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Dynamic Viscosity (dynamic + viscosity)
Selected AbstractsDECREASE IN DYNAMIC VISCOSITY AND AVERAGE MOLECULAR WEIGHT OF ALGINATE FROM LAMINARIA DIGITATA DURING ALKALINE EXTRACTION,JOURNAL OF PHYCOLOGY, Issue 2 2008Peggy Vauchel Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of alginates from alkaline extractions 1,4 h in duration were determined, indicating depolymerization of alginates: average molecular weight decreased significantly during the extraction, falling by a factor of 5 between 1 and 4 h of extraction. These results suggested that reducing extraction time could enable preserving the rheological properties of the extracted alginates. [source] Volume fraction based miscible and immiscible fluid animationCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2010Kai Bao Abstract We propose a volume fraction based approach to effectively simulate the miscible and immiscible flows simultaneously. In this method, a volume fraction is introduced for each fluid component and the mutual interactions between different fluids are simulated by tracking the evolution of the volume fractions. Different techniques are employed to handle the miscible and immiscible interactions and special treatments are introduced to handle flows involving multiple fluids and different kinds of interactions at the same time. With this method, second-order accuracy is preserved in both space and time. The experiment results show that the proposed method can well handle both immiscible and miscible interactions between fluids and much richer mixing detail can be generated. Also, the method shows good controllability. Different mixing effects can be obtained by adjusting the dynamic viscosities and diffusion coefficients. Copyright © 2010 John Wiley & Sons, Ltd. [source] A glassy lowermost outer coreGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009Vernon F. Cormier SUMMARY New theories for the viscosity of metallic melts at core pressures and temperatures, together with observations of translational modes of oscillation of Earth's solid inner core, suggest a rapid increase in the dynamic viscosity near the bottom of the liquid outer core. If the viscosity of the lowermost outer core (F region) is sufficiently high, it may be in a glassy state, characterized by a frequency dependent shear modulus and increased viscoselastic attenuation. In testing this hypothesis, the amplitudes of high-frequency PKiKP waves are found to be consistent with an upper bound to shear velocity in the lowermost outer core of 0.5 km s,1 at 1 Hz. The fit of a Maxwell rheology to the frequency dependent shear modulus constrained by seismic observations at both low and high-frequency favours a model of the F region as a 400-km-thick chemical boundary layer. This layer has both a higher density and higher viscosity than the bulk of the outer core, with a peak viscosity on the order of 109 Pa s or higher near the inner core boundary. If lateral variations in the F region are confirmed to correlate with lateral variations observed in the structure of the uppermost inner core, they may be used to map differences in the solidification process of the inner core and flow in the lowermost outer core. [source] Physical properties and compatibility with dental stones of current alginate impression materialsJOURNAL OF ORAL REHABILITATION, Issue 11 2004H. Murata summary, This study examined physical properties and compatibility with dental stones of two types of alginate impression materials. Five powder-type alginate impression materials (Alginoplast EM, Aroma Fine, Algiace Z, Coe Alginate, Jeltrate Plus) and a paste-type alginate impression material (Tokuso AP-1) were used. The dynamic viscosity immediately after mixing was measured by means of a controlled-stress rheometer. The gelation times were determined according to Japanese Industrial Standards (JIS) T6505, and recovery from deformation, strain in compression and compressive strength were determined according to the International Organization for Standardization (ISO) specification 1563. Detail reproduction and surface roughness of type III dental stones (New Plastone, New Sunstone) and a type IV dental stone (Die Stone) were evaluated using a ruled test block as specified in the ISO specification 1563 and a profilometer, respectively. The alginate impression materials evaluated in this study were all in compliance with the ISO specification 1563 and JIS T6505. The alginate impression materials had similar mechanical properties after gelation, whilst a wide range of dynamic viscosity immediately after being mixed, gelation times and compatibility with dental stones were found among the materials. The paste-type material had a higher dynamic viscosity and a shorter gelation time than the powder-type materials. The best surface quality was obtained with the paste-type material/type III dental stone cast combinations. The materials should be selected in consideration of initial flow, setting characteristics and compatibility with dental stones. The results suggested that a paste-type material would better meet the requirements of an alginate impression material. [source] DECREASE IN DYNAMIC VISCOSITY AND AVERAGE MOLECULAR WEIGHT OF ALGINATE FROM LAMINARIA DIGITATA DURING ALKALINE EXTRACTION,JOURNAL OF PHYCOLOGY, Issue 2 2008Peggy Vauchel Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of alginates from alkaline extractions 1,4 h in duration were determined, indicating depolymerization of alginates: average molecular weight decreased significantly during the extraction, falling by a factor of 5 between 1 and 4 h of extraction. These results suggested that reducing extraction time could enable preserving the rheological properties of the extracted alginates. [source] Viscous behaviour of quaternary fluid solutions at 298.15,KTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009R. K. Shukla Abstract Assuming a quaternary fluid solution to be made up of six binaries, a statistical approach of Flory has been extended to develop the expression for dynamic viscosity of multicomponent system using the concept of absolute rate and free volume approaches of liquid state. A reasonable agreement has been achieved between theory and the experiment for n -hexadecane,+,carbon tetrachloride,+,benzene,+,n -hexane quaternary system at 298.15 over a wide range of composition. An attempt has also been made to explain the nature of the molecular interactions, involved in the light of excess thermodynamic functions whose sign and magnitude depend upon the chain length and size of the component liquids. En supposant une solution de fluide quaternaire composée de six binaires, on a généralisé l'approche statistique de Flory dans le but d'établir l,expression pour la viscosité dynamique du système multicomposant à l,aide du concept de taux absolu et de l,approche des volumes libres de l,état liquide. Un accord raisonnable a été trouvé entre la théorie et l,expérience pour le système quaternaire n-hexadécane,+,tétrachlorure de carbone,+,benzène,+,n-hexane à 298,15 pour une vaste gamme de composition. On a également tenté d'expliquer la nature des interactions moléculaires, intervenant à la lumière des fonctions thermodynamiques d'excès dont le signe et la grandeur dépendent de la longueur de chaîne et de la quantité des composants liquides. [source] Viscoelasticity of Hyaluronan and Nonhyaluronan Based Vocal Fold Injectables: Implications for Mucosal Versus Muscle Use,THE LARYNGOSCOPE, Issue 3 2007Trace Caton BS Abstract Objectives: The purpose of this study was to measure and compare biomechanical properties of commonly used vocal fold injectates Cymetra, Radiesse, Restylane, Hylaform, and one investigational injectate, Carbylan-GSX 5%, to determine suitability for mucosal injection. Study Design: Rheologic investigation. Methods: Oscillatory shear stress was applied to five samples of each injectate using a parallel plate controlled stress rheometer. Shear stress, shear strain, and strain rate associated with the oscillatory shear deformation were computed from the prescribed torque and measured angular velocity; viscoelastic data were obtained on the basis of these functions. Values calculated included elastic shear moduli, viscous moduli, and dynamic viscosity as a function of oscillatory frequency (0.01,150 Hz). Results: Elastic moduli for all samples increased as the frequency increased. Hyaluronan based materials were all comparable with each other and at least an order of magnitude lower than the stiffer and more viscous Cymetra and Radiesse. Carbylan-GSX 5% was found to have almost identical values to Hylaform with the exception of its mean viscosity, which was noticeably lower. Conclusions: Hyaluronan based biomaterials offer less resistance to flow and stiffness and may be better suited for injections into the mucosa, whereas Cymetra and Radiesse appear to be appropriate for injections into muscle. Viscoelastic properties of Hylaform and Carbylan-GSX 5% were found to most resemble that of the human vocal fold mucosa. [source] Viscoelastic and Histologic Properties in Scarred Rabbit Vocal Folds After Mesenchymal Stem Cell Injection,THE LARYNGOSCOPE, Issue 7 2006S Hertegård MD Abstract Objective/Hypothesis: The aim of this study was to analyze the short-term viscoelastic and histologic properties of scarred rabbit vocal folds after injection of human mesenchymal stem cells (MSC) as well as the degree of MSC survival. Because MSCs are antiinflammatory and regenerate mesenchymal tissues, can MSC injection reduce vocal fold scarring after injury? Study Design: Twelve vocal folds from 10 New Zealand rabbits were scarred by a localized resection and injected with human MSC or saline. Eight vocal folds were left as controls. Material and Methods: After 4 weeks, 10 larynges were stained for histology and evaluation of the lamina propria thickness. Collagen type I content was analyzed from six rabbits. MSC survival was analyzed by fluorescent in situ hybridization staining from three rabbits. Viscoelasticity for 10 vocal folds was analyzed in a parallel-plate rheometer. Results: The rheometry on fresh-frozen samples showed decreased dynamic viscosity and lower elastic modulus (P < .01) in the scarred samples injected with MSC as compared with the untreated scarred group. Normal controls had lower dynamic viscosity and elastic modulus as compared with the scarred untreated and treated vocal folds (P < .01). Histologic analysis showed a higher content of collagen type 1 in the scarred samples as compared with the normal vocal folds and with the scarred folds treated with MSC. MSCs remained in all samples analyzed. Conclusions: The treated scarred vocal folds showed persistent MSC. Injection of scarred rabbit vocal folds with MSC rendered improved viscoelastic parameters and less signs of scarring expressed as collagen content in comparison to the untreated scarred vocal folds. [source] | ||||||||||