Sample records for surface dilatational rheology

  1. Dilational surface rheology of polymer solutions

    International Nuclear Information System (INIS)

    Noskov, B A; Bykov, A G


    The review concerns main achievements in dilational rheology of polymer adsorption films at the gas/liquid interfaces reported in the last fifteen years. The theoretical foundations of methods of surface rheology and the key results obtained in studies of solutions of amphiphilic nonionic polymers, polyelectrolytes, proteins and their complexes with low-molecular-mass surfactants are discussed. Interest in the surface dilational rheology is mainly caused by a small number of available experimental methods for investigation of the surface of liquids, by the fact that traditional methods of measurement of the surface tension that are widely used in studies of solutions of low-molecular-mass surfactants provide little information when applied to polymer solutions owing to very slow establishment of equilibrium as well as by weak dependence of the surface tension on the polymer concentration. Progress in the surface rheology is driven by the recent studies of the stability of foams and emulsions that demonstrated a key role of the dilational surface rheological properties in the dynamics of liquid-phase disperse systems. The bibliography includes 191 references

  2. Protein conformational transitions at the liquid-gas interface as studied by dilational surface rheology. (United States)

    Noskov, Boris A


    Experimental results on the dynamic dilational surface elasticity of protein solutions are analyzed and compared. Short reviews of the protein behavior at the liquid-gas interface and the dilational surface rheology precede the main sections of this work. The kinetic dependencies of the surface elasticity differ strongly for the solutions of globular and non-globular proteins. In the latter case these dependencies are similar to those for solutions of non-ionic amphiphilic polymers and have local maxima corresponding to the formation of the distal region of the surface layer (type I). In the former case the dynamic surface elasticity is much higher (>60 mN/m) and the kinetic dependencies are monotonical and similar to the data for aqueous dispersions of solid nanoparticles (type II). The addition of strong denaturants to solutions of bovine serum albumin and β-lactoglobulin results in an abrupt transition from the type II to type I dependencies if the denaturant concentration exceeds a certain critical value. These results give a strong argument in favor of the preservation of the protein globular structure in the course of adsorption without any denaturants. The addition of cationic surfactants also can lead to the non-monotonical kinetic dependencies of the dynamic surface elasticity indicating destruction of the protein tertiary and secondary structures. The addition of anionic surfactants gives similar results only for the protein solutions of high ionic strength. The influence of cationic surfactants on the local maxima of the kinetic dependencies of the dynamic surface elasticity for solutions of a non-globular protein (β-casein) differs from the influence of anionic surfactants due to the heterogeneity of the charge distribution along the protein chain. In this case one can use small admixtures of ionic surfactants as probes of the adsorption mechanism. The effect of polyelectrolytes on the kinetic dependencies of the dynamic surface elasticity of protein

  3. Nonlinear Surface Dilatational Rheology and Foaming Behavior of Protein and Protein Fibrillar Aggregates in the Presence of Natural Surfactant. (United States)

    Wan, Zhili; Yang, Xiaoquan; Sagis, Leonard M C


    The surface and foaming properties of native soy glycinin (11S) and its heat-induced fibrillar aggregates, in the presence of natural surfactant steviol glycoside (STE), were investigated and compared at pH 7.0 to determine the impact of protein structure modification on protein-surfactant interfacial interactions. The adsorption at, and nonlinear dilatational rheological behavior of, the air-water interface were studied by combining drop shape analysis tensiometry, ellipsometry, and large-amplitude oscillatory dilatational rheology. Lissajous plots of surface pressure versus deformation were used to analyze the surface rheological response in terms of interfacial microstructure. The heat treatment generates a mixture of long fibrils and unconverted peptides. The presence of small peptides in 11S fibril samples resulted in a faster adsorption kinetics than that of native 11S. The addition of STE affected the adsorption of 11S significantly, whereas no apparent effect on the adsorption of the 11S fibril-peptide system was observed. The rheological response of interfaces stabilized by 11S-STE mixtures also differed significantly from the response for 11S fibril-peptide-STE mixtures. For 11S, the STE reduces the degree of strain hardening in extension and increases strain hardening in compression, suggesting the interfacial structure may change from a surface gel to a mixed phase of protein patches and STE domains. The foams generated from the mixtures displayed comparable foam stability to that of pure 11S. For 11S fibril-peptide mixtures STE only significantly affects the response in extension, where the degree of strain softening is decreased compared to the pure fibril-peptide system. The foam stability of the fibril-peptide system was significantly reduced by STE. These findings indicate that fibrillization of globular proteins could be a potential strategy to modify the complex surface and foaming behaviors of protein-surfactant mixtures.

  4. Competitive adsorption from mixed hen egg-white lysozyme/surfactant solutions at the air-water interface studied by tensiometry, ellipsometry, and surface dilational rheology. (United States)

    Alahverdjieva, V S; Grigoriev, D O; Fainerman, V B; Aksenenko, E V; Miller, R; Möhwald, H


    The competitive adsorption at the air-water interface from mixed adsorption layers of hen egg-white lysozyme with a non-ionic surfactant (C10DMPO) was studied and compared to the mixture with an ionic surfactant (SDS) using bubble and drop shape analysis tensiometry, ellipsometry, and surface dilational rheology. The set of equilibrium and kinetic data of the mixed solutions is described by a thermodynamic model developed recently. The theoretical description of the mixed system is based on the model parameters for the individual components.

  5. Surface rheology and interface stability.

    Energy Technology Data Exchange (ETDEWEB)

    Yaklin, Melissa A.; Cote, Raymond O.; Moffat, Harry K.; Grillet, Anne Mary; Walker, Lynn; Koehler, Timothy P.; Reichert, Matthew D. (Carnegie Mellon University, Pittsburgh, PA); Castaneda, Jaime N.; Mondy, Lisa Ann; Brooks, Carlton, F.


    We have developed a mature laboratory at Sandia to measure interfacial rheology, using a combination of home-built, commercially available, and customized commercial tools. An Interfacial Shear Rheometer (KSV ISR-400) was modified and the software improved to increase sensitivity and reliability. Another shear rheometer, a TA Instruments AR-G2, was equipped with a du Nouey ring, bicone geometry, and a double wall ring. These interfacial attachments were compared to each other and to the ISR. The best results with the AR-G2 were obtained with the du Nouey ring. A Micro-Interfacial Rheometer (MIR) was developed in house to obtain the much higher sensitivity given by a smaller probe. However, it was found to be difficult to apply this technique for highly elastic surfaces. Interfaces also exhibit dilatational rheology when the interface changes area, such as occurs when bubbles grow or shrink. To measure this rheological response we developed a Surface Dilatational Rheometer (SDR), in which changes in surface tension with surface area are measured during the oscillation of the volume of a pendant drop or bubble. All instruments were tested with various surfactant solutions to determine the limitations of each. In addition, foaming capability and foam stability were tested and compared with the rheology data. It was found that there was no clear correlation of surface rheology with foaming/defoaming with different types of surfactants, but, within a family of surfactants, rheology could predict the foam stability. Diffusion of surfactants to the interface and the behavior of polyelectrolytes were two subjects studied with the new equipment. Finally, surface rheological terms were added to a finite element Navier-Stokes solver and preliminary testing of the code completed. Recommendations for improved implementation were given. When completed we plan to use the computations to better interpret the experimental data and account for the effects of the underlying bulk

  6. Surface shear rheology of saponin adsorption layers. (United States)

    Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Edward; Stoyanov, Simeon D


    Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial biological activities. The molecular mechanisms behind these unusual properties are unknown, and, therefore, the saponins have attracted significant research interest in recent years. In our previous study (Stanimirova et al. Langmuir 2011, 27, 12486-12498), we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 ± 30 mN/m. In this Article, we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins, which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibit purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, a single master curve describes the data for the viscoelastic creep compliance versus deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases, and the adsorption layers eventually transform into viscous ones. The experimental creep-recovery curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers.

  7. Generalized surface momentum balances for the analysis of surface dilatational data

    NARCIS (Netherlands)

    Sagis, L.M.C.


    Dilatational rheological properties of interfaces are often determined using drop tensiometers, in which the interface of the droplet is subjected to oscillatory area changes. A dynamic surface tension is determined either by image analysis of the droplet profile or by measuring the capillary

  8. Interfacial dynamic and dilational rheology of polyelectrolyte/surfactant two-component nanoparticle systems at air–water interface

    International Nuclear Information System (INIS)

    Tong, L.J.; Bao, M.T.; Li, Y.M.; Gong, H.Y.


    Graphical abstract: - Highlights: • DTAB/PSS mixture can self-assemble nanoparticles in bulk solution. • The nanoparticles can adsorb at the interface forming a nanoparticle monolayer. • The nanoparticles spread at the interface undergo a disassembly process with time. • The nanoparticle monolayer presents peculiar dilational viscoelastic behavior. - Abstract: The interfacial characteristics of nanoparticles and consequent inter-particle interactions at the interface are poorly understood. In this work, the interfacial dynamic and corresponding dilational surface rheology of self-assembled polyelectrolyte/surfactant nanoparticles at the air–water interface are characterized. The nanoparticles are prepared from dodecyltrimethylammonium (DTAB) and poly (sodium 4-styrene-sulfonate) (PSS) by mixing them in aqueous solution. The interfacial dynamic characteristics have been carried out by comparing the surface pressure with the dilational rheological response of these nanoparticles at interface. The results indicate that this type of nanoparticles can adsorb at the interface forming a nanoparticle monolayer, which leads to the surface tension decreased markedly. The dependence of surface pressure on time shows the instability and disassembly process of nanoparticles at the interface. On the basis of these observations, it is proposed that the nanoparticles undergo a dynamic process that interface induced nanoparticles disassembly into DTAB/PSS complexes. The presence of PSS in the subphase can promote the process of nanoparticles disassembly. A transition point in dilational elasticity and viscosity response of the nanoparticles versus oscillation frequency further validate the micro dynamic process of nanoparticles and the formation of polyelectrolyte/surfactant complex monolayer at the interface

  9. Dilational rheology of oil/water interfaces covered by amphiphilic polysaccharides derived from dextran. (United States)

    Desbrières, Jacques; López-Gonzalez, Edeluc; Aguilera-Miguel, Antonio; Sadtler, Véronique; Marchal, Philippe; Castel, Christophe; Choplin, Lionel; Durand, Alain


    This work studied the adsorption at dodecane/water interface of amphiphilic polysaccharides derived from dextran (a nonionic bacterial polysaccharide) by random attachment of phenoxy groups along the chains (between 10 and 20 attached phenoxy groups per 100 glucose repeat units). The long-time kinetics of interfacial tension decrease was satisfactorily described assuming diffusion-limited adsorption of hydrophobic units (over 4h). Dilational rheology of dodecane/water interface was studied for the first time with that kind of amphiphilic polysaccharides and evidenced a significant elastic component. For all dextran derivatives, experimental results were conveniently described using Lucassen-van den Tempel model which assumed diffusion-limited of surface active species. The characteristic frequency increased with the number of attached phenoxy groups and its order of magnitude (10 -3 -10 -2 rad.s -1 ) was consistent with estimations based on the previous model. Experimental results were compared to those obtained with commercial stabilizers like Pluronics (L64, P105, F68 and F127) and Tween 80. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. On the rheology of dilative granular media: Bridging solid- and fluid-like behavior (United States)

    Andrade, José E.; Chen, Qiushi; Le, Phong H.; Avila, Carlos F.; Matthew Evans, T.


    A new rate-dependent plasticity model for dilative granular media is presented, aiming to bridge the seemingly disparate solid- and fluid-like behavioral regimes. Up to date, solid-like behavior is typically tackled with rate-independent plasticity models emanating from Mohr-Coulomb and Critical State plasticity theory. On the other hand, the fluid-like behavior of granular media is typically treated using constitutive theories amenable to viscous flow, e.g., Bingham fluid. In our proposed model, the material strength is composed of a dilation part and a rate-dependent residual strength. The dilatancy strength plays a key role during solid-like behavior but vanishes in the fluid-like regime. The residual strength, which in a classical plasticity model is considered constant and rate-independent, is postulated to evolve with strain rate. The main appeal of the model is its simplicity and its ability to reconcile the classic plasticity and rheology camps. The applicability and capability of the model are demonstrated by numerical simulation of granular flow problems, as well as a classical shear banding problem, where the performance of the continuum model is compared to discrete particle simulations and physical experiment. These results shed much-needed light onto the mechanics and physics of granular media at various shear rates.

  11. Impact of lithospheric rheology on surface topography (United States)

    Liao, K.; Becker, T. W.


    The expression of mantle flow such as due to a buoyant plume as surface topography is a classical problem, yet the role of rheological complexities could benefit from further exploration. Here, we investigate the topographic expressions of mantle flow by means of numerical and analytical approaches. In numerical modeling, both conventional, free-slip and more realistic, stress-free boundary conditions are applied. For purely viscous rheology, a high viscosity lithosphere will lead to slight overestimates of topography for certain settings, which can be understood by effectively modified boundary conditions. Under stress-free conditions, numerical and analytical results show that the magnitude of dynamic topography decreases with increasing lithosphere thickness (L) and viscosity (ηL), as L-1 and ηL-3. The wavelength of dynamic topography increases linearly with L and (ηL/ ηM) 1/3. We also explore the time-dependent interactions of a rising plume with the lithosphere. For a layered lithosphere with a decoupling weak lower crust embedded between stronger upper crust and lithospheric mantle, dynamic topography increases with a thinner and weaker lower crust. The dynamic topography saturates when the decoupling viscosity is 3-4 orders lower than the viscosity of upper crust and lithospheric mantle. We further explore the role of visco-elastic and visco-elasto-plastic rheologies.

  12. Effect of enzymatic hydrolysis on surface activity and surface rheology of type I collagen. (United States)

    Kezwoń, Aleksandra; Chromińska, Ilona; Frączyk, Tomasz; Wojciechowski, Kamil


    We describe the adsorption behaviour and rheological properties of a calf skin type I collagen, and of its hydrolysates obtained using a Clostridium histolyticum collagenase (CHC) under moderate conditions (pH 7, 37°C). The effect of CHC concentration (2×10(-9)-2×10(-6)M) and incubation time (35-85min) was studied and optimised to achieve the highest decrease of surface tension and the highest dilational surface viscoelasticity of the adsorbed layers. SDS-PAGE electrophoresis and reverse-phase high performance liquid chromatography (RP-HPLC) were used to characterise the hydrolysis products. The results show that even simple modifications (heat treatment, pH change, partial hydrolysis) of collagen enhances its surface properties, especially in terms of surface dilational elasticity modulus. The use of low enzyme concentration (CHC-to-collagen molar ratio of 4×10(-3)) and short incubation time (<45min) results in moderately hydrolysed products with the highest ability to lower surface tension (γ=53.9mNm(-1)) forming highly elastic adsorbed layers (surface dilational elasticity, E'=74.5mNm(-1)). Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Identification of rheological properties of human body surface tissue. (United States)

    Benevicius, Vincas; Gaidys, Rimvydas; Ostasevicius, Vytautas; Marozas, Vaidotas


    According to World Health Organization obesity is one of the greatest public health challenges of the 21st century. It has tripled since the 1980s and the numbers of those affected continue to rise at an alarming rate, especially among children. There are number of devices that act as a prevention measure to boost person's motivation for physical activity and its levels. The placement of these devices is not restricted thus the measurement errors that appear because of the body rheology, clothes, etc. cannot be eliminated. The main objective of this work is to introduce a tool that can be applied directly to process measured accelerations so human body surface tissue induced errors can be reduced. Both the modeling and experimental techniques are proposed to identify body tissue rheological properties and prelate them to body mass index. Multi-level computational model composed from measurement device model and human body surface tissue rheological model is developed. Human body surface tissue induced inaccuracies can increase the magnitude of measured accelerations up to 34% when accelerations of the magnitude of up to 27 m/s(2) are measured. Although the timeframe of those disruptions are short - up to 0.2 s - they still result in increased overall measurement error. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Surface nucleation in complex rheological systems (United States)

    Herfurth, J.; Ulrich, J.


    Forced nucleation induced by suitable foreign seeds is an important tool to control the production of defined crystalline products. The quality of a surface provided by seed materials represents an important variable in the production of crystallizing layers that means for the nucleation process. Parameters like shape and surface structure, size and size distribution of the seed particles as well as the ability to hold up the moisture (the solvent), can have an influence on the nucleation process of different viscous supersaturated solutions. Here the properties of different starch powders as seeds obtained from corn, potato, rice, tapioca and wheat were tested. It could be found, that the best nucleation behavior of a sugar solution could be reached with the use of corn starch as seed material. Here the surface of the crystallized sugar layer is smooth, crystallization time is short (<3 h) and the shape of the product is easily reproducible. Beneficial properties of seed materials are therefore an edged, uneven surface, small particle sizes as well as low moisture content at ambient conditions within the seed materials.

  15. Rheologic Profile, Specific Gravity, Surface Tension, and pH of Fifteen Over-the-Counter Preparations. (United States)

    Al-Achi, Antoine; Baghat, Tushar; Chukwubeze, Onah; Dembla, Ishwin


    Knowledge of the physical characteristics of commercially available over-the-counter preparations can aid the compounding pharmacist in preparing medication. In this study, 15 over-the-counter products were studied with regard to their specific gravity, surface tension, pH, and rheologic profile. The specific gravities of all the products were greater than 1, with the exceptions of Nivea Lotion and rubbing alcohol, which were less than 1. The majority of the products had an acidic pH. With the exception of two products, Citrucel and Chloraseptic, all products demonstrated a surface tension value less than that of water (72.8 dynes/cm). Chloraseptic had the lowest Newtonian viscosity (1.27 cPs), whereas Vicks DayQuil had the highest (098.86 cPs). Citrucel exhibited dilatant-type flow; Suave Shampoo, herbal shampoo, Tangerine Tickle Herbal Shampoo, and Metamucil pseudoplastic flow; the remaining non-Newtonian formulations, plastic flow profiles.

  16. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology. (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo


    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  17. Solid Character of Membrane Ceramides: A Surface Rheology Study of Their Mixtures with Sphingomyelin (United States)

    Catapano, Elisa R.; Arriaga, Laura R.; Espinosa, Gabriel; Monroy, Francisco; Langevin, Dominique; López-Montero, Iván


    The compression and shear viscoelasticities of egg-ceramide and its mixtures with sphingomyelin were investigated using oscillatory surface rheology performed on Langmuir monolayers. We found high values for the compression and shear moduli for ceramide, compatible with a solid-state membrane, and extremely high surface viscosities when compared to typical fluid lipids. A fluidlike rheological behavior was found for sphingomyelin. Lateral mobilities, measured from particle tracking experiments, were correlated with the monolayer viscosities through the usual hydrodynamic relationships. In conclusion, ceramide increases the solid character of sphingomyelin-based membranes and decreases their fluidity, thus drastically decreasing the lateral mobilities of embedded objects. This mechanical behavior may involve important physiological consequences in biological membranes containing ceramides. PMID:22261061

  18. Interfacial layers from the protein HFBII hydrophobin: dynamic surface tension, dilatational elasticity and relaxation times. (United States)

    Alexandrov, Nikola A; Marinova, Krastanka G; Gurkov, Theodor D; Danov, Krassimir D; Kralchevsky, Peter A; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Arnaudov, Luben N; Pelan, Eddie G; Lips, Alex


    The pendant-drop method (with drop-shape analysis) and Langmuir trough are applied to investigate the characteristic relaxation times and elasticity of interfacial layers from the protein HFBII hydrophobin. Such layers undergo a transition from fluid to elastic solid films. The transition is detected as an increase in the error of the fit of the pendant-drop profile by means of the Laplace equation of capillarity. The relaxation of surface tension after interfacial expansion follows an exponential-decay law, which indicates adsorption kinetics under barrier control. The experimental data for the relaxation time suggest that the adsorption rate is determined by the balance of two opposing factors: (i) the barrier to detachment of protein molecules from bulk aggregates and (ii) the attraction of the detached molecules by the adsorption layer due to the hydrophobic surface force. The hydrophobic attraction can explain why a greater surface coverage leads to a faster adsorption. The relaxation of surface tension after interfacial compression follows a different, square-root law. Such behavior can be attributed to surface diffusion of adsorbed protein molecules that are condensing at the periphery of interfacial protein aggregates. The surface dilatational elasticity, E, is determined in experiments on quick expansion or compression of the interfacial protein layers. At lower surface pressures (<11 mN/m) the experiments on expansion, compression and oscillations give close values of E that are increasing with the rise of surface pressure. At higher surface pressures, E exhibits the opposite tendency and the data are scattered. The latter behavior can be explained with a two-dimensional condensation of adsorbed protein molecules at the higher surface pressures. The results could be important for the understanding and control of dynamic processes in foams and emulsions stabilized by hydrophobins, as well as for the modification of solid surfaces by adsorption of such

  19. Importance of physical vs. chemical interactions in surface shear rheology

    NARCIS (Netherlands)

    Wierenga, P.A.; Kosters, H.; Egmond, M.R.; Voragen, A.G.J.; Jongh, H.H.J. de


    The stability of adsorbed protein layers against deformation has in literature been attributed to the formation of a continuous gel-like network. This hypothesis is mostly based on measurements of the increase of the surface shear elasticity with time. For several proteins this increase has been

  20. Cooling of a channeled lava flow with non-Newtonian rheology: crust formation and surface radiance

    Directory of Open Access Journals (Sweden)

    Stefano Santini


    Full Text Available We present here the results from dynamical and thermal models that describe a channeled lava flow as it cools by radiation. In particular, the effects of power-law rheology and of the presence of bends in the flow are considered, as well as the formation of surface crust and lava tubes. On the basis of the thermal models, we analyze the assumptions implicit in the currently used formulae for evaluation of lava flow rates from satellite thermal imagery. Assuming a steady flow down an inclined rectangular channel, we solve numerically the equation of motion by the finite-volume method and a classical iterative solution. Our results show that the use of power-law rheology results in relevant differences in the average velocity and volume flow rate with respect to Newtonian rheology. Crust formation is strongly influenced by power-law rheology; in particular, the growth rate and the velocity profile inside the channel are strongly modified. In addition, channel curvature affects the flow dynamics and surface morphology. The size and shape of surface solid plates are controlled by competition between the shear stress and the crust yield strength: the degree of crust cover of the channel is studied as a function of the curvature. Simple formulae are currently used to relate the lava flow rate to the energy radiated by the lava flow as inferred from satellite thermal imagery. Such formulae are based on a specific model, and consequently, their validity is subject to the model assumptions. An analysis of these assumptions reveals that the current use of such formulae is not consistent with the model.

  1. Rheological properties of epoxy/MWCNT suspensions associated with the surface modification of MWCNT by physisorption of aromatic ionic salts

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yu-Hsun [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China); Lin, King-Fu, E-mail: [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China)


    The multi-walled carbon nanotubes (MWCNTs) physisorbed by aromatic ionic salts such as 10-methyl-acridinium iodide (MAcI) were found to well disperse in diglycidyl ether of bisphenol-A epoxy resin. As they were subjected to the rheological study at 30 °C, the gelation of epoxy/MWCNT-MAcI suspension occurred at 0.75 wt% MWCNT-MAcI, which was less than that using pristine MWCNT. As to the viscosity measurements, the dilation effect that the viscosity of epoxy/MWCNT suspension increases with shear rate was found and more pronounced by incorporating MWCNT-MAcI. According to the Thomas-modified Einstein viscosity equation, the dilation effect was attributed to the excess amount of epoxy resin trapping in the aggregated domain of MWCNT. By increasing the shear rate to a certain point, the shear thinning effect that the viscosity decreases with shear rate was also observed. Interestingly, the transition point that the dilation effect changes to shear thinning effect shifted to lower shear rate as the content of MWCNT increased and/or MWCNT-MAcI was incorporated. Notably, better dispersion and less aggregated domains for the suspensions with MWCNT-MAcI compared to pristine MWCNT were further supported by small angle x-ray scattering and transmission electron microscopy. - Highlights: • Dilation effect that viscosity of epoxy/MWCNT suspension increases with shear rate was discovered. • Dilation effect was attributed to the excess epoxy resin trapping in the aggregated domain of MWCNT. • The transition point that the dilation effect changes to shear thinning effect was observed.

  2. Dynamic shear rheology of colloidal suspensions of surface-modified silica nanoparticles in PEG (United States)

    Swarna; Pattanayek, Sudip Kumar; Ghosh, Anup Kumar


    The present work illustrates the effect of surface modification of silica nanoparticles (500 nm) with 3-(glycidoxypropyl)trimethoxy silane which was carried out at different reaction times. The suspensions prepared from modified and unmodified silica nanoparticles were evaluated for their shear rate-dependent viscosity and strain-frequency-dependent modulus. The linear viscoelastic moduli, viz., storage modulus and loss modulus, were compared with those of nonlinear moduli. The shear-thickened suspensions displayed strain thinning at low-frequency smaller strains and a strong strain overshoot at higher strains, characteristics of a continuous shear thickening fluids. The shear-thinned suspension, conversely, exhibited a strong elastic dominance at smaller strains, but at higher strains, its strain softened observed in the steady shear viscosity plot indicating characteristics of yielding material. Considering higher order harmonic components, the decomposed elastic and viscous stress revealed a pronounced elastic response up to 10% strain and a high viscous damping at larger strains. The current work is one of a kind in demonstrating the effect of silica surface functionalization on the linear and nonlinear viscoelasticity of suspensions showing a unique rheological fingerprint. The suspensions can thus be predicted through rheological studies for their applicability in energy absorbing and damping materials with respect to their mechanical properties.

  3. d-α-tocopherol nanoemulsions: Size properties, rheological behavior, surface tension, osmolarity and cytotoxicity

    Directory of Open Access Journals (Sweden)

    M.C. Teixeira


    Full Text Available The aim of this study was the assessment of the physicochemical stability of d-α-tocopherol formulated in medium chain triglyceride nanoemulsions, stabilized with Tween®80 and Lipoid®S75 as surfactant and co-surfactant, respectively. d-α-tocopherol was selected as active ingredient because of its well-recognized interesting anti-oxidant properties (such as radical scavenger for food and pharmaceutical industries. A series of nanoemulsions of mean droplet size below 90 nm (polydispersity index < 0.15 have been produced by high-pressure homogenization, and their surface electrical charge (zeta potential, pH, surface tension, osmolarity, and rheological behavior, were characterized as a function of the d-α-tocopherol loading. In vitro studies in Caco-2 cell lines confirmed the safety profile of the developed nanoemulsions with percentage of cell viability above 90% for all formulations.

  4. Comprehensive study of rheological and surface properties of the selected slag system in the context of its internal structure


    Řeháčková, Lenka; Dudek, Rostislav; Rosypalová, Silvie; Matýsek, Dalibor; Dobrovská, Jana


    Rheological (dynamic viscosity, flow curves) and surface properties (surface tension) of real slag system were experimentally investigated. Measurements of dynamic viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. The method of sessile drop was used for measurement of surface tension. Surface tension and dynamic viscosity were measured in the temperature interval from 1 200 to 1 600 °C. The structural characteristics of the selected samples...

  5. Effect of Cationic Surface Modification on the Rheological Behavior and Microstructure of Nanocrystalline Cellulose

    Directory of Open Access Journals (Sweden)

    Yanjun Tang


    Full Text Available In the present work, the microstructure and rheological behavior of nanocrystalline cellulose (NCC and cationically modified NCC (CNCC were comparatively studied. The resultant CNCC generally showed improved dispersion and higher thermal stability in comparison to the un-modified NCC. The rheological behavior demonstrated that the viscosity of the NCC suspension substantially decreased with the increasing shear rate (0.01–100 s−1, showing the typical characteristics of a pseudoplastic fluid. In contrast, the CNCC suspensions displayed a typical three-region behavior, regardless of changes in pH, temperature, and concentration. Moreover, the CNCC suspensions exhibited higher shear stress and viscosity at a given shear rate (0.01–100 s−1 than the NCC suspension. Meanwhile, the dynamic viscoelasticity measurements revealed that the CNCC suspensions possessed a higher elastic (G′ and loss modulus (G″ than NCC suspensions over the whole frequency range (0.1–500 rad·s−1, providing evidence that the surface cationization of NCC makes it prone to behave as a gel-like structure.

  6. Chitosan/titanium dioxide nanocomposite coatings: Rheological behavior and surface application to cellulosic paper. (United States)

    Tang, Yanjun; Hu, Xiulan; Zhang, Xinqi; Guo, Daliang; Zhang, Junhua; Kong, Fangong


    Incorporation of nanofillers into a polymeric matrix has received much attention as a route to reinforced polymer nanocomposites. In the present work, an environmentally friendly chitosan (CTS)/titanium dioxide (TiO2) nanocomposite coating was designed/prepared and subsequently employed for imparting antibacterium and improved mechanical properties to cellulosic paper via surface coating. Effect of TiO2 nanoparticle loadings on the rheological behavior of nanocomposite coatings was investigated. Surface application of CTS/TiO2 nanocomposite coatings to cellulosic paper was performed, and the antibacterial activity and mechanical properties of surface-coated cellulosic paper were examined. Results showed that the increased TiO2 nanoparticle loadings decreased the viscosity and dynamic viscoelasticity of the as-prepared coatings, and improved the antibacterial activity and mechanical properties of surface-coated cellulosic paper. The optimum loading of TiO2 nanoparticles was identified at 10%. This work suggested that CTS/TiO2 nanocomposite coatings may have the potential to be used as a promising antibacterial protective coating for paper packaging. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements. (United States)

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G


    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, E(sh) and η(sh), proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like β-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein β-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of β-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine E(sh) and η(sh) from the measured storage and loss moduli, G' and G″. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets. Copyright © 2014

  8. Numerical study of jumps formed in free-surface flows down an incline : influence of the fluid rheology (United States)

    Naaim, Mohamed; Faug, Thierry


    The discontinuities in height and velocity, namely jumps, formed in free-surface flows are important processes in geophysics, for instance when they are formed during the interaction of avalanche-flows with protection structures. The present study investigates steady state jumps formed in free-surface flows with the help of numerical simulations based on depth-averaged equations. A control constant mass discharge is supplied to an incline. By imposing a difference in basal friction between a upper part of the chute bottom and a lower part of the chute bottom, a supercritical flow is produced upstream while a subcritical flow appears downstream. The transition between both gives birth to a jump located at the transition between the two portions of the chute with different basal friction. Different constitutive equations are tested (laminar, turbulent, local granular rheology, Voellmy, Herschel Bulkley), thus allowing us to quantify the influence of the fluid rheology on the jump properties : position, geometry and size.

  9. Rheology of organoclay suspension

    CSIR Research Space (South Africa)

    Hato, MJ


    Full Text Available The authors have studied the rheological properties of clay suspensions in silicone oil, where clay surfaces were modified with three different types of surfactants. Dynamic oscillation measurements showed a plateau-like behavior for all...

  10. Paschke Dilations

    Directory of Open Access Journals (Sweden)

    Abraham Westerbaan


    Full Text Available In 1973 Paschke defined a factorization for completely positive maps between C*-algebras. In this paper we show that for normal maps between von Neumann algebras, this factorization has a universal property, and coincides with Stinespring's dilation for normal maps into B(H.

  11. Surface Rheology and Adsorption Kinetics Reveal the Relative Amphiphilicity, Interfacial Activity, and Stability of Human Exchangeable Apolipoproteins☆ (United States)

    Bolanos-Garcia, Victor Martin; Renault, Anne; Beaufils, Sylvie


    Exchangeable apolipoproteins are located in the surface of lipoprotein particles and regulate lipid metabolism through direct protein-protein and protein-lipid interactions. These proteins are characterized by the presence of tandem repeats of amphiphatic α-helix segments and a high surface activity in monolayers and lipoprotein surfaces. A noteworthy aspect in the description of the function of exchangeable apolipoproteins is the requirement of a quantitative account of the relation between their physicochemical and structural characteristics and changes in the mesoscopic system parameters such as the maximum surface pressure and relative stability at interfaces. To comply with this demand, we set out to establish the relations among α-helix amphiphilicity, surface concentration, and surface rheology of apolipoproteins ApoA-I, ApoA-II, ApoC-I, ApoC-II, and ApoC-III adsorbed at the air-water interface. Our studies render further insights into the interfacial properties of exchangeable apolipoproteins, including the kinetics of their adsorption and the physical properties of the interfacial layer. PMID:17993480

  12. Dynamic surface properties of poly(methylalkyldiallylammonium chloride) solutions

    Czech Academy of Sciences Publication Activity Database

    Novikova, A. A.; Vlasov, P. S.; Lin, S.-Y.; Sedláková, Zdeňka; Noskov, B. A.


    Roč. 80, November (2017), s. 122-127 ISSN 1876-1070 Institutional support: RVO:61389013 Keywords : polymer solutions * dynamic surface tension * dilational surface rheology Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 4.217, year: 2016

  13. Dilated cardiomyopathy

    International Nuclear Information System (INIS)

    Salvatore, M.; Cuocolo, A.


    Radionuclide techniques are easily obtainable, noninvasive examinations that provide useful information in the evaluation, diagnosis and management of patients with dilated cardiomyopathy. The gated blood pool scan allows the assessment of ventricular size, configuration, and wall and septal thickness. These data allow the functional class of the cardiomyopathy (congestive, restrictive or hypertrophic) to be defined. Often THallium-201 myocardial perfusion imaging adds further information and is particularly useful in distinguishing congestive cardiomyopathy from severe coronary artery disease and in depicting septal abnormalities in hipertrophic cardiomyopathy. Useful as these techniques are, they are not substitutes for conventional approaches to diagnosis. Careful history taking and physical examination, as well as scrutiny of the electrocardiogram, chest X-ray and echocardiogram should be standard practice for the evaluation of patients with suspected cardiomyopathy. Judicious use of noninvasive techniques may obviate the need for cardiac catheterization in many patients

  14. Dilating Eye Drops (United States)

    ... Frequently Asked Questions Español Condiciones Chinese Conditions Dilating Eye Drops En Español Read in Chinese What are dilating eye drops? Dilating eye drops contain medication to enlarge ( ...

  15. Accurate in situ measurement of near-surface volume dilatation in irradiated silica through capacitance monitoring of cantilever deflection

    International Nuclear Information System (INIS)

    Norris, C.B.; EerNisse, E.P.


    Irradiating a solid with short-range particle often induces a net volume change in the range zone which results in a shallow layer of stressed material. Micron-depth volume dilatations in the part-per-million range can be studied using cantilever mounting of a long, thin, metallized specimen, whose stress-induced bending perturbs the capacitance between the cantilever and a small counterelectrode mounted close to the unirradiated face. This approach has been used successfully by many workers for more than 20 yrs. Elsewhere we have reported the construction of a highly sensitive caltilever/capacitor apparatus and its application in the first accurate measurements of ionization dilatation phenomena in fused silica and grown SiO 2 at low-electron energies. In this paper we outline key details of apparatus design and experimental technique for successful cantilever/capacitor work. Many contrasts with the work of Primak and Monahan [Rev. Sci. Instrum. 54, 544 (1983) (preceding paper)] are pointed out. We also highlight previous short-term annealing results which make it clear that the compaction of silica will appear to be significantly less in optical measurements made hours after irradiation than in our cantilever/capacitor measurements made minutes after irradiation

  16. Effects of Lateral Heterogeneity and Power Law Rheology on Glacially Induced Surface Motion and Gravity Rate of Change (United States)

    Wu, P.; Wang, H.; van der Wal, W.


    Modern geodetic measurements from GPS, satellite altimetry, tide-gauges, Satellite Laser Ranging (SLR) and space-borne gravimetry (such as GRACE) have been used to monitor global change. Since these measurements contain contributions from glacial isostatic adjustment (GIA) and other tectonic processes, they must be modeled and removed in order to observe current climate change. In the past, most GIA models assumed that the earth is laterally homogeneous and the rheology is linear. The aim of this paper is to investigate the effects of lateral heterogeneity and Power-Law rheology on GIA induced land uplift rate, horizontal velocities, relative sealevels, J-dot and the secular gravity rate of change in the southern part of Hudson Bay, which is detected by the GRACE mission. Here, GIA is modeled with a spherical, self-gravitating, compressible viscoelastic, laterally heterogeneous earth using the Finite-Element Method. The effect of gravitationally self-consistent sea levels in realistic oceans is also included. Lateral variations in mantle viscosities and lithospheric thickness are inferred from the seismic tomography model S20A using well known scaling relationships. Power-Law rheologies in the whole mantle or in combination with linear rheologies in the upper or lower mantle are also investigated. Both ICE-5G and ICE-4G deglaciation models are used to investigate their effect on the pattern of rebound. Preliminary results show that both lateral heterogeneity and power-law rheology have strong effects on the direction and magnitude of horizontal velocities. The effects of lateral heterogeneity and power-law rheology are also large enough to be detected in land uplift rate, relative sealevels, J-dot and gravity rate of change. Their implication on observing the effects of global warming will also be discussed.

  17. Interfacial rheology: an overview of measuring techniques and its role in dispersions and electrospinning. (United States)

    Pelipenko, Jan; Kristl, Julijana; Rošic, Romana; Baumgartner, Saša; Kocbek, Petra


    Interfacial rheological properties have yet to be thoroughly explored. Only recently, methods have been introduced that provide sufficient sensitivity to reliably determine viscoelastic interfacial properties. In general, interfacial rheology describes the relationship between the deformation of an interface and the stresses exerted on it. Due to the variety in deformations of the interfacial layer (shear and expansions or compressions), the field of interfacial rheology is divided into the subcategories of shear and dilatational rheology. While shear rheology is primarily linked to the long-term stability of dispersions, dilatational rheology provides information regarding short-term stability. Interfacial rheological characteristics become relevant in systems with large interfacial areas, such as emulsions and foams, and in processes that lead to a large increase in the interfacial area, such as electrospinning of nanofibers.

  18. Pnematic Dilation in Achalasia

    Directory of Open Access Journals (Sweden)

    Maximilian Bittinger


    Full Text Available Pneumatic dilation is the most common first-line therapy for the treatment of achalasia. The aim of dilation is a controlled disruption of circular muscle fibres of the lower esophageal sphincter to reduce the functional obstruction. Several types of dilators and different dilation techniques are used, but the achieved results are similar. The mean success rate is about 80% in the short term, but some patients need redilation in the further course (particularly young patients. Best long term results are obtained if the lower esophageal sphincter pressure can be reduced below 10 mmHg. Major complications are rare after pneumatic dilation; the most serious complication is esophageal perforation, which occurs at a mean rate of about 2.5%. Considering the pros and cons of other effective forms of treatment of achalasia (esophagomyotomy and intrasphincteric injection of botulinum toxin, pneumatic dilation is still the treatment of choice in the majority of patients with achalasia.

  19. Salt effects on the air/solution interfacial properties of PEO-containing copolymers: equilibrium, adsorption kinetics and surface rheological behavior. (United States)

    Llamas, Sara; Mendoza, Alma J; Guzmán, Eduardo; Ortega, Francisco; Rubio, Ramón G


    Lithium cations are known to form complexes with the oxygen atoms of poly(oxyethylene) chains. The effect of Li(+) on the surface properties of three block-copolymers containing poly(oxyethylene) (PEO) have been studied. Two types of copolymers have been studied, a water soluble one of the pluronic family, PEO-b-PPO-b-PEO, PPO being poly(propyleneoxyde), and two water insoluble ones: PEO-b-PS and PEO-b-PS-b-PEO, PS being polystyrene. In the case of the pluronic the adsorption kinetics, the equilibrium surface tension isotherm and the aqueous/air surface rheology have been measured, while for the two insoluble copolymers only the surface pressure and the surface rheology have been studied. In all the cases two different Li(+) concentrations have been used. As in the absence of lithium ions, the adsorption kinetics of pluronic solutions shows two processes, and becomes faster as [Li(+)] increases. The kinetics is not diffusion controlled. For a given pluronic concentration the equilibrium surface pressure increases with [Li(+)], and the isotherms show two surface phase transitions, though less marked than for [Li(+)]=0. A similar behavior was found for the equilibrium isotherms of PEO-b-PS and PEO-b-PS-b-PEO. The surface elasticity of these two copolymers was found to increase with [Li(+)] over the whole surface concentration and frequency ranges studied. A smaller effect was found in the case of the pluronic solutions. The results of the pluronic solutions were modeled using a recent theory that takes into account that the molecules can be adsorbed at the surface in two different states. The theory gives a good fit for the adsorption kinetics and a reasonably good prediction of the equilibrium isotherms for low and intermediate concentrations of pluronic. However, the theory is not able to reproduce the isotherm for [Li(+)]=0. Only a semi-quantitative prediction of the surface elasticity is obtained for [pluronic]≤1×10(-3) mM. Copyright © 2013 Elsevier Inc. All

  20. Washcoat Deposition of Ni- and Co-ZrO2 Low Surface Area Powders onto Ceramic Open-Cell Foams: Influence of Slurry Formulation and Rheology

    Directory of Open Access Journals (Sweden)

    Riccardo Balzarotti


    Full Text Available The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while a dip-coating technique was chosen for washcoat deposition on 30 PPI ceramic open-cell foams. The rheological behavior was explained on the bases of both porosity and actual powder density. It was proved that the use of multiple dippings fulfills flexibility requirements for washcoat load management. Multiple depositions with intermediate flash drying steps at 350 °C were carried out. Washcoat loads in the 2.5 to 22 wt. % range were obtained. Pore clogging was seldom observed in a limited extent in samples with high loading (>20 wt. %. Adhesion, evaluated by means of accelerated stress test in ultrasound bath, pointed out good results of all the deposited layers.

  1. Percutaneous dilatational tracheostomy

    DEFF Research Database (Denmark)

    Johnsen, R.


    Introduction Since the introduction and development of percutaneous dilatational tracheostomy (PDT), this procedure is accepted and incorporated in ICUs worldwide. In spite of obvious benefits for the patients, who obtain more comfort and mobility and less use of sedatives, the procedure also...... providers' notes are entered. When searching for -percutaneous dilatation tracheostomy' in the electronic system, we found all patients who had undergone this specific procedure. Afterwards we analyzed each of these patients' hospital records, looking for any periprocedure or postprocedure complications...

  2. Network formation in graphene oxide composites with surface grafted PNIPAM chains in aqueous solution characterized by rheological experiments. (United States)

    GhavamiNejad, Amin; Hashmi, Saud; Joh, Han-Ik; Lee, Sungho; Lee, Youn-Sik; Vatankhah-Varnoosfaderani, Mohammad; Stadler, Florian J


    Poly N-isopropyl acrylamide (PNI) radically polymerized in aqueous solution in the presence of graphene oxide (GO) can significantly change the properties of the resulting solution from a regular polymer solution to a soft solid with a GO content of only 0.176 wt% (3 wt% with respect to PNI). However, these properties require the presence of both grafting and supramolecular interactions between polymer chains and hydrophilic groups on GO (-OH, -COOH), proven by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction and spectroscopy (XRD) and Raman spectra. While very low GO-contents (below 0.05 wt%) only lead to a labile structure, which can be disassembled by shear, higher contents yield composites with solid-like characteristics. This is clearly evident from the rheological behaviour, which changes significantly at a GO content around 0.15 wt%. Intensive shearing destroys the weak network, which cannot reform quickly at lower GO-concentrations, while at intermediate concentrations, restructuring is fast. GO-contents of 0.176 wt% lead to a material behaviour, which almost perfectly recovers from small deformations (creep and creep recovery compliance almost match) but larger deformations lead to permanent damage to the sample.

  3. Impairment of flow-mediated dilation correlates with aortic dilation in patients with Marfan syndrome. (United States)

    Takata, Munenori; Amiya, Eisuke; Watanabe, Masafumi; Omori, Kazuko; Imai, Yasushi; Fujita, Daishi; Nishimura, Hiroshi; Kato, Masayoshi; Morota, Tetsuro; Nawata, Kan; Ozeki, Atsuko; Watanabe, Aya; Kawarasaki, Shuichi; Hosoya, Yumiko; Nakao, Tomoko; Maemura, Koji; Nagai, Ryozo; Hirata, Yasunobu; Komuro, Issei


    Marfan syndrome is an inherited disorder characterized by genetic abnormality of microfibrillar connective tissue proteins. Endothelial dysfunction is thought to cause aortic dilation in subjects with a bicuspid aortic valve; however, the role of endothelial dysfunction and endothelial damaging factors has not been elucidated in Marfan syndrome. Flow-mediated dilation, a noninvasive measurement of endothelial function, was evaluated in 39 patients with Marfan syndrome. Aortic diameter was measured at the aortic annulus, aortic root at the sinus of Valsalva, sinotubular junction and ascending aorta by echocardiography, and adjusted for body surface area (BSA). The mean value of flow-mediated dilation was 6.5 ± 2.4 %. Flow-mediated dilation had a negative correlation with the diameter of the ascending thoracic aorta (AscAd)/BSA (R = -0.39, p = 0.020) and multivariate analysis revealed that flow-mediated dilation was an independent factor predicting AscAd/BSA, whereas other segments of the aorta had no association. Furthermore, Brinkman index had a somewhat greater influence on flow-mediated dilation (R = -0.42, p = 0.008). Although subjects who smoked tended to have a larger AscAd compared with non-smokers (AscA/BSA: 17.3 ± 1.8 versus 15.2 ± 3.0 mm/m(2), p = 0.013), there was no significant change in flow-mediated dilation, suggesting that smoking might affect aortic dilation via an independent pathway. Common atherogenic risks, such as impairment of flow-mediated dilation and smoking status, affected aortic dilation in subjects with Marfan syndrome.

  4. Atomic force microscopy for the examination of single cell rheology. (United States)

    Okajima, Takaharu


    Rheological properties of living cells play important roles in regulating their various biological functions. Therefore, measuring cell rheology is crucial for not only elucidating the relationship between the cell mechanics and functions, but also mechanical diagnosis of single cells. Atomic force microscopy (AFM) is becoming a useful technique for single cell diagnosis because it allows us to measure the rheological properties of adherent cells at any region on the surface without any modifications. In this review, we summarize AFM techniques for examining single cell rheology in frequency and time domains. Recent applications of AFM for investigating the statistical analysis of single cell rheology in comparison to other micro-rheological techniques are reviewed, and we discuss what specificity and universality of cell rheology are extracted using AFM.

  5. Comparison of rheological, mechanical, electrical properties of HDPE filled with BaTiO{sub 3} with different polar surface tension

    Energy Technology Data Exchange (ETDEWEB)

    Su, Jun [Department of Polymer Science and Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); College of Mechanics Engineering, Nanjing Institute of Industry Technology, Nanjing, 210023 (China); Zhang, Jun, E-mail: [Department of Polymer Science and Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China)


    Graphical abstract: - Highlights: • The non-polar and short vinyl groups can greatly reduce G′ of HDPE composites. • Long chains on BaTiO{sub 3} surface enhance the interaction of BaTiO{sub 3} with HDPE. • Polar amino groups on BaTiO{sub 3} surface raise the interaction of BaTiO{sub 3} with HDPE. • Polar amino groups can boost the dielectric constant of HDPE composites. • The potential use in electronic equipment of the KH550 composites is obtained. - Abstract: In this work, three types of coupling agents: isopropyl trioleic titanate (NDZ105), vinyltriethoxysilane (SG-Si151), 3-aminopropyltriethoxysilane (KH550) were applied to modify the surface tension of Barium titanate (BaTiO{sub 3}) particles. The Fourier transform infrared (FT-IR) spectra confirm the chemical adherence of coupling agents to the particle surface. The long hydrocarbon chains in NDZ105 can cover the particle surface and reduce the polar surface tension of BaTiO{sub 3} from 37.53 mJ/m{sup 2} to 7.51 mJ/m{sup 2}, turning it from hydrophilic to oleophilic properties. The short and non-polar vinyl groups in SG-Si151 does not influence the surface tension of BaTiO{sub 3}, but make BaTiO{sub 3} have both hydrophilic and oleophilic properties. The polar amino in KH550 can keep BaTiO{sub 3} still with hydrophilic properties. It is found that SG-Si151 modified BaTiO{sub 3} has the lowest interaction with HDPE matrix, lowering the storage modulus of HDPE composites to the greatest extent. As for mechanical properties, the polar amino groups in KH550 on BaTiO{sub 3} surface can improve the adhesion of BaTiO{sub 3} with HDPE matrix, which increases the elongation at break of HDPE composites to the greatest extent. In terms of electrical properties, the polar amino groups on surface of BaTiO{sub 3} can boost the dielectric properties of HDPE/BaTiO{sub 3} composites and decrease the volume resistivity of HDPE/BaTiO{sub 3} composites. The aim of this study is to investigate how functional groups

  6. The influence of the size and surface modification of TiO2 nanoparticles on the rheological properties of alkyd resin

    Directory of Open Access Journals (Sweden)

    Radoman Tijana


    Full Text Available Spherical TiO2 particles of different size were dispersed in alkyd resin based on soybean oil. Four samples of TiO2 particles were used, three commercial and one obtained by acid catalyzed hydrolysis of titanium tetraisopropoxide. The size of the synthesized nanoparticles was determined by transmission electron microscopy. Surface modification of TiO2 nanoparticles was performed with propyl gallate and lauryl gallate. The influence of the size of TiO2 nanoparticles, their concentration and type of the surface modification on the rheological properties of alkyd resin was investigated. The obtained results have shown that the viscosity of the prepared dispersions was higher than viscosity of the pure resin, it increases with decreasing particle diameter and decreases with frequency increase. Surface modified particles showed higher influence on the viscosity of alkyd resin than unmodified, because their hydrodynamic volume is higher due to the presence of the adsorbed gallates, leading to the increase of effective volume fraction of particles in dispersion. For the lowest TiO2 concentration, the viscosity was higher for sample modified with lauryl gallate, due to the higher thickness of the adsorbed layer. The increase of concentration, because of less dispersion stability of the particles modified with propyl gallate, leads to particles agglomeration. The presence of agglomerates, which was confirmed by a change in the slope of the functional dependence of storage modulus on loss modulus, leads to a rapid increase in viscosity. [Projekat Ministarstva nauke Republike Srbije, br. 172062 i br. 45020

  7. Rheology in Pharmaceutical Sciences

    DEFF Research Database (Denmark)

    Aho, Johanna; Hvidt, Søren; Baldursdottir, Stefania


    Rheology is the science of flow and deformation of matter. Particularly gels and non-Newtonian fluids, which exhibit complex flow behavior, are frequently encountered in pharmaceutical engineering and manufacturing, or when dealing with various in vivo fluids. Therefore understanding rheology is ...

  8. Rheological State Diagrams for Rough Colloids in Shear Flow (United States)

    Hsiao, Lilian C.; Jamali, Safa; Glynos, Emmanouil; Green, Peter F.; Larson, Ronald G.; Solomon, Michael J.


    To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

  9. Rheological phenomena in focus

    CERN Document Server

    Boger, DV


    More than possibly any other scientific discipline, rheology is easily visualized and the relevant literature contains many excellent photographs of unusual and often bizarre phenomena. The present book brings together these photographs for the first time. They are supported by a full explanatory text. Rheological Phenomena in Focus will be an indispensable support manual to all those who teach rheology or have to convince colleagues of the practical relevance of the subject within an industrial setting. For those who teach fluid mechanics, the book clearly illustrates the difference be

  10. Polyelectrolytes thermodynamics and rheology

    CERN Document Server

    P M, Visakh; Picó, Guillermo Alfredo


    This book discusses current development of theoretical models and experimental findings on the thermodynamics of polyelectrolytes. Particular emphasis is placed on the rheological description of polyelectrolyte solutions and hydrogels.

  11. Fluid dynamics of dilatant fluid

    DEFF Research Database (Denmark)

    Nakanishi, Hiizu; Nagahiro, Shin-ichiro; Mitarai, Namiko


    A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation...

  12. Roentgenoendovascular dilatation of brachycephalic arteries

    International Nuclear Information System (INIS)

    Rabkin, I.Kh.; Kachel, R.; Glazer, F.; Matevosov, A.L.; Dzhoraev, I.G.; Medizinische Akademie, Erfurt


    The authors reported the technique, methods of and indications for roentgenoendovascular dilation in stenotic and occlusive lesions of the brachycephalic branches of the aorta. A total of 102 vascular dilations were perfomed in 76 patients resulting in a good angiographic and clinical effect. In 2 patients the first world prosthetics was performed using an original coiled nitinol prosthesis

  13. Potential Hydraulic Modelling Errors Associated with Rheological Data Extrapolation in Laminar Flow

    International Nuclear Information System (INIS)

    Shadday, Martin A. Jr.


    The potential errors associated with the modelling of flows of non-Newtonian slurries through pipes, due to inadequate rheological models and extrapolation outside of the ranges of data bases, are demonstrated. The behaviors of both dilatant and pseudoplastic fluids with yield stresses, and the errors associated with treating them as Bingham plastics, are investigated

  14. Segmental dilatation of the ileum

    Directory of Open Access Journals (Sweden)

    Tune-Yie Shih


    Full Text Available A 2-year-old boy was sent to the emergency department with the chief problem of abdominal pain for 1 day. He was just discharged from the pediatric ward with the diagnosis of mycoplasmal pneumonia and paralytic ileus. After initial examinations and radiographic investigations, midgut volvulus was impressed. An emergency laparotomy was performed. Segmental dilatation of the ileum with volvulus was found. The operative procedure was resection of the dilated ileal segment with anastomosis. The postoperative recovery was uneventful. The unique abnormality of gastrointestinal tract – segmental dilatation of the ileum, is described in details and the literature is reviewed.

  15. Vessel dilatation in coronary angiograms

    Energy Technology Data Exchange (ETDEWEB)

    Hinterauer, L.; Goebel, N.


    Amongst 166 patients with aneurysms, ectasia or megaloarteries shown on coronary angiograms, 86.1% had dilated vessels as part of generalised coronary sclerosis (usually in patients with three-vessel disease). In 9%, dilatation was of iatrogenic origin and in 4.8% it was idiopathic. One patient had Marfan's syndrome. Amongst 9 000 patients, there were eight with megalo-arteries without stenosis; six of these had atypical angina and three suffered an infarct. Patients with definite dilatation of the coronary artery and stagnation of contrast flow required treatment.

  16. Vessel dilatation in coronary angiograms

    International Nuclear Information System (INIS)

    Hinterauer, L.; Goebel, N.


    Amongst 166 patients with aneurysms, ectasia or megaloarteries shown on coronary angiograms, 86.1% had dilated vessels as part of generalised coronary sclerosis (usually in patients with three-vessel disease). In 9%, dilatation was of iatrogenic origin and in 4.8% it was idiopathic. One patient had Marfan's syndrome. Amongst 9 000 patients, there were eight with megalo-arteries without stenosis; six of these had atypical angina and three suffered an infarct. Patients with definite dilatation of the coronary artery and stagnation of contrast flow required treatment. (orig.) [de

  17. Rheology of Supramolecular Polymers

    DEFF Research Database (Denmark)

    Shabbir, Aamir

    efficient processes or biomedical areas. Design and development of supramolecular polymers using ionic, hydrogen bonding or transition metal complexes with tailored properties requires deep understanding of dynamics both in linear and non-linear deformations. While linear rheology is important to understand...... the dynamics under equilibrium conditions, extensional rheology is relevant during the processing or in the usage of polymers utilizing supramolecular associations for example, acrylic based pressure sensitive adhesives are subjected to extensional deformations during the peeling where strain hardening......) hydrogen bonding polymers, and (b) ionic bonding polymers (hereafter termed as ionomers). We study linear and non-linear rheology fora model system of entangled pure poly(n-butyl acrylate), PnBA, homopolymer andfour poly(acrylic acid), PnBA-PAA, copolymers with varying AA side groups synthesizedvia...

  18. Rheology of liquid foam

    International Nuclear Information System (INIS)

    Hoehler, R; Cohen-Addad, S


    Liquid foams can behave like solids or liquids, depending on the applied stress and on the experimental timescale. Understanding the origin of this complex rheology which gives rise to many applications and which resembles that of many other forms of soft condensed matter made of closely packed soft units requires challenging theoretical questions to be solved. We briefly recall the basic physics and physicochemistry of foams and review the experiments, numerical simulations and theoretical models concerning foam rheology published in recent years. (topical review)

  19. Dilatancy in Slow Granular Flows (United States)

    Kabla, Alexandre J.; Senden, Tim J.


    When walking on wet sand, each footstep leaves behind a temporarily dry impression. This counterintuitive observation is the most common illustration of the Reynolds principle of dilatancy: that is, a granular packing tends to expand as it is deformed, therefore increasing the amount of porous space. Although widely called upon in areas such as soil mechanics and geotechnics, a deeper understanding of this principle is constrained by the lack of analytical tools to study this behavior. Using x-ray radiography, we track a broad variety of granular flow profiles and quantify their intrinsic dilatancy behavior. These measurements frame Reynolds dilatancy as a kinematic process. Closer inspection demonstrates, however, the practical importance of flow induced compaction which competes with dilatancy, leading more complex flow properties than expected.

  20. A rheological study of hydrophobic-surface-active polymer systems structuration; Etude rheologique de la structuration de systemes polymere hydrophobe-tensioactif

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, E.


    This work deals with the study of the rheology and the structuration of hydrophobic polymer and surfactant systems. The used associative polymers are acrylamide/nonyl methacrylate copolymers and the surfactant is nonionic. They are particularly used for hydrocarbons extraction techniques as drilling (drilling fluids) or wells cementation. The studied materials are first characterized by different analytic techniques. This preliminary stage of the work gives a good insight of the physico-chemical parameters of the systems. The effect of surfactant was shown by studying the variation of Newtonian viscosity as a function of surfactant concentration. This yields bell curves, whose maximum determines the critical aggregation concentration (cac). The hydrophobic effect is analysed in different polymer concentration regimes, in quasi-static conditions, and under shear. The study of the dynamic visco-elasticity of semi-dilute solutions allows to observe the effect of the hydrophobic associations on the relaxation time of the chains. The system can be described as a superposition of two networks of junctions: the network of physical entanglements and a second one formed by the hydrophobic links. Phenomena of structuration have been observed at room temperature for surfactant concentrations close to the cac. The increase of viscosity or elastic modulus can be 3 to 4 orders of magnitude. The effect of the temperature on the structure of the systems is studied as well. The rheological characterization of the Sol-Gel transition is developed and the rheological behavior of the solutions in a structured state shows a critical stress for rupture of the structure. Microscopic observations of the birefringence of the solutions display the existence of lamellar vesicles, which leads to the following assumption: the formation of big spherulites create a rigidification of the macromolecular network. (author) 190 refs.

  1. Generalized rheology and geophysical consequences (United States)

    Caputo, Michele


    new viscosity parameter introduced with the model is decreasing with depth which would account for the deformation rates observed on the surface of the Earth which should therefore be caused by the fast creep of the lower layers. The rheological model gives more realistic values for the Q of the mantle. The variation of the node of Lageos and that of UT1 are also discussed; it is suggested that these variations may be caused by the cumulative rebounds due to several deglaciations and not by the last one only.

  2. Interparticle Forces and Rheology of Cement Based Suspensions (United States)

    Lowke, D.

    Rheological properties of cement based suspensions are affected by the surface properties of the particles, the properties of the solvent and the adsorbed polymers. To understand the interaction between these parameters and the rheology of cement based suspensions the surface forces of the colloidal powder particles were considered. Three surface forces are taken into consideration - the attractive van der Waals forces, the repulsive double layer forces and the polymer induced steric forces. A theoretical basis for the evaluation of these forces in cement based suspension is given. Within the experimental program the superplasticizer adsorption was determined for cement and ground limestone suspensions. Rheological measurements were performed with these suspensions to determine yield stress and thixotropy. The results indicate a strong correlation between polymer adsorption, rheological properties of the suspensions and evaluated forces.

  3. Activated Sludge Rheology

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Horn, Willi; Helmus, Frank


    Rheological behaviour is an important fluid property that severely impacts its flow behaviour and many aspects related to this. In the case of activated sludge, the apparent viscosity has an influence on e.g. pumping, hydrodynamics, mass transfer rates, sludge-water separation (settling and filtr...

  4. Rheology of concentrated biomass (United States)

    J.R. Samaniuk; J. Wang; T.W. Root; C.T. Scott; D.J. Klingenberg


    Economic processing of lignocellulosic biomass requires handling the biomass at high solids concentration. This creates challenges because concentrated biomass behaves as a Bingham-like material with large yield stresses. Here we employ torque rheometry to measure the rheological properties of concentrated lignocellulosic biomass (corn stover). Yield stresses obtained...

  5. Molecular Rheology of Complex Fluids

    DEFF Research Database (Denmark)

    Huang, Qian; Rasmussen, Henrik Koblitz

    The processing of polymer materials is highly governed by its rheology, and influences the properties of the final product. For example, a recurring problem is instability in extrusion that leads to imperfect plastic parts. The ability to predict and control the rheological behavior of polymer...... flow is the dominant type of deformation. The polymer molecules experience a significant amount of chain orientation and stretching during these processes. Shear rheology measured by conventional shear rheometers is good at describing chain orientation, whereas extensional rheology gives a good way...... of inducing chain stretching. Accurate and reliable stress–strain measurements of extensional flow play a crucial role in the understanding of non–linear rheological properties of polymers. However, the non–linear extensional rheology has not been extensively studied. It is known that the rheology of polymer...

  6. Development of a model colloidal system for rheology simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall; Tallant, David Robert; Piech, Martin (United Technologies Research Center, East Hartford, CT); Bell, Nelson Simmons; Frischknecht, Amalie Lucile


    The objective of the experimental effort is to provide a model particle system that will enable modeling of the macroscopic rheology from the interfacial and environmental structure of the particles and solvent or melt as functions of applied shear and volume fraction of the solid particles. This chapter describes the choice of the model particle system, methods for synthesis and characterization, and results from characterization of colloidal dispersion, particle film formation, and the shear and oscillatory rheology in the system. Surface characterization of the grafted PDMS interface, dispersion characterization of the colloids, and rheological characterization of the dispersions as a function of volume fraction were conducted.

  7. Rheological properties of whey proteins concentrate before and

    Directory of Open Access Journals (Sweden)

    Zoran Herceg


    Full Text Available Hydrocolloids are long-chain polymers, used in food production at small quantities (from 0,05 to 5 % to achieve appropriate rheological properties, prevent syneresis, increase the viscosity and stability of foodstuffs and for crystallization process control. The aim of this work was to investigate the influence of tribomechanical micronization of powdered whey protein concentrate on the rheological properties of whey proteins model systems as well as the influence of severalcarboxymethylcellulose hydrocolloids addition in such systems.Measurements were done using rotational viscosimeter, Brookfield DV-III at temperature 20 oC. The rheological parameters were determined by powerlaw model. The results of investigation have shown that all investigated systems are non-Newtonian. Depending on the pretreatment of whey proteins and the mass fractions of hydrocolloids they exhibited pseudoplastic or dilatant properties.Particle size analysis was performed using Fritsch – laser particle sizer “analysette 22”. The operation of tribomechanical micronization caused the decreasing of particle size and incrasing specific area of whey proteins. Tribomechanical treatment of whey proteins had significant influence on the rheological parameters and the type of flowing.

  8. Rheological behavior of oil and biodiesel from Moringa oleifera

    International Nuclear Information System (INIS)

    Díaz Domínguez, Yosvany; Tabio García, Danger; Rondón Macías, Maylin; Fernández Santana, Elina; Rodríguez Muñoz, Susana; Piloto‐Rodríguez, Ramón


    The seeds of Moringa oleifera contain between 30 and 45% of oil, which has motivated the development of investigations with a view to their possible use. The present work aims to determine the rheological behavior of Moringa oleifera oil and biodiesel. The synthesis of biodiesel from crude Moringa oleifera oil was made using methanol with presence of sodium hydroxide. The average yield of this stage was 93%. The results of the rheological study shown that the viscosity at 40°C of Moringa oleifera oil is independent of the shear rate, which corresponds to the behavior of a Newtonian fluid. However, for biodiesel it was demonstrated that there is a dependence of the viscosity with the shear rate (non-Newtonian fluid). This result is corroborated by the fluidity curve, assuring that Moringa oleifera biodiesel behaves as a dilating fluid. (author)

  9. Rock and soil rheology

    International Nuclear Information System (INIS)

    Cristescu, N.; Ene, H.I.


    The aim of the Euromech Colloquium 196 devoted to Rock and Soil Rheology is to review some of the main results obtained in the last years in this field of research and also to formulate some of the major not yet solved problems which are now under consideration. Exchange of opinions and scientific discussions are quite helpful mainly in those areas where some approaches are controversial and the progress made is quite fast. That is especially true for the rheology of geomaterials, domain of great interest for mining and petroleum engineers, engineering geology, seismology, geophysics, civil engineering, nuclear and industrial waste storage, geothermal energy storage, caverns for sports, culture, telecommunications, storage of goods and foodstuffs (cold, hot and refrigerated storages), underground oil and natural gas reservoirs etc. Some of the last obtained results are mentioned in the present volume. (orig./HP)

  10. Rheology of Active Fluids (United States)

    Saintillan, David


    An active fluid denotes a viscous suspension of particles, cells, or macromolecules able to convert chemical energy into mechanical work by generating stresses on the microscale. By virtue of this internal energy conversion, these systems display unusual macroscopic rheological signatures, including a curious transition to an apparent superfluid-like state where internal activity exactly compensates viscous dissipation. These behaviors are unlike those of classical complex fluids and result from the coupling of particle configurations with both externally applied flows and internally generated fluid disturbances. Focusing on the well-studied example of a suspension of microswimmers, this review summarizes recent experiments, models, and simulations in this area and highlights the critical role played by the rheological response of these active materials in a multitude of phenomena, from the enhanced transport of passive suspended objects to the emergence of spontaneous flows and collective motion.

  11. Rheological properties of soil: a review (United States)

    Zhu, Guangli; Zhu, Long; Yu, Chao


    Recently rheological methods have been applied to investigate the mechanical properties of soil micro-structure. Rheological techniques have a number of quantitative physically based measurements and offer a better understanding of how soil micro-structure behaves when subject to stress. Rheological material is refers to deformation properties similar to the solid and flow properties similar to the liquid of bound water and colloidal substances under stress. Soil rheology is divided into fluid rheology and plasticity rheology. Fluid rheology is produced by rheological material. Plasticity rheology mainly refers to the sliding and peristaltic between soil solid particles under shear stress. It is generally believed that the soft soil rheology mainly belongs to fluid rheology, while the rheology of sand and other coarse grained soil mainly belongs to plasticity rheology. Thus, rheology mechanisms of soft soil and sand are different. This paper introduces the methods of the research progress on the rheology of soil, in the soil rheological mechanism, rheological model and rheological numerical aspects of the research at home and abroad were summarized and analysed, discussed the problems existed in related research, and puts forward some suggestions for the future study on the rheology of soil.

  12. Brain Abscess after Esophageal Dilatation

    DEFF Research Database (Denmark)

    Gaïni, S; Grand, M; Michelsen, J


    with malaise, progressive lethargy, fever, aphasia and hemiparesis. Six days before she had been treated with esophageal dilatation for a stricture caused by accidental ingestion of caustic soda. The brain abscess was treated with surgery and antibiotics. She recovered completely. This clinical case...

  13. Rheological characterization of polyolefin composites with reduced flammability (United States)

    Habrova, Veronika; Kalendova, Alena; Paravanova, Gordana


    In this work, the low-flammability halogen-free polyolefin composites were characterized with three rheological methods. In the extrusion process of the studied materials the end-products with a dissimilar surface quality were produced. Therefore, the diverse melt flow behaviours evaluated with common rheological techniques were also expected. Nevertheless, the conventional rotational and capillary rheometries were not able to describe the differences between investigated flame retarded composites in optimal way. Thus, the non-conventional rheological die Shark skin, originally designed to detect flow instabilities, was tested as a third possibility in order to better understand rheology of the filled polymer melts. It was found that the Shark skin technique is able to characterize the studied two kind flame retardants composites and can also be helpful to qualify the production bathes with identical additives/polymer formulation.

  14. Influence of the nature of surface-active substances on rheology of high-filled pastelike compositions on a base on liquid diene rubber and disperse filler

    Directory of Open Access Journals (Sweden)

    Alexander B. Surovtcev


    Full Text Available Results of researches on reception of pastelike high-filled compositions and estimation of their rheological properties with use cone – plate rheometer are presented. Liquid diene rubber with end hydroxyl groups (as binding, surfaceactive substance (PEAHENS and disperse filler are entered into structure of compositions. The estimation of sedimentation firmness of compositions and their fluidity in the range of pressure of shift 1 – 30 кPа and temperatures from 30 to 50°С is executed. By results of an estimation of influence of concentration dependence of PEAHENS on a viscosity indicator it is shown that its introduction in a pastelike composition at level 0.5 mas. % is expedient. For considered in work low polar liquid diene rubber more effective decrease in viscosity of a pastelike composition provide polyoxypropylene, especially on the average an interval of pressure of shift which basically can be used in practice. Slightly concede them titanorganic derivatives of oligomer polyoxypropylene. The greatest effect of decrease in viscosity for compositions will reach at use oligomer polyoxypropylene with molecular weight 480, in this case viscosity of a composition is at level of 10 Pa ⋅ s for rather wide interval of pressure of shift.

  15. 5th European Rheology Conference

    CERN Document Server


    Global sustainable development of the world economy requires better understanding and utilization of natural recourses. In this endeavor rheology has an indispensable role. The Rheology Conferences are therefore always an important event for science and technology. The Fifth European Rheology Conference, held from September 6 to 11 in the Portoro-z, Slovenia, will be the first AlI-European rheology meeting after the formal constitution of the European Society ofRheology. As such it will be a special historical event. At this meeting the European Society of Rheology will introduce the Weissenberg Medal, to be bestowed every four years to an individual for hislhers contribution to the field of Rheology. The recipient ofthe first award will be professor G. Marrucci ofthe Universita degli Studi di Napoli, Italy. Two mini Symposia will be part of the Conference. The first, on Industrial Rheology, will commemorate the late professor G. Astarita. The second will honor the eightieth birthday of professor N.W. Tschoeg...

  16. Oversampling of wavelet frames for real dilations

    DEFF Research Database (Denmark)

    Bownik, Marcin; Lemvig, Jakob


    We generalize the Second Oversampling Theorem for wavelet frames and dual wavelet frames from the setting of integer dilations to real dilations. We also study the relationship between dilation matrix oversampling of semi-orthogonal Parseval wavelet frames and the additional shift invariance gain...

  17. Balloon dilatation of iatrogenic urethral strictures

    International Nuclear Information System (INIS)

    Acunas, B.; Acunas, G.; Gokmen, E.; Celik, L.


    Balloon dilatation of the urethra was performed in five patients with iatrogenic urethral strictures. The urethral strictures were successfully negotiated and dilated in all patients. Redilatation became necessary in a period ranging from 3 to 10 months. The authors believe that balloon dilatation of the urethra can be safely and successfully performed; the procedure produces minimal trauma and immediate relief of symptoms. (orig.)

  18. Arresting dissolution by interfacial rheology design (United States)

    Beltramo, Peter J.; Gupta, Manish; Alicke, Alexandra; Liascukiene, Irma; Gunes, Deniz Z.; Baroud, Charles N.


    A strategy to halt dissolution of particle-coated air bubbles in water based on interfacial rheology design is presented. Whereas previously a dense monolayer was believed to be required for such an “armored bubble” to resist dissolution, in fact engineering a 2D yield stress interface suffices to achieve such performance at submonolayer particle coverages. We use a suite of interfacial rheology techniques to characterize spherical and ellipsoidal particles at an air–water interface as a function of surface coverage. Bubbles with varying particle coverages are made and their resistance to dissolution evaluated using a microfluidic technique. Whereas a bare bubble only has a single pressure at which a given radius is stable, we find a range of pressures over which bubble dissolution is arrested for armored bubbles. The link between interfacial rheology and macroscopic dissolution of ∼ 100 μm bubbles coated with ∼ 1 μm particles is presented and discussed. The generic design rationale is confirmed by using nonspherical particles, which develop significant yield stress at even lower surface coverages. Hence, it can be applied to successfully inhibit Ostwald ripening in a multitude of foam and emulsion applications. PMID:28893993

  19. Balloon dilatations of esophageal strictures

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Jeong Jin; Juhng, Seon Kwan; Kim, Jae Kyu; Chung, Hyon De [Chonnam National University College of Medicine, Seoul (Korea, Republic of)


    Most benign esophageal strictures can be successfully dilated with conventional bougienage technique. But occasionally strictures are so tight, lengthy, or sometimes irregular that this technique fail, and surgical intervention is required. Since 1974 Gruentzig balloon catheter has succeed when used for strictures in the cardiac and peripheral vasculatures, the biliary and urinary tracts, the colon of neonates after inflammatory disease and also in the esophagus. Fluoroscopically guided balloon catheters were used to dilate 30 esophageal strictures in 30 patients over 3 years at Department of Diagnostic Radiology, Chonnam University, College of Medicine. The distribution of age was from 7 years to 71 days and the ratio of male to female was 15:15. The causes of benign stricture (23 cases) were post-operative strictures (13), chemical (4), achalasia (3), chronic inflammation (2), esophageal rupture (1) and those of malignant stricture (7 cases) were post-radiation stricture of primary esophageal cancer (6) and metastatic esophageal cancer (1). The success rate of procedure was 93% (28/30). The causes of failure were the failure of passage of stricture due to markedly dilated proximal segment of esophagus (1 case) and too long segment of stricture (1 case). Complication of procedure was the diverticular-formation of esophagus in 3 cases, but has no clinical significance in follow-up esophagography. In conclusion, fluoroscopically guided balloon dilation of esophageal stricture appears to be safe, effective treatment and may be have theoretical advantages over conventional bougienage and also should be considered before other methods of treatment are used.

  20. Balloon dilatations of esophageal strictures

    International Nuclear Information System (INIS)

    Seo, Jeong Jin; Juhng, Seon Kwan; Kim, Jae Kyu; Chung, Hyon De


    Most benign esophageal strictures can be successfully dilated with conventional bougienage technique. But occasionally strictures are so tight, lengthy, or sometimes irregular that this technique fail, and surgical intervention is required. Since 1974 Gruentzig balloon catheter has succeed when used for strictures in the cardiac and peripheral vasculatures, the biliary and urinary tracts, the colon of neonates after inflammatory disease and also in the esophagus. Fluoroscopically guided balloon catheters were used to dilate 30 esophageal strictures in 30 patients over 3 years at Department of Diagnostic Radiology, Chonnam University, College of Medicine. The distribution of age was from 7 years to 71 days and the ratio of male to female was 15:15. The causes of benign stricture (23 cases) were post-operative strictures (13), chemical (4), achalasia (3), chronic inflammation (2), esophageal rupture (1) and those of malignant stricture (7 cases) were post-radiation stricture of primary esophageal cancer (6) and metastatic esophageal cancer (1). The success rate of procedure was 93% (28/30). The causes of failure were the failure of passage of stricture due to markedly dilated proximal segment of esophagus (1 case) and too long segment of stricture (1 case). Complication of procedure was the diverticular-formation of esophagus in 3 cases, but has no clinical significance in follow-up esophagography. In conclusion, fluoroscopically guided balloon dilation of esophageal stricture appears to be safe, effective treatment and may be have theoretical advantages over conventional bougienage and also should be considered before other methods of treatment are used

  1. Rheological Characterization of Vegetal Pear (Sechium edule) (United States)

    Castillo-Reyes, José A.; Luna-Solano, Guadalupe; Cantú-Lozano, Denis


    The national production of Mexican vegetal pear (Sechium edule) is located at the present time in more than 130,000 ton/year. The vegetal pear that produced in the center zone of the state of Veracruz is known in international markets; however it is a product that practically has not been studied. This work identifies the rheological behavior of vegetal pear (Sechium edule). A rheometer MCR301 of Anton Paar was utilized for viscosity and shear stress measurements. The objective of this experimental was modeling the rheological behavior of vegetal pear suspensions at three concentrations (1, 2 and 3% w/w), three particle size (1.00, 1.19 and 1.40 mm), at the same conditions of temperature (25, 40 and 70 °C). The results showed that all the suspensions there was a phenomenological behavior as a dilatants fluid (n>1) the performance of flow was represented by the Herschel-Bulkley model, and present values of "yield stress" between from 0.1 to 15 Pa for the different experiments. During evaluation of the activation energy of the suspensions of vegetal pear was found that decreases from 154.4039 kJ/mol to 9.1086 kJ/mol for a particle size of 1.00 mm to 1.4 mm, which implies that the effect of temperature is higher with smaller grains, in this case 1.00 mm. Furthermore, we assessed the effect of particle size by the Péclet number, showing an increase of the viscosity when the Péclet number also increases.

  2. Slug ascent and associated stresses during strombolian activity with non-Newtonian rheology (United States)

    von der Lieth, Jost; Hort, Matthias


    Strombolian activity is generally assumed to be driven by overpressurized gas slugs that rise through the magma-filled volcanic conduit and burst at the surface. We develop an analytical model for this process that incorporates a generic, depth-dependent, and non-Newtonian magma rheology. Our model also describes the film draining after the burst and allows for the computation of the stresses exerted on the conduit walls using a new analytical solution for the thickness of an annular film flow. Using Stromboli volcano, Italy, as reference, it was evaluated with a specifically designed, non-Newtonian rheological model based on petrochemical data. The results show the importance of using a realistic magma viscosity model when modeling the slug ascent: A 100 kg gas slug attains its maximum overpressure of 2.1 bars about 40 s before it rapidly expands and finally bursts at only 1.4 bars. This preburst pressure drop is not reproduced by constant viscosity models. The normal stresses on the conduit wall are generally dilatational above and adjacent to the slug and constrictive below it and after the burst. In both cases their maximum values exceed 3 bars, whereas the shear stresses stay negligible. Furthermore, it was found that the slug needs to start deeper than 25 m to build up its full burst pressure. At greater depth, the burst pressure decreases because of the adiabatic slug gas. Finally, a viscous plug at the top of the conduit is shown to increase the explosive potential of the volcano significantly.

  3. The effect of physiological conditions on the surface structure of proteins: Setting the scene for human digestion of emulsions (United States)

    Maldonado-Valderrama, J.; Gunning, A. P.; Ridout, M. J.; Wilde, P. J.; Morris, V. J.


    Understanding and manipulating the interfacial mechanisms that control human digestion of food emulsions is a crucial step towards improved control of dietary intake. This article reports initial studies on the effects of the physiological conditions within the stomach on the properties of the film formed by the milk protein ( β -lactoglobulin) at the air-water interface. Atomic force microscopy (AFM), surface tension and surface rheology techniques were used to visualize and examine the effect of gastric conditions on the network structure. The effects of changes in temperature, pH and ionic strength on a pre-formed interfacial structure were characterized in order to simulate the actual digestion process. Changes in ionic strength had little effect on the surface properties. In isolation, acidification reduced both the dilatational and the surface shear modulus, mainly due to strong repulsive electrostatic interactions within the surface layer and raising the temperature to body temperature accelerated the rearrangements within the surface layer, resulting in a decrease of the dilatational response and an increase of surface pressure. Together pH and temperature display an unexpected synergism, independent of the ionic strength. Thus, exposure of a pre-formed interfacial β -lactoglobulin film to simulated gastric conditions reduced the surface dilatational modulus and surface shear moduli. This is attributed to a weakening of the surface network in which the surface rearrangements of the protein prior to exposure to gastric conditions might play a crucial role.

  4. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuanping [Iowa State Univ., Ames, IA (United States)


    Colloidal processing is an effective and reliable approach in the fabrication of the advanced ceramic products. Successful colloidal processing of fine ceramic powders requires accurate control of the rheological properties. The accurate control relies on the understanding the influences of various colloidal parameters on the rheological properties. Almost all research done on the rheology paid less attention to the interactions of particle and solvent. However, the interactions of the particles are usually built up through the media in which the particles are suspended. Therefore, interactions of the particle with the media, the adsorbed layers on the particle surface, and chemical and physical properties of media themselves must influence the rheology of the suspension, especially for the dense suspensions containing nanosized particles. Relatively little research work has been reported in this area. This thesis addresses the rheological properties of nanometric alumina aqueous suspensions, and paying more attention to the interactions between particle and solvent, which in turn influence the particle-particle interactions. Dense nanometric alumina aqueous suspensions with low viscosity were achieved by environmentally-benign fructose additives. The rheology of nanometric alumina aqueous suspensions and its variation with the particle volume fraction and concentration of fructose were explored by rheometry. The adsorptions of solute (fructose) and solvent (water) on the nanometric alumina particle surfaces were measured and analyzed by TG/DSC, TOC, and NMR techniques. The mobility of water molecules in the suspensions and its variation with particle volume fractions and fructose additive were determined by the 17O NMR relaxation method. The interactions between the nanometric alumina particles in water and fructose solutions were investigated by AFM. The results indicated that a large number of water layers were physically bound on the particles

  5. Rheology of concentrated biomass (United States)

    Samaniuk, J. R.; Wang, J.; Root, T. W.; Scott, C. T.; Klingenberg, D. J.


    Economic processing of lignocellulosic biomass requires handling the biomass at high solids concentration. This creates challenges because concentrated biomass behaves as a Bingham-like material with large yield stresses. Here we employ torque rheometry to measure the rheological properties of concentrated lignocellulosic biomass (corn stover). Yield stresses obtained using torque rheometry agree with those obtained using other rheometric methods, but torque rheometry can be used at much larger solids concentration (weight fractions of insoluble solids greater than 0.2). Yield stresses decrease with severity of hydrolysis, decrease when water-soluble polymers are added (for nonhydrolyzed biomass), and increase with particle length. Experimental results are qualitatively consistent with those obtained from particle-level simulations.

  6. Rheological properties of a nematic cell oriented in a planar manner

    Energy Technology Data Exchange (ETDEWEB)

    Barbero, G., E-mail: giovanni.barbero@polito.i [Dipartimento di Fisica and C. N. I. S. M., Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)] [Universite de Picardie Jules Verne, Laboratoire de Physique des Systemes Complexes, 33 rue Saint-Leu 80039, Amiens (France); Meyer, C.; Lelidis, I. [Universite de Picardie Jules Verne, Laboratoire de Physique des Systemes Complexes, 33 rue Saint-Leu 80039, Amiens (France)


    We propose a simple model to investigate the rheological properties of a nematic cell oriented in a planar manner. The storage and loss modulus are evaluated in the case of strong and weak anchoring conditions. The contribution of the surface viscosity to the rheological parameters is also considered.

  7. Clinical review: Percutaneous dilatational tracheostomy (United States)

    Al-Ansari, Mariam A; Hijazi, Mohammed H


    As the number of critically ill patients requiring tracheotomy for prolonged ventilation has increased, the demand for a procedural alternative to the surgical tracheostomy (ST) has also emerged. Since its introduction, percutaneous dilatational tracheostomies (PDT) have gained increasing popularity. The most commonly cited advantages are the ease of the familiar technique and the ability to perform the procedure at the bedside. It is now considered a viable alternative to (ST) in the intensive care unit. Evaluation of PDT procedural modifications will require evaluation in randomized clinical trials. Regardless of the PDT technique, meticulous preoperative and postoperative management are necessary to maintain the excellent safety record of PDT. PMID:16356203

  8. Rheological measurements on cement grouts

    International Nuclear Information System (INIS)

    Dalton, M.J.


    This report describes the techniques which have been developed at Winfrith for assessing the rheological properties of cement grouts. A discussion of the theory of rheology and its application to cement is given and the methodology for calibrating a special paddle measuring system for a commercial viscometer is described. The use of the system for determining flow curves, equilibrium viscosity, viscosity as a function of shearing time and structure changes is also discussed. (author)

  9. Dynamical and hamiltonian dilations of stochastic processes

    International Nuclear Information System (INIS)

    Baumgartner, B.; Gruemm, H.-R.


    This is a study of the problem, which stochastic processes could arise from dynamical systems by loss of information. The notions of ''dilation'' and ''approximate dilation'' of a stochastic process are introduced to give exact definitions of this particular relationship. It is shown that every generalized stochastic process is approximately dilatable by a sequence of dynamical systems, but for stochastic processes in full generality one needs nets. (Author)

  10. Aneurysmatic dilatation of the vena portae

    International Nuclear Information System (INIS)

    Dewes, W.; Gormanns, R.; Spangenberger, W.; Staedtisches Krankenhaus Koeln-Merheim


    Anomaleous deviations of the portal venous system are relatively rarely obseved, but ineurysmatic dilatation of the vena portae, or one of its main branches, is an absolute rarity. Aneurysma of the vena portae is defined as a circumscribed dilatation of the vene to more than double the volume of the pre- or postaneurysmatic lumen. Modern, high-resolution ultrasound equipment is well able to diagnose with high reliability an aneurysmatic dilatation of the vena portae. (orig.) [de

  11. Configuration design and accuracy analysis of a novel magneto rheological finishing machine tool for concave surfaces with small radius of curvature

    International Nuclear Information System (INIS)

    Liu, Henan; Chen, Mingjun; Yu, Bo; Zhen, Fang


    Magnetorheological finishing (MRF) is a computer-controlled deterministic polishing technique that is widely used in the production of high-quality optics. In order to overcome the defects of existing MRF processes that are unable to achieve concave surfaces with small radius of curvature, a configuration method of a novel structured MRF machine tool using small ball-end permanent-magnet polishing head is proposed in this paper. The preliminary design focuses on the structural configuration of the machine, which includes the machine body, motion units and accessory equipment, and so on. Structural deformation and fabrication accuracy of the machine are analyzed theoretically, in which the reasonable structure sizes, manufacturing errors and assembly errors of main structural components are given for configuration optimization. Based on the theoretical analysis, a four-axes linkage MRF machine tool is developed. Preliminary experiments of spot polishing are carried out and the results indicate that the proposed MRF process can achieve stable polishing area which meets requirement of deterministic polishing. A typical small-bore complex component is polished on the developed device and fine surface quality is obtained with sphericity of the finished spherical surfaces 1.3 μm and surface roughness Ra less than 0.018 μm.

  12. The effect of diesters and lauric acid on rheological properties of air/water interfaces stabilized by oligofructose lauric acid monoesters. (United States)

    van Kempen, Silvia E H J; Schols, Henk A; van der Linden, Erik; Sagis, Leonard M C


    In this study, the rheological properties of interfaces stabilized by oligofructose fatty acid esters were elucidated. First, the properties of interfaces stabilized by monoesters (ME), diesters (DE), lauric acid (LA), oligofructose (OF), and mixtures of ME with DE, LA, or OF were studied. Second, the properties of interfaces stabilized by the crude product (CP) containing ME, DE, LA, and OF were studied. The dependency of the dilatational modulus on frequency and deformation amplitude indicated the possible formation of a soft glass phase for ME, and a viscous interface for DE. When ME and DE were mixed at a ratio of 0.8/0.2, the experimental results suggest that the interfacial structure consists of islands of a glass phase formed by ME, dispersed in a 2D viscous phase of DE. CP stabilized interfaces, where the ratio ME/DE was higher, lead to a different rheological response. The ratio ME/DE plays an important role in the surface properties of the CP. This may have significant consequences for applications in macroscopic systems such as foams.

  13. [Percutanous dilation tracheotomy: our experience]. (United States)

    Domènech, I; Mateu, T; Cisa, E; Juan, A; Gil, E; Palau, M; Dicenta, M


    Percutaneous dilation Tracheotomy (PDT) is becoming a popular alternative to surgical tracheotomy. In our hospital, we recently adopted the use of the PDT in intensive care unit patients. The objective [corrected] of this investigation is to characterize and quantify the rate of complications for PDT. A prospective study of 60 PDT performed at different intesive care units, betweem September 2002 to July 2003. The intraoperative time for PDT was 8 minutes. Complications included 6 cases of mild intraoperative hemorrhage, 1 case of moderate intraoperative hemorrhage, 4 cases of mild postoperative hemorrhage and 1 case of subcutaneous emphysema. PDT is a good alternative to surgical tracheotomy and should be added to the otolaryngologists armamentarium of surgical airway procedures.

  14. Present status of dilatative arteriopathy (Dolichoectasia)

    International Nuclear Information System (INIS)

    Wu Xi; Liu Jianmin


    Dilatative arteriopathy is also called Dolichoectasia, presenting as enlarged, tortuous, and dilated arteries; especially with involvement of intracranial arteries. The incidence of dolichoectasia is quite low, but it may induce recurrent strokes with poor prognosis and up to now there is no specific management. Our study reviews the potential etiology, epidemiology, symptoms, pathophysiology, prognosis and present status of treatment for dolichoectasia. (authors)

  15. Congenital segmental dilatation of the colon

    African Journals Online (AJOL)

    Congenital segmental dilatation of the colon is a rare cause of intestinal obstruction in neonates. We report a case of congenital segmental dilatation of the colon and highlight the clinical, radiological, and histopathological features of this entity. Proper surgical treatment was initiated on the basis of preoperative radiological ...

  16. Percutaneous balloon dilatation for benign hepaticojejunostomy strictures

    NARCIS (Netherlands)

    Vos, P. M.; van Beek, E. J.; Smits, N. J.; Rauws, E. A.; Gouma, D. J.; Reeders, J. W.


    BACKGROUND: Percutaneous balloon dilatation of biliary tract strictures is generally accepted as a safe and inexpensive procedure. The effectiveness in selected groups of patients remains under discussion. The purpose of this study was to evaluate the results of percutaneous balloon dilatation in

  17. One-day transhepatic billary stricture dilatation

    International Nuclear Information System (INIS)

    Mueller, P.R.; Saini, S.; Hahn, P.F.; Silverman, S.G.; Ferrucci, J.T.


    To overcome technical problems in percutaneous transhepatic dilatation or biliary strictures, the authors performed the entire procedure in a single session with the patient under general anesthesia (N = 7). Six patients had a biliary-enteric anastomosis, and one patient had a traumatic mid common bile duct stricture. All bile ducts were of normal caliber or were minimally dilated by US or transhepatic cholangiography. Dilatation was performed via a fresh transhepatic drainage catheter in six patients and via an in-dwelling T-tube in one patient. High-pressure balloons (10-12 mm) were placed after catheter dilation of the tract, and balloons were inflated for 5-10 minutes three to five times. Dilation was stopped with a waist was no longer present. No strictures have recurred in patients followed up to 24 months

  18. Rheological structure in Mars and its time evolution (United States)

    Azuma, S.; Katayama, I.


    Mars is one of the terrestrial planets which are composed of rock and metal such as the Earth. There is no water, no life, and no plate tectonics on Mars, suggesting that Mars and Earth followed different evolutionary paths. Rheological structure, which indicates the deformation behavior and the strength of planetary interior, plays an important role in the evolution of planets. The rheological behavior of planetary interiors is strongly sensitive to temperature, which may produce strong rheological layering. Rheological structure of Mars in past must be different from the current rheological structure. First, the evolutions of temperature profiles in Mars are inferred from the surface heat flow and the heat conduction equation. The surface heat flow of Mars every 1 billion years was calculated from present abundances of the radioactive isotopes (235U, 235U, 232Th, and 40K) and their half-lives (Hahn et al 2011). Based on the temperature profile, we calculate the rheological structure of Mars every 1 billion years using flow-law of plagioclase and olivine. Calculated rheological structure shows that the brittle-ductile transition of present Mars, which is transition of deformation behavior from brittle failure to viscous flow, is deeper as compared with that of past Mars, suggesting that current elastic thickness also becomes thicker than that of past Mars. Under water-saturated conditions, the rheological structure which simulates the northern lowlands shows the strength contrast between the crust and mantle, indicating that the decoupling might occur at the Moho from 4 Ga to present day. Under dry conditions, lithosphere of northern lowlands has no strength contrast at the Moho, implying that crust and mantle might be coupled from 3 Ga to present day. Viscosity contrast between the surface and planetary interior is key for the mantle convection style (Moresi and Solomatov 1995), and the calculated viscosity contrast at present Mars is ~10-5 (Pa), suggesting that

  19. Studies on rheological, structural, optical, electrical and surface properties of LiMn2O4 thin films by varied spin rates

    Directory of Open Access Journals (Sweden)

    Balakrishnan T.


    Full Text Available LiMn2O4 thin films prepared by cost-effective spin coating method using optimized coating conditions are reported. Spin rate was varied and spin rate dependent properties were studied. Prepared films were characterized for their structural, morphological and optical properties. X-ray diffraction study of LiMn2O4 thin films confirmed the cubic spinel structure with the preferred orientation along (1 1 1 plane. Optical absorption studies showed band gap energy of 3.02 eV for the grown LiMn2O4 films. FT-IR bands assigned to asymmetric stretching modes of MnO6 group were located around 623 cm-1 and 514 cm-1 for the LiMn2O4 thin films. The weak band observed at 437 cm-1 was attributed to the LiO4 tetrahedra. The films showed high conductivity value 0.79 S/cm indicating the generation of effective network of the film for enhanced charge transport. AFM micrographs of the LiMn2O4 films deposited at 3000 rpm and 3500 rpm showed uniform distribution of fine grains throughout the surface without any dark pits, pinholes and cracks.

  20. Monoclonal Antibody Interfaces: Dilatation Mechanics and Bubble Coalescence. (United States)

    Kannan, Aadithya; Shieh, Ian C; Leiske, Danielle L; Fuller, Gerald G


    Monoclonal antibodies (mAbs) are proteins that uniquely identify targets within the body, making them well-suited for therapeutic applications. However, these amphiphilic molecules readily adsorb onto air-solution interfaces where they tend to aggregate. We investigated two mAbs with different propensities to aggregate at air-solution interfaces. The understanding of the interfacial rheological behavior of the two mAbs is crucial in determining their aggregation tendency. In this work, we performed interfacial stress relaxation studies under compressive step strain using a custom-built dilatational rheometer. The dilatational relaxation modulus was determined for these viscoelastic interfaces. The initial value and the equilibrated value of relaxation modulus were larger in magnitude for the mAb with a higher tendency to aggregate in response to interfacial stress. We also performed single-bubble coalescence experiments using a custom-built dynamic fluid-film interferometer (DFI). The bubble coalescence times also correlated to the mAbs aggregation propensity and interfacial viscoelasticity. To study the influence of surfactants in mAb formulations, polyethylene glycol (PEG) was chosen as a model surfactant. In the mixed mAb/PEG system, we observed that the higher aggregating mAb coadsorbed with PEG and formed domains at the interface. In contrast, for the other mAb, PEG entirely covered the interface at the concentrations studied. We studied the mobility of the interfaces, which was manifested by the presence or the lack of Marangoni stresses. These dynamics were strongly correlated with the interfacial viscoelasticity of the mAbs. The influence of competitive destabilization in affecting the bubble coalescence times for the mixed mAb/PEG systems was also studied.

  1. Aortic root dilatation among young competitive athletes: echocardiographic screening of 1929 athletes between 15 and 34 years of age. (United States)

    Kinoshita, N; Mimura, J; Obayashi, C; Katsukawa, F; Onishi, S; Yamazaki, H


    Aortic dilatation can be lethal for young competitive athletes. The prevalence among athletes is not known, however, and thus a reasonable approach to early recognition remains uncertain. Echocardiograms of 1929 normotensive athletes 15 to 34 years of age were analyzed. Five (0.26%) athletes had aortic dilatation; 4 of the 5 played basketball. This made the prevalence of aortic dilatation 0.96% (4 of 415) among basketball and volleyball players, who represented a population of especially tall athletes. Tallness aside, only 2 of the 5 athletes had features of Marfan syndrome. Among the athletes without aortic dilatation, the relation between body surface area and aortic root dimension was nonlinear and best described with a quadratic regression model. Athletes with aortic dilatation fell well outside the 95% confidence interval. Because a higher incidence of aortic dilatation is to be anticipated among very tall athletes, inclusion of echocardiography in screening before participation in certain sports should be considered.

  2. Dilational Response of Voided Polycrystals (United States)

    Savage, Daniel J.; Cazacu, Oana; Knezevic, Marko


    Finite-element (FE) cell model computations have been used to gain insights into the ductile response of porous polycrystals. Generally, the behavior of the matrix is described by a J 2-plasticity model. In this article, we present a new computational approach to FE cell models for porous polycrystals deforming by slip based on crystal plasticity. The cell provides the homogenized dilational response, where the constitutive response of every integration point is based on a single-crystal visco-plasticity law. The calculations are performed for a body-centered cubic polycrystal with random texture. Axisymmetric tensile and compressive loadings are imposed corresponding to the fixed values of the stress triaxiality and to two possible values of the Lode parameter. The resulting numerical yield points are compared with those obtained using a J 2-FE cell and an analytical model. The predictions confirm the combined effects of the mean stress and third-invariant on yielding recently revealed by the analytical model.

  3. Percutaneous catheter dilatation of carotid stenoses

    International Nuclear Information System (INIS)

    Mathias, K.; Mittermayer, C.; Ensinger, H.; Neff, W.


    Thirty-one carotid artery stenoses were produced in thirty dogs by three different techniques. Twenty-three of these could be cured by transfemoral percutaneous catheter dilatation. High grade tight stenoses may present resistance which cannot be overcome by the catheter. Histological examination of the dilated vessels showed circumscribed changes in the vessel wall, with destruction of elastic membranes. From our experience of catheter dilatation of pelvic and lower limb arteries and of renal arteries, we consider it feasible to use this technique in selected patients with carotid stenosis. (orig.) [de

  4. A dynamic rheological model for thin-film lubrication

    International Nuclear Information System (INIS)

    Zhang Xiang-Jun; Huang Ying; Guo Yan-Bao; Tian Yu; Meng Yong-Gang


    In this study, the effects of the non-Newtonian rheological properties of the lubricant in a thin-film lubrication regime between smooth surfaces were investigated. The thin-film lubrication regime typically appears in Stribeck curves with a clearly observable minimum coefficient of friction (COF) and a low-COF region, which is desired for its lower energy dissipation. A dynamic rheology of the lubricant from the hydrodynamic lubrication regime to the thin-film lubrication regime was proposed based on the convected Maxwell constitutive equation. This rheology model includes the increased relaxation time and the yield stress of the confined lubricant thin film, as well as their dependences on the lubricant film thickness. The Deborah number (De number) was adopted to describe the liquid-solid transition of the confined lubricant thin film under shearing. Then a series of Stribeck curves were calculated based on Tichy's extended lubrication equations with a perturbation of the De number. The results show that the minimum COF points in the Stribeck curve correspond to a critical De number of 1.0, indicating a liquid-to-solid transition of the confined lubricant film. Furthermore, the two proposed parameters in the dynamic rheological model, namely negative slipping length b (indicating the lubricant interfacial effect) and the characteristic relaxation time λ 0 , were found to determine the minimum COF and the width of the low-COF region, both of which were required to optimize the shape of the Stribeck curve. The developed dynamic rheological model interprets the correlation between the rheological and interfacial properties of lubricant and its lubrication behavior in the thin-film regime. (condensed matter: structural, mechanical, and thermal properties)

  5. Genetics Home Reference: familial dilated cardiomyopathy (United States)

    ... familial dilated cardiomyopathy can include an irregular heartbeat (arrhythmia), shortness of breath (dyspnea), extreme tiredness (fatigue), fainting ... Celebrates Its 15th Anniversary National DNA Day 2018 Newborn Screening Saves Lives Act Turns 10 All Bulletins ...

  6. An Erupted Dilated Odontoma: A Rare Presentation

    Directory of Open Access Journals (Sweden)

    Gaurav Sharma


    Full Text Available A dilated odontoma is an extremely rare developmental anomaly represented as a dilatation of the crown and root as a consequence of a deep, enamel-lined invagination and is considered a severe variant of dens invaginatus. An oval shape of the tooth lacking morphological characteristics of a crown or root implies that the invagination happened in the initial stages of morphodifferentiation. Spontaneous eruption of an odontoma is a rare occurrence and the occurrence of a dilated odontoma in a supernumerary tooth is even rarer with only a few case reports documented in the English literature. We present an extremely rare case of erupted dilated odontoma occurring in the supernumerary tooth in anterior maxillary region in an 18-year-old male, which, to the best of our knowledge, is the first ever case reported in English literature.

  7. An Erupted Dilated Odontoma: A Rare Presentation (United States)

    Sharma, Gaurav; Nagra, Amritpreet; Singh, Gurkeerat; Nagpal, Archna; Soin, Atul; Bhardwaj, Vishal


    A dilated odontoma is an extremely rare developmental anomaly represented as a dilatation of the crown and root as a consequence of a deep, enamel-lined invagination and is considered a severe variant of dens invaginatus. An oval shape of the tooth lacking morphological characteristics of a crown or root implies that the invagination happened in the initial stages of morphodifferentiation. Spontaneous eruption of an odontoma is a rare occurrence and the occurrence of a dilated odontoma in a supernumerary tooth is even rarer with only a few case reports documented in the English literature. We present an extremely rare case of erupted dilated odontoma occurring in the supernumerary tooth in anterior maxillary region in an 18-year-old male, which, to the best of our knowledge, is the first ever case reported in English literature. PMID:26989523

  8. Fluoroscopic guided benign oesophageal stricture dilatation in ...

    African Journals Online (AJOL)

    Gilliard bougienage (SGB) with balloon dilatation and the combination of both methods for the treatment of BOSs in children at Universitas Hospital, Bloemfontein, South Africa. Methods. A retrospective review of the patient notes on all children 12 ...

  9. On $rho$-dilations of commuting operators

    Czech Academy of Sciences Publication Activity Database

    Müller, Vladimír


    Roč. 78, č. 1 (2017), s. 3-20 ISSN 0379-4024 R&D Projects: GA ČR(CZ) GA14-07880S Institutional support: RVO:67985840 Keywords : regular unitary dilation * rho-dilation Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.524, year: 2016

  10. On $rho$-dilations of commuting operators

    Czech Academy of Sciences Publication Activity Database

    Müller, Vladimír


    Roč. 78, č. 1 (2017), s. 3-20 ISSN 0379-4024 R&D Projects: GA ČR(CZ) GA14-07880S Institutional support: RVO:67985840 Keywords : regular unitary dilation * rho-dilation Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.524, year: 2016 html

  11. Surface Shear Rheology of Saponin Adsorption Layers

    NARCIS (Netherlands)

    Golemanov, K.; Tcholakova, S.; Denkov, N.; Pelan, E.; Stoyanov, S.D.


    Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial

  12. Simple Rheological Analysis Method of Spinnable-Polymer Flow Properties Using MFI Tester

    Directory of Open Access Journals (Sweden)

    Basel Younes


    Full Text Available Rheological characterization of polymers explains the flow behaviour and viscoelastic properties and tests fibre-forming ability. The current method investigates the viscoelastic properties and morphology of polymers and finds the rheological data and the right polymer viscosity, which is determining the best processing temperature. The right processing temperature saves the power, the material, and the time needed for production. After calculating polymers viscosity by using MFI tester, the method investigates rheological properties and surface shape at different temperatures and loads. The method could apply to other polymers to find the viscosity-temperature change and to set the best processing temperature.

  13. Granular Dilatancy and its Effect on Debris-flow Dynamics (United States)

    Iverson, R. M.; George, D. L.


    Landslides and debris flows commonly exhibit the effects of variable granular dilatancy, but incorporation of these effects in predictive models of debris-flow dynamics has been lacking. We have developed a depth-averaged model of debris-flow initiation and motion that includes the effects of variable dilatancy without stipulating its influence on rheology. Instead, the apparent rheology of Coulomb-frictional debris evolves during coupled evolution of the grain concentration m, basal pore-fluid pressure, flow thickness, and flow velocity. The dilatancy angle ψ plays an intermediary role in this evolution and obeys the simple relationship tan ψ = m-meq, where meq is the grain concentration in equilibrium with the ambient stress state and flow rate. Results of recent stress-controlled rheometric experiments by Boyer et al. (DOI: 10.1103/PhysRevLett.107.188301) provide our basis for estimating meq. Relaxation of m toward meq, coupled with evolution of pore pressure, allows our model to simulate a smooth transition from static limiting equilibrium of slopes to disequilibrium flow dynamics. Use of variable friction coefficients or dam-break initial conditions is unnecessary. We have evaluated predictions of our model in three ways: (1) by examining physical implications of exact solutions of simplified model equations, (2) by comparing numerical solutions with results of controlled experiments at the USGS debris-flow flume, and (3) by comparing numerical predictions with the behavior of a large (~50 million m3) debris flow that occurred at Mt. Meager, British Columbia, in 2010. Model predictions depend mostly on initial conditions, flow-path topography, and the value of a single dimensionless parameter that represents the ratio of two key timescales. One timescale governs downslope, gravity-driven motion of debris, and the other governs pore-pressure diffusion. Values of these timescales are readily calculated from source-area geometry and standard geotechnical

  14. Rheological evolution of planetary basalts during cooling and crystallization (United States)

    Sehlke, Alexander

    Basaltic lavas cover large portions of the surface of the Earth and other planets and moons. Planetary basalts are compositionally different from terrestrial basalts, and show a variety of unique large-scale lava flow morphologies unobserved on Earth. They are usually assumed to be much more fluid than basalts on Earth, such as Hawaiian basalt, but their rheology is largely unknown. I synthesized several synthetic silicate melts representing igneous rock compositions of Mars, Mercury, the Moon, Io and Vesta. I measured their viscosity, as well as several terrestrial lavas including Hawaiian basalt, by concentric cylinder and parallel plate viscometry. Planetary melts cover a wide range of viscosity at their liquidus, overlapping with terrestrial basaltic melts. I derived a new viscosity model that is based on the Adam-Gibbs theory of structural relaxation, predicting these viscosities much more accurately than previously published viscosity models. During crystallization, the rheological behavior changes from Newtonian to pseudoplastic. Combining rheology experiments with field observations, the rheological conditions of the pahoehoe to `a`a morphological transition for Hawaiian basalt were determined in strain rate-viscosity space. This transition occurs at temperatures around 1185+/-15°C. For Mercurian lavas, this transition is predicted to occur at higher temperatures around 1250+/-30°C. We find that the rheology of these lavas is broadly similar to terrestrial ones, suggesting that the large smooth volcanic plains observed on Mercury's northern hemisphere are due to flood basalt volcanism rather than unusually fluid lavas. We also show that KREEP lavas, a type of basalt associated with sinuous rilles on the lunar surface, is more likely to form rilles through levee construction, as the high and rapidly increasing viscosity prohibits sufficient thermo-mechanical erosion.

  15. Influence of Dilation on the Strength of Sand – Steel Interfaces (United States)

    Dolzyk-Szypcio, Katarzyna


    In this paper the sand-steel interface behaviour is analysed on the basis of frictional state theory. It is shown that for a small stress level the influence of dilatancy is fundamentally similar for sand-steel and sand-sand behaviour for a direct shear test. The use of the new parameter describes the influence of surface roughness on stress-dilatancy relationship. The peak strength of sand-steel is analysed. Values of the new parameter grow with normalised roughness for smooth surface and are constant for intermediate and rough surfaces. It is also shown that values of normalised friction coefficient obtained theoretically are similar with those shown in literature.

  16. Rheological properties of the soft-disk model of two-dimensional foams

    DEFF Research Database (Denmark)

    Langlois, Vincent; Hutzler, Stefan; Weaire, Denis


    The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel-Bulkley re......The soft-disk model previously developed and applied by Durian [D. J. Durian, Phys. Rev. Lett. 75, 4780 (1995)] is brought to bear on problems of foam rheology of longstanding and current interest, using two-dimensional systems. The questions at issue include the origin of the Herschel......-Bulkley relation, normal stress effects (dilatancy), and localization in the presence of wall drag. We show that even a model that incorporates only linear viscous effects at the local level gives rise to nonlinear (power-law) dependence of the limit stress on strain rate. With wall drag, shear localization...

  17. Summary Of 2009 Rheology Modifier Program

    International Nuclear Information System (INIS)

    Hansen, E.


    The overall objective of the EM-31 Rheological Modifiers and Wetting Agents program is to utilize commercially available rheology modifiers to increase the solids fraction of radioactive sludge based waste streams, resulting in an increase in throughput and decreasing the overall processing time. The program first investigates the impact of rheology modifiers on slurry simulants and then utilizes the most effective rheology modifiers on radioactive slurries. The work presented in this document covers the initial investigation of rheology modifier testing with simulants. This task is supported by both the Savannah River National Laboratory (SRNL) and Pacific Northwest National Laboratory (PNNL). The SRNL EM-31 task, for this year, was to investigate the use of rheology modifiers on simulant Defense Waste Processing Facility (DWPF) melter feeds. The task is to determine, based on the impact of the rheology modifier, if there are rheology modifiers that could reduce the water content of the slurry going to the DWPF melter, hence increasing the melt rate by decreasing the water loading. The rheology modifier in essence would allow a higher solids content slurry to have the same type of rheology or pumpability of a lower solids slurry. The modifiers selected in this report were determined based on previous modifiers used in high level waste melter feed simulants, on-going testing performed by counterparts at PNNL, and experiences gain through use of modifiers in other Department of Energy (DOE) processes such as grout processing. There were 12 rheology modifiers selected for testing, covering both organic and inorganic types and they were tested at four different concentrations for a given melter feed. Five different DWPF melter feeds were available and there was adequate material in one of the melter feeds to increase the solids concentration, resulting in a total of six simulants for testing. The mass of melter feed available in each simulant was not adequate for


    Energy Technology Data Exchange (ETDEWEB)

    Hansen, E.


    The overall objective of the EM-31 Rheological Modifiers and Wetting Agents program is to utilize commercially available rheology modifiers to increase the solids fraction of radioactive sludge based waste streams, resulting in an increase in throughput and decreasing the overall processing time. The program first investigates the impact of rheology modifiers on slurry simulants and then utilizes the most effective rheology modifiers on radioactive slurries. The work presented in this document covers the initial investigation of rheology modifier testing with simulants. This task is supported by both the Savannah River National Laboratory (SRNL) and Pacific Northwest National Laboratory (PNNL). The SRNL EM-31 task, for this year, was to investigate the use of rheology modifiers on simulant Defense Waste Processing Facility (DWPF) melter feeds. The task is to determine, based on the impact of the rheology modifier, if there are rheology modifiers that could reduce the water content of the slurry going to the DWPF melter, hence increasing the melt rate by decreasing the water loading. The rheology modifier in essence would allow a higher solids content slurry to have the same type of rheology or pumpability of a lower solids slurry. The modifiers selected in this report were determined based on previous modifiers used in high level waste melter feed simulants, on-going testing performed by counterparts at PNNL, and experiences gain through use of modifiers in other Department of Energy (DOE) processes such as grout processing. There were 12 rheology modifiers selected for testing, covering both organic and inorganic types and they were tested at four different concentrations for a given melter feed. Five different DWPF melter feeds were available and there was adequate material in one of the melter feeds to increase the solids concentration, resulting in a total of six simulants for testing. The mass of melter feed available in each simulant was not adequate for

  19. Effect of Oil Hydrophobicity on the Adsorption and Rheology of β-Lactoglobulin at Oil-Water Interfaces. (United States)

    Bergfreund, Jotam; Bertsch, Pascal; Kuster, Simon; Fischer, Peter


    The adsorption of protein layers at oil-water interfaces is critical to the formation and stability of various emulsions in, for example, technical applications as well as in biological lipid storage. Effects of ionic strength, pH, temperature, and pretreatments of the proteins are well-known. However, the oil phase has been regarded as exchangeable and its role in protein adsorption has been widely ignored. Herein, the influence of systematically selected oil interfaces of high purity on the formation and properties of β-lactoglobulin (β-lg) adsorption layers was evaluated. Droplet profile tensiometry and interfacial rheometry were employed to determine the adsorption kinetics and dilatational and interfacial shear moduli. We show that depending on the molecular size, flexibility, hydrophobicity, polarity, and polarizability of the oils, globular proteins adsorb distinctively. Stronger interactions of polar oils with the hydrophilic exterior of the native β-lg lead to decelerated protein unfolding. This results in lower surface pressures and slower formation of viscoelastic networks. In addition, polar oils interact stronger with the protein network by hydrophilic bonding and thereby act as softening agents. The observed effects of hydrophobic subphases on the adsorbed protein layers provide knowledge, which promotes higher reproducibility in rheological studies and precise tailoring of interfacial films for enhanced formation and stability of emulsions.

  20. Interaction of polyhedral oligomeric silsesquioxanes and dipalmitoylphosphatidylcholine at the air/water interface: Thermodynamic and rheological study. (United States)

    Skrzypiec, M; Georgiev, G As; Rojewska, M; Prochaska, K


    Polyhedral oligomeric silsesquioxanes (POSS) derivatives containing open silsesquioxane cage bear great potential for biomedical applications and therefore their lateral interactions with phospholipids, major biomembranes and drug vehicles constituent, should be studied in detail. That is why the properties of surface films by two POSS-derivatives, POSS-polyethylene glycol (POSS-PEG) and POSS-perfluoroalkyl (POSS-OFP), pure and in presence of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) were studied using Langmuir surface balance. Side chains of opposite nature (PEG is hydrophilic; OFP is hydrophobic) were selected, so that to evaluate their impact on polymers' surface properties. Two types of measurements were performed: (i) the miscibility of POSS-derivatives with DPPC was evaluated via thermodynamic analysis of the surface pressure (π)-area (A) isotherms and (ii) the dilatational rheology of selected POSS-polymer containing films was studied by the stress relaxation method. Fourier transformation analysis of the relaxation transients allows to access films' dynamic interfacial properties in broad frequency range (10 -5 -1Hz). Film morphology was monitored with Brewster Angle Microscopy. PEG moiety enabled POSS-PEG to stably incorporate in DPPC films, modifying their equilibrium and dynamic properties. In contrast OFP chains excluded from interactions with other molecules and diminished PEG-OFP amphiphilicity. Therefore at high packing densities (π≥25mN/m) PEG-OFP was expelled from the air/water interface in DPPC/PEG-OFP mixtures, and the binary films equilibrium and dynamic surface properties were determined primarily by DPPC. Thus the choice of POSS side chains can play key role in biomedical applications depending on whether strong or weak incorporation of POSS-polymers in lipid environment is aimed for. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Dilatation or no dilatation of the cervix during cesarean section (Dondi Trial): a randomized controlled trial. (United States)

    Kirscht, Jade; Weiss, Christel; Nickol, Jana; Berlit, Sebastian; Tuschy, Benjamin; Hoch, Benjamin; Trebin, Amelie-Verena; Große-Steffen, Thomas; Sütterlin, Marc; Kehl, Sven


    To assess the effects of mechanical dilatation of the cervix during cesarean section on postoperative morbidity. A total of 447 women with elective cesarean section were included in the Dondi trial (Dilatation or no dilatation of the cervix during cesarean section). The primary outcome measure of this randomized controlled trial was postpartum hemorrhage (PPH) within 6 weeks. Infectious morbidity (puerperal fever, endometritis, wound infection, and urinary tract infection), blood loss (need for blood transfusion or change in hemoglobin levels), and operating time were also evaluated. The rate of PPH within 6 weeks was not different between the two groups [dilatation group: 5 (2.4 %), no dilatation group: 3 (1.2 %), p = 0.479]. Infectious morbidity, blood loss, and operating time were not diverse as well. The only significant difference between the two groups was the rate of retained products of conception with fewer cases after cervical dilatation (0 versus 6.2 %, p cesarean section compared with no dilatation of the cervix did not influence the risk of postpartum hemorrhage. However, there were fewer cases with retained products of conception after dilatation.

  2. Scaling of plate tectonic convection with pseudoplastic rheology (United States)

    Korenaga, Jun


    The scaling of plate tectonic convection is investigated by simulating thermal convection with pseudoplastic rheology and strongly temperature-dependent viscosity. The effect of mantle melting is also explored with additional depth-dependent viscosity. Heat flow scaling can be constructed with only two parameters, the internal Rayleigh number and the lithospheric viscosity contrast, the latter of which is determined entirely by rheological properties. The critical viscosity contrast for the transition between plate tectonic and stagnant lid convection is found to be proportional to the square root of the internal Rayleigh number. The relation between mantle temperature and surface heat flux on Earth is discussed on the basis of these scaling laws, and the inverse relationship between them, as previously suggested from the consideration of global energy balance, is confirmed by this fully dynamic approach. In the presence of surface water to reduce the effective friction coefficient, the operation of plate tectonics is suggested to be plausible throughout the Earth history.

  3. The neural substrates of subjective time dilation

    Directory of Open Access Journals (Sweden)

    Marc Wittmann


    Full Text Available An object moving towards an observer is subjectively perceived as longer in duration than the same object that is static or moving away. This 'time dilation effect' has been shown for a number of stimuli that differ from standard events along different feature dimensions (e.g. color, size, and dynamics. We performed an event-related functional magnetic resonance imaging (fMRI, while subjects viewed a stream of five visual events, all of which were static and of identical duration except the fourth one, which was a deviant target consisting of either a looming or a receding disc. The duration of the target was systematically varied and participants judged whether the target was shorter or longer than all other events. A time dilation effect was observed only for looming targets. Relative to the static standards, the looming as well as the receding targets induced increased activation of the anterior insula and anterior cingulate cortices (the “core control network”. The decisive contrast between looming and receding targets representing the time dilation effect showed strong asymmetric activation and, specifically, activation of cortical midline structures (the “default network”. These results provide the first evidence that the illusion of temporal dilation is due to activation of areas that are important for cognitive control and subjective awareness. The involvement of midline structures in the temporal dilation illusion is interpreted as evidence that time perception is related to self-referential processing.

  4. Effects of crack-dilatancy on Rayleigh waves in fluid-saturated ...

    African Journals Online (AJOL)

    Secular equations are derived in closed form for the propagation of Rayleigh waves in the porous media with sealed or fullyopened surface pores. The velocity of ... The opening of surface pores may be an important reason for a faster propagation of Rayleigh waves in any realistic elastic medium. Finally, the dilatancy due ...

  5. Rheology v.3 theory and applications

    CERN Document Server

    Eirich, Frederick


    Rheology: Theory and Applications, Volume 3 is a collection of articles contributed by experts in the field of rheology - the science of deformation and flow. This volume is composed of specialized chapters on the application of normal coordinate analysis to the theory of high polymers; principles of rheometry; and the rheology of cross-linked plastics, poly electrolytes, latexes, inks, pastes, and clay. Also included are a series of technological articles on lubrication, spinning, molding, extrusion, and adhesion and a survey of the general features of industrial rheology. Materials scientist

  6. Rheological properties of magneto-responsive copolymer gels

    NARCIS (Netherlands)

    An, H.


    New magneto rheological systems that respond mechanically to external homogeneous magnetic fields, namely, physically cross-linked magneto rheological (MR) gels, were synthesized and investigated. Various aspects of the rheological behavior were considered such as linear viscoelastic response for

  7. A comparative study on the rheology and wave dissipation of kaolinite and natural Hendijan Coast mud, the Persian Gulf (United States)

    Soltanpour, Mohsen; Samsami, Farzin


    The objective of this paper is to investigate the rheological behavior of kaolinite and Hendijan mud, located at the northwest part of the Persian Gulf, and the dissipative role of this muddy bed on surface water waves. A series of laboratory rheological tests was conducted to investigate the rheological response of mud to rotary and cyclic shear rates. While a viscoplastic Bingham model can successfully be applied for continuous controlled shear-stress tests, the rheology of fluid mud displays complex viscoelastic behavior in time-periodic motion. The comparisons of the behavior of natural Hendijan mud with commercial kaolinite show rheological similarities. A large number of laboratory wave-flume experiments were carried out with a focus on the dissipative role of the fluid mud. Assuming four rheological models of viscous, Kelvin-Voigt viscoelastic, Bingham viscoplastic, and viscoelastic-plastic for fluid mud layer, a numerical multi-layered model was applied to analyze the effects of different parameters of surface wave and muddy bed on wave attenuation. The predicted results based on different rheological models generally agree with the obtained wave-flume data implying that the adopted rheological model does not play an important role in the accuracy of prediction.

  8. Introduction to snow rheology

    International Nuclear Information System (INIS)

    Montmollin, Vincent de


    The tests described in the thesis are rotating shearing tests, with rotational constant speed ranging between 0.00075 rpm and 0.75 rpm. The results obtained are similar to those observed with compression tests at constant speed, except that shearing tests are carried out with densities nearly constant. So, we show three different domains when the rotation speed increases: 1) viscous (without failure) 2) brittle of first type (cycles of brittle failures) and 3) brittle of second type (only one brittle failure and solid friction). These results show clearly that the fundamental mechanism that rules the mechanisms of snow, is fast metamorphosis of bonds, binding ice grains: this metamorphosis is important when solicitation speeds are low (permanent rate of shearing in viscous domain, regeneration of the failure surfaces in the brittle domain of the first type) and this metamorphosis does not exist when speed increases (only one failure and solid friction in the brittle domain of second type). It is also included an important bibliographic analysis of the snow mechanics, and an experimental and theoretical study about shock wave propagation in natural snow covers. (author) [fr

  9. Retrograde transurethral balloon dilation of the prostate

    International Nuclear Information System (INIS)

    Castaneda, F.; Reddy, P.; Wasserman, N.F.; Lund, G.; Hulbert, J.; Hunter, D.; Castaneda-Zuniga, W.R.; Amplatz, K.


    A series of patients with documented benign prostatic hypertrophy evaluated by urodynamic studies, voiding cystourethrography, retrograde urethrography, and MR imaging underwent dilation performed using a retrograde transurethral approach with 25-mm balloon dilators inflated at a pressure of 3-4 atm for 10 minutes. Immediately after the procedure, retrograde and voiding cystourethrography as well as MR imaging were performed. A Foley catheter was left in place for 24 hours. Complete relief of symptoms has occurred in all of the patients during the follow-up period. No significant complications other than transient hematuria resulted from the procedure. Results of the comparison studies and of MR imaging are discussed

  10. Rheology of unstable mineral emulsions

    Directory of Open Access Journals (Sweden)

    Sokolović Dunja S.


    Full Text Available In this paper, the rheology of mineral oils and their unstable water emulsion were investigated. The oil samples were domestic crude oil UA, its fractions UA1, UA4 and blend semi-product UP1, while the concentration of oil in water emulsions was in the range from 1 up to 30%. The results were analyzed based on shear stress. The oil samples UA, UA1 and UP1 are Newtonian fluids, while UA4 is pseudoplastic fluid. The samples UA and UA4 show higher value of shear stress (83.75 Pa, 297 Pa, then other two samples UA1 and UP1 (18.41 Pa, 17.52 Pa. Rheology of investigated oils due to its complex chemical composition should be analyzed as a simultaneous effect of all their components. Therefore, structural composition of the oils was determined, namely content of paraffins, naphthenes, aromatics and asphaltenes. All samples contain paraffins, naphthenes and aromatics but only oils UA and UA4 contain asphaltenes as well. All investigated emulsions except 30% EUA4 are Newtonian fluids. The EUA4 30% emulsion shows pseudoplastic behaviour, and it is the only 30% emulsion among investigated ones that achieves lower shear stress then its oil. The characteristics of oil samples that could have an influence on their properties and their emulsion rheology, were determined. These characteristics are: neutralization number, interfacial tension, dielectric constant, and emulsivity. Oil samples UA and UA4 have significantly higher values of neutralization number, dielectric constants, and emulsivity. The sample UA has the lowest value of interface tension and the greatest emulsivity, indicating that this oil, among all investigated, has the highest preference for building emulsion. This could be the reason why 20% and 30% emulsions of the oil UA achieve the highest shear stress among all investigated emulsions.

  11. Shear rheology of extended nanoparticles (United States)

    Petersen, Matt K.; Lane, J. Matthew D.; Grest, Gary S.


    Nonequilibrium molecular-dynamics simulations are presented for the shear rheology of suspensions of extended “jack”-shaped nanoparticles in an explicit solvent. The shear viscosity is measured for two jack-shaped nanoparticle suspensions for volume fractions from 0.01 to 0.15 and compared to spherical nanoparticles of the same mass. Large differences, in some cases, orders of magnitude, are observed for both the equilibrium viscosity and diffusion constant as the shape of the nanoparticle is varied. The source of enhanced viscosity is the very large effective volume swept out by these extended nanoparticles which allows them to become highly entangled even at low volume fraction.

  12. Using Greener Gels to Explore Rheology (United States)

    Garrett, Brendan; Matharu, Avtar S.; Hurst, Glenn A.


    A laboratory experiment was developed to investigate the rheological properties of a green calcium-cross-linked alginate gel as an alternative to the traditional borax-cross-linked poly(vinyl alcohol) gel. As borax is suspected of damaging fertility and the unborn child, a safe, green alternative is necessary. The rheological properties of a…

  13. Improved Model of Rock Mass Dilatation. (United States)


    uartzite ( Bieniawski , 1967), granite (Brace et al., 1966; Zoback and Byerlee, 1975), .-- marble, sandstone, limestone, etc. Dilatancy therefore appears...prepared for Defense Nuclear Agency. 2. Algorithm 392 of CACM, "Systems of Hyperbolic Partial Differential Equations." 3. Bieniawski , Z.T. (1967

  14. Dilation and Curettage (D&C) (United States)

    ... Dilation and Curettage (D&C) Page Navigation ▼ ACOG Pregnancy Book Patient Education FAQs Patient Education Pamphlets - Spanish FAQ062, February 2016 ... written permission from the publisher. Related FAQs Early Pregnancy Loss (Miscarriage) (FAQ090) Abnormal Uterine Bleeding ... Committee Opinions Practice Bulletins Patient ...

  15. Ventricular dilatation in aging and dementia

    NARCIS (Netherlands)

    Palm, Walter Miguel


    The general objective of this thesis was to study the causes and consequences of ventricular dilatation in aging and dementia. For this purpose, we used ventricular shape analysis to study potential new MRI markers of cognitive decline in aging, subjective memory complaints, mild cognitive

  16. A Symmetry Approach to Time Dilation. (United States)

    Dunne, Peter


    Outlines an approach to introduce students to special relativity using a discussion of stopclocks and measurement of the transmission of light pulses to produce a natural derivation of the time dilation factor. Aims at providing a frame of reference from which they can be tempted to explore special relativity at a more sophisticated level. (JRH)

  17. Hydraulic urethral dilatation after optical internal urethrotomy ...

    African Journals Online (AJOL)

    Objectives: To determine the rate of early recurrence of urethral stricture in the first six months in patients who perform hydraulic urethral dilatation(HUD) after optical internal urethrotomy (OIU) and compare the early recurrence Fate in patients who perform HUD after OIU with the recurrence rates in patients reported in the ...

  18. Intestinal Infarctus following Dilatation and Uterine Curettage

    Directory of Open Access Journals (Sweden)

    N.M. Ngowe


    Full Text Available We present a case of intestinal infarctus through the vagina. This was a consequence of induced abortion done clandestinely. The main objective was to point out the surgical complications of uterine dilatation and curettage by means of this rare case.

  19. Apparent unambiguousness of relativistic time dilation

    International Nuclear Information System (INIS)

    Strel'tsov, V.N.


    It is indicated on the definite analogy between the dependence of visible sizes of relativistic objects and period of the wave, emitted by the moving source from the observation conditions ('retradition factor'). It is noted that the definition of time for moving extended objects, led to relativistic dilation, corresponds to the definition of the relativistic (radar) length led to the 'elongation formula'. 10 refs

  20. Study and rheological characterization of various bone ash porcelain formulations

    International Nuclear Information System (INIS)

    Carus, L.A.; Bento, L.; Braganca, S.R.


    The bone ash porcelain is a widely accepted product on the market because their qualities such as high strength and whiteness, to differ from common table porcelains. Its traditional formulation comes from an English recipe, consisting of 25% of kaolin, 25% of feldspar and 50% of bovine bone ash. In some studies, this proportion is adapted to regional conditions, optimizing the formulation according to the raw materials available. In this study, the rheological behavior of bone porcelain suspensions, in which the flux feldspar is partially substituted by an alternative flux (espudomenio, wollastonite and glass). The results show that the rheological behavior of porcelain is affected by the size, shape, surface area and particle size distribution of particles in suspension

  1. Rheological studies of aqueous stabilised nano-zirconia particle suspensions

    Directory of Open Access Journals (Sweden)

    Asad Ullah Khan


    Full Text Available In the present investigation aqueous suspensions of nano- and colloidal range particles are stabilised by changing the ambient pH. Rheology is used to establish the stability of the suspensions and it is found that the rheology of the suspensions is strongly dependent on the pH values. The viscosity is highest close to the iso-electric point of the powders. At the iso-electric point the net surface charge on the powder particles is zero and is the cause of the high viscosity. Away from the iso-electric point, the particles are charged, giving rise to a double layer phenomenon and causing the reduction in viscosity. It is also found that increasing the solid contents of the suspensions reduces the pH region of low viscosity.

  2. Nonlinear rheology of colloidal dispersions

    International Nuclear Information System (INIS)

    Brader, J M


    Colloidal dispersions are commonly encountered in everyday life and represent an important class of complex fluid. Of particular significance for many commercial products and industrial processes is the ability to control and manipulate the macroscopic flow response of a dispersion by tuning the microscopic interactions between the constituents. An important step towards attaining this goal is the development of robust theoretical methods for predicting from first-principles the rheology and nonequilibrium microstructure of well defined model systems subject to external flow. In this review we give an overview of some promising theoretical approaches and the phenomena they seek to describe, focusing, for simplicity, on systems for which the colloidal particles interact via strongly repulsive, spherically symmetric interactions. In presenting the various theories, we will consider first low volume fraction systems, for which a number of exact results may be derived, before moving on to consider the intermediate and high volume fraction states which present both the most interesting physics and the most demanding technical challenges. In the high volume fraction regime particular emphasis will be given to the rheology of dynamically arrested states. (topical review)

  3. Blood rheology in marine mammals

    Directory of Open Access Journals (Sweden)

    Michael Castellini


    Full Text Available The field of blood oxygen transport and delivery to tissues has been studied by comparative physiologists for many decades. Within this general area, the particular differences in oxygen delivery between marine and terrestrial mammals has focused mainly on oxygen supply differences and delivery to the tissues under low blood flow diving conditions. Yet, the study of the inherent flow properties of the blood itself (hemorheology is rarely discussed when addressing diving. However, hemorheology is important to the study of marine mammals because of the critical nature of the oxygen stores that are carried in the blood during diving periods. This review focuses on the essential elements of hemorheology, how they are defined and on fundamental rheological applications to marine mammals. While the comparative rationale used throughout the review is much broader than the particular problems associated with diving, the basic concepts focus on how changes in the flow properties of whole blood would be critical to oxygen delivery during diving. This review introduces the reader to most of the major rheological concepts that are relevant to the unique and unusual aspects of the diving physiology of marine mammals.


    Directory of Open Access Journals (Sweden)

    Camelia Vizireanu


    Full Text Available The increased social and economic importance of ready–made food production, together with the complexity of production technology, processing, handling and acceptance of these fragile and perishable products requires extensive knowledge of their physical properties. Viscoelastic properties play an important role in the handling and quality attributes of creams.Our study was to investigate the rheological properties of different confectionary creams, by scanning the field of shear rates at constant temperature and frequency, angular frequency scanning at small deformations and quantification of rheological changes during application of deformation voltages. The creams tested were made in the laboratory using specific concentrates as fine powders, marketed by the company “Dr. Oetker” compared with similar creams based on traditional recipes and techniques. Following the researches conducted we could conclude that both traditional creams and the instant ones are semi fluid food products with pseudoplastic and thixotropic shear flow behavior, with structural viscosity. Instant and traditional creams behaved as physical gels with links susceptible to destruction, when subjected to deformation forces.


    Directory of Open Access Journals (Sweden)

    S. I. Niftaliev


    Full Text Available Summary. Obtained hydrophobic filler compositions based on PVC from calcium carbonate, which is a byproduct in the preparation of mineral nitrogen fertilizers. The methods for pretreatment of the chalk used as a filler in PVC compositions. Conducted modifying the properties of chalk with hydrophobic additives: stearic acid, zinc stearate, calcium stearate. When stearic acid treated chalk heating leads to an interaction with the surface layers of calcium carbonate, a thin film of calcium stearate. Therefore, more cost-effective to create compositions with PVC content of one percent of calcium stearate as its hydrophobic surface is easily wetted by the polymer matrix, which provides rapid mixing of PVC compounds. As a result, the excipient serves as an additional stabilizer, providing higher thermal stability of PVC products, compared with its values for the composition of the compared with the other ingredients. Extrusion processes that are central to the processing of PVC compounds filled by acting them filler, fractional increase heat and accelerate melting and increase output. The rheological properties of polymeric compositions created PVC. A significant reduction in viscosity observed for water repellent based on stearic acid. Study viscosity characteristics for hydrophobic additives showed that their activity increased in the series: zinc stearate, calcium stearate, stearic acid. It was established that modifying additives used in the preparation of hydrophobic carbonate filler PVC compositions exhibit both plasticizers and stabilizing properties.

  6. Recent advances in the GPUSPH model for the thermal and rheological evolution of lava flows (United States)

    Zago, Vito; Bilotta, Giuseppe; Cappello, Annalisa; Dalrymple, Robert A.; Fortuna, Luigi; Ganci, Gaetana; Herault, Alexis; Del Negro, Ciro


    GPUSPH is a fully three-dimensional model for the simulation of the thermal and rheological evolution of lava flows that relies on the Smoothed Particle Hydrodynamics (SPH) numerical method. Thanks to the Lagrangian, meshless nature of SPH, the model incorporates a more complete physical description of the emplacement process and rheology of lava that considers the free surface, the irregular boundaries represented by the topography, the solidification fronts and the non-Newtonian rheology. Because of the very high degree of parallelism, GPUSPH is implemented very efficiently on high-performance graphics processing units (GPUs) employing the Compute Unified Device Architecture (CUDA), a parallel programming language developed by NVIDIA for GPU computing. GPUSPH follows the very general Herschel-Bulkley rheological model, which encompasses Newtonian, power-law and Bingham flow behaviour and can thus be used to explore in detail the impact of rheology on the behaviour of lava flows and on their emplacement. We present here the first validation tests of the GPUSPH model against well known analytical problems, considering the different rheological models, heat exchanges by thermal conduction and radiation, and providing the relative error estimates.

  7. Hydrocephalus due to extreme dilation of Virchow-Robin spaces (United States)

    Revel, Frederic; Cotton, Francois; Haine, Max; Gilbert, Thomas


    Virchow-Robin spaces (VRS) are extensions of the subarachnoid space surrounding perforating blood vessels entering the brain parenchyma. VRS are fluid filled, but almost virtual and only visible on MRI of the brain when dilated. Such dilations are commonly asymptomatic. In rare cases, extreme dilations can be observed; the clinical repercussions of which remain unclear. We report the case of a patient presenting symptoms of normal pressure hydrocephalus due to extreme VRS mesencephalon dilations. PMID:25564639

  8. Tear Lipids Interfacial Rheology: Effect of Lysozyme and Lens Care Solutions (United States)

    Svitova, Tatyana F.; Lin, Meng C.


    Purpose To evaluate the interfacial properties of ex vivo tear lipid multilayers with controlled and varying thickness. The influence of lysozyme and surfactant-containing multi-purpose lens care solutions (MPS) on interfacial rheology of lipids and mixed lipid-protein films were studied. Methods Lipids were extracted from lotrafilcon A lenses worn continuously for 1 month. Interfacial properties of the lipids without and with lysozyme in the aqueous phase were examined using tensiometry and step-strain relaxation. Lipid-lysozyme multilayers were exposed to either diluted Optifree Express (OFX) or Optifree Replenish (OFR) for 30 min, and then MPS was displaced from the bulk phase. Surface tension and rheological parameters before and after MPS exposure were measured and compared. Results Thick lipid films exerted high surface pressure at the air-aqueous interface, 50 ± 2 mN/m, with little inter- and intra-subject variability. The rheological storage modulus (E∞; 25.3 ± 2 mN/m) and relaxation time (τ; 87 ± 25 s) were similar among subjects. Neither lysozyme nor MPS changed the surface tension of the lipid multilayers. Lysozyme adsorbed irreversibly onto multilayers without changing E∞, but increased τ 2.5 times. Exposure of mixed multilayers to OFX reduced E∞ to less than a half of its original value (13 ± 4.5 mN/m; p rheology of the ex vivo lipids. OFX and OFR changed rheological properties of the mixed films to different extents. PMID:19901859

  9. Cosmic time dilation: The clock paradox revisited

    International Nuclear Information System (INIS)

    Tomaschitz, Roman


    The relativistic time dilation is reviewed in a cosmological context. We show that a clock or twin paradox does not arise if cosmic time is properly taken into account. The receding galaxy background provides a unique frame of reference, and the proper times of geodesic as well as accelerated observers can be linked to the universal cosmic time parameter. This suggests to compare the proper time differentials of the respective observers by determining their state of motion in the galaxy grid. In this way, each observer can figure out whether his proper time is dilated or contracted relative to any other. In particular one can come to unambiguous conclusions on the aging of uniformly moving observers, without reference to asymmetries in measurement procedures or accelerations they may have undergone

  10. Rheology and microstructure of aqueous suspensions of nanocrystalline cellulose rods. (United States)

    Xu, Yuan; Atrens, Aleks D; Stokes, Jason R


    Nanocrystalline cellulose (NCC) is a negatively charged rod-like colloid obtained from the hydrolysis of plant material. It is thus expected that NCC suspensions display a rich set of phase behaviour with salt and pH because of its anisotropic shape and electrical double layer that gives rise to liquid crystallinity and self-assembly respectively. It should thus be possible to tune the rheological properties of NCC suspensions for a wide variety of end-use applications. Rheology and structural analysis techniques are used to characterise surface-sulphated NCC suspensions as a function of pH, salinity (NaCl) and NCC concentration. Structural techniques include atomic force microscopy, Zeta potential, dynamic light scattering, and scanning electron microscopy. A phase diagram is developed based on the structure-rheology measurements showing various states of NCC that form as a function of salt and NCC concentration, which go well beyond those previously reported. This extended range of conditions reveals regions where the suspension is a viscous fluid and viscoelastic soft solid, as well as regions of instability that is suggested to arise when there is sufficient salt to reduce the electrical double layer (as explained qualitatively using DLVO theory) but insufficient NCC to form a load bearing network. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Analogy between dynamics of thermo-rheological and piezo-rheological pendulums

    Energy Technology Data Exchange (ETDEWEB)

    Hedrih, K [Faculty of Mechanical Engineering University of Nis, Mathematical Institute SANU, ul. Vojvode Tankosic 3/V/22, 18000-Nis (Serbia)], E-mail:, E-mail: khedrih@eunet.yu


    The constitutive stress-strain relations of the standard thermo-rheological and piezo-rheological hereditary element in differential form as well as in two different integro-differential forms are defined. The considered problem of a thermo-rheological hereditary discrete system nonlinear dynamics in the form of thermo-rheological double pendulum system with coupled pendulums gets the significance of two constrained bodies in plane motion problem, as a problem important for studying a sensor dynamics or actuator dynamics in active structure dynamics. System of the averaged equations in the first approximation for amplitudes and phases are derived and qualitatively analyzed. Analogy between nonlinear dynamics of the double pendulum systems with thermo-rheological and piezo-rheological properties between pendulums is pointed out.

  12. Analogy between dynamics of thermo-rheological and piezo-rheological pendulums

    International Nuclear Information System (INIS)

    Hedrih, K


    The constitutive stress-strain relations of the standard thermo-rheological and piezo-rheological hereditary element in differential form as well as in two different integro-differential forms are defined. The considered problem of a thermo-rheological hereditary discrete system nonlinear dynamics in the form of thermo-rheological double pendulum system with coupled pendulums gets the significance of two constrained bodies in plane motion problem, as a problem important for studying a sensor dynamics or actuator dynamics in active structure dynamics. System of the averaged equations in the first approximation for amplitudes and phases are derived and qualitatively analyzed. Analogy between nonlinear dynamics of the double pendulum systems with thermo-rheological and piezo-rheological properties between pendulums is pointed out

  13. Theory of rheology in confinement. (United States)

    Aerov, Artem A; Krüger, Matthias


    The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon, e.g., applying shear. Often the latter are more relevant, which allows a simpler theoretical description, and, e.g., (damped) Brownian particles can be considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on microscopic equations of motion and classical density functional theory. Specifically, we discuss the viscosity for the case of two parallel walls in relative motion as a function of the wall-to-wall distance, analyzing its relation to the slip length found for a single wall. The previously observed [A. A. Aerov and M. Krüger, J. Chem. Phys. 140, 094701 (2014).] deficiency of inhomogeneous (unphysical) stresses under naive application of shear in confinement is healed when hydrodynamic interactions are included.

  14. Granular rheology in zero gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bossis, G [LPMC UMR 6622, Universite de Nice, Parc Valrose, 06108 Nice Cedex 2 (France); Grasselli, Y [EAI Tech CERAM, Rue A Einstein, BP 085, 06902 Sophia Antipolis Cedex (France); Volkova, O [LPMC UMR 6622, Universite de Nice, Parc Valrose, 06108 Nice Cedex 2 (France)


    We present an experimental investigation on the rheological behaviour of model granular media made of nearly elastic spherical particles. The experiments are performed in a cylindrical Couette geometry and the experimental device is placed inside an aeroplane undergoing parabolic flights to cancel the effect of gravity. The corresponding curves, shear stress versus shear rate, are presented, and a comparison with existing theories is proposed. The quadratic dependence on the shear rate is clearly shown, and the behaviour as a function of the solid volume fraction of particles exhibits a power law function. It is shown that theoretical predictions overestimate the experimental results. We observe, at intermediate volume fractions, the formation of rings of particles regularly spaced along the height of the cell. The differences observed between experimental results and theoretical predictions are discussed and related to the structures formed in the granular medium submitted to the external shear.

  15. Rheological profile of raw whey

    Directory of Open Access Journals (Sweden)

    Libor Severa


    Full Text Available The results of raw whey rheological behavior investigation – particularly viscosity, dependence on temperature, time, and share rate, are presented. The whey samples have been examined under temperature ranging from 17 to 90 °C and under share rate ranging from 0.34 to 68  s−1. The measurements have been performed using rotary digital viscometer (concentric cylinders geometry. The material was found to be temperature dependent (non-linearly, time dependent and shear thinning. Received data have been successfully characterized by several mathematical models (power, exponential, and polynomial in MATLAB® software with satisfying correlations between experimental and computed results. Following correlations have been achieved: temperature dependence with r2 = 0.993 using polynomial model, time dependence with r2 = 0.985 using power model, and shear thinning behavior r2 = 0.998 using power model. The results are quite useful for practical design of technological equipment such as pumps and piping.

  16. Rheology of clustering protein solutions (United States)

    Hudson, Steven; Dharmaraj, Vishnu; Godfrin, P. Douglas; Liu, Yun

    Here we explore the rheology of low-salt lysozyme solutions, with special interest in the extremes of high concentration and low temperature. Under these conditions, reversible clustering of protein governed by their competing short-range attraction and long-range repulsion markedly enhances viscosity. Even in these conditions, the solutions exhibit Newtonian behavior over a wide range of shear rates. To test for departures from Newtonian behavior, we examined still higher shear rates. At shear rates in excess of 10,000 /s, we find reversible shear thinning at 40 % mass fraction. These results reveal dynamics of the protein clusters and are compared with other measurements of solution dynamics by neutron spin echo scattering and dynamic light scattering.

  17. Rheology of acrylic bone cements. (United States)

    Ferracane, J L; Greener, E H


    The rheological properties of setting acrylic bone cements were examined with a rotational cone and plate viscometer. The cements were tested over two orders of magnitude of shear rate to determine the nature of any non-Newtonian flow behavior. All three cements behaved with moderate pseudoplasticity (i.e., shear thinning) during setting, suggesting the use of higher pressures during administration for better flow and penetration. The low viscosity brand was found to be nearly one-half as viscous as the conventional cements during the working time (i.e., 2-5 minutes). A series of sieving experiments were performed to determine the particle size distributions of the powder components. Statistical analysis (chi square) showed the cements to have different distributions, with the low viscosity brand containing a larger proportion of smaller polymer particles. This difference is thought to contribute to the lower viscosity of this cement.

  18. Rheology of glasses containing crystalline material

    International Nuclear Information System (INIS)

    Plodinec, M.J.


    The rheology of inhomogeneous glass melts containing crystalline material has not been studied in detail. In this study, the rheology of melts containing simulated nuclear waste is characterized as a function of melt temperature and crystalline content. These melts can be either Newtonian or non-Newtonian fluids, depending on their crystalline contents. Melts free of crystals are strictly Newtonian. Melts containing from 2 to 10 vol% crystals are Newtonian fluids, which obey the Einstein-Smoluchowsky equation. The rheology of the melts containing ≥ 13 vol% is complex, mainly because of the formation of agglomerates

  19. Study on Rheological Behavior of Konjac Glucomannan (United States)

    Wang, Chao; Xu, Mei; Lv, Wen-ping; Qiu, Pei; Gong, Yuan-yuan; Li, Dong-sheng

    Konjac glucomannan (KGM) gum belongs to pseudoplastic fluid. Remarkable non-linear change tendencies of shear rheological behavior of KGM were detected through analysis of the correlation of viscosity (η)-shear rates and shear stress- shear rates respectively. The result shows that the sample concentration, sheer rate and temperature has great influence to its rheological property, and its shear rheological curves conformed to the Power Law (τ=KDn). When the concentration belows 0.55%, the hydrosol behaves approximate Newtonian fluid, and at higher concentration, it behaves pseudoplastically. When temperature changes from 0 to 85°, the viscosity declines remarkably.

  20. Rheology v.2 theory and applications

    CERN Document Server

    Eirich, Frederick


    Rheology: Theory and Applications, Volume II deals with the specific rheological subjects, such as deformational behavior in relation to the classic subjects and topics of rheology. This volume is divided into 13 chapters. Considerable chapters are devoted to the theory and aspects of viscoelastic and relaxation phenomena, as well as the applied theory concerning substances related to these phenomena, including elastomers, gelatins, and fibers. Other chapters cover the general principles of geological deformations derived from the study of less """"immobile"""" objects. The remaining chapt

  1. Cosmological Time Dilation in Gamma Ray Bursts?


    Band, David


    Norris et al. (1994) report that the temporal structure of faint gamma ray bursts is longer than that of bright bursts, as expected for time dilation in the cosmological models of burst origin. I show that the observed trends can easily be produced by a burst luminosity function and thus may not result from cosmological effects. A cosmological signature may be present, but the tests Norris et al. present are not powerful enough to detect these signatures.

  2. The Naimark dilated PT-symmetric brachistochrone


    Guenther, Uwe; Samsonov, Boris F.


    The quantum mechanical brachistochrone system with PT-symmetric Hamiltonian is Naimark dilated and reinterpreted as subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultra-fast brachistochrone regime of [C. M. Bender et al, Phys. Rev. Lett. {\\bf 98}, 040403 (2007)] in an entangled two-spin system.

  3. Naimark-Dilated PT-Symmetric Brachistochrone (United States)

    Günther, Uwe; Samsonov, Boris F.


    The quantum mechanical brachistochrone system with a PT-symmetric Hamiltonian is Naimark-dilated and reinterpreted as a subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultrafast brachistochrone regime of Bender et al. [Phys. Rev. Lett. 98, 040403 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.040403] in an entangled two-spin system.

  4. Stability of wavelet frames with matrix dilations

    DEFF Research Database (Denmark)

    Christensen, Ole; Sun, Wenchang


    Under certain assumptions we show that a wavelet frame {Tau(A(j), b(j,k))psi} (j,k is an element of Z) := {vertical bar detA(j)vertical bar(-1/2) psi(A(j)(-1)(x - b(j,k)))} (j,k is an element of Z) in L-2(R-d) remains a frame when the dilation matrices A(j) and the translation parameters b...

  5. CT in thrombosed dilated posterior epidural vein

    Energy Technology Data Exchange (ETDEWEB)

    Bammatter, S.; Schnyder, P.; Preux, J. de


    The authors report a case of thrombosis of the distal end of an enlarged right posterior epidural vein. The patient had a markedly narrow lumbar canal due to L5 spondylolisthesis. The dilated vein and the thrombosis were displayed by computed tomography but remained unrecognized until surgery. Pathogenesis of this condition is discussed. A review of the English, French and German literature revealed no prior radiological reports of a similar condition.

  6. Effect of Mantle Rheology on Viscous Heating induced during Ice Sheet Cycles (United States)

    Huang, Pingping; Wu, Patrick; van der Wal, Wouter


    Hanyk et al. (2005) studied the viscous shear heating in the mantle induced by the surface loading and unloading of a parabolic-shaped Laurentide-size ice sheet. They found that for linear rheology, viscous heating is mainly concentrated below the ice sheet. The depth extent of the heating in the mantle is determined by the viscosity distribution. Also, the magnitude of viscous heating is significantly affected by the rate of ice thickness change. However, only one ice sheet has been considered in their work and the interactions between ice sheets and ocean loading have been neglected. Furthermore, only linear rheology has been considered, although they suggested that non-Newtonian rheology may have a stronger effect. Here we follow Hanyk et al. (2005) and computed the viscous dissipation for viscoelastic models using the finite element methodology of Wu (2004) and van der Wal et al. (2010). However, the global ICE6G model (Peltier et al. 2015) with realistic oceans is used here to provide the surface loading. In addition, viscous heating in non-linear rheology, composite rheology, in addition to linear rheology with uniform or VM5a profile are computed and compared. Our results for linear rheology mainly confirm the findings of Hanyk et al. (2005). For both non-linear and composite rheologies, viscous heating is also mainly distributed near and under the ice sheets, but, more concentrated; depending on the horizontal dimension of the ice sheet, it can extend into the lower mantle, but for some of the time, not as deep as that for linear rheology. For composite rheology, the viscous heating is dominated by the effect of non-linear relation between the stress and the strain. The ice history controls the time when the local maximum in viscous heating appears. However, the magnitude of the viscous heating is affected by mantle rheology as well as the ice loading. Due to viscosity stratification, the shape of the region with high viscous heating in model VM5a is a

  7. Balloon catheter dilatation of benign urethral strictures

    International Nuclear Information System (INIS)

    Perini, L.; Cavallo, A.; Perin, B.; Bighi, G.


    The authors report their experience of benign urethral stricture dilatation by balloon catheter in 11 male patients. Ten posterior and 2 anterior urethral strictures were treated; in 1 patients several narrowings coexisted at various levels. Etiology was inflammatory in 4 cases, iatrogen in 3, post-traumatic in 2, and equivocal in 2. The patients were studied both before and soon after dilatation by means of retrograde and voiding cystourethrogram and uroflowgraphy; the follow-up (2-14 months) was performed by urodynamic alone. In all cases, dilatation was followed by the restoration of urethral gauge, together with prompt functional improvement of urodynamic parameters. The latter result subsisted in time in 9 patients. In 2 cases recurrences were observed demonstrated at once by clinics and urodynamics. Both lesions were successfully re-treated. Neither early not late complication occurred. In spite of the limited material, the valuable results obtained, together with the absence of complications, the peculiar morphology of recurrences, and the chance of repeating it make the procedure advisable as a valid alternative to conventional techniques for these pathologies

  8. Time dilation in quantum systems and decoherence (United States)

    Pikovski, Igor; Zych, Magdalena; Costa, Fabio; Brukner, Časlav


    Both quantum mechanics and general relativity are based on principles that defy our daily intuitions, such as time dilation, quantum interference and entanglement. Because the regimes where the two theories are typically tested are widely separated, their foundational principles are rarely jointly studied. Recent works have found that novel phenomena appear for quantum particles with an internal structure in the presence of time dilation, which can take place at low energies and in weak gravitational fields. Here we briefly review the effects of time dilation on quantum interference and generalize the results to a variety of systems. In addition, we provide an extended study of the basic principles of quantum theory and relativity that are of relevance for the effects and also address several questions that have been raised, such as the description in different reference frames, the role of the equivalence principle and the effective irreversibility of the decoherence. The manuscript clarifies some of the counterintuitive aspects arising when quantum phenomena and general relativistic effects are jointly considered.

  9. Time dilation in quantum systems and decoherence

    International Nuclear Information System (INIS)

    Pikovski, Igor; Zych, Magdalena; Costa, Fabio; Brukner, Časlav


    Both quantum mechanics and general relativity are based on principles that defy our daily intuitions, such as time dilation, quantum interference and entanglement. Because the regimes where the two theories are typically tested are widely separated, their foundational principles are rarely jointly studied. Recent works have found that novel phenomena appear for quantum particles with an internal structure in the presence of time dilation, which can take place at low energies and in weak gravitational fields. Here we briefly review the effects of time dilation on quantum interference and generalize the results to a variety of systems. In addition, we provide an extended study of the basic principles of quantum theory and relativity that are of relevance for the effects and also address several questions that have been raised, such as the description in different reference frames, the role of the equivalence principle and the effective irreversibility of the decoherence. The manuscript clarifies some of the counterintuitive aspects arising when quantum phenomena and general relativistic effects are jointly considered. (paper)

  10. Coronary dilation with nitrocompounds and calcium antagonists. (United States)

    Jost, S; Rafflenbeul, W; Lichtlen, P R


    The vasodilatory effects of nitrocompounds and calcium antagonists on epicardial coronary arteries represent substantial antianginal mechanisms in the presence of coronary vasospasm or eccentric coronary stenoses. With high doses of nitrocompounds, angiographically normal coronary segments can be dilated by an average of approx. 30%, some coronary stenoses even by up to 100%, usually without severe reduction of blood pressure. With calcium antagonists, a similar extent of dilation of normal coronary arteries and eccentric stenoses can be obtained. Our own group demonstrated an average dilation of normal coronary arteries of about 20% after intravenous administration of dihydropyridine calcium antagonists; however, the average systolic blood pressure dropped below 100 mmHg after these compounds. Hence, although in isolated human coronary arteries high concentrations of calcium antagonists were shown to induce a considerably greater vasodilation than nitrocompounds, the early drop in blood pressure prohibits a higher dosage of calcium antagonists in vivo. In the presence of coronary artery disease, particularly when associated with coronary vasospasm, a combination of the two groups of compounds might be recommendable, since an addition of the effects of coronary vasomotor tone is likely. Furthermore, the antianginal effects of a reduction of preload and afterload are complementary.

  11. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)


    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  12. Foam rheology: a model of viscous phenomena

    International Nuclear Information System (INIS)

    Kraynik, A.M.; Hansen, M.G.


    A theoretical model for foam rheology that includes viscous forces is developed by considering the deformation of two-dimensional, spatially periodic cells in simple shearing and planar extensional flow. The undeformed hexagonal cells are separated by thin liquid films. Plateau border curvature and liquid drainage between films is neglected. Interfacial tension and viscous tractions due to stretching lamellar liquid determine the individual film tensions. The network motion is described by a system of nonlinear ordinary differential equations for which numerical solutions are obtained. Coalescense and disproportionation of Plateau borders results in the relative separation of cells and provides a mechanism for yielding and flow. This process is assumed to occur when a film's length reduces to its thickness. The time and position dependence of the cell-scale dynamics are computed explicitly. The effective continuum stress of the foam is described by instantaneous and time-averaged quantities. The capillary number, a dimensionless deformation rate, represents the relative importance of viscous and surface tension effects. The small-capillary-number or quasistatic response determines a yield stress. The dependence of the shear and normal stress material functions upon deformation rate, foam structure and physical properties is determined. A plausible mechanism for shear-induced material failure, which would determine a shear strength, is revealed for large capillary numbers. The mechanism involves large cell distortion and film thinning, which provide favorable conditions for film rupture

  13. Rheological and fractal hydrodynamics of aerobic granules. (United States)

    Tijani, H I; Abdullah, N; Yuzir, A; Ujang, Zaini


    The structural and hydrodynamic features for granules were characterized using settling experiments, predefined mathematical simulations and ImageJ-particle analyses. This study describes the rheological characterization of these biologically immobilized aggregates under non-Newtonian flows. The second order dimensional analysis defined as D2=1.795 for native clusters and D2=1.099 for dewatered clusters and a characteristic three-dimensional fractal dimension of 2.46 depicts that these relatively porous and differentially permeable fractals had a structural configuration in close proximity with that described for a compact sphere formed via cluster-cluster aggregation. The three-dimensional fractal dimension calculated via settling-fractal correlation, U∝l(D) to characterize immobilized granules validates the quantitative measurements used for describing its structural integrity and aggregate complexity. These results suggest that scaling relationships based on fractal geometry are vital for quantifying the effects of different laminar conditions on the aggregates' morphology and characteristics such as density, porosity, and projected surface area. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Mudflow rheology in a vertically rotating flume (United States)

    Holmes, Robert R.; Westphal, Jerome A.; Jobson, Harvey E.; ,


    Joint research by the U.S. Geological Survey and the University of Missouri-Rolla currently (1990) is being conducted on a 3.05 meters in diameter vertically rotating flume used to simulate mudflows under steady-state conditions. Observed mudflow simulations indicate flow patterns in the flume are similar to those occurring in natural mudflows. Variables such as mean and surface velocity, depth, and average boundary shear stress can be measured in this flume more easily than in the field or in a traditional tilting flume. Sensitive variables such as sediment concentration, grain-size distribution, and Atterberg limits also can be precisely and easily controlled. A known Newtonian fluid, SAE 30 motor oil, was tested in the flume and the computed value for viscosity was within 12.5 percent of the stated viscosity. This provided support that the data from the flume can be used to determine the rheological properties of fluids such as mud. Measurements on mud slurries indicate that flows with sediment concentrations ranging from 81 to 87 percent sediment by weight can be approximated as Bingham plastic for strain rates greater than 1 per second. In this approximation, the yield stress and Bingham viscosity were extremely sensitive to sediment concentration. Generally, the magnitude of the yield stress was large relative to the change in shear stress with increasing mudflow velocity.

  15. Effect of SiO2 Particle Size and Length of Poly(Propylene Glycol Chain on Rheological Properties of Shear Thickening Fluids

    Directory of Open Access Journals (Sweden)

    Antosik A.


    Full Text Available The rheological properties of shear thickening fluids based on silica powder of particles size in range 0.10 – 2.80 μm and poly(propylene glycol of 425, 1000, 2000 g/mol molar mass were investigated. The effect of particle size and the length of the polymeric chain was considered. The objective of this study was to understand basic trends of physicochemical properties of used materials on the onset and the maximum of shear thickening and dilatant effect. Outcome of the research suggested that an increase in the particle size caused a decrease in dilatant effect and shift towards higher shear rate values. Application of carrier fluid of higher molar mass allowed to increase dilatant effect but it resulted in the increase of the initial viscosity of the fluid.


    Directory of Open Access Journals (Sweden)

    G. O. Magomedov


    Full Text Available Summary. The knowledge of regularities of deformation behavior of the processed confectionery masses with certain rheological properties allows to calculate parameters of shaping process and to select processing equipment for its carrying out. The article studies the obtaining of the rheological equation of deformation behavior of sugar dough in the conditions of monoaxial compression which is realized in sugar cookies dough pieces formation processes. The results of the pilot studies confirming adequacy of the offered rheological equation are presented. The behavior of an elastic-, viscous- and plastic body in the conditions of quasistatic test for creeping during which the set size is tension, and the measured one is relative deformation is considered. The main rheological properties of sugar dough received experimentally are given. Values of rheological constants are received and it is revealed that at 95% confidential probability, the rheological equation for the general deformation of an elastic-, viscous- and plastic body adequately describes experimental data. The maximum fault thus makes 2,3%. It is established that dough pieces shaping processes from the sugar dough possessing visco- and plastic properties should be realized at an external tension (power impact from the forming body which exceeds a limit of fluidity of the dough formed. The level of external tension, as well as the duration of its influence (that is formation duration should be chosen taking into account the residual deformations in the processed mass which guarantee giving of a certain geometrical form and drawing on a surface of dough pieces. The rheological model of sugar dough allows to predict its deformation behavior in the formation conditions, and to calculate the parameters of sugar dough formation process.

  17. The neural substrates of subjective time dilation


    Marc Wittmann; Marc Wittmann; Marc Wittmann; Virginie Van Wassenhove; Bud Craig; Martin P Paulus; Martin P Paulus


    An object moving towards an observer is subjectively perceived as longer in duration than the same object that is static or moving away. This 'time dilation effect' has been shown for a number of stimuli that differ from standard events along different feature dimensions (e.g. color, size, and dynamics). We performed an event-related functional magnetic resonance imaging (fMRI), while subjects viewed a stream of five visual events, all of which were static and of identical duration except the...

  18. The Neural Substrates of Subjective Time Dilation


    Wittmann, Marc; van Wassenhove, Virginie; Craig, A. D. (Bud); Paulus, Martin P.


    An object moving towards an observer is subjectively perceived as longer in duration than the same object that is static or moving away. This ”time dilation effect” has been shown for a number of stimuli that differ from standard events along different feature dimensions (e.g. color, size, and dynamics). We performed an event-related functional magnetic resonance imaging (fMRI) study, while subjects viewed a stream of five visual events, all of which were static and of identical duration exce...

  19. Dilated cardiomyopathy following use of xenadrine EFX (United States)

    Riccioni, Graziano; Speziale, Giuseppe; Scotti, Luca; Bucciarelli, Valentina; Cappetti, Silvia; Nasso, Giuseppe; Gallina, Sabina; Bucciarelli, Tonino


    We describe a case of a 35-year-old man presented at the emergency room of our institution with acute onset of dyspnea and dizziness. He was a body builder and had been using Xenadrine EFX for weight loss reduction. The laboratory analyses were normal. A chest radiograph showed an enlarged cardiac silhouette with clear lung fields. Transtoracic two-dimensional color Doppler echocardiography revealed a diffuse hypokinesia with a marked decreased in systolic function and a high teledyastolic diameter. This case document the possible relation to use of Xenadrine EFX for weight loss and the recurrence of dilated cardiomyopathy. PMID:26680256

  20. Rheology of tetraphenylborate precipitate slurry

    International Nuclear Information System (INIS)

    Goren, I.D.; Martin, H.D.; McLain, M.A.


    The rheological properties of tetraphenylborate precipitate slurry were determined. This nonradioactive slurry simulates the radioactive tetraphenylborate precipitate generated at the Savannah River Plant by the In-Tank Precipitation Process. The data obtained in this study was applied in the design of slurry pumps, transfer pumps, transfer lines, and vessel agitation for the Defense Waste Processing Facility and other High Level Waste treatment projects. The precipitate slurry behaves as a Bingham plastic. The yield stress is directly proportional to the concentration of insoluble solids over the range of concentrations studied. The consistency is also a linear function of insoluble solids over the same concentration range. Neither the yield stress nor the consistency was observed to be affected by the presence of the soluble solids. Temperature effects on flow properties of the slurry were also examined: the yield stress is inversely proportional to temperature, but the consistency of the slurry is independent of temperature. No significant time-dependent effects were found. 4 refs., 4 figs., 3 tabs

  1. Associative thickeners : Their adsorption behaviour onto latexes and the rheology of their solutions

    NARCIS (Netherlands)

    Svanholm, T.; Molenaar, F.; Toussaint, A.


    The interaction between an associative thickeners in solution and an anionic surfactant has been studied with rheology and surface tension measurements. Both a HEUR thickener and low molecular weight HMHEC thickener interacted strongly with the surfactant. The addition of surfactant leads in both

  2. Percutaneous Dilatational Tracheostomy via Griggs Technique. (United States)

    Karimpour, Hasan Ali; Vafaii, Kamran; Chalechale, Maryam; Mohammadi, Saeed; Kaviannezhad, Rasool


    Tracheostomy is considered the airway management of choice for patients who need prolonged mechanical ventilation support. Percutaneous Dilatational Tracheotomy (PDT) is a technique that can be performed easily and rapidly at bedside and is particularly useful in the intensive care setting. The Griggs percutaneous tracheotomy is unique in its utilization of a guide wire dilator forceps. We aimed to describe the early perioperative and late postoperative complications of PDT using the Griggs technique in patients in the intensive care unit (ICU). This cross-sectional study was conducted on all patients who underwent tracheostomy in the ICU of the Imam Reza Hospital of Kermanshah, Iran, from June 2011 to June 2015. PDT was performed in 184 patients with the Griggs technique. Demographic variables, as well as perioperative and late postoperative complications were recorded. The mean age of patients was 57.3 ± 15.37 years. The most common primary causes of tracheostomy were hypoxic brain damage disorders (43.2%) and pneumonia (14.8%). Perioperative and early complications occurred in 16.7 % of procedures, of which 9.3% were bleedings (minor, significant and major). Furthermore, the incidence of late complications was 8.6%, including: stomal infection, difficult replace tracheostomy tube, tracheoesophageal fistula, tracheal stenosis, and tracheomalacia. PDT via Griggs technique is a safe, quick, and effective method. The low incidence of complications indicates that bedside percutaneous tracheostomy can be performed safely as a routine procedure for daily care implemented in the ICU.

  3. Gastric Dilation and Volvulus Syndrome in Dog

    Directory of Open Access Journals (Sweden)

    Ami S. Bhatia

    Full Text Available Gastric dilatation and volvulus syndrome (GDV in dogs is an abnormal accumulation of gastric gas (dilatation, which may be complicated by rotation of the stomach (volvulus about its mesentric axis. A number of factors, both environmental and host have been implicated in GDV. This syndrome has a variety of effects on the cardiovascular, respiratory, gastrointestinal, metabolic, haemolymphatic-immune, renal and central nervous systems. Clinical signs include distended, painful, tympanic abdomen, retching, unproductive vomiting, hypersalivation, respiratory distress accompanied by varying degrees of shock. Treatment of GDV includes medical and fluid therapy at shock dosages to initially stabilize the patient followed by gastric decompression. Surgical procedure comprises of gastric derotation followed by partial gastrectomy or spleenectomy depending upon gastric or spleenic viability and lastly, permanent right sided gastropexy. Post surgical considerations include frequent small meals instead of one large meal, avoiding vigorous activity immediately after meals and not allowing animal to gorge on water after meals or activities. [Veterinary World 2010; 3(12.000: 554-557

  4. Influence of superplasticizers on the rheology and stability of limestone and cement pastes

    International Nuclear Information System (INIS)

    Mikanovic, Nikola; Jolicoeur, Carmel


    The influence of superplasticizers on the rheological properties and dynamic stability of cement and reference limestone pastes were examined at room temperature. The pastes were initially formulated to exhibit nearly identical rheological parameters and bleeding-segregation characteristics, with w/c = 0.50 for the limestone and 0.55 for the cement. The former was examined at equilibrium pH ∼ 10 and at pH 12.5 following addition of Ca(OH) 2 to allow distinction of effects related to high pH and Ca +2 from those related to cement hydration reactions. Both polynaphthalene- (PNS) and polyacrylate-type (PC) superplasticizers were investigated, adjusting the dosages to cover the same range of paste fluidity. Superplasticizer-particle interactions were monitored through binding isotherms and zeta potential measurements. The rheology of the pastes was evaluated through the mini-slump test and dynamic viscosity measurements which yielded key rheological parameters: yield stress, elastic and loss moduli (G' and G'') and zero-shear viscosity (η 0 ). The paste stability was monitored as function of time, i.e. migration of solids and liquid phase measured in-situ and in 'real time', through surface bleeding measurements and from a multipoint conductivity method. The results provide new insight on the relative modes of action of PNS- and PC-type superplasticizers as dispersants. Also, the combined rheology and stability data allow an improved description of the processes responsible for bleeding and segregation in cementitious and reference systems

  5. Roentgenoendovascular dilatation and recanalization of vessels of lower extremities

    International Nuclear Information System (INIS)

    Rabkin, I.Kh.; Matevosov, A.L.; Gotman, L.N.


    Advantages and disadvantages of using roentgenoendovascular dilatation (RED) of vessels of lower extremities are presented. RED is recommended in treating patients with short segmented stenoses of common and external illiac arteries and also with the similar damages of surficial femoral arteries. Dilatation is a success when there is permeability in at least one of the three central crus arteries. Success of delayed results of vessel dilatation is to a certain degree in inverse proportion to time and length of occlusion

  6. Design and analysis of magneto rheological fluid brake for an all terrain vehicle (United States)

    George, Luckachan K.; Tamilarasan, N.; Thirumalini, S.


    This work presents an optimised design for a magneto rheological fluid brake for all terrain vehicles. The actuator consists of a disk which is immersed in the magneto rheological fluid surrounded by an electromagnet. The braking torque is controlled by varying the DC current applied to the electromagnet. In the presence of a magnetic field, the magneto rheological fluid particle aligns in a chain like structure, thus increasing the viscosity. The shear stress generated causes friction in the surfaces of the rotating disk. Electromagnetic analysis of the proposed system is carried out using finite element based COMSOL multi-physics software and the amount of magnetic field generated is calculated with the help of COMSOL. The geometry is optimised and performance of the system in terms of braking torque is carried out. Proposed design reveals better performance in terms of braking torque from the existing literature.

  7. Rheological properties of disintegrated sewage sludge (United States)

    Wolski, Paweł


    The rheology of the sludge provides information about the capacity and the flow, which in the case of project tasks for the hydraulic conveying installation is an important control parameter. Accurate knowledge of the rheological properties of sludge requires the designation of rheological models. Models single and multiparameter (Ostwald, Bingham, Herschel-Bulkley'a, and others) allow an approximation of flow curves, and the determination of the boundaries of the flow of modified sludge allows you to control the process compaction or are dewatered sludge undergoing flow. The aim of the study was to determine the rheological parameters and rheological models of sludge conditioned by physical methods before and after the process of anaerobic digestion. So far, studies have shown that the application of conditioning in the preparation of sewage sludge increases shear stress, viscosity as well as the limits of flow in relation to the untreated sludge. Offset yield point by the application of a conditioning agent is associated with decreased flowability tested sludge, which has also been observed by analyzing the structure of the prepared samples. Lowering the yield point, and thus the shear stress was recorded as a result of the fermentation test of disintegrated sludge.

  8. Initial rheological description of high performance concretes

    Directory of Open Access Journals (Sweden)

    Alessandra Lorenzetti de Castro


    Full Text Available Concrete is defined as a composite material and, in rheological terms, it can be understood as a concentrated suspension of solid particles (aggregates in a viscous liquid (cement paste. On a macroscopic scale, concrete flows as a liquid. It is known that the rheological behavior of the concrete is close to that of a Bingham fluid and two rheological parameters regarding its description are needed: yield stress and plastic viscosity. The aim of this paper is to present the initial rheological description of high performance concretes using the modified slump test. According to the results, an increase of yield stress was observed over time, while a slight variation in plastic viscosity was noticed. The incorporation of silica fume showed changes in the rheological properties of fresh concrete. The behavior of these materials also varied with the mixing procedure employed in their production. The addition of superplasticizer meant that there was a large reduction in the mixture's yield stress, while plastic viscosity remained practically constant.

  9. Choanal Atresia: Surgical Management by Hegar's Dilators. (United States)

    Sinha, Vikas; Gurnani, Deepanshu; Modi, Niral R; Barot, Dilavar A; Maniyar, Hiten R; Pandey, Ambuj


    Choanal atresia is one of the more commonly observed congenital abnormalities of the nose. The condition is predominantly found in females with a M:F ratio of 1:2. 65-75 % of patients with choanal atresia are unilateral, and the rest are bilateral. About 50 % of the cases are associated with other congenital anomalies, the most common being coloboma, Heart disease, choanal atresia, mental and growth retardation, genital hypoplasia, ear deformities syndrome. The embryonic origin of choanal atresia is due to persistent bucco-pharyngeal or naso-buccal membrane. Our study was a retrospective study of 14 cases of choanal atresia. All the cases were operated by the first author. Each patient was investigated in detail and recorded by stratifying in sex of patient, age of presentation, type and site of atresia, and associated other congenital anomalies. Patient were operated under general anesthesia and Hegar's dilators were used to perforate the atretic plate as Hegar's dilators are believed to have ideal curvature with respect to the sloping contour of the nasal floor. Out of the total 14 cases, 9 (64 %, n = 14) cases were male and 5 (36 %, n = 14) females. The age variations varied from youngest of 3 days to the oldest 31 year old female. Stents were kept for a period of 6-8 weeks and regular follow up nasal endoscopy was done weekly for suctioning and visualizing the size of the airway. There are five different surgical approaches that have been described for surgical treatment of choanal atresia: (1) trans-nasal, (2) trans-palatal, (3) trans-septal, (4) trans-antral and (5) sublabial-transnasal. In our study M:F ratio was 1.8:1 which is comparable Gosepath et al. (Rhinology 45:158-163, 2007) (2:1). In our study bilateral atresia was seen in 43 % (6, n = 14) and unilateral in 57 % (8, n = 14) which is comparable to Newman et al. (44 % bilateral cases, n = 43). Amicable and prompt referral to the ENT surgeon can be of immense value so as to buy

  10. Self-Supporting Nanodiamond Gels: Elucidating Colloidal Interactions Through Rheology_ (United States)

    Adhikari, Prajesh; Tripathi, Anurodh; Vogel, Nancy A.; Rojas, Orlando J.; Raghavan, Sriunivasa R.; Khan, Saad A.

    This work investigates the colloidal interactions and rheological behavior of nanodiamond (ND) dispersions. While ND represents a promising class of nanofiller due to its high surface area, superior mechanical strength, tailorable surface functionality and biocompatibility, much remains unknown about the behavior of ND dispersions. We hypothesize that controlling interactions in ND dispersions will lead to highly functional systems with tunable modulus and shear response. Steady and dynamic rheology techniques are thus employed to systematically investigate nanodiamonds dispersed in model polar and non-polar media. We find that low concentrations of ND form gels almost instantaneously in a non-polar media. In contrast, ND's in polar media show a time-dependent behavior with the modulus increasing with time. We attribute the difference in behavior to variations in inter-particle interactions as well as the interaction of the ND with the media. Large steady and oscillatory strains are applied to ND colloidal gels to investigate the role of shear in gel microstructure breakdown and recovery. For colloidal gels in non-polar medium, the incomplete recovery of elastic modulus at high strain amplitudes indicates dominance of particle-particle interactions; however, in polar media the complete recovery of elastic modulus even at high strain amplitudes indicates dominance of particle-solvent interactions. These results taken together provide a platform to develop self-supporting gels with tunable properties in terms of ND concentration, and solvent type.

  11. Nonlinear Viscoelastic Rheology and the Occurrence of Aftershocks (United States)

    Shcherbakov, R.; Zhang, X.


    Aftershocks are ubiquitous in nature. They are the manifestation of relaxation phenomena observed in various physical systems. In one prominent example, they typically occur after large earthquakes. The observed aftershock sequences usually obey several well defined non-trivial empirical laws in magnitude, temporal, and spatial domains. In many cases their characteristics follow scale-invariant distributions. The occurrence of aftershocks displays a prominent temporal behavior due to time-dependent mechanisms of stress and/or energy transfer. There are compelling evidences that the lower continental crust and upper mantle are governed by various solid state creep mechanisms. Among those mechanisms a power-law viscous flow was suggested to explain the postseismic surface deformation after large earthquakes. In this work, we consider a slider-block model to mimic the behavior of a seismogenic fault. In the model, we introduce a nonlinear viscoelastic coupling mechanism to capture the essential characteristics of crustal rheology and stress interaction between the blocks and the medium. For this purpose we employ nonlinear Kelvin-Voigt elements consisting of an elastic spring and a dashpot assembled in parallel to introduce viscoelastic coupling between the blocks and the driving plate. By mapping the model into a cellular automaton we derive the functional form of the stress transfer mechanism in the model. We show that the nonlinear viscoelasticity plays a critical role in triggering of aftershocks. It explains the functional form of the Omori-Utsu law and gives physical interpretation of its parameters. The proposed model also suggests that the power-law rheology of the fault gauge and underlying lower crust and upper mantle controls the decay rate of aftershocks. To verify this, we analyze several prominent aftershock sequences to estimate their decay rates and correlate with the rheological properties of the underlying lower crust and mantle, which were estimated

  12. Rheological Characterization Of Nano-Composite Hydrogels (United States)

    Lombardi, Jack

    Engineered Polymer hydrogels and hydrogels from Bio macromolecules have visco-elastic properties that can be measured using Oscillatory Shear Rheology. Manipulation and measurement of physical properties in gels including F-127 Pluronic Block Co-Polymer and Poly(N-isopropylacrylamide)-Clay are shown through OSR by addition of salts, clays and glucose at physiological levels. Rheological analysis of f-127 illustrates changes in G' reduction with phase transition temperature. Measurements also indicate physical changes due to the aforementioned additives vary as a function of the gel physical and chemical structure. In particular, non-enzymatic glycation is shown to change the modulus of elasticity in both of the gels tested. Rheological analysis is also interpreted to produce a reduction In gel mesh size in the PNIPA -clay gels due to a possible co-solvency between phases of varying degrees of hydration.

  13. Rheological Characterization of Unusual DWPF Slurry Samples

    International Nuclear Information System (INIS)

    Koopman, D. C.


    A study was undertaken to identify and clarify examples of unusual rheological behavior in Defense Waste Processing Facility (DWPF) simulant slurry samples. Identification was accomplished by reviewing sludge, Sludge Receipt and Adjustment Tank (SRAT) product, and Slurry Mix Evaporator (SME) product simulant rheological results from the prior year. Clarification of unusual rheological behavior was achieved by developing and implementing new measurement techniques. Development of these new methods is covered in a separate report, WSRC-TR-2004-00334. This report includes a review of recent literature on unusual rheological behavior, followed by a summary of the rheological measurement results obtained on a set of unusual simulant samples. Shifts in rheological behavior of slurries as the wt. % total solids changed have been observed in numerous systems. The main finding of the experimental work was that the various unusual DWPF simulant slurry samples exhibit some degree of time dependent behavior. When a given shear rate is applied to a sample, the apparent viscosity of the slurry changes with time rather than remaining constant. These unusual simulant samples are more rheologically complex than Newtonian liquids or more simple slurries, neither of which shows significant time dependence. The study concludes that the unusual rheological behavior that has been observed is being caused by time dependent rheological properties in the slurries being measured. Most of the changes are due to the effect of time under shear, but SB3 SME products were also changing properties while stored in sample bottles. The most likely source of this shear-related time dependence for sludge is in the simulant preparation. More than a single source of time dependence was inferred for the simulant SME product slurries based on the range of phenomena observed. Rheological property changes were observed on the time-scale of a single measurement (minutes) as well as on a time scale of hours

  14. Influence of superplasticizer on the rheology of fresh cement asphalt paste

    Directory of Open Access Journals (Sweden)

    Jianwei Peng


    Full Text Available Cement asphalt (CA paste is an organic–inorganic composite material of cement and asphalt emulsion. Its complicated rheological behavior affects its site application in high speed railway. Superplasticizers (SPs are usually used to improve the construction properties of fresh CA mortar. However, the principle of SPs acting on the rheology of CA paste is seldom studied. In this paper, the effects of polycarboxylate (PCA and naphthalenesulfonate (PNS on the rheological properties of CA pastes, asphalt emulsions (both anionic and cationic and cement pastes were studied, respectively from the viewpoint of adsorption and zeta potential. Centrifugation method was used to determine the adsorption of asphalt onto cement particle, electroacoustic method was employed to study the zeta potential of cement particles of concentrated paste, and optical microscopy was used to observe the dispersion of particles. The results suggest that both PCA and PNS can decrease the yield stress and apparent viscosity of CA pastes. The effect of SPs on the rheology of CA paste can be explained by two reasons. First, PNS can adsorb on both asphalt and cement surface, change the zeta potential and then decrease their yield stress and viscosity, while PCA only adsorb on cement surface. Second, the competitive adsorption of SPs and asphalt prevents asphalt from adsorbing on cement surface and then more asphalt droplets are released into aqueous solution, thereby enhancing the particle dispersion.

  15. Vaginal dilator therapy for women receiving pelvic radiotherapy. (United States)

    Miles, Tracie; Johnson, Nick


    Many vaginal dilator therapy guidelines advocate routine vaginal dilation during and after pelvic radiotherapy to prevent stenosis (abnormal narrowing of the vagina). The UK Gynaecological Oncology Nurse Forum recommend dilation "three times weekly for an indefinite time period". The UK patient charity Cancer Backup advises using vaginal dilators from two to eight weeks after the end of radiotherapy treatment. Australian guidelines recommend dilation after brachytherapy "as soon as is comfortably possible" and "certainly within four weeks and to continue for three years or indefinitely if possible". However, dilation is intrusive, uses health resources and can be psychologically distressing. It has also caused rare but very serious damage to the rectum. To review the benefits and harms of vaginal dilation therapy associated with pelvic radiotherapy for cancer. Searches included the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 4), MEDLINE (1950 to 2008), EMBASE (1980 to 2008) and CINAHL (1982 to 2008). Any comparative randomised controlled trials (RCT) or data of any type which compared dilation or penetration of the vagina after pelvic radiotherapy treatment for cancer. The review authors independently abstracted data and assessed risk of bias. We analysed the mean difference in sexual function scores and the risk ratio for non-compliance at six weeks and three months in single trial analyses. No trials met the inclusion criteria. Dilation during or immediately after radiotherapy can, in rare cases, cause damage and there is no persuasive evidence from any study to demonstrate that it prevents stenosis. Data from one RCT showed no improvement in sexual scores in women who were encouraged to practice dilation. Two case series and one comparative study using historical controls suggest that dilation might be associated with a longer vaginal length but these data cannot reasonably be interpreted to show that dilation

  16. Rheological studies of creams. I. Rheological functions and structure of creams. (United States)

    Erös, I; Thaleb, A


    Large number of washable (o/w type) creams were prepared for rheological investigation. The rheological functions known from the literature were determined in our studies. Rheological constants were determined by measurements and calculations. From these, we selected those ones which were applicable to characterize the energy status of the coherent structure and which gave the most information for practical work, elaboration of composition and evaluation of stability. These functions and parameters are the following: flow curves, viscosity vs shear time and viscosity vs temperature functions, Bingham-type yield value, plastic viscosity, structure breakdown rate constant, activation energy.

  17. Dilated cardiomyopathy in cats - A case report

    Directory of Open Access Journals (Sweden)

    K. Jeyaraja


    Full Text Available Two cats were brought to Madras Veterinary College Teaching Hospital with the history and clinical signs suggestive of congestive heart failure ie, coughing, exercise intolerance, dyspnea, abdominal distension etc. There was history of feeding the cat with home made diet in one case and in other with commercial dog food. Based on electrocardiographic, radiographic and echocardiographic findings, the diagnosis of dilated cardiomyopathy was done in both the cases. The cases were managed with enalapril maleate, furosemide, dietary taurine supplementation and other supportive therapy. Among these two cases, one cat died on 2nd day of treatment and the other showed recovery after 8 days of treatment. [Vet World 2013; 6(4.000: 226-227

  18. A Case Report of Reversible Dilated Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Abhishek Singhai


    Full Text Available Dilated cardiomyopathy (DCM is mostly an idiopathic disease with a progressive and irreversible course. It carries poor prognosis and outcome. Rarely, a reversible metabolic etiology that is amenable to specific therapy is identified. Alteration in thyroid status can lead to changes in systolic and diastolic function of left ventricle. Heart is sensitive to thyroid hormone changes, and cardiac disorders are commonly associated with both hyper and hypothyroidism. Diastolic dysfunction is the most common abnormality reported in hypothyroidism. In systolic function, prolonged systolic time interval or normal cardiac function has been reported by most workers. DCM is a rare presentation of hypothyroidism. Here, we report a case of 40-year-old female diagnosed with DCM due to hypothyroidism

  19. Isolated dilated pupil: Is it adie's pupil?

    Directory of Open Access Journals (Sweden)

    Uma Sinharoy


    Full Text Available Adie's tonic pupil, though well known in literature is a rarity in practice. Few case reports have mentioned the occurrence of Adie's pupil during a migraine attack. We report a young female with a history of migraine without aura presenting with asymmetric pupils during migraine attack. Her right pupil was dilated, unresponsive to light with poor response to near reflex. She also had a bilateral loss of ankle jerks. In 0.125% pilocarpine test, the affected pupil responded significantly, and Holmes Adie's syndrome was diagnosed. The patient remained asymptomatic after adjustment of refraction of the right eye for the near vision. It is usually a benign condition. Early clinical detection of such condition is necessary to prevent unnecessary and costly investigations as well to reassure the patient.

  20. Intraventricular vortex properties in nonischemic dilated cardiomyopathy (United States)

    Benito, Yolanda; Alhama, Marta; Yotti, Raquel; Martínez-Legazpi, Pablo; del Villar, Candelas Pérez; Pérez-David, Esther; González-Mansilla, Ana; Santa-Marta, Cristina; Barrio, Alicia; Fernández-Avilés, Francisco; del Álamo, Juan C.


    Vortices may have a role in optimizing the mechanical efficiency and blood mixing of the left ventricle (LV). We aimed to characterize the size, position, circulation, and kinetic energy (KE) of LV main vortex cores in patients with nonischemic dilated cardiomyopathy (NIDCM) and analyze their physiological correlates. We used digital processing of color-Doppler images to study flow evolution in 61 patients with NIDCM and 61 age-matched control subjects. Vortex features showed a characteristic biphasic temporal course during diastole. Because late filling contributed significantly to flow entrainment, vortex KE reached its maximum at the time of the peak A wave, storing 26 ± 20% of total KE delivered by inflow (range: 1–74%). Patients with NIDCM showed larger and stronger vortices than control subjects (circulation: 0.008 ± 0.007 vs. 0.006 ± 0.005 m2/s, respectively, P = 0.02; KE: 7 ± 8 vs. 5 ± 5 mJ/m, P = 0.04), even when corrected for LV size. This helped confining the filling jet in the dilated ventricle. The vortex Reynolds number was also higher in the NIDCM group. By multivariate analysis, vortex KE was related to the KE generated by inflow and to chamber short-axis diameter. In 21 patients studied head to head, Doppler measurements of circulation and KE closely correlated with phase-contract magnetic resonance values (intraclass correlation coefficient = 0.82 and 0.76, respectively). Thus, the biphasic nature of filling determines normal vortex physiology. Vortex formation is exaggerated in patients with NIDCM due to chamber remodeling, and enlarged vortices are helpful for ameliorating convective pressure losses and facilitating transport. These findings can be accurately studied using ultrasound. PMID:24414062

  1. Rheological study of chitosan in solution

    International Nuclear Information System (INIS)

    Silva, Italo Guimaraes Medeiros da; Alves, Keila dos Santos; Balaban, Rosangela de Carvalho


    Chitosan is an abundant biopolymer with remarkable physicochemical and biological properties, usually employed in a wide range of applications. It acts as a cationic polyelectrolyte in aqueous acid solutions, leading to unique characteristics. In this work, chitosan was characterized by 1 H NMR and its rheological behavior were studied as function of chitosan sample, shear rate, polymer concentration, ionic strength, time and temperature. In order to calculate rheological parameters and to understand the macromolecular dynamic in solution, the Otswald-de Waele model was fitted. (author)

  2. In situ rheology of yeast biofilms. (United States)

    Brugnoni, Lorena I; Tarifa, María C; Lozano, Jorge E; Genovese, Diego


    The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p rheology and contribute to a thin body of knowledge about fungal biofilm formation.

  3. Becker and Lomnitz rheological models: A comparison (United States)

    Mainardi, Francesco; Spada, Giorgio


    The viscoelastic material functions for the Becker and the Lomnitz rheological models, sometimes employed to describe the transient flow of rocks, are studied and compared. Their creep functions, which are known in a closed form, share a similar time dependence and asymptotic behavior. This is also found for the relaxation functions, obtained by solving numerically a Volterra equation of the second kind. We show that the two rheologies constitute a clear example of broadly similar creep and relaxation patterns associated with neatly distinct retardation spectra, for which analytical expressions are available.

  4. Rheology of dense granular chute flow: simulations to experiments

    Directory of Open Access Journals (Sweden)

    Bharathraj S


    Full Text Available Granular chute flow simulations reveal an interesting transition from a random disordered structure to an ordered one with hexagonally ordered sheets of spherical particles, when the base roughness is modulated. Two types of base roughness are considered. The first is a fixed base, where glued spherical particles form the base, and the base roughness is varied by changing the ratio of diameters of the base and flowing particles. In the second sinusoidal base, a smooth wall with sinusoidal height variation is used; the amplitude and wavelength of the base modulation determine the base roughness. The transition is studied as a function of these roughness parameters. For the fixed base, there is a critical base particle diameter below which ordered states are observed. For the sinusoidal base, the critical amplitude increases linearly with the wavelength at lower wavelengths, reaches a maximum depending on the height of the flowing layer, and then decreases as the wavelength is further increased. There is flow for angles of inclination from 15 ° ≤ θ ≤ 25 ° for the ordered state and 20 ° ≤ θ ≤ 25 ° for the disordered state. Flow confinement by sidewalls also influences the rheology of the system and we see that the ordering is induced by the sidewalls as well. Experiments on chute flow at low angles indicate the presence of two types of rheology depending on the system height. A transition is observed from an erodible base configuration, where a dead zone at the bottom supports a free surface reposing at the top, to a Bagnold rheology with considerable slip at the bottom.

  5. Physical, microbiological and rheological properties of probiotic yogurt supplemented with grape extract. (United States)

    Felix da Silva, Denise; Junior, Nelson Nunes Tenório; Gomes, Raquel Guttierres; Dos Santos Pozza, Magali Soares; Britten, Michel; Matumoto-Pintro, Paula Toshimi


    In this study, yogurt was supplemented with 1.5 and 3.0 g L -1 of grape extract, inoculated culture containing Streptococcus thermophilus , Lactobacillus bulgaricus , Lactobacillus acidophilus and Bifidobacterium bb12 bifidum , fermented and stored at 4 °C. Acid production, microbial growth, gel strength, syneresis, rheological and sensory properties were studied. An increase in grape extract concentration extended fermentation time. Bacterial strains were found in at least 109 CFU100 g -1 of yogurt showing the possibility of probiotic yogurt production with grape extract. Gel strength decreased with increasing concentration of grape extract while syneresis increased. The addition of grape extract changed the dilatant behavior to a pseudoplastic behavior, decreased yield stress, whereas k values increased. Sensory attributes (color, flavor, taste, texture and appearance) didn't differ significantly.

  6. Synthesis, rheology and forming of Y-Ba-Cu-O ceramics

    International Nuclear Information System (INIS)

    Green, T.M.


    A chemical synthesis route is discussed which results in a low- temperature precursor to Y-Ba-Cu-O ceramics; it is based on use of molten Ba(OH) 2 ·8H 2 O flux. Two different chemical systems have been examined; the first one, based on nitrate salts, has been demonstrated to be a viable precursor material for tape casting and extrusion; the second, made from acetate salts, has been used for powder synthesis and extrusion. Rheology of pastes shows that their flow may be fit to either Bingham Plastic or Hershel- Bulkley models. Yield stress is controlled in both pastes by volume fraction solids. Viscosity also follows solids loading in the paste. Shear thinning is controlled by colloidal nature of precursor. The paste has colloidal microstructure. Comparison of concentric cylinder rheometry and piston extrusion rheometry shows order of magnitude differences in yield stress, resulting from the test method and paste dilation

  7. The Evaluation of Endoscopic Balloon Dilation Treatment for

    Directory of Open Access Journals (Sweden)

    Shokri-Shirvani Javad


    Full Text Available Balloon dilatation of stricture is one of the new treatment methods among patients with gastric outlet obstruction (GOO. However, the prevalence and underlying etiologies of GOO in various populations are different. The goal of the present study was to determine the effectiveness of endoscopic balloon dilatation and factors that would affect its success rate patients with benign etiology for GOO. Forty-five patients with the symptoms of benign GOO were randomly selected. Gastric outlet was delineated using double channel videoendoscopy. The information of initial balloon dilation was collected from recorded files. Balloon dilatation was repeated during the mean follow up of 9.9 ± 5.8 months. The severity of gastric pain was measured immediately before balloon dilatation and one month after procedure and was rated on a 10 cm visual analogue scale. The mean age of patients was 43.7 ± 18.1 years and 86.7% of them were men. Furthermore, 71.1% were H pylori positive. Response rate to endoscopic balloon dilatation was 80% and 8 patients underwent surgical resection. Weight loss was more frequent in non-responding group. The pain severity was significantly reduced more in responding subjects. No meaningful relationships were found between the responses to balloon dilatation and positive H pylori and cigarette smoking. Endoscopic balloon dilation is safe and effective for most patients with benign gastric outlet obstruction and has favorable long-term outcome.

  8. 21 CFR 884.4260 - Hygroscopic Laminaria cervical dilator. (United States)


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hygroscopic Laminaria cervical dilator. 884.4260... Devices § 884.4260 Hygroscopic Laminaria cervical dilator. (a) Identification. A hygroscopic Laminaria... conical and expansible material made from the root of a seaweed (Laminaria digitata or Laminaria japonica...

  9. Micrograft dilators: in pursuit of the undetectable hairline. (United States)

    Marritt, E


    The process of single-hair transplanting, though providing obvious cosmetic advantages in hairline refinement, has long been considered too tedious and time consuming to be incorporated into standard transplant sessions. Micrograft dilators provide dilatation, organization, and hemostasis, while permitting large numbers of micrografts to be placed quickly and effortlessly below the standard transplanted hairline.

  10. Acute gastric dilatation secondary to septicemia in newborn: A rare ...

    African Journals Online (AJOL)

    ... case of acute gastric dilatation that developed in a two-days old child who was born premature and was suffering from septicemia and respiratory distress. The causes and the differential diagnosis of the rare condition are discussed. Keywords: Acute, dilatation, gastric, newborn. African Journal of Paediatric Surgery Vol.

  11. Molecular genetics of dilated cardiomyopathy in the Dobermann dog

    NARCIS (Netherlands)

    Stabej, Polona


    Canine dilated cardiomyopathy (DCM) is a disease of the myocardium associated with dilatation and impaired contraction of the ventricles. It primarily affects large and giant breed dogs with Dobermanns being one of the most frequently affected. The high prevalence of DCM in specific breeds suggests

  12. History of urethral catheters and their balloons: drainage, anchorage, dilation, and hemostasis. (United States)

    Marino, R A; Mooppan, U M; Kim, H


    Male urethral catheterization, as practiced in early Greece, was made possible by a sound knowledge of anatomy. It has been preserved by written tradition and advanced by the development of new materials. Balloon dilation, conceived and practiced more than 160 years ago by urologists, has undergone a similar cycle. Some useful ideas, once conceived, have been forgotten and have surfaced again, decades, sometimes centuries, later as new inventions.

  13. The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts (United States)

    Kolzenburg, S.; Di Genova, D.; Giordano, D.; Hess, K. U.; Dingwell, D. B.


    Storage and transport of silicate melts in the Earth's crust and their emplacement on the planet's surface occur almost exclusively at sub-liquidus temperatures. At these conditions, the melts undergo crystallization under a wide range of cooling-rates, deformation-rates, and oxygen fugacities (fO2). Oxygen fugacity is known to influence the thermodynamics and kinetics of crystallization in magmas and lavas. Yet, its influence on sub-liquidus rheology remains largely uncharted. We present the first rheological characterization of crystallizing lavas along natural cooling paths and deformation-rates and at varying fO2. Specifically, we report on apparent viscosity measurements for two crystallizing magmatic suspensions 1) at log ⁡ fO2 of -9.15 (quartz-fayalite-magnetite buffer, QFM, -2.1) and 2) in air. These fugacities span a range of reduced to oxidized conditions pertinent to magma migration and lava emplacement. We find that: 1) crystallization at constant cooling-rates results in a quasi-exponential increase in the apparent viscosity of the magmatic suspensions until they achieve their rheological cut off temperature (Tcutoff), where the melt effectively solidifies 2) the rheological departure and Tcutoff increase with increasing fO2 and 3) increasing fO2 results in decreased crystallization-rates. Based on the experimental results and by comparison with previous rheological isothermal studies we propose a generalisation of the effect of fO2 on the dynamic rheological evolution of natural magmatic and volcanic suspensions. We further discuss the implications for magmatic transport in plumbing and storage systems (e.g. conduits, dikes and magma chambers) and during lava flow emplacement.

  14. From Reactor to Rheology in LDPE Modeling

    International Nuclear Information System (INIS)

    Read, Daniel J.; Das, Chinmay; Auhl, Dietmar; McLeish, Tom C. B.; Kapnistos, Michael; Doelder, Jaap den; Vittorias, Iakovos


    In recent years the association between molecular structure and linear rheology has been established and well-understood through the tube concept and its extensions for well-characterized materials (e.g. McLeish, Adv. Phys. 2002). However, for industrial branched polymeric material at processing conditions this piece of information is missing. A large number of phenomenological models have been developed to describe the nonlinear response of polymers. But none of these models takes into account the underlying molecular structure, leading to a fitting procedure with arbitrary fitting parameters. The goal of applied molecular rheology is a predictive scheme that runs in its entirety from the molecular structure from the reactor to the non-linear rheology of the resin. In our approach, we use a model for the industrial reactor to explicitly generate the molecular structure ensemble of LDPE's, (Tobita, J. Polym. Sci. B 2001), which are consistent with the analytical information. We calculate the linear rheology of the LDPE ensemble with the use of a tube model for branched polymers (Das et al., J. Rheol. 2006). We then, separate the contribution of the stress decay to a large number of pompom modes (McLeish et al., J. Rheol. 1998 and Inkson et al., J. Rheol. 1999) with the stretch time and the priority variables corresponding to the actual ensemble of molecules involved. This multimode pompom model allows us to predict the nonlinear properties without any fitting parameter. We present and analyze our results in comparison with experimental data on industrial materials


    The solution rheology of different generations of hyperbranched polyesters in N-methyl-2- pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amido...

  16. Rheological characterization of media containing Penicillium chrysogenum

    DEFF Research Database (Denmark)

    Pedersen, Annemarie Gade; Bundgaard-Nielsen, Mikael; Nielsen, Jens


    Samples from fed-batch fermentations of Penicillium chrysogenum on complex medium are rheologically characterized. The behavior is well described by a power law model for which the parameters are estimates. Furthermore, two types of model media are characterized and compared with the real...

  17. Rheological properties of olefinic thermoplastic elastomer blends

    NARCIS (Netherlands)

    Sengers, W.G.F.


    Thermoplastic Elastomers (TPE) are a class of materials that have rubber-like properties and can be processed like thermoplastic polymers. In this thesis, the rheological properties of two TPE blends are correlated to their morphology. The thermoplastic vulcanisates (TPV) consist of micron-sized,

  18. Examination of rheological and physicochemical characteristics in ...

    African Journals Online (AJOL)

    The aim of the study was to determine the effect of the biological origin and temperature on rheological and physicochemical characteristics of honey. The honey of the selected varieties differed in color, scent, microstructure, total acidity, moisture, and pH. The level of moisture statistically significantly correlated with the ...

  19. Rheological and textural properties of cosmetic emulsions

    Czech Academy of Sciences Publication Activity Database

    Morávková, Tereza; Štern, Petr


    Roč. 21, č. 3 (2011), č. článku 35200. ISSN 1430-6395 Institutional research plan: CEZ:AV0Z20600510 Keywords : cosmetic emulsions * rheology * texture * sensory analysis * psychorheology Subject RIV: BK - Fluid Dynamics Impact factor: 1.000, year: 2011

  20. Rheological Design of Sustainable Block Copolymers (United States)

    Mannion, Alexander M.

    Block copolymers are extremely versatile materials that microphase separate to give rise to a rich array of complex behavior, making them the ideal platform for the development of rheologically sophisticated soft matter. In line with growing environmental concerns of conventional plastics from petroleum feedstocks, this work focuses on the rheological design of sustainable block copolymers--those derived from renewable sources and are degradable--based on poly(lactide). Although commercially viable, poly(lactide) has a number of inherent deficiencies that result in a host of challenges that require both creative and practical solutions that are cost-effective and amenable to large-scale production. Specifically, this dissertation looks at applications in which both shear and extensional rheology dictate performance attributes, namely chewing gum, pressure-sensitive adhesives, and polymers for blown film extrusion. Structure-property relationships in the context of block polymer architecture, polymer composition, morphology, and branching are explored in depth. The basic principles and fundamental findings presented in this thesis are applicable to a broader range of substances that incorporate block copolymers for which rheology plays a pivotal role.


    African Journals Online (AJOL)


    Dec 31, 2012 ... The microstructure and scaling of rheological properties of colloidal gels of bentonite investigated as a function ... additives, and temperature can effect dispersion stability. Repulsive interparticles ... degree of interparticles attraction, However, the influence that interparticle attractions have on floc structure ...

  2. Comparison of Chemical Nano Structure, Rheological and ...

    African Journals Online (AJOL)

    In this research, chemical nano structures, rheological and mechanical properties of long oil alkyd resin which was synthesized using different polybasic acid catalysts have been studied. These catalyst were phosphoric acid, 1,2,4-benzene tricarboxylic acid and succinic acid. The new compounds were compared with ...


    Directory of Open Access Journals (Sweden)

    Aurelia Ionescu


    Full Text Available Chickpea proteins are used as ingredients in comminuted sausage products and many oriental textured foods. Rheological behaviour of chickpea protein concentrate was studied using a controlled stress rheometer. The protein dispersion prepared with phosphate buffer at pH 7.0 presented non-Newtonian shear thinning behaviour and rheological data well fitted to the Sisko, Carreau and Cross models. The viscoelastic properties of the chickpea protein suspensions were estimated by measuring the storage and loss moduli in oscillatory frequency conditions (0.1-10 Hz at 20°C. Moreover, thermally induced gelation of the chickpea proteins (16, 24 and 36% was studied at pH 7.0 and 4.5 in the temperature range 50 to 100oC and salt concentration ranging from 0 to 1 M. Gelling behaviour was quantified by means of dynamic rheological measurements. Gels formation was preceded by the decrease of storage modulus and loss moduli, coupled with the increase of the phase angle (delta. The beginning of thermal gelation was influenced by protein concentration, pH and salt level. In all studied cases, storage modulus increased rapidly in the temperature range 70-90°C. All rheological parameters measured at 90°C were significantly higher at pH 4.5 compared to pH 7.0.

  4. Shear rheology of molten crumb chocolate. (United States)

    Taylor, J E; Van Damme, I; Johns, M L; Routh, A F; Wilson, D I


    The shear rheology of fresh molten chocolate produced from crumb was studied over 5 decades of shear rate using controlled stress devices. The Carreau model was found to be a more accurate description than the traditional Casson model, especially at shear rates between 0.1 and 1 s(-1). At shear rates around 0.1 s(-1) (shear stress approximately 7 Pa) the material exhibited a transition to a solid regime, similar to the behavior reported by Coussot (2005) for other granular suspensions. The nature of the suspension was explored by investigating the effect of solids concentration (0.20 chocolate was then compared with the rheology of (1) a synthetic chocolate, which contained sunflower oil in place of cocoa butter, and (2) a suspension of sugar of a similar size distribution (volume mean 15 mum) in cocoa butter and emulsifier. The chocolate and synthetic chocolate showed very similar rheological profiles under both steady shear and oscillatory shear. The chocolate and the sugar suspension showed similar Krieger-Dougherty dependency on volume fraction, and a noticeable transition to a stiff state at solids volume fractions above approximately 0.5. Similar behavior has been reported by Citerne and others (2001) for a smooth peanut butter, which had a similar particle size distribution and solids loading to chocolate. The results indicate that the melt rheology of the chocolate is dominated by hydrodynamic interactions, although at high solids volume fractions the emulsifier may contribute to the departure of the apparent viscosity from the predicted trend.

  5. Rheology and structure of milk protein gels

    NARCIS (Netherlands)

    Vliet, van T.; Lakemond, C.M.M.; Visschers, R.W.


    Recent studies on gel formation and rheology of milk gels are reviewed. A distinction is made between gels formed by aggregated casein, gels of `pure` whey proteins and gels in which both casein and whey proteins contribute to their properties. For casein' whey protein mixtures, it has been shown

  6. Cellulose nanoparticles as modifiers for rheology and fluid loss in bentonite water-based fluids. (United States)

    Li, Mei-Chun; Wu, Qinglin; Song, Kunlin; Qing, Yan; Wu, Yiqiang


    Rheological and filtration characteristics of drilling fluids are considered as two critical aspects to ensure the success of a drilling operation. This research demonstrates the effectiveness of cellulose nanoparticles (CNPs), including microfibrillated cellulose (MFC) and cellulose nanocrystals (CNCs) in enhancing the rheological and filtration performances of bentonite (BT) water-based drilling fluids (WDFs). CNCs were isolated from MFC through sulfuric acid hydrolysis. In comparison with MFC, the resultant CNCs had much smaller dimensions, more negative surface charge, higher stability in aqueous solutions, lower viscosity, and less evident shear thinning behavior. These differences resulted in the distinctive microstructures between MFC/BT- and CNC/BT-WDFs. A typical "core-shell" structure was created in CNC/BT-WDFs due to the strong surface interactions among BT layers, CNCs, and immobilized water molecules. However, a similar structure was not formed in MFC/BT-WDFs. As a result, CNC/BT-WDFs had superior rheological properties, higher temperature stability, less fluid loss volume, and thinner filter cakes than BT and MFC/BT-WDFs. Moreover, the presence of polyanionic cellulose (PAC) further improved the rheological and filtration performances of CNC/BT-WDFs, suggesting a synergistic effect between PAC and CNCs.

  7. Lubrication, adsorption, and rheology of aqueous polysaccharide solutions. (United States)

    Stokes, Jason R; Macakova, Lubica; Chojnicka-Paszun, Agnieszka; de Kruif, Cornelis G; de Jongh, Harmen H J


    Aqueous lubrication is currently at the forefront of tribological research due to the desire to learn and potentially mimic how nature lubricates biotribological contacts. We focus here on understanding the lubrication properties of naturally occurring polysaccharides in aqueous solution using a combination of tribology, adsorption, and rheology. The polysaccharides include pectin, xanthan gum, gellan, and locus bean gum that are all widely used in food and nonfood applications. They form rheologically complex fluids in aqueous solution that are both shear thinning and elastic, and their normal stress differences at high shear rates are found to be characteristic of semiflexible/rigid molecules. Lubrication is studied using a ball-on-disk tribometer with hydrophobic elastomer surfaces, mimicking biotribological contacts, and the friction coefficient is measured as a function of speed across the boundary, mixed, and hydrodynamic lubrication regimes. The hydrodynamic regime, where the friction coefficient increases with increasing lubricant entrainment speed, is found to depend on the viscosity of the polysaccharide solutions at shear rates of around 10(4) s(-1). The boundary regime, which occurs at the lowest entrainment speeds, depends on the adsorption of polymer to the substrate. In this regime, the friction coefficient for a rough substrate (400 nm rms roughness) is dependent on the dry mass of polymer adsorbed to the surface (obtained from surface plasmon resonance), while for a smooth substrate (10 nm rms roughness) the friction coefficient is strongly dependent on the hydrated wet mass of adsorbed polymer (obtained from quartz crystal microbalance, QCM-D). The mixed regime is dependent on both the adsorbed film properties and lubricant's viscosity at high shear rates. In addition, the entrainment speed where the friction coefficient is a minimum, which corresponds to the transition between the hydrodynamic and mixed regime, correlates linearly with the ratio

  8. CFD simulation of anaerobic digester with variable sewage sludge rheology. (United States)

    Craig, K J; Nieuwoudt, M N; Niemand, L J


    A computational fluid dynamics (CFD) model that evaluates mechanical mixing in a full-scale anaerobic digester was developed to investigate the influence of sewage sludge rheology on the steady-state digester performance. Mechanical mixing is provided through an impeller located in a draft tube. Use is made of the Multiple Reference Frame model to incorporate the rotating impeller. The non-Newtonian sludge is modeled using the Hershel-Bulkley law because of the yield stress present in the fluid. Water is also used as modeling fluid to illustrate the significant non-Newtonian effects of sewage sludge on mixing patterns. The variation of the sewage sludge rheology as a result of the digestion process is considered to determine its influence on both the required impeller torque and digester mixing patterns. It was found that when modeling the fluid with the Hershel-Bulkley law, the high slope of the sewage stress-strain curve at high shear rates causes significant viscous torque on the impeller surface. Although the overall fluid shear stress property is reduced during digestion, this slope is increased with sludge age, causing an increase in impeller torque for digested sludge due to the high strain rates caused by the pumping impeller. Consideration should be given to using the Bingham law to deal with high strain rates. The overall mixing flow patterns of the digested sludge do however improve slightly. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Effect of Amphiphiles on the Rheology of Triglyceride Networks (United States)

    Seth, Jyoti


    Networks of aggregated crystallites form the structural backbone of many products from the food, cosmetic and pharmaceutical industries. Such materials are generally formulated by cooling a saturated solution to yield the desired solid fraction. Crystal nucleation and growth followed by aggregation leads to formation of a space percolating fractal-network. It is understood that microstructural hierarchy and particle-particle interactions determine material behavior during processing, storage and use. In this talk, rheology of suspensions of triglycerides (TAG, like tristearin) will be explored. TAGs exhibit a rich assortment of polymorphs and form suspensions that are evidently sensitive to surface modifying additives like surfactants and polymers. Here, a theoretical framework will be presented for suspensions containing TAG crystals interacting via pairwise potentials. The work builds on existing models of fractal aggregates to understand microstructure and its correlation with material rheology. Effect of amphiphilic additives is derived through variation of particle-particle interactions. Theoretical predictions for storage modulus will be compared against experimental observations and data from the literature and micro structural predictions against microscopy. Such a theory may serve as a step towards predicting short and long-term behavior of aggregated suspensions formulated via crystallization.

  10. Influence of high power ultrasound on rheological and foaming properties of model ice-cream mixtures

    Directory of Open Access Journals (Sweden)

    Verica Batur


    Full Text Available This paper presents research of the high power ultrasound effect on rheological and foaming properties of ice cream model mixtures. Ice cream model mixtures are prepared according to specific recipes, and afterward undergone through different homogenization techniques: mechanical mixing, ultrasound treatment and combination of mechanical and ultrasound treatment. Specific diameter (12.7 mm of ultrasound probe tip has been used for ultrasound treatment that lasted 5 minutes at 100 percent amplitude. Rheological parameters have been determined using rotational rheometer and expressed as flow index, consistency coefficient and apparent viscosity. From the results it can be concluded that all model mixtures have non-newtonian, dilatant type behavior. The highest viscosities have been observed for model mixtures that were homogenizes with mechanical mixing, and significantly lower values of viscosity have been observed for ultrasound treated ones. Foaming properties are expressed as percentage of increase in foam volume, foam stability index and minimal viscosity. It has been determined that ice cream model mixtures treated only with ultrasound had minimal increase in foam volume, while the highest increase in foam volume has been observed for ice cream mixture that has been treated in combination with mechanical and ultrasound treatment. Also, ice cream mixtures having higher amount of proteins in composition had shown higher foam stability. It has been determined that optimal treatment time is 10 minutes.

  11. Rheology of Prepreg and Properties of Silica/bismaleimide Matrix Copper Clad Laminate

    Directory of Open Access Journals (Sweden)

    DAI Shankai


    Full Text Available The effects of the silica surface treated by coupling agents KH550, KH560 and KH570 on the rheological properties of bismaleimide (BMI resin system were investigated. The rigidity, coefficient of thermal expansion (CTE and thermal stability of the copper clad laminate (CCL were studied by DMA, TMA and TGA. The resin system containing silica surface treated by KH-560, comparing to KH550, KH570 and without surface treatment resin system has better rheological properties and low melt viscosity. The comprehensive properties of the copper clad laminate can be effectively improved by the introduction of silica in the resin system, exhibiting higher storage modulus and lower CTE compare to no silica in the CCL. When the silica mass fraction is 50%, the storage modulus is increased by 83% at 50℃, and the CTE below the glass transition temperature is decreased by 153%.

  12. Quantification of left ventricular dilatation in myocardial perfusion scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Mauren B. Azambuja, E-mail:, E-mail: [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil). Clinica Medica. Programa de Pos-Graduacao em Medicina e Ciencias da Saude; Azambuja, Roberto Alves [Hospital Sao Vicente de Paulo, Passo Fundo, RS (Brazil); Bodanese, Luiz Carlos [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil). Hospital Sao Lucas. Serv. de Cardiologia


    Background: the rate of transient dilatation can be determined by exercise testing or pharmacological stress test. It is unknown whether the type of stress has an impact on average transient dilatation index values. Objective: to compare average transient dilation index values in 99mTc-sestamibi scintigraphy in patients undergoing treadmill stress test, versus dipyridamole stress test. The secondary purpose was to evaluate the impact on the average index value by demographic characteristics, risk factors for coronary artery disease and severity of ischemia. Methods: the cross-sectional study included 200 patients between 40 and 70 years old, with or without risk factors for ischemic heart disease, with or without a previous diagnosis of ischemic heart disease. The separation between groups was sequential. The software 4D-MSPECT calculated the transient dilatation index and provided a scoring system for perfusion analysis. Results: the average transient dilation index value of the group undergoing exercise stress test was 1.06 ({+-}0.23). For the group undergoing the dipyridamole stress test, it was 1.10 ({+-}0.22); (p = 0.200). There was no association between the type of stress and the average transient dilatation index values. An association was found between the average index values and age only for those patients from the exercise test group (p = 0.009). Conclusion: the results of our study demonstrate that the transient dilation index does not differ when patients undergo exercise stress test on a treadmill or pharmacological stress by dipyridamole. (author)

  13. Emulsion stability and dilatational viscoelasticity of ovalbumin/chitosan complexes at the oil-in-water interface. (United States)

    Xiong, Wenfei; Ren, Cong; Tian, Mo; Yang, Xuejun; Li, Jing; Li, Bin


    The contribution of the emulsion rheological properties and the viscoelastic of the interface adsorbed layer to the emulsification mechanism of ovalbumin (OVA)-chitosan (CS) mixtures were investigated. In comparison to the treatment with OVA alone and OVA/CS mixtures at pH 4.0, the addition of CS at pH 5.5 increased the size distribution of emulsion droplets with significant flocculation through polyelectrolyte bridging, remarkably enhancing the emulsions stability against gravity creaming after storage at 25 °C for 14 days. The dynamic rheological properties indicated that the formation of the complex at pH 5.5 increased the elastic modulus (G') and apparent viscosity (η ∗ ) of the emulsions, which is useful for inhibiting creaming. Moreover, the complexation of OVA and CS at pH 5.5 increased the dilatational modulus (E), especially the elastic modulus (E d ), of the oil/water interfacial absorbed layer, which could reduce the droplet coalescence and therefore inhibit the growth of emulsion droplets. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Quadricuspid Aortic Valve Combined with Moderate Ascending Aortic Dilatation (United States)

    Uspenskiy, Vladimir E.; Osadchii, Alexei M.; Gordeev, Mikhail L.


    The quadricuspid aortic valve is a very uncommon malformation associated with aortic insufficiency, aortic stenosis, endocarditis, and ascending aortic dilatation. We report four cases of this aortic valve malformation. One patient with severe aortic regurgitation and moderate aortic dilatation required aortic valve replacement. Three patients had mild or moderate aortic insufficiency combined with moderate ascending aortic dilatation. These patients were referred to follow-up. The presented cases demonstrate that this aortic valve malformation may not be as rare as it appears and that attention must be paid to any quadricuspid findings during computed tomographic angiography and echocardiography. PMID:27390747

  15. Spatial Markov Semigroups Admit Hudson-Parthasarathy Dilations


    Skeide, Michael


    For many Markov semigroups dilations in the sense of Hudson and Parthasarathy, that is a dilation which is a cocycle perturbation of a noise, have been constructed with the help of quantum stochastic calculi. In these notes we show that every Markov semigroup on the algebra of all bounded operators on a separable Hilbert space that is spatial in the sense of Arveson, admits a Hudson-Parthasarathy dilation. In a sense, the opposite is also true. The proof is based on general results on the the...

  16. Characterization and Long-Term Prognosis of Postmyocarditic Dilated Cardiomyopathy Compared With Idiopathic Dilated Cardiomyopathy. (United States)

    Merlo, Marco; Anzini, Marco; Bussani, Rossana; Artico, Jessica; Barbati, Giulia; Stolfo, Davide; Gigli, Marta; Muça, Matilda; Naso, Paola; Ramani, Federica; Di Lenarda, Andrea; Pinamonti, Bruno; Sinagra, Gianfranco


    Dilated cardiomyopathy (DC) is the final common pathway of different pathogenetic processes and presents a significant prognostic heterogeneity, possibly related to its etiologic variety. The characterization and long-term prognosis of postmyocarditic dilated cardiomyopathy (PM-DC) remain unknown. This study assesses the clinical-instrumental evolution and long-term prognosis of a large cohort of patients with PM-DC. We analyzed 175 patients affected with DC consecutively enrolled from 1993 to 2008 with endomyocardial biopsy (EMB) data available. PM-DC was defined in the presence of borderline myocarditis at EMB or persistent left ventricular dysfunction 1 year after diagnosis of active myocarditis at EMB. Other patients were defined as affected by idiopathic dilated cardiomyopathy (IDC). Analysis of follow-up evaluations was performed at 24, 60, and 120 months. We found 72 PM-DC of 175 enrolled patients (41%). Compared with IDC, patients with PM-DC were more frequently females and less frequently presented a familial history of DC. No other baseline significant differences were found. During the long-term follow-up (median 154, first to third interquartile range 78 to 220 months), patients with PM-DC showed a trend toward slower disease progression. Globally, 18 patients with PM-DC (25%) versus 49 with IDC (48%) experienced death/heart transplantation (p = 0.045). The prognostic advantage for patients with PM-DC became significant beyond 40 months of follow-up. At multivariable time-dependent Cox analysis, PM-DC was confirmed to have a global independent protective role (hazard ratio 0.53, 95% confidence interval 0.28 to 0.97, p = 0.04). In conclusion, PM-DC is characterized by better long-term prognosis compared with IDC. An exhaustive etiologic characterization appears relevant in the prognostic assessment of DC. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Rheological properties of human saliva

    NARCIS (Netherlands)

    Waterman, H.A.; Blom, C.; Holterman, H.J.; 's Gravenmade, E.J.; Mellema, J.


    From measurements with a Couette-type viscometer provided with a guard ring it was shown that at the saliva-air interface a protein layer is adsorbed. Measurements of the surface shear modulus of this layer on saliva of 7 healthy subjects were performed at a frequency of about 70 Hz and a

  18. Viscoelastic behavior of human lamin A proteins in the context of dilated cardiomyopathy.

    Directory of Open Access Journals (Sweden)

    Avinanda Banerjee

    Full Text Available Lamins are intermediate filament proteins of type V constituting a nuclear lamina or filamentous meshwork which lines the nucleoplasmic side of the inner nuclear membrane. This protein mesh provides a supporting scaffold for the nuclear envelope and tethers interphase chromosome to the nuclear periphery. Mutations of mainly A-type lamins are found to be causative for at least 11 human diseases collectively termed as laminopathies majority of which are characterised by aberrant nuclei with altered structural rigidity, deformability and poor mechanotransduction behaviour. But the investigation of viscoelastic behavior of lamin A continues to elude the field. In order to address this problem, we hereby present the very first report on viscoelastic properties of wild type human lamin A and some of its mutants linked with Dilated cardiomyopathy (DCM using quantitative rheological measurements. We observed a dramatic strain-softening effect on lamin A network as an outcome of the strain amplitude sweep measurements which could arise from the large compliance of the quasi-cross-links in the network or that of the lamin A rods. In addition, the drastic stiffening of the differential elastic moduli on superposition of rotational and oscillatory shear stress reflect the increase in the stiffness of the laterally associated lamin A rods. These findings present a preliminary insight into distinct biomechanical properties of wild type lamin A protein and its mutants which in turn revealed interesting differences.

  19. Changes in overall ventricular myocardial architecture in the setting of a porcine animal model of right ventricular dilation

    DEFF Research Database (Denmark)

    Agger, Peter; Ilkjær, Christine; Laustsen, Christoffer


    BACKGROUND: Chronic pulmonary regurgitation often leads to myocardial dysfunction and heart failure. It is not fully known why secondary hypertrophy cannot fully protect against the increase in wall stress brought about by the increased end-diastolic volume in ventricular dilation. It has been...... of their hearts permitted measurement of the orientation of the cardiomyocytes. RESULTS: The helical angles in the right ventricle approached a more circumferential orientation in the setting of right ventricular RV dilation (p = 0.007), with an increased proportion of surface-parallel cardiomyocytes. In contrast...... the achievement of normalisation of cardiomyocytic strain, affecting overall contractility. We suggest that the aetiology of the cardiac failure induced by right vetricular dilation may be partly explained by morphological changes in the myocardium itself....

  20. An acidic heteropolysaccharide from Mesona chinensis: Rheological properties, gelling behavior and texture characteristics. (United States)

    Lin, Lihua; Shen, Mingyue; Liu, Suchen; Tang, Wei; Wang, Zhijun; Xie, Mingyong; Xie, Jianhua


    Polysaccharide from Mesona chinensis is becoming increasingly attractive focus because of its gelling property and biological activities. In this study, the rheological properties of an acidic heteropolysaccharide from Mesona chinensis (MCP) were investigated in dilute and semidilute solutions. Dynamic rheology was systematically conducted to investigate the effects of concentration, temperature, pH values, salts and freeze-thaw variations on the rheological properties of MCP. Results showed that the rheological properties of MCP exhibited pseudoplastic characteristic and "gel-like" behavior by the flow behavior detection. A closed hysteresis loop was formed when the MCP concentration reached 4%, and the Gel was generated when the MCP concentration reached 5%. The storage modulu (G') and loss modulu (G″) of MCP solution were increased with increasing oscillation frequency at concentration of 4% and 5%. The phase angel (tanδ) was less than 1, indicating MCP was a weak gel in linear viscoelastic region. The gel exhibited favourable textural properties when MCP at concentration 5%. The scanning electron microscope (SEM) verified MCP had a unique lotus leaf-like shape with some small irregular round-like rods surface morphology. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Interfacial transport processes and rheology

    CERN Document Server

    Brenner, Howard


    This textbook is designed to provide the theory, methods of measurement, and principal applications of the expanding field of interfacial hydrodynamics. It is intended to serve the research needs of both academic and industrial scientists, including chemical or mechanical engineers, material and surface scientists, physical chemists, chemical and biophysicists, rheologists, physiochemical hydrodynamicists, and applied mathematicians (especially those with interests in viscous fluid mechanics and continuum mechanics).As a textbook it provides materials for a one- or two-semester graduate-level

  2. Dilation-and-modulation systems on the half real line

    Directory of Open Access Journals (Sweden)

    Yun-Zhang Li


    Full Text Available Abstract Translation, dilation, and modulation are fundamental operations in wavelet analysis. Affine frames based on translation-and-dilation operation and Gabor frames based on translation-and-modulation operation have been extensively studied and seen great achievements. But dilation-and-modulation frames have not. This paper addresses a class of dilation-and-modulation systems in L 2 ( R + $L^{2}(\\mathbb {R}_{+}$ . We characterize frames, dual frames, and Parseval frames in L 2 ( R + $L^{2}(\\mathbb {R}_{+}$ generated by such systems. Interestingly, it turns out that, for such systems, Parseval frames, orthonormal bases, and orthonormal systems are mutually equivalent to each other, while this is not the case for affine systems and Gabor systems.

  3. Autologous bone marrow mononuclear cell delivery to dilated ...

    African Journals Online (AJOL)

    Autologous bone marrow mononuclear cell delivery to dilated cardiomyopathy patients: A clinical trial. PLN Kaparthi, G Namita, LK Chelluri, VSP Rao, PK Shah, A Vasantha, SK Ratnakar, K Ravindhranath ...

  4. Analytical rheology of metallocene-catalyzed polyethylenes (United States)

    Shanbhag, Sachin; Takeh, Arsia


    A computational algorithm that seeks to invert the linear viscoelastic spectrum of single-site metallocene-catalyzed polyethylenes is presented. The algorithm uses a general linear rheological model of branched polymers as its underlying engine, and is based on a Bayesian formulation that transforms the inverse problem into a sampling problem. Given experimental rheological data on unknown single-site metallocene- catalyzed polyethylenes, it is able to quantitatively describe the range of values of weight-averaged molecular molecular weight, MW , and average branching density, bm , consistent with the data. The algorithm uses a Markov-chain Monte Carlo method to simulate the sampling problem. If, and when information about the molecular weight is available through supplementary experiments, such as chromatography or light scattering, it can easily be incorporated into the algorithm, as demonstrated. Financial support from NSF DMR 0953002.

  5. Rheology essentials of cosmetic and food emulsions

    CERN Document Server

    Brummer, Rüdiger


    Cosmetic emulsions exist today in many forms for a wide variety of applications, including face and hand creams for normal, dry or oily skin, body milks and lotions, as well as sun-block products. Keeping track of them and their properties is not always easy despite informative product names or partial names (e.g. hand or face cream) that clearly indicate their use and properties. This practical manual provides a detailed overview that describes the key properties and explains how to measure them using modern techniques. Written by an expert in flows and flow properties, it focuses on the application of rheological (flow) measurements to cosmetic and food emulsions and the correlation of these results with findings from other tests. Beginning with a brief history of rheology and some fundamental principles, the manual describes in detail the use of modern viscometers and rheometers, including concise explanations of the different available instruments. But the focus remains on practical everyday lab procedure...

  6. Effects of hydration on blood rheology. (United States)

    Vlastos, George A; Tangney, Christine C; Rosenson, Robert S


    This study investigated the impact of oral fluid intake on blood rheology of 17 healthy adults following a 12-14 hour overnight fast from food and drink. An oral fluid load of 500 ml was consumed every 30 minutes for 2 hours. Blood viscosity values at shear rates of 1, 10 and 100 s(-1) were reduced (p<0.05 to p<0.01) at 30 and 120 minutes following hydration; however, these differences were not significant after hematocrit correction. With fluid intake, both uncorrected and corrected viscous component of blood viscoelasticity at oscillatory shear rate of 1 s(-1) and at a constant frequency of 2 Hz were reduced (p<0.05 to p<0.001) at all time points as compared to fasting values. The corrected elastic component of blood viscoelasticity increased 90 minutes after hydration (p<0.05). An overnight fast is accompanied by rheological abnormalities that are altered by fluid intake.

  7. Shear rheology of lipid monolayers and insights on membrane fluidity (United States)

    Espinosa, Gabriel; López-Montero, Iván; Monroy, Francisco; Langevin, Dominique


    The concept of membrane fluidity usually refers to a high molecular mobility inside the lipid bilayer which enables lateral diffusion of embedded proteins. Fluids have the ability to flow under an applied shear stress whereas solids resist shear deformations. Biological membranes require both properties for their function: high lateral fluidity and structural rigidity. Consequently, an adequate account must include, in addition to viscosity, the possibility for a nonzero shear modulus. This knowledge is still lacking as measurements of membrane shear properties have remained incomplete so far. In the present contribution we report a surface shear rheology study of different lipid monolayers that model distinct biologically relevant situations. The results evidence a large variety of mechanical behavior under lateral shear flow. PMID:21444777

  8. Modelling laminar transport phenomena in a Casson rheological fluid from an isothermal sphere with partial slip

    Directory of Open Access Journals (Sweden)

    Subbarao Annasagaram


    Full Text Available The laminar boundary layer flow and heat transfer of Casson non-Newtonian fluid from a permeable isothermal sphere in the presence of thermal and hydrodynamic slip conditions is analyzed. The surface of the sphere is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite-difference scheme. Increasing velocity slip induces acceleration in the flow near the surface of the sphere and the reverse effect further from the surface. Increasing velocity slip consistently enhances temperatures throughout the boundary layer regime. An increase in thermal slip parameter strongly decelerates the flow and also reduces temperatures in the boundary layer regime. An increase in Casson rheological parameter acts to elevate considerably the skin friction (non-dimensional wall shear stress and this effect is pronounced at higher values of tangential coordinate. Temperatures are however very slightly decreased with increasing values of Casson rheological parameter. Increasing mass flow injection (blowing at the sphere surface causes a strong acceleration, whereas increasing suction is found to induce the opposite effect. The study finds applications in rheological chocolate food processing.

  9. Rheological evaluation of pretreated cladding removal waste

    International Nuclear Information System (INIS)

    McCarthy, D.; Chan, M.K.C.; Lokken, R.O.


    Cladding removal waste (CRW) contains concentrations of transuranic (TRU) elements in the 80 to 350 nCi/g range. This waste will require pretreatment before it can be disposed of as glass or grout at Hanford. The CRW will be pretreated with a rare earth strike and solids removal by centrifugation to segregate the TRU fraction from the non-TRU fraction of the waste. The centrifuge centrate will be neutralized with sodium hydroxide. This neutralized cladding removal waste (NCRW) is expected to be suitable for grouting. The TRU solids removed by centrifugation will be vitrified. The goal of the Rheological Evaluation of Pretreated Cladding Removal Waste Program was to evaluate those rheological and transport properties critical to assuring successful handling of the NCRW and TRU solids streams and to demonstrate transfers in a semi-prototypic pumping environment. This goal was achieved by a combination of laboratory and pilot-scale evaluations. The results obtained during these evaluations were correlated with classical rheological models and scaled-up to predict the performance that is likely to occur in the full-scale system. The Program used simulated NCRW and TRU solid slurries. Rockwell Hanford Operations (Rockwell) provided 150 gallons of simulated CRW and 5 gallons of simulated TRU solid slurry. The simulated CRW was neutralized by Pacific Northwest Laboratory (PNL). The physical and rheological properties of the NCRW and TRU solid slurries were evaluated in the laboratory. The properties displayed by NCRW allowed it to be classified as a pseudoplastic or yield-pseudoplastic non-Newtonian fluid. The TRU solids slurry contained very few solids. This slurry exhibited the properties associated with a pseudoplastic non-Newtonian fluid

  10. The Evaluation of Endoscopic Balloon Dilation Treatment for Benign

    Directory of Open Access Journals (Sweden)

    H. Ghofrani


    Full Text Available Background and ObjectiveBalloon dilatation of stricture is one of the new treatment methods for patients with Gastric Outlet Obstruction (GOO. Prevalence and underlying etiologies of GOO in various populations are different. The goal of the present study was to determine the effectiveness of endoscopic balloon dilatation and factors that could affect method advantage among patients with benign etiology for GOO. Methods Forty-five patients with symptoms of benign GOO were randomly selected. The mean age of patients was 43.7±18.1 years and 86.7% of them were men. Gastric outlet was delineated using double channel videoendoscopy. The severity of gastric pain was measured by VAS test immediately before and one month after balloon dilatation. Patients were followed after procedure weekly (for the first month and then monthly. Balloon dilatation was repeated for 27% patients during the follow up period.ResultsPatients were followed for 9.9±5.8 months. Furthermore, 71.1% were H. pylori positive. Positive response percent to endoscopic balloon dilatation was 80% and eight patients were took under surgical resection. Weight loss was seen frequently in the non-respondent group. The pain severity was significantly reduced in respondent subjects. No meaningful correlations were found between the response to balloon dilatation and positive H. pylori and cigarette smoking.ConclusionEndoscopic balloon dilatation is a safe and effective method for treating most of patients with benign gastric outlet obstruction and has favorable long-term outcome. Keywords: Endoscopy, Gastric Outlet Obstruction (GOO, Balloon Dilatation

  11. Minimal Cuntz–Krieger dilations and representations of Cuntz ...

    Indian Academy of Sciences (India)

    A-relations we show that there exists a unique minimal dilation to generators of Cuntz–. Krieger algebras or its ... properties of the minimal Cuntz–Krieger dilation and the WOT-closed algebra generated by it is studied in terms ... is equivalent to saying that the operator (T1,...,Tn) from H ⊕···⊕ H (n-times) to H is a contraction.

  12. Non-obstructive cecal dilatation and perforation after cesarean section

    DEFF Research Database (Denmark)

    Sperling, Lene; Schantz, A L; Toftager-Larsen, K


    A case of non-obstructive cecal dilatation and perforation after cesarean section is reported, with a review of the literature on the diagnosis and management of this entity. Fifteen cases have been described. Attention is called to this rare complication and to the accompanying pseudo......-obstructive syndrome, the diagnosis of which is important in order to avoid cecal perforation. Non-obstructive cecal dilatation is a life threatening complication to cesarean section, and immediate surgical intervention is important....

  13. An unusual triad: Bilateral dilated odontoma, hypodontia and peg laterals

    Directory of Open Access Journals (Sweden)

    Alphy Alphonsa Sebastian


    The aim of this case report is to present a rare case of bilateral dilated odontoma affecting a microdontic permanent lateral incisor in a 30 year old female patient with hypodontia and peglateral teeth with its clinical, radiological and histological features, which has yet been not reported. Bilateral presence of dilated odontoma is not a common occurrence, although a single tooth involvement in each case has been reported in the literature.

  14. Sciatica caused by a dilated epidural vein: MR findings

    Energy Technology Data Exchange (ETDEWEB)

    Demaerel, P.; Petre, C.; Wilms, G. [Dept. of Radiology, Catholic University of Leuven (Belgium); Plets, C. [Dept. of Neurosurgery, Catholic University of Leuven (Belgium)


    We report the MR imaging findings in a 41-year-old woman presenting with sudden low back pain and sciatica. At surgery a dilated epidural vein was found compressing the nerve root. The MR findings may suggest the diagnosis. Magnetic resonance imaging of a dilated epidural vein or varix causing sciatica has not been reported until now. (orig.) (orig.) With 1 fig., 4 refs.


    Directory of Open Access Journals (Sweden)

    Tamara de Souza Jorge


    Full Text Available Avocado oil is rich in bioactive compounds, which can improve human health by acting as an antioxidant. It may be extracted from different varieties of avocado, such as Margarida and Hass varieties, each of them with particular characteristics. Aiming to evaluate the differences between them, avocado fruits and pulps from these were analyzed according to their physicochemical characteristics. After extracted, the oils had their bioactive characteristics studied and rheological behavior determined through a rotational rheometer. They were then compared to commercial avocado oil. The fruits of Margarida variety had greater size, higher weight (664.51 g, and higher pulp yield (72.19% than Hass variety, which showed higher lipid content (65.29 g/100 g dry basis. The commercial oil showed less primary oxidative degradation, whereas Margarida variety had a lower level of secondary degradation products as well as a higher content of bioactive compounds, such as phytosterols (999.60 mg/kg and tocopherols (36.73 mg/kg. The rheological behaviors of both oils were appropriately described through Newton model, with R2 > 0.999 for all temperatures. By an Arrhenius type equation, it was verified that Hass's rheological parameters are more influenced by temperature than Margarida and commercial oil, presenting activation energy of 33.6 kJ/mol.

  16. Treatment of urethral strictures with balloon dilation: A forgotten tale

    Directory of Open Access Journals (Sweden)

    Konstantinos Stamatiou


    Full Text Available Urethral stricture is a common condition that can lead to serious complications such as urinary infections and renal insufficiency secondary to urinary retention. Treatment options include catheterization and dilation, urethroplasty and endoscopic internal urethrotomy as well. Although treatment option depends on the type, length and aetiology of stricture, the choice can be influenced to varying degrees by the simplicity of the method, the preferences of the patient the available accoutrements and the patient health condition. Both urethroplasty and endoscopic internal urethrotomy require anaesthesia and thus are not suitable for many elder and unfit for surgical treatment patients. On the other hand, dilations are easy to perform in every day clinical practice however they have been associated with iatrogenic urethral trauma. In contrast, balloon dilation under vision dilates by radial application of forces against the stricture, avoiding the potentially shearing forces associated with sequential rigid dilation. Since it reduces the possibility of an iatrogenic urethral trauma and the subsequent spongiofibrosis may lead into improved therapeutic outcomes. In this report we describe a technique for the treatment of urethral strictures with balloon dilation in elder and unfit for surgical treatment patients.

  17. Influence of virtual intervention and blood rheology on mass transfer through thoracic aortic aneurysm. (United States)

    Lei, Yu; Chen, Ming; Xiong, Guanglei; Chen, Jie


    Computational fluid dynamics tools have been used to investigate blood flow through the human thoracic aortic models with aneurysm before and after virtual stent graft operation. The impact of blood rheology and aortic geometry on the wall shear stress (WSS), luminal surface low-density lipoproteins (LDL) concentration, and oxygen flux along the arterial wall is investigated. The stent graft at the aneurysm has significant effects on WSS and mass transport in blood flow. Due to the low flow rate, Newtonian blood assumption generally under-estimates the WSS. The non-Newtonian blood rheology play an important role in the LDL transport as well as oxygen transport. It is found that WSS alone is insufficient to correctly predict the location with high risk of atherogenesis. The results suggest that WSS, luminal surface LDL concentration, and the oxygen flux on the wall have to be considered together to evaluate the performance of virtual operation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Influence of the nanotube oxidation on the rheological and electrical properties of CNT/HDPE composites

    Energy Technology Data Exchange (ETDEWEB)

    Nobile, Maria Rossella, E-mail:; Somma, Elvira; Valentino, Olga; Neitzert, Heinz-Christoph [Department of Industrial Engineering – DIIn - Università di Salerno Via Giovanni Paolo II, 132 - 84084 Fisciano (Italy); Simon, George [Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia)


    Rheological and electrical properties of nanocomposites based on multi-walled carbon nanotubes (MWNTs) and high density polyethylene (HDPE), prepared by melt mixing in a micro-twin screw extruder, have been investigated. The effect of MWNT concentration (0.5 and 2.5 wt %) and nanotube surface treatment (oxidative treatment in a tubular furnace at 500°C for 1 hr in a 95% nitrogen, 5% oxygen atmosphere) has been analyzed. It has been found that the sample conductivity with oxidation of the nanotubes decreases more than 2 orders of magnitude. Scanning electron microscopy showed good adhesion and dispersion of nanotubes in the matrix, independently of the surface treatment. Electrical and rheological measurements revealed that the oxidative treatment, causing some reduction of the MWNT quality, decreases the efficiency of the nanotube matrix interaction.

  19. Spectral dilation of L(B,H)-valued measures and its application to stationary dilation for Banach space valued processes (United States)

    Miamee, A. G.


    Let B be a Banach space and H and K to Hilbert spaces. The spectral dilation of L(B,H)-valued measures is studied and it is shown that the recent results of Makagon and Salehi (1986) and Rosenberg (1982) on the dilation of L(K,H)-valued measures can be extended to hold for the general Banach space setting of L(B,H)-valued measures. These L(B,H)-valued measures are closely connected to the Banach space valued processes. This connection is recalled and as application of spectral dilation of L(B,H)-valued measures the well known stationary dilation results for scalar valued processes is extended to the case of Banach space valued processes.


    Directory of Open Access Journals (Sweden)

    I.A. Zaitseva


    Full Text Available Complex research of rheological properties of blood at patients with lacunar tonsillitis lead depending on the period of disease. It is shown, that inflammatory process at patients to a great extent defines disturbances of rheological properties of blood. During normalization of a clinical presentation of disease there is no full recovery of rheological properties of blood due to preservation of blood raised viscosity and low deformability of erythrocytes membranes.

  1. Review Of Rheology Modifiers For Hanford Waste

    International Nuclear Information System (INIS)

    Pareizs, J. M.


    As part of Savannah River National Laboratory (SRNL)'s strategic development scope for the Department of Energy - Office of River Protection (DOE-ORP) Hanford Tank Waste Treatment and Immobilization Plant (WTP) waste feed acceptance and product qualification scope, the SRNL has been requested to recommend candidate rheology modifiers to be evaluated to adjust slurry properties in the Hanford Tank Farm. SRNL has performed extensive testing of rheology modifiers for use with Defense Waste Processing Facility (DWPF) simulated melter feed - a high undissolved solids (UDS) mixture of simulated Savannah River Site (SRS) Tank Farm sludge, nitric and formic acids, and glass frit. A much smaller set of evaluations with Hanford simulated waste have also been completed. This report summarizes past work and recommends modifiers for further evaluation with Hanford simulated wastes followed by verification with actual waste samples. Based on the review of available data, a few compounds/systems appear to hold the most promise. For all types of evaluated simulated wastes (caustic Handford tank waste and DWPF processing samples with pH ranging from slightly acidic to slightly caustic), polyacrylic acid had positive impacts on rheology. Citric acid also showed improvement in yield stress on a wide variety of samples. It is recommended that both polyacrylic acid and citric acid be further evaluated as rheology modifiers for Hanford waste. These materials are weak organic acids with the following potential issues: The acidic nature of the modifiers may impact waste pH, if added in very large doses. If pH is significantly reduced by the modifier addition, dissolution of UDS and increased corrosion of tanks, piping, pumps, and other process equipment could occur. Smaller shifts in pH could reduce aluminum solubility, which would be expected to increase the yield stress of the sludge. Therefore, it is expected that use of an acidic modifier would be limited to concentrations that do not

  2. Dilation Behavior of Thermal Spray Coatings (United States)

    Bejarano Lopez, Miryan Lorena

    Thermal Spray (TS) is a very versatile manufacturing process to deposit thick coatings on a variety of substrates. Coatings are used in protective (i.e. wear, chemical attack, high temperature, etc.) and functional (i.e. sensors) applications. TS coatings have a unique lamellar microstructure as a result of the overlapping of millions of molten and partially-molten particles. During processing, high deformation by impact, high temperature, and rapid solidification lead to a complex hierarchical material system that contains a high amount of microstructural defects. The presence of defects in the microstructure contribute to differences in property values in comparison to bulk materials. Thermal stresses and residual strains arise from processing, thermal gradients and thermal exposure. Evaluation of thermal properties, in this case, the coefficient of thermal expansion (CTE) is of vital importance to enhance coating performance. In this dissertation, expansion measurements of various metals, alloys, ceramics, and cermet coatings; were carried out using various techniques (push rod dilatometry, x-ray diffraction XRD, digital image correlation DIC, and curvature method) to determine the dilation behavior at the atomic, micro- and macro-scale levels. The main results were. 1) Mathematical models (Turner and Kerner) used for composite materials, successfully predicted the CTE property of a TS coating where the primary phase is the coating material and the secondary phases can be oxides, precipitates, etc. (formed as a byproduct of the spraying process). CTE was found not to be affected by porosity. 2) Despite the anisotropic behavior characteristic of TS coatings, the experimental results shown that CTE results to be reasonable isotropic within the scope of this study. 3) The curvature method was found to be an alternative technique to obtain the CTE, as well as the Young's modulus of coating in a bi-material strip, with good approximation. 4) An anomalous expansion

  3. Influence of Chemically Treated Palygorskite Over the Rheological Behavior of Polypropylene Nanocomposites


    Antonio, Soberanis-Monforte Genaro; Iván, González-Chi Pedro; Luis, Gordillo-Rubio José


    Melt compounding was used to prepare thermoplastic composites reinforced with palygorskite; the chemical modification of the palygorskite surface and the control of extrusion parameters were used to promote good dispersion and a good interface with the matrix, affecting the rheological properties of the mixture, since the melt viscoelastic behavior is sensitive to changes in the molecular structures at nanoscale and mesoscale. The palygorskite nanoclay (diameter 30 nm) was e...

  4. Evaluating the Rheological Properties of Waste Natural Rubber Latex Modified Binder (United States)

    Khatijah Abu Bakar, Siti; Ezree Abdulah, Mohd; Mustafa Kamal, Mazlina; Rahman, Raha Abd; Arifin Hadithon, Kamarul; Buhari, Rosnawati; Tajudin, Saiful Azhar Ahmad


    Road surface is designed to be the durable surface material to sustain the traffic loading. However, due to physical and mechanical stress, pavement deterioration is accelerated. Thus, modifying conventional bitumen by improving its properties is seen as the best method to prolong pavement in-service life. The purpose of this paper is to study the effect of waste natural rubber (NR) latex on rheological properties of bitumen. Conventional bitumen PEN 80/100 was modified with different content of waste NR latex using a high shear mixer at temperature of 150°C. The modified binder properties were characterized by conducting physical test (i.e. softening point, penetration and penetration index) and rheological test (i.e. dynamic shear rheometer, DSR). Results showed that, the addition of waste NR latex improved the rheology properties, which indicates by improving of rutting factor (G*/sin δ). This properties improvement has also shows a potential to resist deformation on road surface despite of high traffic loading.

  5. Rheological and tribological behaviour of lubricating oils containing platelet MoS2 nanoparticles (United States)

    Wan, Qingming; Jin, Yi; Sun, Pengcheng; Ding, Yulong


    This work concerns rheological and frictional behaviour of lubricating oils containing platelet molybdenum disulfide (MoS2) nanoparticles (average diameter 50 nm; single layer thickness 3 nm). Stable nano-MoS2 lubricants were formulated and measured for their rheological behaviour and tribological performance. Rheological experiments showed that the nano-MoS2 oils were non-Newtonian following the Bingham plastic fluid model. The viscosity data fitted the classic Hinch-Leal (H-L) model if an agglomeration factor of 1.72 was introduced. Tribological experiments indicated that the use of MoS2 nanoparticles could enhance significantly the tribological performance of the base lubricating oil (reduced frictional coefficient, reduced surface wear and increased stability). Scanning electron microscopy, laser confocal microscope and x-ray energy dispersive spectroscopy analyses suggested that the reduced frictional coefficient and surface wear be associated with surface patching effects. Such patching effects were shown to depend on the concentration of MoS2 nanoparticles, and an effective patching required a concentration over approximately 1 wt%. The increased stability could be attributed to the enhanced heat transfer and lubricating oil film strength due to the presence of nanoparticles.

  6. Evaluating the Rheological Properties of Waste Natural Rubber Latex Modified Binder

    Directory of Open Access Journals (Sweden)

    Abu Bakar Siti Khatijah


    Full Text Available Road surface is designed to be the durable surface material to sustain the traffic loading. However, due to physical and mechanical stress, pavement deterioration is accelerated. Thus, modifying conventional bitumen by improving its properties is seen as the best method to prolong pavement in-service life. The purpose of this paper is to study the effect of waste natural rubber (NR latex on rheological properties of bitumen. Conventional bitumen PEN 80/100 was modified with different content of waste NR latex using a high shear mixer at temperature of 150°C. The modified binder properties were characterized by conducting physical test (i.e. softening point, penetration and penetration index and rheological test (i.e. dynamic shear rheometer, DSR. Results showed that, the addition of waste NR latex improved the rheology properties, which indicates by improving of rutting factor (G*/sin δ. This properties improvement has also shows a potential to resist deformation on road surface despite of high traffic loading.

  7. Treatment of Ureterointestinal Anastomotic Strictures by Diathermal or Cryoplastic Dilatation

    International Nuclear Information System (INIS)

    Orsi, Franco; Penco, Silvia; Matei, Victor; Bonomo, Guido; Vigna, Paolo Della; Monfardini, Lorenzo; Cobelli, Ottavio De


    Background. Ureterointestinal anastomotic strictures (UAS) complicate 10-15% of surgeries for urinary diversion and are the main cause of deterioration in renal function. Treatments are surgical revision, management with autostatic stent, balloon dilatation, endoscopic incision, and percutaneous transrenal diathermy (Acucise). A new option is cryoplastic dilatation (Polar-Cath). Purpose. To assess the feasibility, complications, and preliminary results of UAS treatment using the Acucise and Polar-Cath systems. Methods. Nineteen UAS, diagnosed by ultrasonography or computed tomography and sequential renal scintigraphy, occurred in 15 cancer patients after radical cystectomy and urinary diversion. Fifteen were managed with balloon diathermy and 4 by balloon cryoplasty in a three-stage procedure-percutaneous nephrostomy, diathermal or cryoplastic dilatation, and transnephrostomic control with nephrostomy removal-each separated by 15 days. All patients gave written informed consent. Results. Dilatations were successful in all cases. The procedure is simple and rapid (about 45 min) under fluoroscopic control and sedation. Procedural complications occurred in 1 (5%) patient with UAS after Wallace II uretero-ileocutaneostomy: a common iliac artery lesion was induced by diathermal dilatation, evident subsequently, and required surgical repair. Patency with balloon diathermy was good, with two restenoses developing over 12 months (range 1-22) of follow-up. With balloon cryoplastic dilatation, one restenosis developed in the short term; follow-up is too brief to assess the long-term efficacy. Conclusion. Our short-term results with diathermal and cryoplastic dilatation to resolve UAS are good. If supported by longer follow-up, the techniques may be considered as first-choice approaches to UAS. Surgery should be reserved for cases in which this minimally invasive technique fails

  8. New rheological model for concrete structural analysis

    International Nuclear Information System (INIS)

    Chern, J.C.


    Long time deformation is of interest in estimating stresses of the prestressed concrete reactor vessel, in predicting cracking due to shrinkage or thermal dilatation, and in the design of leak-tight structures. Many interacting influences exist among creep, shrinkage and cracking for concrete. An interaction which researchers have long observed, is that at simultaneous drying and loading, the deformation of a concrete structure under the combined effect is larger than the sum of the shrinkage deformation of the structure at no load and the deformation of the sealed structure. The excess deformation due to the difference between observed test data and conventional analysis is regarded as the Pickett Effect. A constitutive relation explaining the Pickett Effect and other similar superposition problems, which includes creep, shrinkage (or thermal dilation), cracking, aging was developed with an efficient time-step numerical algorithm. The total deformation in the analysis is the sum of strain due to elastic deformation and creep, cracking and shrinkage with thermal dilatation. Instead of a sudden stress reduction to zero after the attainment of the strength limit, the gradual strain-softening of concrete (a gradual decline of stress at increasing strain) is considered

  9. Effect of crushed sand on mortar and concrete rheology

    Directory of Open Access Journals (Sweden)

    Cabrera, O. A.


    Full Text Available This article describes an experimental study conducted on fresh mortars and concretes made with crushed sand. The aim of this research was to assess the effect of aggregate particle shape and surface texture as well as dust content on mortar and concrete rheology. The experimental programme also addressed the impact of angular grains on chemical admixture performance and concrete bleeding. The findings showed that the use of crushed sand induces rheological behaviour that differs from the behaviour observed in natural sand and that superplasticisers can improve this behaviour considerably.

    En el presente trabajo se plantea un estudio experimental del estado fresco de morteros y hormigones con arenas de machaqueo, orientado a la evaluación de la incidencia de la forma y textura superficial de los granos del árido fino y del contenido de polvo sobre la reología de las mezclas. El programa experimental comprendió el estudio del estado fresco de hormigones con arenas con partículas angulares, la influencia de este tipo de partículas sobre la efectividad de los aditivos químicos y la evaluación de la influencia de las características físicas del árido fino sobre la exudación. Los resultados muestran que el empleo de arenas de machaqueo provoca un comportamiento reológico diferente al de hormigones con arenas naturales, y que el efecto de los aditivos superfluidificantes mejora notablemente este comportamiento.

  10. Structure, Ion Transport, and Rheology of Nanoparticle Salts

    KAUST Repository

    Wen, Yu Ho


    Above a critical surface chemistry-dependent particle loading associated with nanoscale interparticle spacing, ligand-ligand interactions-both electrostatic and steric-come into play and govern the structure and dynamics of charged oligomer-functionalized nanoparticle suspensions. We report in particular on the structure, ion transport, and rheology of suspensions of nanoparticle salts created by cofunctionalization of silica particles with tethered sulfonate salts and oligomers. Dispersion of the hairy ionic particles into medium and high dielectric constant liquids yields electrolytes with unique structure and transport properties. We find that electrostatic repulsion imparted by ion dissociation can be tuned to control the dispersion state and rheology through counterion size (i.e., Li+, Na+, and K+) and dielectric properties of the dispersing medium. Analysis of small-angle X-ray scattering (SAXS) structure factors and the mechanical modulus shows that when the interparticle spacing approaches nanometer dimensions, weakly entangled anchored ligands experience strong and long-lived topological constraints analogous to those normally found in well-entangled polymeric fluids. This finding provides insight into the molecular origins of the surprisingly similar rubbery plateau moduli observed in hairy nanoparticle suspensions and entangled polymers of the same chemistry as the tethered ligands. Additionally, we find that a time-composition superposition (TCS) principle exists for the suspensions, which can be used to substantially extend the observation time over which dynamics are observed in jammed, soft glassy suspensions. Application of TCS reveals dynamical similarities between the suspensions and entangled solutions of linear polymer chains; i.e., a hairy particle trapped in a cage appears to exhibit analogous dynamics to a long polymer chain confined to a tube. © 2014 American Chemical Society.

  11. Rheology of milk foams produced by steam injection. (United States)

    Jimenez-Junca, Carlos A; Gumy, Jean C; Sher, Alexander; Niranjan, Keshavan


    Rheology of milk foams generated by steam injection was studied during the transient destabilization process using steady flow and dynamic oscillatory techniques: yield stress (τ(y) ) values were obtained from a stress ramp (0.2 to 25 Pa) and from strain amplitude sweep (0.001 to 3 at 1 Hz of frequency); elastic (G') and viscous (G″) moduli were measured by frequency sweep (0.1 to 10 Hz at 0.05 of strain); and the apparent viscosity (η(a) ) was obtained from the flow curves generated from the stress ramp. The effect of plate roughness and the sweep time on τ(y) was also assessed. Yield stress was found to increase with plate roughness whereas it decreased with the sweep time. The values of yield stress and moduli-G' and G″-increased during foam destabilization as a consequence of the changes in foam properties, especially the gas volume fraction, ϕ, and bubble size, R(32) (Sauter mean bubble radius). Thus, a relationship between τ(y) , ϕ, R(32) , and σ(surface tension) was established. The changes in the apparent viscosity, η, showed that the foams behaved like a shear thinning fluid beyond the yield point, fitting the modified Cross model with the relaxation time parameter (λ) also depending on the gas volume fraction. Overall, it was concluded that the viscoelastic behavior of the foam below the yield point and liquid-like behavior thereafter both vary during destabilization due to changes in the foam characteristics. Studying the transient rheology of milk foams during destabilization contributes to our knowledge of the relationships between the changes in foam properties: texture and mouth feel during the consumption of hot foamed beverages. © 2011 Institute of Food Technologists®

  12. Change in dynamic visual acuity (DVA) by pupil dilation. (United States)

    Ueda, Tetsuo; Nawa, Yoshiaki; Yukawa, Eiichi; Taketani, Futoshi; Hara, Yoshiaki


    This study was conducted to assess dynamic visual acuity (DVA) under pupil dilation. Pupil dilation may negatively affect driving performance. Thirty healthy young adults (mean age 29.4 years) with pupil dilation participated in this study as the Mydrin P group. In addition to them, 15 healthy young adults (mean age 28.5 years) without pupil dilation were enrolled as the control group. DVA was measured binocularly with free-head viewing at 0, 30, 60, 120, and 360 min after mydriatic drop instillation in both eyes. Pupil size was measured at each time. In the Mydrin P group, DVA significantly improved at 30, 60, and 120 min (ANOVA; p DVA did not significantly change at all measured times (ANOVA; p > .9). DVA was significantly (p DVA was related to the enlargement of the pupil. This study suggests that the pupil size is one factor that may affect DVA. Potential applications of this study include useful information to assess the effect of pupil dilation on driving performance.

  13. Exploring Biological Motion Processing in Parkinson's Disease Using Temporal Dilation.

    Directory of Open Access Journals (Sweden)

    Ruihua Cao

    Full Text Available Biological motion (BM perception is the compelling ability of the visual system to perceive complex animated movements effortlessly and promptly. A recent study has shown that BM can automatically lengthen perceived temporal duration independent of global configuration. The present study aimed mainly to investigate this temporal dilation effect of BM signals in Parkinson's disease (PD patients. We used the temporal dilation effect as an implicit measure of visual processing of BM. In all, 32 PD patients (under off-therapy conditions and 32 healthy controls (HCs participated in our study. In each trial, an upright BM sequence and an inverted BM sequence were presented within an interval in the center of the screen. We tested both canonical and scrambled BM sequences; the scrambled ones were generated by disturbing the global configuration of the canonical ones but preserving exactly the same local motion components. Observers were required to make a verbal two-alternative forced choice response to indicate which interval (the first or the second appeared longer. Statistical analyses were conducted on the points of subjective equality (PSEs. We found that the temporal dilation effect was significantly reduced for PD patients compared with HCs in both canonical and scrambled BM conditions. Moreover, no temporal dilation effects of scrambled BM were shown in both early- and late-stage PD patients, while the temporal dilation effect of canonical BM was relatively preserved in the early stages.

  14. Rheology of Three-Phase Magmas (United States)

    Pistone, M.; Caricchi, L.; Ulmer, P.; Reusser, E.; Marone, F.; Burlini, L.


    Luigi Burlini was a conscious supervisor, a brilliant teacher and a dear friend. He instilled in me optimism and passion for research. His scientific eclecticism to combine several disciplines and methodologies to challenge and solve science issues has enhanced my approach of analysis and observation. His "simple" curiosity to test new scientific pathways and truly know the validity of own proposals represents my primary inspiration to continue the academic career. He was the far-seeing and carpe diem man at the same time; from this I learnt to live intensively day by day without forgetting what will be next. The work I will present is dedicated to him. We present experimental results from a study mainly aiming to constrain the dependence of rheology of three-phase magmas (ranging from dilute suspensions to crystal mushes) on the viscosity of the suspending silicate melt, on the relative contents of crystals and bubbles and on the interactions occurring between the three phases during deformation. Hydrous haplogranitic magmas containing variable amounts of quartz crystals (between 24 and 65 vol%), and fixed bubble volume (9-12 vol% CO2-rich bubbles) were deformed in simple shear with a Paterson-type rock deformation apparatus at high temperature (823-1023 K) and high pressure (200 MPa), in strain-rate stepping (5•10-5 s-1 - 4•10-3 s-1) from low to high deformation rate. The rheological results suggest that three-phase suspensions are characterized by strain rate-dependent rheology (non-Newtonian behavior). Two kinds of non-Newtonian behaviors were observed: shear thinning (decrease of viscosity with increasing strain rate) and shear thickening (increase of viscosity with increasing strain rate). Microstructural observations suggest that: shear thinning dominantly occurs in crystal-rich magmas (55-65 vol% crystals) because of crystal size reduction and shear localization; shear thickening prevails in dilute suspensions (24-44 vol% crystals) due to outgassing

  15. Influence of silane coupling agents on the rheological behavior of hemp fiber filled polyamide 1010 biomass composites in molten state (United States)

    Nishitani, Yosuke; Hasumi, Megumi; Kitano, Takeshi


    In order to develop the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the influence of silane coupling agent on the rheological properties of hemp fiber (HF) filled polyamide 1010 (PA1010) biomass composites in molten state was investigated for one step of the fabrication of these materials. PA1010 was made from sebacic acid and decamethylenediamine, which are obtained from plant-derived castor oil. Hemp fibers were surface-treated by two types of surface treatment: a) alkali treatment by NaOH solution and b) surface treatment by silane coupling agents with different concentrations. Three types of silane coupling agents: aminosilane, epoxysilane and ureidosilane were used for surface treatment. HF/PA1010 composites were extruded by a twin screw extruder and compression-molded. Rheological behavior in molten state were evaluated by oscillatory flow testing using a parallel plate type rheometer. It was found that the silane coupling agents remarkably influence on: 1) rheological properties such as storage modulus, loss modulus, loss tangent and complex viscosity in low angular frequency region in molten state, 2) temperature dependences of rheological properties, and 3) relationship between phase angle and complex modulus (van Gurp - Palmen plots). These rheological behavior were also strongly influenced by the type of silane coupling agents. The viscoelastic properties (both storage and loss moduli) of aminosilane and epoxysilane treated composites were lower, however, those of ureidosilane treated ones were higher than the moduli of only alkali treated composites. Ureidosilane treated composites were the least temperature sensitive in the surface treated composites investigated here.

  16. Rheological modelling of the effects of sucrose adulterant on ...

    African Journals Online (AJOL)

    Rheology has been applied as sensitive tool for material characterisation since flow behaviour correlates closely with composition, molecular weight and molecular weight distribution. Pure honey was serially diluted with different percentages of sucrose: 10%, 50%, 70% and 90% and each were analysed rheologically at ...

  17. The Bioadhesive and Rheological properties of some fluconazole gels

    African Journals Online (AJOL)

    An oscillatory rheological technique was employed using a parallel plate viscometer to determine the rheological properties of the formulations. Two dyes, erythrosine and amaranth were added to elucidate diffusional processes occurring during mucociliary transport of the gels. The results obtained indicate that high ...

  18. Morphometric and rheological study of lunar domes of Marius Hills ...

    Indian Academy of Sciences (India)


    data in various Mare basins and high land regions of Moon. In the Marius Hills region, telescopic data based morphometric study of domes is limited to 30 domes (Lena et al.,2009). They also estimated rheological parameters of three domes based on two-phase eruption. Later to this study, rheological parameters of a dome ...

  19. Rheological modification of corn stover biomass at high solids concentrations (United States)

    Joseph R. Samaniuk; C. Tim Scott; Thatcher W. Root; Daniel J. Klingenberg


    Additives were tested for their ability to modify the rheology of lignocellulosic biomass. Additive types included water-soluble polymers (WSPs), surfactants, and fine particles. WSPs were the most effective rheological modifiers, reducing yield stresses of concentrated biomass by 60–80% for additive concentrations of 1–2 wt. % (based on mass of dry biomass solids)....

  20. Differential Rheology Among ABO Blood Group System In Nigerians ...

    African Journals Online (AJOL)

    Background: ABO blood groups have been reported to have rheological significance and association with different disease conditions. The non-O blood groups (A, B, and AB) have shown more susceptibility to arterial and venous thrombotic diseases with no rheological delineation. The determinants of these blood groups ...

  1. Rheology of Cementitious Materials: Alkali-Activated Materials or Geopolymers

    Directory of Open Access Journals (Sweden)

    Puertas F.


    Understanding and controlling the rheology of the AAMs systems will ultimately determine whether they can be implemented in the market, and will open up greater competitive possibilities in a crisis-affected sector. A systematic study of the factors that affect the rheological properties of AAMs (pastes, mortars and concretes is therefore necessary in order to ultimately develop more resistant and durable materials.

  2. Rheological behaviour of self-compacting micro-concrete

    Indian Academy of Sciences (India)

    MS received 12 January 2014; revised 28 April 2014; accepted 11 June 2014. Abstract. The rheological behaviour of Self-Compacting Micro-Concrete (SCMC) mixtures has been investigated within the scope of this paper. Rheological measure- ments have been performed using a novel rheometer equipped with a ball ...

  3. Rheological properties of boehmite sols during ageing at room ...

    Indian Academy of Sciences (India)

    Keywords. Boehmite sol; rheology; shear thinning; yield stress; viscoelasticity; gel point. Abstract. Boehmite sols were obtained by peptizing boehmite precipitates with glacial acetic acid. The sols were aged at room temperature (30 ± 1°C) under closed condition. Rheological properties of the sols were studied at different ...

  4. Effects of an amphipathic drug on the rheological properties of the cell membrane. (United States)

    Bazzoni, G; Rasia, M


    Sodium thiopental, as other amphiphilic molecules, interacts with the membrane by inserting into the lipid bilayer and causing alterations of the membrane properties such as curvature and hypotonic lysis resistance. But can it modify the mechanical properties of the membrane? In the present work it was observed that sodium thiopental affected the membrane rheological properties by improving erythrocyte deformability; this effect resulted from a reduction of both the elastic modulus and surface viscosity. In erythrocytes devoid of sialic acid after treatment with neuraminidase, sodium thiopental membrane concentration was significantly higher than in normal cells, suggesting that drug access to the lipid bilayer be facilitated by the absence of the steric and electrostatic barrier of the glycocalyx negative charges. From a rheological point of view, desialated and normal cells showed the same response to the anesthetic as regards elastic modulus but in opposite direction if surface viscosity was considered. This finding supports the hypothesis that sodium thiopental molecules enter the bilayer of desialated cells in a higher proportion, as compared to the normal erythrocyte, promoting a disorganization that results in a greater inner friction. The changes in the rheological parameters, triggered by sodium thiopental, could be attributed to the bilayer contribution to the membrane mechanical properties, either directly or through interaction between the bilayer and the cytoskeleton.

  5. H∞ /H2 model reduction through dilated linear matrix inequalities

    DEFF Research Database (Denmark)

    Adegas, Fabiano Daher; Stoustrup, Jakob


    This paper presents sufficient dilated linear matrix inequalities (LMI) conditions to the $H_{infty}$ and $H_{2}$ model reduction problem. A special structure of the auxiliary (slack) variables allows the original model of order $n$ to be reduced to an order $r=n/s$ where $n,r,s in field{N}$. Arb......This paper presents sufficient dilated linear matrix inequalities (LMI) conditions to the $H_{infty}$ and $H_{2}$ model reduction problem. A special structure of the auxiliary (slack) variables allows the original model of order $n$ to be reduced to an order $r=n/s$ where $n,r,s in field...... not satisfactorily approximates the original system, an iterative algorithm based on dilated LMIs is proposed to significantly improve the approximation bound. The effectiveness of the method is accessed by numerical experiments. The method is also applied to the $H_2$ order reduction of a flexible wind turbine...

  6. Pulmonary artery dilatation: an overlooked mechanism for angina pectoris. (United States)

    Ginghina, Carmen; Popescu, Bogdan A; Enache, Roxana; Ungureanu, Catalina; Deleanu, Dan; Platon, Pavel


    Dilatation of the pulmonary artery may lead to the compression of adjacent structures. Of those, the extrinsic compression of the left main coronary artery is the most worrisome. We present the case of a 48-year-old woman who was diagnosed with pulmonary artery dilatation due to severe, thromboembolic pulmonary hypertension. She also had angina and coronary angiography revealed a 70% ostial stenosis of the left main coronary artery. The presence of this isolated lesion in a young woman without risk factors for atherosclerosis suggests extrinsic compression of the left main coronary artery by the dilated pulmonary artery as the likely mechanism. The patient underwent direct stenting of the left main coronary stenosis with a good result.

  7. Dilatancy and compaction effects on the submerged granular column collapse (United States)

    Wang, Chun; Wang, Yongqi; Peng, Chong; Meng, Xiannan


    The effects of dilatancy on the collapse dynamics of granular materials in air or in a liquid are studied experimentally and numerically. Experiments show that dilatancy has a critical effect on the collapse of granular columns in the presence of an ambient fluid. Two regimes of the collapse, one being quick and the other being slow, are observed from the experiments and the underlying reasons are analyzed. A two-fluid smoothed particle hydrodynamics model, based on the granular-fluid mixture theory and the critical state theory, is employed to investigate the complex interactions between the solid particles and the ambient water. It is found that dilatancy, resulting in large effective stress and large frictional coefficient between solid particles, helps form the slow regime. Small permeability, representing large inter-phase drag force, also retards the collapse significantly. The proposed numerical model is capable of reproducing these effects qualitatively.

  8. Robust design of dilation and erosion CNN for gray scale image (United States)

    Zhang, Xiaoliang; Min, Lequan; Li, Min


    The cellular neural/nonlinear network (CNN) is a powerful tool for image and video signal processing, as well as robotic and biological visions. The designs for CNN templates are one of the important issues for the practical applications of CNNs. This paper combines two CNN to implement the Dilation CNNs and Erosion CNN for gray scale images and proposes two theorems of robustness designs. The parameters of the templates can range between a hyper plane and a hyper surface in the first quartile. The simulations have been given. The results show the effectiveness of the theoretical results to be implemented in computer simulations.

  9. Rheology and physical-chemical characteristics of the solutions of the medicines (United States)

    Urakov, A.; Urakova, N.


    In the laboratory studied the dynamics of rheology of water solutions with plasma- inflammatory and antiseptic funds when mixing them with blood, plasma and pus under the influence of the following physical and chemical factors of local interaction: gravity, specific gravity, temperature, relative viscosity, internal pressure, sparkling water, total concentration of the ingredients, surface activity, volume of acid and osmotic activity of medicines. Found that the rheology of biological liquids improve hyperthermic, highly alkaline and highly carbonated solution medicines. For the dilution of pus, dense festering mass of sulfur plugs and tear stones invited to apply heated to +39 - +42°C with aqueous solution of 0.5 - 3% hydrogen peroxide and 0.5 - 10% sodium bicarbonate saturated with carbon dioxide to excess pressure 0.2 ATM.

  10. Rheological and physical properties of spray-dried mucilage obtained from Hylocereus undatus cladodes. (United States)

    García-Cruz, E E; Rodríguez-Ramírez, J; Méndez Lagunas, L L; Medina-Torres, L


    This study examines the rheological behavior of reconstituted spray-dried mucilage isolated from the cladodes of pitahaya (Hylocereus undatus), the effects of concentration and its relationship with physical properties were analyzed in reconstituted solutions. Drying process optimization was carried out through the surface response method, utilizing a factorial 2(3) design with three central points, in order to evaluate yield and rheological properties. The reconstituted mucilage exhibited non-Newtonian shear-thinning behavior, which adequately fit the Cross model (R(2)>0.95). This dynamic response suggests a random coil configuration. The steady-shear viscosity and dynamic response are suitably correlated through the Cox-Merz rule, confirming the mucilage's stability of flow. Analysis of the physical properties of the mucilage (Tg, DTP, and particle morphology) explains the shear-thinning behavior. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Power law rheology of ice and the relaxation style and retention of craters on Ganymede (United States)

    Thomas, Paul J.; Schubert, Gerald


    A numerical finite element model of viscous relaxation of craters in ice is presented which incorporates rheological data for ice at temperatures and pressures appropriated to the near-surface regions of Ganymede. For temperature gradients in reasonable agreement with those obtained from thermal and structural models of Ganymede, relaxation times greater than 10 to the 7th years were obtained for craters with diameters less than 100 km. For all craters with diameters greater than 10 km, the dependence of viscosity on stress was found to significantly shorten the relaxation time. The rheological laws which dominate crater relaxation are discussed for craters of various sizes. The results are compared with imagery from Voyager.

  12. Effect of carboxymethylation on rheological and drug release characteristics of Terminalia catappa gum. (United States)

    Sharma, Radhika; Rana, Vikas


    The carboxymethylation of galactomannans, arabinogalactans, arbinoxylan, etc is known to modify solubility, swelling index, rheological behaviour, powder characteristics, etc. Therefore, an attempt had been made to study the effect of carboxymethylation on Terminalia catappa (TC) gum. For this, modified Williamson synthesis reaction was utilized employing Quality by Design (QbD) approach. Grafting of carboxymethyl group on Terminalia catappa was confirmed by ATR-FTIR, H 1 NMR and DSC analyses. The rheological attributes revealed that the carboxymethylation of TC lowers the viscosity, enhance thermal stability (high activation energy), disentanglement was near to re-entanglement, and weak gelling characteristic. However, the soluble fluconazole loaded gel formulation of CMTC showed diffusion based kinetic model indicating good reservoir for effective application on skin/tissue surfaces. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Rheology and physical-chemical characteristics of the solutions of the medicines

    International Nuclear Information System (INIS)

    Urakov, A; Urakova, N


    In the laboratory studied the dynamics of rheology of water solutions with plasma- inflammatory and antiseptic funds when mixing them with blood, plasma and pus under the influence of the following physical and chemical factors of local interaction: gravity, specific gravity, temperature, relative viscosity, internal pressure, sparkling water, total concentration of the ingredients, surface activity, volume of acid and osmotic activity of medicines. Found that the rheology of biological liquids improve hyperthermic, highly alkaline and highly carbonated solution medicines. For the dilution of pus, dense festering mass of sulfur plugs and tear stones invited to apply heated to +39 – +42°C with aqueous solution of 0.5 – 3% hydrogen peroxide and 0.5 – 10% sodium bicarbonate saturated with carbon dioxide to excess pressure 0.2 ATM. (paper)

  14. Changes in cytoskeletal dynamics and nonlinear rheology with metastatic ability in cancer cell lines

    International Nuclear Information System (INIS)

    Coughlin, Mark F; Fredberg, Jeffrey J


    Metastatic outcome is impacted by the biophysical state of the primary tumor cell. To determine if changes in cancer cell biophysical properties facilitate metastasis, we quantified cytoskeletal biophysics in well-characterized human skin, bladder, prostate and kidney cell line pairs that differ in metastatic ability. Using magnetic twisting cytometry with optical detection, cytoskeletal dynamics was observed through spontaneous motion of surface bound marker beads and nonlinear rheology was characterized through large amplitude forced oscillations of probe beads. Measurements of cytoskeletal dynamics and nonlinear rheology differed between strongly and weakly metastatic cells. However, no set of biophysical parameters changed systematically with metastatic ability across all cell lines. Compared to their weakly metastatic counterparts, the strongly metastatic kidney cancer cells exhibited both increased cytoskeletal dynamics and stiffness at large deformation which are thought to facilitate the process of vascular invasion. (paper)

  15. Polyethylene/synthetic boehmite alumina nanocomposites: Structure, thermal and rheological properties

    Directory of Open Access Journals (Sweden)


    Full Text Available Synthetic boehmite alumina (BA has been incorporated up to 8 wt% in low density polyethylene (LDPE and high density polyethylene (HDPE, respectively, by melt compounding. The primary nominal particle size of these two BA grades was 40 and 60 nm, respectively. The dispersion of the BA in polyethylene (PE matrices was investigated by scanning and transmission electron microscopy techniques (SEM and TEM. The thermal (melting and crystallization, thermooxidative (oxidation induction temperature and time, and rheological behaviors of the nanocomposites were determined. It was found that BA is nanoscale dispersed in both LDPE and HDPE without any surface treatment and additional polymeric compatibilizer. BA practically did not influence the thermal (melting and crystallization and rheological properties of the parent PEs. On the other hand, BA worked as a powerful thermooxidative stabilizer for LDPE, and especially for HDPE nanocomposites.

  16. Melt rheology and its applications in the plastics industry

    CERN Document Server

    Dealy, John M


    This is the second edition of Melt Rheology and its Role in Plastics Processing, although the title has changed to reflect its broadened scope. Advances in the recent years in rheometer technology and polymer science have greatly enhanced the usefulness of rheology in the plastics industry. It is now possible to design polymers having specific molecular structures and to predict the flow properties of melts having those structures. In addition, rheological properties now provide more precise information about molecular structure. This book provides all the information that is needed for the intelligent application of rheology in the development of new polymers, the determination of molecular structure and the correlation of processability with laboratory test data. Theory and equations are limited to what is essential for the use of rheology in the characterization of polymers, the development of new plastics materials and the prediction of plastics processing behavior. The emphasis is on information that wil...

  17. Shared Genetic Predisposition in Peripartum and Dilated Cardiomyopathies. (United States)

    Ware, James S; Li, Jian; Mazaika, Erica; Yasso, Christopher M; DeSouza, Tiffany; Cappola, Thomas P; Tsai, Emily J; Hilfiker-Kleiner, Denise; Kamiya, Chizuko A; Mazzarotto, Francesco; Cook, Stuart A; Halder, Indrani; Prasad, Sanjay K; Pisarcik, Jessica; Hanley-Yanez, Karen; Alharethi, Rami; Damp, Julie; Hsich, Eileen; Elkayam, Uri; Sheppard, Richard; Kealey, Angela; Alexis, Jeffrey; Ramani, Gautam; Safirstein, Jordan; Boehmer, John; Pauly, Daniel F; Wittstein, Ilan S; Thohan, Vinay; Zucker, Mark J; Liu, Peter; Gorcsan, John; McNamara, Dennis M; Seidman, Christine E; Seidman, Jonathan G; Arany, Zoltan


    Background Peripartum cardiomyopathy shares some clinical features with idiopathic dilated cardiomyopathy, a disorder caused by mutations in more than 40 genes, including TTN, which encodes the sarcomere protein titin. Methods In 172 women with peripartum cardiomyopathy, we sequenced 43 genes with variants that have been associated with dilated cardiomyopathy. We compared the prevalence of different variant types (nonsense, frameshift, and splicing) in these women with the prevalence of such variants in persons with dilated cardiomyopathy and with population controls. Results We identified 26 distinct, rare truncating variants in eight genes among women with peripartum cardiomyopathy. The prevalence of truncating variants (26 in 172 [15%]) was significantly higher than that in a reference population of 60,706 persons (4.7%, P=1.3×10(-7)) but was similar to that in a cohort of patients with dilated cardiomyopathy (55 of 332 patients [17%], P=0.81). Two thirds of identified truncating variants were in TTN, as seen in 10% of the patients and in 1.4% of the reference population (P=2.7×10(-10)); almost all TTN variants were located in the titin A-band. Seven of the TTN truncating variants were previously reported in patients with idiopathic dilated cardiomyopathy. In a clinically well-characterized cohort of 83 women with peripartum cardiomyopathy, the presence of TTN truncating variants was significantly correlated with a lower ejection fraction at 1-year follow-up (P=0.005). Conclusions The distribution of truncating variants in a large series of women with peripartum cardiomyopathy was remarkably similar to that found in patients with idiopathic dilated cardiomyopathy. TTN truncating variants were the most prevalent genetic predisposition in each disorder.

  18. Passive urethral resistance to dilation in healthy women

    DEFF Research Database (Denmark)

    Bagi, P; Thind, P; Nordsten, M


    The dynamic urethral pressure response to a simulated urine ingression was studied at the bladder neck, in the high pressure zone, and in the distal urethra in 10 healthy female volunteers. The pressure response was characterised by a steep pressure increase simulataneous with the urethral dilation...... at equilibrium, P alpha and P beta express the decline in pressure, and tau alpha and tau beta are time constants. The size of the pressure response proved highly dependent on velocity and size of dilation as well as urethral site of measurement, with the maximum values in the high pressure zone. The time...

  19. Improved test of time dilation in special relativity. (United States)

    Saathoff, G; Karpuk, S; Eisenbarth, U; Huber, G; Krohn, S; Muñoz Horta, R; Reinhardt, S; Schwalm, D; Wolf, A; Gwinner, G


    An improved test of time dilation in special relativity has been performed using laser spectroscopy on fast ions at the heavy-ion storage-ring TSR in Heidelberg. The Doppler-shifted frequencies of a two-level transition in 7Li+ ions at v=0.064c have been measured in the forward and backward direction to an accuracy of Deltanu/nu=1 x 10(-9) using collinear saturation spectroscopy. The result confirms the relativistic Doppler formula and sets a new limit of 2.2 x 10(-7) for deviations from the time dilation factor gamma(SR)=(1-v2/c2)(-1/2).

  20. A Rare Occurance with Epidermolysis Bullosa Disease: Dilated Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Derya Cimen


    Full Text Available Epidermolysis bullosa is a congenital and herediter vesiculobullous disease. Dystrophic form of this disease is characterized by severe malnutrition, failure to thrive, adhesions at fingers, joint contractures related with the formation of scar tissues, carcinoma of the skin, anemia, hipoalbuminemia, wound enfections and sepsis. Rarely, mortal dilated cardiomyopathy may occur in patients. In this report we present a 13 year-old pediatric patient with dilated cardiomyopathy, clinically diagnosed with Epidermolysis bullosa as well as a review of recent related literature.

  1. Development of Alternative Rheological Measurements for DWPF Slurry Samples

    International Nuclear Information System (INIS)

    Koopman, D. c.


    Rheological measurements are used to evaluate the fluid dynamic behavior of Defense Waste Processing Facility, DWPF, slurry samples. Measurements are currently made on non-radioactive simulant slurries using two state-of-the-art rheometers located at the Aiken County Technical Laboratory, ACTL. Measurements are made on plant samples using a rheometer in the Savannah River National Laboratory, SRNL, Shielded Cells facility. Low activity simulants or plant samples can be analyzed using a rheometer located in a radioactive hood in SRNL. Variations in the rheology of SB2 simulants impacted the interpretation of results obtained in a number of related studies. A separate rheological study was initiated with the following four goals: (1) Document the variations seen in the simulant slurries, both by a review of recent data, and by a search for similar samples for further study. (2) Attempt to explain the variations in rheological behavior, or, failing that, reduce the number of possible causes. In particular, to empirically check for rheometer-related variations. (3) Exploit the additional capabilities of the rheometers by developing new measurement methods to study the simulant rheological properties in new ways. (4) Formalize the rheological measurement process for DWPF-related samples into a series of protocols. This report focuses on the third and fourth goals. The emphasis of this report is on the development and formalization of rheological measurement methods used to characterize DWPF slurry samples. The organization is by rheological measurement method. Progress on the first two goals was documented in a concurrent technical report, Koopman (2005). That report focused on the types and possible causes of unusual rheological behavior in simulant slurry samples. It was organized by the sample being studied. The experimental portion of this study was performed in the period of March to April 2004. A general rheology protocol for routine DWPF slurry samples, Koopman

  2. Development of Alternative Rheological Measurements for DWPF Slurry Samples (U)

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D. c.


    Rheological measurements are used to evaluate the fluid dynamic behavior of Defense Waste Processing Facility, DWPF, slurry samples. Measurements are currently made on non-radioactive simulant slurries using two state-of-the-art rheometers located at the Aiken County Technical Laboratory, ACTL. Measurements are made on plant samples using a rheometer in the Savannah River National Laboratory, SRNL, Shielded Cells facility. Low activity simulants or plant samples can be analyzed using a rheometer located in a radioactive hood in SRNL. Variations in the rheology of SB2 simulants impacted the interpretation of results obtained in a number of related studies. A separate rheological study was initiated with the following four goals: (1) Document the variations seen in the simulant slurries, both by a review of recent data, and by a search for similar samples for further study. (2) Attempt to explain the variations in rheological behavior, or, failing that, reduce the number of possible causes. In particular, to empirically check for rheometer-related variations. (3) Exploit the additional capabilities of the rheometers by developing new measurement methods to study the simulant rheological properties in new ways. (4) Formalize the rheological measurement process for DWPF-related samples into a series of protocols. This report focuses on the third and fourth goals. The emphasis of this report is on the development and formalization of rheological measurement methods used to characterize DWPF slurry samples. The organization is by rheological measurement method. Progress on the first two goals was documented in a concurrent technical report, Koopman (2005). That report focused on the types and possible causes of unusual rheological behavior in simulant slurry samples. It was organized by the sample being studied. The experimental portion of this study was performed in the period of March to April 2004. A general rheology protocol for routine DWPF slurry samples, Koopman

  3. Mixed Mode cohesive law with interface dilatation

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Goutianos, Stergios


    Experimental investigations of adhesive joints and fibre composites have shown that under Mode II cracking, the fracture process induces a displacement normal to the fracture plane. This effect can be attributed e.g. to roughness of the fracture surface under dominating tangential crack face disp...... is implemented in the commercial finite element program Abaqus. The model is validated and tested against experimental results under various mode mixities. © 2013 Elsevier Ltd. All rights reserved....

  4. Energy conversion in magneto-rheological elastomers. (United States)

    Sebald, Gael; Nakano, Masami; Lallart, Mickaël; Tian, Tongfei; Diguet, Gildas; Cavaille, Jean-Yves


    Magneto-rheological (MR) elastomers contain micro-/nano-sized ferromagnetic particles dispersed in a soft elastomer matrix, and their rheological properties (storage and loss moduli) exhibit a significant dependence on the application of a magnetic field (namely MR effect). Conversely, it is reported in this work that this multiphysics coupling is associated with an inverse effect (i.e. the dependence of the magnetic properties on mechanical strain), denoted as the pseudo-Villari effect. MR elastomers based on soft and hard silicone rubber matrices and carbonyl iron particles were fabricated and characterized. The pseudo-Villari effect was experimentally quantified: a shear strain of 50 % induces magnetic induction field variations up to 10 mT on anisotropic MR elastomer samples, when placed in a 0.2 T applied field, which might theoretically lead to potential energy conversion density in the mJ cm -3 order of magnitude. In case of anisotropic MR elastomers, the absolute variation of stiffness as a function of applied magnetic field is rather independent of matrix properties. Similarly, the pseudo-Villari effect is found to be independent to the stiffness, thus broadening the adaptability of the materials to sensing and energy harvesting target applications. The potential of the pseudo-Villari effect for energy harvesting applications is finally briefly discussed.

  5. Vortex jamming in superconductors and granular rheology

    International Nuclear Information System (INIS)

    Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo


    We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields-the rheology of soft materials and superconductivity.

  6. Rheology and dynamics of colloidal superballs. (United States)

    Royer, John R; Burton, George L; Blair, Daniel L; Hudson, Steven D


    Recent advances in colloidal synthesis make it possible to generate a wide array of precisely controlled, non-spherical particles. This provides a unique opportunity to probe the role that particle shape plays in the dynamics of colloidal suspensions, particularly at higher volume fractions, where particle interactions are important. We examine the role of particle shape by characterizing both the bulk rheology and micro-scale diffusion in a suspension of pseudo-cubic silica superballs. Working with these well-characterized shaped colloids, we can disentangle shape effects in the hydrodynamics of isolated particles from shape-mediated particle interactions. We find that the hydrodynamic properties of isolated superballs are marginally different from comparably sized hard spheres. However, shape-mediated interactions modify the suspension microstructure, leading to significant differences in the self-diffusion of the superballs. While this excluded volume interaction can be captured with a rescaling of the superball volume fraction, we observe qualitative differences in the shear thickening behavior of moderately concentrated superball suspensions that defy simple rescaling onto hard sphere results. This study helps to define the unknowns associated with the effects of shape on the rheology and dynamics of colloidal solutions.

  7. Dynamics and Rheology of Soft Colloidal Glasses

    KAUST Repository

    Wen, Yu Ho


    © 2015 American Chemical Society. The linear viscoelastic (LVE) spectrum of a soft colloidal glass is accessed with the aid of a time-concentration superposition (TCS) principle, which unveils the glassy particle dynamics from in-cage rattling motion to out-of-cage relaxations over a broad frequency range 10-13 rad/s < ω < 101 rad/s. Progressive dilution of a suspension of hairy nanoparticles leading to increased intercenter distances is demonstrated to enable continuous mapping of the structural relaxation for colloidal glasses. In contrast to existing empirical approaches proposed to extend the rheological map of soft glassy materials, i.e., time-strain superposition (TSS) and strain-rate frequency superposition (SRFS), TCS yields a LVE master curve that satis fies the Kramers-Kronig relations which interrelate the dynamic moduli for materials at equilibrium. The soft glassy rheology (SGR) model and literature data further support the general validity of the TCS concept for soft glassy materials.

  8. Rheological properties of nanocrystalline cellulose suspensions. (United States)

    Chen, Yang; Xu, Chunjiang; Huang, Jing; Wu, Defeng; Lv, Qiaolian


    Rheological behavior, including linear and nonlinear, as well as transient rheology of nanocrystalline cellulose (NCC) suspensions was studied in this work. Two kinds of polymer solutions, aqueous poly(vinyl alcohol) (PVA) with flexible chain structure and aqueous carboxymethyl cellulose (CMC) with semi-rigid chain structure, were used as the suspension media to further explore the role that the interactions among NCC and polymers played during shear flow. The results reveal that NCC has lower values of percolation threshold in the PVA solution than in the CMC one during small amplitude oscillatory shear (SAOS) flow because the flexible PVA chain has higher adsorbed level onto NCC particles than the negatively charged semi-rigid CMC chain, which is further confirmed by the Fourier transformed infrared (FT-IR) spectroscopy tests. As a result, the NCC suspension shows a weak strain overshoot in PVA solution during large amplitude oscillatory shear (LAOS) flow, which cannot be seen on the one in CMC solution. During startup shear flow, both of these two suspensions show evident stress overshoot behavior with the strain-scaling characteristics, indicating the formation of ordered long-term structure of rod-like NCC particles with self-similarity during flow. However, NCC suspension have far stronger stress overshoot response in CMC solution relative to the one in PVA solution. A possible synergy mechanism between NCC and CMC chain is hence proposed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Rheological characterization of Poloxamer 407 nimesulide gels

    Directory of Open Access Journals (Sweden)

    M. N. Freitas


    Full Text Available The thermal gelling property of Poloxamer 407- nimesulide gels was characterized by rheological studies. Nimesulide, a local anti-inflammatory and anesthetic drug used for the treatment of acute and chronic pain, has a short duration of action and a long-acting single-dose injection would be of clinical importance. Thus a poloxamer 407 gel applied intramuscularly could prolong the release and action of nimesulide. In this study, aqueous gels with nimesulide, containing three different concentrations of Poloxamer 407, were prepared. Viscosity measurements were performed by rheologial studies to obtain the optimal sol-gel transition temperature . Poloxamer 407 gels are pseudoplastic and viscoelastic materials, which have an elastic modulus (G', characteristic of the solid, and a viscous modulus (G'', characteristic of the liquid material. Moreover, being pseudoplastic gels, when they are deformed by shearing, their viscosity decreases. Increase of the polymer concentration increased the viscosity of the gels, which could affect the releasing process of nimesulide. Furthermore, the presence of nimesulide led to a lowering of the sol-gel transition temperature. Keywords: Poloxamer 407 gels; nimesulide; rheological characterization; viscosity; sol-gel transition temperature.

  10. Rheological Behavior of Bentonite-Polyester Dispersions (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin


    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  11. Rheological changes in irradiated chicken eggs

    International Nuclear Information System (INIS)

    Ferreira, Lucia F. S.; Del Mastro, Nelida L.


    Pathogenic bacteria may cause foodborne illnesses. Humans may introduce pathogens into foods during production, processing, distribution and or preparation. Some of these microorganisms are able to survive conventional preservation treatments. Heat pasteurization, which is a well established and satisfactory means of decontamination/disinfection of liquid foods, cannot efficiently achieve a similar objective for solid foods. Extensive work carried out worldwide has shown that irradiation is efficient in eradicating foodborne pathogens like Salmonella spp. that can contaminate poultry products. In this work Co-60 gamma irradiation was applied to samples of industrial powder white, yolk and whole egg at doses between 0 and 25 kGy. Samples were rehydrated and the viscosity measured in a Brookfield viscosimeter, model DV III at 5, 15 and 25 degree sign C. The rheological behaviour among the various kinds of samples were markedly different. Irradiation with doses up to 5 kGy, known to reduced bacterial contamination to non-detectable levels, showed almost no variation of viscosity of irradiated egg white samples. On the other hand, whole or yolk egg samples showed some changes in rheological properties depending on the dose level, showing the predominance of whether polimerization or degradation as a result of the irradiation. Additionally, irradiation of yolk egg powder reduced yolk color as a function of the irradiation exposure implemented. The importance of these results are discussed in terms of possible industrial applications

  12. Complex Suspension Rheology Using High Performance Computing (United States)

    Heine, David

    In processing advanced ceramic materials, the properties of the final product depend on the process conditions and the interactions between the materials at the scale of the individual particles. Along with general bulk properties, more subtle properties including particle orientation, segregation, and pore structure must be established during processing to achieve the desired functionality. Accomplishing this requires a thorough understanding of the mesoscale interactions and how they influence the macroscale behavior. We conduct a series of large scale simulations of highly filled polymer-nanoparticle composites as analogs of ceramic pastes and reveal how the ceramic particle and binder properties determine the structure and rheology of the bulk material. As with real ceramic pastes, particle shape and size distribution along with composition determine the shear modulus, extent of segregation, and degree of particle alignment. These factors are influenced by the binder through the rheology of the binder phase and the interaction between binder and particles. This talk presents the results of this study of polymer-nanoparticle composites along with a brief overview of research and development at Corning showing the similarities and differences between research in industry and academia.

  13. Plastic cap evolution law derived from induced transverse isotropy in dilatational triaxial compression.

    Energy Technology Data Exchange (ETDEWEB)

    Macon, David James [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brannon, Rebecca Moss [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Strack, Otto Eric [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    Mechanical testing of porous materials generates physical data that contain contributions from more than one underlying physical phenomenon. All that is measurable is the "ensemble" hardening modulus. This thesis is concerned with the phenomenon of dilatation in triaxial compression of porous media, which has been modeled very accurately in the literature for monotonic loading using models that predict dilatation under triaxial compression (TXC) by presuming that dilatation causes the cap to move outwards. These existing models, however, predict a counter-intuitive (and never validated) increase in hydrostatic compression strength. This work explores an alternative approach for modeling TXC dilatation based on allowing induced elastic anisotropy (which makes the material both less stiff and less strong in the lateral direction) with no increase in hydrostatic strength. Induced elastic anisotropy is introduced through the use of a distortion operator. This operator is a fourth-order tensor consisting of a combination of the undeformed stiffness and deformed compliance and has the same eigenprojectors as the elastic compliance. In the undeformed state, the distortion operator is equal to the fourth-order identity. Through the use of the distortion operator, an evolved stress tensor is introduced. When the evolved stress tensor is substituted into an isotropic yield function, a new anisotropic yield function results. In the case of the von Mises isotropic yield function (which contains only deviatoric components), it is shown that the distortion operator introduces a dilatational contribution without requiring an increase in hydrostatic strength. In the thesis, an introduction and literature review of the cap function is given. A transversely isotropic compliance is presented, based on a linear combination of natural bases constructed about a transverse-symmetry axis. Using a probabilistic distribution of cracks constructed for the case of transverse isotropy, a

  14. Review Of Rheology Modifiers For Hanford Waste

    Energy Technology Data Exchange (ETDEWEB)

    Pareizs, J. M.


    As part of Savannah River National Laboratory (SRNL)'s strategic development scope for the Department of Energy - Office of River Protection (DOE-ORP) Hanford Tank Waste Treatment and Immobilization Plant (WTP) waste feed acceptance and product qualification scope, the SRNL has been requested to recommend candidate rheology modifiers to be evaluated to adjust slurry properties in the Hanford Tank Farm. SRNL has performed extensive testing of rheology modifiers for use with Defense Waste Processing Facility (DWPF) simulated melter feed - a high undissolved solids (UDS) mixture of simulated Savannah River Site (SRS) Tank Farm sludge, nitric and formic acids, and glass frit. A much smaller set of evaluations with Hanford simulated waste have also been completed. This report summarizes past work and recommends modifiers for further evaluation with Hanford simulated wastes followed by verification with actual waste samples. Based on the review of available data, a few compounds/systems appear to hold the most promise. For all types of evaluated simulated wastes (caustic Handford tank waste and DWPF processing samples with pH ranging from slightly acidic to slightly caustic), polyacrylic acid had positive impacts on rheology. Citric acid also showed improvement in yield stress on a wide variety of samples. It is recommended that both polyacrylic acid and citric acid be further evaluated as rheology modifiers for Hanford waste. These materials are weak organic acids with the following potential issues: The acidic nature of the modifiers may impact waste pH, if added in very large doses. If pH is significantly reduced by the modifier addition, dissolution of UDS and increased corrosion of tanks, piping, pumps, and other process equipment could occur. Smaller shifts in pH could reduce aluminum solubility, which would be expected to increase the yield stress of the sludge. Therefore, it is expected that use of an acidic modifier would be limited to concentrations that

  15. Dilated uropathies in children; Dilatation des reins et voies urinaires chez l`enfant

    Energy Technology Data Exchange (ETDEWEB)

    Bouissou, F. [Centre Hospitalier Universitaire Purpan, 31 - Toulouse (France)


    These uropathies are frequent in children and are often diagnosed by ante-natal ultrasound examination. The dilatation, hydronephrosis or uretero-hydro-nephrosis may be due to a large pattern of malformations, either anatomical dysplasia, vesico-ureteric reflux or obstruction of the pelvi-ureteric junction, of the vesical-ureteric junction or due to a chronic urethral obstruction. The investigations must determine the exact urinary tract abnormalities, the renal function and the uro-dynamic change. They are guided by the ultrasound findings and cystography. In obstructive malformation, the MAG3 renogram with furosemide test is the best way to precise the uro-dynamic status, but it requires a careful technique in children and its interpretation is sometimes equivocal. DMSA scan is very useful to give precise separate kidney function and to follow the maturational change with age. All the results must be carefully analysed ; the final therapeutic decision and specially surgery is dependent of the type of uropathy and its natural history. In many cases, surgical treatment is only indicated after a longer follow-up and repeated evaluations. (authors). 11 refs., 2 figs.

  16. Study on the effect of polymeric rheology modifier on the rheological properties of oil-based drilling fluids (United States)

    Ma, C.; Li, L.; Yang, Y. P.; Hao, W. W.; Zhang, Q.; Lv, J.


    A new type of polymeric rheology modifier was synthesized by suspension polymerization, and the effect of rheology modifier on the rheological properties of oil-based drilling fluids was investigated. The results indicated that the obtained polymer had good capacity of improvement of shearing force of oil-based drilling fluids under high temperature and high pressure conditions. Moreover, the obtained polymer can improve the stability of oil-based drilling fluids greatly. As a result, the obtained polymer is a good rheology modifier for oil-based drilling fluids, and it can optimize oil-based drilling fluid system with good rheological properties, good static suspension ability for cuttings and environmental protection function. It can play an essential role in safe drilling jobs and improvement of drilling efficiency.

  17. Modulating surface rheology by electrostatic protein/polysaccharide interactions

    NARCIS (Netherlands)

    Ganzevles, R.A.; Zinoviadou, K.; Vliet, T. van; Stuart, M.A.C.; Jongh, H.H.J. de


    There is a large interest in mixed protein/polysaccharide layers at air-water and oil-water interfaces because of their ability to stabilize foams and emulsions. Mixed protein/polysaccharide adsorbed layers at air-water interfaces can be prepared either by adsorption of soluble protein/

  18. Combination effects of NaOH and NaCl on the rheology and gel characteristics of hen egg white proteins. (United States)

    Li, Junhua; Zhang, Yufan; Fan, Qiao; Teng, Changhao; Xie, Weiying; Shi, Yue; Su, Yujie; Yang, Yanjun


    The effects of NaOH and NaCl on the rheology and gel properties of hen egg white were investigated. As the concentration of NaOH increased, egg white gel exhibited lower opacity and particle turbidity with coincidental increase in zeta potential, while the addition of NaCl resulted in the formation of opaque egg white gel and increase of surface hydrophobicity, particle turbidity and zeta potential. Rheological tests showed that alkali treatment will affect the unfolding state of egg white proteins during the heat stage while NaCl addition can inhibit the unfolding of egg white proteins. The results of correlation analysis indicated that random coil and α-helix were in good correlation with gel textural properties. Therefore, the rheology and gel properties of alkali/salt-induced egg white dispersions were closely related to the changes in surface hydrophobicity, molecule surface charge, and protein secondary structure. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Universal timescales in the rheology of spheroid cell aggregates (United States)

    Yu, Miao; Mahtabfar, Aria; Beleen, Paul; Foty, Ramsey; Zahn, Jeffrey; Shreiber, David; Liu, Liping; Lin, Hao


    The rheological properties of tissue play important roles in key biological processes including embryogenesis, cancer metastasis, and wound healing. Spheroid cell aggregate is a particularly interesting model system for the study of these phenomena. In the long time, they behave like drops with a surface tension. In the short, viscoelasticity also needs to be considered. In this work, we discover two coupled and universal timescales for spheroid aggregates. A total of 12 aggregate types (total aggregate number n =290) derived from L and GBM (glioblastoma multiforme) cells are studied with microtensiometer to obtain their surface tension. They are also allowed to relax upon release of the compression forces. The two timescales are observed during the relaxation process; their values do not depend on compression time nor the degree of deformation, and are consistent among all 12 types. Following prior work (Yu et al., Phys. Rev. Lett., 115:128303; Liu et al., J. Mech. Phys. Solids, 98:309-329) we use a rigorous mathematical theory to interpret the results, which reveals intriguing properties of the aggregates on both tissue and cellular levels. The mechanics of multicellular organization reflects both complexity and regularity due to strong active regulation.

  20. Case Report Percutaneous Dilational Tracheostomy A bed side ...

    African Journals Online (AJOL)

    Introduction: Tracheostomy is one of the most commonly performed procedures in critically ill patients. Percutaneous dilatational tracheostomy (PDT), according to ciaglias technique described in 1985, has become the most popular technique for percutaneous tracheostomy and is demonstrably as safe as surgical.

  1. Cervical ripening with prostaglandin gel and hygroscopic dilators. (United States)

    Hibbard, J U; Shashoua, A; Adamczyk, C; Ismail, M


    OBJECTIVE: To study the effectiveness and morbidity of adding hygroscopic cervical dilators to prostaglandin gel for cervical ripening and labor induction. STUDY DESIGN: Patients of at least 34 weeks' gestation with a medical indication for induction of labor and with a modified Bishop score of 5 or less were randomized to receive either prostaglandin gel or prostaglandin gel with hygroscopic cervical dilators. Primary outcomes were time to delivery, change in cervical score, and infection. Secondary outcomes included cesarean delivery rate and deliveries before 24 hours of induction. Continuous variables were analyzed by Wilcoxon sum rank test and categorical data by chi-square or Fisher exact test, with P intracervical prostaglandin alone and 23 patients received intracervical prostaglandin plus hygroscopic dilators. No demographic differences were noted between the groups. After six hours of ripening, the combined group achieved a greater change in Bishop score (3.6 vs. 2.1, P = 0.007) and tended to have a shorter induction time (21.7 vs. 26.4 hours, P = 0.085). The combined therapy group had a higher infection rate than the prostaglandin-only group (59% vs. 12%, P = 0.003). CONCLUSION: Combining cervical dilators with prostaglandin gel provides more effective cervical ripening and a more rapid induction to delivery interval than prostaglandin alone but with a significant and prohibitive rate of infection. PMID:9678143

  2. Non-obstructive cecal dilatation and perforation after cesarean section

    DEFF Research Database (Denmark)

    Sperling, Lene; Schantz, A L; Toftager-Larsen, K


    A case of non-obstructive cecal dilatation and perforation after cesarean section is reported, with a review of the literature on the diagnosis and management of this entity. Fifteen cases have been described. Attention is called to this rare complication and to the accompanying pseudo...

  3. 28. Critical pulmonary valve stenosis: Medical management beyond balloon dilation

    Directory of Open Access Journals (Sweden)

    Muhammad Arif Khan


    Conclusion: Phentolamine and/or Captopril have a therapeutic role in neonates with critical PVS who remain oxygen dependent after balloon dilation. Both medicationslead to vasodilatation of pulmonary and systemic vascularity. They facilitate inflowto the right ventricle. Right to left shunt across a PFO or/ ASD minimizesand saturation improves leading to a significantreduction in length of hospitalization.

  4. Gravitational time dilation and length contraction in fields exterior to ...

    African Journals Online (AJOL)

    Here, we use our new metric tensor exterior to a massiv3e oblate spheroid to study the gravitational phenomena of time dilation and length contraction. It turns out most profoundly that, the above phenomena hold good in the gravitational field exterior to an oblate spheroid. We then use the oblate spheroidal Earth to ...

  5. Migraine pain associated with middle cerebral artery dilatation

    DEFF Research Database (Denmark)

    Friberg, L; Olesen, J; Iversen, Helle Klingenberg


    returned to normal after treatment with sumatriptan and recovery. Since rCBF in the MCA supply territory was unaffected, the lower velocity can be explained only by dilatation of the MCA. The mean MCA diameter increase was estimated to be 20%. Thus, headache was associated with intracranial large arterial...

  6. unilateral idiopathic dilated episcleral vein with secondary open ...

    African Journals Online (AJOL)


    Olabisi Onabanjo University, Sagamu, Ogun State. Nigeria. Nigerian Journal of Ophthalmology 2008; 16(1): 20-22. Unilateral Idiopathic Dilated Episcleral Vein with Secondary. Open Angle Glaucoma (Radius–Maumenee Syndrome) in an. African – A case report and literature review. TO Otulana, OO Onabolu, VO Fafiolu.

  7. Pattern of cervical dilatation among parturients in Ilorin, Nigeria

    African Journals Online (AJOL)

    8, July-September, 2009. Pattern of cervical dilatation among parturients in. Ilorin, Nigeria. Munir'deen A. Ijaiya, Abiodun P. Aboyeji, Olurotimi O. Fakeye, Olayinka R. Balogun,. Duum C. Nwachukwu, Moses O. Abiodun. Department of Obstetrics and Gynaecology, University of Ilorin Teaching Hospital, Maternity Hospital ...

  8. Thallium scintigraphy for the prognosis of idiopathic dilated cardiomyopathy

    International Nuclear Information System (INIS)

    Yabe, Toshikazu; Furuno, Takashi; Kitaoka, Hiroaki; Matsumura, Yoshihisa; Yamasaki, Naohito; Doi, Yoshinori


    This study evaluated the significance of perfusion defects demonstrated by thallium-201 and age in the prognosis of patients with idiopathic dilated cardiomyopathy. Seventy-four dilated cardiomyopathy patients underwent thallium scintigraphy as well as clinical and hemodynamic examination. Abnormal perfusion defects were present in 23 of 38 patients aged <60 years (61%) and in 26 of 36 elderly patients aged ≥60 years (72%; NS). Univariate analysis showed that such perfusion defects were a significant predictor of cardiac death only in patients aged <60 years (p=0.015). Stepwise discriminant analysis also revealed that perfusion defects were a significant predictor in patients aged <60 years (Wilks' lambda 0.499, chi-square test 20.2, p=0.003). Perfusion defects were not more important than the history of syncope or stroke in elderly dilated cardiomyopathy patients. Twenty-one patients died of disease-related causes during 58±43 months. The five-year survival rate was better in patients aged <60 years without than in those with perfusion defects (100% vs 58.4%, respectively), but not affected in patients aged ≥60 years (66.7% vs 62.2%). Thallium scintigraphy is valuable for the prognosis of patients with dilated cardiomyopathy aged <60 years who are usually candidates for heart transplantation. Absence of thallium perfusion defects may indicate good long-term prognosis. (author)

  9. Gallbladder duplication masquerading as a dilated common bile ...

    African Journals Online (AJOL)

    A duplicate gall bladder was diagnosed at laparoscopy, having been erroneously diagnosed on ultrasonography as a dilated common bile duct with choledocholithiasis. Gallbladder duplication is a congenital abnormality with a rare incidence, occuring in approximately 1 in 4 000 births and 0.020% in al large autopsy ...

  10. Dilatancy of Shear Transformations in a Colloidal Glass (United States)

    Lu, Y. Z.; Jiang, M. Q.; Lu, X.; Qin, Z. X.; Huang, Y. J.; Shen, J.


    Shear transformations, as fundamental rearrangement events operating in local regions, hold the key of plastic flow of amorphous solids. Despite their importance, the dynamic features of shear transformations are far from clear, which is the focus of the present study. Here, we use a colloidal glass under shear as the prototype to directly observe the shear-transformation events in real space. By tracing the colloidal-particle rearrangements, we quantitatively determine two basic properties of shear transformations: local shear strain and dilatation (or free volume). It is revealed that the local free volume undergoes a significantly temporary increase prior to shear transformations, eventually leading to a jump of local shear strain. We clearly demonstrate that shear transformations have no memory of the initial free volume of local regions. Instead, their emergence strongly depends on the dilatancy ability of these local regions, i.e., the dynamic creation of free volume. More specifically, the particles processing the high dilatancy ability directly participate in subsequent shear transformations. These results experimentally enrich Argon's statement about the dilatancy nature of shear transformations and also shed insight into the structural origin of amorphous plasticity.

  11. Arborescent vascular dilatation mimicking Lichtenberg figures from lightning. (United States)

    Tempark, Therdpong; Iwasaki, Julie; Shwayder, Tor


    The clinical presentation of arborizing vascular dilatation can resemble Lichtenberg figures from lightning. Both have a feather-like or ferning pattern. We report an interesting case of pressure-induced vasodilatation (PIV) caused by temporary vascular occlusion from jeans buttons. © 2014 Wiley Periodicals, Inc.

  12. Thallium scintigraphy for the prognosis of idiopathic dilated cardiomyopathy

    Energy Technology Data Exchange (ETDEWEB)

    Yabe, Toshikazu; Furuno, Takashi; Kitaoka, Hiroaki; Matsumura, Yoshihisa; Yamasaki, Naohito; Doi, Yoshinori [Kochi Medical School, Nankoku (Japan)


    This study evaluated the significance of perfusion defects demonstrated by thallium-201 and age in the prognosis of patients with idiopathic dilated cardiomyopathy. Seventy-four dilated cardiomyopathy patients underwent thallium scintigraphy as well as clinical and hemodynamic examination. Abnormal perfusion defects were present in 23 of 38 patients aged <60 years (61%) and in 26 of 36 elderly patients aged {>=}60 years (72%; NS). Univariate analysis showed that such perfusion defects were a significant predictor of cardiac death only in patients aged <60 years (p=0.015). Stepwise discriminant analysis also revealed that perfusion defects were a significant predictor in patients aged <60 years (Wilks' lambda 0.499, chi-square test 20.2, p=0.003). Perfusion defects were not more important than the history of syncope or stroke in elderly dilated cardiomyopathy patients. Twenty-one patients died of disease-related causes during 58{+-}43 months. The five-year survival rate was better in patients aged <60 years without than in those with perfusion defects (100% vs 58.4%, respectively), but not affected in patients aged {>=}60 years (66.7% vs 62.2%). Thallium scintigraphy is valuable for the prognosis of patients with dilated cardiomyopathy aged <60 years who are usually candidates for heart transplantation. Absence of thallium perfusion defects may indicate good long-term prognosis. (author)

  13. Balloon dilatation of isolated severe tricuspid valve stenosis

    Directory of Open Access Journals (Sweden)

    Rajeev Bhardwaj


    Full Text Available Tricuspid valve stenosis is mostly rheumatic in origin. It almost always occurs in association with mitral valve disease. There are only few case reports of isolated tricuspid valve stenosis. We report a case of isolated tricuspid valve stenosis, which was treated with balloon dilatation.

  14. Balloon dilatation of isolated severe tricuspid valve stenosis


    Bhardwaj, Rajeev; Sharma, Rajesh


    Tricuspid valve stenosis is mostly rheumatic in origin. It almost always occurs in association with mitral valve disease. There are only few case reports of isolated tricuspid valve stenosis. We report a case of isolated tricuspid valve stenosis, which was treated with balloon dilatation.

  15. Rheological properties of cupuassu and cocoa fats

    Directory of Open Access Journals (Sweden)

    Gioielli, L. A.


    Full Text Available Cocoa butter is an important ingredient in chocolate formulation as it dictates the main properties (texture, sensation in the mouth, and gloss. In the food industry, the texture of fat-containing products strongly depends on the macroscopic properties of the fat network formed within the finished product. Cupuassu ( Theobroma grandiflorum , Sterculiaceae is an Amazonian native fruit and the seeds can be used to derive a cocoa butter like product. In general, these fats are similar to those of cocoa, although they are different in some physical properties. The objective of this study was to analyze several properties of the cupuassu fat and cocoa butter (crystal formation at 25 ° C, rheological properties, and fatty acid composition and mixtures between the two fats (rheological properties, in order to understand the behavior of these fats for their use in chocolate products. Fat flow was described using common rheological models ( Newton , Power Law, Casson and Bingham plastic.La manteca de cacao es un ingrediente muy importante en la formulación de chocolates y es responsable de la mayor parte de sus propiedades (textura, palatibilidad y brillo. En la industria de alimentos, la textura de productos que contienen grasa depende enormemente de las propiedades macroscópicas de la red cristalina de la grasa en el producto final. El cupuaçu es una fruta nativa de la región amazónica y sus semillas pueden ser usadas para obtener una grasa semejante a la manteca de cacao. En general, esta grasa es similar a la manteca de cacao, pero difiere en algunas de sus propiedades fisicas . El objetivo de este estudio fue analizar algunas propiedades de la grasa de cupuaçu y de la manteca de cacao (formación de cristales a 25 °C, propiedades reológicas y composición en ácidos grasos y de algunas mezclas entre las dos grasas (propiedades reológicas, a fin de conocer el comportamiento de estas grasas para ser usadas en productos de la industria

  16. Rheological responses to plate boundary deformation at the Eastern Volcanic Zone in Iceland (United States)

    Tariqul Islam, Md.; Sturkell, Erik


    Located on the mid-Atlantic ridge, Iceland allows for direct measurement of crustal deformation. Global Positioning System (GPS) data from the Eastern Volcanic Zone (EVZ), Iceland, and crustal deformation of the rift near its southern end at 64°N show a spreading rate of 13.8 ± 1.8 mm yr- 1. About 90% of the deformation occurs in an 80 to 90-km wide zone. To understand how the rheology of the lithosphere influences rifting, we applied a thermo-mechanical stretching model that includes thermal states in Iceland using temperature- and stress-dependent wet and dry olivine rheology. We attempt to reproduce the thermal structure of a rift by defining 700 °C from 5- to 15-km depth at the rift axis that leads to variation in rheological structure, and to estimate the layer (from surface to a depth of 700 °C) where the elastic deformation of the lithosphere is the greatest. At a fixed spreading rate, the deformation field is controlled by the sub-surface thermal state. The vertical subsidence rate at the ridge axis increases almost linearly as the half-velocity increases. The best fitted model suggests a thermal gradient of 54 °C km- 1 at depth below where 700 °C occurs at the ridge axis. The models have little sensitivity to the wet or dry olivine rheology. Estimated viscosity is 1 × 1019 Pa s at 20-km depth at the ridge axis and 1 × 1018 Pa s up to 100-km depth in the model. The spreading rate influences the tangential (non-linearity) shape of the deformation field, and a change in spreading rate affects the deformation field the most. After spreading velocity, the model's second most sensitive parameter is the location of the 700 °C at the rift axis. The thermomechanical model confirms that the rheological responses at the central part of the rift zone in the EVZ, Iceland caused of plate spreading is nonlinear, comparable with surface deformation observed by GPS measurement.

  17. Dilation volumes of sets of bounded perimeter

    DEFF Research Database (Denmark)

    Kiderlen, Markus; Rataj, Jan

    , this derivative coincides up to sign with the directional derivative of the covariogram of A in direction u. By known results for the covariogram, this derivative can therefore be expressed by the cosine transform of the surface area measure of A. We extend this result to sets Q that are at most countable and use...... it to determine the derivative of the contact distribution function of a stationary random closed set at zero. A variant for uncountable Q is given, too. The proofs are based on approximation of the characteristic function of A by smooth functions of bounded variation and showing corresponding formulas for them....

  18. Surface relaxations as a tool to distinguish the dynamic interfacial properties of films formed by normal and diseased meibomian lipids. (United States)

    Georgiev, Georgi As; Yokoi, Norihiko; Ivanova, Slavyana; Tonchev, Vesselin; Nencheva, Yana; Krastev, Rumen


    The surface properties of human meibomian lipids (MGS), the major constituent of the tear film (TF) lipid layer, are of key importance for TF stability. The dynamic interfacial properties of films by MGS from normal eyes (nMGS) and eyes with meibomian gland dysfunction (dMGS) were studied using a Langmuir surface balance. The behavior of the samples during dynamic area changes was evaluated by surface pressure-area isotherms and isocycles. The surface dilatational rheology of the films was examined in the frequency range 10(-5) to 1 Hz by the stress-relaxation method. A significant difference was found, with dMGS showing slow viscosity-dominated relaxation at 10(-4) to 10(-3) Hz, whereas nMGS remained predominantly elastic over the whole range. A Cole-Cole plot revealed two characteristic processes contributing to the relaxation, fast (on the scale of characteristic time τ 100 s), the latter prevailing in dMGS films. Brewster angle microscopy revealed better spreading of nMGS at the air-water interface, whereas dMGS layers were non-uniform and patchy. The distinctions in the interfacial properties of the films in vitro correlated with the accelerated degradation of meibum layer pattern at the air-tear interface and with the decreased stability of TF in vivo. These results, and also recent findings on the modest capability of meibum to suppress the evaporation of the aqueous subphase, suggest the need for a re-evaluation of the role of MGS. The probable key function of meibomian lipids might be to form viscoelastic films capable of opposing dilation of the air-tear interface. The impact of temperature on the meibum surface properties is discussed in terms of its possible effect on the normal structure of the film.

  19. Shear History Extensional Rheology Experiment II (SHERE II) Microgravity Rheology with Non-Newtonian Polymeric Fluids (United States)

    Jaishankar, Aditya; Haward, Simon; Hall, Nancy Rabel; Magee, Kevin; McKinley, Gareth


    The primary objective of SHERE II is to study the effect of torsional preshear on the subsequent extensional behavior of filled viscoelastic suspensions. Microgravity environment eliminates gravitational sagging that makes Earth-based experiments of extensional rheology challenging. Experiments may serve as an idealized model system to study the properties of lunar regolith-polymeric binder based construction materials. Filled polymeric suspensions are ubiquitous in foods, cosmetics, detergents, biomedical materials, etc.

  20. A predictive model for canine dilated cardiomyopathy—a meta-analysis of Doberman Pinscher data

    Directory of Open Access Journals (Sweden)

    Siobhan Simpson


    Full Text Available Dilated cardiomyopathy is a prevalent and often fatal disease in humans and dogs. Indeed dilated cardiomyopathy is the third most common form of cardiac disease in humans, reported to affect approximately 36 individuals per 100,000 individuals. In dogs, dilated cardiomyopathy is the second most common cardiac disease and is most prevalent in the Irish Wolfhound, Doberman Pinscher and Newfoundland breeds. Dilated cardiomyopathy is characterised by ventricular chamber enlargement and systolic dysfunction which often leads to congestive heart failure. Although multiple human loci have been implicated in the pathogenesis of dilated cardiomyopathy, the identified variants are typically associated with rare monogenic forms of dilated cardiomyopathy. The potential for multigenic interactions contributing to human dilated cardiomyopathy remains poorly understood. Consistent with this, several known human dilated cardiomyopathy loci have been excluded as common causes of canine dilated cardiomyopathy, although canine dilated cardiomyopathy resembles the human disease functionally. This suggests additional genetic factors contribute to the dilated cardiomyopathy phenotype.This study represents a meta-analysis of available canine dilated cardiomyopathy genetic datasets with the goal of determining potential multigenic interactions relating the sex chromosome genotype (XX vs. XY with known dilated cardiomyopathy associated loci on chromosome 5 and the PDK4 gene in the incidence and progression of dilated cardiomyopathy. The results show an interaction between known canine dilated cardiomyopathy loci and an unknown X-linked locus. Our study is the first to test a multigenic contribution to dilated cardiomyopathy and suggest a genetic basis for the known sex-disparity in dilated cardiomyopathy outcomes.

  1. Dobutamine Stress Echocardiography in Patients with Dilated Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Miloradovic Vladimir


    Full Text Available A clear distinction between two of the most common forms of dilated cardiomyopathy is very important due to their different prediction and therapeutic approaches. Dobutamine stress echocardiography appears to be a noninvasive selection method due to its clear differentiation potential. Major factors influence test interpretation, resulting in a wide interval of diagnostic accuracy for this test. Fraction flow reserve (FFR is a novel invasive method for estimating coronary artery stenosis responsible for myocardium ischaemia. Decisions about lesion significance in coronary blood vessels have thus far been based on angiographic estimations, but this approach is being replaced by FFR measurements, which serve as a new gold standard and involve a noninvasive test. The goal of this study was to clearly differentiate two forms of dilated cardiomyopathies through analysis of the segmented mobility of the left ventricular wall. Fifty patients were analysed: 20 with ischaemic dilated cardiomyopathy, which was confirmed not only through coronary angiography but also functionally through FFR measurement, and 30 patients with nonischaemic dilated cardiomyopathy, which was confirmed by coronary angiography. A standard dobutamine stress echocardiography protocol was implemented. A positive dobutamine stress echocardiography test was defined as the presence of emerging incidents in segment contractility or worsening of existing incidents in at least one segment. Statistically relevant diff erences in the movement dynamics of a number of differently characterised segments during the observed time intervals (ANOVA p=0.000 was noted in both groups of patients, as was variation in the index value of the summarized mobility of the left chamber wall. In patients with ischaemic cardiomyopathies, regional contractility worsened at the maximum dose of dobutamine; in contrast, this feature slightly improved in nonischaemic cardiomyopathy patients. The results indicate

  2. Synthesis and characterization of magneto-rheological (MR fluids for MR brake application

    Directory of Open Access Journals (Sweden)

    Bhau K. Kumbhar


    Full Text Available Magneto rheological (MR fluid technology has been proven for many industrial applications like shock absorbers, actuators, etc. MR fluid is a smart material whose rheological characteristics change rapidly and can be controlled easily in presence of an applied magnetic field. MR brake is a device to transmit torque by the shear stress of MR fluid. However, MR fluids exhibit yield stress of 50–90 kPa. In this research, an effort has been made to synthesize MR fluid sample/s which will typically meet the requirements of MR brake applications. In this study, various electrolytic and carbonyl iron powder based MR fluids have been synthesized by mixing grease as a stabilizer, oleic acid as an antifriction additive and gaur gum powder as a surface coating to reduce agglomeration of the MR fluid. MR fluid samples based on sunflower oil, which is bio-degradable, environmentally friendly and abundantly available have also been synthesized. These MR fluid samples are characterized for determination of magnetic, morphological and rheological properties. This study helps identify most suitable localized MR fluid meant for MR brake application.

  3. Rheological properties, molecular distribution, and microstructure of Fortunella margarita (Lour.) swingle polysaccharides. (United States)

    Zeng, Hongliang; Zhang, Yi; Jian, Yeye; Tian, Yuting; Miao, Song; Zheng, Baodong


    Fortunella margarita polysaccharides (FMPS) are one of the main bioactive components of F. margarita. The activity is related to their rheological properties and structure. The objective of this study was to investigate the relationship between rheological properties, molecular distribution, and microstructure of crude FMPS (C-FMPS) and purified FMPS (P-FMPS). The results showed that both of solutions were shear-thinning pseudoplastic fluids with flow properties in line with the Power Law model. The pseudoplasticity of P-FMPS was stronger compared to C-FMPS. Additionally, the molecular weight and polydispersity of P-FMPS were greater, whereas the molecular radius was less compared to C-FMPS. The surface of C-FMPS was rough and dense whereas P-FMPS displayed a smooth network structure by environment scanning electron microscopy. According to confocal laser scanning microscopy, C-FMPS dispersed in the medium without connected network, whereas the network of P-FMPS was unevenly distributed in the medium and the shape was compact and smooth. The molecular distribution and microstructure of P-FMPS were attributed to the purification process while rearrangement and aggregation of polysaccharide molecules took place, which resulted in the significant difference of rheological properties between C-FMPS and P-FMPS. © 2015 Institute of Food Technologists®

  4. Effect of Modified and Nonmodified Carbon Nanotubes on the Rheological Behavior of High Density Polyethylene Nanocomposite

    Directory of Open Access Journals (Sweden)

    Adewunmi A. Ahmad


    Full Text Available This paper reports the results of studies on the rheological behavior of nanocomposites of high density polyethylene (HDPE with pristine multiwall carbon nanotubes (CNT as well as phenol and 1-octadecanol (C18 functionalized CNT at 1, 2, 3, 4, 5, and 7 wt% loading. The viscosity reduction at 1 wt% CNT follows the order, pristine CNT < phenol functionalized CNT < C18 functionalized CNT. As the filler loading increases from 1 to 2, 3, and 4 wt%, neat HDPE and filled HDPE systems show similar moduli and viscosity, particularly in the low frequency region. As the filler loading increases further to 5 and 7 wt%, the viscosity and moduli become greater than the neat HDPE. The storage modulus, tan, and the Cole-Cole plots show that CNT network formation occurs at higher CNT loading. The critical CNT loading or the rheological percolation threshold, where network formation occurs is found to be strongly dependant on the functionalization of CNT. For pristine CNT, the rheological percolation threshold is around 4 wt%, but for functionalized CNT it is around 7 wt%. The surface morphologies of CNT and functionalized CNT at 1 wt% loading showed good dispersion while at 7 wt% loading, dispersion was also achieved, but there are few regions with agglomeration of CNT.

  5. Optimization of the functional characteristics, pasting and rheological properties of pearl millet-based composite flour

    Directory of Open Access Journals (Sweden)

    Olugbenga Olufemi Awolu


    Full Text Available Optimisation of composite flour comprising pearl millet, kidney beans and tigernut with xanthan gum was evaluated for rheological evaluations. The functional properties of the composite flour were optimized using optimal design of response surface methodology. The optimum blends, defined as blends with overall best functional characteristics were run 3 (75.956% pearl millet, 17.692% kidney beans, 6.352% tigernut flours, run 7 (85.000% pearl millet, 10.000% kidney beans, 5.000% tigernut flours and run 13 (75.000% pearl millet, 20.000% kidney beans, 5.000% tigernut flours. The pasting characteristics and rheological evaluation of the optimized blends were further evaluated in rapid visco units (RVU. Run 7 had the overall best pasting characteristics; peak viscosity (462 RVU, trough (442 RVU, breakdown viscosity (20 RVU, final viscosity (975 RVU, setback (533 RVU, peak time (5.47 min and pasting temperature (89.60 °C. These values were found to be better than several composite flours consisting mixture of wheat and non-wheat crops. In addition, the rheological characteristics (measured by Mixolab showed that run 7 is the best in terms of dough stability, swelling, water absorption and shelf stability. Composite flour with 85% pearl millet flour in addition to kidney beans and tigernut flours could therefore serve as a viable alternative to 100% wheat flour in bread production.

  6. Rheology and processing of suspensions with fiber, disk and magnetic particles (United States)

    Park, Jang Min; Park, Seong Jin


    This paper introduces recent development and progress in rheology and processing of suspension materials. In particular, three topics with different suspensions will be discussed, which are relevant in polymer- and powder-based manufacturing industries for various applications. The paper begins with a fundamental study of rheological modeling for short fiber suspension in a viscoelastic liquid. Irreversible thermodynamics based approach is presented to describe the polymer viscoelastic deformation with the fiber anisotropy effect taken into account. Several distinguishing features of the model are presented. Then we turn our attention to more industry-oriented subject of pigment disk orientation in injection molding of aesthetic plastic parts. The major difference between fiber and disk orientation kinematics is briefly discussed using Jeffery model. Experimental and numerical results for the disk orientation and the surface color of the molded part are presented. Finally, we introduce our recent efforts regarding the rheology of magnetic particle suspension, which is an essential part for a development of precision magnetic powder injection molding process. Some rheometer data for stainless steel powder suspensions are presented.

  7. Rheological Properties, Water-Holding and Oil-Binding Capacities of Particulate β-Glucans Isolated from Spent Brewer’s Yeast by Three Different Procedures

    Directory of Open Access Journals (Sweden)

    Vlatka Petravić-Tominac


    Full Text Available Particulate β-glucans were isolated from brewer’s yeast using three different procedures – alkaline (A, alkaline-acidic (AA and alkaline-acidic with mannoprotein removal (AAM and dried using three different methods – air drying (AD, lyophilization (L and spray drying (SD. In this work, the obtained β-glucan preparations were tested for their microstructure, rheological properties, swelling, water-holding and oil-binding capacities. According to their rheological properties, suspensions containing 1 and 2 % (by mass of spray-dried samples belong to the category of dilatant fluids. Among the spray-dried samples, rheological behaviour and water-holding capacity of the preparation AA-SD differed from those obtained by other two procedures (A-SD and AAM-SD. Concerning different drying methods applied, swelling was the lowest in the lyophilized samples and the most pronounced in the air-dried ones. Oil-binding capacity was the highest in the lyophilized preparations and increased proportionally to the number of processing steps applied in the isolation procedure.

  8. Attenuation of seismic waves and the universal rheological model of the Earth's mantle (United States)

    Birger, B. I.


    Analysis of results of laboratory studies on creep of mantle rocks, data on seismic wave attenuation in the mantle, and rheological micromechanisms shows that the universal, i.e., relevant to all time scales, rheological model of the mantle can be represented as four rheological elements connected in series. These elements account for elasticity, diffusion rheology, high temperature dislocation rheology, and low temperature dislocation rheology. The diffusion rheology element is described in terms of a Newtonian viscous fluid. The high temperature dislocation rheology element is described by the rheological model previously proposed by the author. This model is a combination of a power-law non-Newtonian fluid model for stationary flows and the linear hereditary Andrade model for flows associated with small strains. The low temperature dislocation rheology element is described by the linear hereditary Lomnitz model.

  9. Impact of Helicobacter Pylori on Mucus Rheology (United States)

    Celli, Jonathan; Keates, Sarah; Kelly, Ciaran; Turner, Bradley; Bansil, Rama; Erramilli, Shyamsunder


    It is well known that the viscoelastic properties of gastric mucin are crucial to the protection of the lining of the stomach against its own acidic secretions and other agents. Helicobacter Pylori, a rod shaped, gram-negative bacteria that dwells in the mucus layer of approximately 50% of the world's population is a class I carcinogen and is associated with gastric ulcers and severe gastritis. The structural damage to the mucus layer caused by H. Pylori is an important aspect of infection with this bacteria. We are examining the impact of H. Pylori on mucin and mucus rheology quantitatively using a combination of dynamic light scattering and multiple particle tracking experiments. Video microscopy data will also be presented on the motility of this bacteria in mucin at different pH and in other viscoelastic gels.

  10. Rheology of suspensions of rodlike particles

    International Nuclear Information System (INIS)

    Powell, R.L.


    Suspensions of rigid rodlike particles in Newtonian suspending fluids are considered. The author discusses the dependence of the relative viscosity μ r upon the volume fraction of particles φ, their aspect ratio a r , and the particle orientation distribution when the particles are sufficiently large that hydrodynamic forces are dominant. Theoretical results are reviewed for a variety of long slender particles. Experimental results obtained using classical rheometrical techniques are discussed. It is shown that when a r ≤25, data from several laboratories agree and they indicate that μ r depends more strongly upon φ than a r . Previous experimental results using falling ball rheometry are discussed as well as some more recent findings. These are shown to provide insights heretofore unavailable into the macroscopic rheology of suspensions of randomly oriented and oriented rods

  11. Nonlinear Rheology in a Model Biological Tissue. (United States)

    Matoz-Fernandez, D A; Agoritsas, Elisabeth; Barrat, Jean-Louis; Bertin, Eric; Martens, Kirsten


    The rheological response of dense active matter is a topic of fundamental importance for many processes in nature such as the mechanics of biological tissues. One prominent way to probe mechanical properties of tissues is to study their response to externally applied forces. Using a particle-based model featuring random apoptosis and environment-dependent division rates, we evidence a crossover from linear flow to a shear-thinning regime with an increasing shear rate. To rationalize this nonlinear flow we derive a theoretical mean-field scenario that accounts for the interplay of mechanical and active noise in local stresses. These noises are, respectively, generated by the elastic response of the cell matrix to cell rearrangements and by the internal activity.

  12. Rheological properties of sodium smectite clay

    International Nuclear Information System (INIS)

    Boergesson, L.; Hoekmark, H.; Karnland, O.


    The rheological properties of Na-smectite Mx-80 have been investigated by various laboratory tests. The investigations include determination of the hydraulic conductivity, the undrained stress-strain-strength properties, the creep properties, the compression and swelling properties in drained and undrained conditions and the undrained thermomechanical properties. Measurements have been made at different densities, clay/sand mixtures and pore water compositions. The influence of temperature, rate of strain and testing technique has also been considered. The investigation has led to a supply of basic data for the material models which will be used at performance calculations. The results have also increased the general understanding of the function of smectitic clay as buffer material. The microstructural behaviour has been considered at the validation of the different test results and the validity of the effective stress theory has been discussed. Comparisons with the properties of Ca-smectite have also been made. (orig.)


    Directory of Open Access Journals (Sweden)

    Erofeev Vladimir Trofimovich


    Full Text Available At the present time the most widely used type of road pavement is asphalt-concrete pavement produced on the basis of oil bitumen. One of the efficient ways to increase the quality and durability of asphalt-concrete pavement is modification of bitumen. Though Russian specialists still don’t have the global view of the ideal and real asphalt cement, the requirements to its quality and durability indicators in the composition of road structure haven’t yet formed. The authors present the investigation results of the properties of oil asphalt cement containing 0.5-2.0% of modifier “Olazol”. The physical, mechanical and rheological properties of the modified bitumen are determined. The dependences of the dynamic viscosity of the modified bitumen from the quantity of introduced modifier, shear rate and reheat temperature are analyzed.

  14. Rheological Characterization of Green Sand Flow

    DEFF Research Database (Denmark)

    Jabbaribehnam, Mirmasoud; Spangenberg, Jon; Hovad, Emil


    The main aim of this paper is to characterize experimentally the flow behaviour of the green sand that is used for casting of sand moulds. After the sand casting process is performed, the sand moulds are used for metal castings. The rheological properties of the green sand is important to quantify...... module for characterizing granular materials. The new module enables viscosity measurements of the green sand as function of the shear rate at different flow rates, i.e. 0, 2, 4, 6, 8, 10, 12 and 15 L/min. The results show generally that the viscosity decreases with both the shear- and flow rate....... In addition, the measurements show that the green sand flow follows a shear-thinning behaviour even after the full fluidization point....

  15. Rheology of Aqueous Dispersions of Phytoglycogen Nanoparticles (United States)

    Shamana, Hurmiz; Dutcher, John

    Phytoglycogen is a natural, highly branched polysaccharide nanoparticle extracted and purified from sweet corn. The nanoparticles possess many unusual properties that suggest a broad range of applications in cosmetics, food and nutrition, and biomedicine. These applications stem from a strong interaction between the nanoparticles and water, which has motivated our studies of aqueous phytoglycogen dispersions. We have measured the rheology of the dispersions as a function of phytoglycogen concentration C. Unlike other polysaccharides such as starch, we find that the zero-shear viscosity of phytoglycogen dispersions remains very low over an extended range of C, increasing significantly only for C >20% w/w. These results imply that the particles do not interact significantly until they are forced into contact at very high concentrations. This is consistent with our small angle neutron scattering measurements that show that the particle spacing becomes equal to the particle diameter for C 25 % w/w.

  16. Rheological and microstructural properties of Irradiated starch

    International Nuclear Information System (INIS)

    Atrous Turki, Hager


    Gamma irradiation ia s fast and efficient method to improve the functional properties of straches. Wheat and potato starches were submitted, in the present study, at 3,5,10 and 20 kGy radiation dose. The changes induced by irradiation on the rheological properties of these starches showed a decrease in the viscosity with increasing radiation dose. Chemicals bond's hydrolysis has been induced by free radicals that have been identified by EPR. Wheat starch presents five EPR signals after irradiation, whiles potato starch has a weak EPR signal. On the other hand, irradiation caused decrease in amylose content. This decrease is more pronounced in potato starch. Dry irradiated starch's MEB revealed no change in the shape, size and distribution of the granules. While, the observation of wheat starch allowed the complete disappearance of the granular structure and the dissolution of its macromolecules after irradiation which justifies the significant decrease in wheat starch's viscosity irradiated at 20 kGy.

  17. Rheological study of a water based oil well drilling fluid

    Energy Technology Data Exchange (ETDEWEB)

    Mahto, Vikas; Sharma, V.P. [Department of Petroleum Engineering, Indian School of Mines, Dhanbad-826004, Jharkhand (India)


    Organic polymers are commonly used to control the rheology and filtrate loss required for water-based drilling fluids. An ecologically-friendly water-based drilling fluid was developed by studying the rheological behavior of tamarind gum and polyanionic cellulose on bentonite water suspensions. The effect of drilling fluid filtrate on formation damage was also analyzed. The drilling fluid that was developed has better rheological properties and fluid loss control which are required for optimum performance of oil well drilling. In addition, the drilling fluid filtrate exhibits minimum formation damage on sandstone cores.

  18. Rheology of high melt strength polypropylene for additive manufacturing

    DEFF Research Database (Denmark)

    Jagenteufel, Ralf; Hofstätter, Thomas; Kamleitner, Florian


    Rheological measurements of high melt strength polypropylene (HMS-PP) were used in order to generate master curves describing the shear-dependent viscosity in comparison to acrylonitrile butadiene styrene copolymer (ABS). The latter material showed specific disadvantages in terms of thermal......, adapted parameters for HMS-PP were determined using a fused deposition modeling test bench. The rheological survey clearly showed changes in the melt viscosity of both ABS and HMS-PP due to thermal degradation. However, the comparison of rheological data of the virgin materials with those of printed...

  19. Rheological Properties of Natural Subduction Zone Interface: Insights from "Digital" Griggs Experiments (United States)

    Ioannidi, P. I.; Le Pourhiet, L.; Moreno, M.; Agard, P.; Oncken, O.; Angiboust, S.


    The physical nature of plate locking and its relation to surface deformation patterns at different time scales (e.g. GPS displacements during the seismic cycle) can be better understood by determining the rheological parameters of the subduction interface. However, since direct rheological measurements are not possible, finite element modelling helps to determine the effective rheological parameters of the subduction interface. We used the open source finite element code pTatin to create 2D models, starting with a homogeneous medium representing shearing at the subduction interface. We tested several boundary conditions that mimic simple shear and opted for the one that best describes the Grigg's type simple shear experiments. After examining different parameters, such as shearing velocity, temperature and viscosity, we added complexity to the geometry by including a second phase. This arises from field observations, where shear zone outcrops are often composites of multiple phases: stronger crustal blocks embedded within a sedimentary and/or serpentinized matrix have been reported for several exhumed subduction zones. We implemented a simplified model to simulate simple shearing of a two-phase medium in order to quantify the effect of heterogeneous rheology on stress and strain localization. Preliminary results show different strength in the models depending on the block-to-matrix ratio. We applied our method to outcrop scale block-in-matrix geometries and by sampling at different depths along exhumed former subduction interfaces, we expect to be able to provide effective friction and viscosity of a natural interface. In a next step, these effective parameters will be used as input into seismic cycle deformation models in an attempt to assess the possible signature of field geometries on the slip behaviour of the plate interface.

  20. Early alterations of red blood cell rheology in critically ill patients. (United States)

    Reggiori, Giulia; Occhipinti, Giovanna; De Gasperi, Andrea; Vincent, Jean-Louis; Piagnerelli, Michael


    To investigate red blood cell rheology in a large intensive care unit population on admission, and to assess the possible influence of comorbidities on the rheology. : Prospective study. Medico-surgical intensive care unit with 31 beds. All intensive care unit admissions during a 5-month period and 20 healthy volunteers. Blood sampling. A total of 196 intensive care patients (160 without and 36 with sepsis) and 20 healthy volunteers were studied. Red blood cell rheology (deformability and aggregation) was assessed ex vivo using the laser-assisted optical rotational cell analyzer (LORCA; Mechatronics Instruments BV, AN Zwaag, Netherlands) within the first 24 hrs after intensive care unit admission. Red blood cell deformability was determined by the elongation index in relation to the shear stress (0.3 to 50 Pa) applied on the red blood cell membrane surface. Aggregation was assessed by the aggregation index. Septic patients were more likely to have anemia, coagulation abnormalities, and comorbidities than were nonseptic patients. Red blood cell deformability was significantly altered in septic compared to nonseptic patients and volunteers for the majority of shear stress rates studied. The aggregation index was greater in septic patients than in volunteers (67.9% [54.7-73.5] vs. 61.8% [58.2-68.4]; p < .05). Only sepsis and hematologic disease influenced the elongation index (both p < .01). Other comorbidities, like cancer, diabetes mellitus, cirrhosis, and terminal renal failure, had no effect on the elongation index. Aggregation index was related to the degree of organ failure (Sequential Organ Failure Assessment score), the red blood cell count, and fibrinogen concentrations. Early alterations of red blood cell rheology are common in intensive care unit patients, especially in those with sepsis. Comorbidities (other than hematologic diseases) do not significantly influence these abnormalities. These alterations could contribute to the microcirculatory alterations

  1. Role of pluronics on rheological, drying and crack initiation of 'suckable' gels of decontamination

    International Nuclear Information System (INIS)

    Bousquet, C.


    The aim of this work was to understand the role of an addition of pluronics on the rheological behaviour, the drying and the fracturing of 'suckable' gels used for nuclear decontamination. The system studied was an aqueous suspension of silica (100 g/L of Aerosil 380) in a strong acidic medium (HNO 3 /H 3 PO 4 1.5 mol/L/1.5 mol/L) in presence of pluronics. Pluronics are amphiphilic tri-blocks copolymers composed of ethylene poly-oxide blocks and of propylene poly-oxide. The first part of this study deals with the characterization of the rheological properties of the gels. From viscosity retaking measurements, flow rheo-grams analysis and the viscoelastic properties of the gels, have been determined an improvement of the rheological properties of the gels significant from the addition of 5 g/L of copolymer. In a second part, the determination of adsorption isotherms coupled to small angles neutrons diffusion measurements has revealed that copolymers are adsorbed flat on silica in bridging the aggregates between them and that the improvement of the rheological behaviour of the gels is due to the increase of the bonds density of the gelled lattice. Moreover, beyond 10 g/L, the adsorption saturation of copolymers at the surface of the silica prevents the bridging of the aggregates which induces the gel destabilization. The last part of this work deals with the characterization of characteristic values of drying and of crack initiation of gels. Then is revealed a relation between the drying kinetics and the formation of cracks in the gel layer. Moreover, the study of the evolution of stresses in the gel layer during time allows to reveal that the addition of pluronics to the formulation of gels allows to improve the gel resistance to the crack initiation and to the delamination. (O.M.)

  2. The Effective Rheology of Natural Subduction Shear Zones: Insights from Numerical Simple Shear Experiments (United States)

    Ioannidi, Paraskevi Io; Le Pourhiet, Laetitia; Moreno, Marcos; Agard, Philippe; Oncken, Onno; Angiboust, Samuel


    Determination of the subduction interface rheological parameters is an interesting aspect of geodynamics since it can help better understand the physical nature of plate locking and its relation to surface deformation patterns observed at different time scales (GPS displacements during the seismic cycle). Since direct rheological measurements are not possible, unfortunately, we herein try to determine the effective rheological parameters of a subduction interface using finite element modelling. We use the open source finite element code pTatin to create 2D models, starting with a homogeneous medium representing shearing at the subduction interface. We tested several boundary conditions trying to find the one that can best mimic simple shear experiments performed on rock samples. After examining different parameters including the shearing velocity, the temperature and the viscosity, we added complexity to the geometry by including a second phase. This complexity arose from field observations, where composite shear zone outcrops often characterize the subduction interface. Stronger crustal blocks embedded within a sedimentary and/or serpentinized matrix have been reported for several exhumed subduction zones. We implemented a simplified model to simulate simple shearing of a two-phase medium in order to quantify the effect of heterogeneous rheology on stress and strain localization. Preliminary results show different strength in the models depending on the block-to-matrix ratio. In order to test our methodology, we first use clast-in-matrix geometries from thin sections taken through lab experiments. In a second stage, we upscale the method to outcrop scale clast-in-matrix geometries. By sampling at different depths along exhumed former subduction interfaces, we expect to be able to provide effective friction of a natural interface. In a next step, these effective frictions will be used as input into seismic cycle deformation models in an attempt to assess the

  3. Changes in overall ventricular myocardial architecture in the setting of a porcine animal model of right ventricular dilation. (United States)

    Agger, Peter; Ilkjær, Christine; Laustsen, Christoffer; Smerup, Morten; Frandsen, Jesper R; Ringgaard, Steffen; Pedersen, Michael; Partridge, John B; Anderson, Robert H; Hjortdal, Vibeke


    Chronic pulmonary regurgitation often leads to myocardial dysfunction and heart failure. It is not fully known why secondary hypertrophy cannot fully protect against the increase in wall stress brought about by the increased end-diastolic volume in ventricular dilation. It has been assumed that mural architecture is not deranged in this situation, but we hypothesised that there might be a change in the pattern of orientation of the aggregations of cardiomyocytes, which would contribute to contractile impairment. We created pulmonary valvular regurgitation by open chest, surgical suturing of its leaflets in seven piglets, performing sham operations in seven control animals. Using cardiovascular magnetic resonance imaging after 12 weeks of recovery, we demonstrated significantly increased right ventricular volumes in the test group. After sacrifice, diffusion tensor imaging of their hearts permitted measurement of the orientation of the cardiomyocytes. The helical angles in the right ventricle approached a more circumferential orientation in the setting of right ventricular RV dilation (p = 0.007), with an increased proportion of surface-parallel cardiomyocytes. In contrast, this proportion decreased in the left ventricle. Also in the left ventricle a higher proportion of E3 angles with a value around zero was found, and conversely a lower proportion of angles was found with a numerical higher value. In the dilated right ventricle the proportion of E3 angles around -90° is increased, while the proportion around 90° is decreased. Contrary to traditional views, there is a change in the orientation of both the left ventricular and right ventricular cardiomyocytes subsequent to right ventricular dilation. This will change their direction of contraction and hinder the achievement of normalisation of cardiomyocytic strain, affecting overall contractility. We suggest that the aetiology of the cardiac failure induced by right vetricular dilation may be partly explained

  4. Influence of the Elastic Dilatation of Mining-Induced Unloading Rock Mass on the Development of Bed Separation

    Directory of Open Access Journals (Sweden)

    Weibing Zhu


    Full Text Available Understanding how mining-induced strata movement, fractures, bed separation, and ground subsidence evolve is an area of great importance for the underground coal mining industry, particularly for disaster control and sustainable mining. Based on the rules of mining-induced strata movement and stress evolution, accumulative dilatation of mining-induced unloading rock mass is first proposed in this paper. Triaxial unloading tests and theoretical calculation were used to investigate the influence of elastic dilatation of mining-induced unloading rock mass on the development of bed separation in the context of district No. 102 where a layer of super-thick igneous sill exists in the Haizi colliery. It is shown that the elastic dilatation coefficient of mining-induced unloading hard rocks and coal were 0.9~1.0‰ and 2.63‰ respectively under the axial load of 16 MPa, which increased to 1.30~1.59‰ and 4.88‰ when the axial load was 32 MPa. After successively excavating working faces No. 1022 and No. 1024, the elastic dilatation of unloading rock mass was 157.9 mm, which represented approximately 6.3% of the mining height, indicating the elastic dilatation of mining-induced unloading rock mass has a moderate influence on the development of bed separation. Drill hole detection results after grouting, showed that only 0.33 m of the total grouting filling thickness (1.67 m was located in the fracture zone and bending zone, which verified the result from previous drill hole detection that only small bed separation developed beneath the igneous sill. Therefore, it was concluded that the influences of elastic dilatation of mining-induced unloading rock mass and bulking of caved rock mass jointly contributed to the small bed separation space beneath the igneous sill. Since the accurate calculation of the unloading dilatation of rock mass is the fundamental basis for quantitative calculation of bed separation and surface subsidence, this paper is expected

  5. Percutaneous dilatational tracheostomy without fiber optic bronchoscopy-Evaluation of 80 intensive care units cases

    NARCIS (Netherlands)

    J.A. Calvache (Jose Andrés); R.A. Molina García (Rodrigo); A.L. Trochez (Adolfo); J. Benitez (Javier); L.A. Flga (Lucía Arroyo)


    textabstractBackground: The development of percutaneous dilatational tracheostomy techniques (PDT) has facilitated the procedure in Intensive Care Units (ICU). Objective: To describe the early intra and post-operative complications in ICU patients requiring percutaneous dilatational tracheostomy

  6. Endoscopic balloon dilatation for Crohn's strictures of the gastrointestinal tract is feasible

    DEFF Research Database (Denmark)

    Karstensen, John Gásdal; Hendel, Jakob; Vilmann, Peter


    Despite optimized medical treatment, Crohn´s disease can cause gastrointestinal (GI) strictures, which requires surgical intervention. Lately, endoscopic balloon dilatation has been established as an alternative to surgery. In the following, we report our experiences with endoscopic dilatation...

  7. Soft particles at fluid interfaces: wetting, structure, and rheology (United States)

    Isa, Lucio

    Most of our current knowledge concerning the behavior of colloidal particles at fluid interfaces is limited to model spherical, hard and uniform objects. Introducing additional complexity, in terms of shape, composition or surface chemistry or by introducing particle softness, opens up a vast range of possibilities to address new fundamental and applied questions in soft matter systems at fluid interfaces. In this talk I will focus on the role of particle softness, taking the case of core-shell microgels as a paradigmatic example. Microgels are highly swollen and cross-linked hydrogel particles that, in parallel with their practical applications, e.g. for emulsion stabilization and surface patterning, are increasingly used as model systems to capture fundamental properties of bulk materials. Most microgel particles develop a core-shell morphology during synthesis, with a more cross-linked core surrounded by a corona of loosely linked and dangling polymer chains. I will first discuss the difference between the wetting of a hard spherical colloid and a core-shell microgel at an oil-water interface, pinpointing the interplay between adsorption at the interface and particle deformation. I will then move on to discuss the interplay between particle morphology and the microstructure and rheological properties of the interface. In particular, I will demonstrate that synchronizing the compression of a core-shell microgel-laden fluid interface with the deposition of the interfacial monolayer makes it possible to transfer the 2D phase diagram of the particles onto a solid substrate, where different positions correspond to different values of the surface pressure and the specific area. Using atomic force microscopy, we analyzed the microstructure of the monolayer and discovered a phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases correspond to shell-shell or core-core inter

  8. Percutaneous Dilational Tracheotomy in Solid-Organ Transplant Recipients. (United States)

    Ozdemirkan, Aycan; Ersoy, Zeynep; Zeyneloglu, Pinar; Gedik, Ender; Pirat, Arash; Haberal, Mehmet


    Solid-organ transplant recipients may require percutaneous dilational tracheotomy because of prolonged mechanical ventilation or airway issues, but data regarding its safety and effectiveness in solid-organ transplant recipients are scarce. Here, we evaluated the safety, effectiveness, and benefits in terms of lung mechanics, complications, and patient comfort of percutaneous dilational tracheotomy in solid-organ transplant recipients. Medical records from 31 solid-organ transplant recipients (median age of 41.0 years [interquartile range, 18.0-53.0 y]) who underwent percutaneous dilational tracheotomy at our hospital between January 2010 and March 2015 were analyzed, including primary diagnosis, comorbidities, duration of orotracheal intubation and mechanical ventilation, length of intensive care unit and hospital stays, the time interval between transplant to percutaneous dilational tracheotomy, Acute Physiology and Chronic Health Evaluation II score, tracheotomy-related complications, and pulmonary compliance and ratio of partial pressure of arterial oxygen to fraction of inspired oxygen. The median Acute Physiology and Chronic Health Evaluation II score on admission was 24.0 (interquartile range, 18.0-29.0). The median interval from transplant to percutaneous dilational tracheotomy was 105.5 days (interquartile range, 13.0-2165.0 d). The only major complication noted was left-sided pneumothorax in 1 patient. There were no significant differences in ratio of partial pressure of arterial oxygen to fraction of inspired oxygen before and after procedure (170.0 [interquartile range, 102.2-302.0] vs 210.0 [interquartile range, 178.5-345.5]; P = .052). However, pulmonary compliance results preprocedure and postprocedure were significantly different (0.020 L/cm H2O [interquartile range, 0.015-0.030 L/cm H2O] vs 0.030 L/cm H2O [interquartile range, 0.020-0.041 L/cm H2O); P = .001]). Need for sedation significantly decreased after tracheotomy (from 17 patients [54.8%] to

  9. Asphalt rheology and strengthening through polymer binders : final report. (United States)


    This term paper investigates the influences of polymer modifications to asphalt rheology as compared to : conventional asphalt pavement sections. The addition of 2% to 3% of polymers into the wearing and base courses : of asphalt (flexible) pavements...

  10. Rheology and Segregation of Granular Mixtures in Dense Flows

    Indian Academy of Sciences (India)

    Devang Khakhar

    IIT Bombay. Rheology and Segregation of. Granular Mixtures in Dense Flows. Devang Khakhar. Department of Chemical Engineering. Indian Institute of Technology Bombay. Mumbai, India. Acknowledgment: Anurag Tripathi. 77th Annual Meeting of IASc, Ahmedabad, 18-20 Nov, 2011 ...

  11. Oral texture perception in relation to rheology for mayonnaise

    NARCIS (Netherlands)

    Terpstra, M.E.J.; Janssen, A.M.; Linden, van der E.; Wijk, de R.A.


    Sensory attributes of commercial mayonnaises have been correlated to rheological curves to obtain those measuring conditions that reflect the oral perception of specific (texture) attributes. Correlations are found mainly with data from flow curve measurements and from dynamic stress measurements


    Directory of Open Access Journals (Sweden)



    Full Text Available The microstructure and scaling of rheological properties of colloidal gels of bentonite investigated as a function of volume fraction and strength of interparticle interaction over a range of volume fractions, elastic modulus is well described with a scaling law functions of volume fractions, while the role of interparticle attractions can be accounted for by expressing these rheological properties as (/g-1n, where g captures the strength of particle interaction and n the microstructure.The scaling variable (p/pc-1, suggested in percolation theory to describe rheological behavior near percolation transition, acts to collapse G’ data suggesting that along lines of constant (/g-1 these gels are rheologically identical.


    Directory of Open Access Journals (Sweden)

    S. Chaoui


    Full Text Available The microstructure and scaling of rheological properties of colloidal gels of bentonite investigated as a function of volume fraction and strength of interparticle interaction over a range of volume fractions, elastic modulus is well described with a scaling law functions of volume fractions, while the role of interparticle attractions can be accounted for by expressing these rheological properties as (f/fg-1n, where fg captures the strength of particle interaction and n the microstructure. The scaling variable (fp/fpc-1, suggested in percolation theory to describe rheological behavior near percolation transition, acts to collapse G’ data suggesting that along lines of constant (f/fg-1 these gels are rheologically identical.

  14. Relation between sensory analysis and rheology of body lotions

    Czech Academy of Sciences Publication Activity Database

    Morávková, Tereza; Filip, Petr


    Roč. 38, č. 6 (2016), s. 558-566 ISSN 0142-5463 Institutional support: RVO:67985874 Keywords : body lotion * empirical model * emulsions * rheology * sensory attribute Subject RIV: BK - Fluid Dynamics Impact factor: 1.581, year: 2016

  15. Dispersion and rheology of surfactant-mediated silver nanoparticle suspensions (United States)

    Chen, Chun-Nan; Huang, Chih-Ta; Tseng, Wenjea J.; Wei, Ming-Hsiung


    Polycrystalline silver (Ag) nanoparticles were dispersed in solvent mixtures consisting of 2-butoxyethyl acetate (BCA) and diethylene glycol monoethyl ether acetate (CA) in a BCA:CA weight ratio of 5:1. Three commercially available polymeric surfactants were used, and the gravitational sedimentation, agglomerate-size distribution, isothermal adsorption, and rheological behavior of the nanoparticle suspensions were examined. One of the surfactants (hereafter termed 9250) was found effective in stabilizing the Ag nanoparticle suspensions. Both the adsorption isotherm and the Fourier transform infrared spectroscopy revealed the preferential adsorption of the 9250 surfactant molecules on the nanoparticle surface, forming a Langmuir-type monolayer adsorption in the given solvents so that a steric stabilization was rendered. An optimal surfactant concentration of 5 wt.% (in terms of the solids weight) was determined experimentally. In addition, the Ag suspensions with a broad range of solids concentration (ϕ = 1-16 vol.%) showed a shear-thinning flow character over a shear-rate range from 1 to 4000 s-1, revealing that an attractive interparticle interaction was operative. Relative viscosity (ηr) of the nanoparticle suspensions deviated from the linearity when ϕ was greater than ˜10 vol.%; at which, the attractive potential began to dominate the interparticle interactions. This ηr-ϕ dependence was compared with various existing models and the (viscosity) predictive capability of the models was discussed.

  16. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds (United States)

    Marshall, J. R.; Borucki, J.; Bratton, C.


    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  17. Study of the rheological behaviour of corium/concrete mixtures

    International Nuclear Information System (INIS)

    Ramacciotti, M.


    In the hypothetical event of a severe accident in a Light Water Reactor, scenarios in which the reactor pressure vessel (RPV) fails and the core melt mixture (called corium) relocates into the reactor cavity, cannot be excluded. The viscosity (in fact, corium rheological behaviour) plays a major role in many phenomena such as core melt down, discharge from reactor pressure vessel, interaction with structural materials (concrete,...) and spreading in a core-catcher. For these reasons, it is important to be able to predict the rheological behaviour of corium melts of different compositions (essentially based on UO 2 , ZrO 2 , Fe x O y and Fe for in-vessel scenarios, plus SiO 2 and CaO for ex-vessel scenarios) at temperatures above solidus temperature. In the case of corium-concrete mixtures, the increase of viscosity depends not only on the increase of particles in the melts but also on the increase of the residual liquid phase viscosity (due to the increase in silica contents). The Urban correlation is used to calculate the viscosity of the carrying liquid with silica. This model was tested and gave good agreements between measured and estimated viscosities of various basalts among which one contained 18 wt% of UO 2 . Then, in the solidification range, the analysis of published data showed that the viscosity cannot be described by a suspension viscosity model of non-interactive spherical particles; consequently we proposed an Arrhenius type law with a multiplying factor such as η r = exp(2.5 Cφ) and the C factor value varies between 4 and 8. This factor is more important in the case of low shear rates and low cooling rates. The analysis of the samples structure after quenching shows a dependence of this factor on the particle morphology. Finally, for a value of 6.1 of the C factor, we obtained the best agreement with experimental data for a corium spreading test at 2100 K on a horizontal surface. (author)

  18. New Constraints on Martian Lava Flow Rheologies From MOLA (United States)

    Glaze, L. S.; Baloga, S. M.; Stofan, E. R.; McColley, S. M.


    The field of physical lava flow modeling (terrestrial and planetary) has long suffered from the paucity of data on flow dimensions. Even Earth lacks high resolution digital topographic information. Data for planetary flows are traditionally even more meager than terrestrial data. We generally have only the planimetric view to work with and crude estimates of slope. Now, with the tremendous volume of Mars Orbiter Laser Altimeter (MOLA) data available (and due to be available in the near future), we are presented with the first opportunity to measure the full three-dimensional character of lava flows on the surface of Mars. The 3-D character of a lava flow is comprised of both longitudinal and transverse profiles, and is influenced by estimates of underlying slope. All of these can be measured with very fine precision and accuracy from the raw MOLA profile data. From such data, we can determine how a lava flow thickens and spreads laterally with distance. This is a very exciting prospect because, for the first time, the high quality dimensional data should allow us to distinguish between differing physics models for lava flow emplacement. This information can be used to assess rheologic changes along the path of the flow and to distinguish between changes due to rheology and slope. We have already begun analysis of several Martian lava flows, through comparison of dimensional data with predicted profiles from physics models in the literature. Based on flow morphology, we can choose from models that describe rapid emplacement (Baloga et al., 1995), loss of material to levees (Baloga et al., 1998; Glaze and Baloga, 1998), degassing (Baloga et al., 2001), lateral spreading (Bruno et al., 1996), cumulative topographic effects, and others. Refs: Baloga, SM, PD Spudis, and JE Guest (1995) JGR 100:24,509-24,519. Baloga, SM, LS Glaze, JA Crisp, and SA Stockman (1998) JGR 103:5133-5142. Baloga, SM, LS Glaze, MN Peitersen, and JA Crisp (2001) JGR 106:13,395-13,405. Bruno, BC

  19. Aplicação de um Modelo Reológico Não-Linear em Sistemas Poliméricos Dilatantes Application of Non-Linear Rheological Model to Shear-Tickening Polymeric Systems

    Directory of Open Access Journals (Sweden)

    Rômulo F. Navarro


    Full Text Available A dilatância é um comportamento reológico comum a vários sistemas poliméricos embora não ocorra em polímeros puros. Existem várias teorias aplicáveis à explicação desse fenômeno e alguns modelos matemáticos para o ajuste de dados experimentais de quatro de suas seis formas de ocorrência. Neste trabalho é dado enfoque à dilatância antecedida por um comportamento newtoniano e sucedida pelo comportamento pseudoplástico. Para ajustar dados constantes da literatura para sistemas desse tipo, é apresentado um modelo híbrido e não-linear. Para o teste do modelo foram utilizados dados existentes na literatura para solução de alfa,ômega poli(t-butilestireno em óleo mineral e suspensão de partículas do copolímero de estireno com acrilato de metila em solução aquosa de poli(ácido acrílico. O modelo proposto apresenta boa concordância com os dados experimentais.Shear-thickening (dilatant behavior is common in several polymeric systems, but not in pure polymers. There are many theories that can be used to describe shear-thickening and some mathematical models that fit experimental data of three of its six types: dilatant, newtonian-dilatant, newtonian-dilatant-pseudoplastic, viscoplastic-dilatant, pseudoplastic-dilatant and newtonian-pseudoplastic-newtonian-dilatant sequences. This work deals with the behavior of newtonian-dilatant-pseudoplastic sequence behavior and proposes a hybrid, non-linear and viscous model to fit the experimental data from systems that present such rheological behavior. The systems under investigation were: a solution of alpha,omega poly(t-butylstyrene in a mineral oil (3g/dl (sample 1 and b suspension of styrene -- methyl acrylate copolymer (S-co-MA particles (15% vol. in a poly(acrylic acid (PAA (1% wt and water solution (sample 2. The proposed model agrees with the experimental data analysed.

  20. Rheology of Carbon Fibre Reinforced Cement-Based Mortar

    International Nuclear Information System (INIS)

    Banfill, Phillip F. G.; Starrs, Gerry; McCarter, W. John


    Carbon fibre reinforced cement based materials (CFRCs) offer the possibility of fabricating 'smart' electrically conductive materials. Rheology of the fresh mix is crucial to satisfactory moulding and fresh CFRC conforms to the Bingham model with slight structural breakdown. Both yield stress and plastic viscosity increase with increasing fibre length and volume concentration. Using a modified Viskomat NT, the concentration dependence of CFRC rheology up to 1.5% fibre volume is reported

  1. Rheological Study of Ageing Soft Glasses of Laponite

    Indian Academy of Sciences (India)

    Table of contents. Rheological Study of Ageing Soft Glasses of Laponite · Colloidal glasses · Laponite Na+0.7[(Si8Mg5.5Li0.3)O20(OH)4]–0.7 · Effect of salt (NaCl) · Arrested state · Relaxation dynamics · Rheology of aging system · Slide 8 · Experimental Protocol · Ageing and Creep experiments · Slide 11 · Slide 12.

  2. Bioactive and rheological properties of rose hip marmalade


    Sagdic, Osman; Toker, Omer Said; Polat, Busra; Arici, Muhammet; Yilmaz, Mustafa Tahsin


    In this study, bioactive (total phenolic, antioxidant and antiradical activity) and rheological properties (steady and dynamic) of rose hip marmalade were investigated. Bioactive properties were determined in rose hip marmalade and extract. Extract had higher total phenolic content (38.5 mg GAE/g dry extract), antioxidant activity (124 mg AAE/g dry extract) and antiradical activity (49.98 %) than marmalade. Steady and dynamic rheological properties of the marmalade were determined at differen...

  3. Effect of ?-cyclodextrin on Rheological Properties of some Viscosity Modifiers


    Rao, G. Chandra Sekhara; Ramadevi, K.; Sirisha, K.


    Cyclodextrins are a group of novel excipients, extensively used in the present pharmaceutical industry. Sometimes they show significant interactions with other conventional additives used in the formulation of dosage forms. The effect of β-cyclodextrin on the rheological properties of aqueous solutions of some selected viscosity modifiers was studied in the present work. β-cyclodextrin showed two different types of effects on the rheology of the selected polymers. In case of natural polymers ...

  4. Surface Chemistry Interactions of Cationorm with Films by Human Meibum and Tear Film Compounds

    Directory of Open Access Journals (Sweden)

    Georgi As. Georgiev


    Full Text Available Cationorm® (CN cationic nanoemulsion was demonstrated to enhance tear film (TF stability in vivo possibly via effects on tear film lipid layer (TFLL. Therefore the interactions of CN with human meibum (MGS and TFLL in vitro and in vivo deserve special study. MGS and CN were spread at the air/water interface of a Langmuir surface balance to ensure a range of MGS/CN oil phase ratios: 20/1, 10/1, 5/1, 3/1, 2/1 and 1/1. The films capability to reorganize during dynamic area changes was evaluated via the surface pressure-area compression isotherms and step/relaxation dilatational rheology studies. Films structure was monitored with Brewster angle microscopy. CN/TFLL interactions at the ocular surface were monitored with non-contact specular microscopy. The in vitro studies of MGS/CN layers showed that (i CN inclusion (at fixed MGS content increased film elasticity and thickness and that (ii CN can compensate for moderate meibum deficiency in MGS/CN films. In vivo CN mixed with TFLL in a manner similar to CN/MGS interactions in vitro, and resulted in enhanced thickness of TFLL. In vitro and in vivo data complement each other and facilitated the study of the composition-structure-function relationship that determines the impact of cationic nanoemulsions on TF.

  5. Assessment of rheological methods for a correlation to sludge filterability. (United States)

    Marinetti, M; Dentel, S K; Malpei, F; Bonomo, L


    To achieve good dewaterability, the conditioning process should create sludge flocs providing a porous cake during compression but also a high resistance to erosional stresses. This suggests that sludge's rheological characteristics, some of which (like the yield stress or the storage modulus) represent its network strength, should be related to the material's dewatering properties. Previous efforts to verify such a correlation--which would allow prediction of full scale dewaterability--have not provided strong correlations. In this work, commonly accepted rheological and dewatering tests were applied to conditioned sludges. Correlations were seen between different rheological parameters, particularly yield stress and specific energy, but not between rheological and filterability properties. Even using high pressure filtration tests, which should reflect the sludge's responses to normal and shear stresses, results were related to the measured rheological properties only in an indirect manner: a threshold shear strength is required beyond which further strength confers no improvement in filterability. Thus, common rheological tests are unlikely to provide useful information regarding full scale filterability. Copyright © 2010 Elsevier Ltd. All rights reserved.

  6. Data of methylome and transcriptome derived from human dilated cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Bong-Seok Jo


    Full Text Available Alterations in DNA methylation and gene expression have been implicated in the development of human dilated cardiomyopathy (DCM. Differentially methylated probes (DMPs and differentially expressed genes (DEGs were identified between the left ventricle (LV, a pathological locus for DCM and the right ventricle (RV, a proxy for normal hearts. The data in this DiB are for supporting our report entitled “Methylome analysis reveals alterations in DNA methylation in the regulatory regions of left ventricle development genes in human dilated cardiomyopathy” (Bong-Seok Jo, In-Uk Koh, Jae-Bum Bae, Ho-Yeong Yu, Eun-Seok Jeon, Hae-Young Lee, Jae-Joong Kim, Murim Choi, Sun Shim Choi, 2016 [1].

  7. Learning a Dilated Residual Network for SAR Image Despeckling (United States)

    Zhang, Qiang; Yuan, Qiangqiang; Li, Jie; Yang, Zhen; Ma, Xiaoshuang


    In this paper, to break the limit of the traditional linear models for synthetic aperture radar (SAR) image despeckling, we propose a novel deep learning approach by learning a non-linear end-to-end mapping between the noisy and clean SAR images with a dilated residual network (SAR-DRN). SAR-DRN is based on dilated convolutions, which can both enlarge the receptive field and maintain the filter size and layer depth with a lightweight structure. In addition, skip connections and residual learning strategy are added to the despeckling model to maintain the image details and reduce the vanishing gradient problem. Compared with the traditional despeckling methods, the proposed method shows superior performance over the state-of-the-art methods on both quantitative and visual assessments, especially for strong speckle noise.

  8. Learning a Dilated Residual Network for SAR Image Despeckling

    Directory of Open Access Journals (Sweden)

    Qiang Zhang


    Full Text Available In this paper, to break the limit of the traditional linear models for synthetic aperture radar (SAR image despeckling, we propose a novel deep learning approach by learning a non-linear end-to-end mapping between the noisy and clean SAR images with a dilated residual network (SAR-DRN. SAR-DRN is based on dilated convolutions, which can both enlarge the receptive field and maintain the filter size and layer depth with a lightweight structure. In addition, skip connections and a residual learning strategy are added to the despeckling model to maintain the image details and reduce the vanishing gradient problem. Compared with the traditional despeckling methods, the proposed method shows a superior performance over the state-of-the-art methods in both quantitative and visual assessments, especially for strong speckle noise.

  9. Dilated Virchow–Robin spaces mimicking a brainstem arteriovenous malformation

    Directory of Open Access Journals (Sweden)

    Thomas J Buell


    Full Text Available Virchow–Robin spaces (VRS are ubiquitous and commonly observed as the resolution of magnetic resonance imaging (MRI continues to improve. The function of VRS and the etiology of their dilation is still a subject of research. Diagnosing dilated VRS (dVRS can be challenging because they may appear similar to other pathologies such as cystic neoplasms, infectious cysts, and even arteriovenous malformations (AVMs on certain MRI pulse sequences. We reported a unique case of brainstem dVRS mimicking an AVM. Furthermore, the extensive pontine involvement of our patient's lesion is rarely described in neurosurgical literature. Understanding the imaging characteristics of dVRS is critical to accurately diagnose these lesions and avoid unnecessary tests and procedures.


    Directory of Open Access Journals (Sweden)

    Monika Bozikova


    Full Text Available This article deals with thermal properties of selected biooils Plahyd S biooil No1 and Plahyd N biooil No2 and rheologic properties of rapeseed oil. Plahyd S is a synthetic, rapidly biodegradable fluid which is based on sustainable raw materials. It is exceptionally suitable for applications in mobile and stationary hydraulic systems. Plahyd N is multigrade hydraulic oil based on rapeseed oil used in agricultural and construction machinery. For thermal parameters measurements was used Hot wire method. The experiment is based on measuring of the temperature rise vs. time evaluation of an electrically heated wire embedded in the tested material. The thermal conductivity is derived from the resulting change in temperature over a known time interval. Dependency of material resistance against the probe rotation was used at measurement of rheologic properties with instrument viscometer Anton Paar DV 3P. For two samples of biooils Plahyd N and Plahyd S were determined basic thermophysical parameters thermal conductivity, thermal diffusivity and volume specific heat. For each biooil samples were made two series of measurements. In the first series were measured thermal conductivity and thermal diffusivity at constant room temperature 20 C. Every thermophysical parameter was measured 10 times for each sample. The results were statistically processed. For biooil No1 thermal conductivity was 0.325 W*m 1 .K1 , it was higher value than we obtained for biooil No2 0.224 W*m 1 .K 1 . The similar results were obtained for thermal diffusivity of biooil No1 2.140.10 7 m 2 *s 1 and biooil No2 2.604.10 7 m 2* s 1 . For samples with constant temperature were calculated basic statistical characteristics as standard deviation for biooil No1 0.056 W*m 1*K 1 and biooil No2 0.054 W*m 1*K 1; probable error of the arithmetic average for biooil No 1 0.012 W*m 1*K 1 and biooil No 2 0.005 W*m 1*K 1, relative probable error in for biooil No1 3.69 per cent and biooil No2 2

  11. Endoscopic Dilatation versus Oesophageal Stent in Benign Oesophageal Stricture

    Directory of Open Access Journals (Sweden)

    Hadyanto Caputra


    Full Text Available Aim: Oesophageal stricture is one of the causes of dysphagia. It is a condition in which the lumen of oesophagus is narrowed by fibrotic tissue in the oesophageal wall. It is usually caused by inflammation or any other cause that leads to necrotizing of tissue. It is mainly differentiated into benign or malignant. The aim of this article is to answer the clinical question on the effectiveness of oesophageal stenting compared to endoscopic dilatation in patient with benign oesophageal stricture due to ingestion of corrosive substances, who had undergone several endoscopic dilatations. Method: We conducted search of relevant articles using PubMed search engine to answer the clinical question. Keywords being used during the search process were: ("oesophageal stricture"[All Fields] OR "oesophageal stenosis"[All Fields] AND (("dilatation"[All Fields] AND ("stents"[MeSH Terms] OR "stents"[All Fields] OR "stent"[All Fields]. Results were further converged by adding specific filters, which were full text articles and clinical trial. Results: The chosen article was further appraised in order to identify its validity and eligibility to answer the clinical question. We chose to use CONSORT (statement to improve the quality of reporting of RCTs to facilitate the critical appraisal and interpretation of RCTs. Conclusion: Stenting was associated with greater dysphagia, co-medication and adverse events. No randomized controlled trials which compared biodegradable stents with other stents or with balloon dilatation was identified. Lack of adequately robust evidence for effectiveness and cost-effectiveness formed the rationale of this trial.

  12. Is there cosmological time dilation in gamma-ray bursts? (United States)

    Band, David L.


    Norris et al. report that the temporal structure of faint gamma-ray bursts is longer than that of bright bursts, as expected for time dilation in the cosmological models of burst origin. I show that the observed trends can easily be produced by a burst luminosity function and thus may not result from cosmological effects. A cosmological signature may be present, but the tests Norris et al. present are not powerful enough to detect these signatures.

  13. Quantum Channels, Wavelets, Dilations and Representations of $O_n$


    Kribs, David W.


    We show that the representations of the Cuntz C$^\\ast$-algebras $O_n$ which arise in wavelet analysis and dilation theory can be classified through a simple analysis of completely positive maps on finite-dimensional space. Based on this analysis, an application in quantum information theory is obtained; namely, a structure theorem for the fixed point set of a unital quantum channel. We also include some open problems motivated by this work.

  14. Effects of mantle rheologies on viscous heating induced by Glacial Isostatic Adjustment (United States)

    Huang, PingPing; Wu, Patrick; van der Wal, Wouter


    It has been argued that viscous dissipation from mantle flow in response to surface loading during glacial cycles can result in short-term heating and thus trigger transient volcanism or changes in mantle properties, which may in turn affect mantle dynamics. Furthermore, heating near the Earth's surface can also affect the stability of ice sheets. We have studied the magnitude and spatial-temporal distribution of viscous heating induced in the mantle by the realistic ice model ICE-6G and gravitationally consistent ocean loads. Three types of mantle rheologies, including linear, non-linear and composite rheologies are considered to see if non-linear creep can induce larger viscous heating than linear rheology. We used the Coupled-Laplace-Finite-Element model of Glacial Isostatic Adjustment (GIA) to compute the strain, stress and shear heating during a glacial cycle. We also investigated the upper bound of temperature change and surface heat flux change due to viscous heating. We found that maximum viscous heating occurs near the end of deglaciation near the edge of the ice sheet with amplitude as high as 120 times larger than that of the chondritic radioactive heating. The maximum heat flux due to viscous heating can reach 30 mW m-2, but the area with large heat flux is small and the timescale of heating is short. As a result, the upper bound of temperature change due to viscous heating is small. Even if 30 glacial cycles are included, the largest temperature change can be of the order of 0.3 °C. Thus, viscous heating induced by GIA cannot induce volcanism and cannot significantly affect mantle material properties, mantle dynamics nor ice-sheet stability.

  15. Mounier-Kuhn syndrome: a rare cause of bronchial dilation. (United States)

    Celik, Burcin; Bilgin, Salih; Yuksel, Canan


    Mounier-Kuhn syndrome, or tracheobronchomegaly, is a rare clinical and radiologic condition characterized by marked tracheobronchial dilation and recurrent lower respiratory tract infections. Diagnosis is typically accomplished with the use of computed tomography and bronchoscopy, as well as pulmonary function testing. Patients may be asymptomatic; however, symptoms can range from minimal with preserved lung function to severe respiratory failure. Therapy, if any, is supportive but minimal. Surgery rarely has a place in the treatment of Mounier-Kuhn syndrome.Herein, we report the case of a 58-year-old man with chronic obstructive pulmonary disease who had a chronic cough, increased sputum production, and chest pain. Thoracic computed tomography showed tracheal dilation (diameter, 34 mm) and multiple diverticula in the posterior region of the trachea. Fiberoptic bronchoscopy revealed enlarged main bronchi, the dilated trachea, and prominent tracheal diverticula. Pulmonary function testing disclosed impaired respiratory function. Histopathologic examination of biopsy specimens from the bronchi and the tracheal wall supported the diagnosis of Mounier-Kuhn syndrome. The patient was released from the hospital and his condition was monitored for 2 years, during which time he developed no lower respiratory tract infections.Regardless of radiologic findings that suggest recurrent lower respiratory tract infection, we recommend that Mounier-Kuhn syndrome be considered in the differential diagnosis.

  16. Ethanol vapour induced dilated cardiomyopathy in chick embryos

    International Nuclear Information System (INIS)

    Kamran, K.; Khan, M.Y.; Minhas, L.A.


    Objective: To study the effects of ethanol vapour inhalation on the heart chambers of chick embryo. Methods: The case-control study was conducted at the College of Physicians and Surgeons Pakistan regional centre in Islamabad from January to October 2007. Both experimental and control groups were divided into three sub-groups each, based on the day of the sacrifice. Each group was dissected on day 7, day 10 and day 22 or hatching whichever was earlier. The experimental sub-groups sacrificed on day 7, day 10 and on hatching, were exposed to ethanol vapours till day 6, 9 and 9 of incubation respectively. The diameter of all 4 chambers was measured in experimental hearts and compared with age-matched controls. SPSS 10 was used for statistical analysis. Results: Ethanol vapour exposure caused widening of all heart chambers in the experimental chick embryos sacrificed on day 7 and day 10 compared to the controls. The chambers of newly hatched chick hearts showed dilatation in all the chambers except the left ventricle. Conclusion: Ethanol vapour exposure during development affects the heart, resulting in the widening of all heart chambers. The exposure is as dangerous as drinking alcohol. Alcohol vapour exposure during development leads to progressive dilatation in different heart chambers, producing dilated cardiomyopathy. (author)

  17. Massively dilated right atrium masquerading as a mediastinal tumor

    Directory of Open Access Journals (Sweden)

    Thomas Schroeter


    Full Text Available Severe tricuspid valve insufficiency causes right atrial dilatation, venous congestion, and reduced atrial contractility, and may eventually lead to right heart failure. We report a case of a patient with severe tricuspid valve insufficiency, right heart failure, and a massively dilated right atrium. The enormously dilated atrium compressed the right lung, resulting in a radiographic appearance of a mediastinal tumor. Tricuspid valve repair and reduction of the right atrium was performed. Follow up examination revealed improvement of liver function, reduced peripheral edema and improved New York Heart Association (NYHA class. The reduction of the atrial size and repair of the tricuspid valve resulted in a restoration of the conduit and reservoir function of the right atrium. Given the chronicity of the disease process and the long-standing atrial fibrillation, there is no impact of this operation on right atrial contraction. In combination with the reconstruction of the tricuspid valve, the reduction atrioplasty will reduce the risk of thrombembolic events and preserve the right ventricular function.

  18. [Aneurysmal dilatation of pulmonary artery and its branches on mitral stenosis: a case report]. (United States)

    Yaméogo, N V; Ndiaye, M B; Diao, M; Cabral-Ciss, E C; Sarr, M; Ba, S A


    Pulmonary arteries aneurysms are rare and the rarely described bilateral aneurysms. A 45-year-old patient carrier of mitral stenosis was admitted for dyspnoea class III of the NYHA, chest pain and a not infectious cough. The clinical examination found semiology of mitral stenosis, tricuspid incapacity and pulmonary arterial hypertension. The electrocardiogram showed atrial fibrillation and right ventricle hypertrophy. Chest X-ray found a cardiomegaly, an aspect of double outline of the inferior right bow, a prominent aspect of the left average bow reminding an aneurysm of the left pulmonary artery. The echocardiography Doppler found a pure tight mitral stenosis (mitral surface=0.6 cm(2)), a dilation of the trunk of the pulmonary artery (diameter=74 mm) and of its branches (diameter of the right pulmonary artery=28 mm, diameter of the left pulmonary artery=36 mm) seat of a spontaneous contrast. The left atrium and right cardiac cavities were also dilated. There was an important tricuspid incapacity with a major pulmonary hypertension (systolic pulmonary arterial=109 mmHg). The thoracic angioscan showed a pseudoaneurysm of the trunk of pulmonary artery and its branches to their distal parts. Under diuretic, anticoagulating and analgesic treatment the clinical signs improved however the spontaneous contrast persisted. The patient was rejected by the surgery for exceeded clinical board. She is at present followed in our service for 5 months. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  19. Dilated odontoma: A report of two cases from a radiological perspective (United States)

    Jayachandran, S.; Kayal, L.; Sharma, Aatman; Priyanka, Khobre


    Dilated odontoma is the most extreme form of dens invaginatus. The lesion appears as a roughly spherical mass that does not resemble a tooth but in a way appears tooth - like on radiographs due to somewhat similar radiodensity. The lesion is mostly spherical in appearance and hence the term “dilated.” Occasionally, we come across cases of simultaneous pathologies. Here, we report two cases of a dilated odontoma one of which is associated with dentigerous cyst and in other case dilated odontoma pushing the maxillary sinus superiorly. Histologically, the mass was composed of dentinal tubules. These morphological and histological features are compatible with those of a dilated odontoma. PMID:27041914

  20. Dilated odontoma: A report of two cases from a radiological perspective

    Directory of Open Access Journals (Sweden)

    S Jayachandran


    Full Text Available Dilated odontoma is the most extreme form of dens invaginatus. The lesion appears as a roughly spherical mass that does not resemble a tooth but in a way appears tooth - like on radiographs due to somewhat similar radiodensity. The lesion is mostly spherical in appearance and hence the term “dilated.” Occasionally, we come across cases of simultaneous pathologies. Here, we report two cases of a dilated odontoma one of which is associated with dentigerous cyst and in other case dilated odontoma pushing the maxillary sinus superiorly. Histologically, the mass was composed of dentinal tubules. These morphological and histological features are compatible with those of a dilated odontoma.

  1. Hybrid cutting balloon dilatation for treatment of cor triatriatum sinister in a cat. (United States)

    Stern, Joshua A; Tou, Sandra P; Barker, Piers C A; Hill, Kevin D; Lodge, Andrew J; Mathews, Kyle G; Keene, Bruce W


    A hybrid surgical approach and balloon dilatation were performed successfully in a cat with cor triatriatum sinister and clinical signs of congestive heart failure. Left lateral thoracotomy was used to access the heart and cutting balloon followed by standard balloon dilatation were utilized to dilate the perforation in the anomalous left atrial membrane. Clinical signs resolved completely after dilation of the anomalous left atrial membrane. Based upon the outcome of this case, balloon dilatation appears to be a viable treatment option for cats affected with cor triatriatum sinister. Published by Elsevier B.V.

  2. Rheological properties of disperse systems based on hydrolyzed lignin and oil (United States)

    Savitskaya, T. A.; Reznikov, I. V.; Shcheglov, V. A.; Tsygankova, N. G.; Telysheva, G. M.; Grinshpan, D. D.


    The rheological properties of oil dispersions of hydrophobized hydrolyzed lignin, which is an effective sorbent of oil and oil products, have been studied. It has been shown that at a lignin concentration of over 10%, free-disperse systems with Newton flow go over to coagulation thixotropic structures, demonstrating the pseudoplastic character of flow. The structural-mechanical characteristics of highly filled (lignin content of 40-45%) dispersions have been determined and the concentration region of existence of an oil-saturated sorbent in the form of a solid product easily removed from the water surface has been established.

  3. Free subduction dynamics of a thermo-mechanical slab with non-linear rheology (United States)

    Holt, A. F.; Becker, T. W.; Buffett, B. A.


    We investigate the dynamic controls on single plate subduction in a visco-plastic rheology using a 2D set up of the finite element code, CitcomCU. In contrast to previous studies, which focus largely on compositional slabs (e.g. Enns et al., 2005), we focus on thermal slabs (i.e. include effects of thermal diffusion). We analyse slabs that develop from plates both with uniform initial thicknesses and half-space cooling plates with thicknesses that vary with sqrt(x). A pseudo-plastic rheology facilitates the decoupling of the slab from the free slip upper surface. It is found that thermal slabs have lower strain rates in the bending region, due to the cooling upper boundary temperature condition, and so lower yield stresses are required to decouple thermal slabs than compositional slabs. As in previous work, it is found that stronger, thicker slabs promote trench advance (after the initial advancing phase). Both boundary conditions (basal and side) and incorporating a plate with half-space cooling thickness variations are shown to have a significant effect on slab dynamics, particularly on the maximum amount of trench retreat. Subsequently, models with non-Newtonian, stress-dependent rheologies are compared to Newtonian models with equivalent slab-mantle viscosity contrasts. Models with power law exponents of both 3, corresponding to dislocation creep, and a large exponent of 14, corresponding to near-pure plasticity (see Buffett and Becker, 2012), are analysed. It is found that, particularly for the n=14 case, the inclusion of a stress dependent rheology dramatically reduces the timescales of both trench migration and slab descent, while modifying slab morphology to a much lesser degree. Using a temperature threshold to confine the non-Newtonian rheology to within the slab prevents weakening in the surrounding mantle and so increases the subduction timescales to values that lie between the equivalent Newtonian and non-Newtonian (non-confined) timescales. While all

  4. Proposal for a revised definition of dilated cardiomyopathy, hypokinetic non-dilated cardiomyopathy, and its implications for clinical practice

    DEFF Research Database (Denmark)

    Pinto, Yigal M; Elliott, Perry M; Arbustini, Eloisa


    In this paper the Working Group on Myocardial and Pericardial Disease proposes a revised definition of dilated cardiomyopathy (DCM) in an attempt to bridge the gap between our recent understanding of the disease spectrum and its clinical presentation in relatives, which is key for early diagnosis...... and the institution of potential preventative measures. We also provide practical hints to identify subsets of the DCM syndrome where aetiology directed management has great clinical relevance....

  5. The extrudate swell of HDPE: Rheological effects (United States)

    Konaganti, Vinod Kumar; Ansari, Mahmoud; Mitsoulis, Evan; Hatzikiriakos, Savvas G.


    The extrudate swell of an industrial grade high molecular weight high-density polyethylene (HDPE) in capillary dies is studied experimentally and numerically using the integral K-BKZ constitutive model. The non-linear viscoelastic flow properties of the polymer resin are studied for a broad range of large step shear strains and high shear rates using the cone partitioned plate (CPP) geometry of the stress/strain controlled rotational rheometer. This allowed the determination of the rheological parameters accurately, in particular the damping function, which is proven to be the most important in simulating transient flows such as extrudate swell. A series of simulations performed using the integral K-BKZ Wagner model with different values of the Wagner exponent n, ranging from n=0.15 to 0.5, demonstrates that the extrudate swell predictions are extremely sensitive to the Wagner damping function exponent. Using the correct n-value resulted in extrudate swell predictions that are in excellent agreement with experimental measurements.

  6. Biodegradable compounds: Rheological, mechanical and thermal properties (United States)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.


    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  7. Influence of Fat Content on Chocolate Rheology (United States)

    Gabriele, D.; Migliori, M.; Baldino, N.; de Cindio, B.


    Molten chocolate is a suspension having properties strongly affected by particle characteristics including not only the dispersed particles but also the fat crystals formed during chocolate cooling and solidification. Even though chocolate rheology is extensively studied, mainly viscosity at high temperature was determined and no information on amount and type of fat crystals can be detected in these conditions. However chocolate texture and stability is strongly affected by the presence of specific crystals. In this work a different approach, based on creep test, was proposed to characterize chocolate samples at typical process temperatures (approximately 30 °C). The analysis of compliance, as time function, at short times enable to evaluate a material "elasticity" related to the solid-like behavior of the material and given by the differential area between the Newtonian and the experimental compliance. Moreover a specific time dependent elasticity was defined as the ratio between the differential area, in a time range, and total area. Chocolate samples having a different fat content were prepared and they were conditioned directly on rheometer plate by applying two different controlled cooling rate; therefore creep were performed by applying a low stress to ensure material linear behavior. Experimental data were analyzed by the proposed method and specific elasticity was related to single crystal properties. It was found that fat crystal amount and properties depend in different way on fat content and cooling rate; moreover creep proved to be able to detect even small differences among tested samples.

  8. On the rheological characteristics of sewage sludge

    Directory of Open Access Journals (Sweden)

    Tomáš Vítěz


    Full Text Available The work is focused on characterization of rheological behavior of sewage sludges sampled at different stages of waste water treatment. The main attention was focused on dynamic viscosity dependence on temperature, and shear rate. The sludge samples were examined under temperature ranging from 1 °C to 25 °C and under shear rate ranging from 0.34 s−1 to 68 s−1. Rotary digital viscometer (concentric cylinders geometry was used to perform the reological measurements. The solids content of the sludge samples ranged from 0.43 % to 21.45 % (A and C samples, respectively and ash free dry mass from 56.21 % to 67.80 % (A and B samples, respectively. The tested materials were found to be of non–Newtoninan nature and temperature dependent. Measured data were successfully cha­ra­cte­ri­zed by several mathematical models (Arrhenius, Bingham Plastic, Casson Law, Exponential, Gaussian, and IPC Paste in MATLAB® software with satisfying correlations between experimental and computed results. The best match (R2 = 0.999 was received with use of Gaussian model, in both cases, shear rate and temperature dependence. The results are quite useful e.g. for the purpose of technological equipment design.

  9. Effects of ioxaglate to blood rheology

    International Nuclear Information System (INIS)

    Schmid-Schoenbein, H.; Teitel, P.; Tietz, G.; Oezlen, A.


    Almen and Aspelin have shown that the use of non-ionic radio contrast media allows to increase the iodine concentration (which is desirable because of its effect on radio opacity) without a very large increase in osmolarity (which is undesirable because it impaires the fluidity of erythrocytes). This latter effect can also be diminished by reducing the osmolarity of a dimeric contrast medium as it has been achieved by incorporating more iodine atoms into the molecule in the case of Ioxaglate (Hexabrix). In various microrheological test systems, the fluidity of packed red cell suspension, the corrected filtration rate though 5 μm pores and the relative apparent viscosity of blood - contrast media mixtures (1 to 50% concentration) were determined in experiments comparing this compound with Urografin 76 of the same iodine content. In all systems, the former showed lesser rheological effects. In whole blood viscometry, this can be detected only after appropriate corrections for the effects of the two contrast media on hematocrit and plasma viscosity. Owing to a more pronounced water shift from the cells to the plasma, Urografin tends to reduce the viscosity of the plasma-contrast media mixture. The concomitant reduction in MCV and hematocrit level tends to screen the macrorheological effect of the dehydrated cells becomes immediately obvious when the viscometric data are corrected for hematocrit value and plasma viscosity effects. (orig.)

  10. Development of a synovial fluid analogue with bio-relevant rheology for wear testing of orthopaedic implants. (United States)

    Smith, Alan M; Fleming, Leigh; Wudebwe, Uchena; Bowen, James; Grover, Liam M


    The rheological properties of synovial fluid (SF) are crucial to the performance of joint prostheses. During the development of joint prostheses, wear tests are performed, which simulate joint movements in diluted solutions (usually between 25 and 33% v/v) of bovine serum which has very different rheological properties compared with native SF, where rheology is maintained by hyaluronan. Consequently, there is a need to develop a more suitable artificial SF. In this study, we used rheological techniques to understand SF flow properties which provided an insight into the mechanical behaviour required of a practical SF analogue. Steady-shear viscosity measurements were performed to reveal changes as a function of shear rate. To analyse the viscoelastic properties small deformation oscillatory measurements of storage modulus (G') loss modulus (G″) and complex viscosity (η(⁎)) were made. The rheological properties of the SF where compared with those of the polysaccharides sodium alginate, gellan gum and mixtures of both polymers. Initial results revealed classic shear thinning behaviour for the SF with a small Newtonian plateau at low shear rates with a gradual reduction in viscosity with increasing shear rate. Viscoelasticity measurements also showed that at low frequencies of oscillation there was a viscous response with G″ greater than G' and at higher frequencies there was an elastic response. Rheological properties were found to be similar to that of a 50:50 mix of 2% w/v high molecular weight alginate and 0.75% w/v gellan gum. Importantly, the lubricating behaviour of the serum differed significantly from the biopolymer blend over a full range of sliding velocities. The biopolymer blend was shown to lubricate the opposing surfaces more effectively. This difference was attributed to the more rapid alignment of the polysaccharide during shear when compared with the bovine albumin (the most abundant protein in serum), which typically exhibits a globular

  11. Modeling and experimental investigation of rheological properties of injectable poly(lactide ethylene oxide fumarate)/hydroxyapatite nanocomposites. (United States)

    Sarvestani, Alireza S; Jabbari, Esmaiel


    Injectable multiphasic polymer/ceramic composites are attractive as bioresorbable scaffolds for bone regeneration because they can be cross-linked in situ and are osteoconductive. The injectability of the composite depends on the nanoparticle content and the energetic interactions at the polymer/particle interface. The objective of this research was to determine experimentally the rheological properties of the PLEOF/apatite composite as an injectable biomaterial and to compare the viscoelastic response with the predictions of a linear elastic dumbbell model. A degradable in situ cross-linkable terpolymer based on low molecular weight poly(L-lactide) and poly(ethylene oxide) linked by unsaturated fumarate groups is synthesized. The poly(L-lactide-co-ethylene oxide-co-fumarate) (PLEOF) terpolymer interacts with the surface of the apatite nanoparticles by polar interactions and hydrogen bonding. A kinetic model is developed that takes into account the adsorption/desorption of polymer chains to/from the nanoparticle surface. Rheological properties of the aqueous dispersion of PLEOF terpolymer reinforced with nanosized hydroxyapatite (HA) particles are investigated using mechanical rheometry. To this end, we performed a series of rheological experiments on un-cross-linked PLEOF reinforced with different volume fractions of HA nanoparticles. The results demonstrate that the observed nonlinear viscoelasticity at higher shear rates is controlled by the energetic interactions between the polymer chains and dispersed particle aggregates and by the rate of the adsorption/desorption of the chains to/from the surface of the nanoparticles.

  12. Impact of Rheological Modifiers on Various Slurries Supporting DOE Waste Processing

    International Nuclear Information System (INIS)

    Chun, Jaehun; Bredt, Paul R.; Hansen, Erich; Bhosale, Prasad S.; Berg, John C.


    Controlling the stability and subsequent rheological properties of slurries has been an important but challenging issue in nuclear waste treatment, one that previous research has yet to sufficiently address. At the Hanford and Savannah River sites, operation of the waste treatment facilities at increased solids loading reduces the evaporative load on the melter systems and thereby increases waste processing rates. However, at these higher solids loadings, increased slurry rheology becomes a significant processing issue. The current study evaluates the use of several rheological modifiers to alleviate increased slurry rheology at high waste solids concentrations. Rheological modifiers change particle interactions in slurry. For colloidal slurries, modifiers mainly alter the electrostatic and steric interactions between particles, leading to a change in slurry rheology. Weak organic acid type rheological modifiers strengthen electrostatic repulsion whereas nonionic/polymer surfactant type rheological modifiers introduce a steric repulsion. We investigated various rheological modifiers using high level waste (HLW) nuclear waste simulants characterized typically by high ionic strength and a wide range of pH from 4 to 13. Using rheological analysis, it was found that citric acid and polyacrylic acid would be good rheological modifiers for the HLW simulants tested, effectively reducing slurry rheology by 40% or more. Physical insights into the mechanisms driving stabilization by these rheological modifiers will be discussed.

  13. Rheological properties of crumb rubber modified bitumen containing antioxidant

    International Nuclear Information System (INIS)

    Mohamed, A. A; Omar, Husaini; Hamzah, M.O; Ismail, H.


    Rheology has become a useful tool in the characterization of the bitumen performance on the pavement. Visco-elastic properties of crumb rubber modified bitumen with antioxidants (CR30) were determined by the means of rheological measurement. This measurement led to a better knowledge of bitumen behavior that occurs when subjected to different thermal and mechanical conditions, as seen during road construction and services in the field. Dynamic Shear Rheometer (DSR) was used to characterize the rheology of the binders before and after oven aging. The binders were aged for 3 and 9 days. Results of a compatibility test showed that the addition of CR30 modified bitumen is compatible with the base bitumen. The results of unaged samples indicated that the addition of 1% CR30 and 5% CR30 modified binders caused an increase in G value as a result of the rheological changes. Results showed that aging has significant influence on bitumen rheology, by increasing complex modulus and decreasing phase angle. (author)

  14. Investigations of Physical and Rheological Properties of Aged Rubberised Bitumen

    Directory of Open Access Journals (Sweden)

    Asim Hassan Ali


    Full Text Available Several road pavement distresses are related to rheological bitumen properties. Rutting and fatigue cracking are the major distresses that lead to permanent failures in pavement construction. Influence of crumb rubber modifier (CRM on rheological properties of bitumen binder such as improvement of high and intermediate temperatures is investigated in the binder’s fatigue and rutting resistance through physical-rheological changes in this research. The bitumen binders were aged by rolling thin film oven (RTFOT to simulate short-term aging and pressure aging vessel (PAV to simulate long-term aging. The effects of aging on the rheological and physical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR, Brookfield viscometer test, softening point test, and penetration test. The results showed that the use of rubberised bitumen binder reduces the aging effect on physical and rheological properties of the bitumen binder as illustrated through lower aging index of viscosity, lower aging index of , and an increase in with crumb rubber modifier content increasing, indicating that the crumb rubber might improve the aging resistance of rubberised bitumen binder. In addition, the results showed that the softening point increment ( and penetration aging ratio (PAR of the rubberised bitumen binder decreased significantly due to crumb rubber modification. Furthermore, the higher crumb rubber content, the lower after PAV aging, which led to higher resistance to fatigue cracking bitumen.

  15. Study of cement pastes rheological behavior using dynamic shear rheometer

    Directory of Open Access Journals (Sweden)

    J. E. S. L. Teixeira

    Full Text Available Concrete, in its fresh state, has flow characteristics that are crucial to its proper launch and densification. These characteristics are usually measured through empirical testing as the slump test, but this test does not quantify completely the material behavior. Since this material is characterized as a Bingham fluid, it is essential the study of its rheological behavior to verify its properties even in fresh state. The use of classical rheology has been employed by the scientific community to obtain rheological parameters determinants to characterize this material, such as yield stress, plastic viscosity and evolution of shear stress to shear rate. Thus, this present study aims to determine the rheological behavior of different cement pastes produced with cement CP III 40 RS, varying between them the hydration periods (20 and 60 min, the water-cement ratio (0.40, 0.45 and 0.50 and the use or not of additive. Samples were assayed by flow test to determine the rheological parameters showing the effect of the variables mentioned above in these parameters.

  16. The bicuspid aortic valve and its relation to aortic dilation

    Directory of Open Access Journals (Sweden)

    Shi-Min Yuan


    Full Text Available BACKGROUND: A bicuspid aortic valve (BAV is a common congenital heart disease, which affects 1-2% of the population. However, the relationship between BAVs and aortic dilation has not been sufficiently elucidated. METHODS: A total of 241 BAV patients who were referred to this hospital for cardiac surgey over a 4.75-year period were included in this study. In addition to the clinical characteristics of the included patients, the morphological features of the aortic valve and aorta, the length of the left main coronary artery, and the laboratory findings (the coagulation and hematological parameters as well as the total cholesterol concentration were determined and compared with those of the tricuspid aortic valve (TAV patients. RESULTS: The BAV patients were younger than the TAV patients for a valve surgery in the last 3 months of the study period. The BAV patients were predominantly male. Most of the BAVs that were surgically treated were stenotic, regurgitant, or combined, and only 19 (7.88% were normally functioning valves. According to echocardiography or operative records, 148 (78.31% were type A, 31 (16.40% were type B, and 10 (5.29% were type C. The left main coronary artery was much shorter in the BAV patients than it was in the TAV patients. There was no significant difference between BAV and TAV patients in the total cholesterol concentrations; whereas differences were noted between patients receiving lipid-lowering therapy and those not receiving lipid-lowering therapy. The dimensions of the aortic root, sinotubular junction, and ascending aorta were beyond normal limits, while they were significantly smaller in the BAV patients than in the TAV patients. They were also much smaller in patients receiving statin therapy than those not receiving statin therapy in both groups. Moreover, the aortic dilation in the BAV group was found to be significantly associated with patient age. CONCLUSIONS: The BAV patients developed aortic wall and


    Energy Technology Data Exchange (ETDEWEB)

    Hansen, E.; Marzolf, A.; Hera, K.


    The vane method has been shown to be an effective tool in measuring the yield stress of both settled and mixed slurries in laboratory bench scale conditions in supporting assessments of both actual and simulant waste slurries. The vane has also been used to characterize dry powders and granular solids, the effect of non-cohesive solids with interstitial fluids and used as a guide to determine if slip is present in the geometries typically used to perform rheological flow curve measurements. The vane has been extensively characterized for measuring the shear strength in soils in both field and laboratory studies. The objectives for this task are: Fabricate vane instrument; Bench top testing to further characterize the effect of cohesive, non-cohesive, and blends of cohesive/non-cohesive simple simulants; Data from measurement of homogenized and settled bed of Kaolin sludge and assessment of the technology. In this document, the assessment using bench scale measurements of non-cohesive materials (beads) and cohesive materials (kaolin) is discussed. The non-cohesive materials include various size beads and the vane was assessed for depth and deaeration (or packing) via tapping measurements. For the cohesive (or non-Newtonian) materials, flow curves and yield stress measurements are performed using the vane and this data is compared to the traditional concentric cylinder flow curve measurement. Finally, a large scale vane was designed, fabricated, and tested with the cohesive (or non-Newtonian) materials to determine how a larger vane performs in measuring the yield stress and flow curve of settled cohesive solids.

  18. Coating Of Model Rheological Fluids In Microchannels (United States)

    Koelling, Kurt; Boehm, Michael


    Researchers have strived to understand and quantify the dynamics within the myriad micro/nano-devices proposed and developed within the last decade. Concepts such as fluid flow, mass transfer, molecule manipulation, and reaction kinetics must be understood in order to intelligently design and operate these devices. In addition to general engineering principles, intelligent design should also focus on material properties (e.g. density, viscosity, conductivity). One key property, viscosity, will play a large part of any fluidic device, including biomedical devices, because the fluids used will, most likely, be non-Newtonian and therefore highly dependent upon the shear rate. Be it a biomedical or macromolecule separation device, or simply the processing of polymeric material, select model polymers and simple flow schemes can be used to investigate the dynamics within micro-devices. Here, we present results for the processing of Newtonian and non-Newtonian polymeric fluids in micro-channels during two-phase penetrating flow. The system investigated is a circular capillary 100 microns in diameter, which is pre-filled with a polymeric liquid. The polymeric liquid is either of Newtonian viscosity, or the same liquid with dispersed high molecular weight polystyrene, which exhibits viscoelastic behavior. A second, immiscible phase, silicone oil of low Newtonian viscosity, is pumped into the system and subsequently cores the polymeric liquid. The dynamics of bubble flow (e.g. bubble velocity and bubble shape) as well as the influence of rheology on coating will be investigated. By studying these model systems, we will learn how complex fluids behave on progressively smaller size scales.

  19. Magnetic resonance imaging of dilated cardiomyopathy; MRT bei dilatativen Kardiomyopathien

    Energy Technology Data Exchange (ETDEWEB)

    D' Anastasi, M. [Klinikum der Ludwig-Maximilians-Universitaet Muenchen, Campus Grosshadern, Institut fuer Klinische Radiologie, Muenchen (Germany); Greif, M. [Klinikum der Ludwig-Maximilians-Universitaet Muenchen, Campus Grosshadern, Medizinische Klinik und Poliklinik I, Muenchen (Germany); Reiser, M.F.; Theisen, D. [Klinikum der Ludwig-Maximilians-Universitaet Muenchen, Campus Grosshadern, Institut fuer Klinische Radiologie, Muenchen (Germany); Deutsches Zentrum fuer Herzkreislaufforschung (DZHK), Muenchen (Germany)


    Dilated cardiomyopathy (DCM) is the most common type of cardiomyopathy with a prevalence of 1 out of 2,500 in adults. Due to mild clinical symptoms in the early phase of the disease, the true prevalence is probably even much higher. Patients present with variable clinical symptoms ranging from mild systolic impairment of left ventricular function to congestive heart failure. Even sudden cardiac death may be the first clinical symptom of DCM. The severity of the disease is defined by the degree of impairment of global left ventricular function. Arrhythmias, such as ventricular or supraventricular tachycardia, atrioventricular (AV) block, ventricular extrasystole and atrial fibrillation are common cardiac manifestations of DCM. Magnetic resonance imaging (MRI) plays an important role in the exact quantification of functional impairment of both ventricles and in the evaluation of regional wall motion abnormalities. With its excellent ability for the assessment of myocardial structure, it is becoming increasingly more important for risk stratification and therapy guidance. (orig.) [German] Die dilatative Kardiomyopathie (DCM) ist die haeufigste Form der Kardiomyopathie mit einer Praevalenz von 1/2500 Erwachsenen. Aufgrund der zunaechst milden klinischen Symptomatik ist jedoch von einer relativ hohen Dunkelziffer auszugehen. Die klinische Praesentation ist variabel, die Schwere der Erkrankung wird vom Ausmass der systolischen Funktionseinschraenkung bestimmt. Herzrhythmusstoerungen, wie ventrikulaere oder supraventrikulaere Tachykardien, AV-Blockierungen, ventrikulaere Extrasystolen und Vorhofflimmern sind moegliche klinische Manifestationen. Bei manchen Patienten ist der ploetzliche Herztod die erste klinische Manifestation der Erkrankung. Die kardiale MRT spielt eine bedeutende Rolle fuer die Beurteilung des Ausmasses der ventrikulaeren Dilatation, Dysfunktion und fuer die Beurteilung regionaler Wandbewegungsstoerungen. Darueber hinaus kann sie zur Anwendung kommen

  20. Time Dilation and Homogeneous, Soft-Spectrum GRBs (United States)

    Norris, J. P.; Bonnell, J. T.; Nemiroff, R. J.; Scargle, J. D.; Pendleton, G. N.; Kouveliotou, C.; Pizzichini, G.


    Recently, BATSE gamma-ray bursts selected for soft average spectra have been shown to follow more nearly a -3/2 power law in their number-intensity relation, indicative of a spatially homogeneous population, unlike the whole BATSE burst sample which deviates significantly from a -3/2 signature. The softer bursts might therefore be closer, and the reported time dilation as a function of peak flux in the whole burst sample (Bonnell et al., ApJ submitted) might be expected to be different for soft bursts. We have investigated this possibility with a sample of 500 long bursts (T_90 > 2 s) from the BATSE 3B catalog, defining soft bursts ( ~ 20% of total) using the three hardness ratios derived from fluences in BATSE's four energy channels (25--55, 55--110, 110--320, > 320 keV). The relative time-dilation factors (TDFs) were calculated using a brightness-independent algorithm for duration. The expected effect is observed: The average log[duration] of soft bursts is significantly lower (factor of ~ 2) than that for harder bursts, or for the whole set, to much dimmer peak fluxes -- consistent with unity TDF (compared to bright bursts in the whole sample) down to peak flux of ~ 1.0 photon cm(-2) s(-1) . Using a Kolmogorov-Smirnov test, we find that T_90 and T_50 duration distributions of soft and hard bursts above this peak flux value are different, with a confidence level > 99%. This result is qualitatively consistent with a GRB luminosity function implied by the apparent homogeneity of the bright-to-intermediate peak-flux soft bursts. However, dimmer soft bursts are time-dilated relative to bright bursts in the whole sample, suggesting that spectral redshift compounds the definition of the soft burst class.

  1. Intragastric balloon for morbid obesity causing chronic gastric dilatation

    International Nuclear Information System (INIS)

    Pretolesi, F.; Derchi, L.E.; Redaelli, G.; Papagni, L.


    We describe the radiographic findings observed in a morbidly obese and diabetic patient with an intragastric air-filled balloon introduced as a therapeutic measure to reduce food intake. The balloon was associated with chronic gastric dilatation and had to be removed 3 months after insertion. However, together with diet and behavioural therapy, it proved effective in reducing body weight and ameliorating glycaemic control. Although rarely used, intragastric balloons for the treatment of morbid obesity are still encountered in radiological practice. Radiologists must be able to recognize them and to understand their complications. (orig.)

  2. Genotype-specific pathogenic effects in human dilated cardiomyopathy. (United States)

    Bollen, Ilse A E; Schuldt, Maike; Harakalova, Magdalena; Vink, Aryan; Asselbergs, Folkert W; Pinto, Jose R; Krüger, Martina; Kuster, Diederik W D; van der Velden, Jolanda


    Mutations in genes encoding cardiac troponin I (TNNI3) and cardiac troponin T (TNNT2) caused altered troponin protein stoichiometry in patients with dilated cardiomyopathy. TNNI3 p.98trunc resulted in haploinsufficiency, increased Ca 2+ -sensitivity and reduced length-dependent activation. TNNT2 p.K217del caused increased passive tension. A mutation in the gene encoding Lamin A/C (LMNA p.R331Q ) led to reduced maximal force development through secondary disease remodelling in patients suffering from dilated cardiomyopathy. Our study shows that different gene mutations induce dilated cardiomyopathy via diverse cellular pathways. Dilated cardiomyopathy (DCM) can be caused by mutations in sarcomeric and non-sarcomeric genes. In this study we defined the pathogenic effects of three DCM-causing mutations: the sarcomeric mutations in genes encoding cardiac troponin I (TNNI3 p.98truncation ) and cardiac troponin T (TNNT2 p.K217deletion ; also known as the p.K210del) and the non-sarcomeric gene mutation encoding lamin A/C (LMNA p.R331Q ). We assessed sarcomeric protein expression and phosphorylation and contractile behaviour in single membrane-permeabilized cardiomyocytes in human left ventricular heart tissue. Exchange with recombinant troponin complex was used to establish the direct pathogenic effects of the mutations in TNNI3 and TNNT2. The TNNI3 p.98trunc and TNNT2 p.K217del mutation showed reduced expression of troponin I to 39% and 51%, troponin T to 64% and 53%, and troponin C to 73% and 97% of controls, respectively, and altered stoichiometry between the three cardiac troponin subunits. The TNNI3 p.98trunc showed pure haploinsufficiency, increased Ca 2+ -sensitivity and impaired length-dependent activation. The TNNT2 p.K217del mutation showed a significant increase in passive tension that was not due to changes in titin isoform composition or phosphorylation. Exchange with wild-type troponin complex corrected troponin protein levels to 83% of controls in the TNNI3

  3. Genotype‐specific pathogenic effects in human dilated cardiomyopathy (United States)

    Schuldt, Maike; Harakalova, Magdalena; Vink, Aryan; Asselbergs, Folkert W.; Pinto, Jose R.; Krüger, Martina; Kuster, Diederik W. D.; van der Velden, Jolanda


    Key points Mutations in genes encoding cardiac troponin I (TNNI3) and cardiac troponin T (TNNT2) caused altered troponin protein stoichiometry in patients with dilated cardiomyopathy. TNNI3p.98trunc resulted in haploinsufficiency, increased Ca2+‐sensitivity and reduced length‐dependent activation. TNNT2p.K217del caused increased passive tension.A mutation in the gene encoding Lamin A/C (LMNA p.R331Q) led to reduced maximal force development through secondary disease remodelling in patients suffering from dilated cardiomyopathy.Our study shows that different gene mutations induce dilated cardiomyopathy via diverse cellular pathways. Abstract Dilated cardiomyopathy (DCM) can be caused by mutations in sarcomeric and non‐sarcomeric genes. In this study we defined the pathogenic effects of three DCM‐causing mutations: the sarcomeric mutations in genes encoding cardiac troponin I (TNNI3p.98truncation) and cardiac troponin T (TNNT2p.K217deletion; also known as the p.K210del) and the non‐sarcomeric gene mutation encoding lamin A/C (LMNAp.R331Q). We assessed sarcomeric protein expression and phosphorylation and contractile behaviour in single membrane‐permeabilized cardiomyocytes in human left ventricular heart tissue. Exchange with recombinant troponin complex was used to establish the direct pathogenic effects of the mutations in TNNI3 and TNNT2. The TNNI3p.98trunc and TNNT2p.K217del mutation showed reduced expression of troponin I to 39% and 51%, troponin T to 64% and 53%, and troponin C to 73% and 97% of controls, respectively, and altered stoichiometry between the three cardiac troponin subunits. The TNNI3p.98trunc showed pure haploinsufficiency, increased Ca2+‐sensitivity and impaired length‐dependent activation. The TNNT2p.K217del mutation showed a significant increase in passive tension that was not due to changes in titin isoform composition or phosphorylation. Exchange with wild‐type troponin complex corrected troponin protein levels to 83% of

  4. Achalasia with massive oesophageal dilation causing tracheomalacia and asthma symptoms

    Directory of Open Access Journals (Sweden)

    Ana Gomez-Larrauri

    Full Text Available Achalasia is an uncommon oesophageal motor disorder characterized by failure of relaxation of the lower oesophageal sphincter and muscle hypertrophy, resulting in a loss of peristalsis and a dilated oesophagus. Gastrointestinal symptoms are invariably present in all cases of achalasia observed in adults. We report a case of a 34 year-old female patient with long standing history of asthma-like symptoms, labelled as uncontrolled and steroid resistant asthma with no gastrointestinal manifestations. Thoracic CT scan revealed a massive oesophagus due to achalasia, which caused severe tracheomalacia as a result of tracheal compression. Her symptoms regressed completely after a laparoscopic Heller myotomy surgery intervention.

  5. Intragastric balloon for morbid obesity causing chronic gastric dilatation

    Energy Technology Data Exchange (ETDEWEB)

    Pretolesi, F.; Derchi, L.E. [Dept. of Radiology, University of Genoa (Italy); Redaelli, G.; Papagni, L. [IRCCS, Ist. Auxologico Italiano, Milan (Italy)


    We describe the radiographic findings observed in a morbidly obese and diabetic patient with an intragastric air-filled balloon introduced as a therapeutic measure to reduce food intake. The balloon was associated with chronic gastric dilatation and had to be removed 3 months after insertion. However, together with diet and behavioural therapy, it proved effective in reducing body weight and ameliorating glycaemic control. Although rarely used, intragastric balloons for the treatment of morbid obesity are still encountered in radiological practice. Radiologists must be able to recognize them and to understand their complications. (orig.)

  6. Impact Features on Europa: Rheological and Thermal States of the Icy Crust (United States)

    Mevel, L.; Grasset, O.; Mercier, E.


    Rheological and thermal characteristics of Europa icy crust are studied in the two impact features Tyre and Callanish. The importance of grain size, composition, and deformation rates, on the rheological structure of the icy crust are investigated.

  7. Basic physiochemical and rheological properties of detergent sclerosants. (United States)

    Wong, Kaichung; Chen, Tony; Connor, David E; Behnia, Masud; Parsi, Kurosh


    To determine the basic physiochemical properties and rheological activity of detergent sclerosants. Sodium tetradecyl sulphate and polidocanol liquid and foam sclerosants were investigated in a range of concentrations (0.1-3%), liquid-plus-air fractions (1+2 to 1+8) and dilutions in water (stock solutions) or in normal saline. The embolic agent ethanol was investigated for comparison. Density was measured using a digital balance. Surface tension was measured by the Du Nuoy ring method and used to determine the critical micellar concentration. Viscosity was measured using a cone-plate rheometer for liquid and a modified parallel plate method for foam. Liquid sclerosant density decreased as the sclerosant concentration increased while foam density decreased with the increasing air fraction. The critical micellar concentration of polidocanol was 0.002% in both normal saline and water while that of sodium tetradecyl sulphate was 0.075% in normal saline and 0.200% in water. Viscosity of liquid sodium tetradecyl sulphate was lower than that of polidocanol. Foam sclerosants were at least 10,000-fold more viscous than liquid sclerosants and ethanol. All agents demonstrated a Non-Newtonian shear-thinning behaviour with a fall in viscosity at lower shear rates (<10 s(-1)). Polidocanol (but not sodium tetradecyl sulphate) foam viscosity progressively increased with increasing sclerosant concentration and liquid-plus-air fractions. Liquid and foam sclerosants and ethanol are Non-Newtonian shear thinning fluids. Foam sclerosants are significantly more viscous than liquid agents. © The Author(s) 2014 Reprints and permissions:

  8. Rheology of lava flows on Mercury: An analog experimental study (United States)

    Sehlke, A.; Whittington, A. G.


    We experimentally determined the rheological evolution of three basaltic analog compositions appropriate to Mercury's surface, during cooling, and crystallization. Investigated compositions are an enstatite basalt, and two magnesian basalts representing the compositional end-members of the northern volcanic plains with 0.19 wt % (NVP) and 6.26 wt % Na2O (NVP-Na). The viscosity-strain rate dependence of lava was quantified using concentric cylinder viscometry. We measured the viscosities of the crystal-free liquids from 1600°C down to the first detection of crystals. Liquidus temperatures of the three compositions studied are around 1360°C, and all three compositions are more viscous than Hawaiian basalt at the same temperature. The onset of pseudoplastic behavior was observed at crystal fractions ~0.05 to 0.10, which is consistent with previous studies on mafic lavas. We show that all lavas develop detectable yield strengths at crystal fractions around 0.20, beyond which the two-phase suspensions are better described as Herschel-Bulkley fluids. By analogy with the viscosity-strain rate conditions at which the pahoehoe to `a`a transition occurs in Kilauea basalt, this transition is predicted to occur at ~1260 ± 10°C for the enstatite basalt, at ~1285 ± 20°C for the NVP, and at ~1240 ± 40°C for the NVP-Na lavas. Our results indicate that Mercury lavas are broadly similar to terrestrial ones, which suggests that the extensive smooth lava plains of Mercury could be due to large effusion rates (flood basalts) and not to unusually fluid lavas.

  9. The Influence of Non-linear 3-D Mantle Rheology on Predictions of Glacial Isostatic Adjustment Models (United States)

    Van Der Wal, W.; Barnhoorn, A.; Stocchi, P.; Drury, M. R.; Wu, P. P.; Vermeersen, B. L.


    Ice melting in Greenland and Antarctica can be estimated from GRACE satellite measurements. The largest source of error in these estimates is uncertainty in models for Glacial Isostatic Adjustment (GIA). GIA models that are used to correct the GRACE data have several shortcomings, including (i) mantle viscosity is only varied with depth, and (ii) stress-dependence of viscosity is ignored. Here we attempt to improve on these two issues with the ultimate goal of providing more realistic GIA predictions in areas that are currently ice covered. The improved model is first tested against observations in Fennoscandia, where there is good coverage with GIA observations, before applying it to Greenland. Deformation laws for diffusion and dislocation creep in olivine are taken from a compilation of laboratory experiments. Temperature is obtained from two different sources: surface heatflow maps as input for the heat transfer equation, and seismic velocity anomalies converted to upper mantle temperatures. Grain size and olivine water content are kept as free parameters. Surface loading is provided by an ice loading history that is constructed from constraints on past ice margins and input from climatology. The finite element model includes self-gravitation but not compressibility and background stresses. It is found that the viscosity in Fennoscandia changes in time by two orders of magnitude for a wet rheology with large grain size. The wet rheology provides the best fit to historic sea level data. However, present-day uplift and gravity rates are too low for such a rheology. We apply a wet rheology on Greenland, and simulate a Little Ice Age (LIA) increase in thickness on top of the ICE-5G ice loading history. Preliminary results show a negative geoid rate of magnitude more than 0.5 mm/year due to the LIA increase in ice thickness in combination with the non-linear upper mantle rheology. More tests are necessary to determine the influence of mantle rheology on GIA model

  10. Rheology of semiflexible bundle networks with transient linkers. (United States)

    Müller, Kei W; Bruinsma, Robijn F; Lieleg, Oliver; Bausch, Andreas R; Wall, Wolfgang A; Levine, Alex J


    We present a theoretical and computational analysis of the rheology of networks made up of bundles of semiflexible filaments bound by transient cross-linkers. Such systems are ubiquitous in the cytoskeleton and can be formed in vitro using filamentous actin and various cross-linkers. We find that their high-frequency rheology is characterized by a scaling behavior that is quite distinct from that of networks of the well-studied single semiflexible filaments. This regime can be understood theoretically in terms of a length-scale-dependent bending modulus for bundles. Next, we observe new dissipative dynamics associated with the shear-induced disruption of the network at intermediate frequencies. Finally, at low frequencies, we encounter a region of non-Newtonian rheology characterized by power-law scaling. This regime is dominated by bundle dissolution and large-scale rearrangements of the network driven by equilibrium thermal fluctuations.

  11. Nanoscale Rheology and Anisotropic Diffusion Using Single Gold Nanorod Probes (United States)

    Molaei, Mehdi; Atefi, Ehsan; Crocker, John C.


    The complex rotational and translational Brownian motion of anisotropic particles depends on their shape and the viscoelasticity of their surroundings. Because of their strong optical scattering and chemical versatility, gold nanorods would seem to provide the ultimate probes of rheology at the nanoscale, but the suitably accurate orientational tracking required to compute rheology has not been demonstrated. Here we image single gold nanorods with a laser-illuminated dark-field microscope and use optical polarization to determine their three-dimensional orientation to better than one degree. We convert the rotational diffusion of single nanorods in viscoelastic polyethylene glycol solutions to rheology and obtain excellent agreement with bulk measurements. Extensions of earlier models of anisotropic translational diffusion to three dimensions and viscoelastic fluids give excellent agreement with the observed motion of single nanorods. We find that nanorod tracking provides a uniquely capable approach to microrheology and provides a powerful tool for probing nanoscale dynamics and structure in a range of soft materials.

  12. Rheological and microbiological study of flour treated by irradiation

    International Nuclear Information System (INIS)

    Laabidi, Othmen


    the aim this work is to study the effectiveness of radio treatment and its effect on the conservation of flour and their various parameters (physico-chemical and rheological). The flour has been treated with different doses (0, 0.75, 1.5 and 3 kGy), physico-chemical, rheological, microbiological and sensory analyses were made.The results show that the irradiation as a treatment for decontamination gave a highly effective. Indeed, a dose of 1.5 kGy allows a total destruction of yeasts and molds. Thus, from the point of view physico-chemical, increasing the dose of radiation causes a change in physical and chemical properties and rheological of flour. for the characteristics of bread, increasing the dose of radiation affects the quality of bread. (Author). 38 refs

  13. Research on rheological properties of micro-fine grouting cement

    Energy Technology Data Exchange (ETDEWEB)

    Guan, X.; Wang, Y.; Yang, L. [Jiaozuo Institute of Technology, Jiaozuo (China). Dept. of Resource and Material Engineering


    This article studies the influence of the fineness of cement, fly ash (FA), its composite admixture and the amount and method by which they are mixed with superplasticizer on the rheological properties of micro-fine cement. By means of modern instruments and technologies (such as XRDF, SEM, laser granulometer and superficial-potential apparatus etc.), the article studies the mineral compositions, the appearance character of the grains, particle size distribution and superficial potential of FA and its composite materials. The reducing mechanism of FA is thoroughly analysed. The study shows that FA and its composite admixture are excellent components which can effectively improve the rheological properties of micro-fine cement, and that the superplasticizer has a saturation point and the mixing method has a great influence on the rheological properties. 8 refs., 7 figs., 6 tabs.

  14. Comparison of Rheological Properties of Hopped Wort and Malt Wort

    Directory of Open Access Journals (Sweden)

    Petr Trávníček


    Full Text Available The aim of this work is determination rheological properties of hopped wort and malt wort and their comparison. In the paper following rheological properties has been described: the dependence of viscosity on a temperature of a sample and hysteresis loop test. The time dependence test was performed for a confirmation thixotropic behaviour. Based on measured values Arrhenius mathematical model has been applied. The activation energy was determined by using of this model. Tests have been carried out in the temperature range from 5 °C to 40 °C. Rheological tests proved that malt wort behaves as Newtonian fluid in all temperatures and hopped wort behaves as non-Newtonian fluid at low temperatures. Thixotropic behaviour is caused by the content of the rests of hops heads or malt scraps.

  15. Fluid rheological effects on particle migration in rectangular microchannels (United States)

    Li, Di; Xuan, Xiangchun


    There has been an increasing interest in the use of viscoelastic solutions for particle focusing and separation in microfluidic devices. These passive manipulations arise from the flow induced elastic lift force that interacts with the inertial lift force for an enhanced control of particle motions. The rheological properties of the suspending fluid are supposed to have a significant impact on particle migration in microchannels. We present in this work an experimental investigation of the elastic and/or inertial focusing of polystyrene particles suspended in the flow of four types of fluids with varying rheological properties through a straight rectangular microchannel. Such a fundamental study is expected to provide useful data for fluid rheological effects on particle migration, which may be used to validate theoretical models. Clemson SEED Grant.

  16. Study of the geopolymer restructuration by impulse rheology

    International Nuclear Information System (INIS)

    Rouyer, J.; Frizon, F.; Poulesquen, A.


    The aim of the study is to describe the evolution of the microstructure during the setting process of the geo-polymer using an original rheological method named Optimal Fourier Rheology (OFR). The alkali activation of meta-kaolin enables physicochemical transformation from a fresh paste to a hard meso-porous matrix. Classically, oscillatory rheology technique provides viscoelastic moduli spectrum and enables to determine rheological comportment of the material under investigation. However the duration to perform a complete spectrum (more than 2.5 h) makes useless this technique in the case of changing material. The OFR technique decreases the measurement duration under 10 minutes and enables to perform several snapshots of the evolving rheological behaviour. Contrary to monochromatic iterations, here the applied stress takes the form of a chirp function which contains the full usable bandwidth. Interpretations of spectrums provide efficient access to structural evolution along the setting. Results show that the number of oligomers increases into the solution due to the dissolution of the meta-kaolin leading to a constant increase of the viscoelastic parameters until the gradual appearance of the percolating networks. The gelling time was rigorously assessed by using the Winter and Chambon criterion. A fractal percolating network is formed inside the material after a reaction time depending on the formulation parameters; corresponding fractal dimensions were established. After the gel point, the viscoelastic moduli grow rapidly until geo-polymers reach a classic viscoelastic state. Structural unit size were determined using moduli curves crossover and equalled to 2.1 nm in the case of Na geo-polymer; this value fits extremely well with value previously obtained by SAXS. Finally, the elasticity becomes constant in a large frequency range and the viscous parameter strongly decreases which means that the solid porous network is under formation. In conclusion, this

  17. Structure and rheology of nanoparticle–polymer suspensions

    KAUST Repository

    Srivastava, Samanvaya


    Structure and rheology of oligomer-tethered nanoparticles suspended in low molecular weight polymeric host are investigated at various particle sizes and loadings. Strong curvature effects introduced by the small size of the nanoparticle cores are found to be important for understanding both the phase stability and rheology of the materials. Small angle X-ray scattering (SAXS) and transmission electron microscopy measurements indicate that PEG-SiO 2/PEG suspensions are more stable against phase separation and aggregation than expected from theory for interacting brushes. SAXS and rheology measurements also reveal that at high particle loadings, the stabilizing oligomer brush is significantly compressed and produces jamming in the suspensions. The jamming transition is accompanied by what appears to be a unique evolution in the transient suspension rheology, along with large increments in the zero-shear, Newtonian viscosity. The linear and nonlinear flow responses of the jammed suspensions are discussed in the framework of the Soft Glassy Rheology (SGR) model, which is shown to predict many features that are consistent with experimental observations, including a two-step relaxation following flow cessation and a facile method for determining the shear-thinning coefficient from linear viscoelastic measurements. Finally, we show that the small sizes of the particles have a significant effect on inter-particle interactions and rheology, leading to stronger deviations from expectations based on planar brushes and hard-sphere suspension theories. In particular, we find that in the high volume fraction limit, tethered nanoparticles interact in their host polymer through short-range forces, which are more analogous to those between soft particles than between spherical polymer brushes. © 2012 The Royal Society of Chemistry.

  18. The rheology of cryovolcanic slurries: Motivation and phenomenology of methanol-water slurries with implications for Titan (United States)

    Zhong, Fang; Mitchell, Karl L.; Hays, Charles C.; Choukroun, Mathieu; Barmatz, Martin; Kargel, Jeffrey S.


    The Cassini spacecraft has revealed landforms on the surface of Titan suggested to be viscous cryovolcanic flows and possibly eruptive domes. In order to relate those surface features to the processes and chemistries that produced them, it is necessary to construct flow models, which rely on characterization of the rheological properties of the eruptants. This paper describes our initial exploratory attempts to understand the rheological characteristics of cryogenic slurries, using a 40% methanol-water mixture, as a precursor to more detailed experiments. We have devised a new automated cryogenic rotational viscometer system to more fully characterize cryovolcanic slurry rheologies. A series of measurements were performed, varying first temperature, and then strain rate, which revealed development of yield stress-like behaviors, shear-rate dependence, and thixotropic behavior, even at relatively low crystal fractions, not previously reported. At fixed shear rate our data are fit well by the Andrade equation, with the activation energy modified by a solid volume fraction. At fixed temperature, depending on shearing history, a Cross model could describe our data over a wide shear rate range. A Bingham plastic model appears to be a good constitutive model for the data measured at high shear rates when the shear was global. The yield stress like behavior implies that levee formation on cryolava flows is more likely than would be inferred from the previous studies, and may provide a partial explanation for features interpreted as steep-sided volcanic constructs on Titan.

  19. Investigation of the rheological properties and die swell of polylactic acid/nanoclay composites in a capillary rheometer (United States)

    Dangtungee, R.; Petcharoen, K.; Pinijsattawong, K.; Siengchin, S.


    The purpose of this research was to investigate the rheological behavior and extrudate swell of polylactic acid (PLA) filled with a nanoclay. The effects of the amount of nanoclay and surface treatment were studied by a capillary rheometer. The dispersion of the nanoclay was inspected by using the scanning electron microscopy. Generally, PLA/nanoclay composites exhibited a pseudoplastic rheological behavior as the shear stress and die swell increased with increasing shear rate. However, the shear viscosity decreased. The die swell also increased with increasing shear stress. The elongation viscosity decreased with increasing elongation rate. The incorporation of nanoclay decreased the shear stress and shear viscosity to a lesser degree than the elongation viscosity.

  20. Dilatation of aortic grafts over time: what to expect and when to be concerned

    DEFF Research Database (Denmark)

    Schroeder, Torben V; Eldrup, Nikolaj; Just, Sven


    insertion of a woven polyester or expanded polytetrafluoroethylene (ePTFE) graft. Patients were followed with computed tomography and ultrasonography for up to 5 years in order to assess the frequency and magnitude of postoperative dilatation. Graft dilatation was documented in patients with polyester...... grafts at 12 months. Thereafter and up to 60 months, polyester grafts did not dilate further. After 5 years, polyester prostheses had dilated by 25% and ePTFE by 12.5%, as determined by computed tomography imaging. These observations suggest that dilatation of prosthetic grafts is more frequent...... with knitted polyester grafts compared with ePTFE. Dilatation occurs within the first year after implantation and can be, in part, explained by a discrepancy between the initial nominal graft diameter and its diameter after clamp release, probably due to an in vivo adaptation of the textile structure...

  1. Microstructural Dynamics and Rheology of Suspensions of Rigid Fibers (United States)

    Butler, Jason E.; Snook, Braden


    The dynamics and rheology of suspensions of rigid, non-Brownian fibers in Newtonian fluids are reviewed. Experiments, theories, and computer simulations are considered, with an emphasis on suspensions at semidilute and concentrated conditions. In these suspensions, interactions between the particles strongly influence the microstructure and rheological properties of the suspension. The interactions can arise from hydrodynamic disturbances, giving multibody interactions at long ranges and pairwise lubrication forces over short distances. For concentrated suspensions, additional interactions due to excluded volume (contacts) and adhesive forces are addressed. The relative importance of the various interactions as a function of fiber concentration is assessed.

  2. Microscale rheology of a soft glassy material close to yielding. (United States)

    Jop, Pierre; Mansard, Vincent; Chaudhuri, Pinaki; Bocquet, Lydéric; Colin, Annie


    Using confocal microscopy, we study the flow of a model soft glassy material: a concentrated emulsion. We demonstrate the micro-macro link between in situ measured movements of droplets during the flow and the macroscopic rheological response of a concentrated emulsion, in the form of scaling relationships connecting the rheological "fluidity" with local standard deviation of the strain-rate tensor. Furthermore, we measure correlations between these local fluctuations, thereby extracting a correlation length which increases while approaching the yielding transition, in accordance with recent theoretical predictions. © 2012 American Physical Society

  3. Rheology of Savannah River site tank 42 HLW radioactive sludge

    International Nuclear Information System (INIS)

    Ha, B.C.


    Knowledge of the rheology of the radioactive sludge slurries at the Savannah River Site is necessary in order to ensure that they can be retrieved from waste tanks and processed for final disposal. At Savannah River Site, Tank 42 sludge represents on of the first HLW radioactive sludges to be vitrified in the Defense Waste Processing Facility. The rheological properties of unwashed Tank 42 sludge slurries at various solids concentrations were measured remotely in the Shielded Cells at the Savannah River Technology Center using a modified Haake Rotovisco viscometer

  4. Cognitive effort and pupil dilation in controlled and automatic processes. (United States)

    Querino, Emanuel; Dos Santos, Lafaiete; Ginani, Giuliano; Nicolau, Eduardo; Miranda, Débora; Romano-Silva, Marco; Malloy-Diniz, Leandro


    The Five Digits Test (FDT) is a Stroop paradigm test that aims to evaluate executive functions. It is composed of four parts, two of which are related to automatic and two of which are related to controlled processes. It is known that pupillary diameter increases as the task's cognitive demand increases. In the present study, we evaluated whether the pupillary diameter could distinguish cognitive effort between automated and controlled cognitive processing during the FDT as the task progressed. As a control task, we used a simple reading paradigm with a similar visual aspect as the FDT. We then divided each of the four parts into two blocks in order to evaluate the differences between the first and second half of the task. Results indicated that, compared to a control task, the FDT required higher cognitive effort for each consecutive part. Moreover, the first half of every part of the FDT induced dilation more than the second. The differences in pupil dilation during the first half of the four FDT parts were statistically significant between the parts 2 and 4 (p=0.023), and between the parts 3 and 4 (p=0.006). These results provide further evidence that cognitive effort and pupil diameter can distinguish controlled from automatic processes.

  5. Laryngotracheal Stenosis: Risk Factors for Tracheostomy Dependence and Dilation Interval (United States)

    Gadkaree, Shekhar K; Pandian, Vinciya; Best, Simon; Motz, Kevin M; Allen, Clint; Kim, Young; Akst, Lee; Hillel, Alexander T


    Objective Laryngotracheal stenosis (LTS) is a fibrotic process that narrows the upper airway and has a significant impact on breathing and phonation. Iatrogenic injury from endotracheal and/or tracheostomy tubes is the most common etiology. This study investigates differences in LTS etiologies as they relate to tracheostomy dependence and dilation interval. Study Design Case series with chart review. Setting Single-center tertiary care facility. Subjects and Methods Review of adult patients with LTS was performed between 2004 and 2015. The association of patient demographics, comorbidities, disease etiology, and treatment modalities with patient outcomes was assessed. Multiple logistic regression analysis and Kaplan-Meier analysis were performed to determine factors associated with tracheostomy dependence and time to second procedure, respectively. Results A total of 262 patients met inclusion criteria. Iatrogenic patients presented with greater stenosis ( P = .023), greater length of stenosis ( P = .004), and stenosis farther from the vocal folds ( P tracheostomy dependence. Nonsmokers, patients without tracheostomy, and idiopathic LTS patients had a significantly longer time to second dilation procedure. Conclusion Iatrogenic LTS presents with a greater disease burden and higher risk of tracheostomy dependence when compared with other etiologies of LTS. Comorbid conditions promoting microvascular injury-including smoking, COPD, and diabetes-were prevalent in the iatrogenic cohort. Changes in hospital practice patterns to promote earlier tracheostomy in high-risk patients could reduce the incidence of LTS.

  6. Percutaneous dilatational tracheostomy for ICU patients with severe brain injury

    Directory of Open Access Journals (Sweden)

    Guo Dongyuan


    Full Text Available 【Abstract】Objective: To sum up our experience in percutaneous dilatational tracheostomy (PDT in ICU patient with severe brain injury. Methods: Between November 2011 and April 2014, PDTs were performed on 32 severe brain injury patients in ICU by a team of physicians and intensivists. The success rate, effi cacy, safety, and complications including stomal infection and bleeding, paratracheal insertion, pneumothorax, pneumomediastinum, tracheal laceration, as well as clinically significant tracheal stenosis were carefully monitored and recorded respectively. Results: The operations took 4-15 minutes (mean 9.1 minutes±4.2 minutes. Totally 4 cases suffered from complications in the operations: 3 cases of stomal bleeding, and 1 case of intratracheal bloody secretion, but none required intervention. Paratracheal insertion, pneumothorax, pneumomediastinum, tracheal laceration, or clinically signifi cant tracheal stenosis were not found in PDT patients. There was no procedure-related death occurring during or after PDT. Conclusion: Our study demonstrats that PDT is a safe, highly effective, and minimally invasive procedure. The appropriate sedation and airway management perioperatively help to reduce complication rates. PDT should be performed or supervised by a team of physicians with extensive experience in this procedure, and also an intensivist with experience in diffi cult airway management. Key words: Brain injuries; Percutaneous dilatational tracheostomy; ICU

  7. Dilated cardiomyopathy with Graves disease in a young child

    Directory of Open Access Journals (Sweden)

    Yu Jung Choi


    Full Text Available Graves disease (GD can lead to complications such as cardiac arrhythmia and heart failure. Although dilated cardiomyopathy (DCMP has been occasionally reported in adults with GD, it is rare in children. We present the case of a 32-month-old boy with DCMP due to GD. He presented with irritability, vomiting, and diarrhea. He also had a history of weight loss over the past few months. On physical examination, he had tachycardia without fever, a mild diffuse goiter, and hepatomegaly. The chest radiograph showed cardiomegaly with pulmonary edema, while the echocardiography revealed a dilated left ventricle with an ejection fraction (EF of 28%. The thyroid function test (TFT showed elevated serum T3 and decreased thyroid stimulating hormone (TSH levels. The TSH receptor autoantibody titer was elevated. He was diagnosed with DCMP with GD; treatment with methylprednisolone, diuretics, inotropics, and methimazole was initiated. The EF improved after the TFT normalized. At follow-up several months later, although the TFT results again showed evidence of hyperthyroidism, his EF had not deteriorated. His cardiac function continues to remain normal 1.5 months after treatment was started, although he still has elevated T3 and high TSH receptor antibody titer levels due to poor compliance with drug therapy. To summarize, we report a young child with GD-induced DCMP who recovered completely with medical therapy and, even though the hyperthyroidism recurred several months later, there was no relapse of the DCMP.

  8. Pneumatic dilation and botulinum toxin: when and why? (United States)

    Bozzi, Rosamaria; Di Martino, Vincenzo; Inzirillo, Antonio; D'Avenia, Eugenio; Inzirillo, Maurizio; Cattaneo, Fabio; Cattaneo, Domenico


    Pneumatic dilation and botulinum toxin:when and why? The endoscopic treatment options of achalasia include botulinum toxin (BT) injection and pneumatic dilation (PD) of the lower esophageal sphincter (LES). BT can reduce the LES pressure by blocking the release of acetylcoline from presynaptic cholinergic nerve terminals in the myenteric plexus. Although the procedure is safe and good initial response is reported, there is a wide variability in the duration of the response and the effect tends to decrease over time. BT is usually recommended for elderly patients or patients with comorbid illnesses, who are poor candidates for more invasive procedures. PD aims at tearing the muscle fibers of the LES and is considered the most effective nonsurgical treatment for achalasia. Technical details of the procedure vary in different institutions and in many clinical settings the choice between PD or minimally invasive surgical myotomy depends upon local expertise in the procedures. Further endoscopic treatment options such as submucosal esophageal myotomy or self-expanding metallic stents are being studied.

  9. Antenatal renal pelvic dilatation; the long-term outlook

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, K.A. [Royal Aberdeen Children' s Hospital and Aberdeen Maternity Hospital, Foresterhill, Aberdeen (United Kingdom)]. E-mail:


    Aim: The purpose of this study was twofold: first to provide data for more accurate counselling of parents with regard to prognosis, and second, to ensure that by following a policy of selective micturating cystourethography (MCUG), significant pathology is not missed, in particular vesicoureteric reflux (VUR). (MCUG is only undertaken if the renal pelvic diameter (RPD) is {>=} 10 mm or if there is calyceal or ureteric dilatation.) Material and methods: Data were collected prospectively over a 6-year period. Pre and postnatal imaging findings were collected for all infants in whom a RPD of {>=} 5 mm was identified at any gestational age. The imaging records of all patients were reviewed in 2005 for evidence of pathology detected after re-presentation with symptoms. The age range at review varied from 2-8 years. Results: Complete data were available in 527 infants. The risk of significant pathology was related to the degree of antenatal renal pelvic dilatation varying from 6% for a RPD of 5 mm at 20 weeks gestation to 38% at 10mm. At 28-33 weeks gestation the risk varied from 5% at 5 mm to 15% at 10 mm. Subsequent imaging record review revealed only one patient with grade II VUR in the study population not picked up by our selective MCUG policy. Conclusion: The present study provides prognostic information that can be given to parents both antenatally and postnatally, and reassurance that a selective MCUG policy is appropriate.

  10. Multiple Genetic Associations with Irish Wolfhound Dilated Cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Siobhan Simpson


    Full Text Available Cardiac disease is a leading cause of morbidity and mortality in dogs and humans, with dilated cardiomyopathy being a large contributor to this. The Irish Wolfhound (IWH is one of the most commonly affected breeds and one of the few breeds with genetic loci associated with the disease. Mutations in more than 50 genes are associated with human dilated cardiomyopathy (DCM, yet very few are also associated with canine DCM. Furthermore, none of the identified canine loci explain many cases of the disease and previous work has indicated that genotypes at multiple loci may act together to influence disease development. In this study, loci previously associated with DCM in IWH were tested for associations in a new cohort both individually and in combination. We have identified loci significantly associated with the disease individually, but no genotypes individually or in pairs conferred a significantly greater risk of developing DCM than the population risk. However combining three loci together did result in the identification of a genotype which conferred a greater risk of disease than the overall population risk. This study suggests multiple rather than individual genetic factors, cooperating to influence DCM risk in IWH.

  11. Management of esophageal perforation after pneumatic dilation for achalasia. (United States)

    Hunt, D R; Wills, V L; Weis, B; Jorgensen, J O; DeCarle, D J; Coo, I J


    Current management of esophageal perforation after pneumatic dilation for achalasia is thoracotomy and repair with myotomy. This study aims to assess the outcome of patients managed by laparotomy, and the role of laparoscopic repair. The study was carried out by means of retrospective case review and prospective follow-up with a symptom questionnaire. Results were compared with results in patients undergoing elective Heller myotomy. Over a 20-year period, 445 dilations for achalasia were performed in 371 patients. There were 10 esophageal perforations. Nine patients were referred for surgery and were successfully managed with a transabdominal repair. Laparoscopic repair was attempted in four patients but was successful in only one because of the perforation site. After a mean follow-up of 5.4 years, grade 1 or 2 Visick scores were recorded in all patients. Residual symptoms of dysphagia occurred in 67% in the emergency group and 88% in the elective group. There was an increased incidence of heart-burn compared to elective myotomy. Early operation after perforation provides good results for treatment of achalasia. Mild dysphagia persists and there is an increasing sensation of heartburn. The site of perforation is typically posterolateral, which makes laparoscopic repair difficult.

  12. Posterior chamber volume does not change significantly during dilation. (United States)

    Dorairaj, S; Liebmann, J M; Tello, C; Barocas, V H; Ritch, R


    To determine whether the volume of the posterior chamber changes during pupillary dilation. Eyes with anatomically narrow angles underwent ultrasound biomicroscopy of the posterior chamber and pupillary margin under dark- and light-room conditions to assess changes in posterior chamber anatomy and volume. All examinations were stored as real-time video. A frame-by-frame analysis was performed using a macro written for the ImageJ image-processing software. Thirteen eyes were assessed. The mean patient age was 63.0 (SD 10.0) years, and the mean refractive error was 1.1 (1.9) dioptres. The horizontal mean pupillary diameter was 2.3 (0.6) mm and 3.5 (0.5) mm under light- and dark-room conditions, respectively (pchamber volumes were unchanged under light and dark conditions (3.76 (1.09) vs 3.63 (0.78) mm(3), p = 0.22, paired t test). Volumes were greater under light conditions in eight eyes and under dark conditions in five eyes. The volume of the posterior chamber does not change significantly during dilation.

  13. [Expansion dilatation balloons for cervical ripening in obstetric practice]. (United States)

    Ducarme, G; Grange, J; Vital, M


    During recent decades, mechanical devices have been substituted by pharmacological methods. Their place in the therapeutic arsenal remains important with a renewed obstetrical interest for these devices. Due to a lack of data they are still not recommended as first-line. This review thus attempted to examine the use of expansion dilatation balloons (Foley catheter and double-balloons) to analyze their effectiveness in case of native uterus and previous cesarean section. Twenty-seven clinical trials had compared balloons catheter and prostaglandins in patients without a history of uterine scar. The risk of cesarean section did not differ. Mechanical methods seemed to be more effective in achieving delivery within 24hours, with fewer episodes of excessive uterine contractions, but they necessitated more oxytocin during labor. Ten clinical trials analyzed dilatation balloons in patients with previous cesarean section. More than 70% women had favorable cervical ripening (Bishop score>6), and vaginal delivery was reported between 35 and 70% of patients. The risk of uterine rupture was low between 0.64 and 0.72%, with neither increased risk of severe neonatal and maternal morbidity nor increased risk of infectious morbidity. Mechanical methods are effective and safe for third trimester cervical ripening, mainly in women with previous cesarean section. Potential advantages may include wide availability and reduction of some of the side effects. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  14. External nasal dilators: definition, background, and current uses

    Directory of Open Access Journals (Sweden)

    Dinardi RR


    Full Text Available Ricardo Reis Dinardi, Cláudia Ribeiro de Andrade, Cássio da Cunha Ibiapina Department of Pediatrics, Pediatric Pulmonology Unit, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Abstract: Our goal was to revise the literature about external nasal dilators (ENDs as to their definition, history, and current uses. We reviewed journals in the PubMed and MEDLINE databases. The current uses hereby presented and discussed are physical exercise, nasal congestion and sleep, snoring, pregnancy, cancer, and healthy individuals. Numerous studies have shown that ENDs increase the cross-sectional area of the nasal valve, reducing nasal resistance and transnasal inspiratory pressure and stabilizing the lateral nasal vestibule, avoiding its collapse during final inspiration. These effects also facilitate breathing and are beneficial to patients with nasal obstruction. Furthermore, END use is simple, noninvasive, painless, affordable, and bears minimum risk to the user. Most studies have limited sample size and are mainly focused on physical exercise. In conclusion, ENDs seem useful, so further studies involving potential effects on the performance of physical tests and improvements in sleep quality are necessary, especially in children and teenagers. Keywords: external nasal dilator, nasal valve, nasal congestion, nasal resistance

  15. Effects of rheology and viscosity of biobased adhesives on bonding performance (United States)

    Rheology is the science of deformation and flow of the matter due to the application of a force. Most rheological tests involve applying a force to a material and measuring its flow or change in shape. Rheological characterization is useful to study the flowability and viscoelastic properties of adh...

  16. Identification of rheological parameters describing the physico-chemical properties of anaerobic sulphidogenic sludge suspensions

    NARCIS (Netherlands)

    Pevere, A.; Guibaud, G.; Hullebusch, van E.D.; Lens, P.N.L.


    This work determined rheological parameters able to describe the rheological properties of the flocculant sludge presents in sulphidogenic anaerobic bioreactors, i.e. a MBR (membrane bioreactor) and a CSTR (continuous stirred tank reactor). Both sludges displayed a non-Newtonian rheological

  17. Introducing Students to Rheological Classification of Foods, Cosmetics, and Pharmaceutical Excipients Using Common Viscous Materials (United States)

    Faustino, Ce´lia; Bettencourt, Ana F.; Alfaia, Anto´nio; Pinheiro, Lídia


    Rheological measurements are very important tools for the characterization of the flow and deformation of a material, as well as for optimization of the rheological parameters. The application and acceptance of pharmaceutical formulations, cosmetics, and foodstuffs depends upon their rheological characteristics, such as texture, consistency, or…

  18. Syneresis, rheological characteristic and sensory consistency of the artichoke sauce (Cynara scolymus L.

    Directory of Open Access Journals (Sweden)

    Francisco Mora Barandiarán


    Full Text Available The effect of the concentration of three hydrocolloids: CMC, guar gum and xanthan gum on the syneresis, rheological features and sensory consistency of the artichoke sauce (Cynara scolymus L. Imperial Star variety was studied. The syneresis was determined by the water loss by centrifugation, the rheological features of the artichoke sauce was determined using a Brookfield RVDV – III model rheometer and finally, the sensory consistency was determined by measuring the degree of satisfaction with hedonic scale of nine points. A simplex lattice design blends with centroid expanded under the response surface methodology was applied to establish the effect of the concentration of hydrocolloid on syneresis, rheological features and sensory consistency. In all treatments, the apparent viscosity decreased with shear rate demonstrating a “non Newtonian” behavior of “general plastic” type with an “n” value less than 1 and an initial shear stress. The flow behavior index “n” was in the range of 0.0856 and 0.3131 (n < 1 and the consistency index “k” in the range of 84.55 y 167.80 , the initial shear stress was in the range of 9,10 y 13,51 Pa and consistency sensory presented score of “like” to “like slightly”. Finally, the hydrocolloid mixture was optimized over the area of feasible formulation. With the optimal mixture, corresponding to 0.28% CMC, 0.13% guar gum and 0.59% xanthan gum is expected to obtain a 0.089% of syneresis and a rating of 6 in terms of sensory consistency.

  19. Microstructure and rheology of particle stabilized emulsions: Effects of particle shape and inter-particle interactions. (United States)

    Katepalli, Hari; John, Vijay T; Tripathi, Anubhav; Bose, Arijit


    Using fumed and spherical silica particles of similar hydrodynamic size, we investigated the effects of particle shape and inter-particle interactions on the formation, stability and rheology of bromohexadecane-in-water Pickering emulsions. The interparticle interactions were varied from repulsive to attractive by modifying the salt concentration in the aqueous phase. Optical microscope images revealed smaller droplet sizes for the fumed silica stabilized emulsions. All the emulsions remained stable for several weeks. Cryo-SEM images of the emulsion droplets showed a hexagonally packed single layer of particles at oil-water interfaces in emulsions stabilized with silica spheres, irrespective of the nature of the inter-particle interactions. Thus, entropic, excluded volume interactions dominate the fate of spherical particles at oil-water interfaces. On the other hand, closely packed layers of particles were observed at oil-water interfaces for the fumed silica stabilized emulsions for both attractive and repulsive interparticle interactions. At the high salt concentrations, attractive inter-particles interactions led to aggregation of fumed silica particles, and multiple layers of these particles were then observed on the droplet surfaces. A network of fumed silica particles was also observed between the emulsion droplets, suggesting that enthalpic interactions are responsible for the determining particle configurations at oil-water interfaces as well as in the aqueous phase. Steady shear viscosity measurements over a range of shear stresses, as well as oscillatory shear measurements at 1Hz confirm the presence of a network in fumed silica suspensions and emulsions, and the lack of such a network when spherical particles are used. The fractal structure of fumed silica leads to several contact points and particle interlocking in the water as well as on the bromohexadecane-water interfaces, with corresponding effects on the structure and rheology of the emulsions

  20. Gas slug ascent through rheologically stratified conduits (United States)

    Capponi, Antonio; James, Mike R.; Lane, Steve J.


    Textural and petrological evidence has indicated the presence of viscous, degassed magma layers at the top of the conduit at Stromboli. This layer acts as a plug through which gas slugs burst and it is thought to have a role in controlling the eruptive dynamics. Here, we present the results of laboratory experiments which detail the range of slug flow configurations that can develop in a rheologically stratified conduit. A gas slug can burst (1) after being fully accommodated within the plug volume, (2) whilst its base is still in the underlying low-viscosity liquid or (3) within a low-viscosity layer dynamically emplaced above the plug during the slug ascent. We illustrate the relevance of the same flow configurations at volcanic-scale through a new experimentally-validated 1D model and 3D computational fluid dynamic simulations. Applied to Stromboli, our results show that gas volume, plug thickness, plug viscosity and conduit radius control the transition between each configuration; in contrast, the configuration distribution seems insensitive to the viscosity of magma beneath the plug, which acts mainly to deliver the slug into the plug. Each identified flow configuration encompasses a variety of processes including dynamic narrowing and widening of the conduit, generation of instabilities along the falling liquid film, transient blockages of the slug path and slug break-up. All these complexities, in turn, lead to variations in the slug overpressure, mirrored by changes in infrasonic signatures which are also associated to different eruptive styles. Acoustic amplitudes are strongly dependent on the flow configuration in which the slugs burst, with both acoustic peak amplitudes and waveform shapes reflecting different burst dynamics. When compared to infrasonic signals from Stromboli, the similarity between real signals and laboratory waveforms suggests that the burst of a slug through a plug may represent a viable first-order mechanism for the generation of

  1. The Rheology of Acoustically Fluidized Sand (United States)

    Conrad, J. W.; Melosh, J.


    The collapse of large craters and the formation of central peaks and peak rings is well modeled by numerical computer codes that incorporate the acoustic fluidization mechanism to temporarily allow the fluid-like flow of rock debris immediately after crater excavation. Furthermore, long runout landslides require a similar mechanism to explain their almost frictionless movement, which is probably also a consequence of their granular composition coupled with internal vibrations. Many different investigators have now confirmed the ability of vibrations to fluidize granular materials. Yet it still remains to fully describe the rheology of vibrated sand as a function of stress, frequency and amplitude of the vibrations in the sand itself. We constructed a rotational viscometer to quantitatively investigate the relation between the stress and strain rate in a horizontal bed of strongly vibrated sand. In addition to the macroscopic stain rate, the amplitude and frequency of the vibrations produced by a pair of pneumatic vibrators were also measured with the aid of miniaturized piezoelectric accelerometers (B&K 4393) whose output was recorded on a digital storage oscilloscope. The initial gathering of the experimental data was difficult due to granular memory, but by having the sand compacted vibrationally for 8 minutes before each run the scatter of data was reduced and we were able to obtain consistent results. Nevertheless, our major source of uncertainty was variations in strain rate from run to run. We find that vibrated sand flows like a highly non-Newtonian fluid, in which the shear strain rate is proportional to stress to a power much greater than one, where the precise power depends on the amplitude and frequency of the applied vibrations. Rapid flow occurs at stresses less than half of the static yield stress (that is, the yield stress when no vibration is applied) when strong vibrations are present. For a Newtonian fluid, such as water, the relation between

  2. Endoscopic Dilation of Pharyngoesophageal Strictures: There Are More Dimensions than a Diameter

    Directory of Open Access Journals (Sweden)

    Diana Martins


    Full Text Available Background/Aims: Dysphagia due to benign pharyngoesophageal strictures (PES often requires repeated dilations; however, a uniform definition for the therapeutic efficacy of this technique has not been yet established. We aimed to assess the overall efficacy of endoscopic dilation of pharyngoesophageal anastomotic or post-radiotherapy (post-RT strictures. Methods: The data of 48 patients with post-RT (n = 29 or anastomotic PES (n = 19 submitted to endoscopic dilation during a 3-year period were retrospectively assessed. The Kochman criteria were used to determine refractoriness and recurrence. Patients were asked to answer a questionnaire determining prospectively the dilation program efficacy as (a dysphagia improvement, (b dysphagia resolution, (c need for further dilations, or (d percutaneous endoscopic gastrostomy (PEG during the previous 6 months. Need for additional therapy was considered an inefficacy criterion. Results: The median number of dilations per patient was 4 (total of 296 dilations with a median follow-up of 29 months. The mean predilation dysphagia Mellow-Pinkas score was 3 and the initial stenosis diameter was 7 mm. Fifteen and 29% of patients presented with the Kochman criteria for refractory and recurrent strictures, respectively. Moreover, 96 and 60% showed dysphagia improvement and resolution, respectively. Seventy-five-percent did not require dilations during 6 months, and 89% did not require PEG. From the patients’ perspective, overall efficacy was achieved in 58% of cases. Nine additional therapies were required. Number of dilations (OR 0.7, stricture diameter (OR 2.2, and nonrecurrence criteria (OR 14.2 appeared as significant predictors of overall efficacy, whereas refractory stenosis criteria did not. Conclusions: Endoscopic dilation seems to be effective for patients with dysphagia after RT or surgery, especially when assessed as patient perception of improvement. Narrow strictures, recurrent ones, and strictures

  3. Sinus Balloon Dilation as Treatment for Acute Sphenoid Sinusitis with Impaired Vision for a Child

    Directory of Open Access Journals (Sweden)

    Yin Zhao


    Full Text Available This paper is about sinus balloon dilatation in treatment of acute left sphenoid sinusitis with left impaired vision in a child. Balloon catheter dilatation (BCD of the sinus ostia is a new technique. It has been shown to be a minimally invasive technique to manage chronic sinusitis. However, this method is rarely used in the treatment of acute sinusitis. So far, we know of no reported cases of sinus balloon dilatation in treatment of this case, especially for children.

  4. Folding in a Cooling Crust with Elasto-visco-plastic Rheology: An Example from Venus (United States)

    Ghent, R.; Phillips, R. J.; Hansen, V.


    We investigate the effects of simultaneous shortening and cooling on fold wavelengths in a crust with elasto-visco-plastic (EVP) rheology, in order to better understand the interplay between rates of shortening and cooling on the anelastic response of the crust. We apply our techniques to Venusian crustal plateaus, which show ubiquitous, low-amplitude folds with a continuous range of wavelengths from 30 km. Previous studies have proposed that these folds (and other characteristic crustal plateau structures) originated during crustal plateau formation by interaction of large mantle plumes with the surface during a time of globally thin lithosphere [1]. In this scenario, a plume arriving at the lithosphere erases existing structures and produces a mechanically homogeneous surface by heating and/or melting the crust. Subsequent cooling results in a surface layer that is capable of recording strains and that thickens with time. We investigate the conditions under which folds matching those observed in Venusian crustal plateaus are created in a finite element model simulating concurrent shortening and cooling, as motivated by the tectonic scenario in [1]. Our models are novel because a) the EVP rheology more accurately represents the actual crust than viscous or viscoelastic models; and b) other models generally specify a priori a folding layer thickness and geometry, with material properties different from those of the surrounding rock, and this pre-determines the resulting fold wavelength(s). By contrast, our models incorporate spatially uniform material properties but temperature-dependent rheology [2], so that the strength profile through the crust evolves with cooling. This allows the thermal and stress conditions to determine the instantaneous effective folding layer thickness at each time step, which in turn determines surface fold wavelengths. We investigate conditions under which short wavelength folds are initiated when the effective folding layer is very thin

  5. The therapy of esophageal stricture caused by erosive through balloon dilation

    International Nuclear Information System (INIS)

    Li Yi; Zeng Xianqiang; Wang Rongqin; Ding Xiaolin; You Guoqing; Shao Hede; Zhang Xinyuan


    Objective: To evaluate the therapy of esophageal stricture caused by erosive burn of esophagus through balloon dilation. Methods: 9 patients of esophageal stricture caused by erosive burn of esophagus have been treated by balloon dilation. Results: 9 patients have been dilated 26 times altogether 7 of them can eat normally. 2 patients' symptoms were improved. Six months to two years after operation, the symptoms were not reoccurred. All of them have no serious complications. Conclusion: Balloon dilation is one of the effective and safe therapy of esophageal stricture caused by erosive burn. (authors)

  6. Dilatant normal faulting in jointed cohesive rocks: insights from physical modeling (United States)

    Kettermann, Michael; von Hagke, Christoph; Urai, Janos


    Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on fault segment linkage and fracture connectivity is not well understood. Studying evolution of dilatancy and influence of fractures on fault development provides insights on geometry of fault zones in brittle rocks and eventually allows for predicting their subsurface appearance. We assess the evolution of dilatant faults in fractured rocks using analogue models with cohesive powder. The upper layer contains pre-formed joint sets, and we vary the angle between joints and a rigid basement fault in our experiments. Analogue models were carried out in a manually driven deformation box (30x28x20 cm) with a 60° dipping pre-defined basement fault and 4.5 cm of displacement. To produce open joints prior to faulting, sheets of paper were mounted in the box to a depth of 5 cm at a spacing of 2.5 cm. Powder was then sieved into the box, embedding the paper almost entirely (column height of 19 cm), and the paper was removed. We tested the influence of different angles between the strike of the basement fault and the joint set (joint fault (JF) angles of 0°, 4°, 8°, 12°, 16°, 20°, and 25°). During deformation we captured structural information by time-lapse photography that allows particle imaging velocimetry analyses (PIV) to detect localized deformation at every increment of displacement. Post-mortem photogrammetry preserves the final 3-dimensional structure of the fault zone. Results show robust structural features in models: damage zone width increases by about 50 % and the number of secondary fractures within this zone by more than 100 % with increasing JF-angle. Interestingly, the map-view area fraction of open gaps increases by only 3%. Secondary joints and fault step-overs are oriented at a high angle to the primary joint orientation. Due to the length of the pre-existing open joints, areas far beyond the fractured regions are connected to the system. In contrast

  7. Extensional terrain formation on Europa and Ganymede: Implications for ocean-surface interaction (United States)

    Howell, S. M.; Pappalardo, R. T.


    Europa and Ganymede, Galilean satellites of Jupiter, exhibit geologic activity in their outer H2O ice shells that might convey material from water oceans within the satellites to their surfaces. Imagery from the Voyager and Galileo spacecraft reveal surfaces rich with tectonic deformation, including dilational bands on Europa and groove lanes on Ganymede. These features are generally attributed to the extension of a brittle ice lithosphere overlaying a possibly convecting ice asthenosphere. To explore band formation and interaction with interior oceans, we employ fully visco-elasto-plastic 2-D models of faulting and convection with complex, realistic pure ice rheologies. In these models, material entering from below is tracked and considered to be "fossilized ocean," ocean material that has frozen into the ice shell and evolves through geologic time. We track the volume fraction of fossil ocean material in the ice shell as a function of depth, and the exposure of both fresh ice and fossil ocean material at the ice shell surface. We vary ice shell thickness, fault localization, melting-temperature ice viscosity, and the presence of pre-existing weaknesses. Mechanisms which act to weaken the ice shell and thin the lithosphere (e.g. vigorous convection, thinner shells, pre-existing weaknesses) tend to plastically yield to form smooth bands at high strains, and are more likely to incorporate fossil ocean material in the ice shell and expose it at the surface. In contrast, lithosphere strengthened by rapid fault annealing or increased viscosity, for example, exhibits large-scale tectonic rifting at low strains superimposed over pre-existing terrains, and inhibits the incorporation and delivery of fossil ocean material to the surface. Thus, our results identify a spectrum of extensional terrain formation mechanisms as linked to lithospheric strength, rather than any specific mechanism being unique to each type of band, and where in this spectrum ocean material

  8. Characterization of fasted human gastric fluid for relevant rheological parameters and gastric lipase activities

    DEFF Research Database (Denmark)

    Pedersen, Pernille Barbre; Vilmann, Peter; Bar-Shalom, Daniel


    characterization of the aspirates was conducted on a TA AR-G2 rheometer, using cone and plate geometry. Lipase activity was measured by continuous titration of released free fatty acid from tributyrate. Further, pH, osmolality, buffer capacity, and surface tension were measured and the total protein content.......8 and 5.4, respectively. pH, surface tension, buffer capacity, bile salt concentration, and osmolality were measured and compared with literature data. CONCLUSION: The rheological behavior and the mean apparent viscosity of HGA are significantly different from that of water and should therefore...... be considered important during development of gastric simulated media. Further, the activity of the HGL is active even under fasted gastric conditions and might contribute to the digestion and emulsification of lipid-based drug delivery systems in the entire gastrointestinal tract. HGL should therefore...

  9. The effect of rheological approximations on the dynamics and topography in 3D subduction-collision models (United States)

    Pusok, Adina E.; Kaus, Boris J. P.; Popov, Anton A.


    Most of the major mountain belts and orogenic plateaus are found within the overlying plate of active or fossil subduction and/or collision zones. Moreover, they evolve differently from one another as the result of specific combinations of surface and mantle processes. These differences arise for several reasons, such as different rheological properties, different amounts of regional isostatic compensation, and different mechanisms by which forces are applied to the convergent plates. Previous 3D geodynamic models of subduction/collision processes have used various rheological approximations, making numerical results difficult to compare, since there is no clear image on the extent of these approximations on the dynamics. Here, we employ the code LaMEM to perform high-resolution long-term 3D simulations of subduction/continental collision in an integrated lithospheric and upper-mantle scale model. We test the effect of rheological approximations on mantle and lithosphere dynamics in a geometrically simplified model setup that resembles a tectonic map of the India-Asia collision zone. We use the "sticky-air" approach to allow for the development of topography and the dynamics of subduction and collision is entirely driven by slab-pull (i.e. "free subduction"). The models exhibit a wide range of behaviours depending on the rheological law employed: from linear to temperature-dependent visco-elasto-plastic rheology that takes into account both diffusion and dislocation creep. For example, we find that slab dynamics varies drastically between end member models: in viscous approximations, slab detachment is slow following a viscous thinning, while for a non-linear visco-elasto-plastic rheology, slab detachment is relatively fast, inducing strong mantle flow in the slab window. We also examine the stress states in the subducting and overriding plates and topography evolution in the upper plate, and we discuss the implications on lithosphere dynamics at convergent margins

  10. Rheological properties of polyvinylsiloxane impression materials before mixing and during setting related to handling characteristics (United States)

    Lee, Hyang-Ok; Lee, In-Bog


    The purpose of this study is to determine and compare the handling and rheological properties of polyvinylsiloxane impression pastes before mixing and during setting, and to investigate the effect of its constituents on the properties of the materials. Five polyvinylsiloxane impression materials (Examixfine, Extrude, Honigum, Imprint II, and Express) were used. A flow test and a drip test were performed to determine the handling characteristics. The rheological properties of each impression material prior to mixing (shear stress, viscosity) and during setting (storage modulus G'), loss modulus G″), loss tangent tanδ) were measured with a stress-controlled rheometer at 25°C and 32°C, respectively. Inorganic filler content of each impression material was measured and observed with a SEM. The molecular weight distribution of polymer matrix was determined with a gel permeation chromatography (GPC). Express and Honigum display lower flow compared to the other materials, due to their high yield-stress values. Examixfine exhibits the greatest flow. All materials display pseudoplastic behavior, excluding the Examixfine catalyst. The viscosities at low shear rate are greatest for Express and Honigum; however, under high shear conditions, the viscosities of Extrude and Honigum are the lowest. Following mixing, each material show an increase in G', finally reaching a plateau, and the tanδ rapidly decreases with time. Imprint II shows the highest final G' as well as the most rapid decrease in tanδ. Express and Imprint II present the highest filler content and rough filler surface, while Honigum shows the lowest filler content and small filler particles. Most products are composed of polymers over 30 kDa and oligomers less than 1 kDa. Each impression material possesses different rheological properties, which significantly affect the handling characteristics. The yield stress of the impression material minimizes unnecessary flow prior to and after seating. Viscoelastic

  11. Rheological and fractal characteristics of unconditioned and conditioned water treatment residuals. (United States)

    Dong, Y J; Wang, Y L; Feng, J


    The rheological and fractal characteristics of raw (unconditioned) and conditioned water treatment residuals (WTRs) were investigated in this study. Variations in morphology, size, and image fractal dimensions of the flocs/aggregates in these WTR systems with increasing polymer doses were analyzed. The results showed that when the raw WTRs were conditioned with the polymer CZ8688, the optimum polymer dosage was observed at 24 kg/ton dry sludge. The average diameter of irregularly shaped flocs/aggregates in the WTR suspensions increased from 42.54 μm to several hundred micrometers with increasing polymer doses. Furthermore, the aggregates in the conditioned WTR system displayed boundary/surface and mass fractals. At the optimum polymer dosage, the aggregates formed had a volumetric average diameter of about 820.7 μm, with a one-dimensional fractal dimension of 1.01 and a mass fractal dimension of 2.74 on the basis of the image analysis. Rheological tests indicated that the conditioned WTRs at the optimum polymer dosage showed higher levels of shear-thinning behavior than the raw WTRs. Variations in the limiting viscosity (η(∞)) of conditioned WTRs with sludge content could be described by a linear equation, which were different from the often-observed empirical exponential relationship for most municipal sludge. With increasing temperature, the η(∞) of the raw WTRs decreased more rapidly than that of the raw WTRs. Good fitting results for the relationships between lgη(∞)∼T using the Arrhenius equation indicate that the WTRs had a much higher activation energy for viscosity of about 17.86-26.91 J/mol compared with that of anaerobic granular sludge (2.51 J/mol) (Mu and Yu, 2006). In addition, the Bingham plastic model adequately described the rheological behavior of the conditioned WTRs, whereas the rheology of the raw WTRs fit the Herschel-Bulkley model well at only certain sludge contents. Considering the good power-law relationships between the

  12. Terapia celular na cardiomiopatia dilatada Cell therapy in dilated cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Helena Furtado Martino


    Full Text Available Homem de 41 anos em insuficiência cardíaca sistólica, CF III NYHA, estágio clínico C, por cardiomiopatia dilatada, foi submetido ao transplante autólogo da fração mononuclear da medula óssea, via sistema arterial coronariano, através de cateterismo cardíaco. Dois meses após o procedimento, houve diminuição do BNP plasmático, diminuição da área cardíaca ao estudo radiológico do tórax e à ressonância nuclear magnética. O ecocardiograma demonstrou diminuição do fluxo regurgitante secundário a dilatação do anel mitral. Na ergoespirometria houve melhor desempenho, com aumento do consumo máximo de oxigênio, sendo possível redução da terapêutica medicamentosa. A ausência de eventos adversos caracterizados por: instabilidade clínica/hemodinâmica, alteração enzimática ou eletrocardiográfica apontam para segurança e exeqüibilidade deste procedimento realizado e descrito com pioneirismo na cardiomiopatia dilatada.A forty-one-year-old male with systolic heart failure, FC-III NYHA, clinical stage C due to dilated cardiomyopathy was submitted to an autologous transplant of the mononuclear fraction of bone marrow via coronary artery system through heart catheterism. Two months after the procedure, there was a decrease in plasma BNP and cardiac area reduction at the thorax X-ray and nuclear magnetic resonance. The echocardiogram showed decrease of the secondary regurgitation and mitral ring dilatation. There was a better performance at the ergospirometry, with increase of the maximum oxygen consumption and consequent reduction in drug therapy. The absence of adverse events characterized by clinical/hemodynamic instability, enzymatic alteration or electrocardiogram demonstrate the safety and feasibility of this procedure carried out and described with pioneering spirit in dilated cardiomyopathy.

  13. Differential Rheology Among ABO Blood Group System In Nigerians

    African Journals Online (AJOL)

    Sci. 3 (1): 30-35, July 2015. Journal of African Association of Physiological Sciences. Official Publication of the African Association of Physiological Sciences Research Article. Differential Rheology Among ABO Blood Group System In. Nigerians. O.I. Ajayi* O.O. Ekakitie**, O.C. Okpalaugo*.

  14. Rheology and extrusion of high-solids biomass (United States)

    Tim Scott; Joseph R. Samaniuk; Daniel J. Klingenberg


    Economical biorefining of lignocellulosic biomass (LCB) requires processing high-solids particulate streams. We have developed new techniques and testing protocols to measure the rheological properties of high-solids LCB using a modified torque rheometer (TR). The flow field in the TR is similar to that of a twin-screw extruder and for modeling purposes can be...

  15. Computer simulation studies of the rheology of soft condensed matter

    International Nuclear Information System (INIS)

    Daivis, P.J.; Snook, I.K.; Matin, M.L.; Kairn, T.; McPhie, M.


    Full text: The rheology of soft condensed matter systems, such as polymer melts, polymer solutions and colloidal dispersions, is a subject of enduring interest - not only because of its importance in materials processing technology, but also because of the fascinating theoretical challenges it presents. Many of the rheological features possessed by these systems, such as normal stress differences, non-Newtonian viscosity and elasticity, are spectacularly evident on the macroscopic scale, but these properties are also crucial to emerging modern technologies such as micro- and nano-fluidics. Over the last seven years, we have studied many different aspects of the rheology of soft condensed matter systems using non-equilibrium molecular dynamics computer simulation techniques. Of particular importance, has been our development of a new algorithm for studying elongational flow, a comparison of the planar elongational and shear flow rheology of molecular fluids, our examination of the approach to the Brownian limit in colloidal fluids, and our detailed investigation of the concentration dependence of the viscosity and normal stress differences in short-chain polymer solutions. In this paper, we review the results of these investigations, discuss the current capabilities and limitations of non-equilibrium molecular dynamics simulations, and discuss our current work and future directions

  16. Topics in macro and micro rheology of blood

    International Nuclear Information System (INIS)

    Suarez Antola, R.


    Introduction Blood and blood vessels: general morphological, physiological, and physicochemical aspects of the cardiovascular system and blood tissue. Chapter I: Deformation and laminar flow of Newtonian and non-Newtonian materials in tubes with rigid walls. Turbulent flows in tubes. Blood flow in tubes with non-extensible walls: stationary flow and oscillating flow of an equivalent homogeneous continuum.Chapter II: Propagation of pressure pulses in tubes with visco-elastic walls. Pulse propagation in arterioles in laminar regimes and in arteries in laminar and turbulent regimes. Chapter III: Deformation and laminar flow of suspensions in tubes of inextensible walls. Macro-rheology of blood. Non-equilibrium thermodynamics and blood flow in vessels. Axial accumulation of blood cells.Chapter IV: The micro-rheological point of view in the study of laminar and oscillating flows of suspensions in tubes of rigid walls. Blood micro-rheology.Conclusions: Some comments about the biological and medical importance of the biophysical study of the macro and micro rheology of blood

  17. Rheology of High-Melt-Strength Polypropylene for Additive Manufacturing

    DEFF Research Database (Denmark)

    Hofstätter, Thomas; Kamleitner, Florian; Jagenteufel, Ralf

    Acrylonitrile butadiene styrene (ABS) is a widely used material for additive manufacturing (AM) fused deposition modeling (FDM). The rheological properties of high-melt-strength polypropylene (HMS-PP) were compared to commercially available ABS 250 filament to study the possibility of using this ...

  18. Rheological properties of boehmite sols during ageing at room ...

    Indian Academy of Sciences (India)

    Boehmite sols were obtained by peptizing boehmite precipitates with glacial acetic acid. The sols were aged at room temperature (30 ± 1°C) under closed condition. Rheological properties of the sols were studied at different ageing times. The sol characteristics were interpreted by measuring their viscosity, areas of ...

  19. Effect of drying methods on the rheological characteristics and ...

    African Journals Online (AJOL)

    The effect of drying methods (sun and oven-drying) on the rheological properties and colour of amala, a thick paste from yam flour, was investigated using two varieties of yam (Dioscorea rotundata and. Dioscorea alata). The yam flour produced was later reconstituted to produce amala of different pasting characteristics, ...

  20. Assesment of mucoadhesion using small deformation rheology revisited

    DEFF Research Database (Denmark)

    Harloff-Helleberg, Stine; Vissing, Karina Juul; Nielsen, Hanne Mørck


    This work revisits the commonly used approach to assess mucoadhesion in drug delivery by small deformation rheology. The results show that biosimilar mucus serves as a more predictive mucus model system when compared to mucin suspensions. Data is fitted including error propagation, different from...

  1. In-line rheological characterisation of wastewater sludges using non ...

    African Journals Online (AJOL)

    In-line process control based on accurate rheological characterisation for treated wastewater sludge could lead to significant savings in chemicals and will optimise dewatering processes producing drier sludges. In this work, a wastewater sludge at three concentrations was tested in order to investigate the capabilities of the ...

  2. Rheological properties of Danwake flour blends from sorghum ...

    African Journals Online (AJOL)

    The rheological properties of seven danwake flour blend formulations from sorghum, wheat and cassava bases were investigated. The different ingredients in the danwake were sorghum flour, cowpea flour, wheat flour, cassava flour, baobab leaf powder, and trona (sodium sesquicarbonate) (kanwa). The viscosity of the ...

  3. Rheology of stabilized cerium-gadolinium oxide (CGO) colloidal system

    DEFF Research Database (Denmark)

    Marani, Debora; Hjelm, Johan; Wandel, Marie

    performed to study the inorganic loading impact on the suspension rheology. To identify a realistic load limit, the parameter h was proposed. It defines the highest volume fraction to meet the processing requirements. A simple method for its determination was also proposed. The maximum solid volume...

  4. A new thermal and rheological model of the European lithosphere

    NARCIS (Netherlands)

    Tesauro, M.; Kaban, M.; Cloetingh, S.A.P.L.


    We present a new thermal and rheological model of the European lithosphere (10°W-35°E; 35°N-60°N), which is based on a combination of recently obtained geophysical models. To determine temperature distribution we use a new tomography model, which is principally improved by an a-priori correction of

  5. Rheology modification in mixed shape colloidal dispersions. Part II: mixtures

    NARCIS (Netherlands)

    ten Brinke, A.J.W.; Bailey, L.; Lekkerkerker, H.N.W.|info:eu-repo/dai/nl/159054885; Matiland, G.C.


    We report the results of a comprehensive study of the rheological properties of a series of mixed colloid systems where the shape of one of the components has been varied systematically. Specifically we have measured the oscillatory, transient (creep) and continuous steady shear flow behaviour of a

  6. Rheological Properties of Calcium Hydroxylapatite With Integral Lidocaine. (United States)

    Meland, Melissa; Groppi, Chris; Lorenc, Z Paul


    Calcium hydroxylapatite with integral lidocaine, CaHA (+), received FDA approval in 2015 and CE mark approval in 2016. This formulation has been associated with significant pain reduction compared to CaHA. In a previous rheometry study, CaHA without lidocaine demonstrated higher viscosity and elasticity when compared with hyaluronic acid fillers. To compare the rheological properties of CaHA (+) lidocaine to CaHA without lidocaine and to compare the rheological measures of CaHA (+) to 5 cross-linked hyaluronic acid (HA) fillers with integral 0.3% lidocaine. The rheological properties of complex viscosity (η*) and elastic modulus (G') were measured for 2 types of CaHA fillers [CaHA without lidocaine and CaHA (+) with integral 0.3% lidocaine] and 5 HA fillers using an oscillation frequency sweep at a sheer stress of 5 pascal tau (Pa) and an interpolation of 0.7 Hz. CaHA with and without integral lidocaine demonstrate similar η* and G' measurements. CaHA with and without integral lidocaine demonstrates higher η* and G' compared with HA fillers with integral lidocaine. CaHA with integral lidocaine has a similar rheological profile to CaHA without lidocaine: the highest η* and G' compared with available HA fillers with integral lidocaine. J Drugs Dermatol. 2016;15(9):1107-1110.

  7. Influence of enzymes and ascorbic acid on dough rheology and ...

    African Journals Online (AJOL)

    The combined action of ascorbic acid and two commercial enzymatic complexes containing amylase and xylanase/amylase was analyzed to determine their effects on dough rheology and bread quality. Seven bread formulations containing different concentrations of these improvers were used in the analysis.

  8. Effects of iron supply on the rheological properties and sensory ...

    African Journals Online (AJOL)

    The most basic is the world wheat crops. In Iran Bread is a staple food staple Food and because, as a bearer of good food to enrich bread with iron has been considered. The effect of flour fortification star with iron, folic acid, the chemical properties (dry gluten, wet gluten, gluten-free number, protein and Ddzlny) Rheological ...

  9. Rheology of Perfluorinated Polyether-based MR Fluids with Nanoparticles

    NARCIS (Netherlands)

    Jonsdottir, F.; Gudmundsson, K.H.; Dijkman, T.B.; Thorsteinsson, F.; Gutfleisch, O.


    Motivated by the use of magneto-rheological (MR) technology in prosthetic devices, the goal of this study is to develop a MR fluid composition that is tailored for the requirements of a prosthetic knee actuator. A MR fluid composition is sought with a suitable balance between the field-induced shear

  10. Rheological properties of nanofiltered Athabasca bitumen and Maya crude oil

    Czech Academy of Sciences Publication Activity Database

    Hasan, M.D.A.; Fulem, Michal; Bazyleva, A.; Shaw, J.M.


    Roč. 23, - (2009), s. 5012-5021 ISSN 0887-0624 Institutional research plan: CEZ:AV0Z10100521 Keywords : viscosity * rheology * Athabasca bitumen * Maya crude oil * phase behavior * asphaltenes * nanofiltration Subject RIV: JJ - Other Materials Impact factor: 2.319, year: 2009

  11. Bitumen and heavy oil rheological properties: reconciliation with viscosity measurements

    Czech Academy of Sciences Publication Activity Database

    Bazyleva, A.B.; Hasan, M.D.A.; Fulem, Michal; Becerra, M.; Shaw, J.M.


    Roč. 55, č. 3 (2010), s. 1389-1397 ISSN 0021-9568 Institutional research plan: CEZ:AV0Z10100521 Keywords : Athabasca bitumen * Maya crude oil * rheological properties * viscosity measurements Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.089, year: 2010

  12. Shear rheological properties of fresh human faeces with different ...

    African Journals Online (AJOL)


    Mar 11, 2014 ... Short communication. Shear rheological properties of fresh human faeces with different moisture content. SM Woolley1, RS Cottingham1, J Pocock1 and CA Buckley1*. 1Pollution Research Group, School of Engineering, University of KwaZulu-Natal, King George V Avenue, Berea 4041, South Africa.

  13. Rheological properties of cementitious materials containing mineral admixtures

    Energy Technology Data Exchange (ETDEWEB)

    C.K. Park; M.H. Noh; T.H. Park [Korea Institute of Industrial Technology, Cheonan (Republic of Korea)


    The rheological properties of cementitious materials containing fine particles, such as mineral admixtures (MA), were investigated using a Rotovisco RT 20 rheometer (Haake) with a cylindrical spindle. The mineral admixtures were finely ground blast furnace slag, fly ash and silica fume. The cementitious materials were designed as one, two and three components systems by replacement of ordinary Portland cement (OPC) with these mineral admixtures. The rheological properties of one-component system (OPC) were improved with increasing the dosage of PNS-based superplasticizer. For two-components systems, yield stress and plastic viscosity decreased with replacing OPC with blast furnace slag (BFS) and fly ash (FA). In the case of OPC-silica fume (SF) system, yield stress and plastic viscosity steeply increased with increasing SF. For three components systems, both OPC-BFS-SF and OPC-FA-SF systems, the rheological properties improved, compared with the sample with SF. In the two and three components systems, the rheological properties of samples containing BFS improved much more than with FA replacement alone.

  14. Rheological Characteristics of Fresh and Dried Okra Dispersions ...

    African Journals Online (AJOL)

    The rheological properties of fresh and dried okra dispersions were investigated at different temperatures using power-law model. Sun-dried and oven-dried okra dispersions were more viscous than the fresh okra dispersion. All samples exhibited pseudoplastic behaviour with flow indices of 0.220 ≤ n ≤ 0.319, 0.182 ≤ n ...

  15. Rheological study of chitosan acetate solutions containing chitin nanofibrils

    Czech Academy of Sciences Publication Activity Database

    Mikešová, Jana; Hašek, Jindřich; Tishchenko, Galina; Morganti, P.


    Roč. 112, 4 November (2014), s. 753-757 ISSN 0144-8617 EU Projects: European Commission(XE) 315233 - N-CHITOPACK Institutional support: RVO:61389013 Keywords : rheology * chitosan solutions * chitin nanofibrils Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.074, year: 2014

  16. Effect of solution physical chemistry on the rheological properties of ...

    African Journals Online (AJOL)

    Knowledge on rheological properties of sludge is important for the design of pumping and transport facilities and as a tool in process control during treatment. Concentrated activated sludge is known to behave as a non-Newtonian material. The contribution to non- Newtonian behaviour is believed to originate from the ...

  17. In-line rheological characterisation of wastewater sludges using non ...

    African Journals Online (AJOL)


    Oct 5, 2015 ... capabilities of the in-line ultrasound technique for different viscosities and fluid properties. The rheological ... in industrial fluids. This is because industrial fluids, including wastewater sludges, exhibit ..... Doppler Methods for Fluid Mechanics and Fluid Engineering, 27–29. August 2014, Strasbourg, France.

  18. Rheological and Sensory Characteristics of Yoghurt-Modified Mayonnaise

    Czech Academy of Sciences Publication Activity Database

    Štern, Petr; Pokorný, J.; Šedivá, A.; Panovská, Z.


    Roč. 26, č. 3 (2008), s. 190-198 ISSN 1212-1800 R&D Projects: GA AV ČR IAA2060404 Institutional research plan: CEZ:AV0Z20600510 Keywords : mayonnaise * rheology * sensory analysis * texture * yoghurt Subject RIV: BK - Fluid Dynamics Impact factor: 0.472, year: 2008

  19. Rheological properties of agar and carrageenan from Ghanaian red seaweeds

    DEFF Research Database (Denmark)

    Rhein-Knudsen, Nanna; Ale, Marcel Tutor; Ajalloueian, Fatemeh


    Red seaweeds contain unique galactose-rich hydrocolloids, carrageenans and agar, which find use as gelling agents in high value applications. This study examined the chemical and rheological properties of hydrocolloids from selected wild red seaweed species collected in Ghana: Hypnea musciformis ...

  20. Rheological behaviour of self-compacting micro-concrete

    Indian Academy of Sciences (India)

    Flow parameters such as yield value and plastic viscosity have been measured along with shear thickening or thinning behaviour. Furthermore, thixotropic behaviour of the various mixtures have been measured using hysteresis areas. Finally, advanced rheological properties of micro-concretes and cement pastes have ...