Lateral downflows in sunspot penumbral filaments and their temporal evolution

We study the temporal evolution of downflows observed at the lateral edges of penumbral filaments in a sunspot located very close to the disk center. Our analysis is based on a sequence of nearly diffraction-limited scans of the Fe I 617.3 nm line taken with the CRisp Imaging Spectro-Polarimeter at the Swedish 1 m Solar Telescope. We compute Dopplergrams from the observed intensity profiles using line bisectors and filter the resulting velocity maps for subsonic oscillations. Lateral downflows appear everywhere in the center-side penumbra as small, weak patches of redshifts next to or along the edges of blueshifted flow channels. These patches have an intermittent life and undergo mergings and fragmentations quite frequently. The lateral downflows move together with the hosting filaments and react to their shape variations, very much resembling the evolution of granular convection in the quiet Sun. There is a good relation between brightness and velocity of the flow structures in the center-side penumbra, with downflows being darker than upflows on average, which is again reminiscent of quiet Sun convection. These results point to the existence of overturning convection in sunspot penumbrae, with elongated cells forming filaments where the flow is upward but very inclined, and weak lateral downward flows. In general, the circular polarization profiles emerging from the lateral downflows do not show sign reversals, although sometimes we detect three-lobed profiles which are suggestive of opposite magnetic polarities in the pixel.Comment: 16 pages, 15 figures. Accepted for publication in ApJ. Movies are available at http://spg.iaa.es/download

Time-Dependent Density-Functional Theory in Massively Parallel Computer Architectures: The Octopus Project

Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn–Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn–Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.Chemistry and Chemical Biolog

Three-dimensional Maxwellian extended Newtonian gravity and flat limit

In the present work we find novel Newtonian gravity models in three space-time dimensions. We first present a Maxwellian version of the extended Newtonian gravity, which is obtained as the non-relativistic limit of a particular U(1)-enlargement of an enhanced Maxwell Chern-Simons gravity. We show that the extended Newtonian gravity appears as a particular sub-case. Then, the introduction of a cosmological constant to the Maxwellian extended Newtonian theory is also explored. To this purpose, we consider the non-relativistic limit of an enlarged symmetry. An alternative method to obtain our results is presented by applying the semigroup expansion method to the enhanced Nappi-Witten algebra. The advantages of considering the Lie algebra expansion procedure is also discussed

Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps

Density-functional calculations of the phonon spectrum and electron-phonon coupling in MgB$_2$ are presented. The $E_{2g}$ phonons, which involve in-plane B displacements, couple strongly to the $p_{x,y}$ electronic bands. The isotropic electron-phonon coupling constant is calculated to be about 0.8. Allowing for different order parameters in different bands, the superconducting $\lambda$ in the clean limit is calculated to be significantly larger. The $E_{2g}$ phonons are strongly anharmonic, and the non-linear contribution to the coupling between the $E_{2g}$ modes and the p$_{x,y}$ bands is significant.Comment: 4 pages, 3 figure

Diets containing sea cucumber (Isostichopus badionotus) meals are hypocholesterolemic in young rats

Peer reviewedPublisher PD

Real-space grids and the Octopus code as tools for the development of new simulation approaches for electronic systems

Real-space grids are a powerful alternative for the simulation of electronic systems. One of the main advantages of the approach is the flexibility and simplicity of working directly in real space where the different fields are discretized on a grid, combined with competitive numerical performance and great potential for parallelization. These properties constitute a great advantage at the time of implementing and testing new physical models. Based on our experience with the Octopus code, in this article we discuss how the real-space approach has allowed for the recent development of new ideas for the simulation of electronic systems. Among these applications are approaches to calculate response properties, modeling of photoemission, optimal control of quantum systems, simulation of plasmonic systems, and the exact solution of the Schrödinger equation for low-dimensionality systems.</p

Efecto de aditivos sobre la coagulación y floculación en el tratamiento de aguas residuales

One of the main problems of oil processing plants of vegetable origin, is to return the water used in the whole process in the best possible state, therefore it is important to carry out studies to optimize the purification of those waters in the plants of wastewater (PTAR), try to improve the effectiveness of these plants without incurring a high cost that affects the final price of the products obtained in the vegetable oil processing plants, so in this work, it was proposed to evaluate the effect of coagulation and flocculation by substance additives in wastewater treatment. The activity of Aluminum Sulphate, which is the commonly used additive, was compared against an Annionic Polymer, as well as the substitution of hydrated lime by caustic soda, which allowed to compare the cost-production relation of good quality water. The results obtained indicate that despite the high costs of some reagents, the use of Aluminum Sulphate, allows a better breakdown of the emulsion, than the test Polymers.Uno de los principales problemas de las plantas procesadoras de aceites de origen vegetal, es la de reciclar el agua empleada durante el proceso en el mejor estado posible, por lo tanto es importante realizar estudios para optimizar la purificación de esas aguas en las plantas de aguas residuales (PTAR), tratar de mejorar la efectividad de estas plantas sin acarrear unalto costo que incida sobre el precio final de los productos que se obtienen en esas plantas, por lo que en este trabajo se propuso evaluar el efecto de la coagulación y floculación por aditivos químicos en el tratamiento de aguas residuales. Se comparó la actividad del Sulfato de Aluminio que es el aditivo comúnmente utilizado, contra un Polímero Aniónico, así como la sustitución de la cal hidratada por la soda cáustica, lo que permitió comparar la relacióncosto- producción de agua de buena calidad. Los resultados obtenidos, indican que, a pesar de los altos costos de algunos reactivos, la utilización del Sulfato de Aluminio permite una mejor ruptura de la emulsión, que los Polímeros de prueba