Adsorption of the Dyes (Methylene Blue and Acridine Orange and Their Mixtures) from Aqueous Solutions on Cholesterol Surface

The adsorption of the dyes, methylene blue and acridine orange, from their aqueous solutions individually as well as in mixtures were investigated with respect to the variation of temperature and concentration of the KCl and the bile salt, sodium cholate. The features of different isotherms were presented and discussed. The isotherms obtained differ from those described by the Langmuir equation. The adsorption process was controlled by the ion-dipole and hydrophobic interactions. While KCl retarded the adsorption, the bile salt enhanced the process due to synergistic effect.     

Chain-transfer constant of fluoroalcohols

Chain transfer constants of some fluoroalcohols [HCF₂(CF₂)_n?1CH₂OH, n = 2, 4, 6] in the catalyzed polymerization of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate at 60°C have been evaluated by a method based on degree of polymerization. Since fluoroalcohols are normally nonsolvents for polymers, a homogeneous reaction phase is maintained by carrying out the polymerization in benzene (except in case of acrylonitrile, where no solvent was used). The transfer constants vary, depending on the reactivity as well as the polarity of the radicals, in the following order: vinyl acetate > styrene > methyl methacrylate > acrylonitrile. Of the three fluoroalcohols studied, the transfer constants increase with the increasing value of n. The results have been interpreted in terms of polar structure contribution in the transition state of the transfer reactions.     

Mode of termination in the copolymerization of vinyl acetate–isobutyl methacrylate and methyl methacrylate–methyl acrylate at 60°C

The mode of termination in the vinyl acetate–isobutyl methacrylate (VA–IBMA) and methyl methacrylate–methyl acrylate (MMA–MA) copolymerization systems has been investigated at 60°C. by using the dye-interaction technique for functional endgroup estimation. The results show that pairs of poly(vinyl acetate) radicals interact almost exclusively through a disproportionation mechanism. In the homopolymerization of methyl methacrylate and methyl acrylate, about 1.16 and 1.22 carboxyl-containing endgroups per polymer molecule have been estimated, which shows the predominance of disproportionation over combination in these termination reactions. In poly(isobutyl methacrylate) about 1.55 tagged initiator fragments per chain indicate that 29% of the total radicals terminate through the disproportionation mechanism. Cross termination in the (VA–IBMA) copolymerization system occurs almost entirely through combination for monomer feeds richer in isobutyl methacrylate content while for the MMA–MA system, combination is more important at intermediate monomer feed ratios. These results have been discussed in the light of different explanations for the reaction mechanism.     

MASS SPECTROMETRIC FRAGMENTATION OF UNSYMMETRICALLY SUBSTITUTED METHYLPHOSPHONATE DIESTERS

Abstract

A series of structurally related unsymmetrically substituted methylphosphonate diesters have been synthesised and subjected to electron impact (El) mass spectral studies. These studies though aimed at total identification of the compounds, resulted in certain interesting observations and hence are being reported. In order to confirm the observations under electron impact and to support the mechanism of fragmentation we have also performed MSNS experiments in both daughter ion and parent ion modes.     

Einheitliche Untersuchung der elektrischen Maschinen mit Hilfe des Poynting-Vektors und des elektromagnetischen Energieflusses im Luftspaltraum

Zusammenfassung In der vorliegenden Arbeit werden elektrische Maschinen, im Hinblick auf die Dichte und den Fluss elektromagnetischer Energie im Luftspaltraum, einheitlich untersucht. Der Grund für derartige Untersuchungen ist, die elektrischen Maschinen als physikalische Gebilde mit Strombelägen, Durchflutungen, elektrischen und magnetischen Feldern zu, betrachten und dementsprechend zu analysieren. Anschliessend sind die aus solchen Analysen erhaltenen Ergebnisse mit denjenigen, bereits bekannten, Ergebnissen zu vergleichen, die sich bei der Betrachtung der elektrischen Maschinen als Netzwerke aus Widerständen, Induktivitäten, Gegeninduktivitäten und Rotationsinduktivitäten ergeben. Um die Analyse systematisch durchführen zu können, wird zunächst eine allgemeine Theorie entwickelt, die der Gegenstand dieses Aufsatzes ist. Mit dieser Theorie werden in einem zweiten Aufsatz verschiedene elektrische Maschinen einheitlich untersucht.

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Summary In this treatise a unified analysis of electrical machines has been presented with respect to the density and the flow of electromagnetic energy in the air-gap space. The reason for such an analysis is to investigate the physical aspects of electrical machines based on current sheets, magnetomotive forces and electric and magnetic fields. The results of such kind of investigations are to be compared with the results obtained by considering the electrical machines as networks having circuit-elements like resistances, inductances, mutual inductances and rotational inductances. For a systematic investigation it is necessary to develop a general theory first, which is, as a matter of fact, the topic of this paper. A unified analysis of several electrical machines by applying the general theory is the theme of a subsequent paper.

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Dieser Aufsatz ist ein stark gekürzter Auszug aus der gleichnamigen Habilitationsschrift des Autors.     

Ultrafast intermolecular electron transfer dynamics: Perylene in electron-accepting micellar medium

The dynamics of ultrafast photoinduced intermolecular electron transfer (ET) from the excited singlet (S1) state of perylene (Pe) to an electron-accepting cationic surfactant molecule, N-cetylpyridinium chloride (CPC), in aqueous micellar solutions has been investigated using the femtosecond transient absorption spectroscopic technique with temporal resolution of 120 fs. The Pe molecule is localized at or near the micellar surface, where it coexists with the pyridinium moieties (headgroups of the micelle) of the surfactant molecule. Following photoexcitation of Pe, an electron is transferred to the neat and geometrically restricted headgroup of the micelle. Dynamics of the forward ET process as well as the geminate recombination or back ET (BET) process have been followed by monitoring the temporal evolution of the S1 state of Pe and the cation radical of Pe (Pe*+), respectively. The multiexponential forward ET process indicates that the ET dynamics is highly correlated with the spatial distributions of the micellar headgroups around a donor Pe molecule and thus dependent on the donor-acceptor distance. The distance-dependent ET and BET rates have been calculated following the method of Weidemaier and Fayer (J. Chem. Phys. 1995, 102, 3820) to get the best fit parameters for the multiexponetial temporal profiles for the S1 state of Pe as well as Pe*+. Because the acceptor is a constituent of the neat micellar medium, their confinement on the surface of the microheterogeneous medium provides a very large concentration such that, even though the forward transfer rate is 0.06 ps(-1) at the distance of closest approach, the ET process is complete within a 200-ps time domain. If the concepts of distribution of ET distances are utilized, the possible role of material diffusion on the kinetics of forward ET is ruled out. This is an experimental study to show, for the first time, the ultrafast distance-dependent light-induced ET dynamics following both the excited state of the donor and the cation radical formed in an ET process using the transient absorption spectroscopic technique in a self-reactive restrictive environment.     

Electrochemical reduction and oxidation of nitrogen through low-current electrolysis

Dissolved nitrogen is reduced to ammonia at a platinum cathode enclosed in a cellophane membrane and is oxidised to nitric acid at a similarly enclosed anode at very low current density (～1 mA/cm²), the electrolyte being distilled water. This is attributed to highly active reducing and oxidising species formed near the cathode and anode respectively under such low-current low-concentration condition of electrolysis.     

Viscosity studies of polyethylene in a cosolvent mixture composed of two nonsolvents

Polyethylene, normally soluble at an elevated temperature in some single solvents, is found to be soluble in the following binary mixtures of nonsolvents at a much lower temperature, (often in the vicinity of room temperature): xylene–carbon disulfide, cyclohexane–carbon disulfide, cyclohexane–trichloroethylene, and cyclohexane–cyclohexanone. The fractionated polymer samples show a maximum in [η] values at the optimum solvent compositions corresponding to a minimum in cloud temperature T_e. The results are discussed with respect to the current theories on solubility. The optimum solvent composition agrees with the prediction of a newly developed theoretical equation in two of the above four mixtures.