Gamma-radiation, production

Japan, and South America, and commercial amounts of wood-plastic flooring were produced for airport terminals and office buildings. Today there is no known commercial gamma radiation production of wood-plastics outside of the United States. 

Guy, A., Molko, D., and Teoule, R (1989) Synthesis of DNA fragments bearing 7,8-dihydro-8-oxo-adenine a gamma radiation product. Nucl Acids Res. Symp. Ser. 21, 135,136... 

Both side-chain and main-chain scission products are observed when polyacrylates are irradiated with gamma radiation (60). The nature of the alkyl side group affects the observed ratio of these two processes (61,62). 

Absorption Coefficient—Fractional absorption of the energy of an unscattered beam of x- or gamma-radiation per unit thickness (linear absorption coefficient), per unit mass (mass absorption coefficient), or per atom (atomic absorption coefficient) of absorber, due to transfer of energy to the absorber. The total absorption coefficient is the sum of individual energy absorption processes (see Compton Effect, Photoelectric Effect, and Pair Production). 

Pair Production—An absorption process for x- and gamma radiation in which the incident photon is absorbed in the vicinity of the nucleus of the absorbing atom, with subsequent production of an electron... 

Precision injection molding where feasible, gamma radiation resistant formulations, and improved production traceability and quality. 

Ascorbic acid is probably the most labile bioactive compound in fruit juices and fruit and vegetable pieces, as we described in the first part of this chapter. Retention of this phytochemical after the nonthermal treatments ranged from 47% to 100%, depending on the intensity of the applied treatment and the product. For example, the greatest losses of vitamin C were found in fresh-cut red lettuce and melon treated with IR and HHP (Fan and others 2008 Wolbang and others 2008), respectively. However, the use of gamma radiation in various vegetables retained 100% of their total ascorbic acid content (Fan and others 2008). 

Exposure to natural sources of radiation is unavoidable. Externally, individuals receive cosmic rays, terrestrial X-rays, and gamma radiation. Internally, naturally occurring radionuclides of Pb, Po, Bi, Ra, Rn, K, C, H, U, and Th contribute to the natural radiation dose from inhalation and ingestion. Potassium-40 is the most abundant radionuclide in foods and in all tissues. The mean effective human dose equivalent from natural radiations is 2.4 milliSieverts (mSv). This value includes the lung dose from radon daughter products and is about 20% higher than a 1982 estimate that did not take lung dose into account (Table 32.4). 

Merika [3.51] emphasized from his 17 years of experience with the quality control of freeze dried transplants the importance of sterility and residual moisture control as the decisive characteristics. Furthermore, the leak tightness of the storage containers was constantly controlled. Merika did not measure the product temperature during drying, but controled the process by measuring water vapor pressure and temperatures of the shelves and the condenser. The residual moisture content after 2 years of storage must be below 5 %. All products were sterilized by gamma radiation. 

High-energy radiation may be classified into photon and particulate radiation. Gamma radiation is utilized for fundamental studies and for low-dose rate irradiations with deep penetration. Radioactive isotopes, particularly cobalt-60, produced by neutron irradiation of naturally occurring cobalt-59 in a nuclear reactor, and caesium-137, which is a fission product of uranium-235, are the main sources of gamma radiation. X-radiation, of lower energy, is produced by electron bombardment of suitable metal targets with electron beams, or in a... 

The preservation of nutrient solutions at the concentrations occurring in natural seawater is a major challenge to the routine production of a nutrient reference material. Preservation techniques must be developed that maintain concentrations stable for periods of at least one to two years. Gamma radiation will produce nitrite that is unstable. Therefore this method appears to be problematic. The feasibility of other techniques, such as autoclaving, ultra-violet or microwave radiation, freezing, and acidification, should be evaluated. 

The gamma-radiation-induced oxidation of 2-propanol has been investigated. Acetone and hydrogen peroxide are the principal products and arise via a chain reaction in aqueous acid solutions at high concentrations of 2-propanol. In neutral solutions of 2-propanol and in solutions of methanol and ethanol, no such chain reactions are observed. The reasons for this are discussed along with the implications of the results for the hydroxyl radical yield in water radiolysis. 

The concentration of silver nanoparticles and ions in solntions was determined by neutron activation analysis [15]. Samples were irradiated in the nuclear reactor at the Institute of Nuclear Physics, Tashkent, Uzbekistan. The product of nuclear reaction ° Ag(n,y)" Ag has the half-life Tj j=253 days. The silver concentration was determined by measnring the intensity of gamma radiation with the energy of 0.657 MeV and 0.884 MeV emitted by "" Ag. A Ge(Li) detector with a resolution of about 1.9 keV at 1.33 MeV and a 6,144-channel analyzer were used for recording gamma-ray quanta. 

Thayer et al. (26) reported the results of nutritional, genetic, and toxicological studies of enzyme-inactivated, radiation-sterilized chicken meat. The study included four enzyme-inactivated chicken meat products 1) a frozen control, 2) a thermally processed product (llS.b C), 3) a gamma-sterilized product, and 4)... 

In this short review it is perhaps sufficient to indicate that in organic materials the primary processes and products of alpha and gamma radiation are usually fairly similar. However, major differences occur in the presence of so-called protecting additives, which are far less effective in the case of alphas. This is to be expected from the high concentration of radicals built up in the dense alpha track, far higher than in gamma or electron spurs. From the data on the effect of radical scavengers on the final product, the diameter of the alpha track can be estimated. 

Data relating to radionuclide deposition (fallout) within a few miles of the Danny Boy, Sedan, and Palanquin nuclear cratering shots are examined for evidence of fractionation. The fractionation index is computed for several fission-product mass chains produced in each event. For the three events studied only Danny Boy showed unambiguous evidence of fractionation in the early fallout, and the degree of fractionation was small. In Danny Boy there was only a factor of four difference between most enriched and most depleted species, compared with the factors of several hundred that have been observed in many late time samples of airborne debris. If this small amount of fractionation proves to be true in general for cratering shots, predictions of early-fallout gamma-radiation patterns will be simplified. 

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