DSP+FPGA数据处理系统的研究与应用

针对铣削加工中心主轴刚度检测系统实时性的要求,重点阐述了DSP FPGA的数字硬件系统和流水线结构的CORDIC算法在FPGA中的实现,并通过仿真和实验对CORDIC算法的理论值和计算数值进行对比分析,结果表明,计算数值非常接近理论值.     

美国流体动力工程研究中心简介

本文简要介绍了美国国家流体动力工程中心的基本情况、研究方向和教学计划.在此基础上对我国流体动力传动与控制的科研单位和企业的发展提出了一些看法.     

增量式旋转轴定向的应用实例

绝对值编码器能够准确地保持坐标位置,因此在需要定位或定向时常选用这种编码器.但某些时候由于改造的机械或者资金情况的限制只能使用增量式编码器,文中旨在讨论在这种情况下如何实现旋转轴的定向和定位.     

船舶ERP选型:集成性是关键

当前,信息化已经渗透到世界船舶工业的设计、生产、管理、服务等方方面面,其应用的深度与广度决定了行业综合水平的高低,成为大至一个国家的船舶工业、小至一个船舶企业能否在市场中生存和发展的关键.当造船业已经普遍意识到,以"信息化推动造船现代化"是中国造船工业追赶国际先进水平的最后机遇时,造船业的生存发展与IT厂商的策略几乎在同一时间不谋而合,在造船业竞争的搏奕中厂商的相助少不了.     

匈牙利农业机械化发展情况特点

匈牙利一向是一个重农国家,它位于欧洲中部的喀尔巴阡山盆地.全国地势低洼,北部为丘陵、南部为平原,气候适宜,耕地平坦.平原约占国土面积的60%,低丘陵地和山地约占40%.农业用地586万公顷,其中可耕地450万公顷,约占国土面积的48%.匈牙利种植的农作物主要有小麦、玉米和马铃薯等,主要出口以肉类和谷类为主的农产品.     

"认知"是信息化应用的绊脚石——访中国航天时代电子公司第十六研究所、七一七一厂信息处处长徐四海

此次航空航天信息化的大型选题报道让记者有幸来到地处关中平原,沃野千里,依山傍水,是与罗马并称为世界古都的"西安"进行一线采访.经过一夜的风雨洗礼,让西安这座古城尤显清新爽朗,仿佛这场风雨是特意为迎接我们而将这座城市冲刷地如此洁净,街道两旁郁郁葱葱的热带植物让你犹如置身南方小城一般.而我们此行的第一站便是位于西安市南郊航天城的中国航天时代电子公司第十六研究所、七一七一厂(以下简称7171厂).     

清理沼气废液废渣仅用五分钟

7月25日上午,江苏省农机具开发应用中心陈新华副主任、农业部南京农机化研究所陈永生主任等5人,来到江苏涟水县与农机局有关人员一起进行沼气清渣车清渣试验.研制成功的清渣车在小李集办事处胡楼村吴国成家中现场进行沼气池清渣,一池沼气废液废渣清理完毕,仅用5分钟,省时,省工,安全,效果很好.     

走区域应用示范与技术创新服务体系新模式

东营市位于黄河入海口,是黄河三角洲的中心城市,是在石油矿区基础上建设起来的新兴工业城市.近年来,除石油工业外,石油化工、盐化工、造纸、机电、轻纺、建材及生物医药等制造业门类得到较快发展,涌现出一批实力较强的企业集团,制造业逐步在东营市经济发展中占据了重要地位.     

2007年中国机床工具行业十大新闻

1.中央和地方省市主要领导频繁视察机床行业企业,国家为数控机床产业发展创造了空前良好的发展环境 胡锦涛、吴邦国、温家宝、贾庆林、李长春等党和国家领导人以及辽宁、黑龙江、山东、江苏、云南、湖北、广东、陕西、浙江、天津、重庆等省市主要领导相继视察了机床工具厂和数控系统厂.各级领导频繁视察,为数控机床产业的发展创造了空前良好的发展环境.     

基于VB和OpenGL的数控铣削仿真系统研究

介绍在Windows XP环境下,利用Visual Basic6.0和OpenGL开发的一个可视化的数控铣削仿真系统.该系统具有良好的界面和交互性,实现了数控加工轨迹的模拟仿真,并较好地完成了NC程序的正确性检查.     

The intracellular distribution of ions and water in rat liver and heart muscle

Local dry mass concentrations of intracellular compartments in rat heart muscle and liver cells were estimated by quantitative electron microscopy and X-ray microanalysis of ultrathin frozen-dried cryosections. The results were used to calculate elemental concentrations per litre of compartment water from the X-ray microanalytical data. Water fractions were between 80.3 ± 1.3% of wet weight in the decondensed chromatin and only 45.1 ± 1.7% in mitochondria of liver cells. The lowest water fraction in heart muscle cells was also found in mitochondria. The ionic concentrations found in the cytoplasm of liver cells and in the myofibrils are in accord with the electroneutrality rule and in osmotic equilibrium with the extracellular concentrations. The concentrations of Na, K, Cl and P both in the cytoplasm and in the regions of decondensed chromatin within the nuclei were found to be equal. However, in regions of condensed chromatin K⁺ concentrations were found to be much higher than expected for a Donnan distribution of ions free in solution. Most probably the activity coefficient for K⁺ is lower in the condensed chromatin than in the decondensed or in the cytoplasm. The same holds true for the A-band as compared to the I-band in heart muscle cells. A sequestration of K⁺ was measured also in the rough endoplasmic reticulum (RER) of hepatocytes. The Cl^? concentration in mitochondria both in heart muscle and liver cells has been measured far in excess of what might be expected from a Nernstian distribution. A coupled inward Cl^? transport in mitochondria must, therefore, be assumed.     

Differential expression of CD95, Bcl-2, and Bax in rat gastric chief and parietal cells

Apoptotic cell death is common in the inflamed gastric mucosa, but its role in the regulation of cell homeostasis in normal gastric mucosa is unknown. We investigated the expression of CD95, Bcl-2, and Bax and their roles in the regulation of apoptosis in normal rat gastric mucosa and in cultures of highly enriched rat chief and parietal cells by immunostaining, Western blotting, and FACS. In intact tissue CD95, Bcl-2, and Bax were localized predominantly in the glandular base region in chief cells. In freshly isolated cells, expression of CD95, Bcl-2, and Bax was much more pronounced in chief cells than in parietal cells. A lower intracellular Bcl-2/Bax ratio suggesting a higher susceptibility to apoptosis was noticed in chief rather than in parietal cells. In extended cultures of parietal and chief cells, Bax expression was upregulated and Bcl-2 expression was downregulated. These regulatory changes, presumably caused by in vitro effects, were not associated with an increase in spontaneous apoptosis. Treatment of chief and parietal cells with Fas-ligand induced apoptosis of all CD95 expressing cells. Expression of CD95, Bcl-2, and Bax predominantly in chief cells suggests that in this cell type regulation of apoptosis may differ from that in parietal cells. Binding of FasL with functionally active CD95 receptors on chief and parietal cells may be relevant for induction of apoptosis in inflamed gastric mucosa.     

Extracellular breakdown of collagen by mice decidual cells. A cytochemical and ultrastructural study.

The interaction of antimesometrial decidual cells and collagen fibrils was studied by light microscopy and ultrastructural cytochemistry in fed and acutely fasted mice on days 9-11 of pregnancy. Fibrillar elements in the extracellular space consisted of collagen fibrils and filamentous aggregates (disintegrating collagen fibrils). Intracellular vacuoles exhibited typical collagen immersed in electron-translucent material (clear vacuoles) and faint cross-banded collagen immersed in electron-opaque material (dark vacuoles). Fibrillar elements showed extracellular acid phosphatase activity which was stronger in the region of mature decidua than in predecidual cells region in all animals; it was conspicuous in mature decidua of fasted animals. Intracellular acid phosphatase activity was observed in dark vacuoles and lysosomes, and was absent in clear vacuoles in all cells studied. Since acid phosphatase activity reflects the presence of lysosomal hydrolases in general, the results indicate that breakdown of extracellular collagen occurs by release of lysosomal enzymes by decidual cells and also by internalization of collagen for intracellular degradation in fed and fasted mice. Collagen breakdown may be part of the process of tissue remodeling in mature and predecidual regions, however, in mature decidua, collagen breakdown is enhanced and may therefore contribute to nutrition of the fetus, specially in acutely fasted mice.     

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures.

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.     

Gender-related changes in the avian vasotocin system during ontogeny

The arginine vasotocin (AVT) system of the avian brain includes a sexually dimorphic part that extends from the caudal part of preoptic region through the medial part of the bed nucleus of stria terminalis (BSTm) to the lateral septum. It is composed of the parvocellular neurons located in the BSTm and the dense innervation of the medial preoptic region and lateral septum. In this part of the brain, AVT expression is stronger in males than in females in a few bird species investigated to date. This review focuses on the ontogeny of sexual differences in the vasotocinergic system of two gallinaceous species, domestic chicken and Japanese quail, and on the role of gonadal hormones in organizing during development and maintaining in adulthood these differences. Parvocellular AVT neurons become discernible in the BSTm of males and females during the second half of embryonic development. These cells undergo a profound and irreversible sexual differentiation during ontogenetic development. Recent findings demonstrate a dual role of estrogens in the organization and activation of sex differences in the AVT system. During the embryonic period of ontogeny, estrogens differentiate the AVT system in a sexually dimorphic manner in parallel with the differentiation of sexual behavior, while in adulthood estrogens, locally produced from testosterone in the male brain, activate AVT synthesis in the BSTm. The sexually dimorphic part of the AVT system is sensitive to a number of abiotic factors such as light, temperature, and water availability. It is suggested that sex dimorphic vasotocinergic systems could be implicated in processes of social recognition in various behavioral contexts.     

A synchrotron X-ray study of the changes occurring in the corneal stroma during processing for electron microscopy

Using a high-intensity synchrotron X-ray source, the structural changes occurring in the corneal stroma were monitored during each stage of several different processing runs for the transmission electron microscope (TEM) and scanning electron microscope (SEM). The parameters studied were interfibrillar spacing, intermolecular spacing, D-periodicity and fibril diameter. The processing schedule that produced the least changes in spacings for TEM specimens involved extended fixation in glutaraldehyde followed by low-temperature embedding in Lowicryl K4M resin. However, interfibrillar material was better preserved after embedding in LR White resin or Nanoplast. Almost every processing stage for electron microscopy produced significant changes in one or more structural parameters in the cornea. Glutaraldehyde fixation significantly increased the intermolecular spacings, while resin infiltration and resin polymerization each resulted in shrinkage of all the spacings monitored. Critical-point drying for SEM specimens resulted in considerable shrinkage in all three spacings, but was still preferable to air drying, which caused reduction in the order of the fibril packing, resulting in loss of the interfibrillar X-ray pattern. Perhaps the most drastic effect was caused by post-fixation in osmium tetroxide, which resulted in loss of the intermolecular pattern, and also increased the amount of shrinkage in the interfibrillar spacings and the D-periodicity which occurred during later stages of processing.     

Distribution of sex steroid hormone receptors in the avian brain: functional implications for neural sex differences and sexual behaviors

Developmental and seasonal changes in the production of androgens, estrogens, and progestins seem to control sex-specific differentiation and seasonal changes in appetitive and consummatory sexual behaviors of birds. This results in profound sex differences in the quality (sex-specific) or quantity (sex-typical) of behaviors such as courtship, territoriality, or copulation. Steroids affect the brain by binding to intracellularly located receptors. The same brain areas express androgen, estrogen, and progesterone receptors in male and female brains. Sex differences in these genetically determined patterns occur in the size of neuron populations that intrinsically express sex steroid receptors. Further permanent sex differences are subsequent to degenerative fates of receptor expressing neuron populations during ontogeny. Transient sex differences in receptor expression appear to be due to area-specific up- and down-regulation of receptor levels, reflecting transient changes in the level of circulating steroids, changes in environmental conditions, or in the physiological status of the individuals. In particular, intrinsic sex differences in the expression pattern of sex steroid receptors and steroid-independent regulation of the expression level of these receptors in the brain are limiting mechanisms for gonad-dependent sexual development and activities.     

Mechanotransduction-The relationship between gravity,cells and tensile loading in extracellular matrix

Gravity plays a central role in vertebrate development and evolution. Mechanotransduction involves the tensile tethering of veins and arteries, connections between the epidermis and dermis in skin, tensile stress concentrations that occur at tissue interfaces, cell-cell interactions, cell-collagen fiber stress transfer in extracellular matrix and fluid shear flow. While attention in the past has been directed at understanding the myriad of biochemical players associated with mechanotransduction pathways, less attention has been focused on determining the tensile mechanical behavior of tissues in vivo. Fibroblasts sit on the surface of collagen fibers in living skin and exert a retractile force on the fibers. This retractile force pulls against the tension in collagen fibers in skin. After fibroblast-collagen fiber interactions are altered either by changes in fibroblast adhesion or after formation of cancer associated fibroblasts, and changes in cell junctions, alterations in the retractive force leads to changes in mechanotransduction. The purpose of this paper is to present a model of tensile forces that occur at the fibroblast-collagen fiber interface and how these forces are important in extracellular matrix physiology in health and disease.     

Application of elemental microanalysis to elucidate the role of spherites in the digestive gland of the helicid snail Chilostoma lefeburiana

In this case study we present an application of different analytical electron microscopic methods in biology, to elucidate their usefulness in such investigations. Using analytical electron microscopy, spherites in the digestive gland cells of the helicid snail Chilostoma lefeburiana were examined at three stages: just before the non-feeding period of over-wintering in November, in the middle of over-wintering in February and at its end in March. A detailed characterization of changes in the elemental composition of the spherites was characterized by a combination of transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy filtering TEM (EFTEM). During over-wintering, the spherites passed the following changes. Before over-wintering in November, they consisted of striking concentric layers of electron-dense and electron-lucent zones, while in February and March they showed clear empty zones between materials of different electron density. In November spherites, C, O, Ca, P, Cl, Fe, Si, Na, K, Mg and S were detected, whereas in February ones C, O, N, Cl, Si and S were found and only C, O, N, Si and Cl were detected in March spherites. It is suggested that the elements missing in February and March were used in different physiological processes during over-wintering, like (1) the maintenance of the appropriate elemental composition of the internal environment, (2) accumulation of non-toxic waste materials that cannot be metabolized and (3) avoiding potential intoxication by contamination with toxic metals.     

Immunohistochemistry of neuronal nitric oxide synthase and protein nitration in the striatum of the aged rat

To ascertain the possible implications of the nitric oxide (NO*) producing system in striatal senescence, and by using immunohistochemistry and image-processing approaches, we describe the presence of the enzyme nitric oxide synthase (NOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and nitrotyrosine-derived complexes (N-Tyr) in the striatum of adult and aged rats. The results showed neuronal NOS immunoreactive (nNOS-IR) aspiny medium-sized neurons and nervous fibres in both age groups, with no variation in the percentage of immunoreactive area but a significant decrease in the intensity and in the number of somata with age, which were not related to the observed increase with age of the striatal bundles of the white matter. In addition, NADPH-d activity was detected in neurons with morphology similar to that of the nNOS-IR cells; a decrease in the percentage of area per field and in the number of cells, but an increase in the intensity of staining for the NADPH-d histochemical marker, were detected with age. The number of neuronal NADPH-d somata was higher than for the nNOS-IR ones in both age groups. Moreover, N-Tyr-IR complexes were observed in cells (neurons and glia) and fibres, with a significant increase in the percentage of the area of immunoreaction, related to the increase of white matter, but a decrease in intensity for the aged group. On the other hand, we did not detect the inducible isoform (iNOS) either in adult or in aged rats. Taken together, these results support the contention that NADPH-d staining is not such an unambiguous marker for nNOS, and that increased protein nitration may participate in striatal aging.