2,318 research outputs found

    Tectonic framework of surface and blind structures from neotectonic and geophysical (gravimetry) analyses, Central Andes of Argentina

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    This work describes new evidence of N–S and oblique trending surface and blind structures in the La Cantera-GualilĂĄn tectonic depression in the Central Precordillera, San Juan Province, Argentina. Two main N–S Quaternary thrusts cross longitudinally the valley located ∌60 km west of San Juan city (30° 50â€Č- 31° 17â€Č S and 68° 55â€Č- 69° 05â€Č W). One of them is located in the eastern piedmont of the Sierra de La Invernada (San Juan Fault) and the other in the western piedmont of the Sierra de La Cantera (La Cantera Fault System), although the northward continuation of this structure has not yet been confirmed. Besides, a smooth water divide or “portezuelo” controlled by an oblique transpressive structure (Divisadero Coba Rubia Fault) separates two N–S elongated river basins with opposite water flow directions. One of these is the GualilĂĄn River, which flows from south to north, and the other corresponds to the La Cantera River, running from north to south. In the present work, we describe some new natural exposures and subtle geomorphological evidence of Quaternary structures identified in the GualilĂĄn-La Cantera tectonic depression. We also use regional and local gravity data to analyze and interpret gravity anomalies related to these surface or blind active structures. Then, based on our geologic and geophysical interpretations, we infer the presence of several, buried cross-strike structures with NW and NE trends, one of them coincident with the drainage divide between the GualilĂĄn and La Cantera opposite river basins, possibly related to the Coba Rubia Fault. Also, we suggest the northward continuation of the La Cantera Fault System (LCFS) as a buried structure in coincidence with the GualilĂĄn River alluvial plain. In this sense, the gravity response of the basement and these river sub-basins shows a close relationship with the surface and subsurface structures. We propose that the oblique structures could represent pre-existing crustal fabrics reactivated during the Andean orogeny, segmenting the N–S Precordillera fold and thrust belt system. Finally, according to the analyzed neotectonic and gravimetric features, we consider the La Cantera-GualilĂĄn Valley as a potentially seismogenic source in this intraplate portion of the Andean Precordillera, crossed by several N–S and oblique surficial and buried/blind active structures. These tectonic features could play a significant role in a regional seismic hazard assessment.Fil: Alcacer Sanchez, Juan Manuel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Rothis, Luis Martin. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Haro Sanchez, Federico Miguel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Colavitto, Bruno. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Vargas, Horacio NicolĂĄs. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Vargas, Mariana. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Onorato, Maria Romina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Blanc, Pablo AndrĂ©s. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan; ArgentinaFil: Miranda, Silvia Alicia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Departamento de GeofĂ­sica y AstronomĂ­a; ArgentinaFil: Perucca, Laura Patricia A.. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - BahĂ­a Blanca. Instituto GeolĂłgico del Sur. Universidad Nacional del Sur. Departamento de GeologĂ­a. Instituto GeolĂłgico del Sur; Argentin

    FenologĂ­a de diez cultivares de Cannabis sativa L. bajo las condiciones ambientales de Palomino Guajira

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    Studies on the phenology of Cannabis sativa L. are important because they are a great tool when carrying out crop management practices, such as fertilizer application, pest and disease management, and identifying the adaptation of the crop. cultivation under different climatic conditions. Phenology studies the occurrence of phases in the life cycle of plants; therefore, to determine the moments of phenological occurrences, it is necessary to use tools that facilitate the process of interpreting the information taken in the field; therefore, the BBCH scale was adapted to determine the phenological phases taking into account the days after transplantation. The objective of the work was to evaluate the phenology of 10 Cannabis sativa L. genotypes to identify the genotypes with the best performance under greenhouse conditions in Palomino. The variables to be evaluated were: plant height, number of shoots, number of inflorescences, harvest index and yield expressed in dry flower. Height, shoots and inflorescence data were recorded 3 times a week for 10 weeks and at week 10 the final height was quantified. Harvest index and yield was estimated at harvest time. The statistical design was completely randomized with 10 treatments and 6 repetitions per treatment. The results showed that, of 58 phenological stages defined for Cannabis, in an asexual cycle only 19 stages are evaluated. In addition, with the data collected on height gain, shoots and inflorescences, it can be predicted which will be the most yielding genotypes. The dry flower yield is influenced by the length of the plant, number of buds and number of inflorescences; likewise, the harvest index proved to be a good indicator when determining the performance of each genotype. The genotype best adapted to the climatic conditions of the trial area was PS111 due to height, the number of vegetative shoots, inflorescences and yield.Los estudios sobre fenologĂ­a de Cannabis sativa L. son una herramienta al momento de realizar prĂĄcticas de manejo del cultivo como la aplicaciĂłn de fertilizantes, el manejo de plagas y enfermedades, y para valorar la adaptaciĂłn del cultivo a las condiciones climĂĄticas. La fenologĂ­a estudia la ocurrencia de las fases en el ciclo de vida de las plantas, para su determinaciĂłn es necesario el uso de la escala BBCH que codifica las etapas fenolĂłgicas dĂ­as despuĂ©s del trasplante. El objetivo del trabajo fue evaluar el comportamiento de 10 genotipos de Cannabis sativa L. bajo condiciones de invernadero en etapas vegetativa, floraciĂłn y cosecha para identificar los genotipos con la mejor adaptaciĂłn a las condiciones climĂĄticas en el corregimiento de Palomino.  Las variables a evaluar fueron: altura de la planta, nĂșmero de brotes, nĂșmero de inflorescencias, Ă­ndice de cosecha y rendimiento expresado en flor seca. Los datos de altura, brotes e inflorescencia se registraron tres veces por semana durante 10 semanas y en la semana 10 se cuantifico la altura final. El Ă­ndice de cosecha y rendimiento se estimĂł al momento de la cosecha. El diseño estadĂ­stico fue completamente al azar con 10 tratamientos y 6 repeticiones por tratamiento. Los resultados mostraron que, de 58 etapas fenolĂłgicas definidas para Cannabis, en un ciclo asexual solo se evalĂșan 19 etapas. AdemĂĄs, con los datos recolectados de ganancia de altura, brotes e inflorescencias, se puede predecir quienes serĂĄn los genotipos mĂĄs rendidores. El rendimiento de flor seca estĂĄ influenciado por la longitud de la planta, nĂșmero de brotes y nĂșmero de inflorescencias; igualmente, el Ă­ndice de cosecha mostrĂł ser un indicador al momento de determinar el rendimiento de cada genotipo.  El genotipo mejor adaptado a la zona de estudio fue PS111 por la altura, la cantidad de brotes vegetativos, inflorescencias y el rendimiento

    Morphotectonic analysis in the southwest piedmont of the andean foreland, Sierras Pampeanas Occidentales, San Juan, Argentina

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    El retroarco andino, entre los 27°S y 33°S, se caracteriza por ser una de las regiones con mayor sismicidad cortical en elmundo, siendo epicentro de importantes terremotos en el territorio argentino. Esta sismicidad produce una intensa deformaciĂłn,provocando cambios en la morfologĂ­a del terreno. En el sector occidental de Sierras Pampeanas Occidentales, en la sierra de laHuerta, se utilizĂł un SIG para diferenciar unidades geomorfolĂłgicas y determinar parĂĄmetros cualitativos y cuantitativos quepermitieran caracterizar las geoformas identificadas y su relaciĂłn con la actividad tectĂłnica. La tectĂłnica andina, que afecta la regiĂłndesde los Ășltimos 5 millones de años, es el principal factor que controla el paisaje de la regiĂłn. Se diferenciaron tres unidadesmorfoestucturales y fallamiento con actividad tectĂłnica cuaternaria, presentando abundantes indicadores morfotectĂłnicos, comoniveles aluviales dislocados, variaciĂłn en el diseño y desvĂ­o de los rĂ­os, aumento en su grado de incisiĂłn, surgentes de agua, abras deviento e inversiĂłn del patrĂłn de drenaje, entre otros. El anĂĄlisis de los indicadores morfotectĂłnicos permitiĂł identificar cĂłmo ladeformaciĂłn disminuye hacia el sur y aumenta de este a oeste. Finalmente, es posible determinar que la deformaciĂłn continĂșa activa,modificando el paisaje actual del piedemonte occidental de la sierra de la Huerta.Palavras-chave: Sierras Pampeanas Occidentales; sierra de la Huerta; indicadores morfotectĂłnicos; unidades morfoestructurales.Between 27° S and 33° S the Andean backarc is one of the most seismically active region in the world, being epicenter of the most important crustal earthquakes that affected Argentina. Associated with the seismicity an intense deformation occurs, causing changes on the land surface morphology. In the western sector of the Sierras Pampeanas Occidentales, in the Sierra de la Huerta, a GIS analysis was applied to define geomorphological units and obtain qualitative and quantitative parameters that allowed characterizing the identified geoforms and their relation with tectonic activity. Andean tectonics affect this region for the last 5 millions of years, controlling it landscape evolution. Three morphostructural units and quaternary active faulting were identify, presenting abundant morphotectonic markers, such as dislocated alluvial levels, changes in river pattern, diversion of river courses, increasing degree of incision, water springs, wind gap and inversion of the pattern drainage, among others. The quantitative and qualitative analysis of the morphotectonic parameters shows that deformation decrease from North to South and increase from East to West. Concluding, according to morphotectonics parameters deformation is still active, modifying the present-day landscape in the Western piedmont of La Huerta range.Fil: Rothis, Luis Martin. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Perucca, Laura Patricia A.. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Santi Malnis, Paula. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto y Museo de Ciencias Naturales; ArgentinaFil: Pantano Zuñiga, Ana Vanesa. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Alcacer Sanchez, Juan Manuel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Departamento de GeofĂ­sica y AstronomĂ­a; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto y Museo de Ciencias Naturales; ArgentinaFil: Haro Sanchez, Federico Miguel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Vargas, NicolĂĄs. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; Argentin

    Anålisis morfotectónico y gravimétrico en un valle intermontano de la Precordillera Central de San Juan, Argentina

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    En este trabajo se efectĂșa un anĂĄlisis morfotectĂłnico y gravimĂ©trico de la cuenca del rĂ­o Talacasto, en Precordillera Central, con Ă©nfasis en el rĂ­o de La Burra. Se describen ademĂĄs las principales estructuras con evidencia de actividad tectĂłnica cuaternaria. La morfologĂ­a irregular de la cuenca y la diversidad de depĂłsitos aluviales encontrados a lo largo del rĂ­o de La Burra (colector principal de la cuenca) permitieron inferir que la misma se encuentra en un ambiente tectĂłnico activo con fuertes controles litolĂłgicos y estructurales. Las principales fallas descritas se ubican en el piedemonte oriental de la Sierra de La Crucecita, y occidental de la sierra de Talacasto (30Âș 54?-31Âș S y 68Âș 47?-68Âș 55? O), unos 70 km al noroeste de San Juan, en el Departamento Ullum. Las mismas se denominaron de norte a sur: Las Crucecitas y Vertientes (en el piedemonte oriental de la sierra de La Crucecita) y el sistema de falla Talacasto occidental (piedemonte occidental de la sierra homĂłnima). Las fallas afectan depĂłsitos asignados al Pleistoceno tardĂ­o y Holoceno y muestran en las exposiciones naturales identificadas, rasgos tĂ­picos de ambientes compresivos y que evidencian su actividad cuaternaria. Las estructuras identificadas coinciden con el estilo estructural de tectĂłnica de piel delgada de vergencia oriental, caracterĂ­stico de Precordillera Central. AdemĂĄs, se identificĂł un control estructural sobre el rĂ­o de La Burra, con la generaciĂłn de al menos tres terrazas de erosiĂłn sobre su margen izquierda. Esta deformaciĂłn se vincula con el tectonismo activo que a escala regional afectĂł y afecta al ĂĄmbito precordillerano. Finalmente, se identificaron las principales estructuras geolĂłgicas a partir del anĂĄlisis e interpretaciĂłn de las anomalĂ­as gravimĂ©tricas, empleando datos obtenidos de WGM12 (World Gravity Map, 2012), que incluye datos de gravedad terrestre y satelital derivados del modelo EGM2008. La respuesta gravimĂ©trica del basamento que compone el ĂĄrea en estudio, muestra una correlaciĂłn con la estructura superficial y podrĂ­a estar asociada a los diferentes dominios morfotectĂłnicos reconocidos en la regiĂłn.In this work, we have made a morphometric analysis of the Talacasto river basin (Central Precordillera), with emphasis on the La Burra River. The main structures with evidence of Quaternary tectonic activity are also described. The irregular morphology of the basin and the diversity of alluvial deposits found along the La Burra River allow the authors to infer that it is in an active tectonic environment with strong lithologic and structural controls. These main structures are located in the eastern piedmont of the Sierra de la Crucecita, and western piedmont of the sierra de Talacasto (30Âș 54’-31Âș S and 68Âș 47’-68Âș 55’ W), about 70 km northwest of San Juan, in the Ullum Department. The faults located in both piedmonts are named from north to south: Las Crucecitas and Vertientes (in the eastern piedmont of the La Crucecita range) and the Western Talacasto fault system (in the western piedmont of the homonymous range). The faults affect alluvial deposits assigned to the Late Pleistocene and Holocene and show typical features of ongoing compressional Quaternary tectonic activity in the evaluated natural exposures. Faults exhibit the east-verging thin-skinned structural style typical of Central Precordillera. This deformation is related to the regional tectonics that affected and currently affects the Precordilleran region. Finally, the main geological structures were identified by the analysis and interpretation of gravimetric anomalies, employing data obtained from WGM12 (World Gravity Map 2012), which includes earth and satellite gravity data derived from the EGM2008 model. The gravimetric response of the crustal blocks that compose the study area shows a correlation with the outcropping crustal structure and could be associated to the different morphotectonic domains recognized in the region.Fil: Perucca, Laura Patricia A.. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Audemard Menessier, Franck. FundaciĂłn Venezolana de Investigaciones SismolĂłgicas; VenezuelaFil: Alcacer Sanchez, Juan Manuel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Rothis, Luis Martin. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Vargas Perucca, Mariana SofĂ­a. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; ArgentinaFil: Haro Sanchez, Federico Miguel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Tejada Recabarren, Flavia Emilce. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Blanc, Pablo AndrĂ©s. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Vargas, NicolĂĄs. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Lara Ferrero, Gabriela Cristina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂ­sicas y Naturales. Instituto de GeologĂ­a "Dr. Emiliano Aparicio". Gabinete de NeotectĂłnica y GeomorfologĂ­a; Argentina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Onorato, Maria Romina. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas FĂ­sicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentin

    Anisotropic Superparamagnetism of Monodispersive Cobalt-Platinum Nanocrystals

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    Based on the high-temperature organometallic route (Sun et al. Science 287, 1989 (2000)), we have synthesized powders containing CoPt_3 single crystals with mean diameters of 3.3(2) nm and 6.0(2) nm and small log-normal widths sigma=0.15(1). In the entire temperature range from 5 K to 400 K, the zero-field cooled susceptibility chi(T) displays significant deviations from ideal superparamagnetism. Approaching the Curie temperature of 450(10) K, the deviations arise from the (mean-field) type reduction of the ferromagnetic moments, while below the blocking temperature T_b, chi(T) is suppressed by the presence of energy barriers, the distributions of which scale with the particle volumes obtained from transmission electron microscopy (TEM). This indication for volume anisotropy is supported by scaling analyses of the shape of the magnetic absorption chi''(T,omega) which reveal distribution functions for the barriers being also consistent with the volume distributions observed by TEM. Above 200 K, the magnetization isotherms M(H,T) display Langevin behavior providing 2.5(1) mu_B per CoPt_3 in agreement with reports on bulk and thin film CoPt_3. The non-Langevin shape of the magnetization curves at lower temperatures is for the first time interpreted as anisotropic superparamagnetism by taking into account an anisotropy energy of the nanoparticles E_A(T). Using the magnitude and temperature variation of E_A(T), the mean energy barriers and 'unphysical' small switching times of the particles obtained from the analyses of chi''(T,omega) are explained. Below T_b hysteresis loops appear and are quantitatively described by a blocking model, which also ignores particle interactions, but takes the size distributions from TEM and the conventional field dependence of E_A into account.Comment: 12 pages with 10 figures and 1 table. Version accepted for publication in Phys. Rev. B . Two-column layou

    Artificial Intelligence, Machine Learning and Modeling for Understanding the Oceans and Climate Change

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    International audienceThe ongoing transformation of climate and biodiversity will have a drastic impact on almost all forms of life in the ocean with further consequences on food security, ecosystem services in coastal and inland communities. Despite these impacts, scientific data and infrastructures are still lacking to understand and quantify the consequences of these perturbations on the marine ecosystem. Understanding this phenomenon is not only an urgent but also a scientifically demanding task. Consequently, it is a problem that must be addressed with a tific cohort approach, where multi-disciplinary teams collaborate to bring the best of different scientific areas. In this proposal paper, we describe our newly launched four-years project focusedon developing new artificial intelligence, machine learning, and mathematical modeling tools to contribute to the understanding of the structure, functioning, and underlying mechanisms and dynamics of the global ocean symbiome and its relation with climate change. These actions should enable the understanding of our oceans and predict and mitigate the consequences of climate and biodiversity changes

    Highlights from the Pierre Auger Observatory

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    The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km2^2 str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our Xmax_{max} data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201

    A search for point sources of EeV photons

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    Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical Journa

    Reconstruction of inclined air showers detected with the Pierre Auger Observatory

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    We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than 60∘60^\circ detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of Cosmology and Astroparticle Physics (JCAP
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