Eric A. Vance

Age, musth and paternity success in wild male African elephants, Loxodonta africana

Male African elephants experience intense intrasexual selection in gaining access to oestrous females, who represent a very scarce and highly mobile resource. An unusual combination of behavioural and physiological traits in males probably reflects this intense selection pressure. Males show prolonged growth, growing throughout much or perhaps all of their long life span (ca. 60e65 years), and they show musth, a physiological and behavioural condition exclusive to elephants, which is manifested by bouts of elevated testosterone and aggression and heightened sexual activity. Most observed matings are by males over 35 years of age and in musth, suggesting that age and musth are both important factors contributing to male reproductive success. Here we report the results of a genetic paternity analysis of a well-studied population of wild African elephants. Patterns of paternity for 119 calves born over a 22-year period showed significant effects of both age and musth on paternity success. Among males in musth, paternity success increased significantly with age until the very oldest age classes, when it modestly declined. When not in musth, males experienced relatively constant, low levels of paternity success at all ages. Thus, despite the importance of both musth and age in determining male paternity success, adult males both in and out of musth, and of all ages, produced calves. In general, however, older males had markedly elevated paternity success compared with younger males, suggesting the possibility of sexual selection for longevity in this species.

Climate Change is Likely to Worsen the Public Health Threat of Diarrheal Disease in Botswana

Diarrheal disease is an important health challenge, accounting for the majority of childhood deaths globally. Climate change is expected to increase the global burden of diarrheal disease but little is known regarding climate drivers, particularly in Africa. Using health data from Botswana spanning a 30-year period (1974–2003), we evaluated monthly reports of diarrheal disease among patients presenting to Botswana health facilities and compared this to climatic variables. Diarrheal case incidence presents with a bimodal cyclical pattern with peaks in March (ANOVA p < 0.001) and October (ANOVA p < 0.001) in the wet and dry season, respectively. There is a strong positive autocorrelation (p < 0.001) in the number of reported diarrhea cases at the one-month lag level. Climatic variables (rainfall, minimum temperature, and vapor pressure) predicted seasonal diarrheal with a one-month lag in variables (p < 0.001). Diarrheal case incidence was highest in the dry season after accounting for other variables, exhibiting on average a 20% increase over the yearly mean (p < 0.001). Our analysis suggests that forecasted climate change increases in temperature and decreases in precipitation may increase dry season diarrheal disease incidence with hot, dry conditions starting earlier and lasting longer. Diarrheal disease incidence in the wet season is likely to decline. Our results identify significant health-climate interactions, highlighting the need for an escalated public health focus on controlling diarrheal disease in Botswana. Study findings have application to other arid countries in Africa where diarrheal disease is a persistent public health problem.

Determining scientific impact using a collaboration index

Researchers collaborate on scientific projects that are often measured by both the quantity and the quality of the resultant peer-reviewed publications. However, not all collaborators contribute to these publications equally, making metrics such as the total number of publications and the H-index insufficient measurements of individual scientific impact. To remedy this, we use an axiomatic approach to assign relative credits to the coauthors of a given paper, referred to as the A-index for its axiomatic foundation. In this paper, we use the A-index to compute the weighted sums of peer-reviewed publications and journal impact factors, denoted as the C- and P-indexes for collaboration and productivity, respectively. We perform an in-depth analysis of bibliometric data for 186 biomedical engineering faculty members and from extensive simulation. It is found that these axiomatically weighted indexes better capture a researcher’s scientific caliber than do the total number of publications and the H-index, allowing for fairer and sharper evaluation of researchers with diverse collaborative behaviors.

Blister Rust Incidence in Treeline Whitebark Pine, Glacier National Park, U.S.A.: Environmental and Topographic Influences

Abstract Whitebark pine (Pinus albicaulis) is a foundation and keystone species of upper subalpine and treeline ecosystems throughout the western United States and Canada. During the past several decades, Cronartium ribicola, an introduced fungal pathogen that causes white pine blister rust in five-needled pines, has caused significant declines in whitebark pine throughout its range. Our research objectives were to examine geographic variation in blister rust infection (total canker density) in whitebark pine found at six alpine treelines east of the Continental Divide in Glacier National Park, Montana, and to determine which environmental factors have the greatest influence on blister rust infection at treeline. Within a total of 30 sampling quadrats (five at each treeline study site), we measured the number of cankers on each whitebark pine in order to assess how blister rust infection varied throughout our study area. We created high-resolution digital elevation models to characterize surface microtopography, and used a geographic information system (GIS) to derive environmental variables of interest. A mixed effects, Poisson regression model determined environmental correlates of blister rust from the resulting set of field and GIS-derived variables. We found that rates of infection varied considerably among treelines, and that treeline sites exhibiting high flow accumulation rates, greater distances to wetlands, slopes facing southwest, higher curvature, greater wind speeds, and close proximity to Ribes and perennial streams had the highest rates of blister rust infection.

Moment estimation in delay tomography with spatial dependence

Parametric models for estimating network link delays with incomplete data that incorporate spatial correlation are formulated. Fast numerical methods for estimation of parameters and confidence intervals are derived. It is shown that including correlation in the model gives better model fit on sample data. Finally, certain results from graphical models are described, which can be applied in model search.

Recent Developments and Their Implications for the Future of Academic Statistical Consulting Centers

I describe how developments over the past 25 years in computing, funding, personnel, purpose, and training have affected academic statistical consulting centers and discuss how these developments and trends point to a range of potential futures. At one extreme, academic statistical consulting centers fail to adapt to competition from other disciplines in an increasingly fragmented market for statistical consulting and spiral downward toward irrelevancy and extinction. At the other extreme, purpose-driven academic statistical consulting centers constantly increase their impact in a virtuous cycle, leading the way toward the profession of statistics having greater positive impact on society. I conclude with actions to take to assure a robust future and increased impact for academic statistical consulting centers.

Developing a Career in the Practice of Statistics: The Mentor's Perspective

ABSTRACT The W.J. Dixon Award for Excellence in Statistical Consulting is given by the American Statistical Association to “a distinguished individual who has demonstrated excellence in statistical consulting or developed and contributed new methods, software, or ways of thinking that improve statistical practice in general.” In this article, five of the seven past recipients of this career-capping award share their experiences and perspectives through 10 stepping stones that move a practicing statistician from consultant to collaborator to leader. We highlight the need for mentorship throughout the discussion, and provide direction for statisticians who would like to incorporate this advice into their careers.

Pit Latrine Fecal Sludge Resistance Using a Dynamic Cone Penetrometer in Low Income Areas in Mzuzu City, Malawi

Pit latrines can provide improved household sanitation, but without effective and inexpensive emptying options, they are often abandoned once full and may pose a public health threat. Emptying techniques can be difficult, as the sludge contents of each pit latrine are different. The design of effective emptying techniques (e.g., pumps) is limited by a lack of data characterizing typical in situ latrine sludge resistance. This investigation aimed to better understand the community education and technical engineering needs necessary to improve pit latrine management. In low income areas within Mzuzu city, Malawi, 300 pit latrines from three distinct areas were assessed using a dynamic cone penetrometer to quantify fecal sludge strength, and household members were surveyed to determine their knowledge of desludging procedures and practices likely to impact fecal sludge characteristics. The results demonstrate that there is a significant difference in sludge strength between lined and unlined pits within a defined area, though sludge hardened with depth, regardless of the pit type or region. There was only limited association between cone penetration depth and household survey data. To promote the adoption of pit emptying, it is recommended that households be provided with information that supports pit emptying, such as latrine construction designs, local pit emptying options, and cost. This study indicates that the use of a penetrometer test in the field prior to pit latrine emptying may facilitate the selection of appropriate pit emptying technology.

Features of a Trust Model for a Complex System

This research focuses on trustworthiness assessment and trust judgment in a complex system such as a distributed sensing system. In our previous IMECE paper, we employed an interdisciplinary approach to highlight trustworthiness characteristics and trust measurements in social sciences and cyberspace. In this paper, we elaborate on these findings and present features of existing models we can leverage in different applications. Trust properties and rules reported in this study are extracted from three classes of trust models that met our design constraints. These models are gleaned from the literature pertaining to wireless sensor networks, social networks, e-commerce, mobile ad-hoc, peer-to-peer, and distributed network services. The trust model provides upfront quantitative assurance and trustworthiness metrics for architecting/engineering new systems as well as a situation awareness/management assessment metrics once the system is deployed.Copyright

The Big Tent for Statistics: Mentoring Required

ABSTRACT Research supports the positive impact of mentoring on both job and career satisfaction. Recognizing this, the American Statistical Association (ASA) has started a new mission-centered focus on mentoring. This article describes the development and implementation of meeting-based mentoring programs at four ASA conferences in 2014 and 2015. We present results of the feedback evaluations from program participants and use them to motivate recommendations for creating and running conference mentoring programs and overcoming common challenges. These recommendations are applicable to creating and running conference mentoring programs in any field. We conclude with a discussion of the opportunities for the ASA to augment its mentoring programs in support of the professional development of its members.