RESUMO
In this study, the convective heating/cooling process assisted by US irradiation is analyzed with the aims of developing a new convective heat transfer correlation. Heat transfer experiments were conducted with different copper machined geometries (cube, sphere and cylinder), fluid velocities (0.93-5.00 × 10-3 m/s), temperatures (5-60 °C), and US intensities (0-6913 W/m2) using water as heat transfer fluid. The Nusselt (Nu) equation was obtained by assuming an apparent Nu number in the US-assisted process, expressed as the sum of contributions of the forced convection and cavitation-acoustic streaming effects. The Nu equation was validated with two sets of experiments conducted with a mixture of ethylene glycol and water (1:1 V/V) or a CaCl2 aqueous solution (30 g/L) as immersion media, achieving a satisfactory reproduction of experimental data, with mean relative deviations of 17.6 and 17.8%, respectively. In addition, a conduction model with source term and the proposed correlation were applied to the analysis of US-accelerated heating kinetics of dry-cured ham reported in literature. Results demonstrated that US improves heating of ham slices because of the increased heat transfer coefficients and the direct absorption of US power by the foodstuff.
RESUMO
An automated method to determine the band gap energy (E g ) of pure and mixed powder compounds using diffuse reflectance spectroscopy is presented. This method is based on a five-step algorithm that mimics the judgment made by an expert analyst in identifying the linear segments in Tauc plots and subsequent estimation of the E g value. It is demonstrated that the method to estimate E g by intersecting the straight-line fit of the Tauc segment with the photon energy axis is not appropriate for those samples containing more than one optical absorbing phase because systematic underestimation of the E g value results. The automated method accounts for such cases by introducing a base line function. The robustness of the implemented algorithm was tested using three model systems, ZnO-Al2O3, ZnO-CoO and ZnO-CdO. The estimated E g 's using the automated method differ in less than 1% than those obtained by its manual counterpart.
RESUMO
BACKGROUND: Huntington's disease (HD) is a hereditary disease of the central nervous system. Its molecular diagnosis has allowed predictive and prenatal diagnosis to be done, and it is now a model for the study of the ethical, legal, and social problems arising from the diagnosis of such diseases. METHODS: This study explores the knowledge and attitudes of a group of Mexican specialists regarding the disease and its diagnosis. A self-administered, 30-item multiple-choice questionnaire was completed anonymously by neurologists, psychiatrists, and psychologists. RESULTS: Fifty-five percent of the professionals had experience with HD patients, 59% claimed to know the hereditary risks, and 20% answered incorrectly concerning the risks. Neurologists had the most exposure to HD; 74% acknowledged the existence of predictive diagnosis, although only 10% knew the international guidelines for testing. Eighty-six percent of the participants recommended predictive diagnosis, the reasons being: 55%, if the patients considered having offspring; 41%, for the patient's professional reasons; 6%, if a treatment was available, and 12% did not answer. In cases in which the patient wanted to have offspring, 38% thought that this should be avoided. Thirty-six percent of the subjects considered prenatal diagnosis justified in a couple with a carrier, and 51% justified abortion for affected fetuses. CONCLUSIONS: Genetic counseling and predictive diagnosis in Mexico must be the responsibility of genetics units and specialists who are aware of inheritance risks and of guidelines for HD programs. The number of patients requiring such attention is increasing rapidly.