2,664 research outputs found
Curved dilatonic brane-worlds and the cosmological constant problem
We construct a model for dilatonic brane worlds with constant curvature on
the brane, i.e. a non-zero four-dimensional cosmological constant, given in
function of the dilaton coupling and the cosmological constant of the bulk. We
compare this family of solutions to other known dilatonic domain wall solutions
and apply a self-tunning mechanism to check the stability of our solutions
under quantum fluctuations living on the brane.Comment: latex, 6 pages. (v2): considerable changes in the conclusion. (v3):
added new discussion on the solutions and some references; version to appear
in CQ
The globular cluster system of the nearest Seyfert II galaxy Circinus
Context. The globular cluster (GC) system of Circinus galaxy has not been
probed previously partly because of the location of the galaxy at - 3.8
Galactic latitude which suffers severely from interstellar extinction, stellar
crowding, and Galactic foreground contamination. However, the deep
near-infrared (NIR) photometry by the VISTA Variables in the Via L\'actea
Extended Survey (VVVX) in combination with the precise astrometry of Gaia EDR3
allow us to map GCs in this region.
Aims. Our long-term goal is to study and characterise the distributions of
GCs and Ultra-compact dwarfs of Circinus galaxy which is the nearest Seyfert II
galaxy. Here we conduct the first pilot search for GCs in this galaxy.
Methods. We use NIR VVVX photometry in combination with Gaia EDR3 astrometric
features such as astrometric excess noise and BP/RP excess factor to build the
first homogeneous catalogue of GCs in Circinus galaxy. A robust combination of
selection criteria allows us to effectively clean interlopers from our sample.
Results. We report the detection of 70 GC candidates in this galaxy at
a 3 confidence level. They show a bimodal colour distribution with the
blue peak at (G-Ks) = 0.9850.127 mag with a dispersion of
0.2110.091 mag and the red peak at (G-Ks) = 1.6250.177 mag with a
dispersion of 0.4820.114 mag. A GC specific frequency (S) of
1.30.2 was derived for the galaxy, and we estimated a total population of
12040 GCs. Based on the projected radial distribution it appears that
Circinus has a different distribution of GC candidates than MW and M31.
Conclusions. We demonstrate that Circinus galaxy hosts a sizeable number of
cluster candidates. This result is the first leap towards understanding the
evolution of old stellar clusters in this galaxy.Comment: 15 pages, 12 figure
Morphosedimentary and phytogeography reconstruction of the middle section of the river Jarama (Madrid, Spain) during the second half of the Holocene.
[Abstract] Two sites located on the alluvial plain of the Jarama River, near Madrid, Spain, have been studied using geological, palynological and xylological techniques. Uniquely for this region, numerous wood subfossils of Alnus and Ulmus have been found together with an strobile of Pinus halepensis. This has allowed the stablishment of a coherent radiocarbon chronology, which demonstrates that these sedimentary environments began to develop during the mid Holocene. The dated sediments, which also contains appreciable amounts of pollen, have been deposited upon older palaeosols which has in turn developed directly on the geological substrate. Palynological analyses of these levels have provided valuable insights into the floristic composition of the communities associated with the different biotopes present in the area. As a result of these multiproxy analyses an interpretation of Holocene landscape history and vegetation dynamics is presente
MODELO EXPERIMENTAL DE GLOMERULONEFRITIS MEMBRANOSA INDUCIDA CON ALBUMINA BOVINA
El objetivo del presente trabajo fue diseñar un modelo experimental de Glomerulonefritis Membranosa (GM) en ratas Wistar, inducida con Seroalbúmina Bovina (BSA), y validarlo mediante la determinación de parámetros bioquímicos, histológicos, ultraestructurales y detección de inmunocomplejos por inmunofluorescencia (IF). Los animales del grupo experimental fueron inmunizados por vía subcutánea, con dosis de 3 mg c/u de BSA/PBS con adyuvante de Freund. Se efectuaron diferentes esquemas de inmunización. Cuando el título de anticuerpos fue ≥1/2, comenzó la administración diaria de 2 mg, por vía endovenosa de BSA/PBS, durante 15 días. Se evaluó la funcionalidad renal por la proteinuria; después de la 5° semana, desde su aparición, se determinó: depuración (clearance) de creatinina, uremia, proteinemia y perfil lipídico. Los dos riñones se usaron para estudios histológicos, ultraestructurales y detección de inmunocomplejos por IF. Los resultados mostraron que la inmunización fue efectiva con 5 R E S U M E N inoculaciones c/15 días. En los animales nefróticos la proteinuria, depuración (clearance) de creatinina, proteinemia , uremia y el perfil lipídico presentaron alteraciones significativas (p<0.0001). Al microscopio óptico se observó hipercelularidad, engrosamiento difuso de las membranas basales de los capilares glomerulares y diferentes grados de atrofia, esclerosis e hialinización de los glomérulos. Por IF se detectó inmunocomplejos IgG en el 100 % de los glomérulos. Ultraestructuralmente, se observaron depósitos subepiteliales electrodensos en la membrana basal engrosada, compatibles con inmunocomplejos . Se encontraron alteraciones en la estructura de los podocitos. En conclusión, los estudios bioquímicos, estructurales y ultraestructurales permitieron inferir la inducción de un síndrome nefrótico experimental. Concluimos que el protocolo utilizado tiene validez para la inducción de una glomerulonefritis membranosa en ratas Wistar
Using radio astronomical receivers for molecular spectroscopic characterization in astrochemical laboratory simulations: A proof of concept
We present a proof of concept on the coupling of radio astronomical receivers
and spectrometers with chemical reactorsand the performances of the resulting
setup for spectroscopy and chemical simulations in laboratory astrophysics.
Several experiments including cold plasma generation and UV photochemistry were
performed in a 40\,cm long gas cell placed in the beam path of the Aries 40\,m
radio telescope receivers operating in the 41-49 GHz frequency range interfaced
with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz
resolution.
The impedance matching of the cell windows has been studied using different
materials. The choice of the material and its thickness was critical to obtain
a sensitivity identical to that of standard radio astronomical observations.
Spectroscopic signals arising from very low partial pressures of CH3OH,
CH3CH2OH, HCOOH, OCS,CS, SO2 (<1E-03 mbar) were detected in a few seconds. Fast
data acquisition was achieved allowing for kinetic measurements in
fragmentation experiments using electron impact or UV irradiation. Time
evolution of chemical reactions involving OCS, O2 and CS2 was also observed
demonstrating that reactive species, such as CS, can be maintained with high
abundance in the gas phase during these experiments.Comment: Accepted for publication in Astronomy and Astrophysics in September
21, 2017. 16 pages, 18 figure
Effects of water stress on the phenolic compounds of ‘Merlot’ grapes in a semi-arid Mediterranean climate
Of all the abiotic stress types to which plants grown in fields are exposed, the most influential is water stress. It is well accepted that adopting controlled deficit irrigation strategies during the growing season has beneficial effects on the chemical compositions of grapes and red wines. However, there is a discrepancy in the timing, intensity and duration of deficit. This study aimed to evaluate the changes in phenolic composition of ‘merlot’ cultivar grapes when subjected to different levels of water stress in a semi-arid Mediterranean climate. Four treatments with different water stress levels were applied within two phenological intervals (flowering-veraison, veraison-maturity) to 128 grapevines for two consecutive years. The water stress levels for Treatments 1, 2, 3 and 4 were: no-light, light-moderate, moderate-intense and intense for the flowering-veraison and veraison-maturity intervals, respectively. Water stress distinctly affected the phenolic compounds in skin and seeds. The concentrations of flavan-3-ols and total polyphenols were much higher in seeds than in skin, and in both fractions, tannins are the major compound
Novel utility-scale photovoltaic plant electroluminescence maintenance technique by means of bidirectional power inverter controller
Nowadays, photovoltaic (PV) silicon plants dominate the growth in renewable energies generation. Utility-scale photovoltaic plants (USPVPs) have increased exponentially in size and power in the last decade and, therefore, it is crucial to develop optimum maintenance techniques. One of the most promising maintenance techniques is the study of electroluminescence (EL) images as a complement of infrared thermography (IRT) analysis. However, its high cost has prevented its use regularly up to date. This paper proposes a maintenance methodology to perform on-site EL inspections as efficiently as possible. First, current USPVP characteristics and the requirements to apply EL on them are studied. Next, an increase over the automation level by means of adding automatic elements in the current PV plant design is studied. The new elements and their configuration are explained, and a control strategy for applying this technique on large photovoltaic plants is developed. With the aim of getting on-site EL images on a real plant, a PV inverter has been developed to validate the proposed methodology on a small-scale solar plant. Both the electrical parameters measured during the tests and the images taken have been analysed. Finally, the implementation cost of the solution has been calculated and optimised. The results conclude the technical viability to perform on-site EL inspections on PV plants without the need to measure and analyse the panel defects out of the PV installation
Un nuevo concepto de la gastronomía desde la bioeconomía y la actividad académica
El proyecto “Ciencia y arte en gastronomía: botánica gastronómica y
gastronomía molecular” se está desarrollando con el objetivo de establecer y
organizar el intercambio de conocimientos y negocio en este ámbito. Con este
objetivo se pretende aunar el conocimiento científico con la salud y el bienestar
social desde la perspectiva bioeconómica promoviendo la creación de riqueza y
trabajo. El proyecto forma parte de los cursos especializados que la Universidad
Complutense de Madrid oferta con el animo de incrementar el conocimiento y
desarrollar competencias personales y profesionales. El programa responde a la
demanda social proporcionando una formación con inmediata proyección
profesional mediante el establecimiento de un nexo directo entre la actividad
académica y la realidad social.Universidad de Sevilla. Cristalografía, Mineralogía y Química Agrícola
The project "Science and art in gastronomy: gastronomic botany and
molecular gastronomy" is being developed with the aim to establish and organize
the exchange of knowledge and business in this area. In this way we are working
to join the scientific knowledge to the health and the social well-being, without
losing the current perspective from the bioeconomy which look forward the generation of wealth and work. The project belongs to specialized courses
offered by The Complutense University of Madrid which aim is to update the
knowledge and develop personal and professional competitions. These programs
answer to a social demand on providing formation with professional immediate
projection establishing a direct relation between the academic activity and the
social reality
Phase separation and enhanced charge-spin coupling near magnetic transitions
The generic changes of the electronic compressibility in systems which show
magnetic instabilities is studied. It is shown that, when going into the
ordered phase, the compressibility is reduced by an amount comparable to the
its original value, making charge instabilities also possible. We discuss,
within this framework, the tendency towards phase separation of the double
exchange systems, the pyrochlores, and other magnetic materials
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