On the Impact of Geometry on Ad Hoc Communication in Wireless Networks

In this work we address the question how important is the knowledge of geometric location and network density to the efficiency of (distributed) wireless communication in ad hoc networks. We study fundamental communication task of broadcast and develop well-scalable, randomized algorithms that do not rely on GPS information, and which efficiency formulas do not depend on how dense the geometric network is. We consider two settings: with and without spontaneous wake-up of nodes. In the former setting, in which all nodes start the protocol at the same time, our algorithm accomplishes broadcast in $O(D\log n + \log^2 n)$ rounds under the SINR model, with high probability (whp), where $D$ is the diameter of the communication graph and $n$ is the number of stations. In the latter setting, in which only the source node containing the original message is active in the beginning, we develop a slightly slower algorithm working in $O(D\log^2 n)$ rounds whp. Both algorithms are based on a novel distributed coloring method, which is of independent interest and potential applicability to other communication tasks under the SINR wireless model

Identidades, sujetos y cultura escolar : acerca de los sentidos de la educación en la “Comunidad Raíces Tobas"

Es objetivo de este trabajo presentar los sentidos construidos acerca de la escuela por los integrantes de la Comunidad Raíces Tobas, ubicada en la periferia de la ciudad de La Plata, Provincia de Buenos Aires. Las indagaciones se vinculan a un proyecto integral comunitario, destinado a la valoración del patrimonio cultural indígena y la educación intercultural bilingüe, denominado "Qom Lataxac" forma de ser y vida Qom, y se enmarcan en una investigación en curso sobre jóvenes qom, escuela secundaria e inter culturalidad. La misma focaliza, a través de los aportes de la antropología y los estudios culturales, en los procesos de identificación de los jóvenes qom de la comunidad, los sentidos construidos en sus prácticas educativas cotidianas en escuelas urbanas de la ciudad de La Plata, y la influencia de los mismos en su identidad, en tanto jóvenes y en tanto indígenas. Se parte del supuesto de que la escuela se presenta como lugar de construcción de sentidos y lazos sociales, pero también como lugar de imposición de saberes. Por ello, aquí se presentan consideraciones devenidas del propósito de conocer la forma en que los jóvenes indígenas y la comunidad, miran la escuela, la viven y la significan, y advertir las tensiones que pueden,o no, producirse entre la cultura escolar y la cultura propia. Se podrá, a partir de allí, problematizar estos supuestos y analizar la existencia de una única cultura escolar hegemónica, desnaturalizando las premisas de la episteme moderna occidental que hacia finales del siglo XIX, le dieron sentido y promovieron su persistencia como talFil: Rozanski, Noelia. Universidad Nacional de La Plat

Trackers

Trackers is a collection of short stories that attest to the oddities and complexities found even in the non-exotic middle-class American suburbs. The characters in these stories experience disappointments that result from the physical and emotional distancing of families. In Tokens, a woman\u27s attempts at revenge on her cheating husband are unsatisfying because she ends up feeling more alone than before. In Trackers, eleven-year old Richard hunts for Bigfoot as he and his family cope with the emotional aftermath of his sister\u27s suicide attempt. In these stories people struggle to maintain normalcy in their lives--sometimes through inappropriate means. When their expectations are destroyed, they are forced to deal not only with specific abandonment, but also the reality that the world around them has no knowledge--let alone appreciation--of their personal struggles or fears. Occasionally, however, some good can come from this realization. In Camilla, a ten-year-old girl learns that she can depend on her own experiences for strength rather than knowledge borrowed from fantasies inspired by a collection of obituaries. A woman recovering from the loss of a romantic relationship strengthens her bond with her young niece in Cattywampus, and they are both strengthened by the world they share as women in different stages of self-discovery

EFFECTS OF 100 mT STATIC MAGNETIC FIELD EXPOSURE ON CYTOSOLIC FREE Ca2+ LEVELS AND HSP70 REPORTER GENE EXPRESSION

Human exposure to electromagnetic fields has prompted investigations into possible effects of static magnetic fields (SMF)s on cellular processes. Discrepancies still remain between studies however, and are likely due to endpoint analysis on potentially small biological effects. The purpose of this research was to investigate the potential effect of SMF exposure on biological systems using real-time methods that are intrisicaly more sensitive than endpoint measurements. This research was divided into two main studies. The first study evaluated basal and activated levels of cytosolic free calcium in HL-60 cells before, during and after a 15 minute 100 mT SMF exposure. The second study used a heat shock protein (hsp70)/luciferase reporter system in NIH3T3 cells to detect changes in heat shock promoter activation before, during and after a 15 minute 100 mT SMF exposure. The first study found no effects of SMF exposure on resting or activated cytosolic free calcium concentration. However, a 100 mT SMF significantly decreased the activation of the heat shock protein promoter, but only when field exposure was combined with an additional heat insult

Deep griz GMOS Imaging of the Dwarf Irregular Galaxy Kar 50

Images obtained with the Gemini Multi-Object Spectrograph (GMOS) are used to investigate the stellar content and distance of the dwarf irregular galaxy Kar 50. The brightest object is an HII region, and the bright stellar content is dominated by stars with g'-r' < 0. The tips of the main sequence and the red giant branch are tentatively identified near r' = 24.9 and i' = 25.5, respectively. The galaxy has a blue integrated color with no significant color gradient, and we conclude that Kar 50 has experienced a recent galaxy-wide episode of star formation. The distance estimated from the brightest blue stars indicates that Kar 50 is behind the M81 group, and this is consistent with the tentative RGB-tip brightness. Kar 50 has a remarkably flat central surface brightness profile, even at wavelengths approaching 1um, although there is no evidence of a bar. In the absence of another large star-forming episode, Kar 50 will evolve into a very low surface brightness galaxy.Comment: 17 pages of text and 8 postscript figures. Accepted for publication in the PAS

Interactions between groundwater and surface water at river banks and the confluence of rivers

Riparian vegetation depends on hydrological resources and has to adapt to changes in water levels and soil moisture conditions. The origin and mixing of water in the streamside corridor were studied in detail. The development of riparian woodland often reflects the evolution of hydrological events. River water levels and topography are certainly the main causes of the exchange between groundwater and river water through the riverbank. Stable isotopes, such as 18O, are useful tools that allow water movement to be traced. Two main water sources are typically present: (i) river water, depleted of heavy isotopes, originating upstream, and (ii) groundwater, which comes mainly from the local rainfall. On the Garonne River bank field site downstream of Toulouse, the mixing of these two waters is variable, and depends mainly on the river level and the geographical position. The output of the groundwater into the river water is not diffuse on a large scale, but localised at few places. At the confluence of two rivers, the water-mixing area is more complex because of the presence of a third source of water. In this situation, groundwater supports the hydrologic pressure of both rivers until they merge, this pressure could influence its outflow. Two cases will be presented. The first is the confluence of the Garonne and the Ariège Rivers in the south-west of France, both rivers coming from the slopes of the Pyrénées mountains. Localised groundwater outputs have been detected about 200 m before the confluence. The second case presented is the confluence of the Ganges and the Yamuna Rivers in the north of India, downstream of the city of Allahabad. These rivers are the two main tributaries of the Ganges, and both originate in the Himalayas. A strong stream of groundwater output was measured at the point of confluence