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1.
Nat Commun ; 12(1): 5072, 2021 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-34417473

RESUMO

In vivo bioprinting has recently emerged as a direct fabrication technique to create artificial tissues and medical devices on target sites within the body, enabling advanced clinical strategies. However, existing in vivo bioprinting methods are often limited to applications near the skin or require open surgery for printing on internal organs. Here, we report a ferromagnetic soft catheter robot (FSCR) system capable of in situ computer-controlled bioprinting in a minimally invasive manner based on magnetic actuation. The FSCR is designed by dispersing ferromagnetic particles in a fiber-reinforced polymer matrix. This design results in stable ink extrusion and allows for printing various materials with different rheological properties and functionalities. A superimposed magnetic field drives the FSCR to achieve digitally controlled printing with high accuracy. We demonstrate printing multiple patterns on planar surfaces, and considering the non-planar surface of natural organs, we then develop an in situ printing strategy for curved surfaces and demonstrate minimally invasive in vivo bioprinting of hydrogels in a rat model. Our catheter robot will permit intelligent and minimally invasive bio-fabrication.


Assuntos
Bioimpressão , Cateteres , Imãs/química , Robótica , Animais , Linhagem Celular , Elasticidade , Condutividade Elétrica , Humanos , Hidrogéis/química , Fígado/diagnóstico por imagem , Ratos Sprague-Dawley , Suínos , Tomografia Computadorizada por Raios X , Viscosidade
2.
Sensors (Basel) ; 21(16)2021 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-34451003

RESUMO

The mechanical properties of biological cells, especially the elastic modulus and viscosity of cells, have been identified to reflect cell viability and cell states. The existing measuring techniques need additional equipment or operation condition. This paper presents a cell's viscoelasticity measurement method based on the spheroidization process of non-spherical shaped cell. The viscoelasticity of porcine fetal fibroblast was measured. Firstly, we introduced the process of recording the spheroidization process of porcine fetal fibroblast. Secondly, we built the viscoelastic model for simulating a cell's spheroidization process. Then, we simulated the spheroidization process of porcine fetal fibroblast and got the simulated spheroidization process. By identifying the parameters in the viscoelastic model, we got the elasticity (500 Pa) and viscosity (10 Pa·s) of porcine fetal fibroblast. The results showed that the magnitude of the elasticity and viscosity were in agreement with those measured by traditional method. To verify the accuracy of the proposed method, we imitated the spheroidization process with silicone oil, a kind of viscous and uniform liquid with determined viscosity. We did the silicone oil's spheroidization experiment and simulated this process. The simulation results also fitted the experimental results well.


Assuntos
Técnicas de Imagem por Elasticidade , Animais , Simulação por Computador , Módulo de Elasticidade , Elasticidade , Suínos , Viscosidade
3.
Med Biol Eng Comput ; 59(10): 2051-2061, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34431026

RESUMO

Modeling the mechanical behavior of soft tissue probe insertion remains a challenging endeavor due to involved interdependent phenomena comprising tissue nonlinear deformation, contact between the probe and the tissue, crack propagation, and viscoelastic effects. To that matter, cohesive elements allow simulating crack formation and propagation, which provides a promising path to modeling the mechanical behavior of probe insertion in soft tissues. As such, the aim of the present study was to investigate the feasibility of devising and integrating an algorithm in a finite element (FE) case study in efforts of reverse engineering the material properties of non-homogeneous soft tissues. A layered nonlinear tissue model with a cohesive zone was created in the commercial software ABAQUS. Material properties were iteratively modified via a hybrid gradient descent optimization algorithm: minimizing the resultant error to first find optimum Ogden's hyperelastic parameters, followed by obtaining the damage parameters. Perceived material properties were then compared to those obtained via experimental human cadaver testing. Under the investigated four-layered muscle model, numerical results overlapped, to a great extent, with six different force-insertion experimental profiles with an average error of [Formula: see text] 15%. The best profile fit was realized when the highest sudden force drop was less than 60% of the peak force. Lastly, the FE analysis revealed an increase in stiffness as the probe advanced inside the tissue. The optimization algorithm demonstrated its capability to reverse engineer the material parameters required for the FE analysis of real, non-homogeneous, soft tissues. The significance of this procedure lies within its ability to extract tissue material parameters, in real time, with little to no intervention or invasive experimental tests. This could potentially further serve as a database for different muscle layers and force-insertion profiles, used for surgeon and physician clinical training purposes.


Assuntos
Fenômenos Biomecânicos , Análise de Elementos Finitos , Dinâmica não Linear , Software , Elasticidade , Estudos de Viabilidade , Humanos , Modelos Biológicos , Estresse Mecânico
4.
Medicine (Baltimore) ; 100(32): e26891, 2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34397912

RESUMO

ABSTRACT: The aim of the study is to evaluate the reliability of shear wave elastography to assess the anterior and middle scalene muscles in healthy adult subjects.The study included 60 scalene muscles in 15 healthy subjects. High-resolution ultrasound and shear wave elastography were used to evaluate the anterior scalene and the middle scalene muscles. Stiffness values were measured.The mean shear elastic modulus showed the following values, right anterior scalene muscle 18.83 ±â€Š5.32 kPa, left anterior scalene muscle 21.71 ±â€Š4.8 kPa, right middle scalene muscle 12.84 ±â€Š5.2 kPa, left middle scalene muscle 19.76 ±â€Š5.30 kPa. Positive correlation was noted between the left middle scalene muscle and body mass index (P = .004). No difference in elasticity was noted between the right and left anterior scalene muscles; however, significant difference was noted between the right and left middle scalene muscles (P = .002).The results obtained in our study could be a reference point for future research considering different scalene muscle pathologies.


Assuntos
Técnicas de Imagem por Elasticidade/métodos , Músculos do Pescoço/diagnóstico por imagem , Adulto , Índice de Massa Corporal , Estudos Transversais , Elasticidade , Feminino , Voluntários Saudáveis , Humanos , Masculino , Músculos do Pescoço/fisiologia , Reprodutibilidade dos Testes , Estudos Retrospectivos , Adulto Jovem
5.
J Phys Chem Lett ; 12(33): 8072-8079, 2021 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-34406018

RESUMO

Mastering mechanical properties of polymers at nanometer scale is highly demanded yet remains challenging. Pioneering advances determined Young's modulus in ultrathin polymer films and attained unprecedented results including rubbery stiffening. However, many viscoelastic properties such as dynamic mechanical behavior of freestanding nanoconfined polymer films are still unknown. Here we demonstrate striking changes of stiffness and the ratio between elastic and viscous responses in thin PDMS films, using a microvibrational system which enables direct measurements of dynamic stress-strain relation of freestanding films. The results show that elastic modulus is enhanced by a factor of 135 in 50 nm films than the bulk, while the viscous response substantially increases at strains >0.05 in 125 nm films. These observations exhibit significant alterations of viscoelasticity under nanoconfinement. With insights on the underlying mechanism of these results, this study is expected to provide new evidence toward gaining a comprehensive understanding of nanoconfinement effect of soft matter.


Assuntos
Elastômeros/química , Nanotecnologia , Dimetilpolisiloxanos/química , Elasticidade , Fenômenos Mecânicos , Membranas Artificiais , Viscosidade
6.
Science ; 373(6552): 337-342, 2021 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-34437153

RESUMO

Piezoelectric biomaterials are intrinsically suitable for coupling mechanical and electrical energy in biological systems to achieve in vivo real-time sensing, actuation, and electricity generation. However, the inability to synthesize and align the piezoelectric phase at a large scale remains a roadblock toward practical applications. We present a wafer-scale approach to creating piezoelectric biomaterial thin films based on γ-glycine crystals. The thin film has a sandwich structure, where a crystalline glycine layer self-assembles and automatically aligns between two polyvinyl alcohol (PVA) thin films. The heterostructured glycine-PVA films exhibit piezoelectric coefficients of 5.3 picocoulombs per newton or 157.5 × 10-3 volt meters per newton and nearly an order of magnitude enhancement of the mechanical flexibility compared with pure glycine crystals. With its natural compatibility and degradability in physiological environments, glycine-PVA films may enable the development of transient implantable electromechanical devices.


Assuntos
Materiais Biocompatíveis/química , Eletricidade , Glicina/química , Álcool de Polivinil/química , Animais , Sobrevivência Celular , Células Cultivadas , Cristalização , Teoria da Densidade Funcional , Elasticidade , Humanos , Ligação de Hidrogênio , Próteses e Implantes , Ratos , Ratos Sprague-Dawley , Estresse Mecânico
7.
J Contemp Dent Pract ; 22(6): 703-706, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34393130

RESUMO

AIM: The aim of this study was to assess the effectiveness of different gingival displacement materials in the management of the width of the gingival sulcus. MATERIALS AND METHODS: Totally, 60 participants who were aged 18 years and more were chosen for this study. The eligible participants were those who required fixed prosthesis with at least one abutment. A modified sectional tray was used to make impressions with elastomeric materials along with additional polysilicon using the double mix single impression technique. All participants were divided randomly into three experimental groups with each group having 20 participants as follows: group I-Expasyl, group II-Magic Foam Cord, and group III-Traxodent. Soon after retraction, impressions were made and assessed in a comparable manner to pre-retraction impressions. Image analysis software was used to measure the quantity of displacement of the gingiva, marked as the distance from the tooth to the gingival crest in the horizontal level under stereomicroscope. RESULTS: The highest mean sulcular gingival width (0.644 ± 0.22) was found in Traxodent group followed by Expasyl group (0.590 ± 0.11) and Magic Foam Cord group (0.528 ± 0.01). A statistically significant difference (p<0.001) was found between the groups. Intergroup comparisons between the gingival displacement materials showed a statistically significant difference (p<0.05) between group II and group III. CONCLUSION: The present study concluded that all three gingival displacement materials lead to gingival displacement, which is needed for impression making. Slightly more retraction was seen in the Traxodent group when compared to the Expasyl group and Magic Foam Cord group. CLINICAL SIGNIFICANCE: The success of fixed prosthodontic treatment depends upon precision and accuracy in every step involved in the procedure.One of the most vital stepsis making precise impressions in relation to dimensional accuracy, tear strength, etc. It is essential to have an adequate thickness of the impression material along the margins to avoid distortion. This objective can be achieved by acceptable gingival retraction.


Assuntos
Gengiva , Técnicas de Retração Gengival , Adolescente , Adulto , Assistência Odontológica , Materiais para Moldagem Odontológica , Técnica de Moldagem Odontológica , Elasticidade , Humanos
8.
Sensors (Basel) ; 21(15)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34372359

RESUMO

A respiratory measurement system composed of pressure and airflow sensors was introduced to precisely control the respiratory condition during animal experiments. The flow sensor was a hot-wire thermal airflow meter with a directional detection and airflow temperature change compensation function based on MEMS technology, and the pressure sensor was a commercially available one also produced by MEMS. The artificial dead space in the system was minimized to the value of 0.11 mL by integrating the two sensors on the same plate (26.0 mm × 15.0 mm). A balloon made of a silicone resin with a hardness of A30 was utilized as the simulated lung system and applied to the elasticity evaluation of the respiratory system in a living rat. The inside of the respiratory system was normally pressurized without damage, and we confirmed that the developed system was able to evaluate the elasticity of the lung tissue in the rat by using the pressure value obtained at the quasi-static conditions in the case of the ventilation in the animal experiments.


Assuntos
Experimentação Animal , Animais , Elasticidade , Pulmão , Miniaturização , Ratos , Respiração Artificial , Ventiladores Mecânicos
9.
Eur J Vasc Endovasc Surg ; 62(3): 358-366, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34266763

RESUMO

OBJECTIVE: Plaque elasticity and intraplaque neovascularisation are strongly suggestive of vulnerable plaque. This study aimed to investigate the relationship between intraplaque neovascularisation and plaque elasticity, and to compare the ultrasound findings with histopathological changes. METHODS: Patients enrolled in this study presented with symptomatic carotid stenosis (> 70%) and later underwent both pre-operative ultrasonography and endarterectomy. Contrast enhanced ultrasound (CEUS) and shear wave elastography (SWE) were used to measure the neovascularisation and elasticity of the plaque, respectively. After removal, plaques were histologically assessed to determine the microvessel density (MVD), matrix metalloproteinase (MMP)-9 expression, and type I/type III collagen ratio using immunohistochemistry staining and morphometry. A correlation analysis was used to establish the relationship among the aforementioned quantitative parameters. Inter- and intra-observer consistency evaluations were performed using the intraclass correlation coefficient and Bland-Altman plots. RESULTS: Ninety-four symptomatic patients with 98 plaques were included. The area under the curve (AUC) of the carotid plaque detected using CEUS correlated with its shear wave velocity (SWV) (r = -.714; p < .001), MVD (r = .842; p < .001), collagen type I/III ratio (r = -.833; p < .001), and MMP-9 (r = .738; p < .001). SWE was positively correlated with the type I/III collagen ratio (r = .805; p < .001). The overall interexaminer consistency of the SWE was acceptable (r = .638; p < .001). The interobserver correlation coefficient of the AUC, time to peak (TP), mean transit time (MTT), and SWV were .719, .756, .733, and .686, respectively. The intra-observer variability values of the AUC, TP, MTT, and SWV were .826, .845, .633, and .748, respectively. CONCLUSION: SWE and CEUS can comprehensively evaluate the vulnerability of the carotid plaque by assessing the elasticity of the plaque and neovascularisation within it. The negative correlation between the intraplaque neovascularisation and elasticity, further validated by histological findings, suggests that the more abundant the neovascularisation, the less elasticity.


Assuntos
Artérias Carótidas/diagnóstico por imagem , Estenose das Carótidas/diagnóstico por imagem , Técnicas de Imagem por Elasticidade , Elasticidade , Neovascularização Patológica/diagnóstico por imagem , Placa Aterosclerótica/diagnóstico por imagem , Adulto , Idoso , Área Sob a Curva , Artérias Carótidas/patologia , Estenose das Carótidas/patologia , Meios de Contraste , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neovascularização Patológica/patologia , Variações Dependentes do Observador , Placa Aterosclerótica/patologia , Medição de Risco
10.
Sensors (Basel) ; 21(12)2021 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-34208168

RESUMO

The aim of this study was to perform a reliability and agreement analysis and to compare lateral abdominal muscles (LAMs) thickness and elasticity results obtained by an experienced operator, by a non-experienced operator, and in an ultrasound imaging probe compression controlled (PCC) condition with minimal force necessary to obtain a proper ultrasound image. The sample consisted of 39 adolescents. An Aixplorer ultrasound scanner was used to evaluate the LAM. The probe in PCC condition was positioned in a prepared probe holder coupled with a pressure sensor. The LAM thickness and elasticity measurements were significantly (p < 0.05) different in the ultrasound PCC condition, compared to results obtained by both examiners. The abdominal oblique external and internal muscle thickness measurements were underestimated and all LAM shear moduli were overestimated during measurements without controlling the probe compression by an external sensor. The intra-class correlation coefficient was excellent in all conditions, but the smallest detectable differences were approximately 43-60% lower during the measurements collected in PCC condition. Differences in LAM measurements between PCC and 'on-hand' conditions may be clinically irrelevant when the force applied by the probe is consciously controlled by the examiner. However, during ultrasound measurements of the LAM morphology, the potential under/over estimation should always be considered when measurements are performed without controlling probe compression by an external sensor.


Assuntos
Músculos Abdominais , Músculos Abdominais/diagnóstico por imagem , Adolescente , Elasticidade , Humanos , Pressão , Reprodutibilidade dos Testes , Ultrassonografia
11.
Sensors (Basel) ; 21(12)2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-34208554

RESUMO

The field of soft robotics has attracted the interest of the medical community due to the ability of soft elastic materials to traverse the abnormal environment of the human body. However, sensing in soft robotics has been challenging due to the sensitivity of soft sensors to various loading conditions and the nonlinear signal responses that can arise under extreme loads. Ideally, soft sensors should provide a linear response under a specific loading condition and provide a different response for other loading directions. With these specifications in mind, our team created a soft elastomeric sensor designed to provide force feedback during cardiac catheter ablation surgery. Analytical and computational methods were explored to define a relationship between resistance and applied force for a semicircular, liquid metal filled channel in the soft elastomeric sensor. Pouillet's Law is utilized to calculate the resistance based on the change in cross-sectional area resulting from various applied pressures. FEA simulations were created to simulate the deformation of the sensor under various loads. To confirm the validity of these simulations, the elastomer was modeled as a neo-Hookean material and the liquid metal was modeled as an incompressible fluid with negligible shear modulus under uniaxial compression. Results show a linearly proportional relationship between the resistance of the sensor and the application of a uniaxial force. Altering the direction of applied force results in a quadratic relationship between total resistance and the magnitude of force.


Assuntos
Cateteres Cardíacos , Robótica , Elasticidade , Elastômeros , Humanos , Pressão
12.
Nat Commun ; 12(1): 3771, 2021 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-34226548

RESUMO

3D printing has emerged as one of the most promising tools to overcome the processing and morphological limitations of traditional tissue engineering scaffold design. However, there is a need for improved minimally invasive, void-filling materials to provide mechanical support, biocompatibility, and surface erosion characteristics to ensure consistent tissue support during the healing process. Herein, soft, elastomeric aliphatic polycarbonate-based materials were designed to undergo photopolymerization into supportive soft tissue engineering scaffolds. The 4D nature of the printed scaffolds is manifested in their shape memory properties, which allows them to fill model soft tissue voids without deforming the surrounding material. In vivo, adipocyte lobules were found to infiltrate the surface-eroding scaffold within 2 months, and neovascularization was observed over the same time. Notably, reduced collagen capsule thickness indicates that these scaffolds are highly promising for adipose tissue engineering and repair.


Assuntos
Tecido Adiposo/citologia , Elasticidade , Cimento de Policarboxilato/química , Impressão Tridimensional/normas , Estereolitografia/normas , Engenharia Tecidual/métodos , Tecidos Suporte/química , Tecido Adiposo/fisiologia , Animais , Células Cultivadas , Masculino , Polímeros , Porosidade , Ratos
13.
Phys Chem Chem Phys ; 23(28): 15292-15301, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34251004

RESUMO

Glasses have applications in regenerative medicine due to their bioactivity, enabling interactions with hard and soft tissues. Soda-lime phosphosilicate glasses, such as 45S5, represent a model system of bioactive glasses. Regardless of their importance as bioactive materials, the relationship between the structure, density, and cooling process has not been studied in detail. This hinders further development of glasses as biomaterials. We used molecular dynamics simulations to study the elastic and structural properties of densified 45S5 bioactive glass and liquids over a wide range of densities. We performed a systematic analysis of the glass structure to density relationship to correlate the change in the properties with the structural change to enhance the mechanical properties of bioactive glasses while preserving their bioactive nature. The results show that the glass structure tends to be repolymerized, as indicated by increased network connectivity and a tetrahedral to octahedral polyhedral transition. We were able to tailor the elastic properties while keeping the bioactivity of the glass. The results presented here will provide some guidance to develop bioactive glasses with enhanced mechanical properties.


Assuntos
Cerâmica/química , Vidro/química , Elasticidade , Simulação de Dinâmica Molecular , Estrutura Molecular , Relação Estrutura-Atividade
14.
Nat Biomed Eng ; 5(7): 641-642, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34272522
15.
Phys Rev Lett ; 127(2): 028101, 2021 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-34296898

RESUMO

DNA torsional elastic properties play a crucial role in DNA structure, topology, and the regulation of motor protein progression. However, direct measurements of these parameters are experimentally challenging. Here, we present a constant-extension method integrated into an angular optical trap to directly measure torque during DNA supercoiling. We measured the twist persistence length of extended DNA to be 22 nm under an extremely low force (∼0.02 pN) and the twist persistence length of plectonemic DNA to be 24 nm. In addition, we implemented a rigorous data analysis scheme that bridged our measurements with existing theoretical models of DNA torsional behavior. This comprehensive set of torsional parameters demonstrates that at least 20% of DNA supercoiling is partitioned into twist for both extended DNA and plectonemic DNA. This work provides a new experimental methodology, as well as an analytical and interpretational framework, which will enable, expand, and enhance future studies of DNA torsional properties.


Assuntos
DNA Super-Helicoidal/química , DNA/química , Elasticidade , Modelos Químicos , Conformação de Ácido Nucleico , Termodinâmica
16.
J Strength Cond Res ; 35(9): 2564-2571, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34265815

RESUMO

ABSTRACT: Saito, A, Namiki, Y, and Okada, K. Elasticity of the flexor carpi ulnaris muscle after an increased number of pitches correlates with increased medial elbow joint space suppression. J Strength Cond Res 35(9): 2564-2571, 2021-This study aimed to measure the medial elbow joint space and elasticity of the forearm flexor-pronator muscles in repetitive pitching and to determine which of the forearm flexor-pronator muscles contribute to elbow valgus stability during pitching. Twenty-six collegiate baseball players performed 7 sets of 15 pitches. The medial elbow joint space and elasticity of the pronator teres, flexor carpi radialis, flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU) were measured using ultrasonography before pitching and after every 15 pitches. Correlations among the rate of change of these parameters were analyzed using Pearson's correlation coefficients. The medial elbow joint space increased after 60 or more pitches compared with that before pitching (all p < 0.001; effect size [ES]: 0.44-1.22). FDS and FCU elasticity increased after 45 and 60 pitches or more in contrast to that before pitching, respectively (FDS: p = 0.047 and p < 0.001, respectively; ES: 1.05-1.42, FCU: p = 0.011 and p < 0.001, respectively; ES: 1.11-1.48). After 75 or more pitches, the rate of change of FCU elasticity correlated negatively with that of the medial elbow joint space (r = -0.395, r = -0.454, and r = -0.404, after 75, 90, and 105 pitches, respectively). Increased FCU elasticity after repetitive pitching correlated with suppression of the increase of the medial elbow joint space. The FCU may be the primary dynamic stabilizer against the elbow valgus force, and evaluation of the FCU elasticity may be important for preventing elbow injuries.


Assuntos
Articulação do Cotovelo , Cotovelo , Fenômenos Biomecânicos , Elasticidade , Cotovelo/diagnóstico por imagem , Articulação do Cotovelo/diagnóstico por imagem , Antebraço , Humanos , Músculo Esquelético/diagnóstico por imagem
17.
Nutrients ; 13(7)2021 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-34203487

RESUMO

Hyaluronan (HA) is present in all connective tissues and organs, including the skin and joint fluid. However, few clinical trials have comprehensively evaluated the impacts of oral HA on skin conditions, including wrinkles and moisturization. In this study, we conducted a placebo-controlled, randomized, double-blind trial of daily HA (120 mg) intake for 12 weeks in 40 healthy Asian men and women (aged 35-64 years). Skin condition was determined by the evaluation of wrinkles, stratum corneum water content, the amount of transepidermal water loss, elasticity, and through image analysis. After 12 weeks, skin condition was significantly improved in terms of wrinkle assessment, stratum corneum water content, transepidermal water loss, and elasticity in the HA group compared to the placebo group. Regarding the percentage change from baseline, wrinkle assessment, stratum corneum water content, and skin elasticity were significantly improved in the HA group versus the placebo group after 8 and 12 weeks of ingestion. The present findings indicate that oral ingestion of HA may suppress wrinkles and improve skin condition.


Assuntos
Ácido Hialurônico/administração & dosagem , Envelhecimento da Pele/efeitos dos fármacos , Pele/efeitos dos fármacos , Adulto , Idoso , Suplementos Nutricionais , Método Duplo-Cego , Elasticidade , Epiderme , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Taiwan
18.
J Mech Behav Biomed Mater ; 122: 104699, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34332451

RESUMO

Elastic arteries are idealised as being incompressible orthotropic nonlinearly elastic cylinders. They are further idealised as being membranes in order to analyse the effect of the experimentally observed pre-stressing of arterial tissue on inflation. The pre-stress is modelled here using the opening-angle method. It is shown that there can be multiple unloaded states of arterial segments of Fung materials, suggesting the corresponding set of material parameters will not yield reliable predictions of arterial stress in three dimensions as there is no experimental evidence to support this non-uniqueness. It is also shown that the circumferential pre-strain has a simple magnifying scaling effect on the pressure-radial strain relation and on the axial force needed to maintain the membrane length during inflation; the effect of the axial pre-strain is more nuanced.


Assuntos
Artérias , Modelos Cardiovasculares , Fenômenos Biomecânicos , Elasticidade , Fenômenos Mecânicos , Estresse Mecânico
19.
Int J Mol Sci ; 22(14)2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34298939

RESUMO

The present study deals with the mathematical modeling of crosslinking kinetics of polymer-phenol conjugates mediated by the Horseradish Peroxidase (HRP)-hydrogen peroxide (H2O2) initiation system. More specifically, a dynamic Monte Carlo (MC) kinetic model is developed to quantify the effects of crosslinking conditions (i.e., polymer concentration, degree of phenol substitution and HRP and H2O2 concentrations) on the gelation onset time; evolution of molecular weight distribution and number and weight average molecular weights of the crosslinkable polymer chains and gel fraction. It is shown that the MC kinetic model can faithfully describe the crosslinking kinetics of a finite sample of crosslinkable polymer chains with time, providing detailed molecular information for the crosslinkable system before and after the gelation point. The MC model is validated using experimental measurements on the crosslinking of a tyramine modified Hyaluronic Acid (HA-Tyr) polymer solution reported in the literature. Based on the rubber elasticity theory and the MC results, the dynamic evolution of hydrogel viscoelastic and molecular properties (i.e., number average molecular weight between crosslinks, Mc, and hydrogel mesh size, ξ) are calculated.


Assuntos
Ácido Hialurônico/química , Tiramina/química , Elasticidade , Peroxidase do Rábano Silvestre/química , Hidrogéis/química , Peróxido de Hidrogênio/química , Cinética , Modelos Teóricos , Método de Monte Carlo , Polímeros/química , Reologia
20.
Int J Mol Sci ; 22(13)2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-34281169

RESUMO

The inelastic interaction between the incident photons and acoustic phonons in the taurine single crystal was investigated by using Brillouin spectroscopy. Three acoustic phonons propagating along the crystallographic b-axis were investigated over a temperature range of -185 to 175 °C. The temperature dependences of the sound velocity, the acoustic absorption coefficient, and the elastic constants were determined for the first time. The elastic behaviors could be explained based on normal lattice anharmonicity. No evidence for the structural phase transition was observed, consistent with previous structural studies. The birefringence in the ac-plane indirectly estimated from the split longitudinal acoustic modes was consistent with one theoretical calculation by using the extrapolation of the measured dielectric functions in the infrared range.


Assuntos
Taurina/química , Acústica , Cristalização , Cristalografia , Elasticidade , Fótons , Análise Espectral
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