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A biokinetic model describes the time course of absorption, distribution, metabolism and excretion of material or radiation introduced into the body of an organism.
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Ernest Rutherford and Niels Bohr developed in the early 20th century a solar system like model of the atoms, in which electrons orbit around the nucleus (protons and neutrons) held by electromagnetic forces (protons - electrons).
The nucleus is held together by a very strong but short distance nuclear force, attracting all nucleons. While the protons positive charges try pushing it apart, is it the balance between protons and neutrons which decide over an elements stability. In their model the energy of orbiting electrons is quantized into fixed values. Electrons in outer orbits are more loosely bound than the ones at inner orbits and affect an atom's chemical properties. Erwin Schrodinger and Werner Heisenberg developed probability functions which assigns the electrons to cloud like spaces instead of fixed orbits. •
Alpha particles consist of two neutrons and two protons (nucleus of He), have a positive charge of 2 and a velocity in air of approximately one-twentieth the speed of light. Discovered by Ernest Rutherford in 1899 (Rutherford-Bohr planetary atom model) alpha particles became emitted by very large atoms in an unstable energy state (high atomic number mostly over 82, with a too low neutrons//protons ratio (e.g. <= 1.5)). Through their relative slow travel speed, they get stopped by e.g. a thin sheet of paper or the outer layers of human skin or travel only inches; once stopped they pick up free electrons and become helium. These alpha particles are only dangerous to humans when the alpha-emitting material is inhaled or ingested (it causes damage that may lead to cancer) or comes into contact with the lens of the eye, caused by their less penetrating properties. Further Reading: Basics:
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• An assay is an analytic test to detect the presence, measure the concentration, and determine the biological activity of molecule, ions, or cells. Assays are based on measurable parameters that enable the evaluation of differences between samples and controls. Sensitivity, the ability to detect small amounts of a substance, and specificity, the ability to detect only the analyte, are essential features of an assay. See also Bioassay, Biochemical, Biohazards, Biokinetic Model and Bioaccumulation Factor. Result Pages : |