In this paper we study the Orlicz-Pettis property for a Boolean algebra. We characterize the countable Boolean algebras with this property and extend that study to some families of P(N). As a consequence, we obtain characterizations of weakly summing families in terms of the space c0 and in terms of some separation properties.
A new species of the monotypic endemic genus
Standl. was discovered in the Sierra Madre Occidental at the western part of the state Oaxaca, near to the border of the state Guerrero. The small leaved new species (
) holding the main characteristics of the genus
, the slightly asymmetrical tubular corolla and the broadly winged filaments inserted in the lower half of the corolla tube, just above of its narrow part, confirms the separation of the genus from
Borhidi. Key words: Mexico, new, Oaxaca,
Two new species of the genus
. Schltdl. et Cham. were collected in the Putla district of Oaxaca state, near to the Oaxaca-Guerrero border near to the southern end of the eastern wing of the Sierra Madre Occidental, both species belong to the group characterised by flowers of funnel-shaped corolla with longer tube than the corolla lobes, short filaments and included anthers in the throat, features different from those of the type species
and related species with rotated flowers with short tube and long corolla lobes, long exerted filaments and anthers. Based on the mentioned floral-morphological differences — similar to those detected formerly in the genus
Standl. — a new section is established for a group of five species under the name
Two new Rogiera species have been detected in the collections of the Andayu group of Oaxaca (R. oaxacensis) and of the State University of Tabasco (R. tabascensis). Both species are notable because of their pending, creeping, liana-like habit growing on calcareous rocks, which is a rare geological formation in the mountainous systems of México formed mostly by old crystalline cordilleras and young volcanic ridges. Up to now only one species of Rogiera, the R. subscandens from Chiapas and Guatemala has been known of this life-form.
Authors:P. Oropesa, A. Hernández, and R. Gutiérrez
The establishment of a quality management system is the best way to comply with international requirements concerning the achievement of confident and traceable analytical results. Some important points dealing with the technical factors of quality management in gamma-ray spectrometry of environmental samples are discussed. The experience obtained from analytical procedure validation is presented. Results of the application of standardized procedures to the analysis of ALMERA intercomparison samples, as well as the outcome of the utilization of certified reference materials for the quality control of measurement are presented. In fact, the implantation of simple technical principles reports reliable results and allows to elevate the quality of the measurements at a cost relatively low according to the real possibilities of the small laboratories, even in developing countries.
Authors:A. Rodríguez, B. López, A. Baca, and C. Gutiérrez
A great variety in retention properties occurs as a result of different methods of preparation of the sorbents. Specific surfaces and porosities, which are mostly connected with the sorption activities, may vary widely. The activation of Al2O3, SnO2 and silica gel, to produce highly active sorbents occurs only if the oxide is contacted with acid immediately after thermal treatment. The efficiency of the separation scheme has been tested using uranium and fission products under static conditions from strongly alkaline aqueous solutions.
Authors:C. Pico, A. Jerez, M. L. Veiga, and E. Gutierrez-Rios
The processes involved in the isothermal dehydration of hexaoxytelluric acid, Te(OH)6, are studied and the kinetic equations and activation energies corresponding to these processes are determined. The results are in agreement with a previously proposed structural model.
Authors:C. González, J. I Gutiérrez, J. R. González-Velasco, A. Cid, A. Arranz, and J. F. Arranz
Thermal decomposition of various synthetic manganese oxides (MnO, Mn3O4, Mn2O3, MnOOH) and a natural manganese dioxide (MnO2) from Gabon was studied with the help of termogravimetry in inert, oxidizing and reducing atmospheres. The compounds were characterized by XRD and electrochemical activity was tested by cyclic voltammetry using a carbon paste electrode. The natural manganese dioxide showed the best oxidizing and reducing capacity, confirmed by the lower temperatures of the transitions, the extent of the reactions and electrochemical performance in cyclic voltammograms.