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  • 1990-1994  (6)
  • 1970-1974
  • 1935-1939
  • 1991  (6)
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  • 1990-1994  (6)
  • 1970-1974
  • 1935-1939
Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 46 (1991), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Accidental cannulation of an extradural vein is a troublesome and potentially serious complication of extradural catheter insertion. This study was conducted to assess the influence of posture, catheter size and the injection of saline before catheter insertion, on its occurrence. Eight different techniques were studied based on combinations of these three factors. There was no difference in incidence with respect to posture. The use of 18-gauge catheters, after injection of 10 ml of 0.9% saline, resulted in a significant (p 〈 0.01) reduction in the incidence of extradural vein cannulation. This technique is recommended in obstetric patients as a means of avoiding accidental intravenous injection of local analgesic.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 27 (1991), S. 129-140 
    ISSN: 1573-0867
    Keywords: Douglas-fir ; nitrogen ; mineral cycling ; growth and yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Forest managers in the Pacific Northwest (PNW) use fertilization as a means to increase timber yields in managed stands. Information on the biological basis for nutrient amendments and stand growth responses to fertilization is required to effectively use fertilization as a silvicultural tool, and research programs in mineral cycling and forest nutrition have been underway in the region for about four decades. Most PNW Douglas-fir forest sites are nitrogen deficient. Mineral cycling research has shown high C/N ratios and low nitrification rates for soils in the region. Research and development projects in the Pacific Northwest have produced an information base that is used to select sites and stands for fertilization and to forecast growth after treatment. Much of the basis for operational fertilization programs in western Oregon and Washington comes from cooperative research programs; current activities for these programs are directed toward improving site-specific response information. Forest fertilization in the Pacific Northwest has become a silvicultural practice of major significance over the past two decades. Forest industry and government organizations managing forest lands in western Oregon and Washington apply nitrogen fertilizer to Douglas-fir stands over a range of soil and stand types (operational fertilization of other species is minor). About 50,000 to 55,000 ha are fertilized each year, and future programs will likely be of similar magnitude. Most current plans for management regimes including fertilization call for multiple applications.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 313-315 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The quasar 3C48 was one of four sources observed during a series of very long baseline interferometer (VLBI) observations at 1.6 GHz in April 1984. Seventeen telescopes in Europe, the Soviet Union and North America contributed to the observations (see refs 4, 5 for a description of the telescopes ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Re — Os isotopic systematics of komatiites and spatially associated basalts from Gorgona Island, Colombia, indicate that they were produced at 155±43 Ma. Subsequent episodes of volcanism produced basalts at 88.1±3.8 Ma and picritic and basaltic lavas at ca. 58 Ma. The age for the ultramafic rocks is important because it coincides with the late-Jurassic, early-Cretaceous disassembly of Pangea, when the North- and South-American plates began to pull apart. Deep-seated mantle upwelling possibly precipitated the break-up of these continental plates and caused a tear in the subducting slab west of Gorgona, providing a rare, late-Phanerozoic conduit for the komatiitic melts. Mantle sources for the komatiites were heterogeneous with respect to Os and Pb isotopic compositions, but had homogeneous Nd isotopic compositions (εNd+9±1). Initial 187Os/186Os normalized to carbonaceous chondrites at 155 Ma (γOs) ranged from 0 to +22, and model-initial μ values ranged from 8.17 to 8.39. The excess radiogenic Os, compared with an assumed bulk-mantle evolution similar to carbonaceous chondrites, was likely produced in portions of the mantle with long-term elevated Re concentrations. The Os, Pb and Nd isotopic compositions, together with major-element constraints, suggest that the sources of the komatiites were enriched more than 1 Ga ago by low (〈20%) and variable amounts of a basalt or komatiite component. This component was added as either subducted oceanic crust or melt derived from greater depths in the mantle. These results suggest that the Re — Os isotope system may be a highly sensitive indicator of the presence of ancient subducted oceanic crust in mantle-source regions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 64 (1991), S. 463-468 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract It is observed that animals often have to resolve difficult tasks of optimization and that this process can be studied by applying the formal framework of neural networks to a simple problem such as the Travelling Salesman Problem. Existing work is reviewed with particular emphasis on recent studies using “self-organizing networks”. An algorithm is described in which general principles developed by Kohonen are applied to the Travelling Salesman Problem. Simulation results are given for problem sets of up to 10,000 cities. The routes generated are reported as being slightly longer than those produced by simulating annealing; compute time is lower and scales less than quadratically with problem size. It is suggested that the ability to perform optimization is an emergent computational property not just of the Kohonen model but of any mechanism capable of producing topology-preserving mappings, including mechanisms within the brain.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2568
    Keywords: duodenal ulcer ; healing ; ranitidine ; antacids ; smoking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The efficacy of ranitidine 150 mg twice daily and Maalox TC three tablets four times daily were compared in patients with endoscopically confirmed duodenal ulcer. Seventy-nine patients were randomly allocated to double-blind, double-dummy treatment, stratified for smokers. Endoscopy was repeated after four weeks. Those unhealed continued treatment for a further two weeks before final endoscopy. Per protocol analysis in 53 patients showed ulcer healing rates at week 4 and at weeks 4 and 6 combined of 78 and 89% on Maalox TC, and of 81 and 91% on ranitidine, respectively. The same analysis gave overall healing rates of 81% in smokers and 100% in nonsmokers, irrespective of treatment. Both treatments provided early ulcer pain relief. Diarrhea was a commoner side effect in patients on Maalox TC. The study showed Maalox TC and ranitidine were equally effective in healing duodenal ulceration.
    Type of Medium: Electronic Resource
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