Absorbed ionizing radiation

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

The theory of radiation-induced grafting has received extensive treatment. The direct effect of ionizing radiation in material is to produce active radical sites. A material s sensitivity to radiation ionization is reflected in its G value, which represents the number of radicals in a specific type (e.g., peroxy or allyl) produced in the material per 100 eV of energy absorbed. For example, the G value of poly(vinyl chloride) is 10-15, of PE is 6-8, and of polystyrene is 1.5-3. Regarding monomers, the G value of methyl methacrylate is 11.5, of acrylonitrile is 5.6, and of styrene is >0.69. 

Absorbed Dose, Radiation—The mean energy imparted to the irradiated medium, per unit mass, by ionizing radiation. Units rad (rad), gray (Gy). 

Absorbed Dose—The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The unit of absorbed dose is the rad. One rad equals 100 ergs per gram. In SI units, the absorbed dose is the gray which is 1 J/kg (see Rad). 

Quality Factor (Q)—The linear-energy-transfer-dependent factor by which absorbed doses are multiplied to obtain (for radiation protection purposes) a quantity that expresses - on a common scale for all ionizing radiation - the approximate biological effectiveness of the absorbed dose. 

Relative Biological Effectiveness (RBE)—The RBE is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e., rad) due to different types of ionizing radiation. More specifically, it is the experimentally determined ratio of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation (typically 60Co gamma rays or 200 keV x rays) required to produce an identical biological effect in a particular experimental organism or tissue (see Quality Factor). 

Rep—Roentgen equivalent, physical A former unit of ionizing radiation equivalent to the dosage of 93 ergs absorbed per gram of tissue (93 erg/gm=0.93 rad). 

Dose equivalent or rem is a special radiation protection quantity that is used, for administrative and radiation safety purposes only, to express the absorbed dose in a manner which considers the difference in biological effectiveness of various kinds of ionizing radiation. The ICRU has defined the dose equivalent, H, as the product of the absorbed dose, D, and the quality factor, Q, at the point of interest in biological tissue. This relationship is expressed as H = D x Q. The dose equivalent concept is applicable only to doses that are not great enough to produce biomedical effects. 

Nonaqueous liquids, semi-solids, and dry powders dry heat at 160°C/120 minutes then dry heat under alternative conditions of time and temperature to achieve a sterility assurance level of 10 6 then an alternative to dry heat, e.g., ionizing radiation with a minimum absorbed dose of not less than 25 kGy then a validated alternative irradiation dose (according to ISO 11137) then aseptic filtration and aseptic processing and then the use of presterilized components and aseptic compounding or filling... 

Absorbed dose Energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest in that material expressed in rad units. 

Ionization smoke detectors contain a small radioactive source (Americium 241) which ionizes air in a small chamber. The ions flow to a charged plate giving a measurable current. Products of combustion in the chamber are not easily ionized and absorb the radiation and reduce the current. The low current trips the alarm circuit. The size and composition of the particles are crucial to successful detection so that some types of smoke or vapor are detected at very low (invisible) levels. 

The epoxy resin formed by tetraglycidyl 4,4 -diamino diphenyl methane and 4,4 -diamino diphenyl sulfone was characterized by dynamic mechanical analysis. Epoxy specimens were exposed to varying dose levels of ionizing radiation (0.5 MeV electrons) up to 10,000 Hrads to assess their endurance in long-term space applications. Ionizing radiation has a limited effect on the mechanical properties of the epoxy. The most notable difference was a decrease of approximately 40°C in Tg after an absorbed dose of 10,000 Mrads. Sorption/desorption studies revealed that plasticization by degradation products was responsible for a portion of the decrease in Tg. 

Unit for the dose absorbed from ionizing radiation. One rad equals 100 ergs of radiation absorbed per gram of tissue. One gray equals 100 rad. 2. Abbreviation for radian. 

A ratio that assesses the biological effectiveness of absorbed radiation doses with respect to different types and energies of ionizing radiation. It is equal to the absorbed dose of a particular radiation divided by the absorbed dose of a standard radiation required to produce identical biological effects in a given organ, tissue, or organism. 

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