University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Sulfur degassing at Erta Ale (Ethiopia) and Masaya (Nicaragua) volcanoes: Implications for degassing processes and oxygen fugacities of basaltic systems†

Abstract: We investigate the relationship between sulfur and oxygen fugacity at Erta Ale and Masaya volcanoes. Oxygen fugacity was assessed utilizing Fe3+/Sigma Fe and major element compositions measured in olivine-hosted melt inclusions and matrix glasses. Erta Ale melts have Fe3+/Sigma Fe of 0.15-0.16, reflecting fO(2) of Delta QFM 0.0 +/- 0.3, which is indistinguishable from fO(2) calculated from CO2/CO ratios in high-temperature gases. Masaya is more oxidized at Delta QFM + 1.7 +/- 0.4, typical of arc settings. Sulfur isotope compositions of gases and scoria at Erta Ale (delta S-34(gas) - 0.5 parts per thousand; delta S-34(scoria) + 0.9 parts per thousand) and Masaya (delta S-34(gas) + 4.8 parts per thousand; delta S-34(scoria) + 7.4 parts per thousand) reflect distinct sulfur sources, as well as isotopic fractionation during degassing (equilibrium and kinetic fractionation effects). Sulfur speciation in melts plays an important role in isotope fractionation during degassing and S6+/Sigma S is 0.67 in Masaya melt inclusions. No change is observed in Fe3+/Sigma Fe or S6+/Sigma S with extent of S degassing at Erta Ale, indicating negligible effect on fO(2), and further suggesting that H2S is the dominant gas species exsolved from the S2--rich melt (i.e., no redistribution of electrons). High SO2/H2S observed in Erta Ale gas emissions is due to gas re-equilibration at low pressure and fixed fO(2). Sulfur budget considerations indicate that the majority of S injected into the systems is emitted as gas, which is therefore representative of the magmatic S isotope composition. The composition of the Masaya gas plume (+4.8 parts per thousand) cannot be explained by fractionation effects but rather reflects recycling of high delta S-34 oxidized sulfur through the subduction zone

State of the Climate in 2018

Abstract: El documento contiene la seccion c. Central America and the Caribbean del capitulo 7. Regional Climates

Latin Americans show wide-spread Converso ancestry and imprint of local Native ancestry on physical appearance

Abstract: Historical records and genetic analyses indicate that Latin Americans trace their ancestry mainly to the intermixing (admixture) of Native Americans, Europeans and Sub-Saharan Africans. Using novel haplotype-based methods, here we infer sub-continental ancestry in over 6,500 Latin Americans and evaluate the impact of regional ancestry variation on physical appearance. We find that Native American ancestry components in Latin Americans correspond geographically to the present-day genetic structure of Native groups, and that sources of non-Native ancestry, and admixture timings, match documented migratory flows. We also detect South/East Mediterranean ancestry across Latin America, probably stemming mostly from the clandestine colonial migration of Christian converts of non-European origin (Conversos). Furthermore, we find that ancestry related to highland (Central Andean) versus lowland (Mapuche) Natives is associated with variation in facial features, particularly nose morphology, and detect significant differences in allele frequencies between these groups at loci previously associated with nose morphology in this sample.