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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Posttreatment with sodium arsenite in log phase synergistically increases the chromosomal aberrations induced by ethyl methanesulfonate in Chinese hamster ovary cells, human fibroblasts, and human lymphocytes. However, posttreatment with sodium arsenite in stationary phase has no apparent effect on the clastogenicity of ethyl methanesulfonate. These results indicate that the cycling state of the cell plays a crucial role in the action of arsenite coclastogenicity. One prediction from this finding is that in combined treatment, posttreatment with sodium arsenite should preferentially kill cancer cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: 78.70.Bj ; 79.90 ; 72.20.Ht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime spectroscopy measurements have been carried out for semi-insulating GaAs with applied electric fields in the samples directed towards, and away from the positron injecting contact. The lifetime spectra have been decomposed into two components, the longer of which (≈400 ps) is characteristic of open volume defects at the metal-semiconductor interface through which positrons are injected. The interesting feature of these experiments is the large increase in the intensity of this interface component as the field is directed towards the contact. We show that this increase is caused by a significant fraction of implanted positrons drifting under the influence of a strong electric field produced by a layer of space-charge formed adjacent to the positron injecting contact. The general trend of the intensity variation is well explained by the proposed model. Experiments involving the application of an ac bias to the samples strengthen the suggestion that the space charge region is largely formed from ionized EL2 donors. The results of the present work indicate that semi-insulating GaAs possesses properties that make it a suitable material for the fabrication of a high efficiency (≈10%) room-temperature field-assisted positron moderator. The extraction of positrons from the GaAs substrate into the vacuum through a thin metalization is discussed based upon available positron affinities for the GaAs and various elemental metals. These data suggest that a few monolayers of a strongly electronegative metal such as Au or Pd may allow vacuum emission through quantum tunneling.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract One method of determining the strains on the surface of a metal part is by the use of a birefringent coating. Because of the thickness of the coating, however, the observed fringe order depends not only on the surface strains but also on two other factors, namely, the curvature that the surface undergoes and the variation of strain acrose the thickness of the coating. These thickness effects have already been studied in a paper dealing with one dimensional variations in strain. In the present paper, the solution is extended to a two-dimensional deformation with radial symmetry. An experiment is described in which the surface strains produced by the impact of a bullet on a flat plate are determined from the birefringence of a surface coating taking into account the effects of strain gradients and curvature. The values of surface strain are compared with measurements made by means of a square grid inscribed on the metal surface. A procedure is suggested for determining an unknown surface strain having radial symmetry from the total birefringence of the surface coating when the change in curvature of the metal surface under load is known or can be determined separately.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of chlorotris(monomethylthiourea)silver(I) has been solved and refined by full-matrix least-squares methods to a finalR of 0·039 from 1150 reflections measured by counter techniques at ambient room temperature. The crystals are orthorhombic:Pmcn, a = 14·824(2),b = 8·524(1),c = 12·671(1) Å,Z = 4,D m = 1·68,D c = 1·72 gcm−3. The structure consists of independent, distorted tetrahedral Ag(I) moieties with only weak hydrogen bonds and/or van der Waals interactions between molecules. These molecules are packed in such a way that Ag, Cl and one entire monomethylthiourea ligand all lie in a crystallographic mirror plane, and the other two ligands are related by this mirror. This arrangement, plus the alternation of the Ag-Cl bond direction, leads to a non-polar sheet of Ag, Cl and monomethylthiourea groups with other monomethylthiourea groups protruding from either side of the sheet. Only N-H⋯Cl hydrogen bonds and van der Waals interactions exist between sheets. The Ag-S distance is somewhat long at 2·649(3) Å, as is one of the Ag-S distances at 2·665(3) Å. The other two Ag-S distances are 2·520(2) Å. The geometry of the complex makes it clear that the Ag-S bond is formed by donation of an electron pair from a sulfur sp2 orbital.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-8145
    Keywords: Enterprise resources planning ; IDEF ; object-oriented methodoloy ; hierarchical design pyramid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Today, manufacturers are measured by their ability to respond quickly to sudden, often unpredictable changes in customer needs and wants. Competition beyond the twenty-first century places an increased emphasis upon receiving business information that is accurate and up to date. In order to achieve this, a business planning and closed-loop manufacturing execution system must reflect how work is done, in order to support the overall business objectives without being limited by any hardware, software and human resource constraints. Enterprise resources planning (ERP) is considered to be the most effective computer application in the modern manufacturing industry which meets these requirements. However, only a few manufacturers can design and implement the system successfully. They encounter various problems during the design and implementation cycle. One of the major reasons why they cannot implement the system successfully is the inappropriate use of design and implementation methodology. A systematic design and implementation methodology is therefore proposed for ERP. Called the hierarchical design pyramid (HDP), it encompasses recent research on the ICAM definition method (IDEF) and the object-oriented methodology (OOM) as well as an architecture for any manufacturers who seriously consider ERP implementation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 1 (1961), S. 109-112 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The cathodic polarization characteristics of CuO and YBa2Cu3O7-δ electrodes were studied in the temperature range 600 to 800°C and at oxygen partial pressures ranging from 10−4 to 0.21 atm. The activity of oxygen reduction on a CuO electrode is closely related to the electronic conductivity and the oxygen ion vacancy density in the surface layer of the electrode. The oxygen ion vacancies created in CuO by doping with Li and the modification of the electronic conductivity by adding Ag provide a new way of enhancing the activity of an oxide electrode for oxygen reduction. It is demonstrated that the rate limiting steps for oxygen reduction at high overpotential and low overpotential are oxygen adsorption and charge transfer on CuO, respectively.
    Type of Medium: Electronic Resource
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