Adriana Osorio

Preparation and characterization of superparamagnetic chitosan microspheres: Application as a support for the immobilization of tyrosinase

Journal of Applied Polymer Science, 2005

Superparamagnetic chitosan microspheres were prepared by a water-in-oil suspension-crosslinking t... more Superparamagnetic chitosan microspheres were prepared by a water-in-oil suspension-crosslinking technique. To this end, magnetite particles were dispersed in a chitosan solution in acetic acid. The dispersion was added to toluene containing Span 20 as a surfactant with stirring. Chitosan solution droplets were hardened with glutaraldehyde. The magnetic chitosan microspheres obtained were characterized with scanning electron microscopy, differential thermal analysis, and vibrational magnetometry. The microspheres had a wide size distribution, ranging from 43 ± 25 to 255 ± 55 μm, that depended on the reaction conditions. The mean particle size decreased with an increase in the concentration of Span 20 or the amount of glutaraldehyde and with the addition of NaCl. However, a major size reduction was achieved by an increase in the stirring rate. Tyrosinase was immobilized on the microspheres. The immobilized enzyme retained 70% of its activity, as determined by the capacity to degrade phenolic compounds. The immobilized tyrosinase resulted in greater stability than the free enzyme. In addition, the enzyme maintained 65% of its phenol oxidation activity after 10 cycles of reuse. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 651–657, 2005

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MOLIENDA DE CLINKER DE CEMENTO: EVALUACIÓN DE LA INFLUENCIA DE LA VELOCIDAD DE GIRO DEL MOLINO, EL TIEMPO DE RESIDENCIA Y LA CARGA DE LOS MEDIOS DE MOLIENDA CEMENT CLINKER GRINDING: EVALUATION OF MILL SPIN SPEED, RESIDENCE TIME AND GRINDING MEDIA LOAD

In this study, the milling of clinker was evaluated by varying the mill speed (24 and 72 RPM), re... more In this study, the milling of clinker was evaluated by varying the mill speed (24 and 72 RPM), residence time (3 and 5 hours) and grinding media load (30 and 40 %) in a ball mill. The experiment was designed as a three level factorial statistical model. The main objective was to assess the effect of these parameters on cumulative

MOLIENDA DE CLINKER DE CEMENTO: EVALUACIÓN DE LA INFLUENCIA DE LA VELOCIDAD DE GIRO DEL MOLINO, EL TIEMPO DE RESIDENCIA Y LA CARGA DE LOS MEDIOS DE MOLIENDA CEMENT CLINKER GRINDING: EVALUATION OF MILL SPIN SPEED, RESIDENCE TIME AND GRINDING MEDIA LOAD

In this study, the milling of clinker was evaluated by varying the mill speed (24 and 72 RPM), re... more In this study, the milling of clinker was evaluated by varying the mill speed (24 and 72 RPM), residence time (3 and 5 hours) and grinding media load (30 and 40 %) in a ball mill. The experiment was designed as a three level factorial statistical model. The main objective was to assess the effect of these parameters on cumulative

Evaluación de diferentes fuentes de carbono y de nitrógeno para la producción de renina a partir del moho Mucor miehei Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor miehei

... Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor... more

Evaluación de diferentes fuentes de carbono y de nitrógeno para la producción de renina a partir del moho Mucor miehei Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor miehei

... Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor... more

Evaluación de diferentes fuentes de carbono y de nitrógeno para la producción de renina a partir del moho Mucor miehei Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor miehei

... Evaluation of different sources of carbon and nitrogen in the production of rennet from Mucor... more

Gas phase thermolysis of allylphosphines, kinetic study

Heteroatom Chemistry, 1992

Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred-flo... more Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred-flow reactor at 380–429°C/7-20 torr, using toluene as carrier gas. The reaction products were propene, 1-phospha-1,3-butadiene, 1-phospha-1,2-diphenylethylene and 1-phosphaethylene.The phospha-alkenes formed evolve into cyclo addition products. The propene elimination reaction showed first-order kinetics with rate coefficients following the Arrhenius equations: Diallylphenylphosphine: k(s−1) = 1010.57 ± 0.31 exp(-143 ± 4 kJ/mol.RT) Allylbenzylphenylphosphine: k(s−1) = 109.71 ± 0.47 exp(-135 ± 6 kJ/mol.RT) Allylbenzylphenylphosphine: k(s−1) = 109.61 ± 0.61 exp(-144 ± 9 kJ/mol.RT) A six-center cyclic transition state unimolecular reaction mechanism, consistent with the above Arrhenius parameters, is proposed for the propene elimination reaction.

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CURSO BASICO DE LATIN

En latín **no existe acento gráfico**. El acento viene marcado por la cantidad[1] de la penúltima... more En latín **no existe acento gráfico**. El acento viene marcado por la cantidad[1] de la penúltima sílaba: si la penúltima sílaba es larga, la palabra es llana (//autumnus//); si la penúltima sílaba es breve, la palabra es esdrújula (//proelium//). Hay que observar que en latín no hay palabras agudas. ----[1] En latín hay **sílabas largas y sílabas breves**. Son sílabas largas las que contienen una vocal larga o diptongo; son sílabas breves las que contienen una vocal breve. Las reglas más generales para determinar la cantidad de las vocales son las siguientes: -Los diptongos son siempre largos. Los diptongos en latín clásico son: **ae, au, oe, eu **(//caelum//). -Una vocal seguida de dos o más consonantes o consonante doble es larga (//ancilla//). -Una vocal seguida de otra vocal es breve (//filia//). Los CASOS son las diferentes formas que pueden adoptar los sustantivos, adjetivos y pronombres según la función que desempeñen en la oración.

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