Photoelectrocatalytic production of active chlorine on nanocrystalline titanium dioxide thin-film electrodes

The production of chlorine and hypochlorite is of great economical and technological interest due to their large-scale use in many kinds of commercial applications. Yet, the current processes are not without problems such as inevitable side reactions and the high cost of production. This work reports the photoelectrocatalytic oxidation of chloride ions to free chlorine as it has been investigated by using titanium dioxide (TiO2) and several metal-doped titanium dioxide (M-TiO2) material electrodes. An average concentration of 800 mg L-1 of free chlorine was obtained in an open-air reactor using a TiO2 thin-film electrode biased at +1.0 V (SCE) and illuminated by UV light. The M-doped electrodes have performed poorly compared with the pure TiO2 counterpart. Test solutions containing 0.05 mol L-1 NaCl pH 2.0-4.0 were found to be the best conditions for fast production of free chlorine. A complete investigation of all parameters that influence the global process of chlorine production by the photoelectrocatalytic method such as applied potential, concentration of NaCl, pH solution, and time is presented in detail. In addition, photocurrent vs potential curves and the reaction order are also discussed.

Adsorption of dihydrogen phosphate ion on platinum electrodes in aqueous media monitored by probe-beam deflection

Probe-beam deflection (PBD) was used to monitor concentration gradients of anions adjacent to the surface of a platinum electrode in acidic aqueous media containing H3PO4. PBD can measure the potential-dependent extent of adsorption of H2PO4- on the Pt electrode surface and permits the Langmuir isotherm to be fitted to the experimental data. The value thus obtained for the surface concentration was 1.3 × 10-11 mol mm -2, or 1.7 atoms of Pt per H2PO4-. Also, the electron transfer number obtained was 0.24, signifying an incomplete transfer of charge, and the equilibrium constant is 1.80 suggesting a reversible adsorption process. © 2005 Elsevier B.V. All rights reserved.

Prediction of voltage over electrodes' filaments of fluorescent lamps during dimming operation

This paper presents an investigation concerning the use of fundamental approximation analysis and a new lamp model for the prediction of the voltage over electrodes' filaments during dimming operation. The lamp model employed in this paper is based on equivalent resistances, which represent the electrodes' filaments and the gas column of a F32T8 lamp. Experimental results are presented in this paper, indicating the validity of the proposed analysis and confirming its potential to serve as an effective tool for the design of dimming electronic ballasts. © 2005 IEEE.

A review on the development and properties of continuous fiber/epoxy/aluminum hybrid composites for aircraft structures

Weight reduction and improved damage tolerance characteristics were the prime drivers to develop new family of materials for the aerospace/ aeronautical industry. Aiming this objective, a new lightweight Fiber/ Metal Laminate (FML) has been developed. The combination of metal and polymer composite laminates can create a synergistic effect on many properties. The mechanical properties of FML shows improvements over the properties of both aluminum alloys and composite materials individually. Due to their excellent properties, FML are being used as fuselage skin structures of the next generation commercial aircrafts. One of the advantages of FML when compared with conventional carbon fiber/epoxy composites is the low moisture absorption. The moisture absorption in FML composites is slower when compared with polymer composites, even under the relatively harsh conditions, due to the barrier of the aluminum outer layers. Due to this favorable atmosphere, recently big companies such as EMBRAER, Aerospatiale, Boing, Airbus, and so one, starting to work with this kind of materials as an alternative to save money and to guarantee the security of their aircrafts.

Anelastic spectroscopy in potassium aluminum metaphosphate glasses

Anelastic spectroscopy (internal friction and the dynamic modulus) was measured by means of a torsion pendulum at 3-12 Hz, in the range of 100-300 K, for a KAP metaphosphate glass. Two thermally activated internal friction peaks appeared at ∼190 and ∼250 K. These peaks were attributed to the behavior of potassium ions (high temperature) and to hydrogen (low temperature). Dynamic modulus showed a gradual decrease with increasing temperature in the range studied for all compositions. © 2006 Elsevier B.V. All rights reserved.

Analysis of the distances covered by first division Brazilian soccer players obtained with an automatic tracking method

Methods based on visual estimation still is the most widely used analysis of the distances that is covered by soccer players during matches, and most description available in the literature were obtained using such an approach. Recently, systems based on computer vision techniques have appeared and the very first results are available for comparisons. The aim of the present study was to analyse the distances covered by Brazilian soccer players and compare the results to the European players', both data measured by automatic tracking system. Four regular Brazilian First Division Championship matches between different teams were filmed. Applying a previously developed automatic tracking system (DVideo, Campinas, Brazil), the results of 55 outline players participated in the whole game (n = 55) are presented. The results of mean distances covered, standard deviations (s) and coefficient of variation (cv) after 90 minutes were 10,012 m, s = 1,024 m and cv = 10.2%, respectively. The results of three-way ANOVA according to playing positions, showed that the distances covered by external defender (10642 ± 663 m), central midfielders (10476 ± 702 m) and external midfielders (10598 ± 890 m) were greater than forwards (9612 ± 772 m) and forwards covered greater distances than central defenders (9029 ± 860 m). The greater distances were covered in standing, walking, or jogging, 5537 ± 263 m, followed by moderate-speed running, 1731 ± 399 m; low speed running, 1615 ± 351 m; high-speed running, 691 ± 190 m and sprinting, 437 ± 171 m. Mean distance covered in the first half was 5,173 m (s = 394 m, cv = 7.6%) highly significant greater (p < 0.001) than the mean value 4,808 m (s = 375 m, cv = 7.8%) in the second half. A minute-by-minute analysis revealed that after eight minutes of the second half, player performance has already decreased and this reduction is maintained throughout the second half. ©Journal of Sports Science and Medicine (2007).

Simulation of needle-type corona electrodes by the finite element method

This paper describes a software tool, called LEVSOFT, suitable for the electric field simulations of corona electrodes by the Finite Element Method (FEM). Special attention was paid to the user friendly construction of geometries with corners and sharp points, and to the fast generation of highly refined triangular meshes and field maps. The execution of self-adaptive meshes was also implemented. These customized features make the code attractive for the simulation of needle-type corona electrodes. Some case examples involving needle type electrodes are presented.

Response of human dental pulp capped with MTA and calcium hydroxide powder

Objectives: To compare the response of human dental pulp capped with a mineral trioxide aggregate (MTA) and Ca(OH) 2 powder. Methods and Material: Pulp exposures were performed on the occlusal floor of 40 permanent premolars. The pulp was then capped with either Ca(OH) 2 powder (CH) or MTA and restored with resin composite. After 30 days (groups CH30 and MTA30) and 60 days (groups CH60 and MTA60), the teeth were extracted and processed for HE and categorized in a histological score system. The data were subjected to Kruskal-Wallis and Conover tests (α=0.05). Results: In regard to dentin bridge formation, CH30 showed a tendency towards superior performance compared to MTA30 (p>0.05), although the products showed comparable results at day 60. In the item Inflammation and General State of the Pulp (p>0.05), CH showed a tendency towards presenting a higher inflammatory response. In the item Other Pulpal Findings, MTA and Ca(OH) 2 showed equal and excellent performance after 30 and 60 days (p>0.05). Conclusion: After 30 days, Ca(OH) 2 powder covered with calcium hydroxide cement showed faster hard tissue bridge formation compared to MTA. After 60 days, Ca(OH) 2 powder or MTA materials showed a similar and excellent histological response with the formation of a hard tissue bridge in almost all cases with low inflammatory infiltrate. © Operative Dentistry, 2008.

The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

The reduction of guanine was studied by microelectrode voltammetry in the room temperature ionic liquids (RTILs) N-hexyltriethylammonium bis (trifluoromethanesulfonyl) imide [N6,2,2,2][N(Tf)2], 1-butyl-3-methylimidazolium hexafluorosphosphate [C4mim][PF6], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide [C4mpyrr][N(Tf)2], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C4mim][N(Tf)2], N-butyl-N-methyl-pyrrolidinium dicyanamide [C4mpyrr][N(NC)2] and tris(P-hexyl)-tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P14,6,6,6][FAP] on a platinum microelectrode. In [N6,2,2,2][NTf2] and [P14,6,6,6][FAP], but not in the other ionic liquids studied, guanine reduction involves a one-electron, diffusion-controlled process at very negative potential to produce an unstable radical anion, which is thought to undergo a dimerization reaction, probably after proton abstraction from the cation of the ionic liquid. The rate of this subsequent reaction depends on the nature of the ionic liquid, and it is faster in the ionic liquid [P14,6,6,6][FAP], in which the formation of the resulting dimer can be voltammetrically monitored at less negative potentials than required for the reduction of the parent molecule. Adenine showed similar behaviour to guanine but the pyrimidines thymine and cytosine did not; thymine was not reduced at potentials less negative than required for solvent (RTIL) decomposition while only a poorly defined wave was seen for cytosine. The possibility for proton abstraction from the cation in [N6,2,2,2][NTf2] and [P14,6,6,6][FAP] is noted and this is thought to aid the electrochemical dimerization process. The resulting rapid reaction is thought to shift the reduction potentials for guanine and adenine to lower values than observed in RTILs where the scope for proton abstraction is not present. Such shifts are characteristic of so-called EC processes where reversible electron transfer is followed by a chemical reaction. © 2009 Elsevier B.V.

Effectiveness of intraoral suction systems and aspirating tips for evacuation of aluminum oxide particles during use of air-abrasion

Aim: The purpose of this study was to compare the effectiveness of a high-volume evacuation and a conventional intraoral suction system and aspirating tips for capturing aluminum oxide particles during use of an air-abrasion device. Methods: A phantom head was fixed at the dental chair head with secured a metallic device with 5 horizontal shafts, corresponding to operator's clockrelated working positions, and one vertical shaft to simulate the operator's nasal cavity. Petri plates were fixed to the shafts at distances of 20, 40 and 60 cm from the center of the oral cavity of the phantom head to collect the aluminum oxide particles spread over during air abrasion. The dust was aspirated with two types of suction tips used with both suction systems: a conventional saliva ejector and a saliva ejector customized by the adaptation of a 55-mm-diameter funnel. Results: The amount of particles showed that the greatest abrasive particle deposition occurred at a distance of 20 cm from the center of the oral cavity of the phantom head at 9 o'clock operatory position with the conventional saliva ejector attached to high-volume evacuation system. Conclusions: The greatest deposition of aluminum oxide particles occurred at the shortest distance between the operator and the center of the oral cavity, while using the high-volume evacuation system associated to the conventional suction tip.

Stress distribution in ceramic restorations over natural tooth using finite element analysis. lithium disilicate x aluminum oxide material

Background: Data on stress distribution in tooth-restoration interface with different ceramic restorative materials are limited. The aim of this chapter was to assess the stress distribution in the interface of ceramic restorations with laminate veneer or full-coverage crown with two different materials (lithium dissilicate and densely sintered aluminum oxide) under different loading areas through finite element analysis. Materials and Methods: Six two-dimensional finite element models were fabricated with different restorations on natural tooth: laminate veneer (IPS Empress, IPS Empress Esthetic and Procera AllCeram) or full-coverage crown (IPS e.max Press and Procera AllCeram). Two different loading areas (L) (50N) were also determined: palatal surface at 45° in relation to the long axis of tooth (L1) and perpendicular to the incisal edge (L2). A model with higid natural tooth was used as control. von Mises equivalent stress (σ vM) and maximum principal stress (σ max) were obtained on Ansys software. Results: The presence of ceramic restoration increased σ vM and σ max in the adhesive interface, mainly for the aluminum oxide (Procera AllCeram system) restorations. The full-coverage crowns generated higher stress in the adhesive interface under L1 while the same result was observed for the laminate veneers under L2. Conclusions: Lithium dissilicate and densely sintered aluminum oxide restorations exhibit different behavior due to different mechanical properties and loading conditions. © 2011 Nova Science Publishers, Inc.

Shear bond strength of resin cement bonded to alumina ceramic after treatment by aluminum oxide sandblasting or silica coating

Purpose: To evaluate the shear bond strength and bond durability between a dual-cured resin cement (RC) and a high alumina ceramic (In-Ceram Alumina), subjected to two surface treatments. Materials and Methods: Forty disc-shaped specimens (sp) (4-mm diameter, 5-mm thick) were fabricated from In-Ceram Alumina and divided into two groups (n = 20) in accordance with surface treatment: (1) sandblasting by aluminum oxide particles (50 μm Al 2O 3) (SB) and (2) silica coating (30 μm SiO x) using the CoJet system (SC). After the 40 sp were bonded to the dual-cured RC, they were stored in distilled water at 37°C for 24 hours. After this period, the sp from each group were divided into two conditions of storage (n = 10): (a) 24 h-shear bond test 24 hours after cementation; (b) Aging-thermocycling (TC) (12,000 times, 5 to 55°C) and water storage (150 days). The shear test was performed in a universal test machine (1 mm/min). Results: ANOVA and Tukey (5%) tests noted no statistically significant difference in the bond strength values between the two surface treatments (p= 0.7897). The bond strengths (MPa) for both surface treatments reduced significantly after aging (SB-24: 8.2 ± 4.6; SB-Aging: 3.7 ± 2.5; SC-24: 8.6 ± 2.2; SC-Aging: 3.5 ± 3.1). Conclusion: Surface conditioning using airborne particle abrasion with either 50 μm alumina or 30 μm silica particles exhibited similar bond strength values and decreased after long-term TC and water storage for both methods. © 2011 by The American College of Prosthodontists.

Effect of brushing with conventional versus whitening dentifrices on surface roughness and biofilm formation of dental ceramics

The aim of this study was to evaluate the effect of conventional and whitening dentifrices on the weight loss, surface roughness, and early in situ biofilm formation on the surface of dental ceramics. Standardized feldspar ceramic specimens (Vita VM7 and Vita VM13) were submitted to the following experimental conditions: no brushing; brushing without a dentifrice; brushing with a conventional dentifrice; and brushing with a whitening dentifrice. A brushing machine was used to simulate brushing. The mass and surface roughness of all specimens from the test groups were evaluated prior to and after brushing. Ten participants used an oral device for eight hours to evaluate the biofilm formed in situ on the specimens. Scanning electron microscopy was used for qualitative and quantitative analysis of the biofilm. ANOVA and Tukey tests were used to analyze the results of weight loss, surface roughness, and presence of bacteria. A one-way Kruskal-Wallis test was used for bacterial colonization results. For both ceramics, brushing with a whitening dentifrice resulted in weight loss that was significantly greater when compared to brushing without a dentifrice or with a conventional dentifrice. Increased surface roughness was noticed on VM13 ceramic samples with both dentifrices, whereas only conventional dentifrice had a significant effect on the surface roughness of VM7 samples. For both VM7 and VM13, no difference was found between the experimental conditions with regard to the presence or number of bacteria. Cocci and short rods were the predominant microbial morphotypes. Granular or fibrillar acellular material partially covered the specimens. Brushing with a whitening dentifrice resulted in significant weight loss of ceramic restorations, while brushing with both conventional and whitening dentifrices can roughen ceramic surfaces. The increase in roughness was not clinically significant to contribute to increased biofilm formation.

Photodynamic inactivation of planktonic cultures and biofilms of Candida albicans mediated by aluminum-chloride-phthalocyanine entrapped in nanoemulsions

New drug delivery systems, such as nanoemulsions (NE), have been developed to allow the use of hydrophobic drugs on the antimicrobial photodynamic therapy. This study evaluated the photodynamic potential of aluminum-chloride- phthalocyanine (ClAlPc) entrapped in cationic and anionic NE to inactivate Candida albicans planktonic cultures and biofilm compared with free ClAlPc. Fungal suspensions were treated with different delivery systems containing ClAlPc and light emitting diode. For planktonic suspensions, colonies were counted and cell metabolism was evaluated by XTT assay. Flow cytometry evaluated cell membrane damage. For biofilms, the metabolic activity was evaluated by XTT and ClAlPc distribution through biofilms was analyzed by confocal laser scanning microscopy (CLSM). Fungal viability was dependent on the delivery system, superficial charge and light dose. Free ClAlPc caused photokilling of the yeast when combined with 100 J cm-2. Cationic NE-ClAlPc reduced significantly both colony counts and cell metabolism (P < 0.05). In addition, cationic NE-ClAlPc and free ClAlPc caused significant damage to the cell membrane (P < 0.05). For the biofilms, cationic NE-ClAlPc reduced cell metabolism by 70%. Anionic NE-ClAlPc did not present antifungal activity. CLSM showed different accumulation on biofilms between the delivery systems. Although NE system showed a lower activity for planktonic culture, cationic NE-ClAlPc showed better results for Candida biofilms. Candida albicans biofilm overview after 30 min of contact with free ClAlPc. This study presents the photodynamic potential of aluminum-chloride-phthalocyanine (ClAlPc) entrapped in cationic and anionic nanoemulsions (NE) to inactivate C. albicans planktonic cultures and biofilm comparing with free ClAlPc. The photodynamic effect was dependent on the delivery system, superficial charge and light dose. Cationic NE-ClAlPc and free ClAlPc caused significant reduction in colony counts, cell metabolism and damage to the cell membrane (P < 0.05). However, only the free ClAlPc was able to cause photokilling of the yeast. The anionic NE-ClAlPc did not present antifungal activity. Although NE system showed a lower activity for planktonic culture, cationic NE-ClAlPc showed better results for Candida biofilms. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

On the application of nanostructured electrodes prepared by Ti/TiO2/WO3 template : A case study of removing toxicity of indigo using visible irradiation

New assays with HepG2 cells indicate that Indigo Carmine (IC), a dye that is widely used as additive in many food and pharmaceutical industries exhibited cytotoxic effects. This work describes the development of a bicomponent nanostructured Ti/TiO2/WO3 electrode prepared by template method and investigates its efficiency in a photoelectrocatalytic method by using visible light irradiation and applied potential of 1V. After 2h of treatment there are reduction of 97% discoloration, 62% of mineralization and formation of three byproducts assigned as: 2-amine-5-sulfo-benzoic acid, 2,3-dioxo-14-indole-5-sulfonic acid, and 2-amino-α-oxo-5-sulfo-benzeneacetic acid were identified by HPLC-MS/MS. But, cytotoxicity was completely removed after 120min of treatment. © 2013 Elsevier Ltd.