3,321 research outputs found
Chemical physics insight of PPy-based modified ion exchange membranes: a fundamental approach
Four commercially available, cost-effective ion exchange membranes (two cationic and two anionic exchange membranes, CEMs and AEMs, respectively) were modified to mitigate crossover phenomena of the redox active species typically observed in Aqueous Organic Redox Flow Batteries (AORFB) systems. The modification strategy was carried out using a pyrrole(Py)-based polymer which successfully reduced the permeation of two redox active organic molecules, a viologen derivative (named BP7 throughout this study) and TEMPOL, by an order of magnitude. Additionally, modified membranes showed not significant changes in ion conductivity, with negligible effect on the electrical conductivity of the membranes at a given conditions. The morphology, physicochemical, mechanical, and electrochemical properties of the membranes were determined to evaluate the impact of these modifications. AEMs modified in this manner were found to have optimal properties, showing an increase in ion exchange capacity while maintaining excellent mechanical stability and unaltered permselectivity. Additionally, the diffusion boundary layer of these AEMs was slightly extended, which suggests a greater double layer stability for ion exchange processes than in the case of CEMs. Our work shows that these modified membranes could be an appealing approach for AORFB applicationsThis work has been funded by the European Union under the HIGREEW project, Affordable High-performance Green Redox Flow batteries (Grant agreement no. 875613). H2020: LC-BAT-4-2019875613
Integral field spectroscopy of nitrogen overabundant blue compact dwarf galaxies
We study the spatial distribution of the physical properties and of oxygen
and nitrogen abundances in three Blue Compact Dwarf Galaxiess (HS 0128+2832, HS
0837+4717 and Mrk 930) with a reported excess of N/O in order to investigate
the nature of this excess and, particularly, if it is associated with
Wolf-Rayet (WR) stars We have observed these BCDs by using PMAS integral field
spectroscopy in the optical spectral range (3700 - 6900 {\AA}), mapping their
physical-chemical properties, using both the direct method and appropriate
strong-line methods. We make a statistical analysis of the resulting
distributions and we compare them with the integrated properties of the
galaxies. Our results indicate that outer parts of the three galaxies are
placed on the "AGN-zone" of the [NII]/H{\alpha} vs. [OIII]/H{\beta} diagnostic
diagram most likely due to a high N/O combined with the excitation structure in
these regions. From the statistical analysis, it is assumed that a certain
property can be considered as spatially homogeneous (or uniform) if a normal
gaussian function fits its distribution in several regions of the galaxy.
Moreover, a disagreement between the integrated properties and the mean values
of the distribution usually appears when a gaussian does not fit the
corresponding distribution. We find that for Mrk 930, the uniformity is found
for all parameters, except for electron density and reddening. The rotation
curve together with the H{\alpha} map and UV images, reveal a perturbed
morphology and possible interacting processes. The N/O is found to be constant
in the three studied objects at spatial scales of the order of several kpc so
we conclude that the number of WR stars estimated from spectroscopy is not
sufficient to pollute the ISM and to produce the observed N/O excess in these
objectsComment: 17 pages, 14 figures, accepted for publication in Astronomy &
Astrophysic
High contrast optical imaging of companions: the case of the brown dwarf binary HD-130948BC
High contrast imaging at optical wavelengths is limited by the modest
correction of conventional near-IR optimized AO systems.We take advantage of
new fast and low-readout-noise detectors to explore the potential of fast
imaging coupled to post-processing techniques to detect faint companions to
stars at small separations. We have focused on I-band direct imaging of the
previously detected brown dwarf binary HD130948BC,attempting to spatially
resolve the L2+L2 benchmark system. We used the Lucky-Imaging instrument
FastCam at the 2.5-m Nordic Telescope to obtain quasi diffraction-limited
images of HD130948 with ~0.1" resolution.In order to improve the detectability
of the faint binary in the vicinity of a bright (I=5.19 \pm 0.03) solar-type
star,we implemented a post-processing technique based on wavelet transform
filtering of the image which allows us to strongly enhance the presence of
point-like sources in regions where the primary halo dominates. We detect for
the first time the BD binary HD130948BC in the optical band I with a SNR~9 at
2.561"\pm 0.007" (46.5 AU) from HD130948A and confirm in two independent
dataset that the object is real,as opposed to time-varying residual speckles.We
do not resolve the binary, which can be explained by astrometric results
posterior to our observations that predict a separation below the NOT
resolution.We reach at this distance a contrast of dI = 11.30 \pm 0.11, and
estimate a combined magnitude for this binary to I = 16.49 \pm 0.11 and a I-J
colour 3.29 \pm 0.13. At 1", we reach a detectability 10.5 mag fainter than the
primary after image post-processing. We obtain on-sky validation of a technique
based on speckle imaging and wavelet-transform processing,which improves the
high contrast capabilities of speckle imaging.The I-J colour measured for the
BD companion is slightly bluer, but still consistent with what typically found
for L2 dwarfs(~3.4-3.6).Comment: accepted in A\&
Evolución del acceso a la universidad y de la elección de titulación universitaria entre población joven en Catalunya
En este artículo se analiza la evolución del acceso a la universidad a lo largo de doce años en los que ha habido cambios institucionales y de contexto importantes. Con datos para Catalunya, primero se analizan los cambios en el acceso según el nivel educativo de los progenitores de los nuevos estudiantes. Los resultados muestran que se han dado oscilaciones en las tasas de nuevo acceso a la universidad que pueden ser atribuidas a modificaciones del contexto, pero la distancia entre los diversos grupos sociales se mantiene a lo largo del tiempo. A continuación se observa la evolución de la frecuencia de elección de titulaciones de precio alto y dificultad alta constatando que se han producido cambios en las elecciones de los estudiantes. Son principalmente las mujeres las que han cambiado sus pautas de elección, pero polarizando sus comportamientos en función de la nota de acceso y de su nivel formativo familiar
Divergent Effects of Glycemic Control and Bariatric Surgery on Circulating Concentrations of TMAO in Newly Diagnosed T2D Patients and Morbidly Obese
High circulating concentrations of the gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) are significantly associated with the risk of obesity and type 2 diabetes (T2D). We aimed at evaluating the impact of glycemic control and bariatric surgery on circulating concentrations of TMAO and its microbiota-dependent intermediate, γ-butyrobetaine (γBB), in newly diagnosed T2D patients and morbidly obese subjects following a within-subject design. Based on HbA1c concentrations, T2D patients achieved glycemic control. However, the plasma TMAO and γBB concentrations were significantly increased, without changes in estimated glomerular filtration rate. Bariatric surgery was very effective in reducing weight in obese subjects. Nevertheless, the surgery reduced plasma γBB concentrations without affecting TMAO concentrations and the estimated glomerular filtration rate. Considering these results, an additional experiment was carried out in male C57BL/6J mice fed a Western-type diet for twelve weeks. Neither diet-induced obesity nor insulin resistance were associated with circulating TMAO and γBB concentrations in these genetically defined mice strains. Our findings do not support that glycemic control or bariatric surgery improve the circulating concentrations of TMAO in newly diagnosed T2D and morbidly obese patients
Global and regional cortical thinning in first-episode psychosis patients: relationships with clinical and cognitive features
BackgroundThe thickness of the cortical mantle is a sensitive measure for identifying alterations in cortical structure. We aimed to explore whether first episode schizophrenia patients already show a significant cortical thinning and whether cortical thickness anomalies may significantly influence clinical and cognitive features.MethodWe investigated regional changes in cortical thickness in a large and heterogeneous sample of schizophrenia spectrum patients (n=142) at their first break of the illness and healthy controls (n=83). Magnetic resonance imaging brain scans (1.5 T) were obtained and images were analyzed by using BRAINS2. The contribution of sociodemographic, cognitive and clinical characterictics was investigated.ResultsPatients showed a significant total cortical thinning (F=17.55, d=−0.62, p0.53). No significant group × gender interactions were observed (all p’s>0.15). There were no significant associations between the clinical and pre-morbid variables and cortical thickness measurements (all r’s<0.12). A weak significant negative correlation between attention and total (r=−0.24, p=0.021) and parietal cortical thickness (r=−0.27, p=0.009) was found in patients (thicker cortex was associated with lower attention). Our data revealed a similar pattern of cortical thickness changes related to age in patients and controls.ConclusionsCortical thinning is independent of gender, age, age of onset and duration of the illness and does not seem to significantly influence clinical and functional symptomatology. These findings support a primary neuro-development disorder affecting the normal cerebral cortex development in schizophrenia
Herschel PEP: The star-formation rates of 1.5<z<2.5 massive galaxies
The star formation rate (SFR) is a key parameter in the study of galaxy
evolution. The accuracy of SFR measurements at z~2 has been questioned
following a disagreement between observations and theoretical models. The
latter predict SFRs at this redshift that are typically a factor 4 or more
lower than the measurements. We present star-formation rates based on
calorimetric measurements of the far-infrared (FIR) luminosities for massive
1.5<z<2.5, normal star-forming galaxies (SFGs), which do not depend on
extinction corrections and/or extrapolations of spectral energy distributions.
The measurements are based on observations in GOODS-N with the Photodetector
Array Camera & Spectrometer (PACS) onboard Herschel, as part of the PACS
Evolutionary Probe (PEP) project, that resolve for the first time individual
SFGs at these redshifts at FIR wavelengths. We compare FIR-based SFRs to the
more commonly used 24 micron and UV SFRs. We find that SFRs from 24 micron
alone are higher by a factor of ~4-7.5 than the true SFRs. This overestimation
depends on luminosity: gradually increasing for log L(24um)>12.2 L_sun. The
SFGs and AGNs tend to exhibit the same 24 micron excess. The UV SFRs are in
closer agreement with the FIR-based SFRs. Using a Calzetti UV extinction
correction results in a mean excess of up to 0.3 dex and a scatter of 0.35 dex
from the FIR SFRs. The previous UV SFRs are thus confirmed and the mean excess,
while narrowing the gap, is insufficient to explain the discrepancy between the
observed SFRs and simulation predictions.Comment: Accepted for publication in the A&A Herschel first results special
issue. v2 Correction to the meta data onl
The Mass-Metallicity relation explored with CALIFA: I. Is there a dependence on the star formation rate?
We present the results on the study of the global and local M-Z relation
based on the first data available from the CALIFA survey (150 galaxies). This
survey provides integral field spectroscopy of the complete optical extent of
each galaxy (up to 2-3 effective radii), with enough resolution to separate
individual HII regions and/or aggregations. Nearly 3000 individual HII
regions have been detected. The spectra cover the wavelength range between
[OII]3727 and [SII]6731, with a sufficient signal-to-noise to derive the oxygen
abundance and star-formation rate associated with each region. In addition, we
have computed the integrated and spatially resolved stellar masses (and surface
densities), based on SDSS photometric data. We explore the relations between
the stellar mass, oxygen abundance and star-formation rate using this dataset.
We derive a tight relation between the integrated stellar mass and the
gas-phase abundance, with a dispersion smaller than the one already reported in
the literature (0.07 dex). Indeed, this
dispersion is only slightly larger than the typical error derived for our
oxygen abundances. However, we do not find any secondary relation with the
star-formation rate, other than the one induced due to the primary relation of
this quantity with the stellar mass. We confirm the result using the 3000
individual HII regions, for the corresponding local relations.
Our results agree with the scenario in which gas recycling in galaxies, both
locally and globally, is much faster than other typical timescales, like that
of gas accretion by inflow and/or metal loss due to outflows. In essence,
late-type/disk dominated galaxies seem to be in a quasi-steady situation, with
a behavior similar to the one expected from an instantaneous
recycling/closed-box model.Comment: 19 Pages, 8 figures, Accepted for Publishing in Astronomy and
Astrophysics (A&A
- …