A 3.5-ns atomic-level computer simulation of a DNA solution was performed. We found that a dodecamer of DNA, which contains the recognition site for Eco RI endonuclease, transforms from B-form to A-form in 0.45 M salt water. This supports an earlier proposal on the A-DNA binding site for transcription factor IIIA.

The magnetic properties in the parent compounds are often intimately related to the microscopic mechanism of superconductivity. Here we report the first direct measurements on the electronic structure of a parent compound of the newly discovered iron-based superconductor, BaFe2As2, which provides a foundation for further studies. We show that the energy of the spin density wave in BaFe2As2 is mainly lowered through exotic exchange splitting of the band structure.

The electronic structure of NaFeAs is studied with angle-resolved photoemission spectroscopy on high quality single crystals. Large portions of the band structure start to shift around the structural transition temperature and smoothly evolve as the temperature lowers through the spin density wave transition. Moreover, band folding due to magnetic order emerges slightly above the structural transition. Our observation provides direct evidence that the structural and magnetic transitions share the same origin and could both be driven by the electronic structure reconstruction in Fe-based superconductors instead of Fermi surface nesting. We did not observe any sign of a gap in the superconducting state, which is likely related to weakened superconductivity in the presence of the spin density wave.

The synthesis of Pt supported on zeolite 5A beads for the decarboxylation of oleic acid to heptadecane is demonstrated. The use of a microporous ZIF-67 crystalline layer on zeolite 5A beads not only improved the heptadecane selectivity but also, most importantly, improved the stability of the resultant catalyst. Heptadecane yields as high as ∼81% were observed for the fresh catalysts. The catalysts displayed only low to moderate loss of catalytic activity after two rounds of recycle. To our best knowledge, the catalytic performance of these catalysts is superior to those of the state-of-the-art catalysts at mild reaction conditions. In addition, as compared to powders, beads are much easier to recycle, can be fully recovered, and are more amenable for potential scale-up. The resultant catalysts are promising for the catalytic conversion of fatty acid molecules into gasoline/diesel-range hydrocarbons.

A series of new Sr 2-x Ba x CuO 3+δ (0≤ x ≤ 0.6) superconductors were prepared using high-pressure and high-temperature synthesis. A Rietveld refinement based on powder x-ray diffraction confirms that the superconductors crystallize in the K 2 NiF 4 -type structure of a space group I4/mmm similar to that of La 2 CuO 4 but with partially occupied apical oxygen sites. It is found that the superconducting transition temperature

High surface area carbon-supported platinum-based catalysts, Pt/C, PtWO x /C, PtRu/C and PtRuWO x /C, were prepared via a chemical reduction route using single metal precursor salts. The catalyst particles were found to be in the nanoscale range, and the addition of Ru clearly decreased the particle size. The Ru was found to be partially incorporated into the face centered cubic lattice of Pt and to form a single Ru catalyst component. X-ray diffraction and X-ray photon spectroscopy did not provide evidence for electronic interactions between WO x and Pt as well as WO x and Ru. However, the addition of tungsten to the PtRuWO x /C catalyst resulted in a high degree of catalyst particle agglomeration. Both Ru containing catalysts showed significantly higher activities for the CH 3 OH oxidation reaction in terms of Pt + Ru mass as well as electroactive Pt + Ru surface area than the Pt/C and PtWO x /C catalysts. The addition of tungsten appeared to mainly result in some 'physical' modification of the catalytically active Pt and Ru surface components such as differences in electroactive surface area rather than promotion of the CH 3 OH oxidation reaction via a true catalytic mechanism.

The electronic structure of LaFeAsO, a parent compound of iron-arsenic superconductors, is studied by angle-resolved photoemission spectroscopy. By examining its dependence on photon energy, polarization, and sodium dosing, both the bulk and the surface contributions are identified. We find that a bulk band moves toward high binding energies below the structural transition temperature, and shifts smoothly across the spin-density-wave transition by about 25 meV. Our data suggest that the band reconstruction may play a crucial role in the spin-density-wave and the structural transitions. For the surface states, both the LaO-terminated and FeAs-terminated components are revealed. Certain small band shifts are observed for the FeAs-terminated surface states in the spin-density-wave state, which might be a reflection of the bulk electronic-structure reconstruction. Moreover, sharp quasiparticle peaks quickly rise at low temperatures, indicating drastic reduction in the scattering rate. A kink structure in one of the surface band is shown to be possibly related to the enhanced electron-phonon interactions on the polar surface.

BACKGROUND: Carboxylic acids obtained from biomass raw materials are attractive starting chemicals in the conversion to linear, paraffinic hydrocarbons. The resultant hydrocarbon products can be used as platform chemicals for the production of fuels, lubricants and other valuable chemicals. RESULTS:The effects of reaction parameters on the decarboxylation of oleic acid to paraffins, and hydrocarbons over Pt supported on zeolite 5A beads coated with ZIF-67 membrane (Pt/ZIF-67 membrane/zeolite 5A) were investigated. Almost complete conversion of oleic acid was observed for all reaction conditions studied here. The catalysts displayed high selectivity to heptadecane even with as low as 0.5 wt% Pt loading. Moderate reaction temperature and pressure were favorable to obtain high yield of heptadecane. The catalysts displayed a slight decrease in catalytic activity after recycling. Interestingly, of all explored reaction conditions, the catalysts exhibited the highest selectivity to heptadecane (∼91%) in the presence of CO 2 . CONCLUSION: The results from this work demonstrate that the studied reaction parameters greatly affected the overall catalytic performance (mainly product distribution) for the decarboxylation of oleic acid into heptadecane over Pt/ZIF-67 membrane/zeolite 5A catalysts.