Electrical and Superconducting Properties in Lap Joints for YBCO Tapes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A method for calculating the compliance of bonded-interfaces under shrinkage: Validation for Class I cavities

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

Effect of delayed start of light-curing on microtensile bond strengths of two adhesives bonded to dentin

The aim of the present study was to evaluate the microtensile bond strength to dentin (ATBS) of two total-etching adhesives applied with delays of 1-30 s for curing. Fifty extracted molar teeth were used. Occlusal enamel was sectioned to expose flat dentin surface, which was further polished with 600-grit paper for smear layer standardization. The specimens were divided into two groups, G1: Single Bond total-etching adhesive (SB), and G2: Prime & Bond NT total-etching adhesive (PB). Each group was further divided into 5 subgroups according to the delayed light-cure initiation after the adhesive systems application (n=5): Subgroup 1s - 1 s; Subgroup 5s -5 s; Subgroup 10s - 10 s; Subgroup 20s - 20 s; Subgroup 30s - 30 s. Composite resin cones 5 mm height and 10 mm in diameter were fabricated. Specimens were stored in distilled water at 37 degrees C for 24 h and sectioned to obtain 1 x 1 mm(2) transversal specimens. Specimens were thermocycled and mu TBS was measured. Data were submitted to two-way ANOVA (AdhesiveXDelay time) and Tukey's test. The level of significance was set at 5%. The results in mean MPa(+/- SD) for interaction between adhesive and delay time were: PB/1s - 23.82 +/- 2.54a; SB/5s - 19.52 +/- 2.67b; PB/5s - 18.56 +/- 3.06bc; SB/1s - 15.49 +/- 2.69cd; SB/20s - 16.33 +/- 2.55d; SB/10s - 13.88 +/- 1.67d; PB/10s - 11.04 +/- 1.28e; PB/30s - 10.89 +/- 1.31e; PB/20s - 10.24 +/- 2.33e; SB/30s - 9.19 +/- 1.91e. It was concluded that light-cure initiation timing of total-etching adhesives interferes negatively with mu TBS to dentin. (C) 2014 Elsevier Ltd. All rights reserved.

Physical and mechanical properties of particleboard bamboo waste bonded with urea formaldehyde and castor oil based adhesive

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

Microstructural, physical, and fluid dynamic assessment of spinel-based and phosphate-bonded investments for dental applications

This work reports the experimental evaluation of physical and gas permeation parameters of four spinel-based investments developed with or without inclusion of sacrificial fillers. Data were compared with those of three commercial formulations. Airflow tests were conducted from 27 to 546°C, and permeability coefficients were fitted from Forchheimer's equation. Skeletal densities found for spinel- (ρs = 3635 ± 165 kg/m3) and phosphate-bonded (ρs = 2686 ± 11 kg/m3) samples were in agreement with the literature. The developed investments were more porous and less permeable than commercial brands, and the differences were ascribed to the different pore morphologies and hydraulic pore sizes of ceramic matrices. The inclusion of both fibers and microbeads resulted in increases of total porosity (42.6–56.6%) and of Darcian permeability coefficient k1 (0.76 × 10−14–7.03 × 10−14 m2). Air permeation was hindered by increasing flow temperatures, and the effect was related to the influence of gas viscosity on ΔP, in accordance with Darcy's law. Casting quality with molten titanium (CP Ti) was directly proportional to the permeability level of the spinel-based investments. However, the high reactivity of the silica-based investment RP and the formation of α-case during casting hindered the benefits of the highest permeability level of this commercial brand.

Mechanical and microstructural characterization of laser-welded joints of 6013-T4 aluminum alloy

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

Kinematic analysis of forelimb and hind limb joints in clinically healthy sheep

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

Resin tag length of one-step and self-etching adhesives bonded to unground enamel

Length of resin tags yielded by utilization of an one-step conventional adhesive system and self-etching adhesive system on unground enamel was observed. In study Groups I and III, the enamel surface was etched for 60 seconds with 35% phosphoric acid gel and adhesive systems PQ1 (Ultradent Products, Inc) and Adper Prompt L Pop (3M/ESPE) were applied. Adper Prompt L Pop (3M/ESPE) was also applied in Group II in accordance with the manufacturer's recommendations. After application of these adhesive systems to dental enamel, specimens were prepared for light microscopy analysis to ascertain degree of penetration (x400). The results were submitted to an analysis of variance at the 5% level; whenever there was significance, the Tukey test was applied at the 5% level. It was found that acid etching prior to application of conventional and self-etching adhesive materials provided higher penetration of the adhesive into the unground enamel surface compared to that achieved solely by application of self-etching adhesive.

Physical and mechanical characteristic of particleboards produced with residues of sugarcane and stem leaves of bamboo bonded with castor oil adhesive

In this research the aim was produce a particleboard with alternative materials and evaluated its physical and mechanical characteristics. The raw materials used are residues from sucarcane bagasse (SC) (Saccharum officinarum) and stem leaves of bamboo (B) (Dendrocalamus giganteus), bonded with a bi component adhesive based on castor oil. It was produced particleboards with five different traces: 100% SC, 75% SC+25% B, 50% SC+50% B, 25% SC +75%B and 100 % B. Their physical and mechanical characteristics were evaluated accordingly to Brazilian standard NBR 14810-3. Regarding the results obtained, it can be detached that for physical and mechanical evaluation it is evident a negative relation among the amount the sugarcane bagasse and their physical and mechanical characteristics, that is particleboards with low concentrations of sugarcane bagasse had better results. However all particleboards could be recommended for use as sealing particleboards in the segment of civil construction.

A study on the viability of minimum quantity lubrication with water in grinding of ceramics using a hybrid-bonded diamond wheel

With the currently strict environmental law in present days, researchers and industries are seeking to reduce the amount of cutting fluid used in machining. Minimum quantity lubrication is a potential alternative to reduce environmental impacts and overall process costs. This technique can substantially reduce cutting fluids in grinding, as well as provide better performance in relation to conventional cutting fluid application (abundant fluid flow). The present work aims to test the viability of minimum quantity lubrication (with and without water) in grinding of advanced ceramics, when compared to conventional method (abundant fluid flow). Measured output variables were grinding power, surface roughness, roundness errors and wheel wear, as well as scanning electron micrographs. The results show that minimum quantity lubrication with water (1:1) was superior to conventional lubrication-cooling in terms of surface quality, also reducing wheel wear, when compared to the other methods tested.

EXPERIMENTAL INVESTIGATION OF FOLDED PLATE GIRDERS AND SLAB JOINTS USED IN MODULAR CONSTRUCTION

The folded plate girder, a newly proposed bridge girder, is investigated through this thesis. The folded plate girder is cold bent out of a single sheet of steel. The cold bending eliminates the costly and inconsistent shop welds found in traditional girders. The folded plate girder is meant for application in short span bridges. The girder was subjected to an equivalent 75 year lifetime loading to investigate the fatigue performance. The rebar detail used in the closure region between adjacent slabs has been investigated in the past by the NCHRP 12-68 project. This thesis will proposes a hooked rebar detail as a cost effective alternative to the previously recommended headed rebar detail. The proposed hooked rebar detail looks to improve upon the headed bar detail by increasing the clear cover, and reducing the cost of fabrication and shipment of the rebar. Six specimens containing closure regions are subjected to both positive and negative moment loading in order to investigate their behavior and failure modes under ultimate load.

A method to investigate the shrinkage stress developed by resin-composites bonded to a single flat surface

Objectives. To purpose a method for predicting the shrinkage stress development in the adhesive layer of resin-composite cylinders that shrink bonded to a single flat surface, by measuring the deflection of a glass coverslip caused by the shrinkage of the bonded cylinders. The correlation between the volume of the bonded resin-composite and the stress-peak was also investigated. Methods. A glass coverslip deflection caused by the shrinkage of a bonded resin-composite cylinder (diameter: d = 8 mm, 4 mm, or 2 mm, height: h = 4 mm, 2 mm, 1 mm, or 0.5 mm) was measured, and the same set-up was simulated by finite element analysis (3D-FEA). Stresses generated in the adhesive layer were plotted versus two geometric variables of the resin-composite cylinder (C-Factor and volume) to verify the existence of correlations between them and stresses. Results. The FEA models were validated. A significant correlation (p < 0.01, Pearson's test) between the stress-peak and the coverslip deflection when the resin-composites were grouped by diameter was found for diameters of 2 and 4 mm. The stress-peak of the whole set of data showed a logarithmic correlation with the bonded resin-composite volume (p < 0.001, Pearson's test), but did not correlate with the C-Factor. Significance. The described method should be considered for standardizing the stress generated by the shrinkage of resin-composite blocks bonded to a single flat surface. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Risk factors for magnetic resonance imaging-detected patellofemoral and tibiofemoral cartilage loss during a six-month period: The Joints On Glucosamine study

Objective To assess several baseline risk factors that may predict patellofemoral and tibiofemoral cartilage loss during a 6-month period. Methods For 177 subjects with chronic knee pain, 3T magnetic resonance imaging (MRI) of both knees was performed at baseline and followup. Knees were semiquantitatively assessed, evaluating cartilage morphology, subchondral bone marrow lesions, meniscal morphology/extrusion, synovitis, and effusion. Age, sex, and body mass index (BMI), bone marrow lesions, meniscal damage/extrusion, synovitis, effusion, and prevalent cartilage damage in the same subregion were evaluated as possible risk factors for cartilage loss. Logistic regression models were applied to predict cartilage loss. Models were adjusted for age, sex, treatment, and BMI. Results Seventy-nine subregions (1.6%) showed incident or worsening cartilage damage at followup. None of the demographic risk factors was predictive of future cartilage loss. Predictors of patellofemoral cartilage loss were effusion, with an adjusted odds ratio (OR) of 3.5 (95% confidence interval [95% CI] 1.39.4), and prevalent cartilage damage in the same subregion with an adjusted OR of 4.3 (95% CI 1.314.1). Risk factors for tibiofemoral cartilage loss were baseline meniscal extrusion (adjusted OR 3.6 [95% CI 1.310.1]), prevalent bone marrow lesions (adjusted OR 4.7 [95% CI 1.119.5]), and prevalent cartilage damage (adjusted OR 15.3 [95% CI 4.947.4]). Conclusion Cartilage loss over 6 months is rare, but may be detected semiquantitatively by 3T MRI and is most commonly observed in knees with Kellgren/Lawrence grade 3. Predictors of patellofemoral cartilage loss were effusion and prevalent cartilage damage in the same subregion. Predictors of tibiofemoral cartilage loss were prevalent cartilage damage, bone marrow lesions, and meniscal extrusion.

Finite element analysis of bonded model Class I 'restorations' after shrinkage

Objectives. The C-Factor has been used widely to rationalize the changes in shrinkage stress occurring at the tooth/resin-composite interfaces. Experimentally, such stresses have been measured in a uniaxial direction between opposed parallel walls. The situation of adjoining cavity walls has been neglected. The aim was to investigate the hypothesis that: within stylized model rectangular cavities of constant volume and wall thickness, the interfacial shrinkage-stress at the adjoining cavity walls increases steadily as the C-Factor increases. Methods. Eight 3D-FEM restored Class I 'rectangular cavity' models were created by MSC.PATRAN/MSC.Marc, r2-2005 and subjected to 1% of shrinkage, while maintaining constant both the volume (20 mm(3)) and the wall thickness (2 mm), but varying the C-Factor (1.9-13.5). An adhesive contact between the composite and the teeth was incorporated. Polymerization shrinkage was simulated by analogy with thermal contraction. Principal stresses and strains were calculated. Peak values of maximum principal (MP) and maximum shear (MS) stresses from the different walls were displayed graphically as a function of C-Factor. The stress-peak association with C-Factor was evaluated by the Pearson correlation between the stress peak and the C-Factor. Results. The hypothesis was rejected: there was no clear increase of stress-peaks with C-Factor. The stress-peaks particularly expressed as MP and MS varied only slightly with increasing C-Factor. Lower stress-peaks were present at the pulpal floor in comparison to the stress at the axial walls. In general, MP and MS were similar when the axial wall dimensions were similar. The Pearson coefficient only expressed associations for the maximum principal stress at the ZX wall and the Z axis. Significance. Increase of the C-Factor did not lead to increase of the calculated stress-peaks in model rectangular Class I cavity walls. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Treatment effects of bonded spurs associated with high-pull chincup therapy in the treatment of patients with anterior open bite

Introduction: The aim of this prospective clinical study was to investigate the cephalometric changes produced by bonded spurs associated with high-pull chincup therapy in children with Angle Class I malocclusion and anterior open bite. Methods: Thirty patients with an initial mean age of 8.14 years and a mean anterior open bite of -3.93 mm were treated with bonded spurs associated with chincup therapy for 12 months. An untreated control group of 30 subjects with an initial mean age of 8.36 years and a mean anterior open bite of -3.93 mm and the same malocclusion was followed for 12 months for comparison. Student t tests were used for intergroup comparisons. Results: The treated group demonstrated a significantly greater decrease of the gonial angle, and increase in overbite, palatal tipping of the maxillary incisors, and vertical dentoalveolar development of the maxillary and mandibular incisors compared with the control group. Conclusions: The association of bonded spurs with high-pull chincup therapy was efficient for the correction of the open bite in 86.7% of the patients, with a 5.23-mm (SD, +/- 1.69) overbite increase. (Am J Orthod Dentofacial Orthop 2012;142:487-93)