Evidence for ψ' decays into γπ0 and γη

The decays ψ'→γπ(0), γη and γη' are studied using data collected with the BESIII detector at the BEPCII e(+)e(-) collider. The processes ψ'→γπ(0) and ψ'→γη are observed for the first time with signal significances of 4.6σ and 4.3σ, respectively. The branching fractions are determined to be B(ψ'→γπ(0))=(1.58±0.40±0.13)×10(-6), B(ψ'→γη)=(1.38±0.48±0.09)×10(-6), and B(ψ'→γη')=(126±3±8)×10(-6), where the first errors are statistical and the second ones systematic.     

Observation of two new N* peaks in J/psi-->ppi-n and ppi+n decays

The decay J/psi-->NNpi provides an effective isospin 1/2 filter for the piN system due to isospin conservation. Using 58x10(6) J/psi decays collected with the Beijing Electromagnetic Spectrometer at the Beijing Electron Positron Collider, more than 100 thousand J/psi-->ppi-n+c.c. events are obtained. Besides the two well-known N* peaks at around 1500 MeV/c2 and 1670 MeV/c2, there are two new, clear N* peaks in the ppi invariant mass spectrum around 1360 MeV/c2 and 2030 MeV/c2 with statistical significance of 11sigma and 13sigma, respectively. We identify these as the first direct observation of the N*(1440) peak and a long-sought missing N* peak above 2 GeV/c2 in the piN invariant mass spectrum.     

Synthetic studies on oxindole spiro-lactones with thalliumd(III) trinitrate: A formal total synthesis of (±)-tryptoquivaline G

(±)-Tryptoquivaline G was formally synthesized through shortened steps from tryptophan, in which oxidation with thallium(III) trinitrate(TTN) was effected at the crucial stage. The present work also constitutes the first synthesis of oxindole lactones carrying 2-alkyl quinazolinones.     

Predicting the wind noise from the pantograph cover of a train

Finite element and boundary element calculations are combined to predict the flow noise radiated from a 1/10th-scale model of an aerodynamic cover used around the pantograph on a train at 250 km h⁻¹. The solutions of the unsteady air flow over the cover and the resulting sound propagation are divided into two parts in order to keep the problem tractable. First the unsteady fluid flow is solved using large-eddy simulation (LES). The pressure histories on the cover are then used to predict the radiated sound, using a boundary element method to solve the Helmholtz equation. The result thus leans heavily on assumptions about the coupling of the two solutions, the propagation of sound in a disturbed medium and the efficacy of LES. The predicted sound pressure levels are compared with experimental measurements made in an anechoic wind tunnel. © 1997 John Wiley & Sons, Ltd.     

Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure

The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density.     

Dependence of V-A characteristics of amorphous semiconductor Ge15Te81S2As2 on hydrostatic pressure

The paper presents the functional expression of V-A characteristics dependent on hydrostatic pressure up to 5 kbar for chalcogenide glass Ge₁₅Te₈₁S₂As₂. The measured V-A characteristics and those derived on the assumption of a linear decrease of the energy gap due to pressure have been compared. Temperature changes caused by current passing through the sample in thermal contact with the environment have been taken into consideration similarly as in the case of paper (2).In conclusion we wish to express our thanks to Doc. J.Krempaský CSc., Ing. P.Dieka, Ing. J.Bielek for their kind help in discussing various points of the problem.     

Asymmetric reductive acylation of aromatic ketoximes by enzyme-metal cocatalysis

We have developed an efficient procedure for the asymmetric synthesis of chiral amides from ketoximes. This one-pot procedure employs two different types of catalysts, Pd nanocatalyst and lipase, for three consecutive transformations including hydrogenation, racemization, and acylation. Eight ketoximes have been efficiently transformed to the corresponding amides in good yields (83-92%) and high enantiomeric excesses (93-98%).