376 research outputs found

    Identification and discrimination of eight Greek grape cultivars (Vitis vinifera L.) by random amplified polymorphic DNA markers

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    Fifteen decamer primers of an arbitrary nucleotide sequence were used to amplify genomic DNA by polymerase chain reaction (PCR-RAPD) in order to identify and discriminate between 8 cultivars of Vitis vinifera L., grown at the Island of Crete. Over 140 reproducible polymorphic fragments were generated by this method. Each grape cultivar showed a unique banding pattern for more than 5 of the primers used. Herefrom, the degree of genetic similarity was calculated and the dendrogram of the 8 cultivars was constructed. The results show that RAPD is a reliable and very useful method for the identification and genomic analysis of grape cultivars

    Operation speed of polariton condensate switches gated by excitons

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    We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polariton condensate switch in a quasi-1D semiconductor microcavity. The polariton flow across the ridge is gated by excitons inducing a barrier potential due to repulsive interactions. A study of the device operation dependence on the power of the pulsed gate beam obtains a satisfactory compromise for the ON/OFF-signal ratio and -switching time of the order of 0.3 and 50\thicksim50 ps, respectively. The opposite transition is governed by the long-lived gate excitons, consequently the OFF/ON-switching time is 200\thicksim200 ps, limiting the overall operation speed of the device to 3\thicksim3 GHz. The experimental results are compared to numerical simulations based on a generalized Gross-Pitaevskii equation, taking into account incoherent pumping, decay and energy relaxation within the condensate.Comment: 11 pages, 11 figure

    Polariton Condensate Transistor Switch

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    A polariton condensate transistor switch is realized through optical excitation of a microcavity ridge with two beams. The ballistically ejected polaritons from a condensate formed at the source are gated using the 20 times weaker second beam to switch on and off the flux of polaritons. In the absence of the gate beam the small built-in detuning creates potential landscape in which ejected polaritons are channelled toward the end of the ridge where they condense. The low loss photon-like propagation combined with strong nonlinearities associated with their excitonic component makes polariton based transistors particularly attractive for the implementation of all-optical integrated circuits
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