In vivo accuracy of two radiographic systems in the detection of Bj?rk-Shiley convexo-concave heart valve outlet strut single leg separations

OBJECTIVE: Modified cineradiographic systems have been used clinically to detect partially broken outlet struts in normally functioning Bj?rk-Shiley convexo-concave heart valves. Almost all such valves were explanted, presuming that full failure would likely follow. Inasmuch as the clinical setting only rarely permits examination of normally rated valves, the accuracy of radiographic detection cannot be clinically defined. This study uses the clinical radiographic technique in sheep implanted with known-status convexo-concave valves, comparing its accuracy and that of a newly developed, geometric image magnification radiography system. METHODS: Twenty-one sheep with mitral convexo-concave valves were studied on both systems. Five were used for extensive training. When operators were expert with both systems, images of four intact valves and 12 valves with outlet strut single leg separations, along with a seventeenth single leg separation valve used for calibration, were integrated into 112 image sets organized into a balanced incomplete block design for evaluation by eight trained, blinded reviewers. RESULTS: Cineradiography sensitivity was 24% versus 31% for direct image magnification. The odds ratio for detection of single leg separation by direct image magnification versus cineradiography was 2.0 (95% confidence interval, 0.76 to 5.9; p = 0.13). Cineradiography specificity was 93% versus 90% for direct image magnification. Sensitivity and specificity varied markedly by reviewer, with sensitivity ranging from 8% to 55% and specificity from 51% to 100% for the combined technologies. CONCLUSIONS: The data support the need for more intensive training for convexo-concave valve imaging and further investigation of unconventional radiographic technologies. Clinical cineradiography of convexo-concave valves may detect as little as 25% of valves having a single leg separation, underestimating the prevalence of single leg separations and thereby implying more rapid progression to full fracture than is actually the case.     

Progesterone induces calcitonin gene expression in human endometrium within the putative window of implantation

The human endometrium acquires the ability to implant the developing embryo within a specific time window that is thought to open between days 19-24 of the secretory phase of the menstrual cycle. During this period the endometrium undergoes pronounced structural and functional changes induced by the ovarian steroids, estrogen and progesterone, that prepare it to be receptive to invasion by the embryo. The identification of reliable biochemical markers to assess this critical receptive phase in the context of the natural cycle remains one of the major challenges in the study of human reproduction. Our previous studies in a rat model system demonstrated that the expression of calcitonin, a peptide hormone involved in calcium homeostasis, is transiently induced by progesterone in the glandular epithelium at the onset of implantation. Attenuation of calcitonin synthesis in the uterus during the preimplantation phase by administration of calcitonin antisense oligodeoxynucleotides severely impairs implantation of rat embryos, suggesting that this peptide hormone plays a critical role in uterine receptivity. To investigate whether calcitonin is also expressed in the human endometrium during implantation, we monitored the spatio-temporal expression of calcitonin on various days of the menstrual cycle. Our studies employing RT-PCR showed that calcitonin messenger ribonucleic acid is expressed in human endometrium during the postovulatory midsecretory phase (days 17-25) of the menstrual cycle, with maximal expression occurring between days 19-21. Very little calcitonin expression was detected in the endometrium in either the preovulatory proliferative (days 5-14) or the late secretory (days 26-28) phase. In situ hybridization and immunocytochemical analyses localized the calcitonin expression predominantly in the glandular epithelial cells of the endometrium. Our studies further showed that calcitonin expression in the human endometrium is under progesterone regulation. Treatment of women with an antiprogestin, mifepristone (RU-486), drastically reduced calcitonin expression in the endometrium. Collectively, these findings reveal that progesterone-induced expression of calcitonin in the secretory endometrium temporally coincides with the putative window of implantation in the human.     

An Evaluation of the Sparsity Degree for Sparse Recovery with Deterministic Measurement Matrices

The paper deals with the estimation of the maximal sparsity degree for which a given measurement matrix allows sparse reconstruction through ? ₁-minimization. This problem is a key issue in different applications featuring particular types of measurement matrices, as for instance in the framework of tomography with low number of views. In this framework, while the exact bound is NP hard to compute, most classical criteria guarantee lower bounds that are numerically too pessimistic. In order to achieve an accurate estimation, we propose an efficient greedy algorithm that provides an upper bound for this maximal sparsity. Based on polytope theory, the algorithm consists in finding sparse vectors that cannot be recovered by ? ₁-minimization. Moreover, in order to deal with noisy measurements, theoretical conditions leading to a more restrictive but reasonable bounds are investigated. Numerical results are presented for discrete versions of tomography measurement matrices, which are stacked Radon transforms corresponding to different tomograph views.     

为太阳能逆变器选择合适的电容器

选择太阳能逆变器中的能量缓冲器会涉及到元件行为特征的很多细节。因此,明智的做法是在设计阶段的早期就与经验丰富的供应商一起工作,确保所选择的技术能满足所需。太阳能逆变器是一种电源转换装置,主要功能是将蓄电池的直流电逆变成交流电。在其基本原理框图中,DC-DC转换器控制着太阳能电池板的工作点,使之达到最大的功率输出;DC-AC转换器把电能输送到电网,同时执行主电网运营商设立的各种管控规则;能量缓冲器会吸收掉两个转换器之间功率流的差值。选择能量缓冲器的依据如何选择能量缓冲器呢?需要考虑能量缓冲器的大小和时长等因素。能量缓冲器的大小是由需储存     

AMOLED电视将继续面临成本困扰

尽管AMOLED电视在今年美国CES展上露面令人振奋,但由于制造困难和原材料成本高昂,未来几年这种电视的全球出货量将非常有限。     

在先进移动设备上应用MEMS传感器

MEMS传感器包括加速度计、陀螺仪、磁力计、压力传感器和麦克风,因其具有低成本、小尺寸、低功耗、高性能等特性,近几年来被大量集成到便携设备中。     

用设计管理功能改变FPGA设计流程

在传统的FPGA系统设计中,不同的尝试必须按顺序依次进行,使得编译时间延长,而采用新的设计工具可并行编译多个实现,用一次编译时间比较两种实现的结果,可加快产品开发速度。     

飞思卡尔:半导体将成为许多解决方案的核心部分

半导体创新是产业的转折点。在以前的PC时代,人们关注的是处理器性能,功耗问题则是通过更大的机箱、添加冷却风扇或使用更大的电池来处理。我们正在进入互联智能时代,嵌入式处理性能需要与功效权衡考虑,系统功能将通过传感器、RF和模拟接口的智能集成来实现。连接性需求始     

A plasma light source for the VUV spectral region

The 5-50-eV spectral range appears to be absent from the planned third generation synchrotron radiation sources (SRS) and the science requiring this radiation can be jeopardized once the second generation SRS light sources are switched off worldwide. Molecular photochemistry, photobiology, atomic physics, solid-state physics are but a few sciences requiring powerful VUV sources. We demonstrate that a compact, laser heated plasma light source can generate efficiently radiation in this spectral region, and that this radiation can be coupled very efficiently from the plasma to the exposure cell, by three simple VUV beam-lines, each providing a different spectral bandwidth     

Rietveld refinement and optical properties of SrWO4:Eu3+powders prepared by the non-hydrolytic sol-gel method

We investigated the effect of annealing time on the structure and optical properties of Sr WO4:Eu3+powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 oC for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4:Eu3+powders were obtained at about 800 oC.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O–W–O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible(UV-vis)diffuse reflectance,and photoluminescence(PL)data which provided the evolution of quantum efficiency(η)and lifetime(τ).UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4:Eu3+powders.PL properties validated that the Eu3+electric-dipole(5D0→7F2)transition in PL emission spectra was dominant which proved that Eu3+ions were positioned in a site without an inversion center.[(5D0→7F2)/(5D0→7F1)]band ratios showed that Eu3+ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4:Eu3+powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800 oC for 8 h.