Study of non-linear viscoelastic behavior of the human red blood cell

The non-linear behavior of human erythrocytes subjected to shear stress was analyzed using data series from the Erythrocyte Rheometer and a theoretical model was developed. Linear behavior was eliminated by means of a slot filter and a sixth order Savisky-Golay filter was applied to the resulting time series that allows the elimination of any possible white noise in the data. A fast Fourier transform was performed on the processed data, which resulted in a series of frequency dominant peaks. Results suggest the presence of a non-linear quadratic term in the Kelvin-Voigt phenomenological model. The correlation dimension studied through recurrence quantification analysis gave C2=2.58. Results suggest that the underlying dynamics is the same in each RBC sample corresponding to healthy donors

Lower Metal Enrichment of Virialized Gas in Minihalos

We differentiate between the metal enrichment of the gas in virialized minihalos and that of the intergalactic medium at high redshift, pertinent to cosmological reionization, with the initial expectation that gas in the high density regions within formed dark matter halos may be more robust thus resistant to mixing with lower density intergalactic medium. Using detailed hydrodynamic simulations of gas clouds in minihalos subject to destructive processes associated with the encompassing intergalactic shocks carrying metal-enriched gas, we find, as an example, that, for realistic shocks of velocities of 10-100km/s, more than (90%,65%) of the high density gas with rho>500 rhob inside a minihalo virialized at z=10 of mass (10^7,10^6)Msun remains at a metallicity lower than 3% of that of the intergalactic medium by redshift z=6. It may be expected that the high density gas in minihalos becomes fuel for subsequent star formation, when they are incorporated into larger halos where efficient atomic cooling can induce gas condensation hence star formation. Since minihalos virialize at high redshift when the universe is not expected to have been significantly reionized, the implication is that gas in virialized minihalos may provide an abundant reservoir of primordial gas to possibly allow for the formation of Population-III metal-free stars to extend to much lower redshift than otherwise expected based on the enrichment of intergalactic medium.Comment: 22 pages, 7 figures, submitted to ApJ, comments welcom

Dual characterization of critical fluctuations: Density functional theory & nonlinear dynamics close to a tangent bifurcation

We improve on the description of the relationship that exists between critical clusters in thermal systems and intermittency near the onset of chaos in low-dimensional systems. We make use of the statistical-mechanical language of inhomogeneous systems and of the renormalization group (RG) method in nonlinear dynamics to provide a more accurate, formal, approach to the subject. The description of this remarkable correspondence encompasses, on the one hand, the density functional formalism, where classical and quantum mechanical analogues match the procedure for one-dimensional clusters, and, on the other, the RG fixed-point map of functional compositions that captures the essential dynamical behavior. We provide details of how the above-referred theoretical approaches interrelate and discuss the implications of the correspondence between the high-dimensional (degrees of freedom) phenomenon and low-dimensional dynamics.Comment: 8 figure

Online Active Linear Regression via Thresholding

We consider the problem of online active learning to collect data for regression modeling. Specifically, we consider a decision maker with a limited experimentation budget who must efficiently learn an underlying linear population model. Our main contribution is a novel threshold-based algorithm for selection of most informative observations; we characterize its performance and fundamental lower bounds. We extend the algorithm and its guarantees to sparse linear regression in high-dimensional settings. Simulations suggest the algorithm is remarkably robust: it provides significant benefits over passive random sampling in real-world datasets that exhibit high nonlinearity and high dimensionality --- significantly reducing both the mean and variance of the squared error.Comment: Published in AAAI 201