DNS of Laminar to Turbulent Transition on NACA 0012 Airfoil with Sand Grain Roughness

The Lattice-Boltzmann-based solver PowerFLOW is used to perform direct numerical simulations of the transitional flow over an airfoil at Reynolds number equal to 0.657 million. The leading edge of the airfoil is covered with sand particles, represented by polyhedra, to mimic the grit used in experiments. The sensitivity of the laminar to turbulent transition to the size of these particles, grid resolution, spanwise length is evaluated and rectangular trips are also tested

On the environment surrounding close-in exoplanets

Exoplanets in extremely close-in orbits are immersed in a local interplanetary medium (i.e., the stellar wind) much denser than the local conditions encountered around the solar system planets. The environment surrounding these exoplanets also differs in terms of dynamics (slower stellar winds, but higher Keplerian velocities) and ambient magnetic fields (likely higher for host stars more active than the Sun). Here, we quantitatively investigate the nature of the interplanetary media surrounding the hot Jupiters HD46375b, HD73256b, HD102195b, HD130322b, HD179949b. We simulate the three-dimensional winds of their host stars, in which we directly incorporate their observed surface magnetic fields. With that, we derive mass-loss rates (1.9 to 8.0 $\times 10^{-13} M_{\odot}$/yr) and the wind properties at the position of the hot-Jupiters' orbits (temperature, velocity, magnetic field intensity and pressure). We show that these exoplanets' orbits are super-magnetosonic, indicating that bow shocks are formed surrounding these planets. Assuming planetary magnetic fields similar to Jupiter's, we estimate planetary magnetospheric sizes of 4.1 to 5.6 planetary radii. We also derive the exoplanetary radio emission released in the dissipation of the stellar wind energy. We find radio fluxes ranging from 0.02 to 0.13 mJy, which are challenging to be observed with present-day technology, but could be detectable with future higher sensitivity arrays (e.g., SKA). Radio emission from systems having closer hot-Jupiters, such as from tau Boo b or HD189733b, or from nearby planetary systems orbiting young stars, are likely to have higher radio fluxes, presenting better prospects for detecting exoplanetary radio emission.Comment: 15 pages, 5 figures, accepted to MNRA

Exoplanet Transit Variability: Bow Shocks and Winds Around HD 189733b

By analogy with the solar system, it is believed that stellar winds will form bow shocks around exoplanets. For hot Jupiters the bow shock will not form directly between the planet and the star, causing an asymmetric distribution of mass around the exoplanet and hence an asymmetric transit. As the planet orbits thorough varying wind conditions, the strength and geometry of its bow shock will change, thus producing transits of varying shape. We model this process using magnetic maps of HD 189733 taken one year apart, coupled with a 3D stellar wind model, to determine the local stellar wind conditions throughout the orbital path of the planet. We predict the time-varying geometry and density of the bow shock that forms around the magnetosphere of the planet and simulate transit light curves. Depending on the nature of the stellar magnetic field, and hence its wind, we find that both the transit duration and ingress time can vary when compared to optical light curves. We conclude that consecutive near-UV transit light curves may vary significantly and can therefore provide an insight into the structure and evolution of the stellar wind.Comment: 9 Pages, 7 figures. Accepted for publication in Monthly Notices of The Royal Astronomical Societ

Assessing Behavioral Health Risks, Health Conditions, and Preventive Health Practices among American Indians/Alaska Natives in Nevada

The 2004 Behavioral Risk Factor Surveillance System (BRFSS) survey was administered to American Indian/Alaska Native (AI/AN) adults in Nevada to determine whether health disparities exist between AI/ANs and the state’s general population. Results showed AI/ANs were 1.5 times more likely to smoke cigarettes, 3.5 times more likely to be exposed to secondhand smoke, 3.2 times more likely to lack leisure-time physical activity, 9.7 times more likely to report fair/poor health status, and 7.7 times more likely to have a disability. In addition, AI/ANs were more likely to have current asthma (OR=5.0) and diabetes (OR=1.8). AI/AN women were 4.8 times as likely to report no Pap test in the past 3 years. Our findings suggest that Nevada’s AI/AN population face many health disparities related to risk behaviors, poor health status and health conditions, and healthcare access. Partnerships among tribal, state and federal public health systems are needed to address these disparities

In silico identification of functional divergence between the multiple groEL gene paralogs in Chlamydiae

<p>Abstract</p> <p>Background</p> <p>Heat-shock proteins are specialized molecules performing different and essential roles in the cell including protein degradation, folding and trafficking. GroEL is a 60 Kda heat-shock protein ubiquitous in bacteria and has been regarded as an important molecule implicated in chronic inflammatory processes caused by <it>Chlamydiae </it>infections. GroEL in <it>Chlamydiae </it>became duplicated at the origin of the <it>Chlamydiae </it>lineage presenting three distinct molecular chaperones, namely the original protein GroEL1 (Ct110), and its paralogous proteins GroEL2 (Ct604) and GroEL3 (Ct755). These chaperones present differential and independent expressions during the different stages of <it>Chlamydiae </it>infections and have been suggested to present differential physiological and regulatory roles.</p> <p>Results</p> <p>In this comprehensive <it>in silico </it>study we show that GroEL protein paralogs have diverged functionally after the different gene duplication events and that this divergence has occurred mainly between GroEL3 and GroEL1. GroEL2 presents an intermediate functional divergence pattern from GroEL1. Our results point to the different protein-protein interaction patterns between GroEL paralogs and known GroEL protein clients supporting their functional divergence after <it>groEL </it>gene duplication. Analysis of selective constraints identifies periods of adaptive evolution after gene duplication that led to the fixation of amino acid replacements in GroEL protein domains involved in the interaction with GroEL protein clients.</p> <p>Conclusion</p> <p>We demonstrate that GroEL protein copies in <it>Chlamydiae </it>species have diverged functionally after the gene duplication events. We also show that functional divergence has occurred in important functional regions of these GroEL proteins and that very probably have affected the ancestral GroEL regulatory role and protein-protein interaction patterns with GroEL client proteins. Most of the amino acid replacements that have affected interaction with protein clients and that were responsible for the functional divergence between GroEL paralogs were fixed by adaptive evolution after the <it>groEL </it>gene duplication events.</p

Describing the structural robustness landscape of bacterial small RNAs

<p>Abstract</p> <p>Background</p> <p>The potential role of RNA molecules as gene expression regulators has led to a new perspective on the intracellular control and genome organization. Because secondary structures are crucial for their regulatory role, we sought to investigate their robustness to mutations and environmental changes.</p> <p>Results</p> <p>Here, we dissected the structural robustness landscape of the small non-coding RNAs (sncRNAs) encoded in the genome of the bacterium <it>Escherichia coli</it>. We found that bacterial sncRNAs are not significantly robust to both mutational and environmental perturbations when compared against artificial, unbiased sequences. However, we found that, on average, bacterial sncRNAs tend to be significantly plastic, and that mutational and environmental robustness strongly correlate. We further found that, on average, epistasis in bacterial sncRNAs is significantly antagonistic, and positively correlates with plasticity. Moreover, the evolution of robustness is likely dependent upon the environmental stability of the cell, with more fluctuating environments leading to the emergence and fixation of more robust molecules. Mutational robustness also appears to be correlated with structural functionality and complexity.</p> <p>Conclusion</p> <p>Our study provides a deep characterization of the structural robustness landscape of bacterial sncRNAs, suggesting that evolvability could be evolved as a consequence of selection for more plastic molecules. It also supports that environmental fluctuations could promote mutational robustness. As a result, plasticity emerges to link robustness, functionality and evolvability.</p

Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure

The Stokes equation with the varying viscosity is considered in a thin tube structure, i.e. in a connected union of thin rectangles with heights of order $\varepsilon<<1$ and with bases of order 1 with smoothened boundary. An asymptotic expansion of the solution is constructed: it contains some Poiseuille type flows in the channels (rectangles) with some boundary layers correctors in the neighborhoods of the bifurcations of the channels. The estimates for the difference of the exact solution and its asymptotic approximation are proved.Comment: 22 pages, 20 figure

Use of Filter Strips for Improved Surface Water Quality

An experiment studied effects of sunn hemp or oat plantings on loss of sediment and nutrients from an agricultural soil in runoff following rainfall. The study concluded that both plants can effectively reduce sediment and nutrient loads coming from idle and fallow fields in Hawaii