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  • 1
    Electronic Resource
    Electronic Resource
    SIMS and flash desorption studies of nickel oxygen interaction (1978)
    Springer
    Applied physics 16 (1978), S. 367-373 
    Details
    ISSN: 1432-0630
    Keywords: 79.20 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract O2 exposure of polycrystalline nickel at 300 K results in characteristics changes of secondary ion emission. These can be described by a model which is in good agreement with corresponding LEED, AES, XPS, and ΔΦ results of other authors. According to this model, oxygen can be bonded on Ni in at least five different phases: 1) chemisorption, indicated by a rapid increase of Ni+, Ni 2 + , and Ni2O+ (≦5 L); 2) a rearranged chemisorption layer, characterized by a drastic decrease of Ni+, Ni 2 + , and Ni2O+ (5–15 L); 3) nickel oxide (NiO) responsible for a strong NiO−- and NiO 2 − -emission (≦40 L); 4) oxygen on top of this NiO layer, producing a final increase of Ni+ and NiO+ and a O2-flash signal at 400 K (〉40 L); 5) bulk dissolved oxygen in thermal equilibrium with a chemisorption layer (after several exposure/heating cycles). During ion bombardment of a 100 L O2 exposed Ni surface these different binding states occur in a reversed order of succession. O2-flash signals at 400 and 1100 K, related to drastic changes in secondary ion emission at 400, 700, and 1100 K, reflect the disappearance of various oxygen binding states. The exchange between different oxygen phases was studied by16O2/18O2 isotope experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885861
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  • 2
    Electronic Resource
    Electronic Resource
    Some aspects of auger electron spectra of 3d transition metal oxides (1977)
    Springer
    Applied physics 13 (1977), S. 43-46 
    Details
    ISSN: 1432-0630
    Keywords: 79.20 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Auger electron spectra of the transition metals Cr, Mn, Fe, Co and Ni as well as their oxides have been investigated in the energy range between 0–100 eV. In each case of the clean metal surface the observed spectrum consists essentially of one Auger line identified asM 2,3 VV transition. After oxidation a line doublet is observed revealing two transitions instead of one. Additional new Auger peaks appear in the low energy range between 0–30 eV. The “splitting” of the Auger line can be explained as resulting from aM 2,3 V dVd and aM 2,3 V pVp transition. The latter is characteristic for the compound and can in a simple way be interpreted as a cross transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890718
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fast LEED intensity measurements with a video camera and a video tape recorder (1979)
    Springer
    Applied physics 19 (1979), S. 287-293 
    Details
    ISSN: 1432-0630
    Keywords: 06.90+v ; 61.14-x ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The measurement of LEED intensities with a TV camera-computer system, which has been published in an earlier paper, is reported to be improved with respect to the speed of data collection by a factor of about 102. Other properties such as sensitivity, reliability and handling facility have also been improved. The new measuring mode, which applies a video tape recorder, allows the simultaneous measurement of all appearing diffraction spots down to a beam current of 10−11 A with a rate of 50 energy points/s. This pushes the total measuring time for LEED spectra to the order of seconds and makes possible to monitor non-stable surfaces. As an example intensity measurements for different adsorption stages of hydrogen on W(100) are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900472
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  • 4
    Electronic Resource
    Electronic Resource
    Variance reduction by simultaneous multi-exponential analysis of data sets from different experiments (1991)
    Springer
    European biophysics journal 19 (1991), S. 231-240 
    Details
    ISSN: 1432-1017
    Keywords: Multi-exponentials ; Relaxation ; Data analysis ; Photocycle ; Bacteriorhodopsin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The analysis of experimental data from the photocycle of bacteriorhodopsin (bR) as sums of exponentials has accumulated a large amount of information on its kinetics which is still controversial. One reason for ambiguous results can be found in the inherent instabilities connected with the fitting of noisy data by sums of exponentials. Nevertheless, there are strategies to optimize the experiments and the data analysis by a proper combination of well known techniques. This paper describes an applicable approach based on the correct weighting of the data, a separation of the linear and the non-linear parameters in the process of the least squares approximation, and a statistical analysis applying the correlation matrix, the determinant of Fisher's information matrix, and the variance of the parameters as a measure of the reliability of the results. In addition, the confidence regions for the linear approximation of the non-linear model are compared with confidence regions for the true non-linear model. Evaluation techniques and rules for an optimum experimental design are mainly exemplified by the analysis of numerically generated model data with increasing complexity. The estimation of the number of exponentials significant for the interpretation of a given set of data is demonstrated by using records from eight absorption and photocurrent experiments on the photocycle of bacteriorhodopsin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00183531
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  • 5
    Electronic Resource
    Electronic Resource
    The photocycle and the structure of iron containing bacteriorhodopsin —a kinetic and Mössbauer spectroscopy investigation (1990)
    Springer
    European biophysics journal 19 (1990), S. 11-18 
    Details
    ISSN: 1432-1017
    Keywords: Bacteriorhodopsin ; Mössbauer spectroscopy ; Cation binding site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Bacteriorhodopsin (bR), converted by deionization to the blue form was reconstituted to the active purple membrane by the addition of Fe2+ or Fe3+ ions. 57Fe Mossbauer spectra of these samples were measured at different pH values (pH 3.9, pH 5.0 and pH 7.0) and at temperatures ranging from 4 K to 300 K. The hyperfine parameters reveal two iron environments with oxygen atoms in the neighbourhood of iron. Iron type 1 is in the 3+ high spin state. It is bound to acid side chains of the protein and/or the phosphate groups of the lipids. Iron type 2 is in the 2+ high spin state and is linked to carboxy groups of the protein in a rather unspecific way. Dynamics as measured by Mossbauer spectroscopy show that the purple membrane becomes flexible only above 220 K. At the interface between membrane and bulk water the mobility is comparable to that of proteins with hydrophilic surfaces. The photocycle of Fe 3+-bR is slowed down compared to native bR. 3–5 Fe3+/bR are sufficient to inhibit the photocycle turnover by one order of magnitude. This specific effect is also found with Cr3+, though it is less pronounced. Mössbauer spectra of Fe3+-bR at 4 K reveal that iron nuclei are spin-coupled, indicating their close spatial proximity. It is proposed that iron trinuclear clusters interact with the proton uptake site of bR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223568
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