Globalização e dinâmicas territoriais em Rondônia. Região Amazônica

Este trabajo analiza las dinámicas territoriales en Rondonia desde el avance espacial de la producción de soja. Tales procesos geográficos son articulados a partir de la expansión de una economía globalizada que tiene impacto directo sobre la región amazónica. La expansión de la soja es seguida por la formación de una geografía agropecuaria que concentra los granos del sur de Rondonia, lo cual muestra un dinamismo económico acompañado por la exclusión y las posibles presiones socio-territoriales en los ambientes más conservados. Como consecuencia de las relaciones sociales, la articulación espacial está basada en la expansión de la producción de soja, llevada a cabo por los agentes hegemónicos en la configuración de una red territorial, cuyas dinámicas son producto de la expansión de los procesos de las áreas globalizadas.

Transformaciones y conflictos en el agro chaqueño durante los ´90. Articulaciones territoriales de una nueva racionalidad productiva

Las transformaciones ocurridas en el sector agrícola del Chaco en los ´90, constituyen un ejemplo concreto de procesos de desarrollo geográfico desigual. A partir de 1999 esta provincia, dejó de ser la principal productora algodonera argentina para incorporarse a la siembra de soja genéticamente modificada, convertida en el principal cultivo nacional. El reemplazo de una lógica productiva que sustentó la organización económica y social provincial durante más de cuatro décadas por otra que privilegió la eficiencia y los menores costos comparativos, suscitó conflictos y reacciones diferenciales en el sector según la vulnerabilidad selectiva de los actores involucrados. El objetivo del trabajo es profundizar en ese proceso de reemplazo, estableciendo las principales características de las transformaciones acontecidas y dimensionando tanto sus efectos, como las respuestas de los distintos agentes del sector (una mayoría de pequeños productores tradicionales apoyados por organizaciones no gubernamentales, una minoría de medianos y grandes productores empresarios y el gobierno provincial)

Tradición movimentista : Una categoría para pensar las relaciones de continuidad y ruptura entre organizaciones agrarias históricas y contemporáneas de Misiones

En este texto se recupera la historia de los conflictos agrarios de Misiones y de las organizaciones gremiales de los agricultores familiares, colonos, con el propósito de rastrear la existencia de procesos de continuidad con el pasado. El objetivo principal es presentar una categoría mediante la cual se puede comprender un proceso de producción y reproducción de una representación social, política y cultural. En el marco de un abordaje etnográfico, la metodología se basó en la triangulación de datos obtenidos por diferentes técnicas (entrevistas abiertas, entrevistas semiestructuradas, observación participante, revisión de archivos documentales y periodísticos) y la revisión de bibliografía sobre el tema

Globalização e dinâmicas territoriais em Rondônia. Região Amazônica

Este trabajo analiza las dinámicas territoriales en Rondonia desde el avance espacial de la producción de soja. Tales procesos geográficos son articulados a partir de la expansión de una economía globalizada que tiene impacto directo sobre la región amazónica. La expansión de la soja es seguida por la formación de una geografía agropecuaria que concentra los granos del sur de Rondonia, lo cual muestra un dinamismo económico acompañado por la exclusión y las posibles presiones socio-territoriales en los ambientes más conservados. Como consecuencia de las relaciones sociales, la articulación espacial está basada en la expansión de la producción de soja, llevada a cabo por los agentes hegemónicos en la configuración de una red territorial, cuyas dinámicas son producto de la expansión de los procesos de las áreas globalizadas.

Vínculos urbano-rurales y construcción de nuevas territorialidades en asentamientos de rango menor

La homogeneización productiva ha trastocado los procesos de construcción territorial induciendo cambios en la naturaleza, intensidad y direccionalidad de los vínculos urbano-rurales en región pampeana. La creación de nuevas articulaciones y/o la redefinición de las interacciones preexistentes involucran dimensiones funcionales, institucionales y espaciales, dando origen a formas específicas de resolución territorial. A partir de enfoques superadores de las aproximaciones sectoriales y dualistas intrínsecas al paradigma de la modernización, que han impregnado la interpretación de procesos de construcción territorial a partir de la oposición "campo-ciudad", se propone la indagación a partir de la convergencia de macroprocesos que trastocan las trayectorias territoriales, al tiempo que renuevan la naturaleza de los vínculos urbano-rurales (avance de la pluriactividad, emergencia de nuevos actores y usos del suelo en los espacios rurales, urbanización difusa). Dentro de esta perspectiva, los asentamientos de rango menor en región pampeana, constituyen ámbitos privilegiados para la exploración de las modalidades que asumen las articulaciones urbano-rurales, en tanto lugares alcanzados por el proceso de homogeneización productiva, mostrando cómo la emergencia de nuevos actores, lógicas y escalas de acción, interpela las aproximaciones tradicionales de análisis de los vínculos urbano-rurales y exige la necesidad de renovar enfoques, regulaciones e instrumentos solidarios con la gestión territorial sustentable

La nueva condición juvenil : Reflexiones sobre los sentidos y prácticas que configuran las trayectorias laborales de jóvenes pobres

En un contexto de desestructuración del mundo del trabajo, persisten viejos y nuevos problemas en la población juvenil, que se presenta como uno de los grupos más vulnerables. En efecto, las nuevas generaciones experimentan la crisis de las distintas instituciones y, en consecuencia, de aquellas pautas de integración consideradas hegemónicas para un momento histórico-social determinado. Los cambios ocurridos durante las últimas décadas, han implicado profundas transformaciones en la condición juvenil, que encuentra una de sus manifestaciones más relevantes en las trayectorias laborales que delinean los jóvenes. En este marco, el presente artículo investiga el modo en que se articulan sentidos y prácticas en la constitución de las trayectorias laborales de jóvenes residentes de un barrio de la periferia sudoeste de la ciudad de La Plata, Provincia de Buenos Aires. Se propone analizar los sentidos que otorgan al trabajo los jóvenes a lo largo de su vida; buscando aprehender al mismo tiempo las lógicas que orientan su accionar en este ámbito, que da cuenta de una compleja trama entre la esfera laboral y otros mundos de la vida. Desde una perspectiva cualitativa, se realizan entrevistas en profundidad buscando aprehender el conjunto de procesos, prácticas e imaginarios juveniles a partir de una caracterización objetiva y subjetiva del itinerario laboral. En esta línea, se presentan algunos puntos que surgen del análisis y que aparecen como temas de reflexión relevantes de cara a generar una discusión más profunda que aporte a la comprensión del fenómeno juvenil.

Navegar en la tormenta : El anticomunismo en la historiografía de los Estados Unidos durante la Guerra Fría

Este artículo indaga la gravitación del anticomunismo en la historiografía norteamericana durante la guerra fría. Comienza con una reconstrucción histórica de tal actitud política en la sociedad americana; luego analiza la expansión, características y perdurabilidad del macartismo y, finalmente, describe sus consecuencias sobre la investigación, enseñanza y divulgación de la historia. Analiza como fuentes principales a las obras historiográficas y a los historiadores que sufrieron las ráfagas del anticomunismo; así como a las resoluciones e interpretaciones que desde el propio campo de la disciplina y de las agencias gubernamentales legitimaron la necesidad de prohibir y expurgar la influencia marxista sobre el campo de la cultura, de la educación y del saber histórico. El artículo explica la manera en que las prácticas persecutorias afectaron la carrera de historiadores izquierdistas o progresistas y cómo impactaron sobre las interpretaciones de procesos y acontecimientos significativos del pasado de la gran nación americana.

Sea surafe temperture calculation for the Arabian Sea

Sea surface temperature (SST) and seawater d18O (d18Ow) were reconstructed in a suite of sediment cores from throughout the Arabian Sea for four distinct time intervals (0 ka, 8 ka, 15 ka, and 20 ka) with the aim of understanding the history of the Indian Monsoon and the climate of the Arabian Sea region. This was accomplished through the use of paired Mg/Ca and d18O measurements of the planktonic foraminifer Globigerinoides ruber. By analyzing basin-wide changes and changes in cross-basinal gradients, we assess both monsoonal and regional-scale climate changes. SST was colder than present for the majority of sites within all three paleotime slices. Furthermore, both the Indian Monsoon and the regional Arabian Sea mean climate have varied substantially over the past 20 kyr. The 20 ka and 15 ka time slices exhibit average negative temperature anomalies of 2.5°-3.5°C attributable, in part, to the influences of glacial atmospheric CO2 concentrations and large continental ice sheets. The elimination of the cross-basinal SST gradient during these two time slices likely reflects a decrease in summer monsoon and an increase in winter monsoon strength. Changes in d18Ow that are smaller than the d18O signal due to global ice volume reflect decreased evaporation and increased winter monsoon mixing. SSTs throughout the Arabian Sea were still cooler than present by an average of 1.4°C in the 8 ka time slice. These cool SSTs, along with lower d18Ow throughout the basin, are attributed to stronger than modern summer and winter monsoons and increased runoff and precipitation. The results of this study underscore the importance of taking a spatial approach to the reconstruction of processes such as monsoon upwelling.

Physical oceanography during five ECOMARGE cruises

The first experiment of the ECOMARGE programme (ECOsystèmes de MARGE continentale) was initiated in 1983-1984, in the Gulf of Lions (northwestern Mediterranean Sea). The objectives of the ECOMARGE-I experiment were: to quantify the transfer of particulate matter, in general, and of organic carbon, in particular, from its introduction to and formation in the waters of the continental shelf-to its consumption or sedimentation on the shelf or its transfer to the slope and deep sea; and to understand the processes involved in that transfer, consumption and sedimentation together with their variability in space and time. The results of that experiment, from 1983 to 1988, are presented in this Special Issue. The highlights of the results are summarised in this paper. These results indicate that, of the particles formed in the waters of the continental shelf and those introduced by rivers, some are deposited as sediments on the shelf. A portion is transported offshore, however, to the slope and deep sea. The Rho^ne River, in the northeastern part of the study area, is the major source of continental material; this is transported to sea in a benthic nepheloid layer and, mostly, alongshore to the southwest. Here, it largely leaves the shelf through the canyons, especially the Lacaze-Duthiers Canyon. In the offshore waters, particle concentrations and distributions show surficial, intermediate and benthic nepheloid layers. These turbid structures increase towards the southwest, corresponding to the seaward shift of the front between the coastal waters and the Liguro-Provençal cyclonic gyre, a major forcing function in the Gulf of Lions. Considering the source and fate of particles (largely biogenic from the euphotic zone and abiogenic from deeper waters) a layered system is described, which is emphasized by the concentrations of natural and artificial elements and compounds. Of the flux of particles to the Lacaze-Duthiers Canyon, on a decadal scale, about 30% (as a minimum) is estimated to be stored as sediment; the remainder is transported down-canyon, towards the deep sea. The temporal variability of processes affecting this net seaward transport, of both biogenic and abiogenic material, is from hours, days to seasonal, and probably interannual, time scales. The response of the system to these variations is rapid, with pulses of increased discharge of particles from the adjacent shelf being detected in sediment traps in the Lacaze-Duthiers Canyon in less than 16 days (the temporal resolution of the traps). Based upon the study of tracers of particulate matter and environmental factors (i.e. river discharge and climatic conditions), it appears that the contribution from the Rho^ne River and its adjacent area is maximal during the winter; at this time, the flow of the Liguro-Provençal Current also increases. In contrast, the maximum relative contribution of the adjacent southwesterly area to the flux in the Lacaze-Duthiers Canyon occurs in summer, during storm events.

Shoreline change on nine reef islands over a seven-decade period

Atoll islands are subject to a variety of processes that influence their geomorphological development. Analysis of historical shoreline changes using remotely sensed images has become an efficient approach to both quantify past changes and estimate future island response. However, the detection of long-term changes in beach width is challenging mainly for two reasons: first, data availability is limited for many remote Pacific islands. Second, beach environments are highly dynamic and strongly influenced by seasonal or episodic shoreline oscillations. Consequently, remote-sensing studies on beach morphodynamics of atoll islands deal with dynamic features covered by a low sampling frequency. Here we present a study of beach dynamics for nine islands on Takú Atoll, Papua New Guinea, over a seven-decade period. A considerable chronological gap between aerial photographs and satellite images was addressed by applying a new method that reweighted positions of the beach limit by identifying "outlier" shoreline positions. On top of natural beach variability observed along the reweighted beach sections, we found that one third of the analyzed islands show a statistically significant decrease in reweighted beach width since 1943. The total loss of beach area for all islands corresponds to 44% of the initial beach area. Variable shoreline trajectories suggest that changes in beach width on Takú Atoll are dependent on local control (that is, human activity and longshore sediment transport). Our results show that remote imagery with a low sampling frequency may be sufficient to characterize prominent morphological changes in planform beach configuration of reef islands.

Metabolic responses to temperature stress under elevated pCO2 in Crepidula fornicata

In the current context of environmental change, ocean acidification is predicted to affect the cellular processes, physiology and behaviour of all marine organisms, impacting survival, growth and reproduction. In relation to thermal tolerance limits, the effects of elevated pCO2 could be expected to be more pronounced at the upper limits of the thermal tolerance window. Our study focused on Crepidula fornicata, an invasive gastropod which colonized shallow waters around European coasts during the 20th century. We investigated the effects of 10 weeks' exposure to current (380 µatm) and elevated (550, 750, 1,000 µatm) pCO2 on this engineer species using an acute temperature increase (1 °C/12 h) as the test. Respiration rates were measured on both males (small individuals) and females (large individuals). Mortality increased suddenly from 34 °C, particularly in females. Respiration rate in C. fornicata increased linearly with temperature between 18 and 34 °C, but no differences were detected between the different pCO2 conditions either in the regressions between respiration rate and temperature or in Q10 values. In the same way, condition indices were similar in all the pCO2 treatments at the end of the experiment, but decreased from the beginning of the experiment. This species was highly resistant to acute exposure to high temperature regardless of pCO2 levels, even though food was limited during the experiment. Crepidula fornicata appears to have either developed resistance mechanisms or a strong phenotypic plasticity to deal with fluctuations of physicochemical parameters in its habitat. This suggests that invasive species may be more resistant to future environmental changes than its native competitors.

Grain size and XRD analysis on Site 162-983

The grain size of deep-sea sediments provides an apparently simple proxy for current speed. However, grain size-based proxies may be ambiguous when the size distribution reflects a combination of processes, with current sorting only one of them. In particular, such sediment mixing hinders reconstruction of deep circulation changes associated with ice-rafting events in the glacial North Atlantic because variable ice-rafted detritus (IRD) input may falsely suggest current speed changes. Inverse modeling has been suggested as a way to overcome this problem. However, this approach requires high-precision size measurements that register small changes in the size distribution. Here we show that such data can be obtained using electrosensing and laser diffraction techniques, despite issues previously raised on the low precision of electrosensing methods and potential grain shape effects on laser diffraction. Down-core size patterns obtained from a sediment core from the North Atlantic are similar for both techniques, reinforcing the conclusion that both techniques yield comparable results. However, IRD input leads to a coarsening that spuriously suggests faster current speed. We show that this IRD influence can be accounted for using inverse modeling as long as wide size spectra are taken into account. This yields current speed variations that are in agreement with other proxies. Our experiments thus show that for current speed reconstruction, the choice of instrument is subordinate to a proper recognition of the various processes that determine the size distribution and that by using inverse modeling meaningful current speed reconstructions can be obtained from mixed sediments.

Benthic foraminifera and stable isotope composition in Paleocene-Eocene sediments

In the late Paleocene to early Eocene, deep sea benthic foraminifera suffered their only global extinction of the last 75 million years and diversity decreased worldwide by 30-50% in a few thousand years. At Maud Rise (Weddell Sea, Antarctica; Sites 689 and 690, palaeodepths 1100 m and 1900 m) and Walvis Ridge (Southeastern Atlantic, Sites 525 and 527, palaeodepths 1600 m and 3400 m) post-extinction faunas were low-diversity and high-dominance, but the dominant species differed by geographical location. At Maud Rise, post-extinction faunas were dominated by small, biserial and triserial species, while the large, thick-walled, long-lived deep sea species Nuttallides truempyi was absent. At Walvis Ridge, by contrast, they were dominated by long-lived species such as N. truempyi, with common to abundant small abyssaminid species. The faunal dominance patterns at the two locations thus suggest different post-extinction seafloor environments: increased flux of organic matter and possibly decreased oxygen levels at Maud Rise, decreased flux at Walvis Ridge. The species-richness remained very low for about 50 000 years, then gradually increased. The extinction was synchronous with a large, negative, short-term excursion of carbon and oxygen isotopes in planktonic and benthic foraminifera and bulk carbonate. The isotope excursions reached peak negative values in a few thousand years and values returned to pre-excursion levels in about 50 000 years. The carbon isotope excursion was about -2 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, and about -4 per mil for planktonic foraminifera at Maud Rise. At the latter sites vertical gradients thus decreased, possibly at least partially as a result of upwelling. The oxygen isotope excursion was about -1.5 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, -1 per mil for planktonic foraminifera at Maud Rise. The rapid oxygen isotope excursion at a time when polar ice-sheets were absent or insignificant can be explained by an increase in temperature by 4-6°C of high latitude surface waters and deep waters world wide. The deep ocean temperature increase could have been caused by warming of surface waters at high latitudes and continued formation of the deep waters at these locations, or by a switch from dominant formation of deep waters at high latitudes to formation at lower latitudes. Benthic foraminiferal post-extinction biogeographical patterns favour the latter explanation. The short-term carbon isotope excursion occurred in deep and surface waters, and in soil concretions and mammal teeth in the continental record. It is associated with increased CaC03-dissolution over a wide depth range in the oceans, suggesting that a rapid transfer of isotopically light carbon from lithosphere or biosphere into the ocean-atmosphere system may have been involved. The rapidity of the initiation of the excursion (a few thousand years) and its short duration (50 000 years) suggest that such a transfer was probably not caused by changes in the ratio of organic carbon to carbonate deposition or erosion. Transfer of carbon from the terrestrial biosphere was probably not the cause, because it would require a much larger biosphere destruction than at the end of the Cretaceous, in conflict with the fossil record. It is difficult to explain the large shift by rapid emission into the atmosphere of volcanogenic CO2, although huge subaerial plateau basalt eruptions occurred at the time in the northern Atlantic. Probably a complex combination of processes and feedback was involved, including volcanogenic emission of CO2, changing circulation patterns, changing productivity in the oceans and possibly on land, and changes in the relative size of the oceanic and atmospheric carbon reservoirs.

Communication-efficient and crash-quiescent Omega with unknown membership

The failure detector class Omega (Ω) provides an eventual leader election functionality, i.e., eventually all correct processes permanently trust the same correct process. An algorithm is communication-efficient if the number of links that carry messages forever is bounded by n, being n the number of processes in the system. It has been defined that an algorithm is crash-quiescent if it eventually stops sending messages to crashed processes. In this regard, it has been recently shown the impossibility of implementing Ω crash quiescently without a majority of correct processes. We say that the membership is unknown if each process pi only knows its own identity and the number of processes in the system (that is, i and n), but pi does not know the identity of the rest of processes of the system. There is a type of link (denoted by ADD link) in which a bounded (but unknown) number of consecutive messages can be delayed or lost. In this work we present the first implementation (to our knowledge) of Ω in partially synchronous systems with ADD links and with unknown membership. Furthermore, it is the first implementation of Ω that combines two very interesting properties: communication-efficiency and crash-quiescence when the majority of processes are correct. Finally, we also obtain with the same algorithm a failure detector () such that every correct process eventually and permanently outputs the set of all correct processes.