In vascular plants, the root is the organ of a plant that lies below the surface of the soil. Roots can be aerial or aerating, that is, growing up above the ground or above water. Furthermore, a stem occurring below ground is not exceptional either. Therefore, the root is best defined as the non-nodes bearing parts of the plant's body. However, important internal structural differences between stems and roots exist; the fossil record of roots—or rather, infilled voids where roots rotted after death—spans back to the late Silurian, about 430 million years ago. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows, they can be discriminated using a range of features. The first root that comes from a plant is called the radicle. A root's four major functions are: absorption of inorganic nutrients. In response to the concentration of nutrients, roots synthesise cytokinin, which acts as a signal as to how fast the shoots can grow. Roots function in storage of food and nutrients.
The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizae, a large range of other organisms including bacteria closely associate with roots. When dissected, the arrangement of the cells in a root is root hair, epiblem, endodermis, pericycle and, the vascular tissue in the centre of a root to transport the water absorbed by the root to other places of the plant; the most striking characteristic of roots is that, roots have an endogenous origin, i.e. it originates and develops from an inner layer of the mother axis. Whereas Stem-branching and leaves are exogenous, i.e. start to develop from the cortex, an outer layer. In its simplest form, the term root architecture refers to the spatial configuration of a plant’s root system; this system can be complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients. The configuration of root systems serves to structurally support the plant, compete with other plants and for uptake of nutrients from the soil.
Roots grow to specific conditions. For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as seasonal changes. Root architecture plays the important role of providing a secure supply of nutrients and water as well as anchorage and support; the main terms used to classify the architecture of a root system are: Branch magnitude: the number of links. Topology: the pattern of branching, including:Herringbone: alternate lateral branching off a parent root Dichotomous: opposite, forked branches Radial: whorl of branches around a rootLink length: the distance between branches. Root angle: the radial angle of a lateral root’s base around the parent root’s circumference, the angle of a lateral root from its parent root, the angle an entire system spreads. Link radius: the diameter of a root. All components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli.
These developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the environmental influences and are interpreted by signal transduction pathways. The extrinsic factors that affect root architecture include gravity, light exposure and oxygen, as well as the availability or lack of nitrogen, sulphur and sodium chloride; the main hormones and respective pathways responsible for root architecture development include: Auxin – Auxin promotes root initiation, root emergence and primary root elongation. Cytokinins – Cytokinins regulate root apical meristem size and promote lateral root elongation. Gibberellins -- Together with ethylene they promote elongation. Together with auxin they promote root elongation. Gibberellins inhibit lateral root primordia initiation. Ethylene – Ethylene promotes crown root formation. Early root growth is one of the functions of the apical meristem located near the tip of the root; the meristem cells more or less continuously divide, producing more meristem, root cap cells, undifferentiated root cells.
The latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. These cells differentiate and mature into specialized cells of the root tissues. Growth from apical meristems is known as primary growth. Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants. For example, storage roots of sweet potato are not woody. Secondary growth occurs at the lateral meristems, namely the vascular cork cambium; the former forms secondary phloem, while the latter forms the periderm. In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a cylinder of tissue along the stem and root; the vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, those on the outside forming secondary phloem cells. As
A spoil tip is a pile built of accumulated spoil – the overburden or other waste rock removed during coal and ore mining. These waste materials are composed of shale, as well as smaller quantities of carboniferous sandstone and various other residues. Spoil tips are not formed of slag; the term "spoil" is used to refer to material removed when digging a foundation, tunnel, or other large excavation. Such material may be ordinary soil and rocks, or may be contaminated with chemical waste, determining how it may be disposed of. Clean spoil may be used for land reclamation. Spoil is distinct from tailings, the processed material that remains after the valuable components have been extracted from ore; the phrase originates from the French word espoilelier, a verb conveying the meaning: to seize by violence, to plunder, to take by force. Spoil tips may be conical in shape, can appear as conspicuous features of the landscape, or they may be much flatter and eroded if vegetation has established itself.
In Loos-en-Gohelle, in the former mining area of Pas-de-Calais, are a series of five perfect cones, of which two rise 100 metres from the plain. Most the term is used for the piles of waste earth materials removed during an excavation process. In surface mining for coal or other underground deposits, earth materials removed to expose the targeted deposit are piled up alongside the excavation site in spoil banks. A dredge in placer mining is used to dig up volumes of gravel and other earth materials which are sent through sluices to remove gold or other minerals, the remaining earth materials are deposited behind the dredge in spoil banks. In hydraulic mining high-pressure jets of water dislodge earth materials which are put through sluices to sort out gold or other minerals, the residuary earth materials are left in spoil banks; the excavation of ditches and canals results in spoil banks being left along the side of the canal or ditch. Spoil banks can refer to refuse heaps formed from removal of excess surface materials.
For example, alongside livestock lots spoil banks are formed of manure and other slurry periodically removed from the surface of the livestock lot areas. Spoil tips sometimes grew to millions of tons, having been abandoned, remain as huge piles today, they trap solar heat, making it difficult for vegetation to take root. Existing techniques for regreening spoil tips include the use of geotextiles to control erosion as the site is resoiled and simple vegetation such as grass is seeded on the slope; the piles create acid rock drainage, which pollutes streams and rivers. Environmental problems have included surface runoff of silt, leaching of noxious chemical compounds from spoil banks exposed to weathering; these cause contamination of ground water, other problems. Today in the United States forward-looking state and federal mining regulations require that the earth materials from excavations be removed in such a fashion that they can be replaced after the mining operations cease in a process called mine reclamation, with oversight of mining corporations, including requiring adequate reserves of monetary bonds to guarantee a completion of the reclamation process when mining becomes unprofitable or stops.
As some spoil tips resulting from industries such as coal or oil shale production can contain a high proportion of hydrocarbons or coal dust, they can commence spontaneous subterranean combustion, which can be followed by surface fires. In some coal mining districts, such fires were considered normal and no attempt was made to extinguish them; such fires can follow slow combustion of residual hydrocarbons. Their extinction can require complete encasement, which can prove impossible for technical and financial reasons. Sprinkling is ineffective and injecting water under pressure counter-productive, because it carries oxygen, bringing the risk of explosion; the perceived weak environmental and public health impact of these fires leads to waiting for their natural extinction, which can take a number of decades. With spoil tips there is a danger of landslip; the best-known example is the Aberfan disaster in Wales of 1966, killing 144. Water from heavy rainfall had built up inside the tip, weakening the structure, until it collapsed onto the school below.
In February 2013, a spoil tip was the cause of a landslip which caused the temporary closure of the Scunthorpe to Doncaster railway line in England. Several techniques of re-utilising the spoil tips exist including either geotechnics or recycling. Most old spoil tips are revegetated to provide valuable green spaces since they are inappropriate for building purposes. At Nœux-les-Mines, an artificial ski slope has been constructed on the tip. If spoil tips are considered to contain sufficient amounts of residual material, various methods are employed to remove the spoil from the site for subsequent processing; the oldest coal-based spoil tips may still contain enough coal to begin spontaneous slow combustion. This results in a form of vitrification of the shale, which acquires sufficient mechanical strength to be of use in road construction; some can therefore have a new life in being thus exploited. Conversely, others are painstakingly preserved on account of their ec
In archaeology, excavation is the exposure and recording of archaeological remains. An excavation site or "dig" is a site being studied; such a site excavation concerns itself with a specific archaeological site or a connected series of sites, may be conducted over as little as several weeks to over a number of years. Numerous specialized techniques each with its particular features are used. Resources and other practical issues do not allow archaeologists to carry out excavations whenever and wherever they choose; these constraints mean. This is with the intention of preserving them for future generations as well as recognising the role they serve in the communities that live near them. Excavation involves the recovery of several types of data from a site; these data include artifacts, ecofacts and, most archaeological context. Ideally, data from the excavation should suffice to reconstruct the site in three-dimensional space; the presence or absence of archaeological remains can be suggested by remote sensing, such as ground-penetrating radar.
Indeed, grosser information about the development of the site may be drawn from this work but the understanding of finer features requires excavation though appropriate use of augering. Excavation techniques have developed over the years from a treasure hunting process to one which seeks to understand the sequence of human activity on a given site and that site's relationship with other sites and with the landscape in which it is set; the history of excavation began with a crude search for treasure and for artifacts which fell into the category of'curio'. These curios were the subject of interest of antiquarians, it was appreciated that digging on a site destroyed the evidence of earlier people's lives which it had contained. Once the curio had been removed from its context, most of the information it held was lost, it was from this realization that antiquarianism began to be replaced by archaeology, a process still being perfected. Archaeological material tends to accumulate in events. A gardener laid a gravel path or planted a bush in a hole.
A builder back-filled the trench. Years someone built a pigsty onto it and drained the pigsty into the nettle patch. Still, the original wall blew over and so on; each event, which may have taken a short or long time to accomplish, leaves a context. This layer cake of events is referred to as the archaeological sequence or record, it is by analysis of this sequence or record that excavation is intended to permit interpretation, which should lead to discussion and understanding. The prominent processual archaeologist Lewis Binford highlighted the fact that the archaeological evidence left at a site may not be indicative of the historical events that took place there. Using an ethnoarchaeological comparison, he looked at how hunters amongst the Nunamiut Iñupiat of north central Alaska spent a great deal of time in a certain area waiting for prey to arrive there, that during this period, they undertook other tasks to pass the time, such as the carving of various objects, including a wooden mould for a mask, a horn spoon and an ivory needle, as well as repairing a skin pouch and a pair of caribou skin socks.
Binford notes that all of these activities would have left evidence in the archaeological record, but that none of them would provide evidence for the primary reason that the hunters were in the area. As he remarked, waiting for animals to hunt "represented 24% of the total man-hours of activity recorded. No tools left on the site were used, there were no immediate material "byproducts" of the "primary" activity. All of the other activities conducted at the site were boredom reducers." There are two basic types of modern archaeological excavation: Research excavation – when time and resources are available to excavate the site and at a leisurely pace. These are now exclusively the preserve of academics or private societies who can muster enough volunteer labour and funds; the size of the excavation can be decided by the director as it goes on. Development-led excavation – undertaken by professional archaeologists when the site is threatened by building development. Funded by the developer meaning that time is more of a factor as well as its being focused only on areas to be affected by building.
The workforce is more skilled however and pre-development excavations provide a comprehensive record of the areas investigated. Rescue archaeology is sometimes thought of as a separate type of excavation but in practice tends to be a similar form of development-led practice. Various new forms of excavation terminology have appeared in recent years such as Strip map and sample some of which have been criticized within the profession as jargon created to cover up for falling standards of practice. There are two main types of trial excavation in professional archaeology both associated with development-led excavation: the test pit or trench and the watching brief; the purpose of trial excavations is to determine the extent and characteristics of archaeological potential in a given area before extensive excavation work is undertaken. This is conducted in development-led excavations as part of Project management planning; the main difference between Trial
An ore is an occurrence of rock or sediment that contains sufficient minerals with economically important elements metals, that can be economically extracted from the deposit. The ores are extracted from the earth through mining; the ore grade, or concentration of an ore mineral or metal, as well as its form of occurrence, will directly affect the costs associated with mining the ore. The cost of extraction must thus be weighed against the metal value contained in the rock to determine what ore can be processed and what ore is of too low a grade to be worth mining. Metal ores are oxides, silicates, or native metals that are not concentrated in the Earth's crust, or noble metals such as gold; the ores must be processed to extract the elements of interest from the waste rock and from the ore minerals. Ore bodies are formed by a variety of geological processes; the process of ore formation is called ore genesis. An ore deposit is an accumulation of ore; this is distinct from a mineral resource. An ore deposit is one occurrence of a particular ore type.
Most ore deposits are named according to their location, or after a discoverer, or after some whimsy, a historical figure, a prominent person, something from mythology or the code name of the resource company which found it. Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis; the classifications below are typical. Mesothermal lode gold deposits, typified by the Golden Mile, Kalgoorlie Archaean conglomerate hosted gold-uranium deposits, typified by Elliot Lake, Ontario and Witwatersrand, South Africa Carlin–type gold deposits, including. Volcanic hosted massive sulfide Cu-Pb-Zn including. Stratiform arkose-hosted and shale-hosted copper, typified by the Zambian copperbelt. Stratiform tungsten, typified by the Erzgebirge deposits, Czechoslovakia Exhalative spilite-chert hosted gold deposits Mississippi valley type zinc-lead deposits Hematite iron ore deposits of altered banded iron formation Sudbury Basin nickel and copper, Canada The basic extraction of ore deposits follows these steps: Prospecting or exploration to find and define the extent and value of ore where it is located Conduct resource estimation to mathematically estimate the size and grade of the deposit Conduct a pre-feasibility study to determine the theoretical economics of the ore deposit.
This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work. Conduct a feasibility study to evaluate the financial viability and financial risks and robustness of the project and make a decision as whether to develop or walk away from a proposed mine project; this includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability and payability of the ore concentrates, engineering and infrastructure costs and equity requirements and a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation. Development to create access to an ore body and building of mine plant and equipment The operation of the mine in an active sense Reclamation to make land where a mine had been suitable for future use Ores are traded internationally and comprise a sizeable portion of international trade in raw materials both in value and volume.
This is because the worldwide distribution of ores is unequal and dislocated from locations of peak demand and from smelting infrastructure. Most base metals are traded internationally on the London Metal Exchange, with
Tailings called mine dumps, culm dumps, tails, leach residue or slickens, terra-cone, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore. Tailings are distinct from overburden, the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed; the extraction of minerals from ore can be done two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires comminution, i.e. grinding the ore into fine particles to facilitate extraction of the target element. Because of this comminution, tailings consist of a slurry of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are produced from the mill in slurry form, a mixture of fine mineral particles and water.
The effluent from the tailings from the mining of sulfidic minerals has been described as "the largest environmental liability of the mining industry". These tailings contain large amounts of pyrite and Iron sulfide, which are rejected from the sought-after ores of copper and nickel, as well as coal. Although harmless underground, these minerals are reactive toward air in the presence of microorganisms, leading to acid mine drainage; when applied to coal mining tailings ponds and oil sands tailings ponds, the term "tailings" refers to fine waste suspended in water. Bauxite tailings is a waste product generated in the industrial production of aluminium. Making provision for the 77 million tons, produced annually is one of the most significant problems for the aluminium mining industry. Early mining operations did not take adequate steps to make tailings areas environmentally safe after closure. Modern mines those in jurisdictions with well-developed mining regulations and those operated by responsible mining companies include the rehabilitation and proper closure of tailings areas in their costs and activities.
For example, the Province of Quebec, requires not only the submission of a closure plan before the start of mining activity, but the deposit of a financial guarantee equal to 100% of the estimated rehabilitation costs. Tailings dams are the most significant environmental liability for a mining project; the fraction of tailings to ore can range from 90–98% for some copper ores to 20–50% of the other minerals. The rejected minerals and rocks liberated through mining and processing have the potential to damage the environment by releasing toxic metals, by acid drainage, or by damaging aquatic wildlife that rely on clear water; the greatest danger of tailings ponds is dam failure, with the most publicized failure in the U. S. being the failure of a coal slurry dam in the West Virginia Buffalo Creek Flood of 1972, which killed 125 people. On average, there is one big accident involving a tailings dam each year. Tailings ponds can be a source of acid drainage, leading to the need for permanent monitoring and treatment of water passing through the tailings dam.
Other disasters caused by tailings dam failures are, the 2000 Baia Mare cyanide spill and the Ajka alumina plant accident. Tailings were disposed of in the most convenient manner, such as in downstream running water or down drains; because of concerns about these sediments in the water and other issues, tailings ponds came into use. The sustainability challenge in the management of tailings and waste rock is to dispose of material, such that it is inert or, if not and contained, to minimise water and energy inputs and the surface footprint of wastes and to move toward finding alternate uses. Bounded by impoundments, these dams use "local materials" including the tailings themselves, may be considered embankment dams. Traditionally, the only option for tailings storage was to deal with a tailings slurry; this slurry is a dilute stream of the tailings solids within water, sent to the tailings storage area. The modern tailings designer has a range of tailings products to choose from depending upon how much water is removed from the slurry prior to discharge.
The removal of water not only can create a better storage system in some cases but can assist in water recovery, a major issue as many mines are in arid regions. In a 1994 description of tailings impoundments, the U. S. EPA stated that dewatering methods may be prohibitively expensive except in special circumstances. Subaqueous storage of tailings has been used. Tailing ponds are areas of refused mining tailings where the waterborne refuse material is pumped into a pond to allow the sedimentation of solids from the water; the pond is impounded with a dam, known as tailings impoundments or tailings dams. It was estimated in 2000; the ponded water is of some benefit as it minimizes fine tailings from being transported by wind into populated areas where the toxic chemicals could be hazardous to human health.
In mining, gangue is the oft commercially worthless material that surrounds, or is mixed with, a wanted mineral in an ore deposit. It is thus distinct from overburden, the waste rock or materials overlying an ore or mineral body that are displaced during mining without being processed, from tailings, rock stripped of valuable minerals; the separation of mineral from gangue is known as mineral processing, mineral dressing, or ore dressing. It is a necessary, significant, aspect of mining, it can be a complicated process, depending on the nature of the minerals involved. For example, galena, an ore of lead, is found in large pieces within its gangue, so it does not need extensive processing to remove it. For any particular ore deposit, at any particular point in time, the concentration of the wanted mineral in the gangue material will determine whether it is commercially viable to mine that deposit; the ease with which the ore can be separated plays an important part. Early mining ventures, having unsophisticated methods could not achieve a high degree of separation, so significant quantities of minerals found their way into the waste mineral dumps of mines.
As the value of a mineral increases, or when new and cheaper means of processing the gangue to extract the ore are introduced, it may become worthwhile to rework such old dumps to retrieve the minerals they still contain. Minerals that were once thought of as gangue, were dumped, may find a commercial use; when this happens, the old dumps are reworked to extract the wanted mineral. For example, in copper mines in the 19th century the mineral arsenopyrite was dumped until arsenic became popular as an insecticide in the century. In the 21st century, the use of gangue has been considered from an environmental point of view. For example, in 2002, about 130 million tons of gangue were produced per year from coal mining in China. This, mixed with the 60 million tons of coal mud produced, could be used for power generation; the estimated cost of such projects would be up to 4 billion yuan, but would be expected to save just over 4 million tons of standard coal per year. Froth flotation Magnetic separation Vanning Extractive Metallurgy Mineral processing An Elementary Outline Of Mechanical Processes, by G. W. Danforth.
1912. Elimination Of Gangue
OCLC Online Computer Library Center, Incorporated d/b/a OCLC is an American nonprofit cooperative organization "dedicated to the public purposes of furthering access to the world's information and reducing information costs". It was founded in 1967 as the Ohio College Library Center. OCLC and its member libraries cooperatively produce and maintain WorldCat, the largest online public access catalog in the world. OCLC is funded by the fees that libraries have to pay for its services. OCLC maintains the Dewey Decimal Classification system. OCLC began in 1967, as the Ohio College Library Center, through a collaboration of university presidents, vice presidents, library directors who wanted to create a cooperative computerized network for libraries in the state of Ohio; the group first met on July 5, 1967 on the campus of the Ohio State University to sign the articles of incorporation for the nonprofit organization, hired Frederick G. Kilgour, a former Yale University medical school librarian, to design the shared cataloging system.
Kilgour wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library. The plan was to merge the catalogs of Ohio libraries electronically through a computer network and database to streamline operations, control costs, increase efficiency in library management, bringing libraries together to cooperatively keep track of the world's information in order to best serve researchers and scholars; the first library to do online cataloging through OCLC was the Alden Library at Ohio University on August 26, 1971. This was the first online cataloging by any library worldwide. Membership in OCLC is based on use of services and contribution of data. Between 1967 and 1977, OCLC membership was limited to institutions in Ohio, but in 1978, a new governance structure was established that allowed institutions from other states to join. In 2002, the governance structure was again modified to accommodate participation from outside the United States.
As OCLC expanded services in the United States outside Ohio, it relied on establishing strategic partnerships with "networks", organizations that provided training and marketing services. By 2008, there were 15 independent United States regional service providers. OCLC networks played a key role in OCLC governance, with networks electing delegates to serve on the OCLC Members Council. During 2008, OCLC commissioned two studies to look at distribution channels. In early 2009, OCLC negotiated new contracts with the former networks and opened a centralized support center. OCLC provides bibliographic and full-text information to anyone. OCLC and its member libraries cooperatively produce and maintain WorldCat—the OCLC Online Union Catalog, the largest online public access catalog in the world. WorldCat has holding records from private libraries worldwide; the Open WorldCat program, launched in late 2003, exposed a subset of WorldCat records to Web users via popular Internet search and bookselling sites.
In October 2005, the OCLC technical staff began a wiki project, WikiD, allowing readers to add commentary and structured-field information associated with any WorldCat record. WikiD was phased out; the Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988. A browser for books with their Dewey Decimal Classifications was available until July 2013; until August 2009, when it was sold to Backstage Library Works, OCLC owned a preservation microfilm and digitization operation called the OCLC Preservation Service Center, with its principal office in Bethlehem, Pennsylvania. The reference management service QuestionPoint provides libraries with tools to communicate with users; this around-the-clock reference service is provided by a cooperative of participating global libraries. Starting in 1971, OCLC produced catalog cards for members alongside its shared online catalog. OCLC commercially sells software, such as CONTENTdm for managing digital collections.
It offers the bibliographic discovery system WorldCat Discovery, which allows for library patrons to use a single search interface to access an institution's catalog, database subscriptions and more. OCLC has been conducting research for the library community for more than 30 years. In accordance with its mission, OCLC makes its research outcomes known through various publications; these publications, including journal articles, reports and presentations, are available through the organization's website. OCLC Publications – Research articles from various journals including Code4Lib Journal, OCLC Research, Reference & User Services Quarterly, College & Research Libraries News, Art Libraries Journal, National Education Association Newsletter; the most recent publications are displayed first, all archived resources, starting in 1970, are available. Membership Reports – A number of significant reports on topics ranging from virtual reference in libraries to perceptions about library funding. Newsletters – Current and archived newsletters for the library and archive community.
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