Central nervous system stem cells in the embryo and adult

The central nervous system is generated from neural stem cells during embryonic development. These cells are multipotent and generate neurons, astrocytes and oligodendrocytes. The last few years it has been found that there are populations of stem cells also in the adult mammalian brain and spinal cord. In this paper, we review the recent development in the field of embryonic and adult neural stem cells. Received 26 March 1998; received after revision 27 April 1998; accepted 27 April 1998     

织轴生产新方法及其相应设备

通过对整经和上浆数学模型的研究．提出了织轴生产工艺参数控制的新方法．并利用这种新方法对有关的设备做了改进，产生了显著的经济效益。     

无线通信——理论和技术

无线通信系统以移动通信形式出现以来．已经快速席卷整个世界。这种系统正在给我们生活带来巨大变化，甚至可以说，无线通信正在改变着我们的生活方式。移动通信不仅仅是一种通信方式，它更是一种商业契机。在过去短短20年当中，手机已经快速从第一代发展到第三代。在未来的20年中，手持电话将会快速取代固定电话，数量将会达到大约7．5亿部。正如评论家所言，移动通信技术是自从计算机普及以来在远程通信当中最为重要的一项技术。     

水平排列硅光二极管色传感器及其特性

简要介绍水平排列硅光二极管色传感器的制作工艺，该器件波长在５００ｎｍ到６５０ｎｍ范围内有一个单调的近于线性的光谱响应。入射光波长为６００ｎｍ时，入射光强度化五个数量级，测出的波长基本不变，器件波长分辨率、最低入射光强、长时间测量的波长漂移以及波长温漂系数等特性的测量结果表明：该类色传感器已达高性能实用要求。     

直线永磁振动电机的磁场与静推力特性分析

主要介绍了一种直线永磁振动电机的结构及其工作原理，并用有限元软件对其在不同位置时的磁场进行了分析，同时搭建实验台做了实际的测试，给出了误差及出现误差的原因。该电机结构简单，可靠性高，寿命长，易维护，并且控制电路简单，运行平稳，适用于小功率电磁间的开关系统中。     

PowerBui1der9．0动态下拉数据窗口的应用

本文介绍在PowerBuilder的数据窗口中利用DropDownDW形式的下拉列表输入枚举型数据的方法，既可提高数据输效率和准确性，又可动态更新下拉列表中枚举型数据，提高软件的适应性。     

Skyrmions in a ferromagnetic Bose-Einstein condensate.

Multi-component Bose-Einstein condensates provide opportunities to explore experimentally the wealth of physics associated with the spin degrees of freedom. The ground-state properties and line-like vortex excitations of these quantum systems have been studied theoretically. In principle, nontrivial spin textures consisting of point-like topological excitations, or skyrmions, could exist in a multi-component Bose-Einstein condensate, owing to the superfluid nature of the gas. Although skyrmion excitations are already known in the context of nuclear physics and the quantum-Hall effect, creating these excitations in an atomic condensate would offer an opportunity to study their physical behaviour in much greater detail, while also enabling an ab initio comparison between theory and experiment. Here we investigate theoretically the stability of skyrmions in a fictitious spin-1/2 condensate of 87Rb atoms. We find that skyrmions can exist in such a gas only as a metastable state, but with a lifetime comparable to (or even longer than) the typical lifetime of the condensate itself.