60Co y-radiation

Irradiation. The samples were irradiated with 60Co y-rays at 77 °K. in ampoules sealed at 10"4-10 5 torr. The ampoules were made from Suprasil quartz which on irradiation gave an ESR signal which was very small compared with the intensity of the sample absorption. The dose rate of the radiation source varied within 300-350 krads/hour. The dose was 3.4 Mrads for most of the experiments. The dose dependence of the radical formation was investigated in the dose range 0.02-10 Mrads. 

Ni(CO)4 is not affected by intense 60Co-y-irradiation and can be looked upon as one of the most radiation stable compounds 44>. A study of the radiolysis of mixtures of cyclohexane and/or benzene and Ni(CO)4 has demonstrated its protective properties. Probably, energy transfer to Ni(CO)4 and the reversible dissociation 

The experiments involved the use of y-radiation of 60Co. The dose rate was commonly equal to — 1016 e.v./ml. sec. The dosimetry was made by the ferrosulfate method. The calculation of the dose was performed while taking into account the difference in electron densities of the dosimetric and investigated solutions. 

For radiation curing, a sealed tube containing the blend film was placed in the y-ray (60Co source) radiation chamber at the dose rate of 1.32 x 10 R/min. for 30 minutes. 

Ionizing radiation. Further studies on the effects of ionizing radiation such as 60Co y-ray radiation and ion beams on polysilanes have been reported.295 304-306 Both positive and negative resist properties can be shown, depending on the side-chain type, branch density, and the presence or absence of radical initiators. 

In tbe first attempt to prepare a two-dimensional crystalline polymer (45), 60Co y-radiation was used to initiate polymerization in monolayers of vinyl stearate (7). Polymerization at the air-water interface was possible but gave a rigid film. The monomeric monolayer was deposited to give X-type layers that could be polymerized in. ////. fills polymerization reaction, quenched by oxygen, proceeds via a free-radical mechanism. 

Similarly Abou Zeid and co-workers made a detailed study on LDPE film, irradiated with different types of radiation such as 60Co y-rays, thermal and fast neutrons, and electron beam irradiation [19]. The structural changes of PE films with thickness varying from 8 to 24 pm, were characterised by FT-IR spectroscopy. The characteristic FT-IR absorption bands of unirradiated, y-irradiated and reactor irradiated LDPE film are presented in Table 5.1. 

There is in addition to the pulse radiolysis technique the classical continuous radiation method. This later procedure uses either the 60Co-y sources or in the case of Pu the self a irradiation due to the radioactive decay. 

The monomer 1 was polymerized by heating the crystals in a vacuum vessel below the melting point or by y-ray or UV irradiation of the crystals at room temperature. 60Co y-ray irradiation with a dose rate of 0.1 Mrad h 1 or a high-pressure mercury lamp (200 W) without filter was used as the radiation sources for the polymerization the conversion ratio was determined by extraction of residual monomer with ethanol. A comparison of the polymerization rates indicates that 60C y-ray irradiation is much more efficient than UV irradiation in inducing polymerization. 

Cholest-4-en-3/3-ol and its 5a-A6- and 5a-A7-isomers gave complex mixtures of oxidation products on treatment with 60Co y-radiation in air. Reaction paths are discussed and compared with those occurring in photosensitized and free-radical oxidations.119 1-Methyl-11-oxo-oestrone (107) is converted by DDQ in 1% aqueous dioxan into the 9/3-hydroxy-derivative (108), apparently by hydration of an intermediate quinone methide.120 

Packer and Richardson (1975) and Packer et al. (1980) made use of the fact that electrons can be generated in water by y-radiation from a 60Co source (Scheme 8-29) to induce a free radical chain reaction between diazonium ions and alcohols, aldehydes, or formate ion. It has to be emphasized that the radiolytically formed solvated electron in Scheme 8-29 is only a part of the initiation steps (Scheme 8-30) by which an aryl radical is formed. The aryl radical initiates the propagation steps shown in Scheme 8-31. Here the alcohol, aldehyde, or formate ion (RH2) is the reducing agent (i.e., the electron donor) for the main reaction. The process is a hydro-de-diazoniation. 

Sterilization of tylon Enzyme Electrodes. Sterilization of in vivo electrodes is essential for clinical use and advisable for applica-tions in the food industry. It was thus of interest to study the behaviour of various carbohydrate sensor membranes before and after irradiation with 60Co-y radiation (Figure 1). Thus, after each membrane calibration in a batch mode, the membrane was detached, placed in a sealed glass tube with phosphate buffer (pH 7) and irradiated to set doses. The membrane was then reattached to the 

Pulse radiolysis has been used to afford the radical cations of thioanisole, p-methylthioanisole, and benzyl phenyl sulfides. The absorption spectra of these radicals and their reaction with a number of nucleophiles and electron donors are reported.302 Exposure of trimethylphosphine sulfide to 60Co y-radiation at 77 K gave the radical anion Me PS , identified by its ESR spectrum, from which other radicals, including Me2PS, were formed at higher temperatures.303 

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