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Clinostat
A clinostat is a device which uses rotation to negate the effects of gravitational pull on plant growth (gravitropism) and development (gravimorphism). It has also been used to study the effects of microgravity on cell cultures, animal embryos and spider webs. Description A single-axis (or horizontal) clinostat consists of a disc attached to a motor. They were originally clockwork but nowadays an electric motor is used. The disc is held vertically and the motor rotates it slowly at rates in the order of one revolution per minute. A plant is attached to the disc so that it is held horizontally. The slow rotation means that the plant experiences a gravitational pull that is averaged over 360 degrees, thus approximating a weightlessness, weightless environment. Clinostats have also been used to cancel out effects of sunlight and other stimuli besides gravity. This type of clinostat must be exactly horizontal to simulate absence of gravity. If the clinostat is at an angle from horizont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Fall Machine
The free fall machine (FFM) is designed to permit the development of small biological sample such as cell cultures with a simulated effect of micro-gravity, under free fall conditions.Schwarzenberg M, Pippia P, Meloni MA, Cossu G, Cogoli-Greuter M, Cogoli A. (1999). Signal transduction in T lymphocytes--a comparison of the data from space, the free fall machine and the random positioning machine. Adv Space Res. 24(6): 793-800 Description The free fall machine (FFM) addresses some of the problems of the simple horizontal clinostat or random positioning machines (RPM). In a typical machine samples are allowed to cycle between free fall for about a metre down a column (micro-gravity simulation, near "0 g") and a "bounce" back to the top of the column that is intended to be so fast (c. 20 g for 20 ms) that it is undetected by the biological sample. Long duration of hyper-gravity is often simulated by machines such as the large diameter centrifuge (LDC) at ESA. To simulate partial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weightlessness
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity. Weight is a measurement of the force on an object at rest in a relatively strong gravitational field (such as on the surface of the Earth). These weight-sensations originate from contact with supporting floors, seats, beds, scales, and the like. A sensation of weight is also produced, even when the gravitational field is zero, when contact forces act upon and overcome a body's inertia by mechanical, non- gravitational forces- such as in a centrifuge, a rotating space station, or within an accelerating vehicle. When the gravitational field is non-uniform, a body in free fall experiences tidal forces and is not stress-free. Near a black hole, such tidal effects can be very strong, leading to ''spaghettification''. In the case of the Earth, the effects are minor, especiall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show ''positive gravitropism'' and stems show ''negative gravitropism''. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside. The mechanism is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microgravity
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity. Weight is a measurement of the force on an object at rest in a relatively strong gravitational field (such as on the surface of the Earth). These weight-sensations originate from contact with supporting floors, seats, beds, scales, and the like. A sensation of weight is also produced, even when the gravitational field is zero, when contact forces act upon and overcome a body's inertia by mechanical, non- gravitational forces- such as in a centrifuge, a rotating space station, or within an accelerating vehicle. When the gravitational field is non-uniform, a body in free fall experiences tidal forces and is not stress-free. Near a black hole, such tidal effects can be very strong, leading to ''spaghettification''. In the case of the Earth, the effects are minor, especiall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Large Diameter Centrifuge
The large diameter centrifuge, or LDC, is any centrifuge extending several meters, which can rotate samples to change their acceleration in space to enhance the effect of gravity. Large diameter centrifuges are used to understand the effect of hyper-gravity (gravitational strengths stronger than that of the Earth) on biological samples, including and not limiting to plants, organs, bacteria, and astronauts (Such as NASA's Human Performance Centrifuge) or non-biological samples to undertake experiments in the field of fluid dynamics, geology, biochemistry and more. Description Frequently, "LDC" is used to refer to the centrifuge at the European Space Agency (ESA)'s campus known as ESTEC (European Space research and TEChnology center). This is an 8-m diameter, four-arm centrifuge covered by a dome, which is available for research. A total of six gondolas, each being able to carry an 80 kg payload, can spin at a maximum of 20 times Earth's gravity, equaling 67 revolutions p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show ''positive gravitropism'' and stems show ''negative gravitropism''. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside. The mechanism is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Positioning Machine
A random positioning machine, or RPM, rotates biological samples along two independent axes to change their orientation in space in complex ways and so eliminate the effect of gravity.Jack J.W.A. van Loon (2007). Some history and use of the random positioning machine, RPM, in gravity related research. Advances in Space Research 39: 1161-1165 RPMs are often used as an alternative to sub-orbital flights or drop towers in research studying the effects of weightlessness or microgravity on biological systems. Description The RPM is a more sophisticated development of the single-axis clinostat. RPMs usually consist of two independently rotating frames. One frame is positioned inside the other giving a very complex net change of orientation to a biological sample mounted in the middle. The RPM is sometimes wrongly referred to as the "3-D clinostat" (which rotates both axis in the same direction, i.e. both clockwise). It is a microweight ('micro-gravity') simulator that is based on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denis Dodart
Denis Dodart was a French physician, naturalist, and botanist. He was born in 1634 in Paris and died on November 5, 1707, in the same city. Biography Childhood and humanist education Denis Dodart was born in 1634 in a Parisian middle class family that belonged to the ''bourgeoisie''. He was a son of Jean Dodart, notary public with a passion for literature, and Marie Dubois, daughter of a lawyer at the Parlement of Paris. He was interested in art and science since young age. He was taught Latin, Greek, music, and drawing. Fontenelle mentioned in his ''Éloge of Monsieur Dodart'' the library of the Dodart family. He studied at the University of Paris and gained his Doctorate of Medicine on 13 October 1660. Denis Dodart was noticed for his erudition, his good eloquency, being open minded. He is described by Guy Patin, dean of the University in a private letter : ''"Ce jourd'hui ic5 Juillet (1660) nous avons fait la Licence de nos vieux Bacheliers, ils sont 7 en nombre, dont ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frank B
Frank, FRANK, or Franks may refer to: People * Frank (given name) * Frank (surname) * Franks (surname) * Franks, a Germanic people in late Roman times * Franks, a term in the Muslim world for all western Europeans, particularly during the Crusades Currency * Liechtenstein franc or frank, the currency of Liechtenstein since 1920 * Swiss franc or frank, the currency of Switzerland since 1850 * Westphalian frank, currency of the Kingdom of Westphalia between 1808 and 1813 * The currencies of the German-speaking cantons of Switzerland (1803–1814): ** Appenzell frank ** Aargau frank ** Basel frank ** Berne frank ** Fribourg frank ** Glarus frank ** Graubünden frank ** Luzern frank ** Schaffhausen frank ** Schwyz frank ** Solothurn frank ** St. Gallen frank ** Thurgau frank ** Unterwalden frank ** Uri frank ** Zürich frank Places * Frank, Alberta, Canada, an urban community, formerly a village * Franks, Illinois, United States, an unincorporated community * Fran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon double bonds). Ethylene is widely used in the chemical industry, and its worldwide production (over 150 million tonnes in 2016) exceeds that of any other organic compound. Much of this production goes toward creating polyethylene, which is a widely used plastic containing polymer chains of ethylene units in various chain lengths. Production greenhouse gas emissions, emits greenhouse gases, including methane from feedstock production and carbon dioxide from any non-sustainable energy used. Ethylene is also an important natural plant hormone and is used in agriculture to induce ripening of fruits. The hydrate of ethylene is ethanol. Structure and properties This hydrocarbon has four hydrogen atoms bound to a pair of carbon atoms that are con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Fall
In classical mechanics, free fall is any motion of a physical object, body where gravity is the only force acting upon it. A freely falling object may not necessarily be falling down in the vertical direction. If the common definition of the word "fall" is used, an object moving upwards is not considered to be falling, but using scientific definitions, if it is subject to only the force of gravity, it is said to be in free fall. The Moon is thus in free fall around the Earth, though its orbital speed keeps it in orbit of the Moon, very far orbit from the Earth's surface. In a roughly uniform gravitational field gravity acts on each part of a body approximately equally. When there are no other forces, such as the normal force exerted between a body (e.g. an astronaut in orbit) and its surrounding objects, it will result in the sensation of weightlessness, a condition that also occurs when the gravitational field is weak (such as when far away from any source of gravity). The ter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
