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     

Animal models for treatment of unresectable liver tumours: a histopathologic and ultra-structural study of cellular toxic changes after electrochemical treatment in rat and dog liver

INTRODUCTION: Electrochemical treatment (EChT) has been taken under serious consideration as being one of several techniques for local treatment of malignancies. The advantage of EChT is the minimal invasive approach and the absence of serious side effects. Macroscopic, histopathological and ultra-structural findings in liver following a four-electrode configuration (dog) and a two-electrode EChT design (dog and rat) were studied. MATERIALS AND METHODS: 30 female Sprague-Dawley rats and four female beagle dogs were studied with EChT using Platinum:Iridium electrodes and the delivered dose was 5, 10 or 90 C (As). After EChT, the animals were euthanized. RESULTS: The distribution of the lesions was predictable, irrespective of dose and electrode configuration. Destruction volumes were found to fit into a logarithmic curve (dose-response). Histopathological examination confirmed a spherical (rat) and cylindrical/ellipsoidal (dog) lesion. The type of necrosis differed due to electrode polarity. Ultra-structural analysis showed distinct features of cell damage depending on the distance from the electrode. Histopathological and ultra-structural examination demonstrated that the liver tissue close to the border of the lesion displayed a normal morphology. CONCLUSIONS: The in vivo dose-planning model is reliable, even in species with larger tissue mass such as dogs. A multi-electrode EChT-design could obtain predictable lesions. The cellular toxicity following EChT is clearly identified and varies with the distance from the electrode and polarity. The distinct border between the lesion and normal tissue suggests that EChT in a clinical setting for the treatment of liver tumours can give a reliable destruction margin.     

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.     

Bridging across length scales: multi-scale ordering of supported lipid bilayers via lipoprotein self-assembly and surface patterning

We show that a two-step process, involving spontaneous self-assembly of lipids and apolipoproteins and surface patterning, produces single, supported lipid bilayers over two discrete and independently adjustable length scales. Specifically, an aqueous phase incubation of DMPC vesicles with purified apolipoprotein A-I results in the reconstitution of high density lipoprotein (rHDL), wherein nanoscale clusters of single lipid bilayers are corralled by the protein. Adsorption of these discoidal particles to clean hydrophilic glass (or silicon) followed by direct exposure to a spatial pattern of short-wavelength UV radiation directly produces microscopic patterns of nanostructured bilayers. Alternatively, simple incubation of aqueous phase rHDL with a chemically patterned hydrophilic/hydrophobic surface produces a novel compositional pattern, caused by an increased affinity for adsorption onto hydrophilic regions relative to the surrounding hydrophobic regions. Further, by simple chemical denaturation of the boundary protein, nanoscale compartmentalization can be selectively erased, thus producing patterns of laterally fluid, lipid bilayers structured solely at the mesoscopic length scale. Since these aqueous phase microarrays of nanostructured lipid bilayers allow for membrane proteins to be embedded within single nanoscale bilayer compartments, they present a viable means of generating high-density membrane protein arrays. Such a system would permit in-depth elucidation of membrane protein structure-function relationships and the consequences of membrane compartmentalization on lipid dynamics.     

Electrochemical treatment of tumours

The electrochemical treatment (EChT) of tumours implies that tumour tissue is treated with a continuous direct current through two or more electrodes placed in or near the tumour. The treatment offers considerable promise of a safe, simple and relatively noninvasive anti-tumour therapy for treatment of localised malignant as well as benign tumours. Although more than 10,000 patients have been treated in China during the past 10 years, EChT has not yet been universally accepted. The reason for this is the lack of essential preclinical studies and controlled clinical trials. Uncertainties regarding the destruction mechanism of EChT also hinder the development of an optimised and reliable dose-planning methodology. This article reviews the collected Chinese and occidental experiences of the electrochemical treatment of tumours, alone and in combination with other therapies. The current knowledge of the destruction mechanism underlying EChT is presented along with different approaches towards a dose planning methodology. In addition, we discuss our view of different important parameters that have to be accounted for, if clinical trials are to be initiated outside of China.     

On the beam propagation through active media

An analytical iterative procedure has been established to determine the amplitude of a laser beam propagating through an active medium. The treatment is valid for both homogeneous and inhomogeneous broadening, and for arbitrary inhomogeneities of the parameters characterizing the active medium, namely, the refractive index, the small-signal gain and the saturation intensity. After a supplementary approximation, a thin-sheet gain approach is derived from the first iteration. The formalism enables us to provide analytical criteria for evaluating both the accuracy of each iteration and the propagation distances for which the thin-sheet solution can be used. This revised version was published online in November 2006 with corrections to the Cover Date.