Comb-shaped chitosan derivatives having oligo(ethylene glycol) side chains

Summary Monoaldehydes have been synthesized from tri- and tetra(ethylene glycol) monosubstituted derivatives and introduced into chitosan by the reductive alkylation technique to give comb-shaped polysaccharide hybrids. The reaction of chitosan with the aldehydes in the presence of sodium cyanoborohydride proceeded efficiently to give chitosan derivatives having oligo(ethylene glycol) side chains at the amino groups. The products were characterized by high affinity for organic solvents as well as water in sharp contrast to the original chitin and chitosan. They showed significant adsorption capacity toward metal cations. Received: 6 November 1998/Revised version: 15 February 1999/Accepted: 22 February 1999     

Preparation and Electrical Resistance Characteristics of Electroless Copper-Nickel Alloy Deposits

Studies have been made of an electroless copper-nickel-phosphorus alloy from a citrate complex bath using hypophosphite as reducing agent and electroless copper-nickel binary alloy from a triethanolamine complex bath using formaldehyde as reducing agent. With an increase in copper content of alloy, the specific resistance of deposit decreased. The TCR of copper-nickel-phosphorus alloy increased remarkably because of the crystallization of Ni₃P after heat treatment. But the increase in TCR of copper-nickel binary alloy was moderate and not so striking as for the phosphorus containing alloy.     

Fabrication of highly interconnected porous carbonate apatite blocks based on the setting reaction of calcium sulfate hemihydrate granules

Interconnected porous carbonate apatite (CO₃Ap) blocks that emulate cancellous bone have potential as an alternative to autografts. The present study aimed to evaluate the feasibility of fabricating a block via a stepwise compositional transformation to CO₃Ap through dissolution-precipitation reactions of an interconnected porous calcium sulfate dihydrate (CSD) block, which was obtained by the setting reaction of calcium sulfate hemihydrate (CSH) granules. Exposure of the CSH granules to water resulted in a setting reaction. However, the gaps between the granules were clogged, preventing the fabrication of interconnected porous structures. Removing the water in the gaps using filter paper was beneficial in avoiding gap clogging and in fabricating interconnected porous CSD blocks. Although the CSD blocks transformed into CaCO₃ blocks, which maintained the interconnected porous structure through a dissolution-precipitation reaction in a Na₂CO₃ solution, their mechanical strength was quite low (diametral tensile strength: DTS = 75 kPa). In contrast, a CaCO₃ block with a much greater mechanical strength (DTS = 0.98 MPa) was fabricated when a calcium sulfate anhydrous block made via the heat treatment of the CSD block was used as a precursor. The CaCO₃ block transformed into a CO₃Ap block (DTS = 2.1 MPa), maintaining the interconnected porous structure through a dissolution-precipitation reaction when immersed in a Na₂HPO₄ solution. The CO₃Ap block had macropores initiated by the gaps between the granules and micropores created by the setting reaction of CSH granules and the dissolution-precipitation reactions to form CO₃Ap. The results obtained in the present study demonstrate that this method is useful for fabricating interconnected porous CO₃Ap blocks.     

Atractylodin Produces Antinociceptive Effect through a Long-Lasting TRPA1 Channel Activation

Atractylodin (ATR) is a bioactive component found in dried rhizomes of Atractylodes lancea (AL) De Candolle. Although AL has accumulated empirical evidence for the treatment of pain, the molecular mechanism underlying the anti-pain effect of ATR remains unclear. In this study, we found that ATR increases transient receptor potential ankyrin-1 (TRPA1) single-channel activity in hTRPA1 expressing HEK293 cells. A bath application of ATR produced a long-lasting calcium response, and the response was completely diminished in the dorsal root ganglion neurons of TRPA1 knockout mice. Intraplantar injection of ATR evoked moderate and prolonged nociceptive behavior compared to the injection of allyl isothiocyanate (AITC). Systemic application of ATR inhibited AITC-induced nociceptive responses in a dose-dependent manner. Co-application of ATR and QX-314 increased the noxious heat threshold compared with AITC in vivo. Collectively, we concluded that ATR is a unique agonist of TRPA1 channels, which produces long-lasting channel activation. Our results indicated ATR-mediated anti-nociceptive effect through the desensitization of TRPA1-expressing nociceptors.     

Direct imaging of native passive film on stainless steel by aberration corrected STEM

A cross-section of a native passive film on a commercial type 304 stainless steel was directly imaged and characterized using an aberration corrected STEM-EDS in combination with FIB sectioning. The technique demonstrated an enrichment of Cr in the lower part of the passive film, and a depletion of Cr and an enrichment of Ni in the matrix side closest to the passive film/matrix interface in accordance with previous studies, further proving the advantage of this technique with respect to spatial resolution. That is, the STEM-EDS showed a compositional profile with higher spatial resolution compared to AES which has been mainly used for this type of investigation. The technique will be applicable to the investigation of nm to sub-nm compositional fluctuation of passive films, steel surfaces adjacent to inclusions and grain boundaries postulated as an initiating site of pitting corrosion or stress corrosion cracking (SCC).     

氢气渗透Nb基合金的设计及特性表征

在Nb40Ti30Ni30合金的初生相(Nb,Ti)和共晶相连线上制作Nb-Ti-Ni合金.研究表明,上述直线上的合金由初生相和共晶相构成,氢渗透度Ф随Nb浓度和初生相(Nb,Ti)体积分数的增大而升高,氢渗透合金的Nb浓度扩展至68 mol%.Nb68Ti17Ni15合金由74%(体积分数)的初生相(Nb,Ti)和26%(体积分数)的共晶相{(Nb,Ti)+TiNi}组成,氢渗透度最大Ф673K达到4.91×10-8mol H2m-1s-1Pa-0.5,是Nb40Ti30Ni30合金的氢渗透度Ф673K的2.5倍,纯钯金的氢渗透度Ф573K的3.5倍.     

Germanium negative-ion implantation into SiO2 layer on Si: Photoluminescence properties and oxidation state of Ge atoms in subsequent heat treatment

Photoluminescence properties (PL) and oxidation state of Ge atoms implanted into a thermally grown SiO₂ layers have been investigated. The samples were prepared by Ge negative-ion implantation at multi-energies of 10-50 keV with various Ge concentrations of 0.5-6 at.% and subsequent two-stage annealing in N₂ at a flow rate of 50 ml/min and in decompressed air at flow rate of 10 ml/min at temperatures of 600 °C-900 °C for 1-3 h. Results showed that the PL emission with a peak at 390 nm depended on both Ge concentration and subsequent annealing temperature. For the low Ge concentrations of 1-1.4 at.%, the strong PL emission could be obtained just after 1 h annealing in N₂ at 700-800 °C. For the high Ge concentration of 3 at.%, the PL emission was improved and increased after annealing in decompressed air, but it still was weaker than that of the Ge sample at 1.4 at.%. XPS analysis showed that almost 60% of Ge atoms were oxidized to form GeO and GeO₂, even as implanted sample and this oxidation decreased to 35% after N₂ annealing. The induced defects of SiO₂ as absorption center recovered while the oxygen defects (ODC) of GeO₂ were reduced during annealing in N₂. The deoxidation of GeO₂ is suppressed by annealing in decompressed air flow. Based on the obtained results, we have discussed the best way of heat treatment to increase ODC by two-stage annealing in N₂ and in decompressed air.     

Equilibrium Dependence of the Conductivity of Pure and Tin-Doped Indium Oxide on Oxygen Partial Pressure and Formation of an Intrinsic Defect Cluster

The dependence of the electrical conductivity of pure (99.999%) and tin-doped indium oxide (In₂O₃) ceramics on oxygen partial pressure     was investigated at 800° and 850°C. The doping amount of tin was 100–1000 ppm, which is within the solubility limit at the temperatures measured. The conductivity of doped ceramics was independent of     , and the carrier concentration was almost the same as the estimated value from the tin content. The conductivity of the pure In₂O₃ ceramic was proportional to     . By considering a singly charged defect cluster of interstitial indium and interstitial oxygen ,     , the conductivity dependence is deduced to be proportional to     . There are large and three adjacent vacant sites, 8a and 16c, in the In₂O₃ structure to enter indium and oxygen.     

Lipid and fatty acid compositions of a novel docosahexaenoic acid-producing marine bacterium

An unidentified bacterial strain, SCRC-21406, isolated from the intestine of a marine fish, Glossanodon semifasciatus, produced docosahexaenoic acid at 23% (mol/mol) [=28% (w/w)] of total fatty acids in a medium containing 0.5% (wt/vol) peptone and 0.1% (wt/vol) yeast extract at 12°C under atmospheric pressure. The cell yield was 0.43 g/L. The major lipids of the strain were phosphatidylethanolamine and phophatidylglycerol. Docosahexaenoic acid was localized at the sn-2 positions of both phospholipids. The amounts of polyunsaturated fatty acids other than docosahexaenoic acid were extremely small [<3% (mol/mol)]. Monousaturated fatty acids of the cis-7, cis-9 and cis-11 types were detected.