On the effect of chaotic orbits on dynamical friction

Chaotic orbits suffer significant changes as a result of small perturbations. One can thus wonder whether the dynamical friction suffered by a satellite on a regular orbit, and interacting with the stars of a galaxy, will be different if the bulk of the stars of the galaxy are in regular or chaotic orbits. In order to check that idea, we investigated the orbital decay (caused by dynamical friction) of a rigid satellite moving within a larger stellar system (a galaxy) whose potential is nonintegrable. We performed numerical experiments using two kinds of triaxial galaxy models: (1) the triaxial generalization of Dehnen´s spherical mass model (Dehnen; Merritt & Fridman); (2) a modified Satoh model (Satoh; Carpintero, Muzzio, & Wachlin). The percentages of chaotic orbits present in these models were increased by perturbing them. In the first case, a central compact object (black hole) was introduced; in the second case, the perturbation was produced by allowing the galaxy to move on a circular orbit in a logarithmic potential. The equations of motion were integrated with a non-self-consistent code. Our results show that the presence of chaotic orbits does not affect significantly the orbital decay of the satellite.Fil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Vergne, Maria Marcela. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Muzzio, Juan Carlos. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentin

On the effect of chaotic orbits on dynamical friction

Chaotic orbits suffer significant changes as a result of small perturbations. One can thus wonder whether the dynamical friction suffered by a satellite on a regular orbit, and interacting with the stars of a galaxy, will be different if the bulk of the stars of the galaxy are in regular or chaotic orbits. In order to check that idea, we investigated the orbital decay (caused by dynamical friction) of a rigid satellite moving within a larger stellar system (a galaxy) whose potential is nonintegrable. We performed numerical experiments using two kinds of triaxial galaxy models: (1) the triaxial generalization of Dehnen´s spherical mass model (Dehnen; Merritt & Fridman); (2) a modified Satoh model (Satoh; Carpintero, Muzzio, & Wachlin). The percentages of chaotic orbits present in these models were increased by perturbing them. In the first case, a central compact object (black hole) was introduced; in the second case, the perturbation was produced by allowing the galaxy to move on a circular orbit in a logarithmic potential. The equations of motion were integrated with a non-self-consistent code. Our results show that the presence of chaotic orbits does not affect significantly the orbital decay of the satellite.Instituto de Astrofísica de La Plat

Poplar leaf rust reduces dry mass accumulation and internal nitrogen recycling more markedly under low soil nitrogen availability, and decreases growth in the following spring

Rust is one of the most important biotic stress factors that affect poplars. The aims of this work were: (i) to analyze the changes in growth and nitrogen (N) accumulation in Populus deltoides W. Bartram ex Marshall plants infected with rust (Melampsora medusae Thümen.) and to determine how internal N stores are affected by the disease, in plants growing under two N availabilities in the soil; and (ii) to evaluate the impact of rust in the early sprout in the following growing season and the cumulative effect of the disease after repeated infections. Two clones with different susceptibility to rust were analyzed. At leaf level, rust reduced gas exchange capacity, water conductance in liquid phase and photosynthetic rate in both clones. At plant level, rust reduced plant growth, accelerated leaf senescence and abscission occurred with a higher concentration of leaf N. Even though N concentration in stems and roots were not significantly reduced by rust, total N accumulation in perennial tissues was reduced in infected plants. The vigor of the early sprout of plants infected by rust in the previous season was lower than that of non-infected plants. Therefore, rust affects plant growth by reducing the photosynthetic capacity and leaf area duration, and by decreasing internal nutrient recycling. As nutrient reserves in perennial tissues are lower, rust infection reduces not only the growth of the current season, but also has a cumulative effect on the following years. The reduction of growth was similar in both clones. High availability of N in the soil had no effect on leaf physiology but increased plant growth, delayed leaf senescence and abscission, and increased total N accumulation. If fertilization increases plant growth (stem and root dry mass) it can mitigate the negative effect of the pathogen in the reduction of nutrient storages and future growth.EEA Delta del ParanáFil: Gortari, Fermín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Gortari, Fermín. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Guiamet, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Guiamet, Juan José. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Cortizo, Silvia Cora. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Delta del Paraná; ArgentinaFil: Graciano, Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal; ArgentinaFil: Graciano, Corina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina.Fil: Graciano, Corina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin

Intracuneate mechanisms underlying primary afferent cutaneous processing in anaesthetized cats

[Abstract] The cutaneous primary afferents from the upper trunk and forelimbs reach the medial cuneate nucleus in their way towards the cerebral cortex. The aim of this work was twofold: (i) to study the mechanisms used by the primary afferents to relay cutaneous information to cuneate cuneolemniscal (CL) and noncuneolemniscal (nCL) cells, and (ii) to determine the intracuneate mechanisms leading to the elaboration of the output signal by CL cells. Extracellular recordings combined with microiontophoresis demonstrated that the primary afferent cutaneous information is communicated to CL and nCL cells through AMPA, NMDA and kainate receptors. These receptors were sequentially activated: AMPA receptors participated mainly during the initial phase of the response, whereas kainate- and NMDA-mediated activity predominated during a later phase. The involvement of NMDA receptors was confirmed by in vivo intracellular recordings. The cutaneous-evoked activation of CL cells was decreased by GABA and increased by glycine acting at a strychnine-sensitive site, indicating that glycine indirectly affects CL cells. Two subgroups of nCL cells were distinguished based on their sensitivity to iontophoretic ejection of glycine and strychnine. Overall, the results support a model whereby the primary afferent cutaneous input induces a centre-surround antagonism in the cuneate nucleus by activating (via AMPA, NMDA and kainate receptors) and disinhibiting (via serial glycinergic–GABAergic interactions) a population of CL cells with overlapped receptive fields that at the same time inhibit (via GABAergic cells) other neighbouring CL cells with different receptive fields.Ministerio de Ciencia y Tecnología; BFI 2003-0194

Berlín: estudio turístico evolutivo a raíz de la caída del muro y su afinidad con el mercado turístico español

Mi objetivo es realizar un análisis de la evolución del turismo en la capital berlinesa. Para llevarlo a cabo, seguiremos una metodología específica, relatando primeramente su historia para situar al lector en un contexto histórico-social, remarcando la caída del muro como el acontecimiento desencadenante de la actividad turísticaGrado en Turism

Entre trabalho e resistência: Uma genealogia da Uniãodos Trabalhadores Desempregados do General Mosconi-Salta

El presente trabajo pretende, desde una perspectiva genealógica y heterárquica desandar los hilos de la historia, que nos permitan identificar y rastrear ciertas procedencias y accidentes, tanto en torno de los procesos de subjetivación, así como de las prácticas de resistencia y autogobierno de los trabajadores y Ypefianos en el Norte Argentino. Pues, este recorrido por la historia efectiva nos permite una proximidad, en las continuas discontinuidades, para con lo que a partir de 1996 se constituirá como la Unión de Trabajadores Desocupados de Gral. Mosconi, Salta (UTD). El presente artículo se realiza en torno de archivos y relatos inéditos, compartidos por Juan Nievas referente fundador de la UTD y ex trabajador de YPF. A partir de lo cual la elaboración del artículo fue realizada en coautoría, poniendo en juego la perspectiva polifónica del autor y el actor, así como recuperando elementos etnográficos para la descripción, compresión, análisis y proximidad a los relatos de vida y la vida relatadFrom a genealogical and heterarchical perspective, this paper aims to unravel the threads of history that allow us to identify and trace certain origins and accidents, both around the processes of subjectivation, as well as the practices of resistance and self-government of Ypefian workers in Northern Argentina.So, this journey through the effective history allows us a proximity, in the continuous discontinuities, for what from 1996 will be constituted as the Union of Unemployed Workers of General Mosconi, Salta (UTD). This article is based on unpublished archives and stories shared by Juan Nievas, founder of the UTD and former worker of YPF. The elaboration of the article was carried out in co-authorship with, putting into play the polyphonic perspective of the author and the actor, as well as recovering ethnographic elements for the description, comprehension, analysis and proximity to the life stories and the life told.O presente trabalho pretende, numa perspectiva genealógica e heterárquica, desvendar os fios da história, o que nos permitirá identificar e traçarcertas procedências e acidentes, tanto em torno dos processos de subjectivação, como das práticas de resistência e auto-governo dos trabalhadores Ypefian no Norte da Argentina.Ora, esta viagem pela história efectiva permite-nos uma proximidade, nas descontinuidades contínuas, com o que a partir de 1996 será constituído como União dos Trabalhadores Desempregados do General Mosconi, Salta (UTD). O presente artigo é baseado emarquivos e histórias não publicadas, partilhadas por Juan Nievas, fundador da UTD e antigo trabalhador da YPF. A elaboração do artigo foi realizada emco-autoria, colocando emjogo a perspectiva polifónica do autor e do actor, bem como recuperando elementos etnográficos para a descrição, compreensão, análise e proximidade com as histórias de vida e a vida contada.Fil: Paulizzi, Maria Cora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Ciencias Sociales y Humanidades. Universidad Nacional de Salta. Facultad de Humanidades. Instituto de Investigaciones en Ciencias Sociales y Humanidades; ArgentinaFil: Nievas, Juan Manuel. Unión de Trabajadores Desocupados de Gral. Mosconi; Argentina. YPF - Tecnología; Argentin

Discontinuity in multipolar expansions

We show that softening does not avoid discontinuities in some multipolar expansions, but they do not affect the results of numerical integrations of the N-body problem.Asociación Argentina de Astronomí

Entre trabalho e resistência: Uma genealogia da Uniãodos Trabalhadores Desempregados do General Mosconi-Salta

El presente trabajo pretende, desde una perspectiva genealógica y heterárquica desandar los hilos de la historia, que nos permitan identificar y rastrear ciertas procedencias y accidentes, tanto en torno de los procesos de subjetivación, así como de las prácticas de resistencia y autogobierno de los trabajadores y Ypefianos en el Norte Argentino. Pues, este recorrido por la historia efectiva nos permite una proximidad, en las continuas discontinuidades, para con lo que a partir de 1996 se constituirá como la Unión de Trabajadores Desocupados de Gral. Mosconi, Salta (UTD). El presente artículo se realiza en torno de archivos y relatos inéditos, compartidos por Juan Nievas referente fundador de la UTD y ex trabajador de YPF. A partir de lo cual la elaboración del artículo fue realizada en coautoría, poniendo en juego la perspectiva polifónica del autor y el actor, así como recuperando elementos etnográficos para la descripción, compresión, análisis y proximidad a los relatos de vida y la vida relatadFrom a genealogical and heterarchical perspective, this paper aims to unravel the threads of history that allow us to identify and trace certain origins and accidents, both around the processes of subjectivation, as well as the practices of resistance and self-government of Ypefian workers in Northern Argentina.So, this journey through the effective history allows us a proximity, in the continuous discontinuities, for what from 1996 will be constituted as the Union of Unemployed Workers of General Mosconi, Salta (UTD). This article is based on unpublished archives and stories shared by Juan Nievas, founder of the UTD and former worker of YPF. The elaboration of the article was carried out in co-authorship with, putting into play the polyphonic perspective of the author and the actor, as well as recovering ethnographic elements for the description, comprehension, analysis and proximity to the life stories and the life told.O presente trabalho pretende, numa perspectiva genealógica e heterárquica, desvendar os fios da história, o que nos permitirá identificar e traçarcertas procedências e acidentes, tanto em torno dos processos de subjectivação, como das práticas de resistência e auto-governo dos trabalhadores Ypefian no Norte da Argentina.Ora, esta viagem pela história efectiva permite-nos uma proximidade, nas descontinuidades contínuas, com o que a partir de 1996 será constituído como União dos Trabalhadores Desempregados do General Mosconi, Salta (UTD). O presente artigo é baseado emarquivos e histórias não publicadas, partilhadas por Juan Nievas, fundador da UTD e antigo trabalhador da YPF. A elaboração do artigo foi realizada emco-autoria, colocando emjogo a perspectiva polifónica do autor e do actor, bem como recuperando elementos etnográficos para a descrição, compreensão, análise e proximidade com as histórias de vida e a vida contada.Fil: Paulizzi, Maria Cora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Ciencias Sociales y Humanidades. Universidad Nacional de Salta. Facultad de Humanidades. Instituto de Investigaciones en Ciencias Sociales y Humanidades; ArgentinaFil: Nievas, Juan Manuel. Unión de Trabajadores Desocupados de Gral. Mosconi; Argentina. YPF - Tecnología; Argentin

DNA-tethered polymersome clusters as nanotheranostic platform

Nanotheranostics combine the use of nanomaterials and biologically active compounds to achieve diagnosis and treatment at the same time. To date, severe limitations compromise the use of nanotheranostic systems as potent nanomaterials are often incompatible with potent biomolecules. Herein we emphasize how a novel type of polymersome clusters loaded with active molecules can be optimized to obtain an efficient nanotheranostic platform. Polymersomes loaded with enzymes and specific dyes, respectively and exposing complementary DNA strands at their external surface formed clusters by means of DNA hybridization. We describe factors at the molecular level and other conditions that need to be optimized at each step of the cluster formation to favor theranostic efficiency