Global Analysis of the Flows of Fluids with Pressure-Dependent Viscosities

 To describe the flows of fluids over a wide range of pressures, it is necessary to take into account the fact that the viscosity of the fluid depends on the pressure. That the viscosity depends on the pressure has been verified by numerous careful experiments. While the existence of solutions local-in-time to the equations governing the flows of such fluids are available for small, special data and rather unrealistic dependence of the viscosity on the pressure, no global existence results are in place. Our interest here is to establish the existence of weak solutions for spatially periodic three-dimensional flows that are global in time, for a large class of physically meaningful viscosity-pressure relationships. (Accepted May 1, 2002) Published online November 15, 2002 Communicated by S. S. ANTMAN     

Guided modes of integrated optical guides. A mathematical study

A waveguide in integrated optics is defined by its refractiveindex. The guide is assumed to be invariant in the propagationdirection while in the transverse direction it is supposed tobe a compact perturbation of an unbounded stratified medium.We are interested in the modes guided by this device, whichare waves with a transverse energy confined in a neighbourhoodof the perturbation. Our goal is to analyse the existence of such guided modes. Underthe assumptions of weak guidance the problem reduces to a two-dimensionaleigenvalue problem for a scalar field. The associated operatoris unbounded, selfadjoint, and bounded from below. Its spectrumconsists of the discrete spectrum corresponding to the guidedmodes and of the essential spectrum corresponding to the radiationmodes. We present existence results of guided modes and an asymptoticstudy at high frequencies, which shows that contrarily to thecase of optical fibers, the number of guided modes can remainbounded. The major tools are the min-max principle and comparisonof results between different eigenvalue problems. The originalityof the present study lies in the stratified character of theunbounded reference medium.     

Interaction of the mu-opioid receptor with GPR177 (Wntless) inhibits Wnt secretion: potential implications for opioid dependence

Background  

Opioid agonist drugs produce analgesia. However, long-term exposure to opioid agonists may lead to opioid dependence. The analgesic and addictive properties of opioid agonist drugs are mediated primarily via the mu-opioid receptor (MOR). Opioid agonists appear to alter neuronal morphology in key brain regions implicated in the development of opioid dependence. However, the precise role of the MOR in the development of these neuronal alterations remains elusive. We hypothesize that identifying and characterizing novel MOR interacting proteins (MORIPs) may help to elucidate the underlying mechanisms involved in the development of opioid dependence.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Test of bell’s inequality using the one-atom micromaser

We examine a local realist bound in the case of a one-atom micromaser. It is shown that such a bound is violated using a simplified treatment of the micromaser. We consider the effect of dissipation in a proposed experiment with the real micromaser. It is seen that the magnitude of violation of a Bell-type inequality depends significantly on the cavity parameters.     

Reactions of diterpenoids on solid supports. I. Oxidation of methyl abietate on the sorbents Al2O3 and SiO2 containing potassium permanganate

The oxidation of methyl abietate on the sorbents Al₂O₃ and SiO₂ containing potassium permanganate has been studied. It has been shown that the following are formed under the conditions selected: compounds of the dehydroabietane series, stereoisomeric mono- and diepoxides of methyl abietate, and the products of their transformation on the sorbents. The structures and stereochemistries of the compounds isolated have been established with the aid of spectral methods and XSA.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–378, May–June, 1994.     

Synthesis, molecular structure, and EPR analysis of the three-coordinate Ni(I) complex [Ni(PPh3)3][BF4

The compound [Ni(PPh(3))(3)][BF(4)] x BF(3) x OEt(2) was isolated in crystalline form from the olefin oligomerization catalyst system Ni(PPh(3))(4)/BF(3) x OEt(2) and structurally characterized by X-ray diffraction. The influence of vibronic coupling on the EPR parameters of three-coordinate metal complexes with a 3d(9) electronic configuration was investigated within the framework of ligand field theory. Analytical expressions for g-tensor components and isotropic hyperfine coupling constants with ligand nuclei were obtained using first-order perturbation theory. It has been shown that the account of the vibronic interaction in the excited state predicts the existence of three-axial anisotropy of the g-tensor even at the level of first-order perturbation theory; two axes of the g-tensor located in a plane of three-coordinate structure can rotate about the main z axis when a compound is distorted by motion of ligands. It has been shown that in three points of the potential energy surface minimum, for which linear and quadric constants of the vibronic interactions have an identical signs, the HFS isotropic constant from one ligand is larger than HFS constants from the other two; for different vibronic constant signs the ratio between HFS constants varies on opposite. This theoretical researches are in the quality consent with experimental data for a three-coordinate Ni(I) and Cu(II) flat complexes.     

Cyclotrimerization and linear oligomerization of phenylacetylene on the nickel(I) monocyclopentadienyl complex CpNi(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>

The reactions of the CpNi(PPh₃)₂ monocyclopentadienyl complex with phenylacetylene and diphenylacetylene in toluene have been studied by ESR. When an alkyne is in twofold molar excess over nickel, it substitutes rapidly for PPh₃ ligands to form the bisalkyne π complex CpNi(η²-C₂PhR)₂, where R = H or Ph. In the case of phenylacetylene, two structural isomers of the Ni(I) π complex have been identified. Irreversible clustering occurs in the system as time passes. When phenylacetylene is in excess, it oligomerizes actively at ambient temperature. The composition of the oligomerization products depends substantially on the reaction temperature: at T = 20°C, the main product is 1,2,4-triphenylbenzene (97% of the conversion products); at T = 40°C, the main products are linear oligomers with an average molecular weight of 1050. The formation and stabilization of active complexes in the system take place when the substrate is in excess. Phenylacetylene trimerization and linear oligomerization schemes in which the Ni(I) monocyclopentadienyl complex stabilized by substrate molecules is the active species are suggested.     

Reactions of diterpenoids on solid supports. I. Oxidation of methyl abietate on the sorbents Al2O3 and SiO2 containing potassium permanganate

The oxidation of methyl abietate on the sorbents Al₂O₃ and SiO₂ containing potassium permanganate has been studied. It has been shown that the following are formed under the conditions selected: compounds of the dehydroabietane series, stereoisomeric mono- and diepoxides of methyl abietate, and the products of their transformation on the sorbents. The structures and stereochemistries of the compounds isolated have been established with the aid of spectral methods and XSA.     

Interaction of (13S)-6-oxolabd-7,14-dien-13-ol with phenols on the clay askanite-bentonite

The alkylation of some phenols with an allyl 6-oxolabdane alcohol in the presence of the clay askanitebentonite has been investigated. It has been shown that during the reaction intermediateortho- adducts of substitution in the aromatic nucleus are cyclized into chroman derivatives containing a bicyclic terpene residue —2-methyl-2(6-′-oxo-δ^τ-tetranorlabd-12′-yl)chromans. Performing the reaction in the presence of heterogeneous catalysts imposes limitations on the yields of certain products. Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences, Novosibirsk, fax 8(3832) 3 54 752; e-mail: shreerd@nioch.nsc.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 653–662, September–October, 1998.