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121.
122.
Marco Olivares Germán Rojas Yerko Vásquez J. R. Villanueva 《Astrophysics and Space Science》2013,347(1):83-89
In the present paper we study the causal structure of a topological black hole presented by Mann R.B. (in J. High Energy Phys. 06:075, 2009) by mean the standard Lagrangian procedure, which allow us analyze qualitatively the behavior of test particles using the effective potential. Then, the geodesic motion of massive and massless particles is obtained analytically. We find that confined orbits are forbidden on this spacetime, however radial photons can escape to infinity in an infinite proper time but in a finite coordinate time, this correspond to an interesting and novel result. 相似文献
123.
Antonio García-Casco A. Rodríguez Vega J. Cárdenas Párraga M. A. Iturralde-Vinent C. Lázaro I. Blanco Quintero Y. Rojas Agramonte A. Kröner K. Núñez Cambra G. Millán R. L. Torres-Roldán S. Carrasquilla 《Contributions to Mineralogy and Petrology》2009,158(1):1-16
A new jadeitite jade locality has been discovered in the serpentinite-matrix subduction mélange of the Sierra del Convento
(eastern Cuba) in a context associated with tectonic blocks of garnet-epidote amphibolite, tonalitic–trondhjemitic epidote
gneiss, and blueschist. The mineral assemblages of jadeitite jade and jadeite rocks are varied and include combinations of
jadeite, omphacite, albite, paragonite, analcime, clinozoisite-epidote, apatite, phlogopite, phengite, chlorite, glaucophane,
titanite, rutile, zircon, and quartz formed during various stages in their P–T evolution. Field relationships are obscure,
but some samples made almost exclusively of jadeite show evidence of crystallization from fluid in veins. In one of these
samples studied in detail jadeite shows complex textural and chemical characteristics (including oscillatory zoning) that
denote growth in a changing chemical medium. It is proposed that interaction of an Al–Na rich fluid with ultramafic rocks
produced Al–Na–Mg–Ca fluids of varying composition. Episodic infiltration of these fluids, as a result of episodic opening
of the veins, developed oscillatory zoning by direct precipitation from fluid and after reaction of fluid with pre-existing
jadeite. The latest infiltrating fluids were richer in Mg–Ca, favouring the formation of omphacite and Mg–Ca rich jadeite
in open voids and the replacement of earlier jadeite by fine-grained omphacite + jadeite at 550–560°C. This new occurrence
of jadeite in Cuba opens important perspectives for archeological studies of pre-Columbian jade artifacts in the Caribbean
region. 相似文献
124.
A simplified storm index method to extrapolate intensity–duration–frequency (IDF) curves for ungauged stations in central Chile 下载免费PDF全文
Most of meteorological stations in Chile register rainfall amounts once every 24 h. The creation of intensity–duration–frequency (IDF) curves requires continuous recorded data, and this insufficiency of proper instrumentation has resulted in a lack of IDF curves nationwide. The objective of this study is to further develop and evaluate the feasibility of a new method to estimate IDF curves in ungauged stations under Mediterranean climates of central Chile. A technique used to address this problem is the use of a storm index (SI), also known as the ‘K’ method, which allows the construction of IDF curves from stations with discontinuous data, by extrapolating data from stations with continuous records, as long as daily rainfall intensities for both stations differ by less than 2 mm h?1. To test the applicability of this method, SI values were calculated for 40 meteorological stations located throughout Central Chile (latitudes 30°S to 40°S). The extrapolated IDF curves were then compared with observed data, and the goodness of fit was determined. The results indicate that the storm index method can adequately estimate hourly IDF curve values for stations lacking of continuous rainfall data. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
125.
K. F. Cheung A. C. Phadke Y. Wei R. Rojas Y. J. -M. Douyere C. D. Martino S. H. Houston P. L. -F. Liu P. J. Lynett N. Dodd S. Liao E. Nakazaki 《Ocean Engineering》2003,30(11):1353-1386
This paper describes a model package that simulates coastal flooding resulting from storm surge and waves generated by tropical cyclones. The package consists of four component models implemented at three levels of nested geographic regions, namely, ocean, coastal, and nearshore. The operation is automated through a preprocessor that prepares the computational grids and input atmospheric conditions and manages the data transfer between components. The third generation spectral wave model WAM and a nonlinear long-wave model calculate respectively the wave conditions and storm surge over the ocean region. The simulation results define the water levels and boundary conditions for the model SWAN to transform the storm waves in coastal regions. The storm surge and local tides define the water level in each nearshore region, where a Boussinesq model uses the wave spectra output from SWAN to simulate the surf-zone processes and runup along the coastline. The package is applied to hindcast the coastal flooding caused by Hurricanes Iwa and Iniki, which hit the Hawaiian Island of Kauai in 1982 and 1992, respectively. The model results indicate good agreement with the storm-water levels and overwash debris lines recorded during and after the events, demonstrating the capability of the model package as a forecast tool for emergency management. 相似文献
126.
Fernando Unrein Inés O’Farrell Irina Izaguirre Rodrigo Sinistro María dos Santos Afonso Guillermo Tell 《Aquatic Sciences - Research Across Boundaries》2010,72(2):179-190
Phosphorus has been traditionally regarded as the controlling nutrient for phytoplankton growth, however, N-limitation is
likely to occur in several environments. For example, nitrogen is considered the main nutrient limiting phytoplankton in floodplain
lakes of the Paraná River basin. However, N2-fixing heterocystous cyanobacteria (N2-cyano) are usually absent in these water bodies. The low pH values frequently found may limit the development of these algae.
We hypothesise that long-term lake isolation allows conspicuous phytoplankton growth during summer, resulting in high photosynthetic
rates and pH. This scenario combined with low DIN (dissolved inorganic nitrogen) would favour the development of N2-cyano. Phytoplankton composition was studied during 16 months in a vegetated and isolated floodplain lake in the Paraná basin.
Additionally, pH was artificially increased in in situ mesocosms to test effects on phytoplankton structure. Lake phytoplankton
was dominated by flagellates (cryptophytes and euglenophytes) and small coccoid algae (chlorophytes and colonial cyanobacteria).
Algal biomass was highest during warm periods. Although pH increased up to 8.8 during the second summer period, N2-cyano remained rare, most likely because of the high DIN concentration recorded. The alkalophilic diatom Cyclotella meneghiniana dominated and was positively correlated with pH. Conversely, PO4= concentrations in the mesocosm experiment were high and DIN remained relatively low. pH enhancement in the treated mesocosms
(avg. pH = 8.2) promoted the development of N2-cyano (Anabaena spp.) and C. meneghiniana, which after 1 month of incubation accounted together for 50% of the biomass in contrast to less than 1.6% in control containers.
Our results support the hypothesis that during the warm season and under low DIN concentration, high pH favours N2-cyano growth in these lakes. We provide new evidence supporting the idea that even under optimal nutrient conditions, N2-cyano do not thrive unless other requirements are satisfied. 相似文献
127.
Ursula Mendoza Arthur Ayres Neto Rodrigo C. Abuchacra Cátia Fernandes Barbosa Alberto G. Figueiredo Jr. Manoela C. Gomes Andre L. Belem Ramsés Capilla Ana Luiza S. Albuquerque 《Geo-Marine Letters》2014,34(4):297-314
The Cabo Frio region in the state of Rio de Janeiro, southeast coast of Brazil, is characterized by a local coastal upwelling system and converging littoral sediment transport systems that are deflected offshore at Cabo Frio, as a consequence of which a thick cross-shelf sediment deposit has developed over time. To investigate the evolution of this muddy deposit, geophysical, sedimentological and geochemical data from four sediment cores (3.8–4.1 m in length) recovered in water depths between 88 and 141 m were analyzed. The high-resolution seismic data show variable sediment thicknesses ranging from 1 to 20 m, comprising two sedimentary units separated by a high-impedance layer at a depth of about 10 m below the seafloor at the coring sites. According to the available age datings, the upper sedimentary unit is late Pleistocene to Holocene in age, whereas the lower unit (not dated) must, by implication, be entirely Pleistocene in age. The boomer-seismic reflection signal can be divided into three echo-types, namely transparent (inner shelf), stratified (middle shelf) and reflective (outer shelf), each type seemingly related to the local sediment composition. The upper 4 m of the upper sedimentary unit is dominated by silty sediment on the middle shelf, and by upward-fining sediments (silty sand to sandy silt) on the inner and outer shelf. The downcore trends of P-wave velocity, gamma-ray density and acoustic impedance are largely similar, but generally reversed to those of water and organic carbon contents. Total organic carbon contents increase with decreasing mean grain size, periodic fluctuations suggesting temporal changes in the regional hydrodynamics and primary productivity fuelled by the local upwelling system. The reconstruction of sedimentation rates in the course of the Holocene is based on 35 AMS age datings of organic material recovered from variable downcore depths. These range from a maximum of 13.3 cm/decade near the base of the inner shelf core (7.73–7.70 ka BP) to generally very low values (<0.11 cm/century) over the last thousand years in all cores. Over the last 6 ka there appear to have been three distinct sedimentation peaks, one between 6 and 5 ka BP, another between 4 and 3 ka PB, and one around 1 ka BP. Due to different time intervals between dates, not every peak is equally well resolved in all four cores. Based on the similar sedimentology of the inner and outer shelf cores, an essentially identical sedimentation model is proposed to have been active in both cases, albeit at different times. Thus, already during the last glacial maximum, alongshore sediment transport was deflected offshore by a change in shoreline orientation caused by the Cabo Frio structural high. The source of terrigenous material was probably a barrier-island complex that was subsequently displaced landward in the course of sea-level rise until it stabilized some 6.5 ka BP along the modern coast. 相似文献
128.
Jorge Alonso‐Henar Walter Montero José J. Martínez‐Díaz José A. Álvarez‐Gómez Juan M. Insua‐Arévalo Wilfredo Rojas 《地学学报》2013,25(5):368-373
On 4 May 1910, the most destructive earthquake in the history of Costa Rica (Ms 6.4) destroyed the city of Cartago, a major city located in the Valle Central of Costa Rica. Using both palaeo‐seismological and morphotectonic analyses, we have found evidence that points to the Aguacaliente Fault (AF) as the source of this earthquake. This structure is a N100° E trending, strike‐slip fault situated to the south of Cartago and within a wide band of deformation. We excavated two trenches near Bermejo, south of Cartago. We found evidence of three surface ruptures within the last 1000 years on this fault. The age of the most recent rupture is consistent with the Cartago 1910 earthquake. The AF is a seismogenic source capable of producing large earthquakes (Mw 6.5–6.9) with an estimated recurrence interval of about 500 years. 相似文献
129.
E. Solano I. Novalbos A. J. Ros M. Cortés-Contreras C. Rodrigo 《Astronomische Nachrichten》2023,344(10):e20230116
The aim of this article is making use of the Gaia DR3 catalogue and virtual observatory tools, to confirm and characterize 428 binary and multiple stellar systems classified as neglected (only one observation) in the Washington Double Star Catalogue (WDS). The components of the stellar systems have the same parallax and proper motion (within the errors) and are separated by less than 50,000 AU, which minimizes the number of by-chance counterparts. Effective temperatures calculated using VOSA were used to estimate stellar masses. Binding energies were calculated for 42 binary systems confirming they are physical pairs. Also we found 75 pairs with F/G- M spectral types, which are very interesting to improve the determination of the metallicity of the M star from the higher mass component. 相似文献
130.
Rémy Roca Rodrigo Guzman Julien Lemond Joke Meijer Laurence Picon Hélène Brogniez 《Surveys in Geophysics》2012,33(3-4):565-583
Free tropospheric humidity (FTH) is a key parameter of the radiation budget of the Earth. In particular, its distribution over the intertropical belt has been identified as an important contributor to the water vapour feedback. Idealized radiative transfer computations are performed to underscore the need to consider the whole probability distribution function (PDF) rather than the arithmetical mean of the FTH. The analysis confirmed the overwhelming role of the dry end of the PDF in the radiative perturbation of the top of atmosphere longwave budget. The physical and dynamical processes responsible for the maintenance of this dry part of the FTH distribution are reviewed, and the lateral mixing between the tropics and the extra-tropics is revealed as a major element of the dry air dynamics. The evolution of this lateral mixing in the framework of the global warming is discussed, and perspectives of work are listed as a mean of a conclusion. 相似文献