共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
3.
用微量热法测定了大肠杆菌及其在2,4-二羟基苯甲醛氨基葡萄糖Schif碱锌配合物(Zn-2,4-L)和两种细菌在锌离子作用下的热谱;计算了在Zn-2,4-L作用下大肠杆菌的生长速率常数k、传代时间G、代谢抑制率I、总产热量Q、单个细胞的平均产热量Q0和每分钟单个细胞的平均产热量Q0;根据k~T数据,拟合了lnk~1/T方程,得到了大肠杆菌生长代谢的激活能Ea和指前因子A;由大肠杆菌生长代谢的参数作图拟合得到了t~k和tr~k方程;计算了大肠杆菌和产气杆菌在锌离子作用下的生长速率常数k、传代时间G、生长代谢抑制率I;探讨了细菌在不同条件下的生长代谢和化合物的抗菌活性。 相似文献
4.
考察了十四烷基二甲基苄基氯化铵(TDBAC)含量在不同污泥含量下(即不同TDBAC污泥负荷比m(TDBAC)/m(MLSS))对反硝化细菌的抑制特性以及对NO3--N还原过程的影响。结果表明,TDBAC对反硝化速率有明显抑制特性,随着TDBAC含量的增加,对反硝化的抑制逐渐升高,当MLSS的质量浓度分别为1 000、2 000 mg.L-1时,拟合曲线计算半抑制的质量浓度(Iρ50)分别为3.95、4.62 mg.L-1;抑制率为50%时负荷比为3.0 mg.g-1,当负荷比为15.8 mg.g-1时,抑制率可达90%。 相似文献
5.
6.
为了研究石油污染对土壤微生态的影响,本文分析了石油污染土壤的基本理化性质并采用了微量量热法探索了不同石油污染程度土壤样品的微生物能量代谢特征。结果表明石油污染不仅严重影响土壤有机质组成,同时,明显干扰土壤介质的蓄水能力;也在一定程度上改变了土壤生态系统N、P等营养元素循环。随着土壤石油污染程度的增加,总放热量Q_(total),生长速率常数k和最大热功率值Pmax均呈现降低的趋势,与此同时,到达最大热功率Pmax时间也在延迟,所有的热功率参数均在一定程度上表明石油污染严重影响了土壤介质中微生物的能量代谢过程,干扰了土壤环境正常的物质代谢和能量流通。。 相似文献
7.
酿酒酵母在硅橡胶膜生物反应器中连续发酵的生长动力学 总被引:11,自引:0,他引:11
实验研究了酿酒酵母在硅橡胶膜生物反应器中的细胞生长速率与操作参数之间的关系。在三水平正交实验基础上,用Gauss Newton非线性最小二乘法拟合了细胞比生长率与葡萄糖浓度、乙醇浓度和细胞浓度3变量之间的关系式,得到硅橡胶膜生物反应器乙醇连续发酵的细胞最大比生长率、饱和常数、产物抑制常数和群聚抑制常数等基本动力学参数,表明当细胞浓度达到15g/L或乙醇浓度达到70g/L时细胞生长受到完全抑制。连续发酵实验验证了硅橡胶膜生物反应器中的细胞生长动力学满足拟合模型的规律。 相似文献
8.
研究了N-乙酰-L-半胱氨酸(NAC)对H2O2刺激的人体皮肤成纤维细胞(HSF)的抗细胞损伤作用。细胞存活率和细胞阳性率实验结果表明:NAC在低质量浓度(50~100 mg·L-1)时对HSF没有明显的细胞毒性;在质量浓度为200~800 mg·L-1时可促进细胞增殖;而在质量浓度较高(1 000 mg·L-1)时则明显抑制HSF生长。空白组、H2O2组、H2O2(500μmol·L-1)+NAC(100 mg·L-1)组和H2O2(500μmol·L-1)+NAC(200 mg·L-1)组细胞阳性率分别为39.90%,69.57%,45.29%和36.60%,NAC可明显降低β-半乳糖苷酶染色阳性率,抵抗由H2O2引起的细胞损伤。 相似文献
9.
过氧亚硝酸根离子(ONOO-)是一氧化氮自由基与超氧阴离子的反应产物,具有强氧化性及强硝化性,能够导致细胞及组织损伤,从而引发疾病。选取3种不同结构的天然食品添加剂桑色素、葛根素、辣椒红作为研究对象,采用荧光光谱法研究了3种天然食品添加剂对ONOO-诱导L-酪氨酸氧化损伤的抑制能力,采用邻苯三酚自氧化法研究了3种天然食品添加剂的抗氧化能力,采用高效液相色谱法研究了3种天然食品添加剂对ONOO-诱导L-酪氨酸硝化损伤的抑制能力。结果表明,随着天然食品添加剂浓度的增加,对L-酪氨酸二聚体的抑制率增大,以抑制率达到50%时的浓度(IC50)判断的抑制能力大小为:辣椒红桑色素葛根素VC,辣椒红的IC50为0.56μmol·L-1;随着天然食品添加剂浓度的增加,对邻苯三酚自氧化抑制率增大,以IC50判断的抑制能力大小为:葛根素桑色素辣椒红VC,葛根素的IC50为0.051mmol·L-1;随着天然食品添加剂浓度的增加,对L-3-硝基酪氨酸的抑制率增大,以IC50判断的抑制能力大小为:葛根素桑色素辣椒红VC,葛根素的IC50为0.00026μmol·L-1。3种食品添加剂抗自由基能力与其分子结构中主要官能团空间结构以及官能团数量密切相关。 相似文献
10.
通过测定对孟烷-1,2,4-三醇在不同浓度下对黑麦草的种子发芽抑制率、根长抑制率及芽长抑制率,研究其对黑麦草的除草活性.结果表明,对孟烷-1,2,4-三醇能明显抑制黑麦草种子的发芽、胚根胚芽的生长,芽前处理对黑麦草的发芽、根长及芽长的抑制中浓度分别为2.93 mmol· L-1、0.50 mmol·L-1和0.97 mmol·L-1,芽后处理对黑麦草的根长和芽长的抑制中浓度分别为1.79 mmol· L-1和2.90 mmol·L-1.表明,对孟烷-1,2,4-三醇对黑麦草具有除草活性,且芽前除草活性高于芽后除草活性. 相似文献
11.
12.
The transport properties of ionic liquids (ILs) are crucial properties in view of their applications in electrochem-ical devices. One of the most important advantages of ILs is that their chemical–physical properties and conse-quently their bulk performances can be well tuned by optimizing the chemical structures of their ions. This will require elucidating the structural features of the ions that fundamentally determine the characteristics of the nanostructures and the viscosities of ILs. Here we showed for the first time that the“rigidity”, the order, and the compactness of the three-dimensional ionic networks generated by the anions and the cation head groups determine the formation and the sizes of the nanostructures in the apolar domains of ILs. We also found that the properties of ionic networks are governed by the conformational flexibility and the symmetry of the anion and/or the cation head group. The thermal stability of the nanostructures of ILs was shown to be con-trolled by the sensitivity of the conformational equilibrium of the anion to the change of temperature. We showed that the viscosity of ILs is strongly related to the symmetry and the flexibility of the constitute ions rather than to the size of the nanostructures of ILs. Therefore, the characteristics of the nanostructures and the viscosities of ILs, especially the thermal stability of the nanostructures, can be fine-tuned by tailoring the symmetry and the conformational flexibility of the anion. 相似文献
13.
14.
Investigation of the effects of fatty acids on the compressive strength of the concrete and the grindability of the cement 总被引:1,自引:0,他引:1
In cement industry, a great energy consumption has been observed during grinding of clinker. To reduce this consumption, some waste products have been used as grinding aids.In this investigation, the effects of sunflower oil (SO), oleic acid (OA), stearic acid (SA), myristic acid (MA) and lauric acid (LA) on the fineness and strength of the cement have been examined. These aids were added into clinker in certain ratios based on the cement clinker weight and the grinding has been done for a definite time at the same condition.All of the fatty acids used increased the fineness as compared with the cement without the grinding additives. SO and OA decreased the strength significantly, LA decreased it to a lesser extent and SA increased it definitely according to the common cement. But MA did not alter the strength of the cement as much as SA. In addition, the covering of the balls influences the grinding of cement clinker unfavourably. 相似文献
15.
16.
17.
18.
Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and 3,5-diaminobanzoic acid (DABA), were used as polyelectrolytes in this study. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to monitor the effect of the various kinds of PEG on the changes in morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO4) dopants. The results of DSC and FT-IR indicate the Li+ ions coordinate with the soft and hard segments. Additionally, the crystallinity of the PEG soft segment and the ordered hydrogen-bonded urea carbonyl groups decreased with increasing salt concentration. Impedance spectroscopy (IS) measurements show that the PUU electrolyte with the high phase separation degree has the high ionic conductivity. The hard-segment Tg and the soft-segment Tm influence the conductivity behavior of polyelectrolytes with increasing measurement temperature. 相似文献
19.
组合凹模的应力分析是一个非常复杂的问题,对其进行精确分析是解决模具寿命的关键。本文采用有限元分析软件Ansys对转子的组合凹模进行了分析,为转子组合凹模的优化设计提供了依据。 相似文献
20.
In spinning basalt fibres, the drafting force is in the same range as in spinning of glass fibres. The effect of the drafting
force can not be considered in the calculation for the strength and rigidity of the bottom of the spinneret.
__________
Translated from Khimicheskie Volokna, No. 5, pp. 47–50, September–October, 2007. 相似文献