239 research outputs found
Anisotropy in Homogeneous Rotating Turbulence
The effective stress tensor of a homogeneous turbulent rotating fluid is
anisotropic. This leads us to consider the most general axisymmetric four-rank
``viscosity tensor'' for a Newtonian fluid and the new terms in the turbulent
effective force on large scales that arise from it, in addition to the
microscopic viscous force. Some of these terms involve couplings to vorticity
and others are angular momentum non conserving (in the rotating frame).
Furthermore, we explore the constraints on the response function and the
two-point velocity correlation due to axisymmetry. Finally, we compare our
viscosity tensor with other four-rank tensors defined in current approaches to
non-rotating anisotropic turbulence.Comment: 14 pages, RevTe
Cortical Folding Patterns and Predicting Cytoarchitecture
The human cerebral cortex is made up of a mosaic of structural areas, frequently referred to as Brodmann areas (BAs). Despite the widespread use of cortical folding patterns to perform ad hoc estimations of the locations of the BAs, little is understood regarding 1) how variable the position of a given BA is with respect to the folds, 2) whether the location of some BAs is more variable than others, and 3) whether the variability is related to the level of a BA in a putative cortical hierarchy. We use whole-brain histology of 10 postmortem human brains and surface-based analysis to test how well the folds predict the locations of the BAs. We show that higher order cortical areas exhibit more variability than primary and secondary areas and that the folds are much better predictors of the BAs than had been previously thought. These results further highlight the significance of cortical folding patterns and suggest a common mechanism for the development of the folds and the cytoarchitectonic fields.National Center for Research Resources (U.S.) (P41-RR14075)National Center for Research Resources (U.S.) (R01-RR16594-01A1)National Center for Research Resources (U.S.) (NCRR BIRN Morphometric Project BIRN002, U24 RR021382)National Institute of Biomedical Imaging and Bioengineering (U.S.) (R01 EB001550)National Institute of Biomedical Imaging and Bioengineering (U.S.) (R01 EB006758)National Institute of Neurological Disorders and Stroke (U.S.) (R01 NS052585-01)Mental Illness and Neuroscience Discovery (MIND) InstituteNational Institutes of Health (U.S.) (NIH Roadmap for Medical Research (grant U54 EB005149))Hermann von Helmholtz-Gemeinschaft Deutscher ForschungszentrenDeutsche Forschungsgemeinschaft (DFG)National Institutes of Health. National Institute for Biomedical Imaging and BioengineeringNational Institute of Neurological Disorders and Stroke (U.S.)National Institute of Mental Health (U.S.
Anomalous scaling of passively advected magnetic field in the presence of strong anisotropy
Inertial-range scaling behavior of high-order (up to order N=51) structure
functions of a passively advected vector field has been analyzed in the
framework of the rapid-change model with strong small-scale anisotropy with the
aid of the renormalization group and the operator-product expansion. It has
been shown that in inertial range the leading terms of the structure functions
are coordinate independent, but powerlike corrections appear with the same
anomalous scaling exponents as for the passively advected scalar field. These
exponents depend on anisotropy parameters in such a way that a specific
hierarchy related to the degree of anisotropy is observed. Deviations from
power-law behavior like oscillations or logarithmic behavior in the corrections
to structure functions have not been found.Comment: 15 pages, 18 figure
Preference-Based Monte Carlo Tree Search
Monte Carlo tree search (MCTS) is a popular choice for solving sequential
anytime problems. However, it depends on a numeric feedback signal, which can
be difficult to define. Real-time MCTS is a variant which may only rarely
encounter states with an explicit, extrinsic reward. To deal with such cases,
the experimenter has to supply an additional numeric feedback signal in the
form of a heuristic, which intrinsically guides the agent. Recent work has
shown evidence that in different areas the underlying structure is ordinal and
not numerical. Hence erroneous and biased heuristics are inevitable, especially
in such domains. In this paper, we propose a MCTS variant which only depends on
qualitative feedback, and therefore opens up new applications for MCTS. We also
find indications that translating absolute into ordinal feedback may be
beneficial. Using a puzzle domain, we show that our preference-based MCTS
variant, wich only receives qualitative feedback, is able to reach a
performance level comparable to a regular MCTS baseline, which obtains
quantitative feedback.Comment: To be publishe
AKARI's infrared view on nearby stars : Using AKARI Infrared Camera All-Sky Survey, 2MASS, and Hipparcos catalog
--Results-- We found that the (B-V) v.s. (V-S9W) color-color diagram is
useful to identify the stars with infrared excess emerged from circumstellar
envelopes/disks. Be stars with infrared excess are well separated from other
types of stars in this diagram. Whereas (J-L18W) v.s. (S9W-L18W) diagram is a
powerful tool to classify several object-types. Carbon-rich asymptotic giant
branch (AGB) stars and OH/IR stars form distinct sequences in this color-color
diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB
stars and planetary nebulae (PNe) have largest mid-infrared color-excess, and
can be identified in infrared catalog. Finally, we plot L18W v.s. (S9W-L18W)
color-magnitude diagram, using the AKARI data together with Hipparcos
parallaxes. This diagram can be used to identify low-mass YSOs, as well as AGB
stars. We found that this diagram is comparable to the [24] vs ([8.0]-[24])
diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope
data. Our understanding of Galactic objects will be used to interpret
color-magnitude diagram of stellar populations in nearby galaxies which Spitzer
Space Telescope has observed. --Conclusions-- Our study of the AKARI
color-color and color-magnitude will be used to explore properties of unknown
objects in future. In addition, our analysis highlights a future key project to
understand stellar evolution with circumstellar envelope, once the forthcoming
astronometrical data with GAIA are available.Comment: 14 pages, 11 figures, accepted for publication in A&A. High
resolution version is available at:
http://www.ir.isas.jaxa.jp/%7Eyita/allsky20100302.pdf (26Mb
BoostingTree: parallel selection of weak learners in boosting, with application to ranking
Boosting algorithms have been found successful in many areas of machine learning and, in particular, in ranking. For typical classes of weak learners used in boosting (such as decision stumps or trees), a large feature space can slow down the training, while a long sequence of weak hypotheses combined by boosting can result in a computationally expensive model. In this paper we propose a strategy that builds several sequences of weak hypotheses in parallel, and extends the ones that are likely to yield a good model. The weak hypothesis sequences are arranged in a boosting tree, and new weak hypotheses are added to promising nodes (both leaves and inner nodes) of the tree using some randomized method. Theoretical results show that the proposed algorithm asymptotically achieves the performance of the base boosting algorithm applied. Experiments are provided in ranking web documents and move ordering in chess, and the results indicate that the new strategy yields better performance when the length of the sequence is limited, and converges to similar performance as the original boosting algorithms otherwise. © 2013 The Author(s)
Mutation update for the GPC3 gene involved in Simpson-Golabi-Behmel syndrome and review of the literature
Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked multiple congenital anomalies and overgrowth syndrome caused by a defect in the glypican-3 gene (GPC3). Until now, GPC3 mutations have been reported in isolated cases or small series and the global genotypic spectrum of these mutations has never been delineated. In this study, we review the 57 previously described GPC3 mutations and significantly expand this mutational spectrum with the description of 29 novel mutations. Compiling our data and those of the literature, we provide an overview of 86 distinct GPC3 mutations identified in 120 unrelated families, ranging from single nucleotide variations to complex genomic rearrangements and dispersed throughout the entire coding region of GPC3. The vast majority of them are deletions or truncating mutations (frameshift, nonsense mutations) predicted to result in a loss-of-function. Missense mutations are rare and the two which were functionally characterized, impaired GPC3 function by preventing GPC3 cleavage and cell surface addressing respectively. This report by describing for the first time the wide mutational spectrum of GPC3 could help clinicians and geneticists in interpreting GPC3 variants identified incidentally by high-throughput sequencing technologies and also reinforces the need for functional validation of non-truncating mutations (missense, in frame mutations, duplications)
Whose right to the city? An analysis of the mediatized politics of place surrounding alojamento local issues in Lisbon and Porto
In view of the proliferation of alojamento local (short-term vacation rentals)
in the major Portuguese cities of Lisbon and Porto, along with the
recent transformation of the historic city centre neighbourhoods, this
study explores the mediatized politics of place by analysing data sets
resulting from different, but interconnected, discursive practices. At the
level of governance, we examine how legislation has enabled and facilitated
this transformation. We then explore the media coverage of the
issues surrounding these recent changes. Finally, we focus on individual
and collective stakeholder voices by analysing the various rights claims
and arguments found in social media communication channels. Framing
our analysis initially in Lefebvre’s concept of ‘the right to the city’, often
invoked as an argument for the promotion of justice, inclusion and sustainability
in the face of urbanisation policies, we argue that a ‘rights in
the city’ approach is better suited to gaining insight into the multiple
tensions and conflicts brought about through the interlinking processes
of regeneration, gentrification and touristification that affect neighbourhoods
with high proportions of short-term rental accommodation, and
conclude that there are many rights claimants within a seemingly unified
group of stakeholders, invoking rights claims which are sometimes
overlapping, but often conflicting.info:eu-repo/semantics/publishedVersio
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