Search results
Results from the WOW.Com Content Network
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.
Biotic material or biological derived material is any material that originates from living organisms. Most such materials contain carbon and are capable of decay . The earliest form of life on Earth arose at least 3.5 billion years ago.
Decomposition is largely inhibited during advanced decay due to the loss of readily available cadaveric material. [15] Insect activity is also reduced during this stage. [ 16 ] When the carcass is located on soil, the area surrounding it will show evidence of vegetation death. [ 15 ]
Radiobiology (also known as radiation biology) is a field of clinical and basic medical sciences that involves the study of the action of radioactivity on biological systems. The controlled action of deleterious radioactivity on living systems is the basis of radiation therapy .
The following list identifies in rank order the possible biological roles of the chemical elements, ranging from a score of 5 for elements essential to all living things, to a score of 1 for elements that have no known effects on living things. There are also letter scores for special functions of the elements.
Even the lightest element, hydrogen, has a well-known radionuclide, tritium. Elements heavier than lead, and the elements technetium and promethium, exist only as radionuclides. Unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm.
The process of biodegradation is threefold: first an object undergoes biodeterioration, which is the mechanical weakening of its structure; then follows biofragmentation, which is the breakdown of materials by microorganisms; and finally assimilation, which is the incorporation of the old material into new cells.
There is a half-life describing any exponential-decay process. For example: As noted above, in radioactive decay the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay. It varies depending on the atom type and isotope, and is usually determined experimentally. See List of nuclides.