26 research outputs found
Impact flux on Jupiter: From superbolides to large-scale collisions
Context. Regular observations of Jupiter by a large number of amateur astronomers have resulted in the serendipitous discovery of short bright flashes in its atmosphere, which have been proposed as being caused by impacts of small objects. Three flashes were detected: one on June 3, 2010, one on August 20, 2010, and one on September 10, 2012. Aims. We show that the flashes are caused by impacting objects that we characterize in terms of their size, and we study the flux of small impacts on Jupiter. Methods. We measured the light curves of these atmospheric airbursts to extract their luminous energy and computed the masses and sizes of the objects. We ran simulations of impacts and compared them with the light curves. We analyzed the statistical significance of these events in the large pool of Jupiter observations. Results. All three objects are in the 5-20 m size category depending on their density, and they released energy comparable to the recent Chelyabinsk airburst. Model simulations approximately agree with the interpretation of the limited observations. Biases in observations of Jupiter suggest a rate of 12-60 similar impacts per year and we provide software tools for amateurs to examine the faint signature of impacts in their data to increase the number of detected collisions. Conclusions. The impact rate agrees with dynamical models of comets. More massive objects (a few 100 m) should impact with Jupiter every few years leaving atmospheric dark debris features that could be detectable about once per decade
Perturbation Centrality and Turbine: A Novel Centrality Measure Obtained Using a Versatile Network Dynamics Tool
Analysis of network dynamics became a focal point to understand and predict
changes of complex systems. Here we introduce Turbine, a generic framework
enabling fast simulation of any algorithmically definable dynamics on very
large networks. Using a perturbation transmission model inspired by
communicating vessels, we define a novel centrality measure: perturbation
centrality. Hubs and inter-modular nodes proved to be highly efficient in
perturbation propagation. High perturbation centrality nodes of the Met-tRNA
synthetase protein structure network were identified as amino acids involved in
intra-protein communication by earlier studies. Changes in perturbation
centralities of yeast interactome nodes upon various stresses well
recapitulated the functional changes of stressed yeast cells. The novelty and
usefulness of perturbation centrality was validated in several other model,
biological and social networks. The Turbine software and the perturbation
centrality measure may provide a large variety of novel options to assess
signaling, drug action, environmental and social interventions. The Turbine
algorithm is available at: http://www.turbine.linkgroup.huComment: 21 pages, 4 figues, 1 table, 58 references + a Supplement of 52
pages, 10 figures, 9 tables and 39 references; Turbine algorithm is available
at: http://www.turbine.linkgroup.h
Defensome against Toxic Diatom Aldehydes in the Sea Urchin Paracentrotus lividus
Many diatom species produce polyunsaturated aldehydes, such as decadienal, which compromise embryonic and larval development in benthic organisms. Here newly fertilized Paracentrotus lividus sea urchins were exposed to low concentration of decadienal and the expression levels of sixteen genes, implicated in a broad range of functional responses, were followed by Real Time qPCR in order to identify potential decadienal targets. We show that at low decadienal concentrations the sea urchin Paracentrotus lividus places in motion different classes of genes to defend itself against this toxic aldehyde, activating hsp60 and two proteases, hat and BP10, at the blastula stage and hsp56 and several other genes (14-3-3ε, p38 MAPK, MTase, and GS) at the prism stage. At this latter stage all genes involved in skeletogenesis (Nec, uni, SM50 and SM30) were also down-expressed, following developmental abnormalities that mainly affected skeleton morphogenesis. Moreover, sea urchin embryos treated with increasing concentrations of decadienal revealed a dose-dependent response of activated target genes. Finally, we suggest that this orchestrated defense system against decadienal represents part of the chemical defensome of P. lividus affording protection from environmental toxicants
Heat shock partially dissociates the overlapping modules of the yeast protein-protein interaction network: a systems level model of adaptation
Network analysis became a powerful tool in recent years. Heat shock is a
well-characterized model of cellular dynamics. S. cerevisiae is an appropriate
model organism, since both its protein-protein interaction network
(interactome) and stress response at the gene expression level have been well
characterized. However, the analysis of the reorganization of the yeast
interactome during stress has not been investigated yet. We calculated the
changes of the interaction-weights of the yeast interactome from the changes of
mRNA expression levels upon heat shock. The major finding of our study is that
heat shock induced a significant decrease in both the overlaps and connections
of yeast interactome modules. In agreement with this the weighted diameter of
the yeast interactome had a 4.9-fold increase in heat shock. Several key
proteins of the heat shock response became centers of heat shock-induced local
communities, as well as bridges providing a residual connection of modules
after heat shock. The observed changes resemble to a "stratus-cumulus" type
transition of the interactome structure, since the unstressed yeast interactome
had a globally connected organization, similar to that of stratus clouds,
whereas the heat shocked interactome had a multifocal organization, similar to
that of cumulus clouds. Our results showed that heat shock induces a partial
disintegration of the global organization of the yeast interactome. This change
may be rather general occurring in many types of stresses. Moreover, other
complex systems, such as single proteins, social networks and ecosystems may
also decrease their inter-modular links, thus develop more compact modules, and
display a partial disintegration of their global structure in the initial phase
of crisis. Thus, our work may provide a model of a general, system-level
adaptation mechanism to environmental changes.Comment: 24 pages, 6 figures, 2 tables, 70 references + 22 pages 8 figures, 4
tables and 8 references in the enclosed Supplemen
Corrigendum: Perivascular Unit: This Must Be the Place. The Anatomical Crossroad Between the Immune, Vascular and Nervous System (Frontiers in Neuroanatomy, (2020), 14, 10.3389/fnana.2020.00017)
In the published article, there was an error in affiliations. Fernanda Troili and Virginia Cipollini, instead of Department of Neurosciences Mental Health and Sensory Organs, Faculty of Medicine and Psychology, Sapienza University of Rome, Rome, Italy, are affiliated to Department of Human Neuroscience, Sapienza University of Rome, Rome, Italy. Emanuele Morena, Virginia Rinaldi, Carmela Romano and Francesco Orzi are affiliated to Department of Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy. Franco Giubile is affiliated to Department of Neurosciences Mental Health and Sensory Organs, Faculty of Medicine and Psychology, Sapienza University of Rome, Rome, Italy
Impact flux on Jupiter: From superbolides to large-scale collisions
Context. Regular observations of Jupiter by a large number of amateur astronomers have resulted in the serendipitous discovery of short bright flashes in its atmosphere, which have been proposed as being caused by impacts of small objects. Three flashes were detected: one on June 3, 2010, one on August 20, 2010, and one on September 10, 2012. Aims. We show that the flashes are caused by impacting objects that we characterize in terms of their size, and we study the flux of small impacts on Jupiter. Methods. We measured the light curves of these atmospheric airbursts to extract their luminous energy and computed the masses and sizes of the objects. We ran simulations of impacts and compared them with the light curves. We analyzed the statistical significance of these events in the large pool of Jupiter observations. Results. All three objects are in the 5-20 m size category depending on their density, and they released energy comparable to the recent Chelyabinsk airburst. Model simulations approximately agree with the interpretation of the limited observations. Biases in observations of Jupiter suggest a rate of 12-60 similar impacts per year and we provide software tools for amateurs to examine the faint signature of impacts in their data to increase the number of detected collisions. Conclusions. The impact rate agrees with dynamical models of comets. More massive objects (a few 100 m) should impact with Jupiter every few years leaving atmospheric dark debris features that could be detectable about once per decade. © ESO, 2013
Reduced accuracy of MRI deep grey matter segmentation in multiple sclerosis: an evaluation of four automated methods against manual reference segmentations in a multi-center cohort
Background: Deep grey matter (DGM) atrophy in multiple sclerosis (MS) and its relation to cognitive and clinical decline requires accurate measurements. MS pathology may deteriorate the performance of automated segmentation methods. Accuracy of DGM segmentation methods is compared between MS and controls, and the relation of performance with lesions and atrophy is studied. Methods: On images of 21 MS subjects and 11 controls, three raters manually outlined caudate nucleus, putamen and thalamus; outlines were combined by majority voting. FSL-FIRST, FreeSurfer, Geodesic Information Flow and volBrain were evaluated. Performance was evaluated volumetrically (intra-class correlation coefficient (ICC)) and spatially (Dice similarity coefficient (DSC)). Spearman's correlations of DSC with global and local lesion volume, structure of interest volume (ROIV), and normalized brain volume (NBV) were assessed. Results: ICC with manual volumes was mostly good and spatial agreement was high. MS exhibited significantly lower DSC than controls for thalamus and putamen. For some combinations of structure and method, DSC correlated negatively with lesion volume or positively with NBV or ROIV. Lesion-filling did not substantially change segmentations. Conclusions: Automated methods have impaired performance in patients. Performance generally deteriorated with higher lesion volume and lower NBV and ROIV, suggesting that these may contribute to the impaired performance