Review of Mesoscopic Modeling of Liquids in Materials Science

Mesoscopic theories can be used in the field of materials science to derive local average properties of relevance to the engineer such as flux, pressure, average density or composition. In the following density functional theory will be described and applied to different systems of interest and in particular, to materials formed from complex liquids as characterized by atomic structure and the type of interaction between the individual particles. The calculation of the solid to liquid transition will be explained in detail as a prototype for other order disorder transitions. The theory of polymers in solution will be revisited and used to calculate phase separation in mixtures. An extension of the theory to include the orientation of rodlike, long molecules will be applied to liquid crystals. In the presence of an interface, the system properties depend strongly on position in space and can be predicted from parameters obtained in the bulk in a square gradient approximation for sufficiently smooth and small deviations from the uniform distribution. A phase transition is often used to prepare heterogeneous materials by nucleation and growth. It will be shown how the equilibrium theory can be extended to study the dynamics of nonequilibrium phenomena.     

Supercritical-fluid chromatography: Open columns vs packed columns

Supercritical-fluid chromatography (SFC) may be performed either in open (capillary) columns or in packed columns. Both approaches have been demonstrated numerous times in the literature. In this contribution it will be attempted to discuss some aspects of columns for SFC. Some advantages of both types of columns will be identified. Attention is paid to the stationary phase film thickness, the speed of analysis, and to the maximum number of theoretical plates (effect of column pressure drop). In this brief contribution many questions will be left unanswered and many significant aspects will be left undiscussed, illustrating that much research remains to be done in this area.     

关于物理化学课程基本内容教学改革的建议

对物理化学教学改革提出以下4条建议：(1)教学内容要适应科学发展;(2)内容构架要以解决科学问题为主线;(3)教学要注重沟通知识模块间的科学联系;(4)明确指出各知识模块的科学应用。     

染料结合2μm无孔硅胶亲和填料的制备与应用

在２μｍ无孔硅胶表面键合３ 氨丙基 三乙氧基硅烷（ＡＰＳ）,并与三嗪染料活性蓝Ｆ３ＧＡ（ＣｉｂａｃｒｏｎＢｌｕｅＦ３ＧＡ,ＣＢ）反应,制得亲和色谱填料,并采用扫描电镜、元素分析、ｐＨ稳定性测试对此填料进行鉴定与表征。该填料具有良好的色谱性能,且对生物大分子有一定的亲和选择性,改变ｐＨ值及离子强度对溶菌酶的结合量有明显影响,可用于分离卵清蛋白（Ｏｖａｌ）和溶菌酶（Ｌｙｓ）,且对α ,β ,γ 球蛋白有不同的亲和作用,并可从鸡蛋清中制备少量溶菌酶。     

A versatile twisted optical fiber sensor

An optical sensor sensitive to changes in light absorption and other optical interactions, and consisting of two fibers twisted around each other, is described. The sensor can be used as a refractometer, is very sensitive to the presence of water in oil, can be used to determine the amount of a solvent in oil, and might be useful in monitoring degradation of internal combustion engine oil. In addition, by surrounding the fibers with a film of solution, and observing the changes in ouput over time, additional information can be obtained. Used in this manner, the sensor can be used to identify specific solutions.     

Über ein neues Verfahren zur Ermittlung des Endpunktes bei registrierten potentiometrischen Titrationen

Among all straight lines originating from one point and intersecting the titration curve three times, there is only one to be bisected by the inner point of intersection or to be divided in proportion to asymmetry factors. This point is to be considered as a more correct approximate value of the equivalence point than that obtained by previous methods. Practicable results are available, because in this way the qualities of asymmetrical titration curves can be taken into consideration. The asymmetry factors can be calculated and taken from tables or can be determined experimentally.     

Microfluidic Apps for off-the-shelf instruments

Within the last decade a huge increase in research activity in microfluidics could be observed. However, despite several commercial success stories, microfluidic chips are still not sold in high numbers in mass markets so far. Here we promote a new concept that could be an alternative approach to commercialization: designing microfluidic chips for existing off-the-shelf instruments. Such "Microfluidic Apps" could significantly lower market entry barriers and provide many advantages: developers of microfluidic chips make use of existing equipment or platforms and do not have to develop instruments from scratch; end-users can profit from microfluidics without the need to invest in new equipment; instrument manufacturers benefit from an expanded customer base due to the new applications that can be implemented in their instruments. Microfluidic Apps could be considered as low-cost disposables which can easily be distributed globally via web-shops. Therefore they could be a door-opener for high-volume mass markets.     

Use of Gel Permeation Chromatography in the Crime Laboratory

Abstract

In this study, the ways in which GPC can be integrated into the crime laboratory's present analytical scheme for polymer products will be examined. Fingerprint chromatograms and chromatograms illustrating molecular weight determination of two types of commonly encountered physical evidence (fibers and tail light lense fragments) will be compared and discussed. The techniques involved in sample preparation and data interpretation will be given. Finally the potential advantages of GPC for use in the crime laboratory will be presented.     

Thin-layer chromatographic determination of aldehydes encountered in foods as dimethones, octahydroxantheines and barbiturates

Aldehydes in foods can conveniently be characterized and determined by thin-layer chromatography (TLC) after converting them into their dimethones. For further confirmation the dimethones can be cyclized on the TLC plates or in solution to give octahydroxanthenes. Aldehydes also can be determined as their barbiturates. The aldehydes could be determined as dimethones and octahydroxanthenes in amounts up to 5 micrograms and as barbiturates in amounts up to 7.5 micrograms at their UV maxima.     

On the effects of doping calamitic and discotic nematics with materials of the opposite aspect ratio

In this paper the inter-mixing of calamitic and discotic materials is discussed. The systems are found to be immiscible near the middle of the phase diagram, as was predicted theoretically. However, a degree of miscibility is seen at each end of the phase diagram, allowing some interesting effects to be explored. A negative permittivity anisotropy is induced in a discotic material by dissolution of a polar calamitic dopant. The relaxation behaviour of the dopant in the material is studied and found to be similar to that in the pure calamitic, as far as can be determined in this experiment. The elastic constants of a calamitic mixture are enhanced by addition of a discotic dopant. This is believed to be due to the packing of the discotic molecules in such a way as to hinder director distortions, and may be useful for changing the values of calamitic elastic constants.     

胆固醇/卵磷脂/壳聚糖体系中碳酸钙模拟生物矿化的研究

本文采用X射线衍射、红外光谱和扫描电子显微镜等方法研究了胆固醇／卵磷脂／壳聚糖体系中碳酸钙模拟生物矿化过程。通过改变有机基质的组成,使有机基质的模板作用 也发生改变,从而使生成方解在一重型里面在酸钙的模板可生成球霰石型的碳酸钙。文中还进一步探讨了体系中壳聚糖、卵磷脂、胆固醇三者的协同作用对生成碳酸钙晶型的影响。     

A simple method for thermoanalysis of evolved gases

Thermoanalytical processes involving the splitting-off of ammonia, water, halogens, inorganic acids or acid anhydrides can be simply observed by using a specimen-holder in which specific reactions with the decomposition products can be induced. A special glass or quartz double crucible can be used for this purpose; the products arising in the lower part of the crucible can be oxidized selectively with reagents placed in the upper part, or can be bound or transformed into other compounds. This double crucible is also suitable for studying reactions taking place between solid and gaseous substances.     

生物质热解液化与美拉德反应

对生物质热解液化和美拉德反应进行了介绍,指出美拉德反应不仅存在于生物质热解液化过程中,而且通过引入适量氨等调控措施,可以促进美拉德反应有选择性地生成吡嗪类杂环化合物等高值化学品,然后再通过分级冷凝将生物油分为化工生物油和燃料生物油,前者用于分离提取高值化学品,后者用于锅炉和窑炉的燃料.引入美拉德反应后,生物质热解液化技术经济性将会得到根本性的改善.     

Inorganic Crystal Structure Data to be Presented in a Form More Useful for Further Studies

To make inorganic structure data more useful for further studies a five-point list of simple procedures to be followed by authors of crystal structure papers is proposed. 1. A crystal structure should be described with the space group corresponding to its true symmetry. 2. A new structure proposal should be tested, if it is realistic in principle. 3. A structure should be described with a space group in a setting given in the International Tables. 4. For a comparison with other structures the structure data should be standardized with the program STRUCTURE TIDY. 5.“New” structure data should be checked in the databases, Chemical Abstracts or on-line intemet resources, if they are really new. The list is supplemented with many explanations, commentaries, examoles and references.     

The analysis of counter performance by cusum techniques

It is necessary in most radiochemical studies to check periodically the efficiency of the detector with a standard or reference source to ensure its constancy. This can lead to a large number of readings which can best be analysed graphically by means of cumulative summation. Minor abrupt changes in counter performance can often be determined by retrospective examination of cusums. Alternatively in an on-going situation the reference source readings may be plotted as they are taken and a significant change detected comparatively rapidly with a V-mask. The standard deviation used in tests of significant change has in practice been found to be greater than that expected simply from the randomness of the disintegration process. The point of change can often be located precisely so that it should be possible if necessary to correct other measurements with the detector.     

Voltammetry of Organic Microparticles

 Solid microparticles of several different insoluble organic compounds were mechanically immobilized on the surface of graphite electrodes and immersed into a liquid electrolyte in order to study their electrochemical reactions. Cyclic staircase voltammetry and square-wave voltammetry were used. Quinhydrone was found to be a stable intermediate in the reversible redox reaction of solid quinone and hydroquinone on the electrode surface. The reaction occurs on the surface of the solid particle which is in contact with water. Indigo can be reduced to leucoindigo and oxidized to dehydroindigo in two separate reversible redox reactions. In strongly basic medium indigo dissolves in water upon electroreduction. A hydroacridine radical was detected as a stable intermediate in the electrochemically irreversible redox reaction of acridine and dihydroacridine. Famotidine can be electrooxidized and the product of this reaction can be electroreduced in two separate chemically irreversible reactions. Probucol is oxidized to a semiquinone radical which can be re-reduced in an electrochemically irreversible redox reaction. Propyl- thiouracil can be also oxidized to an unknown product which can be re-reduced in a chemically reversible, but slow solid state surface redox reaction. Reductions of solid thionicotinoylanilide and nicotinoylanilide are totally irreversible. Received September 22, 1998. Revision March 19, 1999.     

Analysis of trace elements and their physico-chemical forms in natural waters

Trace elements in natural waters can be present in different physico-chemical forms, varying in size, charge and density properties. Knowledge of speciation is essential for understanding the transport, distribution, and biological uptake of trace elements in the environment. The development of techniques to provide reliable information on physico-chemical forms has, therefore, become a challenge within Analytical Chemistry.When selecting analytical methods for the determination of total concentrations or fractions of trace elements in natural waters, no exclusion of species should occur, or at least it must be accounted for. Furthermore, the determination limits must be sufficiently low to allow the actual concentrations to be determined with reasonable precision and accuracy. For very low concentrations, preconcentration techniques are applicable, provided the chemical yield of the spike represents that of the original species present. For methods meeting these criteria, the suitability for routine analysis should be considered.When the physico-chemical forms of trace elements are to be determined, the fractionation should take placein situ or shortly after sampling. As the concentrations involved in speciation studies may be extremely low, there is an increasing awareness of potential sources of errors influencing analytical results. Sample collection and separation/fractionation/concentration procedures prior to analysis are, therefore, essential within Analytical Chemistry, and the whole procedure must be taken into account when interpreting the results. There are, however, several requirements which should be met by techniques applicable for speciation purposes. In general, size fractionation techniques (e.g.in situ hollow fibre ultrafiltration) should be applied prior to the addition of any chemical reagents (charge fractionation techniques).     

N-H carbazole synthesis from 2-chloroanilines via consecutive amination and C-H activation

N-H carbazoles can be produced from 2-chloroanilines and aryl bromides via consecutive catalytic amination and C-H activation. In many instances, this can be done in a tandem manner in one pot. The methodologies developed can be used in the synthesis of a range of carbazoles, including the natural products Clausine P and glycozolidine and a precursor in the synthesis of Clausines H, K, O, and 7-methoxy-O-methylmukonal, and can be extended to the synthesis of indoles.     

Biocompatibility of nanofilm-encapsulated silicone and silicone-hydrogel contact lenses

A material placed in or in contact with a biological system, that causes the minimum perturbation that can be tolerated by the host biological system, can be considered to be biocompatible. The major effects caused by a contact lens can be considered to be 1) the blocking of the natural supply of oxygen to the epithelium cells of the cornea, 2) interference with the normal evaporation of water from the tear fluid layer, and 3) hindrance of the normal functions of blinking for replenishing oxygen-saturated tear fluid and removing dead epithelium cells, which result from apoptosis. The encapsulation of a highly oxygen-permeable contact lens by a nanofilm with an imperturbable surface state minimizes all these terms. The encapsulated contact lens can be worn safely in extended wear.     

NUCLEAR SPIN-SPIN COUPLING CONSTANT AND MOLECULAR STRUCTURE——Ⅰ. The Relationship between Coupling Constants and Bond Lengths (Internuclear Distances)

<正> A discussion on the relationship between nuclear spin-spin coupling constants and bond lengths (internuclear distances) will be presented in this paper. The discussion will be focussed on the R-3 rule, the limit of its application and its influencing factors. Specifically, the causes for two long-existing puzzles in NMR coupling constants will be discussed: (a) the abnormal values of the coupling constants in ethylene and acetylene and (b) the "methyl-substitution rule". It will be pointed out that in solution the coupling of intramolecular nuclear spins is affected by many factors and thus will not strictly obey the R-3rule in general. However, in practice, the R-3 rule will still be valid when various influencing factors are carefully taken into consideration.