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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4963-4972 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) has until now been a technique used primarily for characterization of bulk electronic band structure in semiconductors. However, since reflectance is an interfacial phenomenon, PR should in principle be sensitive to surface treatment as well. The present work appears to be the first quantitative use of PR to measure the effects of surface treatment. In particular, PR spectra of air-oxidized and of annealed GaAs(100) are shown to be substantially different from those of the clean surface. Spectra at the E0 (1.4 eV) and E1 (3.0 eV) transitions respond quite differently to these treatments, and the differences are explained in terms of an optical interference phenomenon due to excitons that occurs only at E0. Effects of slow surface states have been observed with PR for the first time. The effective barrier between these states and the bulk decreases from 21±2 to 16± 2 meV upon air oxidation of the clean surface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6597-6604 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Surface diffusion of hydrogen, deuterium, and CO on Rh(111) has been investigated by laser-induced thermal desorption (LITD) and compared with previous results for these species on Pt(111) and on other metals. As the coverage θ of deuterium increases from 0.02 to 0.33, the preexponential factor D0 remains constant at 8×10−2 cm2/s, but the diffusion activation energy Ediff rises from 3.7 to 4.3 kcal/mol. Ediff for hydrogen is 0.6 kcal/mol lower than for deuterium, consistent with the difference in zero-point energy. For CO, Ediff =7 kcal/mol at all coverages, but D0 rises from 10−3 to 10−2 cm2/s between θ=0.01 and 0.40. Values of Ediff for these adsorbates vary by several orders of magnitude for surfaces on which heats of adsorption are essentially identical. These differences appear to correlate with differences in heats of adsorption in different binding states which form saddle point configurations in surface diffusion. Ediff is found to be nearly identical to the reaction activation energies for the CO and hydrogen oxidation reactions on Rh and on several other transition metal surfaces. This suggests that surface diffusion of the reducing agent may be the rate-limiting step in their bimolecular surface reactions.
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  • 3
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 4
    ISSN: 1435-2451
    Keywords: Cisaprid ; Intraduodenal pH ; Alkalization ; Cisaprid ; Intraduodenaler pH ; Alkalisierung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Cisaprid stimuliert die Motilität des gesamten Intestinaltraktes und beschleunigt die Magenentleerung. Der Effekt dieser Substanz auf den intraduodenalen pH im Vergleich zum intragastralen pH wurde bei 20 gesunden Probanden mittels 24-h-Langzeit-pH-Metrie untersucht. Cisaprid induziert im Vergleich zum Placebo eine signifikante Alkalisierung des Duodenums, pH-eränderungen im Magen kamen nicht zur Beobachtung. Ursache der intraduodenalen Alkalisierung ist möglicherweise eine direkte Stimulation der duodenalen bzw. pankreatischen Bicarbonatsekretion. Dieser Effekt könnte als begleitende Massnahme im Rahmen der konservativen Therapie des Ulcus duodeni zur Anwendung kommen.
    Notes: Summary Cisaprid stimulates the motility of the whole intestine and accelerates gastric emptying. To evaluate the effect of Cisaprid on the intraduodenal pH, in comparison to intragastral pH, long-term pH-metry was performed on 20 healthy volunteers. While no significant change in the gastric pH was observed, Cisaprid induced a significant increase in the intraduodenal pH when compared with a placebo. Alkalization of the duodenum could be due to direct stimulation of pancreatic or duodenal bicarbonate secretion, an effect which might be useful in the conservative treatment of duodenal ulcers.
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  • 5
    ISSN: 1435-2451
    Keywords: Vascular prosthesis ; Microvascular surgery ; Bovine xenograft ; Gefäßprothesen ; Mikrogefäßchirurgie ; Bovines Xenograft
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einer tierexperimentellen Studie wurde die Anwendbarkeit der neuen xenogenen bovinen kollagenen Gefäßprothese (Solcograft-P ®) als kleinkalibriger GefaBersatz (ø 〈 2 mm) untersucht. Beobachtungsdauer: 9 (n= 13), 12 (n=7) Monate. Untersuchungsmethoden: Angiographie, Histomorphologie, Rasterelektronenmikroskop. Die Durchgangigkeitsrate im untersuchten Kaliberbereich betrug insgesamt 95%. Das Prothesenkollagen wurde unter Neubildung von kollagenem und elastischem Bindegewebe teilweise abgebaut. Eine überschießende Neointimabildung war nicht zu beobachten. Die lumenseitige Auskleidung der Prothese erfolgte durch eine homogene endothelartige Zellschicht. In 30% der Fälle traten Verkalkungen bzw. Verknöcherungen auf. In einem Fall war eine aneurysmatische Dilatation in Prothesenmitte zu beobachten. Vor einer klinischen Anwendung sollte die biomechanische Belastbarkeit unter hypertensiven Kreislaufbedingungen überprüft werden.
    Notes: Summary In an animal model, we investigated the applicability of a new bovine vessel xenograft (Solcograft-P) as a small vascular substitute (ø 〈 2 mm). The observation intervals were 9 (n=13) and 12 (n=7) months. Examination methods included: angiography, light microscopy, and scanning electronic microscopy. The small-diameter xenografts examined had an overall patency rate of 95%. The prosthesis collagen was progressively substituted by newly formed collagenous and elastic connective tissue. Neointimal hyperplasia did not occur. The lumen-side surface was formed by an endotheliumlike cell layer. In 6 of 20 cases calcification and ossification were observed. In 1 case we saw an aneurysmal dilatation in the middle of the prosthesis. Before clinical application, the biomechanical properties should be examined under hypertensive circulation conditions.
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  • 6
    ISSN: 1435-2451
    Keywords: Proximal gastric vagotomy ; Gastric secretion tests ; Intragastric long-term pH-monitoring ; Ulcer recurrence ; Proximal gastrische Vagotomie ; Magensekretionsanalyse ; Intragastrale Langzeit-pH-Metrie ; Rezidivulcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einem 4-Jahreszeitraum ( $$\bar x$$ 1,6 Jahre) blieben von 47 Patienten mit PGV wegen Ulcera duodeni 38 rezidivfrei, während 9 endoskopisch nachgewiesene Rezidivulcera entwickelten. Die 2–4 Tage präoperativ und am 10. postoperativen Tag durchgeführte Magensekretionsanalyse mit Stimulation durch Scheinfütterung bzw. Pentagastrin ergab keinen signifikanten Unterschied zwischen den Patienten mit bzw. ohne Rezidiv. Die einzige signifikante Differenz zwischen beiden Gruppen bestand in der postoperativen intragastralen pH-Metrie der Schlafphase für den Median-pH und den Prozentsatz der pH-Werte 52.
    Notes: Summary Forty-seven patients were followed-up for 4 years ( $$\bar x$$ 1.6 years) after PGV because of duodenal ulcers. Thirty-eight remained free of recurrent ulcers, whereas 9 developed new ulcers, which were verified endoscopically. The gastric secretion test, which was performed 2–4 days preoperatively and on postoperative day 10 with stimulation by sham feeding and pentagastrin, showed no significant differences between the patients with or without ulcer recurrence. The only significant difference between the two groups was found in postoperative intragastric pH-monitoring of the sleep-phase for the median pH value and a percentage of pH values of ≦ 2.
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