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.

Shear-banding instabilities

Jan K.G. Dhont,Kyongok Kang,M.P.Lettinga,W. J. Briels 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.4

Gradient-banding and vorticity-banding instabilities, as well as a shear-induced instability due to shear-gradient induced mass transport will be discussed. Various scenarios that underly these instabilities are addressed and simple constitutive relations that allow for a (semi-) quantitative analysis are proposed. A relatively simple constitutive equation that has been proposed some time ago is reviewed, which captures a number of the experimentally observed gradient-banding phenomena. This constitutive equation is based on the usual formal expansion of the stress tensor with respect to gradients in the flow velocity, but now including the second order term. The second order term is necessary to describe the relatively large spatial gradients within the interface between the two bands. The resulting simple constitutive equation is shown to give rise to stationary gradient-banded states, where the shear rates within the bands are constant, it describes stress selection under controlled rate conditions and explains why banding can not occur under controlled stress conditions. The simple constitutive equation does not include coupling to concentration, which may give rise to banding also under controlled stress conditions. Two examples of mechanisms that lead to the strong shear thinning that is necessary for gradient banding are discussed: (i) transient forces due to entanglements in polymer systems, and (ii) critical slowing down. The latter mechanism is shown to be important for a worm-like micellar system. The mechanism that leads to vorticity banding is still under debate. Vorticity banding of fd-virus suspensions within the two-phase isotropic-nematic coexistence will be discussed. Experiments on the kinetics of banding and particle-tracking experiments lead to a recently proposed mechanism for the vorticity-banding instability, where the instability is identified as an elastic instability similar to the polymer-Weissenberg effect. The role of polymer chains in the classic Weissenberg effect is now played by inhomogeneities formed during the initial stages of phase separation. For other systems than fd-virus suspensions that exhibit vorticity banding, the inhomogeneities general have a different origin, like in weakly aggregated colloids and worm-like micellar systems where the inhomogeneities are the colloidal aggregates and the worms, respectively. An instability that has been discovered some time ago, which is an instability due to shear-gradient induced mass transport is also discussed. The coupling between shear-gradients and mass transport has been formally introduced through a shear-rate dependent chemical potential, of which the microscopic origin was not explained. It will be shown that the microscopic origin of this coupling is related to the shear-induced distortion of the pair-correlation function. Contrary to the stationary gradient-banded and vorticity-banded state, it is not yet known what the stationary state is when this shear-concentration-coupling instability occurs.

Rheological evaluation of petroleum jelly as a base material in ointmentand cream formulations with respect to rubbing onto the human body

Eun-Kyoung Park,Ki-Won Song,Ki-Won Song 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.4

The objective of the present study is to systematically characterize a nonlinear viscoelastic behavior of petroleum jelly in large amplitude oscillatory shear flow fields correspondent to the rubbing condition onto the human body. With this aim, using a strain-controlled rheometer, the dynamic viscoelastic properties of commercially available petroleum jelly have been measured at 37oC (body temperature) over a wide range of strain amplitudes at several fixed angular frequencies. In this article, the strain amplitude dependence of the dynamic viscoelastic behavior was firstly reported in detail from the experimentally obtained data and then the results were explained from a structural view-point of petroleum jelly. Nextly, a comparison of elastic and viscous properties was made in small and large strain amplitude ranges and then these results were discussed in depth with a special emphasis on their importance in actual usage situations (i.e., rubbing onto the human body or skin). Main findings obtained from this study can be summarized as follows : (1) Both the storage modulus and loss modulus show a linear behavior only within an extremely small strain amplitude range (g0<0.2%) and exhibit almost an equivalent strain limit of linear response (gEL≈gVL≈0.2 %). (2) Both the storage modulus and loss modulus demonstrate a qualitatively similar strain-dependent nonlinear behavior (i.e., strain-thinning feature), even though the storage modulus shows a stronger dependence on strain amplitude than does the loss modulus. (3) As the strain amplitude is increased, the difference between the storage modulus and loss modulus is gradually decreased and subsequently a viscous property becomes superior to an elastic property at sufficiently large strain amplitude range. (4) A large amplitude oscillatory shear flow behavior can provide a plentiful information for a better understanding of the complicated rheological behavior of semi-solid ointment-like materials in their actual application onto the human body or skin.

Improved diffusing wave spectroscopy based on the automatized determination of the optical transport and absorption mean free path

Chi Zhang,Mathias Reufer,Danila Gaudino,Frank Scheffold 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.4

Diffusing wave spectroscopy (DWS) can be employed as an optical rheology tool with numerous applications for studying the structure, dynamics and linear viscoelastic properties of complex fluids, foams, glasses and gels. To carry out DWS measurements, one first needs to quantify the static optical properties of the sample under investigation, i.e. the transport mean free path l* and the absorption length la. In the absence of absorption this can be done by comparing the diffuse optical transmission to a calibration sample whose l* is known. Performing this comparison however is cumbersome, time consuming, and prone to mistakes by the operator. Moreover, already weak absorption can lead to significant errors. In this paper, we demonstrate the implementation of an automatized approach, based on which the DWS measurement procedure can be simplified significantly. By comparison with a comprehensive set of calibration measurements we cover the entire parameter space relating measured count rates (CRt , CRb) to (l*, la). Based on this approach we can determine l* and la of an unknown sample accurately thus making the additional measurement of a calibration sample obsolete. We illustrate the use of this approach by monitoring the coarsening of a commercially available shaving foam with DWS.

Viscoelastic properties of PLA/PCL blends compatibilized with different methods

신부영,한도흥 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.4

The aim of this study was to observe changes in the viscoelastic properties of PLA/PCL (80/20) blends produced using different compatibilization methods. Reactive extrusion and high-energy radiation methods were used for blend compatibilization. Storage and loss moduli, complex viscosity, transient stress relaxation modulus, and tan δ of blends were analyzed and blend morphologies were examined. All compatibilized PLA/PCL blends had smaller dispersed particle sizes than the non-compatibilized blend, and well compatibilized blends had finer morphologies than poorly compatibilized blends. Viscoelastic properties differentiated well compatibilized and poorly compatibilized blends. Well compatibilized blends had higher storage and loss moduli and complex viscosities than those calculated by the log-additive mixing rule due to strong interfacial adhesion, whereas poorly compatibilized blends showed negative deviations due to weak interfacial adhesion. Moreover, well compatibilized blends had much slower stress relaxation than poorly compatibilized blends and didn’t show tan δ plateau region caused by slippage at the interface between continuous and dispersed phases.

New multifunction materials with both electrorheological performance and luminescence property

Ming-Xing Chen,Yan-Li Shang,Yun-Ling Jia,Xiang-Yu Dong,Jing Ren,Jun-Ran Li 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.1

Novel multifunctional materials, the composites AlOOH-NaYFTb5 and AlOOH-NaYFTb10, containing AlO(OH) and β-NaYF4:5%Tb3+, have been synthesized via a facile hydrothermal route and a simple grinding method. The boehmite [AlO(OH)], yttrium nitrate [Y(NO3)3·6H2O], terbium nitrate, [Tb(NO3)3·6H2O], sodium citrate (Na3C6H5O7·2H2O) and sodium fluoride (NaF) were used as starting materials. The composition, electrorheological (ER) performance, and luminescence property of the functional materials were studied. Our results show that the composites not only have good electrorheological (ER) performance, but also have good optics property. The relative shear stress τr (τr = τE/τ0, τE and τ0 are the shear stresses at the electric field strength E = 4 and 0 kV/mm, respectively) values of the suspension (25 wt.%) of AlOOHNaYFTb5 material in silicone oil are all larger than 50 in a shear rate ranging from 0.06 to 26 s−1, the τr value reaches 1333 at a shear rate of 0.06 s−1. The material with such high ER activity and favorable luminescence performance is advantageous in its application as a multifunctional material.

Analysis of excessive deformation behavior of a PMMA-touch screen panel laminated material in a high temperature condition

Hyeon Lee,Jaeyoon Wang,Seon-Mi Park,홍석무,김낙수 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.4

In this study, the bending and twisting deformations of a laminated material composed of PMMA (Poly Methyl Methacrylate) and TSP (Touch Screen Panel) were analyzed at a high temperature condition. At similar conditions, a PC (Polycarbonate)/TSP material had little deformation, but the PMMA-TSP material showed excessive bending deformation with twisting. To determine the factors that cause the deformation, 5 factors relating to material properties were systematically analyzed using FE (Finite element) analysis. The results demonstrated that variations in each of the 5 factors affect the deformation of material, and the strongest influence on the deformation behavior of the material at high temperature comes from the CTE, residual stress, and the creep effect. The validity of the analytical research was confirmed by comparing not only differences in the material properties of PMMA and PC, but also by comparing the results of the FE analysis of PMMA-TSP and PC-TSP. In the analysis, it was discovered that CTE, creep coefficient, and residual stress are the most significant causes of deformation of the laminated material.

Understanding the effect of short-chain branches by analyzing viscosity functions of linear and short-chain branched polyethylenes

슈타들러,Tahmineh Mahmoudi 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.4

In this paper, we assess the frequency dependent rheological data of several different linear and short-chain branched metallocene catalyzed polyethylenes with respect to the description of the viscosity functions. The aim is to derive material specific relaxation time l from the fit. This characteristic relaxation time follows a similar dependence to the molar mass M_w as the zero shear-rate viscosity, but slightly depends on both molar mass distribution and comonomer content. The transition between the shear-thinning region and the terminal regime is broader for mHDPE than for mLLDPE and widens with increasing molar mass Mw. This finding is explained by the differences in the plateau modulus G_N^0 and the increase of the normalized terminal relaxation time in comparison to the characteristic relaxation time, respectively.

Analysis of excessive deformation behavior of a PMMA-touch screen panel laminated material in a high temperature condition

Lee, Hyeon,Wang, Jae-Yoon,Park, Seon-Mi,Hong, Seok-Moo,Kim, Nak-Soo 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.4

In this study, the bending and twisting deformations of a laminated material composed of PMMA (Poly Methyl Methacrylate) and TSP (Touch Screen Panel) were analyzed at a high temperature condition. At similar conditions, a PC (Polycarbonate)/TSP material had little deformation, but the PMMA-TSP material showed excessive bending deformation with twisting. To determine the factors that cause the deformation, 5 factors relating to material properties were systematically analyzed using FE (Finite element) analysis. The results demonstrated that variations in each of the 5 factors affect the deformation of material, and the strongest influence on the deformation behavior of the material at high temperature comes from the CTE, residual stress, and the creep effect. The validity of the analytical research was confirmed by comparing not only differences in the material properties of PMMA and PC, but also by comparing the results of the FE analysis of PMMA-TSP and PC-TSP. In the analysis, it was discovered that CTE, creep coefficient, and residual stress are the most significant causes of deformation of the laminated material.

Understanding the effect of short-chain branches by analyzing viscosity functions of linear and short-chain branched polyethylenes

Stadler, Florian J.,Mahmoudi, Tahmineh 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.4

In this paper, we assess the frequency dependent rheological data of several different linear and short-chain branched metallocene catalyzed polyethylenes with respect to the description of the viscosity functions. The aim is to derive material specific relaxation time ${\lambda}$ from the fit. This characteristic relaxation time follows a similar dependence to the molar mass $M_w$ as the zero shear-rate viscosity, but slightly depends on both molar mass distribution and comonomer content. The transition between the shear-thinning region and the terminal regime is broader for mHDPE than for mLLDPE and widens with increasing molar mass $M_w$. This finding is explained by the differences in the plateau modulus $G_N^0$ and the increase of the normalized terminal relaxation time in comparison to the characteristic relaxation time, respectively.