Search Results - (Author, Cooperation:F. Hofmann)

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  1. 1
    Staff View
    Publication Date:
    2016-02-26
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Cell Line, Tumor ; Cell Survival ; Cyclin-Dependent Kinase Inhibitor p16/genetics/*metabolism ; Deoxyadenosines/metabolism ; Gene Deletion ; Humans ; Methionine/*metabolism ; Neoplasms/drug therapy/genetics/*metabolism ; Protein-Arginine N-Methyltransferases/genetics/*metabolism ; Purine-Nucleoside Phosphorylase/genetics/*metabolism ; RNA, Small Interfering/genetics ; Thionucleosides/metabolism
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Holger F. Hofmann
    American Physical Society (APS)
    Published 2018
    Staff View
    Publication Date:
    2018-11-07
    Publisher:
    American Physical Society (APS)
    Print ISSN:
    1050-2947
    Electronic ISSN:
    1094-1622
    Topics:
    Physics
    Keywords:
    Fundamental concepts
    Published by:
    http://www.aps.org/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Masataka Iinuma, Masayuki Nakano, Holger F. Hofmann, and Yutaro Suzuki
    American Physical Society (APS)
    Published 2018
    Staff View
    Publication Date:
    2018-12-08
    Publisher:
    American Physical Society (APS)
    Print ISSN:
    1050-2947
    Electronic ISSN:
    1094-1622
    Topics:
    Physics
    Keywords:
    Fundamental concepts
    Published by:
    http://www.aps.org/

    Latest Papers from Table of Contents or Articles in Press
  4. 4
    Staff View
    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

    Articles: DFG German National Licenses
  5. 5
    Staff View
    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

    Articles: DFG German National Licenses
  6. 6
    Weber, W. ; Brox, M. ; Hofmann, F. ; Huber, H. ; Jäger, D. ; Rieger, D.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Hole-trap states in the gate oxide of a Si metal-oxide-semiconductor field-effect transistor (MOSFET) are investigated by inhomogeneous excimer laser irradiation. Subbandgap ultraviolet light photons with an energy exceeding a threshold lying between 5.5 and 6.4 eV were found to excite electrons from these originally neutral states into the SiO2 conduction band. A fixed positive charge is left behind. The degradation in MOSFET performance due to the irradiation is comparable to that accompanying hot-hole injection. Also, subsequent hot-electron stress changes the device characteristics in a way similar to hot-electron stress following hot-hole stress. It is concluded that the traps responsible for hot-carrier degradation cause the optically induced charge trapping.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101218

    Articles: DFG German National Licenses
  7. 7
    Hofmann, F. ; Krautschneider, W. H.

    [S.l.] : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The charge pumping method has been modified to simplify the experimental procedure and data evaluation. The width of a pulse section at midgap voltage was varied to scan the interface-state distribution within the band gap. A straight-forward analysis yields simple evaluation of interface-state distribution. The results obtained from a conventional and a submicron lightly doped drain metal-oxide-semiconductor transistor are presented.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.343034

    Articles: DFG German National Licenses
  8. 8
    Ahnert-Hilger, G. ; Höltje, M. ; Große, G. ; Pickert, G. ; Mucke, C. ; Nixdorf-Bergweiler, B. ; Boquet, P. ; Hofmann, F. ; Just, I.

    Oxford, UK : Blackwell Science Ltd
    Published 2004
    Staff View
    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

    Articles: DFG German National Licenses
  9. 9
    Moret, J.-M. ; Buhlmann, F. ; Fasel, D. ; Hofmann, F. ; Tonetti, G.

    [S.l.] : American Institute of Physics (AIP)
    Published 1998
    Staff View
    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

    Articles: DFG German National Licenses
  10. 10
    RÖHRKASTEN, A. ; NASTAINCZYK, W. ; MEYER, H. E. ; SIEBER, M. ; SCHNEIDER, T. ; REGULLA, ST. ; HOFMANN, F.

    Oxford, UK : Blackwell Publishing Ltd
    Published 1989
    Staff View
    ISSN:
    1749-6632
    Source:
    Blackwell Publishing Journal Backfiles 1879-2005
    Topics:
    Natural Sciences in General
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1111/j.1749-6632.1989.tb24119.x

    Articles: DFG German National Licenses
  11. 11
    Collins, G. A. ; Hofmann, F. ; Joye, B. ; Keller, R. ; Lietti, A. ; Lister, J. B. ; Pochelon, A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1986
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The detailed experimental data obtained on the TCA tokamak [Proceedings of the 11th Symposium on Fusion Technology (CEC, Luxembourg, 1981), Vol. I, p. 601] concerning the antenna loading and wave fields as a function of the Alfvén wave spectrum are presented. The plasma density, plasma current, working gas, toroidal magnetic field, and frequency were varied systematically and the detailed results are compiled and discussed. In addition the phasing of the antenna currents was varied systematically, thereby exciting different combinations of modes, including pure traveling waves. The conclusions relevant to the design of an antenna system have been stressed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.865563

    Articles: DFG German National Licenses
  12. 12
    Hofmann, F. ; Toennies, J. P. ; Manson, J. R.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    We present new measurements of inelastic He atom scattering from the surface phonons of Cu(001) as a function of crystal temperature, incident energy, and parallel momentum transfer. A careful subtraction of the multiphonon intensity and other background contributions from the time-of-flight intensities reveals three distinct surface-localized vibrational modes which are ascribed to the Rayleigh phonon, the longitudinal bulk resonance, and a further acoustic bulk resonance at higher energy transfers. The longitudinal resonance couples very strongly to the scattering He atoms and, for a wide range of incident conditions, gives peaks which are more intense than those due to the Rayleigh mode. The energy and momentum dependence of these peak intensities are analyzed with the aid of a simple distorted wave Born approximation, and the different coupling parameters for the two modes are determined and compared with other available data. The incoherent diffuse elastic peak is shown to decrease as a function of parallel momentum transfer according to the theory of Fraunhofer scattering from a random array of point defects. The multiphonon background is shown to be in agreement with a quick scattering approximation. © 1994 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.468005

    Articles: DFG German National Licenses
  13. 13
    Graham, A. P. ; Hofmann, F. ; Toennies, J. P. ; Manson, J. R.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1996
    Staff View
    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

    Articles: DFG German National Licenses
  14. 14
    Bertino, M. F. ; Hofmann, F. ; Steinhögl, W. ; Toennies, J. P.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1996
    Staff View
    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

    Articles: DFG German National Licenses
  15. 15
    Graham, A. P. ; Bertino, M. F. ; Hofmann, F. ; Silvestri, W. ; Toennies, J. P.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1997
    Staff View
    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

    Articles: DFG German National Licenses
  16. 16
    Graham, A. P. ; Bertino, M. F. ; Hofmann, F. ; Toennies, J. P. ; Wöll, Ch.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1997
    Staff View
    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

    Articles: DFG German National Licenses
  17. 17
    Hofmann, F. ; Toennies, J. P.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1997
    Staff View
    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

    Articles: DFG German National Licenses
  18. 18
    Hofmann, F. ; Hänsch, W.

    [S.l.] : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We calculate the charge pumping current of a metal-oxide-semiconductor transistor in the time domain utilizing a transient two-dimensional device simulation. The dynamics of the interface states are included in the solution of the time-dependent problem with full self-consistency. The calculated charge pumping curve is in good agreement with the experiment, especially the rise and fall patterns of the signal, which are very sensitive to the source/drain profiles in small devices. The extraction of the density of states shows the range of validity of the analytical models and their restrictions. The influence of hot-carrier stress on the charge pumping signal, which relates to inhomogeneous spatial distribution of interface states and fixed oxide charges, is also discussed in experiment and simulation.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.344166

    Articles: DFG German National Licenses
  19. 19
    Graham, A. P. ; Bertino, M. F. ; Hofmann, F. ; Toennies, J. P. ; Wöll, Ch.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1997
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.474806

    Articles: DFG German National Licenses
  20. 20
    Hunton, D. E. ; Hofmann@f @f, M. ; Lindeman, T. G. ; Albertoni, C. R. ; Castleman, A. W.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1985
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Energy resolved photodissociation studies of CO3−⋅(H2O)n, n=1,2,3 are reported for photon energies ranging from 1.95 to 2.2 eV. The only dissociation channel observed is the loss of all attached water molecules to give unclustered CO3− as the sole photofragment ion. The cross section for this mechanism is substantially higher than that for the bare ion, and the sharp structure observed in the spectrum of the bare ion is nearly lost in the clusters. Analysis of the kinetic energy distributions for the photofragment ions places an upper limit of 20 μs on the lifetime of the excited clusters, and demonstrates that approximately 95% of the excess energy in the cluster remains in the CO3− containing fragment rather than being partitioned into relative translation of the photofragments or into internal motion of the water fragments. The dissociation mechanism begins with a bound–bound 2A1←2B1 transition within the core CO3− ion. Internal conversion returns the core ion to the electronic ground state with substantial vibrational excitation; redistribution of this vibrational energy results in vibrational predissociation of the cluster. The relations of this mechanism to those that occur in the bare ion and to other vibrational predissociation experiments on clusters are discussed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.448236

    Articles: DFG German National Licenses