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  • 1
    Electronic Resource
    Electronic Resource
    Modification of low density lipoprotein potentiates its inhibitory effect on catecholamine secretion in cultured bovine adrenal medullary cells (1999)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 360 (1999), S. 99-102 
    Details
    ISSN: 1432-1912
    Keywords: Key words Acetylation ; Adrenal medullary cells ; Atherosclerosis ; Catecholamine secretion ; Low density lipoprotein ; Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Low density lipoprotein (LDL) and lipoprotein(a) suppress catecholamine secretion in cultured adrenal medullary cells. Modification of LDL by oxidation or acetylation potentiates various atherogenic actions of LDL. In the present study, we investigated whether the modification of LDL influences catecholamine secretion in cultured bovine adrenal medullary cells. The exposure of LDL to CuSO4 caused a time-dependent oxidation of LDL. Maximal oxidation of LDL was observed after exposure to CuSO4 for 24 h. Native LDL inhibited catecholamine secretion induced by carbachol to 68.5% of control. Oxidized LDL caused further inhibition of carbachol-evoked secretion to 37.6% of control. Acetylated LDL inhibited it to 41.0% of control. There was a good correlation between the extent of LDL oxidation and the inhibition of catecholamine secretion. These results suggest that oxidation or acetylation of LDL augments its inhibitory effect on the secretion of catecholamines. Since catecholamines are a risk factor of atherosclerosis, the inhibitory effect by such modified LDL may be a mechanism inhibiting atherosclerotic progression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002109900039
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  • 2
    Electronic Resource
    Electronic Resource
    Dilute solution properties of critically branched systems (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 2413-2435 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An kritisch verzweigten Polykondensaten aus 1,3,5-Benzoltriessigsäure und 1,10-Decandiol wurden Lichtstreuungsmessungen ausgeführt. Die Ergebnisse wurden in Anlehnung an die Theorie der Kaskadenprozesse analysiert; diese Theorie wurde, mit Hilfe der Methode der “path-weighting” (Weg-wichtenden) erzeugenden Funktion, speziell für dieses System umgeformt. Es wird postuliert, daß das Ausmaß der Kettenexpansion bei diesen verzweigten Proben im wesentlichen auf Nachbarschafts- (“short range”) Wechselwirkungen und weniger auf weitreichende (“long range”) Wechselwirkungen zurückzuführen ist. Die weitreichenden Wechselwirkungen scheinen im kritisch verzweigten Zustand zu verschwinden. Für die Berechnung der vergleichbaren ungestörten Dimensionen des linearen Homologen aus 1,3-Benzoldiessigsäure und 1,10-Decandiol wurde das Modell der rotationisomeren Zustände herangezogen.
    Notes: Light-scattering measurements were carried out on critically branched polycondensates of 1,3,5-benzenetriacetic acid and 1,10-decanediol, and the results were analysed according to the theory of cascade processes, developed especially for this system, viz. the pathweighting generating function method. It is postulated that the amount of chain expansion found in these branched copolycondensate samples was due to short-range rather than long-range interactions. The long-range interactions seem to vanish in the critically branched state. The rotational isomeric state model was used to calculate the comparative unperturbed dimensions for the linear homologue of the above polycondensate, i.e. poly(1,3-benzenediacetic acid/1,10-decanediol).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760817
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of AlGaAs/GaAs superlattices by means of sputter-assisted AES, SEM and TEMPaper presented at ECASIA 89, Antibes, France, 23-27 October 1989. (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 433-439 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This paper reports the developments of evaluation methods on epitaxially grown superlattices by means of sputterassisted Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). AlGaAs/GaAs semiconductor superlattics were grown epitaxially by metal-organic chemical vapour deposition (MOCVD). The layer thickness of the superlattices ranged from a few to ten nanometers.Firstly, developments of Auger depth profiling were tried by using: (1) a differential pumping-type ion gun instead of a static pressure type to reduce the oxygen adsorbates on the AlGaAs layer; (2) low-energy Auger signals instead of high-energy ones to shorten the escape depth; and (3) the lowest ion etching energy of 0.2 keV instead of 1 keV to reduce the surface roughening effects. It is shown that the depth resolution of sputter-assisted AES is attainable to 1.5 nm.Secondly, high-resolution SEM can be used as an easy evaluation method by observing the cleaved surface of superlattices, since the layers can be distinguished by signal contrast. Also, TEM can be used as an evaluation method by observing the (110) cross-section thinned sample. The dark field image has a high contrast between AlGaAs and GaAs using the (002) diffraction.It is confirmed from these AES, SEM and TEM evaluations that the hetero-interface abruptness of AlGaAs/GaAs superlattices grown by MOCVD is of the order of one monoatomic layer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740150707
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  • 4
    Electronic Resource
    Electronic Resource
    GaAs/AlAs superlattice as a proposed new reference material for sputter depth profiling (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 1061-1066 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A GaAs/AlAs superlattice growth by metal-organic chemical vapour deposition is being proposed as the single crystalline multilayer reference material for sputter depth profiling. This material was characterized by transmission electron microscopy experiments, which showed that the interface between GaAs and AlAs is atomically flat. The preliminary depth profiling experiments were carried out by AES and SIMS.The AES experiments were performed using a Perkin-Elmer SAM 660 scanning Auger microprobe and the SIMS experiments were carried out using a VSW multitechnique XPS/SIMS surface analysis system.The AES and SIMS sputter depth profiling experiments proved that the depth resolution was found to be almost constant for each interface when an Ar+ beam was used for sputtering. Therefore the sputtering-induced roughness is very small for this material with Ar+ beam profiling, the depth resolution deteriorated as a function of depth, indicating oxygen ion beam-induced surface roughening.For both AES and SIMS, the depth resolution improved for ion beams with lower kinetic energy and more glancing angles of incidence.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740201306
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  • 5
    Electronic Resource
    Electronic Resource
    Crystalline effects on depth resolution in AES depth profiling (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 22 (1994), S. 22-26 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An evaluation of the depth resolution of sputter-assisted Auger electron spectroscopy (AES) has been studied for semiconductor superlattices. Zalar et al. have shown that sample rotation is effective in improving the depth resolution of AES depth profiling. Multilayers with two kinds of crystalline states were prepared to test the effectiveness of sample rotation. First, a microcrystalline Zr/Nb (10 nm/10 nm) multilayer was deposited by dc-sputtering. Secondly, an AlAs/GaAs (10 nm/9 nm) and an InP/InGaAs (3 nm/3 nm) single crystalline superlattice were grown by metal-organic chemical vapor deposition.AES depth profiling with Ar+ ion sputtering was performed on these multilayers with and without sample rotation. Comparing the rotational depth profiling results with those obtained on stationary samples, it is found that, in the cases of the Zr/Nb and the InP/InGaAs multilayers, the depth resolution was considerably improved by sample rotation while in the case of AIAs/GaAs multilayer the depth resolution was only little improved by sample rotation. It is shown that the effectiveness of sample rotation strongly depends on the crystalline states of samples and on the degree of preferential sputtering.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740220108
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  • 6
    Electronic Resource
    Electronic Resource
    An AES study of LPCVD Ta2O5 films on Si (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 331-335 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Methods of evaluation of the chemical composition of tantalum oxide films and of the interface between tantalum oxide films and Si substrates were studied by means of sputter-assisted Auger electron spectroscopy (AES). Tantalum oxide films 10-50 nm thick were grown on Si single-crystal substrates by low-pressure chemical vapour deposition (LPCVD). It has been found that reduction of the oxides is induced by ion sputtering during Auger depth profiling. Therefore we optimized the ion-sputtering conditions to minimize the reduction rate. Then, using stoichiometric β-Ta2O5 as reference, it was confirmed that as-deposited tantalum oxide films were oxygen-deficient and that the oxygen content of these films was increased by subsequent annealing in an O2 ambient. By means of Auger depth profiling, we evaluated the thickness of silicon native oxides formed at the Ta2O5/Si interface as 1.5-2 nm. Moreover, we revealed the oxidation mechanism of a silicon nitride intermediate layer (e.g. 10 nm thick) deposited between tantalum oxide film and an Si substrate during heat treatment at 900-1000°C in O2.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740190162
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    Paper (German National Licenses)
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