3,282 research outputs found
Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis
To investigate star formation and assembly processes of massive galaxies, we
present here a spatially-resolved stellar populations analysis of a sample of
45 elliptical galaxies (Es) selected from the CALIFA survey. We find rather
flat age and [Mg/Fe] radial gradients, weakly dependent on the effective
velocity dispersion of the galaxy within half-light radius. However, our
analysis shows that metallicity gradients become steeper with increasing galaxy
velocity dispersion. In addition, we have homogeneously compared the stellar
populations gradients of our sample of Es to a sample of nearby relic galaxies,
i.e., local remnants of the high-z population of red nuggets. This comparison
indicates that, first, the cores of present-day massive galaxies were likely
formed in gas-rich, rapid star formation events at high redshift (z>2). This
led to radial metallicity variations steeper than observed in the local
Universe, and positive [Mg/Fe] gradients. Second, our analysis also suggests
that a later sequence of minor dry mergers, populating the outskirts of
early-type galaxies (ETGs), flattened the pristine [Mg/Fe] and metallicity
gradients. Finally, we find a tight age-[Mg/Fe] relation, supporting that the
duration of the star formation is the main driver of the [Mg/Fe] enhancement in
massive ETGs. However, the star formation time-scale alone is not able to fully
explain our [Mg/Fe] measurements. Interestingly, our results match the expected
effect that a variable stellar initial mass function would have on the [Mg/Fe]
ratio.Comment: Accepted for publication in MNRA
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WH2 and proline-rich domains of WASP-family proteins collaborate to accelerate actin filament elongation.
WASP-family proteins are known to promote assembly of branched actin networks by stimulating the filament-nucleating activity of the Arp2/3 complex. Here, we show that WASP-family proteins also function as polymerases that accelerate elongation of uncapped actin filaments. When clustered on a surface, WASP-family proteins can drive branched actin networks to grow much faster than they could by direct incorporation of soluble monomers. This polymerase activity arises from the coordinated action of two regulatory sequences: (i) a WASP homology 2 (WH2) domain that binds actin, and (ii) a proline-rich sequence that binds profilin-actin complexes. In the absence of profilin, WH2 domains are sufficient to accelerate filament elongation, but in the presence of profilin, proline-rich sequences are required to support polymerase activity by (i) bringing polymerization-competent actin monomers in proximity to growing filament ends, and (ii) promoting shuttling of actin monomers from profilin-actin complexes onto nearby WH2 domains. Unoccupied WH2 domains transiently associate with free filament ends, preventing their growth and dynamically tethering the branched actin network to the WASP-family proteins that create it. Collaboration between WH2 and proline-rich sequences thus strikes a balance between filament growth and tethering. Our work expands the number of critical roles that WASP-family proteins play in the assembly of branched actin networks to at least three: (i) promoting dendritic nucleation; (ii) linking actin networks to membranes; and (iii) accelerating filament elongation
Real extensions of distal minimal flows and continuous topological ergodic decompositions
We prove a structure theorem for topologically recurrent real skew product
extensions of distal minimal compact metric flows with a compactly generated
Abelian acting group (e.g. -flows and -flows). The main result
states that every such extension apart from a coboundary can be represented by
a perturbation of a so-called Rokhlin skew product. We obtain as a corollary
that the topological ergodic decomposition of the skew product extension into
prolongations is continuous and compact with respect to the Fell topology on
the hyperspace. The right translation acts minimally on this decomposition,
therefore providing a minimal compact metric analogue to the Mackey action.
This topological Mackey action is a distal (possibly trivial) extension of a
weakly mixing factor (possibly trivial), and it is distal if and only if
perturbation of the Rokhlin skew product is defined by a topological
coboundary.Comment: This paper is an extension and generalisation of
http://arxiv.org/abs/0909.0192. The result has been generalised from actions
of the group of integers to actions of Abelian compactly generated
transformation groups. Therefore the title had to be changed (homeomorphisms
vs. flows
Products of Borel fixed ideals of maximal minors
We study a large family of products of Borel fixed ideals of maximal minors.
We compute their initial ideals and primary decompositions, and show that they
have linear free resolutions. The main tools are an extension of straightening
law and a very surprising primary decomposition formula. We study also the
homological properties of associated multi-Rees algebra which are shown to be
Cohen-Macaulay, Koszul and defined by a Gr\"obner basis of quadrics
Applying Scriptless Test Automation on Web Applications from the Financial Sector
[EN] This industry showcase presents experiences on application
of testar, an open source tool for scriptless testing through graphical
user interface (GUI), to the web applications of Kuveyt TÂżurk Participation Bank in Turkey. Kuveyt TÂżurk Bank uses Selenium and Appium for
regression testing of mobile and internet banking, but the maintenance
cost of the test scripts is increasing day by day. Therefore, scriptless GUI
testing with testar was evaluated. To provide better support for testing
web-based applications, testar was extended with Selenium WebDriver
integration, JavaScript support, and other new features. Results show
that testar detects GUI elements much better after the improvements,
and it was able to find 2 relevant errors that were not identified by existing scripted test cases.This work has been partially funded by ITEA3 TESTOMAT Project, ITEA3 IVVES project7 and EU H2020 DECODER projecAho, P.; Buijs, G.; Akin, A.; Senturk, S.; Pastor-RicĂłs, F.; De Gouw, S.; Vos, TE. (2021). Applying Scriptless Test Automation on Web Applications from the Financial Sector. SISTEDES. 1-4. http://hdl.handle.net/10251/178254S1
The H3Africa policy framework: negotiating fairness in genomics
Human Heredity and Health in Africa (H3Africa) research seeks to promote fair collaboration between scientists in Africa and those from elsewhere. Here, we outline how concerns over inequality and exploitation led to a policy framework that places a firm focus on African leadership and capacity building as guiding principles for African genomics research
Definitions, Criteria and Global Classification of Mast Cell Disorders with Special Reference to Mast Cell Activation Syndromes: A Consensus Proposal
Activation of tissue mast cells (MCs) and their abnormal growth and accumulation in various organs are typically found in primary MC disorders also referred to as mastocytosis. However, increasing numbers of patients are now being informed that their clinical findings are due to MC activation (MCA) that is neither associated with mastocytosis nor with a defined allergic or inflammatory reaction. In other patients with MCA, MCs appear to be clonal cells, but criteria for diagnosing mastocytosis are not met. A working conference was organized in 2010 with the aim to define criteria for diagnosing MCA and related disorders, and to propose a global unifying classification of all MC disorders and pathologic MC reactions. This classification includes three types of `MCA syndromes' (MCASs), namely primary MCAS, secondary MCAS and idiopathic MCAS. MCA is now defined by robust and generally applicable criteria, including (1) typical clinical symptoms, (2) a substantial transient increase in serum total tryptase level or an increase in other MC-derived mediators, such as histamine or prostaglandin D 2, or their urinary metabolites, and (3) a response of clinical symptoms to agents that attenuate the production or activities of MC mediators. These criteria should assist in the identification and diagnosis of patients with MCAS, and in avoiding misdiagnoses or overinterpretation of clinical symptoms in daily practice. Moreover, the MCAS concept should stimulate research in order to identify and exploit new molecular mechanisms and therapeutic targets. Copyright (C) 2011 S. Karger AG, Base
Intraductal fully covered self-expandable metal stent versus multiple plastic stents for treating biliary anastomotic strictures after liver transplantation
Background and aims: Fully covered metal stents (FCSEMSs) are increasingly used for treatment of biliary anastomotic strictures (ASs) after liver transplantation (LT), requiring fewer endoscopic interventions than does treatment with multiple plastic stents (MPSs). Previous studies, however, have reported adverse events such as stent migration and pancreatitis. The intraductal FCSEMS (ID-FCSEMS) potentially avoids these disadvantages. This study aimed to assess the efficacy and safety of ID-FCSEMSs compared with MPSs for AS. Methods: The cohorts of LT patients treated for AS with endoscopic stenting between 2010 and 2019 from 2 Dutch liver transplantation centers were retrospectively analyzed. Patients treated with ID-FCSEMSs or MPSs were included. Results: 80 patients (44 with ID-FCSEMSs vs 36 with MPSs) were included, with a median follow-up time of 52 versus 64 months (P = .183). Stricture resolution was 93% in the ID-FCSEMS versus 97% in the MPS group (P = 1.000) after a median of 19 and 26 weeks, respectively (P = .031). The median number of ERCPs was 2 in the ID-FCSEMS group versus 4 in the MPS group (P < .001). Stricture recurrence occurred in 33% of ID-FCSEMS versus 29% of MPS patients (P = .653) after a median of 24 and 55 weeks (P = .403). Stent migration occurred in 16% of ID-FCSEMS versus 39% of MPS patients (P = .020). Post-ERCP fever was observed in 34% of ID-FCSEMS patients compared with 14% of MPS patients (P = .038). No significant differences were found in pancreatitis rate between the groups, being 6.8% for ID-FCSEMSs and 5.6% for MPSs (P = .816). Conclusion: ID-FCSEMSs for the treatment of AS after LT provides similar stricture resolution and recurrence rates as MPSs, though with a significant reduction of procedures needed.</p
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