Influence of wall heat loss on the emission characteristics of premixed ammonia-air swirling flames interacting with the combustor wall

The influence of wall heat loss on the emission characteristics of ammonia-air swirling flames has been investigated employing Planar Laser-Induced Fluorescence imaging of OH radicals and Fourier Transform Infrared spectrometry of the exhaust gases in combustors with insulated and uninsulated walls over a range of equivalence ratios, ?, and pressures up to 0.5 MPa. Strong influence of wall heat loss on the flames led to quenching of the flame front near the combustor wall at 0.1 MPa, resulting in large unburned NH₃ emissions, and inhibited the stabilization of flames in the outer recirculating zone (ORZ). A decrease in heat loss effects with an increase in pressure promoted extension of the fuel-rich stabilization limit owing to increased recirculation of H₂ from NH₃ decomposition in the ORZ. The influence of wall heat loss resulted in emission trends that contradict already reported trends in literature. NO emissions were found to be substantially low while unburned NH₃ and N₂O emissions were high at fuel-lean conditions during single-stage combustion, with values such as 55 ppmv of NO, 580 ppmv of N₂O and 4457 ppmv of NH₃ at ? = 0.8. In addition, the response of the flame to wall heat loss as pressure increased was more important than the effects of pressure on fuel-NO emission, thereby leading to an increase in NO emission with pressure. It was found that a reduction in wall heat loss or a sufficiently long fluid residence time in the primary combustion zone is necessary for efficient control of NH₃ and N₂O emissions in two-stage rich-lean ammonia combustors, the latter being more effective for N₂O in addition to NO control. This study demonstrates that the influence of wall heat loss should not be ignored in emissions measurements in NH₃-air combustion, and also advances the understanding of previous studies on ammonia micro gas turbines.     

Synthesis and characterization of a biphenyl-linked hemicryptophane and an endohedral cobalt(II) complex

Hemicryptophanes are covalent molecular cages, constructed from a cyclotriveratrylene-based host unit and a functional unit linked by covalent spacers, which have been designed to accommodate endohedral functionalities in the cavity. In this study, the synthesis and characterization of the rigid, biphenyl-linked hemicryptophane 1 were investigated by NMR, ESI-MS, and X-ray crystallography. The structure of the inclusion complex, in which a dichloromethane molecule was constructed encapsulated within 1, was characterized by X-ray crystallography. An endohedral, cobalt(II) hemicryptophane complex 2 was also synthesized and characterized ESI-MS and X-ray crystallography. The X-ray crystal structure of 2 showed that the biphenyl-linked hemicryptophane had three components—a molecule each of chloroform and acetonitrile, and a cobalt(II) ion—within its cavity.     

Heterocyclic effect for optical properties of naphthoquinone-based pigment: 2-methyl-3-heteroarylthio-1,4-naphthalenedione

Three novel naphthoquinone-based heterocyclic pigments, 2-methyl-3-[(1-methyl-1H-imidazol-2-yl)thio-1,4-naphthalenedione, (4-methyl-4H-1,2,4-triazol-3-yl)thio-1,4-naphthalenedione, and (1-methyl-1H-tetrazol-5-yl)thio]-1,4-naphthalenedione, are synthesized, and their optical properties in both solution and solid states are investigated. Depending on the heteroarylthio ring in the pigment, variation in optical properties is observed, e.g. characteristic colours for each pigment in the solution and solid states. The achiral pigment containing the 1-methyl-1H-tetrazol-5-yl ring exhibits a chiral space group and a CD signal in the solid state.     

Toward the assembly of heparin and heparan sulfate oligosaccharide libraries: efficient synthesis of uronic acid and disaccharide building blocks

The monosaccharide moieties found in heparin (HP) and heparan sulfate (HS), glucosamine and two kinds of uronic acids, glucuronic and iduronic acids, were efficiently synthesized by use of glucosamine hydrochloride and glucurono-6,3-lactone as starting compounds. In the synthesis of the disaccharide building block, the key issues of preparation of uronic acids (glucuronic acid and iduronic acid moieties) were achieved in 12 steps and 15 steps, respectively, without cumbersome C-6 oxidation. The resulting monosaccharide moieties were utilized to the syntheses of HP/HS disaccharide building blocks possessing glucosamine-glucuronic acid (GlcN-GlcA) or iduronic acid (GlcN-IdoA) sequences. The disaccharide building blocks were also suitable for further modification such as glycosylation, selective deprotection, and sulfation.     

Reductive carboxylation of alkyl halides with CO2 by use of photoinduced SmI2/Sm reduction system

Upon visible-light irradiation, reductive carboxylation of alkyl halides takes place by using a SmI₂/Sm mixed system under atmospheric CO₂ to afford the corresponding carboxylic acids in good to excellent yields.     

Hybrid micelle formation from poly(ethylene oxide-b-sodium 2-acrylamido-1-propanesulfonate-b-styrene) and Fe3+ ion in aqueous solution

Organic–inorganic nanohybrid particles are prepared in aqueous solution from poly(ethylene oxide-b-sodium 2-acrylamido-1-propanesulfonate-b-styrene) (PEO-b-PAMPS-b-PS) triblock copolymer and ferric ions. The hybrid micelles were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and zeta-potential measurements. The hydrodynamic diameter of the hybrid micelles ranges from 68 to 118 nm depending on the concentration of the polymer and the amount of ferric ions loaded on the polymer. Zeta-potential measurements revealed that the micelles are assembled mainly by electrostatic interaction between the ferric ions and the negatively charged PAMPS block in the PEO-b-PAMPS-b-PS.     

Monolithic silica spin column extraction and simultaneous derivatization of amphetamines and 3,4-methylenedioxyamphetamines in human urine for gas chromatographic-mass spectrometric detection

A simple, sensitive, and specific method with gas chromatography-mass spectrometry was developed for simultaneous extraction and derivatization of amphetamines (APs) and 3,4-methylenedioxyamphetamines (MDAs) in human urine by using a monolithic silica spin column. All the procedures, such as sample loading, washing, and elution were performed by centrifugation. APs and MDAs in urine were adsorbed on the monolithic silica and derivatized with propyl chloroformate in the column. Methamphetamine-d₅ was used as an internal standard. The linear ranges were 0.01-5.0 μg mL⁻¹ for methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) and 0.02-5.0 μg mL⁻¹ for amphetamine (AP) and 3,4-methylenedioxyamphetamine (MDA) (coefficient of correlation ≧0.995). The recovery of APs and MDAs in urine was 84-94%, and the relative standard deviation of the intra- and interday reproducibility for urine samples containing 0.1, 1.0, and 4.0 μg mL⁻¹ of APs and MDAs ranged from 1.4% to 13.6%. The lowest detection limit (signal-to-noise ratio ≧ 3) in urine was 5 ng mL⁻¹ for MA and MDMA and 10 ng mL⁻¹ for AP and MDA. The proposed method can be used to perform simultaneous extraction and derivatization on spin columns that have been loaded with a small quantity of solvent by using centrifugation.