Iodoetherification of 4-penten-1,3-diols: stereoselective synthesis of cis 2-iodomethyl-3-hydroxytetrahydrofurans

cis 2-Iodomethyl-3-hydroxytetrahydrofurans have been obtained in high yields and in high selectivities by treatment of 4-penten-1,3-diols with iodine (ether-H₂O, NaHCO₃).     

Pressure induced insulator-metal transition in quasi one-dimensional niobium tetraiodide

The resistivity of a quasi one-dimensional semiconductor NbI₄ was measured at high pressures. The resistivity decreased monotonously with increasing pressure. The activation energy of 0.12 eV at atmospheric pressure decreased to 0.06 eV at 100 kbar and to 0.02 eV at 130 kbar. The temperature coefficient of resistivity becomes positive at about 150 kbar.     

Determination of the alpha, beta-adrenoceptor blocker YM-09538 in urine by gas chromatography with a nitrogen-sensitive detector

A gas chromatographic method for the quantitative determination of the alpha, beta-adrenoceptor blocker YM-09538 in urine is described. YM-09538 was extracted from alkalinized urine with ethyl acetate and converted to its cyclic methylboronate derivative. Analysis by gas chromatography using a nitrogen-sensitive detector allowed quantitation of the drug over a concentration range of 0.2-5.0 micrograms/ml. Urinary excretion of YM-09538 was determined in humans after oral administration of 50 mg.     

Eine Absch?tzung der Faltungskonformation von Poly?thyleneinkristallen nach der Methode der Oberfl?chenhalogenierung

Ohne Zusammenfassung     

Simulation study of spatiotemporal correlations of earthquakes as a stick-slip frictional instability

Spatiotemporal correlations of earthquakes are studied numerically on the basis of the one-dimensional spring-block (Burridge-Knopoff) model. As large events approach, the frequency of smaller events gradually increases, while, just before the mainshock, it is dramatically suppressed in a close vicinity of the epicenter of the upcoming mainshock, a phenomenon closely resembling the "Mogi doughnut."     

Tests of the homogeneous nucleation theory with molecular-dynamics simulations. I. Lennard-Jones molecules

Two kinds of the homogeneous nucleation theory exist at the present: the classical nucleation theory and the semiphenomenological model. To test them, we performed molecular-dynamics (MD) simulations of nucleation from vapor to liquid with 5000-20,000 Lennard-Jones-type molecules. Simulations were done for various values of supersaturation ratios (from 2 to 10) and temperatures (from 80 to 120 K). We compared the size distribution of clusters in MD simulations with those in the theoretical models because the number density of critical clusters governs the nucleation rate. We found that the semiphenomenological model achieves excellent agreements in size distributions of the clusters with all MD simulations we done. The classical theory underestimates the number density of the clusters in the temperature range of 80-100 K, but overestimates in 100-120 K. The semiphenomenological model also predicts well the nucleation rate in MD simulations, while the classical nucleation theory does not. Our results confirmed the validity of the semiphenomenological model for Lennard-Jones-type molecules.