Similar features in Z bands of both skeletal and cardiac muscle revealed by image enhancement

We have shown previously that the small square (ss) and basket weave (bw) states of the Z band lattice in cardiac and skeletal muscle are related to the contractile state of the muscle. We have used two-dimensional image processing techniques on digitized electron micrographs to enhance the structural features of each projected lattice form in cardiac and skeletal muscle. Four different processing techniques were employed to assess the effect of enhancement artifacts on the resulting Z band images. We observed only slight differences between enhanced images of a particular Z band form produced by the four different techniques. Every enhanced image showed an approximate four-fold symmetry independent of muscle type or Z band lattice form. Each enhanced image showed four cross-connecting Z-filaments which appeared to connect each axial filament to the four nearest axial filaments. In bw images from both cardiac and skeletal muscle, axial filaments had a greater apparent diameter and a greater interaxial filament spacing than in the ss images. In both muscle types, the cross-connecting Z-filaments appeared to overlap half-way between axial filaments in the ss images while the bw images showed no such overlap. These structural features are consistent with a dynamic Z band lattice that participates in muscle contraction.     

Controlling Pyrene Association in DNA Duplexes by B- to Z-DNA Transitions

B- to Z-DNA transitions play a crucial role in biological systems and have attracted the interest of researchers for their applications in DNA nanotechnology. DNA and DNA analogues have also been used as templates to construct helical chromophore associations with π interactions. In this work, the B- to Z-DNA transition-induced switching of pyrene in an association manner was evaluated using DNA duplexes with non-nucleosidic pyrene residues in the middle of d(CG) repeat sequences. One of the pyrene-labeled DNAs was shown to exhibit inverted exciton coupled circular dichroism signals upon pyrene association through a B- to Z-DNA transition. This observation indicates that pyrene association switches the DNA conformation from right- to left-handed. Interestingly, the fluorescence of the pyrene-labeled DNA duplex also dynamically changed upon switching of the pyrene in an association-based manner. Taken together, these studies demonstrate that pyrene-labeled DNA shows promise as a chiroptical molecular switch.     

热轧卷取温度对HC340LAD+Z带钢力学性能的影响

为了研究热轧卷取温度对热镀锌HC340LAD+Z带钢力学性能的影响规律,对同一炉次、相同规格的3批次钢坯,分别采用580、620、660 ℃3个卷取温度,以及相同的冷轧、热镀锌、退火工艺进行了试验研究。结果表明,随着卷取温度的升高,成品带钢的屈服强度、抗拉强度降低,伸长率稍有增加,均满足EN10346标准对HC340LAD+Z带钢力学性能的要求。热轧卷取温度为620 ℃时,HC340LAD+Z带钢的屈服强度为389.2 MPa,抗拉强度为474.3 MPa,伸长率A80为26.5%,其综合力学性能对比标准指标,富裕量最佳。     

08Ni3DR钢焊接接头最薄弱区域与冲击韧性之间的关系

低温压力容器08Ni3DR钢在极低温度下(-100℃)具有较好的强韧性匹配,在实际工程应用中,保障焊接接头的低温冲击韧性一直是压力容器制造过程中的难题之一。对于实际的焊接接头,最薄弱区域的确定以及最薄弱区域的影响对焊接接头的表征具有重要的意义。通过将夏比V型缺口开在母材、焊缝、热影响区不同位置处,系统研究了08Ni3DR压力容器钢焊接接头的组织和韧性。结果表明:焊接接头韧性最薄弱区域为粗晶热影响区,其粗晶热影响区的显微组织为粗大的粒状贝氏体和板条贝氏体组成的复合组织。粗晶热影响区宽度在缺口尖端前沿所占比例越高,试样的冲击吸收能量越低。当粗晶热影响区宽度所占比例达到100%时,冲击吸收能量为27 J,相比于母材冲击韧性损失高达90.7%。以上两个方面充分体现出焊接接头最薄弱区域对冲击韧性有很大的影响。     

A new arrangement of Z‐source AC–AC converter and its closed‐loop control system

In this study, a Z‐source alternating current‐to‐alternating current (AC–AC) converter with a specific topology, which can provide both buck and boost modes, is investigated. This converter, which can be implemented easily, utilizes only two switches with complemented commands. A comparison between the Z‐source AC–AC converter and a conventional thyristor voltage controlled one is presented here, and it shows that in the most areas, the Z‐source converter provides a faster response and lower total harmonic distortion of the output currents than the conventional one. Moreover, the Z‐source converter is also extended to the multiphase systems. In addition, a new arrangement of this converter is proposed here to remove the isolated single‐phase sources. Furthermore, an open‐loop method is proposed for soft‐starting applications. Finally, a closed‐loop control system is also suggested for a three‐phase Z‐source converter to soft start and control the speed of an induction motor. Computer simulations show the validity and effectiveness of the proposed schemes. Copyright © 2014 John Wiley & Sons, Ltd.     

激光修补技术在修复薄膜图形缺陷上的应用——薄膜图形缺陷激光修补机

阐述了应用激光修补技术在玻璃基板上去除金属及其化合物薄膜和在玻璃基板上沉积金属薄膜的图形缺陷修补原理与方法;简述了影响薄膜图形缺陷修补质量与效率的关键技术;简单介绍了薄膜图形缺陷激光修补机的系统构成及其技术与性能指标.     

13-Hydroxy-9Z,15Z-Octadecadienoic Acid Production by Recombinant Cells Expressing Lactobacillus acidophilus 13-Hydratase

Recombinant Escherichia coli cells expressing linoleate 13‐hydratase from Lactobacillus acidophilus were permeabilized by treating with 0.2 M NaCl. The optimal conditions for the production of 13‐hydroxy‐9,15(Z,Z)‐octadecadienoic acid (13‐HODE) from α‐linolenic acid by permeabilized recombinant cells were pH 6.0, 40 °C, 7.5 % (v/v) methanol, 60 g/l permeabilized cells, and 15 g/l α‐linolenic acid. Under these conditions, permeabilized cells produced 7.5 g/l 13‐HODE after 6 h, with a conversion yield of 50 % (w/w) and a volumetric productivity of 1.25 g/l/h. These values were 161 and 160 % of those obtained by nonpermeabilized cells, respectively. To the best of our knowledge, this is the first report on the process optimization for the biotechnological production of 13‐HODE.     

Cells on biomaterials – some aspects of elemental analysis by means of electron probes

Electron probe X‐ray microanalysis enables concomitant observation of specimens and analysis of their elemental composition. The method is attractive for engineers developing tissue‐compatible biomaterials. Either changes in element composition of cells or biomaterial can be defined according to well‐established preparation and quantification procedures. However, the qualitative and quantitative elemental analysis appears more complicated when cells or thin tissue sections are deposited on biomaterials. X‐ray spectra generated at the cell/tissue–biomaterial interface are modelled using a Monte Carlo simulation of a cell deposited on borosilicate glass. Enhanced electron backscattering from borosilicate glass was noted until the thickness of the biological layer deposited on the substrate reached 1.25 μm. It resulted in significant increase in X‐ray intensities typical for the elements present in the cellular part. In this case, the mean atomic number value of the biomaterial determines the strength of this effect. When elements are present in the cells only, the positive linear relationship appears between X‐ray intensities and cell thickness. Then, spatial dimensions of X‐ray emission for the particular elements are exclusively in the range of the biological part and the intensities of X‐rays become constant. When the elements are present in both the cell and the biomaterial, X‐ray intensities are registered for the biological part and the substrate simultaneously leading to a negative linear relationship of X‐ray intensities in the function of cell thickness. In the case of the analysis of an element typical for the biomaterial, strong decrease in X‐ray emission is observed in the function of cell thickness as the effect of X‐ray absorption and the limited excitation range to biological part rather than to the substrate. Correction procedures for calculations of element concentrations in thin films and coatings deposited on substrates are well established in materials science, but little is known about factors that have to be taken into account to accurately quantify bioelements in thin and semi‐thick biological samples. Thus thorough tests of currently available quantification procedures are required to verify their applicability to cells or tissues deposited on the biomaterials.     

ZigBee技术在远程抄表系统中的应用

将无线射频芯片与单片机系统相结合,可以实现无线远程水表控制和对流量数据的读取,该系统通过射频收发模块实现数据的传输。本文重点介绍以Freescale公司生产的MC9S08GB60单片机和MC13192射频收发模块为核心的远程抄表系统的硬件电路以及软件流程设计。     

Z/M对RFCC催化剂反应性能的影响

以稀土超稳Y型分子筛和拟薄水铝石为主要原料制备了重油催化裂化(RFCC)模型催化剂,通过N 2物理吸附和高级裂化评价装置研究了水热减活RFCC模型催化剂中Y型分子筛与基质比表面积之比(Z/M)及其对催化裂化反应性能的影响。结果表明,拟薄水铝石含量越高,Y型分子筛抵御高温水热破坏的能力越差,Z/M越小。拟薄水铝石质量分数为30%时,水热减活后分子筛比表面积仅为减活前的28.3%,Z/M仅为0.8。拟薄水铝石含量不仅影响催化剂的水热稳定性,还影响催化剂的形貌。拟薄水铝石含量越高,催化剂微球形貌规整性越差,当其质量分数为30%时,催化剂微球表面不仅产生了大量的孔洞,还出现了许多裂纹。随着模型催化剂Z/M下降,目标产物液化石油气和汽油产率之和逐渐降低,轻循环油产率升高,焦炭选择性变差。