463 research outputs found
Flood Hazard Management in Public Mountain Recreation Areas vs. Ungauged Fluvial Basins. Case Study of the Caldera de Taburiente National Park, Canary Islands (Spain)
Las Angustias River is an ungauged stream in the Caldera de Taburiente National Park (Spain), where frequent intense flash-flood events occur. The aim of this research is to analyze the flood hazard at the Playa de Taburiente. Based on the limited information available (short time-series of daily precipitation), a statistical frequency analysis of 24 h rainfall was completed and the precipitation results were transformed into surface runoff. To determine if the model underestimates the flows that are generated in the basin, the dendro-geomorphological information available was used to calibrate results. The results of the HMS model were significantly lower. At this point, both the rainfall data and the rainfall-runoff model were re-analyzed to maximize the rainfall intensity values and the runoff generated (increasing the CN value for the basin). For the 1997 flood event, a 1250 m3·s−1 flood minimizes the RMSE for the disturbed tree sample; this flow value also clearly exceeds any peak flow derived from the rainfall-runoff analysis. It is only when rainfall intensity and surface runoff are maximized that the peak flows obtained approximate those associated with dendro-geomorphological data. The results highlight the difficulties of flood hazard management in ungauged torrential basins in mountain recreational areas (such as National Parks). Thus, in the absence of flow records, when considering the maximum rainfall intensity scenario may be a useful and effective tool for flood risk management
Spectrum of the secondary component and new orbital elements of the massive triple star Delta Ori A
Orionis is the closest massive multiple stellar system and one of
the brightest members of the Orion OB association. The primary (Aa1) is a
unique evolved O star. In this work, we applied a two-step disentangling method
to a series of spectra in the blue region (430 to 450 nm), and we detected
spectral lines of the secondary (Aa2). For the first time, we were able to
constrain the orbit of the tertiary (Ab) - to 55 450 d or 152 yr - using
variable velocities and new speckle interferometric measurements,
which have been published in the Washington Double Star Catalogue. In addition,
the Gaia DR3 parallax of the faint component (Ca+Cb) constrains the distance of
the system to (381 8) pc, which is just in the centre of the Orion OB1b
association, at (382 1) pc. Consequently, we found that the component
masses according to the three-body model are 17.8, 8.5, and 8.7 M,
for Aa1, Aa2, and Ab, respectively, with the uncertainties of the order of
M. We used new photometry from the BRITE satellites together with
astrometry, radial velocities, eclipse timings, eclipse duration, spectral line
profiles, and spectral energy distribution to refine radiative properties. The
components, classified as O9.5 II + B2 V + B0 IV, have radii of 13.1, 4.1, and
12.0 R, which means that Ori A is a pre-mass-transfer
object. The frequency of 0.478 cycles per day, known from the Fourier analysis
of the residual light curve and X-ray observations, was identified as the
rotation frequency of the tertiary. Ori could be related to other
bright stars in Orion, in particular, Ori, which has a similar
architecture, or Ori, which is a single supergiant, and possibly
a post-mass-transfer object.Comment: 22 pages, 22 figure
Properties of Accretion Flows Around Coalescing Supermassive Black Holes
What are the properties of accretion flows in the vicinity of coalescing
supermassive black holes (SBHs)? The answer to this question has direct
implications for the feasibility of coincident detections of electromagnetic
(EM) and gravitational wave (GW) signals from coalescences. Such detections are
considered to be the next observational grand challenge that will enable
testing general relativity in the strong, nonlinear regime and improve our
understanding of evolution and growth of these massive compact objects. In this
paper we review the properties of the environment of coalescing binaries in the
context of the circumbinary disk and hot, radiatively inefficient accretion
flow models and use them to mark the extent of the parameter space spanned by
this problem. We report the results from an ongoing, general relativistic,
hydrodynamical study of the inspiral and merger of black holes, motivated by
the latter scenario. We find that correlated EM+GW oscillations can arise
during the inspiral phase followed by the gradual rise and subsequent drop-off
in the light curve at the time of coalescence. While there are indications that
the latter EM signature is a more robust one, a detection of either signal
coincidentally with GWs would be a convincing evidence for an impending SBH
binary coalescence. The observability of an EM counterpart in the hot accretion
flow scenario depends on the details of a model. In the case of the most
massive binaries observable by the Laser Interferometer Space Antenna, upper
limits on luminosity imply that they may be identified by EM searches out to
z~0.1-1. However, given the radiatively inefficient nature of the gas flow, we
speculate that a majority of massive binaries may appear as low luminosity AGN
in the local universe.Comment: Revised version accepted to Class. Quantum Grav. for proceedings of
8th LISA Symposium. 15 pages, 3 figures, includes changes suggested in
referee report
Recent advances on dendrogeomorphological research applied to flood hazard analysis in Spain.
Estudios dendroecológicos para el análisis de regímentes torrenciales y avenida
Імуногістохімічне виявлення судинного епітеліального ростового фактору в корі великих півкуль головного мозку при порушеннях кровообігу
Порушення кровопостачання мозку – одне з актуальних питань сучасної медицини, що обумовлено, як тяжкістю наслідків кожного конкретного випадку хвороби, так і рівнем показників захворюваності, що сягають пандемії, а смертність від цієї патології становить понад 20% і займає друге місце після серцево-судинних захворювань. Сьогодні зміни при ішемії мозку розглядаються як складний багатовекторний процес зі специфічною кінетикою на перебіг якого можна впливати, а не як одноманітну подію, як вважалось ще 20 років тому
Flood Hazard Analysis in the ”Caldera de Taburiente” National Park (La Palma, Canary Islands, Spain) using Dendrogeomorphology
Aplicación de técnicas dendroecológicas para el estudio de avenidas torrenciales
Temporal Retinal Nerve Fiber Loss in Patients with Spinocerebellar Ataxia Type 1
BACKGROUND: Autosomal dominant spinocerebellar ataxia type 1 is an adult onset progressive disorder with well characterized neurodegeneration in the cerebellum and brainstem. Beyond brain atrophy, few data exist concerning retinal and optic nerve involvement. OBJECTIVE: To evaluate retinal changes in SCA1 patients compared to age and gender matched healthy controls. METHODOLOGY/PRINCIPAL FINDINGS: Nine patients with SCA1 were prospectively recruited from the ataxia clinic and were compared to nine age and gender matched healthy controls. Both cohorts received assessment of visually evoked potentials and eye examination by optical coherence tomography to determine retinal nerve fiber layer thickness and total macular volume. While no differences were found in visually evoked potentials, SCA1 patients showed a significant reduction of mean retinal nerve fiber layer thickness (RNFLT) compared to healthy controls (84±13 µm vs. 97±8 µm, p = 0.004). Temporal areas showed the most prominent RNFLT reduction with high statistical significances (temporal-inferior: p<0.001, temporal: p<0.001, temporal-superior: p = 0.005) whereas RNFLT in nasal areas was in the range of the control group. From six SCA1 patients an additional macular scan was obtained. The comparison to the corresponding healthy control showed a slight but not significant reduction in TMV (8.22±0.68 mm(3) vs. 8.61±0.41 mm(3), p = 0.15). CONCLUSION: In SCA1 patients, we found evidence for degeneration of retinal nerve fibers. The temporal focus of the observed retinal nerve fiber layer reduction suggests an involvement of the papillo-macular bundle which resembles pathology found in toxic or mitochondrial optic nerve disease such as Leber's hereditary optic neuropathy (LHON) or dominant optic atrophy (DOA)
Re-validation of Otocinclus arnoldi Regan and reappraisal of Otocinclus phylogeny (Siluriformes: Loricariidae)
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