Influence of short-range correlations on the phonon spectra of f.c.c. helium and neon

The influence of short-range correlations on the phonon spectra of helium at high pressures and of neon is investigated. It is found that a simple cutoff procedure is insufficient. A more appropriate treatment of the hard core might also be necessary for the heavier rare-gas solids at higher temperatures.     

Lattice dynamics of quantum crystals

A theory of lattice dynamics for quantum crystals is developed. This is done by summing an infinite class of diagrams of the usual anharmonic expansion and by avoiding the harmonic approximation as starting point. The zero order of the expansion given in this paper corresponds to the harmonic approximation with an effective potential. Higher orders correspond to higher anharmonic corrections with the same potential. Since the new potential varies more slowly the expansion seems to converge more rapidly than the usual anharmonic expansion. Numerical calculations on bcc He³ show that the ground state energy is lowered by about 3–4 cal/mol by taking into account long range correlations due to phonons. The elastic constants and the Debye temperature are calculated in zero and second order. The lowering of the bulk modulus due to the second order is about 10%. Experiments agree quite well with the second order results.     

Structure of 72,74Se at high spin

Lifetimes of high spin states up to { }=22⁺ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in ^{72, 74}Se. The Q _t values derived from these measurements indicate that prolate shape stabilizes for ⁷²Se, while a triaxial shape develops for ⁷⁴Se at higher spins. Comparison of the observed trend in Q _t with spin for ^{72, 74}Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency.     

Product studies and laser flash photolysis on alkyl radicals containing two different beta-leaving groups are consonant with the formation of an olefin cation radical.

1-Bromo-2-methoxy-1-phenylpropan-2-yl (3) and 2-methoxy-1-phenyl-1-diphenylphosphatopropan-2-yl (4) were generated under continual photolysis from the respective PTOC precursors in a mixture of acetonitrile and methanol. The radicals undergo heterolytic fragmentation of the substituent in the beta-position to generate the olefin cation radical (5). Z-2-Methoxy-1-phenylpropene (15) is the major product formed in the presence of 1,4-cyclohexadiene, and is believed to result from hydrogen atom transfer to the oxygen of the olefin cation radical, followed by deprotonation. Laser flash photolysis experiments indicate that reaction between 5 and 1,4-cyclohexadiene occurs with a rate constant of approximately 6 x 10(5) M(-1) s(-1). 2,2-Dimethoxy-1-phenylpropane (18) is observed as a minor product. Laser flash photolysis experiments place an upper limit on methanol trapping of 5 at k <1 x 10(3) M(-1) s(-1) and do not provide any evidence for the formation of reactive intermediates other than 5. The use of two PTOC precursors containing different leaving groups to generate a common olefin cation radical enables one to utilize product analysis to probe for the intermediacy of other reactive intermediates. The ratio of 15:18 is dependent upon hydrogen atom donor concentration, but is independent of the PTOC precursor. These observations are consistent with the proposal that both products result from trapping of 5 that is formed via heterolysis of 3 and 4.     

Tissue distribution and metabolism of the putative cancer chemopreventive agent 3′,4′,5′‐trimethoxyflavonol (TMFol) in mice

3′,4′,5′‐Trimethoxyflavonol (TMFol) is a synthetic flavonol with preclinical cancer chemopreventive properties. The hypothesis was tested that, in mice, p.o. administration of TMFol results in measureable levels of the parent in target tissues. A single oral dose (240 mg/kg) was administered to mice (n = 4 per time point) with time points ranging from 5 to 1440 min. TMFol and its metabolites were identified and quantitated in all tissues by high‐performance liquid chromatography (HPLC). Plasma levels of TMFol were at the limit of quantification or below, although metabolites were identified. Peak levels of TMFol in the gastrointestinal tract and the prostate averaged 1671 ± 265 µg/g (5.3 µmol/g) and 6.0 ± 1.6 µg/g (18.4 nmol/g), and occurred 20 and 360 min post‐dose, respectively. The area under the tissue concentration–time curve (AUC) for TMFol was greater than those of the metabolites, indicating that TMFol is relatively metabolically stable. Micromolar TMFol levels are easily achieved in the prostate and gastrointestinal tract, suggesting that TMFol might exert chemopreventive efficacy at these tissue sites. Further investigations are warranted to elucidate the potential chemopreventive potency of TMFol. Copyright © 2012 John Wiley & Sons, Ltd.     

Vibration analysis of a spinning disk using image-derotated holographic interferometry

This paper reports on the application of image-derotated holographic interferometry to study the resonant response of a rotating steel disk at speeds up to 8000 rpm. The rotational motion of the disk is optically removed by passing the image of the rotating disk through a prism that is traveling at half the rotational speed of the disk. Off-axis, double-pulsed, laser holography is then used to record the disk resonant-vibratory response. The first five diametrical modes and one complex mode of disk vibration are obtained at various rpm. The effects of disk imbalance, misalignment of optical and mechanical axes of rotation and system-excited modes of vibration are also addressed. Selected experimental results are compared to those obtained using finite element analysis.     

DER OXIDATIVE ABBAU VON THIOPHOSPHIN- THIOPHOSPHON- UND THIOPHOSPHORSÄUREESTERN MIT HYPOCHLORIT

Abstract

The thioesters R¹R²P(X)SR (X=O,S) 1 to 4 are degradated oxidatively forming R¹R²P(O)OH and R-SO³H. The influence of the following parameters on the oxidation course is investigated using standard conditions: pH, concentration of the hypochlorite, quality of the organic phase and cooperation of phase transfer catalysts and hypochlorite cations.

The thioesters 1 to 4 are degradated by hypochlorite with different rates depending on the type of the ligands R¹ and R² and the employment of an optimal pH. An analytical evaluation is possible.

Die Thioester R¹R²P(X)SR (X=O,S) 1 bis 4 werden durch Hypochlorit oxidativ zu R¹R²P(O)OH und RSO₃H abgebaut. Der Einfluß folgender Parameter auf den Oxidationsverlauf unter Standardbedingungen wird untersucht: pH, Hypochloritkonzentration, Art der organischen Phase, Mitwirkung von Phasentransfer-Katalysatoren und der Hypochlorit Kationen.

Die Thioester 1 bis 4 werden mit Hypochlorit in Abhängigkeit vom Typ der Liganden R¹ und R² und nach Einstellen eines optimalen pH-Wertes unterschiedlich schnell abgebaut. Dieser Unterschied ist analytisch auswertbar.     

Phosphororganische Verbindungen 1001 Thiophosphylverbindungen Durch-Austausch

Abstract

Phosphinic-acid-, phosphonic-acid- and phosphoric-acid-derivatives react in high yields with Lawesson's reagent to form the corresponding thiophosphyl-compounds.

Phosphinsäure-, Phosphonsäure- und Phosphorsäure-derivate setzen sich mit Lawesson's Reagenz 1 in guten Ausbeuten zu den entsprechenden Thiophosphylverbindungen um.     

The sphericalp-spin interaction spin-glass model

The relaxational dynamics for local spin autocorrelations of the sphericalp-spin interaction spin-glass model is studied in the mean field limit. In the high temperature and high external field regime, the dynamics is ergodic and similar to the behaviour in known liquid-glass transition models. In the static limit, we recover the replica symmetric solution for the long time correlation. This phase becomes unstable on a critical line in the (T, h) plane, where critical slowing down is observed with a cross-over to power law decay of the correlation function ∝t ^?ν, with an exponent ν varying along the critical line. For low temperatures and low fields, ergodicity in phase space is broken. For small fields the transition is discontinuous, and approaching this transition from above, two long time scales are seen to emerge. This dynamical transition lies at a somewhat higher temperature than the one obtained within replica theory. For larger fields the transition becomes continuous at some tricritical point. The low temperature phase with broken ergodicity is studied within a modified equilibrium theory and alternatively for adiabatic cooling across the transition line. This latter scheme yields rather detailed insight into the formation and structure of the ergodic components.