2,709 research outputs found
Cascade of Complexity in Evolving Predator-Prey Dynamics
We simulate an individual-based model that represents both the phenotype and
genome of digital organisms with predator-prey interactions. We show how
open-ended growth of complexity arises from the invariance of genetic evolution
operators with respect to changes in the complexity, and that the dynamics
which emerges is controlled by a non-equilibrium critical point. The mechanism
is analogous to the development of the cascade in fluid turbulence.Comment: 5 pages, 3 figures; added comments on system size scaling and
turbulence analogy, added error estimates of data collapse parameters.
Slightly enhanced from the version which will appear in PR
Takotsubo cardiomyopathy and sepsis: a systematic review
Takotsubo cardiomyopathy (TTC) is characterized by a systolic dysfunction localized in the apical and medial aspect of
the left ventricle. It is usually related to physical or emotional stress. Recent evidence highlighting the role of infection
led us to analyze the links between TTC and sepsis. A systematic review of the literature was undertaken to assess any
trends in clinical findings, diagnosis, and outcomes in such patients. We identified 23 selected papers reporting a total of
26 patients, having sepsis, in whom TTC occurred. For each case, we collected data identifying population characteristics,
source of sepsis, clinical disease description, and the results of cardiovascular investigations. The majority of patients
were females (n = 16), mean age was 62.8 (14.0 standard deviation) years, and clinical outcome was favorable in 92.3% of
the cases once the management of sepsis was initiated. A better understanding of the mechanisms of sepsis-associated
TTC may generate novel strategies to treat the complications of this cardiomyopathy and may even help predict and
prevent its occurrence
Using Synthetic Spacecraft Data to Interpret Compressible Fluctuations in Solar Wind Turbulence
Kinetic plasma theory is used to generate synthetic spacecraft data to
analyze and interpret the compressible fluctuations in the inertial range of
solar wind turbulence. The kinetic counterparts of the three familiar linear
MHD wave modes---the fast, Alfven, and slow waves---are identified and the
properties of the density-parallel magnetic field correlation for these kinetic
wave modes is presented. The construction of synthetic spacecraft data, based
on the quasi-linear premise---that some characteristics of magnetized plasma
turbulence can be usefully modeled as a collection of randomly phased, linear
wave modes---is described in detail. Theoretical predictions of the
density-parallel magnetic field correlation based on MHD and Vlasov-Maxwell
linear eigenfunctions are presented and compared to the observational
determination of this correlation based on 10 years of Wind spacecraft data. It
is demonstrated that MHD theory is inadequate to describe the compressible
turbulent fluctuations and that the observed density-parallel magnetic field
correlation is consistent with a statistically negligible kinetic fast wave
energy contribution for the large sample used in this study. A model of the
solar wind inertial range fluctuations is proposed comprised of a mixture of a
critically balanced distribution of incompressible Alfvenic fluctuations and a
critically balanced or more anisotropic than critical balance distribution of
compressible slow wave fluctuations. These results imply that there is little
or no transfer of large scale turbulent energy through the inertial range down
to whistler waves at small scales.Comment: Accepted to Astrophysical Journal. 28 pages, 7 figure
Statistical anisotropy of magnetohydrodynamic turbulence
Direct numerical simulations of decaying and forced magnetohydrodynamic (MHD)
turbulence without and with mean magnetic field are analyzed by higher-order
two-point statistics. The turbulence exhibits statistical anisotropy with
respect to the direction of the local magnetic field even in the case of global
isotropy. A mean magnetic field reduces the parallel-field dynamics while in
the perpendicular direction a gradual transition towards two-dimensional MHD
turbulence is observed with inertial-range scaling of the
perpendicular energy spectrum. An intermittency model based on the Log-Poisson
approach, , is able to describe the observed
structure function scalings.Comment: 4 pages, 3 figures. To appear in Phys.Rev.
Obesity and its association to phenotype and clinical course in hypertrophic cardiomyopathy
ObjectivesThis study sought to assess the impact of body mass index (BMI) on cardiac phenotypic and clinical course in a multicenter hypertrophic cardiomyopathy (HCM) cohort.BackgroundIt is unresolved whether clinical variables promoting left ventricular (LV) hypertrophy in the general population, such as obesity, may influence cardiac phenotypic and clinical course in patients with HCM.MethodsIn 275 adult HCM patients (age 48 ± 14 years; 70% male), we assessed the relation of BMI to LV mass, determined by cardiovascular magnetic resonance (CMR) and heart failure progression.ResultsAt multivariate analysis, BMI proved independently associated with the magnitude of hypertrophy: pre-obese and obese HCM patients (BMI 25 to 30 kg/m2 and >30 kg/m2, respectively) showed a 65% and 310% increased likelihood of an LV mass in the highest quartile (>120 g/m2), compared with normal weight patients (BMI <25 kg/m2; hazard ratio [HR]: 1.65; 95% confidence interval [CI]: 0.73 to 3.74, p = 0.22 and 3.1; 95% CI: 1.42 to 6.86, p = 0.004, respectively). Other features associated with LV mass >120 g/m2 were LV outflow obstruction (HR: 4.9; 95% CI: 2.4 to 9.8; p < 0.001), systemic hypertension (HR: 2.2; 95% CI: 1.1 to 4.5; p = 0.026), and male sex (HR: 2.1; 95% CI: 0.9 to 4.7; p = 0.083). During a median follow-up of 3.7 years (interquartile range: 2.5 to 5.3), obese patients showed an HR of 3.6 (95% CI: 1.2 to 10.7, p = 0.02) for developing New York Heart Association (NYHA) functional class III to IV symptoms compared to nonobese patients, independent of outflow obstruction. Noticeably, the proportion of patients in NYHA functional class III at the end of follow-up was 13% among obese patients, compared with 6% among those of normal weight (p = 0.03).ConclusionsIn HCM patients, extrinsic factors such as obesity are independently associated with increase in LV mass and may dictate progression of heart failure symptoms
A model of nonlinear evolution and saturation of the turbulent MHD dynamo
The growth and saturation of magnetic field in conducting turbulent media
with large magnetic Prandtl numbers are investigated. This regime is very
common in low-density hot astrophysical plasmas. During the early (kinematic)
stage, weak magnetic fluctuations grow exponentially and concentrate at the
resistive scale, which lies far below the hydrodynamic viscous scale. The
evolution becomes nonlinear when the magnetic energy is comparable to the
kinetic energy of the viscous-scale eddies. A physical picture of the ensuing
nonlinear evolution of the MHD dynamo is proposed. Phenomenological
considerations are supplemented with a simple Fokker--Planck model of the
nonlinear evolution of the magnetic-energy spectrum. It is found that, while
the shift of the bulk of the magnetic energy from the subviscous scales to the
velocity scales may be possible, it occurs very slowly -- at the resistive,
rather than dynamical, time scale (for galaxies, this means that generation of
large-scale magnetic fields cannot be explained by this mechanism). The role of
Alfvenic motions and the implications for the fully developed isotropic MHD
turbulence are discussed.Comment: IOP latex, 19 pages, 6 figures; final published versio
Echocardiography in patients with hypertrophic cardiomyopathy: usefulness of old and new techniques in the diagnosis and pathophysiological assessment
Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiomyopathy. The identification of patients with HCM is sometimes still a challenge. Moreover, the pathophysiology of the disease is complex because of left ventricular hyper-contractile state, diastolic dysfunction, ischemia and obstruction which can be coexistent in the same patient. In this review, we discuss the current and emerging echocardiographic methodology that can help physicians in the correct diagnostic and pathophysiological assessment of patients with HCM
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