Short- and long-latency afferent inhibition; uses,mechanisms and influencing factors

Transcranial magnetic stimulation (TMS) is an ideal technique for non-invasively stimulating the brain and assessing intracortical processes. By delivering electrical stimuli to a peripheral nerve prior to a TMS pulse directed to the motor cortex, the excitability and integrity of the sensorimotor system can be probed at short and long time intervals (short latency afferent inhibition, long latency afferent inhibition). The goal of this review is to detail the experimental factors that influence the magnitude and timing of afferent inhibition in the upper limb and these include the intensity of nerve and TMS delivery, and the nerve composition. Second, the neural mechanisms of SAI are discussed highlighting the lack of existing knowledge pertaining to LAI. Third, the usage of SAI and LAI as a tool to probe cognition and sensorimotor function is explored with suggestions for future avenues of research.     

平板式探测器和常规X射线数字化成像未来

本文综合论述、分析和讨论了平板检测器（FPD）主要组成部分和整体检测器工作机理，优良特性和现有水平，将用于数字化X射线摄影（DR）的FPD和传统射线摄影用胶片-增感屏系统（简称屏-片系统）进行了比较，提及了FPDDR系统代表着数字摄影系统优点且较其它系统具有优势，将用于数字化X射线透视（DF）的FPD和传统射线透视用图像增强器-摄像器件系统（简称IIT系统）进行了对比。也简述了FPDDR和DF系统某些产品的应用，文中分析认为，未来常规X射线成像系统是和FPD技术联系在一起的。     

DR系统中平板探测器能量响应特性的研究

目的 研究平板探测器(FPD)对kV、mAs的响应特性。方法使用HOLOGIC公司生产的DR系统，变换摄影条件，通过系统软件功能测出设定各点的原始灰度值，通过比较发现其变化规律，为摄影条件的选择提供指导。结果在100kV内，影像的原始灰度值随着kV值的增加而近乎呈线性增加，而大于100kV后，影像的灰度值随着kV增加而增加的幅度明显下降；FPD对mA和曝光时间的响应特性几近线性。结论胸部数字X射线摄影的最佳kV值在100kV左右。在kV满足穿透力的前提下，不要只通过增加kV值来提高影像的灰度值(高kV摄影除外)；要配合mA和曝光时间的变化来增加或降低影像的灰度值，合理化选择摄影条件的搭配，避免不必要的辐射损伤。     

Adult human heart slices are a multicellular system suitable for electrophysiological and pharmacological studies

Electrophysiological and pharmacological data from the human heart are limited due to the absence of simple but representative experimental model systems of human myocardium. The aim of this study was to establish and characterise adult human myocardial slices from small patients' heart biopsies as a simple, reproducible and relevant preparation suitable for the study of human cardiac tissue at the multicellular level.Vibratome-cut myocardial slices were prepared from left ventricular biopsies obtained from end-stage heart failure patients undergoing heart transplant or ventricular assist device implantation, and from hearts of normal dogs. Multiple slices were prepared from each biopsy. Regular contractility was observed at a range of stimulation frequencies (0.1-2 Hz), and stable electrical activity, monitored using multi-electrode arrays (MEA), was maintained for at least 8 h from slice preparation. ATP/ADP and phosphocreatine/creatine ratios were comparable to intact organ values, and morphology and gap junction distribution were representative of native myocardium. MEA recordings showed that field potential duration (FPD) and conduction velocity (CV) in human and dog slices were similar to the values previously reported for papillary muscles, ventricular wedges and whole hearts. Longitudinal CV was significantly faster than transversal CV, with an anisotropic ratio of 3:1 for human and 2.3:1 for dog slices. Importantly, slices responded to the application of E-4031, chromanol and 4-aminopyridine, three potassium channel blockers known to affect action potential duration, with an increase in FPD.We conclude that viable myocardial slices with preserved structural, biochemical and electrophysiological properties can be prepared from adult human and canine heart biopsies and offer a novel preparation suitable for the study of heart failure and drug screening.     

非晶硒DR探测器平板的结构特点及正常使用要求

从非晶硒DR平板探测器内部结构的角度，讨论其正常工作所需环境温度，介绍在使用环境外DR探测器可能出现的脱膜等故障；并根据其内部结构特点，提出了正常使用的措施。     

化妆品中几种防腐剂的分析方法

目的了解深圳市售化妆品中使用防腐剂的情况。方法采用高效液相色谱法(HPLC)、火焰光度检测器-气相色谱法(FPD-GC)、分光光度法分析化妆品中9种防腐剂。结果化妆品中最常用的防腐剂是对羟基苯甲酸酯类;FPD-GC法测定卡松的灵敏度高于HPLC法;FID-GC法测定丁氨基甲酸-3-碘化-2-丙炔基酯(IBPC)的最低检出浓度为1.8μg/g;甲醛检出率37%。结论FPD-GC法测定卡松灵敏度较高。甲醛检出率较高,可能与某些防腐剂释放甲醛有关。     

固定种植义齿与传统义齿患者满意度的对照分析

目的比较多数牙缺失患者行固定种植义齿和可摘局部义齿、传统固定义齿修复后的主观感受。方法对58例戴用可摘局部义齿后又行固定种植义齿修复的患者及58例传统双端固定义齿患者,采用自拟的问卷调查表,由患者本人就诊时填写后进行统计对照分析。结果种植固定义齿与可摘局部义齿在咀嚼功能、美观程度、方便程度、语言功能方面有统计学差异（P〈0.05）;在固位功能、舒适性方面等方面存在显著性差异（P〈0.01）;种植固定义齿与传统固定义齿在咀嚼功能、美观程度、固定功能、舒适性、方便性、语音功能之间满意度的差别无统计学意义（P〉0.05）。结论多数牙缺失患者行桥式固定种植义齿,较可摘局部义齿修复能更好地满足患者需求,获得高质量的义齿,是传统固定义齿修复的重要补充。     

Marginal fit of anterior 3-unit fixed partial zirconia restorations using different CAD/CAM systems

PURPOSE

Few studies have investigated the marginal accuracy of 3-unit zirconia fixed partial dentures (FPDs) fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) system. The purpose of this study was to compare the marginal fit of zirconia FPDs made using two CAD/CAM systems with that of metal-ceramic FPDs.

MATERIALS AND METHODS

Artificial resin maxillary central and lateral incisors were prepared for 3-unit FPDs and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, 15 three-unit FPDs were fabricated per group (45 in total): Group A, zirconia 3-unit FPDs made with the Everest system; Group B, zirconia 3-unit FPDs made with the Lava system; and Group C, metal-ceramic 3-unit FPDs. They were cemented to resin dies with resin cement. After removal of pontic, each retainer was separated and observed under a microscope (Presize 440C). Marginal gaps of experimental groups were analyzed using one-way ANOVA and Duncan test.

RESULTS

Mean marginal gaps of 3-unit FPDs were 60.46 µm for the Everest group, 78.71 µm for the Lava group, and 81.32 µm for the metal-ceramic group. The Everest group demonstrated significantly smaller marginal gap than the Lava and the metal-ceramic groups (P<.05). The marginal gap did not significantly differ between the Lava and the metal-ceramic groups (P>.05).

CONCLUSION

The marginal gaps of anterior 3-unit zirconia FPD differed according to CAD/CAM systems, but still fell within clinically acceptable ranges compared with conventional metal-ceramic restoration.     

Systematic review of biomonitoring studies to determine the association between exposure to organophosphorus and pyrethroid insecticides and human health outcomes

For the appropriate protection of human health it is necessary to accurately estimate the health effects of human exposure to toxic compounds. In the present review, epidemiological studies on the health effects of human exposure to organophosphorus (OP) and pyrethroid (PYR) insecticides have been critically assessed. This review is focused on studies where the exposure assessment was based on quantification of specific biomarkers in urine or plasma. The 49 studies reviewed used different epidemiological approaches and analytical methods as well as different exposure assessment methodologies. With regard to OP pesticides, the studies reviewed suggested negative effects of prenatal exposure to these pesticides on neurodevelopment and male reproduction. Neurologic effects on adults, DNA damage and adverse birth outcomes were also associated with exposure to OP pesticides. With regard to exposure to PYR pesticides, there are currently few studies investigating the adverse health outcomes due to these pesticides. The effects studied in relation to PYR exposure were mainly male reproductive effects (sperm quality, sperm DNA damage and reproductive hormone disorders). Studies' findings provided evidence to support the hypothesis that PYR exposure is adversely associated with effects on the male reproductive system. The validity of these epidemiological studies is strongly enhanced by exposure assessment based on biomarker quantification. However, for valid and reliable results and conclusions, attention should also be focused on the validity of the analytical methods used, study designs and the measured toxicants characteristics.     

Simulation approach for the evaluation of tracking accuracy in radiotherapy: a preliminary study

Real-time tumor tracking in external radiotherapy can be achieved by diagnostic (kV) X-ray imaging with a dynamic flat-panel detector (FPD). It is important to keep the patient dose as low as possible while maintaining tracking accuracy. A simulation approach would be helpful to optimize the imaging conditions. This study was performed to develop a computer simulation platform based on a noise property of the imaging system for the evaluation of tracking accuracy at any noise level. Flat-field images were obtained using a direct-type dynamic FPD, and noise power spectrum (NPS) analysis was performed. The relationship between incident quantum number and pixel value was addressed, and a conversion function was created. The pixel values were converted into a map of quantum number using the conversion function, and the map was then input into the random number generator to simulate image noise. Simulation images were provided at different noise levels by changing the incident quantum numbers. Subsequently, an implanted marker was tracked automatically and the maximum tracking errors were calculated at different noise levels. The results indicated that the maximum tracking error increased with decreasing incident quantum number in flat-field images with an implanted marker. In addition, the range of errors increased with decreasing incident quantum number. The present method could be used to determine the relationship between image noise and tracking accuracy. The results indicated that the simulation approach would aid in determining exposure dose conditions according to the necessary tracking accuracy.