Mechanical Behavior of Concrete Modified by Replacement of Cement by Rice Husk Ash

ABSTRACT Construction industry is in need of lump sum quantities of materials which has increased both their demand and price. The use of large quantities of cement leads to increasing CO2 emission and as a consequence, the greenhouse effect. Consumption of wastes and byproducts from various sources in the manufacture of concrete has gained a great deal of importance in present days. Various researches are currently being conducted concerning the use of such products in concrete. RHA is a carbon neutral green product. Lots of ways are being thought of for disposing them by making commercial use of this. Rice husk ash is a good super-pozzolan which can be used to make special concrete mixes. The rice husk ash has been taken for this present study due to its easy availability and effective pozzolonic properties that are expected to improve the mechanical strength properties of concrete. Concrete specimens were made for evaluation of Compressive, Split Tensile, Flexural strength and Stress-Strain Behavior of concrete. The tests were conducted at the age of 7 and 28 days. Generally all mixes containing RHA achieved better properties than the conventional mix without RHA. By the experimental investigation the recommendation is given for using optimum percentage of RHA in concrete.

Controlled delivery of ranitidine in the stomach using magnetic field / Administración controlada de ranitidina en el estómago usando campos magnéticos

An attempt has been made to localize ranitidine loaded microspheres in the stomach by magnetic means. Since ranitidine undergoes metabolism by microbial enzymes in the intestine, it is ideal to localize the controlled drug delivery system within the stomach to get uniform release and absorption of the drug for the desired period. Gelatin magnetic microspheres loaded with 9.1, 17.9, 26.3 and 33.3% w/w of ranitidine hydrochloride were prepared by emulsification-cross linking technique. The formulated microspheres were characterized by magnetite content, particle size and in vitro drug release. The efficiency of microspheres to be localized in the stomach is tested in vivo in rats. The prepared microspheres were spherical and had a size distribution from 10 to 105 µm. The in vitro study revealed the capability of microspheres to release the drug over a period of 8 to 12 hours, depending on drug loading. The release was found to be diffusion controlled and followed fickian diffusion principle. The in vivo study showed the efficiency of microspheres to be retained in the stomach over a period of 8 hours.

Se ha hecho el intento por localizar las microesferas cargadas de ranitidina en el estómago mediante medios magnéticos. Como que la ranitidina experimenta metabolismo mediante enzimas microbianas en el intestino, resulta ideal localizar el sistema de administración del medicamento controlado dentro del estómago para alcanzar la liberación y absorción uniformes del medicamento por el período deseado. Microesferas de gelatina magnética cargadas con 9.1, 17.9, 26.3 y 33.3% p/p de hidrocloruro de ranitidina, fueron preparadas mediante una técnica de emulsificación-entrecruzamiento. Las microesferas formuladas se caracterizaron por su contenido de magnetita, el tamaño de las partículas y la liberación del medicamento in vitro. La eficiencia de las microesferas a ser localizadas en el estómago se prueba in vivo en ratas. Las microesferas preparadas eran esféricas y tenían una distribución de tamaño de 10 a 105 µm. El estudio in vitro reveló la capacidad de las microesferas para liberar la droga en un período de 8 a 12 horas, en dependencia de la carga de la droga. Se halló que la liberación estaba sujeta difusión controlada y seguía la ley de Fick para la difusión. El estudio in vivo mostró la eficiencia de las microesferas para ser retenidas en el estómago por un período de 8 horas.

Controlled delivery of ranitidine in the stomach using magnetic field.

An attempt has been made to localize ranitidine loaded microspheres in the stomach by magnetic means. Since ranitidine undergoes metabolism by microbial enzymes in the intestine, it is ideal to localize the controlled drug delivery system within the stomach to get uniform release and absorption of the drug for the desired period. Gelatin magnetic microspheres loaded with 9.1, 17.9, 26.3 and 33.3% w/w of ranitidine hydrochloride were prepared by emulsification-cross linking technique. The formulated microspheres were characterized by magnetite content, particle size and in vitro drug release. The efficiency of microspheres to be localized in the stomach is tested in vivo in rats. The prepared microspheres were spherical and had a size distribution from 10 to 105 microm. The in vitro study revealed the capability of microspheres to release the drug over a period of 8 to 12 hours, depending on drug loading. The release was found to be diffusion controlled and followed fickian diffusion principle. The in vivo study showed the efficiency of microspheres to be retained in the stomach over a period of 8 hours.