Electrical conductivity of alternate layer deposition of pentancene and tetracene superlattices

Superlattice thin films of pentacene (PEN) and tetracene (TET) were fabricated by alternate layer deposition using the sublimation method. The film showed a highly crystalline structure that was due to the strong aggregation tendency of polyacene compounds to form a layered monomolecular column structure. The crystalline structure of the films was drastically changed by doping with iodine. The doped films showed a highly ordered structure where an iodine monomelecular layer was intercalated between molecular columns of acene compounds in both PEN and TET. The doped films exhibited a large lateral conductivity of 10 Ω^?1 cm^?1 and attained giant anisotropy above 10¹². This indicated that molecular columns of TET remained insulating upon doping to form a perfect two-dimensional conductor in the superlattice thin films.     

Generic conformally flat hypersurfaces and surfaces in 3-sphere

Science China Mathematics - The aim of this paper is to verify that the study of generic conformally flat hypersurfaces in 4-dimensional space forms is reduced to a surface theory in the standard...     

Measurement of the time structure of a coherent synchrotron radiation burst in NewSUBARU

The time structure of a burst of coherent synchrotron radiation (CSR) emitted from a high-peak-current beam in the electron storage ring NewSUBARU has been investigated. The source of this CSR burst is fine time structure in a bunch produced by longitudinal beam instability. This burst is unstable but very easy to obtain, so it can be used for some experimental applications with appropriate averaging of data. With an averaging period of 10 ms, the fluctuation of the integrated power was about 10%.     

The hydrogel containing a novel vesicle‐like soft crosslinker,a “trilayered” polymeric micelle,shows characteristic rheological properties

We have developed a novel hydrogel that is formed from a crosslinkable trilayered polymeric micelle and a polyamine for the sustained release of hydrophilic compounds. This hydrogel is quite unique because the vesicle‐like structure of the trilayered polymeric micelle acts as not only a crosslinker of the hydrogel but also a container of hydrophilic compounds. The hydrogel is rapidly formed by mixing both the trilayered polymeric micelle solution and the polyamine solution. The gelation property of the hydrogel, such as the storage modulus, can be changed by tuning the molecular weights, concentrations, and pH of the dissolving solvent of the hydrogel's constituent components. Furthermore, it is clarified that the structural difference among the micelles acting as crosslinkers affects the gelation property of the hydrogel. Amazingly, the hydrogel that is formed from the trilayered polymeric micelles possessing a vesicle‐like flexible structure exhibits a higher storage modulus than the hydrogel that is formed from the bilayered polymeric micelles possessing a highly packed, hard structure. Our results demonstrates that a microscopic structural difference of crosslinkers can induce a macroscopic (and, in some cases, an interesting and unexpected) change in the properties of the resulting hydrogels. For medical applications, the hydrogel proposed in the present article can encapsulate the hydrophilic compounds so that the hydrogel can be available as the material for their sustained release. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Total Synthesis of Marine Eicosanoid (−)‐Hybridalactone

(?)‐Hybridalactone ( 1 ) is a marine eicosanoid isolated from the red alga Laurencia hybrida. This natural product contains cyclopropane, cyclopentane, 13‐membered macrolactone and epoxide ring systems incorporating seven stereogenic centers. Moreover, this compound has an acid‐labile skipped Z,Z‐diene motif. In this paper, we report on the total synthesis of (?)‐hybridalactone ( 1 ). The unique eicosanoid (?)‐hybridalactone ( 1 ) was synthesized starting from optically active γ‐butyrolactone 2 in a linear sequence comprising 21 steps with an overall yield of 21.9 %. A key step in the synthesis of (?)‐hybridalactone ( 1 ) is the methyl phenylsulfonylacetate‐mediated one‐pot synthesis of the cis‐cyclopropane‐γ‐lactone derivative. This reaction provided an efficient and stereoselective access to cis‐cyclopropane‐γ‐lactone 12 . Further elaboration of the latter compounds through desulfonylation, epoxidation, oxidation, Wittig olefination and Shiina macrolactonization afforded (?)‐hybridalactone.     

Cyclopropane-based stereochemical diversity-oriented conformational restriction strategy: histamine H3 and/or H4 receptor ligands with the 2,3-methanobutane backbone

The stereochemical diversity-oriented conformational restriction strategy can be an efficient method for developing specific ligands for drug target proteins. To develop potent histamine H(3) and/or H(4) receptor ligands, a series of conformationally restricted analogs of histamine with a chiral trans- or cis-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane structure was designed based on this strategy. These stereochemically diverse compounds were synthesized from previously developed versatile chiral cyclopropane units. Among these analogs, a trans-cyclopropane-type compound, (2S,3R)-4-(4-chlorobenzylamino)-2,3-methano-1-(1H-imidazol-4-yl)butane (5b), has remarkable antagonistic activity to both the H(3) (K(i) = 4.4 nM) and H(4) (K(i) = 5.5 nM) receptors, and a cis-cyclopropane-type compound, (2R,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (6a), is a potent and selective H(3) receptor partial agonist (K(i) = 5.4 nM). Although (2S,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (5a) does not have a hydrophobic group which the usual H(3) receptor antagonists have, it was found to be a potent H(3) receptor antagonist (K(i) = 20.1 nM). Thus, a variety of compounds with different pharmacological properties depending on the cyclopropane backbones and also on the side-chain functional groups were identified. In addition to the previously used 1,2-methanobutane backbone, the 2,3-methanobutane backbone also worked effectively as a cyclopropane-based conformational restriction structure. Therefore, the combination of these two cyclopropane backbones increases the stereochemical and three-dimensional diversity of compounds in this strategy, which can provide a variety of useful compounds with different pharmacological properties.     

A novel crystal polymorph of volborthite,Cu3V2O7(OH)2·2H2O

A new polymorph of volborthite [tricopper(II) divanadium(V) heptaoxide dihydroxide dihydrate], Cu₃V₂O₇(OH)₂·2H₂O, has been discovered in a single crystal prepared by hydrothermal synthesis. X‐ray analysis reveals that the monoclinic structure has the space group C2/c at room temperature, which is different from that of the previously reported C2/m structure. Both structures have Cu₃O₆(OH)₂ layers composed of edge‐sharing CuO₄(OH)₂ octahedra, with V₂O₇ pillars and water molecules between the layers. The Cu atoms occupy two and three independent crystallographic sites in the C2/m and C2/c structures, respectively, likely giving rise to different magnetic interactions between Cu^II spins in the kagome lattices embedded in the Cu₃O₆(OH)₂ layers.