Three-dimensional flow of colloidal glasses

Recent experiments performed on a variety of soft glassy materials have demonstrated that any imposed shear flow serves to simultaneously fluidize these systems in all spatial directions [Ovarlez et al., Nature Mater. 9, 115–119 (2010)]. When probed with a second shear flow, the viscous response of the experimental system is determined by the rate of the primary, fluidizing flow. Motivated by these findings, we employ a recently developed schematic mode-coupling theory [Brader et al., Proc. Natl. Acad. Sci. U.S.A. 106, 15186–15191 (2009)] to investigate the three-dimensional flow of a colloidal glass, subject to a combination of simple shear and uniaxial compression. Despite differences in the specific choice of superposed flow, the flow curves obtained show a good qualitative agreement with the experimental findings and recover the observed power-law describing the decay of the scaled viscosity as a function of the dominant rate. We, then, proceed to perform a more formal analysis of our constitutive equation for different kind of “mixed” flows consisting of a dominant primary flow subject to a weaker perturbing flow. Our study provides further evidence that the theory of Brader et al., Proc. Natl. Acad. Sci. U.S.A. 106, 15186–15191 (2009) reliably describes the dynamic arrest and mechanical fluidization of dense particulate suspensions

Effective interactions in active Brownian suspensions

Active colloids exhibit persistent motion, which can lead to motility-induced phase separation (MIPS). However, there currently exists no microscopic theory to account for this phenomenon. We report a first-principles theory, free of fit parameters, for active spherical colloids, which shows explicitly how an effective many-body interaction potential is generated by activity and how this can rationalize MIPS. For a passively repulsive system the theory predicts phase separation and pair correlations in quantitative agreement with simulation. For an attractive system the theory shows that phase separation becomes suppressed by moderate activity, consistent with recent experiments and simulations, and suggests a mechanism for reentrant cluster formation at high activity

Labial and Vaginal Microbiology: Effects of Extended Panty Liner Use

Objective: The goals of this study were 1) to better define the labial microflora and 2) to evaluate whether extended non-menstrual use of panty liners would increase genital carriage of undesirable bacteria and predispose to infection

The P450 oxidoreductase, RedA, controls development beyond the mound stage in Dictyostelium discoideum

<p>Abstract</p> <p>Background</p> <p>NADPH-cytochrome-P450 oxidoreductase (CPR) is a ubiquitous enzyme that belongs to a family of diflavin oxidoreductases and is required for activity of the microsomal cytochrome-P450 monooxygenase system. CPR gene-disruption experiments have demonstrated that absence of this enzyme causes developmental defects both in mouse and insect.</p> <p>Results</p> <p>Annotation of the sequenced genome of <it>D. discoideum </it>revealed the presence of three genes (<it>redA</it>, <it>redB </it>and <it>redC</it>) that encode putative members of the diflavin oxidoreductase protein family. <it>redA </it>transcripts are present during growth and early development but then decline, reaching undetectable levels after the mound stage. <it>redB </it>transcripts are present in the same levels during growth and development while <it>redC </it>expression was detected only in vegetative growing cells. We isolated a mutant strain of <it>Dictyostelium discoideum </it>following restriction enzyme-mediated integration (REMI) mutagenesis in which <it>redA </it>was disrupted. This mutant develops only to the mound stage and accumulates a bright yellow pigment. The mound-arrest phenotype is cell-autonomous suggesting that the defect occurs within the cells rather than in intercellular signaling.</p> <p>Conclusion</p> <p>The developmental arrest due to disruption of <it>redA </it>implicates CPR in the metabolism of compounds that control cell differentiation.</p

Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275

Far ultraviolet emission has been detected from a knot of Halpha emission in the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected relative to the brightness of the Halpha line in the same spatial region is very close to that expected from Hydrogen two-photon continuum emission in the particle heating model of Ferland et al. (2009) if reddening internal to the filaments is taken into account. We find no need to invoke other sources of far ultraviolet emission such as hot stars or emission lines from CIV in intermediate temperature gas to explain these data.Comment: 9 pages, 8 figures. Accepted for publication in MNRA

Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies

We present an integral field spectroscopic study of two nearby Luminous Infrared Galaxies (LIRGs) that exhibit evidence of widespread shock excitation induced by ongoing merger activity, IC 1623 and NGC 3256. We show the importance of carefully separating excitation due to shocks vs. excitation by HII regions and the usefulness of IFU data in interpreting the complex processes in LIRGs. Our analysis focuses primarily on the emission line gas which is extensive in both systems and is a result of the abundant ongoing star formation as well as widespread LINER-like excitation from shocks. We use emission-line ratio maps, line kinematics, line-ratio diagnostics and new models as methods for distinguishing and analyzing shocked gas in these systems. We discuss how our results inform the merger sequence associated with local U/LIRGs and the impact that widespread shock excitation has on the interpretation of emission-line spectra and derived quantities of both local and high-redshift galaxies.Comment: 14 pages, 11 figures, Accepted to Ap

Optical IFU Observations of the Brightest Cluster Galaxy NGC 4696: The Case for a Minor Merger and Shock-excited Filaments

We present deep optical integral-field spectroscopic observations of the nearby (z ~ 0.01) brightest cluster galaxy NGC 4696 in the core of the Centaurus Cluster, made with the Wide Field Spectrograph (WiFeS) on the ANU 2.3m telescope at Siding Spring Observatory. We investigate the morphology, kinematics, and excitation of the emission-line filaments and discuss these in the context of a model of a minor merger. We suggest that the emission-line filaments in this object have their origin in the accretion of a gas-rich galaxy and that they are excited by v ~100-200 km/s shocks driven into the cool filament gas by the ram pressure of the transonic passage of the merging system through the hot halo gas of NGC 4696.Comment: 19 pages, 15 figures, accepted for publication in The Astrophysical Journa

Parallel implementation of the aeh technique for the solution of plane multiphasic problems

The Asymptotic Expansion Homogenization (AEH) technique is used to estimate the effective properties of heterogeneous media with periodical microstructure. A considerable computational effort can be necessary even though the adopted models are quite simple. For this reason, parallelization is often necessary to achieve good performance. This work presents a first attempt to parallelize the AEH implementation code. Although the parallelization process is in a very early stage, the preliminary results show that the parallel version provides up to a 30% improvement in application speed. This work consists on a step towards a numerical tool for the analysis of more complex and three-dimensional periodic cells. The two-dimensional AEH was implemented in the C programming language for the future generalization to three-dimensional problems employing the available parallelization tools