Thin film deposition of metal oxides in resistance switching devices: electrode material dependence of resistance switching in manganite films

The electric-pulse-induced resistance switching in layered structures composed of polycrystalline Pr_1−xCa_xMnO₃ (PCMO) sandwiched between Pt bottom electrode and top electrodes of various metals (metal/PCMO/Pt) was studied by direct current current–voltage (I-V) measurements and alternating current impedance spectroscopy. The I-V characteristics showed nonlinear, asymmetric, and hysteretic behavior in PCMO-based devices with top electrode of Al, Ni, and Ag, while no hysteretic behavior was observed in Au/PCMO/Pt devices. The PCMO-based devices with hysteretic I-V curves exhibited an electric-pulse-induced resistance switching between high and low resistance states. Impedance spectroscopy was employed to study the origin of the resistance switching. From comparison of the impedance spectra between the high and low resistance states, the resistance switching in the PCMO-based devices was mainly due to the resistance change in the interface between the film and the electrode. The electronic properties of the devices showed stronger correlation with the oxidation Gibbs free energy than with the work function of the electrode metal, which suggests that the interface impedance is due to an interfacial oxide layer of the electrode metal. The interface component observed by impedance spectroscopy in the Al/PCMO/Pt device might be due to Al oxide layer formed by oxidation of Al top electrode. It is considered that the interfacial oxide layer plays a dominant role in the bipolar resistance switching in manganite film-based devices.     

Micropatterned co-culture of hepatocyte spheroids layered on non-parenchymal cells to understand heterotypic cellular interactions

Abstract

Microfabrication and micropatterning techniques in tissue engineering offer great potential for creating and controlling cellular microenvironments including cell–matrix interactions, soluble stimuli and cell–cell interactions. Here, we present a novel approach to generate layered patterning of hepatocyte spheroids on micropatterned non-parenchymal feeder cells using microfabricated poly(ethylene glycol) (PEG) hydrogels. Micropatterned PEG-hydrogel-treated substrates with two-dimensional arrays of gelatin circular domains (φ = 100 μm) were prepared by photolithographic method. Only on the critical structure of PEG hydrogel with perfect protein rejection, hepatocytes were co-cultured with non-parenchymal cells to be led to enhanced hepatocyte functions. Then, we investigated the mechanism of the functional enhancement in co-culture with respect to the contributions of soluble factors and direct cell–cell interactions. In particular, to elucidate the influence of soluble factors on hepatocyte function, hepatocyte spheroids underlaid with fibroblasts (NIH/3T3 mouse fibroblasts) or endothelial cells (BAECs: bovine aortic endothelial cells) were compared with physically separated co-culture of hepatocyte monospheroids with NIH3T3 or BAEC using trans-well culture systems. Our results suggested that direct heterotypic cell-to-cell contact and soluble factors, both of these between hepatocytes and fibroblasts, significantly enhanced hepatocyte functions. In contrast, direct heterotypic cell-to-cell contact between hepatocytes and endothelial cells only contributed to enhance hepatocyte functions. This patterning technique can be a useful experimental tool for applications in basic science, drug screening and tissue engineering, as well as in the design of artificial liver devices.     

Anisotropic mobility and carrier dynamics in the β-type BEDT-TTF salts as studied by inter-layer transverse magnetoresistance

Abstract

A new method to estimate an in-plane conduction anisotropy in a quasi-two-dimensional (q2D) layered conductor by measuring the inter-layer transverse magnetoresistance is proposed. We applied this method to layered organic conductors β-(BEDT-TTF)₂X (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, C₁₀H₈S₈; X = IBr₂, I₂Br) by applying magnetic field rotating within the basal plane at 4.2 K. We found the anisotropic behaviour of carrier mobility μ. From this, anomalous distribution of carrier lifetime τ on the Fermi surface is derived, by the use of Fermi surface data reported for the materials. Calculations of the non-uniform susceptibility χ₀(q) suggest that carrier scattering is enhanced at specific k-points related to partial nesting of the Fermi surface. The present method is thus demonstrated to be an efficient experimental tool to elucidate anisotropic carrier dynamics in q2D conductors.     

Three-dimensional collective flux pinning in the layered superconductor 2H-NbSe2-xSx

The collective pinning theory was compared with the results of flux pinning in the layered superconductor 2H-NbSe _2–x S _x.The size effect on the flux-pinning force and the angular dependence of the peak effect were investigated. Our sample did not show the size effect. Even when a magnetic field was applied parallel to the crystal layers, the peak effect was observed far below the zero-field critical temperature. These results show that flux pinning is three-dimensional within the frame of the collective pinning theory and that the peak effect is not caused by the dimensional crossover. The peak effect can be qualitatively explained in terms of the dispersion of the tilt modulus of the flux-line lattice.     

Development of fully-automated synthesis systems

This paper describes the development of fully-automated synthesis systems for preparing and isolating various kinds of pharmaceutical compounds. The systems are versatile, and are able to perform most of the chemical reactions currently used in organic chemistry, with the exception of hydrogenation which requires high pressure. An additional benefit is the very user-friendly software.     

Chemical States of Implanted Aluminum Ions in Silica and Silicon Ions in Alumina

Aluminum and silicon ions have been implanted in silica glass and α-alumina single crystal, respectively, to doses ranging from 1 × 10¹⁵ to 1 × 10¹⁷ ions·cm^-2. The chemical states of these implanted ions have been studied by X-ray fluorescence spectroscopy. It is found that the implanted aluminum atoms are coordinated only by oxygen atoms, irrespective of implantation dose. On the other hand, the implanted silicon atoms are coordinated only by oxygen atoms at low doses and by both oxygen and silicon atoms at high doses. Although the chemical state of the aluminum atoms is unchanged by heat treatment, that of the silicon atoms is changed toward a less positively charged state. It is inferred that the chemical states of the implanted atoms are controlled by the transport process, although these tend to obey the thermodynamic stability.     

Status of glass‐bulb development for flat and thin CRTs

Abstract— The next goal to minimize the bulkiness of CRTs is most likely to attain half the depth of conventional CRTs, while keeping the weight within a reasonable range. Several innovations for reducing the bulkiness of glass bulbs for wide‐deflection‐angle CRTs have been made and further technologies are being developed by improving material and structural approaches. The integrated glass technology based on these innovations will provide a lightweight shallow glass bulb and the impetus to achieve this goal.     

The origin of hypersaline liquid in the quaternary kakkonda granite, sampled from well WD-1a, kakkonda geothermal system, Japan

Hypersaline metal-rich liquid (ca. 40 wt% total chloride species) was obtained from a depth of 3708 m in the Kakkonda geothermal system. Sampling of well WD-1a was conducted by reverse circulation after a standing time of about 196 hours (with temperature recovering to >500°C). Tritium content and the relationship between δD and δ¹⁸O showed that the river water that was circulated in the well had mixed with an isotopically heavy fluid during the standing time. Phase separation occurred during temperature recovery, concentrating the hypersaline liquid in the bottom of the well. This original hypersaline liquid has a salinity of about 55 wt% NaCl eq., consisting of Na–Fe–K–Mn–Ca chloride, rich in Zn and Pb but poor in Cu, Au and Ag. The fluid originates from the Kakkonda granite and mixed with circulating water from the well in a zone of fine fractures induced by thermal stress during drilling.     

Enhanced MR imaging with a nonionic contrast gadolinium complex, Gadoteridol, for lumbar disc herniation]

The gamma-glutamyltransferase (EC 2.3.2.2) activity was measured in the blood serum obtained from 25 female patients with the uterine cervix carcinoma 10 and from 21 women with the uterine corpus carcinoma 10, treated by brachytherapy. The enzyme activity was determined in the five time points: before the brachytherapy, in the middle of the treating course, immediately after the application of the full dose of radium and in the seventh and the fourteenth day after the finishing the treatment. It was assumed the changes in the enzyme activity during the treatment course, and the highest values were observed immediately after the brachytherapy. It was noticed, that there is the direct connection between the enzyme activity changes and used brachytherapy method.