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Transparent heating film , also called transparent heating plastic or heating transparent polymer film is a thin and flexible polymer film with a conductive optical coating . Transparent heating films may be rated at 2.5 kW/m 2 at voltages below 48 volts direct current (V DC). This allows heating with secure transformers delivering voltages which will not hurt the human body. Transparent conductive polymer films may be used for heating transparent glasses. A combination with transparent SMD electronic for multipurpose applications, is also possible. It is also a variant of carbon heating film . | https://en.wikipedia.org/wiki/Transparent_heating_film |
Transparent intensional logic (frequently abbreviated as TIL ) is a logical system created by Pavel Tichý . Due to its rich procedural semantics TIL is in particular apt for the logical analysis of natural language . From the formal point of view, TIL is a hyperintensional, partial, typed lambda calculus .
TIL applications cover a wide range of topics from formal semantics , philosophy of language , epistemic logic , philosophical , and formal logic . TIL provides an overarching semantic framework for all sorts of discourse, whether colloquial, scientific, mathematical or logical. The semantic theory is a procedural one, according to which sense is an abstract, pre-linguistic procedure detailing what operations to apply to what procedural constituents to arrive at the product (if any) of the procedure.
TIL procedures, known as constructions , are hyperintensionally individuated. Construction is the single most important notion of transparent intensional logic, being a philosophically well-motivated and formally worked-out conception of Frege ’s notion of mode of presentation. Constructions, and the entities they construct, are organized into a ramified type theory incorporating a simple type theory. The semantics is tailored to the hardest case, as constituted by hyperintensional contexts, and generalized from there to intensional and extensional contexts . The underlying logic is a Frege-style function/argument one, treating functions , rather than relations or sets , as primitive, together with a Church -style logic, centred on the operations of functional abstraction and application .
Key constraints informing the TIL approach to semantic analysis are compositionality and anti-contextualism . The assignment of constructions to expressions as their meanings is context-invariant. Depending on the sort of logical context in which a construction occurs, what is context-dependent is the logical manipulation of the respective meaning itself rather than the meaning assignment.
This linguistics article is a stub . You can help Wikipedia by expanding it .
This logic -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transparent_intensional_logic |
Transparent wood composites are novel wood materials which have up to 90% transparency . Some have better mechanical properties than wood itself. They were made for the first time in 1992. These materials are significantly more biodegradable than glass and plastics . [ 1 ] [ 2 ] [ 3 ] Transparent wood is also shatterproof, making it suitable for applications like cell phone screens. [ 4 ]
A research group led by Professor Lars Berglund [ 6 ] from Swedish KTH University along with a University of Maryland research group led by Professor Liangbing Hu [ 3 ] have developed a method to remove the color and some chemicals from small blocks of wood , followed by adding polymers , such as poly(methyl methacrylate) (PMMA) and epoxy , at the cellular level, thereby rendering them transparent.
As soon as released in between 2015 and 2016, see-through wood had a large press reaction, with articles in ScienceDaily , [ 7 ] Wired , [ 8 ] The Wall Street Journal , [ 9 ] and The New York Times . [ 1 ]
Actually those research groups rediscovered a work from Siegfried Fink (forest ecologist) , a German Researcher, from as early as 1992: with a process very similar to Berglund's and Hu's, the German Researcher turned wood transparent to reveal specific cavities of the wood structure for analytical purpose. [ 10 ]
In 2021 researchers reported a way to manufacture transparent wood lighter and stronger than glass that requires substantially smaller amounts of chemicals and energy than methods used before. The thin wood produced with "solar-assisted chemical brushing" is claimed to be lighter and about 50 times stronger than wood treated with previous processes. [ 11 ] [ 12 ] [ 13 ]
In its natural state, wood is not a transparent material because of its scattering and absorption of light. The tannish color in wood is due to its chemical polymer composition of cellulose , hemicellulose , and lignin . The wood's lignin is mostly responsible for the wood's distinctive color. Consequently, the amount of lignin determines the levels of visibility in the wood, around 80–95%. [ 14 ] To make wood a visible and transparent material, both absorption and scattering need to be reduced in its production. The manufacturing process of transparent wood is based on removing all of the lignin called the delignification process.
The production of transparent wood from the delignification process vary study by study. However, the basics behind it are as follows: a wood sample is drenched in heated (80 °C–100 °C) solutions containing sodium chloride , sodium hypochlorite , or sodium hydroxide / sulfite for about 3–12 hours followed by immersion in boiling hydrogen peroxide . [ 15 ] Then, the lignin is separated from the cellulose and hemicellulose structure, turning the wood white and allowing the resin penetration to start. Finally, the sample is immersed in a matching resin, usually PMMA, under high temperatures (85 °C) and a vacuum for 12 hours. [ 15 ] This process fills the space previously occupied by the lignin and the open wood cellular structure resulting in the final transparent wood composite.
While the delignification process is a successful method of production, it is limited to its laboratory and experimental production of a small, and low-thickness material that is unable to meet its practical application requirements. [ 16 ] However, at Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources in 2018, Xuan Wang and his colleagues developed a new production method of infiltrating a prepolymerized methyl methacrylate (MMA) solution into delignified wood fibers. By utilizing this new technique, large-size transparent wood with any thickness or any measure can be easily made. [ 16 ] Yet in spite of this success in the manufacture, challenges still exist with regard to mechanical stability and adjustable optical performance. [ 14 ]
Wood is a natural growth material that possesses excellent mechanical properties, including high strength, good durability, high moisture content, and high specific gravity. [ 15 ] Wood can be classified in two types of wood, softwood and hardwood. While each type is different—e.g., the longitudinal cells in softwood are shorter in length when compared to hardwood—both types have a similar hierarchical structure, meaning the orientation of the cells is identical in the wood. [ 15 ] This unique anisotropic structure, the properties with distinctive values when measured in several directions, allows it to pump ions and water for photosynthesis in the wood. [ 15 ] Similarly, in transparent wood composites, removing the lignin and maintaining the cellulose fiber tubes it allows it to become a clear wood that can get soaked in a glue-like epoxy that makes it a robust and transparent material. [ 17 ] An excellent raw material with high transmittance and enhanced mechanical properties.
Researchers have successfully tested an eco-friendly alternative: limonene acrylate, a monomer made from limonene , into an acrylate . [ 18 ] Limonene is a common cyclic terpene that can be extracted from industrial waste, via isomerization of α‐pinene (from wood) or from citrus peel oil. The bio-based polymers can offer advantages compared to conventional non‐renewable polymers from fossil resources, and still retain a high mechanical performance and it is lightweight, stemming from its porous and anisotropic cellulosic structure; and is of great interest for large-scale sustainable nanotechnologies. Succinylation of the delignified wood substrate using succinic anhydride results in a nanostructured and mechanically strong biocomposite. The polymer matrix usually accounts for ≈70 vol%, results in nanostructured biocomposites combining an excellent optical transmittance of 90% at 1.2 mm thickness and a remarkably low haze of 30%, with a high mechanical performance (strength 174 MPa, Young's modulus 17 GPa). [ 19 ]
Transparent wood derives its mechanical properties and performance primarily from its cellulose fiber content and the geometric orientation of the fiber tube cells (radial and tangential) structure, providing the structural base for the design of advanced materials applications. [ 15 ]
One aspect of the transparent wood mechanical property is the strength of the material. According to Zhu and his colleagues, transparent wood in the longitudinal direction has an elastic modulus of 2.37 GPa and strength of 45.38 MPa (both which are lower than for pure PMMA [ 20 ] ) and twice as high as those perpendicular to the longitudinal direction, 1.22 GPa and 23.38 MPa respectively. [ 3 ] They conclude that longitudinal to transverse properties decreased for transparent wood, which they expected as the presence of the polymer resin suppresses the cavity space. [ 3 ] Also, the plastic nature of transparent wood composite provides advantages compare to other brittle materials like glass, meaning it does not shatter upon impact. [ 17 ]
The transparent wood, tightly packed and perpendicularly aligned cellulose fibers operate as wideband wave-guides with high transmission scattering losses for light. This unique light management capacity results in a light propagation effect. [ 21 ] By measuring its optical properties with an integrated sphere, Li and her colleagues found that transparent wood exhibits a high transmittance of 90% (lower than for pure PMMA) and a high optical haze of 95%. [ 21 ] As a result, transparent wood as an energy efficient material could be used to decrease the daytime lighting energy usage by efficiently guiding the sunlight into the house while providing uniform and consistent illumination throughout the day. [ 21 ]
Similarly, the transparent wood's thermal conductivity is attributed to the alignment of the wood cellulose fibers, which has been preserved after lignin removal and polymer infiltration. Transparent wood has a thermal conductivity of 0.32 W⋅m −1 ⋅K −1 in the axial direction and 0.15 W⋅m −1 ⋅K −1 in the radial direction respectably. [ 21 ] Based on the study done by Céline Montanari of the KTH Royal Institute of Technology in Stockholm, the transparent wood's thermal conductivity, which transforms from semi-transparent to transparent when heated, could be used to make buildings more energy-efficient by capturing the sun's energy during the day and releasing it later at night into the interior. [ 22 ]
Although the development of transparent wood composites is still at a lab-scale and prototype level, their potential for energy efficiency and operational savings in the building industry are very promising. An essential advantage with transparent wood is its combination of structural and functional performance for load-bearing structures that combine optical, heat-shielding, or magnetic functionalities. [ 23 ] Transparent wood is also researched for potential use for touch-sensitive surfaces. [ 13 ] [ 24 ] [ 25 ]
Such is the case in building applications where artificial light can be replaced by sunlight through a light transmittance design. Based on research and simulation performed by Joseph Arehart at the University of Colorado Boulder, transparent wood as a glass glazing system replacement could reduce the space conditioning energy consumption by 24.6% to 33.3% in medium (climate zone 3C, San Francisco, CA) and large office spaces (climate zone 4C, Seattle, Washington) respectably. [ 26 ] These are relevant insights in transparent wood's potential functionality because it shows lower thermal conductivity and better impact strength compared to popular glass glazing systems.
Another direction for transparent wood applications is as a high optical transmittance for optoelectronic devices as substrates in photovoltaic solar cells. Li and her colleagues at the KTH Royal Institute of Technology studied the high optical transmittance that makes transparent wood a candidate for substrate in perovskite solar cells. They concluded that transparent wood has high optical transmittance of 86% and long term stability with fracture of toughness 3.2 MPa⋅m 1/2 compared to glass substrate fracture of toughness 0.7–0.85 MPa⋅m 1/2 , which meets the substrate's requirements for solar cells. [ 27 ] These are relevant information for transparent wood's possible application because it is a suitable and sustainable solution to the substrate for solar cell assembly with potential in energy-efficient building applications, as well as replacements for glass and lowering the carbon footprint for the devices. [ 27 ]
Transparent wood could transform the material sciences and building industries by enabling new applications such as load-bearing windows. These components could also generate improvements in energy savings and efficiency over glass or other traditional materials. A lot of work and research is needed to understand the interaction between light and the wood structure further, to tune the optical and mechanical properties, and to take advantage of advanced transparent wood composite applications | https://en.wikipedia.org/wiki/Transparent_wood_composite |
Transphosphorylation is a chemical reaction in which a phosphate group or a phosphono group is transferred between a substrate and a receptor . [ 1 ] There are various phosphate esters in living body including nucleic acid , and phosphorylation reaction related to their synthesis and interconversion is the basis of biochemical reaction. [ 2 ] [ 3 ] In most cases, ATP is the substrate of the phosphate group as a substrate and the enzyme that catalyzes these reactions is referred to as kinase . [ 4 ] | https://en.wikipedia.org/wiki/Transphosphorylation |
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves , stems and flowers . It is a passive process that requires no energy expense by the plant. [ 1 ] Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients . When water uptake by the roots is less than the water lost to the atmosphere by evaporation, plants close small pores called stomata to decrease water loss, which slows down nutrient uptake and decreases CO 2 absorption from the atmosphere limiting metabolic processes, photosynthesis , and growth. [ 2 ]
Water is necessary for plants, but only a small amount of water taken up by the roots is used for growth and metabolism. The remaining 97–99.5% is lost by transpiration and guttation . [ 3 ] Water with any dissolved mineral nutrients is absorbed into the roots by osmosis , which travels through the xylem by way of water molecule adhesion and cohesion to the foliage and out small pores called stomata (singular "stoma"). [ 4 ] The stomata are bordered by guard cells and their stomatal accessory cells (together known as stomatal complex) that open and close the pore. [ 5 ] The cohesion-tension theory explains how leaves pull water through the xylem. Water molecules stick together or exhibit cohesion. As a water molecule evaporates from the leaf's surface it pulls on the adjacent water molecule, creating a continuous water flow through the plant. [ 6 ]
Two major factors influence the rate of water flow from the soil to the roots: the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil. Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem. [ 7 ] Mass flow of liquid water from the roots to the leaves is driven in part by capillary action , but primarily driven by water potential differences. If the water potential in the ambient air is lower than that in the leaf airspace of the stomatal pore, water vapor will travel down the gradient and move from the leaf airspace to the atmosphere. This movement lowers the water potential in the leaf airspace and causes evaporation of liquid water from the mesophyll cell walls. This evaporation increases the tension on the water menisci in the cell walls and decreases their radius, thus exerting tension in the cells' water. Because of the cohesive properties of water, the tension travels through the leaf cells to the leaf and stem xylem, where a momentary negative pressure is created as water is pulled up the xylem from the roots. [ 8 ] In taller plants and trees, the force of gravity pulling the water inside can only be overcome by the decrease in hydrostatic pressure in the upper parts of the plants due to the diffusion of water out of stomata into the atmosphere . [ 3 ]
The word transpiration comes from the words trans, a Latin preposition that means "across," and spiration, which comes from the Latin verb spīrāre, meaning "to breathe." The motion suffix adds the meaning "the act of," creating the meaning, "the ACT of breathing across."
Capillary action is the process of a liquid flowing in narrow spaces without the assistance of, or even in opposition to, external forces like gravity . The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper and plaster, in some non-porous materials such as sand and liquefied carbon fiber , or in a biological cell . It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to propel the liquid. [ citation needed ]
Plants regulate the rate of transpiration by controlling the size of the stomatal apertures. The rate of transpiration is also influenced by the evaporative demand of the atmosphere surrounding the leaf such as boundary layer conductance, humidity , temperature , wind, and incident sunlight. Along with above-ground factors, soil temperature and moisture can influence stomatal opening, [ 9 ] and thus transpiration rate. The amount of water lost by a plant also depends on its size and the amount of water absorbed at the roots. Factors that effect root absorption of water include: moisture content of the soil, excessive soil fertility or salt content, poorly developed root systems, and those impacted by pathogenic bacteria and fungi such as pythium or rhizoctonia .
1) An increased rate of evaporation due to a temperature rise will hasten the loss of water. 2) Decreased relative humidity outside the leaf will increase the water potential gradient .
During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000–4,000 U.S. gallons (11,000–15,000 liters) of water each day, and a large oak tree can transpire 40,000 U.S. gallons (150,000 liters) per year. The transpiration ratio is the ratio of the mass of water transpired to the mass of dry matter produced; the transpiration ratio of crops tends to fall between 200 and 1000 ( i.e. , crop plants transpire 200 to 1000 kg of water for every kg of dry matter produced). [ 10 ]
Transpiration rates of plants can be measured by a number of techniques, including potometers , lysimeters , porometers, photosynthesis systems and thermometric sap flow sensors. Isotope measurements indicate transpiration is the larger component of evapotranspiration . [ 11 ] Recent evidence from a global study [ 12 ] of water stable isotopes shows that transpired water is isotopically different from groundwater and streams. This suggests that soil water is not as well mixed as widely assumed. [ 13 ]
Desert plants have specially adapted structures, such as thick cuticles , reduced leaf areas, sunken stomata and hairs to reduce transpiration and conserve water. Many cacti conduct photosynthesis in succulent stems, rather than leaves, so the surface area of the shoot is very low. Many desert plants have a special type of photosynthesis, termed crassulacean acid metabolism or CAM photosynthesis, in which the stomata are closed during the day and open at night when transpiration will be lower. [ 14 ]
To maintain the pressure gradient necessary for a plant to remain healthy they must continuously uptake water with their roots. They need to be able to meet the demands of water lost due to transpiration. If a plant is incapable of bringing in enough water to remain in equilibrium with transpiration an event known as cavitation occurs. [ 15 ] Cavitation is when the plant cannot supply its xylem with adequate water so instead of being filled with water the xylem begins to be filled with water vapor. These particles of water vapor come together and form blockages within the xylem of the plant. This prevents the plant from being able to transport water throughout its vascular system. [ 16 ] There is no apparent pattern of where cavitation occurs throughout the plant's xylem. If not effectively taken care of, cavitation can cause a plant to reach its permanent wilting point, and die. Therefore, the plant must have a method by which to remove this cavitation blockage, or it must create a new connection of vascular tissue throughout the plant. [ 17 ] The plant does this by closing its stomates overnight, which halts the flow of transpiration. This then allows for the roots to generate over 0.05 mPa of pressure, and that is capable of destroying the blockage and refilling the xylem with water, reconnecting the vascular system. If a plant is unable to generate enough pressure to eradicate the blockage it must prevent the blockage from spreading with the use of pit pears and then create new xylem that can re-connect the vascular system of the plant. [ 18 ]
Scientists have begun using magnetic resonance imaging (MRI) to monitor the internal status of the xylem during transpiration, in a non invasive manner. This method of imaging allows for scientists to visualize the movement of water throughout the entirety of the plant. It also is capable of viewing what phase the water is in while in the xylem, which makes it possible to visualize cavitation events. Scientists were able to see that over the course of 20 hours of sunlight more than 10 xylem vessels began filling with gas particles becoming cavitated. MRI technology also made it possible to view the process by which these xylem structures are repaired in the plant. After three hours in darkness it was seen that the vascular tissue was resupplied with liquid water. This was possible because in darkness the stomates of the plant are closed and transpiration no longer occurs. When transpiration is halted the cavitation bubbles are destroyed by the pressure generated by the roots. These observations suggest that MRIs are capable of monitoring the functional status of xylem and allows scientists to view cavitation events for the first time. [ 17 ]
Transpiration cools plants, as the evaporating water carries away heat energy due to its large latent heat of vaporization of 2260 kJ per liter.
Transpirational cooling is the cooling provided as plants transpire water. Excess heat generated from solar radiation is damaging to plant cells and thermal injury occurs during drought or when there is rapid transpiration which produces wilting. [ 19 ] Green vegetation contributes to moderating climate by being cooler than adjacent bare earth or constructed areas. As plant leaves transpire they use energy to evaporate water aggregating up to a huge volume globally every day.
An individual tree can transpire hundreds of liters of water per day. For every 100 liters of water transpired, the tree then cools by 70 kWh. [ 20 ] [ 21 ] Urban heat island effects can be attributed to the replacement of vegetation by constructed surfaces. Deforested areas reveal a higher temperature than adjacent intact forest. Forests and other natural ecosystems support climate stabilisation. | https://en.wikipedia.org/wiki/Transpiration |
Transpirational cooling is the cooling provided as plants transpire water. Excess heat generated from solar radiation is damaging to plant cells and thermal injury occurs during drought or when there is rapid transpiration which produces wilting. [ 1 ] Green vegetation contributes to moderating climate by being cooler than adjacent bare earth or constructed areas. As plant leaves transpire they use energy to evaporate water aggregating up to a huge volume globally every day.
An individual tree can transpire hundreds of liters of water per day. For every 100 liters of water transpired, the tree then cools by 70 kWh. [ 2 ] [ 3 ] Urban heat island effects can be attributed to the replacement of vegetation by constructed surfaces. Deforested areas reveal a higher temperature than adjacent intact forest. Forests and other natural ecosystems support climate stabilisation.
The Earth’s energy budget reveals pathways to mitigate climate change using our knowledge of the efficacy of how plants cool.
Evapotranspiration is the combined processes moving water from the earth’s surface into the atmosphere . Transpiration is the movement of water through a plant and out of its leaves and other aerial parts into the atmosphere. This movement is driven by solar energy. [ 4 ] In the tallest trees, such as Sequoia sempervirens , the water rises well over 100 metres from root-tip to canopy leaves. Such trees also exploit evaporation to keep the surface cool. Water vapour from evapotranspiration mixed with air moves upwards to the point of saturation and then, helped by the emissions of cloud condensation nuclei , forms clouds. Each gram molecule ( mole ) of condensing water will bring about a marked 1200-fold plus reduction in volume.The simultaneous release of latent heat will drive air from below to fill the partial vacuum. The energy required for the surrounding air to move in is readily calculated from the small (one-fifteenth of latent heat) reduction in temperature. [ citation needed ]
A small amount of that water transpired is used for growth and metabolism . Photosynthesis takes place in the cells of plants and other organisms such as algae , that contain chlorophyll . This process uses the radiant energy from the sun to split water molecules into hydrogen and oxygen that when combined with the carbon sourced from carbon dioxide, produces sugars. Photosynthesis is therefore the basis of almost all food production and produces oxygen as a byproduct. [ citation needed ]
Leaves have many functions. In addition to receiving water from the roots and creating the raw materials for photosynthesis, they also have a large internal surface area to enable the exchange of gases. Their stomata control the flow of water vapour out of the leaf and air into the leaf. In many plants, this is achieved in a structure thin enough to be semi-translucent, to enable some light to pass through to neighbouring leaves. The water that becomes raw material for sugar production, also cools the leaf and supports its structure through the pressure of turgidity . [ 5 ] In 2022, attempts to mass-produce artificial leaves to replicate this process and create hydrogen were still in the development stage. [ 6 ] All organic matter, living and dead, originated as sugars. Part of the process of creating those sugars was splitting the water molecule into its component parts. Vegetation has a huge influence on climate, enacted through photosynthesis and transpiration.
Botanists have calculated that there are about 600 square inches [3,871 cm 2 ] of surface inside a leaf for every cubic inch [16.38 cm 3 ] of its bulk and that a large elm tree has in all some 15 million leaves within an area, if spread out whole, of nearly 10 acres [4.05 ha] or, if unfolded into the sum total of air-breathing light-absorbing surfaces of all the internal chloroplasts something like 25 square miles [64.75 square kilometres]. [ 5 ]
Plants cool when they transpire. Evaporating water and transmitting it through leaf stomata requires a lot of energy. Fred Pearce states that “a single tree transpiring a hundred litres of water a day has a cooling power equivalent to two household air-conditioning units” [ 7 ] (p. 29). An individual tree can transpire hundreds of litres of water per day. Transpiring 100 litres is equivalent to a cooling power of 70 kWh. [ 3 ] [ 2 ] Jan Pokorny posits that a tree with a crown of 5 metres diameter covers an area of about 20m 2 . Of the 150 kWh falling on the crown, 1% is used for photosynthesis, 10% reflected as light energy, 5 to 10% as sensible heat with the remaining 79 to 84% entering the process of transpiration. [ 3 ]
If a larger tree has a sufficient water supply, it can evaporate more than 100 L of water a day. In order to evaporate 100 L of water, approximately 70 kWh (250 MJ) of solar energy is needed. This energy is hidden in water vapor as latent heat and is released again during the process of condensation to liquid water. [ 3 ]
Extrapolated to a hectare, the cooling power of a closed canopy is 35,000 kWh a day.
Cities with constructed surfaces and devegetation are typically warmer than adjacent countryside. This phenomenon is known as urban heat islands . For example Tokyo’s average September temperature has increased by almost 2 °C. over 100 years. This differential would increase in the summer months. Significant increases for cities in the tropics such as Dhaka are projected, accelerated by urban growth and intensification. [ 8 ] The city of Melbourne “plans to plant 3000 trees in Melbourne every year to increase the resilience of the urban forest and to cool our city by 4°C.” [ 9 ] Increasing tree cover and evapotranspiration provides a localised mitigation solution.
On a larger scale, The Mau Forest complex in Western Kenya was deforested from 5,200 km 2 in 1986 to 3,400 km 2 in 2009. Satellite images revealed temperature increases with deforested areas being 20 °C hotter or more. [ citation needed ]
There were about six trillion trees on the planet, but human activity has destroyed roughly half. [ 7 ] Increasing terrestrial biomass will cool the planet. Of the latent heat that escapes at recondensation at cloud level half departs the atmosphere into space, as the photons escape in a part of the spectrum that does not get reabsorbed by greenhouse gases.
Using satellite imagery, the impact of regeneration processes restoring vegetation in arid areas is visible from space and can tracked over time. Vegetation restoration is clearly visible in images of the Penbamoto project in Tanzania. Seeing African Restoration from Space: Planet and Justdiggit... The data associated with these images reveal a temperature reduction in the topsoil up to 0.75 °C. [ 10 ] This temperature reduction was achieved in four years. We can anticipate a larger reduction as the vegetation cover increases.
The movement of heat embodied in water vapour as it leaves vegetation is not well understood given the complexity of the dynamics. [ 11 ] While the movement of water into the atmosphere through evapotranspiration and consequent cooling is broadly accepted, the movement of water further into the atmosphere is more contentious. [ 12 ] There are observable phenomena that provide some clues; mornings following cloudless skies will be cooler than cloudy nights, and deserts get very hot during the day and cool rapidly at night. Heat transfer physics are complex, and involve energy carriers including photons . When energy is freed upon condensation, photons are emitted, transferring energy both upward and downward in the atmosphere. [ 13 ] Oceans add further complexity of atmospheric dynamics. [ citation needed ]
A 2022 World Resources Institute report says that albedo , surface roughness, and aerosols , along with evapotranspiration, generate clouds that increase the albedo cooling effect. They calculate that reduced emissions from tropical forest loss could achieve 2.8 gigatonnes of CO 2 per year, and an additional 1.4 gigatonnes of CO 2 per year of additional cooling through these albedo effects. [ 14 ]
Thermal imaging captures the infrared radiation emitted from an object. Michal Kravčík , Jan Pokorný and co-authors used thermographs to demonstrate the temperature differential between vegetation and constructed surfaces in their 2007 Water for the recovery of the climate - a new water paradigm . [ 15 ]
The images to the right were taken with a thermal lens mounted on a mobile phone alongside visual images for reference points. A 20 °C. plus temperature differential between vegetation and was often recorded. [ 16 ] The three images here pair thermal images and visual images. They reveal significant temperature differences between vegetated and bare surfaces. The image of the Coronation Reserve shows an areas of turf and the margin of native forest separated by a herbicide strip. The bottom image is a thermal image with a slightly different perspective, mainly caused by different camera lenses. The key information distilled from these images is the temperature differences. The grass and the forest margin have similar heat signatures. Temperatures range from 29 to 37 °C. while the dividing herbicide strip reaches 53 °C. Note also the vehicle tracks in the top image with roughly proximate higher temperature readings in the bottom image with an 8 °C. differential. Over time vehicles compact soil structure leading to reduced plant growth, especially when vehicles drive on wet soils. This image reveals that turf can be as cooling as forest. [ citation needed ]
A second side-by-side comparison of thermal and visual images are of a traffic meridian. The ground cover plants are Coprosma repens 'Poor Knights'. The mulch, at its hottest, is 61 °C. The coprosma are as cool as 32 °C. - a 29 °C temperature difference. [ citation needed ]
Non-vegetated or constructed surfaces absorb incoming solar radiation striking [ clarification needed ] that energy and re-radiating it as infrared heat with long waveforms. This is sensible heat in that it can be sensed. Temperature is changed without a change of state. By contrast latent heat (hidden heat) results from a change of state without a change of temperature. For example as radiant energy warms a body of water it raises the temperature generating sensible heat. Water evaporated from the body of water changes state as latent heat. [ 17 ] To change one gram of liquid water to vapour requires 540 calories of heat, and if that water vapour condenses back to liquid water 540 calories are released. [ 17 ] One climate mitigation pathway is for water vapour to carry energy back into the atmosphere where some of that energy will dissipate into space.
Earth’s energy budget reveals the pathways of solar energy to earth, its cycling in earth systems and atmosphere, and release back into space. There is an average of 340.4 watts/m 2 of incoming energy. To maintain a stable climate the same amount of energy must return to space. While increased levels of greenhouse gasses retain more heat, there are other pathways that can influence this energy balance. Understanding these dynamics provides more pathways to moderate the climate than simply relying on emissions reductions and sequestration alone. Referencing the NASA earth’s energy budget, an example is reducing the 398.2 watts/m 2 emitted by the surface, by extending terrestrial and marine vegetative cover as a percentage of land cover and by extending the length of seasonal growth. This is achieved through a whole system approach including regenerating the soil carbon sponge , protection of existing forests, reafforestation , and restoring the biotic pump . The heat emitted from the planet (398.2 watts/m 2 ) is greater than incoming solar energy (340.4 watts/m 2 ). [ citation needed ]
[ 18 ]
Increasing vegetative cover will be enhanced by protecting indigenous rights . Deforestation is an expression of the extractive industries of colonisation . Recent scholarship has identified that indigenous communities in Australia [ 19 ] [ clarification needed ] [ 20 ] and North America [ 21 ] maintained landscapes to reduce the incidence of uncontrolled forest fire and maintain biodiversity. A study of 12,000 years of population data found that “three quarters of terrestrial nature has long been shaped by diverse histories of human habitation and use by Indigenous and traditional peoples”. [ 22 ]
With rare exceptions, current biodiversity losses are caused not by human conversion or degradation of untouched ecosystems, but rather by the appropriation, colonization, and intensification of use in lands inhabited and used by prior societies. [ 22 ]
This calls on us to unlearn some of the assumptions embedded in Western epistemologies and the decolonisation of knowledge as a foundation for more effective climate action. [ 23 ] [ 24 ] | https://en.wikipedia.org/wiki/Transpirational_cooling_(biological) |
Transplant engineering (or allograft engineering ) is a variant of genetic organ engineering which comprises allograft , autograft and xenograft engineering. In allograft engineering the graft is substantially modified by altering its genetic composition. The genetic modification can be permanent or transient. The aim of modifying the allograft is usually the mitigation of immunological graft rejection . [ citation needed ]
Transient genetic allograft engineering has been pioneered by Shaf Keshavjee [ 1 ] [ 2 ] and Marcelo Cypel at University Health Network in Toronto by adenoviral transduction for transgenic expression of the IL-10 gene. Permanent genetic allograft engineering has first been done by Rainer Blasczyk and Constanca Figueiredo at Hannover Medical School in Hanover by lentiviral transduction for knocking down MHC expression in pigs (lung) [ 3 ] and rats (kidney). [ 4 ]
This genetics article is a stub . You can help Wikipedia by expanding it .
This article about biological engineering is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transplant_engineering |
A transplastomic plant is a genetically modified plant in which genes are inactivated, modified or new foreign genes are inserted into the DNA of plastids like the chloroplast instead of nuclear DNA.
Currently, the majority of transplastomic plants are a result of chloroplast manipulation due to poor expression in other plastids . [ 1 ] However, the technique has been successfully applied to the chromoplasts of tomatoes . [ 2 ]
Chloroplasts in plants are thought to have originated from an engulfing event of a photosynthetic bacteria ( cyanobacterial ancestor ) by a eukaryote. [ 3 ] There are many advantages to chloroplast DNA manipulation because of its bacterial origin. For example, the ability to introduce multiple genes (operons) in a single step instead of many steps and the simultaneous expression of many genes with its bacterial gene expression system. [ 4 ] Other advantages include the ability to obtain organic products like proteins at a high concentration and the fact that production of these products will not be affected by epigenetic regulation . [ 5 ]
The reason for product synthesis at high concentrations is because a single plant cell can potentially carry up to 100 chloroplasts. If all these plastids are transformed, all of them can express the introduced foreign genes. [ 1 ] This is may be advantageous compared to transformation of the nucleus, because the nucleus typically contains only one or two copies of the gene . [ 1 ]
The advantages provided by chloroplast DNA manipulation has seen growing interest into this field of research and development, particularly in agricultural and pharmaceutical applications. [ 5 ] However, there are some limitations in chloroplast DNA manipulation, such as the inability to manipulate cereal crop DNA material and poor expression of foreign DNA in non- green plastids as mentioned before. [ 5 ] In addition, the lack of post- translational modification capability like glycosylation in plastids may make some human- related protein expression difficult. [ 6 ] Nevertheless, much progress has been made into plant transplastomics, for example, the production of edible vaccines for Tetanus by using a transplastomic tobacco plant. [ 7 ]
The first requirement for transplastomic plant generation is to have a suitable gene construct that can be introduced into a plastid like a chloroplast in the form of an E. coli plasmid vector. [ 8 ] There are several key features of a suitable gene cassette including but not limited to ( 1 ) selectable marker ( 2 ) flanking sequences ( 3 ) gene of interest ( 4 ) promoter sequences ( 5 ) 5' UTR ( 6 ) 3' UTR ( 7 ) intercistronic elements . [ 9 ] The selectable marker typically tends to be an antibiotic resistant gene, which would give the plant cell the ability to tolerate being grown on antibiotic containing agar plates. [ 5 ] Flanking sequences are crucial for introduction of the gene construct at precise predetermined points of the plastid genome through homologous recombination . [ 4 ] The gene of interests introduced have many different applications and can range from pest resistance genes to vaccine antigen production. [ 4 ] Intercistronic elements (IEE) are important for facilitating high levels of gene expression if multiple genes are introduced in the form of an operon . [ 4 ] Finally, the 5' UTR and 3' UTR enhances ribosomal binding and increases transcript stability respectively. [ 4 ]
The most common method for plastid transformations is biolistics : Small gold or tungsten particles are coated with the plasmid vector and shot into young plant cells or plant embryos, penetrating multiple cell layers and into the plastid. [ 8 ] There will then be a homologous recombination event between the shot plasmid vector and the plastid's genome , hopefully resulting in a stable insertion of the gene cassette into the plastid. [ 8 ] Whilst the transformation efficiency is lower than in agrobacterial mediated transformation, which is also common in plant genetic engineering, particle bombardment is especially suitable for chloroplast transformation. Other transformation methods include the use of polyethylene glycol (PEG)- mediated transformation, which involves the removal of the plant cell wall in order to expose the "naked" plant cell to the foreign genetic material for transformation in the presence of PEG. [ 8 ] PEG- mediated transformation however, is notoriously time-consuming, very technical and labor-intensive as it requires the removal of the cell wall which is a key protective structural component of the plant cell. [ 10 ] Interestingly, a paper released in 2018 has described a successful plastid transformation of the chloroplast from the microalgae species N. oceanica and C. reinhardtii through electroporation . [ 10 ] Whilst no study has been attempted yet for plastid transformation of higher plants using electroporation, this could be an interesting area of study for the future.
In order to persist and be stably maintained in the cell, a plasmid DNA molecule must contain an origin of replication , which allows it to be replicated in the cell independently of the chromosome . When foreign DNA is first introduced to the plant tissue, not all chloroplasts will have successfully integrated the introduced genetic material. [ 5 ] There will be a mixture of normal and transformed chloroplast within the plant cells. This mix of normal and transformed chloroplasts are defined to be " heteroplasmic " chloroplast population. [ 5 ] Stable gene expression of the introduced gene requires a " homoplasmic " population of transformed chloroplasts in the plant cells, where all the chloroplasts in the plant cell has successfully integrated the foreign genetic material. [ 5 ] Typically, homoplasmicity can be achieved and identified through multiple rounds of selection on antibiotics. [ 5 ] This is where the transformed plant tissue are grown repeatedly on agar plates that contain antibiotics like spectinomycin. [ 5 ] Only plant cells that have successfully integrated the gene cassette as shown above will be able to express the antibiotic resistance selectable marker and therefore grow normally on agar plates containing antibiotics. [ 5 ] Plant tissue that do not grow normally will have a bleached appearance as the spectinomycin antibiotic inhibits the ribosomes in the plastids of the plant cell, thereby preventing maintenance of the chloroplast [ 5 ] However, as heteroplasmic population of chloroplasts may still be able to grow on agar plates effectively, many rounds of antibiotic selection and regrowth are required to cultivate a plant tissue that is homoplasmic and stable. [ 5 ] Generation of homoplasmic plant tissue is considered to be a major difficulty in transplastomics and incredibly time-consuming. [ 8 ]
Some plant species such as Nicotiana tabacum are more receptive to transplastomics compared to members of the same genus such as Nicotiana glauca and Nicotiana benthamiana . [ 11 ] An experiment conducted in 2012 highlighted the possibility of facilitating transplastomics for difficult plant species using grafting . Grafting occurs when two different plants are joined and continue to grow, this technique has been widely employed in agricultural applications and can even occur naturally in the wild. [ 12 ] A transplastomic N. tabacum plant was engineered to have spectinomycin resistance and GFP fluorescence . [ 11 ] Whilst the nuclear transgenic plants N. benthamiana and N. glauca were engineered to have kanamycin antibiotic resistance and YFP fluorescence . [ 11 ] The transplastomic plant and the nuclear transgenic plants were then grafted unto each other and the grafted tissues were then analysed. [ 11 ] Fluorescence microscopy and antibiotic selection on agar plates with both kanamycin and spectinomycin revealed that the grafted plant tissue had both transplastomics and nuclear transgene DNA material. [ 11 ] This was further confirmed through PCR analysis. [ 11 ] This study highlighted that plastids like the chloroplast are able to pass between cells across graft junctions and result in the transfer of genetic material between two different plant cell lines. [ 11 ] This finding is significant as it provides an alternative pathway for generation of transplastomic plants for species that are not as easily transformed using our current experimental methodology as seen above. [ 11 ]
Inducible expression systems such as theoriboswitches and pentatricopeptide repeat proteins have been widely studied in an effort to control and modulate expression of transgene products in transplastomic plants. [ 13 ] One big advantage in using inducible expression systems is to optimize concentration of transgene protein production. [ 13 ] For example, young plants need to devote energy and resources into growth and development to become mature plants. [ 13 ] Constitutive expression of the transgene would therefore be detrimental for plant growth and development, as it takes away valuable energy and resources to express the foreign gene construct instead. [ 13 ] This would result in a poorly developed transplastomic plant with low product yield. [ 13 ] Inducible expression expression of the transgene would overcome this limitation and allow the plant to mature fully like a normal wildtype plant before it is induced chemically to begin production of the transgene which can then be harvested. [ 13 ]
Genetically modified plants must be safe for the environment and suitable for coexistence with conventional and organic crops . A major hurdle for traditional nuclear genetically modified crops is posed by the potential outcrossing of the transgene via pollen movement. Initially it was thought that, plastid transformation, which yields transplastomic plants in which the pollen does not contain the transgene, not only increases biosafety, but also facilitates the coexistence of genetically modified, conventional and organic agriculture. Therefore, developing such crops was a major goal of research projects such as Co-Extra and Transcontainer.
However, a study conducted on the tobacco plant in 2007 has disproved this theory. Led by Ralph Bock from the Max Planck Institute of Molecular Plant Physiology in Germany, researchers studied genetically modified tobacco in which the transgene was integrated in chloroplasts. [ 14 ] A transplastomic tobacco plant generated through chloroplast mediated transformation was bred with plants that were male sterile with an untouched chloroplast. [ 14 ] The transplastomic plants were engineered to have resistance to the antibiotic spectinomycin and engineered to produce a green fluorescent protein molecule (GFP). [ 14 ] Therefore, it was hypothesized that any offspring produced by from these two lines of tobacco plant should not be able to grow on spectinomycin or be fluorescent, as the genetic material in the chloroplast should not be able to transfer via pollen. [ 14 ] However, it was found that some of the seeds were resistant to the antibiotic and could germinate on spectinomycin agar plates. [ 14 ] Calculations showed that 1 out of every million pollen grains contained plastid genetic material, which would be significant in an agricultural farm setting. [ 14 ] Because tobacco has a strong tendency towards self-fertilisation, the reliability of transplastomic plants is assumed to be even higher under field conditions. Therefore, the researchers believe that only one in 100,000,000 GM tobacco plants actually would transmit the transgene via pollen. Such values are more than satisfactory to ensure coexistence. However, for GM crops used in the production of pharmaceuticals, or in other cases in which absolutely no outcrossing is permitted, the researchers recommend the combination of chloroplast transformation with other biological containment methods, such as cytoplasmic male sterility or transgene mitigation strategies. This study showed that whilst transplastomic plants do not have absolute gene containment, the level of containment is extremely high and would allow for coexistence of conventional and genetically modified agricultural crops. [ 14 ]
There are public concerns regarding a possible transmission of antibiotic resistant genes to unwanted targets including bacteria and weeds. [ 15 ] As a result of this, technologies have been developed to remove the selectable antibiotic resistance gene marker. One such technology that has been implemented is the Cre/lox system , where the nuclear encoded Cre recombinase can be placed under control of an inducible promoter to remove the antibiotic resistant gene once homoplasmicity has been achieved from the transformation process. [ 16 ]
A recent example of transplastomics in agricultural applications was conferring potato plants protection against the Colorado potato beetle . [ 17 ] This beetle is dubbed a "super-pest" internationally because it has gained resistance against many insecticides and are extremely voracious feeders. [ 17 ] The beetle is estimated to cause up to US$1.4 million in crop damages annually in Michigan alone. [ 18 ] A study conducted in 2015 by Zhang utilized transplastomics to introduce double stranded RNA producing transgenes into the plastid genome. [ 17 ] The double stranded RNA confers protection to the transgenic potato plant via a RNA interference methodology, where consumption of the plant tissue by the potato beetle would result in silencing of key genes required by the beetle for survival. [ 17 ] There was a high level of protection conferred, the leaves of the transplastomic potato plant were mostly unconsumed when exposed to the adult beetles and larvae. [ 17 ] The investigation also revealed an 83% killing efficacy for larvae that consumed the leaves of the transplastomic plant. [ 17 ] This study highlights that as pests gain resistance to traditional chemical insecticides, the use of transplastomics to deliver RNAI- mediated crop protection strategies could become increasingly viable in the future. [ 17 ]
Another notable transplastomics based approach is the production of artemisinic acid through transplastomic tobacco plants which is the precursor molecule that can be used to produce artemisinin . [ 19 ] Artemisinin- based combination therapy is the preferred and recommended treatment of choice by the WHO (World Health Organization) against malaria . [ 19 ] Artemisinin is naturally derived from the plant Artemisia annua , however, only low concentrations of artemisinin in the plant can be harvested naturally and there is currently an insufficient supply for the global demand. [ 19 ] A study conducted in 2016 led by Fuentes, managed to introduce the artemisininic acid production pathway into the chloroplast of N. tabacum through a biolistics approach before using their novel synthetic biology tool COSTREL ( co mbinatorial s upertransformation of t ransplastomic r ecipient l ines) to generate a transplastomic N. tabacum plant that had a very high arteminisin acid yield. [ 20 ] This study illustrates the potential benefits of transplastomics for bio-pharmaceutical applications in the future.
Despite transplastomics being non- viable for non green plastids at the moment, plant transplastomics work done on the chloroplast genome has proved extremely valuable. [ 4 ] The applications for chloroplast transformation includes and is not limited to agriculture, bio-fuel and bio-pharmaceuticals. [ 4 ] This is because of a few factors, which include ease of multiple transgene expression in the form of operons and high copy number expression. [ 4 ] The study of transplastomics still remains a work in progress. More research and development is still required to improve other areas such as transplastomics in non- green plastids, inability to transform cereal crops through transplastomics and a way to circumvent the lack of glycosylation capability in the chloroplast. [ 4 ] Further improvements in this field of study will only give us a potential robust biotechnological route in many applications important in our day-to-day lives. | https://en.wikipedia.org/wiki/Transplastomic_plant |
A communications satellite 's transponder is the series of interconnected units that form a communications channel between the receiving and the transmitting antennas. [ 1 ] It is mainly used in satellite communication to transfer the received signals.
A transponder is typically composed of:
Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Most transponders operate on a bent pipe (i.e., u-bend ) principle, sending back to Earth what goes into the conduit with only amplification and a shift from uplink to downlink frequency. However, some modern satellites use on-board processing, where the signal is demodulated, decoded, re-encoded and modulated aboard the satellite. This type, called a "regenerative" transponder, is more complex, but has many advantages, such as improving the signal to noise ratio as the signal is regenerated from the digital domain, and also permits selective processing of the data in the digital domain.
With data compression and multiplexing , several video (including digital video ) and audio channels may travel through a single transponder on a single wideband carrier .
Original analog video only had one channel per transponder, with subcarriers for audio and automatic transmission-identification service ATIS . Non-multiplexed radio stations can also travel in single channel per carrier (SCPC) mode, with multiple carriers (analog or digital) per transponder. This allows each station to transmit directly to the satellite, rather than paying for a whole transponder or using landlines to send it to an Earth station for multiplexing with other stations.
NASA distinguishes between a " transceiver " and "transponder". A transceiver has an independent transmitter and receiver packaged in the same unit. In a transponder the transmit carrier frequency is derived from the received signal. The frequency linkage allows an interrogating ground station to recover the Doppler shift and thus infer range and speed from a communication signal without allocating power to a separate ranging signal. [ 2 ]
A transponder equivalent ( TPE ) is a normalized way to refer to transponder bandwidth. It simply means how many transponders would be used if the same total bandwidths used only 36 MHz transponders. [ 3 ] [ 4 ] [ 5 ] So, for example, the ARSAT-1 has 24 IEEE K u band transponders: 12 with a bandwidth of 36 MHz, 8 with 54 MHz, and 4 with 72 MHz, which totals to 1152 MHz, or 32 TPE (i.e., 1152 MHz divided by 36 MHz). [ 6 ] [ 7 ] | https://en.wikipedia.org/wiki/Transponder_(satellite_communications) |
Transport (in British English ) or transportation (in American English ) is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air , land ( rail and road ), water , cable , pipelines , and space . The field can be divided into infrastructure , vehicles , and operations. Transport enables human trade , which is essential for the development of civilizations .
Transport infrastructure consists of both fixed installations, including roads , railways , airways , waterways , canals , and pipelines , and terminals such as airports , railway stations , bus stations , warehouses , trucking terminals, refueling depots (including fuel docks and fuel stations ), and seaports . Terminals may be used both for the interchange of passengers and cargo and for maintenance.
Means of transport are any of the different kinds of transport facilities used to carry people or cargo. They may include vehicles, riding animals , and pack animals . Vehicles may include wagons , automobiles , bicycles , buses , trains , trucks , helicopters , watercraft , spacecraft , and aircraft .
A mode of transport is a solution that makes use of a certain type of vehicle, infrastructure, and operation. The transport of a person or of cargo may involve one mode or several of the modes, with the latter case being called inter-modal or multi-modal transport. Each mode has its own advantages and disadvantages, and will be chosen on the basis of cost, capability, and route.
Governments deal with the way the vehicles are operated, and the procedures set for this purpose, including financing, legalities, and policies. In the transport industry, operations and ownership of infrastructure can be either public or private, depending on the country and mode.
Passenger transport may be public , where operators provide scheduled services, or private . Freight transport has become focused on containerization , although bulk transport is used for large volumes of durable items. Transport plays an important part in economic growth and globalization , but most types cause air pollution and use large amounts of land . While it is heavily subsidized by governments, good planning of transport is essential to make traffic flow and restrain urban sprawl .
Human-powered transport, a form of sustainable transport , is the transport of people or goods using human muscle-power, in the form of walking , running , and swimming . Modern technology has allowed machines to enhance human power. Human-powered transport remains popular for reasons of cost-saving, leisure , physical exercise , and environmentalism ; it is sometimes the only type available, especially in underdeveloped or inaccessible regions.
Although humans are able to walk without infrastructure, the transport can be enhanced through the use of roads, especially when using the human power with vehicles, such as bicycles and inline skates . Human-powered vehicles have also been developed for difficult environments, such as snow and water, by watercraft rowing and skiing ; even the air can be entered with human-powered aircraft .
Animal-powered transport is the use of working animals for the movement of people and commodities. Humans may ride some of the animals directly, use them as pack animals for carrying goods, or harness them, alone or in teams , to pull sleds or wheeled vehicles .
A fixed-wing aircraft , commonly called an airplane, is a heavier-than-air craft where movement of the air in relation to the wings is used to generate lift. The term is used to distinguish this from rotary-wing aircraft , where the movement of the lift surfaces relative to the air generates lift. A gyroplane is both fixed-wing and rotary wing. Fixed-wing aircraft range from small trainers and recreational aircraft to large airliners and military cargo aircraft.
Two things necessary for aircraft are air flow over the wings for lift and an area for landing . The majority of aircraft also need an airport with the infrastructure for maintenance, restocking, and refueling and for the loading and unloading of crew, cargo, and passengers. [ 1 ] While the vast majority of aircraft land and take off on land, some are capable of take-off and landing on ice, snow, and calm water.
The aircraft is the second fastest method of transport, after the rocket . Commercial jets can reach up to 955 kilometres per hour (593 mph), single-engine aircraft 555 kilometres per hour (345 mph). Aviation is able to quickly transport people and limited amounts of cargo over longer distances, but incurs high costs and energy use; for short distances or in inaccessible places, helicopters can be used. [ 2 ] As of April 28, 2009, The Guardian article notes that "the WHO estimates that up to 500,000 people are on planes at any time." [ 3 ]
Land transport covers all land-based transport systems that provide for the movement of people, goods, and services. Land transport plays a vital role in linking communities to each other. Land transport is a key factor in urban planning . It consists of two kinds, rail and road.
Rail transport is where a train runs along a set of two parallel steel rails, known as a railway or railroad. The rails are anchored perpendicular to ties (or sleepers) of timber, concrete, or steel, to maintain a consistent distance apart, or gauge . The rails and perpendicular beams are placed on a foundation made of concrete or compressed earth and gravel in a bed of ballast. Alternative methods include monorail and maglev .
A train consists of one or more connected vehicles that operate on the rails. Propulsion is commonly provided by a locomotive , that hauls a series of unpowered cars, that can carry passengers or freight. The locomotive can be powered by steam , by diesel , or by electricity supplied by trackside systems . Alternatively, some or all the cars can be powered, known as a multiple unit . Also, a train can be powered by horses , cables , gravity , pneumatics , and gas turbines . Railed vehicles move with much less friction than rubber tires on paved roads, making trains more energy efficient , though not as efficient as ships.
Intercity trains are long-haul services connecting cities; [ 4 ] modern high-speed rail is capable of speeds up to 350 km/h (220 mph), but this requires specially built track. Regional and commuter trains feed cities from suburbs and surrounding areas, while intra-urban transport is performed by high-capacity tramways and rapid transits , often making up the backbone of a city's public transport. Freight trains traditionally used box cars , requiring manual loading and unloading of the cargo . Since the 1960s, container trains have become the dominant solution for general freight, while large quantities of bulk are transported by dedicated trains.
A road is an identifiable route , way, or path between two or more places . [ 5 ] Roads are typically smoothed, paved , or otherwise prepared to allow easy travel; [ 6 ] though they need not be, and historically many roads were simply recognizable routes without any formal construction or maintenance . [ 7 ] In urban areas , roads may pass through a city or village and be named as streets , serving a dual function as urban space easement and route. [ 8 ]
The most common road vehicle is the automobile; a wheeled passenger vehicle that carries its own motor . Other users of roads include buses , trucks , motorcycles , bicycles , and pedestrians . As of 2010, there were 1.015 billion automobiles worldwide.
Road transport offers complete freedom to road users to transfer the vehicle from one lane to the other and from one road to another according to the need and convenience. This flexibility of changes in location, direction, speed, and timings of travel is not available to other modes of transport. It is possible to provide door-to-door service only by road transport.
Automobiles provide high flexibility with low capacity, but require high energy and area use, and are the main source of harmful noise and air pollution in cities; [ 9 ] buses allow for more efficient travel at the cost of reduced flexibility. [ 4 ] Road transport by truck is often the initial and final stage of freight transport.
Water transport is movement by means of a watercraft —such as a barge , boat , ship , or sailboat —over a body of water, such as a sea , ocean , lake , canal , or river . The need for buoyancy is common to watercraft, making the hull a dominant aspect of its construction, maintenance, and appearance.
In the 19th century, the first steam ships were developed, using a steam engine to drive a paddle wheel or propeller to move the ship. The steam was produced in a boiler using wood or coal and fed through a steam external combustion engine . Now most ships have an internal combustion engine using a slightly refined type of petroleum called bunker fuel . Some ships, such as submarines , use nuclear power to produce the steam. Recreational or educational craft still use wind power, while some smaller craft use internal combustion engines to drive one or more propellers or, in the case of jet boats, an inboard water jet. In shallow draft areas, hovercraft are propelled by large pusher-prop fans. (See Marine propulsion .)
Although it is slow compared to other transport, modern sea transport is a highly efficient method of transporting large quantities of goods. Commercial vessels , nearly 35,000 in number, carried 7.4 billion tons of cargo in 2007. [ 10 ] Transport by water is significantly less costly than air transport for transcontinental shipping ; [ 11 ] short sea shipping and ferries remain viable in coastal areas. [ 12 ] [ 13 ]
Pipeline transport sends goods through a pipe ; most commonly liquid and gases are sent, but pneumatic tubes can also send solid capsules using compressed air. For liquids/gases, any chemically stable liquid or gas can be sent through a pipeline. Short-distance systems exist for sewage , slurry , water , and beer , while long-distance networks are used for petroleum and natural gas .
Cable transport is a broad mode where vehicles are pulled by cables instead of an internal power source. It is most commonly used at steep gradient . Typical solutions include aerial tramways , elevators , and ski lifts ; some of these are also categorized as conveyor transport.
Spaceflight is transport outside Earth's atmosphere by means of a spacecraft . It is most frequently used for satellites placed in Earth orbit. However, human spaceflight mission have landed on the Moon and are occasionally used to rotate crew-members to space stations . Uncrewed spacecraft have also been sent to all the planets of the Solar System.
Suborbital spaceflight is the fastest of the existing and planned transport systems from a place on Earth to a distant "other place" on Earth. Faster transport could be achieved through part of a low Earth orbit or by following that trajectory even faster, using the propulsion of the rocket to steer it.
Infrastructure is the fixed installations that allow a vehicle to operate. It consists of a roadway, a terminal, and facilities for parking and maintenance. For rail, pipeline, road, and cable transport, the entire way the vehicle travels must be constructed. Air and watercraft are able to avoid this, since the airway and seaway do not need to be constructed. However, they require fixed infrastructure at terminals.
Terminals such as airports, ports, and stations, are locations where passengers and freight can be transferred from one vehicle or mode to another. For passenger transport, terminals are integrating different modes to allow riders, who are interchanging between modes, to take advantage of each mode's benefits. For instance, airport rail links connect airports to the city centres and suburbs. The terminals for automobiles are parking lots , while buses and coaches can operate from simple stops. [ 14 ] For freight, terminals act as transshipment points, though some cargo is transported directly from the point of production to the point of use.
The financing of infrastructure can either be public or private . Transport is often a natural monopoly and a necessity for the public; roads, and in some countries railways and airports, are funded through taxation . New infrastructure projects can have high costs and are often financed through debt . Many infrastructure owners, therefore, impose usage fees, such as landing fees at airports or toll plazas on roads. Independent of this, authorities may impose taxes on the purchase or use of vehicles. Because of poor forecasting and overestimation of passenger numbers by planners, there is frequently a benefits shortfall for transport infrastructure projects. [ 15 ]
Animals used in transportation include pack animals and riding animals .
A vehicle is a non-living device that is used to move people and goods. Unlike the infrastructure, the vehicle moves along with the cargo and riders. Unless being pulled/pushed by a cable or muscle-power, the vehicle must provide its own propulsion; this is most commonly done through a steam engine , combustion engine , electric motor , jet engine , or rocket , though other means of propulsion also exist. Vehicles also need a system of converting the energy into movement; this is most commonly done through wheels , propellers , and pressure .
Vehicles are most commonly staffed by a driver . However, some systems, such as people movers and some rapid transits, are fully automated . For passenger transport, the vehicle must have a compartment, seat, or platform for the passengers. Simple vehicles, such as automobiles, bicycles, or simple aircraft, may have one of the passengers as a driver. Recently, the progress related to the Fourth Industrial Revolution has brought a lot of new emerging technologies for transportation and automotive fields such as Connected Vehicles and Autonomous Driving. These innovations are said to form future mobility, but concerns remain on safety and cybersecurity, particularly concerning connected and autonomous mobility. [ 16 ]
Private transport is only subject to the owner of the vehicle, who operates the vehicle themselves. For public transport and freight transport, operations are done through private enterprise or by governments . The infrastructure and vehicles may be owned and operated by the same company, or they may be operated by different entities. Traditionally, many countries have had a national airline and national railway . Since the 1980s, many of these have been privatized . International shipping remains a highly competitive industry with little regulation, [ 17 ] but ports can be public-owned. [ 18 ]
As the population of the world increases, cities grow in size and population—according to the United Nations, 55% of the world's population live in cities, and by 2050 this number is expected to rise to 68%. [ 19 ] Public transport policy must evolve to meet the changing priorities of the urban world. [ 20 ] The institution of policy enforces order in transport, which is by nature chaotic as people attempt to travel from one place to another as fast as possible. This policy helps to reduce accidents and save lives.
Relocation of travelers and cargo are the most common uses of transport. However, other uses exist, such as the strategic and tactical relocation of armed forces during warfare , or the civilian mobility construction or emergency equipment.
Passenger transport, or travel, is divided into public and private transport . Public transport is scheduled services on fixed routes, while private is vehicles that provide ad hoc services at the riders desire. The latter offers better flexibility, but has lower capacity and a higher environmental impact. Travel may be as part of daily commuting or for business , leisure, or migration .
Short-haul transport is dominated by the automobile and mass transit. The latter consists of buses in rural and small cities, supplemented with commuter rail, trams, and rapid transit in larger cities. Long-haul transport involves the use of the automobile, trains, coaches , and aircraft, the last of which have become predominantly used for the longest, including intercontinental, travel. Intermodal passenger transport is where a journey is performed through the use of several modes of transport; since all human transport normally starts and ends with walking, all passenger transport can be considered intermodal. Public transport may also involve the intermediate change of vehicle, within or across modes, at a transport hub , such as a bus or railway station .
Taxis and buses can be found on both ends of the public transport spectrum. Buses are the cheapest mode of transport but are not necessarily flexible, and taxis are very flexible but more expensive. In the middle is demand-responsive transport , offering flexibility whilst remaining affordable.
International travel may be restricted for some individuals due to legislation and visa requirements.
An ambulance is a vehicle used to transport people from or between places of treatment, [ 21 ] and in some instances will also provide out-of-hospital medical care to the patient. The word is often associated with road-going "emergency ambulances", which form part of emergency medical services , administering emergency care to those with acute medical problems.
Air medical services is a comprehensive term covering the use of air transport to move patients to and from healthcare facilities and accident scenes. Personnel provide comprehensive prehospital and emergency and critical care to all types of patients during aeromedical evacuation or rescue operations, aboard helicopters, propeller aircraft, or jet aircraft. [ 22 ] [ 23 ]
Freight transport, or shipping, is a key in the value chain in manufacturing. [ 24 ] With increased specialization and globalization , production is being located further away from consumption, rapidly increasing the demand for transport. [ 25 ] Transport creates place utility by moving the goods from the place of production to the place of consumption. [ 26 ] While all modes of transport are used for cargo transport, there is high differentiation between the nature of the cargo transport, in which mode is chosen. [ 27 ] Logistics refers to the entire process of transferring products from producer to consumer, including storage, transport, transshipment, warehousing, material-handling, and packaging, with associated exchange of information. [ 28 ] Incoterm deals with the handling of payment and responsibility of risk during transport. [ 29 ]
Containerization , with the standardization of ISO containers on all vehicles and at all ports, has revolutionized international and domestic trade , offering a huge reduction in transshipment costs. Traditionally, all cargo had to be manually loaded and unloaded into the haul of any ship or car; containerization allows for automated handling and transfer between modes, and the standardized sizes allow for gains in economy of scale in vehicle operation. This has been one of the key driving factors in international trade and globalization since the 1950s. [ 30 ]
Bulk transport is common with cargo that can be handled roughly without deterioration; typical examples are ore , coal, cereals , and petroleum . Because of the uniformity of the product, mechanical handling can allow enormous quantities to be handled quickly and efficiently. The low value of the cargo combined with high volume also means that economies of scale become essential in transport, and gigantic ships and whole trains are commonly used to transport bulk. Liquid products with sufficient volume may also be transported by pipeline.
Air freight has become more common for products of high value; while less than one percent of world transport by volume is by airline, it amounts to forty percent of the value. Time has become especially important in regards to principles such as postponement and just-in-time within the value chain, resulting in a high willingness to pay for quick delivery of key components or items of high value-to-weight ratio. [ 31 ] In addition to mail, common items sent by air include electronics and fashion clothing.
Transport is a key necessity for specialization —allowing production and consumption of products to occur at different locations. Throughout history, transport has been a spur to expansion; better transport allows more trade and a greater spread of people. Economic growth has always been dependent on increasing the capacity and rationality of transport. [ 32 ] But the infrastructure and operation of transport have a great impact on the land, and transport is the largest drainer of energy, making transport sustainability a major issue.
Due to the way modern cities and communities are planned and operated, a physical distinction between home and work is usually created, forcing people to transport themselves to places of work, study, or leisure, as well as to temporarily relocate for other daily activities. Passenger transport is also the essence of tourism , a major part of recreational transport. Commerce requires the transport of people to conduct business, either to allow face-to-face communication for important decisions or to move specialists from their regular place of work to sites where they are needed.
In lean thinking , transporting materials or work in process from one location to another is seen as one of the seven wastes (Japanese term: muda ) which do not add value to a product. [ 33 ]
Transport planning allows for high use and less impact regarding new infrastructure. Using models of transport forecasting , planners are able to predict future transport patterns. On the operative level, logistics allows owners of cargo to plan transport as part of the supply chain . Transport as a field is also studied through transport economics , a component for the creation of regulation policy by authorities. Transport engineering , a sub-discipline of civil engineering , must take into account trip generation , trip distribution , mode choice , and route assignment , while the operative level is handled through traffic engineering .
Because of the negative impacts incurred, transport often becomes the subject of controversy related to choice of mode, as well as increased capacity. Automotive transport can be seen as a tragedy of the commons , where the flexibility and comfort for the individual deteriorate the natural and urban environment for all. Density of development depends on mode of transport, with public transport allowing for better spatial use. Good land use keeps common activities close to people's homes and places higher-density development closer to transport lines and hubs, to minimize the need for transport. There are economies of agglomeration . Beyond transport, some land uses are more efficient when clustered. Transport facilities consume land, and in cities pavement (devoted to streets and parking) can easily exceed 20 percent of the total land use. An efficient transport system can reduce land waste.
Too much infrastructure and too much smoothing for maximum vehicle throughput mean that in many cities there is too much traffic and many—if not all—of the negative impacts that come with it. It is only in recent years that traditional practices have started to be questioned in many places; as a result of new types of analysis which bring in a much broader range of skills than those traditionally relied on—spanning such areas as environmental impact analysis, public health, sociology, and economics—the viability of the old mobility solutions is increasingly being questioned.
Transport is a major use of energy and burns most of the world's petroleum . This creates air pollution, including nitrous oxides and particulates , and is a significant contributor to global warming through emission of carbon dioxide , [ 35 ] for which transport is the fastest-growing emission sector. [ 36 ] According to the International Energy Agency (IEA), the transportation sector accounts for more than one-third of CO2 emissions globally in the early 2020ies. [ 37 ] By sub-sector, road transport is the largest contributor to global warming. [ 38 ] Environmental regulations in developed countries have reduced individual vehicles' emissions; however, this has been offset by increases in the numbers of vehicles and in the use of each vehicle. [ 35 ] Some pathways to reduce the carbon emissions of road vehicles considerably have been studied. [ 39 ] [ 40 ] Energy use and emissions vary largely between modes, causing environmentalists to call for a transition from air and road to rail and human-powered transport, as well as increased transport electrification and energy efficiency .
Other environmental impacts of transport systems include traffic congestion and automobile-oriented urban sprawl , which can consume natural habitat and agricultural lands. By reducing transport emissions globally, it is predicted that there will be significant positive effects on Earth's air quality , acid rain , smog , and climate change. [ 41 ]
While electric cars are being built to cut down CO 2 emission at the point of use, an approach that is becoming popular among cities worldwide is to prioritize public transport, bicycles, and pedestrian movement . Redirecting vehicle movement to create 20-minute neighbourhoods [ 42 ] that promotes exercise while greatly reducing vehicle dependency and pollution. Some policies are levying a congestion charge [ 43 ] to cars for travelling within congested areas during peak time.
Airplane emissions change depending on the flight distance. It takes a lot of energy to take off and land, so longer flights are more efficient per mile traveled. However, longer flights naturally use more fuel in total. Short flights produce the most CO 2 per passenger mile, while long flights produce slightly less. [ 44 ] [ 45 ] Things get worse when planes fly high in the atmosphere . [ 46 ] [ 47 ] Their emissions trap much more heat than those released at ground level. This is not just because of CO 2 , but a mix of other greenhouse gases in the exhaust. [ 48 ] [ 49 ] In 2022 global CO2 emissions from the transport sector grew by more than 250 Mt CO2 to nearly 8 Gt CO2, which represent more than 3% compared to 2021. Aviation was responsible for a significant part of that increase. [ 50 ]
City buses produce about 0.3 kg of CO 2 for every mile traveled per passenger. For long-distance bus trips (over 20 miles), that pollution drops to about 0.08 kg of CO 2 per passenger mile. [ 51 ] [ 44 ] On average, commuter trains produce around 0.17 kg of CO 2 for each mile traveled per passenger. Long-distance trains are slightly higher at about 0.19 kg of CO 2 per passenger mile. [ 51 ] [ 44 ] [ 52 ] The fleet emission average for delivery vans, trucks and big rigs is 10.17 kg (22.4 lb) CO 2 per gallon of diesel consumed. Delivery vans and trucks average about 7.8 mpg (or 1.3 kg of CO 2 per mile) while big rigs average about 5.3 mpg (or 1.92 kg of CO 2 per mile). [ 53 ] [ 54 ]
The United Nations first formally recognized the role of transport in sustainable development in the 1992 United Nations Earth summit . In the 2012 United Nations World Conference, global leaders unanimously recognized that transport and mobility are central to achieving the sustainability targets. In recent years, data has been collected to show that the transport sector contributes to a quarter of the global greenhouse gas emissions , and therefore sustainable transport has been mainstreamed across several of the 2030 Sustainable Development Goals , especially those related to food, security, health, energy, economic growth, infrastructure, and cities and human settlements. Meeting sustainable transport targets is said to be particularly important to achieving the Paris Agreement . [ 55 ]
There are various Sustainable Development Goals (SDGs) that are promoting sustainable transport to meet the defined goals. These include SDG 3 on health (increased road safety), SDG 7 on energy, SDG 8 on decent work and economic growth, SDG 9 on resilient infrastructure, SDG 11 on sustainable cities (access to transport and expanded public transport), SDG 12 on sustainable consumption and production (ending fossil fuel subsidies ), and SDG 14 on oceans, seas, and marine resources. [ 56 ]
Contemporary development studies recognise transportation networks as a key element of economic development, socio-economic well-being and poverty reduction. [ 57 ] However, road network development has not always fulfilled its original intentions and has contributed significantly to environmental degradation and, in some cases, led to the loss of cultural traditions and the marginalisation of indigenous peoples. [ 58 ] [ 59 ] </ref> Compared to roads, the development of air links (helicopters and planes) has had an even more devastating impact. What is more, helicopters used for tourist activities are subject to considerable criticism from a perspective of environmental protection as well as sports ethics. [ 60 ]
Humans' first ways to move included walking, running, and swimming. The domestication of animals introduced a new way to lay the burden of transport on more powerful creatures, allowing the hauling of heavier loads, or humans riding animals for greater speed and duration. Inventions such as the wheel and the sled (U.K. sledge) helped make animal transport more efficient through the introduction of vehicles .
The first forms of road transport involved animals, such as horses ( domesticated in the 4th or the 3rd millennium BCE), oxen (from about 8000 BCE), [ 61 ] or humans carrying goods over dirt tracks that often followed game trails .
Water transport, including rowed and sailed vessels, dates back to time immemorial and was the only efficient way to transport large quantities or over large distances prior to the Industrial Revolution . The first watercraft were canoes cut out from tree trunks . Early water transport was accomplished with ships that were either rowed or used the wind for propulsion, or a combination of the two. The importance of water has led to most cities that grew up as sites for trading being located on rivers or on the sea-shore, often at the intersection of two bodies of water.
Until the Industrial Revolution, transport remained slow and costly, and production and consumption gravitated as close to each other as feasible. [ citation needed ] The Industrial Revolution in the 19th century saw several inventions fundamentally change transport. With telegraphy , communication became instant and independent of the transport of physical objects. The invention of the steam engine , closely followed by its application in rail transport , made land transport independent of human or animal muscles. Both speed and capacity increased, allowing specialization through manufacturing being located independently of natural resources. The 19th century also saw the development of the steam ship , which sped up global transport.
With the development of the combustion engine and the automobile around 1900, road transport became more competitive again, and mechanical private transport originated. The first "modern" highways were constructed during the 19th century [ citation needed ] with macadam . Later, tarmac and concrete became the dominant paving materials.
In 1903 the Wright brothers demonstrated the first successful controllable airplane , and after World War I (1914–1918) aircraft became a fast way to transport people and express goods over long distances. [ 62 ]
After World War II (1939–1945) the automobile and airlines took higher shares of transport, reducing rail and water to freight and short-haul passenger services. [ 63 ] Scientific spaceflight began in the 1950s, with rapid growth until the 1970s, when interest dwindled. In the 1950s the introduction of containerization gave massive efficiency gains in freight transport, fostering globalization . [ 30 ] International air travel became much more accessible in the 1960s with the commercialization of the jet engine . Along with the growth in automobiles and motorways, rail and water transport declined in relative importance. After the introduction of the Shinkansen in Japan in 1964, high-speed rail in Asia and Europe started attracting passengers on long-haul routes away from the airlines. [ 63 ]
Early in U.S. history , [ when? ] private joint-stock corporations owned most aqueducts , bridges , canals , railroads , roads , and tunnels . Most such transport infrastructure came under government control in the late 19th and early 20th centuries, culminating in the nationalization of inter-city passenger rail-service with the establishment of Amtrak . Recently, [ when? ] however, a movement to privatize roads and other infrastructure has gained some [ quantify ] ground and adherents. [ 64 ] | https://en.wikipedia.org/wiki/Transport |
The transport-of-intensity equation ( TIE ) is a computational approach to reconstruct the phase of a complex wave in optical and electron microscopy . [ 1 ] It describes the internal relationship between the intensity and phase distribution of a wave. [ 2 ]
The TIE was first proposed in 1983 by Michael Reed Teague. [ 3 ] Teague suggested to use the law of conservation of energy to write a differential equation for the transport of energy by an optical field . This equation, he stated, could be used as an approach to phase recovery . [ 4 ]
Teague approximated the amplitude of the wave propagating nominally in the z-direction by a parabolic equation and then expressed it in terms of irradiance and phase:
where λ {\displaystyle \lambda } is the wavelength , I ( x , y , z ) {\displaystyle I(x,y,z)} is the irradiance at point ( x , y , z ) {\displaystyle (x,y,z)} , and Φ {\displaystyle \Phi } is the phase of the wave. If the intensity distribution of the wave and its spatial derivative can be measured experimentally, the equation becomes a linear equation that can be solved to obtain the phase distribution Φ {\displaystyle \Phi } . [ 5 ]
For a phase sample with a constant intensity, the TIE simplifies to
It allows measuring the phase distribution of the sample by acquiring a defocused image, i.e. I ( x , y , z + Δ z ) {\displaystyle I(x,y,z+\Delta z)} .
TIE-based approaches are applied in biomedical and technical applications, such as quantitative monitoring of cell growth in culture, [ 6 ] investigation of cellular dynamics and characterization of optical elements. [ 7 ] The TIE method is also applied for phase retrieval in transmission electron microscopy. [ 8 ] | https://en.wikipedia.org/wiki/Transport-of-intensity_equation |
Transport Phenomena is the first textbook about transport phenomena . It is specifically designed for chemical engineering students. The first edition was published in 1960, two years after having been preliminarily published under the title Notes on Transport Phenomena based on mimeographed notes prepared for a chemical engineering course taught at the University of Wisconsin–Madison during the academic year 1957-1958. [ 1 ] [ 2 ] The second edition was published in August 2001. [ 3 ] A revised second edition was published in 2007. [ 4 ] This text is often known simply as BSL after its authors' initials. [ 5 ]
As the chemical engineering profession developed in the first half of the 20th century, the concept of " unit operations " arose as being needed in the education of undergraduate chemical engineers. The theories of mass, momentum and energy transfer were being taught at that time only to the extent necessary for a narrow range of applications. As chemical engineers began moving into a number of new areas, problem definitions and solutions required a deeper knowledge of the fundamentals of transport phenomena than those provided in the textbooks then available on unit operations.
In the 1950s, R. Byron Bird , Warren E. Stewart and Edwin N. Lightfoot stepped forward to develop an undergraduate course at the University of Wisconsin–Madison to integrate the teaching of fluid flow , heat transfer , and diffusion . From this beginning, they prepared their landmark textbook Transport Phenomena . [ 6 ] [ 7 ]
The book is divided into three basic sections, named Momentum Transport , Energy Transport and Mass Transport :
Transport Phenomena contains many instances of hidden messages and other word play .
For example, the first letters of each sentence of the Preface spell out "This book is dedicated to O. A. Hougen." while in the revised second edition, the first letters of each paragraph spell out "Welcome". The first letters of each paragraph in the Postface spell out "On Wisconsin". In the first printing, in Fig. 9.L (p. 305) "Bird" is typeset safely outside the furnace wall.
According to many chemical engineering professors, the first edition is much better than the second edition. There are many reasons in this regard; The second edition has been revised many times despite the fact that there are still many defects and typographical errors in many parts of the book. On account of revision to defects of the revised second edition book, the authors published "Notes for the 2nd revised edition of TRANSPORT PHENOMENA" on 9 Aug 2011. [ 8 ] | https://en.wikipedia.org/wiki/Transport_Phenomena_(book) |
Transport and Map Symbols is a Unicode block containing transportation and map icons, largely for compatibility with Japanese telephone carriers ' emoji implementations of Shift JIS , and to encode characters in the Wingdings and Wingdings 2 character sets.
The Transport and Map Symbols block contains 105 emoji :
U+1F680–U+1F6C5, U+1F6CB–U+1F6D2, U+1F6D5–U+1F6D7, U+1F6DC–U+1F6E5, U+1F6E9, U+1F6EB–U+1F6EC, U+1F6F0 and U+1F6F3–U+1F6FC. [ 3 ] [ 4 ]
The block has 46 standardized variants defined to specify emoji-style (U+FE0F VS16) or text presentation (U+FE0E VS15) for the
following 23 base characters: U+1F687, U+1F68D, U+1F691, U+1F694, U+1F698, U+1F6AD, U+1F6B2, U+1F6B9–U+1F6BA, U+1F6BC, U+1F6CB, U+1F6CD–U+1F6CF, U+1F6E0–U+1F6E5, U+1F6E9, U+1F6F0 and U+1F6F3. [ 5 ] All of these base characters default to a text presentation.
The Transport and Map Symbols block has six emoji that represent people or body parts.
They can be modified using U+1F3FB–U+1F3FF to provide for a range of human skin color using the Fitzpatrick scale : [ 4 ]
Additional human emoji can be found in other Unicode blocks: Dingbats , Emoticons , Miscellaneous Symbols , Miscellaneous Symbols and Pictographs , Supplemental Symbols and Pictographs and Symbols and Pictographs Extended-A .
The following Unicode-related documents record the purpose and process of defining specific characters in the Transport and Map Symbols block: | https://en.wikipedia.org/wiki/Transport_and_Map_Symbols |
Transport by molecular motor proteins ( Kinesin , Dynein and unconventional Myosin ) is essential for cell functioning and survival. Studies of multiple motors are inspired by the fact that multiple motors are involved in many biological processes such as intra-cellular transport and mitosis. This increasing interest in modeling multiple motor transport is particularly due to improved understanding of single motor function. Several models have been proposed in recent year to understand the transport by multiple motors. [ 1 ] [ 2 ] [ 3 ]
Models developed can be broadly divided into two categories (1) mean-field/steady state model and (2) stochastic model. The mean-field model is useful for describing transport by a large group of motors. In mean-field description, fluctuation in the forces that individual motors feel while pulling the cargo is ignored. In stochastic model, fluctuation in the forces that motors feel are not ignored. Steady-state/mean-field model is useful for modeling transport by a large group of motors whereas stochastic model is useful for modeling transport by few motors. | https://en.wikipedia.org/wiki/Transport_by_multiple-motor_proteins |
A transport coefficient γ {\displaystyle \gamma } measures how rapidly a perturbed system returns to equilibrium.
The transport coefficients occur in transport phenomenon with transport laws
where:
Transport coefficients can be expressed via a Green–Kubo relation :
where A {\displaystyle A} is an observable occurring in a perturbed Hamiltonian, ⟨ ⋅ ⟩ {\displaystyle \langle \cdot \rangle } is an ensemble average and the dot above the A denotes the time derivative. [ 1 ] For times t {\displaystyle t} that are greater than the correlation time of the fluctuations of the observable the transport coefficient obeys a generalized Einstein relation :
In general a transport coefficient is a tensor.
For strong gradients the transport equation typically has to be modified with higher order terms (and higher order Transport coefficients). [ 2 ] | https://en.wikipedia.org/wiki/Transport_coefficient |
The transport length in a strongly diffusing medium (noted l*) is the length over which the direction of propagation of the photon is randomized. It is related to the mean free path l by the relation: [ 1 ]
l ∗ = l 1 − g {\displaystyle l^{*}={\frac {l}{1-g}}}
with g: the asymmetry coefficient. g = ⟨ c o s ( θ ) ⟩ {\displaystyle g=\langle cos(\theta )\rangle } or averaging of the scattering angle θ over a high number of scattering events .
g can be evaluated with the Mie theory . If g=0, l=l*. A single scattering is already isotropic. If g→1, l*→infinite. A single scattering doesn't deviate the photons. Then the scattering never gets isotropic.
This length is useful for renormalizing a non-isotropic scattering problem into an isotropic one in order to use classical diffusion laws ( Fick law and Brownian motion ). The transport length might be measured by transmission experiments and backscattering experiments. [ 2 ] [ 3 ]
This scattering –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transport_length |
A transport network , or transportation network , is a network or graph in geographic space, describing an infrastructure that permits and constrains movement or flow. [ 1 ] Examples include but are not limited to road networks , railways , air routes , pipelines , aqueducts , and power lines . The digital representation of these networks, and the methods for their analysis, is a core part of spatial analysis , geographic information systems , public utilities , and transport engineering . Network analysis is an application of the theories and algorithms of graph theory and is a form of proximity analysis .
The applicability of graph theory to geographic phenomena was recognized at an early date. Many of the early problems and theories undertaken by graph theorists were inspired by geographic situations, such as the Seven Bridges of Königsberg problem, which was one of the original foundations of graph theory when it was solved by Leonhard Euler in 1736. [ 2 ]
In the 1970s, the connection was reestablished by the early developers of geographic information systems , who employed it in the topological data structures of polygons (which is not of relevance here), and the analysis of transport networks. Early works, such as Tinkler (1977), focused mainly on simple schematic networks, likely due to the lack of significant volumes of linear data and the computational complexity of many of the algorithms. [ 3 ] The full implementation of network analysis algorithms in GIS software did not appear until the 1990s, [ 4 ] [ 5 ] but rather advanced tools are generally available today.
Network analysis requires detailed data representing the elements of the network and its properties. [ 6 ] The core of a network dataset is a vector layer of polylines representing the paths of travel, either precise geographic routes or schematic diagrams, known as edges . In addition, information is needed on the network topology , representing the connections between the lines, thus enabling the transport from one line to another to be modeled. Typically, these connection points, or nodes , are included as an additional dataset. [ 7 ]
Both the edges and nodes are attributed with properties related to the movement or flow:
A wide range of methods, algorithms, and techniques have been developed for solving problems and tasks relating to network flow. Some of these are common to all types of transport networks, while others are specific to particular application domains. [ 8 ] Many of these algorithms are implemented in commercial and open-source GIS software, such as GRASS GIS and the Network Analyst extension to Esri ArcGIS .
One of the simplest and most common tasks in a network is to find the optimal route connecting two points along the network, with optimal defined as minimizing some form of cost, such as distance, energy expenditure, or time. [ 9 ] A common example is finding directions in a street network, a feature of almost any web street mapping application such as Google Maps . The most popular method of solving this task, implemented in most GIS and mapping software, is Dijkstra's algorithm . [ 10 ]
In addition to the basic point-to-point routing, composite routing problems are also common. The Traveling salesman problem asks for the optimal (least distance/cost) ordering and route to reach a number of destinations; it is an NP-hard problem, but somewhat easier to solve in network space than unconstrained space due to the smaller solution set. [ 11 ] The Vehicle routing problem is a generalization of this, allowing for multiple simultaneous routes to reach the destinations. The Route inspection or "Chinese Postman" problem asks for the optimal (least distance/cost) path that traverses every edge; a common application is the routing of garbage trucks. This turns out to be a much simpler problem to solve, with polynomial time algorithms.
This class of problems aims to find the optimal location for one or more facilities along the network, with optimal defined as minimizing the aggregate or mean travel cost to (or from) another set of points in the network. A common example is determining the location of a warehouse to minimize shipping costs to a set of retail outlets, or the location of a retail outlet to minimize the travel time from the residences of its potential customers. In unconstrained (cartesian coordinate) space, this is an NP-hard problem requiring heuristic solutions such as Lloyd's algorithm , but in a network space it can be solved deterministically. [ 12 ]
Particular applications often add further constraints to the problem, such as the location of pre-existing or competing facilities, facility capacities, or maximum cost.
A network service area is analogous to a buffer in unconstrained space, a depiction of the area that can be reached from a point (typically a service facility) in less than a specified distance or other accumulated cost. [ 13 ] For example, the preferred service area for a fire station would be the set of street segments it can reach in a small amount of time. When there are multiple facilities, each edge would be assigned to the nearest facility, producing a result analogous to a Voronoi diagram . [ 14 ]
A common application in public utility networks is the identification of possible locations of faults or breaks in the network (which is often buried or otherwise difficult to directly observe), deduced from reports that can be easily located, such as customer complaints.
Traffic has been studied extensively using statistical physics methods. [ 15 ] [ 16 ] [ 17 ]
To ensure the railway system is as efficient as possible a complexity/vertical analysis should also be undertaken. This analysis will aid in the analysis of future and existing systems which is crucial in ensuring the sustainability of a system (Bednar, 2022, pp. 75–76). Vertical analysis will consist of knowing the operating activities (day to day operations) of the system, problem prevention, control activities, development of activities and coordination of activities. [ 18 ] | https://en.wikipedia.org/wiki/Transport_network_analysis |
In engineering , physics , and chemistry , the study of transport phenomena concerns the exchange of mass , energy , charge , momentum and angular momentum between observed and studied systems . While it draws from fields as diverse as continuum mechanics and thermodynamics , it places a heavy emphasis on the commonalities between the topics covered. Mass, momentum, and heat transport all share a very similar mathematical framework, and the parallels between them are exploited in the study of transport phenomena to draw deep mathematical connections that often provide very useful tools in the analysis of one field that are directly derived from the others.
The fundamental analysis in all three subfields of mass, heat, and momentum transfer are often grounded in the simple principle that the total sum of the quantities being studied must be conserved by the system and its environment. Thus, the different phenomena that lead to transport are each considered individually with the knowledge that the sum of their contributions must equal zero. This principle is useful for calculating many relevant quantities. For example, in fluid mechanics, a common use of transport analysis is to determine the velocity profile of a fluid flowing through a rigid volume.
Transport phenomena are ubiquitous throughout the engineering disciplines. Some of the most common examples of transport analysis in engineering are seen in the fields of process, chemical, biological, [ 1 ] and mechanical engineering, but the subject is a fundamental component of the curriculum in all disciplines involved in any way with fluid mechanics , heat transfer , and mass transfer . It is now considered to be a part of the engineering discipline as much as thermodynamics , mechanics , and electromagnetism .
Transport phenomena encompass all agents of physical change in the universe . Moreover, they are considered to be fundamental building blocks which developed the universe, and which are responsible for the success of all life on Earth . However, the scope here is limited to the relationship of transport phenomena to artificial engineered systems . [ 2 ]
In physics , transport phenomena are all irreversible processes of statistical nature stemming from the random continuous motion of molecules , mostly observed in fluids . Every aspect of transport phenomena is grounded in two primary concepts : the conservation laws , and the constitutive equations . The conservation laws, which in the context of transport phenomena are formulated as continuity equations , describe how the quantity being studied must be conserved. The constitutive equations describe how the quantity in question responds to various stimuli via transport. Prominent examples include Fourier's law of heat conduction and the Navier–Stokes equations , which describe, respectively, the response of heat flux to temperature gradients and the relationship between fluid flux and the forces applied to the fluid. These equations also demonstrate the deep connection between transport phenomena and thermodynamics , a connection that explains why transport phenomena are irreversible. Almost all of these physical phenomena ultimately involve systems seeking their lowest energy state in keeping with the principle of minimum energy . As they approach this state, they tend to achieve true thermodynamic equilibrium , at which point there are no longer any driving forces in the system and transport ceases. The various aspects of such equilibrium are directly connected to a specific transport: heat transfer is the system's attempt to achieve thermal equilibrium with its environment, just as mass and momentum transport move the system towards chemical and mechanical equilibrium . [ citation needed ]
Examples of transport processes include heat conduction (energy transfer), fluid flow (momentum transfer), molecular diffusion (mass transfer), radiation and electric charge transfer in semiconductors . [ 3 ] [ 4 ] [ 5 ] [ 6 ]
Transport phenomena have wide application. For example, in solid state physics , the motion and interaction of electrons, holes and phonons are studied under "transport phenomena". Another example is in biomedical engineering , where some transport phenomena of interest are thermoregulation , perfusion , and microfluidics . In chemical engineering , transport phenomena are studied in reactor design , analysis of molecular or diffusive transport mechanisms, and metallurgy .
The transport of mass, energy, and momentum can be affected by the presence of external sources:
An important principle in the study of transport phenomena is analogy between phenomena .
There are some notable similarities in equations for momentum, energy, and mass transfer [ 7 ] which can all be transported by diffusion , as illustrated by the following examples:
The molecular transfer equations of Newton's law for fluid momentum, Fourier's law for heat, and Fick's law for mass are very similar. One can convert from one transport coefficient to another in order to compare all three different transport phenomena. [ 8 ]
A great deal of effort has been devoted in the literature to developing analogies among these three transport processes for turbulent transfer so as to allow prediction of one from any of the others. The Reynolds analogy assumes that the turbulent diffusivities are all equal and that the molecular diffusivities of momentum (μ/ρ) and mass (D AB ) are negligible compared to the turbulent diffusivities. When liquids are present and/or drag is present, the analogy is not valid. Other analogies, such as von Karman 's and Prandtl 's, usually result in poor relations.
The most successful and most widely used analogy is the Chilton and Colburn J-factor analogy . [ 9 ] This analogy is based on experimental data for gases and liquids in both the laminar and turbulent regimes. Although it is based on experimental data, it can be shown to satisfy the exact solution derived from laminar flow over a flat plate. All of this information is used to predict transfer of mass.
In fluid systems described in terms of temperature , matter density , and pressure , it is known that temperature differences lead to heat flows from the warmer to the colder parts of the system; similarly, pressure differences will lead to matter flow from high-pressure to low-pressure regions (a "reciprocal relation"). What is remarkable is the observation that, when both pressure and temperature vary, temperature differences at constant pressure can cause matter flow (as in convection ) and pressure differences at constant temperature can cause heat flow. The heat flow per unit of pressure difference and the density (matter) flow per unit of temperature difference are equal.
This equality was shown to be necessary by Lars Onsager using statistical mechanics as a consequence of the time reversibility of microscopic dynamics. The theory developed by Onsager is much more general than this example and capable of treating more than two thermodynamic forces at once. [ 10 ]
In momentum transfer, the fluid is treated as a continuous distribution of matter. The study of momentum transfer, or fluid mechanics can be divided into two branches: fluid statics (fluids at rest), and fluid dynamics (fluids in motion).
When a fluid is flowing in the x-direction parallel to a solid surface, the fluid has x-directed momentum, and its concentration is υ x ρ . By random diffusion of molecules there is an exchange of molecules in the z -direction. Hence the x-directed momentum has been transferred in the z-direction from the faster- to the slower-moving layer.
The equation for momentum transfer is Newton's law of viscosity written as follows:
where τ zx is the flux of x-directed momentum in the z-direction, ν is μ / ρ , the momentum diffusivity, z is the distance of transport or diffusion, ρ is the density, and μ is the dynamic viscosity. Newton's law of viscosity is the simplest relationship between the flux of momentum and the velocity gradient. It may be useful to note that this is an unconventional use of the symbol τ zx ; the indices are reversed as compared with standard usage in solid mechanics, and the sign is reversed. [ 11 ]
When a system contains two or more components whose concentration vary from point to point, there is a natural tendency for mass to be transferred, minimizing any concentration difference within the system. Mass transfer in a system is governed by Fick's first law : 'Diffusion flux from higher concentration to lower concentration is proportional to the gradient of the concentration of the substance and the diffusivity of the substance in the medium.' Mass transfer can take place due to different driving forces. Some of them are: [ 12 ]
This can be compared to Fick's law of diffusion, for a species A in a binary mixture consisting of A and B:
where D is the diffusivity constant.
Many important engineered systems involve heat transfer. Some examples are the heating and cooling of process streams, phase changes, distillation, etc. The basic principle is the Fourier's law which is expressed as follows for a static system:
The net flux of heat through a system equals the conductivity times the rate of change of temperature with respect to position.
For convective transport involving turbulent flow, complex geometries, or difficult boundary conditions, the heat transfer may be represented by a heat transfer coefficient.
where A is the surface area, Δ T {\displaystyle {\Delta T}} is the temperature driving force, Q is the heat flow per unit time, and h is the heat transfer coefficient.
Within heat transfer, two principal types of convection can occur:
Heat transfer is analyzed in packed beds , nuclear reactors and heat exchangers .
The heat and mass analogy allows solutions for mass transfer problems to be obtained from known solutions to heat transfer problems. Its arises from similar non-dimensional governing equations between heat and mass transfer.
The non-dimensional energy equation for fluid flow in a boundary layer can simplify to the following, when heating from viscous dissipation and heat generation can be neglected:
u ∗ ∂ T ∗ ∂ x ∗ + v ∗ ∂ T ∗ ∂ y ∗ = 1 R e L P r ∂ 2 T ∗ ∂ y ∗ 2 {\displaystyle {u^{*}{\frac {\partial T^{*}}{\partial x^{*}}}}+{v^{*}{\frac {\partial T^{*}}{\partial y^{*}}}}={\frac {1}{Re_{L}Pr}}{\frac {\partial ^{2}T^{*}}{\partial y^{*2}}}}
Where u ∗ {\displaystyle {u^{*}}} and v ∗ {\displaystyle {v^{*}}} are the velocities in the x and y directions respectively normalized by the free stream velocity, x ∗ {\displaystyle {x^{*}}} and y ∗ {\displaystyle {y^{*}}} are the x and y coordinates non-dimensionalized by a relevant length scale, R e L {\displaystyle {Re_{L}}} is the Reynolds number , P r {\displaystyle {Pr}} is the Prandtl number , and T ∗ {\displaystyle {T^{*}}} is the non-dimensional temperature, which is defined by the local, minimum, and maximum temperatures:
T ∗ = T − T m i n T m a x − T m i n {\displaystyle T^{*}={\frac {T-T_{min}}{T_{max}-T_{min}}}}
The non-dimensional species transport equation for fluid flow in a boundary layer can be given as the following, assuming no bulk species generation:
u ∗ ∂ C A ∗ ∂ x ∗ + v ∗ ∂ C A ∗ ∂ y ∗ = 1 R e L S c ∂ 2 C A ∗ ∂ y ∗ 2 {\displaystyle {u^{*}{\frac {\partial C_{A}^{*}}{\partial x^{*}}}}+{v^{*}{\frac {\partial C_{A}^{*}}{\partial y^{*}}}}={\frac {1}{Re_{L}Sc}}{\frac {\partial ^{2}C_{A}^{*}}{\partial y^{*2}}}}
Where C A ∗ {\displaystyle {C_{A}^{*}}} is the non-dimensional concentration, and S c {\displaystyle {Sc}} is the Schmidt number .
Transport of heat is driven by temperature differences, while transport of species is due to concentration differences. They differ by the relative diffusion of their transport compared to the diffusion of momentum. For heat, the comparison is between viscous diffusivity ( ν {\displaystyle {\nu }} ) and thermal diffusion ( α {\displaystyle {\alpha }} ), given by the Prandtl number. Meanwhile, for mass transfer, the comparison is between viscous diffusivity ( ν {\displaystyle {\nu }} ) and mass Diffusivity ( D {\displaystyle {D}} ), given by the Schmidt number.
In some cases direct analytic solutions can be found from these equations for the Nusselt and Sherwood numbers. In cases where experimental results are used, one can assume these equations underlie the observed transport.
At an interface, the boundary conditions for both equations are also similar. For heat transfer at an interface, the no-slip condition allows us to equate conduction with convection, thus equating Fourier's law and Newton's law of cooling :
q ″ = k d T d y = h ( T s − T b ) {\displaystyle q''=k{\frac {dT}{dy}}=h(T_{s}-T_{b})}
Where q” is the heat flux, k {\displaystyle {k}} is the thermal conductivity, h {\displaystyle {h}} is the heat transfer coefficient, and the subscripts s {\displaystyle {s}} and b {\displaystyle {b}} compare the surface and bulk values respectively.
For mass transfer at an interface, we can equate Fick's law with Newton's law for convection, yielding:
J = D d C d y = h m ( C m − C b ) {\displaystyle J=D{\frac {dC}{dy}}=h_{m}(C_{m}-C_{b})}
Where J {\displaystyle {J}} is the mass flux [kg/s m 3 {\displaystyle {m^{3}}} ], D {\displaystyle {D}} is the diffusivity of species a in fluid b, and h m {\displaystyle {h_{m}}} is the mass transfer coefficient. As we can see, q ″ {\displaystyle {q''}} and J {\displaystyle {J}} are analogous, k {\displaystyle {k}} and D {\displaystyle {D}} are analogous, while T {\displaystyle {T}} and C {\displaystyle {C}} are analogous.
Heat-Mass Analogy:
Because the Nu and Sh equations are derived from these analogous governing equations, one can directly swap the Nu and Sh and the Pr and Sc numbers to convert these equations between mass and heat.
In many situations, such as flow over a flat plate, the Nu and Sh numbers are functions of the Pr and Sc numbers to some coefficient n {\displaystyle n} . Therefore, one can directly calculate these numbers from one another using:
N u S h = P r n S c n {\displaystyle {\frac {Nu}{Sh}}={\frac {Pr^{n}}{Sc^{n}}}}
Where can be used in most cases, which comes from the analytical solution for the Nusselt Number for laminar flow over a flat plate. For best accuracy, n should be adjusted where correlations have a different exponent.
We can take this further by substituting into this equation the definitions of the heat transfer coefficient, mass transfer coefficient, and Lewis number , yielding:
h h m = k D L e n = ρ C p L e 1 − n {\displaystyle {\frac {h}{h_{m}}}={\frac {k}{DLe^{n}}}=\rho C_{p}Le^{1-n}}
For fully developed turbulent flow, with n=1/3, this becomes the Chilton–Colburn J-factor analogy. [ 13 ] Said analogy also relates viscous forces and heat transfer, like the Reynolds analogy .
The analogy between heat transfer and mass transfer is strictly limited to binary diffusion in dilute ( ideal ) solutions for which the mass transfer rates are low enough that mass transfer has no effect on the velocity field. The concentration of the diffusing species must be low enough that the chemical potential gradient is accurately represented by the concentration gradient (thus, the analogy has limited application to concentrated liquid solutions). When the rate of mass transfer is high or the concentration of the diffusing species is not low, corrections to the low-rate heat transfer coefficient can sometimes help. Further, in multicomponent mixtures, the transport of one species is affected by the chemical potential gradients of other species.
The heat and mass analogy may also break down in cases where the governing equations differ substantially. For instance, situations with substantial contributions from generation terms in the flow, such as bulk heat generation or bulk chemical reactions, may cause solutions to diverge.
The analogy is useful for both using heat and mass transport to predict one another, or for understanding systems which experience simultaneous heat and mass transfer. For example, predicting heat transfer coefficients around turbine blades is challenging and is often done through measuring evaporating of a volatile compound and using the analogy. [ 14 ] Many systems also experience simultaneous mass and heat transfer, and particularly common examples occur in processes with phase change, as the enthalpy of phase change often substantially influences heat transfer. Such examples include: evaporation at a water surface, transport of vapor in the air gap above a membrane distillation desalination membrane, [ 15 ] and HVAC dehumidification equipment that combine heat transfer and selective membranes. [ 16 ]
The study of transport processes is relevant for understanding the release and distribution of pollutants into the environment. In particular, accurate modeling can inform mitigation strategies. Examples include the control of surface water pollution from urban runoff , and policies intended to reduce the copper content of vehicle brake pads in the U.S. [ 17 ] [ 18 ] | https://en.wikipedia.org/wiki/Transport_phenomena |
Transport standards organisations is an article transport Standards organisations , consortia and groups that are involved in producing and maintaining standards that are relevant to the global transport technology, transport journey planning and transport ticket/retailing industry. Transport systems are inherently distributed systems with complex information requirements. Robust modern standards for transport data are important for the safe and efficient operation of transport systems. These include:
The formal development of international standards is organised in three tiers of Standards Development Organisations , recognised by international agreements :
The SDOs conduct their work through a system of working groups, responsible for different areas of expertise. These evolve over time to accommodate changes in technology. key current working groups for transport standards are outlined below.
CEN Allocates responsibility for different areas of transport standardisation to working groups
ISO Technical Committee 204 is responsible for Transport Information and Control Systems . It has a number of standing Working Groups, which set up Subgroups from time to time.
Current ISO TC204 Working Groups, Work program & Countries that provide Secretariat are as follows
For an up-to-date schedule of the remit of TC204, its current Working Groups and their points of contact please refer to: [1]
The U.S. standards developing organization which is tasked with the domestic implementation of ISO TC204 Transport Standards, is the Telecommunications Industry Association .
As well as the formal SDOs, a number of other international bodies undertake work that is important for Transport and Transport Information standards | https://en.wikipedia.org/wiki/Transport_standards_organisations |
The transport theorem (or transport equation , rate of change transport theorem or basic kinematic equation or Bour's formula, named after: Edmond Bour ) is a vector equation that relates the time derivative of a Euclidean vector as evaluated in a non-rotating coordinate system to its time derivative in a rotating reference frame . It has important applications in classical mechanics and analytical dynamics and diverse fields of engineering. A Euclidean vector represents a certain magnitude and direction in space that is independent of the coordinate system in which it is measured. However, when taking a time derivative of such a vector one actually takes the difference between two vectors measured at two different times t and t+dt . In a rotating coordinate system, the coordinate axes can have different directions at these two times, such that even a constant vector can have a non-zero time derivative. As a consequence, the time derivative of a vector measured in a rotating coordinate system can be different from the time derivative of the same vector in a non-rotating reference system. For example, the velocity vector of an airplane as evaluated using a coordinate system that is fixed to the earth (a rotating reference system) is different from its velocity as evaluated using a coordinate system that is fixed in space. The transport theorem provides a way to relate time derivatives of vectors between a rotating and non-rotating coordinate system, it is derived and explained in more detail in rotating reference frame and can be written as: [ 1 ] [ 2 ] [ 3 ]
d d t f = [ ( d d t ) r + Ω × ] f . {\displaystyle {\frac {\mathrm {d} }{\mathrm {d} t}}{\boldsymbol {f}}=\left[\left({\frac {\mathrm {d} }{\mathrm {d} t}}\right)_{\mathrm {r} }+{\boldsymbol {\Omega }}\times \right]{\boldsymbol {f}}\ .}
Here f is the vector of which the time derivative is evaluated in both the non-rotating, and rotating coordinate system. The subscript r designates its time derivative in the rotating coordinate system and the vector Ω is the angular velocity of the rotating coordinate system.
The Transport Theorem is particularly useful for relating velocities and acceleration vectors between rotating and non-rotating coordinate systems. [ 4 ]
Reference [ 2 ] states: "Despite of its importance in classical mechanics and its ubiquitous application in engineering, there is no universally-accepted name for the Euler derivative transformation formula [...] Several terminology are used: kinematic theorem, transport theorem, and transport equation. These terms, although terminologically correct, are more prevalent in the subject of fluid mechanics to refer to entirely different physics concepts." An example of such a different physics concept is Reynolds transport theorem .
Let b i := T B E e i {\displaystyle {\boldsymbol {b}}_{i}:=T_{B}^{E}{\boldsymbol {e}}_{i}} be the basis vectors of B {\displaystyle B} , as seen from the reference frame E {\displaystyle E} , and denote the components of a vector f {\displaystyle {\boldsymbol {f}}} in B {\displaystyle B} by just f i {\displaystyle f_{i}} .
Let
so that this coordinate transformation is generated , in time, according to T ′ = G ⋅ T {\displaystyle T'=G\cdot T} .
Such a generator differential equation is important for trajectories in Lie group theory .
Applying the product rule with implict summation convention ,
For the rotation groups S O ( n ) {\displaystyle {\mathrm {SO} }(n)} , one has T E B := ( T B E ) − 1 = ( T B E ) T {\displaystyle T_{E}^{B}:=(T_{B}^{E})^{-1}=(T_{B}^{E})^{T}} .
In three dimensions, n = 3 {\displaystyle n=3} , the generator G {\displaystyle G} then equals the cross product operation from the left, a skew-symmetric linear map [ Ω E ] × g := Ω E × g {\displaystyle [{\boldsymbol {\Omega }}_{E}]_{\times }{\boldsymbol {g}}:={\boldsymbol {\Omega }}_{E}\times {\boldsymbol {g}}} for any vector g {\displaystyle {\boldsymbol {g}}} . As a matrix, it is also related to the vector as seen from B {\displaystyle B} via | https://en.wikipedia.org/wiki/Transport_theorem |
The Transportable Applications Environment (TAE) was a rapid prototyping graphical user interface development environment created by NASA in the 1980s. It is available for us on DEC VAX ULTRIX , DEC RISC ULTRIX , Sun , VAX/VMS , Silicon Graphics , HP9000 , and IBM RS/6000 based systems.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transportable_Applications_Environment |
Transportation Research Part D: Transport and Environment is a peer-reviewed , international scientific journal which publishes work relating to land, sea, and air transportation systems and their impact on environmental systems . It was established in 1996 and is published by Elsevier . [ 1 ] The editors-in-chief are Robert Noland (Rutgers University) and Jason Cao (University of Minnesota, Twin Cities).
This article about a journal on Earth sciences is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Transportation_Research_Part_D |
Transportation engineering or transport engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation to provide for the safe, efficient, rapid, comfortable, convenient, economical, and environmentally compatible movement of people and goods transport. [ 1 ] [ 2 ]
The planning aspects of transportation engineering relate to elements of urban planning , and involve technical forecasting decisions and political factors. Technical forecasting of passenger travel usually involves an urban transportation planning model , requiring the estimation of trip generation , trip distribution , mode choice , and route assignment . More sophisticated forecasting can include other aspects of traveler decisions, including auto ownership, trip chaining (the decision to link individual trips together in a tour) and the choice of residential or business location (known as land use forecasting ). Passenger trips are the focus of transportation engineering because they often represent the peak of demand on any transportation system. [ 3 ]
A review of descriptions of the scope of various committees indicates that while facility planning and design continue to be the core of the transportation engineering field, such areas as operations planning, logistics, network analysis, financing, and policy analysis are also important, particularly to those working in highway and urban transportation. The National Council of Examiners for Engineering and Surveying (NCEES) list online the safety protocols, geometric design requirements, and signal timing.
Transportation engineering, primarily involves planning, design, construction, maintenance, and operation of transportation facilities. The facilities support air, highway, railroad, pipeline, water, and even space transportation. The design aspects of transportation engineering include the sizing of transportation facilities (how many lanes or how much capacity the facility has), determining the materials and thickness used in pavement designing the geometry (vertical and horizontal alignment) of the roadway (or track).
Before any planning occurs an engineer must take what is known as an inventory of the area or, if it is appropriate, the previous system in place. This inventory or database must include information on population, land use, economic activity, transportation facilities and services, travel patterns and volumes, laws and ordinances, regional financial resources, and community values and expectations. These inventories help the engineer create business models to complete accurate forecasts of the future conditions of the system.
Operations and management involve traffic engineering , so that vehicles move smoothly on the road or track. Older techniques include signs , signals , markings , and tolling . Newer technologies involve intelligent transportation systems , including advanced traveler information systems (such as variable message signs ), advanced traffic control systems (such as ramp meters ), and vehicle infrastructure integration . Human factors are an aspect of transportation engineering, particularly concerning driver-vehicle interface and user interface of road signs, signals, and markings. [ 4 ]
Engineers in this specialization:
Railway engineers handle the design, construction, and operation of railroads and mass transit systems that use a fixed guideway (such as light rail or monorails ).
Typical tasks include:
Railway engineers work to build a cleaner and safer transportation network by reinvesting and revitalizing the rail system to meet future demands. In the United States, railway engineers work with elected officials in Washington, D.C., on rail transportation issues to make sure that the rail system meets the country's transportation needs. [ 5 ]
Railroad engineers can also move into the specialized field of train dispatching which focuses on train movement control.
Port and harbor engineers handle the design, construction, and operation of ports, harbors, canals, and other maritime facilities.
Airport engineers design and construct airports. Airport engineers must account for the impacts and demands of aircraft in their design of airport facilities. These engineers must use the analysis of predominant wind direction to determine runway orientation, determine the size of runway border and safety areas, different wing tip to wing tip clearances for all gates and must designate the clear zones in the entire port. The Civil Engineering Department, consisting of Civil and Structural Engineers, undertakes the structural design of passenger, terminal design and cargo terminals, aircraft hangars (for parking commercial, private and government aircraft), runways and other pavements, technical buildings for installation of airport ground aids etc. for the airports in-house requirements and consultancy projects. They are even responsible for the master plan for airports they are authorized to work with. | https://en.wikipedia.org/wiki/Transportation_engineering |
The Transportation of Dangerous Goods Act, 1992 ( French : Loi de 1992 sur le transport des marchandises dangereuses ) is a Canadian federal statute. Introduced in the 34th Canadian Parliament , and receiving royal assent on June 23, 1992, the act regulates the transportation of dangerous goods in the country.
The TGDA has an "Offences and Punishments" passage in which are detailed liabilities "on indictment to imprisonment for a term not exceeding two years", and that "Proceedings by way of summary conviction may be instituted at any time within, but not later than, five years after the day on which the subject matter of the proceedings arose." The TGDA falls under the control of the Minister of Transport . [ 1 ]
The Hazardous Waste Manifest form is mandated by the TDGA. [ 2 ]
Class 1 placards all have an orange background.
All placards under Class 1 have a placeholder for the product's compatibility group letter.
Class 1.1, 1.2, and 1.3 bear a black exploding bomb symbol and have placeholders for the product's division.
Class 2 placards all bear various symbols and background colours.
Class 2.1, Flammable Gases, bears a black or white flame symbol on a red background.
Class 2.2, Non-flammable and Non-toxic Gases, bears a black or white gas cylinder symbol on a green background.
Class 2.3, Toxic Gases, bears a black skull and crossbones symbol on a white background.
When anhydrous ammonia ( UN 1005 ) is transported, the container must display (in addition to the existing Class 2.3 placard and UN number) a special placard with the product name and the words "inhalation hazard" (French: dangereux par inhalation ).
If a product is an oxidizing gas , a yellow placard with black text and a flaming 'O' symbol must be displayed.
The Class 3 placard bears a black or white flame symbol on a red background.
Class 4 placards all bear flame symbols with various backgrounds.
Class 4.1, Flammable Solids, has a black symbol with a vertically striped red and white background.
Class 4.2, Substances Liable to Spontaneous Combustion, has a black symbol with the upper half of the placard having a white background and the lower half with a red background.
Class 4.3, Water-reactive Substances, has a black or white symbol with a blue background.
Class 5 placards all bear various symbols and background colours.
Class 5.1, Oxidizing Substances, bears a black flaming 'O' symbol on a yellow background.
Class 5.2, Organic Peroxides, bears a black or white flame symbol with the upper half of the placard having a red background and the lower half with a yellow background.
Class 6 placards all bear various symbols on a white background. | https://en.wikipedia.org/wiki/Transportation_of_Dangerous_Goods_Act,_1992 |
The Transporter Classification Database (or TCDB ) is an International Union of Biochemistry and Molecular Biology (IUBMB)-approved classification system for membrane transport proteins , including ion channels . [ 1 ] [ 2 ] [ 3 ]
The upper level of classification and a few examples of proteins with known 3D structure:
They include a number of transmembrane cytochrome b -like proteins including coenzyme Q - cytochrome c reductase (cytochrome bc1 ); cytochrome b6f complex ; formate dehydrogenase, respiratory nitrate reductase ; succinate - coenzyme Q reductase (fumarate reductase); and succinate dehydrogenase . See electron transport chain . | https://en.wikipedia.org/wiki/Transporter_Classification_Database |
A transposable element ( TE ), also transposon , or jumping gene , is a type of mobile genetic element , a nucleic acid sequence in DNA that can change its position within a genome , sometimes creating or reversing mutations and altering the cell's genetic identity and genome size . [ 1 ] [ 2 ]
Transposition often results in duplication of the same genetic material. The discovery of mobile genetic elements earned Barbara McClintock a Nobel Prize in 1983. [ 3 ] Further research into transposons has potential for use in gene therapy , and the finding of new drug targets in personalized medicine . The vast number of variables in the transposon makes data analytics difficult but combined with other sequencing technologies significant advances may be made in the understanding and treatment of disease. [ 4 ]
Transposable elements make up about half of the genome in a eukaryotic cell , accounting for much of human genetic diversity . [ 4 ] Although TEs are selfish genetic elements , many are important in genome function and evolution. [ 5 ] Transposons are also very useful to researchers as a means to alter DNA inside a living organism.
There are at least two classes of TEs: Class I TEs or retrotransposons generally function via reverse transcription , while Class II TEs or DNA transposons encode the protein transposase , which they require for insertion and excision, and some of these TEs also encode other proteins. [ 6 ]
Barbara McClintock discovered the first TEs in maize ( Zea mays ) at the Cold Spring Harbor Laboratory in New York. McClintock was experimenting with maize plants that had broken chromosomes. [ 7 ]
In the winter of 1944–1945, McClintock planted corn kernels that were self-pollinated, meaning that the silk ( style ) of the flower received pollen from its own anther . [ 7 ] These kernels came from a long line of plants that had been self-pollinated, causing broken arms on the end of their ninth chromosomes. [ 7 ] As the maize plants began to grow, McClintock noted unusual color patterns on the leaves. [ 7 ] For example, one leaf had two albino patches of almost identical size, located side by side on the leaf. [ 7 ] McClintock hypothesized that during cell division certain cells lost genetic material, while others gained what they had lost. [ 8 ] However, when comparing the chromosomes of the current generation of plants with the parent generation, she found certain parts of the chromosome had switched position. [ 8 ] This refuted the popular genetic theory of the time that genes were fixed in their position on a chromosome. McClintock found that genes could not only move but they could also be turned on or off due to certain environmental conditions or during different stages of cell development. [ 8 ]
McClintock also showed that gene mutations could be reversed. [ 9 ] She presented her report on her findings in 1951, and published an article on her discoveries in Genetics in November 1953 entitled "Induction of Instability at Selected Loci in Maize". [ 10 ]
At the 1951 Cold Spring Harbor Symposium where she first publicized her findings, her talk was met with silence. [ 11 ] Her work was largely dismissed and ignored until the late 1960s–1970s when, after TEs were found in bacteria, it was rediscovered. [ 12 ] She was awarded a Nobel Prize in Physiology or Medicine in 1983 for her discovery of TEs, more than thirty years after her initial research. [ 13 ]
Transposable elements represent one of several types of mobile genetic elements . TEs are assigned to one of two classes according to their mechanism of transposition, which can be described as either copy and paste (Class I TEs) or cut and paste (Class II TEs). [ 14 ]
Class I TEs are copied in two stages: first, they are transcribed from DNA to RNA , and the RNA produced is then reverse transcribed to DNA. This copied DNA is then inserted back into the genome at a new position. The reverse transcription step is catalyzed by a reverse transcriptase , which is often encoded by the TE itself. The characteristics of retrotransposons are similar to retroviruses , such as HIV .
Despite the potential negative effects of retrotransposons, like inserting itself into the middle of a necessary DNA sequence, which can render important genes unusable, they are still essential to keep a species' ribosomal DNA intact over the generations, preventing infertility. [ 15 ]
Retrotransposons are commonly grouped into three main orders:
Retroviruses can also be considered TEs. For example, after the conversion of retroviral RNA into DNA inside a host cell, the newly produced retroviral DNA is integrated into the genome of the host cell. These integrated DNAs are termed proviruses . The provirus is a specialized form of eukaryotic retrotransposon, which can produce RNA intermediates that may leave the host cell and infect other cells. The transposition cycle of retroviruses has similarities to that of prokaryotic TEs, suggesting a distant relationship between the two.
The cut-and-paste transposition mechanism of class II TEs does not involve an RNA intermediate. The transpositions are catalyzed by several transposase enzymes. Some transposases non-specifically bind to any target site in DNA, whereas others bind to specific target sequences. The transposase makes a staggered cut at the target site producing sticky ends , cuts out the DNA transposon and ligates it into the target site. A DNA polymerase fills in the resulting gaps from the sticky ends and DNA ligase closes the sugar-phosphate backbone. This results in target site duplication and the insertion sites of DNA transposons may be identified by short direct repeats (a staggered cut in the target DNA filled by DNA polymerase) followed by inverted repeats (which are important for the TE excision by transposase ).
Cut-and-paste TEs may be duplicated if their transposition takes place during S phase of the cell cycle , when a donor site has already been replicated but a target site has not yet been replicated. [ citation needed ] Such duplications at the target site can result in gene duplication , which plays an important role in genomic evolution . [ 17 ] : 284
Not all DNA transposons transpose through the cut-and-paste mechanism. In some cases, a replicative transposition is observed in which a transposon replicates itself to a new target site (e.g. helitron ).
Class II TEs comprise less than 2% of the human genome, making the rest Class I. [ 18 ]
Transposition can be classified as either "autonomous" or "non-autonomous" in both Class I and Class II TEs. Autonomous TEs can move by themselves, whereas non-autonomous TEs require the presence of another TE to move. This is often because dependent TEs lack transposase (for Class II) or reverse transcriptase (for Class I).
Activator element ( Ac ) is an example of an autonomous TE, and dissociation elements ( Ds ) is an example of a non-autonomous TE. Without Ac, Ds is not able to transpose.
Some researchers also identify a third class of transposable elements, [ 19 ] which has been described as "a grab-bag consisting of transposons that don't clearly fit into the other two categories". [ 20 ] Examples of such TEs are the Foldback (FB) elements of Drosophila melanogaster , the TU elements of Strongylocentrotus purpuratus , and Miniature Inverted-repeat Transposable Elements . [ 21 ] [ 22 ]
Approximately 64% of the maize genome is made up of TEs, [ 23 ] [ 24 ] as is 44% of the human genome, [ 25 ] and almost half of murine genomes. [ 26 ]
New discoveries of transposable elements have shown the exact distribution of TEs with respect to their transcription start sites (TSSs) and enhancers. A recent study found that a promoter contains 25% of regions that harbor TEs. It is known that older TEs are not found in TSS locations because TEs frequency starts as a function once there is a distance from the TSS. A possible theory for this is that TEs might interfere with the transcription pausing or the first-intro splicing. [ 27 ] Also as mentioned before, the presence of TEs closed by the TSS locations is correlated to their evolutionary age (number of different mutations that TEs can develop during the time).
Transposons have coexisted with eukaryotes for thousands of years and through their coexistence have become integrated in many organisms' genomes. Colloquially known as 'jumping genes', transposons can move within and between genomes allowing for this integration.
While there are many positive effects of transposons in their host eukaryotic genomes, [ further explanation needed ] there are some instances of mutagenic effects that TEs have on genomes leading to disease and malignant genetic alterations. [ 28 ]
TEs are mutagens and due to the contribution to the formation of new cis-regulatory DNA elements that are connected to many transcription factors that are found in living cells; TEs can undergo many evolutionary mutations and alterations. These are often the causes of genetic disease, and gives the potential lethal effects of ectopic expression. [ 27 ]
TEs can damage the genome of their host cell in different ways: [ 28 ]
TEs use a number of different mechanisms to cause genetic instability and disease in their host genomes.
Diseases often caused by TEs include
One study estimated the rate of transposition of a particular retrotransposon, the Ty1 element in Saccharomyces cerevisiae . Using several assumptions, the rate of successful transposition event per single Ty1 element came out to be about once every few months to once every few years. [ 36 ] Some TEs contain heat-shock like promoters and their rate of transposition increases if the cell is subjected to stress, [ 37 ] thus increasing the mutation rate under these conditions, which might be beneficial to the cell.
Cells defend against the proliferation of TEs in a number of ways. These include piRNAs and siRNAs , [ 38 ] which silence TEs after they have been transcribed.
If organisms are mostly composed of TEs, one might assume that disease caused by misplaced TEs is very common, but in most cases TEs are silenced through epigenetic mechanisms like DNA methylation , chromatin remodeling and piRNA, such that little to no phenotypic effects nor movements of TEs occur as in some wild-type plant TEs. Certain mutated plants have been found to have defects in methylation-related enzymes (methyl transferase) which cause the transcription of TEs, thus affecting the phenotype. [ 6 ] [ 39 ]
One hypothesis suggests that only approximately 100 LINE1 related sequences are active, despite their sequences making up 17% of the human genome. In human cells, silencing of LINE1 sequences is triggered by an RNA interference (RNAi) mechanism. Surprisingly, the RNAi sequences are derived from the 5′ untranslated region (UTR) of the LINE1, a long terminal which repeats itself. Supposedly, the 5′ LINE1 UTR that codes for the sense promoter for LINE1 transcription also encodes the antisense promoter for the miRNA that becomes the substrate for siRNA production. Inhibition of the RNAi silencing mechanism in this region showed an increase in LINE1 transcription. [ 6 ] [ 40 ]
TEs are found in almost all life forms, and the scientific community is still exploring their evolution and their effect on genome evolution. It is unclear whether TEs originated in the last universal common ancestor , arose independently multiple times, or arose once and then spread to other kingdoms by horizontal gene transfer . [ 41 ]
Because excessive TE activity can damage exons , many organisms have acquired mechanisms to inhibit their activity. Bacteria may undergo high rates of gene deletion as part of a mechanism to remove TEs and viruses from their genomes, while eukaryotic organisms typically use RNA interference to inhibit TE activity. Nevertheless, some TEs generate large families often associated with speciation events. [ 42 ] Evolution often deactivates DNA transposons, leaving them as introns (inactive gene sequences). In vertebrate animal cells, nearly all 100,000+ DNA transposons per genome have genes that encode inactive transposase polypeptides. [ 43 ] The first synthetic transposon designed for use in vertebrate (including human) cells, the Sleeping Beauty transposon system , is a Tc1/mariner-like transposon. Its dead ("fossil") versions are spread widely in the salmonid genome and a functional version was engineered by comparing those versions. [ 44 ] Human Tc1-like transposons are divided into Hsmar1 and Hsmar2 subfamilies. Although both types are inactive, one copy of Hsmar1 found in the SETMAR gene is under selection as it provides DNA-binding for the histone-modifying protein. [ 45 ] Many other human genes are similarly derived from transposons. [ 46 ] Hsmar2 has been reconstructed multiple times from the fossil sequences. [ 47 ]
The frequency and location of TE integrations influence genomic structure and evolution and affect gene and protein regulatory networks during development and in differentiated cell types. [ 48 ] Large quantities of TEs within genomes may still present evolutionary advantages, however. Interspersed repeats within genomes are created by transposition events accumulating over evolutionary time. Because interspersed repeats block gene conversion , they protect novel gene sequences from being overwritten by similar gene sequences and thereby facilitate the development of new genes. TEs may also have been co-opted by the vertebrate immune system as a means of producing antibody diversity. The V(D)J recombination system operates by a mechanism similar to that of some TEs. TEs also serve to generate repeating sequences that can form dsRNA to act as a substrate for the action of ADAR in RNA editing. [ 49 ]
TEs can contain many types of genes, including those conferring antibiotic resistance and the ability to transpose to conjugative plasmids. Some TEs also contain integrons , genetic elements that can capture and express genes from other sources. These contain integrase , which can integrate gene cassettes . There are over 40 antibiotic resistance genes identified on cassettes, as well as virulence genes.
Transposons do not always excise their elements precisely, sometimes removing the adjacent base pairs; this phenomenon is called exon shuffling . Shuffling two unrelated exons can create a novel gene product or, more likely, an intron. [ 50 ]
Some non-autonomous DNA TEs found in plants can capture coding DNA from genes and shuffle them across the genome. [ 51 ] This process can duplicate genes in the genome (a phenomenon called transduplication), and can contribute to generate novel genes by exon shuffling. [ 52 ]
There is a hypothesis that states that TEs might provide a ready source of DNA that could be co-opted by the cell to help regulate gene expression. Research showed that many diverse modes of TEs co-evolution along with some transcription factors targeting TE-associated genomic elements and chromatin are evolving from TE sequences. Most of the time, these particular modes do not follow the simple model of TEs and regulating host gene expression. [ 27 ]
Transposable elements can be harnessed in laboratory and research settings to study genomes of organisms and even engineer genetic sequences. The use of transposable elements can be split into two categories: for genetic engineering and as a genetic tool.
In addition to the qualities mentioned for Genetic engineering, a Genetic tool also:-
De novo repeat identification is an initial scan of sequence data that seeks to find the repetitive regions of the genome, and to classify these repeats. Many computer programs exist to perform de novo repeat identification, all operating under the same general principles. [ 54 ] As short tandem repeats are generally 1–6 base pairs in length and are often consecutive, their identification is relatively simple. [ 53 ] Dispersed repetitive elements, on the other hand, are more challenging to identify, due to the fact that they are longer and have often acquired mutations. However, it is important to identify these repeats as they are often found to be transposable elements (TEs). [ 54 ]
De novo identification of transposons involves three steps: 1) find all repeats within the genome, 2) build a consensus of each family of sequences, and 3) classify these repeats. There are three groups of algorithms for the first step. One group is referred to as the k-mer approach, where a k-mer is a sequence of length k. In this approach, the genome is scanned for overrepresented k-mers; that is, k-mers that occur more often than is likely based on probability alone. The length k is determined by the type of transposon being searched for. The k-mer approach also allows mismatches, the number of which is determined by the analyst. Some k-mer approach programs use the k-mer as a base, and extend both ends of each repeated k-mer until there is no more similarity between them, indicating the ends of the repeats. [ 54 ] Another group of algorithms employs a method called sequence self-comparison. Sequence self-comparison programs use databases such as AB-BLAST to conduct an initial sequence alignment . As these programs find groups of elements that partially overlap, they are useful for finding highly diverged transposons, or transposons with only a small region copied into other parts of the genome. [ 55 ] Another group of algorithms follows the periodicity approach. These algorithms perform a Fourier transformation on the sequence data, identifying periodicities, regions that are repeated periodically, and are able to use peaks in the resultant spectrum to find candidate repetitive elements. This method works best for tandem repeats, but can be used for dispersed repeats as well. However, it is a slow process, making it an unlikely choice for genome-scale analysis. [ 54 ]
The second step of de novo repeat identification involves building a consensus of each family of sequences. A consensus sequence is a sequence that is created based on the repeats that comprise a TE family. A base pair in a consensus is the one that occurred most often in the sequences being compared to make the consensus. For example, in a family of 50 repeats where 42 have a T base pair in the same position, the consensus sequence would have a T at this position as well, as the base pair is representative of the family as a whole at that particular position, and is most likely the base pair found in the family's ancestor at that position. [ 54 ] Once a consensus sequence has been made for each family, it is then possible to move on to further analysis, such as TE classification and genome masking in order to quantify the overall TE content of the genome.
Transposable elements have been recognized as good candidates for stimulating gene adaptation, through their ability to regulate the expression levels of nearby genes. [ 56 ] Combined with their "mobility", transposable elements can be relocated adjacent to their targeted genes, and control the expression levels of the gene, dependent upon the circumstances.
The study conducted in 2008, "High Rate of Recent Transposable Element–Induced Adaptation in Drosophila melanogaster", used D. melanogaster that had recently migrated from Africa to other parts of the world, as a basis for studying adaptations caused by transposable elements. Although most of the TEs were located on introns, the experiment showed a significant difference in gene expressions between the population in Africa and other parts of the world. The four TEs that caused the selective sweep were more prevalent in D. melanogaster from temperate climates, leading the researchers to conclude that the selective pressures of the climate prompted genetic adaptation. [ 57 ] From this experiment, it has been confirmed that adaptive TEs are prevalent in nature, by enabling organisms to adapt gene expression as a result of new selective pressures.
However, not all effects of adaptive TEs are beneficial to the population. In the research conducted in 2009, "A Recent Adaptive Transposable Element Insertion Near Highly Conserved Developmental Loci in Drosophila melanogaster", a TE, inserted between Jheh 2 and Jheh 3, revealed a downgrade in the expression level of both of the genes. Downregulation of such genes has caused Drosophila to exhibit extended developmental time and reduced egg to adult viability. Although this adaptation was observed in high frequency in all non-African populations, it was not fixed in any of them. [ 58 ] This is not hard to believe, since it is logical for a population to favor higher egg to adult viability, therefore trying to purge the trait caused by this specific TE adaptation.
At the same time, there have been several reports showing the advantageous adaptation caused by TEs. In the research done with silkworms, "An Adaptive Transposable Element insertion in the Regulatory Region of the EO Gene in the Domesticated Silkworm", a TE insertion was observed in the cis-regulatory region of the EO gene, which regulates molting hormone 20E, and enhanced expression was recorded. While populations without the TE insert are often unable to effectively regulate hormone 20E under starvation conditions, those with the insert had a more stable development, which resulted in higher developmental uniformity. [ 60 ]
These three experiments all demonstrated different ways in which TE insertions can be advantageous or disadvantageous, through means of regulating the expression level of adjacent genes. The field of adaptive TE research is still under development and more findings can be expected in the future.
Recent studies have confirmed that TEs can contribute to the generation of transcription factors. However, how this process of contribution can have an impact on the participation of genome control networks. TEs are more common in many regions of the DNA and it makes up 45% of total human DNA. Also, TEs contributed to 16% of transcription factor binding sites. A larger number of motifs are also found in non-TE-derived DNA, and the number is larger than TE-derived DNA. All these factors correlate to the direct participation of TEs in many ways of gene control networks. [ 27 ] | https://en.wikipedia.org/wiki/Transposable_element |
A transposase is any of a class of enzymes capable of binding to the end of a transposon and catalysing its movement to another part of a genome , typically by a cut-and-paste mechanism or a replicative mechanism, in a process known as transposition. The word "transposase" was first coined by the individuals who cloned the enzyme required for transposition of the Tn3 transposon . [ 1 ] The existence of transposons was postulated in the late 1940s by Barbara McClintock , who was studying the inheritance of maize , but the actual molecular basis for transposition was described by later groups. McClintock discovered that some segments of chromosomes changed their position, jumping between different loci or from one chromosome to another. The repositioning of these transposons (which coded for color) allowed other genes for pigment to be expressed. [ 2 ] Transposition in maize causes changes in color; however, in other organisms, such as bacteria, it can cause antibiotic resistance . [ 2 ] Transposition is also important in creating genetic diversity within species and generating adaptability to changing living conditions. [ 3 ]
Transposases are classified under EC number EC 2.7.7. Genes encoding transposases are widespread in the genomes of most organisms and are the most abundant genes known. [ 4 ] During the course of human evolution, as much as 40% of the human genome has moved around via methods such as transposition of transposons. [ 2 ]
Transposase (Tnp) Tn5 is a member of the RNase superfamily of proteins which includes retroviral integrases . Tn5 can be found in Shewanella and Escherichia bacteria. [ 5 ] The transposon codes for antibiotic resistance to kanamycin and other aminoglycoside antibiotics. [ 3 ] [ 6 ]
Tn5 and other transposases are notably inactive. Because DNA transposition events are inherently mutagenic, the low activity of transposases is necessary to reduce the risk of causing a fatal mutation in the host, and thus eliminating the transposable element . One of the reasons Tn5 is so unreactive is because the N- and C-termini are located in relatively close proximity to one another and tend to inhibit each other. This was elucidated by the characterization of several mutations which resulted in hyperactive forms of transposases. One such mutation, L372P, is a mutation of amino acid 372 in the Tn5 transposase. This amino acid is generally a leucine residue in the middle of an alpha helix. When this leucine is replaced with a proline residue the alpha helix is broken, introducing a conformational change to the C-terminal domain, separating it from the N-terminal domain enough to promote higher activity of the protein. [ 3 ] The transposition of a transposon often needs only three pieces: the transposon, the transposase enzyme, and the target DNA for the insertion of the transposon. [ 3 ] This is the case with Tn5, which uses a cut-and-paste mechanism for moving around transposons. [ 3 ]
Tn5 and most other transposases contain a DDE motif, which is the active site that catalyzes the movement of the transposon. Aspartate-97, aspartate-188, and glutamate-326 make up the active site, which is a triad of acidic residues. [ 7 ] The DDE motif is said to coordinate divalent metal ions, most often magnesium and manganese, which are important in the catalytic reaction. [ 7 ] Because transposase is incredibly inactive, the DDE region is mutated so that the transposase becomes hyperactive and catalyzes the movement of the transposon. [ 7 ] The glutamate is transformed into an aspartate and the two aspartates into glutamates. [ 7 ] Through this mutation, the study of Tn5 becomes possible, but some steps in the catalytic process are lost as a result. [ 3 ]
There are several steps which catalyze the movement of the transposon, including Tnp binding, synapsis (the creation of a synaptic complex), cleavage, target capture, and strand transfer. Transposase then binds to the DNA strand and creates a clamp over the transposon end of the DNA and inserts into the active site. Once the transposase binds to the transposon, it produces a synaptic complex in which two transposases are bound in a cis/trans relationship with the transposon. [ 3 ]
In cleavage, the magnesium ions activate oxygen from water molecules and expose them to nucleophilic attack. [ 6 ] This allows the water molecules to nick the 3' strands on both ends and create a hairpin formation, which separates the transposon from the donor DNA. [ 3 ] Next, the transposase moves the transposon to a suitable location. Not much is known about the target capture, although there is a sequence bias which has not yet been determined. [ 3 ] After target capture, the transposase attacks the target DNA nine base pairs apart, resulting in the integration of the transposon into the target DNA. [ 3 ]
As mentioned before, due to the mutations of the DDE, some steps of the process are lost—for example, when this experiment is performed in vitro , and SDS heat treatment denatures the transposase. However, it is still uncertain what happens to the transposase in vivo . [ 3 ]
The study of transposase Tn5 is of general importance because of its similarities to HIV -1 and other retroviral diseases. By studying Tn5, much can also be discovered about other transposases and their activities. [ 3 ]
Tn5 is utilized in genome sequencing by using the Tn5 to append sequencing adaptors and fragment the DNA in a single enzymatic reaction in 2010, [ 8 ] reducing the time and input requirements over traditional next-generation sequencing library preparation. The Tn5-based strategy can simplify the library preparation protocol significantly and can even can be incorporated into the direct colony-PCR for large numbers of bacterial isolates with no obvious coverage bias. [ 8 ] The main disadvantages are less control of fragmented size compared to enzymatic fragmentation and mechanical fragmentation, and a bias toward high G-C content. [ 8 ] This means of library preparation is also used in the ATAC-seq technique.
The Sleeping Beauty (SB) transposase is the recombinase that drives the Sleeping Beauty transposon system . [ 9 ] SB transposase belongs to the DD[E/D] family of transposases, which in turn belong to a large superfamily of polynucleotidyl transferases that includes RNase H, RuvC Holliday resolvase, RAG proteins, and retroviral integrases. [ 10 ] [ 11 ] The SB system is used primarily in vertebrate animals for gene transfer, [ 12 ] including gene therapy, [ 13 ] [ 14 ] and gene discovery. [ 15 ] [ 16 ] The engineered SB100X is an enzyme that directs the high levels of transposon integration. [ 17 ] [ 18 ]
The Tn7 transposon is a mobile genetic element found in many prokaryotes such as Escherichia coli ( E. coli ), and was first discovered as a DNA sequence in bacterial chromosomes and naturally occurring plasmids that encoded resistance to the antibiotics trimethoprim and streptomycin . [ 19 ] [ 20 ] Specifically classified as a transposable element (transposon), the sequence can duplicate and move itself within a genome by utilizing a self-encoded recombinase enzyme called a transposase, resulting in effects such as creating or reversing mutations and changing genome size. The Tn7 transposon has developed two mechanisms to promote its propagation among prokaryotes. [ 21 ] Like many other bacterial transposons, Tn7 transposes at low-frequency and inserts into many different sites with little to no site-selectivity. Through this first pathway, Tn7 is preferentially directed into conjugable plasmids , which can be replicated and distributed between bacteria. However, Tn7 is unique in that it also transposes at high-frequency into a single specific site in bacterial chromosomes called attTn7. [ 22 ] This specific sequence is an essential and highly conserved gene found in many strains of bacteria. However, the recombination is not deleterious to the host bacterium as Tn7 actually transposes downstream of the gene after recognizing it, resulting in a safe way to propagate the transposon without killing the host. This highly evolved and sophisticated target-site selection pathway suggests this pathway evolved to promote coexistence between the transposon and it host, as well as Tn7's successful transmission into future generations of bacterium. [ 21 ]
The Tn7 transposon is 14 kb long and codes for five enzymes. [ 21 ] The ends of the DNA sequence consists of two segments that the Tn7 transposase interacts with during recombination. The left segment (Tn7-L) is 150 bp long and the right sequence (Tn7-R) is 90 bp long. Both ends of the transposon contain a series of 22 bp binding sites that the Tn7 transposase recognizes and binds to. Within the transposon are five discrete genes encoding for proteins that make up the transposition machinery. In addition, the transposon contains an integron , a DNA segment containing several cassettes of genes encoding for antibiotic-resistance. [ 21 ]
The Tn7 transposon codes for five proteins: TnsA, TnsB, TnsC, TnsD, and TnsE. [ 21 ] TnsA and TnsB interact together to form the Tn7 transposase enzyme TnsAB. The enzyme specifically recognizes and binds to the ends of the DNA sequence of the transposon, and excises it by introducing double-stranded DNA breaks to each end. The excised sequence is then inserted to another target DNA site. Much like other characterized transposons, the mechanism for Tn7 transposition involves cleavage of the 3' ends from the donating DNA by the TnsA protein of the TnsAB transposase. However, Tn7 is also uniquely cleaved near the 5' ends, about 5 bp from the 5' end towards the Tn7 transposon, by the TnsB protein of TnsAB. After the insertion of the transposon into the target DNA site, the 3' ends are covalently linked to the target DNA, but the 5 bp gaps are still present at the 5' ends. As a result, repair of these gaps leads to a further 5 bp duplication at the target site. The TnsC protein interacts with the transposase enzyme and the target DNA to promote the excision and insertion processes. The ability of TnsC to activate the transposase depends on its interaction with a target DNA along with its appropriate targeting protein, TnsD or TnsE. The TnsD and TnsE proteins are alternative target selectors that are also DNA binding activators that promote excision and insertion of Tn7. Their ability to interact with a particular target DNA is key to the target-site selection of Tn7. The proteins TnsA, TnsB, and TnsC thus form the core machinery of Tn7: TnsA and TnsB interact together to form the transposase, while TnsC functions as a regulator of the transposase's activity, communicating between the transposase and TnsD and TnsE. When the TnsE protein interacts with the TnsABC core machinery, Tn7 preferentially directs insertions into conjugable plasmids. When the TnsD protein interacts with TnsABC, Tn7 preferentially directs insertions downstream into a single essential and highly conserved site in the bacterial chromosome. This site, attTn7, is specifically recognized by TnsD. [ 21 ] | https://en.wikipedia.org/wiki/Transposase |
In linear algebra , the transpose of a matrix is an operator which flips a matrix over its diagonal;
that is, it switches the row and column indices of the matrix A by producing another matrix, often denoted by A T (among other notations). [ 1 ]
The transpose of a matrix was introduced in 1858 by the British mathematician Arthur Cayley . [ 2 ]
The transpose of a matrix A , denoted by A T , [ 3 ] ⊤ A , A ⊤ , A ⊺ {\displaystyle A^{\intercal }} , [ 4 ] [ 5 ] A′ , [ 6 ] A tr , t A or A t , may be constructed by any one of the following methods:
Formally, the i -th row, j -th column element of A T is the j -th row, i -th column element of A :
If A is an m × n matrix, then A T is an n × m matrix.
In the case of square matrices, A T may also denote the T th power of the matrix A . For avoiding a possible confusion, many authors use left upperscripts, that is, they denote the transpose as T A . An advantage of this notation is that no parentheses are needed when exponents are involved: as ( T A ) n = T ( A n ) , notation T A n is not ambiguous.
In this article, this confusion is avoided by never using the symbol T as a variable name.
A square matrix whose transpose is equal to itself is called a symmetric matrix ; that is, A is symmetric if
A square matrix whose transpose is equal to its negative is called a skew-symmetric matrix ; that is, A is skew-symmetric if
A square complex matrix whose transpose is equal to the matrix with every entry replaced by its complex conjugate (denoted here with an overline) is called a Hermitian matrix (equivalent to the matrix being equal to its conjugate transpose ); that is, A is Hermitian if
A square complex matrix whose transpose is equal to the negation of its complex conjugate is called a skew-Hermitian matrix ; that is, A is skew-Hermitian if
A square matrix whose transpose is equal to its inverse is called an orthogonal matrix ; that is, A is orthogonal if
A square complex matrix whose transpose is equal to its conjugate inverse is called a unitary matrix ; that is, A is unitary if
Let A and B be matrices and c be a scalar .
If A is an m × n matrix and A T is its transpose, then the result of matrix multiplication with these two matrices gives two square matrices: A A T is m × m and A T A is n × n . Furthermore, these products are symmetric matrices . Indeed, the matrix product A A T has entries that are the inner product of a row of A with a column of A T . But the columns of A T are the rows of A , so the entry corresponds to the inner product of two rows of A . If p i j is the entry of the product, it is obtained from rows i and j in A . The entry p j i is also obtained from these rows, thus p i j = p j i , and the product matrix ( p i j ) is symmetric. Similarly, the product A T A is a symmetric matrix.
A quick proof of the symmetry of A A T results from the fact that it is its own transpose:
On a computer , one can often avoid explicitly transposing a matrix in memory by simply accessing the same data in a different order. For example, software libraries for linear algebra , such as BLAS , typically provide options to specify that certain matrices are to be interpreted in transposed order to avoid the necessity of data movement.
However, there remain a number of circumstances in which it is necessary or desirable to physically reorder a matrix in memory to its transposed ordering. For example, with a matrix stored in row-major order , the rows of the matrix are contiguous in memory and the columns are discontiguous. If repeated operations need to be performed on the columns, for example in a fast Fourier transform algorithm, transposing the matrix in memory (to make the columns contiguous) may improve performance by increasing memory locality .
Ideally, one might hope to transpose a matrix with minimal additional storage. This leads to the problem of transposing an n × m matrix in-place , with O(1) additional storage or at most storage much less than mn . For n ≠ m , this involves a complicated permutation of the data elements that is non-trivial to implement in-place. Therefore, efficient in-place matrix transposition has been the subject of numerous research publications in computer science , starting in the late 1950s, and several algorithms have been developed.
As the main use of matrices is to represent linear maps between finite-dimensional vector spaces , the transpose is an operation on matrices that may be seen as the representation of some operation on linear maps.
This leads to a much more general definition of the transpose that works on every linear map, even when linear maps cannot be represented by matrices (such as in the case of infinite dimensional vector spaces). In the finite dimensional case, the matrix representing the transpose of a linear map is the transpose of the matrix representing the linear map, independently of the basis choice.
Let X # denote the algebraic dual space of an R - module X .
Let X and Y be R -modules.
If u : X → Y is a linear map , then its algebraic adjoint or dual , [ 8 ] is the map u # : Y # → X # defined by f ↦ f ∘ u .
The resulting functional u # ( f ) is called the pullback of f by u .
The following relation characterizes the algebraic adjoint of u [ 9 ]
where ⟨•, •⟩ is the natural pairing (i.e. defined by ⟨ h , z ⟩ := h ( z ) ).
This definition also applies unchanged to left modules and to vector spaces. [ 10 ]
The definition of the transpose may be seen to be independent of any bilinear form on the modules, unlike the adjoint ( below ).
The continuous dual space of a topological vector space (TVS) X is denoted by X ' .
If X and Y are TVSs then a linear map u : X → Y is weakly continuous if and only if u # ( Y ' ) ⊆ X ' , in which case we let t u : Y ' → X ' denote the restriction of u # to Y ' .
The map t u is called the transpose [ 11 ] of u .
If the matrix A describes a linear map with respect to bases of V and W , then the matrix A T describes the transpose of that linear map with respect to the dual bases .
Every linear map to the dual space u : X → X # defines a bilinear form B : X × X → F , with the relation B ( x , y ) = u ( x )( y ) .
By defining the transpose of this bilinear form as the bilinear form t B defined by the transpose t u : X ## → X # i.e. t B ( y , x ) = t u (Ψ( y ))( x ) , we find that B ( x , y ) = t B ( y , x ) .
Here, Ψ is the natural homomorphism X → X ## into the double dual .
If the vector spaces X and Y have respectively nondegenerate bilinear forms B X and B Y , a concept known as the adjoint , which is closely related to the transpose, may be defined:
If u : X → Y is a linear map between vector spaces X and Y , we define g as the adjoint of u if g : Y → X satisfies
These bilinear forms define an isomorphism between X and X # , and between Y and Y # , resulting in an isomorphism between the transpose and adjoint of u .
The matrix of the adjoint of a map is the transposed matrix only if the bases are orthonormal with respect to their bilinear forms.
In this context, many authors however, use the term transpose to refer to the adjoint as defined here.
The adjoint allows us to consider whether g : Y → X is equal to u −1 : Y → X .
In particular, this allows the orthogonal group over a vector space X with a quadratic form to be defined without reference to matrices (nor the components thereof) as the set of all linear maps X → X for which the adjoint equals the inverse.
Over a complex vector space, one often works with sesquilinear forms (conjugate-linear in one argument) instead of bilinear forms.
The Hermitian adjoint of a map between such spaces is defined similarly, and the matrix of the Hermitian adjoint is given by the conjugate transpose matrix if the bases are orthonormal. | https://en.wikipedia.org/wiki/Transpose |
In linear algebra , the transpose of a linear map between two vector spaces, defined over the same field , is an induced map between the dual spaces of the two vector spaces.
The transpose or algebraic adjoint of a linear map is often used to study the original linear map. This concept is generalised by adjoint functors .
Let X # {\displaystyle X^{\#}} denote the algebraic dual space of a vector space X . {\displaystyle X.} Let X {\displaystyle X} and Y {\displaystyle Y} be vector spaces over the same field K . {\displaystyle {\mathcal {K}}.} If u : X → Y {\displaystyle u:X\to Y} is a linear map , then its algebraic adjoint or dual , [ 1 ] is the map # u : Y # → X # {\displaystyle {}^{\#}u:Y^{\#}\to X^{\#}} defined by f ↦ f ∘ u . {\displaystyle f\mapsto f\circ u.} The resulting functional # u ( f ) := f ∘ u {\displaystyle {}^{\#}u(f):=f\circ u} is called the pullback of f {\displaystyle f} by u . {\displaystyle u.}
The continuous dual space of a topological vector space (TVS) X {\displaystyle X} is denoted by X ′ . {\displaystyle X^{\prime }.} If X {\displaystyle X} and Y {\displaystyle Y} are TVSs then a linear map u : X → Y {\displaystyle u:X\to Y} is weakly continuous if and only if # u ( Y ′ ) ⊆ X ′ , {\displaystyle {}^{\#}u\left(Y^{\prime }\right)\subseteq X^{\prime },} in which case we let t u : Y ′ → X ′ {\displaystyle {}^{t}u:Y^{\prime }\to X^{\prime }} denote the restriction of # u {\displaystyle {}^{\#}u} to Y ′ . {\displaystyle Y^{\prime }.} The map t u {\displaystyle {}^{t}u} is called the transpose [ 2 ] or algebraic adjoint of u . {\displaystyle u.} The following identity characterizes the transpose of u {\displaystyle u} : [ 3 ] ⟨ t u ( f ) , x ⟩ = ⟨ f , u ( x ) ⟩ for all f ∈ Y ′ and x ∈ X , {\displaystyle \left\langle {}^{t}u(f),x\right\rangle =\left\langle f,u(x)\right\rangle \quad {\text{ for all }}f\in Y^{\prime }{\text{ and }}x\in X,} where ⟨ ⋅ , ⋅ ⟩ {\displaystyle \left\langle \cdot ,\cdot \right\rangle } is the natural pairing defined by ⟨ z , h ⟩ := z ( h ) . {\displaystyle \left\langle z,h\right\rangle :=z(h).}
The assignment u ↦ t u {\displaystyle u\mapsto {}^{t}u} produces an injective linear map between the space of linear operators from X {\displaystyle X} to Y {\displaystyle Y} and the space of linear operators from Y # {\displaystyle Y^{\#}} to X # . {\displaystyle X^{\#}.} If X = Y {\displaystyle X=Y} then the space of linear maps is an algebra under composition of maps , and the assignment is then an antihomomorphism of algebras, meaning that t ( u v ) = t v t u . {\displaystyle {}^{t}(uv)={}^{t}v{}^{t}u.} In the language of category theory , taking the dual of vector spaces and the transpose of linear maps is therefore a contravariant functor from the category of vector spaces over K {\displaystyle {\mathcal {K}}} to itself.
One can identify t ( t u ) {\displaystyle {}^{t}\left({}^{t}u\right)} with u {\displaystyle u} using the natural injection into the double dual.
‖ x ‖ = sup ‖ x ′ ‖ ≤ 1 | x ′ ( x ) | for each x ∈ X {\displaystyle \|x\|=\sup _{\|x^{\prime }\|\leq 1}\left|x^{\prime }(x)\right|\quad {\text{ for each }}x\in X} and if the linear operator u : X → Y {\displaystyle u:X\to Y} is bounded then the operator norm of t u {\displaystyle {}^{t}u} is equal to the norm of u {\displaystyle u} ; that is [ 5 ] [ 6 ] ‖ u ‖ = ‖ t u ‖ , {\displaystyle \|u\|=\left\|{}^{t}u\right\|,} and moreover, ‖ u ‖ = sup { | y ′ ( u x ) | : ‖ x ‖ ≤ 1 , ‖ y ∗ ‖ ≤ 1 where x ∈ X , y ′ ∈ Y ′ } . {\displaystyle \|u\|=\sup \left\{\left|y^{\prime }(ux)\right|:\|x\|\leq 1,\left\|y^{*}\right\|\leq 1{\text{ where }}x\in X,y^{\prime }\in Y^{\prime }\right\}.}
Suppose now that u : X → Y {\displaystyle u:X\to Y} is a weakly continuous linear operator between topological vector spaces X {\displaystyle X} and Y {\displaystyle Y} with continuous dual spaces X ′ {\displaystyle X^{\prime }} and Y ′ , {\displaystyle Y^{\prime },} respectively.
Let ⟨ ⋅ , ⋅ ⟩ : X × X ′ → C {\displaystyle \langle \cdot ,\cdot \rangle :X\times X^{\prime }\to \mathbb {C} } denote the canonical dual system , defined by ⟨ x , x ′ ⟩ = x ′ x {\displaystyle \left\langle x,x^{\prime }\right\rangle =x^{\prime }x} where x {\displaystyle x} and x ′ {\displaystyle x^{\prime }} are said to be orthogonal if ⟨ x , x ′ ⟩ = x ′ x = 0. {\displaystyle \left\langle x,x^{\prime }\right\rangle =x^{\prime }x=0.} For any subsets A ⊆ X {\displaystyle A\subseteq X} and S ′ ⊆ X ′ , {\displaystyle S^{\prime }\subseteq X^{\prime },} let A ∘ = { x ′ ∈ X ′ : sup a ∈ A | x ′ ( a ) | ≤ 1 } and S ∘ = { x ∈ X : sup s ′ ∈ S ′ | s ′ ( x ) | ≤ 1 } {\displaystyle A^{\circ }=\left\{x^{\prime }\in X^{\prime }:\sup _{a\in A}\left|x^{\prime }(a)\right|\leq 1\right\}\qquad {\text{ and }}\qquad S^{\circ }=\left\{x\in X:\sup _{s^{\prime }\in S^{\prime }}\left|s^{\prime }(x)\right|\leq 1\right\}} denote the ( absolute ) polar of A {\displaystyle A} in X ′ {\displaystyle X^{\prime }} (resp. of S ′ {\displaystyle S^{\prime }} in X {\displaystyle X} ).
[ u ( A ) ] ∘ = ( t u ) − 1 ( A ∘ ) {\displaystyle [u(A)]^{\circ }=\left({}^{t}u\right)^{-1}\left(A^{\circ }\right)} and u ( A ) ⊆ B implies t u ( B ∘ ) ⊆ A ∘ . {\displaystyle u(A)\subseteq B\quad {\text{ implies }}\quad {}^{t}u\left(B^{\circ }\right)\subseteq A^{\circ }.}
ker t u = ( Im u ) ∘ . {\displaystyle \operatorname {ker} {}^{t}u=\left(\operatorname {Im} u\right)^{\circ }.}
Suppose X {\displaystyle X} and Y {\displaystyle Y} are topological vector spaces and u : X → Y {\displaystyle u:X\to Y} is a weakly continuous linear operator (so ( t u ) ( Y ′ ) ⊆ X ′ {\displaystyle \left({}^{t}u\right)\left(Y^{\prime }\right)\subseteq X^{\prime }} ). Given subsets M ⊆ X {\displaystyle M\subseteq X} and N ⊆ X ′ , {\displaystyle N\subseteq X^{\prime },} define their annihilators (with respect to the canonical dual system) by [ 6 ]
and
ker t u = ( Im u ) ⊥ {\displaystyle \ker {}^{t}u=(\operatorname {Im} u)^{\bot }}
Let M {\displaystyle M} be a closed vector subspace of a Hausdorff locally convex space X {\displaystyle X} and denote the canonical quotient map by π : X → X / M where π ( x ) := x + M . {\displaystyle \pi :X\to X/M\quad {\text{ where }}\quad \pi (x):=x+M.} Assume X / M {\displaystyle X/M} is endowed with the quotient topology induced by the quotient map π : X → X / M . {\displaystyle \pi :X\to X/M.} Then the transpose of the quotient map is valued in M ⊥ {\displaystyle M^{\bot }} and t π : ( X / M ) ′ → M ⊥ ⊆ X ′ {\displaystyle {}^{t}\pi :(X/M)^{\prime }\to M^{\bot }\subseteq X^{\prime }} is a TVS-isomorphism onto M ⊥ . {\displaystyle M^{\bot }.} If X {\displaystyle X} is a Banach space then t π : ( X / M ) ′ → M ⊥ {\displaystyle {}^{t}\pi :(X/M)^{\prime }\to M^{\bot }} is also an isometry . [ 6 ] Using this transpose, every continuous linear functional on the quotient space X / M {\displaystyle X/M} is canonically identified with a continuous linear functional in the annihilator M ⊥ {\displaystyle M^{\bot }} of M . {\displaystyle M.}
Let M {\displaystyle M} be a closed vector subspace of a Hausdorff locally convex space X . {\displaystyle X.} If m ′ ∈ M ′ {\displaystyle m^{\prime }\in M^{\prime }} and if x ′ ∈ X ′ {\displaystyle x^{\prime }\in X^{\prime }} is a continuous linear extension of m ′ {\displaystyle m^{\prime }} to X {\displaystyle X} then the assignment m ′ ↦ x ′ + M ⊥ {\displaystyle m^{\prime }\mapsto x^{\prime }+M^{\bot }} induces a vector space isomorphism M ′ → X ′ / ( M ⊥ ) , {\displaystyle M^{\prime }\to X^{\prime }/\left(M^{\bot }\right),} which is an isometry if X {\displaystyle X} is a Banach space. [ 6 ]
Denote the inclusion map by In : M → X where In ( m ) := m for all m ∈ M . {\displaystyle \operatorname {In} :M\to X\quad {\text{ where }}\quad \operatorname {In} (m):=m\quad {\text{ for all }}m\in M.} The transpose of the inclusion map is t In : X ′ → M ′ {\displaystyle {}^{t}\operatorname {In} :X^{\prime }\to M^{\prime }} whose kernel is the annihilator M ⊥ = { x ′ ∈ X ′ : ⟨ m , x ′ ⟩ = 0 for all m ∈ M } {\displaystyle M^{\bot }=\left\{x^{\prime }\in X^{\prime }:\left\langle m,x^{\prime }\right\rangle =0{\text{ for all }}m\in M\right\}} and which is surjective by the Hahn–Banach theorem . This map induces an isomorphism of vector spaces X ′ / ( M ⊥ ) → M ′ . {\displaystyle X^{\prime }/\left(M^{\bot }\right)\to M^{\prime }.}
If the linear map u {\displaystyle u} is represented by the matrix A {\displaystyle A} with respect to two bases of X {\displaystyle X} and Y , {\displaystyle Y,} then t u {\displaystyle {}^{t}u} is represented by the transpose matrix A T {\displaystyle A^{T}} with respect to the dual bases of Y ′ {\displaystyle Y^{\prime }} and X ′ , {\displaystyle X^{\prime },} hence the name.
Alternatively, as u {\displaystyle u} is represented by A {\displaystyle A} acting to the right on column vectors, t u {\displaystyle {}^{t}u} is represented by the same matrix acting to the left on row vectors.
These points of view are related by the canonical inner product on R n , {\displaystyle \mathbb {R} ^{n},} which identifies the space of column vectors with the dual space of row vectors.
The identity that characterizes the transpose, that is, [ u ∗ ( f ) , x ] = [ f , u ( x ) ] , {\displaystyle \left[u^{*}(f),x\right]=[f,u(x)],} is formally similar to the definition of the Hermitian adjoint , however, the transpose and the Hermitian adjoint are not the same map.
The transpose is a map Y ′ → X ′ {\displaystyle Y^{\prime }\to X^{\prime }} and is defined for linear maps between any vector spaces X {\displaystyle X} and Y , {\displaystyle Y,} without requiring any additional structure.
The Hermitian adjoint maps Y → X {\displaystyle Y\to X} and is only defined for linear maps between Hilbert spaces, as it is defined in terms of the inner product on the Hilbert space.
The Hermitian adjoint therefore requires more mathematical structure than the transpose.
However, the transpose is often used in contexts where the vector spaces are both equipped with a nondegenerate bilinear form such as the Euclidean dot product or another real inner product .
In this case, the nondegenerate bilinear form is often used implicitly to map between the vector spaces and their duals, to express the transposed map as a map Y → X . {\displaystyle Y\to X.} For a complex Hilbert space, the inner product is sesquilinear and not bilinear, and these conversions change the transpose into the adjoint map.
More precisely: if X {\displaystyle X} and Y {\displaystyle Y} are Hilbert spaces and u : X → Y {\displaystyle u:X\to Y} is a linear map then the transpose of u {\displaystyle u} and the Hermitian adjoint of u , {\displaystyle u,} which we will denote respectively by t u {\displaystyle {}^{t}u} and u ∗ , {\displaystyle u^{*},} are related.
Denote by I : X → X ∗ {\displaystyle I:X\to X^{*}} and J : Y → Y ∗ {\displaystyle J:Y\to Y^{*}} the canonical antilinear isometries of the Hilbert spaces X {\displaystyle X} and Y {\displaystyle Y} onto their duals.
Then u ∗ {\displaystyle u^{*}} is the following composition of maps: [ 10 ]
Suppose that X {\displaystyle X} and Y {\displaystyle Y} are topological vector spaces and that u : X → Y {\displaystyle u:X\to Y} is a linear map, then many of u {\displaystyle u} 's properties are reflected in t u . {\displaystyle {}^{t}u.} | https://en.wikipedia.org/wiki/Transpose_of_a_linear_map |
The transposed Paternò−Büchi reaction involves a ππ* excited state of alkene reacting with a ground state carbonyl functionality. This is reversal of the traditional Paternò−Büchi reaction where an excited carbonyl group reacts with a ground state alkene. This strategy was first reported by Sivaguru and co-workers with reaction of enamides . [ 1 ] | https://en.wikipedia.org/wiki/Transposed_Paternò−Büchi_reaction |
Transposon mutagenesis , or transposition mutagenesis , is a biological process that allows genes to be transferred to a host organism's chromosome , interrupting or modifying the function of an extant gene on the chromosome and causing mutation . [ 1 ] Transposon mutagenesis is much more effective than chemical mutagenesis , with a higher mutation frequency and a lower chance of killing the organism. Other advantages include being able to induce single hit mutations, being able to incorporate selectable markers in strain construction, and being able to recover genes after mutagenesis. [ 2 ] Disadvantages include the low frequency of transposition in living systems, and the inaccuracy of most transposition systems.
Transposon mutagenesis was first studied by Barbara McClintock in the mid-20th century during her Nobel Prize-winning work with corn. McClintock received her BSc in 1923 from Cornell’s College of Agriculture. By 1927 she had her PhD in botany, and she immediately began working on the topic of maize chromosomes. [ 3 ] In the early 1940s, McClintock was studying the progeny of self-pollinated maize plants which resulted from crosses having a broken chromosome 9. These plants were missing their telomeres . This research prompted the first discovery of a transposable element , [ 4 ] and from there transposon mutagenesis has been exploited as a biological tool.
In the case of bacteria , transposition mutagenesis is usually accomplished by way of a plasmid from which a transposon is extracted and inserted into the host chromosome. This usually requires a set of enzymes including transposase to be translated . The transposase can be expressed either on a separate plasmid, or on the plasmid containing the gene to be integrated. Alternatively, an injection of transposase mRNA into the host cell can induce translation and expression . [ 5 ] Early transposon mutagenesis experiments relied on bacteriophages and conjugative bacterial plasmids for the insertion of sequences. These were very non-specific, and made it difficult to incorporate specific genes. A newer technique called shuttle mutagenesis uses specific cloned genes from the host species to incorporate genetic elements. [ 2 ] Another effective approach is to deliver transposons through viral capsids . This facilitates integration into the chromosome and long-term transgene expression. [ 5 ]
The Tn5 transposon system is a model system for the study of transposition and for the application of transposon mutagenesis. Tn5 is a bacterial composite transposon in which genes (the original system containing antibiotic resistance genes) are flanked by two nearly identical insertion sequences , named IS50R and IS50L corresponding to the right and left sides of the transposon respectively. [ 6 ] The IS50R sequence codes for two proteins, Tnp and Inh. These two proteins are identical in sequence, save for the fact that Inh is lacking the 55 N-terminal amino acids . Tnp codes for a transposase for the entire system, and Inh encodes an inhibitor of transposase. The DNA-binding domain of Tnp resides in the 55 N-terminal amino acids, and so these residues are essential for function. [ 6 ] The IS50R and IS50L sequences are both flanked by 19- base pair elements on the inside and outside ends of the transposon, labelled IE and OE respectively. Mutation of these regions results in an inability of transposase genes to bind to the sequences. The binding interactions between transposase and these sequences is very complicated, and is affected by DNA methylation and other epigenetic marks. [ 6 ] In addition, other proteins seem to be able to bind with and affect the transposition of the IS50 elements, such as DnaA.
The most likely pathway of Tn 5 transposition is the common pathway for all transposon systems. It begins with Tnp binding the OE and IE sequences of each IS50 sequence. The two ends are brought together, and through oligomerization of DNA, the sequence is cut out of the chromosome. After introducing 9-base pair 5' ends in target DNA, the transposon and its incorporated genes are inserted into the target DNA, duplicating the regions on either end of the transposon. [ 6 ] Genes of interest can be genetically engineered into the transposon system between the IS50 sequences. By placing the transposon under the control of a host promoter , the genes will be expressed. Incorporated genes usually include, in addition to the gene of interest, a selectable marker to identify transformants, a eukaryotic promoter/ terminator (if expressing in a eukaryote), and 3' UTR sequences to separate genes in a polycistronic stretch of sequence.
The Sleeping Beauty transposon system (SBTS) is the first successful non-viral vector for incorporation of a gene cassette into a vertebrate genome. Up until the development of this system, the major problems with non-viral gene therapy have been the intracellular breakdown of the transgene due to it being recognized as Prokaryotes and the inefficient delivery of the transgene into organ systems. The SBTS revolutionized these issues by combining the advantages of viruses and naked DNA. It consists of a transposon containing the cassette of genes to be expressed, as well as its own transposase enzyme. By transposing the cassette directly into the genome of the organism from the plasmid, sustained expression of the transgene can be attained. [ 2 ] This can be further refined by enhancing the transposon sequences and the transposase enzymes used. SB100X is a hyperactive mammalian transposase which is roughly 100x more efficient than the typical first-generation transposase. Incorporation of this enzyme into the cassette results in even more sustained transgene expression (over one year). Additionally, transgenesis frequencies can be as high as 45% when using pronuclear injection into mouse zygotes . [ 7 ]
The mechanism of the SBTS is similar to the Tn5 transposon system, however the enzyme and gene sequences are eukaryotic in nature as opposed to prokaryotic. The system's tranposase can act in trans as well as in cis , allowing a diverse collection of transposon structures. The transposon itself is flanked by inverted repeat sequences , which are each repeated twice in a direct fashion, designated IR/DR sequences. The internal region consists of the gene or sequence to be transposed, and could also contain the transposase gene. Alternatively, the transposase can be encoded on a separate plasmid or injected in its protein form. Yet another approach is to incorporate both the transposon and the transposase genes into a viral vector, which can target a cell or tissue of choice. The transposase protein is extremely specific in the sequences that it binds, and is able to discern its IR/DR sequences from a similar sequence by three base pairs. Once the enzyme is bound to both ends of the transposon, the IR/DR sequences are brought together and held by the transposase in a Synaptic Complex Formation (SCF). The formation of the SCF is a checkpoint ensuring proper cleavage. HMGB1 is a non- histone protein from the host which is associated with eukaryotic chromatin. It enhances the preferential binding of the transposase to the IR/DR sequences and is likely essential for SCF complex formation/stability. Transposase cleaves the DNA at the target sites, generating 3' overhangs . The enzyme then targets TA dinucleotides in the host genome as target sites for integration. The same enzymatic catalytic site which cleaved the DNA is responsible for integrating the DNA into the genome, duplicating the region of the genome in the process. Although transposase is specific for TA dinucleotides, the high frequency of these pairs in the genome indicates that the transposon undergoes fairly random integration. [ 8 ]
As a result of the capacity of transposon mutagenesis to incorporate genes into most areas of target chromosomes, there are a number of functions associated with the process.
In 1999, the virulence genes associated with Mycobacterium tuberculosis were identified through transposon mutagenesis-mediated gene knockout . A plasmid named pCG113 containing kanamycin resistance genes and the IS 1096 insertion sequence was engineered to contain variable 80-base pair tags. The plasmids were then transformed into M. tuberculosis cells by electroporation . Colonies were plated on kanamycin to select for resistant cells. Colonies that underwent random transposition events were identified by Bam HI digestion and Southern blotting using an internal IS 1096 DNA probe. Colonies were screened for attenuated multiplication to identify colonies with mutations in candidate virulence genes. Mutations leading to an attenuated phenotype were mapped by amplification of adjacent regions to the IS 1096 sequences and compared with the published M. tuberculosis genome. In this instance transposon mutagenesis identified 13 pathogenic loci in the M. tuberculosis genome which were not previously associated with disease. [ 10 ] This is essential information in understanding the infectious cycle of the bacterium.
The PiggyBac (PB) transposon from the cabbage looper moth Trichoplusia ni was engineered to be highly active in mammalian cells, and is capable of genome-wide mutagenesis. Transposons contained both PB and Sleeping Beauty inverted repeats, in order to be recognized by both transposases and increase the frequency of transposition. In addition, the transposon contained promoter and enhancer elements, a splice donor and acceptors to allow gain- or loss-of-function mutations depending on the transposon's orientation, and bidirectional polyadenylation signals. The transposons were transformed into mouse cells in vitro and mutants containing tumours were analyzed. The mechanism of the mutation leading to tumour formation determined if the gene was classified as an oncogene or a tumour-suppressor gene. Oncogenes tended to be characterized by insertions in regions leading to overexpression of a gene, whereas tumour-suppressor genes were classified as such based on loss-of-function mutations. Since the mouse is a model organism for the study of human physiology and disease, this research will help lead to an increased understanding of cancer-causing genes and potential therapeutic targets. [ 9 ] | https://en.wikipedia.org/wiki/Transposon_mutagenesis |
Transposon insertion sequencing ( Tn-seq ) combines transposon insertional mutagenesis with massively parallel sequencing (MPS) of the transposon insertion sites to identify genes contributing to a function of interest in bacteria . The method was originally established by concurrent work in four laboratories under the acronyms HITS, [ 1 ] INSeq, [ 2 ] TraDIS, [ 3 ] and Tn-Seq. [ 4 ] Numerous variations have been subsequently developed and applied to diverse biological systems. Collectively, the methods are often termed Tn-Seq as they all involve monitoring the fitness of transposon insertion mutants via DNA sequencing approaches. [ 5 ]
Transposons are highly regulated, discrete DNA segments that can relocate within the genome. They are universal and are found in Eubacteria , Archaea , and Eukarya , including humans. Transposons have a large influence on gene expression and can be used to determine gene function. In fact, when a transposon inserts itself in a gene, the gene's function will be disrupted. [ 6 ] Because of that property, transposons have been manipulated for use in insertional mutagenesis. [ 7 ] The development of microbial genome sequencing was a major advance for the use of transposon mutagenesis. [ 8 ] [ 9 ] The function affected by a transposon insertion could be linked to the disrupted gene by sequencing the genome to locate the transposon insertion site. Massively parallel sequencing allows simultaneous sequencing of transposon insertion sites in large mixtures of different mutants. Therefore, genome-wide analysis is feasible if transposons are positioned throughout the genome in a mutant collection. [ 5 ]
Transposon sequencing requires the creation of a transposon insertion library, which will contain a group of mutants that collectively have transposon insertions in all non-essential genes. The library is grown under an experimental condition of interest. Mutants with transposons inserted in genes required for growth under the test condition will diminish in frequency from the population. To identify mutants being lost, genomic sequences adjacent to the transposon ends are amplified by PCR and sequenced by MPS to determine the location and abundance of each insertion mutation. The importance of each gene for growth under the test condition is determined by comparing the abundance of each mutant before and after growth under the condition being examined. Tn-seq is useful for both the study of a single gene's fitness as well as gene interactions [ 10 ]
Signature–tagged mutagenesis (STM) is an older technique that also involves pooling transposon insertion mutants to determine the importance of the disrupted genes under selective growth conditions. [ 11 ] High-throughput versions of STM use genomic microarrays, which are less accurate and have a lower dynamic range than massively-parallel sequencing. [ 5 ] With the invention of next generation sequencing, genomic data became increasingly available. However, despite the increase in genomic data, our knowledge of gene function remains the limiting factor in our understanding of the role genes play. [ 12 ] [ 13 ] Therefore, a need for a high throughput approach to study genotype–phenotype relationships like Tn-seq was necessary.
Transposon sequencing begins by transducing [ clarification needed ] bacterial populations with transposable elements [ clarification needed ] using bacteriophages . Tn-seq [ clarification needed ] uses the Himar I Mariner transposon, a common and stable [ clarification needed ] transposon. After transduction, the DNA is cleaved [ clarification needed ] and the inserted sequence amplified through PCR . The recognition sites [ clarification needed ] for MmeI, a type IIS restriction endonuclease [ clarification needed ] , can be introduced by a single nucleotide change in the terminal repeats [ clarification needed ] of Mariner [ clarification needed ] . [ 14 ] It [ clarification needed ] is located 4 base pairs before the end of the terminal repeat.
MmeI makes a 2 base pair staggered cut [ clarification needed ] 20 bases downstream [ clarification needed ] of the recognition site [ clarification needed ] . [ 15 ]
When MmeI digests DNA from a library [ clarification needed ] of transposon insertion mutants [ clarification needed ] , fragmented DNA including the left and right transposon and 16 base pair of surrounding genomic DNA is produced. The 16 base pair fragment is enough to determine the location of the transposon insertion in the bacterial genome. The ligation [ clarification needed ] of the adaptor [ clarification needed ] is facilitated by the 2 base overhang [ clarification needed ] . A primer [ clarification needed ] specific to the adaptor and a primer specific to the transposon are used to amplify the sequence via PCR. The 120 base pair product [ clarification needed ] is then isolated using agarose gel [ clarification needed ] or PAGE [ clarification needed ] purification. Massively parallel sequencing is then used to determine the sequences of the flanking 16 base pairs [ clarification needed ] . [ 10 ]
Gene function is inferred after looking at the effects of the insertion on gene function under certain conditions [ clarification needed ] .
Unlike high-throughput insertion track by deep sequencing (HITS) and transposon-directed insertion site sequencing (TraDIS) [ clarification needed ] , Tn-seq is specific to the Himar I Mariner transposon, and cannot be applied to other transposons or insertional elements. [ 10 ] However, the protocol for Tn-seq [ clarification needed ] is less time intensive [ citation needed ] . HITS and TraDIS [ clarification needed ] use a DNA shearing [ clarification needed ] technique that produce a range of PCR product sizes that could cause shorter DNA templates being preferentially amplified over longer templates. Tn-seq produces a product that is uniform in size, therefore reducing the possibility of PCR bias. [ 10 ]
Tn-seq can be used to identify both the fitness of single genes and to map gene interactions in microorganisms. Existing methods for these types of study are dependent on preexisting genomic microarrays or gene knockout arrays, whereas Tn-seq is not. Tn-seq's utilization of massively parallel sequencing makes this technique easily reproducible, sensitive, and robust. [ 10 ] [ clarification needed ]
Tn-seq has proven to be a useful technique for identifying new gene functions. [ clarification needed ] The highly sensitive nature of Tn-seq [ citation needed ] can be used to determine phenotype-genotype relationships that may have been deemed insignificant by less sensitive methods. Tn-seq identified essential genes and pathways that are important for the utilization of cholesterol in Mycobacterium tuberculosis . [ 16 ]
Tn-seq has been used to study higher order genome organization using gene interactions. [ citation needed ] Genes function as a highly linked network [ citation needed ] . Therefore, in order to study a gene's impact on phenotype , gene interactions must also be considered [ citation needed ] . These gene networks can be studied by screening for synthetic lethality and gene interactions where a double mutant shows an unexpected fitness value compared to each individual mutant [ clarification needed ] [ citation needed ] . Tn-seq was used to determine genetic interactions between five query genes and the rest of the genome in Streptococcus pneumoniae, which revealed both aggravating and alleviating genetic interactions. [ 4 ] [ clarification needed ] [ 10 ]
Tn-seq used in combination with RNA-seq can be utilized to examine the role of non-coding DNA regions. [ 17 ] | https://en.wikipedia.org/wiki/Transposon_sequencing |
Transposon silencing is a form of transcriptional gene silencing targeting transposons. Transcriptional gene silencing is a product of histone modifications that prevent the transcription of a particular area of DNA. Transcriptional silencing of transposons is crucial to the maintenance of a genome. The “jumping” of transposons generates genomic instability and can cause extremely deleterious mutations. Transposable element insertions have been linked to many diseases including hemophilia , severe combined immunodeficiency , and predisposition to cancer . The silencing of transposons is therefore extremely critical in the germline in order to stop transposon mutations from developing and being passed on to the next generation. Additionally, these epigenetic defenses against transposons can be heritable. Studies in Drosophila , Arabidopsis thaliana , and mice all indicate that small interfering RNAs are responsible for transposon silencing. In animals, these siRNAS and piRNAs are most active in the gonads .
Piwi-interacting RNA (piRNA), the largest class of the small RNAs, are between 26 and 31 nucleotides in length and function through interactions with piwi proteins from the Argonaute protein family (gene silencing proteins). Many piRNAs are derived from transposons and other repeated elements, and therefore lack specific loci. Other piRNAs that do map to specific locations are clustered in areas near the centromeres or telomeres of the chromosome. piRNA clusters make up ~1% of the genome. [ 1 ] It is thought that piRNA-PIWI complexes directly control the activity of transposons. piRNAs bound to PIWI proteins seem to use post-transcriptional transcript destruction to silence transposons. [ 1 ] Transposon insertions in introns can escape silencing via the piRNA pathway, suggesting that transcript destruction by piRNAs occurs after nuclear export . piRNAs could, however, act on multiple levels, including guiding heterochromatin assembly and possibly playing a role in translation as well .
The exact biogenesis of piRNAs is still unknown. Most piRNAs are antisense to mRNAs transcribed from the silenced transposons, generally associating with Piwi and Aubergine (Aub) proteins, while sense-strand piRNAs tend to associate with Argonaute 3 (Ago3) instead. [ 1 ] A cycle called “ping pong” amplification proceeds between the sense and anti-sense piRNAs involving extensive trimming and processing to create mature piRNAs. This process is responsible for the production of most piRNAs in the germline and could also explain the origin of piRNAs in germline development. [ 2 ]
piRNAs were first observed in Drosophila in 1990. [ 3 ] In 2003, piRNAs derived largely from repeated sequence elements, including transposons, were found in abundance in male and female Drosophila germlines. [ 4 ] Since then, several studies have identified various piRNAs and piwi-pathways involved in transposon silencing in various species. Two such genome defense systems against transposons are the silencing of the MuDR transposon in maize and the silencing of P elements in Drosophila .
In 2006, a study by Margaret Roth Woodhouse, Michael Freeling, and Damon Lisch identified a gene that inhibits the transcription of both transposons and paramuted color gens in maize. [ 5 ] The gene, called Mediator of paramutation1 (Mop1), codes for an RNA-processing enzyme that is necessary for making the small RNAs that are responsible for silencing the transposon MuDR. A second gene, Mu killer (MuK), is then needed to establish heritable silencing. [ 6 ]
P elements are a family of transposons that recently proliferated within the genome of Drosophila melanogaster . The P elements have an extremely high transposition rate and induce sterility and abnormal gonad development in D. melanogaster . [ 3 ] The flies thus developed a maternally inherited technique for combating the invasive DNA and silencing the transposons, now known as P cytotype. P cytotype detects DNA sequences in areas of telomeric heterochromatin and silences those sequences when they are found elsewhere in the genome. This is referred to as the telomeric-silencing effect (TSE). [ 3 ] Just two P elements in the telomere are enough to suppress over 80 other copies of the P element in the genome. The cytoplasmic factor used for TSE builds up over generations and suppression of the transposons is not fully effective unless the fly's female-line ancestors have had the P element for six generations. [ 3 ] | https://en.wikipedia.org/wiki/Transposon_silencing |
In genetic engineering , transposon tagging is a process where transposons (transposable elements) are amplified inside a biological cell by a tagging technique. Transposon tagging has been used with several species to isolate genes . [ 1 ] [ self-published source? ] Even without knowing the nature of the specific genes, the process can still be used. [ 1 ]
By molecular separation of transposons , from a cell nucleus, the cloning is enabled for genes which contain the transposons. [ 2 ] [ self-published source? ]
By using transposon tagging, researchers have been able to add genetic elements from maize (corn) [ 3 ] and Antirrhinum into some other species (such as tobacco , [ 4 ] aspen [ 5 ] and others). [ 2 ] A gene responsible for a particular phenotype can be cloned within a given species, when movement is accompanied by the presence of a mutant phenotype. [ 2 ]
This genetics article is a stub . You can help Wikipedia by expanding it .
This article about biological engineering is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transposon_tagging |
In the field of molecular biology , transrepression is a process whereby one protein represses (i.e., inhibits) the activity of a second protein through a protein-protein interaction . Since this repression occurs between two different protein molecules ( intermolecular ), it is referred to as a trans-acting process.
The protein that is repressed is usually a transcription factor whose function is to up-regulate (i.e., increase) the rate of gene transcription . Hence the net result of transrepression is down regulation of gene transcription.
An example of transrepression is the ability of the glucocorticoid receptor to inhibit the transcriptional promoting activity of the AP-1 and NF-κB transcription factors. [ 1 ] [ 2 ] In addition to transactivation , transrepression is an important pathway for the anti-inflammatory effects of glucocorticoids . [ 3 ] [ 4 ] Other nuclear receptors such as LXR and PPAR have been demonstrated to also have the ability to transrepress the activity of other proteins. [ 5 ]
This molecular biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transrepression |
In mathematics, the field T L E {\displaystyle \mathbb {T} ^{LE}} of logarithmic-exponential transseries is a non-Archimedean ordered differential field which extends comparability of asymptotic growth rates of elementary nontrigonometric functions to a much broader class of objects. Each log-exp transseries represents a formal asymptotic behavior, and it can be manipulated formally, and when it converges (or in every case if using special semantics such as through infinite surreal numbers ), corresponds to actual behavior. Transseries can also be convenient for representing functions. Through their inclusion of exponentiation and logarithms, transseries are a strong generalization of the power series at infinity ( ∑ n = 0 ∞ a n x n {\textstyle \sum _{n=0}^{\infty }{\frac {a_{n}}{x^{n}}}} ) and other similar asymptotic expansions .
The field T L E {\displaystyle \mathbb {T} ^{LE}} was introduced independently by Dahn-Göring [ 1 ] and Ecalle [ 2 ] in the respective contexts of model theory or exponential fields and of the study of analytic singularity and proof by Ecalle of the Dulac conjectures. It constitutes a formal object, extending the field of exp-log functions of Hardy and the field of accelerando-summable series of Ecalle.
The field T L E {\displaystyle \mathbb {T} ^{LE}} enjoys a rich structure: an ordered field with a notion of generalized series and sums, with a compatible derivation with distinguished antiderivation, compatible exponential and logarithm functions and a notion of formal composition of series.
Informally speaking, exp-log transseries are well-based (i.e. reverse well-ordered) formal Hahn series of real powers of the positive infinite indeterminate x {\displaystyle x} , exponentials, logarithms and their compositions, with real coefficients. Two important additional conditions are that the exponential and logarithmic depth of an exp-log transseries f , {\displaystyle f,} that is the maximal numbers of iterations of exp and log occurring in f , {\displaystyle f,} must be finite.
The following formal series are log-exp transseries:
The following formal series are not log-exp transseries:
It is possible to define differential fields of transseries containing the two last series; they belong respectively to T E L {\displaystyle \mathbb {T} ^{EL}} and R ⟨ ⟨ ω ⟩ ⟩ {\displaystyle \mathbb {R} \langle \langle \omega \rangle \rangle } (see the paragraph Using surreal numbers below).
A remarkable fact is that asymptotic growth rates of elementary nontrigonometric functions and even all functions definable in the model theoretic structure ( R , + , × , < , exp ) {\displaystyle (\mathbb {R} ,+,\times ,<,\exp )} of the ordered exponential field of real numbers are all comparable:
For all such f {\displaystyle f} and g {\displaystyle g} , we have f ≤ ∞ g {\displaystyle f\leq _{\infty }g} or g ≤ ∞ f {\displaystyle g\leq _{\infty }f} , where f ≤ ∞ g {\displaystyle f\leq _{\infty }g} means ∃ x . ∀ y > x . f ( y ) ≤ g ( y ) {\displaystyle \exists x.\forall y>x.f(y)\leq g(y)} . The equivalence class of f {\displaystyle f} under the relation f ≤ ∞ g ∧ g ≤ ∞ f {\displaystyle f\leq _{\infty }g\wedge g\leq _{\infty }f} is the asymptotic behavior of f {\displaystyle f} , also called the germ of f {\displaystyle f} (or the germ of f {\displaystyle f} at infinity).
The field of transseries can be intuitively viewed as a formal generalization of these growth rates: In addition to the elementary operations, transseries are closed under "limits" for appropriate sequences with bounded exponential and logarithmic depth. However, a complication is that growth rates are non- Archimedean and hence do not have the least upper bound property . We can address this by associating a sequence with the least upper bound of minimal complexity, analogously to construction of surreal numbers. For example, ( ∑ k = 0 n x − k ) n ∈ N {\textstyle (\sum _{k=0}^{n}x^{-k})_{n\in \mathbb {N} }} is associated with ∑ k = 0 ∞ x − k {\textstyle \sum _{k=0}^{\infty }x^{-k}} rather than ∑ k = 0 ∞ x − k − e − x {\textstyle \sum _{k=0}^{\infty }x^{-k}-e^{-x}} because e − x {\displaystyle e^{-x}} decays too quickly, and if we identify fast decay with complexity, it has greater complexity than necessary (also, because we care only about asymptotic behavior, pointwise convergence is not dispositive).
Because of the comparability, transseries do not include oscillatory growth rates (such as sin x {\displaystyle \sin x} ). On the other hand, there are transseries such as ∑ k ∈ N k ! e x − k k + 1 {\textstyle \sum _{k\in \mathbb {N} }k!e^{x^{-{\frac {k}{k+1}}}}} that do not directly correspond to convergent series or real valued functions. Another limitation of transseries is that each of them is bounded by a tower of exponentials, i.e. a finite iteration e e . . . e x {\displaystyle e^{e^{.^{.^{.^{e^{x}}}}}}} of e x {\displaystyle e^{x}} , thereby excluding tetration and other transexponential functions, i.e. functions which grow faster than any tower of exponentials. There are ways to construct fields of generalized transseries including formal transexponential terms, for instance formal solutions e ω {\displaystyle e_{\omega }} of the Abel equation e e ω ( x ) = e ω ( x + 1 ) {\displaystyle e^{e_{\omega }(x)}=e_{\omega }(x+1)} . [ 3 ]
Transseries can be defined as formal (potentially infinite) expressions, with rules defining which expressions are valid, comparison of transseries, arithmetic operations, and even differentiation. Appropriate transseries can then be assigned to corresponding functions or germs, but there are subtleties involving convergence. Even transseries that diverge can often be meaningfully (and uniquely) assigned actual growth rates (that agree with the formal operations on transseries) using accelero-summation , which is a generalization of Borel summation .
Transseries can be formalized in several equivalent ways; we use one of the simplest ones here.
A transseries is a well-based sum,
with finite exponential depth, where each a i {\displaystyle a_{i}} is a nonzero real number and m i {\displaystyle m_{i}} is a monic transmonomial ( a i m i {\displaystyle a_{i}m_{i}} is a transmonomial but is not monic unless the coefficient a i = 1 {\displaystyle a_{i}=1} ; each m i {\displaystyle m_{i}} is different; the order of the summands is irrelevant).
The sum might be infinite or transfinite; it is usually written in the order of decreasing m i {\displaystyle m_{i}} .
Here, well-based means that there is no infinite ascending sequence m i 1 < m i 2 < m i 3 < ⋯ {\displaystyle m_{i_{1}}<m_{i_{2}}<m_{i_{3}}<\cdots } (see well-ordering ).
A monic transmonomial is one of 1, x , log x , log log x , ..., e purely_large_transseries .
A purely large transseries is a nonempty transseries ∑ a i m i {\textstyle \sum a_{i}m_{i}} with every m i > 1 {\displaystyle m_{i}>1} .
Transseries have finite exponential depth , where each level of nesting of e or log increases depth by 1 (so we cannot have x + log x + log log x + ...).
Addition of transseries is termwise: ∑ a i m i + ∑ b i m i = ∑ ( a i + b i ) m i {\textstyle \sum a_{i}m_{i}+\sum b_{i}m_{i}=\sum (a_{i}+b_{i})m_{i}} (absence of a term is equated with a zero coefficient).
Comparison:
The most significant term of ∑ a i m i {\textstyle \sum a_{i}m_{i}} is a i m i {\displaystyle a_{i}m_{i}} for the largest m i {\displaystyle m_{i}} (because the sum is well-based, this exists for nonzero transseries). ∑ a i m i {\textstyle \sum a_{i}m_{i}} is positive iff the coefficient of the most significant term is positive (this is why we used 'purely large' above). X > Y iff X − Y is positive.
Comparison of monic transmonomials:
Multiplication:
This essentially applies the distributive law to the product; because the series is well-based, the inner sum is always finite.
Differentiation:
With these definitions, transseries is an ordered differential field. Transseries is also a valued field , with the valuation ν {\displaystyle \nu } given by the leading monic transmonomial, and the corresponding asymptotic relation defined for 0 ≠ f , g ∈ T L E {\displaystyle 0\neq f,g\in \mathbb {T} ^{LE}} by f ≺ g {\displaystyle f\prec g} if ∀ 0 < r ∈ R , | f | < r | g | {\displaystyle \forall 0<r\in \mathbb {R} ,|f|<r|g|} (where | f | = max ( f , − f ) {\displaystyle |f|=\max(f,-f)} is the absolute value).
We first define the subfield T E {\displaystyle \mathbb {T} ^{E}} of T L E {\displaystyle \mathbb {T} ^{LE}} of so-called log-free transseries . Those are transseries which exclude any logarithmic term.
Inductive definition:
For n ∈ N , {\displaystyle n\in \mathbb {N} ,} we will define a linearly ordered multiplicative group of monomials M n {\displaystyle {\mathfrak {M}}_{n}} . We then let T n E {\displaystyle \mathbb {T} _{n}^{E}} denote the field of well-based series R [ [ M n ] ] {\displaystyle \mathbb {R} [[{\mathfrak {M}}_{n}]]} . This is the set of maps R → M n {\displaystyle \mathbb {R} \to {\mathfrak {M}}_{n}} with well-based (i.e. reverse well-ordered) support, equipped with pointwise sum and Cauchy product (see Hahn series ). In T n E {\displaystyle \mathbb {T} _{n}^{E}} , we distinguish the (non-unital) subring T n , ≻ E {\displaystyle \mathbb {T} _{n,\succ }^{E}} of purely large transseries , which are series whose support contains only monomials lying strictly above 1 {\displaystyle 1} .
The natural inclusion of M 0 {\displaystyle {\mathfrak {M}}_{0}} into M 1 {\displaystyle {\mathfrak {M}}_{1}} given by identifying x a {\displaystyle x^{a}} and x a e 0 {\displaystyle x^{a}e^{0}} inductively provides a natural embedding of M n {\displaystyle {\mathfrak {M}}_{n}} into M n + 1 {\displaystyle {\mathfrak {M}}_{n+1}} , and thus a natural embedding of T n E {\displaystyle \mathbb {T} _{n}^{E}} into T n + 1 E {\displaystyle \mathbb {T} _{n+1}^{E}} . We may then define the linearly ordered commutative group M = ⋃ n ∈ N M n {\textstyle {\mathfrak {M}}=\bigcup _{n\in \mathbb {N} }{\mathfrak {M}}_{n}} and the ordered field T E = ⋃ n ∈ N T n E {\textstyle \mathbb {T} ^{E}=\bigcup _{n\in \mathbb {N} }\mathbb {T} _{n}^{E}} which is the field of log-free transseries.
The field T E {\displaystyle \mathbb {T} ^{E}} is a proper subfield of the field R [ [ M ] ] {\displaystyle \mathbb {R} [[{\mathfrak {M}}]]} of well-based series with real coefficients and monomials in M {\displaystyle {\mathfrak {M}}} . Indeed, every series f {\displaystyle f} in T E {\displaystyle \mathbb {T} ^{E}} has a bounded exponential depth, i.e. the least positive integer n {\displaystyle n} such that f ∈ T n E {\displaystyle f\in \mathbb {T} _{n}^{E}} , whereas the series
has no such bound.
Exponentiation on T E {\displaystyle \mathbb {T} ^{E}} :
The field of log-free transseries is equipped with an exponential function which is a specific morphism exp : ( T E , + ) → ( T E , > , × ) {\displaystyle \exp :(\mathbb {T} ^{E},+)\to (\mathbb {T} ^{E,>},\times )} . Let f {\displaystyle f} be a log-free transseries and let n ∈ N {\displaystyle n\in \mathbb {N} } be the exponential depth of f {\displaystyle f} , so f ∈ T n E {\displaystyle f\in \mathbb {T} _{n}^{E}} . Write f {\displaystyle f} as the sum f = θ + r + ε {\displaystyle f=\theta +r+\varepsilon } in T n E , {\displaystyle \mathbb {T} _{n}^{E},} where θ ∈ T n , ≻ E {\displaystyle \theta \in \mathbb {T} _{n,\succ }^{E}} , r {\displaystyle r} is a real number and ε {\displaystyle \varepsilon } is infinitesimal (any of them could be zero). Then the formal Hahn sum
converges in T n E {\displaystyle \mathbb {T} _{n}^{E}} , and we define exp ( f ) = e θ exp ( r ) E ( ε ) ∈ T n + 1 E {\displaystyle \exp(f)=e^{\theta }\exp(r)E(\varepsilon )\in \mathbb {T} _{n+1}^{E}} where exp ( r ) {\displaystyle \exp(r)} is the value of the real exponential function at r {\displaystyle r} .
Right-composition with e x {\displaystyle e^{x}} :
A right composition ∘ e x {\displaystyle \circ _{e^{x}}} with the series e x {\displaystyle e^{x}} can be defined by induction on the exponential depth by
with x r ∘ e x := e r x {\displaystyle x^{r}\circ e^{x}:=e^{rx}} . It follows inductively that monomials are preserved by ∘ e x , {\displaystyle \circ _{e^{x}},} so at each inductive step the sums are well-based and thus well defined.
Definition:
The function exp {\displaystyle \exp } defined above is not onto T E , > {\displaystyle \mathbb {T} ^{E,>}} so the logarithm is only partially defined on T E {\displaystyle \mathbb {T} ^{E}} : for instance the series x {\displaystyle x} has no logarithm. Moreover, every positive infinite log-free transseries is greater than some positive power of x {\displaystyle x} . In order to move from T E {\displaystyle \mathbb {T} ^{E}} to T L E {\displaystyle \mathbb {T} ^{LE}} , one can simply "plug" into the variable x {\displaystyle x} of series formal iterated logarithms ℓ n , n ∈ N {\displaystyle \ell _{n},n\in \mathbb {N} } which will behave like the formal reciprocal of the n {\displaystyle n} -fold iterated exponential term denoted e n {\displaystyle e_{n}} .
For m , n ∈ N , {\displaystyle m,n\in \mathbb {N} ,} let M m , n {\displaystyle {\mathfrak {M}}_{m,n}} denote the set of formal expressions u ∘ ℓ n {\displaystyle {\mathfrak {u}}\circ \ell _{n}} where u ∈ M m {\displaystyle {\mathfrak {u}}\in {\mathfrak {M}}_{m}} . We turn this into an ordered group by defining ( u ∘ ℓ n ) ( v ∘ ℓ n ( x ) ) := ( u v ) ∘ ℓ n {\displaystyle ({\mathfrak {u}}\circ \ell _{n})({\mathfrak {v}}\circ \ell _{n}(x)):=({\mathfrak {u}}{\mathfrak {v}})\circ \ell _{n}} , and defining u ∘ ℓ n ≺ v ∘ ℓ n {\displaystyle {\mathfrak {u}}\circ \ell _{n}\prec {\mathfrak {v}}\circ \ell _{n}} when u ≺ v {\displaystyle {\mathfrak {u}}\prec {\mathfrak {v}}} . We define T m , n L E := R [ [ M m , n ] ] {\displaystyle \mathbb {T} _{m,n}^{LE}:=\mathbb {R} [[{\mathfrak {M}}_{m,n}]]} . If n ′ > n {\displaystyle n'>n} and m ′ ≥ m + ( n ′ − n ) , {\displaystyle m'\geq m+(n'-n),} we embed M m , n {\displaystyle {\mathfrak {M}}_{m,n}} into M m ′ , n ′ {\displaystyle {\mathfrak {M}}_{m',n'}} by identifying an element u ∘ ℓ n {\displaystyle {\mathfrak {u}}\circ \ell _{n}} with the term
We then obtain T L E {\displaystyle \mathbb {T} ^{LE}} as the directed union
On T L E , {\displaystyle \mathbb {T} ^{LE},} the right-composition ∘ ℓ {\displaystyle \circ _{\ell }} with ℓ {\displaystyle \ell } is naturally defined by
Exponential and logarithm:
Exponentiation can be defined on T L E {\displaystyle \mathbb {T} ^{LE}} in a similar way as for log-free transseries, but here also exp {\displaystyle \exp } has a reciprocal log {\displaystyle \log } on T L E , > {\displaystyle \mathbb {T} ^{LE,>}} . Indeed, for a strictly positive series f ∈ T m , n L E , > {\displaystyle f\in \mathbb {T} _{m,n}^{LE,>}} , write f = m r ( 1 + ε ) {\displaystyle f={\mathfrak {m}}r(1+\varepsilon )} where m {\displaystyle {\mathfrak {m}}} is the dominant monomial of f {\displaystyle f} (largest element of its support), r {\displaystyle r} is the corresponding positive real coefficient, and ε := f m r − 1 {\displaystyle \varepsilon :={\frac {f}{{\mathfrak {m}}r}}-1} is infinitesimal. The formal Hahn sum
converges in T m , n L E {\displaystyle \mathbb {T} _{m,n}^{LE}} . Write m = u ∘ ℓ n {\displaystyle {\mathfrak {m}}={\mathfrak {u}}\circ \ell _{n}} where u ∈ M m {\displaystyle {\mathfrak {u}}\in {\mathfrak {M}}_{m}} itself has the form u = x a e θ {\displaystyle {\mathfrak {u}}=x^{a}e^{\theta }} where θ ∈ T m , ≻ E {\displaystyle \theta \in \mathbb {T} _{m,\succ }^{E}} and a ∈ R {\displaystyle a\in \mathbb {R} } . We define ℓ ( m ) := a ℓ n + 1 + θ ∘ ℓ n {\displaystyle \ell ({\mathfrak {m}}):=a\ell _{n+1}+\theta \circ \ell _{n}} . We finally set
One may also define the field of log-exp transseries as a subfield of the ordered field N o {\displaystyle \mathbf {No} } of surreal numbers. [ 4 ] The field N o {\displaystyle \mathbf {No} } is equipped with Gonshor-Kruskal's exponential and logarithm functions [ 5 ] and with its natural structure of field of well-based series under Conway normal form. [ 6 ]
Define F 0 L E = R ( ω ) {\displaystyle F_{0}^{LE}=\mathbb {R} (\omega )} , the subfield of N o {\displaystyle \mathbf {No} } generated by R {\displaystyle \mathbb {R} } and the simplest positive infinite surreal number ω {\displaystyle \omega } (which corresponds naturally to the ordinal ω {\displaystyle \omega } , and as a transseries to the series x {\displaystyle x} ). Then, for n ∈ N {\displaystyle n\in \mathbb {N} } , define F n + 1 L E {\displaystyle F_{n+1}^{LE}} as the field generated by F n L E {\displaystyle F_{n}^{LE}} , exponentials of elements of F n L E {\displaystyle F_{n}^{LE}} and logarithms of strictly positive elements of F n L E {\displaystyle F_{n}^{LE}} , as well as (Hahn) sums of summable families in F n L E {\displaystyle F_{n}^{LE}} . The union F ω L E = ⋃ n ∈ N F n L E {\textstyle F_{\omega }^{LE}=\bigcup _{n\in \mathbb {N} }F_{n}^{LE}} is naturally isomorphic to T L E {\displaystyle \mathbb {T} ^{LE}} . In fact, there is a unique such isomorphism which sends ω {\displaystyle \omega } to x {\displaystyle x} and commutes with exponentiation and sums of summable families in F ω L E {\displaystyle F_{\omega }^{LE}} lying in F ω {\displaystyle F_{\omega }} .
The Berarducci-Mantova derivation [ 8 ] on N o {\displaystyle \mathbf {No} } coincides on T L E {\displaystyle \mathbb {T} ^{LE}} with its natural derivation, and is unique to satisfy compatibility relations with the exponential ordered field structure and generalized series field structure of T E L {\displaystyle \mathbb {T} ^{EL}} and R ⟨ ⟨ ω ⟩ ⟩ . {\displaystyle \mathbb {R} \langle \langle \omega \rangle \rangle .}
Contrary to T L E , {\displaystyle \mathbb {T} ^{LE},} the derivation in T E L {\displaystyle \mathbb {T} ^{EL}} and R ⟨ ⟨ ω ⟩ ⟩ {\displaystyle \mathbb {R} \langle \langle \omega \rangle \rangle } is not surjective: for instance the series
doesn't have an antiderivative in T E L {\displaystyle \mathbb {T} ^{EL}} or R ⟨ ⟨ ω ⟩ ⟩ {\displaystyle \mathbb {R} \langle \langle \omega \rangle \rangle } (this is linked to the fact that those fields contain no transexponential function).
Transseries have very strong closure properties, and many operations can be defined on transseries:
Note 1. The last two properties mean that T L E {\displaystyle \mathbb {T} ^{LE}} is Liouville closed .
Note 2. Just like an elementary nontrigonometric function, each positive infinite transseries f {\displaystyle f} has integral exponentiality, even in this strong sense:
The number k {\displaystyle k} is unique, it is called the exponentiality of f {\displaystyle f} .
An original property of T L E {\displaystyle \mathbb {T} ^{LE}} is that it admits a composition ∘ : T L E × T L E , > , ≻ → T L E {\displaystyle \circ :\mathbb {T} ^{LE}\times \mathbb {T} ^{LE,>,\succ }\to \mathbb {T} ^{LE}} (where T L E , > , ≻ {\displaystyle \mathbb {T} ^{LE,>,\succ }} is the set of positive infinite log-exp transseries) which enables us to see each log-exp transseries f {\displaystyle f} as a function on T L E , > , ≻ {\displaystyle \mathbb {T} ^{LE,>,\succ }} . Informally speaking, for g ∈ T L E , > , ≻ {\displaystyle g\in \mathbb {T} ^{LE,>,\succ }} and f ∈ T L E {\displaystyle f\in \mathbb {T} ^{LE}} , the series f ∘ g {\displaystyle f\circ g} is obtained by replacing each occurrence of the variable x {\displaystyle x} in f {\displaystyle f} by g {\displaystyle g} .
The ⟨ + , × , ∂ , < , ≺ ⟩ {\displaystyle \left\langle +,\times ,\partial ,<,\prec \right\rangle } theory of T L E {\displaystyle \mathbb {T} ^{LE}} is decidable and can be axiomatized as follows (this is Theorem 2.2 of Aschenbrenner et al.):
In this theory, exponentiation is essentially defined for functions (using differentiation) but not constants; in fact, every definable subset of R n {\displaystyle \mathbb {R} ^{n}} is semialgebraic .
The ⟨ + , × , exp , < ⟩ {\displaystyle \langle +,\times ,\exp ,<\rangle } theory of T L E {\displaystyle \mathbb {T} ^{LE}} is that of the exponential real ordered exponential field ( R , + , × , exp , < ) {\displaystyle (\mathbb {R} ,+,\times ,\exp ,<)} , which is model complete by Wilkie's theorem .
T a s {\displaystyle \mathbb {T} _{\mathrm {as} }} is the field of accelero-summable transseries, and using accelero-summation, we have the corresponding Hardy field , which is conjectured to be the maximal Hardy field corresponding to a subfield of T {\displaystyle \mathbb {T} } . (This conjecture is informal since we have not defined which isomorphisms of Hardy fields into differential subfields of T {\displaystyle \mathbb {T} } are permitted.) T a s {\displaystyle \mathbb {T} _{\mathrm {as} }} is conjectured to satisfy the above axioms of T {\displaystyle \mathbb {T} } . Without defining accelero-summation, we note that when operations on convergent transseries produce a divergent one while the same operations on the corresponding germs produce a valid germ, we can then associate the divergent transseries with that germ.
A Hardy field is said maximal if it is properly contained in no Hardy field. By an application of Zorn's lemma, every Hardy field is contained in a maximal Hardy field. It is conjectured that all maximal Hardy fields are elementary equivalent as differential fields, and indeed have the same first order theory as T L E {\displaystyle \mathbb {T} ^{LE}} . [ 10 ] Logarithmic-transseries do not themselves correspond to a maximal Hardy field for not every transseries corresponds to a real function, and maximal Hardy fields always contain transexponential functions. [ 11 ] | https://en.wikipedia.org/wiki/Transseries |
Transuranic waste (TRU) is stated by U.S. regulations, and independent of state or origin, to be waste which has been contaminated with alpha emitting transuranic radionuclides possessing half-lives greater than 20 years and in concentrations greater than 100 nCi /g (3.7 MBq /kg). [ 1 ]
Elements having atomic numbers greater than that of uranium are called transuranic. Elements within TRU are typically man-made and are known to contain americium-241 and several isotopes of plutonium . [ 2 ] Because of the elements' longer half-lives , TRU is disposed of more cautiously than low level waste and intermediate level waste. In the U.S. it is a byproduct of weapons production, nuclear research and power production, and consists of protective gear, tools, residue, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium).
Under U.S. law, TRU is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of the radiation field measured on the waste container's surface. CH TRU has a surface dose rate not greater than 2 mSv per hour (200 mrem /h), whereas RH TRU has rates of 2 mSv/h or higher. CH TRU has neither the high radioactivity of high level waste, nor its high heat generation. In contrast, RH TRU can be highly radioactive, with surface dose rates up to 10 Sv/h (1000 rem/h) [ citation needed ] .
The United States currently permanently disposes of TRU generated from defense nuclear activities at the Waste Isolation Pilot Plant , a deep geologic repository.
Other countries do not include this category, favoring variations of High, Medium/Intermediate, and Low Level waste.
This radioactivity –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transuranic_waste |
The transuranium (or transuranic ) elements are the chemical elements with atomic number greater than 92, which is the atomic number of uranium . All of them are radioactively unstable and decay into other elements. Except for neptunium and plutonium , which have been found in trace amounts in nature, none occur naturally on Earth and they are synthetic .
Of the elements with atomic numbers 1 to 92, most can be found in nature, having stable isotopes (such as oxygen ) or very long-lived radioisotopes (such as uranium ), or existing as common decay products of the decay of uranium and thorium (such as radon ). The exceptions are technetium , promethium , astatine , and francium ; all four occur in nature, but only in very minor branches of the uranium and thorium decay chains, and thus all save francium were first discovered by synthesis in the laboratory rather than in nature.
All elements with higher atomic numbers have been first discovered in the laboratory, with neptunium and plutonium later discovered in nature. They are all radioactive , with a half-life much shorter than the age of the Earth , so any primordial (i.e. present at the Earth's formation) atoms of these elements, have long since decayed. Trace amounts of neptunium and plutonium form in some uranium-rich rock, and small amounts are produced during atmospheric tests of nuclear weapons . These two elements are generated by neutron capture in uranium ore with subsequent beta decays (e.g. 238 U + n → 239 U → 239 Np → 239 Pu ).
All elements beyond plutonium are entirely synthetic ; they are created in nuclear reactors or particle accelerators . The half-lives of these elements show a general trend of decreasing as atomic numbers increase. There are exceptions, however, including several isotopes of curium and dubnium . Some heavier elements in this series, around atomic numbers 110–114, are thought to break the trend and demonstrate increased nuclear stability, comprising the theoretical island of stability . [ 1 ]
Transuranic elements are difficult and expensive to produce, and their prices increase rapidly with atomic number. As of 2008, the cost of weapons-grade plutonium was around $4,000/gram, [ 2 ] and californium exceeded $60,000,000/gram. [ 3 ] Einsteinium is the heaviest element that has been produced in macroscopic quantities. [ 4 ]
Transuranic elements that have not been discovered, or have been discovered but are not yet officially named, use IUPAC 's systematic element names . The naming of transuranic elements may be a source of controversy .
So far, essentially all transuranium elements have been discovered at four laboratories: Lawrence Berkeley National Laboratory (LBNL) in the United States (elements 93–101, 106, and joint credit for 103–105), the Joint Institute for Nuclear Research (JINR) in Russia (elements 102 and 114–118, and joint credit for 103–105), the GSI Helmholtz Centre for Heavy Ion Research in Germany (elements 107–112), and RIKEN in Japan (element 113).
Superheavy elements , (also known as superheavies , or superheavy atoms , commonly abbreviated SHE ) usually refer to the transactinide elements beginning with rutherfordium (atomic number 104). (Lawrencium, the first 6d element, is sometimes but not always included as well.) They have only been made artificially and currently serve no practical purpose because their short half-lives cause them to decay after a very short time, ranging from a few hours to just milliseconds, which also makes them extremely hard to study. [ 5 ] [ 6 ]
Superheavies have all been created since the latter half of the 20th century and are continually being created during the 21st century as technology advances. They are created through the bombardment of elements in a particle accelerator, in quantities on the atomic scale, and no method of mass creation has been found. [ 5 ]
Transuranic elements may be used to synthesize superheavy elements. [ 7 ] Elements of the island of stability have potentially important military applications, including the development of compact nuclear weapons. [ 8 ] The potential everyday applications are vast; americium is used in devices such as smoke detectors and spectrometers . [ 9 ] [ 10 ] | https://en.wikipedia.org/wiki/Transuranium_element |
Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologous chromosome . Transvection can lead to either gene activation or repression. [ 1 ] It can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed.
The first observation of mitotic (i.e. non- meiotic ) chromosome pairing was discovered via microscopy in 1908 by Nettie Stevens . [ 2 ] Edward B. Lewis at Caltech discovered transvection at the bithorax complex in Drosophila in the 1950s. [ 3 ] Since then, transvection has been observed at a number of additional loci in Drosophila , including the genes known as white , decapentaplegic , eyes absent , vestigial , and yellow . [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] As defined by Lewis, "Operationally, transvection is occurring if the phenotype of a given genotype can be altered solely by disruption of somatic (or meiotic) pairing. Such disruption can generally be accomplished by introduction of a heterozygous rearrangement that disrupts pairing in the relevant region but has no position effect of its own on the phenotype" (cited by Ting Wu and Jim Morris, 1999 [ 9 ] ). Recently, pairing-mediated phenomena have been observed in species other than Drosophila , including mice, humans, plants, nematodes, insects, and fungi. In light of these findings, transvection may represent a potent and widespread form of gene regulation . [ 10 ] [ 11 ]
Transvection appears to be dependent upon chromosome pairing. In some cases, if one allele is placed on a different chromosome by a translocation , transvection does not occur. Transvection can sometimes be restored in a translocation homozygote, where both alleles may once again be able to pair. Restoration of phenotype has been observed at bithorax , decapentaplegic , eyes absent , and vestigial , and with transgenes of white . In some cases, transvection between two alleles leads to intragenic complementation while disruption of transvection disrupts the complementation.
Transvection is believed to occur through a variety of mechanisms. In one mechanism, the enhancers of one allele activate the promoter of a paired second allele. Other mechanisms include pairing-sensitive silencing and enhancer bypass of a chromatin insulator through pairing-mediated changes in gene structure. [ 12 ] [ 13 ]
The physiological relevance of transvection has recently been documented in the context of sex-biased gene expression. In Drosophila , transvection acts on the female X-linked gene yellow , which is homozygous in females (XX) versus hemizygous in males (XY). [ 14 ] | https://en.wikipedia.org/wiki/Transvection_(genetics) |
Transversals are a geometric construction on a scientific instrument to allow a graduation to be read to a finer degree of accuracy. Their use creates what is sometimes called a diagonal scale , an engineering measuring instrument which is composed of a set of parallel straight lines which are obliquely crossed by another set of straight lines. Diagonal scales are used to measure small fractions of the unit of measurement . [ 1 ]
Transversals have been replaced in modern times by vernier scales . This method is based on the Intercept theorem (also known as Thales's theorem).
Transversals were used at a time when finely graduated instruments were difficult to make. They were found on instruments starting in the early 14th century, but the inventor is unknown. In 1342 Levi Ben Gerson introduced an instrument called Jacob's staff (apparently invented the previous century by Jacob Ben Makir ) and described the method of the transversal scale applied to the mentioned instrument. [ 2 ] [ 3 ]
Thomas Digges mistakenly attributed the discovery of the transversal scale to the navigator and explorer Richard Chancellor (cited by some authors as watchmaker and with other names, among them: Richard Chansler or Richard Kantzler). [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] Its use on astronomical instruments only began in the late 16th century. Tycho Brahe used them and did much to popularize the technique. [ 10 ] [ 11 ] The technique began to die out once verniers became common in the late 18th century – over a century after Pierre Vernier introduced the technique.
In the interim between transversals and the vernier scale, the nonius system, developed by Pedro Nunes , was used. However, it was never in common use. Tycho also used nonius methods, but he appears to be the only prominent astronomer to do so.
Diagonal scale is derived from the Latin word Diagonalis . The Latin word was originally coined from the Greek word diagōnios where dia means "through" and gonios denotes "corners". [ 1 ] [ 12 ]
Diagonal scale follows the principle of similar triangles where a short length is divided into number of parts in which sides are proportional. [ 13 ] Divided into required number of equal parts
Linear transversals were used on linear graduations. A grid of lines was constructed immediately adjacent to the linear graduations. The lines extending above the graduations formed part of the grid. The number of lines perpendicular to the extended graduation lines in the grid was dependent on the degree of fineness the instrument maker wished to provide.
A grid of five lines would permit determination of the measure to one-fifth of a graduation's division. A ten-line grid would permit tenths to be measured. The distance between the lines is not critical as long as the distance is precisely uniform. Greater distances makes for greater accuracy.
As seen in the illustration on the right, once the grid was scribed, diagonals (transverse lines) were scribed from the uppermost corner of a column in the grid to the opposite lowest corner. This line intersects the cross lines in the grid in equal intervals. By using an indicator such as a cursor or alidade , or by measuring using a pair of dividers with points on the same horizontal grid line, the closest point where the transversal crosses the grid is determined. That indicates the fraction of the graduation for the measure.
In the illustration, the reading is indicated by the vertical red line. This could be the edge of an alidade or a similar device. Since the cursor crosses the transversal closest to the fourth grid line from the top, the reading (assuming the leftmost long graduation line is 0.0) is 0.54.
Diagonal scale is used in engineering to read lengths with higher accuracy as it represents a unit into three different multiple in metres , centimeters and millimeters . [ 14 ] Diagonal scale is an important part in Engineering drawings . [ 15 ]
Circular transversals perform the same function as the linear ones but for circular arcs. In this case, the construction of the grid is significantly more complicated. A rectangular grid will not work. A grid of radial lines and circumferential arcs must be created. In addition, a linear transverse line will not divide the radial grid into equal segments. Circular arc segments must be constructed as transversals to provide the correct proportions.
Tycho Brahe created a grid of transversal lines made with secants between two groups of arcs that form two graduated limbs. The secants are drawn by joining the division of a limb with the next division of the other limb, and so on (see figure with the magnification of 2 degrees of the Tycho Brahe's quadrant of 2m radius). [ 10 ]
He drew, for each degree, six straight transversals in an alternate mode forming a "V" and each transversal consisted of 9 points that divided it into 10 parts, which multiplied by 6 give 60 minutes. [ 16 ] While Abd al-Mun'im al 'Âmilî (16th century) drew them all in the same direction (although his instrument has less precision). [ 17 ]
The method of the "straight transversals" applied to the measurements of angles on circular or semicircular limbs in astronomical and geographic instruments was treated by several authors. Studying the accuracy of the system, some of them indicated the convenience of employing "Circular transversals", instead of the "straight transversals". [ 18 ] | https://en.wikipedia.org/wiki/Transversal_(instrument_making) |
In mathematics , transversality is a notion that describes how spaces can intersect ; transversality can be seen as the "opposite" of tangency , and plays a role in general position . It formalizes the idea of a generic intersection in differential topology . It is defined by considering the linearizations of the intersecting spaces at the points of intersection.
Two submanifolds of a given finite-dimensional smooth manifold are said to intersect transversally if at every point of intersection , their separate tangent spaces at that point together generate the tangent space of the ambient manifold at that point. [ 1 ] Manifolds that do not intersect are vacuously transverse. If the manifolds are of complementary dimension (i.e., their dimensions add up to the dimension of the ambient space ), the condition means that the tangent space to the ambient manifold is the direct sum of the two smaller tangent spaces. If an intersection is transverse, then the intersection will be a submanifold whose codimension is equal to the sums of the codimensions of the two manifolds. In the absence of the transversality condition the intersection may fail to be a submanifold, having some sort of singular point .
In particular, this means that transverse submanifolds of complementary dimension intersect in isolated points (i.e., a 0-manifold ). If both submanifolds and the ambient manifold are oriented , their intersection is oriented. When the intersection is zero-dimensional, the orientation is simply a plus or minus for each point.
One notation for the transverse intersection of two submanifolds L 1 {\displaystyle L_{1}} and L 2 {\displaystyle L_{2}} of a given manifold M {\displaystyle M} is L 1 ⋔ L 2 {\displaystyle L_{1}\pitchfork L_{2}} . This notation can be read in two ways: either as “ L 1 {\displaystyle L_{1}} and L 2 {\displaystyle L_{2}} intersect transversally” or as an alternative notation for the set-theoretic intersection L 1 ∩ L 2 {\displaystyle L_{1}\cap L_{2}} of L 1 {\displaystyle L_{1}} and L 2 {\displaystyle L_{2}} when that intersection is transverse. In this notation, the definition of transversality reads
The notion of transversality of a pair of submanifolds is easily extended to transversality of a submanifold and a map to the ambient manifold, or to a pair of maps to the ambient manifold, by asking whether the pushforwards of the tangent spaces along the preimage of points of intersection of the images generate the entire tangent space of the ambient manifold. [ 2 ] If the maps are embeddings , this is equivalent to transversality of submanifolds.
Suppose we have transverse maps f 1 : L 1 → M {\displaystyle f_{1}:L_{1}\to M} and f 2 : L 2 → M {\displaystyle f_{2}:L_{2}\to M} where L 1 , L 2 {\displaystyle L_{1},L_{2}} and M {\displaystyle M} are manifolds with dimensions ℓ 1 , ℓ 2 {\displaystyle \ell _{1},\ell _{2}} and m {\displaystyle m} respectively.
The meaning of transversality differs a lot depending on the relative dimensions of M , L 1 {\displaystyle M,L_{1}} and L 2 {\displaystyle L_{2}} . The relationship between transversality and tangency is clearest when ℓ 1 + ℓ 2 = m {\displaystyle \ell _{1}+\ell _{2}=m} .
We can consider three separate cases:
Given any two smooth submanifolds, it is possible to perturb either of them by an arbitrarily small amount such that the resulting submanifold intersects transversally with the fixed submanifold. Such perturbations do not affect the homology class of the manifolds or of their intersections. For example, if manifolds of complementary dimension intersect transversally, the signed sum of the number of their intersection points does not change even if we isotope the manifolds to another transverse intersection. (The intersection points can be counted modulo 2, ignoring the signs, to obtain a coarser invariant.) This descends to a bilinear intersection product on homology classes of any dimension, which is Poincaré dual to the cup product on cohomology . Like the cup product, the intersection product is graded-commutative .
The simplest non-trivial example of transversality is of arcs in a surface . An intersection point between two arcs is transverse if and only if it is not a tangency, i.e., their tangent lines inside the tangent plane to the surface are distinct.
In a three-dimensional space, two curves can be transverse only when they have empty intersection, since their tangent spaces could generate at most a two-dimensional space. Curves transverse to surfaces intersect in points, and surfaces transverse to each other intersect in curves. Curves that are tangent to a surface at a point (for instance, curves lying on a surface) do not intersect the surface transversally.
Here is a more specialised example: suppose that G {\displaystyle G} is a simple Lie group and g {\displaystyle {\mathfrak {g}}} is its Lie algebra. By the Jacobson–Morozov theorem every nilpotent element e ∈ g {\displaystyle e\in {\mathfrak {g}}} can be included into an s l 2 {\displaystyle {\mathfrak {sl_{2}}}} -triple ( e , h , f ) {\displaystyle (e,h,f)} . The representation theory of s l 2 {\displaystyle {\mathfrak {sl_{2}}}} tells us that g = [ g , e ] ⊕ g f {\displaystyle {\mathfrak {g}}=[{\mathfrak {g}},e]\oplus {\mathfrak {g}}_{f}} . The space [ g , e ] {\displaystyle [{\mathfrak {g}},e]} is the tangent space at e {\displaystyle e} to the adjoint orbit A d ( G ) e {\displaystyle {\rm {{Ad}(G)e}}} and so the affine space e + g f {\displaystyle e+{\mathfrak {g}}_{f}} intersects the orbit of e {\displaystyle e} transversally. The space e + g f {\displaystyle e+{\mathfrak {g}}_{f}} is known as the "Slodowy slice" after Peter Slodowy .
In fields utilizing the calculus of variations or the related Pontryagin maximum principle , the transversality condition is frequently used to control the types of solutions found in optimization problems. For example, it is a necessary condition for solution curves to problems of the form:
In many of these problems, the solution satisfies the condition that the solution curve should cross transversally the nullcline or some other curve describing terminal conditions.
Using Sard's theorem , whose hypothesis is a special case of the transversality of maps, it can be shown that transverse intersections between submanifolds of a space of complementary dimensions or between submanifolds and maps to a space are themselves smooth submanifolds. For instance, if a smooth section of an oriented manifold's tangent bundle —i.e. a vector field —is viewed as a map from the base to the total space, and intersects the zero-section (viewed either as a map or as a submanifold) transversely, then the zero set of the section—i.e. the singularities of the vector field—forms a smooth 0-dimensional submanifold of the base, i.e. a set of signed points. The signs agree with the indices of the vector field, and thus the sum of the signs—i.e. the fundamental class of the zero set—is equal to the Euler characteristic of the manifold. More generally, for a vector bundle over an oriented smooth closed finite-dimensional manifold, the zero set of a section transverse to the zero section will be a submanifold of the base of codimension equal to the rank of the vector bundle, and its homology class will be Poincaré dual to the Euler class of the bundle.
An extremely special case of this is the following: if a differentiable function from reals to the reals has nonzero derivative at a zero of the function, then the zero is simple, i.e. it the graph is transverse to the x -axis at that zero; a zero derivative would mean a horizontal tangent to the curve, which would agree with the tangent space to the x -axis.
For an infinite-dimensional example, the d-bar operator is a section of a certain Banach space bundle over the space of maps from a Riemann surface into an almost-complex manifold . The zero set of this section consists of holomorphic maps. If the d-bar operator can be shown to be transverse to the zero-section, this moduli space will be a smooth manifold. These considerations play a fundamental role in the theory of pseudoholomorphic curves and Gromov–Witten theory . (Note that for this example, the definition of transversality has to be refined in order to deal with Banach spaces !)
"Transversal" is a noun; the adjective is "transverse."
quote from J.H.C. Whitehead, 1959 [ 3 ] | https://en.wikipedia.org/wiki/Transversality_(mathematics) |
A transversely isotropic (also known as polar anisotropic ) material is one with physical properties that are symmetric about an axis that is normal to a plane of isotropy . This transverse plane has infinite planes of symmetry and thus, within this plane, the material properties are the same in all directions. In geophysics, vertically transverse isotropy (VTI) is also known as radial anisotropy.
This type of material exhibits hexagonal symmetry (though technically this ceases to be true for tensors of rank 6 and higher), so the number of independent constants in the (fourth-rank) elasticity tensor are reduced to 5 (from a total of 21 independent constants in the case of a fully anisotropic solid ). The (second-rank) tensors of electrical resistivity, permeability, etc. have two independent constants.
An example of a transversely isotropic material is the so-called on-axis unidirectional fiber composite lamina where the fibers are circular in cross section. In a unidirectional composite, the plane normal to the fiber direction can be considered as the isotropic plane, at long wavelengths (low frequencies) of excitation. In the figure to the right, the fibers would be aligned with the x 2 {\displaystyle x_{2}} axis, which is normal to the plane of isotropy.
In terms of effective properties, geological layers of rocks are often interpreted as being transversely isotropic. Calculating the effective elastic properties of such layers in petrology has been coined Backus upscaling , which is described below.
The material matrix K _ _ {\displaystyle {\underline {\underline {\boldsymbol {K}}}}} has a symmetry with respect to a given orthogonal transformation ( A {\displaystyle {\boldsymbol {A}}} ) if it does not change when subjected to that transformation.
For invariance of the material properties under such a transformation we require
Hence the condition for material symmetry is (using the definition of an orthogonal transformation)
Orthogonal transformations can be represented in Cartesian coordinates by a 3 × 3 {\displaystyle 3\times 3} matrix A _ _ {\displaystyle {\underline {\underline {\boldsymbol {A}}}}} given by
Therefore, the symmetry condition can be written in matrix form as
For a transversely isotropic material, the matrix A _ _ {\displaystyle {\underline {\underline {\boldsymbol {A}}}}} has the form
where the x 3 {\displaystyle x_{3}} -axis is the axis of symmetry . The material matrix remains invariant under rotation by any angle θ {\displaystyle \theta } about the x 3 {\displaystyle x_{3}} -axis.
Linear material constitutive relations in physics can be expressed in the form
where d , f {\displaystyle \mathbf {d} ,\mathbf {f} } are two vectors representing physical quantities and K {\displaystyle {\boldsymbol {K}}} is a second-order material tensor. In matrix form,
Examples of physical problems that fit the above template are listed in the table below. [ 1 ]
Using θ = π {\displaystyle \theta =\pi } in the A _ _ {\displaystyle {\underline {\underline {\boldsymbol {A}}}}} matrix implies that K 13 = K 31 = K 23 = K 32 = 0 {\displaystyle K_{13}=K_{31}=K_{23}=K_{32}=0} . Using θ = π 2 {\displaystyle \theta ={\tfrac {\pi }{2}}} leads to K 11 = K 22 {\displaystyle K_{11}=K_{22}} and K 12 = − K 21 {\displaystyle K_{12}=-K_{21}} . Energy restrictions usually require K 12 , K 21 ≥ 0 {\displaystyle K_{12},K_{21}\geq 0} and hence we must have K 12 = K 21 = 0 {\displaystyle K_{12}=K_{21}=0} . Therefore, the material properties of a transversely isotropic material are described by the matrix
In linear elasticity , the stress and strain are related by Hooke's law , i.e.,
or, using Voigt notation ,
The condition for material symmetry in linear elastic materials is. [ 2 ]
where
Using the specific values of θ {\displaystyle \theta } in matrix A _ _ {\displaystyle {\underline {\underline {\boldsymbol {A}}}}} , [ 3 ] it can be shown that the fourth-rank elasticity stiffness tensor may be written in 2-index Voigt notation as the matrix
The elasticity stiffness matrix C i j {\displaystyle C_{ij}} has 5 independent constants, which are related to well known engineering elastic moduli in the following way. These engineering moduli are experimentally determined.
The compliance matrix (inverse of the elastic stiffness matrix) is
where Δ := ( C 11 − C 12 ) [ ( C 11 + C 12 ) C 33 − 2 C 13 C 13 ] {\displaystyle \Delta :=(C_{11}-C_{12})[(C_{11}+C_{12})C_{33}-2C_{13}C_{13}]} . In engineering notation,
Comparing these two forms of the compliance matrix shows us that the longitudinal Young's modulus is given by
Similarly, the transverse Young's modulus is
The inplane shear modulus is
and the Poisson's ratio for loading along the polar axis is
Here, L represents the longitudinal (polar) direction and T represents the transverse direction.
In geophysics, a common assumption is that the rock formations of the crust are locally polar anisotropic (transversely isotropic); this is the simplest case of geophysical interest. Backus upscaling [ 4 ] is often used to determine the effective transversely isotropic elastic constants of layered media for long wavelength seismic waves.
Assumptions that are made in the Backus approximation are:
For shorter wavelengths, the behavior of seismic waves is described using the superposition of plane waves . Transversely isotropic media support three types of elastic plane waves:
Solutions to wave propagation problems in such media may be constructed from these plane waves, using Fourier synthesis .
A layered model of homogeneous and isotropic material, can be up-scaled to a transverse isotropic medium, proposed by Backus. [ 4 ]
Backus presented an equivalent medium theory, a heterogeneous medium can be replaced by a homogeneous one that predicts wave propagation in the actual medium. [ 5 ] Backus showed that layering on a scale much finer than the wavelength has an impact and that a number of isotropic layers can be replaced by a homogeneous transversely isotropic medium that behaves exactly in the same manner as the actual medium under static load in the infinite wavelength limit.
If each layer i {\displaystyle i} is described by 5 transversely isotropic parameters ( a i , b i , c i , d i , e i ) {\displaystyle (a_{i},b_{i},c_{i},d_{i},e_{i})} , specifying the matrix
The elastic moduli for the effective medium will be
where
⟨ ⋅ ⟩ {\displaystyle \langle \cdot \rangle } denotes the volume weighted average over all layers.
This includes isotropic layers, as the layer is isotropic if b i = a i − 2 e i {\displaystyle b_{i}=a_{i}-2e_{i}} , a i = c i {\displaystyle a_{i}=c_{i}} and d i = e i {\displaystyle d_{i}=e_{i}} .
Solutions to wave propagation problems in linear elastic transversely isotropic media can be constructed by superposing solutions for the quasi-P wave, the quasi S-wave, and a S-wave polarized orthogonal to the quasi S-wave.
However, the equations for the angular variation of velocity are algebraically complex and the plane-wave velocities are functions of the propagation angle θ {\displaystyle \theta } are. [ 6 ] The direction dependent wave speeds for elastic waves through the material can be found by using the Christoffel equation and are given by [ 7 ]
where θ {\displaystyle {\begin{aligned}\theta \end{aligned}}} is the angle between the axis of symmetry and the wave propagation direction, ρ {\displaystyle \rho } is mass density and the C i j {\displaystyle C_{ij}} are elements of the elastic stiffness matrix . The Thomsen parameters are used to simplify these expressions and make them easier to understand.
Thomsen parameters [ 8 ] are dimensionless combinations of elastic moduli that characterize transversely isotropic materials, which are encountered, for example, in geophysics . In terms of the components of the elastic stiffness matrix , these parameters are defined as:
where index 3 indicates the axis of symmetry ( e 3 {\displaystyle \mathbf {e} _{3}} ) . These parameters, in conjunction with the associated P wave and S wave velocities, can be used to characterize wave propagation through weakly anisotropic, layered media. Empirically, the Thomsen parameters for most layered rock formations are much lower than 1.
The name refers to Leon Thomsen, professor of geophysics at the University of Houston , who proposed these parameters in his 1986 paper "Weak Elastic Anisotropy".
In geophysics the anisotropy in elastic properties is usually weak, in which case δ , γ , ϵ ≪ 1 {\displaystyle \delta ,\gamma ,\epsilon \ll 1} . When the exact expressions for the wave velocities above are linearized in these small quantities, they simplify to
where
are the P and S wave velocities in the direction of the axis of symmetry ( e 3 {\displaystyle \mathbf {e} _{3}} ) (in geophysics, this is usually, but not always, the vertical direction). Note that δ {\displaystyle \delta } may be further linearized, but this does not lead to further simplification.
The approximate expressions for the wave velocities are simple enough to be physically interpreted, and sufficiently accurate for most geophysical applications. These expressions are also useful in some contexts where the anisotropy is not weak. | https://en.wikipedia.org/wiki/Transverse_isotropy |
The transverse mass is a useful quantity to define for use in particle physics as it is invariant under Lorentz boost along the z direction. In natural units , it is: m T 2 = m 2 + p x 2 + p y 2 = E 2 − p z 2 {\displaystyle m_{T}^{2}=m^{2}+p_{x}^{2}+p_{y}^{2}=E^{2}-p_{z}^{2}}
This definition of the transverse mass is used in conjunction with the definition of the (directed) transverse energy E → T = E p → T | p → | = E E 2 − m 2 p → T {\displaystyle {\vec {E}}_{T}=E{\frac {{\vec {p}}_{T}}{|{\vec {p}}|}}={\frac {E}{\sqrt {E^{2}-m^{2}}}}{\vec {p}}_{T}} with the transverse momentum vector p → T = ( p x , p y ) {\displaystyle {\vec {p}}_{T}=(p_{x},p_{y})} . It is easy to see that for vanishing mass ( m = 0 {\displaystyle m=0} ) the three quantities are the same: E T = p T = m T {\displaystyle E_{T}=p_{T}=m_{T}} .
The transverse mass is used together with the rapidity, transverse momentum and polar angle in the parameterization of the four-momentum of a single particle: ( E , p x , p y , p z ) = ( m T cosh y , p T cos ϕ , p T sin ϕ , m T sinh y ) {\displaystyle (E,p_{x},p_{y},p_{z})=(m_{T}\cosh y,\ p_{T}\cos \phi ,\ p_{T}\sin \phi ,\ m_{T}\sinh y)}
Using these definitions (in particular for E T {\displaystyle E_{T}} ) gives for the mass of a two particle system:
Looking at the transverse projection of this system (by setting p a , z = p b , z = 0 {\displaystyle p_{a,z}=p_{b,z}=0} ) gives:
These are also the definitions that are used by the software package ROOT, which is commonly used in high energy physics.
Hadron collider physicists use another definition of transverse mass (and transverse energy), in the case of a decay into two particles. This is often used when one particle cannot be detected directly but is only indicated by missing transverse energy. In that case, the total energy is unknown and the above definition cannot be used.
where E T {\displaystyle E_{T}} is the transverse energy of each daughter, a positive quantity defined using its true invariant mass m {\displaystyle m} as:
which is coincidentally the definition of the transverse mass for a single particle given above.
Using these two definitions, one also gets the form:
(but with slightly different definitions for E T {\displaystyle E_{T}} !)
For massless daughters, where m 1 = m 2 = 0 {\displaystyle m_{1}=m_{2}=0} , we again have E T = p T {\displaystyle E_{T}=p_{T}} , and the transverse mass of the two particle system becomes:
where ϕ {\displaystyle \phi } is the angle between the daughters in the transverse plane.
The distribution of M T {\displaystyle M_{T}} has an end-point at the invariant mass M {\displaystyle M} of the system with M T ≤ M {\displaystyle M_{T}\leq M} . This has been used to determine the W {\displaystyle W} mass at the Tevatron.
This particle physics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transverse_mass |
In high energy particle physics , specifically in hadron -beam scattering experiments, transverse momentum distributions ( TMDs ) are the distributions of the hadron's quark or gluon momenta that are perpendicular to the momentum transfer between the beam and the hadron. Specifically, they are probability distributions to find inside the hadron a parton with a transverse momentum k T {\displaystyle k_{T}} and longitudinal momentum fraction x {\displaystyle x} . TMDs provide information on the confined motion of quarks and gluons inside the hadron and complement the information on the hadron structure provided by parton distribution functions (PDFs) and generalized parton distributions (GPDs). [ 1 ] In all, TMDs and PDFs provide the information of the momentum distribution (transverse and longitudinal, respectively) of the quarks (or gluons), and the GPDs, the information on their spatial distribution.
TMDs are an extension of the concept of parton distribution functions (PDFs) and structure functions that are measured in deep inelastic scattering (DIS). Some TMDs provide the k T {\displaystyle k_{T}} dependence of the probabilities that the PDFs represent and that give rise to the DIS structure functions, namely the quark momentum probability distribution f 1 q ( x ) {\displaystyle f_{1}^{q}(x)} for the unpolarized structure function F 1 ( x ) {\displaystyle F_{1}(x)} and the quark spin probability distribution g 1 q ( x ) {\displaystyle g_{1}^{q}(x)} for the polarized structure functions g 1 ( x ) {\displaystyle g_{1}(x)} . Here, x {\displaystyle x} denotes the fraction of hadron longitudinal momentum carried by the parton, and identifies with the Bjorken scaling variable in the infinite energy-momentum limit. The f 1 q ( x ) {\displaystyle f_{1}^{q}(x)} and g 1 q ( x ) {\displaystyle g_{1}^{q}(x)} PDFs are summed over all the k T {\displaystyle k_{T}} values, and therefore, the k T {\displaystyle k_{T}} -dependence of the probabilities is integrated out. TMDs provides the unintegrated probabilities, with their k T {\displaystyle k_{T}} -dependence. Other TMDs exist that are not directly connected to f 1 q ( x ) {\displaystyle f_{1}^{q}(x)} and g 1 q ( x ) {\displaystyle g_{1}^{q}(x)} . In all, there are 16 dominant ( viz leading-twist) independent TMDs, 8 for the quarks and 8 for the gluons.
TMDs are, in particular, sensitive to correlations between the transverse momentum of partons in the parent hadron and their spin or the hadron spin. In turn, the correlations provide access the dynamics of partons in the transverse plane in momentum space . Thus, TMDs are comparable and directly complementary to the generalized parton distributions (GPDs) which describe the parton dynamics in the transverse plane in position space . Formally, TMDs access the correlations between a parton orbital angular momentum (OAM) and the hadron/parton spin because they require wave function components with nonzero OAM. Therefore, TMDs allow us to study the full three-dimensional dynamics of hadrons, providing more detailed information than that contained in conventional PDF.
One example of the importance of TMDs is that they provide information about the quark and gluon OAM. Those are not directly accessible in regular DIS, but are crucial to understand the spin content of the nucleon and resolve the nucleon spin crisis . In fact, lattice QCD calculations indicate that quark OAM is the dominant contribution to the nucleon spin. [ 2 ]
Similarly to quark TMDs, gluon TMDs allow access to the gluonic orbital angular momentum, another possibly important contribution to the nucleon spin . Just as there are eight TMDs for quarks, there are eight gluon TMDs. [ 3 ] Gluon TMDs were first proposed in 2001. [ 4 ]
In addition to the three above TMDs which are direct extension of the DIS PDFs, there are five other quark TMDs which depend not only on the magnitude of k T {\displaystyle k_{T}} , but also on its direction. Therefore these TMDs vanish if simply integrated over k T {\displaystyle k_{T}} , and do not directly connect to DIS PDFs. They are:
Our initial understanding of the short-distance nucleon structure has come from deep inelastic scattering (DIS) experiments. This description is essentially one-dimensional: DIS provides us with the parton momentum distributions in term of the single variable x, which is interpreted in the infinite momentum limit (the Bjorken limit ) as the fraction of the nucleon momentum carried by the struck partons. Therefore, from DIS we only learn about the relative longitudinal momentum distribution of the partons, i.e. their longitudinal motions inside the nucleon.
The measurement of TMDs allows to go beyond this one-dimensional picture. This entails that to measure TMDs, we need to gather more information from the scattering process. In DIS, only the scattered lepton is detected while the remnants of the shattered nucleon are ignored (inclusive experiment). Semi-inclusive DIS (SIDIS) , where a high momentum (i.e. leading) hadron is detected in addition of the scattered lepton, allows us to obtain the needed additional details about the scattering process kinematics. The detected hadron results from the hadronization of the struck quark. This latter retains the information on its motion inside the nucleon, including its transverse momentum k T {\displaystyle k_{T}} which allows to access the TMDs. In addition of its initial
intrinsic transverse momentum k T {\displaystyle k_{T}} the struck quark also acquires a transverse momentum p T {\displaystyle p_{T}} during the hadronization process. Consequently, the structure functions entering
the SIDIS cross-section or asymmetries are convolutions of a k T {\displaystyle k_{T}} -dependent quark density, the TMD itself, and of a p T {\displaystyle p_{T}} -dependent fragmentation function .
Therefore, precise knowledge of fragmentation functions is important to extract TMDs from experimental results.
Other reactions than SIDIS can be used to access TMDs, such as the Drell–Yan process .
Quark TMDs measurements were pioneered at DESY by the HERMES experiment. They are currently (2021) being measured at CERN by the COMPASS experiment and several experiments at Jefferson Lab . Quark and gluon TDM measurements are an important part of the future electron–ion collider scientific program. [ 9 ] | https://en.wikipedia.org/wiki/Transverse_momentum_distributions |
In telecommunications , a transverse redundancy check (TRC) or vertical redundancy check is a redundancy check for synchronized parallel bits applied once per bit time, across the bit streams. This requires additional parallel channels for the check bit or bits.
The term usually applies to a single parity bit , although it could also be used to refer to a larger Hamming code .
The adjective "transverse" is most often used when it is used in combination with additional error control coding, such as a longitudinal redundancy check . Although parity alone can only detect and not correct errors, it can be part of a system for correcting errors.
An example of a TRC is the parity written to the 9th track of a 9-track tape . | https://en.wikipedia.org/wiki/Transverse_redundancy_check |
In mathematical combinatorics, the Transylvania lottery is a lottery where players selected three numbers from 1 to 14 for each ticket, and then three numbers are chosen randomly. A ticket wins if two of the numbers match the random ones. The problem asks how many tickets the player must buy in order to be certain of winning.
(Javier Martínez, Gloria Gutiérrez & Pablo Cordero et al. 2008 , p.85)( Mazur 2010 , p.280 problem 15)
An upper bound can be given using the Fano plane with a collection of 14 tickets in two sets of seven. Each set of seven uses every line of a Fano plane, labelled with the numbers 1 to 7, and 8 to 14.
At least two of the three randomly chosen numbers must be in one Fano plane set, and any two points on a Fano plane are on a line, so there will be a ticket in the collection containing those two numbers. There is a 6 / 13 × 5 / 12 = 5 / 26 chance that all three randomly chosen numbers are in the same Fano plane set. In this case, there is a 1 / 5 chance that they are on a line, and hence all three numbers are on one ticket, otherwise each of the three pairs are on three different tickets.
This combinatorics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Transylvania_lottery |
In ethology and behavioral ecology , trap-lining or traplining is a feeding strategy in which an individual visits food sources on a regular, repeatable sequence, much as trappers check their lines of traps. [ 1 ] Traplining is usually seen in species foraging for floral resources. [ 2 ] This involves a specified route in which the individual traverses in the same order repeatedly to check specific plants for flowers that hold nectar, even over long distances. Trap-lining has been described in several taxa , including bees , butterflies , tamarins , bats , rats , and hummingbirds and tropical fruit-eating mammals such as opossums , capuchins and kinkajous . [ 1 ] [ 3 ] Traplining is used to term the method in which bumblebees and hummingbirds go about collecting nectar, and consequently, pollinating each plant they visit. The term "traplining" was originally coined by Daniel Janzen , [ 4 ] although the concept was discussed by Charles Darwin and Nikolaas Tinbergen . [ 4 ]
In the instance of hummingbirds and bumblebees, traplining is an evolutionary response to the allocation of resources between species. [ 5 ] Specifically, individual hummingbirds form their own specific routes in order to minimize competition and maximize nutrient availability. Some hummingbird species are territorial (e.g. rufous hummingbird , Selasphorus rufus ,) and defend a specific territory, while others are trapliners (i.e. Long-billed hermit , Phaethornis longirostris ) and constantly check different locations for food. Because of this, territorial hummingbirds will be more robust, while traplining hummingbirds have adaptations such as longer wings for more efficient flying. [ 6 ] Traplining hummingbirds will move from source to source, obtaining nectar from each. Over time, one hummingbird will be the primary visitor to a particular source. [ 7 ] In the case of bumblebees, when competitors are removed, there is an influx to the removal area and less time is spent traplining over long distances. This demonstrates the ability to behaviorally adapt based on surrounding competition. [ 8 ] In addition, bumblebees use traplining to distinguish between high nectar-producing flowers and low-nectar producing flowers by consistently recognizing and visiting those that produce higher levels. [ 9 ] Other types of bees, such as with euglossine bees (i.e. Euglossa imperialis ) use traplining to forage efficiently by flying rapidly from one precise flowering plant to the next in a set circuit, even ignoring newly blooming plants which are adjacent, but outside, of its daily route. By doing so, these euglossine bees significantly reduce the amount of time and energy spent searching for nectar each day. [ 10 ] In general, it is seen that traplining species have higher nutritional rewards than non-traplining species. [ 11 ]
Traplining hummingbirds are known to be active proportionally to nectar production in flowers, decreasing throughout the day. Therefore, traplining hummingbirds can spend less time foraging, and obtain their energy intake from a few number of flowers. [ 12 ] Spending less time searching for food means less energy spent flying and searching. Traplining bumblebees prioritize their routes based on travel distance and reward quantity. [ 13 ] It is seen that the total distance of the trapline is related to the abundance of the reward (nectar) in the environment. [ 14 ]
Traplining can also be an indication of the levels of spatial cognition of species that use the technique. For example, traplining in bumblebees is an indication that bumblebees have spatial reference memory, or spatial memory , that is used to create specific routes in short term foraging. [ 9 ] The ability to remember specific routes long-term cuts down foraging and flying time, consequently conserving energy. This theory has been tested, showing that bumblebees can remember the shortest route to the reward, even when the original path has been changed or obstructed. [ 15 ] Additionally, bees cut down the amount of time spent revisiting sites with little or no nutritive reward. [ 9 ] Bees with access to only short-term memory forage inefficiently. [ 9 ]
One of the main advantages of traplining is that the route can be taught to other members of the population quickly or over a period of hours, leading all members to a reliable food source. When the group works together on finding a particular source of food they can quickly establish where it is and get the route information transferred to all the individuals in the population. This ensures that the entire community is able to quickly find and consume the nutrients that are needed.
Traplining helps foragers that are competing for resources that replenish in a decelerating way. For example, nectar in a plant is slowly replaced over time, while acorns only occur once a year. [ 16 ] Traplining can help plant diversity and evolution by keeping pollen with different genetics flowing from plant to plant. It is mostly pollinators that use traplining as a way to ensure they always know where the food sources they are looking for are. This means that organisms like bumblebees and hummingbirds can transfer pollen anywhere from the starting point of the route to the final food source along the path. Since the path is always the same, it greatly reduces the risk of self-pollination (iterogamy) because the pollinator won't return to the same flower on that particular foraging session. [ 16 ] [ 17 ]
Overall, plant species that are visited by trapliners have increased fitness and evolutionary advantages. [ 18 ] Because of this mutualistic relationship between traplining hummingbirds and plants, traplining hummingbirds have been referred to as "legitimate pollinators", while territorial hummingbirds have been referred to as "nectar thieves". [ 19 ] If an organism that traplines learns where a food source is once, they can always return to that food source because they can remember minute details about the location of the source. This allows them to adapt quickly if one of the major sources suddenly becomes scarce or destroyed. [ 20 ]
Serious obstacles, such as the arrangement of plant life, can hamper traplining. If the route zig zags through the understory of the tropical rainforest, some of the organisms using the route can get lost because of very subtle changes, [ 16 ] such as a treefall gap or heavy rainfall. This could cause an individual to be separated from the entire group if it isn't able to find the path back to the original route. Some food sources can be overlooked because the traplining route in use does not lead the organisms to the area that these resources are in.
Since the route is very specific, the organisms following it may also miss out on opportunities to come in contact with potential mates. Male bumblebees going directly to the source of food have been observed to pass up on female bumblebees as potential mates that are along the same path, preferring to continue foraging and bring food back to the hive. [ 20 ] This can take away from species diversification and could possibly delete some traits in the gene pool that are useful.
Observing traplining in the natural world has proven to be very difficult [ according to whom? ] and little is known about how and why species trapline, but the study of traplining in the natural environment does take place. In one particular study, individual bees trained on five artificial flowers of equal reward were observed traplining between those five flowers. When a new flower of higher reward gets included in the group, the bees subsequently adjust their trapline to include the higher reward flower. Under natural conditions they hypothesized that it would likely be beneficial for bees to prioritize higher reward flowers to either beat out competition or conserve energy.
In other field experiments, ecologists created a "competition vacuum" to observe whether or not bumblebees adjusted their feeding routes based on intense direct competition between other bumblebees. This study showed that bees in areas of higher competition are more productive than the control bees. Bumblebees opportunistically adjust their use of traplining routes in response to activity of other competing bees. [ 8 ] Another effective way to study the behavior of traplining species is via computer simulation and indoor flight cage experiments. Simulation models can be made to show the linkage between pollinator movement and pollen flow. This model considers how service by the pollinators with different foraging patterns would affect the flow of pollen.
Indoor flight cage experiments allow for easier determination between test subjects and easier observation of behavior and patterns. Bees in small study environments seem to demonstrate less traplining tendencies than bees that were studied in environments that stretched over several hectares. A larger working area increases the need for traplining techniques to further conserve energy and maximize nutrient intake and that bees most often trapline due strictly to travel distance. The bees remember these complex flight paths by breaking them into small segments using vectors, landmarks and other environmental factors, each one pointing to the next destination. [ 21 ]
Despite a long history of research on bee learning and navigation, most knowledge has been deduced from the behavior of foragers traveling between their nest and a single feeding location. [ 6 ] Only recently, studies of bumblebees foraging in arrays of artificial flowers fitted with automated tracking systems have started to describe the learning mechanisms behind complex route formation between multiple locations. The demonstration that all these observations can be accurately replicated by a single learning heuristic model holds considerable promises to further investigate these questions and fill a major gap in cognitive ecology. [ 21 ] | https://en.wikipedia.org/wiki/Trap-lining |
In plumbing , a trap is a U-shaped portion of pipe designed to trap liquid or gas to prevent unwanted flow; most notably sewer gases from entering buildings while allowing waste materials to pass through. In oil refineries, traps are used to prevent hydrocarbons and other dangerous gases and chemical fumes from escaping through drains. In heating systems, the same feature is used to prevent thermo-siphoning which would allow heat to escape to locations where it is not wanted. Similarly, some pressure gauges are connected to systems using U bends to maintain a local gas while the system uses liquid. For decorative effect, they can be disguised as complete loops of pipe, creating more than one U for added efficacy.
In domestic applications, traps are typically U, S, Q, or J-shaped pipe located below or within a plumbing fixture . An S-shaped trap is also known as an S-bend . It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The U-bend could not jam, so, unlike the S-bend, it did not need an overflow. In the United States, traps are commonly referred to as P-traps. It is the addition of a 90 degree fitting on the outlet side of a U-bend, thereby creating a P-like shape (oriented horizontally). It is also referred to as a sink trap because it is installed under most sinks.
Because of its shape, the trap retains some water after the fixture's use. This water creates an air seal that prevents sewer gas from passing from the drain pipes back into the building. Essentially all plumbing fixtures including sinks , bathtubs , and showers must be equipped with either an internal or external trap. Toilets almost always have an internal trap.
Because it is a localized low-point in the plumbing, sink traps also tend to capture small and heavy objects (such as jewellery or coins) accidentally dropped down the sink. Traps also tend to collect hair, sand, food waste and other debris and limit the size of objects that enter the plumbing system, thereby catching oversized objects. For all of these reasons, most traps may be disassembled for cleaning or provide a cleanout feature.
Where a volume of water may be rapidly discharged through the trap, a vertical vented pipe called a standpipe may be attached to the trap to prevent the disruption of the seal in other nearby traps. [ 1 ] The most common use of standpipes in houses is for clothes washing machines , which rapidly dispense a large volume of wastewater while draining the wash and rinse cycles. [ 2 ]
In chemical engineering applications, a trap may be known as a lute. [ 3 ]
An S-shaped trap is also known as an S-bend . It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The new U-bend could not jam, so, unlike the S-bend, it did not need an overflow.
Once invented, despite being simple and reasonably reliable, widespread use was slow coming. In Britain, the requirement to use traps was introduced only after the Great Stink in London, in the summer of 1858, when the objectionable smell of the River Thames , which was effectively an open sewer, affected the nearby Houses of Parliament . That motivated the legislators to authorise the construction of a modern sewerage system in the city, of which the S-bend was an essential component. As of 2017 [update] , only about two-thirds of the world population have access to traps, [ citation needed ] in spite of the evidence that good sewage systems significantly improve economic productivity in places that employ them. [ 4 ]
Maintaining the water seal is critical to trap operation; traps might dry out, and poor venting can suction or blow water out of the traps. This is usually avoided by venting the drain pipes downstream of the trap; by being vented to the atmosphere outside the building, the drain lines never operate at a pressure much higher or lower than atmospheric pressure. In the United States, plumbing codes usually provide strict limitations on how far a trap may be located from the nearest vent stack .
When a vent cannot be provided, an air admittance valve may be used instead. These devices avoid negative pressure in the drain pipe by venting room air into the drain pipe (behind the trap). A " Chicago Loop " is another alternative.
When a trap is installed on a fixture that is not routinely used—such as a floor drain—the eventual evaporation of the water in the trap must be considered. In these cases, a trap primer may be installed; these are devices that automatically recharge traps with water to maintain their water seals.
In some regions of the US, "S" traps are no longer accepted by the building codes as unvented S-traps tend to siphon dry. It may be possible to determine whether a household uses an S- or U-bend by the presence of an overflow pipe outlet. [ clarification needed ] What is required instead is a P-trap with proper venting. Certain drum-styled traps are also discouraged or banned. [ 5 ] | https://en.wikipedia.org/wiki/Trap_(plumbing) |
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby target crops. This form of companion planting can save a target crop from decimation by pests without the use of artificial pesticides. A trap crop is used for attracting the insect and pests away from a target crop field. Many trap crops have successfully diverted pests from focal crops in small scale greenhouse, garden and field experiments; [ 1 ] a small portion of these plants have been shown to reduce pest damage at larger commercial scales. [ 1 ] [ 2 ] A common explanation for reported trap cropping failures, is that attractive trap plants only protect nearby plants if the insects do not move back into the target crop. In a review of 100 trap cropping examples in 2006, only 10 trap crops were classified as successful at a commercial scale, [ 2 ] and in all successful cases, trap cropping was supplemented with management practices that specifically limited insect dispersal from the trap crop back into the target crop. [ 2 ]
Examples of trap crops include:
Trap crops can be planted around the circumference of the field to be protected, which is assumed to act as a barrier for entry by pests, or they can be interspersed among the main crop, for example being planted every ninth row. Planting crops in rows helps facilitate supplemental management practices that prevent insect pest dispersal back into the main field, [ 2 ] such as driving a vehicle above the trap crop which then removes insect pests by vacuuming them off of the trap crop row [ 7 ] or targeted insecticides, which are only deployed on the trap crop. [ 8 ] Even if pesticides are used to control insects on the trap crop, total pesticides are greatly reduced in this scenario over conventional agricultural pesticide applications because they are only deployed on a small portion of the farm (the trap crop). [ 2 ] Other strategies that prevent dispersal of insect pests back into the main crop include cutting the trap plants, [ 9 ] applying predators or parasitoids to the trap plant that eat the pest, [ 10 ] and planting a high ratio of trap plants to other plants. [ 2 ]
Trap crops, when used on an industrial scale, are generally planted at a key time in the pest's life-cycle, and then destroyed before that life-cycle finishes and the pest might have transferred from the trap plants to the main crop. [ 11 ]
Recent studies on host-plant finding have shown that flying pests are far less successful if their host-plants are surrounded by any other plant, or even "decoy-plants" made of green plastic, cardboard or any other green material. [ 12 ] The host-plant finding process occurs in three phases.
The first phase is stimulation by odours characteristic to the host-plant. This induces the insect to try to land on the plant it seeks. But insects avoid landing on brown (bare) soil. So if only the host-plant is present, the insects will quasi-systematically find it by landing on the only green thing around. This is called an "appropriate landing". When it does an "inappropriate landing", it flies off to any other nearby patch of green. It eventually leaves the area if there are too many "inappropriate" landings.
The second phase of host-plant finding is for the insect to make short flights from leaf to leaf to assess the plant's overall suitability. The number of leaf-to-leaf flights varies according to the insect species and to the host-plant stimulus received from each leaf. But the insect must accumulate sufficient stimuli from the host-plant to lay eggs; so it must make a certain number of consecutive "appropriate" landings. Hence if it makes an "inappropriate landing", the assessment of that plant is negative and the insect must start the process anew. [ 12 ]
Thus, a clover ground cover was shown to have the same disruptive effect on eight pest species from four insect orders. An experiment showed that 36% of cabbage root flies laid eggs beside cabbages growing in bare soil (which resulted in no crop), compared with only 7% beside cabbages growing in clover (which allowed a good crop). Moreover, simple decoys made of green cardboard disrupted appropriate landings just as well as the clover. [ 12 ] | https://en.wikipedia.org/wiki/Trap_crop |
Trapped-key interlocking utilizes locks and keys for sequential control of equipment and machinery to ensure safe operation. Trapped-key interlocks are widely used to ensure safe access to potentially live or dangerous plant or equipment in an industrial setting.
A safe sequence of operations is enabled through transfer of keys that are either trapped or released in a predetermined order. For example, a key is used to isolate a power source (circuit breaker or supply valve), this key is then released and can then be used to gain access through a gate or door to a high risk area by inserting it into an access lock. The key will then remain trapped until the gate or door is closed. A personnel or safety key can be released from the access lock, this ensures that the gate or door can not be closed and the initial key released until this personnel or safety key is returned (assuming that no duplicate keys are available). This provides increased operator safety.
In 1893, French inventor Paul Bouré created engagement lock devices to ensures train traffic safety. They were used in the French railway system in the 1890s to control track switching operations and were manufactured by Trayvou, now known by the name "Serv Trayvou Interverrouillage" (STI) and owned by Halma . [ 1 ] Later, the Englishman James Harry Castell [ 2 ] (1880–1953), Frenchman B. Trayvou and the American R. L. Kirk [ 3 ] also developed trapped-key interlocking systems. Therefore, such systems are commonly referred to as Castell , Bourré , Trayvou , or Kirk keys . Both worked in the power generation and distribution industries in the early part of the 20th century, and both pioneered the use of trapped-key interlock for switchgear control. Trapped-key interlocks can be found in many industrial settings including electrical utilities, railway, petroleum, and chemical plants as a response to occupational safety and health legislation.
A typical trapped-key interlock device consists of a lock cylinder which operates a sliding bolt through a cam. The assembly is contained in a housing, which is made in different styles to accommodate different applications. The sliding bolt, when extended, mechanically prevents operation of a switch, valve, gate, or other device. Many variations exist, with different shapes of interlock bolt and multiple lock cylinders on an interlock. A significant feature of the interlock is that the key is held or trapped in one position of the lock. Releasing the key indicates that the interlocked device has been made safe; the interlocked device cannot be re-energized until the key has been returned and operated to retract the bolt.
Some complex sequences use key exchange blocks or boxes, that allow alternative sequences of operation.
Interlock devices may have an electrical solenoid which holds the key until an electrical circuit is interrupted; for example, the power supply for a high-voltage cabinet has been de-energized, releasing a key to allow access to the interior of the cabinet. Some interlocks include a time delay function or a rotation detector to ensure a machine has had time to come to a stop before allowing the next step of an interlock sequence to proceed. [ 4 ] A key exchange block may only hold and release keys and may not have a bolt to interlock process equipment, or may be part of the interlock of a particular machine or device.
Manufacturers of trapped-key interlock devices provide application guides showing typical interlock problems and recommended arrangements. Since the reliability and safety of the scheme critically depends on the possession of keys, duplicate keys must be carefully controlled to prevent any possibility of an unsafe operating sequence. For example, a lost key might be replaced only by a duplicate held off-site, or might require ordering a replacement from the original manufacturer.
For example, to prevent access to the inside of an electric kiln while it is operating, a trapped-key system may be used to interlock a disconnecting switch and the kiln door. Whenever the kiln power switch is turned on, the key is automatically held by the interlock, and cannot be manually removed. In order to open the kiln door, the power switch must first be turned off, which releases the key and allows it to be removed from the interlock. The key can then be used to unlock the kiln door. While the key is removed from the switch interlock, a plunger from the interlock mechanically prevents the power switch from being turned on. Power cannot be re-applied to the kiln until the kiln door is locked, releasing the key, and the key is then returned to the power switch interlock. [ 5 ] A similar two-part interlock system can be used anywhere it is necessary to ensure the energy supply to a machine is interrupted before the machine is entered for adjustment or maintenance. | https://en.wikipedia.org/wiki/Trapped-key_interlocking |
In applied mathematics , a trapping region of a dynamical system is a region such that every trajectory that starts within the trapping region will move to the region's interior and remain there as the system evolves.
More precisely, given a dynamical system with flow ϕ t {\displaystyle \phi _{t}} defined on the phase space D {\displaystyle D} , a subset of the phase space N {\displaystyle N} is a trapping region if it is compact and ϕ t ( N ) ⊂ i n t ( N ) {\displaystyle \phi _{t}(N)\subset \mathrm {int} (N)} for all t > 0 {\displaystyle t>0} . [ 1 ]
This mathematics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Trapping_region |
Trastuzumab , sold under the brand name Herceptin among others, is a monoclonal antibody used to treat breast cancer and stomach cancer . [ 29 ] [ 26 ] [ 30 ] [ 31 ] It is specifically used for cancer that is HER2 receptor positive . [ 29 ] It may be used by itself or together with other chemotherapy medication . [ 29 ] Trastuzumab is given by slow injection into a vein and injection just under the skin . [ 29 ] [ 32 ]
Common side effects include fever, infection, cough, headache, trouble sleeping, and rash. [ 29 ] Other severe side effects include heart failure , allergic reactions , and lung disease . [ 29 ] Use during pregnancy may harm the baby. [ 22 ] Trastuzumab works by binding to the HER2 receptor and slowing down cell replication. [ 29 ]
Trastuzumab was approved for medical use in the United States in September 1998, and in the European Union in August 2000. [ 33 ] [ 31 ] It is on the World Health Organization's List of Essential Medicines . [ 34 ]
The safety and efficacy of trastuzumab-containing combination therapies (with chemotherapy, hormone blockers, or lapatinib ) for the treatment of metastatic breast cancer. [ clarification needed ] The overall hazard ratios (HR) for overall survival and progression free survival were 0.82 and 0.61, respectively. [ clarification needed ] It was difficult to accurately ascertain the true impact of trastuzumab on survival, as in three of the seven trials, over half of the patients in the control arm were allowed to cross-over and receive trastuzumab after their cancer began to progress. [ 35 ] Thus, this analysis likely underestimates the true survival benefit associated with trastuzumab treatment in this population. [ 36 ]
In early-stage HER2-positive breast cancer, trastuzumab-containing regimens improved overall survival ( Hazard ratio (HR) = 0.66) and disease-free survival (HR = 0.60). [ 37 ] Increased risk of heart failure (RR = 5.11) and decline in left ventricular ejection fraction ( relative risk RR = 1.83) were seen in these trials as well. [ 37 ] Two trials involving shorter term treatment with trastuzumab did not differ in efficacy from longer trials, but produced less cardiac toxicity. [ 37 ]
The original studies of trastuzumab showed that it improved overall survival in late-stage (metastatic) HER2-positive breast cancer from 20.3 to 25.1 months. [ 38 ] In early-stage HER2-positive breast cancer, it reduces the risk of cancer returning after surgery. The absolute reduction in the risk of cancer returning within three years was 9.5%, and the absolute reduction in the risk of death within 3 years was reduced by 3%. However, it increases serious heart problems by an absolute risk of 2.1%, though the problems may resolve if treatment is stopped. [ 37 ]
Trastuzumab has had a "major impact in the treatment of HER2-positive metastatic breast cancer." [ 39 ] The combination of trastuzumab with chemotherapy has been shown to increase both survival and response rate, in comparison to trastuzumab alone. [ 40 ]
It is possible to determine the "erbB2 status" of a tumor, which can be used to predict efficacy of treatment with trastuzumab. If it is determined that a tumor is overexpressing the erbB2 oncogene and the patient has no significant pre-existing heart disease, then a patient is eligible for treatment with trastuzumab. [ 41 ] It is surprising that although trastuzumab has great affinity for HER2 and high doses can be administered (because of its low toxicity), 70% of HER2+ patients do not respond to treatment. In fact resistance to the treatment develops rapidly, in virtually all patients. A mechanism of resistance involves failure to downregulate p27 Kip1 [ 42 ] as well as suppressing p27 translocation to the nucleus in breast cancer, enabling cdk2 to induce cell proliferation. [ 43 ]
In May 2021, the FDA approved pembrolizumab in combination with trastuzumab, fluoropyrimidine - and platinum-containing chemotherapy for the first-line treatment of people with locally advanced unresectable or metastatic HER2 positive gastric or gastroesophageal junction (GEJ) adenocarcinoma. [ 44 ]
The optimal duration of add-on trastuzumab treatment after surgery for early breast cancer is unknown. One year of treatment is generally accepted based on clinical trial evidence that demonstrated the superiority of one-year treatment over none. [ 45 ] [ 46 ] However, a small Finnish trial also showed similar improvement with nine weeks of treatment over no therapy. [ 47 ] Because of the lack of direct head-to-head comparison in clinical trials, it is unknown whether a shorter duration of treatment may be just as effective (with fewer side effects) than the accepted practice of treatment for one year. Debate about treatment duration has become a relevant issue for many public health policy makers because administering trastuzumab for a year is very expensive. Consequently, some countries with a taxpayer-funded public health system, such as New Zealand, chose to fund limited adjuvant therapy. [ 48 ] However, subsequently New Zealand has revised its policy and now funds trastuzumab treatment for up to 12 months. [ 49 ]
Some of the common side effects of trastuzumab are flu-like symptoms (such as fever, chills and mild pain), nausea and diarrhea . [ 50 ]
One of the more serious complications of trastuzumab is its effect on the heart, although this is rare. [ 50 ] In 2–7% of cases, [ 51 ] trastuzumab is associated with cardiac dysfunction, which includes congestive heart failure . As a result, regular cardiac screening with either a MUGA scan or echocardiography is commonly undertaken during the trastuzumab treatment period. The decline in ejection fraction appears to be reversible. [ 52 ]
Trastuzumab downregulates neuregulin-1 (NRG-1), which is essential for the activation of cell survival pathways in cardiomyocytes and the maintenance of cardiac function. NRG-1 activates the MAPK pathway and the PI3K/AKT pathway as well as focal adhesion kinases (FAK). These are all significant for the function and structure of cardiomyocytes. Trastuzumab can therefore lead to cardiac dysfunction. [ 53 ]
Trastuzumab may harm a developing fetus. [ 54 ] [ 55 ]
The HER2 gene (also known as HER2/neu and ErbB2 gene) is amplified in 20–30% of early-stage breast cancers . [ 42 ] Trastuzumab is a monoclonal antibody targeting HER2, inducing an immune-mediated response that causes internalization and recycling of HER2. It may also upregulate cell cycle inhibitors such as p21 Waf1 and p27 Kip1 . [ 56 ]
The HER2 pathway promotes cell growth and division when it is functioning normally; however, when it is overexpressed, cell growth accelerates beyond its normal limits. In some types of cancer, the pathway is exploited to promote rapid cell growth and proliferation and hence tumor formation. [ 57 ] The EGF pathway includes the receptors HER1 (EGFR), HER2, HER3 , and HER4 ; the binding of ligands (e.g. EGF etc.) to HER receptors is required to activate the pathway. [ 57 ] The pathway initiates the MAP kinase pathway as well as the PI3 kinase/AKT pathway, which in turn activates the NF-κB pathway. [ 58 ] In cancer cells the HER2 protein can be expressed up to 100 times more than in normal cells (2 million versus 20,000 per cell). [ 59 ]
The HER receptors are proteins that are embedded in the cell membrane and communicate molecular signals from outside the cell (molecules called EGFs ) to inside the cell, and turn genes on and off. The HER (human epidermal growth factor receptor) protein, binds to human epidermal growth factor, and stimulates cell proliferation. In some cancers, notably certain types of breast cancer, HER2 is over-expressed and causes cancer cells to reproduce uncontrollably. [ 38 ]
HER2 is localized at the cell surface, and carries signals from outside the cell to the inside. Signaling compounds called mitogens (specifically EGF in this case) arrive at the cell membrane, and bind to the extracellular domain of the HER family of receptors. Those bound proteins then link ( dimerize ), activating the receptor. HER2 sends a signal from its intracellular domain, activating several different biochemical pathways. These include the PI3K / Akt pathway and the MAPK pathway. Signals on these pathways promote cell proliferation and the growth of blood vessels to nourish the tumor ( angiogenesis ). [ 60 ] ERBB2 is the preferred dimerization partner for the other family members and ERBB2 heterodimers signaling is stronger and longer acting compared to heterodimers between other ERBB members. It has been reported that Trastuzumab induces the formation of complementarity-determining regions (CDRs) leading to surface redistribution of ERBB2 and EGFR in CDRs and that the ERBB2-dependent MAPK phosphorylation and EGFR/ERBB1 expression are both required for CDR formation. CDR formation requires activation of both the protein regulator of actin polymerization N-WASP , mediated by ERK1/2, and of the actin-depolymerizing protein cofilin , mediated by EGFR/ERBB1. Furthermore, this latter event may be inhibited by the negative cell motility regulator p140Cap, as we found that p140Cap overexpression led to cofilin deactivation and inhibition of CDR formation.
Normal cell division— mitosis —has checkpoints that keep cell division under control. Some of the proteins that control this cycle are called cdk2 (CDKs). Overexpression of HER2 sidesteps these checkpoints, causing cells to proliferate in an uncontrolled fashion. [ 43 ]
Trastuzumab binds to domain IV of the [ 61 ] extracellular segment of the HER2/neu receptor. Monoclonal antibodies that bind to this region have been shown to reverse the phenotype of HER2/neu expressing tumor cells. [ 62 ] Cells treated with trastuzumab undergo arrest during the G1 phase of the cell cycle so there is reduced proliferation. It has been suggested that trastuzumab does not alter HER-2 expression, but downregulates activation of AKT. [ 43 ] In addition, trastuzumab suppresses angiogenesis both by induction of antiangiogenic factors and repression of proangiogenic factors. It is thought that a contribution to the unregulated growth observed in cancer could be due to proteolytic cleavage of HER2/neu that results in the release of the extracellular domain. One of the most relevant proteins that trastuzumab activates is the tumor suppressor p27 Kip1 , also known as CDKN1B . [ 42 ] Trastuzumab has been shown to inhibit HER2/neu ectodomain cleavage in breast cancer cells. [ 63 ]
Experiments in laboratory animals indicate that antibodies, including trastuzumab, when bound to a cell, induce immune cells to kill that cell, and that such antibody-dependent cell-mediated cytotoxicity is another important mechanism of action. [ 64 ]
Trastuzumab inhibits the effects of overexpression of HER2. If the breast cancer does not overexpress HER2, trastuzumab will have no beneficial effect (and may cause harm). Doctors use laboratory tests to discover whether HER2 is overexpressed. In the routine clinical laboratory , the most commonly employed methods for this are immunohistochemistry (IHC) and either silver, chromogenic or fluorescent in situ hybridisation (SISH/CISH/FISH). HER2 amplification can be detected by virtual karyotyping of formalin-fixed paraffin embedded tumor. Virtual karyotyping has the added advantage of assessing copy number changes throughout the genome, in addition to detecting HER-2 amplification (but not overexpression). Numerous PCR -based methodologies have also been described in the literature. [ 65 ] It is also possible to estimate HER2 copy number from microarray data. [ 66 ]
There are two FDA-approved commercial kits available for HER2 IHC; Dako HercepTest [ 67 ] and Ventana Pathway. [ 68 ]
Fluorescent in situ hybridization (FISH) is viewed as being the "gold standard" technique in identifying patients who would benefit from trastuzumab, but it is expensive and requires fluorescence microscopy and an image capture system. The main expense involved with CISH is in the purchase of FDA-approved kits, and as it is not a fluorescent technique it does not require specialist microscopy and slides may be kept permanently. Comparative studies of CISH and FISH have shown that these two techniques show excellent correlation. The lack of a separate chromosome 17 probe on the same section is an issue with regards to acceptance of CISH. As of June 2011 Roche has obtained FDA approval for the INFORM HER2 Dual ISH DNA Probe cocktail [ 69 ] developed by Ventana Medical Systems . [ 68 ] The DDISH (Dual-chromagen/Dual-hapten In-situ hybridization) cocktail uses both HER2 and Chromosome 17 hybridization probes for chromagenic visualization on the same tissue section. The detection can be achieved by using a combination of ultraView SISH(silver in-situ hybridization) and ultraView Red ISH for deposition of distinct chromgenic precipitates at the site of DNP or DIG labeled probes. [ 70 ]
One of the challenges in the treatment of breast cancer patients by herceptin is our understanding towards herceptin resistance. In the last decade, several assays have been performed to understand the mechanism of Herceptin resistance with/without supplementary drugs. Recently, all this information has been collected and compiled in form of a database HerceptinR. [ 71 ]
The drug was first discovered by scientists including Axel Ullrich and H. Michael Shepard at Genentech, Inc. in South San Francisco, CA. [ 72 ] Earlier discovery about the neu oncogene by Robert Weinberg 's lab [ 73 ] and the monoclonal antibody recognizing the oncogenic receptor by Mark Greene's lab [ 74 ] also contributed to the establishment of HER2 targeted therapies. Dr. Dennis Slamon subsequently worked on trastuzumab's development. A book about Dr. Slamon's work was made into a television film called Living Proof , that premiered in 2008. Genentech developed trastuzumab jointly with UCLA , beginning the first clinical trial with 15 women in 1992. [ 75 ] By 1996, clinical trials had expanded to over 900 women, but due to pressure from advocates based on early success, Genentech worked with the FDA to begin a lottery system allowing 100 women each quarter access to the medication outside the trials. [ 76 ] Herceptin was Fast-tracked by the FDA and gained approval in September 1998. [ 33 ]
Biocon Ltd and its partner Mylan obtained regulatory approval to sell a biosimilar in 2014, but Roche contested the legality of the approval; that litigation ended in 2016, and Biocon and Mylan each introduced their own branded biosimilars. [ 77 ]
Trastuzumab costs about US$70,000 for a full course of treatment. [ 78 ]
Australia has negotiated a lower price of A$50,000 per course of treatment. [ 79 ]
Since October 2006, trastuzumab has been made available for Australian women and men with early-stage breast cancer via the Pharmaceutical Benefits Scheme . This is estimated to cost the country over A$470 million for 4–5 years supply of the drug. [ 80 ]
Roche has agreed [ when? ] with Emcure in India to make an affordable version of this cancer drug available to the Indian market. [ 81 ]
Roche has changed the brand name of the drug and has re-introduced an affordable version of the same in the Indian market. [ when? ] The new drug named Herclon would cost approximately RS75,000 INR ( US$ 870) [ clarification needed ] in the Indian market. [ 82 ]
On 16 September 2014, Genentech notified hospitals in the United States that, as of October, trastuzumab could only be purchased through their selected specialty drugs distributors not through the usual general line wholesalers. By being forced to purchase through specialty pharmacies, hospitals lost rebates from the big wholesalers and the ability to negotiate cost-minus discounts with their wholesalers. [ 83 ]
By 2014, around 20 companies, particularly from emerging markets , were developing biosimilar versions of trastuzumab
after Roche/Genentech's patents expired in 2014 in Europe, and in 2019 in the United States. [ 84 ]
In January 2015, BIOCAD [ clarification needed ] announced the first trastuzumab biosimilar approved by the Ministry of Health of the Russian Federation . Iran also approved its own version of the monoclonal antibody in January 2016, as AryoTrust , and announced its readiness to export the drug to other countries in the Middle-East and Central Asia when trade sanctions were lifted. [ 85 ] [ 86 ]
In 2016, the investigational biosimilar MYL-1401O showed comparable efficacy and safety to the Herceptin branded trastuzumab. [ 87 ] Trastuzumab-dkst (Ogivri, Mylan GmbH) was approved in the United States in December 2017, to "treat people with breast cancer or gastric or gastroesophageal junction adenocarcinoma whose tumors overexpress the HER-2 gene." [ 88 ] [ 89 ] Ogivri was authorized for medical use in the European Union in December 2018. [ 27 ] [ 28 ]
In November 2017, the European Commission authorized Ontruzant, a biosimilar from Samsung Bioepis Co., Ltd, for the treatment of early breast cancer, metastatic breast cancer and metastatic gastric cancer. [ 15 ] [ 16 ] Ontruzant is the first trastuzumab biosimilar to receive regulatory approval in the European Union. [ 90 ]
Herzuma was authorized for medical use in the European Union in February 2018. [ 8 ] [ 9 ] Herzuma, a trastuzumab biosimilar, was approved in the United States in December 2018. [ 91 ] [ 7 ] [ 92 ] The approval was based on comparisons of extensive structural and functional product characterization, animal data, human pharmacokinetic, clinical immunogenicity, and other clinical data demonstrating that Herzuma is biosimilar to US Herceptin. [ 92 ] Herzuma has been approved as a biosimilar, not as an interchangeable product. [ 92 ]
Kanjinti was authorized for medical use in the European Union in May 2018. [ 12 ] [ 13 ]
Trazimera was authorized for medical use in the European Union in July 2018. [ 93 ]
Ogivri was approved for medical use in Canada in May 2019. [ 94 ]
Trazimera was approved for medical use in Canada in August 2019. [ 95 ]
Herzuma was approved for medical use in Canada in September 2019. [ 96 ]
Kanjinti was approved for medical use in Canada in February 2020. [ 97 ]
Zercepac was authorized for medical use in the European Union in July 2020. [ 20 ] [ 21 ]
Trastucip and Tuzucip were approved for medical use in Australia in July 2022. [ 17 ]
In September 2023, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Herwenda, intended for the treatment of HER2-positive breast and gastric cancer. [ 98 ] The applicant for this medicinal product is Sandoz GmbH. [ 98 ] Herwenda was authorized for medical use in the European Union in November 2023. [ 10 ] [ 11 ]
Trastuzumab-strf (Hercessi) was approved for medical use in the United States in April 2024. [ 5 ]
In July 2024, the CHMP adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Tuznue, intended for the treatment of breast and gastric cancer. [ 18 ] The applicant for this medicinal product is Prestige Biopharma Belgium BVBA. [ 18 ] Tuznue is a biosimilar medicinal product. [ 18 ] Tuznue was authorized for medical use in the European Union in September 2024. [ 18 ] [ 19 ]
Adheroza was approved for medical use in Canada in August 2024. [ 6 ] [ 99 ]
In April 2025, the CHMP adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Dazublys, intended for the treatment of breast and gastric cancer. [ 100 ] The applicant for this medicinal product is CuraTeQ Biologics s.r.o. [ 100 ] Dazublys is a biosimilar medicinal product. [ 100 ] It is highly similar to the reference product Herceptin (trastuzumab), which was authorised in the EU in August 2000. [ 100 ]
Trastuzumab is also a component of some antibody-drug conjugates , such as trastuzumab emtansine , [ 101 ] and trastuzumab deruxtecan . [ 102 ] [ 103 ] | https://en.wikipedia.org/wiki/Trastuzumab |
Trastuzumab deruxtecan , sold under the brand name Enhertu , is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the topoisomerase I inhibitor deruxtecan (a derivative of exatecan ). [ 11 ] [ 12 ] It is licensed for the treatment of breast cancer or gastric or gastroesophageal adenocarcinoma . [ 12 ] [ 13 ] Trastuzumab binds to and blocks signaling through epidermal growth factor receptor 2 (HER2/neu) on cancers that rely on it for growth. Additionally, once bound to HER2 receptors, the antibody is internalized by the cell, carrying the bound deruxtecan along with it, where it interferes with the cell's ability to make DNA structural changes and replicate its DNA during cell division , leading to DNA damage when the cell attempts to replicate itself, destroying the cell. [ 13 ]
Trastuzumab deruxtecan was approved for medical use in the United States in December 2019, [ 12 ] in Japan in March 2020, [ 14 ] in the European Union in January 2021, [ 8 ] [ 10 ] and in Australia in October 2021. [ 1 ] It is the first approved therapy by the US Food and Drug Administration (FDA) targeted to people with the HER2-low breast cancer subtype subset of HER2-negative breast cancer. [ 15 ]
Trastuzumab deruxtecan is indicated for the treatment of adults with unresectable (unable to be removed with surgery) or metastatic (when cancer cells spread to other parts of the body) HER2-positive breast cancer who have received two or more prior anti-HER2-based regimens in the metastatic setting and for adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who have received a prior trastuzumab-based regimen. [ 12 ] [ 13 ]
In May 2022, the US Food and Drug Administration (FDA) expanded the indication to include the treatment of adults with unresectable or metastatic HER2-positive breast cancer who have received a prior anti-HER2-based regimen either in the metastatic setting, or in the neoadjuvant or adjuvant setting and have developed disease recurrence during or within six months of completing therapy. [ 16 ] [ 17 ]
In August 2022, the FDA expanded the indication to include the treatment of unresectable or metastatic HER2-low breast cancer. [ 15 ]
In April 2024, the FDA expanded the indication to include the treatment of unresectable or metastatic HER2-positive (IHC3+) solid tumors for adults who have received prior systemic treatment and have no satisfactory alternative treatment options. [ 18 ]
The most common side effects are nausea, fatigue, vomiting, alopecia (hair loss), constipation, decreased appetite, anemia (hemoglobin in blood is below the reference range), decreased neutrophil count (white blood cells that help lead the body's immune system response to fight infection), diarrhea, leukopenia (other white blood cells that help the immune system), cough and decreased platelet count (component of blood whose function is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot). [ 12 ]
The prescribing information for trastuzumab deruxtecan includes a boxed warning about the risk of interstitial lung disease (a group of lung conditions that causes scarring of lung tissues) and embryo-fetal toxicity. [ 12 ] Interstitial lung disease and pneumonitis , including cases resulting in death, have been reported with trastuzumab deruxtecan. [ 12 ]
The US Food and Drug Administration (FDA) approved trastuzumab deruxtecan based on the results of one clinical trial enrolling 184 female participants with HER2-positive, unresectable and/or metastatic breast cancer who had received two or more prior anti-HER2 therapies in the metastatic setting. [ 12 ] These participants were heavily pretreated in the metastatic setting, receiving between two and 17 therapies prior to receiving trastuzumab deruxtecan. [ 12 ] Participants in the clinical trial received trastuzumab deruxtecan every three weeks and tumor imaging was obtained every six weeks. [ 12 ] The overall response rate was 60.3%, which reflects the percentage of participants who had a certain amount of tumor shrinkage with a median duration of response of 14.8 months. [ 12 ]
Efficacy was evaluated in a multicenter, open-label, randomized trial (DESTINY-Gastric01, NCT03329690) in participants with HER2-positive locally advanced or metastatic gastric or GEJ adenocarcinoma who had progressed on at least two prior regimens, including trastuzumab, a fluoropyrimidine- and a platinum-containing chemotherapy. [ 13 ] A total of 188 participants were randomized (2:1) to receive trastuzumab deruxtecan 6.4 mg/kg intravenously every three weeks or physician's choice of either irinotecan or paclitaxel monotherapy. [ 13 ]
Efficacy was based on DESTINY-Breast03 (NCT03529110), a multicenter, open-label, randomized trial that enrolled 524 participants with HER2-positive, unresectable, and/or metastatic breast cancer who received prior trastuzumab and taxane therapy for metastatic disease or developed disease recurrence during or within six months of completing neoadjuvant or adjuvant therapy. [ 16 ] Participants were randomized 1:1 to receive either trastuzumab deruxtecan or trastuzumab emtansine by intravenous infusion every three weeks until unacceptable toxicity or disease progression. [ 16 ] Randomization was stratified by hormone receptor status, prior treatment with pertuzumab , and history of visceral disease. [ 16 ]
The FDA approved trastuzumab deruxtecan for the treatment of HER2-low breast cancer based on DESTINY-Breast04, a randomized, multicenter, open label clinical trial that enrolled 557 adult participants with unresectable or metastatic HER2-low breast cancer. [ 15 ] The trial included two cohorts: 494 hormone receptor positive (HR+) participants and 63 hormone receptor negative (HR-) participants. [ 15 ] Of these participants, 373 randomly received trastuzumab deruxtecan by intravenous infusion every three weeks and 184 randomly received physician's choice of chemotherapy ( eribulin , capecitabine , gemcitabine , nab paclitaxel , or paclitaxel ). [ 15 ] The results showed improvement in both progression-free survival and overall survival in people with unresectable or metastatic HER2-low breast cancer. [ 15 ]
In September 2023, the UK's National Institute for Heath and Care Excellence (NICE) published guidance that it would not recommend Trastuzumab deruxtecan, to be used for treatment HER2 LOW breast cancer by the UK's National Heath Service (NHS), citing the cost of the drug being too high in comparison to its benefits. After talks with drug manufacturers AstraZeneca and Daiichi Sankyo , the NHS failed to negotiate a supply at what it deemed to be an acceptable price, and announced in March 2024 that the treatment would not be available to NHS patients. Roughly 1000 patients in the UK would have qualified for free treatment, had a supply been negotiated. Enhertu was however approved by The Scottish Medicines Consortium for use by NHS Scotland in December 2023. [ 19 ] Trastuzumab deruxetecan remains funded for patients with HER2 positive advanced breast cancers. [ 20 ]
The US Food and Drug Administration (FDA) approved trastuzumab deruxtecan in December 2019. [ 12 ] [ 21 ] The application for trastuzumab deruxtecan was granted accelerated approval , fast track designation, and breakthrough therapy designation. [ 12 ] The FDA granted the approval of Enhertu to Daiichi Sankyo . [ 12 ]
In December 2020, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a conditional marketing authorization for the medicinal product Enhertu, intended for the treatment of metastatic HER2-positive breast cancer. [ 22 ] [ 23 ] Trastuzumab deruxtecan was reviewed under EMA's accelerated assessment program. The applicant for this medicinal product is Daiichi Sankyo Europe GmbH. Trastuzumab deruxtecan was approved for medical use in the European Union in January 2021. [ 8 ] [ 10 ]
In January 2021, the FDA granted accelerated approval to trastuzumab deruxtecan for the treatment of adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal (GEJ) adenocarcinoma who have received a prior trastuzumab-based regimen. [ 13 ] [ 24 ]
In October 2021, the Australian Therapeutic Goods Administration approved trastuzumab deruxtecan for provisional registration indicated for the treatment of adults with unresectable or metastatic HER2-positive breast cancer who have received two or more prior anti HER2-based regimens. [ 1 ] | https://en.wikipedia.org/wiki/Trastuzumab_deruxtecan |
Trastuzumab emtansine , [ 6 ] [ 7 ] sold under the brand name Kadcyla , is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the cytotoxic agent DM1 . [ 8 ] [ 9 ] [ 10 ] [ 11 ] Trastuzumab alone stops growth of cancer cells by binding to the HER2 receptor, whereas trastuzumab emtansine undergoes receptor-mediated internalization into cells, is catabolized in lysosomes where DM1-containing catabolites are released and subsequently bind tubulin to cause mitotic arrest and cell death. [ 12 ] Trastuzumab binding to HER2 prevents homodimerization or heterodimerization (HER2/HER3) of the receptor, ultimately inhibiting the activation of MAPK and PI3K/AKT cellular signalling pathways. Because the monoclonal antibody targets HER2, and HER2 is only over-expressed in cancer cells, the conjugate delivers the cytotoxic agent DM1 specifically to tumor cells. [ 13 ] The conjugate is abbreviated T-DM1 .
In the EMILIA clinical trial [ 14 ] of women with advanced HER2 positive breast cancer who were already resistant to trastuzumab alone, it improved median overall survival by 5.8 months (30.9 months vs. 25.1 months) compared to the combination of lapatinib and capecitabine . [ 13 ] Based on that trial, the U.S. Food and Drug Administration (FDA) approved marketing on 22 February 2013. [ 15 ] [ 16 ] [ 17 ]
Trastuzumab emtansine was developed by Genentech , and is manufactured by Lonza . [ 18 ]
In the United States, trastuzumab emtansine was approved specifically for treatment of HER2-positive metastatic breast cancer (mBC) in patients who have been treated previously with trastuzumab and a taxane ( paclitaxel or docetaxel ), and who have already been treated for mBC or developed tumor recurrence within six months of adjuvant therapy . [ 19 ] [ 4 ]
Approval was based on the EMILIA study, [ 14 ] a phase III clinical trial that compared trastuzumab emtansine versus capecitabine (Xeloda) plus lapatinib (Tykerb) in 991 people with unresectable, locally advanced or metastatic HER2-positive breast cancer who had previously been treated with trastuzumab and taxane chemotherapy . [ 14 ] This trial showed improved progression-free survival in patients treated with trastuzumab emtansine (median 9.6 vs. 6.4 months), along with improved overall survival (median 30.9 vs. 25.1 months) and safety. [ 13 ]
During clinical trials, the most common adverse effects of trastuzumab emtansine were fatigue, nausea, musculoskeletal pain, thrombocytopenia (low platelet counts), headache, increased liver enzyme levels , and constipation. [ 4 ]
Severe adverse events identified during the EMILIA trial included hepatotoxicity (liver damage), including rare cases of liver failure , hepatic encephalopathy , and nodular regenerative hyperplasia ; heart damage (dysfunction of the left ventricle ); interstitial lung disease , including acute interstitial pneumonitis ; thrombocytopenia; and peripheral neuropathy . [ 4 ] Overall, trastuzumab emtansine was better tolerated than the control treatment, a combination of lapatinib (Tykerb) and capecitabine (Xeloda), with 43% of patients in the trastuzumab emtansine group experiencing severe toxic effects, versus 59% of those who received lapatinib/capecitabine; furthermore, fewer patients had to stop treatment due to adverse effects than with lapatinib or capecitabine. [ 4 ] Anemia , low platelet counts, and peripheral neuropathy were more common among patients who received trastuzumab emtansine, whereas heart damage and gastrointestinal effects, such as vomiting, diarrhea, and stomatitis , were more common with lapatinib/capecitabine. [ 4 ]
In the United States, trastuzumab emtansine carries black box warnings for liver toxicity, heart damage (reduction in left ventricular ejection fraction ), and fetal harm if given to pregnant women. [ 4 ] [ 17 ]
Trastuzumab emtansine is an antibody-drug conjugate (ADC), a combination between a monoclonal antibody and a small-molecule drug . Each molecule of trastuzumab emtansine consists of a single trastuzumab molecule with several molecules of DM1, a cytotoxic maytansinoid , attached. [ 20 ] SMCC, or succinimidyl trans -4-(maleimidylmethyl)cyclohexane-1-carboxylate, is a heterobifunctional crosslinker , a type of chemical reagent that contains two reactive functional groups , a succinimide ester and a maleimide . The succinimide group of SMCC reacts with the free amino group of a lysine residue in the trastuzumab molecule [ failed verification ] and the maleimide moiety of SMCC links to the free sulfhydryl group of DM1, forming a covalent bond between the antibody and the DM1. Each trastuzumab molecule may be linked to zero to eight DM1 molecules (3.5 on average). [ 20 ] [ 21 ] DM1 binds at plus ends of cellular microtubules and thereby inhibits cell division in the target tumor cells. [ 22 ]
In 2013, trastuzumab emtansine was approved in the United States for the treatment of adults with HER2-positive, metastatic breast cancer who previously received trastuzumab and a taxane, separately or in combination. [ 17 ] [ 19 ]
Referred to as T-DM1 during clinical research, trastuzumab emtansine was reviewed under the FDA's priority review program. [ 17 ]
The safety and effectiveness of trastuzumab emtansine were evaluated in a clinical study of 991 patients randomly assigned to receive trastuzumab emtansine or lapatinib plus capecitabine, another chemotherapy drug. [ 17 ] Patients received treatment until either the cancer progressed or the side effects became intolerable. [ 17 ] The study was designed to measure progression-free survival, the length of time patients lived without the cancer progressing, and overall survival, the length of time patients lived before death. [ 17 ]
Results showed that patients treated with trastuzumab emtansine had a median progression-free survival of 9.6 months compared to 6.4 months in patients treated with lapatinib plus capecitabine. [ 17 ] The median overall survival was 30.9 months in the trastuzumab emtansine group and 25.1 months in the lapatinib plus capecitabine group. [ 17 ]
The U.S. Food and Drug Administration (FDA) approved trastuzumab emtansine in February 2013, and granted the application for Kadcyla to Genentech. [ 17 ] The FDA granted the application for trastuzumab emtansine priority review and breakthrough therapy designations. [ 23 ]
In 2013, trastuzumab emtansine was approved in the UK, [ 3 ] and the EU. [ 5 ]
In 2019, trastuzumab emtansine was approved in the United States for the adjuvant treatment of patients with HER2-positive early breast cancer (EBC) who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. [ 23 ]
Approval was based on KATHERINE (NCT01772472 [ 24 ] ), a randomized, multicenter, open-label trial of 1486 patients with HER2-positive EBC. [ 23 ] Breast tumor samples were required to demonstrate HER2 overexpression defined as 3+ IHC or ISH amplification ratio ≥ 2.0 determined at a central laboratory using Ventana's PATHWAY anti-HER2-/neu (4B5) Rabbit Monoclonal Primary Antibody or INFORM HER2 Dual ISH DNA Probe Cocktail assays. [ 23 ] Patients were required to have had neoadjuvant taxane and trastuzumab-based therapy with residual invasive tumor in the breast and/or axillary lymph nodes. [ 23 ] Patients received radiotherapy and/or hormonal therapy concurrent with study treatment per local guidelines. [ 23 ] Patients were randomized (1:1) to receive trastuzumab emtansine 3.6 mg/kg intravenously or trastuzumab 6 mg/kg intravenously on day 1 of a 21-day cycle for 14 cycles. [ 23 ]
The trial's primary endpoint was invasive disease-free survival (IDFS), defined as the time from the date of randomization to first occurrence of ipsilateral invasive breast tumor recurrence, ipsilateral local or regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, or death from any cause. [ 23 ] After a median follow-up of 40 months, the trial demonstrated a statistically significant improvement in IDFS in patients who received trastuzumab emtansine compared with those who received trastuzumab (HR 0.50; 95% CI: 0.39, 0.64; p<0.0001). [ 23 ] Overall survival data were not mature at the time of the IDFS analysis. [ 23 ]
In the UK, trastuzumab emtansine was not recommended for use by the National Health Service by advisory body NICE , reportedly because an acceptable pricing agreement could not be reached with Roche . [ 25 ] Originally it cost £5,900 a month. [ 26 ] and NICE estimated it cost £166,000 per QALY [ 27 ] (well over the usual maximum). It has been funded by the English NHS Cancer Drugs Fund but in January 2015 it was proposed to remove it from the approved list. [ 28 ] After a secret discount was agreed by Roche the Cancer Drugs Fund will continue to fund it. [ 26 ]
In June 2017, the NHS Confederation and NHS Chief Executive Simon Stevens announced that the NHS would be offering trastuzumab emtansine to a limited number of women after striking a deal with Roche on the price. [ 29 ]
In 2013, trastuzumab emtansine was approved in the United States with the generic name "ado-trastuzumab emtansine", [ 17 ] [ 19 ] rather than the original United States Adopted Name (USAN) issued in 2009, "trastuzumab emtansine". [ 19 ] Trastuzumab is the anti-HER2 antibody; emtansine refers to the linker-drug (SMCC-DM1). The "ado-" prefix was added at the request of the FDA to help prevent dispensing errors . [ 30 ] [ 19 ] [ 31 ] During preclinical development and clinical trials, the drug was also known as trastuzumab-DM1 or trastuzumab-MCC-DM1 (after the codename for emtansine ), both abbreviated T-DM1, and by the codename PRO132365. [ 10 ]
Since 2013 there have been some more clinical trials: | https://en.wikipedia.org/wiki/Trastuzumab_emtansine |
A Traube cell is an "artificial cell" created by Moritz Traube in order to study the processes of living cells, including growth and osmosis . [ 1 ] The Traube cell is not a true artificial cell, as it is not living and does not have true biological processes of its own.
Mortiz Traube was a German student of the German chemist Justus von Liebig in the mid-19th century. In 1867, Traube developed the Traube cell from copper ferrocyanide , in order to study the properties of plasma membranes . The artificial cell would expand and bud like living cells. Surgeon and professor Wilhelm Pfeffer used this model to study and coin the term "plasma membrane". [ 1 ]
The Traube precipitation membrane consists of copper ferrocyanide and forms readily on a surface of crystal potassium ferrocyanide when the crystal is put into a dilute solution of copper sulfate . The membrane is semi-permeable , and expands rapidly into the Traube cell. Within the cell is a high concentration of potassium ferrocyanide with strong osmotic force. While it cannot diffuse outward, water and the copper sulfate solution can flow inwards. When the expansion caused the membrane to burst, a new membrane was quickly formed. In this way, the cell could "grow" and become several centimeters long. [ 2 ] The ability of the Traube cell membrane to allow water to flow in while retaining the cell solute is comparable to living cells. [ 3 ]
This cell biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traube_cell |
Traugott Sandmeyer (15 September 1854 – 9 April 1922) was a Swiss chemist after whom the Sandmeyer reaction , which he discovered in 1884, was named.
Sandmeyer was born as the last of seven children and attended school in Aarau , studying to become a precision mechanic. His friend, J. Gustav Schmidt, studied chemistry at the Polytechnikum of Zurich (ETH) , and their cooperation in conducting experiments led to Sandmeyer's close contact with chemistry.
In 1882, Sandmeyer was made a chemistry lecturer at the ETH by Viktor Meyer . Meyer and Sandmeyer collaborated in studying the synthesis of thiophene , which Meyer had discovered earlier. When Meyer moved to the University of Göttingen , Sandmeyer followed, but then returned to Zürich after a year to work with Arthur Rudolf Hantzsch .
Sandmeyer began his career in industry in 1888 with Johann Rudolf Geigy-Merian , who was the owner of the chemical factory J. R. Geigy & Cie (later Ciba Geigy , now Novartis ). Sandmeyer was involved in the development of several dyes and invented a new synthesis for indigo .
He also worked on the synthesis of isatin . [ 1 ] and several reactions have been named after him: Sandmeyer isonitrosoacetanilide isatin synthesis (1919) and Sandmeyer diphenylurea isatin synthesis (1903). | https://en.wikipedia.org/wiki/Traugott_Sandmeyer |
The Trauzl lead block test , also called the Trauzl test, or just Trauzl , is a test used to measure the strength of explosive materials . It was developed by Isidor Trauzl in 1885.
The test is performed by loading a 10-gram foil-wrapped sample of the explosive into a hole drilled into a lead block with specific dimensions and properties (a soft lead cylinder, 200 mm diameter and 200 mm high, with the hole 125 mm deep, and 25 mm diameter). [ 1 ] The hole is then topped up with sand, and the sample is detonated electrically. After detonation, the volume increase of the cavity is measured. The result, given in cm 3 , is called the Trauzl number of the explosive.
The Trauzl test is not useful for some modern higher-powered explosives as their power often cracks or otherwise ruptures the lead block, leaving no hole to measure. [ 2 ]
A variant of the test uses an aluminium block to avoid exposure of participants to lead-related hazards . [ citation needed ]
Explosive power of chemical explosives by Trauzl number:
This explosives -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Trauzl_lead_block_test |
TravelSim is a brand-name of Top Connect OÜ, an Estonian telecommunications company headquartered in Tallinn . [ 1 ] [ 2 ]
TravelSim is a prepaid SIM card that provides telecommunications to clients in 190 countries.
TravelSim has 3.5 million subscribers all over the world as of August 2013. [ 3 ] TravelSim has a callback service for voice communications, data, messaging and voicemail. [ 1 ]
Callback service means that when users dial an international number using a TravelSim prepaid SIM card, [ 3 ] [ 4 ] [ 5 ] the company picks up the call, routes it to the number dialed and calls back, connecting the two ends of the line.
In 2014 Top Connect announced that the TravelSim service had saved its user base a collective $200 million in roaming charges in 2013. [ 6 ]
This Estonian corporation or company article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TravelSim |
A traveling block is the freely moving section of a block and tackle that contains a set of pulleys or sheaves through which the drill line (wire rope) is threaded or reeved and is opposite (and under) the crown block (the stationary section).
The combination of the traveling block, crown block and wire rope drill line gives the ability to lift weights in the hundreds of thousands of pounds. On larger drilling rigs , when raising and lowering the derrick, line tensions over a million pounds are not unusual.
This article related to natural gas, petroleum or the petroleum industry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traveling_block |
A travelling microscope is an instrument for measuring length with a resolution typically in the order of 0.01mm. The precision is such that better-quality instruments have measuring scales made from Invar to avoid misreadings due to thermal effects. The instrument comprises a microscope mounted on two rails fixed to, or part of a very rigid bed. The position of the microscope can be varied coarsely by sliding along the rails, or finely by turning a screw . The eyepiece is fitted with fine cross-hairs to fix a precise position, which is then read off the vernier scale . [ 1 ] Some instruments, such as that produced in the 1960s by the Precision Tool and Instrument Company of Thornton Heath, Surrey, England, also measure vertically. The purpose of the microscope is to aim at reference marks with much higher accuracy than is possible using the naked eye. It is used in laboratories to measure the refractive index of flat specimens using the geometrical concepts of ray optics ( Duc de Chaulnes ’ method). [ 2 ] It is also used to measure very short distances precisely, for example the diameter of a capillary tube. This mechanical instrument has now largely been superseded by electronic- and optically based measuring devices that are both very much more accurate and considerably cheaper to produce.
A travelling microscope consists of a cast iron base with machined-Vee-top surface and is fitted with three levelling screws. A metallic carriage clamped to a spring-loaded bar slides with its attached vernier and reading lens along an inlaid strip of metal scale. The scale is divided in half millimeters. Fine adjustments are made by means of a micrometer screw for taking accurate reading. Both vernier reading to 0.01mm or 0.02mm. Microscope tube consists of 10x Eyepice and 15mm or 50mm or 75mm objectives. The microscope, with its rack and pinion attachment, is mounted on a vertical slide, which also runs with an attached vernier along the vertical scale. The microscope is free to rotate n vertical plane. The vertical guide bar is coupled to the horizontal carriage of the microscope. For holding objects a horizontal stage made of a milki [ check spelling ] conolite sheet is provided in the base. | https://en.wikipedia.org/wiki/Traveling_microscope |
A traveling screen is a type of water filtration device that has a continuously moving mesh screen that is used to catch and remove debris. [ 1 ] This type of device is usually found in water intake systems for drinking water and sewage treatment plants. Screening is considered the first step in conventional sewage treatment processes . Screening is also used in cooling water intakes in steam electric power plants , hydroelectric generators , petroleum refineries , and chemical plants . Traveling screens are used to divert fish , shellfish and other aquatic species, and debris including leaves, sticks, and trash; for the purpose of preventing damage to a facility's treatment or cooling system.
This article about a civil engineering topic is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traveling_screen |
The traveling tournament problem (TTP) is a mathematical optimization problem. The question involves scheduling a series of teams such that:
A matrix is provided of the travel distances between each team's home city. All teams start and end at their own home city, and the goal is to minimize the total travel distance for every team over the course of the whole season . [ 1 ]
There have been many papers published on the subject, and a contest exists to find the best solutions for certain specific schedules. [ 2 ]
This mathematics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traveling_tournament_problem |
A traverse , in military fortification , is a mass of earth or other material employed to protect troops against enfilade . It is constructed at right angles to the parapet manned by the defenders, and is continued sufficiently far to the rear to give the protection required by the circumstances, which, moreover, determine its height. A traverse is sometimes utilized as a casemate . Ordinary field works, not less than those of more solid construction, require traversing, though if the trenches , instead of being continuous, are broken into short lengths, they are traversed by the unbroken earth intervening between each length. [ 1 ]
This military -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traverse_(fortification) |
Traverse is a method in the field of surveying to establish control networks . [ 1 ] It is also used in geodesy . Traverse networks involve placing survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point. Connected survey lines form the framework and the directions and lengths of the survey lines are measured with an angle measuring instrument and tape or chain. [ 2 ] Traverse networks have many advantages, including:
The traverse is more accurate than triangulateration [ 3 ] (a combined function of the triangulation and trilateration practice). [ 4 ]
Frequently in surveying engineering and geodetic science , control points (CP) are setting/observing distance and direction ( bearings , angles , azimuths , and elevation ). The CP throughout the control network may consist of monuments , benchmarks , vertical control , etc. There are mainly two types of traverse: | https://en.wikipedia.org/wiki/Traverse_(surveying) |
In trench warfare , a traverse is an adaptation to reduce casualties to defenders occupying a trench. One form of traverse is a U-shaped detour in the trench with the trench going around a protrusion formed of earth and sandbags . The fragments or shrapnel , or shockwave from a shell landing and exploding within a trench then cannot spread horizontally past the obstacle the traverse interposes. Also, an enemy that has entered a trench is unable to fire down the length at the defenders, or otherwise enfilade the trench.
A traverse trench is a trench dug perpendicular to a trench line, but extending away from the enemy. It has two functions. One function is to provide an entry into the main trench. A second function is to provide a place for defenders to shelter and regroup should the enemy have penetrated into the main trench and be able to fire down the main trench's length.
On an approach trench, that is, a trench leading from the rear to the frontline or firing trench, defenders may construct an island traverse. With an island traverse, the approach trench splits to go around both sides of a traverse before coming together again.
Lastly, a flying or bridge traverse is a sandbagged covering for a stretch of trench to block shrapnel or shell fragments from entering the trench.
This military -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Traverse_(trench_warfare) |
Tre recombinase is an experimental enzyme that in lab tests has removed DNA inserted by HIV from infected cells. [ 1 ] Through selective mutation , Cre recombinase which recognizes loxP sites are modified to identify HIV long terminal repeats (loxLTR) instead. As a result, instead of performing Cre-Lox recombination , the new enzyme performs recombination at HIV provirus sites. [ 2 ]
The structure of Tre in complex with loxLTR has been resolved ( PDB : 5U91 ), allowing for analyzing the roles of individual mutations. [ 3 ]
This genetics article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Tre_recombinase |
A treadle (from Old English : tredan , "to tread") is a foot-powered lever mechanism ; it is operated by treading on it repeatedly. A treadle, unlike some other types of pedals, is not directly mounted on the crank (see treadle bicycle for a clear example).
Most treadle machines convert reciprocating motion into rotating motion , using a mechanical linkage to indirectly connect one or two treadles to a crank. The treadle then turns the crank, which powers the machine. Other machines use treadles directly, to generate reciprocating motion. For instance, in a treadle loom , the reciprocating motion is used directly to lift and lower the harnesses or heddles ; a common treadle pump uses the reciprocating motion to raise and lower pistons .
Before the widespread availability of electric power , treadles were the most common way to power a range of machines. They are still widely used as a matter of preference and necessity. A human-powered machine gives the human operator close, instinctive control over the rate at which energy is fed into the machine; this lets them easily vary the rate at which they work. Treadle-operated machines are also used in environments where electric power is not available to power electric machinery .
Other, similar mechanisms for allowing human and animal muscle to power machines are cranks , treadmills , treadwheels , and kick wheels like a potter's kick wheel .
A treadle is operated by pressing down on it repeatedly with one or both feet, causing a rocking motion. [ 1 ] This movement can then be stored as rotational motion via a crankshaft driving a flywheel . Alternatively, energy can be stored in a spring, as in the pole lathe .
Treadles were once used extensively to power most machines including lathes , rotating or reciprocating saws , spinning wheels , looms , and sewing machines .
Today the use of treadle-powered machines is common in areas of the developing world where other forms of power are unavailable. It is also common among artisans, hobbyists and historical re-enactors . [ 2 ]
Some treadle looms in Africa and South Asia use toggles on a string as treadles. The toggles are held between the weaver's toes.
This technology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Treadle |
In molecular biology , treadmilling is a phenomenon observed within protein filaments of the cytoskeletons of many cells , especially in actin filaments and microtubules . It occurs when one end of a filament grows in length while the other end shrinks, resulting in a section of filament seemingly "moving" across a stratum or the cytosol . This is due to the constant removal of the protein subunits from these filaments at one end of the filament, while protein subunits are constantly added at the other end. [ 1 ] Treadmilling was discovered by Wegner, [ 2 ] who defined the thermodynamic and kinetic constraints. Wegner recognized that: “The equilibrium constant (K) for association of a monomer with a polymer is the same at both ends, since the addition of a monomer to each end leads to the same polymer.”; a simple reversible polymer can’t treadmill; ATP hydrolysis is required. GTP is hydrolyzed for microtubule treadmilling.
The cytoskeleton is a highly dynamic part of a cell and cytoskeletal filaments constantly grow and shrink through addition and removal of subunits. Directed crawling motion of cells such as macrophages relies on directed growth of actin filaments at the cell front ( leading edge ).
The two ends of an actin filament differ in their dynamics of subunit addition and removal. They are thus referred to as the plus end (with faster dynamics, also called barbed end) and the minus end (with slower dynamics, also called pointed end). [ 3 ] This difference results from the fact that subunit addition at the minus end requires a conformational change of the subunits. [ 4 ] Note that each subunit is structurally polar and has to attach to the filament in a particular orientation. [ 5 ] As a consequence, the actin filaments are also structurally polar.
Elongating the actin filament occurs when free-actin (G-actin) bound to ATP associates with the filament. Under physiological conditions, it is easier for G-actin to associate at the positive end of the filament, and harder at the negative end. [ 6 ] However, it is possible to elongate the filament at either end. Association of G-actin into F-actin is regulated by the critical concentration outlined below. Actin polymerization can further be regulated by profilin and cofilin . [ 6 ] Cofilin functions by binding to ADP-actin on the negative end of the filament, destabilizing it, and inducing depolymerization. Profilin induces ATP binding to G-actin so that it can be incorporated onto the positive end of the filament.
Two main theories exist on microtubule movement within the cell: dynamic instability and treadmilling. [ 7 ] Dynamic instability occurs when the microtubule assembles and disassembles at one end only, while treadmilling occurs when one end polymerizes while the other end disassembles.
The critical concentration is the concentration of either G-actin (actin) or the alpha,beta- tubulin complex (microtubules) at which the end will remain in an equilibrium state with no net growth or shrinkage. [ 6 ] What determines whether the ends grow or shrink is entirely dependent on the cytosolic concentration of available monomer subunits in the surrounding area. [ 8 ] Critical concentration differs from the plus (C C + ) and the minus end (C C − ), and under normal physiological conditions, the critical concentration is lower at the plus end than the minus end. Examples of how the cytosolic concentration relates to the critical concentration and polymerization are as follows:
Note that the cytosolic concentration of the monomer subunit between the C C + and C C − ends is what is defined as treadmilling in which there is growth at the plus end, and shrinking on the minus end.
The cell attempts to maintain a subunit concentration between the dissociation constants at the plus and minus ends of the polymer.
Microtubules formed from pure tubulin undergo subunit uptake and loss at ends by both random exchange diffusion, and by a directional (treadmilling) element. [ 9 ] Treadmilling is inefficient, and for microtubules at steady state: the Wegner s-value 1 (the reciprocal of the number of molecular events required for the net uptake of a subunit) is equal to 0.0005-0.001; i.e., it requires >1000 events. [ 10 ] Microtubule treadmilling with pure tubulin also occurs with growing microtubules [ 11 ] and is enhanced by proteins that bind to ends 11 . Rapid treadmilling occurs in cells. [ 12 ] [ 13 ] [ 14 ]
FtsZ treadmilling
The bacterial tubulin homolog FtsZ is one of the best documented treadmilling polymers. FtsZ assembles into protofilaments that are one subunit thick, which can further associate into small patches of parallel protofilaments. Single filaments and/or patches have been demonstrated to treadmill in vitro [ 15 ] [ 16 ] and inside bacterial cells. [ 17 ] [ 18 ] A Monte Carlo model of FtsZ treadmilling has been designed, based on a conformational change of subunits upon polymerization and GTP hydrolysis. [ 19 ] | https://en.wikipedia.org/wiki/Treadmilling |
Charles Hayes (1678–1760) was an English mathematician, chronologist and slave trader who wrote a book on the method of fluxions . He also served as an official of the Royal African Company , which engaged in the Atlantic slave trade .
Hayes was a member of Gray's Inn . Having made a voyage to Africa and spent some time there, he had a reputation as a geographer, and was chosen annually to be sub-governor or deputy-governor of the Royal African Company (RAC), which engaged in the Atlantic slave trade . [ 1 ] When the RAC was dissolved in 1752, Hayes settled at Downe, Kent . John Nichols remarks that Hayes spent much time in philosophical experiments. Hayes found favour with his contemporaries from his ‘sedate temper’ and clear exposition; and Charles Hutton remarked that he had erudition concealed by modesty. Hayes died at his chambers in Gray's Inn on 18 December 1760. [ 1 ]
In 1704, appeared his Treatise on Fluxions, or an Introduction to Mathematical Philosophy , London, the first English work explaining Isaac Newton 's method of infinitesimals. After an introduction on conic sections with concise proofs, Hayes applied Newton's method systematically, first to obtain the tangents of curves, then their areas, and lastly to problems of maxima and minima. His preface shows he was well read in mathematical literature. In 1710 he printed a pamphlet, New and Easy Method to find out the Longitude ; and in 1723 The Moon, a Philosophical Dialogue , arguing that she is not opaque, but has some light of her own. [ 1 ]
After studying Hebrew, Hayes in 1736 published his Vindication of the History of the Septuagint , and in 1738 Critical Examination of the Holy Gospels according to St. Matthew and St. Luke , with regard to the history of Christ's birth and infancy. His studies were from then mainly directed to chronology, except for some tracts written to defend the policy of the Royal African Company. In 1747 appeared his Series of Kings of Argos and of Emperors of China from Fohi to Jesus Christ , to prove that their dates and order of succession agreed with the Septuagint , and in 1751 a Dissertation on the Chronology of the Septuagint , a defence of the Chaldean and Egyptian chronology and history. [ 1 ]
In retirement, he became absorbed in a major work, Chronographia Asiatica & Ægyptiaca , which he did not live to complete. Two parts of it only were published, during the last two years of his life, when he had chambers in Gray's Inn: first, Chronographiæ Asiaticæ & Ægyptiacæ Specimen , and the second, subdivided into (1) Origo Chronologiæ LXX interpretum investigatur , and (2) Conspectus totius Operis exhibetur . Part of his argument is that the Seventy (authors of the Septuagint) and Josephus made use of writings preserved in the library of the Second Temple of Jerusalem , which had been omitted in making up the Old Testament canon . [ 1 ]
This article incorporates text from a publication now in the public domain : Anderson, Robert Edward (1891). " Hayes, Charles ". In Stephen, Leslie ; Lee, Sidney (eds.). Dictionary of National Biography . Vol. 25. London: Smith, Elder & Co. | https://en.wikipedia.org/wiki/Treatise_of_Fluxions,_or,_An_Introduction_to_Mathematical_Philosophy |
Treatise on Analysis is a translation by Ian G. Macdonald of the nine-volume work Éléments d'analyse on mathematical analysis by Jean Dieudonné , and is an expansion of his textbook Foundations of Modern Analysis . It is a successor to the various Cours d'Analyse by Augustin-Louis Cauchy , Camille Jordan , and Édouard Goursat .
The first volume was originally a stand-alone graduate textbook with a different title. It was first written in English and later translated into French, unlike the other volumes which were first written in French. It has been republished several times and is much more common than the later volumes of the series.
The contents include
The second volume includes
The third volume includes chapter XVI on differential manifolds and chapter XVII on distributions and differential operators .
The fourth volume includes
Volume V consists of chapter XXI on compact Lie groups.
Volume VI consists of chapter XXII on harmonic analysis (mostly on locally compact groups )
Volume VII consists of the first part of chapter XXIII on linear functional equations. This chapter is considerably more advanced than most of the other chapters.
Volume VIII consists of the second part of chapter XXIII on linear functional equations.
Volume IX contains chapter XXIV on elementary differential topology . Unlike the earlier volumes there is no English translation of it.
Dieudonne planned a final volume containing chapter XXV on nonlinear problems, but this was never published. | https://en.wikipedia.org/wiki/Treatise_on_Analysis |
In mathematics , particularly in differential geometry , a tree-like curve is a generic immersion c : S 1 → R 2 {\displaystyle c:S^{1}\to \mathbb {R} ^{2}} with the property that removing any double point splits the curve into exactly two disjoint connected components . This property gives these curves a tree -like structure, hence their name. They were first systematically studied by Russian mathematicians Boris Shapiro and Vladimir Arnold in the 1990s. [ 1 ] [ 2 ]
For generic curves interpreted as the shadows of knots (that is, knot diagrams from which the over-under relations at each crossing have been erased), the tree-like curves can only be shadows of the unknot . As knot diagrams, these represent connected sums of figure-eight curves . Each figure-eight is unknotted and their connected sum remains unknotted. Random curves with few crossings are likely to be tree-like, and therefore random knot diagrams with few crossings are likely to be unknotted. [ 3 ]
This geometry-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Tree-like_curve |
TreeFam (Tree families database) is a database of phylogenetic trees of animal genes . It aims at developing a curated resource that gives reliable information about ortholog and paralog assignments, and evolutionary history of various gene families. [ 1 ] [ 2 ]
TreeFam defines a gene family as a group of genes that evolved after the speciation of single- metazoan animals. It also tries to include outgroup genes like yeast ( S.cerevisiae and S. pombe ) and plant ( A. thaliana ) to reveal these distant members.
TreeFam is also an ortholog database. Unlike other pairwise alignment based ones, TreeFam infers orthologs by means of gene trees. It fits a gene tree into the universal species tree and finds historical duplications, speciations and losses events. TreeFam uses this information to evaluate tree building, guide manual curation , and infer complex ortholog and paralog relations.
The basic elements of TreeFam are gene families that can be divided into two parts: TreeFam-A and TreeFam-B families. TreeFam-B families are automatically created. They might contain errors given complex phylogenies . TreeFam-A families are manually curated from TreeFam-B ones. Family names and node names are assigned at the same time. The ultimate goal of TreeFam is to present a curated resource for all the families.
TreeFam is being run as a project at the Wellcome Trust Sanger Institute , and its software is housed on SourceForge as "TreeSoft". | https://en.wikipedia.org/wiki/TreeFam |
A tree box filter is a best management practice (BMP) or stormwater treatment system widely implemented along sidewalks, street curbs, and car parks. They are used to control the volume and amount of urban runoff pollutants entering into local waters, by providing areas where water can collect and naturally infiltrate or seep into the ground. Such systems usually consist of a tree planted in a soil media, contained in a small, square, concrete box. Tree box filters are popular bioretention and infiltration practices, as they collect, retain, and filter runoff as it passes through vegetation and microorganisms in the soil. The water is then either consumed by the tree or transferred into the storm drain system. [ 1 ] [ 2 ]
Before construction of the tree box filter, several factors must be considered to maximize the effectiveness and impact of the system. Such factors include:
In order to accommodate such considerations, the location, design, and type of material of the box filter may be altered. [ 2 ] [ 3 ]
Tree box filters are designed to accommodate a low volume of rainfall. [ 2 ] A filter surface area of 48 feet (15 m) can only cover up to 0.25 acres (0.10 ha) of impervious or nonporous surface. [ 3 ] [ 4 ] As a result, strategically positioning multiple tree boxes around the area of coverage is vital, when trying to reduce costs and work.
Tree box filters consist of four main parts. [ 1 ] [ 2 ]
The tree is planted in a soil mixture of construction sand, unscreened topsoil, and compost. [ 5 ] The soil layer must be deep enough to accommodate nutrient and space requirements of the tree. It is recommended that there be
2 cubic feet (0.057 m 3 ) of soil for every 1 cubic foot (0.028 m 3 ) of tree canopy. [ 6 ] Therefore, a five by six foot tree box must contain at least two feet of soil media in order to sustain a tree with a canopy of thirty square feet. Underneath the layer of soil lies the underdrain. This consists of a layer of crushed stone, at least two feet (0.6 meters) deep, surrounding a perforated drainage pipe. The drainage pipe connects to the municipality's existing storm drain system, allowing excess water to flow out, preventing overflow. These layers are encapsulated in a concrete box, hence the name tree box filter. Optionally, a metal grate may be placed on top of the concrete box, blocking large pieces of debris from entering the soil layer. When the tree box filter is located next to the street, a storm drain inlet may be implemented, allowing stormwater to enter from the street gutter. [ 2 ] [ 3 ] [ 7 ] Stormwater from urban roof runoff can also be channeled to the tree-pits via roof drainage pipes. [ 8 ]
Installing a tree box filter may take only two to three days to accomplish, as all the necessary layers are delivered inside the box, ready to plant. First, preexisting, underground pipes and cables around the work site are marked out. Next, a rubber-tire backhoe will excavate the area where the box will be placed. Next, the concrete box containing all the main parts, except the tree, is set into the hole on a leveled base. Then underdrain pipes are connected, and any gaps around the tree box are refilled. Finally, the tree is planted, and if included, the metal grate is installed. Final tests and inspections of the tree box filter's function conclude the installation procedure. Depending on the location and area of coverage, installation can cost between $12,500 and $65,000. [ 3 ] [ 6 ]
Maintenance of tree box filters may include, but is not limited to
The cost of care can range from $100 to $500 per year for each tree box filter. In order to extend the life and efficiency of the tree box filter, it is recommended that inspections be conducted yearly. [ 2 ] [ 3 ] [ 9 ]
When implemented properly, tree box filters can significantly reduce the amount of pollutant in the stormwater that it infiltrates.
The ratio of pollutants exiting versus entering the tree box filter is known as the load ratio. Tree box filters show load ratios of 0.1 to 0.3 in the reduction of soluble metals, 0.35 to 0.6 in the reduction of organics and nutrients, and 0.09 in the reduction of total suspended solids . [ 7 ]
Tree box filters remove about 80-90% of total suspended solids, 38-65% of nitrogen, and 50-80% of phosphorus, 54% of zinc, 40% of copper, and 90% of petroleum hydrocarbons. [ 3 ] Based on these results, it can be concluded that tree box filters can significantly reduce the amount of pollutants in water that flows through the system, greatly lessening the impact on local surface waters. | https://en.wikipedia.org/wiki/Tree_box_filter |
Nicolas Andry de Bois-Regard (1658 – 13 May 1742) was a French physician and writer. He played a significant role in the early history of both parasitology and orthopedics , the name for which is taken from Andry's book Orthopédie .
Andry was born in Lyon , and spent his early life preparing for the priesthood . [ 2 ] His early studies were widespread, however, and he published a book on the usage of the French language in 1692. [ 3 ] In his 30s he studied medicine at Reims and Paris , receiving his degree in 1697, and in 1701 he was appointed to the faculty of the Collège de France and the editorial board of the Journal des savants . [ 2 ]
Andry's early medical work lies within the nascent germ theory of disease . His first book, De la génération des vers dans les corps de l'homme , was published in 1700, and translated into English in 1701 as An Account of the Breeding of Worms in Human Bodies . [ 4 ] The book was an account of Andry's experiments with the microscope , building on the earlier work of Antonie van Leeuwenhoek , whom Andry cites frequently. Unlike Leeuwenhoek, Andry's purpose is specifically medical, and his experiments with the microscope led him to believe that the microorganisms he called "worms" were responsible for smallpox and other diseases. [ 5 ]
The book contains a detailed discussion of spermatozoa , which Andry calls "spermatic worms." He observes: "If you cut up a dog, and after you have taken off one Testicle, by the help of a Microscope examine the Humour that comes out of the deferent vessel , you shall discover in it such a hideous number of little worms, that you shall hardly be able to believe your own Eyes." [ 6 ] Andry confirms an argument previously made by Leeuwenhoek, that spermatozoa are "the occasion of the Generation of all Animals." [ 7 ] Though Andry recognizes the importance of sperm to reproduction, however, he addresses their workings primarily in the context of parasitology, and essentially considers spermatozoa to be a unique species of parasitic worm. [ 8 ]
The book seems to address a general audience in addition to a medical one. As medical historian Clara Pinto Correia has observed, one of Andry's principal purposes was to educate the public about the new science that was emerging from under the microscope. He wrote, "We must admit that there are animals a thousand times less than a grain of dust, which we can scarcely see. [...] Our imagination loses itself in this thought, it is amazed at such a strange littleness; but to what purpose should it deny it? Reason convinces us of the existence of that which we cannot conceive." [ 7 ]
The book was well-received, and became a standard text in the field. [ 9 ] Andry was appointed Dean of the Faculté de Médecine de Paris in 1724. [ 2 ]
Andry published his introduction to orthopedics in 1741 under the title Orthopédie , then a neologism . It was translated into English in 1743 as Orthopædia. [ 10 ] Aimed more at parents than physicians, the book presents a theory of human anatomy, skeletal structure, and growth, along with instructions for correcting deformity. Andry explains in the book that he formed its title "of two Greek Words, viz. Orthos, which signifies straight, free from deformity, and Pais, a Child. Out of these two words I have compounded that of Orthopædia, to express in one Term the Design I Propose, which is to teach the different Methods of preventing and correction of Deformities of Children." [ 11 ]
Though the book was read and cited extensively in the period, its main lasting influence in medicine has been its title, which became the name of the field devoted to skeletal and related injuries and ailments (later modified to "orthopædics" and "orthopaedics" or, in American spelling, "orthopedics"). [ 12 ] Outside of medicine, the principal impact of the book derives from the engraving on the frontispiece, which shows a straight stake tied to a crooked sapling , a metaphor for the correction of deformities in children. The engraving captured the attention of contemporary readers; it is referred to, for example, in George Colman 's 1787 comic opera Inkle and Yarico . [ 13 ]
Andry's frontispiece has played a significant role in the cultural studies of eighteenth-century medicine. It is included, without comment, as the last in a series of ten eighteenth- and nineteenth-century illustrations in Michel Foucault 's influential study of the history of correction, Discipline and Punish . [ 14 ] Scholar Paolo Palladino has explained Foucault's use of the image as showing that "practices as disparate as orthopedics and horticulture were increasingly predicated on operative principles that focused on the manipulation of these different life forms' presumed common material substance. Moreover, the image raises questions of agency, since it is unclear who exactly bound the tree: no human or divine form is visible anywhere in the background; the image therefore accorded with Foucault's understanding that the operation of these principles was invisible and pervasive." [ 15 ]
A simplified version of Andry's illustration continues to serve as the international symbol for orthopedics, used by a number of different institutions in multiple countries. [ 12 ] [ 16 ]
In conjunction with Clinical Orthopaedics and Related Research , the Association of Bone and Joint Surgeons presents three awards annually including the Nicolas Andry Award. [ 17 ] | https://en.wikipedia.org/wiki/Tree_of_Andry |
The Tree of Life Web Project ( ToL ) is an Internet project providing information about the diversity and phylogeny of life on Earth . [ 1 ] [ 2 ]
This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site has not been updated since 2011, however the pages are still accessible. [ 3 ]
The pages are linked hierarchically , in the form of the branching evolutionary tree of life, organized cladistically . [ 1 ] Each page contains information about one particular group of organisms and is organized according to a branched tree-like form, thus showing hypothetical relationships between different groups of organisms.
In 2009 the project ran into funding problems from the University of Arizona . Pages and Treehouses submitted took a considerably longer time to be approved as they were being reviewed by a small group of volunteers, and apparently, around 2011, all activities ended. [ 3 ]
The idea of this project started in the late 1980s. David Maddison was working on a computer program MacClade during his PhD research. This is an application that gives insight into species' phylogenetic trees. He wanted to extend this program with a feature that allowed the user to browse through phylogenetic trees and zoom into other lower or higher taxa. [ 4 ]
Hence, this association was not unique in a stand-alone application. The researchers came up with the idea to export the application into the World Wide Web and this was realized in 1995. From 1996 to 2011, over 300 biologists from around the globe added taxa web pages into the phylogeny browser. [ 4 ]
To ensure the quality of ToL project, the board made use of peer-review . The pages that were reviewed were sent to two or three researchers that specialized in the particular subject. [ 4 ] It is possible to visit the personal page of the author. If this is not accessible then the institution is always at the footnote. [ 5 ] The entire tree structure that contained 35,960 species until the website's demise, is available for download as a csv dataset. [ 6 ] | https://en.wikipedia.org/wiki/Tree_of_Life_Web_Project |
A tree of primitive Pythagorean triples is a mathematical tree in which each node represents a primitive Pythagorean triple and each primitive Pythagorean triple is represented by exactly one node. In two of these trees, Berggren's tree and Price's tree, the root of the tree is the triple (3, 4, 5) , and each node has exactly three children, generated from it by linear transformations .
A Pythagorean triple is a set of three positive integers a , b , and c having the property that they can be respectively the two legs and the hypotenuse of a right triangle , thus satisfying the equation a 2 + b 2 = c 2 {\displaystyle a^{2}+b^{2}=c^{2}} ; the triple is said to be primitive if and only if the greatest common divisor of a , b , and c is one. Primitive Pythagorean triple a , b , and c are also pairwise coprime . The set of all primitive Pythagorean triples has the structure of a rooted tree , specifically a ternary tree , in a natural way. This was first discovered by B. Berggren in 1934. [ 1 ]
F. J. M. Barning showed [ 2 ] that when any of the three matrices
is multiplied on the right by a column vector whose components form a Pythagorean triple, then the result is another column vector whose components are a different Pythagorean triple. If the initial triple is primitive, then so is the one that results. Thus each primitive Pythagorean triple has three "children". All primitive Pythagorean triples are descended in this way from the triple (3, 4, 5) , and no primitive triple appears more than once. The result may be graphically represented as an infinite ternary tree with (3, 4, 5) at the root node (see classic tree at right). This tree also appeared in papers of A. Hall in 1970 [ 3 ] and A. R. Kanga in 1990. [ 4 ] In 2008 V. E. Firstov showed generally that only three such trichotomy trees exist and give explicitly a tree similar to Berggren's but starting with initial node (4, 3, 5) . [ 5 ]
It can be shown inductively that the tree contains primitive Pythagorean triples and nothing else by showing that starting from a primitive Pythagorean triple, such as is present at the initial node with (3, 4, 5) , each generated triple is both Pythagorean and primitive.
If any of the above matrices, say A , is applied to a triple ( a , b , c ) T having the Pythagorean property a 2 + b 2 = c 2 to obtain a new triple ( d , e , f ) T = A ( a , b , c ) T , this new triple is also Pythagorean. This can be seen by writing out each of d , e , and f as the sum of three terms in a , b , and c , squaring each of them, and substituting c 2 = a 2 + b 2 to obtain f 2 = d 2 + e 2 . This holds for B and C as well as for A .
The matrices A , B , and C are all unimodular —that is, they have only integer entries and their determinants are ±1. Thus their inverses are also unimodular and in particular have only integer entries. So if any one of them, for example A , is applied to a primitive Pythagorean triple ( a , b , c ) T to obtain another triple ( d , e , f ) T , we have ( d , e , f ) T = A ( a , b , c ) T and hence ( a , b , c ) T = A −1 ( d , e , f ) T . If any prime factor were shared by any two of (and hence all three of) d , e , and f then by this last equation that prime would also divide each of a , b , and c . So if a , b , and c are in fact pairwise coprime, then d , e , and f must be pairwise coprime as well. This holds for B and C as well as for A .
To show that the tree contains every primitive Pythagorean triple, but no more than once, it suffices to show that for any such triple there is exactly one path back through the tree to the starting node (3, 4, 5) . This can be seen by applying in turn each of the unimodular inverse matrices A −1 , B −1 , and C −1 to an arbitrary primitive Pythagorean triple ( d , e , f ) , noting that by the above reasoning primitivity and the Pythagorean property are retained, and noting that for any triple larger than (3, 4, 5) exactly one of the inverse transition matrices yields a new triple with all positive entries (and a smaller hypotenuse). By induction, this new valid triple itself leads to exactly one smaller valid triple, and so forth. By the finiteness of the number of smaller and smaller potential hypotenuses, eventually (3, 4, 5) is reached. This proves that ( d , e , f ) does in fact occur in the tree, since it can be reached from (3, 4, 5) by reversing the steps; and it occurs uniquely because there was only one path from ( d , e , f ) to (3, 4, 5) .
The transformation using matrix A , if performed repeatedly from ( a , b , c ) = (3, 4, 5) , preserves the feature b + 1 = c ; matrix B preserves a – b = ±1 starting from (3, 4, 5) ; and matrix C preserves the feature a + 2 = c starting from (3, 4, 5) .
A geometric interpretation for this tree involves the excircles present at each node. The three children of any parent triangle “inherit” their inradii from the parent: the parent’s excircle radii become the inradii for the next generation. [ 6 ] : p.7 For example, parent (3, 4, 5) has excircle radii equal to 2, 3 and 6. These are precisely the inradii of the three children (5, 12, 13) , (15, 8, 17) and (21, 20, 29) respectively.
If either of A or C is applied repeatedly from any Pythagorean triple used as an initial condition, then the dynamics of any of a , b , and c can be expressed as the dynamics of x in
which is patterned on the matrices' shared characteristic equation
If B is applied repeatedly, then the dynamics of any of a , b , and c can be expressed as the dynamics of x in
which is patterned on the characteristic equation of B . [ 7 ]
Moreover, an infinitude of other third-order univariate difference equations can be found by multiplying any of the three matrices together an arbitrary number of times in an arbitrary sequence. For instance, the matrix D = CB moves one out the tree by two nodes (across, then down) in a single step; the characteristic equation of D provides the pattern for the third-order dynamics of any of a , b , or c in the non-exhaustive tree formed by D .
Another approach to the dynamics of this tree [ 8 ] relies on the standard formula for generating all primitive Pythagorean triples:
with m > n > 0 and m and n coprime and of opposite parity (i.e., not both odd). Pairs ( m , n ) can be iterated by pre-multiplying them (expressed as a column vector) by any of
each of which preserves the inequalities, coprimeness, and opposite parity. The resulting ternary tree, starting at (2, 1) , contains every such ( m , n ) pair exactly once, and when converted into ( a , b , c ) triples it becomes identical to the tree described above.
Alternatively, start with ( m , n ) = (3, 1) for the root node. [ 9 ] Then the matrix multiplications will preserve the inequalities and coprimeness, and both m and n will remain odd. The corresponding primitive Pythagorean triples will have a = ( m 2 − n 2 ) / 2 , b = mn , and c = ( m 2 + n 2 ) / 2 . This tree will produce the same primitive Pythagorean triples, though with a and b switched.
This approach relies on the standard formula for generating any primitive Pythagorean triple from a half-angle tangent. Specifically one writes t = n / m = b / ( a + c ) , where t is the tangent of half of the interior angle that is opposite to the side of length b . The root node of the tree is t = 1/2 , which is for the primitive Pythagorean triple (3, 4, 5) . For any node with value t , its three children are 1 / (2 − t ) , 1 / (2 + t ) , and t / (1 + 2 t ) . To find the primitive Pythagorean triple associated with any such value t , compute (1 − t 2 , 2 t , 1 + t 2 ) and multiply all three values by the least common multiple of their denominators. (Alternatively, write t = n / m as a fraction in lowest terms and use the formulas from the previous section.) A root node that instead has value t = 1/3 will give the same tree of primitive Pythagorean triples, though with the values of a and b switched.
Alternatively, one may also use three different matrices found by Price: [ 6 ]
The three children produced by the set { A , B , C } and the children produced by the set { A′ , B′ , C′ } are not the same, but each set separately produces all primitive triples.
For example, using [5, 12, 13] as the parent, we get two sets of three children: | https://en.wikipedia.org/wiki/Tree_of_primitive_Pythagorean_triples |
A tree pod burial is a method of burial in which a body or cremated remains are placed in a pod that subsequently serves to nourish a tree planted in the soil above it. It is a form of a natural burial that seeks to reduce the environmental impact of traditional body disposal and create a living landmark to memorialize the decedent.
While some cultures have practiced in environmentally friendly burials since ancient times, [ 1 ] the recent increase of green, or natural burials began in the United Kingdom in the 1990s. [ 2 ] The concept of being buried in a special biodegradable pod with the specific goal of growing a tree originated from Italian company Capsula Mundi in 2003, [ 3 ] [ 4 ] and a variant of a pod designed for use as an urn containing cremated remains was released for sale in 2016. [ 5 ] Similar approaches have also been made available by other companies. [ 6 ]
The tree pod burial process is designed to maximize the return of nutrients that make up the human body to the environment. While a full body pod burial is still theoretical, the differences between a full body pod and a pod designed for ashes is similar. In a full body pod, the unenbalmed body is wrapped in a biodegradable plastic or fibers [ 7 ] and then placed a biodegradable or biopolymer pod in a fetal position . The pod is then sealed and buried in the earth in a natural burial site. [ 5 ] A sapling or larger tree is then planted directly on top of the pod to capture the release of the nutrients. Some companies state an older tree specifically chosen to be suitable for the burial location prior to death is better than a seedling or sapling. An older tree is able to better utilize the nutrients that are released as opposed to younger trees that may not be able to capture them as readily. [ 3 ]
A pod designed as a receptacle of cremated ashes would have a similar process to that of a full body pod. The chief difference would be the placement of the ashes instead of a full body. The pod would also have to be designed to decompose slowly so as to not pollute the area or damage the plant life it is designed to nourish. The pH of cremated ashes is extremely alkaline , and also has an increased level of sodium and other nutrient imbalances that is hostile to plant growth. [ 8 ] Capsula Mundi state their product is designed to degrade slowly over time so the remains have time to balance and mix with the soil surrounding the pod and not overwhelm the equilibrium of the environment. [ 9 ] | https://en.wikipedia.org/wiki/Tree_pod_burial |
Tree rearrangements are deterministic algorithms devoted to search for optimal phylogenetic tree structure . They can be applied to any set of data that are naturally arranged into a tree, but have most applications in computational phylogenetics , especially in maximum parsimony and maximum likelihood searches of phylogenetic trees , which seek to identify one among many possible trees that best explains the evolutionary history of a particular gene or species .
The simplest tree-rearrangement, known as nearest-neighbor interchange , exchanges the connectivity of four subtrees within the main tree. Because there are three possible ways of connecting four subtrees, [ 1 ] and one is the original connectivity, each interchange creates two new trees. Exhaustively searching the possible nearest-neighbors for each possible set of subtrees is the slowest but most optimizing way of performing this search. An alternative, more wide-ranging search, subtree pruning and regrafting (SPR), selects and removes a subtree from the main tree and reinserts it elsewhere on the main tree to create a new node. Finally, tree bisection and reconnection (TBR) detaches a subtree from the main tree at an interior node and then attempts all possible connections between edges of the two trees thus created. The increasing complexity of the tree rearrangement technique correlates with increasing computational time required for the search, although not necessarily with their performance. [ 2 ]
SPR can be further divided into uSPR: Unrooted SPR, rSPR: Rooted SPR. uSPR is applied to unrooted trees, and goes like this: break any edge. Join one end of the edge (selected arbitrarily) to any other edge in the tree. rSPR is applied to rooted trees*, and goes: break any edge except the edge leading to the root node. Join one end of the edge (specifically: the end of the edge that is FURTHEST from the root) and attach it to any other edge of the tree. [ 3 ]
* In this example the root of the tree is marked by a node of degree one, meaning that all nodes in the tree have either degree 1 or degree 3. An alternative approach, used in Bordewich and Semple, is to consider the root node to have degree 2, and to have a special rule for rSPR.
The number of SPR [ 4 ] or TBR [ 5 ] moves needed to get from one tree to another can be calculated by producing a Maximum Agreement Forest comprising (respectively) rooted or unrooted trees. This problem is NP hard but Fixed Parameter Tractable.
The simplest type of tree fusion begins with two trees already identified as near-optimal; thus, they most likely have the majority of their nodes correct but may fail to resolve individual tree "leaves" properly; for example, the separation ((A,B),(C,D)) at a branch tip versus ((A,C),(B,D)) may be unresolved. [ 1 ] Tree fusion swaps these two solutions between two otherwise near-optimal trees. Variants of the method use standard genetic algorithms with a defined objective function to swap high-scoring subtrees into main trees that are high-scoring overall. [ 6 ]
An alternative strategy is to detach part of the tree (which can be selected at random, or using a more strategic approach) and to perform TBR/SPR/NNI on this sub-tree. This optimized sub-tree can then be replaced on the main tree, hopefully improving the p-score. [ 7 ]
To avoid entrapment in local optima, a 'simulated annealing' approach can be used, whereby the algorithm is occasionally permitted to entertain sub-optimal candidate trees, with a probability related to how far they are from the optimum. [ 7 ]
Once a range of equally-optimal trees have been gathered, it is often possible to find a better tree by combining the "good bits" of separate trees. Sub-groups with an identical composition but different topology can be switched and the resultant trees evaluated. [ 7 ] | https://en.wikipedia.org/wiki/Tree_rearrangement |
A tree wrap or tree wrapping is a wrap of garden tree saplings , roses , and other delicate plants to protect them from frost damage (e.g. frost cracks or complete death). In the past it was made of straw ( straw wrap ) . Now there are commercial tree wrap materials, such as crepe paper or burlap tapes. Tree wrapping is also used to prevent saplings from sunscald and drying of the bark. A disadvantage of tape wrapping is dampness under the wrapping during rainy seasons. [ 1 ] | https://en.wikipedia.org/wiki/Tree_wrap |
A treebog is a type of low-tech compost toilet . It consists of a raised platform above a compost pile surrounded by densely planted willow trees or other nutrient-hungry vegetation. It can be considered an example of permaculture design, as it functions as a system for converting urine and feces to biomass , without the need to handle excreta.
Defecating in nature is frowned upon in most countries, as it pollutes the environment and causes health problems. High levels of open defecation are linked to high child mortality , poor nutrition , poverty , and large disparities between the rich and the poor. [ 1 ] [ 2 ] : 11 Human faeces normally take about a year to biodegrade outdoors. [ 3 ] In the UK, a system like this is potentially legal, so long as it not in a public place, i.e. on a large private estate. [ 4 ]
The term "Treebog" was coined by Jay Abrahams. Bog is a British English slang word for toilet , not to be confused with its other meaning of wetland .
The treebog is a simple method of composting wastes. Abrahams claims that from 1995 to 2011, around 1500 treebogs may have been built in Britain. [ 5 ]
In 2011, Abrahams claimed that the treebog had attracted the attention of NGOs and aid workers who hope to develop its potential for shanty towns or refugee camps - anywhere that water is scarce and the population pressure on resources is high. [ 5 ]
A treebog is simply a controlled compost heap whose function has been enhanced by use of moisture or nutrient-hungry trees. They use no water, purify waste as they create a biomass resource, and also contain the organic waste material, thus preventing the spread of disease.
The main requirement is that the planted species should be nutrient-hungry. It is a bonus if they can be harvested or pollarded for productive uses, e.g. willow cultivars. Apart from willows, mint will thrive around a treebog. If left unmanaged, a treebog will soon be surrounded by weed species, such as nettles.
Both the solids and liquids are deposited within the treebog base, where the solids compost and the liquids soak through the soil. The roots and associated mycorrhizal species allow the nitrogen to be absorbed. The faeces should be well ventilated to allow aerobic decomposition.
A seating platform/cubicle is mounted at least one meter high. The area beneath the seating platform is enclosed by two layers of chicken wire or plastic mesh , which act as an effective child-proof barrier and allows air to circulate through the compost heap. Plastic mesh or chicken wire coated in plastic would prevent problems with rusting.
Sawdust, straw, woodchip, ash or other high-carbon matter is used to cover the excrement and balance the high nitrogen content of the urine. One design uses bran to help mitigate the odours. [ 6 ]
The space between the two layers of mesh is stuffed with straw, which acts as a wick to help sop up excess urine, preventing the likelihood of odour problems due to incomplete biological absorption of the nitrogen from the urine. The straw-filled wire also enables the pile to be well-aerated whilst acting as a visual screen for the first year’s use.
The structure is surrounded by two closely planted rows of Salix viminalis or other willow cuttings; this living wall of willow can then be woven into a hurdle-like structure and its annual growth can be harvested. | https://en.wikipedia.org/wiki/Treebog |
Treedom is a platform that allows anyone to plant trees in different countries of the world. [ 1 ] [ 2 ] [ 3 ] [ 4 ] Treedom also allows the 'owner's of the planted trees to receive images of the trees that have just been planted along with its GPS coordinates and updates from the project it is part of. [ 5 ] [ 6 ] [ 7 ]
The project developer who applies to become a "tree planter" has to make a formal request in the form of the "project". The submission is reviewed to exclude projects that require cutting other trees to make the space, violate the law, consider planting invasive species and the like. The farmer confirms the fact of planting the tree with the help of the specialized mobile application that captures both photo and GPS coordinates. These reports are then manually checked, verifying the location, quality of the image and species of the planted tree. Trees that do not take root for the first three years must be replanted. Treedom claims inspecting in place at least 25% of these projects per year. Additionally, 5% of the planted trees are put aside as so called “Project Reserve” that should cover possible loss of trees and the related CO 2 absorption (like trees that die after the third year, for which a substitution is not provided). [ 8 ] A user can then order planting a selected tree online, paying as for a web purchase.
Treedom works in collaboration with small collective of farmers, local community and NGO across different countries including Kenya , [ 9 ] Tanzania , [ 10 ] Guatemala , [ 11 ] Ecuador , [ 12 ] Italy , [ 13 ] Haiti , Nepal , [ 14 ] Pakistan , [ 15 ] Peru , Italy , [ 16 ] etc.
For the trees which bear fruits, the fruits are reckoned to belong to the farmers who planted it. [ 17 ] [ 18 ] [ 1 ] The farmer planting a tree remains responsible for its growth and take care where the organization provides support by arranging agroforestry training and income opportunities. [ 19 ] [ 20 ] The platform is known to promote welfare of farmers, including female farmers for which it announced ' Mothers day campaign ' during March 2020 with the aim to spread awareness about the difficulties faced by female agricultural workers. [ 21 ] [ 22 ]
When a person chooses to own a certain tree, the sapling is planted by the local farmer on behalf of the person. [ 23 ] [ 24 ] The updates of the sapling are provided using GPS location and photographs on regular basis via webpage dedicated to this plant. [ 25 ] [ 26 ] Apart from this, the platform also allows a tree to be gifted. [ 27 ] [ 28 ] It is also possible to view the local weather data in the vicinity of the tree.
Treedom was founded in the year 2010 by Tommaso Speroni and Federico Garcea in Florence , Italy . [ 29 ] [ 30 ] [ 7 ] The objective of the organization was described as The Sustainable Development Goals , [ 31 ] [ 32 ] which includes counter-deforestation , protecting biodiversity , preventing soil erosion , combating CO 2 emission on one side and sustainable food production and income security for farmers on the other side. [ 33 ] [ 34 ] [ 35 ] As in April 2021, Treedom has been reported to collaborate with 75000 farmers and plant more than 2 million trees [ 36 ] across Asia , [ 37 ] Africa [ 38 ] [ 39 ] and Central and South America . [ 40 ] [ 41 ] [ 42 ] [ 43 ] | https://en.wikipedia.org/wiki/Treedom |
Treethanol is an ethanol fuel (more precisely cellulosic ethanol ) made from trees. [ 1 ]
The biofuel is a contender in the race to find an energy alternative to fossil fuels. Proponents of Treethanol claim that its energy yield is higher compared to the energy required for production when compared with more common sources of ethanol i.e. sugar cane and corn. [ 2 ]
Cellulosic ethanol is produced using the lignocellulose biomass that comprises much of the mass of plants. [ 3 ] Essentially at the core of the plant material is cellulose, which can be broken down into simple carbohydrate sugars. After these sugars have been extracted, they can be then be fermented into an alcohol, which is known as ethanol . [ 3 ] The most widely used and promising means of creating cellulosic ethanol is called the cellulolysis process . The process consists of hydrolysis on pretreated lignocellulosic materials. Then enzymes are used to break down cellulose into glucose. This glucose is then fermented and distilled. [ 2 ] The pretreatment step mentioned above is necessary when processing cellulosic ethanol because the glucose (sugars) are not readily accessible as they are with other ethanol sources such as corn or sugar cane. Rather, the cellulose in wood must be separated from the encapsulating hemicellulose and lignin .
There are three types of pretreatment: physical, chemical, and biological. Physical treatment involves physically reducing wood particle size. This can be accomplished through chipping, grinding, etc. Biological treatments involve the use of microorganisms to break down the wood. This type is considered favorable to physical pretreatments because it consumes far less energy in comparison, but the biological method has not proven to be scalable to an industrial level. The chemical method utilizes an alkaline or otherwise acidic medium to make the cellulose within wood fibers more accessible. This has shown to be the most efficient and has the lowest energy cost. [ 4 ]
Forest trees make up more than 90% of the total terrestrial biomass while performing functions such as carbon sequestration , producing oxygen, and promoting biodiversity. Trees are a promising source of ethanol because they grow all year round, require significantly less fertilizer and water and contain far more carbohydrates (the chemical precursors of ethanol) than food crops (like corn) do. [ citation needed ]
Poplar, Willow, and Eucalyptus tree are emerging as favorites in the process of creating Treethanol. [ 5 ] This is due to their ability to grow at a fast rate in many parts of the world. [ 6 ]
Treethanol is not an energy source that promises to power houses in the future, but rather it can be taken advantage of in applications where combustion engines are used. Approximately 85% of US energy consumption is produced from fossil fuels such as natural gas, coal, and oil. With China, India, and other rapidly developing nations increasing their demand for fossil fuels, the world’s total energy use is expected to grow by 57% over the next 20 years. [ 2 ] It is estimated that the U.S. alone uses 140 billion gallons of fuel per year for transportation alone. [ 7 ] Not only can Treethanol be mixed with ordinary fuels, it can also be burned directly in modified engines to greatly reduce greenhouse gas emissions. [ 2 ]
Cellulosic ethanol is an environmentally friendly and renewable transportation fuel that can be produced from forest biomass. Trees are a particularly promising feedstock because they grow all year round, require vastly less fertiliser and water and contain far more carbohydrates (the chemical precursors of ethanol) than food crops do. [ 8 ] Also, compared to corn ethanol, cellulosic biofuel does not require the same quantity of fertilizers, pesticides, energy, or water to grow. [ 9 ] The most important attribute of this type of ethanol is, like all types of ethanol, it is renewable. If you want or need to make more of it, you just grow more trees. [ 1 ]
The development of all types of biofuel, including Treethanol can be of importance for countries looking to decrease their dependence on petroleum, especially those countries that import most of their petroleum and also have plenty of crop/forest land such as New Zealand and Sweden. [ 1 ] [ 10 ]
An important issue is whether Treethanol is a superior alternative to more common forms of ethanol like corn based. The general consensus in an article by Hoover, F., & Abraham, J. (2009), is that most forms of cellulosic ethanol have the potential to yield higher energy outputs and be more sustainable than corn ethanol. They also note that while cellulosic ethanol does not necessarily yield more energy than say, corn based ethanol per unit of measurement, it requires far less energy inputs to produce which could give it a far higher net energy yield at the end of processing. The findings that lignocellulosic biomass has a far greater productivity yield than traditional biofuel sources is supported by Papini, A., & Simeone, M. (2010).
Responsible forestry practices do not contribute to greenhouse gases because the forest is allowed to regenerate following fiber harvesting. For this reason wood can be considered to be an essentially carbon-neutral source of energy. [ citation needed ]
While it seems reasonable that Treethanol could be an alternative to current ethanol types, it has one flaw, which is the extra processing needed to break down the tough cellulose and hemicellulose within the walls of the cell to isolate the sugars. [ 1 ] As discussed above in the production section, creating ethanol from the lignocellulose found in tree biomass requires the extra step of “pre-treatment”. It is this pre-treatment that still requires too much energy to make the Treethanol worth the effort.
That being said, many believe that the potential pros far out-weigh the short-term cons. [ 1 ] [ 2 ] The process of growing the tree biomass is energy efficient compared with growing corn or sugar cane for ethanol. However, it also takes longer to grow trees than to grow corn, and so any accurate research on sustainability and crop rotation (even for fast growing trees) requires a long time commitment, which up to now has been hard to find. It has been estimated that this process, including the building of processing plants and then refining of the growing and processing stage could take at least a decade. [ 11 ]
Another drawback to the processing of cellulosic ethanol is that there is little known about the waste/by products from the processing. Of particular concern to some is the biological method of pre-treatment. It is estimated that there is the possibility of producing almost as much (if not more) waste than usable ethanol, with waste products including mold, bacteria, yeast, biological toxins and allergens produced by these microorganisms, enzymes, and other chemicals. [ 12 ] | https://en.wikipedia.org/wiki/Treethanol |
A trefoil (from Latin trifolium ' three-leaved plant ' ) is a graphic form composed of the outline of three overlapping rings, used in architecture , Pagan and Christian symbolism , among other areas. The term is also applied to other symbols with a threefold shape. A similar shape with four rings is called a quatrefoil .
'Trefoil' is a term in Gothic architecture given to the ornamental foliation or cusping introduced in the heads of window-lights, tracery , and panellings, in which the centre takes the form of a three-lobed leaf (formed from three partially overlapping circles). One of the earliest examples is in the plate tracery at Winchester Cathedral (1222–1235). The fourfold version of an architectural trefoil is a quatrefoil .
A simple trefoil shape in itself can be symbolic of the Trinity , [ 1 ] while a trefoil combined with an equilateral triangle was also a moderately common symbol of the Christian Trinity during the late Middle Ages in some parts of Europe, similar to a barbed quatrefoil . Two forms of a trefoil combined with a triangle are shown below:
A dove , which symbolizes the Holy Spirit , is sometimes depicted within the outlined form of the trefoil combined with a triangle.
In architecture and archaeology, a 'trefoil' describes a layout or floor plan consisting of three apses in clover-leaf shape, as for example in the Megalithic temples of Malta .
Particularly in church architecture, such a layout may be called a "triconchos".
The heraldic 'trefoil' is a stylized clover . It should not be confused with the figure named in French heraldry tiercefeuille ("threefoil"), which is a stylized flower with three petals, and differs from the heraldic trefoil in being not slipped. [ 2 ] [ a ]
Symmetrical trefoils are particularly popular as warning and informational symbols. If a box containing hazardous material is moved around and shifted into different positions, it is still easy to recognize the symbol, [ 5 ] while the distinctive trefoil design of the recycling symbol makes it easy for a consumer to notice and identify the packaging the symbol has been printed on as recyclable. Easily stenciled symbols are also favored.
While the green trefoil is considered by many to be the symbol of Ireland, the harp has much greater officially recognized status. Therefore, shamrocks generally do not appear on Irish coins or postage stamps.
A trefoil is also part of the logo for Adidas Originals , which also includes three stripes. | https://en.wikipedia.org/wiki/Trefoil |
Trehalose (from Turkish tıgala – a sugar derived from insect cocoons + -ose) [ 3 ] is a sugar consisting of two molecules of glucose . It is also known as mycose or tremalose . Some bacteria, fungi, plants and invertebrate animals synthesize it as a source of energy, and to survive freezing and lack of water.
Trehalose has high water retention capabilities, and is used in food, cosmetics and as a drug.
Trehalose is a disaccharide formed by a 1,1- glycosidic bond between two α- glucose units. It is found in nature as a disaccharide and also as a monomer in some polymers. [ 4 ] Two other stereoisomers exist: α,β-trehalose, also called neotrehalose , and β,β-trehalose, also called isotrehalose . Neither of these alternate isomers has been isolated from living organisms, but isotrehalose has been was found in starch hydroisolates. [ 4 ]
At least three biological pathways support trehalose biosynthesis . [ 4 ] An industrial process can derive trehalose from corn starch . [ 5 ]
Trehalose is a nonreducing sugar formed from two glucose units joined by a 1–1 alpha bond, giving it the name α- D -gluco pyranosyl-(1→1)-α- D -gluco pyranoside . The bonding makes trehalose very resistant to acid hydrolysis , and therefore is stable in solution at high temperatures, even under acidic conditions. The bonding keeps nonreducing sugars in closed-ring form, such that the aldehyde or ketone end groups do not bind to the lysine or arginine residues of proteins (a process called glycation ). Trehalose is less soluble than sucrose , except at high temperatures (>80 °C). Trehalose forms a rhomboid crystal as the dihydrate, and has 90% of the calorific content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the dihydrate . Anhydrous forms of trehalose can show interesting physical properties when heat-treated. [ clarification needed ]
Trehalose aqueous solutions show a concentration-dependent clustering tendency. Owing to their ability to form hydrogen bonds , they self-associate in water to form clusters of various sizes. All-atom molecular dynamics simulations showed that concentrations of 1.5–2.2 molar allow trehalose molecular clusters to percolate [ clarification needed ] and form large and continuous aggregates. [ 6 ]
Trehalose directly interacts with nucleic acids, facilitates melting of double stranded DNA and stabilizes single-stranded nucleic acids. [ 7 ]
Organisms ranging from bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants have enzymes that can make trehalose. [ 4 ] In nature, trehalose can be found in plants , and microorganisms . In animals, trehalose is prevalent in shrimp, and also in insects , including grasshoppers, locusts, butterflies, and bees, in which trehalose serves as blood-sugar. [ citation needed ] Trehalase genes are found in tardigrades , the microscopic ecdysozoans found worldwide in diverse extreme environments. [ 8 ]
Trehalose is the major carbohydrate energy storage molecule used by insects for flight. [ 9 ] One possible reason for this is that the glycosidic linkage of trehalose, when acted upon by an insect trehalase, releases two molecules of glucose, which is required for the rapid energy requirements of flight. This is double the efficiency of glucose release from the storage polymer starch , for which cleavage of one glycosidic linkage releases only one glucose molecule. [ citation needed ]
The concentrations of both trehalose and glucose in the insect hemolymph are tightly controlled by multiple enzymes and hormones, including trehalase , insulin -like peptides (ILPs and DILPs), adipokinetic hormone (AKH), leucokinin (LK), octopamine and other mediators, thereby maintaining carbohydrate homeostasis by endocrine and metabolic feedback mechanisms. [ 10 ] [ 11 ] [ 12 ] [ 13 ]
In plants, trehalose is seen in sunflower seeds, moonwort , Selaginella plants, [ 14 ] and sea algae. Within the fungi, it is prevalent in some mushrooms, such as shiitake ( Lentinula edodes ), oyster , king oyster , and golden needle . [ 15 ]
Even within the plant kingdom, Selaginella (sometimes called the resurrection plant), which grows in desert and mountainous areas, may be cracked and dried out, but will turn green again and revive after rain because of the function of trehalose. [ 14 ]
The two prevalent theories as to how trehalose works within the organism in the state of cryptobiosis are the vitrification theory, a state that prevents ice formation, or the water displacement theory, whereby water is replaced by trehalose. [ 8 ] [ 16 ]
In bacterial cell wall, trehalose has a structural role in adaptive responses to stress such as osmotic differences and extreme temperature. [ 17 ] Yeast uses trehalose as a carbon source in response to abiotic stresses. [ 18 ] In humans, the only known function of trehalose is as a neuroprotective, which it accomplishes by inducing autophagy and thereby clearing protein aggregates . [ citation needed ]
Trehalose has also been reported for anti-bacterial, anti-biofilm, and anti-inflammatory ( in vitro and in vivo ) activities, upon its esterification with fatty acids of varying chain lengths. [ 19 ]
Trehalose is rapidly broken down into glucose by the enzyme trehalase , which is present in the brush border of the intestinal mucosa of omnivores (including humans) and herbivores. [ 20 ] : 135 It causes less of a spike in blood sugar than glucose. [ 21 ] Trehalose has about 45% the sweetness of sucrose at concentrations above 22%, but when the concentration is reduced, its sweetness decreases more quickly than that of sucrose, so that a 2.3% solution tastes 6.5 times less sweet as the equivalent sugar solution. [ 22 ] : 444
It is commonly used in prepared frozen foods, like ice cream, because it lowers the freezing point of foods. [ 21 ]
Deficiency of trehalase enzyme is unusual in humans, except in the Greenlandic Inuit , where it is present in only 10–15% of the population. [ 23 ] : 197
Five biosynthesis pathways have been reported for trehalose. The most common pathway is TPS/TPP pathway which is used by organisms that synthesize trehalose using the enzyme trehalose-6-phosphate (T6P) synthase (TPS). [ 24 ] Second, trehalose synthase (TS) in certain types of bacteria could produce trehalose by using maltose and another disaccharide with two glucose units as substrates. [ 25 ] Third, the TreY-TreZ pathway in some bacteria converts starch that contain maltooligosaccharide or glycogen directly into trehalose. [ 26 ] Fourth, in primitive bacteria, trehalose glycisyltransferring synthase (TreT) produces trehalose from ADP-glucose and glucose. [ 27 ] Fifth, trehalose phosphorylase (TreP) either hydrolyses trehalose into glucose-1-phosphate and glucose or may act reversibly in certain species. [ 28 ] Vertebrates do not have the ability to synthesize or store trehalose. [ 29 ] Trehalase in humans is found only in specific location such as the intestinal mucosa, renal brush-border, liver and blood. Expression of this enzyme in vertebrates is initially found during the gestation period that is the highest after weaning. Then, the level of trehalase remained constant in the intestine throughout life. [ 30 ] Meanwhile, diets consisting of plants and fungi contain trehalose. Moderate amount of trehalose in diet is essential and having low amount of trehalose could result in diarrhea, or other intestinal symptoms. [ 31 ]
Trehalose is an ingredient, along with hyaluronic acid , in an artificial tears product used to treat dry eye . [ 32 ] [ 18 ] Outbreaks of Clostridioides difficile were initially associated with trehalose, [ 21 ] [ 33 ] [ 34 ] but this finding was disputed in 2019. [ 35 ]
In 2021, the FDA accepted an Investigational New Drug (IND) application and granted fast track status for an injectable form of trehalose (SLS-005) as a potential treatment for spinocerebellar ataxia type 3 (SCA3). [ 36 ] [ 37 ]
In 1832, H.A.L. Wiggers discovered trehalose in an ergot of rye, [ 38 ] and in 1859 Marcellin Berthelot isolated it from Trehala manna , a substance made by weevils and named it trehalose. [ 39 ]
Trehalose has long been known as an autophagy inducer that acts independently of mTOR . [ 40 ] In 2017, research was published showing that trehalose induces autophagy by activating TFEB , [ 41 ] a protein that acts as a master regulator of the autophagy- lysosome pathway. [ 42 ] | https://en.wikipedia.org/wiki/Trehalose |
Trellis coded modulation ( TCM ) is a modulation scheme that transmits information with high efficiency over band-limited channels such as telephone lines . Gottfried Ungerboeck invented trellis modulation while working for IBM in the 1970s, and first described it in a conference paper in 1976. It went largely unnoticed, however, until he published a new, detailed exposition in 1982 that achieved sudden and widespread recognition.
In the late 1980s, modems operating over plain old telephone service ( POTS ) typically achieved 9.6 kbit/s by employing four bits per symbol QAM modulation at 2,400 baud (symbols/second). This bit rate ceiling existed despite the best efforts of many researchers, and some engineers predicted that without a major upgrade of the public phone infrastructure, the maximum achievable rate for a POTS modem might be 14 kbit/s for two-way communication (3,429 baud × 4 bits/symbol, using QAM). [ citation needed ]
14 kbit/s is only 40% of the theoretical maximum bit rate predicted by Shannon's theorem for POTS lines (approximately 35 kbit/s). [ 1 ] Ungerboeck's theories demonstrated that there was considerable untapped potential in the system, and by applying the concept to new modem standards, speed rapidly increased to 14.4, 28.8 and ultimately 33.6 kbit/s.
The name trellis derives from the fact that a state diagram of the technique closely resembles a trellis lattice . The scheme is basically a convolutional code of rates ( r , r +1). Ungerboeck's unique contribution is to apply the parity check for each symbol , instead of the older technique of applying it to the bit stream then modulating the bits. [ clarification needed ] He called the key idea mapping by set partitions . This idea groups symbols in a tree-like structure, then separates them into two limbs of equal size. At each "limb" of the tree, the symbols are further apart. [ clarification needed ]
Though hard to visualize in multiple dimensions, a simple one-dimension example illustrates the basic procedure. Suppose the symbols are located at [1, 2, 3, 4, ...]. Place all odd symbols in one group, and all even symbols in the second group. (This is not quite accurate, because Ungerboeck was looking at the two dimensional problem, but the principle is the same.) Take every other symbol in each group and repeat the procedure for each tree limb. He next described a method of assigning the encoded bit stream onto the symbols in a very systematic procedure. Once this procedure was fully described, his next step was to program the algorithms into a computer and let the computer search for the best codes. The results were astonishing. Even the most simple code (4 state) produced error rates nearly one one-thousandth of an equivalent uncoded system. For two years Ungerboeck kept these results private and only conveyed them to close colleagues. Finally, in 1982, Ungerboeck published a paper describing the principles of trellis modulation.
A flurry of research activity ensued, and by 1984 the International Telecommunication Union had published a standard, V.32, [ 2 ] for the first trellis-modulated modem at 9.6 kilobit/s (2,400 baud and 4 bits per symbol). Over the next several years further advances in encoding, plus a corresponding symbol rate increase from 2,400 to 3,429 baud, allowed modems to achieve rates up to 34.3 kilobits/s (limited by maximum power regulations to 33.8 kilobits/s). Today, the most common trellis-modulated V.34 modems use a 4-dimensional set partition—achieved by treating two two-dimensional symbols as a single lattice. This set uses 8, 16, or 32 state convolutional codes to squeeze the equivalent of 6 to 10 bits into each symbol the modem sends (for example, 2,400 baud × 8 bits/symbol = 19,200 bit/s). | https://en.wikipedia.org/wiki/Trellis_coded_modulation |
Trellis quantization is an algorithm that can improve data compression in DCT -based encoding methods. It is used to optimize residual DCT coefficients after motion estimation in lossy video compression encoders such as Xvid and x264 . Trellis quantization reduces the size of some DCT coefficients while recovering others to take their place. This process can increase quality because coefficients chosen by Trellis have the lowest rate-distortion ratio. Trellis quantization effectively finds the optimal quantization for each block to maximize the PSNR relative to bitrate . It has varying effectiveness depending on the input data and compression method.
This computer science article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Trellis_quantization |
The trematode mitochondrial code (translation table 21) is a genetic code found in the mitochondria of Trematoda .
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V)
This article incorporates text from the United States National Library of Medicine , which is in the public domain . [ 3 ]
This genetics article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Trematode_mitochondrial_code |
In game theory , trembling hand perfect equilibrium is a type of refinement of a Nash equilibrium that was first proposed by Reinhard Selten . [ 1 ] A trembling hand perfect equilibrium is an equilibrium that takes the possibility of off-the-equilibrium play into account by assuming that the players, through a "slip of the hand" or tremble, may choose unintended strategies , albeit with negligible probability .
First define a perturbed game . A perturbed game is a copy of a base game, with the restriction that only totally mixed strategies are allowed to be played.
A totally mixed strategy is a mixed strategy in an n {\displaystyle n} -player strategic game where every pure strategy is played with positive probability.
This is the "trembling hands" of the players; they sometimes play a different strategy, other than the one they intended to play. Then define a mixed strategy profile σ = ( σ 1 , … , σ n ) {\displaystyle \sigma =(\sigma _{1},\ldots ,\sigma _{n})} as being trembling hand perfect if there is a sequence of perturbed games strategy profiles { σ k } k = 1 , 2 , … {\displaystyle \{\sigma ^{k}\}_{k=1,2,\ldots }} that converges to σ {\displaystyle \sigma } such that for every k {\displaystyle k} and every player 1 ≤ i ≤ n {\displaystyle 1\leq i\leq n} the strategy σ i {\displaystyle \sigma _{i}} is the best reply to σ − i k {\displaystyle \sigma _{-i}^{k}} .
Note: All completely mixed Nash equilibria are perfect.
Note 2: The mixed strategy extension of any finite normal-form game has at least one perfect equilibrium. [ 2 ]
The game represented in the following normal form matrix has two pure strategies Nash equilibria , namely ⟨ Up , Left ⟩ {\displaystyle \langle {\text{Up}},{\text{Left}}\rangle } and ⟨ Down , Right ⟩ {\displaystyle \langle {\text{Down}},{\text{Right}}\rangle } . However, only ⟨ U , L ⟩ {\displaystyle \langle {\text{U}},{\text{L}}\rangle } is trembling-hand perfect.
Assume player 1 (the row player) is playing a mixed strategy ( 1 − ε , ε ) {\displaystyle (1-\varepsilon ,\varepsilon )} , for 0 < ε < 1 {\displaystyle 0<\varepsilon <1} .
Player 2's expected payoff from playing L is:
Player 2's expected payoff from playing the strategy R is:
For small values of ε {\displaystyle \varepsilon } , player 2 maximizes his expected payoff by placing a minimal weight on R and a maximal weight on L. By symmetry, player 1 should place a minimal weight on D and a maximal weight on U if player 2 is playing the mixed strategy ( 1 − ε , ε ) {\displaystyle (1-\varepsilon ,\varepsilon )} . Hence ⟨ U , L ⟩ {\displaystyle \langle {\text{U}},{\text{L}}\rangle } is trembling-hand perfect.
However, a similar analysis fails for the strategy profile ⟨ D , R ⟩ {\displaystyle \langle {\text{D}},{\text{R}}\rangle } .
Assume player 2 is playing a mixed strategy ( ε , 1 − ε ) {\displaystyle (\varepsilon ,1-\varepsilon )} . Player 1's expected payoff from playing U is:
Player 1's expected payoff from playing D is:
For all positive values of ε {\displaystyle \varepsilon } , player 1 maximizes his expected payoff by placing a minimal weight on D and maximal weight on U. Hence ⟨ D , R ⟩ {\displaystyle \langle {\text{D}},{\text{R}}\rangle } is not trembling-hand perfect because player 2 (and, by symmetry, player 1) maximizes his expected payoff by deviating most often to L if there is a small chance of error in the behavior of player 1.
For 2×2 games, the set of trembling-hand perfect equilibria coincides with the set of equilibria consisting of two undominated strategies. In the example above, we see that the equilibrium <Down,Right> is imperfect, as Left (weakly) dominates Right for Player 2 and Up (weakly) dominates Down for Player 1. [ 3 ]
There are two possible ways of extending the definition of trembling hand perfection to extensive form games .
The notions of normal-form and extensive-form trembling hand perfect equilibria are incomparable, i.e., an equilibrium of an extensive-form game may be normal-form trembling hand perfect but not extensive-form trembling hand perfect and vice versa.
As an extreme example of this, Jean-François Mertens has given an example of a two-player extensive form game where no extensive-form trembling hand perfect equilibrium is admissible, i.e., the sets of extensive-form and normal-form trembling hand perfect equilibria for this game are disjoint. [ citation needed ]
An extensive-form trembling hand perfect equilibrium is also a sequential equilibrium . A normal-form trembling hand perfect equilibrium of an extensive form game may be sequential but is not necessarily so. In fact, a normal-form trembling hand perfect equilibrium does not even have to be subgame perfect .
Myerson (1978) [ 4 ] pointed out that perfection is sensitive to the addition of a strictly dominated strategy, and instead proposed another refinement, known as proper equilibrium . | https://en.wikipedia.org/wiki/Trembling_hand_perfect_equilibrium |
A tremie is a watertight pipe, usually of about 250 mm inside diameter (150 to 300 mm), [ 1 ] with a conical hopper at its upper end above the water level. It may have a loose plug or a valve at the bottom end. A tremie is usually used to pour concrete underwater in a way that avoids washout of cement from the mix due to turbulent water contact with the concrete while it is flowing. This produces a more reliable strength of the product. [ 2 ] Common applications include:
The tremie concrete placement method uses a vertical or nearly vertical pipe, through which concrete is placed by gravity feed below water level. [ 4 ]
The lower end of the pipe is kept immersed in fresh concrete so that concrete rising from the bottom displaces the water above it, thus limiting washing out of the cement content of the fresh concrete at the exposed upper surface. The upper end of the tremie pipe is kept above the water level during the pour and is provided with a conical hopper for batch loading, or concrete may be pumped into the top of the tremie pipe. Concrete must be poured at a rate which avoids setting in the tremie. Admixtures may be used to control setting time , slump and workability . Vibration and jerking of the pipe may be applied to encourage slumping and levelling of the upper surface of the pour, and the tremie may need to be raised occasionally during the pour so that the bottom end is not too deeply embedded, but the pipe must not be moved sufficiently to break clear of the mound and expose the bottom opening to the water, as this would allow washout of cement. [ 5 ]
The tremie pipe is usually made up of short pipe sections of about 250 mm inside diameter joined by screw thread with O-ring seal, or by gasketed flanges, so that the length can be adjusted during the pour without getting the top of the pipe below the water or removing the bottom end from below the surface of the poured concrete. To facilitate management of pipe length it may be built up from 1m to 3.5m sections. The tremie is often supported by a working platform above the water level, with a conical hopper at its upper end above the water level.
Various types of foot valve may be used to shut off flow while moving the pipe when pouring small volumes in disjoint areas, where it is impracticable to maintain immersion of the nozzle in the fresh concrete, as in repair work. One type is a rubber sleeve inside a section of the pipe which can be pneumatically inflated to occlude the bore over a short distance. Another uses a hydraulically operated plate moved across the flow. [ 6 ]
The tremie can be inclined to control flow rate when working in small or shallow volumes, where it may be impossible to keep the nozzle adequately immersed. A flexible hose section at the nozzle can facilitate accurate placement by a diver. [ 6 ]
A foam rubber 'pig' or a plug made from cement bags may be used to plug the pipe while introducing the first batch of concrete. [ 1 ] [ 7 ]
To start placement, the tremie pipe is first lowered into position. Air and water must be kept out of the tremie during placement by keeping the pipe full of concrete at all times. This is facilitated if the hopper capacity is at least equal to the volume of the pipe. When initially charging the tremie, a wad of empty cement bags or a foam rubber plug known as a pig may be stuffed into the pipe to keep the flow under control while the first concrete forces the plug down the pipe and displaces the water. The pig will be pushed out of the bottom end of the pipe and will float to the surface. The discharge opening must be kept well immersed in the placed concrete, allowing flow from within the placement. 1.5 metres (5 ft) of embedment should be maintained as a minimum if possible. This can be measured by finding the level of the concrete surface below the top of the pipe with a weighted tape and subtracting from the known length of the tremie. It is critically important to concrete quality that the tremie discharge remains well embedded in the concrete. As the pour progresses, if flow slows or stops, the discharge opening is raised so that the head in the pipe can maintain flow. Continuous flow is desirable if possible. [ 1 ] [ 7 ] The tremie should be raised at about the same rate that the concrete level rises, and the discharge end of the pipe must remain embedded in the fresh concrete deeply enough to prevent water from flowing into the pipe and causing dilution or segregation of the concrete. [ 2 ]
If it is necessary to move the tremie laterally, it is better to lift it out vertically, plug it and start a new pour at the new position than to drag it sideways through freshly placed concrete. If the area of the pour is too large to manage from a single point, it is better to use several tremies in parallel than to shift a single tremie around. A spacing between tremies of between 3.5–5 m (11–16 ft), and a distance of about 2.5 m (8 ft) from the formwork has been recommended. The risk of segregation and uneven setting can be minimised by providing a continuous flow of concrete through all the tremies to maintain a moderately even top surface. [ 7 ]
Concrete for tremie placement should be fluid but resistant to segregation, with a very high slump of about 150 to 200 mm (6 to 8 in), [ 8 ] typically achieved by adding superplasticizers. [ 2 ] | https://en.wikipedia.org/wiki/Tremie |
Trencadís ( Catalan pronunciation: [tɾəŋkəˈðis] ), also known as pique assiette , broken tile mosaics , bits and pieces , memoryware , and shardware , is a type of mosaic made from cemented-together tile shards and broken chinaware. [ 1 ] [ 2 ] It is commonly associated with Antoni Gaudi (see below). Glazed china and ceramics tend to be preferred, glass is sometimes mixed in as well, as are other small materials like buttons and shells. Artists working in this form may create random designs, pictorial scenes, geometric patterns, or a hybrid of any of these. [ 1 ]
Although as a folk art the method itself may be centuries old, the two most commonly used terms are both of modern origin. Trencadís, a Catalan term that means 'broken up', and by extension, 'broken up tiles', is the name for this method as it was revived in early 20th century Catalan Modernisme , while pique assiette is a more general name for the technique that comes from the French language. In French, pique assiette ('plate thief') is a term for a scrounger or sponger, and thus, as a name for this mosaic technique, it refers to the recycled or 'scrounged' nature of the materials. [ 1 ] [ 2 ]
Traditional mosaics, such as classical Roman floors, are made up of individual tesserae , usually small cubes that are uniformly shaped and designed for their intended use. Trencadís differs in that the tesserae are nonuniform pieces broken from tiles and chinaware originally made for other uses. Trencadís is thus a form of bricolage , found object art, or recycled art.
There are two main methods for trencadís. In the first, an initial design is drawn up and the ceramic fragments are carefully fitted into the design; in this case, the mosaic is only cemented together once all of the fragments have been placed. Alternatively, an artist may spontaneously arrange fragments without a prior design; here the success of the finished work depends greatly on their improvisation skills.
The Catalan modernist architects Antoni Gaudí [ 3 ] and Josep Maria Jujol used trencadís in many projects, among which Barcelona 's Parc Güell (1900–1914) is probably the most famous. Gaudí's first use of this technique was at the Güell Pavilions , where the sinuous architecture forced him to break the tiles in order to cover the curved surfaces. [ 4 ]
Gaudí tended to create patterns with his trencadís work, and he leaned towards brightly colored glazed ceramic shards. He often used discarded pieces of ceramic tile collected from the factory Pujol i Bausis located in Esplugues de Llobregat , as well as pieces of white ceramic from broken cups and plates discarded by other Spanish manufacturers. [ citation needed ]
The Valencian architect Demetrio Ribes used trencadís extensively for decoration in the hall of Valencia North Station in 1907.
In France, the term pique assiette is most closely associated with Raymond Edouard Isidore (1900–1964) a French graveyard sweeper and folk artist. Starting in the late 1930s, he spent 30 years covering both the inside and outside of his house as well as his furniture and his garden walls with mosaics. [ 1 ] [ 5 ] He found his materials in the surrounding fields and quarries, in the public dump, and at auctions. [ 1 ] This habit of scavenging earned him the nickname "pique assiette" later shortened to "picassiette". [ 5 ]
Isidore, a very religious man, created many of his mosaic scenes with Christian personages and symbols. [ 6 ] He also built a "sweeper's throne" and a "sweeper's tomb" covered in pique assiette. [ 6 ] As the mosaics expanded, the project became more widely known, and in 1954, Pablo Picasso visited Isidore's house. [ 6 ] Today, the house is a tourist attraction near Chartres known as "Maison Picassiette". [ 1 ]
The Watts Towers in Los Angeles were built over a period of 30 years by Simon Rodia , a construction worker and tile mason. Begun in 1921, the 17 interconnected towers were decorated with fragments of porcelain, tile, glass, seashells and other found objects. Rodia built them without a premade plan, using damaged pieces from local tile companies and materials scavenged by neighborhood children.
A contemporary example is the Bridge of the Dragon, which crosses the Guadaíra River at Alcalá de Guadaíra . [ 7 ] The bridge's support structure emulates a dragon's body and is covered in trencadís. [ 7 ] Designed by engineer José Luis Manzanares, it was directly inspired by Gaudí's dragon fountain in Parc Güell. [ 7 ]
A related form is the memory jug , an American folk art form that memorializes the dead. [ 8 ] The memory jug is a vessel with a mosaic-like surface decoration of glass and ceramic shards, seashells, trinkets, coins and other small objects, especially objects associated with a specific dead person. [ 8 ] [ 9 ] Most known examples date back no further than the early 20th century. [ 8 ] | https://en.wikipedia.org/wiki/Trencadís |
Trench shields (also called trench boxes or trench sheets ) are steel or aluminum structures used to avoid cave-ins and protect utility workers while performing their duties within a trench . They are customarily constructed with sidewalls of varying thicknesses held apart by steel or aluminum spreaders. Spreaders can be interchanged to match the width of the trench. The different materials and building designs lead to a variety of depth ratings: the depth of a trench that the shield can withstand a collapse without buckling. Depth ratings are determined by registered professional engineers . [ clarification needed ] [ citation needed ]
A shield should not be confused with a shore. While they may serve a similar function, trench shoring is a different physical application that holds up the walls of a trench to prevent collapse. [ 1 ]
In the US, use of a trench shield is governed by OSHA 29 CFR Part 1926.650-.652 Subpart P-Excavations. | https://en.wikipedia.org/wiki/Trench_shield |
A trencher is a piece of construction equipment used to dig trenches , especially for laying pipes or electrical cables , for installing drainage , or in preparation for trench warfare . Trenchers may range in size from walk-behind models, to attachments for a skid loader or tractor , to very heavy tracked heavy equipment .
Trenchers come in different sizes and may use different digging implements, depending on the required width and depth of the trench and the hardness of the surface to be cut.
A wheel trencher or rockwheel has a toothed metal wheel. It is cheaper to operate and maintain than chain-type trenchers. It can work in hard or soft soils, either homogeneous (compact rocks, silts, sands) or heterogeneous (split or broken rock, alluvia, moraines). This is particularly true because a cutting wheel works by clearing the soil as a bucket-wheel does, rather than like a rasp (chain trencher). Consequently, it will be less sensitive to the presence of blocks in the soil. They are also used to cut pavement for road maintenance and to gain access to utilities under roads.
Due to its design the wheel may reach variable cutting depths with the same tool, and can keep a constant soil working angle with a relatively small wheel diameter (which reduces the weight and therefore the pressure to the ground, and the height of the unit for transport).
The cutting elements (6 to 8 depending on the diameter) are placed around the wheel, and bear the teeth which are more or less dense depending on the ground they will encounter. These tools can be easily changed manually, and adjusted to allow different cutting widths on the same wheel. The teeth are placed in a semi-spherical configuration to increase the removal of the materials from the trench. The teeth are made of high strength steel ( HSLA steel , tool steel or high speed steel ) or cemented carbide . When the machine is under heavy use, the teeth may need to be replaced frequently, even daily.
A system of spacers and ejectors allows the excavated materials to be moved away from the edges of the trench to avoid possible “recycling”.
Wheel trenchers may be mounted on tracks or rubber tires.
A chain trencher cuts with a digging chain or belt that is driven around a rounded metal frame, or boom which resembles a giant chainsaw . This type of trencher can cut ground that is too hard to cut with a bucket-type excavator , and can also cut narrow and deep trenches.
The angle of the boom can be adjusted to control the depth of the cut. To cut a trench, the boom is held at a fixed angle while the machine creeps slowly.
The chain trencher is used for digging wider trenches (telecommunication, electricity, drainage, water, gas, sanitation, etc.) especially in rural areas. The excavated materials can be removed by conveyor belt reversible either on the right or on the left side.
There are various methods for excavating trenches in rock – principally drill and blast, hydraulic breakers and chain trenchers. Selection of a trench excavation method must take into account a range of rock and machine properties. It is suggested that the advantages of using chain trenchers in suitable rock outweigh the limitations and may have cost benefits and fewer adverse environmental effects compared with alternative methods. [ 1 ]
A micro trencher is a "small rockwheel" specially designed for work in urban areas. It is fitted with a cutting wheel that cuts a microtrench with smaller dimensions than can be achieved with conventional trench digging equipment.
Microtrench widths range from about 30 to 130 mm (1.2 to 5.1 in) with a depth of 500 mm (20 in) or less. These machines are sometimes radio-controlled.
With a micro trencher, the structure of the road is maintained and there is no associated damage to the road. Owing to the reduced trench size, the volume of waste material excavated is also reduced. Micro trenchers are used to minimize traffic or pedestrian disturbance during network laying. For this reason they are often used to install lines such as fiber optic cables in public spaces. A micro trencher can work on sidewalks or in narrow streets of cities, and can cut harder ground than a chain trencher, including cutting through solid stone. They are also used to cut pavement for road maintenance and to gain access to utilities under roads.
Landscapers and lawn care specialist may use a portable trencher to install landscape edging and irrigation lines. These machines are lightweight (around 200 pounds) and are easily maneuverable compared to other types of trenchers. The cutting implement may be a chain or a blade similar to a rotary lawn mower blade oriented so that it rotates in a vertical plane.
Another alternative are handheld trenchers that look similar to a chainsaw, weigh 20Kg (45lbs) or less, and can trench 0-700 mm (0-27 inches ) deep and a minimum of 50 mm (2 inches) wide.
A tractor-mount trencher is a trenching device which needs a creeping gear tractor to operate. This type of trenchers is another type of chain trencher. The tractor should be able to go as slowly as the trencher's trenching speed.
In August 2023, tractor-mounted trenchers were revealed to be in use by the Ukrainian Ground Forces to dig trenches at a rapid pace. The Ukrainians were reportedly using these to secure the territory they captured in their 2023 counteroffensive . [ 2 ]
A trencher may be combined with a drainage pipe or geotextile feeder unit and backfiller, so drain or textile may be placed and the trench filled in one pass. | https://en.wikipedia.org/wiki/Trencher_(machine) |
Trevor Alleyne Thorpe (October 18, 1936 – May 18, 2020) was a plant biotechnologist and professor emeritus at the University of Calgary .
Thorpe was born in Bridgetown , Barbados , to parents Mitchell and Violet (née Alleyne) Thorpe. After graduating from Harrison College in Barbados in 1953, he was awarded a Jawaharlal Nehru Scholarship to pursue his bachelor's degree at the Allahabad Agricultural Institute in Allahabad, India from 1956 to 1960. He continued his graduate studies as a Fulbright Scholar at the University of California, Riverside , where he earned his Ph.D. under doctoral advisor Toshio Murashige . [ 2 ]
Thorpe began his academic career as an assistant professor at the University of Calgary in 1969. While at the University of Calgary, he held various positions, including Head of the Department of Biological Sciences and Assistant and Associate Dean. Thorpe was named professor emeritus [ 3 ] and retired in 2000.
Throughout his career, Thorpe published over 220 scientific works, achieving an h -index of 70. His research was focused on the physiological aspects of plant morphogenesis using explants—excised pieces of plant parts—cultured in vitro . This work contributed significantly to the fundamental understanding of organized plant development both in vivo and in vitro . In his later work, he has made extensive contributions to conifer biotechnology. One of his books, Plant Tissue Culture: Methods and Applications in Agriculture was described as an "essential reference for all plant tissue culturists in the pre-internet era". [ 2 ]
Thorpe was the president and chair for the International Association for Plant Biotechnology (IAPB) from 1974 to 1978. He also played a leading role for the development of the Society for In Vitro Biology (SIVB) in the USA, for which he was award the Lifetime Achievement Award in 2004. [ 1 ] He was the founding Editor-in-Chief of the scientific journal In Vitro Cellular & Developmental Biology – Plant and served on the editorial boards of several other scientific journals, including Plant Cell Tissue and Organ Culture , Tree Physiology , Phytomorphology , and Physiologia Plantarum . [ 2 ] | https://en.wikipedia.org/wiki/Trevor_A._Thorpe |
Trevor Lawley FMedSci is a Faculty member and Senior Group Leader in the Host-Microbiota Interactions Lab at the Wellcome Sanger Institute (WSI) . He is also co-founder and Chief Scientific Officer of the biotech company Microbiotica .
During his career, Lawley has pioneered the application of high throughput genomic and culturing approaches to characterise enteric pathogens and investigate the microbiomes contained on and within host organisms, during periods of health and disease.
Lawley received his bachelor's degree in Biology in 1997 from Acadia University . He then studied for a PhD at the University of Alberta , in the laboratories of Diane Taylor and Laura Frost, where he studied the mechanisms that pathogenic bacteria use to disseminate antibiotic resistance genes. [ 1 ] After his PhD, Trevor was awarded a Canadian Institutes of Health Research post-doctoral fellowship to work in the Laboratories of Stanley Falkow and Denise Monack at Stanford University , where he studied the impact of antibiotic treatment on Salmonella disease and transmission. [ 2 ]
In 2007 Lawley received a Royal Society of London Award to start a research programme on Clostridioides difficile disease and transmission at the Wellcome Sanger Institute . In 2010, he was appointed as a Career Development Fellow in the Sanger Institute Faculty and was promoted to Faculty Group Leader in 2014 and a Senior Group Leader in 2021. Lawley chairs the Wellcome Sanger Institute International Fellows programme , which focuses on empowering scientists from Low- and Middle-Income Countries through access to cutting-edge genomic technologies and training.
In December 2016, Lawley, together with Gordon Dougan and Mike Romanos, co-founded the biotech company Microbiotica through £12M seed funding from Cambridge Innovation Capital , IP Group and Seventure . Microbiotica develops Live Biotherapeutic Products , biomarkers and microbiome-based technologies focused on autoimmune diseases and cancers . In 2018, Microbiotica entered into a collaboration with Genentech to discover, develop and commercialise inflammatory bowel disease (IBD)biomarkers, targets and medicines. [ 3 ] In 2020, Microbiotica entered into a partnership with Cambridge University Hospitals and Cancer Research UK to discover and develop biomarkers and medicines for cancer immunotherapy patients with melanoma, renal cell carcinoma or lung cancer. [ 4 ] In March 2022, Microbiotica secured Series B funding to perform two phase 1 clinical studies for treatment of patients with melanoma ( MELODY-1, NCT06540391 ) or ulcerative colitis ( COMPOSER-1, NCT06582264 ). The two clinical trials started in 2024. [ 5 ] [ 6 ]
Lawley leads the Host-Microbiota Interactions Lab at the Sanger Institute, which explores the relationship between humans and the bacteria and viruses that collectively form their microbiome. [ 7 ]
Lawley and his team use a range of methods and tools, including large scale metagenomic analysis, genetics, mouse and cellular models, state-of-the art microbial culturing , transcriptomics , proteomics and machine learning , to investigate the microbial communities associated with human health and a range of developmental disorders, diseases and poorly understood syndromes. They have a particular interest the roles of the microbiome in infectious disease, autoimmune disease, cancer and childhood developmental disorders. Their work has pioneered concepts, analytical tools and methodologies that, through data- and hypothesis-driven approaches, have led to foundational discoveries and enabled translation of medicines and diagnostics from the human microbiome.
Lawley and his team overturned the "great plate count anomaly dogma" , long held in microbial ecology , by demonstrating the majority of the human gut microbiota is culturable. This breakthrough involved bacterial culturing, biobanking and genome sequencing at scale, leading to the development of fast, affordable, yet sophisticated, high-resolution gut microbiome analysis. [ 8 ] [ 9 ] [ 10 ] A major outcome of biobanking pure cultures has been experimental testing of biological hypotheses derived from metagenomic analysis, which moves the field towards studies of causation and enables the realisation of microbiome derived medicines.
They focus on several key areas including:
Lawley’s group has authored over 100 papers . Their work is regularly covered in the scientific and popular press. [ 32 ] [ 33 ]
Lawley was elected as a Fellow of the Academy of Medical Sciences in 2023. [ 34 ] In 2015 Lawley received the Peggy Lillis Foundation “Innovator Award” for Pioneering Work on Live Biotherapeutics. | https://en.wikipedia.org/wiki/Trevor_Lawley |
Tri-Power was the name for an arrangement of three two-barrel carburetors [ 1 ] installed on large performance V8s offered by the Pontiac Division of General Motors in the late 1950s and 1960s. [ 2 ]
Three individual Rochester 2G carburetors were arranged inline on the intake manifold, the center one operating normally and the outer two acting as secondaries, or "dumpers", for full throttle performance. Tri-Power often included a hood bulge to accommodate the carburetor set-up and identifying badging on the vehicle's exterior.
Tri-Power as original equipment on classic Pontiacs often raises their value today. Tri-Power was offered by GM's Oldsmobile and Chevrolet divisions, with near-identical options for Chrysler , and Ford , all popularly referred to as "Tri power", "tri-power" and related variations of the original General Motors/Pontiac term.
This article about an automotive part or component is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Tri-Power |
Dmitri Mendeleev published a periodic table of the chemical elements in 1869 based on properties that appeared with some regularity as he laid out the elements from lightest to heaviest. [ 1 ] When Mendeleev proposed his periodic table, he noted gaps in the table and predicted that then-unknown elements existed with properties appropriate to fill those gaps. He named them eka-boron, eka-aluminium, eka-silicon, and eka-manganese, with respective atomic masses of 44, 68, 72, and 100.
To give provisional names to his predicted elements, Dmitri Mendeleev used the prefixes eka - / ˈ iː k ə -/ , [ note 1 ] dvi - or dwi- , and tri -, from the Sanskrit names of digits 1, 2, and 3, [ 3 ] depending upon whether the predicted element was one, two, or three places down from the known element of the same group in his table. For example, germanium was called eka-silicon until its discovery in 1886, and rhenium was called dvi- manganese before its discovery in 1926.
The eka- prefix was used by other theorists, and not only in Mendeleev's own predictions. Before the discovery, francium was referred to as eka-caesium , and astatine as eka-iodine . Sometimes, eka- is still used to refer to some of the transuranic elements , for example, eka- radium for unbinilium . However, the current official IUPAC practice is to use a systematic element name based on the atomic number of the element as the provisional name, instead of being based on its position in the periodic table as these prefixes require.
The four predicted elements lighter than the rare-earth elements , eka- boron ( Eb , under boron, B, 5), eka- aluminium ( Ea or El , [ 4 ] under Al, 13), eka- manganese ( Em , under Mn, 25), and eka- silicon ( Es , under Si, 14), proved to be good predictors of the properties of scandium (Sc, 21), gallium (Ga, 31), technetium (Tc, 43), and germanium (Ge, 32) respectively, each of which fill the spot in the periodic table assigned by Mendeleev.
The names were written by Dmitri Mendeleev as экаборъ ( ekabor ), экаалюминій ( ekaaljuminij ), экамарганецъ ( ekamarganec ), and экасилицій ( ekasilicij ) respectively, following the pre-1917 Russian orthography .
Initial versions of the periodic table did not distinguish rare earth elements from transition elements , helping to explain both why Mendeleev's predictions for heavier unknown elements did not fare as well as those for the lighter ones and why they are not as well known or documented.
Scandium oxide was isolated in late 1879 by Lars Fredrick Nilson ; Per Teodor Cleve recognized the correspondence and notified Mendeleev late in that year. Mendeleev had predicted an atomic mass of 44 for eka-boron in 1871, while scandium has an atomic mass of 44.955907.
In 1871, Mendeleev predicted [ 4 ] the existence of a yet-undiscovered element he named eka-aluminium (because of its proximity to aluminium in the periodic table ). The table below compares the qualities of the element predicted by Mendeleev with actual characteristics of gallium, which was discovered, soon after Mendeleev predicted its existence, in 1875 by Paul Emile Lecoq de Boisbaudran .
Technetium was isolated by Carlo Perrier and Emilio Segrè in 1937, well after Mendeleev's lifetime, from samples of molybdenum that had been bombarded with deuterium nuclei in a cyclotron by Ernest Lawrence . Mendeleev had predicted an atomic mass of 100 for eka-manganese in 1871, and the most stable isotopes of technetium are 97 Tc and 98 Tc. [ 5 ]
Germanium was isolated in 1886 and provided the best confirmation of the theory up to that time, due to its contrasting more clearly with its neighboring elements than the two previously confirmed predictions of Mendeleev do with theirs.
The existence of an element between thorium (90) and uranium (92) was predicted by Mendeleev in 1871. In 1900, William Crookes isolated a radioactive material deriving from uranium that he could not identify, which was later proven to be mixture of 234 Th and 234m Pa. Protactinium-234m (named "brevium") was identified in Germany in 1913, [ 6 ] but the name protactinium was not given until 1918, when protactinium-231 was discovered. Since the acceptance of Glenn T. Seaborg 's actinide concept in 1945, thorium, uranium and protactinium have been classified as actinides ; hence, protactinium does not occupy the place of eka- tantalum (under 73) in group 5 . Eka-tantalum is actually the synthetic superheavy element dubnium (105).
Mendeleev's 1869 table had implicitly predicted a heavier analog of titanium (22) and zirconium (40), but in 1871 he placed lanthanum (57) in that spot. The 1923 discovery of hafnium (72) validated Mendeleev's original 1869 prediction.
Some other predictions were unsuccessful because he failed to recognise the presence of the lanthanides in the sixth row. [ 7 ]
In 1902, Bohuslav Brauner placed lanthanides in a special series instead of Mendeleev's extra period, so he renamed Mendeleev's tri-manganese as dvi-manganese and dvi-tellurium as eka-tellurium (polonium had already been discovered, but its chemical properties had not yet been studied). Dvi-caesium was renamed eka-caesium. [ 8 ]
In 1902, having accepted the evidence for elements helium and argon , Mendeleev placed these noble gases in Group 0 in his arrangement of the elements. [ 9 ] As Mendeleev was doubtful of atomic theory to explain the law of definite proportions , he had no a priori reason to believe hydrogen was the lightest of elements, and suggested that a hypothetical lighter member of these chemically inert Group 0 elements could have gone undetected and be responsible for radioactivity . Currently some periodic tables of elements put lone neutrons in this place (see neutronium ) but no such element has ever been detected.
The heavier of the hypothetical proto-helium elements Mendeleev identified with coronium , named by association with an unexplained spectral line in the Sun's corona . A faulty calibration gave a wavelength of 531.68 nm, which was eventually corrected to 530.3 nm, which Grotrian and Edlén identified as originating from Fe XIV (i.e. Fe 13+ ) in 1939. [ 10 ] [ 11 ]
The lightest of the Group 0 gases, the first in the periodic table, was assigned a theoretical atomic mass between 5.3 × 10 −11 u and 9.6 × 10 −7 u . The kinetic velocity of this gas was calculated by Mendeleev to be 2,500,000 meters per second. Nearly massless, these gases were assumed by Mendeleev to permeate all matter, rarely interacting chemically. The high mobility and very small mass of the trans-hydrogen gases would result in the situation that they could be rarefied, yet appear to be very dense. [ 12 ] [ 13 ]
Mendeleev later published a theoretical expression of the ether in a small booklet entitled A Chemical Conception of the Ether (1904). His 1904 publication again contained two atomic elements smaller and lighter than hydrogen. He treated the "ether gas" as an interstellar atmosphere composed of at least two elements lighter than hydrogen. He stated that these gases originated due to violent bombardments internal to stars, the Sun being the most prolific source of such gases. According to Mendeleev's booklet, the interstellar atmosphere was probably composed of several additional elemental species. | https://en.wikipedia.org/wiki/Tri-_(chemistry) |
Tri-cell is one of several location-based services technologies that are used to locate or track the location of a mobile phone. Other technologies include TDOA and AGPS . Tri-cell makes a number of measurements within the phone and sends these measurements to a central server that uses a hybrid of methods to calculate the location of the phone on a continuous basis. Tri-cell was invented by the company Trisent Communication Ltd.
This article related to telecommunications is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Tri-cell |
Tri Edhi Budhi Soesilo (born 31 December 1961) is an Indonesian environmental scientist and a lecturer at the University of Indonesia. He is the director of the university's School of Environmental Science from 2020 until 2025.
Tri Edhi Budhi Soesilo was born in Jakarta, Indonesia on 31 December 1961, as the second of five children to M. Rusdi and Sri Sudarsih. [ 1 ] He spent his childhood in South Jakarta, where he completed his primary education at the 1st North Manggarai State Elementary School in 1972, followed by secondary education at the 3rd Manggarai Junior High School in 1975 and the 8th Jakarta State High School in 1979. He then studied medicine at the University of Indonesia. [ 2 ]
At his second year in the university, Tri began working as a biology teacher at his high school almamater. He was described as a teacher who made complex biological concepts easy to understand for his students, inspiring his students to study biology. He also became a research mentor to students in the school, especially those in the Science and Library subsections. [ 3 ]
He and several of his seniors and juniors from the 8th Jakarta State High School established the BTA 8 tutoring service, which prepared students from the school for university entrance exams. [ 4 ] Aside from teaching at his almamater and BTA, he also taught at the Feksos Nonformal Education Center from 1984 to 1985. [ 2 ]
He graduated as a physician from the University of Indonesia in 1987. [ 2 ] He holds a master's degree and doctorate in environmental science from the University of Indonesia in 1998 and 2005, respectively. [ 1 ] He received the cum laude distinction for his doctorate thesis defense. [ 5 ]
Upon graduating as a physician from the University of Indonesia in 1987, Tri began working as a staff at the cancer surgery department at the Dharma Nugraha Hospital in Matraman, East Jakarta. He continued to teach in several other education institutes, such as the Santa Lusia Nonformal Education Center in Cawang, Santo Lukas Nonformal Education Center, and the 6th Jakarta State High School. [ 2 ] After the BTA tutoring service expanded its services to other provinces in Indonesia, Tri also taught at the center's branch in Ambon, Maluku and Manado . [ 1 ]
Tri joined the Center for Human Resources and Environmental Research (PPSML, Pusat Penelitian Sumber Daya Manusia dan Lingkungan ) at the University of Indonesia as a research staff shortly after receiving his master's degree. He also taught at various departments in the University of Indonesia, and from 2001 to 2004 as an associate lecturer at the Jenderal Soedirman University. [ 1 ]
In 2010, Tri becamethe secretary of the environmental sciences major. [ 6 ] After completing his term as secretary, in July 2014 Tri became the chair of the major. Under his leadership, in 2015 the major prepared an academic manuscript which advocated for the elevation of the environmental science major into a school. [ 7 ] The University of Indonesia School of Environmental Sciences was established in 2016 and Tri became the deputy director of the school a year later. [ 8 ] [ 9 ]
Following the sudden death of director Emil Budianto on 30 September 2020, Tri became the acting director of the school. After undergoing a series of selection, on 22 February 2021 Tri became the permanent director of the school. [ 10 ] He was installed four days later [ 11 ] and served for a four-year term until he was replaced by Supriatna . [ 12 ]
Tri married Susi Soviana in 1989. The couple has two sons and a daughter and currently resides in Bogor. [ 1 ] | https://en.wikipedia.org/wiki/Tri_Edhi_Budhi_Soesilo |
Uridine triacetate ( INN ), [ 1 ] formerly known as vistonuridine , is an orally active tri- acetylated prodrug of uridine [ 2 ] used:
Uridine triacetate was developed, manufactured and distributed by Wellstat Therapeutics . It was granted breakthrough therapy designation by the U.S. Food and Drug Administration (FDA) and approved for use in the United States in 2015. [ 9 ] [ 10 ] [ 11 ]
This drug article relating to the gastrointestinal system is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Triacetyluridine |
The Triad [ 1 ] is an approach by the United States Environmental Protection Agency to decision-making for hazardous-waste site cleanup. [ 2 ] During the late 1990s, technology advocates from the environmental sector in the United States developed the approach by combining innovations in management and technology with ideas from hazardous-waste site cleanup experience.
Their goal was to form a framework for real-time environmental sensors and tools, to improve decision-making at contaminated sites. This resulted in a more formalized set of ideas in 2001 that soon became known as the Triad approach. The ideas spawned a Community of Practice by 2005.
The Triad Community of Practice [ 3 ] includes representatives of federal, state, and private sector organizations in the U.S. and abroad. By 2008, a European CoP had been formed [ 4 ] In 2008, a technical conference led largely by the CoP and covering the Triad Approach was held at the University of Massachusetts in Amherst, "Triad Investigations: New Approaches and Innovative Strategies. [ 5 ] "
The term Triad represents three elements: systematic project planning (SPP), dynamic work strategies, and innovative rapid sampling and analytical technologies. While elements of the Triad have long been used for site cleanup, Triad packages these best management practices together with the guiding principles:
Triad is an open-marketplace idea that is not owned by one entity. There is considerable U.S. Multiagency support for Triad. [ 6 ] Beginning in 2006, The U.S. Environmental Protection Agency Office of Superfund Remediation and Technology Innovation expressed support of Triad by requesting the cooperation of its regional managers to expand the use of Triad at Superfund sites, where appropriate. [ 7 ]
Although the following elements are the legs that gave the impetus for calling the process "Triad," the goal of the Triad approach is to infuse the concepts into hazardous-waste site cleanups, no matter what the lead organization calls the process. (U.S. Army Corps of Engineers Technical Project Planning Process (TPP) [ 8 ] for systematic planning, for example.)
Project planning identifies the problems and encourages stakeholders to negotiate the steps necessary to mediate the risks the environmental contamination pose to human health and ecology. The specific goals of a project (redevelopment, revitalization, etc.) may differ, but the specific objectives during the SPP process are:
Dynamic work strategies are strategies that can be adapted to site conditions as new information becomes available while work is underway. This adaptation may be in response to data collection activities designed to address CSM unknowns, or it may be in response to completely unexpected site conditions encountered during the course of work.
Dynamic work strategies as part of a Triad approach can be included in almost every activity associated with hazardous waste site characterization and remediation. This includes overall project strategies, dynamic sampling and analysis programs (DSP, [ 9 ] ASAP [ 10 ] ) for characterization purposes, remedial action design, implementation, and performance monitoring, long-term monitoring for sites that require it, closure plans, and quality assurance/quality control activities.
Sometimes referred to as 'real-time' measurement systems, these are analytical or measurement technologies [ 11 ] capable of producing data quickly enough to direct the progress of field activities (characterization or remediation) while they are underway [3] , analogous to Real-time business intelligence . Example analytical methods include portable or handheld X-ray Fluorescence (pXRF XRF ), portable gas chromatograph and mass spectrometry (GC-MS) technologies, and immunoassay test kits . [ 12 ] New field analytical methods are fast developing. However, some have used standard laboratory approaches with quick turn-around results. The analysis enables in-field decision-making and ensures logical internal consistency among Triad concepts. [ 13 ]
At the core of each project is the conceptual site model (CSM). [ 14 ] The term CSM is sometimes used to only describe pieces of the whole model. Geological, hydrogeological, contaminant fate and transport all may have computer models referred to as 'conceptual,' and a risk assessment may contain a CSM, but in a Triad sense, a CSM is the holistic model that can effectively portray site concerns significant to the decisions that must be made. | https://en.wikipedia.org/wiki/Triad_(environmental_science) |
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