Asymptotic modeling of short plane-parallel high-pressure glow discharge

Here a self-consistent continuum model is presented for a narrow gap plane-parallel dc glow discharge. The set of governing equations consisting of continuity and momentum equations for positive ions, fast (emitted by the cathode) and slow electrons (generated by fast electron impact ionization) coupled with Poisson's equation is treated by the technique of matched asymptotic expansions. Explicit results are obtained in the asymptotic limit: (chi delta) much less than 1, where chi = e Phi(a)/kT, delta = (r(D)/L)(2) (Phi(a) is the applied voltage, r(D) is the Debye radius) and pL much greater than 1(Hg mm cm), where p is the gas pressure and L is the gap length. In the case of high pressure, the electron energy relaxation length is much smaller than the gap length, and so the local field approximation is valid. The discharge space divides naturally into a cathode fall sheath, a quasineutral plasma region, and an anode fall sheath. The electric potential distribution obtained for each region in a (semi)analytical form is asymptotically matched to the adjoining regions in the region of overlap. The effects of the gas pressure, gap length, and applied voltage on the length of each region are investigated. (C) 2000 American Institute of Physics. [S1070-664X(00)01302-1].

Total Synthesis of Bryostatin 1: A Short Route

A chemical legacy: Keck and his team have chemically pursued the bryostatin 1 structure with great vigor in recent years and, in late 2010, they finally completed their quest of developing a short and efficient total synthesis of this complex natural product (see structure). The present Highlight provides a brief but nevertheless detailed overview of the Keck synthesis and its chemical legacy in terms of new reactions.

Examining acute and chronic effects of short- and long-chain fatty acids on peptide YY (PYY) gene expression, cellular storage and secretion in STC-1 cells

PURPOSE: Peptide YY (PYY) is a gastrointestinal hormone with physiological actions regulating appetite and energy homoeostasis. The cellular mechanisms by which nutrients stimulate PYY secretion from intestinal enteroendocrine cells are still being elucidated.

METHODS: This study comprehensively evaluated the suitability of intestinal STC-1 cells as an in vitro model of PYY secretion. PYY concentrations (both intracellular and in culture media) with other intestinal peptides (CCK, GLP-1 and GIP) demonstrated that PYY is a prominent product of STC-1 cells. Furthermore, acute and chronic PYY responses to 15 short (SCFAs)- and long-chain (LCFAs) dietary fatty acids were measured alongside parameters for DNA synthesis, cell viability and cytotoxicity.

RESULTS: We found STC-1 cells to be reliable secretors of PYY constitutively releasing PYY into cell culture media (but not into non-stimulatory buffer). We demonstrate for the first time that STC-1 cells produce PYY mRNA transcripts; that STC-1 cells produce specific time- and concentration-dependent PYY secretory responses to valeric acid; that linoleic acid and conjugated linoleic acid 9,11 (CLA 9,11) are potent PYY secretagogues; and that chronic exposure of SCFAs and LCFAs can be detrimental to STC-1 cells.

CONCLUSIONS: Our studies demonstrate the potential usefulness of STC-1 cells as an in vitro model for investigating nutrient-stimulated PYY secretion in an acute setting. Furthermore, our discovery that CLA directly stimulates L-cells to secrete PYY indicates another possible mechanism contributing to the observed effects of dietary CLA on weight loss.

A review on the use of corneal implants for the treatment of presbyopia

In recent years there has seen an increased interest in refractive surgery for the correction of presbyopia. This can be attributed to a number of factors such as the increased demand from patients to have perfect vision without the need for glasses, spurred on by the success of high street refractive laser surgery. Also the World Health Organisation (WHO) estimated in 2005 that over a 1.04 billion people worldwide are affected by presbyopia (Holden et al. 2008). This vast number of people is valued as a potential market and is a huge enticement to the ophthalmic industry to try and develop devices and products to treat this condition. Recent advances in technology have renewed interest in the implantation of corneal inlays for surgical treatment of presbyopia. Dexl et al. (2011) suggest that the reason for this is the further development of biomaterial technology, advances in femtosecond laser and the need for a reversible presbyopic treatment.

Magnetic short-range order in the new ternary phase Mn8Pd15Si7

A new compound, Mn8Pd15Si7, is reported to crystallize in a face centered cubic unit cell of dimension a = 12.0141(2) angstrom, space groupFm (3) over barm, and can thus be classified as a G-phase. The crystal structure was studied by single crystal X-ray diffraction, X-ray and neutron powder diffraction and electron diffraction. A filled Mg6Cu16Si7 type structure was found, corresponding to the Sc11Ir4 type structure. The magnetic properties were investigated by magnetization measurements and Reverse Monte Carlo modeling of low temperature magnetic short-range order (SRO). Dominating near neighbor antiferromagnetic correlations were found between the Mn atoms and geometric frustration in combination with random magnetic interactions via metal sites with partial Mn occupancy were suggested to hinder formation of long-range magnetic order.