混凝土超声声速与强度和弹性模量的关系研究

在超声无损检测法的基础上，对四种不同强度等级、不同龄期标准混凝土试块进行超声波测试，同时作了抗压强度和弹性模量试验，通过试验得出了抗压强度、弹性模量和超声声速之间的函数关系式。     

钾盐在烟草燃烧过程中的作用

采用等体积浸渍法分别在烟草中加入硝酸钾KNO3、柠檬酸钾K3C6H5O7、草酸钾K2C2O4及酒石酸钾K2C4H4O6，并用差热分析（differential thermal analysis,DTA)、程序升温反应在线质谱分析（temperature-programmed reaction mass spectrometry on-line analysis,TPR-MS)方法对烟草进行了表征，用气相色谱法考察了主流烟气中CO含量的变化。结果表明，加入钾盐后，CO含量都有不同程度的降低。在钾盐含量为0．2475mmol/g的上述四种烟草样品上，烟气中CO含量按空白烟草T＞KNO3／T＞K2C2O4／T＞K3C6H5O7／T＞K2C4H4O6／T顺序排列。DTA给出的低温峰减弱、高温峰增强的结果表明，K^ 的加入改变了烟草燃烧过程中物质的转化历程，从而降低了卷烟的燃烧温度。通过对TPR－MS和DTA结果的联合分析，得出由于钾与烟草中的有机组分作用，含不同钾盐的烟草燃烧时产生了类似的含钾中间物质。证实了K^ 对烟草燃烧的作用机理，说明了钾盐降低烟草燃烧温度的原因。最后，还分析了主流烟气中CO含量的变化与DTA结果间的联系。     

贵州喀斯特山区农业结构调整与农村经济发展初探——以清镇示范区为例

党和国家西部大开发战略，国务院对当前和今后一个重要时期要集中力量进行的5个全局性重点工作之两点是：调整和优化农业结构，增加农民收入；加强生态环境保护和建设，退耕还林（草）。文章以贵州省清镇示范区为例，在农业产业结构现状分析的基础上，对贵州省喀斯特山区农业结构调整和农村经济发展提出了建议：1）走农业产业化经营之路；2）建立和完善农业市场体系；3）加强农民教育；4）有效转移农村剩余劳动力。     

新型载荷限制器工作原理及主要部件设计方法

提出了一种结构简单、可靠且价格低廉的升降机载荷限制器 ,介绍了工作原理和设计计算方法 ,为解决国内建筑用升降机的限载问题提供了可行方案     

冷连轧机的状态方程式

针对冷连轧过程的多变量最优控制问题,采用线性化的方法,从复杂的连轧过程基本公式出发,导出了冷连轧机最优控制所必须的状态方程式。     

感应电动机双馈调速的3种最佳控制方法

在交流电动机矢量控制的基础上,对双馈电机动的数学模型作了符合工程实际的简单,并且采用求极值的方法,推导了３种最佳控制方式。     

新型的电子式转子位置检测和测速装置

介绍了一种新型的转子位置检测器,它与已往的位置检测器相比较,不同之处在于去掉了与主电机同轴相连的小型绕线式感应电动机以及与其相关的复杂的机械连接部件     

基于线性预测滤波的抗速度欺骗干扰技术

针对调频连续波 (FMCW)雷达 ,提出了采用自适应线性预测滤波预处理实现速度欺骗干扰的检测。与直接对回波进行加速度补偿检测法相比 ,只需进行简单的门限检测即可判断干扰的存在及干扰参数估计 ,无需进行复杂的二维检测处理     

Regulation of BMP4 on the proliferation and differentiation in SVZa neural stem cells

The neural stem cells in the anterior subventricular zone (SVZa) mainly generate the progenitors that will differentiate into neurons, and along a highly circumscribed migratory access Rostral migratory stream (RMS), they migrate to the olfactory bulbs (OB). To understand the effects of BMPs on SVZa neural stem cells, in this study BMP4 at various concentrations was used to induce SVZa neural stem cells, and the living cell labeling using BMP4 promotor conjugated with red fluorescence protein showed the expression of BMP4 dynamically. The results demonstrated that low BMP4 doses (1-5 ng/mL) promoted while high doses (10-100 ng/mL) inhibited the proliferation of SVZa neural stem cells, and BMP4 promotedneuron differentiation in the early stage (1-3 d), howeverm, it inhibited the neuron commitment after 4 d. Noggin, the antagonist of BMP4, blocked the physiological effects of BMP4. In OB, BMP4 is mainly to accelerate the progenitors to withdraw from the cell cycle and trigger the differentiation, and in RMS, it promotes the proliferation of committed progenitors and not differentiation, further in SVZa, BMP4 enhances astrocyte commitment.     

Novel aspects of glypican glycobiology

Mutations in glypican genes cause dysmorphic and overgrowth syndromes in men and mice, abnormal development in flies and worms, and defective gastrulation in zebrafish and ascidians. All glypican core proteins share a characteristic pattern of 14 conserved cysteine residues. Upstream from the C-terminal membrane anchorage are 3–4 heparan sulfate attachment sites. Cysteines in glypican-1 can become nitrosylated by nitric oxide in a copper-dependent reaction. When glypican-1 is exposed to ascorbate, nitric oxide is released and participates in deaminative cleavage of heparan sulfate at sites where the glucosamines have a free amino group. This process takes place while glypican-1 recycles via a nonclassical, caveolin-1-associated route. Glypicans are involved in growth factor signalling and transport, e.g. of polyamines. Cargo can be unloaded from heparan sulfate by nitric oxide-dependent degradation. How glypican and its degradation products and the cargo exit from the recycling route is an enigma.Received 27 November 2003; received after revision 8 January 2004; accepted 13 January 2004