Discrete Approximations of a Controlled Sweeping Process

The paper is devoted to the study of a new class of optimal control problems governed by the classical Moreau sweeping process with the new feature that the polyhe- dral moving set is not fixed while controlled by time-dependent functions. The dynamics of such problems is described by dissipative non-Lipschitzian differential inclusions with state constraints of equality and inequality types. It makes challenging and difficult their anal- ysis and optimization. In this paper we establish some existence results for the sweeping process under consideration and develop the method of discrete approximations that allows us to strongly approximate, in the W^{1,2} topology, optimal solutions of the continuous-type sweeping process by their discrete counterparts

Feasibility experiments on time-resolved fluorosensing applied to oil slicks

The introduction of time resolved observations can provide a very penetrating tool in the practice of laser fluorosensing. The investigations have demonstrated a relevance of multispectral, time resolved analysis for oil fingerprinting. By comparative studies on a variety of crude oils and their most significant fractions, it was found that the process of time decay in a composite oil is characterized by a few steps, which are associated with specific components in the medium light range. The average decay times of these pure fractions are markedly differentiated as to absolute values and spectral spread; as a consequence, the corresponding parameters in the resultant crude are quite sensitive to the particular mixture of these components. Measurements of the time response give then a finer discrimination between oil classes, depending on the relative content of certain fractions. Experiments were pursued with an improved fluorosensor facility, in order to test the application of time resolved fluorosensing to remote samples on water

Optical Spectroscopy of X-Mega targets in the Carina Nebula - VI. FO 15: a new O-Type double-lined eclipsing binary

We report the discovery of a new O-type double-lined spectroscopic binary with a short orbital period of 1.4 days. We find the primary component of this binary, FO 15, to have an approximate spectral type O5.5Vz, i.e. a Zero-Age-Main-Sequence star. The secondary appears to be of spectral type O9.5V. We have performed a numerical model fit to the public ASAS photometry, which shows that FO 15 is also an eclipsing binary. We find an orbital inclination of ~ 80 deg. From a simultaneous light-curve and radial velocity solution we find the masses and radii of the two components to be 30 +/- 1 and 16 +/- 1 solar masses and 7.5 +/- 0.5 and 5.3 +/- 0.5 solar radii. These radii, and hence also the luminosities, are smaller than those of normal O-type stars, but similar to recently born ZAMS O-type stars. The absolute magnitudes derived from our analysis locate FO 15 at the same distance as Eta Carinae. From Chandra and XMM X-ray images we also find that there are two close X-ray sources, one coincident with FO 15 and another one without optical counterpart. This latter seems to be a highly variable source, presumably due to a pre-main-sequence stellar neighbour of FO 15.Comment: 11 pages, 9 figures, 3 tables. Accepted for publication in MNRAS. Higher resolution version available at http://lilen.fcaglp.unlp.edu.ar/papers2006.htm

Late Palaeozoic lithostratigraphy of the Andean Precordillera revisited (San Juan Province, Argentina)

New data on some neopalaeozoic lithostratigraphic units of the central sector of the Argentinean Precordillera are presented. The western Precordillera displays occasional outcrops of siliciclastic rocks of the Late Palaeozoic. These rocks are separated by two main unconformi­ties related to the development of the Chanic (Upper Devonian-early Carboniferous) and Gondwanan (late Carboniferous-early Permian) orogens. A major unconformity marks the beginning of the Andean cycle in middle Permian times. The Del Ratón Formation (800 m) in the studied area is made up of conglomerates and can be divided into two units. The basal part (Lower Member) was deposited in a fjord environment. The Upper Member was generated by an alluvial system that was mainly dominated by upper flow-regime plane beds, whereas its uppermost part accumulated in a fan delta setting. The clast provenance and the main palaeocurrents suggest the existence of a significant topographic high to the W and NW of the present outcrops. The El Planchón Formation (1400 m) is mainly composed of shales and sandstones as a result of sedimentation in a deep-sea fan environment. These lutite-dominated materials graded laterally north­wards into conglomerates in a glacial setting. The Del Ratón and El Planchón formations of the Lower Carboniferous correspond to the synorogenic Chanic sedimentation (Chanic foreland basin). Thereafter, the stratigraphic succession underwent deformation which led to its prolonged subaerial exposure and rubefaction. In Permian times, a marine transgression gave rise to the Del Salto Formation (600 m), which is constituted by beach deposits with some aeolian reworking and which lies unconformably over the Lower Carboniferous rocks. Conglomerates (Quebrada del Alumbre Formation, 100 m) produced by an alluvial system prograded episodically into coastal areas. The Escombrera Formation (350 m) is composed of beach deposits prograding seawards. This formation probably represents the end of the Palaeozoic sedimentary record. Thereafter, a playa-lake and an alluvial fan system were generated (Quebrada de la Arena Formation). This unit (750 m) was the last infill of the Gondwanan retroarc foreland, the total thickness of which was about 4000 m.Se presentan nuevos datos sobre las unidades neopaleozoicas aflorantes en la parte occidental de la Precordillera andina. Esas unidades litoestratigráficas estan separadas por dos discordancias angulares principales asociadas al desarrollo de las orogenias Chánica (Devónico tardío-Carbonífero temprano) y Gondwánica (Carbonífero tardío-Pérmico temprano) respectivamente. Otra nueva discordancia sugiere el inicio del ciclo andino durante el Pérmico medio. La Formación Del Ratón (800 m) está constituida principalmente por conglomerados y puede dividirse en dos unidades de rango menor: la parte basal y la parte superior respectivamente. La parte basal (Miembro inferior) fue acumulada en un fiordo. La parte superior (Miembro superior) fue generada en un sistema alluvial dominado predominantemente por la acumulación de capas planas de alto régimen de flujo, mientras que la parte más alta fue depositada en un entorno de abanico deltaico (fandelta). La procedencia de los clastos y las paleocorrientes principales indican la presencia de un relieve topográfico alto y significativo, situado al O y NO de los afloramientos actuales.La Formación El Planchón (1400 m) constituida principalmente por lutitas y areniscas fue acumulada en un contexto de abanico submarino (deep-sea fan). Estos materiales predominantemente lutíticos pasan lateralmente hacia el norte a conglomerados acumulados en un ambiente sedimentario glacial. Las Formaciones Del Ratón y El Planchón corresponden a la sedimentación sinorogénica Chánica (cuenca de antepaís chánica). Posteriormente, la sucesión estratigráfica sufrió una deformación que dió lugar a una prolongada exposición subaérea y su consiguiente rubefacción. Durante el Pérmico, una transgresión marina produjo la acumulación de la Formación Del Salto (600 m), que está constituída por depósitos de playa con algún retrabajamiento eólico y que recubre discordantemente los materiales del Carbonífero inferior. Un sistema aluvial conglomerático (Formación Quebrada del Alumbre 100 m) pogradó episódicamente sobre las zonas costeras. La Formación Escombrera (350 m), que está constituída por materiales arenosos coste-ros progradantes hacia el mar, representa, muy probablemente, el final del registro sedimentario paleozoico en esta zona. Posteriormente se generó otra discordancia sobre la que se acumularon materiales arenosos en un contexto de cursos fluviales trenzados sobre los que se disponen materiales lutíticos acumulados en una ciénaga (playa-lake) que gradan, primero a cursos trenzados, luego a cursos sinousos y finalmente a abanicos aluviales (Formación Quebrada de la Arena). Esta unidad (750 m) corresponde al último relleno sedimentario de la cuenca Gondwánica de retroarco, cuya potencia es del orden de unos 4000 m.Fil: Colombo, F.. Universidad de Barcelona; EspañaFil: Limarino, Carlos Oscar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; ArgentinaFil: Spalletti, Luis Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Busquets, P. Universidad de Barcelona; EspañaFil: Cardo, R.. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; ArgentinaFil: Mendez Bedia, I. Universidad de Oviedo; EspañaFil: Heredia, N.. Instituto Geológico y Minero de España; Españ

On the oscillations in Mercury's obliquity

One major objective of MESSENGER and BepiColombo spatial missions is to accurately measure Mercury's rotation and its obliquity in order to obtain constraints on internal structure of the planet. Which is the obliquity's dynamical behavior deriving from a complete spin-orbit motion of Mercury simultaneously integrated with planetary interactions? We have used our SONYR model integrating the spin-orbit N-body problem applied to the solar System (Sun and planets). For lack of current accurate observations or ephemerides of Mercury's rotation, and therefore for lack of valid initial conditions for a numerical integration, we have built an original method for finding the libration center of the spin-orbit system and, as a consequence, for avoiding arbitrary amplitudes in librations of the spin-orbit motion as well as in Mercury's obliquity. The method has been carried out in two cases: (1) the spin-orbit motion of Mercury in the 2-body problem case (Sun-Mercury) where an uniform precession of the Keplerian orbital plane is kinematically added at a fixed inclination (S2K case), (2) the spin-orbit motion of Mercury in the N-body problem case (Sun and planets) (Sn case). We find that the remaining amplitude of the oscillations in the Sn case is one order of magnitude larger than in the S2K case, namely 4 versus 0.4 arcseconds (peak-to-peak). The mean obliquity is also larger, namely 1.98 versus 1.80 arcminutes, for a difference of 10.8 arcseconds. These theoretical results are in a good agreement with recent radar observations but it is not excluded that it should be possible to push farther the convergence process by drawing nearer still more precisely to the libration center.Comment: 30 pages, 3 tables, 8 figures, accepted to Icarus (26 Jul 2007