Soot formation and burnout in flames

The amount of soot formed when burning a benzene/hexane mixture in a turbulent combustor was examined. Soot concentration profiles in the same combustor for kerosene fuel are given. The chemistry of the formation of soot precursors, the nucleation, growth and subsequent burnout of soot particles, and the effect of mixing on the previous steps were considered

Transport of Single Molecules Along the Periodic Parallel Lattices with Coupling

General discrete one-dimensional stochastic models to describe the transport of single molecules along coupled parallel lattices with period $N$ are developed. Theoretical analysis that allows to calculate explicitly the steady-state dynamic properties of single molecules, such as mean velocity $V$ and dispersion $D$, is presented for N=1 and N=2 models. For the systems with $N>2$ exact analytic expressions for the large-time dynamic properties are obtained in the limit of strong coupling between the lattices that leads to dynamic equilibrium between two parallel kinetic pathways.Comment: Submitted to J. Chem. Phy

Efficiency at maximum power of interacting molecular machines

We investigate the efficiency of systems of molecular motors operating at maximum power. We consider two models of kinesin motors on a microtubule: for both the simplified and the detailed model, we find that the many-body exclusion effect enhances the efficiency at maximum power of the many-motor system, with respect to the single motor case. Remarkably, we find that this effect occurs in a limited region of the system parameters, compatible with the biologically relevant range.Comment: To appear in Phys. Rev. Let

The MOSS camera on H-1NF

We have configured the modulated optical solid-state spectrometer, a recently developed high-resolution instrument for plasma Dopplerspectroscopy, as an imaging spectroscopiccamera. The camera features a wide field of view (∼10°), large aperture (40 mm), and high spectral resolution ν/Δν greater than 10 000. The camera installation on the H-1NF Heliac is described, together with the steps in the design process, including field widening. Calibration and characterization of the instrument function is discussed and the instrument performance is illustrated with some sample results of spatially resolved ion temperature measurements in H-1NF

Persistence in the Voter model: continuum reaction-diffusion approach

We investigate the persistence probability in the Voter model for dimensions d\geq 2. This is achieved by mapping the Voter model onto a continuum reaction-diffusion system. Using path integral methods, we compute the persistence probability r(q,t), where q is the number of ``opinions'' in the original Voter model. We find r(q,t)\sim exp[-f_2(q)(ln t)^2] in d=2; r(q,t)\sim exp[-f_d(q)t^{(d-2)/2}] for 2<d<4; r(q,t)\sim exp[-f_4(q)t/ln t] in d=4; and r(q,t)\sim exp[-f_d(q)t] for d>4. The results of our analysis are checked by Monte Carlo simulations.Comment: 10 pages, 3 figures, Latex, submitted to J. Phys. A (letters

Bulk-driven non-equilibrium phase transitions in a mesoscopic ring

We study a periodic one-dimensional exclusion process composed of a driven and a diffusive part. In a mesoscopic limit where both dynamics compete we identify bulk-driven phase transitions. We employ mean-field theory complemented by Monte-Carlo simulations to characterize the emerging non-equilibrium steady states. Monte-Carlo simulations reveal interesting correlation effects that we explain phenomenologically.Comment: 4 pages, 3 figure

Simulation model of erosion and deposition on a barchan dune

Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity

Differential Effects of Race and Poverty on Ambulatory Care Sensitive Conditions

This study is a continuation of an earlier study that examined hospitalization rates for ambulatory care sensitive (ACS) conditions, as a proxy for quality of care, and found evidence of a racial disparity among African American and White Medicare beneficiaries. The current study sought to determine whether neighborhood socioeconomic status (SES) explained this disparity. Differences in rates of ACS hospitalizations by race were assessed using Cochran-Mantel Haenszel tests and Poisson regression. Unadjusted rate ratios for ACS hospitalization for African Americans vs. Whites were found to be higher in low poverty areas (rate ratio (RR)=1.13; 95% CI (1.08, 1.17)) than in high poverty areas (RR=0.97; 95% CI (0.89, 1.05)). After controlling for various indicators of area SES in multivariate analyses race differences in ACS hospitalization rates persisted. Rural neighborhoods and those with higher percent of non-high school graduates were associated with greater risk of ACS hospitalizations