1,721,070 research outputs found
Maximal coherence in a three-level autoionising atom for the generation of subpicosecond pulses in the extreme ultraviolet
No full textWe discuss the possibility of using a three-level ladder atomic system, with a final autoionizing state, for the efficient generation of short radiation pulses in the extreme ultraviolet through a process of sum-frequency mixing in the presence of maximal coherence. The results of numerical calculations are presented, investigating the effects of photoionization, dynamic Stark shift and electron impact dephasing on the conversion efficiency in a single atom model.
The results of this investigation can be useful in identifying a real candidate for a possible experiment
Body Composition Assessment of Undernourished Older Subjects by Dual-Energy X-Ray Absorptiometry and Bioelectric Impedance Analysis (1)
Full text linkTemporal compression of short-wavelength laser pulses by coherent control in rare gases
No full textWe present a theoretical study of temporal compression of a short-wavelength laser pulse predicted in a real, Doppler-broadened, atomic system. The compression is the result of the coherent control peculiarities of electromagnetically induced transparency-propagation dynamics. Numerical results are reported and discussed, showing a temporal compression of 2 orders of magnitude (from 10 ns to 100 ps) of a 106.7-nm laser pulse in argon atoms at room temperature
Comment on Large enhancement of four-wave mixing by suppression of photon absorption from electromagnetically induced transparency
No full textIn this Comment we deal with a recent study of Ying Wu et al. Phys. Rev. A 67, 013811 2003 on a four-wave mixing process. We show that the authors’ claim, that a large enhancement of the generation
efficiency can be obtained by suppression of photon absorption from electromagnetically induced transparency, is not correct
Coherent control of temporal pulse shaping by electromagnetically induced transparency
No full textWe present the coherent control of the temporal shape of laser pulses obtained by exploiting the propagation dynamics of electromagnetically induced transparency. Temporal compression, as a special case of pulse tailoring, is discussed. We envisage applications in nonlinear optics processes and control of pulse shapes in the vacuum ultraviolet spectral region
Comment [on Opening optical four-wave mixing channels with giant enhancement using ultraslow pump waves]
No full textIn their recent study [Phys. Rev. Lett. 88, 143902 (2002)] on a four-wave mixing (FWM) process, Deng et al. state that ‘‘many orders of magnitude enhancement in the amplitude of the generated wave’’ is obtained when electromagnetically induced transparency (EIT) is present. Here we will show that their claim is deeply misleading
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Laser pulse compression by coherent control in a Doppler broadened medium: Analytical and numerical studies
No full textWe have studied the temporal compression of laser pulses occurring in a scheme based on the coherent control peculiarities of electromagnetically induced transparency. This work extends earlier model studies, including the effect of Doppler broadening in a real hot medium. For definiteness and consistency of the atomic parameters employed, we have treated a scheme in argon. In this way, we establish a realistic model that enables us to predict quantitatively the performance of laser pulse compression experiments
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