A Secular Relativistic Model For Solar System's Numerical Simulations

Using Gauss' averaged equations, we compute the secular relativistic effects generated by the Sun on the argument of the perihelion and the mean anomaly of an orbit. Then we test different alternative simpler models that have been proposed to reproduce the secular relativistic effects in the orbital elements. Generally, models introduce artificial perturbations that are velocity-independent but that depend on the heliocentric distance. If these perturbations are set as an impulse in a constant timestep integrator, when the particle approaches perihelion the generated impulse could be very strong and badly sampled, originating a spurious orbital evolution. In order to overcome this setback, we propose two new models based on a constant, distance-independent, perturbation. With these models we obtain the correct secular drift in the argument of perihelion and the expected secular orbital evolution is reproduced. We also discuss with some detail the secular effect generated on the mean anomaly by different models.Comment: This work is an expanded version of Venturini and Gallardo (2010

Stellar laboratories. V. The Xe VI ultraviolet spectrum and the xenon abundance in the hot DO-type white dwarf RE0503-289

For the spectral analysis of spectra of hot stars with a high resolution and high signal-to-noise ratio (S/N), advanced non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that are used for their calculation. Reliable Xe VI oscillator strengths are used to identify Xe lines in the ultraviolet spectrum of the DO-type white dwarf RE0503-289 and to determine its photospheric Xe abundance. We publish newly calculated oscillator strengths that are based on a recently measured Xe VI laboratory line spectrum. These strengths were used to consider their radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models to analyze Xe VI lines exhibited in high-resolution and high S/N UV observations of RE0503-289. We identify three hitherto unknown Xe VI lines in the ultraviolet spectrum of RE0503-289 and confirm the previously measured photospheric Xe abundance of this white dwarf (log Xe = -4.2 +/- 0.6). Reliable measurements and calculations of atomic data are prerequisite for stellar-atmosphere modeling. Observed Xe VI line profiles in the ultraviolet spectrum of the white dwarf RE0503-289 were well reproduced with the newly calculated Xe VI oscillator strengths.Comment: 3 pages, 4 figure

The mass-radius relationship from solar-type stars to terrestrial planets: a review

In this review, we summarize our present knowledge of the behaviour of the mass-radius relationship from solar-type stars down to terrestrial planets, across the regime of substellar objects, brown dwarfs and giant planets. Particular attention is paid to the identification of the main physical properties or mechanisms responsible for this behaviour. Indeed, understanding the mechanical structure of an object provides valuable information about its internal structure, composition and heat content as well as its formation history. Although the general description of these properties is reasonably well mastered, disagreement between theory and observation in certain cases points to some missing physics in our present modelling of at least some of these objects. The mass-radius relationship in the overlaping domain between giant planets and low-mass brown dwarfs is shown to represent a powerful diagnostic to distinguish between these two different populations and shows once again that the present IAU distinction between these two populations at a given mass has no valid foundation.Comment: Cool Stars, Stellar Systems and the Sun 15, invited revie

Time boundary terms and Dirac constraints

Time boundary terms usually added to action principles are systematically handled in the framework of Dirac's canonical analysis. The procedure begins with the introduction of the boundary term into the integral Hamiltonian action and then the resulting action is interpreted as a Lagrangian one to which Dirac's method is applied. Once the general theory is developed, the current procedure is implemented and illustrated in various examples which are originally endowed with different types of constraints.Comment: 12 page

Range extension of Sanopus reticulatus (Teleostei: Batrachoididae) in the Yucatán Peninsula

AbstractThe geographic range of Sanopus reticulatus Collette, 1983 in the Yucatán Peninsula is extended about 75km southwest to Celestún and about 200km to Las Coloradas. During the periods of algal blooms in Telchac and Las Coloradas and specific sampling in Celestún, Yucatán, on August 14 and September 26 and 27, 2015, 10 specimens were collected, proving that this species has a distribution all along the Yucatán state coast

Some applications of quasi-velocities in optimal control

In this paper we study optimal control problems for nonholonomic systems defined on Lie algebroids by using quasi-velocities. We consider both kinematic, i.e. systems whose cost functional depends only on position and velocities, and dynamic optimal control problems, i.e. systems whose cost functional depends also on accelerations. The formulation of the problem directly at the level of Lie algebroids turns out to be the correct framework to explain in detail similar results appeared recently (Maruskin and Bloch, 2007). We also provide several examples to illustrate our construction.Comment: Revtex 4.1, 20 pages. To appear in Int. J. Geom. Meth. Modern Physic

Magnetization in AIIIBV semiconductor heterostructures with the depletion layer of manganese

The magnetic moment and magnetization in GaAs/Ga$_{0.84}$In$_{0.16}$As/GaAs heterostructures with Mn deluted in GaAs cover layers and with atomically controlled Mn $\delta$-layer thicknesses near GaInAs-quantum well ($\sim$3 nm) in temperature range T=(1.8-300)K in magnetic field up to 50 kOe have been investigated. The mass magnetization all of the samples of GaAs/Ga$_{0.84}$In$_{0.16}$As/GaAs with Mn increases with the increasing of the magnetic field that pointed out on the presence of low-dimensional ferromagnetism in the manganese depletion layer of GaAs based structures. It has been estimated the manganese content threshold at which the ferromagnetic ordering was found.Comment: 8 pages, 3 figure

Crystal Structures of [Fe]-Hydrogenase from Methanolacinia paynteri Suggest a Path of the FeGP-Cofactor Incorporation Process

[Fe]-hydrogenase (Hmd) catalyzes the reversible heterolytic cleavage of H-2, and hydride transfer to methenyl-tetrahydromethanopterin (methenyl-H4MPT+). The iron-guanylylpyridinol (FeGP) cofactor, the prosthetic group of Hmd, can be extracted from the holoenzyme and inserted back into the protein. Here, we report the crystal structure of an asymmetric homodimer of Hmd fromMethanolacinia paynteri(pHmd), which was composed of one monomer in the open conformation with the FeGP cofactor (holo-form) and a second monomer in the closed conformation without the cofactor (apo-form). In addition, we report the symmetric pHmd-homodimer structure in complex with guanosine monophosphate (GMP) or guanylylpyridinol (GP), in which each ligand was bound to the protein, where the GMP moiety of the FeGP-cofactor is bound in the holo-form. Binding of GMP and GP modified the local protein structure but did not induce the open conformation. The amino-group of the Lys150 appears to interact with the 2-hydroxy group of pyridinol ring in the pHmd-GP complex, which is not the case in the structure of the pHmd-FeGP complex. Lys150Ala mutation decreased the reconstitution rate of the active enzyme with the FeGP cofactor at the physiological pH. These results suggest that Lys150 might be involved in the FeGP-cofactor incorporation into the Hmd protein in vivo