1,721,149 research outputs found
Tuning the Fluorescence Emission Spectra of a Single Molecule with a Variable Optical Subwavelength Metal Microcavity
No full textWe present experimental and theoretical results on changing the fluorescence emission spectrum of a single molecule by embedding it within a tunable planar microcavity with subwavelength spacing. The cavity length is changed with nanometer precision by using a piezoelectric actuator. By varying its length, the local mode structure of the electromagnetic field is changed together with the radiative coupling of the emitting molecule to the field. Because mode structure and coupling are both frequency dependent, this leads to a renormalization of the emission spectrum of the molecule. We develop a theoretical model for these spectral changes and find excellent agreement between theoretical prediction and experimental results
Tight focusing of laser beams in a λ/2-microcavity
No full textWe evaluate the field distribution in the focal spot of the fundamental Gaussian beam as well as radially and azimuthally polarized doughnut beams focused inside a planar metallic sub-wavelength microcavity using a high numerical aperture objective lens. We show that focusing in the cavity results in a much tighter focal spot in longitudinal direction compared to free space and in spatial discrimination between longitudinal and in-plane field components. In order to verify the modeling results we experimentally monitor excitation patterns of fluorescence beads inside the λ/2-cavity and find them in full agreement to the modeling predictions. We discuss the implications of the results for cavity assisted single molecular spectroscopy and intra-cavity single molecular imaging
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Electrodynamic Coupling of Electric Dipole Emitters to a Fluctuating Mode Density within a Nanocavity
No full textWe investigate the impact of rotational diffusion on the electrodynamic coupling of fluorescent dye molecules (oscillating electric dipoles) to a tunable planar metallic nanocavity. Fast rotational diffusion of the molecules leads to a rapidly fluctuating mode density of the electromagnetic field along the molecules’ dipole axis, which significantly changes their coupling to the field as compared to the opposite limit of fixed dipole orientation. We derive a theoretical treatment of the problem and present experimental results for rhodamine 6G molecules in cavities filled with low and high viscosity liquids. The derived theory and presented experimental method is a powerful tool for determining absolute quantum yield values of fluorescence
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Measurement of Vibrational Modes in Single SiO2 Nanoparticles Using a Tunable Metal Resonator with Optical Subwavelength Dimensions
No full textUsing a tunable optical subwavelength microcavity, we demonstrate controlled modification of the vibronic relaxation dynamics in a single SiO2 nanoparticle. By varying the distance between the cavity mirrors we change the electromagnetic field mode structure around a single nanoparticle and the radiative transition probability from the lowest vibronic level of the electronically excited state to the progression of phonon levels in the electronic ground state. We demonstrate redistribution of the photoluminescence spectrum between zero-phonon and phonon-assisted bands and modification of the excited state lifetime of the same individual SiO2 particle measured at different cavity lengths. By comparing the experimental data with a theoretical model, we extract the quantum yield of a single SiO2 nanoparticle
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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