Encapsulation de Dehalococcoides: avantage pour la déhalogénation des solvants chlorés en sites contaminés

Le tétrachloroéthène (PCE) et les éthènes chlorés qui lui sont apparentés ont été abondamment utilisés pour plusieurs applications en industrie dès le début du 20e siècle. Ils sont cependant comptés parmi les polluants les plus communs des sols et de l’eau et beaucoup d’efforts sont déployés afin de les éliminer. Nous croyons que la conversion des éthènes chlorés en éthènes par des microorganismes est une solution prometteuse. Le premier aspect du projet visait donc à établir les conditions pour lesquelles un consortium enrichi en Dehalococcoides ethenogenes permettrait la conversion complète de PCE en éthène. Les expériences réalisées nous ont permis de souligner le rôle de l’acide lactique ajouté aux cultures comme source de carbone et source indirecte d’électrons pour la déhalorespiration. Nous avons également pu établir l’effet de la concentration initiale de biomasse dans les cultures sur le profil de déhalogénation du PCE. Le deuxième aspect du projet visait à développer un protocole d’encapsulation du consortium dans une matrice polymérique afin de profiter des nombreux avantages potentiels de l’encapsulation. Nous avons testé trois montages d’encapsulation différents : atomisation avec jet d’air, atomisation avec vibrations ultrasoniques et « drop-wise ». Le dernier montage prévoyait l’encapsulation des cultures dans des billes d’alginate enrobées de chitosane gélifié par du lignosulfonate. C’est le seul montage qui nous a permis d’encapsuler le consortium de façon efficace sans effet significatifs négatifs sur son activité de déchlorination. Aussi, la comparaison des profils de déhalogénation du PCE de cellules encapsulées et cellules libres a montré une plus faible accumulation de TCE, 1,2-DCE et VC dans les échantillons de cellules encapsulée et, par conséquent, une conversion plus rapide et plus complète du PCE en éthène. Finalement, nous avons observé une tendance favorable à l’idée que les microorganismes encapsulés bénéficient d’un effet de protection contre de faibles concentrations d’oxygène.

La conservation du patrimoine urbain, catalyseur du renouvellement des pratiques urbanistiques? : une réflexion théorique sur l'appropriation de la notion de patrimoine urbain par l'urbanisme

Cette thèse questionne l’apport de la conservation du patrimoine urbain à l’urbanisme. Il y est avancé que l’association entre la conservation du patrimoine urbain et l'urbanisme, dans leur cadre conceptuel actuel, plutôt que d’être le catalyseur du renouvellement de l’urbanisme, a perpétué une appréhension fragmentée et une atomisation de l'établissement, consacrant ainsi le paradigme fonctionnaliste, qui conditionne encore largement les pratiques urbanistiques contemporaines, au Québec notamment. En effet, bien que depuis les années 1960 la conservation du patrimoine soit présentée comme le fil rouge dans le redéploiement de la compétence d’édifier, plusieurs études soulignent les résultats mitigés de nombreuses expériences de conservation ainsi qu’une contribution limitée relativement à la formulation des projets urbains. Plus particulièrement, malgré la reconnaissance de l’intérêt de la patrimonialisation et de la fécondité potentielle de l’idée de patrimoine en général, l’urbanisme n’est pas parvenu à en définir les termes de la contribution, tant au plan conceptuel que processuel, en regard de sa propre projectualité. De ce fait, il ne réussit pas à affranchir la réflexion patrimoniale du registre de la conservation afin de se l’approprier véritablement. Cette thèse explique les causes de cette incapacité à partir d’une analyse des conditions de l’appropriation de la notion de patrimoine urbain mises de l’avant par l’approche giovannonienne. Celle-ci, fondamentalement urbanistique, propose une conception du patrimoine urbain qui s’émancipe du monument historique et du registre de la conservation. Indissociable d’une projectualité urbanistique, l’intérêt pour le patrimoine urbain de Giovannoni relève d’une reconnaissance du déjà là qui fonde des modalités de prises en charge de l’existant. Celles-ci posent les bases d’un renouvellement de la manière de penser l’urbanisme. La notion giovannonienne de patrimoine urbain, qui réfère à l’ensemble urbain patrimonial, devient l’élément de base d’une analyse morphologique urbanistique qui permet de conceptualiser l’agglomération contemporaine comme ensemble marqué par les ruptures et les discontinuités. Prenant appui sur une démarche dialogique, l’approche giovannonienne relève d’une mise en tension des singularités et d’une appréhension conjointe des différentes registres, ceux des formes et des forces, de l’existant et du souhaité, du penser et du faire. Giovannoni dépasse ainsi l’opposition entre continuité et rupture portée par les pratiques afin de penser l’articulation du nouveau à l’ancien. La confrontation de l’approche giovannonienne aux différentes perspectives qui ont marqué l’urbanisme moderne, montre que ces modalités de prise en charge de l’existant sont conditionnelles à l’accomplissement des promesses de la considération du patrimoine urbain. Autrement, l’association de la conservation du patrimoine urbain et de l’urbanisme culmine dans une double assimilation : l’assimilation du patrimoine urbain au monument historique d’architecture conduit à confondre projet d’urbanisme et projet de conservation.

Systematic construction of models for the exchange hole of density functional theory.

Dans ce travail, nous étendons le nombre de conditions physiques actuellement con- nues du trou d’échange exact avec la dérivation de l’expansion de quatrième ordre du trou d’échange sphérique moyenne exacte. Nous comparons les expansions de deux- ième et de quatrième ordre avec le trou d’échange exact pour des systèmes atomiques et moléculaires. Nous avons constaté que, en général, l’expansion du quatrième ordre reproduit plus fidèlement le trou d’échange exact pour les petites valeurs de la distance interélectronique. Nous démontrons que les ensembles de base de type gaussiennes ont une influence significative sur les termes de cette nouvelle condition, en étudiant com- ment les oscillations causées par ces ensembles de bases affectent son premier terme. Aussi, nous proposons quatre modèles de trous d’échange analytiques auxquels nous imposons toutes les conditions actuellement connues du trou d’échange exact et la nou- velle présentée dans ce travail. Nous évaluons la performance des modèles en calculant des énergies d’échange et ses contributions à des énergies d’atomisation. On constate que les oscillations causeés par les bases de type gaussiennes peuvent compromettre la précision et la solution des modèles.

Fabrication of Controlled Release Devices Using Supercritical Antisolvent Method

In this study, the supercritical antisolvent with enhanced mass transfer method (SASEM) is used to fabricate micro and nanoparticles of biocompatible and biodegradable polymer PLGA (poly DL lactide co glycolic acid). This process may be extended to the encapsulation of drugs in these micro and nanoparticles for controlled release purposes. Conventional supercritical antisolvent (SAS) process involves spraying a solution (organic solvent + dissolved polymer) into supercritical fluid (CO[subscript 2]), which acts as an antisolvent. The high rate of mass transfer between organic solvent and supercritical CO[subscript 2] results in supersaturation of the polymer in the spray droplet and precipitation of the polymer as micro or nanoparticles occurs. In the SASEM method, ultrasonic vibration is used to atomize the solution entering the high pressure with supercritical CO[subscript 2]. At the same time, the ultrasonic vibration generated turbulence in the high pressure vessel, leading to better mass transfer between the organic solvent and the supercritical CO₂. In this study, two organic solvents, acetone and dichloromethane (DCM) were used in the SASEM process. Phase Doppler Particle Analyzer (PDPA) was used to study the ultrasonic atomization of liquid using the ultrasonic probe for the SASEM process. Scanning Electron Microscopy (SEM) was used to study the size and morphology of the polymer particles collected at the end of the process.

Tightened Lieb-Oxford Bound for Systems of Fixed Particle Number

The Lieb-Oxford bound is a constraint upon approximate exchange-correlation functionals. We explore a nonempirical tightening of that bound in both universal and electron number-dependent form. The test functional is PBE. Regarding both atomization energies (slightly worsened) and bond lengths (slightly improved), we find the PBE functional to be remarkably insensitive to the value of the Lieb-Oxford bound. This both rationalizes the use of the original Lieb-Oxford constant in PBE and suggests that enhancement factors more sensitive to sharpened constraints await discovery.

Determination of cadmium and lead in cetacean Dolphinidae tissue from the coast of Bahia state in Brazil by GFAAS

In the present study, cadmium and lead in the muscle, lung, liver and kidney of dolphins (Sotalia guianensis and Stenella clymene) of the Bahia coast in the northwest of Brazil were determined by graphite furnace atomic absorption spectrometry. Samples were digested using a diluted oxidant mixture (HNO(3) + H(2)O(2)) with a microwave heating program performed in five steps. The optimized temperatures and chemical modifier for the pyrolysis and atomization were 700 degrees C, 1400 degrees C and Pd plus Mg for Cd, and 900 degrees C, 1800 degrees C and NH(4)H(2)PO(4) for Pb, respectively. Characteristic masses and limits of detections (n = 20, 3 sigma) for Cd and Pb were 1.6 and 9.0 pg and 0.82 ng g(-1) and 0.50 ng g(-1), respectively. Repeatability ranged from 0.87 to 8.22% for Cd and 4.31 to 8.09% for Pb. The found concentrations presented no statistical differences at the 95% confidence level when compared with the ICP OES methods. Addition and recovery tests were also performed and the results ranged between 87 and 112% for both elements. Samples of cetacean Dolphinidae (S. guianensis and S. clymene) were analyzed, and the higher concentrations ranged from 0.09 to 46.2 mu g g(-1) for Cd and 0.04 to 0.47 mu g g(-1) for Pb in liver, and from 0.133 to 277 mu g g(-1) for Cd in the kidney. (C) 2010 Elsevier By. All rights reserved.

Simultaneous determination of chromium and manganese in alumina by slurry sampling graphite furnace atomic absorption spectrometry using NbC and NaF as modifiers

This paper reports a method for the direct and simultaneous determination of Cr and Mn in alumina by slurry sampling graphite furnace atomic absorption spectrometry (SiS-SIMAAS) using niobium carbide (NbC) as a graphite platform modifier and sodium fluoride (NaF) as a matrix modifier. 350 mu g of Nb were thermally deposited on the platform surface allowing the formation of NbC (mp 3500 degrees C) to minimize the reaction between aluminium and carbon of the pyrolytic platform, improving the graphite tube lifetime up to 150 heating cycles. A solution of 0.2 mol L(-1) NaF was used as matrix modifier for alumina dissolution as cryolite-based melt, allowing volatilization during pyrolysis step. Masses (c.a. 50 mg) of sample were suspended in 30 ml of 2.0% (v/v) of HNO(3). Slurry was manually homogenized before sampling. Aliquots of 20 mu l of analytical solutions and slurry samples were co-injected into the graphite tube with 20 mu l of the matrix modifier. In the best conditions of the heating program, pyrolysis and atomization temperatures were 1300 degrees C and 2400 degrees C, respectively. A step of 1000 degrees C was optimized allowing the alumina dissolution to form cryolite. The accuracy of the proposed method has been evaluated by the analysis of standard reference materials. The found concentrations presented no statistical differences compared to the certified values at 95% of the confidence level. Limits of detection were 66 ng g(-1) for Cr and 102 ng g(-1) for Mn and the characteristic masses were 10 and 13 pg for Cr and Mn, respectively.

Theoretical Characterization of Hydrogen Polyoxides: HOOH, HOOOH, HOOOOH, and HOOO

We have investigated the polyoxides HOOH, HOOOH, HOOOOH, and HOOO employing the CCSD(T) methodology, and the correlation consistent basis sets. For all molecules, we have computed fundamental vibrational frequencies, structural parameters, rotational constants, and rotation-vibration corrections. For HOOOH, we have obtained a good agreement between our results and microwave and infrared spectra measurements, although for the symmetric OO stretch some important differences were found. Heats of formation were computed using atomization energies, and our recommendation is as follows: Delta H degrees(f,298)(HOOOH) = -21.50 kcal/mol and Delta H degrees(f,298)(HOOOOH) = -10.61 kcal/mol. In the case of HOOO, to estimate the heat of formation, we have constructed three isodesmic reactions to cancel high order correlation effects. The results obtained confirmed that the latter effects are very important for HOOO. The new Delta H degrees(f,298)(HOOO) obtained is 5.5 kcal/mol. We have also calculated the zero-point energies of DO and DOOO to correct the experimental lower limit determined for the Delta H degrees(f,298)(HOOO). The Delta(Delta ZPE) decreases the binding energy of HOOO by 0.56 kcal/mol. Employing the latter value, the new experimental lower limit for Delta H degrees(f,298)(HOOO) is 3.07 kcal/mol, just 2.4 kcal/mol lower than our determination. We expect that the fundamental vibrational frequencies and rotational constants determined for HOOOOH and DOOOOD contribute to its identification in the gas phase. The vibrational spectrum of HOOOOH shows some overlapping with that of HOOOH thus indicating that one may encounter some difficulties in its characterization. We discuss the consequences of the thermochemical properties determined in this work, and suggest that the amount of HOOO present in the atmosphere is smaller than that proposed recently in this journal (J. Phys. Chem A 2007, 111, 4727).

Spin contamination in XOO radicals X = F, Cl, Br, HO: How is the investigation of the HOOO radical affected

We have analysed the effect of spin contamination in the wavefunction of HOOO. At least, two solutions can be found for the HF wavefunction. One, lower in energy, presents a high spin contamination and gives qualitatively incorrect structural parameters. On the other hand, the less contaminated HF reference gives structural parameters that are in better agreement with experiment, and positive spin densities on all atoms. Some of the problems described during previous investigations of HOOO can now be traced to problems in the HF reference. For the first time we report a CCSD(T) estimation of the structure of HOOO cis employing a HF reference with small spin contamination. (C) 2008 Elsevier B.V. All rights reserved.

Direct determination of iron in sand using solid sampling graphite furnace atomic absorption spectrometry

A fast and reliable method for the direct determination of iron in sand by solid sampling graphite furnace atomic absorption spectrometry was developed. A Zeeman-effect 3-field background corrector was used to decrease the sensitivity of spectrometer measurements. This strategy allowed working with up to 200 mu g of samples, thus improving the representativity. Using samples with small particle sizes (1-50 mu m) and adding 5 mu g Pd as chemical modifier, it was possible to obtain suitable calibration curves with aqueous reference solutions. The pyrolysis and atomization temperatures for the optimized heating program were 1400 and 2500 degrees C, respectively. The characteristic mass, based on integrated absorbance, was 56 pg, and the detection limits, calculated considering the variability of 20 consecutive measurements of platform inserted without sample was 32 pg. The accuracy of the procedure was checked with the analysis of two reference materials (IPT 62 and 63). The determined concentrations were in agreement with the recommended values (95% confidence level). Five sand samples were analyzed, and a good agreement (95% confidence level) was observed using the proposed method and conventional flame atomic absorption spectrometry. The relative standard deviations were lower than 25% (n = 5). The tube and boat platform lifetimes were around 1000 and 250 heating cycles, respectively.

A method for Ca, Fe, Ga, Na, Si and Zn determination in alumina by inductively coupled plasma optical emission spectrometry after aluminum precipitation

In this present work a method for the determination of Ca, Fe, Ga, Na, Si and Zn in alumina (Al(2)O(3)) by inductively coupled plasma optical emission spectrometry (ICP OES) with axial viewing is presented. Preliminary studies revealed intense aluminum spectral interference over the majority of elements and reaction between aluminum and quartz to form aluminosilicate, reducing drastically the lifetime of the torch. To overcome these problems alumina samples (250 mg) were dissolved with 5 mL HCl + 1.5 mLH(2)SO(4) + 1.5 mL H(2)O in a microwave oven. After complete dissolution the volume was completed to 20 mL and aluminum was precipitated as Al(OH)(3) with NH(3) (by bubbling NH(3) into the solution up to a pH similar to 8, for 10 min). The use of internal standards (Fe/Be, Ga/Dy, Zn/In and Na/Sc) was essential to obtain precise and accurate results. The reliability of the proposed method was checked by analysis of alumina certified reference material (Alumina Reduction Grade-699, NIST). The found concentrations (0.037%w(-1) CaO, 0.013% w w(-1) Fe(2)O(3), 0.012%w w(-1)Ga(2)O(3), 0.49% w w(-1) Na(2)O, 0.014% w w(-1) SiO(2) and 0.013% w w(-1) ZnO) presented no statistical differences compared to the certified values at a 95% confidence level. (C) 2011 Elsevier B.V. All rights reserved.

Feasibility study for the preparation of a tuna fish candidate reference material for total As determination

This work describes the evaluation of several parameters for the preparation of a tuna fish candidate as a reference material (RM) in order to measure the total As mass fraction by slurry sampling graphite furnace atomic absorption spectrometry (SLS-GF AAS) and slurry sampling hydride generation atomic absorption spectrometry (SLS-HG AAS). The main parameters investigated were the homogeneity, analyte segregation and composition during material production. For candidate RM preparation, tuna fish was collected at a local market, cleaned, freeze-dried and treated using different procedures as follows: (1) ground in a cutting mill and separated in different particle sizes (2) ground in cryogenic mill. The mass fraction of As in the cryogenically ground sample was (4.77 +/- A 0.19) mu g g(-1) for SLS-GF AAS and (4.61 +/- A 0.34) mu g g(-1) for SLS-HG AAS. The accuracy of the procedures was checked with tuna fish certified reference material (BCR 627) with recoveries of 102 and 94% for SLS-GF AAS and SLS-HG AAS, respectively. The homogeneity factor was calculated for different pretreatment procedures and for particle sizes in the range of 500-150 mu g, indicating good homogeneity, except for raw fish. There was no observed analyte segregation and no losses, no contamination and no changes in the microdistribution of material during preparation.

Tailoring the surface chemistry of carbon fiber and E-glass composites for improved adhesion

The main challenges in the manufacture of composite materials are low surface energy and the presence of silicon-containing contaminants, both of which greatly reduce surface adhesive strength. In this study, carbon fiber (CF) and E-glass epoxy resin composites were surface treated with the Accelerated Thermo-molecular adhesion Process (ATmaP). ATmaP is a multiaction surface treatment process where tailored nitrogen and oxygen functionalities are generated on the surface of the sample through the vaporization and atomization of n-methylpyrrolidone solution, injected via specially designed flame-treatment equipment. The treated surfaces of the polymer composites were analyzed using XPS, time of flight secondary ion mass spectrometry (ToF-SIMS), contact angle (CA) analysis and direct adhesion measurements. ATmaP treatment increased the surface concentration of polar functional groups while reducing surface contamination, resulting in increased adhesion strength. XPS and ToF-SIMS showed a significant decrease in silicon-containing species on the surface after ATmaP treatment. E-glass composite showed higher adhesion strength than CF composite, correlating with higher surface energy, higher concentrations of nitrogen and CO functional groups (from XPS) and higher concentrations of oxygen and nitrogen-containing functional groups (particularly C₂H₃O⁺ and C₂H₅NO⁺ molecular ions, from ToF-SIMS).

Análise de um queimador infravermelho funcionando com combustível híbrido : GLP/Bio-óleo

Biomass is considered the largest renewable energy source that can be used in an environmentally sustainable. From the pyrolysis of biomass is possible to obtain products with higher energy density and better use properties. The liquid resultant of this process is traditionally called bio-oil. The use of infrared burners in industrial applications has many advantages in terms of technical-operational, for example, uniformity in the heat supply in the form of radiation and convection, with a greater control of emissions due to the passage of exhaust gases through a macroporous ceramic bed. This paper presents a commercial infrared burner adapted with an ejector proposed able to burn a hybrid configuration of liquefied petroleum gas (LPG) and bio-oil diluted. The dilution of bio-oil with absolute ethanol aimed to decrease the viscosity of the fluid, and improving the stability and atomization. It was introduced a temperature controller with thermocouple modulating two stages (low heat / high heat), and solenoid valves for fuels supply. The infrared burner has been tested, being the diluted bio-oil atomized, and evaluated its performance by conducting energy balance. The method of thermodynamic analysis to estimate the load was used an aluminum plate located at the exit of combustion gases and the distribution of temperatures measured by thermocouples. The dilution reduced the viscosity of the bio-oil in 75.4% and increased by 11% the lower heating value (LHV) of the same, providing a stable combustion to the burner through the atomizing with compressed air and burns combined with LPG. Injecting the hybrid fuel there was increase in the heat transfer from the plate to the environment in 21.6% and gain useful benefit of 26.7%, due to the improved in the efficiency of the 1st Law of Thermodynamics of infrared burner

Selenium determination in tissue samples of Nile tilapia using ultrasound-assisted extraction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)