Commensurate Growth of Magnetite Microinclusions in Olivine under Mantle Conditions

Magnetite-bearing multiphase solid inclusions hosted in metamorphic olivine have been interpreted as final products of the trapping of the aqueous fluid produced by the subduction-zone dehydration of former serpentinites. We provide here a careful analysis performed by microfocus single-crystal X-ray diffraction of inclusions found in harzburgites from the Almirez Complex (Bétic Cordillera, Spain) to determine the occurrence of preferential crystallographic orientation relationships between the olivine host and the magnetite inclusion. The results demonstrate that the magnetite–olivine interface selectively displays parallelism between crystallographic planes (111) and (100) and between crystallographic directions ⟨110⟩ and ⟨011⟩, respectively. This evidence points to a clear epitaxial growth of magnetite on olivine. The calculation of the geometrical misfit between the two lattices in contact as a function of their relative azimuthal orientation shows that, under the aforementioned reciprocal orientation, a perfect commensurism is achieved; i.e., all of the nodes of the magnetite lattice coincide with nodes of the olivine lattice. This particular relationship must be interpreted as a unique occurrence, playing a fundamental role in favoring the heterogeneous nucleation of magnetite on olivine

Errores en torno a la comprensión de la definición de límite finito de una función real de variable real

En el presente trabajo de investigación analizamos los errores en torno a la comprensión de la definición de límite finito de una función real de variable real, mediante un estudio con una muestra de alumnos de un primer curso universitario de Cálculo. La metodología empleada en nuestro trabajo fue mixta, es decir, cuantitativa y cualitativa. Luego de aplicar un test exploratorio para obtener la información necesaria, en la muestra, y proceder con los análisis cuantitativo y cualitativo correspondientes – usando el enfoque ontosemiótico para estos últimos – podemos afirmar que existen errores conceptuales, simbólicos y gráficos en la comprensión de los alumnos sobre la definición del límite finito de función real de variable real

De la hidrografía imperial a la hidrografía nacional. Reconocimientos del Pacífico sur. Siglos XVIII y XIX

This work identifies the main periods of hydrographic expeditions to Chiles’ South Pacific coast throughout more than a century starting in 1786. The article highlights the milestones of this process and identifies the objectives of the European empires and the Chilean state. It also shows that the reasons behind the need to gather data about Chiles South Pacific were to confront border conflicts and to secure commerce.El trabajo identifica las principales etapas del reconocimiento hidrográfico del Pacífico sur y austral frente a las costas de Chile en el lapso de poco más de un siglo a partir de 1786. Ofrece los hitos de este proceso e identifica los objetivos de cada uno de sus protagonistas, los imperios europeos y el Estado chileno. Muestra cómo la necesidad de hacer frente a amenazas, asegurar el comercio y enfrentar querellas de límites están tras la necesidad de levantar el litoral del Pacífico austral

Expected performance of the ASTRI-SST-2M telescope prototype

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica) strictly linked to the development of the Cherenkov Telescope Array, CTA. Primary goal of the ASTRI program is the design and production of an end-to-end prototype of a Small Size Telescope for the CTA sub-array devoted to the highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be tested on field in Italy during 2014. This telescope will be the first Cherenkov telescope adopting the double reflection layout in a Schwarzschild-Couder configuration with a tessellated primary mirror and a monolithic secondary mirror. The collected light will be focused on a compact and light-weight camera based on silicon photo-multipliers covering a 9.6 deg full field of view. Detailed Monte Carlo simulations have been performed to estimate the performance of the planned telescope. The results regarding its energy threshold, sensitivity and angular resolution are shown and discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers

The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called Radiometer Chain Assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20K and the back-end at 300K, and with an external input load cooled to 4K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.Comment: 15 pages, 18 figures. Accepted for publication in Astronomy and Astrophysic

Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance

We give the calibration and scientific performance parameters of the Planck Low Frequency Instrument (LFI) measured during the ground cryogenic test campaign. These parameters characterise the instrument response and constitute our best pre-launch knowledge of the LFI scientific performance. The LFI shows excellent $1/f$ stability and rejection of instrumental systematic effects; measured noise performance shows that LFI is the most sensitive instrument of its kind. The set of measured calibration parameters will be updated during flight operations through the end of the mission.Comment: Accepted for publications in Astronomy and Astrophysics. Astronomy & Astrophysics, 2010 (acceptance date: 12 Jan 2010

IL-7 Promotes CD95-Induced Apoptosis in B Cells via the IFN-γ/STAT1 Pathway

Interleukin-7 (IL-7) concentrations are increased in the blood of CD4+ T cell depleted individuals, including HIV-1 infected patients. High IL-7 levels might stimulate T cell activation and, as we have shown earlier, IL-7 can prime resting T cell to CD95 induced apoptosis as well. HIV-1 infection leads to B cell abnormalities including increased apoptosis via the CD95 (Fas) death receptor pathway and loss of memory B cells. Peripheral B cells are not sensitive for IL-7, due to the lack of IL-7Ra expression on their surface; however, here we demonstrate that high IL-7 concentration can prime resting B cells to CD95-mediated apoptosis via an indirect mechanism. T cells cultured with IL-7 induced high CD95 expression on resting B cells together with an increased sensitivity to CD95 mediated apoptosis. As the mediator molecule responsible for B cell priming to CD95 mediated apoptosis we identified the cytokine IFN-γ that T cells secreted in high amounts in response to IL-7. These results suggest that the lymphopenia induced cytokine IL-7 can contribute to the increased B cell apoptosis observed in HIV-1 infected individuals

Functions of the multi-interacting protein KIDINS220/ARMS in cancer and other pathologies

Development of an organ and subsequently the whole system from an embryo is a highly integrated process. Although there is evidence that different systems are interconnected during developmental stages, the molecular understanding of this relationship is either not known or only to a limited extent. Nervous system development, amongst all, is maybe the most crucial and complex process. It relies on the correct distribution of specific neuronal growth factors and hormones to the specific receptors. Among the plethora of proteins that are involved in downstream signalling of neuronal growth factors, we find the kinase-D interacting substrate of 220 kDa (KIDINS220), also known as ankyrin-rich repeat membrane spanning (ARMS) protein. KIDINS220 has been shown to play a substantial role in the nervous system and vascular system development as well as in neuronal survival and differentiation. It serves as a downstream regulator for many important neuronal and vascular growth factors such as vascular endothelial growth factor (VEGF), the neurotrophin family, glutamate receptors and ephrin receptors. Moreover, activation and differentiation of B- and T-cells, as well as tumour cell proliferation has also shown to be related to KIDINS220. This review comprehensively summarises the existing research data on this protein, with a particular interest in its role in cancer and in other pathologies