A Comparative Study of Turbulence Methods Applied to the Design of a 3D-Printed Scaffold and the Selection of the Appropriate Numerical Scheme to Simulate the Scaffold for Tissue Engineering

Current commercial software tools implement turbulence models on computational fluid dynamics (CFD) techniques and combine them with fluid-structural interaction (FSI) techniques. There are currently a great variety of turbulence methods that are worth investigating through a comparative study in order to delineate their behavior on scaffolds used in tissue engineering and bone regeneration. Additive manufacturing (AM) offers the opportunity to obtain three-dimensional printed scaffolds (3D scaffolds) that are designed respecting morphologies and that are typically used for the fused deposition model (FDM). These are typically made using biocompatible and biodegradable materials, such as polyetherimide (PEI), ULTEM 1010 biocompatible and polylactic acid (PLA). Starting from our own geometric model, simulations were carried out applying a series of turbulence models which have been proposed due to a variety of properties, such as permeability, speed regime, pressures, depressions and stiffness, that in turn are subject to boundary conditions based on a blood torrent. The obtained results revealed that the detached eddy simulation (DES) model shows better performance for the use of 3D scaffolds in its normal operating regime. Finally, although the results do not present relevant differences between the two materials used in the comparison, the prototypes simulated in PEI ULTEM 1010 do not allow their manufacture in FDM for the required pore size. The printed 3D scaffolds of PLA reveal an elastic behavior and a rigidity that are similar to other prototypes of ceramic composition. Prototypes made of PLA reveal unpredictable variability in pore and layer size which are very similar to cell growth itself and difficult to keep constant

Improvements in the production of fat for biodiesel from sludge from treatment plants wastewater

The final goal of this research project is to improve the production of fat for biodiesel from sludge from treatment plants of wastewater (E.D.A.R). To produce such biodiesel, the methanol and the fats are necessary, and the fats are obtained from the growth of C. elegans in these sludge. It is known that the nematode Caenorhabditis elegans has the ability of generating and accumulating a high percentage of fat (around 35% of dry weight), apart from having a wide range of edible bacteria, which can feed the different microorganisms present in the mud of the sewage treatment plant.This research project could be divided into three different parts. Firstly, for optimal growth of this organism (considered as model), there is a laboratory’s protocol with liquid culture which indicates that would be favorable the addition of seven compounds (NaCl, KH2PO4, cholesterol, Potassium citrate, Trace Metals, CaCl2, MgSO4). One of my goal is to try to reduce the number of compounds used, obtaining the same population growth of worms in the mud.On the other hand, another objective is to try to improve the growth of the nematode population in the mud. To do this, we will apply different pre-treatments to the sludge and observe how the nematodes react to these changes during a week.Finally, the last objective of the research investigation is to try to improve the fat’s production for biodiesel. C. elegans has only a life cycle of three days in which present different stages from hatching: L1, L2, L3, L4 and adults and it may also appear the dauer larva, which is a stage of resistance, created by stress conditions.It is known that dauer and adults are those ones which have a greater capacity to store the fats. To improve fat’s production, we will use different strains of nematode, trying to synchronize so that all of them end up being dauer or adults and thus obtaining a higher amount of fats

Poder de mercado en mercados spot de generación eléctrica: metodología para su análisis

Después de analizar las experiencias internacionales relacionadas con el monitoreo y control de poder de mercado, se establece una metodología acorde a las características del pool eléctrico en Colombia, la cual permite hacer seguimiento sobre comportamientos estratégicos respecto al precio en bolsa en este mercado. Se propone un modelo exponencial para la función de oferta en el pool basado en un modelo de precios spot, explicado por los costos, las condiciones climáticas, las intervenciones de la Comisión de Regulación de Energía y Gas, la demanda diaria, las cantidades generadas y el precio histórico. Por medio de una convolución (técnica similar a la de un Filtro de Kalman) sobre los precios históricos se estiman los parámetros y elasticidades dinámicas asociadas a las cantidades que determinan el comportamiento del precio en bolsa. A su vez, estas estimaciones son utilizadas en la estructura de beneficios en un modelo de Cournot, de competencia en cantidades, que evidencia el efecto positivo, vía disminución del precio de bolsa, de mayores niveles de contratos a futuros en el pool eléctrico colombiano

Use of a PSNM to Increase Precocity and Its Benefits in Greenhouse-Grown Sweet Pepper

The types and varieties of peppers grown in Mediterranean areas are a response to the demand of European markets, although in each Autonomous Community local varieties are grown to satisfy the national demand. Nowadays, the range of shapes, colours, tastes and uses is wider than ever as a result of greenhouse cultivation, national and international tendencies and increased demand. In Murcia, the growing cycle runs from December to July or August, depending on the market and the growth of the crop. Sweet pepper is normally grown in greenhouses, using a variety of technologies: from simple shaded greenhouses, to the most-advanced multitunnels (large, in the form of a round arch or Gothic arch and with sophisticated ventilation). Due to the high cost of fuel, it is impossible to use heating during winter after transplanting, so alternative techniques are used to raise the temperature a few degrees and improve crop production. The aim of this work was to increase the precocity and productivity of sweet pepper grown in greenhouses. The effect of a Polypropylene Spunbonded Nonwoven Microtunnel (PSNM) was studied. The results show that, although the increase in production was not great (lower than 5% in both years of the study), precocity increased by 16% in both years. Since the increased cost of using this technology is not excessive, crop profitability increases if precocity is taken into account, as all our indicators show. The study suggests that the use of a PSNM raises the marketable production and brings forward the first harvests

Statistical tests of symbolic dynamics

A novel general method for constructing nonparametric hypotheses tests based on the field of symbolic analysis is introduced in this paper. Several existing tests based on symbolic entropy that have been used for testing central hypotheses in several branches of science (particularly in economics and statistics) are particular cases of this general approach. This family of symbolic tests uses few assumptions, which increases the general applicability of any symbolic-based test. Additionally, as a theoretical application of this method, we construct and put forward four new statistics to test for the null hypothesis of spatiotemporal independence. There are very few tests in the specialized literature in this regard. The new tests were evaluated with the mean of several Monte Carlo experiments. The results highlight the outstanding performance of the proposed test. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Quistes de Tarlov sintomáticos: diagnóstico y tratamiento

Los quistes de Tarlov se forman a expensas de la duramadre y de la aracnoides alrededor de las raíces sacras o coccígeas. Habitualmente asintomáticos, en ocasiones pueden ocasionar clínica álgica de irritación radicular. El desarrollo de técnicas de imagen, principalmente la resonancia magnética nuclear (RMN), permiten diagnosticarlos con más frecuencia, aunque determinar si son responsables de los síntomas de los pacientes continúa siendo difícil. El tratamiento inicial es conservador mediante analgésicos convencionales y fisioterapia. En caso de quistes sintomáticos de gran tamaño, sin respuesta al tratamiento inicial, puede ser necesario el tratamiento quirúrgico mediante drenaje percutáneo guiado bajo control de la tomografía axial computerizada (TAC), o bien mediante una técnica abierta que permita la eliminación del quiste y la descompresión del nervio. Describimos dos casos clínicos en pacientes con clínica de neuralgia por atrapamiento de las raíces nerviosas lumbosacras, un paciente tratado con infiltración periradicular y otro que requirió un drenaje percutáneo con buen resultado final.Tarlov cysts are formed of the dura mater and the arachnoid around the sacral or coccygeal roots. Usually asymptomatic, they can occasionally cause clinical radicular irritation. Magnetic resonance imaging (MRI) permit to diagnose them more often, but whether they are responsible for the symptoms remains difficult. The initial treatment is conservative with conventional analgesics and physiotherapy. In case of large symptomatic cysts, with no response to initial treatment may require surgical therapy: a guided percutaneous drainage under computerized tomography (CT) control, or by an open technique that allows removal of the cyst and nerve decompression. We describe two cases in patients with symptomatic neuralgia due to entrapment of lumbosacral nerve roots. One patient treated with periradicular infiltration and another that required percutaneous drainage with good final outcome

Veinte años de funcionamiento del Mercado Eléctrico Mayorista en Colombia: algunas reflexiones

El objetivo de este escrito es analizar el desempeño del Mercado Eléctrico Mayorista - MEM en los veinte años de existencia. Después de describir el funcionamiento del mercado spot, el mercado de largo plazo y el cargo por confiabilidad; se analiza el efecto de variables como el fenómeno de El Niño, el nivel de embalse, la relación entre la disponibilidad real y la demanda comercial y algunos efectos de cambios regulatorios sobre el precio spot. También a través de un modelo estocástico se establecen algunas recomendaciones de cómo mejorar el funcionamiento de este mercado con la implementación de contratos estandarizados teniendo en cuenta las experiencias internacionales. A pesar del avance del mercado en estos veinte años de funcionamiento, aún quedan aspectos por resolver, como la implementación de contratos de largo plazo estandarizados, redes inteligentes y la disminución del umbral para acceder al mercado no regulado, pues estos aspectos ayudarían a disminuir el precio spot.The aim of this paper is to analyze wholesale electricity market performance in the twenty years of existence. After describing spot market operation, the market for long-term and reliability charge, we analyzed the effect of variables such as El Niño, the reservoir level, the ratio of the actual availability and market demand and some effects of regulatory changes on the spot price. Also through a stochastic model we set up some recommendations on how to improve the functioning of this market with standardized contracts implementation considering international experience. Despite the market's advance in these twenty years of operation, there are still issues to be resolved, such as contracts standardized long-term implementation, smart grids and lowering the threshold to enter the unregulated market, as these aspects would help to reduce the spot price

Anorèxia nerviosa i pràctica d’exercici físic per perdre pes

A hores d’ara es reconeix i s’accepta que l’anorèxia nerviosa és un trastorn del comportament alimentari de naturalesa multicausal, que en els últims anys, a causa de la difusió dels mitjans de comunicació, les aportacions dels professionals, les associacions que hi lluiten en contra o els relats de les joves que han mort com a conseqüència de la malaltia, ha sensibilitzat l’opinió pública, política i comença a fer-ho amb l’educativa. La intenció amb què emprenem aquesta investigació és la d’estimar la prevalença de la població de risc per a anorèxia nerviosa en adolescents de tots dos sexes que cursen de 1r a 4t d’Educació Secundària Obligatòria, en centres docents, tant privats com a públics, i corroborar que l’exercici físic que practiquen els nostres i les nostres adolescents va encaminat, fonamentalment, a perdre pes

Aflojamiento del componente femoral de prótesis de cadera cementada en el postoperatorio precoz.: a propósito de un caso.

Presentamos el caso clínico de una complicación extremadamente rara de aflojamiento precoz del componente femoral de una prótesis de cadera cementada. Este acontecimiento es consecuencia de la pérdida de adherencia entre la interfaz metal-cemento y tuvo lugar 14 días después de la colocación de una prótesis total de cadera cementada. En la literatura sólo se encuentra descrito un caso similar. Las causas atribuidas son el biomaterial y diseño de la prótesis, y la técnica de cementación.We report a case of an extremely rare complication of early loosening of the femoral component of a hip arthroplasty. This event is a consequence of the loss of adhesion between the metal-cement interface and took place 14 days after the placement of cemented total hip prosthesis. There was only described a similar case in the literature. The causes attributed are the biomaterial and design of the prosthesis, and cementation technique

Anorexia nerviosa y práctica de ejercicio físico para perder peso

Actualmente se reconoce y acepta que la anorexia nerviosa es un trastorno de la conducta alimentaria de naturaleza multicausal que en los últimos años por la difusión de los medios de comunicación, las aportaciones de los profesionales, las asociaciones que luchan contra ella o los relatos de las jóvenes que han fallecido a consecuencia de la enfermedad, ha sensibilizado a la opinión pública, política y empieza a hacerlo con la educativa. La intención con la que se acomete esta investigación es la de estimar la prevalencia de la población de riesgo para anorexia nerviosa en adolescentes de ambos sexos que cursan de 1.º a 4.º de Educación Secundaria Obligatoria en centros docentes tanto privados como públicos y corroborar cómo el ejercicio físico que practican nuestros y nuestras adolescentes está encaminado fundamentalmente a perder peso