57,489 research outputs found
IMPACT OF ALTERNATIVE GRID PRICING STRUCTURES ON CATTLE MARKETING DECISIONS
Quality grade, yield grade, and other feedlot performance factors explain much of the variation in profit under grid pricing. Thus, feedlot owners can change profits by adjusting time on feed to influence these performance factors. This research uses growth models, logistic regression, and an optimization process to determine how the optimal number of days on feed changes under different grid pricing structures. It was found that large quality or small yield discounts increases the optimal number of days on feed and small quality or large yield discounts result in fewer days on feed. Losses associated with a grid having large quality discounts are minimized as cattle fed for more days are able to obtain Choice premiums despite the discounts for more Yield Grade 4 and 5 carcasses. Given small quality discounts, cattle fed for a shorter length of time can obtain the Yield Grade 1 and 2 premiums without a large loss in revenue due to grading Select or Standard. Under cash pricing, cattle are fed for very long periods because there are no discounts applied to the carcasses and, therefore, the more weight they gain, the more revenue they generate. During periods of low feed prices, cattle can be fed longer so more cattle grade Prime but also have more Yield Grade 4 and 5 cattle.grid pricing, profits, animal growth, logistic regression, days on feed, Livestock Production/Industries, Marketing,
Testing the Underlying Chemical Principles of the Biotic Ligand Model (BLM) to Marine Copper Systems: Measuring Copper Speciation Using Fluorescence Quenching
Speciation of copper in marine systems strongly influences the ability of copper to cause toxicity. Natural organic matter (NOM) contains many binding sites which provides a protective effect on copper toxicity. The purpose of this study was to characterize copper binding with NOM using fluorescence quenching techniques. Fluorescence quenching of NOM with copper was performed on nine sea water samples. The resulting stability con- stants and binding capacities were consistent with literature values of marine NOM, show- ing strong binding with log K values from 7.64 to 10.2 and binding capacities ranging from 15 to 3110 nmole mg C −1 . Free copper concentrations estimated at total dissolved copper concentrations corresponding to previously published rotifer effect concentrations, in the same nine samples, were statistically the same as the range of free copper calculated for the effect concentration in NOM-free artificial seawater. These data confirms the applicability of fluorescence spectroscopy techniques for NOM and copper speciation characterization in sea water and demonstrates that such measured speciation is consistent with the chemical principles underlying the Biotic Ligand Model (BLM) approach for bioavailability-based metals risk assessment
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Atmospheric fungal nanoparticle bursts.
Aerosol nanoparticles play an important role in the climate system by affecting cloud formation and properties, as well as in human health because of their deep reach into lungs and the circulatory system. Determining nanoparticle sources and composition is a major challenge in assessing their impacts in these areas. The sudden appearance of large numbers of atmospheric nanoparticles is commonly attributed to secondary formation from gas-phase precursors, but in many cases, the evidence for this is equivocal. We report the detection of a mode of fungal fragments with a mobility diameter of roughly 30 nm released in episodic bursts in ambient air over an agricultural area in northern Oklahoma. These events reached concentrations orders of magnitude higher than other reports of biological particles and show similarities to unclarified events reported previously in the Amazon. These particles potentially represent a large source of both cloud-forming ice nuclei and respirable allergens in a variety of ecosystems
A generic interface between COSMIC/NASTRAN and PATRAN (R)
Despite its powerful analytical capabilities, COSMIC/NASTRAN lacks adequate post-processing adroitness. PATRAN, on the other hand is widely accepted for its graphical capabilities. A nonproprietary, public domain code mnemonically titled CPI (for COSMIC/NASTRAN-PATRAN Interface) is designed to manipulate a large number of files rapidly and efficiently between the two parent codes. In addition to PATRAN's results file preparation, CPI also prepares PATRAN's P/PLOT data files for xy plotting. The user is prompted for necessary information during an interactive session. Current implementation supports NASTRAN's displacement approach including the following rigid formats: (1) static analysis, (2) normal modal analysis, (3) direct transient response, and (4) modal transient response. A wide variety of data blocks are also supported. Error trapping is given special consideration. A sample session with CPI illustrates its simplicity and ease of use
A dynamical collective calculation of supernova neutrino signals
We present the first calculations with three flavors of collective and shock
wave effects for neutrino propagation in core-collapse supernovae using
hydroynamical density profiles and the S matrix formalism. We explore the
interplay between the neutrino-neutrino interaction and the effects of multiple
resonances upon the time signal of positrons in supernova observatories. A
specific signature is found for the inverted hierarchy and a large third
neutrino mixing angle and we predict, in this case, a dearth of lower energy
positrons in Cherenkov detectors midway through the neutrino signal and the
simultaneous revelation of valuable information about the original fluxes. We
show that this feature is also observable with current generation neutrino
detectors at the level of several sigmas.Comment: 4 pages, 5 figure
Physiological Effects of Chronic Copper Exposure to Rainbow Trout (\u3cem\u3eOncorhynchus Mykiss\u3c/em\u3e) in Hard and Soft Water: Evaluation of Chronic Indicators
Effects of chronic copper exposure on a suite of indicators were examined: acute toxicity, acclimation, growth, sprint performance, whole-body electrolytes, tissue residues, and gill copper binding characteristics. Juvenile rainbow trout were exposed for 30 d to waterborne copper in hard water (hardness = 120 μg/L as CaCO3, pH = 8.0, Cu = 20 and 60 μg/L) and soft water (hardness = 20 μg/L as CaCO3, pH = 7.2, Cu = 1 and 2 μg/L). Significant acclimation to the metal occurred only in fish exposed to 60 mg/L, as seen by an approx. twofold increase in 96-h LC50 (153 vs 91 μg Cu/L). Chronic copper exposure had little or no effect on survival, growth, or swimming performance in either water hardness, nor was there any initial whole-body electrolyte loss (Na+ and Cl-). The present data suggest that the availability of food (3% wet body weight/day, distributed as three 1% meals) prevented growth inhibition and initial ion losses that usually result from Cu exposure. Elevated metal burdens in the gills and livers of exposed fish were measures of chronic copper exposure but not of effect. Initial gill binding experiments revealed the necessity of using radiolabeled Cu (64Cu) to detect newly accumulated Cu against gill background levels. Using this method, we verified the presence of saturable Cu-binding sites in the gills of juvenile rainbow trout and were able to make estimates of copperbinding affinity (log Kgill=Cu) and capacity (Bmax). Furthermore, we showed that both chronic exposure to Cu and to low water calcium had important effects on the Cu-binding characteristics of the gills
On the Survivability and Metamorphism of Tidally Disrupted Giant Planets: the Role of Dense Cores
A large population of planetary candidates in short-period orbits have been
found through transit searches. Radial velocity surveys have also revealed
several Jupiter-mass planets with highly eccentric orbits. Measurements of the
Rossiter-McLaughlin effect indicate some misaligned planetary systems. This
diversity could be induced by post-formation dynamical processes such as
planet-planet scattering, the Kozai effect, or secular chaos which brings
planets to the vicinity of their host stars. In this work, we propose a novel
mechanism to form close-in super-Earths and Neptune-like planets through the
tidal disruption of giant planets as a consequence of these dynamical
processes. We model the core-envelope structure of giant planets with composite
polytropes. Using three-dimensional hydrodynamical simulations of close
encounters between planets and their host stars, we find that the presence of a
core with a mass more than ten Earth masses can significantly increase the
fraction of envelope which remains bound to it. After the encounter, planets
with cores are more likely to be retained by their host stars in contrast with
previous studies which suggested that coreless planets are often ejected. As a
substantial fraction of their gaseous envelopes is preferentially lost while
the dense incompressible cores retain most of their original mass, the
resulting metallicity of the surviving planets is increased. Our results
suggest that some gas giant planets can be effectively transformed into either
super-Earths or Neptune-like planets after multiple close stellar passages.
Finally, we analyze the orbits and structure of known planets and Kepler
candidates and find that our model is capable producing some of the
shortest-period objects.Comment: Accepted for publication in ApJ. 15 pages, 9 figures, 3 tables. Two
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