1,721,032 research outputs found
Fabrication of lasing microcavities consisting of highly luminescent colloidal nanocrystals
No full textRole of defect states on Auger processes in resonantly pumped CdSe nanorods
Full text linkThe authors investigated, by femtosecond pump-probe measurements, the effects on Auger and
trapping processes of excitation resonant R to the 1S absorption in CdSe nanorods. They
demonstrate that R pumping allows one to avoid exciton trapping in high energy defect states and
that the presence of empty defect states leads to an enhancement of the Auger relaxation, with
respect to the pumping at energies high above the band gap. Moreover, they show that, despite the
Auger enhancement, R pumping increases the stimulated emission lifetime demonstrating that it is
not limited by Auger scattering, as widely believed, but by photoabsorption processes, involving
defect states
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
Real-time observation of coherent nuclear motion in polydiacetylene isolated chains
No full textBy using sub-10-fs optical pulses we excite and probe vibrational coherence in isolated polydiacetylene
chains in benzene solution. The ultrafast relaxation process following photoexcitation allows selecting ground
state coherence only, as demonstrated by measurements carried out with chirped pulses and further supported
by quantum mechanical simulations. Vibrational ground state dephasing and dynamics are studied in the time
domain. Typically T2 is about 600 fs, but there is evidence of faster dephasing for higher vibrational levels.
Vibrational coherence in the excited state is short lived, but still detectable at the red tail of the broad pulse
spectrum, providing hints on the corresponding mode frequencies, which appear lower than the ground state
ones
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Role of the shell thickness in stimulated emission and photoinduced absorption in CdSe core/shell nanorods
Full text linkThe effect of the shell thickness on stimulated emission and photoinduced absorption transitions in CdSe quantum rods is investigated by femtosecond pump and probe spectroscopy. The role of surface/interface defect states, which result resonant to the high energy states and to the midgap, respectively, is pointed out. We find that the density of such states depend on the shell thickness and that the interface defects can be negligible for thin shells. As a result in the latter case stimulated emission can be observed for longer times
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