Chiral bis(oxazoline)-copper complex catalyzed Diels-Alder reaction in ionic liquids: remarkable reactivity and selectivity enhancement, and efficient recycling of the catalyst

Ionic liquid was found to be an excellent medium for asymmetric Diels-Alder reaction catalyzed by chiral bis(oxazoline)-copper complex. The reactivity and selectivity of reactions were highly dependent upon the property of the ionic liquids. Reactions of β-substituted acryloyl dienophiles in [Bmim]SbF₆ at ambient temperature provided remarkably enhanced reactivity and stereoselectivity compared to homogeneous reactions in non-ionic liquid solvent at −78 °C. Due to the increased reactivity, the amount of metal catalyst could be reduced down to 0.6 mol % without any significant selectivity compromise. Additionally, recycling of the ligand-metal complex was achieved efficiently up to 18 times.     

Pervaporation separation of water-acetic acid mixtures through poly(vinyl alcohol) membranes crosslinked with glutaraldehyde

Poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by a solution method for the pervaporation separation of acetic acid-water mixtures. In the solution method, dry PVA films were crosslinked by immersion for 2 days at 40°C in reaction solutions which contained different contents of GA, acetone and a catalyst, HCl. In order to fabricate the crosslinked PVA membranes which were stable in aqueous solutions, acetone was used as reaction medium in stead of aqueous inorganic salt solutions which have been commonly used in reaction solution for PVA crosslinking reaction. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of GA was characterized by IR spectroscopy. Swelling measurements were carried out in both water and acetic acid to investigate the swelling behavior of the membranes. The swelling behaviour of a membrane fabricated at different GA content in a reaction solution was dependent on crosslinking density and chemical functional groups created as a result of the reaction between PVA and GA, such as the acetal group, ether linkage and unreacted pendent aldehydes in PVA. The pervaporation separation of acetic acid-water mixtures was performed over a range of 70–90 wt% acetic acid in the feed at temperatures varying from 35 to 50°C to examine the separation performances of the PVA membranes. Permeation behaviour through the membranes was analyzed by using pervaporation activation energies which had been calculated from the Arrhenius plots of permeation rates.     

Plasma Characteristics and Antenna Electrical Characteristics of an Internal Linear Inductively Coupled Plasma Source with a Multi-Polar Magnetic Field

The development of a large-area plasma source with high density plasmas is desired for a variety of plasma processes from microelectronics fabrication to flat panel display device fabrication. In this study, a novel internal-type linear inductive antenna referred to as “double comb-type antenna” was used for a large-area plasma source with the substrate area of 880 mm × 660 mm and the effect of plasma confinement by applying multi-polar magnetic field was investigated. High density plasmas on the order of 3.2 × 10¹¹ cm^?3 which is 50% higher than that obtained for the source without the magnetic field could be obtained at the pressure of 15 mTorr Ar and at the inductive power of 5,000 W with good plasma stability. The plasma uniformity <3% could be also obtained within the substrate area. When SiO₂ film was etched using the double comb-type antenna, the average etch rate of about 2,100 Å/min could be obtained with the etch uniformity of 5.4% on the substrate area using 15 mTorr SF₆, 5,000 W of rf power, and ?34 V of dc-bias voltage. The higher plasma density with an excellent uniformity and a lower rf antenna voltage obtained by the application of the magnetic field are related to the electron confinement in a direction normal to the antenna line.     

Inhibition of LPS-induced cyclooxygenase 2 and nitric oxide production by transduced PEP-1-PTEN fusion protein in Raw 264.7 macrophage cells

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor. Although it is well known to have various physiological roles in cancer, its inhibitory effect on inflammation remains poorly understood. In the present study, a human PTEN gene was fused with PEP-1 peptide in a bacterial expression vector to produce a genetic in-frame PEP-1-PTEN fusion protein. The expressed and purified PEP-1-PTEN fusion protein were transduced efficiently into macrophage Raw 264.7 cells in a time- and dose-dependent manner when added exogenously in culture media. Once inside the cells, the transduced PEP-1-PTEN protein was stable for 24 h. Transduced PEP-1-PTEN fusion protein inhibited the LPS-induced cyclooxygenase 2 (COX-2) and iNOS expression levels in a dose-dependent manner. Furthermore, transduced PEP-1-PTEN fusion protein inhibited the activation of NF-κB induced by LPS. These results suggest that the PEP-1-PTEN fusion protein can be used in protein therapy for inflammatory disorders.     

Atomic-scale phase coexistence and fluctuation at the quasi-one-dimensional metal-insulator transition

Scanning tunneling microscopy of a quasi-one-dimensional (1D) metal-insulator transition in an In nanowire array on the Si(111) surface reveals unprecedented details in the transition dynamics. The transition proceeds in microscopic first order, namely, through the domain-by-domain conversion at the nanoscale, from the metallic to the insulating phase or vice versa. The definition of domains and their effective transition temperatures (Tc) are strongly correlated with the distribution of defects. Below Tc, the condensation and the fluctuation of 1D charge density waves are observed within the isolated metallic domains, as well as at the domain boundaries. The appearance of such isolated condensates suggests a strong intrawire coupling: a manifestation of the 1D nature of the critical fluctuation, as well as the origin of the first-order transition.     

Impregnation of tungstophosphoric acid on poly(methacrylamide-co-methyl methacrylate) and its acid catalytic activity in TMB alkylation

A poly(methacrylamide-co-methylmethacrylate) (abbreviated PMAA-MMA) polymer support was studied for supporting a heteropolyacid (tungstophosphoric acid, H₃PW₁₂O₄₀) with its surface positively charged in the polymerization step. PMAA-MMA supports could be obtained in a porous form by eliminating template reagent molecules (benzylmalonic acid) combined with properly selected monomer (methacrylamide). The amount of amine groups in PMAA-MMA directly determined the amount of H₃PW₁₂O₄₀ impregnated, because the amine groups induced a positive charge on the PMAA-MMA surface. Finally, H₃PW₁₂O₄₀/PMAA-MMA showed better acid catalytic activities than unsupported H₃PW₁₂O₄₀ in alkylation of 1,3,5-trimethylbenzene with cyclohexene, which confirmed that PMAA-MMA supported H₃PW₁₂O₄₀ effectively.