Heterosubstituted allylic carbanion based stereocontrol,regio- and stereo- selective reaction of O and S substituted allylic carbanions with aldehydes

Regio- and diastereoselective reaction of oxygen and sulfur substituted allylic carbanions with aldehydes is described. Either threo or erythro isomer can be obtained predominantly or exclusively by merely choosing an additive.     

Brightening of triplet dark excitons by atomic hydrogen adsorption in single-walled carbon nanotubes observed by photoluminescence spectroscopy

Adsorption and desorption of atomic hydrogen on single-walled carbon nanotubes were observed by photoluminescence spectroscopy. A satellite peak appeared at the lower energy side of the E11 photoluminescence emission peak after exposure to atomic hydrogen and then disappeared after annealing at 300?°C in vacuum. The energy difference between the satellite peak and E11 peak was 40-80 meV, depending on the tube diameter. The satellite peak was attributed to the triplet dark exciton that became optically active because of the effectively enhanced spin-orbit interaction induced by adsorbed hydrogen atoms.     

Rate enhancement of Diels-Alder reactions in aqueous perfluorinated emulsions

A marked acceleration property for the Diels-Alder reaction was observed in an aqueous micellar system composed of perfluorohexane and lithium perfluorooctanesulfonate. The reaction rate increased with the concentration of the equimolar mixture of PFH and LiFOS, and the rate in 500 mM PFH and 500 mM LiFOS was about 100-fold greater than that in water without the fluorous field. After completion of the reaction, the products were simply extracted from the aqueous reaction mixture using n-hexane. [reaction: see text].     

CFD-PBM approach for the gas-liquid flow in a nanobubble generator with honeycomb structure

In recent years, nanobubble technologies have drawn great attention due to their wide applications in many fields of science and technology. From previous studies, a kind of honeycomb structure for high efficiency nanobubble generation has been proposed. In this paper, the numerical simulations of bubbly flow in the honeycomb structure were performed by using a computational fluid dynamics–population balance model (CFD-PBM) coupled model. The numerical model was based on the Eulerian multiphase model and the population balance model (PBM) was used to calculate the bubble size distribution. The bubble size distributions in the honeycomb structure under different work conditions were predicted. Two different drag force models (Schiller-Naumann model and Tomiyama model) and two different aggregation models (Luo model and turbulent aggregation model) were investigated. Both two drag models gave similar prediction of bubble number density distribution at the outlet. The results obtained from Luo model had better reflection of the trend of number density distribution. The turbulence dissipation rate ε can be used to evaluate the nanobubble generating ability. The water tank was not included in the CFD model in this work. The bubbles in the water tank should be studied in the future.     

Effect of discrete track medium at high areal density

The degradation of SNR caused by the higher uniaxial crystalline anisotropy field (Hk) of medium and small write fields of narrower write width is one of the problems for achieving higher areal density. The SNR dependence on Hk of a medium with different write fields of head using the discrete track medium (DTM) is investigated by using micromagnetics simulation. As a result, the curves of SNR as a function of Hk have peak values. In DTM, the peak values of SNR are almost constant at any Hk of the medium and different write fields. Higher SNR is realized even at low Hk and small write field in DTM.     

Heavily Doped and Highly Conductive Hierarchical Nanoporous Graphene for Electrochemical Hydrogen Production

Heavy chemical doping and high electrical conductivity are two key factors for metal‐free graphene electrocatalysts to realize superior catalytic performance toward hydrogen evolution. However, heavy chemical doping usually leads to the reduction of electrical conductivity because the catalytically active dopants give rise to additional electron scattering and hence increased electrical resistance. A hierarchical nanoporous graphene, which is comprised of heavily chemical doped domains and a highly conductive pure graphene substrate, is reported. The hierarchical nanoporous graphene can host a remarkably high concentration of N and S dopants up to 9.0 at % without sacrificing the excellent electrical conductivity of graphene. The combination of heavy chemical doping and high conductivity results in high catalytic activity toward electrochemical hydrogen production. This study has an important implication in developing multi‐functional electrocatalysts by 3D nanoarchitecture design.     

Tetrahedral Oligothiophenes; Synthesis,X‐ray Analysis,and Optoelectronic Properties of Highly Symmetrical, 3D‐Branched Oligothiophenes

Tetrakis(bithienyl)methane and tetrakis(terthienyl)methane have been synthesized from tetrakis(2‐thienyl)methane by use of Suzuki–Miyaura coupling as a key reaction. Their trimethylsilyl (TMS) derivatives are also synthesized. X‐ray analysis reveals that each oligothiophene moiety tends to adopt anti‐conformations and show relatively small torsion angles between the adjacent thiophene rings. While the longest absorption maxima of these tetrakis(oligothienyl)methanes exhibit only a slight bathochromic shift compared to the corresponding linear oligothiophene derivative, tetrakis(bithienyl)methane and its TMS derivative exhibit an appreciable red‐shift in their fluorescence spectra. The intramolecular interaction between thienyl groups of tetrakis(2‐thienyl)methane is supported by DFT calculation.     

Crystal structure of the new FeSe(1-x) superconductor

The newly discovered superconductor FeSe(1-x) (x approximately 0.08, T(c)(onset) approximately 13.5 K at ambient pressure rising to 27 K at 1.48 GPa) exhibits a structural phase transition from tetragonal to orthorhombic below 70 K at ambient pressure-the crystal structure in the superconducting state shows remarkable similarities to that of the REFeAsO(1-x)F(x) (RE = rare earth) superconductors.     

Behaviors of chemical elements in the atmosphere,Kawasaki, Japan

A total of 19 elements in the samples of atmospheric deposition collected in Kawasaki, Japan, were determined by neutron activation analysis, ICPAES and flame photometry. The amounts of soil dust depositions were larger in springs and those of Sb and Zn depositions were larger in summers than in the other seasons. The values of the enrichment factors were higher for Sb and Zn than for the other elements determined throughout the sampling period. A factor analysis showed that the two elements were characterized as industrial components. Rubber products like tires that contain noncombustibles and rubber accelerators were a possible origin of high concentrations of Sb and Zn in the present samples.     

Structure activity relationships of quinoxalin-2-one derivatives as platelet-derived growth factor-beta receptor (PDGFbeta R) inhibitors, derived from molecular modeling

We previously reported a quinoxalin-2-one compound (Compound 1) that had inhibitory activity equivalent to existing platelet-derived growth factor-beta receptor (PDGFbeta R) inhibitors. Lead optimization of Compound 1 to increase its activity and selectivity, using structural information regarding PDGFbeta R-ligand interactions, is urgently needed. Here we present models of the PDGFbeta R kinase domain complexed with quinoxalin-2-one derivatives. The models were constructed using comparative modeling, molecular dynamics (MD) and ligand docking. In particular, conformations derived from MD, and ligand binding site information presented by alpha-spheres in the pre-docking processing, allowed us to identify optimal protein structures for docking of target ligands. By carrying out molecular modeling and MD of PDGFbeta R in its inactive state, we obtained two structural models having good Compound 1 binding potentials. In order to distinguish the optimal candidate, we evaluated the structural activity relationships (SAR) between the ligand-binding free energies and inhibitory activity values (IC50 values) for available quinoxalin-2-one derivatives. Consequently, a final model with a high SAR was identified. This model included a molecular interaction between the hydrophobic pocket behind the ATP binding site and the substitution region of the quinoxalin-2-one derivatives. These findings should prove useful in lead optimization of quinoxalin-2-one derivatives as PDGFb R inhibitors.