VARIETAL SALES AND QUALITY DIFFERENTIATION: THE CASE OF CERTIFIED SOYBEAN SEED IN THE SOUTHEASTERN U.S.

Variation in annual soybean plantings contributes to uncertainty in supplies of and demand for soybean seed in the southeastern U.S. This study used an expenditure valuation approach in an hedonic analysis framework to estimate returns to soybean seed quality differentiation. Analysis of pooled cross-sectional and time series observations narrowed important quality characteristics to yield and disease resistance attributes. In general, unexpected environmental factors affect seed crops over time, and the demand for other performance attributes is less predictable than for expected yield attributes. The results also suggest that geographical location is not significantly related to sales of varietal soybean seed in the study area.Crop Production/Industries,

ACREAGE PLANTING DECISION ANALYSIS OF SOUTH CAROLINA TOMATOES: NERLOVIAN VERSUS JUST RISK MODEL

Factors which explain supply response behavior of South Carolina tomato growers were determined. Two well known supply response models were used for comparison: the Nerlovian structural model and the Just risk model. The Just risk model reflected the significance of the risk effect in both stable and unstable periods. An evaluation of forecasting power between the two models was indeterminate. Growers are apparently willing to invest in more information with increased market instability because growers were influenced by the Florida winter price of tomatoes in planting decisions during the period of instability.Crop Production/Industries,

Magnetic fields and spiral arms in the galaxy M51

(Abridged) We use new multi-wavelength radio observations, made with the VLA and Effelsberg telescopes, to study the magnetic field of the nearby galaxy M51 on scales from 200\pc to several \kpc. Interferometric and single dish data are combined to obtain new maps at \wwav{3}{6} in total and polarized emission, and earlier \wav{20} data are re-reduced. We compare the spatial distribution of the radio emission with observations of the neutral gas, derive radio spectral index and Faraday depolarization maps, and model the large-scale variation in Faraday rotation in order to deduce the structure of the regular magnetic field. We find that the \wav{20} emission from the disc is severely depolarized and that a dominating fraction of the observed polarized emission at \wav{6} must be due to anisotropic small-scale magnetic fields. Taking this into account, we derive two components for the regular magnetic field in this galaxy: the disc is dominated by a combination of azimuthal modes, $m=0+2$, but in the halo only an $m=1$ mode is required to fit the observations. We disuss how the observed arm-interarm contrast in radio intensities can be reconciled with evidence for strong gas compression in the spiral shocks. The average arm--interam contrast, representative of the radii r>2\kpc where the spiral arms are broader, is not compatible with straightforward compression: lower arm--interarm contrasts than expected may be due to resolution effects and \emph{decompression} of the magnetic field as it leaves the arms. We suggest a simple method to estimate the turbulent scale in the magneto-ionic medium from the dependence of the standard deviation of the observed Faraday rotation measure on resolution. We thus obtain an estimate of 50\pc for the size of the turbulent eddies.Comment: 21 pages, 18 figures (some at lower resolution than submitted version), accepted for publication in MNRA

Can academic writing retreats function as wellbeing interventions?

Research and academic writing are increasingly difficult to prioritise in Higher Education. Academic writing retreats are growing in popularity as means to help academics to write. However, while they have been shown to enhance productivity their potential as wellbeing interventions has received less attention. We explore the experiences of UK-based academic participants in a structured writing programme through a structured questionnaire and in-depth interviews. Our findings suggest that writing retreats can positively impact on both hedonic and eudaimonic wellbeing. They may help mediate wellbeing threats, such as isolation, the conflict of work priorities and other pressures associated with academic research and time pressures. The opportunity to privilege writing provided our academic participants with positive benefits, yet we conclude that these effects do not endure if interventions are not maintained

Government Payments: Economic Impact on Southeastern Peanut Farms

Southeastern peanut farms with diversified field crops utilize government payments to supplement market receipts. Production in 2002 represented growing conditions under adverse weather, while 2003 represented optimal conditions. Representative farm analysis provides insight into allocation of market receipts and government payments for meeting variable costs and fixed costs.Crop Production/Industries,

Numerical simulations of chromospheric hard X-ray source sizes in solar flares

X-ray observations are a powerful diagnostic tool for transport, acceleration, and heating of electrons in solar flares. Height and size measurements of X-ray footpoints sources can be used to determine the chromospheric density and constrain the parameters of magnetic field convergence and electron pitch-angle evolution. We investigate the influence of the chromospheric density, magnetic mirroring and collisional pitch-angle scattering on the size of X-ray sources. The time-independent Fokker-Planck equation for electron transport is solved numerically and analytically to find the electron distribution as a function of height above the photosphere. From this distribution, the expected X-ray flux as a function of height, its peak height and full width at half maximum are calculated and compared with RHESSI observations. A purely instrumental explanation for the observed source size was ruled out by using simulated RHESSI images. We find that magnetic mirroring and collisional pitch-angle scattering tend to change the electron flux such that electrons are stopped higher in the atmosphere compared with the simple case with collisional energy loss only. However, the resulting X-ray flux is dominated by the density structure in the chromosphere and only marginal increases in source width are found. Very high loop densities (>10^{11} cm^{-3}) could explain the observed sizes at higher energies, but are unrealistic and would result in no footpoint emission below about 40 keV, contrary to observations. We conclude that within a monolithic density model the vertical sizes are given mostly by the density scale-height and are predicted smaller than the RHESSI results show.Comment: 19 pages, 9 figures, accepted for publication in Ap

Transverse Magnetoresistance of GaAs/AlGaAs Heterojunctions in the Presence of Parallel Magnetic Fields

We have calculated the resistivity of a GaAs\slash AlGaAs heterojunction in the presence of both an in--plane magnetic field and a weak perpendicular component using a semiclassical Boltzmann transport theory. These calculations take into account fully the distortion of the Fermi contour which is induced by the parallel magnetic field. The scattering of electrons is assumed to be due to remote ionized impurities. A positive magnetoresistance is found as a function of the perpendicular component, in good qualitative agreement with experimental observations. The main source of this effect is the strong variation of the electronic scattering rate around the Fermi contour which is associated with the variation in the mean distance of the electronic states from the remote impurities. The magnitude of the positive magnetoresistance is strongly correlated with the residual acceptor impurity density in the GaAs layer. The carrier lifetime anisotropy also leads to an observable anisotropy in the resistivity with respect to the angle between the current and the direction of the in--plane magnetic field.Comment: uuencoded file containing a 26 page RevTex file and 14 postscript figures. Submitted to Phys. Rev.

THE DETERMINANTS OF FOOD STAMP PROGRAM PARTICIPATION

Food Security and Poverty,

Quantized charge pumping through a quantum dot by surface acoustic waves

We present a realization of quantized charge pumping. A lateral quantum dot is defined by metallic split gates in a GaAs/AlGaAs heterostructure. A surface acoustic wave whose wavelength is twice the dot length is used to pump single electrons through the dot at a frequency f=3GHz. The pumped current shows a regular pattern of quantization at values I=nef over a range of gate voltage and wave amplitude settings. The observed values of n, the number of electrons transported per wave cycle, are determined by the number of electronic states in the quantum dot brought into resonance with the fermi level of the electron reservoirs during the pumping cycle.Comment: 8 page