Enantioselective synthesis of allenyl carbinols by the CBS reduction in nitroethane: dramatic solvent effect for reactivity and enantioselectivity

Dramatic solvent effect of nitroethane was observed in the catalytic asymmetric reductions of allenyl ketones and alpha,beta-ynones using the oxazaborolidine cayalyst to yield the corresponding alcohols in high levels of enantioselectivity.     

Synthesis of novel pyridazine nucleosides

This paper presents the synthesis of novel pyridazine nucleosides containing the dicyanomethylene group and pyrrolo[2,3‐c]pyridazine nucleoside.     

Effects of fuel blending on first stage and overall ignition processes

The effects of blending ratio on mixtures of an alcohol-to-jet (ATJ) fuel and a conventional petroleum-derived fuel on first stage ignition and overall ignition delay are examined at engine-relevant ambient conditions. Experiments are conducted in a high-temperature pressure vessel that maintains a small flow of dry air at the desired temperature (825 K and 900 K) and pressure (6 MPa and 9 MPa) for fuel injections from a custom single-hole, axially-oriented injector, representing medium (7.5 mg) and high (10 mg) engine loading. Formaldehyde, imaged using planar laser-induced fluorescence, is measured at discrete time steps throughout the first and second stage ignition process and is used as a marker of unburned short-chain hydrocarbons formed after the initial breakdown of the fuel. The formaldehyde images are used to calculate the first stage ignition delay for each ambient and fuel loading condition. Chemiluminescence imaging of excited hydroxyl radical at 75 kHz is used to determine the overall ignition delay. At all conditions, increased volume fraction of ATJ resulted in longer, but non-linearly increasing, overall ignition delay. Across all of the blends, first stage ignition delay accounted for about 15% of the increase in overall ignition delay compared to the military's aviation kerosene, F-24, which is Jet A with additives, while extended first stage ignition duration accounted for 85% of the increase. It is observed that blends consisting of 0–60% by volume of the low cetane number ATJ fuel produced nearly identical first stage ignition delays. These results will inform the development of ignition models that can capture the non-linear effects of fuel blending on ignition processes.     

Singularities in the Density Gradient

The compressible steady state Navier–Stokes system with viscosity is considered on a plane polygonal domain. It is shown that if a solution satisfies certain reasonable regularity conditions, and if the velocity is non-zero and points into the domain at a vertex of the polygon, then the gradient of the density either becomes infinite or has a jump discontinuity at each point of the streamline emanating from the vertex.     

Electrospun ZnO/TiO2 composite nanofibers as a bactericidal agent

Novel ZnO/TiO(2) composite nanofibers were fabricated by an electrospinning method and showed excellent antimicrobial activity against gram-negative Escherichia coli and gram-positive Staphylococcus aureus under UV irradiation and in the absence of light.     

Theoretical study of the inclusion properties of 1,2,4,5-tetra(morpholinocarbonyl)benzene

Molecular inclusion by the new amide host molecule (TMB) has been reconsidered by calculating the crystal stabilization energies for the guest molecules in the TMB + guest system from the simple intermolecular potential functions of Caillet and Claverie. Water, ethylene glycol, methanol, and ethanol have been employed as guest molecules and their relative stabilities have been considered. Water has been found to be the most suitable guest molecule in the TMB + guest system. It also has been found that the guest host interaction is the most important contributor in determining the relative stabilities of the guest molecules in the TMB + guest system, but the guest guest interaction is very important, too. Moreover, the electrostatic interaction has been found to be the most important contributor to the total interaction energy in the TMB + guest system.     

A new classification system for bacterial Rieske non-heme iron aromatic ring-hydroxylating oxygenases

Background  

Rieske non-heme iron aromatic ring-hydroxylating oxygenases (RHOs) are multi-component enzyme systems that are remarkably diverse in bacteria isolated from diverse habitats. Since the first classification in 1990, there has been a need to devise a new classification scheme for these enzymes because many RHOs have been discovered, which do not belong to any group in the previous classification. Here, we present a scheme for classification of RHOs reflecting new sequence information and interactions between RHO enzyme components.     

Application of polysulfone (PSf)– and polyether ether ketone (PEEK)–tungstophosphoric acid (TPA) composite membranes for water electrolysis

The ion exchange membrane using polysulfone (PSf) and polyether ether ketone (PEEK) as a basic material was prepared to apply in the polymer electrolyte membrane electrolysis (PEME). The sulfonated block copolymer of PSf and poly(phenylene sulfide sulfone) (SPSf-co-PPSS) and the sulfonated PEEK (SPEEK) were blended with tungstophosphoric acid (TPA) to avoid water swelling at elevated temperatures led to decrease in mechanical strength. These prepared ion exchange membranes showed some interesting characteristics including physicochemical stabilities, mechanical and membrane properties.The prepared ion exchange membrane was utilized to prepare the membrane electrode assembly (MEA). MEA consisted of Pt/PEM/Pt was prepared by equilibrium and non-equilibrium impregnation–reduction (I–R) methods. The prepared MEA by non-equilibrium I–R method was used in the PEME unit cell. The cell voltages of the MEA using SPSf-co-PPSS/TPA and SPEEK/TPA membranes were 1.83 V and 1.90 V at 1 A/cm² and 80 °C, with platinum loadings of 1.12 and 1.01 mg/cm², respectively.     

A facile synthesis of 1‐alkyl‐5‐arylalkoxy‐6‐methoxy‐3,4‐dihydroisoquinolines

1‐Alkyl‐5‐arylalkoxy‐6‐methoxy‐3,4‐dihydroisoquinolines were synthesized by the alkylation of 1‐alkyl‐5‐hydroxy‐6‐methoxy‐3,4‐dihydroisoquinolines with arylalkyl halide in the presence of potassium carbonate. 1‐Alkyl‐5‐hydroxy‐6‐methoxy‐3,4‐dihydroisoquinolines as key precursor prepared from o‐vaniline via 6 steps.