Gravel is a loose aggregation of rock fragments. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular pebble gravel. ISO 14688 grades gravels as fine and coarse with ranges 2 mm to 6.3 mm to 20 mm to 63 mm. One cubic metre of gravel weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with tarmac. Both sand and small gravel are important for the manufacture of concrete. Large gravel deposits are a common geological feature, being formed as a result of the weathering and erosion of rocks; the action of rivers and waves tends to pile up gravel in large accumulations. This can sometimes result in gravel becoming compacted and lithified into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, or basalt.
Quarries where gravel is extracted are known as gravel pits. Southern England possesses large concentrations of them due to the widespread deposition of gravel in the region during the Ice Ages; as of 2006, the United States is consumer of gravel. The word gravel comes from the Breton language. In Breton, "grav" means coast. Adding the "-el" suffix in Breton denotes the component parts of something larger, thus "gravel" means the small stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravelle. Gravel has the meaning a mixture of different size pieces of stone mixed with sand and some clay. In American English, rocks broken into small pieces by a crusher are known as crushed stone. Types of gravel include: Bank gravel: deposited gravel intermixed with sand or clay found in and next to rivers and streams. Known as "bank run" or "river run". Bench gravel: a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level.
Creek rock or river rock: this is rounded, semi-polished stones of a wide range of types, that are dredged or scooped from stream beds. It is often used as concrete aggregate and less as a paving surface. Crushed stone: rock crushed and graded by screens and mixed to a blend of stones and fines, it is used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone and other rocks. Known as "crusher run", DGA QP, shoulder stone. Fine gravel: gravel consisting of particles with a diameter of 2 to 8 mm. Stone dust: fine, gravel from the final stage of screen separation, such that the gravel is not separated out from fine dust particles. Lag gravel: a surface accumulation of coarse gravel produced by the removal of finer particles. Pay gravel: known as "pay dirt"; the metals are recovered through gold panning. Pea gravel: known as "pea shingle" is gravel that consists of small, rounded stones used in concrete surfaces. Used for walkways, driveways and as a substrate in home aquariums.
Piedmont gravel: a coarse gravel carried down from high places by mountain streams and deposited on flat ground, where the water runs more slowly. Plateau gravel: a layer of gravel on a plateau or other region above the height at which stream-terrace gravel is found. In locales where gravelly soil is predominant, plant life is more sparse; this outcome derives from the inferior ability of gravels to retain moisture, as well as the corresponding paucity of mineral nutrients, since finer soils that contain such minerals are present in smaller amounts. Construction aggregate Pebble Rock Media related to Gravel at Wikimedia Commons
The French are an ethnic group and nation who are identified with the country of France. This connection may be ethnic, historical, or cultural; the heritage of the French people is of Celtic and Germanic origin, descending from the ancient and medieval populations of Gauls, Ligures, Iberians, Franks and Norsemen. France has long been a patchwork of local customs and regional differences, while most French people still speak the French language as their mother tongue, languages like Norman, Catalan, Corsican, French Flemish, Lorraine Franconian and Breton remain spoken in their respective regions. Arabic is widely spoken, arguably the largest minority language in France as of the 21st century. Modern French society is a melting pot. From the middle of the 19th century, it experienced a high rate of inward migration consisting of Arab-Berbers, Sub-Saharan Africans and other peoples from Africa, the Middle East and East Asia, the government, defining France as an inclusive nation with universal values, advocated assimilation through which immigrants were expected to adhere to French values and cultural norms.
Nowadays, while the government has let newcomers retain their distinctive cultures since the mid-1980s and requires from them a mere integration, French citizens still equate their nationality with citizenship as does French law. In addition to mainland France, French people and people of French descent can be found internationally, in overseas departments and territories of France such as the French West Indies, in foreign countries with significant French-speaking population groups or not, such as Switzerland, the United States, Argentina, Brazil and Uruguay. To be French, according to the first article of the French Constitution, is to be a citizen of France, regardless of one's origin, race, or religion. According to its principles, France has devoted itself to the destiny of a proposition nation, a generic territory where people are bounded only by the French language and the assumed willingness to live together, as defined by Ernest Renan's "plébiscite de tous les jours" on the willingness to live together, in Renan's 1882 essay "Qu'est-ce qu'une nation?").
The debate concerning the integration of this view with the principles underlying the European Community remains open. A large number of foreigners have traditionally been permitted to live in France and succeeded in doing so. Indeed, the country has long valued its openness and the quality of services available. Application for French citizenship is interpreted as a renunciation of previous state allegiance unless a dual citizenship agreement exists between the two countries; the European treaties have formally permitted movement and European citizens enjoy formal rights to employment in the state sector. Seeing itself as an inclusive nation with universal values, France has always valued and advocated assimilation. However, the success of such assimilation has been called into question. There is increasing dissatisfaction with, within, growing ethno-cultural enclaves; the 2005 French riots in some troubled and impoverished suburbs were an example of such tensions. However they should not be interpreted as ethnic conflicts but as social conflicts born out of socioeconomic problems endangering proper integration.
French people are the descendants of Gauls and Romans, western European Celtic and Italic peoples, as well as Bretons, Aquitanians and Germanic people arriving at the beginning of the Frankish Empire such as the Franks, the Visigoths, the Suebi, the Saxons, the Allemanni and the Burgundians, Germanic groups such as the Vikings, who settled in Normandy and to a lesser extent in Brittany in the 9th century. The name "France" etymologically derives from the territory of the Franks; the Franks were a Germanic tribe. In the pre-Roman era, all of Gaul was inhabited by a variety of peoples who were known collectively as the Gaulish tribes, their ancestors were Celts who came from Central Europe in the 7th century BCE, non-Celtic peoples including the Ligures, Aquitanians in Aquitaine. Some in the northern and eastern areas, may have had Germanic admixture. Gaul was militarily conquered in 58–51 BCE by the Roman legions under the command of General Julius Caesar. Over the next six centuries, the two cultures intermingled, creating a hybridized Gallo-Roman culture.
In the late Roman era, in addition to colonists from elsewhere in the Empire and Gaulish natives, Gallia became home to some in-migrating populations of Germanic and Scythian origin, such as Alans. The Gaulish language is thought to have survived into the 6th century in France, despite considerable Romanizat
A rhinoceros abbreviated to rhino, is one of any five extant species of odd-toed ungulates in the family Rhinocerotidae, as well as any of the numerous extinct species. Two of the extant species are native to three to Southern Asia; the term "rhinoceros" is more broadly applied to now extinct relatives of the superfamily Rhinocerotoidea. Members of the rhinoceros family are some of the largest remaining megafauna, with all species able to reach or exceed one tonne in weight, they have a herbivorous diet, small brains for mammals of their size, one or two horns, a thick protective skin formed from layers of collagen positioned in a lattice structure. They eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more fibrous plant matter when necessary. Unlike other perissodactyls, the two African species of rhinoceros lack teeth at the front of their mouths, relying instead on their lips to pluck food. Rhinoceros are killed by some humans for their horns, which are bought and sold on the black market, used by some cultures for ornaments or traditional medicine.
East Asia Vietnam, is the largest market for rhino horns. By weight, rhino horns cost as much as gold on the black market. People consume them, believing the dust has therapeutic properties; the horns are made of the same type of protein that makes up hair and fingernails. Both African species and the Sumatran rhinoceros have two horns, while the Indian and Javan rhinoceros have a single horn; the IUCN Red List identifies the Black and Sumatran rhinoceros as critically endangered. The word rhinoceros is derived through Latin from the Ancient Greek: ῥῑνόκερως, composed of ῥῑνο- and κέρας with a horn on the nose; the plural in English is rhinoceroses. The collective noun for a group of rhinoceroses is herd; the name has been in use since the 14th century. The family Rhinocerotidae consists of only four extant genera: Ceratotherium, Diceros and Rhinoceros; the living species fall into three categories. The two African species, the white rhinoceros and the black rhinoceros, belong to the tribe Dicerotini, which originated in the middle Miocene, about 14.2 million years ago.
The species diverged during the early Pliocene. The main difference between black and white rhinos is the shape of their mouths – white rhinos have broad flat lips for grazing, whereas black rhinos have long pointed lips for eating foliage. There are two living Rhinocerotini species, the Indian rhinoceros and the Javan rhinoceros, which diverged from one another about 10 million years ago; the Sumatran rhinoceros is the only surviving representative of the most primitive group, the Dicerorhinini, which emerged in the Miocene. A subspecific hybrid white rhino was bred at the Dvůr Králové Zoo in the Czech Republic in 1977. Interspecific hybridisation of black and white rhinoceros has been confirmed. While the black rhinoceros has 84 chromosomes, all other rhinoceros species have 82 chromosomes. However, chromosomal polymorphism might lead to varying chromosome counts. For instance, in a study there were three northern white rhinoceroses with 81 chromosomes. There are two subspecies of white rhinoceros: the southern white rhinoceros and the northern white rhinoceros.
As of 2013, the southern subspecies has a wild population of 20,405 – making them the most abundant rhino subspecies in the world. However, the northern subspecies is critically endangered, with all, known to remain being two captive females. There is no conclusive explanation of the name "white rhinoceros". A popular idea that "white" is a distortion of either the Afrikaans word wyd or the Dutch word wijd, meaning "wide" and referring to the rhino's square lips, is not supported by linguistic studies; the white rhino has a short neck and broad chest. Females weigh males 2,400 kg; the head-and-body length is 3.5–4.6 m and the shoulder height is 1.8–2 m. On its snout it has two horns; the front horn is larger than averages 90 cm in length and can reach 150 cm. The white rhinoceros has a prominent muscular hump that supports its large head; the colour of this animal can range from yellowish brown to slate grey. Most of its body hair is found on the ear fringes and tail bristles, with the rest distributed rather sparsely over the rest of the body.
White rhinos have the distinctive flat broad mouth, used for grazing. The name "black rhinoceros" was chosen to distinguish this species from the white rhinoceros; this can be confusing, as the two species are not distinguishable by color. There are four subspecies of black rhino: South-central, the most numerous, which once ranged from central Tanzania south through Zambia and Mozambique to northern and eastern South Africa.
Biblioteca Nacional de España
The Biblioteca Nacional de España is a major public library, the largest in Spain, one of the largest in the world. It is located on the Paseo de Recoletos; the library was founded by King Philip V in 1712 as the Palace Public Library. The Royal Letters Patent that he granted, the predecessor of the current legal deposit requirement, made it mandatory for printers to submit a copy of every book printed in Spain to the library. In 1836, the library's status as Crown property was revoked and ownership was transferred to the Ministry of Governance. At the same time, it was renamed the Biblioteca Nacional. During the 19th century, confiscations and donations enabled the Biblioteca Nacional to acquire the majority of the antique and valuable books that it holds. In 1892 the building was used to host the Historical American Exposition. On March 16, 1896, the Biblioteca Nacional opened to the public in the same building in which it is housed and included a vast Reading Room on the main floor designed to hold 320 readers.
In 1931 the Reading Room was reorganised, providing it with a major collection of reference works, the General Reading Room was created to cater for students and general readers. During the Spanish Civil War close to 500,000 volumes were collected by the Confiscation Committee and stored in the Biblioteca Nacional to safeguard works of art and books held until in religious establishments and private houses. During the 20th century numerous modifications were made to the building to adapt its rooms and repositories to its expanding collections, to the growing volume of material received following the modification to the Legal Deposit requirement in 1958, to the numerous works purchased by the library. Among this building work, some of the most noteworthy changes were the alterations made in 1955 to triple the capacity of the library's repositories, those started in 1986 and completed in 2000, which led to the creation of the new building in Alcalá de Henares and complete remodelling of the building on Paseo de Recoletos, Madrid.
In 1986, when Spain's main bibliographic institutions - the National Newspaper Library, the Spanish Bibliographic Institute and the Centre for Documentary and Bibliographic Treasures - were incorporated into the Biblioteca Nacional, the library was established as the State Repository of Spain's Cultural Memory, making all of Spain's bibliographic output on any media available to the Spanish Library System and national and international researchers and cultural and educational institutions. In 1990 it was made an Autonomous Entity attached to the Ministry of Culture; the Madrid premises are shared with the National Archaeological Museum. The Biblioteca Nacional is Spain's highest library institution and is head of the Spanish Library System; as the country's national library, it is the centre responsible for identifying, preserving and disseminating information about Spain's documentary heritage, it aspires to be an essential point of reference for research into Spanish culture. In accordance with its Articles of Association, passed by Royal Decree 1581/1991 of October 31, 1991, its principal functions are to: Compile and conserve bibliographic archives produced in any language of the Spanish state, or any other language, for the purposes of research and information.
Promote research through the study and reproduction of its bibliographic archive. Disseminate information on Spain's bibliographic output based on the entries received through the legal deposit requirement; the library's collection consists of more than 26,000,000 items, including 15,000,000 books and other printed materials, 4,500,000 graphic materials, 600,000 sound recordings, 510,000 music scores, more than 500,000 microforms, 500,000 maps, 143,000 newspapers and serials, 90,000 audiovisuals, 90,000 electronic documents, 30,000 manuscripts. The current director of the Biblioteca Nacional is Ana Santos Aramburo, appointed in 2013. Former directors include her predecessors Glòria Pérez-Salmerón and Milagros del Corral as well as historian Juan Pablo Fusi and author Rosa Regàs. Given its role as the legal deposit for the whole of Spain, since 1991 it has kept most of the overflowing collection at a secondary site in Alcalá de Henares, near Madrid; the Biblioteca Nacional provides access to its collections through the following library services: Guidance and general information on the institution and other libraries.
Bibliographic information about its collection and those held by other libraries or library systems. Access to its automated catalogue, which contains close to 3,000,000 bibliographic records encompassing all of its collections. Archive consultation in the library's reading rooms. Interlibrary loans. Archive reproduction. Biblioteca Digital Hispánica, digital library launched in 2008 by the Biblioteca Nacional de España List of libraries in Spain Media related to Biblioteca Nacional de España at Wikimedia Commons Official site Official web catalog
Human evolution is the evolutionary process that led to the emergence of anatomically modern humans, beginning with the evolutionary history of primates—in particular genus Homo—and leading to the emergence of Homo sapiens as a distinct species of the hominid family, the great apes. This process involved the gradual development of traits such as human bipedalism and language, as well as interbreeding with other hominins, which indicate that human evolution was not linear but a web; the study of human evolution involves several scientific disciplines, including physical anthropology, archaeology, neurobiology, linguistics, evolutionary psychology and genetics. Genetic studies show that primates diverged from other mammals about 85 million years ago, in the Late Cretaceous period, the earliest fossils appear in the Paleocene, around 55 million years ago. Within the Hominoidea superfamily, the Hominidae family diverged from the Hylobatidae family some 15–20 million years ago. Human evolution from its first separation from the last common ancestor of humans and chimpanzees is characterized by a number of morphological, developmental and behavioral changes.
The most significant of these adaptations are bipedalism, increased brain size, lengthened ontogeny, decreased sexual dimorphism. The relationship between these changes is the subject of ongoing debate. Other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H. erectus. Bipedalism is the basic adaptation of the hominid and is considered the main cause behind a suite of skeletal changes shared by all bipedal hominids; the earliest hominin, of primitive bipedalism, is considered to be either Sahelanthropus or Orrorin, both of which arose some 6 to 7 million years ago. The non-bipedal knuckle-walkers, the gorilla and chimpanzee, diverged from the hominin line over a period covering the same time, so either of Sahelanthropus or Orrorin may be our last shared ancestor. Ardipithecus, a full biped, arose 5.6 million years ago. The early bipeds evolved into the australopithecines and still into the genus Homo. There are several theories of the adaptation value of bipedalism.
It is possible that bipedalism was favored because it freed the hands for reaching and carrying food, saved energy during locomotion, enabled long distance running and hunting, provided an enhanced field of vision, helped avoid hyperthermia by reducing the surface area exposed to direct sun. A new study provides support for the hypothesis that walking on two legs, or bipedalism, evolved because it used less energy than quadrupedal knuckle-walking. However, recent studies suggest that bipedality without the ability to use fire would not have allowed global dispersal; this change in gait saw a lengthening of the legs proportionately when compared to the length of the arms, which were shortened through the removal of the need for brachiation. Another change is the shape of the big toe. Recent studies suggest that Australopithecines still lived part of the time in trees as a result of maintaining a grasping big toe; this was progressively lost in Habilines. Anatomically, the evolution of bipedalism has been accompanied by a large number of skeletal changes, not just to the legs and pelvis, but to the vertebral column and ankles, skull.
The femur evolved into a more angular position to move the center of gravity toward the geometric center of the body. The knee and ankle joints became robust to better support increased weight. To support the increased weight on each vertebra in the upright position, the human vertebral column became S-shaped and the lumbar vertebrae became shorter and wider. In the feet the big toe moved into alignment with the other toes to help in forward locomotion; the arms and forearms shortened relative to the legs making it easier to run. The foramen magnum migrated under more anterior; the most significant changes occurred in the pelvic region, where the long downward facing iliac blade was shortened and widened as a requirement for keeping the center of gravity stable while walking. A drawback is that the birth canal of bipedal apes is smaller than in knuckle-walking apes, though there has been a widening of it in comparison to that of australopithecine and modern humans, permitting the passage of newborns due to the increase in cranial size but this is limited to the upper portion, since further increase can hinder normal bipedal movement.
The shortening of the pelvis and smaller birth canal evolved as a requirement for bipedalism and had significant effects on the process of human birth, much more difficult in modern humans than in other primates. During human birth, because of the variation in size of the pelvic region, the fetal head must be in a transverse position during entry into the birth canal and rotate about 90 degrees upon exit; the smaller birth canal became a limiting factor to brain size increases in early humans and prompted a shorter gestation period leading to the relative immaturity of human
A stone tool is, in the most general sense, any tool made either or out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric cultures that have become extinct. Archaeologists study such prehistoric societies, refer to the study of stone tools as lithic analysis. Ethnoarchaeology has been a valuable research field in order to further the understanding and cultural implications of stone tool use and manufacture. Stone has been used to make a wide variety of different tools throughout history, including arrow heads and querns. Stone tools may be made of either ground stone or chipped stone, a person who creates tools out of the latter is known as a flintknapper. Chipped stone tools are made from cryptocrystalline materials such as chert or flint, chalcedony, obsidian and quartzite via a process known as lithic reduction. One simple form of reduction is to strike stone flakes from a nucleus of material using a hammerstone or similar hard hammer fabricator.
If the goal of the reduction strategy is to produce flakes, the remnant lithic core may be discarded once it has become too small to use. In some strategies, however, a flintknapper reduces the core to a rough unifacial or bifacial preform, further reduced using soft hammer flaking techniques or by pressure flaking the edges. More complex forms of reduction include the production of standardized blades, which can be fashioned into a variety of tools such as scrapers, knives and microliths. In general terms, chipped stone tools are nearly ubiquitous in all pre-metal-using societies because they are manufactured, the tool stone is plentiful, they are easy to transport and sharpen. Archaeologists classify stone tools into industries that share distinctive technological or morphological characteristics. In 1969 in the 2nd edition of World Prehistory, Grahame Clark proposed an evolutionary progression of flint-knapping in which the "dominant lithic technologies" occurred in a fixed sequence from Mode 1 through Mode 5.
He assigned to them relative dates: Modes 1 and 2 to the Lower Palaeolithic, 3 to the Middle Palaeolithic, 4 to the Advanced and 5 to the Mesolithic. They were not to be conceived, however, as either universal—that is, they did not account for all lithic technology. Mode 1, for example, was in use in Europe. Clark's scheme was adopted enthusiastically by the archaeological community. One of its advantages was the simplicity of terminology; the transitions are of greatest interest. In the literature the stone tools used in the period of the Palaeolithic are divided into four "modes", each of which designate a different form of complexity, which in most cases followed a rough chronological order. KenyaStone tools found from 2011 to 2014 at Lake Turkana in Kenya, are dated to be 3.3 million years old, predate the genus Homo by half million years. The oldest known Homo fossil is 2.8 million years old compared to the 3.3 million year old stone tools. The stone tools may have been made by Australopithecus afarensis —also called Kenyanthropus platyops— the species whose best fossil example is Lucy, which inhabited East Africa at the same time as the date of the oldest stone tools.
Dating of the tools was by dating volcanic ash layers in which the tools were found and dating the magnetic signature of the rock at the site. EthiopiaGrooved and fractured animal bone fossils, made by using stone tools, were found in Dikika, Ethiopia near the remains of Selam, a young Australopithecus afarensis girl who lived about 3.3 million years ago. The earliest stone tools in the life span of the genus Homo are Mode 1 tools, come from what has been termed the Oldowan Industry, named after the type of site found in Olduvai Gorge, where they were discovered in large quantities. Oldowan tools were characterised by their simple construction; these cores were river pebbles, or rocks similar to them, struck by a spherical hammerstone to cause conchoidal fractures removing flakes from one surface, creating an edge and a sharp tip. The blunt end is the proximal surface. Oldowan is a percussion technology. Grasping the proximal surface, the hominid brought the distal surface down hard on an object he wished to detach or shatter, such as a bone or tuber.
The earliest known Oldowan tools yet found date from 2.6 million years ago, during the Lower Palaeolithic period, have been uncovered at Gona in Ethiopia. After this date, the Oldowan Industry subsequently spread throughout much of Africa, although archaeologists are unsure which Hominan species first developed them, with some speculating that it was Australopithecus garhi, others believing that it was in fact Homo habilis. Homo habilis was the hominin who used the tools for most of the Oldowan in Africa, but at about 1.9-1.8 million years ago Homo erectus inherited them. The Industry flourished in southern and eastern Africa between 2.6 and 1.7 million years ago, but was spread out of Africa and into Eurasia by travelling bands of H. erectus, who took it as far east as Java by 1.8 million years ago and Northern China by 1.6 million years ago. More complex, Mode 2 tools began to be developed through the Acheulean Industry, named after the site