An oxide /ˈɒksaɪd/ is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. Oxide itself is the dianion of oxygen, an O2– atom, Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earths crust consists of oxides, the result of elements being oxidized by the oxygen in air or in water. Hydrocarbon combustion affords the two principal carbon oxides, carbon monoxide and carbon dioxide, even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a skin of Al2O3 that protects the foil from further corrosion. Individual elements can form multiple oxides, each containing different amounts of the element. Certain elements can form many different oxides, such those of nitrogen, due to its electronegativity, oxygen forms stable chemical bonds with almost all elements to give the corresponding oxides. Noble metals are prized because they resist direct chemical combination with oxygen, two independent pathways for corrosion of elements are hydrolysis and oxidation by oxygen.
The combination of water and oxygen is even more corrosive, virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen, some elements— sodium—react rapidly, even dangerously, in part for this reason and alkaline earth metals are not found in nature in their metallic, i. e. native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, the surface of most metals consists of oxides and hydroxides in the presence of air. A well-known example is aluminium foil, which is coated with a film of aluminium oxide that passivates the metal. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising, though solid magnesium and aluminium react slowly with oxygen at STP—they, like most metals, burn in air, generating very high temperatures. Finely grained powders of most metals can be explosive in air. Consequently, they are used in Solid-fuel rockets. In dry oxygen, iron forms iron oxide, but the formation of the hydrated ferric oxides, Fe2O3−x2x.
Free oxygen production by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe2O3 in the important iron ore hematite. Oxides have a range of different structures, from molecules to polymeric
Chert is a fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline silica. Depending on its origin, it can contain either microfossils, small macrofossils, Chert occurs as oval to irregular nodules in greensand, limestone and dolostone formations as a replacement mineral, where it is formed as a result of some type of diagenesis. Where it occurs in chalk or marl, it is usually called flint and it occurs in thin beds, when it is a primary deposit. Thick beds of chert occur in marine deposits. These thickly bedded cherts include the novaculite of the Ouachita Mountains of Arkansas, the banded iron formations of Precambrian age are composed of alternating layers of chert and iron oxides. Chert occurs in deposits and is known as diatomaceous chert. Diatomaceous chert consists of beds and lenses of diatomite which were converted during diagenesis into dense, in petrology the term chert is used to refer generally to all rocks composed primarily of microcrystalline, cryptocrystalline and microfibrous quartz.
The term does not include quartzite, chalcedony is a microfibrous variety of quartz. Strictly speaking, the flint is reserved for varieties of chert which occur in chalk. Among non-geologists, the distinction between flint and chert is often one of quality - chert being lower quality than flint, among petrologists, chalcedony is sometimes considered separately from chert due to its fibrous structure. Since many cherts contain both microcrystalline and microfibrous quartz, it is difficult to classify a rock as completely chalcedony. The cryptocrystalline nature of chert, combined with its above average ability to resist weathering, recrystallization, for example, The 3.2 Ga chert of the Fig Tree Formation in the Barbeton Mountains between Swaziland and South Africa preserved non-colonial unicellular bacteria-like fossils. The Gunflint Chert of western Ontario preserves not only bacteria and cyanobacteria but believed to be ammonia-consuming and some that resemble green algae. The Apex Chert of the Pilbara craton, Australia preserved eleven taxa of prokaryotes, the Bitter Springs Formation of the Amadeus Basin, Central Australia, preserves 850 Ma cyanobacteria and algae.
The Rhynie chert of Scotland has remains of a Devonian land flora, in prehistoric times, chert was often used as a raw material for the construction of stone tools. Like obsidian, as well as some rhyolites, felsites and this results in conchoidal fractures, a characteristic of all minerals with no cleavage planes. When a chert stone is struck against an iron-bearing surface sparks result and this makes chert an excellent tool for starting fires, and both flint and common chert were used in various types of fire-starting tools, such as tinderboxes, throughout history. Cherts are subject to problems when used as concrete aggregates, deeply weathered chert develops surface pop-outs when used in concrete that undergoes freezing and thawing because of the high porosity of weathered chert
Furniture refers to movable objects intended to support various human activities such as seating and sleeping. Furniture is used to hold objects at a convenient height for work, Furniture can be a product of design and is considered a form of decorative art. In addition to furnitures functional role, it can serve a symbolic or religious purpose and it can be made from many materials, including metal and wood. Furniture can be using a variety of woodworking joints which often reflect the local culture. People have been using natural objects, such as stumps and moss. Archaeological research shows that from around 30,000 years ago, people began constructing and carving their own furniture, using wood, early furniture from this period is known from artwork such as a Venus figurine found in Russia, depicting the goddess on a throne. The first surviving extant furniture is in the homes of Skara Brae in Scotland, complex construction techniques such as joinery began in the early dynastic period of ancient Egypt.
This era saw constructed wooden pieces, including stools and tables, sometimes decorated with valuable metals or ivory. The evolution of furniture design continued in ancient Greece and ancient Rome, with thrones being commonplace as well as the klinai, multipurpose couches used for relaxing, the furniture of the Middle Ages was usually heavy and ornamented. Furniture design expanded during the Italian Renaissance of the fourteenth and fifteenth century, the seventeenth century, in both Southern and Northern Europe, was characterized by opulent, often gilded Baroque designs. The nineteenth century is defined by revival styles. The first three-quarters of the century are often seen as the march towards Modernism. One unique outgrowth of post-modern furniture design is a return to natural shapes and textures, the English word furniture is derived from the French word fourniture, the noun form of fournir, which means to supply or provide. Thus fourniture in French means supplies or provisions, the practice of using natural objects as rudimentary pieces of furniture likely dates to the beginning of human civilisation.
Early humans are likely to have used tree stumps as seats, rocks as rudimentary tables, during the late palaeolithic or early neolithic period, from around 30,000 years ago, people began constructing and carving their own furniture, using wood and animal bones. The earliest evidence for the existence of constructed furniture is a Venus figurine found at the Gagarino site in Russia, a similar statue of a Mother Goddess was found in Catal Huyuk in Turkey, dating to between 6000 and 5500 BC. The inclusion of such a seat in the figurines implies that these were already common artefacts of that age, a range of unique stone furniture has been excavated in Skara Brae, a Neolithic village in Orkney, Scotland. Each house shows a degree of sophistication and was equipped with an extensive assortment of stone furniture, ranging from cupboards and beds to shelves, stone seats
Minneapolis City Hall
The structure has served as mainly local government offices since it was built, and today the building is 60 percent occupied by the city and 40 percent occupied by the County. The building is owned by the city and county and managed by the Municipal Building Commission. The Commission consists of the chair of the County Board, the mayor of the City of Minneapolis, a member of the County Board, the County Board chair serves as the president of the Commission and the mayor serves as the vice president. The building bears a resemblance to the city hall buildings in Cincinnati. The City Hall and Courthouse was added to the National Register of Historic Places in 1974, the building replaced an earlier City Hall that existed from 1873 until 1912 near the old intersection between Hennepin Avenue and Nicollet Avenue. That structure eventually was razed to make way for Gateway Park, the building replaced an earlier courthouse and the earlier Hennepin County Jail, which was located where U. S. The building, located at 350 South Fifth Street, is an example of Richardsonian Romanesque architecture, the design is based upon Henry Hobson Richardsons Allegheny County Courthouse in Pittsburgh, Pennsylvania.
Washington School, the first schoolhouse in Minneapolis west of the Mississippi River, was demolished to make way for the new building, groundbreaking took place in 1889, and the cornerstone was laid in 1891. Construction did not officially end until 1906, although the exterior was essentially complete by the end of 1895. The county began moving in to its side in November 1895, cost was about $3,554,000, which works out to 28¢ per cubic foot. When constructed, the claimed to have the worlds largest four-faced chiming clock. At 24 feet,6 inches, the faces are 18 inches wider than those of the Great Clock in London, the tower housing the clock reaches 345 feet in height, and was the tallest structure in the city until the 1920s when the Foshay Tower was built. A 15-bell chime in the tower is played regularly, with noontime concerts provided to the public on holidays and on Fridays, the chime was originally 10 bells, and it was first played on March 10,1896. The building is built of granite quarried in Ortonville, with many stones greater than 20 tonnes in weight.
The granite was originally going to be used for the foundation of the building. However, the public appreciated the appearance of the foundation so much that they lobbied for the building to be made of granite. This may be a reason for the significant cost overruns — it was expected to cost only $1.15 million. Unlike most buildings in downtown Minneapolis, there arent any skyways connecting the city hall to the rest of the city, since exterior alterations are not allowed for buildings on the National Register of Historic Places, tunnels were constructed instead
A metal is a material that is typically hard, opaque and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed.
In bcc, each atom is positioned at the center of a cube of eight others, in fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades.
The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks, inside the nodule, flint is usually dark grey, green, white or brown in colour, and often has a glassy or waxy appearance. A thin layer on the outside of the nodules is usually different in colour, typically white, from a petrological point of view, flint refers specifically to the form of chert which occurs in chalk or marly limestone. Similarly, common chert occurs in limestone, the exact mode of formation of flint is not yet clear but it is thought that it occurs as a result of chemical changes in compressed sedimentary rock formations, during the process of diagenesis. One hypothesis is that a gelatinous material fills cavities in the sediment, such as bored by crustaceans or molluscs. This hypothesis certainly explains the shapes of flint nodules that are found. The source of dissolved silica in the media could be the spicules of silicious sponges.
Certain types of flint, such as that from the south coast of England, pieces of coral and vegetation have been found preserved like amber inside the flint. Thin slices of the stone often reveal this effect, puzzling giant flint formations known as paramoudra and flint circles are found around Europe but especially in Norfolk, England on the beaches at Beeston Bump and West Runton. Flint sometimes occurs in large flint fields in Jurassic or Cretaceous beds, flint was used in the manufacture of tools during the Stone Age as it splits into thin, sharp splinters called flakes or blades when struck by another hard object. This process is referred to as knapping, flint mining is attested since the Palaeolithic, but became more common since the Neolithic. When struck against steel, a flint edge will produce sparks, the hard flint edge shaves off a particle of the steel that exposes iron which reacts with oxygen from the atmosphere and can ignite the proper tinder. Prior to the availability of steel, rocks of pyrite would be used along with the flint.
These methods are popular in woodcraft and among those who wish to use traditional skills, a later, major use of flint and steel was in the flintlock mechanism, used primarily in flintlock firearms, but used on dedicated fire-starting tools. The sparks ignite the powder and that flame, in turn, ignites the main charge, propelling the ball, bullet. While the military use of the flintlock declined after the adoption of the cap from the 1840s onward, flintlock rifles. Flint and steel used to strike sparks were superseded by ferrocerium and this man-made material, when scraped with any hard, sharp edge, produces sparks that are much hotter than obtained with natural flint and steel, allowing use of a wider range of tinders. Because it can produce sparks when wet and can start fires when used correctly, ferrocerium is used in many cigarette lighters, where it is referred to as flint
The sulfate or sulphate ion is a polyatomic anion with the empirical formula SO2−4. Sulfate is the spelling recommended by IUPAC, but sulphate is used in British English, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life, sulfates are salts of sulfuric acid and many are prepared from that acid. The sulfate anion consists of a sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The symmetry is the same as that of methane, the sulfur atom is in the +6 oxidation state while the four oxygen atoms are each in the state. The sulfate ion carries a charge of −2 and it is the conjugate base of the bisulfate ion, HSO−4. Organic sulfate esters, such as sulfate, are covalent compounds. The tetrahedral molecular geometry of the ion is as predicted by VSEPR theory. Later, Linus Pauling used valence bond theory to propose that the most significant resonance canonicals had two pi bonds involving d orbitals and his reasoning was that the charge on sulfur was thus reduced, in accordance with his principle of electroneutrality.
The S−O bond length of 149 pm is shorter than the bond lengths in sulfuric acid of 157 pm for S−OH, the double bonding was taken by Pauling to account for the shortness of the S−O bond. Paulings use of d orbitals provoked a debate on the importance of π bonding. The outcome was a consensus that d orbitals play a role. A widely accepted description involving pπ – dπ bonding was initially proposed by D. W. J. Cruickshank, in this model, fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals. However, in description, despite there being some π character to the S−O bonds. For sulfuric acid, computational analysis confirms a positive charge on sulfur. Therefore, the representation with four single bonds is the optimal Lewis structure rather than the one with two double bonds, in this model, the structure obeys the octet rule and the charge distribution is in agreement with the electronegativity of the atoms. However, the representation of Pauling for sulfate and other main group compounds with oxygen is still a common way of representing the bonding in many textbooks.
On the other hand, in the structure with an ionic bond, exceptions include calcium sulfate, strontium sulfate, lead sulfate, and barium sulfate, which are poorly soluble
Novotel is a mid-up scale hotel brand within the AccorHotels group, typically slotting between the Mercure and Pullman brands. Novotel has close to 400 hotels and resorts in 60 countries, Novotel opened its first hotel in 1967 in Lille Lesquin, France. Hotel management said in a statement that the number of people staying in the room did not correspond with the number registered at the reception, the extra guests were seen moving around inside the hotel, and calls for an explanation remained unanswered, the hotel said. The activists complained they had been detained in their room after the forced entry. Seven of the guests sued Novotel for this incident in September 2014
A coin is a small, round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in quantities at a mint in order to facilitate trade. They are most often issued by a government, Coins are usually metal or alloy, or sometimes made of synthetic materials. Coins made of metal are stored in large quantities as bullion coins. Other coins are used as money in transactions, circulating alongside banknotes. Usually the highest value coin in circulation is less than the lowest-value note. In the last hundred years, the value of circulation coins has occasionally been lower than the value of the metal they contain. Exceptions to the rule of face value being higher than content value occur for some bullion coins made of copper, silver, or gold, while the Eagle, Maple Leaf, and Sovereign coins have nominal face values, the Krugerrand does not. The first coins were developed independently in Iron Age Anatolia and Archaic Greece, Coins spread rapidly in the 6th and 5th centuries BCE, throughout Greece and Persia, and further to the Balkans.
Standardized Roman currency was used throughout the Roman Empire, important Roman gold and silver coins were continued into the Middle Ages. Fiat money first arose in medieval China, with the paper money. Early paper money was introduced in Europe in the Middle Ages, the penny was minted as a silver coin until the 17th century. The first circulating United States coins were cents, produced in 1793, Coins were an evolution of currency systems of the Late Bronze Age, where standard-sized ingots, and tokens such as knife money, were used to store and transfer value. In the late Chinese Bronze Age, standardized cast tokens were made and these were replicas in bronze of earlier Chinese currency, cowrie shells, so they were named Bronze Shell. According to Aristotle and Pollux, the first issuer of coins was Hermodike of Kyme The earliest coins are associated with Iron Age Anatolia. Early electrum coins were not standardized in weight, and in their earliest stage may have been ritual objects, such as badges or medals, issued by priests.
The first Lydian coins were made of electrum, a naturally occurring alloy of silver, most of the early Lydian coins include no writing, only an image of a symbolic animal. Anatolian Artemis was the Πὀτνια Θηρῶν, whose symbol was the stag, a small percentage of early Lydian/Greek coins have a legend
Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can refer generally to the study of the features of any terrestrial planet. Geology gives insight into the history of the Earth by providing the evidence for plate tectonics, the evolutionary history of life. Geology plays a role in engineering and is a major academic discipline. The majority of data comes from research on solid Earth materials. These typically fall into one of two categories and unconsolidated material, the majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three types of rock, igneous and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between three types of rock, and magma. When a rock crystallizes from melt, it is an igneous rock, the sedimentary rock can be subsequently turned into a metamorphic rock due to heat and pressure and is weathered, eroded and lithified, ultimately becoming a sedimentary rock.
Sedimentary rock may be re-eroded and redeposited, and metamorphic rock may undergo additional metamorphism, all three types of rocks may be re-melted, when this happens, a new magma is formed, from which an igneous rock may once again crystallize. Geologists study unlithified material which typically comes from more recent deposits and these materials are superficial deposits which lie above the bedrock. Because of this, the study of material is often known as Quaternary geology. This includes the study of sediment and soils, including studies in geomorphology and this theory is supported by several types of observations, including seafloor spreading, and the global distribution of mountain terrain and seismicity. This coupling between rigid plates moving on the surface of the Earth and the mantle is called plate tectonics. The development of plate tectonics provided a basis for many observations of the solid Earth. Long linear regions of geologic features could be explained as plate boundaries, mid-ocean ridges, high regions on the seafloor where hydrothermal vents and volcanoes exist, were explained as divergent boundaries, where two plates move apart.
Arcs of volcanoes and earthquakes were explained as convergent boundaries, where one plate subducts under another, transform boundaries, such as the San Andreas Fault system, resulted in widespread powerful earthquakes. Plate tectonics provided a mechanism for Alfred Wegeners theory of continental drift and they provided a driving force for crustal deformation, and a new setting for the observations of structural geology
Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably, minerals that typically form nodules include calcite, apatite and pyrite. In sedimentology and geology, nodular is used to describe a sediment or sedimentary rock composed of scattered to loosely packed nodules in matrix of like or unlike character. It is used to describe mineral aggregates that occur in the form of nodules, nodule is used for widely scattered concretionary lumps of manganese, cobalt and nickel found on the floors of the worlds oceans. This is especially true of manganese nodules and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are instead of nodules. Chert and flint nodules are found in beds of limestone
The capital city is Lusaka, in the south-central part of Zambia. The population is concentrated mainly around Lusaka in the south and the Copperbelt Province to the northwest, originally inhabited by Khoisan peoples, the region was affected by the Bantu expansion of the thirteenth century. After visits by European explorers in the century, Zambia became the British protectorate of Northern Rhodesia towards the end of the nineteenth century. For most of the period, Zambia was governed by an administration appointed from London with the advice of the British South Africa Company. On 24 October 1964, Zambia became independent of the United Kingdom, Kaundas socialist United National Independence Party maintained power from 1964 until 1991. Kaunda played a key role in diplomacy, cooperating closely with the United States in search of solutions to conflicts in Rhodesia, Angola. From 1972 to 1991 Zambia was a one-party state with the UNIP as the legal political party under the motto One Zambia. Kaunda was succeeded by Frederick Chiluba of the social-democratic Movement for Multi-Party Democracy in 1991, beginning a period of social-economic growth, after Mwanawasas death, Rupiah Banda presided as Acting President before being elected President in 2008.
Holding office for three years, Banda stepped down after his defeat in the 2011 elections by Patriotic Front party leader Michael Sata. Sata died on 28 October 2014, the second Zambian president to die in office, Guy Scott served briefly as interim president until new elections were held on 20 January 2015, in which Edgar Lungu was elected as the sixth President. In 2010, the World Bank named Zambia one of the worlds fastest economically reformed countries, the Common Market for Eastern and Southern Africa is headquartered in Lusaka. The territory of what is now Zambia was known as Northern Rhodesia from 1911 and it was renamed Zambia at independence in 1964. The new name of Zambia was derived from the Zambezi river, the area of modern Zambia is known to have been inhabited by the Khoisan until around AD300, when migrating Bantu began to settle around these areas. These early hunter-gatherer groups were either annihilated or absorbed by subsequent more organised Bantu groups. Archaeological excavation work on the Zambezi Valley and Kalambo Falls show a succession of human cultures, in particular, ancient camping site tools near the Kalambo Falls have been radiocarbon dated to more than 36,000 year ago.
The fossil skull remains of Broken Hill Man, dated between 300,000 and 125,000 years BC, further shows that the area was inhabited by pre-historic man. The early history of tribes of modern-day Zambia can only be gleaned from knowledge passed down by successive generations through word of mouth, in the 12th century, major waves of Bantu-speaking immigrants arrived during the Bantu expansion. Among them, the Tonga people were the first to settle in Zambia and are believed to have come from the east near the big sea, by the late 12th century, more advanced kingdoms and empires had been established in most regions of modern-day Zambia