101 research outputs found

    New Ideas for in Vivo Detection of RNA

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    Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas

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    We experimentally study the group time delay for a light pulse propagating through hot Rb vapor in the presence of a strong coupling field in a Λ\Lambda configuration. We demonstrate that the ultra-slow pulse propagation is transformed into superluminal propagation as the one-photon detuning of the light increases due to the change in the transmission resonance lineshape. Negative group velocity as low as -c/10^6=-80 m/s is recorded. We also find that the advance time in the regime of the superluminal propagation grows linearly with increasing laser field power.Comment: 5 pages, 6 figure

    Coherent-population-trapping resonances with linearly polarized light for all-optical miniature atomic clocks

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    We present a joint theoretical and experimental characterization of the coherent population trapping (CPT) resonance excited on the D(1) line of (87)Rb atoms by bichromatic linearly polarized laser light. We observe high-contrast transmission resonances (up to approximate to 25%), which makes this excitation scheme promising forminiature all-optical atomic clock applications. We also demonstrate cancellation of the first-order light shift by proper choice of the frequencies and relative intensities of the two laser-field components. Our theoretical predictions are in good agreement with the experimental results

    New Pedagogy for Using Internet-Based Teaching Tools in Physics Course

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    Acquiring the mathematical, conceptual, and problem-solving skills required in university-level physics courses is hard work, and the average student often lacks the knowledge and study skills they need to succeed in the introductory courses. Here we propose a new pedagogical model and a straight-forwardly reproducible set of internet-based testing tools. Our work to address some of the most important student deficiencies is based on three fundamental principles: balancing skill level and challenge, providing clear goals and feedback at every stage, and allowing repetition without penalty. Our tools include an Automated Mathematics Evaluation System (AMES), a Computerized Homework Assignment Grading System (CHAGS), and a set of after-homework quizzes and mini-practice exams (QUizzes Intended to Consolidate Knowledge, or QUICK). We describe how these tools are incorporated into the course, and present some preliminary results on their effectiveness.Comment: 7 pages, 2 figures, submitted to the Physics Teache
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