3,199 research outputs found
A Survey of Monte Carlo Tree Search Methods
Monte Carlo tree search (MCTS) is a recently proposed search method that combines the precision of tree search with the generality of random sampling. It has received considerable interest due to its spectacular success in the difficult problem of computer Go, but has also proved beneficial in a range of other domains. This paper is a survey of the literature to date, intended to provide a snapshot of the state of the art after the first five years of MCTS research. We outline the core algorithm's derivation, impart some structure on the many variations and enhancements that have been proposed, and summarize the results from the key game and nongame domains to which MCTS methods have been applied. A number of open research questions indicate that the field is ripe for future work
Ab initio RNA folding
RNA molecules are essential cellular machines performing a wide variety of
functions for which a specific three-dimensional structure is required. Over
the last several years, experimental determination of RNA structures through
X-ray crystallography and NMR seems to have reached a plateau in the number of
structures resolved each year, but as more and more RNA sequences are being
discovered, need for structure prediction tools to complement experimental data
is strong. Theoretical approaches to RNA folding have been developed since the
late nineties when the first algorithms for secondary structure prediction
appeared. Over the last 10 years a number of prediction methods for 3D
structures have been developed, first based on bioinformatics and data-mining,
and more recently based on a coarse-grained physical representation of the
systems. In this review we are going to present the challenges of RNA structure
prediction and the main ideas behind bioinformatic approaches and physics-based
approaches. We will focus on the description of the more recent physics-based
phenomenological models and on how they are built to include the specificity of
the interactions of RNA bases, whose role is critical in folding. Through
examples from different models, we will point out the strengths of
physics-based approaches, which are able not only to predict equilibrium
structures, but also to investigate dynamical and thermodynamical behavior, and
the open challenges to include more key interactions ruling RNA folding.Comment: 28 pages, 18 figure
TriLoNet: Piecing together small networks to reconstruct reticulate evolutionary histories
Phylogenetic networks are a generalisation of evolutionary trees that can be used to represent reticulate processes such as hybridisation and recombination. Here we introduce a new approach called TriLoNet to construct such networks directly from sequence alignments which works by piecing together smaller phylogenetic networks. More specifically, using a bottom up approach similar to Neighbor-Joining, TriLoNet constructs level-1 networks (networks that are somewhat more general than trees) from smaller level-1 networks on three taxa. In simulations we show that TriLoNet compares well with Lev1athan, a method for reconstructing level-1 networks from three-leaved trees. In particular, in simulations we find that Lev1athan tends to generate networks that overestimate the number of reticulate events as compared with those generated by TriLoNet. We also illustrate TriLoNet’s applicability using simulated and real sequence data involving recombination, demonstrating that it has the potential to reconstruct informative reticulate evolutionary histories. TriLoNet has been implemented in JAVA and is freely available at https://www.uea.ac.uk/computing/TriLoNet
Large scale nested stellar discs in NGC 7217
NGC7217 is an unbarred early-type spiral galaxy having a multi-segment
exponential light profile and a system of starforming rings of the unknown
origin; it also possesses a circumnuclear gaseous polar disc. We analysed new
long slit spectroscopic data for NGC7217 and derived the radial distributions
of its stellar population parameters and stellar and gaseous kinematics up to
the radius of r~100 arcsec (~8 kpc). We performed the dynamical analysis of the
galaxy by recovering its velocity ellipsoid at different radii, and estimated
the scaleheights of its two exponential discs. The inner exponential stellar
disc of NGC7217 appears to be thin and harbours intermediate age stars (t(SSP)
~ 5 Gyr). The outer stellar disc seen between the radii of 4 and 7 kpc is very
thick (z0 = 1...3 kpc), metal-poor, [Fe/H]<-0.4 dex, and has predominantly
young stars, t(SSP) = 2 Gyr. The remnants of minor mergers of gas-rich
satellites with an early-type giant disc galaxy available in the GalMer
database well resemble different structural components of NGC7217, suggesting
two minor merger events in the past responsible for the formation of the inner
polar gaseous disc and large outer starforming ring. Another possibility to
form the outer ring is the re-accretion of the tidal streams created by the
first minor merger.Comment: Accepted to MNRAS, 12 pages, 10 figure
Getting Nervous: An Evolutionary Overhaul for Communication.
The evolution of a nervous system as a control system of the body's functions is a key innovation of animals. Its fundamental units are neurons, highly specialized cells dedicated to fast cell-cell communication. Neurons pass signals to other neurons, muscle cells, or gland cells at specialized junctions, the synapses, where transmitters are released from vesicles in a Ca <sup>2+</sup> -dependent fashion to activate receptors in the membrane of the target cell. Reconstructing the origins of neuronal communication out of a more simple process remains a central challenge in biology. Recent genomic comparisons have revealed that all animals, including the nerveless poriferans and placozoans, share a basic set of genes for neuronal communication. This suggests that the first animal, the Urmetazoan, was already endowed with neurosecretory cells that probably started to connect into neuronal networks soon afterward. Here, we discuss scenarios for this pivotal transition in animal evolution
Migration et violence
Les migrants et les requérants s'asile qui ont survécu à des violences ou à des tortures ont expérimenté des traumatismes physiques et psychologiques qui ont laissé des traces, des plaies béantes. Une fois arrivés dans le pays d'accueil, la violence dont ils ont été l'objet ne s'arrête pas nécessairement, car l'immigration peut générer elle-même de nouvelles formes de violence qui s'adressent à des sujets rendus au départ vulnérables par leurs expériences. En effet, quand les migrants et les requérants d'asile arrivent dans le pays d'accueil, ils se heurtent souvent à une très faible tolérance de la part des population autochtones, à des contrôles policiers et administratifs, à une incertitude permanente quant au bon droit de trouver chez nous protection et sécurité. Le soignant, lorsqu'il prend en charge ces victimes de violence dans un réseau multidisciplinaire de soins, peut panser, en partie, ces plaies et ainsi leur redonner une certaine dignité. [Auteurs]]]>
Emigration and Immigration ; Transients and Migrants ; Violence
fre
oai:serval.unil.ch:BIB_562D08AFA101
2022-05-07T01:18:12Z
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https://serval.unil.ch/notice/serval:BIB_562D08AFA101
Das „Gesicht der Zeit“ und seine feuilletonistischen Facetten : Zur Physiognomik der „kleinen Form“ nach 1900
https://www.rombach-verlag.de/buecher/wissenschaft/rombach/buch/details/physiognomisches-schreiben.html
Utz, Peter
info:eu-repo/semantics/bookPart
incollection
2016
Physiognomisches Schreiben : Stilistik, Rhetorik und Poetik einer gestaltdeutenden Kulturtechnik, pp. 47-66
von Arburg, Hans-Georg (ed.)
Tremp, Benedikt (ed.)
Zimmermann, Elias (ed.)
info:eu-repo/semantics/altIdentifier/isbn/978-3-7930-9856-0
ger
oai:serval.unil.ch:BIB_562D42148454
2022-05-07T01:18:12Z
openaire
documents
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https://serval.unil.ch/notice/serval:BIB_562D42148454
Getting Nervous: An Evolutionary Overhaul for Communication.
info:doi:10.1146/annurev-genet-120116-024648
info:eu-repo/semantics/altIdentifier/doi/10.1146/annurev-genet-120116-024648
info:eu-repo/semantics/altIdentifier/pmid/28934592
Varoqueaux, F.
Fasshauer, D.
info:eu-repo/semantics/review
article
2017-11-27
Annual review of genetics, vol. 51, pp. 455-476
info:eu-repo/semantics/altIdentifier/eissn/1545-2948
urn:issn:0066-4197
<![CDATA[The evolution of a nervous system as a control system of the body's functions is a key innovation of animals. Its fundamental units are neurons, highly specialized cells dedicated to fast cell-cell communication. Neurons pass signals to other neurons, muscle cells, or gland cells at specialized junctions, the synapses, where transmitters are released from vesicles in a Ca <sup>2+</sup> -dependent fashion to activate receptors in the membrane of the target cell. Reconstructing the origins of neuronal communication out of a more simple process remains a central challenge in biology. Recent genomic comparisons have revealed that all animals, including the nerveless poriferans and placozoans, share a basic set of genes for neuronal communication. This suggests that the first animal, the Urmetazoan, was already endowed with neurosecretory cells that probably started to connect into neuronal networks soon afterward. Here, we discuss scenarios for this pivotal transition in animal evolution
The impact of within-herd genetic variation upon inferred transmission trees for foot-and-mouth disease virus
Full-genome sequences have been used to monitor the fine-scale dynamics of epidemics caused by RNA viruses. However, the ability of this approach to confidently reconstruct transmission trees is limited by the knowledge of the genetic diversity of viruses that exist within different epidemiological units. In order to address this question, this study investigated the variability of 45 foot-and-mouth disease virus (FMDV) genome sequences (from 33 animals) that were collected during 2007 from eight premises (10 different herds) in the United Kingdom. Bayesian and statistical parsimony analysis demonstrated that these sequences exhibited clustering which was consistent with a transmission scenario describing herd-to-herd spread of the virus. As an alternative to analysing all of the available samples in future epidemics, the impact of randomly selecting one sequence from each of these herds was used to assess cost-effective methods that might be used to infer transmission trees during FMD outbreaks. Using these approaches, 85% and 91% of the resulting topologies were either identical or differed by only one edge from a reference tree comprising all of the sequences generated within the outbreak. The sequence distances that accrued during sequential transmission events between epidemiological units was estimated to be 4.6 nucleotides, although the genetic variability between viruses recovered from chronic carrier animals was higher than between viruses from animals with acute-stage infection: an observation which poses challenges for the use of simple approaches to infer transmission trees. This study helps to develop strategies for sampling during FMD outbreaks, and provides data that will guide the development of further models to support control policies in the event of virus incursions into FMD free countries
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