Mesoscale structure of 11-20 km winds

Wind speed and direction profiles by tracking spherical superpressure balloon

Quantum theta functions and Gabor frames for modulation spaces

Representations of the celebrated Heisenberg commutation relations in quantum mechanics and their exponentiated versions form the starting point for a number of basic constructions, both in mathematics and mathematical physics (geometric quantization, quantum tori, classical and quantum theta functions) and signal analysis (Gabor analysis). In this paper we try to bridge the two communities, represented by the two co--authors: that of noncommutative geometry and that of signal analysis. After providing a brief comparative dictionary of the two languages, we will show e.g. that the Janssen representation of Gabor frames with generalized Gaussians as Gabor atoms yields in a natural way quantum theta functions, and that the Rieffel scalar product and associativity relations underlie both the functional equations for quantum thetas and the Fundamental Identity of Gabor analysis.Comment: 38 pages, typos corrected, MSC class change

Mobilization of seed storage lipid by Arabidopsis seedlings is retarded in the presence of exogenous sugars

BACKGROUND: Soluble sugar levels must be closely regulated in germinating seeds to ensure an adequate supply of energy and building materials for the developing seedling. Studies on germinating cereal seeds indicate that production of sugars from starch is inhibited by increasing sugar levels. Although numerous studies have focused on the regulation of starch metabolism, very few studies have addressed the control of storage lipid metabolism by germinating oilseeds. RESULTS: Mobilization of storage lipid by germinating seeds of the model oilseed plant Arabidopsis thaliana (L.) Heynh. occurs at a greatly reduced rate in the presence of exogenous glucose or mannose, but not in the presence of equi-molar 3-O-methylglucose or sorbitol. The sugar-insensitive5-1/abscisic acid-insensitive4-101 (sis5-1/abi4-101) mutant is resistant to glucose inhibition of seed storage lipid mobilization. Wild-type seedlings become insensitive to glucose inhibition of storage lipid breakdown within 3 days of the start of imbibition. CONCLUSIONS: Growth in the presence of exogenous glucose significantly retards mobilization of seed storage lipid in germinating seeds from wild-type Arabidopsis. This effect is not solely due to the osmotic potential of the media, as substantially higher concentrations of sorbitol than of glucose are required to exert significant effects on lipid breakdown. The inhibitory effect of glucose on lipid breakdown is limited to a narrow developmental window, suggesting that completion of some critical metabolic transition results in loss of sensitivity to the inhibitory effect of glucose on lipid breakdown

Dewetting of thin polymer films near the glass transition

Dewetting of ultra-thin polymer films near the glass transition exhibits unexpected front morphologies [G. Reiter, Phys. Rev. Lett., 87, 186101 (2001)]. We present here the first theoretical attempt to understand these features, focusing on the shear-thinning behaviour of these films. We analyse the profile of the dewetting film, and characterize the time evolution of the dry region radius, $R_{d}(t)$, and of the rim height, $h_{m}(t)$. After a transient time depending on the initial thickness, $h_{m}(t)$ grows like $\sqrt{t}$ while $R_{d}(t)$ increases like $\exp{(\sqrt{t})}$. Different regimes of growth are expected, depending on the initial film thickness and experimental time range.Comment: 4 pages, 5 figures Revised version, published in Physical Review Letters: F. Saulnier, E. Raphael and P.-G. de Gennes, Phys. Rev. Lett. 88, 196101 (2002

Using Synchronic and Diachronic Relations for Summarizing Multiple Documents Describing Evolving Events

In this paper we present a fresh look at the problem of summarizing evolving events from multiple sources. After a discussion concerning the nature of evolving events we introduce a distinction between linearly and non-linearly evolving events. We present then a general methodology for the automatic creation of summaries from evolving events. At its heart lie the notions of Synchronic and Diachronic cross-document Relations (SDRs), whose aim is the identification of similarities and differences between sources, from a synchronical and diachronical perspective. SDRs do not connect documents or textual elements found therein, but structures one might call messages. Applying this methodology will yield a set of messages and relations, SDRs, connecting them, that is a graph which we call grid. We will show how such a grid can be considered as the starting point of a Natural Language Generation System. The methodology is evaluated in two case-studies, one for linearly evolving events (descriptions of football matches) and another one for non-linearly evolving events (terrorist incidents involving hostages). In both cases we evaluate the results produced by our computational systems.Comment: 45 pages, 6 figures. To appear in the Journal of Intelligent Information System

Depth-dependent ordering, two-length-scale phenomena and crossover behavior in a crystal featuring a skin-layer with defects

Structural defects in a crystal are responsible for the "two length-scale" behavior, in which a sharp central peak is superimposed over a broad peak in critical diffuse X-ray scattering. We have previously measured the scaling behavior of the central peak by scattering from a near-surface region of a V2H crystal, which has a first-order transition in the bulk. As the temperature is lowered toward the critical temperature, a crossover in critical behavior is seen, with the temperature range nearest to the critical point being characterized by mean field exponents. Near the transition, a small two-phase coexistence region is observed. The values of transition and crossover temperatures decay with depth. An explanation of these experimental results is here proposed by means of a theory in which edge dislocations in the near-surface region occur in walls oriented in the two directions normal to the surface. The strain caused by the dislocation lines causes the ordering in the crystal to occur as growth of roughly cylindrically shaped regions. After the regions have reached a certain size, the crossover in the critical behavior occurs, and mean field behavior prevails. At a still lower temperature, the rest of the material between the cylindrical regions orders via a weak first-order transition.Comment: 12 pages, 8 figure

Hole motion in the Ising antiferromagnet: an application of the recursion method

We study hole motion in the Ising antiferromagnet using the recursion method. Using the retraceable path approximation we find the hole's Green's function as well as its wavefunction for arbitrary values of $t/J_z$. The effect of small transverse interaction also is taken into account. Our results provide some additional insight into the self-consistent Born approximation.Comment: 8 pages, RevTex, no figures. Accepted for publication in Phys.Rev.