Nitrogen transformations and fluxes in fish ponds: a modelling approach

Nitrogen is a key element in aquatic environments, and in Aquaculture it is an important pond management variable. In current aquaculture research two important goals are to maintain the water quality within the system, and to improve the retention of nutrients applied to the system in order to minimize the discharge. The principal objectives of this study were to integrate the information available of nitrogen processes in fish ponds into a predictive model, and to investigate further the nitrogen dynamics between the water, the sediments and the biota present in this systems. First, a nitrogen balance in fish ponds was followed along a growing cycle; by combining estimates of the deposition rates of uneaten feed, faeces and dead phytoplankton with measurements of nitrogen accumulation in the sediment, the rate of decomposition of organic matter in the sediment was evaluated. The cumulative recovery at the end of the experiment was almost 100%, meaning that the nitrogen budget in the system studied can be fully explained without any consideration of nitrogen volatilisation, due to either denitrification or ammonia volatilisation. The interactions between various N-species are complex and difficult to integrate. A model that calculates the amounts of various N-compounds in the water column and in the sediment was constructed, and used to gain insight into the relative importance of transformation processes between the various N-compounds. The model was divided into three modules: fish, phytoplankton and sediment-water.All concentrations of the various N-species present were simulated well except the N retained in organic matter in the sediment. To improve our understanding of the bottom organic matter dynamics, and make the model a more comprehensive predictive tool, an estimation of the principal sources of organic matter that accumulate in fish pond bottoms was assessed. Organic matter accumulation in fish ponds was quantified, and the data was used to construct, to calibrate and to validate a dynamic simulation model of organic matter deposition/decomposition in fish ponds. Besides, the rates of sedimentation and resuspension were measured along a growing cycle, following the influence of nutrient input, water parameters, fish biomass and fish size on these processes. Using a dilution analysis method to differentiate between sedimented and resuspended particles, sedimentation and resuspension rates were calculated. The rate of material collected in sediment traps increased from 88.5 to 330 g/m 2 per day along the growing cycle, but the relative resuspension did not change significantly, being always in the range of 42 to 47% of the total collected material. The processes of sedimentation of organic matter and resuspension were included in the original model. The proportion of three principal sources of organic matter that accumulate in the pond bottom were also included as parameters of the sedimentation process. A logistic equation relating the rate of resuspension and the fish biomass was calculated; and seepage, as a potential loss of nitrogen from the system, was also considered. The additions to the model represented a substantial improvement to model simulations.</p

Complicaciones y causas de fallo en cirugía de implante coclear en la población de usuarios del servicio de otorrinolaringología del Hospital Universitario clínica San Rafael

Este estudio corresponde a un análisis descriptivo de los pacientes del Hospital Universitario Clínica San Rafael llevados a cirugía de implante coclear entre Ene/2000 a Dic/2010 y describe la ocurrencia de complicaciones menores y mayores en la cirugía de implante coclear con un mínimo de seguimiento de 12 meses

Analysis of the Process Parameter Influence in Laser Cladding of 316L Stainless Steel

Laser Cladding is one of the leading processes within Additive Manufacturing technologies, which has concentrated a considerable amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for their deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting the laser cladding in single clads, whereas overlap percentage and overlapping strategy also become relevant when dealing with multiple clads. By setting appropriate values for each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and the substrate is obtained, trying simultaneously to maintain processing times at their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads, height and width, as well as the resulting dilution value. Besides the influence of the overlap between contiguous clads and layers, physical defects such as porosity and cracks were also evaluated. Optimum process parameters to maximize productivity were defined as 13 mm/s, 2500 W, 30% of overlap and a 25 g/min powder feed rat

Biochemical comparison of venoms from young Colombian Crotalus durissus cumanensis and their parents

Crotalus durissus cumanensis, a rattlesnake endemic to Colombia and Venezuela, is considered one of the most lethal snake species in Latin America. The aim of the present study was to compare the protein content and biological activity of the venom obtained from eight specimens of C. durissus cumanensis, namely two adults from different localities of Colombia and six offspring born in captivity. Protein profiles of crude venoms were analyzed by SDS-PAGE and RP-HPLC, and biological activities were evaluated for lethality, edema, defibrination, hemolytic and coagulant activities to assess individual venoms of adults and a pool of young snake venoms. Transient edema appeared rapidly after venom inoculation, whereas hemorrhagic effect was not observed. Differences in protein profiles, lethality, hemolytic, coagulant and defibrinating activities between both adult snake venoms were observed; those from the mother snake exhibited higher activities. Venoms from young snakes were similar to the one obtained from the mother, but the coagulant effect was stronger in offspring venoms. Notably, biological effects of the father snake venom were not comparable to those previously described for C. durissus cumanensis from Venezuela and C. durissus terrificus from Brazil, confirming the high variability of the venom from Crotalus species

Análisis de la deserción laboral de recolectores de café en el eje cafetero (2001-2014)

Para el análisis de las causas de la deserción laboral de los recolectores de café en el Eje Cafetero que se desarrollará en este trabajo, se delimitó una etapa de 14 años consecutivos para entender cómo esta región ha presentado cambios en su panorama económico, tales como: aumento del nivel de pobreza y miseria, reducción del crecimiento económico, desigualdad en los ingresos, incremento en el índice de desarrollo económico

App’s como herramientas pedagógicas para el proceso de Enseñanza-Aprendizaje de la Física

In this paper some App’s that are free in the Play Store, are used in order to study uniformly accelerated movement, taking as examples the movement of a car on an inclined plane and the free fall of a smartphone. The graphs of position, velocity and acceleration as a function of time and the value of the acceleration of gravity are obtained, respectively. These applications are tools, easy to access and manipulate, which allow performing inexpensive experiments and articulate theory and practice in the teaching-learning processes of physics. The work was developed by students of the fourth semester of the Degree in Natural Sciences and Environmental Education - face-to-face modality - of the University of Tolima in the course of Fundamental Physics I - Mechanics.En este trabajo se usan algunas App´s gratuitas disponibles en Play Store, para estudiar Movimiento Uniformemente Acelerado, tomando como ejemplos&nbsp;&nbsp; el movimiento de un carro sobre un plano inclinado y la caída libre de un Smartphone. Se obtuvieron las gráficas de posición, velocidad y aceleración en función del tiempo, y el valor de la aceleración de la gravedad, respectivamente. Estas aplicaciones son herramientas, de fácil acceso y manipulación, que permiten realizar experimentos de bajo costo y articular teoría y práctica en los procesos de enseñanza- aprendizaje de la física.&nbsp; El trabajo fue desarrollado por estudiantes de cuarto semestre de la Licenciatura en Ciencias Naturales y Educación Ambiental- modalidad presencial – de la Universidad del Tolima en el curso de Física Fundamental I – Mecánica

Painful violaceous pigmentation, a clinical challenge and diagnostic approach in a tropical country

Millipedes are not considered poisonous animals, although in some cases their chemical defense mechanisms may be deleterious for human beings, manifesting as erythematous, purpuric and/ or cyanotic lesions alongside local pain and paresthesia. According to the exposure, the clinical condition may progress to moderate and severe lesions such as ulcers and blisters. We describe a case of a male child from the Andean region in Colombia, an area with daily temperatures between 15° and 30° C and 72% average humidity. The boy accidentally stepped on a millipede, and this occurrence became a challenge for its diagnosis amongst staff who provided emergency health care

La Imagen y la Narrativa como Herramientas para el Abordaje Psicosocial en Escenarios de Violencia. País Aruba y Colombia, Departamento de Risaralda y Valle del Cauca.

Los eventos traumáticos que viven algunas personas a causa del conflicto armado en nuestro país, hacen un llamado al análisis, acompañamiento e intervención en circunstancias donde el individuo o la comunidad ven comprometidos su integridad, estabilidad, pensamientos, actitudes, comportamientos; un reto importante para los psicólogos, en búsqueda de la superación y el equilibrio psicológico para enfrentar estos traumas y crisis a los que se ven enfrentados. Se propone realizar mediante el análisis de relatos, con un enfoque narrativo el análisis y las estrategias de acompañamiento a las victimas colombianas que han experimentado una realidad sociopolítica difícil. El primer análisis narrativo es de un Joven Afrocolombiano de Nombre Camilo, que debió enfrentar varios hechos de violencia desde su niñez hasta su adultez producto del desplazamiento a causa de la violencia. Este estudio se hace de manera reflexiva mediante la formulación de una serie de preguntas que permiten a futuros profesionales de psicología tener mejor comprensión del contexto de las víctimas de la guerra y su abordaje. De igual manera se realiza un segundo análisis de caso. En esta oportunidad el de la Comunidad “Peñas Coloradas” donde también se estudia el tema a partir de unas preguntas guiadas y partiendo de allí se proponen una serie de estrategias de acercamiento psicosocial a sus habitantes. Brindando una serie de recursos de afrontamiento con el fin que estos pueden superar situaciones de estigmatización y victimización. Posteriormente se realiza un informe razonado y reflexivo de la experiencia de foto voz en los diferentes contextos de violencia, donde las imágenes juegan un papel determinante a la hora de narrar un hecho o circunstancia, por medio de estas representaciones se reconocen la realidad que afecta ya sea de manera individual o colectiva, sirviendo como mecanismo de trasformación social ya que lo que se plasma no se olvida. Lo anterior puede ser consultado en la página Wix con su respectiva conclusión.The traumatic events experienced by the victims of the armed conflict in Colombia require analysis, accompaniment and intervention in circumstances where the individual or the community see their integrity, stability, thoughts, attitudes, and behaviors compromised; an important challenge for psychologists, in search of improvement and psychological balance to face these traumas and crises that they are faced with. It is proposed to carry out an analysis of stories with a narrative approach, the analysis and accompaniment strategies to Colombian victims who have experienced a difficult socio-political reality. The first narrative analysis is of a Young Afro-Colombian named Camilo who had to face various acts of violence from childhood to adulthood as a result of displacement due to violence. This study is done in a reflective way by formulating a series of strategic questions, circular and reflective that allow future psychology professionals to have a better understanding of the context of war victims and these should be approached. In the same way, a second case analysis is carried out. On this occasion, the Community "Peñas Coloradas" where the subject is also addressed and proposed with some guided questions and a series of strategies for psychosocial approach to its inhabitants. Therefore providing a series of coping resources so that they can overcome situations of stigmatization and victimization. Subsequently, an analytical and reflective report is made of the experience of photo-voice in the different contexts of violence, where images play a determining role when narrating an event or circumstance, through these representations the reality that already affects either individually or collectively, serve as a mechanism of social transformation since what is embodied is not forgotten. The information mentioned above can be consulted on the Wix page with its respective conclusion. KeyWords: Displacement, Photovoice, Victimization, Psychosocial Strategies, Stigmatization and Resilience