Configuring the neighbourhood effect in irregular cellular automata based models

Cellular automata (CA) models have been widely employed to simulate urban growth and land use change. In order to represent urban space more realistically, new approaches to CA models have explored the use of vector data instead of traditional regular grids. However, the use of irregular CA-based models brings new challenges as well as opportunities. The most strongly affected factor when using an irregular space is neighbourhood. Although neighbourhood definition in an irregular environment has been reported in the literature, the question of how to model the neighbourhood effect remains largely unexplored. In order to shed light on this question, this paper proposed the use of spatial metrics to characterise and measure the neighbourhood effect in irregular CA-based models. These metrics, originally developed for raster environments, namely the enrichment factor and the neighbourhood index, were adapted and applied in the irregular space employed by the model. Using the results of these metrics, distance-decay functions were calculated to reproduce the push-and-pull effect between the simulated land uses. The outcomes of a total of 55 simulations (5 sets of different distance functions and 11 different neighbourhood definition distances) were compared with observed changes in the study area during the calibration period. Our results demonstrate that the proposed methodology improves the outcomes of the urban growth simulation model tested and could be applied to other irregular CA-based models.     

Impact of trace metals on denitrification in estuarine sediments of the Douro River estuary,Portugal

Denitrification influences the nitrogen budget in estuaries by removing fixed nitrogen from the inorganic pool; rates are dependent on both geological and geographic conditions as well as increasing anthropogenic impacts. In this study the effects of copper (Cu), chromium (Cr), zinc (Zn), cadmium (Cd) and lead (Pb), on the denitrification pathway were evaluated in subtidal and intertidal sediments of the Douro River estuary. Dinitrogen, N₂O and NO₂⁻ production rates were measured in triplicate slurries of field samples under different treatments of metal concentrations. Results demonstrated that similar metal amendments led to different site responses for denitrification, suggesting that variations in sediment properties (metal concentrations, grain size, organic matter content, etc.) and/or differences in denitrifying community tolerance modulate the level of metal toxicity. Denitrifying communities in subtidal muddy sediments were not affected by increasing concentrations of metals. In contrast, intertidal sandy sites revealed high sensitivity to almost all trace metals tested; almost complete inhibition by Cr (95%) and Cu (85%) was observed for 98 and 79 μg per gram of wet sediment respectively, and by Zn (92%) at the highest concentration added (490 μg per gram of wet sediment). Moreover, the addition of trace metals stimulated N₂O and NO₂⁻ accumulation in intertidal sandy (Zn, Cu, Cr and Cd) and muddy sediments (Cu and Zn), demonstrating a pronounced inhibitory effect on specific steps within the denitrification enzymatic system. In summary, the results obtained suggest that, according to the type of estuarine sediment, trace metals cannot only reduce total N removal from an estuary via denitrification but also can enhance the release of N₂O, a powerful greenhouse gas.     

Interpretation of the behaviour of agrowell systems in Sri Lanka using radial flow models

Abstract

This paper describes a study of the use of large diameter “agrowells” used for irrigation in Sri Lanka. Detailed field information for a single location is presented and a numerical radial flow model was used to interpret the field response. Initially the model was used to represent a pumping test in which the pumping and subsequent recovery were monitored. It was then used to investigate the operation of the well during a dry season. Satisfactory agreement could only be obtained when account was taken of the withdrawal of water from below the water table by trees. From the simulation it was possible to show that skilful farming practice could be used in steadily exploiting the resources for irrigation over the whole of the dry season.     

Mass segregation in young clusters: observational biases

We investigate the validity of the mass-segregation indicators most commonly used in the analysis of young stellar clusters. We construct and analyze synthetic massive clusters with a standard, fully sampled stellar initial mass function and a King density distribution function. We find that the commonly used indicators are highly sensitive to the effects of incompleteness in observational data, and that completeness determinations do not provide satisfactory corrections, leading to results that may be severely biased toward mass segregation.     

CEMPS: A prototype spatial decision support system to aid in planning emergency evacuations

CEMPS is a prototype spatial decision support system which links the topographical support and analysis provided by a geographic information system, ARC/INFO, with the ability to simulate the dynamics of an evacuation process. CEMPS has been designed to enable emergency planners to experiment with different emergency evacuation plans in order to devise a plan which meets their requirements. ARC/INFO is used to parameterize a dynamic simulation with topographical information and to display its results. The prototype runs on a Sun SPARCStation cluster but could be modified to run on other hardware and software.     

Antioxidant and antitumor potential of wild and IMTA-cultivated Osmundea pinnatifida

Osmundea pinnatifida is a red edible seaweed known as pepper dulse. O. pinnatifida was cultivated in the farm of ALGAplus(Ilhavo, Portugal). This farm is integrated with a seabream and seabass commercial aquaculture and uses the nutrient-enriched water resultant from the fish production as its cultivation medium in the integrated multi-trophic aquaculture(IMTA) manner. Wild and IMTA-cultivated samples of O. pinnatifida were screened for antioxidant and antitumor activities. The antioxidant capacity of solvent extracts from wild and IMTA cultivated samples was assessed in two methods(2,2-diphenyl-1-picrylhydrazyl(DPPH) and oxygen radical absorbance capacity(ORAC)), and their total phenolic contents(TPC) were estimated. Antitumor activity was evaluated in three different tumor cell lines(HepG-2, MCF-7, and SH-SY5Y) through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay. Among the solvents used for extraction, dichloromethane was the most effective to extract phenolic compounds and presented higher ORAC. A significant correlation was found between TPC and ORAC,which was also sustained by the principal components analysis(PCA). Dichloromethane extracts induced a cytostatic effect on MCF-7 cells and showed weak cytotoxicity to SH-SY5Y cells and weak impact on cell proliferation. Overall, there were no statistically significant differences in the biological activities shown by the wild and IMTA-cultivated samples. Hence, O. pinnatifida can be obtained in an economical and environmentally sustainable way through IMTA, maintaining bioactive properties in a high potential for further nutraceutical purposes.     

FINITE ELEMENT MODELLING OF A DEEP SEA CLAY IN LONG-TERM LABORATORY CREEP TESTS

A new finite element program is introduced and its predictive capabilities are compared to results from two long-term, drained laboratory creep tests on a deep sea clay. The constitutive behaviour is based on Cam clay critical state plasticity theory with creep and time-dependent hardening. Creep is computed using either Singh–Mitchell's three-dimensional equation or Taylor's secondary compression relationship. The experimental creep data include a triaxial specimen subjected to two deviatoric stress increments and a one-dimensional consolidation specimen subjected to three vertical stress increments. In addition, the pore pressure behaviour following an increase in stress is examined in the triaxial sample. Predictions compare favourably to test data, which provide confidence for applying the chosen constitutive model and numerical formulation to solve seabed-related problems on the continental slope that are of interest to geologists, the oil industry and the navy, among others.     

The Merzbacher & Eggler (1984) Geohygrometer: a Cautionary Note on its Suitability for High-K Suites

The use of the popular Merzbacher & Eggler (1984, Geology12, 587–590) experimental geohygrometer for calcalkalineandesites and dacites is critically evaluated and two pitfallsare found. First, calculation of the correct projection parametersis problematic because two endmember calculation schemes arefound in the literature; Baker & Eggler (1983, Journal ofVolcanology and Geothermal Research 18, 387–404) and Walkeret al. (1979, Contributions to Mineralogy and Petrology 70,111–125). Although related, these two schemes have crucialdifferences that can result in very different projection parametersfor the plagioclase component. This is most crucial for high-Kcompositions; H₂O contents estimated using the Walker et al.(1979) scheme can be as much as 100% higher than those estimatedusing the Baker & Eggler (1983) projection. Incorrect projectionparameter calculation has led to overestimation of water contentsin high-K andesites and dacites from the Central Andes. Second,for medium-K and high-K andesitic–dacitic compositionswater contents derived using the Merzbacher & Eggler (1984)geohygrometer deviate considerably from water contents estimatedusing other methods. Experimental data from the literature,and our studies of water contents inferred from melt inclusionsand plagioclase–melt equilibrium for dacites from theAltiplano–Puna Volcanic Complex of the Central Andes indicatethat the Merzbacher & Eggler (1984) geohygrometer shouldnot be applied to compositions with K₂O >1·9 wt %,as originally calibrated. KEY WORDS: magmatic volatiles; pre-eruptive water; experimental geohygrometer; high-K suites; melt inclusion     

Validation of Arenicola marina in field toxicity bioassays using benthic cages: biomarkers as tools for assessing sediment quality

Sediment toxicity assessments using caged organisms present advantages over using laboratory and native community studies. The use of caged Arenicola marina in sediment toxicity assessments was evaluated. Lugworms were exposed in situ to sediments from coastal and port areas in Spain for seven days, and the activities of the biotransformation enzymes ethoxyresorufin O-deethylase, dibenzylfluorescein dealkylase and glutathione S-transferase, the activities of the antioxidant enzymes glutathione reductase and glutathione peroxidase and lipid peroxidation were then analyzed as biomarkers. Biomarker results and sediment physicochemical data were integrated. Cádiz Bay (SW Spain) sediments presented metal contamination that was not linked to a biochemical response. In LPGC Port (SW Spain), Pb contamination exhibited a moderate toxic potential, while PAHs, and presumably pharmaceuticals, provoked biochemical responses that efficiently prevented lipid peroxidation. In Santander Bay (N Spain), exposure to PAHs and, presumably, pharmaceuticals induced biomarker responses, but lipid peroxidation occurred nevertheless. These results indicated that caged A. marina were effective for the assessment of sediment quality and that the selected biomarkers were sufficiently sensitive to identify chemical exposure and toxicity.     

Source characterization and spatio–temporal evolution of the metal pollution in the sediments of the Basque estuaries (Bay of Biscay)

According to Water Framework Directive requirements, Member States must identify and analyze effects derived from human pressures in aquatic systems. As different kind of pressures can impact water bodies at different scales, analyses of spatio-temporal evolution of water bodies becomes essential in order to understand ecosystem responses. In this investigation, an analysis of spatio-temporal evolution of sedimentary metal pollution (Cd, Cr, Cu, Hg, Ni, Pb, Zn) in 12 Basque estuaries (Bay of Biscay) is presented. Data collected in extensive sampling surveys is the basis for the GIS-based statistical approach used. The implementation of pollution abatement measures is reflected in a long-term decontamination process, mostly evident in estuaries with highest historical sediment pollution levels. Spatial evolution is determined by either naturally occurring or human driven processes. Such spatial processes are more obviously being reflected in estuaries with lower historical sediment pollution levels.