Influence of ceramic thickness and light-curing time on the long-term µTBS of silica-based ceramic to human dentin

To evaluate the influence of ceramic thickness, light-curing time and thermal cycling (TC) on the μTBS of a glass ceramic cemented to human dentin. Ninety-six human molars were embedded in acrylic resin and the occlusal surface was sectioned to exposure dentin. Blocks of feldspathic ceramic (Vita PM9) with different thickness (6 × 6 × 1 mm/2 mm/3 mm) were fabricated with wax pattern and sprue. The blocks and teeth were randomly distributed into 12 groups (n = 8) according to the ceramic thickness (V1: 1 mm, V2: 2 mm and V3: 3 mm), light-curing time (40s; 80s), and TC (yes; no). Dentin was etched, washed and dried. The adhesive (Excite, Ivoclar) was applied onto the dentin surface and light-cured (20s), and the ceramic surface was etched with 10% HF, washed, dried and silanized. The ceramic blocks were cemented to dentin (Variolink II, Ivoclar). The assembly ceramic/dentin was stored in distilled water (37 °C; 24 h) and sectioned in X and Y axes to get the sticks. Half of the samples were submitted to TC while the other half underwent micro-tensile bond testing. The data (MPa) were analyzed by 3-way ANOVA and Tukey test (5%). ANOVA revealed significant interaction among the factors (p = 0.0001). Tukey test showed significant higher bond strength for the 2 mm group (V280s = 17.0 ± 9.1 MPa) in comparison to the other groups. V340s TC (2.7 ± 6.3 MPa) presented lower bond strength, which was similar to the groups V180s TC (4.6 ± 4.9 MPa) and V240s TC (5.9 ± 4.4 MPa). Light-curing for 80s promoted significant higher bond strength of thicker ceramic (3 mm) than light-curing for 40s.     

Usage of the sol–gel process on the fabrication of macroporous adsorbent activated-gamma alumina spheres

In this work, we have developed a chemical process to agglomerate activated-gamma alumina microparticles. It is based on the sol–gel process. The process which was developed preserves the characteristics of porosity of the alumina microparticles. It allows us to obtain dried spheres with or without the introduction of a biomass type MDF (medium density fiberboard) with the following characteristics: medium diameter between 2.5 and 3.3 mm; narrow diameter range; high sphericity (0.90); high mechanical resistance (0.04 kg f/sphere); high specific surface area (257 m²/g); a network of micropores, mesopores and macropores which connects the surface and the core of the adsorbent sphere. It also allows us to obtain adsorbent alumina spheres with displaced core from the shallowest layers or even completely hollow. The possibility to add increasingly higher adsorbents biomass contents makes this process cheaper to fabricate adsorbent spheres. Besides that preliminary tests of adsorption show that dried spheres with and without MDF reach, respectively, an efficiency of removing Cd/Cu/Zn/As of 30.9%/13.5%/59.9%/43.9% and 71.3%/24.9%/48.4%/43.7%. All of these described characteristics suggest that the present method produces a good adsorbent for heavy metals and arsenic.     

A framework for enhancing mobile workflow execution through injection of flexible security controls

Mobile workflow execution is gaining importance as traditional process execution systems are employed in many new scenarios such as mobile networks or the Internet of Things. Unfortunately, in these solutions, security is still based on control loops or computer science techniques which have not evolved as fast as current mobile systems and applications. In this context, in order to improve the security level of these systems, it is necessary to create a security framework tightly coupled with the mobile workflow execution platforms. To contribute filling this gap, we propose a framework to inject security controls in workflows, which supports mobile execution and allows a flexible decision making. This solution models security as control points where some relevant previously defined indicators are evaluated. Depending on the obtained values, the framework takes corrective, preventive or adaptive actions, considering also the execution system capabilities and the workflow being executed. In order to evaluate the effectiveness and performance of the proposed solution we include experimental validation.     

Three-dimensional electrical impedance tomography: a topology optimization approach.

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.     

Comparison of peristrophic multiplexing and a combination of angular and peristrophic holographic multiplexing in a thick PVA/acrylamide photopolymer for data storage

Two different types of multiplexing are used to store 90 holograms at the same location in a polyvinyl alcoholacrylamide photopolymer material. In the first, the 90 holograms are stored using only peristrophic multiplexing, whereas in the second a combination of angular and peristrophic multiplexing is used. The results (diffraction efficiency and dynamic range, M#) obtained with these two multiplexing techniques are compared. With the first, the dynamic range was M# = 13 and with the second M# = 8. An exposure schedule method is used to calculate the exposure time necessary to store the holograms with a more uniform, higher diffraction efficiency.     

Film/contact loading method improves the encapsulated amount of triazene anticancer compounds in polymeric micelles

The development of organic solvent-free methods for the encapsulation of hydrophobic molecules is necessary for advances in micelle-mediated drug delivery. In this study we investigated the film/contact approach in which the use of organic solvents is limited to the preparation of a dry film before encapsulation. Unloaded micelles of five structurally related block copolymers were placed in contact with thin homogeneous films of two hydrophobic triazene anticancer compounds (1-(4-amidophenyl)-3-(4-acetylphenyl)triazene (1) and corresponding triazenido complex with triphenylphosphanegold(I) fragment (2)). The micelle surface becomes saturated with the drug, which eventually penetrates as a front into the core. Because the drug interacts with both the shell and the core microenvironments of micelle during the process, the maximum loading capacities were very sensitive to block copolymer micelle composition, ranging from 2.2 to 20.4% (wt./wt. of polymer). We conclude that micelles with poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) cores are the best option for the encapsulation of triazene compounds because i) they are prepared in absence of organic phase; ii) the drug concentration in the particles is high enough for a therapeutic effect and iii) the responsiveness properties of PDPA is appropriate for practical applications in pH-triggered drug release systems.     

In situ and ex situ spectroscopic study of poly(3-hexylthiophene) electrochemically synthesized

In this work, poly(3-hexylthiophene) (P3HT) film was synthesized electrochemically in non-aqueous media through the oxidation of the 3-hexylthiophene monomer using a standard three-electrode cell in acetonitrile with 0.100 mol L^?1 LiClO₄. The polymeric thick film was deposited on platinum plates for best quality control of the process. Cyclic voltammetry of this material showed two bands of oxidation and two bands of reduction attributed to radical cation and dication segments in the polymer chain. These were characterized by reflectance and Raman spectra, of the reduced (chemically de-doped) and oxidized (electrochemically doped) films. The generated film was subjected to anodic potentials of 1.00 and 1.45 V and characterized by an in situ Raman technique, which indicated the stabilization of the radical cation segments. In addition Raman ex situ spectra of as-prepared film was obtained. The increase in the irradiation time of the sample was enough to alter the nature of the constituent species of the oxidized film, preferably favoring the aromatic chains, together with the dication segments. Photoluminescence spectra showed a larger contribution of dication than radical cation segments for the chemically de-doped sample and under this condition showed good stability, even with variation in laser power. SEM images of P3HT film with indication of the thickness and spherical shape of the sample studied were obtained. Aided by these data it was possible to verify the Stokes shift and ionization potential (I _p), electron affinity (E.A.) and energy gap (E _g) parameters.     

Bibliometric analysis in motorcycle accident research: a global overview

Scientometrics - Survivability is one of the features for success in contemporary science ecosystem. In this paper, we analyze the publication records of physicists in American Physical Society...     

Multiplexed holographic data page storage on a polyvinyl alcohol/acrylamide photopolymer memory

Holographic data pages were multiplexed in different thickness layers of a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. A liquid crystal device was used to modify the object beam and store the data pages. A peristrophic multiplexing method is used to store a large number of data pages in the same spot in the material. The bit error rate was calculated fitting the histograms of the images to determine what parameters improve the quality of the images.