A Study of the Reaction of Phosphorus Trichloride with Paraformaldehyde in the Presence of Carboxylic Acids

Abstract

We investigated the mechanism of the reaction of paraformaldehyde with phosphorus trichloride in the presence of carboxylic acids (acetic, propanoic, and formic). Our results revealed that bisphosphonic acids were obtained without the use of water. The structures of the reaction products were studied by 1D and 2D homonuclear and heteronuclear ¹H-, ¹³C-, ³¹P- NMR spectroscopy.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional tables.]     

Flexoelectricity of lipid bilayers

Abstract

The direct flexoeffect in single lipid bilayers in the form of black lipid membranes has been investigated experimentally by the oscillating pressure technique in the regime of voltage measurement. Black lipid membranes of various composition have been studied in order to check the effect of lipid surface charge on the curvature-electric response and its frequency dependence; these include egg yolk lecithin (low negative charge); egg yolk lecithin plus phosphatidyl serine (high negative charge); egg yolk lecithin with surface adsorbed ions of uranyl acetate (high positive charge). An increase of the response has been found by increasing the surface charge and a reversal of the sign of the flexoelectric coefficient from positive to negative has been obtained by changing the sign of the surface charge from negative to positive. These results underline the leading role of the contribution of the surface charge to the flexoelectricity of lyotropics. Their theoretical interpretation provides further insight into the molecular mechanism of this phenomenon.     

Effects of the photocathode non-uniformity on radon measurements by plastic scintillation spectrometry

Journal of Radioanalytical and Nuclear Chemistry - This work shows a study of the effect of the non-uniformity of photocathode response on the energy resolution of plastic scintillators optimized...     

Depicting the dehydration and dehydroxylation processes in very rare hydrogen arsenate minerals

Journal of Thermal Analysis and Calorimetry - The work represents a pioneering attempt to couple TG analysis and hot-stage t-ATR-FTIR spectroscopy to describe the dehydration and dehydroxylation...     

In search of benzene-like Sn6(6-): synthesis of Na4CaSn6 with interconnected cyclohexane-like Sn6(6-)

The title compound was synthesized in an attempt to produce stacked benzene-like Sn6(6-) rings separated by alkaline-earth cations in analogy with the recently reported stacks of aromatic cyclopentadienyl-like Sn5(6-) in Na8BaSn6 (in addition to isolated Sn4- anions). The resulting compound, synthesized from a stoichiometric mixture of the elements at high temperature, has the "correct" stoichiometry with six tin atoms and six positive charges. However, the rings of Sn6(6-) are puckered into chair-type cyclohexanes that are interconnected into isolated cylindrical tubes stuffed with Ca2+ between the rings. Such tubes, if fused to each other, form the hexagonal diamond structure. The new compound is electronically balanced according to magnetic and four-probe resistivity measurements. Reported are also the synthesis and properties of Na10EuSn12 and Na10YbSn12 which are isostructural with the known Na10CaSn12.     

Molecular conduction: do time-dependent simulations tell you more than the Landauer approach?

A dynamical method for simulating steady-state conduction in atomic and molecular wires is presented which is both computationally and conceptually simple. The method is tested by calculating the current-voltage spectrum of a simple diatomic molecular junction, for which the static Landauer approach produces multiple steady-state solutions. The dynamical method quantitatively reproduces the static results and provides information on the stability of the different solutions.     

Operator Hyperreflexivity of Subspace Lattices

We introduce and study the notion of operator hyperreflexivity of subspace lattices. This notion is a natural analogue of the operator reflexivity and is related to hyperreflexivity of subspace lattices introduced by Davidson and Harrison.     

Antibacterial mono- and sesquiterpene esters of benzoic acids from Iranian propolis

Background  

Propolis (bee glue) has been used as a remedy since ancient times. Propolis from unexplored regions attracts the attention of scientists in the search for new bioactive molecules.     

Über die inversen Unterhalbgruppen der endlichen symmetrischen Halbgruppe

Ohne ZusammenfassungDiese Arbeit entstand während eines Aufenthaltes des Verfassers an der G.H. Kassel im Rahmen eines Humboldtstipendiums und wurde unterstützt von Prof. Bosbach, dem der Autor an dieser Stelle seinen Dank ausspricht.