有机溶剂作业场所通风排毒设施常见问题及控制策略

有机溶剂是工业生产中常见的职业病危害因素,所致的各类急慢性中毒时有发生。有机溶剂挥发至空气中呈无色透明状态,了解其在作业场所的挥发和分布特点,选择合适的通风排毒设施对于有机溶剂危害控制至关重要。本文拟通过分析有机溶剂挥发、分布的影响因素,结合各类通风排毒设施存在的常见问题,重点介绍有代表性的有机溶剂作业场所的通风排毒控制策略。     

学龄期儿童前房深度发育状况分析

目的了解7~14岁学龄期儿童前房深度发育情况。探索其与屈光度数间的关系。方法收集2012年6月至2014年6月眼科门诊7~14岁儿童为研究对象，共计521例（1042只眼）。采用IOLMaster人工晶状体生物测量仪测量各屈光参数，同时测量身高、体重。散瞳后验光测得静态屈光度。分析前房深度发育情况及不同屈光状态的学龄期儿童前房深度发育情况。结果（1）随着年龄的增长，7~14岁学龄期的儿童前房深度随之增长，差异具有统计学意义（P＜0.01）。同一年龄段儿童的左右眼之间的均值相近，且生长发育趋势相近（均P＞0.05）。（2）随着年龄的增长，男女的前房深度均逐渐增大，同一年龄段男性前房深度大于女性前房深度（均P＜0.01）。（3）儿童前房深度与身高正相关（P＜0.01）。（4）前房深度随近视度数增高而增大，低度近视组与中度近视组及高度近视组差异有统计学意义（P＜0.05）。结论学龄期儿童的前房深度的发育受到身高、性别及屈光度数的影响，与身高呈正相关，同一年龄段，男性前房深度大于女性。双眼前房深度发育同步。低中度近视的儿童前房深度增大。     

Revisiting the Hydrogen Storage Behavior of the Na-O-H System

Solid-state reactions between sodium hydride and sodium hydroxide are unusual among hydride-hydroxide systems since hydrogen can be stored reversibly. In order to understand the relationship between hydrogen uptake/release properties and phase/structure evolution, the dehydrogenation and hydrogenation behavior of the Na-O-H system has been investigated in detail both ex- and in-situ. Simultaneous thermogravimetric-differential thermal analysis coupled to mass spectrometry (TG-DTA-MS) experiments of NaH-NaOH composites reveal two principal features: Firstly, an H₂ desorption event occurring between 240 and 380 °C and secondly an additional endothermic process at around 170 °C with no associated weight change. In-situ high-resolution synchrotron powder X-ray diffraction showed that NaOH appears to form a solid solution with NaH yielding a new cubic complex hydride phase below 200 °C. The Na-H-OH phase persists up to the maximum temperature of the in-situ diffraction experiment shortly before dehydrogenation occurs. The present work suggests that not only is the inter-phase synergic interaction of protic hydrogen (in NaOH) and hydridic hydrogen (in NaH) important in the dehydrogenation mechanism, but that also an intra-phase H^δ+… H^δ– interaction may be a crucial step in the desorption process.     

Caution! Overestimation of treatment effects of corticosteroid therapy for community-acquired pneumonia in a meta-analysis of randomized controlled trials

It is well known that a meta-analysis of randomized controlled trials aims to increase the power and precision of the estimated intervention effects. However, when a meta-analysis includes a limited number of patients and a small number of events, overestimation of intervention effect estimates may occur and could cause spurious results. Although many biases can cause the overestimation, random error may be the most common cause. Trial sequential analysis (TSA) can explore the independent effect of random error on intervention effect estimates in meta-analyses and protect meta-analyses against overestimation due to random error.