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  • 1
    Digitale Medien
    Digitale Medien
    Quadrupole interaction of 181Ta in anhydrous HfCl4 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1798-1800 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Nuclear quadrupole interaction parameters have been determined at 293 and 77 K at the site of 181Ta nuclei in anhydrous HfCl4 by the method of time-differential perturbed angular correlations. Measurements performed on the 133–482 keV γ–γ cascade in 181Ta following the β decay of 181Hf indicate that HfCl4 does not possess cubic symmetry as claimed by some researchers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.455126
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  • 2
    Digitale Medien
    Digitale Medien
    A new method for fetal weight estimation using real-time ultrasound (1987)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 94 (1987), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary. A method for estimating fetal weight by calculating an approximate fetal volume from abdominal area, head area and femur length has been developed. Birthweights were calculated within 48 h before delivery for 434 patients, using this method and two other methods already in widespread use. Statistical analysis of the three sets of predictions gave standard deviations of 297 g for the new method, compared with 323 g and 342 g for the other methods. Further analysis of the data showed that estimates closest to the true birthweight were obtained in 41% of cases by using the new method, and in 33% and 26% of cases using the other methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1987.tb02335.x
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  • 3
    Digitale Medien
    Digitale Medien
    Novel pseudomorphic high electron mobility transistor structures with GaAs-In0.3Ga0.7As thin strained superlattice active layers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2121-2123 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thin strained superlattice (TSSL) concept is introduced as a means for extending the practical range of application for pseudomorphic Inx Ga1−x As on GaAs. Growth and characterization results are presented for pseudomorphic high electron mobility transistor structures with GaAs-In0.3 Ga0.7 As TSSL active layers grown by molecular beam epitaxy. The TSSLs are composed of three periods of GaAs(15 A(ring))- In0.3 Ga0.7 As(h2 ), where h2 ranges from 30 to 52 A(ring). Modulation doping of the TSSLs is provided by atomic planar-doped Al0.3 Ga0.7 As overlayers with 45 A(ring) undoped spacers. 77 K Hall effect and transmission electron microscopy reveal that relatively thick TSSLs can be grown with high electronic and structural quality, comparable to much thinner In0.3 Ga0.7 As single quantum wells. Results are compared with a model for critical layer thickness and discussed in light of in situ reflection high-energy electron diffraction measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101146
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  • 4
    Digitale Medien
    Digitale Medien
    Growth dynamics of aluminum nitride and aluminum oxide thin films synthesized by ion-assisted deposition (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 760-769 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Some aspects of the dynamics of thin-film synthesis of aluminum nitride and aluminum oxide produced by ion-assisted deposition have been deduced from in situ measurements by ellipsometry, photometry, and ion scattering spectroscopy. Measurements obtained during the etching of aluminum films by nitrogen and oxygen ion beams have established the thickness of the synthesized layer and the rate of compound formation. Some of these measurements have been compared with a theoretical model which predicts the time evolution of the synthesized surface layer as well as the steady-state layer thickness. The breakdown voltage and variation of capacitance with applied voltage of aluminum oxide films prepared by ion-assisted deposition are also presented. Furthermore, the optical properties of ion-assisted AlN and Al2O3 in the visible region are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.340068
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  • 5
    Digitale Medien
    Digitale Medien
    Deep-level transient spectroscopy studies of defects in GaAs-AlGaAs superlattices (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2882-2885 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present preliminary results of a study of defects in GaAs-AlGaAs superlattices using deep-level transient spectroscopy (DLTS). A dramatic difference is observed between the DLTS spectra of two superlattices when the superlattice period is doubled. This is explained by the presence of miniband conduction in the case of the smaller period and its absence in the case of the larger, and by the consequent difference in the distribution of electrons in the superlattice. Observed activation energies must be reinterpreted for comparisons to bulk material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337073
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  • 6
    Digitale Medien
    Digitale Medien
    The structure and properties of ion-beam-synthesized boron nitride films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3980-3986 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Films containing boron and nitrogen were prepared by electron-beam evaporation of boron and bombardment of the growing film with nitrogen ions of energy up to 1500 eV. Hard films of high transparency (extinction coefficient 〈0.01) were prepared with nitrogen-to-boron atomic arrival ratios greater than one. The optical constants in the visible part of the spectrum were determined as a function of B-to-N atomic ratio in the film and substrate temperature using optical photometry. Measurements of the optical constants were extended to 40 eV using a Kramers–Kronig analysis of electron-energy-loss spectra. Boron-to-nitrogen atomic arrival rates were determined and show that as ion energy and substrate temperature are increased ion flux must be increased to achieve the same stoichiometry. Film structure was imaged using high-resolution electron microscopy, and the radial distribution function (RDF) was determined. The RDF of stoichiometric films showed that high substrate temperatures increased the size of the ordered regions. The RDF and high-resolution imaging of all films were consistent with the presence of the hexagonal form of BN with substoichiometric films containing amorphous boron as the other constituent. This conclusion is consistent with the analysis derived from the sum rule obtained from the optical constants. No evidence could be found for the cubic form of BN.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341357
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  • 7
    Digitale Medien
    Digitale Medien
    Analysis of Alcohol Dehydrogenase Gene Expression in Drosophila (1987)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 21 (1987), S. 203-225 
    Details
    ISSN: 0066-4197
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.ge.21.120187.001223
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  • 8
    Digitale Medien
    Digitale Medien
    Characterization of growing thin films by in situ ellipsometry, spectral reflectance and transmittance measurements, and ion-scattering spectroscopy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1995-2003 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A versatile ultrahigh-vacuum thin-film deposition and analysis system is described. Films are deposited by electron beam evaporation with the possibility of ion beam bombardment of the growing film. Measurements of the reflectance and/or transmittance of the coating surface can be made simultaneously at 16 wavelengths across the visible or infrared spectrum. Ellipsometric measurements can also be made in situ, at a single wavelength and single angle of incidence, by an ellipsometer which can operate in either an automatic rotating analyzer mode or a manual nulling mode. The system is also equipped with an ion gun producing a submillimeter spot, and with a hemispherical sector, ion energy analyzer for ion scattering spectroscopy studies of the film surface. Results obtained during the deposition of a gold film are presented to demonstrate the capability of the system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1138408
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  • 9
    Digitale Medien
    Digitale Medien
    KSU project: CRYEBIS for producing slow, bare, heavy-ion beams (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 751-753 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The design and construction of a cryogenic electron beam ion source is in progress at Kansas State University. In about two years this source should produce high yields of bare and few-electron argon ions with low kinetic energies (∼keV–MeV). The design is similar to the latest French designs {CRYEBIS II [J. Arianer, C. Goldstein, H. Laurent, and M. Malard, IEEE Trans. Nucl. Sci. NS-30, 2737 (1983)] and DIONE [B. Gastineau, J. Faure, and A. Courtois, Nucl. Instrum. Methods B9, 538 (1985)]}. However, several significant changes were incorporated in order to get a simpler and more flexible design. The key factors of the operation which are expected to limit the performance are discussed. The general design is outlined which allows significant future upgrading to obtain nongaseous as well as much heavier, highly ionized ions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1138853
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  • 10
    Digitale Medien
    Digitale Medien
    The effects of oral contraceptives and parity on ovarian cancer trends in women under 55 years of age (1989)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 96 (1989), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary. Mortality from epithelial ovarian cancer is falling in women under 55 years of age in England and Wales. The decline does not appear to be a treatment effect nor to be attributable to changes in the rate of oophorectomy. Case-control studies have shown that high parity and oral contraceptive use are protective against the disease. We suggest that the decrease in mortality is compatible in timing and magnitude with exposure to oral contraceptives. No obvious effect on mortality attributable to parity was apparent in this analysis. Oral contraceptives may prove to be a widely acceptable means of preventing ovarian cancer, providing they do not increase breast cancer risk.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1989.tb03316.x
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