最新刊期
      期 4 ， 1984
      • Zhang Wanxi,Sun Jiazhen,Qian Baogong
        Vol. 2, Issue 4, Pages: 1-10(1984)
        摘要：The structure effects of polymers on the relationship between sol fraction and radiation dose are discussed in detail. In consideration of the deviation of experimental results from Charlesby-Pinner's and Chen-Liu-Tang's expressions relating sol fraction to radiation dose, we introduced an exponent β concerned with the structure and property parameters of a polymer (glass transition temperature Tg and molecular internal rotating steric factor σ) and assumed that the fracture density is proportional to Rβ (R is radiation dose). Thus, a general expression, formula (9), relating sol fraction to radiation dose is derived.When β=1 and β=0.5, this expression is reduced to the above said two expressions. Using this general expression, the experimental data of a number of polymers are treated. It is shown that the expression is in good agreement with the experimental results. β value is in the range of 0.5 to 1.0.  
        关键词：Radiation crosslinking;Structure of polymers;Glass transition temperature;Molecular internal rotating steric factor;Stiff chain polymers;Flexible chain polymers   
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        发布时间：2023-04-23
      • Wu Zhili,Chen Xinwei,Zhang Jiashan
        Vol. 2, Issue 4, Pages: 11-19(1984)
        摘要：In this work we have investigated the 60Co gamma ray response characteristics of polymethy methacrylate piece, cellulose triacetate, polystyrene, polyvinyl alcohol, polycarbonate and polyethylene terephthalate films, which can be commercially supplied in chinese market.The absorption spectrum and the wavelength of optical absorbance reading, dose range and precision limits for these clear plastic films are studied. The effect of dose rate and stability of system after irradiation have been illustrated. The effects of temperature and relative humidities during and after irradiation on dose interpretation of this dosimeters are examined. The calibration curves are given under controlled experimental condition. The results show that cause for limited prepecision limits in these dosimeters vary in the thickness of the sensor, the dosimeter reseponse with differences in production batches or in lots supplied by different manufacturers, the environmental conditions, the dose rate denpendence, and the unstability in the systems after irradiation. Hence, when these plastic films are used for routine dosimetry in radiation processing with gamma radiation, the quality of materials must be selected, the thickness of films must be carefully monitored, and the calibration curves must be made under experimental conditions. Except for the polyvinyl alcohol film, others can be satisfied.The polymethyl metharylate piece and the cellulose triacetate film with different thickness are suitable for the doseage from 0.1 Mrad to 100 Mrad. For above 100 Mrad, the polycarbonate film and the polyethylene terephthalate film can be applied. But because polyethylene terephthalate film has strong dose rate dependence, the polycarbonate film should be used below 500 Mrad.  
        关键词：Clear Plastic Films (or Piece) Dosimeter;Dose Response Characteristics;Effects of Environmental Facter;Post-Irradiation Effect.   
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        发布时间：2023-04-23
      • Wang Mingjun,Dong Liaongchang,Du Cong,Ma Ruide
        Vol. 2, Issue 4, Pages: 20-28(1984)
        摘要：This paper is concerned with the theory on electron beam curing of polyether acrylic isocyanate oligomers, which belong to the terminal acrylic type with the structure expressed as follows:As each double bond is a bifunctional group, these oligomers can be considered as the Aa type molecule in the theoretical treatment. In the present work, the respective relationships among PA, PA(S), PA(g) and SA were derived, these parameters are the total reacted extent of group A, the reacted extent of group A in sol, the reacted extent of group A in gel and sol fraction respectively. when SA→1, the critical values ofPA, PA(S) and PA(g) are given with following formulae.Hence, the regularity about the curing process can be described as follows.Before gel point (SA=1), value of PA or PA(S) increases successively since PA=PA(S)and PA(g)=0;At gel point (SA=1):After gel point (0<SA<1): sol and gel coexist,PA(g)>PA>PA(s), and PA and PA(g) increase monotonously but PA(S) decreases.Without sol in system SA=0;The height of the absorption plak in oligomer was measured from I. R. spectra at different total dose. The disappearance rate of double bond can be characterized with the rate of the height reduction, which is approximately equal to the PA value calculated from the equation of PA vs. SA.  
        关键词：Oligomer;Electron beam curing;Theoretical treatment;Gel point;I. R. spectrum;Critical condition   
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        发布时间：2023-04-23
      • Qin Guoliang,Zhang Wenlong,Zhang Jiashan
        Vol. 2, Issue 4, Pages: 29-34(1984)
        摘要：The mechanism of tyrosine sensitizing the dimerization of thymine has been studied in this paper.Deoxidized aqueous solutions of thymine (2.2×10-3~2×10-2M) containing tyrosine (1×10-4~1×10-3M)were irradiated at dry ice temperature using Co-60 γ-rays at 4×107rads of absorbed dose, then a series of yields Gd of the dimer were determined. In the range of studied tyrosine concentrations, it was found that the values Gd varied with the concentrations of thymine and tyrosine and the values (1 - fS)3Gd all equal that obtained from the solution absenting tyrosine, however, the values (1-fS) 2KAG vary with the concentrations of thymine and tyrosine. Therefore it is evident that the mechanism of tyrosine sensitizing the dimerization of thymine is based on the energy transfer from excited state of tyrosine to aggregating state of thymine. The reaction dynamic process has been presented and the relationship between the dimer yield and the concentrations of thymine and tyrosine has been given as follows:The values of G2/G1 and (k5+k7)/k6 have been given in this paper. The following conclusions can be drawn out:1.owing to thymine with tyrosine being formed into mixed stacked aggregating state in frozen aqueous solution, the excited state energy of tyrosine can effectively transfer to aggregating state of thymine, then the yield of the dimer is incresed.2.In the case of higher concentrations of thymine the sensitization of tyrosine to dimerization behaves via the mechanism of energy of excited single state of tyrosine transferring to aggregating state of thymine rather than the mechanism of the excited triplet state.3.The increasing yield of the dimer varies with the concentrations of thymine and tyrosine.  
        关键词：Sensitization of tyrosine;Aggregated state;Single excited state;Triplet excited state;Energy transfer   
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        发布时间：2023-04-23
      • Pan Xianming,Yuan Rongyao,Wu Jilan
        Vol. 2, Issue 4, Pages: 35-44(1984)
        摘要：It has been investigated that TBP labeled with 32p was used as a probe for detecting the excited species of n-hexane produced under γ irradiation of 60Co. This paper studies the relationship between the G(DBP+MBP) and dose of the binary system of n-hexane—TBP. In the condition of extrapolating the dose to zero, the curve and the kinetic equation of sensitization of TBP by n-hexane have been obtained. Theoretical calculation was in harmony with experimental results.It has been found thatTBP can be sensitized by two species of excited state of n-hexane. The G values of excited n-hexane species equal 1.04 and 0.4 respectively and the life time can be estimated by diffusion controlled rate constant, τ1=0.3×10-9, τ2= 0.7×10-9.  
        关键词：Irradiation of TBP;Energy transfer;Irradiation of n-hexane-TBP;Excited states of n-hexane;Dependence of radiolysis of TBPon dose   
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        发布时间：2023-04-23
      • Meng Xiangshun,Zheng Xiulong
        Vol. 2, Issue 4, Pages: 45-49(1984)
        摘要：Hyperthermia, either alone or in combination with radiation, in the treatment of cancer is an area of considerable interest.In this essay, we used our modified millipore filter alkaline elution-fluorometric method to observe the effect of hyperthermia on radiation-induced DNA single strand breaks and rejoining in L7712 cells and to clarify the mechanisms by which hyperthermia potentiates the cell killing effect of radiation.The results showed that hyperthermia alone for 1 hr at temperature up to 42℃ did' not produce any measurable DNA strand breaks. Whereas at higher temperature exceeding 42℃ DNA strand breaks increased dramatically with the rise of heating temperature. Thus we suggested a new concept of "critical energy", which depended on both parameters of heating temperature and heating time at the same temperature. The effect of preirradiation hyperthermia mainly to increase DNA radiation-induced damage, but postirradiation hyperthermia caused the inhibition of rejoining of DNA strand breaks.  
        关键词：Effect of hyperthermia and radiation;DNA single strand breaks and rejoining;Millipore filter alkaline elution;Fluorometric assay;L7712 cells   
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        发布时间：2023-04-23
      • Ma Yuqin,Yu Mingzhu,Song Xueling
        Vol. 2, Issue 4, Pages: 50-53(1984)
        摘要：DNA cross linking is an type of radiation damage as important as DNA strand-break. The DNA interstrand cross-linking in the dilute solution has been studied, and the result showed that DNA interstrand cross-linking only presented with in the irradiation dose range of 20~100 Gy. The effect depends on concentrantions and G-C percentage of DNA and is independent of dose-rate. The radioprotective effects of cysteine and radiosensitive effects of 5'-Bromouracil were demostrated as well.  
        关键词：γ-irradiation;Cross-linking;Sensitizing agent;Protective agent   
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        发布时间：2023-04-23
      • Zhang Weiquin,Lin Zhefu
        Vol. 2, Issue 4, Pages: 54-57(1984)
        摘要：Air-dry rice seeds (Gui-Chao № 2) were exposed to gamma-rays from a 60Co source at different doses. After gamma-irradiation, seeds were germinated. Some enzyme levels (catalase, peroxidase, α-amylase, and phosphatase of the seedlings) were observed during germination. Among the enzymes being studied catalase was extraordinaryly sensitive to and had a positive correlation with the low doses of gamma irradiation, (0, 250, 750, 1500, and 3000 rad, at the dose rate of 750 rad/min).Catalase activity of the control seedlings was stimulated when the seedlings were oxposed to low concentration (about 30 mM) of exogenous H2O2.  
        关键词：Rice seed;Catalase hydrogen peroxide;Exogenous hydrogen peroxide   
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        发布时间：2023-04-23
      • Zhao Xiangzhen
        Vol. 2, Issue 4, Pages: 58-62(1984)
        摘要：Decay of fluorine containing organic radicals produced by fast electron irradiation of potassium 3-oxa fluoroundecane sulfonate potassium ω-chloro 3-oxa fluoroundecane sulfonate was slowly at room temperature, their lifetime were over 1000 days. Radiacals still had active reactivity as they could initiated the polymerization of styrene and acrylonitrile. There were no distinct difference in lifetime of radicals, produced either under vacuum or in the presence of air.  
        关键词：Free radical;Decay;Electron spin resonance;Irradiation;Fluorine compound   
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        发布时间：2023-04-23
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