3,120 research outputs found

    Dynamical Casimir effect entangles artificial atoms

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    We show that the physics underlying the dynamical Casimir effect may generate multipartite quantum correlations. To achieve it, we propose a circuit quantum electrodynamics (cQED) scenario involving superconducting quantum interference devices (SQUIDs), cavities, and superconducting qubits, also called artificial atoms. Our results predict the generation of highly entangled states for two and three superconducting qubits in different geometric configurations with realistic parameters. This proposal paves the way for a scalable method of multipartite entanglement generation in cavity networks through dynamical Casimir physics.Comment: Improved version and references added. Accepted for publication in Physical Review Letter

    Plasma and surface diagnostics of silicon nitride thin film coatings generated by SiH4+NH3 RF discharges.

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    Although plasma processing in low pressure electric discharge reactors has become an extensive and critical step in the fabrication of microelectronic devices, its development has been carried out mostly empirically so far, by changing external reactor parameters in order to develop the best achievable film properties, whereas the intrinsic state of the plasma has been largely unknown [1, 2]. In this work, silicon nitride (SiN) thin films have been grown on silicon samples and on AlGaN/GaN High Electron Mobility Transistors (HEMT) by Plasma Enhanced Chemical Vapor Deposition (PE-CVD). The SiN coatings have been produced in a RF discharge reactor, employing SiH4 and NH3 as precursors, at different electric powers and gas flow ratios. During depositions, the plasmas have been characterized by mass and time resolved quadrupole mass spectrometry, and the depletion ratios of parent gases have been observed. Afterwards, the refractive indexes and growth rates of the films have been analysed by ellipsometry, and their composition, by Fourier Transform Infrared Spectroscopy. The electrical characteristics and frequency responses of these films when deposited on HEMT (where they are just usually employed to passivate these devices against current collapses) have been studied too by means of DC, pulsed currents, and small signal RF measurements. The plasma characteristics for the different deposition conditions have been correlated with the subsequent changes in the properties of the films. A comparison with the results previously reported in the literature is addressed

    Performance evaluation for 68Ga and 18F of the ARGUS small-animal PET scanner based on the NEMA NU-4 standard

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    Proceeding of: 2010 IEEE Nuclear Science Symposium, Medical Imaging Conference and 17th Room Temperature Semiconductor Detector Workshop (IEEE), Knoxville, Tennessee, USA, October 30 - November 6, 201068Ga is one of the non-conventional nuclides that are being used in preclinical imaging. One disadvantage of 68Ga versus 18F is its larger positron range, which deteriorates the effective spatial resolution and the overall image quality. In this work we present a performance evaluation of the ARGUS smallanimal positron emission tomography (PET) scanner for two positron emitters, 68Ga and 18F. These experiments followed the procedure based on the National Electrical Manufacturers Association (NEMA) NU 4-2008 standard. We show how the use of 68Ga may affect the NEMA performance of the system in terms of image quality and spatial resolution. The recovery coefficients (RC) measured in the image-quality phantom ranged from 0.17 to 0.72 for 68Ga and from 0.28 to 0.92 for 18F, using iterative image reconstruction methods and applying all corrections. Under the same conditions the image noise (%STD) in a uniform region was 17.0% for 68Ga and 15.1% for 18F. The respective spillover ratios (SOR) were 0.13 and 0.09 in air, and 0.21 and 0.12 in water. Attenuation correction yielded an improvement of the SOR close to 50% for both radionuclides in the air-filled region. This work evaluates the image reconstruction methods and corrections available in the ARGUS PET for 68Ga and 18F to assess the influence of their physical properties on the NEMA parameters.Publicad

    The gene expression profile of the glucocorticoid receptor 1 (gr1) but not gr2 is modulated in mucosal tissues of gilthead sea bream (Sparus aurata) exposed to acute air-exposure stress

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    The perception of an acute stressor (short-duration; high-intensity) induces a physiological response that activates the hypothalamic-pituitary-interrenal (HPI) axis and the subsequent release of cortisol. Cortisol carries out its effect at the molecular level through its recognition by the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). Recently, we unveiled the nucleotide sequence of the glucocorticoid receptor 1 (gr1) and gr2 in gilthead sea bream (Sparus aurata). Importantly, GR1 and GR2 respond to different levels of cortisol concentration in fish and, consequently, play a differential role in the stress response. To date, and despite their relevance, no data describes the modulation of these receptors in response to an acute stressor in gilthead sea bream (S. aurata). In this study, we evaluated the kinetics of modulation of cortisol receptors expression (gr1, gr2, mr), and its similarity with the expression pattern of selected genes associated with stress (hsp70; enolase) and immune response (lysozyme; c3; il-1 beta; tnf-alpha; il-10; tgf-beta 1) in gilthead sea bream mucosal tissues (skin; gills; anterior gut). To do it, fish were acutely stressed by three-minute air exposure, and the expression profile was evaluated at zero, 1 h, 6 h, and 24 h post-stress (hps). The cortisol level in plasma and skin mucus peaked at 1 hps. All the mucosal tissues showed a time-dependent and tissue-specific upregulation of gr1 and mr. The immune-related genes showed the upregulation of il-1 beta at 6 hps (gills; anterior gut), and tnf-alpha and c3 at 24 hps (anterior gut). Taking together, our study concludes that fish subjected to three-minute air exposure modulated the expression of gr1 but not gr2 in mucosal tissues (skin; gills; anterior gut). Furthermore, our data reinforce the idea of a stimulatory effect induced in genes associated with the innate immune response after acute stress but focused at the mucosal level and in a time- and tissue-dependent manner

    Separación y Almacenamiento de Hidrógeno Mediante Ciclos Redox en Reactores de Lecho Fijo

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    El agotamiento de los combustibles fósiles y los efectos medioambientales generados por su combustión plantean la necesidad de buscar nuevas fuentes de energía que sean limpias y renovables. El hidrógeno podría ser el vector energético del futuro en el aprovechamiento de esas fuentes alternativas. Sin embargo, su implantación en la actualidad no está estandarizada, debido a problemas derivados de su obtención con los niveles de pureza que las pilas de combustible requieren. Este estudio plantea la separación y almacenamiento de corrientes ricas en hidrógeno, por ejemplo las provenientes de la pirolisis de biomasa o de gas natural, mediante el proceso llamado Steam Iron. En este proceso cíclico, una corriente de gas formada principalmente por metano e hidrógeno es alimentada en un reactor de lecho fijo, donde se encuentra contenido un óxido metálico con alto contenido de hematita (Fe2O3). El sólido se reduce por acción del hidrógeno presente en dicha corriente a temperaturas entre 400 a 600 ºC hasta hierro metal. Como producto se obtiene solamente agua, mientras el metano adicionado se mantiene inalterado. En un proceso de oxidación posterior, se hace pasar sobre el metal reducido una corriente de vapor de agua que lo oxida generándose como producto hidrógeno puro.  Fueron probados varios sólidos tanto aditivados como naturales a diferentes presiones parciales de reactante y temperaturas. Además, el efecto del paso de los ciclos también fue estudiado, todo ello con el propósito de encontrar las mejores condiciones de regeneración de hidrógeno puro a partir del sólido

    Producción de hidrógeno a partir de biogás mediante óxidos metálicos

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    La demanda energética actual se abastece principalmente mediante combustibles fósiles, perolas reservas mundiales están disminuyendo a gran velocidad y se estima que se agoten en laspróximas décadas. A la inevitable escasez hay que añadir la contribución de estos combustiblesal conocido como “efecto invernadero”. La búsqueda de otras alternativas energéticas es portanto urgente y perentoria, siendo el hidrógeno utilizado en pilas de combustible una de lasreferencias más eficientes, versátiles y prometedoras. El método de obtención de hidrógenomás ampliamente utilizado en la actualidad es el llamado reformado de metano con vapor deagua, que por el momento utiliza como materia prima combustibles fósiles como el gasnatural. Dadas las actuales circunstancias, la investigación se está centrando en la utilizaciónde biogás como fuente primaria para la obtención del hidrógeno. El biogás es el resultado de ladigestión anaerobia de residuos orgánicos (urbanos, de ganado, de depuradora de aguasresiduales,…), y tiene como componentes mayoritarios metano y dióxido de carbono. En elproceso conocido como “reformado seco”, el metano reacciona catalíticamente con el propiodióxido de carbono contenido en el biogás. La mezcla resultante, que contiene una elevadaproporción de hidrógeno, debe ser purificada previamente a su utilización. La propuesta delCREG consiste en utilizar óxidos de hierro con aditivos para llevar a cabo, tanto la produccióncomo la purificación y de modo simultáneo en un mismo recipiente. Este proceso conocidocomo “steam‐iron” consiste en dos etapas: de reducción del óxido mediante la corriente degas, y de oxidación de hierro metálico mediante vapor de agua en el que se obtiene hidrógenopuro.4

    Changes in iron metabolism and oxidative status in STZ-induced diabetic rats treated with bis(maltolato) oxovanadium(IV) as an antidiabetic agent

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    The role of vanadium as a micronutrient and hypoglycaemic agent has yet to be fully clarified. The present study was undertaken to investigate changes in the metabolism of iron and in antioxidant defences of diabetic STZ rats following treatment with vanadium. Four groups were examined: control; diabetic; diabetic treated with 1 mgV/day; and Diabetic treated with 3 mgV/day. The vanadium was supplied in drinking water as bis(maltolato) oxovanadium (IV) (BMOV). The experiment had a duration of five weeks. Iron was measured in food, faeces, urine, serum, muscle, kidney, liver, spleen, and femur. Superoxide dismutase, catalase, NAD(P)H: quinone-oxidoreductase-1 (NQO1) activity, and protein carbonyl group levels in the liver were determined. In the diabetic rats, higher levels of Fe absorbed, Fe content in kidney, muscle, and femur, and NQO1 activity were recorded, together with decreased catalase activity, in comparison with the control rats. In the rats treated with 3 mgV/day, there was a significant decrease in fasting glycaemia, Fe content in the liver, spleen, and heart, catalase activity, and levels of protein carbonyl groups in comparison with the diabetic group. In conclusion BMOV was a dose-dependent hypoglycaemic agent. Treatment with 3 mgV/day provoked increased Fe deposits in the tissues, which promoted a protein oxidative damage in the liver.The authors are grateful for support received from the Consejería de Innovación, Ciencia y Empresa, Andalusian Regional Government (Project P06-CTS-01435)

    EXPLORING THE IMPACT OF APOE POLYMORPHISM ON THE MOLECULAR, MORPHOLOGICAL AND FUNCTIONAL PROFILE OF iPSC-DERIVED ASTROCYTES FROM ALZHEIMER'S PATIENTS

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    Comunicación presentada a FENS Forum 2022Alzheimer¿s disease (AD) is pathologically characterised by the presence of amyloid-beta plaques, neurofibrillary tangles containing hyperphosphorylated Tau protein, neuroinflammation and neuronal death leading to progressive cognitive impairment. The ¿4 allele of the gene encoding apolipoprotein E (APOE), which is mainly expressed in glial cells, is the strongest genetic risk factor for sporadic AD. Increasing evidence has shown that APOE4 may disrupt normal astrocyte activity, potentially contributing to AD pathology, but the impact of different APOE alleles on astrocyte differentiation, maturation and function is not yet fully understood. To go in depth on these questions, we obtained induced pluripotent stem cells (iPSCs) from fibroblasts of AD patients carrying ¿3 and ¿4 alleles (in homozygosis) and from healthy patients. We also used gene-edited iPSC lines homozygous for the main APOE variants and an APOE knock-out line. iPSC-derived human astrocytes were generated by establishing a differentiation protocol through the consecutive addition of small molecules and growth factors, and the expression of typical markers (GFAP, GLT1, AQP4 and S100beta) and APOE was analysed. In addition, astrocytes exhibited functional features like glutamate uptake capacity and calcium waves production. They also responded to an inflammatory stimulus (IL-1beta and TNF-alpha) or to the presence of amyloid-beta 1-42 peptide by changing their morphology and increasing the expression levels of pro-inflammatory factors and cytokines. Our results shed light on the potential dual role of APOE polymorphism and the individual¿s genetic background in favouring or perhaps preventing AD pathology
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