Free Water Loss–induced Heterogeneous Residual Strain and Reduced Fatigue Resistance in Root Dentin: A 3-dimensional Digital Image Correlation Analysis

IntroductionThis study evaluated free water loss–induced residual strain with and without axial compressive loading and assessed the mechanical effect of cyclic loading in fully hydrated and partially dehydrated root dentin.MethodsRoot dentin sections prepared from freshly extracted human premolars were used. Customized 3-dimensional digital image correlation was used to qualitatively and quantitatively analyze the residual strain induced by 2 hours of free water loss in different regions of root dentin. Residual strain in partially dehydrated root dentin during axial compressive loading was also analyzed using 3-dimensional digital image correlation. The effect of cyclic loading on load to fracture in fully hydrated and partially dehydrated dentin and their fractography were analyzed using micro–computed tomographic imaging.ResultsFree water loss resulted in a heterogeneous distribution of residual strain and an overall formation of residual compressive strain with areas of tensile strain localized to the root canal and outer dentin. More residual compressive strain was observed in the apical dentin compared with the cervical dentin (P < .05), and more residual shear strain was observed in outer dentin compared with inner dentin (P < .05). Axial loading resulted in an increase in the load-induced compressive strain in the direction perpendicular to dentinal tubules (P < .05). Fully hydrated roots displayed a higher mean (P < .05) and median (P < .05) number of cycles to fracture with microcracks characteristic of toughness.ConclusionsAfter free water loss, root dentin displayed an increased formation of heterogenous residual strain, which resulted in increased axial compressive load-induced strain and a decreased resistance to fatigue failure. The effect of free water loss in the loss of mechanical integrity of root-filled teeth needs further investigation.     

灰关联分析应用于因素分析时关联度指标的改进

本文指出在应用灰关联分析进行因素分析时传统的关联度计算方法的不足，并提出采用新的关联度指标来表示因素之间的关联关系，同时给出了实例介绍计算方法。     

Effect of maternal and infant covariates on sibship correlation in birth weight

Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.     

ABO血型与肝炎病毒感染关系的探讨

目的：探讨ABO血型与肝炎病毒感染的关系，方法：应用疾病关联分析方法对HBsAg和,抗－HCV阳性献血者与同期健康献血者的ABO血型资料进行比较分析。结果：ABO血型与HBsAg和抗－HCV阳性率之间无显著性相关关系（P＞0．05），结论：乙型肝炎和丙型肝炎病毒感染与ABO血型无显著性相关。     

In Vitro and in Vivo Evaluation of Whole and Half Tablets of Sustained-Release Adinazolam Mesylate

The mechanism of release from sustained-release adinazolam mesylate tablets was assessed by the Higuchi equation and by analysis of drug release profiles through 60% released using the Peppas equation. Computed values of the diffusional exponent, n, ranged from 0.59 to 0.66. Values of n in this range are consistent with a mixed mechanism of release, with diffusion of drug through the hydrated polymer matrix and relaxation of this matrix being the principal processes controlling release. The rate of in vitro drug release was increased for half tablets relative to whole tablets and is attributed to an increase in the surface to volume ratio of half tablets of about 16%. This increase in surface-to-volume ratio of half tablets was reflected by an increase in the constant, k, from the Peppas equation of 20–23% and by an increase in the slope of Higuchi plots of 12–18% for four lots of tablets. In vivo/in vitro relationships from two bioavailability studies were thoroughly evaluated. Using either a linear or a quadratic relationship, an in vivo/in vitro correlation exists for sustained-release adinazolam mesylate tablets.     

Working‐correlation‐structure identification in generalized estimating equations

Selecting an appropriate working correlation structure is pertinent to clustered data analysis using generalized estimating equations (GEE) because an inappropriate choice will lead to inefficient parameter estimation. We investigate the well‐known criterion of QIC for selecting a working correlation structure, and have found that performance of the QIC is deteriorated by a term that is theoretically independent of the correlation structures but has to be estimated with an error. This leads us to propose a correlation information criterion (CIC) that substantially improves the QIC performance. Extensive simulation studies indicate that the CIC has remarkable improvement in selecting the correct correlation structures. We also illustrate our findings using a data set from the Madras Longitudinal Schizophrenia Study. Copyright © 2008 John Wiley & Sons, Ltd.     

黄连体外改善胰岛素抵抗活性与HPLC指纹图谱的相关性研究

目的：探索黄连体外改善胰岛素抵抗活性与HPLC指纹图谱的相关性。方法：采用RP—HPLC法建立不同产地的黄连样品的指纹图谱，采用主成分分析法进行化学模式识别研究，并采用体外测定药物改善脂肪细胞胰岛素抵抗生物活性，对化学信息和生物效应进行灰色关联分析和多元相关分析，以探索两者的相关性。结果：不同产地黄连药材化学成分含量及生物效应的有一定的差异。HPLC指纹图谱各共有峰中色谱峰10、6、3、7和巴马汀与改善胰岛素抵抗活性相关性较强。结论：基本明确了化学指纹图谱与改善胰岛素抵抗生物效应的相关性，有利于黄连改善胰岛素抵抗活性成分的筛选。     

血清胆红素测定与脑梗塞的关系分析

目的：通过对脑梗塞患者与健康人进行血清胆红素水平测定与观察,分析血清胆红素与脑梗塞疾病的关系。方法：收集我院127例脑梗塞患者作为测定组,并设健康对照组127例,每人清晨抽取空腹静脉血5ml,分离血清,用全自动生化分析仪以化学法测定血清总胆红素（TB）和直接胆红素（DB）。结果：脑梗塞组与健康对照组血清总胆红素测定结果比较差异无统计学意义,直接胆红素测定结果比较差异存在显著统计学意义,脑梗塞组血清直接胆红素水平明显低于健康对照组血清直接胆红素水平。结论：血清直接胆红素水平与脑梗塞的发生存在明显的相关性,测定血清直接胆红素水平,有助于脑梗塞发病的评估,可作为脑梗塞发病的一个独立危险因子。     

上消化道出血相关因素分析及防护对策探讨

目的：分析上消化道出血相关因素，制定预防和护理对策。方法：对120例上消化道出血病人相关因素进行总结分析，提出对策。结果：本病相关因素最多的分别是发病原因系十二指肠溃疡和胃溃疡；有发病诱因，主要是饮食不当、饮酒、药物和劳累；中青年、农村和农民发生率各占72．5％、69．17％和57．50％；中度出血35．00％；出血发生24小时后就诊68．33％。结论：本病应从个人、家庭、社会和早期诊治四方面预防，并通过系统护理，促进疾病康复。     

宁波普通高中教师职业压力、社会支持与亚健康躯体症状的典型相关分析

目的 探讨宁波市普通高中的教师心理压力,社会支持与亚健康状态的相关关系.方法 采用职业压力问卷、社会支持量表与亚健康躯体症状自评量表对随机抽取的128名宁波市普通高中教师进行相关关系分析.结果 当存在社会支持变量时,2组变量的典型相关系数达0.563,0.471( P <0.01).职业压力的增大与社会支持水平的减少都将导致教师亚健康躯体症状的增多.当撤去社会支持变量后,典型相关系数为0.497( P <0.01).典型变量ξ中"考试压力","工作负荷"与"职业期望"的因子负载分别增大为0.801,0.855,0.726.典型变量η中的"疲劳感觉"与"睡眠障碍"的因子负载分别增大为0.774,0.859.结论 社会支持水平在职业压力与亚健康躯体症状之间可能具有中介调节作用.