Free surface motion of an incompressible ideal fluid

We consider the free boundary problem for an incompressible ideal fluid in the two-dimensional space. We show the unique existence of the solution, locally in time, even if the initial surface and the bottom are uneven.     

(+)‐3‐{(4S,5S)‐5‐[1,1‐Di­methyl‐2‐(phenyl­thio)­ethyl]‐2,2‐di­methyl‐1,3‐dioxolan‐4‐yl}prop‐2‐yn‐1‐ol

The absolute configuration was determined for the title compound, (+)‐C₁₈H₂₄O₃S, (I), which was prepared in a synthetic study on the natural products, bryostatins.     

Maltopentaose-Forming Amylase-Mediated p-Nitrophenyl α-Maltohexaoside formation in an Aqueous-Organic Solvent System :A Substrate for Human Amylase in Serum

ABSTRACT

A maltopentaose-forming amylase [EC 3.2.1.1] from Bacillus licheniformis effectively produced p-nitrophenyl α-maltohexaoside (3) through a transglycosylation reaction from maltohexaose as a donor and p-nitrophenyl α-glucoside (1) as an acceptor in an aqueous solution containing hydrophilic organic solvents. The enzyme specifically transferred from maltohexaose to the 4-position of 1. The yield of 3 depended on the kind of donor, concentration of solvent, pH, and temperature. By the addition of solvents such as dimethyl sulfoxide and 1-butanol, respectively, effects of acceleration on transferase activity of the enzyme and improvement of acceptor solubility were achieved, and resulted in a great increase in the formation of 3.     

Nature of magnetic impurity induced superparamagnetism and anomalous Hall effect in β-FeSi2 single crystals

The magnetic properties of β-FeSi₂ single crystals were investigated using magnetization and anomalous Hall effect measurements. These measurements clearly show the appearance of superparamagnetism, the origin of which is attributed to defect-induced magnetic aggregates. Unlike previous reports, based on our combined analysis using magnetization and the anomalous Hall effect, we found that two kinds of aggregates, which are magnetically distinct, exist in our samples. Among the two types found, one gives an anomalous Hall term, which follows a side-jump mechanism while the other is a completely new kind, suggesting that magnetic properties of β-FeSi₂ are very unconventional. The sizes of the aggregates were estimated from our experimental data.     

An Efficient Synthesis of Sulfo Lewis X Analog Containing 1-Deoxynojirimycin 1

Abstract

Sulfo Lewis^x analog containing 1-deoxynojirimycin (13) has been efficiently synthesized. Glycosidation of ethyl 2,3,4-tri-O-benzyl-1-thio-β-D-fucopyranoside (5) with O-2,6-di-O-benzoyl-3,4-isopropylidene-β-D-galactopyranosyl)-(1→4)-2,6-di-O-benzoyl-N-benzyloxycarbonyl-1,5-dideoxy-1,5-imino-D-glucitol (4), prepared from O-β-D-galactopyranosyl-(1→4)-1,5-dideoxy-1,5-imino-D-glucitol (1) via 3 steps, and subsequent acid hydrolysis of the isopropylidene group gave the desired trisaccharide diol derivative (7) in good yield. Compound 7 was easily converted into 3′-O-sulfo Lewis^x analog (13) via 6 steps in high yield.

     

Generation and structure determination of 5,6‐bis(methylthio)‐4,7‐diethylbenzo[1,2,3]trithiole dication MBT(2+)

5,6‐Bis(methylthio)‐4,7‐diethylbenzo‐[1,2,3]‐trithiole [MBT] was oxidized with two equivalents of SbCl₅ to produce a dication, MBT(2+)ċ2SbCl, as a stable, dark‐brown solid. MBT(2+) was unexpectedly silent for ¹H‐NMR in CD₃CN, whereas it was active for ESR, suggesting that MBT(2+) is a triplet‐state dication MBT(2+)‐T. Meanwhile, treatment of 5‐ methylsulfinyl‐6‐methylthio‐4,7‐diethylbenzo[1,2,3]‐ trithiole [MBTMO] with D₂SO₄ produced MBT(2+), whose ¹H‐NMR gave no signals, whereas the solution is active for ESR. These results imply that MBT(2+) prepared from MBTMO is a triplet‐state dication, and a singlet‐state dication, MBT(2+)‐S, initially generated by acidification of MBTMO, isomerized to the triplet‐state dication, MBT(2+)‐T. Since MBT(2+)‐T is active for ESR at room temperature, two molecules of MBT(2+)‐T should form a spin pair in the solution with a sufficient distance between the two radical centers. The structures of MBT(2+)‐S and MBT(2+)‐T were optimized with the DFT method at the B3LYP6‐31G** level. The total energy difference between them was calculated to be 7.90 kcal/mol; MBT(2+)‐T was shown to be more stable than MBT(2+)‐S. A treatment of MBTMO with SbCl₅ gave a 1:1 complex. The structure of the complex was determined with X‐ray crystallography, which showed that the complex is the corresponding sulfonium salt, MBTMOċSbCl₅. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:111–222, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20078     

Efficient pulse operation of Nd:GdVO4 laser with AO Q-switch

We realized an efficient laser diode-pumped Nd:GdVO₄ laser with crystals grown by the floating zone method. In the lasing experiment, a slope efficiency of 78% was achieved with a 1 at.% Nd-doped crystal by pumping at 879 nm. Furthermore, excellent pulsed laser operation was demonstrated with the Nd:GdVO₄ crystal by using an acousto-optical (AO) Q-switch. A pulse width of 7 ns was observed when the pulse-repetition frequency was 40 kHz. It is the shortest pulse width recorded in the case of the AO Q-switched Nd:GdVO₄ laser.     

Observation of Mode Patterns for High Purity Mode Operation in the Submillimeter Wave Gyrotron FU VA

Operation tests of a cavity designed for high purity mode operation of the submillimeter wave gyrotron FU VA has been carried out successfully. The observed emission patterns of several cavity modes appear very pure and are compared with calculated results. High purity mode operation has the advantage of making the conversion to Gaussian-like beams more efficient.