Field observation of sequestration of uranium in iron-rich sediments under sequential reduction-oxidation conditions at the DOE Oak Ridge IFRC

At the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) site, the iron content of shallow subsurface materials (i.e. weathered saprolite) is relatively high (up to 5-6% as w/w), and therefore, the forms of the iron species present plays a critical role in the long-term sequestration of uranium. A long term pilot-scale study of the bioreduction and reoxidation of uranium conducted at the ORIFRC area 3 site, adjacent to the former S-3 disposal ponds (source zone), has provided us with the opportunity to study the impact of iron species on the sequestration of U(VI). The aqueous U(VI) concentrations at the site were decreased to below the EPA MCL through the intermittent injection of ethanol as the electron donor. Previous field tests indicated that both oxygen and nitrate could oxidize the bioreduced U(IV) and cause a short-term rebound of aqueous phase uranium concentration after the oxidative agents were delivered directly to the bioreduced zone.

A field test has been conducted to examine the long-term effect of exposure of bioreduced sediments to nitrate in contaminated groundwater for more than 1,380 days at the Area 3 site. Contaminated groundwater was allowed to invade the previously bioreduced zone via the natural groundwater gradient after an extended period in which reducing conditions were maintained and the bioreduced zone was protected from the influx of upgradient contaminated groundwater. The geochemical response to the invasion of contaminated groundwater was dependent on whether the monitoring location is in the middle or the fringe of the previously bioreduced zone. In general, the nitrate concentrations in the previously bioreduced area, increased gradually from near zero to ~50-300 mM within 200 days and then stabilized. The pH declined from bioreduced levels of 6.2-6.7 to below 5.0. Uranium concentrations rebounded in all monitoring wells but at different rates. At most locations U concentrations rebounded, declined and then rebounded again. Methane gas disappeared while a significant level (20,000 to 44,000 ppmv) N2O was found in the groundwater of monitoring wells after three years of reoxidization.

The U(IV) in sediments was mainly reoxidized to U(VI) species. Based on XANES analysis, the predominate uranium in all samples after re-oxidation was similar to a uranyl nitrate form. But the U content in the sediment remained as high as that determined after bioreduction activates were completed, indicating that much of the U is still sequestrated in situ. SEM observations of surged fine sediments revealed that clusters of colloidal-sized (200-500nm) U-containing precipitates appeared to have formed in situ, regardless from sample of FW106 in non-bioactivity control area or of pre-bioreduced FW101-2 and FW102-3. Additionally, SEM-EDS and microprobe analysis, showed that the U-containing precipitates (~1% U) in FW106 are notably higher in Fe, compared to the precipitates (~1-2.5% U) from FW101-2 and FW102-3. However, XRF analysis indicated that the U content was remained as high as 2180 and 1810 mg/kg with U/Fe ratio at 0.077 and 0.055 vs 0.037 g/g, respectively in pre-bioreduced FW101-2 and FW102-3, suggesting more U sequestrated by Fe in pre-bioreduced sediments.

Seedless synthesis of octahedral gold nanoparticles in condensed surfactant phase

We report a seedless synthetic method of gold octahedral nanoparticles in an aqueous phase. Eight facets with {111} crystalline structures of octahedral nanoparticles could be formed in an aqueous medium when the gold salt was reduced by ascorbic acid at room temperature in the presence of cetyltrimethylammonium bromide as a shape-inducing agent, and hydrogen peroxide as a reaction promoter. The growth kinetics and surface crystalline structures were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy.

Mechanochemical interconversion between discrete complexes and coordination networks - formal hydration/dehydration by LAG

Using a small planetary ball mill, liquid-assisted grinding (LAG) of metal salts or oxides (ZnO, CdO, CdCO3, Cu(OAc)(2)center dot H2O, Co(OAc)(2)center dot 4H(2)O, Mn(OAc)(2)center dot 4H(2)O, Ni(OAc)(2)center dot 4H(2)O, FeSO4 center dot 7H(2)O) with two equivalents of isonicotinic acid (HINA) and small amounts of water ( up to 5.6 molar equivalents) gave discrete aquo complexes trans-[M(INA)(2)(OH2)(4)] (M = Zn, Cd, Cu, Fe, Co, Ni, Mn) efficiently within 30 min. For M = Zn, Cd and Cu these complexes readily undergo reversible formal dehydration to the extended network structures [M(INA)(2)] (M = Zn, Cu) or [Cd(INA)(2)(OH2)]center dot DMF by further LAG with non-aqueous liquids such as methanol or DMF. Overall, the mechanochemical dehydrations are more effective than heating or immersion in bulk solvents. The work demonstrates a two-step mechanochemical synthesis of coordination networks via discrete aquo complexes which may be preferable to single step reactions or grinding-annealing procedures in some cases. For example, the two step method was the only way to prepare [Cd(INA)(2)(OH2)]center dot DMF mechanochemically and the porous network Cu(INA)(2) could not be obtained from the aquo complex by heating.

Placental antioxidant enzyme status and lipid peroxidation in pregnant women with type 1 diabetes: The effect of vitamin C and E supplementation

AIM: In view of the increased rates of pre-eclampsia observed in diabetic pregnancy and the lack of ex vivo data on placental biomarkers of oxidative stress in T1 diabetic pregnancy, the aim of the current investigation was to examine placental antioxidant enzyme status and lipid peroxidation in pregnant women with type 1 diabetes. A further objective of the study was to investigate the putative impact of vitamin C and E supplementation on antioxidant enzyme activity and lipid peroxidation in type 1 diabetic placentae.

METHODS: The current study measured levels of antioxidant enzyme [glutathione peroxidase (Gpx), glutathione reductase (Gred), superoxide dismutase (SOD) and catalase] activity and degree of lipid peroxidation (aqueous phase hydroperoxides and 8-iso-prostaglandin F2α) in matched central and peripheral samples from placentae of DAPIT (n=57) participants. Levels of vitamin C and E were assessed in placentae and cord blood.

RESULTS: Peripheral placentae demonstrated significant increases in Gpx and Gred activities in pre-eclamptic in comparison to non-pre-eclamptic women. Vitamin C and E supplementation had no significant effect on cord blood or placental levels of these vitamins, nor on placental antioxidant enzyme activity or degree of lipid peroxidation in comparison to placebo-supplementation.

CONCLUSION: The finding that maternal supplementation with vitamin C/E does not augment cord or placental levels of these vitamins is likely to explain the lack of effect of such supplementation on placental indices including antioxidant enzymes or markers of lipid peroxidation.

Magnetic impurities in nanostructured materials

Os resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”. O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.

Valorização de resíduos carbonosos de gasificação como precursores de materiais para adsorção de poluentes em fase aquosa

Tese de doutoramento, Energia e Ambiente (Energia e Desenvolvimento Sustentável), Universidade de Lisboa, Faculdade de Ciências, 2014

Implementação e validação de um método analítico para a determinação de surfatantes aniónicos

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica

Successful surgical resection in non-lesional operculo-insular epilepsy without intracranial monitoring.

Pre-operative assessment and surgical management of patients with non-lesional extratemporal epilepsy remain challenging due to a lack of precise localisation of the epileptic zone. In most cases, invasive recording with depth or subdural electrodes is required. Here, we describe the case of 6.5-year-old girl who underwent comprehensive non-invasive phase I video-EEG investigation for drug-resistant epilepsy, including electric source and nuclear imaging. Left operculo-insular epilepsy was diagnosed. Post-operatively, she developed aphasia which resolved within one year, corroborating the notion of enhanced language plasticity in children. The patient remained seizure-free for more than three years.

Modifications to the Suzuki reaction and mechanistic insights on the NBS mediated cleavage of benzylidene acetals /

One of the most challenging tasks for a synthetic organic chemist today, is the development of chemo, regio, and stereoselective methodologies toward the total synthesis of macromolecules. r . The objective of my thesis was to develop methodologies towards this end. The first part of my project was to develop highly functionalized chirons from D-glucose, a cheap, chiral starting material, to be utilized in this capacity. The second part of the project dealt with modifying the carbon-carbon bond forming Suzuki reaction, which is utilized quite often as a means of combining molecular sub units in total synthesis applications. As previously stated the first area of the project was to develop high value chirons from D-glucose, but the mechanism of their formation was also investigated. The free radical initiated oxidative fragmentation of benzylidene acetals was investigated through the use of several test-case substrates in order to unravel the possible mechanistic pathways. This was performed by reacting the different acetals with N-bromosuccinimide and benzoyl peroxide in chlorobenzene at 70^C in all cases. Of the three mechanistic pathways discussed in the literature, it was determined, from the various reaction products obtained, that the fragmentation of the initial benzylic radical does not occur spontaneously but rather, oxidation proceeds to give the benzyl bromide, which then fragments via a polar pathway. It was also discovered that the regioselectivity of the fragmentation step could be altered through incorporation of an allylic system into the benzylidene acetal. This allows for the acquisition of a new set of densely functionalized. chiral, valuable synthetic intermediates in only a few steps and in high yields from a-Dglucose. The second part of the project was the utilization of the phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) as an efficient reusable medium for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts of water and toluene using potassium phosphate and 1% Pd2(dba)3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and afforded complete conversion within 1 hour at 50 ^C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70 ^C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system in which the top hexane phase contained the biaryl products, the palladium catalyst remained fully dissolved in the central THPC layer, while the inorganic salts were extracted into the lower aqueous phase. The catalyst was then recycled by removing the top and bottom layers and adding the reagents to the ionic liquid which was heated again at 50 ^C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences.

Étude de la sorption et de la désorption de neuf contaminants émergents dans les boues usées

Des études de sorption/désorption ont été effectuées pour neuf contaminants émergents sélectionnés (caféine, sulfaméthoxazole, déséthylatrazine, carbamazépine, atrazine, estradiol, éthinylestradiol, noréthindrone et diclofénac) dans les boues usées provenant de trois systèmes différents. Les contaminants incluent une variété de classes de composés (pesticides, hormones et pharmaceutiques) qui possèdent des propriétés physicochimiques différentes. L’objectif de ces travaux est de modéliser leur comportement dans une station d’épuration, en présence d’une phase particulaire et d’une phase aqueuse, et du même coup, de mieux comprendre leur devenir lors de leur rejet dans l’environnement. Le coefficient octanol-eau (log Kow) permet de bien interpréter les résultats et nous permet de classer les composés selon deux types de comportements observés : les composés avec un log Kow inférieur à 3 montrent peu ou pas de sorption alors que les composés avec un log Kow supérieur à 3 montrent une sorption variant de 30 à 90 % durant les premières minutes, suivi d’une sorption lente durant les heures suivantes. Une augmentation du contenu organique favorise la sorption des composés hydrophobes alors qu’un changement de pH peut modifier la charge à la surface des particules et également la charge des analytes. Les résultats ont montré que seul le diclofénac était sensible aux variations de pH étudiés. Dans une telle situation, il est nécessaire d’utiliser le facteur d’hydrophobicité corrigé en fonction du pH (log Dow). Le coefficient de distribution solide-eau (log Kd) a été déterminé pour chaque composé à la fin de chaque expérience de sorption et se situe entre -0.3 et 2.6. Avec l’augmentation de l’hydrophobicité, la désorption diminue avec le temps et avec l’étape de rinçage. Pour simuler le relargage dans les systèmes aquatiques, les facteurs de rinçage ont été déterminés pour estimer le nombre de rinçages qui seraient nécessaire pour désorber 50 et 99 % de la concentration initialement sorbée. Les bilans de masse ont été effectués après chaque expérience dans le but de ne pas surestimer les capacités de sorption d’un composé et se situent entre 7 et 25 % pour l’estradiol, la noréthindrone et le sulfaméthoxazole et entre 44 et 103 % pour l’éthinylestradiol, l’atrazine, la déséthylatrazine, la carbamazépine, la caféine et le diclofénac.

Studies on the Production, Properties and Processability of Low Protein Latex

Latex protein allergy is a serious problem faced by users of natural rubber latex products. This is severe in health care workers, who are constantly using latex products like examination gloves, surgical gloves etc. Out of the total proteins only a small fraction is extractable and only these proteins cause allergic reactions in sensitized people. Enzymic deproteinisation of latex and leaching and chlorination of latex products are the common methods used to reduce the severity of the problem.Enzyme deproteinisation is a cubersome process involving high cost and process loss.Physical properties of such films are poor. Leaching is a lengthy process and in leached latex products presence of extractable proteins is observed on further storing. Chlorination causes yellowing of latex products and reduction in tensile properties.In this context a more simple process of removal of extractable proteins from latex itself was investigated. This thesis reports the application of poly propylene glycol (PPG) to displace extractable proteins from natural latex. PPG is added to 60 % centrifuged natural latex to the extent of 0.2 % m/rn, subssequently diluted to 30 % dry rubber content and again concentrated to obtain a low protein latex.Dilution of concentrated latex and subsequent concentration lead to a total reduction in non - rubber solids in the concentrate, especially proteins and reduction in the ionic concentration in the aqueous phase of the latex. It has been reported that proteins in natural rubber / latex affect its behaviour in the vulcanisation process. Ionic concentration in the aqueous phase of latex influence the stability, viscosity and flow behaviour of natural latex. Hence, a detailed technological evaluation was carried out on this low protein latex. In this study, low protein latex was compared with single centrifuged latex ( the raw material to almost every latex product), double centrifuged latex ( because dilution and second concentration of latex is accompanied by protein removal to some extent and reduction in the ionic concentration of the aqueous phase of latex.). Studies were conducted on Sulphur cure in conventional and EV systems under conditions of post ~ cure and prevulcanisation of latex. Studies were conducted on radiation cure in latex stage. Extractable protein content in vulcanised low protein latex films are observed to be very low. lt is observed that this low protein latex is some what slower curing than single centrifuged latex, but faster than double centrifuged latex. Modulus of low protein latex films were slightly low. In general physical properties of vulcanised low protein latex films are only siightly lower than single centrifuged latex. Ageing properties of the low protein latex films were satisfactory. Viscosity and flow behaviour of low protein latex is much better than double centrifuged latex and almost comparable to single centrifuged latex. On observing that the physical properties and flow behaviour of low protein latex was satisfactory, it was used for the preparation of examination gloves and the gloves were evaluated. It is observed that the properties are conforming to the Indian Standard Specifications. It is thus observed that PPG treatment of natural latex is a simple process of preparing low protein latex. Extractable protein content in these films are very low.The physical properties of the films are comparable to ordinary centrifuged latex and better than conventionally deprotenized latex films. This latex can be used for the production of examination gloves.

Atomistic-continuum modeling of ultrafast laser-induced melting of silicon targets

In this work, we present an atomistic-continuum model for simulations of ultrafast laser-induced melting processes in semiconductors on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with MD method on the atomic level, whereas the laser light absorption, strong generated electron-phonon nonequilibrium, fast heat conduction, and photo-excited free carrier diffusion are accounted for with a continuum TTM-like model (called nTTM). First, we independently consider the applications of nTTM and MD for the description of silicon, and then construct the combined MD-nTTM model. Its development and thorough testing is followed by a comprehensive computational study of fast nonequilibrium processes induced in silicon by an ultrashort laser irradiation. The new model allowed to investigate the effect of laser-induced pressure and temperature of the lattice on the melting kinetics. Two competing melting mechanisms, heterogeneous and homogeneous, were identified in our big-scale simulations. Apart from the classical heterogeneous melting mechanism, the nucleation of the liquid phase homogeneously inside the material significantly contributes to the melting process. The simulations showed, that due to the open diamond structure of the crystal, the laser-generated internal compressive stresses reduce the crystal stability against the homogeneous melting. Consequently, the latter can take a massive character within several picoseconds upon the laser heating. Due to the large negative volume of melting of silicon, the material contracts upon the phase transition, relaxes the compressive stresses, and the subsequent melting proceeds heterogeneously until the excess of thermal energy is consumed. A series of simulations for a range of absorbed fluences allowed us to find the threshold fluence value at which homogeneous liquid nucleation starts contributing to the classical heterogeneous propagation of the solid-liquid interface. A series of simulations for a range of the material thicknesses showed that the sample width we chosen in our simulations (800 nm) corresponds to a thick sample. Additionally, in order to support the main conclusions, the results were verified for a different interatomic potential. Possible improvements of the model to account for nonthermal effects are discussed and certain restrictions on the suitable interatomic potentials are found. As a first step towards the inclusion of these effects into MD-nTTM, we performed nanometer-scale MD simulations with a new interatomic potential, designed to reproduce ab initio calculations at the laser-induced electronic temperature of 18946 K. The simulations demonstrated that, similarly to thermal melting, nonthermal phase transition occurs through nucleation. A series of simulations showed that higher (lower) initial pressure reinforces (hinders) the creation and the growth of nonthermal liquid nuclei. For the example of Si, the laser melting kinetics of semiconductors was found to be noticeably different from that of metals with a face-centered cubic crystal structure. The results of this study, therefore, have important implications for interpretation of experimental data on the kinetics of melting process of semiconductors.

Estimating the direct aerosol radiative perturbation: impact of ocean surface representation and aerosol non-sphericity

Atmospheric aerosols are now actively studied, in particular because of their radiative and climate impacts. Estimations of the direct aerosol radiative perturbation, caused by extinction of incident solar radiation, usually rely on radiative transfer codes and involve simplifying hypotheses. This paper addresses two approximations which are widely used for the sake of simplicity and limiting the computational cost of the calculations. Firstly, it is shown that using a Lambertian albedo instead of the more rigorous bidirectional reflectance distribution function (BRDF) to model the ocean surface radiative properties leads to large relative errors in the instantaneous aerosol radiative perturbation. When averaging over the day, these errors cancel out to acceptable levels of less than 3% (except in the northern hemisphere winter). The other scope of this study is to address aerosol non-sphericity effects. Comparing an experimental phase function with an equivalent Mie-calculated phase function, we found acceptable relative errors if the aerosol radiative perturbation calculated for a given optical thickness is daily averaged. However, retrieval of the optical thickness of non-spherical aerosols assuming spherical particles can lead to significant errors. This is due to significant differences between the spherical and non-spherical phase functions. Discrepancies in aerosol radiative perturbation between the spherical and non-spherical cases are sometimes reduced and sometimes enhanced if the aerosol optical thickness for the spherical case is adjusted to fit the simulated radiance of the non-spherical case.

Hydrophilic sulfonated bis-1,2,4-triazine ligands are highly effective reagents for separating actinides(iii) from lanthanides(iii) via selective formation of aqueous actinide complexes

We report the first examples of hydrophilic 6,6′-bis(1,2,4-triazin-3-yl)-2,2′-bipyridine (BTBP) and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) ligands, and their applications as actinide(III) selective aqueous complexing agents. The combination of a hydrophobic diamide ligand in the organic phase and a hydrophilic tetrasulfonated bis-triazine ligand in the aqueous phase is able to separate Am(III) from Eu(III) by selective Am(III) complex formation across a range of nitric acid concentrations with very high selectivities, and without the use of buffers. In contrast, disulfonated bis-triazine ligands are unable to separate Am(III) from Eu(III) in this system. The greater ability of the tetrasulfonated ligands to retain Am(III) selectively in the aqueous phase than the corresponding disulfonated ligands appears to be due to the higher aqueous solubilities of the complexes of the tetrasulfonated ligands with Am(III). The selectivities for Am(III) complexation observed with hydrophilic tetrasulfonated bis-triazine ligands are in many cases far higher than those found with the polyaminocarboxylate ligands previously used as actinide-selective complexing agents, and are comparable to those found with the parent hydrophobic bis-triazine ligands. Thus we demonstrate a feasible alternative method to separate actinides from lanthanides than the widely studied approach of selective actinide extraction with hydrophobic bis-1,2,4-triazine ligands such as CyMe4-BTBP and CyMe4-BTPhen.

Control and chaos for vibro-impact and non-ideal oscillators

In the paper, we discuss dynamics of two kinds of mechanical systems. Initially, we consider vibro-impact systems which have many implementations in applied mechanics, ranging from drilling machinery and metal cutting processes to gear boxes. Moreover, from the point of view of dynamical systems, vibro-impact systems exhibit a rich variety of phenomena, particularly chaotic motion. In this paper, we review recent works on the dynamics of vibro-impact systems, focusing on chaotic motion and its control. The considered systems are a gear-rattling model and a smart damper to suppress chaotic motion. Furthermore, we investigate systems with non-ideal energy source, represented by a limited power supply. As an example of a non-ideal system, we analyse chaotic dynamics of the damped Duffing oscillator coupled to a rotor. Then, we show how to use a tuned liquid damper to control the attractors of this non-ideal oscillator.