305 research outputs found
Ram pressure feeding super-massive black holes
When supermassive black holes at the center of galaxies accrete matter
(usually gas), they give rise to highly energetic phenomena named Active
Galactic Nuclei (AGN). A number of physical processes have been proposed to
account for the funneling of gas towards the galaxy centers to feed the AGN.
There are also several physical processes that can strip gas from a galaxy, and
one of them is ram pressure stripping in galaxy clusters due to the hot and
dense gas filling the space between galaxies. We report the discovery of a
strong connection between severe ram pressure stripping and the presence of AGN
activity. Searching in galaxy clusters at low redshift, we have selected the
most extreme examples of jellyfish galaxies, which are galaxies with long
tentacles of material extending for dozens of kpc beyond the galaxy disk. Using
the MUSE spectrograph on the ESO Very Large Telescope, we find that 6 out of
the 7 galaxies of this sample host a central AGN, and two of them also have
galactic-scale AGN ionization cones. The high incidence of AGN among the most
striking jellyfishes may be due to ram pressure causing gas to flow towards the
center and triggering the AGN activity, or to an enhancement of the stripping
caused by AGN energy injection, or both. Our analysis of the galaxy position
and velocity relative to the cluster strongly supports the first hypothesis,
and puts forward ram pressure as another, yet unforeseen, possible mechanism
for feeding the central supermassive black hole with gas.Comment: published in Nature, Vol.548, Number 7667, pag.30
Dendritic Spine Shape Analysis: A Clustering Perspective
Functional properties of neurons are strongly coupled with their morphology.
Changes in neuronal activity alter morphological characteristics of dendritic
spines. First step towards understanding the structure-function relationship is
to group spines into main spine classes reported in the literature. Shape
analysis of dendritic spines can help neuroscientists understand the underlying
relationships. Due to unavailability of reliable automated tools, this analysis
is currently performed manually which is a time-intensive and subjective task.
Several studies on spine shape classification have been reported in the
literature, however, there is an on-going debate on whether distinct spine
shape classes exist or whether spines should be modeled through a continuum of
shape variations. Another challenge is the subjectivity and bias that is
introduced due to the supervised nature of classification approaches. In this
paper, we aim to address these issues by presenting a clustering perspective.
In this context, clustering may serve both confirmation of known patterns and
discovery of new ones. We perform cluster analysis on two-photon microscopic
images of spines using morphological, shape, and appearance based features and
gain insights into the spine shape analysis problem. We use histogram of
oriented gradients (HOG), disjunctive normal shape models (DNSM), morphological
features, and intensity profile based features for cluster analysis. We use
x-means to perform cluster analysis that selects the number of clusters
automatically using the Bayesian information criterion (BIC). For all features,
this analysis produces 4 clusters and we observe the formation of at least one
cluster consisting of spines which are difficult to be assigned to a known
class. This observation supports the argument of intermediate shape types.Comment: Accepted for BioImageComputing workshop at ECCV 201
Fostering Continuous Innovation with Engaging IT-Assisted Transparent Information Sharing : A Case Study
The paper received the Honorary Mention – Best Paper Award Nominee.Peer reviewe
Eosinophilic myocarditis mimicking acute coronary syndrome secondary to idiopathic hypereosinophilic syndrome: a case report
<p>Abstract</p> <p>Introduction</p> <p>Eosinophilic myocarditis is a rare form of myocarditis. It is characterized pathologically by diffuse or focal myocardial inflammation with eosinophilic infiltration, often in association with peripheral blood eosinophilia. We report a case of eosinophilic myocarditis secondary to hypereosinophilic syndrome.</p> <p>Case presentation</p> <p>A 74-year-old Caucasian woman with a history of asthma, paroxysmal atrial fibrillation, stroke and coronary artery disease presented to the emergency department of our hospital with chest pain. Evaluations revealed that she had peripheral blood eosinophilia and elevated cardiac enzymes. Electrocardiographic findings were nonspecific. Her electrocardiographic finding and elevated cardiac enzymes pointed to a non-ST-elevated myocardial infarction. Echocardiogram showed a severe decrease in the left ventricular systolic function. Coronary angiogram showed nonobstructive coronary artery disease. She then underwent cardiac magnetic resonance imaging, which showed neither infiltrative myocardial diseases nor any evidence of infarction. This was followed by an endomyocardial biopsy which was consistent with eosinophilic myocarditis. Hematologic workup regarding her eosinophilia was consistent with hypereosinophilic syndrome. After being started on steroid therapy, her peripheral eosinophilia resolved and her symptoms improved. Her left ventricular ejection fraction, however, did not improve.</p> <p>Conclusion</p> <p>Eosinophilic myocarditis can present like an acute myocardial infarction and should be considered in the differential diagnosis of acute coronary syndrome in patients with a history of allergy, asthma or acute reduction of the left ventricular function with or without peripheral eosinophilia.</p
GASP - XVII. H I imaging of the jellyfish galaxy JO206:Gas stripping and enhanced star formation
We present VLA HI observations of JO206, a prototypical ram-pressure stripped
galaxy in the GASP sample. This massive galaxy (M 8.5
10 M) is located at a redshift of 0.0513, near the
centre of the low-mass galaxy cluster, IIZw108 ( km/s). JO206
is characterised by a long tail (90 kpc) of ionised gas stripped away by
ram-pressure. We find a similarly long HI tail in the same direction as the
ionised gas tail and measure a total HI mass of
M. This is about half the expected HI mass given the stellar mass and
surface density of JO206. A total of M (60%) of
the detected HI is in the gas stripped tail. An analysis of the star formation
rate shows that the galaxy is forming more stars compared to galaxies with the
same stellar and HI mass. On average we find a HI gas depletion time of
0.5 Gyr which is about four times shorter than that of "normal" spiral
galaxies. We performed a spatially resolved analysis of the relation between
star formation rate density and gas density in the disc and tail of the galaxy
at the resolution of our HI data. The star formation efficiency of the disc is
about 10 times higher than that of the tail at fixed HI surface densities. Both
the inner and outer parts of JO206 show an enhanced star formation compared to
regions of similar HI surface density in field galaxies. The enhanced star
formation is due to ram-pressure stripping during the galaxy's first infall
into the cluster.Comment: 13 pages, 12 figures, Accepted for publication in MNRA
Relating basic properties of bright early-type dwarf galaxies to their location in Abell 901/902
We present a study of the population of bright early-type dwarf galaxies in
the multiple-cluster system Abell 901/902. We use data from the STAGES survey
and COMBO-17 to investigate the relation between the color and structural
properties of the dwarfs and their location in the cluster. The definition of
the dwarf sample is based on the central surface brightness and includes
galaxies in the luminosity range -16 >= M_B >~-19 mag. Using a fit to the color
magnitude relation of the dwarfs, our sample is divided into a red and blue
subsample. We find a color-density relation in the projected radial
distribution of the dwarf sample: at the same luminosity dwarfs with redder
colors are located closer to the cluster centers than their bluer counterparts.
Furthermore, the redder dwarfs are on average more compact and rounder than the
bluer dwarfs. These findings are consistent with theoretical expectations
assuming that bright early-type dwarfs are the remnants of transformed
late-type disk galaxies involving processes such as ram pressure stripping and
galaxy harassment. This indicates that a considerable fraction of dwarf
elliptical galaxies in clusters are the results of transformation processes
related to interactions with their host cluster.Comment: 12 pages, 8 figures, accepted for publication in A&A, typo corrected
in abstrac
Effectiveness of smoking cessation therapies: a systematic review and meta-analysis
BACKGROUND: Smoking remains the leading preventable cause of premature deaths. Several pharmacological interventions now exist to aid smokers in cessation. These include Nicotine Replacement Therapy [NRT], bupropion, and varenicline. We aimed to assess their relative efficacy in smoking cessation by conducting a systematic review and meta-analysis. METHODS: We searched 10 electronic medical databases (inception to Sept. 2006) and bibliographies of published reviews. We selected randomized controlled trials [RCTs] evaluating interventions for smoking cessation at 1 year, through chemical confirmation. Our primary endpoint was smoking cessation at 1 year. Secondary endpoints included short-term smoking cessation (~3 months) and adverse events. We conducted random-effects meta-analysis and meta-regression. We compared treatment effects across interventions using head-to-head trials and when these did not exist, we calculated indirect comparisons. RESULTS: We identified 70 trials of NRT versus control at 1 year, Odds Ratio [OR] 1.71, 95% Confidence Interval [CI], 1.55–1.88, P =< 0.0001). This was consistent when examining all placebo-controlled trials (49 RCTs, OR 1.78, 95% CI, 1.60–1.99), NRT gum (OR 1.60, 95% CI, 1.37–1.86) or patch (OR 1.63, 95% CI, 1.41–1.89). NRT also reduced smoking at 3 months (OR 1.98, 95% CI, 1.77–2.21). Bupropion trials were superior to controls at 1 year (12 RCTs, OR1.56, 95% CI, 1.10–2.21, P = 0.01) and at 3 months (OR 2.13, 95% CI, 1.72–2.64). Two RCTs evaluated the superiority of bupropion versus NRT at 1 year (OR 1.14, 95% CI, 0.20–6.42). Varenicline was superior to placebo at 1 year (4 RCTs, OR 2.96, 95% CI, 2.12–4.12, P =< 0.0001) and also at approximately 3 months (OR 3.75, 95% CI, 2.65–5.30). Three RCTs evaluated the effectiveness of varenicline versus bupropion at 1 year (OR 1.58, 95% CI, 1.22–2.05) and at approximately 3 months (OR 1.61, 95% CI, 1.16–2.21). Using indirect comparisons, varenicline was superior to NRT when compared to placebo controls (OR 1.66, 95% CI 1.17–2.36, P = 0.004) or to all controls at 1 year (OR 1.73, 95% CI 1.22–2.45, P = 0.001). This was also the case for 3-month data. Adverse events were not systematically different across studies. CONCLUSION: NRT, bupropion and varenicline all provide therapeutic effects in assisting with smoking cessation. Direct and indirect comparisons identify a hierarchy of effectiveness
Exploring Broadband GRB Behavior During gamma-ray Emission
The robotic ROTSE-III telescope network detected prompt optical emission
contemporaneous with the gamma-ray emission of Swift events GRB051109A and
GRB051111. Both datasets have continuous coverage at high signal-to-noise
levels from the prompt phase onwards, thus the early observations are readily
compared to the Swift XRT and BAT high energy detections. In both cases, the
optical afterglow is established, declining steadily during the prompt
emission. For GRB051111, there is evidence of an excess optical component
during the prompt emission. The component is consistent with the flux
spectrally extrapolated from the gamma-rays, using the gamma-ray spectral
index. A compilation of spectral information from previous prompt detections
shows that such a component is unusual. The existence of two prompt optical
components - one connected to the high-energy emission, the other to separate
afterglow flux, as indicated in GRB051111 - is not compatible with a simple
``external-external'' shock model for the GRB and its afterglow.Comment: ApJ accepted. 32 pages (in preprint form), 5 tables, 5 figure
Mesoglycan connects Syndecan-4 and VEGFR2 through Annexin A1 and formyl peptide receptors to promote angiogenesis in vitro.
Mesoglycan is a mixture of glycosaminoglycans (GAG) with fibrinolytic effects and the potential to enhance skin wound repair. Here, we have used endothelial cells isolated from Wild Type (WT) and Syndecan-4 null (Sdc4-/-) C57BL/6 mice to demonstrate that mesoglycan promotes cell motility and in vitro angiogenesis acting on the co-receptor Syndecan-4 (SDC4). This latter is known to participate in the formation and release of extracellular vesicles (EVs). We characterized EVs released by HUVECs and assessed their effect on angiogenesis. Particularly, we focused on Annexin A1 (ANXA1) containing EVs, since they may contribute to tube formation via interactions with Formyl peptide receptors (FPRs). In our model, the bond ANXA1-FPRs stimulates the release of vascular endothelial growth factor (VEGF-A) that interacts with vascular endothelial receptor-2 (VEGFR2) and activates the pathway enhancing cell motility in an autocrine manner, as shown by Wound-Healing/invasion assays, and the induction of Endothelial to Mesenchymal Transition (EndMT). Thus, we have shown for the first time that mesoglycan exerts its pro-angiogenic effects in the healing process triggering the activation of the three interconnected molecular axis: mesoglycan-SDC4, EVs-ANXA1-FPRs and VEGF-A-VEGFR2
Proinflammatory Cytokines Activate the Intrinsic Apoptotic Pathway in β-Cells
OBJECTIVE:Proinflammatory cytokines are cytotoxic to beta-cells and have been implicated in the pathogenesis of type 1 diabetes and islet graft failure. The importance of the intrinsic mitochondrial apoptotic pathway in cytokine-induced beta-cell death is unclear. Here, cytokine activation of the intrinsic apoptotic pathway and the role of the two proapoptotic Bcl-2 proteins, Bad and Bax, were examined in beta-cells.RESEARCH DESIGN AND METHODS:Human and rat islets and INS-1 cells were exposed to a combination of proinflammatory cytokines (interleukin-1beta, interferon-gamma, and/or tumor necrosis factor-alpha). Activation of Bad was determined by Ser136 dephosphorylation, mitochondrial stress by changes in mitochondrial metabolic activity and cytochrome c release, downstream apoptotic signaling by activation of caspase-9 and -3, and DNA fragmentation. The inhibitors FK506 and V5 were used to investigate the role of Bad and Bax activation, respectively. [...
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