Amperometric Response of Alcohols Dissolved in High Resistance Hydrocarbon Media at Microelectrodes Without Supporting Electrolyte

Narrow‐gap cells were fabricated for direct amperometric measurement of alcohol content in liquid hydrocarbon mixtures. Their performance has been investigated using methanol, ethanol, n‐propanol as sample components (ethanol was in most details studied). One type of the insulating materials was applied in order to obtain two copper discs. The surfaces of the copper microdiscs were covered with a Cu_xS modifying layer. The other cell constructed in the similar way had a carbon disc working electrode (with diameter of 30 µm and copper reference/counter electrode 0.3 mm). The amperometric behaviour of the alcohols have been investigated in toluene and n‐heptane solvents without background electrolyte. The amperometric current was found proportional to the ethanol concentration in the investigated range of 0.5–11 v/v%. The sensor’s performance was also tested with ethanol containing fuel products from a gas station.     

Intrinsic spin Hall effect in silicene: transition from spin Hall to normal insulator

An intrinsic contribution to the spin Hall effect in two‐dimensional silicene is considered theoretically within the linear response theory and Green's function formalism. When an external voltage normal to the silicene plane is applied, the spin Hall conductivity is shown to reveal a transition from the spin Hall insulator phase at low bias to the conventional insulator phase at higher voltages. This transition resembles the recently reported phase transition in bilayer graphene. The spin–orbit interaction responsible for this transition in silicene is much stronger than in graphene, which should make the transition observable experimentally. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Direct elemental analysis of cancer cell lines by total reflection X-ray fluorescence

The elemental content of Cu, Fe and Zn in two human adenocarcinoma cell lines was investigated by total reflection X-ray fluorescence (TXRF) spectrometry. Cancer cells were sedimented directly to the quartz plates using a modified cytospin slide holder setup. Special glass stands and caps were also constructed to hold the quartz plates with the cells during the vapour-phase microwave assisted digestion. The method was validated by analysis of certified reference materials. The signal-to-noise ratio was optimized by washing the cells with different solutions. The technique was applied to the determination of Cu, Fe and Zn content of HT-29 and HCA-7 colorectal adenocarcinoma cell lines. Dry mass of the centrifuged cells were determined and the elemental analysis data reported for the two cell lines were referred either to cell numbers, to the total protein content or to the dry mass.     

Magnetization reversal by a single pulse of magnetic field or spin-polarized current

One of the important requirements for spintronic devices concerns an efficient magnetization reversal, which may eventually lead to ultra-fast non-volatile magnetic memory applications. In particular, it is necessary to achieve stable sub-nanosecond switching times and to reduce magnetization “ringing”, so that the reversal will proceed along the shortest ballistic path connecting the initial and the target magnetization states. This paper is dedicated to the numerical simulations of a mono-domain ferromagnetic particle, described by the Landau–Lifshitz–Gilbert equation. We study the general case of arbitrary orientation of the applied field/current pulses, constructing dynamic diagrams for the reversal time. We have found that even short 50 ps pulses, applied at a proper angle, will induce magnetization reversal with minimal ringing effects.     

Determination of the antiproton-to-electron mass ratio by precision laser spectroscopy of pHe+

A femtosecond optical frequency comb and continuous-wave pulse-amplified laser were used to measure 12 transition frequencies of antiprotonic helium to fractional precisions of (9-16)x10(-9). One of these is between two states having microsecond-scale lifetimes hitherto unaccessible to our precision laser spectroscopy method. Comparisons with three-body QED calculations yielded an antiproton-to-electron mass ratio of Mp/me=1836.152674(5).     

X-ray crystallographic and molecular modeling studies of 1-(2,6-difluorobenzoyl)-5-(4-chlorophenyl)biuret

Crystals of 1-(2,6-difluorobenzoyl)-5-(4-chlorophenyl)biuret (BFB), C₁₅H₁₀N₃O₃F₂Cl, were grown by evaporation from an acetonitrile solution. Two polymorphs were obtained. The first polymorph (BFB1) crystallized in the monoclinic space group P2₁/c (Z = 4) with unit cell a = 13.021(3), b = 5.293(1), c = 21.199(6) Å, and = 97.34(2)°. The second polymorph (BFB2) crystallized in the orthorhombic space group P 2₁2₁2₁ (Z = 8) with a = 10.513(1), b = 10.806(1), and c = 26.685(1) Å. The results of crystallographic and molecular modeling studies on BFB were in good agreement. The compound has an extended conformation with the benzene rings coplanar and the intervening –CONHCONHCONH– moiety rotated out of the plane due to steric effects from the two fluorine atoms.     

Structure of copper and nickel amine complexes with polyoxometallates and their adsorption properties relative to lower alcohols

The rates of the adsorption and desorption of methanol and ethanol vapor to and from compounds formed by cationic copper(II) and nickel(II) amine complexes and polyoxometallate anions can be described in the linear driving force transfer model as one or two parallel processes. It was proposed that the differences observed should be attributed to the different crystal structures of the adsorbents. The compound consisting of a nickel tetramine complex and [HSiW₁₂O₄₀]³⁻ anion displays high selectivity toward ethanol relative to methanol. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 291–298, September–October, 2007.     

Photoionization of helium with ultrashort XUV laser pulses

Coupled-channel calculations for multiphoton ionization probabilities of helium through interaction with intensive short laser pulses are presented. Besides Slater-like orbitals we use regular Coulomb wavepackets in our configurational interaction basis to describe the continuum. Linearly polarized laser pulses of 3.8 fs duration and 2.96 x 10¹⁴ Wcm^-2 peak intensity have been used for frequencies between 0.2-1.2 a.u. The results are compared with other ab initio calculations.Received: 8 April 2003, Published online: 9 September 2003PACS: 32.80.Fb Photoionization of atoms and ions - 32.80.Wr Other multiphoton processes