Vapor-liquid equilibrium and equation of state of two-dimensional fluids from a discrete perturbation theory

The interest in the description of the properties of fluids of restricted dimensionality is growing for theoretical and practical reasons. In this work, we have firstly developed an analytical expression for the Helmholtz free energy of the two-dimensional square-well fluid in the Barker--Henderson framework. This equation of state is based on an approximate analytical radial distribution function for $d$-dimensional hard-sphere fluids ($1\leq d\leq 3$) and is validated against existing and new simulation results. The so-obtained equation of state is implemented in a discrete perturbation theory able to account for general potential shapes. The prototypical Lennard-Jones and Yukawa fluids are tested in its two-dimensional version against available and new simulation data with semi-quantitative agreement.Comment: 9 pages, 6 figures; v2: new references adde

Detrital zircon typology and U/Pb geochronology for the Miocene Ladrilleros-Juanchaco sedimentary sequence, Equatorial Pacific (Colombia) : new constraints on provenance and paleogeography in northwestern South America

Typology and internal texture analyses were performed on detrital zircons obtained from the Miocene sandstones of the Ladrilleros-Juanchaco sedimentary sequence (Colombia, Equatorial Pacific). This analysis was complemented with zircon U/Pb dating to identify typology-age associations as indicators of provenance of these sediments. Our results show that zircons with S and P dominant typology have internal structures/zoning that indicate mostly igneous and possibly some metamorphic origins. Morphometric results suggest little transport from source areas. Both typology and U/Pb data point to the Western Cordillera as the main source of the detrital materials of this sedimentary sequence. A paleogeographic reconstruction shows that during Late Miocene times there were significant portions of the Western Cordillera uplifted, eroding away and acting as a fluvio-topographic barrier blocking sediments from the Central Cordillera to reach the Pacific basins. Miocene plutons at the axis of the Western Cordillera were also probably exhumed and played a role as geomorphologically active massifs. This study demonstrates that typologic analysis on detrital zircon grains is a powerful tool as indicator of provenance and paleogeography in complex litho-tectonic areas where overlapping U/Pb signatures can lead to contradictory results

Use of sonic tomography to detect and quantify wood decay in living trees.

Premise of the studyField methodology and image analysis protocols using acoustic tomography were developed and evaluated as a tool to estimate the amount of internal decay and damage of living trees, with special attention to tropical rainforest trees with irregular trunk shapes.Methods and resultsLiving trunks of a diversity of tree species in tropical rainforests in the Republic of Panama were scanned using an Argus Electronic PiCUS 3 Sonic Tomograph and evaluated for the amount and patterns of internal decay. A protocol using ImageJ analysis software was used to quantify the proportions of intact and compromised wood. The protocols provide replicable estimates of internal decay and cavities for trees of varying shapes, wood density, and bark thickness.ConclusionsSonic tomography, coupled with image analysis, provides an efficient, noninvasive approach to evaluate decay patterns and structural integrity of even irregularly shaped living trees

Violencia política y conflictos sociales en América Latina

La violencia socio-económica como categoría de estudio en las ciencias sociales y humanas, ha venido adquiriendo creciente relevancia en América Latina. Los problemas y variables metodológicas asociadas a su investigación han sido abordados con mayor profundidad desde la sociología, el Derecho, la Ciencia política y la Psicología Social. Es por esto, que esta publicación se propone abordar la violencia socio-económica como una categoría de análisis e investigación interdisciplinaria, posibilitando la reflexión académica en torno a las dinámicas de construcción del poder, la institucionalidad y los movimientos sociales en América Latina.Introducción; Parte I. Violencia, derechos humanos y criminalidad. Conflicto y violencias en Colombia / Roberto González Arana, Ivonne Molinares Guerrero; Derechos humanos y seguridad democrática en Colombia: ¿un equilibrio posible? / César Barreira; Conflictividad, violencia y control social: saberes latinoamericanos contemporáneos / José Vicente Tavares-dos-Santos; Pensar la justicia de adolescentes desde el campo jurídico / Nilia Viscardi, Marcia Barbero; Parte ii. Conflictos: armados, étnicos, territoriales y por los recursos naturales. Aproximaciones teórico-conceptuales en torno al conflicto armado colombiano / Luis Fernando Trejos Rosero; El conflicto mapuche y el estado de Chile: una reflexión sobre la violencia y la imagen de Chile en el bicentenario / Loreto Correa V.; Entre la violencia política y social. Una revisión a la inmigración africana subsahariana occidental en Buenos Aires (1990-2010) / Mary Luz Estupiñán Serrano; Producción de nuevas espacialidades y cambios de autoridad. Interacción globalización-conflicto armado-grupos étnicos / Clara Inés Aramburo Siegert; Los recursos mineros y la protesta ciudadana en la Argentina de la última década / Orietta Favaro, Graciela Iuorno; Performances do crime: componentes dramáticos e teatrais dos grandes roubos no Brasil / Jania Perla Diógenes de Aquino

Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments

As a key component of the carbon cycle, soil CO2 efflux (SCE) is being increasingly studied to improve our mechanistic understanding of this important carbon flux. Predicting ecosystem responses to climate change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climatic window for which observations are available to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of the 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable data sets, i.e., those providing high-frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is 'no' - as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions

Exploring rural school students' perceptions, willingness, motivations, and concerns regarding greywater treatment and reuse in southern Peru

Water scarcity affects water availability in Peruvian rural schools without piped systems, yet the perspectives of rural students on school greywater treatment and reuse are mainly unexplored. This study explores students’ perceptions, willingness, and concerns from three rural schools in Pichihua, Socco, and Yanaca (Apurimac Region, Peru) regarding greywater treatment and reuse. Using semi-structured questionnaires answered by 167 secondary students, the study found frequent water shortages (57% weekly) affecting hygiene and sanitation. There was high acceptance for greywater treatment systems (88%), significantly influenced by age and gender (p < 0.05). Students supported reusing treated greywater for handwashing (86%), cleaning (73.2%), garden watering (69%), and toilet flushing (65%). Over half were willing to use treated water for handwashing if it was pathogen-free (51.6%) and high quality (47.7%). Main concerns involved health risks (36%) and water appearance (28%). Recommendations included training on greywater treatment (40%) and regular quality assessments (35%) to mitigate concerns. This study shows that implementing a greywater treatment system is socially feasible for addressing water shortages in rural schools. The findings can help water technology developers create strategies to enhance benefits and reduce risks of reusing treated greywater while supporting policy development for water reuse in rural communities

Photovoltaic System Regulation Based on a PID Fuzzy Controller to Ensure a Fixed Settling Time

El objetivo principal de controlar los sistemas fotovoltaicos (PV) es asegurar la máxima extracción de potencia disponible. Estos controladores usualmente combinan la acción de un algoritmo de seguimiento del punto de máxima potencia (MPPT) con un regulador de tensión, el cual tiene la función de rechazar las perturbaciones en los terminales del panel. Estos controladores se basan comúnmente en estructuras PI-PID que requieren modelos linealizados alrededor del punto de operación. Pero, debido a perturbaciones generadas por el ambiente y la carga, el punto de operación cambia drásticamente, lo que dificulta obtener el desempeño deseado. Este artículo propone regular el sistema PV utilizando un controlador Fuzzy-PID, el cual se adapta a los cambios de irradiancia solar y oscilaciones en la carga. Esta característica garantiza un tiempo de establecimiento constante, el cual se requiere para definir de forma precisa el periodo del algoritmo MPPT. En el caso de controladores lineales, el periodo del MPPT se fija en el peor caso (periodo más largo), lo cual genera pérdidas de potencia adicionales al disminuir la velocidad del seguimiento del punto de operación óptimo. La solución propuesta en este artículo mejora la eficiencia general del sistema. Finalmente, la solución se valida con simulaciones en Matlab®.The main objective of the controllers in photovoltaic systems (PV) is to ensure the maximum extraction of the available power. Those controllers usually combine the action of a maximum power point tracking algorithm (MPPT) with a voltage regulator, which has the function of rejecting disturbances at the panel terminals. Such controllers are commonly based on PI and PID structures, it requiring linearized models at an operating point. But, due to disturbances generated by the environment and the load, the operating point of the system changes drastically, which hinder to obtain the desired system performance. This paper proposes to regulate the PV system using a Fuzzy PID controller, which adapts to changes in solar irradiance and load oscillations. This characteristic guarantees a constant settling time, which is required to precisely define the period of the MPPT algorithm. In the case of classical linear controllers, the period of the MPPT algorithm is set to the worst case (longest period) which generates additional power losses by slowing down the tracking of the optimal operating point. Therefore, the solution proposed in this paper improves the overall system efficiency. Finally, such a solution is validated through simulations in Matlab®