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1.
Int J Prosthodont ; 33(5): 523-526, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32956433

RESUMO

PURPOSE: To investigate the three-point flexural strength of a novel CAD/CAM fiber-reinforced composite (FRC) material following different aging conditions. MATERIALS AND METHODS: The specimens were randomly assigned to one of five groups based on aging condition: (1) control (no treatment); (2) short-term water storage; (3) thermal degradation with autoclaving; (4) chemical degradation with hydrochloric acid; and (5) chemical degradation with citric acid (n = 10 per group). The specimens in the control group received no treatment. Following each treatment protocol, the three-point bending test was used to calculate the flexural strength. Data were statistically analyzed (α = .05), and scanning electron microscopy (SEM) analysis of the specimens was conducted. RESULTS: No significant differences in flexural strength were observed among the groups (P = .199). In addition, no distinct morphologic differences were detected in the SEM images of the specimens. CONCLUSION: The flexural strength of this novel CAD/CAM FRC material was unaffected by different aging methods.


Assuntos
Resinas Compostas , Resistência à Flexão , Desenho Assistido por Computador , Teste de Materiais , Microscopia Eletrônica de Varredura , Projetos Piloto , Maleabilidade , Estresse Mecânico , Propriedades de Superfície
2.
Rev. cient. odontol ; 8(2): e018-e018, mayo-ago. 2020. ilus, tab
Artigo em Espanhol | LILACS, LIPECS | ID: biblio-1119296

RESUMO

Antecedentes: Las limas rotatorias de níquel-titanio con tratamiento termomecánico se desarrollaron para permitir una mayor flexibilidad al instrumentar los conductos radiculares. Los instrumentos permitieron a los operadores tratar las curvaturas de los conductos con mayor facilidad. Los fabricantes están tratando de producir limas que funcionen de manera más eficiente y segura. Conocer las propiedades de las limas comercializadas es especialmente importante porque ayuda a elegir un sistema de lima apropiado. El objetivo de este estudio fue evaluar la flexibilidad de tres limas diferentes de níquel-titanio (NiTi) con tratamiento termomecánico en dos puntos diferentes. Materiales y métodos: Se midió la flexibilidad de tres limas NiTi con tratamiento termomecánico (ProTaper Gold, 2Shape y V-Taper Fanta Gold). Cada lima fue sujetada a 3 mm y 7 mm (n = 10/longitud/lima) y se utilizó una máquina de ensayo universal para doblarla a una fuerza máxima. Todos los datos fueron analizados estadísticamente por análisis de varianza de una vía y prueba de Tukey post hoc (p = 0,05) para determinar cualquier diferencia significativa. Resultados: Se halló diferencias estadísticamente significativas (p < 0,05). En general, V-Taper Fanta Gold fue la más rígida, ProTaper Gold mostró los mayores valores de fuerza y su deformación fue significativamente más flexible. Conclusión: Las limas ProTaper Gold mostraron una mayor flexibilidad en comparación con las otras limas estudiadas. (AU)


Background: Nickel-titanium rotary files with thermomechanical treatment were developed to allow greater flexibility when instrumenting the root canals. The instruments allowed operators to deal with duct curvatures more easily. Manufacturers are trying to produce files that work better efficiently and safely. Knowing the properties of marketed files is especially important in helping you choose an appropriate file system. The objective of this study was to evaluate the flexibility of three different nickel-titanium (NiTi) files with thermomechanical treatment at two different points along the file. Materials and methods: The flexibility of three NiTi files with thermomechanical treatment (Protaper Gold, 2Shape and V-Taper Fanta Gold) was measured. Each file was clamped at 3 mm and 7 mm (n = 10 / length / file) and a universal testing machine was used to bend the files to a maximum strength. All data were statistically analyzed by one-way analysis of variance and post-hoc Tukey test (P = 0.05) to determine any significant differences. Results: There were statistically significant differences (P <0.05). In general, V-Taper Fanta Gold was the most rigid, Protaper Gold showed the highest values of force and deformation was significantly more flexible. Conclusión: Protaper Gold files showed greater flexibility compared to the other files studied. (AU)


Assuntos
Titânio , Maleabilidade , Instrumentos Odontológicos , Ligas , Níquel
3.
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
4.
Artigo em Inglês | MEDLINE | ID: mdl-32560477

RESUMO

During puberty, the growth of the bones is faster than that of the muscles, which may result in muscular tightness. Muscular tightness and asymmetry have been associated with an increase in injury incidence. The assessment of a joint range of motion (ROM) could help to identify athletes classified as high injury risk. The objectives of the present study were to describe the lower-extremity flexibility profile (LEFP) of youth competitive inline hockey players using the ROM-SPORT battery (I) and to identify muscular tightness and asymmetry (II). Seventy-four young players were examined for maximum passive ankle, knee, and hip ROMs. Muscle asymmetry or tightness was classified according to cutoff scores previously described. The LEFP of the 74 players was 10.8° for hip extension, 26° for hip adduction, 33.6° for ankle dorsiflexion, 38.6° for ankle dorsiflexion with knee flexed, 36.7° for hip abduction, 46° for hip internal rotation, 60.6° for hip external rotation, 65.1° for hip abduction with the hip flexed, 66.3° for hip flexion with the knee extended, 119.7° for knee flexion, and 133.7° for hip flexion. The individual analysis of the flexibility values identified tightness in all players for one or more movement, except for hip abduction. A low prevalence of asymmetries was observed (range: 5.4% to 17.6% of players) depending on the ROM.


Assuntos
Hóquei , Amplitude de Movimento Articular , Adolescente , Criança , Humanos , Articulação do Joelho , Extremidade Inferior , Maleabilidade , Maturidade Sexual
5.
Artigo em Inglês | MEDLINE | ID: mdl-32397351

RESUMO

Limited ranges of motion (ROM) have been considered as a relevant risk factor for team sports injuries. The main purposes of the current study were to describe the lower extremity ROM profile, muscular tightness and asymmetries in elite inline hockey players and to examine sex-related differences. Twenty professional inline hockey players from 2 Spanish National Teams (male and female) were measured of passive hip extension [HE], hip adduction with hip flexed 90° [HAD-HF], hip flexion with the knee flexed [HF-KF] and extended [HF-KE], hip abduction with the hip neutral [HAB] and hip flexed 90° [HAB-HF], hip external [HER] and internal [HIR] rotation, knee flexion [KF], ankle dorsiflexion with the knee flexed [ADF-KF] and extended [ADF-KE] ROMs of the dominant and non-dominant leg ROMs were taken. A paired t-test was carried out to assess asymmetries. ROM values were classified as "normal versus tightness", and "normal versus asymmetry" according to the proposed reference values. The effect size for each variable was analyzed. Male team exhibited asymmetry in HF-KF (133.2° dominant vs. 129.8° non-dominant; p = 0.042; d = 0.7243 [moderate effect sizes]) and female team in ADF-KF (38.8° dominant vs. 41.0 non-dominant; p = 0.001; d = 0.6 [moderate effect sizes]) and HAB ROM (41.2° dominant vs. 38.8 non-dominant; p = 0.005; d = 1.1767 [moderate effect sizes]). Male players reported asymmetry in HAD-HF (n = 5), HER (n = 4) and HE (n = 3), whereas female players presented asymmetries in HER (n = 4), HE (n = 3) and KF (n = 2). Overall, 20-100% of all participants showed limited KF, HF_KE, HIR, HE, ADF_KF, HAD-HF, HF-KF, ADF_KE, HTR and HER ROM. The results of this study reinforce the requirement of prescribing exercises aimed at improving hip, knee and ankle ROM within everyday inline hockey practices. In addition, as some asymmetries were found, unilateral flexibility training should be considered where appropriate.


Assuntos
Articulação do Quadril , Hóquei , Amplitude de Movimento Articular , Feminino , Quadril , Humanos , Articulação do Joelho , Masculino , Maleabilidade , Adulto Jovem
6.
Nucleic Acids Res ; 48(11): 6108-6119, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32392345

RESUMO

Protamine proteins dramatically condense DNA in sperm to almost crystalline packing levels. Here, we measure the first step in the in vitro pathway, the folding of DNA into a single loop. Current models for DNA loop formation are one-step, all-or-nothing models with a looped state and an unlooped state. However, when we use a Tethered Particle Motion (TPM) assay to measure the dynamic, real-time looping of DNA by protamine, we observe the presence of multiple folded states that are long-lived (∼100 s) and reversible. In addition, we measure folding on DNA molecules that are too short to form loops. This suggests that protamine is using a multi-step process to loop the DNA rather than a one-step process. To visualize the DNA structures, we used an Atomic Force Microscopy (AFM) assay. We see that some folded DNA molecules are loops with a ∼10-nm radius and some of the folded molecules are partial loops-c-shapes or s-shapes-that have a radius of curvature of ∼10 nm. Further analysis of these structures suggest that protamine is bending the DNA to achieve this curvature rather than increasing the flexibility of the DNA. We therefore conclude that protamine loops DNA in multiple steps, bending it into a loop.


Assuntos
DNA/química , DNA/efeitos dos fármacos , Conformação de Ácido Nucleico/efeitos dos fármacos , Protaminas/química , Protaminas/farmacologia , DNA/ultraestrutura , Microscopia de Força Atômica , Maleabilidade
7.
Dent Mater ; 36(6): 794-807, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32349876

RESUMO

OBJECTIVE: The purpose of this work was to explore the enhancement effect of zinc doped mesoporous silica nanoparticles (Zn-MSNs), which could form micromechanical interlocking with resin matrix and sustainably release Zn2+, on the mechanical and antibacterial properties of the dental resin composites. METHODS: Zn-MSNs were prepared by a sol-gel method, and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption/desorption. The mechanical properties of the dental composites reinforced by Zn-MSNs were measured by a universal mechanical testing machine. Antibacterial activities of dental composites were evaluated by both qualitative and quantitative analysis using Streptococcus mutans (S. mutans). The cytotoxicity of the Zn-MSNs filled dental composites was investigated by osteoblasts (OBs). RESULTS: The synthesized Zn-MSNs possessed good monodispersity with an average particle size of about 138nm. The mechanical properties of the composites gradually increased with the increase of the content of Zn-MSNs. The flexural strength, flexural modulus, compressive strength and micro-hardness of the composites containing 15wt% Zn-MSNs were 31.21%, 50.47%, 53.83% and 26.79% higher than the samples with no Zn-MSNs, respectively. The antibacterial performance was significantly improved by the addition of Zn-MSNs and the antibacterial rate of the composite with 15wt% of Zn-MSNs reached 100%. Cytotoxicity tests revealed that all the composites were biocompatible during OBs incubation. SIGNIFICANCE: The prepared Zn-MSNs can effectively improve the mechanical and antibacterial properties of the dental resin composites.


Assuntos
Nanopartículas , Dióxido de Silício , Antibacterianos/farmacologia , Resinas Compostas , Teste de Materiais , Maleabilidade , Propriedades de Superfície , Zinco
8.
Updates Surg ; 72(3): 845-850, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32399596

RESUMO

BACKGROUND: Transanal total mesorectal excision (TaTME) is routinely performed to excise low rectal tumors. TaTME often relies on transanal endoscopic microsurgery (TEM) or transanal minimally invasive surgery (TAMIS) platform, all using rigid endoscopes. Our study reported a novel approach to TaTME which was completed using flexible endoscope, and we named it F-TaTME. METHODS: The feasibility of rectum resection using F-TaTME was evaluated in five pigs. Firstly, the superior rectal artery and vein were managed under the assistance of laparoscopy. Secondly, the flexible endoscope was used to complete the full-thickness rectotomy and rectal mobilization. Finally, the specimen was removed and the manual colon-rectal anastomosis was performed under direct vision. RESULTS: F-TaTME was accomplished in all 5 pigs. The mean procedure time was 136.6 min (97-162 min). The mean length from the lower edge of the lesion to circumferential dissection line was 1.4 cm (1.0-1.8 cm) and mean length of exteriorized rectum was 12.6 cm (11-14 cm). No injury to colorectal wall, adjacent pelvic or abdominal organs was found. CONCLUSIONS: Our preliminary data suggested that F-TaTME may be a feasible method for TaTME.


Assuntos
Endoscópios Gastrointestinais , Endoscopia Gastrointestinal/instrumentação , Laparoscopia/métodos , Maleabilidade , Neoplasias Retais/cirurgia , Reto/cirurgia , Microcirurgia Endoscópica Transanal/instrumentação , Animais , Endoscopia Gastrointestinal/métodos , Estudos de Viabilidade , Modelos Animais , Duração da Cirurgia , Projetos Piloto , Reto/patologia , Suínos , Microcirurgia Endoscópica Transanal/métodos
9.
J Esthet Restor Dent ; 32(4): 433-440, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32274901

RESUMO

OBJECTIVE: The purpose of this study was to evaluate the effect of three different methods of fiber reinforcement (glass fibers preimpregnated, glass fibers nonpreimpregnated, and polyethylene fibers) on the flexural strength and modulus of elasticity of poly-methyl-methacrylate resin (PMMA) and Bis-Gma materials. MATERIALS AND METHODS: A total of 60 specimens of autopolymerizing PMMA resin specimens were fabricated using a stainless steel matrix with dimensions of (37.5± 2) × (3 ± 0.1) × (3 ± 0.1) mm according to the standards of ISO 10477. The autopolymerizing resins used in this study were: (a) JET, (b) TRIM, (c) PROTEMP. The fibers used in this study were STICK (Glass fiber preimpregnated), POLYDENTIA (Glass fiber nonpreimpregnated), RIBBOND (Polyethylene fiber). The specimens were tested by three-point bending test and the flexural strength and modulus of elasticity were recorded. The data of each resin type were analyzed by analysis of variance using a significance level of 0.05 to determine the mean differences. RESULTS: The integration of reinforcing fibers in the mass of resins for provisional restorations increased both the flexural strength and the modulus of elasticity in all tested combinations compared to control groups. After the three-point bending test, the specimens were not completely fractured and the parts remained together due to the fibers. CONCLUSIONS: Fiber reinforcement is an effective method to increase mechanical properties of provisional restorative resins. Reinforcement with fibers enhances the flexural strength and the modulus of elasticity of the specimens compared to unreinforced (control) group. CLINICAL SIGNIFICANCE: The reinforcement of resin materials used for provisional restorations with fibers can increase mechanical strength and may improve the clinical performance and the longevity of provisional restorations during their clinical function.


Assuntos
Materiais Dentários , Polímeros , Resinas Compostas , Análise do Estresse Dentário , Teste de Materiais , Maleabilidade , Estresse Mecânico , Propriedades de Superfície
10.
Artigo em Inglês | MEDLINE | ID: mdl-32245052

RESUMO

Cured-in-place pipe (CIPP), as a kind of trenchless sewer rehabilitation technology, is a method to repair sewer pipe using unsaturated polyester resin. This study develops a CIPP liner using hot water or steam curing as well as glass fiber, in contrast to traditional methods, which use nonwoven fabric. Composite material samples were fabricated by combining liner materials using various methods, and the structural characteristics of the liners were compared and analyzed through short- and long-term flexural strength tests. A long-term test was conducted for 10,000 h, and the results revealed 13.3 times higher flexural strength and 8 times higher flexural modulus than the American Society for Testing Materials minimum criteria for CIPP short-term properties. The maximum creep retention factor was 0.64, thereby reducing the design thickness of the CIPP by up to 54%. The structural characteristics also improved when glass fibers were mixed with traditional CIPP liner, making it possible to reduce the thickness by 30%. Glass fibers result in high structural strength when combined with unsaturated polyester resin. Structural strength increased, even when glass fibers were mixed with traditional CIPP liner. The main contribution of this research is the development of a high strength CIPP liner and improvement of the structural properties of CIPP lining without using the specially formulated resin or lining materials.


Assuntos
Resinas Compostas , Vidro , Teste de Materiais , Maleabilidade , Estresse Mecânico , Propriedades de Superfície
11.
J Prosthet Dent ; 123(4): 647.e1-647.e7, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32115217

RESUMO

STATEMENT OF PROBLEM: Artificial denture teeth made of polymethyl methacrylate (PMMA) resin have good adhesion to the denture base but are relatively soft and have limited wear resistance during function. PURPOSE: The purpose of this in vitro study was to evaluate the influence of the addition of 2 inorganic nanofillers on the flexural strength, maximal displacement, elastic modulus, Isolde impact resistance, and Brinell hardness of acrylic resin denture teeth. MATERIAL AND METHODS: Heat polymerizing polymethyl methacrylate resin was mixed with silanized silica or silanized feldspar in concentrations of 5 wt%, 10 wt%, and 15 wt%. The first test was conducted after 24 hours of storage in laboratory conditions, and the second assessment was conducted after 3 months of storage in distilled water at 37 °C. The Brinell hardness was evaluated, and the elastic modulus and maximal displacement at fracture were calculated. The flexural strength and Isolde impact resistance were measured with a 3-point flexural test. Acrylic resin specimens without filler addition were used as a control group. Statistical analysis included 2-way ANOVA for independent variables (α=.05) and the Student t test for time-dependent changes (α=.05). These were performed with Statistica 12 software. RESULTS: The acrylic resin specimens modified with the addition of silanized feldspar had significantly higher Brinell hardness, elastic modulus, maximal displacement, and flexural strength and also had no adverse effect on Isolde impact resistance compared with the conventional acrylic resin. Silica filler increased the Brinell hardness and elastic modulus of acrylic resins but significantly reduced the flexural strength and Isolde impact resistance.


Assuntos
Polimetil Metacrilato , Dióxido de Silício , Silicatos de Alumínio , Materiais Dentários , Bases de Dentadura , Dentaduras , Humanos , Teste de Materiais , Maleabilidade , Compostos de Potássio , Estresse Mecânico , Propriedades de Superfície
12.
Coluna/Columna ; 19(1): 13-17, Jan.-Mar. 2020. tab
Artigo em Inglês | LILACS | ID: biblio-1089648

RESUMO

ABSTRACT Objective To determine if there is a statistically significant difference in the flexibility of the curves in the adolescent idiopathic scoliosis (AIS) by using lateral inclination radiographs in supine or prone decubitus. Methods We evaluated 19 patients with AIS, waiting for surgery. Radiographs of the patients were performed in orthostatic anteroposterior incidences and right and left lateral inclinations in prone and supine decubitus. The comparison between prone and supine decubitus was performed through the flexibility rates of the curves measured in each position. Results The mean flexibility rates measured in lateral inclination radiographs with the patient in the supine position were 54.4% ± 38.8% in the proximal thoracic curve, 45.8% ± 15.6% in the main thoracic curve, and 80.5% ± 20.7% in the thoracolumbar / lumbar curve. When the lateral inclination radiographs were performed with the patient in the prone position, we observed mean flexibility rates of 66.4% ± 34.3% in the proximal thoracic curve, 50.1% ± 12.8% in the main thoracic curve, and 80.6% ± 19.0% in the thoracolumbar / lumbar curve. Conclusion This present study did not find a statistically significant difference between the flexibility rates of the curves in the prone and supine positions, suggesting that the two radiographic methods analyzed are similar in the evaluation of the flexibility of the curves in adolescent idiopathic scoliosis. Level of evidence II; Development of diagnostic criteria in consecutive patients (with "gold" reference standard applied).


RESUMO Objetivo Determinar se há diferença estatisticamente significativa na flexibilidade das curvas na escoliose idiopática do adolescente (EIA), ao utilizar radiografias em inclinação lateral em decúbito supino ou prono. Métodos Foram avaliados 19 pacientes com EIA, em espera de cirurgia. Os pacientes realizaram radiografias em incidências anteroposterior em ortostase, inclinações laterais direita e esquerda em decúbito prono e supino. Realizou-se a comparação entre o decúbito prono e supino através das taxas de flexibilidade das curvas aferidas em cada posição. Resultados A taxa de flexibilidade média aferida, quando realizadas as inclinações laterais com o paciente em posição supino, foi de 54,4% ± 38,8% na curva torácica proximal, 45,8% ± 15,6% na curva torácica principal e 80,5% ± 20,7% na curva toracolombar/lombar. Quando realizadas as inclinações laterais com o paciente em posição prono, observou-se taxa de flexibilidade média de 66,4% ± 34,3% na curva torácica proximal, 50,1% ± 12,8% na curva torácica principal e 80,6% ± 19,0% na curva toracolombar/lombar. Conclusão O presente estudo não encontrou diferença com significância estatística nas taxas de flexibilidade das curvas nas posições prono e supino, sugerindo que os dois métodos radiográficos analisados são semelhantes na avaliação da flexibilidade das curvas na escoliose idiopática do adolescente. Nível de evidência II; Desenvolvimento de critérios diagnósticos em pacientes consecutivos (com padrão de referência "ouro" aplicado).


RESUMEN Objetivo Determinar si hay diferencia estadísticamente significativa en la flexibilidad de las curvas en la escoliosis idiopática del adolescente (EIA), al utilizar radiografías en inclinación lateral en decúbito supino o prono. Métodos Se evaluaron 19 pacientes con EIA, en espera de cirugía. Los pacientes realizaron radiografías en incidencias anteroposterior en ortostasis, inclinaciones laterales derecha e izquierda en decúbito prono y supino. Se realizó la comparación entre el decúbito prono y supino a través de las tasas de flexibilidad de las curvas medidas en cada posición. Resultados La tasa de flexibilidad promedio medida, cuando se realizaron las inclinaciones laterales con el paciente en posición supino, fue de 54,4% ± 38,8% en la curva torácica proximal, 45,8% ± 15,6% en la curva torácica principal, y 80,5% ± 20,7% en la curva toracolumbar/lumbar. Cuando se realizaron las inclinaciones laterales con el paciente en posición prono, se observó tasa de flexibilidad promedio de 66,4% ± 34,3% en la curva torácica proximal, 50,1% ± 12,8% en la curva torácica principal, y 80,6% ± 19,0% en la curva toracolumbar/lumbar. Conclusión El presente estudio no encontró diferencia con significancia estadística en las tasas de flexibilidad de las curvas en las posiciones prono y supino, sugiriendo que los dos métodos radiográficos analizados son semejantes en la evaluación de la flexibilidad de las curvas en la escoliosis idiopática del adolescente. Nivel de evidencia II; Desarrollo de criterios diagnósticos en pacientes consecutivos (con el estándar de referencia "oro" aplicado).


Assuntos
Humanos , Escoliose , Radiografia , Adolescente , Maleabilidade
13.
Arch Biochem Biophys ; 684: 108323, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32126206

RESUMO

Electron Paramagnetic Resonance is a spectroscopic technique which, in combination with site-directed spin-labeling, provides structural and dynamic information about proteins in conditions similar to those of their physiological environment. The information is sequence-resolved, as it is based on probing the local dynamics of a paramagnetic label incorporated as a side chain of a selected amino acid. EPR does not impose a limit on the size of the protein or protein complex, as long as it is amenable to site-directed mutagenesis, and is able to obtain reliable distance distributions between two or more labels (identical or different).. The mean value, width and shape of distance distributions, as well as their dependence upon the state of the protein or interactions with physiological partners, provide insight into order-disorder transitions and the roles of protein flexibility. The main potentialities and limitations of the technique are revised and illustrated with examples of proteins for which order-disorder play an important role.


Assuntos
Espectroscopia de Ressonância de Spin Eletrônica/métodos , Proteínas Intrinsicamente Desordenadas/química , Marcadores de Spin , Óxidos N-Cíclicos/química , Cisteína/química , Maleabilidade , Conformação Proteica
14.
Chemistry ; 26(29): 6461-6472, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32159246

RESUMO

Soft and flexible two-dimensional (2D) systems, such as liquid interfaces, would have much more potentials in dynamic regulation on nano-macro connected functions. In this Minireview article, we focus especially on dynamic motional functions at liquid dynamic interfaces as 2D material systems. Several recent examples are selected to be explained for overviewing features and importance of dynamic soft interfaces in a wide range of action systems. The exemplified research systems are mainly classified into three categories: (i) control of microobjects with motional regulations; (ii) control of molecular machines with functions of target discrimination and optical outputs; (iii) control of living cells including molecular machine functions at cell membranes and cell/biomolecular behaviors at liquid interface. Sciences on soft 2D media with motional freedom and their nanoarchitectonics constructions will have increased importance in future technology in addition to popular rigid solid 2D materials.


Assuntos
Nanoestruturas/química , Nanotecnologia/métodos , Rastreamento de Células/métodos , Movimento (Física) , Maleabilidade , Propriedades de Superfície
15.
Nature ; 579(7797): 97-100, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32103182

RESUMO

The stiff human foot enables an efficient push-off when walking or running, and was critical for the evolution of bipedalism1-6. The uniquely arched morphology of the human midfoot is thought to stiffen it5-9, whereas other primates have flat feet that bend severely in the midfoot7,10,11. However, the relationship between midfoot geometry and stiffness remains debated in foot biomechanics12,13, podiatry14,15 and palaeontology4-6. These debates centre on the medial longitudinal arch5,6 and have not considered whether stiffness is affected by the second, transverse tarsal arch of the human foot16. Here we show that the transverse tarsal arch, acting through the inter-metatarsal tissues, is responsible for more than 40% of the longitudinal stiffness of the foot. The underlying principle resembles a floppy currency note that stiffens considerably when it curls transversally. We derive a dimensionless curvature parameter that governs the stiffness contribution of the transverse tarsal arch, demonstrate its predictive power using mechanical models of the foot and find its skeletal correlate in hominin feet. In the foot, the material properties of the inter-metatarsal tissues and the mobility of the metatarsals may additionally influence the longitudinal stiffness of the foot and thus the curvature-stiffness relationship of the transverse tarsal arch. By analysing fossils, we track the evolution of the curvature parameter among extinct hominins and show that a human-like transverse arch was a key step in the evolution of human bipedalism that predates the genus Homo by at least 1.5 million years. This renewed understanding of the foot may improve the clinical treatment of flatfoot disorders, the design of robotic feet and the study of foot function in locomotion.


Assuntos
Evolução Biológica , Fenômenos Biomecânicos , Pé/anatomia & histologia , Pé/fisiologia , Testes de Dureza , Animais , Cadáver , Extinção Biológica , Feminino , Pé/fisiopatologia , Hominidae/anatomia & histologia , Hominidae/fisiologia , Humanos , Pessoa de Meia-Idade , Pan troglodytes/anatomia & histologia , Pan troglodytes/fisiologia , Maleabilidade , Pé Cavo/fisiopatologia
16.
Dent Mater J ; 39(3): 471-482, 2020 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-32092720

RESUMO

This study assessed the impact of surface treatments and repair resin reinforcement with zirconium oxide nano-particles (nano-ZrO2) on flexural strength (FS) of repaired denture base. A total of 320 heat-polymerized acrylic resin specimens were prepared and sectioned creating 2-mm gap. According to repair surface treatment, specimens were distributed into four groups: I) methyl methacrylate (M); II) alumina-blasted (AB); III) AB+silane coupling agent (SC); and IV) AB+methacrylate based composite bonding agent (MA). Groups were subdivided into 4 (n=20) according to nano-ZrO2 concentration (0, 2.5, 5, 7.5 wt%). Half the specimens were thermo-cycled before testing. FS was determined by three-point bending test. Statistical analysis was done using ANOVA and Tukey-Kramer multiple comparison tests, with α=0.05. Alumina-blasting+(SC) or (MA) significantly increased FS of repaired specimens compared to control (p<0.05). All surface-treated specimens combined with nano-ZrO2 reinforced repair resin significantly increased FS.


Assuntos
Bases de Dentadura , Polimetil Metacrilato , Resinas Acrílicas , Resistência à Flexão , Teste de Materiais , Maleabilidade , Propriedades de Superfície
17.
Dent Mater ; 36(4): 551-559, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32089269

RESUMO

The incorporation of antimicrobial agents in restorative dental composites has the potential to slow the development of carious lesions. OBJECTIVE: The objectives of the present study were to develop experimental composite resins with chitosan or chitosan loaded with dibasic calcium phosphate anhydrous (DCPA) particles and to demonstrate their antimicrobial potential without loss of mechanical properties or biocompatibility. METHODS: Chitosan and chitosan/DCPA particles were synthetized by the electrospray method. Experimental composites were formulated by adding 0, 0.5, or 1.0 wt% particles into a resin matrix along with 60 wt% barium glass. The degree of conversion and mechanical properties were measured after 1 and 90 days of aging in water after photoactivation. Cytotoxicity and genotoxicity were evaluated using fibroblasts from dental pulp in conditioned medium. The antimicrobial activity against Streptococcus mutans was assessed by crystal violet biofilm assay. RESULTS: The experimental restorative composites were not found to be cytotoxic or genotoxic, with cell viability of 93.1 ± 8.0% (p = 0.328) and 3.0 ± 0.8% micronucleus per group (p = 0.1078), respectively. The antimicrobial results showed that all composites with approximately 20% less biofilm (p < 0.001) relative to the control. No chitosan release was detected from the composites, suggesting direct contact of the bacteria with exposed chitosan particles on the surface was responsible for the observed antimicrobial effect. The addition of the chitosan and chitosan/DCPA submicrometer (<250 nm average diameter) particles to restorative composites did not change the degree of conversion, flexural strength, elastic modulus and fracture toughness compared to the control group after 90 days aging in water. SIGNIFICANCE: It can be concluded that the addition of chitosan or chitosan/DCPA particles in the restorative composites induced antimicrobial activity without compromising the mechanical properties or biocompatibility of the composites.


Assuntos
Quitosana , Fosfatos de Cálcio , Resinas Compostas , Materiais Dentários , Resistência à Flexão , Teste de Materiais , Maleabilidade , Streptococcus mutans , Propriedades de Superfície
18.
Nature ; 578(7794): 290-295, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32025034

RESUMO

Shear stress on arteries produced by blood flow is important for vascular development and homeostasis but can also initiate atherosclerosis1. Endothelial cells that line the vasculature use molecular mechanosensors to directly detect shear stress profiles that will ultimately lead to atheroprotective or atherogenic responses2. Plexins are key cell-surface receptors of the semaphorin family of cell-guidance signalling proteins and can regulate cellular patterning by modulating the cytoskeleton and focal adhesion structures3-5. However, a role for plexin proteins in mechanotransduction has not been examined. Here we show that plexin D1 (PLXND1) has a role in mechanosensation and mechanically induced disease pathogenesis. PLXND1 is required for the response of endothelial cells to shear stress in vitro and in vivo and regulates the site-specific distribution of atherosclerotic lesions. In endothelial cells, PLXND1 is a direct force sensor and forms a mechanocomplex with neuropilin-1 and VEGFR2 that is necessary and sufficient for conferring mechanosensitivity upstream of the junctional complex and integrins. PLXND1 achieves its binary functions as either a ligand or a force receptor by adopting two distinct molecular conformations. Our results establish a previously undescribed mechanosensor in endothelial cells that regulates cardiovascular pathophysiology, and provide a mechanism by which a single receptor can exhibit a binary biochemical nature.


Assuntos
Células Endoteliais/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Mecanotransdução Celular , Glicoproteínas de Membrana/metabolismo , Estresse Mecânico , Animais , Aterosclerose/metabolismo , Feminino , Integrinas/metabolismo , Camundongos , Neuropilina-1/metabolismo , Maleabilidade , Receptores de Superfície Celular/metabolismo , Semaforinas/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo
19.
Spine Deform ; 8(1): 39-44, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31981151

RESUMO

STUDY DESIGN: Experimental in vivo study of the pressure exerted on the spine of a pig by a new cyclic anterior vertebral body tethering (AVBT) prototype. OBJECTIVES: To evaluate the relationship between the tether tension and the pressures transmitted onto the vertebral end plates by a cyclic AVBT prototype. AVBT is a recent surgical technique for the treatment of pediatric scoliosis that compresses the convex side of the spine with a sustained tension, to modulate the growth to progressively correct the deformity over time. Previous studies demonstrated that cyclic compression has similar growth modulation capacity but with less detrimental effects on the integrity of the discs and growth plates. METHODS: A 3-month-old healthy Duroc pig was anesthetized and a lateral thoracotomy was performed. The T7-T10 segment was instrumented and compressed during 50 s with the load oscillating (0.2 Hz) from + 30 to - 30% of the following mean tensions: 29, 35, 40, 44, and 49 N. The pressure exerted on T9 superior vertebral end plate was monitored during the cyclic loading. Three repetitions of each test were performed. RESULTS: The resulting mean pressure exerted on the vertebral end plate was linearly correlated with the mean tether tension (r2 = 0.86). Each cycle translated in a hysteresis profile of the measured pressure and tension, with amplitudes varying between ± 11.5 and ± 29.9%. CONCLUSIONS: This experimental study documented the relationship between the tether tension and the pressure. This study confirmed the feasibility of cyclic AVBT principle to transfer varying pressures on the vertebral end plates, which is intended to control vertebral growth, while keeping the spine flexibility and preserving the health of soft tissues such as the intervertebral discs and the growth plate but remained to be further verified. LEVEL OF EVIDENCE: Level IV.


Assuntos
Lâmina de Crescimento , Procedimentos Ortopédicos/métodos , Pressão , Escoliose/cirurgia , Coluna Vertebral/cirurgia , Animais , Fenômenos Biomecânicos , Modelos Animais de Doenças , Estudos de Viabilidade , Feminino , Disco Intervertebral , Procedimentos Ortopédicos/instrumentação , Parafusos Pediculares , Maleabilidade , Escoliose/fisiopatologia , Coluna Vertebral/crescimento & desenvolvimento , Coluna Vertebral/fisiopatologia , Suínos
20.
Sensors (Basel) ; 20(2)2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31947525

RESUMO

In this paper, a flexible and stretchable energy harvester based on liquid-metal and fluorinated ethylene propylene (FEP) electret films is proposed and implemented for the application of wearable devices. A gallium liquid-metal alloy with a melting point of 25.0 °C is used to form the stretchable electrode; therefore, the inducted energy harvester will have excellent flexibility and stretchability. The solid-state electrode is wrapped in a dragon-skin silicone rubber shell and then bonded with FEP electret film and conductive film to form a flexible and stretchable energy harvester. Then, the open-circuit voltage of the designed energy harvester is tested and analyzed. Finally, the fabricated energy harvester is mounted on the elbow of a human body to harvest the energy produced by the bending of the elbow. The experimental results show that the flexible and stretchable energy harvester can adapt well to elbow bending and convert elbow motion into electric energy to light the LED in a wearable watch.


Assuntos
Fontes de Energia Bioelétrica , Politetrafluoretileno/análogos & derivados , Dispositivos Eletrônicos Vestíveis , Cotovelo/fisiologia , Eletrodos , Desenho de Equipamento , Humanos , Teste de Materiais , Movimento/fisiologia , Maleabilidade , Politetrafluoretileno/química
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