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  • 1990-1994  (3)
  • 1965-1969
  • 1991  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2438-2440 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a two-step anisotropic etching process to fabricate thin silicon membranes, used to study supercurrent transport in semiconductor coupled weak links. The process uses a shallow BF+2 implantation, and permits easy control of membrane thickness ≤100 nm. Preliminary measurements on membrane-based Nb-Si-Nb junctions reveal the simultaneous occurrence of tunnel behavior and Josephson coupling.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 238 (1991), S. S28 
    ISSN: 1432-1459
    Keywords: Antimigraine drugs ; Migraine ; Pathophysiology ; Pharmacology ; Prophylaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The drugs used in migraine therapy can be divided into two groups: agents that abort an established migraine attack and agents used prophylactically to reduce the number of migraine attacks. Both groups have drugs that are specific for migrainous headaches and that are non-specific, and are used to treat the accompanying headache (analgesics), vomiting (anti-emetics), anxiety (sedatives and anxiolytics), or depression (antidepressants). The main drugs with specific action on migraine include ergot alkaloids (ergotamine, dihydroergotamine), agonists (sumatriptan) or partial agonists (methysergide) at a specific subtype of 5-HT1-like receptors, β-adrenoceptor antagonists (propranolol, metoprolol), calcium antagonists (flunarizine) and anti-inflammatory agents (indomethacin). The pharmacological basis of therapeutic action of several of these drugs is not well understood. In the case of the ergot alkaloids and 5-HT1-like receptor agonists, however, it is likely that the antimigraine effect is related to the potent and rather selective constriction of the large arteries and arteriovenous anastomoses in the scalp and dural regions. In addition, these drugs inhibit plasma extravasation into the dura in response to trigeminal ganglion stimulation, but it is possible that this effect is related to the selective vasoconstriction in the extracerebral vascular bed. The selectivity of the pharmacological effects of these antimigraine drugs (constriction of the extracerebral arteries and arteriovenous anastomoses, poor penetration into the central nervous system and the absence of an antinociceptive effect even after intrathecal administration) strongly suggests that excessive dilatation in the extracerebral cranial vasculature, probably initiated by a neuronal event, is an integral part of the pathophysiology of migraine.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-879X
    Keywords: Spreading ; dehydration ; molybdenum oxide ; silica ; EXAFS ; Raman spectroscopy ; preparation ; clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In contrast to the frequently reported lack of interaction between hexavalent molybdenum and SiO2 and the tendency of silica-supported MoO3 to coalescence, it has been found that on dehydration small molybdenum oxide clusters spread over a silica support. A combined Raman spectroscopy-X-ray absorption study shows a significantly altered structure of the molybdenum oxide phase after dehydration. In EXAFS the total Mo-Mo coordination number drops from 3.27 to 0.20 after anin situ thermal treatment at 673 K. The increase of the peak in the XANES region (Is -→ 4d) indicates that the coordination sphere of the molybdenum atoms strongly alters after dehydration. The Raman spectra reflect the change of the structure through a shift of the position of the terminal Mo=O bond from 944 to 986 cm−1 and the disappearance of the bridged Mo-O-Mo vibration at 880 cm−1. It is concluded that dehydration produces almost isolated molybdenum sites in this highly dispersed sample. Water ligands stabilize the oligomeric clusters under ambient conditions; the removal of water causes spreading of these clusters.
    Type of Medium: Electronic Resource
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