Browsing by Author "Pizarro, Jaime"

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    An island biogeography approach for understanding changes in compositional similarity at present scenario of biotic homogenization
    (ELSEVIER, 2011) Vergara, Pablo M.; Pizarro, Jaime; Castro, Sergio A.
    Local extinction of native species and colonization of non-native species are commonly invoked as responsible for changes in species similarity among biotas of different regions. In this study we used a model of species similarity between islands to assess the emergent, and unexplored, effects of changes in colonization by native species, extinction of non-native species, and propagule pressure on species similarity among insular communities. The model predicts that extinction probability of endemic species has a positive but asymptotic effect on species similarity, which is exacerbated by increasing colonization and reducing extinction of non-native species. Species similarity tends to increase with increasing colonization probability by non-native species, however this effect may be reduced, or even reverted, when the islands are exposed to an elevated number of non-native species that are prone to extinction, high levels of endemic species loss, and an initially large number of native species shared between islands. Species similarity was positively affected by the propagule pressure rate of non-native species only when their colonization and extinction probabilities were large and small enough, respectively. A negative effect of propagule pressure rate can be caused by an increase in the pool size of non-native species, which involves the introduction of different species into different islands, promoting biotic differentiation between islands. Our results indicate that the interactions between colonization, extinction and species pool lead to nonlinear responses and unexpected scenarios of biotic change. In order to validate model predictions, future research programs should focus on understanding the dynamics on such complex meta-communities where coexist native, non-native and endemic species. (C) 2011 Elsevier B.V. All rights reserved.
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    Black carbon and other light-absorbing impurities in snow in the Chilean Andes
    (2019) Rowe, Penny M.; Cordero, Raúl R.; Warren, Stephen G.; Stewart, Emily; Doherty, Sarah J.; Pankow, Alec; Schrempf, Michael; Casassa, Gino; Carrasco, Jorge; Lambert, Fabrice; Pizarro, Jaime; MacDonell, Shelley; Damiani, Alessandro; Rondanelli, Roberto; Huneeus, Nicolás; Fernandoy, Francisco; Neshyba, Steven
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    Contaminant emissions as indicators of chemical elements in the snow along a latitudinal gradient in southern Andes
    (NATURE RESEARCH, 2021) Pizarro, Jaime; Vergara, Pablo M.; Cerda, Sergio; Cordero, Raul R.; Castillo, Ximena; Rowe, Penny M.; Casassa, Gino; Carrasco, Jorge; Damiani, Alessandro; Llanillo, Pedro J.; Lambert, Fabrice; Rondanelli, Roberto; Huneeus, Nicolas; Fernandoy, Francisco; Alfonso, Juan; Neshyba, Steven
    The chemical composition of snow provides insights on atmospheric transport of anthropogenic contaminants at different spatial scales. In this study, we assess how human activities influence the concentration of elements in the Andean mountain snow along a latitudinal transect throughout Chile. The concentration of seven elements (Al, Cu, Fe, Li, Mg, Mn and Zn) was associated to gaseous and particulate contaminants emitted at different spatial scales. Our results indicate carbon monoxide (CO) averaged at 20 km and nitrogen oxide (NOx) at 40 km as the main indicators of the chemical elements analyzed. CO was found to be a significant predictor of most element concentrations while concentrations of Cu, Mn, Mg and Zn were positively associated to emissions of NOx. Emission of 2.5 mu m and 10 mu m particulate matter averaged at different spatial scales was positively associated to concentration of Li. Finally, the concentration of Zn was positively associated to volatile organic compounds (VOC) averaged at 40 km around sampling sites. The association between air contaminants and chemical composition of snow suggests that regions with intensive anthropogenic pollution face reduced quality of freshwater originated from glacier and snow melting.
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    Elemental and mineralogical composition of the western andean snow (18°S–41°S)
    (2019) Alfonso, Juan A.; Cordero, Raul R.; Rowe, Penny M.; Neshyba, Steven; Casassa, Gino; Carrasco, Jorge; MacDonell, Shelley; Lambert, Fabrice; Pizarro, Jaime; Fernandoy, Francisco; Feron, Sarah; Damiani, Alessandro; Llanillo, Pedro; Sepulveda, Edgardo; Jorquera, Jose; Garcia, Belkis; Carrera, Juan M.; Oyola, Pedro; Kang, Choong-Min
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    First approach of fractals nickel-copper dendrites on stainless steel electrodes for ammonia oxidation to nitrogen monitored in operando by differential electrochemical mass spectroscopy
    (2024) Matamala-Troncoso, Felipe; Diaz-Coello, Sergio; Martinez, Francisco; Barrientos, Herna; Lisoni, Judit; Armijo, Francisco; Lozano, David; Pizarro, Jaime; Arevalo, Maria del Carmen; Pastor, Elena; Aguirre, Maria Jesus
    Fractal nickel-copper dendrites were synthesized by electrochemical deposition (ECD) on a stainless steel electrode (SS/NiCu). The electrode surface was characterized using Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffractometry (XRD), and Raman spectroscopy. The Ni-Cu molar ratio and the time applied in the ECD method were studied, revealing that both are critical factors in modifying and controlling the surface morphology. The SS/NiCu electrodes show a higher density current response when exposed to ammonium hydroxide, reaching a limiting current density at concentrations above 0.050 M NH4OH. 4 OH. Ammonia oxidation reaction (AOR) was monitored in operando using differential electrochemical mass spectroscopy (DEMS). When a bias potential over +1.50 V (vs. RHE) was applied, the evolution of oxygen and NO was observed. However, N2 2 was the only oxidation product at a constant potential below +1.50 V (vs. RHE). Oxygen (O2) 2 ) evolution was the main competitive reaction during the AOR. The results show that products are strongly dependent on the electrochemical perturbation applied. The study demonstrated that the SS/NiCu electrodes are suitable for AOR to N2 2 in high alkaline conditions.