Surface viscous flattening kinetics of soda-lime silicate glass by sinusoidal profile decay method

The kinetics of the flattening of surface corrugations of float glasses were investigated in dry nitrogen at 610 to 670°C. The amplitude of the sinusoidal surface profile decayed exponentially with time while its wavelength remained constant. The dependence of decay rate on wavelength indicated that the process is controlled by the viscous flow. From the obtained rate constant the viscosity was calculated using the surface energy value determined independently by the zero-creep method. The viscosity thus obtained reflects the mass transport property in the vicinity of the glass surface. It was several times larger than that determined by the fibre elongation or intrusion method which should reflect the bulk properties. No difference in the decay rate was observed on both the surfaces of float glass of which only one side had been exposed to molten tin during the glass manufacturing process.     

Fraunhofer Diffraction Pattern by a Slit Aperture between a Knife Edge and a Metal Cylinder

The Fraunhofer diffraction pattern of an aperture formed between a knife edge and a smooth surface of a turned metal cylinder or half cylinder is different from the diffraction pattern of an ideal slit aperture. The diffraction pattern is simulated by adding the light reflected by the cylinder surface to the pattern formed by a slit, and is measured using a cylinder that has been partly cut away so that it can represent either a full or half cylinder. The theoretical and measured patterns agree well with each other.     

N,N-Diethyl-3-toluamide Formulation Based on Ethanol Containing 0.1% 2-Hydroxypropyl-β-cyclodextrin Attenuates the Drug’s Skin Penetration and Prolongs the Repellent Effect without Stickiness

N,N-diethyl-3-toluamide (DEET) is one of the most widely used insect repellents in the world. It was reported that a solution containing 6–30% cyclodextrin (CD) as a solvent instead of ethanol (EtOH) provided an enhancement of the repellent action time duration of the DEET formulation, although the high-dose CD caused stickiness. In order to overcome this shortcoming, we attempted to prepare a 10% DEET formulation using EtOH containing low-dose CDs (β-CD, 2-hydroxypropyl-β-CD (HPβCD), methyl-β-CD, and sulfobutylether-β-CD) as solvents (DEET/EtOH/CD formulations). We determined the CD concentration to be 0.1% in the DEET/EtOH/CD formulations, since the stickiness of 0.1% CDs was not felt (approximately 8 × 10⁻³ N). The DEET residue on the skin superficial layers was prolonged, and the drug penetration into the skin tissue was decreased by the addition of 0.1% CD. In particular, the retention time and attenuated penetration of DEET on the rat skin treated with the DEET/EtOH/HPβCD formulation was significantly higher in comparison with that of the DEET/EtOH formulation without CD. Moreover, the repellent effect of DEET was more sustained by the addition of 0.1% HPβCD in the study using Aedes albopictus. In conclusion, we found that the DEET/EtOH/HPβCD formulations reduced the skin penetration of DEET and prolonged the repellent action without stickiness.     

Umwandlung des Fe3S4 von Fd3m nach Pa3, P4/nmm bzw. P63/mmc beim hydrothermalen Prozeß

A hydrothermal process of precipitating iron sulfide gives rise to greigite (space group: Fd3m), pyrite (Pa3), mackinawite (P4/nmm) and pyrrhotite (P6/mmc), as the case may be. Greigite blended with pyrite is formed, when the autoclave for the hydrothermal process is cooled down not rapidly, but slowly from 192°C to room temperature. Greigite and pyrite here form partially a solid solution. A mechanical mixture of greigite-mackinawite and that of greigite-pyrrhotite appear in the hydrothermal process above and below 192°C, respectively. Pure greigite is produced only by rapid quenching of the reaction tube from 192°C, to 10°C.     

Experimental study of internal flow structures in cylindrical rotating detonation engines

The internal flow structures of detonation wave were experimentally analyzed in an optically accessible hollow rotating detonation combustor with multiple chamber lengths. The cylindrical RDC has a glass chamber wall, 20 mm in diameter, which allowed us to capture the combustion self-luminescence. A chamber 70 mm in length was first tested using C₂H₄O₂ and H₂–O₂ as propellants. Images with a strong self-luminescence region near the bottom were obtained, confirming the small extent of the region where most of the heat release occurs as found in our previous research. Based on the visualization experiments, we tested RDCs with shorter chamber walls of 40 and 20 mm. The detonation wave was also observed in the shorter chambers, and its velocity was not affected by the difference in chamber length. Thrust performance was also maintained compared to the longer chamber, and the short cylindrical RDC had the same specific impulse tendency as the cylindrical (hollow) or annular 70-mm chamber RDC. Finally, we calculated the pressure distributions of various chamber lengths, and found they were also consistent with the measured pressure at the bottom and exit. We concluded that the short-chamber cylindrical RDC with equal length and diameter maintained thrust performance similar to the longer annular RDC, further expanding the potential of compact RDCs.     

Deacylative Carbon-Carbon Bond Cleavage of Ketone Equivalents: Applications to Radical Carbon-Carbon Bond Formation Reactions

This article describes the synthetic application of ketone-derived oxaziridines as alkyl radical precursors in copper-catalyzed Carbon-Carbon bond formation reactions. Experimental and computational studies indicate a free radical mechanism, where alkyl radicals are efficiently generated via cleavage of a Carbon-Carbon bond of oxaziridines. Acyclic and unstrained cyclic oxaziridines are applicable to the present radical process, allowing for the generation of various alkyl radicals with good functional group compatibility.     

Direct Catalytic Asymmetric Addition of α-Fluoronitriles to Aldehydes

A fluorine-containing tetrasubstituted stereogenic center is a highly valued structural feature in medicinal chemistry. Herein, we describe the direct coupling of racemic α-fluoronitriles and aldehydes promoted by a chiral Cu^I/Barton's base catalytic system, delivering α-tetrasubstituted α-fluoro-β-hydroxynitriles with satisfactory stereoselection. The stereochemical course was positively biased by the combined use of asymmetrical achiral thiourea as a supplementary ligand for Cu^I, which significantly enhanced the stereoselectivity. Both aromatic and aliphatic aldehydes were implemented to provide densely and stereoselectively functionalized chiral building blocks with aliphatic and aromatic tails.     

Molecular Transformation to Pyrroles,Pentafulvenes, and Pyrrolopyridines by [2+2] Cycloaddition of Propargylamines with Tetracyanoethylene

In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines.     

Depolarization field effect on the ferroelectric behavior of polymers

The effect of the depolarization field in crystallites on the ferroelectric behavior of polymers is discussed on the assumption that the crystallite is a prolate ellipsoid with its major axis directed along the electric field. The theory relates the polarization P and the electric field E in the crystallite to the overall values P and E for the polymer. The determination of the P -E hysteresis of a crystallite from the P-E hysteresis is given with examples for poly(vinylidene fluoride) (PVDF) and vinylidene fluoride (VDF)–trifluoroethylene (TrFE) copolymer. The ratio R = J/(P_s ? P), with J the switching current density and P_s the saturation polarization of polymer, is proved to be free from the depolarization field effect and the plot of logR against logarithmic time is shown to have merit for characterization of switching behavior. Examples of the curves are given for PVDF and VDF-TrFE copolymers. The temporal change of local electric field in the unreversed domains in the crystallite in the course of polarization reversal is predicted by the theory and this change is proved to be a significant mechanism of switching acceleration.     

Remarkable substituent effects found in the base-catalyzed reaction of 5-methyl-2-(4′-substituted-phenyl)-2,4-dihydro-3H-pyrazol-3-ones

Remarkable substituent effects found in the base-catalyzed reaction of 5-methyl-4-(1-methylethylidene)-2-(4′-substituted-phenyl)-2,4-dihydro-3H-pyrazol-3-ones ( 2 ) with acetone at reflux are described.