Detecting diagnostic accuracy of two biomarkers through a bivariate log-normal ROC curve

In biomedical research, two or more biomarkers may be available for diagnosis of a particular disease. Selecting one single biomarker which ideally discriminate a diseased group from a healthy group is confront in a diagnostic process. Frequently, most of the people use the accuracy measure, area under the receiver operating characteristic (ROC) curve to choose the best diagnostic marker among the available markers for diagnosis. Some authors have tried to combine the multiple markers by an optimal linear combination to increase the discriminatory power. In this paper, we propose an alternative method that combines two continuous biomarkers by direct bivariate modeling of the ROC curve under log-normality assumption. The proposed method is applied to simulated data set and prostate cancer diagnostic biomarker data set.     

Construction of Simultaneous Confidence Intervals for Ratios of Means of Lognormal Distributions

For constructing simultaneous confidence intervals for ratios of means for lognormal distributions, two approaches using a two-step method of variance estimates recovery are proposed. The first approach proposes fiducial generalized confidence intervals (FGCIs) in the first step followed by the method of variance estimates recovery (MOVER) in the second step (FGCIs–MOVER). The second approach uses MOVER in the first and second steps (MOVER–MOVER). Performance of proposed approaches is compared with simultaneous fiducial generalized confidence intervals (SFGCIs). Monte Carlo simulation is used to evaluate the performance of these approaches in terms of coverage probability, average interval width, and time consumption.     

Improved Estimates and Confidence Intervals for Regenerative Simulation

In regenerative simulation, one frequently requires an estimate or a confidence interval for the ratio of the means of the two components of a certain bivariate random quantity. Estimation of this ratio has been studied by many authors and most recently by Asmussen and Rydén(2010 Asmussen, S., Rydén, T. (2010). A note on skewness in regenerative simulation. Communications in Statistics—Simulation and Computation 40: 45–57.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). Here, we propose an estimate that performs better than the best of the known estimates. Our estimate is also lot simpler than the best known estimate.     

Static Hedging of Geometric Average Asian Options with Standard Options

In this article, we first establish a theorem that represents the price of an Asian option in terms of standard European options with a shorter term and different strikes. Then using Gauss–Hermite numerical integration, we discretize our theorem so as to use Monte Carlo simulation to examine the error of the static hedging under the Black–Scholes model and the Merton jump-diffusion model. For ease of comparison, we also provide the error of the dynamic hedging. The numerical results show that the static hedging strategy performs better than the dynamic one under both models.     

高校图书馆数字化参考咨询服务的思考

论述了数字化参考咨询服务的概念和类型 ,并在列举了国内外几个典型的数字化参考咨询实例的基础上 ,提出了目前高校图书馆数字化参考咨询服务系统构建应具备的功能模块和服务发展方向。     

“Whatsapping” the continuity of postpartum care in Switzerland: A socio-anthropological study

BackgroundDigital media such as Apps, Internet and social networks have become integral parts of the maternity experience for more than a decade. These media can support or undermine women’s experiences as has been shown in digital sociology research. Using Immediate Messaging Applications to provide information and support to women during the perinatal period is an emerging practice.AimThis article analyses how health and social care professionals – with a focus on community midwives – and women communicate between postpartum home visits through Immediate Message Applications in Switzerland.MethodsA socio-anthropological study that relied on qualitative methods including semi-directed interviews with midwives and health and social care professionals (n = 30) and immigrant women (n = 20).FindingsSince the introduction of Immediate Messaging Applications, women and their carer converse more regularly between post-partum home visits. Women send questions, pictures and videos to them, often allowing swift responses to their concerns. Midwives encounter difficulties answering women’s questions when they cannot be solved through quick communication (e.g. infant crying). To them, texting frequency forms a clinical clue to women’s mental health. Not all women contact their carer through digital messages; immigrant women are less likely to know and use this service.Discussion and conclusionImmediate Messaging Applications form a promising communication tool, complementary to home visits, and contribute to woman-centered care and continuity of care. As an emergent practice, it has not been framed by a guideline yet. Policy makers and practitioners should ensure that its use does not contribute to unequal access to care.     

关于数字图书馆发展的思考

数字图书馆是国家信息基础设施的重要组成部分,目前已成为评价一个国家信息基础设施水平的重要标志,也是世界各国图书馆正在竟相研究和发展的重大课题。如何探讨和研究数字图书馆的概念、特征、发展阶段及现状,是分析数字图书馆发展所面临问题及建议采取相应对策的关键。     

Estimating the Size of Street-Dwelling Populations Using Mark-Resighting Counts

Mark-resighting constitutes an advanced technology for estimating animal abundance. Joint hypergeometric maximum likelihood, Minta-Mangel and Bowden estimators are usually adopted with mark-resighting data. In presence of any tendency of animals to aggregate into groups, the Bowden estimator is the sole reliable method, providing that marks are quite evenly distributed among groups. In some cetacean surveys, marking disturbances are avoided through natural marking. Natural marking with Bowden criterion is used to estimate the abundance of street-dwelling populations. The marked individuals are persons identified and recorded in the initial part of the survey and recognizable in subsequent occasions. A simulation helps determine the performance of the Bowden estimator under a wide set of situations, taking into account key features of street-dwelling populations. When marked individuals are evenly distributed among groups, the strategy is efficient.     

2000m~3二甲醚球罐的在线检测及有限元分析

首先,使用多通道声发射检测仪PAC SAMOS-48检测在用2000m3二甲醚球形储罐,判定出该设备存在表面裂纹缺陷及其所处位置。然后,采用超声波检测方法,确定了裂纹形状和大小。用Newman—Raju方法研究了表征裂纹缺陷前沿应力场以及位移场的重要参量即应力强度因子,并利用ANSYS建立简化的有限元模型,最终得到裂纹的应力云图和该裂纹前沿应力强度因子值,与工程估算方法得到的数值进行对比,结果表明有限元方法应用于压力容器缺陷的分析是适用的。