低剂量率下高线性能量转移碳离子束辐照人类唾液腺细胞的存活效应

利用日本千叶重离子医用加速器HIMAC提供的碳离子束,对人类唾液腺细胞(HSG)在剂量率为0.5Gy/h的低剂量率条件下进行了辐照,运用标准的克隆形成法得到了3种不同剂量平均线性能量转移(LET)碳离子束辐照HSG细胞的剂量存活效应.与先前HSG细胞在治癌剂量率(1￣5Gy/min)下对相近剂量平均LET碳离子束辐照的剂量存活效应数据相比,HSG细胞对高LET碳离子束辐射表现出明显的剂量率效应.为在相同条件下得到碳离子束对HSG细胞的相对生物学效应(RBE),利用60Co-#射线在剂量率为0.5Gy/h的条件下辐照了HSG细胞,得到该细胞系对低LET射线响应的剂量存活效应.与先前在治癌剂量率下得到的RBE值相比,低剂量率条件下得到的RBE值总体减小.由实验发现的剂量率效应及低剂量率条件下RBE值的减小,表明由高LET碳离子束造成的辐射损伤在低剂量率条件下也存在着显著的修复效应.据此,对辐射造成细胞致死的原因进行了探讨.

Thermochemical and thermal analysis on N-(p-methylphenyl)-N '-(2-pyridyl)urea

Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153degreesC) and the melting peak located at 447.01 K (173.86degreesC). The melting enthalpy was 204.445 kJ mol(-1) (899.6 J g(-1)). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11degreesC) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2degreesC).

Heat capacity and enthalpy of fusion of pyrimethanil laurate (C24H37N3O2)

Low-temperature heat capacities of pyrimethanil laurate (C24H37N3O2) were precisely measured with an automated adiabatic calorimeter over the temperature range between T = 78 K and T = 340 K. The sample was observed to melt at (321.52 +/- 0.04) K. The molar enthalpy and entropy of fusion as well as the chemical purity of the compound were determined to be (67244 +/- 11) J (.) mol(-1), (209.28 +/- 0.02) J (.) mol(-1) (.) K-1, (0.9943 +/- 0.0004) mass fraction, respectively. The extrapolated melting temperature for the absolutely pure compound obtained from fractional melting experiments was (322.264 +/- 0.006) K. (C) 2004 Elsevier Ltd. All rights reserved.

康氏木霉产酶发酵固体培养基优化研究

为利用廉价的培养基生产纤维素酶复合制剂,本实验采用培养基配方选择试验和双温度培养法对康氏木霉F244产酶特性进行了研究.在测定滤纸酶(FPA)、棉花酶、羧甲基纤维素酶(CMCase)、β-葡萄糖苷酶和果胶酶活力的基础上利用SPSS建立回归方程,全相关系数分别达到0.852,0.941,0.964,0.703,0.899,而后通过无约束规划求解找到最佳配方,并对酶活进行了预报和对比.结果表明:各酶活最大时对培养基各成分的含量要求不同;应用稻草粉质量分数20.3％,麸皮质量分数26.1％,(NH4)2SO4质量分数7.9％,水分质量分数45.7％的配方发酵时,F244的FPA、棉花酶、CMCase、β-葡萄糖苷酶、果胶酶活可望达14.1,20.1,43.9,21.6,16.8 IU/g,基本与里氏木霉Q9414在其推荐培养基上的产酶水平相当,而且该配方用料来源广泛,成本低廉,工艺简单,产品安全无毒.

施用化学农药对大豆田土壤线虫群落的影响

针对大豆生长期内单一与复合施用乙草胺和呋喃丹对土壤线虫群落结构的影响进行研究。研究结果表明,乙草胺和呋喃丹单一与复合处理中土壤线虫的数量在各采样时期之间、处理之间及二者的交互作用之间均呈现极显著差异(P<0.01);在大豆生长的不同时期,线虫各营养类群的数量受到不同程度的抑制。对线虫生态指数的分析结果表明,乙草胺单一处理对线虫的丰富度表现出促进效应,而呋喃丹单一处理和二者复合处理对线虫丰富度表现出抑制效应;各处理均显著降低了线虫的总成熟度指数(ΣMI),表明线虫群落受到扰动,食物网受到胁迫。

有机酸无机离子对土壤镉铅解吸特性的影响

为深入了解草甸棕壤中镉、铅的解吸行为,采用一次平衡法探讨有机酸、无机离子对镉、铅解吸特性的影响。结果表明,柠檬酸、草酸、组氨酸摩尔浓度较低时,有机配位体抑制镉的释放,而有机酸摩尔浓度较高时(>2 mmol·L-1)将明显促进镉的释放。柠檬酸、草酸、组氨酸对Pb的解吸率随有机酸摩尔浓度提高(0-20 mmol·L-1)而增大,对Cd、Pb浸提能力的大小关系为:柠檬酸﹥草酸﹥组氨酸。随解吸液中无机离子(C1-、SO42-、F-)摩尔浓度的增大,镉、铅的解吸率亦随之提高。无机离子对解吸土壤中Cd的影响力顺序是:C1->SO42->F-;对解吸土壤中Pb的影响力顺序是:SO42->C1->F-。