Non-global parameter estimation using local ensemble Kalman filtering

We study parameter estimation for non-global parameters in a low-dimensional chaotic model using the local ensemble transform Kalman filter (LETKF). By modifying existing techniques for using observational data to estimate global parameters, we present a methodology whereby spatially-varying parameters can be estimated using observations only within a localized region of space. Taking a low-dimensional nonlinear chaotic conceptual model for atmospheric dynamics as our numerical testbed, we show that this parameter estimation methodology accurately estimates parameters which vary in both space and time, as well as parameters representing physics absent from the model

Effects of urbanization on felid populations, interactions, and pathogen dynamics, The

2014 Fall.Urbanization is one of the most ecologically impactful forms of landscape conversion with far-reaching effects on landscape pattern and process, particularly related to animal populations. We evaluated how urbanization affected population density, interspecific interactions, and pathogen exposure in wild felid populations. Specifically, we studied bobcats and pumas across wildland, exurban development, and wildland-urban interface (WUI) habitat to test hypotheses evaluating how urbanization impacts wild felids. Low-density residential development appeared to have a greater impact on felid population density compared to habitat adjacent to a major urban area; point estimates of population density were lower for bobcats and pumas in exurban development compared to wildland habitat, whereas population density for both felids appeared more similar between WUI and wildland habitat. For competitive interactions, occupancy modeling indicated that bobcats did not avoid pumas across broad spatial and temporal scales; however, at finer scales bobcats temporally avoided pumas in wildland areas, but did not appear to avoid pumas in urbanized habitat. Using telemetry data, contact networks revealed that space-use extent was an important predictor of possible social interactions, but that felids associated with urbanization did not appear to exhibit increased potential for interspecific interactions. Lastly, we provided a conceptual framework for evaluating the effects of multiple ecological mechanisms on patterns of pathogen exposure in animal populations; we demonstrated how demographic, social, and environmental characteristics affected the pathogen exposure in bobcat and puma populations across a gradient of urbanization

Report of the Working Conditions of the Students of Howard University

https://dh.howard.edu/hu_pub/1001/thumbnail.jp

A Simple Boltzmann Transport Equation for Ballistic to Diffusive Transient Heat Transport

Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, ii) that phonon transport at early times approach the ballistic limit in samples of any length, and iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.Comment: 9 pages, 5 figure

Policy Point-Counterpoint: The Good and The Bad of the Social Media Revolution

In this policy point-counterpoint, sociology students Jesse Goranson and Lawrence Kastriba discuss whether social media operates as a positive social force or as a negative one. Jesse Goranson argues that social media can act to promote democratization among otherwise disadvantaged groups. By connecting individuals from disadvantaged groups, the scalability of social media increases the social capital of the group members, thus giving the group a greater voice in society and allows them greater participation in the political process

Why Did the Bear Cross the Road? Comparing the Performance of Multiple Resistance Surfaces and Connectivity Modeling Methods

There have been few assessments of the performance of alternative resistance surfaces, and little is known about how connectivity modeling approaches differ in their ability to predict organism movements. In this paper, we evaluate the performance of four connectivity modeling approaches applied to two resistance surfaces in predicting the locations of highway crossings by American black bears in the northern Rocky Mountains, USA. We found that a resistance surface derived directly from movement data greatly outperformed a resistance surface produced from analysis of genetic differentiation, despite their heuristic similarities. Our analysis also suggested differences in the performance of different connectivity modeling approaches. Factorial least cost paths appeared to slightly outperform other methods on the movement-derived resistance surface, but had very poor performance on the resistance surface obtained from multi-model landscape genetic analysis. Cumulative resistant kernels appeared to offer the best combination of high predictive performance and sensitivity to differences in resistance surface parameterization. Our analysis highlights that even when two resistance surfaces include the same variables and have a high spatial correlation of resistance values, they may perform very differently in predicting animal movement and population connectivity

Fast-Thinking Attention and the Disposition Effect

The disposition effect is the tendency of investors to sell stocks that have recently increased in value and hold stocks that have recently decreased in value. Although some evidence suggests that investor attention mitigates the disposition effect, this study finds that a certain type of attention&mdash;fast-thinking or &ldquo;System 1&rdquo; (Kahneman 2011) attention&mdash;has the opposite effect. I examine the disposition effect in investors who are presented with push notifications from the Robinhood brokerage, which I contend generates fast-thinking attention, and find that these notifications exacerbate the disposition effect. My results suggest that fast-thinking attention is detrimental to investors.</p

The Impact of Accreditation on Institutional Assessment of Student Learning Outcomes: A Case Study of Historically Black Colleges and Universities

The accreditation of an institution is one of the most important functions provided by accrediting agencies. All institutions must experience the accreditation process in order to be accountable. Many Historically Black Colleges and Universities (HBCUs) are challenged by accrediting agencies. However, HBCUs have a legacy of creating great leaders who have contributed talents and ideas that generate a significant impact on the American society. The purpose of this study was to explore accreditation problems involving four HBCUs and to evaluate the strategies they used in solving these problems. Emphasis is placed on the management of academic programs and the improvement of student learning outcomes and assessment. This study also embarked upon the mission statement that fosters lifelong learning and academic excellence designed to produce intellectually prepared students. A successful student learning outcomes and assessment program was developed to prepare students for career choices and to improve retention and graduation rates. HBCUs must raise expectations for students to graduate so they can fulfill the mission of the institution and comply with accreditation standards. This study was embedded in qualitative research inquiry using institutional documents, observations, and the interviewing of 39 participants as a means of gathering data. Each participant explained their role, and the strategies and procedures used during the accreditation process. Eight categories emerged from the factors involved in contributing to the reaffirmation of accreditation. Each institution also developed shared goals, common themes, and core expectations. All four HBCUs were awarded reaffirmation by either the Southern Association of Colleges and Schools Commission on Colleges (SACSCOC, or SACS) or the Transnational Association of Christian Colleges and Schools (TRACS). The conclusions and implications of this study revealed that efforts should be made to identify effective and robust strategies that HBCUs can adopt to boost student motivation and enhance student learning outcomes and assessment. These strategies can enhance student learning and improve the validity of outcomes assessment. The results will inform HBCUs of the need for further research in the planning and preparation stages of the accreditation process

Cytosine deamination and the precipitous decline of spontaneous mutation during Earth's history

Cytosine deamination appears to be largely responsible for spontaneous mutations in the modern world. Because of its sensitivity to temperature (Q10 = 4), that reaction would have furnished a mechanism for rapid evolution on a warm earth. As the temperature fell from 100° to 25 °C, the rate of cytosine-based mutation would have fallen by a factor of more than 4,000, with a corresponding increase in the stability of genetic information. Other potentially mutagenic events are known to be even more sensitive to temperature, and would presumably have led to an even steeper decline in the rate of spontaneous mutation as the earth cooled