Thickness dependence of H2 gas sensor in amorphous SnQx films prepared by ion-beam sputtering

Amorphous SnO_x films were deposited by ion-beam sputtering on sintered alumina substrates. Amorphous film sensors were prepared by annealing the films at 300° C for 2 h in air. The thickness dependence of resistivity and hydrogen gas sensitivity were measured at 150° C over the thickness range 1 to 700 nm. A resistivity maximum was observed in ultrathin films. Resistivity increased by three orders of magnitude with increasing film thickness from 0.9 to 7.4 nm and then decreased by five orders of magnitude from 7.4 to 35 nm. Ultrathin film sensors showed sensitivity maxima around a thickness of 10 nm. Sensitivity and resistivity of ultrathin films were significantly influenced by the thermal expansion coefficient and the surface state of the substrate.     

Clinical application of single-shot echo-planar diffusion-weighted imaging with compressed SENSE in prostate MRI at 3T: preliminary experience

Magnetic Resonance Materials in Physics, Biology and Medicine - Image quality (IQ) of diffusion-weighted imaging (DWI) with single-shot echo-planar imaging (ssEPI) suffers from low signal-to-noise...     

A novel sphingophosphonolipid head group 1-hydroxy-2-aminoethyl phosphonate in Bdellovibrio stolpii

Members of the bacterial genus Bdellovibrio include strains that are free-living whereas others are known to invade and parasitize larger Gram-negative bacteria. The bacterium can synthesize several sphingophospholipid compounds including those with phosphoryl bonds as well as phosphonyl bonds. In the present study, the dominant sphingophosphonolipid component was isolated by column chromatography, and the long-chain bases, fatty acids, and polar head groups were identified by thin-layer and gas-liquid chromatographic procedures. The definitive structural identity of the sphingolipid was established by nuclear magnetic resonance and mass spectrometry of hydrolysis products and the intact compound. The compound was identified as N-2′-hydroxypentadecanoyl-2-amino-3,4-dihydroxyheptadecan-1-phosphono-(1-hydroxy-2-aminoethane).     

Polyurea thin film ultrasonic transducers for nondestructive testing and medical imaging

Ultrasonic transducers using polyurea piezoelectric thin film are studied in this paper. Aromatic polyurea thin films, prepared by vapor deposition polymerization, have useful characteristics for use as an ultrasonic transducer. This paper presents the fabrication and experimental evaluation of ultrasonic transducers formed using polyurea films. First, the vapor deposition polymerization process using two monomers is briefly reviewed, and the temperature conditions for higher piezoelectric constants are explored. Second, in order to test the fundamental characteristics of this material as a high-frequency, ultrasonic transducer, a polyurea film of 2.5 microm thickness was deposited on a silicon substrate. In the pulse/echo experiment results, a resonant frequency of about 100 MHz was observed. Third, we fabricated a concave point focus transducer and a cylindrical line focus transducer. To examine the performances of the focus transducers, two-dimensional images of a coin and V(z) curve measurements for an aluminum surface were demonstrated.     

Short channel characteristics of quasi-single-drain MOSFETs

It is clearly demonstrated that source/drain (S/D) elevation is remarkably effective in suppressing the short channel effect against the shrinkage of gate sidewall spacers in MOSFETs. Even if the gate sidewall width is reduced to as very thin as 15 nm, the short channel effect is effectively suppressed by means of the highly elevated S/D regions (80 nm in the present case), though the characteristics of conventional MOSFETs are drastically degraded. This result is explained in terms of the fact that the serious influence due to the deep S/D implantation is suppressed by the formation of a quasi-single-drain configuration. Furthermore, the parasitic S/D resistance decrease, which will bring about drivability enhancement, was observed for reduction in the sidewall width. These favorable experimental results may indicate the definite necessity of elevated S/D engineering for future ultrashort MOSFETs     

Preparation of Cu2ZnSnS4 thin films by sulfurizing electroplated precursors

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing precursors deposited by electroplating. The precursors (Cu/Sn/Zn stacked layers) were deposited by electroplating sequentially onto Mo-coated glass substrates. Aqueous solutions containing copper sulfate for Cu plating, tin sulfate for Sn plating and zinc sulfate for Zn plating were used as the electrolytes. The precursors were sulfurized by annealing with sulfur at temperatures of 300, 400, 500 and 600 °C in an N₂ gas atmosphere. The X-ray diffraction peaks attributable to CZTS were detected in thin films sulfurized at temperatures above 400 °C. A photovoltaic cell using a CZTS thin film produced by sulfurizing an electroplated Sn-rich precursor at 600 °C exhibited an open-circuit voltage of 262 mV, a short-circuit current of 9.85 mA/cm² and an efficiency of 0.98%.     

Quantum Melting of Domain Walls in 2D Incommensurate Phases

We investigate quantum fluctuations of striped and honeycomb domain walls in 2D incommensurate states at T=0 near the commensurate-incommensurate transition point. It is revealed that stripes melt due to quantum fluctuations and become a soliton liquid for a large-wall-spacing region. Zero-point energies of striped and honeycomb phases are calculated using an elastic theory. As a consequence of these results, phase diagrams for soliton-lattice and liquid phases are discussed for various domain-wall masses.     

Seismic proof test of a reinforced concrete containment vessel (RCCV): Part 1: Test model and pressure test

In Japan, the Nuclear Power Engineering Corporation (NUPEC), sponsored by the Ministry of Economy, Trade and Industry (METI), has been conducting a series of seismic reliability proving tests using full-scale or close to full-scale models to simulate actual important equipment that is critical for seismic safety of nuclear power plants. The tests are intended to validate the seismic design and reliability with a sufficient margin even under destructive earthquakes. A series of tests was carried out on a reinforced concrete containment vessel (RCCV) for advanced boiling water reactor (ABWR) from 1992 to 1999. A large-scale high-performance shaking table at Tadotsu Engineering Laboratory, the largest in the world, was used for this test. Part 1 reports the test model and the results of pressure and leak tests. Part 2 describes test procedures, input waves and the results of verification tests such as changes of stiffness, characteristic frequency and damping ratio, the failure of the model and the load deflection. Part 3 shows the seismic safety margin that was evaluated from the energy input during the failure test to a design basis earthquake. Part 4 reports simulation analysis results by a stick model with lumped masses.