[en] Photoelectron measurements were obtained for Yb-C₆₀ and the results are compared to those reported for alkali-metal fullerides and Yb isolated in xenon or solid NH₃. The valence photoelectron spectra for Yb deposited on C₆₀ and C₆₀ on Yb show changes in the Yb 4f peaks, and in the C₆₀ valence states and a metal-induced state just above the Yb 4f bands. The position of this valence feature is near to that found for an analogous feature in the nonsuperconducting K₆C₆₀ fulleride. Similar features also appear when Yb is solvated in condensed ammonia. The appearance and binding energy of the Yb 4f levels argue that the Yb is largely divalent but has a small trivalent component. A comparison of the data for Yb-C₆₀ with that for Yb clusters in xenon shows that the changes in the electronic state of the Yb are not those found for small Yb particles in a nonreactive matrix

[en] Recent developments in NMR spectroscopy, especially multidimensional, multinuclear NMR techniques, have made NMR the most versatile tool available for studying protein structure and function in solution. Unlike diamagnetic proteins, paramagnetic proteins contain centers with unpaired electrons. These unpaired electrons interact with magnetic nuclei either through chemical bonds by a contact mechanism or through space by a pseudocontact mechanism. Such interactions make the acquisition and analysis of NMR spectra of paramagnetic proteins more challenging than those of diamagnetic proteins. Some NMR signals from paramagnetic proteins are shifted outside the chemical shift region characteristic of diamagnetic proteins; these open-quotes hyperfine-shiftedclose quotes resonances originate from nuclei that interact with unpaired electrons from the paramagnetic center. The large chemical shift dispersion in spectra of paramagnetic proteins makes it difficult to excite the entire spectral window and leads to distortions in the baseline. Interactions with paramagnetic centers shorten T₁ and T₂ relaxation times of nuclei; the consequences are line broadening and lower spectral sensitivity. Scalar (through bond) and dipolar (through space) interactions between pairs of nuclei are what give rise to crosspeak signals in multi-dimensional NMR spectra of small diamagnetic proteins. When such interactions involve a nucleus that is strongly relaxed by interaction with a paramagnetic center, specialized methods may be needed for its detection or it may be completely undetectable by present nD NMR methods

[en] Using kaufman ion source to produce low energy hydrogen ion beam bombarding polysilicon solar cells without AR coating in order to passivate the dangling bonds in grain boundaries, the authors found that the lower original photovoltaic efficiency are, the greater the relative improvement and saturated dose are. They used Photoelectron Energy Spectrometer (XPS) to analyze the cell surface for component, found that after hydrogen passivation Si-H bonds will form and the energy of photoelectrons increase about 0.26ev

[en] A novel design concept of molten salt pebble-bed reactor with an ultra-simplified integral primary circuit called 'Nuclear Hot Spring' has been proposed, featured by horizontal coolant flow in a deep pool pebble-bed reactor, providing 'natural safety' features with natural circulation under full power operation and less expensive primary circuit arrangement. In this work, the steady-state physical properties of the equilibrium state of the molten salt pebble-bed reactor are calculated by using the VSOP code, and the steady-state thermo-hydraulic analysis is carried out based on the approximation of absolutely horizontal flow of the coolant through the core. A new concept of 2-dimensional, both axial and radial, multi-pass on-line fuelling scheme is presented. The result reveals that the radial multi-pass scheme provides more flattened power distribution and safer temperature distribution than the one-pass scheme. A parametric analysis is made corresponding to different pebble diameters, the key parameter of the core resistance and the temperature at the pebble center. It is verified that within a wide range of pebble diameters, the maximum pebble center temperatures are far below the safety limit of the fuel, and the core resistance is considerably less than the buoyant force, indicating that the natural circulation under full power operation is achievable and the ultra-simplified integral primary circuit without any pump is possible. For the kinetic properties, it is verified that the negative temperature coefficient is achieved in sufficient under-moderated condition through the preliminary analysis on the temperature coefficients of fuel, coolant and moderator. The requirement of reactivity compensation at the shutdown stages of the operation period is calculated for the further studies on the reactivity control. The molten salt pebble-bed reactor with horizontal coolant flow can provide enhanced safety and economical features. (authors)

[en] Nonlinear characteristic emissions of Kα, Kβ and γ with a significant triplet splitting at room temperature are observed from the long-lived nuclear state of ^103mRh excited by bremsstrahlung irradiation. A pronounced phase-transition-like narrowing of the emission profiles occurs immediately after the sample is cooled down to 77 K. The room temperature profiles reappear again abruptly and almost reversibly as the temperature drifts freely back to approximately the ice point after the filling with liquid nitrogen is stopped. These emission properties at 300 K and at low temperature may indicate that the ^103mRh nuclei are in collective states.

[en] Photoelectron and near-edge spectroscopies are used to characterize a C₆₀ film on a Ta(110) surface. Like similar studies of C₆₀ on a variety of metal surfaces, the valence band, C 1s core level, and photoelectron-derived work-function measurements show that C₆₀ molecular states are aligned with the Fermi level and the charge is transferred from the metal to the fullerene. The photoelectron and near-edge spectra of the C₆₀ peaks closest to the Fermi level show significant changes in intensity identifying those π-like states as interacting with the substrate. A careful examination of the C 1s and Ta 4f core levels suggests that some fraction of the fullerene overlayer decomposes on the clean metal surface leading to or resulting in, a thin layer of carbon between the assembled film and the metal substrate

[en] The problem of hot water circulation pump head shortage is common. In this paper, numerical simulation technology, combined with orthogonal experimental design, was used to research optimal designs to improve the hot water circulation pump's head. CFX software was used to calculate the flow field in the pump, and the head-flow rate curve could be achieved. The accuracy of CFD was validated through comparison between numerical and experimental data. According to the experience, the number of impeller blades, thickness and width of impeller outlet were changed to improve the hot water circulation pump's head. A three factors and level values of model pump orthogonal experiment was designed, and numerical simulation of whole flow field based on CFX was adopted to implement the orthogonal experiment. Finally, the best designed scheme for model pump was obtained. The analysis of results indicates that the head of hot water circulation pump has increased by 7.77% at rated conditions. The distribution in impellers' internal flow field is symmetrical, and accords with the law of fluids flow in the common centrifugal pump

[en] A low-pressure CVD reactor was modified to create continuous compositional spreads of ZrO₂/HfO₂/SnO₂ on a single Si(100) wafer. Anhydrous metal nitrates were used as single-source precursors to grow the films, and the compositions were mapped using Rutherford backscattering spectroscopy (RBS). An array of 100 x 100 μm² capacitors was used to map the dielectric constant. High dielectric constants were observed for the films having high ZrO₂ concentrations, while high SnO₂ concentrations correlated with low values of κ. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

[en] By combining first-principles calculations and symmetry arguments, we propose that the half-metallic phase of K₂Cr₈O₁₆ presents ferromagnetic Weyl fermions. In particular, K₂Cr₈O₁₆ possesses two pairs of Weyl nodes, which originate from two groups of nodal lines connected by the mirror reflection symmetry. We show that the non-trivial topological properties of K₂Cr₈O₁₆ come from the partially occupied t_2g states of Cr, and we also demonstrate that such exotic topological feature is robust. The topological surface states and corresponding Fermi arcs are revealed. As K₂Cr₈O₁₆ is a realistic and widely studied material, our results suggest that K₂Cr₈O₁₆ is an ideal candidate for studying ferromagnetic Weyl fermions. In addition, K₂Cr₈O₁₆ possesses several interesting phenomena, such as the co-existence of charge density wave and Weyl fermions, even pairs of FM Weyl points, and tunable distribution of Weyl points, which will attract intensive attentions in this field. (paper)

No abstract available