78,250 research outputs found
Availability, Attitudes and Willingness to Pay for Local Foods: Results of a Preliminary Survey
This paper presents the results of a preliminary intercept survey of consumers at farmers' markets in Gainesville, Florida in 2007. We developed survey questions to identify: (1) how much fruit and vegetable produce respondents buy from local sources; (2) attitudes regarding local foods; (3) definitions of local by distance and ownership; (4) WTP for local foods; (5) perceptions of the availability and cost of local products; and (6) demographic information. In addition to WTP, we employed several tools- a Likert scale, a cost/availability matrix, and other investigatory and demographic questions - to analyze factors affecting purchasing decisions. These include relative cost, accessibility, attitudes and perceptions of the term 'local.' We report and describe the results of the survey, including a regression analysis of WTP as a function of attitudinal, behavioral, and demographic variables. Given the small sample size, the results are largely not statistically significant. Yet, they are useful for refining the survey instrument for a larger study.Food Consumption/Nutrition/Food Safety,
Isospectral Flow and Liouville-Arnold Integration in Loop Algebras
A number of examples of Hamiltonian systems that are integrable by classical
means are cast within the framework of isospectral flows in loop algebras.
These include: the Neumann oscillator, the cubically nonlinear Schr\"odinger
systems and the sine-Gordon equation. Each system has an associated invariant
spectral curve and may be integrated via the Liouville-Arnold technique. The
linearizing map is the Abel map to the associated Jacobi variety, which is
deduced through separation of variables in hyperellipsoidal coordinates. More
generally, a family of moment maps is derived, identifying certain finite
dimensional symplectic manifolds with rational coadjoint orbits of loop
algebras. Integrable Hamiltonians are obtained by restriction of elements of
the ring of spectral invariants to the image of these moment maps. The
isospectral property follows from the Adler-Kostant-Symes theorem, and gives
rise to invariant spectral curves. {\it Spectral Darboux coordinates} are
introduced on rational coadjoint orbits, generalizing the hyperellipsoidal
coordinates to higher rank cases. Applying the Liouville-Arnold integration
technique, the Liouville generating function is expressed in completely
separated form as an abelian integral, implying the Abel map linearization in
the general case.Comment: 42 pages, 2 Figures, 1 Table. Lectures presented at the VIIIth
Scheveningen Conference, held at Wassenaar, the Netherlands, Aug. 16-21, 199
Lightweight magnesium-lithium alloys show promise
Evaluation tests show that magnesium-lithium alloys are lighter and more ductile than other magnesium alloys. They are being used for packaging, housings, containers, where light weight is more important than strength
Don't Panic! Closed String Tachyons in ALE Spacetimes
We consider closed string tachyons localized at the fixed points of
noncompact nonsupersymmetric orbifolds. We argue that tachyon condensation
drives these orbifolds to flat space or supersymmetric ALE spaces. The decay
proceeds via an expanding shell of dilaton gradients and curvature which
interpolates between two regions of distinct angular geometry. The string
coupling remains weak throughout. For small tachyon VEVs, evidence comes from
quiver theories on D-branes probes, in which deformations by twisted couplings
smoothly connect non-supersymmetric orbifolds to supersymmetric orbifolds of
reduced order. For large tachyon VEVs, evidence comes from worldsheet RG flow
and spacetime gravity. For \IC^2/\IZ_n, we exhibit infinite sequences of
transitions producing SUSY ALE spaces via twisted closed string condensation
from non-supersymmetric ALE spaces. In a -dual description this provides a
mechanism for creating NS5-branes via {\it closed} string tachyon condensation
similar to the creation of D-branes via {\it open} string tachyon condensation.
We also apply our results to recent duality conjectures involving fluxbranes
and the type 0 string.Comment: 48 pages, harvmac big; 13 figures. v2: added references; comment on
gravity regime added to section 5.2. v3: added reference
Binomial-coefficient multiples of irrationals
Denote by a random infinite path in the graph of Pascal's triangle (left
and right turns are selected independently with fixed probabilities) and by
the binomial coefficient at the 'th level along the path . Then
for a dense set of in the unit interval, is almost surely dense but not uniformly distributed modulo 1.Comment: 10 pages, to appear in Monatshefte f. Mat
Targeting chromatin aging - the epigenetic impact of longevity-associated interventions
A rapidly growing body of evidence has shown that chromatin undergoes radical alterations as an organism ages, but how these changes relate to aging itself is an open question. It is likely that these processes contribute to genomic instability and loss of transcriptional fidelity, which in turn drives deleterious age-related phenotypes. Interventions associated with increased healthspan and longevity such as reduced insulin/IGF signalling (IIS), inhibition of mTOR and energy depletion resulting in SIRT1/AMPK activation, all have beneficial effects which ameliorate multiple facets of age-associated decline. The impact of these interventions on the epigenome is less certain. In this review we highlight the potential of these interventions to act directly upon the epigenome and promote a youthful chromatin landscape, maintaining genetic and transcriptional memory throughout the lifecourse. We propose that this is a fundamental mechanism through which these interventions are able to curtail the incidence of age-related disease. By revisiting these well characterised interventions, we may be able to identify targetable effectors of chromatin function and use this knowledge to enhance healthspan and longevity in human populations through the measured application of dietary and small molecule interventions
Magnetically controlled mass loss from extrasolar planets in close orbits
We consider the role magnetic fields play in guiding and controlling
mass-loss via evaporative outflows from exoplanets that experience UV
irradiation. First we present analytic results that account for planetary and
stellar magnetic fields, along with mass-loss from both the star and planet. We
then conduct series of numerical simulations for gas giant planets, and vary
the planetary field strength, background stellar field strength, UV heating
flux, and planet mass. These simulations show that the flow is magnetically
controlled for moderate field strengths and even the highest UV fluxes, i.e.,
planetary surface fields gauss and fluxes
erg s. We thus conclude that outflows from all hot Jupiters with
moderate surface fields are magnetically controlled. The inclusion of magnetic
fields highly suppresses outflow from the night-side of the planet. Only the
magnetic field lines near the pole are open and allow outflow to occur. The
fraction of open field lines depends sensitively on the strength (and geometry)
of the background magnetic field from the star, along with the UV heating rate.
The net effect of the magnetic field is to suppress the mass loss rate by
(approximately) an order of magnitude. Finally, some open field lines do not
allow the flow to pass smoothly through the sonic point; flow along these
streamlines does not reach steady-state, resulting in time-variable mass-loss.Comment: Accepted for publication in MNRAS, 20 pages, 13 figure
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