1,720,981 research outputs found
Full counting statistics for noninteracting fermions: joint probability distributions
No full textThe joint probability distribution in the full counting statistics (FCS) for noninteracting electrons is discussed for an arbitrary number of initially separate subsystems which are connected at t = 0 and separated again at a later time. A simple method to obtain the leading-order long-time contribution to the logarithm of the characteristic function is presented which simplifies earlier approaches. New explicit results for the determinant involving the scattering matrices are found. The joint probability distribution for the charges in two leads is discussed for Y junctions and dots connected to four leads
Core hole screening and decay rates of double core ionized first row hydrides
Full text linkBecause of the high intensity, X-ray free electron lasers allow one to create and probe double core ionized states in molecules. The decay of these multiple core ionized states crucially determines the evolution of radiation damage in single molecule diffractive imaging experiments. Here we have studied the Auger decay in hydrides of first row elements after single and double core ionization by quantum mechanical ab initio calculations. In our approach the continuum wave function of the emitted Auger electron is expanded into spherical harmonics on a radial grid. The obtained decay rates of double K-shell vacancies were found to be systematically larger than those for the respective single K-shell vacancies, markedly exceeding the expected factor of two. This enhancement is attributed to the screening effects induced by the core hole. We propose a simple model, which is able to predict core hole decay rates in molecules with low Z elements based on the electron density in the vicinity of the core hole
Erratum: “Core hole screening and decay rates of double core ionized first row hydrides” [J. Chem. Phys. 138, 164304 (2013)]
No full textErratum: “Auger spectrum of a water molecule after single and double core ionization” [J. Chem. Phys. 136, 144304 (2012)]
No full text
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
Auger spectrum of a water molecule after single and double core ionization
Full text linkThe high intensity of free electron lasers opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules, radiation damage induced by absorp- tion of high intense x-ray radiation is not yet fully understood. One of the striking effects which occurs under intense x-ray illumination is the creation of double core ionized molecules in con- siderable quantity. To provide insight into this process, we have studied the dynamics of water molecules in single and double core ionized states by means of electronic transition rate calcula- tions and ab initio molecular dynamics (MD) simulations. From the MD trajectories, photoioniza- tion and Auger transition rates were computed based on electronic continuum wavefunctions ob- tained by explicit integration of the coupled radial Schrödinger equations. These rates served to solve the master equations for the populations of the relevant electronic states. To account for the nuclear dynamics during the core hole lifetime, the calculated electron emission spectra for differ- ent molecular geometries were incoherently accumulated according to the obtained time-dependent populations, thus neglecting possible interference effects between different decay pathways. We find that, in contrast to the single core ionized water molecule, the nuclear dynamics for the double core ionized water molecule during the core hole lifetime leaves a clear fingerprint in the result- ing electron emission spectra. The lifetime of the double core ionized water was found to be sig- nificantly shorter than half of the single core hole lifetime
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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