Probing the Ba 5d states in BaTiO3 and BaSO4: A resonant x-ray emission study at the Ba-L3 edge

We have directly probed the Ba 5d states in the ferroelectric barium titanate BaTiO₃ using two bulk-sensitive spectroscopic probes, resonant x-ray emission spectroscopy (RXES) and x-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L₃ edge. The results are compared with those of the non-ferroelectric barium sulfate BaSO₄. While the RXES spectra point to a localized character for the Ba 5d states in both compounds, the main peak of the PFY-XAS spectrum, corresponding to the dipolar transitions from 2p to 5d, is found to be significantly broader for BaTiO₃ than for BaSO₄. On the basis of band structure calculations, this broadening is ascribed to strong hybridization between the unoccupied Ba 5d and O 2p states in the ferroelectric. This suggests that the hybridization between the conduction states of the Ba²⁺ and O^2? ions, and not only Ti⁴⁺ and O^2?, plays a central role in determining the electronic structure of BaTiO₃, and is therefore likely to be indirectly correlated with the occurrence of ferroelectricity in this material.     

Conversion of oxido-bridged dinuclear ruthenium complex to dicationic dinitrosyl ruthenium complex using proton and nitric oxide: completion of NO reduction cycle

The hydroxido-bridged dinuclear ruthenium complex 4, which is supported by Tp ligands, has been prepared from protonation of the oxido-bridged dinuclear ruthenium complex 3. Additional protonation of 4, affording the aqua-bridged dinuclear ruthenium complex 5 in situ, and subsequent treatment with NO gave rise to the dicationic dinitrosyl complex 2. These indicate completion of the NO reduction cycle on the dinuclear ruthenium complex.     

Tetrathiafulvalenylallene: a new class of donor molecules having strong chiroptical properties in neutral and doped states

A chiral tetrathiafulvalene (TTF) dimer bridged by an allene framework (1) was synthesized. An X-ray analysis of 1 revealed an effective conjugation between TTF and the allene backbone. Allene 1 was resolved into both enantiomers, which showed strong chiroptical electrochromic properties. Absolute configuration of the allene was validated by theoretical study of the electronic circular dichroism (ECD) spectrum. ECD spectra of cationic species 1(2+) and 1(4+) exhibited intense Cotton Effects over the visible region.     

Structures of the dimeric and monomeric chromanones, gonytolides A-C, isolated from the fungus Gonytrichum sp. and their promoting activities of innate immune responses

Innate immunity is the front line of self-defense against microbial infection. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a novel dimeric chromanone, gonytolide A, as an innate immune promoter from the fungus Gonytrichum sp. along with gonytolides B and C. Gonytolide A also increased TNF-α-stimulated production of IL-8 in human umbilical vein endothelial cells.     

N-(heteroarenesulfonyl)prolinamides-catalyzed aldol reaction between acetone and aryl trihalomethyl ketones

Enantiomerically enriched trihalomethyl-substituted alcohols having a quaternary chiral carbon center can be prepared by the catalytic enantioselective cross-aldol reaction of acetone with trihalomethyl ketones by using N-(8-quinolinesulfonyl)prolinamide as an organocatalyst. The MO calculations elucidate that the hydrogen bonding between the sulfonimide proton and the 8-quinolyl nitrogen atom plays an important role in exerting the enantioselectivity of the reaction.     

Reaction mechanism and the role of copper in the photooxidation of alcohol over Cu/Nb2O5

Loading of a small amount of copper on Nb(2)O(5) significantly enhances the activity of alcohol photooxidation without organic solvents. Alcohol is adsorbed on the Lewis acid site (Nb(V)) to form an alkoxide species. Photogenerated holes and electrons on Cu/Nb(2)O(5) are trapped by the adsorbed alkoxide and Cu(II) species to form the alkoxide carbon radical and Cu(I) species. The formed alkoxide carbon radical is converted to a carbonyl compound and then desorbed. Finally, the reduced Cu(I) sites are reoxidized by reaction with O(2). The alcohol photooxidation over Nb(2)O(5) takes place under not only UV irradiation but also under visible light irradiation up to 450 nm, although the band gap of Nb(2)O(5) is 390 nm (3.2 eV). DFT calculations reveal that 1) the surface donor level derived from the adsorbed alkoxide species is located in the forbidden band, 2) direct electron transition from the surface donor level to the conduction band takes place by absorbing a photon, 3) the excitation energy from surface donor level to the Nb 4d conduction band is lower than that from the O 2p valence band to Nb 4d. The kinetic study and FT/IR spectra suggest that Cu(I) acts as an effective desorption site for the products. Based on these results, we conclude that copper functions as an effective redox promoter and desorption site for the product.     

Photocontrol of cell adhesion on amino-bearing surfaces by reversible conjugation of poly(ethylene glycol) via a photocleavable linker

Dynamic control of cell adhesion on substrates is a useful technology in tissue engineering and basic biology. This paper describes a method for the control of cell adhesion on amino-bearing surfaces by reversible conjugation of an anti-fouling polymer, poly(ethylene glycol) (PEG), via a newly developed photocleavable linker, 1-(5-methoxy-2-nitro-4-prop-2-ynyloxyphenyl)ethyl N-succinimidyl carbonate (1). This molecule has alkyne and succinimidyl carbonate at each end, which are connected by photocleavable 2-nitrobenzyl ester. Under this molecular design, the molecule crosslinked azides and amines, whose linkage cleaved upon application of near-UV light. By using aminosilanised glass and silicon as model substrates, we studied their reversible surface modification with PEG-azide (M(w) = 5000) based on contact angle measurements, ellipsometry, and AFM morphological observations. Protein adsorption and cell adhesion dramatically changed by PEGylation and the following irradiation, which can be used for cellular patterning. Also, the capability of the substrate to change cell adhesiveness by photoirradiation during cell cultivation was demonstrated by inducing cell migration. We believe this method will be useful for dynamic patterning of cells on protein-based scaffolds.     

Acceleration of ammonium nitrite denitrification by freezing: determination of activation energy from the temperature of maximum reaction rate

A reaction of ammonium nitrite in ice was investigated. Upon freezing, some nitrite is oxidized by dissolved oxygen and some nitrite reacts with ammonium to produce nitrogen and water in a denitrification reaction. The former reaction was accelerated only during freezing, and the latter one was accelerated even after the whole sample was frozen. The denitrification reaction proceeded at very low concentration in ice, which were conditions under which the reaction would not proceed in solution. The nitrogen production increased linearly with increasing initial concentration of ammonium nitrite. The concentration factor in the unfrozen solution in ice was estimated to be 50.6 when the initial concentration was 0.5 mmol dm(-3), as obtained from comparison of reaction rates in solution and in ice. A new method for determination of the activation energy is proposed that gives a value of 53 to 61 kJ mol(-1) for denitrification. The reaction order of the denitrification process is also determined using our method, and it is concluded to follow third-order kinetics.     

One-pot synthesis of imines from alcohols and amines with TiO2 loading Pt nanoparticles under UV irradiation

TiO(2) loading Pt nanoparticles (Pt@TiO(2)) promote one-pot synthesis of imines from alcohols and amines under UV irradiation at room temperature. This is achieved via a Pt-assisted photocatalytic oxidation of alcohols and a catalytic condensation of the formed aldehydes with amines on the TiO(2) surface.     

An optimal logarithmic Sobolev inequality with Lipschitz constants

In this paper, we give an optimal logarithmic Sobolev inequality on Rn with Lipschitz constants. This inequality is a limit case of the Lp-logarithmic Sobolev inequality of Gentil (2003) [7] as p→∞. As a result of our inequality, we show that if a Lipschitz continuous function f on Rn fulfills some condition, then its Lipschitz constant can be expressed by using the entropy of f. We also show that a hypercontractivity of exponential type occurs in the heat equation on Rn. This is due to the Lipschitz regularizing effect of the heat equation.