A Probabilistic Formulation of the Diffusion Coefficient in Porous Media as Function of Porosity

We investigate the upscaling of diffusive transport parameters using a stochastic framework. At sub-REV (representative elementary volume) scale, the complexity of the pore space geometry leads to a significant scatter of the observed diffusive transport. We study a large set of volumes reconstructed from focused ion beam-scanning electron microscopy data. Each individual volume provides us sub-REV measurements on porosity and the so-called transport-ability, being a dimensionless parameter representing the ratio of diffusive flux through the porous volume to that through an empty volume. The detected scatter of the transport-ability is mathematically characterized through a probability distribution function (PDF) with a mean and variance as function of porosity, which includes implicitly the effect of pore structure differences among sub-REV volumes. We then investigate domain size effects and predict when REV scale is reached. While the scatter in porosity observations decreases linearly with increasing sample size as expected, the observed scatter in transport-ability does not converge to zero. Our results confirm that differences in pore structure impact transport parameters at all scales. Consequently, the use of PDFs to describe the relationship of effective transport coefficients to porosity is advantageous to deterministic semiempirical functions. We discuss the consequences and advocate the use of PDFs for effective parameters in both continuum equations and data interpretation of experimental or computational work. The presented statistics-based upscaling technique of sub-REV microscopy data provides a new tool in understanding, describing and predicting macroscopic transport behavior of microporous media.

Numerical Simulation of Enhancement of Superficial Tumor Laser Hyperthermia with Silicon Nanoparticles

Biodegradable and low-toxic silicon nanoparticles (SiNPs) have potential in different biomedical applications. Previous experimental studies revealed the efficiency of some types of SiNPs in tumor hyperthermia. To analyse the feasibility of employing SiNPs produced by the laser ablation of silicon nanowire arrays in water and ethanol as agents for laser tumor hyperthermia, we numerically simulated effects of heating a millimeter-size nodal basal-cell carcinoma with embedded nanoparticles by continuous-wave laser radiation at 633 nm. Based on scanning electron microscopy data for the synthesized SiNPs size distributions, we used Mie theory to calculate their optical properties and carried out Monte Carlo simulations of light absorption inside the tumor, with and without the embedded nanoparticles, followed by an evaluation of local temperature increase based on the bioheat transfer equation. Given the same mass concentration, SiNPs obtained by the laser ablation of silicon nanowires in ethanol (eSiNPs) are characterized by smaller absorption and scattering coefficients compared to those synthesized in water (wSiNPs). In contrast, wSiNPs embedded in the tumor provide a lower overall temperature increase than eSiNPs due to the effect of shielding the laser irradiation by the highly absorbing wSiNPs-containing region at the top of the tumor. Effective tumor hyperthermia (temperature increase above 42 °C) can be performed with eSiNPs at nanoparticle mass concentrations of 3 mg/mL and higher, provided that the neighboring healthy tissues remain underheated at the applied irradiation power. The use of a laser beam with the diameter fitting the size of the tumor allows to obtain a higher temperature contrast between the tumor and surrounding normal tissues compared to the case when the beam diameter exceeds the tumor size at the comparable power.

Synthesis of Organic-Inorganic Hybrid Material with a Synergistic Interface as a Release Agent for Free Acid β-Hydroxy-β-Methyl Butyrate

We report the preparation and characterization of a new organic-inorganic hybrid system composed of type-I collagen and ZnAl layered double hydroxide (LDH) particles loaded with β-hydroxy-β-methyl butyrate (HMB) by coprecipitation reaction. X-ray diffraction (peaks well agree with those reported in the literature), infrared spectroscopy (stretching bonds for both organic-inorganic compounds), and X-ray photoelectron spectroscopy confirmed the hybrid system retained HMB in the carboxylate form, and a small fraction turned to the acid form. In both cases, the HMB molecules are assembled to the LDH surface. The hybrid compound results in improved thermal stability for HMB and collagen, as shown by thermal analysis. Scanning electron microscopy data reflects different arrangements from LDH sheets with interesting physicochemical properties since LDH and collagen protect free HMB and make it more bioavailable and functional. In vitro studies as part of high-throughput screening strategies indicated that LDH hybrids reduced cell viability around 75-90%, which is an acceptable viability value because of the L6 cell line susceptibility. However, all new nanomaterials must be carefully analyzed by different toxicity tests because a single test does not evaluate complete physiological compartments.

Physical and anti-aging characteristics of nano-TiO2/irganox 1010 composite modified asphalt

Asphalt aging is the main cause of fatigue failure from asphalt pavements, and it can be divided into thermaloxidative and ultraviolet (UV) aging. In this study, nano-TiO2/Irganox 1010 were added to neat asphalt to simultaneously improve the aging phenomenon of asphalt in a variety of complex conditions of asphalt. We then analyzed and discussed physical properties of nano-TiO2/Irganox 1010 modified asphalt composites. In addition, MSCR (Multiple Stress Creep Recovery) and DSR (Dynamic Shear Rheometer) rheological tests were performed on nano-TiO2/Irganox 1010 modified asphalt with different contents. Aging simulation of nano-TiO2/Irganox 1010 modified asphalt was conducted through the TFOT (The Thin Film Oven Test) and UV test, and microstructure of UV aging was analyzed through scanning electron microscopy. Data analysis showed that the nano-TiO2/Irganox 1010 increased softening point and reduced penetration (25 °C) and ductility (5 °C). The nano-TiO2/Irganox 1010 also improved the creep resistance and rheological properties of the composites. Finally, the analysis of test results under different conditions showed that the addition of nano-TiO2/Irganox 1010 significantly enhanced the ability of asphalt to deal with aging in a variety of complex environments.

Cleaning of long oval canals with WaveOne Gold system associated with different irrigant agitation protocols

Aim: The aim of the study was to evaluate the cleaning of mandibular incisors with WaveOne Gold® (WO) under different preparation techniques. Methods: A total of 210 human mandibular incisors were selected and divided into seven groups (n = 30), prepared by WO single-files (Small 20/.07 – WOS; Primary 25/.07 – WOP; Medium 35/.06 – WOM; or Large 45/.05 - WOL) and sequential-file techniques (WOS to WOP; WOS to WOM; and WOS to WOL). Further subdivision was made according to irrigation protocol: control group (manual irrigation - CON), E1 Irrisonic® - EIR, and EDDY® - EDD. Debris removal and the smear layer were evaluated by scanning electron microscopy. Data were analyzed by using Spearman’s correlation test. The significance level was set at 5%. Results: For debris and smear layer removal, WOS and WOP, EIR differed from CON and EDD (p <0.05). Conclusion: Regardless of the instrumentation used, the agitation of the irrigant solution provided better cleanability. These findings reinforce the need for agitation techniques as adjuvants in cleaning root canal systems in mandibular incisors.

Structural resistance of orthodontic mini-screws inserted for extra-alveolar anchorage

The risk of fracture or strain in mini-screws is higher if diameter, length, type of alloy or insertion angle is selected inappropriately. The aims of this study were to test the structural resistance of two types of orthodontic mini-screws –one made of stainless steel and another of titanium– from an international brand and to evaluate the efficacy of two other titanium miniscrews of Brazilian origin, during an extra-alveolar anchorage procedure. The mini-screws analyzed were: Bomei stainless steel and Bomei titanium / Taiwan, Morelli titanium and Neodent titanium/ Brazil. Experiments were conducted on pig mandibles to simulate the process of extra-alveolar anchorage. Two insertion processes were used: Direct at 30º, and Indirect, starting at 60º and ending at 30º with gradual continuous movement. Strain was evaluated using Optical and Scanning Electron Microscopy. Data were evaluated using Kruskal-Wallis non-parametric statistical analysis and post hoc Tamhane test. Significant statistical differences in strain were observed among the mini-screws used in the extra-alveolar insertions, both for the direct and indirect procedures. In the indirect insertion tests, both stainless steel and titanium mini-screws suffered deformation, showing that angling can be an important factor in mini-screw failure rates. The change in angle during the insertion movement increased deformation rates independently of alloy type, increasing the risk of failure. These results could help orthodontists in choosing mini-screws for extra-alveolar anchorage, which can be performed with direct or indirect insertion. In vivo studies should be conducted to confirm the findings of this study.

A comparative study of dentinal tubule penetration and the retreatability of EndoSequence BC Sealer HiFlow, iRoot SP, and AH Plus with different obturation techniques

Objectives This study aimed to evaluate dentinal tubule penetration and the retreatability of EndoSequence BC Sealer HiFlow (HiFlow), iRoot SP, and AH Plus when using the single-cone (SC) or continuous wave condensation (CWC) technique. Materials and methods Sixty-five single-rooted teeth were instrumented and randomly divided into 5 groups: group 1, AH Plus/CWC; group 2, iRoot SP/CWC; group 3, iRoot SP/SC; group 4, HiFlow/CWC; and group 5, HiFlow/SC. The ability to re-establish patency during endodontic retreatment was recorded, as was the time taken to reach the working length. Dentinal tubule penetration and remaining debris after retreatment were evaluated by confocal microscopy and scanning electron microscopy. Data were analyzed by Kruskal-Wallis test and Dunn’s multiple comparisons test (α = 0.05). Results The HiFlow/CWC and iRoot SP/CWC groups required more time to reach the working length than groups that underwent the SC technique regardless of the sealer used (P < .05). The HiFlow/CWC group showed a significantly higher percentage of sealer penetration area than that of the iRoot SP/SC at 4 mm from the apex (P < .05) and penetrated deeper into dentinal tubules than iRoot SP/SC at both 8-mm and 12-mm levels (P < .05). Moreover, the HiFlow/CWC and HiFlow/SC groups demonstrated less remaining sealer along the canal wall than AH Plus/CWC group at 4-mm level (P < .05). Conclusions HiFlow/CWC technique showed better performance in dentinal tubule penetration than that of iRoot SP/SC. Both HiFlow and iRoot SP combined with CWC technique groups required more retreatment time than the other groups. Furthermore, using HiFlow with either the CWC or SC technique left less remaining sealer at 4-mm level than using AH Plus with the CWC technique during retreatment. Clinical relevance With favorable performance in dentinal tubule penetration and retreatability in endodontic retreatment, the combined use of EndoSequence BC Sealer HiFlow with the recommended continuous wave condensation technique may be a worthwhile choice in root canal treatment.

Synthesis of porous ceramics for ceramic biosensors

Highly porous ceramic materials with open porosity are perspective for manufacture of the biosensors. Those materials are used as a framework and open porosity allows to inject a necessary functional components into internal volume. Electroconductive highly porous ceramics on a base of La1-xCaxMnO3 with variable composition have acceptable hardness and relatively low sintering temperature (about 1450°C). In recent work samples of highly porous ceramic with the composition of La1-xCaxMnO3 (x=0.3, 0.5 and 0.7) were obtained by impregnating a carbon nonwoven material with a slip containing pre-synthesized compounds of the desired composition, followed by annealing at 1415-1450îÑ. Obtained materials according to the scanning electron microscopy data have a pore size of up to 100 µm. The conductivity is 0.5-2.5 S/cm.