1,721,343 research outputs found
Synthesis of Optically Active a-Halogeno Phosphinates via Asymmetric Selection
No full textSynthesis of Optically Active a-Halogeno Phosphinates via Asymmetric Selectio
Drosophila-related expressed sequences.
No full textThe study of model organisms has been instrumental towards the elucidation of the basic mechanisms of human biology. Drosophila melanogaster has been the target of extensive genetic analyses over the past 90 years and a notable amount of information is known about its gene structure, gene regulation and gene function. The vast gene resource generated by the expressed sequence tags (ESTs) efforts was exploited to identify, using a bioinformatic approach, novel human and murine gene transcripts homologous to Drosophila mutant genes. A systematic characterization of these genes, named Drosophila-related expressed sequences (DRES), was performed including genomic mapping in human and mouse and detailed study of their expression pattern by RNA in situ hybridization experiments. Comparison between DRES genes and their putative partners in Drosophila contributes to the understanding of their function in mammals and to the discovery of their possible role in disease
Shock waves in the magnetized cosmic web: the role of obliquity and cosmic ray acceleration
Full text linkStructure formation shocks are believed to be the largest accelerators of cosmic rays in the Universe. However, little is still known about their efficiency in accelerating relativistic electrons and protons as a function of their magnetization properties, i.e. of their magnetic field strength and topology. In this work, we analyzed both uniform and adaptive mesh resolution simulations of large-scale structures with the magnetohydrodynamical grid code Enzo, studying the dependence of shock obliquity with different realistic scenarios of cosmic magnetism. We found that shock obliquities are more often perpendicular than what would be expected from a random three-dimensional distribution of vectors, and that this effect is particularly prominent in the proximity of filaments, due to the action of local shear motions. By coupling these results to recent works from particle-in-cell simulations, we estimated the flux of cosmic-ray protons in galaxy clusters, and showed that in principle the riddle of the missed detection of hadronic γ-ray emission by the Fermi-LAT can be explained if only quasi-parallel shocks accelerate protons. On the other hand, for most of the cosmic web the acceleration of cosmic-ray electrons is still allowed, due to the abundance of quasi-perpendicular shocks. We discuss quantitative differences between the analyzed models of magnetization of cosmic structures, which become more significant at low cosmic overdensities
How to get the best of dbEST
No full textExpressed sequence tags (ESTs) are nucleotide sequences generated from the ends of randomly selected cDNA clones. The remarkable expansion of EST efforts in the past seven years[ 1 , 2 , 3 ]has undoubtedly led to a revolutionary change in the strategies used by molecular geneticists for identifying and cloning novel genes. More than 1 200 000 entries generated from different tissues and species are now stored in the public EST database (dbEST)[ 4 , 5 ], maintained at the National Center for Biotechnology Information (NCBI). Human and mouse sequences form the majority of the data held in this collection, with 833 000 and 237 000 entries, respectively (as of 25 October, 1997)[ 6 ]. For most of the clones, ESTs have been generated at both ends and the corresponding sequence traces can be easily retrieved for quality checking[ 7 ]; furthermore, it is possible to obtain in a few days most of the EST cDNA clones, such as the ones generated by the IMAGE consortium and The Institute for Genomic Research (TIGR)[ 1 , 8 ], from international distributors[ 9 ]. EST clones represent useful molecular tools for gene characterization experiments, expression studies, and expression of recombinant proteins. In most cases, a single EST clone (average insert size around 1.5 kb) does not span the entire coding region of a gene. However, before starting any experimental procedure aimed at the isolation of the remaining part of the transcript, it must be pointed out that several bioinformatic tools exist that allow one to obtain full-length transcript information and refined chromosomal mapping assignment
On the alignment of haloes, filaments and magnetic fields in the simulated cosmic web
Full text linkThe continuous flow of gas and dark matter across scales in the cosmic web can generate correlated dynamical properties of haloes and filaments (and the magnetic fields they contain). With this work, we study the halo spin properties and orientation with respect to filaments, and the morphology of the magnetic field around these objects, for haloes with masses in the range ∼108-1014 M⊙ and filaments up to ∼8 Mpc long. Furthermore, we study how these properties vary in presence, or lack thereof, of different (astro)physical processes and with different magnetic initial conditions. We perform cosmological magnetohydrodynamical simulations with the Eulerian code ENZO and we develop a simple and robust algorithm to study the filamentary connectivity of haloes in three dimensions. We investigate the morphological and magnetic properties and focus on the alignment of the magnetic field along filaments: our analysis suggests that the degree of this alignment is partially dependent on the physical processes involved, as well as on magnetic initial conditions. We discuss the contribution of this effect on a potential attempt to detect the magnetic field surrounding these objects: we find that it introduces a bias in the estimation of the magnetic field from Faraday rotation measure techniques. Specifically, given the strong tendency we find for extragalactic magnetic fields to align with the filaments axis, the value of the magnetic field can be underestimated by a factor ∼3, because this effect contributes to making the line-of-sight magnetic field (for filaments in the plane of the sky) much smaller than the total one
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
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