Palladium-nickel alloys loaded on tungsten carbide as platinum-free anode electrocatalysts for polymer electrolyte membrane fuel cells

The strong interaction between PdNi alloys and WC makes PdNi/WC a novel Pt-free electrocatalyst for the anode hydrogen oxidation reaction of polymer electrolyte membrane fuel cells with activity and stability comparable to those of the conventional Pt/C catalysts.     

Cyclodipeptide-bridged porphyrin dimer supramolecular assemblies

A cyclodipeptide-bridged porphyrin dimer has formed fibrous and toroidal multi-porphyrin array systems by hydrogen bonding-mediated self-assembly.     

Catalyst-free fabrication of graphene nanosheets without substrates using multiwalled carbon nanotubes and a spark plasma sintering process

Catalyst-free graphene nanosheets without substrates were synthesized using pure solid carbon sources of multiwalled carbon nanotubes (MWCNTs) and a spark plasma sintering (SPS) process. Single and few-hundred-nanometer graphene nanosheets were formed from gas-phase carbon atoms which were directly evaporated from MWCNTs at a local high temperature.     

Synthetic approach to flavanones and flavones via ligand-free palladium(ii)-catalyzed conjugate addition of arylboronic acids to chromones

The remarkable catalytic effects of Fe(OTf)(3) in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO(2) to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.     

Rhodium-catalyzed reductive cyclization of 1,6-enynes and stereoselective synthesis of the putative structure of lucentamycin A and its stereoisomers

A Rh-catalyzed diastereoselective reductive cyclization, mediated by hydrogen, of optically active 1,6-enynes using chiral BINAP was successfully applied to the total synthesis of four stereoisomers of the proposed structure of lucentamycin A. In order to synthesize two of these four stereoisomers, we successfully constructed chiral proline derivatives bearing cis-carbon substituents at C2 and C3 positions based on Krische’s methodology, which has very rarely been reported. Anti-proliferative activities on HCT-116 cell line and NMR data of these four stereoisomers were compared with those of naturally occurring lucentamycine A. The results show that the proposed structure of lucentamycin A needs revision.     

Comparison of laser desorption and matrix-assisted laser desorption/ionization for ruthenium and osmium trisbipyridine complexes using Fourier transform mass spectrometry

Metal-bipyridine complexes are a vehicle for developing approaches for studying the fluorescence of gas-phase ions; however, conclusions regarding fluorescence behavior depend on explicitly identifying the ionic species in the gas phase. [Ru(bpy)(3)]X(2) and [Os(bpy(3))]X(2), (where bpy = 2,2'-bipyridine and X = Cl or PF(6)), were studied using direct laser desorption (LD) and matrix-assisted laser desorption/ionization (MALDI) using Fourier transform mass spectrometry (FTMS). LD spectra of the PF(6) salt of the Ru and Os complexes reveal counterion attachment, fluoride transfer, and significant losses of H for a number of peaks. LD of the chloride salt complexes produced loss of a single bpy ligand, chloride attachment, and losses of H. Spectra of [Ru(bpy(3)]X(2) where X = BF(4)(-), CF(3)SO(3)(-), and SCN(-) were also collected using LD and compared with the spectra for Cl(2) and PF(6) salts. Regardless of counterion, loss of H is observed in LD spectra. MALDI spectra of the trisbipyridyl complexes using 2,5-dihydroxybenzoic acid (DHB) and sinapinic acid (SA) as the matrix were also obtained. The spectra using SA as matrix show intact molecular ion peaks with very little fragmentation and no counterion attachment. Unlike SA, the spectra obtained using DHB look similar to LD spectra with significant losses of H. Our results are consistent with a reaction scheme for hydrogen loss from a carbon that also involves breaking of the metalz.sbnd;nitrogen bond, rotation of a pyridine ring, and re-formation of an ortho-metallated complex by a metalz.sbnd;C bond. These results demonstrate the importance of ion generation method and the utilization of FTMS for correct characterization of metal poly(pyridyl) complexes.     

Fluorescence and Ultraviolet Spectroscopic Evaluation of Phenolic Compounds,Antioxidant and Binding Activities in Some Kiwi Fruit Cultivars

Spectrophotometric assays (Folin–Ciocalteu, ferric-reducing/antioxidant power, cupric-reducing antioxidant capacity, and β-carotene linoleate model system) have been used to evaluate the total phenolics and flavonoids in kiwi fruit cultivars in ethanol and water extracts. Fluorescent and infrared measurements were correlated with the obtained spectroscopic data. It was found that the contents of the bioactive compounds and the level of antioxidant activity in different extracts differ significantly (p < 0.05). Bioactive compounds and antioxidant activities were significantly higher in two kiwi fruit cultivars (“Bidan” and “SKK12”) than in other studied samples. To our knowledge this is the first report showing the differences and similarities in new kiwi fruit cultivars, using these spectroscopic data. The ethanol extracts of these cultivars exhibited high binding properties with human serum albumin compared with rutin. In conclusion, the applied analytical methods showed the main compounds in the kiwi fruit cultivars and can be used for determination of these compounds in any plants. The relative knowledge would contribute to the pharmaceutical development and clinical application of extracts of kiwi fruit extracts.     

Task-based exposure assessment of nanoparticles in the workplace

Although task-based sampling is, theoretically, a plausible approach to the assessment of nanoparticle exposure, few studies using this type of sampling have been published. This study characterized and compared task-based nanoparticle exposure profiles for engineered nanoparticle manufacturing workplaces (ENMW) and workplaces that generated welding fumes containing incidental nanoparticles. Two ENMW and two welding workplaces were selected for exposure assessments. Real-time devices were utilized to characterize the concentration profiles and size distributions of airborne nanoparticles. Filter-based sampling was performed to measure time-weighted average (TWA) concentrations, and off-line analysis was performed using an electron microscope. Workplace tasks were recorded by researchers to determine the concentration profiles associated with particular tasks/events. This study demonstrated that exposure profiles differ greatly in terms of concentrations and size distributions according to the task performed. The size distributions recorded during tasks were different from both those recorded during periods with no activity and from the background. The airborne concentration profiles of the nanoparticles varied according to not only the type of workplace but also the concentration metrics. The concentrations measured by surface area and the number concentrations measured by condensation particle counter, particulate matter 1.0, and TWA mass concentrations all showed a similar pattern, whereas the number concentrations measured by scanning mobility particle sizer indicated that the welding fume concentrations at one of the welding workplaces were unexpectedly higher than were those at workplaces that were engineering nanoparticles. This study suggests that a task-based exposure assessment can provide useful information regarding the exposure profiles of nanoparticles and can therefore be used as an exposure assessment tool.     

DNS of buoyancy-dominated turbulent flows on a bluff body using the immersed boundary method

A novel immersed boundary (IB) method has been developed for simulating multi-material heat transfer problem – a cylinder in a channel heated from below with mixed convection. The method is based on a second-order velocity/scalar reconstruction near the IB. A novel algorithm has been developed for the IB method to handle conjugate heat transfer. The fluid–solid interface is constructed as a collection of disjoint faces of control volumes associated to different material zones. Coupling conditions for the material zones have been developed such that continuity and conservation of the scalar flux are satisfied by a second-order interpolation. Predictions of the local Nusselt number on the cylinder surface show good agreement with the experimental data. The effect of the Boussinesq approximation on this problem was also investigated. Comparison with the variable density formulation suggests that, in spite of a small thermal expansion coefficient of water, the variable density formulation in a transitional flow with mixed convection is preferable.     

Photoluminescence investigation of ferromagnetic Ga1−xMnxN layers with GaN templates grown on sapphire (0 0 0 1) substrates

We have investigated the temperature and composition dependent photoluminescence (PL) spectra in Ga_1−xMn_xN layers (where x ≈ 0.1-0.8%) grown on sapphire (0 0 0 1) substrates using the plasma-enhanced molecular beam epitaxy technique. The efficient PL is peaked in the red (1.86 eV), yellow (2.34 eV), and blue (3.29 eV) spectral range. The band-gap energy of the Ga_1−xMn_xN layers decreased with increasing temperature and manganese composition. The band-gap energy of the Ga_1−xMn_xN layers was modeled by the Varshni equation and the parameters were determined to be α = 2.3 × 10⁻⁴, 2.7 × 10⁻⁴, 3.4 × 10⁻⁴ eV/K and β = 210, 210, and 230 K for the manganese composition x = 0.1%, 0.2%, and 0.8%, respectively. As the Mn concentration in the Ga_1−xMn_xN layers increased, the temperature dependence of the band-gap energy was clearly reduced.