A Statistical Study of Photospheric Magnetic Field Changes During 75 Solar Flares

Abrupt and permanent changes of photospheric magnetic fields have been observed during solar flares. The changes seem to be linked to the reconfiguration of magnetic fields, but their origin is still unclear. We carried out a statistical analysis of permanent line-of-sight magnetic field ($B_{\rm LOS}$) changes during 18 X-, 37 M-, 19 C- and 1 B-class flares using data from Solar Dynamics Observatory/Helioseismic and Magnetic Imager. We investigated the properties of permanent changes, such as frequency, areas, and locations. We detected changes of $B_{\rm LOS}$ in 59/75 flares. We find that strong flares are more likely to show changes, with all flares $\ge$ M1.6 exhibiting them. For weaker flares, permanent changes are observed in 6/17 C-flares. 34.3\% of the permanent changes occurred in the penumbra and 18.9\% in the umbra. Parts of the penumbra appeared or disappeared in 23/75 flares. The area where permanent changes occur is larger for stronger flares. Strong flares also show a larger change of flux, but there is no dependence of the magnetic flux change on the heliocentric angle. The mean rate of change of flare-related magnetic field changes is 20.7 Mx cm$^{-2}$ min$^{-1}$. The number of permanent changes decays exponentially with distance from the polarity inversion line. The frequency of the strength of permanent changes decreases exponentially, and permanent changes up to 750 Mx cm$^{-2}$ were observed. We conclude that permanent magnetic field changes are a common phenomenon during flares, and future studies will clarify their relation to accelerated electrons, white light emission, and sunquakes to further investigate their origin.Comment: Piblished in Ap

On the bend number of circular-arc graphs as edge intersection graphs of paths on a grid

Golumbic, Lipshteyn and Stern \cite{Golumbic-epg} proved that every graph can be represented as the edge intersection graph of paths on a grid (EPG graph), i.e., one can associate with each vertex of the graph a nontrivial path on a rectangular grid such that two vertices are adjacent if and only if the corresponding paths share at least one edge of the grid. For a nonnegative integer $k$, $B_k$-EPG graphs are defined as EPG graphs admitting a model in which each path has at most $k$ bends. Circular-arc graphs are intersection graphs of open arcs of a circle. It is easy to see that every circular-arc graph is a $B_4$-EPG graph, by embedding the circle into a rectangle of the grid. In this paper, we prove that every circular-arc graph is $B_3$-EPG, and that there exist circular-arc graphs which are not $B_2$-EPG. If we restrict ourselves to rectangular representations (i.e., the union of the paths used in the model is contained in a rectangle of the grid), we obtain EPR (edge intersection of path in a rectangle) representations. We may define $B_k$-EPR graphs, $k\geq 0$, the same way as $B_k$-EPG graphs. Circular-arc graphs are clearly $B_4$-EPR graphs and we will show that there exist circular-arc graphs that are not $B_3$-EPR graphs. We also show that normal circular-arc graphs are $B_2$-EPR graphs and that there exist normal circular-arc graphs that are not $B_1$-EPR graphs. Finally, we characterize $B_1$-EPR graphs by a family of minimal forbidden induced subgraphs, and show that they form a subclass of normal Helly circular-arc graphs

Ensayo de arcillas modificadas con materia orgánica soluble para la eliminación de Cu y Zn

La contaminación por metales pesados es un tema de gran preocupación. Entre las diversas actividades que contribuyen a aumentar la presencia de metales pesados en el medio ambiente, se encuentra la agricultura. Por ejemplo, el uso de fertilizantes de tipo fosforados y algunos fungicidas incrementan la aparición Cu y Zn en aguas de zonas agrícolas e incluso residuales de la industria agroalimentaria. La eliminación de metales pesados mediante el uso de minerales de la arcilla tipo montmorillonita ha sido objeto de numerosos trabajos (Barbier et al., 2000) dada su alta capacidad de adsorción principalmente asociada a su capacidad de intercambio catiónico (CIC), fácil accesibilidad de su interlámina y a la presencia de grupos hidroxilos de los bordes de ruptura de la capa octaédrica.Este trabajo ha sido financiado con los proyectos de la Junta de Andalucía (P11-AGR-7400) y RECUPERA 2020 (MCINN_CSIC). E. Durán agradece la concesión de la Beca Predoctoral FPI asociada (P11-AGR-7400). A Fertiormont y a Spuny Morón por el material suministrado.Peer Reviewe

String Effects on Fermi--Dirac Correlation Measurements

We investigate some recent measurements of Fermi--Dirac correlations by the LEP collaborations indicating surprisingly small source radii for the production of baryons in $e^+e^-$-annihilation at the $Z^0$ peak. In the hadronization models there are besides the Fermi--Dirac correlation effect also a strong dynamical (anti-)correlation. We demonstrate that the extraction of the pure FD effect is highly dependent on a realistic Monte Carlo event generator, both for separation of those dynamical correlations which are not related to Fermi--Dirac statistics, and for corrections of the data and background subtractions. Although the model can be tuned to well reproduce single particle distributions, there are large model-uncertainties when it comes to correlations between identical baryons. We therefore, unfortunately, have to conclude that it is at present not possible to make any firm conclusion about the source radii relevant for baryon production at LEP

Potencia en flujo laminar impermanente en tuberías

Se deducen expresiones para las componentes viscosa e inercial de la potencia en flujo laminar impermanente en tubos rectos, circulares, para fluidos newtonianos incompresibles. Se evalúan dichas componentes para flujo unidireccionalmente acelerado y flujo oscilatorio, como ilustración del método. Se discute la importancia relativa de las componentes de la potencia para los ejemplos analizados

Structural analysis, magnetic and transport properties of the (Ru1-xCox)Sr2GdCu2O8 system

The effects of Co substitution on structural and superconducting properties of RuSr2GdCu2O8 compound have been studied. Rietveld refinements of the X-ray diffraction patterns indicate that the cobalt ion progressively replaces ruthenium sites. This replacement induces significant changes on the crystal structure and on the magnetic and superconducting properties. The effects Co substitution on the superconducting behaviour, and more particulary on the changes induce by the hole doping mechanism, were investigated in (Ru1-xCox)Sr2GdCu2O8 by a "bond valence sum" analysis with Co content from x= 0.0 to x = 0.2. The weak ferromagnetic transition at Tm= 138.2 K is shifted to lower temperature, and suppressed at higher Co content. From the crystallographic point of view the Ru-O(1)-Cu bond angle, associated to the rotation of the RuO6 octahedra, around the c-axis remain essetially constant when Ru is substituted by Co. Furthermore, increasing Co content has the effect to increase the weak ferromagnetic moment, which may be interpreted as the main responsible for breaking the delicate balance between magnetic and superconducting ordering.Comment: 21 pages, 8 figure

Estudio de especialistas egresados en Farmacia Industrial y Galénica de la Universidad de Alcalá

La Especialidad de Farmacia Industrial y Galénica de la Universidad de Alcalá, es una Especialidad en Ciencias de la Salud en régimen de alumnado (RD 127/1984 de 15 de octubre). Comenzó su puesta en marcha en la Universidad de Alcalá en el año 2005 continuando en la actualidad. Esta Especialidad se imparte por profesores universitarios y cuenta además, con la inestimable colaboración de expertos de la Asociación Española de Farmacéuticos de la Industria, Farmaindustria, laboratorios farmacéuticos, profesionales de la Agencia Española de Medicamentos y Productos Sanitarios e inspectores de la Comunidad de Madrid. En este trabajo, se pretende mostrar la experiencia profesional de los alumnos egresados de ocho promociones así como el nivel de aceptación con respecto a la organización y desarrollo del curso, las instalaciones, infraestructura y recursos utilizados, la calidad y motivación del profesorado. Los resultados obtenidos muestran la elevada adquisición de destrezas y habilidades de todos los estudiantes y su alto nivel de formación para acceder a un puesto de trabajo en la industria farmacéutica y otras instituciones o empresas tras cursar la Especialidad de Farmacia Industrial y Galénica. Se pone de manifiesto también la adecuación de las infraestructuras y recursos de nuestra Universidad

Vortex Plastic Motion in Twinned Superconductors

We present simulations, without electrodynamical assumptions, of $B(x,y,H(t)), M(H(t))$, and $J_c(H(t))$, in hard superconductors, for a variety of twin-boundary pinning potential parameters, and for a range of values of the density and strength of the pinning sites. We numerically solve the overdamped equations of motion of up to 10^4 flux-gradient-driven vortices which can be temporarily trapped at $\sim 10^6$ pinning centers. These simulations relate macroscopic measurements (e.g., M(H), ``flame'' shaped $B(x,y)$ profiles) with the underlying microscopic pinning landscape and the plastic dynamics of individual vortices

Evaluation of the viability of bee eggs Apis mellifera L. when submited to ultra-violet radiation.

En esta investigación se evaluó la viabilidad de huevos de Apis mellifera L. expuestos a radiación UV-A y UV-B mediante un tubo fluorescente con espectro entre los 280 nm a los 720 nm de 30 watts de potencia. El diseño experimental fue completamente al azar evaluándose viabilidad con tiempos de exposición de 0 s, 10 s, 30 s, 60 s y 90 s. El método de evaluación fue la presencia de celdillas operculadas al noveno día después de exponer los huevos de 24 horas a radiación. Los resultados obtenidos de las medias entre los distintos tiempos de exposición demostraron que existen diferencias estadísticamente significativas entre los tratamientos. Se presentó una mayor viabilidad a 0 s con 89,26%, para 10 s de exposición 56,59%, para 30 s 36,47%, para 60 s 31,46% y para 90 s de exposición 21,83% de viabilidad. Con este experimento se obtienen valiosos antecedentes sobre los cuales trabajar a fin de reducir pérdidas en crías de abejas, las cuales son sensibles a exposiciones de radiación UV.This study evaluated the viability of the eggs of Apis mellifera L. (honeybee) when exposed to UV-A and UV-B radiation using a fluorescent tube of 30 watts power with a spectrum between 280 nm and 720 nm. The design of the experiment was completely random, with evaluations of viability after exposure times of 0, 10, 30, 60 and 90 seconds. The evaluation method was the presence of operculate cells on the ninth day after exposure of 24-hour old eggs to radiation. The results obtained from the measurements among the different exposure times showed that there were statistically significant differences between the treatments. The greatest viability occurred at 0 exposure with 89.26%, followed by 56.59% for 10 s exposure, 36.47% for 30 s, 31.46% for 60 s, and 21.83% viability with 90 s exposure,. This experiment provides valuable information with which to reduce bee losses in breeding programmes, since they are sensitive to exposure to UV radiation