Stereoselective synthesis of trans olefins by the reaction of Wittig reagents with selenium. Formation of selenocarbonyl compounds.

Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction.     

Conformational control of benzyl-o-carboranylbenzene derivatives and molecular encapsulation of acetone in the dynamically formed space of 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene

A 1,3,5-substituted benzene platform has been widely used in the fields of supramolecular chemistry and molecular recognition. Here, we show that 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene 6 exhibits solvent-dependent conformation in the crystalline state. Recrystallization from dichloromethane-n-pentane gave the anti conformation 6-anti, while recrystallization from methanol-acetone gave the syn conformation 6-syn, in which the three benzyl-o-carboranyl moieties are located to one side of the central benzene ring. Interestingly, one acetone molecule is captured in the π-rich space of 6-syn and two complexes facing each other encapsulate two acetone molecules in a π-rich container formed by the eight benzene rings. The inclusion involves several weak interactions, that is, T-shaped C-H···π interactions, and C-H···O and C-H···π interactions. Two C-H···O interactions involving benzylic C-H hydrogens activated by the electron-withdrawing character of the o-carborane cage and the oxygen atom of the acetone seem to be the most important. DFT calculations indicate that the binding energy for entrapment of acetone is 6.6 kcal/mol. Inclusion of acetone is achieved through not only multiple C-H···O interactions but also a number of C-H···π interactions. The third benzyl-o-carborane moiety is fixed in the syn conformation by intramolecular and intermolecular C-H···π interactions.     

Synthesis of a highly luminescent three-dimensional pyrene dye based on the spirobifluorene skeleton

We have synthesized a highly luminescent (log e > 5.0, F > 0.9) pyrene dye based on a spirobifluorene skeleton [2,2',7,7'-tetrakis(7-tert-butyl-1-pyrenyl)-9,9'-spirobi[9H-fluorene; 4-PySBF]. The use of spirobifluorene prevents fluorescence quenching by intramolecular energy transfer and/or electron transfer among the chromophores in the excited state. The emission spectra of 4-PySBF exhibited a red shift of 20 nm in comparison to a model compound [9,9'-dioctyl-2,7-bis(7-tert-butyl-1-pyrenyl)-9H-fluorene; 2-PyF], but its UV-Vis spectrum remained unchanged.     

Bending properties and cell wall structure of alkali-treated wood

Bending tests and X-ray diffraction studies were conducted on oven-dried wood samples (Picea jezoensis Carr.) treated with various concentrations of aqueous NaOH solution to investigate the influence of alkali treatment on the longitudinal contraction, bending properties, and cellulose structure. The length of the wood samples decreased and the density increased at NaOH concentrations greater than 10%. The Young’s modulus and the specific Young’s modulus decreased and the strain at yield increased for the same concentration range. However, the stress at yield was almost constant for all concentration ranges. X-ray diffraction analysis showed that lattice transformation from cellulose I to cellulose II did not occur during alkali treatment and the crystallinity index decreased at NaOH concentrations greater than 10%. The crystallinity index was linearly correlated with the changes in longitudinal contraction and the bending properties, which indicates that the increase in the proportion of amorphous components of the cellulose influences the longitudinal contraction and the bending properties of wood samples during alkali treatment.     

Comparison of the characteristics of cellulose microfibril aggregates isolated from fiber and parenchyma cells of Moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens)</Emphasis>

This study examined the relationship between the functions of plant cells and the characteristics of cellulose microfibril aggregates in the cell walls. For this purpose, the mature bamboo (Phyllostachys pubescens) culm was separated into fiber and parenchyma cells, and then the morphological and physical properties of the cellulose microfibril aggregates isolated from both cells were compared. SEM observations revealed that both fiber and parenchyma cells consist of similar microfibril aggregates approximately 15–20 nm in width. Moreover, X-ray analysis and the tensile tests of the sheets prepared from the microfibril aggregates showed that the cellulose microfibrils isolated from fiber and parenchyma cells had almost the same cellulose crystallinity and longitudinal Young’s modulus in the dry state. These results suggest that all the cellulose microfibrils synthesized in the same individual exhibit the same characteristics in the dry state regardless of cell function.     

A maximal domain for strategy-proof and no-vetoer rules in the multi-object choice model

Following “Barberà et al. (1991, Econometrica 59:595–609)”, we study rules (or social choice functions) through which agents select a subset from a set of objects. We investigate domains on which there exist nontrivial strategy-proof rules. We establish that the set of separable preferences is a maximal domain for the existence of rules satisfying strategy-proofness and no-vetoer.     

From hierarchies to well-foundedness

We highlight that the connection of well-foundedness and recursive definitions is more than just convenience. While the consequences of making well-foundedness a sufficient condition for the existence of hierarchies (of various complexity) have been extensively studied, we point out that (if parameters are allowed) well-foundedness is a necessary condition for the existence of hierarchies e.g. that even in an intuitionistic setting \({(\Pi_1^0-\mathsf{CA}_0)_\alpha \vdash \mathsf{wf}(\alpha)\, {\rm where}\, (\Pi_1^0-\mathsf{CA}_0)_\alpha}\) stands for the iteration of \({\Pi^0_1}\) comprehension (with parameters) along some ordinal \({\alpha}\) and \({\mathsf{wf}(\alpha)}\) stands for the well-foundedness of \({\alpha}\) .