Systematic approach to cutoff frequency selection in continuous-wave electron paramagnetic resonance imaging

This article describes a systematic method for determining the cutoff frequency of the low-pass window function that is used for deconvolution in two-dimensional continuous-wave electron paramagnetic resonance (EPR) imaging. An evaluation function for the criterion used to select the cutoff frequency is proposed, and is the product of the effective width of the point spread function for a localized point signal and the noise amplitude of a resultant EPR image. The present method was applied to EPR imaging for a phantom, and the result of cutoff frequency selection was compared with that based on a previously reported method for the same projection data set. The evaluation function has a global minimum point that gives the appropriate cutoff frequency. Images with reasonably good resolution and noise suppression can be obtained from projections with an automatically selected cutoff frequency based on the present method.     

Formation of frozen α-AgI in superionic glass matrices at ambient temperature by rapid quenching

Superionic conducting phase of α-AgI, which is thermodynamically stable only above 147°C, was successfully frozen at ambient temperature in various kinds of glass matrices in the systems AgI---Ag₂O---M_xO_y (M_xO_y=B₂O₃, GeO₂,P₂O₅ and MoO₃) by a rapid quenching technique. The larger composition regions where α-AgI was frozen were observed in the systems with B₂O₃ and GeO₂ than in the systems with P₂O₅ and MoO₃. Since the glasses with B₂O₃ and GeO₂ have higher glass transition temperature than those with P₂O₅ and MoO₃, the former glasses have higher viscosities at 147° C. The former matrix glasses have stronger effect to depress the α-β transformation of AgI rather than the latter glasses in the course of rapid quenching of melts.     

An important role played dianiones in the highly efficient macrocycle formation by an intramolecular alkyltion method: application to the synthesis of zearalenone

A new synthetic method for macrolides based on intramolecular alkylation of dianions, generated from phenylthiomethyl group and protected cyanohydrin, is reported. The use of dianions for the cyclization has several characteristics features; (1) Control of the conformation fo the side-chain, (2) Protection of the ester from a nucleophilic attack, (3) Acceleration of the intramolecular reaction without using high dilution conditions. To prove these speculations, the alkylation using the dianions $\text{5}$ and $\text{6}$ was examined in the synthesis of zearalenone.     

Conversion of anisotropically phase-segregated Pd/gamma-Fe2O3 nanoparticles into exchange-coupled fct-FePd/alpha-Fe nanocomposite magnets

Exchange-coupled fct-FePd/alpha-Fe nanocomposite magnets were fabricated by converting anisotropically phase-segregated Pd/gamma-Fe2O3 nanoparticles via the interfacial atom diffusion. The magnetically hard fct-FePd phases formed by the interdiffusion between alpha-Fe and fcc-Pd phases nearly preserve their sizes at the nanometer scale because they are surrounded by the alpha-Fe matrix. The VSM measurements reveal that the exchange coupling between the soft and hard phases has been realized.     

Mössbauer spectroscopic study of potassium borate glasses at low temperatures

Mössbauer studies of potassium borate glasses containing a small amount of iron were performed at dry ice and liquid nitrogen temperatures in order to investigate the physical properties of non-bridging oxygens in the glasses. The Mössbauer spectra at the temperature of dry ice were almost the same as those at room temperature. On the other hand, the spectra at the temperature of liquid nitrogen consisted of quadrupole doublet and hyperfine structure due to Fe³⁺ ions with tetrahedral symmetry. Magnetic suceptibility measurements revealed that the hyperfine structure was observed because of a paramagnetic relaxation effect. Isomer shift values for both the quadrupole doublet and the hyperfine structure were constant in the alkali region below 20 mol.%, and continuously decreased when the alkali content of the glasses was in the region ? 20 mol.%. The absorption areas for the hyperfine structure were also constant in the alkali region below 20 mol.%, and linearly decreased with alkali content in the region ? 20 mol.%. The internal magnetic field for the hyperfine structure also showed the same tendency as the absorption area. These results were attributed to the formation of non-bridging oxygen at the site adjacent to the iron, and the decrease of the absorption area for the hyperfine structure seemed to be directly related to the fraction of non-bridging oxygen in the oxygens constituting FeO₄ tetrahedra.     

Optical Properties of Oxidized Cholesterol Bilayer Lipid Membranes

Bilayer Lipid Membranes (BLM) formed from oxidized cholesterol in the aqueous phase were prepared to investigate their optical characteristics. As an optical model of BLM, we adopted a uniaxial layer model where the optical axis is perpendicular to the membrane surface. The refractive indices were measured precisely by means of the ellipsometry, and in consequence, in the temperature range from 10°C to 40°C, the ordinary and extraordinary refractive indices for 633 nm decreased from 1.471 to 1.458 and 1.490 to 1.471, respectively, Its positive birefringence also decreased according to temperature. The thickness was also measured, and the value of 7.1 ± 0.9 nm at 30°C was obtained.     

Polymerization of butadiene and vinyl ether with catalyst prepared from π-allyl nickel halide and organic peroxide

The π-allyl nickel halide–organic peroxide system has been found to be active as catalyst for the stereospecific polymerization of butadiene and polymerization of vinyl ether. Benzoyl peroxide is most effective. The catalyst from π-allyl nickel chloride or π-allyl nickel bromide and benzoyl peroxide yields predominantly cis-1,4 polymer with high activity, whereas the catalyst from π-allyl nickel iodide affords predominantly trans-1,4 polymer. The catalyst system can be divided into two parts, a benzene-soluble and a sentially insoluble component. It is concluded that the catalyst activity originates esbenzene-from the insoluble nickel complex which is composed of halogen atom, benzoyloxy group of conjugated structure, allyl group, and nickel. A structure is proposed for the complex.     

Electrochemical detection for dynamic analyses of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device

This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface.     

Direct polyamidation with thionyl chloride in N-methyl-pyrrolidone

Mechanistic features of the reaction promoted by thionyl chloride and amides such as N-methylpyrrolidone (NMP) were studied. The reaction was effective in the amidation of carboxylic acids, but not effective in the esterification. The amidation was affected by the kind and the amount of amides used, most favorably by two equivalents of NMP with respect to the acid. These amides were assumed to be involved in the intermediate formation, and the reaction was proposed to proceed via Vilsmeier adducts derived from thionyl chloride and the amides, and through activation of a carboxylic acid different from an acyl chloride. The reaction was successfully applied to the direct polycondensation of aromatic dicarboxylic acids and diamines in NMP at 70°C to produce polyamides with high molecular weights. Initial reaction of dicarboxylic acids with the adducts, additive effect of tertiary amines, and polycondensation temperatures were studied in terms of the inherent viscosity of the polymers produced.