1,232 research outputs found

    Market Interest Rate Dynamics in Times of Financial Turmoil

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    The significant reduction of the monetary policy rate (MPR) during 2009 has offset the rise in lending rates caused by increased uncertainty in the country and abroad. This paper comes to this conclusion after examining the evolution of interest rates of consumer and commercial loans in order to distinguish between the effects caused by MPR transmission from those caused by the increases in risk premiums occurred in 2008. The above is done through counterfactual simulations using the relevant variables.

    A review of networked microgrid protection: Architectures, challenges, solutions, and future trends

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    The design and selection of advanced protection schemes have become essential for the reliable and secure operation of networked microgrids. Various protection schemes that allow the correct operation of microgrids have been proposed for individual systems in different topologies and connections. Nevertheless, the protection schemes for networked microgrids are still in development, and further research is required to design and operate advanced protection in interconnected systems. The interconnection of these microgrids in different nodes with various interconnection technologies increases the fault occurrence and complicates the protection operation. This paper aims to point out the challenges in developing protection for networked microgrids, potential solutions, and research areas that need to be addressed for their development. First, this article presents a systematic analysis of the different microgrid clusters proposed since 2016, including several architectures of networked microgrids, operation modes, components, and utilization of renewable sources, which have not been widely explored in previous review papers. Second, the paper presents a discussion on the protection systems currently available for microgrid clusters, current challenges, and solutions that have been proposed for these systems. Finally, it discusses the trend of protection schemes in networked microgrids and presents some conclusions related to implementation

    Preliminary research of petrographic, petrophysical and mechanical behavior of natural stones as “Piedra Bogotana” and “Marmol Royal Bronce” used in heritage buildings and new constructions in Colombia

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    La piedra natural ha sido un elemento importante en la construcción colombiana desde la época colonial y hasta la actualidad, especialmente en la ciudad de Bogotá. Rocas areniscas y calizas son elementos decorativos y estructurales de edificaciones patrimoniales y recientes y su uso gana notoriedad con la recuperación de espacios urbanos para el disfrute de la población. En este trabajo se muestran los resultados de algunos ensayos de caracterización tecnológica de dos variedades de rocas ampliamente utilizadas en la construcción, conocidas coloquialmente con los nombres de Piedra Muñeca o Piedra Bogotana y Mármol Royal Bronce, utilizadas tanto en edificaciones patrimoniales como recientes. Los métodos de ensayo seguidos para evaluar algunas de las propiedades petrofísicas y mecánicas de estas dos rocas fueron: Análisis petrográfico, índices físicos (densidad aparente, porosidad aparente y absorción de agua), resistencia a la compresión, resistencia a la flexión, resistencia al desgaste y resistencia al impacto, expuestos en la norma brasileña ABNT NBR15845 de 2010. Los resultados obtenidos permiten determinar, de forma preliminar, que la Piedra bogotana en sus dos variedades (amarilla y rosada) puede ser usada como elemento estructural (muros, columnas, vigas y cimentaciones) y como material de revestimiento de edificios o de pisos y plazoletas, con la recomendación de uso de la variedad amarilla preferiblemente en espacios interiores; el Mármol Royal Bronce puede ser usado en cualquier tipo de revestimiento de paredes, pisos y calles de alto tráfico, como elemento estructural y en acabados.Natural stone has been an important element in Colombian construction since the hispanic period, especially in Bogotá city capital from Colombia. Sandstone and limestone rocks are ornamental and structural elements on heritage buildings and new constructions, and their use is important to revitalization of urban spaces for the enjoyment of the population. This paper shows the results of some technological characterization tests of two rock types widely used in construction, commonly known as Piedra Muñeca or Piedra Bogotana and Marmol Royal Bronce, used in historical buildings as well as modern ones. Petrophysical and mechanical properties of these rocks identified in a preliminary way were: Petrographic analysis, physical properties (bulk density, bulk porosity and water absorption), compressive strength, flexural strength, weathering resistance and impact resistance, as shown in the Brazilian technical standard ABNT NBR15845. The obtained results allows to determine, in an early way, that the two varieties (yellow and pink) of the Piedra bogotana stone can be used as a structural element (walls, columns, beams and foundations) and also as a dimension stone for buildings, floors and squares. It´s recommended the use of yellow variety specially on interior spaces. Marmol Royal Bronce can be used in finishes and also in any type of facing, floor and as a structural element in highly traffic streets

    Selective Photoinduced Antibacterial Activity of Amoxicillin-Coated Gold Nanoparticles: From One-Step Synthesis to in Vivo Cytocompatibility

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    Photoinduced antibacterial gold nanoparticles were developed as an alternative for the treatment of antibiotic-resistant bacteria. Thanks to the amoxicillin coating, they possess high in vivo stability, selectivity for the bacteria wall, a good renal clearance, and are completely nontoxic for eukaryotic cells at the bactericidal concentrations. A simple one-step synthesis of amoxi@AuNP is described at mild temperatures using the antibiotic as both reducing and stabilizing agent. Time-resolved fluorescence microscopy proved these novel nano-photosensitizers, with improved selectivity, are bactericidal but showing excellent biocompatibility toward eukaryotic cells at the same dose (1.5 μg/mL) when co-cultures are analyzed. Their stability in biological media, hemocompatibility, and photo-antibacterial effect against sensitive and antibiotic-resistant Staphylococcus aureus were evaluated in vitro, whereas toxicity, renal clearance, and biodistribution were studied in vivo in male Wistar rats. The use of these nanoparticles to treat antibiotic-resistant infections is promising given their high stability and cytocompatibility

    Validation of a simple method for the interpretation of uterine cytology in cows

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    One of the main drawbacks of using endometrial cytology in cows is the time required for sample collection and interpretation. It is recommended to count a large number of polymorphonuclear neutrophils (PMN) and to calculate their overall percentage. However, since counting a large number of cells is a laborious method, it would be preferable to simplify the analysis by counting the number of PMN in few microscopic fields. Therefore, the aim of this study was to assess whether a simple test, based on calculating the average number of PMN in 10 fields at 1000×, could be a reliable technique for the diagnosis of endometritis. Two hundred and sixty endometrial samples were taken from Holstein cows at different postpartum stages using an adapted cytobrush. Smears obtained were air-dried for fixing and stained with a Romanowsky-type procedure. To evaluate the counting method, the percentage of PMN in 150 cells was calculated as well as the average number of PMN in 10 fields at 1000×. Receiver operating characteristic (ROC) curves was constructed to evaluate both methods, the percentage of PMN (used as reference) and the average number of PMN. It was observed that the area under the curve is (regardless of cut-off used) higher than 0.99 and the correspondence between both methods were 1.58 PMN/field for the cut-off value of 15% and 2.40 PMN/field for the cut-off value of 20%. These results show that this simple method could be used to determine the percentage of PMN in endometrial cytological samples and to diagnose endometritis in cowsSupported by the Xunta de Galicia (Galician Plan for Research and Technological Development; Grant No. PGIDIT07MRU002E) and the Friesian Federation of Galician, A Coruna, SpainS

    Methodology to improve the model of series inductance in CMOS integrated inductors

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    This paper presents a systematic optimization methodology to achieve an accurate estimation of series inductance of inductors implemented in standard CMOS technologies. Proposed method is based on an optimization procedure which aims to obtain adjustment factors associated to main physical inductor characteristics, allowing to estimate more accurate series inductance values that can be used in design stage. Experimental measurements of diverse square inductor geometries are shown and compared with previous approaches in order to demonstrate and validate presented approach.National Council of Science and Technology of México (CONACYT) TEC2013-45638-C3-3-RSpanish Ministry of Economy and Competitiveness TEC2013-45638-C3-3-REuropean Regional Development Fund TEC2013-45638-C3-3-RConsejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía P12-TIC-148

    Diseño protótipo de ejercitador para apoyo en pacientes post covid-19

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    In breathing problems, it is importan to provide a continuous and accurate flow of oxigen, in this study a thorough investigation of the sequelae that can presente a post Covid patient. The results shown are 3D prints of the prototyped design of the air exerciser through the Computer Assistent Design CAD software, in order to search for innovations in ergonomics and its correct funtionality, as well as to monitor, measure and control the main variables such as air flow and indicate time. A particular goal is to generate new statistical information based on the use of the alarms that will be programmed, with the purpose that the patient can have a prompt rehabilitation and above all a better way of breathing. Among the main features of the equipment is that it is portable, lightweight, compact, ergonomic and has the ability to communicate wirelessly trough a standard port such as Bluetooth and this can be connected to smartphone through an application that will be developed specifically for the device, the application will be free and can be downloaded from a public website, just by registering.En problemas de respiración es importante suministrar un flujo continuo y preciso de oxígeno, en este estudio se realiza una profunda investigación de las secuelas que puede presentar un paciente post Covid. Los resultados mostrados son impresiones en 3D del diseño prototipo de ejercitado de aire a través del software Diseño Asistido por Computadora CAD, con el objeto de buscar innovaciones en ergonomía y su correcta funcionabilidad, así como monitorear, medir y controlar las principales variables como el flujo de aire y tiempo indicado.  Un objetivo particular es generar nueva información estadística con base en uso de las alarmas que se vayan a programar, con el propósito que el paciente pueda tener una pronta rehabilitación y sobre todo una mejor forma regular de su respiración. Dentro de las principales características del equipo es que sea portátil, ligero, compacto, ergonómico y que tenga la capacidad de comunicación inalámbrica por medio de un puerto estándar como el bluetooth y de esta forma se pueda conectar a un teléfono inteligente mediante una aplicación que se desarrollará específicamente para este dispositivo, dicha aplicación será gratis y se podrá descargar desde un sitio web público, bastara solo con registrarse

    EFFECT OF TIME OF INCUBATION ON NUCLEAR MATURATION AND CLEAVAGE POST IN VITRO FERTILIZATION OF ALPACA OOCYTES

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    Se evaluó el efecto del tiempo de cultivo sobre la tasa de maduración nuclear y tasa de división post-fecundación a 72 horas de ovocitos de alpacas. Complejos Cumulus-Ovocitos (CCOs) fueron obtenidos de ovarios procedentes de animales beneficiados en el camal y transportados a 35 °C en solución salina 0.9% suplementada con antibiótico antimicótico. Los CCOs fueron aspirados de folículos de 2 a 6 mm. Experimento 1: 502 ovocitos fueron distribuidos en cuatro tiempos de maduración (30, 34, 38 y 42 horas) y madurados en TCM-199 suplementado con 10% suero fetal bovino (SFB), 0.5 µg/mL de FSH, 10 µg/mL de hCG, 0.2 mM de piruvato de sodio, 50 µg/mL de gentamicina y 1 µg/mL de E2, y cultivados a 39 ºC bajo una atmósfera de 5% de CO2 y alta humedad. Posteriormente, los ovocitos fueron removidos, lavados con PBS suplementado con 10% de SFB y 1 mg/ml de hialuronidasa y fijados en solución de etanol y ácido acético (3:1). Los ovocitos fueron colocados en portaobjetos, teñidos con 1% de orceína y examinados bajo un microscopio a 400x para determinar la maduración nuclear. Experimento 2: 533 ovocitos fueron cultivados bajo las mismas condiciones del experimento 1 y fecundados con espermatozoides obtenidos de epidídimos. Los espermatozoides fueron centrifugados a 700 g en una gradiente de Percoll discontinua (22.5:45%) por 25 minutos. El sobrenadante fue removido y el pellet (con espermatozoides viables) reconstituido con TL-Stock. Los gametos fueron co-cultivados por 18 horas a 39 ºC con 5% de CO2 en KSOM suplementado con 10% de SFB, 2 mM de piruvato de sodio y 50 µg/mL gentamicina, y evaluados a las 72 horas. En el Experimento 1 se obtuvo el 26.3±5.4, 52.6±6.7, 68.5±10.6 y 75.3±11.9% de ovocitos en Metafase-II para 30, 34, 38 y 42 h de cultivo, respectivamente, con diferencia estadística entre 30 y 34 h respecto a 38 y 42 h (p<0.05). En el Experimento 2, la tasa de división fue 9.5±4.8, 8.1±5.8, 15.6±9.2 y 19.8±8.0% para 30, 34, 38 y 42 h, sin diferencia estadística entre grupos. Los resultados sugieren que los ovocitos de alpacas requieren 38 a 42 h de maduración para obtener estadios de Metafase-II.The study was carried out to evaluate the effect of incubation time on nuclear maturation and cleavage rate of alpaca oocytes after 72 hours post-fertilization. Cumulusoocyte complexes (CCOs) were collected from ovaries collected at slaughterhouse and transported in saline solution 0.9% with antibiotic antimycotic at 35 ºC. CCOs were aspirated from 2-6 mm follicles. Experiment 1: 502 oocytes were distributed in four maturation times (30, 34, 38, 42 hours), matured in TCM-199 supplemented with 10% fetal calf serum (FCS) (v:v), 0.5 μg/mL FSH, 10 μg/mL hCG, 0.2 mM sodium pyruvate, 50 μg/mL gentamicine and 1 μg/mL oestradiol, and cultivated at 39 ºC in an atmosphere of 5% CO2 and high humidity. After maturation, CCOs were removed from maturation medium and washed with PBS supplemented with 10% FCS and 1 mg/ml of hyaluronidase, and fixed in ethanol and acetic acid (3:1). Oocytes were placed on a glass slide, stained with 1% orcein and examined under microscope at 400x to evaluate nuclear maturation status. Experiment 2: 533 CCOs were culture under similar maturation protocols than experiment 1 and fertilized with epididymal spermatozoa. These were obtained by centrifugation at 700 g on a Percoll discontinuous gradient (22.5:45%) for 25 min. The supernatant was removed by aspiration and the pellet (containing viable spermatozoa) was re-suspended in TL Stock. Gametes were co-incubated for 18 h at 39 °C with 5% CO2 and cultivated in KSOM supplemented with 10% FCS (v:v), 0.2 mM sodium pyruvate and 50 μg/ml gentamicine, and evaluated in 72 hours. In experiment 1, 26.3±5.4, 52.6±6.7, 68.5±10.6 and 75.3±11.9% of oocytes were in M-II stage for the 30, 34, 38, and 42 h of culture respectively, with significant difference between 30 and 34 with respect to 38 and 42 h (p<0.05). In experiment 2, the cleavage rate was 9.5±4.8, 8.1±5.8, 15.6±9.2 and 19.8±8.0% for 30, 34, 38, and 42 h after culture, and without statistical difference between groups. These results indicate that is required 38-42 h for the maturation of alpaca oocytes

    Vitamin D status and risk of incident tuberculosis disease: A nested case-control study, systematic review, and individual-participant data meta-analysis

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    Background: Few studies have evaluated the association between preexisting vitamin D deficiency and incident tuberculosis (TB). We assessed the impact of baseline vitamins D levels on TB disease risk.Methods and Findings: We assessed the association between baseline vitamin D and incident TB in a prospective cohort of 6,751 HIV-negative household contacts of TB patients enrolled between September 1, 2009, and August 29, 2012, in Lima, Peru. We screened for TB disease at 2, 6, and 12 months after enrollment. We defined cases as household contacts who developed TB disease at least 15 days after enrollment of the index patient. For each case, we randomly selected four controls from among contacts who did not develop TB disease, matching on gender and year of age. We also conducted a one-stage individual-participant data (IPD) meta-analysis searching PubMed and Embase to identify prospective studies of vitamin D and TB disease until June 8, 2019. We included studies that assessed vitamin D before TB diagnosis. In the primary analysis, we defined vitamin D deficiency as 25-(OH)D \u3c 50 nmol/L, insufficiency as 50-75 nmol/L, and sufficiency as \u3e75nmol/L. We estimated the association between baseline vitamin D status and incident TB using conditional logistic regression in the Lima cohort and generalized linear mixed models in the meta-analysis. We further defined severe vitamin D deficiency as 25-(OH)D \u3c 25 nmol/L and performed stratified analyses by HIV status in the IPD meta-analysis. In the Lima cohort, we analyzed 180 cases and 709 matched controls. The adjusted odds ratio (aOR) for TB risk among participants with baseline vitamin D deficiency compared to sufficient vitamin D was 1.63 (95% CI 0.75-3.52; p = 0.22). We included seven published studies in the meta-analysis and analyzed 3,544 participants. In the pooled analysis, the aOR was 1.48 (95% CI 1.04-2.10; p = 0.03). The aOR for severe vitamin D deficiency was 2.05 (95% CI 0.87-4.87; p trend for decreasing 25-(OH)D levels from sufficient vitamin D to severe deficiency = 0.02). Among 1,576 HIV-positive patients, vitamin D deficiency conferred a 2-fold (aOR 2.18, 95% CI 1.22-3.90; p = 0.01) increased risk of TB, and the aOR for severe vitamin D deficiency compared to sufficient vitamin D was 4.28 (95% CI 0.85-21.45; p = 0.08). Our Lima cohort study is limited by the short duration of follow-up, and the IPD meta-analysis is limited by the number of possible confounding covariates available across all studies.Conclusion: Our findings suggest vitamin D predicts TB disease risk in a dose-dependent manner and that the risk of TB disease is highest among HIV-positive individuals with severe vitamin D deficiency. Randomized control trials are needed to evaluate the possible role of vitamin D supplementation on reducing TB disease risk
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