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https://www.readbyqxmd.com/read/29243668/chemotactic-droplet-swimmers-in-complex-geometries
#1
Chenyu Jin, Babak Vajdi Hokmabad, Kyle Anthony Baldwin, Corinna Charlotte Maass
Chemotaxis and auto-chemotaxis are key mechanisms in the dynamics of micro-organisms, e.g. in the acquisition of nutrients and in the communication between individuals, influencing the collective behaviour. However, chemical signalling and the natural environment of biological swimmers are generally complex, making them hard to access analytically. We present a well-controlled, tunable artificial model to study chemotaxis and autochemotaxis in complex geometries, using microfluidic assays of self-propelling oil droplets in an aqueous surfactant solution...
December 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29242866/the-curved-kinetic-boundary-layer-of-active-matter
#2
Wen Yan, John F Brady
A body submerged in active matter feels the swim pressure through a kinetic accumulation boundary layer on its surface. The boundary layer results from a balance between translational diffusion and advective swimming and occurs on the microscopic length scale . Here , DT is the Brownian translational diffusivity, τR is the reorientation time and l = U0τR is the swimmer's run length, with U0 the swim speed [Yan and Brady, J. Fluid. Mech., 2015, 785, R1]. In this work we analyze the swim pressure on arbitrary shaped bodies by including the effect of local shape curvature in the kinetic boundary layer...
December 15, 2017: Soft Matter
https://www.readbyqxmd.com/read/29239516/engineering-contactless-particle-particle-interactions-in-active-microswimmers
#3
Amir Nourhani, Daniel Brown, Nicholas Pletzer, John G Gibbs
Artificial self-propelled colloidal particles have recently served as effective building blocks for investigating many dynamic behaviors exhibited by nonequilibrium systems. However, most studies have relied upon excluded volume interactions between the active particles. Experimental systems in which the mobile entities interact over long distances in a well-defined and controllable manner are valuable so that new modes of multiparticle dynamics can be studied systematically in the laboratory. Here, a system of self-propelled microscale Janus particles is engineered to have contactless particle-particle interactions that lead to long-range attraction, short-range repulsion, and mutual alignment between adjacent swimmers...
December 2017: Advanced Materials
https://www.readbyqxmd.com/read/29239442/hydrodynamics-mediated-trapping-of-micro-swimmers-near-drops
#4
Nikhil Desai, Vaseem A Shaik, Arezoo M Ardekani
In this paper, we investigate the swimming characteristics and dynamics of a model micro-swimmer in the vicinity of a clean drop, and of a surfactant covered drop. We model the swimmer as a force dipole and utilize the image-singularity system to study the dynamical behavior of the swimmer. Motivated by bacterial bio-remediation of insoluble hydrocarbons (HCs) released during oil spills, we report the 'trapping characteristics' - critical trapping radius, basin of attraction and trapping time distribution - of deterministic and stochastic swimmers, as a function of viscosity ratio, and dimensionless surface viscosity...
December 14, 2017: Soft Matter
https://www.readbyqxmd.com/read/29238259/front-crawl-swimming-performance-and-bi-lateral-force-asymmetry-during-land-based-and-tethered-swimming-tests
#5
Karini B Dos Santos, Paulo C Barauce Bento, Gleber Pereira, Carl Payton, André L F Rodacki
The aims of this study were to investigate whether land-based and tethered swimming strength tests can explain swimming performance in 200-meter front crawl and, whether these tests were able to identify bilateral symmetry in force production. In the first session, eighteen swimmers completed a maximum effort 200 m front crawl swim (swimming performance) and 15 seconds maximal effort tethered front crawl swim. In the second session, participants performed the upper extremity isometric strength test. Peak force production of tethered swimming and isometric strength tests were significantly correlated for the strongest and weakest sides (r = 0...
December 2017: Journal of Sports Science & Medicine
https://www.readbyqxmd.com/read/29238252/the-effect-of-respiratory-muscle-training-on-fin-swimmers-performance
#6
Jana Vašíčková, Kateřina Neumannová, Zbyněk Svozil
Although respiratory muscle functions can influence swimming performance, respiratory muscle training (RMT) is not routinely used for improving fin-swimmers´ performance. The aim of our study was to verify the benefit of a one month of RMT in young fin-swimmers. We assessed the effect of this training on respiratory muscles and on maximal underwater swimming distance. 28 fin-swimmers were randomly divided into an experimental group (EG) and a control group (CG). The study finished with 20 fin-swimmers (EG: n = 12; average age 12...
December 2017: Journal of Sports Science & Medicine
https://www.readbyqxmd.com/read/29238249/influence-of-competitive-anxiety-on-heart-rate-variability-in-swimmers
#7
Leonardo S Fortes, Bruna D V da Costa, Pedro P Paes, José R A do Nascimento Júnior, Lenamar Fiorese, Maria E C Ferreira
The aim of this study was to analyze the relationship between competitive anxiety and heart rate variability (HRV) in swimming athletes. A total of 66 volunteers (41 male and 27 female) who swam the 400-m freestyle in the Brazilian Swimming Championships participated. Thirty minutes before the 400-m freestyle event, the athletes answered the Competitive Anxiety Inventory (CSAI-2R) questionnaire, then underwent anthropometric (body weight, height, and skinfold thickness) and HRV measurements. Then, at a second meeting, held 3 h after the 400-m freestyle event, the athletes returned to the evaluation room for HRV measurement (Polar® RS800cx, Kempele, Finland)...
December 2017: Journal of Sports Science & Medicine
https://www.readbyqxmd.com/read/29238247/effects-of-hypoxic-training-versus-normoxic-training-on-exercise-performance-in-competitive-swimmers
#8
Hun-Young Park, Kiwon Lim
In swimming competition, optimal swimming performance is characterized by a variety of interchangeable components, such as aerobic exercise capacity, anaerobic power and muscular function. Various hypoxic training methods would potentiate greater performance improvements compared to similar training at sea-level. Therefore, this study aimed to evaluate the effects of six-weeks of hypoxic training on exercise performance in moderately trained competitive swimmers. Twenty swimmers were equally divided into a normoxic training group (n = 10) for residing and training at sea-level (PIO2 = 149...
December 2017: Journal of Sports Science & Medicine
https://www.readbyqxmd.com/read/29234967/finding-efficient-swimming-strategies-in-a-three-dimensional-chaotic-flow-by-reinforcement-learning
#9
K Gustavsson, L Biferale, A Celani, S Colabrese
We apply a reinforcement learning algorithm to show how smart particles can learn approximately optimal strategies to navigate in complex flows. In this paper we consider microswimmers in a paradigmatic three-dimensional case given by a stationary superposition of two Arnold-Beltrami-Childress flows with chaotic advection along streamlines. In such a flow, we study the evolution of point-like particles which can decide in which direction to swim, while keeping the velocity amplitude constant. We show that it is sufficient to endow the swimmers with a very restricted set of actions (six fixed swimming directions in our case) to have enough freedom to find efficient strategies to move upward and escape local fluid traps...
December 14, 2017: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/29224500/transition-phase-clothing-strategies-and-their-effect-on-body-temperature-and-100-m-swimming-performance
#10
Andy Galbraith, Aimee Willmott
OBJECTIVE: Effective warm-ups are attributed to several temperature-related mechanisms. Strategies during the transition phase, preceding swimming competition, have been shown to prolong temperature-related warm-up effects. The purpose of this study was to evaluate the effects of two different clothing strategies during the transition phase, on subsequent 100-m maximal swimming performance. METHODS: Nine competitive swimmers (3 female, 21 ± 3 yrs; 6 male 20 ± 2 yrs, mean performance standard 702 FINA Points, mean 100-m seasons best time 61...
December 10, 2017: European Journal of Sport Science
https://www.readbyqxmd.com/read/29220801/assessment-of-temperature-and-ultraviolet-radiation-effects-on-sunburn-incidence-at-an-inland-u-s-beach-a-cohort-study
#11
Jason W Marion, Jiyoung Lee, James S Rosenblum, Timothy J Buckley
BACKGROUND: Increases in outdoor temperature may lead to increases in sunburn, outdoor exposure, and skin cancer in human populations. OBJECTIVE: This study aimed to quantify sunburn incidence and risk for Ohio beachgoers exposed to varying outdoor conditions. METHODS: Sunburn incidence data were obtained through a prospective cohort study at East Fork Lake (Cincinnati, Ohio, USA). Recruitment occurred over 26 weekend days. Beach interviews and follow-up telephone interviews obtained exposure and health information...
December 5, 2017: Environmental Research
https://www.readbyqxmd.com/read/29216264/a-pressure-based-force-and-torque-prediction-technique-for-the-study-of-fish-like-swimming
#12
Kelsey N Lucas, John O Dabiri, George V Lauder
Many outstanding questions about the evolution and function of fish morphology are linked to swimming dynamics, and a detailed knowledge of time-varying forces and torques along the animal's body is a key component in answering many of these questions. Yet, quantifying these forces and torques experimentally represents a major challenge that to date prevents a full understanding of fish-like swimming. Here, we develop a method for obtaining these force and torque data non-invasively using standard 2D digital particle image velocimetry in conjunction with a pressure field algorithm...
2017: PloS One
https://www.readbyqxmd.com/read/29212722/first-satellite-tracks-of-south-atlantic-sea-turtle-lost-years-seasonal-variation-in-trans-equatorial-movement
#13
Katherine L Mansfield, Milagros L Mendilaharsu, Nathan F Putman, Maria A G Dei Marcovaldi, Alexander E Sacco, Gustave Lopez, Thais Pires, Yonat Swimmer
In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming)...
December 6, 2017: Proceedings. Biological Sciences
https://www.readbyqxmd.com/read/29208541/biological-synthesis-of-silver-nanoparticles-using-%C3%AE-1-3-glucan-binding-protein-and-their-antibacterial-antibiofilm-and-cytotoxic-potential
#14
Mahalingam Anjugam, Baskaralingam Vaseeharan, Arokiadhas Iswarya, Mani Divya, Narayanan Marimuthu Prabhu, Krishnasamy Sankaranarayanan
The present study reports the biological synthesis of silver nanoparticles using crustacean immune molecule β-1, 3 glucan binding protein (β-GBP) purified from the haemolymph of blue swimmer crab Portunus pelagicus. The characterization of synthesized β-GBP based silver nanoparticles (Ppβ-GBP-AgNPs) was made by UV-Vis spectroscopy, XRD, FTIR and TEM analysis. UV-Vis spectra recorded the strong absorbance peak at 420 nm due to its surface plasmon resonance. The XRD analysis revealed the crystalline nature of synthesized nanoparticles with Bragg's reflection peaks at (111), (200), (220), (311) planes...
December 2, 2017: Microbial Pathogenesis
https://www.readbyqxmd.com/read/29207743/comparison-of-microbiological-flora-in-the-external-auditory-canal-of-normal-ear-and-an-ear-with-acute-otitis-externa
#15
Asheesh Dora Ghanpur, Dipak Ranjan Nayak, Kiran Chawla, V Shashidhar, Rohit Singh
Introduction: Acute Otitis Externa (AOE) is also known as swimmer's ear. Investigations initiated during World War II firmly established the role of bacteria in the aetiology of Acute Otitis Externa. Aim: To culture the microbiological flora of the normal ear and compare it with the flora causing AOE and to know the role of normal ear canal flora and anaerobes in the aetiology. Materials and Methods: A prospective observational study was conducted on 64 patients clinically diagnosed with unilateral AOE...
September 2017: Journal of Clinical and Diagnostic Research: JCDR
https://www.readbyqxmd.com/read/29199780/effects-of-increased-training-volume-during-a-10-day-training-camp-on-competitive-performance-in-national-level-youth-swimmers
#16
Frank J Nugent, Thomas M Comyns, Giles D Warrington
BACKGROUND: The purpose of this study was to investigate the effects of increased training volume during a 10 day training camp on competitive performance and internal training load (ITL). In addition, coach and swimmer rating of perceived exertion (RPE) for each session was compared. METHODS: Ten national level swimmers (Gender: 4 males and 6 females; age: 15±1 years; height: 170.5±6.4 cm; body mass: 61.4±7.4 kg) participated in the training camp which involved a 36% increase in swimming volume...
December 1, 2017: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/29196659/rational-design-and-dynamics-of-self-propelled-colloidal-bead-chains-from-rotators-to-flagella
#17
Hanumantha Rao Vutukuri, Bram Bet, René van Roij, Marjolein Dijkstra, Wilhelm T S Huck
The quest for designing new self-propelled colloids is fuelled by the demand for simple experimental models to study the collective behaviour of their more complex natural counterparts. Most synthetic self-propelled particles move by converting the input energy into translational motion. In this work we address the question if simple self-propelled spheres can assemble into more complex structures that exhibit rotational motion, possibly coupled with translational motion as in flagella. We exploit a combination of induced dipolar interactions and a bonding step to create permanent linear bead chains, composed of self-propelled Janus spheres, with a well-controlled internal structure...
December 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29196650/a-polar-bundle-of-flagella-can-drive-bacterial-swimming-by-pushing-pulling-or-coiling-around-the-cell-body
#18
Marius Hintsche, Veronika Waljor, Robert Großmann, Marco J Kühn, Kai M Thormann, Fernando Peruani, Carsten Beta
Bacteria swim in sequences of straight runs that are interrupted by turning events. They drive their swimming locomotion with the help of rotating helical flagella. Depending on the number of flagella and their arrangement across the cell body, different run-and-turn patterns can be observed. Here, we present fluorescence microscopy recordings showing that cells of the soil bacterium Pseudomonas putida that are decorated with a polar tuft of helical flagella, can alternate between two distinct swimming patterns...
December 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29189668/the-role-of-airway-inflammation-and-bronchial-hyperresponsiveness-in-athlete-s-asthma
#19
Julie Stang, Liv Ingunn Bjoner Sikkeland, Ellen Tufvesson, Are Martin Holm, Trine Stensrud, Kai-Håkon Carlsen
PURPOSE: Asthma is frequently reported in endurance athletes. The aim of the present study was to assess the long-term airway inflammatory response to endurance exercise in high-level athletes with and without asthma. METHODS: In a cross-sectional design, 20 asthmatic athletes (10 swimmers, 10 cross-country skiers), 19 athletes without asthma (10 swimmers, 9 cross-country skiers) and 24 healthy non-athletes completed methacholine bronchial challenge, lung function tests and sputum induction on two separate days...
November 7, 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/29187318/instructing-children-with-autism-spectrum-disorder-examining-swim-instructors-knowledge-building-experiences
#20
Erin Kraft, Raymond Leblanc
BACKGROUND: Although there has been a notable increase in Autism Spectrum Disorder (ASD) diagnoses over the past twenty years, children with ASD continue to be underrepresented in physical activity opportunities. Swimming lessons have been suggested as an ideal form of physical activity for this population, but studies exploring instructors' experiences gaining knowledge specific for instructing these swimmers remains limited. Research in this area is warranted, as drowning is a leading injury cause of death for persons with ASD...
November 22, 2017: Disability and Health Journal
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