Protocolo experimental para la evaluación de microemulsiones que modifican la mojabilidad en el medio poroso. Aplicación a campos colombianos

Las reservas de crudo liviano son cada vez más escasas, a diferencia de los descubrimientos de crudo pesado, razón por lo cual se ha enfocado la atención en este tipo de hidrocarburos. Colombia tiene un gran potencial de crudo pesado, sobre todo en las zonas de la Cuenca de los Llanos Orientales (Campos: Rubiales, Castilla, Chichimene, Apiay, Suria), cuyo desarrollo en los últimos años, ha logrado que el 60% de la producción nacional este asociada a este tipo de recurso. La producción de crudo pesado no es fácil, una de las principales dificultades es la alta viscosidad del hidrocarburo, lo cual origina una baja movilidad del mismo y una temprana producción de agua en yacimientos con acuíferos activos. Una de las técnicas más utilizadas para incrementar la productividad en los yacimientos de crudos pesados es la estimulación matricial de pozos, a partir de la cual se pueden modificar las curvas de permeabilidad relativa (alteración de la humectabilidad) y así mejorar la movilidad de estos crudos. Sin embargo es crucial la comprensión de la mojabilidad de la formación para optimizar la recuperación de petróleo. Suponer que una formación es mojable por agua, cuando en realidad no lo es, puede ocasionar daños irreversibles en el yacimiento. Por lo anterior, el presente estudio se centró en desarrollar e implementar un protocolo a nivel de laboratorio, para evaluar tratamientos de estimulación matricial base agua, que tuvieran la capacidad de invertir la mojabilidad natural (generalmente al crudo, debido a la alta afinidad entre el crudo y minerales de roca del yacimiento), hacia una mojabilidad al agua, que conduce a un mejoramiento de la permeabilidad relativa al crudo. El protocolo experimental fue implementado a nivel de laboratorio en el campo Castilla (cuenca de los llanos orientales en Colombia) y se enfocó en tres grandes etapas. 1. Etapa 1: Caracterización básica de fluidos de formación 2. Etapa 2: Evaluación fluido-fluido y comportamiento reológico de fluidos de formación Vs Tratamientos químicos. 3. Etapa 3: Evaluación del efecto sobre la humectabilidad (modificación de ángulos de contacto y permeabilidad relativa). Las principales conclusiones y recomendaciones obtenidas en este estudio son las siguientes: 1. Se desarrolló un protocolo experimental adecuado para la evaluación de microemulsiones y/o aditivos mejoradores de movilidad. 2. La implementación del protocolo permitió seleccionar el mejor tratamiento de alteración de la humectabilidad para el campo Castilla. 3. En la preferencia de la mojabilidad del yacimiento, tienen incidencia: los componentes del petróleo, la química de la salmuera, la superficie mineral, la temperatura, la presión, la tensión interfacial de los fluidos, la presión capilar y la historia de saturación del yacimiento.Reserves of light crude oil are decreasing in contrast to the discoveries of heavy crude which is why attention has been focused on this type of hydrocarbons. Colombia has a high potential in the heavy-crude development especially in the areas of the Llanos Orientales Basin (Campos: Rubiales, Castilla, Chichimene, Apiay, Suria) which have been produced in recent years to achieve that the 60% of the national production is associated with this type of resource. Heavy-oil production is not easy due to its high viscosity which causes low oil mobility and early water production in reservoirs with active aquifers. One of the main techniques used to increase productivity in heavy crude oil fields is the matrix stimulation of wells through the injection of treatments that positively alter the relative permeability curves (alteration of wettability) and thus improve the mobility of these crude oils. However, understanding the formation wettability is essential to optimize oil recovery. To assume that a formation is wettable by water, when in reality it is not, can cause irreversible damage to the reservoir. Therefore, the current study focused on developing and implementing a protocol at the laboratory level, to evaluate water-based matrix stimulation treatments that have ability to reverse natural oil wettability (generally to the oil, due to high affinity between oil and rock minerals of reservoir) towards water wettability, which leads to an improvement of relative permeability to crude oil. The experimental protocol was implemented at laboratory level for the Castilla Oilfield (Llanos Orientales basin in Colombia) and focused on three major stages. 1. Stage 1: Basic characterization of treatment fluids. 2. Stage 2: Fluid-fluid evaluation and rheological behavior of formation fluids Vs. Chemical treatments. 3. Stage 3: Evaluation of effect on wettability (modification of contact angles and relative permeability). The main conclusions and recommendations obtained in this study are the following: 1. A suitable experimental protocol was developed for evaluation of microemulsions and / or mobility enhancing additives. 2. Implementation of protocol allowed selecting the best treatment of alteration of wettability for the Castilla oilfield. 3. The components of the oil, the brine chemistry, the mineral surface, the temperature, the pressure, the interfacial tension, the capillary pressure, the saturation history of reservoir, among other properties have an impact on the reservoir’s wettability

Evaluación fitotoxicológica del efluente de agua residual tratada en lagunas de oxidación utilizada para riego agrícola

El agua residual se considera como una mezcla compleja debido a los diversos compuestos que tiene. Por ello su tratamiento puede dificultarse debido a compuestos y/o mezclas recalcitrantes. Una forma de evaluar la eficiencia de los sistemas de tratamiento de agua residual es a través de bioensayos de toxicidad tales como los que utilizan plantas, ya que presentan las ventajas de ser de bajo costo y fáciles de realizar El objetivo del presente trabajo fue realizar un ensayo fitotoxicológico del agua residual tratada utilizada para riego agrícola en la Facultad de Agronomía de la Universidad Autónoma de Nuevo León (FAUANL) utilizando lechuga Lactuca sativa L y pepino Cucumis sativus L. Se observó que el agua en proceso de tratamiento, así como el efluente utilizado en riego agrícola, producen un efecto inhibitorio en el crecimiento de la radícula de las dos especies utilizadas. Esto sugiere que el tratamiento del agua residual en las lagunas de oxidación no es suficiente para disminuir la toxicidad del influente. Por ello se recomienda realizar evaluaciones ecotoxicológicas más extensas en el área de estudio, a fin de determinar el riesgo ecológico que representa el agua residual utilizada en riego agrícola en la FAUAN

Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic

The Household Water Insecurity Experiences (HWISE) Scale: comparison scores from 27 sites in 22 countries

Abstract Household survey data from 27 sites in 22 countries were collected in 2017–2018 in order to construct and validate a cross-cultural household-level water insecurity scale. The resultant Household Water Insecurity Experiences (HWISE) scale presents a useful tool for monitoring and evaluating water interventions as a complement to traditional metrics used by the development community. It can also help track progress toward achievement of Sustainable Development Goal 6 ‘clean water and sanitation for all’. We present HWISE scale scores from 27 sites as comparative data for future studies using the HWISE scale in low- and middle-income contexts. Site-level mean scores for HWISE-12 (scored 0–36) ranged from 1.64 (SD 4.22) in Pune, India, to 20.90 (7.50) in Cartagena, Colombia, while site-level mean scores for HWISE-4 (scored 0–12) ranged from 0.51 (1.50) in Pune, India, to 8.21 (2.55) in Punjab, Pakistan. Scores tended to be higher in the dry season as expected. Data from this first implementation of the HWISE scale demonstrate the diversity of water insecurity within and across communities and can help to situate findings from future applications of this tool

The conservation value of human-modified landscapes for the world's primates

Land-use change pushes biodiversity into human-modified landscapes, where native ecosystems are surrounded by anthropic land covers (ALCs). Yet, the ability of species to use these emerging covers remains poorly understood. We quantified the use of ALCs by primates worldwide, and analyzed species' attributes that predict such use. Most species use secondary forests and tree plantations, while only few use human settlements. ALCs are used for foraging by at least 86 species with an important conservation outcome: those that tolerate heavily modified ALCs are 26% more likely to have stable or increasing populations than the global average for all primates. There is no phylogenetic signal in ALCs use. Compared to all primates on Earth, species using ALCs are less often threatened with extinction, but more often diurnal, medium or large-bodied, not strictly arboreal, and habitat generalists. These findings provide valuable quantitative information for improving management practices for primate conservation worldwide

Guía de práctica clínica para el tratamiento farmacológico inicial de nefritis lúpica en el Seguro Social del Perú (EsSalud)

Background: This article summarizes the clinical practice guideline (CPG) for the initial pharmacological treatment of lupus nephritis in the Social Security of Peru (EsSalud). Objective: To provide evidence-based clinical recommendations for initial pharmacological treatment of non-refractory adults with class I to V lupus nephritis in EsSalud. Material and Methods: A guideline development group (GDG) was formed, which included specialist physicians and methodologists, who formulated clinical questions. Systematic searches were conducted for systematic reviews and - when deemed relevant - primary studies in PubMed during 2021. Evidence was selected to answer each of the clinical questions posed. The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. In periodic working meetings, the GEG used the GRADE methodology to review the evidence and formulate recommendations. The CPG was reviewed by external experts before its approval. Results: The CPG addressed 6 clinical questions, divided into 2 topics: initial treatment of the induction and maintenance phase. Based on these questions, 11 recommendations were formulated (all conditional), 22 points of good clinical practice, and 2 flow charts. Conclusion: Evidence-based recommendations were issued for the management of patients with this pathology.Introducción: El presente artículo resume la guía de práctica clínica (GPC) para el tratamiento farmacológico inicial nefritis lúpica en el Seguro Social del Perú (EsSalud). Objetivo: Proveer recomendaciones clínicas basadas en evidencia para tratamiento farmacológico inicial de adultos con nefritis lúpica clase I a V no refractarios en EsSalud. Material y Métodos: Se conformó un grupo elaborador de la guía (GEG) que incluyó médicos especialistas y metodólogos, el cual formuló preguntas clínicas. Se realizaron búsquedas sistemáticas de revisiones sistemáticas y –cuando fue considerado pertinente– estudios primarios en PubMed durante el 2021. Se seleccionó la evidencia para responder cada una de las preguntas clínicas planteadas. Se evaluó la certeza de evidencia usando la metodología Grading of Recommendations Assessment, Development, and Evaluation (GRADE). En reuniones de trabajo periódicas, el GEG usó la metodología GRADE para revisar la evidencia y formular las recomendaciones. La GPC fue revisada por expertos externos antes de su aprobación. Resultados: La GPC abordó 6 preguntas clínicas, divididas en 2 temas: tratamiento inicial de la fase de inducción y mantenimiento. En base a dichas preguntas se formularon 11 recomendaciones (todas condicionales), 22 puntos de buena práctica clínica, y 2 flujogramas. Conclusión: Se emitieron recomendaciones basadas en evidencia para el manejo de pacientes con esta patología

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

The Household Water Insecurity Experiences (HWISE) Scale: Comparison scores from 27 sites in 22 countries

Household survey data from 27 sites in 22 countries were collected in 2017–2018 in order to construct and validate a cross-cultural household-level water insecurity scale. The resultant Household Water Insecurity Experiences (HWISE) scale presents a useful tool for monitoring and evaluating water interventions as a complement to traditional metrics used by the development community. It can also help track progress toward achievement of Sustainable Development Goal 6 ‘clean water and sanitation for all’. We present HWISE scale scores from 27 sites as comparative data for future studies using the HWISE scale in low-and middle-income contexts. Site-level mean scores for HWISE-12 (scored 0–36) ranged from 1.64 (SD 4.22) in Pune, India, to 20.90 (7.50) in Cartagena, Colombia, while site-level mean scores for HWISE-4 (scored 0–12) ranged from 0.51 (1.50) in Pune, India, to 8.21 (2.55) in Punjab, Pakistan. Scores tended to be higher in the dry season as expected. Data from this first implementation of the HWISE scale demonstrate the diversity of water insecurity within and across communities and can help to situate findings from future applications of this tool

Primate responses to changing environments in the anthropocene

Most primates have slow life-histories and long generation times. Because environmental change is occurring at an unprecedented rate, gene-based adaptations are unlikely to evolve fast enough to offer successful responses to these changes. The paper reviews the most common types of habitat/landscape alterations, the extent of human-primate interactions, and the impact of climate change. It demonstrates how understanding behavioural flexibility as a response to environmental change will be crucial to optimize conservation efforts by constructing informed management plans. Comparisons across species, space, and time can be used to draw generalizations about primate responses to environmental change while considering their behavioural flexibility