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Se presenta una reseña del artículo "Close-packed structure dynamics with finite-range interaction: Computational mechanics with individual layer interaction" de E. Rodríguez-Horta, E. Estevez-Rams, R. Lora-Serrano y R. Neder, y publicado en la revista "Acta Crystallographica."

The aim of this work was to characterize the natural clinoptilolite from Tasajeras deposit, Cuba, modified by hydrothermal ion-exchange with solutions of iron (II) sulfate and iron (III) nitrate in acid medium. Besides this, its catalytic activity to reduce nitrogen monoxide with carbon monoxide/propene in the presence of oxygen was evaluated. The characterization was performed by Mössbauer and UV-Vis diffuse reflectance spectroscopies and adsorption measurements. The obtained results lead to conclude that in exchanged samples, incorporated divalent and trivalent irons are found in octahedral coordination. Both irons should be mainly in cationic extra-framework positions inside clinoptilolite channels as charge compensating cations, and also as iron oxy-hydroxides resulting from limited hydrolysis of these cations. The iron (III) exchanged samples has a larger amount of iron oxy-hydroxides agglomerates. The iron (II) exchanged samples have additionally iron (II) sulfate adsorbed. The catalytic activity in the nitrogen monoxide reduction is higher in the exchanged zeolites than starting. Among all samples, those exchanged of iron (II) has the higher catalytic activity. This lead to outline that, main catalytically active centers are associated with divalent iron. [ABSTRACT FROM AUTHOR]

Se presenta un obituario del químico cubano José Fernando Fernández-Bertrán

The diabetes mellitus is a chronic metabolic dysfunction whose incidence has left increasing in the entire world. The antihiperglicemiants are drugs that are used in the patient's metabolic control, it is important for our diabetic patients the obtaining of a drug of this type that contributes to control the levels of glucose in blood in the periods postpandrials. Our work group is developing a derived product of the natural zeolites (FZ) that have named Glicolit; in previous studies it has shown effects on the intestinal absorption of glucose, slowing the absorption and the increments in blood after the periods postpandrials, this drug at the same time allows these fellows to improve the quality of life and to slow the complications characteristic of this illness. To know the effectiveness of the drug, as well as to deep in the action mechanisms and the kinetics of absorption of the same one. 15 rats were studied, at 6 of them they were administered a preparation of labeled glucose with 14C, in you fast (group 1 control), and to other 9 remaining they were administered a preparation that contained labeled glucose more Glicolit (group 2) . We carried out extractions of blood and radio-active counts in the plasm at different times: it was observed differences in the areas under the curves of absorption of the glucose between both groups of rats, the Glicolit showed its capacity like antihiperglicemiant. The reached results allow us to continue working in the study of this possible medication. The results obtained by the method radioisotopic with marked glucose with 14 C also corroborate the results of previous studies. [ABSTRACT FROM AUTHOR]

Natural purified mordenite from Palmarito de Cauto (ZP) deposit, Cuba, was subjected to a hydrothermal ion exchange process in acid medium with Fe2+ or Fe3+ salts (Fe2+ZP and Fe3+ZP). The set of samples was characterized regarding their textural properties, morphology, and crystallinity, and tested in the NO reduction with CO/C3H6. Infrared spectroscopy coupled with NO as a probe molecule was used to give a qualitative description of the Fe species' nature and distribution. The exchange process caused an increase in the iron loading of the samples and a redistribution, resulting in more dispersed Fe2+ and Fe3+ species. When contacted with the NO probe, Fe2+ZP showed the highest intensity of nitrosyl bands, assigned to NO adducts on isolated/highly dispersed Fe2+/Fe3+ extra-framework sites and FexOy clusters. This sample is also characterized by the highest NO sorption capacity and activity in NO reduction. Fe3+ZP showed a higher intensity of nitrosonium (NO+) species, without a correlation to NO storage and conversion, pointing to the reactivity of small FexOy aggregates in providing oxygen atoms for the NO to NO+ reaction. The same sites are proposed to be responsible for the higher production of CO2 observed on this sample, and thus to be detrimental to the activity in NO SCR. [ABSTRACT FROM AUTHOR]