A self-sustaining nonlinear dynamo process in Keplerian shear flows

A three-dimensional nonlinear dynamo process is identified in rotating plane Couette flow in the Keplerian regime. It is analogous to the hydrodynamic self-sustaining process in non-rotating shear flows and relies on the magneto-rotational instability of a toroidal magnetic field. Steady nonlinear solutions are computed numerically for a wide range of magnetic Reynolds numbers but are restricted to low Reynolds numbers. This process may be important to explain the sustenance of coherent fields and turbulent motions in Keplerian accretion disks, where all its basic ingredients are present.Comment: 4 pages, 7 figures, accepted for publication in Physical Review Letter

Thermal Conductivity and Chiral Critical Point in Heavy Ion Collisions

Background: Quantum Chromodynamics is expected to have a phase transition in the same static universality class as the 3D Ising model and the liquid-gas phase transition. The properties of the equation of state, the transport coefficients, and especially the location of the critical point are under intense theoretical investigation. Some experiments are underway, and many more are planned, at high energy heavy ion accelerators. Purpose: Develop a model of the thermal conductivity, which diverges at the critical point, and use it to study the impact of hydrodynamic fluctuations on observables in high energy heavy ion collisions. Methods: We apply mode coupling theory, together with a previously developed model of the free energy that incorporates the critical exponents and amplitudes, to construct a model of the thermal conductivity in the vicinity of the critical point. The effect of the thermal conductivity on correlation functions in heavy ion collisions is studied in a boost invariant hydrodynamic model via fluctuations, or noise. Results: We find that the closer a thermodynamic trajectory comes to the critical point the greater is the magnitude of the fluctuations in thermodynamic variables and in the 2-particle correlation functions in momentum space. Conclusions: It may be possible to discern the existence of a critical point, its location, and thermodynamic and transport properties near to it in heavy ion collisions using the methods developed here.Comment: 36 pages, 8 figures. Version published in Phys.Rev.C86, 054911 (2012). It contains some minor improvements with respect to v1: further clarifications, small changes on figures and two extra reference

Mapping the Upper Subsurface of MARS Using Radar Polarimetry

Future human exploration of Mars will require detailed knowledge of the surface and upper several meters of the subsurface in potential landing sites. Likewise, many of the Planetary Science Decadal Survey science goals, such as understanding the history of Mars climate change, determining how the surface was altered through processes like volcanism and fluvial activity, and locating regions that may have been hospitable to life in the past, would be significantly advanced through mapping of the upper meters of the surface. Synthetic aperture radar (SAR) is the only remote sensing technique capable of penetrating through meters of material and imaging buried surfaces at high (meters to tens-of-meters) spatial resolution. SAR is capable of mapping the boundaries of buried units and radar polarimetry can provide quantitative information about the roughness of surface and subsurface units, depth of burial of stratigraphic units, and density of materials. Orbital SAR systems can obtain broad coverage at a spatial scale relevant to human and robotic surface operations. A polarimetric SAR system would greatly increase the safety and utility of future landed systems including sample caching

Metodología para Detección de Características Faciales con Fines de Reconocimiento de Emociones

Se cree que la detección de emociones podrá llevar a determinar el estado de _animo de una persona e incluso un posible fraude. La detección de rasgos faciales claves para la detección de una emoción son de fácil reconocimiento para los humanos, pero la dificultad crece cuando se realiza por medio de software. Por este motivo, la presente investigación aborda el problema de detección mediante varias técnicas, identificando una en especial basada en las proporciones _áureas la cual robustece la detección de rasgos faciales y por consiguiente la detección de la emoción; guardando siempre unas medidas de incertidumbre racionales.It is believed that the detection of emotions could lead to determine the mood of a person or even a possible fraud. The detection of key facial features to detect emotions are of easy recognition for humans, but the diffculty increases when is done by software. For this reason, this investigation addresses the problem of detection of emotions through several techniques, identifying one in particular based on the golden proportions, which strengthens the detection of facial features and therefore the detection of emotion, keeping rational measures of uncertainty

Use of soda lime glass waste as silica supplier in fly ash based geopolymers

Geopolymers have been primarily proposed for the construction industry as a substitute for Portland cement considering the lower CO2 emissions associated with their production. The relatively high compressive strength and chemical inertness of geopolymers, in addition to the possibility to incorporate in the network hazardous waste materials, increase the current interest in this technology. Geopolymers are usually composed of an aluminosilicate source activated with a solution of sodium silicate and sodium hydroxide. The present study evaluates the feasibility of using waste glass as silica source instead of water glass in geopolymer production, using sodium hydroxide as the only non-waste material.The samples were developed changing the SiO2/Al2O3 molar ratio and the molarity of the sodium hydroxide solution. Fig. 1 shows that the compressive strength tends to rise as the molarity of the solution as well as the SiO2/Al2O3 molar ratio increase. The compressive strength values, around 45 MPa, are comparable to those of traditional Portland cement and they are remarkable considering the high amount of waste glass (70% wt.) incorporated in the matrix . SEM pictures demonstrated the formation of a compact matrix indicating the high reaction degree of the raw materials. Please click Additional Files below to see the full abstract