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Critical velocity

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https://www.readbyqxmd.com/read/28644666/frictional-resistance-within-the-wake-of-frictional-rupture-fronts
#1
Ilya Svetlizky, Elsa Bayart, Gil Cohen, Jay Fineberg
Frictional resistance to slip, τ, is determined by the real area of contact, A, and the shear strength of the contacts forming the frictional interface. We perform simultaneous high-speed local measurements of τ and A at the tail of propagating rupture fronts. Rate dependence is investigated over 2 orders of magnitude of local slip velocities which reach up to ∼1  m/s. A critical slip velocity is observed that signifies a transition in the frictional behavior: enhanced velocity weakening of A and τ...
June 9, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28641670/novel-stokesian-metrics-that-quantify-collision-efficiency-floc-strength-and-discrete-settling-behavior
#2
William A S K Mancell-Egala, Haydee De Clippeleir, Chungyung Su, Imre Takacs, John T Novak, Sudhir N Murthy
  Novel parameters were developed to predict the effluent quality and settling behavior in clarifiers that cannot conventionally be achieved using either the conventional flux theory or overflow rates. Simple batch experiments based on the critical settling velocity (CSV) selection were used as the basis for the development of three novel parameters: intrinsic settling classes (ISC), threshold of flocculation/flocculation limitation (TOF/α), and floc strength. ISC was proven to accurately (±2%) determine the granule fraction and discrete particle distribution...
July 1, 2017: Water Environment Research: a Research Publication of the Water Environment Federation
https://www.readbyqxmd.com/read/28638140/imaging-dynamic-fingerprints-of-competing-e2-and-sn2-reactions
#3
Eduardo Carrascosa, Jennifer Meyer, Jiaxu Zhang, Martin Stei, Tim Michaelsen, William L Hase, Li Yang, Roland Wester
The competition between bimolecular nucleophilic substitution and base-induced elimination is of fundamental importance for the synthesis of pure samples in organic chemistry. Many factors that influence this competition have been identified over the years, but the underlying atomistic dynamics have remained difficult to observe. We present product velocity distributions for a series of reactive collisions of the type X(-) + RY with X and Y denoting the halogen atoms fluorine, chlorine and iodine. By increasing the size of the residue R from methyl to tert-butyl in several steps, we find that the dynamics drastically change from backward to dominant forward scattering of the leaving ion relative to the reactant RY velocity...
June 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28633081/deflagration-to-detonation-transition-in-jp-10-mist-air-mixtures-in-a-large-scale-tube
#4
Shuzhuan Li, Qingming Liu, Xu Chen, Jinxiang Huang, Jing Li
Deflagration to detonation transitions (DDTs) in JP-10 mist/air mixtures have been studied in a horizontal multiphase combustion and explosion tube with inner diameter of 199mm and length of 32.8m. The mist/air mixtures were generated by injecting liquid samples into the experimental tube. Experiments were performed at 298k and 101kPa with equivalence ratio ranged from 0.51 to 2.09. The coupling process of deflagration wave with leading shock wave and low-velocity self-sustained detonation were observed in JP-10 mist/air mixture with a concentration of 142...
June 13, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28632062/skeleton-sled-velocity-profiles-a-novel-approach-to-understand-critical-aspects-of-the-elite-athletes-start-phases
#5
Steffi L Colyer, Keith A Stokes, James L J Bilzon, Aki I T Salo
The development of velocity across the skeleton start is critical to performance, yet poorly understood. We aimed to understand which components of the sled velocity profile determine performance and how physical abilities influence these components. Thirteen well-trained skeleton athletes (>85% of athletes in the country) performed dry-land push-starts alongside countermovement jump and sprint tests at multiple time-points. A magnet encoder attached to the sled wheel provided velocity profiles, which were characterised using novel performance descriptors...
February 28, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28630307/nanophotonics-enabled-solar-membrane-distillation-for-off-grid-water-purification
#6
Pratiksha D Dongare, Alessandro Alabastri, Seth Pedersen, Katherine R Zodrow, Nathaniel J Hogan, Oara Neumann, Jinjian Wu, Tianxiao Wang, Akshay Deshmukh, Menachem Elimelech, Qilin Li, Peter Nordlander, Naomi J Halas
With more than a billion people lacking accessible drinking water, there is a critical need to convert nonpotable sources such as seawater to water suitable for human use. However, energy requirements of desalination plants account for half their operating costs, so alternative, lower energy approaches are equally critical. Membrane distillation (MD) has shown potential due to its low operating temperature and pressure requirements, but the requirement of heating the input water makes it energy intensive. Here, we demonstrate nanophotonics-enabled solar membrane distillation (NESMD), where highly localized photothermal heating induced by solar illumination alone drives the distillation process, entirely eliminating the requirement of heating the input water...
June 19, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28619447/similar-movements-are-associated-with-drastically-different-muscle-contraction-velocities
#7
Daniel A Hagen, Francisco J Valero-Cuevas
We investigated how kinematic redundancy interacts with the neurophysiological control mechanisms required for smooth and accurate, rapid limb movements. Biomechanically speaking, tendon excursions are over-determined because the rotation of few joints determines the lengths and velocities of many muscles. But how different are the muscle velocity profiles induced by various, equally valid hand trajectories? We used an 18-muscle sagittal-plane arm model to calculate 100,000 feasible shoulder, elbow, and wrist joint rotations that produced valid basketball free throws with different hand trajectories, but identical initial and final hand positions and velocities...
May 31, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28618570/thermal-rayleigh-marangoni-convection-in-a-three-layer-liquid-metal-battery-model
#8
Thomas Köllner, Thomas Boeck, Jörg Schumacher
The combined effects of buoyancy-driven Rayleigh-Bénard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquid metal battery (LMB). The three-layer model consists of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28618481/crack-propagation-through-disordered-materials-as-a-depinning-transition-a-critical-test-of-the-theory
#9
Laurent Ponson, Nadjime Pindra
The dynamics of a planar crack propagating within a brittle disordered material is investigated numerically. The fracture front evolution is described as the depinning of an elastic line in a random field of toughness. The relevance of this approach is critically tested through the comparison of the roughness front properties, the statistics of avalanches, and the local crack velocity distribution with experimental results. Our simulations capture the main features of the fracture front evolution as measured experimentally...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28607465/spiraling-elliptic-hermite-gaussian-solitons-in-nonlocal-nonlinear-media-without-anisotropy
#10
Guo Liang, Zhiping Dai
We introduce a kind of the spiraling elliptic Hermite-Gaussian solitons in nonlocal nonlinear media without anisotropy, which carries the orbital angular momentum and can rotate in the transverse. The n-th mode of the spiraling elliptic Hermite-Gaussian solitons has n holes nested in the elliptic profile. The analytical spiraling elliptic Hermite-Gaussian solitons solutions are obtained based on the variational approach, which agree well with the numerical simulations. It is found that the critical power and the critical angular velocity for the spiraling elliptic Hermite-Gaussian solitons are the same as the counterpart of the ground mode...
June 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28599361/hydraulic-modelling-of-the-spatial-and-temporal-variability-in-atlantic-salmon-parr-habitat-availability-in-an-upland-stream
#11
Luca Fabris, Iain Archibald Malcolm, Willem Bastiaan Buddendorf, Karen Jane Millidine, Doerthe Tetzlaff, Chris Soulsby
We show how spatial variability in channel bed morphology affects the hydraulic characteristics of river reaches available to Atlantic salmon parr (Salmo salar) under different flow conditions in an upland stream. The study stream, the Girnock Burn, is a long-term monitoring site in the Scottish Highlands. Six site characterised by different bed geometry and morphology were investigated. Detailed site bathymetries were collected and combined with discharge time series in a 2D hydraulic model to obtain spatially distributed depth-averaged velocities under different flow conditions...
June 9, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28597620/critical-velocity-in-swimmers-of-different-ages
#12
Alex Rizzato, Giuseppe Marcolin, Alessandro Rubini, Nicola Olivato, Simone Fava, Antonio Paoli, Gerardo Bosco
BACKGROUND: In swimming one of the most employed training speed among coaches is the non-invasive Theoretical Critical Velocity (TCV) defined as the velocity that can be maintained continuously without exhaustion. METHODS: We calculated the 4mmol/L lactate Critical Velocity (MCV) in a group of swimmers of different ages (Young, Elite and Master), and compared results to the predicted TCV defined starting from the 200 and 400 m freestyle best seasonal performances...
June 8, 2017: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/28596738/intensity-and-duration-based-options-to-regulate-endurance-training
#13
Peter Hofmann, Gerhard Tschakert
The regulation of endurance training is usually based on the prescription of exercise intensity. Exercise duration, another important variable of training load, is rarely prescribed by individual measures and mostly set from experience. As the specific exercise duration for any intensity plays a substantial role regarding the different kind of cellular stressors, degree, and kind of fatigue as well as training effects, concepts integrating the prescription of both intensity and duration within one model are needed...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28595621/transthoracic-echocardiography-an-accurate-and-precise-method-for-estimating-cardiac-output-in-the-critically-ill-patient
#14
Pablo Mercado, Julien Maizel, Christophe Beyls, Dimitri Titeca-Beauport, Magalie Joris, Loay Kontar, Antoine Riviere, Olivier Bonef, Thierry Soupison, Christophe Tribouilloy, Bertrand de Cagny, Michel Slama
BACKGROUND: Cardiac output (CO) monitoring is a valuable tool for the diagnosis and management of critically ill patients. In the critical care setting, few studies have evaluated the level of agreement between CO estimated by transthoracic echocardiography (CO-TTE) and that measured by the reference method, pulmonary artery catheter (CO-PAC). The objective of the present study was to evaluate the precision and accuracy of CO-TTE relative to CO-PAC and the ability of transthoracic echocardiography to track variations in CO, in critically ill mechanically ventilated patients...
June 9, 2017: Critical Care: the Official Journal of the Critical Care Forum
https://www.readbyqxmd.com/read/28592041/-the-effects-of-different-tidal-volume-ventilation-on-right-ventricular-function-in-critical-respiratory-failure-patients
#15
L X Liu, J Q Wu, Q Y Wu, Q Zhang, B Yu, S M Ge, Y Huo, X T Wang, Y G Chao, Z J Hu
Objective: To observe and explore the effects of different tidal volume (VT) ventilation on right ventricular (RV) function in patients with critical respiratory failure. Methods: Consecutive respiratory failure patients who were treated with invasive ventilator over 24 h in the Department of Critical Care Medicine at the Fourth Hospital of Hebei Medical University from June to December in 2015 were enrolled in this study.Clinical data including patients' vital signs, ventilator parameters and RV echocardiography were collected within 6 h (D0), day1(D1), day2 (D2) and day3 (D3) after ventilation started...
June 1, 2017: Zhonghua Nei Ke za Zhi [Chinese Journal of Internal Medicine]
https://www.readbyqxmd.com/read/28591966/-the-value-of-early-diastolic-transmitral-velocity-to-early-mitral-anulus-diastolic-velocity-ratio-for-pulmonary-edema-in-severe-sepsis-patients
#16
Wan-Hong Yin, Yi Li, Yao Qin, Yan Kang, Ji-Yuan Zhao, Tong-Juan Zou, Zhi-Yun Tang
OBJECTIVES: To determine the association between the value of early diastolic transmitral velocity to early mitral anulus diastolic velocity ratio (E/E')measured by bedside ultrasound and pulmonary edema in severe sepsis (including septic shock) patients. METHODS: Data were obtained from the critical ultrasound database between November 2014 and August 2015. The severe sepsis (including septic shock) patients were eligible, but those with chronic heart disease or acute heart failure were excluded...
July 2016: Sichuan da Xue Xue Bao. Yi Xue Ban, Journal of Sichuan University. Medical Science Edition
https://www.readbyqxmd.com/read/28590759/effects-of-nozzle-geometry-on-the-fluid-dynamics-of-thin-liquid-films-flowing-down-vertical-strings-in-the-rayleigh-plateau-regime
#17
Abolfazl Sadeghpour, Zezhi Zeng, Y Sungtaek Ju
Thin-liquid films flowing down vertical strings undergo instability, creating wavy film profiles and traveling beads. Previous studies assumed that the liquid film thickness and velocity profiles within the healing length from a nozzle were specified by the Nusselt solution, independent of the nozzle geometry. As a result, the influence of the nozzle diameter on the flow characteristics, such as the liquid bead size, spacing, and traveling speed, was largely overlooked. We report an experimental and numerical simulation study on liquid-film flows in the Rayleigh-Plateau regime while systematically varying the nozzle diameter from 0...
June 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28585629/a-thermodynamic-model-to-predict-electron-mobility-in-superfluid-helium
#18
Frédéric Aitken, Ferdinand Volino, Luis Guillermo Mendoza-Luna, Klaus von Haeften, Jussi Eloranta
Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure. The model is first calibrated against known electron mobility reference data along the saturated vapor pressure line and then validated to reproduce the existing mobility literature values as a function of pressure and temperature with at least 10% accuracy. Four different electron mobility regimes are identified: (1) Landau critical velocity limit (T ≈ 0), (2) mobility limited by thermal phonons (T < 0...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28585393/orientational-coupling-locally-orchestrates-a-cell-migration-pattern-for-re-epithelialization
#19
Benhui Hu, Wan Ru Leow, Shahrouz Amini, Brenda Nai, Xiaoqian Zhang, Zhiyuan Liu, Pingqiang Cai, Zhuyun Li, Yun-Long Wu, Ali Miserez, Chwee Teck Lim, Xiaodong Chen
Re-epithelialization by collective migration of epithelial cells over a heterogeneous environment to restore tissue integrity and functions is critical for development and regeneration. Here, it is reported that the spatial organization of adjacent adherent paths within sparsely distributed extracellular matrix (ECM) has a significant impact on the orientational coupling between cell polarization and collective cell migration. This coupling effect determines the migration pattern for human keratinocytes to regain their cohesion, which impacts the occupancy of epithelial bridge and the migration velocity in wound repair...
June 6, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28584338/first-signs-of-elderly-gait-for-women
#20
Katarzyna Kaczmarczyk, Ida Wiszomirska, Michalina Błażkiewicz, Michał Wychowański, Andrzej Wit
BACKGROUND: The aims of this study have been twofold: to attempt to reduce the number of spatiotemporal parameters used for describing gait through the factor analysis and component analysis; and to explore the critical age of decline for other gait parameters for healthy women. MATERIAL AND METHODS: A total of 106 women (aged ≥ 40 years old (N = 76) and ≤ 31 years old (N = 30)) were evaluated using a pressure-sensitive mat (Zebris Medical System, Tübingen, Germany) for collecting spatiotemporal gait parameters...
May 22, 2017: Medycyna Pracy
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