290 research outputs found

    Extension of charge-state-distribution calculations for ion-solid collisions towards low velocities and many-electron ions

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    Knowledge of the detailed evolution of the whole charge-state distribution of projectile ions colliding with targets is required in several fields of research such as material science and atomic and nuclear physics but also in accelerator physics, and in particular in regard to the several foreseen large-scale facilities. However, there is a lack of data for collisions in the nonperturbative energy domain and that involve many-electron projectiles. Starting from the etacha model we developed [Rozet, Nucl. Instrum. Methods Phys. Res., Sect. B 107, 67 (1996)10.1016/0168-583X(95)00800-4], we present an extension of its validity domain towards lower velocities and larger distortions. Moreover, the system of rate equations is able to take into account ions with up to 60 orbital states of electrons. The computed data from the different new versions of the etacha code are compared to some test collision systems. The improvements made are clearly illustrated by 28.9MeVu-1Pb56+ ions, and laser-generated carbon ion beams of 0.045 to 0.5MeVu-1, passing through carbon or aluminum targets, respectively. Hence, those new developments can efficiently sustain the experimental programs that are currently in progress on the "next-generation" accelerators or laser facilities.Fil: Lamour, E.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Fainstein, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Galassi, Mariel Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Prigent, C.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Ramirez, C. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rozet, J. P.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Trassinelli, M.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Vernhet, D.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; Franci

    Electron emission in ionization of He and Ne by fast dressed oxygen ions and projectile-charge-state dependence

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    The double-differential cross sections (DDCS) of low-energy electrons emitted at forward, backward, and perpendicular directions are reported for collisions of 3.75 MeV/u Oq+ (q=5, 6, 7, 8) projectiles with He and Ne targets. The measured DDCS are found to be deviating from the q2 dependence throughout the entire energy region. The effect of projectile electrons, for the dressed ions, as a function of the impact parameter is clearly noticeable for large as well as low-impact parameter collisions. We also present a theoretical calculation based on the prior form of the continuum distorted wave-eikonal initial state approximation, in which the projectile-active electron interaction is modeled with the Green-Sellin-Zachor potential. This particular representation of the potential has been proven to give good qualitative results for projectiles with residual electrons. In addition to the total DDCS, the individual contributions from target ionization, projectile electron loss, and simultaneous ionization processes are also calculated. The total DDCS obtained from these calculations are shown to be in excellent agreement with the experimental observations.Fil: Biswas, Shubhadeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kasthurirangan, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; España. Institute of Chemical Technology; IndiaFil: Misra, D.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fainstein, Pablo Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Tribedi, L.C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

    Impact ionization of molecular oxygen by 3.5-MeV/u bare carbon ions

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    We have measured the absolute double-differential cross sections (DDCSs) for electron emission in ionization of O2 molecules under the impact of 3.5-MeV/u C6+ ions. The data were collected between 10 and 600 eV, in an angular range of 30◦ to 150◦. The single-differential cross sections (SDCSs) in emission angle and electron energy are deduced from the electron DDCS spectra. Also, the total cross section has been obtained from the SDCS spectra. The DDCS spectra as well as the SDCS spectra are compared with continuum distorted-wave eikonal initial-state calculations which employ molecular wave functions built as linear combinations of atomic orbitals. The DDCS ratio i.e. σO2/2σO, derived by dividing the experimental DDCS for molecular oxygen with the theoretical DDCS for atomic oxygen, does not show any primary or secondary oscillations arising from Young-type interference, which is apparently in contrast to what has been observed earlier for H2 and in agreement with the model calculation. Similarly, the forward-backward angular asymmetry increases monotonically with the velocity of the emitted electrons. However, the results on the DDCSs, SDCSs, the asymmetry parameter, and the nonexistence of oscillations are in qualitative agreement with the predictions of the model usedOne of the authors (F.M.) acknowledges the financial support from the MICINN Projects No. FIS2010-15127 and No. CSD 2007- 00010. C.A.T., R.D.R., and F.M. acknowledge the Programa de Cooperación Interuniversitaria e Investigación Científica entre España e Iberoamérica AECID Project No. A2/039631/1

    Caracterización paleoambiental y evolución lateral de un sistema aluvial efímero con interacción eólica: formaciones Los Riscos - El Jume (Aptiano), Sierra de las Quijadas, San Luis, Argentina

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    Durante el Mesozoico en el sector centro- oeste y norte de Argentina, se generaron cuencas del tipo rift abortados que tuvieron actividad subsidente en varios pulsos asociados al régimen distensivo producto de la ruptura del último Gondwana. En ese marco se formó la Cuenca de San Luis con tres depocentros, rellenos por el Grupo El Gigante; el cual está conformado por más de 1500 m de sedimentitas silicoclásticas continentales, intercaladas con delgados niveles de evaporitas, tobas y basaltos de intraplaca. En Sierra de las Quijadas la sedimentación tuvo lugar en un hemigraben asimétrico con borde activo al oeste a expensas del cual se habrían depositado uno o más abanicos aluviales asociados a depósitos de crecidas no encauzadas que hacia los sectores depocentrales de la cuenca gradaban a un sistema fluvial efímero en íntima asociación con un extenso sistema de barreal con acción eólica (Rivarola y Spalletti, 2006).Este trabajo tiene por objeto dar a conocer los primeros resultados de una investigación desarrollada en el marco de la tesis doctoral de la primera autora en el Potrero de la Aguada (PdA) en dichas sierras. Esto se llevó a cabo a partir del análisis de facies y sus asociaciones (AF) a fin de caracterizar la evolución paleoambiental de alta resolución de las unidades basales del Grupo el El Gigante, : Formaciones Los Riscos y El Jume. Se relevaron 1200 m de sedimentitas distribuidas en nueve secciones estratigráficas. Se reconocieron 26 facies donde la letra mayúscula indica granulometría y la/s minúsculas indican la estructura y característica dominante. En los sectores más occidentales del PdA, se observó una pila sedimentaria de orden decámetrico donde domina AFI (Gm, Gh, Gp y SGm), interpretada como un sistema fluvial con depósitos residuales de canales y barras. Hacia el este y sudeste, esta asociación engrana con las AFII y III donde AFII (Sp, St, Sl, Sr, Src, Sh, Sm y SGm) es interpretada como un sistema fluvial canalizado; en tanto que AFIII (Gfm, Gem y Sfm) representaría depósitos de crecidas no encauzadas gravosas. Por su parte, hacia el este se observa que AFII pierde expresión y engrana con bancos de espesores decimétritos a métricos constituidos por AFIV (Sh, Sl, Sr, Src, Fm y raramente SGm), interpretada como lóbulos de crecidas no encauzadas arenosos; AFV (Fsr, Fh y Fm) que corresponde a depósitos lacustres efímeros/barreal, tanto de plataforma externa como interna; y AFVI (Shg, Shm, Slg, Slm, Stg, Stm, Ser, Spe y Spr) correspondiente a depósitos eólicos, donde se reconocen mantos de arena y dunas. En el sector central del PdA, la AFVI (eólica) presenta carácter dominante en los tramos inferiores conformando pilas de decenas de metros de potencia; en la cual sólo se intercalan reducidos bancos de AFIV (lóbulos de crecidas). En las laderas este y sur del PdA, se observa un claro dominio de AFV, (depósitos de barreal) con espesores del orden decamétrico, que por sectores intercalan escasos y delgados bancos de AFIV, propia de lóbulos de crecida no encauzadas y AFVI, correspondiente a depósitos eólicos. Las secuencias descritas conforman un complejo mosaico de ambientes en los que se refleja claramente el pasaje de facies proximales a distales el que permite reconstruir un sistema aluvial efímero con interacción eólica.Fil: Nalin Moyano, María Magdalena. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Veiga, Gonzalo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Rivarola, D.. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaVII Congreso Latinoamericano de Sedimentología y XV Reunión Argentina de SedimentologíaSanta RosaArgentinaAsociación Argentina de Sedimentologí

    Insights into the role of DNA methylation in diatoms by genome-wide profiling in Phaeodactylum tricornutum

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    DNA cytosine methylation is a widely conserved epigenetic mark in eukaryotes that appears to have critical roles in the regulation of genome structure and transcription. Genome-wide methylation maps have so far only been established from the supergroups Archaeplastida and Unikont. Here we report the first whole-genome methylome from a stramenopile, the marine model diatom Phaeodactylum tricornutum. Around 6% of the genome is intermittently methylated in a mosaic pattern. We find extensive methylation in transposable elements. We also detect methylation in over 320 genes. Extensive gene methylation correlates strongly with transcriptional silencing and differential expression under specific conditions. By contrast, we find that genes with partial methylation tend to be constitutively expressed. These patterns contrast with those found previously in other eukaryotes. By going beyond plants, animals and fungi, this stramenopile methylome adds significantly to our understanding of the evolution of DNA methylation in eukaryotes.Fil: Veluchamy, Alaguraj. Institut de Biologie de l'École Normale Supérieure; FranciaFil: Lin, Xin. Institut de Biologie de l'École Normale Supérieure; Francia. Xiamen University; ChinaFil: Maumus, Florian.Fil: Rivarola, Maximo Lisandro.Fil: Bhavsar, Jaysheel.Fil: Creasy, Todd.Fil: O'Brien, Kimberly.Fil: Sengamalay, Naomi A..Fil: Tallon, Luke J..Fil: Smith, Andrew D..Fil: Rayko, Edda.Fil: Ahmed, Ikhlak.Fil: Crom, Stéphane Le.Fil: Farrant, Gregory K..Fil: Sgro, Jean-Yves.Fil: Olson, Sue A..Fil: Bondurant, Sandra Splinter.Fil: Allen, Andrew.Fil: Rabinowicz, Pablo D..Fil: Sussman, Michael R..Fil: Bowler, Chris.Fil: Tirichine, Leïla

    Interference Effects Due to Projectile Target Nucleus Scattering in Single Ionization of H₂ by 75-keV Proton Impact

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    Doubly differential cross sections (DDCSs) for single ionization of molecular hydrogen by 75-keV proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. Interference structures are observed in the scattering angular dependence of the DDCSs, which disappear, however, at electron speeds near the projectile speed. The comparison to our calculations shows that the projectile-target nucleus interaction plays a central role. Furthermore, our data suggest that for a given scattering angle, ionization favors well-defined molecular orientations

    Evaluation of Natural Technological Interfaces for Children with Psychomotor Disabilities

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    population with disabilities, there is a group that has intellectual, sensory, motor disabilities, or a combination of them. The International Classification of Functioning, Disability and Health (ICF) defines disability as an umbrella term for impairments, activity limitations and participation restrictions. It is estimated that over 15 % of the world´s population is afflicted by disability in some form. In Argentina this prevalence reaches 7.1%. When these people want to use any technological device, usually find that its physical interfaces are not accessible. Often they need adaptations, raising costs but accessibility is not totally guaranteed. Current technologies allow "more natural" interfaces, where the feedback is immediate. The application of appropriate technology with natural or intuitive interfaces, allow greater accessibility than adaptations commonly used for the overall development of students with psychomotor disorders. The objective of this work is to facilitate the comprehensive development of students with senso psychomotor disorders attending the Special School Beatriz Martinez A. Allio, through the incorporation and implementation of natural interfaces for working with computers in education, offering teaching a complementary tool for the development of their daily activities. The interfaces of hardware and software implementation are proposed to achieve the overall goal. It is intended to make at least a touch screen and at least one interface with the Kinect camera game console Xbox 360.Fil: Beltramone, D. A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Tula, S. M. Ministerio de Educación de la Provincia de Córdoba. Escuela Especial B. A. Martínez Allio; Argentina.Fil: Rivarola, M. F. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Escuela Kinesiología y Fisioterapia; Argentina.Fil: Hidalgo, M. B. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Tancredi, P. D. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Quinteros Quintana, M. L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Diaz, J. M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Marcotti, A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Ingeniería Biomédica; Argentina.Fil: Atea, J. J. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Electrónica; Argentina.Ingeniería Médic

    Interference Effects Due to Projectile Target Nucleus Scattering in Single Ionization of H₂ by 75-keV Proton Impact

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    Doubly differential cross sections (DDCSs) for single ionization of molecular hydrogen by 75-keV proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. Interference structures are observed in the scattering angular dependence of the DDCSs, which disappear, however, at electron speeds near the projectile speed. The comparison to our calculations shows that the projectile-target nucleus interaction plays a central role. Furthermore, our data suggest that for a given scattering angle, ionization favors well-defined molecular orientations
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