61 research outputs found
Structural operational semantics for stochastic and weighted transition systems
We introduce weighted GSOS, a general syntactic framework to specify well-behaved transition systems where transitions are equipped with weights coming from a commutative monoid. We prove that weighted bisimilarity is a congruence on systems defined by weighted GSOS specifications. We illustrate the flexibility of the framework by instantiating it to handle some special cases, most notably that of stochastic transition systems. Through examples we provide weighted-GSOS definitions for common stochastic operators in the literature
A Stochastic Broadcast Pi-Calculus
In this paper we propose a stochastic broadcast PI-calculus which can be used
to model server-client based systems where synchronization is always governed
by only one participant. Therefore, there is no need to determine the joint
synchronization rates. We also take immediate transitions into account which is
useful to model behaviors with no impact on the temporal properties of a
system. Since immediate transitions may introduce non-determinism, we will show
how these non-determinism can be resolved, and as result a valid CTMC will be
obtained finally. Also some practical examples are given to show the
application of this calculus.Comment: In Proceedings QAPL 2011, arXiv:1107.074
Centrosomal microtubule nucleation regulates radial migration of projection neurons independently of polarization in the developing brain
Cortical projection neurons polarize and form an axon while migrating radially. Even though these dynamic processes are closely interwoven, they are regulated separately-the neurons terminate their migration when reaching their destination, the cortical plate, but continue to grow their axons. Here, we show that in rodents, the centrosome distinguishes these processes. Newly developed molecular tools modulating centrosomal microtubule nucleation combined with in vivo imaging uncovered that dysregulation of centro-somal microtubule nucleation abrogated radial migration without affecting axon formation. Tightly regu-lated centrosomal microtubule nucleation was required for periodic formation of the cytoplasmic dilation at the leading process, which is essential for radial migration. The microtubule nucleating factor g-tubulin decreased at neuronal centrosomes during the migratory phase. As distinct microtubule networks drive neuronal polarization and radial migration, this provides insight into how neuronal migratory defects occur without largely affecting axonal tracts in human developmental cortical dysgeneses, caused by mutations in g-tubulin.ISSN:0896-6273ISSN:1097-419
Shipborne measurements of Antarctic submicron organic aerosols: an NMR perspective linking multiple sources and bioregions
Abstract. The concentrations of submicron aerosol particles in maritime regions around
Antarctica are influenced by the extent of sea ice. This effect is two ways:
on one side, sea ice regulates the production of particles by sea spray
(primary aerosols); on the other side, it hosts complex communities of
organisms emitting precursors for secondary particles. Past studies
documenting the chemical composition of fine aerosols in Antarctica indicate
various potential primary and secondary sources active in coastal areas, in
offshore marine regions, and in the sea ice itself. In particular,
beside the well-known sources of organic and sulfur material originating
from the oxidation of dimethylsulfide (DMS) produced by microalgae, recent
findings obtained during the 2015 PEGASO cruise suggest that
nitrogen-containing organic compounds are also produced by the microbiota
colonizing the marginal ice zone. To complement the aerosol source
apportionment performed using online mass spectrometric techniques, here we
discuss the outcomes of offline spectroscopic analysis performed by nuclear
magnetic resonance (NMR) spectroscopy. In this study we (i) present the
composition of ambient aerosols over open-ocean waters across bioregions,
and compare it to the composition of (ii) seawater samples and (iii) bubble-bursting aerosols produced in a sea-spray chamber onboard the ship. Our
results show that the process of aerosolization in the tank enriches primary
marine particles with lipids and sugars while depleting them of free
amino acids, providing an explanation for why amino acids occurred only at
trace concentrations in the marine aerosol samples analyzed. The analysis of
water-soluble organic carbon (WSOC) in ambient submicron aerosol samples
shows distinct NMR fingerprints for three bioregions: (1) the open Southern
Ocean pelagic environments, in which aerosols are enriched with primary
marine particles containing lipids and sugars; (2) sympagic areas in the
Weddell Sea, where secondary organic compounds, including methanesulfonic
acid and semivolatile amines abound in the aerosol composition; and (3)
terrestrial coastal areas, traced by sugars such as sucrose, emitted by land
vegetation. Finally, a new biogenic chemical marker, creatinine, was
identified in the samples from the Weddell Sea, providing another
confirmation of the importance of nitrogen-containing metabolites in
Antarctic polar aerosols
Secondary Electron Interference from Trigonal Warping in Clean Carbon Nanotubes
We investigate Fabry-Perot interference in an ultraclean carbon nanotube resonator. The conductance shows a clear superstructure superimposed onto conventional Fabry-Perot oscillations. A sliding average over the fast oscillations reveals a characteristic slow modulation of the conductance as a function of the gate voltage. We identify the origin of this secondary interference in intervalley and intravalley backscattering processes which involve wave vectors of different magnitude, reflecting the trigonal warping of the Dirac cones. As a consequence, the analysis of the secondary interference pattern allows us to estimate the chiral angle of the carbon nanotube
Cross-talk between monocyte invasion and astrocyte proliferation regulates scarring in brain injury
Scar formation after brain injury is still poorly understood. To further elucidate such processes, here, we examine the interplay between astrocyte proliferation taking place predominantly at the vascular interface and monocyte invasion. Using genetic mouse models that decrease or increase reactive astrocyte proliferation, we demonstrate inverse effects on monocyte numbers in the injury site. Conversely, reducing monocyte invasion using CCR2-/- mice causes a strong increase in astrocyte proliferation, demonstrating an intriguing negative cross-regulation between these cell types at the vascular interface. CCR2-/- mice show reduced scar formation with less extracellular matrix deposition, smaller lesion site and increased neuronal coverage. Surprisingly, the GFAP+ scar area in these mice is also significantly decreased despite increased astrocyte proliferation. Proteomic analysis at the peak of increased astrocyte proliferation reveals a decrease in extracellular matrix synthesizing enzymes in the injury sites of CCR2-/- mice, highlighting how early key aspects of scar formation are initiated. Taken together, we provide novel insights into the cross-regulation of juxtavascular proliferating astrocytes and invading monocytes as a crucial mechanism of scar formation upon brain injury.Instituto de Biotecnologia y Biologia Molecula
Highly conserved elements discovered in vertebrates are present in non-syntenic loci of tunicates, act as enhancers and can be transcribed during development
Co-option of cis-regulatory modules has been suggested as a mechanism for the evolution of expression sites during development. However, the extent and mechanisms involved in mobilization of cisregulatory modules remains elusive. To trace the history of non-coding elements, which may represent candidate ancestral cis-regulatory modules affirmed during chordate evolution, we have searched for conserved elements in tunicate and vertebrate (Olfactores) genomes. We identified, for the first time, 183 non-coding sequences that are highly conserved between the two groups. Our results show that all but one element are conserved in non-syntenic regions between vertebrate and tunicate genomes, while being syntenic among vertebrates. Nevertheless, in all the groups, they are significantly associated with transcription factors showing specific functions fundamental to animal development, such as multicellular organism development and sequence-specific DNA binding. The majority of these regions map onto ultraconserved elements and we demonstrate that they can act as functional enhancers within the organism of origin, as well as in cross-transgenesis experiments, and that they are transcribed in extant species of Olfactores. We refer to the elements as 'Olfactores conserved non-coding elements'. \uc2\ua9 The Author(s) 2013. Published by Oxford University Press
A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.
The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world
Regain of Nef-mediated tetherin antagonism in a chimpanzee experimentally infected with HIV-1
The interferon-inducible host restriction factor tetherin poses a barrier for SIV transmission from apes to humans. After cross-species transmission, the chimpanzee precursor of pandemic HIV-1 M had to switch from the Nef protein to Vpu to efficiently counteract human tetherin due to a deletion of five amino acids in its cytoplasmic tail, which governed susceptibility of Nef in the primate tetherin ortholog. In this thesis, it has been revealed that the experimental reintroduction of HIV-1 M into its original chimpanzee host resulted in a virus that utilizes both Vpu and Nef to antagonize chimpanzee tetherin. Functional analyses identified amino acid changes in and around the highly conserved ExxxLL adaptor protein binding motif within the C-terminal loop of Nef to be critical for the reacquisition of antitetherin activity. Strikingly, just two amino acid changes allowed a HIV-1 M Nef to antagonize chimpanzee tetherin and rescue virus release by enhanced endocytosis of the restriction factor from the cell surface and subsequent sequestration into perinuclear compartments. These data illustrate that primate lentiviruses can regain lost gene functions within a single in vivo passage and suggest that multifunctionality of Nef and the redundant requirement of functional motifs may be beneficial to reacquire antitetherin activity
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