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931.
265Bh(Z=107)同位素的首次观测   总被引:1,自引:0,他引:1  
在兰州的重离子加速器上用26Mg离子束轰击243Am靶,产生了新同位素265Bh.通过观测新同位素265Bh和它的已知子核261Db和257Lr之间的α衰变的关联,实现了对新核素的鉴别.实验中使用了一套新建立的具有数个探测器对的转轮收集探测系统.将该系统用于特殊的母–子核搜索模式,从而大大减少了本底.共测得了8个265Bh的α衰变关联事件;同时4个已知核264Bh的衰变关联事件也被鉴别出来.实验测得265Bh的α衰变能量为(9.24±0.05)MeV,半衰期为0.94+0.70–0.31s.  相似文献   
932.
Grazing incidence x-ray diffraction study of Fe epitaxial ultrathin films (1.5-13 nm) on GaAs (001) reveals an anisotropy of both domain shape and strain, with [110] and [1-10] as the principal directions. It is shown that the observed thickness-dependent strain anisotropy, together with a uniaxial interface term, can provide an unambiguous explanation to the usual in-plane magnetic anisotropy and its thickness dependence observed in this magnetic thin-film system.  相似文献   
933.
Electrical poling induces polar ordering of molecules in a grating that has been holographically inscribed on a thin film of polymer with azobenzene side chains. The resulting chi2 grating, seen by second-harmonic-generation (SHG) near-field scanning optical microscopy, can have a periodic structure that is significantly different from the topographical image. The far-field linear and SHG diffration patterns correlate well with the grating structures. Poling of the thin-film grating, which presumably has photodriven nonuniform material properties within each period, leads to the more complex structure of the chi2 grating.  相似文献   
934.
We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location.  相似文献   
935.
We report a surprising observation that the growth of the [Fe(1 ML)/Co(1 ML)](n) superlattice of L1(0) structure on Cu(100) is stable only up to six atomic layers (n=3), which cannot be rationalized by stress arguments. Instead, first-principles calculations reveal a transition from the L1(0) to the B2 structure due to the effect of dimensionality on the stability of the electronic structure of the superlattice. Whereas the majority-spin electrons are energetically insensitive to the layer thickness, the minority-spin electrons induce the transition at n=3.  相似文献   
936.
The entropy of Einstein—Maxwell-dilaton—axion black holes is calculated by using the improved brick-wall model. Taking into account of the statistical physics, we propose not to consider the superradiant modes. The result shows that the nonsuperradiant modes do contribute exactly the area-law entropy for extreme black hole. Moreover, our cut-off which does not require an angular cut-off is independent of angle . As for the extreme black hole, we found that its entropy is zero.  相似文献   
937.
A SiO2 nanoscale island array was fabricated on a Si substrate by using anodic porous alumina as a mask. Transmission electron microscopy observation and the atomic force microscopy pattern show that the arrangement of SiO2 islands has a quasi-hexagonal symmetry. Ge ions with a dose of 1×1017 cm-2 were subsequently implanted into the SiO2 island array to form Ge-related light-emitting centers. The photoluminescence (PL) spectra of as-implanted and annealed samples show three PL bands at 370, 400 and 415 nm. Their intensities reach maximums in the sample with an annealing temperature of 700 °C. Spectral analysis suggests that the 370 and 415 nm PL bands arise from Ge-Ge and Ge-Si defect centers, while the 400 nm PL is related to GeO color centers in the SiO2 islands. The existence of these PL bands indicates the formation of a Si-based nanoscale light source array. PACS 78.55.Mb; 42.72.Bj; 68.65.+g  相似文献   
938.
In this communication, we report a numerical model that predicts the mechanical deformations associated with the pulsed laser irradiation of a film surface, based on thermal diffusion theory. The model is consequently advanced to produce a method for evaluating film adhesion strength. The epicenter surface displacements within the irradiated fields have been measured using a heterodyne interferometer. The comparison of the experimental data and the displacements calculated by the model shows good agreement. By investigating the propagating acoustic modes under non-destructive and destructive modes, we reveal that, with or without interface delamination, the phase structure of the longitudinal waves will be altered due to the change of reflection mode at the interface. Applying shock dynamics theory, we evaluate the adhesion strength of the TiN/stainless interface. We also indicate the strain rate can be up to 105∼106 s-1 during film interface delamination. Received: 5 April 2002 / Accepted: 24 June 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax: +86-511/879-1919, E-mail: mzhou@ujs.edu.cn  相似文献   
939.
Collecting, organizing, and reviewing chemical information associated with screening hits are human time-consuming. The task depends highly on the individual, and human errors may result in missing leads or wasting resources. To overcome these hurdles, we have developed a decision support system, Hits Analysis Database (HAD). HAD is a software tool that automatically generates an ISIS database file containing compound structures, biological activities, calculated properties such as clogP, hazard fragment labels, structure classifications, etc. All data are processed by available software and packed into a single SD file. In addition to search capabilities, HAD provides an overview of structural classes and associated activity statistics. Chemical structures can be organized by maximum common substructure clustering. The ease of use and customized features make HAD a chief tool in lead selection processes.  相似文献   
940.
Fractionation of the ethanolic extract of the seeds of Calophyllum inophyllum L. has resulted in the isolation of four novel pyranocoumarin derivatives, designated as inocalophyllins A (1), B (2) and their methyl esters (3, 4) in addition to the known calophyllolide. The structures of these compounds have been determined on the basis of spectroscopic analysis including MS, heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and two dimensional incredible natural abundance double quantum transfer experiment (2D-INADEQUATE). Two new methylated products, 5 and 6 were also prepared by methylation of compounds 1 and 2, respectively.  相似文献   
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