Irradiated process

Vulcanised (cross-linked) polyethylene is being used for cable application where service temperatures up to 90°C are encountered. Typical cross-linking agents for this purpose are peroxides such as dicumyl peroxide. The use of such agents is significantly cheaper than irradiation processes for the cross-linking of the polymer. An alternative process involves the use of vinyl silanes (see Section 10.9). 

Miller, C.W., Power sourees for irradiation processing the linear accelerator. In Charlesby, A. (Ed.), Radiation Sources. The MacMillan Company, New York, 1964, pp. 197-219. Sehonberg, R.G., Radiation considerations for operation of a portable 6-MeV Electron Linear Accelerator. Proceedings 20th Midyear Topical Symposium, Health Physics Society, Reno, NV, February 8-12, 1987, p. 297. 

At first, the program which investigated the packaging of irradiation-- processed foods, concentrated on the most advanced type of container, the tinplate can. It had performed successfully for a century as a container for thermoprocessed foods. However, as a container for the irradiation-processed foods, its physical, chemical, and protective characteristics had to be evaluated, including the effects of radiation on enamels and end-sealing compounds. This container was satisfactory for packaging foods that were irradiation sterilized while unfrozen (1, 2). 

With the advent of irradiation processing of frozen foods to maintain acceptable quality in beef, ham, pork, and chicken, questions were posed... 

Extractives from Can Enamels. Earlier work reported by Pratt (1) showed that in a comparison between irradiation processing and thermal processing, no significant differences were found in the amount of extractives obtained from three commercial can enamels—epoxy phenolic, polybutadiene, and oleoresinous—in the presence of three aqueous... 

The evaluation of the components of the tinplate container showed that the preferred enamel for irradiation processing was the epoxy phenolic the preferred end-sealing compound was the blend of cured and uncured isobutylene—isoprene copolymer. Component testing of tinplate and solder for possible changes in mechanical properties, microstructure, and corrosion resistance indicated that the radiation caused... 

Isadore Perlman and I arrived in Chicago aboard the City of San Francisco. Although our trip from Berkeley took almost two full days, we feel that the time has not been wasted. Many lively discussions ensued in the privacy of our bedroom and, with appropriate care, in the club car regarding ways to separate element 94 chemically from uranium (that will be neutron-irradiated in chain-reacting piles) and from the fission by-products that will be produced concurrently in the neutron-irradiation process. 

Product yield The yield of an irradiation process [39] can be defined as the amount of a particular reaction (cross-Unking, degradation, gas formation, formation of unsaturation, etc.) produced per 100 eV of absorbed energy. It is expressed as the G value, for example. 

Thus, silver nanoparticles grow gradually during UV light irradiation (processes al-a3 in Figure 2). Nanoparticles of other noble metals such as gold, copper, platinum, and palladium can also be deposited by this method. 

The question also arises as to where the chiral molecules came from. Were the L-amino acids or the D-sugars selected on the primeval Earth, or are exuaterresuial sources responsible for the homochirality This second possibility is dealt with by hypotheses on the effect of circularly polarised light, of extraterrestrial origin, on chiral molecules in the molecular clouds from which the solar system was formed. One such hypothesis was proposed by Rubenstein et al. (1983) and developed further by others, particularly A. W. Bonner (Bonner and Rubenstein, 1987) both scientists worked at Stanford University. The authors believe that the actual radiation source was synchrotron radiation from supernovae. The excess of one enantiomeric form generated by this irradiation process would have needed to be transported to Earth by comets and meteorites, probably during the bombardment phase around 4.2-3.8 billion years ago. 

Expose the solution to long wavelength UV light at about 365 nm (Philips TL 20W/09 UV light works well) for 10-30 minutes. The solution may be cooled on ice to prevent heating during the irradiation process. 

FIGURE 28. 283-MHz 19F NMR spectra of isomers of 8-F-rhodopsin in CFIAPS before (lower) and after photoirradiation (upper) (a) 11-cis (pulse delay, D5 = 5.0 s, number of acquisitions, NA = 5200, line broadening, LB = 80 Hz) (b) 9-cis (D5 = 50 ms, NA = 160000, LB = 80 Hz). Disappearance of the excess 9-cis aldehyde was due to repeated formation and bleaching of pigment during the irradiation process. Reprinted with permission from Reference 48. Copyright (1996) American Chemical Society... 

EXAMPLE 5.4 Figure 5.8 shows the absorption spectrum of a NaCl crystal containing color centers generated by irradiation. The band peaking at 443 nm is related to the so-called F centers, for which the oscillator strength isf= 0.6. From this absorption band, determine the density of the F centers that have been produced by the irradiation process. Assume a refractive index of n = L6 for NaCl. 

The E center is an electron trapped at a negative Cl vacant site. These centers can be created in NaCl by irradiation or by additive coloration, as shown in the next chapter (Section 6.5). The band at 443 nm corresponds to a certain concentration, iV, of E centers that have been introduced by the irradiation process. The other band peaking at about 280 nm is related to other types of color center (which are formed by F center aggregation), beyond the scope of this example. 

Working on the subject between 1986 and 1998, the EU Scientific Committee of Food (SCF), an independent expert body advising the European Commission on health matters, concluded that the food irradiation process posed no problem for health over a wide ranged of uses, if used under prescribed conditions and endorsed for authorization of 17 irradiated foods/food classes [129]. The Commission proposal in December 1998 for an EU directive contained eight food categories and three products. 

FOOD IRRADIATION PROCESS CONTROL AND DETECTION OF IRRADIATED FOODS... 

Stevenson, M.H. Stewart, E.M. McAteer, N.J. Radiat. Phys. Chem. 1995, 46, 785. Patterson, M.F. Stewart, E. Paper presented at the Second FAO/IAEA Research Coordination Meeting of the Coordinated Research Programme on Development of Shelf-Stable and Ready-to-Eat Food through High Dose Irradiation Processing, Beijing, May 3-8, 1998. Foley, D.M. Reher, E. Caporaso, F. Trimboli, S. Musherraf, Z. Prakash, A. Food Microbiol. 2001, 18, 193. 

Cleland, M.R. Herer, A.S. Cokragan, A. In Irradiation for Food Safety and Quality, Loaharanu, P., Thomas, P., Eds. Technomic Publishing Co., Inc. Lancaster-Basel, 2001 158 pp. Morrison, R.M. In Food Irradiation Processing, International Atomic Energy Agency Vienna, 1985 407 pp. 

Without any doubt, the UV irradiation process is the lower-cost option, since the equipment is simpler, smaller, and considerably less expensive to... 

In industrial irradiation processes, either UV photons with energies between 2.2 and 7.0 eV or accelerated electrons with energies between 100 and 300 eV are used. Fast electrons transfer their energy to the molecules of the reactive substance (liquid or solid) during a series of electrostatic interactions with the outer sphere electrons of the neighboring molecules. This... 

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