Research on the Error Averaging Effect in A Rolling Guide Pair

By studying the e ects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using this assumption,there is a significant error induced in high-precision computer numerical control(CNC) machine tools as compared with reality. One of the most important reasons for this error is failing to consider the error averaging e ect of motion pair elements. Therefore, this work examines a high-precision horizontal machining center as its research object, and analyzes the error averaging mechanism of a rolling guide pair under a deformation of the rolling elements. The carriage bearing forces caused by guideway straightness errors are obtained by constructing a geometric error model of a single carriage. The relationship between guideway straightness errors and carriage bearing forces is described by a transfer function in the spatial frequency domain, and its characteristics are analyzed. It quantifies the so-called error averaging e ect of the rolling guide system and, on this basis, a static model for four carriages is established to reflect the error averaging e ect of the rolling guide pair on the position and orientation errors of the motion pair. In addition, it is found that the wavelengths and phase di erences of guideway errors a ect this error averaging mechanism, but the amplitude and preload have little influence thereon. The experiment result shows that the kinematic straightness errors in the x-and y-directions were approximately 1/3 to 1/2 of the guideway straightness errors in the corresponding directions. The results can be used to guide the precision design and assembly of machine tools.

Mitochondrial energy metabolism changes during aging-mouse cranial nerve cells treated with various doses and forms of Fructus schizandrae

BACKGROUND： During the cellular aging process, the number of mitochondria, generation of adenosine triphosphate （ATP）, activity of respiratory chain enzyme complex 1 and 4, and oxidation decrease. OBJECTIVE： To observe the effects of aqueous and spirituous extract, as well as polysaccharides from Fructus schizandrae （Magnolia Vine） on energy metabolism and mitochondrial anti-oxidation in cranial nerve cells of a D-gal-induced aging mouse model. DESIGN, TIME AND SETTING： A randomized, controlled, animal study. The experiment was conducted at the Department of Biochemistry, Qiqihar Medical College between March and July 2006. MATERIALS： Fifty healthy, Kunming mice of both sexes, aged 2 3 months old and weighing 18 22 g, were used for the present study. Fructus schizandrae was purchased from the Medical College of Jiamusi University. Aqueous extracts, spirituous extracts, and polysaccharides from Fructus schizandrae were prepared. D-galactose （D-gal） is a product of the Second Reagent Factory, Shanghai City, China. Mn-superoxide dismutase （Mn-SOD） kit, malonaldehyde （MDA） kit, protein quantification kit, and inorganic phosphorus testing kit were purchased from Jian Cheng Bioeng. Co., China. METHODS： Fifty mice were randomly divided into five groups, with 10 mice in each group： young control, aging model, aqueous Fructus schizandrae extract, spirituous Fructus schizandrae extract, and Fructus schizandrae polysaccharides. Over a course of 30 days, mice in aging model, aqueous Fructus schizandrae extract, spirituous Fructus schizandrae extract, and Fructus schizandrae polysaccharides groups were injected subcutaneously with D-gal （100 mg/kg） into the nape of the neck daily, and administered intragastrically with an equal volume of sterile, warm water （aging model）, aqueous Fructus schizandrae extract （2 g/kg）, spirituous Fructus schizandrae extract （2 g/kg）, or Fructus schizandrae polysaccharides （0.2 g/kg）, respectively. Mice in the young control group were injected into the nape of the neck with physiological saline and administered intragastrically with sterile, warm water. MAIN OUTCOME MEASURES： Respiratory chain complex I and H^＋-ATP enzyme activities, as well as Mn-SOD and MDA levels, were determined by the Coomassie brilliant blue method. RESULTS： All fifty mice were included in the final analysis. In mitochondria fiom cranial nerve cells of the aging mouse group MDA levels were significantly increased, compared with young control group （P 〈 0.01）; however, Mn-SOD levels, as well as respiratory chain complex I and H＋-ATP enzyme activity, were remarkably decreased （P 〈 0.01 ）. In each Fructus schizandrae group, Mn-SOD levels, as well as respiratory chain complex I and H＋-ATP enzyme activity was enhanced to various extents （P 〈 0.05, P 〈 0.01）, and MDA levels were decreased （P 〈 0.01）, compared with the aging model group. CONCLUSION： Aqueous and spirituous Fructus schizandrae extracts, as well as Fructus schizandrae polysaccharides delayed changes in mitochondrial energy metabolism, increased Mn-SOD levels, and decreased MDA levels in cranial nerve cell mitochondria of an aging mouse model. Fructus schizandrae polysaccharides were particularly capable of protecting mitochondria from oxidative injury.

Physicochemical and structural characteristics of the Venn components of wheat gliadin

The aim of this study was to analyze the physicochemical and structural characteristics of the Venn components of wheat gliadin to provide theoretical basis of gliadin for processing in dough and Chinese steamed bread. Eight Venn components, Gli-8, Gli-9, Gli-10, Gli-11, Gli-12, Gli-13, Gli-14, and Gli-15, were extracted from wheat gliadin based on their solubility. The results of physicochemical characteristics showed that the differences in the contents, TDS,electrical conductivity, particle size and zeta potential of Venn components were significant, respectively. The content of Gli-15 in gliadin was the highest, and the content of Gli-9 was the lowest. The TDS value of Gli-9 was the highest(336.0), and the TDS value of Gli-15 was the lowest(52.0). The electrical conductivity of Gli-9 was the highest,which was 7.54 times the lowest value of Gli-11. The zeta potential of Gli-9 was -25.2 mV, and the zeta potential of the Gli-15 was -7.64 mV. However, the difference in the p H values was not significant. The results of UV spectrum and FTIR analysis showed that the secondary structures of the Venn components had significant differences. The results of the XRD patterns indicated that the Venn components might not be a single substance. The results of CLSM images implied that the molecular interactions among the components were varied. Hence, the results could provide research materials and basic data for deep processing and utilization of gliadin.

多层导电结构缺陷位置和尺寸的无损估计方法研究

针对多层导电结构缺陷位置和尺寸的识别问题,基于脉冲涡流检测数据,提出一种多层导电结构缺陷位置和尺寸的无损估计方法(NEM)。NEM采用傅里叶变换和希尔伯特黄变换等方法,提取时域和频域上共47维特征。提出基于AIC+Fisher的特征降维方法,选择最优的特征降维维度,减少特征冗余且降维后的特征能更好表征缺陷类型,提高分类器的识别效率。最后利用支持向量机(SVM)构造分类器,采用粒子群算法对分类器模型参数进行寻优,从而实现多层导电结构缺陷位置和尺寸的识别。实验结果表明:NEM能够适用于多层导电结构的缺陷位置识别和缺陷尺寸识别,提高了识别的查全率和查准率,降低了缺陷尺寸识别的平均误差值,优于SVM47、AFF、Fisher47和AFR等方法。

Spatial Distribution of Cytoskeletal Mechanical Properties in Vascular Smooth Muscle Cells

The mechanical properties on a whole basis of cell are extensively studied whereas regional mechanical properties of the cytoskeleton (CSK) have not been characterized. To fill this gap, here we provide detailed intracellular maps of regional CSK stiffness and traction forces, as well as the structural rearrangement in vascular smooth muscle cells (VSMCs). We used micropatterning to restrict VSMC to a single island. Regional cell stiffness was measured with optical magnetic twisting cytometry and traction force microscopy was used to measure regional traction forces. Finally, we used F-actin staining to measure the regional F-actin distribution. From traction and cell height data we computed the prestress within a cell using finite element methods. Compared with the cell center, cell edges were systematically stiffer, more fluid-like and supported higher traction forces, and at the same time had slower remodeling dynamics. These findings provide the most detailed characterization to date concerning regional mechanical properties of the intact cytoskeleton.

Unveiling the role of metallic CoP@Ni_(2)P sea-urchin-like nanojunction as a photothermal cocatalyst for enhancing the H_(2) generation and benzaldehyde formation over CdZnS nanoparticles

Aiming to develop a photocatalyst that can simultaneously produce valuable chemicals and clean H_(2) fuel for promoting the utilization efficiency of solar energy,herein,a sea-urchin-like CoP@Ni_(2)P binary nanojunction was employed as an efficient photothermal cocatalyst to couple with zero-dimensional CdZnS(CZS)solid solution for achieving superior coordinative redox reaction.The CoP@Ni_(2)P/CZS hybrid displayed a high solar-driven H_(2) generation rate of 40.92 mmol g^(–1) h^(–1) coupling with a benzaldehyde formation rate of 20.33 mmol g^(–1) h^(–1),which was 16.4 and 8.0 times higher than that of bare CZS.Furthermore,the CoP@Ni_(2)P/CZS hybrid also achieved a high photothermal H_(2) production under a broad light range from 420 to 720 nm,and the H_(2) production reached 44.48μmol g^(–1) h^(–1) under the 720 nm light illumination.The enhanced catalytic performance can be ascribed to that the CoP@Ni_(2)P nanojunction with photothermal effect can speed up the separation and transport of carriers,offer more catalytic active sites,and induce an increase in temperature to optimize reaction kinetics.This study may open a facile route to design novel binary metal phosphides with dual functions in photocatalysis for the full exploitation of solar energy.