Arbitrary axisymmetric steady streaming: flow, force and propulsion

A well-developed method to induce mixing on microscopic scales is to exploit flows generated by steady streaming. Steady streaming is a classical fluid dynamics phenomenon whereby a time-periodic forcing in the bulk or along a boundary is enhanced by inertia to induce a non-zero net flow. Building on classical work for simple geometrical forcing and motivated by the complex shape oscillations of elastic capsules and bubbles, we develop the mathematical framework to quantify the steady streaming of a spherical body with arbitrary axisymmetric time-periodic boundary conditions. We compute the flow asymptotically for small-amplitude oscillations of the boundary in the limit where the viscous penetration length scale is much smaller than the body. In that case, the flow has a boundary layer structure and the fluid motion is solved by asymptotic matching. Our results, presented in the case of no-slip boundary conditions and extended to include the motion of vibrating free surfaces, recovers classical work as particular cases. We illustrate the flow structure given by our solution and propose one application of our results for small-scale force-generation and synthetic locomotion.Engineering and Physical Sciences Research Council, European Union (Marie Curie CIG Grant)This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Springer

Propulsion of bubble-based acoustic microswimmers

Acoustic microswimmers present a great potential for microfluidic applications and targeted drug delivery. Here, we introduce armored microbubbles (size range, 10–20 μm) made by three-dimensional microfabrication, which allows the bubbles to last for hours even under forced oscillations. The acoustic resonance of the armored microbubbles is found to be dictated by capillary forces and not by gas volume, and its measurements agree with a theoretical calculation. We further measure experimentally and predict theoretically the net propulsive flow generated by the bubble vibration. This flow, due to steady streaming in the fluid, can reach 100 mm/s, and is affected by the presence of nearby walls. Finally, microswimmers in motion are shown, either as spinning devices or free swimmers.P. M. acknowledges financial support from the European Community’s Seventh Framework Programme (FP7/2007-2013) ERC Grant Agreement Bubbleboost No. 614655. This work has been performed with the help of the “Plateforme Technologique Amont” de Grenoble, with the financial support of the “Nanosciences aux limites de la Nanoélectronique” Foundation. Support from the EPSRC (T. A. S.) and from a Marie Curie Grant (E. L.) is also gratefully acknowledged.This is the author accepted manuscript. The final version is available from American Physical Society via http://dx.doi.org/10.1103/PhysRevApplied.4.06401

The Epidemiology of Staphylococcus aureus and Panton-Valentine Leucocidin (pvl) in Central Australia, 2006-2010

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Background: The Central Australian Indigenous population has a high incidence of Staphylococcus aureus bacteremia (SAB) but little is known about the local molecular epidemiology. Methods: Prospective observational study of bacteremic and nasal colonizing S.aureus isolates between June 2006 to June 2010. All isolates underwent single nucleotide polymorphism (SNP) genotyping and testing for the presence of the Panton-Valentine Leucocidin (pvl) gene. Results: Invasive isolates (n = 97) were predominantly ST93 (26.6 %) and pvl positive (54.3 %), which was associated with skin and soft tissue infections (OR 4.35, 95 % CI 1.16, 16.31). Non-multiresistant MRSA accounted for 31.9 % of bacteremic samples and showed a trend to being healthcare associated (OR 2.16, 95 % CI 0.86, 5.40). Non-invasive isolates (n = 54) were rarely ST93 (1.9 %) or pvl positive (7.4 %). Conclusions: In Central Australia, ST93 was the dominant S.aureus clone, and was frequently pvl positive and associated with an aggressive clinical phenotype. Whether non-nasal carriage is more important with invasive clones or whether colonization occurs only transiently remains to be elucidated

The combined impact of sauerkraut with Leuconostoc mesenteroides to enhance immunomodulatory activity in Escherichia coli-infected mice

This study investigated the combined impact of sauerkraut and Leuconostoc mesenteroides culture on immunomodulatory activity in experimental animal. The in vivo immunomodulatory activity of Escherichia coli-infected Balb-C mice was ascertained in fermented sauerkrauts [test vs. control]. Both sauerkrauts enhanced the adaptive immune response [evidenced by an increase in CD4+ CD8+ IFN-γ, TNFα] and innate immune response [represented by a decrease of CD68-IL-6]. Nev- ertheless, the in vivo immunomodulatory activity of sauerkraut combined with L. mesenteroides was higher than that shown in sauerkraut control solely

Misogyny, racism, and Islamophobia: street harassment at the intersections

Veiled Muslim women are at an increased risk of street harassment in the current political and economic climate. Their visibility, combined with their popular portrayal as culturally dangerous or threatening means that they are vulnerable to receiving verbal and physical threats, which can be misogynistic and Islamophobic in nature. Drawing on 60 individual and 20 focus group interviews with Muslim women in the United Kingdom who wear the niqab (face veil) and had experienced harassment in public, this qualitative study details their lived experiences. It argues that an intersectional analysis is crucial to understanding the nuances of their lived experiences and the impact street harassment has on their lives. The findings demonstrate that street harassment can produce a hostile environment for veiled Muslim women, which can have a terrorizing effect, limiting their full participation in the public sphere