Chromosomal inversions have been an enduring interest of population geneticists since their discovery in Drosophila melanogaster. Numerous lines of evidence suggest powerful selective pressures govern the distributions of polymorphic inversions, and these observations have spurred the development of many explanatory models. However, due to a paucity of nucleotide data, little progress has been ...

We propose the use of spectrally colored rather than white (i.e., incoherent) population pumping in lasing-without-inversion schemes. We show that colored pumping can lead to a significant enhancement in gain by presenting explicit results for the gain in a three-level ladder system. These results are obtained from Monte Carlo simulations of the coupled density-matrix-equations, which, for a co...

We present a microscopic theory for both equilibrium and nonequilibrium transport properties of coupled double quantum dots (DQD). A general formula for current tunneling through the DQD is derived by the nonequilibrium Green’s function method. Using a Hartree-Fock approach, effects of multilevel coupling and nonequilibrium electron distributions in resonant tunneling are considered. We find th...

An optically-pumped intersubband laser generator is proposed in which the continuum states above an A1 0.2Ga 0.8.4s GaAs A1 o2Ga o.sAs single quantum well with a width of L = 17 nm serve as the highest level in a four-level laser system. The design allows much greater flexibility in the choice of pumping source and simplifies considerabb the device fabrication. We have obtained the electronic s...

Articles you may be interested in Plasma broadening and shifting of analogous spectral lines along isoelectronic sequences AIP Conf. Abstract: Level populations and line intensities are calculated for a pure Ne-like argon plasma showing their dependence on plasma parameters (electron temperature, density, plasma colmnn diameter, electron energy distribution, etc.). It is shown that intensity ra...

Electrical detection of adiabatic rapid passage ARP in quantum dot ensembles is explored by extension of a simple physical model. We include exciton and biexciton states and model the current flow into the external circuit which occurs following ionization of the exciton and tunneling of the separate carriers. The inversion produced by ARP is robust with respect to fluctuations in coupling and ...

We have investigated a solid–state design advanced (Soref et al. SPIE Proceedings, vol. 3795, 516 (1999)) to achieve Terahertz-Amplification-by-the-Stimulated-Emission-of-Radiation (TASER). The original design was based on lightto heavy-hole intersubband transitions in SiGe/Si heterostructures. This work adapts the design to electron intersubband transitions in the more readily available GaAs/G...

an experimental study of the phase inversion behavior of liquid-liquid dispersion has been conducted in a spray extraction column for systems of toluene / water, n-hexane/water, ccl4/water, toluene /water + glycerol (25 % wt), toluene + ccl4 (25 % wt) / water and toluene / acetic acid (5 % wt)/water. the effects of physical properties, mass transfer and column geometry on phase inversion have b...

In an isolated population of Drosophila melanogaster on Ishigaki Island the chromosomal distribution of several retrotransposons, including copia, 412, 297, 17.6, I, and jockey elements, was examined by in situ hybridization. In this population the cosmopolitan inversion, In(2L)t, is known to exist in high frequency. One major haplotype concerning the occupied sites of the transposable elements...