Au(I)-catalyzed efficient synthesis of α-acyloxy-α′-silyl ketones from α-acyloxy-α-alkynylsilanes

The Au(I)-catalyzed novel conversion of α-acyloxy-α-alkynylsilanes to α-acyloxy-α′-silyl ketones is reported. Ph₃PAuOTf in dioxane in the presence of 1 equiv of H₂O efficiently catalyzed both the [3,3] sigmatropic rearrangement and allenic transformation of the resulting ester to give the α-acyloxy-α′-silyl ketones in a one-pot procedure.     

Four-nucleon pickup reaction on 12 ⩽ A ⩽ 94 nuclei

The differential cross sections for the (d, ⁶Li) reaction on targets of ¹²C, ¹⁶O, ²⁴Mg, ⁴⁰Ca, ⁵⁸Ni and ⁹⁴Mo have been measured at E_d = 54.2 MeV. The measured angular distributions have been analyzed by finite-range DWBA calculations, and spectroscopic factors for an α-cluster transfer have been extracted. In the DWBA analysis using an optical model with a phenomenological Woods-Saxon potential, the spin-orbit part of the deuteron optical potential played a significant role in reproducing the measured angular distributions but the spin-orbit part of the ⁶Li optical potential had a minor effect. Relative spectroscopic factors extracted from the present data were compared with theoretical predictions together with the results from the (p, pα) reaction. The relative spectroscopic factors for 1p-shell nuclei were in quantitative agreement with theoretical predictions. However, there were certain discrepancies between the spectroscopic factors extracted from the (d, ⁶Li) reaction and those from the (p, pα) reaction, and the discrepancies increased with target mass number.     

Ionic products in ground polymer. IV. Anions in poly(vinylidene fluoride)

When poly(vinylidene fluoride) (PVDF) was ground with tetracyanoethylene (TCNE) powder in a vibration glass ball mill in vacuum in the dark at 77 K, the TCNE anion radical (TCNE-) was detected in the mixture by ESR spectroscopy. The TCNE.- is formed by the abstraction of electrons by TCNE from the anion that is produced by a heterogeneous bond scission of carbon-carbon bonds in the polymer main chain. The assignment of TCNE.- was carried out by the ESR spectral simulation on the basis of an anisotropic effective hyperfine tensor that includes a forbidden transition term. At least 85% of the bond scission of the PVDF main chain is induced by a heterogeneous process to produce ionic products. The yield of these mechanions seems to increase with the polarity of carbon-carbon bond owing to a substituent group bonded to the carbon in the polymer main chain.     

Freeze-out conditions in ultrarelativistic heavy-ion collisions

We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT _fo and the chemical potentials (μ _q ,μ _s ) are extracted and discussed.     

Ionization wave as an Instability — Evolution and Nonlinear Effect

Evolution from the linear growth to the nonlinearly saturated state of ionization waves (moving striations) is investigated from a viewpoint of an instability which appears in a plasma. The experiments were performed observing backward waves excited below the upper critical current I_c in xenon, argon, and argon-mercury gases at pressures of the order of Torr. It is found that (1) the behavior of the evolution obeys the Landau amplitude equation; (2) the saturated amplitude does not depend on an initial value, but only on plasma parameters; (3) the linear growth and squared saturation level are proportional to the excess over I_c, and when frequency-controlled, they have a parabolic dependence on the frequency; and (4) nonuniform axial changes in the dc state due to the nonlinear effects appear in a form of enhanced ionization in the plasma where the electron temperature and density are increased. The way of these behavior can be applied to a large number of spatially or temporally unstable modes.     

Definite evidences for the population inversion of hot electrons in silver halides

Hot electron kinetics and distribution in pure AgCl and AgBr at crossed electric and magnetic fields have been investigated at 4.2 K up to E_x = 4kVcm^?1 and H_z = 58 kOe, by performing detailed studies of the galvanomagnetic effect in the transient condition. The results of measurements on the tangent of the Hall angle, tan θ, and on the probe current to the hot electron system along the direction of magnetic field, Q_z, established the pictures of an ideal streaming motion of electrons in the range ζ < 1 [where ζV_LO (sE_x/H_z)^?1 and $\text{1}\text{2}\text{m}{}^1\text{V}{}_{\mathrm{<mtext>LO</mtext>}}{}^2\text{}\text{h}\text{?}\text{ω}{}_{\mathrm{<mtext>LO</mtext>}}$] and of a population inversion of hot electrons in the range ζ > 1.     

Prior-form DWBA analysis of (3He,pd) elastic breakup at 90 MeV

Proton-deuteron coincident cross sections in ¹²C,⁵¹V,⁹⁰Zr(³He,pd) elastic breakup at 90 MeV have been calculated within the framework of the prior-form distorted-wave Born approximation (DWBA). Sufficient convergence of the calculations was obtained by including the pd relative angular momenta up to l = 4. The calculations reproduced the general trend of the coincident energy spectra and the angular correlation data, though deficiencies of the calculations were seen at some angles. The peripheral feature of the (³He, pd) elastic breakup is discussed from the angular momentum dependence of the transition amplitude.