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It has long been established that mature forests are mosaics of patches in different development phases but it has seldom explicitly been taken into account in ecological studies. We demonstrate here that these development phases, which are related to the population dynamics of trees, play an important role in the distribution of fauna based on observations on frugivorous birds. In an area close to the Calakmul Biosphere Reserve in Mexico, we studied the abundance of large forest bird species in relation to forest development phases, with a methodology that seems promising for ecological diagnosis and prognosis in forest management planning. Fine-scale forest mapping and bird counts were carried out in two block-transects of 40 m x 3000 m. Tree sampling in a sub-transect was used to generate population characteristics of trees, Large bird species preferred mature or senescent forest patches, whereas relatively young, growing forest patches were avoided. Important large tree species such as Manilkara zapota, Thouinia paucidentata, Guaiacum sanctum and Esenbeckia pentaphylla, characteristic of older forest patches, showed skewed size distributions indicating stress or overexploitation. The population of M. zapota, a key fruiting species that accounted for 26.5% of the total woody biomass, was most heavily affected by stress. A future collapse in the population of M. zapota, a decrease of the total area of older forest, and a decline in the abundance of large birds is likely if stress on the system continues at this level. (C) 2008 Elsevier B.V. All rights reserved.

The influence of compost on the growth of bean plants irrigated with As-contaminated waters and its influence on the mobility of As in the soils and the uptake of As (as NaAs(III)O2) by plant components was studied at various compost application rates (3·10(4) and 6·10(4) kg ha(-1)) and at three As concentrations (1, 2 and 3 mg kg(-1)). The biomass and As and P concentrations of the roots, shoots and beans were determined at harvest time, as well as the chlorophyll content of the leaves and nonspecific and specifically bound As in the soil. The bean plants exposed to As showed typical phytotoxicity symptoms; no plants however died over the study. The biomass of the bean plants increased with the increasing amounts of compost added to the soil, attributed to the phytonutritive capacity of compost. Biomass decreased with increasing As concentrations, however, the reduction in the biomass was significantly lower with the addition of compost, indicating that the As phytotoxicity was alleviated by the compost. For the same As concentration, the As content of the roots, shoots and beans decreased with increasing compost added compared to the Control. This is due to partial immobilization of the As by the organic functional groups on the compost, either directly or through cation bridging. Most of the As adsorbed by the bean plants accumulated in the roots, while a scant allocation of As occurred in the beans. Hence, the addition of compost to soils could be used as an effective means to limit As accumulation in crops from As-contaminated waters.

In our continued efforts in the synthesis of ruthenium(II) polypyridine complexes as potential dyes for use in varied applications, such as the dye-sensitized solar cells (DSSCs), this work particularly describes the synthesis, absorption spectrum, redox behavior and luminescence properties of a new homoleptic ruthenium(II) complex bearing a simple trans-2-methyl-2-butenoic acid functionality as the anchoring ligand on terpyridine moiety. The functionalized terpyridine ligand: 4’-(trans-2-methyl-2-butenoic acid)-terpyridyl (L1) was synthesized by aryl bromide substitution on terpyridine in a basic reaction condition under palladium carbide catalysis. In particular, the photophysical and redox properties of the complex formulated as: bis-4’-(trans-2-methyl-2-butenoic acid)-terpyridyl ruthenium(II) bis-hexafluorophosphate [Ru(L1)2(PF6)2] are significantly better compared to those of [Ru(tpy)2]2+ and compare well with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical and redox properties of the complex may be attributed partly to the presence of a substituted α,β-unsaturated carboxylic acid moiety leading to increase in the length of π-conjugation bond thereby enhancing the MLCT-MC (Metal-to-ligand-charge transfer-metal centred) energy gap, and to the reduced difference between the minima of the excited and ground states potential energy surfaces.

The objective of this study was to determine the potential of Thermus thermophilus HB8 for accumulating a high level of extracellular, thermostable amylolytic enzyme. Initial production tests indicated clearly that only very low levels of amylolytic activity could be detected, solely from cells after extraction using the mild, non-ionic detergent Triton X-100. A sequential optimization strategy, based on statistical designs, was used to enhance greatly the production of extracellular amylolytic activity to achieve industrially attractive enzyme titers. Focus was placed on the optimal level of initial biomass concentration, culture medium composition and temperature for maximizing extracellular amylolytic enzyme accumulation. Empirical models were then developed describing the effects of the experimental parameters and their interactions on extracellular amylolytic enzyme production. Following such efforts, extracellular amylolytic enzyme accumulation was increased more than 70-fold, with enzyme titers in the 76 U/mL range. The crude extracellular enzyme was thereafter partially characterized. The optimal temperature and pH values were found to be 80 °C and 9.0, respectively. 100% of the initial enzyme activity could be recovered after incubation for 24 h at 80 °C, therefore, proving the very high thermostability of the enzyme preparation.

The Las Minas area corresponds to an exhumed geothermal system considered a proxy for the deep part of the nearby Los Humeros active geothermal system. The stratigraphic succession is made up of: Palaeozoic-Miocene granitoids, a thick Jurassic- Cretaceous carbonate succession, Neogene lava flows and volcano-sedimentary deposits. Linked to a Miocene magma intrusion, marble and skarn rock-volumes developed by contact metamorphism and geothermal fluid flow. Faults are arranged in SW- and NNW-striking systems. These controlled the morphological evolution and favored Neogene-Quaternary dyke emplacement. Faulting gave rise to a tectonic depression where lacustrine sediments and pyroclastics deposited. Skarn rocks are mainly located at fault intersections and along pre-existing discontinuities, suggesting the role of bedding and/or fractures in channeling deep fluids. Results give inputs for exploration at depth of Los Humeros geothermal system.

This study reports the fabrication of a new cathode electrode assembly using polyaniline (PANI) and graphene on a stainless steel mesh (SSM) as an alternative for the conventional expensive cathode of microbial electrolysis cells (MECs). With respect to the previous efforts to propose an efficient and cost-effective alternative for platinum (Pt) catalysts and cathode electrodes, the present study investigates the assessment of different catalysts to elucidate the potential of the modified SSM cathode electrode for larger-scale MECs. In the case of feeding dairy wastewater to the MEC, the maximum hydrogen production rate and COD removal were obtained by SSM/PANI/graphene cathode and had the values 0.805 m3 H2 m-3 anolyte day-1 and 82%, respectively, at the applied potential of 1 V. These values were only 20% and 7% lower than those of the MEC with Pt on the carbon cloth cathode, respectively. The coulombic efficiencies of SSM/Pt and SSM/PANI/graphene were seen to be 64.48% and 56.67%, respectively. It was also concluded that the fabrication cost of the modified cathode was 50% lower than the conventional cathodes with Pt on the carbon cloth. Finally, the evaluation of the modified cathode performance was achieved based on Fourier transform infrared spectroscopy, linear sweep voltammetry, scanning electron microscopy, and atomic force microscopy.