Anatomical study on the developmental process of the swollen internodes of Phryma (Phrymaceae, eudicots).

MAIN CONCLUSION: We discovered that the internodal swellings of Phryma (eudicots) stems were same as the internodal pulvini of Poaceae (monocots) from the viewpoints of internal structures and functions. The stems of eudicots are usually rod-shaped and are composed of nodes, attached by leaves, and internodes. The internodes of some species, belonging to the clade 'asterids' and its sister clade 'Caryophyllales' of eudicots, have swellings, which have negative tropism, at the basal or apical part of each internode. To know the internal features of the swollen internodes, we performed outer morphological and anatomical studies on the swollen internodes of Phryma, eudicots, one of the genera having swollen internodes, from the winter bud stage to the flowering stage. The results revealed the following: (i) the swollen regions of the internodes were composed of less lignified tissues (e.g., endodermis without Casparian strips, and xylem having less lignified xylem fibers); (ii) the internodal less lignified parts were supported by collenchyma; (iii) the endodermis includes amyloplasts, having accumulated starch granules, which would function as statoliths for negative gravitropism. Consequently, we determined that the swollen parts of the Phryma internodes are same as the internodal pulvini of Poaceae of monocots from the viewpoints of internal structures and functions.

Publisher Correction: Nanoscale percolation in doped BaZrO3 for high proton mobility.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Nanoscale percolation in doped BaZrO3 for high proton mobility.

Acceptor-doped barium zirconate is a promising proton-conducting oxide for various applications, for example, electrolysers, fuel cells or methane-conversion cells. Despite many experimental and theoretical investigations there is, however, only a limited understanding as to how to connect the complex microscopic proton motion and the macroscopic proton conductivity for the full range of acceptor levels, from diluted acceptors to concentrated solid solutions. Here we show that a combination of density functional theory calculations and kinetic Monte Carlo simulations enables this connection. At low concentrations, acceptors trap protons, which results in a decrease of the average proton mobility. With increasing concentration, however, acceptors form nanoscale percolation pathways with low proton migration energies, which leads to a strong increase of the proton mobility and conductivity. Comparing our simulated proton conductivities with experimental values for yttrium-doped barium zirconate yields excellent agreement. We then predict that ordered dopant structures would not only strongly enhance the proton conductivities, but would also enable one- or two-dimensional proton conduction in barium zirconate. Finally, we show how the properties of other dopants influence the proton conductivity.

Benzyl isothiocyanate attenuates the hydrogen peroxide-induced interleukin-13 expression through glutathione S-transferase P induction in T lymphocytic leukemia cells.

We investigated the effect of benzyl isothiocyanate (BITC) on the hydrogen peroxide-induced gene expression of a T-helper-2 cytokine, interleukin (IL)-13, in T lymphocytic leukemia Jurkat cells. The 24-h pretreatment of BITC significantly inhibited the IL-13 expression enhanced by hydrogen peroxide. Although the BITC pretreatment did not change the enhanced level of the phosphorylated c-Jun N-terminal kinase (JNK), it significantly inhibited the nuclear translocation of c-Jun induced by hydrogen peroxide. BITC also increased the protein expression of glutathione S-transferase (GST) isozymes, GSTP1/2, as well as the total GST activity. A GSTP1/2-specific inhibitor, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX), significantly counteracted the inhibitory effect of BITC on the hydrogen peroxide-enhanced IL-13 upregulation as well as the c-Jun nuclear translocation. Taken together, these results suggested that BITC inhibits the oxidative stress-mediated IL-13 mRNA expression, possibly through interference of the c-Jun phosphorylation by GSTP.

Effects of CO2 adsorption on proton migration on a hydrated ZrO2 surface: an ab initio molecular dynamics study.

Hydration reactions on a carbonate-terminated cubic ZrO2(110) surface were analyzed using ab initio molecular dynamics (AIMD) simulations. After hydration reactions, carbonates were still present on the surface at 500 K. However, these carbonates are very weak conjugate bases and only act as steric hindrance in proton hopping processes between acidic chemisorbed H2O molecules (Zr-OH2) and monodentate hydroxyl groups (Zr-OH-). Similar to a carbonate-free hydrated surface, Zr-OH2, Zr-OH-, and polydentate hydroxyl groups ([double bond splayed left]OH+) were observed, while the ratio of acidic Zr-OH2 was significantly larger than that on the carbonate-free hydrated surface. A thermodynamic discussion and bond property analysis reveal that CO2 adsorption significantly decreases the basicity of surface oxide ions ([double bond splayed left]O), whereas the acidity of Zr-OH2 is not affected. As a result, protons released from [double bond splayed left]OH+ react with Zr-OH- to form Zr-OH2, leading to a deficiency of proton acceptor sites, which decreases the proton conductivity by the hopping mechanism.

Structural and thermal properties of ternary narrow-gap oxide semiconductor; wurtzite-derived ß-CuGaO2.

The crystal structure of the wurtzite-derived ß-CuGaO2 was refined by Rietveld analysis of high-resolution powder diffraction data obtained from synchrotron X-ray radiation. Its structural characteristics are discussed in comparison with the other I-III-VI2 and II-VI oxide semiconductors. The cation and oxygen tetrahedral distortions of the ß-CuGaO2 from an ideal wurtzite structure are small. The direct band-gap nature of the ß-CuGaO2, unlike ß-Ag(Ga,Al)O2, was explained by small cation and oxygen tetrahedral distortions. In terms of the thermal stability, the ß-CuGaO2 irreversibly transforms into delafossite α-CuGaO2 at >460 °C in an Ar atmosphere. The transformation enthalpy was approximately -32 kJ mol(-1), from differential scanning calorimetry. This value is close to the transformation enthalpy of CoO from the metastable zincblende form to the stable rock-salt form. The monovalent copper in ß-CuGaO2 was oxidized to divalent copper in an oxygen atmosphere and transformed into a mixture of CuGa2O4 spinel and CuO at temperatures >350 °C. These thermal properties indicate that ß-CuGaO2 is stable at ≤300 °C in both reducing and oxidizing atmospheres while in its metastable form. Consequently, this material could be of use in optoelectronic devices that do not exceed 300 °C.

Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2 heterointerface probed by an in situ hard x-ray photoemission and soft x-ray absorption spectroscopies.

In situ hard x-ray photoemission spectroscopy (HX-PES) and soft x-ray absorption spectroscopy (SX-XAS) have been employed to investigate a local redox reaction at the carbon/Gd-doped CeO2 (GDC) thin film heterointerface under applied dc bias. In HX-PES, Ce3d and O1s core levels show a parallel chemical shift as large as 3.2 eV, corresponding to the redox window where ionic conductivity is predominant. The window width is equal to the energy gap between donor and acceptor levels of the GDC electrolyte. The Ce M-edge SX-XAS spectra also show a considerable increase of Ce3+ satellite peak intensity, corresponding to electrochemical reduction by oxide ion migration. In addition to the reversible redox reaction, two distinct phenomena by the electrochemical transport of oxide ions are observed as an irreversible reduction of the entire oxide film by O2 evolution from the GDC film to the gas phase, as well as a vigorous precipitation of oxygen gas at the bottom electrode to lift off the GDC film. These in situ spectroscopic observations describe well the electrochemical polarization behavior of a metal/GDC/metal capacitor-like two-electrode cell at room temperature.

X-ray absorption, photoemission spectroscopy, and Raman scattering analysis of amorphous tantalum oxide with a large extent of oxygen nonstoichiometry.

The electronic structure and modification of the local interatomic structure of a reactive sputtered amorphous tantalum oxide (a-TaO(x)) thin film with the variation of oxygen nonstoichiometry, x in a-TaO(x) have been investigated by X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), Raman scattering spectroscopy, and Rutherford back scattering spectroscopy. A parallel chemical shift of Ta4f(7/2) and O1s core levels observed with the variation of x indicates the Fermi level shift by reduction and oxidation in the framework of the rigid band model. Extended X-ray absorption fine structure (EXAFS) suggests both the increase of average coordination number of the first Ta-O shell in polyhedra and a considerable reduction of the average Ta-O bond length with the increase of x. The relative intensity of Raman shift peaks at 670 cm(-1) and 815 cm(-1), corresponding to Ta-O stretching of TaO(6) octahedra and TaO(5) probably with a pyramidal form, respectively, drastically changes between x = 2.47 to 1.86, suggesting the change in the predominant polyhedron from TaO(6) to TaO(5) with a modification in multiplicity of oxygen by the reorganization of the polyhedral network.

Finite size effect of proton-conductivity of amorphous silicate thin films based on mesoscopic fluctuation of glass network.

The finite size effect of proton conductivity of amorphous silicate thin films, a-M(0.1)Si(0.9)O(x) (M = Al, Ga, Hf, Ti, Ta, and La), was investigated. The proton conductivity across films, σ, was measured in dry air by changing the thickness in the range of 10-1000 nm. σ of the films with M = Al, Ga, and Ta was elevated in a power law by decreasing thickness into less than a few hundred nanometers, and the increment was saturated at a thickness of several 10's of nanometers. On the other hand, σ of the films with M = Hf, Ti, and La was not related to the decrease of the thickness in the range of >10 nm. Thickness-dependent conductivity of the former could be numerically simulated by a percolative resistor network model that involves the randomly distributed array of two kinds of resistors R(1) and R(2) (R(1) > R(2)) in the form of a simple cubic-type lattice. High-resolution TEM clarified that a-M(0.1)Si(0.9)O(x) films involved heterogeneous microstructures made of the condensed domain and the surrounding uncondensed matrix due to the fluctuation of glass networks on the nanometer scale. The condensed domain had a wormlike shape with an average length of several 10's of nanometers and performed the role of the proton conduction pathway penetrating through the poorly conducting matrix. It was concluded that the thickness-dependent conductivity could be identical to finite-size scaling of the percolative network of the interconnected domains in the nanometer range.