We report the direct observation of dioxygen molecules physisorbed in the nanochannels of a microporous copper coordination polymer by the MEM (maximum entropy method)/Rietveld method, using in situ high-resolution synchrotron x-ray powder diffraction measurements. The obtained MEM electron density revealed that van der Waals dimers of physisorbed O2 locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. The observed O-O stretching Raman band and magnetic susceptibilities are characteristic of the confined O2 molecules in one-dimensional nanochannels of CPL-1 (coordination polymer 1 with pillared layer structure).

SummaryA cDNA clone, pZmCip1, encoding a maize (Zea mays) cytokinin-inducible protein 1 was isolated utilizing the differential display technique, and studied using the expression of ZmCip1 in nitrogen-starved maize plants. The cloned cDNA contained an open reading frame consisting of 157 amino acids with a predicted molecular mass of 16.7 kDa, which possesses similarity with the response-regulators of bacterial two-component signalling systems. In detached leaves, accumulation of ZmCip1 transcript by t-zeatin was dose-dependent in a range of 10 -9 M to 10 -7 M, and occurred within 30 min after treatment. The effect of t-zeatin was replaceable by isopentenyladenosine or isopentenyl-adenosine-5Ј-monophosphate. Pretreatment of detached leaves with cycloheximide did not inhibit the accumulation of the transcript. In whole plants, ZmCip1 transcript was transiently accumulated exclusively in leaves by supply of nitrate or ammonium ions to the roots, whereas the transcript was not accumulated in detached leaves by supply of the nitrogen nutrients. Both the cytokinin-and nitrate-responsive accumulations of ZmCip1 transcript were accompanied by an increase in the immunotitratable protein. Isopentenyladenosine and/or its phosphorylated form(s) accumulated in roots 2 h after supply of nitrate to plants. These results, taken together, suggest that ZmCip1 is a primary response gene to cytokinins, and that it involves, at least in part, the nitrogen-signal transduction mediated by cytokinin in maize.

Using three-dimensional finite element analysis (3D-FEA), stress distributions in the remaining radicular tooth structure were investigated under the condition of varying diameters of fiber post for fiber post-reinforced composite resin cores (fiber post and core) in maxillary central incisors. Four 3D-FEA models were constructed: (1) fiber post (φ1.2, φ1.4, and φ1.6 mm) and composite resin core; and (2) gold-cast post and core. Maximum stresses in the tooth structure for fiber post and core were higher than that for gold-cast post and core. In the former models, stresses in the tooth structure as well as in the composite resin were slightly reduced with increase in fiber post diameter. These results thus suggested that to reduce stress in the remaining radicular tooth with a large coronal defect, it is recommended to accompany a composite resin core with a fiber post of a large diameter.

Molecules and atoms confined in a nanospace may have properties distinctly different from those of the bulk fluid, owing to the formation of a specific molecular array characteristic of nanospace. In situ synchrotron powder X-ray diffraction measurements have been used to observe confined guest molecules such as N2, O2, Ar, and CH4 in the well-regulated ultramicropore of a copper coordination polymer, 1 ([Cu2(pzdc)2pyz]: pzdc = 2,3-pyrazinedicarboxylate and pyz = pyrazine). The obtained crystal structures indicate that guest molecules are confined in a linear fashion to form crystalline-like regular ordered arrays, in contrast to the situation in the gas and liquid state, even at temperatures above the boiling point, and the ordered arrays are characteristic of the kind of gas molecule and the geometrical and potential properties of the ultramicropore of 1.

We investigated the effects of Cr and Nb doping on the metal-insulator transition (MIT) of single-oriented VO 2 films deposited on Al 2 O 3 substrates. The MIT temperature (T MI ) increased with trivalent Cr doping, whereas it decreased with pentavalent Nb doping. The temperature coefficient of resistance (TCR) and the thermal hysteresis width of the MIT (ΔT MI ) were suppressed by Cr and Nb doping, and Nb doping was about twice as effective as Cr doping for decreasing TCR and ΔT MI . We found that the maximum TCR and ΔT MI for the doped VO 2 films have a correlation with the lattice constant irrespective of doping elements, suggesting that the lattice deformation caused by metal-ion doping is involved in the decreases in TCR and ΔT MI . There is also an apparent correlation between the maximum TCR and ΔT MI for the doped VO 2 films. The present findings suggest that the combination of metal-ion doping with other techniques such as strain control is required to achieve nonhysteretic MIT with a large TCR in VO 2 films.