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  • 1
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    A revision of the subtribe Brulleiina van Achterberg (Hymenoptera: Braconidae: Helconinae) from China (1993)
    In:  Zoologische Mededelingen vol. 67 no. 28, pp. 375-395
    Details
    Publication Date: 2024-01-12
    Description: The species of the genera Brulleia Szepligeti, 1904, and Parabrulleia van Achterberg, 1983, of the subtribe Brulleiina van Achterberg (Braconidae: Helconinae) from China are revised and keyed. Ten species are recognized, and all nine Brulleia species are new to science.\nXuexin Chen & Junhua He, Institute of Applied Entomology, Zhejiang Agricultural University, Hangzhou 310029, China.
    Keywords: Braconidae ; Helconinae ; Brulleiina ; Brulleia ; Parabrulleia ; new species ; key ; distribution ; Oriental ; Palaearctic ; China
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and magnetic properties of rare-earth iron nitrides, carbides and carbonitrides (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6017-6022 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Iron-rich rare-earth (R) compounds, such as R2Fe17 do not show great potential for high-performance magnet materials due primarily to their low Curie temperatures (Tc∼300–400 K). However, relatively large quantities of nitrogen or carbon atoms can be introduced into the structure, resulting in a dramatic enhancement of magnetic properties including Tc (≥700 K). The N or C atoms cause a volume expansion of a few percent of the unit cell without changing the crystal structure. The large increase in Tc can be attributed to the volume dependence of the Fe–Fe exchange interactions. A large uniaxial anisotropy field develops for R=Sm upon nitriding/carbiding with an anisotropy field that is almost double the value for Nd2Fe14B at room temperature. Problems including the precipitation of soft magnetic phases (mainly α–Fe) and the limited thermal stability of the nitrides have so far restricted the applications of these compounds. Here data are presented on combined carbide/nitride alloys prepared using a novel technique. These alloys exhibit many of the advantages of the pure compounds but with greater thermal stability and less interference from precipitated phases. A typical material, Sm2Fe17(NxC1−x)3−δ has a Tc of 758 K and an anisotropy field (μ0HA) of 15 T at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353456
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature dependence of coercivity in MnBi : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6275-6277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In contrast to most ferromagnetic materials, the low-temperature phase of MnBi exhibits an increased coercivity, Hc, with temperature. μ0Hc has a value of 0.2 T at room temperature, and rises dramatically to a maximum value of 1.9 T at 550 K. In the temperature region near its maximum value, Hc is much larger than that of Nd-Fe-B and has a very-low-temperature coefficient. For this reason, MnBi has a great potential as a permanent magnet material at high temperatures. To describe the temperature dependence of Hc, we develop a hybrid domain-wall pinning model which combines Hilzinger and Kronmüller's scaling theory for an anisotropic domain wall with Gaunt's theory of thermal activation. The hybrid model gives an excellent fit to the temperature dependence of Hc and provides good estimates for the domain-wall energy and thickness over the temperature range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352668
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of the chemical nature of transition-metal substrates on chemical-vapor deposition of diamond (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4168-4173 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemical-vapor deposition of diamond on transition-metal substrates of Cu, Ni, Fe, and their alloys NiAl, Ni3Al, FeSi2, and FeSi has been investigated. It is shown that diamond grows easily on Cu with a very small amount of graphite, while on Ni and Fe there is rapid growth of the graphite layer before diamond deposition. The formation of graphite is attributed to the decomposition of carbon-containing precursors due to the strong catalytic reactivity of Ni and Fe substrates with carbon. The deactivation of these substrates by forming NiAl and FeSi2 results in the suppression of graphite and formation of high-quality diamond. However, for Ni3Al and FeSi substrates which are not completely deactivated, deposition of graphite still takes place. A mechanism based on the electronic structure of substrate atoms, particularly on the 3d shell structure of Cu, Ni, and Fe is proposed to understand the above behavior. Requirements for the stabilization of sp3 bonding of carbon on different substrates are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354420
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  • 5
    Electronic Resource
    Electronic Resource
    Specific heat measurements of pressure-induced reentrant superconductivity in Eu0.9Ho0.1Mo6S8 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1886-1891 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Specific heat measurements of Eu0.9Ho0.1Mo6S8 were performed using an ac calorimetry technique under the extreme conditions of low temperature, high magnetic field, and hydrostatic pressure. The title compound is a Chevrel phase material, which is paramagnetic at ambient pressure, becomes superconducting for pressures above 7 kbar, and has a reentrant upper critical field [dHc2(T)/dT≥0, as T→0 K]. Evidence that this material also has a high magnetic field-induced superconducting phase at low temperatures (H≥5 T, T≤1 K) was previously reported. The present ac calorimetry study carried out for 0.15≤T≤6 K, 0≤H≤20 T, and P(approximately-equal-to)8 kbar, shows a sharp superconducting transition for T≤1 K in the specific heat, which broadens at higher fields and temperatures. The results are analyzed to obtain a reentrant phase diagram in agreement with previous transport work, but direct evidence for the high field-induced phase was not found. The mechanism for the field and temperature dependence of the superconductivity of Eu0.9Ho0.1Mo6S8 is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353176
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  • 6
    Electronic Resource
    Electronic Resource
    Mössbauer study of intercalation modified compounds R2Fe17 (R=Y, Sm) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6038-6040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mössbauer studies were carried out at 77 K in two series of R2Fe17 compounds with a magnetic (Sm) and nonmagnetic (Y) rare-earth, intercalated with H, C, and N. The increase in hyperfine field is largest at the 12j(18f) sites for R2Fe17H3.7 and R2Fe17N2.3. While the lattice expansion in R2Fe17C2 is similar to that in the nitrides and hydrides, the small change in hyperfine fields at the 12j(18f) and 12k(18h) sites indicates that the presence of neighboring carbon largely cancels the moment increase associated with the volume increase. For R2Fe17 carbonitrides, a single, sharp magnetic transition indicates a uniform compound. However, Mössbauer spectra suggest the existence of both C-rich and N-rich precipitates in the carbonitrides whose average hyperfine fields and isomer shifts scale with the nitrogen to carbon ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353462
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of Pb (ZrxTi1−x)O3 thin films produced by an automated laser ablation deposition technique (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5197-5207 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric lead zirconium titanate [Pb (ZrxTi1−x)O3] (PZT) thin films have been synthesized by using an automated laser ablation deposition technique with a capability for layer-by-layer or simultaneous deposition of elemental film constituents. The technique is suitable for producing multicomponent and/or multilayered thin films with controlled stoichiometry, such as high-temperature superconductor, ferroelectric, and electro-optic thin films. PZT films were synthesized on MgO (100) by either sequential deposition of layers of ZrO2, TiO2, and PbO, produced by laser ablation of ZrO2, TiO2, and PbO targets, or by simultaneous deposition of all species from ablation of stoichiometric or PbO-rich PZT targets. Films were deposited at 200 °C and subsequently annealed at 600 °C for different periods of time. The orientation, microstructure, surface topography, and composition of the films were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry, respectively. As-deposited layer films consists of highly oriented (001) PbO layers, from which highly oriented (110) PZT films are produced after postdeposition annealing. On the other hand, laser ablation of bulk PZT targets yields amorphous as-deposited films, which evolve into highly oriented (100) PZT films after postdeposition annealing. Preliminary electrical characterization of the PZT films included polarization hysteresis, fatigue, conductivity (ac and dc), and capacitance versus voltage measurements. From the initial electrical measurements, it appears that the remnant polarization of the layered PZT films is similar to that of the films produced by laser ablation of bulk PZT targets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353746
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  • 8
    Electronic Resource
    Electronic Resource
    Alignment of Hg–Ar van der Waals molecule photofragments following photodissociation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 9608-9615 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the alignment of the photofragments produced by photodissociation of Hg–Ar van der Waals molecules using light around 253.7 nm. The molecules are produced in the X0+ ground state in a supersonic expansion. Tunable laser light close to the Hg 6 1S0–6 3P1 transition is then used to excite the molecule to the B1± state, in which it dissociates. The alignment of the resulting Hg(3P1) asymptotic atoms is probed by tuning a delayed second laser to the 435.8 nm Hg 6 3P1–7 3S1 atomic transition and monitoring the subsequent fluorescence on the 7 3S1–6 3P2 transition around 546.1 nm. These measurements have been made, we believe for the first time, as a function of dissociating energy from very close to threshold to higher energies. The alignment shows a significant rise with increasing photon energy in line with a semiclassical picture of orbital locking at lower energies and rapid decoupling at higher energies. The results exhibit good agreement with the results of a fully quantum mechanical theory of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465494
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  • 9
    Electronic Resource
    Electronic Resource
    Two-dimensional self-focusing of short intense laser pulse in underdense plasma (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1336-1348 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simplified set of three-dimensional equations are derived for the propagation of an intense laser pulse of arbitrary strength a=eA/mc2 (where A is the magnetic vector potential of the laser pulse) in cold underdense plasma. In different limits, the equations can be easily reduced to those of previous one-dimensional models [Phys. Fluids 30, 526 (1987); Phys. Rev. A 40, 3230 (1989); 41, 4463 (1990)]. For ||a||≤1, an approximate set of equations from the averaged Lagrangian is obtained. The present study differs from previous work in that wave dispersion is also important for short laser pulse, and is included in the model equations. The axisymmetric two-dimensional model equations are solved numerically to show the effect of dispersion in the self-focusing process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860923
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  • 10
    Electronic Resource
    Electronic Resource
    Microbiological transformations. 27. The first examples for preparative-scale enantioselective or diastereoselective epoxide hydrolyses using microorganisms. An unequivocal access to all four bisabolol stereoisomers (1993)
    s.l. : American Chemical Society
    The @journal of organic chemistry 58 (1993), S. 5528-5532 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00072a043
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