Protective film growth on tin in perchlorate and citric acid electrolytes

Voltammetry has been employed to study the influence of systematic additions of citric acid on the E-I curves of Tin in 0.5 M NaClO4, in order to verify the film growth in the presence of the organic acid and the inhibition of the pitting corrosion of the metal. The minimum concentration of the organic acid needed to change the GI curves is 10(-2) M, in the pH range 1.0-4.0. At pH 3.0 and 4.0, the scan rate dependence on current density, in the potential region of formation and reduction of the film, showed that in a first stage adsorption occurs. In a second stage, the v(1/2) dependence found can he explained by ohmic resistance control. The formation of tin/citric acid complexes, 10(-2) M, is suggested. The pitting inhibition may be due to the formation of a mixed layer of tin in citric acid concentrations higher than 10(-2) oxide and tin citrate complexes on the electrode surface. (C) 2001 Elsevier Science B.V. All rights reserved.

Speciation analysis of inorganic arsenic in river water by Amberlite IRA 910 resin immobilized in a polyacrylamide gel as a selective binding agent for As(v) in diffusive gradient thin film technique

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

Carbon Film Coating of Abutment Surfaces: Effect on the Abutment Screw Removal Torque

Purpose: To evaluate the effect of diamond-like carbon (DLC) coating of prefabricated implant abutment on screw removal torque (RT) before and after mechanical cycling (MC).Materials and Methods: Fifty-four abutments for external-hex implants were divided among 6 groups (n = 9): S, straight abutment (control); SC, straight coated abutment; SCy, straight abutment and MC; SCCy, straight coated abutment and MC; ACy, angled abutment and MC; and ACCy, angled coated abutment and MC. The abutments were attached to the implants by a titanium screw. RT values were measured and registered. Data (in Newton centimeter) were analyzed with analysis of variance and Dunnet test (alpha = 0.05).Results: RT values were significantly affected by MC (P = 0.001) and the interaction between DLC coating and MC (P = 0.038). SCy and ACy showed the lowest RT values, statistically different from the control. The abutment coated groups had no statistical difference compared with the control. Scanning electron microscopy analysis showed DLC film with a thickness of 3 mm uniformly coating the hexagonal abutment.Conclusion: DLC film deposited on the abutment can be used as an alternative procedure to reduce abutment screw loosening.

Development of organic-inorganic polymeric film formers for controlled drug release and wound care

Film forming polymeric systems represents a new and unexplored technology of systems forskin or wounds protection and for controlled drug release. The aim of this work was to study the use of polymeric organic-inorganic ureasil-polyether hybrids synthesized by the sol-gel process as film forming system containing silver sulfadiazine as model drug. The film formationtime can be controlled by changing the precursor/catalyst ratio used during the step of hydrolysis and condensations. The results showed that the precursor/catalyst proportion influences both the visual characteristics and time required to form the film. The precursor/catalyst ratio equal to 20.8 m/v was considered ideal due to promote the homogeneous and transparent film formation in less than 5 minutes. The release profile of sulfadiazine is dependent on the characteristics of the matrixes: matrix more hydrophobic as ureasil-POP provided a slowed released mainly due to the low swelling of the matrix. The more hydrophilic ureasil-POE matrix presents a large capacity to swell and favors the faster release of the drug. The set of results showed the possibility of future use of these systems for treating wounds caused by burns.

Fácies, diagênese e arquitetura estratigráfica de reservatórios deltaico-lacustres da fase rifte (formação pendência), campo Serraria da Bacia Potiguar

Of the four lacustrine deltaic models, which were found in the Pendência formation, two are represented in the Serraria field. Respectively the deltaic models 1 and 3 shows the reservoir zones A and B. The Zone A is divided into six sub-areas. Each is representing a smaller cycle of development of sigmoidal lobes of deltaic front. Zone B produces in reservoirs of Model 3, or so called Full delta. The Zone B is formed by overlapping the deltaic plain system over the deltaic/prodeltaic front (model 1). This work uses the method of zooming with the aim to contextualize the geometric aspects of the sand bodies, highlighting the analysis of facies and diagenesis with help of pictures and testimonies of thin sections. The sigmoidal lobes of Zone A are fine to very fine sandstones, well sorted, with a arcosian composition.;practically with a weak compaction and cementation of a kind of film of clay (if very fine) and overgrowth feldspar (fine texture). This silicate phases are succeeded by cementation of poiquilotópica calcite, and after this a stage of dissolution, containing only regular permoporosity for this reservoir. Zone B has a combination of two types of deltaic plain reservoir. One is the rarest of distributary channel and the other the most common of lobes of crevasse. In the channel coarse to medium-grained and poor to moderate sorted sandstones are formed (tuning up), and with a lytic arcosiana nature. Rarely there are cements, including growth of feldspar and rhombohedral dolomite, which prevent a high permoporosity of the reservoir. In the crevasse lobes, the sandstones are laminated, fine and well sorted, arkosic, rarely with overgrowth feldspar and calcite poiquilotópica, and with a good intergranular permoporosity

A Solid Film Electrode of Intermetallic Ag 2 Hg 3.02 for the Direct Determination of Folic Acid in Fresh and Processed Fruit Juices

AgSIE was used for the direct analysis of folic acid (FA), with a detection limit and lower level of quantitation of 6.8 x10-10 mol L-1 and 2.3 x 10 8 mol L-1. The analysis in fresh and processed fruits was done without any sample pretreatment. In strawberry and acerola juices, FA concentration level values were below the method detection limit. FA was detectable in peach (77.7 0.4 mg L-1 and 64.4 0.5 mgL-1), Persian lime (45.4 0.7 mg L-1), pineapple Hawaii (66.2 0.4 mgL-1), pear pineapple (35.3 0.6 mgL-1), cashew (54.4 0.5 mgL-1) , passion fruit (73.2 0.3 mgL-1), and apple (84.4 0.5 mg L-1 ).

Tetraethylortossilicate plasma thin film with hydrophilic and hydrophobic characteristics: Use on passive mixers

This work aims to obtain plasma thin film composites with hydrophobic/hydrophilic alternated regions, which are useful for the production of miniaturized mixers. These regions were acquired by two different strategies: either the codeposition of TEOS and HFE plasma thin films or the exposition of TEOS plasma films to ultraviolet radiation (UVA and UVC). These films were characterized by several chemical and physical techniques. The refractive indexes vary from 1.4 to 1.7; infrared and photoelectron spectroscopy detect Si-O-Si and CHn species. Silicone-like structures with high or low number of amorphous carbon microparticles and with fluorinated organic clusters were produced. Cluster dimensions were in the 1-5 mm range and they are made of graphite or COF (carbon/oxygen/fluorine) compounds. Scanning electron and optical microscopy showed rough surfaces. Water contact angles were 90º; however, for TEOS films that value changed after 6 hr of UVC exposure. Moreover, after UV exposure, organic polar compounds could be adsorbed in those films and water was not. The passive mixer performance was simulated using the FemLab 3.2® program and was tested with 20 nm thick films on a silicon wafer, showing the capacity of these films to be used in such devices.

Composite Thin Film Obtained Using Tetraethoxysilane and Aimed at VOCs Detection

The aim of this work was production of tetraethoxysilane (TEOS) plasma polymerized thin films and optimization of their physical-chemical characteristic for sensor development. The films were analyzed using several techniques. It was possible to produce composites (graphite clusters imbibed by silicon oxide film) made from only one reactant (TEOS). Deposition rate can vary significantly, reaching a maximum of 30 nm/min; cluster formation and their size widely depending on deposition parameters. The film surface was hydrophobic but can be wetted by organic compounds, probably due to carbon radicals. These films are good candidates for sensor development.

In vitro evaluation of Biosilicate® dissolution on dentin surface: a SEM analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of polyethylene film wrap on cooler shrink and the microbial status of beef carcasses

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Luminescence of Eu3+ in the thin film heterojunction GaAs/SnO2

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photoluminescence of the Eu-doped thin film heterojunction GaAs/SnO2 and rare-earth doping distribution

Tin dioxide (SnO2) thin films doped with Eu3+, are deposited by the sol-gel-dip-coating process on top of GaAs films, which is deposited by resistive evaporation on glass substrate. This heterojunction assembly presents luminescence from the rare-earth ion, unlike the SnO2 deposition directly on a glass substrate, where emissions from the Eu3+ transitions are absent. The Eu3+ transitions are clearly identified and are similar to the observation on SnO2 pressed powder (pellets), thermally treated at much higher temperatures. However, in the form of heterojunction films, the Eu emission comes along a broad band, located at higher energy compared to Eu3+ transitions, which is blue-shifted as the thermal annealing temperature increases. The size of nanocrystallites points toward quantum confinement or electron transfer between oxygen vacancies, originated from the disorder in the material, and trivalent rare-earth ions, which present acceptor-like character in this matrix. This electron transfer may relax for higher temperatures in the case of pellets, and the broad band is eliminated.

Poloxamer-based binary hydrogels for delivering tramadol hydrochloride: sol-gel transition studies, dissolution-release kinetics, in vitro toxicity, and pharmacological evaluation

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

Ozone and nitrogen dioxide gas sensor based on a nanostructured SrTi0.85Fe0.15O3 thin film

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)