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https://www.readbyqxmd.com/read/28102179/a-2-d-suspension-of-active-agents-the-role-of-fluid-mediated-interactions
#1
Hojjat Behmadi, Zahra Fazli, Ali Najafi
Taking into account both the Vicsek short range ordering and the far-field hydrodynamic interactions mediated by the ambient fluid, we investigate the role of long range interactions in the ordering phenomena in a quasi 2-dimensional active suspension. By studying the number fluctuations, the velocity correlation functions and cluster size distribution function, we show that depending on the number density of swimmers and the strength of noise, the hydrodynamic interactions can have significant effects in a suspension...
January 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28098559/lattice-boltzmann-simulations-of-the-bead-spring-microswimmer-with-a-responsive-stroke-from-an-individual-to-swarms
#2
Kristina Pickl, Jayant Pande, Harald Köstler, Ulrich Rüde, Ana-Suncana Smith
Propulsion at low Reynolds numbers is often studied by defining artificial microswimmers which exhibit a particular stroke. The disadvantage of such an approach is that the stroke does not adjust to the environment, in particular the fluid flow, which can diminish the effect of hydrodynamic interactions. To overcome this limitation, we simulate a microswimmer consisting of three beads connected by springs and dampers, using the self-developed waLBerla and <i>pe</i> framework based on the lattice Boltzmann method and the discrete element method...
January 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28098324/ionic-screening-and-dissociation-are-crucial-for-understanding-chemical-self-propulsion-in-polar-solvents
#3
Aidan T Brown, Wilson C K Poon, Christian Holm, Joost de Graaf
Polar solvents like water support the bulk dissociation of themselves and their solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., H2O2 ⇌ H(+) + HO2(-). Using continuum theory, we study the influence of these association-dissociation reactions on the self-propulsion of colloids driven by surface chemical reactions (chemical swimmers). We find that association-dissociation reactions should have a strong influence on swimmers' behaviour, and therefore should be included in future modelling...
January 18, 2017: Soft Matter
https://www.readbyqxmd.com/read/28094380/crystallization-and-flow-in-active-patch-systems
#4
Jaffar Hasnain, Georg Menzl, Swetlana Jungblut, Christoph Dellago
Based upon recent experiments in which Janus particles are made into active swimmers by illuminating them with laser light, we explore the effect of applying a light pattern on the sample, thereby creating activity inducing zones or active patches. We simulate a system of interacting Brownian diffusers that become active swimmers when moving inside an active patch and analyze the structure and dynamics of the ensuing stationary state. We find that, in some respects, the effect of spatially inhomogeneous activity is qualitatively similar to a temperature gradient...
January 17, 2017: Soft Matter
https://www.readbyqxmd.com/read/28094239/performance-variation-due-to-stiffness-in-a-tuna-inspired-flexible-foil-model
#5
Mariel-Luisa N Rosic, Patrick J M Thornycroft, Kara L Feilich, Kelsey N Lucas, George V Lauder
Tuna are fast, economical swimmers in part due to their stiff, high aspect ratio caudal fins and streamlined bodies. Previous studies using passive caudal fin models have suggested that while high aspect ratio tail shapes such as a tuna's generally perform well, tail performance cannot be determined from shape alone. In this study, we analyzed the swimming performance of tuna-tail-shaped hydrofoils of a wide range of stiffnesses, heave amplitudes, and frequencies to determine how stiffness and kinematics affect multiple swimming performance parameters for a single foil shape...
January 17, 2017: Bioinspiration & Biomimetics
https://www.readbyqxmd.com/read/28090139/the-blood-antioxidant-defence-capacity-during-intermittent-hypoxic-training-in-elite-swimmers
#6
S Poprzęcki, M Czuba, A Zając, J Karpiński, R Wilk, G Bril, A Maszczyk, M Toborek
The main objective of this study was to examine the chronic effect of simulated intermittent normobaric hypoxia on blood antioxidant defence capacity in swimmers. The study included 14 male and 14 female competitive swimmers performing part of land training under simulated intermittent normobaric hypoxia (O2 = 15.5%) or in normoxia. Land interval training took place twice per week, with a total of 8 training units during the study, performed with individualized intensity. The activities of blood antioxidant enzymes did not change significantly during the first and last training unit in the hypoxic and normoxic group...
December 2016: Biology of Sport
https://www.readbyqxmd.com/read/28068679/-pneumothorax-following-dry-needling-treatment-legal-and-ethical-aspects
#7
Gianpaolo Ronconi, Fabio De Giorgio, Eleonora Ricci, Loredana Maggi, Antonio G Spagnolo, Paola Emilia Ferrara
Trigger point "dry needling" is a technique used to treat myofascial pain. It involves using filiform needles which are inserted into muscles to give local pain relief. Few cases of serious adverse events following this treatment have been reported in the literature. In this paper we describe the case of a professional swimmer who developed pneumothorax after dry needling treatment and discuss the medicolegal and ethical aspects related to competencies and responsibilities of medical doctors and physiotherapists performing the procedure...
September 2016: Igiene e Sanità Pubblica
https://www.readbyqxmd.com/read/28066850/morphology-of-clusters-of-attractive-dry-and-wet-self-propelled-spherical-particle-suspensions
#8
Francisco Alarcón, Chantal Valeriani, Ignacio Pagonabarraga
In order to assess the effect of hydrodynamics in the assembly of active attractive spheres, we simulate a semi-dilute suspension of attractive self-propelled spherical particles in a quasi-two dimensional geometry comparing the case with and without hydrodynamics interactions. To start with, independent of the presence of hydrodynamics, we observe that depending on the ratio between attraction and propulsion, particles either coarsen or aggregate forming finite-size clusters. Focusing on the clustering regime, we characterize two different cluster parameters, i...
January 9, 2017: Soft Matter
https://www.readbyqxmd.com/read/28065878/coordination-between-antioxidant-defences-might-be-partially-modulated-by-magnesium-status
#9
Cristina Paula Monteiro, Catarina Nunes Matias, Manuel Bicho, Helena Santa-Clara, Maria José Laires
The aim of this study was to compare the redox balance in competitive adult swimmers against recreational practitioners, controlling for Mg intake. Fifteen, competitive swimmers and 16 recreational practitioners, all male and aged 18-25years, were recruited into the study. Oxidative and muscle damage markers, and antioxidant enzymes and non-enzymatic antioxidants were evaluated by photometry (except for thiobarbituric reactive substances (TBARS), which was assessed by fluorimetry). Controlling for the level of exercise, inverse correlations were observed for uric acid and glutathione reductase (GR) or susceptibility of red blood cells to peroxidation (RBCPx); plasma adrenaline oxidase activity (AdOx) and carotenoids; TBARS and GR or Vit E; and direct correlations were observed between AdOx and creatine kinase (CK) or TBARS; CK and superoxide dismutase activity; GR and RBCPx...
January 6, 2017: Magnesium Research: Official Organ of the International Society for the Development of Research on Magnesium
https://www.readbyqxmd.com/read/28059780/separation-control-over-a-grooved-surface-inspired-by-dolphin-skin
#10
Amy Lang, Emily Jones, Farhana Afroz
Over many decades the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow which appear on surfaces such as shark skin, have been well documented. However the skin of dolphins is embedded with sinusoidal grooves that run perpendicular or transverse to the flow over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus acting as a potential mechanism to reduce flow separation and thus pressure drag...
January 6, 2017: Bioinspiration & Biomimetics
https://www.readbyqxmd.com/read/28054499/contribution-of-uncertainty-in-estimation-of-active-drag-using-assisted-towing-method-in-front-crawl-swimming
#11
Pendar Hazrati, Peter James Sinclair, Wayne Spratford, René Edouard Ferdinands, Bruce Robert Mason
Active drag force in swimming can be calculated from a function of five different variables: swim velocity, tow velocity, belt force, power output and exponent of velocity. The accuracy of the drag force value is dependent on the accuracy of each variable, and on the contribution of each variable to drag estimation. To calculate uncertainty in drag value, first the derivatives of the active drag equation with respect to each variable were obtained. Second, these were multiplied by the uncertainty of that variable...
January 5, 2017: Journal of Sports Sciences
https://www.readbyqxmd.com/read/28036211/load-response-of-the-flagellar-beat
#12
Gary S Klindt, Christian Ruloff, Christian Wagner, Benjamin M Friedrich
Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated Chlamydomonas cells to controlled microfluidic flows. A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the energy efficiency of the flagellar beat and its ability to synchronize to oscillatory flows...
December 16, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/28012027/having-bird-schistosomes-in-mind-the-first-detection-of-bilharziella-polonica-kowalewski-1895-in-the-bird-neural-system
#13
Hanna Prüter, Jiljí Sitko, Oliver Krone
Nasal bird schistosomes can cause bilharziosis in birds and have the potential to cause swimmer's itch in humans. We determined the prevalence of bird schistosomes in 106 mallards (Anas plathyrhynchos) from 11 water sources in Germany from 2014. Dissections were performed focusing on parasitic infections of the neural system. Infections with Trichobilharzia regenti (Horák et al. 1998) were found in 21% of the birds (n = 22), whereas Bilharziella polonica (Kowalewski 1895) were found between the brain membranes (meninges) and the brain, in the spinal cord or in the intestine of 12% of the mallards (n = 13)...
December 23, 2016: Parasitology Research
https://www.readbyqxmd.com/read/28011098/serum-igf-i-igfbp-3-and-als-concentrations-and-physical-performance-in-young-swimmers-during-a-training-season
#14
H Tourinho Filho, M Pires, E F Puggina, M Papoti, R Barbieri, C E Martinelli
INTRODUCTION: The GH/IGF-I axis is a system of growth mediators, receptors, and binding proteins that regulate somatic and tissue growth; and it has been shown that exercise programs are related to the anabolic function of this axis. OBJECTIVE: The aim of this study was to analyse the changes of serum IGF-I concentration and that of its binding proteins IGFBP-3 and ALS in adolescent swimmers at different stages of a training season, and compare them with physical performance parameters and body composition of the athletes...
December 18, 2016: Growth Hormone & IGF Research
https://www.readbyqxmd.com/read/28007336/the-combined-frequency-of-igf-and-myostatin-polymorphism-among-track-field-athletes-and-swimmers
#15
Sigal Ben-Zaken, Yoav Meckel, Dan Nemet, Alon Eliakim
OBJECTIVE: The IGF C-1245T (rs35767) and the myostatin (MSTN) Lys(K)-153Arg(R) genetic polymorphism may influence skeletal muscle phenotypes and athletic performance. Carrying the minor IGF T allele and the myostatin rare R allele was associated with higher circulating IGF-I levels, greater muscle mass and improved performance. The aim of the present study was to assess the combined frequency of the IGF 1245T (rs35767) and MSTN 153Arg(R) polymorphism among Israeli track and field athletes (n=111) and swimmers (n=80)...
December 15, 2016: Growth Hormone & IGF Research
https://www.readbyqxmd.com/read/28005561/risk-factors-for-collegiate-swimmers-hospitalized-with-exertional-rhabdomyolysis
#16
Margo R Stanfa, Navjeet N Silles, Amanda Cooper, Sara Arena, Kristin Landis-Piwowar, Carrie Aprik, Tamara Hew-Butler
OBJECTIVE: To identify midseason risk factors for symptomatic exertional rhabdomyolysis (sER) in swimmers after a novel upper body workout. DESIGN: Retrospective (1) survey and (2) analyses of observational laboratory data conducted over a 16-week training period, 2 months before sER. SETTING: Midwest University. PARTICIPANTS: Thirty-four collegiate swimmers. INDEPENDENT VARIABLES: (1) Motivation, symptoms, and supplements for survey variables...
January 2017: Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine
https://www.readbyqxmd.com/read/27999719/immediate-effects-of-deep-trunk-muscle-training-on-swimming-start-performance
#17
Satoshi Iizuka, Atsushi Imai, Keisuke Koizumi, Keisuke Okuno, Koji Kaneoka
BACKGROUND: In recent years, deep trunk muscle training has been adopted in various sports, including swimming. This is performed both in everyday training and as part of the warm-up routine before competitive races. It is suggested that trunk stabilization exercises are effective in preventing injury, and aid in improving performance. However, conclusive evidence of the same is yet to be obtained. The time of start phase of swimming is a factor that can significantly influence competition performance in a swimming race...
December 2016: International Journal of Sports Physical Therapy
https://www.readbyqxmd.com/read/27998206/determination-of-a-quantitative-parameter-to-evaluate-swimming-technique-based-on-the-maximal-tethered-swimming-test
#18
Rafael Soncin, Bruno Mezêncio, Jacielle Carolina Ferreira, Sara Andrade Rodrigues, Rudolf Huebner, Julio Cerca Serrão, Leszek Szmuchrowski
The aim of this study was to propose a new force parameter, associated with swimmers' technique and performance. Twelve swimmers performed five repetitions of 25 m sprint crawl and a tethered swimming test with maximal effort. The parameters calculated were: the mean swimming velocity for crawl sprint, the mean propulsive force of the tethered swimming test as well as an oscillation parameter calculated from force fluctuation. The oscillation parameter evaluates the force variation around the mean force during the tethered test as a measure of swimming technique...
December 21, 2016: Sports Biomechanics
https://www.readbyqxmd.com/read/27995903/experimental-study-of-laminar-and-turbulent-boundary-layer-separation-control-of-shark-skin
#19
Farhana Afroz, Amy Lang, Maria Laura Habegger, Philip Motta, Robert Hueter
The Shortfin Mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility, and has flexible scales known to bristle up to 50° in the flank regions. It is purported that this bristling capability of the scales may result in a unique pass flow control method to control flow separation and reduce drag. It appears that the scales have evolved to be only actuated when the flow over the body is reversed; thereby inducing a method of inhibiting flow reversal close to the surface. In addition, bristled scales form cavities which could induce boundary layer mixing and further assist in delaying flow separation...
December 20, 2016: Bioinspiration & Biomimetics
https://www.readbyqxmd.com/read/27991641/acoustic-actuation-of-bioinspired-microswimmers
#20
Murat Kaynak, Adem Ozcelik, Amir Nourhani, Paul E Lammert, Vincent H Crespi, Tony Jun Huang
Acoustic actuation of bioinspired microswimmers is experimentally demonstrated. Microswimmers are fabricated in situ in a microchannel. Upon acoustic excitation, the flagellum of the microswimmer oscillates, which in turn generates linear or rotary movement depending on the swimmer design. The speed of these bioinspired microswimmers is tuned by adjusting the voltage amplitude applied to the acoustic transducer. Simple microfabrication and remote actuation are promising for biomedical applications.
December 19, 2016: Lab on a Chip
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