10,346 research outputs found
Comparing persistence diagrams through complex vectors
The natural pseudo-distance of spaces endowed with filtering functions is
precious for shape classification and retrieval; its optimal estimate coming
from persistence diagrams is the bottleneck distance, which unfortunately
suffers from combinatorial explosion. A possible algebraic representation of
persistence diagrams is offered by complex polynomials; since far polynomials
represent far persistence diagrams, a fast comparison of the coefficient
vectors can reduce the size of the database to be classified by the bottleneck
distance. This article explores experimentally three transformations from
diagrams to polynomials and three distances between the complex vectors of
coefficients.Comment: 11 pages, 4 figures, 2 table
A Brief Introduction to Multidimensional Persistent Betti Numbers
In this paper, we propose a brief overview about multidimensional persistent Betti numbers (PBNs) and the metric that is usually used to compare them, i.e., the multidimensional matching distance. We recall the main definitions and results, mainly focusing on the 2-dimensional case. An algorithm to approximate n-dimensional PBNs with arbitrary precision is described
Efeito da profundidade de colocação do tubo de rega gota-a-gota na uniformidade de rega e na eficiência do uso da água em tomate de indústria
RESUMO
A influência da profundidade da colocação dos gotejadores na uniformidade de rega e na eficiência do uso da água foi avaliada, durante dois anos, num ensaio em “split-plot”, com quatro repetições, sendo o tratamento principal a profundidade de colocação do tubo de rega: à superfície do solo (P0), a 20 cm (PI) e a 40 cm (PII) e o secundário a cultivar: Brigade e H3044. Nos dois anos, o débito médio dos gotejadores foi semelhante nos diferentes tratamentos. Os coeficientes de uniformidade (CU) e de variação (CV) e a uniformidade de distribuição (UD), determinados após a colheita da cultura, não foram afectados pela profundidade de colocação do tubo, tendo variado respectivamente, entre 96,5 e 98,2%, 1,91 e 4,15% e 94,5 e 97,4%. A rega gota-a-gota subsuperficial, comparativamente com a superficial, contribuiu para o aumento da eficiência do uso da água (Produção comercial/ETa) em 14%, fundamentalmente devido a uma diminuição da ETa, na fase inicial da cultura
Interactive Knowledge Construction in the Collaborative Building of an Encyclopedia
International audienceOne of the major challenges of Applied Artificial Intelligence is to provide environments where high level human activities like learning, constructing theories or performing experiments, are enhanced by Artificial Intelligence technologies. This paper starts with the description of an ambitious project: EnCOrE2. The specific real world EnCOrE scenario, significantly representing a much wider class of potential applicative contexts, is dedicated to the building of an Encyclopedia of Organic Chemistry in the context of Virtual Communities of experts and students. Its description is followed by a brief survey of some major AI questions and propositions in relation with the problems raised by the EnCOrE project. The third part of the paper starts with some definitions of a set of “primitives” for rational actions, and then integrates them in a unified conceptual framework for the interactive construction of knowledge. To end with, we sketch out protocols aimed at guiding both the collaborative construction process and the collaborative learning process in the EnCOrE project.The current major result is the emerging conceptual model supporting interaction between human agents and AI tools integrated in Grid services within a socio-constructivist approach, consisting of cycles of deductions, inductions and abductions upon facts (the shared reality) and concepts (their subjective interpretation) submitted to negotiations, and finally converging to a socially validated consensus
Caractéristiques biochimiques des acides humiques des sols tropicaux du Brésil : distinction fondamentale entre les sols équatoriaux et les sols des régions à climat tropical contrasté
Collision-dependent power law scalings in 2D gyrokinetic turbulence
Nonlinear gyrokinetics provides a suitable framework to describe
short-wavelength turbulence in magnetized laboratory and astrophysical plasmas.
In the electrostatic limit, this system is known to exhibit a free energy
cascade towards small scales in (perpendicular) real and/or velocity space. The
dissipation of free energy is always due to collisions (no matter how weak the
collisionality), but may be spread out across a wide range of scales. Here, we
focus on freely-decaying 2D electrostatic turbulence on sub-ion-gyroradius
scales. An existing scaling theory for the turbulent cascade in the weakly
collisional limit is generalized to the moderately collisional regime. In this
context, non-universal power law scalings due to multiscale dissipation are
predicted, and this prediction is confirmed by means of direct numerical
simulations.Comment: 7 pages, 5 figures, accepted for publication in Physics of Plasma
The Chemokine CCL2 Mediates the Seizure-enhancing Effects of Systemic Inflammation
Epilepsy is a chronic disorder characterized by spontaneous recurrent seizures. Brain inflammation is increasingly recognized as a critical factor for seizure precipitation, but the molecular mediators of such proconvulsant effects are only partly understood. The chemokine CCL2 is one of the most elevated inflammatory mediators in patients with pharmacoresistent epilepsy, but its contribution to seizure generation remains unexplored. Here, we show, for the first time, a crucial role for CCL2 and its receptor CCR2 in seizure control. We imposed a systemic inflammatory challenge via lipopolysaccharide (LPS) administration in mice with mesial temporal lobe epilepsy. We found that LPS dramatically increased seizure frequency and upregulated the expression of many inflammatory proteins, including CCL2. To test the proconvulsant role of CCL2, we administered systemically either a CCL2 transcription inhibitor (bindarit) or a selective antagonist of the CCR2 receptor (RS102895). We found that interference with CCL2 signaling potently suppressed LPS-induced seizures. Intracerebral administration of anti-CCL2 antibodies also abrogated LPS-mediated seizure enhancement in chronically epileptic animals. Our results reveal that CCL2 is a key mediator in the molecular pathways that link peripheral inflammation with neuronal hyperexcitability
Persistent topology for natural data analysis - A survey
Natural data offer a hard challenge to data analysis. One set of tools is
being developed by several teams to face this difficult task: Persistent
topology. After a brief introduction to this theory, some applications to the
analysis and classification of cells, lesions, music pieces, gait, oil and gas
reservoirs, cyclones, galaxies, bones, brain connections, languages,
handwritten and gestured letters are shown
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