Regio- and stereoselective homocoupling of gamma-arylated tert-propargyl alcohols with liberation of a ketone molecule and successive cyclization to produce fluorescent dihydrofuran derivatives

1,1-Disubstituted 3-aryl-2-propyn-1-ols undergo unprecedented regio- and stereoselective homocoupling with liberation of a ketone molecule in the presence of a rhodium catalyst to give the corresponding 2-hydroxymethyl-(E)-enynes. The subsequent cyclization of the enynes in the presence of a base affords fluorescent 2,3-dihydrofuran derivatives.     

Stereoselective synthesis of tetrahydronaphthocyclobuta[1,2-d]pyrimidinediones from 5-fluoro-1,3-dimethyluracil and naphthalenes

Upon UV-irradiation in the presence of piperylene, 5-fluoro-1,3-dimethyluracil (5-FDMU) couples with naphthalenes having either an electron-withdrawing group or an electron-donating group by way of 1,2-cycloaddition via mode selectivity to give the corresponding naphthocyclobutapyrimidines regio- and stereo-selectively.     

Production of ultrafine particles of high-temperature tetragonal WO<Subscript>3</Subscript> by dc arc discharge in Ar–O<Subscript>2</Subscript> gases

Ultrafine particles of WO₃ are successfully produced by dc arc discharge in Ar-O₂ gases. Particle sizes are distributed from 10 nm to 1 m depending on production conditions: gas pressure, collection position and discharge current. Observations of the cooled particles by electron microscopy indicate that the WO₃ particles are tetragonal, a phase that is usually only stable above 725 °C. The octahedral crystals are bounded by eight {1 0 1} faces and occasionally truncated by {1 0 0} and/or {0 0 1} faces. This method of producing WO₃ by dc arc discharge therefore affords a high-temperature phase that is preserved upon cooling to room temperature.     

Addendum to ``Dense subsets of the boundary of a Coxeter system'

In this paper, we investigate boundaries of parabolic subgroups of Coxeter groups. Let be a Coxeter system and let be a subset of such that the parabolic subgroup is infinite. Then we show that if a certain set is quasi-dense in , then is dense in the boundary of the Coxeter system , where is the boundary of .

     

Poly(N-isopropylacrylamide) microparticles produced by radiation pressure of a focused laser beam: a structural analysis by confocal Raman microspectroscopy combined with a laser-trapping technique

We developed a confocal Raman microspectroscopy system combined with a laser trapping technique and applied it to aqueous solutions (H(2)O and D(2)O) of poly(N-isopropylacrylamide) (PNIPA), which is well-known as a representative thermo-responsive polymer, i.e., phase transition/separation between coiled and globular states. By introducing a near-infrared (1064 nm) laser beam into a microscope, PNIPA microparticles were produced at the focused spot of the laser beam, both in H(2)O and D(2)O. By using the present system, we succeeded in obtaining the Raman spectra of PNIPA in the coiled and globular states over a wide wavenumber region (800-3500 cm(-1)) for the first time. For the D(2)O solutions (in which the photothermal effect is negligible and hence the microparticles should be produced purely by the effect of radiation pressure), some significant differences were observed in the Raman spectra for the coiled state, in the globular state, and for laser induced microparticles. By analyzing these spectra in detail, we revealed that the structure of the laser-induced microparticles was analogous to that in the globular state. We also discuss the fundamental mechanism underlying the transformation of the higher order structure of a polymer by radiation pressure.     

Effect of ion skin depth on relaxation of merging spheromaks to a field-reversed configuration

The effect of ion skin depth on the relaxation of merging spheromaks to a field-reversed configuration (FRC) is studied experimentally for a wide range of size parameter S* (ratio of minor radius to ion skin depth) from 1 to 7. The two merging spheromaks are observed to relax to an FRC or a new spheromak depending on whether the initial poloidal eigenvalue is smaller or larger than a threshold value. The bifurcation value is found to increase with decreasing size parameter S*, indicating that the low-S* condition provides a wide bifurcated range of relaxation to an FRC. The FRC-style relaxation under the low-S* conditions was accompanied by the suppression of the low-n modes (n is the toroidal mode number) activity. The fast rotations of the modes were followed by suppression of the low-n modes.     

First-principles study of electron-conduction properties of helical gold nanowires

Multishell helical gold nanowires (HGNs) suspended between semi-infinite electrodes are found to exhibit peculiar electron-conduction properties by first-principles calculations based on the density functional theory. Our results that the numbers of conduction channels in the HGNs and their conductances are smaller than those expected from a single-atom row nanowire verify the recent experiment. In addition, we obtained a more striking result that, in the cases of thin HGNs, distinct magnetic fields are induced by the electronic current helically flowing around the shells. This finding indicates that the HGNs can be good candidates for nanometer-scale solenoids.     

Precision spectroscopy and density-dependent frequency shifts in ultracold Sr

By varying the density of an ultracold 88Sr sample from 10(9) to>10(12) cm(-3), we make the first definitive measurement of the density-related frequency shift and linewidth broadening of the 1S0-3P1 optical clock transition in an alkaline earth system. In addition, we report the most accurate measurement to date of the 88Sr 1S0-3P1 optical clock transition frequency. Including a detailed analysis of systematic errors, the frequency is [434 829 121 312 334+/-20(stat)+/-33(syst)] Hz.     

A specific method for the separation of mercury(II) using a weakly basic cellulose ion exchanger

A systematic study of the behavior of many metal ions on the weakly basic cellulose exchanger DEAE in dilute thiocyanate media showed that few metal ions are adsorbed. The adsorption of mercury(II) allows a rapid and highly selective separation from about 40 metal ions. Quantitative results are quoted for the separation of ca. 100 μg of mercury(II) from milligram amounts of other metal ions; 100 μg to 10 mg of mercury(II) can be quantitatively separated from iron(III) in proportions of mercury(II): iron(III) = 100:1 to 1:8,000 on a column containing only 1 g of DEAE.