Magnetic-field-induced phase separation via spinodal decomposition in epitaxial manganese ferrite thin films.

In this study, we report about the occurrence of phase separation through spinodal decomposition (SD) in spinel manganese ferrite (Mn ferrite) thin films grown by Dynamic Aurora pulsed laser deposition. The driving force behind this SD in Mn ferrite films is considered to be an ion-impingement-enhanced diffusion that is induced by the application of magnetic field during film growth. The phase separation to Mn-rich and Fe-rich phases in Mn ferrite films is confirmed from the Bragg's peak splitting and the appearance of the patterned checkerboard-like domain in the surface. In the cross-sectional microstructure analysis, the distribution of Mn and Fe-signals alternately changes along the lateral (x and y) directions, while it is almost homogeneous in the z-direction. The result suggests that columnar-type phase separation occurs by the up-hill diffusion only along the in-plane directions. The propagation of a quasi-sinusoidal compositional wave in the lateral directions is confirmed from spatially resolved chemical composition analysis, which strongly demonstrates the occurrence of phase separation via SD. It is also found that the composition of Mn-rich and Fe-rich phases in phase-separated Mn ferrite thin films deposited at higher growth temperature and in situ magnetic field does not depend on the corresponding average film composition.

Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects.

Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe4+ cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe4+. In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.

Strain engineering effects on electrical properties of lead-free piezoelectric thin films on Si wafers.

Using radio frequency - magnetron sputtering, calcium-doped barium zirconate titanate ((Ba(0.85)Ca(0.15))(Zr(0.1)Ti(0.9))O(3), BCZT) thin films were deposited on Si wafers with different bottom electrodes. The obtained BCZT thin film on a lanthanum nickel oxide (LNO) electrode had a highly c-axis preferred orientation, while the BCZT thin film on a Pt bottom electrode had (111) preferred orientation. Furthermore, the out-of-plane lattice constant of the BCZT on LNO/Si was 3.4% larger than that of the reported bulk material because of the compressive thermal stress from LNO with a large thermal expansion coefficient. This compressive thermal stress engenders an increase of the Curie temperature. The local piezoelectric response of the BCZT thin film on a LNO/Si structure was measured by piezoresponse force microscope.

Phase diagram and piezoelectric response of (Ba1-xCax)(Zr0.1Ti0.9)O3 solid solution.

We report the phase diagram of (Ba1-xCax)(Zr0.1Ti0.9)O3 solid solution. It is found that substitution of smaller Ca ions for Ba ions can slightly increase the cubic-tetragonal (T) para-ferroelectric phase transition temperature and strongly decrease the T-orthorhombic (O) and O-rhombohedral (R) transition. This unique ferroelectric phase evolution is attributed to Ca off-centering effects. More importantly, lowering of the T-O or O-R phase transitions allows us to prepare the piezoelectric ceramics with a strain response as high as S/E ≈ 800 pm V(-1) (E = 10 kV cm(-1)) over a wide range of compositions with x ≈ 0.1-0.18 at room temperature, which may be interesting for piezoelectric applications.

Expression of an RSV-gag virus-like particle in insect cell lines and silkworm larvae.

Rous sarcoma virus group antigen protein-based virus-like particles (VLPs) are well known for their structural integrity and ease of handling. VLPs play an important role in drug delivery systems because they can be manipulated with ease. In this study, a new method was established for expressing Rous sarcoma virus group antigen protein based VLPs in silkworm larvae and establishing stably expressing insect cell lines. These VLPs have been isolated by ultracentrifugation using a sucrose step gradient of 10-60% (v/v), and their spherical structure has been confirmed using transmission electron microscopy (TEM). The spherical morphology is similar in both the silkworm larvae and in stably expressing cell lines. Silkworm larvae are better suited for producing Rous sarcoma virus group antigen protein-based VLPs on a large scale; yields from silkworm larvae were approximately 8.2-fold higher than yields from stable cell lines. These VLPs provide a new method for large-scale application in vaccine development and drug delivery systems.

Fabrication of two-dimensional close-packed shell structure in ceramic thin films.

TiO2 thin films with a periodical two-dimensional close-packed hemispherical structure were prepared on Si substrates using pulsed laser deposition and close-packed monolayer polystyrene colloidal crystals as a template. Compared with conventional methods, which use a top-down approach, this route supports low-cost production of a periodic structure. Additionally, it is applicable to various ceramics for use in applications related to photonic crystals, surface self-cleaning materials, data storage media, bioassays, and so on.

Magnetic and optical properties of MgAl2O4-(Ni0.5Zn0.5)Fe2O4 thin films prepared by pulsed laser deposition.

Thin films composed of MgAl2O4 and (Ni0.5Zn0.5)Fe2O4 ([MA(100-x)-NZFx] films) were grown on fused SiO2 substrates by pulsed laser deposition. X-ray diffraction measurements revealed that the films were polycrystalline, and that their lattice constant varied linearly with composition, indicating the formation of a solid solution. The film with x=60 was paramagnetic and those with x ≥ 70 were ferromagnetic. The films had a transparency above 75% in the visible range, but the transparency decreased with the x value. The optical band gaps were 2.95, 2.55, 2.30 and 1.89 eV for x=20, 40, 60, 80 and 100, respectively. The Faraday rotation angle increased with x in the visible range, and the film with x=70 exhibited a value of 2000 degrees cm-1 at 570 nm, which is comparable to the rotation angle of Y3Fe5O12. Owing to their high transparency, which extends into the visible range, the [MA(100-x)-NZFx] films can be used in novel magneto-optical devices.

Photocatalytic treatment of municipal wastewater using modified neodymium doped TiO(2) hybrid nanoparticles.

Photocatalytic degradation of municipal wastewater was investigated using reagent grade TiO(2) and modified neodymium doped TiO(2) hybrid nanoparticles. For the first time, surface modification of Nd(3 +) doped TiO(2) hybrid nanoparticles were carried out with n-butylamine as surface modifier under mild hydrothermal conditions. The modified nanoparticles obtained were characterized by Powder XRD, FTIR, DLS, TEM, BET surface area, zeta potential and UV-Vis Spectroscopy. The characterization results indicated better morphology, particle size distribution and low agglomeration of the nanoparticles synthesized. It was found that photodegradation of wastewater using surface modified neodymium doped TiO(2) nanoparticles was more compared to pure TiO(2), which can be attributed to the doping and modification with n-butylamine.

[Retrospective analysis of postoperative nausea and vomiting after craniotomy].

BACKGROUND: Postoperative nausea and vomiting are important complications after craniotomy. METHODS: One hundred and seventy eight patients who had undergone brain tumor resection at Nara Medical University were retrospectively divided to one of two groups; with or without PONV within 24 hours postoperatively. Variables compared between the groups include gender, age, weight, height, site of surgery (supratentorial versus infratentorial craniotomy), size of brain tumor, type of anesthesia (inhalation versus intravenous anesthesia with nitrous oxide), intraoperative fentanyl dose, duration of surgery as well as anesthesia, and intraoperative posture. RESULTS: PONV occurred in 87 patients (49%). The incidence of PONV in patients undergoing infratentorial craniotomy was significantly higher than that in patients undergoing supratentorial craniotomy (75% vs 45%, P = 0.0011). There were no significant associations between PONV and other variables analyzed. CONCLUSIONS: These results indicate that the incidence of PONV after brain tumor resection is high and infratentorial surgery is a risk factor for PONV. Strategies for the prevention of PONV after craniotomy are required.