Sub-electron readout noise in a Skipper CCD fabricated on high resistivity silicon     

Guillermo Fernández Moroni  Juan Estrada  Gustavo Cancelo  Stephen E. Holland  Eduardo E. Paolini  H. Thomas Diehl 《Experimental Astronomy》2012,34(1):43-64

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Incidence of the host galaxy on the measured optical linear polarization of blazars     

I. Andruchow  Sergio A. Cellone  Gustavo E. Romero 《Monthly notices of the Royal Astronomical Society》2008,388(4):1766-1774

We study the incidence of the underlying host galaxy light on the measured optical linear polarization of blazars. Our methodology consists of the implementation of simulated observations obtained under different atmospheric conditions, which are characterized by the Gaussian σ of the seeing function. The simulated host plus active nucleus systems span broad ranges in luminosity, structural properties, redshift and polarization; this allows us to test the response of the results against each of these parameters.
Our simulations show that, as expected, the measured polarization is always lower than the intrinsic value, due to the contamination by non-polarized star light from the host. This effect is more significant when the host is brighter than the active nucleus, and/or a large photometric aperture is used. On the other hand, if seeing changes along the observing time under certain particular conditions, spurious microvariability could be obtained, especially when using a small photometric aperture. We thus give some recommendations in order to minimize both unwanted effects, as well as basic guidelines to estimate a lower limit of the true (nuclear) polarization.
As an example, we apply the results of our simulations to real polarimetric observations, with high temporal resolution, of the blazar PKS 0521−365.  相似文献   

Effects of Physical Processes and Sampling Resolution on Fault Displacement Versus Length Scaling: The Case of the Cantarell Complex Oilfield,Gulf of Mexico     

Shunshan Xu  Angel F. Nieto-Samaniego  Gustavo Murillo-Muñetón  Susana A. Alaniz-Álvarez  José M. Grajales-Nishimura  Luis G. Velasquillo-Martinez 《Pure and Applied Geophysics》2016,173(4):1125-1142

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Evidence of geomagnetic storm effects in the lower atmosphere: A case study     

Gustavo A. Mansilla  Marta Zossi de Artigas 《Studia Geophysica et Geodaetica》2010,54(3):487-494

Disturbances produced by geomagnetic storms in the higher regions of the Earth’s atmosphere, such as in the ionospheric F2 region and in the lower ionosphere, are relatively better known than those produced at lower altitudes, where the effects of geomagnetic storms have been little studied. During magnetically perturbed conditions, some changes in pressure and temperature at high latitudes have been observed, from the surface level to heights of around 30 km, but there are no morphological studies and/or patterns of behavior. Moreover, the physical mechanisms are still unknown and what exists is a matter of controversy. Thus, the aim of this paper is to contribute to the vertical profile of the effects of geomagnetic storms as observed in the lower sectors of the atmosphere. For that, we study the variations of two atmospheric parameters (temperature and wind speed) during an intense geomagnetic storm (minimum Dst = −300 nT), at heights between about 6 km and 20 km. The data used were obtained from weather balloon flights carried out at low, mid and mid-high latitudes in different longitudinal sectors of the northern hemisphere, which took place twice per day: 00:00 and 12:00 UT. Small, but statistically significant changes in temperature and in zonal component of the neutral winds are observed at mid-high latitudes, which can be linked to short-term geomagnetic forcing. However, the results show different atmospheric response to the geomagnetic storm in the different longitudinal sectors at tropospheric and stratospheric levels, which suggests a regional character of the geomagnetic storms effects at tropospheric levels.  相似文献   

Yielding seismic response of code-designed single-storey asymmetric structures     

J. Alberto Escobar  A. Gustavo Ayala-Milin 《地震工程与结构动力学》1998,27(6):525-541

A study on the seismic performance of asymmetric structures with non-linear behaviour and random properties is presented. The structural response of single-storey models, designed using different code criteria is studied using both a deterministic and a probabilistic approach. The worst structural behaviour, in terms of ductility demands, is obtained for symmetric models considering uncertain properties. It is shown that an arbitrary increase of the total lateral strength of the structures does not lead to an increment of the structural safety proportional to the total lateral strength increase, implying that an expensive structure is not always the safest. © 1998 John Wiley & Sons, Ltd.  相似文献   

Response of infilled frames using pseudo-dynamic experimentation     

Khalid M. Mosalam  Richard N. White  Gustavo Ayala 《地震工程与结构动力学》1998,27(6):589-608

An accurate and practical testing technique to study seismic performance of multi-storey infilled frames is formulated. This technique is based on the pseudo-dynamic method which can provide an acceptable approximation of the dynamic performance of structures under the influence of earthquake excitation. The pseudo-dynamic experimental technique is outlined and applied for testing a two-bay, two-storey gravity load designed steel frame infilled with unreinforced concrete block masonry walls. From the discussion of the results, the dynamic performance of the tested structure is assessed. © 1998 John Wiley & Sons, Ltd.  相似文献   

Morphological Variation of the Sea Silverside Odontesthes regia in Regions with Dissimilar Upwelling Intensity along the Humboldt Current System     

Deville  Diego  Sanchez  Gustavo  Barahona  Sergio  Yamashiro  Carmen  Oré-Chávez  Daniel  Bazán  Roger Quiroz  Umino  Tetsuya 《Ocean Science Journal》2020,55(1):33-48

Ocean Science Journal - We evaluated the influence of areas with dissimilar upwelling intensity along the Humboldt Current System on the morphological variation of the economically important sea...  相似文献   

Geographical ecology of the symbiotic crabs Libinia ferreirae and Libinia spinosa: Distributional patterns in south and south-eastern coast of Brazil     

Geslaine Rafaela Lemos Gonçalves  Luana Ferraz da Silveira Palomares  Aline Nonato Sousa  Gilson Stanski  Gustavo Sancinetti  Rogerio Caetano da Costa  Antonio Leão Castilho 《Marine Ecology》2020,41(4):e12606

The Brazilian coast is home to two species of Majoid crabs: Libinia ferreirae and Libinia spinosa, with similar habits, as they live in symbiosis with the jellyfish Lychnorhiza lucerna during their juvenile stage and dwell on the bottom of the ocean near the coast when adults. This study investigated the spatial and temporal distribution of L. ferreirae and L. spinosa during different ontogenic phases on the south and south-eastern coast of Brazil, between latitudes 22º and 27ºS. Our results showed that both species have different distributions during their development in the three studied regions. Libinia ferreirae were more abundant associated with jellyfish, and L. spinosa were more abundant in the free-living phase. Environmental factors, especially temperature and salinity, for associated and free-living crabs, respectively, are the main factors that need to be supported for the establishment of these specimens. We were able to identify that the presence or absence of hosts (given the ecological interactions between the species) is determinant in finding the associated crabs. Geographical variations (morphology of the regions, marine currents and the strength of the tide) are linked directly to the movement of the jellyfish hosts to the coast, influencing the abundance of L. fereirae and L. spinosa populations and affecting their distribution patterns. We can infer that both species are connected with other populations because of the association with the jellyfish, crabs could be passively transported along the south and south-eastern coast of Brazil, maintaining the connection between metapopulations.  相似文献   

Influence of a breakwater on nearby rocky intertidal community structure   总被引：1，自引：0，他引：1  

Gustavo M. Martins  Andr F. Amaral  Francisco M. Wallenstein  Ana I. Neto 《Marine environmental research》2009,67(4-5):237-245

It is widely recognised that coastal-defence structures generally affect the structure of the assemblages they support, yet their impact on adjacent systems has been largely ignored. Breakwaters modify the nearby physical environment (e.g. wave action) suggesting a local impact on biological parameters. In the present study, an ACI (After-Control-Impact) design was used to test the general hypothesis that the artificial sheltering of an exposed coast has a strong effect on the structure and functioning of adjacent systems. The effects of a reduction in hydrodynamics were clear for a number of taxa and included the replacement of barnacles, limpets and frondose algae by an increasing cover of ephemeral algae. These effects were evident both at early and late successional stages. Results suggest that the artificial sheltering of naturally exposed coasts can have a strong impact promoting a shift from consumer- to producer-dominated communities, which has important ecological and energetic consequences for the ecosystem.  相似文献   

Positioning fisheries in a changing world   总被引：1，自引：1，他引：0  

R. Quentin Grafton  Ray Hilborn  Lori Ridgeway  Dale Squires  Meryl Williams  Serge Garcia  Theodore Groves  James Joseph  Kieran Kelleher  Tom Kompas  Gary Libecap  Carl Gustaf Lundin  Mitsutaku Makino  Thorolfur Matthiasson  Richard McLoughlin  Ana Parma  Gustavo San Martin  Ben Satia  Carl-Christian Schmidt  Maree Tait  Lin Xiu Zhang 《Marine Policy》2008,32(4):630-634

Marine capture fisheries face major and complex challenges: habitat degradation, poor economic returns, social hardships from depleted stocks, illegal fishing, and climate change, among others. The key factors that prevent the transition to sustainable fisheries are information failures, transition costs, use and non-use conflicts and capacity constraints. Using the experiences of fisheries successes and failures it is argued only through better governance and institutional change that encompasses the public good of the oceans (biodiversity, ecosystem integrity, sustainability) and societal values (existence, aesthetic and amenity) will fisheries be made sustainable.  相似文献