Search Results - (Author, Cooperation:W. Hartmann)

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  1. 1
    Staff View
    Publication Date:
    2018-01-23
    Publisher:
    American Chemical Society (ACS)
    Print ISSN:
    0002-7863
    Electronic ISSN:
    1520-5126
    Topics:
    Chemistry and Pharmacology
    Published by:
    http://www.acs.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2018-11-28
    Publisher:
    American Chemical Society (ACS)
    Topics:
    Chemistry and Pharmacology
    Published by:
    http://www.acs.org/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Staff View
    Publication Date:
    2014-09-23
    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
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  4. 4
    Hartmann, W. [Verfasser]

    Published 1997
    Staff View
    Type of Medium:
    article
    Publication Date:
    1997
    Keywords:
    Extremwert (Math) ; Grafischer Taschenrechner ; Lösungsalgorithmus ; Lösungsstrategie ; Numerische Mathematik ; Quadratische Funktion
    In:
    Praxis der Mathematik, Bd. 39 (1997) H. 2, S. 79-84, 0032-7042
    Language:
    German

    FIS Bildung Literaturdatenbank
  5. 5
    Staff View
    Type of Medium:
    article
    Publication Date:
    1997
    Keywords:
    Sekundarstufe I ; Sekundarstufe II ; Gymnasium ; Textlernen ; Curriculum ; Unterrichtsmethode ; Programmierung ; Selbstinstruierendes Material ; Rekursion ; Angewandte Mathematik ; Kaufmännisches Rechnen ; Lineare Gleichung ; Mathematikunterricht ; Quadratische Gleichung ; Zinsrechnung ; Lehrgang ; Selbststudium
    In:
    Zentralblatt für Didaktik der Mathematik, Bd. 29 (1997) H. 6, S. 199-206, 0044-4103
    1615-679X
    Language:
    German

    FIS Bildung Literaturdatenbank
  6. 6
    Staff View
    Type of Medium:
    article
    Publication Date:
    1996
    Keywords:
    Bildungsplanung ; Berufsmaturität ; Basel ; Kanton ; Schweiz
    In:
    Basler Schulblatt, (1996) H. 3, S. 21-22, 0258-9869
    Language:
    German

    FIS Bildung Literaturdatenbank
  7. 7
    Felsner, P. ; Stetter, M. ; Hartmann, W. ; Linsenmeyer, A. ; Christiansen, J. ; Frank, K.

    [S.l.] : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The cathode phenomena during the conduction phase of a pseudospark discharge are investigated with different cathode materials: Cu, Mo, Ni, Ta, and W/Re. The discharge gas was hydrogen with a gas pressure of 40 Pa. At a pulse duration of 2.7 μs and a maximum current of 9 kA, i.e., at a transferred charge of 11 mC/discharge, mass erosion rates of the cathode materials showed no significant material dependence after 106 discharges. Fast framing photography (end-on, exposure time: 5 ns) of the light emission from the cathode surface revealed several small spots simultaneously, distributed over a cathode surface of 1 cm2. The distribution of metal and hydrogen spectral lines at the cathode surface and in the gap were compared. Metal lines are localized on the cathode surface, whereas the hydrogen Balmer β-line is diffuse over the electrodes surfaces and the gap. Polished electrodes showed, after a single pulse, about 107 craters with 0.5–5 μm in diameter. This is leading to a local current density of about 108 A/cm2 in a single crater.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.357071

    Articles: DFG German National Licenses
  8. 8
    Hartmann, W. ; Bauer, H. ; Christiansen, J. ; Frank, K. ; Kuhn, H. ; Stetter, M. ; Tkotz, R. ; Wagner, T.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A plasma source suitable for repetitive operation, going beyond single shot experiments for research into soft x-ray lasers, is reported. Successful operation of an ultrafast, small-diameter, highly uniform z pinch has been achieved at currents of 35–50 kA, for a variety of gases and a large range of mass densities. Due to an efficient preionization of the working gas, a high-temperature and a high cooling rate of the plasma column are obtained. The plasma is less than 1 mm in radius, over 30 mm long, and over 1018 cm−3 ion density. A soft x-ray recombination laser experiment for the λ≈182 A(ring) Balmer-alpha-like transition in C vi is proposed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.104812

    Articles: DFG German National Licenses
  9. 9
    Hartmann, W. ; Kirkman, G. F. ; Gundersen, M. A.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A study of current quenching in the pseudospark is presented. Current quenching during the conductive phase limits peak conduction current in certain thyratron switches. The quenching phenomenon also occurs in the pseudospark. However, a remarkable feature is that current quenching is observed only below currents of ≈ 2–3 kA, near the onset of superemissive behavior, and thus in the pseudospark is not an upper limit to high current operation. A mechanism involving an instability caused by ion depletion at the plasma boundary is discussed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.104591

    Articles: DFG German National Licenses
  10. 10
    Hartmann, W. ; Dominic, V. ; Kirkman, G. F. ; Gundersen, M. A.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1988
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    This letter presents evidence for large-area (≈1 cm2) cathode superemission (∼10 000 A/cm2) into a high-current glow discharge in a pseudospark or back lighted thyratron switch. Cathodes studied with a scannning electron microscope following operation at 6–8 kA, ≈1 μs pulse length, and 105 pulses in a low-pressure H2 discharge show evidence of melting of a thin surface layer within a radius of ∼4 mm, indicating that the discharge is a superdense glow with a cross-sectional area of the order of 1 cm2, rather than an arc. Further supporting evidence is provided by streak camera data. An ion beam present during the avalanche phase of the discharge is responsible for heating the cathode surface resulting in a significant field-enhanced thermionic emission.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.100395

    Articles: DFG German National Licenses
  11. 11
    Hartmann, W. J. A. M. ; Luyckx-Smolders, A. M. M. ; Kessel, R. P. v.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The influence of the crystallinity of the alignment layers on the electro-optical behavior of ferroelectric liquid crystals has been quantitatively demonstrated. The degree of crystallization of thin nylon 6.6 alignment layers was varied using thermal anneal methods and determined by Fourier transform infrared spectroscopy. The reaction of an obtained memory state of surface-stabilized ferroelectric liquid-crystal samples to small disturbing electric fields decreased when the degree of crystallization of the incorporated nylon 6.6 alignment layers was higher.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101652

    Articles: DFG German National Licenses
  12. 12
    Kirkman, G. ; Hartmann, W. ; Gundersen, M. A.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1988
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Extremely high cold cathode emission and a plasma current density that is much higher than commercial glow discharge hot cathode switches have been obtained in a flash-triggered hollow cathode thyratron-type switch that operates in a glow mode. The cold cathode emission is higher by several orders of magnitude than emission from thermionic cathodes in high-power hydrogen thyratrons, without arc formation. Peak current 〉17 kA, dI/dt〉3×1011 A/s, and power gain 〉1400 are observed. The switch has been successfully operated as a thyratron substitute in a commercial XeCl excimer laser. The work demonstrates a new approach to thyratron-type switches, and a wide range of technologically useful physical processes that are poorly understood.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.99381

    Articles: DFG German National Licenses
  13. 13
    Hartmann, W. ; Dominic, V. ; Kirkman, G. F. ; Gundersen, M. A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    An analysis of the anomalously large cathode emission recently observed in the superdense glow of pseudospark and back-lighted thyratrons is presented. These switches are low-pressure (27 Pa H2) glow-discharge pulsed-power devices. After operating at peak discharge currents of 6–8 kA and pulse durations of 0.5–1 μs, the surface surrounding the cathode hole was found to have been homogeneously melted within a radius of ≈4 mm indicating that the discharge is a superdense glow discharge, not an arc, with a cross-sectional area on the order of 1 cm2. This conclusion is also supported by streak camera measurements. The current density at the cathode surface under these conditions is 5–10 kA/cm2, several orders of magnitude larger than that of thermionic cathodes in common thyratrons. This high-current density is explained by intense cathode heating from a high-current density ion "beam'' produced in the cathode fall during the initial stage of current buildup. The surface heating resulting from this "beam'' yields a significant field-enhanced thermionic emission of electrons.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.343430

    Articles: DFG German National Licenses
  14. 14
    van de Ven, J. ; Hartmann, W. J. A. M. ; Giling, L. J.

    [S.l.] : American Institute of Physics (AIP)
    Published 1986
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Photoluminescence studies have been performed on undoped and silicon-doped GaAs crystals, which were annealed between 650 and 1000 °C under different arsenic pressures. Samples were also heat treated with the addition of pure elemental Ga, Mn, or Cu. Spectra were taken in the energy range 1.15–1.55 eV at the surfaces of the annealed crystals and at various depths below the surface. Newly observed zero-phonon emissions at 1.31 and 1.347 eV are concluded to be related to CuGa-(VAs)2 and CuGa-VAs, respectively. An emission at 1.467 eV also was found to be related to a CuGa-containing complex. A new emission at 1.342 eV was found to be related to a fast diffusing MnGa-containing complex. Most likely, the emission originates from a MnAs center. The nature of these defects is discussed on the basis of their emission characteristics, diffusion behavior, and dependence on annealing parameters. Through this study it appeared that arsenic vacancies play a crucial role both in the establishment of defect equilibria and in the formation of complexes with MnGa and CuGa. A new luminescence peak at 1.448 eV was found to be related to the VAs defect. Most probably, it has to be associated with the GaAs antisite. The presence of arsenic vacancies also induces a shift of the 1.492-eV emission to 1.484 eV. This shift is attributed to the replacement of CAs by SiAs acceptors. Some evidence was found that a peak at 1.38 eV is associated with VGa. It is concluded that solid-state equilibrium of native defects and impurities is only established at the surfaces but not in the bulk of the crystal during the heat treatments.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.337584

    Articles: DFG German National Licenses
  15. 15
    Kluge, H. ; Hartmann, W. ; Wieczorek, V. ; Zahlten, W.

    Oxford, UK : Blackwell Publishing Ltd
    Published 1972
    Staff View
    ISSN:
    1471-4159
    Source:
    Blackwell Publishing Journal Backfiles 1879-2005
    Topics:
    Medicine
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1111/j.1471-4159.1972.tb01468.x

    Articles: DFG German National Licenses
  16. 16
    Hartmann, W. J. A. M.

    [S.l.] : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    An important characteristic of the surface-stabilized ferroelectric liquid-crystal (SSFLC) effect is charge compensation. Investigations on SSFLC samples, which were electrically isolated after applying a voltage, showed that this voltage drops during the switching as a result of the compensation of the surface polarization caused by the rotation of the permanent dipoles. The final optical state depends exclusively on the initial conditions. Optically it can be observed that domains come into being, grow and stabilize, resulting into a certain distribution of black and white areas. Consequently, the bistable SSFLC effect can be used for a controllable continuous grayshading between black and white.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.343453

    Articles: DFG German National Licenses
  17. 17
    Hartmann, W. J. A. M. ; Luyckx-Smolders, A. M. M.

    [S.l.] : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Low-frequency electric field treatment irreversibly changes the chevron structure of a surface-stabilized ferroelectric liquid-crystal sample: the angle between the smectic layers and the surface normal decreases. As a result different textures appear, and a pronounced effect on the switching behavior is observed. The switching angle and the necessary pulse amplitudes at constant pulse width in order to obtain switching between both stable states have increased. The required reorientation voltages decrease with rising spontaneous polarization. This reorientation process is strongly influenced by the rubbing treatment of the alignment layer. The anchoring properties of the alignment layer seem to be directly responsible for the appearance of defects, for the initial switching angle, for the electric field strength necessary to reorient the chevron structure, and for the pulse amplitudes required to switch between both stable states.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.345700

    Articles: DFG German National Licenses
  18. 18
    PRATT, K. C. ; HARTMANN, W. E. ; MEAD, J. L.

    Provincetown, Mass., etc. : Periodicals Archive Online (PAO)
    Published 1954
    Staff View
    ISSN:
    0022-1325
    Topics:
    Psychology
    URL:
    http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:3284-1954-084-00-000003

    Articles: DFG German National Licenses
  19. 19
    Hartmann, W. ; Galla, H.-J. ; Sackmann, E.

    Amsterdam : Elsevier
    Staff View
    ISSN:
    0005-2736
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1016/0005-2736(78)90135-9

    Articles: DFG German National Licenses
  20. 20
    Hartmann, W. ; Galla, H.-J.

    Amsterdam : Elsevier
    Staff View
    ISSN:
    0005-2736
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://linkinghub.elsevier.com/retrieve/pii/0005-2736(78)90241-9

    Articles: DFG German National Licenses