1,479 research outputs found

    Three-dimensional foam flow resolved by fast X-ray tomographic microscopy

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    Thanks to ultra fast and high resolution X-ray tomography, we managed to capture the evolution of the local structure of the bubble network of a 3D foam flowing around a sphere. As for the 2D foam flow around a circular obstacle, we observed an axisymmetric velocity field with a recirculation zone, and indications of a negative wake downstream the obstacle. The bubble deformations, quantified by a shape tensor, are smaller than in 2D, due to a purely 3D feature: the azimuthal bubble shape variation. Moreover, we were able to detect plastic rearrangements, characterized by the neighbor-swapping of four bubbles. Their spatial structure suggest that rearrangements are triggered when films faces get smaller than a characteristic area.Comment: 5 pages, 5 figure

    Leukocytosis as a Predictor of Severe Injury in Blunt Trauma

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    Objective: The objective of this study was to determine if the white blood cell count can predict severity of injury in blunt trauma victims.Methods: This was a retrospective study comparing two groups of blunt trauma victims by severity of injury, one with significant injury and one without significant injury, and comparing their initial WBC in the emergency department (ED). We also examined if WBC correlates with degree of injury using Injury Severity Score (ISS) in both groups combined. Further, we examined the WBC as a predictor of serious injury.Results: Our study showed a difference in mean WBC between the two groups that was statistically significant (p<0.001). A positive relationship between ISS and WBC was found, although the association was weak (correlation coefficient = 0.369). While the WBC had moderate discriminatory capability for serious injury, it could not, in isolation, reliably rule in or out serious injury. Nevertheless, this study supports using WBC on presentation to the ED as an adjunct for making disposition decisions.Conclusion: A significant elevation in WBC in a blunt trauma patient, even with minimal initial signs of severe injury, should heighten suspicion for occult injury

    Chronography of the Milky Way's Halo System with Field Blue Horizontal-Branch Stars

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    In a pioneering effort, Preston et al. reported that the colors of blue horizontal-branch (BHB) stars in the halo of the Galaxy shift with distance, from regions near the Galactic center to about 12 kpc away, and interpreted this as a correlated variation in the ages of halo stars, from older to younger, spanning a range of a few Gyrs. We have applied this approach to a sample of some 4700 spectroscopically confirmed BHB stars selected from the Sloan Digital Sky Survey to produce the first "chronographic map" of the halo of the Galaxy. We demonstrate that the mean de-reddened g−-r color, , increases outward in the Galaxy from −-0.22 to −-0.08 (over a color window spanning [−-0.3:0.0]) from regions close to the Galactic center to ~40 kpc, independent of the metallicity of the stars. Models of the expected shift in the color of the field BHB stars based on modern stellar evolutionary codes confirm that this color gradient can be associated with an age difference of roughly 2-2.5 Gyrs, with the oldest stars concentrated in the central ~15 kpc of the Galaxy. Within this central region, the age difference spans a mean color range of about 0.05 mag (~0.8 Gyrs). Furthermore, we show that chronographic maps can be used to identify individual substructures, such as the Sagittarius Stream, and overdensities in the direction of Virgo and Monoceros, based on the observed contrast in their mean BHB colors with respect to the foreground/background field population.Comment: 6 pages, 4 figures, ApJ letter

    Integrazioni alla flora vascolare dell’Italia centrale.

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    Additions to the vascular flora of the Central Italy. In this work new floristic records for 46 units are reported for some regions of Central Italy. Particularly 25 are new or confirmed to Abruzzo, 1 is new to Marche and 1 to Molise. In addition new distribution data for 18 units rare or interesting in Abruzzo and 1 in Molise regions have been recorded. The survey was carried out from 2010 to 2015 through field research, revision of herbarium specimens and literature studies. Some recorded species are particularly interesting from a phytogeo¬graphical or conservational point of view as they are very rare in Cen¬tral Italy. The results also show a high presence of new alien species

    A thermodynamical fiber bundle model for the fracture of disordered materials

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    We investigate a disordered version of a thermodynamic fiber bundle model proposed by Selinger, Wang, Gelbart, and Ben-Shaul a few years ago. For simple forms of disorder, the model is analytically tractable and displays some new features. At either constant stress or constant strain, there is a non monotonic increase of the fraction of broken fibers as a function of temperature. Moreover, the same values of some macroscopic quantities as stress and strain may correspond to different microscopic cofigurations, which can be essential for determining the thermal activation time of the fracture. We argue that different microscopic states may be characterized by an experimentally accessible analog of the Edwards-Anderson parameter. At zero temperature, we recover the behavior of the irreversible fiber bundle model.Comment: 18 pages, 10 figure

    Subcritical crack growth in fibrous materials

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    We present experiments on the slow growth of a single crack in a fax paper sheet submitted to a constant force FF. We find that statistically averaged crack growth curves can be described by only two parameters : the mean rupture time τ\tau and a characteristic growth length ζ\zeta. We propose a model based on a thermally activated rupture process that takes into account the microstructure of cellulose fibers. The model is able to reproduce the shape of the growth curve, the dependence of ζ\zeta on FF as well as the effect of temperature on the rupture time τ\tau. We find that the length scale at which rupture occurs in this model is consistently close to the diameter of cellulose microfibrils

    Crackling dynamics in material failure as the signature of a self-organized dynamic phase transition

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    We derive here a linear elastic stochastic description for slow crack growth in heterogeneous materials. This approach succeeds in reproducing quantitatively the intermittent crackling dynamics observed recently during the slow propagation of a crack along a weak heterogeneous plane of a transparent Plexiglas block [M{\aa}l{\o}y {\it et al.}, PRL {\bf 96} 045501]. In this description, the quasi-static failure of heterogeneous media appears as a self-organized critical phase transition. As such, it exhibits universal and to some extent predictable scaling laws, analogue to that of other systems like for example magnetization noise in ferromagnets

    Aggiunte alla flora vascolare d’Abruzzo e aree limitrofe. IV contributo

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    Additions to the vascular flora of Abruzzo and surrounding. IV contribution. In this paper new floristic records for 22 units are reported for Central Italy, mainly for Abruzzo. In particular 14 taxa are native and 8 aliens, 16 are new or confirmed to Abruzzo, 1 is new to Marche. In addition new distribution data for 4 rare or interesting in Abruzzo and 1 in Lazio regions have been recorded. Some of these species are particularly interesting from a phytogeographical or conservational point of view as they are very rare in Central Italy (Antirrhinum siculum, Convolvulus pentapetaloides and Vicia melanops)

    HGDiscovery: an online tool providing functional and phenotypic information on novel variants of homogentisate 1,2- dioxigenase

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    Alkaptonuria (AKU), a rare genetic disorder, is characterized by the accumulation of homogentisic acid (HGA) in the body. Affected individuals lack functional levels of an enzyme required to breakdown HGA. Mutations in the homogentisate 1,2-dioxygenase (HGD) gene cause AKU and they are responsible for deficient levels of functional HGD, which, in turn, leads to excess levels of HGA. Although HGA is rapidly cleared from the body by the kidneys, in the long term it starts accumulating in various tissues, especially cartilage. Over time (rarely before adulthood), it eventually changes the color of affected tissue to slate blue or black. Here we report a comprehensive mutation analysis of 111 pathogenic and 190 non-pathogenic HGD missense mutations using protein structural informa-tion. Using our comprehensive suite of graph-based signature methods, mCSM complemented with sequence-based tools, we studied the functional and molecular consequences of each mutation on protein stability, inter-action and evolutionary conservation. The scores generated from the structure and sequence-based tools were used to train a supervised machine learning algorithm with 89% accuracy. The empirical classifier was used to generate the variant phenotype for novel HGD missense mutations. All this information is deployed as a user friendly freely available web server called HGDiscovery (https://biosig.lab.uq.edu.au/hgdiscovery/)
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