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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 14 (1989), S. 191-196 
    ISSN: 1573-6903
    Keywords: Acetylcholine ; CSF ; cholinergic ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Investigation of neurological diseases involving central cholinergic dysfunction has led to numerous studies seeking a peripheral marker of cholinergic activity in brain. The main objective of these studies was to determine whether the ACh synthesizing activity present in human CSF was due to the presence of the enzyme choline acetyltransferase (ChAT; 68kDa). When CSF was fractionated into low and high molecular weight (Mr) components, 80% of the ACh synthesizing activity (AChSA) was found to be associated with the fraction 〈10 kDa. The remaining 20% was evenly distributed among fractions in the 5–30, 30–50, 50–300, and 300 kDa fractions. Although boiling destroyed all activity 〉10 kDa, the ChAT inhibitor NVP, at concentrations equal to or greater than that required to inhibit ChAT in human cortical tissue, did not alter the ACh-SA in either fraction. Results indicate that normal human CSF does not contain ChAT and all ACh-SA in CSF reflects non-enzymatic imidazole/histidine-like catalyzed synthesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0948-1907
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 39-49 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: When energetic ions penetrate and stop in solids they not only add a new atomic constitutent to the matrix but they also create atomic recoils and defects. The fluxes of these entities can give rise to spatial redistribution of atomic components, which may be partly or completely balanced by reordering and relaxation processes. These latter, in turn, may be influenced by fields and gradients induced by the primary relocation processes and by the energy deposited. These will include quasi-thermal, concentration (or chemical potential) and electrostatic gradients and may act to enhance or suppress atomic redistribution. Some, or all, of these processes will operate, depending upon the system under study, when energetic ions are employed to sputter erode a substrate for depth sectioning and, quite generally, can perturb the atomic depth profile that it is intended to evaluate. Theoretical and computational approaches to modelling such processes will be outlined and experimental examples shown which illustrate specific phenomena.In particular the accumulation of implant species and defect generation or redistribution can modify, with increasing ion fluence, the local sputtering mechanism and create further problems in depth profile analysis as a changing surface topography penetrates the solid. Examples of such topographic evolution and its influence on depth profiling analysis will be given and models to explain general and specific behaviour will be outlined. The commonality of models which examine both depth-dependent composition modification and surface topography evolution will be stressed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Among the several factors which lead to depth resolution deterioration during sputter profiling, surface morphological modification resulting from local differences of sputtering rate can be important. This paper reports the results of direct scanning, electron microscopic studies obtained quasi-dynamically during increasing fluence ion bombardment of the evolution of etch pit structures on Si and Cu, and how such elaboration may be suppressed. It also reports on the elaboration of contaminant-induced cone generation for different ion species bombardment. The influence of such etch pit and cone generation on achievable depth resolution is assessed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 7 (1985), S. 41-48 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A model is developed, assuming mutation of facet lengths to larger values, to explain the experimental observations of the change in the population distribution of the lengths of facets developed during ion bombardment sputtering erosion of Si. The ensuing Gaussian facet length distribution, with mean length increasing linearly with ion fluence, is then used to show that the depth resolution δz/z0 of interface broadening first increases as z-10 and then tends towards a constant value with increasing z0.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 194-208 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An altered layer model is developed, consisting of an outer surface or sputtering layer from which atoms are ejected by ion bombardment and an adjacent deeper layer in which atomic constituents are spatially homogenised by bombardment-induced mixing processes and between which layers atomic constituents are again intermixed. The model is applied to the case of sputtering erosion through an interface, and broadening effects are examined. It is shown that the model relaxes, on the one hand, to earlier treatments of non-distinguishable sputtering and altered layers and, on the other hand, by assuming multiple altered layers, to earlier continuum (non-discretized layer) models. Suggestions for controlled experimental studies for model verification are made.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 511-523 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The quasi-linear partial differential continuity equations that describe the evolution of the depth profiles and surface concentrations of marker atoms in kinematically equivalent systems undergoing sputtering, ion collection and atomic mixing are solved using the method of characteristics. It is shown how atomic mixing probabilities can be deduced from measurements of ion collection depth profiles with increasing ion fluence, and how this information can be used to predict surface concentration evolution. Even with this information, however, it is shown that it is not possible to deconvolute directly the surface concentration measurements to provide initial depth profiles, except when only ion collection and sputtering from the surface layer alone occur. It is demonstrated further that optimal recovery of initial concentration depth profiles could be ensured if the concentration-measuring analytical probe preferentially sampled depths near and at the maximum depth of bombardment-induced perturbations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 572-574 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Consideration of the continuity equation relating atomic fluxes entering and leaving a layer from the instantaneous surface to a fixed depth beyond the extent of any atomic relocation shows that measurements of total atomic exit flux, of a given species, the rate of change with time of the species concentration over the fixed depth, and sputtering speed, can yield initial depth distributions of the atomic species.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 514-520 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The topographic evolution of Si irradiated at room temperature with Ne+ and Ar+ ions in the energy range 5-40 keV at 45° to the substrate normal has been studied. Other than isolated etch pits, no topography results from Ne+ bombardment at all energies and from Ar+ bombardment at 5 and 10 keV. Argon ion bombardment at 20 keV, however, initially produces transverse low-amplitude waves that transform, with increasing erosion, into larger amplitude, corrugated and faceted, wave-like structures. The present data do not conform to existing model predictions but do suggest that light low-energy inert gas ions can be used to inhibit roughening during sputtering erosion.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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