Vol.6,

218

This paper presents numerous physical characteristics of Ca, V, Sn doped yttrium iron garnet (CaVSn:YIG) irradiated with 0.56 GeV carbon ions delivered by the Heavy Ion Research Facility of Lanzhou (HIRFL). The reason for change of the magnetic properties of the samples induced by energetic carbon ions bombardment is discussed. By comparison of this results with the irradiation effects of YIG induced by energetic argon, krypton and xenon obtained on the GANIL, Caen, France, it is concluded that the irradiation effect of 0.56 GeV C⁶⁺ on CaVSn: YIG arises from the electronic energy losses.

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367

For labelling spermatid DNA, male BALB/c mice are injected intratesticularly with ³H-TdR in advance. After 36 d of labelling, spermatozoa are sampled which is just the time required for the germ cells to mature. The period from intraperitoneal injection of ¹⁴⁷Pm to sampling spermatozoa is 12d. After sperm cells have been lysed, 30 ml eluent is added by wriggle pump. Finally, both the DNA remained on the filters and filtrated bottles are determined with a Beckman liquid scintillation device. Results show that after small dose internal irradiation with 185 Bq/g of ¹⁴⁷Pm, an increase in amount of sperm DNA on the filter observed is considerably higher than the control group. This indicates that low level internal radiation of ¹⁴⁷Pm has tendency to stimulate the DNA repair in spermiogenic stages.

505

Using collection film technique combined with Auger electron spectroscopy is analysis, the preferential sputtering of the ternary alloy Cu₇₆Ni₁₅Sn₉ bombarded with 27 keV Ar⁺ at normal incidence is studied. After bombardment, the target surface is examined with SEM, and the surface composition of different topographical feature areas is measured with electron probe micro-analyser (EPMA). The experiment results show that Cu atoms are preferentially ejected compared with Ni atoms, and Sn atoms come third within the ejection angle range from 0° to 60°. The results are discussed from the viewpoint of sputtering from a very rough surface.

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Plasma membrane vesicles were prepared from the developing cotyledons of common bean (Phaseolus vulgaris L cv Diyundou) by aqueous two-phase partitioning and characterized as to their purity by assaying marker enzymes for other membranes. The putative plasma membrane fraction was minimally contaminated by membranes other than plasma membrane and hence was of high purity. It exhibited a Ca²⁺-dependent ATPase activity, which was inhibited by 1 µmol/L EB and promoted by calcium ionophore A23187. Such an activity was responsible for the observed ATP-dependent ⁴⁵Ca²⁺ uptake into inside-out plasma membrane vesicles. This process was stimulated by 0.6 µmol/L CaM and 20 µmol/L IAA but inhibited by 2 µmol/L ABA and abolished by A23187. Possible role of cytoplasmic Ca²⁺ in mediating phytohormones activity is discussed.

221

In this paper a dynamic food chain model for Hong Kong which simulates the transfer of radioactive substances from a fallout deposition via the food chain into the human bodies is built. The model is based on the RADFOOD model and the Birchall-James algorithm. The radionuclides ¹³¹I and ⁹⁰Sr representing the short-term and long-term risk situations have been studied as sample cases. Various types of crops, and the dietary pattern of the public have been considered. The resulting internal radiation doses have been calculated. The results are obtained for food consumption starting at various time after the fallout deposition and for different consumption durations.

231

Cytokinesis-block micronucleus method is used to evaluate the radiosensitivity of a nasopharyngeal carcinoma cell line (CNE-1) and biopsies obtained from 31 patients with nasopharyngeal carcinoma. The number of micronuclei increases with the radiation dose. A good correlation was found between the radiosensitivity determined by the micro-nucleus assay and that measured by the colony-forming assay in CNE-1 cell line (r=-0.998). Moreover, the results of micronucleus assay for tumor cells from biopsies of patients with primary carcinoma look promising for the prediction of tumor radiosensitivity. These results are encouraging but need to be confirmed with a larger number of patients with a longer follow-up.

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Levels of indoor radon in air are studied by a continuous electrostatic radon monitor under normal living conditions to evaluate the influence of air conditioned ventilation on indoor air radon level. Results show that the indoor air radon concentrations are not much more than those without household conditioner living condition, although using household conditioner requires a sealed room which should lead to a higher radon level. Turning on air conditioner helps lower indoor radon level. Therefore, the total indoor air Rn levels are normal >ventilation>exhaust or indraft > exhaust plus indraft.

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