Chemical evolution of dwarf spheroidal and blue compact galaxies     

Gustavo A. Lanfranchi  Francesca Matteucci 《Monthly notices of the Royal Astronomical Society》2003,345(1):71-85

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Gravitational microlensing of γ-ray blazars     

Diego F. Torres  Gustavo E. Romero  Ernesto F. Eiroa  Joachim Wambsganss  Martín E. Pessah 《Monthly notices of the Royal Astronomical Society》2003,339(2):335-352

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Dry spells in the River Plata Basin: an approximation of the diagnosis of droughts using daily data   总被引：1，自引：1，他引：0  

Walter M. Vargas  Gustavo Naumann  Juan L. Minetti 《Theoretical and Applied Climatology》2011,104(1-2):159-173

This study addresses the dry spells observed in the La Plata Basin using daily data from 94 observation stations during sampling periods from 1900 to 2005. Dry days were defined as having less than 0.3?mm of accumulated precipitation. This definition allowed for the assessment of the dryness in the La Plata Basin and a comparison with other regions. The main purpose of this study was to analyse dry spells, especially extreme cases (meteorological droughts), and assess them on a daily basis. Trends and low frequency of droughts were analysed using a general framework to detect and compare properties of dry states based on daily and annual time scales. The trends were estimated using two different methods. Overall, the trends showed a decrease, especially in the eastern basin region during the period of 1972?C1996. The results showed sporadic decreases in dry events and events of extreme dryness (droughts). Spectral structure permits an inference of low-frequency maxima and confirmed an inter-annual 2- to 3-year period of variability in drought occurrence for most of the basin. Furthermore, probabilistic distribution functions of dry spells at basin stations were analysed to confirm that they followed a geometric?Cbinomial distribution. Additional tests were used to determine whether there was a second threshold, using the Weibull and gamma adjustment models. In order to study spatial homogeneity, the field of dry spell maxima in the basin was generated using a vector array based on the occurrence date and length of the maximum spell. Due to the dependence of spell length on the annual cycle, the longest spells were observed from April to the beginning of winter in the Argentine northwest region and in the northern and western regions of the basin. The intensity of droughts decreased in the Pampas and Mesopotamia regions. The drought of 1988 was considered to be the longest dry spell in the basin. The water deficits from this drought resulted in Argentinean economic losses of more than four billion US dollars during 1988.  相似文献   

Corrigendum to “Gillnet fisheries as a major mortality factor of Magellanic penguins in wintering areas” [Mar. Pollut. Bull. 62 (2011) 840-844]     

Luis Gustavo Cardoso  Leandro Bugoni 《Marine pollution bulletin》2011,62(8):1932

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Optical properties and light penetration in a deep,naturally acidic,iron rich lake: Lago Caviahue (Patagonia,Argentina)     

Gustavo D. Baffico 《Limnologica》2013,43(6):475-481

The optical properties and light climate in the deep and extremely acid Lake Caviahue have been studied in order to better understand its characteristics and the possible influence upon the phytoplankton community. The absorption coefficients for the dissolved fraction were maximal in the ultraviolet (UV) region and the water absorption spectra showed a shoulder around 300 nm, which was attributed to the concentration of Fe(III). No radiation was detected in the water column below 360 nm. The depth of the 1% incident radiation was dependent of wavelength, showing its maximum of 13.3 m at 565 nm, compared to 1.7 m and 4.8 m at 400 nm and 700 nm, respectively. Phytoplankton biomass was low and showed an almost constant profile with depth despite the relative darkness of the water column. Optical climate of Lake Caviahue is not typical of high elevation lakes but is more similar to low elevation shallow lakes of the Andean region. The chemical composition of the water, mainly Fe oxidation state and concentration, is the responsible for the high attenuation of the UV radiation (UVR). Living organisms are protected of UVR because Lake Caviahue waters are a shield against UV-B.  相似文献   

Monthly streamflow forecasting using neuro-wavelet techniques and input analysis     

André Gustavo da Silva Melo Honorato  Gustavo Barbosa Lima da Silva  Celso Augusto Guimarães Santos 《水文科学杂志》2013,58(15-16):2060-2075

ABSTRACT

Combinations of low-frequency components (also known as approximations) resulting from the wavelet decomposition are tested as inputs to an artificial neural network (ANN) in a hybrid approach, and compared to classical ANN models for flow forecasting for 1, 3, 6 and 12 months ahead. In addition, the inputs are rewritten in terms of the flow, revealing what type of information was being provided to the network, in order to understand the effect of the approximations on the forecasting performance. The results show that the hybrid approach improved the accuracy of all tested models, especially for 1, 3 and 6 months ahead. The input analyses show that high-frequency components are more important for shorter forecast horizons, while for longer horizons, they may worsen the model accuracy.  相似文献   

Spatial and temporal changes in reef fish assemblages on disturbed coral reefs,north Pacific coast of Costa Rica     

Gustavo Arias‐Godínez  Carlos Jimnez  Carlos Gamboa  Jorge Corts  Mario Espinoza  Juan Jos Alvarado 《Marine Ecology》2019,40(1)

Benthic structure of coral reefs determines the availability of refuges and food sources. Therefore, structural changes caused by natural and anthropogenic disturbances can have negative impacts on reef‐associated communities. During the 1990s, coral reefs from Bahía Culebra were considered among the most diverse ecosystems along the Pacific coast of Costa Rica; however, recently they have undergone severe deterioration as consequence of chronic stressors such as El Niño‐Southern Oscillation and harmful algal blooms. Reef fish populations in this area have also been intensely exploited. This study compared reef fish assemblages during two periods (1995–1996 and 2014–2016), to determine whether they have experienced changes as a result of natural and anthropogenic disturbances. For both periods, benthic composition and reef fish abundance were recorded using underwater visual censuses. Live coral cover (LCC) decreased from 43.09 ± 18.65% in 1995–1996 to 1.25 ± 2.42% in 2014–2016 (U = 36, p < 0.05). Macroalgal cover (%) in 2014–2016 was sixfold higher than mean values reported for the Eastern Tropical Pacific region. Mean (±SD) fish species richness in 1995–1996 (36.67 ± 14.20) was higher than in 2014–2016 (23.00 ± 9.14; U = 20, p < 0.05). Over 40% of reef fish orders observed in 1995–1996 were not detected in the 2014–2016 surveys, including large‐bodied predators. Reduction in abundance of fish predators such as sharks, grunts, and snappers is likely attributed to changes in habitat structure. Herbivorous such as parrotfishes and pufferfishes increased their abundance at sites with low LCC, probably in response to predators decline and increased algal cover. These findings revealed significant degradation and drastic loss of structural complexity in coral reefs from Bahía Culebra, which now are dominated by macroalgae. The large reduction in structural complexity of coral reefs has resulted in the loss of diversity and key ecological roles (e.g., predation and herbivory), thus potentially reducing the resilience of the entire ecosystem.  相似文献   

Quantifying the impact of no-till on sediment yield in southern Brazil at the hillslope and catchment scales     

Ana L. Londero  Jean P. G. Minella  Fabio J. A. Schneider  Dinis Deuschle  Gustavo H. Merten  Olivier Evrard  Madalena Boeni 《水文研究》2021,35(7):e14286

No-till (NT) is a soil management system designed to protect soil resources from water erosion and provide numerous benefits compared to conventional tillage through the increase of organic matter inputs into the soil. However, NT in isolation is not sufficient to control erosion processes caused by an excessive production of surface runoff. This study evaluated soil losses on agricultural hillslopes under no-till characterized by contrasted water, soil, and crop management conditions. To this end, water and soil losses were monitored between 2014 and 2018 at two scales, including four macroplots (0.6 ha; 27 events) and two paired zero-order catchments (2.4 ha; 63 events). The resulting dataset covered a wide range of rainfall conditions that occurred in contrasted soil, crop, and runoff management conditions. Hyetographs, hydrographs, and sedigraphs were constructed, and these data were used to evaluate the impact of management on sediment yields, including that of terraces, scarification, and phytomass on sediment yield. The installation of terraces reduced sediment yield by 58.7%, mainly through surface runoff control. Crop management including an increased phytomass input efficiently controlled soil losses (63%), although it did not reduce runoff volume and peak flow. In contrast, scarification had no impact on runoff and soil losses. The current research demonstrated the need to combine the installation of terraces and leaving a high amount of phytomass on the soil to control surface runoff and erosion and reduce sediment yield. The current research therefore reinforces the relevance of the monitoring strategy conducted at the scale of macroplots and zero-order catchments to evaluate the impact of contrasted water, soil, and crop management methods and select the most effective conservation agriculture practices.  相似文献   

Effects of environmental gradients on sandy beach macrofauna of a semi‐enclosed bay     

Ricardo S. Cardoso  Gustavo Mattos  Carlos H.S. Caetano  Tatiana M.B. Cabrini  Ludmila B. Galhardo  Felipe Meireis 《Marine Ecology》2012,33(1):106-116

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Toroidal,Counter-Toroidal,and Upwelling Flow in the Mantle Wedge of the Rivera and Cocos Plates: Implications for IOB Geochemistry in the Trans-Mexican Volcanic Belt     

Florian Neumann  Alberto Vásquez-Serrano  Gustavo Tolson  Raquel Negrete-Aranda  Juan Contreras 《Pure and Applied Geophysics》2016,173(10-11):3395-3417

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