An Algebraic Method to Compute the Critical Points of the Distance Function Between Two Keplerian Orbits

We describe an efficient algorithm to compute all the critical points of the distance function between two Keplerian orbits (either bounded or unbounded) with a common focus. The critical values of this function are important for different purposes, for example to evaluate the risk of collisions of asteroids or comets with the Solar system planets. Our algorithm is based on the algebraic elimination theory: through the computation of the resultant of two bivariate polynomials, we find a 16th degree univariate polynomial whose real roots give us one component of the critical points. We discuss also some degenerate cases and show several examples, involving the orbits of the known asteroids and comets.      

Magnetostratigraphic dating of an intensification of glacial activity in the southern Italian Alps during Marine Isotope Stage 22

We applied magnetostratigraphy and mammal biostratigraphy to date climate-sensitive pollen cycles and lithostratigraphic units of the Pliocene-Pleistocene Leffe sedimentary succession from the Southern Alps, Italy. The Leffe section was correlated to additional sections (Casnigo, Fornaci di Ranica, and Pianengo) to construct a stratigraphic network along a common fluviatile system (the Serio River) sourced in the Southern Alps and flowing southward into the Po River Basin. We obtained a coherent scenario of climate variability for the last ∼ 2 Myr. At Leffe, lacustrine deposition commenced during the Olduvai Normal Subchron (1.94-1.78 Ma) and lasted up to a chronologic level compatible with Marine Isotope Stage (MIS) 22 (0.87 Ma). Pollen analysis revealed that climate varied cyclically from warm-temperate to cool during this time interval, but never as cold as during glacial intervals. At around MIS 22, climate cooled globally. Gravels, attributed to high-energy braided river systems fed locally by alluvial fans, prograded from the Serio River catchment area over the Leffe Basin and toward the Po Plain in response to a generalized event of vegetation withdrawal and enhanced physical erosion. At this time, Alpine valley glaciers reached their first maximum southward expansion with glacier fronts located at only ∼ 5 km upstream from Leffe.     

Models of dynamic coronal loops

This paper reviews the basic ideas underlying one-dimensional fluid dynamic models of coronal loops and presents some of their most recent applications. These models are an important theoretical support to explore the new scenario provided by the data of Yohkoh, SOHO, and TRACE, and are useful to interpret observations, when supplemented by appropriate spectral synthesis codes. Possible developments are also discussed.     

Plankton-Derived Resting Stages in Marine Coastal Sediments along the Salento Peninsula (Apulia, South-Eastern Italy)

Abstract. An oceanographic survey was carried out along the Salento Peninsula in March 2000. Resting stages of plankton were searched for in coastal sediments to study the microplankton composition in addition to the classical analysis of active stages in the water column. A total of 215 taxa were recognised, 149 as active stages in the water column and 74 as resting stages in the sediments. Cysts were widely distributed and at Brindisi and Alimini their abundance was higher than elsewhere. A general trend was observed with resting stage abundance, species richness and diversity in the sediments: all three decreased with distance from the coast. The integrated water/sediments approach used in this study allowed us to collect 37 species (mainly as resting stages) new for the studied area.     

High‐pressure mineral assemblage in granitic rocks from continental units,Alpine Corsica,France

The Popolasca–Francardo area of northern Corsica contains an assemblage of continental tectonic units affected by an Alpine deformation. In one of these units, Unit II, previously regarded as weakly metamorphosed, a metamorphic mineral assemblage characterized by sodic amphibole, phengite, quartz, albite and epidote has been found in an aplite dyke that cuts the dominant granitoids. Peak‐metamorphic temperature and pressure conditions of 300–370°C and 0.50–0.80 GPa, respectively, have been determined. This finding indicates that a continuous belt of continental slices, characterized by high‐pressure, low‐temperature metamorphism of Tertiary age, extends from the Tenda Massif in the north to the Corte area in the south, thus placing additional constraints on the tectonic evolution of Alpine Corsica. Copyright © 2005 John Wiley & Sons, Ltd.     

Assessment of global wave models on regular and unstructured grids using the Unresolved Obstacles Source Term

Ocean Dynamics - The Unresolved Obstacles Source Term (UOST) is a general methodology for parameterizing the dissipative effects of subscale islands, cliffs, and other unresolved features in ocean...