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排序方式: 共有326条查询结果,搜索用时 125 毫秒
261.
We have developed a simple and low-cost flow injection system coupled to a quadruple ICP-MS for the direct and continuous determination of multi-element in microdialysates. To interface microdialysis sampling to an inductively coupled plasma mass spectrometer (ICP-MS), we employed 3D printing to manufacture an as-designed sample load/inject valve featuring an in-valve sample loop for precise handling of microliter samples with a dissolved solids content of 0.9% NaCl (w/v). To demonstrate the practicality of our developed on-line system, we applied the 3D printed valve equipped a 5-μL sample loop to minimize the occurrence of salt matrix effects and facilitate an online dynamic monitoring of extracellular calcium and zinc ions in living rat brains. Under the practical condition (temporal resolution: 10 h−1), dynamic profiling of these two metal ions in living rat brain extracellular fluid after probe implantation (the basal values for Ca and Zn were 12.11 ± 0.10 mg L−1 and 1.87 ± 0.05 μg L−1, respectively) and real-time monitoring of the physiological response to excitotoxic stress elicited upon perfusing a solution of 2.5 mM N-methyl-d-aspartate were performed. 相似文献
262.
压缩机排气舌簧阀的计算模型及其动态分析 总被引:2,自引:0,他引:2
本文对具有面接触式升程限制器(即背板)的排气舌簧阀提出一个计算模型和相应的分析方法;据此可确定阀片的振型、固有频率、瞬时位移、瞬时速度和加速度、动态应力等.计算结果与实验结果符合良好.本文方法也可用于分析某些增压器、真空泵等设备中的阀片. 相似文献
263.
本文采用任意拉格朗日--欧拉(ALE)有限单无法,将血液视为不可压缩粘性流体,同时将人工机械瓣瓣叶简化为定轴转动刚体。建立了双叶人工机械瓣--血液耦合运动的二维计算模型。在此基础上,对比研究了St.Jude瓣(SJM)、有窦顺向人工机械瓣(DDM)及无窦DDM瓣的启闭过程,以提示窦的作用,本文研究表明:在有窦及无窦的情况下,瓣叶开启规律基本一致。窦对跨瓣压差及剪应力幅值影响也不大,但对瓣叶的关闭却 相似文献
264.
Methods for determining the response of continuous systems with quadratic and cubic nonlinearities are discussed. We show by means of a simple example that perturbation and computational methods based on first discretizing the systems may lead to erroncous results whereas perturbation methods that attack directly the nonlinear partial-differential equations and boundary conditions avoid the pitfalls associated with the analysis of the discretized systems. We describe a perturbation technique that applies either the method of multiple scales or the method of averaging to the Lagrangian of the system rather than the partial-differential equations and boundary conditions. 相似文献
265.
柔性瓣架对生物心脏瓣膜应力的影响 总被引:3,自引:0,他引:3
采用非线性大变形超参数八结点板壳元,针对用猪主动脉瓣制成的人工心瓣所用的瓣架材料,形状,侧边高度等对其应力的影响进行数值模拟分析,其中瓣叶的几何形式保持不变。结果表明:弹性瓣架存在一个合适的弹性模量范围,能使瓣叶的最大应力降低较明显;对同一种瓣叶和具有相同弹性模量的瓣架而言、使瓣架立柱顶端产生位移最大的瓣架形状,往往亦是使瓣叶最大应力降低2的最明显的瓣架形状。 相似文献
266.
Elo Harald Hansen 《应用光谱学评论》2013,48(4):335-357
Abstract One of the current needs within the analytical spectrometric community is the development of straightforward and cost‐effective, yet rugged, sample processing procedures aimed at precluding both spectroscopic and nonspectroscopic matrix interferences while fostering concomitant sample enrichment. Illustrated via selected representative examples, this review presents and discusses the current state of the art in implementing miniaturised and automated sample treatments for environmental and biochemical assays via microfluidic systems exploiting the lab‐on‐valve (LOV) platform in hyphenation with syringe pump propelling devices as a front end to a plethora of spectroscopic detection schemes including ultraviolet‐visible (UV‐Vis) spectrometry, spectrofluorimetry, chemiluminescence, atomic absorption spectrometry (AAS), atomic flourescence spectrometry (AFS), and inductively coupled plasma‐atomic emission spectrometry/mass spectrometry (ICP‐AES/MS). In contrast to lab‐on‐a‐chip units, the versatile configuration of the micromachined LOV readily facilitates the implementation of on‐line unit operations at will encompassing not merely the introduction of minute, well‐defined volumes of sample followed by chemical derivatization, but the potential for accommodation of solid‐phase extraction, hydride/vapor generation, precipitation/coprecipitation, and bead injection protocols with no need for chip redesign. 相似文献
267.
268.
Takashi Sato Masakiyo Tsunoda Migaku Takahashi 《Journal of magnetism and magnetic materials》2002,240(1-3):277-279
Correlation between the unidirectional anisotropy constant, JK, and the degree of ordering of PtMn layer was investigated for Pt55Mn45/Co90Fe10 bilayer, as a function of the annealing time and the PtMn layer thickness, dAF. As a result, we found the linear relations between JK and the degree of ordering, fFCT·S, in the cases of the bilayers with dAF=5–50 nm. From the extrapolation of the linear relations to fFCT·S=1, meaning the perfect ordering of PtMn layer, we obtained the attainable value of JK and the intrinsic critical thickness of the PtMn layer to be 0.26 erg/cm2 and 6 nm, respectively. 相似文献
269.
V. Da Costa A. Iovan K. Ounadjela W. Allen J. F. Gregg B. Dieny 《Journal of magnetism and magnetic materials》2002,240(1-3):140-142
The ultra-thin oxide tunnel barrier employed in magnetic tunnel junctions stack has to be of very high quality in terms of large scale homogeneity of its thickness and height parameters. For controlling precisely oxidation kinetic, we used spin valves as an oxidation progress probe. By measuring the magnetoresistance effect versus the oxidation time we are able to detect under- or over-oxidation of the metallic material. This technique consists of analysing the ability of spin-dependent electron scattering at metal/oxide interfaces. 相似文献
270.
Normal human mitral valve proteome: A preliminary investigation by gel‐based and gel‐free proteomic approaches
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Maura Brioschi Roberta Baetta Stefania Ghilardi Erica Gianazza Anna Guarino Alessandro Parolari Gianluca Polvani Elena Tremoli Cristina Banfi 《Electrophoresis》2016,37(20):2633-2643
The mitral valve is a highly complex structure which regulates blood flow from the left atrium to the left ventricle (LV) avoiding a significant forward gradient during diastole or regurgitation during systole. The integrity of the mitral valve is also essential for the maintenance of normal LV size, geometry, and function. Significant advances in the comprehension of the biological, functional, and mechanical behavior of the mitral valve have recently been made. However, current knowledge of protein components in the normal human mitral valve is still limited and complicated by the low cellularity of this tissue and the presence of high abundant proteins from the extracellular matrix. We employed here an integrated proteomic approach to analyse the protein composition of the normal human mitral valve and reported confident identification of 422 proteins, some of which have not been previously described in this tissue. In particular, we described the ability of pre‐MS separation technique based on liquid‐phase IEF and SDS‐PAGE to identify the largest number of proteins. We also demonstrated that some of these proteins, e.g. αB‐Crystallin, septin‐11, four‐and‐a‐half LIM domains protein 1, and dermatopontin, are synthesised by interstitial cells isolated from human mitral valves. These initial results provide a valuable basis for future studies aimed at analysing in depth the mitral valve protein composition and at investigating potential pathogenetic molecular mechanisms. Data are available via ProteomeXchange with identifier PXD004397. 相似文献