Acid—base equilibria in the mixed solvent 80% dimethyl sulfoxide—20% water : Part I. definition of ph scale and determination of pk values of aliphatic monocarboxylic acids

The acid—base equilibria in the mixed solvent, 80% dimethyl sulfoxide—water, have been investigated by potentiometric measurements with a glass—silver—silver chloride electrode couple. The response of the glass electrode is quick and reproducible over the whole pH scale. The autoprotolysis constant (itK_SH) of the mixed solvent has been determined; the value obtained, pK_SH = 18.40, agrees well with reported data. The pK_a values of the following aliphatic monocarboxylic acids are reported: formic, acetic, propionic, n-butyric, iso-butyric, n-valeric, iso-valeric, capric, pentadecanoic, stearic, monochloroacetic. The mixed solvent offers better titration conditions than water for the determination of these acids.     

Synthesis of high-quality semiconductor nanoparticles in a composite hot-matrix

Semiconductor nanocrystals are of a great interest for many practical applications which motivates the search of low cost and environmental-friendly methods for their manufacturing. Here we report the synthesis of CdSe and CdS nanoparticles utilizing composite matrix of liquid paraffin as a non-coordinating solvent and stearic acid as a coordinating ligand. The nanoparticle growth kinetics is compared to that of the classical synthesis in trioctylphosphine oxide matrix. It is found that the nucleation and crystal growth are remarkably affected by the coordinating ligand. The CdSe and CdS nanocrystals can be isolated and purified from the matrix which makes it possible their large-scale synthesis for applications.     

Thiophene hydrodesulfurization activity of alumina supported heteropoly compounds: nickel effect

Summary Hydrotreating nickel tungsten catalysts have been prepared by impregnation of g-alumina with solutions of H₃PW₁₂O₄₀ acid and its Ni salt. It is shown that the initial heteropolyanion, its lacunar analog, nickel substituted heteropolyanion and other new formed phases are present on the surface. The thiophene conversion is related to the presence of mixed NiWS phase and to the close cooperation between WS₂ and NiS_x phases.     

Trace analysis in highly concentrated salt solutions of sodium chloride and ammonium fluoride using flame atomic absorption spectrometry

Summary Aqueous solutions of high salt concentration are subjected to direct flame atomic absorption analysis. Blockage of nebulizer and burner is eliminated by employing the dosage scheme washing solution — sample — washing solution effected by means of a specially designed device. The microtrace content of bismuth, zinc and copper in sodium chloride and of copper, lead and iron in ammonium fluoride is determined by the standard addition method. Matrix effects are reduced in the analysis of sodium chloride by the addition of ethanol and in the analysis of ammonium fluoride by pre-heating of sample and washing solution. In order to improve the signal-to-noise ratio, ensemble summation is applied.The following trace element concentrations are determined: 0.5 mg/kg of Cu; 5 mg/kg of Bi and 0.25 mg/kg of Zn in sodium chloride and 0.47 mg/kg of Cu; 0.1 mg/kg of Pb and 3.7 mg/kg of Fe in ammonium fluoride.

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Bestimmung von Spurenelementen in hochkonzentrierten Salzlösungen (NaCl, NH₄F) mittels Flammen-Atom-Absorptions-Analyse

     

Zur Selektivität des Ionenaustausches an unterschiedlich dealuminierten Mordeniten

Selectivity of Ion Exchange on Dealuminated Mordenites Ion Exchange selectivity of Na-mordenites dealuminated by HCl for K⁺, Mg⁺⁺, Ca⁺⁺, and Ba⁺⁺ ions was investigated. Selectivity for K⁺ ions decreases nearly linear with increasing dealumination of mordenite whereas the selectivity for alkaline earth ions increases. Due to dealumination of mordenite its characteristical preference for monovalent towards divalent cationa is reversed.     

Quantitative chemical analysis on paper. I

Summary A method has been proposed for the determination of small quantities of Cl^–, SCN^– and I^– in mixtures. The method is based on the use of filter paper evenly impregnated with Ag₂CrO₄. The method permits the determination of 5 to 50g of Cl^–; 15 to 100g of I^– and 10 to 150g of SCN^– with an accuracy of 1.5%.The method may also be used for determination of SCN^– alone.

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Zusammenfassung Ein Verfahren für die Bestimmung kleiner Mengen Chlorid, Rhodanid und Jodid in deren Gemischen wird vorgeschlagen. Es beruht auf der Verwendung eines mit Silberchromat gleichmäßig imprägnierten Filtrierpapierstreifens und ermöglicht die Bestimmung von 5 bis 50g Chlorid,15 bis 100g Jodid und 10 bis 150g Rhodanid mit einer Genauigkeit von 1,5%. Das Verfahren kann auch für die Bestimmung von Rhodanid allein verwendet werden.

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Résumé On a proposé une méthode pour le dosage de petites quantités de Cl^–, SCN^–, et I^– en mélanges. La méthode est fondée sur l'emploi d'un papierfiltre uniformément imprégné d'Ag₂CrO₄. Elle permet le dosage de 5 à 50g de Cl^–, 15 à 100g d'I^– et de 10 à 150g de SON^–, à la précision de 1,5%. On peut aussi utiliser la méthode pour le dosage de SCN^– seul.

     

Copolymerization of new pyrazolone-containing monomers with certain vinyl comonomers

The polymerization ability of two new pyrazolone-containing monomers—3-methyl-1-phenyl-4-crotonoyl-pyrazolone-5 ( Cr ) and 3-methyl-1-phenyl-4-(3′-phenyl-acryloyl) pyrazolone-5 ( Cy )—was investigated. The monomers were obtained by acylation of 3-methyl-1-phenyl-pyrazolone-5 with crotonyl chloride or cinnamoyl chloride, respectively. It was established that the two monomers do not homopolymerize either under the action of ionic and radical initiators nor with γ-rays (doses between 2 and 10 MRad). In contrast to this, the two monomers copolymerize with other vinyl comonomers. Copolymers of Cr and Cy with methacrylic acid (MAA), methyl methacrylate (MMA), and Styrene (St) were synthesized by radical copolymerization. The molecular weights of the polymer products obtained were in the 10,000–65,000 range. It was established that the molecular weight characteristics of the copolymers were affected by the concentration of the pyrazolone-containing monomer and by the chemical nature of the solvent used. The copolymerization of Cr and Cy with MAA was investigated in detail in order to evaluate the relative activity of the new monomers during copolymerization. The reactivity ratios (r) were calculated by three different methods with good agreement. The values obtained for the monomer pairs are: r_MAA = 0.61 ± 0.01, r_Cr = 0.04 ± 0.01; r_MAA = 0.64 ± 0.05, r_Cy = 0.02 ± 0.02. The Q/e values for Cr and Cy were determined using the reactivity ratios of both monomers.     

Optical diffraction by using electrically-controlled spatially patterned nematic pentylcyanobiphenyl films under static electric field

ABSTRACT

Diffractive electro-optics of electrically-induced spatially periodic texture patterns (namely, wide-formed stationary parallel stripes) in planarly-aligned films of the nematic liquid crystal 4-n-pentyl-4′-cyanobiphenyl (5CB) is examined under static electric field in view of its practical application. The longitudinal textural domains electrically-induced with well defined threshold and spatial period have flexo-dielectric nature and differ from the usual flexoelectric stripe distortion, as well as from the electroconvective domains of frequency-dependent morphology. The low-voltage-controlled grating effect through the flexo-dielectric domains can be useful for nematic diffractive optics.     

Controlled Retention and Release of Biomolecular Transport Systems Using Shape‐Changing Polymer Bilayers

Biomolecular transport systems based on cytoskeletal filaments and motor proteins have become promising tools for a wide range of nanotechnological applications. In this paper, we report control of such transport systems using substrates with switchable shape. We demonstrate this approach on the example of microtubules gliding on surfaces of self‐folding polymer bilayers with adsorbed kinesin motors. The polymer bilayers are able to undergo reversible transitions between flat and tube‐like shapes that allow the externally controlled retention and release of gliding microtubules. The demonstrated approach, based on surfaces with reconfigurable topography, opens broad perspectives to control biomolecular transport systems for bioanalytical and sensing applications, as well as for the construction of subcellular compartments in the field of synthetic biology.     

Phytochemical analysis and in vitro cytotoxic activity of volatiles from Astragalus corniculatus

The volatile fractions from Astragalus corniculatus Bieb., cultivated and collected wild, were analyzed at three different phenological phases for the first time. GC/MS analysis showed that the volatile fractions contain hydrocarbons, butyl ethers, acids, alcohols, esters, aldehydes, ketones, terpenes. These fractions were tested for cytotoxic activity in a panel of human tumor cell lines after 48 h, using the MTT-dye reduction assay. Throughout the cytotoxicity evaluation the fraction derived from the flowering phase of wild type plant was found to exert the most prominent cytotoxic activity, which could be ascribed to the high content of hydrocarbons and squalene in particular. Furthermore, the mechanistic elucidation of the mode of action of this volatile fraction in SKW-3 cells revealed that the observed activity is mediated by induction of necrotic type cell death as evidenced by the smear patterns of DNA following a 24 h exposure period.