物理法COD减排理论极限能耗的热力学分析

首先针对系统的可持续性发展提出了三点本质要求,在此基础上提出了基于减排过程节能机制的热力学框架,并根据热力学第一、第二定律建立了计算物理法脱除有机污染物理论极限能耗的热力学分析方法.此外,以典型有机污染物的脱除为例,分别计算了封闭体系中298.15K和1.01325×105Pa下不同初始浓度、不同种类以及不同COD减排量的有机污染物脱除的理论极限能耗.本文的计算结果表明,废水中有机污染物的减排需要很高的能耗,脱除相同量有机污染物所需的理论极限能耗随着初始浓度的减小而显著增加,且不同种类污染物处理的难易程度和能耗高低相差很大,这充分说明减排与节能有着密不可分的联系,充分考虑污染物的种类、物理化学性质、毒性和浓度将有助于减排政策的科学制定.     

Thermodynamic analysis of the theoretical energy consumption in the removal of organic contaminants by physical methods

The essential requirements for evaluating the sustainable development of a system and the thermodynamic framework of the energy conservation mechanism in the waste-removal process are proposed.A thermodynamic method of analysis based on the first and second laws of thermodynamics is suggested as a means to analyze the theoretical energy consumption for the removal of organic contaminants by physical methods.Moreover,the theoretical energy consumption for the removal by physical methods of different kinds of...     

Uncertainty analysis of theoretical methods for adiabatic temperature rise determination in calorimetry

The main methods for the determination of the temperature rise in calorimetric experiments corrected of heat losses to surroundings (called adiabatic temperature rise) are described thereafter. This corrected temperature rise is obtained analytically from experimental temperature–time curves. The general scheme reported by Henri Régnault and Leopold Pfaundler for the first time in the 19th century is considered as the basis for all methods elaborated afterwards. A bibliographical study raised five methods including Régnault–Pfaundler’s. These methods have been applied on five experimental temperature–time curves obtained with an isoperibolic reference gas calorimeter at the French national metrology and testing institute (LNE) on combustion of pure methane. This paper deeply details a new analytical method elaborated at LNE exposing best heat transfer phenomena representation occurring in the water bath calorimeter. A comparative study of the five methods of the temperature rise determination and of their associated uncertainties is here presented.     

Chemical methods in association with physical methods in drug analysis

Physical methods, namely spectroscopy and separation techniques such as high-performance liquid chromatography, in which the analyte is not chemically changed during analysis, have gained increasing popularity in the field of pharmaceutical analysis. Nevertheless, chemical manipulation in combination with such methods will continue to play a vital role, as will be demonstrated with examples selected from methods developed for two new, cardioactive drugs, nadolol and captopril, and from other recent literature references.     

Numerical studies for a theoretical analysis of semiempirical LCAO–CI methods

A numerical investigation of Del Re and Parr's formulas [1] for the treatment of π systems has been preformed in the case of five-membered rings, using two different expressions for the core Hamiltonian and different values for the effective charges. The results obtained are discussed by analysing the three stages of the calculation: (a) a non-iterative LCAO –MO calculation; (b) the same calculation with corrections for exchange and repulsion terms arising from fluctuations of the orbital populations; (c) configuration interaction. The calculations are interesting also because they do not involve the zero differential overlap approximation; a calculation without inclusion of overlap hse been carried out for pyrrole and the results have been compared with those including S . The main conclusions hold also for σ electrons, and can serve to assess better the validity of simple σ calculations.     

Assessment of theoretical methods for the calculation of methyl cation affinities

The methyl cation affinity (MCA; 298 K) of a variety of neutral and anionic bases has been examined computationally with a wide variety of theoretical methods. These include high-level composite procedures such as W1, G3, G3B3, and G2, conventional ab initio methods such as CCSD(T) and MP2, as well as a selection of density functional theory (DFT) methods. Experimental results for a variety of small model systems are well reproduced with practically all these methods, and the performance of DFT based methods are far superior in comparison to their MP2 analogs for these small models. For larger model, systems including motifs frequently encountered in organocatalysts, the performance deteriorates somewhat for DFT methods, while it improves significantly for MP2, rendering the former methods unreliable for common organic bases. Thus, MP2 calculations performed in combination with basis sets such as 6-31+G(2d, p) or larger, appear to offer a practical and reliable approach to compute MCAs of organic bases.     

The development and application of capillary electrophoresis methods for food analysis

Capillary electrophoresis (CE) offers the analyst a number of key advantages for the analysis of the components of foods. CE offers better resolution than, say, high-performance liquid chromatography (HPLC), and is more adept at the simultaneous separation of a number of components of different chemistries within a single matrix. In addition, CE requires less rigorous sample cleanup procedures than HPLC, while offering the same degree of automation. However, despite these advantages, CE remains under-utilized by food analysts. Therefore, this review consolidates and discusses the currently reported applications of CE that are relevant to the analysis of foods. Some discussion is also devoted to the development of these reported methods and to the advantages/disadvantages compared with the more usual methods for each particular analysis. It is the aim of this review to give practicing food analysts an overview of the current scope of CE.     

Adsorption of benzene on coinage metals: a theoretical analysis using wavefunction-based methods

The interaction of benzene with a Ag(111) surface has been determined using reliable ab initio electronic structure calculations. The results are compared to a recent detailed analysis of the interaction of benzene with copper and gold surfaces, thus making it possible to derive a consistent picture for the electronic structure changes encountered when benzene is brought into contact with the densely packed coinage metal surfaces. To avoid the problems encountered when the presently most frequently employed computational approach, density functional theory (DFT), is applied to adsorbate systems where dispersion (or van der Waals) forces contribute substantially, we use a wavefunction-based approach. In this approach, the weak van der Waals interactions, which are dominated by correlation effects, are described using second-order perturbation theory. The surface dipole moment and the work function changes induced upon adsorption are also discussed.     

Chemical and physical methods for characterisation of biofilms

Research on biofilms has developed into interdisciplinary work, in which scientists from different fields are involved. This review summarizes the state- of-the-art including models due to different aspects of biofilms. Techniques for characterization of surfaces and interfaces, e.g. microscopic, spectroscopic and microsensoric methods will be presented. In addition, procedures that involve sampling of biofilms and subsequent separation of the components for their analysis are a part of this article. Analytical methods are summarized for the investigation of extracellular polymeric substances (EPS), mainly polysaccharides beside proteins in the microbial host. Finally, procedures for the analysis of minerals as components of biofilms are presented.     

Development of nuclear and physical methods of element analysis of substance composition in the USSR

An up to date survey of recent trends in nuclear and physical methods developed in the USSR is given.     

Automatization for development of HPLC methods

Within the frame of inprocess analytics of the synthesis of pharmaceutical drugs a lot of HPLC methods are required for checking the quality of intermediates and drug substances. The methods have to be developed in terms of optimal selectivity and low limit of detection, minimum running time and chromatographic robustness. The goal was to shorten the method development process. Therefore, the screening of stationary phases was automated by means of switching modules equipped with 12 HPLC columns. Mobile phase and temperature could be optimized by using Drylab after evaluating chromatograms of gradient elutions performed automatically. The column switching module was applied for more than three dozens of substances, e.g. steroidal intermediates. Resolution (especially of isomeres), peak shape and number of peaks turned out to be the criteria for selection of the appropriate stationary phase. On the basis of the "best" column the composition of the "best" eluent was usually defined rapidly and with less effort. This approach leads to savings in manpower by more than one third. Overnight, impurity profiles of the intermediates were obtained yielding robust HPLC methods with high selectivity and minimized elution time.     

Experimental evidence and theoretical analysis of physical aging in thin and thick amorphous glassy polymer films

Through time‐dependent gas transport properties, we have investigated the physical aging process of amorphous glassy polymer films made from a polynorbornene. By combining the concepts of free volume and the kinetic theory of glass stabilization, it was found that the time dependence of the gas permeability could be rationalized through the thickness dependence of the glass transition temperature. A mathematical relationship was developed that directly relates polymer physical aging (tracked by the gas permeability decay) and sample thickness. It was confirmed by permeation measurements with nitrogen and helium that the aging process is accelerated for thin glassy polymer films (about 8000 Å). The theoretical results show that accelerated aging for thin films compared to thick films can be qualitatively predicted, based on the decrease in the glass transition temperature when the film thickness decreases. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2239–2251, 1999     

Chromatographic methods for the analysis of vancomycin

Four thin-layer chromatographic systems were developed for the separation of vancomycin, related antibiotics and degradation products. Bioautography was suitable for detecting trace amounts of biologically active components. High-performance liquid chromatography was used to examine the composition of vancomycin and other glycopeptide antibiotics and to monitor the stability of vancomycin. Degradation of vancomycin lead to changes in the composition which were not matched by a similar loss of potency.     

Electrophoretic methods for the analysis of nanoparticles

With the development of nanotechnology, there is a need for methodologies to determine and characterize nanomaterials. Electrophoresis has emerged as a useful tool, which has been employed in various formats (e.g., capillary-zone electrophoresis, gel electrophoresis or isotachophoresis) for the size- or shape-based separation of different types of nanoparticle (NP) (e.g., metallic, semi-metallic or carbon). This article reviews the main progress in electrophoresis techniques in order to achieve separation of NPs.     

Stereoisograms for reorganizing the theoretical foundations of stereochemistry and stereoisomerism. Part 3: rational avoidance of misleading standpoints for pro-R/pro-S-descriptors

The stereoisogram approach is introduced to settle the misleading terminology due to ‘prochirality’ in modern stereochemistry. After the term prochirality is redefined as having a purely geometric meaning, a method based on probe stereoisograms and another method based on equivalence classes (orbits) are introduced to determine prochirality and/or pro-RS-stereogenicity. Enantiotopic and RS-diastereotopic relationships appearing in probe stereoisograms are respectively used to determine prochirality and pro-RS-stereogenicity, where ‘stereoheterotopic’ relationships used in modern stereochemistry are abandoned. Alternatively, an enantiospheric orbit for specifying prochirality and an RS-enantiotropic orbit for specifying pro-RS-stereogenicity are emphasized by using coset representations and Young tableaux. The pro-R/pro-S-system is clarified to be based on pro-RS-stereogenicity and not on prochirality.