A Unified Approach to the Characterization of Equivalence Classes of DAGs, Chain Graphs with no Flags and Chain Graphs

Abstract.  A Markov property associates a set of conditional independencies to a graph. Two alternative Markov properties are available for chain graphs (CGs), the Lauritzen–Wermuth–Frydenberg (LWF) and the Andersson–Madigan– Perlman (AMP) Markov properties, which are different in general but coincide for the subclass of CGs with no flags . Markov equivalence induces a partition of the class of CGs into equivalence classes and every equivalence class contains a, possibly empty, subclass of CGs with no flags itself containing a, possibly empty, subclass of directed acyclic graphs (DAGs). LWF-Markov equivalence classes of CGs can be naturally characterized by means of the so-called largest CGs , whereas a graphical characterization of equivalence classes of DAGs is provided by the essential graphs . In this paper, we show the existence of largest CGs with no flags that provide a natural characterization of equivalence classes of CGs of this kind, with respect to both the LWF- and the AMP-Markov properties. We propose a procedure for the construction of the largest CGs, the largest CGs with no flags and the essential graphs, thereby providing a unified approach to the problem. As by-products we obtain a characterization of graphs that are largest CGs with no flags and an alternative characterization of graphs which are largest CGs. Furthermore, a known characterization of the essential graphs is shown to be a special case of our more general framework. The three graphical characterizations have a common structure: they use two versions of a locally verifiable graphical rule. Moreover, in case of DAGs, an immediate comparison of three characterizing graphs is possible.     

媒介再现父职：“新父亲”形象与父职教育契机——基于网络短视频的内容分析

随着网络短视频在日常生活中的广泛渗透,以“爸爸带娃”为主题的家庭父职生活也逐渐媒介化。以微信视频号、小红书和抖音三大主流网络平台的短视频为研究对象,采用内容分析法,探究媒介再现父职中的“新父亲”形象,以及媒介再现父职隐含的父职教育契机。研究发现：媒介再现父职以“关爱父职”为主导,关爱父职影响积极且效果良好;父亲参与意愿和参与主动性强;父亲参与的互动性较为充分;平等、亲和、睿智的父亲形象突出;引流变现下的“花式带娃”等多样化“新父亲”形象。鉴于网络传播的巨大影响力和实效性,媒介再现父职的促进路径为：推动新父职理念的传播与实践转向;设立常人榜样,实现父职教育的日常渗透;明确本土化父职研究方向,拓展父亲情感参与维度。     

《彼拉维德》女权主义思想评析

《彼拉维德》以艺术的方式记录了处在边缘的美国黑人女性在白人和男人双重压迫下的痛苦挣扎和艰难的自我迫寻历程为了拥有一间属于自己的屋子,她们付出了惨重的代价为了摆脱“第二性”的地位,她们用自己的身体写作,以改变她们在历史上作为“隐形人”和“失声集团”的存在;她们打开自己的房间,让男人进来,共同书写那原来只是属于他的故事——历史,而所有这些又都被小说家编织进她那精巧的元小说叙述中去了。     

‘Pains of imprisonment’: narratives of the women partners and children of the incarcerated

This paper focuses on an important line of inquiry in contemporary criminal justice social work research: the collateral consequences of incarceration in the Chinese context. It gives an insight into the impact of incarceration on families from an insider's perspective. An analysis of interviews with 10 partners and 10 children yielded three major themes concerning the impact of imprisonment: the problems associated with the imprisonment of a family member, the coping strategies used and views on the importance of maintaining family ties. It is hoped that this study will give practical guidance regarding what should be done, and how, to reduce the negative consequences brought about by the absence (temporary or permanent) of the imprisoned on their families, including both their partners and vulnerable children.     

The zero-inflated Poisson model and the decayed, missing and filled teeth index in dental epidemiology

For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.     

离子电子法配平方程式的简便方法

本文介绍了离子电子法在配平半反应时,利用离子、电子及溶液的介质,来调节反应式两边的电荷数,使之相等.     

An efficient sequential design of clinical trials

We propose an efficient group sequential monitoring rule for clinical trials. At each interim analysis both efficacy and futility are evaluated through a specified loss structure together with the predicted power. The proposed design is robust to a wide range of priors, and achieves the specified power with a saving of sample size compared to existing adaptive designs. A method is also proposed to obtain a reduced-bias estimator of treatment difference for the proposed design. The new approaches hold great potential for efficiently selecting a more effective treatment in comparative trials. Operating characteristics are evaluated and compared with other group sequential designs in empirical studies. An example is provided to illustrate the application of the method.     

Operating Characteristics for Group Sequential Trials Monitored Under Fractional Brownian Motion

Brownian motion has been used to derive stopping boundaries for group sequential trials, however, when we observe dependent increment in the data, fractional Brownian motion is an alternative to be considered to model such data. In this article we compared expected sample sizes and stopping times for different stopping boundaries based on the power family alpha spending function under various values of Hurst coefficient. Results showed that the expected sample sizes and stopping times will decrease and power increases when the Hurst coefficient increases. With same Hurst coefficient, the closer the boundaries are to that of O'Brien-Fleming, the higher the expected sample sizes and stopping times are; however, power has a decreasing trend for values start from H = 0.6 (early analysis), 0.7 (equal space), 0.8 (late analysis). We also illustrate study design changes using results from the BHAT study.     

Evaluation of a method for setting confidence intervals on the common mean of two normal populations

Let X₁, , X₂, …, X be distributed N(µ, σ² _x), let Y₁, Y₂, …, Y"_n be distributed N(µ, σ² _y), and let X , X , … X_m, Y₁, Y₂, …, Y_n be mutually independent. In this paper a method for setting confidence intervals on the common mean µ is proposed and evaluated.