Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes

The ligand-redistribution reactions of aryl- and alkoxy-hydrosilanes can potentially cause the formation of gaseous hydrosilanes, which are flammable and pyrophoric. The ability of generic nucleophiles to initiate the ligand-redistribution reaction of commonly used hydrosilane reagents was investigated, alongside methods to hinder and halt the formation of hazardous hydrosilanes. Our results show that the ligand-redistribution reaction can be completely inhibited by common electrophiles and first-row transition metal pre-catalysts.     

The importance of polarizability in the modeling of solubility: quantifying the effect of solute polarizability on the solubility of small nonpolar solutes in popular models of water

In recent work by Paschek [J. Chem. Phys. 120, 6674 (2004)] and others [see H. Docherty et al., J. Chem. Phys. 125, 074510 (2006) for a review] it has been suggested that, when coupled to a simple Lennard-Jones model for various small nonpolar solute molecules, the most common models of water (e.g., SPC/E and TIP4P) fail to reproduce quantitatively the solubility of small nonpolar solute molecules in water due in part to failing to account for polarization of the solute molecule. Given the importance of such systems as test-case prototype models of the solubility of proteins and biomolecules, in this work, we investigate the impact of using a polarizable solute model with the SPC/E, TIP3P, TIP4P, TIP4P-Ew, and TIP4P/2005 rigid water models. Specifically we consider Ne, Ar, Kr, Xe, and methane as solutes. In all cases we observe that the use of a polarizable solute improves agreement between experiment and simulations, with the best agreement seen for the largest solutes, Kr, CH(4), and Xe and the modern reparametrizations of the TIP4P model, i.e., the TIP4P-Ew and TIP4P/2005 models.     

Potential polymorphs of aspirin

Aspirin is only found experimentally in one crystal structure. In this article, the method of Karfunkel and Gdanitz is used to predict potential polymorphs of aspirin. The known structure, containing a nonplanar conformer is found, along with a number of other low energy structures, many of which are based on a planar conformer. Semiempirical and ab initio calculations show that the planar conformer is less stable than the experimentally known one. Force field calculations suggest that the planar conformer is more stable. The lattice energy of the experimentally known crystal structure is 1.4 kcal/mol lower than any of the potential crystal structures, even though there are a number of structures with lower total (lattice+intramolecular) energies. Conformational maps indicate that another stable conformation occurs within a few kilocalories per mole of the known structure. Polymorphs are predicted for this conformer, but it is found to pack poorly. It is proposed that routes to producing polymorphs of aspirin might be found if consideration is given to promoting the stability of the planar conformer with appropriate solvents or additives. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 262–273, 1999     

Periodic-Group-Delay Dispersion Compensation Reduces Collision-Induced Timing Shifts in Dispersion-Managed Quasilinear Systems

Periodic-group-delay (PGD) dispersion-compensation modules have recently been proposed as mechanisms to alleviate collision-induced timing shifts in dispersion-managed (DM) systems. We obtain frequency and timing shifts in quasilinear DM systems with PGDs and show that significant reductions are achieved when even a small fraction of the total dispersion is compensated by PGDs.__________Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 1, pp. 6–13, July, 2005.     

A laboratory and simulation comparison of the effectiveness of open entry rooms for protection from high noise levels

The potential of differently shaped barriers to provide a ‘sound shadow’ in an otherwise noisy environment was investigated. A doorless enclosure of two three-sided interlocking rectangular barriers was found to produce attenuation of over 9 dB.To enable these, and similar, barriers to be incorporated with an existing noise control simulation program, computer studies were carried out to simulate the experimental results. These provided close comparison with the empirical data except at the centre of the configuration where simulated values were always higher than laboratory measurements. Reasons for these differences are deduced.     

Both systemic and local application of Granulocyte-colony stimulating factor (G-CSF) is neuroprotective after retinal ganglion cell axotomy

Background  

The hematopoietic Granulocyte-Colony Stimulating Factor (G-CSF) plays a crucial role in controlling the number of neutrophil progenitor cells. Its function is mediated via the G-CSF receptor, which was recently found to be expressed also in the central nervous system. In addition, G-CSF provided neuroprotection in models of neuronal cell death. Here we used the retinal ganglion cell (RGC) axotomy model to compare effects of local and systemic application of neuroprotective molecules.     

Bioconversion of a L-carnitin precursor in a one- or two-phase system

Applied Biochemistry and Biotechnology - The ability of the yeastSaccharomyces cerevisiae to bioconvert stereo-selectively octyl-4-chloroacetoacetate (OCA) into the corresponding chiral alcohol,...     

Measurement of the spin correlation parameter Aoonn and of the analyzing power for pp elastic scattering in the energy range from 0.5 to 0.8 GeV

The spin correlation parameter A_oonn and the analyzing powers A_oono and A_ooon were measured simultaneously, in the energy range 0.5–0.8 GeV and in the angular region 40°–80° CM. The experiment used the polarized proton beam of SATURNE II and the Saclay frozen spin polarized target.