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  • Wiley-Blackwell  (9)
  • American Institute of Physics (AIP)  (6)
  • Oxford University Press  (6)
  • American Chemical Society (ACS)
  • 1990-1994  (21)
  • 1955-1959
  • 1990  (21)
  • 1
    Digitale Medien
    Digitale Medien
    Methods of calculating the Barkas-effect correction to Bethe–Bloch stopping power (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6613-6620 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The low-velocity Barkas-effect correction term for the Bethe–Bloch stopping-power formula has been calculated with each of the three extant formalisms for targets with atomic numbers from 1 to 18 and for projectile velocities from 0.025c to 0.3c. Comparison of each with measurements on aluminum revealed which formalism provided the best fit over three different projectile velocity intervals. The method yielding the generally superior agreement was used to calculate the stopping power of each element (except Li, F, Na, Mg, P, and Cl) for protons and alpha particles with energies between 0.5 and 5.0 MeV. Results corresponded very closely to those of an existing fit to most known experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345094
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  • 2
    Digitale Medien
    Digitale Medien
    Lithium niobate stress gauge current diagnostic for noninductive measurement of fast-rise-time multimegampere currents (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4917-4928 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Accurate modeling of load behavior in Z-pinch plasma radiation sources driven by high-current generators requires the measurement of fast-rise-time multimegampere currents close to the load. Conventional current diagnostics mounted in inductive cavities (such as B-dot loops and Rogowski coils) fail at small radius because of electrical breakdown produced by high dI/dt. In this paper, we describe the use of large-signal, nanosecond-time-resolution lithium niobate piezoelectric stress gauges to directly measure the magnetic pressure B2/2μ0=μ0I2/8π2r2 generated at radius r by a current I flowing in a radial transmission line. Current measurements have been performed at radius r=2.54×10−2 m on Sandia National Laboratories' Proto-II (10 TW) and SATURN (30 TW) gas puff Z-pinch experiments with maximum currents of 10.1 MA and dI/dt to 2.1×1014 A/s. Comparisons with Faraday rotation and B-dot current diagnostic measurements at large radius are presented. Bremsstrahlung noise problems unique to the SATURN gas puff source are discussed. For a Y-cut lithium niobate stress gauge on a pure tungsten electrode, current densities up to I/2πr=78 MA/m can be measured before the electrode yield strength and the piezoelectric operating stress limit are exceeded. Above the Hugoniot elastic limit of the electrode material, the dynamic range and accuracy of the diagnostic are greatly reduced, but it appears that the technique can be extended to higher current densities using an X-cut quartz piezoelectric element and a tungsten-sapphire electrode impedance stack.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347077
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  • 3
    Digitale Medien
    Digitale Medien
    Thermal and magnetic properties of Bi2CuO4 (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5761-5761 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Since the discovery of the high-Tc superconductors, there is a great interest in the magnetic properties of copper oxides due to the possibility of a magnetic origin of the pairing mechanism. With this perspective, we decide to reinvestigate the structure and the magnetic properties of Bi2CuO4, a compound we use successfully as precursor of the Bi-Sr-Ca-Cu high-Tc superconductors. A neutron powder diffraction experiment allowed us to resolve the ambiguity in the structure, and revealed the existence of a magnetic phase transition to a 3D antiferromagnetic ordered state below 50 K. The nuclear structure can be described as formed by stacks of CuO4 units in the c-axis direction, linked in the stacks and with units in other stacks by BiO2 chains, so each stack is connected with four stacks. The space group was confirmed to be P4/ncc. The magnetic space group is P4/n'cc. There is a ferromagnetic ordering of the magnetic moments on Cu atoms along the stacks, and an antiferromagnetic ordering between the stacks. We present an interpretation of the magnetic properties of this compound, at the light of our previous results, and a discussion of a calorimetric experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345956
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  • 4
    Digitale Medien
    Digitale Medien
    Modeling transport in toroidal plasmas: Status and issues (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2913-2925 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The scope and detail of physics contained in computational models for fluid (density, momentum, energy) transport in toroidal plasmas have steadily increased during the past two decades. There has been considerable success in the development and verification of models for sources and sinks of particles, energy, momentum, and magnetic flux. Transport codes have collectively become very useful tools in interpreting experimental data and in providing guidance for new experiments. However, a more thorough understanding of the fundamental transport processes of magnetically confined plasmas and development of improved computational models are needed to enhance the predictive capabilities of transport codes. It is argued that fluid transport modeling by itself cannot lead to a complete understanding of transport—there must be a very strong collaboration among theory, experiment, and modeling on both the fluid and kinetic levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859360
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  • 5
    Digitale Medien
    Digitale Medien
    Crystal structure and magnetism of Co(HPO3)⋅H2O: A novel layered compound of Co(II) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5998-6000 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The crystal structure and magnetic properties of Co(HPO3)⋅H2O have been determined. The solid crystallizes in space group Pca21, a=8.984(2) A(ring), b=7.918(2) A(ring), c=10.139(8) A(ring), V=721.2 A(ring)3. Z=4 dcalc =2.89 g/cm3. The structure consists of layers only connected by hydrogen bonds. These layers can be viewed as formed by zigzag chains of edge-sharing Co(II)O6 octahedra interconnected by a three atom bridge (O-P-O) and a single oxygen bridge. ac magnetic susceptibility measurements show a sharp peak at Tc =(10.8±0.1) K, and are consistent with a transition from one- to two-dimensional magnetic order, in agreement with the structure. An analysis of the χT/C vs ε=(1−Tc/T) data in the critical region, for T〉Tc, using a double-logarithmic plot, yields a critical exponent γ=1.75 for 0.01〈ε〈0.1, which correspond to a two-dimensional Ising model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346042
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  • 6
    Digitale Medien
    Digitale Medien
    Recommended Bethe–Bloch stopping power parameters for Kapton and Havar (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1639-1642 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Previous measurements of the stopping power of Kapton and Havar for 1.1–4.4-MeV protons have been analyzed with modified Bethe–Bloch theory in order to extract some of the parameters required in the formalism. Results suggest the possibility of systematic errors, in that the Havar data appear to have been slightly high and the Kapton data quite low when compared with other reported measurements. Currently recommended values of the mean excitation energy and Barkas-effect parameter are, respectively, 79 eV and 1.34 (Kapton) and 296 eV and 1.36 (Havar). The need for further accurate measurements for Kapton in particular is emphasized.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345630
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  • 7
    Digitale Medien
    Digitale Medien
    Coextrusion of it-polypropylene film (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 455-465 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: it-Polypropylene films were coextruded by using dies of varying extrusion draw ratio (EDR) from 2-10. Among the resulting films, the film coextruded at EDR 9 possesses the most attractive superstructure and the highest modulus. The dynamic modulus at room temperature was 7 GPa and an αc dispersion peak occurred at 100°C in E″-temperature curves, which is higher by about 20°C than that of the multistep zone-drawn and zone-annealed fibers previously reported. Further, to prepare films with higher draw ratio and higher modulus, repetition of the coextrusion was attempted. Consequently, the draw ratio and the E′ at room temperature reached 12 and 13 GPa, respectively. The present paper discusses changes in molecular orientation, crystallinity, uniformity of the superstructure, and dynamic viscoelasticity, with increasing of the used EDR and repeating the coextrusion with some combinations of EDR.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070410302
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  • 8
    Digitale Medien
    Digitale Medien
    Interfacial adsorption and crystallization of polycarbonate in carbon fiber composites (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 1873-1885 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A polycarbonate (PC)/carbon fiber (CF) composite system has been examined with regard to interfacial adsorption and crystallization by altering times and temperatures of annealing. Times up to 180 min and temperatures of 245, 275, and 300°C have been investigated. Tranverse tensile, tranverse toughness, and scanning electron microscopy results on unidirectional, continuous-fiber composites indicate improved fiber/matrix adhesion at longer times and higher temperatures of annealing. Improvements in transverse toughness and transverse tensile strength of a factor of two is achieved. The data indicate that primarily adsorption rather than secondary interfacial crystallization is the likely mechanism for increased adhension. Isothermal transverse toughness values have been found to fit well to a Langmuir-type expression. The temperature dependence of adsorption as measured by transverse toughness is described well by an Arrhenius equation. The dependence of transverse toughness on PC molecular weights from Mw = 26,600 to 39,800 was found to be large, with higher molecular weights adsorbing more effectively.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070390905
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  • 9
    Digitale Medien
    Digitale Medien
    Pressure effects in the capillary flow of amorphous polymers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1355-1356 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070410543
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  • 10
    Digitale Medien
    Digitale Medien
    Integral kinetics of α-galactosidase purified from Glycine max for simultaneous hydrolysis of stachyose and raffinose (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 15-22 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: α-Galactosidase from soybean (Glycine max) was purified by a five-step procedure. The enzyme's natural substrates, raffinose and stachyose, have Km's of 3. 0 mM and 4. 79 mM, respectively. The products, galactose and sucrose, were measured after separation by liquid chromatography. Galactose is a competitive product inhibitor of stachyose and raffinose hydrolysis with a Ki of 0. 12 mM. We determined these parameters by an integral kinetic approach. Stachyose hydrolysis gives a nearly constant level of raffinose shortly after hydrolysis begins. Thus, cleavage of the first α-(1,6)-bond in the tetrasaccharide is the rate-limiting step. Since the stachyose hydrolysis yields raffinose, soybean α-galactosidase simultaneously hydrolyzes two substrates. We present a novel approach for analyzing simultaneous substrate hydrolysis with competitive product inhibition by a modified integral rate expression. The experimentally found kinetic parameters are confirmed by solving the simultaneous equations which describe the hydrolysis. This technique may be applicable to other hydrolytic enzymes with multiple substrates.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260350104
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