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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 315 (1981), S. 219-225 
    ISSN: 1432-1912
    Keywords: 3-Methoxytyramine ; Haloperidol ; Dopamine release ; Dopamine agonists ; Gas chromatography ; Mass Spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The value of 3-methoxytyramine (3-MT) as an indicator of impulse-related dopamine (DA) release has been assessed in rat corpus striatum. Moreover, the turnover of 3-MT was estimated by measuring its disappearance rate after COMT inhibition. Quantitation of 3-MT and DA was performed by gas chromatography/mass spectrometry (selected ion monitoring). Haloperidol in doses between 0.05 and 3 mg/kg p.o. did not increase endogenous 3-MT levels at any time up to 24 h after its administration, whereas it dose-dependently increased homovanillic acid and 3,4-dihydroxyphenylacetic acid. However, in doses above 0.1 mg/kg p.o., it enhanced the accumulation of 3-MT in clorgyline-pretreated animals. Conversely, baclofen in doses of 2 mg/kg i.p. and above decreased endogeneous 3-MT levels, but reduced the accumulation of this amine only poorly at 20 mg/kg i.p. in clorgyline-pretreated rats. A number of dopamine agonists, apomorphine (0.5 mg/kg i.v.), dipropyl-ADTN (0.03 mg/kg i.v.), but not bromocriptine (1 mg/kg i.v.) reduced endogenous 3-MT levels 10 min after administration by approximately 50%. The DA releasing agents d-amphetamine and methylphenidate showed different effects: the former increased endogenous 3-MT greatly, whereas the latter was without effect. The difference is likely to be related to the MAO inhibitory properties of amphetamine. 3-MT disappeared rapidly after COMT inhibition with 50 mg/kg i.v. tropolone (half-life of the initial disappearance about 1 min). The curve flattened off after 5–10 min. Turnover was calculated to be about 7 nmol/g/h, which corresponds to about a third of the turnover of DA. Our results suggest that an important part of DA metabolism occurs through 3-MT and that this amine is very effectively deaminated by MAO-A, so effectively indeed that increased formation does not increase its endogeneous levels. It appears, therefore, that 3-MT is not suitable as an indicator of increased DA release. However, it seems to have some value for an assessment of lowered DA release.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The total cross section fore + e − annihilation into hadrons for center of mass energies from 9.4 to 9.5 GeV has been measured with the nonmagnetic DESY-Heidelberg detector at DORIS. A value ofR=σhad/σµµ=3.8±0.7 for the continuum region around the Υ (9.46) resonance has been determined. The ratioΓ ee Γ had/Γ tot of electronic, hadronic and total widths has been reevaluated to be (1.00±0.23) keV for the Υ resonance and (0.37±0.16) keV for the Υ′. In addition, a search for directly produced pohotons from Υ decays of the type Υ→γ+gluon+gluon has been performed. The Υ decay into muon pairs has also been searched for.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 98-105 
    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: Characterisation of Adherence of Precious Alloy to Dental CeramicLaminated metal-ceramic composites were produced from two Aubase alloys and two ceramic powders. For part of the specimen an extra Aurich layer was brought into the metal-ceramic interface. Microscopic investigations showed enrichment of non precious alloying elements in the metallic region adjacent to the interface and a sheet of enhanced porosity (about 5-15%) in the ceramic region adjacent to the interface. After producing a Chevron notch in the interface the composite specimens were fractured in a controlled mode in four point bending. As the crack was at least partly running along the ceramic zone of enhanced porosity near the interface, the average crack resistance R̄ of the interface could be determined. In specimens without an extra Au-rich layer R̄ was between 3 and 12 J/m2 and thus less than the R̄-value of the ceramic (R̄ 12 J/m2). The relatively large scatter is supposed to be mainly due to internal stresses. Specimens containing an extra Au-rich layer showed high R̄-values (up to 36 J/m2) due to good interlocking of metal and ceramic.
    Notes: Aus zwei Edelmetall-Aufbrennlegierungen und zwei keramischen Massen der Dentaltechnik wurden Metall-Keramik-Schichtverbundproben hergestellt, wobei bei einem Teil der Proben zusätzlich eine goldreiche Schicht zwischen die Verbundpartner eingebracht wurde. Die mikroskopische Untersuchung zeigte, daß sich metallseitig an der Grenzfläche unedle Legierungsbestandteile angereichert hatten und keramikseitig eine flächenhafte Zone erhöhter Porosität (etwa 5-15%) gebildet wurde. Die in der Grenzfläche mit einem Spitzkerb versehenen Proben wurden im Vierpunktbiegeversuch bei Raumtemperatur kontrolliert gebrochen. Der Riß verlief zumindest teilweise in der grenzflächennahen, porösen Zone der Keramik, so daß der mittlere Rißwiderstand R̄ der Grenzfläche bestimmt werden konnte. Für Proben ohne goldreiche Zwischenschicht lag R̄ zwischen 3 und 12 J/m2 und damit in der Regel niedriger als in der Keramik (etwa 12 J/m2). Die relativ große Streuung wird vorwiegend auf herstellungsbedingte innere Spannungen zurückgeführt. Für die hohen R̄-Werte der Proben mit goldreicher Zwischenschicht (bis 36 J/m2) wird die gute Verzahnung zwischen Metall und Keramik als ursächlich angesehen.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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