193 research outputs found
The Solar Radius in the EUV during the Cycle XXIII
Aims. To determine the solar transition region and coronal radius at EUV
wavelengths and its time evolution during Solar Cycle XXIII.
Methods. We use daily 30.4 and 17.1 nm images obtained by the Extreme
Ultraviolet Imager (EIT) aboard the SoHO satellite and derive the solar radius
by fitting a circle to the limb brightness ring.
Results. The weighted mean of the temporal series gives (967''.56 +/- 0''.04)
and (969''.54 +/- 0''.02) at 30.4 and 17.1 nm respectively. No significant
correlation was found with the solar cycle at any of the two wavelengths.
Conclusions. Since the temperature formation of the 30.4 nm line is between
(60 - 80) 10^3 K (Transition Region), the obtained result is bigger than that
derived from present atmospheric models. On the contrary this height is
compatible with radio models.Comment: accepted for publication in Astronomy & Astrophysics minor changes
introduced during review proces
MODELO EXPERIMENTAL DE GLOMERULONEFRITIS MEMBRANOSA INDUCIDA CON ALBUMINA BOVINA
El objetivo del presente trabajo fue diseñar un modelo experimental de Glomerulonefritis Membranosa (GM) en ratas Wistar, inducida con Seroalbúmina Bovina (BSA), y validarlo mediante la determinación de parámetros bioquímicos, histológicos, ultraestructurales y detección de inmunocomplejos por inmunofluorescencia (IF). Los animales del grupo experimental fueron inmunizados por vía subcutánea, con dosis de 3 mg c/u de BSA/PBS con adyuvante de Freund. Se efectuaron diferentes esquemas de inmunización. Cuando el título de anticuerpos fue ≥1/2, comenzó la administración diaria de 2 mg, por vía endovenosa de BSA/PBS, durante 15 días. Se evaluó la funcionalidad renal por la proteinuria; después de la 5° semana, desde su aparición, se determinó: depuración (clearance) de creatinina, uremia, proteinemia y perfil lipídico. Los dos riñones se usaron para estudios histológicos, ultraestructurales y detección de inmunocomplejos por IF. Los resultados mostraron que la inmunización fue efectiva con 5 R E S U M E N inoculaciones c/15 días. En los animales nefróticos la proteinuria, depuración (clearance) de creatinina, proteinemia , uremia y el perfil lipídico presentaron alteraciones significativas (p<0.0001). Al microscopio óptico se observó hipercelularidad, engrosamiento difuso de las membranas basales de los capilares glomerulares y diferentes grados de atrofia, esclerosis e hialinización de los glomérulos. Por IF se detectó inmunocomplejos IgG en el 100 % de los glomérulos. Ultraestructuralmente, se observaron depósitos subepiteliales electrodensos en la membrana basal engrosada, compatibles con inmunocomplejos . Se encontraron alteraciones en la estructura de los podocitos. En conclusión, los estudios bioquímicos, estructurales y ultraestructurales permitieron inferir la inducción de un síndrome nefrótico experimental. Concluimos que el protocolo utilizado tiene validez para la inducción de una glomerulonefritis membranosa en ratas Wistar
Quiet-Sun imaging asymmetries in NaI D1 compared with other strong Fraunhofer lines
Imaging spectroscopy of the solar atmosphere using the NaI D1 line yields
marked asymmetry between the blue and red line wings: sampling a quiet-Sun area
in the blue wing displays reversed granulation, whereas sampling in the red
wing displays normal granulation. The MgI b2 line of comparable strength does
not show this asymmetry, nor does the stronger CaII 8542 line. We demonstrate
the phenomenon with near-simultaneous spectral images in NaI D1, MgI b2, and
CaII 8542 from the Swedish 1-m Solar Telescope. We then explain it with
line-formation insights from classical 1D modeling and with a 3D
magnetohydrodynamical simulation combined with NLTE spectral line synthesis
that permits detailed comparison with the observations in a common format. The
cause of the imaging asymmetry is the combination of correlations between
intensity and Dopplershift modulation in granular overshoot and the sensitivity
to these of the steep profile flanks of the NaI D1 line. The MgI b2 line has
similar core formation but much wider wings due to larger opacity buildup and
damping in the photosphere. Both lines obtain marked core asymmetry from
photospheric shocks in or near strong magnetic concentrations, less from
higher-up internetwork shocks that produce similar asymmetry in the spatially
averaged CaII 8542 profile.Comment: Accepted by Astron & Astrophys. In each in-text citation the year
links to the corresponding ADS abstract pag
Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models
Four spot megrim (Lepidorhombus boscii) weight-length and weight-weight relationships in northern Iberian waters (stock 8.c, 9.a)
Total weight-length, gutted weight-length and total weight-gutted weight relationships were fitted for the Iberian Atlantic stock of four spot megrim (Lepidorhombus boscii) and their temporal variations were analyzed. The large sample size, size range and timeseries available allowed obtaining robust somatic parameters of combined sexes for the total weight-length relationships (a=0.0043, b=3.2008), for the gutted weight-length relationships (a=0.0055, b=3.1139), and the weight conversion factors (1.062).
They are considered to best fit the current biometric relationships and most appropriate to be used in the stock assessment of the status of the stock and they contribute to a deeper knowledge of the life history traits of this species
The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations
The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding
rocket payload built to study the crucial interface between the solar
chromosphere and the corona by observing the strongest line in the solar
spectrum, the Ly-a line at 1216 {\AA}. In two flights, VAULT succeeded in
obtaining the first ever sub-arcsecond (0.5") images of this region with high
sensitivity and cadence. Detailed analyses of those observations have
contributed significantly to new ideas about the nature of the transition
region. Here, we present a broad overview of the Ly-a atmosphere as revealed by
the VAULT observations, and bring together past results and new analyses from
the second VAULT flight to create a synthesis of our current knowledge of the
high-resolution Ly-a Sun. We hope that this work will serve as a good reference
for the design of upcoming Ly-a telescopes and observing plans.Comment: 28 pages, 11 figure
Magnetohydrostatic atmospheres
We show that the atmospheric and magnetic height variations are coupled in
general MHS equilibria with gravity when isolated thin non-force-free flux
tubes are present. In gas-dominated environments, as in stellar photospheres,
flux tubes must expand rapidly with height to maintain pressure balance with
the cool surroundings. But in magnetically dominated environments, as in
stellar coronae, the large-scale background magnetic field determines the
average spreading of embedded flux tubes, and rigidly held flux tubes {\it
require} a specific surrounding atmosphere with a unique temperature profile
for equilibrium. The solar static equilibrium atmosphere exhibits correct
transition-region properties and the accepted base coronal temperature for the
sun's main magnetic spherical harmonic. Steady flows contribute to the overall
pressure, so equilibria with accelerated wind outflows are possible as well.
Flux tubes reflect a mathematical degeneracy in the form of non-force-free
fields, which leads to coupling in general equilibrium conditions. The
equilibrium state characterizes the system average in usual circumstances and
dynamics tend to maintain the MHS atmosphere. Outflows are produced everywhere
external to rigidly held flux tubes that refill a depleted or cool atmosphere
to the equilibrium gas profile, heating the gas compressively.Comment: 12 pages, 5 figures, accepted by A&
Megrim (Lepidorhombus whiffiagonis) weight-length relationships in the northern Bay of Biscay and Celtic Sea
The weight-length relationships are of a great interest in fish biology, stock assessment and fishery management, by predicting weight from length information and allowing to estimate the stock biomass. Weight-length relationships of megrim (Lepidorhombus whiffiagonis), an economically relevant flatfish species, are studied for two decades (2001 to 2019) in northern Bay of Biscay and Celtic Sea (ICES stock Div. 7.b-k, 8.abd), two important European fishing areas. More than 22000 specimens collected from commercial landings by AZTI and IEO were sampled. Total fish length, total weight and commercial gutted weight were obtained. Four five-year periods (quinquennium) (2000-04; 2005-09; 2010-14; 2015-19) were defined in the studied time-series. Both the large sample size and time-series available, as well as the collaboration between both institutions collecting complementary information from this stock, allowed obtaining robust somatic parameters and analyzing their temporal variations. A weight-length relationship model was fitted and the quinquennium and semester factors, which are of interest biologically and for assessment purposes, and their interactions were significant in the preliminary model. The weight-length relationships, both for total and gutted weight and for the combined sexes of the most recent quinquennium are presented in this work and considered the most suitable to be used in the oncoming annual assessment process of the status of this stock in northern Bay of Biscay and Celtic Sea in ICES
- …