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Rate of force production

Alexander V Khalyavkin, Vyacheslav N Krut'ko
Researchers working in the area of ageing have found numerous manifestations of this process at the molecular biological level, including DNA and protein damage, accumulation of metabolic by-products, lipids peroxidation, macromolecular cross-linking, non-enzymatic glycosylation, anti-oxidant/pro-oxidant misbalance, rising of pro-inflammatory cytokines, etc. This results in an increase in the proportion of cells in growth arrest, reduction of the rate of information processing, metabolic rate decrease, and decrease in rates of other processes characterizing dynamic aspects of the organism's interaction with its environment...
September 12, 2017: Biogerontology
Yang Chen, Li-Zi Yin, Ling Zhao, Gang Shu, Zhi-Xiang Yuan, Hua-Lin Fu, Cheng Lv, Ju-Chun Lin
The purpose of this study was to optimize the extraction process of phloridzin from Lithocarpus polystachyus Rehd. leaves using response surface methodology and to determine the antioxidant capacity of the extract. A Box-Behnken design was used to analyze the effects of ethanol concentration, liquid-solid ratio, soak time and extraction time on the extraction yield of phloridzin. The content of phloridzin was determined by high-performance liquid chromatography. To assess the antioxidant capacity of the extract, three in vitro test systems were used (1,1-,diphenyl-2-picrylhydrazyl, hydroxyl radical scavenging test and reduction force)...
September 12, 2017: Journal of Separation Science
M A K Chowdhury, A M M Sharif Ullah, Saqib Anwar
Ti6Al4V alloys are difficult-to-cut materials that have extensive applications in the automotive and aerospace industry. A great deal of effort has been made to develop and improve the machining operations of Ti6Al4V alloys. This paper presents an experimental study that systematically analyzes the effects of the machining conditions (ultrasonic power, feed rate, spindle speed, and tool diameter) on the performance parameters (cutting force, tool wear, overcut error, and cylindricity error), while drilling high precision holes on the workpiece made of Ti6Al4V alloys using rotary ultrasonic machining (RUM)...
September 12, 2017: Materials
Achraf Ammar, Bryan L Riemann, Liwa Masmoudi, Marcel Blaumann, Osama Abdelkarim, Anita Hökelmann
The aim of the present study was to investigate loading effects on kinematic and kinetic variables among elite-weightlifters in order to identify an optimal training load to maximize power production for clean-movement. Nine elite-weightlifter (age: 24 ± 4years, body-mass: 77 ± 6.5kg, height: 176 ± 6.1cm and 1RM clean: 170 ± 5kg) performed 2 separate repetitions of the clean using 85, 90, 95% and 100%, in a randomized order, while standing on a force platform and being recorded using 3D-capture-system. Differences in kinematics (barbell displacement, velocity and acceleration) and kinetics (power, vertical ground reaction force (vGRF), rate of force development (RFD), and work) across the loads were statistically assessed...
September 12, 2017: Journal of Sports Sciences
Lidong Wang, Tieyue Qi, Juan Wang, Shihan Zhang, Huining Xiao, Yongliang Ma
The forced oxidation of magnesium sulfite (MgSO3) aims to not only reclaim the by-product in the magnesia desulfurization, but also lower the risk of secondary pollution. The non-porous titanium dioxide nanoparticle was used as a support to prepare the cobalt catalyst (Co-TiO2) in order to expedite the oxidation rate. This fabricated Co-TiO2 was characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and energy dispersive spectroscopy (EDS) to figure out its catalytic mechanism...
September 8, 2017: Journal of Hazardous Materials
Cheryl E Quenneville, Ed Fournier, Nicholas Shewchenko
INTRODUCTION: The lower legs are at risk of substantial injury during events such as frontal automotive crashes and antivehicular mine blasts. Loading to occupants can be assessed using an instrumented anthropomorphic test device (ATD), whose measurements can be compared to established injury criteria. NATO's AEP-55 STANAG 4569 recognizes two surrogates for lower leg injury assessments from impacts with intruding floor pans resulting from underbelly blast loads; (1) the rigid Hybrid III instrumented lower leg, and; (2) the compliant MILitary Lower eXtremity (MIL-LX)...
September 2017: Military Medicine
Angela R W Raso, Kyle D Custard, Nathaniel W May, David Tanner, Matt K Newburn, Lawrence Walker, Ronald J Moore, L G Huey, Liz Alexander, Paul B Shepson, Kerri A Pratt
During springtime, the Arctic atmospheric boundary layer undergoes frequent rapid depletions in ozone and gaseous elemental mercury due to reactions with halogen atoms, influencing atmospheric composition and pollutant fate. Although bromine chemistry has been shown to initiate ozone depletion events, and it has long been hypothesized that iodine chemistry may contribute, no previous measurements of molecular iodine (I2) have been reported in the Arctic. Iodine chemistry also contributes to atmospheric new particle formation and therefore cloud properties and radiative forcing...
September 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Hamdi Jaafar, Olivier Girard, Hanene Lajili
We examined time of day and verbal instruction separate and combined effects on knee extensor neuromuscular adjustments, with special reference to rapid muscle force production capacity. Ten healthy male participants performed four experimental trials in counterbalanced order: morning-"hard-and-fast" instruction, evening-"hard-and-fast" instruction, morning-"fast" instruction and evening-"fast" instruction. During each experimental trial, neuromuscular performance was assessed from the completion of six maximal isometric voluntary contractions (rest = 2 minutes) of the knee extensors with concomitant quadriceps surface EMG recordings...
September 5, 2017: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
Young Joon Sung, Jaoon Young Hwan Kim, Hong Il Choi, Ho Seok Kwak, Sang Jun Sim
Microalgae - unicellular photosynthetic organisms - have received increasing attention for their ability to biologically convert CO2 into valuable products. The commercial use of microalgae requires screening strains to improve the biomass productivity to achieve a high-throughput. Here, we developed a microfluidic method that uses a magnetic field to separate the microdroplets containing different concentrations of microalgal cells. The separation efficiency is maximized using the following parameters that influence the amount of lateral displacement of the microdroplets: magnetic nanoparticle concentration, flow rate of droplets, x- and y-axis location of the magnet, and diameter of the droplets...
September 4, 2017: Scientific Reports
Wenwen Liu, Bo Liang, Yongjin Ma, Yi Liu, Anquan Zhu, Pengfei Tan, Xiang Xiong, Jun Pan
The construction of a plasmonic photocatalyst is an efficient way to suppress detrimental electrons-holes recombination and extend the spectral range of light absorption in semiconductors. However, the facilitation effect in the aspect of electrons-holes separation is great limited as the lack of a driving force compelled the electrons or holes migration to surface catalytic sites makes them flow randomly in semiconductors. In this work, we confirm that the integration of MoS2 nanosheets formed two dimensional (2D) layered heterojunction with C3N4 with Au-C3N4 plasmonic photocatalyst can further enhance electrons-holes separation through the formation of Au-C3N4-MoS2 nanostructure by a facile ultrasonic chemical method...
August 30, 2017: Journal of Colloid and Interface Science
Weixing Liu, Ningyu Li, Jinxin Zhao, Yumin Su
Numerical simulations are used to investigate the wake structure and hydrodynamic performance of bionic flapping foils. The study is motivated by the quest to understand the fluid dynamics of fish fins and use it in the underwater propulsion. The simulations employ an immersed boundary method that makes it possible to simulate flows with complex moving boundaries on fixed Cartesian grids. A detailed analysis of the vortex topology shows that the wake of flapping foils is dominated by two sets of complex shaped vortex rings that convect at oblique angles to the wake centerline...
September 2017: Saudi Journal of Biological Sciences
Siriporn Phasomkusolsil, Kanchana Pantuwatana, Jaruwan Tawong, Weeraphan Khongtak, Yossasin Kertmanee, Nantaporn Monkanna, Sakon Khaosanorh, Elizabeth W Wanja, Silas A Davidson
Successful mating by male mosquitoes is dependent on several factors, with sugar feeding being particularly important. The effect of ingested vitamins on adult male mosquitoes is poorly understood. This laboratory study used 3 anopheline species, Anopheles campestris, An. dirus, and An. sawadwongporni, to study the effect of sugar and vitamins on male longevity, copulation, and fecundity. Males were fed 1 of 5 diets containing different combinations of sugar and vitamins: 10% glucose, 10% sucrose, 10% multivitamin syrup, 10% multivitamin syrup + 10% glucose, and 10% multivitamin syrup + 10% sucrose...
September 2017: Journal of the American Mosquito Control Association
Edward T Chouchani, Lawrence Kazak, Bruce M Spiegelman
Brown and beige adipose tissues can catabolize stored energy to generate heat, relying on the principal effector of thermogenesis: uncoupling protein 1 (UCP1). This unique capability could be leveraged as a therapy for metabolic disease. Numerous animal and cellular models have now demonstrated that mitochondrial reactive oxygen species (ROS) signal to support adipocyte thermogenic identity and function. Herein, we contextualize these findings within established principles of redox signaling, and mechanistic studies of UCP1 function...
August 24, 2017: Journal of Biological Chemistry
Cassandra Kraaijenbrink, Riemer J K Vegter, Alexander H R Hensen, Heiko Wagner, Lucas H V van der Woude
BACKGROUND: With the introduction of an add-on handcycle, a crank system that can be placed in front of a wheelchair, handcycling was made widely available for daily life. With it, people go into town more easily, e.g. to do groceries; meet up with friends, etc. They have more independency and can be socially active. Our aim is to explore some settings of the handcycle, so that it can be optimally used as a transportation device. Therefore, the effects of cadence and added resistance on gross mechanical efficiency and force application during sub-maximal synchronous handcycling were investigated...
2017: PloS One
Gabriel E Galindo, Sean D Peterson, Byron D Erath, Christian Castro, Robert E Hillman, Matías Zañartu
Purpose: Our goal was to test prevailing assumptions about the underlying biomechanical and aeroacoustic mechanisms associated with phonotraumatic lesions of the vocal folds using a numerical lumped-element model of voice production. Method: A numerical model with a triangular glottis, posterior glottal opening, and arytenoid posturing is proposed. Normal voice is altered by introducing various prephonatory configurations. Potential compensatory mechanisms (increased subglottal pressure, muscle activation, and supraglottal constriction) are adjusted to restore an acoustic target output through a control loop that mimics a simplified version of auditory feedback...
August 23, 2017: Journal of Speech, Language, and Hearing Research: JSLHR
María Sofía Espejo, Ignacio Aiello, Marisa Sepúlveda, Martín G Vila Petroff, Ernesto A Aiello, Verónica C De Giusti
The force-frequency relationship (FFR) is an important intrinsic regulatory mechanism of cardiac contractility. However, a decrease (negative FFR) or no effect (flat FFR) on contractile force in response to an elevation of heart rate is present in the normal rat or in human heart failure. Reactive oxygen species (ROS) can act as intracellular signaling molecules activating diverse kinases as calcium-calmodulin-dependent protein kinase II (CaMKII) and p-38 MAP kinase (p-38K). Our aim was to elucidate the intracellular molecules implicated in the FFR of isolated rat ventricular myocytes...
August 23, 2017: Pflügers Archiv: European Journal of Physiology
Daisuke Shibata, Marco Santello
Dexterous manipulation relies on the ability to modulate grasp forces to variable digit position. However, the sensorimotor mechanisms underlying such critical ability are not well understood. The present study addressed whether digit force-to-position modulation relies entirely on feedback of digit placement and force, or on the integration of such feedback with motor commands responsible for digit positioning. In two experiments, we asked 25 subjects to estimate the index fingertip position relative to the thumb (Perception test), or grasp and lift an object with an asymmetrical mass distribution while preventing object roll (Action test)...
August 23, 2017: Journal of Neurophysiology
Taotao Xu, Junhua Li, Jun Cao, Wenxia Gao, Li Li, Bin He
Poly(pseudo)rotaxane (PPR) nanoparticles was facilely prepared using poly(ethylene glycol) (PEG) modified with protoporphyrin (PpIX) and α-cyclodextrin (α-CD) via host-guest interaction, the effect of α-CD number on the nanoparticle properties was investigated. The PEG with protoporphyrin (PEG-PpIX) end capping was synthesized via coupling reaction and the poly(pseudo)rotaxane nanoparticles with different amount of α-CD were fabricated by host-guest interaction between mPEG-PpIX and α-CDs. The final product was characterized by nuclear magnetic spectrum ((1)H NMR), X-ray diffraction (XRD), atomic force microscope (AFM) and dynamic light scattering (DLS)...
October 15, 2017: Carbohydrate Polymers
Elena A Lashina, Vasily V Kaichev, Andrey A Saraev, Zakhar S Vinokurov, Nataliya A Chumakova, Gennadii A Chumakov, Valerii I Bukhtiyarov
The self-sustained kinetic oscillations in the oxidation of CH4 over Ni foil have been studied at atmospheric pressure using an X-ray diffraction technique and mass spectrometry. It has been shown that the regular oscillations appear under oxygen-deficient conditions; CO, CO2, H2, and H2O are detected as the products. According to in situ X-ray diffraction measurements, nickel periodically oxidizes to NiO initiating the reaction-rate oscillations. To describe the oscillations, we have proposed a five-stage mechanism of the partial oxidation of methane over Ni and a corresponding three-variable kinetic model...
September 6, 2017: Journal of Physical Chemistry. A
Bruna Ferreira Gomes, Pollyana Ferreira da Silva, Carlos Manuel Silva Lobo, Maiara da Silva Santos, Luiz Alberto Colnago
The strong effect of magnetic field on the electrochemical (EC) reduction of a diamagnetic species was monitored in situ in a 600 MHz (14 T) NMR spectrometer. Throughout EC-NMR experiments, the diamagnetic species is influenced by the Lorentz force (cross product of current density and magnetic field), which in turn acts on analyte transport and, as a result, enhances reaction rates. This phenomenon, known as magnetoelectrolysis, has not been considered in several in situ EC-NMR studies in solution, electron paramagnetic resonance (EC-EPR) spectroscopy, and magnetic resonance imaging (EC-MRI) involving the oxidation and reduction of organic compounds and lithium ion batteries...
August 29, 2017: Analytica Chimica Acta
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