Repotenciación del banco de pruebas de pérdidas por accesorios del laboratorio de turbomáquinas de la Facultad de Mecánica de la Escuela Superior Politécnica de Chimborazo

El objetivo de este trabajo fue repotenciar el banco de pruebas de pérdidas por accesorios presente en el laboratorio de turbomáquinas de la Facultad de Mecánica de la Escuela Superior Politécnica de Chimborazo, dejándolo funcional para realizar las pruebas requeridas y comparar con lo obtenido mediante simulación en el software Epanet. La identificación de los problemas presentes en el banco se lo dividió en tres secciones, los hallados en la bomba, en los tanques, y por último en el tablero de accesorios, en ese mismo orden se reparó, cambió e implementó elementos necesarios para corregir el funcionamiento y facilitar la toma de datos para el usuario, optimizando los tiempos de acción que se debe tener al realizar la práctica del laboratorio. Se realizaron rigurosas pruebas para asegurar el funcionamiento de cada una de las partes que conforman el banco para posterior a ello continuar con la etapa de adquisición de datos en el mismo. Se tomaron como mínimo cinco muestras de los diferenciales de presión para cada accesorio presente en el tablero y a partir de esto obtener un valor medio que se acerque al valor real del diferencial. Mediante el software Epanet se realizó la simulación del banco de pruebas con la finalidad de comparar con los resultados obtenidos experimentalmente. Se concluye que el banco de pérdidas se encuentra funcional óptimo para realizar las pruebas de laboratorio, mediante la simulación en el software se obtuvieron resultados aproximados a los hallados experimentalmente. Se recomienda implementar medidores de flujo para cada sección de tubería y obtener más datos para el análisis del comportamiento de los accesorios de forma teórica y experimental.The objective of this work was to repower the accessory loss test bench present in the turbomachinery laboratory of the Faculty of Mechanics of the Escuela Superior Politécnica de Chimborazo, leaving it functional to carry out the required tests and compare with what was obtained by simulation in the Epanet software. The identification of the problems present in the bank was divided into three sections, those found in the pump, in the tanks, and finally in the accessories board, in that same order, necessary elements were repaired, changed, and implemented to correct the problem operation and facilitate the data collection for the user, optimizing the action times that must be taken when carrying out the laboratory practice. Rigorous tests were carried out to ensure the operation of each of the parts that make up the bank and after that, continue with the data acquisition stage in it. At least five samples of the pressure differentials were taken for each accessory present on the board and from this an average value was obtained that brings us closer to the real value of the differential. Using the Epanet software, the simulation of the test bench was carried out to compare with the results obtained experimentally. It is concluded that the loss bank is optimally functional to carry out laboratory tests, by means of simulation in the software, approximate results are obtained to those found experimentally. It is recommended to implement flow meters for each pipe section and obtain more data for the analysis of the behavior of the accessories theoretically and experimentally

Costly arbitrage and asset prices: evidence from closed-end funds

If arbitrage is costly and noise traders are active, asset prices may deviate from fundamental values for long periods of time. We use a sample of 158 closed-end funds to show that noise-trader sentiment, as proxied by retail-investor flows, leads to fluctuations in the discount. Nevertheless, we reject the hypothesis that noise-trader risk is the cause of the long-run discount. Instead we find that funds which are more difficult to arbitrage have larger discounts, due to: (i) the censoring of the discount by the arbitrage bounds, and (ii) the freedom of managers to increase charges when arbitrage is costly

Importancia de desarrollar competencias profesionales en ingeniería.

Los mapas curriculares de los Planes de Estudio de las carreras de ingeniería, de forma tradicional han incluido competencias específicas en las asignaturas que los conforman. Sin embargo, los cambios debidos al proceso de globalización en los mercados laborales, obliga a que se incluyan las competencias genéricas tanto en su perfil de egreso como en  sus mapas curriculares. Esto ha dado lugar a las competencias profesionales las cuales conjuntan a las competencias antes mencionadas. En este documento se presenta un análisis de ambos tipos de competencias, así como sugerencias para trabajarlas con los estudiantes en el aula

Micrositios seguros para la germinación de Symphoricarpos microphyllus (Caprifoliaceae), una especie arbustiva con latencia

Background and Aims: Temperate forests suffer continuous deforestation and other anthropogenic disturbances. Additionally, some types of forest management, such as secondary vegetation removal ("chaponeo"), can be another disturbance that negatively affects the values of some environmental variables important for seed germination. Light, soil temperature and moisture characterize microsites and determine germination percentages. These variables are also affected by slope orientation and vegetation structure. The aim of this study was to characterize microsites for Symphoricarpos microphyllus seed germination in a temperate forest, its response to light qualities in germination cameras, and seed viability during two years.Methods: Twenty-four microsites that differed according to their position in north/south (N/S) facing slopes, and by the presence/absence of secondary vegetation (“chaponeo”) due to forest management (U-undisturbed/P-perturbed) were characterized for light, soil temperature, moisture, pH and nitrogen. We also studied germination under different light qualities (white light, red light, far red light -FRL-, darkness) in germination cameras and seed viability for two years.Key results: All microsites were different in light, temperature and soil moisture. Microsites with the highest germination percentages were those US (undisturbed south) and UN (undisturbed north), where higher soil moisture and lower temperatures were registered, favoring embryo growth of seeds, since they possess morphophysiological dormancy. In cameras, germination percentages were the highest in FRL (32%). Seeds of S. microphyllus can remain viable for two years (60%).Conclusions: We do not recommend secondary vegetation removal because it affects variables of soil moisture (decreasing it) and temperature (increasing it) in microsites. This negatively influences this species germination, which needs a filtering of light and an alternation of high-low temperatures for dormancy breaking. These findings are important if we consider that the populations of this species are reducing due to overexploitation.Antecedentes y Objetivos: Los bosques templados sufren continua deforestación y otros disturbios antropogénicos. Además, algunos tipos de manejo forestal, como la remoción de la vegetación secundaria (chaponeo) pueden representar otro disturbio que afecta negativamente algunas variables ambientales importantes en la germinación de las semillas. La luz, temperatura y humedad del suelo caracterizan micrositios y determinan los porcentajes de germinación de las especies. Estas variables también son afectadas por la orientación de la ladera y la estructura de la vegetación. El objetivo de este estudio fue caracterizar micrositios para la germinación de Symphoricarpos microphyllus en un bosque templado, y su respuesta a calidades de luz en cámaras de germinación, y la viabilidad de las semillas en dos años.Métodos: Se caracterizaron 24 micrositios diferentes de acuerdo a su posición en laderas orientadas al norte/sur (N/S), y por la presencia/ausencia de vegetación secundaria -chaponeo- (U-sin disturbio/P-perturbados) en sus variables de luz, temperatura, humedad, pH y nitrógeno del suelo. Estudiamos la germinación bajo diferentes calidades de luz (luz blanca, luz roja, luz rojo lejano -FRL-, oscuridad) en cámaras de germinación y la viabilidad de las semillas por dos años.Resultados clave: Todos los micrositios fueron diferentes en luz, temperatura y humedad del suelo. Los micrositios con los mayores porcentajes de germinación fueron los US (no perturbados al sur) y UN (no perturbados al norte), registrando los mayores valores de humedad del suelo y menores de temperatura, favoreciendo el crecimiento del embrión, dado que poseen una latencia morfofisiológica. En las cámaras, los mayores porcentajes de germinación de Symphoricarpos microphyllus ocurrieron en FRL (32%), la viabilidad se mantuvo en 60% por dos años.Conclusiones: No recomendamos la eliminación de la vegetación secundaria porque afecta la humedad (disminuyéndola) y temperatura del suelo (incrementándola). Esto tiene una influencia negativa sobre la germinación de las semillas que necesitan una filtración de la luz y una alternancia de altas y bajas temperaturas para romper la latencia. Estos hallazgos son importantes si consideramos que las poblaciones de esta especie están reduciéndose debido a sobreexplotación

What Kind of Seed Dormancy Might Palms Have?

Palm diaspores are reported to have various kinds of dormancy. However, (1) the embryo is underdeveloped; (2) the endocarp is water permeable; and (3) the diaspores take a long time to germinate. Thus, we conclude that the diaspores of the majority of palm species have morphophysiological dormancy (MPD). The ones that do not have MPD are morphologically dormant

Fruit fracture biomechanics and the release of Lepidium didymum pericarp-imposed mechanical dormancy by fungi

Mechanical dormancy imposed by a hard fruit pericarp prevents premature seed germination. Here, the authors show that the pericarp of Lepidium didymum prevents germination by limiting water uptake and that dormancy can be released by fungal activity that weakens predetermined breaking zones in the fruit coat

Tissue culture of ornamental cacti

Cacti species are plants that are well adapted to growing in arid and semiarid regions where the main problem is water availability. Cacti have developed a series of adaptations to cope with water scarcity, such as reduced leaf surface via morphological modifications including spines, cereous cuticles, extended root systems and stem tissue modifications to increase water storage, and crassulacean acid metabolism to reduce transpiration and water loss. Furthermore, seeds of these plants very often exhibit dormancy, a phenomenon that helps to prevent germination when the availability of water is reduced. In general, cactus species exhibit a low growth rate that makes their rapid propagation difficult. Cacti are much appreciated as ornamental plants due to their great variety and diversity of forms and their beautiful short-life flowers; however, due to difficulties in propagating them rapidly to meet market demand, they are very often over-collected in their natural habitats, which leads to numerous species being threatened, endangered or becoming extinct. Therefore, plant tissue culture techniques may facilitate their propagation over a shorter time period than conventional techniques used for commercial purposes; or may help to recover populations of endangered or threatened species for their re-introduction in the wild; or may also be of value to the preservation and conservation of the genetic resources of this important family. Herein we present the state-of-the-art of tissue culture techniques used for ornamental cacti and selected suggestions for solving a number of the problems faced by members of the Cactaceae family

Seed size influence on germination responses to light and temperature of seven pioneer tree species from the Central Amazon

In Amazon secondary forests are dominated by pioneer species that typically produce large amounts of small and dormant seeds that are able to form a persistent soil seed bank. Seed dormancy in this group of species is overcome by environmental conditions found in open areas, such as high irradiation or alternating temperatures. Nevertheless, a variety of germination responses to environmental factors is known among pioneers; some of them may germinate in diffuse light or in darkness condition at constant temperature. Seed mass can be considered as one of the factors that promotes this variety. Regarding species with very small seeds, it seems that the trigger for germination is light and for larger seeds temperature alternation may be a more important stimulus. In this study we established a relationship between seed mass and germination response to light and alternating temperature for a group of seven woody pioneer species from the Amazon forest. We found that an increase in seed mass was followed by a decrease in the need for light and an increase in the tolerance to alternating temperatures. Understanding germination strategies may contribute with the knowledge of species coexistence in high diverse environments and also may assist those involved in forest management and restoration.Na Amazônia as florestas secundárias são dominadas por espécies pioneiras que, normalmente, produzem grandes quantidades de sementes pequenas, dormentes e capazes de formar bancos de sementes no solo. A dormência neste grupo de espécies é superada pelas condições ambientais de áreas abertas, como alta irradiação ou alternância de temperaturas. No entanto, uma variedade de respostas de germinação aos fatores ambientais é conhecida entre as pioneiras; algumas germinam em luz difusa ou no escuro sob temperatura constante. Um dos fatores promotores desta variedade é a massa das sementes. Parece que para as espécies com sementes muito pequenas, o estímulo para que ocorra germinação é a luz e, para sementes maiores, a alternância de temperatura pode ser um estímulo mais importante. Neste estudo, estabeleceu-se uma relação entre a massa das sementes e a resposta de germinação à luz e temperatura para sete espécies pioneiras arbóreas da floresta amazônica. Descobrimos que o aumento na massa da semente foi acompanhado por diminuição da necessidade por luz e aumento da tolerância à alternância de temperatura. Compreender estratégias de germinação pode contribuir para os conhecimentos sobre a coexistência de espécies em ambientes altamente diversos e também pode ajudar aos pesquisadores envolvidos no manejo e restauração florestal

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised