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Search Results: 1 - 10 of 144306 matches for " Mevin B. Hooten "
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An Accessible Method for Implementing Hierarchical Models with Spatio-Temporal Abundance Data
Beth E. Ross, Mevin B. Hooten, David N. Koons
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049395
Abstract: A common goal in ecology and wildlife management is to determine the causes of variation in population dynamics over long periods of time and across large spatial scales. Many assumptions must nevertheless be overcome to make appropriate inference about spatio-temporal variation in population dynamics, such as autocorrelation among data points, excess zeros, and observation error in count data. To address these issues, many scientists and statisticians have recommended the use of Bayesian hierarchical models. Unfortunately, hierarchical statistical models remain somewhat difficult to use because of the necessary quantitative background needed to implement them, or because of the computational demands of using Markov Chain Monte Carlo algorithms to estimate parameters. Fortunately, new tools have recently been developed that make it more feasible for wildlife biologists to fit sophisticated hierarchical Bayesian models (i.e., Integrated Nested Laplace Approximation, ‘INLA’). We present a case study using two important game species in North America, the lesser and greater scaup, to demonstrate how INLA can be used to estimate the parameters in a hierarchical model that decouples observation error from process variation, and accounts for unknown sources of excess zeros as well as spatial and temporal dependence in the data. Ultimately, our goal was to make unbiased inference about spatial variation in population trends over time.
Continuous-time discrete-space models for animal movement
Ephraim M. Hanks,Mevin B. Hooten,Mat W. Alldredge
Statistics , 2012, DOI: 10.1214/14-AOAS803
Abstract: The processes influencing animal movement and resource selection are complex and varied. Past efforts to model behavioral changes over time used Bayesian statistical models with variable parameter space, such as reversible-jump Markov chain Monte Carlo approaches, which are computationally demanding and inaccessible to many practitioners. We present a continuous-time discrete-space (CTDS) model of animal movement that can be fit using standard generalized linear modeling (GLM) methods. This CTDS approach allows for the joint modeling of location-based as well as directional drivers of movement. Changing behavior over time is modeled using a varying-coefficient framework which maintains the computational simplicity of a GLM approach, and variable selection is accomplished using a group lasso penalty. We apply our approach to a study of two mountain lions (Puma concolor) in Colorado, USA.
Velocity-Based Movement Modeling for Individual and Population Level Inference
Ephraim M. Hanks, Mevin B. Hooten, Devin S. Johnson, Jeremy T. Sterling
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022795
Abstract: Understanding animal movement and resource selection provides important information about the ecology of the animal, but an animal's movement and behavior are not typically constant in time. We present a velocity-based approach for modeling animal movement in space and time that allows for temporal heterogeneity in an animal's response to the environment, allows for temporal irregularity in telemetry data, and accounts for the uncertainty in the location information. Population-level inference on movement patterns and resource selection can then be made through cluster analysis of the parameters related to movement and behavior. We illustrate this approach through a study of northern fur seal (Callorhinus ursinus) movement in the Bering Sea, Alaska, USA. Results show sex differentiation, with female northern fur seals exhibiting stronger response to environmental variables.
At–Sea Behavior Varies with Lunar Phase in a Nocturnal Pelagic Seabird, the Swallow-Tailed Gull
Sebastian M. Cruz, Mevin Hooten, Kathryn P. Huyvaert, Carolina B. Proa?o, David J. Anderson, Vsevolod Afanasyev, Martin Wikelski
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056889
Abstract: Strong and predictable environmental variability can reward flexible behaviors among animals. We used long-term records of activity data that cover several lunar cycles to investigate whether behavior at-sea of swallow-tailed gulls Creagrus furcatus, a nocturnal pelagic seabird, varied with lunar phase in the Galápagos Islands. A Bayesian hierarchical model showed that nighttime at-sea activity of 37 breeding swallow-tailed gulls was clearly associated with changes in moon phase. Proportion of nighttime spent on water was highest during darker periods of the lunar cycle, coinciding with the cycle of the diel vertical migration (DVM) that brings prey to the sea surface at night. Our data show that at-sea behavior of a tropical seabird can vary with environmental changes, including lunar phase.
Dynamic social networks based on movement
Henry R. Scharf,Mevin B. Hooten,Bailey K. Fosdick,Devin S. Johnson,Josh M. London,John W. Durban
Statistics , 2015,
Abstract: Network modeling techniques provide a means for quantifying social structure in populations of individuals. Data used to define social connectivity are often expensive to collect and based on case-specific, ad hoc criteria. Moreover, in applications involving animal social networks, collection of these data is often opportunistic and can be invasive. Frequently, the social network of interest for a given population is closely related to the way individuals move. Thus telemetry data, which are minimally-invasive and relatively inexpensive to collect, present an alternative source of information. We develop a framework for using telemetry data to infer social relationships among animals. To achieve this, we propose a Bayesian hierarchical model with an underlying dynamic social network controlling movement of individuals via two mechanisms: an attractive effect, and an aligning effect. We demonstrate the model and its ability to accurately identify complex social behavior in simulation, and apply our model to telemetry data arising from killer whales. Using auxiliary information about the study population, we investigate model validity and find the inferred dynamic social network is consistent with killer whale ecology and expert knowledge.
microRNA Expression Patterns Reveal Differential Expression of Target Genes with Age
Nicole Noren Hooten,Kotb Abdelmohsen,Myriam Gorospe,Ngozi Ejiogu,Alan B. Zonderman,Michele K. Evans
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010724
Abstract: Recent evidence supports a role for microRNAs (miRNAs) in regulating the life span of model organisms. However, little is known about how these small RNAs contribute to human aging. Here, we profiled the expression of over 800 miRNAs in peripheral blood mononuclear cells from young and old individuals by real-time RT-PCR analysis. This genome-wide assessment of miRNA expression revealed that the majority of miRNAs studied decreased in abundance with age. We identified nine miRNAs (miR-103, miR-107, miR-128, miR-130a, miR-155, miR-24, miR-221, miR-496, miR-1538) that were significantly lower in older individuals. Among them, five have been implicated in cancer pathogenesis. Predicted targets of several of these miRNAs, including PI3 kinase (PI3K), c-Kit and H2AX, were found to be elevated with advancing age, supporting a possible role for them in the aging process. Furthermore, we found that decreasing the levels of miR-221 was sufficient to cause a corresponding increase in the expression of the predicted target, PI3K. Taken together, these findings demonstrate that changes in miRNA expression occur with human aging and suggest that miRNAs and their predicted targets have the potential to be diagnostic indicators of age or age-related diseases.
Knee Extensor Strength Is Associated with Pressure Pain Thresholds in Adults with Fibromyalgia
W. Michael Hooten, Casandra J. Rosenberg, Jason S. Eldrige, Wenchun Qu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0059930
Abstract: Objective Individuals with fibromyalgia (FM) have lower muscle strength and lower pressure pain thresholds (PPT). The primary aim of this study was to determine the associations between muscle strength and PPT in adults with FM to test the hypothesis that greater measures of muscle strength would be associated with greater values of PPT. Secondary aims included determining the effects of pain severity and the peak uptake of oxygen (Vo2) on the associations between muscle strength and PPT. Methods Knee extensor and flexor strength (N = 69) was measured in the dominant leg using a dynamometer, and PPT was assessed using an electronic algometer. Pain severity was determined using the Multidimensional Pain Inventory, and peak Vo2 uptake was quantified using an electronically braked cycle ergometer. Results Univariable linear regression analysis demonstrated a significant association between PPT (dependent variable) and isometric knee extensor (P<.001), isokinetic (60°/s) knee extensor (P = .002), and isokinetic (60°/s) knee flexor strength (P = .043). In a multiple variable linear regression analysis adjusted for age, sex, pain severity, body mass index and peak Vo2 uptake, a significant association was found between PPT and isometric knee extensor strength (P = .008). In a similar multiple variable analysis, a significant association was found between PPT and isokinetic knee extensor strength (P = .044). Conclusion Greater measures of isometric and isokinetic knee extensor strength were significantly associated with greater values of PPT in both univariable and multiple variable linear regression models. Trial Registration ClinicalTrials.gov NCT01253395
A Low Concentration of Ethanol Impairs Learning but Not Motor and Sensory Behavior in Drosophila Larvae
Brooks G. Robinson, Sukant Khurana, Jascha B. Pohl, Wen-ke Li, Alfredo Ghezzi, Amanda M. Cady, Kristina Najjar, Michael M. Hatch, Ruchita R. Shah, Amar Bhat, Omar Hariri, Kareem B. Haroun, Melvin C. Young, Kathryn Fife, Jeff Hooten, Tuan Tran, Daniel Goan, Foram Desai, Farhan Husain, Ryan M. Godinez, Jeffrey C. Sun, Jonathan Corpuz, Jacxelyn Moran, Allen C. Zhong, William Y. Chen, Nigel S. Atkinson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037394
Abstract: Drosophila melanogaster has proven to be a useful model system for the genetic analysis of ethanol-associated behaviors. However, past studies have focused on the response of the adult fly to large, and often sedating, doses of ethanol. The pharmacological effects of low and moderate quantities of ethanol have remained understudied. In this study, we tested the acute effects of low doses of ethanol (~7 mM internal concentration) on Drosophila larvae. While ethanol did not affect locomotion or the response to an odorant, we observed that ethanol impaired associative olfactory learning when the heat shock unconditioned stimulus (US) intensity was low but not when the heat shock US intensity was high. We determined that the reduction in learning at low US intensity was not a result of ethanol anesthesia since ethanol-treated larvae responded to the heat shock in the same manner as untreated animals. Instead, low doses of ethanol likely impair the neuronal plasticity that underlies olfactory associative learning. This impairment in learning was reversible indicating that exposure to low doses of ethanol does not leave any long lasting behavioral or physiological effects.
Critical Role of PI3K/Akt/GSK3β in Motoneuron Specification from Human Neural Stem Cells in Response to FGF2 and EGF
Luis Ojeda, Junling Gao, Kristopher G. Hooten, Enyin Wang, Jason R. Thonhoff, Tiffany J. Dunn, Tianyan Gao, Ping Wu
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023414
Abstract: Fibroblast growth factor (FGF) and epidermal growth factor (EGF) are critical for the development of the nervous system. We previously discovered that FGF2 and EGF had opposite effects on motor neuron differentiation from human fetal neural stem cells (hNSCs), but the underlying mechanisms remain unclear. Here, we show that FGF2 and EGF differentially affect the temporal patterns of Akt and glycogen synthase kinase 3 beta (GSK3β) activation. High levels of phosphatidylinositol 3-kinase (PI3K)/Akt activation accompanied with GSK3β inactivation result in reduction of the motor neuron transcription factor HB9. Inhibition of PI3K/Akt by chemical inhibitors or RNA interference or overexpression of a constitutively active form of GSK3β enhances HB9 expression. Consequently, PI3K inhibition increases hNSCs differentiation into HB9+/microtubule-associated protein 2 (MAP2)+ motor neurons in vitro. More importantly, blocking PI3K not only enhances motor neuron differentiation from hNSCs grafted into the ventral horn of adult rat spinal cords, but also permits ectopic generation of motor neurons in the dorsal horn by overriding environmental influences. Our data suggest that FGF2 and EGF affect the motor neuron fate decision in hNSCs differently through a fine tuning of the PI3K/AKT/GSK3β pathway, and that manipulation of this pathway can enhance motor neuron generation.
The Mélange of Innovation and Tradition in Maltese Law: The Essence of the Maltese Mix?
B Andò
Potchefstroom Electronic Law Journal/Potchefstroomse Elektroniese Regsblad , 2012,
Abstract: Aim of this paper is to provide valuable insights into the Maltese legal system with a special focus on private law. The assumption is that this legal system is the byproduct of the "mixing" of innovation and tradition, resulting from the interaction of English law and continental law. A major role in the development of the system is played by courts. Some examples (moral damages and pre-contractual liability) are considered which highlight the importance of the function displayed by Maltese judges. KEYWORDS: Tradition; English law; continental law; hybridity; mixed legal systems; Maltese courts; moral damages; pre-contractual liability; lacunae
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