Synthesis of TiC-C fiber from titanium isopropoxide treated phenolic resin fiber

Precursor fibers for titanium carbide-carbon fibers were synthesized by reacting phenolic resin fibers with titanium isopropoxide (TIP). In this system, titanium oxide gel coated fiber was prepared by hydrolyzing TIP infiltrated resin fiber. The precursor fibers obtained after the hydrolysis were converted into titanium oxide-carbon fibers (TiO₂-C fibers) by pyrolysis at 1273 K. The TiO₂-C fibers were converted into titanium carbide-carbon fibers (TiC-C fibers) by heat treatment at 1373–1973 K. The mechanisms of the conversion from TiO₂-C fibers to TiC-C fibers were characterized by TGA.     

Cyclotomic Z2-extensions of J-fields

Hurwitz-type relations of Iwasawa's λ₂^?-invariants and the 2-ranks of the “narrow” ideal class groups in the 2-extensions of J-fields are given under the assumption of the vanishing of μ₂-invariants.     

Synthesis of gold nanosheets at a liquid/liquid interface using an amphiphilic polyoxometallate/surfactant hybrid photocatalyst

Control of the morphology of gold nanoparticles has received considerable attention because the physical and chemical properties of gold depend significantly on its size and shape. A novel route for obtaining 2-D gold nanostructures has been developed in which chloroaurate ions (AuCl (4)(-)) are reduced at the 2-D interface between water and chloroform using an amphiphilic polyoxometallate (SiW (12)O (40)(4-))/surfactant (dimethyldioctadecylammonium; DODA) hybrid photocatalyst under UV irradiation at room temperature in air. This simple method can readily produce large single-crystalline gold nanosheets (lateral size, ca. 20 microm; thickness, ca. 150 nm).     

Qualitative and quantitative analysis of Swertia herbs by high performance liquid chromatography-diode array detector-mass spectrometry (HPLC-DAD-MS)

We evaluated the composition of Swertia herbs using high performance liquid chromatography-diode array detector-mass spectrometry (HPLC-DAD-MS). Eleven peaks of 6 species were unequivocally identified by comparing their retention times, UV spectra, on-line electrospray ionization mass (ESI-MS) spectra, and collision-induced dissociation mass spectrometry/mass spectrometry (CID-MS/MS) data with those of authentic compounds. We adopted wavelengths of 254 nm, 340 nm and 230 nm to simultaneously determine these 11 compounds. By comparing the overall DAD and total ion current (TIC) profiles of various samples, the 6 species were differentiated in terms of the occurrence and/or relative concentrations of the eleven compounds. Our novel validated HPLC-DAD-MS method not only facilitates quality control and identification of Swertia herbs, but is also applicable to systematic investigations of the distribution of secoiridoids, flavonoids, and xanthones in the genus Swertia.     

Studies on heterobifunctional cross-linking reagents, 6-maleimidohexanoic acid active esters

6-maleimidohexanoic acid N-hydroxysuccinimide ester has been used widely for preparation of enzyme immunoconjugates as a unique heterobifunctional cross-linking reagent. Its heterobifunctional reactivity is good, but its ester portion hydrolyzes easily in the presence of water. Several 6-maleimidohexanoic acid active esters (6-maleimidohexanoic acid 4-nitrophenyl ester, 6-maleimidohexanoic acid N-hydroxy-5-norbornene-endo-2,3-dicarboximide ester, and 6-maleimidohexanoic acid pentafluorophenyl ester) were prepared and their reactivity and stability in an aqueous media were tested. Of the synthetic esters, the pentafluorophenyl ester exhibited the highest reactivity and stability in aqueous media.     

Single 10-fs deep-ultraviolet pulses generated by broadband four-wave mixing and high-order dispersion compensation

Broadband chirped-pulse four-wave mixing and a pulse compressor consisting of a prism pair and a grating pair are used to generate 10.3-fs deep-ultraviolet pulses. A large proportion of the dispersion up to 1000 fs² is compensated without inducing third-order dispersion, which together with the smooth spectral and temporal profiles of the pulses makes them suitable for ultrafast spectroscopy. Unexpected spectral narrowing is observed when short input pulses were used for four-wave mixing. This narrowing is explained in terms of other third-order nonlinear phenomena, namely self-phase and cross-phase modulations, which occur simultaneously with four-wave mixing.     

Self-assembling imidazolium-based ionic liquid in rigid nanopores induces anomalous CO2 adsorption at low pressure

An alkylimidazolium-based long-chain ionic liquid (LCIL) was immobilized in silica nanopores via a supramolecular assembly approach. To discuss the characteristic features of LCIL in a confined nanospace, except for the characteristics of the host materials, we have prepared the silica host with monodisperse morphology and a nanostructured system to immobilize LCIL. The nanostructure is composed of three distinct regions: the silica framework, the hydrophobic interior of the alkyl chains, and the organic-inorganic ionic interface. Anomalous CO(2) adsorption sites were found to be well-ordered locations on the ionic interface fabricated by the π-π-stacked imidazolium heads containing inorganic anions and polar silica surfaces.     

Physiological activities of chitosan and N‐trimethyl chitosan chloride in U937 and 3T3‐L1 cells

Chitosan (CH) is a biopolymer with biocompatible, biodegradable, and bioactive properties. N,N,N‐trimethyl chitosan chloride (TMC) is a quaternized form of CH that is highly cationic and more water soluble than unmodified CH. The physiological activities of CHs with different molecular weights (M_w) and degrees of TMCs quaternization were investigated in U937 and 3T3‐L1 cell lines. ¹H‐NMR spectrometry and size exclusion chromatography were used for characterization of the biopolymers. The half inhibition concentration (IC₅₀) of DPPH‐radical‐scavenging activity was below 0.9 mg/m with quaternized CHs. The IC₅₀ values of chitooligosaccharides, low‐ and medium‐molecular‐weight CHs were 8.4, 10.9, and 13.9 mg/ml, respectively. High‐molecular‐weight CHs and TMCs showed apoptotic activity on U937 cells. T41, a TMC of 549 kDa with a 41% degree of quaternization (DQ), yielded 30.7% apoptotic cell death in U937 at 20 µg/ml and effectively repressed cell differentiation and triglyceride accumulation in 3T3‐L1. Depolymerized CHs reduced triglyceride accumulation but also caused cell differentiation. TMCs showed repressor activity to both cell differentiation and triglyceride accumulation. Increasing the molecular weight of CHs and TMCs generally resulted in increased physiological activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Pretreatment of Rice Straw Using a Butanone or an Acetaldehyde Dilute Solution Explosion for Producing Ethanol

Ethanol conversion from rice straw using butanone and acetaldehyde dilute solution explosions was evaluated based on the optimization of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried and investigated at different temperature. Using a 0.9-mol/L butanone solution explosion, with the explosion pressure set at 3.1 MPa, the residence time at 7 min, the dried rice straw-to-water ratio at 1:3 (w/w), and the exploded slurry drying temperuture at 90 °C for 8 h, the yields of total sugar, glucose, and xylose were 85%, 88%, 82% (w/w), respectively, and the ethanol productivity was 26.0 g/100 g rice straw dry matter. Moreover, 0.5-mol/L acetaldehyde dilute solution explosion improved the efficiency of enzymatic hydrolysis (EH) and simultaneous saccharification and co-fermentation (SSCF), and the residual inhibitors had negligible effects on EH and SSCF after detoxification by drying. The results suggested that compared with pure water explosions, the use of butanone and of acetaldehyde dilute solution explosions lowered the explosive temperature and improved the sugar yield, although relative crystallinity of the rice straw dry matter was increased after the explosion.     

Quadruple Click: A Facile Pathway leading to Tetrakis(4‐(1,2,3‐triazolyl)methyl)‐ethylenediamine Derivatives as a New Class of Extracting Agents for Soft Metal Ions

Tetrakis(triazolylmethyl)ethylenediamine, which is a class of tetrakis(2‐pyridylmethyl)ethylenediamine (TPEN) analogue, is synthesized by a quadruple click reaction of tetrapropargylated ethylenediamine and four equivalents of alkyl azide. The obtained compound efficiently extracted the soft metal cadmium(II) ions by solvent extraction. It is also found that an N‐isopropylacryl amide (NIPA) gel using the triazole ethylenediamine as a cross‐linker exhibits a temperature‐dependent extraction performance.