|
Extended Wulff Constructions
Extended Wulff constructions refers to a number of different ways to model the structure of nanoparticles as well as larger mineral crystals. They can be used to understand the shape of gemstones and Crystal twinning, crystals with twins, and in other areas such as understanding both the shape and how nanoparticles play a role in the commercial production of chemicals using Heterogeneous catalysis, heterogeneous catalysts. Extended Wulff constructions are variants of the Wulff construction, which is used for a solid single crystal in isolation. They include cases for solid particles on substrates, those with internal boundaries and also when growth is important. Depending upon whether there are twins or a substrate, there are different cases as indicated in the Extended Wulff constructions#Figure 1, decision tree figure. The simplest forms of these constructions yield the lowest Gibbs free energy (thermodynamic) shape, or the stable growth form for an isolated particle; it can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rostislaw Kaischew
Rostislaw Kaischew (; February 16, 1908 Old Style, O.S. (February 29, 1908 (New Style, N.S.)), Saint Petersburg, Russian Empire – November 19, 2002, Sofia, Republic of Bulgaria) was a Bulgarian physicochemist and a member of the Bulgarian Academy of Sciences. His most significant contributions to science were within studies of crystal growth and nucleation. Biography Kaischew graduated from Sofia University in 1930 and earned his doctorate at Technische Hochschule of Breslau, Germany in 1932. His doctoral adviser was Franz Simon. In 1933, he was appointed an assistant professor at Sofia University, and in 1947 - a professor. At the Bulgarian Academy of Sciences, Kaischew founded the Institute for Physical Chemistry, and held the position of director there from its creation in 1958 until his retirement in 1989. The Institute is named after him. Selected bibliography * * * * See also *Wulff construction References Further reading * * External links * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanoparticles
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead. Nanoparticles are distinguished from microparticles (1-1000 μm), "fine particles" (sized between 100 and 2500 nm), and "coarse particles" (ranging from 2500 to 10,000 nm), because their smaller size drives very different physical or chemical properties, like colloidal properties and ultrafast optical effects or electric properties. Being more subject to the Brownian motion, they usually do not sediment, like colloid, colloidal particles that conversely are usually understood to range from 1 to 1000 nm. Being much smaller than the wavelengths of visible light (400-700 nm), nanoparticles cannot be seen with ordinary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Icosahedral Twins
An icosahedral twin is an atomic structure found in atomic clusters and also nanoparticles with some thousands of atoms. Their atomic structure is slightly different from what is found for bulk materials, and contains five-fold symmetries. They have been analyzed in many areas of science including crystal growth, crystallography, chemical physics, surface science and materials science, and are sometimes considered as beautiful due to their high symmetry. The simplest form of these clusters is twenty interlinked tetrahedral crystals joined along triangular (e.g. cubic-(111)) faces, although more complex variants of the outer surface also occur. A related structure has five units similarly arranged with twinning, which were known as "fivelings" in the 19th century,H. Hofmeister (2004) "Fivefold twinned nanoparticles" in ''Encyclopedia of Nanoscience and Nanotechnology'' (ed. H. S. Nalwa, Amer. Sci. Publ., Stevenson Ranch CA) vol. 3, pp. 431-452pdf and more recently as "decahedral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiveling
A fiveling, also known as a decahedral nanoparticle, a multiply-twinned particle (MTP), a pentagonal nanoparticle, a pentatwin, or a five-fold twin is a type of twinned crystal that can exist at sizes ranging from nanometers to millimetres. It contains five different single crystals arranged around a common axis. In most cases each unit has a Cubic crystal system#Bravais lattice, face centered cubic (fcc) arrangement of the atoms, although they are also known for other types of crystal structure. They nucleate at quite small sizes in the nanometer range, but can be grown much larger. They have been found in mineral crystals excavated from mines such as pentagonite or native gold from Ukraine, in rods of metals grown via electrochemical processes and in nanoparticles produced by the condensation of metals either onto substrates or in inert gases. They have been investigated for their potential uses in areas such as improving the efficiency of solar cell or heterogeneous catalysis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marks Decahedra
A fiveling, also known as a decahedral nanoparticle, a multiply-twinned particle (MTP), a pentagonal nanoparticle, a pentatwin, or a five-fold twin is a type of twinned crystal that can exist at sizes ranging from nanometers to millimetres. It contains five different single crystals arranged around a common axis. In most cases each unit has a face centered cubic (fcc) arrangement of the atoms, although they are also known for other types of crystal structure. They nucleate at quite small sizes in the nanometer range, but can be grown much larger. They have been found in mineral crystals excavated from mines such as pentagonite or native gold from Ukraine, in rods of metals grown via electrochemical processes and in nanoparticles produced by the condensation of metals either onto substrates or in inert gases. They have been investigated for their potential uses in areas such as improving the efficiency of solar cell or heterogeneous catalysis for more efficient production of c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uzi Landman
Uzi Landman (; May 1944) is an Israeli/American computational physicist, the Fuller E. Callaway Professor of Computational Materials Science at the Georgia Institute of Technology. Career He earned a B.Sc. in chemistry at the Hebrew University, Jerusalem in 1965, an M.Sc. in chemistry from the Weizmann Institute in 1966 and a D.Sc. from the Israel Institute of Technology in 1969. His research interests included surface and materials science, solid state physics and nanoscience. He joined the faculty of Georgia Tech in 1977 as an associate professor of physics and made professor in 1979, In 1988 he was promoted to regents professor of physics, a title he still holds. In 1992 he became director of the Center for Computational Materials science, at Georgia and in 1995 appointed Fuller E. Callaway endowed Chair in Computational Materials Science. Honors and awards In 1989 he was elected a Fellow of the American Physical Society ''"for applications of numerical simulation mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macle
Macle is a term used in crystallography. It is a crystalline form, twin-crystal or double crystal (such as chiastolite). It is crystallographic twin according to the spinel twin law and is seen in octahedral crystals or minerals such as diamond and spinel. The twin law name comes from the fact that is commonly observed in the mineral spinel. A version with five units about a common axis is called a fiveling. ''Macle'' is an old French word, a heraldic term for a voided Lozenge (shape)">lozenge (one diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ... shape within another). Etymologically the word is derived from the Latin ''macula'' meaning spot, mesh, or hole. Bibliography * Georges Friedel (1904) "Étude sur les groupements cristallins", ''Extrait du Bulletin de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Library Of Scotland
The National Library of Scotland (NLS; ; ) is one of Scotland's National Collections. It is one of the largest libraries in the United Kingdom. As well as a public programme of exhibitions, events, workshops, and tours, the National Library of Scotland has reading rooms where visitors can access the collections. It is the legal deposit library of Scotland and is a member of Research Libraries UK (RLUK) and the Consortium of European Research Libraries (CERL). There are over 24 million items held at the Library in various formats including books, annotated manuscripts and first-drafts, postcards, photographs, and newspapers. The library is also home to Scotland's Moving Image Archive, a collection of over 46,000 videos and films. Notable items amongst the collection include copies of the Gutenberg Bible, Charles Darwin's letter with which he submitted the manuscript of ''On the Origin of Species,'' the First Folio of Shakespeare, the Glenriddell Manuscripts, and the last ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinel Twin
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Properties Spinel crystallizes in the isometric system; common crystal forms are octahedra, usually twinned. It has no true cleavage, but shows an octahedral parting and a conchoidal fracture. Its hardness is 8, its specific gravity is 3.5–4.1, and it is transparent to opaque with a vitreous to dull luster. It may be colorless, but is usually various shades of red, lavender, blue, green, brown, black, or yellow. Chromium(III) causes the red color in spinel from Burma. Some spinels are among the most famous gemstones; among them are the Black Prince's Ruby and the "Timur ruby" in the British Crown Jewels, and the "Côte de Bretagne", formerly from the French Crown jewels. The Samarian Spinel is the largest known spinel in the world, weighi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean Taylor
Jean Ellen Taylor (born 1944) is an American mathematician who is a professor emerita at Rutgers University and visiting faculty at the Courant Institute of Mathematical Sciences of New York University. Biography Taylor was born in Northern California. She did her undergraduate studies at Mount Holyoke College, graduating summa cum laude with an A.B. in 1966. She began her graduate studies in chemistry at the University of California, Berkeley, but after receiving an M.Sc. she switched to mathematics under the mentorship of Shiing-Shen Chern and then transferred to the University of Warwick and received a second M.Sc. in mathematics there. She completed a doctorate in 1973 from Princeton University under the supervision of Frederick J. Almgren, Jr. Taylor joined the Rutgers faculty in 1973, and retired in 2002. She was president of the Association for Women in Mathematics from 1999 to 2001. She has been married three times, to mathematicians John Guckenheimer and Frederick Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Play On Words
Word play or wordplay (also: play-on-words) is a literary technique and a form of wit in which words used become the main subject of the work, primarily for the purpose of intended effect or amusement. Examples of word play include puns, phonetic mix-ups such as spoonerisms, obscure words and meanings, clever rhetorical excursions, oddly formed sentences, double entendres, and telling character names (such as in the play ''The Importance of Being Earnest'', ''Ernest'' being a given name that sounds exactly like the adjective ''earnest''). Word play is quite common in oral cultures as a method of reinforcing meaning. Examples of text-based ( orthographic) word play are found in languages with or without alphabet-based scripts, such as homophonic puns in Mandarin Chinese. Techniques ; Tom Swifties: A form of humorous writing where adverbs are chosen to reflect the nature of the situation in a punning way. "Hurry up and get to the back of the ship", Tom said sternly. ;Weller ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anisotropy
Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit very different physical or mechanical properties when measured along different axes, e.g. absorbance, refractive index, conductivity, and tensile strength. An example of anisotropy is light coming through a polarizer. Another is wood, which is easier to split along its grain than across it because of the directional non-uniformity of the grain (the grain is the same in one direction, not all directions). Fields of interest Computer graphics In the field of computer graphics, an anisotropic surface changes in appearance as it rotates about its geometric normal, as is the case with velvet. Anisotropic filtering (AF) is a method of enhancing the image quality of textures on surfaces that are far away and viewed at a shallow angle. Older ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
