Carbon anode materials from polysiloxanes for lithium ion batteries

Three kinds of silicon-containing disordered carbons have been prepared by pyrolysis of polysiloxanes with different amounts of phenyl side groups. X-ray powder diffraction, X-ray photoelectron spectroscopy and electrochemical capacity measurements were performed to study their behaviors. Graphite crystallites, micropores, and silicon species affect their electrochemical performances. All of them present high reversible capacities, >372 mAh/g. Since the graphite crystallites are very small, they contribute very little to reversible capacity. The number of micropores produced by gas emission during the heat-treatment process decides whether they exhibit reversible capacity. Si mainly exists in the form C–Si–O and influences the irreversible capacity. There is no evident capacity fading in the first ten cycles, indicating promising properties for these disordered carbons.     

Fluordiazadiphosphetidine, 3. Mitt.: Die thermische Behandlung von 2,2,2,4,4,4-Hexafluoro-1,3-dimethyl-1,3,2,4-diazadiphosphetidin unter Druck in Gegenwart von Phosphor(V)fluorid und Alkalimetallfluoriden

Prolonged heating of (CH₃NPF₃)₂ in a sealed tube at 120°C yields (CH₃N)₄P₃F₇ and PF₅. Under the experimental conditions these compounds react to (CH₃N)₄P₃F₆ ⁺PF₆ ^–. Reaction of (CH₃NPF₃)₂ in the presence of PF₅ leads to a marked decrease in the formation of the ionic compound. The influence of the fluoride donating saltsMF (M=Li, Na, K, Cs) is investigated.

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Mit 1 Abbildung

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Früher: Alkyliminophosphorsäuretrihalogenide, 1. und 2. Mitt.     

用θ-2θ型衍射仪测定溶液结构的新方法

叙述了用θ－２θ型Ｘ射线衍射仪精确测定电解质溶液结构的新实验技术。设计制作了具有恒温功能的超厚液体样品池，并建立了样品池窗口强度的校正方法。优化了液体Ｘ射线衍射数据和结构参数精细化的计算机程序，获得了非常令人满意的实验结果。由θ－２θ型Ｘ射线衍射仪精确测定的径向分布函数与θ－θ型衍射仪自由散射比较，表明ＤＲＦ分辨率有所提高。     

Thermal and autoxidation reactions of poly-3-methylenecyclobutene and poly-1-methyl-3-methylenecyclobutene

The thermal ring-opening reactions, autoxidation and hydrogenation of polymethy-lenecyclobutene (PMCB) and poly-1-methyl-3-methylenecyclobutene (PMMCB), were investigated. Both polymers were prepared by cationic polymerization and consisted almost entirely of 1,5-repeating units containing cyclobutene rings in the polymer backbone. Both polymers showed well behaved exothermic processes at elevated temperatures which apparently resulted in crosslinking. These processes were investigated by differential scanning calorimetry and interpreted to involve thermal ring-opening reactions. Autoxidation occurred very rapidly in PMCB but much more slowly in PMMCB as predicted by Bolland's rules. Attempts to hydrogenate the cyclobutene rings in both polymers resulted in the occurrence of hydrogenolysis in PMCB and little or no reaction with PMMCB for a Pd-catalyzed reaction and partial hydrogenation of the latter for a diimide reaction.     

Rheological properties of the aqueous mixtures of cationic-anionic surfactants

The rheological properties of the aqueous mixtures of cationic-anionic surfactants, both in single-phase systems and in aqueous two-phase systems, have been studied. Bizarre rheological properties —negative thixotropy, viscoelasticity and hihg viscosity of shear rate dependent at relatively low concentration — have been observed. An unusual viscosity change, that is, viscosity lowering with increasing concentration, was obtained. The negative thixotropy might be due to the existence of lamellar or sheet-like micelles, viscoelasticity might be induced by rodlike and lamellar or sheet-like micelles, the high viscosity might be a consequence of the formation of network by long rodlike micelles and the concentration-induced viscosity lowering could be interpreted in terms of the decrease of micellar dimensions with concentration.     

Behaviour of Solochrome Dark Blue B as a colloidal electrolyte

Summary The electrical conductance of Solochrome Dark Blue B at various dilutions and temperatures have been measured. TheWaldens product has been calculated at different temperatures and it varies with the temperature. The reagent has been found to behave as a colloidal electrolyte. The temperature of zero conductance has been determined to be –20 °C and temperature coefficient per degree centigrade per hundred of conductance 35 °C varies between 1.81 and 1.87.

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Zusammenfassung Die elektrische Leitfähigkeit von Solochrome Dark Blue B bei verschiedener Verdünnung und verschiedenen Temperaturen wurde gemessen, dasWaldensche Produkt bei verschiedenen Temperaturen berechnet. Es variiert mit der Temperatur. Das Reagens benimmt sich wie ein Kolloid. Die Temperatur der Null-Leitfähigkeit wurde zu –20 °C bestimmt und der Temperaturkoeffizient pro Grad in Prozenten der Leitfähigkeit bei 35 °C liegt zwischen 1,81 und 1,87.

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With 2 figures and 3 tables     

Differentiation and quantitation of isomeric dipeptides by low-energy dissociation of copper(II)-bound complexes

Application of the kinetic method based on the dissociation of transition metal centered cluster ions is extended from chiral analysis (Tao, W. A.; Zhang, D.; Nikolaev, E. N.; Cooks, R. G. J. Am. Chem. Soc. 2000, 122, 10598) to quantitative analysis of isomeric mixtures, including those with Leu/Ile substitutions. Copper(II)-bound complexes of pairs of peptide isomers are generated by electrospray ionization mass spectrometry and the trimeric complex [CuII(ref)2(A) - H]+ (analyte A, a mixture of isomeric peptides; reference compound ref, usually a peptide) is caused to undergo collisional dissociation. Competitive loss of the neutral reference compound or the neutral analyte yields two ionic products and the ratio of rates of the two competitive dissociations, viz. the product ion branching ratio R is shown to depend strongly on the regiochemistry of the analyte in the precursor [CuII(A)(ref)2 - H]+ complex ion. Calibration curves are constructed by relating the branching ratio measured by the kinetic method, to the isomeric composition of the mixture to allow rapid quantitative isomer analysis.     

Weighted majority games and the matrix of homogeneity

If a weighted majority game (not necessarily constant sum or super additive) is described by the weights (voting strength) of the players involved and a majority level, then it is desirable to know whether the game is in addition homogeneous. The paper provides a recursive procedure defining a test for homogeneity. This procedure involves the computation of a number theoretical function, the matrix of homogeneity. If this matrix is knownall majority levels with respect to which the given set of weights represents a homogeneous simple weighted majority game are known at once.

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Zusammenfassung Ein gewichtetes Majoritätsspiel (nicht notwendig superadditiv oder mit Konstantsummeneigenschaft) kann beschrieben werden durch die Gewichte (die Abstimmungsstärke) der beteiligten Spieler und durch eine Mehrheitsschranke. Wenn eine solche Darstellung gegeben ist, so ist es wünschenswert, das Spiel zusätzlich auf die Eigenschaft der Homogenität hin zu untersuchen. Die vorliegende Arbeit stellt eine rekursive Prozedur zur Verfügung, die einen Test auf Homogenität einer vorgelegten Darstellung eines Spieles impliziert. Die Prozedur ermöglicht die Berechnung einer zahlentechnischen Funktion, der Homogenitätsmatrix. Wenn diese Matrix bekannt ist, kann man bei einem vorgegebenen Gewichtssatz alle Majoritätsschranken angeben, bezüglich welcher die vorgelegten Gewichte ein homogenes einfaches gewichtetes Majoritätsspiel darstellen.

     

Application of the ellipsoid method in an interactive procedure for multicriteria linear programming

The research reported in this paper is concerned with an application of the ellipsoid algorithm in the interactive multicriteria linear programming step method (STEM) byBenayoun et al. [1971]. Due to this application we eliminate some drawbacks of the original version of STEM and, moreover, we avoid extra computations connected with sensitivity analysis in every iteration. Specifically, we use the ellipsoid algorithm to minimize the Euclidean norm in the criterion space instead of the Chebyshev norm, which ensures that every solution submitted to the decision maker is efficient. As follows from a computational experiment, in comparison with the application of the simplex method, the proposed modification of STEM shows a smaller increase of the computational effort when the number of criteria increases. However, the absolute computation time becomes worse for problems of larger size.

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Zusammenfassung In dieser Arbeit wird über eine Anwendungsmöglichkeit der Khachiyan-Shor-Algorithmus (Ellipsoid-Algorithmus) im Rahmen des STEM-Verfahrens zur interaktiven Lösung linearer Vektoroptimierungsmodelle berichtet. Auf diese Weise können einige spezifische Nachteile des STEM-Verfahrens in seiner Originalversion vermieden werden. Durch die Verwendung der Euklidischen Norm anstelle der beim STEM-Verfahren üblichen Tschebyscheff-Norm wird garantiert, daß dem Entscheidungsträger nur effiziente Lösungen vorgeschlagen werden. Die numerischen Erfahrungen zeigen, daß der Lösungsaufwand der hier vorgeschlagenen Modifikation des STEM-Verfahrens mit steigender Anzahl von Zielfunktionen weniger stark zunimmt als bei der üblichen Version. Dies gilt jedoch nicht hinsichtlich der allgemeinen Problemgröße.