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  • Articles  (9)
  • 2010-2014  (6)
  • 2005-2009  (2)
  • 1990-1994  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The Platanar-Aguas Zarcas volcanic centers, Costa Rica: spatial-temporal association of Quaternary calc-alkaline and alkaline volcanism (1993)
    Springer
    Bulletin of volcanology 55 (1993), S. 443-453 
    Details
    ISSN: 1432-0819
    Keywords: Arc volcano ; magma mixing ; geochemistry ; alkaline ; calc-alkaline ; sector collapse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Platanar volcanic center is dominated by a calc-alkaline, basalt-andesite-dacite-rhyolite magma series with unusual LREE enrichment. Adjacent and overlapping the calc-alkaline rocks are the most alkaline basalts found along the volcanic front of Central America. These basalts are mafic, LIL- and LREE-enriched transitional to alkaline basalts. Several are found on the north flank of Platanar in the Aguas Zarcas region, where there are nine cinder cones and a few isolated flows. However, they are also found in isolated lava outcrops at least as far south as Porvenir volcano along the volcanic front. The addition of mafic alkaline magmas with high La/Yb and low Ba/La into the Platanar magma chamber or chambers may contribute to the LREE-enriched character of the Platanar basaltic andesites and andesites. At Platanar the field and geochemical evidence suggest mixing between calc-alkaline and alkaline magmas, a process that has probably occurred throughout the development of the Cordillera Central of Costa Rica. The presence of negative Ce anomalies in several of the calc-alkaline lavas also make the Platanar complex very unusual compared to the rest of the Central American volcanic front. In the center of the Platanar complex is the Chocosuela caldera, an apparent remnant of an avalanche caldera created by the collapse in the Middle Pleistocene of an ancestral stratovolcano toward the NNW in a directed blast-type eruption. Rhyolite is present as pumice lapilli in pyroclastic flow deposits outside the caldera rim. Whole lapilli analyses span the daciterhyolite range. The previous eruption of high silica tephra as pyroclastic flows, the current long dormant period and the repeated occurrence of earthquake swarms on the flanks of the Platanar complex make it a candidate for volcanic hazard mapping, detailed geological mapping and emergency planning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302004
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    Paper (German National Licenses)
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  • 2
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    Tumor-Infiltrating Lymphocyte Therapy for Melanoma (2012)
    The American Association for Cancer Research (AACR)
    Details
    Publication Date: 2012-12-18
    Description: Purpose: Adoptive cell therapy (ACT) using autologous tumor-infiltrating lymphocytes (TIL) is a promising treatment for metastatic melanoma unresponsive to conventional therapies. We report here on the results of an ongoing phase II clinical trial testing the efficacy of ACT using TIL in patients with metastatic melanoma and the association of specific patient clinical characteristics and the phenotypic attributes of the infused TIL with clinical response. Experimental Design: Altogether, 31 transiently lymphodepleted patients were treated with their expanded TIL, followed by two cycles of high-dose interleukin (IL)-2 therapy. The effects of patient clinical features and the phenotypes of the T cells infused on the clinical response were determined. Results: Overall, 15 of 31 (48.4%) patients had an objective clinical response using immune-related response criteria (irRC) with 2 patients (6.5%) having a complete response. Progression-free survival of more than 12 months was observed for 9 of 15 (60%) of the responding patients. Factors significantly associated with the objective tumor regression included a higher number of TIL infused, a higher proportion of CD8 + T cells in the infusion product, a more differentiated effector phenotype of the CD8 + population, and a higher frequency of CD8 + T cells coexpressing the negative costimulation molecule "B- and T-lymphocyte attenuator" (BTLA). No significant difference in the telomere lengths of TIL between responders and nonresponders was identified. Conclusion: These results indicate that the immunotherapy with expanded autologous TIL is capable of achieving durable clinical responses in patients with metastatic melanoma and that CD8 + T cells in the infused TIL, particularly differentiated effectors cells and cells expressing BTLA, are associated with tumor regression. Clin Cancer Res; 18(24); 6758–70. ©2012 AACR .
    Print ISSN: 1078-0432
    Electronic ISSN: 1557-3265
    Topics: Medicine
    Published by The American Association for Cancer Research (AACR)
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  • 3
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    RNA dimerization plays a role in ribosomal frameshifting of the SARS coronavirus (2013)
    Oxford University Press
    Details
    Publication Date: 2013-02-20
    Description: Messenger RNA encoded signals that are involved in programmed -1 ribosomal frameshifting (-1 PRF) are typically two-stemmed hairpin (H)-type pseudoknots (pks). We previously described an unusual three-stemmed pseudoknot from the severe acute respiratory syndrome (SARS) coronavirus (CoV) that stimulated -1 PRF. The conserved existence of a third stem–loop suggested an important hitherto unknown function. Here we present new information describing structure and function of the third stem of the SARS pseudoknot. We uncovered RNA dimerization through a palindromic sequence embedded in the SARS-CoV Stem 3. Further in vitro analysis revealed that SARS-CoV RNA dimers assemble through ‘kissing’ loop–loop interactions. We also show that loop–loop kissing complex formation becomes more efficient at physiological temperature and in the presence of magnesium. When the palindromic sequence was mutated, in vitro RNA dimerization was abolished, and frameshifting was reduced from 15 to 5.7%. Furthermore, the inability to dimerize caused by the silent codon change in Stem 3 of SARS-CoV changed the viral growth kinetics and affected the levels of genomic and subgenomic RNA in infected cells. These results suggest that the homodimeric RNA complex formed by the SARS pseudoknot occurs in the cellular environment and that loop–loop kissing interactions involving Stem 3 modulate -1 PRF and play a role in subgenomic and full-length RNA synthesis.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    A New Evaluation of Seismic Hazard for the Central America Region (2012)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2012-04-01
    Description: A new evaluation of seismic hazard in Central America has been carried out as part of the cooperation project named RESIS II under the auspices of the Norway Cooperation Agency (NORAD). Several seismic-hazard experts from Costa Rica, Guatemala, Honduras, Nicaragua, El Salvador, Panamá, Norway, and Spain participated in the study, which was aimed at obtaining results suitable for seismic design purposes. The analysis started with a thorough revision of the national seismic catalogs from which a catalog for Central America has been compiled and homogenized to moment magnitude, Mw. Seismotectonic models proposed for the region were revised, and a new regional zonation was proposed, taking into account seismotectonic data, seismicity, focal mechanisms, and GPS observations. Besides, ground-motion prediction equations (GMPEs) for subduction, volcanic, and crustal zones were revised, and the most suitable ones were calibrated with Central American strong-motion data. Subsequently, a seismic-hazard analysis was developed in terms of peak ground acceleration (PGA) and spectral accelerations SA (T?) for periods of 0.1, 0.2, 0.5, 1, and 2 s, by means of the probabilistic seismic-hazard assessment (PSHA) approach. As a result, different hazard maps were obtained for the quoted parameters, together with uniform hazard spectra (UHS) for six of the capital cities of Central America. Disaggregation was also carried out in these capitals for the target motion given by the PGA and SA (1 s) and obtained for return periods of 500 years and 2500 years. Therefore, the control earthquakes for motions of short and long periods were derived. This is the first study developed in Central America at a regional scale after 10 years.Online Material: Table of the largest Central American earthquakes in historical times.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 5
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    Imaging crustal structure in south central Costa Rica with receiver functions (2010)
    In:  Geochemistry Geophysics Geosystems (G3)
    Details
    Publication Date: 2020-02-12
    Description: An array of broadband seismometers transecting the Talamanca Range in southern Costa Rica was operated from 2005 until 2007. In combination with data from a short-period network near Quepos in central Costa Rica, this data is analyzed by the receiver function method to image the crustal structure in south-central Costa Rica. Two strong positive signals are seen in the migrated images, interpreted as the Moho (at around 35 km depth) and an intra-crustal discontinuity (15 km depth). A relatively flat crustal and Moho interface underneath the north-east flank of the Talamanca Range can be followed for a lateral distance of about 50 km parallel to the trench, with only slight changes in the overall geometry. Closer to the coast, the topography of the discontinuities shows several features, most notably a deeper Moho underneath the Talamanca Mountain Range and volcanic arc. Under the highest part of the mountain ranges, the Moho reaches a depth of about 50 km, which indicates that the mountain ranges are approximately isostatically compensated. Local deviations from the crustal thickness expected for isostatic equilibrium occur under the active volcanic arc and in south Costa Rica. In the transition region between the active volcanic arc and the Talamanca Range, both the Moho and intracrustal discontinuity appear distorted, possibly related to the southern edge of the active volcanic zone and deformation within the southern part of the Central Costa Rica Deformed Belt. Near the volcanoes Irazu and Turrialba, a shallow converter occurs, correlating with a low-velocity, low-density body seen in tomography and gravimetry. Applying a grid search for the crustal interface depth and vp/vs ratio cannot constrain vp/vs values well, but points to generally low values (〈1.7) in the upper crust. This is consistent with quartz-rich rocks forming the mountain range.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 6
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    Deep electrical resistivity structure of northwestern Costa Rica (2009)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2020-02-12
    Description: First long-period magnetotelluric investigations were conducted in early 2008 in northwestern Costa Rica, along a profile that extends from the coast of the Pacific Ocean, traverses the volcanic arc and ends currently at the Nicaraguan border. The aim of this study is to gain insight into the electrical resistivity structure and thus fluid distribution at the continental margin where the Cocos plate subducts beneath the Caribbean plate. Preliminary two-dimensional models map the only moderately resistive mafic/ultramafic complexes of the Nicoya Peninsula (resistivity of a few hundred Ωm), the conductive forearc and the backarc basins (several Ωm). Beneath the backarc basin the data image a poor conductor in the basement with a clear termination in the south, which may tentatively be interpreted as the Santa Elena Suture. The volcanic arc shows no pronounced anomaly at depth, but a moderate conductor underlies the backarc with a possible connection to the upper mantle. A conductor at deep-crustal levels in the forearc may reflect fluid release from the downgoing slab.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 7
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    Local earthquake tomography of central Costa Rica: transition from seamount to ridge subduction (2010)
    In:  Geophysical Journal International
    Details
    Publication Date: 2020-02-12
    Description: The structure and seismicity of the subduction zone of central Costa Rica have been investigated with local earthquake tomography down to ca.  50 km depth. Seismic traveltime data sets of three on- and offshore seismic networks were combined for a simultaneous inversion of hypocentre locations, 3-D structure of P-wave velocity and Vp/Vs ratio using about 2000 high-quality events. The seismicity and slab geometry as well as Vp and Vp/Vs show significant lateral variation along the subduction zone corresponding to the changes of the incoming plate which consists of serpentinized oceanic lithosphere in the northwest, a seamount province in the centre and the subducting Cocos Ridge in the southeast of the investigation area. Three prominent features can be identified in the Vp and Vp/Vs tomograms: a high-velocity zone with a perturbation of 4–10 per cent representing the subducting slab, a low-velocity zone (10–20 per cent) in the forearc crust probably caused by deformation, fluid release and hydration and a low-velocity zone below the volcanic arc related to upwelling fluids and magma. Unlike previously suggested, the dip of the subducting slab does not decrease to the south. Instead, an average steepening of the plate interface from 30° to 45° is observed from north to south and a transition from a plane to a step-shaped plate interface. This is connected with a change in the deformation style of the overriding plate where roughly planar, partly conjugated, clusters of seismicity of regionally varying dip are observed. It can be shown that the central Costa Rica Deformation Belt represents a deep crustal transition zone extending from the surface down to 40 km depth. This transition zone indicates the lateral termination of the active part of the volcanic chain and seems to be related to the changing structure of the incoming plate as well.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 8
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    Arc-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua (2008)
    In:  Nature
    Details
    Publication Date: 2020-02-12
    Description: Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge1,2,3 or eroded fore-arc complexes4 but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (63–190 mm yr-1) and are comparable to the magnitude of subducting Cocos plate motion (∼85 mm yr-1). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 9
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    The steeply subducting edge of the Cocos Ridge: Evidence from receiver functions beneath the northern Talamanca Range, south-central Costa Rica (2011)
    In:  Geochemistry Geophysics Geosystems (G3)
    Details
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/article
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