2,765 research outputs found
Distinct dynamical behavior in Erd\H{o}s-R\'enyi networks, regular random networks, ring lattices, and all-to-all neuronal networks
Neuronal network dynamics depends on network structure. In this paper we
study how network topology underpins the emergence of different dynamical
behaviors in neuronal networks. In particular, we consider neuronal network
dynamics on Erd\H{o}s-R\'enyi (ER) networks, regular random (RR) networks, ring
lattices, and all-to-all networks. We solve analytically a neuronal network
model with stochastic binary-state neurons in all the network topologies,
except ring lattices. Given that apart from network structure, all four models
are equivalent, this allows us to understand the role of network structure in
neuronal network dynamics. Whilst ER and RR networks are characterized by
similar phase diagrams, we find strikingly different phase diagrams in the
all-to-all network. Neuronal network dynamics is not only different within
certain parameter ranges, but it also undergoes different bifurcations (with a
richer repertoire of bifurcations in ER and RR compared to all-to-all
networks). This suggests that local heterogeneity in the ratio between
excitation and inhibition plays a crucial role on emergent dynamics.
Furthermore, we also observe one subtle discrepancy between ER and RR networks,
namely ER networks undergo a neuronal activity jump at lower noise levels
compared to RR networks, presumably due to the degree heterogeneity in ER
networks that is absent in RR networks. Finally, a comparison between network
oscillations in RR networks and ring lattices shows the importance of
small-world properties in sustaining stable network oscillations.Comment: 9 pages, 4 figure
Unclassified autoimmune pancreatitis mimicking pancreatic cancer
A 24-year-old black male presented with a 1-week obstructive jaundice and intermittent abdominal pain, with no significant weight loss and an unsuspicious abdominal exam. Blood chemistry showed a cholestatic pattern but a complete immunological and tumoral panel (anti-smooth muscle antibody, anti-mitochondrial antibody, anti-nuclear antibody, anti-neutrophil cytoplasmic antibody, anti-Smith, anti-double-stranded-DNA antibody (anti-dsDNA), complement C3/C4, carcinoembryonic antigen, CA 19-9 and IgG4) were all within normal limits. Abdominal ultrasound revealed dilatation of the intra and extra-hepatic bile ducts. CT scan showed an abnormal dilatation of the distal bile duct but no focal enlargement of the head of the pancreas. Endoscopic ultrasound suggested an inflammatory process but the magnetic resonance cholangio-pancreatography favored a neoplastic obstruction of the distal common bile duct. Fine-needle aspiration cytology was insufficient for definitive diagnosis and the patient underwent major surgery. Follow-up with mild exocrine pancreatic insufficiency treated with enzyme replacement.info:eu-repo/semantics/publishedVersio
Dynamic Active Constraints for Surgical Robots using Vector Field Inequalities
Robotic assistance allows surgeons to perform dexterous and tremor-free
procedures, but robotic aid is still underrepresented in procedures with
constrained workspaces, such as deep brain neurosurgery and endonasal surgery.
In these procedures, surgeons have restricted vision to areas near the surgical
tooltips, which increases the risk of unexpected collisions between the shafts
of the instruments and their surroundings. In this work, our
vector-field-inequalities method is extended to provide dynamic
active-constraints to any number of robots and moving objects sharing the same
workspace. The method is evaluated with experiments and simulations in which
robot tools have to avoid collisions autonomously and in real-time, in a
constrained endonasal surgical environment. Simulations show that with our
method the combined trajectory error of two robotic systems is optimal.
Experiments using a real robotic system show that the method can autonomously
prevent collisions between the moving robots themselves and between the robots
and the environment. Moreover, the framework is also successfully verified
under teleoperation with tool-tissue interactions.Comment: Accepted on T-RO 2019, 19 Page
White dwarfs with a surface electrical charge distribution: Equilibrium and stability
The equilibrium configuration and the radial stability of white dwarfs
composed of charged perfect fluid are investigated. These cases are analyzed
through the results obtained from the solution of the hydrostatic equilibrium
equation. We regard that the fluid pressure and the fluid energy density follow
the relation of a fully degenerate electron gas. For the electric charge
distribution in the object, we consider that it is centralized only close to
the white dwarfs' surfaces. We obtain larger and more massive white dwarfs when
the total electric charge is increased. To appreciate the effects of the
electric charge in the structure of the star, we found that it must be in the
order of with which the electric field is about
. For white dwarfs with electric fields close to the
Schwinger limit, we obtain masses around . We also found that in
a system constituted by charged static equilibrium configurations, the maximum
mass point found on it marks the onset of the instability. This indicates that
the necessary and sufficient conditions to recognize regions constituted by
stable and unstable equilibrium configurations against small radial
perturbations are respectively and .Comment: This is a preprint. The original paper will be published in EPJ
Vírus detectados em germoplasma vegetal introduzido no Brasil pelo laboratório de quarentena (2004-2007).
bitstream/CENARGEN/29614/1/cot172.pd
Stellar equilibrium configurations of white dwarfs in the gravity
In this work we investigate the equilibrium configurations of white dwarfs in
a modified gravity theory, na\-mely, gravity, for which and
stand for the Ricci scalar and trace of the energy-momentum tensor,
respectively. Considering the functional form , with
being a constant, we obtain the hydrostatic equilibrium equation for
the theory. Some physical properties of white dwarfs, such as: mass, radius,
pressure and energy density, as well as their dependence on the parameter
are derived. More massive and larger white dwarfs are found for
negative values of when it decreases. The equilibrium configurations
predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar
limit, with larger radii and lower central densities when compared to standard
gravity outcomes. The most important effect of theory for massive
white dwarfs is the increase of the radius in comparison with GR and also
results. By comparing our results with some observational data of
massive white dwarfs we also find a lower limit for , namely, .Comment: To be published in EPJ
The Kumaraswamy-G Poisson Family of Distributions
For any baseline continuous G distribution, we propose a new generalized family called the Kumaraswamy-G Poisson (denoted with the prefix “Kw-GP”) with three extra positive parameters. Some special distributions in the new family such as the Kw-Weibull Poisson, Kw-gamma Poisson and Kw-beta Poisson distributions are introduced. We derive some mathematical properties of the new family including the ordinary moments, generating function and order statistics. The method of maximum likelihood is used to fit the distributions in the new family. We illustrate its potentiality by means of an application to a real data set
Produção orgânica de carne de ovinos e caprinos.
Resumo: Os movimentos da agricultura orgânica, que tiveram seu começo há cerca de 40 anos atrás, estão atualmente plenamente consolidados e crescem no mundo todo a passos de gigante. Isto porque, a sociedade está cada vez mais consciente da qualidade dos produtos orgânicos e dos problemas ambientais e dos riscos á saúde oriundos dos alimentos contaminados com agrotóxicos. Alcançando patamares significativos em volume de produção em países desenvolvidos, no Brasil a produção orgânica ainda engatinha. No entanto, a demanda externa e interna por produtos ecologicamente certificados se avoluma, a atividade desponta como uma oportunidade impar de inclusão da agricultura familiar nesse crescente mercado. Fundamentada em uma visão holística da produção agrícola, pecuária e madeireira, a agricultura orgânica dá origem a produtos saudáveis, praticamente sem custos ecológicos e sociais. Por princípio, a produção orgânica subentende um aprofundamento do conhecimento dos processos naturais, incluindo o funcionamento do ecos sistema, o desenvolver dos ciclos biogeoquímicos, a visão do solo como um organismo vivo, a importância da matéria orgânica como fonte de reposição e manutenção da fertilidade, o uso integrado dos recursos internos do sistema de produção com redução drástica do aporte de insumos externos. O processo de adoção da produção orgânica deverá resultar em uma mudança substancial nas técnicas e métodos da exploração pastoril, atualmente em voga, mormente com respeito à internalização, em nível de técnicos e produtores, da essencialidade da prática da conservação dos recursos naturais renováveis e da sustentabilidade da produção. No Semi-Árido Nordestino, onde predomina a pequena propriedade de produção familiar, a adoção da agricultura ecológica contribuirá com certeza para a recuperação de seus solos degradados, para incremento qualitativo e quantitativo da produção, para a melhoria da renda familiar e da qualidade de vida de sua população rural
Praga Quarentenária A1. Grapevine flavescence dorée phytoplasma.
bitstream/CENARGEN/29617/1/cot173.pd
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