Método de estudo da adsorção de triadimenol com micro-colunas de solo e centrifugação

Normally, the determination of equilibrium constants (k d) in batch experiments uses a high solution to soil ratio, which does not represent field conditions. In this study we present an alternative method to evaluate adsorption constants, using micro-columns of soil at higher soil to solution ratios. The centrifugation force and equilibration time were investigated. The triadimenol distribution along the column profile is controlled by diffusion and equilibration times greater than 24 h are needed to achieve reproducibility. The centrifugation force must be superior to 670 g in order to guarantee enough extraction of the liquid solution from the soil columns.

Factors affecting Hg (II) adsorption in soils from the Rio Negro basin (Amazon)

Mercury (II) adsorption studies in top soils (top 10 cm) from the Rio Negro basin show this process depends strongly on some selected parameters of the aqueous phase in contact with the soils. Maximum adsorption occurred in the pH range 3.0-5.0 (>90%). Dissolved organic matter shows an inhibitory effect on the availability of Hg (II) to be adsorbed by the soils, whereas a higher chloride content of the solution resulted in a lower adsorption of Hg (II) at pH 5.0. Soils with higher organic matter content were less affected by changes in the salinity. An increase in the initial Hg (II) concentration increased the amount of Hg (II) adsorbed by the soil and decreased the time needed to reach equilibrium. A Freundlich isotherm provided a good model for Hg (II) adsorption in the two types of soil studied. The kinetics of Hg (II) adsorption on Amazonian soils showed to be very fast and followed pseudo-second order kinetics. An environmental implication of these results is discussed under the real scenario present in the Negro River basin, where acidic waters are in contact with a soil naturally rich in mercury.

Síntese de sulfadiazina e sulfadiazina de prata em escala semi-micro: prática experimental em síntese de fármacos

The total synthesis of sulfadiazine and silver sulfadiazine from readily available starting materials was adapted to semi-micro laboratory scale and is proposed as an experiment in drug synthesis for undergraduate courses.

The age of the"Grande Coupure" mammal turnover: New constraints from the Eocene Oligocene record of the Eastern Ebro Basin (NE Spain.)

The Grande Coupure represents a major terrestrial faunal turnover recorded in Eurasia associated with the overall climate shift at the Eocene-Oligocene transition. During this event, a large number of European Eocene endemic mammals became extinct and new Asian immigrants appeared. The absolute age of the Grande Coupure, however, has remained controversial for decades. The Late Eocene-Oligocene continental record of the Eastern Ebro Basin (NE Spain) constitutes a unique opportunity to build a robust magnetostratigraphy- based chronostratigraphy which can contribute with independent age constraints for this important turnover. This study presents new magnetostratigraphic data of a 495-m-thick section (Moià-Santpedor) that ranges from 36.1 Ma to 33.3 Ma. The integration of the new results with previous litho- bio- and magnetostratigraphic records of the Ebro Basin yields accurate ages for the immediately pre- and post-Grand Coupure mammal fossil assemblages found in the study area, bracketing the Grande Coupure to an age embracing the Eocene-Oligocene transition, with a maximum allowable lag of 0.5 Myr with respect to this boundary. The shift to drier conditions that accompanied the global cooling at the Eocene-Oligocene transition probably determined the sedimentary trends in the Eastern Ebro Basin. The occurrence and expansion of an amalgamated-channel sandstone unit is interpreted as the forced response of the fluvial fan system to the transient retraction of the central-basin lake systems. The new results from the Ebro Basin allow us to revisit correlations for the controversial Eocene-Oligocene record of the Hampshire Basin (Isle of Wight, UK), and their implications for the calibration of the Mammal Palaeogene reference levels MP18 to MP21.

20 Myr of eccentricity paced lacustrine cycles in the Cenozoic Ebro Basin

Long-period orbital forcing is a crucial component of the major global climate shifts during the Cenozoic as revealed in marine pelagic records. A complementary regional perspective of climate change can be assessed from internally drained lake basins, which are directly affected by insolation and precipitation balance. The Ebro Basin in northeastern Iberia embraces a 20 Myr long continuous sedimentary record where recurrent expansions and retractions of the central lacustrine system suggest periodic shifts of water balance due to orbital oscillations. In order to test climatic (orbital) forcing a key-piece of the basin, the Los Monegros lacustrine system, has been analyzed in detail. The cyclostratigraphic analysis points to orbital eccentricity as pacemaker of short to long-term lacustrine sequences, and reveals a correlation of maxima of the 100-kyr, 400-kyr and 2.4-Myr eccentricity cycles with periods of lake expansion. A magnetostratigraphy-based chronostratigraphy of the complete continental record allows further assessing long-period orbital forcing at basin scale, a view that challenges alternate scenarios where the stratigraphic architecture in foreland systems is preferably associated to tectonic processes. We conclude that while the location of lacustrine depocenters reacted to the long-term tectonic-driven accommodation changes, shorter wavelenght oscillations of lake environments, still million-year scale, claims for a dominance of orbital forcing. We suggest a decoupling between (tectonic) supply-driven clastic sequences fed from basin margins and (climatic) base level-driven lacustrine sequences in active settings with medium to large sediment transfer systems.

Preparação de amostra de fígado bovino e estudo de micro homogeneidade para a determinação de Cd E Pb por espectrometria de absorção atômica com atomização eletrotérmica e amostragem direta de sólido

This work describes a systematic study for bovine liver sample preparation for Cd and Pb determination by solid sampling electrothermal atomic absorption spectrometry. Samples were prepared using different procedures: (1) drying in a household microwave oven followed by drying in a stove at 60 ºC until constant mass, and (2) freeze-drying. Ball and cryogenic mills were used for grinding. Particle size, sample size and micro sample homogeneity were investigated. All prepared samples showed good homogeneity (He < 10) even for low sample mass, but samples dried in a microwave oven/stove and ground in a ball mill presented the best homogeneity.

Aplicação catalítica de peneiras moleculares básicas micro e mesoporosas

Catalysis by solid acids has received much attention due to its importance in petroleum refining and petrochemical processes. Relatively few studies have focused on catalysis by bases and even les on using basic molecular sieves. This paper deals with the potential application of micro and mesoporous molecular sieves in base catalysis reactions. The paper is divided in two parts, the first one dedicated to the design of the catalysts and the second to some relevant examples of catalytic reactions, which find a huge field of applications essentially in the synthesis of fine chemicals. Here, recent developments in catalysis by basic molecular sieves and the perspectives of applications in correlated catalytic processes are described.

A Practical Micro Mechanical Model Based Local Approach Methodology for the Analysis of Ductile Fracture of Welded T-Joints

This thesis concentrates on developing a practical local approach methodology based on micro mechanical models for the analysis of ductile fracture of welded joints. Two major problems involved in the local approach, namely the dilational constitutive relation reflecting the softening behaviour of material, and the failure criterion associated with the constitutive equation, have been studied in detail. Firstly, considerable efforts were made on the numerical integration and computer implementation for the non trivial dilational Gurson Tvergaard model. Considering the weaknesses of the widely used Euler forward integration algorithms, a family of generalized mid point algorithms is proposed for the Gurson Tvergaard model. Correspondingly, based on the decomposition of stresses into hydrostatic and deviatoric parts, an explicit seven parameter expression for the consistent tangent moduli of the algorithms is presented. This explicit formula avoids any matrix inversion during numerical iteration and thus greatly facilitates the computer implementation of the algorithms and increase the efficiency of the code. The accuracy of the proposed algorithms and other conventional algorithms has been assessed in a systematic manner in order to highlight the best algorithm for this study. The accurate and efficient performance of present finite element implementation of the proposed algorithms has been demonstrated by various numerical examples. It has been found that the true mid point algorithm (a = 0.5) is the most accurate one when the deviatoric strain increment is radial to the yield surface and it is very important to use the consistent tangent moduli in the Newton iteration procedure. Secondly, an assessment of the consistency of current local failure criteria for ductile fracture, the critical void growth criterion, the constant critical void volume fraction criterion and Thomason's plastic limit load failure criterion, has been made. Significant differences in the predictions of ductility by the three criteria were found. By assuming the void grows spherically and using the void volume fraction from the Gurson Tvergaard model to calculate the current void matrix geometry, Thomason's failure criterion has been modified and a new failure criterion for the Gurson Tvergaard model is presented. Comparison with Koplik and Needleman's finite element results shows that the new failure criterion is fairly accurate indeed. A novel feature of the new failure criterion is that a mechanism for void coalescence is incorporated into the constitutive model. Hence the material failure is a natural result of the development of macroscopic plastic flow and the microscopic internal necking mechanism. By the new failure criterion, the critical void volume fraction is not a material constant and the initial void volume fraction and/or void nucleation parameters essentially control the material failure. This feature is very desirable and makes the numerical calibration of void nucleation parameters(s) possible and physically sound. Thirdly, a local approach methodology based on the above two major contributions has been built up in ABAQUS via the user material subroutine UMAT and applied to welded T joints. By using the void nucleation parameters calibrated from simple smooth and notched specimens, it was found that the fracture behaviour of the welded T joints can be well predicted using present methodology. This application has shown how the damage parameters of both base material and heat affected zone (HAZ) material can be obtained in a step by step manner and how useful and capable the local approach methodology is in the analysis of fracture behaviour and crack development as well as structural integrity assessment of practical problems where non homogeneous materials are involved. Finally, a procedure for the possible engineering application of the present methodology is suggested and discussed.

Private micro-irrigation costs using reclaimed water

The cost of reusing water in micro-irrigation at the field level has not been studied in depth although the use of effluents in agriculture is a viable alternative in areas where water is scarce or there is intense competition for its use. The aim of the present study is to analyse the private costs of water reuse in micro-irrigation in an experimental plot. This analysis is intended to provide information about the decision a farmer would make when the choice to use conventional or reclaimed water is guided by cost criteria. The components of the total costs of different combinations of four types of filters and five emitters that can be installed in micro-irrigation systems using reclaimed water have been studied with the data obtained from an experimental plot in conditions similar to those of fruit orchards. Different scenarios that compared the costs of using conventional or reclaimed water in terms of water price and nutrient content were also studied. The results show that a proper combination of filters and emitters can save up to 33% in irrigation costs. Capital costs and maintenance costs were the most variable among the different combinations. Scenario analysis showed that the greater price of reclaimed water could be compensated by high nutrient contents, which would reduce fertilizer costs

Determinação do coeficiente de atividade na diluição infinita (g¥) através da micro-extração em fase sólida (SPME)

In this study a new approach, solid phase micro extraction (SPME), is used in the evaluation of the infinite dilution activity coefficient of the solute in a given solvent. It is the purpose of the current work to demonstrate a different approach to obtain the data needed for studying the solution thermodynamics of binary liquid mixtures as well as for designing multi-component separations. The solutes investigated at the temperature 298.15 K were toluene, ethyl benzene and xylene in the solvent methanol.

Organochlorine pesticides in Piracicaba river basin (São Paulo/Brazil): a survey of sediment, bivalve and fish

The main objective of this paper was to evaluate the level of occurrence of the organochlorine compounds in samples of sediments, bivalves and two fish species collected in the Piracicaba River basin (São Paulo, Brazil). The isomers alpha and gamma of HCH and Heptachlor were most frequently detected in samples of sediments and specimens of bivalve and fish. Therefore, although the levels of these compounds found were not critically high, they are still found in the environment. This fact suggests that they are still being used, despite the fact that the use of these compounds was outlawed more than twenty years ago.

Bioprocessos para remoção de dióxido de carbono e óxido de nitrogênio por micro-algas visando a utilização de gases gerados durante a combustão do carvão

The aim of this work was to study the removal of CO2 and NO by microalgae and to evaluate the kinetic characteristics of the cultures. Spirulina sp. showed µmax and Xmax (0.11 d-1, 1.11 g L-1 d-1) when treated with CO2 and NaNO3. The maximum CO2 removal was 22.97% for S. obliquus treated with KNO3 and atmospheric CO2. The S. obliquus showed maximum NO removal (21.30%) when treated with NO and CO2. Coupling the cultivation of these microalgae with the removal of CO2 and NO has the potential not only to reduce the costs of culture media but also to offset carbon and nitrogen emissions.

Micro- and nanostructuring of poly(ethylene-2,6-naphthalate) surfaces, for biomedical applications, using polymer replication techniques

Here we investigate the formation of superficial micro- and nanostructures in poly(ethylene-2,6-naphthalate) (PEN), with a view to their use in biomedical device applications, and compare its performance with a polymer commonly used for the fabrication of these devices, poly(methyl methacrylate) (PMMA). The PEN is found to replicate both micro- and nanostructures in its surface, albeit requiring more forceful replication conditions than PMMA, producing a slight increase in surface hydrophilicity. This ability to form micro/nanostructures, allied to biocompatibility and good optical transparency, suggests that PEN could be a useful material for production of, or for incorporation into, transparent devices for biomedical applications. Such devices will be able to be autoclaved, due to the polymer's high temperature stability, and will be useful for applications where forceful experimental conditions are required, due to a superior chemical resistance over PMMA.

Determinação de metil-etil-cetona em amostras de urina com amostragem por micro extração em fase sólida (MEFS) em headspace associada à cromatografia gasosa com detector de ionização de chama (CG-DIC)

Methyl ethyl ketone (MEK) is a solvent commonly used in chemical, paint and shoe industry. The aim of this study was to develop and validate a method for urinary quantification of MEK, employing headspace solid phase micro extraction sampling (SPME) coupled to gas chromatography with flame ionization detection (GC-FID). The calibration curve (y=4.6851x-0.0011) presented good linearity with r²=0.9993. Accuracy (94-109%), intra-assay precision (4.07-5.91%) and inter-assay precision (3.03-5.62%) were acceptable. The quantification limit was 0.19 mg/L. This low cost method can be used routinely in the biological monitoring of occupational exposure to MEK, according to the requirements of the Brazilian legislation.

Impacts of climate change on water resources in the Mediterranean basin : a case study in Catalonia, Spain

Most climate change projections show important decreases in water availability in the Mediterranean region by the end of this century. We assess those main climate change impacts on water resources in three medium-sized catchments with varying climatic conditions in north-eastern Spain. A combination of hydrological modelling and climate projections with B1 and A2 IPCC emission scenarios is performed to infer future stream flows. The largest reduction (22-48% for 2076-2100) of stream flows is expected in the headwaters of the two wettest catchments, while lower decreases (22-32% for 2076-2100) are expected in the drier one. In all three catchments, autumn and summer are the seasons with the most notable projected decreases in stream flow, 50% and 34%, respectively (2076-2100). Thus, ecological flows might be noticeably impacted by climate change in the catchments, especially in the headwaters of those wet catchments.