Spectral Properties of H-Reflex Recordings After an Acute Bout of Whole-Body Vibration

Although research supports the use of whole-body vibration (WBV) to improve neuromuscular performance, the mechanisms for these improvements remain unclear. The purpose of this study was to identify the effect ofWBV on the spectral properties of electrically evoked H-reflex recordings in the soleus (SOL) muscle. The H-reflex recordings were measured in the SOL muscle of 20 participants before and after a bout of WBV. The H-reflexes were evoked every 15 seconds for 150 seconds after WBV. A wavelet procedure was used to extract spectral data, which were then quantified with a principle components analysis. Resultant principle component scores were used for statistical analysis. The analysis extracted 1 principle component associated with the intensity of the myoelectric spectra and 1 principle component associated with the frequency. The scores of the principle component that were related to the myoelectric intensity were smaller at 30 and 60 milliseconds after WBV than before WBV. The WBV transiently decreased the intensity of myoelectric spectra during electrically evoked contractions, but it did not influence the frequency of the spectra. The decrease in intensity likely indicates a smaller electrically evoked muscle twitch response, whereas the lack of change in frequency would indicate a similar recruitment pattern of motor units before and after WBV

Fresh-Water Aquifer in the Knox Group (Cambrian–Ordovician) of Central Kentucky

Fresh water can be found in Cambrian and Ordovician carbonate rocks of the Knox Group in central Kentucky. The top of the aquifer is as much as 300 ft above mean sea level (m.s.l.) on the crest of the Cincinnati Arch, but descends off the flanks of the arch. Water is normally found in the upper 100 to 250 ft of the Knox, primarily in secondary porosity apparently associated with the unconformity at the top of the unit. Knox wells commonly exceed 750 ft in total depth, but because the aquifer is artesian, water rises to an elevation of about 500 ft above m.s.l. in most wells in central Kentucky. Some wells near the crest of the Cincinnati Arch produce water with relatively low concentrations of dissolved solids (500 to 3,000 milligrams per liter [mg/L]). Concentrations of dissolved solids commonly exceed 10,000 mg/L away from the crest of the arch. The Knox aquifer provides modest quantities of water (normally on the order of 10 to 20 gallons per minute) with less than 1,000 mg/L of dissolved solids to several wells in the Inner Blue Grass Region. As a result, it is a potential source of water for rural domestic supplies in central Kentucky

Spinal and Supraspinal Motor Control Predictors of Rate of Torque Development

During explosive movements and potentially injurious situations, the ability to rapidly generate torque is critical. Previous research has suggested that different phases of rate of torque development (RTD) are differentiately controlled. However, the extent to which supraspinal and spinal mechanisms predict RTD at different time intervals is unknown. RTD of the plantarflexors across various phases of contraction (i.e., 0–25, 0–50, 0–100, 0–150, 0–200, and 0–250 ms) was measured in 37 participants. The following predictor variables were also measured: (a) gain of the resting soleus H-reflex recruitment curve; (b) gain of the resting homonymous post-activation depression recruitment curve; (c) gain of the GABAergic presynaptic inhibition recruitment curve; (d) the level of postsynaptic recurrent inhibition at rest; (e) level of supraspinal drive assessed by measuring V waves; and (f) the gain of the resting soleus M wave. Stepwise regression analyses were used to determine which variables significantly predicted allometrically scaled RTD. The analyses indicated that supraspinal drive was the dominant predictor of RTD across all phases. Additionally, recurrent inhibition predicted RTD in all of the time intervals except 0–150 ms. These results demonstrate the importance of supraspinal drive and recurrent inhibition to RTD

Crop-phenology and LANDSAT-based irrigated lands inventory in the high plains

Optimal LANDSAT image dates for 1980 were identified based on the weekly crop-weather reports for Colorado, New Mexico, South Dakota, Texas, Oklahoma, Kansas, Nebraska, and Wyoming. The 1979 agricultural statistics data were entered into computer files and a revised questionnaire was developed and mailed to ASCS county agents. A set of computer programs was developed to allow the preparation of computer-assisted graphic displays of much of the collected data

Crop phenology and LANDSAT-based irrigated lands inventory in the high plains

The activity concentrated on identifying crop and irrigation data sources for the eight states within the High Plains Aquifer and making contacts concerning the nature of these data. A mail questionnaire was developed to gather specific data not routinely reported through standard data collection channels. Input/output routines were designed for High Plains crop and irrigation data and initial statistical data on crops were input to computer files

Aerothermodynamic Assessment of Corrugated Panel Thermal Protection Systems

The feasibility of using corrugated panels as a thermal protection system for an advanced space transportation vehicle was investigated. The study consisted of two major tasks: development of improved correlations for wind tunnel heat transfer and pressure data to yield design techniques, and application of the design techniques to determine if corrugated panels have application future aerospace vehicles. A single-stage-to-orbit vehicle was used to assess advantages and aerothermodynamic penalties associated with use of such panels. In the correlation task, experimental turbulent heat transfer and pressure data obtained on corrugation roughened surfaces during wind tunnel testing were analyzed and compared with flat plate data. The correlations and data comparisons included the effects of a large range of geometric, inviscid flow, internal boundary layer, and bulk boundary layer parameters in supersonic and hypersonic flow

Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures

Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N2, but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean - presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N2 pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN2 and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN2 to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO2, and (c) atmospheric oxygenation could have initiated a stepwise pN2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N2 and O2 is a signature of an oxygen-producing biosphere.Comment: 33 pages, 11 figures, 2 tables (includes appendix), published in Astrobiolog

Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints

We discuss data analysis techniques that can be used in the search for gravitational wave bursts from cosmic strings. When data from multiple interferometers are available, we describe consistency checks that can be used to greatly reduce the false alarm rates. We construct an expression for the rate of bursts for arbitrary cosmic string loop distributions and apply it to simple known solutions. The cosmology is solved exactly and includes the effects of a late-time acceleration. We find substantially lower burst rates than previous estimates suggest and explain the disagreement. Initial LIGO is unlikely to detect field theoretic cosmic strings with the usual loop sizes, though it may detect cosmic superstrings as well as cosmic strings and superstrings with non-standard loop sizes (which may be more realistic). In the absence of a detection, we show how to set upper limits based on the loudest event. Using Initial LIGO sensitivity curves, we show that these upper limits may result in interesting constraints on the parameter space of theories that lead to the production of cosmic strings.Comment: Replaced with version accepted for publication in PR