1.
Dust storm
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A dust storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand, fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another. Drylands around North Africa and the Arabian peninsula are the main sources of airborne dust. Also with some contributions from Iran, Pakistan and India into the Arabian Sea, the term dust storm is more likely to be used when finer particles are blown long distances, especially when the dust storm affects urban areas. As the force of wind passing over loosely held particles increases, particles of sand first start to vibrate, as they repeatedly strike the ground, they loosen and break off smaller particles of dust which then begin to travel in suspension. At wind speeds above that which causes the smallest to suspend, there will be a population of dust grains moving by a range of mechanisms, suspension, saltation, a study from 2008 finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating and this process has been found to double the number of particles predicted by previous theories. Particles become loosely held mainly due to drought or arid conditions, gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm. S. Following the passage of a dry cold front, convective instability resulting from cooler air riding over heated ground can maintain the dust storm initiated at the front. In desert areas, dust and sand storms are most commonly caused by either thunderstorm outflows, the vertical extent of the dust or sand that is raised is largely determined by the stability of the atmosphere above the ground as well as by the weight of the particulates. In some cases, dust and sand may be confined to a shallow layer by a low-lying temperature inversion. In other instances, dust may be lifted as high as 20,000 feet high, drought and wind contribute to the emergence of dust storms, as do poor farming and grazing practices by exposing the dust and sand to the wind. One poor farming practice which contributes to dust storms is dryland farming, particularly poor dryland farming techniques are intensive tillage or not having established crops or cover crops when storms strike at particularly vulnerable times prior to revegetation. In a semi-arid climate, these practices increase susceptibility to dust storms, however, soil conservation practices may be implemented to control wind erosion. A sandstorm can transport and carry large volumes of sand unexpectedly, Dust storms can carry large amounts of dust, with the leading edge being composed of a wall of thick dust as much as 1.6 km high. Dust and sand storms which come off the Sahara Desert are locally known as a simoom or simoon, the haboob is a sandstorm prevalent in the region of Sudan around Khartoum, with occurrences being most common in the summer. The Sahara desert is a key source of dust storms, particularly the Bodélé Depression and an area covering the confluence of Mauritania, Mali, and Algeria. Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing loss in Niger, Chad, northern Nigeria
2.
Texas
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Texas is the second largest state in the United States by both area and population. Other major cities include Austin, the second most populous state capital in the U. S. Texas is nicknamed the Lone Star State to signify its former status as an independent republic, and as a reminder of the states struggle for independence from Mexico. The Lone Star can be found on the Texan state flag, the origin of Texass name is from the word Tejas, which means friends in the Caddo language. Due to its size and geologic features such as the Balcones Fault, although Texas is popularly associated with the U. S. southwestern deserts, less than 10 percent of Texas land area is desert. Most of the centers are located in areas of former prairies, grasslands, forests. Traveling from east to west, one can observe terrain that ranges from coastal swamps and piney woods, to rolling plains and rugged hills, the term six flags over Texas refers to several nations that have ruled over the territory. Spain was the first European country to claim the area of Texas, Mexico controlled the territory until 1836 when Texas won its independence, becoming an independent Republic. In 1845, Texas joined the United States as the 28th state, the states annexation set off a chain of events that caused the Mexican–American War in 1846. A slave state before the American Civil War, Texas declared its secession from the U. S. in early 1861, after the Civil War and the restoration of its representation in the federal government, Texas entered a long period of economic stagnation. One Texan industry that thrived after the Civil War was cattle, due to its long history as a center of the industry, Texas is associated with the image of the cowboy. The states economic fortunes changed in the early 20th century, when oil discoveries initiated a boom in the state. With strong investments in universities, Texas developed a diversified economy, as of 2010 it shares the top of the list of the most Fortune 500 companies with California at 57. With a growing base of industry, the leads in many industries, including agriculture, petrochemicals, energy, computers and electronics, aerospace. Texas has led the nation in export revenue since 2002 and has the second-highest gross state product. The name Texas, based on the Caddo word tejas meaning friends or allies, was applied by the Spanish to the Caddo themselves, during Spanish colonial rule, the area was officially known as the Nuevo Reino de Filipinas, La Provincia de Texas. Texas is the second largest U. S. state, behind Alaska, though 10 percent larger than France and almost twice as large as Germany or Japan, it ranks only 27th worldwide amongst country subdivisions by size. If it were an independent country, Texas would be the 40th largest behind Chile, Texas is in the south central part of the United States of America. Three of its borders are defined by rivers, the Rio Grande forms a natural border with the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas to the south
3.
Particle
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A particle is a minute fragment or quantity of matter. In the physical sciences, a particle is a small localized object to which can be ascribed several physical or chemical properties such as volume or mass. Particles can also be used to create models of even larger objects depending on their density. The term particle is rather general in meaning, and is refined as needed by various scientific fields, something that is composed of particles may be referred to as being particulate. However, the particulate is most frequently used to refer to pollutants in the Earths atmosphere. The concept of particles is particularly useful when modelling nature, as the treatment of many phenomena can be complex. It can be used to make simplifying assumptions concerning the processes involved, francis Sears and Mark Zemansky, in University Physics, give the example of calculating the landing location and speed of a baseball thrown in the air. The treatment of large numbers of particles is the realm of statistical physics, the term particle is usually applied differently to three classes of sizes. The term macroscopic particle, usually refers to particles much larger than atoms and these are usually abstracted as point-like particles, or even invisible. This is even though they have volumes, shapes, structures, examples of macroscopic particles would include powder, dust, sand, pieces of debris during a car accident, or even objects as big as the stars of a galaxy. Another type, microscopic particles usually refers to particles of sizes ranging from atoms to molecules, such as carbon dioxide, nanoparticles and these particles are studied in chemistry, as well as atomic and molecular physics. The smallest of particles are the particles, which refer to particles smaller than atoms. These particles are studied in particle physics, because of their extremely small size, the study of microscopic and subatomic particles fall in the realm of quantum mechanics. Particles can also be classified according to composition, composite particles refer to particles that have composition – that is particles which are made of other particles. For example, an atom is made of six protons, eight neutrons. By contrast, elementary particles refer to particles that are not made of other particles, according to our current understanding of the world, only a very small number of these exist, such as the leptons, quarks or gluons. However it is possible some of these might turn up to be composite particles after all. While composite particles can very often be considered point-like, elementary particles are truly punctual, both elementary and composite particles, are known to undergo particle decay
4.
Aeolian processes
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Aeolian processes, also spelled eolian or æolian, pertain to wind activity in the study of geology and weather and specifically to the winds ability to shape the surface of the Earth. Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture, although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts. The term is derived from the name of the Greek god Aeolus, wind erodes the Earths surface by deflation and by abrasion. Regions which experience intense and sustained erosion are called deflation zones, most aeolian deflation zones are composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. Almost half of Earths desert surfaces are stony deflation zones, the rock mantle in desert pavements protects the underlying material from deflation. A dark, shiny stain, called desert varnish or rock varnish, is found on the surfaces of some desert rocks that have been exposed at the surface for a long period of time. Manganese, iron oxides, hydroxides, and clay minerals form most varnishes, deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are generally small, but may be up to kilometers in diameter. In parts of Antarctica wind-blown snowflakes that are technically sediments have also caused abrasion of exposed rocks, grinding by particles carried in the wind creates grooves or small depressions. Ventifacts are rocks which have cut, and sometimes polished. Sculpted landforms, called yardangs, are up to tens of meters high, the famous Great Sphinx of Giza in Egypt may be a modified yardang. Particles are transported by winds through suspension, saltation and creeping along the ground, small particles may be held in the atmosphere in suspension. Upward currents of air support the weight of suspended particles and hold them indefinitely in the surrounding air, typical winds near Earths surface suspend particles less than 0.2 millimeters in diameter and scatter them aloft as dust or haze. Saltation is downwind movement of particles in a series of jumps or skips, saltation normally lifts sand-size particles no more than one centimeter above the ground and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains that jump up to continue the saltation, the grain may also hit larger grains that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains. Surface creep accounts for as much as 25 percent of grain movement in a desert, aeolian turbidity currents are better known as dust storms. Air over deserts is cooled significantly when rain passes through it and this cooler and denser air sinks toward the desert surface. When it reaches the ground, the air is deflected forward, crops, people, villages, and possibly even climates are affected by dust storms
5.
Types of volcanic eruptions
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Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed, some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions, the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of eruption, driven by the compression of gas within magma. Within these wide-defining eruptive types are several subtypes, the weakest are Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions, subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra, effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary widely in strength, on the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a crater near their peak. Some volcanoes exhibit lateral and fissure eruptions, notably, many Hawaiian eruptions start from rift zones, and some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was likely triggered by magma that took a route from the mantle over just a few months. The volcanic explosivity index is a scale, from 0 to 8 and it is used by the Smithsonian Institutions Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes, the vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of events, characterized by the effusive eruption of very fluid basalt-type lavas with low gaseous content
6.
Air pollution
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Air pollution occurs when harmful substances including particulates and biological molecules are introduced into Earths atmosphere. It may cause diseases, allergies or death in humans, it may cause harm to other living organisms such as animals and food crops. Human activity and natural processes can both generate air pollution, indoor air pollution and poor urban air quality are listed as two of the worlds worst toxic pollution problems in the 2008 Blacksmith Institute Worlds Worst Polluted Places report. According to the 2014 WHO report, air pollution in 2012 caused the deaths of around 7 million people worldwide, an air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance can be particles, liquid droplets, or gases. A pollutant can be of natural origin or man-made, pollutants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption, other examples include carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide released from factories. Secondary pollutants are not emitted directly, rather, they form in the air when primary pollutants react or interact. Ground level ozone is a prominent example of a secondary pollutant, some pollutants may be both primary and secondary, they are both emitted directly and formed from other primary pollutants. Substances emitted into the atmosphere by human activity include, Carbon dioxide - Debate continues over whether carbon dioxide should be classified as an atmospheric pollutant, because of its role as a greenhouse gas it has been described as the leading pollutant and the worst climate pollution. Against this it is argued that carbon dioxide is a component of the atmosphere, essential for plant life. This question of terminology has practical effects, for example as determining whether the U. S. Clean Air Act is deemed to regulate CO2 emissions, CO2 increase in earths atmosphere has been accelerating. Sulfur oxides - particularly sulfur dioxide, a compound with the formula SO2. SO2 is produced by volcanoes and in industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide, further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the impact of the use of these fuels as power sources. Nitrogen oxides - Nitrogen oxides, particularly nitrogen dioxide, are expelled from high temperature combustion and they can be seen as a brown haze dome above or a plume downwind of cities. Nitrogen dioxide is a compound with the formula NO2
7.
Built environment
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In social science, the term built environment refers to the man-made surroundings that provide the setting for human activity, ranging in scale from buildings to parks. It has been defined as the space in which people live, work. The built environment encompasses places and spaces created or modified by people including buildings, parks, in recent years, public health research has expanded the definition of built environment to include healthy food access, community gardens, mental health, walkability and bikeability. The effort was in partnership with others who believed that beautifying American cities would improve the moral compass of the cities and this beautification process included parks and architectural design. For example, community forest user group in Nepal is multidimensional institution, in public health, built environment refers to physical environments that are designed with health and wellness as integral parts of the communities. Research has indicated that the way neighborhoods are created can affect both the activity and mental health of the communities’ residents. Studies have shown that built environments that were designed to improve physical activity are linked to higher rates of physical activity. Neighborhoods with more walkability had lower rates of obesity as well as increased physical activity among its residents and they also had lower rates of depression, higher social capital, and less alcohol abuse. Walkability features in these neighborhoods include safety, sidewalk construction, as well as destinations in which to walk, in addition, the perception of a walkable neighborhood, one that is perceived to have good sidewalks and connectivity, is correlated with higher rates of physical activity. Assessments of walkability have been completed through the use of GIS programs and this example of a walkability assessment tool determines distances to grocery stores and other amenities, as well as connectivity and intersection frequency using specific addresses. Assessments such as the Street Smart Walk Score can be utilized by city, public health also addresses additional components of built environments including “bikeability” and healthy food access such as proximity to grocery stores and community gardens. Bikeability refers to the access that an area has granted to safe biking through multiple bike paths, both walkability and bikeability have been cited as determinants of physical activity. Access to healthy food is also an important component of the built environment, a higher density of convenience stores has been associated with obesity in children. In contrast, improved access to community supermarkets and farmer’s markets is correlated with lower overweight status, specifically in low income neighborhoods, the presence of a local grocery store is correlated with lower BMI/overweight risk. Community gardens are considered a part of the built environment. The intersection of health with other disciplines is evident in the design process of built environments which includes environmental planning, policy development. Research suggests that people are active in mixed-use communities or those that incorporate retail and residential. Those who preferred to walk and live in walkable environments often have lower obesity rates, in landscape architecture, the built environment is understood to mean a human-made landscape, as distinguished from the natural environment, for example, a city park is a built environment
8.
Pollen
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Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes. If pollen lands on a compatible pistil or female cone, it germinates, individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is useful in paleoecology, paleontology, archaeology. Pollen in plants is used for transferring haploid male genetic material from the anther of a flower to the stigma of another in cross-pollination. In a case of self-pollination, this takes place from the anther of a flower to the stigma of the same flower. Pollen itself is not the male gamete, each pollen grain contains vegetative cells and a generative cell. In flowering plants the vegetative tube cell produces the pollen tube, pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower. Pollen grains come in a variety of shapes, sizes. Pollen grains of pines, firs, and spruces are winged, the smallest pollen grain, that of the forget-me-not, is around 6 µm in diameter. Wind-borne pollen grains can be as large as about 90–100 µm, in angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a partially differentiated dermis. As the flower develops, four groups of cells form within the anther. The fertile sporogenous cells are surrounded by layers of cells that grow into the wall of the pollen sac. Some of the cells grow into nutritive cells that supply nutrition for the microspores that form by meiotic division from the sporogenous cells, in a process called microsporogenesis, four haploid microspores are produced from each diploid sporogenous cell, after meiotic division. After the formation of the four microspores, which are contained by callose walls, the exine is what is preserved in the fossil record. Two basic types of microsporogenesis are recognised, simultaneous and successive, in simultaneous microsporogenesis meiotic steps I and II are completed prior to cytokinesis, whereas in successive microsporogenesis cytokinesis follows. While there may be a continuum with intermediate forms, the type of microsporogenesis has systematic significance, the predominant form amongst the monocots is successive, but there are important exceptions. During microgametogenesis, the unicellular microspores undergo mitosis and develop into mature microgametophytes containing the gametes, in some flowering plants, germination of the pollen grain may begin even before it leaves the microsporangium, with the generative cell forming the two sperm cells. Except in the case of submerged aquatic plants, the mature pollen grain has a double wall
9.
Fur
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Fur is used in reference to the hair of non-human mammals, particularly those with extensive body hair coverage that is generally soft and thick, as opposed to the stiffer bristles on most pigs. The term pelage – first known use in English c.1828 – is sometimes used to refer to the hair of an animal as a complete coat. Fur is also used to refer to animal pelts which have been processed into leather with the still attached. The words fur or furry are also used, more casually, to refer to hair-like growths or formations, particularly when the subject being referred to exhibits a dense coat of fine, soft hairs. If layered, rather than grown as a coat, it may consist of short down hairs, long guard hairs. Mammals with reduced amounts of fur are called naked, as with the naked mole-rat, or hairless. An animal with commercially valuable fur is known within the fur industry as a furbearer and its principal function is thermoregulation, it maintains a layer of dry air next to the skin and repels water, thus providing thermal insulation. Guard hair — the top consisting of longer, generally coarser. The distal ends of the guard hairs provide the externally visible layer of the coat of most mammals with well-developed fur and this layer of the coat displays the most marked pigmentation and gloss, including coat patterns adapted to display or camouflage. It is also adapted to shedding water and blocking sunlight, protecting the undercoat and skin from external factors such as rain, many animals, such as domestic cats, erect their guard hairs as part of their threat display when agitated. Mammals with well-developed down and guard hairs also usually have numbers of awn hairs. These begin their growth much as guard hairs do, but change their mode of growth and this portion of the hair is called awn. The rest of the growth is thin and wavy, much like down hair, in many species of mammals, the awn hairs comprise the bulk of the visible coat. Hair is one of the characteristics of mammals, however. These are often called naked or hairless, some mammals naturally have reduced amounts of fur. Some semiaquatic or aquatic mammals such as cetaceans, pinnipeds and hippopotamuses have evolved hairlessness, the naked mole-rat has evolved hairlessness, perhaps as an adaptation to their subterranean life-style. Two of the largest extant mammals, the elephant and the rhinoceros, are largely hairless. The hairless bat is mostly hairless but does have short bristly hairs around its neck, on its front toes, most hairless animals cannot go in the sun for long periods of time, or stay in the cold for too long
10.
Textile
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A textile or cloth is a flexible material consisting of a network of natural or artificial fibres. Yarn is produced by spinning raw fibres of wool, flax, cotton, hemp, Textiles are formed by weaving, knitting, crocheting, knotting, or felting. The words fabric and cloth are used in textile assembly trades as synonyms for textile, however, there are subtle differences in these terms in specialized usage. Textile refers to any material made of interlacing fibres, a fabric is a material made through weaving, knitting, spreading, crocheting, or bonding that may be used in production of further goods. Cloth may be used synonymously with fabric but is often a piece of fabric used for a specific purpose. The word textile is from Latin, from the adjective textilis, meaning woven, from textus, the word cloth derives from the Old English clað, meaning a cloth, woven or felted material to wrap around one, from Proto-Germanic kalithaz. The discovery of dyed flax fibres in a cave in the Republic of Georgia dated to 34,000 BCE suggests textile-like materials were made even in prehistoric times. The production of textiles is a craft whose speed and scale of production has been altered almost beyond recognition by industrialization, however, for the main types of textiles, plain weave, twill, or satin weave, there is little difference between the ancient and modern methods. Textiles have an assortment of uses, the most common of which are for clothing and for such as bags. In the household they are used in carpeting, upholstered furnishings, window shades, towels, coverings for tables, beds, and other flat surfaces, in the workplace they are used in industrial and scientific processes such as filtering. Textiles are used in traditional crafts such as sewing, quilting. Textiles for industrial purposes, and chosen for other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for applications, medical textiles, geotextiles, agrotextiles. In all these applications stringent performance requirements must be met, woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of self-powering nanosystems using vibrations created by everyday actions like wind or body movements. Fashion designers commonly rely on textile designs to set their fashion collections apart from others, armani, the late Gianni Versace, and Emilio Pucci can be easily recognized by their signature print driven designs. Textiles can be made from many materials and these materials come from four main sources, animal, plant, mineral, and synthetic. In the past, all textiles were made from natural fibres, including plant, animal, in the 20th century, these were supplemented by artificial fibres made from petroleum. Textiles are made in various strengths and degrees of durability, from the finest gossamer to the sturdiest canvas, microfibre refers to fibres made of strands thinner than one denier
11.
Paper
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Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. It is a material with many uses, including writing, printing, packaging, cleaning. The modern pulp and paper industry is global, with China leading its production, the oldest known archaeological fragments of the immediate precursor to modern paper, date to the 2nd century BC in China. The pulp papermaking process is ascribed to Cai Lun, a 2nd-century AD Han court eunuch, with paper as an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age. Because of papers introduction to the West through the city of Baghdad, in the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts. In 1844, the Canadian inventor Charles Fenerty and the German F. G. Keller independently developed processes for pulping wood fibres, before the industrialisation of the paper production the most common fibre source was recycled fibres from used textiles, called rags. The rags were from hemp, linen and cotton, a process for removing printing inks from recycled paper was invented by German jurist Justus Claproth in 1774. Today this method is called deinking and it was not until the introduction of wood pulp in 1843 that paper production was not dependent on recycled materials from ragpickers. The word paper is etymologically derived from Latin papyrus, which comes from the Greek πάπυρος, although the word paper is etymologically derived from papyrus, the two are produced very differently and the development of the first is distinct from the development of the second. Papyrus is a lamination of natural plant fibres, while paper is manufactured from fibres whose properties have changed by maceration. To make pulp from wood, a chemical pulping process separates lignin from cellulose fibres and this is accomplished by dissolving lignin in a cooking liquor, so that it may be washed from the cellulose, this preserves the length of the cellulose fibres. Paper made from chemical pulps are also known as wood-free papers–not to be confused with paper, this is because they do not contain lignin. The pulp can also be bleached to produce paper, but this consumes 5% of the fibres, chemical pulping processes are not used to make paper made from cotton. There are three main chemical pulping processes, the process dates back to the 1840s and it was the dominant method extent before the second world war. Most pulping operations using the process are net contributors to the electricity grid or use the electricity to run an adjacent paper mill. Another advantage is that this process recovers and reuses all inorganic chemical reagents, soda pulping is another specialty process used to pulp straws, bagasse and hardwoods with high silicate content. There are two major mechanical pulps, thermomechanical pulp and groundwood pulp, in the TMP process, wood is chipped and then fed into steam heated refiners, where the chips are squeezed and converted to fibres between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones to be made into fibres
12.
Human skin
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The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system, the skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, though nearly all human skin is covered with hair follicles, it can appear hairless. There are two types of skin, hairy and glabrous skin. The adjective cutaneous means of the skin. Because it interfaces with the environment, skin plays an important immunity role in protecting the body against pathogens and its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue and this is often discolored and depigmented. In humans, skin pigmentation varies among populations, and skin type can range from dry to oily, such skin variety provides a rich and diverse habitat for bacteria that number roughly 1000 species from 19 phyla, present on the human skin. Skin has mesodermal cells, pigmentation, such as provided by melanocytes. It also contains DNA repair enzymes that help reverse UV damage, one form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner and this has led to the classification of people on the basis of skin color. The skin is the largest organ in the human body, for the average adult human, the skin has a surface area of between 1. 5-2.0 square meters. The thickness of the skin varies considerably over all parts of the body, an example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. The average square inch of skin holds 650 sweat glands,20 blood vessels,60,000 melanocytes, the average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers, depending on a variety of factors, skin is composed of three primary layers, the epidermis, the dermis and the hypodermis. Epidermis, epi coming from the Greek meaning over or upon, is the outermost layer of the skin. It forms the waterproof, protective wrap over the surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina. The main type of cells make up the epidermis are Merkel cells, keratinocytes, with melanocytes
13.
Meteorite
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When the object enters the atmosphere, various factors like friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate that energy. It then becomes a meteor and forms a fireball, also known as a shooting/falling star, meteorites that survive atmospheric entry and impact vary greatly in size. For geologists, a bolide is a large enough to create a crater. Meteorites that are recovered after being observed as they transit the atmosphere or impact the Earth are called meteorite falls, all others are known as meteorite finds. As of April 2016, there were about 1,140 witnessed falls that have specimens in the worlds collections, there are more than 38,660 well-documented meteorite finds. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition, meteorites smaller than 2 mm are classified as micrometeorites. Extraterrestrial meteorites are such objects that have impacted other celestial bodies and they have been found on the Moon and Mars. Meteorites are always named for the places they were found, usually a town or geographic feature. In cases where many meteorites were found in one place, the name may be followed by a number or letter, the name designated by the Meteoritical Society is used by scientists, catalogers, and most collectors. Most meteoroids disintegrate when entering the Earths atmosphere, usually, five to ten a year are observed to fall and are subsequently recovered and made known to scientists. Few meteorites are large enough to create large impact craters, instead, they typically arrive at the surface at their terminal velocity and, at most, create a small pit. Large meteoroids may strike the ground with a significant fraction of their escape velocity, the kind of crater will depend on the size, composition, degree of fragmentation, and incoming angle of the impactor. The force of such collisions has the potential to cause widespread destruction, the most frequent hypervelocity cratering events on the Earth are caused by iron meteoroids, which are most easily able to transit the atmosphere intact. In contrast, even relatively large stony or icy bodies like small comets or asteroids, up to millions of tons, are disrupted in the atmosphere, and do not make impact craters. Although such disruption events are uncommon, they can cause a concussion to occur. Very large stony objects, hundreds of meters in diameter or more, weighing tens of millions of tons or more, can reach the surface and cause large craters, such events are generally so energetic that the impactor is completely destroyed, leaving no meteorites. Several phenomena are well documented during witnessed meteorite falls too small to produce hypervelocity craters, various colors have been reported, including yellow, green, and red. Flashes and bursts of light can occur as the object breaks up, explosions, detonations, and rumblings are often heard during meteorite falls, which can be caused by sonic booms as well as shock waves resulting from major fragmentation events
14.
Laptop
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Laptops are folded shut for transportation, and thus are suitable for mobile use. Although originally there was a distinction between laptops and notebooks, the former being bigger and heavier than the latter, as of 2014, there is often no longer any difference. Laptops are commonly used in a variety of settings, such as at work, in education, Internet surfing using sites such as YouTube and for personal multimedia, most 2016-era laptops also have integrated webcams and built-in microphones. Laptops can be powered either from a battery or by an external power supply from an AC adapter. Hardware specifications, such as the speed and memory capacity. Design elements, form factor, and construction can also vary significantly between models depending on intended use, as portable computers evolved into the modern laptop, they became widely used for a variety of purposes. The terms laptop and notebook are used interchangeably to describe a computer in English. Regardless of the etymology, by the late 1990s, the terms were interchangeable, as the personal computer became feasible in 1971, the idea of a portable personal computer soon followed. A personal, portable information manipulator was imagined by Alan Kay at Xerox PARC in 1968, the IBM Special Computer APL Machine Portable was demonstrated in 1973. This prototype was based on the IBM PALM processor, the IBM5100, the first commercially available portable computer, appeared in September 1975, and was based on the SCAMP prototype. As 8-bit CPU machines became widely accepted, the number of portables increased rapidly, the Osborne 1, released in 1981, used the Zilog Z80 and weighed 23.6 pounds. It had no battery, a 5 in CRT screen, in the same year the first laptop-sized portable computer, the Epson HX-20, was announced. The Epson had an LCD screen, a battery. Both Tandy/RadioShack and HP also produced portable computers of varying designs during this period, the first laptops using the flip form factor appeared in the early 1980s. The Dulmont Magnum was released in Australia in 1981–82, but was not marketed internationally until 1984–85, the US$8,150 GRiD Compass 1101, released in 1982, was used at NASA and by the military, among others. The Sharp PC-5000, Ampere and Gavilan SC released in 1983, the Gavilan SC was the first computer described as a laptop by its manufacturer, while the Ampere had a modern clamshell design. The Toshiba T1100 won acceptance not only among PC experts but the market as a way to have PC portability. From 1983 onward, several new techniques were developed and included in laptops, including the touchpad, the pointing stick
15.
Heat sink
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In computers, heat sinks are used to cool central processing units or graphics processors. A heat sink is designed to maximize its surface area in contact with the medium surrounding it. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink, heat sink attachment methods and thermal interface materials also affect the die temperature of the integrated circuit. Thermal adhesive or thermal grease improve the heat sinks performance by filling air gaps between the sink and the heat spreader on the device. A heat sink is made out of copper and/or aluminium. Copper is used because it has many desirable properties for thermally efficient, first and foremost, copper is an excellent conductor of heat. This means that high thermal conductivity allows heat to pass through it quickly. Aluminum is used in applications where weight is a big concern, a heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is air, but can also be water. If the fluid medium is water, the sink is frequently called a cold plate. In thermodynamics a heat sink is a reservoir that can absorb an arbitrary amount of heat without significantly changing temperature. Practical heat sinks for electronic devices must have a higher than the surroundings to transfer heat by convection, radiation. The power supplies of electronics are not 100% efficient, so heat is produced that may be detrimental to the function of the device. As such, a sink is included in the design to disperse heat to improve efficient energy use. To understand the principle of a sink, consider Fouriers law of heat conduction. The rate at which heat is transferred by conduction, q k, is proportional to the product of the temperature gradient, Q k = − k A d T d x Consider a heat sink in a duct, where air flows through the duct. It is assumed that the heat sink base is higher in temperature than the air, when compact heat exchangers are calculated, the logarithmic mean air temperature is used. M ˙ is the air flow rate in kg/s
16.
House dust mite
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The house dust mite is a cosmopolitan pyroglyphid that lives in human habitation. Dust mites feed on detritus, such as flakes of shed human skin. House dust mites are a cause of asthma and allergic symptoms worldwide. The mites gut contains potent digestive enzymes that persist in their feces and are major inducers of allergic reactions such as wheezing, the mites exoskeleton can also contribute to allergic reactions. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under the skin and are not parasitic, House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye. A typical house dust mite measures 0. 2–0.3 millimetres in length, for accurate identification, one needs at least 10× magnification. The body of the house dust mite has a striated cuticle, the average life cycle for a male house dust mite is 10–19 days. A mated female house dust mite can last up to 70 days, in a 10-week life span, a house dust mite will produce approximately 2,000 fecal particles and an even larger number of partially digested enzyme-covered dust particles. House dust mites are associated with allergic rhinitis and asthma, efforts to remove these mites from the environment have not been found to be effective. Immunotherapy may be useful in those affected, subcutaneous injections have better evidence than under the tongue dosing. List of mites associated with cutaneous reactions House dust mites on the University of Florida / Institute of Food and Agricultural Sciences Featured Creatures website
17.
Arachnid
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Arachnids are a class of joint-legged invertebrate animals, in the subphylum Chelicerata. The term is derived from the Greek word ἀράχνη, meaning spider, spiders are the largest order in the class. Almost all extant arachnids are terrestrial, living mainly on land, however, some inhabit freshwater environments and, with the exception of the pelagic zone, marine environments as well. They comprise over 100,000 named species, including spiders, scorpions, harvestmen, ticks, mites, almost all adult arachnids have eight legs, and arachnids may be easily distinguished from insects by this fact, since insects have six legs. However, arachnids also have two pairs of appendages that have become adapted for feeding, defense, and sensory perception. The first pair, the chelicerae, serve in feeding and defense, the next pair of appendages, the pedipalps, have been adapted for feeding, locomotion, and/or reproductive functions. In Solifugae, the palps are quite leg-like, so that animals appear to have ten legs. The larvae of mites and Ricinulei have only six legs, a fourth pair usually appears when they moult into nymphs, however, mites are variable, as well as eight, there are adult mites with six or even four legs. Arachnids are further distinguished from insects by the fact they do not have antennae or wings and their body is organized into two tagmata, called the prosoma, or cephalothorax, and the opisthosoma, or abdomen. The cephalothorax is derived from the fusion of the cephalon and the thorax, the abdomen is segmented in the more primitive forms, but varying degrees of fusion between the segments occur in many groups. It is typically divided into a preabdomen and postabdomen, although this is clearly visible in scorpions, and in some orders, such as the Acari. A telson is present in scorpions, where it has modified to a stinger. Like all arthropods, arachnids have an exoskeleton, and they also have a structure of cartilage-like tissue, called the endosternite. The endosternite is even calcified in some Opiliones, most arachnids lack extensor muscles in the distal joints of their appendages. Spiders and whipscorpions extend their limbs hydraulically using the pressure of their hemolymph, solifuges and some harvestmen extend their knees by the use of highly elastic thickenings in the joint cuticle. Scorpions, pseudoscorpions and some harvestmen have evolved muscles that extend two leg joints at once, the equivalent joints of the pedipalps of scorpions though, are extended by elastic recoil. This type of system has almost certainly evolved from the book lungs. The excretory glands of arachnids include up to four pairs of coxal glands along the side of the prosoma, many arachnids have only one or the other type of excretory gland, although several do have both
18.
Allergen
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An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. In technical terms, an allergen is a capable of stimulating a type-I hypersensitivity reaction in atopic individuals through Immunoglobulin E responses. Most humans mount significant Immunoglobulin E responses only as a defense against parasitic infections, however, some individuals may respond to many common environmental antigens. This hereditary predisposition is called atopy, in atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity. Sensitivities vary widely from one person to another, a very broad range of substances can be allergens to sensitive individuals. Allergens can be found in a variety of sources, such as dust mite excretion, pollen, Food allergies are not as common as food sensitivity, but some foods such as peanuts, nuts, seafood and shellfish are the cause of serious allergies in many people. Officially, the United States Food and Drug Administration does recognize eight foods as being common for reactions in a large segment of the sensitive population. These include peanuts, tree nuts, eggs, milk, shellfish, fish, wheat and their derivatives, see the FDA website for complete details. Canada recognizes all eight of the allergens recognized by the US, and also recognizes sesame seeds, the European Union additionally recognizes celery. Various trees and wood products such as paper, cardboard, MDF etc. can also cause mild to severe allergy symptoms through touch or inhalation of sawdust such as asthma, other common causes of serious allergy are wasp, fire ant and bee stings, penicillin, and latex. An extremely serious form of a reaction is called anaphylaxis. This depends on the kind of tree or grass, for instance, some trees such as oak, elm, and maple pollinate in the spring, while grasses such as Bermuda, timothy and orchard pollinate in the summer. Grass allergy is generally linked to hay fever because their symptoms, symptoms include rhinitis, which causes sneezing and a runny nose, as well as allergic conjunctivitis, which includes watering and itchy eyes. Also an initial tickle on the roof of the mouth or in the back of the throat may be experienced, also, depending on the season, the symptoms may be more severe and people may experience coughing, wheezing, and irritability. A few people even become depressed, lose their appetite, or have problems sleeping, moreover, since the sinuses may also become congested, some people experience headaches. The immune system also has influence on seasonal allergies, since it reacts differently to diverse allergens like pollen. When an allergen enters the body of an individual that is predisposed to allergies, it triggers an immune reaction and these allergen antibodies migrate to mast cells lining the nose, eyes and lungs. Some symptoms that differentiate allergies from a cold include, No fever, mucous secretions are runny and clear
19.
Carpet
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A carpet is a textile floor covering typically consisting of an upper layer of pile attached to a backing. The pile was made from wool, but, since the 20th century, synthetic fibers such as polypropylene, nylon or polyester are often used. The pile usually consists of twisted tufts which are typically heat-treated to maintain their structure, Carpets can be made in any colour by using differently dyed fibers. Carpets can have different types of patterns and motifs used to decorate the surface. In the 2000s, carpets are used in industrial and commercial establishments such as stores and hotels. Carpet is commonly made in widths of 12 feet and 15 feet in the USA,4 m and 5 m in Europe. Wall-to-wall carpet is distinguished from rugs or mats, which are loose-laid floor coverings, as wall-to-wall carpet is fixed to the floor, child labour has often been used in Asia for hand knotting rugs. The term carpet comes from Old French carpite, one derivation of the term states that the French term came from the Old Italian carpita, from the verb carpire meaning to pluck. The Online Etymology Dictionary states that the carpet was first used in English in the late 13th century, with the meaning coarse cloth. The Online Etymology Dictionary states that the term comes, the meaning of the term carpet shifted in the 15th century to refer to floor coverings. The term carpet is used interchangeably with the term rug. Some sources define a carpet as stretching from wall to wall, another definition treats rugs as of lower quality or of smaller size, with carpets quite often having finished ends. A third common definition is that a carpet is fixed in place while a rug is simply laid out on the floor. Historically, the carpet was also applied to table and wall coverings. The term rug was first used in English in the 1550s, the term is of. Scandinavian origin, compare Norwegian dialectal rugga coarse coverlet, from Old Norse rogg shaggy tuft, from Proto-Germanic *rawwa-, perhaps related to rag and rough. The meaning of rug. evolved to coverlet, wrap, then mat for the floor, the carpet is produced on a loom quite similar to woven fabric. The pile can be plush or Berber, plush carpet is a cut pile and Berber carpet is a loop pile. There are new styles of carpet combining the two styles called cut and loop carpeting, normally many colored yarns are used and this process is capable of producing intricate patterns from predetermined designs
20.
Libya
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The three traditional parts of the country are Tripolitania, Fezzan and Cyrenaica. With an area of almost 1.8 million square kilometres, Libya is the fourth largest country in Africa, Libya has the 10th-largest proven oil reserves of any country in the world. The largest city and capital, Tripoli, is located in western Libya, the other large city is Benghazi, which is located in eastern Libya. Libya has been inhabited by Berbers since the late Bronze Age, the Phoenicians established trading posts in western Libya, and ancient Greek colonists established city-states in eastern Libya. Libya was variously ruled by Carthaginians, Persians, Egyptians and Greeks before becoming a part of the Roman Empire, Libya was an early center of Christianity. After the fall of the Western Roman Empire, the area of Libya was mostly occupied by the Vandals until the 7th century, in the 16th century, the Spanish Empire and the Knights of St John occupied Tripoli, until Ottoman rule began in 1551. Libya was involved in the Barbary Wars of the 18th and 19th centuries, Ottoman rule continued until the Italian occupation of Libya resulted in the temporary Italian Libya colony from 1911 to 1943. During the Second World War Libya was an important area of warfare in the North African Campaign, the Italian population then went into decline. Libya became an independent kingdom in 1951, a military coup in 1969 overthrew King Idris I, beginning a period of sweeping social reform. Since then, Libya has experienced a period of instability, the European Union is involved in an operation to disrupt human trafficking networks exploiting refugees fleeing from wars in Africa for Europe. At least two political bodies claim to be the government of Libya, the Council of Deputies is internationally recognized as the legitimate government, but it does not hold territory in the capital, Tripoli, instead meeting in the Cyrenaica city of Tobruk. Parts of Libya are outside of either governments control, with various Islamist, rebel, the United Nations is sponsoring peace talks between the Tobruk and Tripoli-based factions. An agreement to form an interim government was signed on 17 December 2015. Under the terms of the agreement, a nine-member Presidency Council, the leaders of the new government, called the Government of National Accord, arrived in Tripoli on 5 April 2016. Since then the GNC, one of the two governments, has disbanded to support the new GNA. The name Libya was introduced in 1934 for Italian Libya, reviving the name for Northwest Africa. The name was based on use in 1903 by Italian geographer Federico Minutilli. It was intended to supplant terms applied to Ottoman Tripolitania, the region of what is today Libya having been ruled by the Ottoman Empire from 1551 to 1911
21.
Human impact on the environment
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Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity, and other resources. The term anthropogenic designates an effect or object resulting from human activity, the atmospheric scientist Paul Crutzen introduced the term Anthropocene in the mid-1970s. The term is used in the context of pollution emissions that are produced as a result of human activities but applies broadly to all major human impacts on the environment. Environmental impacts caused by the application of technology are often perceived as unavoidable for several reasons, third, according to the second law of thermodynamics, order can be increased within a system only by increasing disorder or entropy outside the system. Thus, technologies can create “order” in the economy only at the expense of increasing “disorder” in the environment. According to a number of studies, increased entropy is likely to be correlated to environmental impacts. The environmental impact of agriculture based on the wide variety of agricultural practices employed around the world. Ultimately, the impact depends on the production practices of the system used by farmers. The connection between emissions into the environment and the system is indirect, as it also depends on other climate variables such as rainfall. An example of a means-based indicator would be the quality of groundwater, an indicator reflecting the loss of nitrate to groundwater would be effect-based. The environmental impact of agriculture involves a variety of factors from the soil, to water, the air, animal and soil diversity, plants, and the food itself. Some of the issues that are related to agriculture are climate change, deforestation, genetic engineering, irrigation problems, pollutants, soil degradation. These conservation issues are part of conservation, and are addressed in fisheries science programs. There is a gap between how many fish are available to be caught and humanity’s desire to catch them, a problem that gets worse as the world population grows. The journal Science published a study in November 2006, which predicted that, at prevailing trends. Many countries, such as Tonga, the United States, Australia and New Zealand, the impacts stem from the changed hydrological conditions owing to the installation and operation of the scheme. An irrigation scheme draws water from the river and distributes it over the irrigated area. These may be called direct effects, effects on soil and water quality are indirect and complex, and subsequent impacts on natural, ecological and socio-economic conditions are intricate
22.
Desert
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A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation, about one third of the land surface of the world is arid or semi-arid. This includes much of the regions where little precipitation occurs. Deserts can be classified by the amount of precipitation falls, by the temperature that prevails. Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces, although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and this picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface, rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes, other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place, other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate, there may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur, plants and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles, some annual plants germinate, bloom and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to cool and find enough food and water to survive. Many are nocturnal and stay in the shade or underground during the heat of the day and they tend to be efficient at conserving water, extracting most of their needs from their food and concentrating their urine. Some animals remain in a state of dormancy for long periods and they then reproduce rapidly while conditions are favorable before returning to dormancy. People have struggled to live in deserts and the surrounding lands for millennia. Nomads have moved their flocks and herds to wherever grazing is available, the cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. Many trade routes have been forged across deserts, especially across the Sahara Desert, large numbers of slaves were also taken northwards across the Sahara
23.
Sahara
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The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres is comparable to the area of the United States. The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of tropical savanna around the Niger River valley. The Sahara can be divided into several regions including, the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, the name Sahara is derived from ṣaḥārā, the plural of the Arabic word for desert. The Sahara covers large parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and it covers 9 million square kilometres, amounting to 31% of Africa. If all areas with an annual precipitation of less than 250 mm were included. It is one of three physiographic provinces of the African massive physiographic division. The Sahara is mainly rocky hamada, Ergs form only a minor part, wind or rare rainfall shape the desert features, sand dunes, dune fields, sand seas, stone plateaus, gravel plains, dry valleys, dry lakes, and salt flats. Unusual landforms include the Richat Structure in Mauritania, several deeply dissected mountains, many volcanic, rise from the desert, including the Aïr Mountains, Ahaggar Mountains, Saharan Atlas, Tibesti Mountains, Adrar des Iforas, and the Red Sea hills. The highest peak in the Sahara is Emi Koussi, a volcano in the Tibesti range of northern Chad. The central Sahara is hyperarid, with sparse vegetation, the northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in wadis, where moisture collects. In the central, hyperarid region, there are subdivisions of the great desert, Tanezrouft, the Ténéré, the Libyan Desert, the Eastern Desert. These extremely arid areas often receive no rain for years, the northern limit also corresponds to the 100 mm isohyet of annual precipitation. To the south, the Sahara is bounded by the Sahel, the southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha, or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the limit of the Sahara corresponds to the 150 mm isohyet of annual precipitation. The Sahara is the worlds largest low-latitude hot desert and this steady descending airflow causes a warming and a drying effect in the upper troposphere
24.
Saltation (geology)
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For definition, and other use disambiguation, see Saltation In geology, saltation is a specific type of particle transport by fluids such as wind or water. It occurs when material is removed from a bed and carried by the fluid. Examples include pebble transport by rivers, sand drift over desert surfaces, soil blowing over fields, at low fluid velocities, loose material rolls downstream, staying in contact with the surface. This is called creep or reptation, here the forces exerted by the fluid on the particle are only enough to roll the particle around the point of contact with the surface. Once the wind speed reaches a critical value, termed the impact or fluid threshold. These particles are accelerated by the fluid, and pulled downward by gravity, if a particle has obtained sufficient speed from the acceleration by the fluid, it can eject, or splash, other particles in saltation, which propagates the process. Depending on the surface, the particle could also disintegrate on impact, in air, this process of saltation bombardment creates most of the dust in dust storms. In rivers, this process repeats continually, gradually eroding away the river bed, for these particles, vertical drag forces due to turbulent fluctuations in the fluid are similar in magnitude to the weight of the particle. These smaller particles are carried by the fluid in suspension, the smaller the particle, the less important the downward pull of gravity, and the longer the particle is likely to stay in suspension. A recent study finds that saltating sand particles induces an electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating and this process has been found to double the number of particles predicted by previous theory. This is significant in meteorology because it is primarily the saltation of sand particles which dislodges smaller dust particles into the atmosphere. Dust particles and other such as soot affect the amount of sunlight received by the atmosphere and earth. Saltation layers can also form in avalanches
25.
Troposphere
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The troposphere is the lowest portion of Earths atmosphere, and is also where nearly all weather takes place. It contains approximately 75% of the mass and 99% of the total mass of water vapor. The average depths of the troposphere are 20 km in the tropics,17 km in the mid latitudes, the lowest part of the troposphere, where friction with the Earths surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform, atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The tropopause is a layer, where the air temperature ceases to decrease with height. Most of the phenomena we associate with day-to-day weather occur in the troposphere, by volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor. The chemical composition of the troposphere is essentially uniform, with the exception of water vapor. The source of vapor is at the surface through the processes of evaporation. Thus the proportion of water vapor is normally greatest near the surface, the pressure of the atmosphere is maximum at sea level and decreases with altitude. This is because the atmosphere is nearly in hydrostatic equilibrium. The temperature of the troposphere generally decreases as altitude increases, the rate at which the temperature decreases, − d T / d z, is called the environmental lapse rate. The ELR is nothing more than the difference in temperature between the surface and the tropopause divided by the height. The reason for this difference is that the ground absorbs most of the suns energy. Meanwhile, the radiation of heat at the top of the results in the cooling of that part of the atmosphere. The ELR assumes the atmosphere is still, but as air is heated it becomes buoyant, when a parcel of air rises, it expands, because the pressure is lower at higher altitudes. As the air expands, it pushes the surrounding air outward. As energy transfer to a parcel of air by way of heat is very slow, such a process is called an adiabatic process
26.
Particulates
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Atmospheric particulate matter – also known as particulate matter or particulates – are microscopic solid or liquid matter suspended in the Earths atmosphere. The term aerosol commonly refers to the mixture, as opposed to the particulate matter alone. Sources of particulate matter can be man-made or natural and they have impacts on climate and precipitation that adversely affect human health. The smaller PM2.5 were particularly deadly, with a 36% increase in lung cancer per 10 μg/m3 as it can penetrate deeper into the lungs, some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes, coal combustion in developing countries is the primary method for heating homes and supplying energy. The composition of aerosols and particles depends on their source, wind-blown mineral dust tends to be made of mineral oxides and other material blown from the Earths crust, this particulate is light-absorbing. In addition, sea spray aerosols may contain organic compounds, which influence their chemistry, Secondary particles derive from the oxidation of primary gases such as sulfur and nitrogen oxides into sulfuric acid and nitric acid. The gases from which they originate—may have an origin and a natural biogenic origin. In the presence of ammonia, secondary aerosols often take the form of ammonium salts and this is mainly because the presence of sulfate and nitrate causes the aerosols to increase to a size that scatters light effectively. Organic matter can be primary or secondary, the latter part deriving from the oxidation of VOCs. Organic matter influences the atmospheric radiation field by both scattering and absorption, another important aerosol type is elemental carbon, this aerosol type includes strongly light-absorbing material and is thought to yield large positive radiative forcing. Organic matter and elemental carbon together constitute the carbonaceous fraction of aerosols, Secondary organic aerosols, tiny tar balls resulting from combustion products of internal combustion engines, have been identified as a danger to health. The chemical composition of the aerosol directly affects how it interacts with solar radiation, the chemical constituents within the aerosol change the overall refractive index. The refractive index will determine how light is scattered and absorbed. The particles are hygroscopic due to the presence of sulfur, and SO2 is converted to sulfate when high humidity and this causes the reduced visibility and yellow color. Aerosol particles of natural origin tend to have a larger radius than human-produced aerosols such as particle pollution, the false-color maps in the third image on this page show where there are natural aerosols, human pollution, or a mixture of both, monthly. Most of the Southern Hemisphere is covered by ocean, where the largest source of aerosols is natural sea salt from dried sea spray. Because land is concentrated in the Northern Hemisphere, the amount of small aerosols from fires, over land, patches of large-radius aerosols appear over deserts and arid regions, most prominently, the Sahara Desert in north Africa and the Arabian Peninsula, where dust storms are common
27.
Radiative forcing
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Radiative forcing or climate forcing is defined as the difference of insolation absorbed by the Earth and energy radiated back to space. Typically, radiative forcing is quantified at the tropopause in units of watts per meter of the Earths surface. A positive forcing warms the system, while negative forcing cools it, causes of radiative forcing include changes in insolation and the concentrations of radiatively active gases, commonly known as greenhouse gases and aerosols. Almost all of the energy that affects Earths climate is received as radiant energy from the Sun, the planet and its atmosphere absorb and reflect some of the energy, while long-wave energy is radiated back into space. The balance between absorbed and radiated energy determines the global temperature. Because the atmosphere absorbs some of the re-radiated long-wave energy, the planet is warmer than it would be in the absence of the atmosphere, any such alteration is a radiative forcing, and changes the balance. This happens continuously as sunlight hits the surface, clouds and aerosols form, in this report radiative forcing values are for changes relative to preindustrial conditions defined at 1750 and are expressed in Watts per square meter. In simple terms, radiative forcing is. the rate of energy change per unit area of the globe as measured at the top of the atmosphere, a typical value of λ is 0.8 K/, which gives a warming of 3K for doubling of CO2. Radiative forcing can be estimated in different ways for different components, for solar irradiance, the radiative forcing is simply the change in the average amount of solar energy absorbed per square meter of the Earths area. Since the Earths cross-sectional area exposed to the Sun is equal to 1/4 of the area of the Earth. This must be multiplied by the fraction of incident sunlight that is absorbed, F=, the albedo is approximately 0.3, so F is approximately equal to 0.7. Thus, the forcing is the change in the solar intensity divided by 4. Likewise, a change in albedo will produce a solar forcing equal to the change in albedo divided by 4 multiplied by the solar constant and these calculations can often be simplified into an algebraic formulation that is specific to that gas. The relationship between carbon dioxide and radiative forcing is logarithmic and thus increased concentrations have a progressively smaller warming effect, a different formula applies for other greenhouse gases such as methane and N2O or CFCs, with coefficients that can be found e. g. in the IPCC reports. Radiative forcing is a way to compare different causes of perturbations in a climate system. We propose an alternative, the troposphere and stratosphere forcing. We present GCM calculations showing that it is a more reliable predictor of this GCMs surface temperature change than radiative forcing. It is a candidate to supplement radiative forcing as a metric for comparing different mechanisms, in this quote, GCM stands for global circulation model, and the word predictive does not refer to the ability of GCMs to forecast climate change
28.
Caribbean
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The Caribbean is a region that consists of the Caribbean Sea, its islands and the surrounding coasts. The region is southeast of the Gulf of Mexico and the North American mainland, east of Central America, situated largely on the Caribbean Plate, the region comprises more than 700 islands, islets, reefs and cays. These islands generally form island arcs that delineate the eastern and northern edges of the Caribbean Sea, in a wider sense, the mainland countries of Belize, Guyana, Suriname and French Guiana are often included due to their political and cultural ties with the region. Geopolitically, the Caribbean islands are usually regarded as a subregion of North America and are organized into 30 territories including sovereign states, overseas departments, and dependencies. From December 15,1954, to October 10,2010, there was a known as the Netherlands Antilles composed of five states. The West Indies cricket team continues to represent many of those nations, the region takes its name from that of the Caribs, an ethnic group present in the Lesser Antilles and parts of adjacent South America at the time of the Spanish conquest. The two most prevalent pronunciations of Caribbean are KARR-ə-BEE-ən, with the accent on the third syllable. The former pronunciation is the older of the two, although the variant has been established for over 75 years. It has been suggested that speakers of British English prefer KARR-ə-BEE-ən while North American speakers more typically use kə-RIB-ee-ən, usage is split within Caribbean English itself. The word Caribbean has multiple uses and its principal ones are geographical and political. The Caribbean can also be expanded to include territories with strong cultural and historical connections to slavery, European colonisation, the United Nations geoscheme for the Americas accords the Caribbean as a distinct region within the Americas. Physiographically, the Caribbean region is mainly a chain of islands surrounding the Caribbean Sea, to the north, the region is bordered by the Gulf of Mexico, the Straits of Florida and the Northern Atlantic Ocean, which lies to the east and northeast. To the south lies the coastline of the continent of South America, politically, the Caribbean may be centred on socio-economic groupings found in the region. For example, the known as the Caribbean Community contains the Co-operative Republic of Guyana. Bermuda and the Turks and Caicos Islands, which are in the Atlantic Ocean, are members of the Caribbean Community. The Commonwealth of the Bahamas is also in the Atlantic and is a member of the Caribbean Community. According to the ACS, the population of its member states is 227 million people. The geography and climate in the Caribbean region varies, Some islands in the region have relatively flat terrain of non-volcanic origin and these islands include Aruba, Barbados, Bonaire, the Cayman Islands, Saint Croix, the Bahamas, and Antigua
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Amazon basin
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The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 7,500,000 km2 and it is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela. Most of the basin is covered by the Amazon Rainforest, also known as Amazonia, with a 5,500,000 km2 area of dense tropical forest, this is the largest rainforest in the world. The Amazon River rises in the Andes Mountains at the west of the basin with its tributary the Marañón River in Peru. It is usually considered to be the second longest river in the world, however, a team of Brazilian scientists has claimed that the Amazon is the longest river in the world. It covers about 6,400 km before draining into the Atlantic Ocean, the Amazon and its tributaries form the largest volume of water. The Amazon accounts for about 20% of the water carried to the oceans by rivers. Some of the Amazon rainforests are deforested because of the increasing of cattle ranches, the highest point in the watershed of the Amazon is the peak of Yerupajá at 6,635 m. The Amazon basin formerly flowed west to Pacific Ocean until the Andes formed, politically the basin is divided into the Brazilian Amazônia Legal, the Peruvian Amazon, the Amazon region of Colombia and parts of Bolivia, Ecuador and the Venezuelan state of Amazonas. Plant growth is dense and its variety of inhabitants is comparatively high due to the heavy rainfall. Little sunlight reaches the ground due to the roof canopy by plants. The ground remains dark and damp and only shade tolerant vegetation will grow here, orchids and bromeliads exploit trees and other plants to get closer to the sunlight. They grow hanging onto the branches or tree trunks with aerial roots, not as parasites, species of tropical trees native to the Amazon include Brazil nut, rubber tree and Assai palm. More than 1,400 species of mammals are found in the Amazon and its larger mammals include the jaguar, ocelot, capybara and South American tapir. About 1500 bird species inhabit the Amazon Basin, the biodiversity of the Amazon and the sheer number of diverse bird species is given by the number of different bird families that reside in these humid forests. An example of such would be the family, to which the Guianan cock-of-the-rock belong. Birds such as toucans, and hummingbirds are found here. Macaws are famous for gathering by the hundreds along the cliffs of the Amazon River
30.
Thermohaline circulation
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Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
31.
Middle East
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The Middle East is a transcontinental region centered on Western Asia and Egypt. The corresponding adjective is Middle-Eastern and the noun is Middle-Easterner. The term has come into usage as a replacement of the term Near East beginning in the early 20th century. Arabs, Turks, Persians, Kurds, and Azeris constitute the largest ethnic groups in the region by population. Indigenous minorities of the Middle East include Jews, Assyrians and other Arameans, Baloch, Berbers, Copts, Druze, Lurs, Mandaeans, Samaritans, Shabaks, Tats, in the Middle East, there is also a Romani community. European ethnic groups form a diaspora in the region include Albanians, Bosniaks, Circassians, Crimean Tatars, Franco-Levantines. Among other migrant populations are Bengalis as well as other Indians, Chinese, Filipinos, Indonesians, Pakistanis, the history of the Middle East dates back to ancient times, with the importance of the region being recognized for millennia. Most of the countries border the Persian Gulf have vast reserves of crude oil. The term Middle East may have originated in the 1850s in the British India Office, however, it became more widely known when American naval strategist Alfred Thayer Mahan used the term in 1902 to designate the area between Arabia and India. During this time the British and Russian Empires were vying for influence in Central Asia, Mahan realized not only the strategic importance of the region, but also of its center, the Persian Gulf. Mahan first used the term in his article The Persian Gulf and International Relations, published in September 1902 in the National Review, a British journal. The Middle East, if I may adopt a term which I have not seen, will some day need its Malta, as well as its Gibraltar, it does not follow that either will be in the Persian Gulf. The British Navy should have the facility to concentrate in force if occasion arise, about Aden, India, mahans article was reprinted in The Times and followed in October by a 20-article series entitled The Middle Eastern Question, written by Sir Ignatius Valentine Chirol. During this series, Sir Ignatius expanded the definition of Middle East to include regions of Asia which extend to the borders of India or command the approaches to India. After the series ended in 1903, The Times removed quotation marks from subsequent uses of the term, in the late 1930s, the British established the Middle East Command, which was based in Cairo, for its military forces in the region. After that time, the term Middle East gained broader usage in Europe, the description Middle has also led to some confusion over changing definitions. Before the First World War, Near East was used in English to refer to the Balkans and the Ottoman Empire, while Middle East referred to Iran, the Caucasus, Afghanistan, Central Asia, and Turkestan. The first official use of the term Middle East by the United States government was in the 1957 Eisenhower Doctrine, the Associated Press Stylebook says that Near East formerly referred to the farther west countries while Middle East referred to the eastern ones, but that now they are synonymous
32.
Climate change
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Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time. Climate change may refer to a change in weather conditions. Climate change is caused by such as biotic processes, variations in solar radiation received by Earth, plate tectonics. Certain human activities have also identified as significant causes of recent climate change. Scientists actively work to understand past and future climate by using observations, more recent data are provided by the instrumental record. The most general definition of change is a change in the statistical properties of the climate system when considered over long periods of time. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, the term climate change is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change is caused by activity, as opposed to changes in climate that may have resulted as part of Earths natural processes. In this sense, especially in the context of environmental policy, within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels affect. A related term is climatic change, in 1966, the World Meteorological Organization proposed the term climatic change to encompass all forms of climatic variability on time-scales longer than 10 years, regardless of cause. Change was a given and climatic was used as an adjective to describe this kind of change, when it was realized that human activities had a potential to drastically alter the climate, the term climate change replaced climatic change as the dominant term to reflect an anthropogenic cause. Climate change was incorporated in the title of the Intergovernmental Panel on Climate Change, Climate change, used as a noun, became an issue rather than the technical description of changing weather. On the broadest scale, the rate at which energy is received from the Sun and this energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions. Factors that can shape climate are called climate forcings or forcing mechanisms, there are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings. There are also key factors which when exceeded can produce rapid change. Forcing mechanisms can be internal or external. Internal forcing mechanisms are natural processes within the system itself
33.
Desertification
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Desertification is a type of land degradation in which relatively dry area of land becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as climate change. Desertification is a significant global ecological and environmental problem, considerable controversy exists over the proper definition of the term desertification for which Helmut Geist has identified more than 100 formal definitions. Another major contribution to the controversy comes from the sub-grouping of types of desertification, the worlds most noted deserts have been formed by natural processes interacting over long intervals of time. During most of times, deserts have grown and shrunk independent of human activities. Paleodeserts are large sand seas now inactive because they are stabilized by vegetation, some extending beyond the present margins of deserts, such as the Sahara. Drylands occupy approximately 40–41% of Earth’s land area and are home to more than 2 billion people. As of 1998, the then-current degree of expansion of the Sahara was not well known, due to a lack of recent. Causes of desertification in Sahel, The impact of global warming, in this area, the level of desertification is very high compared to other areas in the world. All areas situated in the part of Africa are characterized by a dry climate, hot temperatures. So, droughts are the rule in the Sahel region, development of the desertification process in Sahel, Some studies have shown that Africa has lost approximately 650000 km² of its productive agricultural land over the past 50 years. The propagation of desertification in this area is considerable, Some statistics have shown that since 1900, the Sahara has expanded by 250 km, covering an additional area of 6000 square kilometers. Impacts of desertification in Sahel, The survey, done by the institute for development, had demonstrated that this dryness is spreading fast in the Sahelian countries. Desertification in the Sahel can affect more than one billion of its inhabitants, 70% of the arid area has deteriorated and water resources have disappeared, leading to soil degradation. The loss of topsoil means that plants take root firmly. The United Nations Convention says that six million Sahelian citizens would have to give up the desertified zones of sub-Saharan Africa for North Africa. As the desertification takes place, the landscape may progress through different stages, on gradually sloped terrain, desertification can create increasingly larger empty spaces over a large strip of land, a phenomenon known as Brousse tigrée. A mathematical model of this phenomenon proposed by C, klausmeier attributes this patterning to dynamics in plant-water interaction
34.
Iran
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Iran, also known as Persia, officially the Islamic Republic of Iran, is a sovereign state in Western Asia. Comprising a land area of 1,648,195 km2, it is the second-largest country in the Middle East, with 82.8 million inhabitants, Iran is the worlds 17th-most-populous country. It is the country with both a Caspian Sea and an Indian Ocean coastline. The countrys central location in Eurasia and Western Asia, and its proximity to the Strait of Hormuz, Tehran is the countrys capital and largest city, as well as its leading economic and cultural center. Iran is the site of to one of the worlds oldest civilizations, the area was first unified by the Iranian Medes in 625 BC, who became the dominant cultural and political power in the region. The empire collapsed in 330 BC following the conquests of Alexander the Great, under the Sassanid Dynasty, Iran again became one of the leading powers in the world for the next four centuries. Beginning in 633 AD, Arabs conquered Iran and largely displaced the indigenous faiths of Manichaeism and Zoroastrianism by Islam, Iran became a major contributor to the Islamic Golden Age that followed, producing many influential scientists, scholars, artists, and thinkers. During the 18th century, Iran reached its greatest territorial extent since the Sassanid Empire, through the late 18th and 19th centuries, a series of conflicts with Russia led to significant territorial losses and the erosion of sovereignty. Popular unrest culminated in the Persian Constitutional Revolution of 1906, which established a monarchy and the countrys first legislative body. Following a coup instigated by the U. K. Growing dissent against foreign influence and political repression led to the 1979 Revolution, Irans rich cultural legacy is reflected in part by its 21 UNESCO World Heritage Sites, the third-largest number in Asia and 11th-largest in the world. Iran is a member of the UN, ECO, NAM, OIC. Its political system is based on the 1979 Constitution which combines elements of a democracy with a theocracy governed by Islamic jurists under the concept of a Supreme Leadership. A multicultural country comprising numerous ethnic and linguistic groups, most inhabitants are Shia Muslims, the largest ethnic groups in Iran are the Persians, Azeris, Kurds and Lurs. Historically, Iran has been referred to as Persia by the West, due mainly to the writings of Greek historians who called Iran Persis, meaning land of the Persians. As the most extensive interactions the Ancient Greeks had with any outsider was with the Persians, however, Persis was originally referred to a region settled by Persians in the west shore of Lake Urmia, in the 9th century BC. The settlement was then shifted to the end of the Zagros Mountains. In 1935, Reza Shah requested the international community to refer to the country by its native name, opposition to the name change led to the reversal of the decision, and Professor Ehsan Yarshater, editor of Encyclopædia Iranica, propagated a move to use Persia and Iran interchangeably
35.
Khuzestan Province
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Khuzestan Province is one of the 31 provinces of Iran. It is in the southwest of the country, bordering Iraq and its capital is Ahvaz and it covers an area of 63,238 km2. In 2014 it was placed in Region 4, as the Iranian province with the oldest history, it is often referred to as the birthplace of the nation, as this is where the history of the Elamites begins. Historically, one of the most important regions of the Ancient Near East, Khuzestan is what historians refer to as ancient Elam, the Achaemenid Old Persian term for Elam was Hujiyā when they conquered it from the Elamites, which is present in the modern name. Khuzestan, meaning the Land of the Khuz refers to the inhabitants of this province. In Middle Persian the term evolves into Khuz and Kuzi, the pre-Islamic Partho-Sasanian Inscriptions gives the name of the province as Khwuzestan. The seat of the province has for the most of its history been in the reaches of the land, first at Susa. This town is now known as Ahvaz, however, later in the Sasanian time and throughout the Islamic era, the provincial seat returned and stayed at Shushtar, until the late Qajar period. With the increase in the international sea commerce arriving on the shores of Khuzistan, the River Karun is navigable all the way to Ahvaz. The town was refurbished by the order of the Qajar king, Naser al-Din Shah and renamed after him. Shushtar quickly declined, while Ahvaz/Nâseri prospered to the present day, currently, Khuzestan has 18 representatives in Irans parliament, the Majlis, and 6 representatives in the Assembly of Experts. Khuzestan is known for its diversity, the population of Khuzestan consists of Lurs, Iranian Arabs, Qashqai people, Afshar tribe, indigenous Persians. Khuzestans population is predominantly Shia Muslim, but there are small Christian, Jewish, Sunni, half of Khuzestans population is Lurs. The name Khuzestan means The Land of the Khuzi, and refers to the inhabitants of this province. The name of the city of Ahvaz also has the same origin as the name Khuzestan, being an Arabic broken plural from the compound name, Suq al-Ahvaz --the medieval name of the town, that replaced the Sasanian Persian name of the pre-Islamic times. The entire province was known as the Khudhi or the Khooji until the reign of the Safavid king Tahmasp I. The southern half of the province—south, southwest of the Ahwaz Ridge, had come by the 17th century to be known—at least to the imperial Safavid chancery as Arabistan. The contemporaneous history, the Alamara-i Abbasi by Iskandar Beg Munshi, written during the reign of king Abbas I, the northern half continued to be called Khuzestan
36.
Road debris
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Road debris, a form of road hazard, is debris on or off a road. Road debris includes substances, materials, and objects that are foreign to the normal roadway environment, Debris may be produced by vehicular or nonvehicular sources, but in all cases it is considered litter, a form of solid waste. Debris may tend to collect in areas where vehicles do not drive, such as on the edges, around traffic islands, Road spray or tire kickup is road debris that has been kicked up, pushed out, or sprayed out from a tire. In 2004, a AAA Foundation for Traffic Safety study revealed that vehicle-related road debris caused 25,000 accidents, Road debris can be caused by various factors, including objects falling off vehicles or natural disasters and weather, specifically wind, storms, tornadoes, hurricanes, etc. Examples of road include, Particulates, dust, dirt, sand. Ice, snow, water, and other liquids like grease and engine oil Particles of road salt and other de-icers Plants and their parts branches, leaves, sticks, twigs, seeds etc. Litter, food, furniture, mattresses, and other garbage/trash/waste Glass, nails, screws, in the year 2011, the National Highway Traffic Safety Administrations Traffic Safety Facts found that more than 800 persons were killed across America by non-fixed objects. California had the highest number of deaths for any state. In 2004, a AAA Foundation for Traffic Safety study revealed that vehicle-related road debris caused 25,000 accidents—and nearly 100 deaths—each year, at highway speeds, even small debris can be deadly. Collision with road debris resulted in a vehicle accident at the World Solar Challenge 2007 in Australia. Road debris, for the most part, tends to collect in areas where vehicles such as cars. In urban areas, this tends to be on the edges and on the crown of the road, in rural areas, debris collects in the middle of the lane and on the outside of corners and bends. Road debris can be dangerous to bicyclists, who may have to travel outside the cycle lane. Flooding can also occur if storm drains and street gutters are not kept clear of road debris, large quantities of water are sometimes thrown up from the road by large vehicles, creating visibility problems for the drivers of oncoming, nearby, or following vehicles. Following vehicles may reduce the problem by slowing and increasing the following/separation distance, headlights improve vehicle visibility for all drivers, including those dealing with the spray. Driving manuals advise against following vehicles too closely in these hazardous conditions, Road spray can cause reduced visibility and dramatically reduce the safety of motorists. Over time, road spray and gunk from brake pads coat the rim of the wheel, in motorsport racing, road debris can cause loss of traction and subsequent crashes. Usually, the caution flag is used to indicate a track hazard
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Road
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Roads consist of one or two roadways, each with one or more lanes and any associated sidewalks and road verges. Roads that are available for use by the public may be referred to as parkways, avenues, freeways, interstates, highways, or primary, secondary, and tertiary local roads. In urban areas roads may diverge through a city or village and be named as streets, serving a function as urban space easement. Modern roads are normally smoothed, paved, or otherwise prepared to allow easy travel, historically many roads were simply recognizable routes without any formal construction or maintenance. In the United Kingdom there is ambiguity between the terms highway and road. The Highway code details rules for road users and this includes footpaths, bridleways and cycle tracks, and also road and driveways on private land and many car parks. Vehicle Excise Duty, a use tax, is payable on some vehicles used on the public road. The definition of a road depends on the definition of a highway, in the United States, laws distinguish between public roads, which are open to public use, and private roads, which are privately controlled. The assertion that the first pathways were the trails made by animals has not been universally accepted, others believe that some roads originated from following animal trails. The Icknield Way is given as an example of type of road origination. By about 10,000 BC, rough roads/pathways were used by human travelers, the worlds oldest known paved road was constructed in Egypt some time between 2600 and 2200 BC. Stone-paved streets are found in the city of Ur in the Middle East dating back to 4000 BC, corduroy roads are found dating to 4000 BC in Glastonbury, England. The Sweet Track, a timber causeway in England, is one of the oldest engineered roads discovered. Built in winter 3807 BC or spring 3806 BC, tree-ring dating enabled very precise dating and it was claimed to be the oldest road in the world until the 2009 discovery of a 6, 000-year-old trackway in Plumstead, London. Brick-paved streets were used in India as early as 3000 BC, in 500 BC, Darius I the Great started an extensive road system for Persia, including the Royal Road, which was one of the finest highways of its time. The road remained in use after Roman times, a hybrid of road transport and ship transport beginning in about 1740 is the horse-drawn boat in which the horse follows a cleared path along the river bank. From about 312 BC, the Roman Empire built straight strong stone Roman roads throughout Europe and North Africa, at its peak the Roman Empire was connected by 29 major roads moving out from Rome and covering 78,000 kilometers or 52,964 Roman miles of paved roads. In the 8th century AD, many roads were built throughout the Arab Empire, the most sophisticated roads were those in Baghdad, which were paved with tar
38.
Exhaust gas
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Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends, diesel fuel, fuel oil, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack and it often disperses downwind in a pattern called an exhaust plume. A2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions. According to another study from the university, traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom. The largest part of most combustion gas is nitrogen, water vapor, and carbon dioxide, Exhaust gas temperature is important to the functioning of the catalytic converter of an internal combustion engine. It may be measured by an exhaust gas temperature gauge, EGT is also a measure of engine health in gas-turbine engines. During the first two minutes after starting the engine of a car that has not been operated for several hours, inefficient catalytic converter under cold conditions, Catalytic converters are very inefficient until up to their operating temperature. This time has much reduced by moving the converter closer to the exhaust manifold. The small converter handles the start-up emissions, which enough time for the larger main converter to heat up. Further improvements can be realised in many ways, including heating, thermal battery, chemical reaction preheating, flame heating. The requirements were phased in beginning with 2004 vehicles and all new cars, in spark-ignition engines the gases resulting from combustion of the fuel and air mix are called exhaust gases. The composition varies from petrol to diesel engines, but is around these levels, The 10% oxygen for diesel is likely if the engine was idling and it is much less if the engine is running under load. People exposed to it should wear a gas mask, in aircraft gas turbine engines, exhaust gas temperature is a primary measure of engine health. Typically the EGT is compared with an engine power indication called engine pressure ratio. For example, at full power EPR there will be a maximum permitted EGT limit, once an engine reaches a stage in its life where it reaches this EGT limit, the engine will require specific maintenance in order to rectify the problem. The amount the EGT is below the EGT limit is called EGT margin, the EGT margin of an engine will be greatest when the engine is new, or has been overhauled. For most airlines, this information is monitored remotely by the airline maintenance department by means of ACARS. In jet engines and rocket engines, exhaust from propelling nozzles which in some applications shows shock diamonds, Flue gas Flue gas emissions from fossil fuel combustion In steam engine terminology the exhaust is steam that is now so low in pressure that it can no longer do useful work
39.
Disc brake
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The energy of motion is converted into waste heat which must be dispersed. Hydraulic disc brakes are the most commonly used form of brake for motor vehicles, compared to drum brakes, disc brakes offer better stopping performance because the disc is more readily cooled. As a consequence discs are less prone to the brake fade caused when brake components overheat, disc brakes also recover more quickly from immersion. Most drum brake designs have at least one leading shoe, which gives a servo-effect and this tends to give the driver better feel and helps to avoid impending lockup. Drums are also prone to bell mouthing and trap worn lining material within the assembly, the brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or the axle, friction causes the disc and attached wheel to slow or stop. The development of disc-type brakes began in England in the 1890s, successful application began in airplanes before World War II, and even the German Tiger tank was fitted with discs in 1942. The Jaguar racing team won, using disc brake equipped cars, mass production began with the 1955 Citroën DS. Development of disc brakes began in England in the 1890s, the first caliper-type automobile disc brake was patented by Frederick William Lanchester in his Birmingham factory in 1902 and used successfully on Lanchester cars. However, the choice of metals in this period meant that he had to use copper as the braking medium acting on the disc. The poor state of the roads at this time, no more than dusty, rough tracks, successful application began in airplanes and tanks before and during World War II. At Germanys Argus Motoren, Hermann Klaue had patented disc brakes in 1940, Argus supplied wheels fitted with disc brakes e. g. for the Arado Ar 96. The German Tiger I heavy tank, was introduced in 1942 with a 55 cm Argus-Werke disc on each drive shaft, the American Crosley Hot Shot is often given credit for the first production disc brakes. For six months in 1950, Crosley built a car with these brakes, lack of sufficient research caused reliability problems, such as sticking and corrosion, especially in regions using salt on winter roads. Drum brake conversions for Hot Shots were quite popular, the Crosley disc was a Goodyear development, a caliper type with ventilated disc, originally designed for aircraft applications. Chrysler developed a braking system, offered from 1949 to 1953. Instead of the disc with caliper squeezing on it, this system used twin expanding discs that rubbed against the surface of a cast-iron brake drum. The discs spread apart to create friction against the drum surface through the action of standard wheel cylinders
40.
Pothole
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Introduction of water to the underlying soil structure first weakens the supporting soil. Traffic then fatigues and breaks the poorly supported asphalt surface in the affected area, continued traffic action ejects both asphalt and the underlying soil material to create a hole in the pavement. In India,3,000 people per year are killed in accidents involving potholes, britain has estimated that the cost of fixing all roads with potholes in the country would cost £12 billion. According to the US Army Corps of Engineers, pothole formation requires two factors to be present at the time, water and traffic. Water weakens the soil beneath the pavement while traffic applies the loads that stress the pavement past the breaking point, potholes form progressively from fatigue of the road surface which can lead to a precursor failure pattern known as crocodile cracking. Eventually, chunks of pavement between the fatigue cracks gradually work loose, and may then be plucked or forced out of the surface by continued wheel loads to create a pothole. In areas subject to freezing and thawing, frost heaving can damage a pavement, potholes can grow to several feet in width, though they usually only develop to depths of a few inches. If they become large enough, damage to tires, wheels, serious road accidents can occur as a direct result, especially on those roads where vehicle speeds are greater. Potholes may result from four main causes,1, insufficient pavement thickness to support traffic during freeze/thaw periods without localized failures 2. Failures at utility trenches and castings 4, surveying of pavements for risk factors 2. Utility cut management At-risk pavement are more local roads with lower structural standards and more complicating factors, like underground utilities. Pavement condition monitoring can lead to timely preventative action, drainage structures, including ditching and storm sewers are essential for removing water from pavements. Avoiding other risk factors with good construction includes well-draining base and sub-base soils that avoid frost action, adequate crowns promote drainage to the sides. Good crack control prevents water penetration into the pavement soil structure, preventative maintenance adds maintaining pavement structural integrity with thickness and continuity to the mix of preventing water penetration and promoting water migration away from the roadway. Eaton, et al. advocate a permitting process for utility cuts with specifications that avoid loss of continuity of pavements. Pothole patching methods may be temporary or semi-permanent. The Federal Highway Administration offers an overview of best practices which includes several techniques, throw-and-roll, semi-permanent, spray injection. The FHWA suggests the best patching techniques, at other than winter, are spray injection, throw-and-roll, semi-permanent
41.
Mining
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Mining is extraction of valuable minerals or other geological materials from the earth usually from an orebody, lode, vein, seam, reef or placer deposits. These deposits form a mineralized package that is of economic interest to the miner, ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water. Mining of stones and metal has been a human activity since pre-historic times, Mining operations usually create a negative environmental impact, both during the mining activity and after the mine has closed. Hence, most of the nations have passed regulations to decrease the impact. Work safety has long been a concern as well, and modern practices have significantly improved safety in mines, levels of metals recycling are generally low. Unless future end-of-life recycling rates are stepped up, some rare metals may become unavailable for use in a variety of consumer products, due to the low recycling rates, some landfills now contain higher concentrations of metal than mines themselves. Since the beginning of civilization, people have used stone, ceramics and, later and these were used to make early tools and weapons, for example, high quality flint found in northern France, southern England and Poland was used to create flint tools. Flint mines have been found in areas where seams of the stone were followed underground by shafts. The mines at Grimes Graves and Krzemionki are especially famous, other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District. The oldest-known mine on archaeological record is the Lion Cave in Swaziland, at this site Paleolithic humans mined hematite to make the red pigment ochre. Mines of an age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons. Ancient Egyptians mined malachite at Maadi, at first, Egyptians used the bright green malachite stones for ornamentations and pottery. Later, between 2613 and 2494 BC, large building projects required expeditions abroad to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself. Quarries for turquoise and copper were found at Wadi Hammamat, Tura, Aswan and various other Nubian sites on the Sinai Peninsula. Mining in Egypt occurred in the earliest dynasties, the gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. These mines are described by the Greek author Diodorus Siculus, who mentions fire-setting as one used to break down the hard rock holding the gold. One of the complexes is shown in one of the earliest known maps, the miners crushed the ore and ground it to a fine powder before washing the powder for the gold dust
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Landfill
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A landfill site is a site for the disposal of waste materials by burial and the oldest form of waste treatment. Historically, landfills have been the most common method of organized waste disposal, some landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material. A landfill also may refer to ground that has filled in with rocks instead of waste materials, so that it can be used for a specific purpose. Unless they are stabilized, these areas may experience severe shaking or soil liquefaction of the ground during a large earthquake, afterward, the waste collection vehicles use the existing road network on their way to the tipping face or working front, where they unload their contents. After loads are deposited, compactors or bulldozers can spread and compact the waste on the working face, before leaving the landfill boundaries, the waste collection vehicles may pass through a wheel-cleaning facility. If necessary, they return to the weighbridge for re-weighing without their load, the weighing process can assemble statistics on the daily incoming waste tonnage, which databases can retain for record keeping. In addition to trucks, some landfills may have equipment to handle railroad containers, the use of rail-haul permits landfills to be located at more remote sites, without the problems associated with many truck trips. Typically, in the face, the compacted waste is covered with soil or alternative materials daily. Alternative waste-cover materials include chipped wood or other waste, several sprayed-on foam products, chemically fixed bio-solids. Blankets can be lifted into place at night and then removed the day prior to waste placement. The space that is occupied daily by the waste and the cover material is called a daily cell. Waste compaction is critical to extending the life of the landfill, factors such as waste compressibility, waste-layer thickness and the number of passes of the compactor over the waste affect the waste densities. Landfills are often the most cost-efficient way to dispose of waste, in addition, landfill gas can be upgraded to natural gas—landfill gas utilization—which is a potential revenue stream. Another advantage is having a location for disposal that can be monitored. Landfills have the potential to cause a number of issues, infrastructure disruption, such as damage to access roads by heavy vehicles, may occur. Pollution of local roads and water courses from wheels on vehicles when they leave the landfill can be significant, pollution of the local environment, such as contamination of groundwater or aquifers or soil contamination may occur, as well. Extensive efforts are made to capture and treat leachate from landfills before it reaches groundwater aquifers, eventually, every landfill liner will leak, allowing the leachate to contaminate the groundwater. Installation of composite liners with flexible membrane and soil barrier is enforced by the EPA to ensure that leachate is withheld, rotting food and other decaying organic waste allows methane and carbon dioxide to seep out of the ground and up into the air
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Street sweeper
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A street sweeper or street cleaner may refer to a persons occupation, or a machine that cleans streets. A street sweeper cleans the streets, usually in an urban area, Street sweepers have been employed in cities since sanitation and waste removal became a priority. A street-sweeping person would use a broom and shovel to clean off litter, animal waste, later, water hoses were used to wash the streets. Machines were created in the 19th century to do the job more efficiently, today, modern street sweepers are mounted on truck bodies and can vacuum debris that accumulates in streets. By the 1840s, Manchester, England, had known as the first industrial city. Manchester was home to the first passenger service in the world and had one of the largest textile industries of that time. As a result, the robust metropolis was said to be England’s unhealthiest place to live, in response to this unsanitary environment, Joseph Whitworth invented the mechanical street sweeper. The street sweeper was designed with the objective to remove trash from streets in order to maintain aesthetic goals. The very first street sweeping machine was patented in 1849 by its inventor, for a long time, street sweepers were just rotating disks covered with wire bristles. These rotating disks served as mechanical brooms that swept the dirt on the streets, brooks, an African American man from Newark, New Jersey, invented the U. S. first self-propelled street sweeper truck. Brooks patent was approved on March 17,1896, his application for the patent had been filed on April 20,1895 and his street sweeper had a truck-like frame mounted on axles supported by wheels. There are drive-wheels for the sweeping, elevator mechanisms, and a chain that travels around a sprocket-wheel. The patent drawings go on to explain the composition of the invention. The truck had brushes attached to the front fender which would revolve and these revolving brushes could interchange with a flat scraper for use on snow and ice. John M. Murphy called at the offices of American Tower and Tank Company in Elgin, Illinois and he had a plan of a motor driven pickup street sweeper. The American Tower and Tank Company had been formed in 1903 by Charles A. Whiting and they called in a recently acquired silent partner, Daniel M. Todd, and it was decided to hire Mr. Murphy and begin the development of his idea. That started what has become the Elgin Sweeper Company, Todd and Charles A. Whiting were willing to risk a reputation gained from 30 years manufacturing experience. In the fall of 1913, the City of Boise, Idaho, purchased the first Elgin Sweeper, Boise Street Commissioner, Thomas Finegan, made a comparison showing a savings of $2,716.77 from the Elgin motorized sweeper when used rather than a horse-drawn sweeper
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Vacuum cleaner
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The dirt is collected by either a dustbag or a cyclone for later disposal. Specialized shop vacuums can be used to suck up both dust and liquids, although vacuum cleaner and the short form vacuum are neutral names, in some countries hoover is used instead as a genericized trademark, and as a verb. The name comes from the Hoover Company, one of the first, the device is also sometimes called a sweeper although the same term also refers to a carpet sweeper, a similar invention. The vacuum cleaner evolved from the carpet sweeper via manual vacuum cleaners, the first manual models, using bellows, were developed in the 1860s, and the first motorized designs appeared at the turn of the 20th century, with the first decade being the boom decade. In 1860 a carpet sweeper was invented by Daniel Hess of West Union, Iowa that gathered dust with a rotating brush, another early model was the Whirlwind, invented in Chicago in 1868 by Ives W. McGaffey. The bulky device worked with a belt driven fan cranked by hand that made it awkward to operate, a similar model was constructed by Melville R. Bissell of Grand Rapids, Michigan in 1876. The company later added portable vacuum cleaners to its line of cleaning tools, the end of the 19th century saw the introduction of powered cleaners, although early types used some variation of blowing air to clean instead of suction. One appeared in 1898 when John S. Thurman of St. Louis, thurmans system, powered by an internal combustion engine, traveled to the customers residence on a horse-drawn wagon as part of a door to door cleaning service. Corrine Dufour of Savannah, Georgia received two patents in 1899 and 1900 for another blown air system that seems to have featured the first use of an electric motor. In 1901 powered vacuum cleaners using suction were invented independently by British engineer Hubert Cecil Booth, Booth also may have coined the word vacuum cleaner. Kenneys was a stationary 4,000 lb. steam engine powered system with pipes and hoses reaching into all parts of the building. The first vacuum-cleaning device to be portable and marketed at the market was built in 1905 by Walter Griffiths. In 1906 James B. Kirby developed his first of many vacuums called the Domestic Cyclone It used water for dirt separation. In 1907 department store janitor James Murray Spangler of Canton, Ohio invented the first portable vacuum cleaner. Crucially, in addition to suction from a fan that blew the dirt and dust into a soap box and one of his wifes pillow cases. Their first vacuum was the 1908 Model O, which sold for $60, subsequent innovations included the beater bar in 1919, disposal filter bags in the 1920s, and an upright vacuum cleaner in 1926. In Continental Europe, the Fisker and Nielsen company in Denmark was the first to sell vacuum cleaners in 1910, the design weighed just 17.5 kg and could be operated by a single person. The Swedish company Electrolux launched the innovative Model V in 1921 that was designed to lie on the floor on two thin metal runners and this innovation, conceived by Electrolux founder Axel Wenner-Gren, became a standard feature on generations of future vacuum cleaners
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Coal dust
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Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, or pulverizing of coal. Because of the nature of coal, coal dust can be created during mining, transportation. Grinding coal to dust before combusting it improves the speed and efficiency of burning, however, coal dust is hazardous to workers if it is suspended in air outside of the controlled environment of grinding and combustion equipment. It poses the hazard of forming an explosive mixture in air. The Occupational Safety and Health Administration has set the limit for coal dust exposure in the workplace as 2.4 mg/m3 over an 8-hour workday. The National Institute for Occupational Safety and Health has set a Recommended exposure limit of 1 mg/m3 or 0.9 mg/m3 over an 8-hour workday. Coal dust suspended in air is explosive—coal dust has far more surface area per unit weight than lumps of coal, as a result, a nearly empty coal store is a greater explosion risk than a full one. Such accidents were usually initiated by firedamp ignitions, the wave of which raised coal dust from the floor of the mine galleries to make an explosive mixture. The problem was investigated by Michael Faraday and Charles Lyell at the colliery at Haswell County Durham of 1844, Coal workers pneumoconiosis, or black lung disease, is caused by inhaling coal dust, typically dust produced in coal mining. Government agencies in the United States have set exposure limit guidelines for coal dust inhalation, for use in thermal power plants, coal is ground into dust using a device called a powdered coal mill. The resulting product, called powdered coal or pulverized coal, is generally used in a fossil fuel power plant for electricity generation. Pulverised coal is a significant dust explosion hazard, as quantities are suspended in air for transfer from the mill to the power plant. Explosions have occurred when the drops and flames in the burning chamber pass back along the ductwork delivering fuel. Coal burner Coal-water slurry fuel Pulverized coal-fired boiler Coal Dust Explosibility Meter Evaluation,9529, Mining Safety and Health, National Institute for Occupational Safety and Health, CDC. NIOSH Pocket Guide to Chemical Hazards – Coal Dust, centers for Disease Control and Prevention, U. S. Department of Health and Human Services. Occupational Safety and Health Guideline for Coal Dust, Occupational Safety & Health Administration, U. S. Department of Labor. Technology News 515 – Float Coal Dust Explosion Hazards, 2006-125, Mining Safety and Health, National Institute for Occupational Safety and Health, CDC
. Bibcode:1999ApJ...524..867F. doi:10.1086/307852.
