Ultrafast Measurement of Optical DPSK Signals Using 1-Symbol Delayed Dual-Channel Linear Optical Sampling

We propose and demonstrate a 1-symbol delayed dual-channel linear optical sampling for observing optical differential phase-shift keying (DPSK) signals. As this technique is based on optical gate processing by means of interference with local short pulses, its performance allows ultrafast measurement for a symbol rate of greater than 100 Gsymbol/s. Moreover, as the new measurement apparatus employs a two-series interferometer system with a 1-symbol delay, the measured phase distribution reflects the signal quality between adjacent symbols of the optical DPSK signals. In our experiment, we successfully observe the waveform degradation caused by the coherence of the light source and the pattern effect of the phase modulator. The measurement system noise is also discussed.     

A variational method for geometric regularization of vascular segmentation in medical images

In this paper, a level-set-based geometric regularization method is proposed which has the ability to estimate the local orientation of the evolving front and utilize it as shape induced information for anisotropic propagation. We show that preserving anisotropic fronts can improve elongations of the extracted structures, while minimizing the risk of leakage. To that end, for an evolving front using its shape-offset level-set representation, a novel energy functional is defined. It is shown that constrained optimization of this functional results in an anisotropic expansion flow which is usefull for vessel segmentation. We have validated our method using synthetic data sets, 2-D retinal angiogram images and magnetic resonance angiography volumetric data sets. A comparison has been made with two state-of-the-art vessel segmentation methods. Quantitative results, as well as qualitative comparisons of segmentations, indicate that our regularization method is a promising tool to improve the efficiency of both techniques.     

Excess estrogen sulfoconjugation as the possible cause for a poor sign of parturition in pregnant cows carrying somatic cell clone fetuses

We conducted this study to elucidate a factor causing a poor sign of parturition and prolonged gestation, which is frequently observed in cows carrying somatic clone fetuses. Pre-partum rises in concentrations of plasma estrone and estradiol-17beta in the recipient cows pregnant with clones were subtle. By contrast, the plasma concentration of estrone sulfate in clone pregnancies increased gradually from pre-initiation of parturition induction whereas control cows that received in vivo-derived embryos showed a significant increase at parturition. Therefore, in clone pregnancies, the ratio of estrone/estrone sulfate was low during the pre-partum period compared with control. Messenger RNA expression of estrogen sulfotransferase (SULT1E1) in the placenta at parturition was significantly higher in clone pregnancies than control pregnancies and was localized in binucleate cells (BNC). SULT1E1 mRNA abundance was negatively and positively correlated with concentrations of maternal estrone and estrone sulfate at parturition respectively. Messenger RNA expressions of estrogen sulfatase (STS) and aromatase (CYP19) were similar between clone and control pregnancies and were localized in BNC and caruncular epithelial cells. STS and CYP19 mRNA abundances showed positive correlations with maternal estradiol-17beta concentration. The population of BNC in the placenta did not differ between clone and control pregnancies. Plasma cortisol concentration of vaginally delivered newborn clone calves was comparable with those of control, although cesarean section delivered clone calves showed a low concentration. These results suggest that excess estrogen sulfoconjugation is the reason for the perturbed low ratio of active to inactive estrogens and the resulting hormonal imbalance contributes to the lack of overt signs of readiness for parturition in cows pregnant with clones.     

水平井电缆牵引器滚轮与管壁压力的测量

水平井电缆牵引器滚轮与管壁之间的压力是进行牵引器结构设计和作业控制的一项关键参数。如果压力施加不当,滚轮将出现打滑或堵转。由于套管细长,滚轮与管壁的接触位置又不断在发生变化,因此压力测量的难度很大。笔者提出在套管上开窗口并用球头立柱支撑压板,使立柱与压板始终处于单面点接触状态,确保压板发生变形时立柱只受到压力。为防止压板从窗口掉入套管,将压板的两个侧立面加工为楔形,与窗口侧立面具有相同的锥度。研究介绍了测力系统的设计和工作原理,提出了有无预紧力2种情况下支撑立柱的压力计算模型,建立了测试系统,并对牵引器在套管内爬行时的压力进行了测量。根据得到的16根支撑立柱的应变值,计算和分析了压板和立柱上的压力分配。     

一种全差动折叠共源共栅的CMOS放大器

设计了一种可用于∑-△A/D转换器的全差动放大器.放大器采用0.5μm CMOS工艺实现,采用折叠式共源共栅结构,并采用开关电容反馈电路.对所设计的放大器进行了详细分析,给出了具体设计过程.SPICE仿真结果表明,其开环直流增益A0为74.2dB,相位裕度不小于60°,单位增益带宽为40MHz,输出摆幅可以达到-200mV(Vdd)-+200mV(Vss).     

Observation of GaAs—AlxGa1 — x as heterostructures and quantum-well-wire structures using backscattered electron image

As a microscale tool for observing GaAs-Al_x Ga_1–xAs heterostructures, backscattered electron (BE) images in the scanning electron microscope (SEM) were compared with conventional secondary electron (SE) images. BE images were found to be more sensitive to compositional differences between GaAs and Al_xGa_1–xAs and less sensitive to surface roughness. BE images have a spatial resolution of 10 nm or better. This method enables the nondestructive observation of ultrafine lateral periodic structures, such as quantum-well-wire (QWW) structures, fabricated by compositional disordering technology using focused Ga ion-beam (Ga-FIB) implantation into GaAs-Al_xGa_1–xAs material.     

Effects of Size and Distribution of Spheroidized Cementite on Void Initiation in the Punched Surface of Medium-Carbon Steel

Metallurgical and Materials Transactions A - In this study, we investigated the effects of the size and distribution of spheroidized cementite on the characteristics of a punched surface as well as...     

Induction of donor-specific ACAID can prolong orthotopic corneal allograft survival in "high-risk" eyes

PURPOSE: To examine the effect of donor-specific anterior chamber-associated immune deviation (ACAID) induction on the survival of orthotopic corneal allografts in neovascularized graft beds. METHODS: To induce donor-specific ACAID in recipients, peritoneal exudate cells (PEC) from C57BL/6 mice were incubated overnight with transforming growth factor (TGF)-beta. Cultured PEC were injected intravenously (i.v.) into BALB/c mice, and, 1 week later, these animals received orthotopic corneal allografts from C57BL/6 donors into neovascularized graft beds. Control mice received i.v. injection of syngeneic (BALB/c) PEC, cultured overnight with TGF-beta, and then received orthotopic corneal allografts from C57BL/6 donors. RESULTS: All corneal allografts (15 out of 15) were rejected within 2 weeks after grafting in the neovascularized graft beds of control animals. However, only 6 out of 16 (37.5%) of corneal allografts were rejected in recipients in which donor-specific ACAID had been induced by injection of allogeneic PEC cultured with TGF-beta. CONCLUSION: Previous studies revealed that rejection of orthotopic corneal allografts in neovascularized graft beds in mice correlated with acquisition of donor-specific delayed hypersensitivity (DH). The results of this study suggest that induction of donor-specific ACAID, which selectively impairs DH responses to donor antigens, effectively prolongs corneal allograft survival in "high-risk" eyes.     

Successful treatment of severe cytomegalovirus retinitis with foscarnet and intraocular injection of ganciclovir in a myelosuppressed unrelated bone marrow transplant patient

PURPOSE: To compare U.S. medical student Match results in 1996 for 19 categorical residency positions by specialty with those of the overall Match reported by the National Resident Matching Program (NRMP). METHOD: Data for the numbers of "active" senior U.S. student applicants (those who submitted rank lists), the numbers of U.S. seniors matched, and the numbers of unfilled positions for 19 specialties were obtained from a variety of sources. Chi-square analysis was performed to compare Match results for each independent specialty with the overall Match results. The level for statistical significant was set at p < .005. RESULTS: Eight specialties were identified as significantly more competitive than the overall Match process for both the percentage of U.S. seniors who successfully matched in that specialty and the ratio of unmatched U.S. senior applicants to unfilled categorical positions. Five specialties were identified as significantly less competitive for these two measures. Six specialties showed no significant difference in the percentages of U.S. students matching, but for three of these specialties there were more unmatched students than unfilled categorical positions. CONCLUSION: U.S. medical student Match results for categorical residency positions for different specialties vary significantly from the overall Match process. This information can be used in counseling senior medical students on their specialty selection and the residency application process.