首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 328 毫秒
1.
氧硫化碳(COS)主要是石油加工和有机物合成等生产中产生的,是有机中常见的有机物中间体,对人体有毒害作用。介绍了COS的危害、来源及制备等和各种脱除方法包括还原法、吸收法、水解法、吸附法、光解法等方法。归纳了脱除COS方法的反应机理和动力学研究。展望了脱除COS方法的研究前景。  相似文献   

2.
论化学方法与教学方法的融合   总被引:2,自引:0,他引:2  
王祖浩 《化学教育》1997,18(6):12-15
针对化学教育中对学科方法的研究尚待深化的现状,作者从理论与实践的结合上论述了化学方法与教学方法的关系,从中得出化学方法与教学方法融合的必然结论。  相似文献   

3.
邻苯二甲酸酯类增塑剂分析方法进展   总被引:15,自引:0,他引:15  
本文详细介绍了国内外邻苯二甲酸酯类增塑剂检测方法的研究进展。对环境(大气、水体、土壤)中和塑料产品中的邻苯二甲酸酯的样品的预处理方法和检测技术作了综述,并提出了检测中存在的问题和研究前景。  相似文献   

4.
自由基是卷烟烟气中主要的一类有害物质,能导致人体组织和细胞的氧化,损害细胞膜上的脂类和蛋白质。引发癌症等疾病。对烟草中自由基的研究情况、自由基的检测方法、降低卷烟中自由基含量的研究等方面进行了综述。  相似文献   

5.
本文根据高分子行业的发展对人才的需求及高分子专业的培养目标定位,提出了在高等院校高分子专业本科阶段加强教授聚合物流变学内容的必要性,在介绍聚合物流变学的研究内容和研究方法的基础上归纳了其特点和重要性,根据高分子专业课程体系的承接性提出了流变学教学设置,进而结合高分子专业学生特点探讨了聚合物流变学本科教学的讲授内容和课时安排,并对教学过程中采用的教学方法和手段进行了探讨,还提出了在高分子实验中开设与流变学相关的实验促进教学的方法。  相似文献   

6.
方法检出限三个评估方法标准解读与比较   总被引:2,自引:0,他引:2  
文献中有多项方法检出限评估标准,如何正确理解和运用这些标准得到可比较的参数对基层实验室具有指导意义。对目前国内外方法检出限评估方法标准进行了系统总结和梳理,介绍了不同方法的特点、适用范围和注意事项。利用实验室实例和文献数据,比较了三种代表性方法计算结果。基于科学性和可操作性的原则,针对不同需求,提出了检出限评估改进建议及实施方案。  相似文献   

7.
本文研究了气相色谱分析羊水中痕量有机酸的各种预分离方法。对各种结构类型的标准有机酸水溶液进行回收实验以及实际的羊水样品分析表明,硅酸吸附法具有比较全面的优越性,是研究羊水中痕量有机酸较为理想的预分离方法。离子交换法对大多数有机酸也具有较高的回收率,但它的操作过程比较冗长。溶剂萃取法对柠檬酸、甘油酸等某些多元酸或羟基酸的回收不很理想,但对其它许多有机酸也可以取得较好的结果。所研究的方法均能分离除去羊水中大量的磷酸盐和硫酸盐,消除它们对有机酸气相色谱分析的干扰。  相似文献   

8.
超分子中分子间弱要互作用力的研究方法概述   总被引:5,自引:0,他引:5  
陈强  谭民裕等 《化学通报》2001,64(4):236-239
随着超分子化学研究的深入,对分子间弱相互作用力的研究越来越爱到世界科学界的重视,对其本质的研究已成为超分子化学急待解决的问题,本文介绍了超分子体系弱相互作用力的种类及其理论和实验研究方法。  相似文献   

9.
纳米铝微粒制备的研究进展   总被引:1,自引:0,他引:1  
综述了近年来铝纳米微粒制备方法的研究进展,详细介绍了物理气相沉积法、化学法和机械法的方法原理、特点及其制备研究中存在的问题,并对其未来研究进行了展望:(1)深入地研究纳米铝微粒的结构和性质及制备机理;(2)发展和完善现有制备工艺,寻求适合工业化生产的高效、廉价制备途径;(3)纳米铝微粒的表面改性和修饰技术研究.  相似文献   

10.
石墨电极的纯度对光谱分析的影响只是在一些书中提及,表作试验研究和分析,对电极的纯度的检验未作有效论述。文中就此问题提出了作者的见解,拟定了检验电极纯度的方法。  相似文献   

11.
New methods for separation and determination of actinides, widely used in analysis of actinides in technological and environmental samples are reviewed. Special attention is paid to obtaining and stabilizing transplutonium elements. (TPE) in extreme oxidation states. Their use in analytical practice resulted in expanding possibilities of methods for separation and determination of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Methods of separation in gas phase and some other methods such as precipitation and coprecipitation are applied, however, to a lesser degree. Trends of development of these methods including those of various types of membrane extraction that succeeded in separation of TPE in both trivalent and other valence states have been shown. Attention is paid mainly to consideration of modern methods for determination of actinides, special distinction of such methods being low limits of determination, high precision and selectivity. Alpha- and beta-spectrometric methods with semiconductor detectors are the most advanced among various methods based on registration of nuclear radiation. Tremendous success has been achieved in development of emission-spectrometric methods for determination of trace amounts of actinides and various impure elements occurring in samples of actinides. Sensitive mass-spectrometric methods are widely used for determination of both isotope composition and content of elements in various samples including those which are highly radioactive. More simple and precise titrimetric methods based on using oxidizing-reducing or complexing agents are developed successfully. A large number of coulometric methods for determination of americium and berkelium, characterizing high precision and selectivity as well as luminescence methods have been developed.  相似文献   

12.
Special Session B at the 29th Symposium on Biotechnology for Fuels and Chemicals was the first invited session at this symposium devoted to analytical methods. The special topic was added in response to numerous requests for information on new and innovative methods that could be applied in the growing renewable fuels industry. Presentation topics include analytical methods for the characterization and analysis of maize traits, tools for investigating cell wall limitations to enzymatic degradation, methods for customizing enzyme cocktails for biomass, new techniques for the analysis of carbohydrates, analytical methods that enhance our understanding of pretreatment, improved methods for monitoring process intermediates, and published standard analytical methods for biomass conversion processes.  相似文献   

13.
Genetically modified organisms (GMOs) entered the European food market in 1996. Current legislation demands the labeling of food products if they contain <1% GMO, as assessed for each ingredient of the product. To create confidence in the testing methods and to complement enforcement requirements, there is an urgent need for internationally validated methods, which could serve as reference methods. To date, several methods have been submitted to validation trials at an international level; approaches now exist that can be used in different circumstances and for different food matrixes. Moreover, the requirement for the formal validation of methods is clearly accepted; several national and international bodies are active in organizing studies. Further validation studies, especially on the quantitative polymerase chain reaction methods, need to be performed to cover the rising demand for new extraction methods and other background matrixes, as well as for novel GMO constructs.  相似文献   

14.
There are many methods for analyzing solid-state kinetic data. They are generally grouped into two categories, model-fitting and isoconversional (model-free) methods. Historically, model-fitting methods were widely used because of their ability to directly determine the kinetic triplet (i.e., frequency factor [A], activation energy [E(a)], and model). However, these methods suffer from several problems among which is their inability to uniquely determine the reaction model. This has led to the decline of these methods in favor of isoconversional methods that evaluate kinetics without modelistic assumptions. This work proposes an approach that combines the power of isoconversional methods with model-fitting methods. It is based on using isoconversional methods instead of traditional statistical fitting methods to select the reaction model. Once a reaction model has been selected, the activation energy and frequency factor can be determined for that model. This approach was investigated for simulated and real experimental data for desolvation reactions of sulfameter solvates.  相似文献   

15.
This review of methods for determining antimalarial drugs in biological fluids has focused on the various analytical techniques for the assay of chloroquine, quinine, amodiaquine, mefloquine, proguanil, pyrimethamine, sulphadoxine, primaquine and some of their metabolites. The methods for determining antimalarials and their metabolites in biological samples have changed rapidly during the last eight to ten years with the increased use of chromatographic techniques. Chloroquine is still the most used antimalarial drug, and various methods of different complexity exist for the determination of chloroquine and its metabolites in biological fluids. The pharmacokinetics of chloroquine and other antimalarials have been updated using these new methods. The various analytical techniques have been discussed, from simple colorimetric methods of intermediate selectivity and sensitivity to highly sophisticated, selective and sensitive chromatographic methods applied in a modern analytical laboratory. Knowledge concerning the method for a particular study is determined by the type of application and the facilities, equipment and personnel available. Often is it useful to apply various methods when conducting a clinical study in malaria-endemic areas. Field-adapted methods for the analysis of urine samples can be applied at the study site for screening, and corresponding blood samples can be preserved for subsequent analysis in the laboratory. Selecting samples for laboratory analysis is based on clinical, parasitological and field-assay data. The wide array of methods available for chloroquine permit carefully tailored approaches to acquire the necessary analytical information in clinical field studies concerning the use of this drug. The development of additional field-adapted and field-interfaced methods for other commonly used antimalarials will provide similar flexibility in field studies of these drugs.  相似文献   

16.
Two spectrophotometric methods, derivative and multivariate methods, were applied for the determination of binary, ternary, and quaternary mixtures of the water-soluble vitamins thiamine HCI (I), pyridoxine HCI (II), riboflavin (III), and cyanocobalamin (IV). The first method is divided into first derivative and first derivative of ratio spectra methods, and the second into classical least squares and principal components regression methods. Both methods are based on spectrophotometric measurements of the studied vitamins in 0.1 M HCl solution in the range of 200-500 nm for all components. The linear calibration curves were obtained from 2.5-90 microg/mL, and the correlation coefficients ranged from 0.9991 to 0.9999. These methods were applied for the analysis of the following mixtures: (I) and (II); (I), (II), and (III); (I), (II), and (IV); and (I), (II), (III), and (IV). The described methods were successfully applied for the determination of vitamin combinations in synthetic mixtures and dosage forms from different manufacturers. The recovery ranged from 96.1 +/- 1.2 to 101.2 +/- 1.0% for derivative methods and 97.0 +/- 0.5 to 101.9 +/- 1.3% for multivariate methods. The results of the developed methods were compared with those of reported methods, and gave good accuracy and precision.  相似文献   

17.
Prediction methods of structural features in 1D represent a useful tool for the understanding of folding, classification, and function of proteins, and, in particular, for 3D structure prediction. Among the structural aspects characterizing a protein, solvent accessibility has received great attention in recent years. The available methods proposed for predicting accessibility have never considered the combination of the results deriving from different methods to construct a consensus prediction able to provide more reliable results. A consensus approach that increases prediction accuracy using three high-performance methods is described. The results of our method for three different protein data sets show that up to 3.0% improvement in prediction accuracy of solvent accessibility may be obtained by a consensus approach. The improvement also extends to the correlation coefficient. Application of our consensus approach to the accessibility prediction using only three prediction methods gives results better than single methods combined for consensus formation. Currently, the scarce availability of predictors with similar parameters defining solvent accessibility hinders the testing of other methods in our consensus procedure.  相似文献   

18.
We compare the performance of four recently developed DFT methods (MPW1B95, MPWB1K, PW6B95, and PWB6K) and two previous, generally successful DFT methods (B3LYP and B97-1) for the calculation of stacking interactions in six nucleic acid bases complexes and five amino acid pairs and for the calculation of hydrogen bonding interactions in two Watson-Crick type base pairs. We found that the four newly developed DFT methods give reasonable results for the stacking interactions in the DNA base pairs and amino acid pairs, whereas the previous DFT methods fail to describe interactions in these stacked complexes. We conclude that the new generation of DFT methods have greatly improved performance for stacking interaction as compared to previously available methods. We recommend the PWB6K method for investigating large DNA or protein systems where stacking plays an important role.  相似文献   

19.
Over the years nuclear methods have proved to be a valuable asset to industry in general and to the automotive industry in particular. This paper summarizes some of the most important recent contributions of nuclear technology to the development of vehicles having high quality and long-term durability. Radiotracer methods are used to measure engine oil consumption and the wear rates of inaccessible components. Radiographic and tomographic methods are used to image fluids and structures in engines and accessory components. Tracers are used to understand combustion chemistry and quantify fluid flow. Gauging methods are used for inspection and process control. Nuclear analytical methods are used routinely for materials characterization and problem solving. Although nuclear methods are usually considered as the means of last resort, they can often be applied more easily and quickly than conventional methods when those in industrial engineering and R&D are aware of their unique capabilities.  相似文献   

20.
The density functional theory (DFT) is the most popular method for evaluating bond dis-sociation enthalpies (BDEs) of most molecules. Thus, we are committed to looking for alternative methods that can balance the computational cost and higher precision to the best for large systems. The performance of DFT, double-hybrid DFT, and high-level com-posite methods are examined. The tested sets contain monocyclic and polycyclic aromatic molecules, branched hydrocarbons, small inorganic molecules, etc. The results show that the mPW2PLYP and G4MP2 methods achieve reasonable agreement with the benchmark values for most tested molecules, and the mean absolute deviations are 2.43 and 1.96 kcal/mol after excluding the BDEs of branched hydrocarbons. We recommend the G4MP2 is the most appropriate method for small systems (atoms number ≤20); the double-hybrid DFT methods are advised for large aromatic molecules in medium size (20 ≤atoms number ≤50), and the double-hybrid DFT methods with empirical dispersion correction are recommended for long-chain and branched hydrocarbons in the same size scope; the DFT methods are advised to apply for large systems (atoms number ≥50), and the M06-2X and B3P86 methods are also favorable. Moreover, the di erences of optimized geometry of different methods are discussed and the effects of basis sets for various methods are investigated.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号