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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1815-1817 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A cryogenic refrigeration scheme is presented which utilizes the discrete energy levels of quantum dots to customize the electronic Fermi–Dirac distribution, cooling a small but macroscopic reservoir to far below the ambient temperature. Several physical limitations of this scheme are discussed within the context of a model device constructed from a two-dimensional electron gas. These are explored in a simple example where, at an ambient operating temperature of 150 mK, this quantum-dot refrigerator can achieve a cooling power of 1 μW/cm2, a base temperature of 10 mK, and a cooling efficiency of 35%.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1520-5835
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 13 (1994), S. 43-48 
    ISSN: 1476-5535
    Schlagwort(e): Milbemycin ; Fructose ; Starch ; Carbon:nitrogen ratio
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Milbemycin production byStreptomyces hygroscopicus RB4569D was examined in media containing different carbohydrates. Total milbemycin titer could be increased by substitution of fructose for glucose and by selection of the appropriate starch type. Total titer could be further enhanced by increasing the concentration of fructose and/or starch in the medium. Rates of carbohydrate utilization were shown to be independent of their initial concentration and increased titers in high carbohydrate media were shown to be due to a prolonged production phase rather than an increased accretion rate. The pattern of individual milbemycin components was governed by the carbon:nitrogen ratio of the medium rather than carbohydrate concentration and there was a critical C:N ratio below which no milbemycin was produced.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1573-1111
    Schlagwort(e): Force constant calculations ; n-alkanes ; mono-halo and di-halo alkanes ; urea inclusion compounds ; LAM-1 modes ; accordion vibrational modes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Force constants were determined for the C8, C10, C12 and C14 series ofn-alkanes C n H2n + 2 using an approximate SVFF calculation and observed LAM = 1 wave numbers. In this calculation the hydrogen atoms were neglected and only the carbon backbone chain and terminal atoms were considered; this was valid since only low-frequency vibrations were under consideration. Using force constant transfer, the wavenumbers of the LAM = 1 accordion modes for the analogous α-Cn H2n + 1 X and α,ω-Cn H2nX2 species, where X = C1, Br or I were calculated. For α-chloroalkanes and α,ω-dichloroalkanes, them = 1 accordion modes are calculated to be in the 220–130 cm−1 and 200–120 cm−1 regions, respectively. For the bromo- and iodo-analogues them = 1 accordion modes are calculated to be in the 200–100 cm−1, 150–90 cm−1 and in the 170–100, 135–80 cm−1 regions, respectively.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 607-611 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The pressure-broadening coefficients for the self-broadened S0(0), S0(1) and S0(2) pure rotational Raman lines of hydrogen and the S0(0) to S0(4) lines of deuterium were determined experimentally over the pressure range 1-100 bar and the temperature range 90-375 K. Broadening coefficients were also determined for the same lines in hydrogen and deuterium perturbed by helium, argon, oxygen, nitrogen, carbon monoxide and hydrogen chloride over the pressure range 2-100 bar, with a partial pressure of the host gas of 1 bar and a temperature of 293 K. In addition, the S0(0) pure rotational line of deuterium broadened by carbon monoxide and nitrogen was studied over the same pressure range and a temperature range of 100-293 K. The results are discussed and compared with those of previous studies in the literature.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 613-618 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Raman spectra of the α-, β-, γ- and smectic polymorphs of isotactic polypropylene were recorded at 298 and 16.5 K. At 298 K the spectra of the polymorphs were very similar except in the antisymmetric C—H stretching region. However, at 16 K the Raman spectra of the polymorphs show different features in several wavenumber shift regions. Comparisons are made with infrared spectra recorded at 298 and 100 K and interpretations are made on the basis of non-equivalent sites in the monoclinic unit cells.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The dissociation constants for an acetonitrile-zinc complex, (CH3CN)Zn2+, were measured in aqueous solutions containing zinc salts (40-80%, w/w) and acetonitrile by Raman spectroscopy. Quantitative measurements of the intensity of the free and complexed ν(CN) Raman bands at 2264 and 2320 cm-1, respectively, were used to determine the average enthalpy and entropy of the complex dissociation to free acetonitrile in the temperature range 293-343 K for a 70% (w/w) solution of zinc chloride (0.052 mol) in an aqueous solution containing acetonitrile (0.024 mol); δH° and δS° values of 8.4 ± 0.5 kJ mol-1, respectively, were determined.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 23 (1992), S. 641-645 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Fourier transform (FT) Raman and infrared spectra of the outermost layer of human skin, the stratum corneum, were recorded. Assignments consistent with the FT Raman vibrations were made for the first time and compared with assignments from the FTIR spectrum. The results demonstrate that FT Raman spectroscopy holds several advantages over FTIR in studies of human skin. The molecular and conformational nature of human skin, and modifications induced by drug or chemical treatments, may be assessed by FT Raman spectroscopy.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 24 (1993), S. 475-483 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The application of Raman spectroscopy to polymers and polymerization processes is surveyed and the advent of recent advances in instrumental techniques to polymer analysis is highlighted. Some of the problems of the more widely-used infrared spectroscopic methods, for example in microstructural analysis of polydienes and copolymers, are discussed and the advantages of the Raman spectroscopic technique are explained. The use of near-infrared excitation and Fourier-transform Raman instrumentation for process monitoring and polymer composite studies is discussed. Raman microscopic and waveguide spectroscopic studies of small samples and polymer coatings on substrates are considered. Other applications are mentioned in the areas of polymer orientation, surface-enhanced Raman scattering, conducting polymers, biopolymers and time-resolved studies.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 24 (1993), S. 545-550 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The quantitative determination of crystallinites of polyethylene samples from the analysis of vibrational bands due to δ(CH2) twisting and v(CC) stretching in the Raman spectra between 950 and 1500 cm-1 was assessed. Several methods based on manual resolution of band envelopes and on computer-derived information using Gaussian and Lorentzian profiles were compared. The major source of error was found to be the estimation of the amorphous and crystalline interphase content, αb. A new method for the determination of sample crystallinity is proposed based on the time-dependent Fourier transform deconvolution of the spectral region between 950 and 1500 cm-1, which takes into account the baseline corrections and the influence of vibrational band shoulders in this region to obtain consistent values of αa, αb and αc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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