Temperature- and field-driven spin reorientations in triple-layer ruthenate Sr4Ru3O10.

Sr4Ru3O10, the n = 3 member of the Ruddlesden-Popper type ruthenate Srn+1Ru n O3n+1, is known to exhibit a peculiar metamagnetic transition in an in-plane magnetic field. However, the nature of both the temperature- and field-dependent phase transitions remains as a topic of debate. Here, we have investigated the magnetic transitions of Sr4Ru3O10 via single-crystal neutron diffraction measurements. At zero field, we find that the system undergoes a ferromagnetic transition with both in-plane and out-of-plane magnetic components at Tc ≈ 100 K. Below T * = 50 K, the magnetic moments incline continuously toward the out-of-plane direction. At T = 1.5 K, where the spins are nearly aligned along the c axis, a spin reorientation occurs above a critical field Bc, giving rise to a spin component perpendicular to the plane defined by the field direction and the c axis. We suggest that both the temperature- and field-driven spin reorientations are associated with a change in the magnetocrystalline anisotropy, which is strongly coupled to the lattice degrees of freedom. This study elucidates the long-standing puzzles on the zero-field magnetic orders of Sr4Ru3O10 and provides new insights into the nature of the field-induced metamagnetic transition.

Optimization of Growth Temperature of ß-Ga2O3 Thin Films for Solar-Blind Photodetectors.

Monoclinic gallium oxide thin films were deposited on c-plane sapphire substrates at various substrate temperatures ranging from 450 °C to 700 °C by radio frequency magnetron sputtering technology. X-ray diffraction results showed that the deposited ß-Ga2O3 films were oriented at ( 2 ¯ 01) direction. As the substrate temperature increased, the intensity of ß-Ga2O3 peaks increased and bandgap decreased accordingly. Metal/semiconductor/metal structured solar-blind photodetectors based on ß-Ga2O3 thin films growing at various substrate temperatures had been fabricated. The growth temperatures of thin films had no obvious influence on dark current and response to 365 nm light illuminations. The photoelectric properties such as responsivity and response speed of the thin films to 254 nm light illuminations were growth temperature dependent. At an applied bias of 50 V, the photodetectors prepared with 450 °C grown film had the highest responsivity of 2.18 A/W, and the photodetectors prepared with 700 °C grown film had the shortest rising time of 0.95 s under 254 nm light illuminations.

Electrical and Optical Properties of In2O3 Thin Films Deposited on Sapphire Substrate.

In2O3 thin films were prepared on c-plane sapphire substrates using laser molecular beam epitaxy technique. The X-ray diffraction (XRD) patterns revealed that the In2O3 thin films were highly oriented along the (111) direction. The intensity of (222) diffraction peaks mainly depend on growth temperature, and the crystallite sizes mainly depend on oxygen pressure. The carrier concentrations exhibit a decrease with increasing growth temperature and oxygen pressure, meantime, the resistivity increase. The red shift of In2O3 thin films respect to that of bulk In2O3 can be explained by defect energy levels formation, the blue shift of In2O3 thin films depends on carrier concentration, can be explained by Burstein-Moss band-filling effect.

Cations substitution tuning phase stability in hybrid perovskite single crystals by strain relaxation.

Methylammonium (MA) and formamidinium (FA) are two typical A site cations in lead halide perovskites. Instability of synthesised crystals will degrade the properties of the photoelectrical device constructed by such perovskites. MAPbI3 and FAPbI3 in cubic crystal structure have been demonstrated to be the most stable at room temperature. Herein we synthesised MA(EA)PbI3 and FA(MA)PbI3 single crystals using an inverse-temperature crystallization strategy by partially substituting the methylammonium (MA) with ethylammonium (EA) and the formamidinium (FA) with methylammonium (MA) respectively. The XRD results show that both crystal structures are cubic, which means organic incorporation can stabilize the crystal structure of lead halide perovskites. The lattice distortion decrease and strain relaxation in single crystals were considered to be the reason leading to higher stability. The single crystals of MA(EA)PbI3 and FA(MA)PbI3 with low trap state density exhibit excellent light-absorbing properties, indicating their potential applications in photoelectric devices.

Poly(9,9-dihexylfluorene)/ZnO Nanoparticles Based Inorganic/Organic Heterojunction Structure: Electrical and Photoconductivity Properties.

ZnO nanoparticles in size of -5 nm were synthesized by wet chemical method, P-type (9,9-dihexylfluorene) (PFH) and the synthesized n-type ZnO nanoparticles were used to fabricate PFH/ZnO heterojunction structure using spin coating method. The current-voltage characteristic of the heterojunction demonstrates the typical p-n junction rectifying behavior, but such rectifying behavior disappeared in vacuum, which is considered to be related to the oxygen in ZnO. The heterojunction shown an fast and stable response to UV and blue light. The responsivity of heterostruture can be tuned by the bias. The conductivities of organic/inorganic heterojunction increase with the increase of temperature, and the derived active energy (Ea) decreased linearly with the increase of bias.

Endothelial injury preceding intracranial aneurysm formation in rabbits.

OBJECTIVE: This study investigates the change of endothelial cell morphology and function at the rabbit basilar bifurcations in response to sustained high blood flow after bilateral common carotid artery ligation. METHODS: Fifteen adult female New Zealand white rabbits were divided into experimental and sham control groups. The experimental group was subjected to bilateral common carotid artery ligation to increase the compensatory basilar artery flow. Basilar artery flow was monitored by transcranial Doppler after surgery. The endothelial cells at the arterial bifurcations were studied morphologically by electron microscopy and immunohistochemistry using ß-catenin antibodies. Basilar artery flow increased significantly following common carotid artery ligation. RESULTS: Early-stage basilar artery bifurcation aneurysms were present in all rabbits at three months after ligation. The endothelial cells changed from a fusiform to column shape at the basilar artery bifurcation. Gaps between endothelial cells of the experimental group appeared wider in the electron microscopic photographs compared with those of the control group. The expression of endothelial ß-catenin at the arterial bifurcations also decreased. CONCLUSION: This study is the first to present endothelial cell changes of basilar artery bifurcation in response to sustained high blood flow in rabbits. Endothelial cell impairment possibly initiates aneurysm formation.

Optoelectronic properties of CdSe0.75S0.25 nanocrystals assembled into micro-electrodes.

CdSe0.75S0.25 semiconductor nanocrystals were synthesized by chemical colloidal route. The crystal structure, morphology and optical properties of synthesized CdSe0.75S0.25 nanocrystals were characterized by XRD, TEM and UV-Vis absorption spectroscopy respectively. The crystal structure of CdSe0.75S0.25 is face-centered Cubic sphalerite phase. The average size is about 7 nm in diameter. A gold tip-to-tip structure electrode with the gap size -20 microm was fabricated using conventional optical lithography technique followed by film deposition and standard lift-off process. An optoelectronics device was fabricated based on CdSe0.75S0.25 by assembling nanocrystals into electrodes by using dielectrophoresis (DEP) process. The electrical transport properties and opto-electrical transport properties of the fabricated device were measured at temperature range from 5 K to 305 K. The results show that the resistance of CdSe0.75S0.25 NCs increases with the temperature decreases, indicating a typical semiconductor behavior. An obvious photoconductive behavior was observed, demonstrated potential application in nano-optoelectronics devices. After data analyzing, the conductivity shows the 0.5 exponent of Efros-Shklovskii variable-range-hopping (ES-VRH) model.

Solvothermal route to S-deficient CoS nanoplates and their cathodoluminescence and magnetic properties.

A facile solvothermal method was developed to fabricate CoS nanoplates using ethylenediamine as solvent. The microstructure characterizations indicate that the CoS nanoplates have well-crystalline hexagonal phase and regular hexagonal or pentagonal shape. The XPS and ICP-AES measurements confirm the chemical composition of nanoplates is S-deficient CoS0.921. Cathodoluminescence spectra of both a large area of the nanoplates and individual nanoplate show broad emission bands centered at 615 nm. Magnetic measurements including magnetization dependence of temperature and magnetic hysteresis loops reveals that the CoS nanoplates exhibit room-temperature ferromagnetic behavior. It is found that intrinsic point defects mainly as V(s), Co(i) and/or the complex defects of V(s) and Co(i) should be responsible for both the broad emission band and the unique ferromagnetism.

Lake ecosystem health assessment: indicators and methods.

A set of ecological indicators including structural, functional, and system-level aspects were proposed for a lake ecosystem health assessment, according to the structural, functional, and system-level responses of lake ecosystems to chemical stresses including acidification, eutrophication and copper, oil and pesticide contamination. The structural indicators included phytoplankton cell size and biomass, zooplankton body size and biomass, species diversity, macro- and micro-zooplankton biomass, the zooplankton phytoplankton ratio, and the macrozooplankton microzooplankton ratio. The functional indicators encompassed the algal C assimilation ratio, resource use efficiency, community production, gross production/respiration (i.e. P/R) ratio, gross production standing crop biomass (i.e. P/B) ratio, and standing crop biomass unit energy flow (i.e. B/E) ratio. The ecosystem-level indicators conisisted of ecological buffer capacities, energy, and structural energy. Based on these indicators, a direct measurement method (DMM) and an ecological modeling method (EMM) for lake ecosystem health assessment were developed. The DMM procedures were designed to: (1) identify key indicators; (2) measure directly or calculate indirectly the selected indicators; and, (3) assess ecosystem health on the basis of the indicator values. The EMM procedures were designed to: (1) determine the structure and complexity of the ecological model according to the lake's ecosystem structure; (2) establish an ecological model by designing a conceptual diagram, establishing model equations, and estimating model pararmeters; (3) compare the simulated values of important state variables and process rates with actual observations; (4) calculate ecosystem health indicators using the ecological model; and, (5) assess lake ecosystem health according to the values of the ecological indicators. The results of a case study demonstrated that both methods provided similar results which corresponded with the lake's actual trophic state.