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1.
全氟辛烷磺酰基化合物(PFOS)的污染现状与研究趋势   总被引:28,自引:0,他引:28  
全氟辛烷磺酰基化合物(PFOS,perfluorooctane sulfonate)所造成的污染已经逐渐成为全球性环境问题,发达国家非常重视PFOS等全氟化合物的研究,已经成为持久性有机污染物研究的又一个热点。本文对目前PFOS研究的现状、进展,以及存在的问题做了简要回顾,并且对今后研究重点做了预测,希望对PFOS研究者提供参考。  相似文献   

2.
方泉  张邦治  王锐 《化学进展》2007,19(12):1977-1985
多肽在机体中具有重要的生理功能,并且它具有化学合成和修饰的便利性,因此它吸引了越来越多的化学、生物学及其交叉领域研究人员的研究兴趣。神经肽FF(NPFF)作为阿片调节肽在阿片耐受等药理学方面具有重要的调节作用,然而迄今为止仍缺乏NPFF受体高选择性的激动剂和拮抗剂,从而阻碍了NPFF药理学功能及其作用机制的研究。本文简述了NPFF的发现,并综述了近几年来在NPFF的前体、受体和生理学功能等方面所取得的最新进展,结合本实验室的工作重点介绍了NPFF构效关系方面的研究,并展望了该研究方向今后的发展趋势。  相似文献   

3.
朱晶  姜雪峰 《应用化学》2023,(4):610-614
通过对伍德沃德科学思想和方法的考察,分析他将物理仪器引入有机化学的思想和过程,提出仪器的引入不仅带来了化学学科在研究方法上的改变,还给化学研究带来了新的思维方式,助力化学从经验研究转为基于规则的推理。  相似文献   

4.
于文皓  祁艳霞  靳艳 《色谱》2019,37(5):471-476
人乳是新生儿最理想的天然食物,蛋白质是人乳中最主要的营养成分之一。随着蛋白质组学技术的发展,利用蛋白质组学的方法研究人乳蛋白质也取得了一些研究成果。本文综述了近年来蛋白质组学技术在人乳蛋白质研究中的应用,分别从人乳蛋白质的组成研究、动态变化、人乳与其他来源乳汁的蛋白质差异比较、人乳磷酸化蛋白和糖基化蛋白研究、人乳内源肽的研究及人乳蛋白与疾病等几个方面进行了阐述。蛋白质组学技术使人乳蛋白质的研究进入了微量营养研究的时代,人乳蛋白质组学的研究成果将为母婴健康提供更好的保障。  相似文献   

5.
利用知识图谱梳理了625篇有关实验能力研究的文献,分析了当前国内实验能力研究领域的热点关键词,围绕这些热点探讨了国内实验能力研究主题领域与现状。并尝试从共性和差异性的角度,总结基础教育领域各学科实验能力研究的内容与特点。  相似文献   

6.
研究血红蛋白与H2O2的相互作用过程及其反应机理具有重要的意义,关于H2O2与血红蛋白相互作用的研究已有报道,但观点不尽相同,结论各异,快速混合停流光谱是研究快速反应动力学的主要手段,在解释化学和生化反应机理方面发挥了重要的作用,本文利用停流时间分辨光谱研究了氧  相似文献   

7.
魏春英  杨频 《化学进展》2002,14(4):246-250
本文主要对国内稀土离子跨膜运输研究的进展作了评述,着重介绍了用荧光法及膜片钳法研究的结果,并对该领域的研究前景作了展望。  相似文献   

8.
陈凯 《化学教育》2019,40(24):80-90
通过文献的计量分析和阅读总结,我国物理化学课程与教学研究还局限于经验与思辨。我们梳理了国际权威期刊上研究物理化学教学的文献,将其分为教科书研究、学习研究、教学研究、教师研究和教学媒体研究等5类,并对其中核心成果进行评述。总结出国外物理化学课程与教学研究注重学习证据的收集和分析,注重教育研究方法的运用,并对于未来高等化学教育研究提出建议。  相似文献   

9.
低浓度三分子双曲型反应-扩散方程的非线性理论   总被引:2,自引:0,他引:2  
龚玉斌 《物理化学学报》1998,14(10):913-918
建立了低浓度三分子模型双曲型反应-扩散的波动方程,研究了定态的稳定性,重点研究了Turing不稳定问题,指出双曲型方程的Turing不稳定不受扩散系数不相等(Dx≠Dy)这一条件的约束,进而对方程作近似的分支分析,讨论了出现极限环的条件,最后对极限环和定态不稳定作了数值研究.  相似文献   

10.
在3.0-5.0 GPa,1150-1750 ℃,1-480 min条件范围内,合成了钠铝辉石,通过XRD、SEM及IR分析对比研究了人工翡翠和天然翡翠的微观精细结构;通过DAT分析测定了人工翡翠与天然翡翠的熔点,淬火实验检验了人工翡翠的熔点,通过退火及老化实验研究了翡翠的热稳定性。同时还就人工翡翠和天然翡翠的硬度、密度及折射率等其它物化性质进行了比较研究。根据上述研究总结了合成优质钠铝辉石翡翠的最佳实验条件为压力>4.0 GPa,温度>1450 ℃,晶化时间>45 min。  相似文献   

11.
根据中国及日本药典,对测定尿激酶活性的两种方法的灵敏度和重复性进行了考察对比,对不同样品测定结果进行了比较。  相似文献   

12.
The stages of the formation of metal hydroxide particles in water medium were described. The first stage is the formation of complexes between the stabilizer and metal ion or of metal polyions containing a few metal ions. Dependence between the number of metal ions in polyion and its charge on the pH is described. The second stage is the formation of the metal hydroxide particles by the aggregation of polyions or their adsorption on/in the stabilizer. The distribution of the polyion number in the particles in polyion aggregation is described by the equation p(k) = k(ks-1)(k-1)/ksk and in polyion adsorption on/in the stabilizer particles is more narrow and is described by the equation p(k) = exp(-ks)/ks(-k)/k!, where k and ks are the number and the average number of polyions in the particle.  相似文献   

13.
The Hamilton dynamics of a molecule in a translationally and/or rotationally symmetric field is kept rigorously constrained in its phase space. The relevant dynamical laws should therefore be extracted from these constrained motions. An internal space that is induced by a projection of such a limited phase space onto configuration space is an intrinsically curved space even for a system of zero total angular momentum. In this paper we discuss the general effects of this curvedness on dynamics and structures of molecules in such a manner that is invariant with respect to the selection of coordinates. It is shown that the regular coordinate originally defined by Riemann is particularly useful to expose the curvature correction to the dynamics and statistical properties of molecules. These effects are significant both qualitatively and quantitatively and are studied in two aspects. One is the direct effect on dynamics: A trajectory receives a Lorentz-like force from the curved space as though it was placed in a magnetic field. The well-known problem of the trapping phenomenon at the transition state is analyzed from this point of view. By showing that the trapping force is explicitly described in terms of the curvature of the internal space, we clarify that the physical origin of the trapped motion is indeed originated from the curvature of the internal space and hence is not dependent of the selection of coordinate system. The other aspect is the effect of phase space volume arising from the curvedness: We formulate a general expression of the curvature correction of the classical density of states and extract its physical significance in the molecular geometry along with reaction rate in terms of the scalar curvature and volume loss (gain) due to the curvature. The transition state theory is reformulated from this point of view and it is applied to the structural transition of linear chain molecules in the so-called dihedral angle model. It is shown that the curvature effect becomes large roughly linearly with the size of molecule.  相似文献   

14.
We present statistical thermodynamics of pressure denaturation of proteins, in which the three-dimensional integral equation theory is employed. It is applied to a simple model system focusing on the translational entropy of the solvent. The partial molar volume governing the pressure dependence of the structural stability of a protein is expressed for each structure in terms of the excluded volume for the solvent molecules, the solvent-accessible surface area (ASA), and a parameter related to the solvent-density profile formed near the protein surface. It is argued that the entropic effect originating from the translational movement of water molecules plays critical roles in the pressure-induced denaturation. We also show that the exceptionally small size of water molecules among dense liquids in nature is crucial for pressure denaturation. An unfolded structure, which is only moderately less compact than the native structure but has much larger ASA, is shown to turn more stable than the native one at an elevated pressure. The water entropy for the native structure is higher than that for the unfolded structure in the low-pressure region, whereas the opposite is true in the high-pressure region. Such a structure is characterized by the cleft and/or swelling and the water penetration into the interior. In another solvent whose molecular size is 1.5 times larger than that of water, however, the inversion of the stability does not occur any longer. The random coil becomes relatively more destabilized with rising pressure, irrespective of the molecular size of the solvent. These theoretical predictions are in qualitatively good agreement with the experimental observations.  相似文献   

15.
Kragten J 《Talanta》1971,18(3):311-322
The photometric titration of the metal indicator complex MI with a ligand L is discussed. A tangent procedure is adopted for the determination of the end-point. From this procedure, in combination with an assumed maximum titration error, titration conditions have been derived. A procedure is introduced which, in conjunction with the derived titration conditions, permits the selection of a suitable titration medium by means of a diagram in which log K, log alpha and log chi are plotted vs. pH. The procedure is applied to determination of lead and zinc in the presence of citric acid, the medium used for their paper-electrophoretic separation. The use of citric acid introduces some limitations; it is shown that the method developed is generally applicable.  相似文献   

16.
The mechanism by which a typical fire retardant chloroparaffin imparts fire retardant characteristics to high density polyethylene, polypropylene and polystyrene is studied by comparing the oxygen indices of these mixtures measured before and after dehydrochlorination. It is shown that flame poisoning by HCl evolved from the chloroparaffin is negligible in polystyrene and high density polyethylene, whereas it is noticeable in polypropylene. The results obtained are related to previous data on the thermal degradation of these mixtures. It is concluded that the chloroparaffin acts mainly by modifying the mechanism of pyrolysis of these polymers in the burning process. Only in the case of polypropylene is there an appreciable contribution by flame poisoning.  相似文献   

17.
The variation of balance rest point reproducibility over a wide range of sensitivities is surveyed. At low sensitivities, the reproducibility in scale units is a constant. The weighing reproducibility in milligram units in this region is limited by the readability of the scale and may be improved by increasing balance sensitivity or replacing the regular scale with a micro scale and magnifier. As the sensitivity is increased above a certain limit, control of milligram reproducibility passes from scale readability to the mechanical error of the balance. At high sensitivities, reproducibility in milligram units is practically constant and this constant is a criterion of the mechanical character of the balance.  相似文献   

18.
The thermodynamics of swelling of copolymers of acrylic acid β-vinyloxyethylamide with acrylamide and N-vinylpyrrolidone of various compositions in water and ethanol is investigated. It is established that the swelling of the copolymers in water is characterized by high negative enthalpy values and that the swelling in ethanol is an endothermic process. It is found experimentally that the hydrogels obtained experience contraction at elevated temperatures.  相似文献   

19.
A structural interpretation of the catalytic action of carbon nanotubes on the curing of epoxy polymers is proposed. It is based on the fractal analysis ideas. It is shown that essentially the only factor determining the kinetics of the curing process is the microgel structure characterized by its fractal dimension. The most important conclusion from the obtained results is the fact that the reaction rate dependences on the structural parameters are described by the same correlation for the epoxy polymer curing reaction both in the presence and absence of carbon nanotubes. This means that the catalytic effect of carbon nanotubes consists in a change in the structure of microgels.  相似文献   

20.
钱人元 《中国化学》2003,21(12):1562-1564
A new formulation of the Lindemann mechanism of unimolecular reactions in gaseous phase is presented, without the use of steady state hypothesis. It is hereby shown that the nature of applicability of steady state hypothesis in the regime of high reactant gas pressure is different from that in the regime of low gas pressure. In the former case it is an equilibrium approximation, while in the latter case it is a highly reactive intermediate approximation in no connection with a steady state. Furthermore for the latter case it is shown that in the classical formulation of Lindemann mecbRnism the use of steady state hypothesis is an ad hoc assumption. A highly reactive intermediate in the sense that its concentration is very small during the whole course of reaction is a necessary condition for the applicability of very reactive intermediate approximation. When the two distinctive nature of the applicability of steady state hypothesis is mlxed-up, wrong or useless conclusion may be arrived at. The only possible case of realizing a true steady state in a complex reaction is pointed out.  相似文献   

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