The effects of geomorphic controls on sediment yield in the andean rivers of Colombia

This paper examines sediment yield rates and its response to control variables in the principal rivers of Colombian draining into the Caribbean and Pacific coasts. Based on a multi-year dataset of sediment load from six rivers, including Mira, Patía, and San Juan on the Pacific margin, and Magdalena, Atrato, and Sinú, on the Caribbean basin, various morphometric, hydrologic, and climatic variables were estimated in order to understand and predict the variation in sediment yield. A multiple regression model, including two control variables, runoff and relief ratio (the ratio of the maximum height of the drainage basin and the basin length), explains 83% of the variance in sediment yield. This model is efficient (ME = 0.93) and is a valuable tool for predicting total sediment yield from Colombian rivers. These two selected estimators refer to the relative importance of the fluvial transport component in the sediment routing system. Thus, regional-scale variance of sediment yield in the Andean basins of Colombia seems to be explained by the combined influence of tectonics (relief) and surface runoff available for weathering and transport processes. In general, high sediment yielded rivers are high runoff systems with narrow alluvial plains (i.e. Pacific rivers), while low sediment yielded rivers like the Caribbean systems, contain large sections with not significant gradient in their longitudinal profiles. These sections coincide with large floodplains, which all provide sediment storage capacity within the catchments. When considering the three gauged Pacific rivers at their furthest downstream stations, the combined annual sediment load from these rivers into the Pacific Ocean is ~40 Mt yr–1. In contrast, the Magdalena, Atrato and Sinu rivers deliver ~173 Mt yr-1 into the Caribbean. Overall, Andean rivers of Colombia exhibit the highest sediment yields of all medium-large sized rivers of South America due to the interplay of (1) high rates of runoff (1,750-7,300 mm yr-1), (2) steep relief within catchments, (3) low values of discharge variability (Qmax-Qmin), and (4) episodic sediment delivery due to either geologic events or climatic anomalies

Monitoring water discharge and floodplain connectivity for the northern Andes utilizing satellite data: A tool for river planning and science-based decision-making

River discharge data and magnitudes of floods are often not readily available for decision makers of many developing nations, including Colombia. And this while flooding for these regions is often devastating, causing many fatalities and insurmountable damage to the most vulnerable communities. During the we season, in strong La Nina years, infrastructural damages of over $US 7.2 billion have occurred. Mitigation of such natural disasters lacks data-supported scientific approaches for evaluating river response to extreme climate events. Here, we propose a satellite-based technique to measure river discharge at selected sites for the main northern Andean River, the Magdalena. This method has the advantage of back calculating daily river discharges over a period of two decades, and thus making it possible to calculate return intervals of significant flood events. The study shows that satellite based river discharges well capture a) the inter-annual variability of river discharge; b) the natural seasonality of water discharge along the floodplains; and c) peak discharges that were observed during La Nina conditions between 2008 and 2011. The last is likely more accurate compared to ground-based gauging stations, as ground-based stations tend to overflow during large flood events and as such are hampered to accurately monitor peak discharges. Furthermore, we show that these derived discharges can form the base to study river-floodplain connectivity, providing environmental decision makers with a technique that makes it possible to better monitor river and ecosystem processes

Network connectivity during mergers and growth: optimizing the addition of a module

The principal eigenvalue $\lambda$ of a network's adjacency matrix often determines dynamics on the network (e.g., in synchronization and spreading processes) and some of its structural properties (e.g., robustness against failure or attack) and is therefore a good indicator for how ``strongly'' a network is connected. We study how $\lambda$ is modified by the addition of a module, or community, which has broad applications, ranging from those involving a single modification (e.g., introduction of a drug into a biological process) to those involving repeated additions (e.g., power-grid and transit development). We describe how to optimally connect the module to the network to either maximize or minimize the shift in $\lambda$, noting several applications of directing dynamics on networks.Comment: 7 pages, 5 figure

Megaprojetos de infraestrutura territorial em face da vulnerabilidade urbana regional-sub-Regional. O Caso do Departamento de Antioquia

The main objective of this paper is to address the impact of mega infrastructure projects on the planning and management of the territory in accordance with its vulnerability. As a methodology, it describes, from the point of view of social transaction costs, the infrastructure, order and territorial planning, which allow to orientate the components that are required so that the mega-projects cohere the diffuse conditions derived from the physical space of the territory. As main contributions, the management of mega-projects from the point of view of territorial ordering, planning and ecological dependence, must pass to the scenario of the applied and masterly chair, through the research and proposal foundation as a line of work.El escrito tiene como principal objetivo el abordaje de la incidencia de los megaproyectos de infraestructura en el ordenamiento y la planeación conforme a la vulnerabilidad territorial. Como metodología, describe desde la óptica de los costos sociales de transacción, la infraestructura, ordenamiento y planeación territorial, que permiten orientar los componentes que se requieren para que los megaproyectos cohesionen las condiciones difusas derivadas de lo físico espacial del territorio. Como principales aportes resalta la gestión de los megaproyectos desde el ordenamiento, la planeación y la dependencia ecológica territorial, deben pasar al escenario de la cátedra aplicada y magistral, a través, de la fundamentación investigativa y propositiva como línea de trabajo.L'objectif principal de ce document est d'aborder l'impact des mégaprojets d'infrastructure sur la planification et la gestion en fonction de la vulnérabilité du territoire. En tant que méthodologie, elle décrit, sous l'angle des coûts de transaction sociaux, les infrastructures, la planification et l'aménagement du territoire, qui permettent d'orienter les composantes nécessaires aux mégaprojets pour mettre en cohérence les conditions diffuses issues de l'espace physique du territoire. Comme contributions principales, la gestion des méga-projets du point de vue de l'ordonnancement territorial, de la planification et de la dépendance écologique, doit passer au scénario de la chaire appliquée et magistrale, à travers la fondation de recherche et de proposition comme ligne de travail.Oprincipal objetivo deste trabalho é abordar o impacto dos megaprojetos de infra-estrutura no planejamento e gestão de acordo com a vulnerabilidade territorial. Como metodologia, descreve, do ponto de vista dos custos de transação social, infra-estrutura, planejamento e ordenação territorial, que permitem orientar os componentes necessários para que os megaprojetos coexistam as condições difusas derivadas do espaço físico do território. Como principais contribuições, a gestão de megaprojetos do ponto de vista da ordenação territorial, planejamento e dependência ecológica, deve passar para o cenário da cadeira aplicada e magistral, através da pesquisa e da fundamentação da proposta como uma linha de trabalho

Dimension reduction for systems with slow relaxation

We develop reduced, stochastic models for high dimensional, dissipative dynamical systems that relax very slowly to equilibrium and can encode long term memory. We present a variety of empirical and first principles approaches for model reduction, and build a mathematical framework for analyzing the reduced models. We introduce the notions of universal and asymptotic filters to characterize `optimal' model reductions for sloppy linear models. We illustrate our methods by applying them to the practically important problem of modeling evaporation in oil spills.Comment: 48 Pages, 13 figures. Paper dedicated to the memory of Leo Kadanof

Pyramidal core-shell quantum dot under applied electric and magnetic fields

We have theoretically investigated the electronic states in a core/shell pyramidal quantum dot with GaAs core embedded in AlGaAs matrix. This system has a quite similar recent experimental realization through a cone/shell structure [Phys. Status Solidi-RRL 13, 1800245 (2018)]. The research has been performed within the efective mass approximation taking into account position-dependent efective masses and the presence of external electric and magnetic felds. For the numerical solution of the resulting three-dimensional partial diferential equation we have used a fnite element method. A detailed study of the conduction band states wave functions and their associated energy levels is presented, with the analysis of the efect of the geometry and the external probes. The calculation of the non-permanent electric polarization via the of-diagonal intraband dipole moment matrix elements allows to consider the related optical response by evaluating the coefcients of light absorption and relative refractive index changes, under diferent applied magnetic feld confgurations

A network-specific approach to percolation in networks with bidirectional links

Methods for determining the percolation threshold usually study the behavior of network ensembles and are often restricted to a particular type of probabilistic node/link removal strategy. We propose a network-specific method to determine the connectivity of nodes below the percolation threshold and offer an estimate to the percolation threshold in networks with bidirectional links. Our analysis does not require the assumption that a network belongs to a specific ensemble and can at the same time easily handle arbitrary removal strategies (previously an open problem for undirected networks). In validating our analysis, we find that it predicts the effects of many known complex structures (e.g., degree correlations) and may be used to study both probabilistic and deterministic attacks.Comment: 6 pages, 8 figure

Macroalgal-Associated Dinoflagellates Belonging to the Genus Symbiodinium in Caribbean Reefs

Coral-algal symbiosis has been a subject of great attention during the last two decades in response to global coral reef decline. However, the occurrence and dispersion of free-living dinoflagellates belonging to the genus Symbiodinium are less documented. Here ecological and molecular evidence is presented demonstrating the existence of demersal free-living Symbiodinium populations in Caribbean reefs and the possible role of the stoplight parrotfish (Sparisoma viride) as Symbiodinium spp. dispersers. Communities of free-living Symbiodinium were found within macroalgal beds consisting of Halimeda spp., Lobophora variegata, Amphiroa spp., Caulerpa spp. and Dictyota spp. Viable Symbiodinium spp. cells were isolated and cultured from macroalgal beds and S. viride feces. Further identification of Symbiodinium spp. type was determined by length variation in the Internal Transcribed Spacer 2 (ITS2, nuclear rDNA) and length variation in domain V of the chloroplast large subunit ribosomal DNA (cp23S-rDNA). Determination of free-living Symbiodinium and mechanisms of dispersal is important in understanding the life cycle of Symbiodinium spp

Protocolo neuropsicopedagógico en la evaluación multidimensional del trastorno por déficit atencional/hiperactividad –TDAH–: Implementación de una experiencia investigativa.

Avances investigativos generados en la especialización en neuropsicopedagogía, adscrita al Programa de Psicología de la Facultad de Ciencias Sociales y Humanas de la Universidad de Manizales, permitieron proponer una aproximación multidimensional precisa, objetiva e integral para la caracterización neuropsicopedagógica de niños y niñas con Trastorno por Déficit Atencional/Hiperactividad –TDAH–. Dicha aproximación contempla también la evaluación neurofisiológica por medio de potenciales evocados cognitivos y la posibilidad de realizar un análisis automatizado de las bioseñales obtenidas. Lo anterior constituye una herramienta fundamental para implementar procesos de identificación del TDAH y para posteriores estudios sobre desórdenes de comportamiento en la población infantil. En particular, con la sistematización de perfiles neuropsicopedagógicos se pretende arrojar datos potencialmente útiles para el desarrollo de un sistema de evaluación informatizado con aplicabilidad en los campos clínico y educativo, lo cual permitirá no solo un mejor conocimiento del trastorno, sino también mejores criterios predictivos sobre el pronóstico y la respuesta de planes de intervención establecidos, entre otros. En este artículo se presentan los componentes que permitieron estructurar el protocolo neuropsicopedagógico y la articulación de los componentes neurofisiológicos y biomédicos, así como algunos resultados preliminares en cada uno de dichos componentes

An RNAi in silico approach to find an optimal shRNA cocktail against HIV-1

<p>Abstract</p> <p>Background</p> <p>HIV-1 can be inhibited by RNA interference <it>in vitro </it>through the expression of short hairpin RNAs (shRNAs) that target conserved genome sequences. <it>In silico </it>shRNA design for HIV has lacked a detailed study of virus variability constituting a possible breaking point in a clinical setting. We designed shRNAs against HIV-1 considering the variability observed in naïve and drug-resistant isolates available at public databases.</p> <p>Methods</p> <p>A Bioperl-based algorithm was developed to automatically scan multiple sequence alignments of HIV, while evaluating the possibility of identifying dominant and subdominant viral variants that could be used as efficient silencing molecules. Student t-test and Bonferroni Dunn correction test were used to assess statistical significance of our findings.</p> <p>Results</p> <p>Our <it>in silico </it>approach identified the most common viral variants within highly conserved genome regions, with a calculated free energy of ≥ -6.6 kcal/mol. This is crucial for strand loading to RISC complex and for a predicted silencing efficiency score, which could be used in combination for achieving over 90% silencing. Resistant and naïve isolate variability revealed that the most frequent shRNA per region targets a maximum of 85% of viral sequences. Adding more divergent sequences maintained this percentage. Specific sequence features that have been found to be related with higher silencing efficiency were hardly accomplished in conserved regions, even when lower entropy values correlated with better scores. We identified a conserved region among most HIV-1 genomes, which meets as many sequence features for efficient silencing.</p> <p>Conclusions</p> <p>HIV-1 variability is an obstacle to achieving absolute silencing using shRNAs designed against a consensus sequence, mainly because there are many functional viral variants. Our shRNA cocktail could be truly effective at silencing dominant and subdominant naïve viral variants. Additionally, resistant isolates might be targeted under specific antiretroviral selective pressure, but in both cases these should be tested exhaustively prior to clinical use.</p