Sangolqui, Ecuador

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Sangolqui, Ecuador
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Pistolesi M.,University of Pisa | Rosi M.,University of Pisa | Cion R.,University of Cagliari | Cashman K.V.,University of Oregon | And 2 more authors.
Bulletin of the Geological Society of America | Year: 2011

Cotopaxi volcano, situated in the Eastern Cordillera of the Ecuadorian Andes, is one of the most active volcanoes on Earth. The volcano is well known for the magnificence of its almost perfectly symmetrical cone topped by ice and snow and for the destructive power of its large-scale, syneruptive lahars. This paper presents a stratigraphic study of the post-twelfth-century eruptive products that reveals the existence of 21 continuous tephra beds. Most of them were characterized from both a physical (dispersal areas, deposit volumes, peak Mass Discharge Rate [MDR] of the eruptions) and compositional point of view. New 14C dates, linked with a new examination of historical chronicles, allow us to create a new chronostratigraphic scheme for this period of activity, which is bracketed by the emplacement of a regional tephra marker (A.D. 1140 ash bed from Quilotoa volcano) and the present day. The first period (A.D. 1150-1742) included only two moderate-intensity explosive eruptions, the oldest being possibly related to a dome disruption. In contrast, the period A.D. 1742-1880 started with two high-intensity, Plinian eruptions (maximum column heights of 25 and 29 km), followed by several short-lived but sustained, convective episodes. Deposits of pyroclastic surges and scoria flows were emplaced during some of these short-lived events and may have been related to column collapse and boiling over activity, respectively. Post-1880 activity, reported in 1904, 1906, and 1912, likely consisted of minor explosions that affected only the crater area. Our study of recent activity at Cotopaxi shows that high dispersive power (peak mass discharge rates from 1.1 to 9.3 × 107 kg/s) is associated with the eruption of only moderate amounts of magma (1.1 × 1010-6.0 × 1011 kg, or ~0.005-0.2 km3, Dense Rock Equivalent [DRE]). Additionally, although the past 2000 yr of activity at Coto-paxi have been interpreted to reflect a fairly uniform magma supply rate, detailed analysis of the past centuries, and a reanalysis of data from the past 2000 yr show that Coto-paxi's eruptive activity is characterized by clusters of eruptive events that are separated by periods of long quiescence punctuated by isolated eruptions, often of slightly more evolved magma. No systematic variations in composition emerge in the time sequence. Although new magmatic phases commonly start with the eruption of mafic magma, this is not always observed. Additionally, eruption clusters may show either compositional trends of increasing SiO2 content or abrupt compositional changes within a cluster. We interpret the temporal and compositional variations in eruptive activity to reflect the complex interplay of deep versus shallow magmatic processes. An important result from the perspective of volcanic hazards is our conclusion that, over the studied period, no clear relation exists among repose time, eruption magnitude, and magma composition. This conclusion contrasts with the periodic eruptive behavior that has been postulated at many central volcanoes worldwide, thus inviting a reexamination of other intermediate-composition volcanic systems and a reassessment of the assumption of periodic activity. © 2011 Geological Society of America.


Pistolesi M.,University of Pisa | Cioni R.,University of Cagliari | Rosi M.,University of Pisa | Cashman K.V.,University of Oregon | Aguilera E.,Army Polytechnic School
Bulletin of Volcanology | Year: 2013

Cotopaxi volcano is situated in the Eastern Cordillera of the Ecuadorian Andes and consists of a symmetric volcanic cone that reaches an altitude of 5,897 m above sea level; it is capped over its upper 1,000 m by a permanent glacier. The volcano has erupted frequently in the past few centuries and, according to the archival records, has produced dozens of lahars by catastrophic snow and ice melting during eruptions. In this work, we present a detailed map and a stratigraphic study of the lahar deposits of the past 800 years in two different topographic settings. A thorough knowledge of the tephrostratigraphy of the explosive activity over the same time period was a first-order pre-requisite for the complete reconstruction and dating of lahar activity and also allowed us to precisely link lahar units to eruptive phases of individual eruptions. Results indicate that, during the thirteenth to seventeenth centuries, high-intensity eruptions (Plinian events or blast-like explosions) produced large debris flows that transported meter-sized boulders. A subsequent period of activity that started in 1742 was characterized by several lahar-generating eruptive episodes that were smaller in scale but with significant variability in size (the 1877 being the smallest and most recent). Analysis of events occurring in the eighteenth century suggests that eruption style affects the volume and energy of the resulting lahars, with different pyroclastic flow types causing different mechanisms of water release from the summit glacier. Lahars produced during this time period were triggered by: (1) dilute pumice and ash-rich radially distributed density currents and (2) column collapse-related radially distributed scoria and lithic-rich pyroclastic-flows. The former produced lahar deposits that are matrix-rich, block-poor, and valley-confined, while the high erosive capacity of the latter produced lahars that are block-rich, highly energetic, and widespread. The youngest (1853 and 1877) lahars were triggered by (3) confined scoria-flow lobes that had less capacity to scour and melt the glacier; resulting flows had lower energy and smaller volumes than lahars produced by eighteenth-century eruptions. We conclude that the dynamics of pyroclastic-density-current can exert a major control on the size and destructive capacity of lahar at ice-capped volcanoes. Moreover, the total extent of the glacier at the moment of eruption, which is commonly considered to exert a major control on lahar formation, may actually be a second-order factor compared with the way in which the eruptive products interact with the glacier. © 2013 Springer-Verlag Berlin Heidelberg.


De Leo M.,University of Pisa | Saltos M.B.V.,Army Polytechnic School | Puente B.F.N.,Army Polytechnic School | De Tommasi N.,University of Salerno | Braca A.,University of Pisa
Phytochemistry | Year: 2010

Six compounds, eudesm-11(13)-en-4β,9β-diol, 15R,16-dihydroxy-3-oxoisopimar-9(11)-ene, 15S,16-dihydroxy-3-oxoisopimar-9(11)-ene, 1α-hydroxy-7-oxo-iso-anhydrooplopanone, 10α-hydroxy-11,13-dihydro-5-epi-psilostachyin, and 4β-hydroxypseudoguaian-12,6-olide 4-O-β-d-glucopyranoside, together with 12 known sesquiterpenes, were isolated from the leaves of Ambrosia arborescens. Structures were elucidated by 1D and 2D NMR spectroscopy including 1D-TOCSY, DQF-COSY, 2D-ROESY, HSQC, and HMBC experiments, as well as by ESI mass spectrometry. The absolute configuration of the 15,16-diol moiety in 15R,16-dihydroxy-3-oxoisopimar-9(11)-ene and 15S,16-dihydroxy-3-oxoisopimar-9(11)-ene was determined using Snatzke's method. All compounds were evaluated for antiproliferative activity. © 2010 Elsevier Ltd. All rights reserved.


Falconi C.E.,Army Polytechnic School | Visser R.G.F.,Wageningen UR Plant Breeding | van Heusden A.W.,Wageningen UR Plant Breeding
Plant Disease | Year: 2013

Anthracnose is a serious problem of both Andean lupine and tamarillo in Ecuador. Morphological features, internal transcribed spacer (ITS) sequences, and host specificity were used to characterize Colletotrichum isolates from lupine and tamarillo. Based on phenotypic and molecular characterization, the causal agent of anthracnose on both hosts was Colletotrichum acutatum. All isolates were identified in a C. acutatum-specific polymerase chain reaction assay. Colony diameter, conidia shape, and insensitivity to benomyl also placed isolates from both hosts in the C. acutatum group. However, a detailed analysis of the ITS sequences placed the lupine and tamarillo isolates from the Ecuadorian Andean zone in two clades, with both lupine and tamarillo isolates in each clade. C. acutatum isolates from Andean lupine were distinct from other C. acutatum isolates on lupine around the world. In cross-infection studies, the diameter of lesions produced by isolates from each host was compared on the main stem of two tamarillo and three lupine cultivars. Some isolates produced larger lesions on the host from which they were isolated but others showed similar aggressiveness on their alternate host. Isolates from both hosts were biotrophic on lupine stems, producing little necrosis and abundant sporulation whereas, on tamarillo stems, they produced dark lesions with few conidia. The collection of C. acutatum isolates from lupine and tamarillo provides interesting material for the study quantitative host adaptation. © 2013 The American Phytopathological Society.


Alierta J.A.,Army Polytechnic School | Perez M.A.,Aragon Institute of Engineering Research | Garcia-Aznar J.M.,Aragon Institute of Engineering Research
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2014

After fractures, bone can experience different potential outcomes: successful bone consolidation, non-union and bone failure. Although, there are a lot of factors that influence fracture healing, experimental studies have shown that the interfragmentary movement (IFM) is one of the main regulators for the course of bone healing. In this sense, computational models may help to improve the development of mechanical-based treatments for bone fracture healing. Hence, based on this fact, we propose a combined repair-failure mechanistic computational model to describe bone fracture healing. Despite being a simple model, it is able to correctly estimate the time course evolution of the IFM compared to in vivo measurements under different mechanical conditions. Therefore, this mathematical approach is especially suitable for modeling the healing response of bone to fractures treated with different mechanical fixators, simulating realistic clinical conditions. This model will be a useful tool to identify factors and define targets for patient specific therapeutics interventions. © 2013 Elsevier Ltd.


Beker U.,Yildiz Technical University | Cumbal L.,Army Polytechnic School | Duranoglu D.,Yildiz Technical University | Kucuk I.,Yildiz Technical University | Sengupta A.K.,Lehigh University
Environmental Geochemistry and Health | Year: 2010

The objective of this study is to examine the adsorption-desorption behavior of a magnetically active hybrid sorbent (MAHS) material, prepared by dispersing colloid-like hydrated iron oxide particles in the outer periphery of a macroporous ion-exchange resin (Amberlite XAD-2). The experimental results show that the new sorbent material can simultaneously remove arsenic (V) and a chlorinated organic compound (2,6-dichlorophenol [2,6-DCP]) from aqueous solutions at around neutral pH. The recovery of arsenic and 2,6-DCP from MAHS was conducted using a regenerant containing 50% (v/v) CH3OH + 3% (w/v) NaOH. In less than 10 bed volumes of regenerant, more than 90% of As(V) and 2,6-DCP were recovered. © 2010 Springer Science+Business Media B.V.


Thomas C.M.,Texas A&M University | Yong Q.C.,Texas A&M University | Seqqat R.,Texas A&M University | Seqqat R.,Army Polytechnic School | And 4 more authors.
Clinical Science | Year: 2013

Hyperglycaemia up-regulates intracellular AngII (angiotensin II) production in cardiac myocytes, effects of which are blocked more effectively by renin inhibition than ARBs (angiotensin receptor blockers) or ACEis (angiotensin-converting enzyme inhibitors). In the present study, we determined whether renin inhibition is more effective at preventing diabetic cardiomyopathy than an ARB or ACEi. Diabetes was induced in adult mice for 10 weeks by STZ (streptozotocin). Diabetic mice were treated with insulin, aliskiren (a renin inhibitor), benazeprilat (an ACEi) or valsartan (an ARB) via subcutaneous mini-pumps. Significant impairment in diastolic and systolic cardiac functions was observed in diabetic mice, which was completely prevented by all three RAS (renin-angiotensin system) inhibitors. Hyperglycaemia significantly increased cardiac oxidative stress and circulating inflammatory cytokines, which were blocked by aliskiren and benazeprilat, whereas valsartan was partially effective. Diabetes increased cardiac PRR (prorenin receptor) expression and nuclear translocation of PLZF (promyelocytic zinc finger protein), which was completely prevented by aliskiren and valsartan, and partially by benazeprilat. Renin inhibition provided similar protection of cardiac function to ARBs and ACEis. Activation of PLZF by PRR represented a novel mechanism in diabetic cardiomyopathy. Differential effects of the three agents on oxidative stress, cytokines and PRR expression suggested subtle differences in their mechanisms of action. © The Authors Journal compilation © 2013 Biochemical Society.


Yong Q.C.,Texas A&M University | Thomas C.M.,Texas A&M University | Seqqat R.,Texas A&M University | Seqqat R.,Army Polytechnic School | And 3 more authors.
Cardiovascular Diabetology | Year: 2013

Background: Diabetes-induced organ damage is significantly associated with the activation of the renin-angiotensin system (RAS). Recently, several studies have demonstrated a change in the RAS from an extracellular to an intracellular system, in several cell types, in response to high ambient glucose levels. In cardiac myocytes, intracellular angiotensin (ANG) II synthesis and actions are ACE and AT1 independent, respectively. However, a role of this system in diabetes-induced organ damage is not clear.Methods: To determine a role of the intracellular ANG II in diabetic cardiomyopathy, we induced diabetes using streptozotocin in AT1a receptor deficient (AT1a-KO) mice to exclude any effects of extracellular ANG II. Further, diabetic animals were treated with a renin inhibitor aliskiren, an ACE inhibitor benazeprilat, and an AT1 receptor blocker valsartan.Results: AT1a-KO mice developed significant diastolic and systolic dysfunction following 10 wks of diabetes, as determined by echocardiography. All three drugs prevented the development of cardiac dysfunction in these animals, without affecting blood pressure or glucose levels. A significant down regulation of components of the kallikrein-kinin system (KKS) was observed in diabetic animals, which was largely prevented by benazeprilat and valsartan, while aliskiren normalized kininogen expression.Conclusions: These data indicated that the AT1a receptor, thus extracellular ANG II, are not required for the development of diabetic cardiomyopathy. The KKS might contribute to the beneficial effects of benazeprilat and valsartan in diabetic cardiomyopathy. A role of intracellular ANG II is suggested by the inhibitory effects of aliskiren, which needs confirmation in future studies. © 2013 Yong et al.; licensee BioMed Central Ltd.


Petrucci V.,Federal University of Fluminense | Carrera E.V.,Army Polytechnic School | Loques O.,Federal University of Fluminense | Leite J.C.B.,Federal University of Fluminense | Mosse D.,University of Pittsburgh
Proceedings - 11th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, CCGrid 2011 | Year: 2011

This paper proposes and evaluates an approach for power and performance management in virtualized server clusters. The major goal of our approach is to reduce power consumption in the cluster while meeting performance requirements. The contributions of this paper are: (1) a simple but effective way of modeling power consumption and capacity of servers even under heterogeneous and changing workloads, and (2) an optimization strategy based on a mixed integer programming model for achieving improvements on power-efficiency while providing performance guarantees in the virtualized cluster. In the optimization model, we address application workload balancing and the often ignored switching costs due to frequent and undesirable turning servers on/off and VM relocations. We show the effectiveness of the approach applied to a server cluster test bed. Our experiments show that our approach conserves about 50 of the energy required by a system designed for peak workload scenario, with little impact on the applications' performance goals. Also, by using prediction in our optimization strategy, further QoS improvement was achieved. © 2011 IEEE.


Duchicela J.,Indiana University | Duchicela J.,Army Polytechnic School | Vogelsang K.M.,Indiana University | Schultz P.A.,Indiana University | And 3 more authors.
New Phytologist | Year: 2012

• Soil aggregate stability is an important ecosystem property that is altered by anthropogenic disturbance. Yet, the generalization of these alterations and the identification of the main contributors are limited by the absence of cross-site comparisons and the application of inconsistent methodologies across regions. • We assessed aggregate stability in paired remnant and post-disturbance grasslands across California, shortgrass and tallgrass prairies, and in manipulative experiments of plant composition and soil microbial inoculation. • Grasslands recovering from anthropogenic disturbance consistently had lower aggregate stability than remnants. Across all grasslands, non-native plant diversity was significantly associated with reduced soil aggregate stability. A negative effect of non-native plants on aggregate stability was also observed in a mesocosm experiment comparing native and non-native plants from California grasslands. Moreover, an inoculation study demonstrated that the degradation of the microbial community also contributes to the decline in soil aggregate stability in disturbed grasslands. • Anthropogenic disturbance consistently reduced water-stable aggregates. The stability of aggregates was reduced by non-native plants and the degradation of the native soil microbial community. This latter effect might contribute to the sustained decline in aggregate stability following anthropogenic disturbance. Further exploration is advocated to understand the generality of these potential mechanisms. © 2012 The Authors New Phytologist © 2012 New Phytologist Trust.

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