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Cycling power

Alejandro Pérez-Castilla, Paul Comfort, John J McMahon, Francisco Luis Pestaña-Melero, Amador García-Ramos
The aim of this study was to compare the temporal and mechanical variables between the concentric-only and eccentric-concentric bench press (BP) variants. Twenty-one men (age: 22.0±4.2 years, body mass: 73.4±7.7 kg, height: 177.2±8.0 cm; one-repetition maximum [1RM]: 1.12±0.12 kg⋅kg) were evaluated during the concentric-only and eccentric-concentric BP variants using 80% 1RM. Temporal (concentric phase duration, propulsive phase duration, and time to reach the maximum values of force, velocity, and power) and mechanical variables (force, velocity, and power), determined using a linear velocity transducer, were compared between both BP variants...
January 17, 2018: Journal of Strength and Conditioning Research
Mehrez Hammami, Nawel Gaamouri, Roy J Shephard, Mohamed Souhaiel Chelly
The aim was to compare the effects of two differing 8-week in-season strength training programs (contrast strength training [CST] vs. plyometric training [PT]) on selected performance tests (5 and 40m sprints, S 4 X 5 m change of direction test, squat (SJ) and countermovement (CMJ) jumps , leg peak power on a cycle ergometer force-velocity test, 1-repetition maximal (1-RM) half squat, and electromyographic [EMG] activity of the vastus lateralis, vastus medialis and rectus femoris muscles during vertical jump tests)...
January 17, 2018: Journal of Strength and Conditioning Research
David J Ellerby, Shauna Cyr, Angela X Han, Mika Lin, Lloyd A Trueblood
Skeletal muscle has diverse mechanical roles during locomotion. In swimming fish, power-producing muscles work in concert with the accessory muscles of the fins which augment and control power transfer to the water. Although fin muscles represent a significant proportion of the locomotor muscle mass, their physiological properties are poorly characterized. To examine the relationship between muscle metabolism and the differing mechanical demands placed on distinct muscle groups, we quantified the aerobic and glycolytic capacities of the myotomal, pectoral and caudal muscles of bluegill sunfish...
January 19, 2018: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Chunxue Hao, Lidan Wang, Fusheng Wen, Jianyong Xiang, Lei Li, Wentao Hu, Zhongyuan Liu
In this work, bismuth selenides (Bi2Se3 and Bi3Se4), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi2Se3 nanoplates exhibit much better performance as an electrode material than Bi3Se4 nanoparticles do, delivering a higher specific capacitance (272.9 F g-1) than that of Bi3Se4 (193.6 F g-1) at 5 mV s-1. This result may be attributed to the fact that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi3Se4)...
January 19, 2018: Nanotechnology
Enyuan Hu, Xuelong Wang, Xiqian Yu, Xiao-Qing Yang
The rechargeable lithium-ion battery (LIB) is the most promising energy storage system to power electric vehicles with high energy density and long cycling life. However, in order to meet customers' demands for fast charging, the power performances of current LIBs need to be improved. From the cathode aspect, layer-structured cathode materials are widely used in today's market and will continue to play important roles in the near future. The high rate capability of layered cathode materials during charging and discharging is critical to the power performance of the whole cell and the thermal stability is closely related to the safety issues...
January 19, 2018: Accounts of Chemical Research
Mingdao Zhang, Quanbin Dai, Hegen Zheng, Mindong Chen, Liming Dai
Metal-organic frameworks (MOFs) and MOF-derived materials have recently attracted considerable interest as alternatives to noble-metal electrocatalysts. Herein, the rational design and synthesis of a new class of Co@N-C materials (C-MOF-C2-T) from a pair of enantiotopic chiral 3D MOFs by pyrolysis at temperature T is reported. The newly developed C-MOF-C2-900 with a unique 3D hierarchical rodlike structure, consisting of homogeneously distributed cobalt nanoparticles encapsulated by partially graphitized N-doped carbon rings along the rod length, exhibits higher electrocatalytic activities for oxygen reduction and oxygen evolution reactions (ORR and OER) than that of commercial Pt/C and RuO2 , respectively...
January 19, 2018: Advanced Materials
Lucianno A C A Defaveri, Welles A M Morgado, Sílvio M Duarte Queirós
We propose a method that makes use of the nonlinear properties of some hypothetical microscopic solid material as the working substance for a microscopic machine. The protocols used are simple (step and elliptic) and allow us to obtain the work and heat exchanged between machine and reservoirs. We calculate the work for a nonlinear single-particle machine that can be treated perturbingly. We obtain the instantaneous work and heat for the machine undergoing cycles that mimic the Carnot and multireservoir protocols...
November 2017: Physical Review. E
I Reyes-Ramírez, J Gonzalez-Ayala, A Calvo Hernández, M Santillán
In this paper we address the stability of a low-dissipation (LD) heat engine (HE) under maximum power conditions. The LD system dynamics are analyzed in terms of the contact times between the engine and the external heat reservoirs, which determine the amount of heat exchanged by the system. We study two different scenarios that secure the existence of a single stable steady state. In these scenarios, contact times dynamics are governed by restitutive forces that are linear functions of either the heat amounts exchanged per cycle, or the corresponding heat fluxes...
October 2017: Physical Review. E
Yuting Lou, Jufeng Xia, Wei Tang, Yu Chen
The fight against biological aging (bio-aging) is long-standing, with the focus of intense research aimed at maintaining high rates of tissue regeneration to promote health and longevity. Nevertheless, there are overwhelming complexities associated with the quantitative analysis of aging. In this study, we sought to quantify bio-aging based on physical aging, by mapping instances of multicellular regeneration to the relaxation of physical systems. An experiment of delayed wound healing assays was devised to obtain delay-dependent healing data...
December 2017: Physical Review. E
Haggai Bonneau, Aviv Hassid, Ofer Biham, Reimer Kühn, Eytan Katzav
We present analytical results for the distribution of shortest cycle lengths (DSCL) in random networks. The approach is based on the relation between the DSCL and the distribution of shortest path lengths (DSPL). We apply this approach to configuration model networks, for which analytical results for the DSPL were obtained before. We first calculate the fraction of nodes in the network which reside on at least one cycle. Conditioning on being on a cycle, we provide the DSCL over ensembles of configuration model networks with degree distributions which follow a Poisson distribution (Erdős-Rényi network), degenerate distribution (random regular graph), and a power-law distribution (scale-free network)...
December 2017: Physical Review. E
Ali Ü C Hardal, Nur Aslan, C M Wilson, Özgür E Müstecaplıoğlu
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case...
December 2017: Physical Review. E
Honghui Wang, Jizhou He, Jianhui Wang
We analyze general models of quantum heat engines operating a cycle of two adiabatic and two isothermal processes. We use the quantum master equation for a system to describe heat transfer current during a thermodynamic process in contact with a heat reservoir, with no use of phenomenological thermal conduction. We apply the endoreversibility description to such engine models working in the linear response regime and derive expressions of the efficiency and the power. By analyzing the entropy production rate along a single cycle, we identify the thermodynamic flux and force that a linear relation connects...
July 2017: Physical Review. E
Yuki Izumida, Koji Okuda
We identify a velocity distribution function of ideal gas particles that is compatible with the local equilibrium assumption and the fundamental thermodynamic relation satisfying the endoreversibility. We find that this distribution is a Maxwell-Boltzmann distribution with a spatially uniform temperature and a spatially varying local center-of-mass velocity. We construct the local equilibrium Carnot cycle of an ideal gas, based on this distribution, and show that the efficiency of the present cycle is given by the endoreversible Carnot efficiency using the molecular kinetic temperatures of the gas...
July 2017: Physical Review. E
Viktor Holubec, Artem Ryabov
We investigate fluctuations of output work for a class of Stirling heat engines with working fluid composed of interacting units and compare these fluctuations to an average work output. In particular, we focus on engine performance close to a critical point where Carnot's efficiency may be attained at a finite power as reported by M. Campisi and R. Fazio [Nat. Commun. 7, 11895 (2016)2041-172310.1038/ncomms11895]. We show that the variance of work output per cycle scales with the same critical exponent as the heat capacity of the working fluid...
September 2017: Physical Review. E
Pengfei Zhao, Navneet Soin, K Prashanthi, Jinkai Chen, Shurong Dong, Erping Zhou, Zhigang Zhu, Anand Arcot Narasimulu, Carlo D Montemagno, Liyang Yu, Jikui Luo
Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilised against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which further corroborated by FTIR measurements...
January 18, 2018: ACS Applied Materials & Interfaces
Yixian Wang, Wei Tian, Luhai Wang, Haoran Zhang, Jialiang Liu, Tingyue Peng, Lei Pan, Xiaobo Wang, Mingbo Wu
Amorphous carbon is regarded as a promising alternative to commercial graphite as the lithium-ion battery anode due to its capability to reversibly store more lithium ions. However, the structural disorder with a large number of defects can lead to low electrical conductivity of the amorphous carbon, thus limiting its application for high power output. Herein, ultrathin amorphous carbon nanosheets were prepared from petroleum asphalt through tuning the carbonization temperature in a molten-salt medium. The amorphous nanostructure with expanded carbon interlayer spacing can provide substantial active sites for lithium storage while the two-dimensional (2D) morphology can facilitate fast electrical conductivity...
January 18, 2018: ACS Applied Materials & Interfaces
Jenniffer Bustillos, Cheng Zhang, Benjamin Boesl, Arvind Agarwal
The adhesion of ice severely compromises the aerodynamic performance of aircrafts operating under critically low-temperature conditions to their surfaces. In this study, highly thermally and electrically conductive graphene foam polymer composite is fabricated. GrF - polydimethylsiloxane (PDMS) deicing composite exhibit superior deicing efficiency of 477 % and electrical conductivities of 500 S∙m-1 with only 0.1 vol. % Graphene foam addition as compared to other nanocarbon - based deicing systems. The three-dimensional interconnected architecture of GrF allows the effective deicing of surfaces by employing low power densities (0...
January 18, 2018: ACS Applied Materials & Interfaces
Kunzhen Li, Shikuo Li, Fangzhi Huang, Xin-Yao Yu, Yan Lu, Lei Wang, Hong Chen, Hui Zhang
The hierarchical porous structure with phosphorus-doped Ni(OH)2 (P-Ni(OH)2) rods as the core and MnO2 nanosheets as the shell is fabricated directly by growth on a three-dimensional (3D) flexible Ni foam (NF) via a two-step hydrothermal process. As a binder-free electrode material, this unique hybrid structure exhibits excellent electrochemical properties, including an ultrahigh areal capacitance of 5.75 F cm-2 at a current density of 2 mA cm-2 and great cyclic stability without capacitance loss at a current density of 20 mA cm-2 after 10 000 cycles...
January 18, 2018: Nanoscale
Virender Kumar, Hanuman S Jat, Parbodh C Sharma, Balwinder-Singh, Mahesh K Gathala, Ram K Malik, Baldev R Kamboj, Arvind K Yadav, Jagdish K Ladha, Anitha Raman, D K Sharma, Andrew McDonald
In the most productive area of the Indo-Gangetic Plains in Northwest India where high yields of rice and wheat are commonplace, a medium-term cropping system trial was conducted in Haryana State. The goal of the study was to identify integrated management options for further improving productivity and profitability while rationalizing resource use and reducing environmental externalities (i.e., "sustainable intensification", SI) by drawing on the principles of diversification, precision management, and conservation agriculture...
January 15, 2018: Agriculture, Ecosystems & Environment
S Brüningk, G Powathil, P Ziegenhein, J Ijaz, I Rivens, S Nill, M Chaplain, U Oelfke, G Ter Haar
Combined radiotherapy and hyperthermia offer great potential for the successful treatment of radio-resistant tumours through thermo-radiosensitization. Tumour response heterogeneity, due to intrinsic, or micro-environmentally induced factors, may greatly influence treatment outcome, but is difficult to account for using traditional treatment planning approaches. Systems oncology simulation, using mathematical models designed to predict tumour growth and treatment response, provides a powerful tool for analysis and optimization of combined treatments...
January 2018: Journal of the Royal Society, Interface
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