Oscillating holograms recorded in photorefractive crystals by a frequency detuned feedback loop

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

Development of silicon carbide substrates for aerospace applications

Payload and high-tech are important characteristics when the goals are aerospace applications. The development of the technologies associated to these applications has interests that transcend national boundaries and are of strategic importance to the nations. Ultra lightweight mirrors, supports and structures for optical systems are important part of this subject. This paper reports the development of SiC substrates, obtained by pressing, to be applied on embedded precision reflective optics. Different SiC granulometries, having YAG as sintering additive, were processed by: ball milling, drying and deagglomeration, sift, uniaxial and isostatic pressing, and, finally, argon atmosphere sintering at 1900°C. Different porosities were obtained according to the amount of organic material added. Into one side of the samples pellets of organic material were introduced to generate voids to reduce the weight of samples as a whole. The substrates were grinding and polished, looking for a SiC surface having low porosity, as porosity is directly related to light scattering that should be avoided on optical surfaces. Laser surface treatments were applied (using or not SiC barbotine) as a method to improve the surface quality. The samples were characterized by optical and laser confocal microscopy, roughness measurements and mechanical tests. The results are very promissory for future applications. © 2012 Materials Research Society.

Fast dynamics in the optical storage with Langmuir-Blodgett films of a diazocrown ether molecule

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

Evaluation of Bulk and Surfaces Absorption Edge Energy of Sol-Gel-Dip-Coating SnO2 Thin Films

The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition.

Biomechanical and histologic evaluation of non-washed resorbable blasting media and alumina-blasted/acid-etched surfaces

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

Characterization of Five Different Implant Surfaces and Their Effect on Osseointegration: A Study in Dogs

Background: Chemical modification of implant surface is typically associated with surface topographic alterations that may affect early osseointegration. This study investigates the effects of controlled surface alterations in early osseointegration in an animal model.Methods: Five implant surfaces were evaluated: 1) alumina-blasting, 2) biologic blasting, 3) plasma, 4) microblasted resorbable blasting media (microblasted RBM), and 5) alumina-blasting/acid-etched (AB/AE). Surface topography was characterized by scanning electron microscopy and optical interferometry, and chemical assessment by x-ray photoelectron spectroscopy. The implants were placed in the radius of six dogs, remaining 2 and 4 weeks in vivo. After euthanization, specimens were torqued-to-interface failure and non-decalcified - processed for histomorphologic bone-implant contact, and bone area fraction-occupied evaluation. Statistical evaluation was performed by one-way analysis of variance (P < 0.05) and post hoc testing by the Tukey test.Results: The alumina-blasting surface presented the highest average surface roughness and mean root square of the surface values, the biologic blasting the lowest, and AB/AE an intermediate value. The remaining surfaces presented intermediate values between the biologic blasting and AB/AE. The x-ray photoelectron spectroscopy spectra revealed calcium and phosphorus for the biologic blasting and microblasted RBM surfaces, and the highest oxygen levels for the plasma, microblasted RBM, and AB/AE surfaces. Significantly higher torque was observed at 2 weeks for the microblasted RBM surface (P < 0.04), but no differences existed between surfaces at 4 weeks (P > 0.74). No significant differences in bone-implant contact and bone area fraction-occupied values were observed at 2 and 4 weeks.Conclusion: The five surfaces were osteoconductive and resulted in high degrees of osseointegration and biomechanical fixation. J Periodontol 2011;82:742-750.

Adhesive Bonding of Resin Composite to Various Ni-Cr Alloy Surfaces Using Different Metal Conditioners and a Surface Modification System

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

Diffusion analysis of one photosensitizer in bovine teeth using fluorescence optical imaging

Some photosensitizers (PSs) used for PACT (Antimicrobial Photodynamic Therapy) show an affinity for bacterial walls and can be photo-activated to cause the desired damage. However, on dentine bacterias may be less susceptible to PACT as a result of limited penetration of the PS. The aim of this study was to evaluate the diffusion of one PS based on hematoporphyrin on dentine structures. Twelve bovine incisors were used. Class III cavities (3 x 3 x 1 mm) were prepared on the mesial or distal surfaces using a diamond bur. Photogem (R) solution at 1 mg/mL (10 uL for each cavity) was used. The experimental Groups were divided according to thickness of dentine remaining and etched or no-etched before the PS application. The fluorescence excitation source was a VelScope (R) system. For image capture a scientific CCD color camera PixelFly (R) was coupled to VelScope. For image acquisition and processing, a computational routine was developed at Matlab (R). Fick's Law was used to obtain the average diffusion coefficient of PS. Differences were found between all Groups. The longitudinal temporal diffusion was influenced by the different times, thickness and acid etching.

In vitro study of the Nd : YAG laser effect on human dental enamel: Optical and scanning electron microscope analysis

Objective: the Nd:YAG laser irradiation of dental enamel was evaluated in enamel demineralization experiments in a Streptococcus mutans culture media. Summary Background Data: Previous studies had shown that a continuous wave Nd:YAG laser at an energy of approximately 67 mJ may induce an increased acid resistance in human dental enamel when exposed to severe demineralization conditions. Methods: Enamel windows of 3 x 4 cm in the buccal surface were irradiated with a continuous wave Nd:YAG laser at a wavelength of 1,064 Ecm using energy densities of from 83.75 to 187.50 J/cm(2), Enamel windows of 3 x 4 cm on the lingual surface served as control (without the laser irradiation). The enamel windows were then exposed to a Streptococcus mutans culture media at a temperature of 37 degrees C for 15 and 21 days. The laser effects and demineralization were examined both by optical microscopy and scanning electron microscopy (SEM), Results: A comparison between the lased and the unlased windows of enamel showed fusion and recrystalization of the enamel and increased acid-resistance in all groups irradiated with the Nd:YAG laser, on the other hand, the 3 x 4 delimited enamel surfaces from the control group (not irradiated with the Nd:YAG laser) showed 100% deminerization, Conclusions: These findings are consistent with the finding that laser irradiation of dental results in significant reduction of the effective solubility of enamel mineral.

Optical properties of Mg doped LiNbO3 thin films grown by polymeric precursor method.

Polymeric precursor solution was used to deposit by spin-coating pure and Mg doped LiNbO3 thin films on sapphire substrates. The effects of magnesium addition on crystallinity, morphology and optical properties of the annealed films were investigated. X-ray diffraction patterns indicate the oriented growth of the films. AFM studies show that the films are very homogeneous, dense and present smooth surfaces. The refractive index and optical losses obtained by the prism coupling method were influenced by the magnesium addition.

Evaluation of Different Methods of Optical Impression Making on the Marginal Gap of Onlays Created with CEREC 3D

Objectives: This study evaluated the marginal gaps on several surfaces of onlays created with the Cerec 3D system using one intraoral and two extraoral optical impression methods. Methods: A human molar (#19) was mounted with its adjacent teeth on a typodont (Frasaco) and prepared for a MODL onlay. The typodont was assembled in the mannequin head in order to simulate clinical conditions. The same operator took 36 individual optical impressions using a CEREC 3D camera. For group 1 (IP), a thin layer of titanium dioxide powder (CEREC powder-VITA) was applied directly onto the surface of the preparation for imaging (n=12). For group 2 (EP), a sectional impression was taken with hydrocolloid Identic Syringable (Dux Dental), a die made with polyvinylsiloxane KwikkModel Scan (R-dental Dentalerzeugnisse GmbH) and powdered with titanium dioxide for imaging (n=12). For group 3 (ES), a sectional impression was taken with PVS and a sectional stock tray, a die fabricated in stone (Diamond die- HI-TEC Dental Products) and the die being imaged without powdering (n=12). One operator designed and machined the onlays in Vita Blocks Mark II for Cerec (VITA) using a CEREC 3D. The marginal gaps (pm) were measured with an optical microscope (50x) at 12 points, three on each surface of the MODL. The results were analyzed by two-way ANOVA/Tukey's (p=0.05). Results: The overall mean marginal gaps (mu m) for the three methods were: IP=111.6 (+/- 34.0); EP=161.4 (+/- 37.6) and ES=116.8 (+/- 42.3). IP and ES were equal, but both were significantly less than EP. The pooled mean marginal gaps (mu m) for the occlusal = 110.5 (+/- 39) and lingual = 111.5 (+/- 30.5) surfaces were equivalent and significantly less than the distal = 136.5 (+/- 42.5) and mesial = 161.1 (+/- 43.3). Conclusion: The marginal gap of CEREC 3D onlay restorations was not different when the optical impression was taken intraorally vs extraorally using a stone cast that does not require powdering. The lingual and occlusal surfaces showed the lowest gaps.

Nanomechanical properties of glass-ceramic films obtained by pressure impregnation of oxide powders on commercial float glass surfaces

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis of PTSH-modified CeO2 nanoparticles: Effect of the modifier on structure, optical properties, and dispersibility

CeO2 nanoparticles were synthesized by the precipitation method and modified with para-toluene sulfonic acid (PTSH), either in situ or post-synthesis. The presence of PTSH in the samples was confirmed by FTIR. PXRD and FTIR analyses showed that the post-synthesis PTSH modification altered the CeO2 structure, whereas the in situ modification maintained intact the crystalline structure and UV-vis absorbance properties. For both in situ and post-synthesis modifications, TEM images revealed the presence of nanoparticles that were 5nm in size. The dispersibility of the in situ PTSH-modified material in a hydrophilic ureasil-poly(ethylene oxide) matrix was investigated using SAXS measurements, which indicated that CeO2 nanoparticles modified with PTSH in situ were less aggregated within the matrix, compared to unmodified CeO2 nanoparticles. © 2013 Elsevier B.V.

Silica-based Nano-coating on Zirconia Surfaces Using Reactive Magnetron Sputtering: Effect on Chemical Adhesion of Resin Cements

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

First principles investigations on the electronic structure of anchor groups on ZnO nanowires and surfaces

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)