300km/h高速铁路PC槽型梁动力试验研究

介绍北方交通大学与比利时鲁汶大学、布鲁塞尔自由大学、比利时铁路公司合作,在巴黎至布鲁塞尔之间高速铁路线上的Antoing大桥进行的二次高速铁路桥梁动力试验。试验桥梁由跨度50m的多跨预应力混凝土简支槽型梁构成,试验中列车速度达265-310km/h。通过现场试验和实验结果分析,得到了桥梁的频率、振型、阻尼等自振特性,以及桥梁在高速列车作用下的动挠度、梁和桥墩的横向和竖向加速度、橡胶支座的相对位移、梁体的动应变等动力响应特性。试验经验和测试结果对于充实高速铁路桥梁动力分析理论、改进数值分析模型、验证计算结果、提高高速铁路桥梁的动力设计水平、保证行车安全,具有重要的意义。     

Temporary leukocyte depletion reduces ventricular dysfunction during prolonged postischemic reperfusion

Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation.     

Recurrent erosion after photorefractive keratectomy

Recurrent erosion of the corneal epithelium has been treated successfully by phototherapeutic keratectomy when convention therapy has failed. We present a case of recurrent corneal erosion occurring 1 year after photorefractive keratectomy in a 55-year-old myopic woman. No corneal abnormalities were previously identified in either the affected or the fellow eye. This case demonstrates the potential for ineffective healing of the corneal epithelial basement membrane complex after excimer laser photorefractive keratectomy.     

Some scientist-practitioners do.

Comments on the argument of L. T. Hoshmand and D. E. Polkinghorn (see record 1992-21300-001) that psychological practice should inform science to the same degree that science informs practice. Based on a survey of 121 faculty members in programs accredited by the American Psychological Association, 65% reported practice activity. The authors agree that the problem involves a much more complex integrative task that goes beyond simply recognizing knowledge gained in practice settings as valid. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Apoptosis and delayed neuronal damage after carbon monoxide poisoning in the rat

Delayed neurological damage after CO hypoxia was studied in rats to determine whether programmed cell death (PCD), in addition to necrosis, is involved in neuronal death. In rats exposed to either air or CO (2500 ppm), microdialysis in brain cortex and hippocampus was performed to determine the extent of glutamate release and hydroxyl radical generation during the exposures. Groups of control and CO-exposed rats also were tested in a radial maze to assess the effects of the CO exposures on learning and memory. At 3, 7, and 21 days after CO exposure brains were perfusion-fixed and hematoxylin-eosin (H&E) was used to assess injury and to select regions for further examination. DNA fragmentation was sought by examining cryosections with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) reaction. We found significant increases in glutamate release and .OH generation during and immediately after CO hypoxia. CO-exposed rats showed learning and memory deficits after exposure associated with heterogeneous cell loss in cortex, globus pallidus, and cerebellum. The frontal cortex was affected most seriously; the damage was slight at Day 3, increased at Day 7, and persistent at Day 21 after CO exposure. TUNEL staining was positive at all three time points, and TUNEL-labeled cells were distributed similarly to eosinophilic cells. The number of cells stained by TUNEL was less than by H&E and amounted to 2 to 5% of all cell nuclei in regions of injury. Ultrastructural features of both neuronal necrosis and apoptosis also were observed readily by electron microscopy. These findings indicate that both necrosis and apoptosis (PCD) contribute to CO poisoning-induced brain cell death.     

On the Consistency of the Normalized Eight-Point Algorithm

A recently proposed argument to explain the improved performance of the eight-point algorithm that results from using normalized data (Chojnacki, W., et al. in IEEE Trans. Pattern Anal. Mach. Intell. 25(9):1172–1177, 2003) relies upon adoption of a certain model for statistical data distribution. Under this model, the cost function that underlies the algorithm operating on the normalized data is statistically more advantageous than the cost function that underpins the algorithm using unnormalized data. Here we extend this explanation by introducing a more refined, structured model for data distribution. Under the extended model, the normalized eight-point algorithm turns out to be approximately consistent in a statistical sense. The proposed extension provides a link between the existing statistical rationalization of the normalized eight-point algorithm and the approach of Mühlich and Mester for enhancing total least squares estimation methods via equilibration. The paper forms part of a wider effort to rationalize and interrelate foundational methods in vision parameter estimation.     

Mantle cell lymphoma: a clinicopathologic study of 80 cases

Mantle cell lymphoma (MCL) is a relatively uncommon yet distinct type of malignant lymphoma whose clinical and pathological characterization has been limited by the small numbers of cases published to date. We studied 80 cases of MCL seen at a single institution over 7 years to determine both clinical and pathological prognostic factors. The patients in this study were predominantly male (70%) and older (mean age, 63 years) and presented with advanced-stage disease (88%). Extranodal involvement was common. Median overall survival (OS) was 43 months. Except for performance status, prognosis was not significantly influenced by clinical prognostic factors. Histologically, MCL architecture was classified as diffuse (78%), nodular (16%), or mantle zone (6%); the OS among these groups was identical. Increased mitotic activity (>20 mitotic figures per 10 high power fields), blastic transformation, and peripheral blood involvement at diagnosis also predicted for a worse outcome, but bone marrow involvement did not. The presence or absence of a translocation t(11; 14) by cytogenetic analysis or a bcl-1 rearrangement by Southern analysis did not significantly predict outcome. In summary, this study of 80 cases of MCL highlights its distinctive clinicopathologic features and shows that increased mitotic activity, blastic morphology, and peripheral blood involvement at diagnosis are prognostically important factors.     

Functional and defective components of avian endogenous virus long terminal repeat enhancer sequences

Oncogenic avian retroviruses, such as Rous sarcoma virus (RSV) and the avian leukosis viruses, contain a strong enhancer in the U3 portion of the proviral long terminal repeat (LTR). The LTRs of a second class of avian retroviruses, the endogenous viruses (ev) lack detectable enhancer activity. By creating ev-RSV hybrid LTRs, we previously demonstrated that, despite the lack of independent enhancer activity in the ev U3 region, ev LTRs contain sequences that are able to functionally replace essential enhancer domains from the RSV enhancer. A hypothesis proposed to explain these data was that ev LTRs contain a partial enhancer that includes sequences necessary but not sufficient for enhancer activity and that these sequences were complemented by RSV enhancer domains present in the original hybrid constructs to generate a functional enhancer. Studies described in this report were designed to define sequences from both the ev and RSV LTRs required to generate this composite enhancer. This was approached by generating additional ev-RSV hybrid LTRs that exchanged defined regions between ev and RSV and by directly testing the requirement for specific motifs by site-directed mutagenesis. Results obtained demonstrate that ev enhancer sequences are present in the same relative location as upstream enhancer sequences from RSV, with which they share limited sequence similarity. In addition, a 67-bp region from the internal portion of the RSV LTR that is required to complement ev enhancer sequences was identified. Finally, data showing that CArG motifs are essential for high-level activity, a finding that has not been previously demonstrated for retroviral LTRs, are presented.