Interpolating point spread function anisotropy

Planned wide-field weak lensing surveys are expected to reduce the statistical errors on the shear field to unprecedented levels. In contrast, systematic errors like those induced by the convolution with the point spread function (PSF) will not benefit from that scaling effect and will require very accurate modeling and correction. While numerous methods have been devised to carry out the PSF correction itself, modeling of the PSF shape and its spatial variations across the instrument field of view has, so far, attracted much less attention. This step is nevertheless crucial because the PSF is only known at star positions while the correction has to be performed at any position on the sky. A reliable interpolation scheme is therefore mandatory and a popular approach has been to use low-order bivariate polynomials. In the present paper, we evaluate four other classical spatial interpolation methods based on splines (B-splines), inverse distance weighting (IDW), radial basis functions (RBF) and ordinary Kriging (OK). These methods are tested on the Star-challenge part of the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) simulated data and are compared with the classical polynomial fitting (Polyfit). We also test all our interpolation methods independently of the way the PSF is modeled, by interpolating the GREAT10 star fields themselves (i.e., the PSF parameters are known exactly at star positions). We find in that case RBF to be the clear winner, closely followed by the other local methods, IDW and OK. The global methods, Polyfit and B-splines, are largely behind, especially in fields with (ground-based) turbulent PSFs. In fields with non-turbulent PSFs, all interpolators reach a variance on PSF systematics $\sigma_{sys}^2$ better than the $1\times10^{-7}$ upper bound expected by future space-based surveys, with the local interpolators performing better than the global ones

On the adhesion of particles to a cell layer under flow

The non-specific adhesion of spherical particles to a cell substrate is analyzed in a parallel plate flow chamber, addressing the effect of the particle size. Differently from other experiments, the total volume of the injected particles has been fixed, rather than the total number of particles, as the diameter d of the particles is changed from 500 nm up to 10 $\mu$m. From the analysis of the experimental data, simple and instructive scaling adhesion laws have been derived showing that (i) the number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d^(-1.7) ; and consequently (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d^(+1.3). These results are of importance in the "rational design" of nanoparticles for drug delivery and biomedical imaging.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Testing baryon-induced core formation in Λ\LambdaCDM: A comparison of the DC14 and coreNFW dark matter halo models on galaxy rotation curves

Recent cosmological hydrodynamical simulations suggest that baryonic processes, and in particular supernova feedback after bursts of star formation, can alter the structure of dark matter haloes and transform primordial cusps into shallower cores. To assess whether this mechanism offers a solution to the cusp-core controversy, simulated haloes must be compared to real dark matter haloes inferred from galaxy rotation curves. For this purpose, two new dark matter density profiles were recently derived from simulations of galaxies in complementary mass ranges: the DC14 halo ($10^{10} < M_{\text{halo}}/M_{\odot} < 8 \times 10^{11}$) and the coreNFW halo ($10^{7} < M_{\text{halo}}/M_{\odot} < 10^{9}$). Both models have individually been found to give good fits to observed rotation curves. For the DC14 model, however, the agreement of the predicted halo properties with cosmological scaling relations was confirmed by one study, but strongly refuted by another. A next question is whether the two models converge to the same solution in the mass range where both should be appropriate. To investigate this, we tested the DC14 and cNFW halo models on the rotation curves of a selection of galaxies with halo masses in the range $4 \times 10^{9}$ - $7 \times 10^{10}$ $M_{\odot}$. We further applied the DC14 model to a set of rotation curves at higher halo masses, up to $9 \times 10^{11}$ $M_{\odot}$, to verify the agreement with the cosmological scaling relations. We find that both models are generally able to reproduce the observed rotation curves, in line with earlier results, and the predicted dark matter haloes are consistent with the cosmological $c-M_{\text{halo}}$ and $M_{*}-M_{\text{halo}}$ relations. The DC14 and cNFW models are also in fairly good agreement with each other, even though DC14 tends to predict slightly less extended cores and somewhat more concentrated haloes than cNFW.Comment: 19 pages, 12 figures, accepted for publication in A&

A fluctuation theorem in a random environment

A simple class of chaotic systems in a random environment is considered and the fluctuation theorem is extended under the assumption of reversibility.Comment: 9 page

First results of systematic studies done with different types of Silicon Photomultipliers

The presented results are obtained during the first steps taken in order to develop a setup and measurement procedures which allow to compare properties of diverse kinds of silicon photomultipliers. The response to low-intensity light was studied for silicon photomultipliers produced by CPTA (Russia), Hamamatsu (Japan), ITC-irst (Italy) and SensL (Ireland).Comment: 3 pages, 3 figures, proceedings of the Internationa Linear Collider Workshop LCWS2007, Hamburg, German

Gallbladder cancer: South American experience

Large differences in terms of incidence and mortality due to gallbladder cancer (GBC) have been reported worldwide. Moreover, it seems that GBC has unique characteristics in South America. We surveyed the literature looking for information about the epidemiology, basic and translational research, and clinical trials performed in South America in order to critically analyze the magnitude of this health problem in the region. Compared to other geographic areas, age-standardized mortality rates (ASMR) for GBC in women are very high, particularly in many western areas of South America. Genetic, as well as dietary and environmental factors likely contribute to the pathogenesis of this disease in the area. Compared to other regions the profile of abnormalities of key genes such as KRAS and TP53 in GBC seems to slightly differ in South America, while the clinical behavior appears to be similar with a median overall survival (OS) of 6.5 to 8 months in advanced GBC. In contrast to Europe and USA, prophylactic cholecystectomy is a common practice in western areas of South America. GBC particularly affects women in South America, and represents a significant public health problem. It appears to have peculiarities that pose an urgent need for additional research aimed to discover risk factors, molecular events associated with its development and new treatment options for this lethal disease.Fil: Arroyo, Gerardo F.. Intergrupo Latinoamericano de Oncología Gastrointestinal; ArgentinaFil: Gentile, Alberto. Provincia de Salta. Ministerio de Salud Pública; ArgentinaFil: Parada, Luis Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Patología Experimental. Universidad Nacional de Salta. Facultad de Ciencias de la Salud. Instituto de Patología Experimental; Argentin

Resummation of perturbation series and reducibility for Bryuno skew-product flows

We consider skew-product systems on T^d x SL(2,R) for Bryuno base flows close to constant coefficients, depending on a parameter, in any dimension d, and we prove reducibility for a large measure set of values of the parameter. The proof is based on a resummation procedure of the formal power series for the conjugation, and uses techniques of renormalisation group in quantum field theory.Comment: 30 pages, 12 figure

Alle radici della mentalità tecnologica: L'uomo tolemaico di Sergio Cotta.

Veinticinco aitos despues de su publicacion, se analiza en profundidad el texto de Sergio Cotta, L'uomo tolemaico, hasta llegar a la conclusion de que resulta plenamente actual. Y en efecto, el subjetivismo, la hipertrofia del yo -raices ultimas de la sociedad tecnologica, en el diagnostico/denuncia de Cotta-, parecen haberse difimdido y radicalizado en nuestros dias. Tal estado de cosas exige una radical y autentica metanoia: no es la ciencia la que redime al hombre, sino solo el amor; un amor incondicionado y no sometido a la muerte

The use of the McIlwain L-parameter to estimate cosmic ray vertical cutoff rigidities for different epochs of the geomagnetic field

Secular changes in the geomagnetic field between 1955 and 1980 have been large enough to produce significant differences in both the verical cutoff rigidities and in the L-value for a specified position. A useful relationship employing the McIlwain L-parameter to estimate vertical cutoff rigidities has been derived for the twenty-five year period