Biomedical subjects
I Magaña
Publications and source records attributed to I Magaña.
Modeling column regeneration effects on ion-exchange chromatography.
The effect of in-place regeneration on equilibrium and kinetic characteristics of the adsorption of bovine serum albumin to a DEAE-cellulose anion exchanger has been determined. Regeneration with sodium hydroxide and time of exposure showed no effect on equilibrium behavior. Breakthrough curves were measured for protein adsorption on fixed-bed columns and analyzed by a simple model to determine the relevant rate constants for the adsorption process. It was found that forward adsorption rate constant decreased exponentially with the chemical treatment exposure time. The implications of the results on the design and optimization of ion-exchange chromatographic processes are discussed.
A multiprocessor architecture for medical image compression in a PACS environment.
We present a new multiprocessor architecture for medical image compression using digital signal processors. The system has been designed to be used in a NuBus-based workstation and to apply different image compression algorithms to medical images. The system has been tested with a full-frame cosine transform and bit allocation table on several imaging modalities ranging from ultrasound to magnetic resonance imaging. Results show that image quality is acceptable when the allocation tables are calculated for each specific image modality. Implementation of algorithms such as wavelet transforms and vector quantization which respond to the characteristics of each type of image is in progress.
Delta'-dehydrogenation of steroids by Arthrobacter simplex immobilized in calcium polygalacturonate beads.
Arthrobacter simplex ATCC 6946 (viable cells) was immobilized in a calcium polygalacturonate gel. The trapped cells were used for repeated batchwise bioconversion of steroids. Reichstein's compound S and hydrocortisone were dehydrogenated introducing a double bond between C1 and C2 of ring A. The products 1-dehydro S and prednisolone, respectively, were identified by high pressure liquid chromatography. Steroid dehydrogenase activity increased in the system when an artificial electron acceptor, such as menadione (vitamin K3) was present in the reaction mixture. An airlift-type reactor was used to bioconvert up to 90% of substrate in 15 min, under optimal conditions. The gel entrapped cell preparations were used for repeated batch bioconversion during 30 days; 69 batch bioconversions for Reichstein's compound S were performed during 15 days of operation of the reactor. The operational stability of the process and the feasibility of repeated batch bioconversions was shown to be comparable to similar processes.
[Surgical experience in the management of penetrating injuries of the rectum].
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