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1.
 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  相似文献   
2.
The results of the investigation of the electronic structure of the conduction band in the energy range 5–25 eV above the Fermi level EF and the interfacial potential barrier upon deposition of aziridinylphenylpyrrolofullerene (APP-C60) and fullerene (C60) films on the surface of the real germanium oxide ((GeO2)Ge) have been presented. The content of the oxide on the (GeO2)Ge surface has been determined using X-ray photoelectron spectroscopy. The electronic properties have been measured using the very low energy electron diffraction (VLEED) technique in the total current spectroscopy (TCS) mode. The regularities of the change in the fine structure of total current spectra (FSTCS) with an increase in the thickness of the APP-C60 and C60 coatings to 7 nm have been investigated. A comparison of the structures of the FSTCS maxima for the C60 and APP-C60 films has made it possible to reveal the energy range (6–10 eV above the Fermi level EF) in which the energy states are determined by both the π* and σ* states and the FSTCS spectra have different structures of the maxima for the APP-C60 and unsubstituted C60 films. The formation of the interfacial potential barrier upon deposition of APP-C60 and C60 on the (GeO2)Ge surface is accompanied by an increase in the work function of the surface EvacEF by the value of 0.2–0.3 eV, which corresponds to the transfer of the electron density from the substrate to the organic films under investigation. The largest changes occur with an increase in the coating thickness to 3 nm, and with further deposition of APP-C60 and C60, the work function of the surface changes only slightly.  相似文献   
3.
Physics of the Solid State - The formation of unoccupied electronic states and the boundary potential barrier during thermal deposition of tetracyanoquinodimethane (TCNQ) films to 7 nm in thickness...  相似文献   
4.
In total current spectroscopy (TCS) a beam of low energy (0–15 eV) electrons is directed upon a solid sample and secondary electron emission investigated by monitoring the current to the target, rather than by direct energy analysis of emitted electrons. A TCS signal is the derivative of the direct current with respect to the incident energy E1 displayed as a function of that energy, and obtained experimentally in ultra high vacuum conditions using simple modulation and lock in amplification techniques. A typical experimental arrangement is described and factors influencing a typical spectrum outlined. A simple background theory is discussed and it is shown how TCS is a powerful tool for studying not only the surface and near surface regions, but also bulk physics. In particular the technique has already found application in studies of work function, chemi- and physisorption, epitaxy, interband transitions, densities of states, excitons, impurity atom excitation, plasmons, radiation damage and the measurement of thicknesses of very thin surface layers.  相似文献   
5.
Surface plasmon resonance spectroscopy allows the study of protein interaction dynamics in real-time. Application of this technique to G-protein coupled receptors, the largest family of receptors involved in signal transduction, has been complicated by their low level of expression and the critical dependence of their native conformation on the hydrophobic transmembrane lipid environment. Here, we investigate and compare three different strategies to immobilize rhodopsin, a prototypical G-protein coupled receptor on a sensor chip surface using antibodies and a lectin for receptor capturing. By further probing of different experimental conditions (pH, detergent type) we identified the optimal factors to maintain rhodopsin in a functional conformation and extended this approach to recombinant rhodopsin that was heterologously expressed in COS cells. Functional operation of rhodopsin on the sensor chip surface was proven by its activation and subsequent light-stimulated G-protein coupling. The influence of these experimental parameters on the association and dissociation kinetics of G-protein receptor coupling was determined. Thereby, we found that the kinetics of Gt interaction were not changed by the strategy of immobilization or the type of detergent. Regeneration of opsin directly on a chip allowed recycling of the immobilized native and recombinant receptor. Thus, the approach provides an experimental framework for choosing the most suitable conditions for the solubilization, immobilization, and for functional tests of rhodopsin on a biosensor surface.  相似文献   
6.
The results on the electronic structure of the unoccupied electronic states of the polycrystalline SnO2 in the energy range from 5 eV to 25 eV above the Fermi level are presented. The modification of the electronic structure and of the surface potential upon deposition of the ultrathin films of copper phthalocyanine (CuPc) and of perylene tetracarboxylic acid dianhydride (PTCDA) film onto the SnO2 surface were studied using the very low energy electron diffraction (VLEED) method and the total current spectroscopy (TCS) measurement scheme. A substantial attenuation of the TCS signal coming from the SnO2 surface was observed upon formation of a 1.5–2 nm thick organic deposit layer while no new spectral features from the deposit were distinguishable. It was observed that the electronic structure typical for the organic films was formed within the organic deposit thickness range from 2 nm to 7 nm. The interfacial charge transfer was characterized by the formation of the polarization layer up to 5 nm thick in the organic films. The PTCDA deposition on SnO2 was accompanied by the negative charge transfer onto the organic layer and to the 0.65 eV increase the surface work function. At the CuPc/SnO2 interface, the negative charge was transferred to the SnO2 surface and the overall surface work function decreased by 0.15 eV.  相似文献   
7.
An investigation is made of the conditions for the nucleation of optical breakdown in transparent material when recombination-stimulated defect-formation reactions occur in it. It is shown that a positive feedback between the conduction electron concentration and point defects activates defect formation even if the medium is not heated. Under real conditions, where heating of the medium by the light is important, lowering of the activation barrier by thermal defect generation aided by conduction electrons results in optical breakdown of the medium at light intensities much lower than predicted in the classical “semiconductor” or “thermochemical” models of thermal breakdown. The analysis confirms that optical breakdown of transparent condensed media is due to electron-aided defect formation reactions over a broad range of illumination conditions. Zh. Tekh. Fiz. 67, 48–53 (May 1997)  相似文献   
8.
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.  相似文献   
9.

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.  相似文献   
10.
A theoretical interpretation is given of the fine structure in the total-current spectra obtained from the (0001) plane of MoS2, ZrS2, and NbSe2 single crystals. The calculations took into account the energy dependences of band energy-level broadening and of the density of unfilled electronic states which become occupied by electrons entering a solid. The dominant contribution of the bulk band structure to the spectra is demonstrated. Fiz. Tverd. Tela (St. Petersburg) 41, 1875–1878 (October 1999)  相似文献   
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