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Yan Y, Gong R, Cao M, Han B, Li H, Liu G. The effect of different mechanism combinations on sliding between brace and lower limb during walking and leg-raising. Proc Inst Mech Eng H 2024; 238:500-507. [PMID: 38534031 DOI: 10.1177/09544119241241440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Knee braces are commonly used to support the knee joint and improve function. However, brace sliding caused by the misalignment between brace and knee during motion is a common problem, which reduces the therapeutic effect and leads to brace abandonment. To investigate the effect of mechanism combinations on sliding, an experimental brace was designed to isolate the mechanism as the sole variable. Ten healthy participants were recruited, each of whom worn four combinations of lateral/medial mechanisms: lateral and medial single-axis (SA), lateral super gear (SG) and medial non-circular gear (NCG), lateral four-bar linkage (FL) and medial SG, and lateral FL and medial NCG. The knee flexion angle was collected using inertial measurement units, and brace sliding was measured by 3D motion capture system. All combinations had significant changes in peak sliding of thigh and shank compared to the SA combination (p < 0.05), but lateral FL and medial NCG combination had the lowest peak and final sliding during walking and leg-raising, with significant reductions of 40.7 and 85.3% in peak sliding of thigh, and significant reductions of 56.3 and 72.0% in peak sliding of shank, respectively (p < 0.05). Moreover, the mechanism combination did not significantly impact the knee range of motion (p > 0.05). The mechanism combination that fit the instantaneous center of rotation of lateral/medial condyle of knee joint demonstrates a significant reduction in brace sliding. Additionally, the peak sliding during motion is significantly higher than the final sliding.
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Affiliation(s)
- Yuzhou Yan
- Innovation Center of Bioengineering, Shaanxi Engineering Laboratory for Transmissions and Controls, Northwestern Polytechnical University, Xi'an, Shaanxi, P.R. China
| | - Ruitao Gong
- Innovation Center of Bioengineering, Shaanxi Engineering Laboratory for Transmissions and Controls, Northwestern Polytechnical University, Xi'an, Shaanxi, P.R. China
| | - Mengzhao Cao
- Innovation Center of Bioengineering, Shaanxi Engineering Laboratory for Transmissions and Controls, Northwestern Polytechnical University, Xi'an, Shaanxi, P.R. China
| | - Bing Han
- Innovation Center of Bioengineering, Shaanxi Engineering Laboratory for Transmissions and Controls, Northwestern Polytechnical University, Xi'an, Shaanxi, P.R. China
| | - Hui Li
- Joint Surgery Department, Xi'an Hong-hui Hospital, Xi'an Jiaotong University College of Medicine, Xi'an, Shaanxi, P.R. China
| | - Geng Liu
- Innovation Center of Bioengineering, Shaanxi Engineering Laboratory for Transmissions and Controls, Northwestern Polytechnical University, Xi'an, Shaanxi, P.R. China
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Gidi Y, Robert A, Tordo A, Lovell TC, Ramos-Sanchez J, Sakaya A, Götte M, Cosa G. Binding and Sliding Dynamics of the Hepatitis C Virus Polymerase: Hunting the 3' Terminus. ACS Infect Dis 2023; 9:1488-1498. [PMID: 37436367 DOI: 10.1021/acsinfecdis.3c00048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/13/2023]
Abstract
The hepatitis C virus (HCV) nonstructural protein 5B (NS5B) polymerase catalyzes the replication of the (+) single-stranded RNA genome of HCV. In vitro studies have shown that replication can be performed in the absence of a primer. However, the dynamics and mechanism by which NS5B locates the 3'-terminus of the RNA template to initiate de novo synthesis remain elusive. Here, we performed single-molecule fluorescence studies based on protein-induced fluorescence enhancement reporting on NS5B dynamics on a short model RNA substrate. Our results suggest that NS5B exists in a fully open conformation in solution wherefrom it accesses its binding site along RNA and then closes. Our results revealed two NS5B binding modes: an unstable one resulting in rapid dissociation, and a stable one characterized by a larger residence time on the substrate. We associate these bindings to an unproductive and productive orientation, respectively. Addition of extra mono (Na+)- and divalent (Mg2+) ions increases the mobility of NS5B along its RNA substrate. However, only Mg2+ ions induce a decrease in NS5B residence time. Dwell times of residence increase with the length of the single-stranded template, suggesting that NS5B unbinds its substrate by unthreading the template rather than by spontaneous opening.
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Affiliation(s)
- Yasser Gidi
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Anaïs Robert
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Alix Tordo
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Terri C Lovell
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Jorge Ramos-Sanchez
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Aya Sakaya
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Gonzalo Cosa
- Department of Chemistry and Quebec Center for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada
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Maity I, Mostofi AA, Lischner J. Electrons Surf Phason Waves in Moiré Bilayers. Nano Lett 2023. [PMID: 37235740 DOI: 10.1021/acs.nanolett.3c00490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We investigate the effect of thermal fluctuations on the atomic and electronic structure of a twisted MoSe2/WSe2 heterobilayer using a combination of classical molecular dynamics and ab initio density functional theory calculations. Our calculations reveal that thermally excited phason modes give rise to an almost rigid motion of the moiré lattice. Electrons and holes in low-energy states are localized in specific stacking regions of the moiré unit cell and follow the thermal motion of these regions. In other words, charge carriers surf phason waves that are excited at finite temperatures. We also show that such surfing survives in the presence of a substrate and frozen potential. This effect has potential implications for the design of charge and exciton transport devices based on moiré materials.
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Affiliation(s)
- Indrajit Maity
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Arash A Mostofi
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Johannes Lischner
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
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Munirathinam P, Chandrasekhar A. Self-Powered Triboelectric Nanogenerator for Security Applications. Micromachines (Basel) 2023; 14:592. [PMID: 36984999 PMCID: PMC10056479 DOI: 10.3390/mi14030592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/06/2023] [Accepted: 02/16/2023] [Indexed: 06/18/2023]
Abstract
Valuable jewels, documents, and files left in hotel rooms by guests can be stolen at any time by an unauthorized person. This could have a serious psychological and economic impact on the guests. The house/hotel owners should make efforts to prevent theft from occurring. In this study, a self-powered sliding-mode triboelectric nanogenerator (TENG) is used as a sensor on a drawer. It is fixed to the side of the drawer and works in the lateral sliding mode. The electricity generated by the device during the push-pull action of the draw is ~125 V and F~12.5 µA. An analysis of the electrical performance was carried out using PET, paper, and nitrile as sliding materials. The electrical output from the device is used to notify the guest or hotel owner of any theft by an unidentified individual via Arduino and node MCU devices. Finally, this device can be helpful at night and can be extended using different materials.
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Moon YJ, Kim C, Choi E, Shin DY, Kang KT. The Effect of Pre-Stretched Substrate on the Electrical Resistance of Printed Ag Nanowires. Nanomaterials (Basel) 2023; 13:719. [PMID: 36839086 PMCID: PMC9963882 DOI: 10.3390/nano13040719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/03/2023] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
One-dimensional nanomaterials have drawn attention as an alternative electrode material for stretchable electronics. In particular, silver nanowires (Ag NWs) have been studied as stretchable electrodes for strain sensors, 3D electronics, and freeform-shaped electronic circuits. In this study, Ag NWs ink was printed on the pre-stretched silicone rubber film up to 40% in length using a drop-on-demand dispenser. After printing, silicone rubber film was released and stretched up to 20% as a cyclic test with 10-time repetition, and the ratios of the resistance of the stretched state to that of the released state (Rstretched/Rreleased) were measured at each cycle. For Ag NWs electrode printed on the pre-stretched silicone rubber at 30%, Rstretched/Rreleased at 10% and 20% strain was 1.05, and 1.57, respectively, which is significantly less than about 7 for Ag NWs at the 10% strain without pre-stretched substrate. In the case of 10% strain on the 30% pre-stretched substrate, the substrate is stretched and the contact points with Ag NWs were not changed much as the silicone rubber film stretched, which meant that Ag NWs may slide between other Ag NWs. Ag NWs electrode on the 40% pre-stretched substrate was stretched, strain was concentrated on the Ag NWs electrode and failure of electrode occurred, because cracks occurred at the surface of silicone rubber film when it was pre-stretched to 40%. We confirmed that printed Ag NWs on the pre-stretched film showed more contact points and less electric resistance compared to printed Ag NWs on the film without pre-stretching.
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McCartney W, Ober C, Benito M. Lateral Approach and Plate Rod Sliding Humeral Osteotomy in Dogs-A Short Case Series. Vet Sci 2023; 10. [PMID: 36851374 DOI: 10.3390/vetsci10020070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023] Open
Abstract
Five dogs of different breeds and ages were diagnosed with medial compartment disease of the elbow (MCDE). To resolve the condition, a modified technique using a lateral approach and plate/rod sliding humeral osteotomy (SHO) was considered. All dogs recovered uneventfully after surgery. There were no major complications, and all dogs were significantly improved compared to pre-operative condition. This novel technique of adding a pin, based on the alteration of the original technique, optimized resistance to fixation failure. An additional benefit was that the lateral approach was surgically familiar and easily allowed bone grafting. All five dogs treated with the novel approach had improved scores for pain and lameness. This study showed that SHO was more stable and less technically demanding with the addition of an intramedullary pin. This is the first report of a lateral approach and plate rod sliding humeral osteotomy to treat MCDE in dogs.
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Zegadło K, Gieroń M, Żarnowiec P, Durlik-Popińska K, Kręcisz B, Kaca W, Czerwonka G. Bacterial Motility and Its Role in Skin and Wound Infections. Int J Mol Sci 2023; 24. [PMID: 36675220 DOI: 10.3390/ijms24021707] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 01/06/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023] Open
Abstract
Skin and wound infections are serious medical problems, and the diversity of bacteria makes such infections difficult to treat. Bacteria possess many virulence factors, among which motility plays a key role in skin infections. This feature allows for movement over the skin surface and relocation into the wound. The aim of this paper is to review the type of bacterial movement and to indicate the underlying mechanisms than can serve as a target for developing or modifying antibacterial therapies applied in wound infection treatment. Five types of bacterial movement are distinguished: appendage-dependent (swimming, swarming, and twitching) and appendage-independent (gliding and sliding). All of them allow bacteria to relocate and aid bacteria during infection. Swimming motility allows bacteria to spread from 'persister cells' in biofilm microcolonies and colonise other tissues. Twitching motility enables bacteria to press through the tissues during infection, whereas sliding motility allows cocci (defined as non-motile) to migrate over surfaces. Bacteria during swarming display greater resistance to antimicrobials. Molecular motors generating the focal adhesion complexes in the bacterial cell leaflet generate a 'wave', which pushes bacterial cells lacking appendages, thereby enabling movement. Here, we present the five main types of bacterial motility, their molecular mechanisms, and examples of bacteria that utilise them. Bacterial migration mechanisms can be considered not only as a virulence factor but also as a target for antibacterial therapy.
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Abstract
Traditional ferroelectrics undergo thermally induced phase transitions whereby their structural symmetry increases. The associated higher-symmetry structure is dubbed paraelectric. Ferroelectric transition-metal dichalcogenide bilayers have been recently shown to become paraelectric, but not much has been said of the atomistic configuration of such a phase. As discovered through numerical calculations that include molecular dynamics here, their paraelectricity can only be ascribed to a time average of ferroelectric phases with opposing intrinsic polarizations, whose switching requires macroscopically large areas to slip in unison.
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Affiliation(s)
- Juan M Marmolejo-Tejada
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
- MonArk NSF Quantum Foundry, Montana State University, Bozeman, Montana 59717, United States
| | - Joseph E Roll
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Shiva Prasad Poudel
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Salvador Barraza-Lopez
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Martín A Mosquera
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
- MonArk NSF Quantum Foundry, Montana State University, Bozeman, Montana 59717, United States
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Yang Q, Song C, Meng S. Laser-induced enhancement of vertical polarization in ferroelectric bilayer WTe 2. J Phys Condens Matter 2022; 34:424003. [PMID: 35944555 DOI: 10.1088/1361-648x/ac885b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
Light-matter interaction is one of the key means to manipulate the structural and electronic properties of materials, especially in two-dimensional (2D) layered materials, which are optically accessible due to their atomic thickness. We propose that an ultrashort laser pulse could drastically enhance the ferroelectric polarization of bilayer WTe2by our real-time time-dependent density functional theory simulations. It is noted that bilayer WTe2is a 2D sliding ferroelectric material recently discovered whose vertical polarization can be controlled by a slight horizontal displacement. We demonstrate that interlayer sliding and compression are simultaneously achieved upon illumination of linearly polarized near-infrared laser pulse, leading to an ultrafast electric polarization enhancement by ∼230% within hundreds of femtosecond. Two major contributions have been identified: (a) the piezoelectric effect due to laser-induced interlayer compression, caused by interlayer charge transfer and dipole-dipole interaction; (b) the interlayer sliding along the opposite direction of ferroelectric switching, induced by inhomogeneous excited carrier distribution and specific electron-phonon couplings. This work provides new insights on controlling ferroelectricity of layered materials, which may extend to other van der Waals bilayers and even bulk materials.
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Affiliation(s)
- Qing Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics,Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Chenchen Song
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics,Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics,Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
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Li R, Xu F. Competition between Sliding and Peeling of Graphene Nanoribbons under Horizontal Drag. Materials (Basel) 2022; 15:3284. [PMID: 35591618 DOI: 10.3390/ma15093284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/01/2022] [Accepted: 05/02/2022] [Indexed: 12/10/2022]
Abstract
In the process of graphene nanoribbons’ (GNRs) preparation and measurement, mechanical methods such as lifting and dragging are inevitably used to move GNRs, and manipulation of GNRs using these approaches results in intriguing responses such as peeling and sliding. Understanding the mechanical behaviors of GNRs is crucial for the effective use of mechanical deformation as a tool for the measurement and characteristics of low-dimensional material properties. Here, we explore intricate coupling behaviors of peeling and sliding of GNRs under horizontal drag. Using molecular dynamics simulation, we explore effects of lifting height, dragging velocity, length, and orientation of GNRs on mechanical behaviors. We reveal a competition between sliding and peeling of GNRs under horizontal drag and provide a phase diagram. The peeling behavior is found to be originated from the decrease of sliding velocity caused by the sinking of tail atoms. The results not only advance our insightful understanding of the underlying mechanism of different mechanical responses of GNRs but may also guide the precise manipulations of nano surfaces and interfaces.
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Kamagata K. Single-Molecule Microscopy Meets Molecular Dynamics Simulations for Characterizing the Molecular Action of Proteins on DNA and in Liquid Condensates. Front Mol Biosci 2021; 8:795367. [PMID: 34869607 PMCID: PMC8639857 DOI: 10.3389/fmolb.2021.795367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 11/03/2021] [Indexed: 11/13/2022] Open
Abstract
DNA-binding proteins trigger various cellular functions and determine cellular fate. Before performing functions such as transcription, DNA repair, and DNA recombination, DNA-binding proteins need to search for and bind to their target sites in genomic DNA. Under evolutionary pressure, DNA-binding proteins have gained accurate and rapid target search and binding strategies that combine three-dimensional search in solution, one-dimensional sliding along DNA, hopping and jumping on DNA, and intersegmental transfer between two DNA molecules. These mechanisms can be achieved by the unique structural and dynamic properties of these proteins. Single-molecule fluorescence microscopy and molecular dynamics simulations have characterized the molecular actions of DNA-binding proteins in detail. Furthermore, these methodologies have begun to characterize liquid condensates induced by liquid-liquid phase separation, e.g., molecular principles of uptake and dynamics in droplets. This review discusses the molecular action of DNA-binding proteins on DNA and in liquid condensate based on the latest studies that mainly focused on the model protein p53.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
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Stepanov FI, Torskaya EV. Modeling of Fatigue Wear of Viscoelastic Coatings. Materials (Basel) 2021; 14:ma14216513. [PMID: 34772037 PMCID: PMC8585156 DOI: 10.3390/ma14216513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 11/16/2022]
Abstract
A new model for studying the kinetics of fatigue wear of a viscoelastic coating bonded to a rigid substrate is proposed. The fatigue mechanism is due to the cyclic interaction of the coating with a rough counterbody, which is modeled by a periodic system of smooth indenters. The study includes the solution of the problem of sliding contact of the indenter at a constant velocity along the viscoelastic coating, the calculation of stresses taking into account the mutual effect, and study of the process of damage accumulation in the material. The calculation of the damage function of the surface layer was carried out using the reduced stress criterion. Assuming the possibility of summation of accumulated damage, two processes were considered: delamination of surface layers of the coating and continuous fracture of the surface by the fatigue mechanism. The effect of the sliding velocity and viscoelastic properties of the material on the damage accumulation and the coating wear rate was analyzed. Two types of load, constant and stochastically varying, were used in modeling and analysis. It was found that the rate of fatigue wear of the coating increased and then became constant.
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Lim EJ, Sakong S, Son WS, Cho JW, Oh JK, Kim CH. Comparison of sliding distance of lag screw and nonunion rate according to anteromedial cortical support in intertrochanteric fracture fixation: A systematic review and meta-analysis. Injury 2021; 52:2787-94. [PMID: 34417003 DOI: 10.1016/j.injury.2021.08.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 07/07/2021] [Accepted: 08/05/2021] [Indexed: 02/02/2023]
Abstract
INTRODUCTION We compared the sliding distance of the lag screw, change in neck-shaft angle (NSA), and nonunion rates according to the anteromedial cortical support on anteroposterior (AP) and lateral view radiographs post intertrochanteric fracture reduction. MATERIAL AND METHODS In this systematic review and meta-analysis, MEDLINE, Embase, and Cochrane Library databases were searched systematically for studies published before September 26, 2020. We performed synthetic analyses of the amount of lag screw sliding, change in NSA, and incidence of nonunion following reduction of intertrochanteric fractures by extramedullary reduction (EMR), neutral reduction (NR), and intramedullary reduction (IMR). The combined data of EMR and NR comprised the non-IMR group. RESULTS Our study enrolled eight studies, representing 1,363 patients who underwent surgery for intertrochanteric fractures. A pooled analysis showed a larger sliding distance in the IMR group than in the non-IMR group (standard mean difference [SMD] = 1.47, 95% confidence interval [CI]: 0.73-2.20; P < 0.0001 and SMD = 1.27, 95% CI: 0.56-1.99; P = 0.0005, respectively) in both AP and lateral views. The pooled mean difference of change in NSA in the IMR group was -3.11° and differed significantly from that of the non-IMR group (95% CI: -4.07 to -2.16; P < 0.0001). In the lateral view, the nonunion rate was significantly higher in the IMR group than in the non-IMR group (odds ratio [OR] = 11.61; 95% CI, 3.32-40.62; P = 0.0001). In the subgroup analysis, the NR group showed a larger sliding distance than that of the EMR group in the AP view (SMD = 0.40, 95% CI: 0.04-0.76; P = 0.03); however, the reverse was true in the lateral view (SMD = 0.68, 95% CI: 0.38-0.97; P < 0.00001). CONCLUSION In the current meta-analysis, larger sliding distances, more varus in NSA, and higher nonunion rates were observed in the IMR group than the non-IMR group, in both AP and lateral views. However, in the comparison between EMR and NR, it was difficult to conclude which of them was the ideal reduction method because of inconsistent results.
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Liu P, Quan Y, Wan J, Yu L. Experimental Investigation on the Wear and Damage Behaviors of Machined Wheel-Rail Materials under Dry Sliding Conditions. Materials (Basel) 2021; 14:ma14030540. [PMID: 33498672 PMCID: PMC7866242 DOI: 10.3390/ma14030540] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/16/2021] [Accepted: 01/19/2021] [Indexed: 11/16/2022]
Abstract
Rail grinding and wheel turning can effectively remove surface defects and unevenness, which is a crucial process for the safe and smooth operation of trains. Machined surface integrity of wheel/rail materials significantly influences their tribological property. In this study, firstly, the rail blocks were ground via a cylindrical grinding machine, and the wheel rings were turned by a computer numerical control (CNC) lathe with varied parameters. Then, the sliding wear and damage characteristics of the machined wheel/rail samples under dry conditions were studied by virtue of a block-on-ring tribometer. The results show that the surface microhardness of the ground rail blocks is larger than that of wheel rings, while the surface roughness and the thickness of the subsurface plastic deformation layer (SPDL) of rail blocks are much smaller than those of wheel rings. After sliding, the surface microhardness of wheel/rail samples increases remarkably. The thickness of the SPDL, the wear loss, and the increase degree of surface microhardness of rail blocks are larger than those of wheel rings. Surface microhardness, roughness and the SPDL of the machined wheel/rail samples impose a combined influence on the anti-wear property, and the tribological pair with proper initial surface roughness and microhardness engenders the smallest amount of total wear loss.
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Drozd K, Walczak M, Szala M, Gancarczyk K. Tribological Behavior of AlCrSiN-Coated Tool Steel K340 Versus Popular Tool Steel Grades. Materials (Basel) 2020; 13:ma13214895. [PMID: 33142788 PMCID: PMC7662346 DOI: 10.3390/ma13214895] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/23/2020] [Accepted: 10/28/2020] [Indexed: 11/16/2022]
Abstract
The tribological performance of metalwork steel tools is of vital importance in both cold and hot working processes. One solution for improving metal tool life is the application of coatings. This paper investigates the differences in quantitative wear behavior and wear mechanisms between AlCrSiN-coated and bare steel K340 and five reference tool steels: X155CrVMo12-1, X37CrMoV5-1, X40CrMoV5-1, 40CrMnMo7 and 90MnCrV8. The investigated tool steels were heat-treated, while K340 was subjected to thermochemical treatment and then coated with an AlCrSiN hard film (K340/AlCrSiN). The hardness, chemical composition, phase structure and microstructure of steels K340 and K340/AlCrSiN were examined. Tribological tests were conducted using the ball-on-disc tester in compliance with the ASTM G99 standard. The tests were performed under dry unidirectional sliding conditions, using an Al2O3 ball as a counterbody. The wear factor and coefficient of friction were estimated and analyzed with respect to hardness and alloying composition of the materials under study. Scanning electron microscopy (SEM) observations were made to identify the sliding wear mechanisms of the analyzed tool steels and physical vapor deposition (PVD)- coated K340 steel. In contrast to the harsh abrasive–adhesive wear mechanism observed for uncoated tool steels, the abrasive wear dominates in case of the AlCrSiN. The deposited thin film effectively prevents the K340 substrate from harsh wear severe degradation. Moreover, thanks to the deposited coating, the K340/AlCrSiN sample has a coefficient of friction (COF) of 0.529 and a wear factor of K = 5.68 × 10−7 m3 N−1 m−1, while the COF of the reference tool steels ranges from 0.70 to 0.89 and their wear factor ranges from 1.68 × 10−5 to 3.67 × 10−5 m3 N−1 m−1. The AlCrSiN deposition reduces the wear of the K340 steel and improves its sliding properties, which makes it a promising method for prolonging the service life of metalwork tools.
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Affiliation(s)
- Kazimierz Drozd
- Department of Materials Engineering, Faculty of Mechanical Engineering, Lublin University of Technology, 20-618 Lublin, Poland; (K.D.); (M.W.)
| | - Mariusz Walczak
- Department of Materials Engineering, Faculty of Mechanical Engineering, Lublin University of Technology, 20-618 Lublin, Poland; (K.D.); (M.W.)
| | - Mirosław Szala
- Department of Materials Engineering, Faculty of Mechanical Engineering, Lublin University of Technology, 20-618 Lublin, Poland; (K.D.); (M.W.)
- Correspondence:
| | - Kamil Gancarczyk
- Department of Materials Science, Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, Powstancow Warszawy 12, 35-959 Rzeszow, Poland;
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16
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Kamagata K, Itoh Y, Subekti DRG. How p53 Molecules Solve the Target DNA Search Problem: A Review. Int J Mol Sci 2020; 21:E1031. [PMID: 32033163 PMCID: PMC7037437 DOI: 10.3390/ijms21031031] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/11/2020] [Accepted: 01/31/2020] [Indexed: 12/14/2022] Open
Abstract
Interactions between DNA and DNA-binding proteins play an important role in many essential cellular processes. A key function of the DNA-binding protein p53 is to search for and bind to target sites incorporated in genomic DNA, which triggers transcriptional regulation. How do p53 molecules achieve "rapid" and "accurate" target search in living cells? The search dynamics of p53 were expected to include 3D diffusion in solution, 1D diffusion along DNA, and intersegmental transfer between two different DNA strands. Single-molecule fluorescence microscopy enabled the tracking of p53 molecules on DNA and the characterization of these dynamics quantitatively. Recent intensive single-molecule studies of p53 succeeded in revealing each of these search dynamics. Here, we review these studies and discuss the target search mechanisms of p53.
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Affiliation(s)
- Kiyoto Kamagata
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Yuji Itoh
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Dwiky Rendra Graha Subekti
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; (Y.I.); (D.R.G.S.)
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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17
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Bodrug T, Wilson-Kubalek EM, Nithianantham S, Thompson AF, Alfieri A, Gaska I, Major J, Debs G, Inagaki S, Gutierrez P, Gheber L, McKenney RJ, Sindelar CV, Milligan R, Stumpff J, Rosenfeld SS, Forth ST, Al-Bassam J. The kinesin-5 tail domain directly modulates the mechanochemical cycle of the motor domain for anti-parallel microtubule sliding. eLife 2020; 9:e51131. [PMID: 31958056 PMCID: PMC7015671 DOI: 10.7554/elife.51131] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 01/16/2020] [Indexed: 12/29/2022] Open
Abstract
Kinesin-5 motors organize mitotic spindles by sliding apart microtubules. They are homotetramers with dimeric motor and tail domains at both ends of a bipolar minifilament. Here, we describe a regulatory mechanism involving direct binding between tail and motor domains and its fundamental role in microtubule sliding. Kinesin-5 tails decrease microtubule-stimulated ATP-hydrolysis by specifically engaging motor domains in the nucleotide-free or ADP states. Cryo-EM reveals that tail binding stabilizes an open motor domain ATP-active site. Full-length motors undergo slow motility and cluster together along microtubules, while tail-deleted motors exhibit rapid motility without clustering. The tail is critical for motors to zipper together two microtubules by generating substantial sliding forces. The tail is essential for mitotic spindle localization, which becomes severely reduced in tail-deleted motors. Our studies suggest a revised microtubule-sliding model, in which kinesin-5 tails stabilize motor domains in the microtubule-bound state by slowing ATP-binding, resulting in high-force production at both homotetramer ends.
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Affiliation(s)
- Tatyana Bodrug
- Department of Molecular and Cellular BiologyUniversity of California, DavisDavisUnited States
| | - Elizabeth M Wilson-Kubalek
- Department of Integrative Structural and Computational BiologyScripps Research InstituteLa JollaUnited States
| | - Stanley Nithianantham
- Department of Molecular and Cellular BiologyUniversity of California, DavisDavisUnited States
| | - Alex F Thompson
- Department of Molecular Physiology and BiophysicsUniversity of VermontBurlingtonUnited States
| | - April Alfieri
- Department of Biological SciencesRensselaer Polytechnic InstituteTroyUnited States
| | - Ignas Gaska
- Department of Biological SciencesRensselaer Polytechnic InstituteTroyUnited States
| | - Jennifer Major
- Department of Cancer BiologyLerner Research Institute, Cleveland ClinicLorainUnited States
- Department of PharmacologyMayo ClinicJacksonvilleUnited States
| | - Garrett Debs
- Department of Molecular Biophysics and BiochemistryYale UniversityNew HavenUnited States
| | - Sayaka Inagaki
- Department of PharmacologyMayo ClinicJacksonvilleUnited States
| | - Pedro Gutierrez
- Department of Molecular and Cellular BiologyUniversity of California, DavisDavisUnited States
| | - Larisa Gheber
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and TechnologyBen-Gurion University of the NegevNegevIsrael
| | - Richard J McKenney
- Department of Molecular and Cellular BiologyUniversity of California, DavisDavisUnited States
| | | | - Ronald Milligan
- Department of Integrative Structural and Computational BiologyScripps Research InstituteLa JollaUnited States
| | - Jason Stumpff
- Department of Molecular Physiology and BiophysicsUniversity of VermontBurlingtonUnited States
| | - Steven S Rosenfeld
- Department of Cancer BiologyLerner Research Institute, Cleveland ClinicLorainUnited States
- Department of PharmacologyMayo ClinicJacksonvilleUnited States
| | - Scott T Forth
- Department of Biological SciencesRensselaer Polytechnic InstituteTroyUnited States
| | - Jawdat Al-Bassam
- Department of Molecular and Cellular BiologyUniversity of California, DavisDavisUnited States
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18
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Bimbo J, Turco E, Ghazaei Ardakani M, Pozzi M, Salvietti G, Bo V, Malvezzi M, Prattichizzo D. Exploiting Robot Hand Compliance and Environmental Constraints for Edge Grasps. Front Robot AI 2019; 6:135. [PMID: 33501150 PMCID: PMC7805883 DOI: 10.3389/frobt.2019.00135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 11/21/2019] [Indexed: 12/01/2022] Open
Abstract
This paper presents a method to grasp objects that cannot be picked directly from a table, using a soft, underactuated hand. These grasps are achieved by dragging the object to the edge of a table, and grasping it from the protruding part, performing so-called slide-to-edge grasps. This type of approach, which uses the environment to facilitate the grasp, is named Environmental Constraint Exploitation (ECE), and has been shown to improve the robustness of grasps while reducing the planning effort. The paper proposes two strategies, namely Continuous Slide and Grasp and Pivot and Re-Grasp, that are designed to deal with different objects. In the first strategy, the hand is positioned over the object and assumed to stick to it during the sliding until the edge, where the fingers wrap around the object and pick it up. In the second strategy, instead, the sliding motion is performed using pivoting, and thus the object is allowed to rotate with respect to the hand that drags it toward the edge. Then, as soon as the object reaches the desired position, the hand detaches from the object and moves to grasp the object from the side. In both strategies, the hand positioning for grasping the object is implemented using a recently proposed functional model for soft hands, the closure signature, whereas the sliding motion on the table is executed by using a hybrid force-velocity controller. We conducted 320 grasping trials with 16 different objects using a soft hand attached to a collaborative robot arm. Experiments showed that the Continuous Slide and Grasp is more suitable for small objects (e.g., a credit card), whereas the Pivot and Re-Grasp performs better with larger objects (e.g., a big book). The gathered data were used to train a classifier that selects the most suitable strategy to use, according to the object size and weight. Implementing ECE strategies with soft hands is a first step toward their use in real-world scenarios, where the environment should be seen more as a help than as a hindrance.
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Affiliation(s)
- Joao Bimbo
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Enrico Turco
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy.,Department of Information Engineering, University of Pisa, Pisa, Italy
| | | | - Maria Pozzi
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy.,Department of Information Engineering and Mathematics, University of Siena, Siena, Italy
| | - Gionata Salvietti
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy.,Department of Information Engineering and Mathematics, University of Siena, Siena, Italy
| | - Valerio Bo
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Monica Malvezzi
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy.,Department of Information Engineering and Mathematics, University of Siena, Siena, Italy
| | - Domenico Prattichizzo
- Department of Advanced Robotics, Istituto Italiano di Tecnologia, Genoa, Italy.,Department of Information Engineering and Mathematics, University of Siena, Siena, Italy
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19
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Del Castillo U, Norkett R, Gelfand VI. Unconventional Roles of Cytoskeletal Mitotic Machinery in Neurodevelopment. Trends Cell Biol 2019; 29:901-911. [PMID: 31597609 DOI: 10.1016/j.tcb.2019.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 12/20/2022]
Abstract
At first look, cell division and neurite formation seem to be two different, essential biological processes. However, both processes require extensive reorganization of the cytoskeleton, and especially microtubules. Remarkably, in recent years, independent work from several groups has shown that multiple cytoskeletal components previously considered specific for the mitotic machinery play important roles in neurite initiation and extension. In this review article, we describe how several cytoplasmic and mitotic microtubule motors, components of mitotic kinetochores, and cortical actin participate in reorganization of the microtubule network required to form and maintain axons and dendrites. The emerging similarities between these two biological processes will certainly generate new insights into the mechanisms generating the unique morphology of neurons.
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Affiliation(s)
- Urko Del Castillo
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Rosalind Norkett
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Vladimir I Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
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20
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Chen ZH, Fang R, Li W, Guan J. Stretchable Transparent Conductors: from Micro/Macromechanics to Applications. Adv Mater 2019; 31:e1900756. [PMID: 31206898 DOI: 10.1002/adma.201900756] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/05/2019] [Indexed: 06/09/2023]
Abstract
Stretchable transparent conductors (STCs), generally consisting of conducting networks and stretchable transparent elastomers, can maintain stable conductivity and transparency even at large tensile strain, beyond the reach of rigid/flexible transparent conductors. They are essential components in stretchable/wearable electronics for using on irregular 3D conformable surfaces and have attracted tremendous attention in recent years. This review aims to provide systematical correlation of the conducting element-substrate interaction with the structural stability of conducting networks, as well as the properties and device applications of STCs. It starts with the micromechanics for stretching of conducting elements on substrates, including the mechanical mismatch, distribution/level of interfacial shear stress, and the deformation behavior of conducting elements on substrates. The macromechanics for stretching of conducting networks on substrates are then further illustrated from a more statistical point of view, namely sliding/preferred orientation of percolation networks, unfolding of buckled structures, and unit cell distortion/distributed rupture of nanomeshes. The structure-dependent properties as well as the state-of-the-art applications of STCs are summarized before ending with the conclusions and outlooks for STCs.
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Affiliation(s)
- Zhi Hong Chen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, P. R. China
- Department of Physics, School of Science, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Rui Fang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Wei Li
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, P. R. China
| | - Jianguo Guan
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, P. R. China
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21
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Lee AH, Elliott DM. Multi-Scale Loading and Damage Mechanisms of Plantaris and Rat Tail Tendons. J Orthop Res 2019; 37:1827-1837. [PMID: 30977538 PMCID: PMC6790141 DOI: 10.1002/jor.24309] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 02/21/2019] [Accepted: 03/13/2019] [Indexed: 02/04/2023]
Abstract
Tendinopathy, degeneration of the tendon that leads to pain and dysfunction, is common in both sports and occupational settings, but multi-scale mechanisms for tendinopathy are still unknown. We recently showed that micro-scale sliding (shear) is responsible for both load transfer and damage mechanisms in the rat tail tendon; however, the rat tail tendon is a specialized non-load-bearing tendon, and thus the load transfer and damage mechanisms are still unknown for load-bearing tendons. The objective of this study was to investigate the load transfer and damage mechanisms of load-bearing tendons using the rat plantaris tendon. We demonstrated that micro-scale sliding is a key component for both mechanisms in the plantaris tendon, similar to the tail tendon. Namely, the micro-scale sliding was correlated with applied strain, demonstrating that load was transferred via micro-scale sliding in the plantaris and tail tendons. In addition, while the micro-scale strain fully recovered, the micro-scale sliding was non-recoverable and strain-dependent, and correlated with tissue-scale mechanical parameters. When the applied strain was normalized, the % magnitudes of non-recoverable sliding was similar between the plantaris and tail tendons. Statement of clinical significance: Understanding the mechanisms responsible for the pathogenesis and progression of tendinopathy can improve prevention and rehabilitation strategies and guide therapies and the design of engineered constructs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1827-1837, 2019.
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Affiliation(s)
| | - Dawn M. Elliott
- Corresponding author: Tel.: +1 302 831 1295, Address: 161 Colburn Lab, 150 Academy Street, Newark, DE 19716, United States., (D.M. Elliott)
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22
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Zhao B, Xu H, Lu X. Sliding Interaction for Coated Asperity with Power-Law Hardening Elastic-Plastic Coatings. Materials (Basel) 2019; 12:ma12152388. [PMID: 31357455 PMCID: PMC6695790 DOI: 10.3390/ma12152388] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 07/11/2019] [Accepted: 07/25/2019] [Indexed: 11/16/2022]
Abstract
Sliding between asperities occurs inevitably in the friction pair, which affects the efficiency and reliability in both lubricated and non-lubricated conditions. In this work, the contact parameters in the coated asperity sliding process are studied, and the universal expressions of the average contact force and the friction coefficient are obtained. The effect of the interference between asperities, the material and geometrical parameters including the Young’s modulus ratio and yield strength ratio of the coating and substrate, and the hardening exponent and thickness of the coating on the average contact forces and friction coefficient is considered. It shows both normal and tangential contact forces increase with the increasing interference, increasing Young’s modulus ratio, decreasing yield strength ratio, and decreasing coating thickness; while the trend is different for the effect of the hardening exponent of the coating. The normal force increases and the tangential force decreases as the hardening exponent increases. Based on this, the influence of these parameters on the effective friction coefficient is obtained further. It reveals that the friction coefficient increases as the interference and Young’s modulus ratio enlarge and decreases as the yield strength ratio, the coating’s hardening exponent, and thickness increase. The universal expressions for the contact force and friction coefficient in the sliding process are obtained. This work might give some useful results to help choose the optimum coatings for specific substrates to reduce friction in cases where the asperity contact exists, especially in the focused field of the journal bearing in the marine engine under poor lubrication conditions.
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Affiliation(s)
- Bin Zhao
- College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China
| | - Hanzhang Xu
- College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China
| | - Xiqun Lu
- College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China.
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23
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Haraguchi Y, Kagawa Y, Kubo H, Shimizu T. Analysis of force vector field during centrifugation for optimizing cell sheet adhesion. Biotechnol Prog 2019; 35:e2857. [PMID: 31148395 DOI: 10.1002/btpr.2857] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 05/16/2019] [Accepted: 05/24/2019] [Indexed: 11/08/2022]
Abstract
A three-dimensional tissue was fabricated by layering cell sheets with centrifugation. In this system, an optimal centrifugal force promoted the adhesion between (a) a cell sheet and a culture dish, and (b) layered cell sheets, resulting in a significant decrease in the fabrication time of the tissue. However, negative effects like sliding/significant deformation of cell sheets were observed upon high rotational speed use. These negative effects inhibit the further shortening of the fabrication time. The sliding/deformation suggests that the centrifugal forces were applied on the cell sheets in unwanted directions. Studies on the force vector field applied to the object placed on the plate during centrifugation are not available, and thus, the reason for the occurrence of such negative effects is unclear. Here, we theoretically derived the spatial distribution of acceleration applied on a plate during centrifugation. Using this theory, we found that the negative effects were triggered by the centrifugal force in the direction parallel to the plate surface, which appeared due to an inclination of the plate surface against a horizontal plane. Therefore, by adding weights on the plate edge to maintain the plate surface in a horizontal position, we succeeded in eliminating the negative effects and in increasing the rotational speed, with the minimum risk of sliding/deformation of cell sheets. We succeeded in reducing the time to establish tight adhesion between a mouse myoblast sheet and a culture dish, and layered cell sheets by increasing the centrifugal force from 5 min to 1 min without significant cytotoxicity.
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Affiliation(s)
- Yuji Haraguchi
- Institute of Advanced Biomedical Engineering and Science, TWIns, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, Japan
| | - Yuki Kagawa
- Ogino Memorial Laboratory, Nihon Kohden Corporation, TWIns, Shinjuku-ku, Tokyo, Japan
| | - Hirotsugu Kubo
- Ogino Memorial Laboratory, Nihon Kohden Corporation, TWIns, Shinjuku-ku, Tokyo, Japan
| | - Tatsuya Shimizu
- Institute of Advanced Biomedical Engineering and Science, TWIns, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, Japan
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24
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Rasch J, Ünal CM, Klages A, Karsli Ü, Heinsohn N, Brouwer RMHJ, Richter M, Dellmann A, Steinert M. Peptidyl-Prolyl- cis/ trans-Isomerases Mip and PpiB of Legionella pneumophila Contribute to Surface Translocation, Growth at Suboptimal Temperature, and Infection. Infect Immun 2019; 87:e00939-17. [PMID: 30323027 DOI: 10.1128/IAI.00939-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 09/12/2018] [Indexed: 12/31/2022] Open
Abstract
The gammaproteobacterium Legionella pneumophila is the causative agent of Legionnaires' disease, an atypical pneumonia that manifests itself with severe lung damage. L. pneumophila, a common inhabitant of freshwater environments, replicates in free-living amoebae and persists in biofilms in natural and man-made water systems. Its environmental versatility is reflected in its ability to survive and grow within a broad temperature range as well as its capability to colonize and infect a wide range of hosts, including protozoa and humans. Peptidyl-prolyl-cis/trans-isomerases (PPIases) are multifunctional proteins that are mainly involved in protein folding and secretion in bacteria. In L. pneumophila the surface-associated PPIase Mip was shown to facilitate the establishment of the intracellular infection cycle in its early stages. The cytoplasmic PpiB was shown to promote cold tolerance. Here, we set out to analyze the interrelationship of these two relevant PPIases in the context of environmental fitness and infection. We demonstrate that the PPIases Mip and PpiB are important for surfactant-dependent sliding motility and adaptation to suboptimal temperatures, features that contribute to the environmental fitness of L. pneumophila Furthermore, they contribute to infection of the natural host Acanthamoeba castellanii as well as human macrophages and human explanted lung tissue. These effects were additive in the case of sliding motility or synergistic in the case of temperature tolerance and infection, as assessed by the behavior of the double mutant. Accordingly, we propose that Mip and PpiB are virulence modulators of L. pneumophila with compensatory action and pleiotropic effects.
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25
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Tweedie MEP, Sheng Y, Sarwat SG, Xu W, Bhaskaran H, Warner JH. Inhomogeneous Strain Release during Bending of WS 2 on Flexible Substrates. ACS Appl Mater Interfaces 2018; 10:39177-39186. [PMID: 30383356 DOI: 10.1021/acsami.8b12707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional (2D) materials hold great promise in flexible electronics, but the weak van der Waals interlayer bonding may pose a problem during bending, where easy interlayer sliding can occur. Furthermore, thin films of rigid materials are often observed to delaminate from soft substrates during straining. Here, we study the influence of substrate strain on some of the heterostructure configurations we expect to find in devices, composed of three common 2D materials: graphene, tungsten disulfide, and boron nitride. We used photoluminescence (PL) spectroscopy to measure changes in the heterostructures with strain applied in situ. All heterostructures were fabricated directly on polymer substrates, using materials synthesized by chemical vapor deposition. We observed an inhomogeneous release of strain in all structures, leading to a nonrecoverable broadening of the PL peak and shift of the bandgap. This suggests the need for preconditioning devices before service to ensure stable behavior. A gradual time-dependent relaxation of strain between strain cycles was characterized using time-dependent measurements-an effect which could lead to drift of device behavior during operation. Furthermore, possible degradation was assessed by performing the strain and relax the cycle up to 200 times, where we found little further change after the initial shifts had stabilized. These results have important ramifications for devices fabricated from these and other 2D materials, as they suggest extra processing steps and considerations that must be taken to achieve consistent and stable properties.
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Affiliation(s)
- Martin E P Tweedie
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Yuewen Sheng
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Syed Ghazi Sarwat
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Wenshuo Xu
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Harish Bhaskaran
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Jamie H Warner
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
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26
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Zhang S, Kai Y, Sunami Y. Tactile Sliding Behavior of R2R Mass-Produced PLLA Nanosheet towards Biomedical Device in Skin Applications. Nanomaterials (Basel) 2018; 8:nano8040210. [PMID: 29601509 PMCID: PMC5923540 DOI: 10.3390/nano8040210] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 03/27/2018] [Accepted: 03/29/2018] [Indexed: 12/20/2022]
Abstract
In this research, sliding friction was measured between the fingertip and nanosheet on a silicon substrate under two conditions: dry and wet. By using a force transducer, the tactile friction force and applied load were measured. According to the experimental results, the relationship of friction force and applied load exhibits a positive correlation under both dry and wet conditions. In addition, the nanosheets are able to reduce the friction force and coefficient of friction (COF) compared to the reference sample, especially under the wet condition. Under the assumption of a full contact condition, the estimated contact area increases with larger applied loads. Furthermore, based on the wear observation, the skin sliding performance caused slight abrasions to the surface of the nanosheet samples with a mild wear track along the sliding direction. Overall, the sliding behavior between the skin and nanosheet was investigated in terms of friction force, COF, applied load, contact area, and wear. These findings can contribute to the nanosheet-related research towards biomedical devices in skin applications.
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Affiliation(s)
- Sheng Zhang
- Micro/Nano Technology Center, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan.
| | - Yoshitomo Kai
- Course of Mechanical Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan.
| | - Yuta Sunami
- Micro/Nano Technology Center, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan.
- Department of Mechanical Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan.
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Mattingly AE, Weaver AA, Dimkovikj A, Shrout JD. Assessing Travel Conditions: Environmental and Host Influences On Bacterial Surface Motility. J Bacteriol 2018; 200:e00014-18. [PMID: 29555698 PMCID: PMC5952383 DOI: 10.1128/jb.00014-18] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The degree to which surface motile bacteria explore their surroundings is influenced by aspects of their local environment. Accordingly, regulation of surface motility is controlled by numerous chemical, physical, and biological stimuli. Discernment of such regulation due to these multiple cues is a formidable challenge. Additionally inherent ambiguity and variability from the assays used to assess surface motility can be an obstacle to clear delineation of regulated surface motility behavior. Numerous studies have reported single environmental determinants of microbial motility and lifestyle behavior but the translation of these data to understand surface motility and bacterial colonization of human host or environmental surfaces is unclear. Here, we describe the current state of the field and our understanding of exogenous factors that influence bacterial surface motility.
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Affiliation(s)
- Anne E. Mattingly
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Abigail A. Weaver
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Aleksandar Dimkovikj
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Joshua D. Shrout
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
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28
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Kato K, Nemoto K, Mayumi K, Yokoyama H, Ito K. Ductile Glass of Polyrotaxane Toughened by Stretch-Induced Intramolecular Phase Separation. ACS Appl Mater Interfaces 2017; 9:32436-32440. [PMID: 28915000 DOI: 10.1021/acsami.7b10845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A new class of ductile glasses is created from a thermoplastic polyrotaxane. The hard glass, which has a Young's modulus of 1 GPa, shows crazing, necking, and strain hardening with a total elongation of 330%. Stress concentration is prevented through a unique stretch-induced intramolecular phase separation of the cyclic components and the exposed backbone. In situ synchrotron X-ray scattering studies indicate that the backbone polymer chains slip through the cyclic components in the regions where the stress is concentrated.
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Affiliation(s)
- Kazuaki Kato
- Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
- Research Center for Structural Materials, National Institute for Materials Science , 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - Kaito Nemoto
- Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Koichi Mayumi
- Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Hideaki Yokoyama
- Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - Kohzo Ito
- Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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29
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Mhatre E, Sundaram A, Hölscher T, Mühlstädt M, Bossert J, Kovács ÁT. Presence of Calcium Lowers the Expansion of Bacillus subtilis Colony Biofilms. Microorganisms 2017; 5:E7. [PMID: 28212310 DOI: 10.3390/microorganisms5010007] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/02/2017] [Accepted: 02/08/2017] [Indexed: 11/17/2022] Open
Abstract
Robust colony formation by Bacillus subtilis is recognized as one of the sessile, multicellular lifestyles of this bacterium. Numerous pathways and genes are responsible for the architecturally complex colony structure development. Cells in the biofilm colony secrete extracellular polysaccharides (EPS) and protein components (TasA and the hydrophobin BslA) that hold them together and provide a protective hydrophobic shield. Cells also secrete surfactin with antimicrobial as well as surface tension reducing properties that aid cells to colonize the solid surface. Depending on the environmental conditions, these secreted components of the colony biofilm can also promote the flagellum-independent surface spreading of B. subtilis, called sliding. In this study, we emphasize the influence of Ca2+ in the medium on colony expansion of B. subtilis. Interestingly, the availability of Ca2+ has no major impact on the induction of complex colony morphology. However, in the absence of this divalent ion, peripheral cells of the colony expand radially at later stages of development, causing colony size to increase. We demonstrate that the secreted extracellular compounds, EPS, BslA, and surfactin facilitate colony expansion after biofilm maturation. We propose that Ca2+ hinders biofilm colony expansion by modifying the amphiphilic properties of surfactin.
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Hashiguchi K, Ueno M, Kuwayama T, Suzuki N, Yonemura S, Yoshikawa N. Constitutive equation of friction based on the subloading-surface concept. Proc Math Phys Eng Sci 2016; 472:20160212. [PMID: 27493570 PMCID: PMC4971246 DOI: 10.1098/rspa.2016.0212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The subloading-friction model is capable of describing static friction, the smooth transition from static to kinetic friction and the recovery to static friction after sliding stops or sliding velocity decreases. This causes a negative rate sensitivity (i.e. a decrease in friction resistance with increasing sliding velocity). A generalized subloading-friction model is formulated in this article by incorporating the concept of overstress for viscoplastic sliding velocity into the subloading-friction model to describe not only negative rate sensitivity but also positive rate sensitivity (i.e. an increase in friction resistance with increasing sliding velocity) at a general sliding velocity ranging from quasi-static to impact sliding. The validity of the model is verified by numerical experiments and comparisons with test data obtained from friction tests using a lubricated steel specimen.
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Affiliation(s)
- Koichi Hashiguchi
- MSC Software Ltd , Shinjuku First West 8F, 23-7 Nishishinjuku, 1-chome , Tokyo 160-0023, Japan
| | - Masami Ueno
- Department of Agricultural Engineering , University of the Ryukyus, 1 Senbaru , Nishihara, Okinawa 903-0213, Japan
| | - Takuya Kuwayama
- Steel Research Laboratories , Nippon Steel and Sumitomo Metal Corporation, 20-1 Shintomi , Futtsu, Chiba 293-8511, Japan
| | - Noriyuki Suzuki
- Steel Research Laboratories , Nippon Steel and Sumitomo Metal Corporation, 20-1 Shintomi , Futtsu, Chiba 293-8511, Japan
| | - Shigeru Yonemura
- Steel Research Laboratories , Nippon Steel and Sumitomo Metal Corporation, 20-1 Shintomi , Futtsu, Chiba 293-8511, Japan
| | - Nobuo Yoshikawa
- Steel Research Laboratories , Nippon Steel and Sumitomo Metal Corporation, 20-1 Shintomi , Futtsu, Chiba 293-8511, Japan
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31
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Kim K, Lee J. Reciprocal Sliding Friction Model for an Electro-Deposited Coating and Its Parameter Estimation Using Markov Chain Monte Carlo Method. Materials (Basel) 2016; 9:ma9040237. [PMID: 28773359 PMCID: PMC5502884 DOI: 10.3390/ma9040237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 03/18/2016] [Accepted: 03/23/2016] [Indexed: 11/17/2022]
Abstract
This paper describes a sliding friction model for an electro-deposited coating. Reciprocating sliding tests using ball-on-flat plate test apparatus are performed to determine an evolution of the kinetic friction coefficient. The evolution of the friction coefficient is classified into the initial running-in period, steady-state sliding, and transition to higher friction. The friction coefficient during the initial running-in period and steady-state sliding is expressed as a simple linear function. The friction coefficient in the transition to higher friction is described with a mathematical model derived from Kachanov-type damage law. The model parameters are then estimated using the Markov Chain Monte Carlo (MCMC) approach. It is identified that estimated friction coefficients obtained by MCMC approach are in good agreement with measured ones.
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Affiliation(s)
- Kyungmok Kim
- School of Aerospace and Mechanical Engineering, Korea Aerospace University, 76 Hanggongdaehang-ro, Deogyang-gu, Goyang-si, Gyeonggi-do 412-791, Korea.
| | - Jaewook Lee
- School of Aerospace and Mechanical Engineering, Korea Aerospace University, 76 Hanggongdaehang-ro, Deogyang-gu, Goyang-si, Gyeonggi-do 412-791, Korea.
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32
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Abstract
A recent study showed that Salmonella enterica serovar Typhimurium exhibits sliding motility under magnesium-limited conditions. Overall, bacteria that exhibit this passive surface movement described as sliding share few common traits. This discovery provides an opportunity to revisit and better characterize appendage-independent bacterial motility.
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Affiliation(s)
- Joshua D Shrout
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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33
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Koutmou KS, Schuller AP, Brunelle JL, Radhakrishnan A, Djuranovic S, Green R. Ribosomes slide on lysine-encoding homopolymeric A stretches. eLife 2015; 4:e05534. [PMID: 25695637 PMCID: PMC4363877 DOI: 10.7554/elife.05534] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 02/18/2015] [Indexed: 01/29/2023] Open
Abstract
Protein output from synonymous codons is thought to be equivalent if appropriate tRNAs are sufficiently abundant. Here we show that mRNAs encoding iterated lysine codons, AAA or AAG, differentially impact protein synthesis: insertion of iterated AAA codons into an ORF diminishes protein expression more than insertion of synonymous AAG codons. Kinetic studies in E. coli reveal that differential protein production results from pausing on consecutive AAA-lysines followed by ribosome sliding on homopolymeric A sequence. Translation in a cell-free expression system demonstrates that diminished output from AAA-codon-containing reporters results from premature translation termination on out of frame stop codons following ribosome sliding. In eukaryotes, these premature termination events target the mRNAs for Nonsense-Mediated-Decay (NMD). The finding that ribosomes slide on homopolymeric A sequences explains bioinformatic analyses indicating that consecutive AAA codons are under-represented in gene-coding sequences. Ribosome 'sliding' represents an unexpected type of ribosome movement possible during translation.
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Affiliation(s)
- Kristin S Koutmou
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, United States
| | - Anthony P Schuller
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, United States
| | - Julie L Brunelle
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, United States
- Howard Hughes Medical Institute, Johns Hopkins School of Medicine, Baltimore, United States
| | - Aditya Radhakrishnan
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, United States
| | - Sergej Djuranovic
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, United States
- Howard Hughes Medical Institute, Johns Hopkins School of Medicine, Baltimore, United States
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34
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Mahato A, Guo Y, Sundaram NK, Chandrasekar S. Surface folding in metals: a mechanism for delamination wear in sliding. Proc Math Phys Eng Sci 2014; 470:20140297. [PMID: 25197251 DOI: 10.1098/rspa.2014.0297] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 06/24/2014] [Indexed: 11/12/2022] Open
Abstract
Using high-resolution, in situ imaging of a hard, wedge-shaped model asperity sliding against a metal surface, we demonstrate a new mechanism for particle formation and delamination wear. Damage to the residual surface is caused by the occurrence of folds on the free surface of the prow-shaped region ahead of the wedge. This damage manifests itself as shallow crack-like features and surface tears, which are inclined at very acute angles to the surface. The transformation of folds into cracks, tears and particles is directly captured. Notably, a single sliding pass is sufficient to damage the surface, and subsequent passes result in the generation of platelet-like wear particles. Tracking the folding process at every stage from surface bumps to folds to cracks/tears/particles ensures that there is no ambiguity in capturing the mechanism of wear. Because fold formation and consequent delamination are quite general, our findings have broad applicability beyond wear itself, including implications for design of surface generation and conditioning processes.
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Affiliation(s)
- Anirban Mahato
- Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN 47907, USA
| | - Yang Guo
- M4 Sciences LLC , West Lafayette, IN 47907, USA
| | - Narayan K Sundaram
- Department of Civil Engineering , Indian Institute of Science , Bangalore, Karnataka 560012, India
| | - Srinivasan Chandrasekar
- Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN 47907, USA
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35
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Abstract
To better understand the role of surface roughness and tip geometry in the adhesion of gecko synthetic adhesives, a model is developed that attempts to uncover the relationship between surface feature size and the adhesive terminal feature shape. This model is the first to predict the adhesive behaviour of a plurality of hairs acting in shear on simulated rough surfaces using analytically derived contact models. The models showed that the nanoscale geometry of the tip shape alters the macroscale adhesion of the array of fibres by nearly an order of magnitude, and that on sinusoidal surfaces with amplitudes much larger than the nanoscale features, spatula-shaped features can increase adhesive forces by 2.5 times on smooth surfaces and 10 times on rough surfaces. Interestingly, the summation of the fibres acting in concert shows behaviour much more complex that what could be predicted with the pull-off model of a single fibre. Both the Johnson-Kendall-Roberts and Kendall peel models can explain the experimentally observed frictional adhesion effect previously described in the literature. Similar to experimental results recently reported on the macroscale features of the gecko adhesive system, adhesion drops dramatically when surface roughness exceeds the size and spacing of the adhesive fibrillar features.
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Affiliation(s)
- Andrew G Gillies
- Department of Mechanical Engineering, University of California, , Berkeley, CA 94720, USA
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36
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Abstract
Smooth contact pads that evolved in insects, amphibians and mammals to enhance the attachment abilities of the animals' feet are often dressed with surface micropatterns of different shapes that act in the presence of a fluid secretion. One of the most striking surface patterns observed in contact pads of these animals is based on a hexagonal texture, which is recognized as a friction-oriented feature capable of suppressing both stick-slip and hydroplaning while enabling friction tuning. Here, we compare this design of natural friction surfaces to textures developed for working in similar conditions in disposable safety razors. When slid against lubricated human skin, the hexagonal surface texture is capable of generating about twice the friction of its technical competitors, which is related to it being much more effective at channelling of the lubricant fluid out of the contact zone. The draining channel shape and contact area fraction are found to be the most important geometrical parameters governing the fluid drainage rate.
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Affiliation(s)
- Alexey Tsipenyuk
- Department of Mechanical Engineering, Technion, , Haifa 32000, Israel
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37
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Cantarella D, Lombardo L, Siciliani G. The dynforce archwire. Ann Stomatol (Roma) 2013; 4:204-11. [PMID: 23991272 PMCID: PMC3755796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This article is a presentation of a clinical methodology aimed at minimizing binding in fixed orthodontic appliances. The dynforce archwire is explained. The dynforce archwire has a full size anterior segment (e.g. .021×.025) and undersized posterior segments with rectangular cross-section (e.g. .018×.025 or .018×.022), and is used in the orthodontic phase of space closure with or without TAD miniscrews. Two clinical cases are presented.
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Affiliation(s)
| | - Luca Lombardo
- Postgraduate School of Orthodontics, Ferrara University, Italy
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38
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Abstract
Objectives: Frictional resistance is an important counterforce to orthodontic tooth movement during sliding mechanics. This study was carried out to evaluate the effect of different bracket-archwire-ligation combinations on “resistance to sliding” during simulated canine retraction on typodont model. Materials and Methods: the frictional resistance was tested between three modern orthodontic brackets-stainless steel, ceramic, and ceramic with metal slot (0.022-inch), and seven different archwires (0.019 × 0.025-inch)-stainless steel, nickel-titanium, Teflon coated stainless steel, stainless steel with the reverse curve of spee (RCS), Teflon coated stainless steel with RCS, Teflon coated nickel-titanium and nickel-titanium with RCS ligated with stainless steel ligature wire and regular clear elastomeric modules. All tests were carried out in a dry state on an Instron universal testing machine (crosshead speed: 0.5 mm/min). 10 measurements were made from each bracket-archwire-ligature combinations. Results: The highest mean frictional resistance was found in ceramic brackets with nickel-titanium RCS archwire ligated with elastomeric modules while minimum frictional resistance was found in stainless steel brackets with Teflon coated stainless steel archwire ligated with stainless steel ligature. Metal slot ceramic brackets generated significantly lower frictional forces than ceramic brackets, but higher values than stainless steel brackets. Teflon coated archwires shows highly significant reduction of the frictional resistance than their corresponding uncoated archwires. Archwires with RCS had the higher frictional resistance than normal counterpart archwires. Conclusion: Ceramic brackets with metal slot and Teflon coated SS archwires seem to be a good alternative to conventional stainless steel brackets and archwires in space closure with sliding mechanics in patients with esthetic demands.
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Affiliation(s)
- Ram Sukh
- Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India
| | - Gulshan K Singh
- Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India
| | - Pradeep Tandon
- Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India
| | - Gyan P Singh
- Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India
| | - Alka Singh
- Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India
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39
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Abstract
We introduce a probabilistic model for protein sliding motion along DNA during the search of a target sequence. The model accounts for possible effects due to sequence-dependent interaction between the nonspecific DNA and the protein. Hydrogen bonds formed at the target site are used as the main sequence-dependent interaction between protein and DNA. The resulting dynamical properties and the possibility of an experimental verification are discussed in details. We show that, while at large times the process reaches a linear diffusion regime, it initially displays a sub-diffusive behavior. The sub-diffusive regime can last sufficiently long to be of biological interest.
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Affiliation(s)
- Maria Barbi
- Dipartimento di Fisica "E.R. Caianiell" and INFM, Università di Salerno, Baronissi (SA), Italy ; Laboratoire de Physique Théorique des Liquides, Université Pierre et Marie Curie, case courrier 121, 4 Place Jussieu, 75252 Paris cedex 05, France
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40
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Honda H, Kikuchi K, Hatori K, Imai E, Shimada K, Matsuno K. Longitudinal distortions and transversal fluctuations of an actin filament sliding on Myosin molecules. J Biol Phys 2013; 28:359-65. [PMID: 23345781 DOI: 10.1023/a:1020304420132] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An actin filament sliding on myosin moleculesdemonstrates both longitudinal distortions and transversal fluctuationswith the linear dimension far exceeding the diameter of an actinmonomer. Local swaying of a single actin filament was identified byreading speckled fluorescent markers attached on the filament. Theaccuracy of reading each speckled marker was about 10.4 nm (r.m.s.).Longitudinal distortions of an actin filament at a low ATP concentrationof 20 μM were as much as 0.5 μm for the average filament lengthof 5.4 μm. The magnitude of transversal fluctuations was as much as60 nm, that was independent of the filament length. Both longitudinaldistortions and transversal fluctuations are suggested to play a pivotalrole for facilitating a smooth sliding movement of an actin filament.
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Affiliation(s)
- H Honda
- Department of BioEngineering, Nagaoka University of Technology, Nagaoka, 940-2188 Japan
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41
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Lin DS, Lian KJ, Hong JY, Ding ZQ, Zhai WL. Effects of a sliding plate on morphology of the epiphyseal plate in goat distal femur. Int J Med Sci 2012; 9:178-83. [PMID: 22359485 PMCID: PMC3283865 DOI: 10.7150/ijms.3610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Accepted: 01/18/2012] [Indexed: 11/29/2022] Open
Abstract
The aim of this study was to observe the effects of a sliding plate on the morphology of the epiphyseal plate in goat distal femur. Eighteen premature female goats were divided randomly into sliding plate, regular plate and control groups. Radiographic analysis and histological staining were performed to evaluate the development of epiphyseal plate at 4 and 8 weeks after surgery. In the sliding plate group, the plate extended accordingly as the epiphyseal plate grows, and the epiphyseal morphology was kept essential normal. However, the phenomenon of the epiphyseal growth retardation and premature closure were very common in the regular plate group. In addition, the sliding plate group exhibited more normal histologic features and Safranin O staining compared to the regular plate group. Our results suggest that the sliding plate can provide reliable internal fixation of epiphyseal fracture without inhibiting epiphyseal growth.
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Affiliation(s)
- Da-sheng Lin
- Department of Orthopaedic Surgery, the Affiliated Southeast Hospital of Xiamen University, Orthopaedic Center of People's Liberation Army, Zhangzhou 363000, China
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42
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Abstract
While an extensive body of knowledge has accumulated on the structures of transcription factors, DNA and their complexes from both NMR and crystallography, much less is known at a molecular level regarding the mechanisms whereby transcription factors locate their specific DNA target site within an overwhelming sea of non-specific DNA sites. Indirect kinetic data suggested that three processes are involved in the search procedure: jumping by dissociation of the protein from the DNA followed by re-association at another site, direct transfer from one DNA molecule or segment to another, and one-dimensional sliding. In this brief perspective I summarize recent NMR developments from our laboratory that have permitted direct characterization of the species and molecular mechanisms involved in the target search process, including the detection of highly transient sparsely-populated states. The main tool in these studies involves the application of paramagnetic relaxation enhancement, supplemented by z-exchange spectroscopy, lineshape analysis and residual dipolar couplings. These studies led to the first direct demonstration of rotation-coupled sliding of a protein along the DNA and the direct transfer of a protein from one DNA molecule to another without dissociating into free solution.
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Affiliation(s)
- G Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 02892-0520, USA.
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43
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Abstract
The structures of a number of processive enzymes have been determined recently. These proteins remain attached to their polymeric substrates and may perform thousands of rounds of catalysis before dissociating. Based on the degree of enclosure of the substrate, the structures fall into two broad categories. In one group, the substrate is partially enclosed, while in the other class, enclosure is complete. In the latter case, enclosure is achieved by way of an asymmetric structure for some enzymes while others use a symmetrical toroid. In those cases where the protein completely encloses its polymeric substrate, the two are topologically linked and an immediate explanation for processivity is provided. In cases where there is only partial enclosure, the structural basis for processivity is less obvious. There are, for example, pairs of proteins that have quite similar structures but differ substantially in their processivity. It does appear, however, that the enzymes that are processive tend to be those that more completely enclose their substrates. In general terms, proteins that do not use topological restraint appear to achieve processivity by using a large interaction surface. This allows the enzyme to bind with moderate affinity at a multitude of adjacent sites distributed along its polymeric substrate. At the same time, the use of a large interaction surface minimizes the possibility that the enzyme might bind at a small number of sites with much higher affinity, which would interfere with sliding. Proteins that can both slide along a polymeric substrate, and, as well, recognize highly specific sites (e.g., some site-specific DNA-binding proteins) appear to undergo a conformational change between the cognate and noncognate-binding modes.
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Affiliation(s)
- W A Breyer
- Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, Oregon 97403-1229, USA
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