1,721,136 research outputs found
Gravity-driven deepwater fold-and-thrust belts as Critical Coulomb Wedges: Model limitations and the role of friction vs. fluid pressure
No full textGravity-driven Deepwater Fold-and-thrust Belts (GDFB) are the result of gravitational collapse of the sedimentary pile along the continental shelf. These systems can be described in the framework of the Critical Coulomb Wedge (CCW) mechanics to infer their mechanical properties and hydrological conditions. However, not all GDFB can be considered as critical wedges and their mechanical/hydrological parameters should be critically assessed. GDFB driven by gravity spreading and detached onto brittle overpressured shales are the most suitable systems to be modeled via the original CCW theory. In addition, the self-limiting mechanism of gravitational collapse implies that GDFB can reach the critical state only during limited time intervals (in some cases less than similar to 10 Myr), in the presence of large sedimentary loads and shortening rates higher than 1.5-2 mm/yr. We present a compilation of GDFB that most likely represent examples of critical tapers, almost exclusively located downdip of large deltas. We then analyze several analytical solutions to the CCW equation, constrained by laboratory and geophysical data, to discuss the role of material friction and fluid pressures in GDFB. Low friction and moderate fluid overpressure localized in the basal detachment are both essential to explain the observed shape of GDFB. Frictional and overpressure discontinuities between detachment and the overlying wedge are likely to be maintained in GDFB
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
Astigmatismo corneale e taglio corneo-sclerale nell'intervento di estrazione intracapsulare di cataratta
No full textWhat PLS can still do for Imaging Genetics in Alzheimer's disease
No full textIn this work we exploited Partial Least Squares (PLS) model for analyzing the genetic underpinning of grey matter atrophy in Alzheimer's Disease (AD). To this end, 42 features derived from T1-weighted Magnetic Resonance Imaging, including cortical thicknesses and subcortical volumes were considered to describe the imaging phenotype, while the genotype information consisted of 14 recently proposed AD related Polygenic Risk Scores (PRS), calculated by including Single Nucleotide Polymorphism passing different significance thresholds. The PLS model was applied on a large study cohort obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database including both healthy individuals and AD patients, and validated on an independent ADNI Mild Cognitive Impairment (MCI) cohort, including Early (EMCI) and Late MCI (LMCI). The experimental results confirm the existence of a joint dynamics between brain atrophy and genotype data in AD, while providing important generalization results when tested on a clinically heterogeneous cohort. In particular, less AD specific PRS scores were negatively correlated with cortical thicknesses, while highly AD specific PRSs showed a peculiar correlation pattern among specific subcortical volumes and cortical thicknesses. While the first outcome is in line with the well known neurodegeneration process in AD, the second could be revealing of different AD subtypes
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
Genetic diversity at three palindromic sequences of the human Y chromosome
No full textOne of the most striking structural features of the male specific region of the human Y
chromosome (MSY) is the presence, within the ampliconic sequences, of eight massive
palindromes (P1-P8). Each palindrome is composed of two large inverted repeats (arms)
separated by a small “spacer” sequence at the centre. These elements, ranging from 30 kb
to 2.9 Mb, contain many testis-specific genes and typically exhibit > 99.9% intra-palindromic
(arm-to-arm) sequence identity. It has been hypothesized that the high observed sequence
similarity is due to abundant gene conversion events between the arms of each palindrome.
Although the occurrence of arm-to-arm gene conversion has been clearly demonstrated,
the effect of this molecular mechanism on the genetic diversity of palindromes, as well as
its rate and extension, remain largely unexplored. To gain new insights into the evolutionary
history of the human Y chromosome palindromic sequences and to shed light into the
dynamics of intra-palindrome gene conversion, we analysed by high-coverage next-
generation sequencing (50x) the shortest known palindromes (P6, P7 and P8) and their
relative spacers (for a total of about 0.3 Mb) in 158 samples chosen to represent most of the
independent evolutionary lineages (haplogroups) of the MSY. By this analysis we identified
several gene conversion events and a peculiar mutational pattern of the palindrome arms
with respect to the spacer. Moreover, we found few phylogenetically conserved paralogous
sequence variants (PSVs), suggestive of a high arm-to-arm gene conversion activity.
Because Y chromosomes are clonally inherited from father to son, it has been possible
to capture their evolutionary relationships in a robust phylogenetic tree with known age
of each node. By mapping gene conversion events across a Y tree based on thousands
of stable mutations obtained from 3.3 Mb of single copy MSY sequences, we were able to
calculate a precise Y-Y gene conversion rate for each of the palindromes here analysed
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