Synthesis of copolymer beads with various phenolic derivatives attached via different linkages and their antioxidation activity

Macroporous copolymer beads with various phenolic derivatives introduced via three types of linkages—amide, methylene, and ether—were prepared from chloromethyl styrene/tetra(ethylene glycol) dimethacrylate copolymer beads. The antioxidation activity of these phenolic copolymer beads was investigated by the measurement of the inhibition activity against the hydroperoxidation of 1,4-dioxane. The phenolic copolymer beads with the dihydroxybenzene moiety exhibited the highest antioxidation activity, and the antioxidation activity of methylene- or ether-linked phenolic copolymer beads was higher than that of amide-linked copolymer beads. Thus, the antioxidation activity of the phenolic copolymer beads was affected by not only the kinds of phenolic moieties attached but also the type of linkage group. In addition, the swelling of the copolymer beads in an organic solvent was greatly affected by the linkage type of the phenolic copolymer beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sugar consumption and ethanol fermentation by transporter-overexpressed xylose-metabolizing Saccharomyces cerevisiae harboring a xyloseisomerase pathway

Four kinds of transporters, HXT1 and HXY7 from Saccharomyces cerevisiae, and GXF1 and GXS1 from Candida intermedia, were overexpressed in xylose-metabolizing S. cerevisiae harboring a xyloseisomerase-based pathway. Overexpression of transporter enhanced sugar consumption and ethanol production, and GXF1 was efficient for ethanol fermentation from both glucose and xylose.     

Community structure, abundance, and in situ activity of nitrifying bacteria in river sediments as determined by the combined use of molecular techniques and microelectrodes

The community structure, spatial distributions, and in situ activity of ammonia-oxidizing bacteria (AOB) representing the Betaproteobacteria and nitrite-oxidizing bacteria (NOB) representing the genus Nitrospira in three different river sediments with different pollution sources and levels along the Niida River, Hachinohe, Japan, were investigated by the combined use of 16S rRNA gene-cloning analysis, real-time quantitative polymerase chain reaction (RTQ-PCR) assays, and microelectrodes. The goal of this research was to evaluate the contribution of nitrifying activity in the sediment to the overall nitrogen elimination rate in this river. The 16S rRNA gene-cloning analysis revealed that the community structures of AOB and Nitrospira-like NOB are present in three sediments. On the basis of the results of 16S rRNA gene-cloning analysis, the RTQ-PCR assay using a TaqMan probe was developed and optimized for the quantification of the Nitrospira-like NOB. In the sediments, AOB specific 16S rRNA genes were detected in the range of 10(6) to 10(7) copies/cm3 and evenly distributed over the sampled sediment depth (0-5 mm), whereas the Nitrospira-like NOB 16S rRNA gene copy numbers per cm3 were 1-2 orders of magnitude higher than the AOB copy numbers. Under light conditions, intensive oxygenic photosynthesis occurred in the surface and increased the maximal O2 concentration and O2 penetration depth in all sediments. This concomitantly stimulated nitrifying bacteria present in diurnally anoxic deeper zones and expanded nitrification zones, which consequently increased the total NH4+ consumption rate in the sediment (i.e., total NH4+ flux into the sediment). The results suggested that the in situ nitrifying activity was restricted mainly to the surface 2 mm of the sediment and linked with photosynthetic activity, which obviously plays an important role in nitrogen elimination in this river.     

Fate of coliphage in a wastewater treatment process

The fate of coliphage in a wastewater treatment plant in the central part of Japan was investigated from March to December 2001. A relative abundance of coliphage, 1000-10,000 PFU/ml determined with three different Escherichia coli strains, was detected in the influent. But, no remarkable seasonal change in the phage concentration in the influent was observed during the ten-month test period. Almost ten times higher coliphage concentration was detected by the F+ E. coli strain than by the other two F- strains. The RNA phage was more stable than the DNA phage against aerobic treatment using activated sludge. Most of the phages in the influent and primary settling tank were detected as suspended forms. Anaerobic-aerobic treatment enhanced adsorption of the phage by the solid particles. Almost no phage was detected in the effluent. Aerobic treatment using activated sludge and/or the addition of flocculants such as PAC was effective for the removal of coliphage, an index of enteric viral pollution.     

Wetting and reaction between Si droplet and SiO<Subscript>2</Subscript> substrate

The wetting and reaction between Si melt and SiO₂ substrate were investigated as a function of the atmosphere, temperature, and degree of vacuum. The results revealed that below 2 Torr with an Ar flow, the wetting angle is finally 90°. The Si droplet was stationary at a wetting angle of 90°. Videos indicated that the droplets moved and vibrated; Above 20 Torr, the Si droplet vibrated up and down with a frequency of approximately 2 Hz, thereby changing the wetting angle. Further, the droplet remained stationary on a substrate on which grooves with a width of 100 μm and depth of 100 μm were etched with a pitch of 1 mm. The presence of grooves or dimples on the substrates facilitated the leakage of SiO gas; as a result, the Si droplet did not vibrate. A vibration model was proposed in which the SiO gas produced at the interface between the Si droplet and the substrate according to the reaction Si + SiO = 2SiO expands and leaks continuously.     

A Monolayer MoS2 FET with an EOT of 1.1 nm Achieved by the Direct Formation of a High-κ Er2O3 Insulator Through Thermal Evaporation

Achieving the direct growth of an ultrathin gate insulator with high uniformity and high quality on monolayer transition metal dichalcogenides (TMDCs) remains a challenge due to the chemically inert surface of TMDCs. Although the main solution for this challenge is utilizing buffer layers before oxide is deposited on the atomic layer, this method drastically degrades the total capacitance of the gate stack. In this work, we constructed a novel direct high-κ Er₂O₃ deposition system based on thermal evaporation in a differential-pressure-type chamber. A uniform Er₂O₃ layer with an equivalent oxide thickness of 1.1 nm was achieved as the gate insulator for top-gated MoS₂ field-effect transistors (FETs). The top gate Er₂O₃ insulator without the buffer layer on MoS₂ exhibited a high dielectric constant that reached 18.0, which is comparable to that of bulk Er₂O₃ and is the highest among thin insulators (< 10 nm) on TMDCs to date. Furthermore, the Er₂O₃/MoS₂ interface (D_it ≈ 6 × 10¹¹ cm⁻² eV⁻¹) is confirmed to be clean and is comparable with that of the h-BN/MoS₂ heterostructure. These results prove that high-quality dielectric properties with retained interface quality can be achieved by this novel deposition technique, facilitating the future development of 2D electronics.     

Effect of degree of neutralization of sodium-based ionomers on hot-tack properties

The hot-tack properties of ethylene-methacrylic acid copolymers neutralized with sodium (Na) cations to produce ionomers were investigated. Specimens with neutralization degrees of 20%, 54%, and 70% were examined. After testing at low sealing temperatures (<130°C), the highest hot-tack strength was obtained from a specimen with a neutralization degree of 20%. In contrast, at high sealing temperatures (>140°C), the hot-tack strength increased with an increasing degree of neutralization. Observations of the surfaces of samples tested at low sealing temperatures after hot-tack tests showed that specimens having a neutralization degree of 20% exhibited cohesive breakdown while the 54% and 70% specimens underwent interfacial delamination. The effect of sealing temperature on hot-tack strength was determined by assessing the rheological properties of molten ionomers. The results suggested that, when testing at low sealing temperatures, a low melt viscosity provided high hot-tack strength by allowing flow diffusivity of the resin at the sealed interface. At high sealing temperatures, uniaxial elongational viscosity related to strain hardening contributed to the high hot-tack strength of these Na-based ionomers. The present study highlights the important effect of ionic aggregates on hot-tack properties.     

Dual-Function Near-Infrared Emitting Aerogel-Based Device for Detection and Sunlight-Driven Photodegradation of Antibiotics: Realizing the Processability of Silsesquioxane-Based Fluorescent Porous Materials

It is highly desirable to develop facile methods to improve the processability of porous materials for industrial applications. Herein, the preparation of a novel near-infrared emitting hybrid aerogel (PCS-CA) is reported by physically blending a porous material with chitosan. The applied porous material (PCS-CZ-O-DCM) is obtained from a near-infrared emission semiconductor compound (CZ-O-DCM) and octavinylsilsesquioxane (OVS). PCS-CZ-O-DCM can detect tetracycline hydrochloride selectively and rapidly in various solution with an extremely low detection limit of 0.29 µm for fluorescence quenching. It also exhibits an outstanding sunlight-driven photodegradation activity for antibiotics even in the absence of additional oxidation agents or pH control. PCS-CA also performs better than PCS-CZ-O-DCM powder. A PCS-CA-based glass device is further fabricated, which enables a larger amount of water purification of antibiotics by a continuous flow-through system by light-driven degradation. By blending with a soft polymer matrix, improved processability can be applied to insoluble porous materials. As a result, a novel functional devices can be realized which provides a new way to apply insoluble porous materials.     

Synthesis,Characterization, and Reaction of Divinyl‐substituted Laddersiloxanes

Silicon - Silsesquioxanes with well-defined structures have been of great interest recently because of their superior properties. Among them, laddersiloxanes (ladder-type silsesquioxanes with...