Analytic solution of the algebraic equation associated to the Ricci tensor in extended Palatini gravity

In this work we discuss the exact solution to the algebraic equation associated to the Ricci tensor in the quadratic $f(R,Q)$ extension of Palatini gravity. We show that an exact solution always exists, and in the general case it can be found by a simple matrix diagonalization. Furthermore, the general implications of the solution are analysed in detail, including the generation of an effective cosmological constant, and the recovery of the $f(R)$ and $f(Q)$ theories as particular cases in their corresponding limit. In addition, it is proposed a power series expansion of the solution which is successfully applied to the case of the electromagnetic field. We show that this power series expansion may be useful to deal perturbatively with some problems in the context of Palatini gravity.Comment: arXiv admin note: text overlap with arXiv:1101.3864, arXiv:1306.6537, arXiv:1112.2223 by other author

κ(R,T)\kappa(R,T) gravity

In this note we explore a modified theory of gravitation that is not based on the least action principle, but on a natural generalization of the original Einstein's field equations. This approach leads to the non-covariant conservation of the stress-energy tensor, a feature shared with other Lagrangian theories of gravity such as the $f(R,T)$ case. We consider the cosmological implications of a pair of particular models within this theory, and we show that they have some interesting properties. In particular, for some of the studied models we find that the density is bounded from above, and cannot exceed a maximum value that depends on certain physical constants. In the last part of the work we compare the theory to the $f(R,T)$ case and show that they lead to different predictions for the motion of test particles.Comment: 9 pages, 1 figure. Typos corrected, two subsections adde

Las cristalizaciones freáticas

[spa] Las oscilaciones del nivel del Mediterráneo durante el Pleistoceno, implican la consiguiente oscilación del nivel freático de las zonas litorales; las cotas alcanzadas por dicho nivel freático durante el Pleistoceno medio y superior han quedado registradas, en el interior de algunas cavidades del karst mallorquín, a través de las cristalizaciones freáticas que cada época ha originado. En este trabajo se analizan las principales características de estas cristalizaciones. En el grupo de las cristalizaciones que se forman actualmente en la superficie del agua, flotando por tensión superficial, aparecen Iáminas de Calcita flotante ("Calcite Rafts") con cristales romboédricos, y láminas flotantes de Aragonito con cristales de hábito prismático. En ambos casos los cristales tienen un crecimiento rápido y se disponen radialmente alrededor de un núcleo que, por lo general, es de materia orgánica. En los depósitos de estas cristalizaciones se observa una fuerte microsparitización de los romboedros calcíticos; en los depósitos actuales este proceso está relacionado con la actividad de microorganismos. Los depósitos aragoníticos, tanto actuales como fósiles, presentan claras huellas de inversión a Calcita. Entre las cristalizaciones formadas bajo la superficie freática, se reconocen tres tipos: Cristalizaciones de agujas de Aragonito, dispuestas radialmente sobre los extremos de estalactitas vadosas u otro soporte, con morfología externa lisa y frecuentes huellas de Inversión ("decalcificaciones"); Cristalizaciones de calcita con extinción pseudoondulante, con morfología externa "rugosa" que da formas de gran belleza; Crista de calcita romboédrica, creciendo indistintamente sobre cristalizaciones aragoníticas, de calcita pseudoondulante, o sobre la roca carbonatada de la pared de la cavidad. Podemos suponer que las diferencias petrológicas, geoquímicas y mineralógicas existentes en I depósitos de las diferentes épocas pleistocenas, permitirán precisar las condiciones climáticas en que se han formado, así como la evolución de éstas en el tiempo.[fre] Les oscillations du niveau de la Méditerrannée pendant le Pléistocene, comportent I'oscillation de la nappe phréatique des zones littorales; les hauteurs que cette nappe phréatique a atteint pendant le Pléistocene Moyen et Supérieur ont restées enrégistrées, a I'intérieur de quelques cavités du karst Majorquin (Espagne), parmi les cristallisations phréatiques que chaque époque a originé. Dans ce travail on analyse les principales caractéristiques de cettes cristallisations. Dans le groupe des cristallisations qui sont en train de se former actuellement sur la surfacede I'eau, on y trouve des lames de Calcite "Flottante" ("Calcite Rafts") avec des cristaux rhomboédriquesret des lames flottantes d’Aragonite au cristaux prismatiques. Dans I'un et I'autre cas les cristaux ont un accroissement tres rapide en se disposant radiallement autour d'un noyau que, fréquemment, est en matiere organique. Dans les dépots de cettes cristallisations ont peut observer une forte microsparitisation des rhomboedres calcitiques; et dans les dépots actuels, ce proces est en rélation avec I'activité des microorganismes. Les dépots aragonitiques, meme les actuels comme les fossiles, présentent des traces tres clares d'une inversion a Calcite. Parmi les cristallisations formées sous la surface phréatique, on peut y reconnaitre trois types: Cristallisations d'aiguilles d'Aragonite, disposées radiallement sur les bouts de stalactites vadoses, ou n'importe que autre support, avec une morphologie externe lisse et des fréquantes traces d'inversion ("decalcifications"); Cristallisations de Calcite avec extintion pseudoondulante, avec una morphologie externe "rugueuse" que , permet des formes d'une énorme beauté; Cristallisations de Calcite Rhornboédrique, qui accroient, indistinctement, sur des cristallisations Aragonitiques, de Calcite pseudoondulante, ou sur les roches carbonnatées des murs de la cavité. On peut supposer que les différences pétrologiques, géochimiques et minéralogiques existantes dans les dépots des époques pléistocenes, nous permettrons de preciser les conditions climatiques dans lesquelles se sont formés, ainsi que I'evolution de ceux-ci a travers le temps.[eng] Oscillations in the level of the Mediterranean sea during the Pleistocene produced corresponding oscillations in the level of the ground water-table, in the coastal areas. The levels reached by the ground water-table in the middle and upper Pleistocene have been recorded inside some caves in the Majorcan karst, by means of the phreatic crystallisations left by each epoch. In this study, we propose to analyse the principal characteristics of these crystallisations. In the group of crystals that forms at the present time, floating at the water surface by means of surface tensions, we find rhombohedrally crystallized floating calcite (calcite rafts) and floating plates of aragonite (whose crystals are grouped in prismatically - shaped rods). In both cases growth is rapid and the crystals are formed radially around a nucleus, often of organic material. In these deposits we can often observe a strong microsparitisation of the rhombohedrical crystals; in the present day deposits this process is related to the activity of microorganisms. The deposits of aragonite, both present-day and ancient, show clear traces of a process of conversion into calcite. Among the crystals formed below the water surface we can recognise three types; 1 .- Needle - like crystals of aragonite, arranged radially around the tip of those stalactites which penetrate the water surface, or around any other suitable support. These have a smooth outer texture, and frequently show signs of the process of conversion into calcite. 2.- Calcite crystals with a pseudo-undulating profile and a wrinkled outer texture, often forming themselves into very beautiful shapes. 3.- Rhombohedral calcite crystals, growing indiscriminately on the aragonite crystals, the pseudo-undulating calcite, or on the limestone rock of the cave walls. We may suppose that the petrological, geochemical and mineralogical differences existing in the deposits left by the different Pleistocene epochs, will allow us to determine the climatic conditions under which they were formed, and by the same token, the evolution with time undergone by these conditions

Texture changes during chilled storage of wild and farmed blacspot seabream (Pagellus bogaraveo) fed different diets

The impact of changes in dietary lipids and protein sources on texture was evaluated on farmed blackspot seabream (Pagellus bogaraveo) throughout 14 days of ice storage and compared with wild fish. A commercial diet formulated with a high proportion of lipids, and two diets formulated with an important reduction of lipid levels by 60% and adding either plant protein sources (LL diet) or fishmeal (LL + diet) were supplied during growth until commercial size was attained. In the wild fish, the raw fillet hardness was significantly higher than in farmed fish during the entire ice-storage period. In the farmed fish, an increase of muscle lipid accumulation and change of fiber density were responsible for the variations in texture in the raw fillet. The highest reduction was found in fish fed with diets LL+ and LL. The texture parameters studied on the cooked fillets showed no significant differences, neither attributable to the diets nor to the ice-storage period.JUNTA ASESORA DE CULTIVOS MARINOS (JACUMAR)Postprin

Two-photon luminescence thermometry: towards 3D high-resolution thermal imaging of waveguides

We report on the use of the Erbium-based luminescence thermometry to realize high resolution, three dimensional thermal imaging of optical waveguides. Proof of concept is demonstrated in a 980-nm laser pumped ultrafast laser inscribed waveguide in Er:Yb phosphate glass. Multi-photon microscopy images revealed the existence of well confined intra-waveguide temperature increments as large as 200 °C for moderate 980-nm pump powers of 120 mW. Numerical simulations and experimental data reveal that thermal loading can be substantially reduced if pump events are separated more than the characteristic thermal time that for the waveguides investigated is in the ms time scale.Ministerio de Economía y Competitividad of Spain (MINECO) (FIS2013-44174-P, MAT2013-47395-C4-1-R); National Natural Science Foundation of China (NSFC) (11274203)