1,720,995 research outputs found
Extraction of a one-particle reduced density matrix from a quantum monte carlo electronic density: A new tool for studying nondynamic correlation
Full text linkIn this work, we present a method to build a first order reduced density matrix (1-RDM) of a molecule from variational Quantum Monte Carlo (VMC) computations by means of a given correlated mapping wave function. Such a wave function is modeled on a Generalized Valence Bond plus Complete Active Space Configuration Interaction form and fits at best the density resulting from the Slater-Jastrow wave function of VMC. The accuracy of the method proposed has been proved by comparing the resulting kinetic energy with the corresponding VMC value. This 1-RDM is used to analyze the amount of correlation eventually captured in Kohn-Sham calculations performed in an unrestricted approach (UKS-DFT) and with different energy functionals. We performed test calculations on a selected set of molecules that show a significant multireference character. In this analysis, we compared both local and global indicators of nondynamic and dynamic correlation. Moreover, following the natural orbital decomposition of the 1-RDM, we also compared the effective temperatures of the corresponding Fermi-like distributions. Although there is a general agreement between UKS-DFT and VMC, we found the best match with the functional LC-BLYP
Common fragile sites: a new tool to study chromosome instability diseases
Full text linkReplication stress is a major cause of Chromosomal Instability (CIN) that manifests as chromosome rearrangements, gaps and breaks, including those cytological expressed within specific chromosome regions named Common Fragile Sites (CFSs). The molecular mechanisms of CFSs instability have not been completely elucidated yet. In the first part of my work, I characterized the expression and the replication timing of human CFSs upon treatment with aphidicolin (APH), a DNA polymerase α (alpha) inhibitor, in three cellular lines: Glioblastoma Multiforme U-251 MG cell line and two isogenic Fanconi Anemia lymphoblastoid lines (the mutated HSC72 FA-A and the corrected HSC72 FANCA). GBM and FA cell lines are both associated with high physiological levels of CIN and thus are good genetic models to understand the causes underlying CFSs instability. Glioblastoma Multiforme (GBM) is a tumor of the Central Nervous System (CNS) and Fanconi Anemia (FA) is a rare multigenic disorder caused by mutations in FA DNA repair genes. I identified CFSs that showed a frequency equal to at least 1% of the total gaps/breaks: 17 CFSs in GBM, 16 CFSs in HSC72 FA-A, 19 CFSs in HSC72 FANCA. Only few of them were found to be cell type-specific. In the last part of my work, CFSs induced by 4', 6′-diamidino-2-phenylindole hydrochloride (DAPI), a DNA dye binding to AT-rich sequences and acting as an under-condensing agent in G2-phase, were analyzed in a pathological background such as FA cells (which are characterized by a prolonged G2-phase upon DNA damage) to understand how the post-replicative chromatin compaction is essential to their integrity. Presence of long genes, incomplete replication, improper chromatin condensation and DNA synthesis during mitosis (MiDAS) after APH and DAPI treatment suggest that impaired replication process and defective chromatin compaction may contribute to the loci-specific fragility in U-251 MG cells and in both HSC72 FA lymphoblasts cell lines. Altogether, my work offers a comprehensive characterization of CFSs expressed in GBM and FA cells that may be further exploited for cytogenetic and clinical studies to advance our understanding of the physiological status and these genic and genetic disorders
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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