Preparation and properties of poly(methylmethacrylate)-silica hybrid materials incorporating reactive silica nanoparticles

In this study, poly(methylmethacrylate) (PMMA)-based hybrid materials were prepared from reactive silica nanoparticles. These nanoparticles were obtained by the reaction of 2-(methacryloyloxy)ethyl isocyanate with colloidal silica dispersed in ethyl acetate, and they were copolymerized in various ratios with methyl methacrylate. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and visible spectrometry were performed to evaluate the physical properties of the resulting hybrid materials. The PMMA-silica hybrid copolymers maintained high transparency, and their storage elastic modulus and surface hardness increased with increasing silica content. Moreover, in comparison with PMMA, the hybrid copolymers had greater heat resistance and lower volume contraction.     

Method for grinding and delaminating muscovite

A method of dry grinding muscovite based on the use of knife-mills is reported. It was possible to produce mica with a particle size below 100 and 45 μm. After grinding, the samples were submitted to sonication treatment, which promoted delamination of the material. The particle size distribution shows that sonicated mica has more particles in the size range 10-50 μm than does non-sonicated mica have.This also indicates a decrease in the average particle size. Characterization of the treated muscovite by scanning electron microscopy revealed a highly delaminated material with a plate-like structure. The products were characterized by chemical analysis and X-ray diffraction, too. This mica has already been used for the synthesis of pearlescent pigments.     

Human-sized anthropomorphic robot hand with detachable mechanism at the wrist

In this paper, we proposed a human-sized multi-fingered robot hand with detachable mechanism at the wrist. The fingers are tendon-driven by wires and the actuators are embedded in the arm part. The driving forces from the arm part are transmitted to the hand part by a gear mechanism at the wrist. The gear mechanism makes the hand part and the arm part splittable. The detachable mechanism enables separate maintenance of the hand and arm parts. To avoid undesired joint mutual interferences due to the tendon-driven mechanism, a joint motion correction control is implemented in that counteracting motions are ordered to actuators. The correction coefficient can be calculated based on the mechanical configuration. The developed robot hand has the size of 200[mm](length) × 78[mm](width) × 24.6[mm](thickness) and can exert 10[N] at the fingertip. The performance of the developed robot hand was shown by a motion control experiment.     

Effect of glass transition temperature on heat‐responsive gas bubbles formation from polymers containing tert‐butoxycarbonyl moiety

Various types of polymers containing tert‐butoxycarbonyl (BOC) moiety as the typical protecting group of functional moieties have been used for the design of stimuli‐responsive polymer materials. In this study, we investigated the heat‐responsive deprotection behavior of BOC‐containing polymers obtained by radical polymerization of 4‐(tert‐butoxycarbonyloxy)styrene (BSt) and copolymerizations of BSt with styrene and methyl acrylate. The deprotection of BOC groups accompanying the evolution of isobutene and carbon dioxide as gaseous products was monitored by thermogravimetric analyses at different temperature circumstances; that is, on heating at a rate of 10 °C/min and under isothermal conditions at various temperatures. The deprotection resulted in a significant decrease in the transmittance of visible light due to the formation of a large number of gas bubbles, that is, foaming, in the polymer films when a heating temperature was close to the glass transition temperature of the used polymer. The potential of BOC‐containing polymers was also evaluated as the heat‐responsive adhesive polymers for dismantlable adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46252.     

Tunnelling through an embankment using all ground fasten method

The Tohoku Shinkansen Railway between Morioka and Hachinoe was opened on December 1, 2002. In this section, there are 20 tunnels. Second Itsukaichi tunnel is one of them, and it is a relatively short tunnel of 1175 m. At the Morioka portal, this tunnel crosses under National Highway No. 4 with a small depth of overburden 2–5 m where approximately 15,000 vehicles pass a day. The tunnel was excavated by NATM method. All Ground Fasten method was used as an auxiliary method. As a result, the face was prevented from collapsing and the tunnel was excavated while keeping the ground surface settlement to a minimum without interfering with road traffic.     

The effects of surfactant on the multiscale structure of bubbly flows

It is well known that a bubble in contaminated water rises much slower than one in purified water, and the rising velocity in a contaminated system can be less than half that in a purified system. This phenomenon is explained by the so-called Marangoni effect caused by surfactant adsorption on the bubble surface. In other words, while a bubble is rising, there exists a surface concentration distribution of surfactant along the bubble surface because the adsorbed surfactant is swept off from the front part and accumulates in the rear part by advection. Owing to this surfactant accumulation in the rear part, a variation of surface tension appears along the surface and this causes a tangential shear stress on the bubble surface. This shear stress results in the decrease in the rising velocity of the bubble in contaminated liquid. More interestingly, this Marangoni effect influences not only the bubble's rising velocity but also its lateral migration in the presence of mean shear. Together, these influences cause a drastic change of the whole bubbly flow structures. In this paper, we discuss some experimental results related to this drastic change in bubbly flow structure. We show that bubble clustering phenomena are observed in an upward bubbly channel flow under certain conditions of surfactant concentrations. This cluster disappears with an increase in the concentration. We explain this phenomenon by reference to the lift force acting on a bubble in aqueous surfactant solutions. It is shown that the shear-induced lift force acting on a contaminated bubble of 1mm size can be much smaller than that on a clean bubble.     

Efficacy of Chemical Mimicry by Aphid Predators Depends on Aphid-Learning by Ants

Chemical mimicry is an effective strategy when signal receivers recognize and discriminate models by relying on chemical cues. Some aphid enemies mimic the cuticular chemicals of aphids through various means thus avoiding detection and attack by aphid-tending ants. However, because ants have been reported to learn the chemical signatures of aphids in order to distinguish the aphids, the efficacy of chemical mimicry is predicted to depend on the experience of the ants that had tended aphids. The present study tested this hypothesis using two predator species: larvae of the green lacewing Mallada desjardinsi, and larvae of the ladybeetle Scymnus posticalis. Lacewing larvae carry the carcasses of aphids on which they have preyed upon their backs, and these function via chemical camouflage to reduce the aggressiveness of aphid-tending ants toward the larvae. Ladybeetle larvae reportedly produce a covering of wax structures, and their chemicals appear to attenuate ant aggression. We examined whether the behavior of the ant Tetramorium tsushimae toward these predators changed depending on their aphid-tending experience. Ants moderated their aggressiveness toward both predators when they had previously tended aphids, indicating that chemical mimicry by both aphid predators is dependent on previous experience of the ants in tending aphids. Chemical mimicry by the predators of ant-tended aphids is therefore considered to exploit learning-dependent aphid recognition systems of ants.     

Keratanase II-catalyzed synthesis of keratan sulfate oligomers by using sugar oxazolines as transition-state analogue substrate monomers: a novel insight into the enzymatic catalysis mechanism

Keratan sulfate (KS) oligomers with well-defined structures were synthesized by keratanase II (KSase II)-catalyzed transglycosylation. N-Acetyllactosamine [Galbeta(1-->4)GlcNAc; LacNAc] oxazoline derivatives with sulfate groups at the C-6 (1 a) and both the C-6 and the C-6' (1 b) were prepared as transition-state analogue substrate monomers for KSase II. Monomer 1 a was effectively oligomerized by the enzyme under weak alkaline conditions, to give alternating 6-sulfated KS oligomers (2 a) in good yields, and with total control of regioselectivity and stereochemistry. KSase II also recognized 1 b, which provided fully 6-sulfated KS oligomers (2 b) in good yields under similar conditions. Nonsulfated LacNAc oxazoline was difficult to oligomerize enzymatically. These results imply that the catalysis mechanism of KSase II involves a sugar oxazolinium ion that requires the 6-sulfate group in the GlcNAc residue not only in hydrolysis of KS chains, but also in oligomerization of oxazoline monomers. This is the first report of KSase II-catalyzed transglycosylation to form beta(1-->3)-glycosidic bond through a substrate-assisted mechanism.     

Effect of medium-chain triacylglycerols on anti-obesity effect of fucoxanthin

Dietary effects of medium-chain triacylglycerols (MCT) and fucoxanthin (Fc) on abdominal fat weight were determined using KK-Ay obese mouse. Experimental diet contained MCT(0.9%), Fc (0.1%), or MCT (0.9%) +Fc (0.1%). The abdominal fat weight of mice fed with Fc was significantly lower than that of mice fed with MCT. Uncoupling protein 1 (UCP1), a key molecule for metabolic thermogenesis, was clearly expressed in the white adipose tissue (WAT) of mice fed Fc, but little expression in that of the mice fed MCT. The anti-obesity effect of Fc was increased by mixing Fc with MCT. This increase would be due to the increase in the absorption rate of Fc by MCT.