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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of Mg2+ with the allosteric site of muscarinic M2 receptors (1998)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 357 (1998), S. 363-370 
    Details
    ISSN: 1432-1912
    Keywords: Key words Porcine M2 receptors ; Allosteric interactions ; Mg2+-effects ; W84 ; Chin3/6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Mg2+-ions have been suspected to attenuate the inhibitory effect of allosteric modulators on the dissociation of orthosteric ligands from muscarinic M2 receptors. It was aimed to gain more insight into the molecular events underlying the effect of Mg2+. The interaction of Mg2+ with the allosteric model compounds W84 (hexane-1,6-bis [dimethyl-3’-phthalimidopropylammonium bromide]) and Chin3/6 (hexane-1,6-bis[dimethyl-3’-{4-oxo-2-phenyl-3,4-dihydro-2H-quinazolin-1-yl}propylammonium bromide]) was studied in porcine heart muscarinic receptors, the primary binding site of which was occupied by the ligand [3H]N-methylscopolamine ([3H]NMS). The incubation buffer was composed of 4 mM Na2HPO4 and 1 mM KH2PO4 (pH 7.4, 23°C). The retardation of [3H]NMS dissociation (control t1/2 = 5.6 min) induced by the allosteric test compounds was diminished by 3 mM Mg2+ to a greater extent than to be expected with regard to its contribution to the ionic strength of the buffer solution. Concentration-effect curves for the allosteric retardation of [3H]NMS dissociation by W84 (half maximal effective concentration EC0.5 = 24 nM in the absence of Mg2+) and by Chin3/6 (EC0.5 = 28 nM) were shifted by Mg2+ to the right in a parallel fashion. The curve-shift was compatible with a competitive interplay between Mg2+ and the modulators. The pK b-values as a measure of the antagonistic potency of Mg2+, however, differed depending on the modulator, i.e. pK b = 3.4 with W84 and pK b = 2.8 with Chin3/6. Mg2+ itself was capable of slowing the dissociation of [3H]NMS; the maximal retardation of [3H]NMS dissociation was about 3fold, the concentration-effect relationship was compatible with a two-site model using the above-mentioned pK b-values as affinity constants. Since the equilibrium-binding of [3H]NMS remained unchanged up to a Mg2+-concentration of 3 mM, the cation appears to inhibit the association and dissociation of [3H]NMS to the same extent in this concentration range. Taken together, the findings indicate that Mg2+ may bind to the allosteric region of muscarinic M2 receptors and that more than one site is involved in this interaction. The sites of action may represent divalent cation binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005180
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  • 2
    Electronic Resource
    Electronic Resource
    In-vivo investigation of material quality of bone tissue by measuring apparent phalangeal ultrasound transmission velocity (1995)
    Springer
    Clinical rheumatology 14 (1995), S. 26-34 
    Details
    ISSN: 1434-9949
    Keywords: Ultrasound ; Bone ; Material Quality ; Modulus of Elasticity ; Age ; Bone Mineral Density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The square of ultrasound transmission velocity in a material is related to the modulus of elasticity, which is known to be an indicator of stability in bone. The aim of our study was to use ultrasound transmission velocity to obtain information about the material properties of bone tissue, keeping other factors possibly influencing ultrasound transmission as constant as possible. Apparent phalangeal ultrasound transmission velocity (APU) measured in 54 isolated, fresh pig phalanges was shown to be independent of bone mineral density (BMD) measured by SPA. Fastest sound transmission led exclusively through cortical bone so that intertrabecular connectivity in spongious bone could not influence the result. In humans APU was measured in the mediolateral direction at the midphalanx of the middle finger. In 53 healthy subjects (15–81 years old; 27 women, 26 men), there was a decrease of APU with age (r=−0.30, p〈0.05). Further, when comparing the results of both hands intraindividually almost identical values indicated constant intraindividual architecture of bone at this location. There was no evidence for a relation of APU to physical load comparing dominant and nondominant hand and relating the results to subjectively estimated physical load. In a second group of 43 perimenopausal women (47–60 years old), APU, which again decreased with age (r=−0.33, p〈0.05), was found not be correlated to BMD measured by SPA at the distal forearm (cortical bone). In a third group of 40 women (17–78 years old), APU again decreased with age (r=−0.60, p〈0.001) and was not correlated to BMD measured by SPA at the midphalanx of the middle finger, i.e. the same measuring location as APU. We conclude that this method provides information about the modulus of elasticity of bone with negligible influence of bone mineral density. Our results indicate that there is a deterioration of bone material quality with age independent of decreasing bone mineral density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208081
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  • 3
    Electronic Resource
    Electronic Resource
    Environmental statistics and data analysis. Von Wayne R. Ott, 336 S., CRC Press, Lewis Publishers Boca Raton 1995, £55.00, ISBN 0-87371-848-8 (1997)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 48 (1997), S. 463-463 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19970480716
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of surface defects on polymer lenses depending on moisture absorption (1995)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 353 (1995), S. 740-742 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Lenses for eye glasses of thermosetting material CR39 and optical lenses of polycarbonate have been investigated with respect to their moisture absorption behavior. The moisture content of polymer lenses has been determined by analyzing transmission spectra in the near infrared (NIR). The surface topography was characterized by Atomic Force Microscopy (AFM). In spite of the fact that CR39 takes up essentially more water, the formation of surface defects is not remarkable compared with lenses of polycarbonate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321361
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  • 5
    Electronic Resource
    Electronic Resource
    Design and Properties of Thermal Barrier Coatings for advanced turbine enginesDedicated to Prof. Wolfgang Bunk on the occasion of his 70th birthday (1997)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 28 (1997), S. 357-362 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Herstellung und Eigenschaften von Wärmedämmschichten für fortschrittliche GasturbinenDie Verbesserung des Wirkungsgrades stationärer wie auch fliegender Gasturbinen erfordert eine Erhöhung der Prozeßtemperaturen und damit auch der Werkstoffeinsatztemperaturen. Trotz aufwendiger Kühlung und einkristalliner Bauweise stoßen die höchstbeanspruchten rotierenden Teile in der Turbine - die Turbinenschaufeln - heute an Einsatzgrenzen, die durch den Schmelzpunkt der Ni-Superlegierungen vorgegeben sind. Hier haben Wärmedämmschichten eine zentrale Bedeutung erlangt. Aufgrund der im Vergleich zum Substrat äußerst geringen Wärmeleitfähigkeit dieser keramischen Schichten lassen sich bei innengekühlten Turbinenschaufeln Gastemperaturerhöhungen von bis zu 150°C erzielen. Wärmedämmschichten werden primär durch thermisches Spritzen (PS) oder Elektronenstrahlverdampfung (EB-PVD) hergestellt. Während PS kostengünstiger ist, weisen EB-PVD-Wärmedämmschichten ein überlegenes Schadenstoleranzverhalten auf. Zudem werden durch das Aufdampfen die Kühlluftbohrungen nicht verstopft, und aerodynamisch glatte Oberflächen bleiben erhalten. Zum Schluß wird ein Ausblick auf Forschungs- und Entwicklungstrends in der Wärmedämmschichttechnologie gegeben.
    Notes: The efficiency and performance of advanced aircraft turbines can be markedly increased if higher gas temperatures are used. Although the highly loaded blades and vanes in the high pressure turbine are heavily cooled, today's substrate materials are unable to provide sufficient strength in the temperature range up to 1500°C and above. If thermal barrier coatings (TBCs) are applied on superalloy turbine blades a substantial temperature drop of the parts can be achieved. The resulting increase in efficiency comes from reduced cooling and/or increased gas turbine inlet temperatures of up to 150°C. TBCs are either processed by plasma spraying (PS) or electron beam physical vapour deposition (EB-PVD). While PS is lower in cost EB-PVD leads to superior strain and thermoshock tolerant coatings. Furthermore, cooling hole closure of turbine blades and vanes is prevented and aerodynamic design maintained. Finally, future research and development needs in TBC technology are stressed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19970280807
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  • 6
    Electronic Resource
    Electronic Resource
    Thermocyclic Behavior of Differently Stabilized and structured EB-PVD thermal barrier coatingsDedicated to Prof. Wolfgang Bunk on the occasion of his 70th birthday (1997)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 28 (1997), S. 370-376 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Thermowechselverhalten von EB-PVD Wärmedämmschichten mit unterschiedlicher Zusammensetzung und StrukturDurch das Elektronenstrahl-Verdatnpfungsverfahren (EB-PVD) werden spezifische, kolumnare Schutzschichten auf Gasturbinen- bauteilen erzeugt. Der hauptsächliche Vorteil dieser Struktur liegt in ihrer herausragenden Beständigkeit gegen Dehnungen, Erosion und Thermoschockbelastungen, was zu einer Lebensdauerverlän- gerung führt. Der Einfluß der chemischen Zusammensetzung so- wie der Mikrostruktur auf die Lebensdauer von EB-PVD Wärme- dämmschichten auf Zirkondioxidbasis wird in einem zyklischen Heißgas- sowie in einem Thermowechselversuch untersucht. Die Möglichkeit zur Herstellung von anwendungsangepaßten Wärme- dammschichten durch Parametervariation beim EB-PVD-Verfah- ren wird aufgezeigt. Das Strukturzonendiagramm für PVD-Verfahren wird weiterentwickelt, indem der Einfluß der Substratrotation auf die Ausbildung der Mikrostruktur eingearbeitet wird. Einige grundlegende Aspekte von Einquellen- und Zweiquellenverdamp- fung werden verglichen.
    Notes: The electron-beam physical vapor deposition (EB-PVD) process provides distinctive coatings of a unique columnar microstructure for gas turbine components. Main advantage of this structure is superior tolerance against straining, erosion and thermoshock, thus giving it a major edge in lifetime. This paper outlines the interaction between chemical composition and microstructural evolution EB-PVD zirconia-based thermal barrier coatings (TBCs) and their respective lifetimes in cyclic burner rig and furnace tests. Customizing TBC microstructure by adjusting EB-PVD processing parameters is emphasized. A structural zone diagram for PVD is modified by interconnecting the influence of substrate rotation with microstructural evolutions. Finally, some basic aspects of single source and dual source evaporation are compared.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19970280811
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  • 7
    Electronic Resource
    Electronic Resource
    Graded Thermal Barrier Coating Systems for gas turbine applicationsDedicated to Prof. Wolfgang Bunk on the occasion of his 70th birthday (1997)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 28 (1997), S. 391-394 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Gradierte Wärmedämmschichtsysteme für Anwendungen in der GasturbineFortschrittliche Wärmedämmschichten tragen zu einer erhöhten Effektivität von Triebwerken bei. Ein bedeutsames Problem ist die thermische Instabilität von Verbundwerkstoffen bei den hohen Einsatztemperaturen. Interdiffusion, Oxidation und Sintereffekte begrenzen dabei die Lebensdauer der Schichten. Verschiedene Ansätze zu Verlängerung der Lebensdauer und/oder zur Erhöhung der Einsatztemperatur sind im System Substrat-Schutzschicht möglich. Einige Lösungen enthalten die Anwendung des Konzepts der gradierten Werkstoffe. Im folgenden werden mögliche Anwendungen gradierter Werkstoffe in Wärmedämmschichtsystemen vorgestellt sowie ein Überblick über aktuelle Forschungsergebnisse auf diesem Gebiet gegeben.
    Notes: Improved thermal barrier coatings can lead to increased engine operating efficiency. A significant problem is that multilayer systems are not thermally stable at elevated temperatures. Phenomena such as interdiffusion, oxidation and sintering take place, limiting coating lifetime. In order to extend lifetimes and/or increase service temperatures several modifications can be made to coating-substrate systems. Some solutions involve the utilization of the functionally graded material concept. In this paper, potential applications for functionally graded materials in thermal barrier coating systems are discussed, and research results are summarized providing an overview of the state-of-the-art.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19970280817
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