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  • Electronic Resource  (30)
  • 2000-2004  (9)
  • 1995-1999  (18)
  • 1915-1919  (3)
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  • Electronic Resource  (30)
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  • 1
    Electronic Resource
    Electronic Resource
    Steady-state fully noninductive operation with electron cyclotron current drive and current profile control in the tokamak à configuration variable (TCV) : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2199-2207 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fully noninductive, steady-state electron cyclotron current drive (ECCD) has been demonstrated for the first time in experiments carried out in the tokamak à configuration variable (TCV) [O. Sauter et al., Phys. Rev. Lett. 84, 3322 (2000)]. By appropriately distributing six 0.45 MW ECCD sources over the discharge cross section, fully noninductive, stable, and stationary plasmas with Ip up to 210 kA were obtained for the full discharge duration of 1.9 s, corresponding to more than 900 energy confinement times and more than 10 current redistribution times at an average current drive efficiency η20CD=0.01[1020 A W−1 m−2]. These experiments have also demonstrated for the first time the steady recharging of the ohmic transformer using ECCD only. The effect of localized off-axis electron cyclotron heating (ECH) and EC current drive (ECCD) (co- and counter-) is investigated showing that locally driven currents amounting to only 1% of Ip significantly alter sawtooth periods and crash amplitudes. An improved quasi-stationary core confinement regime, with little or no sawtooth activity, has been obtained by a combination of off-axis ECH and on-axis CNTR–ECCD. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355317
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  • 2
    Electronic Resource
    Electronic Resource
    Central electron temperature enhancements due to sawtooth stabilization during counter electron cyclotron current drive in Tokamak à Configuration Variable (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2909-2914 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the Tokamak à Configuration Variable (TCV), the central electron temperature obtained in discharges with counter (CNTR) electron cyclotron current drive (ECCD) is larger than with CO-ECCD or electron cyclotron resonance heating (ECRH) alone. Comparison of experimental results with calculations by the transport code PRETOR [IAEA Technical Conference on Advances in Simulation and Models of Thermonuclear Plasmas. Montreal 142 (International Atomic Energy Agency, Vienna 1992)] indicates that sawtooth stabilization is responsible for the increased confinement time and the attendant twofold enhancement of the central temperature. Sawtooth stabilization is caused in turn by the central safety factor q0 rising above 1 for CNTR-ECCD; by contrast, the simulation results show that q0〈1 in the sawtoothing CO-ECCD and ECRH cases. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874141
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  • 3
    Electronic Resource
    Electronic Resource
    Differential effects of Rho GTPases on axonal and dendritic development in hippocampal neurones (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 90 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Formation of neurites and their differentiation into axons and dendrites requires precisely controlled changes in the cytoskeleton. While small GTPases of the Rho family appear to be involved in this regulation, it is still unclear how Rho function affects axonal and dendritic growth during development. Using hippocampal neurones at defined states of differentiation, we have dissected the function of RhoA in axonal and dendritic growth. Expression of a dominant negative RhoA variant inhibited axonal growth, whereas dendritic growth was promoted. The opposite phenotype was observed when a constitutively active RhoA variant was expressed. Inactivation of Rho by C3-catalysed ADP-ribosylation using C3 isoforms (Clostridium limosum, C3lim or Staphylococcus aureus, C3stau2), diminished axonal branching. By contrast, extracellularly applied nanomolar concentrations of C3 from C. botulinum (C3bot) or enzymatically dead C3bot significantly increased axon growth and axon branching. Taken together, axonal development requires activation of RhoA, whereas dendritic development benefits from its inactivation. However, extracellular application of enzymatically active or dead C3bot exclusively promotes axonal growth and branching suggesting a novel neurotrophic function of C3 that is independent from its enzymatic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02475.x
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic measurements on the TCV Tokamak (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2333-2348 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TCV Tokamak was designed to create a large variety of plasma shapes. Such a large flexibility requires high precision magnetic measurements with a good spatial coverage. This article gives a detailed description of the magnetic sensor geometry, fabrication, calibration, the associated electronics, and the diagnostic operation and monitoring. A substantial effort has been made to quantify the precision in the measurements and a novel method has been developed to derive corrections in the sensor position and calibration which optimise the consistency of the entire measurement set. Accuracy of 0.5 mWb in the poloidal flux and 1 mT in the magnetic field with a position error of a few mm have been achieved. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148940
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  • 5
    Electronic Resource
    Electronic Resource
    Helium atom scattering from isolated CO molecules on copper(001) (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2093-2098 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Angular distributions have been measured for helium atoms scattering from isolated CO molecules chemisorbed on a Cu(001) surface as a function of incident beam energy between 9.4 and 100 meV and surface coverage from 1.3% ML to 9.3% ML. Up to five oscillations are clearly observed in the angular distributions. The parallel wave vector transfers of the peaks vary only slightly with incident energy and are independent of coverage up to 20% of a c(2×2) layer. New hard wall scattering calculations show that all of the distinct peaks observed can be explained by interference structures involving both Fraunhofer diffraction and illuminated face scattering from CO molecules with an approximate hard wall radius of 2.4 A(ring) with no evidence of the classical rainbows predicted in several recent theoretical studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472075
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  • 6
    Electronic Resource
    Electronic Resource
    Quasielastic helium atom scattering measurements of microscopic diffusion of CO on the Ni(110) surface (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11297-11304 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microscopic diffusion of CO on the Ni(110) surface has been studied by quasielastic helium atom scattering. From the temperature dependence of the energetic broadening of the quasielastic peak measured at a parallel wave vector near the Brillouin zone boundary, the activation energies for diffusion have been determined to be Ediff=57±4 and 35±4 meV for diffusion parallel to the rows (〈11¯0〉) and perpendicular to the rows (〈001〉), respectively. The activation energies are a factor 2–6 smaller and the preexponential diffusion coefficients orders of magnitude larger than obtained in recent laser measurements of chemical diffusion coefficients, indicating that diffusion over distances from about a few A(ring)ngstroms up to 30 A(ring) is much faster than over the much larger distances probed in macroscopic diffusion measurements. The difference is attributed to the impeding effect of step edges or impurities on the latter measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472983
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  • 7
    Electronic Resource
    Electronic Resource
    Caoutchouc Substances (1915)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 7 (1915), S. 83-83 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50073a639
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  • 8
    Electronic Resource
    Electronic Resource
    A helium atom scattering study of the growth and dynamics of CH4 and C2H6 on Cu(001) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2502-2512 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The growth, structure and dynamics of methane and ethane monolayers on Cu(001) have been studied using high resolution helium atom scattering. Specular intensity measurements of the growth behavior reveal an island growth mode for methane and ethane, indicative of an attractive interatomic interaction. Diffraction measurements show that the methane monolayer forms a hexagonal structure, incommensurate in one direction, with a lattice constant of 4.18 Å, while ethane forms a structure with an interatomic distance of 5.10 Å. The frustrated translational vibrations perpendicular to the surface (S mode) of methane and ethane have been measured with inelastic helium scattering and have frequencies of 6.5 meV and 6.8 meV, respectively. In addition, the desorption energies were determined to be 165 meV for methane and 260 meV for ethane, in both cases independent of coverage. These results are compared with recent measurements made for C2H4 and larger alkanes adsorbed on Cu(001). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473156
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental determination of a longitudinal phonon dispersion curve in a quasi-two-dimensional system (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 6194-6197 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structural and dynamical properties of a monolayer of Xe atoms adsorbed on a Cu(001) surface have been studied with high-resolution He-atom scattering. Angular distributions reveal a phase-transition from the high-temperature in commensurate phase to a new, more densely packed, phase upon cooling below 65 K. For both phases the strongly dispersive longitudinal phonon mode could be detected. A lattice-dynamical analysis yields a substrate mediated softening of the Xe–Xe radial force constant down to 25% of that obtained from gas-phase potentials and a fit of Xe bulk phonon data. This decrease is much larger than assumed in previous work for noble gas atoms adsorbed on metals. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473242
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  • 10
    Electronic Resource
    Electronic Resource
    The transition from single phonon to multiphonon energy transfer in atom–surface collisions (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1234-1247 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The angular distributions and time-of-flight spectra of nearly monoenergetic He atoms with incident energies of 82 meV and 112 meV have been measured after scattering from a clean Cu(001) surface over a large range of crystal temperatures from 100 K to 1000 K. With increasing temperatures the sharp diffraction and phonon peaks of the low temperature quantum regime become broad and featureless as expected for the multiphonon classical regime. The results are compared with a quantum mechanical theory which is able to explain the height, position, width, and area under the multiphonon maximum. In the classical regime, the temperature dependence of the inelastic intensity indicates that the He atoms are reflected by a smooth vibrating barrier presumably due to the surface electron density, and not by a lattice of discrete repulsive surface atomic cores. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473220
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