4,944 research outputs found
Cost of energy and mutual shadows in a two-axis tracking PV system
The performance improvement obtained from the use of trackers in a PV system cannot be separated from the higher requirement of land due to the mutual shadows between generators. Thus, the optimal choice of distances between trackers is a compromise between productivity and land use to minimize the cost of the energy produced by the PV system during its lifetime.
This paper develops a method for the estimation and optimization of the cost of energy function. It is built upon a set of equations to model the mutual shadows geometry and a procedure for the optimal choice of the wire cross-section. Several examples illustrate the use of the method with a particular PV system under different conditions of land and equipment costs.
This method is implemented using free software available as supplementary material
Spectroscopic characterization and detection of Ethyl Mercaptan in Orion
New laboratory data of ethyl mercaptan, CHCHSH, in the millimeter
and submillimeter-wave domains (up to 880 GHz) provided very precise values of
the spectroscopic constants that allowed the detection of
-CHCHSH towards Orion KL. 77 unblended or slightly blended
lines plus no missing transitions in the range 80-280 GHz support this
identification. A detection of methyl mercaptan, CHSH, in the spectral
survey of Orion KL is reported as well. Our column density results indicate
that methyl mercaptan is 5 times more abundant than ethyl mercaptan in
the hot core of Orion KL.Comment: Accepted for publication in ApJL (30 January 2014)/ submitted (8
January 2014
Propuesta de intervención para jóvenes y adultos con Síndrome de Asperger de Grado 1
El presente trabajo se centra en el Síndrome de Asperger, situado en el extremo de “alto funcionamiento” de los Trastornos del Espectro Autista, lo que dificulta en ocasiones, su detección y por tanto una intervención temprana. Las personas bajo esta condición por lo general, se pueden desenvolver con normalidad en el día a día, pero en ocasiones, necesitan apoyos que varían en función de las diferentes etapas evolutivas.
En consecuencia, el presente estudio pretende mostrar las principales características, dificultades comunicativas y emocionales que se dan en las personas jóvenes y adultas con menor grado de afectación de dicho síndrome. Presentando finalmente una propuesta de intervención enfocada a desarrollar las capacidades necesarias que les permitan transitar hacia la vida adulta de una manera más eficaz.Grado en Educación Socia
ALMA polarimetry measures magnetically aligned dust grains in the torus of NGC 1068
The obscuring structure surrounding active galactic nuclei (AGN) can be
explained as a dust and gas flow cycle that fundamentally connects the AGN with
their host galaxies. This structure is believed to be associated with dusty
winds driven by radiation pressure. However, the role of magnetic fields, which
are invoked in almost all models for accretion onto a supermassive black hole
and outflows, is not thoroughly studied. Here we report the first detection of
polarized thermal emission by means of magnetically aligned dust grains in the
dusty torus of NGC 1068 using ALMA Cycle 4 polarimetric dust continuum
observations (, pc; 348.5 GHz, m). The polarized torus
has an asymmetric variation across the equatorial axis with a peak polarization
of \% and position angle of (B-vector) at
pc east from the core. We compute synthetic polarimetric observations of
magnetically aligned dust grains assuming a toroidal magnetic field and
homogeneous grain alignment. We conclude that the measured 860 m continuum
polarization arises from magnetically aligned dust grains in an optically thin
region of the torus. The asymmetric polarization across the equatorial axis of
the torus arises from 1) an inhomogeneous optical depth, and 2) a variation of
the velocity dispersion, i.e. variation of the magnetic field turbulence at
sub-pc scales, from the eastern to the western region of the torus. These
observations and modeling constrain the torus properties beyond spectral energy
distribution results. This study strongly supports that magnetic fields up to a
few pc contribute to the accretion flow onto the active nuclei.Comment: 19 pages, 11 figures (Accepted for Publication to ApJ
Temperature-dependent release of ATP from human erythrocytes: Mechanism for the control of local tissue perfusion
Copyright @ 2012 The AuthorsThis article has been made available through the Brunel Open Access Publishing Fund.Human limb muscle and skin blood flow increases significantly with elevations in temperature, possibly through physiological processes that involve temperature-sensitive regulatory mechanisms. Here we tested the hypothesis that the release of the vasodilator ATP from human erythrocytes is sensitive to physiological increases in temperature both in vitro and in vivo, and examined potential channel/transporters involved. To investigate the source of ATP release, whole blood, red blood cells (RBCs), plasma and serum were heated in vitro to 33, 36, 39 and 42°C. In vitro heating augmented plasma or ‘bathing solution’ ATP in whole blood and RBC samples, but not in either isolated plasma or serum samples. Heat-induced ATP release was blocked by niflumic acid and glibenclamide, but was not affected by inhibitors of nucleoside transport or anion exchange. Heating blood to 42°C enhanced (P < 0.05) membrane protein abundance of cystic fibrosis transmembrane conductance regulator (CFTR) in RBCs. In a parallel in vivo study in humans exposed to whole-body heating at rest and during exercise, increases in muscle temperature from 35 to 40°C correlated strongly with elevations in arterial plasma ATP (r2 = 0.91; P = 0.0001), but not with femoral venous plasma ATP (r2 = 0.61; P = 0.14). In vitro, however, the increase in ATP release from RBCs was similar in arterial and venous samples heated to 39°C. Our findings demonstrate that erythrocyte ATP release is sensitive to physiological increases in temperature, possibly via activation of CFTR-like channels, and suggest that temperature-dependent release of ATP from erythrocytes might be an important mechanism regulating human limb muscle and skin perfusion in conditions that alter blood and tissue temperature.This article is made available through the Brunel Open Access Publishing Fund
Ocular accommodation and wavelength: The effect of longitudinal chromatic aberration on the stimulus-response curve.
The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye
On the algorithmic construction of classifying spaces and the isomorphism problem for biautomatic groups
We show that the isomorphism problem is solvable in the class of central
extensions of word-hyperbolic groups, and that the isomorphism problem for
biautomatic groups reduces to that for biautomatic groups with finite centre.
We describe an algorithm that, given an arbitrary finite presentation of an
automatic group , will construct explicit finite models for the skeleta
of and hence compute the integral homology and cohomology of
.Comment: 21 pages, 4 figure
A High Spatial Resolution Mid-Infrared Spectroscopic Study of the Nuclei and Star-Forming Regions in Luminous Infrared Galaxies
We present a high spatial (diffraction-limited) resolution (~0.3")
mid-infrared (MIR) spectroscopic study of the nuclei and star-forming regions
of 4 local luminous infrared galaxies (LIRGs) using T-ReCS on the Gemini South
telescope. We investigate the spatial variations of the features seen in the
N-band spectra of LIRGs on scales of ~100 pc, which allow us to separate the
AGN emission from that of the star formation (SF). We compare our Gemini T-ReCS
nuclear and integrated spectra of LIRGs with those obtained with Spitzer IRS.
The 9.7um silicate absorption feature is weaker in the nuclei of the LIRGs than
in the surrounding regions. This is probably due to the either clumpy or
compact environment of the central AGN or young, nuclear starburst. We find
that the [NeII] luminosity surface density is tightly and directly correlated
with that of Pa-alpha for the LIRG star-forming regions (slope of 1.00+-0.02).
Although the 11.3um PAH feature shows also a trend with Pa-alpha, this is not
common for all the regions. We also find that the [NeII]\Pa-alpha ratio does
not depend on the Pa-alpha equivalent width (EW), i.e., on the age of the
ionizing stellar populations, suggesting that, on the scales probed here, the
[NeII] emission line is a good tracer of the SF activity in LIRGs. On the other
hand, the 11.3um PAH\Pa-alpha ratio increases for smaller values of the
Pa-alpha EW (increasing ages), indicating that the 11.3um PAH feature can also
be excited by older stars than those responsible for the Pa-alpha emission.
Additional high spatial resolution observations are essential to investigate,
in a statistical way, the star formation in local LIRGs at the smallest scales
and to probe ultimately whether they share the same physical properties as
high-z LIRGs, ULIRGs and submillimiter galaxies.Comment: 23 pages (apjstyle), 19 figures, accepted for publicacion in Ap
Local Luminous Infrared Galaxies. I. Spatially resolved observations with Spitzer/IRS
We present results from the Spitzer/IRS spectral mapping observations of 15
local luminous infrared galaxies (LIRGs). In this paper we investigate the
spatial variations of the mid-IR emission which includes: fine structure lines,
molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum
emission and the 9.7um silicate feature. We also compare the nuclear and
integrated spectra. We find that the star formation takes place in extended
regions (several kpc) as probed by the PAH emission as well as the [NeII] and
[NeIII] emissions. The behavior of the integrated PAH emission and 9.7um
silicate feature is similar to that of local starburst galaxies. We also find
that the minima of the [NeIII]/[NeII] ratio tends to be located at the nuclei
and its value is lower than that of HII regions in our LIRGs and nearby
galaxies. It is likely that increased densities in the nuclei of LIRGs are
responsible for the smaller nuclear [NeIII]/[NeII] ratios. This includes the
possibility that some of the most massive stars in the nuclei are still
embedded in ultracompact HII regions. In a large fraction of our sample the
11.3um PAH emission appears more extended than the dust 5.5um continuum
emission. We find a dependency of the 11.3um PAH/7.7 um PAH and [NeII]/11.3um
PAH ratios with the age of the stellar populations. Smaller and larger ratios
respectively indicate recent star formation. The estimated warm (300 K < T <
1000 K) molecular hydrogen masses are of the order of 10^8 M_Sun, which are
similar to those found in ULIRGs, local starbursts and Seyfert galaxies.
Finally we find that the [NeII] velocity fields for most of the LIRGs in our
sample are compatible with a rotating disk at ~kpc scales, and they are in a
good agreement with H-alpha velocity fields.Comment: Comments: 52 pages, accepted for publicacion in ApJ
GRADE Evidence to Decision (EtD) frameworks : A systematic and transparent approach to making well-informed healthcare choices. 1. Introduction
Funding: Work on this article has been partially funded by the European Commission FP7 Program (grant agreement 258583) as part of the DECIDE project. Sole responsibility lies with the authors; the European Commission is not responsible for any use that may be made of the information contained therein.Peer reviewedPublisher PD
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