New fluorescent probes applicable to aggregates of fluorocarbon surfactants

We developed new benzofurazan (NBD) labeled probes for fluorocarbon surfactant systems. The fluorescence behavior depended on the solubilization site of the fluorescent probes in the surfactant aggregates. The NBD-labeled probes suffered virtually complete reduction in the presence of Na(2)S(2)O(4) owing to the solubilization at the surface of 2-hydroxy-1,1,2,3,3-pentahydroperfluoroundecyldiethylammonium bromide (FC(8)DAB) aggregates. On the other hand, N-(3-sulfopropyl)acridinium (SPA) in FC(8)DAB aggregates showed residual fluorescence in spite of NaBH(4) addition. The large vesicles of FC(8)DAB were confirmed by DLS measurements. These facts suggest that SPA is solubilized in an inner water phase of the vesicles. The NBD labeled fluorescence probe is quite effective for the study of the aggregation behavior of fluorocarbon surfactants.     

Synthesis of thermosensitive copolymer beads containing pyridinium groups and their antibacterial activity

Thermosensitive 4VP‐NIPAAm‐4G copolymer beads containing pyridyl groups were first prepared by suspension copolymerization of 4‐vinylpyridine (4VP), N‐isopropylacrylamide(NIPAAm), and tetraethylene glycol dimethacrylate (4G; crosslinking reagent) in a saturated Na₂SO₄ aqueous solution in the presence of surfactant and MgCO₃ as dispersants. Then the copolymer beads containing pyridinium groups were obtained by the quaternization of the copolymer beads with various alkyl iodides (CH₃I, C₄H₉I, C₈H₁₇I) in N,N‐dimethylformamide. The 4VP‐NIPAAm‐4G (15 : 97 : 3) copolymer bead and the 4VP‐NIPAAm‐4G copolymer beads quaternized with butyl iodide exhibited high thermosensitivity in water, although the 4VP‐NIPAAm‐4G copolymer beads quaternized with methyl iodide or octyl iodide hardly exhibited thermosensitivity. All the quaternized copolymer beads exhibited antibacterial activity against Escherichia coli (E. coli), although the 4VP‐NIPAAm‐4G copolymer bead did not. In particular, the copolymer bead quaternized with butyl iodide exhibited the highest antibacterial activity against E. coli at 30°C. It was also found that the antibacterial activity of the quaternized 4VP‐NIPAAm‐4G copolymer beads was greatly affected by not only chain length of alkyl groups in alkyl iodides, with which the 4VP‐NIPAAm‐4G copolymer beads were quaternized, but also by temperature of the solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Upgrading and dewatering of raw tropical peat by hydrothermal treatment

In this study, hydrothermal upgrading and dewatering of raw tropical peat derived from Pontianak, West Kalimantan-Indonesia was evaluated at temperatures ranging from 150 to 380 °C, a maximum final pressure of 25.1 MPa and a residence time of 30 min. The moisture content of the raw peat was approximately 90 wt.%. Raw peat was hydrothermally upgraded without the addition of water in the laboratory scale. The yield of the solid products was between 53.0 and 99.7 wt.% and the effective calorific value of hydrothermally dewatered peat was between 17,290 and 29,209 kJ/kg following hydrothermal upgrading. In addition, the oxygen content in the solid product was varied from 38.4 to 15.6 wt.% after upgrading, while the carbon content from 55.2 to 77.8 wt.%. The hydrothermally upgraded peat fuel product also had an equilibrium moisture content of 2.3 wt.% and a maximum equilibrium moisture content of 17.6 wt.%. Upgraded peat is characteristically resistant to moisture adsorption at high humidity, which makes it promising for fuel based combustion. The change in the carbon-functional groups and their properties, as determined by FTIR and ¹³C NMR, are discussed in terms of the hydrothermal upgrading and dewatering process.     

Control of Oxidation State of Eu Ions in Na2O–Al2O3–SiO2 Glasses

Glasses doped with well‐controlled Eu³⁺ and Eu²⁺ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their ⁵D₀→⁷F_j and 5d–4f electron transitions. Glasses were prepared to dope Eu³⁺ ions in a Na₂O–Al₂O₃–SiO₂ system, and the changes in the valence state of Eu³⁺ ions and the glass structure surrounding the Eu atoms during heating under H₂ atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and ²⁷Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu³⁺ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al³⁺ ions formed the AlO₄ network structure accompanied by the Na⁺ ions as charge compensators; the Eu³⁺ ions occupied the interstitial positions in the SiO₄ network structure and were not reduced even under heating in H₂ gas. On the other hand, in the glasses containing Al₂O₃ with the Al/Na ratio exceeding unity, the Eu³⁺ ions commenced to be coordinated by the AlO₄ units in addition to the SiO₄ network structure. When heated in H₂ gas, H₂ gas molecules reacted with the AlO₄ units surrounding Eu³⁺ ions to form AlO₆ units terminated with OH bonds, and reduced Eu³⁺ ions to Eu²⁺ via the extracted electrons.     

X-ray photoemission spectroscopy of nitrogen-doped UNCD/a-C:H films prepared by pulsed laser deposition

Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were deposited by pulsed laser deposition (PLD). Nitrogen contents in the films were controlled by varying a ratio in the inflow amount between nitrogen and hydrogen gases. The film doped with a nitrogen content of 7.9 at.% possessed n-type conduction with an electrical conductivity of 18 Ω^? 1 cm^? 1 at 300 K. X-ray photoemission spectra, which were measured using synchrotron radiation, were decomposed into four component spectra due to sp², sp³ hybridized carbons, C=N and C–N. A full-width at half-maximum of the sp³ peak was 0.91 eV. This small value is specific to UNCD/a-C:H films. The sp²/(sp³ + sp²) value was enhanced from 32 to 40% with an increase in the nitrogen content from 0 to 7.9 at.%. This increment probably originates from the nitrogen incorporation into an a-C:H matrix and grain boundaries of UNCD crystallites. Since an electrical conductivity of a-C:H does not dramatically enhance for this doping amount according to previous reports, we believe that the electrical conductivity enhancement is predominantly due to the nitrogen incorporation into grain boundaries.     

Peptide and protein mimetics inhibiting amyloid beta-peptide aggregation

Protein misfolding is related to some fatal diseases including Alzheimer's disease (AD). Amyloid beta-peptide (Abeta) generated from amyloid precursor protein can aggregate into amyloid fibrils, which are known to be a major component of Abeta deposits (senile plaques). The fibril formation of Abeta is typical of a nucleation-dependent process through self-recognition. Moreover, during fibrillization, several metastable intermediates such as soluble oligomers, including Abeta-derived diffusible ligands (ADDLs) and Abeta*56, are produced, which are thought to be the most toxic species to neuronal cells. Therefore, construction of molecules that decrease the Abeta aggregates, including soluble oligomers, protofibrils, and amyloid fibrils, might further our understanding of the mechanism(s) behind fibril formation and enable targeted drug discovery against AD. To this aim, various peptides and peptide derivatives have been constructed using the "Abeta binding element" based on the structural models of Abeta amyloid fibrils and the mechanisms of self-assembly. The central hydrophobic amino acid sequence, LVFF, of Abeta is a key sequence to self-assemble into amyloid fibrils. By combination of this core sequence with a hydrophobic or hydrophilic moiety, such as cholic acid or aminoethoxy ethoxy acetic acid units, respectively, good inhibitors of Abeta aggregation can be designed and synthesized. A peptide, LF, consisting of the sequence Ac-KQKLLLFLEE-NH 2, was designed based on the core sequence of Abeta but with a simplified amino acid sequence. The LF peptide can form amyloid-like fibrils that efficiently coassemble with mature Abeta1-42 fibrils. The LF peptide was also observed to immediately transform the soluble oligomers of Abeta1-42, which are thought to pose toxicity in AD, into amyloid-like fibrils. On the other hand, two Abeta-like beta-strands with a parallel orientation were embedded in green fluorescent protein (GFP), comprised of a beta-barrel structure, to make pseudo-Abeta beta-sheets on its surface. The GFP variant P13H binds to Abeta1-42 and inhibits Abeta1-42 oligomerization effectively in a substoichiometric condition. Thus, molecules capable of binding to Abeta can be designed based on structural similarities with the Abeta molecule. The peptide and protein mimetics based on the structural features of Abeta might lead to the development of drug candidates against AD.     

Effect of sweep gas species on tritium release behavior from lithium titanate packed bed during 14 MeV neutron irradiation

In a fusion reactor, the prediction of tritium release behavior from breeder blanket is important to design the tritium recovery system, but the amount of tritium generated is necessary information to do that. Hence, tritium generation and recovery studies on lithium ceramics packed bed have been started by using fusion neutron source (FNS) in Japan Atomic Energy Agency (JAEA). Lithium titanate (Li₂TiO₃) was selected as tritium breeding material, and its packed bed was enclosed by the beryllium blocks, and was kept at certain temperature during fusion neutron irradiation. During irradiation, the packed bed was purged with the sweep gas continuously, and tritium released was trapped in each gas absorber selectively by chemical form. In this work, the effect of sweep gas species on tritium release behavior was investigated. In the case of sweep by helium with 1% of hydrogen, tritium in water form was released sensitively corresponding to the irradiation. This is due to existence of the water vapor in the sweep gas. On the other hand, in the case of sweep by helium without water vapor, tritium in gaseous form was released first, and release of tritium in water form was delayed from gaseous tritium and was gradually increased.     

Preparation of resins having various phosphonium groups and their adsorption and elution behavior for anionic surfactants

Resins containing phosphonium groups were prepared by reaction of chlorohydroxylated glycidylmethacrylate–divinylbenzene macroreticular resins with three trialkylphosphines. Triethylphosphine, tributylphosphine, and trioctylphosphine were used as trialkylphosphines. Adsorption and elution behavior of sodium benzenesulfonate (SBS) and sodium dodecylbenzenesulfonate (SDBS) on the resins were studied. Adsorption of SBS and SDBS increased with increasing the alkyl chain length of phosphonium groups in the resins. The adsorption of SBS decreased with increasing ionic strength of the solution, while the adsorption of SDBS increased with increasing ionic strength of the solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 371–378, 1999