Biscayne aquifer in Dade and Broward Counties, Florida

The Biscayne Aquifer is the principal source of water for the heavily populated area in the vicinity of West Palm Beach and Miami. The publication of this data is timely and will assist in the intelligent development of the water resources of the area.(PDF has 64 pages

Small Displacement, Long Life On-Orbit Compressor Design and Fabrication

The focus is the generation of technology and fabrication of prototype hardware applicable to seven Space Station compressor system applications. The compressors are of the single acting reciprocating piston type and, in general, may be termed miniature in size compared with normal commercially available equipment. The initial technology development is focused on improved valve designs, and the control of pulsations and heating effects in order to increase compressor efficiency and reduce cycle temperatures, thus permitting significantly increased stage pressure ratios. The initial test compressor was successfully operated at pressure ratios of up to 50:1, and this significant extension of allowable pressure ratio will result in a reduction of the number of required stages and, hence, total hardware thereby reducing system weight and volume. These experiments have also identified the need to employ low shaft speeds, on the order of 250 to 500 rpm, to enhance heat transfer and increase life. The prototype compressor currently being designed, is to be driven by a low-speed brushless dc motor sealed in a case common to the compressor drive mechanism case. The compressor and motor case will communicate with stage suction pressure so that any minor gas leakage past the piston rings will be returned to the suction. Emphasis in this prototype design is being placed on simplicity, durability, commonality of components, and high efficiency

A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: Hipparcos-Tycho cool stars

The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. We present a uniform, large-scale survey of X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares - both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. The 2XMM Catalogue and the associated time-series (`light-curve') data products have been used as the basis for a survey of X-ray flares from cool stars in the Hipparcos Tycho-2 catalogue. In addition, we have generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray light-curves. Where available, we have compared XMM OM UV/optical data with the X-ray light-curves. Our sample contains ~130 flares with well-observed profiles; they originate from ~70 stars. The flares range in duration from ~1e3 to ~1e4 s, have peak X-ray fluxes from ~1e-13 to ~1e-11 erg/cm2/s, peak X-ray luminosities from ~1e29 to ~1e32 erg/s, and X-ray energy output from ~1e32 to ~1e35 erg. Most of the ~30 serendipitously-observed stars have little previously reported information. The hardness-ratio plots clearly illustrate the spectral (and hence inferred temperature) variations characteristic of many flares, and provide an easily accessible overview of the data. We present flare frequency distributions from both target and serendipitous observations. The latter provide an unbiased (with respect to stellar activity) study of flare energetics; in addition, they allow us to predict numbers of stellar flares that may be detected in future X-ray wide-field surveys. The serendipitous sample demonstrates the need for care when calculating flaring rates.Comment: 26 pages, 24 figures. Additional tables and figures available as 4 ancillary files. To be published in Astronomy and Astrophysic

DETERMINANTS OF COW-CALF PAIR PRICES

Cow-calf prices are determined by interaction of many factors. At a particular auction, cow-calf pair prices often had a range of 75% of the mean price. This variability suggests that producers need to be informed regarding cow-calf price determinants. This study uses auction data during 1993 to estimate price differentials associated with cow-calf pair characteristics using a hedonic model. Cow breed, age, health, conditions, horns, frame, and whether the cow had been bred back were significant price determinants. Calf weight, health, and frame had significant price impacts. Highest prices were paid for pens containing 9-12 pairs of young Angus, dehorned, bred back, healthy cows with heavy healthy calves.Demand and Price Analysis,

FUTURES-BASED PRICE FORECASTS FOR AGRICULTURAL PRODUCERS AND BUSINESSES

The forecasting accuracy of five competing naïve and futures-based localized cash price forecasts is determined. The third-week's price each month from 1987-96 is forecasted from several vantage points. Commodities examine include those relevant to Midwest producers: the major grains, slaughter steers, slaughter hogs, several classes of feeder cattle, cull cows, and sows. Relative forecasting accuracy across forecast method is compared using regression models of forecast error. The traditional forecast method deferred futures plus historical basis has the greatest accuracy- even for cull cows. Adding complexity to forecasts, such as including regression models to capture nonlinear bases or biases in futures markets, does not improve accuracy.Demand and Price Analysis,

IDENTIFYING ECONOMIC RISK IN CATTLE FEEDING

Closeout data from two western Kansas commercial feedlots are examined to determine how cattle prices, feed costs, and animal performance impact the variability of cattle feeding profits. The relative impacts of these factors are studied across sex, placement weight, and placement month using standardized beta coefficients. Feeder cattle prices have a greater impact on profit variability for spring and fall placements. The effect of animal performance on variability of cattle feeding profits is greater for fall placements. Results suggest that fed cattle and feeder cattle prices should be emphasized in managing the overall risk in cattle feeding because they are the largest contributors to profit variability.cattle finishing profitability, cattle performance, feedlot closeouts, standardized beta coefficients, Livestock Production/Industries,

Feedback in a cavity QED system for control of quantum beats

Conditional measurements on the undriven mode of a two-mode cavity QED system prepare a coherent superposition of ground states which generate quantum beats. The continuous system drive induces decoherence through the phase interruptions from Rayleigh scattering, which manifests as a decrease of the beat amplitude and an increase of the frequency of oscillation. We report recent experiments that implement a simple feedback mechanism to protect the quantum beat. We continuously drive the system until a photon is detected, heralding the presence of a coherent superposition. We then turn off the drive and let the superposition evolve in the dark, protecting it against decoherence. At a later time we reinstate the drive to measure the amplitude, phase, and frequency of the beats. The amplitude can increase by more than fifty percent, while the frequency is unchanged by the feedback.Comment: 13 pages, 5 figures, ICAP 2012 23rd International Conference on Atomic Physic

Novel virus dynamics in an Emiliania huxleyi bloom

Diel studies of an Emiliania huxleyi bloom within a mesocosm revealed a highly dynamic associated viral community, changing on small times scales of hours