Improvement of the corrosion resistance of polysiloxane hybrid coatings by cerium doping

Polysiloxane hybrid films were deposited on stainless steel by dip-coating using a sol prepared by hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyltrimethoxysilane (MPTS), followed by radical polymerization of methacrylic moieties. The TEOS/MPTS ratio was chosen equal to 2 and the Ce/Si ratio varied between 0.01 and 0.1. The effects of cerium concentration and valence (Ce(III) and Ce (IV)) on the structural features of polysiloxane films were studied by X-ray photoelectron spectroscopy (XPS) and (29)Si nuclear magnetic resonance (NMR). The corrosion protection of stainless steel by the hybrid coatings was investigated by XPS, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves, after immersion in saline and acid solutions. The NMR results have shown for Ce(IV) doped films a high degree of polycondensation of up to 89%. Electrochemical analysis has evidenced that hybrid films with the lowest Ce concentration act as an efficient diffusion barrier by increasing the corrosion resistance and reducing the current densities up to 3 orders of magnitude compared to bare stainless steel. The analysis of structural effects induced by Ce(III) and Ce(IV) species, performed by XPS, indicates that the improved corrosion protection of Ce(IV) doped films might be mainly related to the enhanced polymerization of siloxane groups. (C) 2010 Elsevier B.V. All rights reserved.

Effect of thermal stress on physiological parameters, feed intake and plasma thyroid hormones concentration in Alentejana, Mertolenga, Frisian and Limousine cattle breeds

The aim of the present study was to assess the heat tolerance of animals of two Portuguese (Alentejana and Mertolenga) and two exotic (Frisian and Limousine) cattle breeds, through the monitoring of physiological acclimatization reactions in different thermal situations characterized by alternate periods of thermoneutrality and heat stress simulated in climatic chambers. In the experiment, six heifers of the Alentejana, Frisian and Mertolenga breeds and four heifers of the Limousine breed were used. The increase in chamber temperatures had different consequences on the animals of each breed. When submitted to heat stress, the Frisian animals developed high thermal polypnea (more than 105 breath movements per minute), which did not prevent an increase in the rectal temperature (from 38.7 degrees C to 40.0 degrees C). However, only a slight depression in food intake and in blood thyroid hormone concentrations was observed under thermal stressful conditions. Under the thermal stressful conditions, Limousine animals decreased food intake by 11.4% and blood triiodothyronine (T3) hormone concentration decreased to 76% of the level observed in thermoneutral conditions. Alentejana animals had similar reactions. The Mertolenga cattle exhibited the highest capacity for maintaining homeothermy: under heat stressful conditions, the mean thermal polypnea increased twofold, but mean rectal temperature did not increase. Mean food intake decreased by only 2% and mean T3 blood concentration was lowered to 85,6% of the concentration observed under thermoneutral conditions. These results lead to the conclusion that the Frisian animals had more difficulty in tolerating high temperatures, the Limousine and Alentejana ones had an intermediate difficulty, and the Mertolenga animals were by far the most heat tolerant.

Wettability and photodegradation activity of sol-gel dip-coated zinc oxide films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of helium ion irradiation on fluorinated plasma polymers

The effects of ion irradiation on fluorinated plasma polymer films are investigated using profilometry, surface contact-angle measurements, infrared reflection absorption spectroscopy (IRRAS) and X-ray photoelectron spectroscopy (XPS). Remarkably, helium plasma immersion ion implantation (PIII) of several amorphous hydrogenated fluorinated plasma polymers deposited from C(2)H(2)-SF(6), C(6)H(6)-SF(6) or C(6)F(6) produces film compactions of up to 40%, and modifies the surface energy in the 35 to 65 dyn cm(-1) range. As revealed by IRRAS and XPS, the films contain C-H, C-C, C=C, C=O, O-H and C-F groups. XPS spectra confirm the presence of N (typically similar to 5%). The films produced from SF(6)-containing plasmas also contain S. For irradiation times of 80 min, the film carbon content is increased, and the fluorine content is greatly reduced, by factors of about 3 to 15, depending on the initial film composition. (C) 2010 Elsevier B.V. All rights reserved.

Repair characteristics of horizontal root fracture: a case report

Radicular fractures in permanent teeth are uncommon injuries among dental traumas, comprising 0.5-7% of the cases. Fracture occurs most often in the middle-third of the root and rarely at the apical-third. The present paper reports a clinical case of a horizontal radicular fracture located between the middle- and apical-third of a upper left-central incisor followed-up for over 3 years. The tooth was extracted owing to periodontal reasons. Histomorphologically, it showed pulp-vitality preservation and root healing by hard-tissue deposition.

Small-angle X-ray and nuclear-magnetic resonance study of siloxane-PMMA hybrids prepared by the sol-gel process

Transparent siloxane-polymethylmethacrylate (PMMA) hybrids were synthesized by the sol-gel process through hydrolysis of methacryloxyproyltrimethoxysilane (TMSM), tetramethoxysilane (TMOS) and polymerization of methylmethacrylate (MMA) using benzol peroxide (BPO) as catalyst. These composites have a good chemical stability due to the presence of covalent bonds between the inorganic (siloxane) and organic (PMMA) phases. The effects of siloxane content, pH of the initial sol and BPO content on the structure of the dried gels were analyzed by small-angle X-ray scattering (SAXS). SAXS results revealed the presence of an interference (or correlation) peak at medium q-range for all compositions, suggesting that siloxane groups located at the ends of PMMA chains form isolated clusters that are spatially correlated. The average intercluster distance - estimated from the q-value corresponding to the maximum in SAXS spectra - decreases for samples prepared with increasing amount of TMSM-TMOS. This effect was assigned to the expected increase in the number density of siloxane groups for progressively higher siloxane content. The increase of BPO content promotes a more efficient polymerization of MMA monomers but has no noticeable effect on the average intercluster distance. High pH favors polycondensation reactions between silicon species of both TMOS and TMSM silicon alcoxides, leading to a structure in which all siloxane clusters are bonded to PMMA chains. This effect was confirmed by Si-29 nuclear-magnetic resonance (NMR) measurements.

Gelation and drying of weakly bonded silica-PPO nanocomposites

Silica-poly(oxypropylene) (PPO) nanocomposites containing PPO with weak physical bonds between the organic (PPO) and inorganic (silica) phases were obtained by the sol-gel procedure. Three precursor sols containing silica and PPO with molecular weights of 1000, 2000 and 4000g/mol were prepared. The structure changes during the whole sol-gel process, i.e. sol formation, sol-gel transition and gel aging and drying were investigated in situ by small angle X-ray scattering (SAXS). The experimental SAXS curves corresponding to sols and wet gels containing PPO of molecular weight 1000g/mol indicate that the aggregates formed during the studied process are fractal objects. Close to the sol-gel transition and during gel aging the fractal dimension is D=2.5. A clearly different structure evolution occurs in samples prepared with PPO with molecular weights 2000 and 4000 g/mol. Our SAXS results indicate the presence of two coexisting and well-defined structure levels, one of them corresponding to small silica clusters and the other to large silica aggregates. These two levels remain along the whole transformation. The SAXS curves of all dry samples are similar to those of the corresponding wet gels suggesting that no significant changes at nanoscopic scale occur during the drying process.

SAXS study of monodispersed silica nanospheres obtained by an amino acid route

Spherical silica nanoparticles were prepared using a basic amino acid catalysis route and the kinetics of the particles growth was investigated by small angle X-ray scattering (SAXS). L-arginine was used in the polar aqueous phase as the basic catalyst whereas the tetraethylorthosilicate (TEOS) was dissolved in the cyclohexane oil phase as the silicate monomer source. The SAXS measurements were taken in the aqueous phase at different reaction times. A high degree of monodispersity was clearly evidenced for the spherical nanoparticles as a result of the pronounced high-order oscillations observed in the SAXS curves. The SAXS data show that the particles number density remains unchanged since both the particle size as well as the volume fraction gradually increase. This process was discussed based on a reaction-controlled addition of monomer species at the surface of the growing particles. Consequently, the monodispersed spherical nanoparticles radius can as such be finely tuned from 7 to 12 nm by varying the reaction time. (C) 2010 Elsevier B.V. All rights reserved.

Stimuli-responsive controlled growth of mono- and bidimensional particles from basic zirconium sulfate hydrosols

A thermostimulated sol-gel transition in a system prepared by mixing a ZrOCl(2) acidified solution to a hot H(2)SO(4) aqueous solution was studied by dynamic theological measurements and quasi-elastic light scattering. The effect of temperature and of molar ratio R(S) = [Zr]/[SO(4)] on the gelation kinetics was analyzed using the mass fractal aggregate growth model. This study shows that the linear growth of aggregates occurs at the early period of transformation, while bidimensional growth occurs at the advanced stage. The bidimensional growth can be shifted toward monodimensional growth by decreasing the aggregation rate by controlling the temperature and/or molar ratio R(S). EXAFS and Raman results gave evidence that the linear chain growth is supported by covalent sulfate bonding between primary building blocks. At the advanced stage of aggregation, the assembly of linear chains through hydrogen bonding gave rise to the growth of bidimensional particles.

In Situ and Simultaneous UV-vis/SAXS and UV-vis/XAFS Time-Resolved Monitoring of ZnO Quantum Dots Formation and Growth

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

Controlled fluorination of a-C:F:H films by PECVD of ethylene-hexafluorobenzene mixtures

Highly fluorinated plasma polymers are chemically inert,acid resistant and have low friction coefficients, thereby being useful in chemical laboratories and for tribological applications. Here we report the plasma polymerization of ethylene-hexafluorobenzene mixtures by PECVD. The principal parameter of interest is the proportion of C(6)F(6) in the feed, R(F). Films were analyzed using near-normal and grazing-angle Infrared Reflection Absorption Spectroscopy (IRRAS), the latter being particularly useful for detecting modes not usually observed at near-normal incidence. The presence of CH and CF(x) (x=1 to 2) groups was thus confirmed in films deposited with R(F)>= 40%. Depending on R(F) IRRAS also revealed the presence of -CH(x) (x=1 to 3) -C=C, -C=O and phenyl rings. Deconvolution of C is spectra obtained by X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of CH, CF and CF(2) groups in films deposited with R(F)>= 40%. Atomic ratios of F:C calculated from the XPS spectral data show that the degree of fluorination rises with increasing RF Some unbound fluorine is present in the films. Post-deposition reactions account for the presence of oxygen (similar to 5%) in the films. Surface energies, determined from contact angle measurements, fall with increasing R(F). (C) 2008 Elsevier B.V. All rights reserved.

Controlled growth of anodic aluminium oxide films with hexagonal array of nanometer-sized pores filled with textured copper nanowires

Anodic aluminium oxide (AAO) films exhibiting a homogeneous morphology of parallel pores perpendicular to the surface were prepared in a two-step anodization process and filled with copper by electrochemical deposition. The optimum growth conditions for the formation of freestanding AAO films with hexagonal compact array of cylindrical pores were studied by field emission scanning electron microscopy and small angle X-ray scattering. The results show well-defined periodic structures with uniform pores size distribution for films with pore diameters between 40 and 70 nm prepared using different voltages and temperatures during the second anodization step. X-ray photoelectron spectroscopy and X-ray diffraction analysis of AAO films filled with copper show the formation of nanowires with high structural order, exhibiting a preferential crystalline orientation along the (2 2 0) axis and only small fraction of copper oxides. The best results for textured Cu nanowires were obtained at a reduction potential of -300 mV. (C) 2009 Elsevier Ltd. All rights reserved.

CD147 overexpression allows an accurate discrimination of bladder cancer patients' prognosis

Background: Urothelial bladder carcinoma (UBC) is a chemo-sensitive tumour, but the response to treatment is heterogeneous. CD 147 has been associated with chemotherapy resistance. We aimed to define tumours with an aggressive phenotype by the combined analysis of clinicopathological and biological parameters.Methods: 77 patients with T1G3 or muscle-invasive UBC treated by radical cystectomy were studied. Immunohistochemistry was performed to detect CD147, heparanase, CD31 (blood vessels identification) and D2-40 (lymphatic vessels identification) expressions. The immunohistochemical reactions were correlated with the clinicopathological and the outcome parameters. 5-year disease-free survival (DFS) and overall survival (OS) rates were estimated using the Kaplan-Meier method. Multivariate analysis was performed by Cox proportional hazards analysis.Results: The 5-year DFS and OS rates were significantly influenced by the classical clinicopathological parameters, and by the occurrence of lymphovascular invasion. CD 147 and heparanase immunoexpression did not affect patients' outcome. However, patients with pT3/pT4 tumours had a median OS time of 14.7 months (95% CI 7.1-22.3, p = 0.003), which was reduced to 9.2 months (95% CI 1.5-17.0, p = 0.008) if the tumours were CD147 positive. We developed a model of tumour aggressiveness using parameters as stage, grade, lymphovascular invasion and CD147 immunoexpression, which separated a low aggressiveness from a high aggressiveness group, remaining as an independent prognostic factor of DFS (HR 3.746; 95% CI 1.244-11.285; p = 0.019) and OS (HR 3.247; 95% CI 1.015-10.388, p = 0.047).Conclusion: CD 147 overexpression, included in a model of UBC aggressiveness, may help surgeons to identify patients who could benefit from a personalized therapeutic regimen. Additional validation is needed. (C) 2011 Elsevier Ltd. All rights reserved.

Effects of pretreatment with rosemary (Rosmarinus officinalis L.) in the prevention of lipid oxidation in salted tilapia fillets

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

Drug-matrix interaction of sodium diclofenac incorporated into ureasilpoly(ethylene oxide) hybrid materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)