In Vitro Study on the Piezodynamic Therapy with a BaTiO3-Coating Titanium Scaffold under Low-Intensity Pulsed Ultrasound Stimulation.

To solve the poor sustainability of electroactive stimulation in clinical therapy, a strategy of combining a piezoelectric BaTiO3-coated Ti6Al4V scaffold and low-intensity pulsed ultrasound (LIPUS) was unveiled and named here as piezodynamic therapy. Thus, cell behavior could be regulated phenomenally by force and electricity simultaneously. First, BaTiO3 was deposited uniformly on the surface of the three-dimensional (3D) printed porous Ti6Al4V scaffold, which endowed the scaffold with excellent force-electricity responsiveness under pulsed ultrasound exposure. The results of live/dead staining, cell scanning electron microscopy, and F-actin staining showed that cells had better viability, better pseudo-foot adhesion, and more muscular actin bundles when they underwent the piezodynamic effect of ultrasound and piezoelectric coating. This piezodynamic therapy activated more mitochondria at the initial stage that intervened in the cell cycle by promoting cells' proliferation and weakened the apoptotic damage. The quantitative real-time polymerase chain reaction data further confirmed that the costimulation of the ultrasound and the piezoelectric scaffolds could trigger adequate current to upregulated the expression of osteogenic-related genes. The continuous electric cues could be generated by the BaTiO3-coated scaffold and intermittent LIPUS stimulation; thereon, more efficient bone healing would be promoted by piezodynamic therapy in future treatment.

A surface plasmon resonance enhanced photoelectrochemical immunoassay based on perovskite metal oxide@gold nanoparticle heterostructures.

An innovative visible light-driven photoelectrochemical (PEC) immunosensing system was reasonably established for the sensitive detection of prostate-specific antigen (PSA) by using perovskite metal oxide@gold nanoparticle heterostructures (BaTiO3/Au) as the photoactive materials. When plasmonic Au nanoparticles were directly decorated on BaTiO3, a several times surface plasmon resonance (SPR) enhancement of photocurrent density was induced via the injection of hot electrons from visible light-excited Au nanoparticles into the conduction band of BaTiO3, and the combination of BaTiO3 and Au nanoparticles was employed as a promising platform for developing a photoelectrochemical bioanalysis. As a proof of concept, PSA had been detected by the BaTiO3/Au nanocomposite-based PEC sensor. To design such an immunoassay protocol, a monoclonal anti-PSA capture antibody (cAb)-coated microplate and glucose oxidase/polyclonal anti-PSA detection antibody-modified gold nanoparticles (GOx-Au NP-dAb) were used as the immunoreaction platform and signal probe, respectively. Upon the addition of target PSA, a sandwiched immunocomplex was formed accompanying the immuno-recognition between the antigen and antibody, and then the carried GOx could oxidize glucose to produce H2O2. The photocurrent of the BaTiO3/Au nanocomposite-functionalized electrode amplified with increasing H2O2 concentration since H2O2 is considered as a good hole scavenger. On the basis of the above-mentioned mechanisms and the optimized conditions, the assembled PEC immunosensor was linear with the logarithm of the PSA concentration in the range of 0.01-40 ng mL-1 with a detection limit of 4.2 pg mL-1. It afforded rapid response, good precision, and high stability and specificity, implying its great promise in photoelectrochemical immunoassays. More generally, this system sets up an ideal PEC immunosensing system based on the BaTiO3/Au nanocomposites and represents an innovative and low-cost "signal-on" assay scheme for the practical quantitative screening of low-abundance proteins.

Preparation of BaTiO3/Cu2O and BaTiO3/Cu2O/Au Complexes: Their Photocatalytic and Antipathogenic Effect.

BaTiO3/Cu2O and BaTiO3/Cu2O/Au complexes were prepared from CuCl2, HAuCl4 solution, and BaTiO3 by the solution method. BaTiO3 particles were dispersed in a CuCl2 solution, and the BaTiO3/CuO complex was produced through crystallization of CuO onto the BaTiO3 surface by hydrolysis of CuCl2 in the first stage. After the reaction, CuO was reduced to Cu2O by treatment with glucose, thereby yielding the BaTiO3/Cu2O complex. The BaTiO3/Cu2O/Au complex was prepared by treating the BaTiO3/Cu2O particles with HAuCl4. Under visible light, the obtained BaTiO3/Cu2O0/Au complex showed higher photocatalytic activity than the Degussa P-25sample. In addition, the BaTiO3/Cu2O complex showed excellent antipathogenic effect.

A reentrant phenomenon in magnetic and dielectric properties of Dy2BaNiO5 and an intriguing influence of external magnetic field.

We report that the spin-chain compound Dy2BaNiO5, recently proven by us to exhibit magnetoelectric coupling below its Néel temperature (TN) of 58 K, exhibits strong frequency-dependent behavior in ac magnetic susceptibility and complex dielectric properties at low temperatures (<10 K), mimicking the 'reentrant' multiglass phenomenon. Such a behavior is not known among undoped compounds. A new finding in the field of multiferroics is that the characteristic magnetic feature at low temperatures moves towards higher temperatures in the presence of a magnetic field (H), whereas the corresponding dielectric feature shifts towards lower temperatures with H, unlike the situation near TN. This observation indicates that the alignment of spins by external magnetic fields tends to inhibit glassy-like slow electric-dipole dynamics, at least in this system, possibly arising from peculiarities in the magnetic structure.

Design and production of antireflection coating for the 8-10 µm spectral region.

A special design procedure allowing to trap layer thicknesses inside specified limits is applied for designing of antireflection coating (AR) for the infrared spectral band of 8-10 µm. The obtained AR design has no too thick layers that may cause delaminating of the deposited AR coating. A special monitoring procedure taking into account wavelength positions of monitoring signal extrema is applied for coating deposition. The manufactured coating features excellent AR properties in the requested spectral region and possesses high mechanical stability.

Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3.

Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

Effect of solution combusted TiO2 nanopowder within commercial BaTiO3 dielectric layer on the photoelectric properties for AC powder electroluminescence devices.

A unique synthesis method was developed, which is called solution combustion method (SCM). TiO2 nanopowder was synthesized by this method. This SCM TiO2 nanopowder (-35 nm) was added to the dielectric layer of AC powder electroluminescence (EL) device. The dielectric layer was made of commercial BaTiO3 powder (-1.2 microm) and binding polymer. 0, 5, 10 and 15 wt% of SCM TiO2 nanopowder was added to the dielectric layer during fabrication of AC powder EL device respectively. Dielectric constant of these four kinds of dielectric layers was measured. The brightness and current density of AC powder EL device were also measured. When 10 wt% of SCM TiO2 nanopowder was added, dielectric constant and brightness were increased by 30% and 101% respectively. Furthermore, the current density was decreased by 71%. This means that the brightness was double and the power consumption was one third.

Hybrid multiferroic nanostructure with magnetic-dielectric coupling.

The development of methods to economically synthesize single wire structured multiferroic systems with room temperature spin-charge coupling is expected to be important for building next-generation multifunctional devices with ultralow power consumption. We demonstrate the fabrication of a single nanowire multiferroic system, a new geometry, exhibiting room temperature magnetodielectric coupling. A coaxial nanotube/nanowire heterostructure of barium titanate (BaTiO(3), BTO) and cobalt (Co) has been synthesized using a template-assisted method. Room temperature ferromagnetism and ferroelectricity were exhibited by this coaxial system, indicating the coexistence of more than one ferroic interaction in this composite system.

Numerical simulations of sonochemical production of BaTiO3 nanoparticles.

Numerical simulations of sonochemical production of nanoparticles have been performed for the first time under the experimental condition of Dang et al. [Jpn. J. Appl. Phys. 48 (2009) 09KC02] on the production of BaTiO(3). The results of the numerical simulations have suggested that only primary particles aggregate with other particles. It is also shown that larger aggregates are produced for lower initial concentration of BaCl(2) and TiCl(4). This is caused by longer reaction time as the reaction rate is lower for lower concentration and by lower viscosity which results in higher rate of aggregation.

Microwave assisted synthesis and characterization of barium titanate nanoparticles for multi layered ceramic capacitor applications.

Barium titanate is a common ferroelectric electro-ceramic material having high dielectric constant, with photorefractive effect and piezoelectric properties. In this research work, nano-scale barium titanate powders were synthesized by microwave assisted mechano-chemical route. Suitable precursors were ball milled for 20 hours. TGA studies were performed to study the thermal stability of the powders. The powders were characterized by XRD, SEM and EDX Analysis. Microwave and Conventional heating were performed at 1000 degrees C. The overall heating schedule was reduced by 8 hours in microwave heating thereby reducing the energy and time requirement. The nano-scale, impurity-free and defect-free microstructure was clearly evident from the SEM micrograph and EDX patterns. LCR meter was used to measure the dielectric constant and dielectric loss values at various frequencies. Microwave heated powders showed superior dielectric constant value with low dielectric loss which is highly essential for the fabrication of Multi Layered Ceramic Capacitors.

Response of alanine and barium dithionate EPR dosimeters.

The response of alanine and barium dithionate EPR dosimeters to proton irradiation with energies ranging from 6.6-25 MeV has been investigated. EPR dosimeters were calibrated using calibrated gamma sources. Alanine dosimeters show a value 29% higher than those obtained by a Markus chamber at the same energy, and barium dithionate shows a value 22% smaller. The response of the EPR dosimeters to irradiation at a mean dose of about 40 Gy depends on the proton energy. Using experimental data, the yield of the radicals in the tracks for the alanine pellets was calculated. The yield of the radicals was determined to be proportional to the linear energy transfer (LET) on the straight-line length of the proton track, and the proportional coefficient for alanine is equal to 0.109 eV-1. In the area of the Bragg peak, the probability of recombination of the ionized electrons with cations is increased. As a result, approximately 4.6 MeV of proton energy is used for ionization that results in electron-cation recombination instead of formation of radicals, and maximum LET does not coincide with the maximum concentration of the radicals.

Dielectric properties of Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5)O3 solid solutions.

Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) solid solutions are prepared by a solid-state reaction method, and their dielectric and tunable characteristics are investigated. The solid solutions with cubic perovskite structures are obtained for compositions of 10-50 mol% Sr(Ga(0.5)Ta(0.5))O(3). It is observed that the addition of Sr(Ga(0.5)Ta(0.5))O(3) into Ba(0.6)Sr(0.4)TiO(3) causes a shift in the phase transition peak to a lower temperature. Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) solid solutions exhibit depressed and broadened phase transition peaks, resulting in decreased dielectric constants and dielectric losses at room temperature. With the increase of Sr(Ga(0.5)Ta(0.5))O(3) content, the dielectric constant, loss tangent, and tunability are decreased. 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1Sr(Ga(0.5)Ta(0.5))O(3) has a dielectric constant epsilon = 534 and a tunability of 16% at 100 kHz under 2.63 kV/mm. The dielectric characteristics of Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) ceramics at microwave frequencies are also evaluated.

Depth of cure of dental resin composites: ISO 4049 depth and microhardness of types of materials and shades.

The optimal degree of curing throughout the bulk of a visible light-activated dental resin composite is acknowledged to be important to the clinical success of a resin composite restoration. Unfortunately, the dentist has no means of monitoring the cure of the resin surfaces not directly exposed to the curing light. Techniques, such as the layered buildup of restorations in 2 mm increments with longer activation times than 20 seconds, have been suggested. This study investigated the depth of cure (DOC) of a commercial resin composite in three types: flowable, hybrid and packable and in three shades: B1, A3 and D3 after 20 second activation with a quartz halogen light (620 mW/cm2). Depth of cure was measured by scraping the uncured material and by using a Knoop Hardness profile, starting from the surface exposed to the light. Using a minimum Knoop Hardness ratio of 0.8 bottom/top only, the flowable in shade B1 achieved a 2 mm DOC. Using the less restrictive scraping test, only the B1 shade of flowable and hybrid significantly exceeded a 2 mm DOC. Knoop Hardness at the DOC obtained by scraping ranged from 55%-70% of the top surface hardness. These data suggest that a 2 mm buildup layering technique may not result in adequate curing of the bottom layer for such a wide range of materials and that manufacturers need to provide quantitative information about DOC at specific activation times and light intensities for their entire range of resin materials and shades so that the dentist can devise a placement technique that will ensure adequate cure of the bulk of a restoration.

Anti-Stokes luminescence cooling of Tm3+ doped BaY2F8.

We report laser-induced cooling with thulium-doped BaY2F8 single crystals grown using the Czochralski technique. The spectroscopic characterization of the crystals has been used to evaluate the laser cooling performance of the samples. Cooling by 3 degrees below ambient temperature is obtained in a single-pass geometry with 4.4 Watts of pump laser power at lambda = 1855 nm.

Dose response of BaFBrl: Eu2+ storage phosphor plates exposed to megavoltage photon beams.

The BaFBrI:Eu2+ storage phosphor plate (SPP) is a reusable radiation image detector, widely used in diagnostic computed radiography, x-ray crystallography and radioactive tracer studies. When exposed to ionizing radiation, the SPP stores a latent image until it is scanned with a red reading laser which causes blue photostimulated luminescent (PSL) photons to be emitted. The mechanism of formation of the latent image is still poorly understood, especially for megavoltage photon beams. In order to gain insight into this mechanism and aid applications to high-energy beam dosimetry, the authors have directly determined the SPP generation efficiency, W, the energy required to produce one quantum of emitted PSL when it is irradiated by 60Co and 6 MV photon beams. This was done in four steps: 1. The SPP, in a water-equivalent plastic (WEP) phantom, was exposed to a 60Co or 6 MV beam, which had been calibrated to give a known absorbed dose to water in a water phantom at the position of the sensitive layer of the SPP. 2. Monte Carlo simulations were used to calculate the ratio of the dose to the sensitive layer in the WEP phantom to the dose to water at the same position in a water phantom. 3. A bleaching experiment was used to determine the number of photons emitted by a plate given a known dose. 4. The generation efficiency was calculated from the number of photons and the dose. This method is much more direct than previous calculations for kilovoltage x-ray beams based on quantum noise analysis. W was found, within experimental uncertainty, to be 190 eV for 60Co and 160 eV for 6 MV, independent of dose. The values for kilovoltage x-ray beams determined previously agree, within their large uncertainty, with these values for megavoltage beams.

Evolution of nanodomains in the uniaxial relaxor Sr0.61Ba0.39Nb2O6:Ce.

The evolution of the nanodomain pattern of the uniaxial relaxor ferroelectric strontium barium niobate doped with cerium was studied by piezoresponse force microscopy (PFM). The fractal-like nanodomains observed at room temperature decay on heating. At temperatures up to about 15 K above the Curie temperature, Tc = 320 K, areas of correlated polarization are still visible. On cooling from the paraelectric state to below Tc, a slow isothermal growth of nanodomain was found. The mean domain size increases according to a logarithmic law as predicted for the three-dimensional random field Ising model.

Dielectric spectroscopy of nano BaTiO3 confined in MCM-41 mesoporous molecular sieve materials.

Dielectric properties of barium titanate (BaTiO3) particles, synthesized directly in the pores of MCM-41 materials, have been investigated in the frequency range from 20 Hz to 1 MHz for temperature intervals from 100 K to 500 K. The dielectric spectra of BaTiO3 confined in these molecular sieves were compared with the results obtained from the investigation of pure MCM-41 materials. Obtained results confirmed successful incorporation of BaTiO3 into porous matrix, but no phase transition from paraelectric to ferroelectric phase was observed due to the particle size being smaller than the critical size. Also, the overall dielectric response of investigated materials is strongly influenced by adsorbed water molecules.

Paraelectric thin films by nanoscale engineering of epitaxy and planar anisotropy for microwave phase shifter applications.

Epitaxial and (110) oriented paraelectric thin films of Ba0.60Sro.40TiO3 were grown on (100) oriented NdGaO3 orthorhombic substrates, and the nonlinear dielectric properties were studied at 10 GHz along selected in-plane crystallographic directions in the film thickness range of 25-1200 nm. The measured dielectric properties show strong residual strain and in-plane directional dependence. For instance, the in-plane relative permittivity is found to vary from as much as 500 to 150 along [110] and [001], respectively, in the 600 nm film. Tunability was found to vary from as much as 54% to 20% in all films and directions. In a given film, the best tunability is observed along the compressed axis in a mixed strain state, 54% along [110] in the 600 nm film. It is shown that, by nanoscale manipulation of epitaxy and planar anisotropy, the return loss and phase shift in a paraelectric can be tuned over a rather wide range. The approach presented herein opens avenues for obtaining various degrees of phase shift on the same film, enabling one with an additional degree of freedom in device design and fabrication as well as multifunctionality.

Ferroelectric phase transition in individual single-crystalline BaTiO3 nanowires.

We report scanned probe characterizations of the ferroelectric phase transition in individual barium titanate (BaTiO3) nanowires. Variable-temperature electrostatic force microscopy is used to manipulate, image, and evaluate the diameter-dependent stability of ferroelectric polarizations. These measurements show that the ferroelectric phase transition temperature (TC) is depressed as the nanowire diameter (dnw) decreases, following a 1/dnw scaling. The diameter at which TC falls below room temperature is determined to be approximately 3 nm, and extrapolation of the data indicates that nanowires with dnw as small as 0.8 nm can support ferroelectricity at lower temperatures. We also present density functional theory (DFT) calculations of bare and molecule-covered BaTiO3 surfaces. These calculations indicate that ferroelectricity in nanowires is stabilized by molecular adsorbates such as OH and carboxylates. These adsorbates are found to passivate polarization charge more effectively than metallic electrodes, explaining the observed stability of ferroelectricity in small-diameter BaTiO3 nanowires.

Barium dithionate as an EPR dosemeter.

Electron paramagnetic resonance (EPR) dosimetry is growing in popularity and this success has encouraged the search for other dosimetric materials. Previous studies of gamma-irradiated barium dithionate (BaS(2)O(6) x 2H(2)O) have shown promise for its use as a radiation dosemeter. This work studies in greater detail several essential attributes of the system. Special attention has been directed to the study of EPR response dependences on microwave power, irradiation temperature, minimum detectable dose and post-irradiation stability.