Here we present a new proof of Blatter's result: a normed space is complete if every bounded closed convex subset has an element of minimum norm. We also present geometrical conditions for the existence of minimum-norm elements in bounded closed convex sets. Also, we characterize reflexivity in the class of Banach spaces by means of contraction functions. Furthermore, we study what happens if we remove the completeness hypothesis.
A refined chemical procedure for speciation studies of sediments has been thoroughly examined. The suggested method, although only tested on210Pb (210Po), could be applied to other chemical species, especially heavy metals and radioactive nuclides. Successive dissolutions using dilute HC1 (1–2.5%) and NaOH (0.5–1%) proved that the geochemistry of fulvic, humic, and mineral compounds plays an important role in the mobility, transport, and accumulation of210Pb in various aquatic systems. This work demonstrates that210Pb, as well as analogous isotopes and metals-based dating and tracing applications, could be further improved and extended using proper speciation techniques. The procedure given here allows not only evaluation of supported and unsupported210Pb but also the resolution of anomalies in modelling biogeochemical cycles.
Authors:M. Bordons, F. García-Jover, and S. Barrigon
The present study is a bibliometric analysis, of publications of Spanish pharmacologists, referenced in the journals of the Pharmacology & Pharmacy subfield of the Science Citation Index- CD Edition from 1984 to 1989. During this time the scientific output of Spanish pharmacologists has been growing at an impressive rate being almost doubled. This rate being notably greater than that corresponding to publications of Spain in all science fields. This increase in scientific output was accompanied by a time-dependent decrease on year by year step basis in the expected impact factor (EIF) of publications (Articles plus Notes), from 1.71 in 1984 to 1.28 in 1989, in close correlation with an increase of mean number of authors per paper, from 3.67 to 4.16 authors/paper, respectively. Moreover, the larger the number of authors/paper, the smaller the EIF. Only 8 journals cumulated more than 50% of the papers. The scientific production was geographically localized at a high extent (Barcelona, Madrid, Valencia accounted for the 63.7% of all the papers) in governmental institutions (University, 75.2%, Hospitals, 14.1%; CSIC, 10.5%) with one large geographical area lacking any productivity.
Authors:A. García-Villaraco Velasco, A. Probanza, F. Gutierrez Mañero, B. Ramos, and J. Lucas García
Activity and functional diversity of rhizosphere bacterial communities and fungal composition were studied in order to assess the effects of different genotypes (N8035, N224 and N8637) of
on these communities growing in different soils. Genotype effect and soil effect were studied independently. Also, the interactions between both factors (genotypes and soils) were considered. The activity was determined by thymidine and leucine incorporation analysis, and Biolog ECO plates were used to study bacterial functional diversity. Additionally, fungi groups (genera and/or species) were studied in the different rhizospheres. Statistical differences on thymidine incorporation between plant genotypes were only found in two of the soils. In addition, functional diversity (measured by Shanonn-Weaver index), showed statistical differences only in soil 1 for line N8035 (line B)
. the other lines. Redundancy analysis (RDA) performed with Biolog data indicated and important effect of soil type, but also an effect of genotype since line N8035 (line B) was separated from the other lines within each soil in the RDA ordination, in spite of genotypic differences between them were minimum. Furthermore, carboxylic acids and amino acids were found to be the Biolog plate substrates with more influence in samples ordination in the Redundancy Analysis (RDA). However, fungi seem to be less labile to plant selection than bacteria probably due to a lower turn-over time of fungi than bacteria coupled with the short phenology of
. In this paper, plant-soil-micro-organism relationships in the rhizosphere were studied, and the complex interactions between them were highlighted. More studies are necessary to go deep in these interactions and to be able to asses the impact of genetically modified plants.
Authors:J. Prieto Méndez, O. Acevedo Sandoval, and F. Prieto García
Soil structure stability depends on several factors and its assessment is conducted using different methods and prediction indices. One of the indicators is soil organic matter (SOM), since this helps to keep mineral particles together against destabilizing forces such as wetting and raindrop impact. However, previous studies have emphasized the relationship between aggregate stability and SOM content without considering its type or quality. Therefore, in this study the association between the quality and content of SOM and the structural stability of the surface layer was evaluated in three soils used for growing malting barley in the southern part of Hidalgo State, Mexico. With simple random sampling nine observation points were selected in each soil, where samples were taken in order to determine the stable aggregate size distribution, particle size distribution, content and fractionation of SOM, and the prediction indices of surface sealing and crusting derived from these characteristics. The soils showed low structural stability (except in Apan), as shown by the percentage runoff recorded in the field. There was a close association between the size (from 4 to 2 mm and <0.25 mm) of water-stable aggregates and the different fractions of SOM, while the fulvic acid (FA) fraction had a negative relationship with smaller aggregates (R = −0.84). Finally, it was found that only the FAO crusting index was able to predict the structural stability level in the soil.
Authors:G. Manjón, F. El-Daoushy, and R. García-Tenorio
For a better understanding of the behaviour of90Sr in aquatic systems, this -emitter has been determined in the different layers of a lake sediment core which has been previously dated using the well established210Pb dating method. For this, a radiochemical technique has been developed for the isolation of strontium from the sediment samples and for its activity measurement with a low-level gas-flow proportional counter. A conservative behaviour of90Sr in the water column remaining dissolved in the water body, can be inferred from the data obtained. Consequently, a possible90Sr transport pathway through the outflowing waters of the lake can be deduced.
Authors:F. Arellano, I. García-Sosa, and M. Solache-Ríos
The sorption behavior of cobalt and cadmium by zeolite Y has been investigated. Cobalt and cadmium solutions were exchanged with the zeolite at different pH's. Cobalt, cadmium and sodium in the samples were determined by neutron activation analysis. The sorption of cadmium was higher than that of cobalt, however, the selectivity for both cations by the zeolite was low.
Authors:M. Alonso, M. Oliet, J. García, F. Rodríguez, and J. Echeverría
Kinetics of thermosetting polymers curing is difficult to study by isothermal
methods based on the differential scanning calorimetry (DSC) technique. The
difficulty is due to the low sensitivity of the equipment for total reaction
heat measurements during high temperature process. The aim of this paper is
to display the equivalence between a dynamic model, the Ozawa method, and
an isothermal isoconversional fit, which allows predicting the isothermal
behavior of the resol resins cure through dynamic runs by DSC. In this work,
lignin–phenol–formaldehyde and commercial phenol–formaldehyde
resol resins were employed. In addition, the isothermal kinetic parameters
for both resins were performed by means of transformation of the data obtained
from the dynamic Ozawa method.
Authors:V. Braga, F. Garcia, J. Dias, and Sílvia Dias
Nb2O5 supported on SiO2-Al2O3 were prepared with a wide loading range (2, 5, 10, 15, 20 and 25 mass%) and analyzed by simultaneous thermogravimetric (TG)
and differential thermal analysis (DTA). The materials presented a phase transition close to 1364°C. This phase transition
was studied by XRD, FTIR and Raman spectroscopy. Amixture of orthorhombic (T) andmonoclinic (H andM) crystalline phases was
evidenced in the supported samples, which is coverage dependent, in contrast to the formation of only the monoclinic phase
(H and M) when pure Nb2O5 is heated under the same conditions. These results indicate the stabilization of Nb2O5 on silica-alumina surface.