Compositional variations and magma mixing in the 1991 eruptions of Hudson volcano, Chile

The August 1991 eruptions of Hudson volcano produced ∼2.7 km3 (dense rock equivalent, DRE) of basaltic to trachyandesitic pyroclastic deposits, making it one of the largest historical eruptions in South America. Phase 1 of the eruption (P1, April 8) involved both lava flows and a phreatomagmatic eruption from a fissure located in the NW corner of the caldera. The paroxysmal phase (P2) began several days later (April 12) with a Plinian-style eruption from a different vent 4 km to the south-southeast. Tephra from the 1991 eruption ranges in composition from basalt (phase 1) to trachyandesite (phase 2), with a distinct gap between the two erupted phases from 54-60 wt% SiO2. A trend of decreasing SiO2 is evident from the earliest part of the phase 2 eruption (unit A, 63-65 wt% SiO2) to the end (unit D, 60-63 wt% SiO2). Melt inclusion data and textures suggest that mixing occurred in magmas from both eruptive phases. The basaltic and trachyandesitic magmas can be genetically related through both magma mixing and fractional crystallization processes. A combination of observed phase assemblages, inferred water content, crystallinity, and geothermometry estimates suggest pre-eruptive storage of the phase 2 trachyandesite at pressures between ∼50-100 megapascal (MPa) at 972 ± 6°C under water-saturated conditions (log fO2 -10.33 (±0.2)). It is proposed that rising P1 basaltic magma intersected the lower part of the P2 magma storage region between 2 and 3 km depth. Subsequent mixing between the two magmas preferentially hybridized the lower part of the chamber. Basaltic magma continued advancing towards the surface as a dyke to eventually be erupted in the northwestern part of the Hudson caldera. The presence of tachylite in the P1 products suggests that some of the magma was stalled close to the surface (<0.5 km) prior to eruption. Seismicity related to magma movement and the P1 eruption, combined with chamber overpressure associated with basalt injection, may have created a pathway to the surface for the trachyandesite magma and subsequent P2 eruption at a different vent 4 km to the south-southeast.Fil: Kratzmann, David J.. University of Rhode Island; Estados UnidosFil: Carey, Steven N.. University of Rhode Island; Estados UnidosFil: Scasso, Roberto Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Naranjo, Jose Antonio. Servicio Nacional de Geología y Minería; Chil

Angiotensin receptor-neprilysin inhibitor improves coronary collateral perfusion

BACKGROUND: We investigated the pleiotropic effects of an angiotensin receptor-neprilysin inhibitor (ARNi) on collateral-dependent myocardial perfusion in a rat model of coronary arteriogenesis, and performed comprehensive analyses to uncover the underlying molecular mechanisms. METHODS: A rat model of coronary arteriogenesis was established by implanting an inflatable occluder on the left anterior descending coronary artery followed by a 7-day repetitive occlusion procedure (ROP). Coronary collateral perfusion was measured by using a myocardial particle infusion technique. The putative ARNi-induced pro-arteriogenic effects were further investigated and compared with an angiotensin-converting enzyme inhibitor (ACEi). Expression of the membrane receptors and key enzymes in the natriuretic peptide system (NPS), renin-angiotensin-aldosterone system (RAAS) and kallikrein-kinin system (KKS) were analyzed by quantitative polymerase chain reaction (qPCR) and immunoblot assay, respectively. Protein levels of pro-arteriogenic cytokines were measured by enzyme-linked immunosorbent assay, and mitochondrial DNA copy number was assessed by qPCR due to their roles in arteriogenesis. Furthermore, murine heart endothelial cells (MHEC5-T) were treated with a neprilysin inhibitor (NEPi) alone, or in combination with bradykinin receptor antagonists. MHEC5-T proliferation was analyzed by colorimetric assay. RESULTS: The in vivo study showed that ARNis markedly improved coronary collateral perfusion, regulated the gene expression of KKS, and increased the concentrations of relevant pro-arteriogenic cytokines. The in vitro study demonstrated that NEPis significantly promoted MHEC5-T proliferation, which was diminished by bradykinin receptor antagonists. CONCLUSION: ARNis improve coronary collateral perfusion and exert pro-arteriogenic effects via the bradykinin receptor signaling pathway

Preschool Teachers’ Perspectives About the Engagement of Immigrant and Non-Immigrant Parents in Their Children’s Early Education

The present study explores the perceptions of teachers about the engagement of immigrant and non-immigrant parents in preschool. Data were drawn from a larger evaluation study of a government initiative for preschools in Germany, which was designed to foster inclusive pedagogy and parent cooperation. In these analyses, teachers’ perceptions of the engagement of immigrant parents and non-immigrant parents were rated for each parent group, on a 10-item measure, to identify how teacher ratings varied for the different parent groups. Data from 1397 preschool teachers, employed across 203 preschools, were analyzed using multilevel modeling. This statistical approach takes account of the clustered nature of the data. Teacher ratings of engagement for immigrant and non-immigrant parent groups differed between preschools. Most variability in the ratings could be ascribed to preschool characteristics. In preschools, in which staff held a shared understanding of dealing with cultural diversity and in which the director of the preschool had a multicultural mindset, teachers perceived engagement of parents more positively, especially for immigrant parents. Overall, the findings identified the importance of self-efficacy for inclusion and more positive beliefs about multiculturalism among preschool teachers. Such qualities are important for working with all parents. However, unfavorable social structures, such as those found in disadvantaged areas, may present major challenges for parent cooperation and engagement

Compositional variations and magma mixing in the 1991 eruptions of Hudson volcano, Chile

The August 1991 eruptions of Hudson volcano produced ∼2.7 km3 (dense rock equivalent, DRE) of basaltic to trachyandesitic pyroclastic deposits, making it one of the largest historical eruptions in South America. Phase 1 of the eruption (P1, April 8) involved both lava flows and a phreatomagmatic eruption from a fissure located in the NW corner of the caldera. The paroxysmal phase (P2) began several days later (April 12) with a Plinian-style eruption from a different vent 4 km to the south-southeast. Tephra from the 1991 eruption ranges in composition from basalt (phase 1) to trachyandesite (phase 2), with a distinct gap between the two erupted phases from 54-60 wt% SiO2. A trend of decreasing SiO2 is evident from the earliest part of the phase 2 eruption (unit A, 63-65 wt% SiO2) to the end (unit D, 60-63 wt% SiO2). Melt inclusion data and textures suggest that mixing occurred in magmas from both eruptive phases. The basaltic and trachyandesitic magmas can be genetically related through both magma mixing and fractional crystallization processes. A combination of observed phase assemblages, inferred water content, crystallinity, and geothermometry estimates suggest pre-eruptive storage of the phase 2 trachyandesite at pressures between ∼50-100 megapascal (MPa) at 972 ± 6°C under water-saturated conditions (log fO2 -10.33 (±0.2)). It is proposed that rising P1 basaltic magma intersected the lower part of the P2 magma storage region between 2 and 3 km depth. Subsequent mixing between the two magmas preferentially hybridized the lower part of the chamber. Basaltic magma continued advancing towards the surface as a dyke to eventually be erupted in the northwestern part of the Hudson caldera. The presence of tachylite in the P1 products suggests that some of the magma was stalled close to the surface (<0.5 km) prior to eruption. Seismicity related to magma movement and the P1 eruption, combined with chamber overpressure associated with basalt injection, may have created a pathway to the surface for the trachyandesite magma and subsequent P2 eruption at a different vent 4 km to the south-southeast.Fil: Kratzmann, David J.. University of Rhode Island; Estados UnidosFil: Carey, Steven N.. University of Rhode Island; Estados UnidosFil: Scasso, Roberto Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Naranjo, Jose Antonio. Servicio Nacional de Geología y Minería; Chil

Simulations of tephra dispersal from the 1991 explosive eruptions of Hudson volcano, Chile

The 1991 explosive eruptions of Hudson volcano in southern Chile produced 2.7 km3 (dense rock equivalent) of basalt and trachyandesite tephra during the period August 8-15. The initial basaltic phase (phase I, August 8-9) produced a maximum column height of 12 km above sea level (ASL) and tephra fallout was directed to the north and northeast by the prevailing winds. The paroxysmal trachyandesitic phase (phase II, August 12-15) involved at least three separate events with a maximum ∼ 18-km-high (ASL) eruption column inferred from satellite temperature data. During the initial 24 h of this phase the plume was advected almost directly south, before swinging towards the east as the wind changed direction. The plume was ultimately directed to the southeast and stayed relatively fixed at this bearing for the remainder of the eruption. These temporal variations in the main dispersal direction during the earlier stages of the phase II eruption produced a much wider overall deposit than would be expected from a plume with a relatively fixed transport direction (e.g., latter stages of phase II). The Lagrangian ash tracking model PUFF was utilized to simulate the 1991 explosive eruptions and was able to successfully reproduce the aerial distribution and temporal evolution of the plumes. The optimal agreement between the observed and simulated plumes occurs when the highest concentration of ash particles coincides with the tropopause, a height that is typically lower than the maximum observed column heights for the 1991 eruptions. Gravitational settling of the laterally spreading umbrella region (e.g., Pinatubo 1991) may result in the concentration of ash at this level. This may account for differences in column height estimates between ground- or satellite-based and lithic-based models. The plume associated with the paroxysmal phase (August 12-15, 1991) produced a multilayered deposit composed of alternating layers of fine ash and pumice lapilli. The highly stratified nature of the fall deposit is likely the result of multiple eruptive events coupled with a time varying wind field. A strongly changing wind direction that occurred during the earlier stages of the paroxysmal eruption could have produced variations in the dominant grain size being deposited between fine ash and pumice lapilli during individual eruptive sequences.Fil: Kratzmann, David J.. University of Rhode Island; Estados UnidosFil: Carey, Steven N.. University of Rhode Island; Estados UnidosFil: Fero, Julie. University of Rhode Island; Estados UnidosFil: Scasso, Roberto Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Naranjo, Jose Antonio. Servicio Nacional de Geología y Minería; Chil