Photoacoustic spectrometric determination of trace phosphorus as molybdenum blue adsorbed on uniform anion-exchange beads

Photoacoustic spectrometry was applied to the determination of phosphorus as molybdenum blue species adsorbed on an anion-exchange resin (10 mg of uniform beads). The photoacoustic intensity of ten resin particles on a glass plate was measured at 760 nm. The calibration graph obtained was linear in the range of 0.05–0.5 μg of phosphorus. The relative standard deviation for ten determinations of 0.3 μg P was 5.0%. The detection limit was 2 ng P ml^?1.     

Hydration structure of human lysozyme investigated by molecular dynamics simulation and cryogenic X-ray crystal structure analyses: on the correlation between crystal water sites,solvent density,and solvent dipole

The hydration structure of human lysozyme was studied with cryogenic X-ray diffraction experiment and molecular dynamics simulations. The crystal structure analysis at a resolution of 1.4 A provided 405 crystal water molecules around the enzyme. In the simulations at 300 K, the crystal structure was immersed in explicit water molecules. We examined correlations between crystal water sites and two physical quantities calculated from the 1-ns simulation trajectories: the solvent density reflecting the time-averaged distribution of water molecules, and the solvent dipole measuring the orientational ordering of water molecules around the enzyme. The local high solvent density sites were consistent with the crystal water sites, and better correlation was observed around surface residues with smaller conformational fluctuations during the simulations. Solvent dipoles around those sites exhibited coherent and persistent ordering, indicating that the hydration water molecules at the crystal water sites were highly oriented through the interactions with hydrophilic residues. Those water molecules restrained the orientational motions of adjoining water molecules and induced a solvent dipole field, which was persistent during the simulations around the enzyme. The coherent ordering was particularly prominent in and around the active site cleft of the enzyme. Because the ordering was significant up to the third to fourth solvent layer region from the enzyme surface, the coherently ordered solvent dipoles likely contributed to the molecular recognition of the enzyme in a long-distance range. The present work may provide a new approach combining computational and the experimental studies to understand protein hydration.     

Parity violation in a single domain of spin-triplet Sr2RuO4 superconductors

We observed an unconventional parity-violating vortex in single domain Sr₂RuO₄ single crystals using a transport measurement. The current–voltage characteristics of submicron Sr₂RuO₄ show that the induced voltage has anomalous components which are even functions of the bias current. The results may suggest that the vortex itself has a helical internal structure characterized by a Hopf invariant (a topological invariant). We also discuss that the hydrodynamics of such a helical vortex causes the parity violation to retain the topological invariant.     

Impedance spectra analysis of thermoresponsive poly(acryloyl‐L‐proline methyl ester) gel membrane in LiCl solution

Impedance spectra analysis of a thermoresponsive poly(acryloyl‐L ‐proline methyl ester) (poly(A‐ProOMe)) hydrogel membranes in an aqueous solution of LiCl was carried out using a simple equivalent model. The hydrogel membrane was synthesized by γ‐radiation‐induced polymerization and crosslinking of A‐ProOMe monomer aqueous solution in a glass‐cast. By means of the impedance spectra analysis, a novel method for the calculation of the ionic conductivity of the hydrogel membranes in LiCl solution was proposed. The calculated ionic conductivity was in agreement with the determined value. In addition, effects of temperature and LiCl concentration on the impedance spectra and ionic conductivity of the gel membrane were analyzed. Results indicated that the impedance spectra analysis is a very useful tool for evaluating the electric properties of gel membranes in an electrolyte solution. The poly (A‐ProOMe) gel membrane in 1.0 M LiCl solution showed a high ionic conductivity of about 0.2 S/cm at 14 °C. The temperature‐dependence of the ionic conductivity was a complex nonlinear form due to the volume phase transition of the thermoresponsive poly(A‐ProOMe) gel membrane, and the volume phase transition temperature appeared to be decreased with the increase in the LiCl concentration. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2843–2851, 2005     

Color speckle measurement errors using system with <Emphasis Type="Italic">XYZ</Emphasis> filters

Measurement errors of color speckle are analyzed for a measurement system equipped with revolving XYZ filters and a 2D sensor. One of the errors is caused by the filter characteristics unfitted to the ideal color matching functions. The other is caused by uncorrelations among the optical paths via the XYZ filters. The unfitted color speckle errors of all the pixel data can be easily calibrated by conversion between the measured BGR chromaticity triangle and the true triangle obtained by the BGR wavelength measurements. For the uncorrelated errors, the measured BGR chromaticity values spread over around the true values. As a result, it would be more complicated to calibrate the uncorrelated errors, repeating the triangular conversion pixel by pixel. Color speckle and its errors greatly affect also chromaticity measurements and image quality of displays using coherent light sources.     

Josephson current through a half metal at low temperatures

We study the Josephson effect in the superconductor/diffusive half metal/superconductor junctions by using the recursive Green function method. In the presence of spin-flip scatterings at the interface, odd-frequency spin-triplet Cooper pairs penetrate deeply into a half metal and carry Josephson current. The critical Josephson current increases with decreasing temperatures near the transition temperature. At low temperatures, however, the critical current decreases with decreasing temperatures. Such reentrant behavior is unusual in the case of s-wave superconductor junctions. The penetration of odd-frequency pairs modifies quasiparticle density of states in a half metal near the Fermi energy, which is responsible for the nonmonotonic temperature dependence of critical Josephson current.     

The first detection of photomodulation by both DC and in-phase AC susceptibility for organic/inorganic hybrid materials containing cyano-bridged Gd–Cr complex and azobenzene

New organic/inorganic hybrid material containing a ferrimagnetic cyano-bridged binuclear complex, [Gd(DMF)₄(H₂O)₃Cr(CN)₆]·H₂O (DMF=N,N′-dimethylformamide), and photochromic azobenzene in poly(methylmethacrylate) (PMMA) cast films has been prepared. We characterized magnetic properties of bulk [Gd(DMF)₄(H₂O)₃Cr(CN)₆]·H₂O and confirmed that it was not changed by light illumination at all. For the first time, we could detect reversible changes of both DC and in-phase AC susceptibility for the hybrid materials accompanying with cis–trans photoisomerization of azobenzene after UV and visible light illumination for 3 min at 3 K. We also discuss the kind of detectable magnetic changes (e.g. DC, in-phase AC, and both DC and in-phase AC) and the nature of some photo-magnetic functional hybrid materials (cis–trans photoisomerization and increase/decrease of magnetization) known to estimate their mechanism and interactions.     

Design of Photostable,Activatable Near‐Infrared Photoacoustic Probes Using Tautomeric Benziphthalocyanine as a Platform

Near‐infrared (NIR) imaging techniques have attracted significant attention for biological and medicinal applications due to the ability of NIR to penetrate deeply into tissues. However, there are very few stable, activatable molecular probes that can utilize NIR light in the wavelength range beyond 800 nm. Herein, we report a new activatable NIR system for photoacoustic imaging based on tautomeric benziphthalocyanines (BPcs). We found that the existence of a free hydroxyl group is crucial for NIR absorption of BPcs. Synthesized water‐soluble hydroxy BPcs exhibited high photostability and no fluorescence, which are desirable features for photoacoustic imaging. We synthesized BPcs in which the free hydroxyl group was masked by an esterase‐labile or an H₂O₂‐labile group. The photoacoustic signals of these hydroxy‐masked BPcs were increased upon NIR excitation at 880 nm in the presence of esterase or H₂O₂, respectively. These are rare examples of activatable probes utilizing NIR light at around 900 nm.