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Search Results: 1 - 10 of 59 matches for " Thyler Dill "
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Optical plasma microelectronic devices
Ebrahim Forati,Shiva Piltan,Thyler Dill,Dan Sievenpiper
Physics , 2015,
Abstract: The semiconductor channel in conventional microelectronic devices was successfully replaced with an optically triggered gas plasma channel. The combination of DC and laser-induced gas ionizations controls the conductivity of the channel, enabling us to realize different electronic devices such as transistors, switches, modulators, etc. A special micro-scale metasurface was used to enhance the laser-gas interaction, as well as combining it with DC ionization properly. Optical plasma devices benefit form the advantages of plasma/vacuum electronic devices while preserving most of the integrablity of semiconductor based devices.
An Improved EZW Hyperspectral Image Compression  [PDF]
Kai-Jen Cheng, Jeffrey C. Dill
Journal of Computer and Communications (JCC) , 2014, DOI: 10.4236/jcc.2014.22006

The paper describes an efficient lossy and lossless three dimensional (3D) image compression of hyperspectral images. The method adopts the 3D spatial-spectral hybrid transform and the proposed transform-based coder. The hybrid transforms are that Karhunen-Loève Transform (KLT) which decorrelates spectral data of a hyperspectral image, and the integer Discrete Wavelet Transform (DWT) which is applied to the spatial data and produces decorrelated wavelet coefficients. Our simpler transform-based coder is inspired by Shapiro’s EZW algorithm, but encodes residual values and only implements dominant pass incorporating six symbols. The proposed method will be examined on AVIRIS images and evaluated using compression ratio for both lossless and lossy compression, and signal to noise ratio (SNR) for lossy compression. Experimental results show that the proposed image compression not only is more efficient but also has better compression ratio.

Human-caused Disturbance Stimuli as a Form of Predation Risk
Alejandro Frid,Lawrence M. Dill
Ecology and Society , 2002,
Abstract: A growing number of studies quantify the impact of nonlethal human disturbance on the behavior and reproductive success of animals. Athough many are well designed and analytically sophisticated, most lack a theoretical framework for making predictions and for understanding why particular responses occur. Behavioral ecologists have recently begun to fill this theoretical vacuum by applying economic models of antipredator behavior to disturbance studies. In this emerging paradigm, predation and nonlethal disturbance stimuli create similar trade-offs between avoiding perceived risk and other fitness-enhancing activities, such as feeding, parental care, or mating. A vast literature supports the hypothesis that antipredator behavior has a cost to other activities, and that this trade-off is optimized when investment in antipredator behavior tracks short-term changes in predation risk. Prey have evolved antipredator responses to generalized threatening stimuli, such as loud noises and rapidly approaching objects. Thus, when encountering disturbance stimuli ranging from the dramatic, low-flying helicopter to the quiet wildlife photographer, animal responses are likely to follow the same economic principles used by prey encountering predators. Some authors have argued that, similar to predation risk, disturbance stimuli can indirectly affect fitness and population dynamics via the energetic and lost opportunity costs of risk avoidance. We elaborate on this argument by discussing why, from an evolutionary perspective, disturbance stimuli should be analogous to predation risk. We then consider disturbance effects on the behavior of individuals—vigilance, fleeing, habitat selection, mating displays, and parental investment—as well as indirect effects on populations and communities. A wider application of predation risk theory to disturbance studies should increase the generality of predictions and make mitigation more effective without over-regulating human activities.
Folding Very Short Peptides Using Molecular Dynamics
Bosco K Ho ,Ken A Dill
PLOS Computational Biology , 2006, DOI: 10.1371/journal.pcbi.0020027
Abstract: Peptides often have conformational preferences. We simulated 133 peptide 8-mer fragments from six different proteins, sampled by replica-exchange molecular dynamics using Amber7 with a GB/SA (generalized-Born/solvent-accessible electrostatic approximation to water) implicit solvent. We found that 85 of the peptides have no preferred structure, while 48 of them converge to a preferred structure. In 85% of the converged cases (41 peptides), the structures found by the simulations bear some resemblance to their native structures, based on a coarse-grained backbone description. In particular, all seven of the β hairpins in the native structures contain a fragment in the turn that is highly structured. In the eight cases where the bioinformatics-based I-sites library picks out native-like structures, the present simulations are largely in agreement. Such physics-based modeling may be useful for identifying early nuclei in folding kinetics and for assisting in protein-structure prediction methods that utilize the assembly of peptide fragments.
Correction: Folding Very Short Peptides Using Molecular Dynamics
Bosco K Ho,Ken A Dill
PLOS Computational Biology , 2006, DOI: 10.1371/journal.pcbi.0020060
Associations between street connectivity and active transportation
David Berrigan, Linda W Pickle, Jennifer Dill
International Journal of Health Geographics , 2010, DOI: 10.1186/1476-072x-9-20
Abstract: Principal components analysis indicated that ~85% of the variance in nine measures of street connectivity are accounted for by two components representing buffers with short blocks and dense nodes (PRIN1) or buffers with longer blocks that still maintain a grid like structure (PRIN2). PRIN1 and PRIN2 were positively associated with active transportation (AT) after adjustment for diverse demographic and health related variables. Propensity and duration of AT were correlated in both Los Angeles (r = 0.14) and San Diego (r = 0.49) at the zip code level. Multivariate analysis could account for the correlation between the two outcomes.After controlling for demography, measures of the built environment and other factors, no spatial autocorrelation remained for propensity to report AT (i.e., report of AT appeared to be independent among neighborhood residents). However, very localized correlation was evident in duration of AT, particularly in San Diego, where the variance of duration, after accounting for spatial autocorrelation, was 5% smaller within small neighborhoods (~0.01 square latitude/longitude degrees = 0.6 mile diameter) compared to within larger zip code areas. Thus a finer spatial scale of analysis seems to be more appropriate for explaining variation in connectivity and AT.Joint analysis of the propensity and duration of AT behavior and an explicitly geographic approach can strengthen studies of the built environment and physical activity (PA), specifically AT. More rigorous analytical work on cross-sectional data, such as in the present study, continues to support the need for experimental and longitudinal study designs including the analysis of natural experiments to evaluate the utility of environmental interventions aimed at increasing PA.Physical activity contributes to health through its direct effects on disease risk as well as its indirect effects via contributions to weight loss and weight maintenance. These benefits have been comprehensively reviewe
Use of the methylcellulose gum for fat up-take absorption in coated products
Marcia de Mello Luvielmo,Daniele Domingues Dill
Semina : Ciências Exatas e Tecnológicas , 2008,
Abstract: Even though coated meats have added value to products and gained consumers confidence, by improving these product’s appearance and taste, they go through a pre-frying stage during processing which releases the water and allows fat to enter the product, thus increasing fat content. The purpose of this work was to develop a coating system that absorbs less fat during the pre-frying stage of a chicken coated product. To do that, methylcellulose gum was added (MC) in different concentrations in the covering systems, batter (coating liquid) and breading (covering expresses). Five experiments were carried out, a standard experiment, without ingredient addition with technological function, formulations with addition of MC in the batter (0,5% and 2,0%), with addition of MC in the batter and in the breading (1% in each) and with addition of MC in the breading (2,0%). Results showed that fat uptake reduction in formulations with 0,5 and 2,0% of MC in the batter were of 5,81% and 8,40%, respectively, and in experiments with 1% of MC in the batter and 1% of MC in the breading was of 7,66%. In experiments that received 2% of MC in the breading , fat uptake reduction was of 10,51%. Formulations with 2% of MC added to the breading (10,51%) and 2% of MC added to the batter (8,40%) presented the largest reductions in fat uptake during the pre-fried stage. Analysis of sensorial acceptance showed that all formulations had a superior acceptance index of 70%, with no significant difference among the other tested formulations acceptance results (p <0,05). These findings show the efficiency of MC as a fat uptake barrier during the pre-fried stage, increasing humidity content, and becoming an advantageous technological alternative for the food industry.
Impact of the Built Environment on Mental and Sexual Health: Policy Implications and Recommendations
David Satcher,Martha Okafor,LeConté J. Dill
ISRN Public Health , 2012, DOI: 10.5402/2012/806792
Abstract: Research related to the intersection of the built environment and health has particularly flourished in the last decade. The authors highlight the theoretical and policy insights that have been made while also noting paucity in this literature as specifically related to mental and sexual health. Overall, the authors discuss policy implications of aspects of the built environment on both mental and sexual health behaviors and outcomes and suggest avenues for future research, program implementation, and policymaking for advancing health equity in these areas. 1. Introduction The built environment has been defined as “all buildings, spaces, and products that are created and modified by humans” [1]. Connections between the built environment and health can be traced back at least to Hippocrates’ work On Airs, Waters and Places initially published more than 2600 years ago [2]. By studying the living conditions of populations in Europe and Asia, Hippocrates, a physician, asserted that human health and illness were associated with a desirable state of equilibrium between the human organism and his or her immediate environment [2]. In the United States, social science scholar and activist W. E. B. Du Bois established that health was a function of living conditions [3]. In particular, Du Bois’ research illuminated the impact that urban planning decisions have on the most vulnerable populations in our society, namely, the very young, the poor, and people of color [3]. These vulnerable populations fare the most disproportionately in their health outcomes from untimely decision making and inaction on issues related to the built environment. In the 19th and early 20th centuries, issues related to the built environment were focused on sanitation, workplace safety, fire codes, lead abatement, access for people with disabilities, and other efforts to specifically combat communicable diseases. The 21st century is an opportunity for decisions related to the built environment to address the nation’s greatest current public health concerns, including obesity, cardiovascular disease, diabetes, asthma, injuries, violence, mental illness, substance abuse, sexual assault, and social inequities. Core areas of the built environment include land use, zoning, buildings, transportation systems, services, and public resources. Land use refers to the ways in which specific parcels of land and areas within communities are used [4]. Mixed use is a term to describe more than one type of land use in a given location (i.e., a business with an apartment above it). Zoning refers to the
Inferring microscopic kinetics of a Markov process using maximum caliber
Purushottam D. Dixit,Ken A. Dill
Physics , 2014,
Abstract: We present a principled approach for estimating the matrix of microscopic rates among states of a Markov process, given only its stationary state population distribution and a single average global kinetic observable. We adapt Maximum Caliber, a variational principle in which a path entropy is maximized over the distribution of all the possible trajectories, subject to basic kinetic constraints and some average dynamical observables. We show that this approach leads, under appropriate conditions, to the continuous-time master equation and a Smoluchowski-like equation that is valid for both equilibrium and non-equilibrium stationary states. We illustrate the method by computing the solvation dynamics of water molecules from molecular dynamics trajectories.
Electrostatics and aggregation: how charge can turn a crystal into a gel
Jeremy Schmit,Stephen Whitelam,Ken Dill
Physics , 2010, DOI: 10.1063/1.3626803
Abstract: The crystallization of proteins or colloids is often hindered by the appearance of aggregates of low fractal dimension called gels. Here we study the effect of electrostatics upon crystal and gel formation using an analytic model of hard spheres bearing point charges and short range attractive interactions. We find that the chief electrostatic free energy cost of forming assemblies comes from the entropic loss of counterions that render assemblies charge-neutral. Because there exists more accessible volume for these counterions around an open gel than a dense crystal, there exists an electrostatic entropic driving force favoring the gel over the crystal. This driving force increases with increasing sphere charge, but can be counteracted by increasing counterion concentration. We show that these effects cannot be fully captured by pairwise-additive macroion interactions of the kind often used in simulations, and we show where on the phase diagram to go in order to suppress gel formation.
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