Local and global gauge symmetries in temporal gauge

In the temporal gauge formalism, in order to make a distinction between the global limit of local gauge transformations and global ones a non-local operator, θ, is introduced. It is claimed that what kind of θ is used is equivalent to what kind of gauge-fixing schemes is chosen. Along this idea, in non-abelian theories the coulomb, axial and unitary gauges have been investigated. In the unitary gauge spontaneous breakdown of global gauge symmetry has been found to be reduced to a problem of the boundary condition for the Higgs field and the occurrence of symmetry breaking has been concluded.     

An Ethylenediamine‐based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials

Polyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine‐tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di‐protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET‐Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET‐Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.     

Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

The two‐electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na₂S₂O₄ gave a corresponding isophlorin ( Iph ) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetramethylated Iph . Further reduction of Iph proceeded to form an unprecedented four‐electron‐reduced porphyrin ( IphH₂ ), which was fully characterized by spectroscopic and X‐ray crystallographic analysis. IphH₂ , with a unique conformation, could be oxidized to reproduce the starting porphyrin, resulting in a proton‐coupled four‐electron reversible redox system.     

Intramolecular construction of trifluoromethyl group by the palladium-catalyzed reaction of 2,3,3-trifluoroallylic carbonates with O-nucleophiles

The synthesis of the trifluoromethyl group containing enol ethers by the palladium-catalyzed intermolecular reaction of 2,3,3-trifluoroallylic carbonates with oxygen nucleophiles was accomplished. The reaction proceeds through the intermolecular attack of oxygen nucleophiles on the C-2 carbon atom of the allylic unit, and the intramolecular fluorine atom shift from the C-2 position to the C-3 position. The reactions with several types of alcohols and phenols proceeded smoothly, and afforded the corresponding trifluoromethyl group containing enol ethers in good to high yields.     

NMR characterization of α- and β-mannopyranurono-2,6-lactones

Determining the stereochemistry at the anomeric position of glycosides is imperative in chemical synthesis. As for 1,2-cis-β-glycosides such as β-mannosides, ¹³C-¹H coupling constants, ¹J_CHs, are conventionally used when glycosides are in an ordinary chair conformation. In this work, we searched for appropriate criteria to determine the stereochemistry of products in a recently developed glycosylation reaction using 2,6-lactones. As a result, we found that α-glycosides exhibited vicinal coupling constants of around 3.0?Hz?at the anomeric proton, as well as a long-range coupling between protons at C-1 and C-5, whereas β-glycosides had coupling constants of 1.2?Hz?at most. These figures are expected to be useful for future assignments. In addition, the observations obtained from this study revealed the conformation of glycosides with a 2,6-lactone moiety.     

Double amination of 2-fluoroallylic acetates by palladium catalysts

We accomplished the palladium-catalyzed double substitution of 2-haloallylic acetates with nitrogen nucleophiles. During the Pd₂(dba)₃/DPPE-catalyzed reaction of 2-fluoroallylic acetates with N-substituted-p-toluenesulfonamide, two equivalents of nitrogen nucleophiles were introduced to the allyl unit with a Z-selectivity through the carbon–fluorine bond cleavage. We further demonstrated the reaction of 2-chloroallylic acetates, and succeeded in obtaining the same doubly-substituted products in good yields with a high Z-selectivity.     

High quality a-Si film produced by horizontal plasma furnace

A series of investigation on the a-Si film quality in a p-i-n junction has been made by employing the separated three chamber system of horizontal plasma mode. A clear improvement of film quality has been experimentally verified in a-Si films prepared by this system as compared with those by the single chamber system. On the basis of these investigation, a-SiC/a-Si/μc-Si heterojunction solar cells having more than 9% conversion efficiency have been developed.