Hole-LO phonon interaction in InAs/GaAs quantum dots

We investigate the valence intraband transitions in p-doped self-assembled InAs quantum dots using far-infrared magneto-optical technique with polarized radiation. We show that a purely electronic model is unable to account for the experimental data. We calculate the coupling between the mixed hole LO-phonon states using the Fr\"ohlich Hamiltonian, from which we determine the polaron states as well as the energies and oscillator strengths of the valence intraband transitions. The good agreement between the experiments and calculations provides strong evidence for the existence of hole-polarons and demonstrates that the intraband magneto-optical transitions occur between polaron states

Is the homophone advantage influenced by post-lexical effects?

No Abstract availabl

Temperature dependence of polarization relaxation in semiconductor quantum dots

The decay time of the linear polarization degree of the luminescence in strongly confined semiconductor quantum dots with asymmetrical shape is calculated in the frame of second-order quasielastic interaction between quantum dot charge carriers and LO phonons. The phonon bottleneck does not prevent significantly the relaxation processes and the calculated decay times can be of the order of a few tens picoseconds at temperature $T \simeq 100$K, consistent with recent experiments by Paillard et al. [Phys. Rev. Lett. {\bf86}, 1634 (2001)].Comment: 4 pages, 4 figure

Optical Phonon Lasing in Semiconductor Double Quantum Dots

We propose optical phonon lasing for a double quantum dot (DQD) fabricated in a semiconductor substrate. We show that the DQD is weakly coupled to only two LO phonon modes that act as a natural cavity. The lasing occurs for pumping the DQD via electronic tunneling at rates much higher than the phonon decay rate, whereas an antibunching of phonon emission is observed in the opposite regime of slow tunneling. Both effects disappear with an effective thermalization induced by the Franck-Condon effect in a DQD fabricated in a carbon nanotube with a strong electron-phonon coupling.Comment: 8 pages, 4 figure

HIV-1 Protease and Reverse Transcriptase Control the Architecture of Their Nucleocapsid Partner

The HIV-1 nucleocapsid is formed during protease (PR)-directed viral maturation, and is transformed into pre-integration complexes following reverse transcription in the cytoplasm of the infected cell. Here, we report a detailed transmission electron microscopy analysis of the impact of HIV-1 PR and reverse transcriptase (RT) on nucleocapsid plasticity, using in vitro reconstitutions. After binding to nucleic acids, NCp15, a proteolytic intermediate of nucleocapsid protein (NC), was processed at its C-terminus by PR, yielding premature NC (NCp9) followed by mature NC (NCp7), through the consecutive removal of p6 and p1. This allowed NC co-aggregation with its single-stranded nucleic-acid substrate. Examination of these co-aggregates for the ability of RT to catalyse reverse transcription showed an effective synthesis of double-stranded DNA that, remarkably, escaped from the aggregates more efficiently with NCp7 than with NCp9. These data offer a compelling explanation for results from previous virological studies that focused on i) Gag processing leading to nucleocapsid condensation, and ii) the disappearance of NCp7 from the HIV-1 pre-integration complexes. We propose that HIV-1 PR and RT, by controlling the nucleocapsid architecture during the steps of condensation and dismantling, engage in a successive nucleoprotein-remodelling process that spatiotemporally coordinates the pre-integration steps of HIV-1. Finally we suggest that nucleoprotein remodelling mechanisms are common features developed by mobile genetic elements to ensure successful replication

Absorption of Terahertz Radiation in Ge/Si(001) Heterostructures with Quantum Dots

The terahertz spectra of the dynamic conductivity and radiation absorption coefficient in germanium-silicon heterostructures with arrays of Ge hut clusters (quantum dots) have been measured for the first time in the frequency range of 0.3-1.2 THz at room temperature. It has been found that the effective dynamic conductivity and effective radiation absorption coefficient in the heterostructure due to the presence of germanium quantum dots in it are much larger than the respective quantities of both the bulk Ge single crystal and Ge/Si(001) without arrays of quantum dots. The possible microscopic mechanisms of the detected increase in the absorption in arrays of quantum dots have been discussed.Comment: 9 pages, 4 figures; typos correcte

Unbound states in quantum heterostructures

We report in this review on the electronic continuum states of semiconductor Quantum Wells and Quantum Dots and highlight the decisive part played by the virtual bound states in the optical properties of these structures. The two particles continuum states of Quantum Dots control the decoherence of the excited electron – hole states. The part played by Auger scattering in Quantum Dots is also discussed

Ageing with bilingualism: benefits and challenges

Much of the world’s population speaks more than one language, and there has been a great deal of media attention given to the potential benefits of bilingualism. In this paper we provide a critical overview of the literature on bilingualism as it relates to older adults. We address whether there is indeed a cognitive advantage from speaking more than one language, and whether it can help preserve cognitive and linguistic function as we age, and potentially reduce the impact of dementia. We also focus on the patterns of language impairment after stroke (aphasia) in bilingual speakers and the issues relating to clinical management of bilingual aphasia

Effects of phonological neighbourhood density and frequency in picture naming

This research investigated the effect of several phonological neighbourhood measures on spoken word production. More specifically, it investigated the hypothesis, derived from predictions of the Neighbourhood Activation Model (Luce & Pisoni, 1998) in auditory word recognition, that effects of phonological neighbours would be stronger on targets of lower frequency compared to targets of higher frequency, and that effects of phonological neighbours of higher frequency than the target would have stronger effects than phonological neighbours overall. This possibility was first investigated in a simple picture naming study involving 40 Australian speakers (Australian data file). An significant interaction was found between target log frequency and summed higher frequency PNF (the summed frequency of phonological neighbours of higher frequency than the target) on picture naming response times. Next, these analyses were replicated in another publicly available dataset (UK Johnston data file) and the critical interaction was replicated (in addition to an interaction between target log frequency and higher frequency PND (the number of neighbours of higher frequency than the target). In a third experiment, simulations were run with a modified version of the DRC model of reading (Coltheart et al.) created to simulate spoken word production from semantics, to find a set of parameters capable of simulating the effect that was found in both of the behavioural experiments. The Excel file explains column names for the 3 datasets

Data for: Effects of phonological neighbourhood density and frequency in picture naming.

This data includes raw data for the Australian picture naming data, the British picture naming data, and the DRC-SEM simulations data. The additional Excel file includes column names in full for each of these datasets, if relevant.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV