Grant W.,VA Technology |
Curthoys I.,University of Sydney
Hearing Research | Year: 2017
Vestibular otolithic organs are recognized as transducers of head acceleration and they function as such up to their corner frequency or undamped natural frequency. It is well recognized that these organs respond to frequencies above their corner frequency up to the 2–3 kHz range (Curthoys et al., 2016). A mechanics model for the transduction of these organs is developed that predicts the response below the undamped natural frequency as an accelerometer and above that frequency as a seismometer. The model is converted to a transfer function using hair cell bundle deflection. Measured threshold acceleration stimuli are used along with threshold deflections for threshold transfer function values. These are compared to model predicted values, both below and above their undamped natural frequency. Threshold deflection values are adjusted to match the model transfer function. The resulting threshold deflection values were well within in measure threshold bundle deflection ranges. Vestibular Evoked Myogenic Potentials (VEMPs) today routinely uses stimulus frequencies of 500 and 1000 Hz, and otoliths have been established incontrovertibly by clinical and neural evidence as the stimulus source. The mechanism for stimulus at these frequencies above the undamped natural frequency of otoliths is presented where otoliths are utilizing a seismometer mode of response for VEMP transduction. © 2017 Elsevier B.V.
Wisniewski R.,Information and Analysis Center |
Schafrlk S.,VA Technology
2014 SME Annual Meeting and Exhibit, SME 2014: Leadership in Uncertain Times | Year: 2014
Every underground coal mine in the United States must deploy and operate a wireless communication and tracking system. This paper addresses the reliability and availability of an installed tracking system and the communications infrastructure that supports it. A particular interest is the requirements for the systems to operate continuously without failure after a mine disaster for 96 hours, and the requirements In the MINER Act for the tracking systems to be "calculated to be serviceable" and the communications systems "redundancy". These requirements imply a certain reliability and availability. This paper describes a quantitative way to assess these systems requirements, using the tools that are available and commonly used by the Reliability, Maintainability, & Availability community.
Hall A.B.,Virginia Polytechnic Institute and State University |
Hall A.B.,Fralin Life Science Institute |
Basu S.,Fralin Life Science Institute |
Jiang X.,Virginia Polytechnic Institute and State University |
And 16 more authors.
Science | Year: 2015
Sex determination in the mosquito Aedes aegypti is governed by a dominant male-determining factor (M factor) located within a Y chromosome-like region called the M locus. Here, we show that an M-locus gene, Nix, functions as an M factor in A. aegypti. Nix exhibits persistent M linkage and early embryonic expression, two characteristics required of an M factor. Nix knockout with clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 resulted in largely feminized genetic males and the production of female isoforms of two key regulators of sexual differentiation: doublesex and fruitless. Ectopic expression of Nix resulted in genetic females with nearly complete male genitalia. Thus, Nix is both required and sufficient to initiate male development. This study provides a foundation for mosquito control strategies that convert female mosquitoes into harmless males.
Morse J.L.,Cary Institute of Ecosystem Studies |
Morse J.L.,Portland State University |
Werner S.F.,Syracuse University |
Gillin C.P.,VA Technology |
And 5 more authors.
Journal of Geophysical Research G: Biogeosciences | Year: 2014
Understanding and predicting the extent, location, and function of biogeochemical hot spots at the watershed scale is a frontier in environmental science. We applied a hydropedologic approach to identify (1) biogeochemical differences among morphologically distinct hydropedologic settings and (2) hot spots of microbial carbon (C) and nitrogen (N) cycling activity in a northern hardwood forest in Hubbard Brook Experimental Forest, New Hampshire, USA. We assessed variables related to C and N cycling in spodic hydropedologic settings (typical podzols, bimodal podzols, and Bh podzols) and groundwater seeps during August 2010. We found that soil horizons (Oi/Oe, Oa/A, and B) differed significantly for most variables. B horizons (>10 cm) accounted for 71% (±11%) of C pools and 62% (±10%) ofmicrobial biomass C in the sampled soil profile, whereas the surface horizons (Oi/Oe and Oa/A; 0-10cm) were dominant zones for N-cycle-related variables. Watershed-wide estimates of C and N cycling were higher by 34 to 43% (±17-19%) when rates, horizon thickness, and areal extent of each hydropedologic setting were incorporated, versus conventionally calculated estimates for typical podzols that included only the top 10cm of mineral soil. Despite the variation in profile development in typical, bimodal, and Bh podzols, we did not detect significant differences in C and N cycling among them. Across all soil horizons and hydropedologic settings, we found strong links between biogeochemical cycling and soil C, suggesting that the accumulation of C in soils may be a robust indicator of microbial C and N cycling capacity in the landscape. ©2014. American Geophysical Union. All Rights Reserved.
Nilsen E.T.,VA Technology |
Freeman J.,University of North Florida |
Grene R.,Physiology and Weed Science |
Tokuhisa J.,VA Technology
PLoS ONE | Year: 2014
The development of water stress resistant lines of commercial tomato by breeding or genetic engineering is possible, but will take considerable time before commercial varieties are available for production. However, grafting commercial tomato lines on drought resistant rootstock may produce drought tolerant commercial tomato lines much more rapidly. Due to changing climates and the need for commercial production of vegetables in low quality fields there is an urgent need for stress tolerant commercial lines of vegetables such as tomato. In previous observations we identified a scion root stock combination ('BHN 602' scion grafted onto 'Jjak Kkung' rootstock hereafter identified as 602/Jjak) that had a qualitative drought-tolerance phenotype when compared to the non-grafted line. Based on this initial observation, we studied photosynthesis and vegetative above-ground growth during mild-drought for the 602/Jjak compared with another scion-rootstock combination ('BHN 602' scion grafted onto 'Cheong Gang' rootstock hereafter identified as 602/Cheong) and a non-grafted control. Overall above ground vegetative growth was significantly lower for 602/Jjak in comparison to the other plant lines. Moreover, water potential reduction in response to mild drought was significantly less for 602/Jjak, yet stomatal conductance of all plant-lines were equally inhibited by mild-drought. Light saturated photosynthesis of 602/Jjak was less affected by low water potential than the other two lines as was the % reduction in mesophyll conductance. Therefore, the Jjak Kkung rootstock caused aboveground growth reduction, water conservation and increased photosynthetic tolerance of mild drought. These data show that different rootstocks can change the photosynthetic responses to drought of a high yielding, commercial tomato line. Also, this rapid discovery of one scion-rootstock combination that provided milddrought tolerance suggests that screening more scion-rootstock combination for stress tolerance may rapidly yield commercially viable, stress tolerant lines of tomato. ©2014 Nilsen et al.
Arat S.,VA Technology |
Arat S.,Virginia Polytechnic Institute and State University |
Bullerjahn G.S.,Bowling Green State University |
Laubenbacher R.,University of Connecticut Health Center |
Laubenbacher R.,The Jackson Laboratory
PLoS ONE | Year: 2015
Pseudomonas aeruginosa is a metabolically flexible member of the Gammaproteobacteria. Under anaerobic conditions and the presence of nitrate, P. aeruginosa can perform (complete) denitrification, a respiratory process of dissimilatory nitrate reduction to nitrogen gas via nitrite (NO2), nitric oxide (NO) and nitrous oxide (N2O). This study focuses on understanding the influence of environmental conditions on bacterial denitrification performance, using a mathematical model of a metabolic network in P. aeruginosa. To our knowledge, this is the first mathematical model of denitrification for this bacterium. Analysis of the longterm behavior of the network under changing concentration levels of oxygen (O2), nitrate (NO3), and phosphate (PO4) suggests that PO4 concentration strongly affects denitrification performance. The model provides three predictions on denitrification activity of P. aeruginosa under various environmental conditions, and these predictions are either experimentally validated or supported by pertinent biological literature. One motivation for this study is to capture the effect of PO4 on a denitrification metabolic network of P. aeruginosa in order to shed light on mechanisms for greenhouse gas N2O accumulation during seasonal oxygen depletion in aquatic environments such as Lake Erie (Laurentian Great Lakes, USA). Simulating the microbial production of greenhouse gases in anaerobic aquatic systems such as Lake Erie allows a deeper understanding of the contributing environmental effects that will inform studies on, and remediation strategies for, other hypoxic sites worldwide. © 2015 Arat et al.
Dang H.X.,VA Technology |
Dang H.X.,University of Washington |
Pryor B.,University of AZ |
Peever T.,Washington State University |
And 2 more authors.
BMC Genomics | Year: 2015
Background: Alternaria is considered one of the most common saprophytic fungal genera on the planet. It is comprised of many species that exhibit a necrotrophic phytopathogenic lifestyle. Several species are clinically associated with allergic respiratory disorders although rarely found to cause invasive infections in humans. Finally, Alternaria spp. are among the most well known producers of diverse fungal secondary metabolites, especially toxins. Description: We have recently sequenced and annotated the genomes of 25 Alternaria spp. including but not limited to many necrotrophic plant pathogens such as A. brassicicola (a pathogen of Brassicaceous crops like cabbage and canola) and A. solani (a major pathogen of Solanaceous plants like potato and tomato), and several saprophytes that cause allergy in human such as A. alternata isolates. These genomes were annotated and compared. Multiple genetic differences were found in the context of plant and human pathogenicity, notably the pro-inflammatory potential of A. alternata. The Alternaria genomes database was built to provide a public platform to access the whole genome sequences, genome annotations, and comparative genomics data of these species. Genome annotation and comparison were performed using a pipeline that integrated multiple computational and comparative genomics tools. Alternaria genome sequences together with their annotation and comparison data were ported to Ensembl database schemas using a self-developed tool (EnsImport). Collectively, data are currently hosted using a customized installation of the Ensembl genome browser platform. Conclusion: Recent efforts in fungal genome sequencing have facilitated the studies of the molecular basis of fungal pathogenicity as a whole system. The Alternaria genomes database provides a comprehensive resource of genomics and comparative data of an important saprophytic and plant/human pathogenic fungal genus. The database will be updated regularly with new genomes when they become available. The Alternaria genomes database is freely available for non-profit use at http://alternaria.vbi.vt.edu. © Dang et al.; licensee BioMed Central.
Bumgardner M.,U.S. Department of Agriculture |
Buehlmann U.,VA Technology
Wood and Fiber Science | Year: 2015
Small firms are a critical component of the secondary woodworking industry and are important to hardwood lumber demand in the US. Understanding managers' perceptions of competitiveness in these firms is important to those working with the industry to help maintain a viable wood manufacturing base. One area of interest relative to the overall business environment involves attribution: to what do managers attribute their firms' success? In this study, attribution theory was applied to a sample of secondary woodworking manufacturers to test for a "self-serving" attribution effect (ie success is caused by internal factors, whereas a lack of success is caused by external factors), which has been shown in some other industries. Also of interest was determining if the effect was amplified for small firms. The presence of an overall attribution effect among secondary woodworking manufacturers was generally supported, but little evidence was found of an effect related specifically to small firms. The presence of an overall attribution effect is discussed in terms of the implications for research and outreach directed toward the secondary woodworking industry. © 2015 by the Society of Wood Science and Technology.
Dunlap M.D.,VA Technology |
Spoon C.E.,VA Technology |
Grant J.W.,VA Technology
Journal of Vestibular Research: Equilibrium and Orientation | Year: 2012
The utricle of the red-eared turtle was subjected to forced sinusoidal oscillations across various frequencies (10-125 Hz) and amplitudes (5-9 μm) to determine dynamic characteristics of the utricle under natural inertial stimulation. The utricle was maintained in physiologic solution during the entire experiment. Utricular specimens were prepared so that the Otoconial Layer (OL) crystals were exposed yet undisturbed, and the neuroepithelium was secured to a glass slide with dental floss strands. A piezoelectric-actuated platform, fitted to the stage of the microscope, created controlled sinusoidal displacement along the utricle's medial-lateral direction. The OL surface displacement was measured through the microscope with high-speed video at 1500 fps. A sub-pixel image registration algorithm was used to achieve displacement resolution ≤ 15 nm. The Membranous Shelf (MS), that overlies the macula, was recorded with high-speed video under identical amplitude and frequency inputs and was used as a reference point. Maximum displacement amplitudes of the OL and MS were used to determine the Amplitude Ratio (AR) of the OL relative to the MS. ARs at various frequencies were fit to a single degree of freedom model of the utricle to determine the utricle's natural frequency of 363 Hz (95% confidence intervals: 328, 397) with a damping ratio of 0. 96 (0. 8, 1. 12). © 2012 - IOS Press and the authors. All rights reserved.
Jan M.,CEA Saclay Nuclear Research Center |
Zaourar L.,CEA Saclay Nuclear Research Center |
Legout V.,VA Technology |
Pautet L.,Telecom ParisTech
Ada User Journal | Year: 2014
Mixed Criticality helps reducing the impact of pessimistic evaluation of Worst Case Execution Time for real-time systems. This is achieved by hosting lowcriticality tasks on a same hardware architecture in addition to the classical high-critical tasks, when considering two-criticality levels. The Time-Triggered paradigm (TT) is a classical approach within industry to develop high-criticality tasks. Extending TT systems in order to integrate the support of MC scheduling therefore requires the generation of two schedule tables, one for each criticality level. However, a switch between the schedule tables must not lead to an unschedulable situation for the high-criticality tasks. In this work, we show how a linear programming approach can be used to generate these schedule tables in a consistent way for dual-critical problems on multiprocessor architectures.