Neurobehavioral indicators of early brain insult in high-risk neonates.

Neurobehavioral (NB) performance was evaluated in 248 neurologically at-risk neonates at neonatal intensive care unit discharge to investigate the relation between behavior and brain insult. Six brain insult groups were defined on the basis of findings from cranial ultrasonography and brainstem auditory evoked response tests. The NB evaluation consisted of a modification and condensation of the Einstein Neonatal NB Assessment Scale and the assessment of activated motor patterns described by Katona. Logistic regression analysis of normal vs. abnormal judgments of behavioral categories revealed that, independent of the effects of prematurity, different patterns of NB abnormalities were associated with different degrees and types of brain insult. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Alcohol consumption by young actively growing rats: a study of cortical bone histomorphometry and mechanical properties

Alcohol consumption by young actively growing rats has been previously demonstrated to decrease cortical and cancellous bone density, to reduce trabecular bone volume, and to inhibit bone growth at the epiphyseal growth plate. This study addresses the action of alcohol on cortical bone growth using histomorphometric techniques and on mechanical properties by three-point bending. Four-week-old, female Sprague-Dawley rats were divided into three groups. Alcohol-treated animals were fed a modified Lieber-DeCarli diet ad libitum containing 35% ethanol-derived calories, whereas the pair-fed animals (weight-matched to ethanol rats) received an isocaloric liquid diet in which maltose-dextrin-substituted calories were supplied by ethanol. Chow animals were fed a standard rat chow ad libitum. Femora were removed for analysis after 2, 4, 6, or 8 weeks on the diets. Cortical bone area, bone formation rates, and mineral apposition rates were reduced in the alcohol-fed animals. Bone stiffness, strength, and energy absorbed to fracture were significantly lower in the alcohol-fed animals. This distinctive alcohol effect was revealed to be caused by lower quality bone tissue as reflected by lower elastic moduli and yield strengths.     

Analysis and design of integrated active circulator antennas

A study on the analysis and design of active integrated antennas based on active quasi-circulators is reported in this paper. The antenna consists of a novel hybrid active circulator and a short-circuited quarter-wavelength microstrip antenna, which combine to form an active antenna with transmit and receive action at the same frequency. A full-wave model of the configuration using the extended finite-difference time-domain method is devised to analyze its operation, to study parasitic electromagnetic coupling effects, and to derive design guidelines. Experimental results for a hybrid model are also presented     

Elastic buckling of elliptical tubes

Hot-rolled and cold-formed structural steel tubular members of elliptical cross-section have recently been introduced into the construction sector. However, there is currently limited knowledge of their structural behaviour and stability, and comprehensive design guidance is not yet available. This paper examines the elastic buckling response of elliptical hollow sections in compression, which has been shown to be intermediate between that of circular hollow sections and flat plates. The transition between these two boundaries is dependant upon both the aspect ratio and relative thickness of the section. Based on the results of numerical and analytical studies, formulae to accurately predict the elastic buckling stress of elliptical tubes have been proposed, and shortcomings of existing expressions have been highlighted. Length effects have also been investigated. The findings have been employed to derive slenderness parameters in a system of cross-section classification for elliptical hollow sections, and form the basis for the development of effective section properties for slender elliptical tubes.     

In0.53Ga0.47As junction field-effecttransistors as tunable feedback resistors for integrated receiverpreamplifiers

In_0.53Ga_0.47As active feedback junction field-effect transistors (JFETs) for use in integrated transimpedance photoreceivers are discussed. By varying the gate-to-source voltage V_GS, the resistance can be continuously tuned between 3 and 40 kΩ with a drain-to-source capacitance of <10 fF. The temperature coefficient of resistance is between -5 and -20 Ω/°C (for V_GS less than the pinch-off voltage). The combination of large resistance and low capacitance can result in high receiver sensitivity without sacrificing amplifier dynamic range. The feedback FET was fabricated adjacent to 1.8-μm-gate-length JFETs with transconductances of 110 mS/mm, gate-to-source capacitances of 1.3 pF/mm, and DC amplifier voltage gains of 100. The compatibility of these transistor structures indicates that an integrated preamplifier with dynamically tunable bandwidth can be realized     

碳钢和不锈钢管状支撑构件循环试验和数值模型

为了研究由热轧碳钢、冷弯碳钢、冷弯不锈钢三种材料所构成的管状支撑构件的响应,在轴向循环荷载下,进行了16个方形、长方形空心截面构件的试验,对三种材料试件的荷载-位移滞回响应、抗压强度、侧向挠度、能量耗散、断裂寿命进行研究。此外,采用有限元模型验证试验结果,并基于应变破坏预测方法进行参数研究。研究表明:现有的预测抗压屈曲、屈曲后抗压强度的经验公式可同时用于碳钢和不锈钢试件。然而,构件延性和长细比之间的关系不能代表整体的长细比,亦不能用于冷弯不锈钢构件。对于每种材料,考虑整体和局部长细比,提出新的公式。对于不同的材料,整个加载周期的切线刚度不同,这是决定局部屈曲阻力、循环次数、支撑破坏的关键因素。