Mechanism of point-defect diffusion in a two-dimensional colloidal crystal

The dynamics and mechanism of migration of a vacancy point defect in a two-dimensional (2D) colloidal crystal are studied using numerical simulations. We find that the migration of a vacancy is always realized by topology switching between its different configurations. From the temperature dependence of the topology switch frequencies, we obtain the activation energies for possible topology transitions associated with the vacancy diffusion in the 2D crystal. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615287]

Partial magnetic ordering and crystal structure of the ludwigites Co(2)FeO(2)BO(3) and Ni(2)FeO(2)BO(3)

We present an extensive study of the structural, magnetic, and thermodynamic properties of the two heterometallic oxyborates: Co(2)FeO(2)BO(3) and Ni(2)FeO(2)BO(3). This has been carried out through x-ray diffraction at room temperature (RT) and 150 K, dc and ac magnetic susceptibilities, and specific-heat experiments in single crystals above 2 K. The magnetic properties of these iron ludwigites are discussed in comparison with those of the other two known homometallic ludwigites: Fe(3)O(2)BO(3) and Co(3)O(2)BO(3). In both ludwigites now studied we have found that the magnetic ordering of the Fe(3+) ions occurs at temperatures very near to which they order in Fe(3)O(2)BO(3). A freezing of the divalent ions (Co and Ni) is observed at lower temperatures. Our x-ray diffraction study of both ludwigites at RT and 150 K showed very small ionic disorder in apparent contrast with the freezing of the divalent ion spins. The structural transition that occurs in homometallic Fe(3)O(2)BO(3) has not been found in the present mixed ludwigites in the temperature range investigated.

Nonlinear refraction and absorption through phase transition in a Nd:SBN laser crystal

Time-resolved Z-scan measurements were performed in a Nd(3+)-doped Sr(0.61)Ba(0.39)Nb(2)O(6) laser crystal through ferroelectric phase transition. Both the differences in electronic polarizability (Delta alpha(p)) and cross section (Delta sigma) of the neodymium ions have been found to be strongly modified in the surroundings of the transition temperature. This observed unusual behavior is concluded to be caused by the remarkable influence that the structural changes associated to the ferro-to-paraelectric phase transition has on the 4f -> 5d transition probabilities. The maximum polarizability change value Delta alpha(p)=1.2x10(-25) cm(3) obtained at room temperature is the largest ever measured for a Nd(3+)-doped transparent material.

A monohydrate pseudopolymorph of 3,4-dihydroxybenzophenone and the role of water in the crystal assembly of benzophenones

During a polymorphism screening of hydroxybenzophenone derivatives, a monohydrate pseudopolymorph of (3,4-dihydroxyphenyl)(phenyl)methanone, C(13)H(10)O(3)center dot H(2)O, (I), was obtained. Structural relationships and the role of water in crystal assembly were established on the basis of the known anhydrous form [Cox, Kechagias & Kelly (2008). Acta Cryst. B64, 206-216]. The crystal packing of (I) is stabilized by classical intermolecular O-H...O hydrogen bonds, generating a three-dimensional network.

Toxicity of High-Dose Intravitreal Adalimumab (Humira) in the Rabbit

Purpose: To evaluate the ocular toxicity of escalating doses of intravitreous adalimumab (Humira (R)) in the rabbit eye. Methods: Thirty New Zealand albino rabbits received intravitreous injections of 0.5mg (6 eyes), 1.0mg (6 eyes), 2.5mg (6 eyes), 5mg (6 eyes), and 10mg (6 eyes) adalimumab. Slit lamp biomicroscopy and fundoscopy were carried out at baseline, day 7, and day 14 after intravitreous injection, whereas electroretinography (ERG) was carried out at baseline and day 14. Animals were euthanized on day 14, and histopathological examination of the eyes was performed. Results: Slit lamp biomicroscopy and fundoscopy were normal in all eyes receiving doses up to 5mg. In the 10mg group, 3 of 6 eyes showed mild anterior chamber inflammatory reaction on day 7. Similarly, scotopic and photopic a- and b-wave ERG amplitudes at baseline and day 14 were similar in all groups up to 5mg, but there was a significant decrease in the photopic-wave ERG response in the 10mg group (P = 0.046). Finally, histopathology demonstrated no differences among eyes receiving balanced salt solution, 0.5, 1.0, 2.5, 5.0, or 10mg of adalimumab. Conclusions: Intravitreous adalimumab exhibited no associated ocular short-term toxicity in rabbit eyes up to the 5mg dose. In the 10mg group mild clinical findings and ERG amplitude reduction could reflect early toxicity.

Influence of Poly(Vinyl Alcohol) (PVA) on the Cyclic-Voltammetry Behavior of Single-Crystal Pt Surfaces in Aqueous H(2)SO(4)

In the present work we investigated the electrochemical behavior of PVA on polycrystalline Pt and single-crystal Pt electrodes. PVA hampered the characteristic hydrogen UPD and anion adsorption on all investigated surfaces, with the processes on Pt(110) being the most affected by the PVA presence. Several oxidation waves appeared as the potential was swept in the positive direction and the Pt(111) was found to be the most active for the oxidation processes. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3615965] All rights reserved.

Surface structure effects on the electrochemical oxidation of ethanol on platinum single crystal electrodes

Ethanol oxidation has been studied on Pt(111), Pt(100) and Pt(110) electrodes in order to investigate the effect of the surface structure and adsorbing anions using electrochemical and FTIR techniques. The results indicate that the surface structure and anion adsorption affect significantly the reactivity of the electrode. Thus, the main product of the oxidation of ethanol on the Pt(111) electrode is acetic acid, and acetaldehyde is formed as secondary product. Moreover, the amount of CO formed is very small, and probably associated with the defects present on the electrode surface. For that reason, the amount of CO(2) is also small. This electrode has the highest catalytic activity for the formation of acetic acid in perchloric acid. However, the formation of acetic acid is inhibited by the presence of specifically adsorbed anions, such as (bi) sulfate or acetate, which is the result of the formation of acetic acid. On the other hand, CO is readily formed at low potentials on the Pt(100) electrode, blocking completely the surface. Between 0.65 and 0.80 V, the CO layer is oxidized and the production of acetaldehyde and acetic acid is detected. The Pt(110) electrode displays the highest catalytic activity for the splitting of the C-C bond. Reactions giving rise to CO formation, from either ethanol or acetaldehyde, occur at high rate at any potential. On the other hand, the oxidation of acetaldehyde to acetic acid has probably the lower reaction rate of the three basal planes.

EBSD characterization of an ECAP deformed Nb single crystal

A niobium single crystal was subjected to equal channel angular pressing (ECAP) at room temperature after orienting the crystal such that [1 -1 -1] ayen ND, [0 1 -1] ayen ED, and [-2 -1 -1] ayen TD. Electron backscatter diffraction (EBSD) was used to characterize the microstructures both on the transverse and the longitudinal sections of the deformed sample. After one pass of ECAP the single crystal exhibits a group of homogeneously distributed large misorientation sheets and a well formed cell structure in the matrix. The traces of the large misorientation sheets match very well with the most favorably oriented slip plane and one of the slip directions is macroscopically aligned with the simple shear plane. The lattice rotation during deformation was quantitatively estimated through comparison of the orientations parallel to three macroscopic axes before and after deformation. An effort has been made to link the microstructure with the initial crystal orientation. Collinear slip systems are believed to be activated during deformation. The full constraints Taylor model was used to simulate the orientation evolution during ECAP. The result matched only partially with the experimental observation.

TOXICITY EVALUATION AS A TOOL TO ASSES THE PERFORMANCE OF AN ANAEROBIC IMMOBILIZED BIOMASS REACTOR

Effluents from pulp mill are usually toxic and mutagenic. This characteristic is mainly a consequence of xenobiotic compounds that are formed during the process. Global parameters such as chemical oxidation demand, total organic carbon and others, do not permit identify whether the toxic potential was remedied by the treatments or not. The objective of this research was to evaluate the performance of an horizontal-flow anaerobic immobilized biomass reactor (HAIB) treating the bleaching effluent from a Kraft pulp mill using toxicological (Daphnia similis - Ceriodaphnia sdvestrii) mutagenicity and citotoxicological assays (Allium cepa L). The results showed high sensibility of the test-organisms and capability of the anaerobic reactor to remove compounds that are exerting toxic and mutagenic effects. The bioassays represented an attractive alternative to water quality analyzes and the performance evaluation of treatments.

Suitability of Daphnia similis as an alternative organism in ecotoxicological tests: implications for metal toxicity

The acute toxicity of metals to Daphnia similis was determined and compared to other daphnid species to evaluate the suitability of this organism in ecotoxicology bioassays. To verify the performance D. similis in toxicity tests, we also investigated the effect of Pseudokirchneriella subcapitata at 1 x 10(5) and 1 x 10(6) cells ml(-1) on Cd and Cr acute toxicity to the cladoceran. Daphnid neonates were exposed to a range of chromium and cadmium concentrations in the absence and presence of the algal cells. Metal speciation calculations using MINEQL(+) showed that total dissolved metal concentrations in zooplankton culture corresponded to 96.2% free Cd and 100% free Cr concentrations. Initial total dissolved metal concentrations were used for 48 h-LC(50) determination. LC(50) for D. similis was 5.15 x 10(-7) mol l(-1) dissolved Cd without algal cells, whereas with 1 x 10(5) cells ml(-1), it was significantly higher (7.15 x 10(-7) mol l(-1) dissolved Cd). For Cr, the 48 h-LC(50) value of 9.17 x 10(-7) mol l(-1) obtained for the cladoceran in tests with 1 x 10(6) cells ml(-1) of P. subcapitata was also significantly higher than that obtained in tests without algal cells (5.28 x 10(-7) mol l(-1) dissolved Cr). The presence of algal cells reduced the toxicity of metals to D. similis, as observed in other studies that investigated the effects of food on metal toxicity to standard cladocerans. Comparing our results to those of literature, we observed that D. similis is as sensitive to metals as other standardized Daphnia species and may serve as a potential test species in ecotoxicological evaluations.

Biodegradability and toxicity assessment of bleach plant effluents treated anaerobically

As part of an experimental project on the treatment of bleach plant effluents the results of biodegradability and toxicity assessment of effluents from a bench-scale horizontal anaerobic immobilized bioreactor (HAIB) are discussed in this paper. The biodegradability of the bleach plant effluents from a Kraft pulp mill treated in the HAIB was evaluated using the modified Zahn-Wellens test. The inoculum came from a pulp mill wastewater treatment plant and the dissolved organic carbon (DOC) was used as the indicator of organic matter removal. The acute and chronic toxicity removal during the anaerobic treatment was estimated using Daphnia similis and Ceriodaphnia silvestrii respectively. Moreover, the evaluation of chromosome aberrations (CA), micronucleus frequencies (MN) and mitotic index (IM) in Allium cepa cells were used as genotoxicity indicators. The results indicate that the effluents from the anaerobic reactor are amenable to aerobic polishing. Acute and chronic toxicity were reduced by 90 and 81%, respectively. The largest CA and MN incidence in the meristematic cells of A. cepa were observed after exposure to the raw bleach plant effluent. The HAIB was able to reduce the acute and chronic toxicity as well as chromosome aberrations and the occurrence of micronucleus.

Toxicity and recalcitrant compound removal from bleaching pulp plant effluents by an integrated system: anaerobic packed-bed bioreactor and ozone

Effluents originated in cellulose pulp manufacturing processes are usually toxic and recalcitrant, specially the bleaching effluents, which exhibit high contents of aromatic compounds (e.g. residual lignin derivates). Although biological processes are normally used, their efficiency for the removal of toxic lignin derivates is low. The toxicity and recalcitrance of a bleached Kraft pulp mill were assessed through bioassays and ultraviolet absorption measurements, i.e. acid soluble lignin (ASL), UV(280), and specific ultraviolet absorption (SUVA), before and after treatment by an integrated system comprised of an anaerobic packed-bed bioreactor and oxidation step with ozone. Furthermore, adsorbable organic halides (AOX) were measured. The results demonstrated not only that the toxic recalcitrant compounds can be removed successfully using integrated system, but also the ultraviolet absorption measurements can be an interesting control-parameter in a wastewater treatment.

Toxicity-directed approach of polyester manufacturing industry wastewater provides useful information for conducting treatability studies

A broader characterization of industrial wastewaters, especially in respect to hazardous compounds and their potential toxicity, is often necessary in order to determine the best practical treatment (or pretreatment) technology available to reduce the discharge of harmful pollutants to the environment or publicly owned treatment works. Using a toxicity-directed approach, this paper sets the base for a rational treatability study of polyester resin manufacturing. Relevant physical and chemical characteristics were determined. Respirometry was used for toxicity reduction evaluation after physical and chemical effluent fractionation. Of all the procedures investigated, only air stripping was significantly effective in reducing wastewater toxicity. Air stripping in pH 7 reduced toxicity in 18.2%, while in pH 11 a toxicity reduction of 62.5% was observed. Results indicated that toxicants responsible for the most significant fraction of the effluent`s instantaneous toxic effect to unadapted activated sludge were organic compounds poorly or not volatilized in acid conditions. These results led to useful directions for conducting treatability studies which will be grounded on actual effluent properties rather than empirical or based on the rare specific data on this kind of industrial wastewater. (C) 2008 Elsevier B.V. All rights reserved.

Influence of the sidewall crystal orientation, HfSiO nitridation and TiN metal gate thickness on n-MuGFETs under analog operation

This work characterizes the analog performance of SOI n-MuGFETs with HfSiO gate dielectric and TiN metal gate with respect to the influence of the high-k post-nitridation. TiN thickness and device rotation. A thinner TiN metal gate is found favorable for improved analog characteristics showing an increase in intrinsic voltage gain. The devices where the high-k material is subjected to a nitridation step indicated a degradation of the Early voltage (V(EA)) values which resulted in a lower voltage gain. The 45 degrees rotated devices have a smaller V(EA) than the standard ones when a HfSiO dielectric is used. However, the higher transconductance of these devices, due to the increased mobility in the (1 0 0) sidewall orientation, compensates this V(EA) degradation of the voltage gain, keeping it nearly equal to the voltage gain values of the standard devices. (C) 2011 Elsevier Ltd. All rights reserved.

Use of Sugar Cane Vinasse to Mitigate Aluminum Toxicity to Saccharomyces cerevisiae

Owing to its toxicity, aluminum (Al), which is one of the most abundant metals, inhibits the productivity of many cultures and affects the microbial metabolism. The aim of this work was to investigate the capacity of sugar cane vinasse to mitigate the adverse effects of Al on cell growth, viability, and budding, as the likely result of possible chelating action. For this purpose, Fleischmann`s yeast (Saccharomyces cerevisiae) was used in growth tests performed in 125-mL Erlenmeyer flasks containing 30 mL of YED medium (5.0 g/L yeast extract plus 20 g/L glucose) supplemented with the selected amounts of either vinasse or Al in the form of AlCl(3) center dot A H(2)O. Without vinasse, the addition of increasing levels of Al up to 54 mg/L reduced the specific growth rate by 18%, whereas no significant reduction was observed in its presence. The toxic effect of Al on S. cerevisiae growth and the mitigating effect of sugar cane vinasse were quantified by the exponential model of Ciftci et al. (Biotechnol Bioeng 25:2007-2023, 1983). The cell viability decreased from 97.7% at the start to 84.0% at the end of runs without vinasse and to 92.3% with vinasse. On the other hand, the cell budding increased from 7.62% at the start to 8.84% at the end of runs without vinasse and to 17.8% with vinasse. These results demonstrate the ability of this raw material to stimulate cell growth and mitigate the toxic effect of Al.