Interaction between gaseous oxygen and germanium melt

Interaction between the residual gaseous oxygen and germanium melt is analyzed. There is a quantitative relationship between oxygen concentration in a growing germanium single crystal, oxygen partial pressure in an inert gas, and water vapor pressure in hydrogen. The suggested theoretical interpretation of the interaction between oxygen and germanium melt is experimentally validated.     

Van der Waals Emulsions: Emulsions Stabilized by Surface‐Inactive,Hydrophilic Particles via van der Waals Attraction

Surface‐inactive, highly hydrophilic particles are utilized to effectively and reversibly stabilize oil‐in‐water emulsions. This is a result of attractive van der Waals forces between particles and oil droplets in water, which are sufficient to trap the particles in close proximity to oil–water interfaces when repulsive forces between particles and oil droplets are suppressed. The emulsifying efficiency of the highly hydrophilic particles is determined by van der Waals attraction between particle monolayer shells and oil droplets enclosed therein and is inversely proportional to the particle size, while their stabilizing efficiency is determined by van der Waals attraction between single particles and oil droplets, which is proportional to the particle size. This differentiation in mechanism between emulsification and stabilization will significantly advance our knowledge of emulsions, thus enabling better control and design of emulsion‐based technologies in practice.     

Measuring forces with the AFM: polymeric surfaces in liquids

This review links together for the first time both the practicalities of force measurement and the work carried out to date on force detection between polymeric surfaces in liquids using the atomic force microscope (AFM). Also included is some of the recent work that has been carried out between surfactant surfaces and biologically coated surfaces with the AFM. The emphasis in this review is on the practical issues involved with force measurement between these types of surfaces, and the similarities and irregularities between the observed types of forces measured. Comparison is made between AFM and surface force apparatus (SFA) measurements, as there is a much longer history of work with the latter. Results indicate that forces between the surfaces reviewed here are a complicated mixture of steric-type repulsion, conformational behaviour on separation and long-range attraction, which is often ascribed to 'hydrophobic' forces. The origin of this latter force remains uncertain, despite its almost ubiquitous appearance in force measurements with these types of surfaces.     

Enthalpies of interaction between cellobiose and the derivatives of cellulose in aqueous solutions

The enthalpy of interaction between cellobiose and sodium carboxymethyl cellulose, methyl cellulose, and 2-hydroxyethyl cellulose in water is determined. The exothermal nature of the interaction between cellulose and cellulose ethers is established. The strongest intermolecular interaction is found between cellobiose and 2-hydroxyethyl cellulose. The results are discussed in the context of the polysaccharide molecular structure.     

Van der Waals Emulsions: Emulsions Stabilized by Surface‐Inactive,Hydrophilic Particles via van der Waals Attraction

Surface‐inactive, highly hydrophilic particles are utilized to effectively and reversibly stabilize oil‐in‐water emulsions. This is a result of attractive van der Waals forces between particles and oil droplets in water, which are sufficient to trap the particles in close proximity to oil–water interfaces when repulsive forces between particles and oil droplets are suppressed. The emulsifying efficiency of the highly hydrophilic particles is determined by van der Waals attraction between particle monolayer shells and oil droplets enclosed therein and is inversely proportional to the particle size, while their stabilizing efficiency is determined by van der Waals attraction between single particles and oil droplets, which is proportional to the particle size. This differentiation in mechanism between emulsification and stabilization will significantly advance our knowledge of emulsions, thus enabling better control and design of emulsion‐based technologies in practice.     

Orthogonalization in momentum space

Since the overlap integral between two functions in position space is the same as the overlap integral between their counterparts in momentum space, there is an intimate connection between orthonormalization procedures in the two spaces. It is pointed out that in certain cases this situation can be used to simplify the orthogonalization.     

Differentiation of walnut wood species and steam treatment using ATR-FTIR and partial least squares discriminant analysis (PLS-DA)

Wood is a ubiquitous material used in everyday life. Accurate identification of species can be of importance in a historical context enabling appropriate conservation treatment and adequate choice of material to be applied to historic wooden objects, and in a more modern context, in the identification of forgeries. Wood is also often treated to improve certain physical characteristics, often strength and durability. However, determination of whether or not a piece of wood has been treated can be very difficult. Infrared spectroscopy has previously been applied to differentiate between different wood species or between treated and untreated wood, often in conjunction with chemometric analysis techniques. Here, we report the use of mid-IR spectroscopy, coupled with partial least squares discriminant analysis for the discrimination between two walnut wood species and to differentiate between steam-treated and untreated samples of each of these wood species. We show that the discrimination between species and between steam-treated and non-steam-treated wood from Juglans nigra is very clear and, while analysis of the quality of the discrimination between steam-treated and non-steam-treated J. regia samples is not as good, it is, nevertheless, sufficient for discrimination between the two groups with a statistical significance of P < 0.0001.     

Fourty years of thermal analysis in Hungary

A brief survey is presented of the development of thermoanalytical methods, in Hungary and abroad between 1900 and 1990, and reveals a connection between the processes.An overall picture is given of the activity of Hungarian thermoanalysts in basic research, the development of instruments and organizational work in science between 1950 and 1990.     

杯[4]吡咯在不同溶液中的分子动力学模拟研究

运用分子动力学(MD)模拟方法对杯[4]吡咯与不同溶剂之间的相互作用能、杯[4]吡咯在不同溶液中的构象变化以及杯[4]吡咯与溶剂分子之间的氢键相互作用进行了计算研究.模拟发现,杯[4]吡咯与不同溶剂间的相互作用能受溶剂分子偶极矩和杯[4]吡咯-溶剂分子间氢键相互作用影响.杯[4]吡咯在不同溶液中的构象发生翻转的主导因素是杯[4]吡咯与溶剂分子间形成氢键相互作用,溶剂分子的偶极矩不是杯[4]吡咯发生构象转化的主要因素.     

The bridging force between two plates by polyelectrolyte chains

The interaction between particles in a colloidal system can be significantly affected by their bridging by polyelectrolyte chains. In this paper, the bridging is investigated by using a self-consistent field approach which takes into account the van der Waals interactions between the segments of the polyelectrolyte molecules and the plates, as well as the electrostatic and volume exclusion interactions. A positive contribution to the force between two plates is generated by the van der Waals interactions between the segments and the plates. This positive (repulsive) contribution plays an important role in the force when the distances between the plates are small. With increasing van der Waals interaction strength between segments and plates, the force between the plates becomes more repulsive at small distances and more attractive at large distances. When the surfaces of the plates have a constant surface electrical potential and a charge sign opposite to that of the polyelectrolyte chains, the force between the two plates becomes less attractive as the bulk polyelectrolyte concentration increases. This behavior is due to a higher bulk counterion concentration dissociated from the polyelectrolyte molecules. At short distances, the force between plates is more repulsive for stiffer chains. A comparison between theoretical and experimental results regarding the contraction of the interlayer separation between the platelets of vermiculite clays against the concentration of poly(vinyl methyl ether) was made.     

Interaction of Surface-active Fluorescence Probes with Bovine Serum Albumin

The binding between three surface-active substituted 3H-indole fluorescence probes and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence quenching. The binding constants of 3H-indole molecules with BSA were obtained. According to the Foerster resonance energy transfer theory, the distances between 3H-indole molecules and tryptophan of BSA were calculated. The results show that the oligoethyloxyethylene chain of 3H-indole molecules is longer, the binding between them is stronger, the energy transfer efficiency is higher, and the distance between tryptophan and 3H-indole is nearer.     

微波消解-ICP-MS测定电镀污泥中的重金属

采用微波消解系统对某电镀污泥进行消解,利用ICP-MS对污泥中的重金属进行测定。称取制备后样品,置于消解罐中充分反应后,赶酸、定容后利用电感耦合等离子体质谱法进行测定。电镀污泥中的铬为18845.2mg/kg、镉为10.3mg/kg、镍为5200.0mg/kg、铅为189.7mg/kg、铜为3271.7mg/kg、锌为49632.6mg/kg。测定结果表明所检测项目工作曲线线性关系好,相关系数r均大于0.999。铬加标回收率在91.6～97.7%之间、镉加标回收率在92.0～97.0%之间、镍加标回收率在95.1～98.0%之间、铅加标回收率在94.3～95.2%之间、铜加标回收率在97.1～102%之间、锌加标回收率在96.3～98.7%之间,均满足相关测定要求。计算的潜在生态危害系数、潜在生态危害指数结果表明,电镀污泥中的铬、镉、铅、铜、锌为轻微生态危害,镍为强生态危害;潜在生态危害指数RI计算值为216.69,属于中等生态危害。     

Effect of primary radical termination on chain length and initiator efficiency

In polymerization with primary radical termination, when reaction between primary radicals, which escape from solvent cage, is not negligible, a relation between chain length and polymerization rate is found regardless of tractable approximate procedures. Such a relation is applied to the kinetic data obtained in the polymerizations of methyl methacrylate (MMA) and vinyl acetate (VA) initiated by 2,2′-azobis(2,4-valeronitrile) at 50.0°C. Further, when the primary radical termination is high, an initiator efficiency can not be approximated to a ratio of the primary radicals escaping from the cage to the total primary radicals formed in the cage. In the polymerization of MMA, after the primary radicals escapes from the cage, they immediately react with the monomer. Thus, the reaction between the primary radicals is not significant. However, in the polymerization of VA, the rate of reaction between the primary radical and the monomer might be comparable to the rate of reaction between the primary radicals when the initiator concentration is quite high.     

NMR study of water bound to soft segments in thermoplastic elastomers

The interaction between water absorbed in four hard-soft segment block-copolymers and the polymer chains is investigated by pulsed field gradient echo NMR spectroscopy and Nuclear Overhauser NMR spectroscopy. The results show, depending on the structure and mass fraction of the soft segments, a strong interaction between water and the soft segments. Most likely this is due to a hydrogen bond between water and the ether groups. The self-diffusion of water has been determined and is described as a jumping process between the ether sites with a residence time t and a time between sites t. It is found that the residence time is of the order of a few ns and also that the ratio t/τ decreases with increasing soft segment rigidity.     

n-GaAs(100)、Si(111)表面修饰卟啉分子的光致界面电荷转移特性的研究

利用表面光电压谱研究了四碘化四-(4-三甲胺苯基)卟啉(TTMAPPIH₂)修饰n-GaAS(100)和n-Si(111)半导体表面的光致界面电荷转移特性,结果表明,n-GaAs(100)表面修饰TTMAPPIH₂分子的光致界面电荷转移效率远比n-Si(111)表面修饰的高,并且发现在该卟啉分子的非吸收区也有明显的光致界面电荷转移现象,而与n-Si(111)间则没有这种转移特性。用电化学测量和UV光谱确定了TTMAPPIH₂相对于n-GaAs(100)、n-si(111)的能级位置关系,对TTMAPPIH₂分子与n-GaAs(100)和n-Si(111)间的不同光致界面电荷转移特性进行了解释。     

Modeling the gel electrophoresis of short duplex DNA by Brownian dynamics: cubic gel lattice with direct interaction

The technique of Brownian dynamics is used to model the electrophoretic mobility of spherical and rod-like particles in a three-dimensional cubic gel lattice. In addition to excluded volume interactions between the migrating particle and the gel, direct interactions are also included. The methodology is first applied to spherical particles in the absence of direct interactions and the resulting mobilities are shown to agree with independent studies. The methodology is then applied to rod-like models of short duplex DNA fragments 10-50 base pairs in length. In the absence of direct interactions between gel and DNA, calculated mobilities show a much weaker dependence on gel concentration than observed in experiments of DNA in Tris-acetate buffer and polyacrylamide gels. When an attractive interaction between gel and DNA of approximately -0.3 k(B)T per base pair at contact is included, good agreement between calculated and experimental mobilities is achieved.     

Discrimination between ginseng from Korea and China by light stable isotope analysis

Ginseng is a health food and traditional medicine highly valued in Asia. Ginseng from certain origins is higher valued than from other origins, so that a reliable method for differentiation of geographical origin is important for the economics of ginseng production. To discriminate between ginseng samples from South Korea and PR China, 29 samples have been analyzed for the isotopic composition of the elements H, C and N. The results showed δ(2)H values between -94 and -79‰, for δ(13)C -27.9 to -23.7‰ and for δ(15)N 1.3-5.4‰ for Chinese ginseng. Korean ginseng gave δ(2)H ratios between -91 and -69‰, δ(13)C ratios between -31.2 and -22.4‰ and δ(15)N ratios between -2.4 and +7‰. Despite the overlap between the values for individual isotopes, a combination of the isotope systems gave a reasonable differentiation between the two geographic origins. Especially the statistically significant difference in δ(2)H ratios facilitated the differentiation between Korean and Chinese ginseng samples.     

Molecular dynamics investigation into the effect of temperature on the structure and properties of methyl methacrylate thin films on a Au(111) surface

An atomistic modeling approach is performed to investigate the effect of temperature on the structural properties of the MMA (methyl methacrylate) thin film and a Au(111) surface. The density profile and orientation of the MMA molecule in the thin film have been analyzed. We found that there is a significant effect on the density profile and orientation of the MMA molecule in the region near the interface between the thin film and the Au substrate. As the temperature increases, the density clearly decreases in this region; in addition, the orientation of the MMA molecule also changes. Next, we calculated and examined the relationships between the stress, surface tension, and free energy and the density profile. Finally, we analyzed the influence of temperature on the interaction strength between the MMA molecules and between the MMA molecules and the Au(111) surface. We found that the influence of the interaction strength is more significant between MMA molecules than between MMA molecules and the Au(111) surface.     

聚芳醚酮类聚合物晶体结构醚酮等效性的研究

半结晶的聚芳醚酮类聚合物 ( PAEKs)因其性能优异而在机械、航天等高技术领域中得到广泛应用 .有关其晶体结构的研究亦有许多文献报道[1～ 11] ,而醚基与酮基在晶体结构方面是否等效一直存在争议 .虽然醚酮等效性的观点已被广泛接受 [4～ 8] ,但对于聚合物主链中含联苯基团的 PAEKs的醚酮等效性的研究则复杂得多 .文献 [1 ]报道醚酮等效性在主链含有联苯基团时不再成立 .本文首次发现醚酮等效性在主链含有联苯基团时在适当条件下仍可成立 ,并对聚芳醚酮类聚合物晶体结构的醚酮等效性问题进行了系统阐述 .1　实验部分　　样品联苯聚醚酮 …     

FTIR Studies of Doped PMMA - PVC Blend System

The IR spectroscopy study shows miscibility between PMMA-PVC blends due to hydrogen bonding between CO of PMMA and hydrogen from CHCl of PVC. This blend system is doped by Camphor Sulphonic Acid (CSA) in the entire composition range. The doping of CSA in PVC, in PMMA and in PMMA-PVC blends shows changes in FTIR spectra. The interaction between PVC and CSA is through hydrogen bonding between CO of CSA and CHCl of PVC. Doping PMMA with CSA, indicate an interaction between H⁺ ion of CSA and oxygen atoms of CO and  OCH₃ of PMMA. Whereas in PMMA–PVC blend interaction between H⁺ ion of CSA and oxygen atom of CO of PMMA.