1.
Archaeology
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Archaeology, or archeology, is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, Archaeology can be considered both a social science and a branch of the humanities. In North America, archaeology is considered a sub-field of anthropology, archaeologists study human prehistory and history, from the development of the first stone tools at Lomekwi in East Africa 3.3 million years ago up until recent decades. Archaeology as a field is distinct from the discipline of palaeontology, Archaeology is particularly important for learning about prehistoric societies, for whom there may be no written records to study. Prehistory includes over 99% of the human past, from the Paleolithic until the advent of literacy in societies across the world, Archaeology has various goals, which range from understanding culture history to reconstructing past lifeways to documenting and explaining changes in human societies through time. The discipline involves surveying, excavation and eventually analysis of data collected to learn more about the past, in broad scope, archaeology relies on cross-disciplinary research. Archaeology developed out of antiquarianism in Europe during the 19th century, Archaeology has been used by nation-states to create particular visions of the past. Nonetheless, today, archaeologists face many problems, such as dealing with pseudoarchaeology, the looting of artifacts, a lack of public interest, the science of archaeology grew out of the older multi-disciplinary study known as antiquarianism. Antiquarians studied history with attention to ancient artifacts and manuscripts. Tentative steps towards the systematization of archaeology as a science took place during the Enlightenment era in Europe in the 17th and 18th centuries, in Europe, philosophical interest in the remains of Greco-Roman civilization and the rediscovery of classical culture began in the late Middle Age. Antiquarians, including John Leland and William Camden, conducted surveys of the English countryside, one of the first sites to undergo archaeological excavation was Stonehenge and other megalithic monuments in England. John Aubrey was a pioneer archaeologist who recorded numerous megalithic and other monuments in southern England. He was also ahead of his time in the analysis of his findings and he attempted to chart the chronological stylistic evolution of handwriting, medieval architecture, costume, and shield-shapes. Excavations were also carried out in the ancient towns of Pompeii and Herculaneum and these excavations began in 1748 in Pompeii, while in Herculaneum they began in 1738. The discovery of entire towns, complete with utensils and even human shapes, however, prior to the development of modern techniques, excavations tended to be haphazard, the importance of concepts such as stratification and context were overlooked. The father of archaeological excavation was William Cunnington and he undertook excavations in Wiltshire from around 1798, funded by Sir Richard Colt Hoare. Cunnington made meticulous recordings of neolithic and Bronze Age barrows, one of the major achievements of 19th century archaeology was the development of stratigraphy. The idea of overlapping strata tracing back to successive periods was borrowed from the new geological and paleontological work of scholars like William Smith, James Hutton, the application of stratigraphy to archaeology first took place with the excavations of prehistorical and Bronze Age sites
2.
Geology
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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 also 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 also 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, rock 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, sedimentary, 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 then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also 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 also 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, sedimentology 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 also provided a mechanism for Alfred Wegeners theory of continental drift and they also provided a driving force for crustal deformation, and a new setting for the observations of structural geology
3.
Recorded history
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Recorded history or written history is a historical narrative based on a written record or other documented communication. Recorded history can be contrasted with other narratives of the past, for broader world history, recorded history begins with the accounts of the ancient world around the 4th millennium BC, and coincides with the invention of writing. Examples of written texts, however, can be found dating as far back as 1750 BCE in Ancient Mesopotamia, for some geographic regions or cultures, written history is limited to a relatively recent period in human history because of the limited use of written records. Because of these limits, recorded history in different contexts may refer to different periods of time depending on the historical topic. The question of the nature, and even the possibility, of a method for interpreting recorded history is raised in the philosophy of history as a question of epistemology. Prehistory traditionally refers to the span of time before recorded history, prehistory refers to the past in an area where no written records exist, or where the writing of a culture is not understood. Protohistory refers to the period between prehistory and history, after the advent of literacy in a society but before the writings of the first historians. Protohistory may also refer to the period during which a culture or civilization has not yet developed writing, more complete writing systems were preceded by proto-writing. Early examples are the Jiahu symbols, Vinča signs, early Indus script, earliest recorded history, which varies greatly in quality and reliability, deals with Pharaohs and their reigns, made by ancient Egyptians. Much of the earliest recorded history was re-discovered relatively recently due to archaeological dig sites findings, since these initial accounts, a number of different traditions have developed in different parts of the world in how to handle the writing and production of historical accounts. In China, the earliest history was recorded in oracle bone script which was deciphered, the Zuo Zhuan, attributed to Zuo Qiuming in the 5th century BCE, is the earliest written of narrative history in the world and covers the period from 722 to 468 BCE. The Classic of History is one of the Five Classics of Chinese classic texts and it is traditionally attributed to Confucius. Zhan Guo Ce was a renowned ancient Chinese historical compilation of materials on the Warring States period compiled between the 3rd and 1st centuries BCE. Sima Qian was the first in China to lay the groundwork for professional historical writing and his written work was the Shiji, a monumental lifelong achievement in literature. His work influenced every subsequent author of history in China, including the prestigious Ban family of the Eastern Han Dynasty era, Herodotus of Halicarnassus has generally been acclaimed as the father of history composing his The Histories written from 450s to the 420s BCE. However, his contemporary Thucydides is credited with having first approached history with a historical method in his work the History of the Peloponnesian War. Thucydides, unlike Herodotus, regarded history as being the product of the choices and actions of human beings, saint Augustine was influential in Christian and Western thought at the beginning of the medieval period. Through the Medieval and Renaissance periods, history was studied through a sacred or religious perspective
4.
Dendrochronology
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Dendrochronology is the scientific method of dating tree rings to the exact year they were formed in order to analyze atmospheric conditions during different periods in history. Dendrochronology is useful for determining the timing of events and rates of change in the environment and also in works of art and architecture, such as old panel paintings on wood, buildings and it is also used in radiocarbon dating to calibrate radiocarbon ages. New growth in trees occurs in a layer of cells near the bark, a trees growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings. Each ring marks a complete cycle of seasons, or one year, as of 2013, the oldest tree-ring measurements in the Northern Hemisphere extend back 13,900 years. Dendrochronology derives from Ancient Greek, δένδρον, meaning tree limb, χρόνος, meaning time, and -λογία, the Greek botanist Theophrastus first mentioned that the wood of trees has rings. In his Trattato della Pittura, Leonardo da Vinci was the first person to mention that trees form rings annually, in 1737, French investigators Henri-Louis Duhamel du Monceau and Georges-Louis Leclerc de Buffon examined the effect of growing conditions on the shape of tree rings. They found that in 1709, a severe winter produced a distinctly dark tree ring, the English polymath Charles Babbage proposed using dendrochronology to date the remains of trees in peat bogs or even in geological strata. During the latter half of the century, the scientific study of tree rings. In 1859, the German-American Jacob Kuechler used crossdating to examine oaks in order to study the record of climate in western Texas, in 1866, the German botanist, entomologist, and forester Julius Ratzeburg observed the effects on tree rings of defoliation caused by insect infestations. By 1882, this observation was already appearing in forestry textbooks, in the 1870s, the Dutch astronomer Jacobus C. Kapteyn was using crossdating to reconstruct the climates of the Netherlands, in 1881, the Swiss-Austrian forester Arthur von Seckendorff-Gudent was using crossdating. From 1869 to 1901, Robert Hartig, a German professor of forest pathology, wrote a series of papers on the anatomy, in 1892, the Russian physicist Fedor Nikiforovich Shvedov wrote that he had used patterns found in tree rings to predict droughts in 1882 and 1891. During the first half of the 20th century, the astronomer A. E. Douglass founded the Laboratory of Tree-Ring Research at the University of Arizona. Growth rings, also referred to as tree rings or annual rings, growth rings are the result of new growth in the vascular cambium, a layer of cells near the bark that is classified as a lateral meristem, this growth in diameter is known as secondary growth. Visible rings result from the change in speed through the seasons of the year, thus, critical for the title method. If the bark of the tree has been removed in a particular area, the rings are more visible in temperate zones, where the seasons differ more markedly. The inner portion of a ring is formed early in the growing season, when growth is comparatively rapid and is known as early wood. Many trees in temperate zones make one growth ring each year, hence, for the entire period of a trees life, a year-by-year record or ring pattern is formed that reflects the age of the tree and the climatic conditions in which the tree grew
5.
Radiocarbon dating
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Radiocarbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed by Willard Libby in the late 1940s, Libby received the Nobel Prize for his work in 1960. The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting radiocarbon combines with oxygen to form radioactive carbon dioxide. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The idea behind radiocarbon dating is straightforward, but years of work were required to develop the technique to the point where accurate dates could be obtained. Research has been ongoing since the 1960s to determine what the proportion of 14C in the atmosphere has been over the past fifty thousand years. The resulting data, in the form of a curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the samples calendar age. Other corrections must be made to account for the proportion of 14C in different types of organisms, additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s. Conversely, nuclear testing increased the amount of 14C in the atmosphere, measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying 14C atoms in a sample. The development of dating has had a profound impact on archaeology. In addition to permitting more accurate dating within archaeological sites than previous methods, histories of archaeology often refer to its impact as the radiocarbon revolution. Radiocarbon dating has allowed key transitions in prehistory to be dated, such as the end of the last ice age, and they synthesized 14C using the laboratorys cyclotron accelerator and soon discovered that the atoms half-life was far longer than had been previously thought. This was followed by a prediction by Serge A. Korff, then employed at the Franklin Institute in Philadelphia and it had previously been thought that 14C would be more likely to be created by deuterons interacting with 13C. At some time during World War II, Willard Libby, who was then at Berkeley, learned of Korffs research, in 1945, Libby moved to the University of Chicago where he began his work on radiocarbon dating. He published a paper in 1946 in which he proposed that the carbon in living matter might include 14C as well as non-radioactive carbon, by contrast, methane created from petroleum showed no radiocarbon activity because of its age. The results were summarized in a paper in Science in 1947, Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages
6.
Thermoluminescence dating
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As a crystalline material is heated during measurements the process of thermoluminescence starts. Thermoluminescence emits a light signal that is proportional to the radiation dose absorbed by the material. It is a type of luminescence dating, the technique has wide application, and is relatively cheap at some US$300–700 per object, ideally a number of samples are tested. Sediments are more expensive to date, the destruction of a relatively significant amount of sample material is necessary, which can be a limitation in the case of artworks. The heating must have taken the object above 500° C, which covers most ceramics and it will often work well with stones that have been heated by fire. The clay core of bronze sculptures made by lost wax casting can also be tested, different materials vary considerably in their suitability for the technique, depending on several factors. Subsequent irradiation, for if an x-ray is taken, can affect accuracy. Ideally this is assessed by measurements made at the precise findspot over a long period, for artworks, it may be sufficient to confirm whether a piece is broadly ancient or modern, and this may be possible even if a precise date cannot be estimated. These imperfections lead to local humps and dips in the crystalline materials electric potential, where there is a dip, a free electron may be attracted and trapped. The flux of ionizing radiation—both from cosmic radiation and from natural radioactivity—excites electrons from atoms in the lattice into the conduction band where they can move freely. Most excited electrons will recombine with lattice ions, but some will be trapped. Depending on the depth of the traps the storage time of trapped electrons will vary as some traps are sufficiently deep to store charge for hundreds of thousands of years. In the process of recombining with an ion, they lose energy and emit photons. The amount of light produced is proportional to the number of trapped electrons that have been freed which is in turn proportional to the dose accumulated. In order to relate the signal to the dose that caused it, it is necessary to calibrate the material with known doses of radiation since the density of traps is highly variable. Thermoluminescence dating presupposes a zeroing event in the history of the material, either heating or exposure to sunlight, therefore, at that point the thermoluminescence signal is zero. As time goes on, the radiation field around the material causes the trapped electrons to accumulate. In the laboratory, the radiation dose can be measured
7.
Argon
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Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the table and is a noble gas. Argon is the third-most abundant gas in the Earths atmosphere, at 0. 934% and it is more than twice as abundant as water vapor,23 times as abundant as carbon dioxide, and more than 500 times as abundant as neon. Argon is the most abundant noble gas in Earths crust, comprising 0. 00015% of the crust, nearly all of the argon in Earths atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earths crust. In the universe, argon-36 is by far the most common argon isotope, the name argon is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning lazy or inactive, as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet in the atomic shell makes argon stable. Its triple point temperature of 83.8058 K is a fixed point in the International Temperature Scale of 1990. Argon is produced industrially by the distillation of liquid air. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes, Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters, Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas, Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a gas, it can form some compounds under extreme conditions. Argon fluorohydride, a compound of argon with fluorine and hydrogen that is stable below 17 K, has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, ions, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized, Argon was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water and they had determined that nitrogen produced from chemical compounds was 0. 5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months and they concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall, each observed new lines in the color spectrum of air that did not match known elements
8.
Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
9.
Bristol Zoo
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Bristol Zoo is a zoo in the city of Bristol in South West England. Among species now on view at Bristol which are rare or absent in other UK zoos are Livingstones fruit bats and successful breeding groups of western lowland gorillas, the lakes islands are home to gorillas, tamarins, marmosets, gibbons and pelicans. Seal and Penguin Coasts is an attraction at the zoo, opened in 1999, it allows South American fur seals. The two pools contain 145,000 imperial gallons of water, with waves, waterfalls, rocks. The exhibit has a net over the top to allow Inca terns. Explorers Creek opened in May 2009 and features three areas – a water area, a tropical bird house and a walk-through lorikeet feeding area. Gorilla Island is home to a family of western lowland gorillas, as well as an indoor house which is also home to okapis, they have a large island which they share with the De Brazzas monkeys from Monkey Jungle. The gorillas are herbivores, and are not aggressive, however the keepers do not enter their island home because it is the zoos policy to keep the animals captive environment as similar as possible to that of their natural African forest habitat. The Terrace is one of the oldest parts of the zoo, by exchanging night and day, the animals can be observed during daylight hours. The lights allow a transition from night to day and vice versa. Twilight world is split into four zones, the Desert, the Rainforest, the Cave, the Reptile House houses a collection of reptiles and amphibians. The house itself is heated and gives a sense of the heat of the rainforest, there are three sections to the house, Desert, Rainforest and the Rearing Room where visitors can view the raising of reptiles and amphibian and also learn about the zoos conservation work. Outside, but still considered part of the house, is a giant tortoise and rhinoceros iguana enclosure where the animals have access to a heated indoor house. The Aquarium has around 70 species of fish, the aquarium has three sections, The Amazon River, Africa and the coral reef. On the outside of the building there is a water sculpture, there are several exhibits of conservation significance on view. Notably, there is a display of endangered cichlids from Lake Barombi Mbo in Cameroon, bug World, the zoos collection of invertebrates, includes species such as Partula snails, stick and leaf insects, corals and peacock mantis shrimp. Other displays include tarantulas, black widow spiders, giant millipedes, honey bees, leaf-cutting ants, zona Brazil includes a tropical house that has Amazon tree boas and tarantulas. The two monkey enclosures house Geoffreys marmosets, black lion tamarins and titi monkeys, outside, there are aviaries for red-tailed amazon parrots, an enclosure for golden lion tamarins and three linked paddocks for tapirs and capybaras
10.
Ecology
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Ecology is the scientific analysis and study of interactions among organisms and their environment. It is a field that includes biology, geography. Ecology includes the study of interactions that organisms have with other, other organisms. Ecosystems are composed of dynamically interacting parts including organisms, the communities make up. Ecosystem processes, such as production, pedogenesis, nutrient cycling. These processes are sustained by organisms with specific life history traits, biodiversity, which refers to the varieties of species, genes, and ecosystems, enhances certain ecosystem services. Ecology is not synonymous with environment, environmentalism, natural history and it is closely related to evolutionary biology, genetics, and ethology. An important focus for ecologists is to improve the understanding of how biodiversity affects ecological function, Ecology is a human science as well. For example, the Circles of Sustainability approach treats ecology as more than the environment out there and it is not treated as separate from humans. Organisms and resources compose ecosystems which, in turn, maintain biophysical feedback mechanisms that moderate processes acting on living and non-living components of the planet, the word ecology was coined in 1866 by the German scientist Ernst Haeckel. Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics, ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology became a more rigorous science in the late 19th century. Evolutionary concepts relating to adaptation and natural selection became the cornerstones of modern ecological theory, the scope of ecology contains a wide array of interacting levels of organization spanning micro-level to a planetary scale phenomena. Ecosystems, for example, contain abiotic resources and interacting life forms, an ecosystems area can vary greatly, from tiny to vast. A single tree is of consequence to the classification of a forest ecosystem. Several generations of a population can exist over the lifespan of a single leaf. Each of those aphids, in turn, support diverse bacterial communities, biodiversity describes the diversity of life from genes to ecosystems and spans every level of biological organization. The term has several interpretations, and there are ways to index, measure, characterize
11.
Forensic science
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Forensic scientists collect, preserve, and analyze scientific evidence during the course of an investigation. In addition to their role, forensic scientists testify as expert witnesses in both criminal and civil cases and can work for either the prosecution or the defense. While any field could technically be forensic, certain sections have developed over time to encompass the majority of forensically related cases, the word forensic comes from the Latin term forensis, meaning of or before the forum. The history of the term originates from Roman times, during which a charge meant presenting the case before a group of public individuals in the forum. Both the person accused of the crime and the accuser would give speeches based on their sides of the story, the case would be decided in favor of the individual with the best argument and delivery. This origin is the source of the two usages of the word forensic – as a form of legal evidence and as a category of public presentation. In modern use, the term forensics in the place of science can be considered correct. However, the term is now so closely associated with the field that many dictionaries include the meaning that equates the word forensics with forensic science. The ancient world lacked standardized forensic practices, which aided criminals in escaping punishment, Criminal investigations and trials heavily relied on forced confessions and witness testimony. However, ancient sources do contain several accounts of techniques that foreshadow concepts in science that were developed centuries later. The first written account of using medicine and entomology to solve criminal cases is attributed to the book of Xi Yuan Lu, written in China by Song Ci in 1248, during the Song Dynasty. In one of the accounts, the case of a person murdered with a sickle was solved by an investigator who instructed everyone to bring his sickle to one location, flies, attracted by the smell of blood, eventually gathered on a single sickle. In light of this, the murderer confessed, methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the Polygraph test. In ancient India, some suspects were made to fill their mouths with dried rice, similarly, in Ancient China, those accused of a crime would have rice powder placed in their mouths. In ancient middle-eastern cultures, the accused were made to lick hot metal rods briefly, in 16th-century Europe, medical practitioners in army and university settings began to gather information on the cause and manner of death. Ambroise Paré, a French army surgeon, systematically studied the effects of violent death on internal organs, two Italian surgeons, Fortunato Fidelis and Paolo Zacchia, laid the foundation of modern pathology by studying changes that occurred in the structure of the body as the result of disease. In the late 18th century, writings on these began to appear. Two examples of English forensic science in individual legal proceedings demonstrate the use of logic
12.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
