165 research outputs found

    Microscopic energy flows in disordered Ising spin systems

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    An efficient microcanonical dynamics has been recently introduced for Ising spin models embedded in a generic connected graph even in the presence of disorder i.e. with the spin couplings chosen from a random distribution. Such a dynamics allows a coherent definition of local temperatures also when open boundaries are coupled to thermostats, imposing an energy flow. Within this framework, here we introduce a consistent definition for local energy currents and we study their dependence on the disorder. In the linear response regime, when the global gradient between thermostats is small, we also define local conductivities following a Fourier dicretized picture. Then, we work out a linearized "mean-field approximation", where local conductivities are supposed to depend on local couplings and temperatures only. We compare the approximated currents with the exact results of the nonlinear system, showing the reliability range of the mean-field approach, which proves very good at high temperatures and not so efficient in the critical region. In the numerical studies we focus on the disordered cylinder but our results could be extended to an arbitrary, disordered spin model on a generic discrete structures.Comment: 12 pages, 6 figure

    Differences in trunk and thigh muscle strength, endurance and thickness between elite sailors and non-sailors

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    International audienceDinghy sailors lean their upper body over the windward side of the boat ('hiking') to keep the boat's balance and maximise its speed. Sustaining the hiking position is essential for competitive performance and this study examined sport-specific differences of muscles relevant for hiking in elite sailors. Knee extensor muscle strength as well as trunk muscle strength, muscle endurance and muscle thickness were assessed in elite dinghy sailors (n = 15) and compared to matched, non-sailing controls (n = 15). Isometric extensor strength was significantly higher in sailors at 60° (+14%) but not at 20° knee flexion. Sailors showed significantly higher trunk flexor (but not extensor) strength under isometric (+18%) and eccentric (+11%) conditions, which was associated to greater muscle thickness (rectus abdominis +40%; external oblique +26%) and higher endurance for ventral (+66%) and lateral (+61%) muscle chains compared to non-sailors. Greater muscles thickness and the particular biomechanical requirements to maintain the hiking position may drive the increases in isometric and eccentric muscle strength as well as ventral and lateral trunk endurance. The current findings identified sport-specific muscle function differences and provide performance benchmarks for muscle strength and endurance in elite sailors

    Slow relaxation in microcanonical warming of a Ising lattice

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    We study the warming process of a semi-infinite cylindrical Ising lattice initially ordered and coupled at the boundary to a heat reservoir. The adoption of a proper microcanonical dynamics allows a detailed study of the time evolution of the system. As expected, thermal propagation displays a diffusive character and the spatial correlations decay exponentially in the direction orthogonal to the heat flow. However, we show that the approach to equilibrium presents an unexpected slow behavior. In particular, when the thermostat is at infinite temperature, correlations decay to their asymptotic values by a power law. This can be rephrased in terms of a correlation length vanishing logarithmically with time. At finite temperature, the approach to equilibrium is also a power law, but the exponents depend on the temperature in a non-trivial way. This complex behavior could be explained in terms of two dynamical regimes characterizing finite and infinite temperatures, respectively. When finite sizes are considered, we evidence the emergence of a much more rapid equilibration, and this confirms that the microcanonical dynamics can be successfully applied on finite structures. Indeed, the slowness exhibited by correlations in approaching the asymptotic values are expected to be related to the presence of an unsteady heat flow in an infinite system.Comment: 8 pages, 4 figures; Published in Eur. Phys. J. B (2011

    Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase

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    Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex

    Determining the reference range of blood presepsin in term and preterm neonates

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    Introduction Sepsis is still a major cause of morbidity and mortality in neonates, especially in preterm infants. Mortality can reach 60-70% in very low birth weight infants (birthweight 0.20). This reduced model explains 3.8% of the total sum of squares. After adjustment for all the factors in the model, presepsin levels appear to be significantly lower in twins (496 pg/ml \uf0b1 65.5 vs 655 pg/ml \uf0b1 11.8) and in neonates with Apgar at 1 min 658 (644 pg/ml \uf0b1 11.8 vs 774 pg/ml \uf0b1 56.2). So none of the above factors seems worth to be taken into account in determining the reference limits for presepsin blood levels in healthy term neonates. Preterm neonates. The largest differences in presepsin level are observed between small for gestational age (SGA) (903 pg/ml \uf0b1 57.1) and adequate for gestational age (AGA) neonates (703 pg/ml \uf0b1 26.7), between neonates with and without mechanical ventilation at blood sampling (1090 pg/ml \uf0b1 86.9 vs 711 pg/ml \uf0b1 24.7) and at delivery (855 pg/ml \uf0b1 87.3 vs 729 pg/ml \uf0b1 25.8), between neonates with and without venous catether (801 pg/ml \uf0b1 47.5 vs 716 pg/ml \uf0b1 28.9), between neonates who underwent blood sampling after the 4th day or before (797 pg/ml \uf0b1 46.2 vs 716 pg/ml \uf0b1 29.2), between males and females (778 pg/ml \uf0b1 35.1 vs 701 pg/ml \uf0b1 34.7). All these factors, when simultaneously introduced into a multivariable linear model, explain only 18.8% of the total sum of squares. A second multivariable linear model was fitted after removing the factors that showed the lowest effect on presepsin level (those associated with a p-value >0.50). This reduced model explains 13.4% of the total sum of squares. A third and more parsimonious multivariable linear model was fitted after removing the factors that showed the lowest effect on presepsin level (those associated with a p-value >0.20). This reduced model explains 12.3% of the total sum of squares. After adjustment for all the factors in the model, presepsin levels result to be significantly lower in AGA neonates (706 pg/ml \uf0b1 25.7 vs 890 pg/ml \uf0b1 55.0) and between neonates with and without mechanical ventilation at blood sampling (1074 pg/ml \uf0b1 85.3 vs 712 pg/ml \uf0b1 24.2). Even in this case, none of the above factors is expected to substantially affect the reference limits for presepsin blood levels in preterm neonates. Conclusion Presepsin blood levels seem to be quite independent of most of maternal and neonatal conditions examined in this study both in preterm and term neonates. The factors exerting significant effects (multiple birth and Apgar at 1 min, in term neonates, weight by gestational age and mechanical ventilation in preterm neonates) are expected to affect presepsin reference limits only to minor extent. References [1] Evaluation of a newly identified soluble CD14 subtype as a marker for sepsis. Yaegashi Y., Shirakawa K., Sato N., Suzuki Y., Kojika M., Imai S., Takahashi G., Miyata M., Furusako S., Endo S. J Infect Chemother. 2005;11:234-8. [2] CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infection in the acute care setting. Horan T.C., Andrus M., Dudeck M.A. Am J Infect Control. 2008;36:309-32