In vitro hemorheological effects of parenteral agents used in peripheral arterial disease

Biro, Katalin,Sandor, Barbara,Toth, Andras,Koltai, Katalin,Papp, Judit,Rabai, Miklos,Toth, Kalman,Kesmarky, Gabor 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.2

Peripheral arterial disease (PAD) is a frequent manifestation of systemic atherosclerosis. In PAD hemorheological parameters were defined as risk factors in a number of studies and several therapeutic agents were tried in these conditions. Our study aims to investigate and compare the in vitro hemorheological effects of various drugs generally used in the parenteral treatment of intermittent claudication and critical limb ischemia. Blood samples of healthy male volunteers were incubated with iloprost, alprostadil, pentoxifylline, sulodexide or pentosan polysulfate at calculated therapeutic serum concentration. Hematocrit (Hct) was determined by microhematocrit centrifuge. Plasma and apparent whole blood viscosities (WBV) were evaluated by capillary viscometer. Red blood cell aggregation was measured by LORCA (laserassisted optical rotational cell analyzer) aggregometer, and LORCA ektacytometer was used for measuring erythrocyte deformability at $37^{\circ}C$. Iloprost, alprostadil, and pentoxifylline incubation did not have any significant effect on plasma and apparent WBV. Elongation index increased in samples incubated with alprostadil at low shear stresses 0.95 and 0.53 Pa (p < 0.05). Sulodexide significantly improved WBV and Hct/WBV ratio (p < 0.05). Incubation with pentosan polysulfate resulted in higher WBV, lower Hct/WBV ratio and deterioration in the aggregation parameters (p < 0.05). Sulodexide may have beneficial effect on a macrorheological parameter; alprostadil may improve a microrheological parameter. Hemorheological alterations could be important in PAD patients with hampered vasodilator capacity.

Numerical analysis of internal flow and mixing performance in polymer extruder I: Single screw element

김낙수,이재욱,김홍범 한국유변학회 2006 Korea-Australia rheology journal Vol.18 No.3

We analyzed the non-Newtonian and non-isothermal flow in a single screw extruder system and investigated the mixing performance with respect to the screw speed and the screw pitch. The viscosity of polymer melt was described with Carreau-Yasuda model. The mixing performance was computed numerically by tracking the motions of particles in the screw element system. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the strain. The results revealed that the high screw speed reduces the residence time but increases the deformation rate while the small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance and the small screw pitch increases the distributive mixing performance.

Thermoplastic resin transfer molding of carbon fiber reinforced polyamide 6 composite with the improved processability using zeolite particle

이재효,손승모,유중재,김상우,Yi Jin Woo,성동기 한국유변학회 2023 Korea-Australia rheology journal Vol.35 No.1

Thermoplastic resin transfer molding (T-RTM) of polyamide 6-based composite is one of the promising process to massproduce an environmentally friendly textile composite with recyclable thermoplastic resin, in which ε-caprolactam monomer with low viscosity is injected and in situ polymerized into the fabric. The side reactions caused by water in the anionic polymerization process of the monomer is a crucial problem for fabricating the composite with a high quality. In this study, we introduced zeolite, a porous ceramic water-absorbing particle, into the ε-caprolactam to improve the moisture sensitivity during the anionic polymerization. The selective water-absorbing eff ect of zeolite particle was verifi ed by measuring the monomer conversion, viscosity-average molecular weight, and viscosity change during polymerization, and mechanical properties of the resultant carbon fi ber reinforced polyamide composite were investigated. It is expected that processability of the T-RTM is remarkably improved by reducing both the drying time during process and quality deviation of the composite by variation of humidity, which can make T-RTM process a viable technology for mass-production of thermoplastic composites.

Mathematical model on magneto-hydrodynamic dispersion in a porous medium under the influence of bulk chemical reaction

Ashis Kumar Roy,Apu Kumar Saha,R. Ponalagusamy,Sudip Debnath 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.4

The mathematical model of hydrodynamic dispersion through a porous medium is developed in the presence of transversely applied magnetic fields and axial harmonic pressure gradient. The solute introduce into the flow is experienced a first-order chemical reaction with flowing liquid. The dispersion coefficient is numerically determined using Aris’s moment equation of solute concentration. The numerical technique employed here is a finite difference implicit scheme. Dispersion coefficient behavior with Darcy number, Hartmann number and bulk flow reaction parameter is investigated. This study highlighted that the dependency of Hartmann number and Darcy number on dispersion shows different natures in different ranges of these parameters.

Internal Mixer에서의 고분자 유동 및 혼합거동에 관한연구

김진국 한국유변학회 1990 Korea-Australia rheology journal Vol.2 No.1

혼합공정은 화학공학, 식품공학, 건축공학등 여러 가지 산업분야에 걸쳐 이용되는데 최근 고분자 분야에서도 신소재 개발 또는 제품의 물성을 향상시키기 위하여 이에대한 연구 가 활발해지고 있다. 고분자 가공에서 혼합에 이용되는 대표적인 기계로는 twin screw extruder, internal mixer, two roll mill 등이 있는데 본 연구에서는 internal mixer에서의 고 분자 유동 및 혼합거동을 파악하고자 하였다. 실험적으로는 flow visualization 방법을 써서 순환시간을 측정하였고, 시뮬레이션을 통하여 이론적으로 이를 검토하였다. 고분자 거동은 비뉴우톤을 유체로서 설명되기 때문에 본 연구에서는 혼합기의 구조적 특성을 고려한 모델 로서 $\eta$ = $\frac{\eta_o}{1+A[2trd^2]^\frac{1-n}{2}}$

비등온 방사공정에서의 Draw Resonance

현재천 한국유변학회 1989 Korea-Australia rheology journal Vol.1 No.1

임계연신비로 특징지어지는 비등온 방사공정에서의 Draw Resonance 발생을, White 의 변형속도에 따라 변하는 물질의 이완시간 모델에 의한 convected Maxwell 유체의 방사 모형을 사용해서 연구했다. 임계연신비의 계산에는 다른 연구자들이 이용하는 통상의 복잡 한 수치계산인 eigenvalue 방법을 쓰지 않고 전파하는 동적 waves 에 근거한 간단한 Hyun 의 이론을 사용했다. 그 결과 Staton Number와 냉각 공기온도로서 나타내지는 방사공정의 냉각이 공정을 안정시킨다는 것이 밝혀졌다. 다시 말해서 연신점도가 변형후화인 유체이거 나 변형박화인 유체이거난 상관없이 항상 Stanton Number가 켜지거나 또는 냉각공기온도 가 낮아질수록(즉냉각효과가 커질 때) 임계연신비가 커지는 것이다(단변형박화 dvcp의 빌부 구간을 제외하고) 한편 Draw Resonacnce 에 미치는 냉각의 효과는 무차원 이완시간(a Weissenberg Number 혹은 a Deborah number)이 커질수록 작아진다는 것도 발견됐다. 이 것은 process Time 이 작아지면 열전달이 작아지기 때문이다. 이러한 내용들은 다른 연구 자들의 결과와도 잘 부합된다.

Particle trajectory and orientation evolution of ellipsoidal particles in bounded shear flow of Giesekus fluids

Bingrui Liu,Jianzhong Lin,Xiaoke Ku,Zhaosheng Yu 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.4

The migration of ellipsoidal particles in bounded shear flow of Giesekus fluids is studied numerically using the direct forcing/fictitious domain method for the Weissenberg number ranging from 0.1 to 3.0, the mobility parameter α which quantifies the shear-thinning effect ranging from 0.1 to 0.7. The model and numerical method are validated by comparing the present results with available theoretical and numerical results in other literatures. The results show that the trajectory of particles depends on their initial orientation and vertical position, and the particle migration can be roughly classified into returning and passing pattern. The values of initial vertical position of particle corresponding to the separatrix between the returning and passing pattern decrease with increasing Weissenberg number regardless of the initial orientation of particle, and the shear thinning has the opposite effect. The evolution of particle orientation depends on the initial particle orientation. For the particles whose initial orientation is parallel to the shear plane, the particle rotates with the semi-major axis as radius in the shear plane. For the particles whose initial orientation is perpendicular to the shear plane, the particle rotates with the semi-minor axis as radius. For the particles whose initial orientation has a certain angle with the shear plane, the particle rotates with the vorticity axis and the orientation vector is gradually close to the vorticity vector. The evolution of the particle orientation becomes slow with increasing Wi whether it is in passing behavior or in returning behavior.

Effects of silica nanoparticles on the rheological properties and morphologies of polyvinyl alcohol/silver nanowire suspensions

Seung Hak Lee,Si Yoon Kim,Reza Salehiyan,현규 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.4

We investigated the effects of silica nanoparticles (SiNPs) on the rheological properties and microstructures of polyvinyl alcohol (PVA)/silver nanowire (AgNW) suspensions. For PVA/AgNW suspensions without SiNPs, rheological percolation threshold was calculated using storage modulus determined by small amplitude oscillatory shear (SAOS) tests. Results from SAOS tests revealed that PVA/AgNW suspensions had two transition concentrations, which led to different structure developments. Storage modulus from large amplitude oscillatory shear (LAOS) tests showed double-step strain softening behavior at all AgNW concentrations tested, and elastic stress components, also obtained by LAOS tests, exhibited trends similar to storage modulus development. Furthermore, two distinguishable structures were observed when large strain amplitude shear was applied. When SiNPs were added to PVA/AgNW suspensions, the rheological properties of PVA/AgNW suspensions from SAOS tests increased. LAOS results showed storage modulus and elastic stress components of PVA/AgNW suspensions were dependent on AgNW concentration. Doublestep strain softening disappeared for PVA/AgNW suspensions containing SiNPs at low AgNW concentrations, whereas at high AgNW concentrations double-step strain softening behavior was observed.

Mucoadhesive and pH-responsive behavior of gelatin containing hydrogels for protein drug delivery applications

Jihwan Oh,김범상 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.1

Novel gelatin-containing polymer hydrogels that can be used as mucoadhesive delivery systems were developed. Poly(acrylic acid) hydrogels were modified by copolymerizing gelatin as adhesion promoter, to improve the adhesion to the mucus layer and the synthesized copolymer of acrylic acid (AA) and methacrylated gelatin (GelMA) were designated as P(AA-co-GelMA). The pH-sensitivity and the mucoadhesive property of the P(AA-co-GelMA) hydrogel were investigated as carries of an oral protein delivery system activated by pH changes of the human GI tract. There was a drastic change in the weight swelling ratio of P(AA-co-GelMA) hydrogels at a pH of around 5, that is, low swelling ratios at a pH below 5, while high swelling ratios at a pH greater than 5. In addition, the swelling ratio increased at a pH above 5, when the AA content in the hydrogel increased. In mucoadhesive experiments using the rheometer, when the GelMA concentration in the P(AA-co-GelMA) hydrogel increased, the maximum force of detachment increased, indicating that the mucoadhesion of the hydrogel was improved. The P(AA-co-GelMA) hydrogels also showed a pH-responsive release behavior. The ratio of the cumulative amounts of Rh-B released from P(AA-co-GelMA) hydrogels at pH 2.6 to pH 7.0 increased, when the AA content in the hydrogel decreased.

Numerical flow analysis on warpage of film insert molded parts withfiber reinforced polymer substrate

김성륜,Jin Young Kim,Sung Ho Kim,Seung Hwan Lee,윤재륜,Sung Hee Lee,Wung Kim 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.3

Non-uniform temperature distribution is developed in the thickness direction of the film insert molded (FIM) product during filling and cooling stages due to retardation of the heat transfer through the solid film. Since the non-uniform temperature distribution causes non-uniform shrinkage of the product after ejection and warpage is generated by the non-uniform shrinkage, warpage of the FIM specimen is larger than that of the injection molded specimen. A new mold design was suggested in this study in order to prevent warpage of FIM specimens. Warpage of FIM specimens obtained by using the new mold was smaller than that of FIM specimens obtained by using the conventional mold. Fiber reinforced polymer resins were also used as the substrate to prepare the FIM specimens. Warpage of the FIM specimens with the fiber composite substrate was reduced with increasing the fiber loadings. Warpage of the FIM specimens with carbon fiber (CF) reinforced PC (polycarbonate)/ABS (acrylonitrile-butadiene-styrene) blend was predicted by considering anisotropic material properties such as fiber orientation, thermal expansion coefficient, Poisson's ratio, and elastic modulus.