Sodium titanium germanate with a semicrystalline framework (STG) of the formula Na3H(TiO)3(GeO)(GeO4)3·7H2O was synthesized under mild hydrothermal conditions and its proton form, H4(TiO)3(GeO)(GeO4)3·8H2O (STG-H), was prepared by acid treatment of the sodium compound. The STG was characterized by elemental analysis, TGA, FT-IR,
and X-ray powder diffraction. A comparative ion exchange examination of the STG-H towards alkali and alkaline earth metals
in a broad pH and concentration range was carried out. It was found that the STG is a moderately weak cation exchanger, possessing
high ion exchange capacity (up to 4.0 meq/g) and showing preference for heavy alkali and alkaline earth metals. The STG selectivity
towards Cs+ and Sr2+ ions in the presence of competitive metal ions and certain organic compounds was also studied. The data obtained suggest
that the sodium titanium germanate is a more selective exchanger for Sr2+ ion than its titanium silicate analogue, K3H(TiO)4(SiO4)3·4H2O.
A new species of the genus
(Guettardeae, Rubiaceae) from Chiapas, South Mexico, was collected by the second author.
sp. n. is closely related to
C. M. Taylor, but differs from it by having short 4-lobed inflorescence axes and flowers occulted by long bracteoles.
From the excellent collection of Albert Reyes-García made in Sierra Morena (southwestern part of the Sierra Madre de Chiapas) appeared some plants of high interest; among them two beautiful new species, belonging to the recently described
genus considered formerly as a monotypic endemic one. The present paper contains the description of the two new species named
, and the amplified description of the genus.
The new Psychotria species belongs to the panamensis-mexiae complex with its large long deciduous ferrugineous terminal stipules, but differs from them by having shorter inflorescence, 2–3 times larger flowers, smaller leaves and less numerous secondary nerves. It is of allopatric distribution being endemic to Jalisco state, while the area of P. mexiae Standl. extends from Veracruz to Costa Rica and the populations of P. panamensis Standl. are found from Veracruz to Colombia.
was described in 2006 based on a fruited specimen collected by the experts of INEGI in Jalisco. Two years later, several unidentified specimens arrived to the MEXU from the collection of the Estación de Investigaciones Biológicas de la UNAM in Chamela. Several flowering specimens of this collection permitted to the authors to complete the original description of this notable species endemic to state Jalisco.
The valuable plant collection of INEGI has not been
considered according to its merit. A preliminary study of the Rubiaceae family
led to the discovery of two new species: Bouvardia castilloi and Randia
Authors:E. Berriochoa, A. Cachafeiro, and J. García-Amor
We characterize the supports of the measures having quadrature formulae with similar exactness as Gauss’ theorem. Indeed we
obtain the supports of the measures from which an m-point quadrature formula can be obtained such that it exactly integrates functions in the space ℙm−k,m−k[
Authors:R. Mercader, E. Baran, and A. López-García
The Mössbauer parameters of anhydrous monoclinic tin/II/ phosphate, Sn3/PO4/2, are reported and briefly discussed. The results agree with the interactions expected from the crystalline structure but differ from previously reported data.