Field Effect (semiconductor), Gating
Field effect may refer to: relative influence of electricity to the substrate within a given field. * Field effect (chemistry), an effect that a pole (either an unipole or dipole) has on a remote reaction centre (reaction rates, equilibrium). This effect operates through space not through bonds which distinguishes it from the inductive effect. * Field effect (semiconductor), the physical mechanism modulating the conductivity of a semiconductor using an applied voltage difference. * Field effect also known as field cancerization, a field of molecular and cellular changes in normal appearing tissue, which predispose to the development of cancer. * Wien effect The Wien effect is the experimentally observed increase in ionic mobility or conductivity of electrolytes at very high gradient of electrical potential. A theoretical explanation has been proposed by Lars Onsager. A related phenomenon is known as ...

Field Effect (chemistry)
A field effect is the chemical polarity, polarization of a molecule through space. The effect is a result of an electric field produced by Electric charge, charge localization in a molecule. This field, which is substituent and Conformational isomerism, conformation dependent, can influence structure and reactivity by manipulating the location of electron density in bonds and/or the overall molecule. The polarization of a molecule through its bonds is a separate phenomenon known as Inductive effect, induction. Field effects are relatively weak, and diminish rapidly with distance, but have still been found to alter molecular properties such as acidity. Field sources Field effects can arise from the Electric dipole moment, electric dipole field of a bond containing an Electronegativity, electronegative atom or electron-withdrawing substituent, as well as from an atom or substituent bearing a formal charge. The directionality of a dipole, and concentration of charge, can both define ...
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Inductive Effect
In Organic chemistry, the inductive effect in a molecule is a local change in the electron density due to electron-withdrawing or electron-donating groups elsewhere in the molecule, resulting in a permanent dipole in a bond. It is present in a σ (sigma) bond, unlike the electromeric effect which is present in a π (pi) bond. The halogen atoms in an alkyl halide are electron withdrawing while the alkyl groups have electron donating tendencies. If the electronegative atom (missing an electron, thus having a positive charge) is then joined to a chain of atoms, typically carbon, the positive charge is relayed to the other atoms in the chain. This is the electron-withdrawing inductive effect, also known as the −''I'' effect. In short, alkyl groups tend to donate electrons, leading to the +''I'' effect. Its experimental basis is the ionization constant. It is distinct from and often opposite to the mesomeric effect. Bond polarization Covalent bonds can be polarized depending ...
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Field Effect (semiconductor)
In physics, the field effect refers to the modulation of the electrical conductivity of a material by the application of an external electric field. In a metal, the electron density that responds to applied fields is so large that an external electric field can penetrate only a very short distance into the material. However, in a semiconductor the lower density of electrons (and possibly holes) that can respond to an applied field is sufficiently small that the field can penetrate quite far into the material. This field penetration alters the conductivity of the semiconductor near its surface, and is called the ''field effect''. The field effect underlies the operation of the Schottky diode and of field-effect transistors, notably the MOSFET, the JFET and the MESFET.The acronyms stand for ''M''etal ''O''xide ''S''emiconductor ''F''ield ''E''ffect ''T''ransistor, ''J''unction ''F''ield ''E''ffect ''T''ransistor, and ''ME''tal ''S''emiconductor ''F''ield ''E''ffect ''T''ransistor. ...
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Field Cancerization
Field cancerization or field effect (also termed field change, field change cancerization, field carcinogenesis, cancer field effect or premalignant field defect) is a biological process in which large areas of cells at a tissue surface or within an organ are affected by carcinogenic alterations. The process arises from exposure to an injurious environment, often over a lengthy period. How it arises The initial step in field cancerization is associated with various molecular lesions such as acquired genetic mutations and epigenetic changes, occurring over a widespread, multi-focal "field". These initial molecular changes may subsequently progress to cytologically recognizable premalignant foci of dysplasia, and eventually to carcinoma in situ (CIS) or cancer. The image of a longitudinally opened colon resection on this page shows an area of a colon resection that likely has a field cancerization or field defect. It has one cancer and four premalignant polyps. Field cancer ...
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