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Shear force

Floris J Bikker, Michel A Hoogenkamp, Amine Malhaoui, Kamran Nazmi, Jessica Neilands, Bastiaan P Krom
Dental biofilms are formed in a multistep process that is initiated by the adhesion of oral bacteria to the dental hard surface. As dental biofilms are associated with oral diseases their control is necessary in order to maintain oral health. Recently, it was revealed that phytosphingosine (PHS)-treated hydroxyapatite discs showed anti-adhesive activity in a static in vitro biofilm model against Streptococcus mutans. The goal of the present study was to further unravel the anti-adhesive and anti-biofilm properties of PHS in both static and dynamic in vitro biofilm models against a full salivary inoculum...
December 13, 2017: Caries Research
Nicholaus Meyers, Julian Schülke, Anita Ignatius, Lutz Claes
BACKGROUND: Distraction osteogenesis is a procedure widely used for the correction of large bone defects. However, a high complication rate persists, likely due to insufficient stability during maturation. Numerical fracture healing models predict bone regeneration under different mechanical conditions allowing fixation stiffness optimization. However, most models apply a linear elastic material law inappropriate for the transient stresses/strains present during limb lengthening or segment transport...
2017: PloS One
Christian Dietz
Dynamic force microscopy (DFM) is an excellent tool for the study of the compositional and nanomechanical properties of polymers that exploits the flexural eigenmodes of a cantilever comprising a sharp tip vibrating perpendicular to the sample surface. However, the in-plane nanomechanical properties of a specimen cannot be detected by this technique. Here, a bimodal approach was developed where flexural and torsional eigenmodes are driven simultaneously. The corresponding vibrational amplitude and phase shift of the vertical tip motion were utilized for topographical feedback and out-of-plane dissipative interaction acquisition, respectively, whereas the frequency shift and the drive amplitude of the lateral tip motion mapped the in-plane conservative and dissipative interactions of two heterogeneous polymers: an elastomeric polypropylene (ePP) and a polystyrene-block-polybutadiene diblock copolymer (SB)...
December 11, 2017: Nanoscale
Youngwoo Choo, Paweł W Majewski, Masafumi Fukuto, Chinedum O Osuji, Kevin G Yager
While the ultimate driving force in self-assembly is energy minimization and the corresponding evolution towards equilibrium, kinetic effects can also play a very strong role. These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome. Here, we instead exploit these effects to engineer a desired final nano-structure in a block copolymer thin film, by selecting a particular ordering pathway through the self-assembly energy landscape...
December 11, 2017: Nanoscale
David S P Heidsieck, Jan Harm Koolstra, Maurits H T de Ruiter, Aarnoud Hoekema, Jan de Lange
PURPOSE: Mandibular advancement devices are commonly used in the treatment of patients with mild to moderate obstructive sleep apnea (OSA). Designed to maintain the mandible in forced protrusion while being worn, mandibular advancement devices (MADs) are intended to increase the upper airway during sleep, thereby reducing OSA symptoms. Depending on the extent of mandibular protrusion, side effects including temporomandibular joint dysfunction are frequently reported. These are likely to reduce overall treatment success by affecting therapeutic adherence...
November 22, 2017: Journal of Cranio-maxillo-facial Surgery
Sascha Gehrke, Hans Tobias Alznauer, Hossein Ali Karimi-Varzaneh, Jörg August Becker
Sulfur crosslinked polyisoprene (rubber) is used in important material components for a number of technical tasks (e.g., in tires and sealings). If mechanical stress, like tension or shear, is applied on these material components, the sulfur crosslinks suffer from homolytic bond breaking. In this work, we have simulated the bond breaking mechanism of sulfur crosslinks between polyisoprene chains using Car-Parrinello molecular dynamic simulations and investigated the maximum forces which can be resisted by the crosslinks...
December 7, 2017: Journal of Chemical Physics
A Manacorda, A Puglisi
We derive the hydrodynamic equations with fluctuating currents for the density, momentum, and energy fields for an active system in the dilute limit. In our model, nonoverdamped self-propelled particles (such as grains or birds) move on a lattice, interacting by means of aligning dissipative forces and excluded volume repulsion. Our macroscopic equations, in a specific case, reproduce a transition line from a disordered phase to a swarming phase and a linear dispersion law accounting for underdamped wave propagation...
November 17, 2017: Physical Review Letters
M Foglino, A N Morozov, O Henrich, D Marenduzzo
We study the rheology of a suspension of soft deformable droplets subjected to a pressure-driven flow. Through computer simulations, we measure the apparent viscosity as a function of droplet concentration and pressure gradient, and provide evidence of a discontinuous shear thinning behavior, which occurs at a concentration-dependent value of the forcing. We further show that this response is associated with a nonequilibrium transition between a "hard" (or less deformable) phase, which is nearly jammed and flows very slowly, and a "soft" (or more deformable) phase, which flows much more easily...
November 17, 2017: Physical Review Letters
So Hyun Park, Seung Soo Lee, Ji-Youn Sung, Kiyong Na, Hyoung Jung Kim, So Yeon Kim, Beom Jin Park, Jae Ho Byun
OBJECTIVES: To determine the feasibility of acoustic radiation force impulse (ARFI) elastography in the evaluation of hepatic sinusoidal obstruction syndrome (SOS) in rat models. METHODS: Rat SOS models of various severities were created by monocrotaline gavage (n = 40) or by intraperitoneal injection of 5-fluorouracil, leucovorin and oxaliplatin (FOLFOX) (n = 16). Liver shear-wave velocity (SWV) was measured using ARFI elastography. Liver samples were analysed for the SOS score, steatosis, lobular inflammation and fibrosis...
December 7, 2017: European Radiology
Kelsey N Lucas, John O Dabiri, George V Lauder
Many outstanding questions about the evolution and function of fish morphology are linked to swimming dynamics, and a detailed knowledge of time-varying forces and torques along the animal's body is a key component in answering many of these questions. Yet, quantifying these forces and torques experimentally represents a major challenge that to date prevents a full understanding of fish-like swimming. Here, we develop a method for obtaining these force and torque data non-invasively using standard 2D digital particle image velocimetry in conjunction with a pressure field algorithm...
2017: PloS One
Qiyun Qiao, Wanlin Cao, Zhiwei Qian, Xiangyu Li, Wenwen Zhang, Wenchao Liu
In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied...
December 7, 2017: Materials
Guillaume Chatté, Jean Comtet, Antoine Niguès, Lydéric Bocquet, Alessandro Siria, Guylaine Ducouret, François Lequeux, Nicolas Lenoir, Guillaume Ovarlez, Annie Colin
We study the flow of suspensions of non-Brownian particles dispersed into a Newtonian solvent. Combining capillary rheometry and conventional rheometry, we evidence a succession of two shear thinning regimes separated by a shear thickening one. Through X-ray radiography measurements, we show that during each of those regimes, the flow remains homogeneous and does not involve particle migration. Using a quartz-tuning fork based atomic force microscope, we measure the repulsive force profile and the microscopic friction coefficient μ between two particles immersed into the solvent, as a function of normal load...
December 7, 2017: Soft Matter
Hemant Kumar Raut, Avinash Baji, Hassan Hussein Hariri, Hashina Parveen, Gim Song Soh, Hong Yee Low, Kristin L Wood
The unusual ability of geckos to climb vertical walls underlies a unique combination of hierarchical structural design and a stiffer material composition. While a dense array of microscopic hierarchical structures enable the gecko toe pads to adhere to various surfaces, a stiffer material (beta-keratin) composition enables them to maintain reliable adhesion over innumerable cycles. This unique strategy has been seldom implemented in engineered dry-adhesives because fabrication of high aspect ratio hierarchical structures using a stiffer polymer is challenging...
December 7, 2017: ACS Applied Materials & Interfaces
Xi Zhuo Jiang, Haipeng Gong, Kai Hong Luo, Yiannis Ventikos
The glycocalyx has a prominent role in orchestrating multiple biological processes occurring at the plasma membrane. In this paper, an all-atom flow/glycocalyx system is constructed with the bulk flow velocity in the physiologically relevant ranges for the first time. The system is simulated by molecular dynamics using 5.8 million atoms. Flow dynamics and statistics in the presence of the glycocalyx are presented and discussed. Complex dynamic behaviours of the glycocalyx, particularly the sugar chains, are observed in response to blood flow...
December 2017: Journal of the Royal Society, Interface
Zhuang Lu, Xiaofang He, Bingbing Ma, Lin Zhang, Jiaolong Li, Yun Jiang, Guanghong Zhou, Feng Gao
We investigated the molecular mechanisms of chronic heat stress impairing broilers breast meat quality. Broilers were assigned to three groups including normal control (NC) group, heat stress (HS) group and pair-fed (PF) group. After 7d of heat exposure (32°C), high temperature caused oxidative stress, and elevated the activity of citrate synthase (CS), mRNA expression of M-CPT1, and phosphorylation level of AMPKα, and reduced the mRNA expression of avUCP. After 14d of heat exposure, heat stress increased lightness and drip loss and decreased pH and shear force of breast meat...
December 7, 2017: Journal of Agricultural and Food Chemistry
Divya Iska, Raghu Devanna, Madhvi Singh, Rajkiran Chitumalla, Sai C Bala Balasubramanian, Manish Goutam
INTRODUCTION: Esthetics is one of the common issues because of which patients consult dental orthodontic treatment. Two ways of tooth bleaching are available these days, which includes in-office bleach and home bleach. Various bleaching protocols are available these days for treating the tooth surfaces. Hence, we planned the present study for investigating the impact of various intracoronal bleaching protocols on shear bond strength of ceramic brackets bonded to tooth surface after bleaching...
December 1, 2017: Journal of Contemporary Dental Practice
Pauline Vitry, Claire Valotteau, Cécile Feuillie, Simon Bernard, David Alsteens, Joan A Geoghegan, Yves F Dufrêne
Bacterial pathogens that colonize host surfaces are subjected to physical stresses such as fluid flow and cell surface contacts. How bacteria respond to such mechanical cues is an important yet poorly understood issue. Staphylococcus aureus uses a repertoire of surface proteins to resist shear stress during the colonization of host tissues, but whether their adhesive functions can be modulated by physical forces is not known. Here, we show that the interaction of S. aureus clumping factor B (ClfB) with the squamous epithelial cell envelope protein loricrin is enhanced by mechanical force...
December 5, 2017: MBio
Tae-Il Kim, Vijayakumar Mayakrishnan, Dong-Hyun Lim, Jeong-Ha Yeon, Kwang-Soo Baek
This study was conducted to assess the effects of fermented total mixed ration (FTMR) on the growth performance, carcass and meat quality traits of Hanwoo steers. The present study evidenced that the FTMR had a strong effect on dry matter intake, body weight, daily gain, slaughter weight and carcass characteristics compared with control animals. The results showed that the dry matter intake (7.17 ± 0.13 kg), average body weight (615.20 ± 112.82 kg), and daily gain (0.56 ± 0.16 kg) were greater in animals receiving FTMR than in control animals (P < 0...
December 4, 2017: Animal Science Journal, Nihon Chikusan Gakkaihō
M Edward Quach, Matthew A Dragovich, Wenchun Chen, Anum K Syed, Wenpeng Cao, Xin Liang, Wei Deng, Simon F De Meyer, Guangheng Zhu, Jun Peng, Heyu Ni, Carolyn M Bennett, Ming Hou, Jerry Ware, Hans Deckmyn, X Frank Zhang, Renhao Li
Immune thrombocytopenia (ITP) is a prevalent autoimmune disease characterized by autoantibody-induced platelet clearance. Some ITP patients are refractory to standard immunosuppressive treatments such as intravenous immunoglobulin (IVIG). These patients often have autoantibodies targeting the ligand-binding domain (LBD) of glycoprotein (GP)Ibα, a major subunit of the platelet mechanoreceptor complex GPIb-IX. However, the molecular mechanism of this Fc-independent platelet clearance is not clear. Here, we report that many anti-LBD monoclonal antibodies such as 6B4, but not AK2, activated GPIb-IX in a shear-dependent manner and induced IVIG-resistant platelet clearance in mice...
December 4, 2017: Blood
Tatum D Mortimer, Douglas S Annis, Mary B O'Neill, Lindsey L Bohr, Tracy M Smith, Hendrik N Poinar, Deane F Mosher, Caitlin S Pepperell
Human-pathogenic bacteria are found in a variety of niches, including free-living, zoonotic, and microbiome environments. Identifying bacterial adaptations that enable invasive disease is an important means of gaining insight into the molecular basis of pathogenesis and understanding pathogen emergence. Staphylococcus saprophyticus, a leading cause of urinary tract infections, can be found in the environment, food, animals, and the human microbiome. We identified a selective sweep in the gene encoding the Aas adhesin, a key virulence factor that binds host fibronectin...
November 2017: MSphere
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