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  • 1
    Electronic Resource
    Electronic Resource
    Assessment of renal artery stenosis by phase-contrast magnetic resonance angiography (1993)
    Springer
    European radiology 3 (1993), S. 493-498 
    Details
    ISSN: 1432-1084
    Keywords: Renal artery obstruction ; Magnetic resonance ; Blood flow velocity ; Hypertension, renal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three-dimensional (3D) phase-contrast magnetic resonance angiography (MRA) and velocity-encoded cine magnetic resonance (VEC-MR) imaging were performed in 23 subjects to assess the severity of renal artery stenosis. MRA was used for detection of stenosis, demonstrating a sensitivity of 100% and a specificity of 80%; the severity of stenosis was overestimated in 33%. VEC-MR was used to quantify the renal flow oattern and was successful in 11 subjects. Mean blood flow of normal renal arteries (420 +- 107 ml/min) was significantly higher (P 〈 0.01) than mean blood flow of stenotic arteries (131 +- 46ml/min). The flow profile displayed both systolic and diastolic peaks in 75% of the normal arteries, while the flow in stenotic arteries showed only a single systolic peak in all cases. The systolic peak in stenotic arteries occurred significantly later (32 +- 3% of the period of one cardiac cycle) than in normal subjects (21 +- 7%) (P 〈 0.05). Phase-contrast MR is likely to gain considerable importance in the noninvasive aetection and quantification of renal artery stenosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169596
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  • 2
    Electronic Resource
    Electronic Resource
    The Northeast Water polynya, Greenland Sea (1994)
    Springer
    Polar biology 14 (1994), S. 491-503 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During a pilot study in June 1991 meso-and macrozooplankton investigations were carried out in the region of the Northeast Water (NEW), a polynya located off Northeast Greenland at about 80°N. The mesozooplankton collected by bongo net was dominated by the large herbivorous copepods Calanus glacialis, C. hyperboreus and C. finmarchicus. At most stations the Calanus populations consisted of overwintering stages, except for an ice-free site in the northwestern corner of the study area, where young copepodids of C. hyperboreus and C. glacialis occurred. Young C. finmarchicus were only found at stations influenced by Atlantic water masses, whereas C. glacialis was the prevailing species on the East Greenland shelf. Egg production of this species was variable, but spawning activity appeared to be related to ambient chlorophyll a concentrations. Carbon requirements of herbivorous Zooplankton were estimated from egg production rates of C. glacialis. Due to low mesoplankton biomass, a mean of only 10% (ranging from 〈1% to 53%) of the phytoplankton carbon were grazed. Macrozooplankton was collected at three stations by a Rectangular Midwater Trawl (RMT 1+8). Major components were chaetognaths, hyperiid amphipods and large copepods. Macroplankton biomass was extremely low (1–3 mg AFDW m−3), about one order of magnitude less than that of the mesoplankton. Based on these limited data we hypothesize that macroplankton plays only a minor role as food for higher trophic levels and as predators controlling mesoplankton in the NEW polynya. These findings seem todisprove the concept of a rich pelagic community in the polynya amongst “a desert of ice”. They do, however, fit well with the notion of strong pelago-benthic coupling of primary production supporting a rich benthos within the polynya area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239054
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  • 3
    Electronic Resource
    Electronic Resource
    On a class of hybrid methods for smooth constrained optimization (1992)
    Springer
    Journal of optimization theory and applications 73 (1992), S. 465-499 
    Details
    ISSN: 1573-2878
    Keywords: Nonlinear programming algorithms ; locally superlinearly convergent methods ; globally convergent methods ; hybrid techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract With reference to smooth nonlinearly constrained optimization problems, we consider combinations of locally superlinearly convergent methods with globally convergent ones. The aim of this paper is threefold: to give a survey on well-known as well as possible unknown hybrid optimization methods, based on a special construction principle; to present a general convergence result for the class of hybrid algorithms; and to derive further methods for this class with new convergence properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940052
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  • 4
    Electronic Resource
    Electronic Resource
    Polarisation effects in electron transfer reactions with laser excited Na(3P) at medium energies (1994)
    Springer
    The European physical journal 30 (1994), S. 211-215 
    Details
    ISSN: 1434-6079
    Keywords: 34.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report new experimental data for the investigation of the role of electronic orbital alignment and orientation in charge transfer processes, in the medium energy range where the collision velocityv c and the velocity of the active electronv e are of the same order of magnitude. The results obtained for the H 2 + -Na(3p) and He+-Na(3p) collisions are discussed in comparison with the experimental and theoretical findings obtained for the H+-Na(3p) system. Recent time-of-flight measurements for charge transfer in Li+-Na(3s and 3p) collisions are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426075
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  • 5
    Electronic Resource
    Electronic Resource
    Collision spectroscopy with aligned and oriented atoms (1991)
    Springer
    The European physical journal 18 (1991), S. 231-234 
    Details
    ISSN: 1434-6079
    Keywords: 34.00 ; 34.70 ; 32.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neutralisation processes in 0.15–1.5 keV collisions of H− with Na atoms in the 3s ground state or in the excited 3p state have been investigated by means of time-of-flight analysis of the neutral H atoms produced. The H− - Na(3p) system, investigated here for the first time, is particularly interesting since the entrance channel is embedded in the [H - Na(3s)] +e − continuum, enabling Penning detachment to occur. The measured relative neutralisation cross section ratios σ(3p)/σ(3s) decrease from 3 to 1.6 with increasing energy. Based on earlier published results for σ(3s), σ(3p) total cross sections exceeding 100 Å2 are estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437076
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  • 6
    Electronic Resource
    Electronic Resource
    Surface roughening during depth profiling by Secondary Ion Mass Spectrometry (SIMS) in GaAlAs and GaAs (1991)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 341 (1991), S. 31-34 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary During bombardment of Ga1−xAlxAs and GaAs with oxygen we found an abrupt transition to higher sputter rates, change of the useful yield and significant increase of surface roughness at a well defined depth, which is essentially deeper than the penetration depth of the primary ions. Using oxygen and cesium as primary ions ‘varying’ energy and angle of incidence, residual gas pressure and matrix composition their effects on the phenomena were investigated. Although some remarkable properties of the sample modification process could be found, no theoretical description can be given up to now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00322102
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  • 7
    Electronic Resource
    Electronic Resource
    Zur Regioselektivität der Umsetzung von Methallylisothiocyanat mit monosubstituierten HydrazinenHerrn Professor Dr. Rolf Borsdorf zum 60. Geburtstag gewidmet (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 60-66 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regioselectivity of the Reaction of Methallyl Isothiocyanate with Monosubstituted HydrazinesMethallyl isothiocyanate 1 reacts with substituted aryl hydrazines to 1,4- respectively 2,4-disubstituted thiosemicarbazides 4 and 5 in dependence on the reaction conditions and the nature of the aryl group. The influence of the substituents is discussed. The novel N′-mono- and disubstituted N-methallylic thioureas 2 and 3 are synthesized.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340111
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  • 8
    Electronic Resource
    Electronic Resource
    Synthese von 2-aminosubstituierten 4,5-Dihydro-1,3-thiazolenHerrn Professor Dr. E. Hoyer zum 60. Geburtstag gewidmet (1991)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 333 (1991), S. 407-412 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 2-Amino-Substituted 4,5-Dihydro-1,3-thiazoles.The reaction of 2-substituted 4-methallylthiosemicarbazides 1 with carbonyl compounds catalyzed by weak acids gives thiosemicarbazones 2 and 1,2,4-triazolidine-3-thiones 3. By contrast under strong acidic conditions the reaction occurs by electrophilic cyclisation with participation of the methallyl and thiono groups, and 4,5-dihydro-1,3-thiazoles 5 are formed after neutralisation. The electrophilic cyclisation of N-methallyl substituted thioureas 6 and 1,4-disubstituted thiosemicarbazides 7 is also described.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19913330305
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