远离稳定线核研究进展

近几年在对远离核的实验研究中,观测到了理论预言的新衰变模式,如45Fe的双质子衰变,β-缓发裂变;对中子滴线外一些核的存在可能性也进行了较多的实验探索和理论分析;开始了对人们一直关注的中子集团存在可能性的实验探索.远离核谱学和衰变性质研究逐渐深入,通过对一些远离核第一激发态能量的系统比较和许多远离核β衰变Q值的测量,以及核质量的精确测量,发现在远离核区,原有的一些幻数消失,代之产生了一些新的幻数,对其产生原因的理论分析做了简要的综述. Recently the predicted new decay model, for instance two-proton decay and β~(-)delayed fission have been observed in the investigations of the nuclei far from stability line. The existence of the nuclei located beyond the drip-line has already been studied experimentally and theoretically. It has been started to search for the neutron cluster in experiment by using neutron-rich nuclei. The researches of the spectroscopy and decay properties of the nuclei far from stability line are more and deeper, and...     

Phase behaviour and physical properties of the cationic quaternary system tetradecyldimethylamine oxide hydrochloric acid 1-hexanol water

 The phase behaviour and properties of the tetradecyldimethylamine oxide/HCl/hexanol/water quaternary surfactant system have been studied by means of electric conductivity, rheology, freeze-fracture transmission electron microscopy (FF-TEM) and small-angle neutron scattering (SANS). In this system the originally zwitterionic surfactant can become increasingly charged by protonation through the addition of HCl, i.e. the degree of charging can be changed continuously. An interesting, isotropic phase (L₁ ^* phase) of low viscosity was observed for intermediate degrees of charging. From viscosity and conductivity measurements this phase can clearly be distinguished from the conventional L₁ phase that is composed of micelles. Investigation of the structures present by means of FF-TEM and SANS showed that the L₁ ^* phase is made up of unilamellar vesicles of extremely small diameter of 8–10 nm. Evidently such highly curved structures are stabilized by the electrostatic conditions in this system. Received: 11 July 1999/Accepted: 25 August 1999     

奇奇核与奇A核n-p相互作用

从结合能实验值提取n-p相互作用能ε_ip-jn,系统比较了奇奇核单质子单中子相互作用能ε_1p-1n与相邻奇A核相应量的平均值,发现前者普遍大于后者.提出奇奇核n-p增强的解释为,GMshift效应和同类核子对关联对奇A核n-p相互作用的削弱效应.同时指出,奇质子核的ε_1p-2n相当好地近似等于同质量数奇中子核的ε_2p-1n,并且这与Garvey-Kelson关系是等价的.     

Effect of Ligand Polarity on the Internal Dipoles and Ferroelectric Distortion in BaTiO3 Nanocubes

Surface adsorbates and surrounding matrix species have been demonstrated to affect the properties of nanoscale ferroelectrics and nanoscale ferroelectric composites; potentially counteracting performance losses that can occur in small particle sizes. In this work, the effects of nonpolar oleic acid (OA) and polar tetrafluoroborate (BF₄⁻) ligand capping on the surface of various sizes of BaTiO₃ nanocubes have been investigated with combined neutron diffraction and neutron pair distribution function (PDF), density functional theory (DFT), and ab initio molecular dynamics (AIMD) methods. The low real space PDF region provides an unobstructed view of rhombohedral (split short and long) Ti−O distances in BaTiO₃ nanocubes, mimicking the well-established order-disorder local structure found in bulk BaTiO₃. Interestingly, the intermediate-range order in nanocubes is found to be orthorhombic, rather than tetragonal. It is concluded that polar ligands adsorbed at BaTiO₃ surfaces stabilize the correlation length scale of local rhombohedral distortions in ferroelectric nanoparticles relative to nonpolar ligands.     

Anwendung de Neutronenaktivierungsanalyse für die industrielle Gütekontrolle von Halbleitermaterialien

Die Anwendung der Neutronenaktivierungsanalyse als Verfahren zur Bestimmung von Spurenverunreinigungen in hochreinen Materialien, von Zusammensetzungen bei Mehrkomponenten-systemen, von Verteilungen eines Elements in einer anders-artigen Matrix und von Umgruppierungen bestimmter Elemente im Verlauf technologischer Teilschritte ist seit langem bekannt und nimmt einen festen Platz vor allem auch in der Halbleiter-technik ein [1, 2]. Die extremen Empfindlichkeitsanforderungen bei der Bestimmung von Mikroverunreinigungen sprechen trotz des relativ hohen Arbeits-und Zeitaufwands oftmals für die Aktivierungsanalyse, zumal die in der letzten Zeit erzielten Fort-schritte in der Meßtechnik und bei der rechnergestützten Auswertung einen neuen Qualitätsaspekt bewirkten.     

Erste Ergebnisse zur Anwendung der prompten Gammastrahlung im Hinblick auf die vor Ort Anwendung in der Bauzustandsanalyse

Im Hinblick auf eine vor Ort Anwendung auf dem Gebiet der Bauwerksdiagnostik stellt die vorliegende Arbeit erste Ergebnissc vor, die unter Ausnutzung der prompten Gammastrahlung erzielt wurden. Dabei werden ausschlieβlich, unelastische Streuprozesse schneller Neutronen an der Probenmatrix betrachtet. Dic Anregung erfolgte mit einer ²³⁸Pu/Be-Neutronenquelle mit einem Neutronenfluβ von ca. 5 × 10⁷ s^?1 und die Registrierung der prompten Gammastrahlung mit einem NaI(Tl)-Kristall. Besonderes Augenmerk galt den Elementen Mg, Al, Si und Fe als qualitätsbeeinflussende Parameter des Betons.

This publication is a contribution to the application of nuclear metltods in civil engineering. In view of in situ determination of elements in walls of concrete the first results of applying prompt gamma radiation, due to inelastic scattering of fast neutrons in the sample are shown. The stimulation of prompt gamma-rays is carried out by means of a ²³⁸Pu/Bneutron source with a flux of neutrons of about 5 × 10⁷ s^?1 and the detection of gamma radiation by means of a Nal(Tl)- deteclor. The elements Mg, Al, Si and Fe as the parameters of quality of concrete were the elements of interest.     

Untersuchungen an syenitoiden und gabbroiden Gesteinen mittels Mößbauer-Spektroskopie und Neutronenaktivierungsanalyse

The study of trace element distribution in minerals from basic and intermediate igneous rocks is actually important, esp. in connection with tectonic and magmatic processes. We can find some information about metallogenetic aspects by means of combination of ⁵⁷Fe Moessbauer spectrometric investigation and trace clement geochemistry, esp. the method of instrumental neutron activation analysis.     

Absolute Cross Sections for some Reactions Induced by Differential Neutron Flux

The measurements of activation cross sections for some reactions induced by a differential neutron flux of (D-T) compact neutrons generator were discussed. The comparison of measured cross sections with those averages calculated from the energy cross section curves found in the literature gives good agreement. The used thin targets were prepared under vacuum by both evaporation and sputtering techniques.     

随机时滞教学系统的最优习得策略

认识非线性随机时滞现象的内在机理、运演性态和掌握其内在规律己成为当今非线性随机动力学理论分析与数值分析的重要主题.基于教学论、自组织理论和非线性随机时滞动力学等理论及其有关研究成果,构建教学系统的非线性随机时滞Logistic模型,寻求教学系统的演化规律,并在此基础上研究教学系统的最优习得策略和提出相应教学建议,期望能促进教学系统有序发展;同时,也期望能促使教学论与非线性随机动力学等理论"联姻",拓展与丰富教学论的研究领域,为教学论研究提供一个新的学科视角的支持与论证.     

Certain Trace Metal Disorders in Urinary Bladder of Bilharzial Patients suffering Bladder Carcinoma

The objective of the present work is to investigate any possible role which could have been played by the long-term treatment with antimony as an antibilharzial drug, and the development of urinary bladder carcinoma in patients suffering bilharzial complications. The present work has been planned to investigate the concentration levels of copper, zinc and antimony in urinary bladder tissues sampled from normal, bilharzial and bladder cancer patients subjected to surgical intervention. Both atomic absorption spectrophotometry and neutron activation analysis have been utilized for elemental estimations. The data obtained showed significant increase in the concentration levels of the three investigated metals in bladder cancer tumours as compared with their control levels under either normal or cancer-free bilharzial complications. The results have been statistically evaluated and discussed in view of the relevant literature. It has been concluded that the contributing role of the antibilharzial antimonial treatment in development of urinary bladder cancer cases cannot be overlooked and awaits further investigation.