Magnetoelectric coefficient in strontium ruthenate buffered lanthanum modified bismuth ferrite thin films grown by chemical method

This paper focuses on the magnetoelectric coupling (ME) at room temperature in lanthanum modified bismuth ferrite thin film (BLFO) deposited on SrRuO 3-buffered Pt/TiO 2/SiO 2/Si(100) substrates by the soft chemical method. BLFO film was coherently grown at a temperature of 500 °C. The magnetoelectric coefficient measurement was performed to evidence magnetoelectric coupling behavior. Room temperature magnetic coercive field indicates that the film is magnetically soft. The maximum magnetoelectric coefficient in the longitudinal direction was close to 12 V/cmOe. Dielectric permittivity and dielectric loss demonstrated only slight dispersion with frequency due the less two-dimensional stress in the plane of the film. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. We observed that various types of domain behavior such as 71 ° and 180° domain switching, and pinned domain formation occurred. Copyright © 2009 American Scientific Publishers All rights reserved.

Observation of piezoelectric response on tungsten doped barium zirconium titanate ceramics

This study describes observation of piezoelectric response of Ba(Zr 0.10Ti 0.90.O3 ceramics modified with tungsten (BZT:2W) by the mixed oxide method. According to X ray diffraction analysis, the ceramics are free of secondary phases. Transmission electron microscopy (TEM) analyses reveals the absence of segregates in the grain boundaries indicates the high solubility of WO3 in the BZT matrix. The dielectric permittivity measured at a frequency of 10 KHz was equal to 6500 with dieletric loss of 0.15. A typical hysteresis loop was observed at room temperature. Electron Paramagnetic Resonance (EPR) analyses reveals that substitution of W6+ by Ti4+ causes distortion in the crystal structure changing lattice parameter. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. Piezoelectric force microscopy images reveals that in-plane response may not change its sign upon polarization switching, while the out-of-plane response does. Copyright © 2010 American Scientific Publishers.

Rietveld analyses and piezoelectric properties of niobium doped bismuth titanate systems

Bi 4Ti 3- xNbxO 12 (BITNb) samples, with × ranging from 0 to 0.40 were obtained using a polymeric precursor solution. Rietveld analyses confirmed that the powders crystallize in an orthorhombic structure free of secondary phases with space group Fmmm. Raman analysis evidenced a sharp increase in the bands intensity located at 129 cm -1 and 190 cm -1 due the lattice distortion in BIT02Nb and BIT04Nb compositions. UV-vis spectra indicated that addition of niobium causes a reduction of defects in the BIT lattice due the suppression of oxygen vacancies located at BO-6 octahedral. Size and morphology of particles as well as electrical behavior of BIT ceramics were affected by addition of donor dopant. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning and was investigated by piezoresponse force microscopy (PFM). PFM measurements revealed a decrease in piezoelectric response with increasing Nb concentration originating from a reduced polarizability along the a-axis. High spontaneous polarization is noted for the less doped sample due the reduction of strain energy and pin charged defects after niobium addition. Copyright © 2010 American Scientific Publishers.

Scanning electron microscopy analysis of RinsEndo system and conventional irrigation for debris removal

A new device for irrigation, which presents hydrodynamic activation based on the pressure-suction technology, has recently been introduced to the market: the Rinsendo system. This study compared the efficacy of the Rinsendo system and conventional (manualdynamic) irrigation in the removal of debris from the root canal walls, using scanning electron microscopy (SEM). Twenty mandibular premolars with completely formed roots were selected and randomly divided into group 1 (irrigation with the Rinsendo system) and group 2 (conventional irrigation). The canals were irrigated with 1 ml of saline at each change of instrument. instrumentation started with a #15 K file and continued up to a #40 K file, which was standardized as the working length instrument. Then, the teeth were sectioned in buccolingual direction and the halves were sputter-coated with gold and examined by SEM. The apical, middle and cervical root canal thirds were evaluated, and the results were analyzed statistically by the Mann-Whitney test for comparison between methods, Kruskal-Wallis test for comparison among thirds, and Miller test for individual comparisons. A significance level of 5% was set for all analyses. The results did not show significant differences (p>0.05) between methods at each third and among thirds for each technique analyzed individually. in conclusion, there was no difference in the cleaning ability of the Rinsendo system and conventional irrigation.

Calcium hydroxide intracanal dressing removal with different rotary instruments and irrigating solutions: A scanning electron microscopy study

This study evaluated the efficacy of 2 types of rotary instruments employed in association with sodium hypochlorite (NaOCl) or EDTA in removing calcium hydroxide (CH) residues from root canals dentin walls. Forty-two mandibular human incisors were instrumented with the ProTaper System up to F2 instrument, irrigated with 2.5% NaOCl followed by 17% EDTA and filled with a CH intracanal dressing. After 7 days, the CH dressing was removed using 4 techniques: NiTi rotary instrument size 25, 0.06 taper (K3 Endo) and irrigation with 17% EDTA (Group 1), NiTi rotary F1 instrument (ProTaper) and irrigation with 17% EDTA (Group 2), NiTi rotary instrument size 25, 0.06 taper and irrigation with 2.5% NaOCl (Group 3) and NiTi rotary F1 instrument and irrigation with 2.5% NaOCl (Group 4). Two roots without intracanal dressing were used as negative controls. Teeth were evaluated by scanning electron microscopy, in the cervical and apical canal thirds. None of the techniques removed the CH dressing completely. In the apical and cervical thirds, F1 instrument was better than instrument size 25, 0.06 taper in removing CH residues (p<0.05), regardless of the final irrigating solution. No difference was found between the irrigating solutions in the groups of F1 instrument and of instrument size 25, 0.06 taper (p>0.05). The negative controls had no CH residues on the dentin walls. In conclusion, the ProTaper F1 instrument was better than K3 Endo instrument size 25, 0.06 taper in the removal of CH intracanal medication, regardless of irrigating solution used.

Influence of microwave energy on structural and piezoelectric response of Bi 4Ti 3O 12 ceramics

Bismuth titanate ceramics (Bi 4Ti 3O 12) with 10 wt% in excess of bismuth (BIT10) were prepared by the polymeric precursor method and sinterized in microwave (MW) and conventional furnaces (CF). The effect of microwave energy on structural and electrical behavior of BIT10 ceramics was investigated by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrical measurements. The results of the BIT10 ceramics processed in the microwave furnace (MW) showed a high structural organization compared to conventional treatment (CF). Size of grains and dieletrical properties are influenced by annealing conditions while coercitive field is not dependent on it. The maximum dielectric permittivity (12000) was obtained for the sample sintered in the microwave furnace. Piezoelectric force microscopy images reveals that in-plane response may not change its sign upon polarization switching, while the out-of-plane response does with the influence of microwave energy. Copyright © 2010 American Scientific Publishers All rights reserved.

Local electromethanical properties of the CaCu 3Ti 4O 12 ceramics

Scanning probe microscopy (SPM) was used to probe piezoelectric vibrations and local conductivity in CaCu 3Ti 4O 12 (CCTO) ceramics at room temperature. Piezoelectric contrast was observed on the polished surfaces of CCTO in both vertical (out-of-plane) and lateral (in-plane) modes and depended on the grain orientation varying in sign and amplitude. The piezoelectric contrast is shown to be controlled by the electrical bias (local poling) and displayed a ferroelectric-like reversible hysteresis accompanied with a change of the phase of piezoelectric signal. Flexoelectric effect (strain-gradient-induced polarization) due to surface relaxation was invoked to explain the observed contrast inside the grains. © 2010 Materials Research Society.

Study of ITO@PMMA composites by transmission electron microscopy

ITO nanowires were synthesized by carbothermal reduction process, using a co-evaporation method, and have controlled size, shape, and chemical composition. The electrical measurements of nanowires showed they have a resistance of about 102 Ω. In order to produce nanocomposites films, nanowires were dispersed in toluene using an ultrasonic cleaner, so the PMMA polymer was added, and the system was kept under agitation up to obtain a clear suspension. The PMMA polymer was filled with 1, 2, 5 and 10% in weight of nanowires, and the films were done by tape casting. The results showed that the electrical resistance of nanocomposites changed by over 7 orders of magnitude by increasing the amount of filler, and using 5 wt% of filler the composite resistance decreased from 1010 Ω to about 104 Ω, which means that percolation threshold of wires occurred at this concentration. This is an interesting result once for nanocomposites filled with ITO nanoparticles is necessary about 18% in weight to obtain percolation. The addition of filler up to 10 wt% decreased the resistance of the composite to 103 Ω, which is a value close to the resistance of wires. The composites were also analyzed by transmission electron microscopy (TEM), and the TEM results are in agreement with the electrical ones about percolation of nanowires. These results are promising once indicates that is possible to produce conductive and transparent in the visible range films by the addition of ITO nanowires in a polymeric matrix using a simple route. © 2011 Materials Research Society.

Effect of bleaching on sound enamel and with early artificial caries lesions using confocal laser microscopy

The aim of this study was to evaluate effect of bleaching agents on sound enamel (SE) and enamel with early artificial caries lesions (CL) using confocal laser scanning microscopy (CLSM). Eighty blocks (4 × 5 × 5 mm) of bovine enamel were used and half of them were submitted to a pH cycling model to induce CL. Eight experimental groups were obtained from the treatments and mineralization level of the enamel (SE or CL) (n=10). SE groups: G1 - unbleached (control); G2 - 4% hydrogen peroxide (4 HP); G3 - 4 HP containing 0.05% Ca (Ca); G4 - 7.5% hydrogen peroxide (7.5 HP) containing amorphous calcium phosphate (ACP). CL groups: G5 - unbleached; G6 - 4 HP; G7 - 4 HP containing Ca; G8 - 7.5 HP ACP. G2, G3, G6, G7 were treated with the bleaching agents for 8 h/day during 14 days, while G4 and G8 were exposed to the bleaching agents for 30 min twice a day during 14 days. The enamel blocks were stained with 0.1 mM rhodamine B solution and the demineralization was quantified using fluorescence intensity detected by CLSM. Data were analyzed using ANOVA and Fisher's tests (α=0.05). For the SE groups, the bleaching treatments increased significantly the demineralization area when compared with the unbleached group. In the CL groups, no statistically significant difference was observed (p>0.05). The addition of ACP or Ca in the composition of the whitening products did not overcome the effects caused by bleaching treatments on SE and neither was able to promote remineralization of CL.

Forced oscillations with continuum models of atomic force microscopy

The dynamics of the AFM-atomic force microscope follows a model based in a Timoshenko cantilever beam with a tip attached at the free end and acting with the surface of a sample. General boundary conditions arise when the tip is either in contact or non-contact with the surface. The governing equations are given in matrix conservative form subject to localized loads. The eigenanalysis is done with a fundamental matrix response of a damped second-order matrix differential equation. Forced responses are found by using a Galerkin approximation of the matrix impulse response. Simulations results with harmonic and pulse forcing show the filtering character and the effects of the tip-sample interaction at the end of the beam. © 2012 American Institute of Physics.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.

Bothropstoxin-I reduces evoked acetylcholine release from rat motor nerve terminals: Radiochemical and real-time video-microscopy studies

Understanding the biological activity profile of the snake venom components is fundamental for improving the treatment of snakebite envenomings and may also contribute for the development of new potential therapeutic agents. In this work, we tested the effects of BthTX-I, a Lys49 PLA2 homologue from the Bothrops jararacussu snake venom. While this toxin induces conspicuous myonecrosis by a catalytically independent mechanism, a series of in vitro studies support the hypothesis that BthTX-I might also exert a neuromuscular blocking activity due to its ability to alter the integrity of muscle cell membranes. To gain insight into the mechanisms of this inhibitory neuromuscular effect, for the first time, the influence of BthTX-I on nerve-evoked ACh release was directly quantified by radiochemical and real-time video-microscopy methods. Our results show that the neuromuscular blockade produced by in vitro exposure to BthTX-I (1 μM) results from the summation of both pre- and postsynaptic effects. Modifications affecting the presynaptic apparatus were revealed by the significant reduction of nerve-evoked [3H]-ACh release; real-time measurements of transmitter exocytosis using the FM4-64 fluorescent dye fully supported radiochemical data. The postsynaptic effect of BthTX-I was characterized by typical histological alterations in the architecture of skeletal muscle fibers, increase in the outflow of the intracellular lactate dehydrogenase enzyme and progressive depolarization of the muscle resting membrane potential. In conclusion, these findings suggest that the neuromuscular blockade produced by BthTX-I results from transient depolarization of skeletal muscle fibers, consequent to its general membrane-destabilizing effect, and subsequent decrease of evoked ACh release from motor nerve terminals. © 2012 Elsevier Ltd.

Trafficking of phagocytic peritoneal cells in hypoinsulinemic-hyperglycemic mice with systemic candidiasis

Background: Candidemia is a severe fungal infection that primarily affects hospitalized and/or immunocompromised patients. Mononuclear phagocytes have been recognized as pivotal immune cells which act in the recognition of pathogens, phagocytosis, inflammation, polarization of adaptive immune response and tissue repair. Experimental studies have showed that the systemic candidiasis could be controlled by activated peritoneal macrophages. However, the mechanism to explain how these cells act in distant tissue during a systemic fungal infection is still to be elucidated. In the present study we investigate the in vivo trafficking of phagocytic peritoneal cells into infected organs in hypoinsulinemic-hyperglycemic (HH) mice with systemic candidiasis. Methods: The red fluorescent vital dye PKH-26 PCL was injected into the peritoneal cavity of Swiss mice 24 hours before the intravenous inoculation with Candida albicans. After 24 and 48 hours and 7 days of infection, samples of the spleen, liver, kidneys, brain and lungs were submitted to the microbiological evaluation as well as to phagocytic peritoneal cell trafficking analyses by fluorescence microscopy. Results: In the present study, PKH+ cells were observed in the peritoneum, kidney, spleen and liver samples from all groups. In infected mice, we also found PKH+ cells in the lung and brain. The HH condition did not affect this process. Conclusions: In the present study we have observed that peritoneal phagocytes migrate to tissues infected by C. albicans and the HH condition did not interfere in this process. © 2013 Fraga-Silva et al.; licensee BioMed Central Ltd.

Piezoresponse force microscopy characterization of rare-earth doped BiFeO3 thin films grown by the soft chemical method

The multiferroic behavior with ion modification using rare-earth cations on crystal structures, along with the insulating properties of BiFeO3 (BFO) thin films was investigated using piezoresponse force microscopy. Rare-earth-substituted BFO films with chemical compositions of (Bi 1.00-xRExFe1.00O3 (x=0; 0.15), RE=La and Nd were fabricated on Pt (111)/Ti/SiO2/Si substrates using a chemical solution deposition technique. A crystalline phase of tetragonal BFO was obtained by heat treatment in ambient atmosphere at 500 °C for 2 h. Ion modification using La3+ and Nd3+ cations lowered the leakage current density of the BFO films at room temperature from approximately 10-6 down to 10-8 A/cm2. The observed improved magnetism of the Nd3+ substituted BFO thin films can be related to the plate-like morphology in a nanometer scale. We observed that various types of domain behavior such as 71° and 180° domain switching, and pinned domain formation occurred. The maximum magnetoelectric coefficient in the longitudinal direction was close to 12 V/cm Oe. © 2012 Elsevier Ltd and Techna Group S.r.l.

Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier, increasing the total impedance by 4 orders of magnitude and reducing the current densities by more than 3 orders of magnitude, compared to the bare steel electrode. © 2013 Elsevier B.V. All rights reserved.