Scaling behavior of the first arrival time of a random-walking magnetic domain

We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34+/-0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls.     

Direct observation of dispersive Kondo resonance peaks in a heavy-fermion system

Ce 4d-4f resonant angle-resolved photoemission spectroscopy was carried out to study the electronic structure of strongly correlated Ce 4f electrons in a quasi-two-dimensional nonmagnetic heavy-fermion system CeCoGe1.2Si0.8. For the first time, dispersive coherent peaks of an f state crossing the Fermi level, the so-called Kondo resonance, are directly observed together with the hybridized conduction band. Moreover, the experimental band dispersion is quantitatively in good agreement with a simple hybridization-band picture based on the periodic Anderson model. The obtained physical quantities, i.e., coherent temperature, Kondo temperature, and mass enhancement, are comparable to the results of thermodynamic measurements. These results manifest an itinerant nature of Ce 4f electrons in heavy-fermion systems and clarify their microscopic hybridization mechanism.     

A Directly Patternable,Click‐Active Polymer Film via Initiated Chemical Vapor Deposition

Click‐active surfaces patterned at 200 nm resolution are demonstrated using the dual functional polymeric film, poly(propargyl methacrylate) (PPMA). The commercially available monomer of propargyl methacrylate (PMA) is polymerized in a single step by initiated chemical vapor deposition (iCVD). FT‐IR and X‐ray photoelectron spectroscopy confirm retention of the click‐active acetylene functional group in the bulk and surface of the iCVD film, respectively. Treating substrates with silane coupling agents prior to deposition results in grafting of iCVD PPMA polymers onto various inorganic surfaces. This grafting technique provides the chemical and mechanical stability required for the PPMA layer to survive the subsequent wet chemical steps used for click functionalization. Successful attachment of an azido‐functionalized coumarin dye is demonstrated. Moreover, the PPMA film displays direct positive‐tone sensitivity to e‐beam irradiation, which enables e‐beam patterning without the use of a resist layer. Direct e‐beam exposure of the multifunctional PPMA iCVD layer results in a 200 nm pattern to which quantum dot nanoparticles are selectively conjugated on the substrates by click chemistry.

     

Characteristics of polypropylene biocomposites: effect of chemical treatment to produce cellulose microparticle

Cellulose - In this study, cellulose microparticle were prepared by sulfuric acid hydrolysis, glyoxal crosslinking and acetylation followed by air classifying mill, and their properties including...     

Copper diisobutyl-t-butoxyaluminum hydride: A novel reagent for chemoselective reduction of tertiary amides over esters

We demonstrate that copper diisobutyl-t-butoxyaluminum hydride, readily prepared from lithium diisobutyl-t-butoxyaluminum hydride and CuI, effectively and chemoselectively reduces tertiary amides over esters at ambient temperature, affording the corresponding aldehydes in excellent yields.     

Convergent total synthesis of the racemic HIF-1 inhibitor laurenditerpenol

The convergent total synthesis of the HIF-1 inhibitor laurenditerpenol 1a is reported. The key step is the Julia olefination-reduction process between the two components, the sulfone 4 (prepared from the dimethylfuran-maleic anhydride Diels-Alder adduct) and the aldehyde 3 (prepared from 3-methylcyclohexenone).     

Improved capacitance characteristics of electrospun ACFs by pore size control and vanadium catalyst

Nano-sized carbon fibers were prepared by using electrospinning, and their electrochemical properties were investigated as a possible electrode material for use as an electric double-layer capacitor (EDLC). To improve the electrode capacitance of EDLC, we implemented a three-step optimization. First, metal catalyst was introduced into the carbon fibers due to the excellent conductivity of metal. Vanadium pentoxide was used because it could be converted to vanadium for improved conductivity as the pore structure develops during the carbonization step. Vanadium catalyst was well dispersed in the carbon fibers, improving the capacitance of the electrode. Second, pore-size development was manipulated to obtain small mesopore sizes ranging from 2 to 5 nm. Through chemical activation, carbon fibers with controlled pore sizes were prepared with a high specific surface and pore volume, and their pore structure was investigated by using a BET apparatus. Finally, polyacrylonitrile was used as a carbon precursor to enrich for nitrogen content in the final product because nitrogen is known to improve electrode capacitance. Ultimately, the electrospun activated carbon fibers containing vanadium show improved functionality in charge/discharge, cyclic voltammetry, and specific capacitance compared with other samples because of an optimal combination of vanadium, nitrogen, and fixed pore structures.