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  • 1990-1994  (1.393)
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  • 1
    Digitale Medien
    Digitale Medien
    Macrocyclic trichothecenes produced by Stachybotrys isolated from Egypt and Eastern Europe (1991)
    Springer
    Mycopathologia 113 (1991), S. 109-115 
    Details
    ISSN: 1573-0832
    Schlagwort(e): Mycotoxins ; macrocyclic trichothecenes ; Stachybotrys ; fungi
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Twenty seven isolates of Stachybotrys chartarum, S. albipes, S. kampalensis and S. microspora from Egypt and Eastern Europe were tested for production of macrocyclic trichothecenes. Twenty of the 27 isolates, grown on rice seeds, were toxic to brine shrimp larvae. Based on TLC and HPLC analyses, 5 macrocyclic trichothecenes (verrucarin J, roridin E, satratoxins F, G & H) as well as trichoverrols were identified. When grown in liquid culture on rice extract medium, only 3 isolates were toxic and produced verrucarin J, roridin E and satratoxins G & H. Extracts from mycelial mats were more toxic than culture filterates of two isolates grown on rice extract and both contained the same macrocyclic trichothecenes (285.5 mg/4 L), in addition to trichoverrols A & B (31 mg/4 L) found in mycelial mats only. When grown on 3% sucrose Czapek's medium supplemented with peptone and yeast extract (still cultures), all isolates were non-toxic to brine shrimp and no trichothecenes could be detected in the extracts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00442419
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  • 2
    Digitale Medien
    Digitale Medien
    Some New Heterocyclic Sulphonates with potential antimicrobial activity (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 791-796 
    Details
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 4-(Phenylhydrazono-4′-benzenesulphonato)-3-methyl-2-pyrazolin-5-one (2) was prepared by treating 4-(4′-hydroxyphenylhydrazono)-3-methyl-2-pyrazolin-5-one (1) with benzenesulphonyl chloride. Heating 2 with acetic anhydride, chloroacetyl chloride and benzenesulphonyl chloride afforded the N-acetyl (3), N-chloroacetyl (4) and O-benzenesulphonyl (5) derivatives, respectively. 2 reacted with benzenesulphonyl chloride under cooling conditions to give the N-benzenesulphonyl derivative (6). 2 undergoes Mannich reaction to give the N-Mannich base (7). Reaction of 2 with formaldehyde in methanol afforded the N-hydroxymethyl derivative (8) which undergoes condensation with ethyl acetoacetate, ethyl cyanoacetate and malononitrile to give compounds 9, 10 and 11 respectively. The antimicrobial activity of these products against gram-positive (+ve), gram-negative (-ve) bacteria and fungi was screened. They showed potential bactericidal activity and some of them exhibited high fungicidal activity.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prac.19903320531
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  • 3
    Digitale Medien
    Digitale Medien
    Microscopic organic analysis using two-step laser mass spectrometry: application to meteoritic acid residues (1992)
    s.l. : American Chemical Society
    Analytical chemistry 64 (1992), S. 682-690 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00030a021
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  • 4
    Digitale Medien
    Digitale Medien
    Time-resolved temperature measurements during rapid solidification of Si-As alloys induced by pulsed-laser melting (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3725-3733 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The solidification of Si-As alloys induced by pulsed-laser melting was studied at regrowth velocities where the partition coefficient is close to unity. The congruent melting temperatures T0 of Si-As alloys were determined using a temperature measurement technique developed for this work, and was confirmed with T0 measurements using three other methods. The time-resolved temperature measurement uses a thin-film platinum thermistor, below and electrically isolated from the Si-As alloy layer, to directly measure the temperature during solidification. The other techniques compared the results of heat flow simulations with the fluence dependence of the peak melt depth obtained by transient conductance, the fluence dependence of the melt duration determined from time-resolved reflectivity and transient conductance, and the fluence threshold for the initiation of melting. This combination of measurements in conjunction with Rutherford backscattering spectrometry permitted the determination of the solid-liquid interface temperature, velocity and partition coefficient, the latent heat of fusion and T0 for Si-4.5 at. % As and Si-9 at. % As alloys. The values of T0 determined by all four independent methods were consistent, indicating overall agreement between the direct experimental measurements and the analyses based on heat flow simulations. T0 was determined to be 1565±25 K for 4.5 at. % As and 1425±25 K for 9 at. % As. In addition, the enthalpy of fusion was determined to be independent of composition for the range studied. The values obtained in this work are compared with previous measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352903
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  • 5
    Digitale Medien
    Digitale Medien
    Isochronal annealing of local vibrational modes in proton- and deuteron-implanted InP (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 78-83 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have performed isochronal annealing experiments on the hydrogen-related local vibrational modes (LVMs) created by proton and deuteron implantation of InP. Implanted samples were annealed in 50 °C increments in the 200–600 °C temperature range for 30 min each and then measured by infrared absorption. A group of four different LVMs is observed, each of which arises from the hydrogen-phosphorus stretching vibration with different defects or impurities at nearest-neighbor sites. Each LVM exhibits an annealing behavior that is different than any of the other LVMs. The annealing results are shown and discussed in relation to the possible microscopic structure of the defect responsible for each LVM.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353832
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  • 6
    Digitale Medien
    Digitale Medien
    Experimental determination of the upper critical field of epitaxially grown thin films of YBa2Cu3O7−δ down to He temperature (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2230-2233 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The upper critical field of YBa2(Cu1−xFex)3O7−δ with x=0 and 0.05 is determined over the whole temperature range from 4.2 K to Tc. The data behave according to the theory of Werthamer, Helfand, and Hohenberg [N. R. Werthamer, E. Helfand, and P. C. Hohenberg, Phys. Rev. 147, 295 (1966)]. However, at low temperatures the upper critical field is larger than expected from the original expressions of Werthamer and co-workers. Generalized equations, which take into account the anisotropy of the Fermi surface, yield values for the upper critical field, which are in excellent agreement with the experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349435
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  • 7
    Digitale Medien
    Digitale Medien
    Temperature influence on the damage induced in Si+-implanted InP (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 752-757 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In situ transmission electron microscopy observations during 50-keV Si+ ion implantation in InP were performed from 15 to 600 K. The implantation dose temperature dependence of the cluster density was studied in the 15–400-K range, and the results are discussed. It is shown that the result of increasing damage is either amorphization (T≤400 K) or phase precipitation (T≥500 K). The threshold fluence for these phenomena increases with the implantation temperature (from 8 × 1011 Si/cm2 at 15 K to 4 × 1015 Si/cm2 at 600 K). The formation of an amorphous layer is ascribed to the defect zone overlap of the displacement cascade outskirts. The precipitate structure and evolution are studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349631
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  • 8
    Digitale Medien
    Digitale Medien
    On Schottky barrier inhomogeneities at silicide/silicon interfaces (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3351-3353 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Schottky-barrier heights of several silicides on both n- and p-Si(100) have been measured in the temperature range 77–295 K. The results deviate significantly from the predictions of a recent model based on the assumption of barrier height inhomogeneities at such interfaces. For all these interfaces, the sum of the barrier heights to n- and p-Si(100) is always equal, within the experimental accuracy, to the indirect band gap of Si. Furthermore, the temperature dependence of the barrier height suggests that the Fermi level at these interfaces is pinned relative to the Si valence-band edge.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348564
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  • 9
    Digitale Medien
    Digitale Medien
    Variation of threshold current with cavity length in strained-layer InGaAs/GaAs quantum well lasers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1882-1891 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The variation of the threshold current on the cavity length in strained-layer InGaAs/GaAs quantum well lasers was studied both theoretically and experimentally. The radiative recombination rates were calculated, while the nonradiative recombination rates were described phenomenologically. Broad-area lasers of various cavity lengths were fabricated on the same wafer for use in the experiments. The valence subband structures were calculated from the Kohn–Luttinger Hamiltonian plus the strain Hamiltonian with appropriate boundary conditions. When lasers were forward biased, the quasi-Fermi levels were determined by the charge neutrality. From the dielectric function in the self-consistent-field method including the band-gap shrinkage effect, the gain and the spontaneous emission rate spectra were obtained. At the threshold of lasing, the current was a sum of the radiative and nonradiative components. In the nonradiative component, we consider two mechanisms: the Auger and the interface recombinations. We found that (1) each subband structure possesses a cutoff in k space; (2) the dominant polarization of the emitted light from lasers under investigation is in TE mode; (3) for long cavity lengths, currents originating from the radiative and interface recombinations are dominant, while for short cavity lengths, current originating from the Auger process is dominant; and (4) as the cavity length decreases, the threshold current first decreases and then drastically increases. Therefore there is an optimum cavity length. Theoretical and experimental results were compared and presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348758
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  • 10
    Digitale Medien
    Digitale Medien
    A normal-incidence type-II quantum-well infrared photodetector using an indirect AlAs/Al0.5Ga0.5As system grown on (110) GaAs for mid- and long-wavelength multicolor detection (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1382-1387 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A normal-incidence type-II indirect AlAs/Al0.5Ga0.5As quantum-well infrared photodetector grown on (110) GaAs by molecular-beam epitaxy for mid- and long-wavelength multispectrum detection has been developed. The normal-incident excitation of long-wavelength intersubband transition was achieved in the [110] X-band-confined AlAs quantum wells. Six absorption peaks including four from X-band to Γ-band intersubband resonant transitions were observed at wavelengths, λp1−6=2.2, 2.7, 3.5, 4.8, 6.5, and 12.5 μm. The resonant transport from X band to Γ band gives rise to high photoconductive gain, which is highly desirable for focal plane arrays image sensor applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354896
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