440 research outputs found

    Reply to a Commentary "Asking photons where they have been without telling them what to say"

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    Interesting objections to conclusions of our experiment with nested interferometers raised by Salih in a recent Commentary are analysed and refuted.Comment: Published version (Frontiers in Physics) to revised version of the Commentar

    Practical Quantum Bit Commitment Protocol

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    A quantum protocol for bit commitment the security of which is based on technological limitations on nondemolition measurements and long-term quantum memory is presented.Comment: Quantum Inf. Process. (2011

    Raman scattering in a two-dimensional electron gas: Boltzmann equation approach

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    The inelastic light scattering in a 2-d electron gas is studied theoretically using the Boltzmann equation techniques. Electron-hole excitations produce the Raman spectrum essentially different from the one predicted for the 3-d case. In the clean limit it has the form of a strong non-symmetric resonance due to the square root singularity at the electron-hole frequency ω=vk\omega = vk while in the opposite dirty limit the usual Lorentzian shape of the cross section is reestablished. The effects of electromagnetic field are considered self-consistently and the contribution from collective plasmon modes is found. It is shown that unlike 3-d metals where plasmon excitations are unobservable (because of very large required transfered frequencies), the two-dimensional electron system gives rise to a low-frequency (ωk1/2\omega \propto k^{1/2}) plasmon peak. A measurement of the width of this peak can provide data on the magnitude of the electron scattering rate.Comment: 4 pages, 3 figures. to appear in Phys. Rev. B 59 (1999

    Temporary Trans-gastric Stent Deployment Over a 20 French Gastrostomy for Single-Stage Endoscopic Retrograde Cholangiopancreatography After Gastric Bypass

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    Introduction: Treatment of pancreato-biliary disorders after gastric bypass is challenging due to altered anatomy. Several techniques have been proposed to overcome this condition; however, none has emerged as the gold standard treatment. Furthermore, a decision-making algorithm evaluating when and why apply one technique over another is still lacking. Objectives: To describe a novel trans-gastric approach to allow endoscopic retrograde cholangiopancreatography (ERCP) in Roux-en-Y gastric bypass (RYGB) anatomy soon after prior laparoscopic cholecystectomy (LC) and to propose a decision-making algorithm for selection of the most suitable technique according a tailored approach. Setting: Private hospital. Methods: Between January and March 2020, patients with Roux-en-Y gastric bypass anatomy referred to our tertiary center to undergo ERCP after recent laparoscopic cholecystectomy were retrospectively evaluated. A 20 french (Fr) gastrostomy was performed during cholecystectomy. A single-stage ERCP was carried out by means of temporary trans-gastric stent deployment over a 20 Fr gastrostomy. Results: A total of 5 patients (mean age 41; mean body mass index 48.3) were enrolled. ERCP was performed after an average of 2 days from surgery. Technical and clinical success was achieved in 100%. No adverse events occurred. Spontaneous closure of the gastrostomy after its bedside removal was observed in all cases. Conclusions: Our approach allows to perform a single-stage ERCP in RYGB patients, early after LC, with no need of any other re-interventions. Any surgeon facing unexpected biliary disorders, during LC, can easily perform a 20 Fr gastrostomy thus allowing the patient to undergo early ERCP without any delay

    Inelastic light scattering and the excited states of many-electron quantum dots

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    A consistent calculation of resonant inelastic (Raman) scattering amplitudes for relatively large quantum dots, which takes account of valence-band mixing, discrete character of the spectrum in intermediate and final states, and interference effects, is presented. Raman peaks in charge and spin channels are compared with multipole strengths and with the density of energy levels in final states. A qualitative comparison with the available experimental results is given.Comment: 5 pages, accepted in J. Phys.: Condens. Matte

    Semiquantitative theory of electronic Raman scattering from medium-size quantum dots

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    A consistent semiquantitative theoretical analysis of electronic Raman scattering from many-electron quantum dots under resonance excitation conditions has been performed. The theory is based on random-phase-approximation-like wave functions, with the Coulomb interactions treated exactly, and hole valence-band mixing accounted for within the Kohn-Luttinger Hamiltonian framework. The widths of intermediate and final states in the scattering process, although treated phenomenologically, play a significant role in the calculations, particularly for well above band gap excitation. The calculated polarized and unpolarized Raman spectra reveal a great complexity of features and details when the incident light energy is swept from below, through, and above the quantum dot band gap. Incoming and outgoing resonances dramatically modify the Raman intensities of the single particle, charge density, and spin density excitations. The theoretical results are presented in detail and discussed with regard to experimental observations.Comment: Submitted to Phys. Rev.

    2005 French Salmonella Network data on antimicrobial resistance in the swine channels

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    The Salmonella Network is gathering, on a voluntary participation scheme, from approximately 150 public and private laboratories dissemmated throughout France, Salmonella strains and/or epidemiological information. Those non-human Salmonella strains are isolated either from animal health and production or food, feed and the environment sectors. Thus, in 2005, a total of 527 isolations from the swine channels were reported. The top 5 prevalent serotypes were : Typhimurium, Derby, Manhattan, lnfantis and Kedougou. Two-hundred and ninety five strains were received at the laboratory and, after double clearance, 185 strains were tested for their antimicrobial resistance against 16 antibiotics by the disk diffusion method. Twenty-one strains were associated to the animal health and production sector and 164 to the food sector

    First Principles Calculation of Anomalous Hall Conductivity in Ferromagnetic bcc Fe

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    We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. The theory is able to account for both dc and magneto-optical Hall conductivities with no adjustable parameters.Comment: 4 pages, 6 figures, author list correcte

    Smart subtitles for vocabulary learning

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    Language learners often use subtitled videos to help them learn. However, standard subtitles are geared more towards comprehension than vocabulary learning, as translations are nonliteral and are provided only for phrases, not vocabulary. This paper presents Smart Subtitles, which are interactive subtitles tailored towards vocabulary learning. Smart Subtitles can be automatically generated from common video sources such as subtitled DVDs. They provide features such as vocabulary definitions on hover, and dialog-based video navigation. In our pilot study with intermediate learners studying Chinese, participants correctly defined over twice as many new words in a post-viewing vocabulary test when they used Smart Subtitles, compared to dual Chinese-English subtitles. Learners spent the same amount of time watching clips with each tool, and enjoyed viewing videos with Smart Subtitles as much as with dual subtitles. Learners understood videos equally well using either tool, as indicated by self-assessments and independent evaluations of their summaries
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