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1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2262-2265, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018458

RESUMO

Cardiac muscle cells are the fundamental building blocks of the heart, yet little is known about their mechanical properties in either healthy or diseased states. While many have explored unloaded myocyte behavior under a variety of interventions, methods for force measurements are limited due to cell fragility. Here, we present a custom device for manipulation and mechanical testing of hydrogels embedded with delicate cardiac muscle cells. Consisting of a custom disposable flexure, which is easily interchangeable, the device has the potential for high throughput testing of cell-gel constructs. Additionally, the mechanical testing device is the size of a microscope slide - appropriate for use in most microscopes, for simultaneous imaging of the sample. The mechanical properties of a gelatin-methacryloyl hydrogel sample were assessed, and 3D volumes of gel imaged using a confocal microscope. The Young's modulus of the gel was found to be 33kPa.Clinical Relevance- High-throughput testing provides the potential to gain insight into cardiac cell mechanics. Experimentation under the influence of a variety of pharmacological interventions could improve the rate at which treatments for cardiac disease are developed. Furthermore, methods may be extended to other embedded biological tissues.


Assuntos
Materiais Biocompatíveis , Hidrogéis , Gelatina , Fenômenos Mecânicos , Tecidos Suporte
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3388-3392, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018731

RESUMO

This paper reports on the customized thinning of neural probes based on silicon (Si) using deep reactive ion etching (DRIE) as a post-processing step. The reduced probe dimensions are expected to minimize local tissue trauma, while guaranteeing probe integrity during implantation. For DRIE, the probes are partially masked by a micromachined Si cover chip comprising tailored cavities enabling any desired thinned length l and probe thickness t by a proper choice of cover chip design and DRIE parameters, respectively. A broad variety of probe designs were realized with shank tip thicknesses ranging from 35 µm down to 2 µm. All probes could successfully be implanted into a brain tissue phantom, demonstrating a pronounced reduction in insertion force from 0.55 mN for unprocessed probes to 0.08 mN for 2-µm-thin shanks. When the dura mater was mimicked by a polyethylene (PE) membrane, forces were reduced from 28.9 mN to 16.6 mN for 15-µm-thin shanks.


Assuntos
Fenômenos Mecânicos , Silício , Encéfalo , Dura-Máter , Íons
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 5248-5251, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019168

RESUMO

In the present study, a sensor-free force control framework for tendon-driven steerable catheters was proposed and validated. The hypothesis of this study was that the contact force between the catheter tip and the tissue could be controlled using the estimated force with a previously validated displacement-based viscoelastic tissue model. The tissue model was used in a feedback control loop. The model estimated the contact force based on a realtime estimation of catheter-tissue indentation depth performed by a data-driven inverse kinematic model. To test the hypothesis, a tendon-driven catheter (φ6 × 40mm) and a robotic catheter intervention system were prototyped and characterized. Three validation studies were performed to test the performance of the proposed system with static and dynamic inputs. The results showed that the system was capable of reaching to the desired force with a root-mean-square error of 0.03 ± 0.02N for static tests and 0.05 ± 0.04N for dynamic inputs. The main contribution of this study was providing a computationally efficient and sensor-free force control schema for tendon-driven catheters.


Assuntos
Ablação por Cateter , Cateteres , Desenho de Equipamento , Fenômenos Mecânicos , Tendões
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 984-987, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018150

RESUMO

This paper presents a signal analysis approach to identify the contact objects at the tip of a flexible ureteroscope. First, a miniature triaxial fiber optic sensor based on Fiber Bragg Grating(FBG) is devised to measure the interactive force signals at the ureteroscope tip. Due to the multidimensional properties of these force signals, the principal components analysis(PCA) method is introduced to reduce dimensions. The signal features are then extracted from the representative principal component signals using the wavelet transform(WT) method. Experimental results show that the contact objects at the tip of a ureteroscope are readily discriminated from the measured force signals with the proposed approach.Clinical Relevance-This work commits to analyze the contact force signals at the tip of a flexible ureteroscope for the purpose of contact objects identification.


Assuntos
Fenômenos Mecânicos , Ureteroscópios , Tecnologia de Fibra Óptica , Fenômenos Físicos , Análise de Ondaletas
7.
Nat Commun ; 11(1): 4032, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32788575

RESUMO

Hydrogel-based devices are widely used as flexible electronics, biosensors, soft robots, and intelligent human-machine interfaces. In these applications, high stretchability, low hysteresis, and anti-fatigue fracture are essential but can be rarely met in the same hydrogels simultaneously. Here, we demonstrate a hydrogel design using tandem-repeat proteins as the cross-linkers and random coiled polymers as the percolating network. Such a design allows the polyprotein cross-linkers only to experience considerable forces at the fracture zone and unfold to prevent crack propagation. Thus, we are able to decouple the hysteresis-toughness correlation and create hydrogels of high stretchability (~1100%), low hysteresis (< 5%), and high fracture toughness (~900 J m-2). Moreover, the hydrogels show a high fatigue threshold of ~126 J m-2 and can undergo 5000 load-unload cycles up to 500% strain without noticeable mechanical changes. Our study provides a general route to decouple network elasticity and local mechanical response in synthetic hydrogels.


Assuntos
Reagentes para Ligações Cruzadas/química , Hidrogéis/química , Poliproteínas/química , Estresse Mecânico , Resinas Acrílicas/química , Fluorescência , Fenômenos Mecânicos
8.
Nat Commun ; 11(1): 4321, 2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32859904

RESUMO

Bacterial colonization of the human intestine requires firm adhesion of bacteria to insoluble substrates under hydrodynamic flow. Here we report the molecular mechanism behind an ultrastable protein complex responsible for resisting shear forces and adhering bacteria to cellulose fibers in the human gut. Using single-molecule force spectroscopy (SMFS), single-molecule FRET (smFRET), and molecular dynamics (MD) simulations, we resolve two binding modes and three unbinding reaction pathways of a mechanically ultrastable R. champanellensis (Rc) Dockerin:Cohesin (Doc:Coh) complex. The complex assembles in two discrete binding modes with significantly different mechanical properties, with one breaking at ~500 pN and the other at ~200 pN at loading rates from 1-100 nN s-1. A neighboring X-module domain allosterically regulates the binding interaction and inhibits one of the low-force pathways at high loading rates, giving rise to a catch bonding mechanism that manifests under force ramp protocols. Multi-state Monte Carlo simulations show strong agreement with experimental results, validating the proposed kinetic scheme. These results explain mechanistically how gut microbes regulate cell adhesion strength at high shear stress through intricate molecular mechanisms including dual-binding modes, mechanical allostery and catch bonds.


Assuntos
Aderência Bacteriana/fisiologia , Microbioma Gastrointestinal/fisiologia , Fenômenos Mecânicos , Fenômenos Físicos , Bactérias , Aderência Bacteriana/genética , Proteínas de Ciclo Celular , Proteínas Cromossômicas não Histona , Trato Gastrointestinal/microbiologia , Técnicas de Inativação de Genes , Humanos , Cinética , Simulação de Dinâmica Molecular , Método de Monte Carlo , Ligação Proteica , Conformação Proteica , Imagem Individual de Molécula , Estresse Mecânico
9.
PLoS One ; 15(8): e0237382, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32817709

RESUMO

BACKGROUND: Pes planus (flatfoot) is a common deformity characterized by the midfoot arch collapses during walking. As the midfoot is responsible for shock absorption, persons with flatfoot experience increased risk of injuries such as thumb valgus, tendinitis, plantar fasciitis, metatarsal pain, knee pain, lower-back pain with prolonged uphill, downhill, and level walking, depriving them of the physical and mental health benefits of walking as an exercise. METHODS: Fifteen female college students with flatfoot were recruited. A wireless plantar-pressure system was used to measure the stance time, cadence, plantar pressure, and contact area. Parameters were compared between wearing flat and arch-support insoles using a two-way repeated measures ANOVA with on an incline, decline, and level surface, respectively. The significance level α was set to 0.05. The effect size (ES) was calculated as a measure of the practical relevance of the significance using Cohen's d. RESULTS: On the level surface, the stance time in the arch-support insole was significantly shorter than in the flat insole (p<0.05; ES = 0.48). The peak pressure of the big toe in the arch-support insole was significantly greater than in the flat insole on the uphill (p<0.05; ES = 0.53) and level surfaces (p<0.05; ES = 0.71). The peak pressure of the metatarsals 2-4 and the contact area of the midfoot in the arch-support insole were significantly greater than in the flat insole on all surfaces (all p< 0.05). CONCLUSIONS: These results imply that wearing an arch-support insole provides benefits in the shortened stance time and generation of propulsion force to the big toe while walking on uphill and level surfaces and to the metatarsals 2-4 while walking on the level surface. More evenly distributed contact areas across the midfoot may help absorb shock during uphill, downhill and level walking.


Assuntos
Pé Chato/fisiopatologia , Órtoses do Pé , Fenômenos Mecânicos , Pressão , Adulto , Desenho de Equipamento , Feminino , Humanos , Fatores de Tempo , Caminhada
10.
PLoS One ; 15(8): e0235229, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32797117

RESUMO

With desirable physical performances of impressive actuation strain, high energy density, high degree of electromechanical coupling and high mechanical compliance, dielectric elastomer actuators (DEAs) are widely employed to actuate the soft robots. However, there are many challenges to establish the dynamic models for DEAs, such as their inherent nonlinearity, complex electromechanical coupling, and time-dependent viscoelastic behavior. Moreover, most previous studies concentrated on the planar DEAs, but the studies on DEAs with some other functional shapes are insufficient. In this paper, by investigating a conical DEA with the material of polydimethylsiloxane and considering the influence of inertia, we propose a dynamic model based on the principles of nonequilibrium thermodynamics. This dynamic model can describe the complex motion characteristics of the conical DEA. Based on the experimental data, the differential evolution algorithm is employed to identify the undetermined parameters of the developed dynamic model. The result of the model validation demonstrates the effectiveness of the model.


Assuntos
Dimetilpolisiloxanos/química , Elastômeros/química , Simulação de Dinâmica Molecular , Eletricidade , Fenômenos Mecânicos
11.
AAPS PharmSciTech ; 21(6): 230, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32779033

RESUMO

The vaginal rings research is almost exclusively focused on rings for human medicine, although the dosage form offers improvement of therapeutic effect in other mammals as well. This contribution studied an effect of varying dimension parameters (diameter 20, 30 or 40 mm; height 3, 4 or 5 mm; width of annulus 5, 7.5 or 10 mm) on mechanical properties and dissolution behaviour of silicone vaginal rings with constant drug amount, intended for use in dogs. Results showed that altering dimensions influenced mechanical properties (compressive force, tensile strength and resistance of removal thread), in vitro drug release and water uptake. The removal thread resistance was increasing with increasing height and width. Compression force was higher for the rings with smaller diameter. The total drug release was increasing with decreasing height and rising diameter, surface area and water uptake during dissolution test. The initial dissolution rate was slower for the rings with higher width. As the best candidate for use in model dog subjects, the ring with 30 mm diameter, 3 mm height and 7.5 mm width was found. These drug-free vaginal rings were further tested in in vivo safety study. The results did not show any major deviation from the physiological conditions. Graphical abstract.


Assuntos
Dispositivos Anticoncepcionais Femininos , Animais , Cães , Liberação Controlada de Fármacos , Feminino , Fenômenos Mecânicos , Solubilidade , Resistência à Tração , Testes de Toxicidade
12.
PLoS One ; 15(8): e0237379, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32780753

RESUMO

This paper provides a solution for fast haptic information gain during soft tissue palpation using a Variable Lever Mechanism (VLM) probe. More specifically, we investigate the impact of stiffness variation of the probe to condition likelihood functions of the kinesthetic force and tactile sensors measurements during a palpation task for two sweeping directions. Using knowledge obtained from past probing trials or Finite Element (FE) simulations, we implemented this likelihood conditioning in an autonomous palpation control strategy. Based on a recursive Bayesian inferencing framework, this new control strategy adapts the sweeping direction and the stiffness of the probe to detect abnormal stiff inclusions in soft tissues. This original control strategy for compliant palpation probes shows a sub-millimeter accuracy for the 3D localization of the nodules in a soft tissue phantom as well as a 100% reliability detecting the existence of nodules in a soft phantom.


Assuntos
Fenômenos Mecânicos , Palpação , Percepção do Tato , Algoritmos , Fenômenos Biomecânicos , Análise de Elementos Finitos , Imagens de Fantasmas
13.
PLoS One ; 15(8): e0237841, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32813733

RESUMO

To function effectively, a lower limb prosthetic socket must remain securely coupled to the residual limb during walking, running and other activities of daily living; this coupling is referred to as suspension. When this coupling is insufficient longitudinal pistoning of the socket relative to the residual limb occurs. Increasing friction of the socket/liner interface may improve socket suspension and textured sockets may be fabricated relatively easily with 3D printing. The aim of this study was to investigate longitudinal displacement of sockets with different types of textures under two suspension conditions: passive suction and active vacuum. In order to do this, we developed a mock residual limb and mechanical testing protocol. Prosthetic sockets, 14 textured sockets and an Original Squirt-Shape (OSS) Socket, were fabricated from polypropylene copolymer using the Squirt-Shape™ 3D Printer and compared to a smooth socket thermoformed from polypropylene copolymer. Sockets were mounted onto a dual durometer mock residual limb and subjected to four levels of distraction forces (100 N, 250 N, 500 N and 650 N) using a hydraulic material testing system. There was a statistically significant three-way interaction between suspension, force level and texture (p < 0.0005). Longitudinal displacements between textured and reference sockets, for all force levels and both suspension conditions, were significantly different (p < 0.0005). Using these newly developed mechanical testing protocols, it was demonstrated that texturing of polypropylene copolymer sockets fabricated using Squirt-Shape significantly decreased longitudinal displacements compared to a smooth socket. However, none of the novel textured sockets significantly reduced longitudinal displacement compared to the OSS socket under passive suction suspension.


Assuntos
Extremidade Inferior/fisiologia , Teste de Materiais , Fenômenos Mecânicos , Desenho de Prótese , Processamento de Imagem Assistida por Computador , Sucção , Vácuo
14.
PLoS One ; 15(8): e0238074, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853254

RESUMO

To reduce the incidence of safety accidents during the construction of all-steel-type attached lifting scaffolds and address the research gaps in related fields, in this study a theoretical model of trajectory crossing accidents was coupled with an analysis of similar safety accidents to determine the causes of accidents in the construction of high-rise buildings using steel-type attached lifting scaffolds. To do so, a safety evaluation index system covering all steel-type attached lifting scaffolds that comprises five first-level indicators and 17 second-level indicators was established. The first-level indicators cover three risk dimensions: unsafe human behavior (personal operations), unsafe conditions (material performance, structural calculation, components and connections), and lack of management (safety management). A combined multi-agent-based modeling (MABM) method and structural entropy weight were used to calculate a comprehensive weight for better alignment of the weight calculation results with objective laws. A safety assessment model for an all-steel-type attached lifting scaffolding was constructed using grey relative Euclidean weighted correlation theory to enable the calculation of a grey-to-Euclidean weighted correlation degree that directly correlates with the degree of security. Using the established assessment model, four projects were subjected to a safety evaluation, with the results validating the model by revealing that its output was consistent with the actual security situation.


Assuntos
Materiais de Construção , Modelos Teóricos , Segurança , Aço , Fenômenos Mecânicos
15.
Nat Commun ; 11(1): 4000, 2020 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778657

RESUMO

Additive manufacturing permits innovative soft device architectures with micron resolution. The processing requirements, however, restrict the available materials, and joining chemically dissimilar components remains a challenge. Here we report silicone double networks (SilDNs) that participate in orthogonal crosslinking mechanisms-photocurable thiol-ene reactions and condensation reactions-to exercise independent control over both the shape forming process (3D printing) and final mechanical properties. SilDNs simultaneously possess low elastic modulus (E100% < 700kPa) as well as large ultimate strains (dL/L0 up to ~ 400 %), toughnesses (U ~ 1.4 MJ·m-3), and strengths (σ ~ 1 MPa). Importantly, the latent condensation reaction permits cohesive bonding of printed objects to dissimilar substrates with modulus gradients that span more than seven orders of magnitude. We demonstrate soft devices relevant to a broad range of disciplines: models that simulate the geometries and mechanical properties of soft tissue systems and multimaterial assemblies for next generation wearable devices and robotics.


Assuntos
Teste de Materiais , Impressão Tridimensional , Silicones/química , Tecnologia Biomédica , Módulo de Elasticidade , Fenômenos Mecânicos , Polímeros , Reologia , Robótica , Resistência à Tração , Fatores de Tempo , Dispositivos Eletrônicos Vestíveis
16.
Nat Commun ; 11(1): 3880, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32759942

RESUMO

Geological sources of H2 and abiotic CH4 have had a critical role in the evolution of our planet and the development of life and sustainability of the deep subsurface biosphere. Yet the origins of these sources are largely unconstrained. Hydration of mantle rocks, or serpentinization, is widely recognized to produce H2 and favour the abiotic genesis of CH4 in shallow settings. However, deeper sources of H2 and abiotic CH4 are missing from current models, which mainly invoke more oxidized fluids at convergent margins. Here we combine data from exhumed subduction zone high-pressure rocks and thermodynamic modelling to show that deep serpentinization (40-80 km) generates significant amounts of H2 and abiotic CH4, as well as H2S and NH3. Our results suggest that subduction, worldwide, hosts large sources of deep H2 and abiotic CH4, potentially providing energy to the overlying subsurface biosphere in the forearc regions of convergent margins.


Assuntos
Ecossistema , Hidrogênio/química , Metano/química , Minerais/química , Compostos Orgânicos/química , Termodinâmica , Amônia/química , Fenômenos Químicos , Fenômenos Geológicos , Sulfeto de Hidrogênio/química , Fenômenos Mecânicos , Fenômenos de Química Orgânica , Alcaloides de Triptamina e Secologanina/química , Erupções Vulcânicas
17.
PLoS One ; 15(8): e0237039, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32776956

RESUMO

The deformation law for axisymmetric deformation during the drawing of a core filled tube (CORFT) has been studied. However, the results of such studies could not be used in the flat rolling process of the CORFT, which is a plan deformation condition. In this paper, the inner core material and outer steel tube were successively analyzed based on the slab method during the flat rolling process (plan deformation) of the CORFT, and equations for wall thickness, core density, and roll force have been developed. The theoretical results solved by the developed equations were compared with the experimental results, revealing adequate accuracy for engineering requirements. The influences of rolling parameters on the roll force and the ultimate value of the relative density of the core material were studied, and the limiting condition for a larger roll force or higher value for relative density was obtained.


Assuntos
Aço/química , Força Compressiva , Simulação por Computador , Materiais de Construção , Manufaturas , Fenômenos Mecânicos , Resistência à Tração
18.
Nat Commun ; 11(1): 3541, 2020 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-32669562

RESUMO

Dynamic spatiotemporal patterns that arise from out-of-equilibrium biochemical reactions generate forces in living cells. Despite considerable recent efforts, rational design of spatiotemporal patterns in artificial molecular systems remains at an early stage of development. Here, we describe force generation by a propagating wave of supramolecular nanofibers. Inspired by actin dynamics, a reaction network is designed to control the formation and degradation of nanofibers by two chemically orthogonal stimuli. Real-time fluorescent imaging successfully visualizes the propagating wave based on spatiotemporally coupled generation and collapse of nanofibers. Numerical simulation indicates that the concentration gradient of degradation stimulus and the smaller diffusion coefficient of the nanofiber are critical for wave emergence. Moreover, the force (0.005 pN) generated by chemophoresis and/or depletion force of this propagating wave can move nanobeads along the wave direction.


Assuntos
Modelos Químicos , Nanofibras/química , Hidrogéis/química , Cinética , Fenômenos Mecânicos , Estrutura Molecular , Nanofibras/ultraestrutura , Espectroscopia de Prótons por Ressonância Magnética
19.
PLoS Genet ; 16(7): e1008884, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32639996

RESUMO

The membrane protein ANKH was known to prevent pathological mineralization of joints and was thought to export pyrophosphate (PPi) from cells. This did not explain, however, the presence of ANKH in tissues, such as brain, blood vessels and muscle. We now report that in cultured cells ANKH exports ATP, rather than PPi, and, unexpectedly, also citrate as a prominent metabolite. The extracellular ATP is rapidly converted into PPi, explaining the role of ANKH in preventing ankylosis. Mice lacking functional Ank (Ankank/ank mice) had plasma citrate concentrations that were 65% lower than those detected in wild type control animals. Consequently, citrate excretion via the urine was substantially reduced in Ankank/ank mice. Citrate was even undetectable in the urine of a human patient lacking functional ANKH. The hydroxyapatite of Ankank/ank mice contained dramatically reduced levels of both, citrate and PPi and displayed diminished strength. Our results show that ANKH is a critical contributor to extracellular citrate and PPi homeostasis and profoundly affects bone matrix composition and, consequently, bone quality.


Assuntos
Osso e Ossos/metabolismo , Calcinose/genética , Ácido Cítrico/metabolismo , Proteínas de Transporte de Fosfato/genética , Trifosfato de Adenosina/metabolismo , Animais , Desenvolvimento Ósseo/genética , Calcinose/metabolismo , Calcinose/patologia , Diferenciação Celular , Células Cultivadas , Difosfatos/metabolismo , Humanos , Fenômenos Mecânicos , Camundongos , Mutação/genética , Proteínas de Transporte de Fosfato/metabolismo
20.
PLoS One ; 15(7): e0234071, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32667926

RESUMO

The objective is to study the design method of roadway support and provide technical support for coal mining and other mining methods that need deep roadway excavation. Through literature review, the occurrence, development mechanism and influencing factors of surrounding loose rock zones of roadways are analyzed. A method of detecting is selected according to the characteristics of surrounding rock loosening. Knowledge of elastoplastic mechanics is used to theoretically study the failure mechanism of surrounding rock in deep re-mining roadways. Based on the artificial neural network prediction model (ANN), the surrounding rock is classified and a support network model of the decision system is constructed. After the design of roadway support, a sharp change of vault subsidence normally occurs within about 7 days after excavation, and the total subsidence is 14 mm. In the following month, deformation is slow, subsidence is small, and it is basically stable after one month. The curve of the vault subsidence rate shows that the vault subsidence rate is less than or equal to 1mm/d after 7 days. The convergence rate is also less than 1 mm/d after 7 days. There are two cave mouths AB and CD, and the convergence value of AB is 6.47mm, CD is 10.26mm: CD is slightly larger than AB, and it is close to stable one month later. It is essentially consistent with the time of vault settlement and stability, and the amount of deformation is approximately the same. This shows that, with the advance of the working face, the displacement of the surrounding rock in the section away from the working face will gradually decrease and the surrounding rock will be stable. The stability time of surrounding rock displacement of the portal section is the same as that of vault subsidence under the initial support, and the amount of deformation is approximately the same, indicating that the support parameters and construction methods are reasonable.


Assuntos
Minas de Carvão , Técnicas de Apoio para a Decisão , Aprendizado Profundo , Engenharia/métodos , Fenômenos Geológicos , Deslizamentos de Terra , Elasticidade , Fenômenos Mecânicos , Maleabilidade
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