Non-ignorable missing covariate data in survival analysis: a case-study of an International Breast Cancer Study Group trial

Summary.  Non-ignorable missing data, a serious problem in both clinical trials and observational studies, can lead to biased inferences. Quality-of-life measures have become increasingly popular in clinical trials. However, these measures are often incompletely observed, and investigators may suspect that missing quality-of-life data are likely to be non-ignorable. Although several recent references have addressed missing covariates in survival analysis, they all required the assumption that missingness is at random or that all covariates are discrete. We present a method for estimating the parameters in the Cox proportional hazards model when missing covariates may be non-ignorable and continuous or discrete. Our method is useful in reducing the bias and improving efficiency in the presence of missing data. The methodology clearly specifies assumptions about the missing data mechanism and, through sensitivity analysis, helps investigators to understand the potential effect of missing data on study results.     

Passenger Rail Security,Planning, and Resilience: Application of Network,Plume, and Economic Simulation Models as Decision Support Tools

We built three simulation models that can assist rail transit planners and operators to evaluate high and low probability rail‐centered hazard events that could lead to serious consequences for rail‐centered networks and their surrounding regions. Our key objective is to provide these models to users who, through planning with these models, can prevent events or more effectively react to them. The first of the three models is an industrial systems simulation tool that closely replicates rail passenger traffic flows between New York Penn Station and Trenton, New Jersey. Second, we built and used a line source plume model to trace chemical plumes released by a slow‐moving freight train that could impact rail passengers, as well as people in surrounding areas. Third, we crafted an economic simulation model that estimates the regional economic consequences of a variety of rail‐related hazard events through the year 2020. Each model can work independently of the others. However, used together they help provide a coherent story about what could happen and set the stage for planning that should make rail‐centered transport systems more resistant and resilient to hazard events. We highlight the limitations and opportunities presented by using these models individually or in sequence.     

Vulnerabilities and risks in population and environment studies

In the study of risks , different sciences use the same category in different ways, each related to its own ontological assumptions. But many of these fields communicate very little with one another. This article seeks to approximate two of these areas of study that have shown similar concerns and that can mutually strengthen one another, namely, geography and demography. Geography was one of the first disciplines to include risk in its environmental dimension and has had broad experience in simultaneously focusing on social and natural dynamics. Demography, on the other hand, faces greater difficulties because only recently has it incorporated the environmental dimension into its scientific scope. Both have brought the concept of vulnerability into their conceptual framework as complementary to that of risk. Geographers understand vulnerability as a more symbiotic form of the relationship between society and nature, whereas demographers give it a strong socioeconomic component. In this regard, the conceptual discussion on risks and vulnerabilities, in its attempt at approximating these two fields, is a way of conceptually advancing and strengthening the different approaches to empirical work, especially in population–environment studies which is the common ground for the dialogue between the two disciplines.

Corporate communications managers in large firms: new challenges

The new organisational form of large corporations (horizontal organisation), is affecting the communications job. This corporate transformation leads to new challenges for the corporate communications manager and his team. On the one hand, he has to develop a fully integrated strategy which enables the different forms of communication to contribute to the success of the firm's mission (a common goal). On the other hand, he has to provide small business units, led by strong front-line managers, with professional services. The analysis of several companies will show that the position of the corporate communications department is subject to various pressures and that the development of the `communications function' is calling into question the corporate communications manager's `profession'.     

当代中国的音乐及社会差序——京剧票友会与摇滚乐队“派对”比较研究

本文主要探讨当代中国的两种音乐活动形式——京剧票友会以及摇滚乐队派对。这两种音乐形式虽然在风格上截然不同,但是两种社团在结构上却存在着一定的相似性。这两种活动形式基本上都具有我们所称之为＂为位＂（positioning）的行为,参与者由此在音乐活动中找到他们各自的位置。而且,两种活动形式都涉及到＂外来者的融入＂（outsider integration）,即允许陌生人的参与并在活动中找到他们的位置。