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  • 1
    Electronic Resource
    Electronic Resource
    Calculations on the Jahn–Teller configurations of the benzene cation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10550-10554 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The analysis of the zero-electron-kinetic-energy photoelectron spectra of benzene has led to a reinvestigation by ab initio methods of the electronic states of the C6H6+ cation resulting from Jahn–Teller distortions on ionization. The calculations involving a range of currently used methodologies all verify that the two cation configurations, 2B2g and 2B3g of D2h symmetry, resulting from removal of an electron from the e1g(π) degenerate MOs of C6H6, comprise a true minimum and a transition state, differing only slightly in energy. These are linked through the in-plane b1g vibration, confirming that b1g is actually a pseudorotational coordinate. Hence C6H6+ exhibits similar structural floppiness to the cations of methane and cyclopropane although with a much smaller barrier to pseudorotation than for these smaller species. These results support the general proposition that such Jahn–Teller distortions associated with molecular ionization (of stable closed-shell hydrocarbon molecules of high symmetry) generally involve a quadratic contribution which leads to a single global minimum cation structure, with all other derived stationary states being transition states each characterized by a single imaginary vibration frequency. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480407
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  • 2
    Electronic Resource
    Electronic Resource
    Theory of proton relaxation induced by superparamagnetic particles (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5403-5411 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Evaluating and understanding the performances of magnetic colloids as contrast agents for MRI requires a theory describing their magnetic interactions with water protons. The field dependence of the proton longitudinal relaxation rate (nuclear magnetic relaxation dispersion profiles) in aqueous colloidal suspensions of superparamagnetic particles is based on the so-called Curie relaxation, which essentially accounts for the high field part of the NMRD profiles (B0〉0.02 T). The low-field part of the NMRD profiles can only be explained by the crystal's internal anisotropy energy, a concept which clarifies the important difference between superpara- and paramagnetic compounds: the anisotropy energy modifies both the electronic precession frequencies and the thermodynamic probability of occupation of the crystal magnetic states. Our theory clearly explains why a low-field dispersion exists for suspensions of small size crystals, and why it does not for large crystals' suspensions. This important effect is due to the Boltzmann factors depending on the anisotropy energy, which is itself proportional to the particle volume. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478435
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  • 3
    Electronic Resource
    Electronic Resource
    Enthusiastic Embrace or Critical Reception? The German HRM Debate (1999)
    Oxford, UK and Boston, USA : Blackwell Publishers Ltd
    Journal of management studies 36 (1999), S. 0 
    Details
    ISSN: 1467-6486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: This paper discusses the reception of human resource management (HRM) in Germany. A review of the German HRM debate shows that this is dominated by business administration academics specializing in this field. In the past, these scholars as well as practitioners have generally embraced the techniques as well as the ideology of HRM. This finding can be explained by a relatively low emphasis on empirical research, a neglect of industrial relations issues, and a strong impact of theories and concepts developed in the USA. Today, however, there appears to be a change towards a more critical appreciation of the US HRM model and a more positive assessment of the German HRM model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1467-6486.00145
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  • 4
    Electronic Resource
    Electronic Resource
    Study of nonlinear dibit interactions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4705-4707 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate isolated dibit interactions by varying the intradibit spacing and observing position fluctuations using a magnetic force microscope. We see that the measured dibit spacing deviates at a recording density that depends on the remanence–thickness product Mrδ of the medium. The increased dibit separation may be partially due to the demagnetization fields during write: we find that partial erasure annihilates the narrower crosstrack parts of the dibit, effectively inducing an increase in dibit separation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370454
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  • 5
    Electronic Resource
    Electronic Resource
    Spin-stand measurements of time and temperature dependence of magnetic recordings (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4994-4996 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin-stand experiments were performed to study the effect of temperature and demagnetizing fields on the stability of magnetic recordings. Tracks of varying linear bit densities were written on a low Mrδ medium that was heated in situ to different temperatures. The readback amplitude, which reflects the changes in the magnetization of the recordings, was observed from 32 ms to 12 h after the tracks were written. The readback amplitude was found to decay with time. The rate of decay increased at higher densities due to higher demagnetizing fields. A further increase in the decay rate was observed at higher temperatures. This increase in decay rate exceeded that predicted by proportional temperature scaling. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370069
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  • 6
    Electronic Resource
    Electronic Resource
    Mesoscopic composition fluctuations in semiconductor alloys: Effect on infrared devices (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2343-2345 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semiconductor alloys like Hg1−xCdxTe and Al1−xGaxAs, where there is a close lattice constant match between the constituents, are nearly random. Consider mesoscopic size scales of radius r that are large compared with a lattice constant (∼25 A〈r〈∼250 A), but small compared with typical device dimensions. In such regions the number of substitutional sites is small enough so the root-mean-square concentration fluctuation 〈(Δx)2〉1/2 is sufficiently large to produce random arrays of mesoscopic "quantum dots" that adversely affect many device properties. The influence of the adverse effects differ among various properties—for example, electron and hole mobilities, lifetimes, and so on—but, in general, are worse the smaller the fundamental gap becomes. These kinds of fluctuations are suppressed in lattice-mismatched alloys like Hg1−xZnxTe and Ga1−xInxAs because there is a long-range strain energy penalty associated with them. Thus, lattice-mismatched alloys are more spatially uniform than lattice-matched alloys. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123845
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  • 7
    Electronic Resource
    Electronic Resource
    Activity-Dependent Phosphorylation of SNAP-25 in Hippocampal Organotypic Cultures (1999)
    Oxford UK : Blackwell Science Ltd
    Journal of neurochemistry 72 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Synaptosomal-associated protein of 25 kDa (SNAP-25) is thought to play a key role in vesicle exocytosis and in the control of transmitter release. However, the precise mechanisms of action as well as the regulation of SNAP-25 remain unclear. Here we show by immunoprecipitation that activation of protein kinase C (PKC) by phorbol esters results in an increase in SNAP-25 phosphorylation. In addition, immunochemical analysis of two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels shows that SNAP-25 focuses as three or four distinct spots in the expected range of molecular weight and isoelectric point. Changing the phosphorylation level of the protein by incubating the slices in the presence of either a PKC agonist (phorbol 12, 13-dibutyrate) or antagonist (chelerythrine) modified the distribution of SNAP-25 among these spots. Phorbol 12, 13-dibutryate increased the intensity of the spots with higher molecular weight and lower isoelectric point, whereas chelerythrine produced the opposite effect. This effect was specific for regulators of PKC, as agonists of other kinases did not produce similar changes. Induction of long-term potentiation, a property involved in learning mechanisms, and production of seizures with a GABAA receptor antagonist also increased the intensity of the spots with higher molecular weight and lower isoelectric point. This effect was prevented by the PKC inhibitor chelerythrine. We conclude that SNAP-25 can be phosphorylated in situ by PKC in an activity-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.721699.x
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  • 8
    Electronic Resource
    Electronic Resource
    Simultaneous analyses of chromosomes in root meristems and of the biochemical status of needle tissues of three different clones of Norway spruce trees challenged with moderate ozone levels (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Forest pathology 29 (1999), S. 0 
    Details
    ISSN: 1439-0329
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Biochemical effects of both low and high ozone impact in long-term and short-term experiments are well investigated and documented; however, short-term treatments with moderate ozone levels have revealed divergent information concerning the biochemistry of needle tissues. Damage to the meristems of spruce trees have been found for several ozone treatments, in the form of an enhanced number of chromosomal aberrations, which appeared to be persistent for up to 2 years after the ozone challenge. One of the main aims of the present study was to determine whether a moderate ozone concentration is able to induce damage in needle biochemistry and/or only in the genetic material of root meristems. In the experiment three different clones of Norway spruce trees (Picea abies) were challenged with moderate ozone concentrations (up to 80 nl/l) for 11 weeks in greenhouses. Simultaneous investigations of root tip meristematic cells and the biochemical status of needle tissues regarding antioxidants and pigments were performed at two different sampling times: directly after the ozone treatment and 1 year later. Ozone effects in needles were absent both at the end of the fumigation and also after 1 year, but different clonal behaviour was found. Effect of ozone on chromosomal aberration rates in root tip meristems were observed and also the types of persisting chromosomal aberrations changed within the time course and within the different clones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0329.1999.00156.x
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  • 9
    Electronic Resource
    Electronic Resource
    Human Resource Management under Institutional Constraints: The Case of Germany[I thank Da] (1999)
    Oxford, UK and Boston, USA : Blackwell Publishers Ltd
    British journal of management 10 (1999), S. 0 
    Details
    ISSN: 1467-8551
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: Most human resource management (HRM) research has been conducted in countries that have relatively weak labour market institutions such as the UK and the USA. There is little research about the scope for and constraints on the adoption of HRM practices in countries with strong statutory regulations. The research presented here is based on 16 case studies of banks and chemical firms operating in Germany, that comply with the requirements of the German labour market institutions of collective bargaining, co-determination and initial vocational training, and hence operate under strong institutional constraints. The evidence presented shows that institutional features of the German system encourage the implementation of some ingredients of the HRM ‘recipe’ and inhibit others. It also indicates that constraining influences notwithstanding, a pluralist version of HRM appears to be quite compatible with the highly regulated German context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1467-8551.10.s1.4
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  • 10
    Electronic Resource
    Electronic Resource
    Gliadins as biochemical markers for Aegilops turcomanica genes in wheat lines (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 118 (1999), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An Aegilops turcomanica-typical gliadin was discovered in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of ethanol-soluble seed proteins from wheat lines Tr. 476, 482 and 492, which had been derived from a direct cross of Ae. turcomanica and Triticum aestivum and which revealed powdery mildew resistance due to a putative Ae. turcomanica-introgression. This Ae. turcomanica-derived gliadin was tested for its suitability as biochemical marker. For this purpose, doubled-haploid lines were produced via anther culture from crosses of Tr. 482 and Tr. 492 with actual winter wheat cultivars and breeding lines. Until now, 173 lines with Ae. turcomanica-gene(s) have been selected from 297 doubled haploid wheat lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0523.1999.00392.x
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