Propiedades físicas-mecánicas-biológicas del poli (metilmetacrilato) enriquecido con óxido de grafeno como potencial biomaterial.

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulpdental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: T he G O w as c haracterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical-mechanical tests (flexural strength and elastic  modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's post-hoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 ?m. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical-mechanical properties of PMMA.Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulpdental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: T he G O w as c haracterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical-mechanical tests (flexural strength and elastic  modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's post-hoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 ?m. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical-mechanical properties of PMMA

Passive neutron area monitor with pairs of TLDs as neutron detector

A passive neutron area monitor has been designed using Monte Carlo methods; the monitor is a polyethylene cylinder with pairs of thermoluminescent dosimeters (TLD600 and TLD700) as thermal neutron detector. The monitor was calibrated with a bare and a thermalzed 241AmBe neutron sources and its performance was evaluated measuring the ambient dose equivalent due to photoneutrons produced by a 15 MV linear accelerator for radiotherapy and the neutrons in the output of a TRIGA Mark III radial beam port

Neutron area monitor with passive detector

Using Monte Carlo methods the responses of a passive neutron monitor area has been calculated. To detect thermal neutrons the monitor has a gold foil that is located at the center of a polyethylene cylinder. Impinging neutrons are moderated by polyethylene nuclei reaching the gold foil with the energy to induce activation through the reaction 197Au (n,γ) 198Au. The198Au decays emitting 0.411 MeV gamma rays with a half life of 2.7 days. The induced activity is intended to be measured with a gamma-ray spectrometer with a 3”Ø×3” NaI(Tl) scintillator and the saturation activity is correlated to the ambient dose equivalent. The response was calculated for 47 monoenergetic neutron sources ranging from 1×10−9 to 20 MeV. Calculated fluence response was compared with the response of neutron monitor area LB 6411. = Se utilizó el método de Monte Carlo para calcular las respuestas de un monitor de neutrones pasivo. Para detectar los neutrones térmicos el monitor tiene una lámina de oro que se encuentra en el centro de un cilindro de polietileno. Los neutrones que inciden son moderados por los núcleos de polietileno que llega a la lámina de oro con la energía para inducir la activación a través de la 197Au reacción (n,γ)198 Au. El 197Au decae emitiendo rayos gamma de 0.411 MeV con una vida media de 2.7 días. La actividad inducida se destina a medir con un espectrómetro de rayos gamma con un detector de centelleo de 3”Ø×3” NaI (Tl) y la actividad de saturación se correlaciona con la dosis equivalente ambiental. La respuesta se calculó para 47 fuentes de neutrones monoenergéticos desde 1×10−9 a 20 MeV. La respuesta a la fluencia se comparó con la respuesta del monitor de área LB 6411

Neutron detectors of 10B+ZnS(Ag) as an alternative to 3He-based installed in the Radiation Portal Monitors in homeland Security

Using Monte Carlo method features of 10B+ZnS(Ag) neutron detector under real operational conditions has been calculated, this results were compared against measurements. This detector is a viable substitute for 3He detectors installed in custom borders to prevent the illicit traffic of special nuclear materials, SNM

Correlación de los saberes del área de matemáticas con el uso de los conocimientos científicos en química

En el modelo educativo que se ha implementado en la mayoría de instituciones de educación media de nuestro país los conocimientos que se imparten tienden a transmitirse de una manera segmentada y parcializada destacándose una carencia de interacción en los aprendizajes, lo cual redunda en que los estudiantes abordan cada materia como independiente y/o sin relación con las otras y, en consecuencia, tienen serios inconvenientes cuando se trata de construir un nuevo conocimiento. En el presente trabajo de grado los autores, en su calidad de docentes de química, han evidenciado la dificultad que encuentran los estudiantes cuando tienen que aplicar sus conocimientos de matemáticas en los procesos propios de la química, puesto que tienen problemas cuando tratan de implementar los procedimientos matemáticos para llevar a cabo los cálculos cuantitativos indispensables para realizar actividades prácticas de química, es decir, tienen inconvenientes para aplicar las matemáticas en química. Así pues, para solucionar este inconveniente se hace necesario correlacionar de manera adecuada los saberes de las asignaturas química y matemáticas para favorecer el proceso de enseñanza de los conceptos y procedimientos cuantitativos de química.The educational model implemented in the majority of institutions in high school education of our country the knowledge that gives they tends to be transmitted in a segmented and biased manner emphasizing a lack of interaction in learning, which results redounds in students approaching each subject independent and / or unrelated to the others subjects and, consequently, they have serious issues when it comes to build new knowledge The aim of this degree work of the authors, speaking as chemistry teachers, they have shown the difficulties who find in the students when they have to apply their knowledge in mathematics their own processes of chemistry, since they have problems when try to conduct the mathematical procedures for implementing the indispensable qualitative calculations to perform chemistry activities, it means they have problems to apply the mathematics in chemistry. Therefore, to solve this problem is necessary to correlate in correct way the knowledge of the chemical and mathematical subjects to strengthen the process of teaching the concepts and quantitative procedures of chemistry.Magíster en EducaciónMaestrí

Passive neutron area monitor with TLD pairs

The response of a passive neutron area monitor with pairs of thermoluminescent dosimeters has been calculated using the Monte Carlo code MCNP5. The response was calculated for one TLD 600 located at the center of a polyethylene moderator. The response was calculated for 47 monoenergetic neutron sources ranging from 1E(-9) to 20 MeV. Response was calculated using two irradiation geometries, one with an upper source and another with a lateral source. For both irradiation schemes the response was calculated with the TLD in two positions, one parallel to the source and another perpendicular to the source. The advantage of this passive neutron monitor area is that can be used in locations with intense, pulsed and mixed radiation fields like those in radiotherapy vault rooms with linear accelerators. La respuesta de un monitor de área pasivo para neutrones con pares de dosímetros termoluminiscentes TLDs ha sido calculada mediante métodos Montecarlo con el código MCNP5. La respuesta fue calculada para un TLD 600 localizado en el centro del moderador cilíndrico de polietileno. La respuesta se calculó para 47 fuentes mono energéticas de neutrones con energías de 1E (-9) a 20 MeV. La respuesta se calculó para dos geometrías de irradiación, una con una fuente superior y la otra con una fuente lateral, para ambas geometrías la respuesta se obtuvo con el TLD en dos posiciones respecto a la fuente, una perpendicular y la otra paralela. La ventaja del monitor pasivo es que puede ser usado en instalaciones con campos de radiación intensos, pulsados y mixtos como los que se producen en los bunkers de radioterapia con aceleradores lineales

10B+ZnS(Ag)as an alternative to 3He-based detectors for Radiation Portal Monitors

Typical radiation portal monitor systems, RPM, deployed to detect illicit trafficking of radioactive materials include a set of gamma-ray detectors and neutron detectors. Usually the employed neutron detectors are pressurized 3 He-based neutron detectors tubes. Due the shortage of 3 He reported since 2009, the amount of 3 He available for use in gas proportional counter neutron detectors has become limited, while the demand has significantly increased, especially for homeland security applications. For this reason, many different alternatives are being investigated for its use in RPM systems. The aim of this work is to study a scintillation detector ZnS(Ag) mixed with highly enriched 10B, 10B+ZnS(Ag). Using Monte Carlo methods, MCNPX code, the response of two neutron detectors based on 10B+ZnS(Ag), manufactured by BridgePort Instruments LLC with different geometries, were estimated by calculating the number of 10B(n,α) 7 Li reactions for 29 monoenergetic neutron sources. Measurements and models were made, and both detectors were compared. The importance of the distance with respect to the ground was studied. The response with a 252Cf moderated neutron source (0.5 cm lead and 2.5 cm polyethylene) was calculated in order to compare with other studied alternatives in the USA by Pacific National Northwest Laboratory, PNNL. With these results we conclude that neutron detectors using 10B+ZnS(Ag) are an interesting alternative for replacing 3 He detectors. From the analysis with MCNPX we propose an improvement in the detector design

Photon Shielding Features of Quarry Tuff

Cantera is a quarry tuff widely used in the building industry; in this work the shielding features of cantera were determined. The shielding characteristics were calculated using XCOM and MCNP5 codes for 0.03, 0.07, 0.1, 0.3, 0.662, 1, 2, and 3 MeV photons. With XCOM the mass interaction coefficients, and the total mass attenuation coefficients, were calculated. With the MCNP5 code a transmission experiment was modelled using a point-like source located 42 cm apart from a point-like detector. Between the source and the detector, cantera pieces with different thickness, ranging from 0 to 40 cm were included. The collided and uncollided photon fluence, the Kerma in air and the Ambient dose equivalent were estimated. With the uncollided fluence the linear attenuation coefficients were determined and compared with those calculated with XCOM. The linear attenuation coefficient for 0.662 MeV photons was compared with the coefficient measured with a NaI(Tl)-based -ray spectrometer and a 137Cs source

Efecto de la densidad de siembra y riego complementario en la morfo-fenología, rendimiento, rentabilidad y eficiencia de la fertilización del plátano

This research aimed to evaluate the effect of planting density and complementary irrigation on the morpho-phenology, yield, profitability, and efficiency of banana fertilization in the Carrizal River Valley, Ecuador. The treatments consisted of two production systems (irrigation and rainfed) and four planting densities (1500, 2000, 2500 and 3000 plants ha-1). The variables recorded were bunch weight (kg), fruit yield (boxes ha-1), net economic benefit (USD ha-1) and NPK agronomic efficiency. Supplementary irrigation increased production by 30%, compared to the rainfed system. The bunch weight was inversely proportional to the crop densities, while the fruit yield was proportional to the densities. The linear regression model showed an increase of 6.50 kg of fruit plant-1 with supplementary irrigation, while in rainfed the production was 4.99 kg of fruit plant-1, signaling a loss of 1.51 kg of fruit plant-1 due to lack of supplementary irrigation. The highest commercial yield and net economic benefit was 1398 boxes of fruit and 3665 USD ha-1, respectively, with 3000 plants ha-1 under supplementary irrigation.El objetivo de la investigación fue evaluar el efecto de la densidad de siembra y riego complementario en la morfo-fenología, rendimiento, rentabilidad y eficiencia de la fertilización del plátano en el valle del río Carrizal, Ecuador. Los tratamientos consistieron en dos sistemas de producción (riego y secano) y cuatro densidades de siembra (1500, 2000, 2500 y 3000 plantas ha-1). Las variables registradas fueron peso de racimo (kg), rendimiento de fruta (cajas ha-1), beneficio económico neto (USD ha-1) y eficiencia agronómica de NPK. El riego complementario incrementó la producción en 30%, en comparación al sistema de secano. El peso de racimo fue inversamente proporcional a las densidades de siembra, mientras que el rendimiento de fruta fue proporcional a las densidades. El modelo de regresión lineal mostró un incremento de 6,50 kg de fruta planta-1 con riego complementario, mientras que en secano fue de 4,99 kg de fruta planta-1, lo cual indicó una pérdida de 1,51 kg de fruta planta-1 por falta de riego complementario. El mayor rendimiento comercial y beneficio económico neto fue 1398 cajas de fruta y 3665 USD ha-1, respectivamente, con 3000 plantas ha-1 bajo riego complementario