Reversible Control of Radius and Morphology of Fluorene‐Azobenzene Copolymer Nanowires by Light Exposure

The preparation of photoresponsive polymer nanowires comprising photochromic azobenzene (Azo) and π‐conjugated fluorene (FO) units is reported. Well‐defined and uniform nanowires of the copolymer (PFOAzo) were successfully fabricated by the single particle nanofabrication technique after optimizing the FO:Azo ratio and the development conditions. Azo units in the PFOAzo nanowires underwent reversible trans–cis–trans isomerization upon exposure to ultraviolet or visible light, leading to changes in the radius (between ca. 6 and 8 nm) and morphology (straight or wavy) of the nanowires. The oligo(alkylfluorene) units in the backbone are found to profit the crosslinking efficiency upon high‐energy ion beam irradiation, and more importantly, provide sufficient flexibility to allow reversible photoswitching. This demonstration of the photoluminescence, semiconducting, and mechanical properties of the PFOAzo nanowires is an important advance in the evolution of electro‐mechanical nanomaterials.     

Inclusion-exclusion for k-CNF formulas

We show that the number of satisfying assignments of a k-CNF formula is determined uniquely from the numbers of unsatisfying assignments for clause-sets of size up to ⌊logk⌋+2. This amount of information is also shown to be necessary.     

Oxidation behavior of isoprene polymers and butadiene polymers

The oxidation behavior of cis-1,4-polyisoprene, emulsion polyisoprene, emulsion isoprene/styrene copolymers, and emulsion butadiene/styrene copolymers by heat aging or ultraviolet irradiation has been investigated from the change of gel fraction and molecular weight distribution. It was determined that the oxidation behavior of both isoprene and butadiene polymers is strongly dependent on the composition of the polymers as well as on the microstructure of the polymers. In the case of oxidation by heat aging, the probability ratio of chain scission to crosslinking of both isoprene and butadiene copolymers increases gradually with increasing styrene fraction. In the case of oxidation by ultraviolet irradiation, isoprene copolymers show a remarkable increase in the probability ratio of chain scission to crosslinking, whereas butadiene copolymers show substantially no change with increase in styrene fraction. It was also demonstrated that both isoprene and butadiene polymers show a greater tendency for crosslinking with oxidation by ultraviolet irradiation than with oxidation by heat aging.     

Influence of the structure of the nanotube on the mechanical properties of binder-free multi-walled carbon nanotube solids

We prepared and characterized multi-walled carbon nanotube (MWCNT) solids by de-fluorination of fluorinated MWCNTs using spark plasma sintering. In order to investigate the influence of the structure of MWCNT on the mechanical strength of the resulting solids, MWCNTs used in this experiment were as-defected MWCNTs modified by nitric acid and as-purified ones as non-defected nanotubes by comparison. The bend strength and modulus of the resulting solids were lower than those of de-fluorinated MWCNT solids derived from as-purified MWCNTs. The mechanical properties of the resulting MWCNT solids were found to be strongly dependent on the structure of the MWCNT.     

Cs-Te photocathode RF electron gun for applied research at the Waseda University

A compact electron accelerator based on photo-cathode RF electron gun is under development for applied research at the Waseda University. Higher charge and higher energy are key issues for applications such as pulse radiolysis experiment and laser-Compton X-ray generation. The new RF-gun cavity with cesium telluride (Cs-Te) photo-cathode which has higher quantum efficiency (Q.E.) compared with metal cathodes has been installed. The evaluation of Q.E. of the photo-cathode has been performed and the value obtained is more than 5% at the preparation stage. For understanding the Cs-Te cathode properties and the higher Q.E. operation, fundamental studies by single bunch beam operation have been performed resulting in more than 6 nC bunch charge with a high Q.E. of 2.9%. Additionally, the new RF-gun cavity was improved for obtaining a higher Q value. Higher beam energy, i.e. shunt impedance compared with old type cavity, was observed. The shunt impedance increased by about 20%. These successful results will considerably contribute to the applied research.     

A study on thermal conductivity of a mixture of magnesia particles and molten nitrate by a transient hot wire method

In this study, the effective thermal conductivity of a mixture of magnesia particles and molten nitrate used in a high temperature thermal energy storage system was investigated by a transient hot wire method. The effective thermal conductivity of the mixture was around 2.0W/(m·K) in the temperature range of 423 K to 703 K, although it decreased about 5% with increasing temperature. This value was about 10 times larger than that of the packed bed of magnesia particles including air. The effective thermal conductivity increased about 3% with a 1% increase in the volume ratio of magnesia particles in the mixture with molten nitrate. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(4): 245–253, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20116     

Effects of hydrophobic interaction on rheological behavior and microstructure of carboxylated core‐shell latex suspension

We have investigated the effects of hydrophobic interactions on the rheological behavior and microstructure of suspension of carboxylated core‐shell latex particles with changing hydrophobicity of shell polymer and suspending medium. The carboxylated core‐shell latex particles formed lattice‐like microstructures in aqueous suspension with dissociation of carboxyl groups. With increasing hydrophobicity of the shell polymer, the interparticle distance ξ in the microstructure decreased. However, ξ increased with increasing hydrophobicity of the suspending medium. The effect of hydrophobic interaction on ξ was explained by the steric stabilization theory for particles with grafted polymer on the surface. As the carboxylated core‐shell latex particles overlapped each other in the microstructure, an attractive force was generated between the particles in aqueous suspension. With increasing hydrophobicity of the shell, the attractive force increased, but with increasing hydrophobicity of the suspending medium, the attractive force decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4153–4158, 2006     

Surface cracks initiation on carbon steel railway wheels under concurrent load of continuous rolling contact and cyclic frictional heat

Focusing on the durability of carbon steel railway wheels, so-called tread thermal cracks, one of severe damages on the tread surface, were investigated to understand the cracks generation processes involving initiation and propagation. We have demonstrated that tread thermal cracks can be experimentally reproduced under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, through the experiments using an actual railway wheel. Relations of residual stress, cracks configuration and fracture surface were examined to consider the crack generation process. Plastic deformation and thermal stress near the surface result in substantial tensile residual stress, which causes the generation of cracks.     

Lead Evaluation of Tetrahydroquinolines as Nonsteroidal Selective Androgen Receptor Modulators for the Treatment of Osteoporosis

Tetrahydroquinoline (THQ) was deemed to be a suitable scaffold for our nonsteroidal selective androgen receptor modulator (SARM) concept. We adapted the strategy of switching the antagonist function of cyano‐group‐containing THQ (CN‐THQ) to the agonist function and optimized CN‐THQ as an orally available drug candidate with suitable pharmacological and ADME profiles. Based on binding mode analyses and synthetic accessibility, we designed and synthesized a compound that possesses a para‐substituted aromatic ring attached through an amide linker. The long‐tail THQ derivative 6‐acetamido‐N‐(2‐(8‐cyano‐3a,4,5,9b‐tetrahydro‐3H‐cyclopenta[c]quinolin‐4‐yl)‐2‐methylpropyl)nicotinamide ( 1 d ), which bears a para‐acetamide‐substituted aromatic group, showed an appropriate in vitro biological profile, as expected. We considered that the large conformational change at Trp741 of the androgen receptor (AR) and the hydrogen bond between 1 d and helix 12 of the AR could maintain the structure of the AR in its agonist form; indeed, 1 d displays strong AR agonistic activity. Furthermore, 1 d showed an appropriate in vivo profile for use as an orally available SARM, displaying clear tissue selectivity, with a separation between its desirable osteoanabolic effect on femoral bone mineral density and its undesirable virilizing effects on the uterus and clitoral gland in a female osteoporosis model.     

Processability and mechanical properties of ternary composites PP/EPDM/GF

The enhancement of the mechanical properties of neat PP is achieved by the addition of glass fibers and EPDM rubber. The Young's modulus and notched Charpy impact strength of the composites obtained are improved with respect to the original polymer, leading to a new composite material with a very good balance of toughness and rigidity properties. The tensile behavior of these multiphase systems is successfully compared with theoretical predictions using the Halpin‐Tsai/Nielsen theory for uniaxially short fiber composites, which considers the matrix as a blend with spherical particles and can predict the tensile modulus considering an average fiber orientation angle. An accurate morphological study performed by scanning electron microscopy (SEM) shows a very good dispersion of the rubbery phase into the neat matrix. No special affinity between the rubber and the fibers is reported. The good dispersion and the small particle diameter indicate the good processability of the ternary systems studied.