Tandem Oxidation Sequence to Prepare Ethyl (E)‐4,5‐Dioxo‐2‐hexadecenoate: A Formal Synthesis of Podoscyphic Acid

A tandem oxidation reaction has been utilized to prepare ethyl (E)‐4,5‐dioxo‐2‐hexadecenoate, the immediate precusor to the antiviral fungal metabolite podoscyphic acid.     

The equilibrium and preequilibrium neutron-emission spectra of some structural fusion materials for (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">xn</Emphasis>) reactions up to 16 MeV energy

In this study, neutron-emission spectra produced by (n, xn) reactions for some structural fusion materials as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, and ⁵⁶Fe have been investigated by a neutron beam up to 16 MeV. Multiple preequilibrium mean-free-path constant from internal transition and the preequilibrium and equilibrium level-density parameters have been investigated for some (n, xn) neutron-emission spectra calculated in this study. Preequilibrium neutron-emission spectra were calculated by using new-evaluated hybrid model and geometry-dependent hybrid model, full-exciton model, and cascade-exciton model. The reaction equilibrium component was calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other. The text was submitted by the authors in English.     

A new force field for simulating phosphatidylcholine bilayers

A new force field for the simulation of dipalmitoylphosphatidylcholine (DPPC) in the liquid‐crystalline, fluid phase at zero surface tension is presented. The structure of the bilayer with the area per lipid (0.629 nm²; experiment 0.629–0.64 nm²), the volume per lipid (1.226 nm³; experiment 1.229–1.232 nm³), and the ordering of the palmitoyl chains (order parameters) are all in very good agreement with experiment. Experimental electron density profiles are well reproduced in particular with regard to the penetration of water into the bilayer. The force field was further validated by simulating the spontaneous assembly of DPPC into a bilayer in water. Notably, the timescale on which membrane sealing was observed using this model appears closer to the timescales for membrane resealing suggested by electroporation experiments than previous simulations using existing models. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Statistics of branched flow in a weak correlated random potential

Recent images of electron flow through a two-dimensional electron gas device show branching behavior that is reproduced in numerical simulations of motion in a correlated random potential [M. A. Topinka, Nature 410, 183 (2001)]]. We show how such branching arises from caustics in the classical flow and find a simple scaling behavior of the branching under variation of the random potential strength. Analytic results describing statistical properties of the branching are confirmed by classical and quantum numerical tests.     

Measuring scars of periodic orbits

The phenomenon of periodic orbit scarring of eigenstates of classically chaotic systems is attracting increasing attention. Scarring is one of the most important "corrections" to the ideal random eigenstates suggested by random matrix theory. This paper discusses measures of scars and in so doing also tries to clarify the concepts and effects of eigenfunction scarring. We propose a universal scar measure which takes into account an entire periodic orbit and the linearized dynamics in its vicinity. This measure is tuned to pick out those structures which are induced in quantum eigenstates by unstable periodic orbits and their manifolds. It gives enhanced scarring strength as measured by eigenstate overlaps and inverse participation ratios, especially for longer orbits. We also discuss off-resonance scars which appear naturally on either side of an unstable periodic orbit.     

Cyclotron-resonance line width in InSb in the quantum limit

The width of the free electron cyclotron resonance in InSb has been studied as a function of resonant magnetic field, by means of laser spectrometers operating at seven different wavelengths. Comparison of the data with theories of line width in the quantum limit, shows that the nature of the field dependence is determined by the size of the parameter l/a, where l is the magnetic length and a the screening length.     

High resolution magneto-optical studies of p-InSb

High resolution photoconductivity and transmission spectra in p-InSb are obtained over a wide temperature range at magnetic fields from 9 to 100 kG using a CO₂ laser. The low temperature results are described in terms of hole transitions from the acceptor ground state to excited states associated with free light-hole Landau states.