531 research outputs found
Nota sobre las características estructurales de la zona de "Cueto Negro" (Cordillera Cantábrica)
Se citan algunos datos estructurales respecto a la zona comprendida entre los puertos Pajares y La Cubilla (Cordillera Cantábrica). Se destaca la presencia de una ventana tectónica, en la zona de Cueto negro, relacionada con la unidad cabalgante de Bodón, ampliamente replegada. Estos elementos se integran dentro del haz de estructuras que caracterizan el "arco medio" de la Rodilla Astúrica (Cordillera Cantábrica, España)
The generalized MIC-Kepler system
This paper deals with dynamical system that generalizes the MIC-Kepler
system. It is shown that the Schr\"{o}dinger equation for this generalized
MIC-Kepler system can be separated in spherical and parabolic coordinates. The
spectral problem in spherical and parabolic coordinates is solved.Comment: 8 page
Perceived risks of infection, hospitalization, and death from COVID-19 at the Equator: Ecuador and Kenya
Objectives: This study''s goal was to determine the perceived risks of infection as well as the perceived risks of hospitalization and death from COVID-19 in Ecuador and Kenya. It also assessed the factors associated with the risk-related perceptions. Methods: Cross-sectional studies with samples from the adult populations in both countries were conducted to assess the perceived risks of contracting COVID-19. Data were collected online using the Qualtrics platform from samples of 1, 050 heads of households ages 18 years or older in each country. Three statistical analyses were conducted: summary statistics, correlation, and linear regression. Results: The average perceived risks of COVID-19 infection, hospitalization, and death in the Kenyan sample were 27.1%, 43.2%, and 17.2%, respectively, and the values for the Ecuadorian sample were 34%, 32.8%, and 23.3%, respectively. The Pearson''s correlation coefficients between the risk measures in each country were less than 0.38. Risk measures were associated with several sociodemographic variables (e.g., income, gender, location) but not age. Conclusions: The perceived risks of COVID-19 infection, hospitalization, and death in Kenya and Ecuador were significantly higher relative to the statistics reported; however, no strong association existed between perceived risk and age, which is a key factor in adverse health outcomes, including death, among COVID-19 infected individuals
Obscuration in AGNs: near-infrared luminosity relations and dust colors
We combine two approaches to isolate the AGN luminosity at near-infrared
wavelengths and relate the near-IR pure AGN luminosity to other tracers of the
AGN. Using integral-field spectroscopic data of an archival sample of 51 local
AGNs, we estimate the fraction of non-stellar light by comparing the nuclear
equivalent width of the stellar 2.3 micron CO absorption feature with the
intrinsic value for each galaxy. We compare this fraction to that derived from
a spectral decomposition of the integrated light in the central arc second and
find them to be consistent with each other. Using our estimates of the near-IR
AGN light, we find a strong correlation with presumably isotropic AGN tracers.
We show that a significant offset exists between type 1 and type 2 sources in
the sense that type 1 sources are 7 (10) times brighter in the near-IR at log
L_MIR = 42.5 (log L_X = 42.5). These offsets only becomes clear when treating
infrared type 1 sources as type 1 AGNs.
All AGNs have very red near-to-mid-IR dust colors. This, as well as the range
of observed near-IR temperatures, can be explained with a simple model with
only two free parameters: the obscuration to the hot dust and the ratio between
the warm and hot dust areas. We find obscurations of A_V (hot) = 5 - 15 mag for
infrared type 1 sources and A_V (hot) = 15 - 35 mag for type 2 sources. The
ratio of hot dust to warm dust areas of about 1000 is nicely consistent with
the ratio of radii of the respective regions as found by infrared
interferometry.Comment: 17 pages, 10 Figures, 3 Tables, accepted by A&
On the relation of optical obscuration and X-ray absorption in Seyfert galaxies
The optical classification of a Seyfert galaxy and whether it is considered
X-ray absorbed are often used interchangeably. But there are many borderline
cases and also numerous examples where the optical and X-ray classifications
appear to be in conflict. In this article we re-visit the relation between
optical obscuration and X-ray absorption in AGNs. We make use of our "dust
color" method (Burtscher et al. 2015) to derive the optical obscuration A_V and
consistently estimated X-ray absorbing columns using 0.3--150 keV spectral
energy distributions. We also take into account the variable nature of the
neutral gas column N_H and derive the Seyfert sub-classes of all our objects in
a consistent way.
We show in a sample of 25 local, hard-X-ray detected Seyfert galaxies (log
L_X / (erg/s) ~ 41.5 - 43.5) that there can actually be a good agreement
between optical and X-ray classification. If Seyfert types 1.8 and 1.9 are
considered unobscured, the threshold between X-ray unabsorbed and absorbed
should be chosen at a column N_H = 10^22.3 / cm^2 to be consistent with the
optical classification.
We find that N_H is related to A_V and that the N_H/A_V ratio is
approximately Galactic or higher in all sources, as indicated previously. But
in several objects we also see that deviations from the Galactic ratio are only
due to a variable X-ray column, showing that (1) deviations from the Galactic
N_H/A_V can simply be explained by dust-free neutral gas within the broad line
region in some sources, that (2) the dust properties in AGNs can be similar to
Galactic dust and that (3) the dust color method is a robust way to estimate
the optical extinction towards the sublimation radius in all but the most
obscured AGNs.Comment: 7 pages, 3 figures, accepted for publication by A&A; updated PDF to
include abstrac
Financial crisis and pension reform in Spain:the effect of labour market dynamics
We analyse the effect of post-financial crisis unemployment dynamics on the Spanish pension system’s financial health using Aggregate Accounting. We compare the basic scenario where the current labour market dynamics persist with a full employment (best-case) scenario. We find that economic risk is the main driver of unsustainability in the short run. However, in the long run, the main driver of expenditures lies in the ageing demographic structure. Our results suggest that future reforms should increase labour market participation but confirm that recent pension reforms do not attain sustainability in the long run, indicating the need of further pension reforms
Three-dimensional stability of Burgers vortices
Burgers vortices are explicit stationary solutions of the Navier-Stokes
equations which are often used to describe the vortex tubes observed in
numerical simulations of three-dimensional turbulence. In this model, the
velocity field is a two-dimensional perturbation of a linear straining flow
with axial symmetry. The only free parameter is the Reynolds number , where is the total circulation of the vortex and is
the kinematic viscosity. The purpose of this paper is to show that Burgers
vortex is asymptotically stable with respect to general three-dimensional
perturbations, for all values of the Reynolds number. This definitive result
subsumes earlier studies by various authors, which were either restricted to
small Reynolds numbers or to two-dimensional perturbations. Our proof relies on
the crucial observation that the linearized operator at Burgers vortex has a
simple and very specific dependence upon the axial variable. This allows to
reduce the full linearized equations to a vectorial two-dimensional problem,
which can be treated using an extension of the techniques developped in earlier
works. Although Burgers vortices are found to be stable for all Reynolds
numbers, the proof indicates that perturbations may undergo an important
transient amplification if is large, a phenomenon that was indeed observed
in numerical simulations.Comment: 31 pages, no figur
High cut-off membrane for in- vivo dialysis of free plasma hemoglobin in a patient with massive hemolysis
Background: The possibility of clearing Cell-free Plasma Hemoglobin (CPH) from human plasma may appear attractive, especially when considering the noxious effects that CPH has on the immune function and the renal damage caused by its filtration. The existence of the so-called High Cut-Off (HCO) filters, possessing pores as big as 60 kDa, could potentially allow the clearance of the αβ dimers (31.3 kDa), the form in which the α2β2 hemoglobin tetramers (62.6 kDa) physiologically dissociate in plasma. We present herein the first reported case in which such an attempt was made. Case presentation: The patient was a 51-year-old man with hemolytic crisis due to glucose-6-phosphate dehydrogenase deficiency, further complicated by pigment-induced nephropathy. He underwent a 48-h CVVHD session, in which a HCO filter was used. The Sieving Coefficient (SC) for CPH was initially 0.08 and decreased to 0.02 after 24 h. This unexpected low SC was due to the initial high concentration of CPH (4.24 g/L). At such concentrations, the α2β2 tetramer poorly dissociates into the αβ dimer; but increases exponentially at concentrations lower than 1 g/L. Conclusions: Clearance of CPH through a HCO filter is technically feasible but its performance markedly relies on the initial concentration of CPH. Critically ill patients with smoldering hemolysis, as it happens during septic shock or ECMO treatment, may benefit the most from the use of this membrane in order to clear CPH
Gas and dust in a submillimeter galaxy at z = 4.24 from the Herschel ATLAS
We report ground-based follow-up observations of the exceptional source,
ID141, one the brightest sources detected so far in the H-ATLAS cosmological
survey. ID141 was observed using the IRAM 30-meter telescope and Plateau de
Bure interferometer (PdBI), the Submillimeter Array (SMA) and the Atacama
Pathfinder Experiment (APEX) submillimeter telescope to measure the dust
continuum and emission lines of the main isotope of carbon monoxide and carbon
([C I] and [C II]). The detection of strong CO emission lines with the PdBI
confirms that ID141 is at high redshift (z=4.243 +/- 0.001). The strength of
the continuum and emission lines suggests that ID141 is gravitationally lensed.
The width (Delta V (FWHM) ~ 800 km/s}) and asymmetric profiles of the CO and
carbon lines indicate orbital motion in a disc or a merger. The properties
derived for ID141 are compatible with a ultraluminous (L_FIR ~ 8.5 +/- 0.3 x
10^13/mu_L Lsun, where mu_L is the amplification factor, dense (n ~ 10^4 cm^-3)
and warm (T_kin ~ 40K) starburst galaxy, with an estimated star-formation rate
of (0.7 to 1.7) x 10^4/mu_L Msun/yr. The carbon emission lines indicate a dense
(n ~ 10^4 cm^-3) Photo-Dominated Region, illuminated by a far-UV radiation
field a few thousand times more intense than that in our Galaxy. In conclusion,
the physical properties of the high-z galaxy, ID141, are remarkably similar to
those of local ultraluminous infrared galaxies.Comment: To appear in Ap
Molecules as tracers of galaxy evolution: an EMIR survey. I. Presentation of the data and first results
We investigate the molecular gas properties of a sample of 23 galaxies in
order to find and test chemical signatures of galaxy evolution and to compare
them to IR evolutionary tracers. Observation at 3 mm wavelengths were obtained
with the EMIR broadband receiver, mounted on the IRAM 30 m telescope on Pico
Veleta, Spain. We compare the emission of the main molecular species with
existing models of chemical evolution by means of line intensity ratios
diagrams and principal component analysis. We detect molecular emission in 19
galaxies in two 8 GHz-wide bands centred at 88 and 112 GHz. The main detected
transitions are the J=1-0 lines of CO, 13CO, HCN, HNC, HCO+, CN, and C2H. We
also detect HC3N J=10-9 in the galaxies IRAS 17208, IC 860, NGC 4418, NGC 7771,
and NGC 1068. The only HC3N detections are in objects with HCO+/HCN<1 and warm
IRAS colours. Galaxies with the highest HC3N/HCN ratios have warm IRAS colours
(60/100 {\mu}m>0.8). The brightest HC3N emission is found in IC 860, where we
also detect the molecule in its vibrationally excited state.We find low HNC/HCN
line ratios (<0.5), that cannot be explained by existing PDR or XDR chemical
models. Bright HC3N emission in HCO+-faint objects may imply that these are not
dominated by X-ray chemistry. Thus the HCN/HCO+ line ratio is not, by itself, a
reliable tracer of XDRs. Bright HC3N and faint HCO+ could be signatures of
embedded starformation, instead of AGN activity
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