Thermodynamic Behavior of Stable Carbon Isotopic Compositions of Individual Polycyclic Aromatic Hydrocarbons Derived from Automobiles

Concentrations, molecular compositions, and compound-specific stable carbon isotopic compositions ( i 13 C) of polycyclic aromatic hydrocarbons (PAHs) in gasoline exhaust particles (GEPs) and diesel exhaust particles (DEPs) were investigated in this study. i 13 C of PAHs in GEPs ranged from m 13.3 to m 26.8, and that in DEPs ranged from m 21.7 to m 26.3. The interspecies i 13 C variations in each sample were 5.3 - 2.2 in GEPs and 2.6 - 1.3 in DEPs. PAHs in GEPs show larger interspecies i 13 C variation than those in DEPs; hence, a degree of carbon isotopic fractionation during the conversion from fuel to PAH seems to be larger in gasoline engines than that in diesel engines. Pyrene series PAHs, which consist of only hexagonal rings, in almost all GEP samples show strong negative correlation between the H/C ratio and i 13 C whereas fluoranthene series PAHs, which contain a pentagonal ring, show less systematic isotopic behavior in GEP samples. A kinetic isotope effect in thermal cracking of organic macromolecules may be minor for PAH formation in vehicle engines. We suggest that the isotopic trend of pyrene series in GEPs can be explained by a thermodynamic isotope effect, and that disturbance from isotopic equilibrium may cause a weak correlation between the isotopic behavior and the H/C ratio among the interspecies PAHs.     

Fast redox of composite electrode of nitroxide radical polymer and carbon with polyacrylate binder

For organic radical batteries, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) has been reported as a promising positive electrode material. The PTMA/C composite electrode prepared with polyacrylate binder demonstrated the fast redox performance for the application to aprotic secondary batteries. When the variation in discharge capacities of the PTMA/C composite electrode was tested galvanostatically at 20C rates, the electrode retained 96% of the initial capacity after 1000 cycles. This is attributed to the fact that the redox of PTMA is a simple reaction to form the oxoammonium salt doped with ClO₄^? anions in the electrolyte. When the PTMA/C composite electrode was discharged at different C rates, the electrode retained 81% of the theoretical capacity even at 50C rates. This remarkably high rate capability originates from the fast electron-transfer kinetic of the 2,2,6,6-tetramethylpiperidine-N-oxyl (so-called TEMPO) radical, partially jelled polyacrylate binder, and the improved conductivity throughout the electrode by thoroughly mixing with carbon.     

Correlation between electrical properties and crystalline phases for ZnO-Bi2O3 based varistor ceramics with rare earth additives

In this study, the correlation between the electrical properties and crystalline phases of ZnO-Bi₂O₃ based varistor ceramics with rare earth additives was investigated. The additives used were in the form R₂O₃, where R represents Eu, Ho, Y, Er, Yb, or Lu. It was found that the incorporation of rare earth additives led to an increase in the varistor voltage in the nonlinear region, an increase in the leakage current in the pre-breakdown region, and a reduction in the limiting voltage in the upturn region. In the sample with added Y₂O₃, a phase referred to as the R-phase, which contained Y, Bi, Sb, Zn, Mn, and O, was observed to be homogeneously distributed at ZnO grain boundaries. X-ray diffraction analysis revealed that the amount of the Zn-Sb-O spinel and Bi-Cr-O phases present was reduced by the rare earth addition, and that rare earth elements were incorporated into a common crystalline phase. It is suggested that the formation of the R-phase at ZnO grain boundaries and the reduction in the Bi₂O₃ liquid phase during the sintering process might be responsible for suppressing ZnO grain growth, thus leading to an increase in the varistor voltage.     

Microstructure of high battery-performance Li2FeSiO4/C composite powder synthesized by combining different carbon sources in spray-freezing/freeze-drying process

Spray-freezing/freeze-drying technique was applied to the synthesis of Li₂FeSiO₄/C composite powders using solutions containing various carbon sources, water-soluble and colloidal carbon, followed by heat treatment. The effects of the carbon sources on the microstructure and battery performance of the synthesized composite powders were investigated. The microstructures of the composite powders were clearly different when different carbon sources were used, ascribed from the thermal behavior of the carbon sources during the heat treatment. It was possible to control the microstructures of Li₂FeSiO₄/C composite powders by combining different carbon sources, and the synthesized composite powders exhibited high discharge capacities by mixing with only a binder for cathode. The composite powders using glucose and Ketjenblack dispersion as carbon sources delivered 165 mAh/g at first discharge capacity at 0.1?C. The developed chain structure suitable for conducting paths in the electrodes and a higher-specific BET surface area, attributed from Ketjenblack, were likely responsible for the higher performance.     

Direct ortho‐Hydroxylation of 2‐Phenylpyridines using Palladium(II) Chloride and Hydrogen Peroxide

Direct functionalization of the ubiquitous C H bond is receiving much attention because complex structures can be formed from simple precursors. This paper reports a useful method for the direct hydroxylation of 2‐phenylpyridines using palladium(II) chloride and aqueous hydrogen peroxide. In this method, hydrogen peroxide, which has high atom efficiency, is employed as the oxidant and phenol derivatives are generated via C H activation.

     

Chemical-Labeling-Assisted Detection of Nucleobase Modifications by Quantum-Tunneling-Based Single-Molecule Sensing

Quantum-tunneling-based DNA sensing is a single-molecule technique that promises direct mapping of nucleobase modifications. However, its applicability is seriously limited because of the small difference in conductivity between modified and unmodified nucleobases. Herein, a chemical labeling strategy is presented that facilitates the detection of modified nucleotides by quantum tunneling. We used 5-Formyl-2′-deoxyuridine as a model compound and demonstrated that chemical labeling dramatically alters its molecular conductance compared with that of canonical nucleotides; thus, facilitating statistical discrimination, which is impeded in the unlabeled state. This work introduces a chemical strategy that overcomes the intrinsic difficulty in quantum-tunneling-based modification analysis—the similarity of the molecular conductance of the nucleobases of interest.     

Synthesis and Characterization of Nano-Hetero-Structured Dy Doped CeO2 Solid Electrolytes Using a Combination of Spark Plasma Sintering and Conventional Sintering

Doped ceria (CeO₂) compounds are fluorite-type oxides that show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for "low" (500°–650°C) temperature operation of solid oxide fuel cells (SOFCs). To improve the conductivity in dysprosium (Dy) doped CeO₂, nano-size round shape particles were prepared using a coprecipitation method. The dense sintered bodies with small grain sizes (<300 nm) were fabricated using a combined process of spark plasma sintering (SPS) and conventional sintering (CS). Dy-doped CeO₂ sintered body with large grains (1.1 μm) had large micro-domains. The conductivity in the sintered body was low (−3.2 S/cm at 500°C). On the other hand, the conductivity in the specimens obtained by the combined process was considerably improved. The micro-domain size in the grain was minimized using the present process. It is concluded that the enhancement of conductivity in dense specimens produced by the combined process (SPS+CS) is attributable to the microstructural changes within the grains.     

Terpolymer films having semipolar structure: Preparation,wettability, and mechanical properties

A terpolymer, obtained by the free‐radical terpolymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMMA), methyl methacrylate(MMA), and isobutyl methacrylate (IBMA), was allowed to react with hydrogen peroxide, chloroacetic acid, and diethyl sulfate to form the corresponding modified terpolymers: (1) N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)amine N‐oxide, MMA and IBMA (DMANO series); (2) N‐(carboxymethyl)‐N,N‐dimethyl‐ N‐(2‐methacryloyloxyethyl)ethyl ammonium, MMA and IBMA (CDME series); and (3) N‐(ethyl)‐N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)ethyl ammonium ethylsulfonate, MMA and IBMA (EDMEES series), respectively. The terpolymer compositions were determined using ¹³C NMR spectrometry. Surface free energies of the terpolymers were estimated by measuring the contact angles of water and methylene iodide on the three series films (DMANO, CDME, and EDMEES), and the effect of the N‐oxide group on wettability was discussed. It was found that the upper surface of the films for the DMANO and CDME series are more hydrophobic than that for the EDMEES series. Notably, elongation to break for the DMANO series was relatively larger than that for the CDME series because of the water bound to the N‐oxide functional group. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1235–1243, 2005     

Synthesis of nanosized (Pb,Sr)TiO3 perovskite powders by coprecipitation processing

Nanosized perovskite lead strontium titanate (Pb_xSr_1−x)TiO₃ (PST) powders were successfully prepared by a simple coprecipitation method. Lead-strontium titanyl oxalate (PSTO) precursor was first synthesized at room temperature, and the precursor was then calcined at 600 °C for 1 h to produce the single phase perovskite PST powders. Characterization studies were carried out on the as-dried precursor and the calcined PST powders by various techniques. The results showed a strong dependence of the chemical composition of final PST powders on pH value in the coprecipitation reaction. PST powders with desired composition could be synthesized by adding 25 mol% excess Sr. PST particles were found to be spherical in nature with an average size of 10 nm.