Influence of a solar proton event on stratospheric ozone

Ozone depletion in the stratosphere associated with the solar proton event of August 4, 1972, was observed with the backscattered ultraviolet experiment on the Nimbus 4 satellite. An abrupt ozone decrease in the 75-80 deg N zone of about 0.002 atm-cm above 4 mb was observed to persist throughout the month of August. A decrease was noted in the 55-65 deg N zone on days 219 and 220, but recovery occurred on day 221. Thereafter, a more gradual decrease was observed. The equatorial zone also showed gradual decrease after day 218, but these were not uniquely distinguished from seasonal variations. The observed change in total ozone following the event was -0.003 atm-cm for the 75-80 deg N zone, corresponding to a 1.3 percent reduction in the 0.305 atm-cm zonal average, but within the 0.019 atm-cm standard deviation. Above the 10 mb surface in the 75-80 deg N zone however, a decrease of 0.004 atm-cm may be compared with a standard deviation of 0.001 atm-cm

On Deviations from Bimaximal Neutrino Mixing

The PMNS neutrino mixing matrix U_{PMNS} is in general a product of two unitary matrices U_{lep} and U_{\nu} arising from the diagonalization of the charged lepton and neutrino mass matrices, U_{PMNS} = U^{\dagger}_{lep} U_{\nu}. Assuming that U_{\nu} is a bimaximal mixing matrix, we investigate the possible forms of U_{lep}. We identify three possible generic structures of U_{lep}, which are compatible with the existing data on neutrino mixing. One corresponds to a hierarchical ``CKM-like'' matrix. In this case relatively large values of the solar neutrino mixing angle \theta_{sol}, and of |U_{e3}|^2, are typically predicted, \tan^2\theta_{sol} \gtap 0.42, |U_{e3}|^2 \gtap 0.02, while the atmospheric neutrino mixing angle \theta_{atm} can deviate noticeably from \pi/4, \sin^2 2\theta_{atm} \gtap 0.95. The second corresponds to one of the mixing angles in U_{lep} being equal to \pi/2, and predicts practically maximal atmospheric neutrino mixing \sin^2 2\theta_{atm} \simeq 1. Large atmospheric neutrino mixing, \sin^2 2\theta_{atm} \gtap 0.95, is naturally predicted by the third possible generic structure of U_{lep}, which corresponds to all three mixing angles in U_{lep} being large. We focus especially on the case of CP-nonconservation, analyzing it in detail. We show how the CP-violating phases, arising from the diagonalization of the neutrino and charged lepton mass matrices, contribute to the measured neutrino mixing observables.Comment: 26 pages, 6 figures. Typos corrected, references added, to appear in NP

High pressure operation of the triple-GEM detector in pure Ne, Ar and Xe

We study the performance of the triple-GEM (Gas Electron Multiplier) detector in pure noble gases Ne, Ar and Xe, at different pressures varying from 1 to 10 atm. In Ar and Xe, the maximum attainable gain of the detector abruptly drops down for pressures exceeding 3 atm. In contrast, the maximum gain in Ne was found to increase with pressure, reaching a value of 100,000 at 7 atm. The results obtained are of particular interest for developing noble gas-based cryogenic particle detectors for solar neutrino and dark matter search.Comment: 7 pages, 4 figures. Submitted to Nucl. Instr. and Meth. A as a letter to the Edito

Deposisi Lapisan Tipis Zno:al Pada Substrat Alumina Untuk Bahan Sensor Gas

DEPOSISI LAPISAN TIPIS ZnO:Al PADA SUBSTRAT ALUMINA UNTUK BAHAN SENSOR GAS. Telah dilakukandeposisi lapisan tipis ZnO:Al pada substrat alumina menggunakan teknik DC Sputtering untuk aplikasi sensor gas.Deposisi lapisan tipis ZnO:Al dilakukan dengan parameter proses sputtering tegangan elektroda DC sebesar 2.2 kV,arus 10 mA dan suhu substrat 250oC, waktu deposisi divariasi 30 - 150 menit dengan interval 30 menit dan tekanandivariasi masing-masing : 1 ´ 10-2 atm, 2 ´ 10-2 atm, 3 ´ 10-2 atm, 4 ´ 10-2 atm dan 5 ´ 10-2 atm. Dari hasilkarakterisasi diperoleh nilai resistansi terendah sebesar 64 kΩ diperoleh pada kondisi waktu deposisi 90 menit dantekanan operasi 4 ´ 10-2 atm. Hasil pengukuran sensitivitas menunjukkan bahwa sensor gas dari bahan ZnO:Almempunyai sensitivitas tertinggi terhadap gas sensor C2H5OH sebesar 24%, untuk gas NH3 sebesar 19,77% danuntuk gas SO2 sebesar 17,53% pada 141,54 konsentrasi/volume

Microstructural development, electrical properties and oxygen permeation of zirconia-palladium composites

Yttria-stabilized cubic zirconia (YSZ)-palladium dual phase composites have been investigated. The percolative composite containing 40 vol% Pd (ZYPd40) showed a much larger oxygen permeability than that of the non-percolative composite containing 30 vol% Pd (ZYPd30). For a 2.0 mm thick percolative composite, an oxygen flux of 4.3 × 10−8 mol/cm2/s was measured at 1100 °C with oxygen partial pressures at the feed and permeate sides being 0.209 and 0.014 atm, respectively. This value is two orders of magnitude larger than that observed for a 2.0 mm thick non-percolative composite at the same temperature with the oxygen partial pressures at the feed and permeate sides being 0.209 and 1.5 × 10−4 atm, respectively. From the dependence of the oxygen permeation on the temperature and on the oxygen partial pressures, it was concluded that the transport of the oxygen ions through the YSZ phase in the percolative system was the rate limiting step

Gas phase homolytic bond dissociation enthalpies of common laboratory solvents: A G4 theoretical study

Gas phase standard state (298.15 K, 1 atm) calculations were conducted at the Gaussian-4 (G4) composite method level of theory to estimate the bond dissociation enthalpies (BDEs) of various common laboratory solvents. Excellent agreement was obtained between experimental and G4 estimated BDEs. The current study demonstrates the BDE prediction accuracy of the G4 method, and is also intended to function as a potentially useful resource in any reevaluations of the preferred BDEs for these common laboratory solvents