PHOTOLUMINESCENCE STUDIES ON VERY HIGH-DENSITY 2-DIMENSIONAL ELECTRON GASES IN PSEUDOMORPHIC MODULATION-DOPED QUANTUM-WELLS

We present photoluminescence studies on highly dense two-dimensional electron gases in selectively Si delta-doped GaAs/In0.18Ga0.82As/Al0.25Ga0.75As quantum wells (N(s) = 4.24 x 10(12) cm-2). Five well-resolved photoluminescence lines centered at 1.4194, 1.4506, 1.4609, 1.4695 and 1.4808 eV were observed, which are attributed to the subband excition emission. The subband separations clearly exhibit the feature of a typical quantum well with triangle and square potential. These very intensive and sharp luminescence peaks with linewidths of 2.2 to 3.5 meV indicate the high quality of the structures. Their dependence on the excitation intensity and temperatures are also discussed.

Carbonaceous aerosols in PM10 and pollution gases in winter in Beijing

IEECAS SKLLQG

Retrieval of Electron Return Time from High-order Harmonics Generated in a Mixture of He and Ne Gases

In terms of single-atom induced dipole moment by Lewenstein model, we present the macroscopic high-order harmonic generation from mixed He and Ne gases with different mixture ratios by solving three-dimensional Maxwell's equation of harmonic field. And then we show the validity of mixture formulation by Wagner et al. [Phys. Rev. A 76 (2007) 061403(R)] in macroscopic response level. Finally, using least squares fitting we retrieve the electron return time of short trajectory by formulation in Kanai et al. [Phys. Rev. Lett. 98 (2007) 153904] when the gas jet is put after the laser focus.

A Comparison of the Contribution of Various Gases to the Greenhouse Effect

The current concern about an anthropogenic impact on global climate has made it of interest to compare the potential effect of various human activities. A case in point is the comparison between the emission of greenhouse gases from the use of natural gas and that from other fossil fuels. This comparison requires an evaluation of the effect of methane emissions relative to that of carbon dioxide emissions. A rough analysis based on the use of currently accepted values shows that natural gas is preferable to other fossil fuels in consideration of the greenhouse effect as long as its leakage can be limited to 3 to 6 percent.

Application of acetone and dimethyl ether chemical ionization reagent gases to structural analysis

Acetone and dimethyl ether( DME) have been shown to be reagent gases of exceptional utitlity and versatility for the characterization of a variety of class of organic compounds. The fragmentation mechanisms of the adduct product ions, formed by ion/molceule reaction of the substrate with the ionized gases, have been studied and substantiated by experiments with acetone-d(6) and DME-d(6).

AN EXTENSION OF THE METHOD FOR PREDICTING PERMEABILITY THROUGH POLYMER MEMBRANES FROM SIMPLE GASES TO WATER-VAPOR

It is found that there is a linear relationship between log P-w, and the parameter term V-f/0.5 E(coh) [1+(delta(w) - delta(p))(2)/delta(p)(2), from the water permeability (P-w) data of 21 polymers covering 4 orders of magnitude. This correlation may be useful in choosing membrane materials for dehumidification of gases.

STUDIES ON THE SULFONATION OF POLY(PHENYLENE OXIDE) (PPO) AND PERMEATION BEHAVIOR OF GASES AND WATER-VAPOR THROUGH SULFONATED PPO MEMBRANES .3. SORPTION BEHAVIOR OF WATER-VAPOR IN PPO AND SULFONATED PPO MEMBRANES

Water vapor absorption and desorption by poly (phenylene oxide) (PPO) and sulfonated PPO (SPPO) membranes were studied at a constant temperature of 30-degrees-C and over a broad range of water activity (0.05 less-than-or-equal-to a < 0.8) by the weighing

Efeito do lodo de esgoto nos fluxos de gases na interface solo-atmosfera.

O objetivo do presente trabalho foi estudar o efeito da aplicação a longo prazo e continuada de lodo de esgoto da Estação de Tratamento de Esgoto de Barueri, SP, no fluxo de gases na interface soloatmosfera sob condições de campo e em condições tropicais.