Regionalization and redistribution of membrane phospholipids and cholesterol in mouse spermatozoa during in vitro capacitation

Fracture-label, surface-replica, and routine freeze-fracture techniques were used in combination with phospholipase A2-colloidal gold (PLA2-CG) and filipin as probes to study changes in the distribution of phospholipids and cholesterol, respectively, in morphologically defined plasma membrane domains of mouse spermatozoa during in vitro capacitation. In noncapacitated spermatozoa, quantitative analysis revealed that the fractured plasma membrane overlying the equatorial segment carried the highest PLA2-CG labeling density. The next highest labeling densities were found in the anterior acrosome region and the post-acrosomal region. On the external surface of the plasma membrane revealed by surface replicas, a uniform distribution of PLA2-CG was confined mainly to the acrosomal region of the head. The plasma membrane of the sperm tail had a relatively low labeling density for PLA2-CG. In freeze-fracture replicas of filipin-treated spermatozoa, the labeling density of filipin/sterol complexes (FSCs) was high in the plasma membrane over the acrosomal region where the FSCs were uniformly distributed. The postacrosomal region was weakly labeled. After in vitro capacitation, the densities of PLA2-CG and FSCs were significantly reduced in the fractured plasma membrane of the sperm head and the middle piece of the tail. However, surface replicas revealed an increased PLA2-CG labeling on the external surface of the plasma membrane covering the postacrosomal region, the middle piece, and the principal piece. Another major change detected in capacitated spermatozoa was the presence of small aggregates and patches of elevated, membrane-associated particles on the surface-replicated plasma membrane in the upper portion of the postacrosomal domain. Here the PLA2-CG labeling density was found to be higher than in noncapacitated spermatozoa. These results provide new information with respect to the reorganization and redistribution of phospholipids in specific regions of the plasma membrane during capacitation and provide further support for the concept that removal or loss of antifusigenic sterol from the sperm plasma membrane constitutes an important step of the capacitation process.     

Photoacoustic ultrasound: pulse production and detection of 0.5% Liposyn

Theoretical predictions and experimental measurements of photoacoustic pulse production within a 0.5% solution of Liposyn, a highly scattering, optical propagation medium, are reported. A simple model for photoacoustic energetics is developed that predicts photoacoustic signal pressure as a function of depth within a turbid medium following surface irradiation from an infrared source. The model is valid for very short irradiation duration. The model predicts that the acoustic pressure produced at a distance r from the center of a small, highly absorbing sphere of radius R consists of two, opposite polarity pulses, one originating from the near and one from the far side of the sphere. The magnitude of these biphasic pulses is expected to be proportional to the energy fluence (E) incident on the surface of the sphere and to the ratio, R/r. Furthermore, the energy fluence (E) that reaches the sphere is roughly proportional to e-mu effZ, where mu eff is the effective attenuation coefficient of the turbid medium and Z is the depth of the embedded sphere below the irradiated surface. The variation of E with depth within the absorber and biphasic acoustic pulse production have been verified experimentally. Further experiments demonstrate that a small (3-mm diameter), highly absorbing sphere can be detected and localized at a depth of 37.5 mm within a 0.5% solution of Liposyn with a spatial resolution of 1 x 6 mm2, using a biologically safe level of infrared irradiation (lambda = 1064 nm) and a conventional ultrasound transducer (frequency = 2.25 MHz). These results suggest that photoacoustic ultrasound imaging may have application to biologic systems such as the human breast.     

Confocal analysis of the molecular heterogeneity in the pericellular microenvironment produced by adult canine chondrocytes cultured in agarose gel

Adult articular chondrocytes are each surrounded by a heterogeneous microenvironment and together form the chondron. Since little is known of chondron development, agarose gel culture, confocal immunohistochemistry and image analysis have been used to characterize the molecular anatomy and temporal development of the chondrocyte pericellular microenvironment in vitro. Two structurally distinct domains were identified during the 12-week culture period. The first comprised a narrow glycocalyx, 1-3 microns in width, which consolidated over time and was rich in collagen types II, VI, IX and XI, fibronectin, decorin and the aggrecan epitopes, 5D4 and HABR. The second region emerged after 4-6 weeks in culture and progressively developed a broad territorial region up to 12 microns wide around the chondrocyte and pericellular glycocalyx. Co-localization studies confirmed the dominance of aggrecan epitopes 2B6, EFG-4, 5D4 and HABR in the territorial domain, whereas surface density mapping with NIH image revealed two patterns of staining, one punctate and stippled, the other more uniform in distribution. The pericellular differentiation identified appeared analogous to the chondrons of adult articular cartilage, and provides an appropriate in vitro model for further studies of cell surface receptor function in the orchestration of pericellular matrix assembly.     

线切割的电流密度对无取向电工钢切面的影响

对无取向电工钢进行电火花线切割实验，研究切割过程中不同的电流密度水平对切割面形貌的影响。采用三维测量激光显微镜对原始切割面的形貌进行观察，采用扫描电子显微镜观察经同等水平的超声振动方式处理后的切割面，以衡量表面附着层的附着能力。结果表明，随着电流密度水平的升高，切割面呈粗糙化趋势，由均匀光滑的小幅度凸起区和凹陷区逐渐替代为易于氧化的不规则台阶，台阶在高度方向的过渡区域为近垂直状；在过高的电流密度下，出现被氧化区包围的光亮近球形再凝固体。所以，高电流密度对控制切割面质量不利，采用较低电流密度的电火花线切割技术具有较高优势。     

Pulsed laser induced deformation in an Fe-3 Wt Pct Si alloy

The plastic deformation produced by laser induced stress waves was investigated on an Fe-3 wt pct Si alloy. The intensity and duration of the stress waves were varied by changing the intensity and pulse length of the high energy pulsed laser beam, and also by using different overlays on the surfaces of the specimens. The resulting differences in the distribution and intensity of the deformation caused by the stress waves within the samples were determined by sectioning the specimens and etching (etch pitting) the transverse sections. The magnitude of the laser shock induced deformation depended on the laser beam power density and the type of surface overlay. A combination transparent plus opaque overlay of fused quartz and lead generated the most plastic deformation. For both the quartz and the quartz plus lead overlays, intermediate laser power densities of about 5×10⁸ w/cm² caused the most deformation. The shock induced deformation became more uniform as the thickness of the material decreased, and uniform shock hardening, corresponding to about 1 pct tensile strain, was observed in the thinnest specimens (0.02 cm thick). 200 ns laser pulses caused some surface melting, which was not observed for 30 ns pulses, the pulse length used in most of the experiments. Deformation of the Fe-3 wt pct Si alloy occurred by both slip and twinning. B. A. WILCOX, formerly affiliated with Battelle, Columbus Laboratories     

Modification of the T15K6 hard alloy with high-power pulsed ion beams and compression plasma fluxes

The change in the morphology, phase composition, hardness of surface layers, microstructure, and elemental composition of the inner layers of an alloy under the effect of high-power pulsed ion beams (HIBs) and compression plasma streams (CPSs) is investigated. It is found that the thickness of the molten surface layer increases to 3–4 μm after the HIB effect: 300 pulses 9 × 10^?2 μm long with a summary energy density of 430 J/cm². The features of the CPF treatment are a larger time of pulse effect (100 μs) and the preferential convection agitation of the molten layer. As a result, a thicker layer of the (W, Ti)C solid solution with uniform elemental distribution over the depth and high hardness (30 GPa) is formed.     

基于随机响应面法的金鸡岭岩质边坡可靠度分析及抽样方法对比

结合有限元滑面应力法和Hermite随机响应面法建立了金鸡岭岩质边坡稳定可靠度非侵入式分析模型，在此基础上研究了均匀设计抽样、LHS抽样、改进LHS抽样和分层抽样4种抽样配点方法对随机响应面的拟合精度、边坡失效概率及安全系数统计特征的影响。结果表明：（1）金鸡岭岩质边坡未支护状态下的失效概率约为18.4%，失稳风险较大，需采取支护加固措施；（2）改进LHS抽样和LHS抽样所构造的随机响应面具有较好的拟合精度，抽样配点效果优于分层抽样和均匀设计抽样；（3）建议边坡可靠度非侵入式随机分析采用改进LHS抽样或LHS抽样进行随机响应面的抽样配点计算，并尽可能多地选取样本点以外的验算点对随机响应面拟合精度进行校验。     

2-D center-surround effects on 3-D structure-from-motion.

This study investigates how mechanisms for amplifying 2-D motion contrast influence the assignment of 3-D depth values. The authors found that the direction of movement of a random-dot conveyor belt strongly inclined observers to report that the front surface of a superimposed, transparent, rotating, random-dot sphere moved in a direction opposite to the belt. This motion-contrast effect was direction selective and demonstrated substantial spatial integration. Varying the stereo depth of the belt did not compromise the main effect, precluding a mechanical interpretation (sphere rolling belt). Varying the speed of the surfaces of the sphere also did not greatly affect the interpretation of rotation direction. These results suggest that 2-D center-surround interactions influence 3-D depth assignment by differentially modulating the strength of response to the moving surfaces of an object (their prominence) without affecting featural specificity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The genome organization of the broad bean necrosis virus (BBNV)

In this study the effect of lipoprotein lipase (LPL) on the selective uptake of high density lipoprotein (HDL) cholesteryl esters (CE) by hepatic cells was investigated. Human HDL3 (d 1.125-1.21 g/ml) was radiolabeled with 125I in the protein moiety and with 3H in the CE moiety. LPL was prepared from bovine milk. Human hepatocytes in primary culture and human Hep3B hepatoma cells were incubated in medium containing doubly radiolabeled HDL3 with or without LPL. Without LPL, apparent HDL3 particle uptake according to the lipid tracer (3H) was in excess of that due to the protein label (125I) indicating selective CE uptake from HDL3. Addition of LPL increased selective CE uptake up to 7-fold. This stimulation of HDL3 selective CE uptake was independent of the lipolytic activity of LPL as suggested by several experimental approaches. Cell surface heparan sulfate proteoglycan deficiency decreased the LPL-mediated increase in selective CE uptake suggesting an important role for these molecules. In low density lipoprotein (LDL) receptor- or LDL receptor-related protein-(LRP)-deficient cells, LPL increased selective CE uptake as it did in normal cells yielding no evidence that these receptors play a role in the LPL effect on selective CE uptake. In summary, lipoprotein lipase increases the selective uptake of high density lipoprotein-associated cholesteryl ester by hepatic cells in culture. This effect is dependent on cell surface heparan sulfate proteoglycans but independent of lipolysis and of endocytosis mediated by low density lipoprotein receptor-related or low density lipoprotein receptors.     

Power spectral density of unevenly sampled data by least-square analysis: performance and application to heart rate signals

This work studies the frequency behavior of a least-square method to estimate the power spectral density of unevenly sampled signals. When the uneven sampling can be modeled as uniform sampling plus a stationary random deviation, this spectrum results in a periodic repetition of the original continuous time spectrum at the mean Nyquist frequency, with a low-pass effect affecting upper frequency bands that depends on the sampling dispersion. If the dispersion is small compared with the mean sampling period, the estimation at the base band is unbiased with practically no dispersion. When uneven sampling is modeled by a deterministic sinusoidal variation respect to the uniform sampling the obtained results are in agreement with those obtained for small random deviation. This approximation is usually well satisfied in signals like heart rate (HR) series. The theoretically predicted performance has been tested and corroborated with simulated and real HR signals. The Lomb method has been compared with the classical power spectral density (PSD) estimators that include resampling to get uniform sampling. We have found that the Lomb method avoids the major problem of classical methods: the low-pass effect of the resampling. Also only frequencies up to the mean Nyquist frequency should be considered (lower than 0.5 Hz if the HR is lower than 60 bpm). We conclude that for PSD estimation of unevenly sampled signals the Lomb method is more suitable than fast Fourier transform or autoregressive estimate with linear or cubic interpolation. In extreme situations (low-HR or high-frequency components) the Lomb estimate still introduces high-frequency contamination that suggest further studies of superior performance interpolators. In the case of HR signals we have also marked the convenience of selecting a stationary heart rate period to carry out a heart rate variability analysis.     

An efficient method for small field treatment dose calculation for stereotactic radiosurgery using a LINAC

The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the location of the isocenter of radiation and viewing the isodose curves on two-dimensional computed tomography (CT) or magnetic resonance imaging (MRI) image planes. Automatic optimization procedures have also been used to optimize beam weight or beam size. However, either process is very time consuming. To improve the speed of the dose calculation, a random sampling method has been proposed. Unfortunately, the sampled values of an objective function are different from one sample to another. Such a sampling method cannot be used in automatic optimization because the next move in an optimization process is based on the current and past objective function values. To this end, an adaptive method based on the size of the collimators is proposed and used to determine a small volume in the shape of a hollow sphere for which the dose is calculated. With an appropriate choice of an adaptive hollow sphere, the objective function calculated based on such a hollow sphere is the same as that calculated with the traditional three-dimensional (3-D) cube matrix. However, with the new adaptive method, the speed of calculating a dose can be improved by a factor of 4 to a factor of 100. Because of the improvement in the speed of calculating a treatment dose, the new adaptive hollow sphere method for calculating a treatment dose can be used routinely in designing a treatment plan.     

氮离子束轰击对电弧离子镀已沉积的TiAlN膜层性能影响的研究

采用俄罗斯UVN 0.5D2I离子束辅助电弧离子镀沉积设备,利用N离子束轰击高速钢W18Cr4V基材上电弧离子镀已沉积完毕的TiAlN膜层。研究了不同能量的N离子束轰击对TiAlN膜层表面形貌、显微硬度和相结构的影响。SEM分析表明:TiAlN膜层表面"大颗粒"消失,凹坑浅而平整,粗糙度降低。X射线衍射分析表明:无N离子轰击时,TiAlN膜层是由TiAlN相和Ti2AlN相组成;随着轰击能量的增加,TiAlN膜层的相结构没有发生变化,但TiAlN(111)取向减弱,而(200)和(220)取向均增强;Ti2AlN(211)取向减弱。力学性能测试表明:N离子束轰击,使膜层的显微硬度由原来的2 100HV0.01提高到2 300HV0.01。     

Imaging RNA and dynamic protein segments with low-resolution virus crystallography: experimental design, data processing and implications of electron density maps

Single crystal diffraction data were collected from virus crystals in the resolution range of 270 to 14 A using a synchrotron X-ray source and a small-angle scattering instrument adapted for single crystal measurements. Reflections were measured from single crystals of the capsid of the double-stranded DNA bacteriophage HK97 and synthetic Flock House virus-like particles (sFHV). The quality of the low-resolution measurements was confirmed by excellent scaling statistics for both data sets. The sFHV amplitudes between 270 and 90 A resolution were closely similar to independently measured solution scattering data, and to data calculated from the Fourier transform of a uniform density sphere of 315 A diameter. A rotation function computed with the sFHV data between 70 and 20 A resolution was readily interpretable. A uniform density sphere model was used to compute phases for measured amplitudes between 270 and 68 A resolution. The calculated phases were refined and extended to 14 A resolution with real space averaging employing an external mask shape defined by the high-resolution structure. The resulting electron density map displayed regions interpretable as loosely ordered RNA that connected ordered RNA segments seen in a published 3.0 A resolution map. The published high-resolution electron density map lacked data inside 15 A resolution and the interior of the particle in that map appeared hollow. Difference electron density maps corresponding to bulk RNA were computed by subtracting the contribution of the protein shell, based on the available high-resolution atomic model, from either the cryo-electron microscopy density or the low-resolution X-ray density. Features of the RNA were closely similar in the cryo-electron microscopy and X-ray maps, demonstrating the consistency of the two imaging methods. Electron density maps computed at 14 and 6 A resolution with the X-ray amplitudes showed that RNA contributed little to the scattering beyond 14 A resolution.     

不锈钢粉的3D凝胶打印成形技术研究

通过一种新型3D打印方法——3D凝胶打印,打印出不锈钢零件,并且对金属料浆的流变性能进行了分析研究。结果表明:固含量为61.5%(体积分数)的金属料浆具有较好的流变特性,适合3D凝胶打印技术;打印出的坯体表面质量较好,没有明显的分层现象;打印的不锈钢坯体在1 350℃保温1 h烧结后,相对密度可达95.7%。     

脉冲等离子爆炸工艺表面改性H13钢

 为研究脉冲等离子爆炸工艺制备H13钢(4Cr5MoSiV1)表面改性层的组织和性能,通过对显微组织形貌、相结构、残余应力、硬度和耐磨性的分析,对脉冲等离子爆炸工艺的改性机制和影响进行了讨论。结果表明,脉冲等离子爆炸工艺使H13钢表面发生快速熔凝和快速淬火过程,在材料表面形成厚度均匀、组织致密、高硬度的改性层;改性层中马氏体细化,同时由于不同物理变化过程分别形成残余奥氏体和逆变奥氏体;随着脉冲次数的增加,材料表面的残余应力经历了由压应力先增大后减小然后转变成拉应力的过程;改性层的厚度和硬度随脉冲次数的增加而提高,但同时表面熔化程度加剧,表层低硬度熔凝区厚度增加。当脉冲次数为8次时,H13钢具有最优的耐磨损性能。     

Superior Yield Strength and High-Tensile-Toughness Matching of Medium-Mn Steel with Gradient Structure Developed by Cyclic Torsion

A multiphase-gradient-structured medium-Mn steel with dislocation/stacking fault (SF) density gradient, austenite fraction gradient, and grain size gradient is designed and fabricated by cyclic torsion. It exhibits higher yield strength (YS) (942 MPa), ultimate tensile strength (1295 MPa), and tensile toughness (290 mJ mm⁻³) than its homogeneous counterpart (672, 1273 MPa, and 278 mJ mm⁻³, respectively). High-density-interlaced SFs are generated at the surface region because of the change in strain path and stress state during cyclic torsion. These massive interactive SFs promote the persistent martensite transformation of the retained austenite in the surface region within the entire uniform strain range. Therefore, in addition to the central layer, the surface region in the gradient structures provides strong strain hardening. Moreover, the continuous martensite transformation in the surface region allows the gradient structure to be retained even after tensile failure, which is beneficial for improving the heterogeneous-deformation-induced (HDI) hardening of the gradient-structured sample during tensile deformation. Thus, the combination of active and persistent transformation-induced plasticity effect and HDI hardening contributes to its excellent tensile toughness and ductility. Quantitative analysis indicates that HDI strengthening and dislocation strengthening play a dominant role in the sample's ultrahigh YS.     

Far-field analysis of coupled bulk and boundary layer diffusion toward an ion channel entrance

We present a far-field analysis of ion diffusion toward a channel embedded in a membrane with a fixed charge density. The Smoluchowski equation, which represents the 3D problem, is approximated by a system of coupled three- and two-dimensional diffusions. The 2D diffusion models the quasi-two-dimensional diffusion of ions in a boundary layer in which the electrical potential interaction with the membrane surface charge is important. The 3D diffusion models ion transport in the bulk region outside the boundary layer. Analytical expressions for concentration and flux are developed that are accurate far from the channel entrance. These provide boundary conditions for a numerical solution of the problem. Our results are used to calculate far-field ion flows corresponding to experiments of Bell and Miller (Biophys. J. 45:279, 1984).     

分层取样方式对碳酸氢铵沉淀法生产碳酸稀土过程混合RECl3溶液理化指标检测结果的影响研究

稀土的提取与分离需要经过硫酸焙烧、水浸、萃取、反萃和碳沉等一系列过程,其中混合RECl₃溶液是稀土产业线中的重要中间产品,该混合稀土溶液的REO浓度、配分、密度等理化指标是评价混合RECl₃溶液产品质量的主要参数。针对一定存储条件下的混合RECl₃溶液,按照国家标准分析方法,结合X射线荧光光谱法(XRF)、电感耦合等离子体原子发射光谱法(ICP-AES)和重量法等手段,对该溶液中的REO浓度、配分、密度等项目进行检测,研究分层取样方式对3项理化指标的影响及变化规律。通过不同存放时间的变化因素绘制混合RECl₃溶液中REO浓度、密度的变化曲线,得出混合RECl₃溶液的存放时间越长,不同层面取样时这两个指标检测结果差异越大的结论;浅析了混合RECl₃溶液取样深度变化对检测结果的影响因素,对混合RECl₃溶液从表层到底层按照均匀间隔取样进行检测,得出REO浓度和密度的检测结果呈递增趋势,配分的检测结果呈轻稀土含量减少、重稀土含量增加的趋势等结论;研究了混合RECl₃溶液中REO浓度范围差异与存放一定时间内REO浓度的变化趋势,得出REO质量浓度小于50 g/L或大于250 g/L时,其检测结果变化缓慢,REO质量浓度在100～200 g/L时,其检测结果变化快速的结论。深入剖析了分层取样方式影响检测结果的基础理论,此研究可用于指导用于稀土应用产品的混合RECl₃溶液的质量控制,对规范混合RECl₃溶液的取样操作具有重要的指导意义。     

Soil Water Content and Dry Density by Time Domain Reflectometry

Soil water content and dry density are two important properties for compaction quality control. This paper presents a new method for determining soil water content and dry density using a single time domain reflectometry test, which is an improvement over that designated by ASTM D6780. This new method is based on simultaneous measurement of apparent dielectric constant and bulk electrical conductivity on the same soil sample. Calibration equations correlate these two parameters with soil gravimetric water content and dry density, which are simultaneously solved after adjusting field-measured conductivity to a standard conductivity. The method compensates for temperature effects. The test process takes about 3 min and all calculations are automated. Testing may be done in situ using a special probe that provides sufficient sampling volume or in a compaction mold adapted to form a probe. Laboratory and field tests results show this one-step method is a fast, accurate, and safe method for construction quality control.     

Surface-crack formation in the manufacture of microalloyed steel pipe

Deform-3D software is used to model surface-crack formation in the rolling of thick sheet on a 5000 mill. The calculations show that the temperature field and stress state are relatively uniform over the width of the sheet, except at the edges. The minimum temperature of the surface layers of metal hardly depends on the sheet thickness and the relative reduction per pass. The Cockroft–Latham criterion is used to analyze the probability of steel failure in rolling. Analysis shows that metal failure may occur at points where ferrite appears, especially at the instant that the metal leaves the deformation region. Considerable tensile stress acts at those points.