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  • 2000-2004  (26)
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  • 1
    Electronic Resource
    Electronic Resource
    Raman study of ZnxBe1−xSe alloy (100) epitaxial layers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 519-521 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Long wavelength longitudinal optical (LO) and transverse optical (TO) phonons of BeSe and ZnxBe1−xSe layers are identified in a wide composition range by using Raman spectroscopy. A two-mode behavior is clearly evidenced. As predicted by the dielectric model of Hon and Faust, the eigenfrequencies of the BeSe- and ZnSe-like LO modes correspond to the maxima of Im〈−cursive-epsilon(ω, x)−1〉. Excellent agreement is obtained with a model where the calculations are performed by using the equations of motion and polarization derived from the modified random element isodisplacement model. Besides, the TO and LO frequencies for BeSe are determined to be 501 and 579 cm−1, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.127030
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  • 2
    Electronic Resource
    Electronic Resource
    Percolation behavior in the Raman spectra of ZnBeTe alloy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 3081-3083 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zone-center longitudinal (LO) and transverse (TO) optical phonons of Zn1−xBexTe epilayers are identified by Raman spectroscopy. On top of the expected BeTe- and ZnTe-like modes, which obey the modified-random-element-isodisplacement model, we observe an extra BeTe-like (TO, LO) doublet at intermediate x values. It has the same atypical characteristics as its BeSe-like counterpart in ZnBeSe alloy. Its activation validates our percolative picture for multimode description in Be–chalcogenide alloys that open the attractive class of mixed crystals with a sharp contrast in the bond stiffness. Also, the local modes of Be in ZnTe and of Zn in BeTe are identified at 411 cm−1 and 195 cm−1, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467711
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  • 3
    Electronic Resource
    Electronic Resource
    First-Order Schemes in the Numerical Quantization Method (2003)
    350 Main Street , Malden , MA 02148 , USA , and 108 Cowley Road , Oxford OX4 IJF , UK . : Blackwell Publishers, Inc.
    Mathematical finance 13 (2003), S. 0 
    Details
    ISSN: 1467-9965
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mathematics , Economics
    Notes: The numerical quantization method is a grid method that relies on the approximation of the solution to a nonlinear problem by piecewise constant functions. Its purpose is to compute a large number of conditional expectations along the path of the associated diffusion process. We give here an improvement of this method by describing a first-order scheme based on piecewise linear approximations. Main ingredients are correction terms in the transition probability weights. We emphasize the fact that in the case of optimal quantization, many of these correcting terms vanish. We think that this is a strong argument to use it. The problem of pricing and hedging American options is investigated and a priori estimates of the errors are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1467-9965.t01-1-00002
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  • 4
    Electronic Resource
    Electronic Resource
    Interacting effects of CO2 partial pressure and temperature on photosynthesis and calcification in a scleractinian coral (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We show here that CO2 partial pressure (pCO2) and temperature significantly interact on coral physiology. The effects of increased pCO2 and temperature on photosynthesis, respiration and calcification rates were investigated in the scleractinian coral Stylophora pistillata. Cuttings were exposed to temperatures of 25°C or 28°C and to pCO2 values of ca. 460 or 760 μatm for 5 weeks. The contents of chlorophyll c2 and protein remained constant throughout the experiment, while the chlorophyll a content was significantly affected by temperature, and was higher under the ‘high-temperature–high-pCO2’ condition. The cell-specific density was higher at ‘high pCO2’ than at ‘normal pCO2’ (1.7 vs. 1.4). The net photosynthesis normalized per unit protein was affected by both temperature and pCO2, whereas respiration was not affected by the treatments. Calcification decreased by 50% when temperature and pCO2 were both elevated. Calcification under normal temperature did not change in response to an increased pCO2. This is not in agreement with numerous published papers that describe a negative relationship between marine calcification and CO2. The confounding effect of temperature has the potential to explain a large portion of the variability of the relationship between calcification and pCO2 reported in the literature, and warrants a re-evaluation of the projected decrease of marine calcification by the year 2100.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00678.x
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  • 5
    Electronic Resource
    Electronic Resource
    Addictive and non-addictive drugs induce distinct and specific patterns of ERK activation in mouse brain (2004)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 19 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A major goal of research on addiction is to identify the molecular mechanisms of long-lasting behavioural alterations induced by drugs of abuse. Cocaine and delta-9-tetrahydrocannabinol (THC) activate extracellular signal-regulated kinase (ERK) in the striatum and blockade of the ERK pathway prevents establishment of conditioned place preference to these drugs. However, it is not known whether activation of ERK in the striatum is specific for these two drugs and/or this brain region. We studied the appearance of phospho-ERK immunoreactive neurons in CD−1 mouse brain following acute administration of drugs commonly abused by humans, cocaine, morphine, nicotine and THC, or of other psychoactive compounds including caffeine, scopolamine, antidepressants and antipsychotics. Each drug generated a distinct regional pattern of ERK activation. All drugs of abuse increased ERK phosphorylation in nucleus accumbens, lateral bed nucleus of the stria terminalis, central amygdala and deep layers of prefrontal cortex, through a dopamine D1 receptor-dependent mechanism. Although some non-addictive drugs moderately activated ERK in a few of these areas, they never induced this combined pattern of strong activation. Antidepressants and caffeine activated ERK in hippocampus and cerebral cortex. Typical antipsychotics mildly activated ERK in dorsal striatum and superficial prefrontal cortex, whereas clozapine had no effect in the striatum, but more widespread effects in cortex and amygdala. Our results outline a subset of structures in which ERK activation might specifically contribute to the long-term effects of drugs of abuse, and suggest mapping ERK activation in brain as a way to identify potential sites of action of psychoactive drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03278.x
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  • 6
    Electronic Resource
    Electronic Resource
    Δ9-tetrahydrocannabinol-induced MAPK/ERK and Elk-1 activation in vivo depends on dopaminergic transmission (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 14 (2001), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It is now well established that central effects of Δ9-tetrahydrocannabinol (THC), the main psychoactive component of marijuana, are mediated by CB1 cannabinoid receptors. However, intraneuronal signalling pathways activated in vivo by THC remain poorly understood. We show that acute administration of THC induces a progressive and transient activation (i.e. phosphorylation) of the mitogen activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) in the dorsal striatum and the nucleus accumbens (NA). This activation, corresponding to both neuronal cell bodies and the surrounding neuropil, is totally inhibited by the selective antagonist of CB1 cannabinoid receptors, SR 141716A. However, blockade of dopaminergic (DA) D1 receptors by administration of SCH 23390, prior to THC, totally prevents ERK activation in the striatum, thus demonstrating a critical involvement of DA systems in THC-induced ERK activation. DA-D2 and glutamate receptors of NMDA subtypes also participate, albeit to a lesser extent, to THC-induced ERK activation in the striatum, as shown after injection of selective antagonists (raclopride and MK801, respectively). Furthermore, THC-induced phosphorylation of the transcription factor Elk-1, and up-regulation of zif268 mRNA expression are blocked by SL327, a specific inhibitor of MAPK/ERK kinase (MEK), the upstream kinase of ERK, as well as SCH 23390. Finally, using the place-preference paradigm, we show that ERK inhibition blocks THC-induced rewarding properties. Altogether, our data strongly support that ERK activation in the striatum is critically involved in long-term neuronal adaptive responses underlying THC-induced long-term behaviours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0953-816x.2001.01652.x
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  • 7
    Electronic Resource
    Electronic Resource
    A new mechanism of antibiotic resistance in Enterobacteriaceae induced by a structural modification of the major porin (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 41 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Enterobacter aerogenes, multidrug resistance involves a decrease in outer membrane permeability associated with changes in an as yet uncharacterized porin. We purified the major porin from the wild-type strain and a resistant strain. We characterized this porin, which was found to be an OmpC/OmpF-like protein and analysed its pore-forming properties in lipid bilayers. The porin from the resistant strain was compared with the wild-type protein and we observed (i) that its single-channel conductance was 70% lower than that of the wild type; (ii) that it was three times more selective for cations; (iii) a lack of voltage sensitivity. These results indicate that the clinical strain is able to synthesize a modified porin that decreases the permeability of the outer membrane. Mass spectrometry experiments identified a G to D mutation in the putative loop 3 of the porin. Given the known importance of this loop in determining the pore properties of porins, we suggest that this mutation is responsible for the novel resistance mechanism developed by this clinical strain, with changes in porin channel function acting as a new bacterial strategy for controlling β-lactam diffusion via porins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02501.x
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  • 8
    Electronic Resource
    Electronic Resource
    Multiple facets of bacterial porins (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 199 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Porins form channels allowing the transport of molecules across lipid bilayer membranes. Their structure, location and large number on the bacterial surface lend them multiple functions. Porin loops are potential targets for adhesion to other cells and binding of bactericidal compounds to the surface of Gram-negative bacteria. Variation of the loop structure as a mechanism to escape immune pressure, or modulation of the porin expression in response to the presence of antibiotics, are survival strategies developed by some pathogenic bacteria. Porins may play a significant role as pathogenesis effectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10642.x
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  • 9
    Electronic Resource
    Electronic Resource
    Pulmonary metastases from a chromophobe renal cell carcinoma: 10 years' evolution (2002)
    Oxford UK : Blackwell Science Ltd.
    Histopathology 40 (2002), S. 0 
    Details
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2559.2002.1363e.x
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  • 10
    Electronic Resource
    Electronic Resource
    PANEL PERFORMANCE AND NUMBER OF EVALUATIONS IN A DESCRIPTIVE SENSORY STUDY (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of sensory studies 19 (2004), S. 0 
    Details
    ISSN: 1745-459X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The assessor performance is a key point in a sensory evaluation. In particular, at the end of a session, a decrease of the performance can be feared. We propose to analyze this performance with various criteria: usual ones as the main product effect or the error variance; a new one measuring the perceived products variability. The performance can then be studied all along the session from two points of view: in taking into account the only products tested at a given instant (named instantaneous); in taking into account all the products tested up to a given instant (named cumulative). In the presented example, in spite of the large number of products successively tested by each assessor, the instantaneous performance of the panel shows no significant deterioration. Furthermore, when the number of products tested by each assessor increases, more significant product effects can be obtained thanks to the accumulation of the amount of data. This shows that the number of products that can be reasonably studied by one assessor during one session is generally underestimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-459X.2004.tb00148.x
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