Radiation, as initiation

Graft Copolymerization Using Radiations as Initiators Different types of radiations can be used for the graft copolymerization of vinyl monomers onto polysaccharides, e.g., y-radiations and microwave irradiation methods [22-24]. Initiation of grafting using microwave radiations is explained below Initiation ... 

By contrast with the ionizing radiation grafting studies, little additive enhancement work has been reported for UV initiated grafting reactions. It is the purpose of this paper to compare UV with ionizing radiation as initiators for grafting to cellulose, especially with respect to possible common parameters Including additives which may determine optimum yields in both systems. The copolymerization... 

The growth in popularity of radiation as the initiating system for grafting arises from the improvement in availability and cost of ionizing radiation. This is due to the introduction of more powerful nuclear reactors. Apart from its inexpensiveness, radiation is a very convenient method for graft initiation because it allows a considerable degree of control to be exercised over such structural... 

It is well known that y or X photons have energies suitable for excitation of inner electrons. We can use ultraviolet and visible radiation to initiate chemical reactions (photochemistry). Infrared radiation excites bond vibrations only whereas hyperfrequencies excite molecular rotation. In Tab. 1.1 the energies associated with chemical bonds and Brownian motion are compared with the microwave photon corresponding to the frequency used in microwave heating systems such as domestic and industrial ovens (2.45 GHz, 12.22 cm). 

Aldehydes are oxidized by dioxygen by the chain mechanism in reactions brought about in different ways initiated, thermal, photochemical, and induced by radiation as well as in the presence of transition metal compounds [4-8]. Oxidation chains are usually very long from 200 to 50,000 units [4], Acyl radicals add dioxygen very rapidly with a rate constant of 10s—109 Lmol V1 [4], Therefore, the initiated chain oxidation of aldehyde includes the following elementary steps at high dioxygen pressures [4-7] ... 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

The selection of salvage therapy depends on what was used as initial therapy. Radiotherapy can be used after radical prostatectomy. Androgen ablation can be used after radiation therapy or radical prostatectomy. 

In order to synthesize the IPN, the urethane elastomer was swelled with styrene containing 0.4% benzoin as initiator and 1% divinyl benzene (DVB) as crosslinker. Polymerization of the styrene was carried out by ultraviolet radiation at room temperature for 24 hours. 

Keane TJ, Cummings B J, O Sullivan B, et al. A randomized trial of radiation therapy compared to split course radiation therapy combined with mitomycin C and 5 fluorouracil as initial treatment for advanced laryngeal and hypopharyngeal squamous carcinoma. Int J Radiat Oncol Biol Phys 1993 25 613-618. 

The differences in slopes for reactor and gamma irradiations shown in Figure 3 are real rather than the result of inaccurate dose measurement since hydrogen production was observed to be greater in the reactor (14). Radiation yields are presented as initial G values in Table III, along with yields and reaction rates for the other types of polybutadiene. Irradia-... 

Most c/s-azoalkanes do this on heating, or on irradiation with shorter-wavelength radiation, and photolysis of azoalkanes provides a convenient source of certain radicals the photochemical process can be more readily controlled than the thermal reaction. Radicals produced in this way may be employed as initiators for the polymerization of alkenes. and a widely used compound for this purpose is azobisisobutyronitrile (ABIN, 5.20). 

Alpha particles as initiators of deton 1 A131 see also Radiation effects on expis, proplnts and pyrots 9 R5-R6 (a particle irradiation)... 

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