确保更精确的高电阻测量

0引言高电阻测量已成为多种测试应用的组成部分,包括印制电路板的表面电阻（SIR）测试、绝缘材料和半导体的电阻率测量、高欧姆值电阻的电压系数测试等。确保高电阻测量（即高于1G【109欧姆】的电阻）的精度需要使用大量的特殊技术和仪器,例如静电计、源测量单元（SMU）、或皮可安培计／电压源组合。静电计可以采用恒压或恒流的方法测量高电阻。     

High‐dose cefazolin on consecutive hemodialysis in anuric patients with Staphylococcal bacteremia

Methicillin‐sensitive Staphylococcus aureus (MSSA) bacteremia is a leading cause of infection in hemodialysis (HD) patients. Cloxacillin, cefazolin, and vancomycin are the mainstay antimicrobials. Cloxacillin administration leads to frequent drug dosing, longer length of stay (LOS), and higher cost, while resistance and poorer outcomes are associated with vancomycin use. Dosing cefazolin during HD allows for prolonged blood therapeutic levels. We assessed the outcomes and safety of a strategy of treating MSSA bacteremia with 2–3 g cefazolin on HD only. All HD patients with MSSA bacteremia admitted in June–December 2009 at our center and receiving this regime were compared with historical controls who received cloxacillin. Demographic characteristics and outcome measures like mortality, LOS, cost, recrudescence, and adverse drug reactions were assessed. Of 27 consecutive episodes reviewed, 14 and 13 patients received cefazolin and cloxacillin, respectively. Baseline demographics were comparable between the 2 treatment groups. More than one‐third of the bacteremia was related to tunneled catheter infection. The 30‐day mortality of cloxacillin‐ and cefazolin‐treated patients was 15% and 7%, respectively (P=0.14). Two of the 11 survivors treated with cloxacillin (18%) had recrudescent bacteremia while none was observed in cefazolin‐treated survivors. Cefazolin was associated with shorter LOS (10 vs. 20 days, P<0.05) and lower cost (US$8262.00 vs. US$15,367.00, P<0.05). Cefazolin use resulted in 3 idiosyncratic adverse drug reactions. Cefazolin dosed on each HD in MSSA bacteremia leads to earlier discharge and less cost. Larger prospective studies are, however, warranted to fully assess its safety and efficacy.     

德国中小城镇在国土开发中扮演的重要角色

与大多数欧洲城市相比,德国的城镇体系属于均衡发展的典范。地区的高度自治、联邦体制以及强有力的州政府使德国在两千多年的城市发展历程中,逐渐形成了大中小城市遍布全国的空间形态。这些城市都具有相似的生活质量、便捷的交通和便利的服务。基于对中小城镇的概括定义,本文将首先简要介绍城市均衡发展的历史渊源及小城镇在德国的重要作用,并举例分析一些进行中的都市化过程,随后将选取纽伦堡城市区域作为中小城镇的成功案例重点介绍,最后简要说明支持城镇发展的联邦政策规划。     

Disassembly and Mislocalization of AQP4 in Incipient Scar Formation after Experimental Stroke

There is an urgent need to better understand the mechanisms involved in scar formation in the brain. It is well known that astrocytes are critically engaged in this process. Here, we analyze incipient scar formation one week after a discrete ischemic insult to the cerebral cortex. We show that the infarct border zone is characterized by pronounced changes in the organization and subcellular localization of the major astrocytic protein AQP4. Specifically, there is a loss of AQP4 from astrocytic endfoot membranes that anchor astrocytes to pericapillary basal laminae and a disassembly of the supramolecular AQP4 complexes that normally abound in these membranes. This disassembly may be mechanistically coupled to a downregulation of the newly discovered AQP4 isoform AQP4ex. AQP4 has adhesive properties and is assumed to facilitate astrocyte mobility by permitting rapid volume changes at the leading edges of migrating astrocytes. Thus, the present findings provide new insight in the molecular basis of incipient scar formation.     

Environmental testing of high strength molding compounds

Tensile and short beam shear tests were performed on five high strength vinyl ester molding compounds after immersion in water at various temperatures. These tests were conducted in order to characterize the degradation of these properties with environmental exposure and to isolate problem areas which contribute to the degradation. Reductions of up to 70 percent were found for both tensile and short beam shear strength, when tested at high temperatures. This loss of properties is primarily a result of degradation of the glass/resin interface and is essentially irreversible.     

A model of passive thermal nondestructive evaluation of composite laminates

A numerical model of passive thermal nondestructive evaluation (NDE) of composite laminates was developed. This model, based on a transient, three-dimensional, finite difference solution to the heat conduction equations, can be used to characterize in-plane defects in the laminates and to predict the laminate response to the thermal test. The model was experimentally verified using two material systems. A parametric study was then conducted to ascertain which variables were critical to the success of passive thermal NDE, and how flaw resolution might be improved.     

Sulfur in wheat gluten: In situ analysis by X-ray absorption near edge structure (XANES) spectroscopy

The sulfur containing gluten proteins largely determine the baking quality of wheat. In order to probe the speciation of sulfur, gluten proteins [gliadin, high molecular weight (HMW) and low molecular weight (LMW) subunits of glutenin], stored glutenin subunits as well as flour were investigated in situ by S K-edge X-ray near edge absorption structure (XANES) spectroscopy. The spectra confirmed the existence of disulfide bonds in oxidised (oxygen stream) glutenin subunits, supporting their significance for the formation of gluten networks. Additionally, glutenin subunits, which were stored under ambient air and temperature conditions, predominantly contained sulfur of higher oxidation states (sulfoxide, sulfonic acid). The disulfide state and also sulfoxide and sulfonic acid states were detected after reoxidation of glutenin subunits with potassium bromate.     

Safety Evaluation of Green Tea Polyphenols Consumption in Middle‐aged Ovariectomized Rat Model

This work evaluates chronic safety in middle‐aged ovariectomized rats supplemented with different dosages of green tea polyphenols (GTP) in drinking water. The experiment used 6‐mo‐old sham (n = 39) and ovariectomized (OVX, n = 143) female rats. All sham (n = 39) and 39 of the OVX animals received no GTP treatment and their samples were collected for outcome measures at baseline, 3 mo, and 6 mo (n = 13 per group for each). The remaining OVX animals were randomized into 4 groups receiving 0.15%, 0.5%, 1%, and 1.5% (n = 26 for each) of GTP (wt/vol), respectively, in drinking water for 3 and 6 mo. No mortality or abnormal treatment‐related findings in clinical observations or ophthalmologic examinations were noted. No treatment‐related macroscopic or microscopic findings were noted for animals administered 1.5% GTP supplementation. Throughout the study, there was no difference in the body weight among all OVX groups. In all OVX groups, feed intake and water consumption significantly decreased with GTP dose throughout the study period. At 6 mo, GTP intake did not affect hematology, clinical chemistry, and urinalysis, except for phosphorus and blood urea nitrogen (increased), total cholesterol, lactate dehydrogenase, and urine pH (decreased). This study reveals that the no‐observed‐adverse‐effect level (NOAEL) of GTP is 1.5% (wt/vol) in drinking water, the highest dose used in this study.