在nNaF·AlF_3-Al_2O_3-MgF_2-CaF_2系熔体中铝损失的数学模型

本文采用了差重法与气相确定剩余铝量的方法,研究了金属铝在 nNaF·AlF_3-Al_2O_3-MgF_2-CaF_2 系熔体中的溶解损失规律,利用三因子二次回归正交设计建立起了金属铝在该系熔体中溶解损失的数学模型。     

Inositol 1,4,5-trisphosphate induces calcium release from sarcoplasmic reticulum of skeletal muscle

The sarcoplasmic reticulum of skeletal muscle is a specialized form of endoplasmic reticulum that controls myoplasmic calcium concentration and, therefore, the contraction-relaxation cycle. Ultrastructural studies have shown that the sarcoplasmic reticulum is a continuous but heterogeneous membranous network composed of longitudinal tubules that surround myofibrils and terminal cisternae. These cisternae are junctionally associated, via bridging structures called 'feet', with sarcolemmal invaginations (the transverse tubules) to form the triadic junction. Following transverse tubule depolarization, a signal, transmitted along the triadic junction, triggers Ca2+ release from terminal cisternae, but the mechanism of this coupling is still unknown. Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) has recently been shown to mobilize Ca2+ from intracellular stores, referable to endoplasmic reticulum, in a variety of cell types (see ref. 8 for review), including smooth muscle cells of the porcine coronary artery and canine cardiac muscle cells. Here we show that Ins(1,4,5)P3 releases Ca2+ from isolated, purified sarcoplasmic reticulum fractions of rabbit fast-twitch skeletal muscle, the effect being more pronounced on a fraction of terminal cisternae that contains morphologically intact feet structures; and elicits isometric force development in chemically skinned muscle fibres.     

Tissue protection against oxidative stress

We used an enhanced luminescence technique to study the response of rat tissues, such as liver, heart, muscle and blood, to oxidative stress and to determine their antioxidant capacity. As previously found for liver homogenate, the intensity of light emission (E) of tissue homogenates and blood samples, stressed with sodium perborate, is dependent on concentration, and the dose-response curves can be described by the equation E=a·C/exp(b·C). Theb value depends on the antioxidant defence capability of the tissues. In fact, it increases when homogenates are supplemented with an antioxidant, and is correlated with tissue antioxidant capacity, evaluated by two previously set up methods both using the same luminescence technique. Our results indicate that the order of antioxidant capacity of the tissues is liver>blood>heart>muscle. Thea value depends on the systems catalysing the production of radical species. In fact, it is related to the tissue level of hemoproteins, which are known to act as catalysts in radical production from hydroperoxides. The equation proposed to describe the dose-response relation is simple to handle and permits an immediate connection with the two characteristics of the systems analysed which determine their response to the pro-oxidant treatment. However, the equation which best describes the above relation for all the tissues is the following: E=·C/exp(·C). The parameter assumes values smaller than 1, which seem to depend on relative amounts of tissue hemoproteins and antioxidants. The extension of the analysis to mitochondria shows that they respond to oxidative stress in a way analogous to the tissues, and that the adherence of the dose-response curve to the course predicted from the equation E=a·C/exp(b·C) is again dependent on hemoprotein content.     

Cyercenes,novel pyrones from the ascoglossan molluscCyerce cristallina. Tissue distribution,biosynthesis and possible involvement in defense and regenerative processes

The extraordinary regenerative phenomena in the marine ascoglossan molluscCyerce cristallina are described here for the first time. The possible correlation between cyercenes, pyrones recently isolated from the mollusc regenerating dorsal appendages (cerata), and the processes of chemical defense and regeneration in the mollusc, was investigated by studying the tissue distribution, biological activity and biogenesis of cyercenes. Differences in distribution between theC. cristallina mantle, cerata and mucous secretion were found. Cyercenes showed activity in theHydra vulgaris regeneration assay and the mosquito fish ichthyotoxicity assay. The de novo biosynthesis of cyercenes from propionic acid was demonstrated by means of in vivo adsorption experiments with radiolabeled propionate.     

The control of the frog (Rana esculenta) thumb pad

Summary Extirpation of the pars distalis of the pituitary or castration in any period of the year cause thumb pad regression. Thumb pad development is regulated by an interaction of both temperature and androgenic hormones.Work done under the C.N.R.-finalized project Biologia della Riproduzione.     

Glutathione-related enzyme activities in pregnant rat liver

Summary The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in -glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Effect of acetylsalicylate on surgical bleeding, postoperative mortality and allograft survival in rats undergoing heart transplantation.

18 rats were treated with L-ASA before heart transplantation and daily thereafter until death or rejection. 22 animals acted as controls. A significantly higher post-operative mortality rate, without any significant modification of the transplant survival time, was found in L-ASA-treated group.     

草酸中多孔阳极氧化铝膜生长动力学和形态结构研究

为分析多孔阳极氧化铝膜形态参数和氧化条件的关系,在恒流条件下对0.3 mol·L-1草酸电解中形成多孔膜的生长动力学进行了研究.采用扫描电子显微镜和氧化膜质量测定方法检验了电流密度、温度和氧化时间对氧化膜生长动力学和氧化膜形态的影响.通过电压-时间曲线研究了氧化膜的电化学特征,并采用一元线性回归模型预测了氧化膜的生长速率.实验结果表明氧化膜的生长速率随电流密度的升高而升高,随温度的升高而下降.氧化膜质量的增长速率也随着电流密度的升高而增大.     

基于扩展的层次有色petri网的组合服务测试用例生成

为了更好地对Web组合服务中各个服务间的交互行为进行测试,提出了一种基于扩展的层次有色petri网的组合服务测试用例生成方法.首先将OWL-S文档映射成为扩展的层次有色petri网,使其中丰富的语义信息、数据流信息和控制流信息模型化.然后利用扩展的层次有色petri网,着重对各服务之间的数据流关系进行分析,找到所有的输出输入定义使用链,并将其扩展成可执行的测试序列,最后将测试序列和测试数据组合,生成测试用例.其中生成的所有测试序列符合全定义一使用路径覆盖标准.     

Three-dimensional atomic-scale structure of size-selected gold nanoclusters

An unambiguous determination of the three-dimensional structure of nanoparticles is challenging. Electron tomography requires a series of images taken for many different specimen orientations. This approach is ideal for stable and stationary structures. But ultrasmall nanoparticles are intrinsically structurally unstable and may interact with the incident electron beam, constraining the electron beam density that can be used and the duration of the observation. Here we use aberration-corrected scanning transmission electron microscopy, coupled with simple imaging simulation, to determine with atomic resolution the size, three-dimensional shape, orientation and atomic arrangement of size-selected gold nanoclusters that are preformed in the gas phase and soft-landed on an amorphous carbon substrate. The structures of gold nanoclusters containing 3096 atoms can be identified with either Ino-decahedral, cuboctahedral or icosahedral geometries. Comparison with theoretical modelling of the system suggests that the structures are consistent with energetic considerations. The discovery that nanoscale gold particles function as active and selective catalysts for a variety of important chemical reactions has provoked much research interest in recent years. We believe that the detailed structure information we provide will help to unravel the role of these nanoclusters in size- and structure-specific catalytic reactions. We note that the technique will be of use in investigations of other supported ultrasmall metal cluster systems.