Role of intracellular contents to facilitate supercooling capability in beech (Fagus crenata) xylem parenchyma cells

In order to find the possible role of intracellular contents in facilitating the supercooling capability of xylem parenchyma cells, changes in the temperature of supercooling levels were compared before and after the release of intracellular substances from beech xylem parenchyma cells by DTA. Various methods were employed to release intracellular substances from xylem parenchyma cells and all resulted in a reduction of supercooling ability. It was concluded that the reduction of supercooling ability primarily resulted from changes of intracellular conditions, including the release of intracellular contents or their mixing with extracellular solutions, rather than due to changes of cell wall structures. It is therefore suggested that any unidentified intracellular contents may function to facilitate supercooling capability in xylem parenchyma cells.     

Structural and Electrochemical Studies of Dicupric Wells–Dawson Sandwich-Type Complexes

A new Wells–Dawson sandwich polyoxometalate, -[(NaOH₂)₂(Cu^II)₂ (P₂W₁₅O₅₆)₂]¹⁸⁻ (2P), has been obtained in good yield by the dissolution of solid -Na₁₂[P₂W₁₅O₅₆]·18H₂O in an aqueous solution of Cu(II) and L-glutamic acid at pH 10. The arsenic analogue, -[(NaOH₂)₂(Cu^II)₂(As₂W₁₅O₅₆)₂]¹⁸⁻ (2As), is likewise prepared by using Na₁₂[As₂W₁₅O₅₆]·21H₂O instead of Na₁₂[P₂W₁₅O₅₆]·18H₂O. Diffraction quality crystals of both 2P and 2As were obtained by slow evaporation in air over several days. The X-ray structures of 2P and 2As reveal that two Cu(II) atoms are sandwiched between two -[P₂W₁₅O₅₆]¹²⁻ or two -[As₂W₁₅O₅₆]¹²⁻ ligands, respectively, while the other two positions of the central belt unit are occupied by two Na⁺ cations. Higher yields of 2As can be obtained by mixing CuCl₂·2H₂O and [Na₁₂As₂W₁₅O₅₆]·21H₂O in acetate buffer. The electrochemistry of 2P and 2As is characterized by cyclic voltammograms in which the reduction of the Cu(II) centers is close to the redox pattern of the W-centers. The two Cu(II)-centers are simultaneously reduced to Cu(0); the separate steps could not be resolved for the individual Cu(II) centers. Complexes 2P and 2As constitute the second example, after -[(NaOH₂)₂(Fe^III)₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (1P) and -[(NaOH₂)₂(Fe^III)₂(As₂W₁₅O₅₆)₂]¹⁶⁻ (1As), of a transition-metal-substituted sandwich polyoxometalate containing two electroactive d-electron metals.Dedicated in honor of Professor Michael T. Pope on the occasion of his retirement.     

Photoresponsive molecular wires of FeII triazole complexes in organic media and light-induced morphological transformations

A lipophilic linear FeII 1,2,4-triazole complex containing azobenzene chromophores forms molecular wires in organic solvents; photoisomerization of azobenzene units induced morphological changes that lead to reversible, macroscopic gel-to-sol transition phenomena.     

Excited state behaviors of the dodecamolybdocerate (IV) anion: (NH4)6H2(CeMo12O42).9H2O

The polyoxometalate (NH(4))(6)H(2)(CeMo(12)O(42)).9H(2)O (abbreviated as Ce(IV)Mo(12)) was synthesized, and its Ce(III) form was obtained by exhaustive electrochemical reduction. Both forms are fairly stable in pH 0.0 media. This stability decreases when the pH increases. The Ce(IV) species, in which the central metal is in the f(0) electronic configuration, is found to fluoresce, a feature that is only straightforwardly explained with the Ce(III) state. As the results of a series of experiments converge to confirm the stability of Ce(IV)Mo(12) in the media studied, a suggested rationale is that the emission originates from a higher-energy ligand-to-metal charge transfer and follows a scheme which is ultimately equivalent to the classical metal-centered fluorescence of Ce(III). Detailed studies of the influences of pH and ionic strength were carried out and suggest that protonated and/or ion-paired assemblies are the fluorescent species. A reproducible increase of the fluorescence intensity of Ce(IV)Mo(12) as a function of time was also observed.     

The Dirac delta function in two settings of Reverse Mathematics

The program of Reverse Mathematics (Simpson 2009) has provided us with the insight that most theorems of ordinary mathematics are either equivalent to one of a select few logical principles, or provable in a weak base theory. In this paper, we study the properties of the Dirac delta function (Dirac 1927; Schwartz 1951) in two settings of Reverse Mathematics. In particular, we consider the Dirac Delta Theorem, which formalizes the well-known property ${\int_\mathbb{R}f(x)\delta(x)\,dx=f(0)}$ of the Dirac delta function. We show that the Dirac Delta Theorem is equivalent to weak K?nig’s Lemma (see Yu and Simpson in Arch Math Log 30(3):171–180, 1990) in classical Reverse Mathematics. This further validates the status of WWKL₀ as one of the ‘Big’ systems of Reverse Mathematics. In the context of ERNA’s Reverse Mathematics (Sanders in J Symb Log 76(2):637–664, 2011), we show that the Dirac Delta Theorem is equivalent to the Universal Transfer Principle. Since the Universal Transfer Principle corresponds to WKL, it seems that, in ERNA’s Reverse Mathematics, the principles corresponding to WKL and WWKL coincide. Hence, ERNA’s Reverse Mathematics is actually coarser than classical Reverse Mathematics, although the base theory has lower first-order strength.     

Experimental study on the reaction pathway of α‐haloacetophenones with nucleophiles: direct substitution or carbonyl addition?

The reaction of PhCOCH₂Cl with OH^– gave the expected α‐substituted alcohol (PhCOCH₂OH) in addition to three dimer products. To clarify whether the substitution product is formed by direct S_N2 or via carbonyl addition, the reaction of PhCOCH₂Cl and OMe^– was examined. The reaction gave two products, PhCOCH₂OH as the major product after acid hydrolysis and PhCOCH₂OMe as the minor product. An electron‐withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was concluded that the alcohol was formed via carbonyl addition‐epoxidation route, whereas the ether was formed by the direct substitution route. Copyright © 2012 John Wiley & Sons, Ltd.     

Phase diagram and oxygen annealing effect of FeTe1−xSex iron-based superconductor

Phase diagrams of as-grown and O₂-annealed FeTe_1?xSe_x determined from magnetic susceptibility measurement were obtained. For as-grown samples, the antiferromagnetic order was fully suppressed in the range region x≥0.15, and weak superconductivity appeared when x≥0.1. Beginning at x=0.5, weak superconductivity was found to evolve into bulk superconductivity. Interestingly, for O₂-annealed samples, complete suppression of magnetic order and the occurrence of bulk superconductivity were observed when x≥0.1. We found that O₂-annealing induces bulk superconductivity for FeTe_1?xSe_x. Oxygen probably plays a key role in the suppression of the magnetic order and the appearance of bulk superconductivity.     

Asymmetric epoxidation catalyzed by novel azacrown ether-type chiral quaternary ammonium salts under phase-transfer catalytic conditions

Asymmetric epoxidation of (E)-chalcone with alkaline hydrogen peroxide by novel chiral phase-transfer catalysts (chiral PTCs) with quaternary ammonium salts of azacrown ether proceeded in high yield and good enantioselectivity. Remarkably, this reaction depended on the length of the carbon chain on the nitrogen atom with the chiral PTCs and on the bulk of the base.