Numerical and experimental study of a micro-blast wave generated by pulsed-laser beam focusing

This paper describes a numerical and experimental study of a micro-blast wave which is produced from the source of several tens microns in dia. and propagates in the length scale of a few centimeter in diameter. The micro-blast wave was generated by focusing a Nd:Glass pulsed-laser beam in ambient air. Its propagation and reflection were visualized by using double exposure holographic interferometry and simulated numerically using the dispersion-controlled scheme to solve the Euler and Navier-Stokes equations with initial conditions of a point-source explosion specified with the Taylor similarity law. Good agreement was obtained between numerical solutions and experimental results, and this spherical micro-blast wave was shown to be a handy model of blast waves created in large scale explosions. Received 28 October 1997 / Accepted 30 April 1998     

Investigations on the Interface Microstructure of Stainless Steel/Aluminum Joints Created by the Surface Activated Bonding Method

Stainless steel and aluminum have been bonded by the surfaceactivated bonding method. Both transmission electron microscopy (TEM)and scanning electron microscopy (SEM) have been used to investigatethe interface microstructure of the as-bonded and annealed joints. Aperfect interface did not show any microcracks or porosity for theas-bonded joints. An 10 nm thick intermediate layer composed ofmainly silicon and certain amounts of oxygen and carbon was foundbetween stainless steel and aluminum by means of high resolutionelectron microscopy (HRTEM). The interface morphology of the jointsvaried gradually as the bonded joints are heated at elevatedtemperature. When heated to 573 K, individual precipitate-likefluctuation at the interface area was detected, with slightmodification of the interface morphology. Bulky intermetalliccompounds finally formed throughout the original interface boundarywhen heated to 873 K and contributed to the weakening of theinterface boundary of the joints.     

Ruthenium-catalyzed reactions of 1-cyclopropyl-2-propyn-1-ols with anilines and water via allenylidene intermediates: selective preparation of tri- and tetrasubstituted conjugated enynes

Ruthenium-catalyzed efficient preparation of the conjugated enynes can be carried out in the reactions of 1-cyclopropyl-2-propyn-1-ols with nitrogen- and oxygen-centered nucleophiles such as anilines and water in the presence of a catalytic amount of sulfur-bridged diruthenium complexes. The use of such complexes as catalysts realizes the completely stereoselective preparation of tri- and tetrasubstituted conjugated enynes, where ruthenium-allenylidene complexes work as key intermediates. The direct attack of nucleophiles on a cyclopropane ring connected to an allenylidene ligand is a key step to obtain the enynes stereoselectively.     

Comparative studies of carbohydrate-binding proteins from Xenopus laevis skin and eggs. Sugar-binding specificities and affinity purification

Salt and detergent extracts of acetone-dried powder of Xenopus laevis skin and eggs were fractionated on sugar-Sepharose columns, to which lactose, melibiose, galactose, rhamnose and mannose had been covalently linked, by successive elution with chelating reagent and specific sugars, resulting in separation of the different Ca2(+)-dependent and Ca2(+)-independent carbohydrate-binding proteins. The skin of X. laevis contains a salt-extractable Ca2(+)-dependent lactose-binding lectin of 30 kilodalton (kDa) and the eggs a similar lectin of 43 kDa, but they both lack Ca2(+)-dependent galactose-binding lectins. The 30 kDa lactose-binding lectin which agglutinates human A erythrocytes was isolated by successive affinity chromatography on two linked sugar-Sepharose columns, i.e., a galactose-Sepharose-lactose-Sepharose (GL) column system. Since the 30 kDa lectin was not recovered in the Ca2(+)-dependent lactose-binding protein fraction from the GL column system under the dithiothreitol (DDT)-free conditions, it was concluded that the lectin requires the presence of DTT and calcium for binding to the lactose-Sepharose column.     

Inclusion complex of α-lipoic acid and modified cyclodextrins

The solubility of α-lipoic acid (LA) with the addition of modified cyclodextrins was investigated using the solubility method. The solubility of LA in the presence of β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), mono-6-O-glucopyranosyl-β-cyclodextrin (mono-G₁-β-CD), methyl-β-cyclodextrin (Me-β-CD), 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD), and sulfobutylether-β-cyclodextrin (SBE-β-CD) was higher than that of LA itself. In particular, the solubility of LA in the presence of SBE-β-CD was 20 times higher than that of LA alone. The structure of the inclusion complex of SBE-β-CD and LA in aqueous solution was examined by ¹H-¹H ROESY NMR spectroscopy. The 1,2-dithiolane moiety of LA was included from the secondary hydroxyl face of SBE-β-CD. The solid complexes of LA and SBE-β-CD were prepared by the kneading and freeze-drying methods. Formation of the solid complexes was confirmed by X-ray diffraction patterns (XRD), differential scanning calorimetry (DSC), and infrared spectroscopy (IR). The kneading and freeze-drying methods were successful for obtaining the solid inclusion complexes with improved thermal stability.