Ξ Resonances in Ξ− Be interactions II. Properties of Ξ(1820) and Ξ(1960) in the\Lambda \bar K^0 and\Sigma ^0 \bar K^0 channels

In an experiment at the CERN-SPS charged hyperon beam, we have investigated the inclusive \(\Lambda \bar K^0 \) and \(\Sigma ^0 \bar K^0 \) final states formed in Ξ^? Be interactions. In the \(\Lambda \bar K^0 \) channel, we observe a signal at 1826 MeV/c² which can be identified with the known Ξ(1820) resonance. We determine its mass and width to be:M=1826±4 MeV/c², Г=12±14 MeV/c². A moment analysis is consistent with a spin of 3/2 and indicates a negative parity for this spin assignment. Also in the \(\Lambda \bar K^0 \) channel, we observe a 3.6σ signal with the following parameters:M=1963±5 MeV/c², Г=25±15 MeV/c². This state, which we call Ξ(1960), is not observed in the \(\Sigma ^0 \bar K^0 \) channel, leading to an upper limit on the ratio of partial widths \(\Sigma \bar K/\Lambda \bar K\) of 2.3 (90% confidence level). A moment analysis of the \(\Lambda \bar K^0 \) final state indicates a spin of 5/2 or greater in the natural spin-parity series 5/2⁺, 7/2^?, etc.     

Millimeter and submillimeter detection using Ga1?xAlxAs/GaAs heterostructures

We have shown that a Ga_1–xAl_xAs/GaAs heterostructure can be used as a sensitive tunable detector of mm-wave/sub-mm-wave radiation. The mechanism for detection requires the application of a magnetic field varying from approximately 0.2T at 94GHz (3.2mm wavelength) to 6.2T at 2500GHz (119m wavelength). The responsivity and N.E.P. at 3.2mm have been roughly estimated at 200V/W and 5×10^–11W/Hz respectively. The speed of such a detector could be several orders of magnitude greater than comparable InSb detectors.     

Use of the64Ni(36S,34,35Si)66,65Zn reactions to measure the masses of34Si and35Si

The ground-state masses of³⁵Si and³⁴Si have been measured using the reactions⁶⁴Ni(³⁶S,^35,34Si)^65,66Zn at a³⁶S beam energy of 198 MeV.^34,35Si¹⁴⁺ ions were analysed and identified in a QMG/2 magnetic spectrometer and gas-filled focal-plane detector. The experimental mass excess of³⁵Si was determined to be ?14.58± _0.12 ^0.07 MeV while that of³⁴Si was measured as ?19.961±0.034 MeV. A comparison is made with the results of mass model predictions.     

The esterolytic activity of poly(N-alkylimidazoles). The effect of ester chain length in the substrate and alkyl chain length in the catalyst on the esterolytic activity of poly(N-alkylimidazoles).

In an effort to exploit the enhancement in catalytic activity which might be derived through hydrophobic interactions between polymeric catalyst and substrate, 1-methyl-5-vinylimidazole (1-Me-5-VIm), 1-methyl-4-vinylimidazole (1-Me-4-VIm), 1-butyl-5-vinylimidazole (1-Bu-5-VIm), and 1-butyl-4-vinylimidazole (1-Bu-4-VIm) have been synthesized and polymerized. In 28.5% ethanol-water, poly(1-alkyl-5-vinylimidazoles)proved to be efficient catalysts for the hydrolysis of various 3-nitro-4-acyloxybenzoic acids (Sn-, where n denotes the acyl chain length). Order of magnitude rate enhancements, as compared to the model compound, 1,5-dimethylimidazole (1,5-DMIm) were observed in the poly(1-alkyl-5-vinylimidazole)-catalyzed solvolysis of S12- and S18-. Poly(1-Me-5-VIm) catalyzes the hydrolysis of S18-88 times faster than does 1,5-DMIm. The poly(1-Me-5-VIm)-catalyzed hydrolysis of S18- in ethanol-water was analyzed in terms of a simple Michaelis-Menten type mechanism. Vmax and Km were determined to be 40.2 X 10(-7) M min-1 and 2.20 X 10(-5) M, respectively.