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Kiffa Beads
Kiffa beads are rare powder glass beads. They are named after the Mauritanian city of Kiffa, where French ethnologist R. Mauny documented them first in 1949. Kiffa beads represent one of the highest levels of artistic skill and ingenuity in beadmaking, being manufactured with the simplest materials and tools available: pulverized European glass beads or fragments of them, bottle glass, pottery shards, tin cans, twigs, steel needles, some gum arabic, and open fires. The term Kiffa bead, named after one of the old bead making centres of Kiffa in Mauritania, was coined by United States bead collectors during the 1980s. According to Peter Francis, Jr., the making of powder glass beads in West Africa may date back a few hundred years, and to possibly 1200 CE in Mauritania. Maure powder glass beads are believed to copy older, Islamic beads, of the type made in Fustat and elsewhere. Although the making of Mauritanian powder glass beads appears to be an ancient tradition, no archaeolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiffa Bead Cone
Kiffa () is a large town in the far south region of Mauritania, and the name of an administrative area within the local Assaba Region. Kiffa is located at , some from the coast and at the western end of the Aoukar sand sea of southern Mauritania. Climate Kiffa has a hot desert climate (Köppen climate classification ''BWh''). The climate is Sahelian, with April to June as the hottest months and eighty-five percent of the low annual rainfall occurring from July to September. In the 1990s and early 2000s Kiffa benefited from higher rainfall levels than elsewhere in the western Sahel. While Kiffa benefits from the ongoing "greening of the Sahel" the area's rangeland forage ecosystems remain vulnerable and can be subject to damaging overgrazing. Population, infrastructure and agriculture Kiffa was allowed to grow haphazardly and to sprawl during the later 20th century, and it has continued to do so. Near Kiffa is Kiffa Airport which has a tarmac runway of over 1,600 yards in lengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Africa
West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo, as well as Saint Helena, Ascension and Tristan da Cunha ( United Kingdom Overseas Territory).Paul R. Masson, Catherine Anne Pattillo, "Monetary union in West Africa (ECOWAS): is it desirable and how could it be achieved?" (Introduction). International Monetary Fund, 2001. The population of West Africa is estimated at about million people as of , and at 381,981,000 as of 2017, of which 189,672,000 are female and 192,309,000 male. The region is demographically and economically one of the fastest growing on the African continent. Early history in West Africa included a number of prominent regional powers that dominated different parts of both the coastal and internal trade networks, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obverse
Obverse and its opposite, reverse, refer to the two flat faces of coins and some other two-sided objects, including paper money, flags, seals, medals, drawings, old master prints and other works of art, and printed fabrics. In this usage, ''obverse'' means the front face of the object and ''reverse'' means the back face. The obverse of a coin is commonly called ''heads'', because it often depicts the head of a prominent person, and the reverse ''tails''. In numismatics, the abbreviation ''obv.'' is used for ''obverse'',David Sear. ''Greek Imperial Coins and Their Values.'' Spink Books, 1982. p. xxxv. while ℞, )(Jonathan Edwards. ''Catalogue of the Greek and Roman Coins in the Numismatic Collection of Yale College, Volume 2.'' Tuttle, Morehouse & Taylor, 1880. p. 228. and rev.Allen G. Berman. ''Warman's Coins And Paper Money: Identification and Price Guide.'' Penguin, 2008. are used for reverse. In fields of scholarship outside numismatics, the term ''front'' is more commo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oblate Spheroid
A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circular symmetry. If the ellipse is rotated about its major axis, the result is a ''prolate spheroid'', elongated like a rugby ball. The American football is similar but has a pointier end than a spheroid could. If the ellipse is rotated about its minor axis, the result is an ''oblate spheroid'', flattened like a lentil or a plain M&M. If the generating ellipse is a circle, the result is a sphere. Due to the combined effects of gravity and rotation, the figure of the Earth (and of all planets) is not quite a sphere, but instead is slightly flattened in the direction of its axis of rotation. For that reason, in cartography and geodesy the Earth is often approximated by an oblate spheroid, known as the reference ellipsoid, instead of a spher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychromatic
Polychrome is the "practice of decorating architectural elements, sculpture, etc., in a variety of colors." The term is used to refer to certain styles of architecture, pottery or sculpture in multiple colors. Ancient Egypt Colossal statue of Tutankhamun Paris 2019 A.jpg, Polychrome quartzite colossal statue of Tutankhamun, 1355-1315 BC Nofretete Neues Museum.jpg, Polychrome limestone and plaster ''Nefertiti Bust, Bust of Nefertiti'', 1352–1336 BC Composite Papyrus Capital MET 10.177.2 EGDP018080.jpg, Polychrome sandstone Composite papyrus capital, 380–343 BC Medinet Habu 2016-03-23g.jpg, Polychrome winged sun on a cavetto from the Medinet Habu temple complex, unknown date Classical world Some very early polychrome pottery has been excavated on Minoan civilization, Minoan Crete such as at the Bronze Age site of Phaistos. In ancient Greece sculptures were painted in strong colors. The paint was frequently limited to parts depicting clothing, hair, and so on, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molding (process)
Molding (American English) or moulding (British and Commonwealth English; see spelling differences) is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have been made using a pattern or model of the final object. A mold or mould is a hollowed-out block that is filled with a liquid or pliable material such as plastic, glass, metal, or ceramic raw material. The liquid hardens or sets inside the mold, adopting its shape. A mold is a counterpart to a cast. The very common bi-valve molding process uses two molds, one for each half of the object. Articulated molds have multiple pieces that come together to form the complete mold, and then disassemble to release the finished casting; they are expensive, but necessary when the casting shape has complex overhangs. Piece-molding uses a number of different molds, each creating a section of a complicated object. This is generally only used for larger a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant typically need an additional 11% chromium. Because of its high tensile strength and low cost, steel is used in buildings, infrastructure, tools, ships, trains, cars, machines, electrical appliances, weapons, and rockets. Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slurry
A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pump. The size of solid particles may vary from 1 micrometre up to hundreds of millimetres. The particles may settle below a certain transport velocity and the mixture can behave like a Newtonian or non-Newtonian fluid. Depending on the mixture, the slurry may be abrasive and/or corrosive. Examples Examples of slurries include: *Cement slurry, a mixture of cement, water, and assorted dry and liquid additives used in the petroleum and other industries *Soil/cement slurry, also called Controlled Low-Strength Material (CLSM), flowable fill, controlled density fill, flowable mortar, plastic soil-cement, K-Krete, and other names *A mixture of thickening agent, oxidizers, and water used to form a gel explosive *A mixture of pyroclastic material, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saliva
Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lipase and amylase), antimicrobial agents (such as secretory IgA, and lysozymes). The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, thus protecting teeth from bacterial decay. Saliva also performs a lubricating function, wetting food and permitting the initiation of swallowing, and protecting the oral mucosa from drying out. Various animal species have special uses for saliva that go beyond predigestion. Some swifts use their gummy saliva to build nests. ''Aerodramus'' nests form the basis of bird's nest soup. Cobras, vipers, and certain other membe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binder (material)
A binder or binding agent is any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, by adhesion or cohesion. In a more narrow sense, binders are liquid or dough-like substances that harden by a chemical or physical process and bind fibres, filler powder and other particles added into it. Examples include glue, adhesive and thickening. Examples of mechanical binders are bond stones in masonry and tie beams in timber framing. Classification Binders are loosely classified as organic ( bitums, animal and plant glues, polymers) and inorganic ( lime, cement, gypsum, liquid glass, etc.). These can be either metallic or ceramic as well as polymeric depending on the nature of the main material. For example, in the compound WC-Co (Tungsten Carbide used in cutting tools) Co constitutes the binding agent for the WC particles. Based on their chemical resistance, binders are classified by the field of use: non-hydra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiffa Bead Cylinder
Kiffa () is a large town in the far south region of Mauritania, and the name of an administrative area within the local Assaba Region. Kiffa is located at , some from the coast and at the western end of the Aoukar sand sea of southern Mauritania. Climate Kiffa has a hot desert climate (Köppen climate classification ''BWh''). The climate is Sahelian, with April to June as the hottest months and eighty-five percent of the low annual rainfall occurring from July to September. In the 1990s and early 2000s Kiffa benefited from higher rainfall levels than elsewhere in the western Sahel. While Kiffa benefits from the ongoing "greening of the Sahel" the area's rangeland forage ecosystems remain vulnerable and can be subject to damaging overgrazing. Population, infrastructure and agriculture Kiffa was allowed to grow haphazardly and to sprawl during the later 20th century, and it has continued to do so. Near Kiffa is Kiffa Airport which has a tarmac runway of over 1,600 yards in lengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
