithmetic crystal classes. The 14 Bravais lattices are grouped into seven lattice systems: triclinic, monoclinic, orthorhombic, tetragonal, rhombohedral, hexagonal, and cubic.  In a crystal system, a set of point groups and their corresponding space groups are assigned to a lattice system. Of the 32 point groups that exist in three dimensions, most are assigned to only one lattice system, in which case both the crystal and lattice systems have the same name. However, five point groups are assigned to two lattice systems, rhombohedral and hexagonal, because both exhibit threefold rotational symmetry. These point groups are assigned to the trigonal crystal system. In total there are seven crystal systems: triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic.  A crystal family is determined by lattices and point groups. It is formed by combining crystal systems which have space groups assigned to a common lattice system. In three dimensions, the crystal families and systems are identical, except the hexagonal and trigonal crystal systems, which are combined into one hexagonal crystal family. In total there are six crystal families: triclinic, monoclinic, orthorhombic, tetragonal, hexagonal, and cubic.  Spaces with less than three dimensions have the same number of crystal systems, crystal families and lattice systems. In one-dimensional space, there is one crystal system. In 2D space, there are four crystal systems: oblique, rectangular, square, and hexagonal.  The relation between three-dimensional crystal families, crystal systems and lattice systems is shown in the following table:

Crystal classes.

The 7 crystal systems consist of 32 crystal classes (corresponding to the 32 crystallographic point groups) as shown in the following table below:  The point symmetry of a structure can be further described as follows. Consider the points that make up the structure, and reflect them all through a single point, so that ("x","y","z") becomes (−"x",−"y",−"z"). This is the 'inverted structure'. If the original structure and inverted structure are identical, then the structure is "centrosymmetric". Otherwise it is "non-centrosymmetric". Still, even in the non-centrosymmetric case, the inverted structure can in some cases be rotated to align with the original structure. This is a non-centrosymmetric "achiral" structure. If the inverted structure cannot be rotated to align with the original structure, then the structure is "chiral" or "enantiomorphic" and its symmetry group is "enantiomorphic".  A direction (meaning a line without an arrow) is called "polar" if its two directional senses are geometrically or physically different. A symmetry direction of a crystal that is polar is called a "polar axis". Groups containing a polar axis are called "polar". A polar crystal possesses a unique polar axis (more precisely, all polar axes are parallel). Some geometrical or physical property is different at the two ends of this axis: for example, there might develop a dielectric polarization as in pyroelectric crystals. A polar axis can occur only in non-centrosymmetric structures. There cannot be a mirror plane or twofold axis perpendicular to the polar axis, because they would make the two directions of the axis equivalent.  The crystal structures of chiral biological molecules (such as protein structures) can only occur in the 65 enantiomorphic space groups (biological molecules are usually chiral).

Bravais lattices.

There are seven different kinds of crystal systems, and each kind of crystal system has four different kinds of centerings (primitive, base-centered, body-centered, face-centered). However, not all of the combinations are unique; some of the combinations are equivalent while other combinations are not possible due to symmetry reasons. This reduces the number of unique lattices to the 14 Bravais lattices.  The distribution of the 14 Bravais lattices into lattice systems and crystal families is given in the following table.  In geometry and crystallography, a Bravais lattice is a category of translative symmetry groups (also known as lattices) in three directions.  Such symmetry groups consist of translations by vectors of the form  where "n", "n", and "n" are integers and a, a, and a are three non-coplanar vectors, called "primitive vectors".  These lattices are classified by the space group of the lattice itself, viewed as a collection of points; there are 14 Bravais lattices in three dimensions; each belongs to one lattice system only. They represent the maximum symmetry a structure with the given translational symmetry can have.  All crystalline materials (not including quasicrystals) must, by definition, fit into one of these arrangements.  For convenience a Bravais lattice is depicted by a unit cell which is a factor 1, 2, 3 or 4 larger than the primitive cell. Depending on the symmetry of a crystal or other pattern, the fundamental domain is again smaller, up to a factor 48.  The Bravais lattices were studied by Moritz Ludwig Frankenheim in 1842, who found that there were 15 Bravais lattices. This was corrected to 14 by A. Bravais in 1848.

In four-dimensional space.

The four-dimensional unit cell is defined by four edge lengths ("a", "b", "c", "d") and six interaxial angles ("α", "β", "γ", "δ", "ε", "ζ"). The following conditions for the lattice parameters define 23 crystal families  The names here are given according to Whittaker. They are almost the same as in Brown "et al", with exception for names of the crystal families 9, 13, and 22. The names for these three families according to Brown "et al" are given in parenthesis.  The relation between four-dimensional crystal families, crystal systems, and lattice systems is shown in the following table. Enantiomorphic systems are marked with an asterisk. The number of enantiomorphic pairs are given in parentheses. Here the term "enantiomorphic" has a different meaning than in the table for three-dimensional crystal classes. The latter means, that enantiomorphic point groups describe chiral (enantiomorphic) structures. In the current table, "enantiomorphic" means that a group itself (considered as a geometric object) is enantiomorphic, like enantiomorphic pairs of three-dimensional space groups P3 and P3, P422 and P422. Starting from four-dimensional space, point groups also can be enantiomorphic in this sense.

In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals. Informally, two crystals are in the same crystal system if they have similar symmetries, although there are many exceptions to this.


Notation.

Capital-sigma notation.

Mathematical notation uses a symbol that compactly represents summation of many similar terms: the "summation symbol", formula_1, an enlarged form of the upright capital Greek letter Sigma. This is defined as where is the index of summation; is an indexed variable representing each term of the sum; is the lower bound of summation, and is the upper bound of summation. The "" under the summation symbol means that the index starts out equal to. The index,, is incremented by one for each successive term, stopping when.  This is read as "sum of, from to ".  Here is an example showing the summation of squares:  Informal writing sometimes omits the definition of the index and bounds of summation when these are clear from context, as in:  One often sees generalizations of this notation in which an arbitrary logical condition is supplied, and the sum is intended to be taken over all values satisfying the condition. Here are some common examples: is the sum of formula_9 over all (integers) formula_10 in the specified range, is the sum of formula_12 over all elements formula_13 in the set formula_14, and is the sum of formula_16 over all positive integers formula_17 dividing formula_18.  There are also ways to generalize the use of many sigma signs. For example, is the same as  A similar notation is applied when it comes to denoting the product of a sequence, which is similar to its summation, but which uses the multiplication operation instead of addition (and gives 1 for an empty sequence instead of 0). The same basic structure is used, with formula_21, an enlarged form of the Greek capital letter pi, replacing the formula_1.

Special cases.

It is possible to sum fewer than 2 numbers:  These degenerate cases are usually only used when the summation notation gives a degenerate result in a special case. For example, if formula_25 in the definition above, then there is only one term in the sum; if formula_26, then there is none.

Formal definition.

Summation may be defined recursively as follows

Measure theory notation.

In the notation of measure and integration theory, a sum can be expressed as a definite integral,  where formula_31 is the subset of the integers from formula_32 to formula_33, and where formula_34 is the counting measure.

Calculus of finite differences.

Given a function that is defined over the integers in the interval, one has  This is the analogue in calculus of finite differences of the fundamental theorem of calculus, which states where is the derivative of.  An example of application of the above equation is Using binomial theorem, this may be rewritten  The above formula is more commonly used for inverting of the difference operator formula_40 defined by where is a function defined on the nonnegative integers. Thus, given such a function, the problem is to compute the antidifference of, that is, a function formula_42 such that formula_43, that is,formula_44 This function is defined up to the addition of a constant, and may be chosen as  There is not always a closed-form expression for such a summation, but Faulhaber's formula provides a closed form in the case of formula_46 and, by linearity for every polynomial function of.

Approximation by definite integrals.

Many such approximations can be obtained by the following connection between sums and integrals, which holds for any:  increasing function "f":  decreasing function "f":  For more general approximations, see the Euler–Maclaurin formula.  For summations in which the summand is given (or can be interpolated) by an integrable function of the index, the summation can be interpreted as a Riemann sum occurring in the definition of the corresponding definite integral. One can therefore expect that for instance  since the right hand side is by definition the limit for formula_50 of the left hand side. However, for a given summation "n" is fixed, and little can be said about the error in the above approximation without additional assumptions about "f": it is clear that for wildly oscillating functions the Riemann sum can be arbitrarily far from the Riemann integral.

Identities.

The formulae below involve finite sums; for infinite summations or finite summations of expressions involving trigonometric functions or other transcendental functions, see list of mathematical series.

Powers and logarithm of arithmetic progressions.

More generally, one has Faulhaber's formula where formula_75 denotes a Bernoulli number, and formula_76 is a binomial coefficient.

Summation index in exponents.

In the following summations, is assumed to be different from 1.

Binomial coefficients and factorials.

There exist very many summation identities involving binomial coefficients (a whole chapter of "Concrete Mathematics" is devoted to just the basic techniques). Some of the most basic ones are the following.

Involving permutation numbers.

In the following summations, formula_87 is the number of -permutations of.

Growth rates.

The following are useful approximations (using theta notation):

In mathematics, summation is the addition of a sequence of any kind of numbers, called "addends" or "summands"; the result is their "sum" or "total". Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.


Habsburg empire.

Born into a Jewish family, Roth was born and grew up in Brody, a small town near Lemberg (now Lviv) in East Galicia, in the easternmost reaches of what was then the Austro-Hungarian empire. Jewish culture played an important role in the life of the town, which had a large Jewish population. Roth grew up with his mother and her relatives; he never saw his father, who had disappeared before he was born.  After secondary school, Joseph Roth moved to Lemberg to begin his university studies in 1913, before transferring to the University of Vienna in 1914 to study philosophy and German literature. In 1916, Roth broke off his university studies and volunteered to serve in the Imperial Habsburg army fighting on the Eastern Front, "though possibly only as an army journalist or censor." This experience had a major and long-lasting influence on his life. So, too, did the collapse in 1918 of the Habsburg Empire, which marked the beginning of a pronounced sense of "homelessness" that was to feature regularly in his work. As he wrote: "My strongest experience was the War and the destruction of my fatherland, the only one I ever had, the Dual Monarchy of Austria-Hungary."

Germany.

In 1918, Roth returned to Vienna and began writing for left-wing newspapers, signing articles published by "Vorwärts" as "Der rote Joseph" ("The red Joseph", a play on his surname, which is homophonous with German "rot", "red", which is also the signalling color of leftwing parties in Europe). In 1920 he moved to Berlin, where he worked as a successful journalist for the "Neue Berliner Zeitung" and, from 1921, for the "Berliner Börsen-Courier". In 1923 he began his association with the liberal "Frankfurter Zeitung", traveling widely throughout Europe, and reporting from the South of France, the USSR, Albania, Poland, Italy, and Germany. According to his main English translator, Michael Hofmann, "He was one of the most distinguished and best-paid journalists of the period, being paid at the dream rate of one Deutschmark per line." In 1925 he spent a period working in France. He never again resided permanently in Berlin.

Marriage and family.

Roth married Friederike (Friedl) Reichler in 1922. In the late 1920s, his wife became schizophrenic, which threw Roth into a deep crisis, both emotionally and financially. She lived for years in a sanatorium and was later murdered in the Action T4 programme.  In 1929 he met Andrea Manga Bell who was to share his destiny for the next six years. Andrea Manga Bell was born in Hamburg and unhappily married to Alexandre Douala Manga Bell, Prince of Douala in Cameroon. Her husband had returned to Cameroon while she and their children stayed in Europe. When Roth met her, she was editor of the Ullstein magazine "Gebrauchsgraphik".

Novels.

In 1923, Roth's first (unfinished) novel, "The Spider's Web", was serialized in an Austrian newspaper. He went on to achieve moderate success as a novelist with a series of books exploring life in post-war Europe, but only upon publication of "Job" and "Radetzky March" did he achieve acclaim for his fiction rather than his journalism.  From 1930, Roth's fiction became less concerned with contemporary society, with which he had become increasingly disillusioned, and began to evoke a melancholic nostalgia for life in imperial Central Europe before 1914. He often portrayed the fate of homeless wanderers looking for a place to live, in particular Jews and former citizens of the old Austria-Hungary, who, with the downfall of the monarchy, had lost their only possible "Heimat" ("true home"). In his later works, Roth appeared to wish that the monarchy could be restored. His longing for a more tolerant past may be partly explained as a reaction against the political extremism of the time, which culminated in Germany with National Socialism. The novel "Radetzky March" (1932) and the story "The Bust of the Emperor" (1935) are typical of this late phase. In another novel, "The Emperor's Tomb" (1938), Roth describes the fate of a cousin of the hero of "Radetzky March" up to Germany's annexation of Austria in 1938.  Of his works dealing with Judaism, the novel "Job" is perhaps the best-known.

Paris.

Being a prominent liberal Jewish journalist, Roth left Germany when Adolf Hitler became Reich Chancellor on 30 January 1933. Andrea Manga Bell accompanied him with her children. He spent most of the next six years in Paris, a city he loved. His essays written in France display a delight in the city and its culture.  Shortly after Hitler's rise to power, in February 1933, Roth wrote in a prophetic letter to his friend, the Austrian writer Stefan Zweig:  The relationship with Andrea Manga Bell failed due to financial problems and Roth's jealousy. From 1936 to 1938, Roth had a romantic relationship with Irmgard Keun. They worked together, traveling to various cities such as Paris, Wilna, Lemberg, Warsaw, Vienna, Salzburg, Brussels and Amsterdam.  Without intending to deny his Jewish origins, Roth considered his relationship to Catholicism very important. In the final years of his life, he may even have converted: Michael Hofmann states in the preface to the collection of essays " The White Cities" (also published as "Report from a Parisian Paradise") that Roth "was said to have had two funerals, one Jewish, one Catholic."  Roth's last years were difficult. He moved from hotel to hotel, drinking heavily, and becoming increasingly anxious about money and the future. Despite suffering from chronic alcoholism, he remained prolific until his premature death in Paris in 1939. His novella "The Legend of the Holy Drinker" (1939) chronicles the attempts made by an alcoholic vagrant to regain his dignity and honor a debt.  Roth's final collapse was precipitated by hearing the news that the playwright Ernst Toller had hanged himself in New York.  Roth is interred in the Cimetière de Thiais, south of Paris.

Works.

Fiction  Non-Fiction

Joseph Roth, born Moses Joseph Roth (2 September 1894 – 27 May 1939), was an Austrian journalist and novelist, best known for his family saga "Radetzky March" (1932), about the decline and fall of the Austro-Hungarian Empire, his novel of Jewish life, "Job" (1930), and his seminal essay "Juden auf Wanderschaft" (1927; translated into English in "The Wandering Jews"), a fragmented account of the Jewish migrations from eastern to western Europe in the aftermath of World War I and the Russian Revolution. In the 21st century, publications in English of "Radetzky March" and of collections of his journalism from Berlin and Paris created a revival of interest in Roth.


Major ranges.

Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt. The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Japan, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is long and is often considered the world's longest mountain system.  The Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, and ends in the Spanish mountains and the Atlas Mountains. The belt also includes other European and Asian mountain ranges. The Himalayas contain the highest mountains in the world, including Mount Everest, which is high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains, then the Ocean Ridges form the longest continuous mountain system on Earth, with a length of.

Divisions and categories.

The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is often expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, and the White Mountains and the Blue Ridge Mountains are children of the Appalachians.  The parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is a parent to the Northern Presidential Range and Southern Presidential Range.

Climate.

The position of mountains influences climate, such as rain or snow. When air masses move up and over mountains, the air cools producing orographic precipitation (rain or snow). As the air descends on the leeward side, it warms again (in accordance with the adiabatic lapse rate) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect the leeward side of a range.

Erosion.

Mountain ranges are constantly subjected to erosional forces which work to tear them down. The basins adjacent to an eroding mountain range are then filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains.  The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some of mostly Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east. This mass of rock was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted isostatically in response to the removed weight.  Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides.

Extraterrestrial "Montes".

Mountains on other planets and natural satellites of the Solar System are often isolated and formed mainly by processes such as impacts, though there are examples of mountain ranges (or "Montes") somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed mainly of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, and Tenzing Montes and Hillary Montes on Pluto. Some terrestrial planets other than Earth also exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes.

A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are also found on many planetary mass objects in the Solar System and are likely a feature of most terrestrial planets.


Etymology and historical development.

The etymology of the term "internal medicine" in English is rooted in the German term "Innere Medizin" from the 19th century. Internal medicine delved into underlying pathological causes of symptoms and syndromes by use of laboratory investigations in addition to bedside clinical assessment of patients. In contrast, physicians in previous generations, such as the 17th-century physician Thomas Sydenham, who is known as the father of English medicine or "the English Hippocrates", had developed nosology (the study of diseases) via the clinical approach to diagnosis and management, by careful bedside study of the natural history of diseases and their treatment. Sydenham eschewed dissection of corpses and scrutiny of the internal workings of the body, for considering the internal mechanisms and causes of symptoms. It was thus subsequent to the 17th century that there was a rise in anatomical pathology and laboratory studies, with Giovanni Battista Morgagni, an Italian anatomist of the 18th century, being considered the father of anatomical pathology. Laboratory investigations became increasingly significant, with contribution of doctors including German physician and bacteriologist Robert Koch in the 19th century. The 19th century saw the rise of internal medicine that combined the clinical approach with use of investigations. Many early-20th-century American physicians studied medicine in Germany and brought this medical field to the United States. Thus, the name "internal medicine" was adopted in imitation of the existing German term.  Historically, some of the oldest traces of internal medicine can be traced from Ancient India and Ancient China. Earliest texts about internal medicine are the Ayurvedic anthologies of Charaka.

Role of internal medicine physicians.

Internal medicine specialists, also known as general internal medicine specialists or general medicine physicians in Commonwealth countries, are specialist physicians trained to manage particularly complex or multisystem disease conditions that single-organ-disease specialists may not be trained to deal with. They may be asked to tackle undifferentiated presentations that cannot be easily fitted within the expertise of a single-organ specialty, such as dyspnoea, fatigue, weight loss, chest pain, confusion or change in conscious state. They may manage serious acute illnesses that affect multiple organ systems at the same time in a single patient, and they may manage multiple chronic diseases or "comorbidities" that a single patient may have.  General internal medicine specialists do not provide necessarily less expertise than single-organ specialists, rather, they are trained for a specific role of caring for patients with multiple simultaneous problems or complex comorbidities.  Perhaps because it is complex to explain treatment of diseases that are not localised to a single-organ, there has been confusion about the meaning of internal medicine and the role of an "internist." Internists are qualified physicians with postgraduate training in internal medicine and should not be confused with "interns", who are doctors in their first year of residency training (officially the term intern is no longer in use). Although internists may act as primary care physicians, they are not "family physicians," "family practitioners," or "general practitioners," or "GPs," whose training is not solely concentrated on adults and may include surgery, obstetrics, and pediatrics. The American College of Physicians defines internists as "physicians who specialize in the prevention, detection and treatment of illnesses in adults".

Education and training of internists.

The training and career pathways for internists vary considerably across the world.  Many programs require previous undergraduate education prior to medical school admission. This "pre-medical" education is typically four or five years in length. Graduate medical education programs vary in length by country. Medical education programs are tertiary-level courses, undertaken at a medical school attached to a university. In the United States, medical school consists of four years. Hence, gaining a basic medical education may typically take eight years, depending on jurisdiction and university.  Following completion of entry-level training, newly graduated medical practitioners are often required to undertake a period of supervised practice before the licensure, or "registration", is granted, typically one or two years. This period may be referred to as "internship", "conditional registration", or "foundation programme". Then, doctors may finally follow specialty training in internal medicine if they wish, typically being selected to training programs through competition. In North America, this period of postgraduate training is referred to as residency training, followed by an optional fellowship if the internist decides to train in a subspecialty.  In the United States and in most countries, residency training for internal medicine lasts three years and centers on secondary and tertiary levels of care. In Commonwealth countries trainees are often called senior house officers for four years after the completion of their medical degree (foundation and core years). After this period, they are able to advance to registrar grade when they undergo a compulsory subspecialty training (including acute internal medicine or a dual subspecialty including internal medicine). This latter stage of training is achieved through competition rather than just by yearly progress as the first years of postgraduate training.

Certification of specialists.

In the United States, three organizations are responsible for certification of trained internists (i.e., doctors who have completed an accredited residency training program) in terms of their knowledge, skills, and attitudes that are essential for excellent patient care: the American Board of Internal Medicine, the American Osteopathic Board of Internal Medicine and the Board of Certification in Internal Medicine.

Subspecialties.

United States.

In the United States, two organizations are responsible for certification of subspecialists within the field: the American Board of Internal Medicine and the American Osteopathic Board of Internal Medicine. Physicians (not only internists) who successfully pass board exams receive "board certified" status.

American Board of Internal Medicine.

The following are the subspecialties recognized by the American Board of Internal Medicine.

American College of Osteopathic Internists.

The American College of Osteopathic Internists recognizes the following subspecialties:

United Kingdom.

In the United Kingdom, the three medical Royal Colleges (the Royal College of Physicians of London, the Royal College of Physicians of Edinburgh and the Royal College of Physicians and Surgeons of Glasgow) are responsible for setting curricula and training programmes through the Joint Royal Colleges Postgraduate Training Board (JRCPTB), although the process is monitored and accredited by the General Medical Council (which also maintains the specialist register).  Doctors who have completed medical school spend two years in foundation training completing a basic postgraduate curriculum. After two years of Core Medical Training (CT1/CT2) and attaining the Membership of the Royal College of Physicians, physicians commit to one of the medical specialties:  Many training programmes provide dual accreditation with general (internal) medicine and are involved in the general care to hospitalised patients. These are acute medicine, cardiology, Clinical Pharmacology and Therapeutics, endocrinology and diabetes mellitus, gastroenterology, infectious diseases, renal medicine, respiratory medicine and often, rheumatology. The role of general medicine, after a period of decline, was reemphasised by the Royal College of Physicians of London report from the Future Hospital Commission (2013).

Medical diagnosis and treatment.

Medicine is mainly focused on the art of diagnosis and treatment with medication, but many subspecialties administer procedural treatment:

Internal medicine or general internal medicine (in Commonwealth nations) is the medical specialty dealing with the prevention, diagnosis, and treatment of internal diseases. Physicians specializing in internal medicine are called internists, or physicians (without a modifier) in Commonwealth nations. Internists are skilled in the management of patients who have undifferentiated or multi-system disease processes. Internists care for hospitalized and ambulatory patients and may play a major role in teaching and research. Of note is that internal medicine and family medicine are often confused as equal in the Commonwealth nations (see below).