最新刊期
      期 3 ， 1985
      • Chen Xinfang,Tang Auchin,Zhang Yiqun,Zhang Zicheng
        Vol. 3, Issue 3, Pages: 1-7(1985)
        摘要：In this paper we have theoretically discussed two kinds of the ways for enhancing radiation crosslinking of polymers, that is: (1) a second unit which crosslinks more easily is introduced into a linear polymeric chain, (2) a reactive polyfunctional monomer is mixed with a linear polymer before irradiation. According to the first model of enhanced crosslinking, the chain structure of the polymer can be described bywhere A and B are the units which react at different rates. During irradiation three crosslinking structures may be formed as follows:If the rates forming the structures of Type (Ⅱ) and (Ⅲ) are greater than that of Type(Ⅰ), we say that B has an enhancing effect on the radiation crosslinking of linear polymers with the main structural units of A. For instance, the radiation crosslinking of polydimethylsiloxane containing some methylvinylsiloxane units is of this model. On the basis of the elementary laws of probability, two general relations between sol fraction(1)(2)where W1 is the weight fraction of i-mers of the initial polymers, XA and XB are the number fractions of A and B, qA and qB are the number fractions of crosslinked units of Type A and B, S is the sol fraction, and φ is the probability that a crosslinked unit selected at random links up with the finite chains through a crosslink bridge.Considering the second model of enhanced crosslinking, for the mixture systems of a linear polymer and a bifunctional monomer the radiation may induce the crosslinking reactions of following two main types:where C—C is the bifunctional monomer, kAA and kAC are the rate constants of two different crosslinking reactions. If kAC>kAA, the bifunctional monomer has an enhancing effect on the radiation crosslinking of polymers composed of the structural units of A. Those polymers, such as polyethylene, polydimethylsiloxane and others, mixed with a reactive bifunctional monomer like ethylene glycol dimethacrylate can be irradiated to crosslink in such a way. Regarding XB the ratio of the numbers of bifunctional groups to that of the structural units of polymers, then, Eqs. (1) and (2) may also be applicable to the second model.From Eqs. (1) and (2) three special cases of the molecular weight distributions of initial polymers, namely uniform, Flory's and Schulz-Zimm's, are discussed.  
        关键词：Enhanced crosslinking;Radiation crosslinking;Crosslinking theory;Sol fraction;Crosslink density;Yeild of crosslinking;Kinetics of crosslinking reaction   
        3
        |
        1
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426783 false
        发布时间：2023-04-26
      • Chen Xinfang,Tang Xiaohui,Guan Hongtao,Zhang Zicheng,Zhang Lihua,Li Shuhua,Zhang Jiabing,Zhang Yiqun
        Vol. 3, Issue 3, Pages: 8-13(1985)
        摘要：We have discussed the two kinds of enhanced crosslinking of polymers and derived the general relationship between sol fraction and crosslink densities in the previous paper[1]. This paper applies the authers' theory to the special cases, that is: (1) the bifunctional monomer, ethylene glycol dimethacrylate (EGDMA), is used to enhance the radiation crosslinking reaction of polydimethylsiloxane; (2)some vinyl groups contained in the structural units of polydimethylsiloxane play an enhancing role in crosslink reactions during irradiation. Let us consider the first special case. By GPC method we have determined the molecular weight distribution of polydimethylsiloxane obeys Flory's. Thus, from Eqs. (12) and (15) in the previous paper we have(1)(2)where C represents the enhancing effect, qOA the number fraction of A crosslinked units at a unit of dose (its value can be calculated from Fig. 1), α the initial number-average degree of degradation being equal to the reciprocal of the number average degree of polymerization, and R the radiation dose. The physical meanings of XA, S, and φ are the same as in the previous paper. Using Eqs.(1) and (2) the theoretical curves relating S to R are shown in Fig. (2) and compared with the experimental data. The results show that the theoretical prediction at C=50 is in agreement with the experimental data in the region of low doses. It means that EGDMA has an enhancing effect on the radiation crosslinking of polydimethylsiloxane, and this is more remarkable in the range of low doses. The total yield of radiation crosslinking for the system is the sum of the yields of two kinds of different crosslinked bridges and can be calculated by the following relation:(3)where GA=0.48×106qOA/m (the value of m is equal to 74 for polydimethylsiloxane). According to Eqs. (1), (2) and (3)G(crosslink)-values of various irradiated samples calculated from experimental data are listed in Table 1, and show that the total crosslinking yield, becomes smaller as the dose increases and approaches a limited value of 1.6. This is a reasonable rule and can be interpreted as follows. At the beginning of the reaction the bifunctional monomer has a more enhancing effect on the radiation crosslinking of polydimethylsiloxane; and this effect decreases progressively with the reaction and finally disappears as the small amount of EGDMA in the system is nearly used up.Analogous to the treatment mentioned above the enhancing effect of some vinyl groups on the radiation crosslinking of polydimethylsiloxane with a small structural units of methylvinylsiloxane has been also investigated and illustrated in Fig. 3. By comparison of the experimental data of sol fraction for various radiation samples with the theoretical curves it can be concluded that the enhancing effects of a small amount of vinyl double bond on the radiation crosslinking of polymethylvinylsiloxane are very remarkable. The total yields of radiation crosslinking for polydimethylsiloxane with some vinylmethylsiloxane units are listed in Table 2, showing that G-value decreases with increasing the radiation dose.  
        关键词：Polydimethylsiloxane;polymethylvinylsiloxane;Radiation crosslinking;Enhanced radiation crosslinking   
        3
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426770 false
        发布时间：2023-04-26
      • Wang Gaodong,Wang Zailan,Zhang Jiashan
        Vol. 3, Issue 3, Pages: 14-18(1985)
        摘要：The mechamism of releasing inorganic phosphate from Deoxythymidine-5'-monophosphate(dTMP) and radiation protection on releasing inorganic phosphat from dTMP by Histidine have been inverstigated.The release of inorganic phosphate from dTMP results mainly from the acting of OH radical with H atom at position . It was calculated that rate constant for reaction of OH radical with position is (1.7±0.1)×108M-1S-1 and the rate constant for reaction of OH radical with dTMP is (5.0±0.2)×109M-1S-1.Because the OH radical was scavenged by Histidine effectively, the radiation protection from releasing inorganic phosphate from dTMP by Histidine was obvious. It may be seen from viscosity change of DNA after irradiation that Histidine exhibits marked protection from denaturation and degradation of DNA.  
        关键词：Deoxythymidine-5'-monophosphate;Deoxyribonucleic acid;Histidine;Radiation protection   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426695 false
        发布时间：2023-04-26
      • Xu Hansheng,Zhang Zhicheng,Liu Wei
        Vol. 3, Issue 3, Pages: 19-24(1985)
        摘要：The reactivity ratios of radiation copolymerization of the system of acrylamide (AM) and sodium acrylate (AANa) were studied in aqueous solution at room temperature and pH range from 7.4 to 12.1. The copolymerization carried out with high conversion and the monomer reactivity ratios r1 (AM) and r2 (AANa) were calculated using the Mayo-Lewis integration equation. There are no evident differences since r1 varies from 0.9 to 1.18 and r2 from 0.32 to 0.48 respectively.  
        关键词：Acrylamide;Sodium acrylate;Radiation copolymerization;Reactivity ratio   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426676 false
        发布时间：2023-04-26
      • Xu Hansheng,Zhang Zhicheng,Jin Yunzheng
        Vol. 3, Issue 3, Pages: 25-30(1985)
        摘要：The radiation and post-radiation polymerizations of acrylamide in solid state have been studied. But polymers were insoluble unfortunatly due to intermolecular crosslinking.When the chain transfer agent, isopropyl alcohol, was added, which effectively inhibits the crosslinking to give water soluble polymer, 95% conversion and molecular weight more than 5×106 polyacrylamide were obtained at a monomer concentration 65% in ice bath.  
        关键词：Acrylamide;Radiation polymerization in solid state;Radiation polymerization in pseudo solid state   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426672 false
        发布时间：2023-04-26
      • Liu Jinwen,Cheng Guodong,Zhang Rulin,Yao Yanyu
        Vol. 3, Issue 3, Pages: 31-36(1985)
        摘要：The change of cell division cycle, the sister-chromatid exchange frequency, chromosome aberration and satellite association are studied by using the BudR-Giemsa Labeling chromosomes. They are carried out after radiation of human peripheral blood in two different doses (0.5 and 1.0 Gy)under the condition of three continued culture times (51, 71 and 96 hr).The results show that the cell division cycle is apparently changed, a few changes of SCE frequency have not bearing on both culture time and dose, the chromosome aberration has negative correlation with the culture time but positive correlation with dose, the SAc and DGc indexes of the satellite associations are decreased with the dose increase, the satellite association type ratio, C/T is not changed greatly corresponding to the random allocation of genetic basic principle.  
        关键词：Satellite association;Chromosome aberration;BudR-Giemsa labeling chromosome;Sister chromatid exchange   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426768 false
        发布时间：2023-04-26
      • He Shaoqin,Liu Taifu
        Vol. 3, Issue 3, Pages: 37-43(1985)
        摘要：The system of Multicellular Tumor Spheroids (MTS) as an additional in vitro model, has been broadly used in cancer research since the 70's to study the characteristics of solid tumors and the effects of anti-cancer agents, particularly of radiation. This paper reviews and evaluates the method according to the authors' experience in using MTS in experiments. MTS simulates conditions found in those solid tumors which have similar histological structures, such as the existence of hypoxic and/or necrotic areas and the manifestation of a decrease of growth fraction as they increase in size.Various assays with samples in detail have been developed and adopted in MTS experiments including many of the techniques used in tumor biology to determine the dose response of tumors to radiation such as volume change, cell survival, cell viability, histology, cell loss, and cell cycle kinetics. Cells in MTS grown in close contact had an enhanced capability to accumulate and repair the damages induced by treatment, representing a higher resistance to treatment than monolayer cells. TO certain extent the MTS system, being biologically somewhere between in vivo and conventional in vitro monolayer cells, is an attrative modeldue to its low expense high turnover speed and copvience for use.  
        关键词：Multicelltlar tumor. spheroid;Growth fraction;surviving fraction;cell viability;cell Loss;"contact inhibition";Cell Kinetics   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426759 false
        发布时间：2023-04-26
      • Liu Renzhong,Ni Minghua,Lin Nianyun
        Vol. 3, Issue 3, Pages: 44-51(1985)
        摘要：It is important either for clinical potential or mechanism elucidation to study abnormal efficient radiosensitizer. Various 4-nitroimidazoles 5-substituted by sulphonamide, sulphonate or thioether groups have shown much more efficient radiosensitization effect than that predicted by their one electron reduction potential (). Accordingly, Some of them have been calculated by MO-CNDO/2 method. The calculated results were summarized as follows:In nitroimidazoles, the positive charge concentrates on nitrogen atom of the nitro group, but there are two positive charge centers in these ortho-substituted 4-nitroimidazales. One of them located on nitrogen atom of the nitro group, and the other located on sulphur atom of the 5-substituted group. The positive charge on sulphur atom is more than that on nitrogen atom.Another character of abnormal radiosensitizers is that their three frontier empty orbital energies are all lower than the lowest empty orbital energy of the target molecules, thymine. For nitroimidazoles, only their lowest empty orbital energies are lower than that of the target molecules. For imidazoles 5-substituted by sulphonamide, sulpohnate or thioether groups, their two frontier empty orbital energies are lower than the lowest empty orbital energy of the target molecules.The electron density distributions of three frontier empty orbit of calculated abnormal radiosensitizers were given and it was shown that their electron densities concentrates on 5-substituted group for both the first (ie the lowest empty orbit) and the third frontier empty orbit, but the electron densities for the second frontier empty orbit concentrates on nitro group and imidazole ring. Therefor the combination of the 5-substituted sulfur containig groups, and the nitro group induced the much more efficient radiosensitive effect of the ortho-substituted 4-nitroimidazoles. In these compounds, 5-substituted sulfur containing groups may be more impartant than nitro groups for their abnormal radiosensitization.  
        关键词：nitroheterocyclic compounds;Abnormal radiosensitizers;Radiation sensitization;Ortho-substituted 4-nitro-imidazoles;MO CNDO/2 calculations   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426831 false
        发布时间：2023-04-26
      • Zhou Mei,Chen yuan,Ji Fengju,Huang Wen wei,Pan Zheng rao
        Vol. 3, Issue 3, Pages: 52-58(1985)
        摘要：In Order to investigate the features of the response of Various tissues to radiation-induced lipoperoxidation stress, the SeGsHpx activity in RBC, plasma, liver, Spleen and small intestine of mice irradiated with various doses (500, 1000 and 2000 rad)and at various intervals after irradiation was determinated. The results showed that the forms of the response of Various tissues to radiation-induced lipoperoxidation were different from each other and might be grouped under four heads: 1) The tissues such as mature RBC, which cannot synthesize SeGSHPx. The characteristic change was that the enzyme activity decreased after irradiation; the extent of inhibition was increased with the increase of irradiation dasage, and became higher as time elapsed after irradiation with large dose (2000 rad). 2) non radiation sensitive tissues such as liver, which can synthesize SeGSHPx. It can response to radiation induced lipoperoxidation stress, but when the irradiation dosage was large enough to damage liver cells, the increase in the enzyme activity became less, in severe damage (2000 rad), SeGSHPx activity was decreased on the contrary; 3) Radiationsensitive tissues such as spleen. Owing to the necrosis of most spleen cells, the measured SeGSHPx activity could not entirely reflect that of lymphocytes and was thought to be influenced by the relative content of reticular cells in the spleen. In the sensitive tissue of small intestine, when irradiation dose was 2000 rad, as the intestinal mucosa was extensively detached the enzgme activity was decreased. But when the sensitive tissue that was damaged (1000 rad) reProduced again, the SeGSHPx activity could present an increase; 4) The enzyme activity in plasma was primarily decreased but it would become higher at some time after irradiation. This increase was mainly based on the release of SeGSHPx into blood from the destoyed spleen cells.  
        关键词：Radiation effect;Selenum-dependent-glutathion peroxidase;Radiation-induced Lipoperoxidation stress;Radiation-induced Lipoperoxidation stree reaction   
        2
        |
        0
        |
        0
        <HTML>
        <L-PDF><Meta-XML>
        <引用本文> <批量引用> 36426830 false
        发布时间：2023-04-26
      0