Poly(sulfonated phenylene)-block-poly(arylene ether sulfone) copolymer for polymer electrolyte fuel cell application

Novel poly(2-(3-sulfo)benzoyl-1,4-phenylene)-block-poly(arylene ether sulfone) copolymers (PSP-b-PAESs) were successfully synthesized by Ni(0)-catalyzed copolymerization of 2,5-dichloro-3′-sulfo-benzophenone (DCSB) and chlorobenzophenone-endcapped oligo(arylene ether sulfone). Their physical property, morphology and polymer electrolyte fuel cell (PEFC) performance were investigated compared to those of the DCSB-based random copolymers and Nafion112. PSP-b-PAES with a measured ion exchange capacity (IEC) of 1.82 meq g^?1, of which the hydrophilic/hydrophobic block lengths were evaluated as 17/8.4, showed the relatively small number of water molecules sorbed per sulfonic acid group (λ = 15) in water and the anisotropic membrane swelling with 2.4 times larger through-plane swelling than in-plane one, whereas it showed the almost isotropic proton conductivity. The PSP-b-PAES exhibited a microphase-separated structure composed of hydrophobic and hydrophilic domains, whereas the random copolymers exhibited a homogenous morphology. The PSP-b-PAES had the larger proton conductivity than the random copolymer with an IEC of 2.01 meq g^?1, especially under the low relative humidities. Even at a low humidification of 17% RH at 90 °C and 0.2 MPa, the PSP-b-PAES exhibited the high PEFC performance; namely, cell voltage of 0.69 V at load current density of 0.5 A cm^?2 and maximum output of 0.73 W cm^?2, which were much higher than those at 30% RH for the random copolymer (0.65 V and 0.51 W cm^?2) and Nafion112 (0.70 V and 0.61 W cm^?2). The PSP-b-PAES showed the fairly high durability of 750 h under PEFC operation at 90 °C in spite of the relatively low molecular weight. PSP-b-PAESs have the high potential as polymer electrolyte membrane for PEFC applications.     

Mechanical and physical properties of epoxy composites reinforced by vapor grown carbon nanofibers

Epoxy/vapor grown carbon nanofiber composites (VGCF) with different proportions of VGCF were fabricated by the in situ process.The VGCFs were well dispersed in both of the low and high viscosity epoxy matrices, although occasional small aggregates were observed in a high viscosity epoxy of 20 wt.%. The dynamic mechanical behavior of the nanocomposite sheets was studied. The storage modulus and the glass transition temperature (T_g) of the polymer were increased by the incorporation of VGCFs.The electrical and mechanical properties of the epoxy-VGCFs nanocomposite sheets with different weight percentages of VGCFs were discussed. The results were that both had maximum tensile strength and Young’s modulus at 5 wt.% for both materials and reduced the fracture strain with increasing filler content. The electrical resistivity was decreased with the addition of filler content. Mechanical, electrical and thermal properties of low viscosity epoxy composites were resulted better than that of the high viscosity composites.     

Deterioration of diacylglycerol‐ and triacylglycerol‐rich oils during frying of potatoes

The stabilities of a commercial diacylglycerol‐rich oil (DAG) and a salad oil (TAG) that had been prepared from a mixture of rapeseed and soybean oils were compared while frying potatoes at 180 °C for 3 h. The representative chemical and physical characteristics of the oils were assessed before and after frying, together with the amount of volatile aldehydes in the exhaust of frying. Among the deterioration indications, the carbonyl value, polymer content, and residual polyunsaturated fatty acid content were similar and not significantly different between the TAG and DAG. On the other hand, the characteristics relating to free fatty acids, i.e. the acid value and emission of chemiluminescence at 100 °C, were greater and the smoke and flash points were lower in the DAG than in the TAG. An irritating odor was generated from the DAG after 1 h of frying and got stronger as frying continued. These results suggested that DAG more easily forms free fatty acids under frying conditions than TAG.     

Examining prepotent response suppression in aging: A kinematic analysis.

Two experiments were designed to explore how age differences in conflict detection may contribute to poorer motor performance. In each experiment, 12 young adults (YAs) and 12 older adults (OAs) performed a finger sequencing task in which the frequency of specific critical transitions was varied. These critical transitions were contrasted with violation transitions to assess the ability to detect a conflict in response requirements. In addition to accuracy and reaction time, the authors used kinematic data to parse movements into planning and motor execution phases. OAs were differentially slower to respond to violations than YAs, in line with other research on executive control, prepotent response suppression, and aging. Kinematic analyses revealed that YAs executed movements more rapidly on violation than critical transitions, whereas OAs executed movements at the same speed regardless of response predictability and increased planning time. The authors argue that OAs are unable to reprogram prepotent movement plans to overcome slowed movement planning in cognitively challenging situations. The results are discussed in terms of the influence of age-related cognitive inefficiency on motor control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Methacrylate-based ionic liquid: radical polymerization/copolymerization with methyl methacrylate and evaluation of molecular weight of the obtained homopolymers

Azobisisobutyronitlite (AIBN)-induced free radical polymerization of a methacrylate-based ionic liquid monomer, 1-(2-methacryloxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Met-IL) was carried out in a common organic solvent, N,N-dimethylformamide (DMF), and an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI). The molecular weight of the obtained poly(Met-IL) was evaluated by transforming it to non-ionic poly(methyl methacrylate) with hydrolysis of the imidazolium-salt-substituted pendant ester groups and methyl esterification. Radical copolymerization with methyl methacrylate (MMA) was also carried out in both DMF and EMImTFSI. Analysis of copolymer composition revealed that the reactivity of Met-IL was lower than that of MMA in both DMF and EMImTFSI solutions.     

Preparation of avidin-containing polyelectrolyte microcapsules and their uptake and release properties

Avidin-containing polyelectrolyte microcapsules were prepared by a layer-by-layer deposition technique and uptake and release of biotin-labelled fluorescein (b-FITC) was studied. The polyelectrolyte microcapsules were prepared by coating the surface of calcium carbonate (CaCO₃) microparticles containing avidin-poly(styrene sulfonate) (PSS) conjugate, followed by dissolution of CaCO₃ core in an ethylenediaminetetraacetic acid solution. Release of avidin from the microcapsules was markedly suppressed due to formation of a high molecular weight of avidin-PSS conjugate in the microcapsules. The uptake of b-FITC into the microcapsules was highly enhanced through a strong binding of b-FITC to avidin, as compared to the uptake into avidin-free microcapsules. Release of b-FITC from the microcapsules was accelerated upon addition of biotin, 2-iminobiotin, or lipoic acid in the solution due to the competitive binding of the additives to the binding site of avidin.     

Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds

Prolonged (up to 2 h) heat treatment at 1600 °C of nanodiamond particles (5 nm) leads to their conversion to the mixture of quasi-spherical carbon onions and multi-shell polyhedral nanographites. Structural and magnetic properties of two (A and B) series of nanographite samples obtained at various annealing intervals were studied. XRD data show that both multi-shell nanographite samples have practically the same crystalline structures. HRTEM evidences that the most of particles obtained by short time (7 min) annealing have a spherical like shape whereas the long time (~ 2 h) annealing leads to the majority of particles having a polyhedral shape with a hollow inside. Electronic and magnetic properties of these nanocarbons were investigated by magnetic susceptibility and EPR. Annealing results in entire transformation of the EPR signal of nanodiamond to new EPR signals of various line shapes and widths. These signals are extremely sensitive to ambient oxygen. Concentrations for all EPR active spins vary from ~ 1 × 10¹⁹ spins/g (7 min) to ~ 2 × 10¹⁹ spins/g (2 h). Temperature dependences of EPR spectra' parameters were obtained for vacuum-processed samples within the range 4?600 K. Intensity vs. T plots may be well-fitted by the combination of Curie–Weiss and temperature-independent Pauli susceptibility contributions. The latter one increases on heat treatment. Significant extension of electron spin-lattice relaxation time on decreasing temperature was found.     

Mercury and selenium concentrations in the internal organs of toothed whales and dolphins marketed for human consumption in Japan

Small cetaceans (toothed whales odontoceti and dolphins delphinidae) have been traditionally hunted along the coast of Japan and fresh red meat and blubber, as well as boiled internal organs such as liver, kidney, lung and small intestine, are still being sold for human consumption. We surveyed mercury contamination in boiled liver, kidney and lung products marketed in Japan between 1999-2001. The average +/- S.D. of total mercury (T-Hg) was 370 +/- 525 (range: 7.60 approximately 1980, n = 26) microg/g in liver, 40.5 +/- 48.5 (7.30-95.1, n = 15) microg/g in kidney and 42.8 +/- 43.8 (2.10-79.6, n = 23) microg/g in lung. A high correlation was observed between T-Hg and selenium (Se) concentrations in these organs, supporting the formation of a Hg-Se complex. The formation of a Hg-Se complex probably contribute to the detoxification of Hg for cetaceans and allows a very large accumulation of Hg in livers. The provisional permitted level of T-Hg in marine foods set by the Japanese Ministry of Health and Welfare is 0.4 microg/ g, and the provisional permitted weekly intake (PTWI) set by WHO is 5 microg/kg bw/week. The maximal T-Hg detected in boiled liver (1,980 microg/g) exceeds the permitted level by approximately 5,000 times and the consumption of only 0.15 g of liver exceeds the PTWI of 60 kg of body weight of the consumer, suggesting the possibility of an acute intoxication by T-Hg even after a single consumption of the product.     

Microsequencing of glycans using 2-aminobenzamide and MALDI-TOF mass spectrometry: occurrence of unique linkage-dependent fragmentation

2-Aminobenzamide-derivatized oligosaccharides were separated by three lectin column chromatographies and then subjected to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for structural characterization of the carbohydrates. The combination of sequential exoglycosidase digestion and MALDI-TOF MS greatly facilitates the monosaccharide sequencing and is more feasible than size-exclusion column chromatography in terms of the time consumed and the laboriousness of the procedure. By this strategy, microsequencing of 2-3 pmol of oligosaccharide derivatives could be achieved. Furthermore, spectra obtained by the post source decay (PSD) mode provide excellent sequence information. The relative intensities of metastable ions due to fragmentation at glycosidic linkages were different among linkage isomers of particular oligosaccharides. These results demonstrate that PSD analysis possesses significant potential for the estimation of glycosidic linkage in carbohydrate structures.     

Improvement of productivity of active horseradish peroxidase in Escherichia coli by coexpression of Dsb proteins

Coexpression of two classes of folding accessory proteins, molecular chaperones and foldases, can be expected to improve the productivity of soluble and active recombinant proteins. In this study, horseradish peroxidase (HRP), which has four disulfide bonds, was selected as a model enzyme and overexpressed in Escherichia coli. The effects of coexpression of a series of folding accessory proteins (DnaK, DnaJ, GrpE, GroEL/ES, trigger factor (TF), DsbA, DsbB, DsbC, DsbD, and thioredoxin (Trx)) on the productivity of active HRP in E. coli were examined. Active HRP was produced by very mild induction with 1 microM isopropyl-beta-D-thiogalactopyranoside (IPTG) at 37 degrees C, whereas the amount of active HRP produced by the induction with 1 mM IPTG was negligibly small. Active HRP production was increased significantly by coexpression of DsbA-DsbB (DsbAB) or DsbC-DsbD (DsbCD), while coexpression of molecular chaperones did not improve active HRP production. The growth of E. coli cells was inhibited significantly by the induction with 1 mM IPTG in a HRP single expression system. In contrast, when HRP was coexpressed with DsbCD, the growth inhibition of E. coli was not observed. Therefore, coexpression of Dsb proteins improves both the cell growth and the productivity of HRP.