Synthesis and magnetic properties of the size-controlled Mn-Zn ferrite nanoparticles by oxidation method

Size-controlled Mn_0.67Zn_0.33Fe₂O₄ nanoparticles in the wide range from 80 to 20 nm have been synthesized, for the first time, using the oxidation method. It has been demonstrated that the particle size can be tailor-made by varying the concentration of the oxidant. The magnetization of the 80 nm particles was 49 A m² kg⁻¹ compared to 34 A m² kg⁻¹ for the 20 nm particles. The Curie temperatures for all the samples are found to be within 630±5 K suggesting that there is no size-dependent cation distribution. The critical particle size for the superparamagnetic limit is found to be about 25 nm. The effective magnetic anisotropy constant is experimentally determined to be 7.78 kJ m⁻³ for the 25 nm particles, which is about an order of magnitude higher than that of the bulk ferrite.     

Optical frequency comb generation using a quasi-velocity-matched Fabry-Perot phase modulator

We report about the optical frequency comb generation by means of a bulk type phase modulator with periodic domain inversion. The phase modulator operates as a quasi-velocity-matched electro-optical phase modulator having high modulation efficiency. It is possible to generate a broadband optical frequency comb by using the modulator installed into an Fabry-Perot resonator. In this experiment, we made the quasi-velocity-matched phase modulator and then used it to generate the efficient optical frequency comb. From this result, we could confirm operation characteristics of the optical frequency comb and the utility of the phase modulator respectively.     

Fluorine chemistry at Central Glass

Central Glass produces a diverse range of fluorocompounds for pharmaceuticals, agrochemicals as well as for semiconductor industries. Some of its products and chemistry developed at Central Glass in the field of industrial fluorine compounds are described.     

PFG-NMR approach to determining the water transport mechanism in polymer electrolyte membranes conditioned at different temperatures

Two types of polymer electrolyte membranes (PEMs), Nafion (NR-212) and sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (sPPBP), were conditioned under air flow in independently controlled temperature and relative humidity conditions. The effects of temperature and relative humidity on the diffusion behavior of water in the PEMs were investigated by pulsed field gradient (PFG) NMR. The two PEMs show different tendencies, especially with respect to their temperature effects. In a comparison of diffusion data with proton conductivity, mechanisms for proton conduction in the PEMs were considered. It was suggested that proton conduction by proton hopping occurs to a larger extent in NR-212 than in a hydrocarbon-based membrane. Temperature-affected microstructural changes below the glass transition temperature are also discussed.     

Smooth Fano Polytopes Arising from Finite Partially Ordered Sets

Gorenstein Fano polytopes arising from finite partially ordered sets will be introduced. Then we study the problem of which partially ordered sets yield smooth Fano polytopes.     

Mechanism of generation of photoelastic birefringence in methacrylate polymers for optical devices

We clarified the birefringence properties of poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate), poly(cyclohexyl methacrylate), poly(isopropyl methacrylate), and poly(tert‐butyl methacrylate). We demonstrated that the conformational change in polymer molecules that causes orientational birefringence differs from that causing photoelastic birefringence. Orientational birefringence depends mainly on the orientation of the main chains of the methacrylate polymers above T_g. On the other hand, photoelastic birefringence in elastic deformation below T_g depends mainly on the orientation of the side chains while the main chains are scarcely oriented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2029–2037, 2010     

Chirality Sensing and Size Discrimination of Anions by Macrotricyclic Cyclen–Disodium Complexes

Two macrotricyclic ligands composed of two face-to-face octadentate metal chelates were synthesized. These cage-shaped disodium complexes had special recognition ability for various counter anions. Specific chiral dicarboxylates bound to the complexes within the cavity and exhibited chirality induction properties. For instance, N-Boc-Asp dianion strongly induced circular dichroism (CD) signals, but N-Boc-Glu dianion, which is one carbon longer, did not.