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  • 1
    Electronic Resource
    Electronic Resource
    The utilization of DSC in studies of oligomers (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3591-3595 
    Details
    ISSN: 0021-8995
    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
    Notes: Oligomers are potentially useful as well characterized models for studying the chemical and physical properties of their long chain homologues. These model compounds are often available only as mixtures which must be separated. This separation may be accomplished using chromatographic techniques, i.e., GPC. Polydispersity (Mw/Mn) is often used as a criteria for the extent to which separation has been achieved. Values of polydispersity of 1.01-1.03 are considered indicative of very narrow fractions in the high polymer area. A purpose of this paper is to show that such low values of polydispersity are misleading when applied to oligomers containing 2-20 repeat units. Further, the existence of a single “sharp” melting endotherm is not necessarily proof that one has separated out a single molecular weight component. An intimate mixture of different molecular weight oligomers can give a single narrow endotherm.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270933
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of extracolumn effects in recycle gas chromatography with capillary columns (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 783-787 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Recycle GC ; Peak distortion ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extracolumn band broadening in multidimensional systems utilizing flow switching is clearly undesirable. In certain cases, i.e. capillary recycle gas chromatography, the success of an experiment is contingent on the minimization of pre- and post-column dispersion of the peaks. Knowledge of these sources of peak distortion is necessary to optimize the experimental design. A system that extracts statistical parameters from real chromatographic peaks is discussed and used to evaluate band broadening in a capillary recycle experiment.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240111107
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  • 3
    Electronic Resource
    Electronic Resource
    Enhancing the LC analysis of nicotine and its metabolites in urine using meldrums acid as a complexing agent (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 74-77 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; Nicotine and metabolites ; Complexation with Meldrums acid ; Urine analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130118
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  • 4
    Electronic Resource
    Electronic Resource
    Use of computerized pattern recognition in the analysis of stress induced changes in coffee aroma (1987)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 244-247 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Coffee aroma ; Pattern recognition ; Gas phase extraction ; Mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of the study was to evaluate changes in the aroma of coffee that has been exposed to heat for some time. Coffee grinds were extracted with water. The coffee was kept hot and sampled periodically using a continuous gas phase extraction method. Gas chromatography/mass spectrometry was used to follow changes in chromatographic profiles. Data were subjected to pattern recognition. About 20 substances were found that significantly changed when exposed to heat.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240100507
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  • 5
    Electronic Resource
    Electronic Resource
    Plane strain fracture toughness of polyethylene pipe materials (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 404-411 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: The plane strain fracture toughness of medium density polyethylene pipe materials has been investigated over a range of test temperatures and rates. Conditions are defined under which valid fracture toughness values can be obtained; at higher temperatures the material is notch-insensitive. Fracture surface morphology is described, and features are compared with predictions from the Dugdale model. The toughness derives from a band of fibrillar, drawn morphology associated with crack initiation or slow growth. The plane strain fracture toughness correlates with percent crystallinity according to the same relationship whether the crystallinity is varied by thermal treatment, comonomer content, or molecular weight.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760230707
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  • 6
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    Quasi-periodic transverse plasma flow associated with an evolving MHD vortex street in the outer heliosphere (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We study a transverse plasma flow induced by the evolution of a Karman vortex street using a Chebyshev-Fourier spectral algorithm to solve both the compressible Navier-Stokes and MHD equations. The evolving vortex street is formed by the nonlinear interaction of two vortex sheets initially in equilibrium. We study spatial profiles of the total plasma velocity, the density, the meridional flow angle and the location of sector boundaries and find generally good agreement with Voyager 2 measurements of quasi-periodic transverse flow in the outer heliosphere. The pressure pulses associated with the meridional flows in the simulation are too small, although they are correctly located, and this may be due to the lack of any 'warp' in the current sheet in this model. A strong, flow-aligned magnetic field, such as would occur in the inner heliosphere, is shown to lead to weak effects that would be masked by the background interplanetary turbulence. We also study the plasma and magnetic transport resulting from the meridional flow and find that deficits of magnetic quantities do occur near the ecliptic. While the effect is relatively small, it is in general agreement with the most recent analysis of 'flux deficit' in the outer heliosphere.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A8; p. 13,233-13,246.
    Format: text
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  • 7
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    The structure of helical interplanetary magnetic fields (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The interplanetary magnetic field is known to be highly helical. Although the detailed spatial structure of the fields has yet to be elucidated, the helicity spectrum has been conjectured to result from a random walk in the direction of a constant magnitude magnetic field vector. A model using three-dimensional fluctuations with variations in B is demonstrated giving a good fit to the helicity spectrum as well as to other properties of the interplanetary magnetic field.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 1505-150
    Format: text
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  • 8
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    Spectral signatures of jumps and turbulence in interplanetary speed and magnetic field data (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: It is shown here that, consistent with a suggestion of Burlaga and Mish (1987), the f exp -2 spectra in the magnitudes of the magnetic and velocity fields in the solar wind result from jumps due to various rapid changes in the time series for these quantities. If these jumps are removed from the data, the spectra of the resulting 'difference' time series have the f exp -5/3 form. It is concluded that f exp -2 spectra in these magnitudes arise from phase coherent structures that can be distinguished clearly from incoherent turbulent fluctuations.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 10
    Format: text
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  • 9
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    Numerical simulation of the generation of turbulence from cometary ion pick-up (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Observations of magnetic field fluctuations near Comet Halley have revealed a rapid development of a Kolmogoroff-like turbulence spectrum extending from below 0.01 Hz to above 0.1 Hz. Spectra obtained far from the comet have a strong peak in power near the Doppler-shifted ion-cyclotron frequency of singly ionized water. Closer to the comet, the spectrum at higher frequencies is enhanced in power level over the background solar wind spectrum by approximately an order of magnitude. The equations of incompressible MHD are solved using a two-dimensional 256 x 256 mode spectral method code to simulate this spectral evolution as an inertial range turbulent cascade. The initial conditions contained a constant magnetic field and a single coherent wave mode at a low wave number. The solar wind turbulence was modeled by a background noise spectrum having a Kolmogoroff spectral index. The coherent mode decayed into an inertial range spectrum with Kolmogoroff slope within a few eddy-turnover times. Both the time scale and the increase in power level of the turbulence seen in the simulation are in accord with the Giotto observations.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 14; 860-863
    Format: text
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  • 10
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    The evolution of space mechanisms in the ESA R and D program (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The status of recently completed and already ongoing technology developments, as well as some of the most important future developments of the European Space Agency are discussed. Among the subjects considered are Scientific Satellites, Columbus space station development, applications spacecraft for communications, Earth observation and meteorology, and the Ariane V and Hermes space transportation systems.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA, Marshall Space Flight Center, The 23rd Aerospace Mechanisms Symposiums; p 1-16
    Format: application/pdf
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