4,281 research outputs found
Interpretación de anisotropías petrográficas en granitos ornamentales basada en la medida de la velocidad de las ondas P
The existence of a possible anisotropy, determined by the orientation of any mineral or by microcrack network in granite rock, isn´t easily detected by the naked eye. Five granitic rocks from Galicia (Spain), namely Albero, Gris Alba, Gris Mondariz, Rosa Porriño and Traspielas, were characterized petrographically by means of textural and mineralogical studies, using optical polarizing microscopy, and fractographic studies were carried out under scanning electron microscopy. Longitudinal wave propagation velocity was measured in three orthogonal directions on cubic samples, oriented according to rift surface (known in quarry works like the preferential partition surface visible in the blocks). Vp was measured on dry and water saturated samples. All the dry samples showed an anisotropic behaviour of Vp. Models of microcrack network distribution and possible mineral grain orientation were developed based on the obtained data.La existencia de una posible anisotropía originada por orientación de minerales y/o redes de microfisuración en rocas graníticas no es fácilmente detectable a simple vista. Cinco rocas graníticas de Galicia, denominadas comercialmente Albero, gris Alba, gris Mondariz, rosa Porriño y Traspielas, se caracterizaron petrográficamente, mediante estudios texturales y mineralógicos utilizando microscopía óptica de polarización, realizándose también estudios fractográficos bajo microscopía electrónica de barrido. Se midieron las velocidades de propagación de las ondas longitudinales (Vp) en tres direcciones ortogonales en muestras cúbicas orientadas según el rift (denominado así en cantería como la superficie preferente de partición). Vp se midió en muestras secas y saturadas. Todas las muestras secas mostraron un comportamiento anisótropo de Vp. A partir de los datos obtenidos se han interpretado las redes de distribución de microfisuras y la orientación de minerales
Density and reproductive characteristics of female brown bears in the Cantabrian Mountains, NW Spain
Here we present annual nearest-neighbour distances (as a proxy of density) between females with cubs-of-the-year (hereafter FCOY) and reproductive characteristics of brown bears Ursus arctos in the Cantabrian Mountains (NW Spain), from 1989 to 2017. FCOY nearest-neighbour distances and reproduction parameters of 19 focal females followed over several consecutive years (from 2004 to 2017) were obtained from bears inhabiting the western sector of the Cantabrian Mountains, where most of the bear population resides. In contrast, general reproductive characteristics were studied in the whole Cantabrian Mountains (western and eastern sectors together) on a sample of 362 litter sizes and 695 cubs. Mean nearest-neighbour distance between FCOY was 2559 ± 1222 m (range = 1305–4757 m). Mean litter size was significantly larger in the west (1.8 ± 0.2 cubs) than in the east (1.3 ± 0.6 cubs). Mean litter size for the whole of the Cantabrian Mountains was 1.6 ± 0.3 cubs. Litter sizes of one, two and three cubs represented 33.4, 56.1 and 10.5% of observed family groups, respectively. Interannual variations in litter size were not significant for both the western and the eastern areas. Mean cub mortality was 0.2 ± 0.5 cubs and did not vary among years. Cub mortality per litter size was 3.9% for one cub, 69.2% for two cubs and 26.9% for three cubs. Mean reproductive rate of the 19 focal females was 1.5 ± 0.6 cubs (n = 58 litters). Litter size of focal FCOY did not differ from the litter size obtained from systematic observations in the whole Cantabrian Mountains. During this period, cub mortality occurred in 24.1% of the 58 litters. Females usually bred every second year (average litter interval = 2.2 years). The estimated reproductive rate for the bear population was 0.7 young born/year/reproductive adult female
Forward Brillouin Scattering Spectroscopy in Optical Fibers with Whispering-Gallery Modes
Opto-mechanical interactions in different photonic platforms as optical fibers and optical microresonators are raising great attention, and new exciting achievements have been reported in the last few years. Transverse acoustic mode resonances (TAMRs) in optical fibers -which can be excited optically via electrostriction and generate forward Brillouin scattering (FBS)- are being promoted as the physical mechanism for new fiber-sensing concepts. Here, the study reports a novel approach to detect and characterize opto-excited TAMRs of an optical fiber based on the interplay with optical surface wave resonances, i.e., optical whispering-gallery mode (WGM) resonances. TAMRs induce perturbations in the geometry and the dielectric permittivity of the fiber over the entire cross-section. It is shown that these perturbations couple the acoustic with the optical resonances and affect WGMs in a noticeable way. The study proposes and demonstrates the use of WGMs for probing opto-excited TAMRs in optical fibers. This probing technique provides the narrowest linewidths ever reported for the TAMRs and demonstrates an optimum efficiency for the detection of low-order TAMRs. The interplay between sensitivity, bandwidth, and Q factor of the WGM resonance is discussed
Properties of the ionized gas in HH202. I: Results from integral field spectroscopy with PMAS
We present results from integral field spectroscopy with the Potsdam
multi-Aperture Spectrograph of the head of the Herbig-Haro object HH 202 with a
spatial sampling of 1"x1". We have obtained maps of different emission lines,
physical conditions --such as electron temperature and density-- and ionic
abundances from recombination and collisionally excited lines. We present the
first map of the Balmer temperature and of the temperature fluctuation
parameter, t^2. We have calculated the t^2 in the plane of the sky, which is
substantially smaller than that determined along the line of sight. We have
mapped the abundance discrepancy factor of O^{2+}, ADF(O^{2+}), finding its
maximum value at the HH 202-S position. We have explored the relations between
the ADF(O^{2+}) and the electron density, the Balmer and [O III] temperatures,
the ionization degree as well as the t^2 parameter. We do not find clear
correlations between these properties and the results seem to support that the
ADF and t^2 are independent phenomena. We have found a weak negative
correlation between the O^{2+} abundance determined from recombination lines
and the temperature, which is the expected behaviour in an ionized nebula,
hence it seems that there is not evidence for the presence of super-metal rich
droplets in H II regions.Comment: 12 pages, 11 figures. Accepted for publication in MNRA
Multicolor photometry of ten Seyfert 1 galaxies
We present BVI photometry of ten Seyfert 1 galaxies and narrow band H-alpha
images for six of these objects as well. The results indicate that the
luminosity sample distribution has an amplitude of almost 4 magnitudes with an
average of M_B=-20.7. The observed morphologies are confined to early type
galaxies. A barred structure is found in only 2 objects. Despite that early
morphological types are dominant in this sample, integrated (B-V) colors are
very blue. For instance, the SO galaxies show, on average, a (B-V)=0.78. This
effect seems to be caused by the luminosity contribution of the active nucleus
and/or the disk to the total luminosity of the galaxy. In the B band, the
contribution of the active galactic nucleus to the total luminosity of the
galaxy varies from 3% to almost 60% and the bulge to disk luminosity ratio
(L_bulge/L_disk) ranges from 0.6 to 22. Signs of tidal interactions seems to be
a common characteristic since they are observed in 6 of the objects and one of
them seems to be located in a poor cluster not yet identified in the
literature. H_alpha extended emission is rare, with only 1 galaxy showing clear
evidence of it. Luminosity profile decomposition shows that the model Gauss +
bulge + disk properly reproduces the surface brightness of the galaxies.
However, in order to account for the luminosity profile, most of the disk
galaxies needs the inner truncated exponential form with a central cutoff
radius ranging from 3 to 10 kpc. This is interpreted in terms of reddened
regions that are well identified in the B-V color maps. These regions present
very similar colors among them, with (B-V)~1.2. This fact could be associated
to the presence of dust confined in the inner regions of the galaxies.Comment: 14 pages, 25 figures. Accepted to Astronomy & Astrophysic
Nearby supernova host galaxies from the CALIFA Survey: II. SN environmental metallicity
The metallicity of a supernova (SN) progenitor, together with its mass, is
one of the main parameters that rules their outcome. We present a metallicity
study of 115 nearby SN host galaxies (0.005<z<0.03) which hosted 142 SNe using
Integral Field Spectroscopy (IFS) from the CALIFA survey. Using O3N2 we found
no statistically significant differences between the gas-phase metallicities at
the locations of the three main SN types (Ia, Ib/c and II) all having
~8.500.02 dex. The total galaxy metallicities are also very similar and we
argue that this is because our sample consists only of SNe discovered in
massive galaxies (log(M/Msun)>10 dex) by targeted searches. We also found no
evidence that the metallicity at the SN location differs from the average
metallicity at the GCD of the SNe. By extending our SN sample with published
metallicities at the SN location, we studied the metallicity distributions for
all SN subtypes split into SN discovered in targeted and untargeted searches.
We confirm a bias toward higher host masses and metallicities in the targeted
searches. Combining data from targeted and untargeted searches we found a
sequence from higher to lower local metallicity: SN Ia, Ic, and II show the
highest metallicity, which is significantly higher than SN Ib, IIb, and Ic-BL.
Our results support the picture of SN Ib resulting from binary progenitors and,
at least part of, SN Ic being the result of single massive stars stripped of
their outer layers by metallicity driven winds. We studied several proxies of
the local metallicity frequently used in the literature and found that the
total host metallicity allows for the estimation of the metallicity at the SN
location with an accuracy better than 0.08 dex and very small bias. In
addition, weak AGNs not seen in total spectra may only weakly bias (by 0.04
dex) the metallicity estimate from integrated spectra. (abridged)Comment: 24 pages, 16 Figures, 13 Tables, Accepted in A&
Aperture effects on the oxygen abundance determinations from CALIFA data
This paper aims at providing aperture corrections for emission lines in a
sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey
(CALIFA) database. In particular, we explore the behavior of the
log([OIII]5007/Hbeta)/([NII]6583/Halpha) (O3N2) and log[NII]6583/Halpha (N2)
flux ratios since they are closely connected to different empirical
calibrations of the oxygen abundances in star forming galaxies.
We compute median growth curves of Halpha, Halpha/Hbeta, O3N2 and N2 up to
2.5R_50 and 1.5 disk R_eff. The growth curves simulate the effect of observing
galaxies through apertures of varying radii. The median growth curve of the
Halpha/Hbeta ratio monotonically decreases from the center towards larger
radii, showing for small apertures a maximum value of ~10% larger than the
integrated one. The median growth curve of N2 shows a similar behavior,
decreasing from the center towards larger radii. No strong dependence is seen
with the inclination, morphological type and stellar mass for these growth
curves. Finally, the median growth curve of O3N2 increases monotonically with
radius. However, at small radii it shows systematically higher values for
galaxies of earlier morphological types and for high stellar mass galaxies.
Applying our aperture corrections to a sample of galaxies from the SDSS
survey at 0.02<=z<=0.3 shows that the average difference between fiber-based
and aperture corrected oxygen abundances, for different galaxy stellar mass and
redshift ranges, reaches typically to ~11%, depending on the abundance
calibration used. This average difference is found to be systematically biased,
though still within the typical uncertainties of oxygen abundances derived from
empirical calibrations. Caution must be exercised when using observations of
galaxies for small radii (e.g. below 0.5R_eff) given the high dispersion shown
around the median growth curves.Comment: Accepted for publication in Ap
Impact of the 'Seguro Médico Siglo XXI'medical insurance programme on neonatal and infant mortality in Mexico, 2006-14: an ecological approach to estimation
The ‘Seguro Medico Siglo XXI’ (SMSXXI), a universal coveragemedical insurance programme for children under 5 years of age, started in 2006 to help avoid catastrophic health expenditures in poor families without social security in Mexico. The study used information from the National Health Information System for the 2006–14 period. An ecological approach was followed with a panel of the 2457 municipalities of Mexico as the units of analysis. The outcome variables were the municipality-level neonatal mortality and infant mortality rates in population without access to social security. The programme variable was the coverage of the SMSXXI programme at the municipality level, expressed as a proportion. Demographic and economic variables defined at the municipality level were included as covariates. Impact was estimated by fitting a fixed-effects negative binomial regression model. Results reveal that the SMSXXI significantly reduced both infant and neonatSal mortality in the target population, although in a non-linear fashion, with minimum mortality levels found around the 70% coverage range. The effect is mostly given by the transition from the first quintile to the fourth quintile of coverage (<13% vs 70.5–93.7% coverage), and it is attenuated significantly at coverage levels very close to or at 100%. The observed risk reduction amounted to an estimated total of 11 358 infant deaths being avoided due to the SMSXXI during the 2006–14 period, of which 48% were neonatal. In conclusion, we found a significant impact of the SMSXXI programme on both infant mortality and neonatal mortality. An attenuation of the effect of the insurance on mortality rates at levels close to 100% coverage may reflect the saturation of health units in detriment of the quality of care
The O3N2 and N2 abundance indicators revisited: improved calibrations based on CALIFA and Te-based literature data
The use of IFS is since recently allowing to measure the emission line fluxes
of an increasingly large number of star-forming galaxies both locally and at
high redshift. The main goal of this study is to review the most widely used
empirical oxygen calibrations, O3N2 and N2, by using new direct abundance
measurements. We pay special attention to the expected uncertainty of these
calibrations as a function of the index value or abundance derived and the
presence of possible systematic offsets. This is possible thanks to the
analysis of the most ambitious compilation of Te-based HII regions to date.
This new dataset compiles the Te-based abundances of 603 HII regions extracted
from the literature but also includes new measurements from the CALIFA survey.
Besides providing new and improved empirical calibrations for the gas
abundance, we also present here a comparison between our revisited calibrations
with a total of 3423 additional CALIFA HII complexes with abundances derived
using the ONS calibration by Pilyugin et al. (2010). The combined analysis of
Te-based and ONS abundances allows us to derive their most accurate calibration
to date for both the O3N2 and N2 single-ratio indicators, in terms of all
statistical significance, quality and coverage of the space of parameters. In
particular, we infer that these indicators show shallower abundance
dependencies and statistically-significant offsets compared to those of Pettini
and Pagel (2004), Nagao et al. (2006) and P\'erez-Montero and Contini (2009).
The O3N2 and N2 indicators can be empirically applied to derive oxygen
abundances calibrations from either direct abundance determinations with random
errors of 0.18 and 0.16, respectively, or from indirect ones (but based on a
large amount of data) reaching an average precision of 0.08 and 0.09 dex
(random) and 0.02 and 0.08 dex (systematic; compared to the direct
estimations),respectively.Comment: 12 pages, 5 figures, accepted for publication in A&
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