Curvature and velocity of methane-air Bunsen flame tips

PIV and photographic recording are used to measure the velocity of the fresh gas and the shape of the reaction layer in a region around the tip of a methane- air Bunsen flame attached to a cylindrical burner. The results compare well with numerical simulations carried out with an infinite activation energy reaction model. The experimental and numerical results confirm that the well-known linear relation between flame velocity and flame stretch derived from asymptotic theory for weakly curved and strained flames is valid for small and moderate values of the flame stretch if the modified definition of stretch introduced by Echekki and Mungal (Proc Combust Inst 23:455–461,1990) and Poinsot et al. (Combust Sci Technol 81:45–73,1992) is used. However, the relation between flame velocity and modified stretch ceases to be linear and approaches a square root law for large values of the stretch, when the curvature of the flame tip becomes large compared to the inverse of the thickness of a planar flam

Measurement of the burning velocity of strongly curved methane-air flames

An experimental and numerical study has been carried out of the region around the tip of a methane-air premixed flame attached to a circular laminar jet burner. On the experimental side, photographic records and PIV have been used to measure the shape of the reaction layer and the velocity of the gas around the tip of the flame. The numerical part of the study includes simulations of stationary axisymmetric flames with infinitely high activation energy reactions. The experimental and numerical results compare well with each other and allow to determine the curvature of the reaction layer at the tip and the velocity and strain rate of the fresh gas flow along the axis of the burner. These data, together with the planar flame velocity determined by extrapolating the velocity of the flame at the tip to the limit of zero stretch, are used to assess the well-known linear flame-velocity/flame-stretch relationship originally proposed by Markstein and later derived in the asymptotic limit of weakly curved and strained flames [1, 2], as well as the phenomenological modification proposed more recently by Mungal and coworker

Curvature and burning velocity of Bunsen Flame tips.

The burning velocity of a premixed flame propagating in a given flammable mixture is known to depend on the difference between the curvature of the flame and the so-called curvature of the flow, which is the strain rate of the flow of fresh gas along the normal to the flame divided by the burning velocity of the planar flame. The difference between the local burning velocity and the burning velocity of a planar flame in a gas at rest is proportional to the difference of the flame and flow curvatures. The proportionality factor is the product of the burning velocity of the planar flame and the Markstein length, which is an intrinsic property of the flame that characterizes its dynamics. The Markstein length can be determined experimentally by simultaneously measuring the curvature of the flame and the strain rate of the flow. To achieve this goal, we have set up a laminar jet burner and used two PIV systems to measure the gas flow velocity in two perpendicular planes normal to the flame. Each PIV system is composed by two Q-switched Nd: YAG pulse lasers (New Wave, maximum 120 mJ/pulse at 532 nm wavelength), a double-shuttered cross-correlation camera (PCO, 1392 × 1040 pixels) and a pulse generator (ILA GmbH) to synchronize all the components as well as the two PIV systems. Oil droplets are used for tracking the flow and the flame. They are formed by condensation after oil evaporation in a seeding chamber placed in the air line. Seeded air and fuel gas (CO,H2, CH4) are mixed in a settling chamber upstream of the burner and burned in a stationary Bunsen flame. The oil droplets evaporate in the flame preheating region, thereby allowing a dual tomography of the front

Local burning velocity in a Bunsen jet flame

A PIV-based system has been set-up for the simultaneous measurement of the local burning velocity of premixed flames and the flame stretch due to the flame front curvature and the incoming flow strain rate. For moderately short jet flames, these measurements allow an indirect determination of the Markstein length, according to Clavin and Joulin (C–J) theory. For tall flames, the flame curvature becomes relatively large in a region around the tip where the C–J theory breaks down. However, our experiments confirm the appearance of a new linear relation between burning velocity and curvature at the flame tip. This relation defines a new proportionality factor which is probably associated to the evolution from rounded tips to slender tips when the jet velocity is increased

Sweetened nopal flakes: a functional snack

Nopal (Opuntia spp. and Nopalea spp. genera) is a crop, recognized for its nutritional and medicinal properties; however, there are some underused species, despite the great genetic diversity in Mexico. The genus Opuntia spp. is the most consumed nopal, whereas Nopalea spp. has low commercial demand, possibly because their nutraceutical attributes are unknown. Additionally, the nopal pads or cladodes are little accepted by many consumers, due to their texture and flavor. The study objectives were 1) evaluate the nutraceutical content and antioxidant activity of four nopal cultivars: Nopalea cochenillifera cv. Texas (NT) and Opuntia ficus-indica cv. Jade (OJ), Milpa Alta (OMA), and Atlixco (OA); 2) develop nopal flakes, sweetened with rebaudioside A, from the cultivar with the best nutraceutical quality and sensory acceptability. Ascorbic acid, total phenolics, and total flavonoids were determined by spectrophotometric methods, individual flavonoids (quercetin, kaempferol, and isorhamnetin) by HPLC, and antioxidant activity by the DPPH assay. OA was the cultivar with the best nutraceutical quality. The sweetened nopal flakes of OA, at a concentration of 1.1 mg g-1 rebaudioside A, had the highest sensory acceptability by the panelists in intensity and sweetness preference. The addition of rebaudioside A improved the product’s flavor and contributed to preserve the flavonoids and antioxidant activity. These results will contribute to the chemotaxonomy of O. ficus-indica and N. cochellinifera species,and to the utilization of nopals as functional foods, due to their nutraceutical quality

Nutritional value and antioxidant activity of the maguey syrup (Agave salmiana and A. mapisaga) obtained through three treatments

During the Pre-Colombian period magueys were used in Mesoamerica for their sap, which is named “aguamiel” (literally “honey water” in Spanish). Aguamiel is then fermented into “pulque”, followed by (in order of importance): textiles, apparel, different thicknesses cords, food (sweetener, syrup, vinegar, flower buds, and cooked immature flowering stalks), firewood and construction materials. The maguey syrup is a product that is traditionally obtained by concentrating the aguamiel by means of an artisanal evaporation treatment (high temperatures, atmospheric pressure and prolonged times). The nutritional and nutraceutical value of this concentrate is unknown despite its wide consumption since pre-Hispanic times in various regions of Mexico. The objective of this work was to evaluate the nutritional value and the content of antioxidant compounds of the maguey syrup obtained from the aguamiel (Agave salmiana and A. mapisaga) through three elaboration treatments (artisanal evaporation, evaporation under reduced pressure and lyophilization). The best species for the production of maguey syrup turned out to be the aguamiel of the A. salmiana due to its nutritional and nutraceutical attributes, higher content of reducing sugars and lower sucrose compared to that of A. mapisaga. The maguey syrup is a sweetener with a higher content of protein (3320 mg 100-1) in comparison to bee honey (152.7 mg 100 g-1). The maguey syrup obtained by lyophilization (LYT) retained the nutraceutical value; but its antioxidant activity was statistically equal to the syrup obtained by evaporation under reduced pressure (RPT), and the artisanal evaporation treatment (AET) had a decrease in vitamin C content in comparison to LYT and RPT. The syrups obtained by RPT and AET presented different degrees of non-enzymatic darkening, possibly due to the formation of melanoidins (dark pigments). The darkest syrup obtained by AET had the highest antioxidant capacity (987.24 μM TE 100 g-1) associated to a higher content of phenolic compounds (593.74 mg GAE 100 g-1)

Una emulsión lipídica basada exclusivamente en aceite de pescado revierte la colestasis

Prolonged parenteral nutrition (PN) leads to liver damage. Recent interest has focused on the lipid component of PN. A lipid emulsion based on w-3 fatty acids decrease conjugated bilirubin. A mixed lipid emulsion derived from soybean, coconut, olive, and fish oils reverses jaundice. Here we report the reversal of cholestasis and the improvement of enteral feeding tolerance in 1 infant with intestinal failure-associated liver disease. Treatment involved the substitution of a mixed lipid emulsion with one containing primarily omega-3 fatty acids during 37 days. Growth and biochemical tests of liver function improved significantly. This suggests that fat emulsions made from fish oils may be more effective means of treating this condition compared with an intravenous lipid emulsion containing soybean oil, medium -chain triglycerides, olive oil, and fish oilLa nutrición parenteral prolongada produce daño hepático. Recientemente se ha comunicado el efecto de las emulsiones lipídicas intravenosas basadas exclusivamente en ácidos grasos omega-3 en la resolución de la colestasis. Lo mismo se ha observado con el uso de emulsiones lipídicas mixta derivadas del aceite de soja, coco, oliva y pescado. Comunicamos la desaparición de colestasis y mejoría de la tolerancia enteral en un niño con enfermedad hepática asociada a nutrición parenteral. El tratamiento consistió en sustituir una emulsión lipídica mixta por otra que contenía de forma exclusiva aceite de pescado durante 37 días. El crecimiento y los datos bioquímicos de función hepática mejoraron de forma significativa. Este caso sugiere que emulsiones lipídicas intravenosas a partir de aceite de pescado pueden ser mas eficaces para tratar la colestasis si se comparan con emulsiones mixta

SISTEMA PARA LA GESTIÓN DE INDICADORES ECONÓMICOS PARA LA DIRECCIÓN MUNICIPAL DE ECONOMÍA Y PLANIFICACIÓN DE CIEGO DE ÁVILA

El presente artículo se basa en el diseño, implementación y prueba del sistema informático de gestión de indicadores económicos. Expone las temáticas fundamentales sobre la obtención de información de cómo se reviste el desarrollo a nivel empresarial de la Dirección Provincial de Economía y Planificación de Ciego de Ávila. Se fundamenta la información obtenida como base para la comprensión y análisis del conocimiento teórico, para generarla toma de decisiones, siendo el resultado la creación de un sistema informático para la gestión de los indicadores económicos. Se basa en el perfeccionamiento del servicio y mostrando un control en la organización de la información de manera más fácil, sencilla, segura y rápida. Se brinda una variedad de reportes y vistas de cada uno de los indicadores de forma mensual y anual. Todas estas propuestas en conjunto llevaran a facilitar en una mayor escala la labor de los trabajadores convirtiendo todo el proceso en una aplicación semiautomática dando paso al desarrollo de las tecnologías en el sector laborar del país

Fruits of the pitahaya Hylocereus undatus and H. ocamponis: nutritional components and antioxidants

The pitahaya (Hylocereus spp.) is a cactus native to America. Despite the great diversity of species located in Mexico, there are few studies on the nutritional and nutraceutical value of its exotic fruits, ancestrally consumed in the Mayan culture. An evaluation was made regarding the physical-chemical characteristics, the nutritional components and the antioxidants of the fruits of H. ocamponis (mesocarp or red pulp) and H. undatus (white pulp), species of great commercial importance. The pulp of the fruits presented nutritional and nutraceutical differences between both species. The red pulp of H. ocamponis presented the highest content of betalains (15.94 mg 100 g-1), ascorbic acid (10.13 AAE mg 100 g-1) and antioxidant activity (2009.58 μM TE 100 g-1) compared to that of H. undatus. The seeds of both species had a higher content of linoleic acid (ω-6) compared to other fatty acids. The underused skin (epicarp) of the white pulp pitahaya presented a higher content of betalains (19.83 mg 100 g-1) than that found in the pulp and the red skin of the other species (13.21 mg 100 g-1). The red pitahaya that is for regional consumption presented a better functional quality. The skin of both species could be a source of pigments in the food industry

Sitio web Salvemos el planeta para la preparación de los estudiantes en educación ambiental

Uno de los retos de la pedagogía cubana es lograr la dirección eficiente de la formación integral de los jóvenes. La investigación aborda la necesidad de perfeccionar el proceso de formación integral de los estudiantes. El objetivo de la misma se direcciona hacia la validación del Sitio Web Salvemos el planeta para contribuir a la preparación del tercer año del Instituto Politécnico de Servicios “José Ramón Fuerte Cano” del municipio de Cabaiguán en la educación ambiental. Los resultados confirman la posibilidad de mejorar la preparación de los estudiantes, denotándose un cambio significativo en los mismos. Con la Web se logró un diseño integral, coherente y práctico para trabajar los contenidos relacionados con la educación ambiental en este nivel de enseñanza