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https://www.readbyqxmd.com/read/28346787/assembly-and-speed-in-ion-exchange-based-modular-phoretic-micro-swimmers
#1
Ran Niu, Denis Botin, Julian Weber, Alexander Reinmüller, Thomas Palberg
We report an experimental study on ion-exchange based modular micro-swimmers in low-salt water. Cationic ion-exchange particles and passive cargo particles assemble into self-propelling complexes, showing self-propulsion at speeds of several microns per second over extended distances and times. We quantify the assembly and speed of the complexes for different combinations of ion exchange particles and cargo particles, substrate types, salt types and concentrations, and cell geometries. Irrespective of experimental boundary conditions, we observe a regular development of the assembly shape with increasing number of cargo...
March 27, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28345093/diffusion-of-active-dimers-in-a-couette-flow
#2
Tanwi Debnath, Pulak K Ghosh, Franco Nori, Yunyun Li, Fabio Marchesoni, Baowen Li
We study the 3D dynamics of an elastic dimer consisting of an active swimmer bound to a passive cargo, both suspended in a Couette flow. Using numerical simulations, we determine the diffusivity of such an active dimer in the presence of long-range hydrodynamic interactions for different values of its self-propulsion speed and the Couette flow. We observe that the effect of hydrodynamic interactions is greatly enhanced under the condition that self-propulsion is strong enough to contrast the shear flow. The magnitude of the effect grows with the size of the dimer's constituents relative to their distance, which makes it appreciable under experimental conditions...
March 27, 2017: Soft Matter
https://www.readbyqxmd.com/read/28344456/caffeine-ingestion-improves-repeated-freestyle-sprints-in-elite-male-swimmers
#3
Paul S R Goods, Grant Landers, Sacha Fulton
The purpose of this investigation was to determine the efficacy of a moderate dose of caffeine to improve repeat-sprint performance in elite freestyle sprinters. Nine highly trained male swimmers performed 6 x 75 m freestyle sprints on two occasions 1-h after consuming either 3 mg·kg(-1) caffeine (CAF), or placebo, in a cross-over manner. Capillary blood samples for the analysis of blood lactate concentration and pH were collected after the 1(st), 3(rd), and 5(th) sprint, while heart rate and perceived exertion (RPE) were collected after every sprint...
March 2017: Journal of Sports Science & Medicine
https://www.readbyqxmd.com/read/28331587/a-simple-fast-and-repeatable-survey-method-for-underwater-visual-3d-benthic-mapping-and-monitoring
#4
Oscar Pizarro, Ariell Friedman, Mitch Bryson, Stefan B Williams, Joshua Madin
Visual 3D reconstruction techniques provide rich ecological and habitat structural information from underwater imagery. However, an unaided swimmer or diver struggles to navigate precisely over larger extents with consistent image overlap needed for visual reconstruction. While underwater robots have demonstrated systematic coverage of areas much larger than the footprint of a single image, access to suitable robotic systems is limited and requires specialized operators. Furthermore, robots are poor at navigating hydrodynamic habitats such as shallow coral reefs...
March 2017: Ecology and Evolution
https://www.readbyqxmd.com/read/28328201/double-fueled-janus-swimmers-with-magnetotactic-behaviour
#5
Philipp Sebastian Schattling, Miguel Alexandre Ramos-Docampo, Veronica Salgueiriño, Brigitte Städler
Self-propelled particles attract a great deal of attention due to the auspicious range of application nanobots can be used for. In a biomedical context, self-propelled swimmers hold promise to autonomously navigate to a desired location in an attempt to counteract cell/tissue defects either by releasing drugs or performing surgical tasks. The vast majority of prior reports deal with single engine assemblies, often utilizing fuel molecules which are considered as highly cytotoxic. Herein, we introduce two engines: 1) a motor which couples enzymes i...
March 22, 2017: ACS Nano
https://www.readbyqxmd.com/read/28325014/real-time-monitoring-of-swimming-performance
#6
R Delgado-Gonzalo, A Lemkaddem, Ph Renevey, E Muntane Calvo, M Lemay, K Cox, D Ashby, J Willardson, M Bertschi
This article presents the performance results of a novel algorithm for swimming analysis in real-time within a low-power wrist-worn device. The estimated parameters are: lap count, stroke count, time in lap, total swimming time, pace/speed per lap, total swam distance, and swimming efficiency (SWOLF). In addition, several swimming styles are automatically detected. Results were obtained using a database composed of 13 different swimmers spanning 646 laps and 858.78 min of total swam time. The final precision achieved in lap detection ranges between 99...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28299891/biohybrid-microtube-swimmers-driven-by-single-captured-bacteria
#7
Morgan M Stanton, Byung-Wook Park, Albert Miguel-López, Xing Ma, Metin Sitti, Samuel Sánchez
Bacteria biohybrids employ the motility and power of swimming bacteria to carry and maneuver microscale particles. They have the potential to perform microdrug and cargo delivery in vivo, but have been limited by poor design, reduced swimming capabilities, and impeded functionality. To address these challenge, motile Escherichia coli are captured inside electropolymerized microtubes, exhibiting the first report of a bacteria microswimmer that does not utilize a spherical particle chassis. Single bacterium becomes partially trapped within the tube and becomes a bioengine to push the microtube though biological media...
March 16, 2017: Small
https://www.readbyqxmd.com/read/28298467/swimming-and-diving-energetics-in-dolphins-a-stroke-by-stroke-analysis-for-predicting-the-cost-of-flight-responses-in-wild-odontocetes
#8
Terrie M Williams, Traci L Kendall, Beau P Richter, Courtney R Ribeiro-French, Jason S John, Kim L Odell, Barbara A Losch, David A Feuerbach, M Andrew Stamper
Exponential increases in hydrodynamic drag and physical exertion occur when swimmers move quickly through water, and underlie the preference for relatively slow routine speeds by marine mammals regardless of body size. Because of this and the need to balance limited oxygen stores when submerged, flight (escape) responses may be especially challenging for this group. To examine this, we used open-flow respirometry to measure the energetic cost of producing a swimming stroke during different levels of exercise in bottlenose dolphins (Tursiops truncatus)...
March 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28297979/brownian-motion-of-a-circle-swimmer-in-a-harmonic-trap
#9
Soudeh Jahanshahi, Hartmut Löwen, Borge Ten Hagen
We study the dynamics of a Brownian circle swimmer with a time-dependent self-propulsion velocity in an external temporally varying harmonic potential. For several situations, the noise-free swimming paths, the noise-averaged mean trajectories, and the mean-square displacements are calculated analytically or by computer simulation. Based on our results, we discuss optimal swimming strategies in order to explore a maximum spatial range around the trap center. In particular, we find a resonance situation for the maximum escape distance as a function of the various frequencies in the system...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297968/lattice-boltzmann-simulations-of-microswimmer-tracer-interactions
#10
Joost de Graaf, Joakim Stenhammar
Hydrodynamic interactions in systems composed of self-propelled particles, such as swimming microorganisms and passive tracers, have a significant impact on the tracer dynamics compared to the equivalent "dry" sample. However, such interactions are often difficult to take into account in simulations due to their computational cost. Here, we perform a systematic investigation of swimmer-tracer interaction using an efficient force-counterforce-based lattice-Boltzmann (LB) algorithm [De Graaf et al., J. Chem...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297912/long-range-nematic-order-and-anomalous-fluctuations-in-suspensions-of-swimming-filamentous-bacteria
#11
Daiki Nishiguchi, Ken H Nagai, Hugues Chaté, Masaki Sano
We study the collective dynamics of elongated swimmers in a very thin fluid layer by devising long filamentous nontumbling bacteria. The strong confinement induces weak nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. This homogeneous but fluctuating phase, observed on the largest experimentally accessible scale of millimeters, exhibits the properties predicted by standard models for flocking, such as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and nontrivial giant number fluctuations...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297904/scale-dependent-colocalization-in-a-population-of-gyrotactic-swimmers
#12
M Borgnino, F De Lillo, G Boffetta
We study the small scale clustering of gyrotactic swimmers transported by a turbulent flow, when the intrinsic variability of the swimming parameters within the population is considered. By means of extensive numerical simulations, we find that the variety of the population introduces a characteristic scale R^{*} in its spatial distribution. At scales smaller than R^{*} the swimmers are homogeneously distributed, while at larger scales an inhomogeneous distribution is observed with a fractal dimension close to what observed for a monodisperse population characterized by mean parameters...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297638/buckling-instabilities-and-complex-trajectories-in-a-simple-model-of-uniflagellar-bacteria
#13
Frank T M Nguyen, Michael D Graham
Observations of uniflagellar bacteria show that buckling instabilities of the hook protein connecting the cell body and flagellum play a role in locomotion. To understand this phenomenon, we develop models at varying levels of description with a particular focus on the parameter dependence of the buckling instability. A key dimensionless group called the flexibility number measures the hook flexibility relative to the thrust exerted by the flagellum; this parameter and the geometric parameters of the cell determine the stability of straight swimming...
March 14, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28293929/is-performance-of-a-modified-eucapnic-voluntary-hyperpnea-test-in-high-ventilation-athletes-reproducible
#14
Michael D Kennedy, Craig D Steinback, Rachel Skow, Eric C Parent
PURPOSE: Exercise-induced bronchoconstriction (EIB) is common in "high ventilation" athletes, and the Eucapnic Voluntary Hyperpnea (EVH) airway provocation test is the standard EIB screen. Although the EVH test is widely used, the in-test performance in high ventilation athletes as well as the reproducibility of that performance has not been determined. Reproducibility of pre- and post-test spirometry and self-reported atopy/cough was also examined. METHODS: High ventilation athletes (competitive swimmers; n=11, 5 males) completed an atopy/cough questionnaire and EVH testing (operator controlled FiCO₂) on 2 consecutive days...
May 2017: Allergy, Asthma & Immunology Research
https://www.readbyqxmd.com/read/28292904/optimal-run-and-tumble-based-transportation-of-a-janus-particle-with-active-steering
#15
Tomoyuki Mano, Jean-Baptiste Delfau, Junichiro Iwasawa, Masaki Sano
Although making artificial micrometric swimmers has been made possible by using various propulsion mechanisms, guiding their motion in the presence of thermal fluctuations still remains a great challenge. Such a task is essential in biological systems, which present a number of intriguing solutions that are robust against noisy environmental conditions as well as variability in individual genetic makeup. Using synthetic Janus particles driven by an electric field, we present a feedback-based particle-guiding method quite analogous to the "run-and-tumbling" behavior of Escherichia coli but with a deterministic steering in the tumbling phase: the particle is set to the run state when its orientation vector aligns with the target, whereas the transition to the "steering" state is triggered when it exceeds a tolerance angle [Formula: see text] The active and deterministic reorientation of the particle is achieved by a characteristic rotational motion that can be switched on and off by modulating the ac frequency of the electric field, which is reported in this work...
March 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28277423/effect-of-an-11-week-in-water-training-program-with-increased-resistance-on-the-swimming-performance-and-the-basic-kinematic-characteristics-of-the-front-crawl-stroke
#16
Vassilios Gourgoulis, Ioannis Valkoumas, Alexia Boli, Nikolaos Aggeloussis, Panagiotis Antoniou
The purpose of the study was to assess the effect of an 11 week in-water training program with increased resistance on the swimming performance and the basic kinematic characteristics of the front crawl stroke in young female swimmers. Twelve swimmers were matched in pairs according to their best performance in 50 m front crawl swimming and then were randomly assigned to an experimental or to a control group. Both groups followed exactly the same swimming training program. The only exception was that the experimental group performed a sprint training section with increased resistance pulling a water parachute, while the control group performed the same section without parachute...
March 8, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28276490/magnetically-controlled-ferromagnetic-swimmers
#17
Joshua K Hamilton, Peter G Petrov, C Peter Winlove, Andrew D Gilbert, Matthew T Bryan, Feodor Y Ogrin
Microscopic swimming devices hold promise for radically new applications in lab-on-a-chip and microfluidic technology, diagnostics and drug delivery etc. In this paper, we demonstrate the experimental verification of a new class of autonomous ferromagnetic swimming devices, actuated and controlled solely by an oscillating magnetic field. These devices are based on a pair of interacting ferromagnetic particles of different size and different anisotropic properties joined by an elastic link and actuated by an external time-dependent magnetic field...
March 9, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28273149/effect-of-thermal-processing-on-t-cell-reactivity-of-shellfish-allergens-discordance-with-ige-reactivity
#18
Jodie B Abramovitch, Andreas L Lopata, Robyn E O'Hehir, Jennifer M Rolland
Crustacean allergy is a major cause of food-induced anaphylaxis. We showed previously that heating increases IgE reactivity of crustacean allergens. Here we investigate the effects of thermal processing of crustacean extracts on cellular immune reactivity. Raw and cooked black tiger prawn, banana prawn, mud crab and blue swimmer crab extracts were prepared and IgE reactivity assessed by ELISA. Mass spectrometry revealed a mix of several allergens in the raw mud crab extract but predominant heat-stable tropomyosin in the cooked extract...
2017: PloS One
https://www.readbyqxmd.com/read/28272998/assessing-fat-mass-of-adolescent-swimmers-using-anthropometric-equations-a-dxa-validation-study
#19
Gabriel Lozano-Berges, Alejandro Gómez-Bruton, Ángel Matute-Llorente, Cristina Julián-Almárcegui, Alba Gómez-Cabello, Alejandro González-Agüero, José A Casajús, Germán Vicente-Rodríguez
PURPOSE: The aim of the present study was to determine which of the published anthropometric equations is the most appropriate to estimate body-fat percentage (BF%) in adolescent swimmers. METHOD: Eighty-eight swimmers (45 boys, 43 girls) participated in this study. Following the recommendations of the International Society of the Advancement of Kinanthropometry, biceps, triceps, subscapular, iliac-crest, supraspinale, front-thigh, and medial calf skinfold thicknesses were measured...
March 8, 2017: Research Quarterly for Exercise and Sport
https://www.readbyqxmd.com/read/28268690/a-wearable-biofeedback-control-system-based-body-area-network-for-freestyle-swimming
#20
Rui Li, Zibo Cai, WeeSit Lee, Daniel T H Lai
Wearable posture measurement units are capable of enabling real-time performance evaluation and providing feedback to end users. This paper presents a wearable feedback prototype designed for freestyle swimming with focus on trunk rotation measurement. The system consists of a nine-degree-of-freedom inertial sensor, which is built in a central data collection and processing unit, and two vibration motors for delivering real-time feedback. Theses devices form a fundamental body area network (BAN). In the experiment setup, four recreational swimmers were asked to do two sets of 4 x 25m freestyle swimming without and with feedback provided respectively...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
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