• Biomolecules & Therapeutics
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• v.23 no.4
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• pp.301-312
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• 2015

Metastasis is one of hallmarks of cancer and a major cause of cancer death. Combatting metastasis is highly challenging. To overcome these difficulties, researchers have focused on physical properties of metastatic cancer cells. Metastatic cancer cells from patients are softer than benign cancer or normal cells. Changes of viscoelasticity of cancer cells are related to the keratin network. Unexpectedly, keratin network is dynamic and regulation of keratin network is important to the metastasis of cancer. Keratin is composed of heteropolymer of type I and II. Keratin connects from the plasma membrane to nucleus. Several proteins including kinases, and protein phosphatases bind to keratin intermediate filaments. Several endogenous compounds or toxic compounds induce phosphorylation and reorganization of keratin network in cancer cells, leading to increased migration. Continuous phosphorylation of keratin results in loss of keratin, which is one of the features of epithelial mesenchymal transition (EMT). Therefore, several proteins involved in phosphorylation and reorganization of keratin also have a role in EMT. It is likely that compounds controlling phosphorylation and reorganization of keratin are potential candidates for combating EMT and metastasis.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.66-69
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• 1999

A large number of works have been Performed to understand the electrochemical growth of Polypynole on conducting substrates in aqueous as well as in nonaqueous solutions. Recently most researches with Polypyrrole have tended to be directed toward technological applications, but many fundamental physical and chemical properties of Polypyrrole remain unknown. In Particular, microrheological Property of polypyrrole has been largely neglected until the advanced electrochemical quartz crystal microbalance technique was introduced recently. To study anion effects on microrheolosical Property of Polypyrrole, we investigated changes in viscoelasticity of Polypyrrole during electrochemical growth in neutral aqueous solutions by means of in siか electrochemical quartz crystal oscillator method. The results showed that the films of Polypyrrole synthesized in $KPF_6\;and\;KCIO_4$ were more viscoelastic than the ones in $KCI,\;KNO_3,\;KBr,\;KBF_4,\;K_2SO_4$, sodium tosylate (NaOTs), and sodium dodecyl sulfate (SDS). The growth rate of Polypyrrole in SDS was faster than that in the others utilized. Polypyrroles synthesized in buffered neutral solutions were more elastic than those in unbuffered neutral solutions.

• Korea-Australia Rheology Journal
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• v.17 no.3
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• pp.131-140
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• 2005

In this work we show the results of our most recent Direct Numerical Simulations (DNS) of turbulent viscoelastic channel flow using spectral spatial approximations and a stabilizing artificial diffusion in the viscoelastic constitutive model. The Finite-Elasticity Non-Linear Elastic Dumbbell model with the Peterlin approximation (FENE-P) is used to represent the effect of polymer molecules in solution, The corresponding rheological parameters are chosen so that to get closer to the conditions corresponding to maximum drag reduction: A high extensibility parameter (60) and a moderate solvent viscosity ratio (0.8) are used with two different friction Weissenberg numbers (50 and 100). We then first find that the corresponding achieved drag reduction, in the range of friction Reynolds numbers used in this work (180-590), is insensitive to the Reynolds number (in accordance to previous work). The obtained drag reduction is at the level of $49\%\;and\;63\%$, for the friction Weissenberg numbers 50 and 100, respectively. The largest value is substantially higher than any of our previous simulations, performed at more moderate levels of viscoelasticity (i.e. higher viscosity ratio and smaller extensibility parameter values). Therefore, the maximum extensional viscosity exhibited by the modeled system and the friction Weissenberg number can still be considered as the dominant factors determining the levels of drag reduction. These can reach high values, even for of dilute polymer solution (the system modeled by the FENE-P model), provided the flow viscoelasticity is high, corresponding to a high polymer molecular weight (which translates to a high extensibility parameter) and a high friction Weissenberg number. Based on that and the changes observed in the turbulent structure and in the most prevalent statistics, as presented in this work, we can still rationalize for an increasing extensional resistance-based drag reduction mechanism as the most prevalent mechanism for drag reduction, the same one evidenced in our previous work: As the polymer elasticity increases, so does the resistance offered to extensional deformation. That, in turn, changes the structure of the most energy-containing turbulent eddies (they become wider, more well correlated, and weaker in intensity) so that they become less efficient in transferring momentum, thus leading to drag reduction. Such a continuum, rheology-based, mechanism has first been proposed in the early 70s independently by Metzner and Lamley and is to be contrasted against any molecularly based explanations.

• Proceedings of the KACD Conference
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• 2008.05a
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• pp.235-245
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• 2008

The aim of this study was to develop a method for measuring the slumping resistance of resin composites and to relate it to the rheological characteristics. Five commercial hybrid composites (Z100. Z250. DenFil, Tetric Ceram. ClearFil) and a nanofill composite (Z350) were used to make disc-shaped specimens of 2 mm thickness. An aluminum mold with square shaped cutting surface was pressed onto the composite discs to make standardized imprints. The imprints were light-cured either immediately (non-slumped) or after waiting for 3 minutes at $25^{\circ}C$ (slumped). White stone replicas were made and then scanned for topography using a laser 3-D profilometer. Slumping resistance index (SRI) was defined as the ratio of the groove depth of the slumped specimen to that of the non-slumped specimen. The pre-cure viscoelasticity of each composite was evaluated by an oscillatory shear test and normal stress was measured by a squeeze test using a rheometer. Flow test was also performed using a flow tester. Correlation analysis was performed to investigate the relationship between the viscoelastic properties and the SRI. SRI varied between the six materials (Z100 < DenFil < Z250 < ClearFil < Tetric Ceram < Z350). The SRI was strongly correlated with the viscous (loss) shear modulus G' but not with the loss tangent. Also. slumping resistance was more closely related to the resistance to shear flow than to the normal stress. Slumping tendency could be quantified using the imprint method and SRI. The index may be applicable to evaluate the clinical handling characteristics of composites.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.235-245
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• 2008

The aim of this study was to develop a method for measuring the slumping resistance of resin composites and to relate it to the rheological characteristics. Five commercial hybrid composites (Z100, Z250, DenFil, Tetric Ceram, ClearFil) and a nanofill composite (Z350) were used to make disc-shaped specimens of 2 mm thickness. An aluminum mold with square shaped cutting surface was pressed onto the composite discs to make standardized imprints. The imprints were light-cured either immediately (non-slumped) or after waiting for 3 minutes at $25{\circ}C$ (slumped). White stone replicas were made and then scanned for topography using a laser 3-D profilometer. Slumping resistance index (SRI) was defined as the ratio of the groove depth of the slumped specimen to that of the nonslumped specimen. The pre-cure viscoelasticity of each composite was evaluated by an oscillatory shear test and normal stress was measured by a squeeze test using a rheometer. Flow test was also performed using a flow tester. Correlation analysis was performed to investigate the relationship between the viscoelastic properties and the SRI. SRI varied between the six materials (Z100 < DenFil < Z250 < ClearFil < Tetric Ceram < Z350). The SRI was strongly correlated with the viscous (loss) shear modulus G' but not with the loss tangent. Also, slumping resistance was more closely related to the resistance to shear flow than to the normal stress. Slumping tendency could be quantified using the imprint method and SRI. The index may be applicable to evaluate the clinical handling characteristics of composites.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.5
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• pp.738-746
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• 2011

We manufactured rice-whole soybean curd by a microbial transglutaminase (MTGase) with a mixture of hydrolyzed rice and micronized whole soybean powder (MWSP) and analyzed its rheological properties, including texture, viscoelasticity, protein cross-linking, and surface structure. A 40% rice suspension digested with a Termamyl enzyme at $85^{\circ}C$ for 20 min showed a 9.0% reducing sugar and a consistency of $1.27\;Pa{\cdot}s^n$, resulting in a great reduction in consistency. A MWSP suspension with 22% solid content was transformed into a typical tofu texture. MWSP curd fortified with 7.5% rice showed enhanced texture properties, with a hardness of 639.6 dyne/$cm^2$, and a springiness of 0.96. In a MWSP suspension (18~22% w/v) treated with 5% MTGase, viscoelasticity increased dependently with MWSP concentration, and a 22% MWSP indicated a G' value of 5.1 Pa and a G'' value of 9.0 Pa. Furthermore, soybean proteins present in the 22% MWSP curd largely disappeared or formed polymers with a high molecular weight by MTGase reaction within 30 min. MWSP (22%) fortified with 7.5% rice showed similar polymerization patterns on SDS-PAGE. The surface structure of the rice-MWSP curds was more dense and homogeneous network due to the addition of hydrolyzed rice. However, the surface structure of all rice-MWSP curds became rough and showed a non-homogeneous network after cold storage.

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.143-146
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• 2009

Breakthrough of high Weisenberg number problem is related with keeping the positive definiteness of the conformation tensor in numerical procedures. In this paper, we suggest a simple method to preserve the positive definiteness by use of vector decomposition of the conformation tensor which does not require eigenvalue problem. We also derive the constitutive equation of tensor-logarithmic transform in simpler way than that of Fattal and Kupferman and discuss the comparison between the vector decomposition and tensor-logarithmic transformation.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.1
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• pp.37-42
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• 2003

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping have been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

• Bulletin of the Korean Mathematical Society
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• v.52 no.3
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• pp.907-914
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• 2015

In this paper, we consider a viscoelastic plate equation with p-Laplacian $u^{{\prime}{\prime}}+{\Delta}^2u-div({\mid}{\nabla}u{\mid}^{p-2}{\nabla}u)+{\sigma}(t){\int}_{0}^{t}g(t-s){\Delta}u(s)ds-{\Delta}u^{\prime}=0$. By introducing suitable energy and Lyapunov functionals, we establish a general decay estimate for the energy, which depends on the behavior of both ${\sigma}$ and g.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.103-118
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• 1993

The near field is discretized into finite elements, and the far field into infinite elements. Closed form far-field solutions to three fundamental problems are used as the shape functions of the infinite elements. Such infinite elements are capable of transmitting all surface and body waves. An efficient scheme to integrate numerically the stiffness and mass matrices of these elements in presented. Results agree closely with those obtained by others.