989 research outputs found

    Molecular Diagnostics in the Mycosphaerella Leaf Spot Disease Complex of Banana and for Radopholus similis

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    Mycosphaerella leaf spots and nematodes threaten banana cultivation worldwide. The Mycosphaerella disease complex involves three related ascomycetous fungi: Mycosphaerella fijiensis, M. musicola and M. eumusae. The exact distribution of these three species and their disease epidemiology remain unclear, since their symptoms and life cycles are rather similar. Diagnosing these diseases and the respective causal agents is based on the presence of host symptoms and fungal fruiting structures, but is time consuming and not conducive to preventive management. In the present study, we developed rapid and robust species-specific diagnostic tools to detect and quantify M. fijiensis, M. musicola and M. eumusae. Conventional species-specific PCR primers were developed based on the actin gene that detected as little as 100, 1 and 10 pg/µl DNA from, respectively, M. fijiensis, M. musicola and M. eumusae. Furthermore, TaqMan real-time quantitative PCR assays that were developed based on the ß-tubulin gene detected quantities as low as 1 pg/µl DNA of each species from pure cultures and 1.6 pg/µl DNA/mg of M. fijiensis from dry leaf tissue. The efficacy of the tests was validated using naturally infected banana leaves. Similar technology has been used to develop a quantitative PCR assay for the banana burrowing nematode, Radopholus similis, which is currently being validate

    Adaptaciones posturales en el plano sagital y posterior de hombres chilenos Hockistas sobre césped de alto rendimiento.

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    Tesis (Licenciado en Kinesiología)RESUMEN: Introducción: La Postura es un tema que ha sido motivo de diversos estudios desde hace muchos años. Mantener una postura determinada, es esencial al momento de realizar una actividad relacionada con la vida diaria, como en la realización de un gesto o actividad deportiva. Respecto a esto último se ha establecido que la práctica repetitiva de una disciplina deportiva por un tiempo prolongado genera adaptaciones posturales en los sujetos en diferentes segmentos corporales y planos anatómicos. Objetivo:El objetivo de este estudio fue describir las principales adaptaciones posturales en deportistas chilenos hombres de alto rendimiento de la especialidad Hockey sobre Césped. Materiales y Métodos:Se realizó una evaluación postural a través del análisis fotográfico de 15 hombres hockistas sobre césped de alto rendimiento y de 15 sujetos hombres no deportistas, ambos grupos pertenecientes a un rango etario de entre 20 y 30 años. Además se cuantificó la angulación de las curvaturas de la columna mediante dos inclinómetros validados. Resultados y Discusión: Los deportistas de alto rendimiento presentaron una tendencia al aumento de la lordosis lumbar y un ascenso del hemicuerpo derecho respecto al izquierdo en comparación con el grupo control. Comparando ambos grupos se estableció que existían diferencias significativas (p<0,05) en la curvatura lumbar y posición de la pelvis en el plano sagital, mientras que en el plano posterior fue significativa la diferencia sólo en la posición de los hombros. Finalmente se observó que existía anteposición de cabeza en ambos grupos, lo que podría significar que tal adaptación postural no es consecuencia de la práctica deportiva sino que podría estar presente en la población en general

    Self-regulation learning as active inference: dynamic causal modeling of an fMRI neurofeedback task

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    Introduction: Learning to self-regulate brain activity by neurofeedback has been shown to lead to changes in the brain and behavior, with beneficial clinical and non-clinical outcomes. Neurofeedback uses a brain-computer interface to guide participants to change some feature of their brain activity. However, the neural mechanism of self-regulation learning remains unclear, with only 50% of the participants succeeding in achieving it. To bridge this knowledge gap, our study delves into the neural mechanisms of self-regulation learning via neurofeedback and investigates the brain processes associated with successful brain self-regulation. Methods: We study the neural underpinnings of self-regulation learning by employing dynamical causal modeling (DCM) in conjunction with real-time functional MRI data. The study involved a cohort of 18 participants undergoing neurofeedback training targeting the supplementary motor area. A critical focus was the comparison between top-down hierarchical connectivity models proposed by Active Inference and alternative bottom-up connectivity models like reinforcement learning. Results: Our analysis revealed a crucial distinction in brain connectivity patterns between successful and non-successful learners. Particularly, successful learners evinced a significantly stronger top-down effective connectivity towards the target area implicated in self-regulation. This heightened top-down network engagement closely resembles the patterns observed in goal-oriented and cognitive control studies, shedding light on the intricate cognitive processes intertwined with self-regulation learning. Discussion: The findings from our investigation underscore the significance of cognitive mechanisms in the process of self-regulation learning through neurofeedback. The observed stronger top-down effective connectivity in successful learners indicates the involvement of hierarchical cognitive control, which aligns with the tenets of Active Inference. This study contributes to a deeper understanding of the neural dynamics behind successful self-regulation learning and provides insights into the potential cognitive architecture underpinning this process

    3D shear wave velocity imaging of the subsurface structure of granite rocks in the arid climate of Pan de Azúcar, Chile, revealed by Bayesian inversion of HVSR curves

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    Seismic methods are emerging as efficient tools for imaging the subsurface to investigate the weathering zone. The structure of the weathering zone can be identified by differing shear wave velocities as various weathering processes will alter the properties of rocks. Currently, 3D subsurface modelling of the weathering zone is gaining increasing importance as results allow the identification of the weathering imprint in the subsurface not only from top to bottom but also in three dimensions. We investigated the 3D weathering structure of monzogranite bedrock near the Pan de Azúcar National Park (Atacama Desert, northern Chile), where the weathering is weak due to the arid climate conditions. We set up an array measurement that records seismic ambient noise, which we used to extract the horizontal-to-vertical spectral ratio (HVSR) curves. The curves were then used to invert for 1D shear wave velocity (Vs) models, which we then used to compile a pseudo-3D model of the subsurface structure in our study area. To invert the 1D Vs model, we applied a transdimensional hierarchical Bayesian inversion scheme, allowing us to invert the HVSR curve with minimal prior information. The resulting 3D model allowed us to image the granite gradient from the surface down to ca. 50 m depth and confirmed the presence of dikes of mafic composition intruding the granite. We identified three main zones of fractured granite, altered granite, and the granite bedrock in addition to the mafic dikes with relatively higher Vs. The fractured granite layer was identified with Vs of 1.4 km s−1 at 30–40 m depth, while the granite bedrock was delineated with Vs of 2.5 km s−1 and a depth range between 10 and 50 m depth. We compared the resulting subsurface structure to other sites in the Chilean coastal cordillera located in various climatic conditions and found that the weathering depth and structure at a given location depend on a complex interaction between surface processes such as precipitation rate, tectonic uplift and fracturing, and erosion. Moreover, these local geological features such as the intrusion of mafic dikes can create significant spatial variations to the weathering structure and therefore emphasize the importance of 3D imaging of the weathering structure. The imaged structure of the subsurface in Pan de Azúcar provides the unique opportunity to image the heterogeneities of a rock preconditioned for weathering but one that has never experienced extensive weathering given the absence of precipitation.</p

    Epigean Insects of Chañaral Island (Pingüino de Humboldt National Reserve, Atacama, Chile)

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    The Pingüino de Humboldt National Reserve in Chile is an area of biodiversity conservation in arid island ecosystems. The reserve is located both in the Atacama and Coquimbo regions and is composed of the Choros (29º 15’ S, 71º 32’ W), Damas (29º 13’ S, 71º 31’ W) and Chañaral (29°02’ S, 71°36’ W) islands. Pitfall traps were used to study the taxonomic diversity of epigean insects in Chañaral Island. The study area was divided into 3 vegetationally contrasting ecotopes: E1 represented by a subdesert steppe, E2 represented by a xeric shrubland and E3 represented by a xeric shrub steppe. A total of 730 specimens were captured, belonging to 40 species arranged in 34 genera and 17 families. Four insect orders were recorded, of which the most diverse were Coleoptera, with 29 species, and Hymenoptera, with 7 species. Coleoptera was the most represented group, with 24 genera grouped in 11 families. The richest families were Curculionidae (9 species) and Tenebrionidae (8 species). The highest species richness was recorded in E1 (28 species), followed by E2 (21 species) and E3 (19 species). The number of exclusive species varied between habitats, with E1 showing the highest number (14), and E2 and E3 being represented by 5 and 3 species, respectively. On the other hand, 10 species were common to all three sampled sites. The differences in vegetation between the sites were clearly reflected in the relative abundance and species richness of epigean insects. We did not record the presence of Gyriosomus granulipennis, an endemic species of Choros Island, which confirms that this species is restricted to a specific area of the reserve. This work is the first biological inventory of epigean insects on Chañaral Island.Fil: Pizarro Araya, Jaime. Universidad de la Serena; ChileFil: Alfaro, Fermin M.. Universidad de la Serena; Chile. Universidad de Chile; ChileFil: Cortes Contreras, Maximiliano. Universidad de la Serena; ChileFil: Rivera, Cristian. Reserva Nacional Pingüino de Humboldt; ChileFil: Vargas Talciani, Paola. Centro de Estudios Avanzados en Zonas Áridas; ChileFil: Ojanguren Affilastro, Andres Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

    Shear-wave velocity imaging of weathered granite in La Campana (Chile) from Bayesian inversion of micro-tremor H/V spectral ratios

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    Subsurface imaging of the regolith layer is an important tool for weathering zone characterization. For example, the extent of bedrock modification by weathering processes can be modelled by means of differing seismic velocities. We acquired a 360 m-long seismic profile in central Chile to characterise weathering at a semi-arid site. We used 87 3-component geophones, which continuously recorded ambient seismic noise for three days. The seismic line was centered at an 88 m deep borehole, providing core and downhole logging data for calibration. We extract Horizontal-to-Vertical Spectral Ratio (HVSR) curves along the seismic line to image the subsurface. Temporal analysis of the HVSR curves shows that the ambient noise vibrations recorded during the nighttime provide more stable HVSR curves. The trans-dimensional Bayesian Markov chain Monte Carlo (McMC) approach was used to invert the micro-tremor HVSR curves at each station to reconstruct 1D shear-wave velocity (Vs) models. The resulting individual 1D Vs models were merged to create a 2D Vs model along the linear seismic array in La Campana. The resulting Vs model shows an increase from 0.85 km/s at the surface to ca. 2.5 km/s at 100 m depth. We use the interface probability as a by-product of the Bayesian inversion to apply a more data-driven approach in identifying the different weathering layers. This method identified the boundary between saprolite and fractured bedrock at 42 m depth at the borehole, as evidenced by the interpretation of downhole logging data such as magnetic susceptibility. The resulting 2D Vs model of this site in Mediterranean climate shows a strong correlation between the interpreted weathering front at around 90-m depth and a higher precipitation rate in the study site compared to arid sites. The horizontal alignment of the weathering front indicates a correlation between the weathering front depth with topography and fractures in the bedrock

    Inmunodeficiencia común variable: manifestaciones clínicas iniciales

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    La inmunodeficiencia común variable (IDCV) es una inmunodeficiencia primaria caracterizada por hipogammaglobulinemia de comienzo tardío, que se manifiesta principalmente con infecciones recurrentes. Objetivo: describir las manifestaciones clínicas iniciales de pacientes con IDCV diagnosticados en el Hospital de Niños Sor Maria Ludovica entre 1981 y 2019. Diecinueve pacientes fueron incluidos. Todos los pacientes tenían historia de infecciones recurrentes, siendo las más frecuentemente observadas la neumonía (74%) y la otitis media (42%). Se documentó diarrea crónica en 9 pacientes (47%), con malabsorción asociada en 6 de ellos. El 32% de los pacientes presentó desnutrición severa y uno de ellos metaplasia gástrica. Un paciente presentó esplenomegalia y otro síndrome de Evans. Bronquiectasias fueron observadas en el 42% de los pacientes al diagnóstico. Conocer las manifestaciones clínicas iniciales de la IDCV es fundamental para el diagnóstico precoz y tratamiento oportuno.Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by late onset hypogammaglobulinemia, that can manifest as recurrent infections, autoimmunity, digestive disorders and granulomatous disease. Objectives: to describe the initial clinical findings of patients with CVID diagnosed at Hospital de NiñosSorMariaLudovica, between 1981 and 2019. 19 patients were included, 14 were male (74%). All Patients Had a history of recurrent infections, most frequently pneumonia (74%) and acute otitis media (42%). 9 patients suffered from chronic diarrhea (47%), with associated malabsorption in 6 of them. Thirty-two presented with severe malnutrition and 1 patient with gastric metaplasia. One Patient Had Splenomegaly and 1 had Evans´ syndrome. Bronchiectasis were found in 42% of patients at the time of diagnosis. Early suspicion of CVID from pediatricians is essential in order to arrive at a proper diagnosis

    Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data

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    In active volcanic arcs such as the Andean volcanic mountain belt, magmatically‐sourced fluids are channelled through the brittle crust by faults and fracture networks. In the Andes, volcanoes, geothermal springs and major mineral deposits have a spatial and genetic relationship with NNE‐trending, margin‐parallel faults and margin‐oblique, NW‐trending Andean Transverse Faults (ATF). The Tinguiririca and Planchón‐Peteroa volcanoes in the Andean Southern Volcanic Zone (SVZ) demonstrate this relationship, as their spatially associated thermal springs show strike alignment to the NNE‐oriented El Fierro Thrust Fault System. We constrain the fault system architecture and its interaction with volcanically sourced hydrothermal fluids using a combined magnetotelluric (MT) and seismic survey that was deployed for 20 months. High conductivity zones are located along the axis of the active volcanic chain, delineating fluids and/or melt. A distinct WNW‐trending cluster of seismicity correlates with resistivity contrasts, considered to be a reactivated ATF. Seismicity occurs below 4 km, suggesting activity is limited to basement rocks, and the cessation of seismicity at 9 km delineates the local brittle‐ductile transition. As seismicity is not seen west of the El Fierro fault, we hypothesize that this structure plays a key role in compartmentalizing magmatically‐derived hydrothermal fluids to the east, where the fault zone acts as a barrier to cross‐fault fluid migration and channels fault‐parallel fluid flow to the surface from depth. Increases in fluid pressure above hydrostatic may facilitate reactivation. This site‐specific case study provides the first three‐dimensional seismic and magnetotelluric observations of the mechanics behind the reactivation of an ATF
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