Effect of microwave pretreatment of coal for improvement of rheological characteristics of coal-water slurries

Indian high-ash coal contains alpha-silica components of the mineral matter. When coal is transported in the form of a slurry, alpha-silica adds to the settling properties of coal and enhances erosion of pipelines. As such any technique that will contribute to changing the characteristics of mineral matter by selective demineralization is bound to supplement the knowledge of coal slurries in the science of rheology. One such method is the use of a novel microwave technology, which changes the alpha-silica to less harmful beta-silica. Thus microwave-treated coal slurry facilitates enhanced flow characteristics and abates the erosion problem in pipeline transport as well as in coal-slurry injection furnaces. This paper reports on the rheological study of closely sized coal particles of medium-volatile, low-ash, low-moisture cleans and high-ash rejects with and without microwave treatment. Viscosity of suspensions of microwave-treated coal was found to be less than that of untreated coal, in the case of both cleans and rejects. Microwave pretreatment thus reduces the viscosity and the pumping cost and opens a new outlook for pipeline transport. An attempt has been made to quantify the improvement of rheological characteristics due to microwave pretreatment.     

Study of Self-Ignition of PVC

The self-ignition of rigid PVC has been studied under static and dynamic conditions. Only a high-temperature boundary has been found, and the self-ignition temperature in air at atmospheric pressure lies between 555 and 560°C. The effect of preliminary HC1 evolution has been investigated, and it is shown that the more the HC1 evolution, the higher the self-ignition limit. It has been impossible to make polyacetylene ignite spontaneously in the presence of HC1 in oxygen up to 900° C. This is attributed to a special role of HC1 in combustion of PVC. The rate of HC1 release was measured by a potentiometric method, and the overall activation energy of the process was found to be 9.4 kcal/mole. This low value seems to be due to the presence of oxygen. Chromatographic analysis showed CH4 and CO to be the major gaseous products of oxidation of PVC in this parametric zone.     

Precision of Flash Pyrolysis-GC-MS Analysis: Experimental Evaluation of the Sources of Variability

The present study was carried out to evaluate the precision and to identify significant sources of variability in flash pyrolysis-GC-MS experiments. The analysis of variance has been applied to the example of polyethylene pyrolysis to estimate the impact of several controlled factors: sample handling, flash pyrolysis filament ageing and calibration. It was demonstrated that to get the best precision in experimental results, it is recommended to set the operator to reduce the impact of sample handling procedure and the filament to avoid variability due to changes in filament characteristics. In comparison, filament ageing and filament calibration are shown to influence in a limited extent the experimental results.     

Elucidation of the mechanism of redox grafting of diazotated anthraquinone

Redox grafting of aryldiazonium salts containing redox units may be used to form exceptionally thick covalently attached conducting films, even in the micrometers range, in a controlled manner on glassy carbon and gold substrates. With the objective to investigate the mechanism of this process in detail, 1-anthraquinone (AQ) redox units were immobilized on these substrates by electroreduction of 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate. Electrochemical quartz crystal microbalance was employed to follow the grafting process during a cyclic voltammetric sweep by recording the frequency change. The redox grafting is shown to have two mass gain regions/phases: an irreversible one due to the addition of AQ units to the substrate/film and a reversible one due to the association of cations from the supporting electrolyte with the AQ radical anions formed during the sweeping process. Scanning electrochemical microscopy was used to study the relationship between the conductivity of the film and the charging level of the AQ redox units in the grafted film. For that purpose, approach curves were recorded at a platinum ultramicroelectrode for AQ-containing films on gold and glassy carbon surfaces using the ferro/ferricyanide redox system as redox probe. It is concluded that the film growth has its origin in electron transfer processes occurring through the layer mediated by the redox moieties embedded in the organic film.     

Efficient quantification of the importance of contacts for the dynamical stability of proteins

Understanding the stability of the native state and the dynamics of a protein is of great importance for all areas of biomolecular design. The efficient estimation of the influence of individual contacts between amino acids in a protein structure is a first step in the reengineering of a particular protein for technological or pharmacological purposes. At the same time, the functional annotation of molecular evolution can be facilitated by such insight. Here, we use a recently suggested, information theoretical measure in biomolecular design - the Kullback-Leibler-divergence - to quantify and therefore rank residue-residue contacts within proteins according to their overall contribution to the molecular mechanics. We implement this protocol on the basis of a reduced molecular model, which allows us to use a well-known lemma of linear algebra to speed up the computation. The increase in computational performance is around 10(1)- to 10(4)-fold. We applied the method to two proteins to illustrate the protocol and its results. We found that our method can reliably identify key residues in the molecular mechanics and the protein fold in comparison to well-known properties in the serine protease inhibitor. We found significant correlations to experimental results, e.g., dissociation constants and Φ values.     

中国法上的行为能力宣告：制度内涵与解释论重塑

中国民法典编纂已经接近尾声,如何对民法典中的规则采取妥当的解释论立场是一个有待学界充分讨论的重要问题。结合《民法总则》行为能力宣告制度的分析,可以展示一种更加积极进取的理论立场。虽然《民法总则》关于行为能力宣告制度的规定与先前的规定差别不大,但通过条文的细致梳理,可以认为中国民法其实确立了有中国特色的二级制成年监护制度,区分了成年监护与成年照顾制度。在这一框架之下,通过法律解释的续造,可以在中国民法中构造出一个既尊重现行法,又符合世界发展潮流,而且能够有效应对中国老龄化趋势的制度体系。     

Application of boundary element method to calculation of the complex permittivity of suspensions of cells in shape of Dinfinityh symmetry

A numerical method using the boundary element method was developed to calculate the complex permittivity of suspensions of particles in the shape of Dinfinityh symmetry covered with a shell phase. It was an extension of the analytical methods based on Maxwell-Wagner-Sillars' effects in suspensions of shelled ellipsoids. This method was applied to particles, which were relevant to budding yeast cells and erythrocytes, to examine the effects of the shape on frequency-dependence of the permittivity and conductivity of their suspensions. Results of the calculations showed that the permittivity and conductivity at high frequencies were insensitive to the change in the shape. The change in shape affected the permittivity and conductivity at low frequencies and their frequency-dependence in the intermediate frequency region. This behavior could not be imitated by the calculation using analytical methods with shelled spheroid models.     

Formation of ring-shaped deposits as a result of evaporating droplets of dispersions of silver nanoparticles and study of their fine structure

Scanning electron microscopy is employed to study ring-shaped deposits formed at different time moments of evaporating droplets of silver colloidal solutions on a glass substrate. It is shown that, in addition to an external fringe, several rings are formed at intermediate stages of evaporation; these rings are, in the course of time, transformed into one dense fringe and a transition zone adjacent to its internal side. The time dependences of the height and width of the fringe are determined. It is established that an increase in the width and height of the fringe is due to the transfer of silver nanoparticles to this region, which play a key role in imparting specific structural organization to the fringe. It is noted that the height of the formed fringe may be qualitatively determined by energy dispersive X-ray microanalysis.     

Effects of micelle properties on the conformation of oligocholates and importance of rigidity of foldamers

The conformation of a cholate hexamer with a clicked tether in between two tricholate units and pyrene groups at the chain ends was studied by fluorescence spectroscopy. In contrast to the parent cholate hexamer that folded in all micelles investigated, the folding of the clicked hexamer was highly dependent on the type of surfactant used to solubilize the compound. The clicked oligocholate folded in the Brij 35 micelle, possibly due to the latter's small size and strong internal hydrophobicity. The oligocholate formed intermolecular aggregates in SDS solutions below the CMC of the surfactant. The aggregates were dissociated by the SDS micelles but the individual oligocholate stayed unfolded. In Triton X-100 and sodium cholate solutions, the aggregated, unfolded, and folded oligocholates coexisted and gradual unfolding occurred with an increasing concentration of the surfactant. The conformation of the clicked oligocholate was sensitive to the nonideal mixing of ionic/nonionic micelles and to the unconventional aggregation of sodium cholate.     

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.     

Synthesis of a Pair of Derivatives of N-Methylpyrrole Polyamide

A pair of derivatives of tetrameric N-methylpyrrole polyamide were synthesized in order to develop a new method for the study of interaction of the polyamide derivatives with DNA. Indole acetic acid and nicotinic acid were introduced to the polyamide in the synthesized compound, which showed an expected red shift in the UV spectrum. These compounds may function as a potential tool in the detection of the polyamide binding to DNA.     

Bioinformatic analysis of molecular network of glucosinolate biosynthesis

Glucosinolates constitute a major group of secondary metabolites in Arabidopsis, which play an important role in plant interaction with pathogens and insects. Advances in glucosinolate research have defined the biosynthetic pathways. However, cross-talk and interaction between glucosinolate pathway and other molecular pathways are largely unknown. Here three bioinformatics tools were used to explore novel components and pathway connections in glucosinolate network. Although none of the software tools were prefect to predict glucosinolate genes, combination of results generated by all the tools led to successful prediction of all known glucosinolate genes. This approach was used to predict new genes in glucosinolate network. A total of 330 genes were found with high potential to relate to glucosinolate biosynthesis. Among them 64 genes were selected to construct glucosinolate network because their individual connection to at least one known glucosinolate gene was predicted by all the software tools. Microarray data of candidate gene mutants were used for validation of the results. The mutants of nine genes predicted by glucosinolate seed genes all exhibited changes in the expression of glucosinolate genes. Four of the genes have been well-known to functionally interact with glucosinolate biosynthesis. These results indicate that the approach we took provides a powerful way to reveal new players in glucosinolate networks. Creation of an in silico network of glucosinolate biosynthesis will allow the generation of many testable hypotheses and ultimately enable predictive biology.     

Characterization of the barrier properties of composites of HDPE and purified cellulose fibers

The present work presents and discusses the interrelation between composition, morphology, thermal history, mechanical and barrier properties to oxygen and limonene of composites of HDPE/MA-PE/cellulose fibers of significant interest in, among others, food packaging applications. From the overall results, it was observed that increasing the loading of purified alpha-cellulose fibers in the polyethylene matrix beyond 10 wt.% led to a decrease in the permeability coefficient of d-limonene, effect which was found to be primarily related to a decrease in the overall solubility of this strongly plasticizing aroma component. On the other hand, the oxygen permeability was found to decrease to a significant extend with increasing fiber content beyond 5 wt.%, but this effect was more strongly ascribed to a significant decrease in the diffusion coefficient. Therefore, the fibers are thought to generate a more tortuous path for the non-interacting gas molecules to travel across the composites thickness, even when tested at high relative humidity conditions. Optimum fiber loading levels in terms of overall property balance were found to be around 20 wt.%.     

聚丙烯酰胺胶状杂质的形成因为

在聚丙烯酰胺(PAM)配制现场发现过滤器滤袋内存在大量黑色和黄色且有刺鼻腐臭气味的胶状条形物;这类杂质造成过滤装置严重堵塞和设备腐蚀.鉴于此,从细菌和无机离子含量两方面着手分析了聚丙烯酰胺胶状条形杂质的形成因为.结果表明:由于细菌和金属离子Fe3+含量的增加,PAM的侧酰胺基降解成羧基;而含大量金属离子的PAM溶液经缠...     

Structural investigations of a series of petrified woods of different origin

Since the investigations on petrified wood performed so far have not proved the assumption that the ring structure is coupled to the changes in the crystalline form of silica, attention was paid to other possible reasons. Using small angle X-ray scattering methods we determined the Porod curves and pore size distributions for five different samples of petrified wood, of different origin. We observed clear porosity differences in different samples. In addition, the normal X-ray diffractometric measurements were carried out, which gave a totally uniform image of the crystallographic structure of all the samples. All of them were made of pure α-quartz. The differentiation of rings in dark and bright zones should be put down to the changes in porosity rather than to other factors. The pores seem to be much more concentrated in those ring locations, which correspond to the original dark wood positions in living wood.     

荧光关联光谱在高分子单链研究中的应用

荧光关联光谱(fluorescence correlation spectroscopy,FCS)是一项用于研究体系动力学性质的统计光谱技术,随着它被引入材料与化学研究领域,近年来取得了大量全新的研究成果.该技术在高分子科学研究中也逐渐发挥出越来越大的作用,特别是在聚合物结构和动力学方面,这表明它在高分子领域的巨大潜力.本文将从FCS的基本原理、实验技巧以及在一些具有挑战性体系中的应用等方面展开,着重介绍它在高分子溶液,如聚电解质溶液、高分子混致不溶现象,以及不同的表界面体系中取得的新成果,展示FCS区别于其他传统技术的特点和优势.     

Structure and mechanism of the deposition of multilayers of polyelectrolytes and nanoparticles

MD simulation of the layer-by-layer assembly of polyelectrolytes (PEs) and nanoparticles (NPs) revealed that the assembly process is electrostatically driven with alternating charge reversal and an overcompensation mechanism. Layers were observed to grow in the lateral direction as well as in a direction normal to the surface. Weakly adsorbed PE molecules were observed to desorb from the flat and NP surfaces. Those molecules are attracted by suspended NPs in solution. PE molecules do not only pull NPs toward the surface but bridge NPs both in solution and on the surface, forming agglomerates and islands. The first double layer differs in structure from the second double layer as a result of strong adsorption of the PE molecules to the rigid surface.     

Study of the influence of location of substitutions on the surface energy of dioctahedral smectites

The surface energy of some clays belonging to the smectite group has been calculated starting from crystal structures and combining a partial charge model with the computation of the lattice energy. The dioctahedral smectites studied here include montmorillonite; beidellites; and nontronite. One of the differences between these clays is the location of the substitution in the octahedral sheet or in the tetrahedral one. Another is the possibility of vacancies in cis- or trans-octahedral positions. These locations and vacancies have an effect on the distortion of the crystal framework and therefore on the surface energy. Calculated surface energies of the solid samples increase in the order beidellites > montmorillonite > nontronite. The bond energy between the interlayer cation and the layer appears to follow the same order and to depend both on the nature of the most electropositive elements of the layer and on their location. The trends obtained provide elements for an analysis of data related to interlayer enlargement.     

Dynamics of solvent and rotational relaxation of glycerol in the nanocavity of reverse micelles

The dynamics of solvent and rotational relaxation of Coumarin 480 and Coumarin 490 in glycerol containing bis-2-ethyl hexyl sulfosuccinate sodium salt (AOT) reverse micelles have been investigated with steady-state and time-resolved fluorescence spectroscopy. We observed slower solvent relaxation of glycerol confined in the nanocavity of AOT reverse micelles compared to that in pure glycerol. However, the slowing down in the solvation time on going from neat glycerol to glycerol confined reverse micelles is not comparable to that on going from pure water or acetonitrile to water or acetonitrile confined AOT reverse micellar aggregates. While solvent relaxation times were found to decrease with increasing glycerol content in the reverse micellar pool, rotational relaxation times were found to increase with increase in glycerol content.     

Quasi-relativistic study of electronic structure of uranium tetrafluoride

Conclusions A comparison of the results obtained in a calculation of the electronic structure of UF₄, performed in the NR and QR approximations of the X-SW method, leads to a number of conclusions as to the role of relativistic effects in the electronic structure of molecules. a) An accounting for relativistic effects leads to changes in the spatial distribution of charge in the molecules and to a consequent change in the interpretation of the bond in terms of the ratio of ionic and covalent components. b) Relativistic compression of the wave functions of the s and p electrons (primary relativistic effects) and delocalization of the d and f functions (secondary relativistic effects) lead to substantial changes in the orbital energies and the corresponding ionization potentials in heavy molecules. c) Primary and secondary relativistic effects are responsible for considerable changes in the electronic excitation energies and the EA, changes that may account to as much as 200%. d) An accounting for spin-orbit interaction effects is extremely important in interpreting photoelectron and optical spectra. In the example of UF₄, it has been shown that NR wave functions are inadequate for use in calculating spin—orbit splittings in heavy molecules. Just as inadequate may be an accounting for spin—orbit interaction in first-order perturbation theory for systems of closelying MOs, the charge density of which is determined to a considerable degree by AOs of a single type (for example, 5f AOs of uranium in UF₄).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 20, No. 4, pp. 406–415, July–August, 1984.The authors wish to express their appreciation to M. I. Timokhin for assistance in performing the calculations.