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Cleavage (mathematics)
Cleavage may refer to: Science * Cleavage (crystal), in mineralogy and materials science, a process of splitting a crystal * Cleavage (geology), the foliation perpendicular to stress as a result of ductile deformation * Cleavage (embryo), in embryology, the division of cells in the early embryo * Cleavage (fiber), in optical fibers * Bond cleavage in chemistry and biochemistry, the splitting of chemical bonds * Cleavage factor * In cell biology, the cleavage furrow is the indentation that begins the process of cleavage, by which animal cells undergo cytokinesis * Proteolysis, also called peptide cleavage, the breaking down of proteins Anatomy * Cleavage (breasts), the partial exposure of the gap between a woman's breasts * Buttock cleavage, the minor exposure of the buttocks and the gluteal cleft between them * Toe cleavage, the partial exposure of toes in shoes * Teeth cleavage or tooth cleavage, slang for diastema, the gap between a person's two front teeth Other uses * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage (crystal)
Cleavage, in mineralogy and materials science, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. If bonds in certain directions are weaker than others, the crystal will tend to split along the weakly bonded planes. These flat breaks are termed "cleavage."Hurlbut, Cornelius S.; Klein, Cornelis, 1985, '' Manual of Mineralogy'', 20th ed., Wiley, The classic example of cleavage is mica, which cleaves in a single direction along the basal pinacoid, making the layers seem like pages in a book. In fact, mineralogists often refer to "books of mica." Diamond and graphite provide examples of cleavage. Both are composed solely of a single element, carbon. But in diamond, each carbon atom is bonded to four others in a tetrahedral pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage (geology)
Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally, these structures are formed in fine grained rocks composed of minerals affected by pressure solution. Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a rock. Foliation is separated into two groups: primary and secondary. Primary deals with igneous and sedimentary rocks, while secondary deals with rocks that undergo metamorphism as a result of deformation. Cleavage is a type of secondary foliation associated with fine grained rocks. For coarser grained rocks, schistosity is used to describe secondary foliation. There are a variety of definitions for cleavage, which may cause confusion and debate. The terminology used in this article is based largely on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage (embryo)
In embryology, cleavage is the division of cells in the early development of the embryo, following fertilization. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula, or of the blastocyst in mammals. Depending mostly on the concentration of yolk in the egg, the cleavage can be holoblastic (total or entire cleavage) or meroblastic (partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the vegetal pole while the opposite is referred to as the animal pole. Cleavage differs from other forms of cell division in that it increases the number of cells and nuclear mass without increasing the cytoplasmic mass. This means that with each successive subdivision, there is roughly half the cyto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage (fiber)
A cleave in an optical fiber is a deliberate, controlled break, intended to create a perfectly flat end face perpendicular to the fiber's longitudinal axis. The process of cleaving an optical fiber forms one of the steps in the preparation for a fiber splice operation regardless of the subsequent splice being a fusion splice or a mechanical splice; the other steps in the preparation being those of stripping and fiber alignment. A good cleave is required for a successful low loss splice of an optical fiber, often it is the case that fibers spliced by identical methods tend to have different losses, this difference can often be attributed to the quality of their initial cleaves. The general method of cleaving involves a general strategy known as the scribe-and-tension or scribe-and-break strategy. This strategy involves the introduction of a small crack into the fiber and the subsequent application of a tensile force in the vicinity of the crack that causes the fiber to cleave. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bond Cleavage
In chemistry, bond cleavage, or bond fission, is the splitting of chemical bonds. This can be generally referred to as dissociation when a molecule is cleaved into two or more fragments. In general, there are two classifications for bond cleavage: ''homo''lytic and ''hetero''lytic, depending on the nature of the process. The triplet and singlet excitation energies of a sigma bond can be used to determine if a bond will follow the homolytic or heterolytic pathway. A metal−metal sigma bond is an exception because the bond's excitation energy is extremely high, thus cannot be used for observation purposes. In some cases, bond cleavage requires catalysts. Due to the high bond-dissociation energy of C-H bonds, around , a large amount of energy is required to cleave the hydrogen atom from the carbon and bond a different atom to the carbon. Homolytic cleavage In homolytic cleavage, or homolysis, the two electrons in a cleaved covalent bond are divided equally between th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage Factor
__NOTOC__ Cleavage factors are two closely associated protein complexes involved in the cleavage of the 3' untranslated region of a newly synthesized pre-messenger RNA (mRNA) molecule in the process of gene transcription. The cleavage is the first step in adding a polyadenine tail to the pre-mRNA, which is one of the necessary post-transcriptional modifications necessary for producing a mature mRNA molecule. In mammals the two cleavage factors are known as CFIm and CFIIm. The proteins that constitute these complexes are recruited to the cleavage site by cleavage and polyadenylation specificity factor and cleavage stimulatory factor, and form a larger complex that also includes polyadenine polymerase (PAP), which performs the polyadenylation reaction. The CFIm complex Involved in the earliest step for the formation of the active cleavage complex, the CFIm complex is formed by three proteins of 25, 59 and 68 kDa, respectively: *CFIm25 (or CPSF5/NUDT21) *CFIm59 (or CPSF7 Cleavage an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage Furrow
In cell biology, the cleavage furrow is the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division. The same proteins responsible for muscle contraction, actin and myosin, begin the process of forming the cleavage furrow, creating an actomyosin ring. Other cytoskeletal proteins and actin binding proteins are involved in the procedure. Mechanism Plant cells do not perform cytokinesis through this exact method but the two procedures are not totally different. Animal cells form an actin-myosin contractile ring within the equatorial region of the cell membrane that constricts to form the cleavage furrow. In plant cells, Golgi vesicle secretions form a cell plate or septum on the equatorial plane of the cell wall by the action of microtubules of the phragmoplast. The cleavage furrow in animal cells and the phragmoplast in plant cells ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteolysis
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion. Proteolysis in organisms serves many purposes; for example, digestive enzymes break down proteins in food to provide amino acids for the organism, while proteolytic processing of a polypeptide chain after its synthesis may be necessary for the production of an active protein. It is also important in the regulation of some physiological and cellular processes including apoptosis, as well as preventing the accumulation of unwanted or misfolded proteins in cells. Consequently, abnormality in the regulation of proteolysis can cause disease. Proteolysis can also be used as an analytical tool for studying proteins in the laboratory, and it may also be used in industry, for example in food proc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleavage (breasts)
Cleavage is the narrow depression or hollow between the breasts of a woman. The superior portion of cleavage may be accentuated by clothing such as a low-cut neckline that exposes the division, and often the term is used to describe the low neckline itself, instead of the term décolletage. Joseph Breen, head of the U.S. film industry's Production Code Administration, coined the term in its current meaning when evaluating the 1943 film ''The Outlaw'', starring Jane Russell. The term was explained in ''Time'' magazine on August 5, 1946. It is most commonly used in the parlance of Western female fashion to refer to necklines that reveal or emphasize ''décolletage'' (display of the upper breast area). In many cultures, though not all, men typically derive erotic pleasure from the visible display of cleavage. This tendency has been attributed to many reasons, including evolutionary psychology, a patriarchal revolution, and dissociation from breastfeeding. Since at least the 15t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buttock Cleavage
Buttock cleavage is minor exposure of the buttocks and the intergluteal cleft between them, often because of low-rise pants. The ''crena'' is a formal term for the cleft between the buttocks. History When faced with indecency issues back in the 1930s, W. G. Cassidy explained in an essay titled "Private Parts: A Judicial View" that exposure of a buttock cleavage may come under "other private parts" in Australian law, though indecency generally involves exposure of the genital area. In the early 2000s, it became fashionable for young women and men to expose their buttocks this way, often in tandem with low rise jeans. ''The Cincinnati Enquirer'' called it the "new cleavage", and expressed views that "It's virtually impossible to find jeans to cover your hipbone". In August 2001, '' The Sun'' celebrated a "bum cleavage week" claiming that "bums are the new tits". In reaction to this trend, ''Saturday Night Live'' aired a parody advertisement in their April 16, 2006 episode for a pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toe Cleavage
Toe cleavage is the partial exposure of toes in shoes that are cut low enough at the vamp. Low cut shoes reveal toe cleavage similar to how low cut tops reveal breast cleavage. Toe cleavage is considered to be fashionable by stylists such as Susan Conterno, columnist for ''FAMOUS'' magazine. Manolo Blahnik himself opined that "the secret of toe cleavage, a very important part of the sexuality of the shoe" is that "You must only show the first two cracks.". In an ''"InStyle"'' magazine article, Samuel Ogden writes about the low cut angle in the bend of the shoe cover, stating that the curve creates a balance between the skin of the lower foot and the beginning of the toes. Shoe designer Christian Louboutin takes a more provocative view of toe cleavage and states, "The point is, it's more provocative to show a low toe cleavage than it is wearing sandals that reveal all. In flip-flops you see everything but that is not at all sexy." He takes this further by relating, "The curved ins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diastema (dentistry)
A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to as gap teeth or tooth gap. In humans, the term is most commonly applied to an open space between the upper incisors (front teeth). It happens when there is an unequal relationship between the size of the teeth and the jaw. Diastemata are common for children and can exist in adult teeth as well. In humans Causes 1. Oversized Labial Frenulum: Diastema is sometimes caused or exacerbated by the action of a labial frenulum (the tissue connecting the lip to the gum), causing high mucosal attachment and less attached keratinized tissue. This is more prone to recession or by tongue thrusting, which can push the teeth apart. 2. Periodontal Disease: Periodontal disease, also known as gum disease, can result in bone loss that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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