A group-theoretic approach to formalizing bootstrapping problems

The bootstrapping problem consists in designing agents that learn a model of themselves and the world, and utilize it to achieve useful tasks. It is different from other learning problems as the agent starts with uninterpreted observations and commands, and with minimal prior information about the world. In this paper, we give a mathematical formalization of this aspect of the problem. We argue that the vague constraint of having "no prior information" can be recast as a precise algebraic condition on the agent: that its behavior is invariant to particular classes of nuisances on the world, which we show can be well represented by actions of groups (diffeomorphisms, permutations, linear transformations) on observations and commands. We then introduce the class of bilinear gradient dynamics sensors (BGDS) as a candidate for learning generic robotic sensorimotor cascades. We show how framing the problem as rejection of group nuisances allows a compact and modular analysis of typical preprocessing stages, such as learning the topology of the sensors. We demonstrate learning and using such models on real-world range-finder and camera data from publicly available datasets

Real-valued average consensus over noisy quantized channels

This paper concerns the average consensus problem with the constraint of quantized communication between nodes. A broad class of algorithms is analyzed, in which the transmission strategy, which decides what value to communicate to the neighbours, can include various kinds of rounding, probabilistic quantization, and bounded noise. The arbitrariness of the transmission strategy is compensated by a feedback mechanism which can be interpreted as a self-inhibitory action. The result is that the average of the nodes state is not conserved across iterations, and the nodes do not converge to a consensus; however, we show that both errors can be made as small as desired. Bounds on these quantities involve the spectral properties of the graph and can be proved by employing elementary techniques of LTI systems analysis

Bootstrapping bilinear models of robotic sensorimotor cascades

We consider the bootstrapping problem, which consists in learning a model of the agent's sensors and actuators starting from zero prior information, and we take the problem of servoing as a cross-modal task to validate the learned models. We study the class of bilinear dynamics sensors, in which the derivative of the observations are a bilinear form of the control commands and the observations themselves. This class of models is simple yet general enough to represent the main phenomena of three representative robotics sensors (field sampler, camera, and range-finder), apparently very different from one another. It also allows a bootstrapping algorithm based on hebbian learning, and that leads to a simple and bioplausible control strategy. The convergence properties of learning and control are demonstrated with extensive simulations and by analytical arguments

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Footprints in Paradise

In Okinawa, the southernmost prefecture of Japan, “ecotourism” promises to provide employment for a dwindling population of rural youth while preserving the natural environment and bolstering regional pride. Footprints in Paradise centers on how Okinawans’ sense of place is transforming rapidly, along with language, landscapes, cultural traditions, and wildlife: from marginalized and exoticized island phenomena into global heritage resources worth cherishing by insiders and outsiders. Footprints in Paradise is intended for readers interested in the anthropology of US-Japan-Okinawa relations, tourism and island environments, the politics of ecological sustainability, and the shifting ethics of human-animal relationships in the early twenty-first century

Mapping the Outer Edge of the Young Stellar Cluster in the Galactic Center

We present new near-infrared spectroscopic observations of the outer edges of the young stellar cluster around the supermassive black hole at the Galactic center. The observations show a break in the surface-density profile of young stars at approximately 13 arcsec (0.52 pc). These observations spectroscopically confirm previous suggestions of a break based on photometry. Using Gemini North's Near-Infrared Integral Field Spectrometer (NIFS) we are able to detect and separate early- and late-type stars with a 75% completeness at Ks = 15.5. We sample a region with radii between 7" to 23" (0.28 pc to 0.92 pc) from Sgr A*, and present new spectral classifications of 144 stars brighter than Ks = 15.5, where 140 stars are late-type (> 1 Gyr) and only four stars are early-type (young, 4-6 Myr). A broken power-law fit of the early-type surface-density matches well with our data and previously published values. The projected surface-density of late-type stars is also measured and found to be consistent with previous results. We find that the observed early-type surface-density profile is inconsistent with the theory of the young stars originating from a tightly bound infalling cluster, as no significant trail of young stars is found at radii above 13". We also note that either a simple disk instability criterion or a cloud-cloud collision could explain the location of the outer edge, though we lack information to make conclusive remarks on either alternative. If this break in surface-density represents an edge to the young stellar cluster it would set an important scale for the most recent episode of star formation at the Galactic center.Comment: 17 pages, 11 figures, 3 tables, ApJ accepte

A chromatin modifying enzyme, SDG8, is involved in morphological, gene expression, and epigenetic responses to mechanical stimulation

Thigmomorphogenesis is viewed as being a response process of acclimation to short repetitive bursts of mechanical stimulation or touch. The underlying molecular mechanisms that coordinate changes in how touch signals lead to long-term morphological changes are enigmatic. Touch responsive gene expression is rapid and transient, and no transcription factor or DNA regulatory motif has been reported that could confer a genome wide mechanical stimulus. We report here on a chromatin modifying enzyme, SDG8/ASHH2, which can regulate the expression of many touch responsive genes identified in Arabidopsis. SDG8 is required for the permissive expression of touch induced genes; and the loss of function of sdg8 perturbs the maximum levels of induction on selected touch gene targets. SDG8 is required to maintain permissive H3K4 trimethylation marks surrounding the Arabidopsis touch-inducible gene TOUCH 3 (TCH3), which encodes a calmodulin-like protein (CML12). The gene neighboring was also slightly down regulated, revealing a new target for SDG8 mediated chromatin modification. Finally, sdg8 mutants show perturbed morphological response to wind-agitated mechanical stimuli, implicating an epigenetic memory-forming process in the acclimation response of thigmomorphogenesis

Morphological and immunochemical characterization of the pollen grains of Chenopodium album L. (Chenopodiaceae) in a temperate urban area in Argentina

Chenopodium album es una hierba cosmopolita, anual, muy polimórfica, que crece en forma espontánea en baldíos con suelos modificados de los barrios periféricos de Bahía Blanca. En esta ciudad, el periodo de floración es principalmente entre febrero y marzo, que coincide con la mayor concentración de este tipo de polen en la atmósfera. El objetivo de este estudio fue caracterizar morfológica e inmunoquímicamente a los granos de polen de Chenopodium album obtenidos en diferentes zonas del área urbana de la Bahía Blanca. Las muestras fueron colectadas en tres zonas de la ciudad. La estructura y la morfología de los granos fueron analizados con microscopía óptica y electrónica. Los perfiles proteicos y antigénicos fueron estudiados mediante Tricine-SDS-PAGE y western blot, empleando un suero policlonal obtenido en conejo. El análisis morfológico mostró diferencias significativas en relación al diámetro de los granos de polen en una de las áreas estudiadas. En esa misma área se encontraron diferencias en la expresión de proteínas, aunque el perfil antigénico fue conservado. Estas variaciones en la morfología y en el perfil proteico podrían ser causadas por los efectos de las condiciones ambientales sobre el polen y la presencia de contaminantes urbanos provenientes del tráfico vehicular.Chenopodium album is a very polymorphic, cosmopolitan, annual herb that grows spontaneously in modified soils in wasteland in the outlying urban zones of Bahía Blanca. In this city, the flowering period is mainly during February and March, which coincides with the highest concentrations of this pollen type in the atmosphere of the city. The objective of this study was to characterize the pollen grains of Chenopodium album, both morphologically and immunochemically, that were obtained from three different zones in the urban area of Bahía Blanca. Samples were collected from the three separate zones in the city that were far apart. The structure and morphology of the grains were analyzed using light and electron microscopy. The protein and antigenic profiles were studied with Tricine-SDS-PAGE and western blot with a polyclonal rabbit serum, respectively. The morphological analysis showed significant differences in relation to the diameters of the pollen grains in one of the studied areas. Differences in the protein expression were seen for the same area although the antigenic profile was conserved. The variations in the morphology and the protein profile may be caused by the effect of environmental conditions on the pollen, and the presence of urban contaminants from vehicular traffic.Fil: Bianchimano, Andrea Susana. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Murray, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Aztiria, María Eugenia. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Inmunología; ArgentinaFil: Montes, Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Calfuán, Melina Lorena. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Prat, María Inés. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin