1,720,985 research outputs found
Companies and non-contractual liability in private international law
Get PDFCompanies with extraterritorial actions or activities may become involved in different cases that may fall within the sphere of non-contractual liability. Private international law must analyze and give specific treatment to each category of liability according to its particularities, in order to provide an appropriate solution to each of themFil: Laje, Rodrigo. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Internacional Privado. Buenos Aires, ArgentinaFil: Laje, Rodrigo. Universidad Abierta Interamericana. Facultad de Derecho. Cátedra Derecho Internacional Privado. Buenos Aires, ArgentinaFil: Laje, Rodrigo. Universidad de Morón. Facultad de Derecho. Cátedra Derecho Internacional Privado. Morón, ArgentinaLas sociedades en su actuación extraterritorial pueden quedar involucradas en diferentes supuestos que son susceptibles de ser encuadrados en la órbita de la responsabilidad extracontractual. Con el objeto de dar adecuada solución a cada uno de ellos, desde el derecho internacional privado corresponde analizar y dar tratamiento específico a cada categoría de responsabilidad en atención a sus particularidade
Clases de ciencia, herramientas mentales, mi abuela y una papa
No full textHay ya muchos trabajos de investigación que muestran repetidamente que las formas de enseñar basadas en la indagación y el aprendizaje activo, es decir las que tienen en cuenta aspectos más reales de cómo funciona la ciencia, son mucho más eficientes que las formas tradicionales. La sugerencia es modificar apenas un poco un par de clases en el año, en lo posible al comienzo, incorporando algunas de estas y otras sugerencias, para que la dinámica en el aula se dé vuelta y los chicos pasen a ser participantes activos. Hagamos que la ciencia escolar sea diferente, mostremos cómo son los vericuetos del pensamiento científico, qué significa saber algo en base a evidencia, cómo podemos hacer predicciones informadas, perdamos el miedo a lo que no sabemos y el respeto a lo que supuestamente sabemos. Esa ciencia será más real, más posible, más apasionante, más humana.Fil: Laje, Rodrigo. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Spatiotemporal perturbations in paced finger tapping suggest a common mechanism for the processing of time errors
Get PDFPaced finger tapping is a sensorimotor synchronization task where a subject has to keep pace with a metronome while the time differences (asynchronies) between each stimulus and its response are recorded. A usual way to study the underlying error correction mechanism is to perform unexpected temporal perturbations to the stimuli sequence. An overlooked issue is that at the moment of a temporal perturbation two things change: the stimuli period (a parameter) and the asynchrony (a variable). In terms of experimental manipulation, it would be desirable to have separate, independent control of parameter and variable values. In this work we perform paced finger tapping experiments combining simple temporal perturbations (tempo step change) and spatial perturbations with temporal effect (raised or lowered point of contact). In this way we decouple the parameter-and-variable confounding, performing novel perturbations where either the parameter or the variable changes. Our results show nonlinear features like asymmetry and are compatible with a common error correction mechanism for all types of asynchronies. We suggest taking this confounding into account when analyzing perturbations of any kind in finger tapping tasks but also in other areas of sensorimotor synchronization, like music performance experiments and paced walking in gait coordination studies.Fil: Lopez, Sabrina Laura. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Laje, Rodrigo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Exploring weight initialization, diversity of solutions, and degradation in recurrent neural networks trained for temporal and decision-making tasks
No full textRecurrent Neural Networks (RNNs) are frequently used to model aspects of brain function and structure. In this work, we trained small fully-connected RNNs to perform temporal and flow control tasks with time-varying stimuli. Our results show that different RNNs can solve the same task by converging to different underlying dynamics and also how the performance gracefully degrades as either network size is decreased, interval duration is increased, or connectivity damage is induced. For the considered tasks, we explored how robust the network obtained after training can be according to task parameterization. In the process, we developed a framework that can be useful to parameterize other tasks of interest in computational neuroscience. Our results are useful to quantify different aspects of the models, which are normally used as black boxes and need to be understood in order to model the biological response of cerebral cortex areas.Fil: Jarne, Cecilia Gisele. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Laje, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentin
Time‐oriented attention improves accuracy in a paced finger‐tapping task
Get PDFFinger tapping is a task widely used in a variety of experimental paradigms, in particular to understand sensorimotor synchronization and time processing in the range of hundreds of milliseconds (millisecond timing). Normally, subjects do not receive any instruction about what to attend to and the results are seldom interpreted taking into account the possible effects of attention. In this work we show that attention can be oriented to the purely temporal aspects of a paced finger-tapping task and that it affects performance. Specifically, time-oriented attention improves the accuracy in paced finger tapping and it also increases the resynchronization efficiency after a period perturbation. We use two markers of the attention level: auditory ERPs and subjective report of the mental workload. In addition, we propose a novel algorithm to separate the auditory, stimulus-related components from the somatosensory, response-related ones, which are naturally overlapped in the recorded EEG.Fil: Versaci, Leonardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Laje, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentin
The physics of birdsong
No full textEsta tesis está dedicada al análisis y modelado de los mecanismos físicos de la fonación en el órgano vocal de las aves canoras, la siringe. Algunas aves son popularmente conocidas por su capacidad de imitar sonidos. Se trata de todas las especies del suborden Oscinos (aves canoras), más los loros y los colibríes. Más allá del hecho curioso, la gran cantidad de similitudes entre la adquisición del habla en humanos y el aprendizaje del canto convierte a estas aves en un modelo invaluable para estudiar los mecanismos neuronales del habla en particular, y de aprendizaje y control motor de un comportamiento complejo en general. Entender cómo el cerebro del ave organiza las acciones motoras del canto es una motivación central en dicho programa. El vínculo entre actividad neuronal y comportamiento observado lo establece la siringe, el aparato vocal de las aves. La siringe en Oscinos produce sonido por vibración de los labia (tejidos móviles análogos a las cuerdas vocales humanas); es un dispositivo mecánico que muestra una riquísima variedad de soluciones oscilatorias. La comprensión de los mecanismos físicos de la fonación es de fundamental importancia para establecer el mapa de control motor y evaluar posibles restricciones a nivel periférico. En esta tesis presentamos un modelo matemático de fonación en aves canoras cuyos parámetros tienen estrecha relación con parámetros fisiológicos relevantes, como actividad muscular y presión del saco aéreo. Este modelo está basado en un detallado conocimiento de la función de diferentes estructuras en la siringe, gracias a recientes mediciones electrofisiológicas in vivo. Proponemos además que una gran variedad de vocalizaciones pueden interpretarse en términos de dos gestos motores cíclicos básicos: la presión del saco aéreo y la tensión de los labia. El parámetro clave para generar sílabas diversas es el desfasaje entre los gestos motores propuestos. El incipiente estudio de sonidos complejos en aves (frecuencias subarmónicas, espectros anarmónicos y saltos de frecuencia, por ejemplo) dió por tierra con la idea tácitamente aceptada de que hay una relación directa entre las instrucciones neuronales y las propiedades acústicas del sonido emitido. Los orígenes físicos de la complejidad, sin embargo, distan de ser entendidos completamente. Aquí presentamos un modelo que permite estudiar el acople acústico entre fuente sonora y tracto vocal, así como la interacción acústica entre las dos fuentes sonoras presentes en la siringe. Mostramos que el acople acústico y la realimentación acústica retrasada son posibles causas de sonidos complejos en un sonograma, y proponemos experimentos sencillos para evaluar los orígenes de la complejidad en el canto de algunas aves. Por último, la idea de los gestos motores nos da un marco para analizar el sorprendente canto a dúo del hornero. Más allá de la física del aparato fonador, la hipótesis de los gestos motores nos permite intuir comportamientos no lineales en los centros neuronales que controlan el canto. Este resultado es una de las pocas evidencias de sincronización de ritmos corporales en animales intactos.This thesis is dedicated to the analysis and modeling of the physical mechanisms of phonation in the avian vocal organ, the syrinx. Some birds are known due to their ability to imitate sounds. We are referring to songbirds (all species in suborder Oscines), together with parrots and hummingbirds. Beyond the simple curiosity, the large number of similarities between speech acquisition in humans and song learning in these birds makes them an invaluable model to study the neural mechanisms underlying speech and, more generally, learning and motor control of a complex behaviour. Understanding the mechanisms by which the bird brain organizes the song motor gestures is a central motivation in such a program. The link between neural activity and observed behaviour is established by the syrinx, the avian vocal organ. The syrinx in Oscines generates sound through vibration of the labia (mobile tissues analogous to the human vocal cords); it is a mechanical device displaying a rich variety of oscilatory solutions. The comprehension of the physical mechanisms playing at phonation is of fundamental importance in order to build the motor control map and evaluate possible peripheral constraints. In this thesis we present a mathematical model for the phonation in songbirds whose parameters are closely related to relevant physiological parameters such as muscular activity and air sac pressure. This model is based upon a detailed knowledge of the function of different structures in the syrinx, due to recent in vivo electrophysiological measurements. We propose in addition that a large number of different vocalizations can be interpreted in terms of two cyclic, basic motor gestures: air sac pressure and labia tension. The key parameter needed to generate a diversity of syllables is the phase difference between the proposed motor gestures. The incipient study of complex sounds in birds (subharmonic frequencies, anharmonic spectra and frequency jumps, for instance) abolished the unexpressed belief of a direct relationship between neural instructions and acoustic properties of the emitted sound. The physical origins of complexity, however, remain obscure. Here we present a model that allows us to study the acoustic coupling between sound source and vocal tract, as well as the acoustic interaction between the two sound sources in the syrinx. We show that acoustic coupling and delayed acoustic feedback are possible origins of complex sounds in a sonogram, and propose simple experiments to evaluate the source of complexity in the song of some birds. Last, the motor gestures hypothesis gives us a framework to study the surprising song of the duetting bird hornero. Beyond the physics of the vocal organ, we found a nonlinear behaviour that allows us to have an insight into the neural circuits driving the song. This result is one of the few evidences of synchronization of bodily rhythms in intact animals.Fil: Laje, Rodrigo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Small perturbations in a finger-tapping task reveal inherent nonlinearities of the underlying error correction mechanism
Get PDFTime estimation is critical for survival and control of a variety of behaviors, both in humans and other animals. Time processing in the few hundred milliseconds range, known as millisecond timing, is involved in motor control, speech generation and recognition, and sensorimotor synchronization like playing music or finger tapping to an external beat. In finger tapping, a mechanistic explanation in terms of neuronal activations of how the brain achieves average synchronization against inherent noise and perturbations in the stimulus sequence is still missing despite considerable research. In this work we show that nonlinear effects are important for the recovery of synchronization following a perturbation (a step change in stimulus period), even for perturbation magnitudes smaller than 10% of the period, which is well below the amount of perturbation needed to display other nonlinear effects like saturation. We build a mathematical model for the error correction mechanism and test its predictions, and further propose a framework that allows us to unify the description of the three common types of perturbations and all perturbation magnitudes with a single set of parameter values. While previous works have proposed that multiple mechanisms/strategies are used for correcting different perturbation conditions (based on fitting the model?s parameters separately to different perturbation types and sizes), our results suggest that the synchronization behavior can be interpreted as the outcome of a single mechanism/strategy, and call for a revision of the idea of multiple strategies.Fil: Bavassi, Mariana Luz. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia; ArgentinaFil: Tagliazucchi, Enzo Rodolfo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia; ArgentinaFil: Laje, Rodrigo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia; Argentina. University Of California; Estados Unidos de América
Response to perturbations as a built-in feature in a mathematical model for paced finger tapping
Get PDFPaced finger tapping is one of the simplest tasks to study sensorimotor synchronization. The subject is instructed to tap in synchrony with a periodic sequence of brief tones, and the time difference (called asynchrony) between each response and the corresponding stimulus is recorded. Despite its simplicity, this task helps to unveil interesting features of the underlying neural system and the error-correction mechanism responsible for synchronization. Perturbation experiments are usually performed to probe the subject´s response, for example, in the form of a step change, i.e., an unexpected change in tempo. The asynchrony is the usual observable in such experiments and it is chosen as the main variable in many mathematical models that attempt to describe the phenomenon. In this work we show that although asynchrony can be perfectly described in operational terms, it is not well defined as a model variable when tempo perturbations are considered. We introduce an alternative variable and a mathematical model that intrinsically takes into account the perturbation and make theoretical predictions about the response to novel perturbations based on the geometrical organization of the trajectories in phase space. Our proposal is relevant to understand interpersonal synchronization and the synchronization to nonperiodic stimuli.Fil: González, Claudia Roxana. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Laboratorio de Dinamica Sensomotora.; ArgentinaFil: Bavassi, Mariana Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Laje, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Laboratorio de Dinamica Sensomotora.; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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