Authors:J. Ontiveros-Cuadras, A. Ruiz-Fernández, J. Sanchez-Cabeza, L. Wee-Kwong, and L. Pérez-Bernal
210Pb activities were analyzed in surface sediments from the Coatzacoalcos River (Gulf of Mexico) to evaluate its distribution
according to sediment grain size and in different geochemical compartments by using sequential extraction techniques. The
geochemical fractionation experiments provided compatible results: by using the Tessier’s method [<cite>1</cite>] more than 90% of the 210Pb activity in the samples was found the residual fraction (primary and secondary minerals) and the remaining (<10%) in the
iron and manganese oxides fraction of the sediments; whereas using the Huerta-Diaz and Morse method [<cite>2</cite>] the 210Pb content was found in comparative amounts in the reactive, the silicate, and the pyrite fractions (accounting together for
>80%), and the rest was found in the residual fraction. The grain size fractionation analyses showed that the 210Pb activities were mostly retained in the clay fraction, accounting up to 60–70% of the 210Pb total activity in the sediment sample and therefore, it is concluded that the separation of the clay fraction can be useful
to improve the analysis of low 210Pb content sediments for dating purposes.
Motivated by the well known Kadec-Pełczynski disjointification theorem, we undertake an analysis of the supports of non-zero functions in strongly embedded subspaces of Banach functions spaces. The main aim is to isolate those properties that bring additional information on strongly embedded subspaces. This is the case of the support localization property, which is a necessary condition fulfilled by all strongly embedded subspaces. Several examples that involve Rademacher functions, the Volterra operator, Lorentz spaces or Orlicz spaces are provided.
Authors:L. Franco, C. Sánchez, R. Bravo, A. Rodriguez, C. Barriga, and Javier Juánez
The hop (Humulus lupulus), a component of beer, is a sedative plant whose pharmacological activity is due principally to its bitter resins, especially to the α-acid component 2-methyl-3-buten-2-ol. The mechanism of action of the resin of hop consists of increasing the activity of the neurotransmitter γ-aminobutyric (GABA), inhibiting the central nervous system (CNS). Objectives: To analyze in an experimental model of diurnal animal the sedative effect of hop, a component of beer, on the activity/rest rhythm. Methods: Experiments were performed with common quail (Coturnix coturnix) similar to humans in the sleep-wake rhythm, isolated in 25 × 25 × 25 cm methacrylate cages, with food and water ad libitum, in a room with artificial ventilation (22 ± 1 °C) and a lighting cycle of 12L/12D (n = 5). The doses administered, close to the content of non-alcoholic beer, were 1, 2 and 11 mg extract of hop as one capsule per day, at 18:00 h for one week. A control group received capsules only with a methylcellulose excipient and a basal group received no treatment. The chronobiological analysis of the animals’ activity captured and logged by the software DAS24 was performed using the Ritme computer program (cosinor methods). Results: With the dose of 2 mg, there was a statistically significant (p < 0.05) reduction of the arithmetic mean nocturnal activity (23 ± 3.0) with respect to the basal (38.56 ± 2.79), control (38.1 ± 2.8) and other doses groups 1 mg (52.04 ± 3.65) and 11 mg (47.47 ± 5.88). This dose of 2 mg, similar to the concentration in beer, was more effective in reducing nocturnal activity than the other doses of 1 and 11 mg, as well as preserving the circadian activity/rest rhythm. Conclusion: The concentration of 2 mg of hop extract effectively decreased nocturnal activity in the circadian activity rhythm. On the basis of this investigation, administration of non-alcoholic beer would be recommended due to its hop content and consequent sedative action, which would be an aid to nocturnal sleep.
Authors:E. T. Stepkowska, S. Yariv, J. L. Pérez-Rodríguez, A. Justo, A. Ruiz-Conde, and P. Sánchez-Soto
A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM).
Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10–50 μm, formation of macropores of similar size, unhomogeneity and fissures between aggregates and “super-aggregates”. Macropores were detectable by the initial drying rate especially at 45°C. They indicated a tendency of collapsing at a lower drying rate at 30°C. This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying.
The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure.
XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower.
From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.
Authors:J. M. Ginés, M. J. Arias, A. M. Rabasco, C. Novák, A. Ruiz-Conde, and P. J. Sánchez-Soto
In the present study, the effect of the molecular weight and thermal treatments on commercial polyethylene glycols (PEG) samples used in the pharmaceutical processing technology, has been analyzed using DSC and HSM. The molecular weight of these polymers range from 1500 to 200000. Thermal investigations on the melting behavior of original PEG samples (as received from the manufacturer) showed only one single melting DSC endotherm effect before 373 K. This fact was associated to the presence of only one type of polymeric chain. Using standard conditions, PEG samples were solidified from the melt at 373 K, either by flash cooling (using liquid nitrogen and an ice bath) and by slow cooling, soaked and by slow cooling at room temperature. They were further studied by DSC. It was found that after cooling, PEG with molecular weight 1500 and 15000 showed DSC thermograms with a single endothermic peak. However, thermograms for PEG 4000 and 6000 produced a splitted melting endotherm. This fact was attributed to the presence of two types of chains, that are the folded and extended chains.
Authors:F. J. Martínez Casado, M. Ramos Riesco, M. I. Redondo Yélamos, A. Sánchez Arenas, and J. A. Rodríguez Cheda
Four mesomorphic states of matter are known: liquid crystal, plastic crystal, condis phase, and rotator phase, all of them are solid phases, except liquid crystal, which is fluid. Plastic crystal (also called ODIC, orientational disordered crystal), rotator phase, and even condis phase have been considered the same phase by many authors. Differences between them will be established to define their own characteristics. Two organic salts series have been used for discussion in this presentation: (1) thallium(I) alkanoate series, that presents a condis mesophase, and (2) lead(II) alkanoate series, that present a rotator one, both forming a smectic A-like liquid crystal phase. Based in the literature data of the alkyl ammonium bromide series it can be established that the short chain length members would present a rotator phase, and, the large chain ones, a condis phase. Five different glass states are known (four with partial crystalline order), corresponding with the above mentioned mesophases, and the ordinary (amorphous) glass state.
Authors:O.N. Campas-Baypoli, D.I. Sánchez-Machado, C. Bueno-Solano, A.A. Escárcega-Galaz, and J. López-Cervantes
Moringa oleifera tree has been recognized internationally for its nutritional, therapeutic and medicinal properties. Dry seeds are rich sources of oil with a high potential of commercial exploitation. The present study reports the physicochemical characterization, polyphenol content, DPPH radical scavenging capacity and fatty acid profile of moringa seed oil, and the chemical composition of the seed cultivated in Sonora, Mexico. Moisture, ash, protein and lipid contents in the seed were found to be 4.7, 5.8, 26 and 39%, respectively. The oil showed a refractive index of 1.4642. The saponification number was 183 mg KOH/g oil, iodine value: 75 g I/100 g of oil, acid value: 0.49 (% oleic acid). The polyphenol content was 0.137 mg of gallic acid equivalent/g and DPPH radical scavenging capacity was 87.39%. The moringa seed oil was rich (68%) in the major fatty acid, oleic acid (C18:1n9). Moringa oil extracted by sonication showed a fatty acid profile and physicochemical properties comparable to the oil from seeds grown in different regions of the world. The optimization of the oil extraction process on a large scale shows high potential, as the oil could be marketed as edible vegetable oil, for frying purposes, or as a functional ingredient.
Authors:C. Wehenkel, A. Reyes-Martínez, J. H. Martínez-Guerrero, C. Pinedo-Alvarez, and C. A. López-Sánchez
Bird migration constitutes a redistribution of bird diversity that radically changes the composition of the bird community worldwide. It comprises about 19% of the world’s bird species. Several studies have indicated that changes in avian community structure and differences in bird richness in different seasons are mainly driven by seasonality and by winter harshness, and that the associated costs increase with the distance involved. Western Mexico is an important wintering area for most passerines that breed in western North America, and that travel long on the long-distance Central and Pacific migration routes. In this study, we examined bird species richness and diversity during the breeding and wintering seasons in the Central Sierra Madre Occidental (SMO), North Durango (Mexico) in relation to i) tree species diversity, ii) tree dimension, iii) forest stand density and site quality, iv) density and dimension of snag trees, and v) various climate variables. The overall aim of the study was to determine how the observed associations between bird species diversity and variables i-v are affected by the season considered (breeding or wintering). The diversity of bird species in the breeding season was not affected by any of the climate and forest stand variables considered. In contrast, bird species diversity in the wintering season was significantly and weakly to moderately associated with climate variables, tree species diversity and stand density, although not with density or dimension of snag trees. Bird species diversity was higher at lower elevations and in drier and warmer locations of the SMO. The association detected is therefore mainly a local migratory phenomenon.
Authors:M. A. García del Cid, M. G. Prolongo, C. Salom, C. Arribas, M. Sánchez-Cabezudo, and R. M. Masegosa
Epoxy–clay nanocomposites have been prepared with an organically modified montmorillonite. The epoxy network was based on diglycidyl ether of bisphenol A (DGEBA) cured with diaminodiphenylmethane (DDM). The stoichiometry DGEBA–DDM was varied, the molar ratio of amine hydrogen/epoxy groups, r, ranged from 0.85 to 1.15. The influence of stoichiometry on curing and properties of the nanocomposites was studied using differential scanning calorimetry, dynamic mechanical thermal analysis and X-ray diffraction. All nanocomposites had intercalated clay structures. The clays accelerated the curing reaction whose rate was also increased when increasing r. The heat of reaction, −ΔH (J/g epoxy), increased as r increased, reaching a constant value for r ≥ 1. In the presence of clays −ΔH was lower than in the neat DGEBA–DDM. The glass transition temperature (Tg) of the neat epoxy thermosets reached a maximum at r = 1; however, the nanocomposites showed the Tg maximum at 0.9 < r < 1. The presence of clay lowered the Tg for r > 0.94 and raised Tg for r ≤ 0.85. The elastic modulus of neat epoxy thermosets reached a maximum in the rubber state and a minimum in the glassy state at r = 1. The nanocomposites showed similar behavior, but the maximum and the minimum values of the elastic modulus were reached at stoichiometry r < 1. The comparison of the properties of neat epoxy with those of the nanocomposites varying the stoichiometry indicates that the clay itself induces stoichiometric changes in the system.
Authors:L. E. Garcia-Megias, E. Colacio-Rodriguez, A. Garcia-Rodriguez, J. Ruiz-Sanchez, and J. M. Salas-Peregrin
The thermal behaviour of 6-amino-5-formyluracil (HFU), 6-amino-1-methyl-5-formyluracil (1-MFU), 6-amino-3-methyl-5-formyluracil (3-HFU) and 6-amino-1,3-dimethyl-5-formyluracil (HDFU) is described. Only HDFU is shown to contain crystallization water. Dehydration and fusion enthalpy values have been calculated from the DSC curves. Likewise, the thermal behaviour of new complexes obtained by reaction between the above pyrimidine derivatives and Ni(II), Cu(II) and Pd(II) ions is reported.