77,196 research outputs found

    Profiling Techniques in Archaeology

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    Availability, Attitudes and Willingness to Pay for Local Foods: Results of a Preliminary Survey

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    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

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    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

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    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

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    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 TT-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

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    Denote by xx a random infinite path in the graph of Pascal's triangle (left and right turns are selected independently with fixed probabilities) and by dn(x)d_n(x) the binomial coefficient at the nn'th level along the path xx. Then for a dense GδG_{\delta} set of θ\theta in the unit interval, {dn(x)θ}\{d_n(x)\theta \} 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

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    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

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    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 BP0.3B_P\gtrsim 0.3 gauss and fluxes FUV106F_{UV}\sim10^{6} erg s1^{-1}. 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