Hayhoe M.M.,University Station |
Rothkopf C.A.,Goethe University Frankfurt
Wiley Interdisciplinary Reviews: Cognitive Science | Year: 2011
Historically, the study of visual perception has followed a reductionist strategy, with the goal of understanding complex visually guided behavior by separate analysis of its elemental components. Recent developments in monitoring behavior, such as measurement of eye movements in unconstrained observers, have allowed investigation of the use of vision in the natural world. This has led to a variety of insights that would be difficult to achieve in more constrained experimental contexts. In general, it shifts the focus of vision away from the properties of the stimulus toward a consideration of the behavioral goals of the observer. It appears that behavioral goals are a critical factor in controlling the acquisition of visual information from the world. This insight has been accompanied by a growing understanding of the importance of reward in modulating the underlying neural mechanisms and by theoretical developments using reinforcement learning models of complex behavior. These developments provide us with the tools to understanding how tasks are represented in the brain, and how they control acquisition of information through use of gaze. © 2010 John Wiley & Sons, Ltd.
PubMed | University of Florida, University Station and University of New Haven
Type: | Journal: Forensic science international | Year: 2016
Once forensic speaker identification (SI) was recognized as an entity, it was predicted that valid computer based identification systems would quickly become a reality. This has not happened and the review to follow will provide some of the reasons why. Notable among them are (1) the sharp underestimation of its complexity and (2) its confounding with speaker verification (SV). Consideration of these (and related) issues will be followed by a brief history about how the need for SI developed and some of the responses to the problem. Since much of the SI development preceded the structuring of appropriate standards, the recommended stop-gap response described here is based on somewhat uncoordinated, but extensive, research. The product of that effort will be reviewed and organized into a platform which supports SI procedures consistent with the forensic model. Also discussed are the standards which have been established, their impact on SI development and its present limitations. How the cited approach interacts both with progress in verification and the developing SI machine-based identification systems also will be considered. Finally, a few suggestions will be made that should assist in upgrading the effectiveness of aural perceptual speaker identification (AP SI).
Rios Perez C.A.,University of Texas at Austin |
Rios Perez C.A.,University Station |
Lowrey J.D.,University of Texas at Austin |
Lowrey J.D.,University Station |
And 3 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2012
Developing a better understanding of xenon transport through porous systems is critical to predicting how this gas will enter the atmosphere after a below ground nuclear weapons test. Radioxenon monitoring is a vital part of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System. This work details the development of prompt gamma activation analysis for measuring the diffusion rates of xenon and argon gases through a porous medium. The University of Texas at Austin maintains a prompt gamma activation analysis facility with a peak neutron flux of ∼1.5 × 107 cm-2 s-1 and a beam diameter of 1 cm. Due to the relatively large prompt gamma cross sections of many stable xenon isotopes at thermal and sub-thermal neutron energies, prompt gamma activation analysis is a suitable technique for in situ non-destructive analysis of natural xenon. A test chamber has been designed and constructed to utilize prompt gamma activation analysis to measure xenon and argon diffusion through geological materials (e.g., sand, soil, etc.). Initial experiments have been conducted to determine the detection limits for stable gas measurements. The results from these experiments will be utilized to benchmark parts of a xenon transport model that is being used to determine diffusion coefficients for xenon and argon. © Akadémiai Kiadó, Budapest, Hungary 2011.
Ocampo C.,University of Texas at Austin |
Ocampo C.,University Station |
Munoz J.-P.,University of Texas at Austin |
Munoz J.-P.,University Station
Journal of Guidance, Control, and Dynamics | Year: 2010
Linear perturbation theory is used to develop the variational equations needed to determine the sensitivities of the state at some final time with respect to all of the independent variables associated with a spacecraft trajectory model that is general enough for most applications of interest. The state vector is an augmented vector that includes the position, velocity, mass, and all other control-related variables, such as thrust magnitude and direction. The force model is general and the trajectory can have any number of impulsive and/or finite burn maneuvers. The gradient expressions depend, in part, on the system state transition matrix associated with the given state and its corresponding equations of motion. As an example, the procedure developed is applied to the numerical optimization of a multi-impulse escape trajectory from the moon. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.
PubMed | Goethe University Frankfurt and University Station
Type: Journal Article | Journal: Wiley interdisciplinary reviews. Cognitive science | Year: 2015
Historically, the study of visual perception has followed a reductionist strategy, with the goal of understanding complex visually guided behavior by separate analysis of its elemental components. Recent developments in monitoring behavior, such as measurement of eye movements in unconstrained observers, have allowed investigation of the use of vision in the natural world. This has led to a variety of insights that would be difficult to achieve in more constrained experimental contexts. In general, it shifts the focus of vision away from the properties of the stimulus toward a consideration of the behavioral goals of the observer. It appears that behavioral goals are a critical factor in controlling the acquisition of visual information from the world. This insight has been accompanied by a growing understanding of the importance of reward in modulating the underlying neural mechanisms and by theoretical developments using reinforcement learning models of complex behavior. These developments provide us with the tools to understanding how tasks are represented in the brain, and how they control acquisition of information through use of gaze. WIREs Cogni Sci 2011 2 158-166 DOI: 10.1002/wcs.113 For further resources related to this article, please visit the WIREs website.
Fugate K.K.,University Station |
Suttle J.C.,University Station |
Campbell L.G.,University Station
Postharvest Biology and Technology | Year: 2010
Ethylene elevates respiration, is induced by wounding, and contributes to wound-induced respiration in most postharvest plant products. Ethylene production and its effects on respiration rate, however, have not been determined during storage of sugarbeet (Beta vulgaris L.) root, even though any elevation in respiration due to ethylene would increase storage losses and reduce postharvest quality. To determine the effect of ethylene on sugarbeet root storage respiration rate, sugarbeet root ethylene production was quantified, and the effects of exogenous ethylene, an ethylene biosynthesis inhibitor, and ethylene response inhibitors on root respiration rate were determined using uninjured, severely injured, and conventionally harvested roots. Ethylene production was low (0.045-0.047 pmol kg-1 s-1) in uninjured and conventionally harvested and piled roots. Consequently, ethylene concentrations in commercial piles 0-67 d after piling were low, ranging from <0.001 to 0.054 μL L-1. Exogenous ethylene at concentrations of 0.020-14 μL L-1 increased root respiration. The increase in respiration rate, however, was transient at ethylene concentrations ≤0.11 μL L-1 suggesting that any ethylene effects on respiration rate in commercial piles would be short term. Severe injury induced ethylene production an average of 3.7-fold and increased respiration rate 3-4 d after injury. Wound-induced ethylene production, however, was not directly responsible for wound-induced respiration since elimination of wound-induced ethylene production by the ethylene synthesis inhibitor aminoethoxyvinylglycine had no effect on wound-induced respiration. The ethylene response inhibitors 1-methylcyclopropene (1-MCP) and silver thiosulfate reduced wound-induced respiration 3-4 d after injury when applied after wounding. A portion of the increase in respiration due to wounding, therefore, required ethylene perception. However, when applied prior to wounding, 1-MCP elevated wound-induced respiration 3-4 d after injury, suggesting that blockage of ethylene receptors prior to injury was ineffective at eliminating ethylene perception after wounding, possibly due to the synthesis of new receptors after the injury. Moreover, 1-MCP effects on root respiration rate occurred only when roots were severely injured; 1-MCP had no effect on respiration rate of uninjured or conventionally harvested roots. Postharvest sugarbeet roots, therefore, produce ethylene, increase ethylene production in response to wounding, and respond to exogenous ethylene with an increase in respiration rate, but ethylene production and ethylene effects on root respiration rate are likely to be small under commercial storage conditions and of limited economic significance.
PubMed | University Station
Type: Journal Article | Journal: Environmental geochemistry and health | Year: 2013
Although numerous studies with rats, hamsters, minipigs, goats and chicks have indicated that arsenic is an essential nutrient, the physiological role of arsenic is open to conjecture. Recent studies have suggested that arsenic has a physiological role that affects the formation of various metabolites of methionine metabolism including taurine and the polyamines. The concentration of plasma taurine is decreased in arsenic-deprived rats and hamsters. The hepatic concentration of polyamines and the specific activity of an enzyme necessary for the synthesis of spermidine and spermine, S-adenosylmethionine decarboxylase, are also decreased in arsenic-deprived rats. Thus, evidence has been obtained which indicates that arsenic is of physiological importance, especially when methionine metabolism is stressed (e.g. pregnancy, lactation, methionine deficiency, vitamin B6 deprivation). Any possible nutritional requirement by humans can be estimated only by using data from animal studies. The arsenic requirement for growing chicks and rats has been suggested to be near 25 ng g(-1) diet. Thus, a possible human requirement is 12 g day(-1). The reported arsenic content of diets from various parts of the world indicates that the average intake of arsenic is in the range of 12-40 g. Fish, grain and cereal products contribute most arsenic to the diet.