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Dynamic elastance

Manuel Toledano, Estrella Osorio, Fátima S Aguilera, Manuel Toledano-Osorio, Modesto T López-López, Raquel Osorio
The aim of this research was to ascertain the mechanical and chemical behavior of sound and caries-affected dentin (CAD), after the placement of Zn-free vs containing amalgam restorations. Peritubular and intertubular dentin were evaluated using, a) nanoindenter in scanning mode; the load and displacement responses were used to perform the nano-Dynamic mechanical analysis and to estimate the complex (E * ) and storage modulus (E'); b) Raman spectroscopy was used to describe the hierarchical cluster analysis (HCA)...
December 6, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Haihua Chen, Hao Liang, Fang Peng, Huishan Li, Bin Wang, Xinxin Xia, Xiaodong Li, Pei Wang, Liping Wang
Zirconium disilicide (ZrSi2 ) has been investigated experimentally and theoretically for its structural and physical properties at high pressures. In situ compression experiments demonstrate that at low pressure, ZrSi2 adopts the C49 structure (space group Cmcm), which persists up to 54.5 GPa at room temperature, and the unit cell of ZrSi2 along b-axis is at least twice as compressible as along a- and c-axis. A bulk modulus of 170.0 ± 0.7 GPa ( K'0 = 4) is derived from the compression experiment employing methanol-ethanol mixture as the pressure-transmitting medium...
December 14, 2018: Inorganic Chemistry
N David Rodríguez-Marin, Aylin A Figueroa-Chaverra, Mayerly A Sánchez-Jiménez, Vanessa Orozco-Orrego, Constanza Bohórquez-Orozco, Omar R García, Magda I Pinzón, Leidy T Sánchez, Cristian C Villa
Growing interest in processed frozen products with similar characteristics to natural products has generated the study of new products in the food industry field. The characteristics of each matrix, the process of elaboration, composition, and structure of the additives and the interactions amongst these modify the food's texture, structure, physical and sensory properties and, hence, interfere directly with consumer acceptance. This research studied the effect of adding cryoprotectors during frozen storage on the rheological, physicochemical, structural, and microbiological properties in a Mafafa-quinoa-olive oil puree...
December 13, 2018: Journal of Texture Studies
Mangor Pedersen, Andrew Zalesky, Amir Omidvarnia, Graeme D Jackson
Large-scale brain dynamics are characterized by repeating spatiotemporal connectivity patterns that reflect a range of putative different brain states that underlie the dynamic repertoire of brain functions. The role of transition between brain networks is poorly understood, and whether switching between these states is important for behavior has been little studied. Our aim was to model switching between functional brain networks using multilayer network methods and test for associations between model parameters and behavioral measures...
December 13, 2018: Proceedings of the National Academy of Sciences of the United States of America
Mark Andrew Borden
Lipid-coated microbubbles are currently used clinically as ultrasound contrast agents for echocardiography and radiology, and are being developed for many new diagnostic and therapeutic applications. Accordingly, there is a growing need to engineer specific formulations by employing rational design to guide lipid selection and processing. This approach requires a quantitative relationship between lipid chemistry and interfacial properties of the microbubble shell. Just such a model is proposed here based on lateral coulomb and van der Waals interactions between lipid head and tail groups, using previous coarse graining and force fields developed for molecular dynamics simulations...
December 13, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Justin D Berman, Manjari Randeria, Robert W Style, Qin Xu, James R Nichols, Aidan J Duncan, Michael Loewenberg, Eric R Dufresne, Katharine E Jensen
We characterize the mechanical recovery of compliant silicone gels following adhesive contact failure. We establish broad, stable adhesive contacts between rigid microspheres and soft gels, then stretch the gels to large deformations by pulling quasi-statically on the contact. Eventually, the adhesive contact begins to fail, and ultimately slides to a final contact point on the bottom of the sphere. Immediately after detachment, the gel recoils quickly with a self-similar surface profile that evolves as a power law in time, suggesting that the adhesive detachment point is singular...
December 12, 2018: Soft Matter
Xiao Tang, Weiguo Sun, Cheng Lu, Liangzhi Kou, Changfeng Chen
Two-dimensional (2D) Dirac materials have attracted extensive research interest due to their high carrier mobility and ballistic charge transport, and they hold great promise for next-generation nanoscale devices. Here, we report a computational discovery of a stable 2D Dirac material, an NiB6 monolayer, which is identified by an extensive structure search, and its dynamic and thermal stabilities are confirmed by phonon and ab initio molecular dynamics (AIMD) simulations. This monolayer structure possesses anisotropic elastic properties with a Young's modulus of 189 N m-1, which is higher than that of phosphorene or silicene...
December 12, 2018: Physical Chemistry Chemical Physics: PCCP
Kristian Peters, James Bradbury, Sven Bergmann, Marco Capuccini, Marta Cascante, Pedro de Atauri, Timothy M D Ebbels, Carles Foguet, Robert Glen, Alejandra Gonzalez-Beltran, Ulrich L Günther, Evangelos Handakas, Thomas Hankemeier, Kenneth Haug, Stephanie Herman, Petr Holub, Massimiliano Izzo, Daniel Jacob, David Johnson, Fabien Jourdan, Namrata Kale, Ibrahim Karaman, Bita Khalili, Payam Emami Khonsari, Kim Kultima, Samuel Lampa, Anders Larsson, Christian Ludwig, Pablo Moreno, Steffen Neumann, Jon Ander Novella, Claire O'Donovan, Jake T M Pearce, Alina Peluso, Marco Enrico Piras, Luca Pireddu, Michelle A C Reed, Philippe Rocca-Serra, Pierrick Roger, Antonio Rosato, Rico Rueedi, Christoph Ruttkies, Noureddin Sadawi, Reza M Salek, Susanna-Assunta Sansone, Vitaly Selivanov, Ola Spjuth, Daniel Schober, Etienne A Thévenot, Mattia Tomasoni, Merlijn van Rijswijk, Michael van Vliet, Mark R Viant, Ralf J M Weber, Gianluigi Zanetti, Christoph Steinbeck
Background: Metabolomics is the comprehensive study of a multitude of small molecules to gain insight into an organism's metabolism. The research field is dynamic and expanding with applications across biomedical, biotechnological and many other applied biological domains. Its computationally-intensive nature has driven requirements for open data formats, data repositories and data analysis tools. However, the rapid progress has resulted in a mosaic of independent-and sometimes incompatible-analysis methods that are difficult to connect into a useful and complete data analysis solution...
December 7, 2018: GigaScience
Matthew Brownell, Arun K Nair
Polytetrafluoroethylene (PTFE) has not only a low coefficient of friction but also a high wear rate. Numerous studies investigating the possibility of reducing wear and the mechanisms of deformation have been conducted using experimental and computational studies. In this paper the deformation and mechanical failure of single chains and bulk PTFE are investigated using molecular dynamics (MD). Due to the length scale limitations of the model that MD simulations can investigate, a coarse-grained model is developed and PTFE particles of varying densities are generated to investigate their mechanical properties at the microscale...
December 11, 2018: Physical Chemistry Chemical Physics: PCCP
Ramona Häberle, Florian Schellenberg, Renate List, Michael Plüss, William R Taylor, Silvio Lorenzetti
Background: Internal and external rotation exercises of the shoulder are frequently performed to avoid injury and pain. Knowledge about the motion and loadings of the upper extremities during these exercises is crucial for the development of optimal training recommendations. However, a comparison of the angles and corresponding moments in the upper extremities that are achieved during internal and external rotation exercises for the shoulder by using different resistance types has not yet been performed...
2018: BMC Sports Science, Medicine and Rehabilitation
Reinhard Blickhan, Emanuel Andrada, Eishi Hirasaki, Naomichi Ogihara
Macaques trained to perform bipedally use grounded running, skipping and aerial running, but avoid walking. The preference for grounded running across a wide range of speeds is substantially different from the locomotion habits observed in humans, which may be the result of differences in leg compliance. In the present study, based on kinematic and dynamic observations of three individuals crossing an experimental track, we investigated global leg properties such as leg stiffness and viscous damping during grounded and aerial running...
December 10, 2018: Journal of Experimental Biology
Gargi Ghoshal, Sapna Mehta
The aim of this study was to develop fiber-enriched functional bread containing selected concentration of chitosan (0.1%, 0.5%, 1%, 1.5%, and 2% w/w). Dynamic rheology of bread dough established that viscous moduli were lower than elastic moduli. Until 1% chitosan concentration, dough extensibility increased. Avrami nonlinear regression equation was selected as a convenient mathematical tool to model bread crumb staling kinetics. Scanning electron microscopy, Fourier-transform infrared, differential scanning calorimetry, and extensibility tests were used to examine the changes of the structure of control dough and chitosan containing dough...
December 10, 2018: Food Science and Technology International, Ciencia y Tecnología de Los Alimentos Internacional
William Barford, Jonathan R Mannouch
We develop a model of excitons coupled to the rotational motion of monomers to study the torsionally induced relaxation and decoherence of excitons in π -conjugated polymers. The model assumes that the monomer units are described by elastically uncoupled harmonic oscillators and that there is a linear exciton-roton coupling. Although the rotational degrees of freedom are much slower than the exciton, so that the adiabatic approximation is generally expected to be valid, we also investigate possible quantized roton corrections via coupled time evolving block decimation-Ehrenfest equations of motion...
December 7, 2018: Journal of Chemical Physics
Claire A Lemarchand, Michael L Greenfield, Jeppe C Dyre, J S Hansen
We present a mesoscopic model for bitumen and bituminous mixtures. The model, which is based on dissipative particle dynamics, consists of different dynamical entities that represent the different characteristic time scales. Through the stress relaxation function, the mechanical properties of the model are investigated. For pure bitumen, the viscosity features super-Arrhenius behavior in the low-temperature regime in agreement with experimental data. The frequency-dependent viscoelastic properties show purely viscous behavior at low frequencies with increasing elasticity and hardening at higher frequencies, as expected...
December 7, 2018: Journal of Chemical Physics
Christopher J Cox, Brentley Hovey, Timothy D Fornes, Saad A Khan
ATH/PDMS systems are often used as potting compounds in electronic assemblies to guard the electronics from shock, vibration, corrosive agents and moisture. In this study, we use dynamic rheology and confocal/optical microscopy to understand the dramatic effects miniscule levels of water have on the microstructure and corresponding rheological behavior of PDMS filled with ATH. In the absence of water, PDMS containing 20 wt.% ATH readily flows, exhibiting viscoelastic behavior with some weak particle flocculation...
December 7, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Othmar J Wess, Juergen Mayer
Shock wave lithotripsy is the only non-invasive stone therapy and in clinical use since 1980. In spite of decades with millions of patients treated, the mechanism of fragmentation is still under debate. Detailed knowledge of the fragmentation process is required for improvements regarding safety and efficiency. The purpose of this paper is to gain a deeper insight into the mechanism of fragmentation by drawing attention to basic physical laws of inertia and momentum transfer. Many fragmentation experiments are based on the overall efficiency of multiple shock waves in crushing kidney stones or artificial model stones utilizing small baskets or latex pouches...
December 6, 2018: Urolithiasis
Stephanie G Konarski, Michael R Haberman, Mark F Hamilton
One emerging research area within the fields of acoustic and elastic metamaterials involves designing subwavelength structures that display elastic instabilities in order to generate an effective medium response that is strongly nonlinear. To capture the overall frequency-dependent and dispersive macroscopic response of such heterogeneous media with subwavelength heterogeneities, a theoretical framework is developed that accounts for higher-order stiffnesses of a resonant, nonlinear inclusion that varies with a macroscopic pre-strain, and the inherent inertia associated with an inclusion embedded in a nearly incompressible elastic matrix material...
November 2018: Journal of the Acoustical Society of America
Andrew T Kleinschmidt, Darren J Lipomi
The field of π-conjugated (semiconducting) polymers has been underwritten largely because of the promise of flexible (and increasingly, stretchable) devices for energy and health care. Our research group has spent much of the past six years studying the mechanical properties of conjugated polymers. Mechanically robust materials can extend the life spans of devices such as solar cells and organic light-emitting diode (OLED) panels and enable high throughput processing techniques such as roll-to-roll printing...
December 5, 2018: Accounts of Chemical Research
Yi Zhu, Li He, Jing Qu, Yong Zhou
The intracellular concentration of calcium ion ([Ca2+]i) is a critical regulator of cell signaling and contractility of vascular smooth muscle cells (VSMCs). In this study, we employed an atomic force microscopy (AFM) nanoindentation-based approach to investigate the role of [Ca2+]i in regulating the cortical elasticity of rat cremaster VSMCs and the ability of rat VSMCs to adhere to fibronectin (Fn) matrix. Elevation of [Ca2+]i by ionomycin treatment increased rat VSMC stiffness and cell adhesion to Fn-biofunctionalized AFM probes, whereas attenuation of [Ca2+]i by 1,2-Bis (2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM) treatment decreased the mechanical and matrix adhesive properties of VSMCs...
December 5, 2018: Microscopy and Microanalysis
Shuai Wei, Zach Evenson, Moritz Stolpe, Pierre Lucas, C Austen Angell
The dynamic properties of liquid phase-change materials (PCMs), such as viscosity η and the atomic self-diffusion coefficient D , play an essential role in the ultrafast phase switching behavior of novel nonvolatile phase-change memory applications. To connect η to D , the Stokes-Einstein relation (SER) is commonly assumed to be valid at high temperatures near or above the melting temperature T m and is often used for assessing liquid fragility (or crystal growth velocity) of technologically important PCMs...
November 2018: Science Advances
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