A Fast Splitting Method for efficient Split Bregman Iterations

In this paper we propose a new fast splitting algorithm to solve the Weighted Split Bregman minimization problem in the backward step of an accelerated Forward-Backward algorithm. Beside proving the convergence of the method, numerical tests, carried out on different imaging applications, prove the accuracy and computational efficiency of the proposed algorithm

A probabilistic approach to quantifying hydrologic thresholds regulating migration of adult Atlantic salmon into spawning streams

Acknowledgment Data to support this study are provided by the Marine Scotland Science Freshwater Laboratory (MSS-FL) and are available for free download on line [Glover and Malcolm, 2015a, 2015b].Peer reviewedPublisher PD

Long-term dynamics of Methone, Anthe and Pallene

We numerically investigate the long-term dynamics of the Saturn's small satellites Methone (S/2004 S1), Anthe (S/2007 S4) and Pallene (S/2004 S2). In our numerical integrations, these satellites are disturbed by non-spherical shape of Saturn and the six nearest regular satellites. The stability of the small bodies is studied here by analyzing long-term evolution of their orbital elements. We show that long-term evolution of Pallene is dictated by a quasi secular resonance involving the ascending nodes ($\Omega$) and longitudes of pericentric distances ($\varpi$) of Mimas (subscript 1) and Pallene (subscript 2), which critical argument is $\varpi_2-\varpi_1-\Omega_1+\Omega_2$. Long-term orbital evolution of Methone and Anthe are probably chaotic since: i) their orbits randomly cross the orbit of Mimas in time scales of thousands years); ii) numerical simulations involving both small satellites are strongly affected by small changes in the initial conditions.Comment: 9 pages; 4 figures. Submitted to Proceedings IAU Symposium No. S263, 200

Magnetic island evolution under the action of electron cyclotron current drive

The magnetic island evolution under the action of an externally current generated by electron cyclotron (ECCD) wave beams is studied using a reduced resistive magnetohydrodynamics (RRMHD) plasma model. We found interesting and somewhat unexpected features of the actual nonlinear 2-D evolution of the magnetic perturbation depending on the injection time of the radio frequency control. In particular in the linear phase of the magnetic island growth we observe that the complete annihilation of the island width is followed by a spatial phase shift of the island, referred as «flip»instability. On the other hand, a current drive deposition in the Rutherford regime can be accompained by the occurrence of a Kelvin-Helmholtz type shear flow instability, responsible for the onset of a plasma turbulent behavior

A dynamical and observational study of an unstable TNO: 59358 (1999CL158)

Context: The physical surface properties of a trans-Neptunian Object is believed to be mainly produced as a result of interplay between irradiation from different kinds of cosmic rays and collisions. Objects recently resurfaced by collisions are likely to have very different physical properties from those of the bulk population. In particular, pristine ices from the interior are expected to be present on the surface. A possible way to identify a trans-Neptunian object that has suffered a major collision is by investigating the lifetime of the orbit near its present location. If the lifetime is very short, a physical encounter is a possible way by which the TNO has evolved into such a short lived orbit. Aims: The goal of this investigation is to search for tracers of a young surface on objects with very short orbital lifetimes in the trans-Neptunian Belt. We are looking for any evidence that indicates that they reached their current unstable orbits through collisions. In particular, we have studied the case of 59358 (1999CL{158}), a trans-Neptunian object that currently has the most chaotic orbit in the Classical Belt. Methods: By numerically integration its orbit, we estimate that 59358 (1999CL{158}) has resided near its location for about 10 Myr. We have also obtained a near-infrared spectrum of 59358 (1999CL{158}) in the region between 1.43-1.96 microns using the near infrared imager and spectrograph, NIRI, at Gemini North 8-m telescope. These NIR observations are of the faintest and smallest TNO so far observed. Results: We present the results of the search of ice-bands, such as CH4 and H2O, having found evidence of the presence of the first mentioned molecule. Conclusions: The detection of methane implies that it must be an abundant component of this object. Methane is also evidence of a young surface, therefore we conclude that it is likely that 59358 (1999CL{158}) has experienced a recent collision or collisions. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina).Fil: Alvarez Candal, A.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; BrasilFil: Jones, D.. University Of London; Reino UnidoFil: Lazzaro, D.. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; BrasilFil: Williams, I. P.. University Of London; Reino UnidoFil: Melita, Mario Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin