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  • 1
    ISSN: 1434-6079
    Keywords: 52.40.Mj ; 41.80.Gg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Focusing of a heavy ion beam by the azimuthal magnetic field of a z-pinch discharge was observed. The experiment was carried out with a device, which has been designed to generate controlled plasma states for the investigation of the interaction of heavy ion beams with hot matter. A focusing factor of 5 in beam diameter was detected with high speed photographic methods. The experimental results are in agreement with numerical calculations.
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  • 2
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Laboratory studies on the precipitation of metals from a synthetic wastewater simulating the composition of semiconductor manufacturing were performed. Residual soluble metals, in many cases, were dependent upon the age of the waste prior to precipitation. Based upon these studies, it was concluded that equilibrium information alone does not provide a complete understanding of metal removal by chemical precipitation.
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  • 3
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The kinetics of metal uptake from solutions of multi-metal, multi-ligand systems of composition similar to printed circuit board/semiconductor manufacturing wastes by a chelating ion exchange resin were examined. Solution pH and waste aging strongly influenced the observed uptake kinetics. There was no qualitative agreement between the rates of uptake of individual metals and their selectivity constants as determined earlier. Half lives for uptake ranged between 1 min and 10 hr. Desorption of metal could generally be accomplished using HCI treatment.
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  • 4
    ISSN: 1434-6079
    Keywords: 52.40.Mj ; 34.50.Bw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The energy loss of heavy ions with an energy of 1.4 MeV/u in a hydrogen plasma has been measured. A 20 cm longz-pinch has been used as plasma target. Our data show a strong enhancement of the stopping power of the plasma compared to that of a cold gas with equal density. The results completely confirm the predictions of the standard stopping power model.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 93 (1994), S. 1389-1394 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation of Sb-H complexes in n-type Si after the induction of H by low-energy implantation has been investigated using119Sb →119Sn source Mössbauer spectroscopy. We have studied the different Mössbauer fractions as a function of H- and Sb-dose and as a function of H-implantation temperature. We can explain our results by assuming thermal equilibrium between Sb-H complexes and clustered H 2 * pairs, attributing the visible hydrogen associated fraction to SbH and the “invisible fraction to SbH2 complexes. The results show that the binding energy of hydrogen in these three forms differ only by about 0.1 eV, being the highest for H 2 * and the lowest for SbH.
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  • 6
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Iron in its divalent and trivalent form can be substituted in the catalytic zinc site of alcohol dehydrogenase from horse liver (HLADH). Fe-HLADH in either oxidation state does not show enzymatic activity in the oxidation of ethanol. Nevertheless, Mössbauer studies of this material are of considerable interest, because they elucidate the effect of pH and coenzyme-induced conformational changes of the protein on the metal ion. It is of importance to note that zinc itself due to the lack of suitable chromophoric and magnetic properties does not provide any comparable information.
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  • 7
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of Fe(II) substituting Zn in Horse Liver Alcohol Dehydrogenase was investigated by Mössbauer spectroscopy at various temperatures and applied magnetic fields and by spin Hamiltonian analysis of the results. The novelty we found, is an unusually weak spin coupling of Fe(II) with a diradical (S=1). From ESR results and biochemical findings we conclude, that the corresponding chemical species is triplet oxygen (O2). Oxidation experiments, followed by Mössbauer spectroscopy, show that the spin-coupled species is an outer-sphere Fe(II)… O2 complex occuring as an intermediate of the dioxygen activation reaction, catalysed by Fe(II). A second Fe(II)−O2 complex could be detected, which corresponds to an inner-sphere complex with O2 directly bound to iron. The spin hamiltonian parameters in the coupled system describing the electronic properties of iron are presented. The results are compared with those of iron in other nonheme iron proteins.
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  • 8
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 0392-6737
    Keywords: Impurities: concentration, distribution, and gradients ; Doping and impurity implantation in germanium and silicon ; Interaction between different crystal defects ; gettering effect ; Calculations of total electronic binding energy ; Elemental semiconductors ; Mössbauer effect ; other γ-ray spectroscopy ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Experimental results are presented on the study of Sb-H complexes in crystalline silicon, employing119Sb→119Sn source Mössbauer spectroscopy and a low-energy H implantation technique. In addition to a visible component, we observe a large decrease of the Mössbauer intensity associated with the trapping of hydrogen, even at low temperatures. This is interpreted as the formation of a component with a negligible recoilless fraction. The different Mössbauer components were studied as a function of H dose, H-implantation temperature and annealing temperature. The data show that the visible component is associated with the well-known SbH complex, whereas the invisible component is associated with the formation of SbH n (n≥2) complexes. We show that these complexes are in thermal equilibrium with a larger hydrogen reservoir (H 2 * ), which governs their thermal stability. No Sb-H complexes are observed inp-type Si after H-implantation, in agreement with the current belief that hydrogen has a deep donor level in the gap. The microscopic structure of the various Sb-H and Sn-H complexes was studied with first-principles calculations using the pseudopotentialdensity-functional approach. The structure of the Sb-H complex is found to be similar to the P-H complex, with the H in an antibonding site of a Si atom neighbouring the Sb impurity. For SbH2 three configurations are found with energies differing by less than ≈ 0.1 eV. We find that the reaction SbH+H≠SbH2 is exothermic. We argue that the SbH2 complexes are shallow donors, irrespective of the structure. Therefore, the formation of SbH2 may depassivate the sample.
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  • 10
    ISSN: 1432-1017
    Keywords: 1H-NMR, 13C-NMR, electronic spectra ; Co(II)-substituted horse liver alcohol dehydrogenase acetate, imidazole, pyraxole binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract 1H-NMR and electronic spectroscopic data are reported for the interaction of the effector molecule imidazole and the inhibitor molecule pyrazole with horse liver alcohol dehydrogenase whose catalytic zinc ions were replaced by Co(II). In addition 13C-NMR and optical data are given for the binding of acetate to this enzyme species. For the binary complex with imidazole an assignment of the protons of the metal-coordinated imidazole has been made and it was found that the rate of exchange of the effector molecule is slow on the NMR time scale. In the presence of NADH which is bound to the open conformation of the binary complex, the most pronounced change is a shift of the β-CH2 protons of the metal-coordinated cysteine residues which is attributed to hydrogen bonding interactions between the carboxamide group of the nicotinamide moiety with cysteine 46. The 1H-NMR spectra of the binary complex of Co(II)-HLADH with pyrazole show resonances assigned to the protons in the 3-and 4-positions of the bound inhibitor, the NH proton resonance is not detectable. In the ternary complex with pyrazole and NAD+ only the resonances of the β-CH2 protons (beyond 150 ppm) are changed whereas the protons of histidine 67 and the bound inhibitor are unchanged. The data demonstrate that the coordination environment of the catalytic metal ion is changed very little when the protein changes from the open to the closed conformation. The only changes observed are the β-CH2 proton resonances of the metal-coordinating cysteines which are sensitive to local conformational changes within the ternary complex Co(II)-HLADH · Imidazole · NADH in the open conformation or global changes in the ternary complex Co(II)-HLADH · Pyrazole · NAD+ in the closed conformation. Acetate which can be regarded as a substrate model was shown to induce a similar change in the optical spectra of the Co(II) enzyme as all other anions observed so far. From the optical changes a dissociation constant of acetate at the catalytic metal site of 200±50 mM was calculated and from the changes of the 13C-NMR linewidth of 13C acetate direct bonding of the anion to the catalytic Co(II) ion can be demonstrated to occur under the conditions of rapid exchange. The implications of these data for the assessment of tetracoordination around the catalytic metal ion as well as the chemical nature of intermediates occurring along the catalytic pathway are discussed.
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