Effects of land cover on chemical characteristics of streams in the Cerrado region of Brazil

The Cerrado is the second largest Brazilian biome and contains the headwaters of three major hydrological basins in Brazil. In spite of the biological and ecological relevance of this biome, there is little information about how land use changes affect the chemistry of low-order streams in the Cerrado. To evaluate these effects streams that drain areas under natural, rural, and urban land cover were sampled near Brasilia, Brazil. Water samples were collected between September 2004 and December 2006. Chemical concentrations generally followed the pattern of Urban > Rural > Natural. Median conductivity of stream water of 21.6 (interquartile: 22.7) mu S/cm in urban streams was three and five-fold greater relative to rural and natural areas, respectively. In the wet season, despite of increasing discharge, concentration of many solutes were higher, particularly in rural and natural streams. Streams also presented higher total dissolved N (TDN) loads from natural to rural and urban although DIN:DON ratios did not differ significantly. In natural and urban streams TDN was 80 and 77% dissolved organic N, respectively. These results indicate that alterations in land cover from natural to rural and urban are changing stream water chemistry in the Cerrado with increasing solute concentrations, in addition to increased TDN output in areas under urban cover, with potential effects on ecosystem function.

Natural and human forcing in recent geomorphic change; case studies in the Rio de la Plata basin

An analysis of geomorphic system`s response to change in human and natural drivers in some areas within the Rio de la Plata basin is presented The aim is to determine whether an acceleration of geomorphic processes has taken place in recent years and, if so, to what extent it is due to natural (climate) or human (land-use) drivers Study areas of different size, socio-economic and geomorphic conditions have been selected: the Rio de la Plata estuary and three sub-basins within its watershed Sediment cores were extracted and dated ((210)Pb) to determine sedimentation rates since the end of the 19th century. Rates were compared with time series on rainfall as well as human drivers such as population, GDP, livestock load, crop area, energy consumption or cement consumption, all of them related to human capacity to disturb land surface Data on river discharge were also gathered Results obtained indicate that sedimentation rates during the last century have remained essentially constant in a remote Andean basin, whereas they show important increases in the other two, particularly one located by the Sao Paulo metropolitan area Rates in the estuary are somewhere in between It appears that there is an intensification of denudation/sedimentation processes within the basin. Rainfall remained stable or varied very slightly during the period analysed and does not seem to explain increases of sedimentation rates observed. Human drivers, particularly those more directly related to capacity to disturb land surface (GDP, energy or cement consumption) show variations that suggest human forcing is a more likely explanation for the observed change in geomorphic processes It appears that a marked increase in denudation, of a ""technological"" nature, is taking place in this basin and leading to an acceleration of sediment supply This is coherent with similar increases observed in other regions (C) 2010 Elsevier B V All rights reserved

Stepped and smooth spillways: resistance effects on stilling basin lengths

The Darcy-Weisbach equation was used in the analysis of flow over spillways, furnishing theoretical tools to design stilling basins. Predictions for the length of hydraulic jump stilling basins downstream of stepped and smooth spillways are presented, together with ranges of values for the Darcy-Weisbach friction factor of both spillways. The experimental data were compared with results of the theoretical solution of the gradually varied flow equation. All comparisons were made in non-dimensional form. The values of the Darcy-Weisbach friction factor were roughly five times smaller for smooth spillways than for stepped spillways. The theoretical predictions and the experimental data allow to present approximate equations for a preliminary evaluation of the length and the bed level of hydraulic jump stilling basins. In the same way, approximate equations were presented for the evaluation of the friction factor in smooth and stepped spillways, as a function of the Froude number at the downstream cross-section.

Assessment of groundwater recharge and water fluxes of the Guarani Aquifer System, Brazil

The groundwater recharge and water fluxes of the Guarani Aquifer System in the state of Sao Paulo in Brazil were assessed through a numeric model. The study area (6,748 km(2)) comprises Jacar,-Gua double dagger A(0) and Jacar,-Pepira River watersheds, tributaries of the Tiet River in the central region of the state. GIS based tools were used in the storage, processing and analysis of data. Main hydrologic phenomena were selected, leading to a groundwater conceptual model, taking into account the significant outcrops occurring in the study area. Six recharge zones were related to the geologic formation and structures of the semi-confined and phreatic aquifer. The model was calibrated against the baseflows and static water levels of the wells. The results emphasize the strong interaction of groundwater flows between watersheds and the groundwater inflow into the rivers. It has been concluded that lateral groundwater exchanges between basins, the deep discharges to the regional system, and well exploitation were not significant aquifer outflows when compared to the aquifer recharge. The results have shown that the inflows from the river into the aquifer are significant and have the utmost importance since the aquifer is potentially more vulnerable in these places.

Novel sources of witches` broom resistance (causal agent Moniliophthora perniciosa) from natural populations of Theobroma cacao from the Brazilian Amazon

Witches` broom is a severe disease of Theobroma cacao L. (cacao), caused by the basidiomycete Moniliophthora perniciosa. The use of resistant cultivars is the ultimate method of control, but there are limited sources of resistance. Further, resistance from the most widely used source (`Scavina 6`) has been overcome after a few years of deployment. New sources of resistance have been intensively searched for in the Amazon basin. Here, we evaluated for witches` broom resistance, cacao accessions from various natural cacao populations originally collected in the Brazilian Amazon. Resistance of 43 families was evaluated under nursery and/or field conditions by artificial or natural infection, respectively, based on disease incidence. Screening for resistance by artificial inoculation under nursery conditions appeared to be efficient in identifying these novel resistance sources, confirmed by natural field evaluation over a nine-year period. The increase in natural field infection of `Scavina 6` was clearly demonstrated. Among the evaluated families with the least witches` broom incidence, there were accessions originally collected from distinct river basins, including the Jamari river (`CAB 0371`; `CAB 0388`; `CAB 0392`; and `CAB 0410`); Acre (`CAB 0169`); Javari (`CAB 0352`); Solimes (`CAB 0270`); and from the Purus river basin, the two most outstanding resistant accessions, `CAB 0208` and `CAB 0214`. The large genetic diversity found in cacao populations occurring at river basins from Acre and Amazonas states, Brazil, increased the chance that the selected resistant accessions would be genetically more dissimilar, and represent distinct sources of resistance to M. perniciosa from `Scavina 6`.

WATER RESOURCES SITUATION AT PIRACICABA, CAPIVARI AND JUNDIAI WATERSHEDS USING A DYNAMIC SYSTEMS MODEL

Using a dynamic systems model specifically developed for Piracicaba, Capivari and Jundia River Water Basins (BH-PCJ) as a tool to help to analyze water resources management alternatives for policy makers and decision takers, five simulations for 50 years timeframe were performed. The model estimates water supply and demand, as well as wastewater generation from the consumers at BH-PCJ. A run was performed using mean precipitation value constant, and keeping the actual water supply and demand rates, the business as usual scenario. Under these considerations, it is expected an increment of about similar to 76% on water demand, that similar to 39% of available water volume will come from wastewater reuse, and that waste load increases to similar to 91%. Falkenmark Index will change from 1,403 m(3) person(-1) year(-1) in 2004, to 734 m(3) P(-1) year(-1) by 2054, and the Sustainability Index from 0.44 to 0.20. Another four simulations were performed by affecting the annual precipitation by 90 and 110%; considering an ecological flow equal to 30% of the mean daily flow; and keeping the same rates for all other factors except for ecological flow and household water consumption. All of them showed a tendency to a water crisis in the near future at BH-PCJ.

Cultural revolution in whale songs

Humpbacks have picked up a catchy tune sung by immigrants from a distant ocean. The song patterns of humpback whales (Megaptera novaeangliae) depend on where they live, with populations inhabiting different ocean basins normally singing quite distinct songs. Here we record a unique and radical song change in the song of humpback whales in the Pacific Ocean off the Australian east coast. Their song was replaced rapidly and completely by the song of the Australian west coast population from the Indian Ocean, apparently as a result of the introduction of only a small number of 'foreign' singers. Such a revolutionary change is unprecedented in animal cultural vocal traditions and suggests that novelty may stimulate change in humpback whale songs.

Relative motions of Africa, Iberia and Europe during Alpine orogeny

A revised kinematic model for the motions of Africa and Iberia relative to Europe since the Middle Jurassic is presented in order to provide boundary conditions for Alpine-Mediterranean reconstructions. These motions were calculated using up-to-date kinematic data predominantly based on magnetic isochrons in the Atlantic Ocean and published by various authors during the last 15 years. It is shown that convergence of Africa with respect to Europe commenced during the Cretaceous Normal Superchron (CNS), between chrons MO and 34 (120-83 Ma). This motion was subjected to fluctuations in convergence rates characterised by two periods of relatively rapid convergence (during Late Cretaceous and Eocene-Oligocene times) that alternated with periods of slower convergence (during the Paleocene and since the Early Miocene). Distinct changes in plate kinematics are recognised in the motion of Iberia with respect to Europe, indicated by: (1) a Late Jurassic-Early Cretaceous left-lateral strike-slip motion; (2) Late Cretaceous convergence; (3) Paleocene quiescence; (4) a short period of right-lateral strike-slip motion; and (5) final Eocene-Oligocene convergence. Based on these results, it is speculated that a collisional episode in the Alpine orogeny at ca. 65 Ma resulted in a dramatic decrease in the relative plate motions and that a slower motion since the Early Miocene promoted extension in the Mediterranean back-arc basins. (C) 2002 Elsevier Science B.V. All rights reserved.

Effects of hot intrusions on pore-fluid flow and heat transfer in fluid-saturated rocks

We use the finite element method to solve coupled problems between pore-fluid flow and heat transfer in fluid-saturated porous rocks. In particular, we investigate the effects of both the hot pluton intrusion and topographically driven horizontal flow on the distributions of the pore-flow velocity and temperature in large-scale hydrothermal systems. Since general mineralization patterns are strongly dependent on distributions of both the pore-fluid velocity and temperature fields, the modern mineralization theory has been used to predict the general mineralization patterns in several realistic hydrothermal systems. The related numerical results have demonstrated that: (1) The existence of a hot intrusion can cause an increase in the maximum value of the pore-fluid velocity in the hydrothermal system. (2) The permeability of an intruded pluton is one of the sensitive parameters to control the pore-fluid flow, heat transfer and ore body formation in hydrothermal systems. (3) The maximum value of the pore-fluid velocity increases when the bottom temperature of the hydrothermal system is increased. (4) The topographically driven flow has significant effects on the pore-fluid flow, temperature distribution and precipitation pattern of minerals in hydrothermal systems. (5) The size of the computational domain may have some effects on the pore-fluid flow and heat transfer, indicating that the size of a hydrothermal system may affect the pore-fluid flow and heat transfer within the system. (C) 2003 Elsevier Science B.V. All rights reserved.

Theoretical and numerical analyses of convective instability in porous media with temperature-dependent viscosity

Exact analytical solutions of the critical Rayleigh numbers have been obtained for a hydrothermal system consisting of a horizontal porous layer with temperature-dependent viscosity. The boundary conditions considered are constant temperature and zero vertical Darcy velocity at both the top and bottom of the layer. Not only can the derived analytical solutions be readily used to examine the effect of the temperature-dependent viscosity on the temperature-gradient driven convective flow, but also they can be used to validate the numerical methods such as the finite-element method and finite-difference method for dealing with the same kind of problem. The related analytical and numerical results demonstrated that the temperature-dependent viscosity destabilizes the temperature-gradient driven convective flow and therefore, may affect the ore body formation and mineralization in the upper crust of the Earth. Copyright (C) 2003 John Wiley Sons, Ltd.

The Mesozoic and Cenozoic motion of Adria (central Mediterranean): a review of constraints and limitations

This paper presents kinematic analysis on the motion of Adria, which is the continental mass that bridges Africa and Europe in the central Mediterranean. Palaeomagnetic data show a general coherence between the motion of Adria and Africa since the Late Paleozoic. This mutual motion, for the period from 120 Ma and the present, is verified by comparing inferred palaeolatitudes from relatively stable parts of Adria (Apulia, Gargano, Istria, and the Southern Alps) and the Hyblean Plateau, with latitudinal changes that are calculated from the motion of Africa with respect to hotspots. Additional constraints on the motion of Adria are provided from the Late Paleozoic-Early Mesozoic passive margin of Adria in the Ionian Sea. The seismic structure of the floor of the Ionian Sea resembles the structure of the oceanic crust in marginal back-arc basins, suggesting that it formed as a small ocean basin. Furthermore, the Ionian lithosphere in the Calabrian arc has been subjected to rapid rollback, which commonly occurs only when the subducting slab is made of oceanic lithosphere. This oceanic domain marks the Pennian-Triassic to Jurassic plate boundary between Adria and Africa, suggesting that a small amount of independent motion between Adria and Africa took place at that time. Since the Jurassic, Adria and Africa have shared a relatively coherent motion path. (C) 2004 Lavoisier SAS. All rights reserved.

A Computational Study of Tetrafluoro-[2.2]Cyclophanes

A computational study of the isomers of tetrafluorinated [2.2]cyclophanes persubstituted in one ring, namely F-4-[2.2]paracyclophane (4), F-4-anti-[2.2]metacyclophane (5a), F-4-syn-[2.2]metacyclophane (5b), and F-4-[2.2]metaparacyclophane (6a and 6b), was carried out. The effects of fluorination on the geometries, relative energies, local and global aromaticity, and strain energies of the bridges and rings were investigated. An analysis of the electron density by B3PW91/6-31+G(d,p), B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) was carried out using the natural bond orbitals (NBO), natural steric analysis (NSA), and atoms in molecules (AIM) methods. The analysis of frontier molecular orbitals (MOs) was also employed. The results indicated that the molecular structure of [2.2]paracyclophane is the most affected by the fluorination. Isodesmic reactions showed that the fluorinated rings are more strained than the nonfluorinated ones. The NICS, HOMA, and PDI criteria evidenced that the fluorination affects the aromaticity of both the fluorinated and the nonfluorinated rings. The NBO and NSA analyses gave an indication that the fluorination increases not only the number of through-space interactions but also their magnitude. The AIM analysis suggested that the through-space interactions are restricted to the F-4-[2.2]metacyclophanes. In addition, the atomic properties, computed over the atomic basins, shave evidence that not only the substitution, but also the position of the bridges could affect the atomic charges. the first atomic moments, and the atomic volumes.

Continental extension: From core complexes to rigid block faulting

Extension of overthickened continental crust is commonly characterized by an early core complex stage of extension followed by a later stage of crustal-scale rigid block faulting. These two stages are clearly recognized during the extensional destruction of the Alpine orogen in northeast Corsica, where rigid block faulting overprinting core complex formation eventually led to crustal separation and the formation of a new oceanic backarc basin (the Ligurian Sea). Here we investigate the geodynamic evolution of continental extension by using a novel, fully coupled thermomechanical numerical model of the continental crust. We consider that the dynamic evolution is governed by fault weakening, which is generated by the evolution of the natural-state variables (i.e., pressure, deviatoric stress, temperature, and strain rate) and their associated energy fluxes. Our results show the appearance of a detachment layer that controls the initial separation of the brittle crust on characteristic listric faults, and a core complex formation that is exhuming strongly deformed rocks of the detachment zone and relatively undeformed crustal cores. This process is followed by a transitional period, characterized by an apparent tectonic quiescence, in which deformation is not localized and energy stored in the upper crust is transferred downward and causes self-organized mobilization of the lower crust. Eventually, the entire crust ruptures on major crosscutting faults, shifting the tectonic regime from core complex formation to wholesale rigid block faulting.

Metastable chaos in the ammonia ring laser

We report experimental studies of metastable chaos in the far-infrared ammonia ring: laser. When the laser pump power is switched from above chaos threshold to slightly below, chaotic intensity pulsations continue for a varying time afterward before decaying to either periodic or cw emission. The behavior is in good qualitative agreement with that predicted by the Lorenz equations, previously used to describe this laser. The statistical distribution of the duration of the chaotic transient is measured and shown to be in excellent agreement with the Lorenz equations in showing a modified exponential distribution. We also give a brief numerical analysis and graphical visualization of the Lorenz equations in phase space illustrating the boundary between the metastable chaotic and the stable fixed point basins of attraction. This provides an intuitive understanding of the metastable dynamics of the Lorenz equations and the experimental system.

Development and characterization of 15 microsatellite loci for Cariniana estrellensis and transferability to Cariniana legalis, two endangered tropical tree species

From a genomic library enriched for GA/CA repeats, 15 highly polymorphic microsatellite markers were developed for Cariniana estrellensis, a tropical forest tree. The microsatellite loci were screened in 49 mature trees found between Pardo river and Mogi-Gua double dagger u river basins, in the state of So Paulo, Brazil. A total of 140 alleles were detected with an average of 9.33 alleles per locus. The expected heterozygosity ranged from 0.37 to 0.88. These loci showed a high probability of paternity exclusion. Additionally, 12 loci were effectively transferred to Cariniana legalis. High levels of polymorphism make the present SSR markers useful for population genetic studies.