Surface characterization of absorbing polymer films deposited on transparent glasses

PANI films were deposited on glass substrates by in-situ polymerization and characterized by UV-VIS spectroscopy and atomic force microscopy. A method is developed to accurately analyze ellipsometric data obtained for transparent glass substrates before and after modification with absorbing polymer films. Surface modification was made with an overlayer such as polyaniline ( PANI), which exhibits different optical properties by varying its oxidation state. First, the issue of using transparent substrates for ellipsometry studies was examined and then, spectroscopic ellipsometry was used to characterize absorbing overlayers on transparent glasses. The same methodologies of data analysis can be also applied to other absorbing films on transparent substrates, and deposited by different techniques.

Surface characterization of Ti-7.5Mo alloy modified by biomimetic method

Titanium and its alloys have been used in dentistry due to their excellent corrosion resistance and biocompatibility. It was shown that even a pure titanium metal and its alloys spontaneously form a bone-like apatite layer on their surfaces within a living body. The purpose of this work was to evaluate the growth of calcium phosphates at the surface of the experimental alloy Ti-7.5Mo. We produced ingots from pure titanium and molybdenum using an arc-melting furnace We then submitted these Ingots to heat treatment at 1100 degrees C for one hour, cooled the samples in water, and cold-worked the cooled material by swaging and machining. We measured the media roughness (Ra) with a roughness meter (1.3 and 2.6 mu m) and cut discs (13 mm in diameter and 4 mm in thickness) from each sample group. The samples were treated by biomimetic methods for 7 or 14 days to form an apatite coating on the surface. We then characterized the surfaces with an optical profilometer, a scanning electron microscope and contact angle measurements. The results of this study indicate that apatite can form on the surface of a Ti-7.5Mo alloy, and that a more complete apatite layer formed on the Ra = 2 6 mu m material. This Increased apatite formation resulted in a lower contact angle (C) 2010 Elsevier B.V. All rights reserved

Electrochemical treatment of tannery wastewater using DSA (R) electrodes

In this work we studied the electrochemical treatment of a tannery wastewater using dimensionally stable anodes (DSA (R)) containing tin, iridium, ruthenium, and titanium. The electrodes were prepared by thermal decomposition of the polymeric precursors. The electrolyses were performed under galvanostatic conditions, at room temperature. Effects of the oxide composition, current density, and effluent conductivity were investigated, and the current efficiency was calculated as a function of the time for the performed electrolyses. Results showed that all the studied electrodes led to a decrease in the content of both total phenolic compounds and total organic carbon (TOC), as well as lower absorbance in the UV-vis region. Toxicity tests using Daphnia similis demonstrated that the electrochemical treatment reduced the wastewater toxicity. The use of DSA (R) type electrodes in the electrochemical treatment of tannery wastewater proved to be useful since it can promote a decrease in total phenolic compounds, TOC, absorbance, and toxicity. (C) 2007 Elsevier B.V. All rights reserved.

Corrosion behavior of carbon steel protected with single and bi-layer of silane films filled with silica nanoparticles

The electrochemical behaviour of carbon steel coated with bis-[trimethoxysilylpropyl]amine (BTSPA) filled with silica nanoparticles in naturally aerated 0.1 mol L-1 NaCl solutions was evaluated. The coating was prepared by adding different concentrations of silica nanoparticles (100, 200, 300, 400 and 500 ppm) to the hydrolysis solution and then a second layer without silica nanoparticles was applied. The electrochemical behavior of the coated steel was evaluated by means of open-circuit potential (E-OC), electrochemical impedance spectroscopy (EIS) and polarization curves. Surface characterization was made by atomic force microscopy (AFM), and its hydrophobicity assessed by contact angle measurements. EIS diagrams have shown an improvement of the barrier properties of the silane layer with the silica addition, which was further improved on the bi-layer system. However, a dependence on the filler concentration was verified, and the best electrochemical response was obtained for samples modified with 300 ppm of silica nanoparticles. AFM images have shown a homogeneous distribution of the silica nanoparticles on the sample surface; however particles agglomeration was detected, which degraded the corrosion protection performance. The results were explained on the basis of the improvement of the barrier properties of the coating due to the filler addition and on the onset of defective regions on the more heavily filled coatings allowing easier electrolyte penetration. (C) 2007 Elsevier B.V. All rights reserved.

Response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate membrane

This study investigated the response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate (P(VDF-TrFE)/BT) membrane. Osteoblastic cells were cultured in osteogenic conditions either on P(VDF-TrFE)/BT or polytetrafluoroethylene (PTFE) for up to 14 days. At 7 and 14 days, the mRNA expression of Runt-related transcription factor 2 (RUNX2), Type I collagen (COL I), Osteopontin (OPN), Alkaline phosphatase (ALP), Bone sialoprotein (BSP), and Osteocalcin (OC), key markers of the osteoblastic phenotype, and of Bcl2-associated X protein (Bax), B-cell CLL/lymphoma 2 (Bcl-2), and Survivin (SUR), associated with the control of the apoptotic cell death, was assayed by real-time PCR. In situ ALP activity was qualitatively evaluated by means of Fast red staining. Surface characterization was also qualitatively and quantitatively assayed in terms of topography, roughness, and wettability. Cells grown on P(VDF-TrFE)/BT exhibited a significantly higher mRNA expression for all markers compared to the ones on PTFE, except for Bcl-2, which was not detected for both groups. Additionally, Fast red staining was noticeably stronger in cultures on P(VDF-TrFE)/BT at 7 and 14 days. At micron-and submicron scale, SEM images and roughness analysis revealed that PTFE and P(VDF-TrFE)/BT exhibited a smooth topography and a similar roughness, respectively. PTFE membrane displayed higher contact angles compared with P(VDF-TrFE)/BT, as indicated by wettability assay. The novel P(VDF-TrFE)/BT membrane supports the acquisition of the osteoblastic phenotype in vitro, while up-regulating the expression of apoptotic markers. Further in vivo experiments should be carried out to confirm the capacity of P(VDF-TrFE)/BT membrane in promoting bone formation in guided bone regeneration.

Sisal chemically modified with lignins: Correlation between fibers and phenolic composites properties

Sisal fibers have been chemically modified by reaction with lignins, extracted from sugarcane bagasse and Pinus-type wood and then hydroxymethylated, to increase adhesion in resol-type phenolic thermoset matrices. Inverse gas chromatography (IGC) results showed that acidic sites predominate for unmodified/modified sisal fibers and for phenolic thermoset, indicating that the phenolic matrix has properties that favor the interaction with sisal fibers. The IGC results also showed that the phenolic thermoset has a dispersive component closer to those of the modified fibers suggesting that thermoset interactions with the less polar modified fibers are favored. Surface SEM images of the modified fibers showed that the fiber bundle deaggregation increased after the treatment, making the interfibrillar structure less dense in comparison with that of unmodified fibers, which increased the contact area and encouraged microbial biodegradation in simulated soil. Water diffusion was observed to be faster for composites reinforced with modified fibers, since the phenolic resin penetrated better into modified fibers, thereby blocking water passage through their channels. Overall, composites` properties showed that modified fibers promote a significant reduction in the hydrophilic character, and consequently of the reinforced composite without a major effect on impact strength and with increased storage modulus. (c) 2008 Elsevier Ltd. All rights reserved.

SnO(2)-based materials for pesticide degradation

This study presents the results of the degradation of the pesticide atrazine using electrochemical and photo-assisted electrochemical degradation techniques using SnO(2)-containing electrode of nominal composition electrodes of composition Ti/Ru(x)Sni-(x)O(2) (where X = 0.10, 0.15, 0.20, 0.25 and 0.30). The materials were characterized ex situ and in situ in order to correlate the observed atrazine removal rates with electrode morphology/composition. The results obtained demonstrate the effectiveness of the photo-assisted electrochemical degradation. Using purely electrochemical methods the rate of atrazine removal is almost zero at all the electrodes studied. However, the application of photo-assisted degradation results in almost complete atrazine removal in 1 h of electrolysis. The efficiency of atrazine degradation does not seem to be greatly affected by the electrode material or by SnO(2) content, but the overall COD removal is dependent on the SnO(2) content. Overall, the SnO(2)-containing electrodes do not reach the level of COD removal (maximum similar to 21%) seen for the Ti/Ru(0.3)Ti(0.2)O(2) electrode. An interesting correlation between the morphology factor (phi) and chemical oxygen demand removal is observed. (C) 2010 Elsevier B.V. All rights reserved.

Observational Characterization of the Downward Atmospheric Longwave Radiation at the Surface in the City of Sao Paulo

This work describes the seasonal and diurnal variations of downward longwave atmospheric irradiance (LW) at the surface in Sao Paulo, Brazil, using 5-min-averaged values of LW, air temperature, relative humidity, and solar radiation observed continuously and simultaneously from 1997 to 2006 on a micrometeorological platform, located at the top of a 4-story building. An objective procedure, including 2-step filtering and dome emission effect correction, was used to evaluate the quality of the 9-yr-long LW dataset. The comparison between LW values observed and yielded by the Surface Radiation Budget project shows spatial and temporal agreement, indicating that monthly and annual average values of LW observed in one point of Sao Paulo can be used as representative of the entire metropolitan region of Sao Paulo. The maximum monthly averaged value of the LW is observed during summer (389 +/- 14 W m(-2): January), and the minimum is observed during winter (332 +/- 12 W m(-2); July). The effective emissivity follows the LW and shows a maximum in summer (0.907 +/- 0.032; January) and a minimum in winter (0.818 +/- 0.029; June). The mean cloud effect, identified objectively by comparing the monthly averaged values of the LW during clear-sky days and all-sky conditions, intensified the monthly average LW by about 32.0 +/- 3.5 W m(-2) and the atmospheric effective emissivity by about 0.088 +/- 0.024. In August, the driest month of the year in Sao Paulo, the diurnal evolution of the LW shows a minimum (325 +/- 11 W m(-2)) at 0900 LT and a maximum (345 12 W m-2) at 1800 LT, which lags behind (by 4 h) the maximum diurnal variation of the screen temperature. The diurnal evolution of effective emissivity shows a minimum (0.781 +/- 0.027) during daytime and a maximum (0.842 +/- 0.030) during nighttime. The diurnal evolution of all-sky condition and clear-sky day differences in the effective emissivity remain relatively constant (7% +/- 1%), indicating that clouds do not change the emissivity diurnal pattern. The relationship between effective emissivity and screen air temperature and between effective emissivity and water vapor is complex. During the night, when the planetary boundary layer is shallower, the effective emissivity can be estimated by screen parameters. During the day, the relationship between effective emissivity and screen parameters varies from place to place and depends on the planetary boundary layer process. Because the empirical expressions do not contain enough information about the diurnal variation of the vertical stratification of air temperature and moisture in Sao Paulo, they are likely to fail in reproducing the diurnal variation of the surface emissivity. The most accurate way to estimate the LW for clear-sky conditions in Sao Paulo is to use an expression derived from a purely empirical approach.

Identification and Characterization of Ixodes scapularis Antigens That Elicit Tick Immunity Using Yeast Surface Display

Repeated exposure of rabbits and other animals to ticks results in acquired resistance or immunity to subsequent tick bites and is partially elicited by antibodies directed against tick antigens. In this study we demonstrate the utility of a yeast surface display approach to identify tick salivary antigens that react with tick-immune serum. We constructed an Ixodes scapularis nymphal salivary gland yeast surface display library and screened the library with nymph-immune rabbit sera and identified five salivary antigens. Four of these proteins, designated P8, P19, P23 and P32, had a predicted signal sequence. We generated recombinant (r) P8, P19 and P23 in a Drosophila expression system for functional and immunization studies. rP8 showed anti-complement activity and rP23 demonstrated anti-coagulant activity. Ixodes scapularis feeding was significantly impaired when nymphs were fed on rabbits immunized with a cocktail of rP8, rP19 and rP23, a hall mark of tick-immunity. These studies also suggest that these antigens may serve as potential vaccine candidates to thwart tick feeding.

Biophysical characterization of the recombinant merozoite surface protein-3 of Plasmodium vivax

Plasmodium vivax Merozoite Surface Protein-3 alpha and 3 beta are members of a family of related merozoite surface proteins that contain a central alanine-rich domain with heptad repeats that is predicted to form alpha-helical secondary and coiled-coil tertiary structures. Seven recombinant proteins representing different regions of MSP-3 alpha and MSP-3 beta of P. vivax were generated to investigate their structure. Circular dichroism spectra analysis revealed that some proteins are folded with a high degree of alpha-helices as secondary structure, whereas other products contain a high content of random coil. Using size exclusion chromatography, we found that the two smaller fragments of the MSP-3 alpha, named CC4 and CC5, predicted to form coiled-coil (CC) structures, eluted at volumes corresponding to molecular weights larger than their monomeric masses. This result suggests that both proteins are oligomeric molecules. Analytical ultracentrifugation experiments showed that the CC5 oligomers are elongated molecules. Together, these data may help to understand important aspects of P. vivax biology. (C) 2008 Elsevier B.V. All rights reserved.

Functional Characterization of LcpA, a Surface-Exposed Protein of Leptospira spp. That Binds the Human Complement Regulator C4BP

We have previously shown that pathogenic leptospiral strains are able to bind C4b binding protein (C4BP). Surface-bound C4BP retains its cofactor activity, indicating that acquisition of this complement regulator may contribute to leptospiral serum resistance. In the present study, the abilities of seven recombinant putative leptospiral outer membrane proteins to interact with C4BP were evaluated. The protein encoded by LIC11947 interacted with this human complement regulator in a dose-dependent manner. The cofactor activity of C4BP bound to immobilized recombinant LIC11947 (rLIC11947) was confirmed by detecting factor I-mediated cleavage of C4b. rLIC11947 was therefore named LcpA (for leptospiral complement regulator-acquiring protein A). LcpA was shown to be an outer membrane protein by using immunoelectron microscopy, cell surface proteolysis, and Triton X-114 fractionation. The gene coding for LcpA is conserved among pathogenic leptospiral strains. This is the first characterization of a Leptospira surface protein that binds to the human complement regulator C4BP in a manner that allows this important regulator to control complement system activation mediated either by the classical pathway or by the lectin pathway. This newly identified protein may play a role in immune evasion by Leptospira spp. and may therefore represent a target for the development of a human vaccine against leptospirosis.

Oxide surface modification: Synthesis and characterization of zirconia-coated alumina

Four aluminas were used as Supports for impregnation with a zirconium oxide with the aim to achieve a coating, without phase separation, between Support and modifier. The Supports were impregnated with different concentrations Of zirconium aqueous resin, obtained through the polymeric precursor method. After impregnation the samples were calcined and then characterized by XRD, which led to identification of crystalline zirconia in different concentrations from each support used. Using a simple geometric model the maximum amount Of Surface modifier Oxide required for the complete coating of a support with a layer of unit cells was estimated. According to this estimate, only the support should be identified below the limit proposed and crystalline zirconium oxide Should be identified above this limit when a complete coating is reached. The results obtained From XRD agree with the estimated values and to confirm the coating, the samples were also characterized by EDS/STEM, HRTEM, XPS, and XAS. The results showed that the zirconium oxide oil the Surface of alumina Support reached the coating in the limit of 15 Zr nm(-2), without the formation of the ZrO(2) phase. (c) 2009 Elsevier Inc. All rights reserved.

The reaction of methyl radical with nitrogen atom on the triplet potential energy surface: A CCSD(T)/CBS characterization

CCSD(T)/cc-pVnZ (n = D, T, Q) calculations followed by extrapolations to the CBS limit are used to characterize stationary states of species participating in the N((4)S) + CH(3) (2A ``) reaction on the triplet PES. A mechanistic model is investigated and reaction rates are computed for every step and the overall reaction. Our best CBS estimate (1.93 x 10(10) cm(3) molecule(1) s(1)) for the overall rate constant leading to the formation of H(2)CN + H compares well with the experimental values (8.5 x 10 (11) and 1.3 x 10(10) cm(3) molecule(1) s(1)), thus reducing significantly the discrepancy of a previous theoretical result (9.1 x 10(12) cm(3) molecule(1) s(1)). (C) 2008 Elsevier B.V. All rights reserved.

Surface and subsurface erosion of primary enamel by acid beverages over time

This study evaluated the influence of a cola-type soft drink and a soy-based orange juice on the surface and subsurface erosion of primary enamel, as a function of the exposure time. Seventy-five primary incisors were divided for microhardness test (n=45) or scanning electron microscopy (SEM) analysis (n=30). The specimens were randomly assigned to 3 groups: 1 - artificial saliva (control); 2 - cola-type soft drink; and 3 - soy-based orange juice. Immersion cycles in the beverages were undertaken under agitation for 5 min, 3 times a day, during 60 days. Surface microhardness was measured at 7, 15, 30, 45 and 60 days. After 60 days, specimens were bisected and subsurface microhardness was measured at 30, 60, 90, 120, 150 and 200 µm from the surface exposed. Data were analyzed by ANOVA and Tukey’s test (a=0.05). Groups 2 and 3 presented similar decrease of surface microhardness. Regarding subsurface microhardness, group 2 presented the lowest values. SEM images revealed that after 60 days the surfaces clearly exhibited structural loss, unlike those immersed in artificial saliva. It may be concluded that erosion of the surfaces exposed to the cola-type soft drink was more accentuated and directly proportional to the exposure time.

Characterization of thiol-functionalised silica films deposited on electrode surfaces

Thiol-functionalised silica films were deposited on various electrode surfaces (gold, platinum, glassy carbon) by spin-coating sol-gel mixtures in the presence of a surfactant template. Film formation occurred by evaporation induced self-assembly (EISA) involving the hydrolysis and (co)condensation of silane and organosilane precursors on the electrode surface. The characterization of such material was performed by IR spectroscopy, thermogravimetry (TG), elemental analysis (EA), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV).