Cascade radical reactions catalyzed by a Pd/light system: cyclizative multiple carbonylation of 4-alkenyl iodides

Cascade reactions of 4-alkenyl iodides, involving a carbonylation-cyclization-carbonylation sequence, were accomplished by a hnu/Pd system. The stereochemical outcomes suggest that radical carbonylation and subsequent acyl radical cyclization may be involved in this reaction.     

High conversion of olefins to cis-diols by non-heme iron catalysts and H2O2

Efficient and highly stereoselective oxidation of olefins to cis-diols as the major product is obtained by using biomimetic non-heme FeII catalysts in combination with H2O2.     

Indium-incorporation-induced transformation of optical, photoluminescence and lasing properties of InGaN epilayers

A comparative combined study of photoluminescence (PL), PL kinetics, stimulated emission (SE) and photoreflectance (PR) properties in In_xGa_1−xN epilayers is carried out in the composition range 0≤x≤0.19. In-incorporation up to 4% leads to the sufficient longer radiative recombination decay time due to the decrease in non-radiative recombination channels, which are peculiar to GaN, and band-to-band optical transitions predominate the spontaneous PL spectrum. Further In-incorporation (x>4%) leads to the localization of carriers and/or excitons at band-tails in the In-rich areas. Correlation between the position of dominant low-energy PR oscillation due to the main band gap and SE peak position shows that band-to-band transitions are responsible for lasing and dominate the PL spectrum in all highly pumped In_xGa_1−xN samples.     

Electrical and optical activation studies of high dose Si-implanted Al0.18Ga0.82N

Both electrical and optical activation studies of Si-implanted Al_0.18Ga_0.82N have been made as a function of anneal time and anneal temperature to obtain maximum possible electrical activation efficiency. Silicon ions were implanted at 200 keV with doses of 5×10¹⁴ and 1×10¹⁵ cm⁻², and the samples were annealed from 1100 to 1250 ^°C for 5-25 min with a 500 Å thick AlN cap in a nitrogen environment. The electrical activation efficiency and Hall mobility increase with anneal time and anneal temperature. Nearly 100 and 95% electrical activation efficiencies were obtained for Si-implanted Al_0.18Ga_0.82N with doses of 5×10¹⁴ and 1×10¹⁵ cm⁻² and annealing at 1250 and 1200 ^°C for 25 min, respectively. The photoluminescence measurements show an excellent implantation damage recovery after annealing at these optimum anneal conditions, showing a strong near band emission. These optical results correlate well with the electrical results.     

Coexistence theorem of steady states for nonlinear self-cross diffusion systems with competitive dynamics

In this paper, we discuss the existence of positive solutions to certain nonlinear elliptic systems representing competitive interaction with self-cross diffusions between two species. The method employed is the fixed point index theory in a positive cone. Sufficient conditions for the existence of positive solutions are provided.     

Production of bacterial cellulose by Gluconacetobacter sp. RKY5 isolated from persimmon vinegar

The optimum fermentation medium for the production of bacterial cellulose (BC) by a newly isolated Gluconacetobacter sp. RKY5 was investigated. The optimized medium composition for cellulose production was determined to be 15 g/L glycerol, 8 g/L yeast extract, 3 g/L K₂HPO₄, and 3 g/L acetic acid. Under these optimized culture medium, Gluconacetobacter sp. RKY5 produced 5.63 g/L of BC after 144 h of shaken culture, although 4.59 g/L of BC was produced after 144 h of static culture. The amount of BC produced by Gluconacetobacter sp. RKY5 was more than 2 times in the optimized medium found in this study than in a standard Hestrin and Shramm medium, which was generally used for the cultivation of BC-producing organisms.     

Hydrogenation and dehalogenation under aqueous conditions with an amphiphilic-polymer-supported nanopalladium catalyst

An amphiphilic polystyrene-poly(ethylene glycol) resin supported nanopalladium particle catalyzed hydrogenation of olefins and hydrodechlorination of chloroarenes under aqueous conditions is presented.     

Rapid molecular weight analysis of polymers by temperature gradient interaction chromatography

Temperature gradient interaction chromatography (TGIC) has been established as a high-resolution technique for the characterization of synthetic polymers. So far, most of the TGIC investigations focused on the high-resolution analysis and little effort has been made on the reduction of the analysis time. In this study, we examined the effect of the column heating rate, the eluent flow rate, and the column length on the TGIC analysis time. We found that the heating rate is the most important experimental parameter to control the TGIC retention time. With a C18 silica column (50 mm x 4.6mm I.D.), a set of PS standards of wide molecular weight range (5 - 648 kg/mol) could be separated within 4 min at a heating rate of 8 degrees C/min.     

Dexamethasone differentiates NG108-15 cells through cyclooxygenase 1 induction

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid into prostanoids which participate in various cellular functions including apoptosis, mitogenesis, inflammation, immune modulation and differentiation. Moreover, the synthetic glucocorticoid, dexamethasone has immune modulating and anti-inflammatory effects in vivo. Recently, dexamethasone was found to enhance retinoic acid-induced neuronal differentiation. In this study, we investigated the mechanisms of dexamethasone-mediated neuronal differentiation. Immunoblotting and morphological analysis demonstrated that dexamethasone induced neuronal differentiation through COX 1 induction. This phenomenon was inhibited by indomethacin, a COX inhibitor. In addition, the addition of exogenous prostaglandin E2 (PGE2), a substance produced by the COX-mediated pathway, triggered neurite outgrowth of cells treated with COX inhibitor. Taken together, COX 1 appears to play an important role in dexamethasone-mediated neuronal differentiation.     

Self-assembly of copper(II) tetraaza macrocyclic complex with cyclohexane-1,3-dicarboxylic acid-5-monocarboxylate linked by hydrogen bond

A novel complex with the composition {[Cu(L)](Cl)(H,H-cdc)(H₂O)} _n (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane; H,H-cdc = cyclohexane-1,3-dicarboxylic acid-5-monocarboxylate) has been synthesized and structurally characterized by X-ray diffraction method. It crystallizes in the monoclinic system P2₁/n with a = 9.507(9), b = 12.624(3), c = 26.922(4) Å, = 96.79(1)°, V = 3208(3) ų, Z = 4. The complex contains a 1D hydrogen-bonded polymeric chain with copper(II) macrocycle and bridging H,H-cdc ligand. The copper(II) coordination geometry is best described as a square-plane with four Cu–N bonds. The weak interaction between copper(II) ion and the chloride ion is also found.