[en] Differential cross sections for neutrons scattered from natural Pb and 99.9% isotopically pure ²³⁸U have been measured at 0.5⁰, 1.0⁰ and 1.5⁰. A neutron energy continuum was produced by bombarding a thick natural lithium target with a 4 MeV, nanosecond-pulsed proton beam. Neutron energies were determined by time-of-flight techniques. Flight paths from the neutron source to the scatterer and from the scatterer to the detector were each about 5 m. For the 0.5⁰ measurements an annular detector geometry with an angular resolution of +-0.1⁰ was developed to maximize detection solid angle. Data were averaged over 100 keV intervals from 0.6 to 2.2 MeV and were corrected for backgrounds, multiple scattering and inelastic scattering. Measured cross sections were compared to optical-model calculations which included electromagnetic interactions of neutrons with the nuclear Coulomb field. Inclusion of an induced neutron electric dipole moment interaction was not warranted by the data. The angular dependence of the cross section was fitted with a function A+B cot²1/2-theta at each energy. Mean values of B for ²³⁸U are in agreement with theoretical predictions. Values of B for Pb are apparently 15% too low. (Auth.)

[en] A new molybdenum phosphide (MoP) catalyst was successfully synthesized for CO/sub 2/ reforming of CH/sub 4/ reaction. The catalysts were prepared by temperature-programmed reduction (TPR) of phosphomolybdate precursors which were modified by citric acid (CA) at the molar ratio of MoP:CA = 1: x (x = 0, 1.0, 2.0, 3.0), which were characterized by means of X-ray diffraction(XRD), N/sub 2/ adsorption-desorption and CO/sub 2/-TPD techniques. The results showed that the addition of citric acid can affect the catalytic activity and that the MoP catalyst had the highest catalytic activity at 1073 K and X=1. After reduced in H2 flow at 923 K, the activity of the post-reaction catalyst can be well restored, while its structure remains unchanged. In higher temperatures, the samples exhibit good anti-sintering ability and stability. (author)

[en] Fission of ²³²Th was induced by a pulsed beam of monoenergetic fast neutrons. A heavy-ion surface barrier detector was used for the detection of fission fragments. Fragment mass was determined from measured fragment energy and fragment flight time. Fragment mass distribution and correlation of fragment kinetic energy with fragment mass were obtained for neutron incident energies of 1.6, 3.1, and 5.2 MeV. A strong dependence on shell energy is suggested from the increase of the most probable total kinetic energy of the fission fragments with increase in excitation energy of the compound nucleus

[en] Shot peening is an effective surface treatment method, which can improve the fatigue properties of metallic materials. In the present paper, the residual compressive stress field induced in TC4-DT titanium alloy under different shot peening conditions and the thermal relaxation behaviors of shot-peened TC4-DT were discussed. The shot peening can cause residual compressive stress on the material surface compared to un-peened materials. The subsurface residual stress distributions of original and shot-peened specimens were measured by an X-ray diffraction method. The residual compressive stress profiles accord with the characteristic curve of residual stress field. The maximum residual compressive stress is located at subsurface layer. Surface roughness also increases with increasing shot peening intensity. There is relaxation of residual compressive stress during temperature. Thermal relaxation behavior of residual stress was studied at 150 and 300 deg. C with different ageing time. The residual stress relaxation is influenced by temperature and time during ageing. Thermal relaxation of residual stress is a thermal recovery process. The relaxation process of thermal residual stress is analyzed by applying the Zener-Wert-Avrami function.

[en] Arsenic (As) is widely found in marine organisms, mainly as organic arsenical compounds. With the introduction of regulations for As species in foodstuffs and for environmental control, it has become more important to quantify the amount of arsenic species present. To address this concern new reference materials (RMs) for validation and quality assurance of As speciation measurements are being developed, including a tuna fish tissue and a robalo liver tissue. Instrumental neutron activation analysis (INAA) is used in this work as a proven analytical tool for As determinations and for validating the As mass fraction determined by liquid chromatography coupled to inductively coupled mass spectrometry (LC-ICP-MS) in extracts of the candidate RMs and other fish samples including certified RMs. Various methods for the extraction of water-soluble As species were evaluated. The best results were acquired after methanol/acetone/water extraction yielding in 93 % extractable As in the tuna RM. This procedure was used for the LC-ICP-MS studies. The results demonstrate that INAA can account for 100 % of the distribution of As species in analytical processes. It complements LC-ICP-MS for the validation of the characterization of As species in the development of RMs for such species. Excellent agreement of measured results in certified RMs with the reported values confirms the validity of the applied procedures. (author)

[en] Methods for the calculation of laser tunneling ionization in explicit particle-in-cell codes used for modeling laser–plasma interactions are compared and validated against theoretical predictions. Improved accuracy is obtained by using the direct current form for the ionization rate. Multi level ionization in a single time step and energy conservation have been considered during the ionization process. The effects of grid resolution and number of macro-particles per cell are examined. Implementation of the ionization algorithm in two different particle-in-cell codes is compared for the case of ionization-based electron injection in a laser–plasma accelerator

[en] Bismuth titanate (Bi₄Ti₃O₁₂ (BTO)) nanocrystals have been prepared by metal-organic decomposition. X-ray diffraction revealed that the BTO nanocrystals belong to the orthorhombic system with average size of ∼60 nm. Raman scattering and Fourier-Transform infrared measurements of BTO nanocrystals showed a large decrease of the number of peaks comparing to the space group theoretical analysis. It could be interpreted by the fact that the characteristic vibration modes of BTO nanocrystals arise mainly from the internal modes of TiO₆ octahedra, which in return lead to modes degeneration. Raman shifts and infrared absorption bands of BTO nanocrystals were tentatively assigned. Large distortions in Ti(2)O₆ octahedra lead originally Raman active modes to become IR active as well and are testified by our FTIR result. An inactive mode for has been found in both our Raman and FTIR data. That might be originated from oxygen vacancies and internal strain, which is commonly explained for the mechanism of the fatigue in BTO