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  • Polymer and Materials Science  (27)
  • Computational Chemistry and Molecular Modeling  (6)
  • Solar Physics  (4)
  • Capillary electrochromatography
  • 1995-1999  (40)
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Year
  • 1
    Publication Date: 2011-08-24
    Description: We characterize the dynamic properties of He ions of the solar wind. Because of the non-negligible abundance and the significant fraction of momentum flux inherent in helium ions, this species has an influence on the state of turbulence. Especially, we analyze the helium dynamic properties of different solar wind types. After a discussion of the influence of measurement errors on the statistical analysis of He bulk velocities, we investigate the structure function dependency on the solar wind state. We find a self-similar sealing in the range of minutes to days with characteristic structure function slopes deviating from the canonical Kolmogorov values. For comparison with previous studies, we also analyze H structure functions of the same time periods and discuss differences of coinciding He and H structure functions in the framework of the concept of intermittency.
    Keywords: Solar Physics
    Type: International Solar Wind 8 Conference; 73; NASA-CR-199940
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  • 2
    Publication Date: 2019-07-17
    Description: We perform a parameter study of the temporal evolution of a test particle distribution function in MHD turbulence. The turbulent fields are calculated using a pseudo-spectral method and periodic boundary conditions on a regular grid of 180(exp 3) points, appropriate for incompressible, homogeneous and isotropic turbulence. Initially, the kinetic and the magnetic energy are equal on the average. Both, deterministic and random initial conditions are used, in the former case with zeros of the magnetic field located at grid points, in the latter case located by interpolation between grid points. The evolution of the minor ion distribution function is studied in detail as these turbulent fields evolve, developing strong current and vorticity sheets. Using the full collisionless equation of motion for the test particles, the efficiency of nonlinear interactions can be studied. The results are compared to theoretical predictions and are then discussed in connection with the observations of the dynamical properties of solar wind minor ions derived from in situ observations.
    Keywords: Solar Physics
    Type: ; 82
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  • 3
    Publication Date: 2019-07-17
    Description: We have investigated small-scale variations of the solar wind ion flux measured with Faraday cups onboard the Prognoz-8 satellite. These measurements have a high time resolution of 1.24 seconds for intervals with a duration of several hours and as high as 0.02 seconds for some periods of about 1 hour duration. The main goal of this work is the determination of the quantitative features of fast ion flux fluctuations using mainly spectral analysis but also other methods. We also identify their association with interplanetary plasma parameters. Particularly, it is shown that the slope of the power spectra in the frequency range from 1E-4 to 6E-2 Hz is close to the classical Kolmogorov (-5/3) law. We also discuss some intervals with a very high level of the relative amplitude of flux fluctuations (10-20 percent) which were observed near the Earth's bow shock in the foreshock region. The use of the wavelet method for the long time series allows us to study the temporal evolution of power spectra.
    Keywords: Solar Physics
    Type: ; 82
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  • 4
    Publication Date: 2019-07-17
    Description: The MASS instrument on WIND contains the first isochronous time-offlight spectrometer to be flown in the solar wind. The first spectra obtained with this instrument has demonstrated its capability to measure the abundances of several high-and low-FIP elements in the solar wind. The derivation of these abundances requires a careful calibration of the charge exchange efficiencies of the relevant ions in carbon foils. These efficiencies and the corresponding instrument functions have been determined in extensive calibration campaigns at different institutions. We present first and preliminary results obtained in slow solar wind streams and we compare these results with those obtained from previous investigations of solar wind abundances and of coronal abundances as derived from Solar Energetic Particles. Recent models of the FIP related fractionation effect predict a depletion of a factor of typically 4 to 5 for high-FIP elements (He, N, O, Ne, Ar, etc.) relative to low-FIP elements (Mg, Fe, Si, etc.). We also compare our results with the detailed predictions of the different models and we discuss the resulting evidence to validate or to invalidate different physical scenarios explaining the feeding and the acceleration of slow stream solar wind.
    Keywords: Solar Physics
    Type: ; 35
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 81-87 
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxolanes, benzoyl peroxide reaction of ; 2-methylene-1,3-oxazolidines, benzoyl peroxide reaction of ; polyacetals ; charge-transfer polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines with benzoyl peroxide (acceptor radical) and with N-ethylmaleimide (acceptor) was investigated. It was shown that benzoyl peroxide adds to monomers 1a and 1b, giving the corresponding linear diester amides 1a and 1b respectively. The oxazolidine 1c adds benzoyl peroxide, without ring opening, by addition to the exomethylene group. Together with N-ethylmaleimide the oxazolidines 1a or 1b produce deep-colored charge transfer complexes, resulting in high molecular poly-N-ethylmaleimides probably via a radical mechanism. The 1,3-dioxolanes 2a and 2b were radically polymerized to produce polyacetals by vinyl polymerization. 2c was polymerized to produce randomly containing acetal units and ester units. The mechanism of polymerization of 2e is complex, affording polymers of nonuniform character. 2-Methylene-4-phenyl-1,3-dioxolane polymerization leads to polyester as the main structure, and to a lesser degree polyacetal structures. The chemical structures of the polymers were confirmed by NMR spectra and elemental analysis. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 49-54 
    ISSN: 0887-624X
    Keywords: polymer membranes ; poly(vinyl pyrrolidone) ; hypochlorite ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sodium hypochlorite solutions are used to treat membranes prepared from a polymeric blend containing poly(vinyl pyrrolidone) (PVP) to increase their water permeability. Sodium hypochlorite affects the membrane material in such a way that PVP is selectively removed from the membrane matrix. The mechanism of the reaction between hypochlorite and PVP is investigated by several chemical analysis techniques of the reaction products. Strong indications are found that the reaction involves chain scission of PVP according to a radical mechanism. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. S49 
    ISSN: 1612-1112
    Keywords: Capillary electrochromatography ; Electroosmotic flow ; Submicron silica beads ; Mixed mode phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase stationary phases based on porous silica beads in the range 0.2–3 μm have been prepared to study the dependency of electroosmotic flow (EOF) on particle diameter. Additionally, the influence of the mobile phase composition, i.e. organic modifier content, pH of buffer solution and concentration of buffer salt, on the magnitude of the electroosmotic flow velocity has been investigated. To perform separations in an aqueous acidic mobile-phase, mixed mode stationary phases containing both alkyl chains and strong cationexchange groups have been applied.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 49 (1999), S. S35 
    ISSN: 1612-1112
    Keywords: Capillary electrochromatography ; Packing materials ; Mixed-mode phase ; Active ingredients and preservatives in creams ; Cortisone derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary electrochromatography (CEC) is an analytical method of growing interest to the pharmaceutical industry. Because CEC is a combination of high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) it has the advantages of the high selectivity of HPLC and the high efficiency of CE. The capillaries can be packed with different packing materials. The mixed-mode phase consisting of a strong cation exchanger and alkyl chains on the silica surface has some advantages over conventional reversed-phase (RP) packing materials. In this article the authors describe the use of CEC to separate the active ingredients and preservatives in creams from different manufactures. On the basis of the high efficiency of CEC it was possible to develop one isocratic method for all the compounds in the different samples. The method was validated with regard to identification, reproducibility, linearity, limit of detection, and quantitation.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Influence of mean stresses and mean strains on the cyclic deformation behavior and the plasticity-induced martensite formation of X6CrNiTi1810 stainless steelThis paper describes some aspects of the fatigue behavior of the metastable austenitic stainless steel X6CrNiTi1810 (German material number 1.4541). The aim of the present investigation is to determine the influence of plasticity-induced martensite formation on the cyclic deformation behaviour at room temperature and T = 300°C. Several specimen batches were tested under stress and total strain control with different R-values, a frequency of 5 Hz and triangular load-time functions, s̰-hysteresis and nondestructive magnetic measurements are used to characterize the fatigue behavior. Characteristic results are presented and discussed.
    Notes: Anhand von einstufigen spannungs- und totaldehnungskontrollierten Versuchen werden Zusammenhänge zwischen dem zyklischen Verformungsverhalten und der verformungsinduzierten Martensitbildung des metastabilen austenitischen Stahls X6CrNiTi1810 (Werkstoff-Nr. 1.4541) bei Raumtemperatur und T = 300°C untersucht. Besondere Beachtung findet hierbei der Einfluß von Mittelbeanspruchungen. Alle Versuche wurden mit einem dreieckförmigen Beanspruchung-Zeit-Verlauf und einer Frequenz von 5 Hz durchgeführt. Zur Charakterisierung des Wechselverformungsverhaltens dient neben den aus σ-Hysteresen ermittelten mechanischen Kennwerten, der on-line mittels eines Wirbelstromsensors gemessene magnetische Phasenanteil. Ausgewählte Versuchsergebnisse werden vorgestellt und diskutiert.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 26 (1995), S. 553-559 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Bestimmung der Spannungstensoren in dünnen, texturierten Kupferschichten mittels Röntgenbeugung bei streifendem EinfallIonenplattierte Kupferschichten wurden mittels Röntgenbeugung hinsichtlich Texturen und Eigenspannungen untersucht. Die vollständigen Orientierungsverteilungsfunktionen wurden bestimmt und scharfe (111)-Fasertexturen gefunden. Die Messung der Dehnungen erfolgte unter streifendem Strahleinfall. Zur Berechnung der Spannungstensoren wurden sowohl texturgewichtete elastische Moduln als auch texturunabhängige elastische Moduln verwendet. Die Bedeutung der Texturmessung für die Spannungstensorbestimmung wird diskutiert. Die gefundenen Spannungen können als thermisch verursacht verstanden werden.
    Notes: Ion-platted thin copper films were examined for residual stresses and texture by X-ray diffraction. The complete orientation distribution functions were determined and sharp (111)-fibre textures were found. The strains were measured by grazing incidence diffraction. The stress tensors were calculated using both texture-weighted elastic compliances and texture-independent X-ray elastic constants. The importance of the texture measurement for the stress tensor determination is discussed. The found stresses can be interpreted as thermally induced.
    Additional Material: 5 Ill.
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