Irradiation sensitivity

Another application involves the measurement of copper via the radioisotope Cu (12.6-hour half-life). Since Cu decays by electron capture to Ni ( Cu Ni), a necessary consequence is the emission of X rays from Ni at 7.5 keV. By using X-ray spectrometry following irradiation, sensitive Cu analysis can be accomplished. Because of the short range of the low-energy X rays, near-surface analytical data are obtained without chemical etching. A combination of neutron activation with X-ray spectrometry also can be applied to other elements, such as Zn and Ge. 

Bicyclo[2.2.l]hepta-2,5-diene, irradiation sensitized by acetophenone to give qua-dricyclane, 51, 133 Bicyclo[2.2.0]hexa-2,5-diene,... 

DNA synthesis in irradiated sensitive bacterial cells is permanently inhibited by doses which produce about 5 thymine dimers per single strand of DNA (1000 p.). In the cells of resistant bacteria, DNA synthesis is inhibited only by doses of radiation which produce about 500 dimers per cell. The difference between the two types of bacteria is caused by the presence in the resistant cells of efficient enzymatic mechanisms for repairing the damage done by thymine dimerization. 

Figure 6. Sample of irradiation-sensitive tape. Note uniformity of color.

Figure 6 shows dramatically the good results achieved with the irradiation-sensitive tape. It is intended for a go/no-go check and has a sharp color change. The indicated dose was of the order of 1.5 Mrad, but more exact data are not available. It is interesting to note that after five days at room temperature no obvious breakdown or other injury could be noted with this sample. To facilitate comparison over the full spherical area, the tapes were stripped from the fruit and laid out for examination. 

Egg-induced immunity appears to involve stage-specific immunogens against (a) the tissue phase of egg challenge (early response) and (b) the lumen phase of cysticercoid challenge (late response). This immunogenetic pattern is thus similar to the development of early and late immunity in larval taeniid cestodes (Fig. 11.7). The effector mechanism of the early response has been shown to be thymus dependent, X-irradiation sensitive, cell mediated and antibody mediated the response is visualised by eosinophilia infiltration around the invading oncospheres (Fig. 11.6) (353). 

Inactivation by X-irradiation Sensitive Primed cells for helper effect, cytotoxic effect and cell-mediated immunity resistant unprimed cells sensitive... 

Although major change in alloying components has not occurred, special attention has been paid to the control of impurity elements for achieving good toughness and lower neutron irradiation sensitivity. 

The two atropisomers 35 and 36 are different conformations with different physicochemical characteristics and can be specifically irradiated/sensitized for selective reactions (see, for instance, [28-32]) to form differently substituted cyclobutanes 37 and 38 (Scheme 8.17). 

Moreover, the morphology of specimens can be stabilized by applying chemical fixation and staining treatments, essentially by cross-linking the macromolecules and incorporating atoms of heavy elements. On the other hand, it is possible to make use of the irradiation sensitivities of polymers for special effects for contrast development see Section 2.2.4. 

The first experimental evidence for the existence of alkylnitrenes was provided by ESR spectroscopy in glassy matrixes. Very weak ESR signals were detected upon direct irradiation. Sensitized photolysis of alkyl azides was found to be the most appropriate procedure to generate triplet alkylnitrenes in glassy matrixes. ... 

Current experimental results are not conclusive in attributing any influence to Mn. Moreover, it was shown that Si reduces irradiation sensitivity. 

In addition to its effect of increasing the irradiation sensitivity of steel, there are indications that the high Cu content in RPV steel retards the recovery of its mechanical properties during the post-irradiation annealing process. 

Effect of Phosphorus. The effect of P content is mainly to increase the irradiation sensitivity of RPV steels. However, it has less of an effect than Cu, and this effect... 

Effect of Nickel. The contribution of Ni content to irradiation hardening and embrittlement was not realised until recently. The Ni effect was noticed in the case of RPV steel plates, forging, as well as weldments. It was shown that this effect is important for steels with Ni contents of > 0.4 wt% [59]. Materials with high Cu and Ni contents will have high irradiation sensitivities, while those with low Cu and Ni contents will be practically insensitive to irradiation [53]. 

Recent advances in techniques used, in particular availability of high-resolution transmission electron microscopes, as well as interpreting and processing the images, have allowed resolutions of the order of atomic structures in inorganic crystal (below 0.1 nm). However, the best resolution achieved in polymers is, in practice, poorer than this because of polymer-specific problems with high electron irradiation sensitivity and low contrast. 

Simple Cycloalkenes Direct Irradiation Sensitized Irradiation of Cycloalkenes. 16-2... 

Bicyclo[2.2.2]octenones with a-methoxy groups undergo a remarkable photoreaction. Rogers and Parker investigated the photochemistry of 114 and its isomer 117, and other related ketones, upon sensitized as well as direct irradiation. Sensitized (acetone or acetophenone in benzene) irradiation of the enone 114, with a methoxy group at the a-position, was found to give the dione 116 in major quantity the expected ODPM product was obtained only in minor amounts (Scheme 22). It was... 

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