Effects of vapor‐phase‐formaldehyde treatments on thermal conductivity and diffusivity of ramie fibers in the range of low temperature

To understand the influence to thermal conductivity by bridging in the polymer fibers, the thermal conductivity, and thermal diffusivity of ramie fiber and those bridged by formaldehyde (HCHO) using vapor‐phase method (VP‐HCHO treatment) were investigated in the lower temperature range. The thermal conductivities of ramie fiber with and without VP‐HCHO treatments decreased with decreasing temperature. Thermal diffusivities of ramie fiber with and without VP‐HCHO treatments were almost constant in the temperature range of 250–50 K, and increased by decreasing temperature below 50 K. Thermal conductivity and thermal diffusivity of ramie fiber decreased by VP‐HCHO treatment. The crystallinities and orientation angles of ramie fibers with and without VP‐HCHO treatment were measured using solid state NMR and X‐ray diffraction. These were almost independent of VP‐HCHO treatment. Although tensile modulus decreased slightly by VP‐HCHO treatment, the decrease could not explain the decrease in thermal conductivity and diffusivity with decreasing sound velocity. The decrease of the thermal diffusivity and thermal conductivity by VP‐HCHO treatment suggested the possibility of the reduction of the mean free path of phonon by HCHO in VP‐HCHO treated ramie fiber. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2754–2766, 2005     

Determination of human blood glucose levels using microchip electrophoresis

A high-performance monitoring system for human blood glucose levels was developed using microchip electrophoresis with a plastic chip. The combination of reductive amination as glucose labeling with fluorescent 2-aminoacridone (AMAC) and glucose-borate complex formation realized the highly selective detection of glucose even in a complex matrix such as a blood sample. The migration time of a single peak, observed on an electropherogram of AMAC-labeled plasma, closely resembled that of glucose standard solution. The treatment of plasma with hexokinase or glucokinase for glucose phosphorylation resulted in a peak shift from approximately 145 to 70 s, corresponding to glucose and glucose-6-phosphate, respectively. A double-logarithm plot revealed a linear relationship between glucose concentration and fluorescence intensity in the range of 1-300 microM of glucose (r(2) = 0.9963; p <0.01), and the detection limit was 0.92 microM. Furthermore, blood glucose concentrations estimated from the standard curves of three subjects were compared with results obtained by conventional colorimetric analysis using glucose dehydrogenase. Good correlation was observed between methods according to simple linear regression analysis (p <0.05). The reproducibility of the assay was about 6.3-9.1% (RSD) and the within-days and between-days reproducibility were 1.6-8.4 and 5.2-7.2%, respectively. This system enables us to determine blood glucose with high sensitivity and accuracy, and will be applicable to clinical diagnosis.     

Colloidal crystallization of poly(n-butyl acrylate) spheres in deionized aqueous suspension and the melting during dryness

Colloidal crystallization of poly(n-butyl acrylate) spheres (ammonium persulfate-poly(n-butyl acrylate) (APS-PBA), 320?±?50 nm in diameter) was studied in deionized aqueous suspension. Coexistence of the crystal and distorted crystal structures was observed by the reflection spectroscopy. The critical concentrations of melting were ca. 0.01 and 0.03 in volume fraction in the presence of ion-exchange resins and in their absence, respectively. Crystal structures melted away during dryness by fusion of each spheres on the substrates, i.e., cover glass, watch glass, and Petri glass dish. Thickness profiles of the dried film changed sharply from the broad ring to the round hill as sphere concentration increased. The sharpness parameter S was evaluated from the ratio of the film size (diameter) against the full width at half maximum in the thickness profiles of the ring and/or the round hill. The S values decreased sharply from 30 to 1.2 as initial volume fraction of the spheres increased from 0.0005 to 0.1. The S values were significantly low compared with those of typical colloidal spheres, which supports the aggregate and/or fusion of the spheres resulting in their low convectional flow during dryness. The round hill profile at the high sphere concentration also supports that the fusion takes place easier during dryness. Microscopic observation of the dried film supports the formation of the homogeneous fused structures. It was clarified that colloidal crystallization of APS-PBA spheres takes place by the extended electrical double layers around the spheres like typical colloidal crystals of hard spheres. However, APS-PBA spheres are not so stable by the fusion especially at the high sphere concentrations and on the substrates.     

Anomalous fluorescence spectra of benz[a]azulene derivatives

The electronic and fluorescence spectra of banz[a]azulene derivatives have been measured. the fluorescence from the second excited singlet state have been observed for these compounds. The fluorescence quantum yields (φ_f) is sensitive to the energy difference between the first excited singlet (S₁) and the second excited singlet state (S₂).     

Reaction of arynes with amino acid esters

An efficient route to a variety of 2-phenylindolin-3-ones from amino acid methyl esters has been developed. The reaction of amino acid methyl esters with benzyne prepared from 2-(trimethylsilyl)phenyl triflate and CsF gave 2-phenylindolin-3-ones in moderate to good yields.     

Microfluidic baker's transformation device for three-dimensional rapid mixing

We developed a new passive-type micromixer based on the baker's transformation and realized a fast mixing of a protein solution, which has lower diffusion constant. The baker's transformation is an ideal mixing method, but there is no report on the microfluidic baker's transformation (MBT), since it is required to fabricate the complicated three-dimensional (3D) structure to realize the MBT device. In this note, we successfully fabricate the MBT device by using precision diamond cutting of an oxygen-free copper substrate for the mould fabrication and PDMS replication. The MBT device with 10.4 mm mixing length enables us to achieve complete mixing of a FITC solution (D = 2.6 × 10(-10) m(2) s(-1)) within 51 ms and an IgG solution (D = 4.6 × 10(-11) m(2) s(-1)) within 306 ms. Its mixing speed is 70-fold higher for a FITC solution and 900-fold higher for an IgG solution than the mixing speed by the microchannel without MBT structures. The Péclet number to attain complete mixing in the MBT device is estimated to be 6.9 × 10(4).     

Formation of Pickering emulsions stabilized via interaction between nanoparticles dispersed in aqueous phase and polymer end groups dissolved in oil phase

The influence of end groups of a polymer dissolved in an oil phase on the formation of a Pickering-type hydroxyapatite (HAp) nanoparticle-stabilized emulsion and on the morphology of HAp nanoparticle-coated microspheres prepared by evaporating solvent from the emulsion was investigated. Polystyrene (PS) molecules with varying end groups and molecular weights were used as model polymers. Although HAp nanoparticles alone could not function as a particulate emulsifier for stabilizing dichloromethane (oil) droplets, oil droplets could be stabilized with the aid of carboxyl end groups of the polymers dissolved in the oil phase. Lower-molecular-weight PS molecules containing carboxyl end groups formed small droplets and deflated microspheres, due to the higher concentration of carboxyl groups on the droplet/microsphere surface and hence stronger adsorption of the nanoparticles at the water/oil interface. In addition, Pickering-type suspension polymerization of styrene droplets stabilized by PS molecules containing carboxyl end groups successfully led to the formation of spherical HAp-coated microspheres.     

An experimental spatio-temporal state transition of coupled magneto-elastic system

In this paper the vibration and the traveling wave in a coupled magneto-elastic beam system are discussed experimentally. The vibration excited by the periodical forcing at the beam system propagates to another as a wave through the coupling elastic beams. Each magneto-elastic beam shows the variety of vibrations caused by the nonlinearity of the potential well and the wave propagation with time delay. The temporal vibration of the magneto-elastic beam is explained with relations to the spatial state transition based on the experimental results. (c) 1997 American Institute of Physics.     

Lorentzian similarity manifolds

An (m+2)-dimensional Lorentzian similarity manifold M is an affine flat manifold locally modeled on (G,ℝ ^m+2), where G = ℝ ^m+2 ⋊ (O(m+1, 1)×ℝ⁺). M is also a conformally flat Lorentzian manifold because G is isomorphic to the stabilizer of the Lorentzian group PO(m+2, 2) of the Lorentz model S ^m+1,1. We discuss the properties of compact Lorentzian similarity manifolds using developing maps and holonomy representations.     

On the holomorphic torus-Bott tower of aspherical manifolds

We introduce a notion of holomorphic torus-Bott tower which is an iterated holomorphic Seifert fiber space with fiber a complex torus. This is thought of as a holomorphic version of a real Bott tower. The top space of the holomorphic torus-Bott tower is called a holomorphic torus-Bott manifold. We discuss the structure of holomorphic torus-Bott manifolds and particularly the holomorphic rigidity of holomorphic torus-Bott manifolds.