Preliminary evaluation of radar imagery of Yellowstone Park, Wyoming

Evaluation of radar imagery of Yellowstone Park, Wyomin

Non-integrability of the mixmaster universe

We comment on an analysis by Contopoulos et al. which demonstrates that the governing six-dimensional Einstein equations for the mixmaster space-time metric pass the ARS or reduced Painlev\'{e} test. We note that this is the case irrespective of the value, $I$, of the generating Hamiltonian which is a constant of motion. For $I < 0$ we find numerous closed orbits with two unstable eigenvalues strongly indicating that there cannot exist two additional first integrals apart from the Hamiltonian and thus that the system, at least for this case, is very likely not integrable. In addition, we present numerical evidence that the average Lyapunov exponent nevertheless vanishes. The model is thus a very interesting example of a Hamiltonian dynamical system, which is likely non-integrable yet passes the reduced Painlev\'{e} test.Comment: 11 pages LaTeX in J.Phys.A style (ioplppt.sty) + 6 PostScript figures compressed and uuencoded with uufiles. Revised version to appear in J Phys.

Exact Periodic Solutions of Shells Models of Turbulence

We derive exact analytical solutions of the GOY shell model of turbulence. In the absence of forcing and viscosity we obtain closed form solutions in terms of Jacobi elliptic functions. With three shells the model is integrable. In the case of many shells, we derive exact recursion relations for the amplitudes of the Jacobi functions relating the different shells and we obtain a Kolmogorov solution in the limit of infinitely many shells. For the special case of six and nine shells, these recursions relations are solved giving specific analytic solutions. Some of these solutions are stable whereas others are unstable. All our predictions are substantiated by numerical simulations of the GOY shell model. From these simulations we also identify cases where the models exhibits transitions to chaotic states lying on strange attractors or ergodic energy surfaces.Comment: 25 pages, 7 figure

Co-feeding between Svalbard Rock Ptarmigan (Lagopus muta hyperborea) and Svalbard Reindeer (Rangifer tarandus platyrhynchus)

Co-feeding between Svalbard rock ptarmigan (Lagopus muta hyperborea) and Svalbard reindeer (Rangifer tarandus platyrhynchus) on Svalbard, Norway, was observed during our annual point transect survey of territorial Svalbard ptarmigan cocks in two side valleys of Adventdalen and Sassendalen. Both pairs and single hens or cocks used the feeding craters excavated by reindeer in search of food. We suggest that the use of reindeer feeding craters may be important to the Svalbard rock ptarmigan during snow-rich events in winter or after terrestrial ice-crust formation resulting from mild spells and rain-on-snow events. We expect that such co-feeding may be particularly important for saving energy in periods when territorial defence and preparation for the breeding season make high energy demands on ptarmigan of both sexes.La co-alimentation entre le lagopède alpin de Svalbard (Lagopus mutus hyperboreus) et le renne de Svalbard (Rangifer tarandus platyrhynchus) à Svalbard, en Norvège, a été observée dans le cadre de notre enquête transect annuelle des coqs lagopèdes territoriaux de Svalbard dans deux vallées latérales d’Adventdalen et de Sassendalen. Les poules et les coqs en couples ou célibataires se servaient des fosses de broutage creusées par les rennes à la recherche de nourriture. On suggère que l’utilisation des fosses de broutage des rennes peut revêtir de l’importance pour le lagopède alpin de Svalbard pendant les périodes hivernales riches en neige ou après la formation de glace sur la couche terrestre résultant du temps doux ou de pluie sur la neige. On s’attend à ce que la co-alimentation de ce genre soit particulièrement importante lorsque vient le temps de conserver l’énergie pendant les périodes où la défense du territoire et la préparation pour la saison de reproduction occasionnent de fortes demandes d’énergie chez les lagopèdes des deux sexes

Thermal shifts and intermittent linear response of aging systems

At time $t$ after an initial quench, an aging system responds to a perturbation turned on at time $t_{\rm w} < t$ in a way mainly depending on the number of intermittent energy fluctuations, so-called quakes, which fall within the observation interval $(t_{\rm w},t]$ [Sibani et al. Phys. Rev. B, 74, 224407 and Eur. J. of Physics B, 58,483-491, 2007]. The temporal distribution of the quakes implies a functional dependence of the average response on the ratio $t/t_{\rm w}$. Further insight is obtained imposing small temperature steps, so-called $T$-shifts. The average response as a function of $t/t_{\rm w,eff}$, where $t_{\rm w,eff}$ is the effective age, is similar to the response of a system aged isothermally at the final temperature. Using an Ising model with plaquette interactions, the applicability of analytic formulae for the average isothermal magnetization is confirmed. The $T$-shifted aging behavior of the model is described using effective ages. Large positive shifts nearly reset the effective age. Negative $T$-shifts offer a more detailed probe of the dynamics. Assuming the marginal stability of the `current' attractor against thermal noise fluctuations, the scaling form $t_{\rm w,eff} = t_{\rm w}^x$, and the dependence of the exponent $x$ on the aging temperatures before and after the shift are theoretically available. The predicted form of $x$ has no adjustable parameters. Both the algebraic scaling of the effective age and the form of the exponent agree with the data. The simulations thus confirm the crucial r\^{o}le of marginal stability in glassy relaxation.Comment: 10 pages, 17 figures, RevTeX styl

Gluon distributions in nucleons and pions at a low resolution scale

In this paper we study the gluon distribution functions in nucleons and pions at a low resolution $Q^2$ scale. This is an important issue since parton densities at low $Q^2$ have always been taken as an external input which is adjusted through DGLAP evolution to fit the experimental data at higher scales. Here, in the framework of a model recently developed, it is shown that the hypothetical cloud of {\it neutral} pions surrounding nucleons and pions appears to be responsible for the characteristic valence-like gluon distributions needed at the inital low scale. As an additional result, we get the remarkable prediction that neutral and charged pions have different intrinsic sea flavor contents.Comment: final version to appear in Phys. Rev. D. Discussion on several points enlarge

Linear response subordination to intermittent energy release in off-equilibrium aging dynamics

The interpretation of experimental and numerical data describing off-equilibrium aging dynamics crucially depends on the connection between spontaneous and induced fluctuations. The hypothesis that linear response fluctuations are statistically subordinated to irreversible outbursts of energy, so-called quakes, leads to predictions for averages and fluctuations spectra of physical observables in reasonable agreement with experimental results [see e.g. Sibani et al., Phys. Rev. B74:224407, 2006]. Using simulational data from a simple but representative Ising model with plaquette interactions, direct statistical evidence supporting the hypothesis is presented and discussed in this work. A strict temporal correlation between quakes and intermittent magnetization fluctuations is demonstrated. The external magnetic field is shown to bias the pre-existent intermittent tails of the magnetic fluctuation distribution, with little or no effect on the Gaussian part of the latter. Its impact on energy fluctuations is shown to be negligible. Linear response is thus controlled by the quakes and inherits their temporal statistics. These findings provide a theoretical basis for analyzing intermittent linear response data from aging system in the same way as thermal energy fluctuations, which are far more difficult to measure.Comment: 9 pages, 10 figures. Text improve

Arbitrariness, iconicity, and systematicity in language

The notion that the form of a word bears an arbitrary relation to its meaning accounts only partly for the attested relations between form and meaning in the languages of the world. Recent research suggests a more textured view of vocabulary structure, in which arbitrariness is complemented by iconicity (aspects of form resemble aspects of meaning) and systematicity (statistical regularities in forms predict function). Experimental evidence suggests these form-to-meaning correspondences serve different functions in language processing, development, and communication: systematicity facilitates category learning by means of phonological cues, iconicity facilitates word learning and communication by means of perceptuomotor analogies, and arbitrariness facilitates meaning individuation through distinctive forms. Processes of cultural evolution help to explain how these competing motivations shape vocabulary structure

Believing in food addiction: helpful or counter-productive for eating behaviour?

Objective: Obesity is often attributed to an addiction to food, and many people believe themselves to be “food addicts.” However, little is known about how such beliefs may affect dietary control and weight management. The current research examined the impact of experimentally manipulating participants' personal food addiction beliefs on eating behavior. Methods In two studies, female participants (study 1: N  = 64; study 2: N  = 90) completed food‐related computerized tasks and were given bogus feedback on their performance which indicated that they had high, low, or average food addiction tendencies. Food intake was then assessed in an ad libitum taste test. Dietary concern and time taken to complete the taste test were recorded in study 2. Results: In study 1, participants in the high‐addiction condition consumed fewer calories than those in the low‐addiction condition, F (1,60) = 7.61, P  = 0.008, η p2 = 0.11. Study 2 replicated and extended this finding, showing that the effect of the high‐addiction condition on food intake was mediated by increased dietary concern, which reduced the amount of time participants willingly spent exposed to the foods during the taste test, b  = −0.06 (0.03), 95% confidence interval = −0.13 to −0.01. Conclusions: Believing oneself to be a food addict is associated with short‐term dietary restriction. The longer‐term effects on weight management now warrant attention

Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Drill Core, Central Snake River Plain, Idaho: 5.5-Million-Years of Petrogenesis in a Mid-crustal Sill Complex

Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1,912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5–10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319, 1045, 1,078, and 1,189 m, evolved and high K-Fe flows are compositionally unrelated to SROT magmas and represent highly fractionated basalt, probably accompanied by crustal assimilation. These evolved lavas may be sourced from the Craters of the Moon/Great Rift system to the northeast. The Kimama drill core is the longest record of geochemical variation in the central Snake River Plain and reinforces the concept of magma processing in a layered complex