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  • Wiley-Blackwell  (7)
  • American Institute of Physics (AIP)  (6)
  • EMBO Press  (6)
  • 2005-2009  (1)
  • 1995-1999  (9)
  • 1990-1994  (7)
  • 1985-1989  (2)
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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Rutherford scattering diagnostic has been applied at the TEXTOR tokamak to obtain spatially and temporally resolved information on the temperature of the bulk ions in the plasma. In the experimental setup, a helium atomic beam (30-keV, 12-mA equivalent current) passes vertically through the plasma core. A small part of the injected atoms is scattered elastically by the thermally moving plasma ions. The ion temperature in the scattering volume can be determined from the broadening of the energy spectrum of the scattered particles. Energy analysis of the scattered atoms is performed by a mass-selective time-of-flight analyzer detecting the particles at an observation angle which is selectable between 3° and 8°. Coincidence techniques have been successfully applied in this detector for rejection of background events triggered by detections of neutrons and gamma radiation. Ion temperature profiles were measured on a shot-to-shot basis by shifting the cross section of the diagnostic beam and the observational volume of the analyzer through the plasma. The ion temperatures measured in ohmic deuterium plasmas were found to be in reasonable agreement with those obtained from passive neutral particle analysis. Up to now, ion temperatures have been measured throughout the complete discharge with an accuracy of 8% and a time and space resolution of 100 ms and 0.10 m at a scattering angle of 7°. Deuteron density profiles could be deduced from the scattering yield measured at different radial positions in the plasma. The ratio of the isotopes, hydrogen and deuterium, was determined from their separate contributions to the spectrum of helium particles scattered on hydrogen and deuterium. Although theoretical predictions showed that the majority of the probing helium atoms loses one of its electrons during the elastic scattering process on multiply charged carbon and oxygen ions, contributions from impurities to the observed experimental spectrum are shown to appear dominant for impure plasmas.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3310-3319 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the fabrication and operating principles of a device suitable for measuring displacements, stresses, strains, accelerations, and forces. The device consists of an elastomeric material with a surface relief diffraction grating embossed on its surface. Mechanical compression of this element changes the way that it diffracts light. This article also describes designs and performance characteristics of simple accelerometers and pressure sensors based on these devices. © 1996 American Institute of Physics.
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Rutherford scattering diagnostic at TEXTOR has been used to investigate the time evolution of the ion velocity distribution during sawtooth activity. Coherent averaging techniques have been employed to obtain better statistics. The time evolutions of central ion and electron density were found to be strongly correlated in four out of five cases. In one case, where saturation of the sawteeth occurred, a discrepancy between the two has been found, which could be attributed to an influx of impurities towards the end of the sawtooth. Changes of about 20% in the central toroidal rotation of the bulk ions have been found during sawtooth crashes of neutral beam injected discharges, whereas no changes were found in the ohmic case. No statistically reliable statements can be made about changes in the ion temperature. © 1995 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4439-4447 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new 20-channel electron cyclotron absorption diagnostic has been developed at the Rijnhuizen tokamak project. It is the first time the electron pressure profile in a tokamak plasma can be measured directly with a time resolution of 1 ms. The diagnostic measures simultaneously the emission and absorption of the second harmonic electron cyclotron frequencies. Microwaves are injected from the high field side and detected at the low field side in the equatorial midplane. The transmitted power is measured after a single pass through the plasma column. The absorption measurements are complicated by nonresonant losses: refraction of the injected microwaves (losses up to 100%), and scattering of microwaves by density fluctuations (losses 2%–3%). A fast algorithm has been developed to obtain a quantitative measure for these nonresonant losses. This calculation method is based on a parametrization of the experimental data. Combining the electron cyclotron absorption (ECA) measurements and the parametrization provides a reliable tool for determining the optical depth, the electron temperature, and the electron pressure. A good agreement was found between pressure and temperature profiles, measured with ECA and other diagnostics. © 1997 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4583-4585 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Rutherford scattering diagnostic at TEXTOR is used to perform temporal and spatial resolved measurements of the ion temperature. Function parametrization techniques are used for fast analysis of the complex spectra, which also contain information about the presence of impurities in the scattering volume. The (perpendicular) central ion temperature has been determined for a series of discharges, where neutral beam coinjection (hydrogen) was applied to plasmas of different densities. A temperature of 2.8 keV was found for a line-averaged electron density of 1.5×1019 m−3, decreasing monotonically for higher densities to 0.8 keV at 6.0×1019 m−3. When deuterium was used as heating beam species, scattering on a high-Z impurity, probably tungsten from the filaments of the NBI sources, gave a dominant contribution to the spectra.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2016-2024 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present and discuss experimental results on molecular mobility in propylene glycol and its three oligomers confined to the ∼100 A(ring) pores of a controlled porous glass. The objective is to elucidate the finite size effects on the dynamics of hydrogen-bonded liquids of different molecular weights but identical chemical composition. The methods of dielectric and neutron spectroscopy have been employed to investigate both the low- and high-frequency features as a function of temperature. We find that all fluids in pores separate into two distinct liquid phases. (i) molecules physisorbed at the surface which exhibit a dramatic frustration of their mobility related to a substantial positive shift of the glass transition temperature Tg by up to ΔTg≈+47 K; and (ii) relatively "free'' molecules in the inner pore space subject to only moderate retardation of the α and normal mode relaxation and substantial broadening of the distribution of relaxation times. The shift in Tg for the α process with ΔTg≈+5 K is maximal for the monomer liquid and gradually diminishes with increasing molecular weight or decreasing intermolecular hydrogen bonding. The inelastic neutron spectrum of confined propylene glycol shows the boson peak as expected in bulk strong and intermediate glass formers in the vicinity of Tg. This effect can be attributed to the finite-size induced crossover from long wave vibrations characteristic of a continuous medium to localized vibrations in a confined geometry. © 1995 American Institute of Physics.
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  • 7
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
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  • 8
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A specific and sensitive gas chromatographic/mass spectrometric method was developed and validated for the determination of the antidepressant levoprotiline in blood, plasma and urine and the simultaneous determination of levoprotiline and its desmethyl metabolite in urine. Deuterium-labelled analogues were used as internal standards. The compounds were isolated from the biological fluids by liquid-liquid extraction under basic conditions. Following derivatization with perfluoropropionic anhydride, the samples were analysed by capillary column gas chroma-tography/electron impact mass spectrometry with selected ion monitoring. The analysis of spiked samples demonstrated the high accuracy and precision of the method. Blood concentrations of levoprotiline down to 0.7 nmol I-1 (1 ml used for analysis) could be quantified with a coefficient of variation of 10% or less. The method is suitable for use in pharmacokinetic and bioavailability studies of levoprotiline in humans.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 249-258 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units of Oligosaccharides, LXXVIII. - Synthesis of KDO-Containing Lipid A AnaloguesThe non-neighbouring group supported glycosidation of 12 with the suitably protected glycosyl bromide 9 of 2-azido-2-deoxy-D-glucose leads - in the presence of a heterogeneous silver catalyst - to the formation of the β-(1→6)-glycosidically linked disaccharide 14. It consists of two 2-azido-2-deoxy-D-glucose units. Partial deblocking of 14 furnishes 15. On glycosidation with KDO bromide this compound yields the trisaccharide 16, which contains a KDO unit in an α-(2→6) ketosidic bond. Reduction of the two azido groups followed by amidation with (R)-3-hydroxymyristic acid and further deblocking generates the trisaccharide α-KDO-(2→6)-β-D-GlcA-(1→6)-D-GlcA 20 with two 3-hydroxy fatty acid residues in an amidic linkage.
    Notes: Die Umsetzung des Pyranosylbromids 9 der 2-Azido-2-desoxy-D-glucose mit dem Akzeptor 12 führt bei Gegenwart eines heterogenen Silberkatalysators ohne Nachbargruppenbeteiligung unter Inversion zum β-(1→6)-glycosidisch verknüpften Disaccharid 14 aus zwei 2-Azido-2-desoxy-D-glucose-Einheiten. Nach partieller Entblockierung zu 15 ist die Anknüpfung eines KDO-Restes unter Bildung einer α-(2→6)-ketosidischen Bindung zum Trisaccharid 16 möglich. Nach Reduktion der Azidogruppen und Anknüpfung von (R)-3-Hydroxymyristinsäure-Resten gelangt man nach Entblockierung zum Trisaccharid α-KDO-(2→6)-β-D-GlcA-(1→6)-D-GlcA 20, das amidartig zwei 3-Hydroxyfettsäure-Reste gebunden enthält.
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  • 10
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Branched and Chain-extended Sugars, XXX.  -  Diastereoselective Synthesis of L-glycero-D-manno-Heptose, a Constituent of the Inner Core Region of LipopolysaccharidesReaction of 2,3;5,6-di-O-isopropylidene-D-mannofuranose (1) with 2-lithio-1,3-dithiane affords diastereoselectively the 3,4;6,7-di-O-isopropylidene-D-glycero-D-galacto-heptose trimethylene dithioacetal (3). Conversion of compound 3 by a sequence of steps gives the tri-O-isopropylidene-D-glycero-D-galacto-heptit 16 which is oxidized with 1,1′-(azodicarbonyl)-dipiperidine to give the tri-O-isopropylidene-L-glycero-D-manno-heptose 17. Finally, compound 17 is transferred via the acetate 19 into the L-glycero-D-manno-heptopyranose 18.
    Notes: 2,3;5,6-Di-O-isopropyliden-D-mannofuranose (1) reagiert diastereoselektiv mit 2-Lithio-1,3-dithian zum 3,4;6,7-Di-O-isopropyliden-D-glycero-D-galacto-heptose-trimethylendithioacetal (3). Nach Umwandlung von 3 über eine Reihe von Zwischenstufen zum Tri-O-isopropyliden-D-glycero-D-galacto-heptit 16 läßt sich dieser mit 1,1′-(Azodicarbonyl)dipiperidin zur Tri-O-isopropyliden-L-glycero-D-manno-heptose 17 oxidieren. Hieraus ist über das Acetat 19 die freie L-glycero-D-manno-heptopyranose 18 zu gewinnen.
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