Photoemission of LaI2 and CeI2

The electronic structure of the layered compounds LaI₂ and CeI₂ was investigated by photoemission and electron energy loss spectroscopy. From the experimental results we are able to confirm the metallic nature of these compounds, and by using photon energy dependent measurements of the valence band we can identify the orbital character of the conduction band as essentially 5d¹-like. A detailed analysis of the Ce 3d and 4f spectra yields a remarkably small 4f-5d hybridization strength, almost completely decoupling the f-electron from the conduction band, which makes CeI₂ a somewhat unusual system compared to other metallic Ce compounds. Band structure calculations by Jepsen and Andersen [1] confirm these experimental results.     

机载大斜视SAR的运动补偿方法

对机载大斜视的合成孔径雷达成像因速度变化引起的运动补偿方面的问题展开了研究 ,提出了大斜视角条件下运动补偿的方法 ,对其分别进行一次和二次相位补偿 ,并在进行方位压缩时考虑三次相位 ,其结果能较好地实现运动补偿。同时对补偿性能也作了分析 ,对基于运动参数估计的窄波束宽幅SAR成像算法进行了改进 ,增加一次和二次相位补偿的步骤 ,成为适用于机载大斜视SAR的成像算法     

Public-key encryption based on generalized synchronization of coupled map lattices

Currently used public-key cryptosystems are based on difficulties in solving certain numeric theoretic problems, in which the way to predict the private key from the knowledge of the public key is computationally infeasible. Here we propose a method of constructing public-key cryptosystems by generalized synchronization of coupled map lattices, in which the difficulty in predicting the synchronous function is used as the trap-door function to deduce the private key from the public key. In specific, we implement this idea on the method of "Merkle's puzzles," and find that, incorporated with the chaotic dynamics, this traditional method is equipped with some new features and can be practical in certain situations.     

Fluorescence fluctuation spectroscopy and its artifacts: simulations and tests

Fluorescence fluctuation spectroscopy (FFS)[1,2] is a kind of fluorescence detection techniques suitable for monitoring interaction and transportation processes in a small detection zone of biological systems. FFS detects and analyzes the fluorescence signal of the fluorescent molecules in the detection zone to retrieve the dynamical parameters of the system including concentration, diffusion coefficient and interaction constants. FFS utilizes various statistical methods to analyze the data,…     

Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide glasses

Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 micros. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth-tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications.     

Ice tessellation on a hydroxylated silica surface

The adsorption of water on a fully hydroxylated silica surface is studied by using density-functional total-energy and molecular dynamics calculations. The (100) surface of beta(alpha)-cristobalite covered by geminal hydroxyls has been taken as the substrate. A well-ordered and stable two-dimensional ice with quadrangular and octagonal patterns of hydrogen bond (H-bond) networks-an ice tessellation-is found on the surface for the first time. With the vibrational recognition, the four water molecules in the quadrangle are found to be bonded by strong H bonds while the quadrangles are connected to each other by weak H bonds. This configuration is the most stable, because all the water molecules are fully saturated with H bonds either to each other or to the surface hydroxyl groups.     

Octanuclear metallocyclic Ni4Fc4 compound: synthesis, crystal structure, and electrochemical sensing for Mg2+

New, neutral octanuclearmacrocyclic compound Ni(4)Fc(4) was achieved via self-assembly from Ni(BF(4))(2) and a ferrocene-containing bis-tridentate ligand. The compound exhibits a channeled structure with cavities inside and senses the Mg(2+) electrochemically in the solid state.     

A fast Fourier transform on multipoles (FFTM) algorithm for solving Helmholtz equation in acoustics analysis

This article presents a fast algorithm for the efficient solution of the Helmholtz equation. The method is based on the translation theory of the multipole expansions. Here, the speedup comes from the convolution nature of the translation operators, which can be evaluated rapidly using fast Fourier transform algorithms. Also, the computations of the translation operators are accelerated by using the recursive formulas developed recently by Gumerov and Duraiswami [SIAM J. Sci. Comput. 25, 1344-1381(2003)]. It is demonstrated that the algorithm can produce good accuracy with a relatively low order of expansion. Efficiency analyses of the algorithm reveal that it has computational complexities of O(Na), where a ranges from 1.05 to 1.24. However, this method requires substantially more memory to store the translation operators as compared to the fast multipole method. Hence, despite its simplicity in implementation, this memory requirement issue may limit the application of this algorithm to solving very large-scale problems.     

Freeze-drying of mononuclear cells and whole blood of human cord blood

The research on haematopoietic stem cells of human cord blood has become more important recently. People have concentrated on the preservation of cord blood stem cells. At present, cord blood can be preserved at ultra-low temperatures. In this study, we try to preserve cord blood and its constituents by freeze-drying. The experiments on both the mononuclear cell content and the whole blood of human cord blood were carried out respectively. The samples were frozen firstly by different cooling protocols in the presence of PVP, sucrose, and mannitol. Afterwards, they were vacuum-dried at a selected shelf temperature of -30 degree C for the main drying stage, and then vacuum-dried at 15 degree C for the second drying stage. The entire time of the freeze drying was 52 hours. Samples were stored at room temperature for 2 days prior to evaluation. Subsequently, the dried samples were suspended in an isotonic phosphate-buffered saline solution. The recovery of the cells were tested by a haemacytometer, and the highest cell numerical count recovery of MNC was 75.0 percent (SD = 4.1 percent) (P = 0.01), obtained in the protocol of 40 percent PVP + 20 percent sucrose + 10 percent Mannitol. The viability of the nucleated cells measured by PI staining and the ratio of the number of CD34+ to the number of lymphocytes (by the FITC anti-human CD34+ conjugated antibody method) were measured using a flow cytometer (FCM). The protocol of 40 percent PVP + 20 percent sucrose + 10 percent fetal bovine serum had the highest viability of 98.6 percent (SD = 0.7 percent) (P = 0.01). The highest ratio of CD34+ to lymphocytes was 1.2%, and the highest recovery of CD34+ was 68.4 percent (SD = 39.5 percent) (P = 0.05). Comparing the results of the lyophilized MNC subfraction with that of the whole blood, the lyophilization of the isolated MNC was more successful than that of whole blood.     

Configuration assignments of yrare high-spin structures in 126Cs

High-spin states in ¹²⁶Cs were populated in the reaction ¹¹⁶Cd(¹⁴N, 4n) at a beam energy of 65 MeV. About 50 new transitions were placed in a level scheme that consists of six rotational structures, three of which have been observed for the first time. The newly observed bands and a previously reported but uninterpreted band were assigned configurations based on their population, aligned angular momentum, energy signature splitting and B(M1)/B(E2) ratios (for the strongly coupled bands).Received: 16 September 2002, Revised: 10 March 2003, Published online: 1 July 2003PACS: 21.10.Re Collective levels - 27.60.+j