California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U. S. the third-largest by area. The state capital is Sacramento; the Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, the country's second most populous, after New York City. California has the nation's most populous county, Los Angeles County, its largest county by area, San Bernardino County; the City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs. California's $3.0 trillion economy is larger than that of any other state, larger than those of Texas and Florida combined, the largest sub-national economy in the world. If it were a country, California would be the 5th largest economy in the world, the 36th most populous as of 2017.
The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second- and third-largest urban economies, after the New York metropolitan area. The San Francisco Bay Area PSA had the nation's highest GDP per capita in 2017 among large PSAs, is home to three of the world's ten largest companies by market capitalization and four of the world's ten richest people. California is considered a global trendsetter in popular culture, innovation and politics, it is considered the origin of the American film industry, the hippie counterculture, fast food, the Internet, the personal computer, among others. The San Francisco Bay Area and the Greater Los Angeles Area are seen as global centers of the technology and entertainment industries, respectively. California has a diverse economy: 58% of the state's economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5% of the state's economy, California's agriculture industry has the highest output of any U.
S. state. California is bordered by Oregon to the north and Arizona to the east, the Mexican state of Baja California to the south; the state's diverse geography ranges from the Pacific Coast in the west to the Sierra Nevada mountain range in the east, from the redwood–Douglas fir forests in the northwest to the Mojave Desert in the southeast. The Central Valley, a major agricultural area, dominates the state's center. Although California is well-known for its warm Mediterranean climate, the large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. Over time and wildfires have become more pervasive features. What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries; the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War.
The western portion of Alta California was organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom; the word California referred to the Baja California Peninsula of Mexico. The name derived from the mythical island California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo; this work was the fifth in a popular Spanish chivalric romance series that began with Amadis de Gaula. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful black women who wore gold armor and lived like Amazons, as well as griffins and other strange beasts. In the fictional paradise, the ruler Queen Calafia fought alongside Muslims and her name may have been chosen to echo the title of a Muslim leader, the Caliph. It's possible.
Know ye that at the right hand of the Indies there is an island called California close to that part of the Terrestrial Paradise, inhabited by black women without a single man among them, they lived in the manner of Amazons. They were robust of body with great virtue; the island itself is one of the wildest in the world on account of the craggy rocks. Shortened forms of the state's name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Various estimates of the native population range from 100,000 to 300,000; the Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their political organization with bands, villages, on the resource-rich coasts, large chiefdoms, such as the Chumash and Salinan.
Trade, intermarriage a
Hexagonal crystal family
In crystallography, the hexagonal crystal family is one of the 6 crystal families, which includes 2 crystal systems and 2 lattice systems. The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, is the union of the hexagonal crystal system and the trigonal crystal system. There are 52 space groups associated with it, which are those whose Bravais lattice is either hexagonal or rhombohedral; the hexagonal crystal family consists of two lattice systems: rhombohedral. Each lattice system consists of one Bravais lattice. In the hexagonal family, the crystal is conventionally described by a right rhombic prism unit cell with two equal axes, an included angle of 120° and a height perpendicular to the two base axes; the hexagonal unit cell for the rhombohedral Bravais lattice is the R-centered cell, consisting of two additional lattice points which occupy one body diagonal of the unit cell with coordinates and.
Hence, there are 3 lattice points per unit cell in total and the lattice is non-primitive. The Bravais lattices in the hexagonal crystal family can be described by rhombohedral axes; the unit cell is a rhombohedron. This is a unit cell with parameters a = b = c. In practice, the hexagonal description is more used because it is easier to deal with a coordinate system with two 90° angles. However, the rhombohedral axes are shown in textbooks because this cell reveals 3m symmetry of crystal lattice; the rhombohedral unit cell for the hexagonal Bravais lattice is the D-centered cell, consisting of two additional lattice points which occupy one body diagonal of the unit cell with coordinates and. However, such a description is used; the hexagonal crystal family consists of two crystal systems: hexagonal. A crystal system is a set of point groups in which the point groups themselves and their corresponding space groups are assigned to a lattice system; the trigonal crystal system consists of the 5 point groups that have a single three-fold rotation axis.
These 5 point groups have 7 corresponding space groups assigned to the rhombohedral lattice system and 18 corresponding space groups assigned to the hexagonal lattice system. The hexagonal crystal system consists of the 7 point groups that have a single six-fold rotation axis; these 7 point groups have 27 space groups, all of which are assigned to the hexagonal lattice system. Graphite is an example of a crystal; the trigonal crystal system is the only crystal system whose point groups have more than one lattice system associated with their space groups: the hexagonal and rhombohedral lattices both appear. The 5 point groups in this crystal system are listed below, with their international number and notation, their space groups in name and example crystals; the point groups in this crystal system are listed below, followed by their representations in Hermann–Mauguin or international notation and Schoenflies notation, mineral examples, if they exist. Hexagonal close packed is one of the two simple types of atomic packing with the highest density, the other being the face centered cubic.
However, unlike the fcc, it is not a Bravais lattice as there are two nonequivalent sets of lattice points. Instead, it can be constructed from the hexagonal Bravais lattice by using a two atom motif associated with each lattice point. Quartz is a crystal that belongs to the hexagonal lattice system but exists in two polymorphs that are in two different crystal systems; the crystal structures of α-quartz are described by two of the 18 space groups associated with the trigonal crystal system, while the crystal structures of β-quartz are described by two of the 27 space groups associated with the hexagonal crystal system. The lattice angles and the lengths of the lattice vectors are all the same for both the cubic and rhombohedral lattice systems; the lattice angles for simple cubic, face-centered cubic, body-centered cubic lattices are π/2 radians, π/3 radians, arccos radians, respectively. A rhombohedral lattice will result from lattice angles other than these. Crystal structure Close-packing Wurtzite Hahn, Theo, ed..
International Tables for Crystallography, Volume A: Space Group Symmetry. A. Berlin, New York: Springer-Verlag. Doi:10.1107/97809553602060000100. ISBN 978-0-7923-6590-7. Media related to Trigonal lattices at Wikimedia Commons Mineralogy database
Death Valley is a desert valley located in Eastern California, in the northern Mojave Desert bordering the Great Basin Desert. It is one of the hottest places in the world along with deserts in the Middle East. Death Valley's Badwater Basin is the point of the lowest elevation in North America, at 282 feet below sea level; this point is 84.6 miles east-southeast of Mount Whitney, the highest point in the contiguous United States, with an elevation of 14,505 feet. On the afternoon of July 10, 1913, the United States Weather Bureau recorded a high temperature of 134 °F at Furnace Creek in Death Valley; this temperature stands as the highest ambient air temperature recorded at the surface of the Earth. Located near the border of California and Nevada, in the Great Basin, east of the Sierra Nevada mountains, Death Valley constitutes much of Death Valley National Park and is the principal feature of the Mojave and Colorado Deserts Biosphere Reserve, it is located in Inyo County, California. It runs from north to south between the Amargosa Range on the east and the Panamint Range on the west.
It has an area of about 3,000 sq mi. The highest point in Death Valley itself is Telescope Peak in the Panamint Range, which has an elevation of 11,043 feet. Death Valley is an excellent example of a graben, or a downdropped block of land between two mountain ranges, it lies at the southern end of a geological trough known as Walker Lane. The valley is bisected by a right lateral strike slip fault system, represented by the Death Valley Fault and the Furnace Creek Fault; the eastern end of the left lateral Garlock Fault intersects the Death Valley Fault. Furnace Creek and the Amargosa River flow through the valley but disappear into the sands of the valley floor. Death Valley contains salt pans. According to current geological consensus, at various times during the middle of the Pleistocene era, which ended 10,000–12,000 years ago, an inland lake referred to as Lake Manly formed in Death Valley. Lake Manly was nearly 100 miles long and 600 feet deep, the end-basin in a chain of lakes that began with Mono Lake in the north and continued through multiple basins down the Owens River Valley through Searles and China Lakes and the Panamint Valley to the immediate west.
As the area turned to desert, the water evaporated, leaving the abundance of evaporitic salts such as common sodium salts and borax, which were exploited during the modern history of the region 1883 to 1907. Death Valley has a subtropical, hot desert climate, with long hot summers and short, mild winters, as well as little rainfall; as a general rule, lower altitudes tend to have higher temperatures. When the sun heats the ground, that heat is radiated upward, but the dense below-sea-level air absorbs some of this radiation and radiates some of it back towards the ground. In addition, the high valley walls trap rising hot air and recycle it back down to the valley floor, where it is heated by compression; this process is important in Death Valley, as it provides its specific climate and geography. The valley is surrounded by mountains, while its surface is flat and devoid of plants, so much of the sun's heat can reach the ground, absorbed by soil and rock; when air at ground level is heated, it begins to rise, moving up past steep, high mountain ranges, which cools sinking back down towards the valley more compressed.
This air is reheated by the sun to a higher temperature, moving up the mountain again, whereby the air moves up and down in a circular motion in cycles, similar to how a convection oven works. This heated air increases ground temperature markedly, forming the hot wind currents that are trapped by atmospheric pressure and mountains and thus stay within the valley; such hot wind currents contribute to perpetual drought-like conditions in Death Valley and prevent much cloud formation from passing through the confines of the valley, where precipitation is in the form of a virga. Death Valley holds temperature records because it has an unusually high number of factors that lead to high atmospheric temperatures; the depth and shape of Death Valley influence its summer temperatures. The valley is a long, narrow basin 282 feet below sea level, yet is walled by high, steep mountain ranges; the clear, dry air and sparse plant cover allow sunlight to heat the desert surface. Summer nights provide little relief.
Moving masses of super-heated air blow through the valley creating high temperatures. The hottest air temperature recorded in Death Valley was 134 °F on July 10, 1913, at Greenland Ranch, the highest atmospheric temperature recorded on earth. A report of a temperature of 58 °C recorded in Libya in 1922 was determined to be inaccurate. During the heat wave that peaked with that record, five consecutive days reached 129 above; some meteorologists dispute the accuracy of the 1913 temperature measurement. The highest surface temperature recorded in Death Valley was 201.0 °F on July 15, 1972, at Furnace Creek, the highest ground surface temperature recorded on earth, as well as the only recorded surface temperature of above 200 °F. The greatest number of consecutive days with a maximum temperature of 100 °F or above was 154 days in the summer of 2001; the summer of 1996 had 40 days over 120 °F, 105 days over 110 °F. The summer of 1917 had 52 days where the temperature
Niter, or nitre, is the mineral form of potassium nitrate, KNO3 known as saltpeter or saltpetre. The term niter was not well differentiated from natron, both of which have been vaguely defined but refer to compounds of sodium or potassium joined with carbonate or nitrate ions. Related minerals are soda niter, ammonia niter or gwihabaite, nitrostrontianite, nitromagnesite and two copper nitrates and buttgenbachite. Niter was used to refer to nitrated salts known as various types of saltpeter by the time niter and its derivative nitric acid were first used to name the element nitrogen, in 1790; because of its ready solubility in water, niter is most found in arid environments and in conjunction with other soluble minerals like halides, borates and rarer carbonates and sulphates. A major source of sodium nitrate mineral is the Atacama Desert in Chile. Potassium and other nitrates are of great importance for use in fertilizers and gunpowder. Much of the world's demand is now met by synthetically produced nitrates, though the natural mineral is still mined and is still of significant commercial value.
Niter is a colorless to white mineral crystallizing in the orthorhombic crystal system. It is found as massive encrustations and efflorescent growths on cavern walls and ceilings where solutions containing alkali potassium and nitrate seep into the openings, it occurs as prismatic acicular crystal groups, individual crystals show twinning. Nitre and other nitrates can form in association with deposits of guano and similar organic materials. Niter is the accepted term for sugar sand, a by-product of maple syrup production, the sandy sediment that accumulates at the bottom of a pan when maple sap is boiled; the substance's main constituent is a calcium salt of malic acid. Niter as a term has been known since ancient times, although there is much historical confusion with natron, not all of the ancient salts known by this name or similar names in the ancient world contained nitrate; the name is from the Ancient Greek νιτρων nitron from Ancient Egyptian netjeri, related to the Hebrew néter, for salt-derived ashes.
The Hebrew néter may have been used as, or in conjunction with soap, as implied by Jeremiah 2:22, "For though thou wash thee with nitre, take thee much soap..." However, it is not certain which substance the Biblical "neter" refers to, with some suggesting sodium carbonate. Indeed, the Neo Latin word for sodium, natrium, is derived from this same class of desert minerals called natron from Spanish natrón through Greek νίτρον, derived from Ancient Egyptian netjeri, referring to the sodium carbonate salts occurring in the deserts of Egypt, not the nitrated sodium salts occurring in the deserts of Chile. A term which translates as "foam of niter" was a regular purchase in a fourth-century AD series of financial accounts, since it was expressed as being "for the baths" was used as soap. Niter was used to refer to nitrated salts known as various types of saltpeter by the time niter and its derivative nitric acid were first used to name the element nitrogen, in 1790. Nitrary, a place for making Nitre Etymology of "niter" Saltpeter images Poe's The Cask of Amontillado
The angstrom or ångström is a unit of length equal to 10−10 m. Its symbol is a letter of the Swedish alphabet; the angstrom is not a part of the SI system of units, but it can be considered part of the metric system. While deprecated by the IBWM and the NIST, the unit is still used in the natural sciences and technology to express sizes of atoms, microscopic biological structures, lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, dimensions of integrated circuit parts; the atomic radii of phosphorus and chlorine are about 1 angstrom, while that of hydrogen is about 0.5 angstrom. Visible light has wavelengths in the range of 4000–7000 Å; the unit is named after the nineteenth-century Swedish physicist Anders Jonas Ångström. The IBWM and the NIST spell it as ångström; the symbol should always be "Å". The angstrom is used extensively in crystallography, solid-state physics and chemistry as a unit for d-spacings, cell parameters, inter-atomic distances and x-ray wavelengths, as these values are in the 1–10 Å range.
For example, the Inorganic Crystal Structure Database presents all these values using the angstrom. Anders Jonas Ångström was a pioneer in the field of spectroscopy, he is well known for his studies of astrophysics, heat transfer, terrestrial magnetism, the aurora borealis. In 1852, Ångström formulated in Optiska undersökningar, a law of absorption modified somewhat and known as Kirchhoff's law of thermal radiation. In 1868, Ångström created a chart of the spectrum of sunlight, in which he expressed the wavelengths of electromagnetic radiation in the electromagnetic spectrum in multiples of one ten-millionth of a millimetre Because the human eye is sensitive to wavelengths from about 4000 to 7000 Å, that choice of unit supported sufficiently accurate measurements of visible wavelengths without resorting to fractional numbers. Ångström's chart and table of wavelengths in the solar spectrum became used in solar physics, which adopted the unit and named it after him. It subsequently spread to the rest of astronomical spectroscopy, atomic spectroscopy, subsequently to other sciences that deal with atomic-scale structures.
Though intended to correspond to 10−10 metres, for precise spectral analysis, the angstrom had to be defined more than the metre, which until 1960 was still defined based on the length of a bar of metal held in Paris. The use of metal bars had been involved in an early error in the value of the angstrom of about one part in 6000. Ångström took the precaution of having the standard bar he used checked against a standard in Paris, but the metrologist Henri Tresca reported it to be so much shorter than it was that Ångström's corrected results were more in error than the uncorrected ones. In 1892–1895, Albert A. Michelson defined the angstrom so that the red line of cadmium was equal to 6438.47 angstroms. "In 1907, the International Union for Cooperation in Solar Research defined the international angstrom by declaring the wavelength of the red line of cadmium equal to 6438.4696 international angstroms, this definition was endorsed by the International Bureau of Weights and Measures in 1927. From 1927 to 1960, the angstrom remained a secondary unit of length for use in spectroscopy, defined separately from the metre.
In 1960, the metre itself was redefined in spectroscopic terms, which allowed the angstrom to be redefined as being 0.1 nanometres. The angstrom is internationally recognized, but is not a formal part of the International System of Units; the closest SI unit is the nanometre. The International Committee for Weights and Measures discourages its use, it is not included in the European Union's catalogue of units of measure that may be used within its internal market. For compatibility reasons, Unicode includes the formal symbol at U+212B Å ANGSTROM SIGN. However, the angstrom sign is normalized into U+00C5 Å LATIN CAPITAL LETTER A WITH RING ABOVE The Unicode consortium recommends to use the regular letter. Before digital typesetting, the angstrom was sometimes written as "A. U.". This use is evident in Bragg's paper on the structure of ice, which gives the c- and a-axis lattice constants as 4.52 A. U. and 7.34 A. U. respectively. Nowadays the atomic unit of length stands for bohrs, not angstroms. 100 picometres X unit Conversion of units
In crystallography, the terms crystal system, crystal family, lattice system each refer to one of several classes of space groups, 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. Crystal systems, crystal families and lattice systems are similar but different, there is widespread confusion between them: in particular the trigonal crystal system is confused with the rhombohedral lattice system, the term "crystal system" is sometimes used to mean "lattice system" or "crystal family". Space groups and crystals are divided into seven crystal systems according to their point groups, into seven lattice systems according to their Bravais lattices. Five of the crystal systems are the same as five of the lattice systems, but the hexagonal and trigonal crystal systems differ from the hexagonal and rhombohedral lattice systems; the six crystal families are formed by combining the hexagonal and trigonal crystal systems into one hexagonal family, in order to eliminate this confusion.
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, orthorhombic, rhombohedral 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 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, orthorhombic, trigonal 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, orthorhombic, tetragonal 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 and hexagonal; the relation between three-dimensional crystal families, crystal systems and lattice systems is shown in the following table: Note: there is no "trigonal" lattice system. To avoid confusion of terminology, the term "trigonal lattice" is not used; the 7 crystal systems consist of 32 crystal classes as shown in the following table: The point symmetry of a structure can be further described as follows. Consider the points that make up the structure, reflect them all through a single point, so that becomes; this is the'inverted structure'. If the original structure and inverted structure are identical the structure is centrosymmetric. Otherwise it is non-centrosymmetric.
Still 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 the structure is chiral or enantiomorphic and its symmetry group is enantiomorphic. A direction is called polar if its two directional senses are physically different. A symmetry direction of a crystal, polar is called a polar axis. Groups containing a polar axis are called polar. A polar crystal possesses a unique polar axis; 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 can only occur in the 65 enantiomorphic space groups.
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 in three directions; such symmetry groups consist of translations by vectors of the form R = n1a1 + n2a2 + n3a3,where n1, n2, n3 are integers and a1, a2, a3 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, they represent the maximum symmetry. All crystalline materials must, by definition, fit into one of these arrangements. For convenience a Bravais lattice is depicted by a unit cell, 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 we
In mineralogy, crystal habit is the characteristic external shape of an individual crystal or crystal group. A single crystal's habit is a description of its general shape and its crystallographic forms, plus how well developed each form is. Recognizing the habit may help in identifying a mineral; when the faces are well-developed due to uncrowded growth a crystal is called euhedral, one with developed faces is subhedral, one with undeveloped crystal faces is called anhedral. The long axis of a euhedral quartz crystal has a six-sided prismatic habit with parallel opposite faces. Aggregates can be formed of individual crystals with euhedral to anhedral grains; the arrangement of crystals within the aggregate can be characteristic of certain minerals. For example, minerals used for asbestos insulation grow in a fibrous habit, a mass of fine fibers; the terms used by mineralogists to report crystal habits describe the typical appearance of an ideal mineral. Recognizing the habit can aid in identification as some habits are characteristic.
Most minerals, however, do not display ideal habits due to conditions during crystallization. Euhedral crystals formed in uncrowded conditions with no adjacent crystal grains are not common. Factors influencing habit include: a combination of two or more crystal forms. Minerals belonging to the same crystal system do not exhibit the same habit; some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum; some minerals may replace other existing minerals while preserving the original's habit: this process is called pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos replaced by silica. While quartz forms prismatic crystals, in tiger's eye the original fibrous habit of crocidolite is preserved; the names of crystal habits are derived from: Predominant crystal faces.
Crystal forms. Aggregation of crystals or aggregates. Crystal appearance. Abnormal grain growth Grain growth