Preparation and properties of sulfonated ETFE‐g‐polyvinyltoluene membranes for application in fuel cells

A new polymer electrolyte membrane prepared by radiation grafting of vinyltoluene into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) film and subsequent sulfonation was developed for application in fuel cells. The effect of grafting condition on the degree of grafting was investigated in detail. Results indicated that the degree of grafting can be controlled over a wide range. The grafted films were sulfonated in a chlorosulfonic acid solution to obtain the polymer electrolyte membranes, which were characterized with respect to their use in fuel cells. It is concluded that the substituted methyl group on the vinyltoluene can improve the chemical stability of the resulting membranes, and the crosslinked ETFE‐g‐poly(vinyltoluene‐co‐divinylbenzene) membranes can be proposed for the future development of alternative low‐cost and high‐performance membranes for fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2661–2667, 2006     

Solution properties of polyamic acids and their amine salts

Solution properties such as viscosity, critical concentration, radius of gyration, and activation energy in aqueous solutions are described for [BPDA/PDA]polyamic acid (PAA) and their salts with various amines (PAS). Although PAA and their salts with Bu₃N, Hex₃N, Oct₃N, and pyridine, were insoluble in H₂O, only the salt with Et₃N (PAS(Et₃N)) was soluble in H₂O. The different solubility of PAS suggests that higher base strength as well as shorter alkyl length of amines enhance water solubility of PAS. PAS(Et₃N) showed critical concentrations at 18, 14, and 7.8 wt% in NMP, NMP/H₂O (1/1), and H₂O, respectively. The radius of gyration, which is calculated from the critical concentration, in H₂O is 1.3 times larger than that in NMP; that is, the polymer chain expands in H₂O rather than in NMP. PAS(Et₃N) in H₂O showed larger activation energy of viscosity than that in NMP. However, PAA and PAS(Et₃N) showed similar activation energies in the NMP solution. Therefore, it is concluded that the amine salts of the polyamic acids are hydrated by several water molecules in H₂O, resulting in the larger radius of gyration and lager activation energies.     

Epitaxial growth of binary and ternary metallic strained superlattices and their magnetic properties

Since the structure at/near the interface of superlattices influences physical properties such as magnetic property, it is important to investigate details of the structure. The interface structure is characterized by the factors like atomic species, strain, mixing and roughness. The reflection high-energy electron diffraction (RHEED) system installed in our molecular-beam epitaxy (MBE) system enables us to observe, continuously, the change of the surface in-plane lattice constant, which is affected by atomic species, strain and/or mixing, on a realtime basis. Ternary superlattices consisting of three elements can clarify the effect of stacking sequence by comparison between the two types of superlattices with the reverse deposition sequences, since the effect caused by the combination of the same atomic species is cancelled out and the effect caused by the different stacking sequences remains. In the present paper, we review growth behaviors of binary and ternary metallic strained superlattices, especially magnetic ones, investigated mainly by our group, and summarize the discussion on their magnetic properties, mainly on the magnetic anisotropy, in terms of their structural characteristics. First, we introduce our RHEED system that works efficiently under a magnetic field arising from evaporation sources for low vapor-pressure materials. Then, MBE-grown binary strained superlattices, Co/Au, Co/Pt and Cu/Au, are discussed, with comparing to incoherent superlattices of Co/Ag and Cu/Ag having nearly the same lattice mismatch of constituents. Next, we review ternary strained superlattices with immiscible constituents with reverse deposition order, Au/Co/Ag and Ag/Co/Au superlattices, and Au/Co/Cu and Cu/Co/Au superlattices, in relation to the growth behaviors of binary superlattices. Finally, ternary strained superlattices containing both miscible and immiscible constituents, Pt/Co/Ag and Ag/Co/Pt superlattices, and Au/Ni/Ag and Ag/Ni/Au superlattices, are reviewed.     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.     

Thermal neutron imaging with rare-earth-ion-doped LiCaAlF6 scintillators and a sealed Cf source

Thermal neutron imaging with Ce-doped LiCaAlF₆ crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF₆ scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF₆ single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 50×2 mm² was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The ²⁵²Cf source (<1 MBq) was sealed with 43 mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2 mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF₆.     

Luminescence properties and gamma-ray response of the Ce and Ca co-doped (Gd,Y)F3 single crystals

The Ca0.5% and Ce1%, 3%, 7%, 10% co-doped Gd_0.5Y_0.5F₃ single crystals were grown by the μ-PD method. In the Ca0.5% and Ce3% co-doped sample, Ce³⁺-perturbed luminescence at 380 nm was observed with 32.4 ns photoluminescence decay time. The energy transfer in the sequence of the regular Ce³⁺→ (Gd³⁺)_n→ the perturbed Ce³⁺ sites was evidenced through observation of decay time shortening of the regular Ce³⁺ and Gd³⁺ centers and the change between the Gd³⁺ and Ce³⁺-perturbed emission intensity. The gamma-ray excited scintillation response of the Ca0.5%, Ce7% co-doped Gd_0.5Y_0.5F₃ sample was investigated with the help of the pulse height spectra and the light yield, energy resolution and non-proportionality was evaluated in the interval of energies of 59.4-1274 keV.     

Super black and ultrathin amorphous carbon film inspired by anti-reflection architecture in butterfly wing

An ultrathin and super black amorphous carbon (a-C) film has been fabricated by borrowing the inverse V-type anti-reflection nano-architecture from the black wings of butterfly Ornithoptera goliath through vacuum sintering process. The biomimetic a-C film shows good optical absorption (99%) at low reflectance (<1%) in visible light (380–795 nm), which is comparable to the previously fabricated darkest materials, while with a thickness (5 μm) of only 15% of those materials. Experimental results as well as theoretical simulation which is based on finite difference time domain method (FDTD) show that reflection of the fabricated inverse V-type structured a-C film is merely 1/13 of that of the flat surface a-C film, and 1/8 of that of glassy carbon. Complex refractive index of the derived a-C for visible light (380–795 nm) has also been calculated.     

A Low-Field Scaling Rule of Minor Hysteresis Loops in Plastically Deformed Steels

A scaling rule of magnetic minor hysteresis loops at low applied fields has been examined in plastically deformed low carbon steel and pure Ni. It was found that a power law between hysteresis loss and remanence of a minor loop holds true over the wide range of magnetization from the very low to intermediate range unlike the well-known Steinmetz law. The power-law exponent was an almost constant value of 1.35 being independent of the types of magnetic materials, the level of plastic deformation, and sample shape. The coefficient of the scaling rule increases with deformation and is in linear proportion to coercivity. This behavior was qualitatively explained on the basis of the Rayleigh law and NÉel theory.      

Catechol - an Oviposition Stimulant for Cigarette Beetle in Roasted Coffee Beans

The cigarette beetle, Lasioderma serricorne, is a serious global pest that preys on stored food products. Larvae of the beetle cannot grow on roasted coffee beans or dried black or green tea leaves, although they oviposit on such products. We investigated oviposition by the beetles on MeOH extracts of the above products. The number of eggs laid increased with an increase in dose of each extract, indicating that chemical factors stimulate oviposition by the beetles. This was especially true for \ coffee bean extracts, which elicited high numbers of eggs even at a low dose (0.1 g bean equivalent/ml) compared to other extracts. Coffee beans were extracted in hexane, chloroform, 1-butanol, MeOH, and 20 % MeOH in water. The number of eggs laid was higher on filter papers treated with chloroform, 1-butanol, MeOH, and 20 % MeOH in water extracts than on control (solvent alone) papers. The chloroform extract was fractionated by silica-gel column chromatography. Nine compounds were identified by gas chromatography/mass spectrometry from an active fraction. Of these compounds, only a significant ovipositional response to catechol was observed.     

Impurity‐Induced First‐Order Phase Transitions in Highly Crystalline V2O3 Nanocrystals

A first‐order phase transition in a bulk material is generally considered to arise at extended defects such as grain boundaries or dislocations, where the energetic barrier between the two phases is reduced. Downsizing a crystal to the nanoscale can exclude the number of defects, leading to enhanced kinetic stabilization of the metastable phase. Here, the disappearance of the first‐order metal–insulator transition in defect‐free V₂O₃ nanocrystals and the revival of the transition by introducing a certain Cr or Ti impurity content are investigated. The hysteresis width of the transition corresponding to the barrier height decreases with the impurity content. It is proposed that homogeneous impurity doping is a universal method that can control the occurrence of a first‐order phase transition in nanoscale materials.