2,223 research outputs found
Live and Feeder Cattle Options Markets: Returns, Risk, and Volatility Forecasting
The paper examines empirical returns from holding thirty- and ninety-day call and put positions, and the forecasting performance of implied volatility in the live and feeder cattle options markets. In both markets, implied volatility is an upwardly biased and inefficient predictor of realized volatility, with bias most prominent in live cattle. While significant returns exist holding several market positions, most strategies are strongly affected by a drift in futures market prices. However, the returns from selling live cattle puts are persistent, and evidence from straddle returns identifies that the market overprices volatility. This overpricing is consistent with a short-term risk premium whose effect is magnified by extreme changes in market conditions.live cattle, feeder cattle, options, returns, risk, volatility forecasting, Agribusiness, Agricultural and Food Policy, Agricultural Finance, Community/Rural/Urban Development, Farm Management, Financial Economics, Livestock Production/Industries, Marketing, Research Methods/ Statistical Methods,
Mycobacterium tuberculosis complex DNA from an extinct bison dated 17,000 years before the present
Impaired desynchronization of beta activity underlies memory deficits in people with Parkinson's disease
Structural Properties, Order-Disorder Phenomena and Phase Stability of Orotic Acid Crystal Forms
Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1) and dimethylsulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135°C and loses only a small part of the water when stored over desiccants (25°C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen-bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a non-layer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions different levels of order-disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration
Post-Outburst Observations of V1647 Ori: Detection of a Brief Warm, Molecular Outflow
We present new observations of the fundamental ro-vibrational CO spectrum of
V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula.
Previous spectra, acquired during outburst in 2004 February and July, had shown
the CO emission lines to be broad and centrally peaked-similar to the CO
spectrum of a typical classical T Tauri star. In this paper, we present CO
spectra acquired shortly after the luminosity of the source returned to its
pre-outburst level (2006 February) and roughly one year later (2006 December
and 2007 February). The spectrum taken in 2006 February revealed blue-shifted
CO absorption lines superimposed on the previously observed CO emission lines.
The projected velocity, column density, and temperature of this outflowing gas
was 30 km/s, 3^{+2}_{-1}E18 cm^{-2$, and 700^{+300}_{-100} K, respectively. The
absorption lines were not observed in the 2006 December and 2007 February data,
and so their strengths must have decreased in the interim by a factor of 9 or
more. We discuss three mechanisms that could give rise to this unusual outflow.Comment: 14 pages, 2 figures, accepted for publication in ApJ
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Evidence for a Trade-Off Strategy in Stone Oak (Lithocarpus) Seeds between Physical and Chemical Defense Highlights Fiber as an Important Antifeedant
Trees in the beech or oak family (Fagaceae) have a mutualistic relationship with scatter-hoarding rodents. Rodents obtain nutrients and energy by consuming seeds, while providing seed dispersal for the tree by allowing some cached seeds to germinate. Seed predation and caching behavior of rodents is primarily affected by seed size, mechanical protection, macronutrient content, and chemical antifeedants. To enhance seed dispersal, trees must optimize trade-offs in investment between macronutrients and antifeedants. Here, we examine this important chemical balance in the seeds of tropical stone oak species with two substantially different fruit morphologies. These two distinct fruit morphologies in Lithocarpus differ in the degree of mechanical protection of the seed. For ‘acorn’ fruit, a thin exocarp forms a shell around the seed while for ‘enclosed receptacle’ (ER) fruit, the seed is embedded in a woody receptacle. We compared the chemical composition of numerous macronutrient and antifeedant in seeds from several Lithocarpus species, focusing on two pairs of sympatric species with different fruit morphologies. We found that macronutrients, particularly total non-structural carbohydrate, was more concentrated in seeds of ER fruits while antifeedants, primarily fibers, were more concentrated in seeds of acorn fruits. The trade-off in these two major chemical components was more evident between the two sympatric lowland species than between two highland species. Surprisingly, no significant difference in overall tannin concentrations in the seeds was observed between the two fruit morphologies. Instead, the major trade-off between macronutrients and antifeedants involved indigestible fibers. Future studies of this complex mutualism should carefully consider the role of indigestible fibers in the foraging behavior of scatter-hoarding rodents.Human Evolutionary Biolog
Subsonic high-angle-of-attack aerodynamic characteristics of a cone and cylinder with triangular cross sections and a cone with a square cross section
Experiments were conducted in the 12-Foot Pressure Wind Tunnel at Ames Research Center on three models with noncircular cross sections: a cone having a square cross section with rounded corners and a cone and cylinder with triangular cross sections and rounded vertices. The cones were tested with both sharp and blunt noses. Surface pressures and force and moment measurements were obtained over an angle of attack range from 30 deg to 90 deg and selected oil-flow experiments were conducted to visualize surface flow patterns. Unit Reynolds numbers ranged from 0.8x1,000,000/m to 13.0x1,000,000/m at a Mach number of 0.25, except for a few low-Reynolds-number runs at a Mach number of 0.17. Pressure data, as well as force data and oil-flow photographs, reveal that the three dimensional flow structure at angles of attack up to 75 deg is very complex and is highly dependent on nose bluntness and Reynolds number. For angles of attack from 75 deg to 90 deg the sectional aerodynamic characteristics are similar to those of a two dimensional cylinder with the same cross section
Creating an enduring developmental legacy from FIFA 2010: The Football Foundation of South Africa (FFSA)
Research question: The legacies of sport mega-events are widely contested. Whilst the short-term impacts of the 2010 FIFA World Cup™ in South Africa have been largely considered to be positive, there is little evidence of longer term outcomes. This paper contributes to the sport mega-event legacy literature by presenting empirical evidence of the longer term developmental legacy using a case study of a community-focused sports project. Key factors underpinning sustainable legacy outcomes are identified. Research methods: The Football Foundation of South Africa (FFSA) was selected as a case study due to the novel ways in which the project developed. Thirty-eight interviews were conducted with stakeholders involved directly in the FFSA’s day-to-day delivery and management, people from organisations who deliver sport and recreation services at the local and regional levels and children who use the facility. The interviews were recorded and transcribed, and the data were analysed using qualitative content analysis approach. Results and findings: The FFSA is achieving substantial and increasing reach into local, especially disadvantaged, communities. Children expressed very strong positive feelings about the contribution it makes to their lives. Several factors have enabled the FFSA to be successful, with the most critical being the strong institutional context within which the project is embedded involving local, regional, national and global organisations. Implications: The success of the FFSA highlights gaps in mega-event legacy planning. International sport bodies should develop formal mechanisms for drawing their corporate stakeholders together with community-based groups to identify and deliver sustainable developmental programmes.</p
Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed?
High-resolution infrared spectroscopy in the 2.3-4.6 micron region is
reported for the peculiar A supergiant, single-lined spectroscopic binary HR
4049. Lines from the CO fundamental and first overtone, OH fundamental, and
several H2O vibration-rotation transitions have been observed in the
near-infrared spectrum. The spectrum of HR 4049 appears principally in emission
through the 3 and 4.6 micron region and in absorption in the 2 micron region.
The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the
spectral lines observed in the 2.3-4.6 micron spectrum are shown to be
circumbinary in origin. The presence of OH and H2O lines confirm the
oxygen-rich nature of the circumbinary gas which is in contrast to the
previously detected carbon-rich material. The emission and absorption line
profiles show that the circumbinary gas is located in a thin, rotating layer
near the dust disk. The properties of the dust and gas circumbinary disk and
the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar
and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity
of 1 km/s. The severe depletion of refractory elements but near-solar
abundances of volatile elements observed in HR 4049 results from abundance
winnowing. The separation of the volatiles from the grains in the disk and the
subsequent accretion by the star are discussed. Contrary to prior reports, the
HR 4049 carbon and oxygen isotopic abundances are typical AGB values:
12C/13C=6^{+9}_{-4} and 16O/17O>200.Comment: 42 pages, 14 figures, Accepted by Ap
The neonicotinoid insecticide Imidacloprid repels pollinating flies and beetles at field-realistic concentrations
Neonicotinoids are widely used systemic insecticides which, when applied to flowering crops, are translocated to the nectar and pollen where they may impact upon pollinators. Given global concerns over pollinator declines, this potential impact has recently received much attention. Field exposure of pollinators to neonicotinoids depends on the concentrations present in flowering crops and the degree to which pollinators choose to feed upon them. Here we describe a simple experiment using paired yellow pan traps with or without insecticide to assess whether the commonly used neonicotinoid imidacloprid repels or attracts flying insects. Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 μg L-1, with Diptera avoiding concentrations as low as 0.01 μg L-1. This is to our knowledge the first evidence for any biological activity at such low concentrations, which are below the limits of laboratory detection using most commonly available techniques. Catch of spiders in pan traps was also slightly reduced by the highest concentrations of imidacloprid used (1 μg L-1), but catch was increased by lower concentrations. It remains to be seen if the repellent effect on insects occurs when neonicotinoids are present in real flowers, but if so then this could have implications for exposure of pollinators to neonicotinoids and for crop pollination. © 2013 Easton, Goulson
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