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  • Articles  (59)
  • Springer  (51)
  • American Institute of Physics (AIP)  (5)
  • Institute of Physics  (3)
  • 1985-1989  (59)
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  • Articles  (59)
Year
Journal
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3933-3933 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Most of the metallic rare-earth chalcogenides of RE3X4 type, where X stands for S, Se, Te, show marked elastic anomalies which appear either in conjunction with a structural transformation or with a magnetic ordering transition. In this contribution we report on results obtained from Nd3Se4 where the elastic constants display a particular magnetic field dependence. Single crystals were grown by a Bridgman–Stockbarger method and the three cubic elastic constants were measured by ultrasonic techniques as function of temperature and in an external magnetic field. The occurrence of magnetic ordering was proved independently by susceptibility measurements. Nd3Se4 has been found to order ferromagnetically at Tc =52 K. In the absence of an external magnetic field approaching Tc from above, the shear elastic constants (C11−C12)/2 softens by about 40%. Below Tc the elastic constants harden again where the increment of C11 follows the Brillouin function of the magnetization. An external magnetic field parallel to the propagation direction of the sound waves affects the elastic anomalies in the paramagnetic as well as in the ferromagnetic phase. Above Tc the sound velocities exhibit a H2 field dependence, as is expected from a magnetoelastic coupling mechanism. At temperatures smaller Tc the field-dependent elastic anomalies are related to the hysteresis loop M(H). The change of the elastic constants as a function of the magnetic field is proportional to the field derivative dM/dH. The coupling coefficient has an opposite sign for the C44 and (C11−C12)/2 shear elastic constants.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1265-1268 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The HP 4274A and HP 4275A LCR meters are widely used in the fields of semiconductor device characterization and component test. A bias voltage can be applied to the test samples either from an external power supply or from the built-in HP-IB controllable voltage source. The total series resistance of the bias filtering circuit should be in the range of about 100 Ω (HP 4275A). Detailed measurements and checking the measuring circuit diagrams revealed that the effective series resistance can be much higher, depending on the measuring range of the bridge. Therefore, admittance measurements on low-ohmic samples, especially Schottky or pn junctions under heavy forward bias conditions, are seriously affected by bias voltage reduction between the front HI/LOW terminals. Thus, e.g., a reduced apparent capacitance is measured. Consequently, the doping concentration near the pn junction will be determined erroneously. To avoid these effects, a bias regulating circuit is inserted into the LCR meters to guarantee the feedthrough of the bias voltage without any attenuation. Examples of admittance vs frequency and doping profiles near the pn junction of quaternary (Ga0.046In0.954As0.1P0.9) diodes are given for explanation.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 3134-3135 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ultrahigh vacuum sample mount for insulators which allows both good thermal conduction to the mount and accurate temperature measurement is described: good thermal connection between sample and mount is made with an indium layer. By melting an edge of the sample a thermocouple can be inserted directly into the crystal for accurate temperature measurement.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 869-872 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Ag7 metal cluster was formed in a solid neon matrix at 4 K. The identity of the cluster was established via X-band electron-spin-resonance (ESR) spectroscopy, and its structure was found to be a pentagonal bipyramid (D5h symmetry) with a 2A‘2 ground state. Thus its properties are completely analogous to its Group IA alkali-metal counterparts.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 738-744 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser irradiation at 193 nm of multilayer of CH3Br physisorbed on LiF at 30 K leads to both photofragmentation and photodesorption of molecules. One-photon photofragmentation was observed leading to broad velocity distributions for ejected CH3 and Br. Fragments as fast as those found in gas-phase photofragmentation were seen as well as collisionally slowed fragments. High energy (2 eV, four times the gas-phase kinetic energy) Br fragments were also observed due to collisions with rebounding CH3. Collisionally ejected molecules were also seen. A small fraction of molecules desorbed via a thermal process, associated perhaps with small amounts of adsorbed particulate contaminants. This mechanism may be responsible for some of the molecular desorption seen by other groups. Thermal desorption studies show that CH3Br (or CO2, Xe, or H2O) does not wet LiF, indicating a general trend important to all alkali–halide overlayer studies.
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  • 6
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the measurements of the spin correlation parameterA ookk (np). A longitudinally polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the longitudinally polarized Saclay frozen-spin proton target. Measurements were carried out at SATURNE II, at neutron beam kinetic energies of 0.63, 0.88, 0.98 and 1.08 GeV. The data points cover the angular region from about 40° to 110° CM. The observed angular dependence ofA ookk (np) at 0.63 GeV agree with the phase shift analysis predictions except at small angles.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 68 (1986), S. 580-584 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of host plant patch size on the abundances of two specialist herbivores (the chrysomelid beetle, Acalymma innubum and the pentatomid bug, Piezosternum subulatum) were investigated in a natural forest community in the Virgin Islands. Abundances were compared early and late in the season in different sized patches of the cucurbit host plant (Cayaponia americana) growing in open habitat (with no surrounding plant community) and forest habitat (with diverse surrounding plant community). For both herbivore species, adult abundances per patch were positively correlated with patch leaf area, but there was a significant patch size effect (i.e., correlation between herbivore density per unit plant and patch leaf area) only for beetles in the forest habitat. Both herbivore species were significantly affected by surrounding plant diversity, but in opposite ways: beetles were more abundant in open patches whereas bugs were more abundant in forest patches. Relationships between abundance and patch size in open and forest patches changed through the season for both herbivore species. These changing abundance patterns are discussed with respect to (1) increases in the diversity of the plant community surrounding host plant patches, and (2) differences in herbivore movement patterns.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archive for history of exact sciences 40 (1989), S. 173-206 
    ISSN: 1432-0657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Natural Sciences in General
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 12 (1987), S. 527-534 
    ISSN: 1432-0983
    Keywords: Fission yeast ; OMPdecase ; Cloning ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary URA4, the gene coding for orotidine monophosphate decarboxylase (OMPdecase), has been cloned from the fission yeast by homologous complementation and restricted in an Escherichia coli-Schizosaccharomyces pombe (E. coli-S. pombe) replicative plasmid to a 1.76 kb HindIII fragment. This plasmid is maintained at a high copy number in S. pombe and allows OMPdecase expression in Saccharomyces cerevisiae (S. cerevisiae) as well as in E. coli. After characterisation by restriction mapping and Southern hybridisation, the cloned gene was used as a probe to measure URA4 transcription and to examine its regulation. Messenger RNA levels were measured by DNA/RNA filter-hybridisation with pulse labelled RNAs during 6-azauridine (6-AUR) inhibited growth in wild type and 6-AUR sensitive strains. We found that in S. pombe the OMP analogue 6-AUR does not regulate the level of OMPdecase formation as it does in S. cerevisiae but rather modifies the ratio of total polyA+ to polyA− RNAs in the cell. Based on these results and on corresponding enzyme activities this study demonstrates divergent pyrimidine pathway regulation in the two yeasts S. cerevisiae and S. pombe. Finally, we propose the use of the URA4 gene as a convenient selective marker for genetic engineering in S. pombe.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 35 (1985), S. 323-339 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Zur Abschätzung einer möglichen Klimaänderung als Folge einer Verdopplung der CO2-Konzentration in der Atmosphäre dienen die Ergebnisse von Studien mit drei-dimensionalen Modellen der atmosphärischen Zirkulation. Diese Ergebnisse können nicht als Klimavorhersagen betrachtet werden, da die gegenwärtigen Modelle noch erhebliche Mängel aufweisen. Sie bilden jedoch die Grundlage zur Entwicklung von Klimaszenarien. Klimamodelle sind gegenwärtig die einzigen Hilfsmittel, um die Reaktion des Klimasystems auf eine externe Störung in physikalisch konsistenter Weise und in hoher zeitlicher und räumlicher Auflösung zu simulieren. Für den Mittelmeerraum werden die Ergebnisse dreier verschiedener Klimamodelle (British Meteorological Office (BMO); Goddard Institute for Space Studies (GISS); National Center for Atmospheric Research (NCAR)) anhand der regionalen und saisonalen Verteilungen von Temperatur, Niederschlag und Bodenfeuchte vorgestellt. Die durch einen CO2-Anstieg verursachte Änderung der Temperaturverteilung ist bei den drei Modellergebnissen ähnlich. Die räumlichen Mittelwerte liegen zwischen 2,5 und 4,0 K. Der Vergleich der Verteilung hydrologischer Größen ergibt dagegen kein einheitliches Bild. Die den simulierten Klimaänderungen zugrunde liegenden physikalischen Mechanismen werden benannt und die statistische Signifikanz der Klimaänderung wird getestet. Diese Arbeit dient zur Entwicklung einer Methodologie für den Einsatz von Klimamodellszenarien bei der Impaktanalyse.
    Notes: Summary For the estimation of a potential climatic change induced by a doubling of atmospheric CO2 we use the results of three-dimensional general circulation models (GCM). Although the results from present climate modeling cannot be considered as predictions of future climatic conditions due to the inherent models' deficiencies, they can still serve a useful purpose in climate change scenarios. The reason for this is that climate models are the only tools available to study the response of the climate system to a perturbation in a physically consistent manner and that such types of models can provide a consistent data set of high temporal and spatial resolution. For the Mediterranean area, the results obtained from three different GCMs, namely, the British Meteorological Office model (BMO), the Goddard Institute for Space Studies model (GISS), and the National Center for Atmospheric Research model (NCAR) are shown. The regional and seasonal distributions of temperature, precipitation, and soil moisture are used to study the potential changes. The results indicate that the CO2-induced changes for temperature generated by the three models are of similar magnitude. The values of the area mean change range between 2.5 and 4.0 K. The precipitation response results in a diverse pattern. The physical mechanism likely to be responsible for the simulated climatic changes are identified and their statistical significance is tested. This type of work will help us develop the methodology and assist us in gaining insight into the use of climate model scenarios for impact analysis.
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