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  • 1
    Electronic Resource
    Electronic Resource
    A fast interface solver for the biharmonic Dirichlet problem on polygonal domains (1998)
    Springer
    Numerische Mathematik 78 (1998), S. 577-596 
    Details
    ISSN: 0945-3245
    Keywords: Mathematics Subject Classification (1991): 31A30, 35J40, 65N30, 65N12
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary. In this paper we propose and analyze an efficient discretization scheme for the boundary reduction of the biharmonic Dirichlet problem on convex polygonal domains. We show that the biharmonic Dirichlet problem can be reduced to the solution of a harmonic Dirichlet problem and of an equation with a Poincaré-Steklov operator acting between subspaces of the trace spaces. We then propose a mixed FE discretization (by linear elements) of this equation which admits efficient preconditioning and matrix compression resulting in the complexity $\log \varepsilon^{-1} O ( N \log^qN)$ . Here $N$ is the number of degrees of freedom on the underlying boundary, $\varepsilon 〉 0$ is an error reduction factor, $q = 2$ or $q = 3$ for rectangular or polygonal boundaries, respectively. As a consequence an asymptotically optimal iterative interface solver for boundary reductions of the biharmonic Dirichlet problem on convex polygonal domains is derived. A numerical example confirms the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002110050326
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  • 2
    Electronic Resource
    Electronic Resource
    Injection and detection of a spin-polarized current in a light-emitting diode (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 402 (1999), S. 787-790 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The field of magnetoelectronics has been growing in practical importance in recent years. For example, devices that harness electronic spin—such as giant-magnetoresistive sensors and magnetoresistive memory cells—are now appearing on the market. In contrast, magnetoelectronic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/45502
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  • 3
    Electronic Resource
    Electronic Resource
    Local transport barrier formation and relaxation in reverse-shear plasmas on the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1736-1744 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E×B and Shafranov shift effects was performed by varying the E×B shear through changes in the toroidal velocity with nearly steady-state pressure profiles. Transport and fluctuation levels increase only when E×B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balance injection. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872275
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  • 4
    Electronic Resource
    Electronic Resource
    High resolution observations of pellet emission on TFTR (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 841-841 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: High resolution, rapidly sampled measurements of the light emission from injected impurity pellets have recently been carried out on TFTR. Both wide and narrow views of the pellet light have been accomplished with a tightly collimated fanned array of fiber-optically coupled photomultipliers. Deep (≈100%), high frequency (40–90 kHz) modulation of the pellet emission has been observed in both neutral beam and rf heated discharges with as little as ≈1.5 MW of heating. This finding is consistent with recent work carried out on ASDEXb) with the exception that this modulation phenomenon is seen not only with hydrogenic pellets but also with lithium and boron pellets. This observation seems to point to an instability associated with the plasma surrounding the pellet rather than an instability which depends upon the atomic physics of the pellet. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146243
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of elevated temperature on the photosynthetic efficiency of zooxanthellae in hospite from four different species of reef coral: a novel approach (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bleaching of reef corals is a phenomenon linked to temperature stress which involves loss of the symbiotic algae of the coral, which are known as zooxanthellae, and/or loss of algal pigments. The photosynthetic efficiency of zooxanthellae within the corals Montastrea annularis, Agaricia lamarki, Agaricia agaricites and Siderastrea radians was examined by pulse-amplitude modulation fluorometry (PAM) during exposure to elevated temperatures (30–36°C). Zooxanthellae within M. annularis and A. lamarki were found to be more sensitive to elevated temperature, virtually complete disruption of photosynthesis being noted during exposure to temperatures of 32 and 34°C. The photosynthetic efficiency of zooxanthellae within S. radians and A. agaricites decreased to a lesser extent. Differences in the loss of algal cells on an aerial basis and in the cellular chlorophyll concentration were also found between these species. By combining the non-invasive PAM technique with whole-cell fluorescence of freshly isolated zooxanthellae, we have identified fundamental differences in the physiology of the symbionts within different species of coral. Zooxanthellae within M. annularis appear to be more susceptible to heat-induced damage at or near the reaction centre of Photosystem II, while zooxanthellae living in S. radians remain capable of dissipating excess excitation energy through non-photochemical pathways, thereby protecting the photosystem from damage during heat exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00251.x
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  • 6
    Electronic Resource
    Electronic Resource
    Repression of lipopolysaccharide biosynthesis in Escherichia coli by an antisense RNA of Acetobacter methanolicus phage Acm1 (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 15 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lysogenic Acetobacter methanolicus strains carrying the prophage Acm1 were found to be unable to synthesize both the capsutar polysaccharide (CPS) and the O-specific side-chain of lipopolysaccharide (LPS) and to represent rough variants of the host bacterium. A 262 bp DNA fragment of phage Acm1, obviously required for interference with LPS biosynthesis, was cloned and expressed in Escherichia coli Independently of the O-type, transformation of various E. coli strains with the recombinant DNA resulted in a suppression of biosynthesis of the O-specific chains. The DNA fragment of phage Acm1 contained three very short open reading frames of 21, 24, and 36 bp. However, attempts to express phage-encoded peptides were not successful. Instead, the Acm1-derived DNA fragment was shown to code for the synthesis of a trans-acting RNA molecule of 97 nucleotides, designated lbi (LPS biosynthesis-interfering) RNA. This RNA contains sequence complementarity to E. coli target RNA sequences and appears to have the ability to form intracellularly RNA hybrid duplexes with mRNA. The data presented in this study support the hypothesis that the phenotypic effect of conversion to rough-type LPS is accompanied by the expression of an antisense RNA of phage Acm1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02285.x
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  • 7
    Electronic Resource
    Electronic Resource
    Gas chromatographic-mass spectrometric determination of natural profiles of androgens, progestogens, and glucocorticoids in muscle tissue of male cattle (1999)
    Springer
    European food research and technology 209 (1999), S. 393-399 
    Details
    ISSN: 1438-2385
    Keywords: Key words Hormone pattern ; Gas chromatography-mass spectrometry ; Beef ; Bulls ; Steers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A rapid and economical method was developed for the simultaneous determination of androgens, progestogens, and glucocorticoids and their precursors and metabolites in meat. Steroids were isolated with liquid extraction followed by C18-solid-phase extraction (C18-SPE). Corticoids were separated from the less polar steroids by Si-SPE. The non-polar steroids required additional purification by filtration through an NH2 cartridge. The fractions were combined and derivatized with a universally applicable trimethylsilylation of both hydroxyl and keto groups. Determination was performed with gas chromatography-mass selective detection (determination limits: 0.02–0.1 μg/kg). Hormone profiles of 15 muscle tissue samples of both bulls and steers were analysed. Beef from bulls contained higher concentrations of testosterone and epitestosterone (P〈0.001), 11-deoxycorticosterone (P〈0.01), androstenedione (P〈0.05) and cortisone (P〈0.05), and significantly lower proportions of cortisol (P〈0.001) than beef from steers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002170050515
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  • 8
    Electronic Resource
    Electronic Resource
    Small-angle neutron scattering from a hexagonal phase under shear (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 85-88 
    Details
    ISSN: 1435-1536
    Keywords: Hexagonal phase ; small-angle neutron scattering ; shear orientation ; nonionic surfactant ; lyotropic liquid crystal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The shear orientation of a micellar hexagonal liquid crystalline phase was investigated by small-angle neutron scattering. The hexagonal phase in the quiescent state showed a symmetrical scattering pattern typical of a polydomain structure. Enhanced scattering along the flow direction was observed during shear and the anisotropy of scattering intensity became stronger with increasing shear rate. The anisotropic scattering pattern corresponds to an orientation perpendicular to the flow direction and can be interpreted as a log-rolling state. The oriented sample did not relax after cessation of shear. The results from small-angle neutron scattering confirm data obtained previously from rheo-small angle light scattering measurements and are discussed in comparison to shear alignment of lyotropic liquid crystalline polymer solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658914
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  • 9
    Electronic Resource
    Electronic Resource
    Functional serotonin 5-HT1D receptors and 5-HT1Db receptor mRNA expression in human umbilical vein endothelial cells (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 580-582 
    Details
    ISSN: 1432-1912
    Keywords: Key words 5-Hydroxytryptamine (5-HT ; serotonin) ; 5-HT1D receptors ; 5-HT1Dβ receptors ; Endothelial cells ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pharmacological evidence has suggested the presence of 5-hydroxytryptamine (5-HT, serotonin), 5-HT1D receptors on endothelial cells but these receptors have never been identified unambiguously on this type of cells. We now report that human umbilical vein endothelial cells (HUVEC) express 5-HT1D receptors coupled to inhibition of cyclic AMP formation. 5-HT and the 5-HT1D receptor agonists 5-carboxamidotryptamine (5-CT) and sumatriptan were approximately equipotent at inhibiting forskolin-stimulated cyclic AMP accumulation in HUVEC (mean pEC50 7.6–8.2, maximal effect 30% inhibition). The 5-HT1A receptor agonist, 8-OH-DPAT was clearly less potent (pEC50 6.2) and less efficacious. The selective 5-HT1D receptor antagonist, GR127935 (1 nM) markedly inhibited the effect of 5-HT (apparent pKB 10.8). Reverse transcription-polymerase chain reaction analysis showed the mRNA for 5-HT1Dβ receptors to be expressed in HUVEC. These results demonstrate the presence of functional 5-HT1D receptors and the expression of 5-HT1Dβ receptor mRNA in HUVEC. They support the involvement of 5-HT1Dβ receptors in endothelial-mediated responses to 5-HT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169394
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  • 10
    Electronic Resource
    Electronic Resource
    Functional serotonin 5-HT1D receptors and 5-HT1Dβ receptor mRNA expression in human umbilical vein endothelial cells (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 580-582 
    Details
    ISSN: 1432-1912
    Keywords: 5-Hydroxytryptamine (5-HT, serotonin) ; 5-HT1D receptors ; 5-HT1Dβ receptors ; Endothelial cells ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pharmacological evidence has suggested the presence of 5-hydroxytryptamine (5-HT, serotonin), 5-HT1D receptors on endothelial cells but these receptors have never been identified unamiguously on this type of cells. We now report that human umbilical vein endothelial cells (HUVEC) express 5-HT1D receptors coupled to inhibitiion of cyclic AMP formatin. 5-HT and the 5-HT1D receptor agaonists 5-carboxamidotryptamine (5-CT) and sumatriptan were approximately equipotent at inhibiting forskolin-stimulated cyclic AMP accumulation in HUVEC (mean pEC50 7.6–8.2, maximal effect 30% inhibition). The 5-HT1A receptor agonist, 8-OH-DPAT was clearly less potent (pEC50 6.2) and less efficacious. The selective 5-HT1D receptor antagonist, GR127935 (1 nM) markedly inhibited the effct pf 5-HT (apparent pKB 10.8). Reverse transcription-polymerase chain reaction analysis showed the mRNA for 5-HT1Dβ receptors to be expressed in HUVEC. These results demonstrate the presence of functional 5-HT1D receptors and the expression of 5-HT1Dβreceptor mRNA in HUVEC. They support he involvement of 5-HT1Dβ receptors in endothelial-mediated responses to 5-HT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169394
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