645 research outputs found
Collision problems treated with the Generalized Hyperspherical Sturmian method
An hyperspherical Sturmian approach recently developed for three-body break-up processes is presented. To test several of its features, the method is applied to two simplified models. Excellent agreement is found when compared with the results of an analytically solvable problem. For the Temkin-Poet model of the double ionization of He by high energy electron impact, the present method is compared with the Spherical Sturmian approach, and again excellent agreement is found. Finally, a study of the channels appearing in the break-up three-body wave function is presented.Fil: Mitnik, Dario Marcelo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Gasaneo, Gustavo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de FÃsica; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Ancarani, Lorenzo Ugo. Universite de Lorraine; FranciaFil: Ambrosio, Marcelo José. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentin
Modeling and vibration mode analysis of a ball screw drive
Positioning systems for machine tools are generally driven by ball screws due to their high stiffness and low sensitivity to external perturbations. However, as modern machine tools increase their velocity and acceleration of positioning, the resonant modes of these systems could be excited degrading the trajectory tracking accuracy. Therefore, a dynamic model including the vibration modes is required for machine design as well as for controller selection and tuning. This work presents a high-frequency dynamic model of a ball screw drive. The analytical formulation follows a comprehensive approach, where the screw is modeled as a continuous subsystem, using Ritz series approximation to obtain an approximate N-degree-of-freedom model. Based on this model, the axial and angular components of each mode function are studied for different transmission ratios to determine the degree of coupling between them. After that, the frequency variation of each mode was studied for different carriage positions and different moving masses. Finally, an analysis of these results applied to controller design and parameter estimation is also presented.Fil: Vicente, Diego Alberto. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Hecker, Rogelio Lorenzo. Universidad Nacional de la Pampa. Facultad de IngenierÃa; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Villegas, Fernando Javier. Universidad Nacional de la Pampa. Facultad de IngenierÃa; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Flores, Gustavo Marcelo. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentin
Sistema para el monitoreo de fuerza y temperatura en torneado
La continua demanda sobre la calidad y reducción de costos de los productos de manufactura mecánica impulsa el desarrollo de equipamiento para medir y controlar las principales variables de los procesos. Particularmente en los procesos de remoción de material el monitoreo de variables tales como fuerzas de corte, temperatura de la herramienta y vibraciones pueden conducir tanto a la optimización del proceso como la detección temprana de fallas. Siguiendo este lineamiento se presenta el desarrollo de una plataforma para monitorear las fuerzas de corte y la temperatura en la interfase herramienta-viruta en procesos de torneado. La medición de fuerza es una aplicación sencilla con el sólo objeto de probar el sistema desarrollado y se basa en la instalación de galgas extensiométricas en el mango porta-insertos. Mientras que para la medición de la temperatura en la zona de corte se presenta el desarrollo de un sistema que permite la estimación de dicho valor a partir de la medición de temperatura en la base del inserto de corte usando un termopar y filtros iterativos para la estimación. Finalmente, se detalla la implementación del sistema de monitoreo y se presentan datos experimentales obtenidos a partir de operaciones de cilindrado en un torno CNC.Fil: Hecker, Rogelio Lorenzo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Patagonia Confluencia; Argentina. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Flores, Gustavo Marcelo. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Vicente, Diego Alberto. Universidad Nacional de la Pampa. Facultad de IngenierÃa; Argentin
Sintonización de un controlador para un posicionador lineal usando la dinámica de alta frecuencia del sistema
Las máquinas herramientas modernas requieren de sistemas de posicionamiento capaces de seguir, con errores reducidos, trayectorias con valores elevados de velocidad y aceleración. Para ello, estos sistemas deben ser diseñados y controlados para obtener un ancho de banda adecuado y buena robustez a las perturbaciones externas y a las dinámicas no compensadas. Este trabajo presenta la dinámica de alta frecuencia y un modelo reducido de un dispositivo de posicionamiento lineal compuesto por: un motor eléctrico, un sistema tornillo-tuerca de bolas recirculantes y un carro que se desliza sobre guÃas lineales, también de bolas recirculantes. Además, se incluyen los parámetros estimados del modelo reducido y de la fricción de Coulomb. Luego se presenta un esquema de control compuesto por: ubicación de polos de lazo cerrado mediante la técnica de variables de estado, más un prefiltro que tiene en cuenta la dinámica del sistema (Zero Phase Error Tracking Controller, ZPETC) y adicionalmente un compensador para la fricción dinámica. La dinámica deseada de lazo cerrada se selecciona mediante un análisis de estabilidad utilizando el modelo de alta frecuencia del sistema. Finalmente, se muestran resultados experimentales donde se constatan valores de error reducidos en seguimiento de trayectorias exigentes. Para trayectorias a velocidad constante entre dos posiciones determinadas, incluyendo arranque y parada, se detecta un error medio menor a 41 μm y para trayectorias sinusoidales se observa un error medio menor a 38 μm, siendo estos valores apropiados para máquinas herramientas modernas.Fil: Casquero, AgustÃn. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Hecker, Rogelio Lorenzo. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Vicente, Diego. Universidad Nacional de la Pampa. Facultad de IngenierÃa; ArgentinaFil: Flores, Gustavo Marcelo. Universidad Nacional de la Pampa. Facultad de IngenierÃa; Argentin
Sensor con celdas de carga embebidas para la medición de la resistencia mecánica del suelo
La compactación de los suelos agrÃcolas es un fenómeno que afecta el normal desarrollo de las raÃces de los
cultivos y consecuentemente su posterior rendimiento. Por lo tanto, disponer de la información del estado de
compactación del suelo será relevante en un futuro en lo que respecta a la agricultura de precisión. La información
usual recolectada en campo relacionada con la compactación del suelo es el Ãndice de cono (CI), obtenido
mediante el uso del penetrómetro. Sin embargo, la obtención de dicha información con una alta resolución
espacial a partir del penetrómetro resulta ineficiente y altamente costosa. Atendiendo a esta dificultad, se han
desarrollado sensores on-the-go, cuya principal caracterÃstica es su capacidad de registrar de manera continua la
resistencia mecánica del suelo, con una alta resolución espacial tanto en el plano horizontal como en el vertical.
Dicha caracterÃstica reduce de manera significativa los tiempos y los costos de adquisición de la información
de la resistencia mecánica del suelo, por la cual a partir de la misma se estima el estado de compactación del
suelo. En este trabajo se presenta un sensor para medir de forma continua la resistencia mecánica del suelo en
tres profundidades diferentes del suelo. En este dispositivo se utilizan celdas de cargas embebidas en el propio
seno de dicho sensor promoviendo asà un desempeño robusto y con una alta sensibilidad. El prototipo de este
sensor fue en primera instancia evaluado y calibrado en laboratorio, para luego finalmente evaluar su desempeño
en pruebas a campo. La resistencia mecánica horizontal del suelo en los tres intervalos de profundidad relevados
por dicho sensor ha sido correlacionada con el Ãndice de cono (CI) obtenido mediante un penetrómetro, mostrando
que resulta factible la utilización de la información relevada por este sensor en la estimación del estado
de compactación del suelo.Soil compaction is an important degradation phenomenon that can affect root growth, and consequently crop
yield. Therefore it becomes relevant to have soil compaction data for future improvements on precision agriculture management. A traditional on-the-field data related to soil compaction is cone index obtained using a
penetrometer; however, this methodology is time consuming for a high density data. Therefore, on-the-go sensors
have been developed to continually estimate the variable of interest. This work proposes an on-the-go sensor to
estimate the soil horizontal resistance at different depths. The main design concept is based on embedded load
cells at three different depths, resulting in a robust sensor with high sensitivity. The prototype was first tested and
calibrated in laboratory, and then, it was tested in the field. The calculated horizontal resistance index (HRI) at
the three depths was correlated with the cone index (CI) using a cone penetrometer, showing that this sensor can
replace the penetrometer data, allowing the possibility of taking continuous data on the field.EEA ANGUILFil: Fernández, Romina. Instituto Nacional de TecnologÃa Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil; ArgentinaFil: Masch, Federico Rafael. Universidad Nacional de La Pampa (UNLPam). Facultad de IngenierÃa; ArgentinaFil: Hecker, Rogelio Lorenzo. Universidad Nacional de La Pampa (UNLPam). Facultad de IngenierÃa; ArgentinaFil: Flores, Gustavo Marcelo. Universidad Nacional de La Pampa (UNLPam). Facultad de IngenierÃa; ArgentinaFil: RamÃrez, Pablo. Universidad Nacional de La Pampa (UNLPam). Facultad de IngenierÃa; Argentin
Genome of Rhodnius prolixus, an insect vector of Chagas disease, reveals unique adaptations to hematophagy and parasite infection
Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (?702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immunedeficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods.Fil: Calderón Fernández, Gustavo Mario. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; ArgentinaFil: Esponda Behrens, Natalia Irene. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Juarez, Marta Patricia. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; ArgentinaFil: Latorre Estivalis, Jose Manuel. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Fundación Oswaldo Cruz; Brasil. Instituto Nacional de Ciencia e Tecnologia en EntomologÃa Molecular; BrasilFil: Lavore, Andres Esteban. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Lazzari, Claudio Ricardo. Université François Rabelais; Francia. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Lorenzo, Marcelo Gustavo. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Fundación Oswaldo Cruz; Brasil. Instituto Nacional de Ciencia e Tecnologia en EntomologÃa Molecular; BrasilFil: Ons, Sheila. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Pagola, Lucia Elena. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Pascual, Agustina. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Pedrini, Nicolás. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones BioquÃmicas de La Plata "Prof. Dr. Rodolfo R. Brenner"; ArgentinaFil: Sterkel, Marcos. Universidade Federal do Rio de Janeiro; Brasil. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; Argentin
Trypanosomes Modify the Behavior of Their Insect Hosts: Effects on Locomotion and on the Expression of a Related Gene
Background
As a result of evolution, the biology of triatomines must have been significantly adapted to accommodate trypanosome infection in a complex network of vector-vertebrate-parasite interactions. Arthropod-borne parasites have probably developed mechanisms, largely still unknown, to exploit the vector-vertebrate host interactions to ensure their transmission to suitable hosts. Triatomines exhibit a strong negative phototaxis and nocturnal activity, believed to be important for insect survival against its predators.
Methodology/Principal Findings
In this study we quantified phototaxis and locomotion in starved fifth instar nymphs of Rhodnius prolixus infected with Trypanosoma cruzi or Trypanosoma rangeli. T. cruzi infection did not alter insect phototaxis, but induced an overall 20% decrease in the number of bug locomotory events. Furthermore, the significant differences induced by this parasite were concentrated at the beginning of the scotophase. Conversely, T. rangeli modified both behaviors, as it significantly decreased bug negative phototaxis, while it induced a 23% increase in the number of locomotory events in infected bugs. In this case, the significant effects were observed during the photophase. We also investigated the expression of Rpfor, the triatomine ortholog of the foraging gene known to modulate locomotion in other insects, and found a 4.8 fold increase for T. rangeli infected insects.
Conclusions/Significance
We demonstrated for the first time that trypanosome infection modulates the locomotory activity of the invertebrate host. T. rangeli infection seems to be more broadly effective, as besides affecting the intensity of locomotion this parasite also diminished negative phototaxis and the expression of a behavior-associated gene in the triatomine vector
Molecular basis of peripheral olfactory plasticity in Rhodnius prolixus, a Chagas disease vector
Olfaction is fundamental for most animals and critical for different aspects of triatomine biology, including host-seeking, reproduction, avoidance of predators, and aggregation in shelters. Ethological and physiological aspects of these olfactory-mediated behaviors are well-understood, but their molecular bases are still largely unknown. Here we investigated changes in the molecular mechanisms at the peripheral olfactory level in response to different physiological and developmental conditions. For this, the antennal expression levels of the odorant (Orco) and ionotropic (IR8a, IR25a, and IR76b) coreceptor genes were determined in Rhodnius prolixus by means of quantitative real-time PCR (qRT-PCR) analysis. Gene expression changes were analyzed to test the effect of feeding and imaginal molt for both sexes. Moreover, we analyzed whether expression of these genes changed during the early life of adult bugs. Under these conditions bugs display distinct behavioral responses to diverse chemical stimuli. A significantly decreased expression was induced by blood feeding on all coreceptor genes. The expression of all genes was significantly increased following the imaginal molt. These results show that olfactory coreceptor genes have their expression altered as a response to physiological or developmental changes. Our study suggests that olfactory coreceptor genes confer adaptability to the peripheral olfactory function, probably underlying the known plasticity of triatomine olfactory-mediated behavior
a study from ecological theory and social network analysis perspective
The objective of the present study was to analyze and compare the setter's decision-making (DM) in the offensive construction of the side-out (attack from the reception) in high-level men's volleyball. The sample consisted of the analysis of 132 games of the Brazilian men's volleyball Super-League 2021/2022, with 22 games for each team. The results showed that the eigenvector values were higher for setting to position 3, central attacker next to the setter, simple block, and obtaining the attack point. In addition, the setter's DM was similar between teams, suggesting that the game strategies aim to provide subsidies for the setter to make the
decisions according to the game context in a flexible way and generate benefits for the attackers about the number of blockers, being that under ideal conditions and due to the lifter's correct choices in distribution, central blockers avoid anticipating the setting, and this fact allows the conditions of a single block or double-broken blocks in most cases. As a practical application, setting for the central attacker in position 3 becomes an interesting option for point acquisition and is capable of influencing the number of blockers, as well as the optimal blocking condition. Another application would be for the central attacker to position themselves close to the setter, a strategy that would enable the use of the "pipe" attack in other areas of the court with lower defensive blocking power.9E1A-F9DD-3EB8 | Filipe Manuel ClementeN/
Inter e intra-variability of the best ranked teams : a network analysis in male high-level volleyball
The present research objective was to analyze the offensive phase from Complex I in highlevel male volleyball teams in a macro- and micro-level view, through the inter e intra-team variability analysis of eight best teams of the 2018 Men’s Volleyball World Championship over the social network analysis and eigenvector centrality. The sample consisted of 22 matches and 2,743 offensive actions, resulting in 8 sub-networks with 368 nodes and 6221 edges. The results showed from macro view the variables that presented highest centrality values were Attack Zone 4 (range 0.56–0.90), Attack Tempo 2 (0.65–0.87), Power Attack (0.62–0.94), No Touch Block (0.61–1), Attack Effect Continuity (0.59–0.94), and Middle Blocker Centralized (0.60–0.95). In a micro view, Reception Effect, Play Position, Reception Zone, and Block Composition showed high variability in each sub-network. The intra- and inter-team variability presented the importance of to respect each team idiosyncrasies and to consider the different approaches to the game and success
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