document_title: Atmosphere of Earth

question_text: how far is the atmosphere from the earth

root

text: Atmosphere of Earth

text: Composition

text: The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by volume in the coldest portions of the atmosphere to as much as 5% by volume in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor).[5] The remaining gases are often referred to as trace gases,[6] among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores, sea spray, and volcanic ash. Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO2) may be derived from natural sources or from industrial air pollution.

tag: p

text:
Major constituents of dry air, by volume[7]

Gas

Volume(A)

Name

Formula

in ppmv(B)

in %

Nitrogen

N2

780,840

78.084

Oxygen

O2

209,460

20.946

Argon

Ar

9,340

0.9340

Carbon dioxide

CO2

400

0.04[8]

Neon

Ne

18.18

0.001818

Helium

He

5.24

0.000524

Methane

CH4

1.79

0.000179

Not included in above dry atmosphere:

Water vapor(C)

H2O

10–50,000(D)

0.001%–5%(D)

notes:
(A) volume fraction is equal to mole fraction for ideal gas only,     also see volume (thermodynamics)
(B) ppmv: parts per million by volume
(C) Water vapor is about 0.25% by mass over full atmosphere
(D) Water vapor strongly varies locally[5]

tag: table

text: The relative concentration of gasses remains constant until about 10,000 m (33,000 ft).[9]

text: Structure of the atmosphere

text: Principal layers

text: In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions (see the temperature section, below). Because the general pattern of the temperature/altitude profile is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided (called atmospheric stratification) into five main layers. Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere.[10] From highest to lowest, the five main layers are:

text:
Exosphere: 700 to 10,000 km (440 to 6,200 miles)
Thermosphere: 80 to 700 km (50 to 440 miles)[11]
Mesosphere: 50 to 80 km (31 to 50 miles)
Stratosphere: 12 to 50 km (7 to 31 miles)
Troposphere: 0 to 12 km (0 to 7 miles)[12]

tag: ul

text: Exosphere

text: The exosphere is the outermost layer of Earth's atmosphere (i.e. the upper limit of the atmosphere). It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km (6,200 mi; 33,000,000 ft) where it merges into the solar wind.

text: This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind.

text: The exosphere is located too far above Earth for any meteorological phenomena to be possible. However, the aurora borealis and aurora australis sometimes occur in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains most of the satellites orbiting Earth.

text: Thermosphere

text: The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of the thermopause varies considerably due to changes in solar activity.[11] Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase. The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere.

text: The temperature of the thermosphere gradually increases with height. Unlike the stratosphere beneath it, wherein a temperature inversion is due to the absorption of radiation by ozone, the inversion in the thermosphere occurs due to the extremely low density of its molecules. The temperature of this layer can rise as high as 1500 °C (2700 °F), though the gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule (of oxygen, for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules.[13] Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density is too low to conduct a significant amount of energy to or from the skin.

text: This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi).

text: Mesosphere

text: The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level.

text: Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K).[14][15]

text: Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can be sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or a similar length of time before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft.

text: Stratosphere

text: The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft).

text: The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level. It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines a layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation (UV) radiation from the Sun by the ozone layer, which restricts turbulence and mixing. Although the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C.[16]

text: The stratospheric temperature profile creates very stable atmospheric conditions, so the stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft.

text: Troposphere

text: The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator,[12] with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone which is isothermal with height.[17][18]

text: Although variations do occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface. Thus, the lowest part of the troposphere (i.e. Earth's surface) is typically the warmest section of the troposphere. This promotes vertical mixing (hence, the origin of its name in the Greek word τρόπος, tropos, meaning "turn"). The troposphere contains roughly 80% of the mass of Earth's atmosphere.[19] The troposphere is denser than all its overlying atmospheric layers because a larger atmospheric weight sits on top of the troposphere and causes it to be most severely compressed. Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (3.5 mi; 18,000 ft) of the troposphere.

text: Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate the tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft.

text: Other layers

text: Within the five principal layers that are largely determined by temperature, several secondary layers may be distinguished by other properties:

text:
The ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–21.7 mi; 49,000–115,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in Earth's atmosphere is contained in the stratosphere.
The ionosphere is a region of the atmosphere that is ionized by solar radiation. It is responsible for auroras. During daytime hours, it stretches from 50 to 1,000 km (31 to 621 mi; 160,000 to 3,280,000 ft) and includes the mesosphere, thermosphere, and parts of the exosphere. However, ionization in the mesosphere largely ceases during the night, so auroras are normally seen only in the thermosphere and lower exosphere. The ionosphere forms the inner edge of the magnetosphere. It has practical importance because it influences, for example, radio propagation on Earth.
The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. The surface-based homosphere includes the troposphere, stratosphere, mesosphere, and the lowest part of the thermosphere, where the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence.[21] This relatively homogeneous layer ends at the turbopause found at about 100 km (62 mi; 330,000 ft), the very edge of space itself as accepted by the FAI, which places it about 20 km (12 mi; 66,000 ft) above the mesopause.

text: The planetary boundary layer is the part of the troposphere that is closest to Earth's surface and is directly affected by it, mainly through turbulent diffusion. During the day the planetary boundary layer usually is well-mixed, whereas at night it becomes stably stratified with weak or intermittent mixing. The depth of the planetary boundary layer ranges from as little as about 100 metres (330 ft) on clear, calm nights to 3,000 m (9,800 ft) or more during the afternoon in dry regions.

text: The average temperature of the atmosphere at Earth's surface is 14 °C (57 °F; 287 K)[22] or 15 °C (59 °F; 288 K),[23] depending on the reference.[24][25][26]

text: Physical properties

text: Pressure and thickness

text: The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00 Torr; 14.6959 psi; 760.00 mmHg). This is sometimes referred to as a unit of standard atmospheres (atm). Total atmospheric mass is 5.1480×1018 kg (1.135×1019 lb),[28] about 2.5% less than would be inferred from the average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather.

text: If the entire mass of the atmosphere had a uniform density from sea level, it would terminate abruptly at an altitude of 8.50 km (27,900 ft). It actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by a factor of 1/e every 7.64 km (25,100 ft), the average scale height of the atmosphere below 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account.

text: In summary, the mass of Earth's atmosphere is distributed approximately as follows:[29]

text:
50% is below 5.6 km (18,000 ft).
90% is below 16 km (52,000 ft).
99.99997% is below 100 km (62 mi; 330,000 ft), the Kármán line. By international convention, this marks the beginning of space where human travelers are considered astronauts.

text:
By comparison, the summit of Mt. Everest is at 8,848 m (29,029 ft);
commercial airliners typically cruise between 10 and 13 km (33,000 and 43,000 ft) where the thinner air improves fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft).

text: Even above the Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply. The various layers of Earth's ionosphere, important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within the F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months. Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as 700–800 km.

text: Temperature and speed of sound

text: The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where the temperature stabilizes through a large vertical distance through the rest of the troposphere. In the stratosphere, starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by capture of significant ultraviolet radiation from the Sun by the dioxygen and ozone gas in this region. Still another region of increasing temperature with altitude occurs at very high altitudes, in the aptly-named thermosphere above 90 km.

text: Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on the gas pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile (see illustration to the right), and does not mirror altitudinal changes in density or pressure.

text: Density and mass

text: The density of air at sea level is about 1.2 kg/m3 (1.2 g/L, 0.0012 g/cm3). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used to predict orbital decay of satellites.

text: The average mass of the atmosphere is about 5 quadrillion (5×1015) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg."

text: Optical properties

text: This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2013) (Learn how and when to remove this template message)

text: Solar radiation (or sunlight) is the energy Earth receives from the Sun. Earth also emits radiation back into space, but at longer wavelengths that we cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. In May 2017, glints of light, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in the atmosphere.[31][32]

text: Scattering

text: When light passes through Earth's atmosphere, photons interact with it through scattering. If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow there is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering, shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal to reach your eye. Much of the blue light has been scattered out, leaving the red light in a sunset.

text: Absorption

text: Different molecules absorb different wavelengths of radiation. For example, O2 and O3 absorb almost all wavelengths shorter than 300 nanometers. Water (H2O) absorbs many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. This heats the atmosphere, but the atmosphere also cools by emitting radiation, as discussed below.

text: The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity, allowing the transmission of only certain bands of light. The optical window runs from around 300 nm (ultraviolet-C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to the infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimeter to about eleven-meter waves.

text: Emission

text: Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their "black body" emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example, the Sun is approximately 6,000 K (5,730 °C; 10,340 °F), its radiation peaks near 500 nm, and is visible to the human eye. Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans.

text: Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This is because clouds (H2O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations.

text: The greenhouse effect is directly related to this absorption and emission effect. Some gases in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these are CO2 and H2O.

text: Refractive index

text: The refractive index of air is close to, but just greater than 1. Systematic variations in refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers onboard ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of Earth's surface.

text: The refractive index of air depends on temperature,[33] giving rise to refraction effects when the temperature gradient is large. An example of such effects is the mirage.

text: Circulation

text: Atmospheric circulation is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed around Earth. The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant because it is determined by Earth's rotation rate and the difference in solar radiation between the equator and poles.

text: Evolution of Earth's atmosphere

text: Earliest atmosphere

text: The first atmosphere consisted of gases in the solar nebula, primarily hydrogen. There were probably simple hydrides such as those now found in the gas giants (Jupiter and Saturn), notably water vapor, methane and ammonia.[34]

text: Second atmosphere

text: Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced the next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases.[34] A major part of carbon-dioxide emissions dissolved in water and reacted with metals such as calcium and magnesium during weathering of crustal rocks to form carbonates that were deposited as sediments. Water-related sediments have been found that date from as early as 3.8 billion years ago.[35]

text: About 3.4 billion years ago, nitrogen formed the major part of the then stable "second atmosphere". The influence of life has to be taken into account rather soon in the history of the atmosphere, because hints of early life-forms appear as early as 3.5 billion years ago.[36] How Earth at that time maintained a climate warm enough for liquid water and life, if the early Sun put out 30% lower solar radiance than today, is a puzzle known as the "faint young Sun paradox".

text: The geological record however shows a continuous relatively warm surface during the complete early temperature record of Earth – with the exception of one cold glacial phase about 2.4 billion years ago. In the late Archean Eon an oxygen-containing atmosphere began to develop, apparently produced by photosynthesizing cyanobacteria (see Great Oxygenation Event), which have been found as stromatolite fossils from 2.7 billion years ago. The early basic carbon isotopy (isotope ratio proportions) strongly suggests conditions similar to the current, and that the fundamental features of the carbon cycle became established as early as 4 billion years ago.

text: Ancient sediments in the Gabon dating from between about 2,150 and 2,080 million years ago provide a record of Earth's dynamic oxygenation evolution. These fluctuations in oxygenation were likely driven by the Lomagundi carbon isotope excursion.[37]

text: Third atmosphere

text: The constant re-arrangement of continents by plate tectonics influences the long-term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2.4 billion years ago during the Great Oxygenation Event and its appearance is indicated by the end of the banded iron formations.

text: Before this time, any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron. Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials that removed oxygen. This point signifies a shift from a reducing atmosphere to an oxidizing atmosphere. O2 showed major variations until reaching a steady state of more than 15% by the end of the Precambrian.[40] The following time span from 541 million years ago to the present day is the Phanerozoic Eon, during the earliest period of which, the Cambrian, oxygen-requiring metazoan life forms began to appear.

text: The amount of oxygen in the atmosphere has fluctuated over the last 600 million years, reaching a peak of about 30% around 280 million years ago, significantly higher than today's 21%. Two main processes govern changes in the atmosphere: Plants use carbon dioxide from the atmosphere, releasing oxygen. Breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which oxidizes and hence reduces the amount of oxygen in the atmosphere. However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen. The exact cause of the variation of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with rapid development of animals. Today's atmosphere contains 21% oxygen, which is great enough for this rapid development of animals.[41]

text: Air pollution

text: Air pollution is the introduction into the atmosphere of chemicals, particulate matter or biological materials that cause harm or discomfort to organisms.[42] Stratospheric ozone depletion is caused by air pollution, chiefly from chlorofluorocarbons and other ozone-depleting substances.

text: The scientific consensus is that the anthropogenic greenhouse gases currently accumulating in the atmosphere are the main cause of global warming.[43]

text: Images from space

text: On October 19, 2015 NASA started a website containing daily images of the full sunlit side of Earth on http://epic.gsfc.nasa.gov/. The images are taken from the Deep Space Climate Observatory (DSCOVR) and show Earth as it rotates during a day.[44]


document_title: Acadian orogeny

question_text: which deltaic complex in north america originated as a result of the taconic (acadian) orogeny

question_tokens: which deltaic complex in north america originated as a result of the taconic ( acadian ) orogeny

text: Acadian orogeny

text: Palaeogeography[edit]

text: During the time of the Acadian orogeny, Middle Devonian(385 Ma), the paleolatitude of the Laurentia was in the southern hemisphere near the equator, between 0° to 30°S latitude.[6] Laurentia did not change much with respect to paleolatitude during the Devonian. Gondwana, on the other hand, traveled a large distance, such that in the Ordovician the South pole was located in northern Africa, where it then moved west of southern Chile during the Silurian, and moved back to central Africa during the Devonian.[7] However, more recent research, from Scotese & McKerrow, suggests that in Late Devonian, the South Pole was in north-central Argentina rather than Northern Africa, which was supported with paleoclimatic evidence.[6] The paleolatitude of Gondwana during the Middle to Late Devonian resided around intermediate latitudes of about 50°S.[7]

text: The collision creating the Acadian orogeny resulted in the closing of the southern Iapetus ocean and the formation of a high mountain belt.[6] After the Acadian collision took place, Gondwana began to retreat from Laurentia with the newly accreted Avalonian terranes left behind. As Gondwana moved away, a new ocean opened up, the Rheic Ocean, during the Middle to Late Devonian, and subsequently its closure would result in the formation of the Alleghanian orogeny.[7]

text: Laurentia[edit]

text: Laurentia is the North American paleocontinent, which also includes present day Northwest Ireland, Scotland, Greenland, the North Slope of Alaska, and the Chukotsk peninsula of NE Russia.[6] During the Ordovician-Devonian time, Laurentia remained at the same paleolatitude, slightly south of the equator in the southern hemisphere, with relatively the same paleolongitude.[7] Major defining tectonic events include the Neoproterozoic rift sequence from the breakup of Grenville basement rocks, thermal subsidence related to the Early Cambrian to Middle Ordovician drift sequence during the opening of the Iapetus ocean, the Appalachian accretionary events to the eastern continental margin, and the resulting foreland-basin and clastic wedges.[8]

text: Avalonian Terranes[edit]

text: Avalonian terranes that constitute Avalonia are the modern day countries Northern France and Ardennes of Belgium, England, Wales, southeastern Ireland, eastern Newfoundland, Nova Scotia, southern New Brunswick and some coastal parts of New England. The basement consisted of Late Precambrian age arc rocks, and is believed to come from the margin of Gondwana, sometime in the Early Ordovician.[6] Avalonia rifted from Gondwana, during the onset of igneous activity in the Ardennes, Wales, and SE Ireland that consumed the Tornquist Sea oceanic crust. It drifted in a northerly direction and probably collided with Baltica in the Late Ordovician, and then with Laurentia in the Late Devonian. Evidence for this is consistent with paleomagnetic data which place Avalonia at a temperate latitude during the Ordovician and in a subtropical latitude during the Late Ordovician through the Devonian.[6]

text: Overview of Orogenic Events[edit]

text: The Acadian orogeny resulted from oblique convergence or major transcurrent movement along a large strike-slip fault which represents the zone of convergence between Lauruassia/Laurentia (North America) and Avalon terranes.[4] One or more of the Avalonian terranes accreted with the eastern margin of Laurentia, most likely beginning in the late Early Devonian.[9]

text: The evidence for the Acadian orogeny is abundant and widespread in the northern Appalachians, recorded by the plutonism and the migration of the northern Appalachian deformation front toward the craton. In the central to southern Appalachians, evidence for the Acadian orogeny is poor, and is found primarily in the plutonism of the Blue Ridge and metamorphism of the Cat Square terrane.[10]

text: The Acadian orogeny experienced at least three major phases of deformation, and in places, unconformities were recognized.[4] These phases were called tectophases, and represented the sequence of collisions that occurred from the Avalonian terranes accreting to Laurentia. As a result of these tectophases, deltas developed on the adjacent parts of the stable craton, eastern margin of Laurentia.[11] These deltas are described as foreland-basin, delta-complex clastic wedges, which are responsible for the large volumes of sediment input into the Appalachian basin.[9]

text: Collision[edit]

text: As mentioned previously, the Acadian Orogeny formed from the oblique convergence or major transcurrent movement along a large strike-slip fault moving in a southeasterly direction. Avalonian terranes accreted to the eastern margin of Laurentia during the Late to Middle Devonian.[4] This was a continent-continent collision with Baltica/Avalonia obliquely subducting below the eastern Laurentia margin, and closing the southern Iapetus ocean that resulted in a high mountain belt.[6]

text: The collision initiated a sequence of events where the older rocks on Laurentia and Avalonia were subjected deformation, plutonism, metamorphism, and uplift that occurred over a large area of eastern Laurentia (Naylor).[12] During the course of the orogeny, new faults formed, while older faults were reactivated.[2] Acadian deformation and metamorphism were asymmetric across the strike of the orogen. The Acadian plutons intruded every belt, unlike the deformation/metamorphism, where Avalonia escaped much of the damage suffered by the rocks in other localities (Bradley).[13] During the Middle Devonian, centers for volcanoes and uplift formed in the New England region and shed fine-grained clastic material into an inland seaway that covered a large part of southern and central Appalachia. Today, portions of the ancient Avalonia landmass occur in scattered outcrop belts along the eastern margin of North America. One belt occurs in Newfoundland, another forms the bedrock of much of the coastal region of New England from eastern Connecticut to northern Maine, where it is known as the Coastal Lithotectonic Block.[2]

text: The collision between Laurentia and Avalonian terranes is actually more complex than described above. The collision is broken into three, or possibly four tectophases, which represent a successive collision of the Avalonian terranes with eastern Laurentia.[4]

text: Tectophases[edit]

text: Because major clastic wedges and basinal deposits are distributed in a southwestward progression, it is assumed they originated from areas near promontories, areas along the continental margin where deformation is concentrated. As mention above, it was postulated that there are three, possibly four tectophases that represent increased convergence or possible collision between the continental margin promontories and Avalon terranes.[11] The earliest tectophase was located at the St. Lawrence Promontory in northern New England and in the Canadian Maritime Provinces.[9] The St. Lawrence tectophase was active during the Early to Middle Devonian with intense transpressional deformation which formed a basin in the Gaspé Peninsula, northern New Brunswick, and northern New England.[11] Clastic wedges were present in this area, but the evidence for them has been mostly destroyed by succeeding tectonism.[9]

text: The second tectophase, during the Middle Devonian, represents the collision with the New York promontory. The southward migration of deformation reflected the third tectophase, which marks the collision of Avalon terranes with the Virginia promontory in the Middle to Late Devonian time. The effects of the New York and Virginia promontories together produced the Catskill Delta complex.[9]

text: As the migration of deformation continued southward along the fault zone, during the Early Mississippian time, the final collision occurred with the Alabama promontory .[11] Ettensohn later refers to the fourth tectophase as the Mississippian tectophase of the Acadian Orogeny, since it demonstrated an unusually long duration (Mississippian-Early Pennsylvanian).[9] Subsequently, the Pocono & equivalent clastic wedges essentially filled the epicontinental sea. The deposition of Middle Mississippian carbonates marks the end of the Acadian Orogeny and Catskill Delta complex.[11]

text: The Acadian Foreland Basin[edit]

text: Foreland basins are a product of tectonic deformational loading, or crustal thickening along the orogen, a consequence of overthrusting and folding. The Acadian foreland basin is categorized as a retroarc foreland basin, which occurs on the overriding continental lithosphere, adjacent to a foreland fold-thrust belt behind a continental margin arc.[4] The initial result of loading is a bulge move out and uplift of the foreland, which generates a localized unconformity. The distributions of unconformities display an asymmetric pattern in relation to the promontories.[14] Subsidence follows bulge movement and uplift, and is produced on the cratonic side of the orogen due to regional isostatic adjustment to the load by the lithosphere.[4] Once thrust propagation declines, substantial relief and drainage nets have had time to develop, and the as a resulting coarser clastic sediment is eroded and transported to the foreland basin.[14]

text: The basement structures of the Appalachian foreland basin at the onset of the Acadian orogeny were reactivated during foreland lithospheric flexure. These structures affected the foreland basin evolution and sedimentation patterns, and the preexisting faults partitioned the basin into regions of fault-controlled uplift and depocenters.[15]

text: The Acadian Delta Complex[edit]

text: The Appalachian basin, during the Middle Devonian and Early Mississippian, is characterized by large volumes of deltaic sedimentary rocks that were deposited in the Acadian foreland basin as a response to the Acadian orogeny. These deposits extend from central New York and Pennsylvania westward to Ohio, and south along the Appalachian Mountains through Virginia and Tennessee to Alabama. The Acadian delta complex is categorized into two deltas, the Catskill Delta of Middle and Upper Devonian age, and the Price-Rockwell (Pocono) delta of Late Devonian and Early Mississippian age.[16] The Acadian delta complex is coupled to the four tectophases of the Acadian orogeny, both in terms of provenance and depositional settings. The relief resulting from the orogeny was the fundamental source of the delta sediments.[11]

text: The Catskill Delta complex consists of a coarsening upward sequence of rocks. Its thickness is greatest in eastern Pennsylvania and thins westward into Ohio. The Catskill paleogeography appears to consist of many small streams, which deposited their sedimentary load along a coastal alluvial plain that was hundreds of miles long.[16][16]

text: The Middle Devonian to Lower Mississippian siliciclastic strata, deposited by the Catskill Delta, includes black shale, gray shale, sandstone, red beds, and minor argillaceous limestone. The strata is deposited in a four-stage pattern that is observed in each tectophase. The formation of the foreland basin through rapid subsidence initiated a transgressive sequences that deposited basinal black shales. After the black shales are deposited, the migration of deformation continues southward, and regression dominates, particularly on the east side of the basin. As collision intensified, subsidence in the foreland basin declined, and sedimentation was replaced by an influx of calcareous silty shales and carbonates. These deposits reflect small transgressive-regressive cycles in a delta-front and delta platform environments. The third stage is represented by regional uplift, which accompanied the collision of an Avalon terrane with a promontory, and subsequently, developed a regional disconformity. The fourth and final stage is represented by tectonic quiescence with a widespread carbonate deposition in a slowly transgressing sea.[11]


document_title: The Frog Prince

question_text: who kissed the frog that turned into a prince

text: The Frog Prince

text: Origins[edit]

text: Although the story is best known today through the Grimm Brothers' rendition of it, parts of it may extend back until at least Roman times; a version of the story is apparently referred to in Petronius's Satyricon, in which the character Trimalchio remarks that, "qui fuit rana nunc est rex" ("The man who was once a frog is now a king.").[1] Other scholars, however, argue that this may actually be a jab at the emperor Nero, who was often mockingly compared to a frog.[2]

text: Plot[edit]

text: In the tale, a spoiled princess reluctantly befriends the Frog Prince (meeting him after dropping a gold ball into a pond), who magically transforms into a handsome prince. Although in modern versions the transformation is invariably triggered by the princess kissing the frog, in the original Grimm version of the story the frog's spell was broken when the princess threw it against a wall in disgust.[3]

text: In other early versions it was sufficient for the frog to spend the night on the princess' pillow.

text: The frog prince also has a loyal servant named Henry (or Harry) who had three iron bands affixed around his heart to prevent it from breaking in his sadness over his master's curse, but when the prince was reverted to his human form Henry's overwhelming happiness caused all three bands to break, freeing his heart from its bonds.[4]

text: A Russian folk version "Tsarevna Lyagushka" (The Frog Princess) has the male and female roles reversed: the male prince Ivan Tsarevich discovers the enchanted female frog who becomes Vasilisa the Wise, a female sorceress.

text: Similar folktales[edit]

text: It is Aarne–Thompson type 440.[5] Other folktales similar to the Frog Prince are:

text:
"The Frog Prince". The first English translation of the above tale. Edgar Taylor, the translator, not only changed the title, but altered the ending in a substantial and interesting manner.
"The Wonderful Frog" (W. Henry Jones and Lewis L. Kropf, Hungary).
"The Tale of the Queen Who Sought a Drink From a Certain Well" (J. F. Campbell, Scotland).
"The Well of the World's End"
"The Paddo" (Robert Chambers, Scotland).
"The Maiden and the Frog" (James Orchard Halliwell-Phillipps, England).
"The Kind Stepdaughter and the Frog" (W. Henry Jones and Lewis L. Kropf, England).
"The Frog Prince" (H. Parker, Sri Lanka).
"A Frog for a Husband" (William Elliot Griffis, Korea).
"The Toad Bridegroom" (Zong In-Sob, Korea).

tag: ol

text: Modern interpretations[edit]

text:
The Frog (1908), directed by Segundo de Chomón, is the first film adaptation of "The Frog Prince".[6]
Stevie Smith's poem "The Frog Prince" (1966) suggests the thoughts of the prince as he waits for disenchantment.[7]
Anne Sexton wrote an adaptation as a poem called "The Frog Prince" in her collection Transformations (1971), a book in which she re-envisions sixteen of the Grimms' fairy tales.[8]
"The Tale of the Frog Prince" was the first story presented by Shelley Duvall's Faerie Tale Theatre in 1982, with Robin Williams as the witty Frog Prince and Teri Garr as the vain princess.
Robin McKinley's collection of short stories The Door in the Hedge contains a version of the tale, entitled "The Princess and the Frog".
The Frog Prince is a 1986 film starring John Paragon and Aileen Quinn.
"The Frog Prince" was one of the fairy tales featured in Grimm's Fairy Tale Classics in its Grimm Masterpiece Theater season (1987).
In the second episode of Adventures from the Book of Virtues (1996), Plato the Bison and Annie try to convince their friend Zach to tell his father the truth by telling him three stories, including one about "The Frog Prince." In this version, the title character was transformed into a frog for lying to a witch and breaking his promise. He is voiced by Jeff Bennett while the princess is voiced by Paige O'Hara.
Prince Charming is a 2001 film starring Martin Short, Christina Applegate and Sean Maguire as the title character.
A musical version of The Frog Prince, written by Dieter Stegmann and Alexander S. Bermange, was presented at the Amphitheater Park Schloss Philippsruhe, Hanau, Germany as part of the Brothers Grimm Festival in 2005.[citation needed]
A chamber opera for children based upon The Frog Prince, written by Jacob A. Greenberg for Brown Opera Productions and the Providence Athenaeum, was performed in 2008.[9]
The Princess and the Frog, a 2009 Disney animated film, is loosely based on the 2002 novel The Frog Princess by E. D. Baker, which in turn was inspired by "The Frog Prince." The film starred Anika Noni Rose and Bruno Campos and was directed by Ron Clements and John Musker. The Frog Prince story itself is mentioned several times in the film, being read to Tiana as a child and inspiring Prince Naveen (who has been transformed into a frog) to suggest Tiana kiss him to break his spell. However, as she is only dressed as a princess for Mardi Gras, the kiss fails, turning her into a frog as well.


document_title: Airline meal

question_text: when was the first airline meal served during a flight

text: Airline meal

text: History[edit]

text: The first airline meals were served by Handley Page Transport, an airline company founded in 1919, to serve the London–Paris route in October of that year.[2] Passengers could choose from a selection of sandwiches and fruit.[3]

text: Contents[edit]

text: The type of food varies depending upon the airline company and class of travel. Meals may be served on one tray or in multiple courses with no tray and with a tablecloth, metal cutlery, and glassware (generally in first and business classes). Often the food is reflective of the culture of the country the airline is based in.

text: The airline dinner typically includes meat (most commonly chicken or beef), fish, or pasta; a salad or vegetable; a small bread roll; and a dessert. Condiments (typically salt, pepper, and sugar) are supplied in small sachets or shakers.

text: Caterers usually produce alternative meals for passengers with restrictive diets. These must usually be ordered in advance, sometimes when buying the ticket. Some of the more common examples include:

text:
Cultural diets, such as Turkish, French, Italian, Chinese, Korean, Japanese or Indian style.
Infant and baby meals. Some airlines also offer children's meals, containing foods that children will enjoy such as baked beans, mini-hamburgers and hot dogs.
Medical diets, including low/high fiber, low fat/cholesterol, diabetic, peanut free, non-lactose, low salt/sodium, low-purine, low-calorie, low-protein, bland (non-spicy) and gluten-free meals.
Religious diets, including kosher, halal, and Hindu, Buddhist and Jain vegetarian (sometimes termed Asian vegetarian) meals.
Vegetarian and vegan meals. Some airlines do not offer a specific meal for non-vegan vegetarians; instead, they are given a vegan meal.

text: Halal food[edit]

text: For several Islamic airlines (e.g. EgyptAir, Emirates, Etihad Airways, Garuda Indonesia, Batik Air, Malindo Air, Gulf Air, Iran Air, Mahan Air, Iran Aseman Airlines, Oman Air, Yemenia, Kuwait Airways, Iraqi Airways, Qatar Airways, Saudia, Biman Bangladesh Airlines, Malaysia Airlines, Royal Brunei Airlines, Royal Air Maroc, Libyan Airlines, Afriqiyah Airways, Tunisair, Air Algérie and Turkish Airlines), in accordance with Islamic customs, all classes and dishes on the plane are served a Muslim meal with Halal certification – without pork and alcohol. While Emirates, Etihad, and Qatar are still providing bottles of wine to non-Muslim passengers, the cabin crew does not deliver alcoholic beverages lest to violate Islamic customs, unless those non-Muslim passengers request it. Because Iran and Saudi Arabia apply strict Sharia regulations, those countries' airlines do not deliver pork or alcoholic beverages, and all airlines flying to or from Iran or Saudi Arabia are prohibited from serving either.[citation needed] However, Garuda Indonesia is still serving alcoholic beverages (whiskey, beer, champagne and wine) to non-Muslim passengers.

text: Kosher food[edit]

text: In the case the Israeli airlines El Al, Arkia and Israir, all meals served are kosher-certified by Rabbis. Even destinations outside Israel, sky chefs must be supervised by rabbis to make kosher meals and load their planes.[citation needed]

text: Cutlery and tableware[edit]

text: Before the September 11 attacks in 2001, first class passengers were often provided with full sets of metal cutlery. Afterward, common household items were evaluated more closely for their potential use as weapons on aircraft, and both first class and coach class passengers were restricted to plastic utensils. Some airlines switched from metal to all-plastic or plastic-handled cutlery during the SARS outbreak in 2003, since the SARS virus transfers from person to person easily, and plastic cutlery can be thrown away after use. Many airlines later switched back to metal cutlery. However, Singapore Airlines continue to use metal utensils even in economy class as of 2017.

text: In May 2010, concerns were raised in Australia and New Zealand over their respective flag carriers, Qantas and Air New Zealand, reusing their plastic cutlery for international flights between 10 and 30 times before replacement. Both airlines cited cost saving, international quarantine, and environmental as the reasons for the choice. Both have also said that the plastic cutlery is commercially washed and sterilized before reuse.[4][5][6] Reusing plastic tablewares though is a regular practice among many airliners and food caterers.

text: For cleanliness, most meals come with a napkin and a moist towelette. First and business class passengers are often provided with hot towels.

text: Breakfast[edit]

text: During morning flights a cooked breakfast or smaller continental-style may be served. On long haul flights (and short/medium haul flights within Asia) breakfast normally includes an entrée of pancakes or eggs, traditional fried breakfast foods such as sausages and grilled tomatoes, and often muffins or pastries, fruits and breakfast cereal on the side. On shorter flights a continental-style breakfast, generally including a miniature box of breakfast cereal, fruits and either a muffin, pastry, or bagel. Coffee and tea are offered as well, and sometimes hot chocolate.

text: Cost[edit]

text: Food on board a flight is usually free on full-service Asian airlines and on almost all long-distance flights, while they might cost extra on low-cost airlines or European full-service airline flights. Quality may also fluctuate due to shifts in the economics of the airline industry.

text: On long-haul international flights in first class and business class, most Asian and European airlines serve gourmet meals, while legacy carriers based in the US tend to serve multicourse meals including a cocktail snack, appetizer, soup, salad, entrée (chicken, beef, fish, or pasta), cheeses with fruit, and ice cream. Some long-haul flights in first and business class offer such delicacies as caviar, champagne, and sorbet (intermezzo).

text: The cost and availability of meals on US airlines has changed considerably in recent years, as financial pressures have forced some airlines to either begin charging for meals, or abandon them altogether in favor of small snacks, as in the case of Southwest Airlines. Eliminating free pretzels saved Northwest $2 million annually.[citation needed] Nowadays, the main US legacy carriers (American, Delta and United) have discontinued full meal service in economy class on short-haul US domestic and North American flights, while retaining it on most intercontinental routes;[7][8][9] and at least one European carrier, Icelandair, follows this policy on intercontinental runs as well.[10]

text: As of 2016, all 4 major U.S. legacy airlines now offer free snacks on board in economy class. United Airlines re-introduced free snacks in February 2016.[11] Starting in April 2016, American Airlines will fully restore free snacks on all domestic flights in economy class.[12] Free meals will also be available on certain domestic routes.[13] Delta and Southwest have already been offering free snacks for years.[14]

text: Hawaiian Airlines is the only remaining major US airline that offers complimentary in–flight meals on its domestic flights.

text: Air China has reported that each domestic flight's meal requires RMB50 (US$7.30) while international flights require RMB70 (US$10).[15] However, this figure varies from airline to airline, as some have reported costs to be as low as US$3.50.[16] Air China is also minimizing costs by loading only 95% of all meals to reduce leftovers and storing non-perishable foods for emergencies.

text: In 1958 Pan Am and several European airlines entered into a legal dispute over whether certain airline food sandwiches counted as a "meal".[17]

text: Preparation[edit]

text: Meals must generally be prepared on the ground before takeoff. Guillaume de Syon, a history professor at Albright College who wrote about the history of airline meals,[18] said that the higher altitudes alter the taste of the food and the function of the taste buds (although that's not case on Dreamliner or A350); according to de Syon the food may taste "dry and flavorless" as a result of the pressurization and passengers, feeling thirsty due to pressurization, many drink alcohol when they ought to drink water.[19] Tests have shown that the perception of saltiness and sweetness drops 30% at high altitudes. The low humidity in airline cabins also dries out the nose which decreases olfactory sensors which are essential for tasting flavor in dishes.[20]

text: Food safety is paramount in the airline catering industry. A case of mass food poisoning amongst the passengers on an airliner could have disastrous consequences. For example, on February 20, 1992, shrimp tainted with cholera was served on Aerolíneas Argentinas Flight 386. An elderly passenger died and other passengers fell ill. For this reason catering firms and airlines have worked together to provide a set of industry guidelines specific to the needs of airline catering. The World Food Safety Guidelines for Airline Catering is offered free of charge by the International Flight Service Association.[21]


document_title: Drum (container)

question_text: what are the dimensions of a 55 gallon plastic drum

text: Drum (container)

text: Background[edit]

text: It is common to hear a drum referred to as a barrel and the two terms are used nearly interchangeably. Many drums have a common nominal volume of 208 litres (55 US gal; 46 imp gal) and nominally measure just under 880 millimetres (35 in) tall with a diameter just under 610 millimetres (24 in) and differ by holding about thirteen gallons more than a barrel of crude oil. In the United States, 25-US-gallon (95 l; 21 imp gal) drums are also in common use and have the same height. This allows easy stacking of mixed pallets. Barrels can be constructed of plastic, laminated paperboard or steel.

text: The two common sub-types of drums are the open top and the welded top (with 51-millimetre (2 in) NPS bung holes). The latter are almost universally called "barrels" in preference to drums in the United States. They cannot efficaciously either dispense or be filled with powdered goods, though they might store them very well, so are not used for such goods, being reserved for liquids transport and storage. Plastic drums are manufactured using injection blow moulding technology and have either a separate lid (similar to those on fiber drums) or a welded type top with the bung holes molded in. Metal drums are manufactured with cold-rolled steel sheets, welded themselves into long pipe-like sections then forged on a stamping press into drum bodies. A rolled seam is then made for the drum bottom, or bottom and top both.

text: Some drums have reinforcing rings of thickened metal or plastic, called "chimes", at four places: top, bottom, and one each a third of the way from each end ring. This sufficiently strengthens them so that they can readily be turned on their sides and rolled when filled with heavy materials, like liquids. Over short to medium distances, drums can be tipped and rolled on the bottom rim while being held at an angle, balanced, and rotated with a two-handed top grip that also supplies the torque (rotational or rolling force).

text: The open-top sub-type is sealed by a mechanical ring clamp (concave inwards) that exerts sufficient pressure to hold many non-volatile liquids and make an airtight seal against a gasket, as it exerts force inward and downward when tightened by a normal three-quarter inch wrench or ratchet wrench. Tops exist with bung holes as above, and these hybrid drums with lid can be used to ship many non-volatile liquids as well as industrial powders. Many drums are used to ship and store powdered products as well as liquids, such as plastic beads for injection moulding, extrusion, and purified industrial grade powders like cleansers (e.g., fertilizers, and powdered aluminum). If used to transport dangerous goods across international boundaries, they may need to have UN certification. In general, drum usage is limited to wholesale distribution of bulk products, which are then further processed or sub-divided in a factory.

text: These metal drums have two openings with flanges (2 in NPS and ¾ in NPS). Once the drums are filled, the plugs (bungs) are screwed in the flanges using pneumatic or hand operated bung tightener (plug wrench). To secure the contents of the drums against theft and adulteration during shipment, cap-seals made of metal and other types like metal-plastic laminates are used. These cap-seals sit on top of the flanges and are crimped, using a drum cap-seal crimping tool, also called a drum cap sealer. Once cap-seals are crimped, the plugs can be unscrewed only by breaking these cap-seals. Pneumatic and hand-operated cap-seal crimping tools are available. Pneumatic ones are used in production lines for high production.

text: The fiber drums referred to above will easily hold 180–270 kilograms (400–600 lb), and are usually coated internally with a urethane or plastic protective coating. They have steel reinforcement rims at their ends, and are sufficiently strong that this is the only type of drum that is not reinforced in the middle third, but that is almost certainly due to the difficulty in creating a "vee" rib in a paper layer that essentially spirals out from a single end seam.

text: International standard size[edit]

text: A 200-litre drum (known as a 55-gallon drum in the United States and a 44-gallon drum in the United Kingdom) is a cylindrical container with a nominal capacity of 200 litres (55 US or 44 imp gal). The exact capacity varies by manufacturer, purpose, or other factors. Standard drums have inside dimensions of 572 millimetres (22.5 in) diameter and 851 millimetres (33.5 in) height. These dimensions yield a volume of about 218,681 cm3 or 218.681 litres (57.8 US gal; 48.1 imp gal), but they are commonly filled to about 200 litres.

text: The outside dimensions of a 200-litre drum are typically 584 millimetres (23 in) diameter at the top or bottom rim, 597 millimetres (23.5 in) diameter at the chines (ridges around drum), and 876 millimetres (34.5 in) height. Exact dimensions are specified in ANSI MH2.

text: The drums are typically made of steel with a ribbed outer wall to improve rigidity and for rolling. The lids can be welded or secured with a head gasket and bolt ring. Drums can also be made of durable plastic or paperboard. They are commonly used for transporting oils, fuels, chemicals, and dry goods. The construction and performance of drums used for shipment of hazardous materials are governed by UN, country, and carrier regulations.

text: Drums are frequently transported on pallets for ease of handling by a fork truck and for shipping. The drum's size, shape, and weight distribution lends itself to being moved about readily on the loading dock or factory floor with a two-wheeled hand truck. They can be turned on side and rolled. They can also be moved by hand short distances on firm surfaces by tilting and then rolling along the base, or by using a drum handler, which is designed especially for that purpose.

text: Henry Wehrhahn, employee of Nellie Bly’s Iron Clad Manufacturing Company of New York, received two patents in December 1905 that would lead to the modern 55-gallon steel barrel.[2] Use of 200-litre drums became widespread in World War II, the first war in which trucks, cold rolled steel, stamp or pattern forging machinery and welding were widely available. They were first developed by the Axis powers (Germany and Italy), but were quickly adopted by Allies.[3] The drums helped win the Guadalcanal Campaign in the first U.S. offensive in the South Pacific Theater. The U.S. Navy could not maintain command of the sea long enough to offload aviation gasoline for aircraft ashore, so the drums were often transported to the island on fast ships, such as destroyers, and shoved over the sides (or, time permitting, lowered in cargo nets). Because gasoline's density is much less than that of water, the drums floated. Navy Seabees in small craft corralled the drums.

text: Closed-head steel barrels and drums used for shipment of chemicals and petroleum products have a standardised bunghole arrangement, with one 51-millimetre (2 in) (DN50) NPT and one 19-millimetre (3⁄4 in) (DN20) NPT threaded bunghole on opposite sides of the top head. This arrangement is echoed in many plastic drums in the same size. Various components can be mounted to the drum, such as drum pumps and bung mixers.

text: In the past, hazardous waste was often placed in drums of this size and stored in open fields or buried. Over time, some drums would corrode and leak. As a result, these drums have become iconic of pollution problems, even though they have numerous uses and are ubiquitous in commerce. Drums are often cleaned or re-conditioned and then used for storing or shipping various liquids or materials.

text: Drums are frequently reused for many purposes including as barricades to protect construction workers from oncoming traffic, and perhaps most famously as musical instruments.

text: Although crude oil is sometimes shipped in 55-US-gallon drums, the measurement of oil in barrels is based on the whiskey barrels of the 1870s which measured 42 US gallons (35 imp gal; 159 L).[4] The measure of 42 US or wine gallons, corresponds to a wine tierce (third-pipe). A wine barrel, or 1/8 tun, measures 31.5 US gallons (26.2 imp gal; 119.2 L).


document_title: Jack (playing card)

question_text: who does the jack represent in a deck of cards

text: Jack (playing card)

text: History[edit]

text: The earliest predecessor of the knave was the thānī nā'ib (second or under-deputy) in the Mamluk card deck.  This was the lowest of the three court cards and like all court cards was depicted through abstract art or calligraphy.  When brought over to Italy and Spain, the thānī nā'ib was made into an infantry soldier or page ranking below the knight card. In France, where the card was called the valet, the queen was inserted between the king and knight. The knight was subsequently dropped out of non-Tarot decks leaving the valet directly under the queen. The king-queen-valet format then made its way into England.

text: As early as the mid-16th century the card was known in England as the knave (meaning a male servant of royalty). Although jack  was in common usage to designate the knave, the term became more entrenched when, in 1864,[1] American cardmaker Samuel Hart published a deck using "J" instead of "Kn" to designate the lowest-ranking court card. The knave card had been called a jack as part of the terminology of the game All Fours since the 17th century, but this usage was considered common or low class. However, because the card abbreviation for knave was so close to that of the king ("Kn" versus "K"), the two were easily confused.  This confusion was even more pronounced after the markings indicating suits and rankings were moved to the corners of the card, a move which enabled players to "fan" a hand of cards without obscuring the individual suits and ranks. The earliest deck known of this type is from 1693, but such positioning did not become widespread until reintroduced by Hart in 1864, together with the knave-to-jack change.  Books of card games published in the third quarter of the 19th century still referred to the "knave" however, a term that is still recognized in the United Kingdom. (Note the exclamation by Estella in Charles Dickens's novel Great Expectations: "He calls the knaves, jacks, this boy!")

text: Representations[edit]

text: In the English pattern,[2] the jack and the other face cards represent no one in particular,[3] in contrast to the historical French practice, in which each court card is said to represent a particular historical or mythological personage. The valets in the Paris pattern have traditionally been associated with such figures as Ogier the Dane (a knight of Charlemagne and legendary hero of the chansons de geste) for the jack of spades;[4] La Hire (French warrior) for the Jack of Hearts; Hector (mythological hero of the Iliad) for the jack of diamonds; and  Lancelot or Judas Maccabeus for the jack of clubs.[5][6]

text: In some southern Italian decks, there are androgynous knaves that are sometimes referred to as maids.  In the Sicilian Tarot deck, the knaves are unambiguously female and are also known as maids.[7]  As this deck also includes queens, it is the only traditional set to survive into modern times with two ranks of female face cards. This pack may have been influenced by the obsolete Portuguese deck which also had female knaves. The modern Mexican pattern also has female knaves.[8]

text: Poetry[edit]

text: The figure of the jack has been used in many literary works throughout history. Among these is one by 17th-century English writer Samuel Rowlands. The Four Knaves is a series of Satirical Tracts, with Introduction and Notes by E. F. Rimbault, upon the subject of playing cards. His "The Knave of Clubbs: Tis Merry When Knaves Meet" was first published in 1600, then again in 1609 and 1611. In accordance with a promise at the end of this book, Rowlands went on with his series of Knaves, and in 1612 wrote "The Knave of Harts: Haile Fellowe, Well Meet", where his "Supplication to Card-Makers" appears,[9] thought to have been written to the English manufacturers who copied to the English decks the court figures created by the French.

text: Example cards[edit]

text: The cards shown here are from a Paris pattern deck (where the rank is known as the "valet"), and include the historical and mythological names associated with them. The English pattern of the jacks can be seen in the photo at the top of the article.

text:
Jack of spades: Ogier

Jack of hearts: La Hire

Jack of diamonds: Hector

Jack of clubs: Lancelot

text: Trickster figure[edit]

text: The jack, traditionally the lowest face card, has often been promoted to a higher or the highest position in the traditional ranking of cards, where the ace or king generally occupied the first rank.  This is seen in the earliest known European card games, such as Karnöffel, as well as in more recent ones such as Euchre.  Games with such promotion include:

text:
All Fours
Belote
Bezique
Black Maria
Cribbage
Doppelkopf
Egyptian Ratscrew
Euchre
Five-hundred
Forty-fives
Hearts
Jass
Karnöffel
Klaberjass
La Bête
Loo
Marjolet
Maw
Napoleon
Noddy
Pinochle
Polignac
Primero
Reversis
Ruff
Schafkopf
Sheepshead
Skat
Spoil Five
Sueca
Trappola
Twenty Eight


document_title: Human skin

question_text: what type of tissue makes up the most external skin region

text: Human skin

text: Structure[edit]

text: Skin has mesodermal cells, pigmentation, such as melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight. It also contains DNA repair enzymes that help reverse UV damage, such that people lacking the genes for these enzymes suffer high rates of skin cancer. 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. This has led to the classification of people(s) on the basis of skin color.[9]

text: In terms of surface area, the skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old. 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.[10] The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings.[11][better source needed] The average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers (squared), depending on a variety of factors.

text: Skin is composed of three primary layers: the epidermis, the dermis and the hypodermis.[10]

text: Epidermis[edit]

text: 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 body's surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.

text: The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost exclusively by diffused oxygen from the surrounding air[12] and to a far lesser degree by blood capillaries extending to the outer layers of the dermis. The main type of cells which make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, basale. Cells are formed through mitosis at the basale layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation). This process is called "keratinization". This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection.

text: Components[edit]

text: The epidermis contains no blood vessels, and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkel cells. The epidermis helps the skin to regulate body temperature.

text: Layers[edit]

text: Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and are sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells.

text: Sublayers[edit]

text: Epidermis is divided into the following 5 sublayers or strata:

text:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum germinativum (also called "stratum basale").

text: Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips.

text: Genes and proteins expressed in the epidermis[edit]

text: About 70% of all human protein-coding genes are expressed in the skin.[13][14] Almost 500 genes have an elevated pattern of expression in the skin. There are less than 100 genes that are specific for the skin and these are expressed in the epidermis.[15] An analysis of the corresponding proteins show that these are mainly expressed in keratinocytes and have functions related to squamous differentiation and cornification.

text: Dermis[edit]

text: The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the Stratum basale of the epidermis.

text: The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region.

text: Papillary region[edit]

text: The papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae, that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin.

text: In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These epidermal ridges occur in patterns (see: fingerprint) that are genetically and epigenetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of identification.

text: Reticular region[edit]

text: The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity.

text: Also located within the reticular region are the roots of the hairs, sebaceous glands, sweat glands, receptors, nails, and blood vessels.

text: Tattoo ink is held in the dermis. Stretch marks often from pregnancy and obesity, are also located in the dermis.

text: Subcutaneous tissue[edit]

text: The subcutaneous tissue (also hypodermis and subcutis) is not part of the skin, and lies below the dermis of the cutis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body.

text: Cross-section[edit]

text: Development[edit]

text: Skin color[edit]

text: Human skin shows high skin color variety from the darkest brown to the lightest pinkish-white hues. Human skin shows higher variation in color than any other single mammalian species and is the result of natural selection. Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation (UVR) penetrating the skin, controlling its biochemical effects.[16]

text: The actual skin color of different humans is affected by many substances, although the single most important substance determining human skin color is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or the stimulation of the nervous system (anger, fear), arterioles dilate.[17]

text: There are at least five different pigments that determine the color of the skin.[18][19] These pigments are present at different levels and places.

text:
Melanin: It is brown in color and present in the basal layer of the epidermis.
Melanoid: It resembles melanin but is present diffusely throughout the epidermis.
Carotene: This pigment is yellow to orange in color. It is present in the stratum corneum and fat cells of dermis and superficial fascia.
Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple color.
Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red color.

text: There is a correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator. Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations.[20]

text: In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation, and vitamin D which is synthesized from sunlight helps in absorbing calcium. For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium.[21]

text: The Fitzpatrick scale[22][23] is a numerical classification schema for human skin color developed in 1975 as a way to classify the typical response of different types of skin to ultraviolet (UV) light:

text:
I

Always burns, never tans

Pale, Fair, Freckles

II

Usually burns, sometimes tans

Fair

III

May burn, usually tans

Light Brown

IV

Rarely burns, always tans

Olive brown

V

Moderate constitutional pigmentation

Brown

VI

Marked constitutional pigmentation

Black

text: Aging[edit]

text: As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages.

text: Among other things, skin aging is noted by a decrease in volume and elasticity. There are many internal and external causes to skin aging. For example, aging skin receives less blood flow and lower glandular activity.

text: A validated comprehensive grading scale has categorized the clinical findings of skin aging as laxity (sagging), rhytids (wrinkles), and the various facets of photoaging, including erythema (redness), and telangiectasia, dyspigmentation (brown discoloration), solar elastosis (yellowing), keratoses (abnormal growths) and poor texture.[24]

text: Cortisol causes degradation of collagen,[25] accelerating skin aging.[26]

text: Anti-aging supplements are used to treat skin aging.

text: Photoaging[edit]

text: Photoaging has two main concerns: an increased risk for skin cancer and the appearance of damaged skin. In younger skin, sun damage will heal faster since the cells in the epidermis have a faster turnover rate, while in the older population the skin becomes thinner and the epidermis turnover rate for cell repair is lower which may result in the dermis layer being damaged.[27]

text: Functions[edit]

text: Skin performs the following functions:

text:
Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.[5][6] Perspiration contains lysozyme that break the bonds within the cell walls of bacteria.[28]
Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptics.
Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.[6] Loss of this function contributes to the massive fluid loss in burns.
Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness.
Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.
Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.
Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible".[12] In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.
Water resistance: The skin acts as a water-resistant barrier so essential nutrients are not washed out of the body.

text: Skin flora[edit]

text:
The human skin is a rich environment for microbes.[7][8] Around 1000 species of bacteria from 19 bacterial phyla have been found. Most come from only four phyla: Actinobacteria (51.8%), Firmicutes (24.4%), Proteobacteria (16.5%), and Bacteroidetes (6.3%). Propionibacteria and Staphylococci species were the main species in sebaceous areas. There are three main ecological areas: moist, dry and sebaceous. In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture of species but dominated by b-Proteobacteria and Flavobacteriales. Ecologically, sebaceous areas had greater species richness than moist and dry ones. The areas with least similarity between people in species were the spaces between fingers, the spaces between toes, axillae, and umbilical cord stump. Most similarly were beside the nostril, nares (inside
the nostril), and on the back.

text: Reflecting upon the diversity of the human skin researchers on the human skin microbiome have observed: "hairy, moist underarms lie a short distance from smooth dry forearms, but these two niches are likely as ecologically dissimilar as rainforests are to deserts."[7]

text: The NIH has launched the Human Microbiome Project to characterize the human microbiota which includes that on the skin and the role of this microbiome in health and disease.[29]

text: Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings.

text: Clinical significance[edit]

text: Diseases of the skin include skin infections and skin neoplasms (including skin cancer).

text: Dermatology is the branch of medicine that deals with conditions of the skin.[4]

text: Society and culture[edit]

text: Hygiene and skin care[edit]

text: The skin supports its own ecosystems of microorganisms, including yeasts and bacteria, which cannot be removed by any amount of cleaning. Estimates place the number of individual bacteria on the surface of one square inch (6.5 square cm) of human skin at 50 million, though this figure varies greatly over the average 20 square feet (1.9 m2) of human skin. Oily surfaces, such as the face, may contain over 500 million bacteria per square inch (6.5 cm²). Despite these vast quantities, all of the bacteria found on the skin's surface would fit into a volume the size of a pea.[30] In general, the microorganisms keep one another in check and are part of a healthy skin. When the balance is disturbed, there may be an overgrowth and infection, such as when antibiotics kill microbes, resulting in an overgrowth of yeast. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of microbes.

text: Cosmetics should be used carefully on the skin because these may cause allergic reactions. Each season requires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy.

text: Oily skin[edit]

text: Oily skin is caused by over-active sebaceous glands, that produce a substance called sebum, a naturally healthy skin lubricant.[1] When the skin produces excessive sebum, it becomes heavy and thick in texture. Oily skin is typified by shininess, blemishes and pimples.[1] The oily-skin type is not necessarily bad, since such skin is less prone to wrinkling, or other signs of aging,[1] because the oil helps to keep needed moisture locked into the epidermis (outermost layer of skin).

text: The negative aspect of the oily-skin type is that oily complexions are especially susceptible to clogged pores, blackheads, and buildup of dead skin cells on the surface of the skin.[1] Oily skin can be sallow and rough in texture and tends to have large, clearly visible pores everywhere, except around the eyes and neck.[1]

text: Permeability[edit]

text: Human skin has a low permeability; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles.[31][32] This protects the body from external particles such as toxins by not allowing them to come into contact with internal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin. Potential medical applications of such particle transfer has prompted developments in nanomedicine and biology to increase skin permeability. One application of transcutaneous particle delivery could be to locate and treat cancer. Nanomedical researchers seek to target the epidermis and other layers of active cell division where nanoparticles can interact directly with cells that have lost their growth-control mechanisms (cancer cells). Such direct interaction could be used to more accurately diagnose properties of specific tumors or to treat them by delivering drugs with cellular specificity.

text: Nanoparticles[edit]

text: Nanoparticles 40 nm in diameter and smaller have been successful in penetrating the skin.[33][34][35] Research confirms that nanoparticles larger than 40 nm do not penetrate the skin past the stratum corneum.[33] Most particles that do penetrate will diffuse through skin cells, but some will travel down hair follicles and reach the dermis layer.

text: The permeability of skin relative to different shapes of nanoparticles has also been studied. Research has shown that spherical particles have a better ability to penetrate the skin compared to oblong (ellipsoidal) particles because spheres are symmetric in all three spatial dimensions.[35] One study compared the two shapes and recorded data that showed spherical particles located deep in the epidermis and dermis whereas ellipsoidal particles were mainly found in the stratum corneum and epidermal layers.[36] Nanorods are used in experiments because of their unique fluorescent properties but have shown mediocre penetration.

text: Nanoparticles of different materials have shown skin’s permeability limitations. In many experiments, gold nanoparticles 40 nm in diameter or smaller are used and have shown to penetrate to the epidermis. Titanium oxide (TiO2), zinc oxide (ZnO), and silver nanoparticles are ineffective in penetrating the skin past the stratum corneum.[37][38] Cadmium selenide (CdSe) quantum dots have proven to penetrate very effectively when they have certain properties. Because CdSe is toxic to living organisms, the particle must be covered in a surface group. An experiment comparing the permeability of quantum dots coated in polyethylene glycol (PEG), PEG-amine, and carboxylic acid concluded the PEG and PEG-amine surface groups allowed for the greatest penetration of particles. The carboxylic acid coated particles did not penetrate past the stratum corneum.[36]

text: Increasing permeability[edit]

text: Scientists previously believed that the skin was an effective barrier to inorganic particles. Damage from mechanical stressors was believed to be the only way to increase its permeability.[39] Recently, however, simpler and more effective methods for increasing skin permeability have been developed. For example, ultraviolet radiation (UVR) has been used to slightly damage the surface of skin, causing a time-dependent defect allowing easier penetration of nanoparticles.[40] The UVR’s high energy causes a restructuring of cells, weakening the boundary between the stratum corneum and the epidermal layer.[40][41] The damage of the skin is typically measured by the transepidermal water loss (TEWL), though it may take 3–5 days for the TEWL to reach its peak value. When the TEWL reaches its highest value, the maximum density of nanoparticles is able to permeate the skin. Studies confirm that UVR damaged skin significantly increases the permeability.[40][41] The effects of increased permeability after UVR exposure can lead to an increase in the number of particles that permeate the skin. However, the specific permeability of skin after UVR exposure relative to particles of different sizes and materials has not been determined.[40]

text: Other skin damaging methods used to increase nanoparticle penetration include tape stripping, skin abrasion, and chemical enhancement. Tape stripping is the process in which tape is applied to skin then lifted to remove the top layer of skin. Skin abrasion is done by shaving the top 5-10 micrometers off the surface of the skin. Chemical enhancement is the process in which chemicals such as polyvinylpyrrolidone (PVP), dimethyl sulfoxide (DMSO), and oleic acid are applied to the surface of the skin to increase permeability.[42][43]

text: Electroporation is the application of short pulses of electric fields on skin and has proven to increase skin permeability. The pulses are high voltage and on the order of milliseconds when applied. Charged molecules penetrate the skin more frequently than neutral molecules after the skin has been exposed to electric field pulses. Results have shown molecules on the order of 100 micrometers to easily permeate electroporated skin.[43]

text: Applications[edit]

text: A large area of interest in nanomedicine is the transdermal patch because of the possibility of a painless application of therapeutic agents with very few side effects. Transdermal patches have been limited to administer a small number of drugs, such as nicotine, because of the limitations in permeability of the skin. Development of techniques that increase skin permeability has led to more drugs that can be applied via transdermal patches and more options for patients.[43]

text: Increasing the permeability of skin allows nanoparticles to penetrate and target cancer cells. Nanoparticles along with multi-modal imaging techniques have been used as a way to diagnose cancer non-invasively. Skin with high permeability allowed quantum dots with an antibody attached to the surface for active targeting to successfully penetrate and identify cancerous tumors in mice. Tumor targeting is beneficial because the particles can be excited using fluorescence microscopy and emit light energy and heat that will destroy cancer cells.[44]

text: Sunblock and sunscreen[edit]

text: Sunblock and sunscreen are different important skin-care products though both offer full protection from the sun.[45][46]

text: Sunblock—Sunblock is opaque and stronger than sunscreen, since it is able to block most of the UVA/UVB rays and radiation from the sun, and does not need to be reapplied several times in a day. Titanium dioxide and zinc oxide are two of the important ingredients in sunblock.[47]

text: Sunscreen—Sunscreen is more transparent once applied to the skin and also has the ability to protect against UVA/UVB rays, although the sunscreen's ingredients have the ability to break down at a faster rate once exposed to sunlight, and some of the radiation is able to penetrate to the skin. In order for sunscreen to be more effective it is necessary to consistently reapply and use one with a higher sun protection factor.

text: Diet[edit]

text: Vitamin A, also known as retinoids, benefits the skin by normalizing keratinization, downregulating sebum production which contributes to acne, and reversing and treating photodamage, striae, and cellulite.

text: Vitamin D and analogs are used to downregulate the cutaneous immune system and epithelial proliferation while promoting differentiation.

text: Vitamin C is an antioxidant that regulates collagen synthesis, forms barrier lipids, regenerates vitamin E, and provides photoprotection.

text:
Vitamin E is a membrane antioxidant that protects against oxidative damage and also provides protection against harmful UV rays.
[48]

text:
Several scientific studies confirmed that changes in baseline nutritional status affects skin condition.
[49]

text: The Mayo Clinic lists foods they state help the skin: fruits and vegetables, whole-grains, dark leafy greens, nuts, and seeds.[50]


document_title: To hell in a handbasket

question_text: where did the term going to hell in a handbasket come from

text: To hell in a handbasket

text: "Going to hell in a handbasket", "going to hell in a handcart", "going to hell in a handbag", "go to hell in a bucket",[1] "sending something to hell in a handbasket" and "something being like hell in a handbasket" are variations on an American allegorical locution of unclear origin, which describes a situation headed for disaster inescapably or precipitately.

text: I. Windslow Ayer's 1865 polemic[2] alleges, "Judge Morris of the Circuit Court of Illinois at an August meeting of Order of the Sons of Liberty said: "Thousands of our best men were prisoners in Camp Douglas, and if once at liberty would 'send abolitionists to hell in a hand basket.'"[3]

text: In popular culture[edit]

text: The phrase also appeared in the title of several published works and other media:

text:
"To Hell in a Handbasket" is the name of humorist H. Allen Smith's 1962 autobiography.
Hell in a Handbasket was the title of a 1988 Star Trek comic book.
Hell in a Handbasket is the title of a 2006 book (ISBN 1585424587) by American cartoonist Tom Tomorrow, who authors the cartoon strip This Modern World.
"Hell in a handbasket" was the name of an undescribed con requiring a trained cat referenced in the 2004 film, Ocean's Twelve.
Hell in a Handbasket is a song from Voltaire's Ooky Spooky album.
Hell in a Handbasket is the title of a 2011 Meat Loaf album
A number of fictional characters have used a name that puns on the phrase, including:

Helena Handbasket is the name of a character in the TV show Friends. It is the stage name for Chandler's crossdressing dad.
Helena Handbasket is also a fictional nymph in the 2011 video game Rayman Origins.
Helena Handbasket is also the pseudonym of the author of Twilight's Last Gleaming: The Decline and Fall of the United States.

2015 video game Fallout 4 in the prequel it includes a "Vault Tec Representative" (Vault Tec is a fictional company in the Fallout franchise) and refers to the phrase "Heck in a handbasket"