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1.
Texto & contexto enferm ; 29: e20180515, Jan.-Dec. 2020. tab
Artigo em Inglês | LILACS, BDENF - Enfermagem | ID: biblio-1059152

RESUMO

ABSTRACT Objective: to analyze the prevalence of friction injuries and associated factors in the elderly admitted to the Intensive Care Unit. Method: a cross-sectional analytical study, developed in an Intensive Care Unit of a Teaching hospital, with a sample of 101 elderly. Data collection was conducted from November 2017 to May 2018, through interviews, consulting medical records and physical examination. For analysis, descriptive and inferential statistics were performed. Strength of associations between variables measured by odds ratio and 95% confidence intervals. Statistical significance level was set at 5% for all analyzes. Results: the sample studied had a mean age of 71.39 years, mostly male, married and without schooling, with more than one comorbidity, dependent, with dry and scaly skin and bruising on the extremities. The prevalence of friction injury was 28.7%, with an average of 1.93 injuries per elderly. There was a statistically significant association between the occurrence of friction injury with age, comorbidities, dry and scaly skin. Conclusion: the prevalence of friction injury was high and associated with age, comorbidities, dry and scaly skin, and mean duration of corticosteroid use.


RESUMEN Objetivo: analizar la prevalencia de lesiones por fricción y los factores asociados en los ancianos ingresados en la Unidad de Terapia Intensiva. Método: estudio transversal y analítico, desarrollado en una Unidad de terapia intensiva de un hospital universitario, con una muestra de 101 ancianos. La recolección de datos se realizó de noviembre de 2017 a mayo de 2018, mediante entrevistas, consulta de registros médicos y examen físico. Para el análisis, se realizaron estadísticas descriptivas e inferenciales. Fuerza de las asociaciones entre variables medidas por odds ratio e intervalos de confianza del 95%. Nivel de significación estadística establecido en 5% para todos los análisis. Resultados: la muestra estudiada tenía una edad media de 71.39 años, en su mayoría hombres, casados y sin educación, con más de una comorbilidad, dependiente, con piel seca y con descamación y hematomas en las extremidades. La prevalencia de lesiones por fricción fue del 28,7%, un promedio de 1,93 lesiones por ancianos. Hubo una asociación estadísticamente significativa entre la aparición de lesiones por fricción con la edad, comorbilidades, piel seca y descamación. Conclusión: la prevalencia de lesiones por fricción fue alta y se asoció con la edad, las comorbilidades, la piel seca y con descamación, y la media del uso de corticoides.


RESUMO Objetivo: analisar a prevalência de lesões por fricção e fatores associados em idosos internados em Unidade de Terapia Intensiva. Método: estudo transversal e analítico, desenvolvido em Unidade de Terapia Intensiva de Hospital Escola, com amostra de 101 idosos. Coleta de dados realizada de novembro de 2017 a maio de 2018, por meio de entrevista, consulta ao prontuário e exame físico. Para análise, realizou-se estatística descritiva e inferencial. Força das associações entre as variáveis aferida pelo odds-ratio e intervalos de confiança de 95%. Nível de significância estatística estabelecido de 5% para todas as análises. Resultados: a amostra estudada apresentava média de idade de 71,39 anos, maioria do sexo masculino, casados e sem escolaridade, com mais de uma comorbidade, dependentes, com pele seca e descamativa e com hematomas nas extremidades. A prevalência de lesão por fricção foi de 28,7%, média de 1,93 lesões por idoso. Verificou-se associação estatisticamente significativa da ocorrência de lesão por fricção com idade, comorbidades, pele seca e descamativa. Conclusão: a prevalência de lesão por fricção foi elevada e associada à idade, comorbidades, pele seca e descamativa e média do tempo do uso de corticoide.


Assuntos
Humanos , Idoso , Ferimentos e Lesões , Idoso , Envelhecimento da Pele , Enfermagem , Fricção
2.
Orthod Fr ; 91(3): 249-262, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33146619

RESUMO

The use of self-ligating brackets has largely developed in orthodontic practice thanks to numerous advantages, including the reduction of frictional forces during sliding orthodontic mechanic. Faced with scientific evidence, this advantage still seems to be debatable. Our objective was to evaluate in vivo the frictional force of self-ligating brackets by searching for micro-morphological and chemical effects on the active slot surface, after phase of alignment-leveling and after a period in the mouth. 16 brackets from four commercial brands were selected (Damon®, In-Ovation®, Smart-clip® and Carriere®). These brackets were visualized using a scanning electron microscope (SEM) and dispersive energy spectroscopy to study their surface and initial chemical composition. After a period in the mouth, these brackets were debonded and evaluated with SEM, to search topographic and chemical changes in relation to the frictional forces. After a period of three months used for dental alignment, all the brackets show considerable changes in topographic and chemical properties related to frictional forces, with deposit of organic debris whose importance is related to the initial surface different from one manufacturer to another.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Teste de Materiais , Desenho de Aparelho Ortodôntico , Aço Inoxidável , Propriedades de Superfície
3.
Proc Biol Sci ; 287(1931): 20201410, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-33043862

RESUMO

Joint friction has never previously been considered in the computation of mechanical and metabolic energy balance of human and animal (loco)motion, which heretofore included just muscle work to move the body centre of mass (external work) and body segments with respect to it. This happened mainly because, having been previously measured ex vivo, friction was considered to be almost negligible. Present evidences of in vivo damping of limb oscillations, motion captured and processed by a suited mathematical model, show that: (a) the time course is exponential, suggesting a viscous friction operated by the all biological tissues involved; (b) during the swing phase, upper limbs report a friction close to one-sixth of the lower limbs; (c) when lower limbs are loaded, in an upside-down body posture allowing to investigate the hip joint subjected to compressive forces as during the stance phase, friction is much higher and load dependent; and (d) the friction of the four limbs during locomotion leads to an additional internal work that is a remarkable fraction of the mechanical external work. These unprecedented results redefine the partitioning of the energy balance of locomotion, the internal work components, muscle and transmission efficiency, and potentially readjust the mechanical paradigm of the different gaits.


Assuntos
Extremidades , Articulações , Locomoção , Animais , Fricção , Humanos , Metabolismo , Estresse Mecânico
4.
Science ; 370(6514): 335-338, 2020 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-33060358

RESUMO

The lubrication of hydrogels arises from fluid or solvated surface phases. By contrast, the lubricity of articular cartilage, a complex biohydrogel, has been at least partially attributed to nonfluid, lipid-exposing boundary layers. We emulated this behavior in synthetic hydrogels by incorporating trace lipid concentrations to create a molecularly thin, lipid-based boundary layer that renews continuously. We observed a 80% to 99.3% reduction in friction and wear relative to the lipid-free gel, over a wide range of conditions. This effect persists when the gels are dried and then rehydrated. Our approach may provide a method for sustained, extreme lubrication of hydrogels in applications from tissue engineering to clinical diagnostics.


Assuntos
Cartilagem Articular/química , Hidrogéis/química , Lubrificantes/química , Lubrificação , Fricção , Lipídeos/química
5.
Nat Commun ; 11(1): 5166, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33056999

RESUMO

Many creatures have the ability to traverse challenging environments by using their active muscles with anisotropic structures as the motors in a highly coordinated fashion. However, most artificial robots require multiple independently activated actuators to achieve similar purposes. Here we report a hydrogel-based, biomimetic soft robot capable of multimodal locomotion fueled and steered by light irradiation. A muscle-like poly(N-isopropylacrylamide) nanocomposite hydrogel is prepared by electrical orientation of nanosheets and subsequent gelation. Patterned anisotropic hydrogels are fabricated by multi-step electrical orientation and photolithographic polymerization, affording programmed deformations. Under light irradiation, the gold-nanoparticle-incorporated hydrogels undergo concurrent fast isochoric deformation and rapid increase in friction against a hydrophobic substrate. Versatile motion gaits including crawling, walking, and turning with controllable directions are realized in the soft robots by dynamic synergy of localized shape-changing and friction manipulation under spatiotemporal light stimuli. The principle and strategy should merit designing of continuum soft robots with biomimetic mechanisms.


Assuntos
Biomimética/métodos , Locomoção , Nanogéis/química , Robótica/métodos , Fricção , Músculo Esquelético/fisiologia
6.
PLoS One ; 15(9): e0239363, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32970710

RESUMO

BACKGROUND: Healthcare workers around the world are experiencing skin injury due to the extended use of personal protective equipment (PPE) during the COVID-19 pandemic. These injuries are the result of high shear stresses acting on the skin, caused by friction with the PPE. This study aims to provide a practical lubricating solution for frontline medical staff working a 4+ hours shift wearing PPE. METHODS: A literature review into skin friction and skin lubrication was conducted to identify products and substances that can reduce friction. We evaluated the lubricating performance of commercially available products in vivo using a custom-built tribometer. FINDINGS: Most lubricants provide a strong initial friction reduction, but only few products provide lubrication that lasts for four hours. The response of skin to friction is a complex interplay between the lubricating properties and durability of the film deposited on the surface and the response of skin to the lubricating substance, which include epidermal absorption, occlusion, and water retention. INTERPRETATION: Talcum powder, a petrolatum-lanolin mixture, and a coconut oil-cocoa butter-beeswax mixture showed excellent long-lasting low friction. Moisturising the skin results in excessive friction, and the use of products that are aimed at 'moisturising without leaving a non-greasy feel' should be prevented. Most investigated dressings also demonstrate excellent performance.


Assuntos
Infecções por Coronavirus/complicações , Lubrificantes/uso terapêutico , Equipamento de Proteção Individual/efeitos adversos , Pneumonia Viral/complicações , Pele/lesões , Adulto , Betacoronavirus , Fenômenos Biomecânicos , Fricção , Humanos , Masculino , Corpo Clínico , Pandemias
7.
Am J Vet Res ; 81(10): 821-826, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32969726

RESUMO

OBJECTIVE: To evaluate holding security of 4 friction knots created with various monofilament and multifilament sutures in a vascular ligation model. SAMPLE: 280 friction knot constructs. PROCEDURES: 10 friction knots of 4 types (surgeon's throw, Miller knot, Ashley modification of the Miller knot, and strangle knot) created with 2-0 monofilament (polyglyconate, polydioxanone, poliglecaprone-25, and glycomer-631) and braided multifilament (silk, lactomer, and polyglactin-910) sutures were separately tied on a mock pedicle and pressure tested to the point of leakage. Linear regression analysis was performed to compare leakage pressures among suture materials (within friction knot type) and among knot types (within suture material). RESULTS: Mean leakage pressure of surgeon's throws was significantly lower than that of all other knots tested, regardless of the suture material used. All the other knots had mean leakage pressures considered supraphysiological. Significant differences in mean leakage pressure were detected between various friction knots tied with the same type of suture and various suture types used to create a given knot. Variability in leakage pressure among knots other than the surgeon's throw was greatest for poliglecaprone-25 and lowest for polydioxanone. CONCLUSIONS AND CLINICAL RELEVANCE: Most differences in knot security, although statistically significant, may not have been clinically relevant. However, results of these in vitro tests suggested the surgeon's throw should be avoided as a first throw for pedicle ligation and that poliglecaprone-25 may be more prone to friction knot slippage than the other suture materials evaluated.


Assuntos
Técnicas de Sutura/veterinária , Suturas/veterinária , Animais , Fricção , Polidioxanona , Poliglactina 910 , Resistência à Tração
10.
Phys Rev Lett ; 125(7): 078101, 2020 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-32857554

RESUMO

The friction between cytoskeletal filaments is of central importance for the formation of cellular structures such as the mitotic spindle and the cytokinetic ring. This friction is caused by passive cross-linkers, yet the underlying mechanism and the dependence on cross-linker density are poorly understood. Here, we use theory and computer simulations to study the friction between two filaments that are cross-linked by passive proteins, which can hop between discrete binding sites while physically excluding each other. The simulations reveal that filaments move via rare discrete jumps, which are associated with free-energy barrier crossings. We identify the reaction coordinate that governs the relative microtubule movement and derive an exact analytical expression for the free-energy barrier and the friction coefficient. Our analysis not only elucidates the molecular mechanism underlying cross-linker-induced filament friction, but also predicts that the friction coefficient scales superexponentially with the density of cross-linkers.


Assuntos
Citoesqueleto/química , Citoesqueleto/fisiologia , Modelos Biológicos , Modelos Químicos , Proteínas Motores Moleculares/química , Proteínas Motores Moleculares/fisiologia , Sítios de Ligação , Citoesqueleto/metabolismo , Fricção , Microtúbulos/química , Microtúbulos/metabolismo , Proteínas Motores Moleculares/metabolismo , Termodinâmica
11.
Wiad Lek ; 73(4): 751-754, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32731710

RESUMO

OBJECTIVE: The aim: Mathematical modeling and peculiarities of the proposed telescopic connection design. PATIENTS AND METHODS: Materials and methods: For the implementation of the mathematical model of telescopic joints of removable dentures, elements of the external and internal parts of such a design having the same nominal angles of cones, or identical nominal cones of these parts are considered. RESULTS: Results: Dependence of retention force is determined from various parameters, equating it with equilibrium values of compressive dynamic force and the total force of friction. Connection is set between the separate geometricalparameters of elements of telescopic cone connection andoperating between them various internal and external efforts.At creation of different individual modifications of theseconnections, gives possibility, attracting the values ofcorresponding geometrical or po wer elements, that isrationed or accepted on results measuring or scanouts, toexpect other parameters that is determined in dependenceon preliminary appointed. CONCLUSION: Conclusions: The given mathematical dependences can be represented as algorithms of calculation and realized by computer programs.


Assuntos
Músculo Esquelético , Prótese Parcial Removível , Fricção
13.
Shanghai Kou Qiang Yi Xue ; 29(1): 19-24, 2020 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-32524115

RESUMO

PURPOSE: The purpose of this study was to observe the friction and wear characteristics of dental fluorapatite glass ceramics, feldspathic porcelain and natural tooth in dry friction and saliva lubrication. METHODS: Two kinds of veneering porcelain (IPS-emaxcream and Vita vm9) coated zirconia-decorative porcelain double-layer material sample were prepared (size 20 mm × 20 mm × 4.5 mm), each group had 20 specimens. Friction and wear tests were carried out on 2 kinds of zirconia-decorative porcelain sample under dry friction and saliva accompanying environment respectively by setting different sizes of vertical load and sliding frequency using MMV-1 friction and wear testing machine. SPSS 17.0 software package was used for one-way ANOVA and t test to determine whether there were differences in friction coefficient and wear amount between two groups. RESULTS: The dynamic friction coefficient and wear amount of fluorapatite glass ceramics under saliva lubrication condition were significantly greater than those under dry friction condition. On the contrary to fluorapatite glass ceramics, the dynamic friction coefficient and wear amount of feldspathic decorative ceramics under dry friction condition were significantly greater than those under saliva lubrication condition. Under dry friction and saliva lubrication, the wear amount of fluorapatite glass ceramics was significantly smaller than that of feldspathic decorative ceramics. Scanning electron microscopy showed that under saliva lubrication condition, fluorapatite glass ceramics and the corresponding natural teeth had more severe wear surface than dry friction. Under dry friction condition, feldspathic decorative porcelain and corresponding natural teeth wear more seriously than fluorapatite glass ceramic, and the difference in saliva lubrication condition was relatively small. CONCLUSIONS: Compared with feldspathic decorative porcelain, fluorapatite glass ceramics and natural teeth shows superior wear resistance under dry friction condition. The addition of saliva can reduce the difference between the friction and wear performance of the two decorative porcelains.


Assuntos
Cerâmica , Porcelana Dentária , Apatitas , Fricção , Teste de Materiais , Propriedades de Superfície , Zircônio
14.
J Vis Exp ; (159)2020 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-32478748

RESUMO

Osteochondral defects in middle-aged patients might be treated with focal metallic implants. First developed for defects in the knee joint, implants are now available for the shoulder, hip, ankle and the first metatarsalphalangeal joint. While providing pain reduction and clinical improvement, progressive degenerative changes of the opposing cartilage are observed in many patients. The mechanisms leading to this damage are not fully understood. This protocol describes a tribological experiment to simulate a metal-on-cartilage pairing and comprehensive analysis of the articular cartilage. Metal implant material is tested against bovine osteochondral cylinders as a model for human articular cartilage. By applying different loads and sliding speeds, physiological loading conditions can be imitated. To provide a comprehensive analysis of the effects on the articular cartilage, histology, metabolic activity and gene expression analysis are described in this protocol. The main advantage of tribological testing is that loading parameters can be adjusted freely to simulate in vivo conditions. Furthermore, different testing solutions might be used to investigate the influence of lubrication or pro-inflammatory agents. By using gene expression analysis for cartilage-specific genes and catabolic genes, early changes in the metabolism of articular chondrocytes in response to mechanical loading might be detected.


Assuntos
Cartilagem Articular/fisiologia , Metais/farmacologia , Próteses e Implantes , Animais , Osso e Ossos/efeitos dos fármacos , Cartilagem Articular/efeitos dos fármacos , Bovinos , Condrócitos/efeitos dos fármacos , Condrócitos/metabolismo , DNA Complementar/biossíntese , Fricção , Regulação da Expressão Gênica , Fatores de Tempo
15.
PLoS One ; 15(6): e0233148, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32525868

RESUMO

Creating a secure and comfortable linkage between the residual limb and prosthetic socket in persons with lower limb amputation is a critical factor for successful rehabilitation, including ambulation and other activities of daily living. Unwanted rotation within the socket can be a clinical problem for prosthesis users. One way of addressing issues experienced with transverse plane control of the socket may be through increased friction interface forces. It has been proposed that friction at the residual limb/socket interface may be increased by adding texture to interface components. Three-dimensional (3D) printing may be used to fabricate sockets with texture patterns added to the inner socket surface. Hence, the aim of this study was to investigate the effects of socket texturing on transverse plane rotation of the socket on a mock residual limb under two suspension conditions: passive suction and active vacuum. To conduct this study, we developed a mechanical testing protocol as no standardized tests currently exist to assess prosthetic sockets. Sockets with 14 different texture patterns were fabricated using the Squirt-Shape™ 3D printer. Textured sockets were compared to an Original Squirt-Shape (OSS) socket and a smooth thermoformed socket. Sockets were fitted with a mock residual limb and bi-axially loaded to 350 N compression with simultaneous rotation (2.5°, 5° and 7.5°) using a custom rotation assembly attached to a uniaxial hydraulic material testing system. There was a statistically significant three-way interaction between suspension, angle and texture (p < 0.0005). Torques between textured and reference sockets, for all rotation angles and both suspension conditions, were significantly different (p < 0.0005). Using newly developed testing protocols, it was demonstrated that some texture patterns significantly increased torque (i.e., resistance against unwanted rotation) in the transverse plane compared to both OSS and smooth sockets, especially for passive suction. Rotation testing of sockets may provide insight into socket design to improve suspension in the transverse plane.


Assuntos
Fricção/fisiologia , Teste de Materiais/métodos , Desenho de Prótese/métodos , Membros Artificiais/efeitos adversos , Humanos , Fenômenos Mecânicos , Pressão , Ajuste de Prótese/métodos , Rotação , Suporte de Carga/fisiologia
16.
Med Probl Perform Art ; 35(2): 96-102, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32479585

RESUMO

BACKGROUND: Dancing with legs externally rotated (turnout) is a fundamental element of ballet technique. A reliance on floor friction to achieve turnout may contribute toward the high injury rate in dancers. Joint strategies used by dancers in high and low friction turnout conditions are not well understood. OBJECTIVES: To quantify the lower limb and lumbar spine joint strategies used by female pre-professional dancers to achieve turnout in low-friction (rotation discs) and high-friction (functional and forced) conditions. METHODS: Twenty-three pre-professional female dancers participated in the study. A 12-camera motion analysis system collected hip and knee external rotation (ER), ankle abduction, and lumbar extension angles in three turnout conditions and passive hip ER range of motion angles. Repeated measures ANOVA analysed the differences between joint angles, maximum turnout angle (foot relative to pelvis), and available hip ER. RESULTS: Dancers demonstrated lower knee ER (18.5±4.8°) and ankle abduction (6.0±7.7°) angles during low-friction turnout compared to higher friction conditions (p<0.05). Dancers utilised between 70-83% of available hip ER within all conditions. Low-friction turnout demonstrated greater hip ER contribution within maximum turnout (43%) compared to higher friction conditions. Dancers demonstrated greater lumbar extension angles in low-friction turnout compared to higher friction conditions (p<0.05). CONCLUSIONS: Further hip ER strength training is required to promote greater hip ER range within the position. Rotation discs may be a valuable training tool as dancers demonstrated greater hip ER utilisation with less knee ER and ankle abduction; however, this position did promote undesirable lumbar extension.


Assuntos
Articulação do Tornozelo , Dança , Articulação do Quadril , Dança/fisiologia , Feminino , Fricção , Humanos , Amplitude de Movimento Articular , Rotação
17.
Nat Biomed Eng ; 4(8): 778-786, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32483298

RESUMO

Falls and subsequent complications are major contributors to morbidity and mortality, especially in older adults. Here, by taking inspiration from claws and scales found in nature, we show that buckling kirigami structures applied to footwear outsoles generate higher friction forces in the forefoot and transversally to the direction of movement. We identified optimal kirigami designs capable of modulating friction for a range of surfaces, including ice, by evaluating the performance of the dynamic kirigami outsoles through numerical simulations and in vitro friction testing, as well as via human-gait force-plate measurements. We anticipate that lightweight kirigami metasurfaces applied to footwear outsoles could help mitigate the risk of slips and falls in a range of environments.


Assuntos
Acidentes por Quedas/prevenção & controle , Materiais Biomiméticos , Sapatos , Fenômenos Biomecânicos , Desenho de Equipamento , Fricção , Marcha/fisiologia , Humanos , Movimento/fisiologia , Sapatos/efeitos adversos , Propriedades de Superfície
18.
Proc Biol Sci ; 287(1926): 20200123, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32370666

RESUMO

Remarkable progress has been made characterizing one of nature's most integrated, hierarchical structures--the fibrillar adhesive system of geckos. Nonetheless, we lack an understanding of how multiple toes coordinate to facilitate geckos' acrobatic locomotion. Here, we tested the control function of gecko toes by running them on vertical substrates varying in orientation, friction and roughness. Sideways wall-running geckos realigned the toes of their top feet upward to resist gravity. Toe contact area was not compromised, but redistributed. Geckos aligned all toes upward to resist slipping when encountering low-friction patches during sideways wall-running. Negotiation of intermittent slippery strips showed an increased contribution of particular toes to compensate for toes that lost adhesion. Increasing substrate roughness using discrete rods perpendicular to sideways locomotion resulted in geckos bending and/or rotating toes to conform to and even grasp the rods, with potential forces more than five times body weight. Geckos increase their effectiveness of manoeuvrability in demanding environments by taking advantage of the distributed control afforded by multiple toes. Our findings provide insight on biological attachment and offer inspiration to advance gecko-inspired robotics and other biomimetic applications.


Assuntos
Lagartos/anatomia & histologia , Dedos do Pé , Adesividade , Animais , Fenômenos Biomecânicos , Fricção , Lagartos/fisiologia , Locomoção , Modelos Biológicos , Corrida , Propriedades de Superfície
19.
Dent Mater J ; 39(5): 735-741, 2020 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-32404564

RESUMO

The play between bracket slots and archwires affects tooth movement and the transmission of orthodontic force by multi-bracket appliances. We assessed play by quantifying the play behavior of three-point brackets and comparing the amount of play that occurred with square and rectangular slots, respectively, by using archwires of various sizes. Horizontal play with the square slot was significantly smaller than that with the rectangular slot. These data demonstrate that brackets with square slots can more effectively bring about tooth movement in the labio-lingual direction and control rotational movement with round and square archwires. Since the horizontal and vertical play ratios for the round and square wires within the square slot were approximately 1.0, three-dimensional tooth movement may also be achieved with uniform play in the vertical and horizontal directions.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Teste de Materiais , Desenho de Aparelho Ortodôntico , Aço Inoxidável , Técnicas de Movimentação Dentária
20.
PLoS One ; 15(4): e0231464, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32330141

RESUMO

In deep underground engineering, in a large spatial, high-stress environment, rapid excavation is likely to affect the loading rate of the fault structure and to cause stick-slip. In this study, an experiment was conducted to explore the stick-slip characteristics at different loading rates. A double-sided shear experiment and the digital speckle correlation method were used to analyze the evolution of the displacement field, the slip displacement, and the slip rate of the fault's stick-slip activity at different loading rates as well as their correlation with the loading rate. The loading rate, moment magnitude, and stress drop of the fault's stick-slip and their corresponding relationships were studied. The results show that the occurrence of stick-slip is inversely proportional to the loading rate. The evolution of the fault-slip displacement field at different loading rates is similar. At a given loading rate, the magnitude is positively correlated with the stress drop. The magnitude and stress drop are inversely related to the loading rate.


Assuntos
Fricção , Estresse Mecânico
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