Combustion and emission characteristics of converging group-hole nozzle under lean engine operating conditions

This paper describes the combustion and emission characteristics of converging group-hole nozzles and compares the results to those of a single hole nozzle with the same overall nozzle exit hole area. Engine experiments were performed using a single-cylinder diesel engine operating under overall lean conditions (i.e., equivalence ratio 0.45). The considered nozzle configurations in the experiments included a converging group-hole nozzle (cGHN) with 3° converging angle, 0.090 mm hole diameter, and a single hole nozzle (SHN) of 0.128 mm hole diameter. The CFD calculations used the KIVA engine simulation code integrated with a Gasjet superposition model. Using the validated calculation models, the test conditions were also expanded to consider wider converging angle cGHNs (up to 12°). The results show that the evaporation of sprays from the cGHN-3° nozzle is more delayed than that of the SHN case and the cGHNs entrain more ambient gas due to smaller droplet sizes in the outer spray periphery. In addition, an increase in the converging angle of the cGHNs promotes fuel evaporation and produces a more homogeneous fuel–air mixture.     

The use of microwave irradiation for the easy synthesis of graphene-supported transition metal nanoparticles in ionic liquids

Stable ruthenium or rhodium metal nanoparticles were supported on chemically derived graphene (CDG) surfaces with small and uniform particle sizes (Ru 2.2 ± 0.4 nm and Rh 2.8 ± 0.5 nm) by decomposition of their metal carbonyl precursors by rapid microwave irradiation in a suspension of CDG in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The graphene-supported hybrid nanoparticles were shown to be active and could be re-used at least 10 times as catalysts for the hydrogenation of cyclohexene and benzene under organic-solvent-free conditions with constant activities up to 1570 mol cyclohexane × (mol metal)⁻¹ × h⁻¹ at 4 bar and 75 °C.     

Kinetics of Solid-State Reactions in Heterogeneous Catalysis from Time-Resolved X-Ray Absorption Spectroscopy

The potentials of X-ray absorption spectroscopy (XAS) (quantitative phase composition and average valence together with a short-range order structure analysis) combined with a time-resolution in the second range make time-resolved (TR-) XAS a powerful tool for investigating the reactivity of solids in catalysis and solid-state chemistry. General aspects of TR-XAS investigations are discussed (i.e., instrumentation, data analysis). In addition, some experiments illustrate how the kinetics of solid-state reactions in heterogeneous catalysis can be elucidated from TR-XAS studies.     

On the relationship between wavelength and perceived hue

Unlike in the case of sound where there is a compressed but straightforward relationship between frequency of sound waves and the perceived pitch, in the case of color the relationship is highly nonlinear, as first pointed out by Ostwald in 1916. In this article, the relationship between the perceptual Munsell hue scale and the related dominant wavelengths of the color chips involved is investigated. A hypothesis is proposed according to which the immediate cause of the nonlinearity can be found in the relative activation of the kinds of chromatically opponent functions shown to exist in neurons of the lateral geniculate nuclei. However, at this time, the relationship is only correlational, given the lack of deeper understanding of the relationship between the physiological operation of the color vision system and conscious experiences of color. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;     

Graphenated Ceramic Particles as Functional Fillers for Nonisocyanate Polyhydroxyurethane Composites

Graphenation of corundum and silicon carbide filler particles simultaneously improves mechanical properties and electrical conductivity of nonisocyanate polyhydroxyurethanes (NIPU) composites prepared by amine cure of polyfunctional cyclic carbonates. Typically, the ceramic fillers coated with either glucose, polydopamine, or graphite oxide (GO) are thermolyzed to produce an ultrathin graphene shell around the ceramic core, as verified by transmission electron microscopy. As compared to a blend of corundum particles with the thermally reduced graphite oxide (TRGO) nanofiller, graphenation of corundum with GO at a similar total carbon content significantly improves the Young’s modulus (7000 MPa, +184%) of trimethylolpropane glycidylether carbonate (TMPGC) cured with diethylenetriamine (DETA). Moreover, up to 30 wt% of the graphenated corundum filler is uniformly dispersed, whereas a few percent of neat TRGO account for intolerable high viscosity. Furthermore, NIPU composites containing graphenated ceramic fillers exhibit electrical conductivities of up 2.58 × 10^?5 S m^?1 well below the percolation threshold of neat TRGO in the same NIPU matrix. Hence, the graphenation of inorganic particles represents a facile and universal synthetic route toward tailoring functional fillers and combines the two worlds of functionalized graphene and inorganic fillers in an economic way by eliminating the tedious syntheses and handling typical for graphene nanofillers.     

Synthesis of Novel Niobium Aluminide-Based Composites

A reactive sintering process has been used to produce almost fully dense composites with interpenetrating networks of NbAl₃ and Al₂O₃. The process involves the reaction synthesis of niobium aluminides and Al₂O₃ from compacts of intensively milled aluminum and Nb₂O₅ powder mixtures. During carefully controlled heating under an inert atmosphere, the oxide reduction by aluminum to form niobium aluminides and Al₂O₃ proceeds at temperatures below the melting point of aluminum. At temperatures of >1000°C, the reaction-formed niobium aluminides and Al₂O₃ sinter. The present paper discusses processing parameters, such as attrition milling, the heating cycle, and the metal:ceramic ratio in the starting mixture, that control microstructure development and mechanical properties.     

Advanced Mutasynthesis Studies on the Natural α‐Pyrone Antibiotic Myxopyronin from Myxococcus fulvus

Myxopyronin is a natural α‐pyrone antibiotic from the soil bacterium Myxococcus fulvus Mx f50. Myxopyronin inhibits bacterial RNA polymerase (RNAP) by binding to a part of the enzyme not targeted by the clinically used rifamycins. This mode of action makes myxopyronins promising molecules for the development of novel broad‐spectrum antibacterials. We describe the derivatization of myxopyronins by an advanced mutasynthesis approach as a first step towards this goal. Site‐directed mutagenesis of the biosynthetic machinery was used to block myxopyronin biosynthesis at different stages. The resulting mutants were fed with diverse precursors that mimic the biosynthetic intermediates to restore production. Mutasynthon incorporation and production of novel myxopyronin derivatives were analyzed by HPLC‐MS/MS. This work sets the stage for accessing numerous myxopyronin derivatives, thus significantly expanding the chemical space of f α‐pyrone antibiotics.     

Structure–Activity Relationships of 2‐Sufonylpyrimidines as Quorum‐Sensing Inhibitors to Tackle Biofilm Formation and eDNA Release of Pseudomonas aeruginosa

Drug‐resistant Pseudomonas aeruginosa (PA) strains are on the rise, making treatment with current antibiotics ineffective. Hence, circumventing resistance or restoring the activity of antibiotics by novel approaches is of high demand. Targeting the Pseudomonas quinolone signal quorum sensing (PQS‐QS) system is an intriguing strategy to abolish PA pathogenicity without affecting the viability of the pathogen. Herein we report the structure–activity relationships of 2‐sulfonylpyrimidines, which were previously identified as dual‐target inhibitors of the PQS receptor PqsR and the PQS synthase PqsD. The SAR elucidation was guided by a combined approach using ligand efficiency and ligand lipophilicity efficiency to select the most promising compounds. In addition, the most effective inhibitors were rationally modified by the guidance of QSAR using Hansch analyses. Finally, these inhibitors showed the capacity to decrease biofilm mass and extracellular DNA, which are important determinants for antibiotic resistance.