1,870 research outputs found
Tau Phosphorylation, Aggregation, and Cell Toxicity
Protein aggregation takes place in many neurodegenerative disorders. However, there is a controversy about the possible toxicity of these protein aggregates. In this review, this controversy is discussed, focussing on the tau aggregation that takes place in those disorders known as tauopathies
BVRI Surface Photometry of (S+S) Binary Galaxies. I. The data
We present multicolour broad band () photometry for a sample of 33
spiral-spiral (S+S) binary galaxies drawn from the Karachentsev Catalogue of
Isolated Pairs of Galaxies (KPG). The data is part of a joint observational
programme devoted to systematic photometric study of one of the most complete
and homogeneous pair samples available in the literature. We present
azimuthally averaged colour and surface brightness profiles, colour index (B-I)
maps, B band and sharp/filtered B band images as well as integrated magnitudes,
magnitudes at different circular apertures and integrated colours for each
pair. Internal and external data comparisons show consistency within the
estimated errors. Two thirds of the sample have total aperture parameters
homogeneously derived for the first time. After reevaluating morphology for all
the pairs, we find a change in Hubble type for 24 galaxies compared to the
original POSS classifications. More than half of our pairs show morphological
concordance which could explain, in part, the strong correlation in the (B-V)
colour indices (Holmberg Effect) between pair components. We find a tendency
for barred galaxies to show grand design morphologies and flat colour profiles.
The measurements will be used in a series of forthcoming papers where we try to
identify and isolate the main structural and photometric properties of disk
galaxies at different stages of interaction.Comment: 23 pages. 5 Figures. Accepted for publication in Astronomy and
Astrophysics. Mosaics for all pairs can be found at
http://www.inaoep.mx/~puerari/binar
The Effects of Interactions on the Structure and Morphology of Elliptical/Lenticular galaxies in Pairs
We present a photometric and structural analysis of 42 E/S0 galaxies in (E/S0
+ S) pairs observed in the BVRI color bands. We empirically determine the
effects of interactions on their morphology, structure and stellar populations
as seen from the light concentration (C), asymmetry (A), and clumpiness (S)
parameters. We further compare these values to a control sample of 67 mostly
isolated, non-interacting E/S0 galaxies. The paired E/S0 galaxies occupy a more
scattered loci in CAS space than non-interacting E/S0's, and the structural
effects of interactions on E/S0's are minor, in contrast to disk galaxies
involved in interactions. This suggests that observational methods for
recognizing interactions at high z, such the CAS methodology, would hardly
detect E/S0's involved in interactions (related to early phases of the so
called `dry-mergers'). We however find statistical differences in A when
comparing isolated and interacting E/S0s. In the mean, paired E/S0 galaxies
have A values 2.96+-0.72 times larger than the ones of non-interacting E/S0's.
For the subset of presumably strongly interacting E/S0's, A and S can be
several times larger than the typical values of the isolated E/S0's. We show
that the asymmetries are consistent with several internal and external
morphological distortions. We conclude that the interacting E/S0s in pairs
should be dense, gas poor galaxies in systems spaning a wide range of
interaction stages, with typical merging timescales >~ 0.1-0.5 Gyr. We use the
observed phenomenology of these galaxies to predict the approximate loci of
`dry pre-mergers' in the CAS space.(Abridged)Comment: 23 pages, 9 figures included. To appear in The Astronomical Journa
SDSS-IV MaNGA: global and local stellar population properties of elliptical galaxies
We study the spatially resolved properties of 343 elliptical galaxies with
the MaNGA/SDSS-IV survey. We used the DESI Legacy Imaging Surveys for
morphological classification. Based on integrated spectroscopic properties and
colors, we classified seven classes of ellipticals. We inferred the stellar age
and metallicity () gradients out to a 1.5 effective radius of classical "red
and dead", recently quenched, and blue star-forming ellipticals (CLEs, RQEs,
and BSFs), corresponding to 73%, 10%, and 4% of the sample, respectively. We
reconstructed their global and radial histories of star formation and mass
growth. We find the mass- and luminosity-weighted age gradients of CLEs are
nearly flat or mildly negative. The respective gradients are negative,
being flatter as the mass is smaller. The more massive CLEs formed stars
earlier and quenched faster than the less massive ones. The CLEs show a weak
inside-out growth and a clear inside-out quenching. They finished their
quenching globally 3.8 1.2 Gyr ago, with quenching time-scales of 3.4
0.8 Gyr. At masses < 10 , the age and gradients
of the RQEs and BSFs are flatter than those of the CLEs but with larger
scatters. They show very weak inside-out growth and quenching, which is slow
and even not completed at for the BSFs. Instead, the massive RQEs show
an outside-in quenching and positive gradients in the luminosity-weighted age
and stellar metallicities. The RQEs of all masses quenched 1.2 0.9 Gyr
ago on average. Our results for the CLEs are consistent with a two-phase
scenario where their inner parts formed by an early and coeval dissipative
collapse with a consequent burst of star formation and further quenching,
whereas the outer parts continued their assembly likely by dry mergers. We also
discuss some evolutionary scenarios for the RQE and BSF galaxies.Comment: 24 pages and 18 figures without appendix. We added Table 1 with a
list of acronyms. Original article published in Astronomy & Astrophysic
ESPRESSO: The next European exoplanet hunter
The acronym ESPRESSO stems for Echelle SPectrograph for Rocky Exoplanets and
Stable Spectroscopic Observations; this instrument will be the next VLT high
resolution spectrograph. The spectrograph will be installed at the
Combined-Coud\'e Laboratory of the VLT and linked to the four 8.2 m Unit
Telescopes (UT) through four optical Coud\'e trains. ESPRESSO will combine
efficiency and extreme spectroscopic precision. ESPRESSO is foreseen to achieve
a gain of two magnitudes with respect to its predecessor HARPS, and to improve
the instrumental radial-velocity precision to reach the 10 cm/s level. It can
be operated either with a single UT or with up to four UTs, enabling an
additional gain in the latter mode. The incoherent combination of four
telescopes and the extreme precision requirements called for many innovative
design solutions while ensuring the technical heritage of the successful HARPS
experience. ESPRESSO will allow to explore new frontiers in most domains of
astrophysics that require precision and sensitivity. The main scientific
drivers are the search and characterization of rocky exoplanets in the
habitable zone of quiet, nearby G to M-dwarfs and the analysis of the
variability of fundamental physical constants. The project passed the final
design review in May 2013 and entered the manufacturing phase. ESPRESSO will be
installed at the Paranal Observatory in 2016 and its operation is planned to
start by the end of the same year.Comment: 12 pages, figures included, accepted for publication in Astron. Nach
Association between the plasma/whole blood lead ratio and history of spontaneous abortion: a nested cross-sectional study
<p>Abstract</p> <p>Background</p> <p>Blood lead has been associated with an elevated risk of miscarriage. The plasmatic fraction of lead represents the toxicologically active fraction of lead. Women with a tendency to have a higher plasma/whole blood Pb ratio could tend towards an elevated risk of miscarriage due to a higher plasma Pb for a given whole blood Pb and would consequently have a history of spontaneous abortion.</p> <p>Methods</p> <p>We studied 207 pregnant Mexico City residents during the 1<sup>st </sup>trimester of pregnancy, originally recruited for two cohorts between 1997 and 2004. Criteria for inclusion in this study were having had at least one previous pregnancy, and having valid plasma and blood Pb measurements. Pb was measured in whole blood and plasma by inductively coupled plasma mass spectrometry using ultra-clean techniques. History of miscarriage in previous pregnancies was obtained by interview. The incidence rate of spontaneous abortion was defined as the proportion of previous pregnancies that resulted in miscarriage. Data were analyzed by means of Poisson regression models featuring the incidence rate of spontaneous abortion as the outcome and continuous or categorized plasma/blood Pb ratios as predictor variables. All models were adjusted for age and schooling. Additionally, logistic regression models featuring inclusion in the study sample as the outcome were fitted to assess potential selection bias.</p> <p>Results</p> <p>The mean number of miscarriages was 0.42 (range 0 to 4); mean Pb concentrations were 62.4 and 0.14 μg/L in whole blood and plasma respectively. Mean plasma/blood Pb ratio was 0.22%. We estimated that a 0.1% increment in the plasma/blood Pb ratio lead was associated to a 12% greater incidence of spontaneous abortion (p = 0.02). Women in the upper tertile of the plasma/blood Pb ratio had twice the incidence rate of those in the lower tertile (p = 0.02). Conditional on recruitment cohort, inclusion in the study sample was unrelated to observable characteristics such as number of abortions, number of pregnancies, blood Pb levels, age schooling, weight and height.</p> <p>Conclusion</p> <p>Women with a large plasma/whole blood Pb ratio may be at higher risk of miscarriage, which could be due to a greater availability of placental barrier-crossing Pb.</p
Dietary intake, lung function and airway inflammation in Mexico City school children exposed to air pollutants
<p>Abstract</p> <p>Introduction</p> <p>Air pollutant exposure has been associated with an increase in inflammatory markers and a decline in lung function in asthmatic children. Several studies suggest that dietary intake of fruits and vegetables might modify the adverse effect of air pollutants.</p> <p>Methods</p> <p>A total of 158 asthmatic children recruited at the Children's Hospital of Mexico and 50 non-asthmatic children were followed for 22 weeks. Pulmonary function was measured and nasal lavage collected and analyzed every 2 weeks. Dietary intake was evaluated using a 108-item food frequency questionnaire and a fruit and vegetable index (FVI) and a Mediterranean diet index (MDI) were constructed. The impact of these indices on lung function and interleukin-8 (IL-8) and their interaction with air pollutants were determined using mixed regression models with random intercept and random slope.</p> <p>Results</p> <p>FVI was inversely related to IL-8 levels in nasal lavage (p < 0.02) with a significant inverse trend (test for trend p < 0.001), MDI was positively related to lung function (p < 0.05), and children in the highest category of MDI had a higher FEV<sub>1 </sub>(test for trend p < 0.12) and FVC (test for trend p < 0.06) than children in the lowest category. A significant interaction was observed between FVI and ozone for FEV<sub>1 </sub>and FVC as was with MDI and ozone for FVC. No effect of diet was observed among healthy children.</p> <p>Conclusion</p> <p>Our results suggest that fruit and vegetable intake and close adherence to the Mediterranean diet have a beneficial effect on inflammatory response and lung function in asthmatic children living in Mexico City.</p
VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory
VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l.
in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design,
construction techniques and data acquisition system of the HAWC observatory.
HAWC is an air-shower array currently under construction at the same site of
VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water
Cherenkov detectors and two different data acquisition systems. It was in
operation between October 2011 and May 2012 with an average live time of 30%.
Besides the scientific verification purposes, the eight months of data were
used to obtain the results presented in this paper: the detector response to
the Forbush decrease of March 2012, and the analysis of possible emission, at
energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages,
10 figures). Corresponding authors: A.Marinelli and D.Zaboro
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