Dynamic photoelastic analysis by optical heterodyne polarimetry

This paper describes the mapping of the spatiotemporal principal stress distribution evolved with time in an epoxy photoelastic sample. In the optical heterodyne polarimeter exploited, the signal beam of light transmitted by the sample under continuously loaded condition is photomixed with the local oscillator beam of light made up of orthogonal linearly polarized two-frequency components. Every pixel of a MOS video camera used generates a beat photocurrent that possesses the two orthogonal field components of the elliptically polarized signal beam. The spatiotemporal principal stress distributions can be uniquely determined simultaneously and independently from these two orthogonal field components, and are successfully mapped in a time-sequential form. The spatial and temporal resolutions in the maps are 0.18 mm and 2.9 ms, respectively.     

A microporous membrane-based continuous generation system for trace-level standard mixtures of atmospheric gases.

A reliable and convenient system to generate accurate and stable standard gas mixtures of various atmospheric compounds at parts-per-billion levels has been developed. The system is of simple design; the generator is a coil consisting of an inner tube of microporous polytetrafuluoroethylene (PTFE) membrane tubing and an outer tube of silicone tubing. An aqueous solution of the given compound continuously flows through the inner microporous tube and the purge gas flows through the annulus between the inner and outer tubes. In addition to the generation of gas mixtures based on Henry's law, the proposed flow-type system offers generation based on chemical reactions, leading to a distinct advantage of the availability of continuous sources of various compounds. The generation system was tested for preparing standard gas mixtures of HCHO and H2O2 on the basis of Henry's law, and those of HNO2, NO, and SO2 on the basis of chemical reactions. A stable generation of the desired low concentrations of various kinds of gas mixtures can be readily achieved by adjusting the concentration of the solution without the use of high-dilution flow.     

Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)₂ (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.     

Chemical dosimetry system for γ-ray irradiation based on the formation of phenol from aqueous benzene solutions

A chemical dosimetry system based on the radiochemical formation of phenol from aqueous benzene solutions was applied to measure the intensity of γ-ray irradiation. Using a simple and sensitive isocratic fluorometric HPLC system, radiochemically generated phenol was determined. The radiochemical formation of phenol was linear up to 100 Gy and the lower limit of detection calculated from the detection limits of phenol was estimated to be 7 mGy. The phenol formation rates were not affected by the oxygen saturation. The chemical dosimetry system investigated in this study was sensitive and was easier to use than traditional chemical dosimeters.     

Effects of 3,4-dihydrophenyl groups in water-soluble phospholipid polymer on stable surface modification of titanium alloy

The surface of a titanium (Ti) alloy substrate was modified by a simple and quick process using a water-soluble polymer, and the effects of 3,4-dihydroxyphenyl (DHP) groups in the polymer side chain on the modification process were examined. The polymers (PMDP) composed of both 2-methacryloyloxyethyl phosphorylcholine (MPC) unit and 3,4-dihydroxyphenyl methacrylate unit were synthesized for surface anchoring. The Ti alloy substrate was coated with PMDP using an aqueous solution of the polymer. A PMDP layer with a thickness of 20 nm was formed on the Ti alloy substrate simply by dip coating for 10 s without drying. Even when the Ti alloy substrate with PMDP coating was immersed in the aqueous medium for 1 week, no change in the thickness was observed, i.e., the PMDP layer was bound to the surface very stably. Oxidation of the DHP groups reduced the stability of the polymer layer significantly. Thus, the DHP groups play a significant role in achieving stable binding. Protein was adsorbed on the Ti alloy substrate; however, this was not observed for the PMDP-coated Ti alloy substrate. In conclusion, we confirmed the effects of DHP groups in PMDP on the stability of the coating on the Ti alloy substrate. Moreover, we found that surface treatment using PMDP was simple, quick, and reliable, and thus, it has great potential for improving biofouling of Ti alloy substrates used in medical devices.     

Molecular-glue-triggered DNA assembly to form a robust and photoresponsive nano-network

A robust and photoresponsive DNA network has been designed and constructed from branched DNA and molecular glue. The molecular glue is photoswitchable and can specifically bind to G-G mismatched double-stranded DNA. The assembly process can be reversibly controlled by manipulating the wavelength of light. The approach is flexible, allowing tuning of the size, morphology as well as the cavity of the network by variation of the molar ratio and the isotropic/anisotropic character of the branched building blocks. The assembled architectures are versatile and heat tolerant. These properties should allow the use of the network in further applications.     

Sodium or lithium ion-binding-induced structural changes in the K-ring of V-ATPase from Enterococcus hirae revealed by ATR-FTIR spectroscopy

V-ATPase from Enterococcus hirae forms a large supramolecular protein complex (total molecular weight ～700,000) and physiologically transports Na(+) and Li(+) across a hydrophobic lipid bilayer. Stabilization of these cations in the binding site has been discussed on the basis of X-ray crystal structures of a membrane-embedded domain, the K-ring (Na(+)- and Li(+)-bound forms). Here, sodium or lithium ion-binding-induced difference IR spectra of the intact V-ATPase have for the first time been measured at physiological temperature under a sufficient amount of hydration. The results suggest that sodium or lithium ion binding induces the deprotonation of Glu139, a hydrogen-bonding change in the tyrosine residue, and a small conformational change in the K-ring. These structural changes, especially the deprotonation of Glu139, are considered to be important for reducing energetic barriers to the transport of cations through the membrane.     

Use of tube radial distribution of ternary mixed carrier solvents for introduction of absorption reagent for metal ion separation and online detection into capillary

When ternary mixed solvents consisting of water-hydrophilic/hydrophobic organic solvents are fed into a micro-space under laminar flow conditions, the solvent molecules are radially distributed in the micro-space. The specific fluidic behavior of the solvents is called the "tube radial distribution phenomenon (TRDP)". A novel capillary chromatography method was developed based on the TRDP that creates the inner major and outer minor phases in a tube, where the outer phase acts as a pseudo-stationary phase. This is called "tube radial distribution chromatography (TRDC)". In this study, Chrome Azurol S as an absorption reagent was introduced into the TRDC system for metal ion separation and online detection. The fused-silica capillary tube (75 μm id and 110 cm length) and water-acetonitrile-ethyl acetate mixture (3:8:4 volume ratio) including 20 mM Chrome Azurol S as a carrier solution were used. Metal ions, i.e. Co(II), Cu(II), Ni(II), Al(III), and Fe(III), as models were injected into the present TRDC system. Characteristic individual absorption characteristics and elution times were obtained as the result of complex formation between the metal ions and Chrome Azurol S in the water-acetonitrile-ethyl acetate mixture solution. The elution times of the metal ions were examined based on their absorption behavior; Co(II), Ni(II), Al(III), Fe(III), and Cu(II) were eluted in this order over the elution times of 4.7-6.8 min. The elution orders were determined from the molar ratios of metal ion to Chrome Azurol S and Irving-Williams series for bivalent metal ions.