Evaluation Of Viscoelastic Properties Research Articles

Evaluation of Viscoelastic Properties, Blood Coagulation, and Cellular Responses of a Temperature-Sensitive Gel for Hemostatic Application.

Hemorrhagic blood loss from traumatic injury is the leading cause of death in severe accidents and combat injuries. Treating and stopping blood loss in a timely and effective manner is essential for the survival of the patient. Currently, QuikClot and dry fibrin sealant dressing are well-known approaches for hemostatic treatment. However, these dressings have limitations in slowing blood loss such as being brittle, low blood absorption, and a poor sealant of the injury site. Temperature-sensitive gels may have potential as a platform for delivery of coagulation factors to improve hemostasis and wound sealing in the treatment of traumatic injuries. Here, we developed a temperature-sensitive triblock copolymer (poly ethylene oxide (PEO)-poly propylene oxide (PPO)-poly ethylene oxide (PEO)) containing fibrinogen to promote blood coagulation through gel formation at body temperature. This temperature sensitive solution-to-gel (sol-gel) transition does not require cross-linking agents or UV photoinitiation. We determined that 22 wt % (weight percent) copolymers with and without fibrinogen was the maximum concentration for sol-gel transition at body temperature. Rheology results further confirmed this sol-gel transition of 22 wt % copolymers at body temperature. We showed that fibrinogen itself promoted blood coagulation. Additionally, 22 wt % copolymer with fibrinogen successfully demonstrated stable blood coagulation within the gel compared to 22 wt % copolymer without fibrinogen. Twenty-two weight percent copolymers with and without fibrinogen also exhibited excellent biocompatibility based on cell viability, proliferation, and morphology analysis. In addition, treatment of 22 wt % copolymers did not stimulate pro-inflammatory TNF-α production from differentiated human monocytes. Our results suggest that 22 wt % of a temperature-sensitive copolymer gel containing fibrinogen has great potential as a hemostatic agent stimulating coagulation and providing immediate wound coverage for protection through a sol-gel transition at body temperature.

Evaluation of viscoelastic properties, hardness, and glass transition temperature of soft denture liners and tissue conditioner.

Soft denture liners and tissue conditioners are widely used for the denture patients to cushion masticatory force and conditionabused tissues, respectively. This study assessed methods for the evaluation of the viscoelasticity and glass transition temperature (Tg) of the silicone permanent soft liner, acrylic permanent soft liner, and tissue conditioner. Three rheological parameters of storage modulus (E'), loss modulus (E''), and loss tangent ([Formula: see text]), Tg, and hardness were determined using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and the Shore A0 hardness test. Five specimens were measured for each material. The time-temperature superposition principle was applied to produce master curves of E', E'', and [Formula: see text] for the tested materials at a reference temperature of 37°C. The acrylic permanent soft liner and tissue conditioner exhibited viscoelastic behavior and sensitivity to frequency, especially at lower frequencies. The silicone permanent soft liner showed elastic behavior and was frequency-independent. Tg for the acrylic permanent soft liner was higher than that for the tissue conditioner, which in turn was higher than that for the siliconepermanent soft liner for both DMA and DSC. In DMA, a higher frequency led to higher Tg values. A positive linear relationship was found between Shore A0 hardness and E' values, but not E'' and [Formula: see text] values. Shore hardness reflects elasticity, but not viscosity. The results of the present study can be used to improve methods for evaluating the viscoelasticity and Tg of soft denture liners and tissue conditioners.

Evaluation Method of Mechanical Properties of Living NSCLC Cells Based on Nano-indentation

Background:In AFM study of cell mechanical properties, the apparent elastic modulus of a cell is affected by many factors, especially the AFM tip geometry, indentation site of the cell, the application of the mathematical model and testing conditions.Background:In AFM study of cell mechanical properties, the apparent elastic modulus of a cell is affected by many factors, especially the AFM tip geometry, indentation site of the cell, the application of the mathematical model and testing conditions.Methods:In this study, indentation experiments of living cells under different conditions were performed aiming to build an accurate evaluation system of mechanical properties of lung cancer cells based on AFM. Comparisons of the effects of spherical and pyramid AFM tips, Hertz model of semiinfinite and finite thickness, cell nuclear and cytoplasmic indentation regions on the cell apparent elastic modulus were accomplished.Methods:In this study, indentation experiments of living cells under different conditions were performed aiming to build an accurate evaluation system of mechanical properties of lung cancer cells based on AFM. Comparisons of the effects of spherical and pyramid AFM tips, Hertz model of semiinfinite and finite thickness, cell nuclear and cytoplasmic indentation regions on the cell apparent elastic modulus were accomplished.Results:Compared with the calculated results by spherical tip, the elastic modulus distribution of non-small lung cancer cells (NSCLC) by pyramid tip was observed to be similar while the absolute values increased obviously, which were more than twice the numerical values by the spherical tip (p<0.05). The apparent elastic modulus values were the overvalued cause of the underestimation of the contact region in pyramidal tip measurement. Two different indentations over nucleus or lamellipodium of NCI-H520 cell and NCI-H1299 cell were analyzed. Consequently, the exact elastic modulus over the nucleus area can be calculated accurately using the semi-infinite Hertz model while the finite thickness Hertz model should be used for elasticity assessment of cell lamellipodium with a small thickness.Results:Compared with the calculated results by spherical tip, the elastic modulus distribution of non-small lung cancer cells (NSCLC) by pyramid tip was observed to be similar while the absolute values increased obviously, which were more than twice the numerical values by the spherical tip (p<0.05). The apparent elastic modulus values were the overvalued cause of the underestimation of the contact region in pyramidal tip measurement. Two different indentations over nucleus or lamellipodium of NCI-H520 cell and NCI-H1299 cell were analyzed. Consequently, the exact elastic modulus over the nucleus area can be calculated accurately using the semi-infinite Hertz model while the finite thickness Hertz model should be used for elasticity assessment of cell lamellipodium with a small thickness.Conclusion:This evaluation system provides technological support for accurate evaluation of viscoelastic properties of living cancer cells.Conclusion:This evaluation system provides technological support for accurate evaluation of viscoelastic properties of living cancer cells.

804 ナノインデンテーション法によるガスケットの長期・高温粘弾性特性評価 : 球状圧子による粘弾性特性評価(フランジガスケット締結体の力学と密封性能評価I,オーガナイズドセッション,学術講演)

804 ナノインデンテーション法によるガスケットの長期・高温粘弾性特性評価 : 球状圧子による粘弾性特性評価(フランジガスケット締結体の力学と密封性能評価I,オーガナイズドセッション,学術講演)

Synthesis and evaluation of antibacterial polyurethane coatings made from soybean oil functionalized with dimethylphenylammonium iodide and hydroxyl groups

Preparation of antibacterial polyurethane coatings from novel functional soybean oil was considered in this work. First, epoxidized soybean oil (ESBO) as a low price and widely available renewable resource raw material was subjected to the reaction with aniline using an ionic liquid as a green catalyst. The intermediate phenylamine containing polyol (SAP) was then methylated by reaction with methyl iodide to produce a polyol (QAP) with pendant dimethylphenylammonium iodide groups. To regulate the physical and mechanical properties as well as biological characteristics of final coatings, QAP was mixed with different portions of a similar soybean oil-based polyol (MSP) without quaternary ammonium groups. The mixtures were reacted with isophorone diisocyanate to produce crosslinked polyurethane coatings. Evaluation of viscoelastic properties by DMA method revealed single phase structure with Tg in the range of 50-82°C. Stress-strain analysis of the prepared polyurethanes showed initial modulus, tensile strength, and elongation at break in the ranges of 13-299 MPa, 4.5-13.8 MPa, and 16-109%, respectively. Additionally, the coatings showed good adherence to aluminum and PVC substrates. The solvent extracted samples showed excellent biocompatibility as determined by monitoring L929 fibroblast cells morphology and MTT assay. Meanwhile, very promising antibacterial properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria with bacterial reduction in the range of 83-100% was observed.

Evaluation of viscoelastic properties and air-bubble structure of bread containing gelatinized rice

The impact of addition of gelatinized rice porridge to bread has been investigated on loaf volume, viscoelastic properties and air-bubble structure. We prepared four variety of bread: bread containing rice porridge (rice porridge bread), bread containing gelatinized rice flour (gelatinized rice flour bread), and wheat flour and rice flour breads for references. Instrumental analyses the bread samples were carried out by volume measurement of loaf samples, creep test and digital image analysis of crumb samples. Rice porridge bread showed the maximum specific volume of 4.51cm3/g, and even gelatinized rice flour bread showed 4.30cm3/g, which was larger than the reference bread samples (wheat and rice flour breads). The values of viscoelastic moduli of gelatinized rice flour bread and rice porridge bread were significantly smaller (p < 0.05) than those of wheat flour and rice flour breads, which indicates addition of gelatinized rice flour or rice porridge to bread dough encouraged breads softer. Bubble parameters such as mean air- bubble area, number of air-bubble, air-bubble area ratio (ratio of bubble area to whole area) were not significantly different among the bread crumb samples. Therefore, the bubble structures of the bread samples seemed to similar, which implied that difference of viscoelasticity was attributed to air-bubble wall (solid phase of bread crumb) rather than air-bubble. This study showed that addition of gelatinized rice to bread dough makes the bread with larger loaf volume and soft texture without additional agents such as gluten.

656 TMAによるガスケットの粘弾性特性評価(フランジガスケット締結体の力学と密封性能評価IV)

656 TMAによるガスケットの粘弾性特性評価(フランジガスケット締結体の力学と密封性能評価IV)

554 フランジ継手用ガスケットの高温粘弾性特性の評価 : 常温におけるボルト軸力低下を考慮した場合(フランジガスケット締結体の力学と密封性能評価III,オーガナイズドセッション)

554 フランジ継手用ガスケットの高温粘弾性特性の評価 : 常温におけるボルト軸力低下を考慮した場合(フランジガスケット締結体の力学と密封性能評価III,オーガナイズドセッション)

422 水晶振動子マイクロバランスを用いた固体表面近傍液膜の粘弾性評価 : 表面近傍での構造化(T03-4 マイクロナノ理工学:nmからmmまでのテクスチャリングの創成と機能(4),大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

422 水晶振動子マイクロバランスを用いた固体表面近傍液膜の粘弾性評価 : 表面近傍での構造化(T03-4 マイクロナノ理工学:nmからmmまでのテクスチャリングの創成と機能(4),大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Creep of polyester resin filled with minerals

An attempt of application of a structural approach in evaluation of viscoelastic properties of two polyester based concretes and their matrices-polymer resin filled with minerals at various filler volume content-was undertaken. It was found that the approach can be used in evaluation of the creep compliance curves of the composites under compression either in conditionally initial state or after aging. The results of calculation by Kerner's model and the generalized Christensen's model are in close agreement. They gave good description of the experiment. The higher calculated values of the elastic moduli of the composites than the experimental values were obtained. A better description is obtained using Kerner's model of composite consisting of the resin (matrix) and filler (small- and large-dimensional particles). The application of the structural approach for description of elastic and viscoelastic properties of the composites made it possible to evaluate interphase properties and content and porosity of the composites and their changes during creep.

Remotely induced shear acoustic waves in tissues by radiation force of focused ultrasound.

A new acoustic approach to medical imaging and diagnostics based on the remote evaluation of shear elasticity modulus of soft tissues is considered. The new method, called shear wave elasticity imaging, is based on the detection of shear waves remotely generated in tissues by radiation pressure of amplitude‐modulated focused ultrasound. Remotely induced shear wave is fully attenuated within a short distance and the induced strain in the tissue can be extremely localized. By choosing appropriate temporal characteristics of the amplitude‐modulated ultrasonic pulse, the volume of tissue involved in the mechanical excitation can be kept on the order of 1=A0 cm3, in contrast to other methods of elasticity imaging where the complete organ is subjected to shear stress. Consequently, evaluation of viscoelastic properties of tissue is greatly simplified since trivial boundary conditions can be assumed and an infinite medium model can be used to reconstruct the mechanical properties of tissue. Analytical equations ...

A simple novel technique for evaluation of viscoelastic properties of ceramic composites

Relatively large residual and processing stresses may be developed during the manufacturing of ceramic composites. Such stresses can be responsible for generating microcracks during the cooldown cycle of hot pressing, or can remain in the body and contribute to the formation of cracks during the service life of the components. These stresses can be effectively modeled by the finite element method (FEM), in conjunction with a viscoelastic constitutive material model. The FEM, however requires parameters, such as the elastic and viscoelastic properties, that are not readily available. Although there are techniques available for measuring the elastic properties as a function of porosity and temperature, limited measurement values are available at elevated temperatures. Moreover, measurement of the viscoelastic parameters is very complicated. In this paper we discuss a simple yet elegant approach for evaluating the viscoelastic properties of ceramic composites. The method uses readily available data (i.e. hot pressing pressure and ram displacement, both time dependent quantities). The method therefore produces ‘in-processing’ viscosity data. The properties obtained using the method was used to conduct transient nonlinear viscoelastic finite element analysis (FEA). The FEA results were in close agreement with those measured experimentally, thereby validating the integrity of the proposed method.