Modeling Individual Cell Lag Time Distributions for Listeria monocytogenes

The food industry faces two paradoxical demands: on the one hand, foods need to be microbiologically safe for consumption and on the other hand, consumers want fresh, minimally processed foods. To meet these demands, more insight into the mechanisms of microbial growth is needed, which includes, among others, the microbial lag phase. This is the time needed by bacterial cells to adapt to a new environment (for example, after food product contamination) before starting an exponential growth regime. Since food products are often contaminated with low amounts of pathogenic microorganisms, it is important to know the distribution of these individual cell lag times to make accurate predictions concerning food safety. More precisely, cells with the shortest lag times (i.e., appearing in the left tail of the distribution) are largely decisive for the outgrowth of the population. In this study, an integrated modeling approach is proposed and applied to an existing data set of individual cell lag time measurements of Listeria monocytogenes. In a first step, a logistic modeling approach is applied to predict the fraction of zero-lag cells (which start growing immediately) as a function of temperature, pH, and water activity. For the nonzero-lag cells, the mean and variance of the lag time distribution are modeled with a hyperbolic-type model structure. This mean and variance allow identification of the parameters of a two-parameter Weibull distribution, representing the nonzero-lag cell lag time distribution. The integration of the developed models allows prediction of a global distribution of individual cell lag times for any combination of environmental conditions in the interpolation domain of the original temperature, pH, and water activity settings. The global fitting quality of the model is quantified using several measures indicating that the model gives accurate predictions, erring slightly on the fail-safe side when predicting the shortest lag times.     

Democracy in Arts Development 1

Too often in the arts, projects are undertaken without clear‐cut aims and ways of assessing whether these aims are accomplished. With regard to “Art for Social Change” projects, it is not difficult to identify activities that might be labelled “dishonest”, “ill‐conceived” or even “unethical”. It is argued here that it is possible, and necessary, to set clear aims, and also to devise effective assessment strategies. It is essential for artists to embrace evaluation in order to help them improve and better understand their work.

     

Evaluation of the U.S. Air Force Family Support Center Program

This article provides an overview of the implementation and evaluation of Family Support Centers (FSC) in the U.S. Air Force. After describing the FSC model, the quantitative aspect of the evaluation is discussed, including the evaluation design, implementation methods, survey response rates, and procedures for data analysis. A summary of evaluation results also are presented as well as a discussion of administrative and methodological issues encountered in performing the evaluation. The results of the evaluation suggest that the FSC has become an integral part of the base human service delivery system, especially for married members and civilian spouses.     

From waterfall plots to spaghetti plots in early oncology clinical development

Waterfall plots are used to describe changes in tumor size observed in clinical studies. They are frequently used to illustrate the overall drug response in oncology clinical trials because of its simple representation of results. Unfortunately, this visual display suffers a number of limitations including (1) potential misguidance by masking the time dynamics of tumor size, (2) ambiguous labelling of the y‐axis, and (3) low data‐to‐ink ratio. We offer some alternatives to address these shortcomings and recommend moving away from waterfall plots to the benefit of plots showing the individual time profiles of sum of lesion diameters (according to RECIST). The spider plot presents the individual changes in tumor measurements over time relative to baseline tumor burden. Baseline tumor size is a well‐known confounding factor of drug effect which has to be accounted for when analyzing data in early clinical trials. While spider plots are conveniently correct for baseline tumor size, they cannot be presented in isolation. Indeed, percentage change from baseline has suboptimal statistical properties (including skewed distribution) and can be overly optimistic in favor of drug efficacy. We argued that plots of raw data (referred to as spaghetti plots) should always accompany spider plots to provide an equipoised illustration of the drug effect on lesion diameters.     

Outlier detection based on extreme value theory and applications

Whether an extreme observation is an outlier or not depends strongly on the corresponding tail behavior of the underlying distribution. We develop an automatic, data-driven method rooted in the mathematical theory of extremes to identify observations that deviate from the intermediate and central characteristics. The proposed algorithm is an extension of a method previously proposed in the literature for the specific case of heavy tailed Pareto-type distributions to all max-domains of attraction. We propose some applications such as a tail-adjusted boxplot which yields a more accurate representation of possible outliers, and the identification of outliers in a multivariate context through an analysis of associated random variables such as local outlier factors. Several examples and simulation results illustrate the finite sample behavior of the algorithm and its applications.     

All glamour, no substance? How public relations majors and potential majors in an exemplar program view the industry and function

Studies in public relations often conclude that the field is misunderstood [Kopenhaver, L. L. (1985). Aligning values of practitioners and journalists. Public Relations Review, 11(1), 34–42; Stacks, D. W., Botan, C., & Turk, J. V. (1999). Perceptions of pubic relations education. Public Relations Review, 25, 9–29] and misrepresented in media [Spicer, C. (2000). Public relations in a democratic society: Value and values. Journal of Public Relations Research, 12(1), 115–130]. Public relations professionals themselves often do not know what is involved in or support public relations education [Wright, D. K., & Turk, J. V. (2007). Public relations knowledge and professionalism: Challenges to educators and practitioners. In E.L. Toth (Ed.), The future of excellence in public relations and communication management: Challenges for the next generation (pp. 571–588). Mahwah, NJ: Lawrence Erlbaum]. Both the special issue (Public Relations Review, 1999) on public relations education and a following study published in this journal [Bowen, S. A. (2003). I thought it would be more glamorous: Preconceptions and misconceptions of public relations among students in the principles course. Public Relations Review, 29, 199–214] argued that public relations majors often do not realize what is involved in the academic discipline or the professional field. This research builds on the findings of those studies to ask: are public relations educators doing any better in communicating the core competencies, responsibilities, knowledge requirements, skills, and abilities of the discipline and the public relations major? Through the use of 10 focus groups across majors at a top research university, we can see that little is known about public relations among non-majors, but public relations majors can articulate the requirements and functions of the field. Several primary areas of confusion emerged about public relations related to: marketing or promotion, spinning the truth, image, and public relations as a career choice. These ideas show a critical lack of transparency in public relations. Credibility of the public relations function is hampered by this failure to communicate about the functions and core competencies of the field. Implications for both the public relations practice and for public relations education are discussed.     

大学的发展与制度创新

上世纪九十年代以来 ,围绕建设一流大学 ,高等教育在宏观体制方面进行了大刀阔斧的改革 ,并开始了以人事分配制度改革为主要内容的大学内部管理结构和运行机制创新的大胆尝试 ,但这些并不能直接解决人才培养质量问题。促进大学的跨越式发展、达到一流的建设目标 ,还必须将高等教育改革的触角进一步深入到大学内部 ,通过为大学定性定位、营造发展的环境氛围、构建现代大学制度体系 ,努力推进现代大学制度创新 ,并以此改造大学 ,实现大学自身的发展。     

In the Context of Adult Support: The Influence of Peer Support on the Psychological Well-Being of Middle-School Students

This study examines the influence of adult and peer support on the psychological well-being of middle-school students. Using data representing 13,843 middle-school students from seven U.S. states, which were collected with the School Success Profile, hierarchical regression analysis is used to examine a hypothesis in 2 models of relationships: continuity/cognitive and compensatory/competition. Results support the continuity/cognitive model, and indicate peer support is an important contributor to middle-school students’ psychological well-being at various levels of adult support. When adult support is low, high levels of peer support do not improve psychological well-being. Implications for research and practice are discussed.