Spatially modulated tunnel magnetoresistance on the nanoscale

We investigate the local tunnel magnetoresistance (TMR) effect within a single Co nanoisland using spin-polarized scanning tunneling microscopy. We observe a clear spatial modulation of the TMR ratio with an amplitude of ~20% and a spacing of ~1.3 nm between maxima and minima around the Fermi level. This result can be ascribed to a spatially modulated spin polarization within the Co island due to spin-dependent quantum interference. Our combined experimental and theoretical study reveals that spin-dependent electron confinement affects all transport properties such as differential conductance, conductance, and TMR. We demonstrate that the TMR within a nanostructured magnetic tunnel junction can be controlled on a length scale of 1 nm through spin-dependent quantum interference.     

High‐rate crystallization of polycarbonate in spincast thin film

Surface morphology of bisphenol‐A polycarbonate (BAPC) thin films, with thickness ranging from 30 to 1000 nm on silicon substrates was studied by atomic force microscopy. The films were prepared by spincasting from 1,2‐dichloroethane solutions of 0.25–5.0 wt % BAPC. Even though longer annealing than 250 h was necessary for complete crystallization for bulk BAPC, high crystallinity was observed for 30 nm thick film after annealing at 200 °C for 48 h in vacuum. Positron annihilation lifetime spectroscopy measurements showed that the free volume hole size in 30 nm thick film was larger than that of bulk at 200 °C. Comparison of the BAPC concentration in the precursor solution with the overlap concentration suggests that the high crystallinity of the 30 nm BAPC film is due to less entangled chains caused by rapid removal of the solvent from the dilute solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Preparation and characterization of hydrophobic calcium hydroxyapatite particles grafting oleylphosphate groups

Grafting of oleylphosphate (OP) molecules to the surface of calcium hydroxyapatite particles (HAP) was carried out by a coprecipitation method with a Ca(OH)₂–H₃PO₄ system in the presence of disodium oleylphosphate (DSOP). All the particles exhibited a single-crystal nature with rod-like shape and were elongated along c-axis from 36 to 122 nm in particle length with an increase in the concentration of DSOP. It was suggested that 084% of the phosphate ions exposed on the ac or bc faces of the HAP particles are exchanged with phosphate ions of DSOP molecules directing oleyl groups outward. The hydrophobicity of OP-grafted HAP particles was enhanced with an increase in the DSOP concentration. This high surface hydrophobicity was further confirmed by water adsorption experiments. The materials with the surface oleyl groups adsorbed much less water than the HAP particles produced without DSOP.     

Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor

For the iron-based high T_c superconductor LaFeAsO_1?xF_x, we construct a minimal model, where all of the five Fe d bands turn out to be involved. We then investigate the origin of superconductivity with a five-band random-phase approximation by solving the Eliashberg equation. We conclude that the spin fluctuation modes arising from the nesting between the disconnected Fermi pockets realise, basically, an extended s-wave pairing, where the gap changes sign across the nesting vector.     

Thermal behavior of poly(bisphenol A carbonate) in the presence of phosphorus compounds

To clarify the interaction between poly(bisphenol A carbonate) (PBAC) and phosphorus compounds such as triphenylphosphine oxide (TPPO), triphenyl phosphate (TPP), and resorcinol bis(diphenyl phosphate) (RDP), PBAC was heated in the presence of these phosphorus compounds at 240 °C for 2 h, and the resulting polymers were analyzed by ¹H NMR spectroscopy and gel permeation chromatography. When heated in the presence of TPPO, the PBAC sample decomposed extensively, resulting in a substantial decrease in molecular weight. On the other hand, thermal treatment in the presence of the phosphates increased the molecular weight. In both cases the molecular weight distribution became narrower. Thermal treatment of PBAC in the presence of both TPPO and TPP allowed us to control the molecular weight with a narrower distribution. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1069–1074, 2004     

Finding synthetically versatile and common intermediates for multiple useful products with the aid of a synthesis design system

With the aid of a synthesis design system, we searched for common intermediates in routes to sets of target molecules. Finding such common intermediates will be a great help in constructing cost-effective synthetic routes. We tried to look for new common intermediates with 24 investigational or commercially produced antidepressants as target molecules. Most of the common intermediates were usually found to lead to more than two targets.     

Application of an electrochemical membrane reactor to the thermochemical water splitting IS process for hydrogen production

The Bunsen reaction (SO₂ + I₂ + 2H₂O = H₂SO₄ + 2HI) in the thermochemical IS process to produce hydrogen was successfully employed using an electrochemical membrane reactor. H₂SO₄ and HI were concentrated in the anode side and the cathode side of the reactor, respectively. I₂ is the dominant bulk of the recycling chemicals in this process, and I₂ concentration at the outlet of the reactor was reduced ca. 93% by using this technique. The electric energy consumption for the reaction was about 50% smaller by reducing the concentration of I₂ indicating that the IS process can be operate efficiently at low I₂ concentration. The reaction was carried out for 4 h, and the HI concentration was increased by 26%. This amount was the same within 10% as the values calculated from the total loaded electricity. In order to decrease the overpotential at the anode side, small amount of HI was added to the anode side solution. The total voltage was reduced by 0.03 V by the addition of HI.     

Ion-exclusion chromatography of aliphatic car☐ylic acids on a cation-exchange resin by elution with polyvinyl alcohol

Ion-exclusion chromatography of aliphatic car☐ylic acids of different acidity (pK_a) and hydrophobicity was investigated on a polystyrene-divinylbenzene (PS-DVB) based strongly acidic cation-exchange resin in the H⁺ form and conductivity detection by elution with polyvinyl alcohol (PVA). When water was used as an eluent, the resolution of the car☐ylic acids was very low and the peak accompanied a fronting depending on their hydrophobicities. Therefore, to improve the peak shape and the peak resolution, aqueous eluents containing PVAs (degrees of polymerization, n=500, 1500and2000) with many OH groups were tested for the ion-exclusion chromatographic separation of the car☐ylic acids. When aqueous eluents containing PVA were used, the fronting was decreased dramatically by the effect of increased hydrophilicity of the PS-DVB cation-exchange resin surface due to adsorption of OH group in PVA. The high resolution ion-exclusion chromatographic separation without the fronting and highly sensitive conductimetric detection of the car☐ylic acids was accomplished successfully by elution with a 0.2% PVA (n=1500)-10% methanol-water.     

A Multi-Spectral Polarimeter for Measurements of Direct Solar and Diffused Sky Radiation: Calibration and Measurements

A multi-spectral polarimeter (FPR1000) is designed to measure the radiance and degree of polarization of the sky radiation as well as the extinction of solar irradiance using the same optical system. This enables us to make consistent measurements of the direct solar and diffused sky radiation. Measurements are made at the same wavelength regions as Polarization and Directionality of the Earth’s Reflectances (POLDER) and Ocean Color and Temperature Scanner (OCTS) onboard Advanced Earth Observing Satellite (ADEOS). Based on measurements for the Langley plot calibration made at Mauna Loa Observatory, the calibration constants are obtained by considering the effect of absorption by water vapor and uniformly mixed gas. Preliminary analyses of the measurements of sky radiation and direct solar irradiance carried out in the western part of the Pacific Ocean are presented. Combined measurements of the extinction of solar irradiance, and the radiance and degree of polarization of sky radiation could be useful in improving retrieval of optical characteristics of aerosol and for atmospheric correction.     

Synthesis and properties of novel macrocyclic compounds bearing thiourea moieties by use of chemical feature of hypervalent sulfur

Macrocyclic compounds 5a‐i bearing two tetraazathiapentalene frameworks were synthesized by the reaction of 10‐S‐3 tetraazathiapentalene derivatives 3a‐f with compounds having various diisothiocyanate functions 4a‐e. The reduction of the macrocyclic compounds with NaBH₄ afforded the ring‐opened macrocyclic compounds 11a‐b and 11e‐h by elimination of the hypervalent sulfur. The structures of these compounds were established by their spectral data and also by the X‐ray crystallographic analysis of lla. The other ring‐opened macrocyclic compounds 14a and 14e‐h that bear four thiourea groups were synthesized by alkaline hydrolysis of 5a and 5e‐h in that elimination of the C=S^IV moiety in the tetraazathiapentalene rings occurred.