Star Formation History in two fields of the Small Magellanic Cloud Bar

The Bar is the most productive region of the Small Magellanic Cloud in terms of star formation but also the least studied one. In this paper we investigate the star formation history of two fields located in the SW and in the NE portion of the Bar using two independent and well tested procedures applied to the color-magnitude diagrams of their stellar populations resolved by means of deep HST photometry. We find that the Bar experienced a negligible star formation activity in the first few Gyr, followed by a dramatic enhancement from 6 to 4 Gyr ago and a nearly constant activity since then. The two examined fields differ both in the rate of star formation and in the ratio of recent over past activity, but share the very low level of initial activity and its sudden increase around 5 Gyr ago. The striking similarity between the timing of the enhancement and the timing of the major episode in the Large Magellanic Cloud is suggestive of a close encounter triggering star formation.Comment: 30 pages, 22 figures, accepted for publication in Ap

Global Existence and Regularity for the 3D Stochastic Primitive Equations of the Ocean and Atmosphere with Multiplicative White Noise

The Primitive Equations are a basic model in the study of large scale Oceanic and Atmospheric dynamics. These systems form the analytical core of the most advanced General Circulation Models. For this reason and due to their challenging nonlinear and anisotropic structure the Primitive Equations have recently received considerable attention from the mathematical community. In view of the complex multi-scale nature of the earth's climate system, many uncertainties appear that should be accounted for in the basic dynamical models of atmospheric and oceanic processes. In the climate community stochastic methods have come into extensive use in this connection. For this reason there has appeared a need to further develop the foundations of nonlinear stochastic partial differential equations in connection with the Primitive Equations and more generally. In this work we study a stochastic version of the Primitive Equations. We establish the global existence of strong, pathwise solutions for these equations in dimension 3 for the case of a nonlinear multiplicative noise. The proof makes use of anisotropic estimates, $L^{p}_{t}L^{q}_{x}$ estimates on the pressure and stopping time arguments.Comment: To appear in Nonlinearit

Allometric length-weight relationships for benthic prey of aquatic wildlife in coastal marine habitats

We developed models to estimate the soft tissue content of benthic marine invertebrates that are prey for aquatic wildlife. Allometric regression models of tissue wet weight with shell length for 10 species of benthic invertebrates had r2 values ranging from 0.29 for hermit crabs Pagurus longicarpus to 0.98 for green crabs Carcinus maenas. As a class, bivalves had the highest r2 values (0.84) and crustaceans the lowest (0.48). Energy and nutrient content of soft tissue is also presented for the 10 benthic species. The energy content was lowest in crabs, and ranged within 2.20–4.71 kcal g-1 dry weight. Fat content was highly variable (range: 3.5–16.0%), and protein content ranged within 43.1–68.1% and was highest for shrimp Palaemonetes pugio. Comparison between classes of organisms of the amount of soft tissue per unit shell length showed that crustaceans yield five times more soft tissue per unit shell length than bivalves, and four times more than gastropods. The models we present use simple measures, such as the length of shell or wet weight of the entire animal, to quantitatively estimate the amount of available soft tissue in benthic prey that are usually consumed in total (with shell and soft tissue intact) but for which only the soft tissue is used for nutritional gain. This information can be combined with energy and nutrient content data to calculate energy or nutrient based carrying capacities that can help assess available resources for shorebirds, waterfowl and marine mammals

Structure and pressure drop of real and virtual metal wire meshes

An efficient mathematical model to virtually generate woven metal wire meshes is presented. The accuracy of this model is verified by the comparison of virtual structures with three-dimensional images of real meshes, which are produced via computer tomography. Virtual structures are generated for three types of metal wire meshes using only easy to measure parameters. For these geometries the velocity-dependent pressure drop is simulated and compared with measurements performed by the GKD - Gebr. Kufferath AG. The simulation results lie within the tolerances of the measurements. The generation of the structures and the numerical simulations were done at GKD using the Fraunhofer GeoDict software

The many faces of early-type dwarf galaxies

We present a study of 413 early-type dwarf (dE) galaxies in the Virgo Cluster with SDSS multicolour imaging. Several dE subclasses show systematic differences in shape, clustering properties, and stellar content. We find different colour-magnitude relations for nucleated and non-nucleated dEs, as well as for dE samples populating regions of different densitie