Electrochemical methods for speciation of trace elements in marine waters. Dynamic aspects

The contribution of electrochemical methods to the knowledge of dynamic speciation of toxic trace elements in marine waters is critically reviewed. Due to the importance of dynamic considerations in the interpretation of the electrochemical signal, the principles and recent developments of kinetic features in the interconversion of metal complex species will be presented. As dynamic electrochemical methods, only stripping techniques (anodic stripping voltammetry and stripping chronopotentiometry) will be used because they are the most important for the determination of trace elements. Competitive ligand ex- change-adsorptive cathodic stripping voltammetry, which should be considered an equilibrium technique rather than a dynamic method, will be also discussed because the complexing parameters may be affected by some kinetic limitations if equilibrium before analysis is not attained and/or the flux of the adsorbed complex is in fluenced by the lability of the natural complexes in the water sample. For a correct data interpretation and system characterization the comparison of results obtained from different techniques seems essential in the articulation of a serious discussion of their meaning

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Evaluation of rodent peroxisome proliferators in two species of fish (rainbow trout; Salmo gairdneri and Japanese medaka; Oryzias latipes)

Rainbow trout (Salmo gairdneri) and Japanese medaka (Oryzias latipes) were exposed to three or four compounds, respectively, which have been shown to cause peroxisome proliferation in rodents. Trout were injected (intraperitoneally) daily for two weeks to the following chemicals and doses; the dimethylamine salt of 2,4-dichlorophenoxyacetic acid (DMA of 2,4-D) at 0, 2.5, 5 and 10 mg/kg/d, trichloroethylene (TCE) at 0, 10, 50 and 100 mg/kg/d or gemfibrozil at 0, 46, 87 and 152 mg/kg/d. Japanese medaka were exposed to di (2-ethylhexyl) phthalate (DEHP), 2,4-D (DMA) or gemfibrozil in water for two weeks in a static renewal system. Nominal doses used were 0, 90, 180 and 360 ppb, 0, 50, 100 and 200 ppm and 0, 1.25, 2.5 and 5 ppm for DEHP, 2,4-D and gemfibrozil, respectively. Medaka were also exposed to TCE for 16 hours in a closed system at doses of 0, 25 and 50 ppm. Peroxisome proliferation was assessed by measuring fatty acyl-CoA oxidase (FAO) activity and relative percent increase in peroxisomal bifunctional enzyme (PBE); enzymes which are involved in peroxisomal beta-oxidation. In addition, changes in liver weight/body weight ratios were measured. Results indicate that a mild peroxisome proliferative response was observed in rainbow trout exposed to gemfibrozil (significant increase in FAO activity at all three dose levels and a significant increase in liver weight/body weight ratios at the highest dose level only). There was no difference between control and treated groups in the trout exposed to 2,4-D or TCE. In the medaka experiments, a marginal response was observed in the gemfibrozil experiment (significant increase in PBE at the highest dose level and a non-significant increase in FAO activity in the mid- and high-dose groups). There were no significant, treatment related differences between control and treated fish in the TCE, 2,4-D and DEHP medaka experiments. It was concluded that fish may not be a sensitive model to screen chemicals for their ability to induce peroxisome proliferation

Evaluation of Integral Forces and Pressure Fields from Planar Velocimetry Data for Incompressible and Compressible Flows

The approach to determine pressure fields and integral loads from planar velocimetry data is discussed, in relation to the implementation for incompressible and compressible flows around two-dimensional objects. The method relies upon the application of control-volume approaches in combination with the deduction of the pressure field from the experimental data, by making use of the flow constitutive equations. In this paper the implementation for two specific application areas is addressed. The first is time-mean pressure field and force evaluation from velocity ensemble statistics, as obtained from time-uncorrelated PIV acquisition, for incompressible flow. Two test cases are considered for this flow regime: the unsteady vortical flow around a square section cylinder at incidence, as well as the force characterization of a low-speed airfoil. The second topic considers the extension of the method to steady compressible flow, with the supersonic flow around a bi-convex airfoil as experimental test case. As in this flow regime the density appears as an extra unknown in the momentum equation, additional flow equations need to be invoked. A convenient approach for this was found, using the gas law and the adiabatic flow condition, with which the pressure-integration procedure becomes essentially the same as for the incompressible case

On the velocity of ghost particles and the bias errors in Tomographic-PIV

The paper discusses bias errors introduced in Tomographic-PIV velocity measurements by the coherent motion of ghost particles under some circumstances. It occurs when a ghost particle is formed from the same set of actual particles in both reconstructed volumes used in the cross-correlation analysis. The displacement of the resulting ghost particle pair is approximately the average displacement of the set of associated actual particles. The effect is further quantified in a theoretical analysis and in numerical simulations and illustrated in an actual experiment. It is shown that the bias error does not significantly affect the measured flow topology as deduced in an evaluation of the local velocity gradients. Instead, it leads to a systematic underestimation of the measured particle displacement gradient magnitude. This phenomenon is alleviated when the difference between particles displacement along the volume depth is increased beyond a particle image diameter, or when the reconstruction quality is increased or when the accuracy of the tomographic reconstruction is improved. Furthermore, guidelines to detect and avoid such bias errors are proposed.Process and EnergyMechanical, Maritime and Materials Engineerin

Exploring Current Read-across Applications and Needs Among Selected U.S. Federal Agencies

Read-across is a well-established data gap-filling technique applied for regulatory purposes. While the application of read-across has garnered much attention in the European Union and Organisation for Economic Co-operation and Development member countries, the extent of uptake and acceptance of read-across among U.S. federal agencies is less clear. In an effort to build read-across capacity, raise awareness of the state of the science, and work towards a harmonization of read-across approaches across U.S. agencies, a new read-across workgroup was established under the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM). This is one of several ad hoc groups ICCVAM has convened to implement the ICCVAM Strategic Roadmap. In this article, we outline the charge and scope of the workgroup and summarize the current applications, tools used, and needs of the agencies represented on the workgroup for read-across. Of the agencies surveyed, the Environmental Protection Agency (EPA) had the greatest experience in using read-across whereas other agencies indicated that they would benefit from gaining a perspective of the landscape of the tools and available guidance. Two practical case studies are also described to illustrate how the read-across approaches applied by different agencies vary on account of decision context.JRC.F.3-Chemicals Safety and Alternative Method

Alternative approaches for identifying acute systemic toxicity: Moving from research to regulatory testing

Acute systemic toxicity testing provides the basis for hazard labeling and risk management of chemicals. A number of international efforts have been directed at identifying non-animal alternatives for in vivo acute systemic toxicity tests. A September 2015 workshop, Alternative Approaches for Identifying Acute Systemic Toxicity: Moving from Research to Regulatory Testing, reviewed the state-of-the-science of non-animal alternatives for this testing and explored ways to facilitate implementation of alternatives. Workshop attendees included representatives from international regulatory agencies, academia, nongovernmental organizations, and industry. Resources identified as necessary for meaningful progress in implementing alternatives included compiling and making available high-quality reference data, training on use and interpretation of in vitro and in silico approaches, and global harmonization of testing requirements. Attendees particularly noted the need to characterize variability in reference data to evaluate new approaches. They also noted the importance of understanding the mechanisms of acute toxicity, which could be facilitated by the development of adverse outcome pathways. Workshop breakout groups explored different approaches to reducing or replacing animal use for acute toxicity testing, with each group crafting a roadmap and strategy to accomplish near-term progress. The workshop steering committee has organized efforts to implement the recommendations of the workshop participants.JRC.F.3-Chemicals Safety and Alternative Method