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Dynamic stretching

Christopher L Jones, Derek G Kamper
Finger-thumb coordination is crucial to manual dexterity but remains incompletely understood, particularly following neurological injury such as stroke. While being controlled independently, the index finger and thumb especially must work in concert to perform a variety of tasks requiring lateral or palmar pinch. The impact of stroke on this functionally critical sensorimotor control during dynamic tasks has been largely unexplored. In this study, we explored finger-thumb coupling during close-open pinching motions in stroke survivors with chronic hemiparesis...
2018: Frontiers in Neurology
Michael J Willatt, Michele Ceriotti, Stuart C Althorpe
Matsubara dynamics is the quantum-Boltzmann-conserving classical dynamics which remains when real-time coherences are taken out of the exact quantum Liouvillian [T. J. H. Hele et al., J. Chem. Phys. 142, 134103 (2015)]; because of a phase-term, it cannot be used as a practical method without further approximation. Recently, Smith et al. [J. Chem. Phys. 142, 244112 (2015)] developed a "planetary" model dynamics which conserves the Feynman-Kleinert (FK) approximation to the quantum-Boltzmann distribution...
March 14, 2018: Journal of Chemical Physics
Nancy Makri
It is shown that dynamical properties of extended systems (spin arrays, large organic molecules, or molecular aggregates) characterized primarily by local potential interactions (bond stretching, bending, and torsional interactions) can be obtained efficiently from fully quantum mechanical path integral calculations through sequential linking of the quantum paths or path integral necklaces corresponding to adjacent groups of atoms, which comprise the "modules." The scheme is applicable to complex chemical systems and is characterized by linear or sublinear scaling with system size...
March 14, 2018: Journal of Chemical Physics
Deepak Ojha, Andrés Henao, Thomas D Kühne
Based on quantum-mechanical path-integral molecular dynamics simulations, the impact of nuclear quantum effects on the vibrational and hydrogen bond dynamics in liquid water is investigated. The instantaneous fluctuations in the frequencies of the O-H stretch modes are calculated using the wavelet method of time-series analysis, while the time scales of the vibrational spectral diffusion are determined from frequency-time correlation functions, joint probability distributions, and the slope of three-pulse photon echo...
March 14, 2018: Journal of Chemical Physics
Giovanni Di Liberto, Riccardo Conte, Michele Ceotto
We present an investigation of vibrational features in water clusters performed by means of our recently established divide-and-conquer semiclassical approach [M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 119, 010401 (2017)]. This technique allows us to simulate quantum vibrational spectra of high-dimensional systems starting from full-dimensional classical trajectories and projection of the semiclassical propagator onto a set of lower dimensional subspaces. The potential energy surface employed is a many-body representation up to three-body terms, in which monomers and two-body interactions are described by the high level Wang-Huang-Braams-Bowman (WHBB) water potential, while, for three-body interactions, calculations adopt a fast permutationally invariant ab initio surface at the same level of theory of the WHBB 3-body potential...
March 14, 2018: Journal of Chemical Physics
Dongshuai Hou, Tiejun Yang, Jinhui Tang, Shaochun Li
Graphene oxide (GO) reinforced cement nanocomposites open up a new path for sustainable concrete design. In this paper, reactive force-field molecular dynamics was utilized to investigate the structure, reactivity and interfacial bonding of calcium silicate hydrate (C-S-H)/GO nanocomposite functionalized by hydroxyl (C-OH), epoxy (C-O-C), carboxyl (COOH) and sulfonic (SO3 H) groups with a coverage of 10%. The silicate chains in the hydrophilic C-S-H substrate provided numerous non-bridging oxygen sites and counter ions (Ca ions) with high reactivity, which allowed interlayer water molecules to dissociate into Si-OH and Ca-OH...
March 15, 2018: Physical Chemistry Chemical Physics: PCCP
Serhat Tozburun, Cedric Blatter, Meena Siddiqui, Eelco F J Meijer, Benjamin J Vakoc
We present a swept-wavelength optical coherence tomography (OCT) system with a 19 MHz laser source and electronic phase-locking of the source, acquisition clock, and beam scanning mirrors. The laser is based on stretched-pulse active mode-locking using an electro-optic modulator. Beam scanning in the fast axis uses a resonant micro-electromechanical systems (MEMS) -based mirror at ~23.8 kHz. Acquisition is performed at 1.78 Gigasamples per second using an external fixed clock. Phase sensitive imaging without need for k-clocking, A-line triggers, or phase-calibration methods is demonstrated...
March 1, 2018: Biomedical Optics Express
Amir Pourmorteza, Noemie Keller, Richard Chen, Albert Lardo, Henry Halperin, Marcus Y Chen, Elliot McVeigh
Resting regional wall motion abnormality (RWMA) has significant prognostic value beyond the findings of computed tomography (CT) coronary angiography. Stretch quantification of endocardial engraved zones (SQUEEZ) has been proposed as a measure of regional cardiac function. The purpose of the work reported here was to determine the effect of lowering the radiation dose on the precision of automatic SQUEEZ assessments of RWMA. Chronic myocardial infarction was created by a 2-h occlusion of the left anterior descending coronary artery in 10 swine (heart rates 80-100, ejection fraction 25-57%)...
March 13, 2018: International Journal of Cardiovascular Imaging
Horacio Parraga, Francisco Javier Arranz, Rosa Maria Benito, Florentino Borondo
The dynamical characteristics of a region of regular vibrational motion in the sea of chaos above the saddle point corresponding to the linear C-N-K configuration is examined in detail. To explain the origin of this regularity, the associated phase space structures have been characterized using suitably defined Poincar\'e surfaces of section, identifying the different resonances between the stretching and bending modes, as a function of excitation energy. The corresponding topology is elucidated by means of periodic orbit analysis...
March 13, 2018: Journal of Physical Chemistry. A
Marco Sbroscia, Armida Sodo, Fabio Bruni, Tommaso Corridoni, Maria Antonietta Ricci
The concept of ions being either water "structure makers" or "breakers" seems to be not consistent with the existence of a critical number of water molecules per ion dictating the properties of an aqueous solution, independently of the ion identity. To investigate this issue, Raman spectra of hydroxides aqueous solutions in the region of the OH stretching mode have been obtained at ambient conditions and at concentrations ranging from extreme dilution to the solubility limit. Spectra have been analyzed with a relatively model free approach, in terms of a superposition of contributions due to the vibrations of the OH ions, with two contributions due to the solvent...
March 13, 2018: Journal of Physical Chemistry. B
Paola Occhetta, Giuseppe Isu, Marta Lemme, Chiara Conficconi, Philipp Oertle, Christian Räz, Roberta Visone, Giulia Cerino, Marija Plodinec, Marco Rasponi, Anna Marsano
In vitro cardiac models able to mimic the fibrotic process are paramount to develop an effective anti-fibrosis therapy that can regulate fibroblast behaviour upon myocardial injury. In previously developed in vitro models, typical fibrosis features were induced by using scar-like stiffness substrates and/or potent morphogen supplementation in monolayer cultures. In our model, we aimed to mimic in vitro a fibrosis-like environment by applying cyclic stretching of cardiac fibroblasts embedded in three-dimensional fibrin-hydrogels alone...
March 13, 2018: Integrative Biology: Quantitative Biosciences From Nano to Macro
Shunli Liu, Kewen Li, Imtiaz Hussain, Olayinka Oderinde, Fang Yao, Jiuyang Zhang, Guo Dong Fu
Mechanically-tough and electrical conductive self-healing hydrogels may have broad applications in wearable electronics, health-monitoring systems, and smart robotics in the following years. Here, we proposed a new design strategy to synthesize a dual physical cross-linked polyethylene glycol/poly(acrylic acid) (PEG/PAA) double network hydrogel, consisting of an ferric ions cross-linked linear chain extension of PEG (2, 6-pyridinedicarbonyl moieties incorporated in the PEG backbone, PEG-H2pdca) as the first physical network and a PAA-Fe3+ gel as the second physical network...
March 13, 2018: Chemistry: a European Journal
Jiří Novák, Branislav Vrana, Tatsiana Rusina, Krzysztof Okonski, Roman Grabic, Peta A Neale, Beate I Escher, Miroslava Macová, Selim Ait-Aissa, Nicolas Creusot, Ian Allan, Klára Hilscherová
Many aquatic pollutants can be present at low concentrations, but their mixtures can still affect health or behavior of exposed organisms. In this study, toxicological and chemical analyses were combined for spatial contamination profiling using an innovative passive sampling approach. A novel Dynamic Passive Sampler (DPS) was employed as a mobile sampler from a ship cruising along 2130km of the Danube river during the Joint Danube Survey 3 (JDS3). The sampling was performed in eight subsequent river stretches with two types of complementary passive samplers: silicone rubber sheets (SR) used for non-polar chemicals and SDB-RPS Empore™ disks (ED) for more hydrophilic compounds...
March 9, 2018: Science of the Total Environment
Meng Wei, Pengxiang Xu, Yizhong Yuan, Xiaohui Tian, Jinyu Sun, Jiaping Lin
A coarse-grained model-based molecular dynamics simulation was employed to investigate the mechanical properties of NR-graft-rigid-polymer/rigid-polymer systems (N30 -g-(R3 )6 /R10 ). An external factor (the strain rate) as well as internal factors such as the nonbonding interaction strength, the proportion of rigid polymers, and architecture parameters (the length and number of graft chains in a molecule) were examined for their effect on the tensional behavior of N30 -g-(R3 )6 /R10 systems. Simulation results show that a higher strain rate can promote the enhancement of mechanical performance, such as a higher modulus or yield stress...
March 12, 2018: Physical Chemistry Chemical Physics: PCCP
Mickaël F El Hachmane, Charlotta S Olofsson
Ca2+ impacts a large array of cellular processes in every known cell type. In the white adipocyte, Ca2+ is involved in regulation of metabolic processes such as lipolysis, glucose uptake and hormone secretion. Although the importance of Ca2+ in control of white adipocyte function is clear, knowledge is still lacking regarding the control of dynamic Ca2+ alterations within adipocytes and mechanisms inducing intracellular Ca2+ changes remain elusive. Own work has recently demonstrated the existence of store-operated Ca2+ entry (SOCE) in lipid filled adipocytes...
March 7, 2018: Biochemical and Biophysical Research Communications
Christopher P Caridi, Laetitia Delabaere, Harianto Tjong, Hannah Hopp, Devika Das, Frank Alber, Irene Chiolo
Heterochromatin is mostly composed of long stretches of repeated DNA sequences prone to ectopic recombination during double-strand break (DSB) repair. In Drosophila, "safe" homologous recombination (HR) repair of heterochromatic DSBs relies on a striking relocalization of repair sites to the nuclear periphery. Central to understanding heterochromatin repair is the ability to investigate the 4D dynamics (movement in space and time) of repair sites. A specific challenge of these studies is preventing phototoxicity and photobleaching effects while imaging the sample over long periods of time, and with sufficient time points and Z-stacks to track repair foci over time...
2018: Methods in Enzymology
Giseong Lee, Dorota Kossowska, JoonHyung Lim, Soobin Kim, Hogyu Han, Kyungwon Kwak, Minhaeng Cho
Infrared (IR) probes based on terminally blocked β-cyanamidoalanine (AlaNHCN) 1 and p-cyanamidophenylalanine (PheNHCN) 2 were synthesized and the vibrational properties of their CN stretch mode were studied using FTIR and femtosecond IR pump-probe (PP) spectroscopies in combination with quantum chemical calculations. From FTIR studies, it is found that the transition dipole strengths of the cyanamide (NHCN) group in 1 and 2 are much larger than those of the nitrile (CN) group, but comparable to those of the isonitrile (NC) and azido (N3 ) groups in their previously studied analogs...
March 8, 2018: Journal of Physical Chemistry. B
Maciej Śmiechowski
Infrared (IR) spectroscopy is a commonly used and invaluable tool in the studies of solvation phenomena in aqueous solutions. Concurrently, ab initio molecular dynamics (AIMD) simulations deliver the solvation shell picture at a molecular detail level and allow for a consistent decomposition of the theoretical IR spectrum into underlying spatial correlations. Here, we demonstrate how the novel spectral decomposition techniques can extract important information from the computed IR spectra of aqueous solutions of BF4 - and PF6 - , interesting weakly-coordinating anions that have been known for a long time to alter the IR spectrum of water in an unusual manner...
March 7, 2018: Journal of Physical Chemistry. B
Jiangxin Wang, Guofa Cai, Shaohui Li, Dace Gao, Jiaqing Xiong, Pooi See Lee
Stretchable conductors are vital and indispensable components in soft electronic systems. The development for stretchable conductors has been highly motivated with different approaches established to address the dilemma in the conductivity and stretchability trade-offs to some extent. Here, a new strategy to achieve superelastic conductors with high conductivity and stable electrical performance under stretching is reported. It is demonstrated that by electrically anchoring conductive fillers with eutectic gallium indium particles (EGaInPs), significant improvement in stretchability and durability can be achieved in stretchable conductors...
March 7, 2018: Advanced Materials
Jessy Lauer, João Paulo Vilas-Boas, Annie Hélène Rouard
BACKGROUND: The mechanical demands of underwater shoulder exercises have only been assessed indirectly via electromyographical measurements. Yet, this is insufficient to understand all the clinical implications. The purpose of this study was to evaluate musculoskeletal system loading during slow (30°/s) scapular plane arm elevation and lowering performed in two media (air vs water) and body positions (sitting vs supine). METHODS: Eighteen participants' upper bodies were scanned and virtually animated within unsteady numerical fluid flow simulations to compute hydrodynamic forces...
February 27, 2018: Clinical Biomechanics
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