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Ion implantation

Ion implantation is a low-temperature process by which ions of one element are accelerated into a solid target, thereby changing the physical, chemical, or electrical properties of the target. Ion implantation is used in semiconductor device fabrication and in metal finishing, as well as in materials science research; the ions can alter the elemental composition of the target if they remain in the target. Ion implantation causes chemical and physical changes when the ions impinge on the target at high energy; the crystal structure of the target can be damaged or destroyed by the energetic collision cascades, ions of sufficiently high energy can cause nuclear transmutation. Ion implantation equipment consists of an ion source, where ions of the desired element are produced, an accelerator, where the ions are electrostatically accelerated to a high energy, a target chamber, where the ions impinge on a target, the material to be implanted, thus ion implantation is a special case of particle radiation.

Each ion is a single atom or molecule, thus the actual amount of material implanted in the target is the integral over time of the ion current. This amount is called the dose; the currents supplied by implants are small, thus the dose which can be implanted in a reasonable amount of time is small. Therefore, ion implantation finds application in cases where the amount of chemical change required is small. Typical ion energies are in the range of 10 to 500 keV. Energies in the range 1 to 10 keV can be used, but result in a penetration of only a few nanometers or less. Energies lower than this result in little damage to the target, fall under the designation ion beam deposition. Higher energies can be used: accelerators capable of 5 MeV are common. However, there is great structural damage to the target, because the depth distribution is broad, the net composition change at any point in the target will be small; the energy of the ions, as well as the ion species and the composition of the target determine the depth of penetration of the ions in the solid: A monoenergetic ion beam will have a broad depth distribution.

The average penetration depth is called the range of the ions. Under typical circumstances ion ranges will be between 1 micrometer. Thus, ion implantation is useful in cases where the chemical or structural change is desired to be near the surface of the target. Ions lose their energy as they travel through the solid, both from occasional collisions with target atoms and from a mild drag from overlap of electron orbitals, a continuous process; the loss of ion energy in the target is called stopping and can be simulated with the binary collision approximation method. Accelerator systems for ion implantation are classified into medium current, high current, high energy, high dose. All varieties of ion implantation beamline designs contain certain general groups of functional components; the first major segment of an ion beamline includes a device known as an ion source to generate the ion species. The source is coupled to biased electrodes for extraction of the ions into the beamline and most to some means of selecting a particular ion species for transport into the main accelerator section.

The "mass" selection is accompanied by passage of the extracted ion beam through a magnetic field region with an exit path restricted by blocking apertures, or "slits", that allow only ions with a specific value of the product of mass and velocity/charge to continue down the beamline. If the target surface is larger than the ion beam diameter and a uniform distribution of implanted dose is desired over the target surface some combination of beam scanning and wafer motion is used; the implanted surface is coupled with some method for collecting the accumulated charge of the implanted ions so that the delivered dose can be measured in a continuous fashion and the implant process stopped at the desired dose level. Semiconductor doping with boron, phosphorus, or arsenic is a common application of ion implantation; when implanted in a semiconductor, each dopant atom can create a charge carrier in the semiconductor after annealing. A hole can be created for a p-type dopant, an electron for an n-type dopant.

This modifies the conductivity of the semiconductor in its vicinity. The technique is used, for example, for adjusting the threshold of a MOSFET. Ion implantation was developed as a method of producing the p-n junction of photovoltaic devices in the late 1970s and early 1980s, along with the use of pulsed-electron beam for rapid annealing, although it has not to date been used for commercial production. One prominent method for preparing silicon on insulator substrates from conventional silicon substrates is the SIMOX process, wherein a buried high dose oxygen implant is converted to silicon oxide by a high temperature annealing process. Mesotaxy is the term for the growth of a crystallographically matching phase underneath the surface of the host crystal. In this process, ions are implanted at a high enough energy and dose into a material to create a layer of a second phase, the temperature is controlled so that the crystal structure of the target is not destroyed; the crystal orie

Taxus canadensis

Taxus canadensis, the Canada yew or Canadian yew, is a conifer native to central and eastern North America, thriving in swampy woods, riverbanks and on lake shores. Locally called "yew", this species is referred to as American yew or ground-hemlock. Most of its range is well north of the Ohio River, it is, found as a rare ice age relict in some coves of the Appalachian Mountains. The southernmost colonies are known from Watauga Counties in North Carolina, it is a sprawling shrub exceeding 2.5 m tall. It sometimes forms strong upright central leaders, but these cannot be formed from spreading branches, only from the original leader of the seedling plant; the shrub has thin scaly brown bark. The leaves are lanceolate, dark green, 1–2.5 cm long and 1–2.4 mm broad, arranged in two flat rows either side of the branch. The seed cones are modified, each cone containing a single seed surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, open at the end.

The seeds are eaten by thrushes and other birds, which disperse the hard seeds undamaged in their droppings. The male cones are 3 mm diameter, it is a monoecious plant – one of the few in the genus. All parts of Canadian yew, save the aril, are toxic. Tribes in its native range used small quantities of yew leaf tea topically or internally for a variety of ailments – notably rheumatism. Tribes are been said to have used yew twigs in steam baths to help alleviate rheumatism. Again, the plant is quite toxic and modern herbalists prefer safer, more effective herbs. Taxus canadensis is being harvested in northern Ontario, Québec and Atlantic Canada as the plant is a source of the class of poisonous chemicals known as taxanes, which have been a focus for cancer research. T. canadensis is much more abundant than the near-threatened Taxus brevifolia, the "greens" can be harvested sustainably every five years, instead of stripping the bark and killing the plant. The most abundant taxane in T. canadensis is 9-dihydro-13-acetylbaccatin III, which can be converted to 10-deacetylbaccatin III, used in the production of paclitaxel.

Two additional taxanes have been identified from T. canadensis, including 7β,10β,13α-triacetoxy-5α-oxy-2α-hydroxy-2abeotaxa-4,11-dien-9-one and 2α,10β-diacetoxy-9α-hydroxy-5α-oxy-3,11-cyclotax-4-en-13-one. Media related to Taxus canadensis at Wikimedia Commons

United States military casualties of war

This article lists the United States's military dead and missing person totals for wars and major deployments. Note: "Total U. S. casualties" includes wounded and non-combat deaths but not missing in action. "Deaths – other" includes all non-combat deaths including those from accidents, disease and murder. "Deaths per day" is the total number of Americans killed in military service, divided by the number of days between the dates of the commencement and end of hostilities. "Deaths per population" is the total number of deaths in military service, divided by the U. S. population of the year indicated. A. ^ Revolutionary War: All figures from the Revolutionary War are rounded estimates. Cited casualty figures provided by the Department of Defense are 4,435 killed and 6,188 wounded, although the original government report that generated these numbers warned that the totals were incomplete and far too low. In 1974, historian Howard Peckham and a team of researchers came up with a total of 6,824 killed in action and 8,445 wounded.

Because of incomplete records, Peckham estimated that this new total number of killed in action was still about 1,000 too low. Military historian John Shy subsequently estimated the total killed in action at 8,000, argued that the number of wounded was far higher, about 25,000; the "other" deaths are from disease, including prisoners who died on British prison ships. B. ^ Other Actions Against Pirates: Includes actions fought in the West Indies, the Greek Isles, off of Louisiana and Vietnam. Other deaths resulted from disease and accidents. C. ^ Civil War: All Union casualty figures, Confederate killed in action, from The Oxford Companion to American Military History except where noted. Estimate of total Confederate dead from James M. McPherson, Battle Cry of Freedom, 854. Newer estimates place the total death toll at 650,000 to 850,000. 148 of the Union dead were U. S. ^ Civil War April 2, 2012 Doctor David Hacker after extensive research offered new casualty rates higher by 20%. D. ^ World War I figures include expeditions in North Siberia.

See World War I casualties da.^ World War II Note: as of March 31, 1946 there were an estimated 286,959 dead of whom 246,492 were identified. As of April 6, 1946 there were 539 American Military Cemeteries. Note the American Battle Monuments Commission database for the World War II reports that in 18 ABMC Cemeteries total of 93,238 buried and 78,979 missing and that "The World War II database on this web site contains the names of those buried at our cemeteries, or listed as Missing in Action, buried or lost at sea, it does not contain the names of the 233,174 Americans returned to the United States for burial..." The ABMC Records do not cover inter-War deaths such as the Port Chicago disaster in which 320 died. As of June 2018 total of US World War II casualties listed. ^ Korean War: Note: gives Dead as 33,746 and Wounded as 103, 284 and MIA as 8,177. The American Battle Monuments Commission database for the Korean War reports that "The Department of Defense reports that 54,246 American service men and women lost their lives during the Korean War.

This includes all losses worldwide. Since the Korean War Veterans Memorial in Washington, D. C. honors all U. S. Military who lost their lives during the War, we have tried to obtain the names of those who died in other areas besides Korea during the period June 27, 1950 to July 27, 1954, one year after the Korean Armistice...". After their retreat in 1950, dead Marines and soldiers were buried at a temporary gravesite near Hungnam, North Korea. During "Operation Glory" which occurred from July to November 1954 the dead of each side were exchanged. After "Operation Glory" 416 Korean War "unknowns" were buried in the Punchbowl Cemetery. According to a DPMO white paper. 1,394 names were transmitted during "Operation Glory" from the Chinese and North Koreans, of whom 858 names proved to be correct. Of 239 Korean War unaccounted for: 186 not associated with Punchbowl unknowns; the W. A. Johnson listing of 496 POWs—including 25 civilians—who died in North Korea can be found here and thereListed as MIA: 7,683ea.

^ Cold War – Korea and Vietnam and Middle East-additional US Casualties: North Korea 1959:1968–1969. USS Liberty incident 1967 killed 34. ^ Iraq War. See Casualties of the Iraq War. Sources:.g. ^ Afghanistan. Casualties include those that occurred in Pakistan, Djibouti, Ethiopia, Guantanamo Bay, Kenya, Philippines, Sudan, Tajikistan and Yemen. Military history of the United States World War II casualties American War and Military Operations Casualties: Lists and Statistics Congressional Research Serv

Impressions of Mary Lou

Impressions of Mary Lou is an album by pianist John Hicks, recorded in 1998 and released on the HighNote label. The album features eight compositions by Mary Lou Williams along with five by Hicks. Allmusic reviewed the album stating "What is so compelling about Hicks' salute to Williams is that he ignores her best known secular works. Recommended". JazzTimes said "Hicks does a good job getting inside the tunes and developing them in his own way... Admirers of Hicks and Williams should enjoy this well-executed homage". All compositions by Mary Lou Williams except as indicated "Lord Have Mercy" - 4:31 "Ballad for Mary Lou" - 3:21 "O. W." - 4:08 "Old Time Spiritual" - 3:45 "Mary Lou's Interlude" - 4:09 "Medi II" - 7:54 "Not Just Your Blues" - 4:31 "Intermission" - 4:58 "Not Too Straight" - 4:03 "Two for You" - 4:31 "Aries" - 2:15 "The Lord Says" - 3:55 John Hicks - piano Dwayne Dolphin - bass Cecil Brooks III - drums Cecil Brooks III - producer George Heid - engineer

Central configuration

In celestial mechanics and the mathematics of the n-body problem, a central configuration is a system of point masses with the property that each mass is pulled by the combined gravitational force of the system directly towards the center of mass, with acceleration proportional to its distance from the center. Central configurations may be studied in Euclidean spaces of any dimension, although only dimensions one and three are directly relevant for celestial mechanics. For n equal masses, one possible central configuration places the masses at the vertices of a regular polygon, a Platonic solid, or a regular polytope in higher dimensions; the centrality of the configuration follows from its symmetry. It is possible to place an additional point, of arbitrary mass, at the center of mass of the system without changing its centrality. Placing three masses in an equilateral triangle, four at the vertices of a regular tetrahedron, or more n masses at the vertices of a regular simplex produces a central configuration when the masses are not equal.

This is the only central configuration for these masses that does not lie in a lower-dimensional subspace. Under Newton's law of universal gravitation, bodies placed at rest in a central configuration will maintain the configuration as they collapse to a collision at their center of mass. Systems of bodies in a two-dimensional central configuration can orbit stably around their center of mass, maintaining their relative positions, with circular orbits around the center of mass or in elliptical orbits with the center of mass at a focus of the ellipse; these are the only possible stable orbits in three-dimensional space in which the system of particles always remains similar to its initial configuration. More any system of particles moving under Newtonian gravitation that all collide at a single point in time and space will approximate a central configuration, in the limit as time tends to the collision time. A system of particles that all escape each other at the escape velocity will approximate a central configuration in the limit as time tends to infinity.

And any system of particles that move under Newtonian gravitation as if they are a rigid body must do so in a central configuration. Vortices in two-dimensional fluid dynamics, such as large storm systems on the earth's oceans tend to arrange themselves in central configurations. Two central configurations are considered to be equivalent if they are similar, that is, they can be transformed into each other by some combination of rotation and scaling. With this definition of equivalence, there is only one configuration of one or two points, it is always central. In the case of three bodies, there are three one-dimensional central configurations, found by Leonhard Euler; the finiteness of the set of three-point central configurations was shown by Joseph-Louis Lagrange in his solution to the three-body problem. Four points in any dimension have only finitely many central configurations; the number of configurations in this case is at least 32 and at most 8472, depending on the masses of the points.

The only convex central configuration of four equal masses is a square. The only central configuration of four masses that spans three dimensions is the configuration formed by the vertices of a regular tetrahedron. For arbitrarily many points in one dimension, there are again only finitely many solutions, one for each of the n!/2 linear orderings of the points on a line. For every set of n point masses, every dimension less than n, there exists at least one central configuration of that dimension. For all n-tuples of masses there are finitely many "Dziobek" configurations that span n − 2 dimensions, it is an unsolved problem, posed by Chazy and Wintner, whether there is always a bounded number of central configurations for five or more masses in two or more dimensions. In 1998, Stephen Smale included this problem as the sixth in his list of "mathematical problems for the next century"; as partial progress, for all 5-tuples of masses, there are only a bounded number of two-dimensional central configurations of five points.

A central configuration is said to be stacked if a subset of three or more of its masses form a central configuration. For example this can be true for equal masses forming a square pyramid, with the four masses at the base of the pyramid forming a central configuration, or for masses forming a triangular bipyramid, with the three masses in the central triangle of the bipyramid forming a central configuration. A spiderweb central configuration is a configuration in which the masses lie at the intersection points of a collection of concentric circles with another collection of lines, meeting at the center of the circles with equal angles; the intersection points of the lines with a single circle should all be occupied by points of equal mass, but the masses may vary from circle to circle. An additional mass is placed at the center of the system. For any desired number of lines, number of circles, profile of the masses on each concentric circle of a spiderweb central configuration, it is possible to find a spiderweb central configuration matching those parameters.

One can obtain central configurations for families of nested Platonic solids, or more group-theoretic orbits of any finite subgroup of the orthogonal group. James Clerk Maxwell suggested that a special case of these configurations with one circle, a massive central body, much lighter bodies at spaced points on the circle could be

John S. Baker House

The John S. Baker House is a historic house in the East Walnut Hills neighborhood of Cincinnati, United States. Built in 1854 according to a design by Cincinnati architect James Keys Wilson, it was the home of New Jersey native John S. Baker, who settled in Cincinnati in 1814; the Baker House is a brick structure with some elements of weatherboarding. Its architecture is prominent in many ways, most significant of which are its overall style: no other large brick houses in the Cincinnati area feature such a distinctively Gothic Revival style. Many details produce the sense of a castle, such as its tower, its battlements and crenallations, the decorations on the unusually placed and shaped windows; the appearance is further improved by the house's location: sitting atop a river bluff, it is visible from a great distance. In 1979, the Baker House was listed on the National Register of Historic Places because of its significant architecture. Included in the listing were two related buildings, a studio and residence for servants.