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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3711-3716 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In recent years, Au/Ni/p-GaN ohmic contacts annealed in air have been studied extensively because they provide low specific contact resistances and high transparency. In this article we focus on the environmental and thermal degradation that we have observed in these contacts. When the contacts were not protected from the environment, degradation of the contacts always occurred over a period of days, and after sitting 30 days in the laboratory at room temperature, the current–voltage characteristics of the originally ohmic contacts were nonlinear and the contacts were significantly more resistive. To pinpoint the degradation mechanism, samples were stored at room temperature in dry nitrogen, dry oxygen, dry air, air saturated with water vapor, nitrogen gas saturated with water vapor, or vacuum. These experiments revealed that water vapor was the cause of the room temperature degradation. Since no change in the sheet resistance of the p-type GaN was observed upon aging, four point probe measurements and x-ray photoelectron spectroscopy depth profiles were carried out to determine the interaction between water vapor and the p-type NiO present in the annealed contact metallization. The measurements indicated that hydroxyl groups were incorporated in the NiO, leading to a reduction in its conductivity and presumably a decrease in its hole concentration. Aging studies at 200 °C further revealed poor thermal stability of the contacts not only in water vapor but also in nitrogen gas and vacuum, and this degradation was again linked to a degradation in the conductivity of the NiO component of the contact metallization. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The components of the first 50 MeV accelerator in the chain of injectors to the 820 GeV HERA proton ring are described including the high energy transport line. An H− beam originates in the cesium loaded magnetron source, is preaccelerated by a radio frequency quadrupole to 750 keV, raised to 50 MeV energy in three rf resonators, and is analyzed in the transport line. The H− ions are converted to protons by stripping, when the beam is injected over several turns into the synchrotron DESY3.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9412-9420 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quadrupolar and chemical shift tensors, as well as the relative orientation of the two principle axis systems, are accurately determined using a two-dimensional nuclear magnetic resonance technique. Good agreement between experimental and simulated two-dimensional spectra is obtained for a series of rubidium and sodium compounds at multiple magnetic field strengths. Extension of this technique to correlate the quadrupolar and dipolar interactions, as well as the incorporation of a purely isotropic dimension resulting in a three-dimensional experiment is also discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 115 (1996), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In a field experiment with topless faba beans, parental inbred lines and FI hybrids of a 7 × 7-diallel were evaluated for traits related to the P, N and K efficiency. In addition, the parental inbreds were cultivated in a pot experiment at two P levels (100 vs. 700 mg P per pot). Significant heterosis for grain yield, uptake and utilization efficiency of nutrients in the field experiment highlighted the enhancement of nutrient efficiency in the hybrids. Amongst both parental inbreds and hybrids, significant genotypic variation was found for nearly all recorded traits. In the diallel analysis, the GCA effects generally proved to be highly significant and in most cases considerably higher than the SCA effects. In the pot experiment, grain yield ranking of the parental lines at the high P level (= P700) was very similar to that in the field experiment, whereas at the low P level (= P100, – P deficiency) the ranking of the lines changed considerably. Correspondingly, the P level-line interaction was highly significant. High tolerance towards P deficiency was found for those two parental inbreds derived from cultivars bred under Syrian conditions. At the high P supply, P efficiency was more favoured by a high P uptake, but at P deficiency by a high internal P utilization.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    BBA - Enzymological Subjects 81 (1964), S. 435-441 
    ISSN: 0926-6569
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Section 41 (1985), S. 37-41 
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 7 (1983), S. 322-330 
    ISSN: 0275-1062
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline (LC) block copolymers comprising polystyrene and LC polyester blocks were obtained by a three-step procedure. In a first step, hydroxyl-terminated oligoesters were obtained by polycondensation reaction of methylhydroquinone and 4,4′-dicarboxy-1, 10-dibenzoyloxydecane in pyridine solution in the presence of tosyl chloride and dimethylformamide. Hydroxyl-terminated oligoesters were then further polymerized with 4,4′-azo-bis(4-cyanopentanoyl chloride) to form azo-macroinitiators which, in a third step, were employed in the free-radical polymerization of styrene to form block copolymers. The thermal and LC properties of the copolymers are presented and discussed in terms of the dependence upon the molecular weight of the polystyrene block.
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  • 9
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Ein 24jähriger Mann klagte seit drei Monaten über unklares abdominelles Völlegefühl und einen dumpfen, leicht epigastrischen Schmerz. Zwei Monate vor Aufnahme war in einem klinischen Zentrum ein Pankreaskopftumor festgestellt worden. Sonographisch, durch endoskopische retrograde Cholangiopankreatographie und Computertomographie des Abdomens wurde der Pankreaskopftumor bestätigt. Wegen des hochgradigen Verdachtes auf Pankreaskopfkarzinom wurde eine Laparotomie vorgenommen. Dabei fand sich im Pankreaskopf eine indurierte Masse, vergrößerte Lymphknoten und weiße Tuberkel auf dem Darm. Die histologische Untersuchung bestätigte das Vorliegen tuberkulöser Granulome. Säurefeste Stäbchen konnten histologisch ebenfalls nachgewiesen werden. Der Patient wurde mit Tuberkulostatika behandelt und ist jetzt in guter Verfassung. Um unnötige Laparotomien zu vermeiden, sollte bei Patienten mit Pankreastumor eine computertomographisch oder sonographisch kontrollierte Aspirationsbiopsie mit zytologischer oder histologischer Untersuchung durchgeführt und auch kulturell der Nachweis von Mykobakterien versucht werden. Dies gilt vor allem für Regionen, in denen die Lungentuberkulose und abdominelle Tuberkulosen keine Seltenheit darstellen.
    Notes: Summary A 24-year-old man presented with vague abdominal fullness and a mild epigastric dull pain for about 3 months was found to have a pancreatic head tumor at a medical center 2 months ago. He came to our hospital for further treatment. Ultrasonography, endoscopic retrograde cholangiopancreatography (ERCP) and abdominal computed tomography (CT) all revealede a pancreatic head tumor. Laparotomy was performed because pancreatic head carcinoma was highly suspected. Indurated mass in the pancreatic head, enlarged lymph nodes and white tubercles on the intestine proved to be tuberculosis on histological examination of a frozen section. Acid fast bacilli were also found. The patient was given antituberculous therapy and is now doing well. To avoid unnecessary laparotomy, CT, echo-guided percutaneous aspiration cytology or biopsy and culture of the tissue for mycobacteria should be done in a patient with pancreatic mass, especially in a region where pulmonary and abdominal tuberculosis are common.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 250 (1993), S. 245-248 
    ISSN: 1434-4726
    Keywords: Cocaine ; Human nasal mucosa ; Sympathetic functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of cocaine on the contractile response of isolated human nasal mucosal blood vessels to field stimulation and methoxamine were investigated. Results showed that cocaine antagonized methoxamine and inhibited field stimulation. The drug increased resting tension in human nasal mucosa in vitro through direct actions and potentiated mucosal contractions by norepinephrine and epinephrine. The study indicated that high concentrations of cocaine may actually antagonize α-adrenoceptors, but these concentrations are not necessary in eliciting desired degrees of vasoconstriction in nasal blood vessels while being applied as a local anesthetic.
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