Solid-state shear pulverization as effective treatment for dispersing lignocellulose nanofibers in polypropylene composites

Lignocellulose nanofibers (LCNFs) were prepared by the wet-disk milling of wood flour and were subsequently used as a reinforcing filler for a polypropylene (PP) polymer matrix. The specific surface area and the smallest fiber width of the LCNFs were found to be 106 m²/g and 20 nm, respectively. Solid-state shear pulverization (SSSP) using a batch-type kneader was performed at a temperature lower than the PP melting point in order to improve the dispersion of the LCNFs in the PP matrix, which also contained 5 wt% maleic anhydride-grafted PP. The SSSP treatment improved LCNF dispersion; this was determined through optical and scanning electron microscopy observations. The improvement in LCNF dispersion after the SSSP treatment increased the Young’s moduli, yield strengths, and toughnesses of the resulting composites. The composites showed higher Young’s moduli and yield strengths that those of the neat PP matrix; this was true in the case of both the tensile and the bending tests. However, the impact strengths of the composites were not significantly different from that of the neat matrix. Finally, the crystallization rate of the PP matrix also increased with the increase in LCNF dispersion.     

Structure determination of Pb/Ge(111)-β-(√3 × √3)R30° by dynamical low-energy electron diffraction analysis and first-principles calculation

We have determined the atomic structure of the Pb/Ge(111)-β-(√3 × √3)R30° surface, which was shown to exhibit a large Rashba spin splitting in a metallic surface state by dynamical low-energy electron diffraction analysis. The Pb coverage for the optimized atomic structure is 4/3 with one Pb atom located at every third H(3) site of the bulk-truncated Ge(111) surface and the other three near the T(1) sites but slightly displaced towards the T(4) sites. The determined atomic structure agrees well with the energetically optimized one obtained from the first-principles calculation. The calculation also revealed that the potential for the Pb atoms on the H(3) sites is very soft along the surface normal, suggesting that their vertical position is distributed within a range of about 0.2-0.3 ?. The previously proposed phase transition associated with the surface melting is discussed.     

Global well-posedness for Keller-Segel system in Besov type spaces

The Cauchy problems for Keller-Segel system are studied using homogeneous Besov spaces. With the homogeneous Besov spaces , which is the scaling critical case for Keller-Segel system, global solutions for small initial data are obtained in the space. In addition, ill-posedness for Keller-Segel system is also studied.     

Synthesis of bicyclic dioxetanes tethering a fluororescer through an ω-carbamoyl-substituted linker and their high-performance chemiluminescence in an aqueous system

Bicyclic dioxetanes 3 and 4 tethering a fluorescein or 4-(benzothiazol-2-yl)-3-hydroxyphenyl moiety through a linker were synthesized by the use of dihydrofuran-intermediate 5 or its advanced intermediate 6. These dioxetanes underwent base-induced decomposition to effectively give light due to intramolecular energy-transfer from an excited oxidobenzoate to a tethered fluorophore. Although the chemiluminescence efficiency Φ^CL values for 3 and 4 were only ca. 2-fold greater than that for parent 2 in a TBAF/acetonitrile system, these values were 30–550-fold greater than that for 2 in a NaOH/H₂O system. Such marked increase of Φ^CL was hardly observed by the simple addition of 25 or 26 as a model of a tethered fluorescer.     

Oxidation of nitroxyl radicals: electrochemical and computational studies

We have developed azaadamantane-type nitroxyl radicals (AZADOs) and azabicyclo-type nitroxyl radicals (ABNOs) as highly active alcohol oxidation catalysts. Herein, the electrochemical properties of these nitroxyl radicals were investigated by measuring their formal potentials using cyclic voltammetry (CV). The redox potentials were rationalized with the aid of density functional theory (DFT) calculations. A good correlation between the experimental redox potential and the DFT-computed energy differences (ΔE) between nitroxyl radicals and oxoammonium species was obtained, which shows the effectiveness of DFT in predicting the redox potentials of nitroxyl radicals. Redox potential appears to be an important factor of catalytic activity.     

Micro fluorescent analysis system integrating GaN-light-emitting-diode on a silicon platform

A micro fluorescent analysis system is proposed using silicon micromachining. GaN blue light-emitting diode (LED) monolithically integrated on a silicon substrate is used as a light source for the fluorescent analysis system. The blue light suits the excitation of several dyes used commonly in fluorescent analysis. Silicon photodiode (Si-PD) that matches the visible and near infrared fluorescent wavelengths of dyes is integrated on a silicon substrate. Polydimethylsiloxane (PDMS) micro-channels are also stacked for flowing dye-sensitized liquid. Therefore, the proposed system is an integrated system that can be composed on a silicon platform, i.e. a bottom layer of Si-PD, a middle layer of GaN-LED on silicon substrate and a top layer of micro PDMS channel. An aperture is opened into the GaN-LED layer by deep reactive ion etching to create a ring-shaped GaN-LED and a through-hole for detection. The light from the ring-shaped GaN-LED in the middle layer excites the dye-sensitized liquid in the top micro-channel layer. The fluorescence emitted from dye is detected by the Si-PD on the bottom layer at an angle larger than 90 degrees from the direction of excitation. Therefore, the detection optics consist basically of a dark-field illumination optical system. In order to evaluate the performance of the integrated system, fluorescence of fluorescein isothiocyanate (FITC) solution flowing in the micro channel is measured. From the measurement, the noise, sensitivity and limit of detection in the fabricated system are evaluated for FITC dye to be 0.57 pA, 1.21 pA μM(-1) and 469 nM, respectively. From these results, a compact fluorescence analysis system is demonstrated.     

Chemical constituents of the aerial parts of Scutellaria lateriflora and their alpha-glucosidase inhibitory activities

MeOH extracts of 37 herbs were tested in screening experiments for rat intestinal alpha-glucosidase. The MeOH extract of the aerial parts of Scutellaria lateriflora L. (Lamiaceae) significantly inhibited sucrase and maltase activities, using sucrose and maltase as the substrates. Enzyme inhibition guided-fractionation of the MeOH extract of S. lateriflora resulted in the isolation of a new diterpene glucoside, deacetylajugarin-IV 18-O-beta-D-glucopyranoside (1), along with 20 known phenolics (2-21). The structures of 1-21 were elucidated on the basis of MS and NMR data analyses. Baicalein (4) and baicalin (10), a glycoside of 4, showed moderate sucrase inhibitory activities at IC50 values of 14.9 and 36.3 microM, respectively, whereas luteolin (3), acteoside (16), leucosceptoside A (18), and isoacteoside (20) showed weak inhibitory activities at IC50 values of 811, 522, 727, and 443 microM, respectively. This is the first report on mammalian alpha-glucosidase inhibitory activities of S. lateriflora extract and identification of the constituents responsible for the activities. Apigenin (2), luteolin (3), 6-methoxyluteolin 4'-methyl ether (6), isoscutellarin 8-O-beta-D-glucuronide (7), luteolin 7-O-beta-D-glucuronide (9), wogonin 7-O-beta-D-glucuronide methyl ester (12), eriodictyol (13), naringenin (14), naringenin 7-O-beta-D-glucuronide (15), jionoside D (17), leucosceptoside A (18), and (+)-syringaresinol 4'-O-beta-D-glucopyranoside (21) were isolated from this plant for the first time. The inhibitory properties of S. lateriflora extract against alpha-glucosidase provide a prospect for its antidiabetic usage.