Effects of nucleus initialization on event-by-event observables

In this work we present a study of the influence of nucleus initializations on the event-by-event elliptic flow coefficient, $v_2$. In most Monte-Carlo models, the initial positions of the nucleons in a nucleus are completely uncorrelated, which can lead to very high density regions. In a simple, yet more realistic model where overlapping of the nucleons is avoided, fluctuations in the initial conditions are reduced. However, $v_2$ distributions are not very sensitive to the initialization choice.Comment: 4 pages, 5 figures, to appear in the Bras. Jour. Phy

Impacts of in vivo and in vitro exposures to tamoxifen: comparative effects on human cells and marine organisms

Tamoxifen (TAM) is a first generation-SERM administered for hormone receptor-positive (HER+) breast cancer in both pre- and post-menopausal patients and may undergo metabolic activation in organisms that share similar receptors and thus face comparable mechanisms of response. The present study aimed to assess whether environmental trace concentrations of TAM are bioavailable to the filter feeder M. galloprovincialis (100 ng L-1) and to the deposit feeder N. diversicolor (0.5, 10, 25 and 100 ng L-1) after 14 days of exposure. Behavioural impairment (burrowing kinetic), neurotoxicity (AChE activity), endocrine disruption by alkali-labile phosphate (ALP) content, oxidative stress (SOD, CAT, GPXs activities), biotransformation (GST activity), oxidative damage (LPO) and genotoxicity (DNA damage) were assessed. Moreover, this study also pertained to compare TAM cytotoxicity effects to mussels and targeted human (i.e. immortalized retinal pigment epithelium - RPE; and human transformed endothelial cells - HeLa) cell lines, in a range of concentrations from 0.5 ng L-1 to 50 μg L-1. In polychaetes N. diversicolor, TAM exerted remarkable oxidative stress and damage at the lowest concentration (0.5 ng L-1), whereas significant genotoxicity was reported at the highest exposure level (100 ng L-1). In mussels M. galloprovincialis, 100 ng L-1 TAM caused endocrine disruption in males, neurotoxicity, and an induction in GST activity and LPO byproducts in gills, corroborating in genotoxicity over the exposure days. Although cytotoxicity assays conducted with mussel haemocytes following in vivo exposure was not effective, in vitro exposure showed to be a feasible alternative, with comparable sensitivity to human cell line (HeLa).info:eu-repo/semantics/publishedVersio

Removal of chromium (VI) and cadmium (II) from aqueous solution by a bacterial biofilm supported on granular activated carbon

A biofilm of Arthrobacter viscosus, supported on granular activated carbon, removed between 100% and 50% of Cr(VI) and between 100% and 20% of Cd(II) from solutions with initial concentrations between 4–11 mgmetal Lˉ¹ and a flow residence time of 1.2 min. For experiments of lower initial concentrations, a steady-state removal of 50% was reached after 71 bed volumes of Cr solution passed through the biosorbent bed and a steady-state removal of 30% was reached after 47 bed volumes of Cd solution passed through a similar bed. Final uptakes of 8.5 mgCr gˉ¹ carbon and 4.2 mgCd gˉ¹ carbon were determined for initial concentrations of 10 mgCr Lˉ¹ and 11 mgCd Lˉ¹, respectively. The influence on the overall process of two different surface treatments of the support was evaluated and compared with the behavior of a support not treated.Fundação para a Ciência e Tecnologia (FCT) - PRAXIS/P/EQU/12017/1998

Fixação simultânea de metais pesados e compostos orgânicos em matriz biológica

Foi utilizado um biofilme de Arthrobacter viscosus suportado em carvão activado granular (GAC) para remover metais pesados e compostos orgânicos presentes em soluções líquidas diluídas. Nos ensaios com metais pesados e na ausência de compostos orgânicos foram utilizados dois diferentes suportes: um tratado com HNO3 e outro com H2O2. Os ensaios realizados com soluções mistas tiveram como suporte do biofilme, o carvão activado sem qualquer tipo de tratamento. A gama de concentrações estudadas, para as soluções de um só metal, variou de 4-77 mg/l para o crómio, 5-95 mg/l para o cádmio, 8-165 mg/l para o chumbo e 2.5-42 mg/l para o ferro. Em relação às soluções mistas, foram utilizadas concentrações iniciais de crómio entre 10-200 mg/l para uma concentração de composto orgânico de 60 mg/l. De uma forma global conseguiram-se melhores resultados com os metais crómio, chumbo e ferro, tendo-se concluído que o cádmio exerce um efeito tóxico sobre as bactérias. Em relação às soluções mistas, fixou-se a atenção na remoção de crómio e verificou-se que esta é ligeiramente afectada pela presença do composto orgânico (ortocresol>fenol>clorofenol). O estudo comparativo entre os três compostos orgânicos indica que a sua remoção não é sensível a concentrações crescentes do metal no caso do fenol e do clorofenol, ao contrário da remoção de ortocresol que é evidentemente afectada pela presença do Cr em concentrações crescentes.Fundação para a Ciência e a Tecnologia (FCT

Diffusion-limited deposition of dipolar particles

Deposits of dipolar particles are investigated by means of extensive Monte Carlo simulations. We found that the effect of the interactions is described by an initial, non-universal, scaling regime characterized by orientationally ordered deposits. In the dipolar regime, the order and geometry of the clusters depend on the strength of the interactions and the magnetic properties are tunable by controlling the growth conditions. At later stages, the growth is dominated by thermal effects and the diffusion-limited universal regime obtains, at finite temperatures. At low temperatures the crossover size increases exponentially as T decreases and at T=0 only the dipolar regime is observed.Comment: 5 pages, 4 figure

Equilibrium modelling of a biosorption system consisting of a bacterial biofilm supported on a GAC for removal of chromium (VI) and organics compounds from a aqueous solution

The removal of heavy metals linked to organic compounds like phenol, chlorophenol, and o- cresol, is one of the most important environmental problems yet to be solved. The retention of these contaminants by a biofilm supported on granular activated carbon is a promising technology for the treatment of diluted solutions, as the biofilm is able to retain the metallic ions and the support will help to fix them for further catalytic applications. The addition of three different organic compounds, i.e., phenol, o-cresol, and chlorophenol, to the metallic solution was studied to better describe the real industrial effluent. A modeling approach for an expanded bed biosorption system was presented using the ADR (Advection-Dispersion Reaction) equation as the basis of the mathematical description. Several biosorption studies were made using a bacterial biofilm of Arthrobacter viscous supported on pre-treated granular activated carbon in a mini-column arrangement and the obtained data were compared with the predicted by the model. The initial chromium (VI) and organic compound concentration ranged from 10 to 100 mg/L. This is an abstract of a paper presented at the 7th World Congress of Chemical Engineering (Glasgow, Scotland 7/10-14/2005).(undefined

Topological defects in lattice models and affine Temperley-Lieb algebra

This paper is the first in a series where we attempt to define defects in critical lattice models that give rise to conformal field theory topological defects in the continuum limit. We focus mostly on models based on the Temperley-Lieb algebra, with future applications to restricted solid-on-solid (also called anyonic chains) models, as well as non-unitary models like percolation or self-avoiding walks. Our approach is essentially algebraic and focusses on the defects from two points of view: the "crossed channel" where the defect is seen as an operator acting on the Hilbert space of the models, and the "direct channel" where it corresponds to a modification of the basic Hamiltonian with some sort of impurity. Algebraic characterizations and constructions are proposed in both points of view. In the crossed channel, this leads us to new results about the center of the affine Temperley-Lieb algebra; in particular we find there a special subalgebra with non-negative integer structure constants that are interpreted as fusion rules of defects. In the direct channel, meanwhile, this leads to the introduction of fusion products and fusion quotients, with interesting mathematical properties that allow to describe representations content of the lattice model with a defect, and to describe its spectrum.Comment: 41

Remoção de metais pesados por biofilmes suportados em carvão activado

Instituto de Biotecnologia e Química Fina (IBQF)

Remoção de metais pesados por biofilmes suportados em carvão activado

Instituto de Biotecnologia e Química Fina (IBQF)

Removal of chromium from wastewater by adsorption and by biosorption

The objective of this work is the definition of an efficient biosorption system based on the ability of some microorganisms, metabolica1ly active or not, to retain heavy metals, specially the hexavalent fonn of Cr. Metallic solutions were passed through mini-colunms in which a biotilm was developed at pre-established conditions. As industrial wastewater usually contains organic and inorganic compounds, besides metallic ions, it would be desirable to co-extract several pollutants at the same time. The utilization of granular activated carbon (GAC) as a support for the biofilm seems to be advantageous, as it can retain other substances while the biofilm removes the heavy metal. To quantify the contribution of GAC to the overall removal of chromium, adsorption studies were carried out with the determination the effect of pH and of the presence of concurrent species on the adsorption isotherms. Biosorption studies were done with three different bacteria, Pseudomonasjluorescens, Escherichia coli and Arthrobacter viscosus. Among microorganisms, bacteria are particularly interesting for the purpose as they are able to excrete polysaccharides allowing a good adhesion to the support, implementing the retention capacity of the biosystem and protecting the cells from the xenobiotic effect of the heavy metal ions. Removal efficiencies were compared between the three biosystems