Analysis of Moon impact flashes detected during the 2012 and 2013 Perseids

We present the results of our Moon impact flashes detection campaigns performed around the maximum activity period of the Perseid meteor shower in 2012 and 2013. Just one flash produced by a Perseid meteoroid was detected in 2012 because of very unfavourable geometric conditions, but 12 of these were confirmed in 2013. The visual magnitude of the flashes ranged between 6.6 and 9.3. A luminous efficiency of 1.8 $\times$ 10$^{-3}$ has been estimated for meteoroids from this stream. According to this value, impactor masses would range between 1.9 and 190 g. In addition, we propose a criterion to establish, from a statistical point of view, the likely origin of impact flashes recorded on the lunar surface.Comment: Accepted for publication in Astronomy and Astrophysics on March 11, 201

New objects in old structures: The Iron Age hoard of the Palacio III megalithic funerary complex (Almadén de la Plata, Seville, Spain)

Cultural contact, exchange and interaction feature high in the list of challenging topics of current research on European Prehistory. Not far off is the issue of the changing role of monuments in the making and maintaining of key cultural devices such as memory and identity. Addressing both these highly-debated issues from a science-based perspective, in this paper we look at an unusual case study set in southern Iberia and illustrate how these archaeological questions can benefit from robust materials-science approaches.We present the contextual, morphological and analytical study of an exceptional Early Iron Age hoard composed of a number of different (and mostly exotic) materials such as amber, quartz, silver and ceramic. This hoard, found under the fallen orthostat of a megalithic structure built at least 2000 years earlier, throws new light on long-distance exchange networks and the effect they could have had on the cultural identities and social relations of local Iberian Early Iron Age communities. Moreover, the archaeometric study reveals how diverse and distant the sources of these item are (Northern Europe to Eastern and Western Mediterranean raw materials, as well as local and eastern technologies), therefore raising questions concerning the social mechanisms used to establish change and resistance in contexts of colonial encounter

A revised distance to IRAS 16293−-2422 from VLBA astrometry of associated water masers

IRAS 16293-2422 is a very well studied young stellar system seen in projection towards the L1689N cloud in the Ophiuchus complex. However, its distance is still uncertain with a range of values from 120 pc to 180 pc. Our goal is to measure the trigonometric parallax of this young star by means of H$_2$O maser emission. We use archival data from 15 epochs of VLBA observations of the 22.2 GHz water maser line. By modeling the displacement on the sky of the H$_2$O maser spots, we derived a trigonometric parallax of $7.1\pm1.3$ mas, corresponding to a distance of $141_{-21}^{+30}$ pc. This new distance is in good agreement with recent values obtained for other magnetically active young stars in the L1689 cloud. We relate the kinematics of these masers with the outflows and the recent ejections powered by source A in the system.Comment: 14 pages, 6 tables, 8 figures. Accepted to be published in Astronomy \& Astrophysic

The prolific polytypism of silicon carbide

A worked example of polytypism is presented, aimed at assisting undergraduates in the learning and instructors in the teaching of this topic. In particular, this crystallography concept, not necessarily obvious for beginners, is illustrated pedagogically using to that end the model case of the prolific polytypism of silicon carbide (SiC). On the basis of concepts that are easily assimilated by students (i.e. simple topological constraints) this article first presents a unified description of the polytypism phenomenon in SiC that allows one to understand without difficulty the existence of its numerous polytypic variants and how they develop. Then the various notations used to designate these different polytypes are described, and finally the crystal structures of the most common are discussed. This worked example is thus expected to contribute to motivating undergraduates in the study of a crystallography topic that often is not treated in sufficient depth in class.Ministerio de Ciencia y Tecnología MAT2010-1684

¿Cómo estamos haciendo del ITESO una universidad enredada?

Pensar la universidad en red y facilitar su transformación hacia una universidad propia de nuestra época es parte de las tareas del Centro de Aprendizaje en Red del ITESO. Compartimos en este documento las apuestas y propuestas de esta tarea compleja, a la que nos aproximamos de manera experimental y reflexiva.ITESO, A.C

Resolución algebraica de problemas estequiométricos

La resolución de problemas, entendida como la metodología para enfrentar situaciones nuevas que impliquen un reto personal, es una estrategia didáctica eficaz que permite generar, consolidar e integrar conocimientos. La resolución de un problema típico en ciencias parte de la comprensión de su enunciado, constituido por un texto corto escrito en lenguaje natural; la traducción de dicha situación al lenguaje matemático constituye un obstáculo en el proceso de resolución de problemas con estructura matemática subyacente. Para desarrollar en los estudiantes de ingeniería química las habilidades matemática y de traducción de lenguajes coloquial-científico-algebraico, se diseñaron enunciados de problemas basados en la estequiometría de compuestos y reacciones, los cuales involucran el planteamiento y resolución de sistemas de ecuaciones algebraicas lineales

Directed Irradiation Synthesis as an Advanced Plasma Technology for Surface Modification to Activate Porous and “as-received” Titanium Surfaces

For the design of smart titanium implants, it is essential to balance the surface properties without any detrimental effect on the bulk properties of the material. Therefore, in this study, an irradiation-driven surface modification called directed irradiation synthesis (DIS) has been developed to nanopattern porousand“as-received”c.p. Tisur faces with the aim of improving cellular viability. Nano features were developed using singly-charged argon ions at 0.5 and 1.0 keV energies, incident angles from 0◦ to 75◦ degrees, and fluences up to 5.0×1017 cm−2. Irradiated surfaces were evaluated by scanning electron microscopy, atomic force microscopy and contact angle, observing an increased hydrophilicity (a contact angle reduction of 73.4% and 49.3%) and a higher roughness on both surfaces except for higher incident angles, which showed the smoothest surface. In-vitro studies demonstrated the biocompatibility of directed irradiation synthesis (DIS) reaching 84% and 87% cell viability levels at 1 and 7 days respectively, and a lower percentage of damaged DNA in tail compared to the control c.p. Ti. All these results confirm the potential of the DIS technique to modify complex surfaces at the nanoscale level promoting their biological performance.Department of Defense (Spain) contract W81XWH-11-2-0067Ministry of Economy and Competitiveness of Spain grant MAT2015-71284-

Comparación entre TAC y radiografía en el diagnóstico de afectación del oído medio en felinos con enfermedad vestibular periférica

Estudio prospectivo diseñado para describir y comparar los hallazgos obtenidos mediante tomografía axial computerizada (TAC) y radiografía en gatos con sintomatología compatible con síndrome vestibular periférico

Origin of the (2)E <->(4)T(2) Fano resonance in Cr(3+)-doped LiCaAlF(6): Pressure-induced excited-state crossover.

This work investigates pressure-induced phase transition (PT) and excited-state-crossover effects on the photoluminescence (PL) properties of LiCaAlF(6):Cr(3+). We report a PL study by means of time-resolved emission, excitation, and lifetime measurements as a function of pressure. We focus on Cr(3+) PL variations around pressure-induced trigonal-to-monoclinic first-order PT in LiCaAlF6 at 7 GPa. Moreover, the structural requirements for changing Cr(3+) PL from a broadband emission at 1.59 eV (781 nm) at ambient conditions, to a rubylike narrow-line emission at 1.87 eV (663 nm) are analyzed in the 0-35 GPa range. We show how pressure progressively transforms Cr(3+) broadband PL into a rubylike emission that becomes the dominant feature of the room-temperature emission spectrum at 28 GPa. This behavior, together with the pressure dependences of the (2)E and (4)T(2) excited-states energy and PL lifetime, are explained on the basis of the electron-phonon coupling associated with the (4)T(2) and (2)E states. We demonstrate that both excited states interact through spin-orbit coupling yielding Fano resonance rather than antiresonance as is frequently assumed