DOE Office of Scientific and Technical Information (OSTI.GOV)

Monnai, Akihiko; Mukherjee, Swagato; Yin, Yi

In the proximity of the QCD critical point the bulk viscosity of quark-gluon matter is expected to be proportional to nearly the third power of the critical correlation length, and become significantly enhanced. Here, this work is the first attempt to study the phenomenological consequences of enhanced bulk viscosity near the QCD critical point. For this purpose, we implement the expected critical behavior of the bulk viscosity within a non-boost-invariant, longitudinally expanding 1 + 1 dimensional causal relativistic hydrodynamical evolution at nonzero baryon density. We demonstrate that the critically enhanced bulk viscosity induces a substantial nonequilibrium pressure, effectively softening themore » equation of state, and leads to sizable effects in the flow velocity and single-particle distributions at the freeze-out. In conclusion, the observable effects that may arise due to the enhanced bulk viscosity in the vicinity of the QCD critical point can be used as complementary information to facilitate searches for the QCD critical point.« less

Progress on Acoustic Measurements of the Bulk Viscosity of Near-Critical Xenon (BVX)

NASA Technical Reports Server (NTRS)

Gillis, Keith A.; Shinder, Iosif I.; Moldover, Michael R.; Zimmerli, Gregory A.

2004-01-01

We plan to determine the bulk viscosity of xenon 10 times closer [in reduced temperature tau = (T-Tc)/Tc] to its liquid-vapor critical point than ever before. (Tc is the critical temperature.) To do so, we must measure the dispersion and attenuation of sound at frequencies 1/100 of those used previously. In general, sound attenuation has contributions from the bulk viscosity acting throughout the volume of the xenon as well as contributions from the thermal conductivity and the shear viscosity acting within thin thermoacoustic boundary layers at the interface between the xenon and the solid walls of the resonator. Thus, we can determine the bulk viscosity only when the boundary layer attenuation is small and well understood. We present a comparison of calculations and measurements of sound attenuation in the acoustic boundary layer of xenon near its liquid-vapor critical point.

Universal Scaling Laws for Dense Particle Suspensions in Turbulent Wall-Bounded Flows.

PubMed

Costa, Pedro; Picano, Francesco; Brandt, Luca; Breugem, Wim-Paul

2016-09-23

The macroscopic behavior of dense suspensions of neutrally buoyant spheres in turbulent plane channel flow is examined. We show that particles larger than the smallest turbulence scales cause the suspension to deviate from the continuum limit in which its dynamics is well described by an effective suspension viscosity. This deviation is caused by the formation of a particle layer close to the wall with significant slip velocity. By assuming two distinct transport mechanisms in the near-wall layer and the turbulence in the bulk, we define an effective wall location such that the flow in the bulk can still be accurately described by an effective suspension viscosity. We thus propose scaling laws for the mean velocity profile of the suspension flow, together with a master equation able to predict the increase in drag as a function of the particle size and volume fraction.

Bulk Viscous Anisotropic Cosmological Models with Variable G and Λ

NASA Astrophysics Data System (ADS)

Pradhan, Anirudh; Yadav, Vinod Kumar; Dolgov, A.

The Einstein field equations with bulk viscosity and variable G and Λ for Bianchi-type universes are studied under the assumption of a power-law time variation of the expansion factor, achieved via a suitable power-law assumption for the Hubble parameter suggested by M. S. Berman. All the models have a power-law variation of pressure and density and are singular at the epoch t = 0. The variation of G(t) as (1)/(t) and Λ(t) as (1)/(t2) is consistent with these models.

Accelerated and decelerated expansion in a causal dissipative cosmology

NASA Astrophysics Data System (ADS)

Cruz, Miguel; Cruz, Norman; Lepe, Samuel

2017-12-01

In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic equation of state (EoS) p =ω ρ , in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form ξ =ξ0ρ1 /2. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, cb. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for ω , ξ0, cb accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions d S /d t >0 (growth of the entropy) and d2S /d t2<0 (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations.

Bulk viscosity of molecular fluids

NASA Astrophysics Data System (ADS)

Jaeger, Frederike; Matar, Omar K.; Müller, Erich A.

2018-05-01

The bulk viscosity of molecular models of gases and liquids is determined by molecular simulations as a combination of a dilute gas contribution, arising due to the relaxation of internal degrees of freedom, and a configurational contribution, due to the presence of intermolecular interactions. The dilute gas contribution is evaluated using experimental data for the relaxation times of vibrational and rotational degrees of freedom. The configurational part is calculated using Green-Kubo relations for the fluctuations of the pressure tensor obtained from equilibrium microcanonical molecular dynamics simulations. As a benchmark, the Lennard-Jones fluid is studied. Both atomistic and coarse-grained force fields for water, CO2, and n-decane are considered and tested for their accuracy, and where possible, compared to experimental data. The dilute gas contribution to the bulk viscosity is seen to be significant only in the cases when intramolecular relaxation times are in the μs range, and for low vibrational wave numbers (<1000 cm-1); This explains the abnormally high values of bulk viscosity reported for CO2. In all other cases studied, the dilute gas contribution is negligible and the configurational contribution dominates the overall behavior. In particular, the configurational term is responsible for the enhancement of the bulk viscosity near the critical point.

Natural entropy production in an inflationary model for a polarized vacuum

NASA Astrophysics Data System (ADS)

Berman, Marcelo Samuel; Som, Murari M.

2007-08-01

Though entropy production is forbidden in standard FRW Cosmology, Berman and Som presented a simple inflationary model where entropy production by bulk viscosity, during standard inflation without ad hoc pressure terms can be accommodated with Robertson Walker’s metric, so the requirement that the early Universe be anisotropic is not essential in order to have entropy growth during inflationary phase, as we show. Entropy also grows due to shear viscosity, for the anisotropic case. The intrinsically inflationary metric that we propose can be thought of as defining a polarized vacuum, and leads directly to the desired effects without the need of introducing extra pressure terms.

Importance of the Bulk Viscosity of QCD in Ultrarelativistic Heavy-Ion Collisions

DOE PAGES

Ryu, S.; Paquet, J. -F.; Shen, C.; ...

2015-09-22

In this study, we investigate the consequences of a nonzero bulk viscosity coefficient on the transverse momentum spectra, azimuthal momentum anisotropy, and multiplicity of charged hadrons produced in heavy ion collisions at LHC energies. The agreement between a realistic 3D hybrid simulation and the experimentally measured data considerably improves with the addition of a bulk viscosity coefficient for strongly interacting matter. Lastly, this paves the way for an eventual quantitative determination of several QCD transport coefficients from the experimental heavy ion and hadron-nucleus collision programs.

Radiating gravitational collapse with shearing motion and bulk viscosity

NASA Astrophysics Data System (ADS)

Chan, R.

2001-03-01

A model is proposed of a collapsing radiating star consisting of a shearing fluid with bulk viscosity undergoing radial heat flow with outgoing radiation. The pressure of the star, at the beginning of the collapse, is isotropic but due to the presence of the bulk viscosity the pressure becomes more and more anisotropic. The behavior of the density, pressure, mass, luminosity, the effective adiabatic index and the Kretschmann scalar is analyzed. Our work is compared to the case of a collapsing shearing fluid of a previous model, for a star with 6 Msun.

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

NASA Astrophysics Data System (ADS)

Singh, C. P.; Srivastava, Milan

2018-03-01

In this work, we study a flat Friedmann-Robertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to Λ CDM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ =ζ 0+ζ 1H, where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r-s and r-q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the Λ CDM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe.

Bulk viscosity of water in acoustic modal analysis and experiment

NASA Astrophysics Data System (ADS)

Kůrečka, Jan; Habán, Vladimír; Himr, Daniel

2018-06-01

Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.

A bulk viscosity approach for shock capturing on unstructured grids

NASA Astrophysics Data System (ADS)

Shoeybi, Mohammad; Larsson, Nils Johan; Ham, Frank; Moin, Parviz

2008-11-01

The bulk viscosity approach for shock capturing (Cook and Cabot, JCP, 2005) augments the bulk part of the viscous stress tensor. The intention is to capture shock waves without dissipating turbulent structures. The present work extends and modifies this method for unstructured grids. We propose a method that properly scales the bulk viscosity with the grid spacing normal to the shock for unstructured grid for which the shock is not necessarily aligned with the grid. The magnitude of the strain rate tensor used in the original formulation is replaced with the dilatation, which appears to be more appropriate in the vortical turbulent flow regions (Mani et al., 2008). The original form of the model is found to have an impact on dilatational motions away form the shock wave, which is eliminated by a proposed localization of the bulk viscosity. Finally, to allow for grid adaptation around shock waves, an explicit/implicit time advancement scheme has been developed that adaptively identifies the stiff regions. The full method has been verified with several test cases, including 2D shock-vorticity entropy interaction, homogenous isotropic turbulence, and turbulent flow over a cylinder.

Prediction of the rate of the rise of an air bubble in nanofluids in a vertical tube.

PubMed

Cho, Heon Ki; Nikolov, Alex D; Wasan, Darsh T

2018-04-19

Our recent experiments have demonstrated that when a bubble rises through a nanofluid (a liquid containing dispersed nanoparticles) in a vertical tube, a nanofluidic film with several particle layers is formed between the gas bubble and the glass tube wall, which significantly changes the bubble velocity due to the nanoparticle layering phenomenon in the film. We calculated the structural nanofilm viscosity as a function of the number of particle layers confined in it and found that the film viscosity increases rather steeply when the film contains only one or two particle layers. The nanofilm viscosity was found to be several times higher than the bulk viscosity of the fluid. Consequently, the Bretherton equation cannot accurately predict the rate of the rise of a slow-moving long bubble in a vertical tube in a nanofluid because it is valid only for very thick films and uses the bulk viscosity of the fluid. However, in this brief note, we demonstrate that the Bretherton equation can indeed be used for predicting the rate of the rise of a long single bubble through a vertical tube filled with a nanofluid by simply replacing the bulk viscosity with the proper structural nanofilm viscosity of the fluid. Copyright © 2018. Published by Elsevier Inc.

Shock-wave structure for a polyatomic gas with large bulk viscosity

NASA Astrophysics Data System (ADS)

Kosuge, Shingo; Aoki, Kazuo

2018-02-01

The structure of a standing plane shock wave in a polyatomic gas is investigated on the basis of kinetic theory, with special interest in gases with large bulk viscosities, such as CO2 gas. The ellipsoidal statistical model for a polyatomic gas is employed. First, the shock structure is computed numerically for various upstream Mach numbers and for various (large) values of the ratio of the bulk viscosity to the shear viscosity, and different types of profiles, such as the double-layer structure consisting of a thin upstream layer with a steep change and a much thicker downstream layer with a mild change, are obtained. Then, an asymptotic analysis for large values of the ratio is carried out, and an analytical solution that describes the different types of profiles obtained by the numerical analysis, such as the double-layer structure, correctly is obtained.

Longitudinal and bulk viscosities of Lennard-Jones fluids

NASA Astrophysics Data System (ADS)

Tankeshwar, K.; Pathak, K. N.; Ranganathan, S.

1996-12-01

Expressions for the longitudinal and bulk viscosities have been derived using Green Kubo formulae involving the time integral of the longitudinal and bulk stress autocorrelation functions. The time evolution of stress autocorrelation functions are determined using the Mori formalism and a memory function which is obtained from the Mori equation of motion. The memory function is of hyperbolic secant form and involves two parameters which are related to the microscopic sum rules of the respective autocorrelation function. We have derived expressions for the zeroth-, second-and fourth- order sum rules of the longitudinal and bulk stress autocorrelation functions. These involve static correlation functions up to four particles. The final expressions for these have been put in a form suitable for numerical calculations using low- order decoupling approximations. The numerical results have been obtained for the sum rules of longitudinal and bulk stress autocorrelation functions. These have been used to calculate the longitudinal and bulk viscosities and time evolution of the longitudinal stress autocorrelation function of the Lennard-Jones fluids over wide ranges of densities and temperatures. We have compared our results with the available computer simulation data and found reasonable agreement.

Nonlinear viscosity in brane-world cosmology with a Gauss–Bonnet term

NASA Astrophysics Data System (ADS)

Debnath, P. S.; Beesham, A.; Paul, B. C.

2018-06-01

Cosmological solutions are obtained with nonlinear bulk viscous cosmological fluid in the Randall–Sundrum type II (RS) brane-world model with or without Gauss–Bonnet (GB) terms. To describe such a viscous fluid, we consider the nonlinear transport equation which may be used far from equilibrium during inflation or reheating. Cosmological models are explored for both (i) power law and (ii) exponential evolution of the early universe in the presence of an imperfect fluid described by the non-linear Israel and Stewart theory (nIS). We obtain analytic solutions and the complex field equations are also analyzed numerically to study the evolution of the universe. The stability analysis of the equilibrium points of the dynamical system associated with the evolution of the nonlinear bulk viscous fluid in the RS Brane in the presence (or absence) of a GB term are also studied.

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bastero-Gil, Mar; Cerezo, Rafael; Berera, Arjun

2012-11-01

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causalmore » theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done; the methodology developed in this paper could be extended to apply to these other problems.« less

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2012 CFR

2012-10-01

... materials that are transported as bulk liquids by water in § 153.40. High viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is...

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2011 CFR

2011-10-01

... materials that are transported as bulk liquids by water in § 153.40. High viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is...

Shear and bulk viscosity of high-temperature gluon plasma

NASA Astrophysics Data System (ADS)

Zhang, Le; Hou, De-Fu

2018-05-01

We calculate the shear viscosity (η) and bulk viscosity (ζ) to entropy density (s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic {gg}≤ftrightarrow {gg} forward scattering and the inelastic soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} processes. Due to the suppressed contribution to η and ζ in the {gg}≤ftrightarrow {gg} forward scattering and the effective g≤ftrightarrow {gg} gluon splitting, Arnold, Moore and Yaffe (AMY) and Arnold, Dogan and Moore (ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} process with an analytic method. We find that the contribution of the collision term from the {gg}≤ftrightarrow {ggg} soft gluon bremsstrahlung process is just a small perturbation to the {gg}≤ftrightarrow {gg} scattering process and that the correction is at ∼5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula \\zeta \\propto \\tfrac{{α }s2{T}3}{ln}{α }s-1} in high-temperature gluon plasma. Supported by Ministry of Science and Technology of China (MSTC) under the “973” Project (2015CB856904(4)) and National Natural Science Foundation of China (11735007, 11521064)

Dynamics of viscous cosmologies in the full Israel-Stewart formalism

NASA Astrophysics Data System (ADS)

Lepe, Samuel; Otalora, Giovanni; Saavedra, Joel

2017-07-01

A detailed dynamical analysis for a bulk viscosity model in the full Israel-Stewart formalism for a spatially flat Friedmann-Robertson-Walker universe is performed. In our study we have considered the total cosmic fluid constituted by radiation, dark matter, and dark energy. The dark matter fluid is treated as an imperfect fluid which has a bulk viscosity that depends on its energy density in the usual form ξ (ρm)=ξ0ρm1 /2, whereas the other components are assumed to behave as perfect fluids with constant equation of state parameter. We show that the thermal history of the Universe is reproduced provided that the viscous coefficient satisfies the condition ξ0≪1 , either for a zero or a suitable nonzero coupling between dark energy and viscous dark matter. In this case, the final attractor is a dark-energy-dominated, accelerating universe, with an effective equation of state parameter in the quintessence-like, cosmological constant-like, or phantom-like regime, in agreement with observations. As our main result, we show that in order to obtain a viable cosmological evolution and at the same time alleviating the cosmological coincidence problem via the mechanism of scaling solution, an explicit interaction between dark energy and viscous dark matter seems inevitable. This result is consistent with the well-known fact that models where dark matter and dark energy interact with each other have been proposed to solve the coincidence problem. Furthermore, by insisting on above, we show that in the present context a phantom nature of this interacting dark energy fluid is also favored.

The Coefficient of First Viscosity Via Three-Phonon Processes in Bulk Liquid Helium

DTIC Science & Technology

1988-06-01

of Chemistry and Physics State University of New York at Buffalo Buffalo, New York 14260 June 1988 Reproduction in whole or in part is permitted for...NUBUFFALO/DC/88/TR-71 6.. NAME OF PERFORMING ORGANIZATION I 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION Depts. Chemistry & Physics j (If... Chemistry Program Buffalo, New York 14260 800 N. Quincy Street _ __ _Arlington, Virginia 22217 Ba. NAME OF FUND:NG/SPONSORING 8b. OFFICE SYMBOL 9

Stability of the accelerated expansion in nonlinear electrodynamics

NASA Astrophysics Data System (ADS)

Sharif, M.; Mumtaz, Saadia

2017-02-01

This paper is devoted to the phase space analysis of an isotropic and homogeneous model of the universe by taking a noninteracting mixture of the electromagnetic and viscous radiating fluids whose viscous pressure satisfies a nonlinear version of the Israel-Stewart transport equation. We establish an autonomous system of equations by introducing normalized dimensionless variables. In order to analyze the stability of the system, we find corresponding critical points for different values of the parameters. We also evaluate the power-law scale factor whose behavior indicates different phases of the universe in this model. It is concluded that the bulk viscosity as well as electromagnetic field enhances the stability of the accelerated expansion of the isotropic and homogeneous model of the universe.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Kyle J.; Glynos, Emmanouil; Maroulas, Serafeim-Dionysios

Incorporating nanoparticles (NPs) within a polymer host to create polymer nanocomposites (PNCs) while having the effect of increasing the functionality (e.g., sensing, energy conversion) of these materials influences other properties. One challenge is to understand the effects of nanoparticles on the viscosity of nanoscale thick polymer films. A new mechanism that contributes to an enhancement of the viscosity of nanoscale thick polymer/nanoparticle films is identified. We show that while the viscosities of neat homopolymer poly(2-vinylpyridine) (P2VP) films as thin as 50 nm remained the same as the bulk, polymer/nanoparticle films containing P2VP brush-coated gold NPs, spaced 50 nm apart, exhibitedmore » unprecedented increases in viscosities of over an order of magnitude. For thicker films or more widely separated NPs, the chain dynamics and viscosities were comparable to the bulk values. These results - NP proximities and suppression of their dynamics - suggest a new mechanism by which the viscosities of polymeric liquids could be controlled for nanoscale applications.« less

Kubo formulas for the shear and bulk viscosity relaxation times and the scalar field theory shear τπ calculation

NASA Astrophysics Data System (ADS)

Czajka, Alina; Jeon, Sangyong

2017-06-01

In this paper we provide a quantum field theoretical study on the shear and bulk relaxation times. First, we find Kubo formulas for the shear and the bulk relaxation times, respectively. They are found by examining response functions of the stress-energy tensor. We use general properties of correlation functions and the gravitational Ward identity to parametrize analytical structures of the Green functions describing both sound and diffusion mode. We find that the hydrodynamic limits of the real parts of the respective energy-momentum tensor correlation functions provide us with the method of computing both the shear and bulk viscosity relaxation times. Next, we calculate the shear viscosity relaxation time using the diagrammatic approach in the Keldysh basis for the massless λ ϕ4 theory. We derive a respective integral equation which enables us to compute η τπ and then we extract the shear relaxation time. The relaxation time is shown to be inversely related to the thermal width as it should be.

Bulk viscosity of the Lennard-Jones fluid for a wide range of states computed by equilibrium molecular dynamics

NASA Astrophysics Data System (ADS)

Hoheisel, C.; Vogelsang, R.; Schoen, M.

1987-12-01

Accurate data for the bulk viscosity ηv have been obtained by molecular dynamics calculations. Many thermodynamic states of the Lennard-Jones fluid were considered. The Green-Kubo integrand of ηv is analyzed in terms of partial correlation functions constituting the total one. These partial functions behave rather differently from those found for the shear viscosity or the thermal conductivity. Generally the total autocorrelation function of ηv shows a steeper initial decay and a more pronounced long time form than those of the shear viscosity or the thermal conductivity. For states near transition to solid phases, like the pseudotriple point of argon, the Green-Kubo integrand of ηv has a significantly longer ranged time behavior than that of the shear viscosity. Hence, for the latter states, a systematic error is expected for ηv using equilibrium molecular dynamics for its computation.

Transient Cooperative Processes in Dewetting Polymer Melts.

PubMed

Chandran, Sivasurender; Reiter, Günter

2016-02-26

We compare the high velocity dewetting behavior, at elevated temperatures, of atactic polystyrene (aPS) and isotactic polystyrene (iPS) films, with the zero shear bulk viscosity (η_{bulk}) of aPS being approximately ten times larger than iPS. As expected, for aPS the apparent viscosity of the films (η_{f}) derived from high-shear dewetting is less than η_{bulk}, displaying a shear thinning behavior. Surprisingly, for iPS films, η_{f} is always larger than η_{bulk}, even at about 50 °C above the melting point, with η_{f}/η_{bulk} following an Arrhenius behavior. The corresponding activation energy of ∼160±10  kJ/mol for iPS films suggests a cooperative motion of segments which are aligned and agglomerated by fast dewetting.

Do Clustering Monoclonal Antibody Solutions Really Have a Concentration Dependence of Viscosity?

PubMed Central

Pathak, Jai A.; Sologuren, Rumi R.; Narwal, Rojaramani

2013-01-01

Protein solution rheology data in the biophysics literature have incompletely identified factors that govern hydrodynamics. Whereas spontaneous protein adsorption at the air/water (A/W) interface increases the apparent viscosity of surfactant-free globular protein solutions, it is demonstrated here that irreversible clusters also increase system viscosity in the zero shear limit. Solution rheology measured with double gap geometry in a stress-controlled rheometer on a surfactant-free Immunoglobulin solution demonstrated that both irreversible clusters and the A/W interface increased the apparent low shear rate viscosity. Interfacial shear rheology data showed that the A/W interface yields, i.e., shows solid-like behavior. The A/W interface contribution was smaller, yet nonnegligible, in double gap compared to cone-plate geometry. Apparent nonmonotonic composition dependence of viscosity at low shear rates due to irreversible (nonequilibrium) clusters was resolved by filtration to recover a monotonically increasing viscosity-concentration curve, as expected. Although smaller equilibrium clusters also existed, their size and effective volume fraction were unaffected by filtration, rendering their contribution to viscosity invariant. Surfactant-free antibody systems containing clusters have complex hydrodynamic response, reflecting distinct bulk and interface-adsorbed protein as well as irreversible cluster contributions. Literature models for solution viscosity lack the appropriate physics to describe the bulk shear viscosity of unstable surfactant-free antibody solutions. PMID:23442970

Models for viscosity and shear localization in bubble-rich magmas

NASA Astrophysics Data System (ADS)

Vona, Alessandro; Ryan, Amy G.; Russell, James K.; Romano, Claudia

2016-09-01

Bubble content influences magma rheology and, thus, styles of volcanic eruption. Increasing magma vesicularity affects the bulk viscosity of the bubble-melt suspension and has the potential to promote non-Newtonian behavior in the form of shear localization or brittle failure. Here, we present a series of high temperature uniaxial deformation experiments designed to investigate the effect of bubbles on the magma bulk viscosity. The starting materials are cores of natural rhyolitic obsidian synthesized to have variable vesicularity (ϕ = 0- 66%). The foamed cores were deformed isothermally (T = 750 °C) at atmospheric conditions using a high-temperature uniaxial press under constant displacement rates (strain rates between 0.5- 1 ×10-4 s-1) and to total strains of 10-40%. The viscosity of the bubble-free melt (η0) was measured by micropenetration and parallel plate methods to establish a baseline for experiments on the vesicle rich cores. At the experimental conditions, rising vesicle content produces a marked decrease in bulk viscosity that is best described by a two-parameter empirical equation: log10 ⁡ηBulk =log10 ⁡η0 - 1.47[ ϕ / (1 - ϕ) ] 0.48. Our parameterization of the bubble-melt rheology is combined with Maxwell relaxation theory to map the potential onset of non-Newtonian behavior (shear localization) in magmas as a function of melt viscosity, vesicularity, and strain rate. For low degrees of strain (i.e. as in our study), the rheological properties of vesicular magmas under different flow types (pure vs. simple shear) are indistinguishable. For high strain or strain rates where simple and pure shear viscosity values may diverge, our model represents a maximum boundary condition. Vesicular magmas can behave as non-Newtonian fluids at lower strain rates than unvesiculated melts, thereby, promoting shear localization and (explosive or non-explosive) magma fragmentation. The extent of shear localization in magma influences outgassing efficiency, thereby, affecting magma ascent and the potential for explosivity.

Challenges in Determining Intrinsic Viscosity Under Low Ionic Strength Solution Conditions.

PubMed

Pindrus, Mariya A; Shire, Steven J; Yadav, Sandeep; Kalonia, Devendra S

2017-04-01

To determine the intrinsic viscosity of several monoclonal antibodies (mAbs) under varying pH and ionic strength solution conditions. An online viscosity detector attached to HPLC (Viscotek®) was used to determine the intrinsic viscosity of mAbs. The Ross and Minton equation was used for viscosity prediction at high protein concentrations. Bulk viscosity was determined by a Cambridge viscometer. At 15 mM ionic strength, intrinsic viscosity of the mAbs determined by the single-point approach varied from 5.6 to 6.4 mL/g with changes in pH. High ionic strength did not significantly alter intrinsic viscosity, while a significant increase (up to 24.0 mL/g) was observed near zero mM. No difference in bulk viscosity of mAb3 was observed around pH 6 as a function of ionic strength. Data analysis revealed that near zero mM ionic strength limitations of the single-point technique result in erroneously high intrinsic viscosity. Intrinsic viscosity is a valuable tool that can be used to model baseline viscosity at higher protein concentrations. However, it is not predictive of solution non-ideality at higher protein concentrations. Furthermore, breakdown of numerous assumptions limits the applicability of experimental techniques near zero mM ionic strength conditions. For molecules and conditions studied, the single-point approach produced reliable intrinsic viscosity results at 15 mM. However, this approach must be used with caution near zero mM ionic strength. Data analysis can be used to reveal whether determined intrinsic viscosity is reliable or erroneously high.

Viscosity of a multichannel one-dimensional Fermi gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeGottardi, Wade; Matveev, K. A.

Many one-dimensional systems of experimental interest possess multiple bands arising from shallow confining potentials. In this paper, we study a gas of weakly interacting fermions and show that the bulk viscosity is dramatically altered by the occupation of more than one band. The reasons for this are twofold: a multichannel system is more easily displaced from equilibrium and the associated relaxation processes lead to more rapid equilibration than in the single channel case. We estimate the bulk viscosity in terms of the underlying microscopic interactions. The experimental relevance of this physics is discussed in the context of quantum wires andmore » trapped cold atomic gases.« less

Shear-enhanced compaction in viscoplastic rocks

NASA Astrophysics Data System (ADS)

Yarushina, V. M.; Podladchikov, Y. Y.

2012-04-01

The phenomenon of mutual influence of compaction and shear deformation was repeatedly reported in the literature over the past years. Dilatancy and shear-enhanced compaction of porous rocks were experimentally observed during both rate-independent and rate-dependent inelastic deformation. Plastic pore collapse was preceding the onset of dilatancy and shear-enhanced compaction. Effective bulk viscosity is commonly used to describe compaction driven fluid flow in porous rocks. Experimental data suggest that bulk viscosity of a fluid saturated rock might be a function of both the effective pressure and the shear stress. Dilatancy and shear-enhanced compaction can alter the transport properties of rocks through their influence on permeability and compaction length scale. Recent investigations show that shear stresses in deep mantle rocks can be responsible for spontaneous development of localized melt-rich bands and segregation of small amounts of melt from the solid rock matrix through shear channeling instability. Usually it is assumed that effective viscosity is a function of porosity only. Thus coupling between compaction and shear deformation is ignored. Spherical model which considers a hollow sphere subjected to homogeneous tractions on the outer boundary as a representative elementary volume succeeded in predicting the volumetric compaction behavior of porous rocks and metals to a hydrostatic pressure in a wide range of porosities. Following the success of this simple model we propose a cylindrical model of void compaction and decompaction due to the non-hydrostatic load. The infinite viscoplastic layer with a cylindrical hole is considered as a representative volume element. The remote boundary of the volume is subjected to a homogeneous non-hydrostatic load such that plane strain conditions are fulfilled through the volume. At some critical values of remote stresses plastic zone develops around the hole. The dependence of the effective bulk viscosity on the properties of individual components as well as on the stress state is examined. We show that bulk viscosity is a function of porosity, effective pressure and shear stress. Decreasing porosity tends to increase bulk viscosity whereas increasing shear stress and increasing effective pressure reduce it.

Viscous flow of the Pd43Ni10Cu27P20 bulk metallic glass-forming liquid

NASA Astrophysics Data System (ADS)

Fan, G. J.; Fecht, H.-J.; Lavernia, E. J.

2004-01-01

The equilibrium viscosity of the Pd43Ni10Cu27P20 bulk metallic glass-forming liquid was measured over a wide temperature range from the equilibrium supercooled liquid state to the glass transition region using parallel-plate rheometry and three-point beam bending. Based on the measured viscosity data, the fragility of this liquid was quantitatively determined. The Pd43Ni10Cu27P20 alloy, despite exhibiting the best glass-forming ability reported thus far, is relatively fragile compared with other bulk glass-forming liquids, such as Vit 1 and Vit 4.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khvorostukhin, A. S.; Joint Institute for Nuclear Research, 141980 Dubna; Institute of Applied Physics, Moldova Academy of Science, MD-2028 Kishineu

Shear {eta} and bulk {zeta} viscosities are calculated in a quasiparticle model within a relaxation-time approximation for pure gluon matter. Below T{sub c}, the confined sector is described within a quasiparticle glueball model. The constructed equation of state reproduces the first-order phase transition for the glue matter. It is shown that with this equation of state, it is possible to describe the temperature dependence of the shear viscosity to entropy ratio {eta}/s and the bulk viscosity to entropy ratio {zeta}/s in reasonable agreement with available lattice data, but absolute values of the {zeta}/s ratio underestimate the upper limits of thismore » ratio in the lattice measurements typically by an order of magnitude.« less

Hyperscaling-violating Lifshitz hydrodynamics from black-holes: part II

NASA Astrophysics Data System (ADS)

Kiritsis, Elias; Matsuo, Yoshinori

2017-03-01

The derivation of Lifshitz-invariant hydrodynamics from holography, presented in [1] is generalized to arbitrary hyperscaling violating Lifshitz scaling theories with an unbroken U(1) symmetry. The hydrodynamics emerging is non-relativistic with scalar "forcing". By a redefinition of the pressure it becomes standard non-relativistic hydrodynamics in the presence of specific chemical potential for the mass current. The hydrodynamics is compatible with the scaling theory of Lifshitz invariance with hyperscaling violation. The bulk viscosity vanishes while the shear viscosity to entropy ratio is the same as in the relativistic case. We also consider the dimensional reduction ansatz for the hydrodynamics and clarify the difference with previous results suggesting a non-vanishing bulk viscosity.

Production of photons in relativistic heavy-ion collisions

DOE PAGES

Jean -Francois Paquet; Denicol, Gabriel S.; Shen, Chun; ...

2016-04-18

In this work it is shown that the use of a hydrodynamical model of heavy-ion collisions which incorporates recent developments, together with updated photon emission rates, greatly improves agreement with both ALICE and PHENIX measurements of direct photons, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy. The event-by-event hydrodynamical model uses the impact parameter dependent Glasma model (IP-Glasma) initial states and includes, for the first time, both shear and bulk viscosities, along with second-order couplings between the two viscosities. Furthermore, the effect of both shear and bulk viscosities on the photon rates ismore » studied, and those transport coefficients are shown to have measurable consequences on the photon momentum anisotropy.« less

The Drainage of Thin, Vertical, Model Polyurethane Liquid Films

NASA Astrophysics Data System (ADS)

Snow, Steven; Pernisz, Udo; Braun, Richard; Naire, Shailesh

1999-11-01

We have successfully measured the drainage rate of thin, vertically-aligned, liquid films prepared from model polyurethane foam formulations. The pattern of interference fringes in these films was consistent with a wedge-shaped film profile. The time evolution of this wedge shape (the ``collapsing wedge") obeyed a power law relationship between fringe density s and time t of s = k t^m. Experimentally, m ranged from -0.47 to -0.92. The lower bound for m represented a case where the surface viscosity of the film was very high (a ``rigid" surface). Theoretical modeling of this case yielded m = -0.5, in excellent agreement with experiment. Instantaneous film drainage rate (dV/dt) could be extracted from the ``Collapsing Wedge" model. As expected, dV/dt scaled inversely with bulk viscosity. As surfactant concentration was varied at constant bulk viscosity, dV/dt passed through a maximum value, consistent with a model where the rigidity of the surface was a function of both the intensity of surface tension gradients and the surface viscosity of the film. The influence of surface viscosity on dV/dt was also modeled theoretically.

Local equilibrium solutions in simple anisotropic cosmological models, as described by relativistic fluid dynamics

NASA Astrophysics Data System (ADS)

Shogin, Dmitry; Amund Amundsen, Per

2016-10-01

We test the physical relevance of the full and the truncated versions of the Israel-Stewart (IS) theory of irreversible thermodynamics in a cosmological setting. Using a dynamical systems method, we determine the asymptotic future of plane symmetric Bianchi type I spacetimes with a viscous mathematical fluid, keeping track of the magnitude of the relative dissipative fluxes, which determines the applicability of the IS theory. We consider the situations where the dissipative mechanisms of shear and bulk viscosity are involved separately and simultaneously. It is demonstrated that the only case in the given model when the fluid asymptotically approaches local thermal equilibrium, and the underlying assumptions of the IS theory are therefore not violated, is that of a dissipative fluid with vanishing bulk viscosity. The truncated IS equations for shear viscosity are found to produce solutions which manifest pathological dynamical features and, in addition, to be strongly sensitive to the choice of initial conditions. Since these features are observed already in the case of an oversimplified mathematical fluid model, we have no reason to assume that the truncation of the IS transport equations will produce relevant results for physically more realistic fluids. The possible role of bulk and shear viscosity in cosmological evolution is also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Kyle J.; Glynos, Emmanouil; Maroulas, Serafeim-Dionysios

Incorporating nanoparticles (NPs) within a polymer host to create polymer nanocomposites (PNCs) while having the effect of increasing the functionality (e.g.: sensing, energy conversion) of these materials, introduces additional complications with regard to the processing-morphology-function behavior. A primary challenge is to understand and control the viscosity of a PNC with decreasing film thickness confinement for nanoscale applications. Using a combination of X-ray photon correlation spectroscopy (XPCS) and X-ray standing wave based resonance enhanced XPCS to study the dynamics of neat poly-2-vinyl pyridine (P2VP) chains and the nanoparticle dynamics, respectively, we identified a new mechanism that dictates the viscosity of PNCmore » films in the nanoscale regime. We show that while the viscosities of neat P2VP films as thin as 50 nm remained the same as the bulk, PNC films containing P2VP brush-coated gold NPs, spaced 50 nm apart, exhibited unprecedented increases in viscosities of over an order of magnitude. For thicker films or more widely separated NPs, the chain dynamics and viscosities were equal to the bulk values. These results -NP proximities and suppression of their dynamics -suggest a new mechanism by which the viscosities of polymeric liquids could be controlled for 2D and 3D nanoscale applications.« less

Hierarchical viscosity of aqueous solution of tilapia scale collagen investigated via dielectric spectroscopy between 500 MHz and 2.5 THz

PubMed Central

Kawamata, H.; Kuwaki, S.; Mishina, T.; Ikoma, T.; Tanaka, J.; Nozaki, R.

2017-01-01

Aqueous solutions of biomolecules such as proteins are very important model systems for understanding the functions of biomolecules in actual life processes because interactions between biomolecules and the surrounding water molecules are considered to be important determinants of biomolecules’ functions. Globule proteins have been extensively studied via dielectric spectroscopy; the results indicate three relaxation processes originating from fluctuations in the protein molecule, the bound water and the bulk water. However, the characteristics of aqueous solutions of collagens have rarely been investigated. In this work, based on broadband dielectric measurements between 500 MHz and 2.5 THz, we demonstrate that the high viscosity of a collagen aqueous solution is due to the network structure being constructed of rod-like collagen molecules surrounding free water molecules and that the water molecules are not responsible for the viscosity. We determine that the macroscopic viscosity is related to the mean lifetime of the collagen-collagen interactions supporting the networks and that the local viscosity of the water surrounded by the networks is governed by the viscosity of free water as in the bulk. This hierarchical structure in the dynamics of the aqueous solution of biomolecules has been revealed for the first time. PMID:28345664

Damping of drop oscillations by surfactants and surface viscosity

NASA Technical Reports Server (NTRS)

Rush, Brian M.; Nadim, Ali

1999-01-01

An energy equation is derived for the general case of a viscous drop suspended in a viscous medium with surfactants contaminating the interface. It contains terms that clearly identify dissipation contributions from the viscous effects in the bulk fluids, surface shear and dilatational viscosity effects at the interface, and surfactant transport. An efficient boundary integral method is developed which incorporates the effects of a constant surface dilatational viscosity in simulations of an oscillating two-dimensional inviscid drop. Surface dilatational viscosity is shown to have a significant damping effect on the otherwise undamped inviscid oscillations.

Bulk viscosity of strongly interacting matter in the relaxation time approximation

DOE PAGES

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun; ...

2018-04-24

Here, we show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio ofmore » the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the β λ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ς/τ R for gases obeying Bose-Einstein statistics.« less

Bulk viscosity of strongly interacting matter in the relaxation time approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun

Here, we show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio ofmore » the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the β λ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ς/τ R for gases obeying Bose-Einstein statistics.« less

Bulk viscosity of strongly interacting matter in the relaxation time approximation

NASA Astrophysics Data System (ADS)

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun; Jeon, Sangyong; Gale, Charles

2018-04-01

We show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio of the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the βλ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ζ /τR for gases obeying Bose-Einstein statistics.

Decorrelation-based viscosity measurement using phase-sensitive optical coherence tomography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Blackburn, Brecken J.; Gu, Shi; Jenkins, Michael W.; Rollins, Andrew M.

2017-02-01

A robust method to measure viscosity of microquantities of biological samples, such as blood and mucus, could lead to a better understanding and diagnosis of diseases. Microsamples have presented persistent challenges to conventional rheology, which requires bulk quantities of a sample. Alternatively, fluid viscosity can be probed by monitoring microscale motion of particles. Here, we present a decorrelation-based method using M-mode phase-sensitive optical coherence tomography (OCT) to measure particle Brownian motion. This is similar to previous methods using laser speckle decorrelation but with sensitivity to nanometer-scale displacement. This allows for the measurement of decorrelation in less than 1 millisecond and significantly decreases sensitivity to bulk motion, thereby potentially enabling in vivo and in situ applications. From first principles, an analytical method is established using M-mode images obtained from a 47 kHz spectral-domain OCT system. A g(1) first-order autocorrelation is calculated from windows containing several pixels over a time frame of 200-1000 microseconds. Total imaging time is 500 milliseconds for averaging purposes. The autocorrelation coefficient over this short time frame decreases linearly and at a rate proportional to the diffusion constant of the particles, allowing viscosity to be calculated. In verification experiments using phantoms of microbeads in 200 µL glycerol-water mixtures, this method showed insensitivity to 2 mm/s lateral bulk motion and accurate viscosity measurements over a depth of 400 µm. In addition, the method measured a significant decrease of the apparent diffusion constant of soft tissue after formalin fixation, suggesting potential applications in mapping tissue stiffness.

The shear and bulk relaxation times from the general correlation functions

NASA Astrophysics Data System (ADS)

Czajka, Alina; Jeon, Sangyong

2017-11-01

In this paper we present two quantum field theoretical analyses on the shear and bulk relaxation times. First, we discuss how to find Kubo formulas for the shear and the bulk relaxation times. Next, we provide results on the shear viscosity relaxation time obtained within the diagrammatic approach for the massless λϕ4 theory.

Energy flow and energy dissipation in a free surface.

NASA Astrophysics Data System (ADS)

Goldburg, Walter; Cressman, John

2005-11-01

Turbulent flows on a free surface are strongly compressible [1] and do not conserve energy in the absence of viscosity as bulk fluids do. Despite violation of assumptions essential to Kolmogorov's theory of 1941 (K41) [2, 3], surface flows show strong agreement with Kolmogorov scaling, though intermittency is larger there. Steady state turbulence is generated in a tank of water, and the spatially averaged energy flux is measured from the four-fifth's law at each instant of time. Likewise, the energy dissipation rate as measured from velocity gradients is also a random variable in this experiment. The energy flux - dissipation rate cross-correlation is measured to be correlated in incompressible bulk flows, but strongly anti-correlated on the surface. We argue that the reason for this discrepancy between surface and bulk flows is due to compressible effects present on the surface. [1] J. R. Cressman, J. Davoudi, W. I. Goldburg, and J. Schumacher, New Journal of Physics, 6, 53, 2004. [2] U. Frisch. Turbulence: The legacy of A. N. Kolmogorov, Cambridge University Press, Cambridge, 1995. [3] A. N. Kolmogorov, Doklady Akad. Nauk SSSR, 32, 16, 1941.

Coupled kinetic equations for fermions and bosons in the relaxation-time approximation

NASA Astrophysics Data System (ADS)

Florkowski, Wojciech; Maksymiuk, Ewa; Ryblewski, Radoslaw

2018-02-01

Kinetic equations for fermions and bosons are solved numerically in the relaxation-time approximation for the case of one-dimensional boost-invariant geometry. Fermions are massive and carry baryon number, while bosons are massless. The conservation laws for the baryon number, energy, and momentum lead to two Landau matching conditions, which specify the coupling between the fermionic and bosonic sectors and determine the proper-time dependence of the effective temperature and baryon chemical potential of the system. The numerical results illustrate how a nonequilibrium mixture of fermions and bosons approaches hydrodynamic regime described by the Navier-Stokes equations with appropriate forms of the kinetic coefficients. The shear viscosity of a mixture is the sum of the shear viscosities of fermion and boson components, while the bulk viscosity is given by the formula known for a gas of fermions, however, with the thermodynamic variables characterising the mixture. Thus, we find that massless bosons contribute in a nontrivial way to the bulk viscosity of a mixture, provided fermions are massive. We further observe the hydrodynamization effect, which takes place earlier in the shear sector than in the bulk one. The numerical studies of the ratio of the longitudinal and transverse pressures show, to a good approximation, that it depends on the ratio of the relaxation and proper times only. This behavior is connected with the existence of an attractor solution for conformal systems.

Kaluza-Klein Bulk Viscous Fluid Cosmological Models and the Validity of the Second Law of Thermodynamics in f(R, T) Gravity

NASA Astrophysics Data System (ADS)

Samanta, Gauranga Charan; Myrzakulov, Ratbay; Shah, Parth

2017-04-01

The authors considered the bulk viscous fluid in f(R, T) gravity within the framework of Kaluza-Klein space time. The bulk viscous coefficient (ξ) expressed as ξ = {ξ_0} + {ξ_1}{{\\dot a} \\over a} + {ξ_2}{{\\ddot a} \\over {\\dot a}}, where ξ0, ξ1, and ξ2 are positive constants. We take p=(γ-1)ρ, where 0≤γ≤2 as an equation of state for perfect fluid. The exact solutions to the corresponding field equations are given by assuming a particular model of the form of f(R, T)=R+2f(T), where f(T)=λT, λ is constant. We studied the cosmological model in two stages, in first stage: we studied the model with no viscosity, and in second stage: we studied the model involve with viscosity. The cosmological model involve with viscosity is studied by five possible scenarios for bulk viscous fluid coefficient (ξ). The total bulk viscous coefficient seems to be negative, when the bulk viscous coefficient is proportional to {ξ _2}{{\\ddot a} \\over {\\dot a}}, hence, the second law of thermodynamics is not valid; however, it is valid with the generalised second law of thermodynamics. The total bulk viscous coefficient seems to be positive, when the bulk viscous coefficient is proportional to ξ = {ξ _1}{{\\dot a} \\over a} + {ξ _2}{{\\ddot a} \\over {\\dot a}} and ξ = {ξ _0} + {ξ _1}{{\\dot a} \\over a} + {ξ _2}{{\\ddot a} \\over {\\dot a}}, so the second law of thermodynamics and the generalised second law of thermodynamics is satisfied throughout the evolution. We calculate statefinder parameters of the model and observed that it is different from the ∧CDM model. Finally, some physical and geometrical properties of the models are discussed.

Monitoring corneal crosslinking using phase-decorrelation OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Blackburn, Brecken J.; Gu, Shi; Jenkins, Michael W.; Rollins, Andrew M.

2017-02-01

Viscosity is often a critical characteristic of biological fluids such as blood and mucus. However, traditional rheology is often inadequate when only small quantities of sample are available. A robust method to measure viscosity of microquantities of biological samples could lead to a better understanding and diagnosis of diseases. Here, we present a method to measure viscosity by observing particle Brownian motion within a sample. M-mode optical coherence tomography (OCT) imaging, obtained with a phase-sensitive 47 kHz spectral domain system, yields a viscosity measurement from multiple 200-1000 microsecond frames. This very short period of continuous acquisition, as compared to laser speckle decorrelation, decreases sensitivity to bulk motion, thereby potentially enabling in vivo and in situ applications. The theory linking g(1) first-order image autocorrelation to viscosity is derived from first principles of Brownian motion and the Stokes-Einstein relation. To improve precision, multiple windows acquired over 500 milliseconds are analyzed and the resulting linear fit parameters are averaged. Verification experiments were performed with 200 µL samples of glycerol and water with polystyrene microbeads. Lateral bulk motion up to 2 mm/s was tolerated and accurate viscosity measurements were obtained to a depth of 400 µm or more. Additionally, the method measured a significant decrease of the apparent diffusion constant of soft tissue after formalin fixation, suggesting potential for mapping tissue stiffness over a volume.

Viscous Dissipation in One-Dimensional Quantum Liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matveev, K. A.; Pustilnik, M.

We develop a theory of viscous dissipation in one-dimensional single-component quantum liquids at low temperatures. Such liquids are characterized by a single viscosity coefficient, the bulk viscosity. We show that for a generic interaction between the constituent particles this viscosity diverges in the zerotemperature limit. In the special case of integrable models, the viscosity is infinite at any temperature, which can be interpreted as a breakdown of the hydrodynamic description. In conclusion, our consideration is applicable to all single-component Galilean- invariant one-dimensional quantum liquids, regardless of the statistics of the constituent particles and the interaction strength.

Viscous Dissipation in One-Dimensional Quantum Liquids

DOE PAGES

Matveev, K. A.; Pustilnik, M.

2017-07-20

We develop a theory of viscous dissipation in one-dimensional single-component quantum liquids at low temperatures. Such liquids are characterized by a single viscosity coefficient, the bulk viscosity. We show that for a generic interaction between the constituent particles this viscosity diverges in the zerotemperature limit. In the special case of integrable models, the viscosity is infinite at any temperature, which can be interpreted as a breakdown of the hydrodynamic description. In conclusion, our consideration is applicable to all single-component Galilean- invariant one-dimensional quantum liquids, regardless of the statistics of the constituent particles and the interaction strength.

Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin

2015-05-18

The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glassmore » network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.« less

Rayleigh-Brillouin scattering studies of the rotation-translation coupling and bulk viscosity relaxation of liquids composed of anisotropic molecules: p-Anisaldehyde and aniline

NASA Astrophysics Data System (ADS)

O'Steen, B. L.; Wang, C. H.; Fytas, G.

1984-04-01

The coupling of reorientational motion to longitudinal acoustic modes was investigated by studying the Rayleigh-Brillouin spectra of aniline and p-anisaldehyde over a wide range of scattering angles. Aniline and p-anisaldehyde were chosen for investigation since their depolarized spectra at the temperature of interest show a pronounced coupling between orientation and shear modes. The experimental results for attenuation and velocity of the longitudinal waves show that there is indeed relaxation in the shear viscosity. However, shear relaxation due to the coupling of the longitudinal acoustic mode to reorientation plays only a minor role in causing the dispersion of the hypersonic longitudinal waves. To account for the large dispersion, it is essential to consider the mechanism associated with the relaxation of the bulk viscosity through the T-V energy transfer.

Coarse-Grain Molecular Dynamics Simulations To Investigate the Bulk Viscosity and Critical Micelle Concentration of the Ionic Surfactant Sodium Dodecyl Sulfate (SDS) in Aqueous Solution.

PubMed

Ruiz-Morales, Yosadara; Romero-Martínez, Ascención

2018-04-12

The first critical micelle concentration (CMC) of the ionic surfactant sodium dodecyl sulfate (SDS) in diluted aqueous solution has been determined at room temperature from the investigation of the bulk viscosity, at several concentrations of SDS, by means of coarse-grain molecular dynamics simulations. The coarse-grained model molecules at the mesoscale level are adopted. The bulk viscosity of SDS was calculated at several millimolar concentrations of SDS in water using the MARTINI force field by means of NVT shear Mesocite molecular dynamics. The definition of each bead in the MARTINI force field is established, as well as their radius, volume, and mass. The effect of the size of the simulation box on the obtained CMC has been investigated, as well as the effect of the number of SDS molecules, in the simulations, on the formation of aggregates. The CMC, which was obtained from a graph of the calculated viscosities versus concentration, is in good agreement with the reported experimental data and does not depend on the size of the box used in the simulation. The formation of a spherical micelle-like aggregate is observed, where the dodecyl sulfate tails point inward and the heads point outward the aggregation micelle, in accordance with experimental observations. The advantage of using coarse-grain molecular dynamics is the possibility of treating explicitly charged beads, applying a shear flow for viscosity calculation, and processing much larger spatial and temporal scales than atomistic molecular dynamics can. Furthermore, the CMC of SDS obtained with the coarse-grained model is in much better agreement with the experimental value than the value obtained with atomistic simulations.

Effects of bulk viscosity and hadronic rescattering in heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

NASA Astrophysics Data System (ADS)

Ryu, Sangwook; Paquet, Jean-François; Shen, Chun; Denicol, Gabriel; Schenke, Björn; Jeon, Sangyong; Gale, Charles

2018-03-01

We describe ultrarelativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider with a hybrid model using the IP-Glasma model for the earliest stage and viscous hydrodynamics and microscopic transport for the later stages of the collision. We demonstrate that within this framework the bulk viscosity of the plasma plays an important role in describing the experimentally observed radial flow and azimuthal anisotropy simultaneously. We further investigate the dependence of observables on the temperature below which we employ the microscopic transport description.

An estimate of the bulk viscosity of the hadronic medium

NASA Astrophysics Data System (ADS)

Sarwar, Golam; Chatterjee, Sandeep; Alam, Jane

2017-05-01

The bulk viscosity (ζ) of the hadronic medium has been estimated within the ambit of the Hadron Resonance Gas (HRG) model including the Hagedorn density of states. The HRG thermodynamics within a grand canonical ensemble provides the mean hadron number as well as its fluctuation. The fluctuation in the chemical composition of the hadronic medium in the grand canonical ensemble can result in non-zero divergence of the hadronic fluid flow velocity, allowing us to estimate the ζ of the hadronic matter up to a relaxation time. We study the influence of the hadronic spectrum on ζ and find its correlation with the conformal symmetry breaking measure, ε -3P. We estimate ζ along the contours with constant, S/{N}B (total entropy/net baryon number) in the T-μ plane (temperature-baryonic chemical potential) for S/{N}B=30,45 and 300. We also assess the value of ζ on the chemical freeze-out curve for various centers of mass energy (\\sqrt{{s}{NN}}) and find that the bulk viscosity to entropy density ratio, \\zeta /s is larger in the energy range of the beam energy scan program of RHIC, low energy SPS run, AGS, NICA and FAIR, than LHC energies.

Causal dissipation and shock profiles in the relativistic fluid dynamics of pure radiation.

PubMed

Freistühler, Heinrich; Temple, Blake

2014-06-08

CURRENT THEORIES OF DISSIPATION IN THE RELATIVISTIC REGIME SUFFER FROM ONE OF TWO DEFICITS: either their dissipation is not causal or no profiles for strong shock waves exist. This paper proposes a relativistic Navier-Stokes-Fourier-type viscosity and heat conduction tensor such that the resulting second-order system of partial differential equations for the fluid dynamics of pure radiation is symmetric hyperbolic. This system has causal dissipation as well as the property that all shock waves of arbitrary strength have smooth profiles. Entropy production is positive both on gradients near those of solutions to the dissipation-free equations and on gradients of shock profiles. This shows that the new dissipation stress tensor complies to leading order with the principles of thermodynamics. Whether higher order modifications of the ansatz are required to obtain full compatibility with the second law far from the zero-dissipation equilibrium is left to further investigations. The system has exactly three a priori free parameters χ , η , ζ , corresponding physically to heat conductivity, shear viscosity and bulk viscosity. If the bulk viscosity is zero (as is stated in the literature) and the total stress-energy tensor is trace free, the entire viscosity and heat conduction tensor is determined to within a constant factor.

Causal dissipation and shock profiles in the relativistic fluid dynamics of pure radiation

PubMed Central

Freistühler, Heinrich; Temple, Blake

2014-01-01

Current theories of dissipation in the relativistic regime suffer from one of two deficits: either their dissipation is not causal or no profiles for strong shock waves exist. This paper proposes a relativistic Navier–Stokes–Fourier-type viscosity and heat conduction tensor such that the resulting second-order system of partial differential equations for the fluid dynamics of pure radiation is symmetric hyperbolic. This system has causal dissipation as well as the property that all shock waves of arbitrary strength have smooth profiles. Entropy production is positive both on gradients near those of solutions to the dissipation-free equations and on gradients of shock profiles. This shows that the new dissipation stress tensor complies to leading order with the principles of thermodynamics. Whether higher order modifications of the ansatz are required to obtain full compatibility with the second law far from the zero-dissipation equilibrium is left to further investigations. The system has exactly three a priori free parameters χ,η,ζ, corresponding physically to heat conductivity, shear viscosity and bulk viscosity. If the bulk viscosity is zero (as is stated in the literature) and the total stress–energy tensor is trace free, the entire viscosity and heat conduction tensor is determined to within a constant factor. PMID:24910526

Viscosity and stability of ultra-high internal phase CO2-in-water foams stabilized with surfactants and nanoparticles with or without polyelectrolytes.

PubMed

Xue, Zheng; Worthen, Andrew; Qajar, Ali; Robert, Isaiah; Bryant, Steven L; Huh, Chun; Prodanović, Maša; Johnston, Keith P

2016-01-01

To date, relatively few examples of ultra-high internal phase supercritical CO2-in-water foams (also referred to as macroemulsions) have been observed, despite interest in applications including "waterless" hydraulic fracturing in energy production. The viscosities and stabilities of foams up to 0.98 CO2 volume fraction were investigated in terms of foam bubble size, interfacial tension, and bulk and surface viscosity. The foams were stabilized with laurylamidopropyl betaine (LAPB) surfactant and silica nanoparticles (NPs), with and without partially hydrolyzed polyacrylamide (HPAM). For foams stabilized with mixture of LAPB and NPs, fine ∼70 μm bubbles and high viscosities on the order of 100 cP at>0.90 internal phase fraction were stabilized for hours to days. The surfactant reduces interfacial tension, and thus facilitates bubble generation and decreases the capillary pressure to reduce the drainage rate of the lamella. The LAPB, which is in the cationic protonated form, also attracts anionic NPs (and anionic HPAM in systems containing polymer) to the interface. The adsorbed NPs at the interface are shown to slow down Ostwald ripening (with or without polymer added) and increase foam stability. In systems with added HPAM, the increase in the bulk and surface viscosity of the aqueous phase further decreases the lamella drainage rate and inhibits coalescence of foams. Thus, the added polymer increases the foam viscosity by threefold. Scaling law analysis shows the viscosity of 0.90 volume fraction foams is inversely proportional to the bubble size. Copyright © 2015 Elsevier Inc. All rights reserved.

Compositional dependence of lower crustal viscosity

NASA Astrophysics Data System (ADS)

Shinevar, William J.; Behn, Mark D.; Hirth, Greg

2015-10-01

We calculate the viscosity structure of the lower continental crust as a function of its bulk composition using multiphase mixing theory. We use the Gibbs free-energy minimization routine Perple_X to calculate mineral assemblages for different crustal compositions under pressure and temperature conditions appropriate for the lower continental crust. The effective aggregate viscosities are then calculated using a rheologic mixing model and flow laws for the major crust-forming minerals. We investigate the viscosity of two lower crustal compositions: (i) basaltic (53 wt % SiO2) and (ii) andesitic (64 wt % SiO2). The andesitic model predicts aggregate viscosities similar to feldspar and approximately 1 order of magnitude greater than that of wet quartz. The viscosity range calculated for the andesitic crustal composition (particularly when hydrous phases are stable) is most similar to independent estimates of lower crust viscosity in actively deforming regions based on postglacial isostatic rebound, postseismic relaxation, and paleolake shoreline deflection.

Macromolecular crowding gives rise to microviscosity, anomalous diffusion and accelerated actin polymerization

NASA Astrophysics Data System (ADS)

Rashid, Rafi; Chee, Stella Min Ling; Raghunath, Michael; Wohland, Thorsten

2015-05-01

Macromolecular crowding (MMC) has been used in various in vitro experimental systems to mimic in vivo physiology. This is because the crowded cytoplasm of cells contains many different types of solutes dissolved in an aqueous medium. MMC in the extracellular microenvironment is involved in maintaining stem cells in their undifferentiated state (niche) as well as in aiding their differentiation after they have travelled to new locations outside the niche. MMC at physiologically relevant fractional volume occupancies (FVOs) significantly enhances the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells during chemically induced adipogenesis. The mechanism by which MMC produces this enhancement is not entirely known. In the context of extracellular collagen deposition, we have recently reported the importance of optimizing the FVO while minimizing the bulk viscosity. Two opposing properties will determine the net rate of a biochemical reaction: the negative effect of bulk viscosity and the positive effect of the excluded volume, the latter being expressed by the FVO. In this study we have looked more closely at the effect of viscosity on reaction rates. We have used fluorimetry to measure the rate of actin polymerization and fluorescence correlation spectroscopy (FCS) to measure diffusion of various probes in solutions containing the crowder Ficoll at physiological concentrations. Similar to its effect on collagen, Ficoll enhanced the actin polymerization rate despite increasing the bulk viscosity. Our FCS measurements reveal a relatively minor component of anomalous diffusion. In addition, our measurements do suggest that microviscosity becomes relevant in a crowded environment. We ruled out bulk viscosity as a cause of the rate enhancement by performing the actin polymerization assay in glycerol. These opposite effects of Ficoll and glycerol led us to conclude that microviscosity becomes relevant at the length scale of the reacting molecules within a crowded microenvironment. The excluded volume effect (arising from crowding) increases the effective concentration of actin, which increases the reaction rate, while the microviscosity does not increase sufficiently to lower the reaction rate. This study reveals finer details about the mechanism of MMC.

Macromolecular crowding gives rise to microviscosity, anomalous diffusion and accelerated actin polymerization.

PubMed

Rashid, Rafi; Chee, Stella Min Ling; Raghunath, Michael; Wohland, Thorsten

2015-04-30

Macromolecular crowding (MMC) has been used in various in vitro experimental systems to mimic in vivo physiology. This is because the crowded cytoplasm of cells contains many different types of solutes dissolved in an aqueous medium. MMC in the extracellular microenvironment is involved in maintaining stem cells in their undifferentiated state (niche) as well as in aiding their differentiation after they have travelled to new locations outside the niche. MMC at physiologically relevant fractional volume occupancies (FVOs) significantly enhances the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells during chemically induced adipogenesis. The mechanism by which MMC produces this enhancement is not entirely known. In the context of extracellular collagen deposition, we have recently reported the importance of optimizing the FVO while minimizing the bulk viscosity. Two opposing properties will determine the net rate of a biochemical reaction: the negative effect of bulk viscosity and the positive effect of the excluded volume, the latter being expressed by the FVO. In this study we have looked more closely at the effect of viscosity on reaction rates. We have used fluorimetry to measure the rate of actin polymerization and fluorescence correlation spectroscopy (FCS) to measure diffusion of various probes in solutions containing the crowder Ficoll at physiological concentrations. Similar to its effect on collagen, Ficoll enhanced the actin polymerization rate despite increasing the bulk viscosity. Our FCS measurements reveal a relatively minor component of anomalous diffusion. In addition, our measurements do suggest that microviscosity becomes relevant in a crowded environment. We ruled out bulk viscosity as a cause of the rate enhancement by performing the actin polymerization assay in glycerol. These opposite effects of Ficoll and glycerol led us to conclude that microviscosity becomes relevant at the length scale of the reacting molecules within a crowded microenvironment. The excluded volume effect (arising from crowding) increases the effective concentration of actin, which increases the reaction rate, while the microviscosity does not increase sufficiently to lower the reaction rate. This study reveals finer details about the mechanism of MMC.

Effects of surface tension and viscosity on gold and silver sputtered onto liquid substrates

NASA Astrophysics Data System (ADS)

De Luna, Mark M.; Gupta, Malancha

2018-05-01

In this paper, we study DC magnetron sputtering of gold and silver onto liquid substrates of varying viscosities and surface tensions. We were able to separate the effects of viscosity from surface tension by depositing the metals onto silicone oils with a range of viscosities. The effects of surface tension were studied by depositing the metals onto squalene, poly(ethylene glycol), and glycerol. It was found that dispersed nanoparticles were formed on liquids with low surface tension and low viscosity whereas dense films were formed on liquids with low surface tension and high viscosity. Nanoparticles were formed on both the liquid surface and within the bulk liquid for high surface tension liquids. Our results can be used to tailor the metal and liquid interaction to fabricate particles and films for various applications in optics, electronics, and catalysis.

Dynamics of charged bulk viscous collapsing cylindrical source with heat flux

NASA Astrophysics Data System (ADS)

Shah, S. M.; Abbas, G.

2017-04-01

In this paper, we have explored the effects of dissipation on the dynamics of charged bulk viscous collapsing cylindrical source which allows the out-flow of heat flux in the form of radiations. The Misner-Sharp formalism has been implemented to drive the dynamical equation in terms of proper time and radial derivatives. We have investigated the effects of charge and bulk viscosity on the dynamics of collapsing cylinder. To determine the effects of radial heat flux, we have formulated the heat transport equations in the context of Müller-Israel-Stewart theory by assuming that thermodynamics viscous/heat coupling coefficients can be neglected within some approximations. In our discussion, we have introduced the viscosity by the standard (non-causal) thermodynamics approach. The dynamical equations have been coupled with the heat transport equation; the consequences of the resulting coupled heat equation have been analyzed in detail.

Experimental understanding of the viscosity reduction ability of TLCPs with different PEs

NASA Astrophysics Data System (ADS)

Tang, Youhong; Zuo, Min; Gao, Ping

2014-08-01

In this study, two thermotropic liquid crystalline polyesters (TLCPs) synthesized by polycondensation of p-hydroxybenzoic acid /hydroquinone/ poly dicarboxylic acid were used as viscosity reduction agents for polyethylene (PE). The TLCPs had different thermal, rheological and other physical properties that were quantitatively characterized. The two TLCPs were blended with high density PE (HDPE) and high molecular mass PE (HMMPE) by simple twin screw extrusion under the same weight ratio of 1.0 wt% and were each rheologically characterized at 190°C. The TLCPs acted as processing modifiers for the PEs and the bulk viscosity of the blends decreased dramatically. However, the viscosity reduction ability was not identical: one TLCP had obviously higher viscosity reduction ability on the HDPE, with a maximum viscosity reduction ratio of 68.1%, whereas the other TLCP had higher viscosity reduction ability on the HMMPE, with a maximum viscosity reduction ratio of 98.7%. Proposed explanations for these differences are evaluated.

Linear response and Berry curvature in two-dimensional topological phases

NASA Astrophysics Data System (ADS)

Bradlyn, Barry J.

In this thesis we examine the viscous and thermal transport properties of chiral topological phases, and their relationship to topological invariants. We start by developing a Kubo formalism for calculating the frequency dependent viscosity tensor of a general quantum system, both with and without a uniform external magnetic field. The importance of contact terms is emphasized. We apply this formalism to the study of integer and fractional quantum Hall states, as well as p + ip paired superfluids, and verify the relationship between the Hall viscosity and the mean orbital spin density. We also elucidate the connection between our Kubo formulas and prior adiabatic transport calculations of the Hall viscosity. Additionally, we derive a general relationship between the frequency dependent viscosity and conductivity tensors for Galilean-invariant systems. We comment on the implications of this relationship towards the measurement of Hall viscosity in solid-state systems. To address the question of thermal transport, we first review the standard Kubo formalism of Luttinger for computing thermoelectric coefficients. We apply this to the specific case of non-interacting electrons in the integer quantum Hall regime, paying careful attention to the roles of bulk and edge effects. In order to generalize our discussion to interacting systems, we construct a low-energy effective action for a two-dimensional non-relativistic topological phase of matter in a continuum, which completely describes all of its bulk thermoelectric and visco-elastic properties in the limit of low frequencies, long distances, and zero temperature, without assuming either Lorentz or Galilean invariance, by coupling the microscopic degrees of freedom to the background spacetime geometry. We derive the most general form of a local bulk induced action to first order in derivatives of the background fields, from which thermodynamic and transport properties can be obtained. We show that the gapped bulk cannot contribute to low-temperature thermoelectric transport other than the ordinary Hall conductivity; the other thermoelectric effects (if they occur) are thus purely edge effects. The stress response to time-dependent strains is given by the Hall viscosity, which is robust against perturbations and related to the spin current. Finally, we address the issue of calculating the topological central charge from bulk wavefunctions for a topological phase. Using the form of the topological terms in the induced action, we show that we can calculate the various coefficients of these terms as Berry curvatures associated to certain metric and electromagnetic vector potential perturbations. We carry out this computation explicitly for quantum Hall trial wavefunctions that can be represented as conformal blocks in a chiral conformal field theory (CFT). These calculations make use of the gauge and gravitational anomalies in the underlying chiral CFT.

Viscosity Dependence of Some Protein and Enzyme Reaction Rates: Seventy-Five Years after Kramers.

PubMed

Sashi, Pulikallu; Bhuyan, Abani K

2015-07-28

Kramers rate theory is a milestone in chemical reaction research, but concerns regarding the basic understanding of condensed phase reaction rates of large molecules in viscous milieu persist. Experimental studies of Kramers theory rely on scaling reaction rates with inverse solvent viscosity, which is often equated with the bulk friction coefficient based on simple hydrodynamic relations. Apart from the difficulty of abstraction of the prefactor details from experimental data, it is not clear why the linearity of rate versus inverse viscosity, k ∝ η(-1), deviates widely for many reactions studied. In most cases, the deviation simulates a power law k ∝ η(-n), where the exponent n assumes fractional values. In rate-viscosity studies presented here, results for two reactions, unfolding of cytochrome c and cysteine protease activity of human ribosomal protein S4, show an exceedingly overdamped rate over a wide viscosity range, registering n values up to 2.4. Although the origin of this extraordinary reaction friction is not known at present, the results indicate that the viscosity exponent need not be bound by the 0-1 limit as generally suggested. For the third reaction studied here, thermal dissociation of CO from nativelike cytochrome c, the rate-viscosity behavior can be explained using Grote-Hynes theory of time-dependent friction in conjunction with correlated motions intrinsic to the protein. Analysis of the glycerol viscosity-dependent rate for the CO dissociation reaction in the presence of urea as the second variable shows that the protein stabilizing effect of subdenaturing amounts of urea is not affected by the bulk viscosity. It appears that a myriad of factors as diverse as parameter uncertainty due to the difficulty of knowing the exact reaction friction and both mode and consequences of protein-solvent interaction work in a complex manner to convey as though Kramers rate equation is not absolute.

Effects of bulk viscosity and hadronic rescattering in heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, Sangwook; Paquet, Jean-Francois; Shen, Chun

Here, we describe ultrarelativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider with a hybrid model using the IP-Glasma model for the earliest stage and viscous hydrodynamics and microscopic transport for the later stages of the collision. We demonstrate that within this framework the bulk viscosity of the plasma plays an important role in describing the experimentally observed radial flow and azimuthal anisotropy simultaneously. Finally, we further investigate the dependence of observables on the temperature below which we employ the microscopic transport description.

Effects of bulk viscosity and hadronic rescattering in heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

DOE PAGES

Ryu, Sangwook; Paquet, Jean-Francois; Shen, Chun; ...

2018-03-15

Here, we describe ultrarelativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider with a hybrid model using the IP-Glasma model for the earliest stage and viscous hydrodynamics and microscopic transport for the later stages of the collision. We demonstrate that within this framework the bulk viscosity of the plasma plays an important role in describing the experimentally observed radial flow and azimuthal anisotropy simultaneously. Finally, we further investigate the dependence of observables on the temperature below which we employ the microscopic transport description.

Opto-mechano-fluidic viscometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Kewen, E-mail: khan56@illinois.edu; Zhu, Kaiyuan; Bahl, Gaurav, E-mail: bahl@illinois.edu

2014-07-07

The recent development of opto-mechano-fluidic resonators has provided—by harnessing photon radiation pressure—a microfluidics platform for the optical sensing of fluid density and bulk modulus. Here, we show that fluid viscosity can also be determined through optomechanical measurement of the vibrational noise spectrum of the resonator mechanical modes. A linear relationship between the spectral linewidth and root-viscosity is predicted and experimentally verified in the low viscosity regime. Our result is a step towards multi-frequency measurement of viscoelasticity of arbitrary fluids, without sample contamination, using highly sensitive optomechanics techniques.

STUDIES ON THE ANOMALOUS VISCOSITY AND FLOW-BIREFRINGENCE OF PROTEIN SOLUTIONS

PubMed Central

Lawrence, A. S. C.; Needham, Joseph; Shen, Shih-Chang

1944-01-01

1. A coaxial viscosimeter which permits the simultaneous determination of relative and anomalous viscosity and of flow-birefringence is described. Flow-anomaly and flow-birefringence are regarded as characteristic of elongated micelles and molecules. 2. Such methods have been applied to dilute solutions of proteins. The conditions under which the coaxial (Couette) viscosimeter measures the viscosity of the bulk phase and the surface film phase respectively have been investigated and are described. 3. The general behaviour of protein solutions subjected to shear is summarised. PMID:19873384

Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites.

PubMed

Bucuta, Stefan; Ilie, Nicoleta

2014-11-01

The aim of this study was to quantify the blue light that passes through different incremental thicknesses of bulk fill in comparison to conventional resin-based composites (RBCs) and to relate it to the induced mechanical properties. Seven bulk fill, five nanohybrid and two flowable RBCs were analysed. Specimens (n = 5) of three incremental thicknesses (2, 4 and 6 mm) were cured from the top for 20 s, while at the bottom, a spectrometer monitored in real time the transmitted irradiance. Micro-mechanical properties (Vickers hardness, HV, and indentation modulus, E) were measured at the top and bottom after 24 h of storage in distilled water at 37 °C. Electron microscope images were taken for assessing the filler distribution and size. Bulk fill RBCs (except SonicFill) were more translucent than conventional RBCs. Low-viscosity bulk fill materials showed the lowest mechanical properties. HV depends highly on the following parameters: material (ηp (2) = 0.952), incremental thickness (0.826), filler volume (0.747), filler weight (0.746) and transmitted irradiance (0.491). The bottom-to-top HV ratio (HVbt) was higher than 80 % in all materials in 2- and 4-mm increments (except for Premise), whereas in 6-mm increments, this is valid only in four bulk fill materials (Venus Bulk Fill, SDR, x-tra fil, Tetric EvoCeram Bulk Fill). The depth of cure is dependent on the RBC's translucency. Low-viscosity bulk fill RBCs have lower mechanical properties than all other types of analysed materials. All bulk fill RBCs (except SonicFill) are more translucent for blue light than conventional RBCs. Although bulk fill RBCs are generally more translucent, the practitioner has to follow the manufacturer's recommendations on curing technique and maximum incremental thickness.

Viscosity of Common Seed and Vegetable Oils

NASA Astrophysics Data System (ADS)

Wes Fountain, C.; Jennings, Jeanne; McKie, Cheryl K.; Oakman, Patrice; Fetterolf, Monty L.

1997-02-01

Viscosity experiments using Ostwald-type gravity flow viscometers are not new to the physical chemistry laboratory. Several physical chemistry laboratory texts (1 - 3) contain at least one experiment studying polymer solutions or other well-defined systems. Several recently published articles (4 - 8) indicated the continued interest in using viscosity measurements in the teaching lab to illustrate molecular interpretation of bulk phenomena. Most of these discussions and teaching experiments are designed around an extensive theory of viscous flow and models of molecular shape that allow a full data interpretation to be attempted. This approach to viscosity experiments may not be appropriate for all teaching situations (e.g., high schools, general chemistry labs, and nonmajor physical chemistry labs). A viscosity experiment is presented here that is designed around common seed and vegetable oils. With the importance of viscosity to foodstuffs (9) and the importance of fatty acids to nutrition (10), an experiment using these common, recognizable oils has broad appeal.

Removal of xylenol orange from its aqueous solution using SDS self-microemulsifying systems: optimization by Box-Behnken statistical design.

PubMed

Shakeel, Faiyaz; Haq, Nazrul; Alanazi, Fars K; Alsarra, Ibrahim A

2014-04-01

The aim of present study was to develop and evaluate sodium dodecyl sulfate (SDS) self-microemulsifying systems (SMES) for the removal of an anionic dye xylenol orange (XO) from its bulk aqueous media via liquid-liquid adsorption. The composition of SDS SMES was optimized by Box-Behnken statistical design for the maximum removal of XO from its aqueous solution. Various SDS formulations were prepared by spontaneous emulsification method and characterized for thermodynamic stability, self-microemulsification efficiency, droplet size, and viscosity. Adsorption studies were conducted at 8, 16, and 24 h by mixing small amounts of SDS formulations with relatively large amounts of bulk aqueous solution of XO. Droplet size and viscosity of SDS formulations were significantly influenced by oil phase concentration (triacetin), while surfactant concentration had little impact on droplet size and viscosity. However, the percentage of removal of XO was influenced by triacetin concentration, surfactant concentration, and adsorption time. Based on lowest droplet size (35.97 nm), lowest viscosity (29.62 cp), and highest percentage of removal efficiency (89.77 %), formulation F14, containing 2 % w/w of triacetin and 40 % w/w of surfactant mixture (20 % w/w of SDS and 20 % w/w of polyethylene glycol 400), was selected as an optimized formulation for the removal of XO from its bulk aqueous media after 16 h. These results indicated that SDS SMES could be suitable alternates of solid-liquid adsorption for the removal of toxic dyes such as XO from its aqueous solution through liquid-liquid adsorption.

Free volume dependence of an ionic molecular rotor in Fluoroalkylphosphate (FAP) based ionic liquids

NASA Astrophysics Data System (ADS)

Singh, Prabhat K.; Mora, Aruna K.; Nath, Sukhendu

2016-01-01

The emission properties of Thioflavin-T (ThT), a cationic molecular rotor, have been investigated in two fluoroalkylphosphate ([FAP]) anion based ionic liquids, namely, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate and 1-(2-hydroxyethyl)-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, over a wide temperature range. The micro-viscosities of ionic liquids around ThT, measured from the emission quantum yield, are found to be quite different from their bulk viscosities. The temperature dependence of the viscosity and the emission quantum yield reveals that, despite the very low shear viscosity of these ILs, the non-radiative torsional relaxation has a strong dependence on the free volume of these [FAP] anion based ILs.

Thermo-hydro-mechanical coupling in long-term sedimentary rock response

NASA Astrophysics Data System (ADS)

Makhnenko, R. Y.; Podladchikov, Y.

2017-12-01

Storage of nuclear waste or CO2 affects the state of stress and pore pressure in the subsurface and may induce large thermal gradients in the rock formations. In general, the associated coupled thermo-hydro-mechanical effect on long-term rock deformation and fluid flow have to be studied. Principles behind mathematical models for poroviscoelastic response are reviewed, and poroviscous model parameter, the bulk viscosity, is included in the constitutive equations. Time-dependent response (creep) of fluid-filled sedimentary rocks is experimentally quantified at isotropic stress states. Three poroelastic parameters are measured by drained, undrained, and unjacketed geomechanical tests for quartz-rich Berea sandstone, calcite-rich Apulian limestone, and clay-rich Jurassic shale. The bulk viscosity is calculated from the measurements of pore pressure growth under undrained conditions, which requires time scales 104 s. The bulk viscosity is reported to be on the order of 1015 Pa•s for the sandstone, limestone, and shale. It is found to be decreasing with the increase of pore pressure despite corresponding decrease in the effective stress. Additionally, increase of temperature (from 24 ºC to 40 ºC) enhances creep, where the most pronounced effect is reported for the shale with bulk viscosity decrease by a factor of 3. Viscous compaction of fluid-filled porous media allows a generation of a special type of fluid flow instability that leads to formation of high-porosity, high-permeability domains that are able to self-propagate upwards due to interplay between buoyancy and viscous resistance of the deforming porous matrix. This instability is known as "porosity wave" and its formation is possible under conditions applicable to deep CO2 storage in reservoirs and explains creation of high-porosity channels and chimneys. The reported experiments show that the formation of high-permeability pathways is most likely to occur in low-permeable clay-rich materials (caprock representatives) at elevated temperatures.

Experiments on the rheology of vesicle-bearing magmas

NASA Astrophysics Data System (ADS)

Vona, Alessandro; Ryan, Amy G.; Russell, James K.; Romano, Claudia

2016-04-01

We present a series of high temperature uniaxial deformation experiments designed to investigate the effect of bubbles on the magma bulk viscosity. Starting materials having variable vesicularity (φ = 0 - 66%) were synthesized by high-temperature foaming (T = 900 - 1050 ° C and P = 1 bar) of cores of natural rhyolitic obsidian from Hrafntinnuhryggur, Krafla, Iceland. These cores were subsequently deformed using a high-temperature uniaxial press at dry atmospheric conditions. Each experiment involved deforming vesicle-bearing cores isothermally (T = 750 ° C), at constant displacement rates (strain rates between 0.5-1 x 10-4 s-1), and to total strains (ɛ) of 10-40%. The viscosity of the bubble-free melt (η0) was measured by micropenetration and parallel plate methods and establishes a baseline for comparing data derived from experiments on vesicle rich cores. At the experimental conditions, the presence of vesicles has a major impact on the rheological response, producing a marked decrease of bulk viscosity (maximum decrease of 2 log units Pa s) that is best described by a two-parameter empirical equation: log ηBulk = log η0 - 1.47 * [φ/(1-φ)]0.48. Our model provides a means to compare the diverse behaviour of vesicle-bearing melts reported in the literature and reflecting material properties (e.g., analogue vs. natural), geometry and distribution of pores (e.g. foamed/natural vs. unconsolidated/sintered materials), and flow regime. Lastly, we apply principles of Maxwell relaxation theory, combined with our parameterization of bubble-melt rheology, to map the potential onset of non-Newtonian behaviour (strain localization) in vesiculated magmas and lavas as a function of melt viscosity, vesicularity, strain rate, and geological condition. Increasing vesicularity in magmas can initiate non-Newtonian behaviour at constant strain rates. Lower melt viscosity sustains homogeneous Newtonian flow in vesiculated magmas even at relatively high strain rates.

Small Particle Driven Chain Disentanglements in Polymer Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senses, Erkan; Ansar, Siyam M.; Kitchens, Christopher L.

2017-04-01

Using neutron spin-echo spectroscopy, X-ray photon correlation spectroscopy and bulk rheology, we studied the effect of particle size on the single chain dynamics, particle mobility, and bulk viscosity in athermal polyethylene oxide-gold nanoparticle composites. The results reveal an ≈ 25 % increase in the reptation tube diameter with addition of nanoparticles smaller than the entanglement mesh size (≈ 5 nm), at a volume fraction of 20 %. The tube diameter remains unchanged in the composite with larger (20 nm) nanoparticles at the same loading. In both cases, the Rouse dynamics is insensitive to particle size. These results provide a directmore » experimental observation of particle size driven disentanglements that can cause non-Einstein-like viscosity trends often observed in polymer nanocomposites.« less

Live Cell Imaging of Viscosity in 3D Tumour Cell Models.

PubMed

Shirmanova, Marina V; Shimolina, Lubov' E; Lukina, Maria M; Zagaynova, Elena V; Kuimova, Marina K

2017-01-01

Abnormal levels of viscosity in tissues and cells are known to be associated with disease and malfunction. While methods to measure bulk macroscopic viscosity of bio-tissues are well developed, imaging viscosity at the microscopic scale remains a challenge, especially in vivo. Molecular rotors are small synthetic viscosity-sensitive fluorophores in which fluorescence parameters are strongly correlated to the microviscosity of their immediate environment. Hence, molecular rotors represent a promising instrument for mapping of viscosity in living cells and tissues at the microscopic level. Quantitative measurements of viscosity can be achieved by recording time-resolved fluorescence decays of molecular rotor using fluorescence lifetime imaging microscopy (FLIM), which is also suitable for dynamic viscosity mapping, both in cellulo and in vivo. Among tools of experimental oncology, 3D tumour cultures, or spheroids, are considered a more adequate in vitro model compared to a cellular monolayer, and represent a less labour-intensive and more unified approach compared to animal tumour models. This chapter describes a methodology for microviscosity imaging in tumour spheroids using BODIPY-based molecular rotors and two photon-excited FLIM.

Representing ductile damage with the dual domain material point method

DOE PAGES

Long, C. C.; Zhang, D. Z.; Bronkhorst, C. A.; ...

2015-12-14

In this study, we incorporate a ductile damage material model into a computational framework based on the Dual Domain Material Point (DDMP) method. As an example, simulations of a flyer plate experiment involving ductile void growth and material failure are performed. The results are compared with experiments performed on high purity tantalum. We also compare the numerical results obtained from the DDMP method with those obtained from the traditional Material Point Method (MPM). Effects of an overstress model, artificial viscosity, and physical viscosity are investigated. Our results show that a physical bulk viscosity and overstress model are important in thismore » impact and failure problem, while physical shear viscosity and artificial shock viscosity have negligible effects. A simple numerical procedure with guaranteed convergence is introduced to solve for the equilibrium plastic state from the ductile damage model.« less

Vortex lattices and defect-mediated viscosity reduction in active liquids

NASA Astrophysics Data System (ADS)

Slomka, Jonasz; Dunkel, Jorn

2016-11-01

Generic pattern-formation and viscosity-reduction mechanisms in active fluids are investigated using a generalized Navier-Stokes model that captures the experimentally observed bulk vortex dynamics in microbial suspensions. We present exact analytical solutions including stress-free vortex lattices and introduce a computational framework that allows the efficient treatment of previously intractable higher-order shear boundary conditions. Large-scale parameter scans identify the conditions for spontaneous flow symmetry breaking, defect-mediated low-viscosity phases and negative-viscosity states amenable to energy harvesting in confined suspensions. The theory uses only generic assumptions about the symmetries and long-wavelength structure of active stress tensors, suggesting that inviscid phases may be achievable in a broad class of non-equilibrium fluids by tuning confinement geometry and pattern scale selection.

Geometry-dependent viscosity reduction in sheared active fluids

NASA Astrophysics Data System (ADS)

Słomka, Jonasz; Dunkel, Jörn

2017-04-01

We investigate flow pattern formation and viscosity reduction mechanisms in active fluids by studying a generalized Navier-Stokes model that captures the experimentally observed bulk vortex dynamics in microbial suspensions. We present exact analytical solutions including stress-free vortex lattices and introduce a computational framework that allows the efficient treatment of higher-order shear boundary conditions. Large-scale parameter scans identify the conditions for spontaneous flow symmetry breaking, geometry-dependent viscosity reduction, and negative-viscosity states amenable to energy harvesting in confined suspensions. The theory uses only generic assumptions about the symmetries and long-wavelength structure of active stress tensors, suggesting that inviscid phases may be achievable in a broad class of nonequilibrium fluids by tuning confinement geometry and pattern scale selection.

Investigation of Tokamak Solid Divertor Target Options.

DTIC Science & Technology

1981-05-26

but materials are not known which could operate at the high resulting wall temperatures . Mist- steam flows would also demand a relatively high ...flux P = coolant density = bulk coolant viscosity w = coolant viscosity at average wall temperature = units conversion At high heat loads and moderate...therefore, the inner wall temperature will be over 300 OF, posing a high temp- erature materials challenge. E. Swirl and Mixed Flow Schemes Extensive work

Hydrodynamic resistance and mobility of deformable objects in microfluidic channels

PubMed Central

Sajeesh, P.; Doble, M.; Sen, A. K.

2014-01-01

This work reports experimental and theoretical studies of hydrodynamic behaviour of deformable objects such as droplets and cells in a microchannel. Effects of mechanical properties including size and viscosity of these objects on their deformability, mobility, and induced hydrodynamic resistance are investigated. The experimental results revealed that the deformability of droplets, which is quantified in terms of deformability index (D.I.), depends on the droplet-to-channel size ratio ρ and droplet-to-medium viscosity ratio λ. Using a large set of experimental data, for the first time, we provide a mathematical formula that correlates induced hydrodynamic resistance of a single droplet ΔRd with the droplet size ρ and viscosity λ. A simple theoretical model is developed to obtain closed form expressions for droplet mobility ϕ and ΔRd. The predictions of the theoretical model successfully confront the experimental results in terms of the droplet mobility ϕ and induced hydrodynamic resistance ΔRd. Numerical simulations are carried out using volume-of-fluid model to predict droplet generation and deformation of droplets of different size ratio ρ and viscosity ratio λ, which compare well with that obtained from the experiments. In a novel effort, we performed experiments to measure the bulk induced hydrodynamic resistance ΔR of different biological cells (yeast, L6, and HEK 293). The results reveal that the bulk induced hydrodynamic resistance ΔR is related to the cell concentration and apparent viscosity of the cells. PMID:25538806

Effect of Molecular Architecture on Polymer Melt Surface Dynamics

NASA Astrophysics Data System (ADS)

Foster, Mark

The dynamics of the thermally stimulated surface height fluctuations in a polymer melt dictate wetting, adhesion, and tribology at that surface. These surface fluctuations can be profoundly altered by tethering of the chains. One type of tethering is the tethering of one part of a molecule to another part of the same molecule. This tethering is found in both long chain branched polymers and in macrocycles. We have studied the surface fluctuations with X-ray Photon Correlation Spectroscopy for melts of well-defined, anionically polymerized polystyrenes of various architectures, including linear, 6 arm star, pom-pom, comb and cyclic architectures. For linear chains, the variation of surface relaxation time with in-plane scattering vector can be fit using a hydrodynamic continuum theory (HCT) of thermally stimulated capillary waves that knows nothing of the chain architecture. Assuming the theory is applicable, apparent viscosities of the films may then be inferred from the XPCS data. For unentangled linear chains, the viscosity inferred from XPCS data in this manner is the same as that measured by conventional bulk rheometry. The HCT does a reasonable job of describing the variation of relaxation time with scattering vector for long branched chains also, but only if a viscosity much larger than that of the bulk is assumed. The discrepancy between the viscosity inferred from surface relaxation times using the HCT and that derived from conventional rheometry grows larger as the bulk Tg is approached and is different for each long chain branched architecture. However, for densely branched combs and cyclic chains different behaviors are found. Acknowledgement: Thanks to NSF (CBET 0730692) and the Advanced Photon Source, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. W-31-109-ENG-38.

Compaction Around a Spherical Inclusion in Partially Molten Rock

NASA Astrophysics Data System (ADS)

Alisic, Laura; Rhebergen, Sander; Rudge, John F.; Katz, Richard F.; Wells, Garth N.

2015-04-01

Conservation laws that describe the behavior of partially molten mantle rock have been established for several decades, but the associated rheology remains poorly understood. Constraints on the rheology may be obtained from recently published torsion experiments involving deformation of partially molten rock around a rigid, spherical inclusion. These experiments give rise to patterns of melt segregation that exhibit the competing effects of pressure shadows around the inclusion and melt-rich bands through the medium. Such patterns provide an opportunity to infer rheological parameters through comparison with models based on the conservation laws and constitutive relations that hypothetically govern the system. To this end, we have developed software tools using the automated code generation package FEniCS to simulate finite strain, two-phase flow around a rigid, spherical inclusion in a three-dimensional configuration that mirrors the laboratory experiments. The equations for compaction and advection-diffusion of a porous medium are solved utilising newly developed matrix preconditioning techniques. Simulations indicate that the evolution of porosity and therefore of melt distribution is predominantly controlled by the non-linear porosity-weakening exponent of the shear viscosity and the poorly known bulk viscosity. In the simulations presented here, we find that the balance of pressure shadows and melt-rich bands observed in experiments only occurs for bulk-to-shear viscosity ratio of less than about five. However, the evolution of porosity in simulations with such low bulk viscosity exceeds physical bounds at unrealistically small strain due to the unchecked, exponential growth of the porosity variations. Processes that limit or balance porosity localization will have to be incorporated in the formulation of the model to produce results that are consistent with the porosity evolution in experiments.

Nanostructure, hydrogen bonding and rheology in choline chloride deep eutectic solvents as a function of the hydrogen bond donor.

PubMed

Stefanovic, Ryan; Ludwig, Michael; Webber, Grant B; Atkin, Rob; Page, Alister J

2017-01-25

Deep eutectic solvents (DESs) are a mixture of a salt and a molecular hydrogen bond donor, which form a eutectic liquid with a depressed melting point. Quantum mechanical molecular dynamics (QM/MD) simulations have been used to probe the 1 : 2 choline chloride-urea (ChCl : U), choline chloride-ethylene glycol (ChCl : EG) and choline chloride-glycerol (ChCl : Gly) DESs. DES nanostructure and interactions between the ions is used to rationalise differences in DES eutectic point temperatures and viscosity. Simulations show that the structure of the bulk hydrogen bond donor is largely preserved for hydroxyl based hydrogen bond donors (ChCl:Gly and ChCl:EG), resulting in a smaller melting point depression. By contrast, ChCl:U exhibits a well-established hydrogen bond network between the salt and hydrogen bond donor, leading to a larger melting point depression. This extensive hydrogen bond network in ChCl:U also leads to substantially higher viscosity, compared to ChCl:EG and ChCl:Gly. Of the two hydroxyl based DESs, ChCl:Gly also exhibits a higher viscosity than ChCl:EG. This is attributed to the over-saturation of hydrogen bond donor groups in the ChCl:Gly bulk, which leads to more extensive hydrogen bond donor self-interaction and hence higher cohesive forces within the bulk liquid.

Integrated Solvent Design for CO 2 Capture and Viscosity Tuning

DOE PAGES

Cantu, David C.; Malhotra, Deepika; Koech, Phillip K.; ...

2017-08-18

We present novel design strategies for reduced viscosity single-component, water-lean CO 2 capture organic solvent systems. Through molecular simulation, we identify the main molecular-level descriptor that influences bulk solvent viscosity. Upon loading, a zwitterionic structure forms with a small activation energy of ca 16 kJ/mol and a small stabilization of ca 6 kJ/mol. Viscosity increases exponentially with CO 2 loading due to hydrogen-bonding between neighboring Zwitterions. We find that molecular structures that promote internal hydrogen bonding (within the same molecule) and suppress interactions with neighboring molecules have low viscosities. In addition, tuning the acid/base properties leads to a shift ofmore » the equilibrium toward a non-charged (acid) form that further reduces the viscosity. Here, based on the above structural criteria, a reduced order model is also presented that allows for the quick screening of large compound libraries and down selection of promising candidates for synthesis and testing.« less

Dissipative properties of hot and dense hadronic matter in an excluded-volume hadron resonance gas model

NASA Astrophysics Data System (ADS)

Kadam, Guru Prakash; Mishra, Hiranmaya

2015-09-01

We estimate dissipative properties, viz., shear and bulk viscosities of hadronic matter using relativistic Boltzmann equation in relaxation time approximation within the framework of excluded-volume hadron resonance gas (EHRG) model. We find that at zero baryon chemical potential the shear viscosity to entropy ratio (η /s ) decreases with temperature while at finite baryon chemical potential this ratio shows the same behavior as a function of temperature but reaches close to the Kovtun-Son-Starinets (KSS) bound. Further along the chemical freezeout curve, ratio η /s is almost constant apart from small initial monotonic rise. This observation may have some relevance to the experimental finding that the differential elliptic flow of charged hadrons does not change considerably at lower center-of-mass energy. We further find that bulk viscosity to entropy density (ζ /s ) decreases with temperature while this ratio has higher value at finite baryon chemical potential at higher temperature. Along the freezeout curve ζ /s decreases monotonically at lower center-of-mass energy and then saturates.

Exceptionally Slow Movement of Gold Nanoparticles at a Solid/Liquid Interface Investigated by Scanning Transmission Electron Microscopy.

PubMed

Verch, Andreas; Pfaff, Marina; de Jonge, Niels

2015-06-30

Gold nanoparticles were observed to move at a liquid/solid interface 3 orders of magnitude slower than expected for the movement in a bulk liquid by Brownian motion. The nanoscale movement was studied with scanning transmission electron microscopy (STEM) using a liquid enclosure consisting of microchips with silicon nitride windows. The experiments involved a variation of the electron dose, the coating of the nanoparticles, the surface charge of the enclosing membrane, the viscosity, and the liquid thickness. The observed slow movement was not a result of hydrodynamic hindrance near a wall but instead explained by the presence of a layer of ordered liquid exhibiting a viscosity 5 orders of magnitude larger than a bulk liquid. The increased viscosity presumably led to a dramatic slowdown of the movement. The layer was formed as a result of the surface charge of the silicon nitride windows. The exceptionally slow motion is a crucial aspect of electron microscopy of specimens in liquid, enabling a direct observation of the movement and agglomeration of nanoscale objects in liquid.

Various continuum approaches for studying shock wave structure in carbon dioxide

NASA Astrophysics Data System (ADS)

Alekseev, I. V.; Kosareva, A. A.; Kustova, E. V.; Nagnibeda, E. A.

2018-05-01

Shock wave structure in carbon dioxide is studied using different continuum models within the framework of one-temperature thermal equilibrium flow description. Navier-Stokes and Euler equations as well as commonly used Rankine-Hugoniot equations with different specific heat ratios are used to find the gas-dynamic parameters behind the shock wave. The accuracy of the Rankine-Hugoniot relations in polyatomic gases is assessed, and it is shown that they give a considerable error in the predicted values of fluid-dynamic variables. The effect of bulk viscosity on the shock wave structure in CO2 is evaluated. Taking into account bulk viscosity yields a significant increase in the shock wave width; for the complete model, the shock wave thickness varies non-monotonically with the Mach number.

Physicochemical Properties of Defatted Rambutan (Nephelium lappaceum) Seed Flour after Alkaline Treatment.

PubMed

Eiamwat, Jirawat; Wanlapa, Sorada; Kampruengdet, Sukit

2016-03-31

Rambutan seeds were subjected to SC-CO₂ extraction at 35 MPa, 45 °C to obtain defatted rambutan seed flour. Its physicochemical properties before and after treatment with alkali solution using 0.075 N NaOH were investigated. Alkali-treated flour had a significant increment in bulk density, swelling power, water adsorption capacity, emulsion capacity and stability but a reduction in turbidity, solubility and oil absorption capacity. Pasting measurements showed peak viscosity, breakdown, setback and final viscosity increased significantly for the alkali-treated flour, while pasting temperature decreased. The alkaline treatment decreased the least gelation concentration, but increased the apparent viscosity.

Generalized hydrodynamic transport in lattice-gas automata

NASA Technical Reports Server (NTRS)

Luo, Li-Shi; Chen, Hudong; Chen, Shiyi; Doolen, Gary D.; Lee, Yee-Chun

1991-01-01

The generalized hydrodynamics of two-dimensional lattice-gas automata is solved analytically in the linearized Boltzmann approximation. The dependence of the transport coefficients (kinematic viscosity, bulk viscosity, and sound speed) upon wave number k is obtained analytically. Anisotropy of these coefficients due to the lattice symmetry is studied for the entire range of wave number, k. Boundary effects due to a finite mean free path (Knudsen layer) are analyzed, and accurate comparisons are made with lattice-gas simulations.

Physico-chemical properties and extrusion behaviour of selected common bean varieties.

PubMed

Natabirwa, Hedwig; Muyonga, John H; Nakimbugwe, Dorothy; Lungaho, Mercy

2018-03-01

Extrusion processing offers the possibility of processing common beans industrially into highly nutritious and functional products. However, there is limited information on properties of extrudates from different bean varieties and their association with raw material characteristics and extrusion conditions. In this study, physico-chemical properties of raw and extruded Bishaz, K131, NABE19, Roba1 and RWR2245 common beans were determined. The relationships between bean characteristics and extrusion conditions on the extrudate properties were analysed. Extrudate physico-chemical and pasting properties varied significantly (P < 0.05) among bean varieties. Expansion ratio and water solubility decreased, while bulk density, water absorption, peak and breakdown viscosities increased as feed moisture increased. Protein exhibited significant positive correlation (P < 0.05) with water solubility index, and negative correlations (P < 0.05) with water absorption, bulk density and pasting viscosities. Iron and dietary fibre showed positive correlation while total ash exhibited negative correlation with peak viscosity, final viscosity and setback. Similar trends were observed in principal component analysis. Extrudate physico-chemical properties were found to be associated with beans protein, starch, iron, zinc and fibre contents. Therefore, bean chemical composition may serve as an indicator for beans extrusion behaviour and could be useful in selection of beans for extrusion. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

21 CFR 178.3740 - Plasticizers in polymeric substances.

Code of Federal Regulations, 2014 CFR

2014-04-01

..., hydrogenated (minimum viscosity at 99 °F, 39 Saybolt Universal seconds, as determined by ASTM methods D445-82 (“Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)”) and D2161-82 (“Standard Method for Conversion of Kinematic Viscosity to Saybolt...

Porphyrin and bodipy molecular rotors as microviscometers

NASA Astrophysics Data System (ADS)

Kimball, Joseph Daniel, III

Viscosity, a fluid's internal resistance to flow and resist molecular diffusion, is a fundamental property of fluid media. Determining the bulk viscosity of a fluid has been easy to relatively simple to accomplish for many years, yet in the recent decade there has been a focus on techniques to measure a fluid's microviscosity. Microviscosity differs from bulk viscosity such that microviscosity is the friction experienced by a single particle interacting with its micron-sized local environment. Macroscopic methods to evaluate the viscosity are well established, but methods to determine viscosity on the microscale level remains unclear. This work determines the viability of three molecular rotors designed as probes for microviscosity in organic media, ionic liquids, and in the cellular microenvironment. Understanding microviscosity is important because it one of the main properties of any fluid and thus has an effect on any diffusion related processes. A variety of mass and signal transport phenomena as well as intermolecular interactions are often governed by viscosity. Molecular rotors are a subclass of intramolecular charge transfer fluorophores which form a lower energy twisted state. This results in a charge separated species which is highly sensitive to its surrounding microenviroment's viscosity as high viscosity limits its ability to form this twisted state. Once excited, there are deactivation routes which the excited fluorophore can undergo: radiative and non-radiative. Both were studied in this work. In the case of a radiative decay, as seen in porphyrin dimer, the energy is released in the form of a photon and is seen as a shifted band in the emission structure. The conformation of the porphyrin dimer was found to be influenced differently by ionic liquids as compared to molecular solvents, indicating the microheterogenous nature of ionic liquids play a role in the conformation. For non-radiative decays, BODIPY dyads and triads were investigated. The triad has an extinction coefficient in the range of 200,000 M -1 cm-1, making it an extremely useful and sensitive fluorescent molecular rotor. Their fluorescent lifetimes were proven to correlate linearly with viscosity. Thus they were both encapsulated into lipds to determine their viability for cellular studies. The dyes were readily uptaken into three cancer cell lines, SKOV3, Calu 3 and Du 145. The lifetimes were then recorded using FLIM to map the viscosity of the cellular cytoplasm, mitochondria, lysosomes and other various organelles. A longer than expected lifetime in the cytoplasm was observed. This could be due to binding onto cytoplasmic proteins distributed throughout the cytoplasm, not due to viscosity as the theory of molecular rotors predicts..

The incompressible Rindler fluid versus the Schwarzschild-AdS fluid

NASA Astrophysics Data System (ADS)

Matsuo, Yoshinori; Natsuume, Makoto; Ohta, Masahiro; Okamura, Takashi

2013-02-01

We study the proposal by Bredberg et al. [J. High Energy Phys. 1103, 141 (2011)], where the fluid is defined by the Brown-York tensor on a timelike surface at r = rc in black hole backgrounds. We consider both Rindler space and the Schwarzschild-AdS (SAdS) black hole. The former describes an incompressible fluid, whereas the latter describes the vanishing bulk viscosity at arbitrary rc. Although the near-horizon limit of the SAdS black hole is Rindler space, these two results do not contradict each other. We also find an interesting "coincidence" with the black hole membrane paradigm that gives a negative bulk viscosity. In order to show these results, we rewrite the hydrodynamic stress tensor via metric perturbations using the conservation equation. The resulting expressions are suitable to compare with the Brown-York tensor.

Shock wave structure in rarefied polyatomic gases with large relaxation time for the dynamic pressure

NASA Astrophysics Data System (ADS)

Taniguchi, Shigeru; Arima, Takashi; Ruggeri, Tommaso; Sugiyama, Masaru

2018-05-01

The shock wave structure in rarefied polyatomic gases is analyzed based on extended thermodynamics (ET). In particular, the case with large relaxation time for the dynamic pressure, which corresponds to large bulk viscosity, is considered by adopting the simplest version of extended thermodynamics with only 6 independent fields (ET6); the mass density, the velocity, the temperature and the dynamic pressure. Recently, the validity of the theoretical predictions by ET was confirmed by the numerical analysis based on the kinetic theory in [S Kosuge and K Aoki: Phys. Rev. Fluids, Vol. 3, 023401 (2018)]. It was shown that numerical results using the polyatomic version of ellipsoidal statistical model agree with the theoretical predictions by ET for small or moderately large Mach numbers. In the present paper, first, we compare the theoretical predictions by ET6 with the ones by kinetic theory for large Mach number under the same assumptions, that is, the gas is polytropic and the bulk viscosity is proportional to the temperature. Second, the shock wave structure for large Mach number in a non-polytropic gas is analyzed with the particular interest in the effect of the temperature dependence of specific heat and the bulk viscosity on the shock wave structure. Through the analysis of the case of a rarefied carbon dioxide (CO2) gas, it is shown that these temperature dependences play important roles in the precise analysis of the structure for strong shock waves.

Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers.

PubMed

Alford, Mark G; Bovard, Luke; Hanauske, Matthias; Rezzolla, Luciano; Schwenzer, Kai

2018-01-26

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in the survival time of the post-merger object. We calculate time scales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above 10 MeV and gradients over length scales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations right after merger. When comparing with data from state-of-the-art merger simulations, we find that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers

NASA Astrophysics Data System (ADS)

Alford, Mark G.; Bovard, Luke; Hanauske, Matthias; Rezzolla, Luciano; Schwenzer, Kai

2018-01-01

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in the survival time of the post-merger object. We calculate time scales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above 10 MeV and gradients over length scales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations right after merger. When comparing with data from state-of-the-art merger simulations, we find that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

Temporal and spatial variation in porosity and compaction pressure for the viscoelastic slab

NASA Astrophysics Data System (ADS)

Morishige, M.; Van Keken, P. E.

2017-12-01

Fluid is considered to play key roles in subduction zones. It triggers various types of earthquakes by elevating pore-fluid pressure or forming hydrous minerals, and it also facilitates magma genesis by lowering the solidus temperatures of mantle and crustal rocks. Several previous numerical studies have worked on how fluid migrates and how porosity changes in time and space, but our knowledge of the fluid behavior remains limited. In this presentation, we demonstrate the detailed fluid behavior in the slab. The main features of this study are that (1) viscoelasticity is included, and that (2) fluid flow toward the inner part of the slab is also considered. We construct 2D and 3D finite element models for viscoelastic slab based on a theory of two-phase flow, which allows us to treat the movement of rock- and fluid- phases simultaneously. We solve the equations for porosity and compaction pressure which is defined as the pressure difference in between the two phases. Fluid source is fixed in time and space, and a uniform slab velocity is imposed for the whole model domain. There are several important parameters affecting the fluid behavior which includes bulk viscosity, bulk modulus, permeability, and fluid viscosity. Among these we fix bulk modulus and change the other parameters to investigate their effects on fluid migration. We find that when bulk viscosity is relatively high, elasticity is dominant and large amount of fluid is trapped in and around the fluid source. In addition, fluid migrates along the fluid source when relatively high ratio of permeability to fluid viscosity is assumed. Fluid generally moves with the slab when the ratio of permeability to fluid viscosity is low. One interesting feature is that in some cases porosity increases also in the deeper part of the fluid source due to the diffusion of compaction pressure. It suggests that the effects of resistance to volume change can be an alternative mechanism to effectively hydrate the inner part in the slab. In 3D, we find that fluid migrates in the maximum-dip direction of the slab. It leads to a fluid focusing where the slab bends away from the trench and it results in the increase in porosity and compaction pressure there. This finding may be useful to explain the observed along-arc variation in short-term slow slip events and the upper plane of double seismic zone.

Efficiency of polymerization of bulk-fill composite resins: a systematic review.

PubMed

Reis, André Figueiredo; Vestphal, Mariana; Amaral, Roberto Cesar do; Rodrigues, José Augusto; Roulet, Jean-François; Roscoe, Marina Guimarães

2017-08-28

This systematic review assessed the literature to evaluate the efficiency of polymerization of bulk-fill composite resins at 4 mm restoration depth. PubMed, Cochrane, Scopus and Web of Science databases were searched with no restrictions on year, publication status, or article's language. Selection criteria included studies that evaluated bulk-fill composite resin when inserted in a minimum thickness of 4 mm, followed by curing according to the manufacturers' instructions; presented sound statistical data; and comparison with a control group and/or a reference measurement of quality of polymerization. The evidence level was evaluated by qualitative scoring system and classified as high-, moderate- and low- evidence level. A total of 534 articles were retrieved in the initial search. After the review process, only 10 full-text articles met the inclusion criteria. Most articles included (80%) were classified as high evidence level. Among several techniques, microhardness was the most frequently method performed by the studies included in this systematic review. Irrespective to the "in vitro" method performed, bulk fill RBCs were partially likely to fulfill the important requirement regarding properly curing in 4 mm of cavity depth measured by depth of cure and / or degree of conversion. In general, low viscosities BFCs performed better regarding polymerization efficiency compared to the high viscosities BFCs.

Structure–property reduced order model for viscosity prediction in single-component CO 2 -binding organic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantu, David C.; Malhotra, Deepika; Koech, Phillip K.

2016-01-01

CO2 capture from power generation with aqueous solvents remains energy intensive due to the high water content of the current technology, or the high viscosity of non-aqueous alternatives. Quantitative reduced models, connecting molecular structure to bulk properties, are key for developing structure-property relationships that enable molecular design. In this work, we describe such a model that quantitatively predicts viscosities of CO2 binding organic liquids (CO2BOLs) based solely on molecular structure and the amount of bound CO2. The functional form of the model correlates the viscosity with the CO2 loading and an electrostatic term describing the charge distribution between the CO2-bearingmore » functional group and the proton-receiving amine. Molecular simulations identify the proton shuttle between these groups within the same molecule to be the critical indicator of low viscosity. The model, developed to allow for quick screening of solvent libraries, paves the way towards the rational design of low viscosity non-aqueous solvent systems for post-combustion CO2 capture. Following these theoretical recommendations, synthetic efforts of promising candidates and viscosity measurement provide experimental validation and verification.« less

Transport Coefficients in weakly compressible turbulence

NASA Technical Reports Server (NTRS)

Rubinstein, Robert; Erlebacher, Gordon

1996-01-01

A theory of transport coefficients in weakly compressible turbulence is derived by applying Yoshizawa's two-scale direct interaction approximation to the compressible equations of motion linearized about a state of incompressible turbulence. The result is a generalization of the eddy viscosity representation of incompressible turbulence. In addition to the usual incompressible eddy viscosity, the calculation generates eddy diffusivities for entropy and pressure, and an effective bulk viscosity acting on the mean flow. The compressible fluctuations also generate an effective turbulent mean pressure and corrections to the speed of sound. Finally, a prediction unique to Yoshizawa's two-scale approximation is that terms containing gradients of incompressible turbulence quantities also appear in the mean flow equations. The form these terms take is described.

Energy-absorption spectroscopy of unitary Fermi gases in a uniform potential

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Yu, Zhenhua

2018-04-01

We propose to use the energy absorption spectroscopy to measure the kinetic coefficients of unitary Fermi gases in a uniform potential. We show that, in our scheme, the energy absorption spectrum is proportional to the dynamic structure factor of the system. The profile of the spectrum depends on the shear viscosity η , the thermal conductivity κ , and the superfluid bulk viscosity ξ3. We show that extraction of these coefficients from the spectrum is achievable in present experiments.

Effects of heat conduction on artificial viscosity methods for shock capturing

DOE PAGES

Cook, Andrew W.

2013-12-01

Here we investigate the efficacy of artificial thermal conductivity for shock capturing. The conductivity model is derived from artificial bulk and shear viscosities, such that stagnation enthalpy remains constant across shocks. By thus fixing the Prandtl number, more physical shock profiles are obtained, only on a larger scale. The conductivity model does not contain any empirical constants. It increases the net dissipation of a computational algorithm but is found to better preserve symmetry and produce more robust solutions for strong-shock problems.

Dynamic acid/base equilibrium in single component switchable ionic liquids and consequences on viscosity

DOE PAGES

Cantu, David C.; Lee, Juntaek; Lee, Mal -Soon; ...

2016-03-28

The deployment of transformational non-aqueous CO 2-capture solvent systems is encumbered by high viscosity even at intermediate uptakes. Using single-molecule CO 2 binding organic liquids as a prototypical example, we identify the key molecular features controlling bulk liquid viscosity and CO 2 uptake kinetics. Fast uptake kinetics arise from close proximity of the alcohol and amine sites that are involved in CO 2 binding. This process results in the concerted formation of a Zwitterion containing both an alkylcarbonate and a protonated amine. The hydrogen bonding between the two functional groups ultimately determines the solution viscosity. Based on molecular simulation, thismore » work reveals options to significantly reduce viscosity with molecular modifications that shift the proton transfer equilibrium towards a neutral acid/amine species as opposed to the ubiquitously accepted Zwitterionic state. Lastly, the molecular design concepts proposed here, for the alkyl-carbonate systems, are readily extensible to other CO 2 capture technologies, such as the carbamate- or imidazole-based solvent chemistries.« less

Hyperviscosity for unstructured ALE meshes

NASA Astrophysics Data System (ADS)

Cook, Andrew W.; Ulitsky, Mark S.; Miller, Douglas S.

2013-01-01

An artificial viscosity, originally designed for Eulerian schemes, is adapted for use in arbitrary Lagrangian-Eulerian simulations. Changes to the Eulerian model (dubbed 'hyperviscosity') are discussed, which enable it to work within a Lagrangian framework. New features include a velocity-weighted grid scale and a generalised filtering procedure, applicable to either structured or unstructured grids. The model employs an artificial shear viscosity for treating small-scale vorticity and an artificial bulk viscosity for shock capturing. The model is based on the Navier-Stokes form of the viscous stress tensor, including the diagonal rate-of-expansion tensor. A second-order version of the model is presented, in which Laplacian operators act on the velocity divergence and the grid-weighted strain-rate magnitude to ensure that the velocity field remains smooth at the grid scale. Unlike sound-speed-based artificial viscosities, the hyperviscosity model is compatible with the low Mach number limit. The new model outperforms a commonly used Lagrangian artificial viscosity on a variety of test problems.

Thickness Dependent Effective Viscosity of a Polymer Solution near an Interface Probed by a Quartz Crystal Microbalance with Dissipation Method

PubMed Central

Fang, Jiajie; Zhu, Tao; Sheng, Jie; Jiang, Zhongying; Ma, Yuqiang

2015-01-01

The solution viscosity near an interface, which affects the solution behavior and the molecular dynamics in the solution, differs from the bulk. This paper measured the effective viscosity of a dilute poly (ethylene glycol) (PEG) solution adjacent to a Au electrode using the quartz crystal microbalance with dissipation (QCM-D) technique. We evidenced that the effect of an adsorbed PEG layer can be ignored, and calculated the zero shear rate effective viscosity to remove attenuation of high shear frequency oscillations. By increasing the overtone n from 3 to 13, the thickness of the sensed polymer solution decreased from ~70 to 30 nm. The zero shear rate effective viscosity of the polymer solution and longest relaxation time of PEG chains within it decrease with increasing solution thickness. The change trends are independent of the relation between the apparent viscosity and shear frequency and the values of the involved parameter, suggesting that the polymer solution and polymer chains closer to a solid substrate have a greater effective viscosity and slower relaxation mode, respectively. This method can study the effect of an interface presence on behavior and phenomena relating to the effective viscosity of polymer solutions, including the dynamics of discrete polymer chains. PMID:25684747

Confinement in Melts of Chains with Junction Points, but No Ends

NASA Astrophysics Data System (ADS)

Foster, Mark; He, Qiming; Zhou, Yang; Zhang, Fan; Huang, Chongwen; Narayanan, Suresh

Measurements of surface fluctuations of 4-arm star and ''8-shaped'' analogs of the same polystyrene (PS) chain show that elimination of chain ends is much more important in dictating the fragility in a thin film than is the introduction of a branch point in the molecule. Both the viscosities derived from surface fluctuations and rheological measurements for the 8-shaped PS manifest a lower value than the 4-arm star PS analog, with the discrepancy increasing as the temperature approaches the glass transition temperature, Tg , bulk. Comparison among different chain topologies shows the effect of the number of chain ends and junction point on the viscosity. The viscosity behavior of the 8-shaped PS is quite different from that of the star analog, but similar to that of the simple cycle analog. The fragility of the 8-shaped molecule in the thin film is reduced relative to that in the bulk, manifesting a nanoconfinement effect. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

PubMed

Francis, Laurent A; Friedt, Jean-Michel; Zhou, Cheng; Bertrand, Patrick

2006-06-15

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

Micro-rheology and interparticle interactions in aerosols probed with optical tweezers

NASA Astrophysics Data System (ADS)

Reid, Jonathan P.; Power, Rory M.; Cai, Chen; Simpson, Stephen H.

2014-09-01

Using optical tweezers for micro-rheological investigations of a surrounding fluid has been routinely demonstrated. In this work, we will demonstrate that rheological measurements of the bulk and surface properties of aerosol particles can be made directly using optical tweezers, providing important insights into the phase behavior of materials in confined environments and the rate of molecular diffusion in viscous phases. The use of holographic optical tweezers to manipulate aerosol particles has become standard practice in recent years, providing an invaluable tool to investigate particle dynamics, including evaporation/ condensation kinetics, chemical aging and phase transformation. When combined with non-linear Raman spectroscopy, the size and refractive index of a particle can be determined with unprecedented accuracy <+/- 0.05%). Active control of the relative positions of pairs of particles can allow studies of the coalescence of particles, providing a unique opportunity to investigate the bulk and surface properties that govern the hydrodynamic relaxation in particle shape. In particular, we will show how the viscosity and surface tension of particles can be measured directly in the under-damped regime at low viscosity. In the over-damped regime, we will show that viscosity measurements can extend close to the glass transition, allowing measurements over an impressive dynamic range of 12 orders of magnitude in relaxation timescale and viscosity. Indeed, prior to the coalescence event, we will show how the Brownian trajectories of trapped particles can yield important and unique insights into the interactions of aerosol particles.

Numerical computations of the dynamics of fluidic membranes and vesicles

NASA Astrophysics Data System (ADS)

Barrett, John W.; Garcke, Harald; Nürnberg, Robert

2015-11-01

Vesicles and many biological membranes are made of two monolayers of lipid molecules and form closed lipid bilayers. The dynamical behavior of vesicles is very complex and a variety of forms and shapes appear. Lipid bilayers can be considered as a surface fluid and hence the governing equations for the evolution include the surface (Navier-)Stokes equations, which in particular take the membrane viscosity into account. The evolution is driven by forces stemming from the curvature elasticity of the membrane. In addition, the surface fluid equations are coupled to bulk (Navier-)Stokes equations. We introduce a parametric finite-element method to solve this complex free boundary problem and present the first three-dimensional numerical computations based on the full (Navier-)Stokes system for several different scenarios. For example, the effects of the membrane viscosity, spontaneous curvature, and area difference elasticity (ADE) are studied. In particular, it turns out, that even in the case of no viscosity contrast between the bulk fluids, the tank treading to tumbling transition can be obtained by increasing the membrane viscosity. Besides the classical tank treading and tumbling motions, another mode (called the transition mode in this paper, but originally called the vacillating-breathing mode and subsequently also called trembling, transition, and swinging mode) separating these classical modes appears and is studied by us numerically. We also study how features of equilibrium shapes in the ADE and spontaneous curvature models, like budding behavior or starfish forms, behave in a shear flow.

Resin additive improves performance of high-temperature hydrocarbon lubricants

NASA Technical Reports Server (NTRS)

Johnson, R. L.; Loomis, W. R.

1971-01-01

Paraffinic resins, in high temperature applications, improve strength of thin lubricant film in Hertzian contacts even though they do not increase bulk oil viscosity. Use of resin circumvents corrosivity and high volatility problems inherent with many chemical additives.

Influence of mixing conditions on the rheological properties and structure of capillary suspensions

PubMed Central

Bossler, Frank; Weyrauch, Lydia; Schmidt, Robert; Koos, Erin

2017-01-01

The rheological properties of a suspension can be dramatically altered by adding a small amount of a secondary fluid that is immiscible with the bulk liquid. These capillary suspensions exist either in the pendular state where the secondary fluid preferentially wets the particles or the capillary state where the bulk fluid is preferentially wetting. The yield stress, as well as storage and loss moduli, depends on the size and distribution of secondary phase droplets created during sample preparation. Enhanced droplet breakup leads to stronger sample structures. In capillary state systems, this can be achieved by increasing the mixing speed and time of turbulent mixing using a dissolver stirrer. In the pendular state, increased mixing speed also leads to better droplet breakup, but spherical agglomeration is favored at longer times decreasing the yield stress. Additional mixing with a ball mill is shown to be beneficial to sample strength. The influence of viscosity variance between the bulk and second fluid on the droplet breakup is excluded by performing experiments with viscosity-matched fluids. These experiments show that the capillary state competes with the formation of Pickering emulsion droplets and is often more difficult to achieve than the pendular state. PMID:28194044

Dynamics and structures of transitional viscoelastic turbulence in channel flow

NASA Astrophysics Data System (ADS)

Shekar, Ashwin; Wang, Sung-Ning; Graham, Michael

2017-11-01

Introducing a trace amount of polymer into turbulent flows can result in a substantial reduction of drag. However, the mechanism is not fully understood at high levels of drag reduction. In this work we perform direct numerical simulations (DNS) of viscoelastic channel flow turbulence using a scheme that guarantees the positive-definiteness of polymer conformation tensor without artificial diffusion. Here we present the results of two parametric studies with the bulk Reynolds number fixed at 2000. First, the Weissenberg number (Wi) is kept at 100 and we vary the viscosity ratio (ratio ratio of the solvent viscosity and the total viscosity). Maximum drag reduction (MDR) is observed with viscosity ratio <0.95. As we decrease the viscosity ratio, i.e. increase polymer concentration, the mean velocity profile is almost invariant. However, this is accompanied by a decrease in velocity fluctuations but the flow stays turbulent. Turbulent kinetic energy budget analysis shows that, in this parameter regime, polymer becomes the major source of velocity fluctuations, replacing the energy transfer from the mean flow. In the second study, we fix the viscosity ratio at 0.95 and trace the Wi up to this regime and present the accompanying changes in flow quantities and structures.

Passive non-linear microrheology for determining extensional viscosity

NASA Astrophysics Data System (ADS)

Hsiao, Kai-Wen; Dinic, Jelena; Ren, Yi; Sharma, Vivek; Schroeder, Charles M.

2017-12-01

Extensional viscosity is a key property of complex fluids that greatly influences the non-equilibrium behavior and processing of polymer solutions, melts, and colloidal suspensions. In this work, we use microfluidics to determine steady extensional viscosity for polymer solutions by directly observing particle migration in planar extensional flow. Tracer particles are suspended in semi-dilute solutions of DNA and polyethylene oxide, and a Stokes trap is used to confine single particles in extensional flows of polymer solutions in a cross-slot device. Particles are observed to migrate in the direction transverse to flow due to normal stresses, and particle migration is tracked and quantified using a piezo-nanopositioning stage during the microfluidic flow experiment. Particle migration trajectories are then analyzed using a second-order fluid model that accurately predicts that migration arises due to normal stress differences. Using this analytical framework, extensional viscosities can be determined from particle migration experiments, and the results are in reasonable agreement with bulk rheological measurements of extensional viscosity based on a dripping-onto-substrate method. Overall, this work demonstrates that non-equilibrium properties of complex fluids can be determined by passive yet non-linear microrheology.

Crustal Viscosity Structure Estimated from Multi-Phase Mixing Theory

NASA Astrophysics Data System (ADS)

Shinevar, W. J.; Behn, M. D.; Hirth, G.

2014-12-01

Estimates of lower crustal viscosity are typically constrained by analyses of isostatic rebound, post seismic creep, and laboratory-derived flow laws for crustal rocks and minerals. Here we follow a new approach for calculating the viscosity structure of the lower continental crust. We use Perple_X to calculate mineral assemblages for different crustal compositions. Effective viscosity is then calculated using the rheologic mixing model of Huet et al. (2014) incorporating flow laws for each mineral phase. Calculations are performed along geotherms appropriate for the Basin and Range, Tibetan Plateau, Colorado Plateau, and the San Andreas Fault. To assess the role of crustal composition on viscosity, we examined two compositional gradients extending from an upper crust with ~67 wt% SiO2 to a lower crust that is either: (i) basaltic with ~53 wt% SiO2 (Rudnick and Gao, 2003), or (ii) andesitic with ~64% SiO2 (Hacker et al., 2011). In all cases, the middle continental crust has a viscosity that is 2-3 orders of magnitude greater than that inferred for wet quartz, a common proxy for mid-crustal viscosities. An andesitic lower crust results in viscosities of 1020-1021 Pa-s and 1021-1022 Pa-s for hotter and colder crustal geotherms, respectively. A mafic lower crust predicts viscosities that are an order of magnitude higher for the same geotherm. In all cases, the viscosity calculated from the mixing model decreases less with depth compared to single-phase estimates. Lastly, for anhydrous conditions in which alpha quartz is stable, we find that there is a strong correlation between Vp/Vs and bulk viscosity; in contrast, little to no correlation exists for hydrous conditions.

The University of Arizona program in solid propellants

NASA Technical Reports Server (NTRS)

Ramohalli, Kumar

1989-01-01

The University of Arizona program is aimed at introducing scientific rigor to the predictability and quality assurance of composite solid propellants. Two separate approaches are followed: to use the modern analytical techniques to experimentally study carefully controlled propellant batches to discern trends in mixing, casting, and cure; and to examine a vast bank of data, that has fairly detailed information on the ingredients, processing, and rocket firing results. The experimental and analytical work is described briefly. The principle findings were that: (1) pre- (dry) blending of the coarse and fine ammonium perchlorate can significantly improve the uniformity of mixing; (2) the Fourier transformed IR spectra of the uncured and cured polymer have valuable data on the state of the fuel; (3) there are considerable non-uniformities in the propellant slurry composition near the solid surfaces (blades, walls) compared to the bulk slurry; and (4) in situ measurements of slurry viscosity continuously during mixing can give a good indication of the state of the slurry. Several important observations in the study of the data bank are discussed.

Two fluid anisotropic dark energy models in a scale invariant theory

NASA Astrophysics Data System (ADS)

Tripathy, S. K.; Mishra, B.; Sahoo, P. K.

2017-09-01

Some anisotropic Bianchi V dark energy models are investigated in a scale invariant theory of gravity. We consider two non-interacting fluids such as dark energy and a bulk viscous fluid. Dark energy pressure is considered to be anisotropic in different spatial directions. A dynamically evolving pressure anisotropy is obtained from the models. The models favour phantom behaviour. It is observed that, in presence of dark energy, bulk viscosity has no appreciable effect on the cosmic dynamics.

Progression towards optimization of viscosity of highly concentrated carbonaceous solid-water slurries by incorporating and modifying surface chemistry parameters with and without additives

NASA Astrophysics Data System (ADS)

Mukherjee, Amrita

Carbonaceous solid-water slurries (CSWS) are concentrated suspensions of coal, petcoke bitumen, pitch etc. in water which are used as feedstock for gasifiers. The high solid loading (60-75 wt.%) in the slurry increases CSWS viscosity. For easier handling and pumping of these highly loaded mixtures, low viscosities are desirable. Depending on the nature of the carbonaceous solid, solids loading in the slurry and the particle size distribution, viscosity of a slurry can vary significantly. Ability to accurately predict the viscosity of a slurry will provide a better control over the design of slurry transport system and for viscosity optimization. The existing viscosity prediction models were originally developed for hard-sphere suspensions and therefore do not take into account surface chemistry. As a result, the viscosity predictions using these models for CSWS are not very accurate. Additives are commonly added to decrease viscosity of the CSWS by altering the surface chemistry. Since additives are specific to CSWS, selection of appropriate additives is crucial. The goal of this research was to aid in optimization of CSWS viscosity through improved prediction and selection of appropriate additive. To incorporate effect of surface chemistry in the models predicting suspension viscosity, the effect of the different interfacial interactions caused by different surface chemistries has to be accounted for. Slurries of five carbonaceous solids with varying O/C ratio (to represent different surface chemistry parameters) were used for the study. To determine the interparticle interactions of the carbonaceous solids in water, interfacial energies were calculated on the basis of surface chemistries, characterized by contact angles and zeta potential measurements. The carbonaceous solid particles in the slurries were assumed to be spherical. Polar interaction energy (hydrophobic/hydrophilic interaction energy), which was observed to be 5-6 orders of magnitude higher than the electrostatic interaction energy, and the van der Waals interaction energy, was clearly the dominant interaction energy for such a system. Hydrophobic interactions lead to the formation of aggregation networks of solids in the suspensions, entrapping a part of the bulk water, whereas hydrophilic interactions result in the formation of hydration layers around carbonaceous solids. Both of these phenomena cause a loss of bulk water from the slurry and increase the effective solid volume fraction, resulting in an increase in slurry viscosity. The water in the bulk of the slurry, responsible for the fluidity of the slurry is called free water. The amount of free water was determined using thermogravimetric analysis and was observed to increase with an increase in the O/C ratio of a carbonaceous solid (up to ˜20%). The free water to total water ratio was observed to be constant for the slurry of a particular carbonaceous solid for various loadings of solids (44 wt.% to 67 wt.%). The increase in the effective solid volume fractions of slurries was determined using viscosity measurements. A relationship between the effective solid volume fraction and the O/C ratio of the carbonaceous solid was developed. This correlation was then incorporated into the existing equation for viscosity prediction (developed based on particle size distribution and solid volume fraction), to account for the surface chemistry of the carbonaceous solid and hence improve the predictive capabilities. This modified equation was validated using three concentrated carbonaceous slurries with different particle size distributions and was observed to significantly improve accuracy of prediction (deviation of predicted results decreased from up to 96% to 25%). The validation was performed with a lignite, bituminous coal and a petcoke-all with low ash yield. Additives modify the surface chemistry of the carbonaceous solids, thereby affecting the interfacial interactions. Through this research, the effects of additives on the interfacial interactions and hence on slurry viscosity were determined. Since the additives used are specific to the surface chemistry of the solids in the slurry, this knowledge aids in the selection of the appropriate additive. The study was conducted using three carbonaceous solids with different O/C ratios and an anionic and a non-ionic additive. The adsorption of the additives on the carbonaceous solids, the change in the zeta potential and hydrophobicity/hydrophilicity of the solids and the change in the free water content of the slurries were determined. The adsorption of the additives increased with an increase in the mineral matter content of the carbonaceous solids. There was also an increase in the zeta potential of the carbonaceous solids in water upon the addition of the anionic additive (up to ˜30%). However, the calculated resultant electrostatic repulsion energy upon the addition of the anionic additive was 5-6 orders of magnitude lower than the polar interaction energy of the carbonaceous solids in water. Contact angle measurements indicated that both additives changed the hydrophobicity/hydrophilicity of the solid surface (by up to 70°). This resulted in the release of bound water into the bulk slurries (up to 6%), resulting in greater fluidity. The increase in free water content of the slurries with additives was confirmed by thermogravimetric analysis (TGA). A correlation predicting the slurry viscosity on the basis of the weight fraction of free water in the slurries with additives was also developed.

Reversing the direction of galvanotaxis with controlled increases in boundary layer viscosity

NASA Astrophysics Data System (ADS)

Kobylkevich, Brian M.; Sarkar, Anyesha; Carlberg, Brady R.; Huang, Ling; Ranjit, Suman; Graham, David M.; Messerli, Mark A.

2018-05-01

Weak external electric fields (EFs) polarize cellular structure and direct most migrating cells (galvanotaxis) toward the cathode, making it a useful tool during tissue engineering and for healing epidermal wounds. However, the biophysical mechanisms for sensing weak EFs remain elusive. We have reinvestigated the mechanism of cathode-directed water flow (electro-osmosis) in the boundary layer of cells, by reducing it with neutral, viscous polymers. We report that increasing viscosity with low molecular weight polymers decreases cathodal migration and promotes anodal migration in a concentration dependent manner. In contrast, increased viscosity with high molecular weight polymers does not affect directionality. We explain the contradictory results in terms of porosity and hydraulic permeability between the polymers rather than in terms of bulk viscosity. These results provide the first evidence for controlled reversal of galvanotaxis using viscous agents and position the field closer to identifying the putative electric field receptor, a fundamental, outside-in signaling receptor that controls cellular polarity for different cell types.

Reversing the direction of galvanotaxis with controlled increases in boundary layer viscosity.

PubMed

Kobylkevich, Brian M; Sarkar, Anyesha; Carlberg, Brady R; Huang, Ling; Ranjit, Suman; Graham, David M; Messerli, Mark A

2018-03-09

Weak external electric fields (EFs) polarize cellular structure and direct most migrating cells (galvanotaxis) toward the cathode, making it a useful tool during tissue engineering and for healing epidermal wounds. However, the biophysical mechanisms for sensing weak EFs remain elusive. We have reinvestigated the mechanism of cathode-directed water flow (electro-osmosis) in the boundary layer of cells, by reducing it with neutral, viscous polymers. We report that increasing viscosity with low molecular weight polymers decreases cathodal migration and promotes anodal migration in a concentration dependent manner. In contrast, increased viscosity with high molecular weight polymers does not affect directionality. We explain the contradictory results in terms of porosity and hydraulic permeability between the polymers rather than in terms of bulk viscosity. These results provide the first evidence for controlled reversal of galvanotaxis using viscous agents and position the field closer to identifying the putative electric field receptor, a fundamental, outside-in signaling receptor that controls cellular polarity for different cell types.

Bulk viscosity and relaxation time of causal dissipative relativistic fluid dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang Xuguang; Rischke, Dirk H.; Institut fuer Theoretische Physik, J.W. Goethe-Universitaet, D-60438 Frankfurt am Main

2011-02-15

The microscopic formulas of the bulk viscosity {zeta} and the corresponding relaxation time {tau}{sub {Pi}} in causal dissipative relativistic fluid dynamics are derived by using the projection operator method. In applying these formulas to the pionic fluid, we find that the renormalizable energy-momentum tensor should be employed to obtain consistent results. In the leading-order approximation in the chiral perturbation theory, the relaxation time is enhanced near the QCD phase transition, and {tau}{sub {Pi}} and {zeta} are related as {tau}{sub {Pi}={zeta}}/[{beta}{l_brace}(1/3-c{sub s}{sup 2})({epsilon}+P)-2({epsilon}-3P)/9{r_brace}], where {epsilon}, P, and c{sub s} are the energy density, pressure, and velocity of sound, respectively. The predictedmore » {zeta} and {tau}{sub {Pi}} should satisfy the so-called causality condition. We compare our result with the results of the kinetic calculation by Israel and Stewart and the string theory, and confirm that all three approaches are consistent with the causality condition.« less

Probing the micro-rheological properties of aerosol particles using optical tweezers

NASA Astrophysics Data System (ADS)

Power, Rory M.; Reid, Jonathan P.

2014-07-01

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability.

Thermomechanical earthquake cycle simulations with rate-and-state friction and nonlinear viscoelasticity

NASA Astrophysics Data System (ADS)

Allison, K. L.; Dunham, E. M.

2017-12-01

We simulate earthquake cycles on a 2D strike-slip fault, modeling both rate-and-state fault friction and an off-fault nonlinear power-law rheology. The power-law rheology involves an effective viscosity that is a function of temperature and stress, and therefore varies both spatially and temporally. All phases of the earthquake cycle are simulated, allowing the model to spontaneously generate earthquakes, and to capture frictional afterslip and postseismic and interseismic viscous flow. We investigate the interaction between fault slip and bulk viscous flow, using experimentally-based flow laws for quartz-diorite in the crust and olivine in the mantle, representative of the Mojave Desert region in Southern California. We first consider a suite of three linear geotherms which are constant in time, with dT/dz = 20, 25, and 30 K/km. Though the simulations produce very different deformation styles in the lower crust, ranging from significant interseismc fault creep to purely bulk viscous flow, they have almost identical earthquake recurrence interval, nucleation depth, and down-dip coseismic slip limit. This indicates that bulk viscous flow and interseismic fault creep load the brittle crust similarly. The simulations also predict unrealistically high stresses in the upper crust, resulting from the fact that the lower crust and upper mantle are relatively weak far from the fault, and from the relatively small role that basal tractions on the base of the crust play in the force balance of the lithosphere. We also find that for the warmest model, the effective viscosity varies by an order of magnitude in the interseismic period, whereas for the cooler models it remains roughly constant. Because the rheology is highly sensitive to changes in temperature, in addition to the simulations with constant temperature we also consider the effect of heat generation. We capture both frictional heat generation and off-fault viscous shear heating, allowing these in turn to alter the effective viscosity. The resulting temperature changes may reduce the width of the shear zone in the lower crust and upper mantle, and reduce the effective viscosity.

Internal friction controls the speed of protein folding from a compact configuration.

PubMed

Pabit, Suzette A; Roder, Heinrich; Hagen, Stephen J

2004-10-05

Several studies have found millisecond protein folding reactions to be controlled by the viscosity of the solvent: Reducing the viscosity allows folding to accelerate. In the limit of very low solvent viscosity, however, one expects a different behavior. Internal interactions, occurring within the solvent-excluded interior of a compact molecule, should impose a solvent-independent upper limit to folding speed once the bulk diffusional motions become sufficiently rapid. Why has this not been observed? We have studied the effect of solvent viscosity on the folding of cytochrome c from a highly compact, late-stage intermediate configuration. Although the folding rate accelerates as the viscosity declines, it tends toward a finite limiting value approximately 10(5) s(-1) as the viscosity tends toward zero. This limiting rate is independent of the cosolutes used to adjust solvent friction. Therefore, interactions within the interior of a compact denatured polypeptide can limit the folding rate, but the limiting time scale is very fast. It is only observable when the solvent-controlled stages of folding are exceedingly rapid or else absent. Interestingly, we find a very strong temperature dependence in these "internal friction"-controlled dynamics, indicating a large energy scale for the interactions that govern reconfiguration within compact, near-native states of a protein.

Long-time tails of the green-kubo integrands for a binary mixture

NASA Astrophysics Data System (ADS)

Wood, W. W.

1989-11-01

The long-time tails for the mutual diffusion coefficient, the thermal diffusivity, the thermal conductivity, and the shear and longitudinal viscosities (from which the tail of the bulk viscosity can be calculated) of a nonreactive binary mixture are calculated from mode-coupling theory, and compared with a prior calculation by Pomeau. Three different choices of the thermal forces and currents are considered, with the results found to take their simplest form in the case of the de Groot "double-primed set". The decompositions into the kinetic, potential, and cross terms are given.

Microrheology with optical tweezers: measuring the relative viscosity of solutions 'at a glance'.

PubMed

Tassieri, Manlio; Del Giudice, Francesco; Robertson, Emma J; Jain, Neena; Fries, Bettina; Wilson, Rab; Glidle, Andrew; Greco, Francesco; Netti, Paolo Antonio; Maffettone, Pier Luca; Bicanic, Tihana; Cooper, Jonathan M

2015-03-06

We present a straightforward method for measuring the relative viscosity of fluids via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method are evident when it is adopted for measurements of materials whose availability is limited, such as those involved in biological studies. The method has been validated by direct comparison with conventional bulk rheology methods, and has been applied both to characterise synthetic linear polyelectrolytes solutions and to study biomedical samples.

Microrheology with Optical Tweezers: Measuring the relative viscosity of solutions ‘at a glance'

PubMed Central

Tassieri, Manlio; Giudice, Francesco Del; Robertson, Emma J.; Jain, Neena; Fries, Bettina; Wilson, Rab; Glidle, Andrew; Greco, Francesco; Netti, Paolo Antonio; Maffettone, Pier Luca; Bicanic, Tihana; Cooper, Jonathan M.

2015-01-01

We present a straightforward method for measuring the relative viscosity of fluids via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method are evident when it is adopted for measurements of materials whose availability is limited, such as those involved in biological studies. The method has been validated by direct comparison with conventional bulk rheology methods, and has been applied both to characterise synthetic linear polyelectrolytes solutions and to study biomedical samples. PMID:25743468

A Classical Phase Space Framework For the Description of Supercooled Liquids and an Apparent Universal Viscosity Collapse

NASA Astrophysics Data System (ADS)

Weingartner, Nicholas; Pueblo, Chris; Nogueira, Flavio; Kelton, Kenneth; Nussinov, Zohar

A fundamental understanding of the phenomenology of the metastable supercooled liquid state remains elusive. Two of the most pressing questions in this field are how to describe the temperature dependence of the viscosity, and determine whether or not the dynamical behaviors are universal. To address these questions, we have devised a simple first-principles classical phase space description of supercooled liquids that (along with a complementary quantum approach) predicts a unique functional form for the viscosity which relies on only a single parameter. We tested this form for 45 liquids of all types and fragilities, and have demonstrated that it provides a statistically significant fit to all liquids. Additionally, by scaling the viscosity of all studied liquids using the single parameter, we have observed a complete collapse of the data of all 45 liquids to a single scaling curve over 16 decades, suggesting an underlying universality in the dynamics of supercooled liquids. In this talk I will outline the basic approach of our model, as well as demonstrate the quality of the model performance and collapse of the data.

Entropy production due to gravitational-wave viscosity in a Kaluza-Klein inflationary universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomita, K.; Ishihara, H.

1985-10-15

The role of viscosity due to the transport of gravitational radiation in a Kaluza-Klein multidimensional universe is considered, and it is shown that vast entropy may be produced by it owing to inflation of the external (ordinary) space and collapse of the internal (compact) space. The inflation and collapse factors necessary for increasing the total entropy by a factor approx.10/sup 88/ are derived.

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications

NASA Astrophysics Data System (ADS)

Robinson, Joshua W.; Zhou, Yan; Bhattacharya, Priyanka; Erck, Robert; Qu, Jun; Bays, J. Timothy; Cosimbescu, Lelia

2016-01-01

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acids (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach.

Online measurement of viscosity for biological systems in stirred tank bioreactors.

PubMed

Schelden, Maximilian; Lima, William; Doerr, Eric Will; Wunderlich, Martin; Rehmann, Lars; Büchs, Jochen; Regestein, Lars

2017-05-01

One of the most critical parameters in chemical and biochemical processes is the viscosity of the medium. Its impact on mixing, as well as on mass and energy transfer is substantial. An increase of viscosity with reaction time can be caused by the formation of biopolymers like xanthan or by filamentous growth of microorganisms. In either case the properties of fermentation broth are changing and frequently non-Newtonian behavior are observed, resulting in major challenges for the measurement and control of mixing and mass transfer. This study demonstrates a method for the online determination of the viscosity inside a stirred tank reactor. The presented method is based on online measurement of heat transfer capacity from the bulk medium to the jacket of the reactor. To prove the feasibility of the method, fermentations with the xanthan producing bacterium Xanthomonas campestris pv. campestris B100 as model system were performed. Excellent correlation between offline measured apparent viscosity and online determined heat transfer capacity were found. The developed tool should be applicable to any other process with formation of biopolymers and filamentous growth. Biotechnol. Bioeng. 2017;114: 990-997. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

On the measurement of the relative viscosity of suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acrivos, A.; Fan, X.; Mauri, R.

The relative viscosity of a suspension of rigid, noncolloidal particles immersed in a Newtonian fluid was measured in a Couette device and was found to be shear thinning even for values of the solids fraction as low as 20%. Although such behavior was reported previously, no satisfactory explanation appears to have been given thus far. It shall be shown presently, however, that, at least for our systems, this shear-thinning effect was due to a slight mismatch in the densities of the two phases. Moreover, the apparent relative viscosities measured in our apparatus were found to be in excellent agreement withmore » those predicted theoretically using a model, originally proposed by Leighton and Acrivos [Chem. Eng. Sci. [bold 41], 1377--1384 (1986)], to describe viscous resuspension, according to which the measured relative viscosity should depend on the bulk particle concentration and on the dimensionless Shields number [ital A], and should attain its correct value for a well-mixed suspension only as [ital A][r arrow][infinity]. The predictions of this model are also in excellent agreement with the measured transient response of the apparent relative viscosity due to a sudden change in the shear rate.« less

Cryovolcanic emplacement of domes on Europa

NASA Astrophysics Data System (ADS)

Quick, Lynnae C.; Glaze, Lori S.; Baloga, Stephen M.

2017-03-01

Here we explore the hypothesis that certain domes on Europa may have been produced by the extrusion of viscous cryolavas. A new mathematical method for the emplacement and relaxation of viscous lava domes is presented and applied to putative cryovolcanic domes on Europa. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry, and dome relaxation is explored assuming a volume of cryolava has been rapidly emplaced onto the surface. Nonphysical singularities inherent in previous models for dome relaxation have been eliminated, and cryolava cooling is represented by a time-variable viscosity. We find that at the onset of relaxation, bulk kinematic viscosities may lie in the range between 103 and 106 m2/s, while the actual fluid lava viscosity may be much lower. Plausible relaxation times to form the domes, which are linked to bulk cryolava rheology, are found to range from 3.6 days to 7.5 years. We find that cooling of the cryolava, while dominated by conduction through an icy skin, should not prevent fluids from advancing and relaxing to form domes within the timescales considered. Determining the range of emplacement conditions for putative cryolava domes will shed light on Europa's resurfacing history. In addition, the rheologies and compositions of erupted cryolavas have implications for subsurface cryomagma ascent and local surface stress conditions on Europa.

Cryovolcanic Emplacement of Domes on Europa

NASA Technical Reports Server (NTRS)

Quick, Lynnae C.; Glaze, Lori S.; Baloga, Stephen M.

2016-01-01

Here we explore the hypothesis that certain domes on Europa may have been produced by the extrusion of viscous cryolavas. A new mathematical method for the emplacement and relaxation of viscous lava domes is presented and applied to putative cryovolcanic domes on Europa. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry, and dome relaxation is explored assuming a volume of cryolava has been rapidly emplaced onto the surface. Nonphysical sin- gularities inherent in previous models for dome relaxation have been eliminated, and cryolava cooling is represented by a time-variable viscosity. We find that at the onset of relaxation, bulk kinematic viscosities may lie in the range between 10(exp 3) and 10(exp 6) sq m/s, while the actual fluid lava viscosity may be much lower. Plausible relaxation times to form the domes, which are linked to bulk cryolava rheology, are found to range from 3.6 days to 7.5 years. We find that cooling of the cryolava, while dominated by conduction through an icy skin, should not prevent fluids from advancing and relaxing to form domes within the timescales considered. Determining the range of emplacement conditions for putative cryolava domes will shed light on Europa's resurfacing history. In addition, the rheologies and compositions of erupted cryolavas have implications for subsurface cryomagma ascent and local surface stress conditions on Europa.

Effects of extrusion variables on the properties of waxy hulless barley extrudates.

PubMed

Köksel, Hamit; Ryu, Gy-Hyung; Başman, Arzu; Demiralp, Hande; Ng, Perry K W

2004-02-01

The objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory-scale corotating twin-screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170 degrees C) to develop a snack food with high beta-glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and beta-glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although beta-glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower beta-glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high beta-glucan content, especially using LS conditions.

Stress tensor and viscosity of water: Molecular dynamics and generalized hydrodynamics results

NASA Astrophysics Data System (ADS)

Bertolini, Davide; Tani, Alessandro

1995-08-01

The time correlation functions (CF's) of diagonal and off-diagonal components of the stress tensor of water have been calculated at 245 and 298 K in a molecular dynamics (MD) study on 343 molecules in the microcanonical ensemble. We present results obtained at wave number k=0 and at a few finite values of k, in the atomic and molecular formalism. In all cases, more than 98% of these functions are due to the potential term of the stress tensor. At k=0, their main features are a fast oscillatory initial decay, followed by a long-time tail more apparent in the supercooled region. Bulk and shear viscosities, calculated via Green-Kubo integration of the relevant CF at k=0, are underestimated with respect to experimental data, mainly at low temperature, but their ratio (~=2) is correctly reproduced. Both shear and bulk viscosity decrease as a function of k, the latter more rapidly, so that they become almost equal at ~=1 Å-1. Also, both viscosities drop rapidly from their maximum at ω=0. This behavior has been related to the large narrowing observed in the acoustic band, mainly in the supercooled region. The infinite frequency bulk and shear rigidity moduli have been shown to be in fair agreement with the experimental data, provided the MD value used for comparison is that corresponding to the frequency range relevant to ultrasonic measurements. The MD results of stress-stress CF's compare well with those predicted by Bertolini and Tani [Phys. Rev. E 51, 1091 (1995)] at k=0, by an application of generalized hydrodynamics [de Schepper et al., Phys. Rev. A 38, 271 (1988)] in the molecular formalism, to the same model of water (TIP4P) [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)]. These CF's are essentially equal in the atomic and molecular formalism, the only minor difference being restricted to the high frequency librational region of the shear function. By a comparison of atomic and molecular results, we show here that neglecting libration has no effect on the density-density and longitudinal current CF's and very little effect on transverse properties. On the other hand, this study points out the importance of including the oscillation in the nearest-neighbor cage in the memory function of the longitudinal and transverse current CF. The oscillatory local motion turns out to play an important role in all CF's and hence contributes significantly to the value of viscosity and of rigidity moduli.

Influence of fluid viscosity and wetting on multiscale viscoelastic lubrication in soft tribological contacts.

PubMed

Selway, Nichola; Chan, Vincent; Stokes, Jason R

2017-02-22

Friction (and lubrication) between soft contacts is prevalent in many natural and engineered systems and plays a crucial role in determining their functionality. The contribution of viscoelastic hysteresis losses to friction in these systems has been well-established and defined for dry contacts; however, the influence of fluid viscosity and wetting on these components of friction has largely been overlooked. We provide systematic experimental evidence of the influence of lubricant viscosity and wetting on lubrication across multiple regimes within a viscoelastic contact. These effects are investigated for comparatively smooth and rough elastomeric contacts (PTFE-PDMS and PDMS-PDMS) lubricated by a series of Newtonian fluids with systematically controlled viscosity and static wetting properties, using a ball-on-disc tribometer. The distinct tribological behaviour, characterised generally by a decrease in the friction coefficient with increasing fluid viscosity and wettability, is explained in terms of lubricant dewetting and squeeze-out dynamics and their impact on multi-scale viscoelastic dissipation mechanisms at the bulk-, asperity-, sub-asperity- and molecular-scale. It is proposed that lubrication within the (non-molecularly) smooth contact is governed by localised fluid entrapment and molecular-scale (interfacial) viscoelastic effects, while additional rubber hysteresis stimulated by fluid-asperity interactions, combined with rapid fluid drainage at low speeds within the rough contact, alter the general shape of the Stribeck curve. This fluid viscosity effect is in some agreement with theoretical predictions. Conventional methods for analysing and interpreting tribological data, which typically involve scaling sliding velocity with lubricant viscosity, need to be revised for viscoelastic contacts with consideration of these indirect viscosity effects.

Anisotropic flow of identified particles in Pb-Pb collisions at √SNN = 5.02 TeV

NASA Astrophysics Data System (ADS)

Bertens, Redmer Alexander

2018-02-01

Anisotropic flow is sensitive to the shear (η/s) and bulk (ζ/s) viscosity of the quark-gluon plasma created in heavy-ion collisions, as well as the initial state of such collisions and hadronization mechanisms. In these proceedings, elliptic (υ2) and higher harmonic (υ3, υ4) flow coefficients of π±, K±, p(p) and the ϕ-meson, are presented for Pb—Pb collisions at the highest-ever center-of-mass energy of = 5.02 TeV. Comparisons to hydrodynamic calculations (IP-Glasma, MUSIC, UrQMD) are shown to constrain the initial conditions and viscosity of the medium.

Analytical attractor and the divergence of the slow-roll expansion in relativistic hydrodynamics

NASA Astrophysics Data System (ADS)

Denicol, Gabriel S.; Noronha, Jorge

2018-03-01

We find the general analytical solution of the viscous relativistic hydrodynamic equations (in the absence of bulk viscosity and chemical potential) for a Bjorken expanding fluid with an ideal gas equation of state and a constant shear viscosity relaxation time. We analytically determine the hydrodynamic attractor of this fluid and discuss its properties. We show for the first time that the slow-roll expansion, a commonly used approach to characterize the attractor, diverges. This is shown to hold also in a conformal plasma. The gradient expansion is found to converge in an example where causality and stability are violated.

Detection of Liposome Membrane Viscosity Perturbations with Ratiometric Molecular Rotors

PubMed Central

Nipper, Matthew E.; Dakanali, Marianna; Theodorakis, Emmanuel

2011-01-01

Molecular rotors are a form of fluorescent intramolecular charge-transfer complexes that can undergo intramolecular twisting motion upon photoexcitation. Twisted-state formation leads to non-radiative relaxation that competes with fluorescence emission. In bulk solutions, these molecules exhibit a viscosity-dependent quantum yield. On the molecular scale, the fluorescence emission is a function of the local free volume, which in turn is related to the local microviscosity. Membrane viscosity, and the inverse; fluidity, are characteristic terms used to describe the ease of movement withing the membrane. Often, changes in membrane viscosity govern intracellular processes and are indicative of a disease state. Molecular rotors have been used to investigate viscosity changes in liposomes and cells, but accuracy is affected by local concentration gradients and sample optical properties. We have developed self-calibrating ratiometric molecular rotors to overcome this challenge and integrated the new molecules into a DLPC liposome model exposed to the membrane-fluidizing agent propanol. We show that the ratiometric emission intensity linearly decreases with the pentanol exposure and that the ratiometric intensity is widely independent of the total liposome concentration. Conversely, dye concentration inside liposomes influences the sensitivity of the system. We suggest that the new self-calibrating dyes can be used for real-time viscosity sensing in liposome systems with the advantages of lifetime measurements, but with low-cost steady-state instrumentation. PMID:21354253

Transport coefficients of Quark-Gluon plasma with full QCD potential

NASA Astrophysics Data System (ADS)

J. P., Prasanth; Bannur, Vishnu M.

2018-05-01

The shear viscosity η, bulk viscosity ζ and their ratio with the entropy density, η / s, ζ / s have been studied in a quark-gluon plasma (QGP) within the cluster expansion method. The cluster expansion method allows us to include the interaction between the partons in the deconfined phase and to calculate the equation of state of quark-gluon plasma. It has been argued that the interactions present in the equation of state, the modified Cornell potential significantly contributes to the viscosity. The results obtained within our approaches agree with lattice quantum chromodynamics (LQCD) equation of state. We obtained η / s ≈ 0 . 128 within the temperature range T /Tc ∈ [ 0 . 9 , 1 . 5 ] which is very close to the theoretical lower bound η / s ≥ 1 /(4 π) in Yang-Mills theory. We also demonstrate that the effects of ζ / s at freezeout are possibly large.

Microfluidic rheology of active particle suspensions: Kinetic theory.

PubMed

Alonso-Matilla, Roberto; Ezhilan, Barath; Saintillan, David

2016-07-01

We analyze the effective rheology of a dilute suspension of self-propelled slender particles confined between two infinite parallel plates and subject to a pressure-driven flow. We use a continuum kinetic model to describe the configuration of the particles in the system, in which the disturbance flows induced by the swimmers are taken into account, and use it to calculate estimates of the suspension viscosity for a range of channel widths and flow strengths typical of microfluidic experiments. Our results are in agreement with previous bulk models, and in particular, demonstrate that the effect of activity is strongest at low flow rates, where pushers tend to decrease the suspension viscosity whereas pullers enhance it. In stronger flows, dissipative stresses overcome the effects of activity leading to increased viscosities followed by shear-thinning. The effects of confinement and number density are also analyzed, and our results confirm the apparent transition to superfluidity reported in recent experiments on pusher suspensions at intermediate densities. We also derive an approximate analytical expression for the effective viscosity in the limit of weak flows and wide channels, and demonstrate good agreement between theory and numerical calculations.

Capillary waves with surface viscosity

NASA Astrophysics Data System (ADS)

Shen, Li; Denner, Fabian; Morgan, Neal; van Wachem, Berend; Dini, Daniele

2017-11-01

Experiments over the last 50 years have suggested a correlation between the surface (shear) viscosity and the stability of a foam or emulsion. With recent techniques allowing more accurate measurements of the elusive surface viscosity, we examine this link theoretically using small-amplitude capillary waves in the presence of the Marangoni effect and surface viscosity modelled via the Boussinesq-Scriven model. The surface viscosity effect is found to contribute a damping effect on the amplitude of the capillary wave with subtle differences to the effect of the convective-diffusive Marangoni transport. The general wave dispersion is augmented to take into account the Marangoni and surface viscosity effects, and a first-order correction to the critical damping wavelength is derived. The authors acknowledge the financial support of the Shell University Technology Centre for fuels and lubricants.

Jeans instability in a universe with dissipation

NASA Astrophysics Data System (ADS)

Kremer, Gilberto M.; Richarte, Martín G.; Teston, Felipe

2018-01-01

The problem of Jeans gravitational instability is investigated for static and expanding universes within the context of the five and thirteen field theories which account for viscous and thermal effects. For the five-field theory a general dispersion relation has been derived with the help of relevant linearized perturbation equations, showing that the shear viscosity parameter alters the propagating modes for large and small wavelengths. The behavior of density and temperature contrasts are analyzed for the hard-sphere model in detail. In the small wavelengths regime, increasing the amount of shear viscosity into the system forces the harmonic perturbations to damp faster, however, in the opposite limit larger values of shear viscosity lead to smaller values of density and temperature contrasts. We also consider the hyperbolic case associated with the thirteen-field theory which involves two related parameters, namely the shear viscosity and the collision frequency, the last one is due to the production terms which appear in the Grad method. The dispersion relation becomes a polynomial in the frequency with two orders higher in relation to the five-field theory, indicating that the effects associated with the shear viscosity and heat flux are nontrivial. The profile of Jeans mass in terms of the temperature and number density is explored by contrasting with several data of molecular clouds. Regarding the dynamical evolution of the density, temperature, stress and heat flux contrasts for a universe dominated by pressureless matter, we obtain also damped harmonic waves for small wavelengths. In the case of large wavelengths, the density and temperature contrasts grow with time (due to the Jeans mechanism) while the stress and heat flux contrasts heavily decay with time. For an expanding universe, the Jeans mass and Jeans length are obtained and their physical consequences are explored.

Modified Alternan: A Novel Microbial Gum with Potential as a Low-Viscosity Bulking Agent

USDA-ARS?s Scientific Manuscript database

Alternan is a microbial gum produced by rare strains of the GRAS lactic acid bacterium, Leuconostoc mesenteroides. The unique alternating alpha-(1,6) and alpha-(1,3) linkage pattern of this glucan imparts high solubility and resistance to most digestive enzymes. Previously, we invented a bioconver...

Chemically exfoliating large sheets of phosphorene via choline chloride urea viscosity-tuning

NASA Astrophysics Data System (ADS)

Ng, A.; Sutto, T. E.; Matis, B. R.; Deng, Y.; Ye, P. D.; Stroud, R. M.; Brintlinger, T. H.; Bassim, N. D.

2017-04-01

Exfoliation of two-dimensional phosphorene from bulk black phosphorous through chemical means is demonstrated where the solvent system of choice (choline chloride urea diluted with ethanol) has the ability to successfully exfoliate large-area multi-layer phosphorene sheets and further protect the flakes from ambient degradation. The intercalant solvent molecules, aided by low-powered sonication, diffuse between the layers of the bulk black phosphorus, allowing for the exfoliation of the multi-layer phosphorene through breaking of the interlayer van der Waals bonds. Through viscosity tuning, the optimal parameters (1:1 ratio between the intercalant and the diluting solvent) at which the exfoliation takes place is determined. Our exfoliation technique is shown to produce multi-layer phosphorene flakes with surface areas greater than 3 μm2 (a factor of three larger than what has previously been reported for a similar exfoliation method) while limiting exposure to the ambient environment, thereby protecting the flakes from degradation. Characterization techniques such as optical microscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, and (scanning) transmission electron microscopy are used to investigate the quality, quantity, and thickness of the exfoliated flakes.

ZnO Film Bulk Acoustic Resonator for the Kinetics Study of Human Blood Coagulation

PubMed Central

Chen, Da; Zhang, Zhen; Ma, Jilong; Wang, Wei

2017-01-01

Miniaturized and rapid blood coagulation assay technologies are critical in many clinical settings. In this paper, we present a ZnO film bulk acoustic resonator for the kinetic analysis of human blood coagulation. The resonator operated in thickness shear resonance mode at 1.4 GHz. When the resonator contacted the liquid environment, the viscous loading effect was considered as the additional resistance and inductance in the equivalent circuits, resulting in a linear relationship with a slope of approximately −217 kHz/cP between the liquid viscosity and the frequency of the resonator. The downshift of the resonant frequency and the viscosity change during the blood coagulation were correlated to monitor the coagulation process. The sigmoidal trend was observed in the frequency response for the blood samples activated by thromboplastin and calcium ions. The coagulation kinetics involving sequential phases of steady reaction, growth and saturation were revealed through the time-dependent frequency profiles. The enzymatic cascade time, the coagulation rate, the coagulation time and the clot degree were provided by fitting the time-frequency curves. The prothrombin times were compared with the results measured by a standard coagulometer and show a good correlation. Thanks to the excellent potential of integration, miniaturization and the availability of direct digital signals, the film bulk acoustic resonator has promising application for both clinical and personal use coagulation testing technologies. PMID:28467374

Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes

PubMed Central

Gugliuzza, Annarosa; Perrotta, Maria Luisa; Drioli, Enrico

2016-01-01

This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly. PMID:27196938

Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes.

PubMed

Gugliuzza, Annarosa; Perrotta, Maria Luisa; Drioli, Enrico

2016-05-16

This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly.

REVIEWS OF TOPICAL PROBLEMS: Universal viscosity growth in metallic melts at megabar pressures: the vitreous state of the Earth's inner core

NASA Astrophysics Data System (ADS)

Brazhkin, Vadim V.; Lyapin, A. G.

2000-05-01

Experimental data on and theoretical models for the viscosity of various types of liquids and melts under pressure are reviewed. Experimentally, the least studied melts are those of metals, whose viscosity is considered to be virtually constant along the melting curve. The authors' new approach to the viscosity of melts involves the measurement of the grain size in solidified samples. Measurements on liquid metals at pressures up to 10 GPa using this method show, contrary to the empirical approach, that the melt viscosity grows considerably along the melting curves. Based on the experimental data and on the critical analysis of current theories, a hypothesis of a universal viscosity behavior is introduced for liquids under pressure. Extrapolating the liquid iron results to the pressures and temperatures at the Earth's core reveals that the Earth's outer core is a very viscous melt with viscosity values ranging from 102 Pa s to 1011 Pa s depending on the depth. The Earth's inner core is presumably an ultraviscous (>1011 Pa s) glass-like liquid — in disagreement with the current idea of a crystalline inner core. The notion of the highly viscous interior of celestial bodies sheds light on many mysteries of planetary geophysics and astronomy. From the analysis of the pressure variation of the melting and glass-transition temperatures, an entirely new concept of a stable metallic vitreous state arises, calling for further experimental and theoretical study.

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications

PubMed Central

Robinson, Joshua W.; Zhou, Yan; Bhattacharya, Priyanka; Erck, Robert; Qu, Jun; Bays, J. Timothy; Cosimbescu, Lelia

2016-01-01

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acids (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach. PMID:26727881

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Joshua W.; Zhou, Yan; Bhattacharya, Priyanka

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acidsmore » (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach.« less

Two-point active microrheology in a viscous medium exploiting a motional resonance excited in dual-trap optical tweezers

NASA Astrophysics Data System (ADS)

Paul, Shuvojit; Kumar, Randhir; Banerjee, Ayan

2018-04-01

Two-point microrheology measurements from widely separated colloidal particles approach the bulk viscosity of the host medium more reliably than corresponding single-point measurements. In addition, active microrheology offers the advantage of enhanced signal to noise over passive techniques. Recently, we reported the observation of a motional resonance induced in a probe particle in dual-trap optical tweezers when the control particle was driven externally [Paul et al., Phys. Rev. E 96, 050102(R) (2017), 10.1103/PhysRevE.96.050102]. We now demonstrate that the amplitude and phase characteristics of the motional resonance can be used as a sensitive tool for active two-point microrheology to measure the viscosity of a viscous fluid. Thus, we measure the viscosity of viscous liquids from both the amplitude and phase response of the resonance, and demonstrate that the zero crossing of the phase response of the probe particle with respect to the external drive is superior compared to the amplitude response in measuring viscosity at large particle separations. We compare our viscosity measurements with those using a commercial rheometer and obtain an agreement ˜1 % . The method can be extended to viscoelastic material where the frequency dependence of the resonance may provide further accuracy for active microrheological measurements.

Laparoscopy and tribology: the effect of laparoscopic gas on peritoneal fluid.

PubMed

Ott, D E

2001-02-01

To assess the changes in viscosity of peritoneal fluid during laparoscopic exposure to CO2 insufflation. Analysis and mathematic modeling of peritoneal fluid viscosity in vivo and in vitro as a result of exposure to unconditioned CO2 (Canadian Task Force classification II-2). Medical school university research laboratory and hospital. Peritoneal fluid from 45 women. Peritoneal fluid was obtained at laparoscopy before insufflation and tested for viscosity after exposure to currently used raw dry unconditioned CO2. Peritoneal fluid viscosity was tested by viscometric methods and mathematic modeling. Initial viscosity of peritoneal fluid before gas exposure was 1.425 centipoise (cP). Viscosity measurements were obtained at 20-second intervals for gas flows of 1 and 3 L/minute. Increases in viscosity occur rapidly, and by 200 seconds it was 59 cP and 98 cP for 1 and 3 L flow rates, respectively. Very dry CO2 for laparoscopy causes peritoneal fluid viscosity to increase dramatically. (J Am Assoc Gynecol Laparosc 8(1):117-123, 2001)

Investigation of process and product parameters for physicochemical properties of rice and mung bean (Vigna radiata) flour based extruded snacks.

PubMed

Sharma, Chetan; Singh, Baljit; Hussain, Syed Zameer; Sharma, Savita

2017-05-01

PR 106 and SML 668 cultivars of rice and mung bean respectively, were studied for their potential to serve as a nutritious snack with improved protein quality and quantity. The effect of extrusion conditions, including feed moisture content (14-18%), screw speed (400-550 rpm) and barrel temperature (130-170°C) on the physicochemical properties (bulk density, water absorption index (WAI), water solubility index (WSI) and hardness) was investigated. The replacement of rice flour at 30% level with mung bean flour for making extruded snacks was evaluated. Pasting temperature increased (84-93 °C) while peak viscosity (2768-408 cP), hold viscosity (2018-369 cP), breakdown (750-39 cP), setback (2697-622 cP) and final viscosity (4715-991 cP) decreased with increasing mung bean flour addition. Increasing feed moisture lowered the specific mechanical energy (SME), WAI and WSI of extrudates whereas increased bulk density and hardness. Higher screw speed had linear positive effect on SME of extruder and negative linear effect on WAI. Positive curvilinear quadratic effect of screw speed was also observed on WSI and density. Higher barrel temperature linearly decreased the SME, density and hardness of extrudates. Developed extrusion cooked rice-mung bean snacks with increased protein content and improved protein quality along with higher dietary fibre and minerals have good potential in effectively delivering the nutrition to the population.

Physicochemical and Thermal Properties of Extruded Instant Functional Rice Porridge Powder as Affected by the Addition of Soybean or Mung Bean.

PubMed

Mayachiew, Pornpimon; Charunuch, Chulaluck; Devahastin, Sakamon

2015-12-01

Legumes contain protein, micronutrients, and bioactive compounds, which provide various health benefits. In this study, soybean or mung bean was mixed in rice flour to produce by extrusion instant functional legume-rice porridge powder. The effects of the type and percentage (10%, 20%, or 30%, w/w) of legumes on the expansion ratio of the extrudates were first evaluated. Amino acid composition, color, and selected physicochemical (bulk density, water absorption index, and water solubility index), thermal (onset temperature, peak temperature, and transition enthalpy), and pasting (peak viscosity, trough viscosity, and final viscosity) properties of the powder were determined. The crystalline structure and formation of amylose-lipid complexes and the total phenolics content (TPC) and antioxidant activity of the powder were also measured. Soybean-blended porridge powder exhibited higher TPC, 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity, ferric reducing antioxidant power, amino acid, and fat contents than the mung bean-blended porridge powder. Incorporating either legume affected the product properties by decreasing the lightness and bulk density, while increasing the greenness and yellowness and the peak temperature and transition enthalpy. Expansion capacity of the extrudates increased with percentage of mung bean in the mixture but decreased as the percentage of soybean increased. Amylose-lipid complexes formation was confirmed by X-ray diffraction analysis results. Addition of soybean or mung bean resulted in significant pasting property changes of the porridge powder. © 2015 Institute of Food Technologists®

A new flux-limited, two-dimensional, nonsymmetric tensor shock viscosity for DYNA2D: Progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, D.J.

1988-08-15

A new artificial viscosity that is being developed for DYNA2D is described in this progress report. It incorporates the one- dimensional, flux-limited viscosity developed by Randy Christensen into a two-dimensional setting. In addition, it tries to overcome some of the difficulties associated with traditional bulk viscosity formulations by using an nonsymmetric viscosity tensor. A different nonsymmetric approach (and a symmetrized version of it) is being used in SHALE by Len Margolin with great success. In a later section of this paper, the results of DYNA2D and SHALE for the ''Saltzman problem'' are compared. The general organization of this report ismore » as follows: First it presents the one-dimensional, flux-limited viscosity developed by Christensen. An nonsymmetric tensor viscosity is then developed and the addition of flux-limiting to it is discussed. The issue of boundary conditions turns out to be crucial, and some issues associated with them are unresolved. The current boundary conditions and the issues associated with them are discussed. Example calculations are also given. The current work is summarized and future work is outlined in the first chapter. This brief progress report is the basis of a future journal paper. The work presented in here is unfinished, and some of the results and algorithms will undoubtedly be changed before the final paper. No attempt has been made to survey the results of others in this report, but a limited survey will be incorporated in the journal paper. 7 refs., 39 figs.« less

The relationship between blood viscosity and blood pressure in a random sample of the population aged 55 to 74 years.

PubMed

Fowkes, F G; Lowe, G D; Rumley, A; Lennie, S E; Smith, F B; Donnan, P T

1993-05-01

Blood viscosity is elevated in hypertensive subjects, but the association of viscosity with arterial blood pressure in the general population, and the influence of social, lifestyle and disease characteristics on this association, are not established. In the Edinburgh Artery Study, 1592 men and women aged 55-74 years selected randomly from the general population attended a university clinic. A fasting blood sample was taken for the measurement of blood viscosity and its major determinants (haematocrit, plasma viscosity and fibrinogen). Systolic pressure was related univariately to blood viscosity (P < 0.001), plasma viscosity (P < 0.001) and plasma fibrinogen (P < 0.01), but the association with fibrinogen did not persist after adjusting for body mass index. Diastolic pressure was related univariately to blood viscosity (P < 0.001) and plasma viscosity (P < 0.001) and haematocrit (P < 0.001) but not to fibrinogen. The only difference between the sexes was that the association between blood viscosity and systolic pressure was confined to males. Blood viscosity was associated equally with systolic and diastolic pressures in males, and remained independently related on multivariate analysis adjusting for age, sex, body mass index, social class, smoking, alcohol intake, exercise, angina, HDL and non-HDL cholesterol, diabetes mellitus, plasma viscosity, fibrinogen, and haematocrit.

Bulk viscous corrections to screening and damping in QCD at high temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Qianqian; Dumitru, Adrian; Guo, Yun

2017-01-01

Non-equilibrium corrections to the distribution functions of quarks and gluons in a hot and dense QCD medium modify the \\hard thermal loops" (HTL). The HTLs determine the retarded, advanced, and symmetric (time-ordered) propagators for gluons with soft momenta as well as the Debye screening and Landau damping mass scales. Here, we compute such corrections to a thermal as well as to a non-thermal fixed point. The screening and damping mass scales are sensitive to the bulk pressure and hence to (pseudo-) critical dynamical scaling of the bulk viscosity in the vicinity of a second-order critical point. This could be reectedmore » in the properties of quarkonium bound states in the deconfined phase and in the dynamics of soft gluon fields.« less

Foamed Bulk Metallic Glass (Foam) Investigation

NASA Technical Reports Server (NTRS)

2004-01-01

This soldering iron has an evacuated copper capsule at the tip that contains a pellet of Bulk Metallic Glass (BMG) aboard the International Space Station (ISS). Prior to flight, researchers sealed a pellet of bulk metallic glass mixed with microscopic gas-generating particles into the copper ampoule under vacuum. Once heated in space, such as in this photograph, the particles generated gas and the BMG becomes a viscous liquid. The released gas made the sample foam within the capsule where each microscopic particle formed a gas-filled pore within the foam. The inset image shows the oxidation of the sample after several minutes of applying heat. Although hidden within the brass sleeve, the sample retained the foam shape when cooled, because the viscosity increased during cooling until it was solid.

Fluid property measurements study

NASA Technical Reports Server (NTRS)

Devaney, W. E.

1976-01-01

Fluid properties of refrigerant-21 were investigated at temperatures from the freezing point to 423 Kelvin and at pressures to 1.38 x 10 to the 8th power N/sq m (20,000 psia). The fluid properties included were: density, vapor pressure, viscosity, specific heat, thermal conductivity, thermal expansion coefficient, freezing point and bulk modulus. Tables of smooth values are reported.

Polymerization Behavior and Mechanical Properties of High-Viscosity Bulk Fill and Low Shrinkage Resin Composites.

PubMed

Shibasaki, S; Takamizawa, T; Nojiri, K; Imai, A; Tsujimoto, A; Endo, H; Suzuki, S; Suda, S; Barkmeier, W W; Latta, M A; Miyazaki, M

The present study determined the mechanical properties and volumetric polymerization shrinkage of different categories of resin composite. Three high viscosity bulk fill resin composites were tested: Tetric EvoCeram Bulk Fill (TB, Ivoclar Vivadent), Filtek Bulk Fill posterior restorative (FB, 3M ESPE), and Sonic Fill (SF, Kerr Corp). Two low-shrinkage resin composites, Kalore (KL, GC Corp) and Filtek LS Posterior (LS, 3M ESPE), were used. Three conventional resin composites, Herculite Ultra (HU, Kerr Corp), Estelite ∑ Quick (EQ, Tokuyama Dental), and Filtek Supreme Ultra (SU, 3M ESPE), were used as comparison materials. Following ISO Specification 4049, six specimens for each resin composite were used to determine flexural strength, elastic modulus, and resilience. Volumetric polymerization shrinkage was determined using a water-filled dilatometer. Data were evaluated using analysis of variance followed by Tukey's honestly significant difference test (α=0.05). The flexural strength of the resin composites ranged from 115.4 to 148.1 MPa, the elastic modulus ranged from 5.6 to 13.4 GPa, and the resilience ranged from 0.70 to 1.0 MJ/m 3 . There were significant differences in flexural properties between the materials but no clear outliers. Volumetric changes as a function of time over a duration of 180 seconds depended on the type of resin composite. However, for all the resin composites, apart from LS, volumetric shrinkage began soon after the start of light irradiation, and a rapid decrease in volume during light irradiation followed by a slower decrease was observed. The low shrinkage resin composites KL and LS showed significantly lower volumetric shrinkage than the other tested materials at the measuring point of 180 seconds. In contrast, the three bulk fill resin composites showed higher volumetric change than the other resin composites. The findings from this study provide clinicians with valuable information regarding the mechanical properties and polymerization kinetics of these categories of current resin composite.

Can a grain size-dependent viscosity help yielding realistic seismic velocities of LLSVPs?

NASA Astrophysics Data System (ADS)

Schierjott, J.; Cheng, K. W.; Rozel, A.; Tackley, P. J.

2017-12-01

Seismic studies show two antipodal regions of low shear velocity at the core-mantle boundary (CMB), one beneath the Pacific and one beneath Africa. These regions, called Large Low Shear Velocity Provinces (LLSVPs), are thought to be thermally and chemically distinct and thus have a different density and viscosity. Whereas there is some general consensus about the density of the LLSVPs the viscosity is still a very debated topic. So far, in numerical studies the viscosity is treated as either depth- and/or temperature- dependent but the potential grain size- dependence of the viscosity is neglected most of the time. In this study we use a self-consistent convection model which includes a grain size- dependent rheology based on the approach by Rozel et al. (2011) and Rozel (2012). Further, we consider a primordial layer and a time-dependent basalt production at the surface to dynamically form the present-day chemical heterogeneities, similar to earlier studies, e.g by Nakagawa & Tackley (2014). With this model we perform a parameter study which includes different densities and viscosities of the imposed primordial layer. We detect possible thermochemical piles based on different criterions, compute their average effective viscosity, density, rheology and grain size and investigate which detecting criterion yields the most realistic results. Our preliminary results show that a higher density and/or viscosity of the piles is needed to keep them at the core-mantle boundary (CMB). Relatively to the ambient mantle grain size is high in the piles but due to the temperature at the CMB the viscosity is not remarkably different than the one of ordinary plumes. We observe that grain size is lower if the density of the LLSVP is lower than the one of our MORB material. In that case the average temperature of the LLSVP is also reduced. Interestingly, changing the reference viscosity is responsible for a change in the average viscosity of the LLSVP but not for a different average grain size. Finally, we compare the numerical results with seismological observations by computing 1D seismic velocity profiles (p-wave, shear-wave and bulk velocities) inside and outside our detected piles using thermodynamic data calculated from Perple_X .

Direct measurement of friction of a fluctuating contact line

NASA Astrophysics Data System (ADS)

Guo, Shuo; Gao, Min; Xiong, Xiaomin; Wang, Yong Jian; Wang, Xiaoping; Sheng, Ping; Tong, Penger

2013-03-01

What happens at a moving contact line, where one fluid displaces another (immiscible) fluid over a solid surface, is a fundamental issue in fluid dynamics. In this presentation, we report a direct measurement of the friction coefficient in the immediate vicinity of a fluctuating contact line using a micron-sized vertical glass fiber with one end glued to an atomic force microscope (AFM) cantilever beam and the other end touching a liquid-air interface. By measuring the broadening of the resonance peak of the cantilever system with varying liquid viscosity η, we obtain the friction coefficient ξc associated with the contact line fluctuations on the glass fiber of diameter d and find it has the universal form, ξc = 0 . 8 πdη , independent of the contact angle. The result is further confirmed by using a soap film system whose bulk effect is negligibly small. This is the first time that the friction coefficient of a fluctuating contact line is measured. *Work supported by the Research Grants Council of Hong Kong SAR.

Entropy Viscosity and L1-based Approximations of PDEs: Exploiting Sparsity

DTIC Science & Technology

2015-10-23

AFRL-AFOSR-VA-TR-2015-0337 Entropy Viscosity and L1-based Approximations of PDEs: Exploiting Sparsity Jean-Luc Guermond TEXAS A & M UNIVERSITY 750...REPORT DATE (DD-MM-YYYY) 09-05-2015 2. REPORT TYPE Final report 3. DATES COVERED (From - To) 01-07-2012 - 30-06-2015 4. TITLE AND SUBTITLE Entropy ...conservation equations can be stabilized by using the so-called entropy viscosity method and we proposed to to investigate this new technique. We

Rate of deoxygenation modulates rheologic behavior of sickle red blood cells at a given mean corpuscular hemoglobin concentration.

PubMed

Kaul, D K; Liu, X D

1999-01-01

Although the mean corpuscular hemoglobin concentration (MCHC) plays a dominant role in the rheologic behavior of deoxygenated density-defined sickle red blood cells (SS RBCs), previous studies have not explored the relationship between the rate of deoxygenation and the bulk viscosity of SS RBCs at a given MCHC. In the present study, we have subjected density-defined SS classes (i.e., medium-density SS4 and dense SS5 discocytes) to varying deoxygenation rates. This approach has allowed us to minimize the effects of SS RBC heterogeneity and investigate the effect of deoxygenation rates at a given MCHC. The results show that the percentages of granular cells, classic sickle cells and holly leaf forms in deoxygenated samples are significantly influenced by the rate of deoxygenation and the MCHC of a given discocyte subpopulation. Increasing the deoxygenation rate using high K+ medium (pH 6.8), results in a greater percentage of granular cells in SS4 suspensions, accompanied by a pronounced increase in the bulk viscosity of these cells compared with gradually deoxygenated samples (mainly classic sickle cells and holly leaf forms). The effect of MCHC becomes apparent when SS5 dense cells are subjected to varying deoxygenation rates. At a given deoxygenation rate, SS5 dense discocytes show a greater increase in the percentage of granular cells than that observed for SS4 RBCs. Also, at a given deoxygenation rate, SS5 suspensions exhibit a higher viscosity than SS4 suspensions with fast deoxygenation resulting in maximal increase in viscosity. Although MCHC is the main determinant of SS RBC rheologic behavior, these studies demonstrate for the first time that at a given MCHC, the rate of deoxygenation (hence HbS polymerization rates) further modulates the rheologic behavior of SS RBCs. Thus, both MCHC and the deoxygenation rate may contribute to microcirculatory flow behavior of SS RBCs.

Transport coefficients and heat fluxes in non-equilibrium high-temperature flows with electronic excitation

NASA Astrophysics Data System (ADS)

Istomin, V. A.; Kustova, E. V.

2017-02-01

The influence of electronic excitation on transport processes in non-equilibrium high-temperature ionized mixture flows is studied. Two five-component mixtures, N 2 / N2 + / N / N + / e - and O 2 / O2 + / O / O + / e - , are considered taking into account the electronic degrees of freedom for atomic species as well as the rotational-vibrational-electronic degrees of freedom for molecular species, both neutral and ionized. Using the modified Chapman-Enskog method, the transport coefficients (thermal conductivity, shear viscosity and bulk viscosity, diffusion and thermal diffusion) are calculated in the temperature range 500-50 000 K. Thermal conductivity and bulk viscosity coefficients are strongly affected by electronic states, especially for neutral atomic species. Shear viscosity, diffusion, and thermal diffusion coefficients are not sensible to electronic excitation if the size of excited states is assumed to be constant. The limits of applicability for the Stokes relation are discussed; at high temperatures, this relation is violated not only for molecular species but also for electronically excited atomic gases. Two test cases of strongly non-equilibrium flows behind plane shock waves corresponding to the spacecraft re-entry (Hermes and Fire II) are simulated numerically. Fluid-dynamic variables and heat fluxes are evaluated in gases with electronic excitation. In inviscid flows without chemical-radiative coupling, the flow-field is weakly affected by electronic states; however, in viscous flows, their influence can be more important, in particular, on the convective heat flux. The contribution of different dissipative processes to the heat transfer is evaluated as well as the effect of reaction rate coefficients. The competition of diffusion and heat conduction processes reduces the overall effect of electronic excitation on the convective heating, especially for the Fire II test case. It is shown that reliable models of chemical reaction rates are of great importance for accurate predictions of the fluid dynamic variables and heat fluxes.

Universality Results for Multi-layer Radial Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir; Gin, Craig; Daripa Research Team

2014-03-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface separating two immiscible fluids. We study linear stability of this displacement process in multi-layer radial Hele-Shaw geometry involving an arbitrary number of immiscible fluid phases. Universal stability results have been obtained and applied to design displacement processes that are considerably less unstable than the pure Saffman-Taylor case. In particular, we derive universal formula which gives specific values of the viscosities of the fluid layers corresponding to smallest unstable band. Other similar universal results will also be presented. The talk is based on ongoing work. Supported by an NPRP Grant # 08-777-1-141 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications

DOE PAGES

Robinson, Joshua W.; Zhou, Yan; Bhattacharya, Priyanka; ...

2016-01-05

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acidsmore » (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. Increased branching and degree of polymerization, and thus molecular weight, were found to reduce the solubility of these systems in the base oil. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated improved viscosity index and reduced friction coefficient, validating the basic approach.« less

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Joshua W.; Zhou, Yan; Bhattacharya, Priyanka

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acidsmore » (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. Increased branching and degree of polymerization, and thus molecular weight, were found to reduce the solubility of these systems in the base oil. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated improved viscosity index and reduced friction coefficient, validating the basic approach.« less

Comparing the mechanism of water condensation and evaporation in glassy aerosol.

PubMed

Bones, David L; Reid, Jonathan P; Lienhard, Daniel M; Krieger, Ulrich K

2012-07-17

Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3-4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ≫10(3) s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from < 0.1 to > 10(13) Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk.

Anisotropic Bianchi Type-I and Type-II Bulk Viscous String Cosmological Models Coupled with Zero Mass Scalar Field

NASA Astrophysics Data System (ADS)

Venkateswarlu, R.; Sreenivas, K.

2014-06-01

The LRS Bianchi type-I and type-II string cosmological models are studied when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings together with zero-mass scalar field. We have obtained the solutions of the field equations assuming a functional relationship between metric coefficients when the metric is Bianchi type-I and constant deceleration parameter in case of Bianchi type-II metric. The physical and kinematical properties of the models are discussed in each case. The effects of Viscosity on the physical and kinematical properties are also studied.

Physical and chemical properties of some new perfluoropolyalkylether lubricants prepared by direct fluorination

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Bierschenk, T. R.; Juhlke, T. J.; Kawa, H.; Lagow, R. J.

1993-01-01

A series of perfluoropolyalkylether (PFPAE) fluids was synthesized by direct fluorination. Viscosity-temperature properties, oxidation stabilities, oxidation-corrosion properties, bulk modulus, lubricity, surface tension and density were measured. It was shown that as the carbon to oxygen ratio in the polymer repeating unit decreases, the viscometric properties improve, the fluids may become poorer boundary lubricants, the bulk modulus increases, the surface tension increases and the fluid density increases. The presence of difluoromethylene oxide units in the polymer does not significantly lower the oxidation and oxidation-corrosion stabilities as long as the difluoromethylene oxide units are separated by other units.

Imaging aerosol viscosity

NASA Astrophysics Data System (ADS)

Pope, Francis; Athanasiadis, Thanos; Botchway, Stan; Davdison, Nicholas; Fitzgerald, Clare; Gallimore, Peter; Hosny, Neveen; Kalberer, Markus; Kuimova, Marina; Vysniauskas, Aurimas; Ward, Andy

2017-04-01

Organic aerosol particles play major roles in atmospheric chemistry, climate, and public health. Aerosol particle viscosity is important since it can determine the ability of chemical species such as oxidants, organics or water to diffuse into the particle bulk. Recent measurements indicate that OA may be present in highly viscous states; however, diffusion rates of small molecules such as water appear not to be limited by these high viscosities. We have developed a technique for measuring viscosity that allows for the imaging of aerosol viscosity in micron sized aerosols through use of fluorescence lifetime imaging of viscosity sensitive dyes which are also known as 'molecular rotors'. These rotors can be introduced into laboratory generated aerosol by adding minute quantities of the rotor to aerosol precursor prior to aerosolization. Real world aerosols can also be studied by doping them in situ with the rotors. The doping is achieved through generation of ultrafine aerosol particles that contain the rotors; the ultrafine aerosol particles deliver the rotors to the aerosol of interest via impaction and coagulation. This work has been conducted both on aerosols deposited on microscope coverslips and on particles that are levitated in their true aerosol phase through the use of a bespoke optical trap developed at the Central Laser Facility. The technique allows for the direct observation of kinetic barriers caused by high viscosity and low diffusivity in aerosol particles. The technique is non-destructive thereby allowing for multiple experiments to be carried out on the same sample. It can dynamically quantify and track viscosity changes during atmospherically relevant processes such oxidation and hygroscopic growth (1). This presentation will focus on the oxidation of aerosol particles composed of unsaturated and saturated organic species. It will discuss how the type of oxidant, oxidation rate and the composition of the oxidized products affect the time dependent aerosol viscosity. (1) Hosny, N. A., C. Fitzgerald, A. Vysniauskas, T. Athanasiadis, T. Berkemeier, N. Uygur, U. Pöschl, M. Shiraiwa, M. Kalberer, F.D. Pope and M.K. Kuimova (2016) 'Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging'. Chemical Science, 17, 32194-32203. http://dx.doi.org/doi:10.1039/C5SC02959G

Calculation of eddy viscosity in a compressible turbulent boundary layer with mass injection and chemical reaction, volume 2. [computer programs

NASA Technical Reports Server (NTRS)

Omori, S.

1973-01-01

As described in Vol. 1, the eddy viscosity is calculated through the turbulent kinetic energy, in order to include the history of the flow and the effect of chemical reaction on boundary layer characteristics. Calculations can be performed for two different cooling concepts; that is, transpiration and regeneratively cooled wall cases. For the regenerative cooling option, coolant and gas side wall temperature and coolant bulk temperature in a rocket engine can be computed along the nozzle axis. Thus, this computer program is useful in designing coolant flow rate and cooling tube geometry, including the tube wall thickness as well as in predicting the effects of boundary layers along the gas side wall on thrust performances.

Hydrodynamics of soap films probed by two-particle microrheology

NASA Astrophysics Data System (ADS)

Prasad, Vikram; Weeks, Eric R.

2007-11-01

A soap film consists of a thin water layer that is separated from two bulk air phases above and below it by surfactant monolayers. The flow fields in the soap film created in response to a perturbation depend on coupling between these different phases, the exact nature of which is unknown. In order to determine this coupling, we use polystyrene spheres as tracer particles and track their diffusive motions in the soap film. The correlated Brownian motion of pairs of particles (two-particle microrheology) maps out the flow field, and provides a measure of the surface viscosity of the soap film as well. This measured surface viscosity agrees well with the value obtained from self diffusion of single particles (one-particle microrheology) in the film.

Observation of scale invariance and conformal symmetry breaking in expanding Fermi gases

NASA Astrophysics Data System (ADS)

Elliott, Ethan; Joseph, James; Thomas, John

2014-05-01

We precisely test scale invariance and examine local thermal equilibrium in the hydrodynamic expansion of a Fermi gas of atoms as a function of interaction strength. After release from an anisotropic optical trap, we observe that a resonantly interacting gas obeys scale-invariant hydrodynamics, where the mean square cloud size = expands ballistically (like a noninteracting gas) and the energy-averaged bulk viscosity is consistent with zero, 0 . 00 (0 . 04) ℏ n , with n the density. In contrast, the aspect ratios of the cloud exhibit anisotropic ``elliptic'' flow with an energy-dependent shear viscosity. Tuning away from resonance, we observe conformal symmetry breaking, where deviates from ballistic flow. NSF, DOE, ARO, AFO.

Two-particle microrheology of quasi-2D viscous systems.

PubMed

Prasad, V; Koehler, S A; Weeks, Eric R

2006-10-27

We study the spatially correlated motions of colloidal particles in a quasi-2D system (human serum albumin protein molecules at an air-water interface) for different surface viscosities eta s. We observe a transition in the behavior of the correlated motion, from 2D interface dominated at high eta s to bulk fluid dependent at low eta s. The correlated motions can be scaled onto a master curve which captures the features of this transition. This master curve also characterizes the spatial dependence of the flow field of a viscous interface in response to a force. The scale factors used for the master curve allow for the calculation of the surface viscosity eta s that can be compared to one-particle measurements.

Analysis and improvement of Brinkman lattice Boltzmann schemes: bulk, boundary, interface. Similarity and distinctness with finite elements in heterogeneous porous media.

PubMed

Ginzburg, Irina; Silva, Goncalo; Talon, Laurent

2015-02-01

This work focuses on the numerical solution of the Stokes-Brinkman equation for a voxel-type porous-media grid, resolved by one to eight spacings per permeability contrast of 1 to 10 orders in magnitude. It is first analytically demonstrated that the lattice Boltzmann method (LBM) and the linear-finite-element method (FEM) both suffer from the viscosity correction induced by the linear variation of the resistance with the velocity. This numerical artefact may lead to an apparent negative viscosity in low-permeable blocks, inducing spurious velocity oscillations. The two-relaxation-times (TRT) LBM may control this effect thanks to free-tunable two-rates combination Λ. Moreover, the Brinkman-force-based BF-TRT schemes may maintain the nondimensional Darcy group and produce viscosity-independent permeability provided that the spatial distribution of Λ is fixed independently of the kinematic viscosity. Such a property is lost not only in the BF-BGK scheme but also by "partial bounce-back" TRT gray models, as shown in this work. Further, we propose a consistent and improved IBF-TRT model which vanishes viscosity correction via simple specific adjusting of the viscous-mode relaxation rate to local permeability value. This prevents the model from velocity fluctuations and, in parallel, improves for effective permeability measurements, from porous channel to multidimensions. The framework of our exact analysis employs a symbolic approach developed for both LBM and FEM in single and stratified, unconfined, and bounded channels. It shows that even with similar bulk discretization, BF, IBF, and FEM may manifest quite different velocity profiles on the coarse grids due to their intrinsic contrasts in the setting of interface continuity and no-slip conditions. While FEM enforces them on the grid vertexes, the LBM prescribes them implicitly. We derive effective LBM continuity conditions and show that the heterogeneous viscosity correction impacts them, a property also shared by FEM for shear stress. But, in contrast with FEM, effective velocity conditions in LBM give rise to slip velocity jumps which depend on (i) neighbor permeability values, (ii) resolution, and (iii) control parameter Λ, ranging its reliable values from Poiseuille bounce-back solution in open flow to zero in Darcy's limit. We suggest an "upscaling" algorithm for Λ, from multilayers to multidimensions in random extremely dispersive samples. Finally, on the positive side for LBM besides its overall versatility, the implicit boundary layers allow for smooth accommodation of the flat discontinuous Darcy profiles, quite deficient in FEM.

Measurement of the Surface Dilatational Viscosity of an Insoluble Surfactant Monolayer at the Air/Water Interface Using a Pendant Drop Apparatus

NASA Technical Reports Server (NTRS)

Lorenzo, Jose; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

2000-01-01

When a fluid interface with surfactants is at rest, the interfacial stress is isotropic (as given by the equilibrium interfacial tension), and is described by the equation of state which relates the surface tension to the surfactant surface concentration. When surfactants are subjected to shear and dilatational flows, flow induced interaction of the surfactants; can create interfacial stresses apart from the equilibrium surface tension. The simplest relationship between surface strain rate and surface stress is the Boussinesq-Scriven constitutive equation completely characterized by three coefficients: equilibrium interfacial tension, surface shear viscosity, and surface dilatational viscosity Equilibrium interfacial tension and surface shear viscosity measurements are very well established. On the other hand, surface dilatational viscosity measurements are difficult because a flow which change the surface area also changes the surfactant surface concentration creating changes in the equilibrium interfacial tension that must be also taken into account. Surface dilatational viscosity measurements of existing techniques differ by five orders of magnitude and use spatially damped surface waves and rapidly expanding bubbles. In this presentation we introduce a new technique for measuring the surface dilatational viscosity by contracting an aqueous pendant drop attached to a needle tip and having and insoluble surfactant monolayer at the air-water interface. The isotropic total tension on the surface consists of the equilibrium surface tension and the tension due to the dilation. Compression rates are undertaken slow enough so that bulk hydrodynamic stresses are small compared to the surface tension force. Under these conditions we show that the total tension is uniform along the surface and that the Young-Laplace equation governs the drop shape with the equilibrium surface tension replaced by the constant surface isotropic stress. We illustrate this technique using DPPC as the insoluble surfacant monolayer and measured for it a surface dilatational viscosity in the LE phase that is 20 surface poise.

Universality Results for Multi-phase Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2013-03-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface separating two immiscible fluids. We study linear stability of displacement processes in a Hele-Shaw cell involving an arbitrary number of immiscible fluid phases. This is a problem involving many interfaces. Universal stability results have been obtained for this multi-phase immiscible flow in the sense that the results hold for arbitrary number of interfaces. These stability results have been applied to design displacement processes that are considerably less unstable than the pure Saffman-Taylor case. In particular, we derive universal formula which gives specific values of the viscosities of the fluid layers corresponding to smallest unstable band. Other similar universal results will also be presented. The talk is based on the following paper. This work was supported by the Qatar National Research Fund (a member of The Qatar Foundation).

Cellular Viscosity in Prokaryotes and Thermal Stability of Low Molecular Weight Biomolecules.

PubMed

Cuecas, Alba; Cruces, Jorge; Galisteo-López, Juan F; Peng, Xiaojun; Gonzalez, Juan M

2016-08-23

Some low molecular weight biomolecules, i.e., NAD(P)H, are unstable at high temperatures. The use of these biomolecules by thermophilic microorganisms has been scarcely analyzed. Herein, NADH stability has been studied at different temperatures and viscosities. NADH decay increased at increasing temperatures. At increasing viscosities, NADH decay rates decreased. Thus, maintaining relatively high cellular viscosity in cells could result in increased stability of low molecular weight biomolecules (i.e., NADH) at high temperatures, unlike what was previously deduced from studies in diluted water solutions. Cellular viscosity was determined using a fluorescent molecular rotor in various prokaryotes covering the range from 10 to 100°C. Some mesophiles showed the capability of changing cellular viscosity depending on growth temperature. Thermophiles and extreme thermophiles presented a relatively high cellular viscosity, suggesting this strategy as a reasonable mechanism to thrive under these high temperatures. Results substantiate the capability of thermophiles and extreme thermophiles (growth range 50-80°C) to stabilize and use generally considered unstable, universal low molecular weight biomolecules. In addition, this study represents a first report, to our knowledge, on cellular viscosity measurements in prokaryotes and it shows the dependency of prokaryotic cellular viscosity on species and growth temperature. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Measurement and computation of hydrodynamic coupling at an air/water interface with an insoluble monolayer

NASA Astrophysics Data System (ADS)

Hirsa, Amir H.; Lopez, Juan M.; Miraghaie, Reza

2001-09-01

The coupling between a bulk vortical flow and a surfactant-influenced air/water interface has been examined in a canonical flow geometry through experiments and computations. The flow in an annular region bounded by stationary inner and outer cylinders is driven by the constant rotation of the floor and the free surface is initially covered by a uniformly distributed insoluble monolayer. When driven slowly, this geometry is referred to as the deep-channel surface viscometer and the flow is essentially azimuthal. The only interfacial property that affects the flow in this regime is the surface shear viscosity, [mu]s, which is uniform on the surface due to the vanishingly small concentration gradient. However, when operated at higher Reynolds number, secondary flow drives the surfactant film towards the inner cylinder until the Marangoni stress balances the shear stress on the bulk fluid. In general, the flow can be influenced by the surface tension, [sigma], and the surface dilatational viscosity, [kappa]s, as well as [mu]s. However, because of the small capillary number of the present flow, the effects of surface tension gradients dominate the surface viscosities in the radial stress balance, and the effect of [mu]s can only come through the azimuthal stress. Vitamin K1 was chosen for this study since it forms a well-behaved insoluble monolayer on water and [mu]s is essentially zero in the range of concentration on the surface, c, encountered. Thus the effect of Marangoni elasticity on the interfacial stress could be isolated. The flow near the interface was measured in an optical channel using digital particle image velocimetry. Steady axisymmetric flow was observed at the nominal Reynolds number of 8500. A numerical model has been developed using the axisymmetric Navier Stokes equations to examine the details of the coupling between the bulk and the interface. The nonlinear equation of state, [sigma](c), for the vitamin K1 monolayer was measured and utilized in the computations. Agreement was demonstrated between the measurements and computations, but the flow is critically dependent on the nonlinear equation of state.

Is the boundary layer of an ionic liquid equally lubricating at higher temperature?

PubMed

Hjalmarsson, Nicklas; Atkin, Rob; Rutland, Mark W

2016-04-07

Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.

Methods of synthesizing hydroxyapatite powders and bulk materials

DOEpatents

Luo, Ping

1999-01-12

Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 .mu.m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogenous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided.

Methods of synthesizing hydroxyapatite powders and bulk materials

DOEpatents

Luo, P.

1999-01-12

Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 {micro}m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogeneous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided. 26 figs.

The dynamical crossover phenomenon in bulk water, confined water and protein hydration water.

PubMed

Mallamace, Francesco; Corsaro, Carmelo; Baglioni, Piero; Fratini, Emiliano; Chen, Sow-Hsin

2012-02-15

We discuss a phenomenon regarding water that was until recently a subject of scientific controversy, i.e. the dynamical crossover from fragile-to-strong glass-forming material, for both bulk and protein hydration water. Such a crossover is characterized by a temperature T(L) at which significant dynamical changes occur, such as violation of the Stokes-Einstein relation and changes of behaviour of homologous transport parameters such as the density relaxation time and the viscosity. In this respect we will consider carefully the dynamic properties of water-protein systems. More precisely, we will study proteins and their hydration water as far as bulk and confined water. In order to clarify the controversy we will discuss in a comparative way many previous and new experimental data that have emerged using different techniques and molecular dynamic simulation (MD). We point out the reasons for the different dynamical findings from the use of different experimental techniques.

Bulk viscous cosmology with causal transport theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piattella, Oliver F.; Fabris, Júlio C.; Zimdahl, Winfried, E-mail: oliver.piattella@gmail.com, E-mail: fabris@pq.cnpq.br, E-mail: winfried.zimdahl@pq.cnpq.br

2011-05-01

We consider cosmological scenarios originating from a single imperfect fluid with bulk viscosity and apply Eckart's and both the full and the truncated Müller-Israel-Stewart's theories as descriptions of the non-equilibrium processes. Our principal objective is to investigate if the dynamical properties of Dark Matter and Dark Energy can be described by a single viscous fluid and how such description changes when a causal theory (Müller-Israel-Stewart's, both in its full and truncated forms) is taken into account instead of Eckart's non-causal one. To this purpose, we find numerical solutions for the gravitational potential and compare its behaviour with the corresponding ΛCDMmore » case. Eckart's and the full causal theory seem to be disfavoured, whereas the truncated theory leads to results similar to those of the ΛCDM model for a bulk viscous speed in the interval 10{sup −11} || cb{sup 2} ∼< 10{sup −8}.« less

Measuring Viscosity with a Levitating Magnet: Application to Complex Fluids

ERIC Educational Resources Information Center

Even, C.; Bouquet, F.; Remond, J.; Deloche, B.

2009-01-01

As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10[superscript 6] mPa s are obtained. This experiment is used as an introduction to complex…

Effects of CO2 injection and Kerogen Maturation on Low-Field Nuclear Magnetic Resonance Response

NASA Astrophysics Data System (ADS)

Prasad, M.; Livo, K.

2017-12-01

Low-field Nuclear Magnetic Resonance (NMR) is commonly used in petrophysical analysis of petroleum reservoir rocks. NMR experiments record the relaxation and polarization of in-situ hydrogen protons present in gaseous phases such as free-gas intervals and solution gas fluids, bulk fluid phases such as oil and aquifer intervals, and immovable fractions of kerogen and bitumen. Analysis of NMR relaxation spectra is performed to record how fluid composition, maturity, and viscosity change NMR experimental results. We present T1-T2 maps as thermal maturity of a water-saturated, sub-mature Woodford shale is increased at temperatures from 125 to 400 degrees Celsius. Experiments with applied fluid pressure in paraffinic mineral oil and DI water with varying fluid pH have been performed to mimic reservoir conditions in analysis of the relaxation of bulk fluid phases. We have recorded NMR spectra, T1-T2 maps, and fluid diffusion coefficients using a low-field (2 MHz) MagritekTM NMR. CO2 was injected at a pressure of 900 psi in an in house developed NMR pressure vessel made of torlon plastic. Observable 2D NMR shifts in immature kerogen formations as thermal maturity is increased show generation of lighter oils with increased maturity. CO2 injection leads to a decrease in bulk fluid relaxation time that is attributed to viscosity modification with gas presence. pH variation with increased CO2 presence were shown to not effect NMR spectra. From this, fluid properties have been shown to greatly affect NMR readings and must be taken into account for more accurate NMR reservoir characterization.

Some physical and functional properties of finger millet (Eleusine coracana) obtained in sub-Saharan Africa.

PubMed

Ramashia, S E; Gwata, E T; Meddows-Taylor, S; Anyasi, T A; Jideani, A I O

2018-02-01

The study determined the physical properties of finger millet (FM) (Eluesine coracana) grains and the functional properties of FM flour. Physical properties such as colour attributes, sample weight, bulk density, true density, porosity, surface area, sample volume, aspect ratio, sphericity, dimensional properties and moisture content of grain cultivars were determined. Water absorption capacity (WAC), bulk density (BD), dispersibility, viscosity and micro-structure of FM flours were also evaluated. Data collected were analyzed using SPSS statistical software version 23.0. Results showed that milky cream cultivar was significantly higher (p<0.05) than other samples in sample weight, bulk density, true density, aspect ratio and sphericity. However, pearl millet, used as a control, was significantly different from FM flour on all dimensional properties. Moisture content of milky cream showed higher significant difference for both grains and flours as compared to brown and black grain/flours. Milky cream cultivar was significantly different in L*, b*, C*, H* values, WAC, BD and dispersibility for both FM grains and flours. Data showed that brown flour was significantly higher in viscosity than in milky and black flours. Microstructure results revealed that starch granules of raw FM flours had oval/spherical and smooth surface. The study is important for agricultural and food engineers, designers, scientists and processors in the design of equipment for FM grain processing. Results are likely to be useful in assessing the quality of grains used to fortify FM flour. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Transport coefficients of liquid CF4 and SF6 computed by molecular dynamics using polycenter Lennard-Jones potentials

NASA Astrophysics Data System (ADS)

Hoheisel, C.

1989-01-01

For several liquid states of CF4 and SF4, the shear and the bulk viscosity as well as the thermal conductivity were determined by equilibrium molecular dynamics (MD) calculations. Lennard-Jones four- and six-center pair potentials were applied, and the method of constraints was chosen for the MD. The computed Green-Kubo integrands show a steep time decay, and no particular longtime behavior occurs. The molecule number dependence of the results is found to be small, and 3×105 integration steps allow an accuracy of about 10% for the shear viscosity and the thermal conductivity coefficient. Comparison with experimental data shows a fair agreement for CF4, while for SF6 the transport coefficients fall below the experimental ones by about 30%.

Hydrodynamic correlation functions of hard-sphere fluids at short times

NASA Astrophysics Data System (ADS)

Leegwater, Jan A.; van Beijeren, Henk

1989-11-01

The short-time behavior of the coherent intermediate scattering function for a fluid of hard-sphere particles is calculated exactly through order t 4, and the other hydrodynamic correlation functions are calculated exactly through order t 2. It is shown that for all of the correlation functions considered the Enskog theory gives a fair approximation. Also, the initial time behavior of various Green-Kubo integrands is studied. For the shear-viscosity integrand it is found that at density nσ3=0.837 the prediction of the Enskog theory is 32% too low. The initial value of the bulk viscosity integrand is nonzero, in contrast to the Enskog result. The initial value of the thermal conductivity integrand at high densities is predicted well by Enskog theory.

Determining Quiescent Colloidal Suspension Viscosities Using the Green-Kubo Relation and Image-Based Stress Measurements

NASA Astrophysics Data System (ADS)

Lin, Neil Y. C.; Bierbaum, Matthew; Cohen, Itai

2017-09-01

By combining confocal microscopy and stress assessment from local structural anisotropy, we directly measure stresses in 3D quiescent colloidal liquids. Our noninvasive and nonperturbative method allows us to measure forces ≲50 fN with a small and tunable probing volume, enabling us to resolve the stress fluctuations arising from particle thermal motions. We use the Green-Kubo relation to relate these measured stress fluctuations to the bulk Brownian viscosity at different volume fractions, comparing against simulations and conventional rheometry measurements. We find that the Green-Kubo analysis gives excellent agreement with these prior results, suggesting that similar methods could be applied to investigations of local flow properties in many poorly understood far-from-equilibrium systems, including suspensions that are glassy, strongly sheared, or highly confined.

Containerless Measurement of Thermophysical Properties of Ti-Zr-Ni Alloys

NASA Technical Reports Server (NTRS)

Hyers, Robert; Bradshaw, Richard C.; Rogers, Jan C.; Rathz, Thomas J.; Lee, Geun W.; Gangopadhyay, Anup K.; Kelton, Kenneth F.

2004-01-01

The surface tension, viscosity, density, and thermal expansion of Ti-Zr-Ni alloys were measured for a number of compositions by electrostatic levitation methods. Containerless methods greatly reduce heterogeneous nucleation, increasing access to the undercooled liquid regime at finite cooling rates. The density and thermal expansion are measured optically, while the surface tension and viscosity are measured by the oscillating drop method. The measured alloys include compositions which form a metastable quasicrystal phase from the undercooled liquid, and alloys close to the composition of several multi-component bulk metallic glass-forming alloys. Measurements of surface tension show behavior typical of transition metals at high temperature, but a sudden decrease in the deeply undercooled liquid for alloys near the quasicrystal-forming composition range, but not for compositions which form the solid-solution phase first.

Molecular dynamics study of rhodamine 6G diffusion at n-decane-water interfaces.

PubMed

Popov, Piotr; Steinkerchner, Leo; Mann, Elizabeth K

2015-05-01

Two-dimensional diffusion of a rhodamine 6G fluorescent tracer molecule at the n-decane-water interface was studied with all-atom molecular dynamics simulations. In agreement with experimental data, we find increased mobility of the tracer at the n-decane-water interfaces in comparison to its mobility in bulk water. Orientational ordering of water and n-decane molecules near the interface is observed, and may change the interfacial viscosity as suggested to explain the experimental data. However, the restricted rotational motion of the rhodamine molecule at the interface suggests that the Saffman-Delbrück model may be a more appropriate approximation of rhodamine diffusion at n-decane-water interfaces, and, without any decrease in interfacial viscosity, suggests faster diffusion consistent with both experimental and simulation values.

Instant polysaccharide-based emulsions: impact of microstructure on lipolysis.

PubMed

Torcello-Gómez, Amelia; Foster, Timothy J

2017-06-21

The development of emulsion-based products through optimisation of ingredients, reduction in energy-input during manufacture, while fulfilling healthy attributes, are major objectives within the food industry. Instant emulsions can meet these features, but comprehensive studies are necessary to investigate the effect of the initial formulation on the final microstructure and, in turn, on the in vitro lipolysis, comprising the double aim of this work. The instant emulsion is formed within 1.5-3 min after pouring the aqueous phase into the oil phase which contains a mixture of emulsifier (Tween 20), swelling particles (Sephadex) and thickeners (hydroxypropylmethylcellulose, HPMC, and guar gum, GG) under mild shearing (180 rpm). The creation of oil-in-water emulsions is monitored in situ by viscosity analysis, the final microstructure visualised by microscopy and the release of free fatty acids under simulated intestinal conditions quantified by titration. Increasing the concentration and molecular weight (M w ) of GG leads to smaller emulsion droplets due to increased bulk viscosity upon shearing. This droplet size reduction is magnified when increasing the M w of HPMC or swelling capacity of viscosifying particles. In addition, in the absence of the emulsifier Tween 20, the sole use of high-Mw HPMC is effective in emulsification due to combined increased bulk viscosity and interfacial activity. Hence, optimisation of the ingredient choice and usage level is possible when designing microstructures. Finally, emulsions with larger droplet size (>20 μm) display a slower rate and lower extent of lipolysis, while finer emulsions (droplet size ≤20 μm) exhibit maximum rate and extent profiles. This correlates with the extent of emulsion destabilisation observed under intestinal conditions.

The influence of physical state on shikimic acid ozonolysis: a case for in situ microspectroscopy

NASA Astrophysics Data System (ADS)

Steimer, S. S.; Lampimäki, M.; Coz, E.; Grzinic, G.; Ammann, M.

2014-03-01

Atmospheric soluble organic aerosol material can become solid or semi-solid. Due to increasing viscosity and decreasing diffusivity, this can impact important processes such as gas uptake and reactivity within aerosols containing such substances. This work explores the dependence of shikimic acid ozonolysis on humidity and thereby viscosity. Shikimic acid, a proxy for oxygenated reactive organic material, reacts with O3 in a Criegee-type reaction. We used an environmental microreactor embedded in a Scanning Transmission X-ray Microscope (STXM) to probe this oxidation process. This technique facilitates in situ measurements with single micron-sized particles and allows to obtain Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra with high spatial resolution. Thus, the chemical evolution of the interior of the particles can be followed under reaction conditions. The experiments show that the overall degradation rate of shikimic acid is depending on the relative humidity in a way that is controlled by the decreasing diffusivity of ozone with decreasing humidity. This decreasing diffusivity is most likely linked to the increasing viscosity of the shikimic acid-water mixture. The degradation rate was also depending on particle size, most congruent with a reacto-diffusion limited kinetic case where the reaction progresses only in a shallow layer within the bulk. No gradient in the shikimic acid concentration was observed within the bulk material at any humidity indicating that the diffusivity of shikimic acid is still high enough to allow its equilibration throughout the particles on the time scale of hours at higher humidity and that the thickness of the oxidized layer under dry conditions, where the particles are solid, is beyond the resolution of STXM.

The influence of physical state on shikimic acid ozonolysis: a case for in situ microspectroscopy

NASA Astrophysics Data System (ADS)

Steimer, S. S.; Lampimäki, M.; Coz, E.; Grzinic, G.; Ammann, M.

2014-10-01

Atmospheric soluble organic aerosol material can become solid or semi-solid. Due to increasing viscosity and decreasing diffusivity, this can impact important processes such as gas uptake and reactivity within aerosols containing such substances. This work explores the dependence of shikimic acid ozonolysis on humidity and thereby viscosity. Shikimic acid, a proxy for oxygenated reactive organic material, reacts with O3 in a Criegee-type reaction. We used an environmental microreactor embedded in a scanning transmission X-ray microscope (STXM) to probe this oxidation process. This technique facilitates in situ measurements with single micron-sized particles and allows to obtain near-edge X-ray absorption fine structure (NEXAFS) spectra with high spatial resolution. Thus, the chemical evolution of the interior of the particles can be followed under reaction conditions. The experiments show that the overall degradation rate of shikimic acid is depending on the relative humidity in a way that is controlled by the decreasing diffusivity of ozone with decreasing humidity. This decreasing diffusivity is most likely linked to the increasing viscosity of the shikimic acid-water mixture. The degradation rate was also depending on particle size, most congruent with a reacto-diffusion limited kinetic case where the reaction progresses only in a shallow layer within the bulk. No gradient in the shikimic acid concentration was observed within the bulk material at any humidity indicating that the diffusivity of shikimic acid is still high enough to allow its equilibration throughout the particles on the timescale of hours at higher humidity and that the thickness of the oxidized layer under dry conditions, where the particles are solid, is beyond the resolution of STXM.

Compatibility Studies Of Blends Of PPG 4000 And PEG 4000 Using Viscosity Technique

NASA Astrophysics Data System (ADS)

Venkatramanan, K.; Arumugam, V.

2010-06-01

Certain properties of polymers can be enhanced by mixing it with another polymer. When two or more polymers are intimately mixed in a single continuous solid product, the composition is generally referred to as a polymer blend or polyblend. Depending upon the degree of miscibility or immiscibility, such a polyblend may resemble a random copolymer or a block or graft copolymer or it may show micro or macro heterogeneous separation into a multiphase system. Viscosity method is simple and it offers very useful information about the relationship between dilute solution properties and bulk structure of the polymer blend. The basic idea of using viscosity as a parameter for compatibility determination of polymer blends lies in the fact that in solution the repulsive interaction may cause shrinkage of polymer coils resulting in a viscosity of the polymer mixture that is lower than the value calculated from viscosities of the pure components on the assumption of the additive law. In the present study, an attempt has been made to blend PPG 4000 with PEG 4000 in 1,4 -Dioxane at 303K at 1% concentration. The blend compositions were formed in the ratio 0:1, 0.2:0.8, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.8:0.2, 1:0. Relative viscosity of the blend compositions was determined and the values are nonlinear which showed incompatibility. Miscibility nature of the blends were determined further using additive law, log additive law and free volume additive law and the experimental values in all the cases showed negative deviation which is a characteristic of immiscible blend. The miscibility nature of the blend was further confirmed through density, ultrasonic velocity, refractive index and other techniques. The blend showed immiscibility.

[Effect of sludge bulking on membrane fouling of MBR under low temperature].

PubMed

Ren, Nan-qi; Liu, Jiao; Wang, Xiu-heng

2009-01-01

The performance and membrane fouling of submerged membrane bioreactor were studied in the case of active sludge bulking under low temperature. The factors contributing to membrane fouling were discussed from the microorganism aspect. The results showed that COD removal efficiencies of supernatant and permeate were 85% and 92% respectively and filamentous sludge bulking had little impact on them. The sludge settleability became bad and the filament index (FI) increased from 2 to 5 during the formation of filamentous sludge bulking under low temperature. The filamentous bacteria extending from the sludge flocs formed net structure. Membrane fouling changed with time in linear under low temperature and the operation period of MBR was 15 d. However, membrane fouling was more serious in the condition of filamentous sludge bulking at low temperature, shortening the operation period of MBR to 7 d. The extracellular polymeric substances (EPS) content of bulking sludge was three times as that of normal sludge and the relative hydrophobicity (RH) of sludge flocs was decreased as FI increased. The increase of EPS and RH may cause more materials to deposit on the membrane surface, thus the membrane fouling rate improved and the operation period of MBR became short. Further analysis indicated that the mixed liquid viscosity, Zeta potential and sludge floc structure were all important factors of membrane fouling.

STUDIES ON THE ANOMALOUS VISCOSITY AND FLOW-BIREFRINGENCE OF PROTEIN SOLUTIONS

PubMed Central

Lawrence, A. S. C.; Miall, Margaret; Needham, Joseph; Shen, Shih-Chang

1944-01-01

1. An extensive investigation has been made of protein particle shape using the methods of flow-birefringence and anomalous viscosity measurement in the coaxial cell. 2. As a result of investigations on a number of proteins, it is concluded that they may be divided into four groups. Group A consists of those which show flow-anomaly both in the bulk phase and in the surface film. These also show flow-birefringence in the bulk phase. Examples: tobacco mosaic disease virus nucleoprotein; myosin. Though corpuscular proteins, they have elongated particles before denaturation. Group B consists of those which show flow-anomaly only (in the first instance) in the surface film, and no flow-birefringence in the bulk phase. They are probably close to spherical in shape in solution, but form elongated particles as they denature in the surface film. After this process has been completed, they may show flow-anomaly also in the bulk phase. Some proteins show flow-anomaly in the surface film immediately it forms, others only show it after a certain time has elapsed for the building up of the film. We designate the former as group B1 and the latter as group B2. Group B1, immediate surface film flow-anomaly. Examples: serum euglobulin, amphibian embryo euglobulin b. Group B2, slowly appearing surface film flow-anomaly. After the film has once been fully formed and then dispersed by shaking, the solution may have the properties of that of a protein in group B1; i.e., anomalous flow in the film may occur immediately on testing in the viscosimeter. Examples: avian ovalbumin, amphibian embryo pseudoglobulin. Group C consists of those proteins which show flow-anomaly neither in the bulk phase nor in the surface film, under the conditions used by us. They are probably close to spherical in shape. Examples: insulin, methaemoglobin, amphibian embryo euglobulin c, mucoproteins. 3. The theoretical significance of protein fibre molecules, whether native or formed by denaturation in the living cell, is discussed, especially in relation to experimental morphology and cytology. PMID:19873385

Unveiling the relationships among the viscosity equations of glass liquids and colloidal suspensions for obtaining universal equations with the generic free volume concept.

PubMed

Hao, Tian

2015-09-14

The underlying relationships among viscosity equations of glass liquids and colloidal suspensions are explored with the aid of free volume concept. Viscosity equations of glass liquids available in literature are focused and found to have a same physical basis but different mathematical expressions for the free volume. The glass transitions induced by temperatures in glass liquids and the percolation transition induced by particle volume fractions in colloidal suspensions essentially are a second order phase transition: both those two transitions could induce the free volume changes, which in turn determines how the viscosities are going to change with temperatures and/or particle volume fractions. Unified correlations of the free volume to both temperatures and particle volume fractions are thus proposed. The resulted viscosity equations are reducible to many popular viscosity equations currently widely used in literature; those equations should be able to cover many different types of materials over a wide temperature range. For demonstration purpose, one of the simplified versions of those newly developed equations is compared with popular viscosity equations and the experimental data: it can well fit the experimental data over a wide temperature range. The current work reveals common physical grounds among various viscosity equations, deepening our understanding on viscosity and unifying the free volume theory across many different systems.

Viscous self interacting dark matter and cosmic acceleration

NASA Astrophysics Data System (ADS)

Atreya, Abhishek; Bhatt, Jitesh R.; Mishra, Arvind

2018-02-01

Self interacting dark matter (SIDM) provides us with a consistent solution to certain astrophysical observations in conflict with collision-less cold DM paradigm. In this work we estimate the shear viscosity (η) and bulk viscosity (ζ) of SIDM, within kinetic theory formalism, for galactic and cluster size SIDM halos. To that extent we make use of the recent constraints on SIDM cross-section for the dwarf galaxies, LSB galaxies and clusters. We also estimate the change in solution of Einstein's equation due to these viscous effects and find that σ/m constraints on SIDM from astrophysical data provide us with sufficient viscosity to account for the observed cosmic acceleration at present epoch, without the need of any additional dark energy component. Using the estimates of dark matter density for galactic and cluster size halo we find that the mean free path of dark matter ~ few Mpc. Thus the smallest scale at which the viscous effect start playing the role is cluster scale. Astrophysical data for dwarf, LSB galaxies and clusters also seems to suggest the same. The entire analysis is independent of any specific particle physics motivated model for SIDM.

Crossing the phantom divide with dissipative normal matter in the Israel-Stewart formalism

NASA Astrophysics Data System (ADS)

Cruz, Norman; Lepe, Samuel

2017-04-01

A phantom solution in the framework of the causal Israel-Stewart (IS) formalism is discussed. We assume a late time behavior of the cosmic evolution by considering only one dominant matter fluid with viscosity. In the model it is assumed a bulk viscosity of the form ξ =ξ0ρ 1 / 2, where ρ is the energy density of the fluid. We evaluate and discuss the behavior of the thermodynamical parameters associated to this solution, like the temperature, rate of entropy, entropy, relaxation time, effective pressure and effective EoS. A discussion about the assumption of near equilibrium of the formalism and the accelerated expansion of the solution is presented. The solution allows to cross the phantom divide without evoking an exotic matter fluid and the effective EoS parameter is always lesser than -1 and time independent. A future singularity (big rip) occurs, but different from the Type I (big rip) solution classified in S. Nojiri, S.D. Odintsov and S. Tsujikawa (2005) [2], if we consider other thermodynamics parameters like, for example, the effective pressure in the presence of viscosity or the relaxation time.

Effect of Viscosity on the Crystallization of Undercooled Liquids

NASA Technical Reports Server (NTRS)

2003-01-01

There have been numerous studies of glasses indicating that low-gravity processing enhances glass formation. NASA PI s are investigating the effect of low-g processing on the nucleation and crystal growth rates. Dr. Ethridge is investigating a potential mechanism for glass crystallization involving shear thinning of liquids in 1-g. For shear thinning liquids, low-g (low convection) processing will enhance glass formation. The study of the viscosity of glass forming substances at low shear rates is important to understand these new crystallization mechanisms. The temperature dependence of the viscosity of undercooled liquids is also very important for NASA s containerless processing studies. In general, the viscosity of undercooled liquids is not known, yet knowledge of viscosity is required for crystallization calculations. Many researchers have used the Turnbull equation in error. Subsequent nucleation and crystallization calculations can be in error by many orders of magnitude. This demonstrates the requirement for better methods for interpolating and extrapolating the viscosity of undercooled liquids. This is also true for undercooled water. Since amorphous water ice is the predominant form of water in the universe, astrophysicists have modeled the crystallization of amorphous water ice with viscosity relations that may be in error by five orders-of-magnitude.

Investigation of Preparation and Mechanisms of a Dispersed Particle Gel Formed from a Polymer Gel at Room Temperature

PubMed Central

Zhao, Guang; Dai, Caili; Zhao, Mingwei; You, Qing; Chen, Ang

2013-01-01

A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles. PMID:24324817

Dynamics of confined water reconstructed from inelastic x-ray scattering measurements of bulk response functions

NASA Astrophysics Data System (ADS)

Coridan, Robert H.; Schmidt, Nathan W.; Lai, Ghee Hwee; Abbamonte, Peter; Wong, Gerard C. L.

2012-03-01

Nanoconfined water and surface-structured water impacts a broad range of fields. For water confined between hydrophilic surfaces, measurements and simulations have shown conflicting results ranging from “liquidlike” to “solidlike” behavior, from bulklike water viscosity to viscosity orders of magnitude higher. Here, we investigate how a homogeneous fluid behaves under nanoconfinement using its bulk response function: The Green's function of water extracted from a library of S(q,ω) inelastic x-ray scattering data is used to make femtosecond movies of nanoconfined water. Between two confining surfaces, the structure undergoes drastic changes as a function of surface separation. For surface separations of ≈9 Å, although the surface-associated hydration layers are highly deformed, they are separated by a layer of bulklike water. For separations of ≈6 Å, the two surface-associated hydration layers are forced to reconstruct into a single layer that modulates between localized “frozen’ and delocalized “melted” structures due to interference of density fields. These results potentially reconcile recent conflicting experiments. Importantly, we find a different delocalized wetting regime for nanoconfined water between surfaces with high spatial frequency charge densities, where water is organized into delocalized hydration layers instead of localized hydration shells, and are strongly resistant to `freezing' down to molecular distances (<6 Å).

Oscillatory fluid flow in deformable tubes: Implications for pore-scale hydromechanics from comparing experimental observations with theoretical predictions.

PubMed

Kurzeja, Patrick; Steeb, Holger; Strutz, Marc A; Renner, Jörg

2016-12-01

Oscillatory flow of four fluids (air, water, two aqueous sodium-tungstate solutions) was excited at frequencies up to 250 Hz in tubes of two materials (steel, silicone) covering a wide range in length, diameter, and thickness. The hydrodynamical response was characterized by phase shift and amplitude ratio between pressures in an upstream (pressure excitation) and a downstream reservoir connected by the tubes. The resulting standing flow waves reflect viscosity-controlled diffusive behavior and inertia-controlled wave behavior for oscillation frequencies relatively low and high compared to Biot's critical frequency, respectively. Rigid-tube theories correspond well with the experimental results for steel tubes filled with air or water. The wave modes observed for silicone tubes filled with the rather incompressible liquids or air, however, require accounting for the solid's shear and bulk modulus to correctly predict speed of pressure propagation and deformation mode. The shear mode may be responsible for significant macroscopic attenuation in porous materials with effective frame-shear moduli lower than the bulk modulus of the pore fluid. Despite notable effects of the ratio of densities and of acoustic and shear velocity of fluid and solid, Biot's frequency remains an approximate indicator of the transition from the viscosity to the inertia controlled regime.

Viscosity and thermal conductivity of moderately dense gas mixtures.

NASA Technical Reports Server (NTRS)

Wakeham, W. A.; Kestin, J.; Mason, E. A.; Sandler, S. I.

1972-01-01

Derivation of a simple, semitheoretical expression for the initial density dependence of the viscosity and thermal conductivity of gaseous mixtures in terms of the appropriate properties of the pure components and of their interaction quantities. The derivation is based on Enskog's theory of dense gases and yields an equation in which the composition dependence of the linear factor in the density expansion is explicit. The interaction quantities are directly related to those of the mixture extrapolated to zero density and to a universal function valid for all gases. The reliability of the formulation is assessed with respect to the viscosity of several binary mixtures. It is found that the calculated viscosities of binary mixtures agree with the experimental data with a precision which is comparable to that of the most precise measurements.

A Comparison of the Viscosities of Thickened Liquids for Pediatric Dysphagia.

NASA Astrophysics Data System (ADS)

Wijesinghe, Ranjith; Clifton, Mekale; Tarlton, Morgan; Heinsohn, Erica; Ewing, Mary

It has been reported that Speech Language Pathologists in different facilities across the nation use a variety of thickening agents and recipes as therapeutic measures for infants and children diagnosed with dysphagia. Limited research has been completed in this area. Viscosity was tested to determine the thickness of each thickening agent mixed with infant formula. The values were then compared to the National Dysphagia Diet liquid levels to determine which thickening agent resulted in the desired viscosity levels. The thickeners were mixed with common infant formulas and soy formulas to determine if the type of formula impacted the viscosity. The main goal was to determine if the assumed thickness level (viscosity) of prescribed thickened liquids was actually being met. This topic is of high concern because of its impact on the safety and well-being of clients with dysphagia. A viscometer was used to collect the viscosity levels. Commercially available formulas selected for this study. The final results of our investigation will be presented during the APS meeting. This work is supported by a Ball State University Immersive Learning Grant.

A causal viscous cosmology without singularities

NASA Astrophysics Data System (ADS)

Laciana, Carlos E.

2017-05-01

An isotropic and homogeneous cosmological model with a source of dark energy is studied. That source is simulated with a viscous relativistic fluid with minimal causal correction. In this model the restrictions on the parameters coming from the following conditions are analized: (a) energy density without singularities along time, (b) scale factor increasing with time, (c) universe accelerated at present time, (d) state equation for dark energy with " w" bounded and close to -1. It is found that those conditions are satisfied for the following two cases. (i) When the transport coefficient (τ _{Π}), associated to the causal correction, is negative, with the additional restriction ζ | τ _{Π}| >2/3, where ζ is the relativistic bulk viscosity coefficient. The state equation is in the "phantom" energy sector. (ii) For τ _{Π} positive, in the "k-essence" sector. It is performed an exact calculation for the case where the equation of state is constant, finding that option (ii) is favored in relation to (i), because in (ii) the entropy is always increasing, while this does no happen in (i).

Notes on hyperscaling violating Lifshitz and shear diffusion

NASA Astrophysics Data System (ADS)

Kolekar, Kedar S.; Mukherjee, Debangshu; Narayan, K.

2017-07-01

We explore in greater detail our investigations of shear diffusion in hyperscaling violating Lifshitz theories in Phys. Lett. B 760, 86 (2016), 10.1016/j.physletb.2016.06.046. This adapts and generalizes the membrane-paradigm-like analysis of Kovtun, Son, and Starinets for shear gravitational perturbations in the near horizon region given certain self-consistent approximations, leading to the shear diffusion constant on an appropriately defined stretched horizon. In theories containing a gauge field, some of the metric perturbations mix with some of the gauge field perturbations and the above analysis is somewhat more complicated. We find a similar near-horizon analysis can be obtained in terms of new field variables involving a linear combination of the metric and the gauge field perturbation resulting in a corresponding diffusion equation. Thereby as before, for theories with Lifshitz and hyperscaling violating exponents z , θ satisfying z <4 -θ in four bulk dimensions, our analysis here results in a similar expression for the shear diffusion constant with power-law scaling with temperature suggesting universal behavior in relation to the viscosity bound. For z =4 -θ , we find logarithmic behavior.

It's harder to splash on soft solids

NASA Astrophysics Data System (ADS)

Howison, Sam; Howland, Christopher; Antkowiak, Arnaud; Castrejon-Pita, Rafael; Oliver, James; Style, Robert; Castrejon-Pita, Alfonso

2016-11-01

Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses we show that substrate stiffness also affects the splashing thresh- old. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli < 100kPa reduce splashing, in agreement with simple scaling arguments. Thus materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets. EPSRC (CJH), John Fell Oxford University Press (OUP) Research Fund (AACP and RWS), The Royal Society (AAC-P).

Material Science

NASA Image and Video Library

2004-07-12

This soldering iron has an evacuated copper capsule at the tip that contains a pellet of Bulk Metallic Glass (BMG) aboard the International Space Station (ISS). Prior to flight, researchers sealed a pellet of bulk metallic glass mixed with microscopic gas-generating particles into the copper ampoule under vacuum. Once heated in space, such as in this photograph, the particles generated gas and the BMG becomes a viscous liquid. The released gas made the sample foam within the capsule where each microscopic particle formed a gas-filled pore within the foam. The inset image shows the oxidation of the sample after several minutes of applying heat. Although hidden within the brass sleeve, the sample retained the foam shape when cooled, because the viscosity increased during cooling until it was solid.

Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.

Particles composed of secondary organic material (SOM) are abundant in the lower troposphere and play important roles in climate, air quality, and health. The viscosity of these particles is a fundamental property that is presently poorly quantified for conditions relevant to the lower troposphere. Using two new techniques, namely a bead-mobility technique and a poke-flow technique, in conjunction with simulations of fluid flow, we measure the viscosity of the watersoluble component of SOM produced by α-pinene ozonolysis. The viscosity is comparable to that of honey at 90% relative humidity (RH), comparable to that of peanut butter at 70% RH andmore » greater than or comparable to that of bitumen for ≤ 30% RH, implying that the studied SOM ranges from liquid to semisolid/solid at ambient relative humidities. With the Stokes-Einstein relation, the measured viscosities further imply that the growth and evaporation of SOM by the exchange of organic molecules between the gas and condensed phases may be confined to the surface region when RH ≤ 30%, suggesting the importance of an adsorption-type mechanism for partitioning in this regime. By comparison, for RH ≥ 70% partitioning of organic molecules may effectively occur by an absorption mechanism throughout the bulk of the particle. Finally, the net uptake rates of semi-reactive atmospheric oxidants such as O3 are expected to decrease by two to five orders of magnitude for a change in RH from 90% to ≤ 30% RH, with possible implications for the rates of chemical aging of SOM particles in the atmosphere.« less

Surfactant-Influenced Gas-Liquid Interfaces: Nonlinear Equation of State and Finite Surface Viscosities.

PubMed

Lopez; Hirsa

2000-09-15

A canonical flow geometry was utilized for a fundamental study of the coupling between bulk flow and a Newtonian gas-liquid interface in the presence of an insoluble surfactant. We develop a Navier-Stokes numerical model of the flow in the deep-channel surface viscometer geometry, which consists of stationary inner and outer cylinders, a floor rotating at a constant angular velocity, and an interface covered initially by a uniformly distributed surfactant. Here, the floor of the annular channel is rotated fast enough so the flow is nonlinear and drives the film toward the inner cylinder. The boundary conditions at the interface are functions of the surface tension, surface shear viscosity, and surface dilatational viscosity, as described by the Boussinesq-Scriven surface model. A physical surfactant system, namely hemicyanine, an insoluble monolayer on an air-water interface, with measured values of surface tension and surface shear viscosity versus concentration, was used in this study. We find that a surfactant front can form, depending on the Reynolds number and the initial surfactant concentration. The stress balance in the radial direction was found to be dominated by the Marangoni stress, but the azimuthal stress was only due to the surface shear viscosity. Numerical studies are presented comparing results of surfactant-influenced interface cases implementing the derived viscoelastic interfacial stress balance with those using a number of idealized stress balances, as well as a rigid no-slip surface, providing added insight into the altered dynamics that result from the presence of a surfactant monolayer. Copyright 2000 Academic Press.

Damping and Amplification of Seismic Waves in Gas-Charged Magma

NASA Astrophysics Data System (ADS)

Neuberg, J. W.; Lensky, N. G.

2001-12-01

Low-frequency seismic signals are generated at the interface betweeen a solid medium and a magmatic melt. The existence of gas bubbles in the magma introduces a damping mechanism which depends mainly on the gas volume fraction and on the viscosity of the melt. However, in case of a sudden unloading (e.g. by lava dome failure) a decompressional wave propagates through the magma which becomes now supersaturated. Diffusion of gas into the bubbles leads to an exponential bubble growth which is in general frequency dependent. Such a system can be represented by a negative bulk viscosity which results in a net amplification rather than damping of the decompressional wave. Furthermore, the effects of a harmonically varying pressure on the supersaturated melt is explored, as it is caused by seismic tremor and prolongued conduit resonance.

Dynamics of charged viscous dissipative cylindrical collapse with full causal approach

NASA Astrophysics Data System (ADS)

Shah, S. M.; Abbas, G.

2017-11-01

The aim of this paper is to investigate the dynamical aspects of a charged viscous cylindrical source by using the Misner approach. To this end, we have considered the more general charged dissipative fluid enclosed by the cylindrical symmetric spacetime. The dissipative nature of the source is due to the presence of dissipative variables in the stress-energy tensor. The dynamical equations resulting from such charged cylindrical dissipative source have been coupled with the causal transport equations for heat flux, shear and bulk viscosity, in the context of the Israel-Steward theory. In this case, we have the considered Israel-Steward transportation equations without excluding the thermodynamics viscous/heat coupling coefficients. The results are compared with the previous works in which such coefficients were excluded and viscosity variables do not satisfy the casual transportation equations.

Estimation of viscosity based on transverse momentum correlations

NASA Astrophysics Data System (ADS)

Sharma, Monika

2010-02-01

The heavy ion program at RHIC created a paradigm shift in the exploration of strongly interacting hot and dense matter. An important milestone achieved is the discovery of the formation of strongly interacting matter which seemingly flows like a perfect liquid at temperatures on the scale of T ˜ 2 x10^12 K [1]. As a next step, we consider measurements of transport coefficients such as kinematic, shear or bulk viscosity? Many calculations based on event anisotropy measurements indicate that the shear viscosity to the entropy density ratio (η/s) of the fluid formed at RHIC is significantly below that of all known fluids including the superfluid ^4He [2]. Precise determination of η/s ratio is currently a subject of extensive study. We present an alternative technique for the determination of medium viscosity proposed by Gavin and Aziz [3]. Preliminary results of measurements of the evolution of the transverse momentum correlation function with collision centrality of Au + Au interactions at √sNN = 200 GeV will be shown. We present results on differential version of the correlation measure and describe its use for the experimental determination of η/s.[4pt] [1] J. Adams et al., [STAR Collaboration], Nucl. Phys. A 757 (2005) 102.[0pt] [2] R. A. Lacey et al., Phys. Rev. Lett. 98 (2007) 092301.[0pt] [3] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302. )

Rheology and tribology of lubricants with polymeric viscosity modifiers

NASA Astrophysics Data System (ADS)

Babak, LotfizadehDehkordi

Elastohydrodynamic lubrication (EHL) theory has been used to model the lubrication state of antifriction machine elements, where initial viscosity and pressure viscosity coefficients are essential parameters in film thickness modeling. Since the pressures of lubricants in the contact zone can be very high, it is important to know the rheological properties of lubricants in these pressure and temperature regimes. The characteristics of viscosity behavior as a function of pressure are also essential for a universal definition of the pressure viscosity coefficient in order to estimate film thickness in an EHL regime. In this study, viscosities and pressure-viscosity coefficients of ten commercial engine and gear oils and seventeen laboratory-produced oil/polymer viscosity modifiers (VM) additives are measured up to 1.3 GPa at 40, 75 and 100 °C. For the first time, a sharp increase in the viscosity and piezoviscous factor is observed in both mineral-based and synthetic-based oils with different VMs. Analysis of the experimental results indicates that sharp increase in viscosity observed in these experiments are believed to arise from physical changes in the VMs, that is liquid-solid phase transition. Evidence is offered that polymer properties such as molecular weight, concentration and structure influence the onset of the phase transitions. A modified Yasutomi model, which normally describes the pressure dependence of the viscosity of lubricants very well, fails to predict the viscosity of the specimens above the onset of sharp increase in viscosity. A design of experiment (DOE) analysis using Design-Expert software indicates that pressure and temperature are the most critical parameters in the viscosity variation. Tribological tests demonstrate that wear in the contact, zone occurs at temperatures and stresses that coincides with the VM phase transitions in both commercial and laboratory synthesized oil/VMs. Tribological results also indicate that the onset of the sharp increase in viscosity can have significant and unanticipated consequences on the elastohydrodynamic contact and can adversely affect EHL theory. The onset of the steep rise in viscosity may also affect the torque and power losses in a mechanical system. Hence, this previously unknown behavior of the lubricant with VMs should be seriously considered in the application of lubricant in mechanical system.

Mechanisms for the Crystallization of ZBLAN

NASA Technical Reports Server (NTRS)

Ethridge, Edwin C.; Tucker, Dennis S.; Kaukler, William; Antar, Basil

2003-01-01

The objective of this ground based study is to test the hypothesis that shear thinning (the non-Newtonian response of viscosity to shear rate) is a viable mechanism to explain the observation of enhanced glass formation in numerous low-g experiments. In 1-g, fluid motion results from buoyancy forces and surface tension driven convection. This fluid flow will introduce shear in undercooled liquids in 1-g. In low-g it is known that fluid flows are greatly reduced so that the shear rate in fluids can be extremely low. It is believed that some fluids may have weak structure in the absence of flow. Very small shear rates could cause this structure to collapse in response to shear resulting in a lowering of the viscosity of the fluid. The hypothesis of this research is that: Shear thinning in undercooled liquids decreases the viscosity, increasing the rate of nucleation and crystallization of glass forming melts. Shear in the melt can be reduced in low-g, thus enhancing undercooling and glass formation. The viscosity of a model glass (lithium di-silicate, L2S) often used for crystallization studies has been measured at very low shear rates using a dynamic mechanical thermal analyzer. Our results are consistent with increasing viscosity with a lowering of shear rates. The viscosity of L2S may vary as much as an order of magnitude depending on the shear rate in the temperature region of maximum nucleation and crystal growth. Classical equations for nucleation and crystal growth rates, are inversely related to the viscosity and viscosity to the third power respectively. An order of magnitude variation in viscosity (with shear) at a given temperature would have dramatic effects on glass crystallization Crystallization studies with the heavy metal fluoride glass ZBLAN (ZrF2-BaF2-LaF3-AlF3-NaF) to examine the effect of shear on crystallization are being initiated. Samples are to be melted and quenched under quiescent conditions at different shear rates to determine the effect on crystallization. The results from this study are expected to advance the current scientific understanding of glass formation in low-g and glass crystallization under glass molding conditions and will improve the scientific understanding of technological processes such as fiber pulling, bulk amorphous alloys, and glass fabrication processes.

An integrated mathematical model for chemical oxygen demand (COD) removal in moving bed biofilm reactors (MBBR) including predation and hydrolysis.

PubMed

Revilla, Marta; Galán, Berta; Viguri, Javier R

2016-07-01

An integrated mathematical model is proposed for modelling a moving bed biofilm reactor (MBBR) for removal of chemical oxygen demand (COD) under aerobic conditions. The composite model combines the following: (i) a one-dimensional biofilm model, (ii) a bulk liquid model, and (iii) biological processes in the bulk liquid and biofilm considering the interactions among autotrophic, heterotrophic and predator microorganisms. Depending on the values for the soluble biodegradable COD loading rate (SCLR), the model takes into account a) the hydrolysis of slowly biodegradable compounds in the bulk liquid, and b) the growth of predator microorganisms in the bulk liquid and in the biofilm. The integration of the model and the SCLR allows a general description of the behaviour of COD removal by the MBBR under various conditions. The model is applied for two in-series MBBR wastewater plant from an integrated cellulose and viscose production and accurately describes the experimental concentrations of COD, total suspended solids (TSS), nitrogen and phosphorous obtained during 14 months working at different SCLRs and nutrient dosages. The representation of the microorganism group distribution in the biofilm and in the bulk liquid allow for verification of the presence of predator microorganisms in the second reactor under some operational conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Universality Results for Multi-Layer Hele-Shaw and Porous Media Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2012-11-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface. Motivated by a need to understand the effect of various injection policies currently in practice for chemical enhanced oil recovery, we study linear stability of displacement processes in a Hele-Shaw cell involving injection of an arbitrary number of immiscible fluid phases in succession. This is a problem involving many interfaces. Universal stability results have been obtained for this multi-layer (multi-region) flow in the sense that the results hold with arbitrary number of interfaces. These stability results have been applied to design injection policies that are considerably less unstable than the pure Saffman-Taylor case. In particular, we determine specific values of the viscosity of the fluid layers corresponding to smallest unstable band. Moreover, we discuss universal selection principle of optimal viscous profiles. The talk is based on following papers. Qatar National Fund (a member of the Qatar Foundation).

Viscosity of dysphagia-oriented cold-thickened beverages: effect of setting time at refrigeration temperature.

PubMed

Kim, Sung-Gun; Yoo, Byoungseung

2015-01-01

Although extensive literature is available on the viscosity of thickened beverages with food thickeners, no attempt has been made to study the effect of setting time on the viscosity of pudding-like cold-thickened beverages with xanthan gum (XG)-based thickeners by using a rheometer. In particular, it is of considerable practical importance to investigate the effect of setting time on their viscosity at 5°C because some cold-thickened beverages will be prepared in the kitchen in bulk and stored at 5°C before serving or consuming rather than serving immediately upon mixing with thickeners. To examine the effect of different setting times (15-120 min) on the viscosity of cold-thickened beverages prepared with various XG-based food thickeners, and also to compare the viscosity differences among the various cold beverages and XG-based food thickeners in beverage-thickener mixture systems. Four commercially available XG-based food thickeners (A-D) and three cold beverages (water, orange juice and milk) were used for the preparation of cold-thickened beverages. The thickened sample was portioned into six samples for the designated setting times and then stored at 5°C over setting time. Their apparent viscosity (η(a,50)) at 50 s(-1) was measured using a rheometer. The largest increases in η(a,50) values for thickened beverages, except for water, were observed at 15 min (p < 0.05), showing a pudding-like fluid, and at longer time periods their η(a,50) values gradually increased or were constant with an increase in setting time. The percentage increase in viscosity values at different setting times (15-120 min) as compared with the control (0 min) was less pronounced in the thickened orange juice and milk samples with thickener A over setting time, indicating that the thickened beverages with thickener A had more stable structure compared with those with other thickeners (B-D) over time. Statistical analysis showed that changes in the viscosity of cold-thickened beverages over setting time are greatly influenced by the type of beverages and thickeners. Cold-thickened beverages should be carefully prepared with instant commercial XG-based food thickeners because they produced different thickening patterns over setting time which clinicians must consider for a safe and easy swallowing. The information presented in this study will provide both clinicians and patients with additional knowledge to prepare cold-thickened beverages with the corrected viscosity for safe swallowing. © 2014 Royal College of Speech and Language Therapists.

Thermophysical Property Measurements of Silicon-Transition Metal Alloys

NASA Technical Reports Server (NTRS)

Banish, R. Michael; Erwin, William R.; Sansoucie, Michael P.; Lee, Jonghyun; Gave, Matthew A.

2014-01-01

Metals and metallic alloys often have high melting temperatures and highly reactive liquids. Processing reactive liquids in containers can result in significant contamination and limited undercooling. This is particularly true for molten silicon and it alloys. Silicon is commonly termed "the universal solvent". The viscosity, surface tension, and density of several silicon-transition metal alloys were determined using the Electrostatic Levitator system at the Marshall Space Flight Center. The temperature dependence of the viscosity followed an Arrhenius dependence, and the surface tension followed a linear temperature dependence. The density of the melts, including the undercooled region, showed a linear behavior as well. Viscosity and surface tension values were obtain for several of the alloys in the undercooled region.

Influence of interfacial slip on the suspension rheology of a dilute emulsion of surfactant-laden deformable drops in linear flows

NASA Astrophysics Data System (ADS)

Das, Sayan; Bhattacharjee, Anirban; Chakraborty, Suman

2018-03-01

The present study deals with the effect of interfacial slip on the deformation and emulsion rheology of a dilute suspension of droplets in a linear flow. The droplets are laden with surfactants that are bulk-insoluble and get transported only along the interface. An asymptotic approach is adopted for the present analysis in order to tackle the nonlinearity present due to deformation of droplets. The analysis is carried out for two different limiting scenarios, namely, surface diffusion-dominated-surfactant transport and surface convection-dominated surfactant transport. For either of the limiting cases, we look into the droplet dynamics for two commonly encountered bulk flows—uniaxial extensional and simple shear flow. Under the assumption of negligible fluid inertia in either phase, it is shown that slip at the droplet interface significantly affects the surfactant-induced Marangoni stress and hence droplet deformation and emulsion rheology. The presence of interfacial slip not only brings about a decrease in the droplet deformation but also reduces the effective viscosity of the emulsion. The fall in both droplet deformation and effective viscosity is found to be more severe for the limiting case of surface convection-dominated surfactant transport. For the case of an imposed simple shear flow, the normal stress differences generated due to droplet deformation are affected as well due to the presence of interfacial slip.

Thermodynamic assessment of the magmatic history of Blue Rock shield volcano, Jackson Co., Oregon: application of a new DNi (olivine-melt) geothermometer and other models

NASA Astrophysics Data System (ADS)

Crabtree, Stephen M.; Huber, Abigail; Beck, Karl

2017-05-01

Blue Rock is a basaltic shield volcano in the southern Oregon Cascades, north of Mt. McLoughlin, showing bulk phenocryst abundances ranging from 5 to 28 vol%, and a variety of groundmass textures. Compositional analyses of olivine and plagioclase phenocrysts and glomerocrysts allowed for the sequential application of a new {D}_{Ni}^{olivine-melt} thermometer, a plagioclase-melt hygrometer, and a viscosity model to define olivine-in conditions for a suite of lavas erupted from this edifice. Calculated olivine-in temperatures were compared to results from the anhydrous MELTS model, and the D (Mg) model of Beattie (1993). Model results were consistent with experimental data for hydrous arc basalts with respect to temperature (1053-1146 °C), dissolved-H2O contents (0.9-2.4 wt% H2O), and viscosity (1.9-2.2 log10 Pa s), confirming the utility of these models in assessing the thermodynamic properties of mafic, hydrous arc lavas over a broad range in crystallinity, requiring only the completion of bulk geochemical and microprobe analyses. These studies also reinforced the significant and predictable role of water, affecting the compositions of crystals grown during magmatic ascent, and allowed the definition of a reasonable multi-stage eruptive sequence consistent with the degassing of magmas on ascent in the formation of this small-scale basaltic edifice.

Plasma kinetic effects on atomistic mix in one dimension and at structured interfaces (I)

NASA Astrophysics Data System (ADS)

Yin, L.; Albright, B. J.; Vold, E. L.; Taitano, W.; Chacon, L.; Simakov, A.

2017-10-01

Kinetic effects on interfacial mix are examined using VPIC simulations. In 1D, comparisons are made to the results of analytic theory in the small Knudsen number limit. While the bulk mixing properties of interfaces are in general agreement, differences arise near the low-concentration fronts during the early evolution of a sharp interface when the species' perpendicular scattering rate dominates over the slowing down rate. In kinetic simulations, the diffusion velocities can be larger or comparable to the ion thermal speeds, and the Knudsen number can be large. Super-diffusive growth in mix widths (Δx ta where a >=1/2) is seen before transition to the slow diffusive process predicted from theory (a =1/2). Mixing at interfaces leads to persistent, bulk, hydrodynamic features in the center of mass flow profiles as a result of diffusion and momentum conservation. These conclusions are drawn from VPIC results together with simulations from the RAGE hydrodynamics code with an implementation of diffusion and viscosity from theory and an implicit Vlasov-Fokker-Planck code iFP. In perturbed 2D and 3D interfaces, it is found that 1D ambipolarity is still valid and that initial perturbations flatten out on a-few-ps time scale, implying that finite diffusivity and viscosity can slow instability growth in ICF and HED settings. Work supported by the LANL ASC and Science programs.

The development of new, low-cost perfluoroalkylether fluids with excellent low and high-temperature properties

NASA Technical Reports Server (NTRS)

Bierschenk, Thomas R.; Kawa, Hajimu; Juhlke, Timothy J.; Lagow, Richard J.

1988-01-01

A series of perfluoroalkylether (PFAE) fluids were synthesized by direct fluorination. Viscosity-temperature properties, oxidation stabilities, oxidation-corrosion properties, and lubricity were determined. The fluids were tested in the presence of common elastomers to check for compatibility. The bulk modulus of each was measured to determine if any could be used as nonflammable aircraft hydraulic fluid. It was determined that as the carbon to oxygen ratio decreases, the viscometric properties improve, the fluids may become poor lubricants, the bulk modulus increases, the surface tension increases, and the fluid density increases. The presence of difluoromethylene oxide units in the polymer does not seriously lower the oxidation and oxidation-corrosion stabilities as long as the difluoromethylene oxide units are separated by other units.

Bulk viscous quintessential inflation

NASA Astrophysics Data System (ADS)

Haro, Jaume; Pan, Supriya

In a spatially-flat Friedmann-Lemaître-Robertson-Walker universe, the incorporation of bulk viscous process in general relativity leads to an appearance of a nonsingular background of the universe that both at early and late times depicts an accelerated universe. These early and late scenarios of the universe can be analytically calculated and mimicked, in the context of general relativity, by a single scalar field whose potential could also be obtained analytically where the early inflationary phase is described by a one-dimensional Higgs potential and the current acceleration is realized by an exponential potential. We show that the early inflationary universe leads to a power spectrum of the cosmological perturbations which match with current observational data, and after leaving the inflationary phase, the universe suffers a phase transition needed to explain the reheating of the universe via gravitational particle production. Furthermore, we find that at late times, the universe enters into the de Sitter phase that can explain the current cosmic acceleration. Finally, we also find that such bulk viscous-dominated universe attains the thermodynamical equilibrium, but in an asymptotic manner.

Industrial grade versus scientific pure: Influence on melt properties

NASA Astrophysics Data System (ADS)

Jonas, I.; Hembree, W.; Yang, F.; Busch, R.; Meyer, A.

2018-04-01

Viscosity, density, and the undercooling ability of the Zr-based bulk glass forming melt, which was manufactured in two different degrees of purity, have been studied. Investigations have been carried out by means of Couette rheometry and electrostatic and electromagnetic levitation with the latter under microgravity conditions. We found that oxygen and impurities present in industrial grade metals do not significantly alter the melt viscosity and density, while they clearly affect the undercooling ability. Comparing container based and containerless results showed that Couette rheometry can be applied in the temperature range between 1150 K and 1375 K, where it provides reliable data, but only at a rather low oxygen content. Higher oxygen contents, as in the case of the industrial grade alloy, cause measurement artefacts. In the case of Zr59.3Cu28.8Al10.4Nb1.5 alloys, these findings allow a better localization of the key factors dominating the glass forming ability.

Polar symmetric flow of a viscous compressible atmosphere; an application to Mars

NASA Technical Reports Server (NTRS)

Pirraglia, J. A.

1974-01-01

The atmosphere is assumed to be driven by a polar symmetric temperature field and the equations of motion in pressure ratio coordinates are linearized by considering the zero order in terms of a thermal Rossby number R delta I/(2a omega) sq where delta T is a measure of the latitudinal temperature gradient. When the eddy viscosity is greater than 1 million sq cm/sec, the boundary layer extends far up into the atmosphere, making the geostrophic approximation invalid for the bulk of the atmosphere. A temperature model for Mars was used which was based on Mariner 9 infrared spectral data with a 30% increase in the depth averaged temperature from the winter pole to the subsolar point. The results obtained for the increase in surface pressure from the subsolar point to the winter pole, as a function of eddy viscosity and with no-slip conditions imposed at the surface, are given.

Resonance Raman and UV-visible spectroscopy of black dyes on textiles.

PubMed

Abbott, Laurence C; Batchelor, Stephen N; Smith, John R Lindsay; Moore, John N

2010-10-10

Resonance Raman and UV-visible diffuse reflectance spectra were recorded from samples of cotton, viscose, polyester, nylon, and acrylic textile swatches dyed black with one of seven single dyes, a mixture of two dyes, or one of seven mixtures of three dyes. The samples generally gave characteristic Raman spectra of the dyes, demonstrating that the technique is applicable for the forensic analysis of dyed black textiles. Survey studies of the widely used dye Reactive Black 5 show that essentially the same Raman spectrum is obtained on bulk sampling from the dye in solution, on viscose, on cotton at different uptakes, and on microscope sampling from the dye in cotton threads and single fibres. The effects of laser irradiation on the Raman bands and emission backgrounds from textile samples with and without dye are also reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Finite amplitude effects on drop levitation for material properties measurement

NASA Astrophysics Data System (ADS)

Ansari Hosseinzadeh, Vahideh; Holt, R. Glynn

2017-05-01

The method of exciting shape oscillation of drops to extract material properties has a long history, which is most often coupled with the technique of acoustic levitation to achieve non-contact manipulation of the drop sample. We revisit this method with application to the inference of bulk shear viscosity and surface tension. The literature is replete with references to a "10% oscillation amplitude" as a sufficient condition for the application of Lamb's analytical expressions for the shape oscillations of viscous liquids. Our results show that even a 10% oscillation amplitude leads to dynamic effects which render Lamb's results inapplicable. By comparison with samples of known viscosity and surface tension, we illustrate the complicating finite-amplitude effects (mode-splitting and excess dissipation associated with vorticity) that can occur and then show that sufficiently small oscillations allow us to recover the correct material properties using Lamb's formula.

Artificial fluid properties for large-eddy simulation of compressible turbulent mixing

NASA Astrophysics Data System (ADS)

Cook, Andrew W.

2007-05-01

An alternative methodology is described for large-eddy simulation (LES) of flows involving shocks, turbulence, and mixing. In lieu of filtering the governing equations, it is postulated that the large-scale behavior of a LES fluid, i.e., a fluid with artificial properties, will be similar to that of a real fluid, provided the artificial properties obey certain constraints. The artificial properties consist of modifications to the shear viscosity, bulk viscosity, thermal conductivity, and species diffusivity of a fluid. The modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes. Requisite behavior of the artificial properties is discussed and results are shown for a variety of test problems, each designed to exercise different aspects of the models. When combined with a tenth-order compact scheme, the overall method exhibits excellent resolution characteristics for turbulent mixing, while capturing shocks and material interfaces in a crisp fashion.

Effects of causality on the fluidity and viscous horizon of quark-gluon plasma

NASA Astrophysics Data System (ADS)

Rahaman, Mahfuzur; Alam, Jan-e.

2018-05-01

The second-order Israel-Stewart-M u ̈ller relativistic hydrodynamics was applied to study the effects of causality on the acoustic oscillation in relativistic fluid. Causal dispersion relations have been derived with nonvanishing shear viscosity, bulk viscosity, and thermal conductivity at nonzero temperature and baryonic chemical potential. These relations have been used to investigate the fluidity of quark-gluon plasma (QGP) at finite temperature (T ). Results of the first-order dissipative hydrodynamics have been obtained as a limiting case of the second-order theory. The effects of the causality on the fluidity near the transition point and on the viscous horizon are found to be significant. We observe that the inclusion of causality increases the value of fluidity measure of QGP near Tc and hence makes the flow strenuous. It was also shown that the inclusion of the large magnetic field in the causal hydrodynamics alters the fluidity of QGP.

Sucralose Destabilization of Protein Structure.

PubMed

Chen, Lee; Shukla, Nimesh; Cho, Inha; Cohn, Erin; Taylor, Erika A; Othon, Christina M

2015-04-16

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence anisotropy. Tryptophan exhibits rotational diffusion proportional to the measured bulk viscosity for sucrose solutions over a wide range of concentrations, consistent with a Stokes-Einstein model. For sucralose solutions, however, the diffusion is dependent on the concentration, strongly diverging from the viscosity predictions, and results in heterogeneous rotational diffusion.

Influence of a thin compressible insoluble liquid film on the eddy currents generated by interacting surface waves

NASA Astrophysics Data System (ADS)

Parfenyev, Vladimir M.; Vergeles, Sergey S.

2018-06-01

Recently the generation of eddy currents by interacting surface waves was observed experimentally. The phenomenon provides the possibility for manipulation of particles which are immersed in the fluid. The analysis shows that the amplitude of the established eddy currents produced by stationary surface waves does not depend on the fluid viscosity in the free surface case. The currents become parametrically larger, being inversely proportional to the square root of the fluid viscosity in the case when the fluid surface is covered by an almost incompressible thin liquid (i.e., shear elasticity is zero) film formed by an insoluble agent with negligible internal viscous losses as compared to the dissipation in the fluid bulk. Here we extend the theory for a thin insoluble film with zero shear elasticity and small shear and dilational viscosities on the case of an arbitrary elastic compression modulus. We find both contributions into the Lagrangian motion of passive tracers, which are the advection by the Eulerian vertical vorticity and the Stokes drift. Whereas the Stokes drift contribution preserves its value for the free surface case outside a thin viscous sublayer, the Eulerian vertical vorticity strongly depends on the fluid viscosity at high values of the film compression modulus. The Stokes drift acquires a strong dependence on the fluid viscosity inside the viscous sublayer; however, the change is compensated by an opposite change in the Eulerian vertical vorticity. As a result, the vertical dependence of the intensity of eddy currents is given by a sum of two decaying exponents with both decrements being of the order of the wave number. The decrements are numerically different, so the Eulerian contribution becomes dominant at some depth for the surface film with any compression modulus.

Project SQUID: The Viscosity of the Isotopes of Hydrogen and Their Intermolecular Force Potentials

DTIC Science & Technology

1963-12-01

values of the pseudo- Lennard - Jones potential for either hydrogen o- deuteriua. On the present evidence, and cn the present evidence alone, it would...W4drogesror deuterium forces the conclusion that neither gas obeys a lenrArd- Jones six- twelve potential , it is, nevertheless, useful to discuss the values...VISCOSITY OF THE ISOTOPES OF HYDROGEN AND THEIR INTERMOLECULAR FORCE POTENTIALS * by S. Kestir and A Nagashima Broow University December 1963 PROJECT SQUID

Effect of curvature squared corrections to gravitational action on viscosity-to-entropy ratio of the dual gauge theory

NASA Astrophysics Data System (ADS)

Petrov, Pavel

In this thesis we study the properties of strongly-coupled large-N conformal field theories (CFT's) using AdS/CFT correspondence. Chapter 1 serves as an introduction. In Chapter 2 we study the shear viscosity of strongly-coupled large-N conformal field theories. We find that it is affected by R2 corrections to the AdS action and present an example of 4D theory in which the the conjectured universal lower bound on viscosity-to-entropy ratio η/s > 1/4π is violated by 1/N corrections. This fact proves that there is no universal lower bound of 1/4π on viscosity-to-entropy ratio and may be relevant for the studies of QCD quark-gluon plasma for which this ratio is experimentally found to be close to 1/4π. In Chapter 3 we study the formation of the electron star in 4D AdS space. We show that in a gravity theory with charged fermions a layer of charged fermion fluid may form at a finite distance from the charged black hole. We show that these “electron stars” are candidate gravity duals for strongly interacting fermion systems at finite density and finite temperature. Entropy density for such systems scales as s ˜ T2/z at low temperatures as expected from IR criticality of electron stars solutions.

Influence of complex interfacial rheology on the thermocapillary migration of a surfactant-laden droplet in Poiseuille flow

NASA Astrophysics Data System (ADS)

Das, Sayan; Chakraborty, Suman

2018-02-01

The effect of surface viscosity on the motion of a surfactant-laden droplet in the presence of a non-isothermal Poiseuille flow is studied, both analytically and numerically. The presence of bulk-insoluble surfactants along the droplet surface results in interfacial shear and dilatational viscosities. This, in turn, is responsible for the generation of surface-excess viscous stresses that obey the Boussinesq-Scriven constitutive law for constant values of surface shear and dilatational viscosities. The present study is primarily focused on finding out how this confluence can be used to modulate droplet dynamics in the presence of Marangoni stress induced by nonuniform distribution of surfactants and temperature along the droplet surface, by exploiting an intricate interplay of the respective forcing parameters influencing the interfacial stresses. Under the assumption of negligible fluid inertia and thermal convection, the steady-state migration velocity of a non-deformable spherical droplet, placed at the centerline of an imposed unbounded Poiseuille flow, is obtained for the limiting case when the surfactant transport along the interface is dominated by surface diffusion. Our analysis proves that the droplet migration velocity is unaffected by the shear viscosity whereas the dilatational viscosity has a significant effect on the same. The surface viscous effects always retard the migration of a surfactant-laden droplet when the temperature in the far-field increases in the direction of the imposed flow although the droplet always migrates towards the hotter region. On the contrary, if a large temperature gradient is applied in a direction opposite to that of the imposed flow, the direction of droplet migration gets reversed. However, for a sufficiently high value of dilatational surface viscosity, the direction of droplet migration reverses. For the limiting case in which the surfactant transport along the droplet surface is dominated by surface convection, on the other hand, surface viscosities do not have any effect on the motion of the droplet. These results are likely to have far-reaching consequences in designing an optimal migration path in droplet-based microfluidic technology.

Quantification of bulk solution limits for liquid and interfacial transport in nanoconfinements.

PubMed

Kelly, Shaina; Balhoff, Matthew T; Torres-Verdín, Carlos

2015-02-24

Liquid imbibition, the capillary-pressure-driven flow of a liquid into a gas, provides a mechanism for studying the effects of solid-liquid and solid-liquid-gas interfaces on nanoscale transport. Deviations from the classic Washburn equation for imbibition are generally observed for nanoscale imbibition, but the identification of the origin of these irregularities in terms of transport variables varies greatly among investigators. We present an experimental method and corresponding image and data analysis scheme that enable the determination of independent effective values of nanoscale capillary pressure, liquid viscosity, and interfacial gas partitioning coefficients, all critical transport variables, from imbibition within nanochannels. Experiments documented herein are performed within two-dimensional siliceous nanochannels of varying size and as small as 30 nm × 60 nm in cross section. The wetting fluid used is the organic solvent isopropanol and the nonwetting fluid is air, but investigations are not limited to these fluids. Optical data of dynamic flow are rare in geometries that are nanoscale in two dimensions due to the limited resolution of optical microscopy. We are able to capture tracer-free liquid imbibition with reflected differential interference contrast microscopy. Results with isopropanol show a significant departure from bulk transport values in the nanochannels: reduced capillary pressures, increased liquid viscosity, and nonconstant interfacial mass-transfer coefficients. The findings equate to the nucleation of structured, quasi-crystalline boundary layers consistently ∼10-25 nm in extent. This length is far thicker than the boundary layer range prescribed by long-range intermolecular force interactions. Slower but linear imbibition in some experimental cases suggests that structured boundary layers may inhibit viscous drag at confinement walls for critical nanochannel dimensions. Probing the effects of nanoconfinement on the definitions of capillary pressure, viscosity, and interfacial mass transfer is critical in determining and improving the functionality and fluid transport efficacy of geological, biological, and synthetic nanoporous media and materials.

Use of containers to carry bulk and break bulk commodities and its impact on gulf region ports and international trade.

DOT National Transportation Integrated Search

2014-08-01

The University of New Orleans Transportation Institute was tasked by the Louisiana Transportation Research Center (LTRC) in mid-2012 to assess the use of containers to transport bulk and break bulk commodities and to determine what their impact would...

A 3D Finite Element Model with Improved Spatial Resolution to Investigate the Effect of Varying Viscosity on Antarctica

NASA Astrophysics Data System (ADS)

Blank, B.; van der Wal, W.; Pappa, F.; Ebbing, J.

2017-12-01

B. Blank1, H. Hu1, W. van der Wal1, F Pappa2, J. Ebbing21Delft University of Technology 2Christian-Albrechts-University of KielSince the beginning of the 2000's time-variable gravity data from GRACE has proved to be an effective method for mapping ice mass loss in Antarctica. However, Glacial Isostatic Adjustment (GIA) models are required to correct for GIA induced mass changes. While most GIA models have adopted an Earth model that only varies radially in parameters, it has long been clear that the Earth structure also varies with longitude and latitude. For this study a new global 3D GIA model has been developed within the finite element software package ABAQUS, which can be modified to operate on a spatial resolution down to 50 km locally. The model is being benchmarked against normal model models for surface loading. It will be used to investigate the effects of a 3D varying lithosphere and upper asthenosphere in Antarctica. Viscosity which will be computed from temperature estimates with laboratory based flow laws. A new 3D temperature map of the Antarctic lithosphere has been developed within ESA's GOCE+ project based on seismic data as well as on GOCE and GRACE inferred gravity gradients. Output from the GIA model with this new temperature estimates will be compared to that of 1D viscosity profiles and other recent 3D viscosity models based on seismic data. From these side to side comparisons we want to investigate the influence of the viscosity map on uplift rates and horizontal movement. Finally the results can be compared to GPS measurement to investigate the validity of all models.

Safety Assessment of Synthetic Fluorphlogopite as Used in Cosmetics.

PubMed

Becker, Lillian C; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

2015-01-01

The Cosmetic Ingredient Review Expert Panel (the Panel) reviewed the safety of synthetic fluorphlogopite as used in cosmetics. Synthetic fluorphlogopite functions as a bulking agent and a viscosity-increasing agent. The Panel reviewed available animal and human data related to this ingredient along with a previous safety assessment of other magnesium silicates. The Panel concluded that synthetic fluorphlogopite was safe as cosmetic ingredients in the practices of use and concentration as given in this safety assessment. © The Author(s) 2015.

Proposal for Universality in the Viscosity of Metallic Liquids

DOE PAGES

Blodgett, M. E.; Egami, Takeshi; Nussinov, Z.; ...

2015-09-09

The range of magnitude of the liquid viscosity, η, as a function of temperature is one of the most impressive of any physical property, changing by approximately 17 orders of magnitude from its extrapolated value at infinite temperature (η o) to that at the glass transition temperature, T g. We present experimental measurements of containerlessly processed metallic liquids that suggest that log(η/η o) as a function of T A/T is a potentially universal scaled curve. In stark contrast to previous approaches, the scaling requires only two fitting parameters, which are on average predictable. The temperature T A corresponds to themore » onset of cooperative motion and is strongly correlated with T g, suggesting that the processes underlying the glass transition first appear in the high temperature liquid.« less

Brownian motion studies of viscoelastic colloidal gels by rotational single particle tracking

DOE PAGES

Liang, Mengning; Harder, Ross; Robinson, Ian K.

2014-04-14

Colloidal gels have unique properties due to a complex microstructure which forms into an extended network. Although the bulk properties of colloidal gels have been studied, there has been difficulty correlating those properties with individual colloidal dynamics on the microscale due to the very high viscosity and elasticity of the material. We utilize rotational X-ray tracking (RXT) to investigate the rotational motion of component crystalline colloidal particles in a colloidal gel of alumina and decanoic acid. Our investigation has determined that the high elasticity of the bulk is echoed by a high elasticity experienced by individual colloidal particles themselves butmore » also finds an unexpected high degree of rotational diffusion, indicating a large degree of freedom in the rotational motion of individual colloids even within a tightly bound system.« less

A priori study of subgrid-scale features in turbulent Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Dabbagh, F.; Trias, F. X.; Gorobets, A.; Oliva, A.

2017-10-01

At the crossroad between flow topology analysis and turbulence modeling, a priori studies are a reliable tool to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent flows. In this paper, properties of the SGS features in the framework of a large-eddy simulation are studied for a turbulent Rayleigh-Bénard convection (RBC). To do so, data from direct numerical simulation (DNS) of a turbulent air-filled RBC in a rectangular cavity of aspect ratio unity and π spanwise open-ended distance are used at two Rayleigh numbers R a ∈{1 08,1 010 } [Dabbagh et al., "On the evolution of flow topology in turbulent Rayleigh-Bénard convection," Phys. Fluids 28, 115105 (2016)]. First, DNS at Ra = 108 is used to assess the performance of eddy-viscosity models such as QR, Wall-Adapting Local Eddy-viscosity (WALE), and the recent S3PQR-models proposed by Trias et al. ["Building proper invariants for eddy-viscosity subgrid-scale models," Phys. Fluids 27, 065103 (2015)]. The outcomes imply that the eddy-viscosity modeling smoothes the coarse-grained viscous straining and retrieves fairly well the effect of the kinetic unfiltered scales in order to reproduce the coherent large scales. However, these models fail to approach the exact evolution of the SGS heat flux and are incapable to reproduce well the further dominant rotational enstrophy pertaining to the buoyant production. Afterwards, the key ingredients of eddy-viscosity, νt, and eddy-diffusivity, κt, are calculated a priori and revealed positive prevalent values to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. The topological analysis suggests that the effective turbulent diffusion paradigm and the hypothesis of a constant turbulent Prandtl number are only applicable in the large-scale strain-dominated areas in the bulk. It is shown that the bulk-dominated rotational structures of vortex-stretching (and its synchronous viscous dissipative structures) hold the highest positive values of νt; however, the zones of backscatter energy and counter-gradient heat transport are related to the areas of compressed focal vorticity. More arguments have been attained through a priori investigation of the alignment trends imposed by existing parameterizations for the SGS heat flux, tested here inside RBC. It is shown that the parameterizations based linearly on the resolved thermal gradient are invalid in RBC. Alternatively, the tensor-diffusivity approach becomes a crucial choice of modeling the SGS heat flux, in particular, the tensorial diffusivity that includes the SGS stress tensor. This and other crucial scrutinies on a future modeling to the SGS heat flux in RBC are sought.

Physical, proximate, functional and pasting properties of flour produced from gamma irradiated cowpea (Vigna unguiculata, L. Walp)

NASA Astrophysics Data System (ADS)

Darfour, B.; Wilson, D. D.; Ofosu, D. O.; Ocloo, F. C. K.

2012-04-01

Cowpeas are leguminous seeds widely produced and consumed in most developing countries of sub Saharan Africa. The aim of this study was to determine the physical, proximate, functional and pasting properties of flour obtained from gamma irradiated cowpea. Four cowpea cultivars were irradiated with gamma radiation at dose levels of 0.25, 0.5, 0.75, 1.0 and 1.5 kGy with the unirradiated cultivars serving as controls. The samples were hammer milled, sieved and stored at 4 °C for analysis. Physical, proximate, functional, pasting properties were determined using appropriate methods. In general, the irradiation dose applied to cowpea for insect control did not significantly affect the physical and proximate properties of the flour. However, significant increase (p<0.05) was achieved in paste bulk density, water and oil absorption capacities, foam capacities and least gelation concentrations of flour in general, which may be attributed to the irradiation. The radiation reduced the swelling power and water solubility index significantly. The peak temperature, peak viscosity and setback viscosity of the pastes were significantly (p<0.05) reduced while breakdown viscosity was significantly (p<0.05) increased by the radiation. It was established that the doses used on cowpea affected both the functional and pasting properties of the flour.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atutov, S. N., E-mail: atutovsn@mail.ru; Plekhanov, A. I.

We present the results of a systematic study of Knudsen’s flow of Rb atoms in cylindrical capillary cells coated with a polydimethylsiloxane (PDMS) compound. The purpose of the investigation is to determine the characterization of the coating in terms of the sticking probability and sticking time of Rb on the two types of coating of high and medium viscosities. We report the measurement of the sticking probability of a Rb atom to the coating equal to 4.3 × 10{sup −5}, which corresponds to the number of bounces 2.3 × 10{sup 4} at room temperature. These parameters are the same formore » the two kinds of PDMS used. We find that at room temperature, the respective sticking times for high-viscosity and medium-viscosity PDMS are 22 ± 3 μs and 49 ± 6 μs. These sticking times are about million times larger than the sticking time derived from the surface Rb atom adsorption energy and temperature of the coating. A tentative explanation of this surprising result is proposed based on the bulk diffusion of the atoms that collide with the surface and penetrate inside the coating. The results can be important in many resonance cell experiments, such as the efficient magnetooptical trapping of rare elements or radioactive isotopes and in experiments on the light-induced drift effect.« less

Galilean-invariant Nosé-Hoover-type thermostats.

PubMed

Pieprzyk, S; Heyes, D M; Maćkowiak, Sz; Brańka, A C

2015-03-01

A new pairwise Nosé-Hoover type thermostat for molecular dynamics (MD) simulations which is similar in construction to the pair-velocity thermostat of Allen and Schmid, [Mol. Simul. 33, 21 (2007)] (AS) but is based on the configurational thermostat is proposed and tested. Both thermostats generate the canonical velocity distribution, are Galilean invariant, and conserve linear and angular momentum. The unique feature of the pairwise thermostats is an unconditional conservation of the total angular momentum, which is important for thermalizing isolated systems and those nonequilibrium bulk systems manifesting local rotating currents. These thermostats were benchmarked against the corresponding Nosé-Hoover (NH) and Braga-Travis prescriptions, being based on the kinetic and configurational definitions of temperature, respectively. Some differences between the shear-rate-dependent shear viscosity from Sllod nonequilibrium MD are observed at high shear rates using the different thermostats. The thermostats based on the configurational temperature produced very similar monotically decaying shear viscosity (shear thinning) with increasing shear rate, while the NH method showed discontinuous shear thinning into a string phase, and the AS method produced a continuous increase of viscosity (shear thickening), after a shear thinning region at lower shear rates. Both pairwise additive thermostats are neither purely kinetic nor configurational in definition, and possible directions for further improvement in certain aspects are discussed.

Galilean-invariant Nosé-Hoover-type thermostats

NASA Astrophysics Data System (ADS)

Pieprzyk, S.; Heyes, D. M.; Maćkowiak, Sz.; Brańka, A. C.

2015-03-01

A new pairwise Nosé-Hoover type thermostat for molecular dynamics (MD) simulations which is similar in construction to the pair-velocity thermostat of Allen and Schmid, [Mol. Simul. 33, 21 (2007), 10.1080/08927020601052856] (AS) but is based on the configurational thermostat is proposed and tested. Both thermostats generate the canonical velocity distribution, are Galilean invariant, and conserve linear and angular momentum. The unique feature of the pairwise thermostats is an unconditional conservation of the total angular momentum, which is important for thermalizing isolated systems and those nonequilibrium bulk systems manifesting local rotating currents. These thermostats were benchmarked against the corresponding Nosé-Hoover (NH) and Braga-Travis prescriptions, being based on the kinetic and configurational definitions of temperature, respectively. Some differences between the shear-rate-dependent shear viscosity from Sllod nonequilibrium MD are observed at high shear rates using the different thermostats. The thermostats based on the configurational temperature produced very similar monotically decaying shear viscosity (shear thinning) with increasing shear rate, while the NH method showed discontinuous shear thinning into a string phase, and the AS method produced a continuous increase of viscosity (shear thickening), after a shear thinning region at lower shear rates. Both pairwise additive thermostats are neither purely kinetic nor configurational in definition, and possible directions for further improvement in certain aspects are discussed.

Bioinspired model of mechanical energy harvesting based on flexoelectric membranes.

PubMed

Rey, Alejandro D; Servio, P; Herrera-Valencia, E E

2013-02-01

Membrane flexoelectricity is an electromechanical coupling process that describes membrane electrical polarization due to bending and membrane bending under electric fields. In this paper we propose, formulate, and characterize a mechanical energy harvesting system consisting of a deformable soft flexoelectric thin membrane subjected to harmonic forcing from contacting bulk fluids. The key elements of the energy harvester are formulated and characterized, including (i) the mechanical-to-electrical energy conversion efficiency, (ii) the electromechanical shape equation connecting fluid forces with membrane curvature and electric displacement, and (iii) the electric power generation and efficiency. The energy conversion efficiency is cast as the ratio of flexoelectric coupling to the product of electric and bending elasticity. The device is described by a second-order curvature dynamics coupled to the electric displacement equation and as such results in mechanical power absorption with a resonant peak whose amplitude decreases with bending viscosity. The electric power generation is proportional to the conversion factor and the power efficiency decreases with frequency. Under high bending viscosity, the power efficiency increases with the conversion factor and under low viscosities it decreases with the conversion factor. The theoretical results presented contribute to the ongoing experimental efforts to develop mechanical energy harvesting from fluid flow energy through solid-fluid interactions and electromechanical transduction.

Role of hydrodynamic viscosity on phonon transport in suspended graphene

NASA Astrophysics Data System (ADS)

Li, Xun; Lee, Sangyeop

2018-03-01

When phonon transport is in the hydrodynamic regime, the thermal conductivity exhibits peculiar dependences on temperatures (T ) and sample widths (W ). These features were used in the past to experimentally confirm the hydrodynamic phonon transport in three-dimensional bulk materials. Suspended graphene was recently predicted to exhibit strong hydrodynamic features in thermal transport at much higher temperature than the three-dimensional bulk materials, but its experimental confirmation requires quantitative guidance by theory and simulation. Here we quantitatively predict those peculiar dependences using the Monte Carlo solution of the Peierls-Boltzmann equation with an ab initio full three-phonon scattering matrix. Thermal conductivity is found to increase as Tα where α ranges from 1.89 to 2.49 depending on a sample width at low temperatures, much larger than 1.68 of the ballistic case. The thermal conductivity has a width dependence of W1.17 at 100 K, clearly distinguished from the sublinear dependence of the ballistic-diffusive regime. These peculiar features are explained with a phonon viscous damping effect of the hydrodynamic regime. We derive an expression for the phonon hydrodynamic viscosity from the Peierls-Boltzmann equation, and discuss the fact that the phonon viscous damping explains well those peculiar dependences of thermal conductivity at 100 K. The phonon viscous damping still causes significant thermal resistance when a temperature is 300 K and a sample width is around 1 µm, even though the hydrodynamic regime is not dominant over other regimes at this condition.

Exact solutions of bulk viscous with string cloud attached to strange quark matter for higher dimensional FRW universe in Lyra geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Çağlar, Halife, E-mail: hlfcglr@gmail.com; Aygün, Sezgin, E-mail: saygun@comu.edu.tr

In this study, we have investigated bulk viscous with strange quark matter attached to the string cloud for higher dimensional Friedman-Robertson-Walker (FRW) universe in Lyra geometry. By using varying deceleration parameter and conservation equations we have solved Einstein Field Equations (EFE’s) and obtained generalized exact solutions for our model. Also we have found that string is not survived for bulk viscous with strange quark matter attached to the string cloud in framework higher dimensional FRW universe in Lyra geometry. This result agrees with Kiran and Reddy, Krori et al, Sahoo and Mishra and Mohanty et al. in four and fivemore » dimensions.« less

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

NASA Astrophysics Data System (ADS)

Costa, Pedro; Picano, Francesco; Brandt, Luca; Breugem, Wim-Paul

2018-05-01

We use interface-resolved simulations to study finite-size effects in turbulent channel flow of neutrally-buoyant spheres. Two cases with particle sizes differing by a factor of 2, at the same solid volume fraction of 20% and bulk Reynolds number are considered. These are complemented with two reference single-phase flows: the unladen case, and the flow of a Newtonian fluid with the effective suspension viscosity of the same mixture in the laminar regime. As recently highlighted in Costa et al. (PRL 117, 134501), a particle-wall layer is responsible for deviations of the statistics from what is observed in the continuum limit where the suspension is modeled as a Newtonian fluid with an effective viscosity. Here we investigate the fluid and particle dynamics in this layer and in the bulk. In the particle-wall layer, the near wall inhomogeneity has an influence on the suspension micro-structure over a distance proportional to the particle size. In this layer, particles have a significant (apparent) slip velocity that is reflected in the distribution of wall shear stresses. This is characterized by extreme events (both much higher and much lower than the mean). Based on these observations we provide a scaling for the particle-to-fluid apparent slip velocity as a function of the flow parameters. We also extend the flow scaling laws in to second-order Eulerian statistics in the homogeneous suspension region away from the wall. Finite-size effects in the bulk of the channel become important for larger particles, while negligible for lower-order statistics and smaller particles. Finally, we study the particle dynamics along the wall-normal direction. Our results suggest that 1-point dispersion is dominated by particle-turbulence (and not particle-particle) interactions, while differences in 2-point dispersion and collisional dynamics are consistent with a picture of shear-driven interactions.

Dynamic nuclear polarization enhanced nuclear magnetic resonance and electron spin resonance studies of hydration and local water dynamics in micelle and vesicle assemblies.

PubMed

McCarney, Evan R; Armstrong, Brandon D; Kausik, Ravinath; Han, Songi

2008-09-16

We present a unique analysis tool for the selective detection of local water inside soft molecular assemblies (hydrophobic cores, vesicular bilayers, and micellar structures) suspended in bulk water. Through the use of dynamic nuclear polarization (DNP), the (1)H NMR signal of water is amplified, as it interacts with stable radicals that possess approximately 658 times higher spin polarization. We utilized stable nitroxide radicals covalently attached along the hydrophobic tail of stearic acid molecules that incorporate themselves into surfactant-based micelle or vesicle structures. Here, we present a study of local water content and fluid viscosity inside oleate micelles and vesicles and Triton X-100 micelles to serve as model systems for soft molecular assemblies. This approach is unique because the amplification of the NMR signal is performed in bulk solution and under ambient conditions with site-specific spin labels that only detect the water that is directly interacting with the localized spin labels. Continuous wave (cw) electron spin resonance (ESR) analysis provides rotational dynamics of the spin-labeled molecular chain segments and local polarity parameters that can be related to hydration properties, whereas we show that DNP-enhanced (1)H NMR analysis of fluid samples directly provides translational water dynamics and permeability of the local environment probed by the spin label. Our technique therefore has the potential to become a powerful analysis tool, complementary to cw ESR, to study hydration characteristics of surfactant assemblies, lipid bilayers, or protein aggregates, where water dynamics is a key parameter of their structure and function. In this study, we find that there is significant penetration of water inside the oleate micelles with a higher average local water viscosity (approximately 1.8 cP) than in bulk water, and Triton X-100 micelles and oleate vesicle bilayers mostly exclude water while allowing for considerable surfactant chain motion and measurable water permeation through the soft structure.

Investigation on Viscosity and Nonisothermal Crystallization Behavior of P-Bearing Steelmaking Slags with Varying TiO2 Content

NASA Astrophysics Data System (ADS)

Wang, Zhanjun; Sun, Yongqi; Sridrar, Seetharaman; Zhang, Mei; Zhang, Zuotai

2017-02-01

The viscous flow and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-TiO2 steelmaking slags have been investigated over a wide range of temperatures under Ar (High purity, >99.999 pct) atmosphere, and the relationship between viscosity and structure was determined. The results indicated that the viscosity of the slags slightly decreased with increasing TiO2 content. The constructed nonisothermal continuous cooling transformation (CCT) diagrams revealed that the addition of TiO2 lowered the crystallization temperature. This can mainly be ascribed to that addition of TiO2 promotes the formation of [TiO6]-octahedra units and, consequently, the formation of MgFe2O4-Mg2TiO4 solid solution. Moreover, the decreasing viscosity has a significant effect on enhancing the diffusion of ion units, such as Ca2+ and [TiO4]-tetrahedra, from bulk melts to the crystal-melt interface. The crystallization of CaTiO3 and CaSiTiO5 was consequently accelerated, which can improve the phosphorus content in P-enriched phase ( n2CaO·SiO2-3CaO·P2O5). Finally, the nonisothermal crystallization kinetics was characterized and the activation energy for the primary crystal growth was derived such that the activation energy increases from -265.93 to -185.41 KJ·mol-1 with the addition of TiO2 content, suggesting that TiO2 lowered the tendency for the slags to crystallize.

Viscosity of Xenon Examined in Microgravity

NASA Technical Reports Server (NTRS)

Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.

1999-01-01

Why does water flow faster than honey? The short answer, that honey has a greater viscosity, merely rephrases the question. The fundamental answer is that viscosity originates in the interactions between a fluid s molecules. These interactions are so complicated that, except for low-density gases, the viscosity of a fluid cannot be accurately predicted. Progress in understanding viscosity has been made by studying moderately dense gases and, more recently, fluids near the critical point. Modern theories predict a universal behavior for all pure fluids near the liquid-vapor critical point, and they relate the increase in viscosity to spontaneous fluctuations in density near this point. The Critical Viscosity of Xenon (CVX) experiment tested these theories with unprecedented precision when it flew aboard the Space Shuttle Discovery (STS-85) in August 1997. Near the critical point, xenon is a billion times more compressible than water, yet it has about the same density. Because the fluid is so "soft," it collapses under its own weight when exposed to the force of Earth s gravity - much like a very soft spring. Because the CVX experiment is conducted in microgravity, it achieves a very uniform fluid density even very close to the critical point. At the heart of the CVX experiment is a novel viscometer built around a small nickel screen. An oscillating electric field forces the screen to oscillate between pairs of electrodes. Viscosity, which dampens the oscillations, can be calculated by measuring the screen motion and the force applied to the screen. So that the fluid s delicate state near the critical point will not be disrupted, the screen oscillations are set to be both slow and small.

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

NASA Astrophysics Data System (ADS)

Radić, Valentina; Menounos, Brian; Shea, Joseph; Fitzpatrick, Noel; Tessema, Mekdes A.; Déry, Stephen J.

2017-12-01

As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods), commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible- and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddy-covariance (OPEC) method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin-Obukhov (M-O) stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M-O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the KInt method) outperforms any C method in simulating the friction velocity; however, the C methods outperform the KInt method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the KInt approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in the measured meteorological variables and the roughness lengths produce errors in the modeled fluxes that are smaller than the differences between the modeled and observed fluxes. This implies that further advances will require improvement to model theory rather than better measurements of input variables. Further data from different glaciers are needed to investigate any universality of these findings.

Fluid dynamic propagation of initial baryon number perturbations on a Bjorken flow background

DOE PAGES

Floerchinger, Stefan; Martinez, Mauricio

2015-12-11

Baryon number density perturbations offer a possible route to experimentally measure baryon number susceptibilities and heat conductivity of the quark gluon plasma. We study the fluid dynamical evolution of local and event-by-event fluctuations of baryon number density, flow velocity, and energy density on top of a (generalized) Bjorken expansion. To that end we use a background-fluctuation splitting and a Bessel-Fourier decomposition for the fluctuating part of the fluid dynamical fields with respect to the azimuthal angle, the radius in the transverse plane, and rapidity. Here, we examine how the time evolution of linear perturbations depends on the equation of statemore » as well as on shear viscosity, bulk viscosity, and heat conductivity for modes with different azimuthal, radial, and rapidity wave numbers. Finally we discuss how this information is accessible to experiments in terms of the transverse and rapidity dependence of correlation functions for baryonic particles in high energy nuclear collisions.« less

Accessing thermoplastic processing windows in metallic glasses using rapid capacitive discharge

PubMed Central

Kaltenboeck, Georg; Harris, Thomas; Sun, Kerry; Tran, Thomas; Chang, Gregory; Schramm, Joseph P.; Demetriou, Marios D.; Johnson, William L.

2014-01-01

The ability of the rapid-capacitive discharge approach to access optimal viscosity ranges in metallic glasses for thermoplastic processing is explored. Using high-speed thermal imaging, the heating uniformity and stability against crystallization of Zr35Ti30Cu7.5Be27.5 metallic glass heated deeply into the supercooled region is investigated. The method enables homogeneous volumetric heating of bulk samples throughout the entire supercooled liquid region at high rates (~105 K/s) sufficient to bypass crystallization throughout. The crystallization onsets at temperatures in the vicinity of the “crystallization nose” were identified and a Time-Temperature-Transformation diagram is constructed, revealing a “critical heating rate” for the metallic glass of ~1000 K/s. Thermoplastic process windows in the optimal viscosity range of 100–104 Pa·s are identified, being confined between the glass relaxation and the eutectic crystallization transition. Within this process window, near-net forging of a fine precision metallic glass part is demonstrated. PMID:25269892

Electrically Conductive Silver Paste Obtained by Use of Silver Neodecanoate as Precursor

NASA Astrophysics Data System (ADS)

Shen, Longguang; Liu, Jianguo; Zeng, Xiaoyan; Ren, Zhao

2015-02-01

An electrically conductive silver paste has been prepared from an organometallic compound, silver neodecanoate, as silver precursor. The precursor was highly soluble in organic solvents and decomposed into metallic silver at low sintering temperatures (<200°C). Thermogravimetric analysis showed the silver content of the paste was approximately 25 wt.%. Viscosity studies indicated the paste was a pseudoplastic liquid with viscosity in the range 6.5-9 Pa s. The paste was compatible with the micro-pen direct-writing process, enabling production of silver lines on a substrate. The electrical resistivity of the silver lines was 9 × 10-6 Ω cm after sintering at 115°C for 60 min, 5.8 × 10-6 Ω cm when sintered at 150°C for 60 min, and 3 × 10-6 Ω cm when sintered above 300°C, values which are similar to those of bulk silver. Hence, the prepared paste can be successfully used on flexible substrates such as polymers.

Structural changes during a liquid-liquid transition in the deeply undercooled Z r58.5C u15.6N i12.8A l10.3N b2.8 bulk metallic glass forming melt

NASA Astrophysics Data System (ADS)

Stolpe, Moritz; Jonas, Isabell; Wei, Shuai; Evenson, Zach; Hembree, William; Yang, Fan; Meyer, Andreas; Busch, Ralf

2016-01-01

Using high energy synchrotron x-ray radiation combined with electrostatic levitation, in situ structural analysis of a bulk metallic glass forming liquid is performed from above the liquidus temperature down to the glass transition. The data indicate a liquid-liquid transition (LLT) in the deeply undercooled state at T /Tg˜1.2 which manifests as a maximum in the heat capacity and an abrupt shift in the first peak position of the total structure factor in the absence of a pronounced density change. Analysis of the corresponding real-space data shows that the LLT involves changes in short- and medium-range order. The structural changes on the length scale of medium-range order imply a fragile-strong transition in agreement with experimental viscosity data.

Stress as an order parameter for the glass transition

NASA Astrophysics Data System (ADS)

Visscher, P. B.; Logan, W. T.

1990-09-01

The stress tensor has been considered as a possible order parameter for the liquid-glass transition, and its autocorrelation matrix (elements of which are the integrands in the Green-Kubo formulas for bulk and shear viscosity) have been measured in simulations. However, only the k=0 spatial Fourier component has apparently been previously measured. We have measured four Fourier components of all matrix elements of the stress-stress correlation function, and we find that some of those with nonzero wave vector are significantly more persistent (slower decaying) than the k=0 component.

Fluid Dynamics for Physicists

NASA Astrophysics Data System (ADS)

Faber, T. E.

1995-08-01

This textbook provides an accessible and comprehensive account of fluid dynamics that emphasizes fundamental physical principles and stresses connections with other branches of physics. Beginning with a basic introduction, the book goes on to cover many topics not typically treated in texts, such as compressible flow and shock waves, sound attenuation and bulk viscosity, solitary waves and ship waves, thermal convection, instabilities, turbulence, and the behavior of anisotropic, non-Newtonian and quantum fluids. Undergraduate or graduate students in physics or engineering who are taking courses in fluid dynamics will find this book invaluable.

[Comparison of wear resistance and flexural strength of three kinds of bulk-fill composite resins].

PubMed

Zhang, Huan; Zhang, Meng-Long; Qiu, Li-Hong; Yu, Jing-Tao; Zhan, Fu-Liang

2016-06-01

To compare the abrasion resistance and flexure strength of three bulk-fill resin composites with an universal nano-hybrid composite resins. The specimens were prepared with three kinds of bulk fill composites (SDR , sonicfill, Tetric N-Ceram Bulk Fill) and an universal nano-hybrid composite resins(Herculite Precis). 10 mm in diameter × 2mm in height specimens were prepared for abrasion resistance, while 2 mm in width × 2 mm in depth×25 mm in length specimens were prepared for flexure strength. The specimens were mounted in a bal1-on-disc wear testing machine and abraded with the media artificial saliva(50 N loads, 10000 cycles).Flexural test was performed with an Universal Testing Machine at a cross-head speed of 1mm/min. One-way variance analysis was used to determine the statistical differences of volume loss and flexural strength among groups with SPSS 13.0 software package(P<0.05). The volume loss was as follows: SDR (1.2433±0.11) mm30.05). With regard to wear resistance and flexural strength, Tetric N-Ceram Bulk Fill is recommended as an alternative for posterior restorations.

Low- and high-order accurate boundary conditions: From Stokes to Darcy porous flow modeled with standard and improved Brinkman lattice Boltzmann schemes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, Goncalo, E-mail: goncalo.nuno.silva@gmail.com; Talon, Laurent, E-mail: talon@fast.u-psud.fr; Ginzburg, Irina, E-mail: irina.ginzburg@irstea.fr

The present contribution focuses on the accuracy of reflection-type boundary conditions in the Stokes–Brinkman–Darcy modeling of porous flows solved with the lattice Boltzmann method (LBM), which we operate with the two-relaxation-time (TRT) collision and the Brinkman-force based scheme (BF), called BF-TRT scheme. In parallel, we compare it with the Stokes–Brinkman–Darcy linear finite element method (FEM) where the Dirichlet boundary conditions are enforced on grid vertices. In bulk, both BF-TRT and FEM share the same defect: in their discretization a correction to the modeled Brinkman equation appears, given by the discrete Laplacian of the velocity-proportional resistance force. This correction modifies themore » effective Brinkman viscosity, playing a crucial role in the triggering of spurious oscillations in the bulk solution. While the exact form of this defect is available in lattice-aligned, straight or diagonal, flows; in arbitrary flow/lattice orientations its approximation is constructed. At boundaries, we verify that such a Brinkman viscosity correction has an even more harmful impact. Already at the first order, it shifts the location of the no-slip wall condition supported by traditional LBM boundary schemes, such as the bounce-back rule. For that reason, this work develops a new class of boundary schemes to prescribe the Dirichlet velocity condition at an arbitrary wall/boundary-node distance and that supports a higher order accuracy in the accommodation of the TRT-Brinkman solutions. For their modeling, we consider the standard BF scheme and its improved version, called IBF; this latter is generalized in this work to suppress or to reduce the viscosity correction in arbitrarily oriented flows. Our framework extends the one- and two-point families of linear and parabolic link-wise boundary schemes, respectively called B-LI and B-MLI, which avoid the interference of the Brinkman viscosity correction in their closure relations. The performance of LBM and FEM is thoroughly evaluated in three benchmark tests, which are run throughout three distinctive permeability regimes. The first configuration is a horizontal porous channel, studied with a symbolic approach, where we construct the exact solutions of FEM and BF/IBF with different boundary schemes. The second problem refers to an inclined porous channel flow, which brings in as new challenge the formation of spurious boundary layers in LBM; that is, numerical artefacts that arise due to a deficient accommodation of the bulk solution by the low-accurate boundary scheme. The third problem considers a porous flow past a periodic square array of solid cylinders, which intensifies the previous two tests with the simulation of a more complex flow pattern. The ensemble of numerical tests provides guidelines on the effect of grid resolution and the TRT free collision parameter over the accuracy and the quality of the velocity field, spanning from Stokes to Darcy permeability regimes. It is shown that, with the use of the high-order accurate boundary schemes, the simple, uniform-mesh-based TRT-LBM formulation can even surpass the accuracy of FEM employing hardworking body-fitted meshes.« less

Low- and high-order accurate boundary conditions: From Stokes to Darcy porous flow modeled with standard and improved Brinkman lattice Boltzmann schemes

NASA Astrophysics Data System (ADS)

Silva, Goncalo; Talon, Laurent; Ginzburg, Irina

2017-04-01

The present contribution focuses on the accuracy of reflection-type boundary conditions in the Stokes-Brinkman-Darcy modeling of porous flows solved with the lattice Boltzmann method (LBM), which we operate with the two-relaxation-time (TRT) collision and the Brinkman-force based scheme (BF), called BF-TRT scheme. In parallel, we compare it with the Stokes-Brinkman-Darcy linear finite element method (FEM) where the Dirichlet boundary conditions are enforced on grid vertices. In bulk, both BF-TRT and FEM share the same defect: in their discretization a correction to the modeled Brinkman equation appears, given by the discrete Laplacian of the velocity-proportional resistance force. This correction modifies the effective Brinkman viscosity, playing a crucial role in the triggering of spurious oscillations in the bulk solution. While the exact form of this defect is available in lattice-aligned, straight or diagonal, flows; in arbitrary flow/lattice orientations its approximation is constructed. At boundaries, we verify that such a Brinkman viscosity correction has an even more harmful impact. Already at the first order, it shifts the location of the no-slip wall condition supported by traditional LBM boundary schemes, such as the bounce-back rule. For that reason, this work develops a new class of boundary schemes to prescribe the Dirichlet velocity condition at an arbitrary wall/boundary-node distance and that supports a higher order accuracy in the accommodation of the TRT-Brinkman solutions. For their modeling, we consider the standard BF scheme and its improved version, called IBF; this latter is generalized in this work to suppress or to reduce the viscosity correction in arbitrarily oriented flows. Our framework extends the one- and two-point families of linear and parabolic link-wise boundary schemes, respectively called B-LI and B-MLI, which avoid the interference of the Brinkman viscosity correction in their closure relations. The performance of LBM and FEM is thoroughly evaluated in three benchmark tests, which are run throughout three distinctive permeability regimes. The first configuration is a horizontal porous channel, studied with a symbolic approach, where we construct the exact solutions of FEM and BF/IBF with different boundary schemes. The second problem refers to an inclined porous channel flow, which brings in as new challenge the formation of spurious boundary layers in LBM; that is, numerical artefacts that arise due to a deficient accommodation of the bulk solution by the low-accurate boundary scheme. The third problem considers a porous flow past a periodic square array of solid cylinders, which intensifies the previous two tests with the simulation of a more complex flow pattern. The ensemble of numerical tests provides guidelines on the effect of grid resolution and the TRT free collision parameter over the accuracy and the quality of the velocity field, spanning from Stokes to Darcy permeability regimes. It is shown that, with the use of the high-order accurate boundary schemes, the simple, uniform-mesh-based TRT-LBM formulation can even surpass the accuracy of FEM employing hardworking body-fitted meshes.

Evaluation of Heating and Shearing on the Viscoelastic Properties of Calcium Hydroxyapatite Used in Injection Laryngoplasty.

PubMed

Mahboubi, Hossein; Mohraz, Ali; Verma, Sunil P

2016-03-01

To compare the viscoelastic properties of calcium hydroxyapatite (CaHA) to carboxymethylcellulose (CMC) injectables used for injection laryngoplasty and determine if they are affected by heating and shearing. Experimental. University laboratory. Vocal fold injection laryngoplasty with CaHA is oftentimes challenging due to the amount of pressure necessary to push the injectate through a needle. Anecdotal techniques, such as heating the product, have been suggested to facilitate injection. The viscoelastic properties of CaHA and CMC were measured with a rheometer. The effects of heating and shearing on sample viscoelasticity were recorded. CaHA was 9.5 times more viscous than CMC (43,100 vs 4540 Pa·s). Heating temporarily decreased the viscosity of CaHA by 32%. However, it also caused the viscosity to subsequently increase after time. Shearing of CaHA reduced its viscosity by 26%. Heating and shearing together temporarily reduced the viscosity of CaHA by 52%. A combination of heating and shearing had a more profound effect than heating or shearing alone on the viscosity of CaHA, potentially making it easier to inject temporarily. Long-term and in vivo studies are required to further analyze the effect of heating and shearing on CaHA injectables. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016.

Melt transport - a personal cashing-up

NASA Astrophysics Data System (ADS)

Renner, J.

2005-12-01

The flow of fluids through rocks transports heat and material and changes bulk composition. The large-scale chemical differentiation of the Earth is related to flow of partial melts. From the perspective of current understanding of tectonic processes, prominent examples of such transport processes are the formation of oceanic crust from ascending basic melts at mid-ocean ridges, melt segregation involved in the solidification of the Earth's core, and dissolution-precipitation creep in subduction channels. Transport and deformation cannot be separated for partially molten aggregates. Permeability is only defined as an instantaneous parameter in the sense that Darcy's law is assumed to be valid; it is not an explicit parameter in the fundamental mechanical conservation laws but can be derived from them in certain circumstances as a result of averaging schemes. The governing, explicit physical properties in the mechanical equations are the shear and bulk viscosities of the solid framework and the fluid viscosity and compressibility. Constraints on the magnitude of these properties are available today from experiments at specific loading configurations, i.e., more or less well constrained initial and boundary conditions. The melt pressure remains the least controlled parameter. While the fluid viscosity is often much lower than the solid's the two-phase aggregate may exhibit considerable strength owing to the difficulty of moving the fluid through the branched pore network. The extremes in behavior depend on the time scale of loading, as known from daily live experiences (spounge, Danish coffee-pot, human tissue between neighboring bones). Several theoretical approaches attempted to formulate mechanical constitutive equations for two-phase aggregates. An important issue is the handling of internal variables in these equations. At experimental conditions, grain size, melt pocket orientation and crystallographic orientation -prime candidates for internal variables- change considerably and potentially contribute significantly to the total dissipation of the external work. Theoretically founded evolution equations for these internal variables are lacking. In experiments, both the kinetics of grain growth but also the resultant shape of grains is affected by the presence of melt. The latter is linked to the alignment of melt pockets with the maximum principle stress. Thus, the melt redistribution causes direct anisotropy but also indirect through a shape-preferred orientation of solid grains. Notably, the foliation is parallel to the maximum principle stress in contrast to deformation controlled by crystal defects alone. Extremum principles developed for dissipation potentials in the framework of irreversible thermodynamics may allow us to postulate evolution equations. Owing to their significant effect on aggregate viscosities understanding the evolution of internal variables is mandatory for substantial large-scale modeling.

The Anatomy of the Blue Dragon: Changes in Lava Flow Morphology and Physical Properties Observed in an Open Channel Lava Flow as a Planetary Analogue

NASA Astrophysics Data System (ADS)

Sehlke, A.; Kobs-Nawotniak, S. E.; Hughes, S. S.; Sears, D. W. G.; Downs, M.; Whittington, A. G.; Lim, D. S. S.; Heldmann, J. L.

2017-12-01

Lava terrains on other planets and moons exhibit morphologies similar to those found on Earth, such as smooth pāhoehoe transitioning to rough `a`ā terrains based on the viscosity - strain rate relationship of the lava. Therefore, the morphology of lava flows is governed by eruptive conditions such as effusion rate, underlying slope, and the fundamental thermo-physical properties of the lava, including temperature (T), composition (X), viscosity (η), fraction of crystals (φc) and vesicles (φb), as well as bulk density (ρ). These textural and rheological changes were previously studied for Hawaiian lava, where the lava flow started as channelized pāhoehoe and transitioned into `a`ā, demonstrating a systematic trend in T, X, η, φc, φb, and ρ. NASA's FINESSE focuses on Science and Exploration through analogue research. One of the field sites is Craters of the Moon, Idaho. We present field work done at a 3.0 km long lava flow belonging to the Blue Dragon lavas erupted from a chain of spatter cones, which then coalesced into channelized flows. We acquired UAV imagery along the entire length of the flow, and generated a high resolution DTM of 5 cm/pixel, from which we derived height profiles and surface roughness values. Field work included mapping the change in surface morphology and sample collection every 150 meters. In the laboratory, we measured φc, φb, and ρ for all collected samples. Viscosity measurements were carried out by concentric cylinder viscometry at subliquidus temperatures between 1310ºC to 1160ºC to study the rheology of the lava, enabling us to relate changes in flow behavior to T and φc. Our results are consistent with observations made for Hawaiian lava, including increasing bulk density downflow, and porosity changing from connected to isolated pore space. Crystallinity increases downflow, and the transition from pāhoehoe to `a`ā occurs between 1230ºC to 1150ºC, which is prompted by nucleation and growth of plagioclase microcrystals, strongly increasing the viscosity of the lava several orders of magnitude. The results of this study allows us to correlate T, X, η, φc, φb, and ρ to the lava flow morphology expressed as surface roughness, which can then be used as a tool to infer these physical properties of the rocks for open channel lava flows on other airless bodies, such as the Moon and Mercury, based on DTMs.

On the universality of Marangoni-driven spreading

NASA Astrophysics Data System (ADS)

Visser, Claas; van Capelleveen, Bram; Koldeweij, Robin; Lohse, Detlef

2017-11-01

When two liquids of different surface tensions come into contact, the liquid with lower surface tension spreads over the other. Here we measure the dynamics of this Marangoni-driven spreading in the drop-drop geometry, revealing universal behavior with respect to the control parameters as well as other geometries (such as spreading over a flat interface). The distance L over which the low-surface-tension liquid has covered the high-surface-tension droplet is measured as a function of time t, surface tension difference between the liquids Δσ , and viscosity η, revealing power-law behavior L(t) tα . The exponent α is discussed for the early and late spreading regimes. Spreading inhibition is observed at high viscosity, for which the threshold is discussed. Finally, we show that our results collapse onto a single curve of dimensionless L(t) as a function of dimensionless time, which also captures previous results for different geometries, surface tension modifiers, and miscibility. As this curve spans 7 orders of magnitude, Marangoni-induced spreading can be considered a universal phenomenon for many practically encountered liquid-liquid systems.

Viscosity bound versus the universal relaxation bound

NASA Astrophysics Data System (ADS)

Hod, Shahar

2017-10-01

For gauge theories with an Einstein gravity dual, the AdS/CFT correspondence predicts a universal value for the ratio of the shear viscosity to the entropy density, η / s = 1 / 4 π. The holographic calculations have motivated the formulation of the celebrated KSS conjecture, according to which all fluids conform to the lower bound η / s ≥ 1 / 4 π. The bound on η / s may be regarded as a lower bound on the relaxation properties of perturbed fluids and it has been the focus of much recent attention. In particular, it was argued that for a class of field theories with Gauss-Bonnet gravity dual, the shear viscosity to entropy density ratio, η / s, could violate the conjectured KSS bound. In the present paper we argue that the proposed violations of the KSS bound are strongly constrained by Bekenstein's generalized second law (GSL) of thermodynamics. In particular, it is shown that physical consistency of the Gauss-Bonnet theory with the GSL requires its coupling constant to be bounded by λGB ≲ 0 . 063. We further argue that the genuine physical bound on the relaxation properties of physically consistent fluids is ℑω(k > 2 πT) > πT, where ω and k are respectively the proper frequency and the wavenumber of a perturbation mode in the fluid.

The failure of 1D seismic model fitting to constrain lower mantle composition

NASA Astrophysics Data System (ADS)

Houser, C. T.; Hernlund, J. W.; Valencia-Cardona, J. J.; Wentzcovitch, R.

2017-12-01

Tests of lower mantle composition models often compare mineral physics data bearing on the elasticity and density of lower mantle phases to the average seismic velocity profile determined by seismology, such a PREM or ak135. We demonstrate why such comparisons between mineralogy and seismology are an inadequate method for definitive discrimination between different scenarios. One issue is that the seismic velocity is more sensitive to temperature than composition for most lower mantle minerals. In practice, this allows one the freedom to choose the geotherm that brings the predicted seismic and density data into agreement with observations. It is commonly assumed that the temperature profile should be adiabatic, however, such a profile presupposes a particular state of the mantle and is only applicable in the absence of layering, buoyancy fluctuations, compositional segregation, and rheological complexities. The mantle temperature should depend on the composition since the latter influences the viscosity of rocks. However, the precise relation between composition, viscosity, and heat transfer would need to be specified, but unfortunately remains highly uncertain. If the mantle contains a mixture of domains with multiple bulk compositions, then the 1D seismic profile comparison is inherently non-unique. Rocks with different bulk composition likely have different isotopic abundances, and can exhibit differing degrees of internal heating and therefore distinct temperatures. Different composition domains can also exhibit variable densities, and tend to congregate at different depths in ways that also affect their thermal evolution and temperature. Therefore, fitting a 1D seismic model alone is an inadequate tool to evaluate lower mantle composition.

Amplification of seismic waves beneath active volcanoes

NASA Astrophysics Data System (ADS)

Navon, O.; Lensky, N. G.; Collier, L.; Neuberg, J.; Lyakhovsky, V.

2003-04-01

Long-period (LP) seismic events are typical for many volcanoes and are attributed to energy leaking from waves traveling along the conduit - country-rock interface. While the wave propagation is well understood, their actual trigger mechanism and their energy source are not. Here we test the hypothesis that energy may be supplied by volatile-release from a supersaturated melt. If bubbles are initially in equilibrium with the melt in the conduit, and the melt is suddenly decompressed, the transfer of volatiles from the supersaturated melt into the bubbles transforms stored potential energy into expansion work. For example, small dome collapse, opening of a crack or a displacement along the brittle part of the conduit may decompress the magma by a few bars and create the needed supersaturation. This energy is released over the timescale of accelerated expansion, which is longer than a typical LP event. Following decompression, when the transfer of volatiles into bubbles is fast enough, expansion accelerates and the bulk viscosity of the bubbly magma is negative (Lensky et al., 2002). New calculations show that under such conditions a sinusoidal P-wave is amplified. We note that seismic waves created by tectonic earthquakes that are not associated with net decompression, do not lead to net release of volatiles or to net expansion. In this case, the bulk viscosity is positive and waves traveling through the magma should attenuate. The proposed model explains how weak seismic signals may be amplified as they travel through a conduit that contains supersaturated bubbly magma. It provides the general framework for amplifying volcanic seismicity such as long-period events.

Capillary Rise: Validity of the Dynamic Contact Angle Models.

PubMed

Wu, Pingkeng; Nikolov, Alex D; Wasan, Darsh T

2017-08-15

The classical Lucas-Washburn-Rideal (LWR) equation, using the equilibrium contact angle, predicts a faster capillary rise process than experiments in many cases. The major contributor to the faster prediction is believed to be the velocity dependent dynamic contact angle. In this work, we investigated the dynamic contact angle models for their ability to correct the dynamic contact angle effect in the capillary rise process. We conducted capillary rise experiments of various wetting liquids in borosilicate glass capillaries and compared the model predictions with our experimental data. The results show that the LWR equations modified by the molecular kinetic theory and hydrodynamic model provide good predictions on the capillary rise of all the testing liquids with fitting parameters, while the one modified by Joos' empirical equation works for specific liquids, such as silicone oils. The LWR equation modified by molecular self-layering model predicts well the capillary rise of carbon tetrachloride, octamethylcyclotetrasiloxane, and n-alkanes with the molecular diameter or measured solvation force data. The molecular self-layering model modified LWR equation also has good predictions on the capillary rise of silicone oils covering a wide range of bulk viscosities with the same key parameter W(0), which results from the molecular self-layering. The advantage of the molecular self-layering model over the other models reveals the importance of the layered molecularly thin wetting film ahead of the main meniscus in the energy dissipation associated with dynamic contact angle. The analysis of the capillary rise of silicone oils with a wide range of bulk viscosities provides new insights into the capillary dynamics of polymer melts.

Textural and sensory properties of trifoliate yam (Dioscorea dumetorum) flour and stiff dough 'amala'.

PubMed

Abiodun, O A; Akinoso, R

2015-05-01

The use of trifoliate yam (Dioscorea dumetorum) flour for stiff dough 'amala' production is one of the ways to curb under-utilization of the tuber. The study evaluates the textural and sensory properties of trifoliate yam flour and stiff dough. Freshly harvested trifoliate yam tubers were peeled, washed, sliced and blanched (60 (°)C for 10 min). The sliced yam were soaked in water for 12 h, dried and milled into flour. Pasting viscosities, functional properties, brown index and sensory attributes of the flour and stiff dough were analyzed. Peak, holding strength and final viscosities ranged from 84.09 to 213.33 RVU, 81.25 to 157.00 RVU and 127.58 to 236.17 RVU respectively. White raw flour had higher viscosity than the yellow flours. The swelling index, water absorption capacity and bulk density ranged from 1.46 to 2.28, 2.11 to 2.92 ml H2O/g and 0.71 to 0.88 g/cm(3) respectively. Blanching method employed improved the swelling index and water absorption capacity of flour. The brown index values of flour and stiff dough ranged from 6.73 to 18.36 and 14.63-46.72 respectively. Sensory evaluation revealed significant differences in the colour, odour and general acceptability of the product when compared with the stiff dough from white yam.

Viscous constitutive relations of solid-liquid composites in terms of grain boundary contiguity: 1. Grain boundary diffusion control model

NASA Astrophysics Data System (ADS)

Takei, Yasuko; Holtzman, Benjamin K.

2009-06-01

Viscous constitutive relations of partially molten rocks deforming in the regime of grain boundary (GB) diffusion creep are derived theoretically on the basis of microstructural processes at the grain scale. The viscous constitutive relation developed in this study is based on contiguity as an internal state variable, which enables us to take into account the detailed effects of grain-scale melt distribution observed in experiments. Compared to the elasticities derived previously for the same microstructural model, the viscosities are much more sensitive to the presence of melt and variations in contiguity. As explored in this series of three companion papers, this "contiguity" model predicts that a very small amount of melt (ϕ < 0.01) significantly reduces the bulk and shear viscosities. Furthermore, a large anisotropy in viscosity is produced by anisotropy in contiguity, which occurs in deforming partially molten rocks. These results have important implications for deformation and melt extraction at small melt fractions, as well as for shear-induced melt segregation. The viscous and elastic constitutive relations derived in terms of contiguity bridge microscopic grain-scale and macroscopic continuum properties. These constitutive relations are essential for investigating melt migration dynamics in a forward sense on the basis of the basic equations of two-phase dynamics and in an inverse sense on the basis of seismological observations.

Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity

PubMed Central

Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J.; Shilling, John E.; Martin, Scot T.; Bertram, Allan K.

2013-01-01

Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a “bead-mobility” technique and a “poke-flow” technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by α-pinene ozonolysis is quantified for 20- to 50-μm particles at 293–295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ≤30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ≤ 30%; (ii) at ≤30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate. PMID:23620520

Precise, contactless measurements of the surface tension of picolitre aerosol droplets† †Electronic supplementary information (ESI) available: Parametrizations used to infer concentration, density, viscosity, and surface tension from refractive index for sodium chloride and glutaric acid; description of the semi-analytical T-matrix calculations; Fig. S1 and S2. See DOI: 10.1039/c5sc03184b Click here for additional data file.

PubMed Central

Bzdek, Bryan R.; Power, Rory M.; Simpson, Stephen H.; Royall, C. Patrick

2016-01-01

The surface composition and surface tension of aqueous droplets can influence key aerosol characteristics and processes including the critical supersaturation required for activation to form cloud droplets in the atmosphere. Despite its fundamental importance, surface tension measurements on droplets represent a considerable challenge owing to their small volumes. In this work, we utilize holographic optical tweezers to study the damped surface oscillations of a suspended droplet (<10 μm radius) following the controlled coalescence of a pair of droplets and report the first contactless measurements of the surface tension and viscosity of droplets containing only 1–4 pL of material. An advantage of performing the measurement in aerosol is that supersaturated solute states (common in atmospheric aerosol) may be accessed. For pairs of droplets starting at their equilibrium surface composition, surface tensions and viscosities are consistent with bulk equilibrium values, indicating that droplet surfaces respond to changes in surface area on microsecond timescales and suggesting that equilibrium values can be assumed for growing atmospheric droplets. Furthermore, droplet surfaces are shown to be rapidly modified by trace species thereby altering their surface tension. This equilibration of droplet surface tension to the local environmental conditions is illustrated for unknown contaminants in laboratory air and also for droplets exposed to gas passing through a water–ethanol solution. This approach enables precise measurements of surface tension and viscosity over long time periods, properties that currently are poorly constrained. PMID:28758004

Fluid Film Bearing Code Development

NASA Technical Reports Server (NTRS)

1995-01-01

The next generation of rocket engine turbopumps is being developed by industry through Government-directed contracts. These turbopumps will use fluid film bearings because they eliminate the life and shaft-speed limitations of rolling-element bearings, increase turbopump design flexibility, and reduce the need for turbopump overhauls and maintenance. The design of the fluid film bearings for these turbopumps, however, requires sophisticated analysis tools to model the complex physical behavior characteristic of fluid film bearings operating at high speeds with low viscosity fluids. State-of-the-art analysis and design tools are being developed at the Texas A&M University under a grant guided by the NASA Lewis Research Center. The latest version of the code, HYDROFLEXT, is a thermohydrodynamic bulk flow analysis with fluid compressibility, full inertia, and fully developed turbulence models. It can predict the static and dynamic force response of rigid and flexible pad hydrodynamic bearings and of rigid and tilting pad hydrostatic bearings. The Texas A&M code is a comprehensive analysis tool, incorporating key fluid phenomenon pertinent to bearings that operate at high speeds with low-viscosity fluids typical of those used in rocket engine turbopumps. Specifically, the energy equation was implemented into the code to enable fluid properties to vary with temperature and pressure. This is particularly important for cryogenic fluids because their properties are sensitive to temperature as well as pressure. As shown in the figure, predicted bearing mass flow rates vary significantly depending on the fluid model used. Because cryogens are semicompressible fluids and the bearing dynamic characteristics are highly sensitive to fluid compressibility, fluid compressibility effects are also modeled. The code contains fluid properties for liquid hydrogen, liquid oxygen, and liquid nitrogen as well as for water and air. Other fluids can be handled by the code provided that the user inputs information that relates the fluid transport properties to the temperature.

Dynamic bulk and shear moduli due to grain-scale local fluid flow in fluid-saturated cracked poroelastic rocks: Theoretical model

NASA Astrophysics Data System (ADS)

Song, Yongjia; Hu, Hengshan; Rudnicki, John W.

2016-07-01

Grain-scale local fluid flow is an important loss mechanism for attenuating waves in cracked fluid-saturated poroelastic rocks. In this study, a dynamic elastic modulus model is developed to quantify local flow effect on wave attenuation and velocity dispersion in porous isotropic rocks. The Eshelby transform technique, inclusion-based effective medium model (the Mori-Tanaka scheme), fluid dynamics and mass conservation principle are combined to analyze pore-fluid pressure relaxation and its influences on overall elastic properties. The derivation gives fully analytic, frequency-dependent effective bulk and shear moduli of a fluid-saturated porous rock. It is shown that the derived bulk and shear moduli rigorously satisfy the Biot-Gassmann relationship of poroelasticity in the low-frequency limit, while they are consistent with isolated-pore effective medium theory in the high-frequency limit. In particular, a simplified model is proposed to quantify the squirt-flow dispersion for frequencies lower than stiff-pore relaxation frequency. The main advantage of the proposed model over previous models is its ability to predict the dispersion due to squirt flow between pores and cracks with distributed aspect ratio instead of flow in a simply conceptual double-porosity structure. Independent input parameters include pore aspect ratio distribution, fluid bulk modulus and viscosity, and bulk and shear moduli of the solid grain. Physical assumptions made in this model include (1) pores are inter-connected and (2) crack thickness is smaller than the viscous skin depth. This study is restricted to linear elastic, well-consolidated granular rocks.

Fused Bead Analysis of Diogenite Meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D.W.; Beck, B.W.; McSween, H.Y.; Lee, C.T. A.

2009-01-01

Bulk rock chemistry is an essential dataset in meteoritics and planetary science [1]. A common method used to obtain the bulk chemistry of meteorites is ICP-MS. While the accuracy, precision and low detection limits of this process are advantageous [2], the sample size used for analysis (approx.70 mg) can be a problem in a field where small and finite samples are the norm. Fused bead analysis is another bulk rock analytical technique that has been used in meteoritics [3]. This technique involves forming a glass bead from 10 mg of sample and measuring its chemistry using a defocused beam on a microprobe. Though the ICP-MS has lower detection limits than the microprobe, the fused bead method destroys a much smaller sample of the meteorite. Fused bead analysis was initially designed for samples with near-eutectic compositions and low viscosities. Melts generated of this type homogenize at relatively low temperatures and produce primary melts near the sample s bulk composition [3]. The application of fused bead analysis to samples with noneutectic melt compositions has not been validated. The purpose of this study is to test if fused bead analysis can accurately determine the bulk rock chemistry of non-eutectic melt composition meteorites. To determine this, we conduct two examinations of the fused bead. First, we compare ICP-MS and fused bead results of the same samples using statistical analysis. Secondly, we inspect the beads for the presence of crystals and chemical heterogeneity. The presence of either of these would indicate incomplete melting and quenching of the bead.

Fluid/gravity correspondence for massive gravity

NASA Astrophysics Data System (ADS)

Pan, Wen-Jian; Huang, Yong-Chang

2016-11-01

In this paper, we investigate the fluid/gravity correspondence in the framework of massive Einstein gravity. Treating the gravitational mass terms as an effective energy-momentum tensor and utilizing the Petrov-like boundary condition on a timelike hypersurface, we find that the perturbation effects of massive gravity in bulk can be completely governed by the incompressible Navier-Stokes equation living on the cutoff surface under the near horizon and nonrelativistic limits. Furthermore, we have concisely computed the ratio of dynamical viscosity to entropy density for two massive Einstein gravity theories, and found that they still saturate the Kovtun-Son-Starinets (KSS) bound.

Assessment of passive knee stiffness and viscosity in individuals with spinal cord injury using pendulum test.

PubMed

Joghtaei, Mahmoud; Arab, Amir Massoud; Hashemi-Nasl, Hamed; Joghataei, Mohammad Taghi; Tokhi, Mohammad Osman

2015-03-01

Stiffness and viscosity represent passive resistances to joint motion related with the structural properties of the joint tissue and of the musculotendinous complex. Both parameters can be affected in patients with spinal cord injury (SCI). The purpose of this study was to measure passive knee stiffness and viscosity in patients with SCI with paraplegia and healthy subjects using Wartenberg pendulum test. Non-experimental, cross-sectional, case-control design. An outpatient physical therapy clinic, University of social welfare and Rehabilitation Science, Iran. A sample of convenience sample of 30 subjects participated in the study. Subjects were categorized into two groups: individuals with paraplegic SCI (n = 15, age: 34.60 ± 9.18 years) and 15 able-bodied individuals as control group (n = 15, age: 30.66 ± 11.13 years). Not applicable. Passive pendulum test of Wartenberg was used to measure passive viscous-elastic parameters of the knee (stiffness, viscosity) in all subjects. Statistical analysis (independent t-test) revealed significant difference in the joint stiffness between healthy subjects and those with paraplegic SCI (P = 0.01). However, no significant difference was found in the viscosity between two groups (P = 0.17). Except for first peak flexion angle, all other displacement kinematic parameters exhibited no statistically significant difference between normal subjects and subjects with SCI. Patients with SCI have significantly greater joint stiffness compared to able-bodied subjects.

Ultrasonication-assisted preparation and characterization of emulsions and emulsion gels for topical drug delivery.

PubMed

Singh, Vinay K; Behera, Baikuntha; Pramanik, Krishna; Pal, Kunal

2015-03-01

The current study describes the use of ultrasonication for the preparation of biphasic emulsions and emulsion gels for topical drug delivery. Sorbitan monostearate (SMS) was used as the surfactant for stabilizing the interface of sesame oil (apolar phase) and water (polar phase). Emulsions were formed at lower concentrations of SMS, whereas emulsion gels were formed at higher concentrations of SMS. The formulations were characterized by fluorescent microscopy, X-ray diffraction, viscosity, stress relaxation, spreadability, and differential scanning calorimetry studies. Fluorescence microscopy suggested formation of oil-in-water type of formulations. There was an increase in the viscosity, bulk resistance, and firmness of the formulations as the proportions of SMS was increased. The emulsion gels were viscoelastic in nature. Thermal studies suggested higher thermodynamic stability at higher proportions of either SMS or water. Metronidazole, a model antimicrobial drug, was incorporated within the formulations. The release of the drug from the formulations was found to be diffusion mediated. The drug-loaded formulations showed sufficient antimicrobial efficiency to be used as carriers for topical antimicrobial drug delivery. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Multiscale Spectroscopy of Diffusing Molecules in Crowded Environments

NASA Astrophysics Data System (ADS)

Heikal, Ahmed A.

2015-06-01

Living cells are known to be crowded with organelles, biomembranes, and macromolecules such as proteins, DNA, RNA, and actin filaments. It is believed that such macromolecular crowding affect biomolecular diffusion, protein-protein and protein-substrate interaction, and protein folding. In this contribution, I will discuss our recent results on rotational and translational diffusion of small and large molecules in crowded environments using time-resolved anisotropy and fluorescence correlation spectroscopy methods. In these studies, rhodamine green and enhanced green fluorescent protein are used as fluorescent probes diffusing in buffers enriched with biomimetic crowding agents such as Ficoll-70, bovine serum albumin (BSA), and ovalbumin. Controlled experiments on pure and glycerol-rich buffers were carried out as environments with variable, homogeneous viscosity. Our results indicate that the microviscosity differs from the corresponding bulk viscosity, depending on the nature of crowding agents (i.e., proteins versus polymers), the concentration of crowding agents and spatio-temporal scaling of our experimental approach. Our findings provide a foundation for fluorescence-based studies of diffusion and binding of biomolecules in the crowded milieu of living cells.

Thermophysical and Optical Properties of Semiconducting Ga2Te3 Melt

NASA Technical Reports Server (NTRS)

Li, Chao; Su, Ching-Hua; Lehoczky, Sandor L.; Scripa, Rosalie N.; Ban, Heng

2005-01-01

The majority of bulk semiconductor single crystals are presently grown from their melts. The thermophysical and optical properties of the melts provide a fundamental understanding of the melt structure and can be used to optimize the growth conditions to obtain higher quality crystals. In this paper, we report several thermophysical and optical properties for Ga2Te3 melts, such as electrical conductivity, viscosity, and optical transmission for temperatures ranging from the melting point up to approximately 990 C. The conductivity and viscosity of the melts are determined using the transient torque technique. The optical transmission of the melts is measured between the wavelengths of 300 and 2000 nm by an dual beam reversed-optics spectrophotometer. The measured properties are in good agreement with the published data. The conductivities indicate that the Ga2Te3 melt is semiconductor-like. The anomalous behavior in the measured properties are used as an indication of a structural transformation in the Ga2Te3 melt and discussed in terms of Eyring's and Bachinskii's predicted behaviors for homogeneous melts.

On a viable first-order formulation of relativistic viscous fluids and its applications to cosmology

NASA Astrophysics Data System (ADS)

Disconzi, Marcelo M.; Kephart, Thomas W.; Scherrer, Robert J.

We consider a first-order formulation of relativistic fluids with bulk viscosity based on a stress-energy tensor introduced by Lichnerowicz. Choosing a barotropic equation-of-state, we show that this theory satisfies basic physical requirements and, under the further assumption of vanishing vorticity, that the equations of motion are causal, both in the case of a fixed background and when the equations are coupled to Einstein's equations. Furthermore, Lichnerowicz's proposal does not fit into the general framework of first-order theories studied by Hiscock and Lindblom, and hence their instability results do not apply. These conclusions apply to the full-fledged nonlinear theory, without any equilibrium or near equilibrium assumptions. Similarities and differences between the approach explored here and other theories of relativistic viscosity, including the Mueller-Israel-Stewart formulation, are addressed. Cosmological models based on the Lichnerowicz stress-energy tensor are studied. As the topic of (relativistic) viscous fluids is also of interest outside the general relativity and cosmology communities, such as, for instance, in applications involving heavy-ion collisions, we make our presentation largely self-contained.

Effects of storage and yogurt matrix on the stability of tocotrienols encapsulated in chitosan-alginate microcapsules.

PubMed

Tan, Phui Yee; Tan, Tai Boon; Chang, Hon Weng; Tey, Beng Ti; Chan, Eng Seng; Lai, Oi Ming; Baharin, Badlishah Sham; Nehdi, Imededdine Arbi; Tan, Chin Ping

2018-02-15

Tocotrienol microcapsules (TM) were formed by firstly preparing Pickering emulsion containing tocotrienols, which was then gelled into microcapsules using alginate and chitosan. In this study, we examined the stability of TM during storage and when applied into a model food system, i.e. yogurt. During storage at 40°C, TM displayed remarkably lower tocotrienols loss (50.8%) as compared to non-encapsulated tocotrienols in bulk oil (87.5%). When the tocotrienols were incorporated into yogurt, the TM and bulk oil forms showed a loss of 23.5% and 81.0%, respectively. Generally, the tocotrienols were stable in the TM form and showed highest stability when these TM were added into yogurt. δ-Tocotrienol was the most stable isomer in both forms during storage and when incorporated into yogurt. The addition of TM into yogurt caused minimal changes in the yogurt's color and texture but slightly altered the yogurt's viscosity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Momentum and charge transport in non-relativistic holographic fluids from Hořava gravity

NASA Astrophysics Data System (ADS)

Davison, Richard A.; Grozdanov, Sašo; Janiszewski, Stefan; Kaminski, Matthias

2016-11-01

We study the linearized transport of transverse momentum and charge in a conjectured field theory dual to a black brane solution of Hořava gravity with Lifshitz exponent z = 1. As expected from general hydrodynamic reasoning, we find that both of these quantities are diffusive over distance and time scales larger than the inverse temperature. We compute the diffusion constants and conductivities of transverse momentum and charge, as well the ratio of shear viscosity to entropy density, and find that they differ from their relativistic counterparts. To derive these results, we propose how the holographic dictionary should be modified to deal with the multiple horizons and differing propagation speeds of bulk excitations in Hořava gravity. When possible, as a check on our methods and results, we use the covariant Einstein-Aether formulation of Hořava gravity, along with field redefinitions, to re-derive our results from a relativistic bulk theory.

Understanding the influence of tellurium oxide in front Ag paste for contacting silicon solar cells with homogeneous high sheet resistance emitter

NASA Astrophysics Data System (ADS)

Ebong, Abasifreke; Bezawada, Nirupama; Batchu, Kartheek

2017-08-01

This paper investigates TeO2, one of the front Ag paste additives, to understand its role in low contact and gridline resistances for screen-printed Si solar cell. It is concluded that TeO2 aids the reduction of molten glass frit viscosity during contact co-firing. This in turn, leads to uniform flow of molten glass frit, both in the gridline bulk and interface of gridline and SiN x . Therefore, the uniform wetting and etching of SiN x and consequently larger contact area of metal to Si compared to its counterpart without TeO2. Hence, the current transport mechanism from Si to gridline can be said to be both direct and tunneling. The Raman spectra showed a blue shift in the phase of the TeO2 after contact co-firing in the gridline bulk confirming a crystalline γ-TeO2.

Size-Dependent Particle Dynamics in Entangled Polymer Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangal, Rahul; Srivastava, Samanvaya; Narayanan, Suresh

Polymer-grafted nanoparticles with diameter d homogeneously dispersed in entangled polymer melts with varying random coil radius R0, but fixed entanglement mesh size ae, are used to study particle motions in entangled polymers. We focus on materials in the transition region between the continuum regime (d > R0), where the classical Stokes-Einstein (S-E) equation is known to describe polymer drag on particles, and the non-continuum regime (d < ae), in which several recent studies report faster diffusion of particles than expected from continuum S-E analysis, based on the bulk polymer viscosity. Specifically, we consider dynamics of particles with sizes d ≥more » ae in entangled polymers with varying molecular weight Mw in order to investigate how the transition from non-continuum to continuum dynamics occur. We take advantage of favorable enthalpic interactions between SiO2 nanoparticles tethered with PEO molecules and entangled PMMA host polymers to create model nanoparticle-polymer composites, in which spherical nanoparticles are uniformly dispersed in entangled polymers. Investigation of the particle dynamics via X-ray photon correlation spectroscopy measurements reveal a transition from fast to slow particle motion as the PMMA molecular weight is increased beyond the entanglement threshold, with a much weaker Mw dependence for Mw>Me than expected from S-E analysis based on bulk viscosity of entangled PMMA melts. We rationalize these observations using a simple force balance analysis around particles and find that nanoparticle motion in entangled melts can be described using a variant of the S-E analysis in which motion of particles is assumed to only disturb sub-chain entangled host segments with sizes comparable to the particle diameter.« less

Amplification of seismic waves beneath active volcanoes

NASA Astrophysics Data System (ADS)

Navon, O.; Lensky, N. G.; Collier, L.; Neuberg, J.; Lyakhovsky, V.

2003-04-01

Long-period (LP) seismic events are typical of many volcanoes and are attributed to energy leaking from waves traveling through the volcanic conduit or along the conduit - country-rock interface. The LP events are triggered locally, at the volcanic edifice, but the source of energy for the formation of tens of events per day is not clear. Energy may be supplied by volatile-release from a supersaturated melt. If bubbles are present in equilibrium with the melt in the conduit, and the melt is suddenly decompressed, transfer of volatiles from the supersaturated melt into the bubbles transforms stored potential energy into expansion work. For example, small dome collapses may decompress the conduit by a few bars and lead to solubility decrease, exsolution of volatiles and, consequently, to work done by the expansion of the bubbles under pressure. This energy is released over a timescale that is similar to that of LP events and may amplify the original weak seismic signals associated with the collapse. Using the formulation of Lensky et al. (2002), following the decompression, when the transfer of volatiles into bubbles is fast enough, expansion accelerates and the bulk viscosity of the bubbly magma is negative. New calculations show that under such conditions a sinusoidal P-wave is amplified. We note that seismic waves created by tectonic earthquakes that are not associated with net decompression, do not lead to net release of volatiles or to net expansion. In this case, the bulk viscosity is positive and waves traveling through the magma should attenuate. The proposed model explains how weak seismic signals may be amplified as they travel through a conduit that contains supersaturated bubbly magma. It provides the general framework for amplifying volcanic seismicity such as the signals associated with long-period events.

Size-Dependent Particle Dynamics in Entangled Polymer Nanocomposites.

PubMed

Mangal, Rahul; Srivastava, Samanvaya; Narayanan, Suresh; Archer, Lynden A

2016-01-19

Polymer-grafted nanoparticles with diameter d homogeneously dispersed in entangled polymer melts with varying random coil radius R0, but fixed entanglement mesh size a(e), are used to study particle motions in entangled polymers. We focus on materials in the transition region between the continuum regime (d > R0), where the classical Stokes-Einstein (S-E) equation is known to describe polymer drag on particles, and the noncontinuum regime (d < a(e)), in which several recent studies report faster diffusion of particles than expected from continuum S-E analysis, based on the bulk polymer viscosity. Specifically, we consider dynamics of particles with sizes d ≥ a(e) in entangled polymers with varying molecular weight M(w) in order to investigate how the transition from noncontinuum to continuum dynamics occur. We take advantage of favorable enthalpic interactions between SiO2 nanoparticles tethered with PEO molecules and entangled PMMA host polymers to create model nanoparticle-polymer composites, in which spherical nanoparticles are uniformly dispersed in entangled polymers. Investigation of the particle dynamics via X-ray photon correlation spectroscopy measurements reveals a transition from fast to slow particle motion as the PMMA molecular weight is increased beyond the entanglement threshold, with a much weaker M(w) dependence for M(w) > M(e) than expected from S-E analysis based on bulk viscosity of entangled PMMA melts. We rationalize these observations using a simple force balance analysis around particles and find that nanoparticle motion in entangled melts can be described using a variant of the S-E analysis in which motion of particles is assumed to only disturb subchain entangled host segments with sizes comparable to the particle diameter.

Effect of bulk-fill base material on fracture strength of root-filled teeth restored with laminate resin composite restorations.

PubMed

Taha, N A; Maghaireh, G A; Ghannam, A S; Palamara, J E

2017-08-01

To evaluate the effect of using a bulk-fill flowable base material on fracture strength and fracture patterns of root-filled maxillary premolars with MOD preparations restored with laminate restorations. Fifty extracted maxillary premolars were selected for the study. Standardized MOD cavities with endodontic treatment were prepared for all teeth, except for intact control. The teeth were divided randomly into five groups (n=10); (Group 1) sound teeth, (Group 2) unrestored teeth; (Group 3) MOD cavities with Vitrebond base and resin-based composite (Ceram. X One Universal); (Group 4) MOD cavities with 2mm GIC base (Fuji IX GP) and resin-based composite (Ceram. X One Universal) open laminate, (Group 5) MOD cavities were restored with 4mm of bulk-fill flowable base material (SDR) and resin-based composite (Ceram. X One Universal). All teeth were thermocycled and subjected to a 45° ramped oblique load in a universal testing machine. Fracture load and fracture patterns were recorded. Data were analyzed using one-way ANOVA and Dunnett's T3 test. Restoration in general increased the fracture strength compared to unrestored teeth. The fracture strength of group 5 (bulk-fill) was significantly higher than the fracture strength of the GIC laminate groups and not significantly different from the intact teeth (355±112N, P=0.118). The type of failure was unfavorable for most of the groups, with the majority being mixed failures. The use of a bulk-fill flowable base material significantly increased the fracture strength of extracted root-filled teeth with MOD cavities; however it did not improve fracture patterns to more favorable ones. Investigating restorative techniques that may improve the longevity of root-filled premolar teeth restored with direct resin restorations. Copyright © 2017 Elsevier Ltd. All rights reserved.

An overview of rotating machine systems with high-temperature bulk superconductors

NASA Astrophysics Data System (ADS)

Zhou, Difan; Izumi, Mitsuru; Miki, Motohiro; Felder, Brice; Ida, Tetsuya; Kitano, Masahiro

2012-10-01

The paper contains a review of recent advancements in rotating machines with bulk high-temperature superconductors (HTS). The high critical current density of bulk HTS enables us to design rotating machines with a compact configuration in a practical scheme. The development of an axial-gap-type trapped flux synchronous rotating machine together with the systematic research works at the Tokyo University of Marine Science and Technology since 2001 are briefly introduced. Developments in bulk HTS rotating machines in other research groups are also summarized. The key issues of bulk HTS machines, including material progress of bulk HTS, in situ magnetization, and cooling together with AC loss at low-temperature operation are discussed.

Optimization of NMR spectroscopy of encapsulated proteins dissolved in low viscosity fluids

PubMed Central

Nucci, Nathaniel V.; Marques, Bryan S.; Bédard, Sabrina; Dogan, Jakob; Gledhill, John M.; Moorman, Veronica R.; Peterson, Ronald W.; Valentine, Kathleen G.; Wand, Alison L.; Wand, A. Joshua

2014-01-01

Comprehensive application of solution NMR spectroscopy to studies of macromolecules remains fundamentally limited by the molecular rotational correlation time. For proteins, molecules larger than 30 kDa require complex experimental methods, such as TROSY in conjunction with isotopic labeling schemes that are often expensive and generally reduce the potential information available. We have developed the reverse micelle encapsulation strategy as an alternative approach. Encapsulation of proteins within the protective nano-scale water pool of a reverse micelle dissolved in ultra-low viscosity nonpolar solvents overcomes the slow tumbling problem presented by large proteins. Here, we characterize the contributions from the various components of the protein-containing reverse micelle system to the rotational correlation time of the encapsulated protein. Importantly, we demonstrate that the protein encapsulated in the reverse micelle maintains a hydration shell comparable in size to that seen in bulk solution. Using moderate pressures, encapsulation in ultra-low viscosity propane or ethane can be used to magnify this advantage. We show that encapsulation in liquid ethane can be used to reduce the tumbling time of the 43 kDa maltose binding protein from ~23 ns to ~10 ns. These conditions enable, for example, acquisition of TOCSY-type data resolved on the adjacent amide NH for the 42 kDa encapsulated maltose binding protein dissolved in liquid ethane, which is typically impossible for proteins of such size without use of extensive deuteration or the TROSY effect. PMID:21748265

Relativistic theory of particles in a scattering flow III: photon transport.

NASA Astrophysics Data System (ADS)

Achterberg, A.; Norman, C. A.

2018-06-01

We use the theory developed in Achterberg & Norman (2018a) and Achterberg & Norman (2018b) to calculate the stress due to photons that are scattered elastically by a relativistic flow. We show that the energy-momentum tensor of the radiation takes the form proposed by Eckart (1940). In particular we show that no terms associated with a bulk viscosity appear if one makes the diffusion approximation for radiation transport and treats the radiation as a separate fluid. We find only shear (dynamic) viscosity terms and heat flow terms in our expression for the energy-momentum tensor. This conclusion holds quite generally for different forms of scattering: Krook-type integral scattering, diffusive (Fokker-Planck) scattering and Thomson scattering. We also derive the transport equation in the diffusion approximation that shows the effects of the flow on the photon gas in the form of a combination of adiabatic heating and an irreversible heating term. We find no diffusive changes to the comoving number density and energy density of the scattered photons, in contrast with some published results in Radiation Hydrodynamics. It is demonstrated that these diffusive corrections to the number- and energy density of the photons are in fact higher-order terms that can (and should) be neglected in the diffusion approximation. Our approach eliminates these terms at the root of the expansion that yields the anisotropic terms in the phase-space density of particles and photons, the terms responsible for the photon viscosity.

Mobility of power-law and Carreau fluids through fibrous media.

PubMed

Shahsavari, Setareh; McKinley, Gareth H

2015-12-01

The flow of generalized Newtonian fluids with a rate-dependent viscosity through fibrous media is studied, with a focus on developing relationships for evaluating the effective fluid mobility. Three methods are used here: (i) a numerical solution of the Cauchy momentum equation with the Carreau or power-law constitutive equations for pressure-driven flow in a fiber bed consisting of a periodic array of cylindrical fibers, (ii) an analytical solution for a unit cell model representing the flow characteristics of a periodic fibrous medium, and (iii) a scaling analysis of characteristic bulk parameters such as the effective shear rate, the effective viscosity, geometrical parameters of the system, and the fluid rheology. Our scaling analysis yields simple expressions for evaluating the transverse mobility functions for each model, which can be used for a wide range of medium porosity and fluid rheological parameters. While the dimensionless mobility is, in general, a function of the Carreau number and the medium porosity, our results show that for porosities less than ɛ≃0.65, the dimensionless mobility becomes independent of the Carreau number and the mobility function exhibits power-law characteristics as a result of the high shear rates at the pore scale. We derive a suitable criterion for determining the flow regime and the transition from a constant viscosity Newtonian response to a power-law regime in terms of a new Carreau number rescaled with a dimensionless function which incorporates the medium porosity and the arrangement of fibers.

Thermodynamic properties, melting temperature and viscosity of the mantles of Super Earths

NASA Astrophysics Data System (ADS)

Stamenkovic, V.; Spohn, T.; Breuer, D.

2010-12-01

The recent dicscovery of extrasolar planets with radii of about twice the Earth radius and masses of several Earth masses such as e.g., Corot-7b (approx 5Mearth and 1.6Rearth, Queloz et al. 2009) has increased the interest in the properties of rock at extremely high pressures. While the pressure at the Earth’s core-mantle boundary is about 135GPa, pressures at the base of the mantles of extraterrestrial rocky planets - if these are at all differentiated into mantles and cores - may reach Tera Pascals. Although the properties and the mineralogy of rock at extremely high pressure is little known there have been speculations about mantle convection, plate tectonics and dynamo action in these “Super-Earths”. We assume that the mantles of these planets can be thought of as consisting of perovskite but we discuss the effects of the post-perovskite transition and of MgO. We use the Keane equation of state and the Slater relation (see e.g., Stacey and Davies 2004) to derive an infinite pressure value for the Grüneisen parameter of 1.035. To derive this value we adopted the infinite pressure limit for K’ (pressure derivative of the bulk modulus) of 2.41 as derived by Stacey and Davies (2004) by fitting PREM. We further use the Lindeman law to calculate the melting curve. We gauge the melting curve using the available experimental data for pressures up to 120GPa. The melting temperature profile reaches 6000K at 135GPa and increases to temperatures between 12,000K and 24,000K at 1.1TPa with a preferred value of 21,000K. We find the adiabatic temperature increase to reach 2,500K at 135GPa and 5,400K at 1.1TPa. To calculate the pressure dependence of the viscosity we assume that the rheology is diffusion controlled and calculate the partial derivative with respect to pressure of the activation enthalpy. We cast the partial derivative in terms of an activation volume and use the semi-empirical homologous temperature scaling (e.g., Karato 2008). We find that the activation volume decreases from 2.4cm^3/mol at 135GPa to 1.6cm^3/mol at 1.1TPa. An estimate of the viscosity increase across the mantle to a pressure of 1.1TPa using the adiabat calculated above results in an increase of the viscosity of 19 orders of magnitude. This value raises questions about the differentiation of these planets, heat transfer in their deep interiors, and magnetic field generation.(Ref.: Karato, S. 2008. Deformation of Earth Materials, Cambridge University Press.; Stacey, F.D., Davies, P.M. 2004. PEPI 142: 137; Queloz, D. et al., 2009. Astronomy and Astrophysics 506: 303.)

Tachyon with an inverse power-law potential in a braneworld cosmology

NASA Astrophysics Data System (ADS)

Bilić, Neven; Domazet, Silvije; Djordjevic, Goran S.

2017-08-01

We study a tachyon cosmological model based on the dynamics of a 3-brane in the bulk of the second Randall-Sundrum model extended to more general warp functions. A well known prototype of such a generalization is the bulk with a selfinteracting scalar field. As a consequence of a generalized bulk geometry the cosmology on the observer brane is modified by the scale dependent four-dimensional gravitational constant. In particular, we study a power law warp factor which generates an inverse power-law potential V\\propto \\varphi-n of the tachyon field φ. We find a critical power n cr that divides two subclasses with distinct asymptotic behaviors: a dust universe for n>n_cr and a quasi de Sitter universe for 0.

Physico-mechanical characteristics of commercially available bulk-fill composites.

PubMed

Leprince, Julian G; Palin, William M; Vanacker, Julie; Sabbagh, Joseph; Devaux, Jacques; Leloup, Gaetane

2014-08-01

Bulk-fill composites have emerged, arguably, as a new "class" of resin-based composites, which are claimed to enable restoration in thick layers, up to 4mm. The objective of this work was to compare, under optimal curing conditions, the physico-mechanical properties of most currently available bulk-fill composites to those of two conventional composite materials chosen as references, one highly filled and one flowable "nano-hybrid" composite. Tetric EvoCeram Bulk Fill (Ivoclar-Vivadent), Venus Bulk Fill (Heraeus-Kulzer), SDR (Dentsply), X-tra Fil (VOCO), X-tra Base (VOCO), Sonic Fill (Kerr), Filtek Bulk Fill (3M-Espe), Xenius (GC) were compared to the two reference materials. The materials were light-cured for 40s in a 2mm×2mm×25mm Teflon mould. Degree of conversion was measured by Raman spectroscopy, Elastic modulus and flexural strength were evaluated by three point bending, surface hardness using Vickers microindentation before and after 24h ethanol storage, and filler weight content by thermogravimetric analysis. The ratio of surface hardness before and after ethanol storage was considered as an evaluation of polymer softening. Data were analyzed by one-way ANOVA and post hoc Tukey's test (p=0.05). The mechanical properties of the bulk-fill composites were mostly lower compared with the conventional high viscosity material, and, at best, comparable to the conventional flowable composite. Linear correlations of the mechanical properties investigated were poor with degree of conversion (0.090.8). Softening in ethanol revealed differences in polymer network density between material types. The reduction of time and improvement of convenience associated with bulk-fill materials is a clear advantage of this particular material class. However, a compromise with mechanical properties compared with more conventional commercially-available nano-hybrid materials was demonstrated by the present work. Given the lower mechanical properties of most bulk-fill materials compared to a highly filled nano-hybrid composite, their use for restorations under high occlusal load is subject to caution. Further, the swelling behaviour of some of the bulk-fill materials may be a reason for concern, which highlights the critical requirement for a veneering material, not only to improve aesthetic quality of the translucent material, but to reduce the impact of degradation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Astroparticle physics and cosmology.

PubMed

Mitton, Simon

2006-05-20

Astroparticle physics is an interdisciplinary field that explores the connections between the physics of elementary particles and the large-scale properties of the universe. Particle physicists have developed a standard model to describe the properties of matter in the quantum world. This model explains the bewildering array of particles in terms of constructs made from two or three quarks. Quarks, leptons, and three of the fundamental forces of physics are the main components of this standard model. Cosmologists have also developed a standard model to describe the bulk properties of the universe. In this new framework, ordinary matter, such as stars and galaxies, makes up only around 4% of the material universe. The bulk of the universe is dark matter (roughly 23%) and dark energy (about 73%). This dark energy drives an acceleration that means that the expanding universe will grow ever larger. String theory, in which the universe has several invisible dimensions, might offer an opportunity to unite the quantum description of the particle world with the gravitational properties of the large-scale universe.

Stability of ferrous-iron-rich bridgmanite under reducing midmantle conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shim, Sang-Heon; Grocholski, Brent; Ye, Yu

2017-06-05

Our current understanding of the electronic state of iron in lower-mantle minerals leads to a 8 considerable disagreement in bulk sound speed with seismic measurements if the lower mantle 9 has the same composition as the upper mantle (pyrolite). In the modelling studies, the content 10 and oxidation state of Fe in the minerals have been assumed to be constant throughout the lower 11 mantle. Here, we report high pressure experimental results in which Fe becomes dominantly 1 Fe2+ 12 in bridgmanite synthesized at 40–70GPa and 2,000K, while it is in mixed oxidation state (Fe3+/ P Fe = 60%) inmore » the samples synthesized below and above the pressure range. Little Fe3+ 13 14 in bridgmanite combined with the strong partitioning of Fe2+ into ferropericlase will alter the Fe 15 content for these minerals at 1,100–1,700 km depths. Our calculations show that the change in 16 iron content harmonizes the bulk sound speed of pyrolite with the seismic values in this region. 17 Our experiments support no significant changes in bulk composition for most of the mantle, 18 while possible changes in physical properties and processes (such as viscosity and mantle flow 19 patterns) in the mid mantle.« less

Dietary fiber and satiety: the effects of oats on satiety.

PubMed

Rebello, Candida J; O'Neil, Carol E; Greenway, Frank L

2016-02-01

This review examines the effect of β-glucan, the viscous soluble fiber in oats, on satiety. A literature search for studies that examined delivery of the fiber in whole foods or as an extract was conducted. Viscosity interferes with the peristaltic mixing process in the small intestine to impede digestion and absorption of nutrients, which precipitates satiety signals. From measurements of the physicochemical and rheological properties of β-glucan, it appears that viscosity plays a key role in modulating satiety. However, the lack of standardized methods to measure viscosity and the inherent nature of appetite make it difficult to pinpoint the reasons for inconsistent results of the effects of oats on satiety. Nevertheless, the majority of the evidence suggests that oat β-glucan has a positive effect on perceptions of satiety. © The Author(s) 2016. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Assessment of passive knee stiffness and viscosity in individuals with spinal cord injury using pendulum test

PubMed Central

Joghtaei, Mahmoud; Arab, Amir Massoud; Hashemi-Nasl, Hamed; Joghataei, Mohammad Taghi; Tokhi, Mohammad Osman

2015-01-01

Objective Stiffness and viscosity represent passive resistances to joint motion related with the structural properties of the joint tissue and of the musculotendinous complex. Both parameters can be affected in patients with spinal cord injury (SCI). The purpose of this study was to measure passive knee stiffness and viscosity in patients with SCI with paraplegia and healthy subjects using Wartenberg pendulum test. Design Non-experimental, cross-sectional, case–control design. Setting An outpatient physical therapy clinic, University of social welfare and Rehabilitation Science, Iran. Patients A sample of convenience sample of 30 subjects participated in the study. Subjects were categorized into two groups: individuals with paraplegic SCI (n = 15, age: 34.60 ± 9.18 years) and 15 able-bodied individuals as control group (n = 15, age: 30.66 ± 11.13 years). Interventions Not applicable. Main measures Passive pendulum test of Wartenberg was used to measure passive viscous-elastic parameters of the knee (stiffness, viscosity) in all subjects. Results Statistical analysis (independent t-test) revealed significant difference in the joint stiffness between healthy subjects and those with paraplegic SCI (P = 0.01). However, no significant difference was found in the viscosity between two groups (P = 0.17). Except for first peak flexion angle, all other displacement kinematic parameters exhibited no statistically significant difference between normal subjects and subjects with SCI. Conclusions Patients with SCI have significantly greater joint stiffness compared to able-bodied subjects. PMID:25437824

On some universal features of the holographic quantum complexity of bulk singularities

NASA Astrophysics Data System (ADS)

Bolognesi, Stefano; Rabinovici, Eliezer; Roy, Shubho R.

2018-06-01

We perform a comparative study of the time dependence of the holographic quantum complexity of some space like singular bulk gravitational backgrounds. This is done by considering the two available notions of complexity, one that relates it to the maximal spatial volume and the other that relates it to the classical action of the Wheeler-de Witt patch. We calculate and compare the leading and the next to leading terms and find some universal features. The complexity decreases towards the singularity for both definitions, for all types of singularities studied. In addition the leading terms have the same quantitative behavior for both definitions in restricted number of cases and the behaviour itself is different for different singular backgrounds. The quantitative details of the next to leading terms, such as their specific form of time dependence, are found not to be universal. They vary between the different cases and between the different bulk definitions of complexity. We also address some technical points inherent to the calculation.

Microthrix parvicella abundance associates with activated sludge settling velocity and rheology - Quantifying and modelling filamentous bulking.

PubMed

Wágner, Dorottya S; Ramin, Elham; Szabo, Peter; Dechesne, Arnaud; Plósz, Benedek Gy

2015-07-01

The objective of this work is to identify relevant settling velocity and rheology model parameters and to assess the underlying filamentous microbial community characteristics that can influence the solids mixing and transport in secondary settling tanks. Parameter values for hindered, transient and compression settling velocity functions were estimated by carrying out biweekly batch settling tests using a novel column setup through a four-month long measurement campaign. To estimate viscosity model parameters, rheological experiments were carried out on the same sludge sample using a rotational viscometer. Quantitative fluorescence in-situ hybridisation (qFISH) analysis, targeting Microthrix parvicella and phylum Chloroflexi, was used. This study finds that M. parvicella - predominantly residing inside the microbial flocs in our samples - can significantly influence secondary settling through altering the hindered settling velocity and yield stress parameter. Strikingly, this is not the case for Chloroflexi, occurring in more than double the abundance of M. parvicella, and forming filaments primarily protruding from the flocs. The transient and compression settling parameters show a comparably high variability, and no significant association with filamentous abundance. A two-dimensional, axi-symmetrical computational fluid dynamics (CFD) model was used to assess calibration scenarios to model filamentous bulking. Our results suggest that model predictions can significantly benefit from explicitly accounting for filamentous bulking by calibrating the hindered settling velocity function. Furthermore, accounting for the transient and compression settling velocity in the computational domain is crucial to improve model accuracy when modelling filamentous bulking. However, the case-specific calibration of transient and compression settling parameters as well as yield stress is not necessary, and an average parameter set - obtained under bulking and good settling conditions - can be used. Copyright © 2015 Elsevier Ltd. All rights reserved.

The role of ascitic fluid viscosity in differentiating the nature of ascites and in the prediction of renal impairment and duration of ICU stay.

PubMed

Hanafy, Amr S

2016-09-01

Serum-ascites albumin gradient (SAAG) has been used in the classification of ascites for the last 20 years but it has some drawbacks. This study searches for possible correlations between ascitic fluid viscosity and the etiology of ascites, renal impairment, and length of ICU stay. The study was conducted in Zagazig University Hospital, Egypt. It included 240 patients with ascites due to various causes. The patients were divided into two groups: the cirrhotic ascites group, which included 120 patients, and the noncirrhotic ascites group, which included 120 patients. Ascitic patients on medical management with diuretics, antibiotics, paracentesis, and infusion of plasma or albumin were excluded.The laboratory analysis included routine investigations to detect the cause of ascites as well as specific investigations such as ascitic fluid viscosity using a falling ball viscosimeter (microviscosimeter) at 37°C. The mean ascitic viscosity of patients with SAAG at least 1.1 was 1.16±0.56, which was associated with serum creatinine 1.35±0.52 mg/dl and ICU stay of 3.3±1.2 days. In patients with SAAG less than 1.1 g/dl, the mean ascitic viscosity was 2.98±0.87, with serum creatinine 2.1±0.56 mg/dl and ICU stay of 7.1±1.3 days. Ascitic viscosity can discriminate ascites due to portal hypertension from those associated with nonportal hypertension at a cut-off value of 1.65; it can predict renal impairment in hepatic patients at a cut-off of 1.35 and long ICU stay at a cut-off of 1.995 using receiver operating characteristic analysis. Ascitic viscosity measurement is rapid, inexpensive, and requires small sample volumes. Ascitic viscosity can discriminate ascites due to portal hypertension from those associated with nonportal hypertension at a cut-off value of 1.65. It can predict renal impairment in hepatic patients at a cut-off of 1.35 and long ICU stay at a cut-off of 1.995.

A possible structural signature of the onset of cooperativity in metallic liquids

NASA Astrophysics Data System (ADS)

Dai, R.; Ashcraft, R.; Kelton, K. F.

2018-05-01

It is widely, although not universally, believed that there must be a connection between liquid dynamics and the structure. Previous supporting studies, for example, have demonstrated a link between the structural evolution in the liquid and kinetic fragility. Here, new results are presented that strengthen the evidence for a connection. By combining the results from high-energy synchrotron X-ray scattering studies of containerlessly processed supercooled liquids with viscosity measurements, an accelerated rate of structural ordering beyond the nearest neighbors in the liquid is demonstrated to correlate with the temperature at which the viscosity transitions from Arrhenius to super-Arrhenius behavior. This is the first confirmation of predictions from several recent molecular dynamics studies.

Electrical and Thermal Transport in Inhomogeneous Luttinger Liquids

DOE PAGES

DeGottardi, Wade; Matveev, K. A.

2015-06-12

In this paper, we study the transport properties of long quantum wires by generalizing the Luttinger liquid approach to allow for the finite lifetime of the bosonic excitations. Our theory accounts for long-range disorder and strong electron interactions, both of which are common features of experiments with quantum wires. We obtain the electrical and thermal resistances and thermoelectric properties of such quantum wires and find a strong deviation from perfect conductance quantization. Finally, we cast our results in terms of the thermal conductivity and bulk viscosity of the electron liquid and give the temperature scale above which the transport canmore » be described by classical hydrodynamics.« less

Highly resolved fluid flows: "liquid plasmas" at the kinetic level.

PubMed

Morfill, Gregor E; Rubin-Zuzic, Milenko; Rothermel, Hermann; Ivlev, Alexei V; Klumov, Boris A; Thomas, Hubertus M; Konopka, Uwe; Steinberg, Victor

2004-04-30

Fluid flow around an obstacle was observed at the kinetic (individual particle) level using "complex (dusty) plasmas" in their liquid state. These "liquid plasmas" have bulk properties similar to water (e.g., viscosity), and a comparison in terms of similarity parameters suggests that they can provide a unique tool to model classical fluids. This allows us to study "nanofluidics" at the most elementary-the particle-level, including the transition from fluid behavior to purely kinetic transport. In this (first) experimental investigation we describe the kinetic flow topology, discuss our observations in terms of fluid theories, and follow this up with numerical simulations.

In vitro analysis of the physical properties of contact lens blister pack solutions.

PubMed

Menzies, Kara L; Jones, Lyndon

2011-04-01

Since the initial development of silicone hydrogels, many modifications to the bulk and surface properties of the lenses have been undertaken to improve the wettability and comfort of the lenses. Recently, manufacturers have incorporated various "wetting agents" or surface-active agents into the blister packaging solutions (BPSs) of the lenses to improve initial comfort of the lens on eye. The purpose of this study was to measure and compare the pH, surface tension (ST), viscosity, and osmolality of BPSs for a variety of silicone hydrogel and polyHEMA-based hydrogel lenses. In addition, two saline solutions were tested for comparison purposes. The pH, osmolality, ST, and viscosity were measured for the BPSs for lotrafilcon B and lotrafilcon A and lotrafilcon B with a "modified BPS" (m-lotrafilcon A, m-lotrafilcon B) (CIBA Vision, Duluth, GA); balafilcon A (Bausch & Lomb, Rochester, NY); galyfilcon A, senofilcon A, and narafilcon A (Johnson & Johnson, Jacksonville, FL); and comfilcon A and enfilcon A (CooperVision, Pleasanton, CA) and BPSs from two conventional polyHEMA-based materials-etafilcon A (Johnson & Johnson) and omafilcon A (CooperVision). The two saline solutions tested were Unisol (Alcon, Fort Worth, TX) and Softwear Saline (CIBA Vision). The pH results for the two saline solutions and all BPSs remained in the pH range of tears (6.6-7.8). The ST of the modified BPS was significantly lower (p < 0.01) than the original non-modified BPS. Viscosity measurements ranged between 0.90 and 1.00 cP for all BPSs and saline solutions, except for the modified BPS, which had significantly higher viscosities (p < 0.001). Osmolality measurements were not significantly different (p > 0.05) between BPSs made by the same manufacturer but were significantly different compared with BPSs made by different manufacturers (p < 0.05). The incorporation of wetting agents and surfactants into BPSs does alter the physical properties of the BPSs, which may have clinical implications regarding initial in-eye comfort.

Bulk flow in the combined 2MTF and 6dFGSv surveys

NASA Astrophysics Data System (ADS)

Qin, Fei; Howlett, Cullan; Staveley-Smith, Lister; Hong, Tao

2018-07-01

We create a combined sample of 10 904 late- and early-type galaxies from the 2MTF and 6dFGSv surveys in order to accurately measure bulk flow in the local Universe. Galaxies and groups of galaxies common between the two surveys are used to verify that the difference in zero-points is <0.02 dex. We introduce a maximum likelihood estimator (ηMLE) for bulk flow measurements that allows for more accurate measurement in the presence of non-Gaussian measurement errors. To calibrate out residual biases due to the subtle interaction of selection effects, Malmquist bias and anisotropic sky distribution, the estimator is tested on mock catalogues generated from 16 independent large-scale GiggleZ and SURFS simulations. The bulk flow of the local Universe using the combined data set, corresponding to a scale size of 40 h-1 Mpc, is 288 ± 24 km s-1 in the direction (l, b) = (296 ± 6°, 21 ± 5°). This is the most accurate bulk flow measurement to date, and the amplitude of the flow is consistent with the Λ cold dark matter expectation for similar size scales.

Bulk flow in the combined 2MTF and 6dFGSv surveys

NASA Astrophysics Data System (ADS)

Qin, Fei; Howlett, Cullan; Staveley-Smith, Lister; Hong, Tao

2018-04-01

We create a combined sample of 10,904 late and early-type galaxies from the 2MTF and 6dFGSv surveys in order to accurately measure bulk flow in the local Universe. Galaxies and groups of galaxies common between the two surveys are used to verify that the difference in zero-points is <0.02 dex. We introduce a new maximum likelihood estimator (ηMLE) for bulk flow measurements which allows for more accurate measurement in the presence non-Gaussian measurement errors. To calibrate out residual biases due to the subtle interaction of selection effects, Malmquist bias and anisotropic sky distribution, the estimator is tested on mock catalogues generated from 16 independent large-scale GiggleZ and SURFS simulations. The bulk flow of the local Universe using the combined data set, corresponding to a scale size of 40 h-1 Mpc, is 288 ± 24 km s-1 in the direction (l, b) = (296 ± 6°, 21 ± 5°). This is the most accurate bulk flow measurement to date, and the amplitude of the flow is consistent with the ΛCDM expectation for similar size scales.

Hyper-mobility of water around actin filaments revealed using pulse-field gradient spin-echo {sup 1}H NMR and fluorescence spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wazawa, Tetsuichi; CREST, JST, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012; Sagawa, Takashi

2011-01-28

Research highlights: {yields} Translationally hyper-mobile water has been detected around actin filaments. {yields} Translationally hyper-mobile water is formed upon polymerization of actin. {yields} Low water viscosity was found around F-actin using fluorescence anisotropy. {yields} Formation of hyper-mobile water may explain endothermic actin polymerization. -- Abstract: This paper reports that water molecules around F-actin, a polymerized form of actin, are more mobile than those around G-actin or in bulk water. A measurement using pulse-field gradient spin-echo {sup 1}H NMR showed that the self-diffusion coefficient of water in aqueous F-actin solution increased with actin concentration by {approx}5%, whereas that in G-actin solutionmore » was close to that of pure water. This indicates that an F-actin/water interaction is responsible for the high self-diffusion of water. The local viscosity around actin was also investigated by fluorescence measurements of Cy3, a fluorescent dye, conjugated to Cys 374 of actin. The steady-state fluorescence anisotropy of Cy3 attached to F-actin was 0.270, which was lower than that for G-actin, 0.334. Taking into account the fluorescence lifetimes of the Cy3 bound to actin, their rotational correlation times were estimated to be 3.8 and 9.1 ns for F- and G-actin, respectively. This indicates that Cy3 bound to F-actin rotates more freely than that bound to G-actin, and therefore the local water viscosity is lower around F-actin than around G-actin.« less

An acidic pH independent piperazine–TPE AIEgen as a unique bioprobe for lysosome tracing† †Electronic supplementary information (ESI) available: NMR, single crystal X-ray crystallography of PIP–TPE, live cell and fixed cell fluorescence imaging, MTT, photostability, and theoretical calculations. CCDC 1555412. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03515b

PubMed Central

Cai, Yuanjing; Gui, Chen; Samedov, Kerim; Su, Huifang; Gu, Xinggui; Li, Shiwu; Luo, Wenwen; Sung, Herman H. Y.; Lam, Jacky W. Y.; Kwok, Ryan T. K.; Williams, Ian D.

2017-01-01

Lysosomes are involved in a multitude of cellular processes and their dysfunction is associated with various diseases. They are the most acidic organelles (pH 3.8–6.6, size 0.1–1.2 μm) with the highest viscosity (47–190 cP at 25 °C) in the cell. Because of their acidity, pH dependent non-AIE active fluorescent lysosomal probes have been developed that rely on protonation inhibited photoinduced electron transfer (PET). In this work, an acidic pH independent lysosome targetable piperazine–TPE (PIP–TPE) AIEgen has been designed with unique photophysical properties making it a suitable probe for quantifying viscosity. In a non-aggregated state PIP–TPE shows deep-blue emission as opposed to its yellowish-green emission in the bulk. It possesses high specificity for lysosomes with negligible cytotoxicity and good tracing ability due to its better photostability compared to LysoTracker Red. In contrast to most known lysosome probes that rely solely on PET, restriction of intramolecular motion (RIM) due to the larger viscosity inside the lysosomes is the mechanism responsible for PIP–TPE’s fluorescence. PIP–TPE’s high selectivity is attributed to its unique molecular design that features piperazine fragments providing a perfect balance between lipophilicity and polarity. PMID:29568423

Impact of structure and functionality of core polyol in highly functional biobased epoxy resins.

PubMed

Pan, Xiao; Webster, Dean C

2011-09-01

Highly functional biobased epoxy resins were prepared using dipentaerythritol (DPE), tripentaerythritol (TPE), and sucrose as core polyols that were substituted with epoxidized soybean oil fatty acids, and the impact of structure and functionality of the core polyol on the properties of the macromolecular resins and their epoxy-anhydride thermosets was explored. The chemical structures, functional groups, molecular weights, and compositions of epoxies were characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI MS). The epoxies were also studied for their bulk viscosity, intrinsic viscosity, and density. Crosslinked with dodecenyl succinic anhydride (DDSA), epoxy-anhydride thermosets were evaluated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests, and tests of coating properties. Epoxidized soybean oil (ESO) was used as a control. Overall, the sucrose-based thermosets exhibited the highest moduli, having the most rigid and ductile performance while maintaining the highest biobased content. DPE/TPE-based thermosets showed modestly better thermosetting performance than the control ESO thermoset. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of hot-water extraction on alkaline pulping of bagasse.

PubMed

Lei, Yichao; Liu, Shijie; Li, Jiang; Sun, Runcang

2010-01-01

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 degrees C for 30min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 degrees C and 155 degrees C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied. Copyright 2010 Elsevier Inc. All rights reserved.

Synergistic performance of lecithin and glycerol monostearate in oil/water emulsions.

PubMed

Moran-Valero, María I; Ruiz-Henestrosa, Víctor M Pizones; Pilosof, Ana M R

2017-03-01

The effects of the combination of two low-molecular weight emulsifiers (lecithin and glycerol-monostearate (GMS)) on the stability, the dynamic interfacial properties and rheology of emulsions have been studied. Different lecithin/GMS ratios were tested in order to assess their impact in the formation and stabilization of oil in water emulsions. The combination of the two surfactants showed a synergistic behaviour, mainly when combined at the same ratio. The dynamic film properties and ζ-potential showed that lecithin dominated the surface of oil droplets, providing stability to the emulsions against flocculation and coalescence, while allowing the formation of small oil droplets. At long times of adsorption, all of the mixtures showed similar interfacial activity. However, higher values of interfacial pressure at the initial times were reached when lecithin and GMS were at the same ratio. Interfacial viscoelasticity and viscosity of mixed films were also similar to that of lecithin alone. On the other hand, emulsions viscosity was dominated by GMS. The synergistic performance of lecithin-GMS blends as stabilizers of oil/water emulsions is attributed to their interaction both in the bulk and at the interface. Copyright © 2016 Elsevier B.V. All rights reserved.

Liquid Aluminum: Atomic diffusion and viscosity from ab initio molecular dynamics

PubMed Central

Jakse, Noel; Pasturel, Alain

2013-01-01

We present a study of dynamic properties of liquid aluminum using density-functional theory within the local-density (LDA) and generalized gradient (GGA) approximations. We determine the temperature dependence of the self-diffusion coefficient as well the viscosity using direct methods. Comparisons with experimental data favor the LDA approximation to compute dynamic properties of liquid aluminum. We show that the GGA approximation induce more important backscattering effects due to an enhancement of the icosahedral short range order (ISRO) that impact directly dynamic properties like the self-diffusion coefficient. All these results are then used to test the Stokes-Einstein relation and the universal scaling law relating the diffusion coefficient and the excess entropy of a liquid. PMID:24190311

Comparison of Structural Relaxation Behavior in As-Cast and Pre-Annealed Zr-Based Bulk Metallic Glasses Just below Glass Transition

DOE PAGES

Haruyama, Osami; Yoshikawa, Kazuyoshi; Yamazaki, Yoshikatsu; ...

2015-04-25

In this paper, the α-relaxation of pre-annealed Zr 55Cu 30Ni 5Al 10 bulk metallic glasses (BMGs) was compared with that of as-cast Zr-based BMGs including Zr 55Cu 30Ni 5Al 10. The α-relaxation was investigated by volume relaxation. The relaxation behavior was well described by a stretched exponential relaxation function, Φ (t) ≈ exp [ - (t/τ α ) β α ], with the isothermal relaxation time, τ α, and the Kohlrausch exponent, β α. The β α exhibited the strong temperature dependence for the pre-annealed BMG, while the weak temperature dependence was visualized for the as-cast BMG similar to themore » dynamic relaxation. The τ α’s were modified by Moynihan and Narayanaswamy-Tool-Moynihan methods that reduce the difference in the thermal history of sample. Finally, as a result, the relaxation kinetics in the glass resembled that of a liquid deduced from the behavior of viscosity in the supercooled liquid.« less

A size-dependent constitutive model of bulk metallic glasses in the supercooled liquid region

PubMed Central

Yao, Di; Deng, Lei; Zhang, Mao; Wang, Xinyun; Tang, Na; Li, Jianjun

2015-01-01

Size effect is of great importance in micro forming processes. In this paper, micro cylinder compression was conducted to investigate the deformation behavior of bulk metallic glasses (BMGs) in supercooled liquid region with different deformation variables including sample size, temperature and strain rate. It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size. The free volume and defect concentration were introduced to explain the size effect. In order to demonstrate the influence of deformation variables on steady stress, elastic modulus and overshoot phenomenon, four size-dependent factors were proposed to construct a size-dependent constitutive model based on the Maxwell-pulse type model previously presented by the authors according to viscosity theory and free volume model. The proposed constitutive model was then adopted in finite element method simulations, and validated by comparing the micro cylinder compression and micro double cup extrusion experimental data with the numerical results. Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs. PMID:25626690

Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature

PubMed Central

2012-01-01

This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y2O3), yttrium aluminum garnet (Y3Al5O12) and magnesium aluminum spinel (MgAl2O4) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s−1) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y2O3 suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y2O3 and Y3Al5O12) due to sedimentation effect. PMID:22824064

Beyond baking soda: Demonstrating the link between volcanic eruptions and viscosity to all ages

NASA Astrophysics Data System (ADS)

Smithka, I. N.; Walters, R. L.; Harpp, K. S.

2014-12-01

Public interest in volcanic eruptions and societal relevance of volcanic hazards provide an excellent basis for successful earth science outreach. During a museum-based earth science outreach event free and open to the public, we used two new interactive experiments to illustrate the relationship between gas content, magma viscosity, and eruption style. Learning objectives for visitors are to understand: how gas drives volcanic eruptions, the differences between effusive and explosive eruption styles, viscosity's control on gas pressure within a magma reservoir, and the role of gas pressure on eruption style. Visitors apply the scientific method by asking research questions and testing hypotheses by conducting the experiments. The demonstrations are framed with real life examples of volcanic eruptions (e.g., Mt. St. Helens eruption in 1980), providing context for the scientific concepts. The first activity demonstrates the concept of fluid viscosity and how gas interacts with fluids of different viscosities. Visitors blow bubbles into water and corn syrup. The corn syrup is so viscous that bubbles are trapped, showing how a more viscous material builds up higher gas pressure. Visitors are asked which kind of magma (high or low viscosity) will produce an explosive eruption. To demonstrate an explosive eruption, visitors add an Alka-Seltzer tablet to water in a snap-top film canister. The reaction rapidly produces carbon dioxide gas, increasing pressure in the canister until the lid pops off and the canister launches a few meters into the air (tinyurl.com/nzsgfoe). Increasing gas pressure in the canister is analogous to gas pressure building within a magma reservoir beneath a volcano. The lid represents high-viscosity magma that prevents degassing, causing gas pressure to reach explosive levels. This interactive activity is combined with a display of an effusive eruption: add vinegar to baking soda in a model volcano to produce a quick-flowing eruption. These demonstrations were implemented in March 2014 at "Can You Dig It?", a popular annual collaborative outreach event hosted by the Florida Museum of Natural History and the University of Florida Department of Geological Sciences (>1,500 visitors). These experiments were also used to illustrate volcanic processes at the VGP Exploration Station, AGU 2013.

Hemorheological alterations in adults with prediabetes identified by hemoglobin A1c levels.

PubMed

Marini, M A; Fiorentino, T V; Andreozzi, F; Mannino, G C; Succurro, E; Sciacqua, A; Perticone, F; Sesti, G

2017-07-01

A link between increased blood viscosity and type 2 diabetes has been previously reported. Herein, we investigated the association of blood viscosity with prediabetes, identified by glycated hemoglobin A1c (HbA1c) according to the new American Diabetes Association criteria, and subclinical atherosclerosis. The study cohort includes 1136 non-diabetic adults submitted to anthropometrical evaluation, an oral glucose tolerance test and ultrasound measurement of carotid intima-media thickness (IMT). Whole blood viscosity was estimated using a validated formula based on hematocrit and total plasma proteins. After adjusting for age, and gender, individuals with HbA1c-defined prediabetes (HbA1c 5.7-6.4% [39-47 mmol/mol]) exhibited significantly higher values of hematocrit, and predicted blood viscosity as compared with controls. Increased levels of IMT were observed in subjects with HbA1c-defined prediabetes in comparison to controls. Predicted blood viscosity was positively correlated with age, waist circumference, blood pressure, cholesterol, triglycerides, fibrinogen, white blood cell, HbA1c, fasting and 2-h post-load glucose levels, fasting insulin, IMT and inversely correlated with HDL and Matsuda index of insulin sensitivity. Of the three glycemic parameters, i.e. HbA1c, fasting and 2-h post-load glucose, only HbA1c showed a significant correlation with predicted blood viscosity (β = 0.054, P = 0.04) in a multivariate regression analysis model including multiple atherosclerosis risk factors. The study shows that individuals with HbA1c-defined prediabetes have increased predicted blood viscosity and IMT. The HbA1c criterion may be helpful to capture individuals with an increased risk of diabetes and cardiovascular disease who may benefit from an intensive lifestyle intervention. Copyright © 2017 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.

Getting the gas out - developing gas networks in magmatic systems

NASA Astrophysics Data System (ADS)

Cashman, Katharine; Rust, Alison; Oppenheimer, Julie; Belien, Isolde

2015-04-01

Volcanic eruption style, and explosive potential, are strongly controlled by the pre-eruptive history of the magmatic volatiles: specifically, the more efficient the gas loss prior to eruption, the lower the likelihood of primary (magmatic) explosive activity. Commonly considered gas loss mechanisms include separated flow, where individual bubbles (or bubble clouds) travel at a rate that is faster than the host magma, and permeable flow, where gas escapes through permeable (connected) pathways developed within a (relatively) static matrix. Importantly, gas loss via separated flow is episodic, while gas loss via permeable flow is likely to be continuous. Analogue experiments and numerical models on three phase (solid-liquid-gas) systems also suggest a third mechanism of gas loss that involves the opening and closing of 'pseudo fractures'. Pseudo fractures form at a critical crystallinity that is close to the maximum particle packing. Fractures form by local rearrangement of solid particles and liquid to form a through-going gas fracture; gas escape is episodic, and modulated by the available gas volume and the rate of return flow of interstitial liquid back into the fracture. In all of the gas escape scenarios described above, a fundamental control on gas behaviour is the melt viscosity, which affects the rate of individual bubble rise, the rate of bubble expansion, the rate of film thinning (required for bubble coalescence), and the rate of melt flow into gas-generated fractures. From the perspective of magma degassing, rates of gas expansion and film thinning are key to the formation of an interconnected (permeable) gas pathway. Experiments with both analogue and natural materials show that bubble coalescence is relatively slow, and, in particle-poor melts, does not necessarily create permeable gas networks. As a result, degassing efficiency is modulated by the time scales required either (1) to produce large individual bubbles or bubble clouds (in low viscosity melts) or (2) to develop sufficient porosity for full connectivity of a bubble network (in high viscosity melts). In contrast, our experiments suggest that the presence of solid particles may greatly enhance gas escape. On the one hand, the addition of solid particles increases the bulk viscosity of the mixture, which reduces the migration rate of large single bubbles. On the other hand, the strength of networks created by touching crystals inhibits bulk magma deformation and forces smaller bubbles to deform to occupy the spaces between particles, thereby increasing both the bubble shape anisotropy and, correspondingly, the probability of bubble coalescence. Gas pathways created in this way take advantage of inhomogeneities in the spatial distribution of crystals and allow large-scale gas release at relatively low vesicularities. This mechanism of gas escape is likely to be important not only in mafic arc volcanoes, where shallow conduits are likely to be highly crystalline, but also for degassing of crystal-mush-dominated magmatic systems.

Li-Doped Ionic Liquid Electrolytes: From Bulk Phase to Interfacial Behavior

NASA Technical Reports Server (NTRS)

Haskins, Justin B.; Lawson, John W.

2016-01-01

Ionic liquids have been proposed as candidate electrolytes for high-energy density, rechargeable batteries. We present an extensive computational analysis supported by experimental comparisons of the bulk and interfacial properties of a representative set of these electrolytes as a function of Li-salt doping. We begin by investigating the bulk electrolyte using quantum chemistry and ab initio molecular dynamics to elucidate the solvation structure of Li(+). MD simulations using the polarizable force field of Borodin and coworkers were then performed, from which we obtain an array of thermodynamic and transport properties. Excellent agreement is found with experiments for diffusion, ionic conductivity, and viscosity. Combining MD simulations with electronic structure computations, we computed the electrochemical window of the electrolytes across a range of Li(+)-doping levels and comment on the role of the liquid environment. Finally, we performed a suite of simulations of these Li-doped electrolytes at ideal electrified interfaces to evaluate the differential capacitance and the equilibrium Li(+) distribution in the double layer. The magnitude of differential capacitance is in good agreement with our experiments and exhibits the characteristic camel-shaped profile. In addition, the simulations reveal Li(+) to be highly localized to the second molecular layer of the double layer, which is supported by additional computations that find this layer to be a free energy minimum with respect to Li(+) translation.

Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA.

PubMed

Lopez-Hilfiker, F D; Mohr, C; D'Ambro, E L; Lutz, A; Riedel, T P; Gaston, C J; Iyer, S; Zhang, Z; Gold, A; Surratt, J D; Lee, B H; Kurten, T; Hu, W W; Jimenez, J; Hallquist, M; Thornton, J A

2016-03-01

We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) μg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.

Lower crustal relaxation beneath the Tibetan Plateau and Qaidam Basin following the 2001 Kokoxili earthquake

USGS Publications Warehouse

Ryder, I.; Burgmann, R.; Pollitz, F.

2011-01-01

In 2001 November a magnitude 7.8 earthquake ruptured a 400 km long portion of the Kunlun fault, northeastern Tibet. In this study, we analyse over five years of post-seismic geodetic data and interpret the observed surface deformation in terms of stress relaxation in the thick Tibetan lower crust. We model GPS time-series (first year) and InSAR line of sight measurements (years two to five) and infer that the most likely mechanism of post-seismic stress relaxation is time-dependent distributed creep of viscoelastic material in the lower crust. Since a single relaxation time is not sufficient to model the observed deformation, viscous flow is modelled by a lower crustal Burgers rheology, which has two material relaxation times. The optimum model has a transient viscosity 9 ?? 1017 Pa s, steady-state viscosity 1 ?? 1019 Pa s and a ratio of long term to Maxwell shear modulus of 2:3. This model gives a good fit to GPS stations south of the Kunlun Fault, while displacements at stations north of the fault are over-predicted. We attribute this asymmetry in the GPS residual to lateral heterogeneity in rheological structure across the southern margin of the Qaidam Basin, with thinner crust/higher viscosities beneath the basin than beneath the Tibetan Plateau. Deep afterslip localized in a shear zone beneath the fault rupture gives a reasonable match to the observed InSAR data, but the slip model does not fit the earlier GPS data well. We conclude that while some localized afterslip likely occurred during the early post-seismic phase, the bulk of the observed deformation signal is due to viscous flow in the lower crust. To investigate regional variability in rheological structure, we also analyse post-seismic displacements following the 1997 Manyi earthquake that occurred 250 km west of the Kokoxili rupture. We find that viscoelastic properties are the same as for the Kokoxili area except for the transient viscosity, which is 5 ?? 1017 Pa s. The viscosities estimated for the Manyi and Kokoxili areas are consistent with constraints obtained from other earthquakes in the northwest and south central parts of the Tibetan Plateau. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.

Galilean-invariant algorithm coupling immersed moving boundary conditions and Lees-Edwards boundary conditions

NASA Astrophysics Data System (ADS)

Zhou, Guofeng; Wang, Limin; Wang, Xiaowei; Ge, Wei

2011-12-01

Many investigators have coupled the Lees-Edwards boundary conditions (LEBCs) and suspension methods in the framework of the lattice Boltzmann method to study the pure bulk properties of particle-fluid suspensions. However, these suspension methods are all link-based and are more or less exposed to the disadvantages of violating Galilean invariance. In this paper, we have coupled LEBCs with a node-based suspension method, which is demonstrated to be Galilean invariant in benchmark simulations. We use the coupled algorithm to predict the viscosity of a particle-fluid suspension at very low Reynolds number, and the simulation results are in good agreement with the semiempirical Krieger-Dougherty formula.

Composition, properties and health benefits of indigestible carbohydrate polymers as dietary fiber: a review.

PubMed

Mudgil, Deepak; Barak, Sheweta

2013-10-01

In last few decades, indigestible carbohydrates as dietary fiber have attracted interest of food scientists and technologists due to its several physiological benefits. Dietary fibers are generally of two types based on their solubility, i.e. soluble and insoluble dietary fiber. Significant physicochemical properties of dietary fiber include solubility, viscosity, water holding capacity, bulking and fermentability. Some important dietary fibers are celluloses, hemicelluloses, hydrocolloids, resistant starches and non-digestible oligosaccharides. Inclusion of these fibers in daily diet imparts several health benefits such as prevention or reduction of bowel disorders, and decrease risk of coronary heart disease and type 2 diabetes. Copyright © 2013 Elsevier B.V. All rights reserved.

Capillary instability of periodic polymer structures: Influence of viscosity, substrate confinement and local curvature

NASA Astrophysics Data System (ADS)

Zhang, Zheng; Ding, Yifu

2015-03-01

NMR spectrum and spin-lattice relaxation time(T1) of CaF2 thin film samples deposited on a silicon cantilever tip were obtained by magnetic resonance force microscopy(MRFM). Thickness of the thin films were 50nm and 150nm. In order to measure T1, a cyclic adiabatic inversion method was used with periodic phase inversion. A comparison of the bulk and two thin films showed that T1 becomes shorter as the film thickness decreases. To make the comparison as accurate as possible, all three samples were loaded onto different beams of a multi-cantilever array and measured in the same experimental conditions such as temperature and magnetic field.

Electrorheology for energy production and conservation

NASA Astrophysics Data System (ADS)

Huang, Ke

Recently, based on the physics of viscosity, we developed a new technology, which utilizes electric or magnetic fields to change the rheology of complex fluids to reduce the viscosity, while keeping the temperature unchanged. The method is universal and applicable to all complex fluids with suspended particles of nano-meter, submicrometer, or micrometer size. Completely different from the traditional viscosity reduction method, raising the temperature, this technology is energy-efficient, as it only requires small amount of energy to aggregate the suspended particles. In this thesis, we will first discuss this new technology in detail, both in theory and practice. Then, we will report applications of our technology to energy science research. Presently, 80% of all energy sources are liquid fuels. The viscosity of liquid fuels plays an important role in energy production and energy conservation. With an electric field, we can reduce the viscosity of asphalt-based crude oil. This is important and useful for heavy crude oil and off-shore crude oil production and transportation. Especially, since there is no practical way to raise the temperature of crude oil inside the deepwater pipelines, our technology may play a key role in future off-shore crude oil production. Electrorehology can also be used to reduce the viscosity of refinery fuels, such as diesel fuel and gasoline. When we apply this technology to fuel injection, the fuel droplets in the fuel atomization become smaller, leading to faster combustion in the engine chambers. As the fuel efficiency of internal combustion engines depends on the combustion speed and timing, the fast combustion produces much higher fuel efficiency. Therefore, adding our technology on existing engines improves the engine efficiency significantly. A theoretical model for the engine combustion, which explains how fast combustion improves the engine efficiency, is also presented in the thesis. As energy is the key to our national security, we believe that our technology is important and will have a strong impact on energy production and conversation in the future.

Federal Tax Policy regarding Universities: Endowments and beyond

ERIC Educational Resources Information Center

Vedder, Richard

2008-01-01

The vast bulk of economic activity in the United States is taxed by the federal government. There are exceptions carved out, primarily for charitable operations, including universities. The rationale is that these organizations serve the public good and should not be reduced in magnitude by the deleterious effects of taxes. Universities in…

Towards a universal master curve in magnetorheology

NASA Astrophysics Data System (ADS)

Ruiz-López, José Antonio; Hidalgo-Alvarez, Roque; de Vicente, Juan

2017-05-01

We demonstrate that inverse ferrofluids behave as model magnetorheological fluids. A universal master curve is proposed, using a reduced Mason number, under the frame of a structural viscosity model where the magnetic field strength dependence is solely contained in the Mason number and the particle concentration is solely contained in the critical Mason number (i.e. the yield stress). A linear dependence of the critical Mason number with the particle concentration is observed that is in good agreement with a mean (average) magnetization approximation, particle level dynamic simulations and micromechanical models available in the literature.

Emergence and expansion of cosmic space as due to M0-branes

NASA Astrophysics Data System (ADS)

Sepehri, Alireza; Setare, Mohammad Reza; Capozziello, Salvatore

2015-12-01

Recently, Padmanabhan (arXiv:1206.4916 [hep-th]) discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and N D0-branes are created. Then N D0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe's D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe's brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe's brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration.

First measurement of the bulk flow of nearby galaxies using the cosmic microwave background

NASA Astrophysics Data System (ADS)

Lavaux, Guilhem; Afshordi, Niayesh; Hudson, Michael J.

2013-04-01

Peculiar velocities in the nearby Universe can be measured via the kinetic Sunyaev-Zel'dovich (kSZ) effect. Using a statistical method based on an optimized cross-correlation with nearby galaxies, we extract the kSZ signal generated by plasma halo of galaxies from the cosmic microwave background (CMB) temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP). Marginalizing over the thermal Sunyaev-Zel'dovich contribution from clusters of galaxies, possible unresolved point source contamination, and Galactic foregrounds, we find a kSZ bulk flow signal present at the ˜90 per cent confidence level in the seven-year WMAP data. When only galaxies within 50 h-1 Mpc are included in the kSZ template, we find a bulk flow in the CMB frame of |V| = 533 ± 263 km s-1, in the direction l = 324 ± 27, b = -7 ± 17, consistent with bulk flow measurements on a similar scale using classical distance indicators. We show how this comparison constrains, for the first time, the (ionized) baryonic budget in the local universe. On very large (˜500 h-1 Mpc) scales, we find a 95 per cent upper limit of 470 km s-1, inconsistent with some analyses of bulk flow of clusters from the kSZ. We estimate that the significance of the bulk flow signal may increase to 3σ-5σ using data from the Planck probe.

Academic Interface at the New University of Florida Water Reclamation Facility

DTIC Science & Technology

1992-05-01

of polymer solutions at viscosities up to carbon, 1.1 lb per gallon of water, diatomaceous earth , 5500 cp at 195 spin. or to 10.000 cps at 114 spin...does not contain this upper sand distribution cone. The physical process of the DynaSand® filter of adsorbing suspended solids onto a granular medium

Social Science Research Institutes in the Quality American University. Final Technical Report.

ERIC Educational Resources Information Center

Totman, Theodore L.

The technical report presents a chapter outline and thesis summary of an investigation of social science research institutes in American universities. The bulk of the report presents the thesis in four sections. Section I proposes a typology of organized social research units (OSRUs) in the 11 universities studied. Dimensions used to classify the…

The distribution of tilt angles in newly born NSs: role of interior viscosity and magnetic field

NASA Astrophysics Data System (ADS)

Dall'Osso, Simone; Perna, Rosalba

2017-12-01

We study how the viscosity of neutron star (NS) matter affects the distribution of tilt angles (χ) between the spin and magnetic axes in young pulsars. Under the hypothesis that the NS shape is determined by the magnetically induced deformation, and that the toroidal component of the internal magnetic field exceeds the poloidal one, we show that the dissipation of precessional motions by bulk viscosity can naturally produce a bi-modal distribution of tilt angles, as observed in radio/γ-ray pulsars, with a low probability of achieving χ ˜ (20°-70°) if the interior B-field is ˜(1011-1015) G and the birth spin period is ˜10-300 ms. As a corollary of the model, the idea that the NS shape is solely determined by the poloidal magnetic field, or by the centrifugal deformation of the crust, is found to be inconsistent with the tilt angle distribution in young pulsars. When applied to the Crab pulsar, with χ ˜ 45°-70° and birth spin ≳20 ms, our model implies that: (I) the magnetically induced ellipticity is ɛB ≳ 3 × 10-6; and (II) the measured positive\\dot{χ } ˜ 3.6 × 10^{-12} rad s-1 requires an additional viscous process, acting on a time-scale ≲104 yr. We interpret the latter as crust-core coupling via mutual friction in the superfluid NS interior. One critical implication of our model is a gravitational wave signal at (twice) the spin frequency of the NS. For ɛB ˜ 10-6, this could be detectable by Advanced LIGO/Virgo operating at design sensitivity.

Multiscale diffusion of a molecular probe in a crowded environment: a concept

NASA Astrophysics Data System (ADS)

Currie, Megan; Thao, Chang; Timerman, Randi; Welty, Robb; Berry, Brenden; Sheets, Erin D.; Heikal, Ahmed A.

2015-08-01

Living cells are crowded with macromolecules and organelles. Yet, it is not fully understood how macromolecular crowding affects the myriad of biochemical reactions, transport and the structural stability of biomolecules that are essential to cellular function and survival. These molecular processes, with or without electrostatic interactions, in living cells are therefore expected to be distinct from those carried out in test tube in dilute solutions where excluded volumes are absent. Thus there is an urgent need to understand the macromolecular crowding effects on cellular and molecular biophysics towards quantitative cell biology. In this report, we investigated how biomimetic crowding affects both the rotational and translation diffusion of a small probe (rhodamine green, RhG). For biomimetic crowding agents, we used Ficoll-70 (synthetic polymer), bovine serum albumin and ovalbumin (proteins) at various concentrations in a buffer at room temperature. As a control, we carried out similar measurements on glycerolenriched buffer as an environment with homogeneous viscosity as a function of glycerol concentration. The corresponding bulk viscosity was measured independently to test the validity of the Stokes-Einstein model of a diffusing species undergoing a random walk. For rotational diffusion (ps-ns time scale), we used time-resolved anisotropy measurements to examine potential binding of RhG as a function of the crowding agents (surface structure and size). For translational diffusion (μs-s time scale), we used fluorescence correlation spectroscopy for single-molecule fluctuation analysis. Our results allow us to examine the diffusion model of a molecular probe in crowded environments as a function of concentration, length scale, homogeneous versus heterogeneous viscosity, size and surface structures. These biomimetic crowding studies, using non-invasive fluorescence spectroscopy methods, represent an important step towards understanding cellular biophysics and quantitative cell biology.

Simulation of shear thickening in attractive colloidal suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F.

2017-01-01

The influence of attractive forces between particles under conditions of large particle volume fraction is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris & M. M. Denn, PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one amore » contact frictional interaction and the second a repulsive force common in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress and a characteristic stress based on the combination of interparticle force with kT the thermal energy. At sufficiently large volume fraction, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan & C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.« less

How water manifests the structural regimes in ionic liquids.

PubMed

Singh, Akhil Pratap; Gardas, Ramesh L; Senapati, Sanjib

2017-03-22

Ionic liquids (ILs) are being considered as greener alternatives to the conventional organic solvents. However, highly viscous nature of ILs often limits their applications. Hence studies on IL/water binary mixtures have received tremendous attention. These mixtures exhibit much lower viscosity, but almost similar density, compressibility and other properties as that of the neat ILs, up to certain water content. Hence, determining the IL-water ratio till which the solution behaves like IL and subsequently changes to a state of solute IL dissolved in continuous water phase is of paramount importance. Noting the very different and characteristic behaviours of neat ILs and pure water over a temperature range, herein, we measured the various thermophysical properties of the binary mixtures of tetramethylguanidinium benzoate/water and tetramethylguanidinium salicylate/water with water content varying from 20 wt% to 95 wt% for a temperature range of 298 K to 343 K. The results show that similar to neat ILs, the measured densities and compressibility of these mixtures display a linear change, and viscosity decreases rapidly as temperature is increased for water content up to 50 wt%. At higher water concentrations, the measured density and compressibility exhibit nonlinear behaviour and the decrease in viscosity with increased temperature is minute, mimicking the behaviour of bulk water. MD simulations were carried out to explain the experimental observations. Simulation results show a greater temperature-induced disintegration of IL ion-water interactions in dense systems, explaining the rapid decay of the properties with temperature. The results also exhibit the presence of a neat, IL-like, H-bond mediated expanded structure in concentrated solution versus a collapsed IL structure in dilute solution.

A systematic study of Rayleigh-Brillouin scattering in air, N₂, and O₂ gases.

PubMed

Gu, Ziyu; Ubachs, Wim

2014-09-14

Spontaneous Rayleigh-Brillouin scattering experiments in air, N2, and O2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90° scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N2 and O2. Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in the 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy for N2 and O2, as well as for air. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm, and for the pressure-temperature parameter space covered in the present study (250-340 K and 0.6-3 bars). In the application of the Tenti S6 model, based on the transport coefficients of the gases, such as thermal conductivity κ, internal specific heat capacity c(int) and shear viscosity η, as well as their temperature dependencies taken as inputs, values for the more elusive bulk viscosity η(b) for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of the Earth's atmosphere. Based on the present findings at 90° scattering and the determination of η(b) values, predictions can be made on the spectral profiles for a typical LIDAR backscatter geometry. These Tenti S6 predictions for Rayleigh-Brillouin scattering deviate by some 7% from purely Gaussian profiles at realistic sub-atmospheric pressures occurring at 3-5 km altitude in the Earth's atmosphere.

Holographic equipartition and the maximization of entropy

NASA Astrophysics Data System (ADS)

Krishna, P. B.; Mathew, Titus K.

2017-09-01

The accelerated expansion of the Universe can be interpreted as a tendency to satisfy holographic equipartition. It can be expressed by a simple law, Δ V =Δ t (Nsurf-ɛ Nbulk) , where V is the Hubble volume in Planck units, t is the cosmic time in Planck units, and Nsurf /bulk is the number of degrees of freedom on the horizon/bulk of the Universe. We show that this holographic equipartition law effectively implies the maximization of entropy. In the cosmological context, a system that obeys the holographic equipartition law behaves as an ordinary macroscopic system that proceeds to an equilibrium state of maximum entropy. We consider the standard Λ CDM model of the Universe and show that it is consistent with the holographic equipartition law. Analyzing the entropy evolution, we find that it also proceeds to an equilibrium state of maximum entropy.

Coherent Timescales and Mechanical Structure of Multicellular Aggregates.

PubMed

Yu, Miao; Mahtabfar, Aria; Beelen, Paul; Demiryurek, Yasir; Shreiber, David I; Zahn, Jeffrey D; Foty, Ramsey A; Liu, Liping; Lin, Hao

2018-06-05

Multicellular aggregates are an excellent model system to explore the role of tissue biomechanics in specifying multicellular reorganization during embryonic developments and malignant invasion. Tissue-like spheroids, when subjected to a compressive force, are known to exhibit liquid-like behaviors at long timescales (hours), largely because of cell rearrangements that serve to effectively dissipate the applied stress. At short timescales (seconds to minutes), before cell rearrangement, the mechanical behavior is strikingly different. The current work uses shape relaxation to investigate the structural characteristics of aggregates and discovers two coherent timescales: one on the order of seconds, the other tens of seconds. These timescales are universal, conserved across a variety of tested species, and persist despite great differences in other properties such as tissue surface tension and adhesion. A precise mathematical theory is used to correlate the timescales with mechanical properties and reveals that aggregates have a relatively strong envelope and an unusually "soft" interior (weak bulk elastic modulus). This characteristic is peculiar, considering that both layers consist of identical units (cells), but is consistent with the fact that this structure can engender both structural integrity and the flexibility required for remodeling. In addition, tissue surface tension, elastic modulus, and viscosity are proportional to each other. Considering that these tissue-level properties intrinsically derive from cellular-level properties, the proportionalities imply precise coregulation of the latter and in particular of the tension on the cell-medium and cell-cell interfaces. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Implementing Inclusive Design for Learning in an introductory geology laboratory

NASA Astrophysics Data System (ADS)

Robert, G.; Merriman, J. D.; Ceylan, G. M.

2013-12-01

As an expansion of universal design for learning, IDL provides a framework for opening up and adapting classroom interaction systems, minimizing barriers through promoting perception, engagement, expression, and accommodation for diverse learners. We implemented an introductory-level laboratory for communicating the concept of magma viscosity using the guidelines and principles of IDL. We developed the lab as a mini-implementation project for an IDL course offered by the University of Missouri (MU) Graduate School. The laboratory was subsequently taught during the summer session of Principles of Geology in our Department of Geological Sciences. Traditional geology laboratories rely heavily on visual aids, either physical (rocks and minerals) or representative (idealized cartoons of processes, videos), with very few alternative representations and descriptions made available to the students. Our main focus for this new lab was to diversify the means of representation available to the students (and instructor) to make the lab as equitable and flexible as possible. We considered potential barriers to learning arising from the physical lab environment, from the means of representation, engagement and expression, and tried to minimize them upfront. We centred the laboratory on the link between volcano shape and viscosity as an applied way to convey that viscosity is the resistance to flow. The learning goal was to have the students observe that more viscous eruptives resulted in steeper-sided volcanoes through experimentation. Students built their own volcanoes by erupting lava (foods of various viscosities) onto the Earth's surface (a piece of sturdy cardboard with a hole for the 'vent') through a conduit (pastry bag). Such a hands on lab exercise allows students to gain a tactile and visual, i.e., physical representation of an abstract concept. This specific exercise was supported by other, more traditional, means of representation (e.g., lecture, videos, cartoons, 3D models, online resources, textbook) in lecture and lab. We will discuss the details of the design, the implementation experience, and the insights for lab improvement in future iterations. This exercise represents the initial steps toward (re)designing introductory geoscience labs to more effectively include diverse learners.

Constrasting Conductance/Viscosity Relations in Liquid States of Vitreous and Polymer Solid Electrolytes.

DTIC Science & Technology

1987-11-01

State lonics, 9 & 10, 617 (1983). 17. 11. Tweer, N. Laberge , and P.B. Macedo, J. Am. Ceram. Soc., 54, 121 (1971). p 18. R. Weiler, S. Blaser, and P.B...Bressel, Ph.D. Thesis, Purdue University, (1971). 25. S. Schantz, J. Sandahl, L. Borjesson, L.M. Torell and J.R. Stevens . Solid State lonics (in press). 26

Falsification of Dark Energy by Fluid Mechanics

NASA Astrophysics Data System (ADS)

Gibson, Carl H.

2012-03-01

The 2011 Nobel Prize in Physics was awarded for the discovery of accelerating super- novae dimness, suggesting a remarkable reversal in the expansion rate of the Universe from a decrease to an increase, driven by anti-gravity forces of a mysterious dark energy material comprising 70% of the Universe mass-energy. Fluid mechanics and Herschel- Planck-Spitzer-Hubble etc. space telescope observations falsify both the accelerating ex- pansion rate and dark energy concepts. Kinematic viscosity is neglected in models of self-gravitational structure formation. Large plasma photon viscosity predicts protosu- perclustervoid fragmentation early in the plasma epoch and protogalaxies at the end. At the plasma-gas transition, the gas protogalaxies fragment into Earth-mass rogue plan- ets in highly persistent, trillion-planet clumps (proto-globular-star-cluster PGCs). PGC planets freeze to form the dark matter of galaxies and merge to form their stars, giving the hydrogen triple-point (14 K) infrared emissions observed. Dark energy is a system- atic dimming error for Supernovae Ia caused by partially evaporated planets feeding hot white dwarf stars at the Chandrasekhar carbon limit. Planet atmospheres may or may not dim light from SNe-Ia events depending on the line of sight.

Initial eccentricity and constituent quark number scaling of elliptic flow in ideal and viscous dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhuri, A. K.

2010-04-15

In the Israel-Stewart theory of dissipative hydrodynamics, the scaling properties of elliptic flow in Au+Au collisions are studied. The initial energy density of the fluid was fixed to reproduce STAR data on phi-meson multiplicity in 0-5% Au+Au collisions such that, irrespective of fluid viscosity, entropy at the freeze-out is similar in ideal or in viscous evolution. The initial eccentricity or constituent quark number scaling is only approximate in ideal or minimally viscous (eta/s=1/4pi) fluid. Eccentricity scaling becomes nearly exact in more viscous fluid (eta/s>=0.12). However, in more viscous fluid, constituent quark number scaled elliptic flow for mesons and baryons splitsmore » into separate scaling functions. Simulated flows also do not exhibit 'universal scaling'; that is, elliptic flow scaled by the constituent quark number and charged particles v{sub 2} is not a single function of transverse kinetic energy scaled by the quark number. From a study of the violation of universal scaling, we obtain an estimate of quark-gluon plasma viscosity, eta/s=0.12+-0.03. The error is statistical only. The systematic error in eta/s could be as large.« less

NVP melt/magma viscosity: insight on Mercury lava flows

NASA Astrophysics Data System (ADS)

Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

2016-04-01

After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy). The change of melt viscosity induced by crystallization of a NVP composition was measured in the temperature ranges from 1463 to 1229 °C. Results showed an increase in effective viscosity from 4.3 Pa s to 1090 Pa s as the crystal content increased from 0 vol% to ca. 25 vol.%. The crystallization processes in the nominally dry NVP began at 1308 °C. Interestingly, melts viscosity changes from 4 to 16 Pa s as temperature varies from 1463 to 1327 °C. The extreme Mercurian lava fluidity experimentally measured has revealed the potentiality of NVP lavas to cover huge areas as shown by satellite data. Keywords: Viscosity, Concentric cylinders, NVP, Mercury.

Eigenvalue density of cross-correlations in Sri Lankan financial market

NASA Astrophysics Data System (ADS)

Nilantha, K. G. D. R.; Ranasinghe; Malmini, P. K. C.

2007-05-01

We apply the universal properties with Gaussian orthogonal ensemble (GOE) of random matrices namely spectral properties, distribution of eigenvalues, eigenvalue spacing predicted by random matrix theory (RMT) to compare cross-correlation matrix estimators from emerging market data. The daily stock prices of the Sri Lankan All share price index and Milanka price index from August 2004 to March 2005 were analyzed. Most eigenvalues in the spectrum of the cross-correlation matrix of stock price changes agree with the universal predictions of RMT. We find that the cross-correlation matrix satisfies the universal properties of the GOE of real symmetric random matrices. The eigen distribution follows the RMT predictions in the bulk but there are some deviations at the large eigenvalues. The nearest-neighbor spacing and the next nearest-neighbor spacing of the eigenvalues were examined and found that they follow the universality of GOE. RMT with deterministic correlations found that each eigenvalue from deterministic correlations is observed at values, which are repelled from the bulk distribution.

Simple shear of deformable square objects

NASA Astrophysics Data System (ADS)

Treagus, Susan H.; Lan, Labao

2003-12-01

Finite element models of square objects in a contrasting matrix in simple shear show that the objects deform to a variety of shapes. For a range of viscosity contrasts, we catalogue the changing shapes and orientations of objects in progressive simple shear. At moderate simple shear ( γ=1.5), the shapes are virtually indistinguishable from those in equivalent pure shear models with the same bulk strain ( RS=4), examined in a previous study. In theory, differences would be expected, especially for very stiff objects or at very large strain. In all our simple shear models, relatively competent square objects become asymmetric barrel shapes with concave shortened edges, similar to some types of boudin. Incompetent objects develop shapes surprisingly similar to mica fish described in mylonites.

A preview of a modular surface light scattering instrument with autotracking optics

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tin, Padetha; Mann, J. Adin, Jr.; Cheung, H. Michael; Rogers, Richard B.; Lading, Lars

1994-01-01

NASA's Advanced Technology Development (ATD) program is sponsoring the development of a new generation of surface light scattering hardware. This instrument is designed to non-invasively measure the surface response function of liquids over a wide range of operating conditions while automatically compensating for a sloshing surface. The surface response function can be used to compute surface tension, properties of monolayers present, viscosity, surface tension gradient and surface temperature. The instrument uses optical and electronic building blocks developed for the laser light scattering program at NASA Lewis along with several unique surface light scattering components. The emphasis of this paper is the compensation for bulk surface motion (slosh). Some data processing background information is also included.

Rheology of dilute suspensions of red blood cells: experimental and theoretical approaches

NASA Astrophysics Data System (ADS)

Drochon, A.

2003-05-01

Shear viscosity measurements with dilute suspensions of red blood cells are interpreted using a microrheological model that relates the bulk measurements to the physical properties of the suspended cells. It is thus possible to quantify the average deformability of a RBC population in terms of a mean value of the membrane shear elastic modulus E_s. The values obtained for normal cells are in good agreement with those given in the literature. The method allows to discriminate between normal and altered (diamide or glutaraldehyde treated) cells or pathological cells (scleroderma). The predictions of the microrheological model, based on analytic calculations, are also compared with the numerical results of Ramanujan and Pozrikidis (JFM 361, 1998) for dilute suspensions of capsules in simple shear flow.

Thickness shear mode (TSM) resonators used for biosensing

NASA Astrophysics Data System (ADS)

Bailey, Claude A.; Fiebor, Ben; Yen, Wei; Vodyanoy, Vitaly; Cernosek, Richard W.; Chin, Bryan A.

2002-02-01

The Auburn University Detection and Food Safety Center has demonstrated real-time biosensor for the detection of Salmonella typimhurium, consisting of a thickness shear-mode (TSM) quartz resonator with antibodies immobilized in a Langmuir-Blodgett surface film. Scanning Electron Microscopy (SEM) images of bound Salmonella bacteria to both polished and unpolished TSM resonators were taken to correlate the mass of the bound organism to the Sauerbrey equation. Theoretical frequency shifts for unpolished TSM resonators predicted by the Sauerbrey equation are much smaller than experimentally measured frequency shift. The Salmonella detector operates in a liquid environment. The viscous properties of this liquid overlayer could influence the TSM resonator's response. Various liquid media were studied as a function of temperature (0 to 50 degree(s)C). The chicken exudate samples with varying fat content show coagulation occurring at temperatures above 35 degree(s)C. Kinematic viscosity test were performed with buffer solutions containing varying quantities of Salmonella bacteria. Since the TSM resonators only entrain a boundary layer of fluid near the surface, they do not respond to these background viscous property changes. Bilk viscosity increases when bacteria concentrations are high. This paper describes investigations of TSM resonator surface acoustic interactions - mass, fluid viscosity, and viscoelasticity - that affect the sensor.

Communication: Non-Newtonian rheology of inorganic glass-forming liquids: Universal patterns and outstanding questions

NASA Astrophysics Data System (ADS)

Zhu, W.; Aitken, B. G.; Sen, S.

2017-02-01

All families of inorganic glass-forming liquids display non-Newtonian rheological behavior in the form of shear thinning at high shear rates. Experimental evidence is presented to demonstrate the existence of remarkable universality in this behavior, irrespective of chemical composition, structure, topology, and viscosity. However, contrary to intuition, in all cases the characteristic shear rates that mark the onset of shear thinning in these liquids are orders of magnitude slower than the global shear relaxation rates. Attempt is made to reconcile such differences within the framework of the cooperative structural relaxation model of glass-forming liquids.

Diffusion of aqueous solutions of ionic, zwitterionic, and polar solutes

NASA Astrophysics Data System (ADS)

Teng, Xiaojing; Huang, Qi; Dharmawardhana, Chamila Chathuranga; Ichiye, Toshiko

2018-06-01

The properties of aqueous solutions of ionic, zwitterionic, and polar solutes are of interest to many fields. For instance, one of the many anomalous properties of aqueous solutions is the behavior of water diffusion in different monovalent salt solutions. In addition, solutes can affect the stabilities of macromolecules such as proteins in aqueous solution. Here, the diffusivities of aqueous solutions of sodium chloride, potassium chloride, tri-methylamine oxide (TMAO), urea, and TMAO-urea are examined in molecular dynamics simulations. The decrease in the diffusivity of water with the concentration of simple ions and urea can be described by a simple model in which the water molecules hydrogen bonded to the solutes are considered to diffuse at the same rate as the solutes, while the remainder of the water molecules are considered to be bulk and diffuse at almost the same rate as pure water. On the other hand, the decrease in the diffusivity of water with the concentration of TMAO is apparently affected by a decrease in the diffusion rate of the bulk water molecules in addition to the decrease due to the water molecules hydrogen bonded to TMAO. In other words, TMAO enhances the viscosity of water, while urea barely affects it. Overall, this separation of water molecules into those that are hydrogen bonded to solute and those that are bulk can provide a useful means of understanding the short- and long-range effects of solutes on water.

Communication: Contrasting effects of glycerol and DMSO on lipid membrane surface hydration dynamics and forces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrader, Alex M.; Cheng, Chi-Yuan; Israelachvili, Jacob N.

2016-07-28

Glycerol and dimethyl sulfoxide (DMSO) are commonly used cryoprotectants in cellular systems, but due to the challenges of measuring the properties of surface-bound solvent, fundamental questions remain regarding the concentration, interactions, and conformation of these solutes at lipid membrane surfaces. We measured the surface water diffusivity at gel-phase dipalmitoylphosphatidylcholine (DPPC) bilayer surfaces in aqueous solutions containing ≤7.5 mol. % of DMSO or glycerol using Overhauser dynamic nuclear polarization. We found that glycerol similarly affects the diffusivity of water near the bilayer surface and that in the bulk solution (within 20%), while DMSO substantially increases the diffusivity of surface water relativemore » to bulk water. We compare these measurements of water dynamics with those of equilibrium forces between DPPC bilayers in the same solvent mixtures. DMSO greatly decreases the range and magnitude of the repulsive forces between the bilayers, whereas glycerol increases it. We propose that the differences in hydrogen bonding capability of the two solutes leads DMSO to dehydrate the lipid head groups, while glycerol affects surface hydration only as much as it affects the bulk water properties. The results suggest that the mechanism of the two most common cryoprotectants must be fundamentally different: in the case of DMSO by decoupling the solvent from the lipid surface, and in the case of glycerol by altering the hydrogen bond structure and intermolecular cohesion of the global solvent, as manifested by increased solvent viscosity.« less

Solutions on a brane in a bulk spacetime with Kalb–Ramond field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Sumanta, E-mail: sumanta@iucaa.in; SenGupta, Soumitra, E-mail: tpssg@iacs.res.in

Effective gravitational field equations on a brane have been derived, when the bulk spacetime is endowed with the second rank antisymmetric Kalb–Ramond field. Since both the graviton and the Kalb–Ramond field are closed string excitations, they can propagate in the bulk. After deriving the effective gravitational field equations on the brane, we solve them for a static spherically symmetric solution. It turns out that the solution so obtained represents a black hole or naked singularity depending on the parameter space of the model. The stability of this model is also discussed. Cosmological solutions to the gravitational field equations have beenmore » obtained, where the Kalb–Ramond field is found to behave as normal pressure free matter. For certain specific choices of the parameters in the cosmological solution, the solution exhibits a transition in the behaviour of the scale factor and hence a transition in the expansion history of the universe. The possibility of accelerated expansion of the universe in this scenario is also discussed.« less

Wavelength-versatile graphene-gold film saturable absorber mirror for ultra-broadband mode-locking of bulk lasers.

PubMed

Ma, Jie; Xie, Guoqiang; Lv, Peng; Gao, Wenlan; Yuan, Peng; Qian, Liejia; Griebner, Uwe; Petrov, Valentin; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

2014-05-23

An ultra-broadband graphene-gold film saturable absorber mirror (GG-SAM) with a spectral coverage exceeding 1300 nm is experimentally demonstrated for mode-locking of bulk solid-state lasers. Owing to the p-type doping effect caused by graphene-gold film interaction, the graphene on gold-film substrate shows a remarkably lower light absorption relative to pristine graphene, which is very helpful to achieve continuous-wave mode-locking in low-gain bulk lasers. Using the GG-SAM sample, stable mode-locking is realized in a Yb:YCOB bulk laser near 1 μm, a Tm:CLNGG bulk laser near 2 μm and a Cr:ZnSe bulk laser near 2.4 μm. The saturable absorption is characterised at an intermediate wavelength of 1.56 μm by pump-probe measurements. The as-fabricated GG-SAM with ultra-broad bandwidth, ultrafast recovery time, low absorption, and low cost has great potential as a universal saturable absorber mirror for mode-locking of various bulk lasers with unprecedented spectral coverage.

Wavelength-Versatile Graphene-Gold Film Saturable Absorber Mirror for Ultra-Broadband Mode-Locking of Bulk Lasers

PubMed Central

Ma, Jie; Xie, Guoqiang; Lv, Peng; Gao, Wenlan; Yuan, Peng; Qian, Liejia; Griebner, Uwe; Petrov, Valentin; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

2014-01-01

An ultra-broadband graphene-gold film saturable absorber mirror (GG-SAM) with a spectral coverage exceeding 1300 nm is experimentally demonstrated for mode-locking of bulk solid-state lasers. Owing to the p-type doping effect caused by graphene-gold film interaction, the graphene on gold-film substrate shows a remarkably lower light absorption relative to pristine graphene, which is very helpful to achieve continuous-wave mode-locking in low-gain bulk lasers. Using the GG-SAM sample, stable mode-locking is realized in a Yb:YCOB bulk laser near 1 μm, a Tm:CLNGG bulk laser near 2 μm and a Cr:ZnSe bulk laser near 2.4 μm. The saturable absorption is characterised at an intermediate wavelength of 1.56 μm by pump-probe measurements. The as-fabricated GG-SAM with ultra-broad bandwidth, ultrafast recovery time, low absorption, and low cost has great potential as a universal saturable absorber mirror for mode-locking of various bulk lasers with unprecedented spectral coverage. PMID:24853072

Hydrodynamics with conserved current via AdS/CFT correspondence in the Maxwell-Gauss-Bonnet gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu Yapeng; Sun Peng; Zhang Jianhui

2011-06-15

Using the AdS/CFT correspondence, we study the hydrodynamics with conserved current from the dual Maxwell-Gauss-Bonnet gravity. After constructing the perturbative solution to the first order based on the boosted black brane solution in the bulk Maxwell-Gauss-Bonnet gravity, we extract the stress tensor and conserved current of the dual conformal fluid on its boundary, and also find the effect of the Gauss-Bonnet term on the dual conformal fluid. Our results show that the Gauss-Bonnet term can affect the parameters such as the shear viscosity {eta}, entropy density s, thermal conductivity {kappa} and electrical conductivity {sigma}. However, it does not affect themore » so-called Wiedemann-Franz law which relates {kappa} to {sigma}, while it affects the ratio {eta}/s. In addition, another interesting result is that {eta}/s can also be affected by the bulk Maxwell field in our case, which is consistent with some previous results predicted through the Kubo formula. Moreover, the anomalous magnetic and vortical effects by adding the Chern-Simons term are also considered in our case in the Maxwell-Gauss-Bonnet gravity.« less

Glycerol in micellar confinement with tunable rigidity

NASA Astrophysics Data System (ADS)

Lannert, Michael; Müller, Allyn; Gouirand, Emmanuel; Talluto, Vincenzo; Rosenstihl, Markus; Walther, Thomas; Stühn, Bernd; Blochowicz, Thomas; Vogel, Michael

2016-12-01

We investigate the glassy dynamics of glycerol in the confinement of a microemulsion system, which is stable on cooling down to the glass transition of its components. By changing the composition, we vary the viscosity of the matrix, while keeping the confining geometry intact, as is demonstrated by small angle X-ray scattering. By means of 2H NMR, differential scanning calorimetry, and triplet solvation dynamics we, thus, probe the dynamics of glycerol in confinements of varying rigidity. 2H NMR results show that, at higher temperatures, the dynamics of confined glycerol is unchanged compared to bulk behavior, while the reorientation of glycerol molecules becomes significantly faster than in the bulk in the deeply supercooled regime. However, comparison of different 2H NMR findings with data from calorimetry and solvation dynamics reveals that this acceleration is not due to the changed structural relaxation of glycerol, but rather due to the rotational motion of essentially rigid glycerol droplets or of aggregates of such droplets in a more fluid matrix. Thus, independent of the matrix mobility, the glycerol dynamics remains unchanged except for the smallest droplets, where an increase of Tg and, thus, a slowdown of the structural relaxation is observed even in a fluid matrix.

Modeling and measuring non-Newtonian shear flows of soft interfaces

NASA Astrophysics Data System (ADS)

Lopez, Juan; Raghunandan, Aditya; Underhill, Patrick; Hirsa, Amir

2017-11-01

Soft interfaces of polymers, particles, and proteins between fluid phases are ubiquitous in industrial and natural processes. The flow response of such systems to deformation is often not linear, as one would expect for Newtonian interfaces. The resistance to (pure shear) flow of interfaces is generally characterized by a single intrinsic material property, the surface shear viscosity. Predicted shear responses of Newtonian interfaces have achieved consensus across a wide range of flow conditions and measurement devices, when the nonlinear hydrodynamic coupling to the bulk phase is correctly accounted for. However, predicting the flows of sheared non-Newtonian interfaces remains a challenge. Here, we introduce a computational model that incorporates a non-Newtonian constitutive equation for the sheared interface and properly accounts for the coupled interfacial and bulk phase flows. We compare predictions to experiments performed with a model phospholipid system, DPPC - the main constituent of mammalian lung surfactant. Densely packed films of DPPC are directly sheared in a knife-edge surface viscometer. Yield-stress and shear thinning behaviors are shown to be accurately captured across hydrodynamic regimes straddling the Stokes flow limit to inertia dominated flows. Supported by NASA Grant NNX13AQ22G.

Local geology controlled the feasibility of vitrifying Iron Age buildings.

PubMed

Wadsworth, Fabian B; Heap, Michael J; Damby, David E; Hess, Kai-Uwe; Najorka, Jens; Vasseur, Jérémie; Fahrner, Dominik; Dingwell, Donald B

2017-01-12

During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called 'vitrified forts'. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

Real-time monitoring of human blood clotting using a lateral excited film bulk acoustic resonator

NASA Astrophysics Data System (ADS)

Chen, Da; Wang, Jingjng; Wang, Peng; Guo, Qiuquan; Zhang, Zhen; Ma, Jilong

2017-04-01

Frequent assay of hemostatic status is an essential issue for the millions of patients using anticoagulant drugs. In this paper, we presented a micro-fabricated film bulk acoustic sensor for the real-time monitoring of blood clotting and the measurement of hemostatic parameters. The device was made of an Au/ZnO/Si3N4 film stack and excited by a lateral electric field. It operated under a shear mode resonance with the frequency of 1.42 GHz and had a quality factor of 342 in human blood. During the clotting process of blood, the resonant frequency decreased along with the change of blood viscosity and showed an apparent step-ladder curve, revealing the sequential clotting stages. An important hemostatic parameter, prothrombin time, was quantitatively determined from the frequency response for different dilutions of the blood samples. The effect of a typical anticoagulant drug (heparin) on the prothrombin time was exemplarily shown. The proposed sensor displayed a good consistency and clinical comparability with the standard coagulometric methods. Thanks to the availability of direct digital signals, excellent potentials of miniaturization and integration, the proposed sensor has promising application for point-of-care coagulation technologies.

Spreading of a liquid film on a substrate by the evaporation-adsorption process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wayner, P.C. Jr.; Schonberg, J.

1992-09-01

The importance of evaporation followed by multilayer adsorption in comparison to liquid flow at the leading edge of a volatile spreading film is analyzed. Presuming that both flows are functions of the same chemical potential gradient, a dimensionless group (N) which delineates the relative importance of vapor diffusion flow to viscous flow on the surface is obtained: N = [rho][sub i]D[nu]x/([minus][bar A][pi]). The relative importance of vapor flow increases with the vapor-pressure dependent partial density, [rho][sub i], and diffusivity, D, of the diffusing vapor, the kinematic viscosity of the liquid, [nu], and the distance downstream from the bulk liquid region,more » x, and decreases with the Hamaker constant, 6[pi][bar A]. Using physical properties the modifiers volatile'' and nonvolatile'' can thereby be put in perspective. Changes in the interfacial force field are a function of [bar A]. The spreading velocity due to the vapor diffusion process is obtained and is found to decrease with a decrease in the interfacial force field and the bulk vapor pressure. The infinite stress at the contact line can be easily relieved by evaporation-adsorption in many systems.« less

Identification and calculation of the universal asymptote for drag reduction by polymers in wall bounded turbulence.

PubMed

Benzi, Roberto; De Angelis, Elisabetta; L'vov, Victor S; Procaccia, Itamar

2005-11-04

Drag reduction by polymers in wall turbulence is bounded from above by a universal maximal drag reduction (MDR) velocity profile that is a log law, estimated experimentally by Virk as V+(y+) approximately 11.7logy+ - 17. Here V+(y+) and y+ are the mean streamwise velocity and the distance from the wall in "wall" units. In this Letter we propose that this MDR profile is an edge solution of the Navier-Stokes equations (with an effective viscosity profile) beyond which no turbulent solutions exist. This insight rationalizes the universality of the MDR and provides a maximum principle which allows an ab initio calculation of the parameters in this law without any viscoelastic experimental input.

Diffuse neutrino supernova background as a cosmological test

NASA Astrophysics Data System (ADS)

Barranco, J.; Bernal, A.; Delepine, D.

2018-05-01

The future detection and measurement of the diffuse neutrino supernova background will provide us with information about supernova neutrino emission and the cosmic core-collapse supernova rate. Little has been said about the information that this measurement could give us about the expansion history of the Universe. The purpose of this article is to study the change of the predicted diffuse supernova neutrino background as a function of the cosmological model. In particular, we study three different models: the Λ–Cold Dark Matter model, the Logotropic universe and a bulk viscous matter-dominated universe. By fitting the free parameters of each model with the supernova Ia probe, we calculate the predicted number of events in these three models. We found that the spectra and number of events for the Λ–Cold dark matter model and the Logotropic model are almost indistinguishable, while a bulk viscous matter-dominated cosmological model predicts more events.

Asymmetric Wormholes via Electrically Charged Lightlike Branes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guendelman, E.; Kaganovich, A.; Nissimov, E.

2010-06-17

We consider a self-consistent Einstein-Maxwell-Kalb-Ramond system in the bulk D = 4 space-time interacting with a variable-tension electrically charged lightlike brane. The latter serves both as a material and charge source for gravity and electromagnetism, as well as it dynamically generates a bulk space varying cosmological constant. We find an asymmetric wormhole solution describing two 'universes' with different spherically symmetric black-hole-type geometries connected through a 'throat' occupied by the lightlike brane. The electrically neutral 'left universe' comprises the exterior region of Schwarzschild-de-Sitter (or pure Schwarzschild) space-time above the inner(Schwarzschild-type) horizon, whereas the electrically charged 'right universe' consists of the exteriormore » Reissner-Nordstroem (or Reissner-Nordstroem-de-Sitter) black hole region beyond the outer Reissner-Nordstroem horizon. All physical parameters of the wormhole are uniquely determined by two free parameters - the electric charge and Kalb-Ramond coupling of the lightlike brane.« less

The Viscoelastic Properties of Nematic Monodomains Containing Liquid Crystal Polymers.

NASA Astrophysics Data System (ADS)

Gu, Dongfeng

The work presented here investigates the viscoelastic properties of nematic materials containing liquid crystal polymers (LCP). We focus on how the elastic constants and the viscosity coefficients of the mixture systems are influenced by polymer architectures. In dynamic light scattering studies of the relaxation of the director orientation fluctuations for the splay, twist, and bend deformation modes, decrease of the relaxation rates was observed when LCPs were dissolved into low molar mass nematics (LMMN). For the side-chain LCPs, the slowing down in the bend mode is comparable to or larger than those of the splay and twist modes. For main-chain LCPs, the relative changes in the relaxation rates for the twist and splay modes are about one order of magnitude larger than that for the bend mode. The results of light scattering under an electric field show that the decrease in the twist relaxation rate is due to a large increase in the twist viscosity and a minor decrease in the twist elastic constant. These changes were found to increase with decrease of the spacer length, with increase of molecular weight, and with decrease of the backbone flexibility. In Freedericksz transition measurements, the splay and bend elastic constants and the dielectric anisotropies of the nematic mixtures were determined and the values are 5~15% lower than those of the pure solvent. From the analysis of the results of Freedericksz transition and light scattering experiments, a complete set of the elastic constants and viscosity coefficients corresponding to the three director deformation modes were obtained for the LCP mixtures. The changes in the viscosity coefficients due to addition of LCPs were analysed to estimate the anisotropic shapes of the polymer backbone via a hydrodynamic model. The results suggest that an oblate backbone configuration is maintained by the side-chain LCPs and a prolate chain configuration appears for the main-chain LCPs. The rheological behavior of a side-chain and a main-chain LCP nematic solutions were investigated. The addition of the side-chain LCP into a flow-aligning LMMN (5CB) induces director tumbling in the mixture, and, the dissolution of the main-chain LCP into a director tumbling LMMN (8CB) makes the solution become a flow-aligning nematic. Based on the hydrodynamic theory, these observations are further confirmation of the chain anisotropies of the LCPs investigated. Ericksen's transversely isotropic fluid model was used to extract the various viscosity coefficients with good accuracy. In addition, we believe that this is the first time the bulk rheological consequences of director tumbling in LMMNs has been observed.

Relaxation of the bulk modulus in partially molten dunite?

NASA Astrophysics Data System (ADS)

Cline, C. J.; Jackson, I.

2016-11-01

To address the possibility of melt-related bulk modulus relaxation, a forced oscillation experiment was conducted at seismic frequencies on a partially molten synthetic dunite specimen (melt fraction = 0.026) utilizing the enhanced capacity of the Australian National University attenuation apparatus to operate in both torsional and flexural oscillation modes. Shear modulus and dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background. Flexural data exhibit a monotonic decrease in complex Young's modulus with increasing temperature under transsolidus temperatures. The observed variation of Young's modulus is well described by the relationship 1/E 1/3G, without requiring relaxation of the bulk modulus. At high homologous temperatures, when shear modulus is low, extensional and flexural oscillation measurements have little resolution of bulk modulus, and thus, only pressure oscillation measurements can definitively constrain bulk properties at these conditions.

Viscosity Measurement: A Virtual Experiment - Abstract of Issues 9907W

NASA Astrophysics Data System (ADS)

Papadopoulos, N.; Pitta, A. T.; Markopoulos, N.; Limniou, M.; Lemos, M. A. N. D. A.; Lemos, F.; Freire, F. G.

1999-11-01

Viscosity Measurement: A Virtual Experiment simulates a series of viscosity experiments. Viscosity is an important subject in chemistry and chemical engineering. It is important when dealing with intermolecular forces in liquids and gases and it has enormous relevance in all technological aspects of equipment dealing with liquids or gases. Most university-level chemistry courses include viscosity to some extent. Viscosity Measurement includes three virtual experiments: an Ostwald viscometer simulator, a falling-ball viscometer simulator, and a balance simulator for a simple determination of the density of a liquid. The Ostwald viscometer simulator and the balance simulator allow the student to find out how composition and temperature influence the density and viscosity of an ethanol-water mixture. The falling-ball viscometer simulator allows the student to determine experimentally the size and density of the ball required to measure viscosity of various liquids. Each virtual experiment includes a corresponding theoretical section. Support from the program is sufficient to enable the students to carry out a virtual experiment sensibly and on their own. Preparation is not essential. Students can use the program unsupervised, thus saving staff time and allowing flexibility in students' time. The design of the program interface plays a key role in the success of a simulated experiment. Direct manipulation has greater intuitive appeal than alternative interface forms such as menus and has been observed to provide performance and learning advantages (1). We tried to design an interface that is visually attractive, is user friendly with simple and intuitive navigation, and provides appropriate schematic animations to clarify the principles of the laboratory procedures. The opening screen presents the virtual experiments that can be selected. Clicking an icon takes the student to the appropriate section. Viscosity Measurement allows the student to concentrate on the experiments at hand and not on learning how to use the program. It communicates its ideas visually with pictures and diagrams relegating on-screen text to the minimum required for the student to understand the presentation. A full presentation of viscosity is reserved for the textbook, which the computer cannot replace. It is well established (2) that people read text on a computer screen more slowly and with greater strain than they do text in a book. Moreover, relatively open-ended exploration does not appear to be a successful method of practice, because practice devised by the learner tends, not to be well conceived and well integrated in the students' learning path (3). For every virtual experiment we suggest a set of coherent exercises that highlight what we want students to know before they enter the real laboratory. Acknowledgment The Greek Ministry of Education and the European Community provided financial help to create the New Educational Technologies for the Teaching of Chemistry course that made development of the viscosity simulator possible. Literature Cited

1. Bensebasat, I.; Todd, P. Int. J. Man-Machine Studies 1993, 38, 369-402.
2. Gould, J. D.; Alfato, L.; Finn, R.; Haupt, B.; Minununo, A. Human Factors 1987, 26, 497-515.
3. Wiedenbeck, S.; Zila, P. L. ACM Transactions on Computer-Human Interaction 1997, 4, 169-196.

Increased plasma viscosity in young women with polycystic ovary syndrome using an oral contraceptive containing 35 μg ethinyl estradiol and 2 mg cyproterone acetate.

PubMed

Markantes, George; Saltamavros, Alexandros D; Vervita, Vasiliki; Armeni, Anastasia K; Karela, Anastasia; Adonakis, George; Decavalas, George; Georgopoulos, Neoklis A

2011-12-01

To investigate the influence of 6 months of treatment with an oral contraceptive (OC) containing 35 μ g ethinyl estradiol and 2 mg cyproterone acetate on plasma viscosity (PV) in young women with polycystic ovary syndrome (PCOS). Patients with PCOS were assessed for PV before and after 6 months of treatment with an OC containing 35 μg ethinyl estradiol and 2 mg cyproterone acetate. PV was determined by a viscometer Type 53610/I SCHOTT-Instruments, Mainz at 37°C. Subjects were recruited from the Department of Obstetrics and Gynaecology, Division of Reproductive Endocrinology at the University Hospital of Patras, Greece. The study included 66 young women with PCOS. PV. In PCOS women as a whole, PV at baseline was 1.249 ± 0.049 mm(2)/s (n = 66). After 6 months of treatment with an OC containing 35 μg ethinyl estradiol and 2 mg cyproterone acetate, PV was increased to 1.268 ± 0.065 mm(2)/s (p = 0.038). The difference between PV before and after 6 months of treatment with an OC containing 35 μg ethinyl estradiol and 2 mg cyproterone acetate (Δviscosity) was 0.01864 ± 0.071452 mm(2)/s. ΔViscosity was related to ?fibrinogen (r = 0.270, p = 0.046), to Δhematocrit (r = 0.514, p = 0.09) and to Δtriglycerides (r = 0.292, p = 0.021). Young women with PCOS presented an increased PV under OC treatment with 35 μg ethinyl estradiol and 2 mg cyproterone acetate.

Viscosity structure of Earth's mantle inferred from rotational variations due to GIA process and recent melting events

NASA Astrophysics Data System (ADS)

Nakada, Masao; Okuno, Jun'ichi; Lambeck, Kurt; Purcell, Anthony

2015-08-01

We examine the geodetically derived rotational variations for the rate of change of degree-two harmonics of Earth's geopotential, skew5dot J_2, and true polar wander, combining a recent melting model of glaciers and the Greenland and Antarctic ice sheets taken from the IPCC 2013 Report (AR5) with two representative GIA ice models describing the last deglaciation, ICE5G and the ANU model developed at the Australian National University. Geodetically derived observations of skew4dot J_2 are characterized by temporal changes of -(3.7 ± 0.1) × 10-11 yr-1 for the period 1976-1990 and -(0.3 ± 0.1) × 10-11 yr-1 after ˜2000. The AR5 results make it possible to evaluate the recent melting of the major ice sheets and glaciers for three periods, 1900-1990, 1991-2001 and after 2002. The observed skew4dot J_2 and the component of skew4dot J_2 due to recent melting for different periods indicate a long-term change in skew4dot J_2-attributed to the Earth's response to the last glacial cycle-of -(6.0-6.5) × 10-11 yr-1, significantly different from the values adopted to infer the viscosity structure of the mantle in most previous studies. This is a main conclusion of this study. We next compare this estimate with the values of skew4dot J_2 predicted by GIA ice models to infer the viscosity structure of the mantle, and consequently obtain two permissible solutions for the lower mantle viscosity (ηlm), ˜1022 and (5-10) × 1022 Pa s, for both adopted ice models. These two solutions are largely insensitive to the lithospheric thickness and upper mantle viscosity as indicated by previous studies and relatively insensitive to the viscosity structure of the D″ layer. The ESL contributions from the Antarctic ice sheet since the last glacial maximum (LGM) for ICE5G and ANU are about 20 and 30 m, respectively, but glaciological reconstructions of the Antarctic LGM ice sheet have suggested that its ESL contribution may have been less than ˜10 m. The GIA-induced skew4dot J_2 for GIA ice models with an Antarctic ESL component of ˜10 m suggests two permissible lower mantle viscosity solutions of ηlm ˜ 2 × 1022 and ˜5 × 1022 Pa s or one solution with (2-5) × 1022 Pa s. These results suggest that the effective lower mantle viscosity is larger than ˜1022 Pa s regardless of the uncertainties for an Antarctic ESL component. We also examine the polar wander due to recent melting and GIA processes, suggesting that the observed polar wander may be significantly attributed to convection motions in the mantle and/or another cause, particularly for permissible lower mantle viscosity solution of (5-10) × 1022 Pa s.

Rheological and Magnetorheological Behaviour of Some Magnetic Fluids on Polar and Nonpolar Carrier Liquids

NASA Astrophysics Data System (ADS)

Bălău, Oana; Bica, Doina; Koneracka, Martina; Kopčansky, Peter; Susan-Resiga, Daniela; Vékás, Ladislau

Rheological and magnetorheological behaviour of monolayer and double layer sterically stabilized magnetic fluids, with transformer oil (UTR), diloctilsebacate (DOS), heptanol (Hept), pentanol (Pent) and water (W) as carrier liquids, were investigated. The data for volumic concentration dependence of dynamic viscosity of high colloidal stability UTR, DOS, Hept and Pent samples are particularly well fitted by the formulas given by Vand (1948) and Chow (1994). The Chow type dependence proved its universal character as the viscosity data for dilution series of various magnetic fluids are well fitted by the same curve, regardless the nonpolar or polar charcater of the sample. The magnetorheological effect measured for low and medium concentration water based magnetic fluids is much higher, due to agglomerate formation process, than the corresponding values obtained for the well stabilized UTR, DOS, Hept and Pent samples, even at very high volumic fraction of magnetic nanoparticles.

Final Report - IHLW PCT, Spinel T1%, Electrical Conductivity, and Viscosity Model Development, VSL-07R1240-4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, Albert A.; Piepel, Gregory F.; Landmesser, S. M.

2013-11-13

This report is the last in a series of currently scheduled reports that presents the results from the High Level Waste (HLW) glass formulation development and testing work performed at the Vitreous State Laboratory (VSL) of the Catholic University of America (CUA) and the development of IHLW property-composition models performed jointly by Pacific Northwest National Laboratory (PNNL) and VSL for the River Protection Project-Waste Treatment and Immobilization Plant (RPP-WTP). Specifically, this report presents results of glass testing at VSL and model development at PNNL for Product Consistency Test (PCT), one-percent crystal fraction temperature (T1%), electrical conductivity (EC), and viscosity ofmore » HLW glasses. The models presented in this report may be augmented and additional validation work performed during any future immobilized HLW (IHLW) model development work. Completion of the test objectives is addressed.« less

Experimental study of the effect of polyanionic cellulose on process of filtrate loss of low-solids drilling fluid

NASA Astrophysics Data System (ADS)

yang, P.

2013-12-01

Experimental study of the effect of polyanionic cellulose on process of filtrate loss of low-solids drilling fluid Ping Yang 1,2, Min-hui Wu2, Xue-wen Zhu2, Tao Deng2, Xue-qing Sun2 1. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092,China 2. Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China Abstract The process of filtrate loss of low-solids drilling fluid was tested by changing the polyanionic cellulose content in low-solids drilling fluid. The effect of polyanionic cellulose on process of filtrate loss of low-solids drilling fluid was analyzed. The test results showed that when time of filtration is same, the volume of filtrate loss decreases linearly with increasing polyanionic cellulose content. When polyanionic cellulose content is same, the rate of filtrate loss decreases nonlinearly with increasing time and the rate of filtrate loss will reach a stable value.The volume of filtrate loss in 7 to 8 minutes can reaches half of the total volume of filtrate loss. At the same time, the rate of filtrate loss of drilling fluid decreases nonlinearly with increasing viscosity.When the apparent viscosity is between 3.5~4.15 MPa.s, decrease speed of rate of filtrate loss of drilling fluid is quick. The results are helpful for characteristics evaluation of filtrate loss of drilling fluid and control of filtrate loss. Keyword Polyanionic Cellulose,Drilling Fluid,Process of Filtrate Loss Acknowledgments This investigation was supported by the National Natural Science Foundation of China (projects No. 41002093 and 41072205); the Fundamental Research Funds for the Central Universities; the Shanghai Leading Academic Discipline Project (project No. B308), Tongji University; and the Program for Young Excellent Talents, Tongji University. The authors are extremely grateful for the financial support from these five organizations.

Conditions and timescales for welding block-and-ash flow deposits

NASA Astrophysics Data System (ADS)

Heap, M. J.; Kolzenburg, S.; Russell, J. K.; Campbell, M. E.; Welles, J.; Farquharson, J. I.; Ryan, A.

2014-12-01

Welding of pyroclastic deposits to reform a coherent rock mass is a common phenomenon, especially for pumiceous pyroclastic density current deposits (i.e., ignimbrites). However, and despite the pervasive abundance of block-and-ash flow (BAF) deposits in the geological and modern record, instances of strongly welded BAF deposits are few. Here, we present a series of high-temperature (800-900 °C) compaction experiments designed to map the conditions (deposit thickness/stress and temperature/viscosity) and timescales that permit or inhibit the welding of BAF deposits. Our experiments were performed on unconsolidated aggregates (containing an ash and lapilli component) derived from crushed and sieved lava blocks (containing 25% crystals) taken from the well-documented welded BAF deposit at Mount Meager volcano (British Columbia, Canada). The experiments demonstrate that welding efficiency increases with increasing time and temperature. Progressive welding is expressed by increasing axial strain, porosity loss, and bulk density. The rate of change of each of these physical properties reduces as welding progresses. Microstructural analysis of the experimental products shows that the loss of interclast porosity during welding results from the progressive sintering and amalgamation of vitric fragments, and that the pore shape changes from sub-equant pores to stretched lenses sandwiched between vitric and crystal fragments. The coincidence between the microstructure and rock physical properties of the natural and experimental samples highlight that we have successfully reproduced welded BAF in the laboratory. Furthermore, our permeability measurements highlight a hysteresis in the return journey of the "there-and-back-again" volcanic permeability cycle (expressed by an increase in permeability due to vesiculation and fragmentation followed by a decrease due to welding). This hysteresis cannot be described by a single porosity-permeability power law relationship and reflects the change in pore shape and connectivity during welding. Finally, we show that a simple model for welding can accurately forecast the welding timescales of the BAF deposit at Mount Meager (as reconstructed from the collapse of the Lillooet River valley dam) using our experimental data. We use this validation as a platform to provide a universal window for the welding of BAF deposits, also applicable for comparable welded deposits (e.g., welded autobreccias in block-lavas and lava domes), for a broad range of deposit thickness (or stress) and effective viscosity.

Hydrodynamics Defines the Stable Swimming Direction of Spherical Squirmers in a Nematic Liquid Crystal.

PubMed

Lintuvuori, J S; Würger, A; Stratford, K

2017-08-11

We present a study of the hydrodynamics of an active particle-a model squirmer-in an environment with a broken rotational symmetry: a nematic liquid crystal. By combining simulations with analytic calculations, we show that the hydrodynamic coupling between the squirmer flow field and liquid crystalline director can lead to reorientation of the swimmers. The preferred orientation depends on the exact details of the squirmer flow field. In a steady state, pushers are shown to swim parallel with the nematic director while pullers swim perpendicular to the nematic director. This behavior arises solely from hydrodynamic coupling between the squirmer flow field and anisotropic viscosities of the host fluid. Our results suggest that an anisotropic swimming medium can be used to characterize and guide spherical microswimmers in the bulk.

Nanoparticles in Polymers: Assembly, Rheology and Properties

NASA Astrophysics Data System (ADS)

Rao, Yuanqiao

Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties. Jeff Munro, Stephanie Potisek, Phillip Hustad; all of the Dow Chemical Company are co-authors.

Thermoacoustic effects in supercritical fluids near the critical point: Resonance, piston effect, and acoustic emission and reflection

NASA Astrophysics Data System (ADS)

Onuki, Akira

2007-12-01

We present a general theory of thermoacoustic phenomena in one phase states of one-component fluids. Singular behavior is predicted in supercritical fluids near the critical point. In a one-dimensional geometry we start with linearized hydrodynamic equations taking into account the effects of heat conduction in the boundary walls and the bulk viscosity. We introduce a coefficient Z(ω) characterizing reflection of sound with frequency ω at the boundary in a rigid cell. As applications, we examine acoustic eigenmodes, response to time-dependent perturbations, and sound emission and reflection. Resonance and rapid adiabatic changes are noteworthy. In these processes, the role of the thermal diffusion layers is enhanced near the critical point because of the strong critical divergence of the thermal expansion.

Massively parallel simulations of relativistic fluid dynamics on graphics processing units with CUDA

NASA Astrophysics Data System (ADS)

Bazow, Dennis; Heinz, Ulrich; Strickland, Michael

2018-04-01

Relativistic fluid dynamics is a major component in dynamical simulations of the quark-gluon plasma created in relativistic heavy-ion collisions. Simulations of the full three-dimensional dissipative dynamics of the quark-gluon plasma with fluctuating initial conditions are computationally expensive and typically require some degree of parallelization. In this paper, we present a GPU implementation of the Kurganov-Tadmor algorithm which solves the 3 + 1d relativistic viscous hydrodynamics equations including the effects of both bulk and shear viscosities. We demonstrate that the resulting CUDA-based GPU code is approximately two orders of magnitude faster than the corresponding serial implementation of the Kurganov-Tadmor algorithm. We validate the code using (semi-)analytic tests such as the relativistic shock-tube and Gubser flow.

The Use of Index-Matched Beads in Optical Particle Counters

PubMed Central

Hu, Zhishang; Ripple, Dean C

2014-01-01

In this paper, we demonstrate the use of 2-pyridinemethanol (2P) aqueous solutions as a refractive index matching liquid. The high refractive index and low viscosity of 2P-water mixtures enables refractive index matching of beads that cannot be index matched with glycerol-water or sucrose-water solutions, such as silica beads that have the refractive index of bulk fused silica or of polymethylmethacrylate beads. Suspensions of beads in a nearly index-matching liquid are a useful tool to understand the response of particle counting instruments to particles of low optical contrast, such as aggregated protein particles. Data from flow imaging and light obscuration instruments are presented for bead diameters ranging from 6 µm to 69 µm, in a matrix liquid spanning the point of matched refractive index. PMID:26601049

Falsification of dark energy by fluid mechanics

NASA Astrophysics Data System (ADS)

Gibson, Carl H.

2011-11-01

The 2011 Nobel Prize in Physics has been awarded for the discovery from observations of increased supernovae dimness interpreted as distance, so that the Universe expansion rate has changed from a rate decreasing since the big bang to one that is now increasing, driven by anti-gravity forces of a mysterious dark energy material comprising 70% of the Universe mass-energy. Fluid mechanical considerations falsify both the accelerating expansion and dark energy concepts. Kinematic viscosity is neglected in current stan- dard models of self-gravitational structure formation, which rely on cold dark matter CDM condensations and clusterings that are also falsified by fluid mechanics. Weakly collisional CDM particles do not condense but diffuse away. Photon viscosity predicts su- perclustervoid fragmentation early in the plasma epoch and protogalaxies at the end. At the plasma-gas transition, the plasma fragments into Earth-mass gas planets in trillion planet clumps (proto-globular-star-cluster PGCs). The hydrogen planets freeze to form the dark matter of galaxies and merge to form their stars. Dark energy is a systematic dimming error for Supernovae Ia caused by dark matter planets near hot white dwarf stars at the Chandrasekhar carbon limit. Evaporated planet atmospheres may or may not scatter light from the events depending on the line of sight.

Correlating the synthesis protocol of aromatic polyimide film with the properties of polyamic acid precursor

NASA Astrophysics Data System (ADS)

Tan, P. C.; Ooi, B. S.; Ahmad, A. L.; Low, S. C.

2017-06-01

Thousands of different copolyimide combinations render it technically impossible to have a single universal synthesis method to produce aromatic polyimide film. This study aimed to outline the selection of synthesis protocol, either through the casting of chemically imidized polyimide solution or thermal imidization of polyamic acid (PAA), to produce the polyimide film. The rheological behaviour, molecular weight, and solubility of five structurally different PAA were analysed and correlated to both imidization methods. In this work, a tough polyimide film was successfully synthesized by casting the chemically imidized polyimide derived from high viscosity (> 81 cP) and high molecular weight (≥ 1.35 x 106 g/mol) PAA. On the contrary, both low viscosity (< 13 cP) and high viscosity (> 81 cP) PAA demonstrated the possibility to produce polyimide film via thermal imidization route. The longer molecular chain of ODPA-6FpDA:DABA (3:2) polyimide produced from thermal imidization had restricted the passage of CO2 across the polyimide film when it was applied in the gas separation application. The outcome from this work serves as a guideline for the selection of suitable polyimide film synthesis protocol, which will minimize the time and chemical consumption in future exploration of new polyimide structure.

Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrillo, Jan-Michael; Brown, W Michael; Dobrynin, Andrey

2012-01-01

We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. In our simulations the solvent molecules were treated explicitly. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbonemore » deformation. This deformation mode manifests itself in the backbone deformation ratio, , and shear viscosity, , to be universal functions of the Weissenberg number W. The value of the friction coefficient, , and viscosity, , are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, , and friction coefficient, , approaching corresponding values obtained for neutral brush systems.« less

Substitute fluid examinations for liquid manure

NASA Astrophysics Data System (ADS)

Schrader, Kevin; Riedel, Marco; Eichert, Helmut

For the farming industry it is essential to use liquid manure as natural fertilizer. Through new agricultural regulation 2015 in Germany the industry must develop new liquid manure spreader systems because the ammonia and methane emission are limited. In a research project the University of Applied Sciences Zwickau and some other industry partners will develop such a new innovative liquid manure spreader. The new liquid manure spreader should use pulsating air to distribute the liquid manure exactly. The pulsating air, which flows through the pipelines, should be analysed at a test station. For examinations at this test station it is important to find another substitute fluid because liquid manure smells strong, is not transparent and is also not homogeneous enough for scientific investigations. Furthermore it is important to ensure that the substitute fluid is, like liquid manure, a non-Newtonian fluid. The substitute fluid must be a shear-thinning substance - this means the viscosity decrease at higher shear rate. Many different samples like soap-water-farragoes, jelly-water-farragoes, agar-water-farragoes, soap-ethanol-farragoes and more are, for the project, examined in regard of their physical properties to find the best substitute fluid. The samples are examined at the rotational viscometer for viscosity at various shear rates and then compared with the viscosity values of liquid manure.

Temperature-Induced Transitions in the Structure and Interfacial Rheology of Human Meibum

PubMed Central

Leiske, Danielle L.; Leiske, Christopher I.; Leiske, Daniel R.; Toney, Michael F.; Senchyna, Michelle; Ketelson, Howard A.; Meadows, David L.; Fuller, Gerald G.

2012-01-01

Meibomian lipids are the primary component of the lipid layer of the tear film. Composed primarily of a mixture of lipids, meibum exhibits a range of melt temperatures. Compositional changes that occur with disease may alter the temperature at which meibum melts. Here we explore how the mechanical properties and structure of meibum from healthy subjects depend on temperature. Interfacial films of meibum were highly viscoelastic at 17°C, but as the films were heated to 30°C the surface moduli decreased by more than two orders of magnitude. Brewster angle microscopy revealed the presence of micron-scale inhomogeneities in meibum films at higher temperatures. Crystalline structure was probed by small angle x-ray scattering of bulk meibum, which showed evidence of a majority crystalline structure in all samples with lamellar spacing of 49 Å that melted at 34°C. A minority structure was observed in some samples with d-spacing at 110 Å that persisted up to 40°C. The melting of crystalline phases accompanied by a reduction in interfacial viscosity and elasticity has implications in meibum behavior in the tear film. If the melt temperature of meibum was altered significantly from disease-induced compositional changes, the resultant change in viscosity could alter secretion of lipids from meibomian glands, or tear-film stabilization properties of the lipid layer. PMID:22339874

Gravity field and shape of Ceres from Dawn

NASA Astrophysics Data System (ADS)

Park, Ryan; Konopliv, Alexander; Vaughan, Andrew; Bills, Bruce; Castillo-Rogez, Julie; Ermakov, Anton; Fu, Roger; Raymond, Carol; Russell, Chris; Zuber, Maria

2017-04-01

The Dawn gravity science investigation utilizes the DSN radio tracking of the spacecraft and on-board framing camera images to determine the gravity field and global shape of Ceres. The gravity science data collected during Approach, Survey, High-Altitude Mapping Orbit, and Low-Altitude Mapping Orbit phases were processed. The final gravity science solution yielded a degree and order 18 gravity field, called CERES18C, which is globally accurate to degree and order 14. Also, the final Ceres shape using the stereo-photoclinometry method is available with the height uncertainty better than 30 meters. The degree-2 gravity harmonics show that the rotation of Ceres is very nearly about a principal axis. Combining the gravity field and topography gives the bulk density of 2162.6±2.0 kg/m3. The estimated spin pole vector yields RA=(291.42744±0.00022)° and Dec=(66.76065±0.00022)° with the prime meridian and rotation rate of (170.374±0.012)° and (952.1532638±0.0000019)°/day, respectively. The low Bouguer gravity at high topographic areas, and vice versa, indicates that the topography of Ceres is compensated, which can be explained by a low-viscosity layer at depth. Further studies on Ceres interior show that low gravity-topography admittances are consistent with Airy isostasy and finite-element modeling require a decrease of viscosity with depth.

Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

DOE PAGES

Chong, Leebyn; Lai, Yungchieh; Gray, McMahan; ...

2017-03-15

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends betweenmore » each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.« less

Maxwell-Stefan diffusion: a framework for predicting condensed phase diffusion and phase separation in atmospheric aerosol

NASA Astrophysics Data System (ADS)

Fowler, Kathryn; Connolly, Paul J.; Topping, David O.; O'Meara, Simon

2018-02-01

The composition of atmospheric aerosol particles has been found to influence their micro-physical properties and their interaction with water vapour in the atmosphere. Core-shell models have been used to investigate the relationship between composition, viscosity and equilibration timescales. These models have traditionally relied on the Fickian laws of diffusion with no explicit account of non-ideal interactions. We introduce the Maxwell-Stefan diffusion framework as an alternative method, which explicitly accounts for non-ideal interactions through activity coefficients. e-folding time is the time it takes for the difference in surface and bulk concentration to change by an exponential factor and was used to investigate the interplay between viscosity and solubility and the effect this has on equilibration timescales within individual aerosol particles. The e-folding time was estimated after instantaneous increases in relative humidity to binary systems of water and an organic component. At low water mole fractions, viscous effects were found to dominate mixing. However, at high water mole fractions, equilibration times were more sensitive to a range in solubility, shown through the greater variation in e-folding times. This is the first time the Maxwell-Stefan framework has been applied to an atmospheric aerosol core-shell model and shows that there is a complex interplay between the viscous and solubility effects on aerosol composition that requires further investigation.

Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chong, Leebyn; Lai, Yungchieh; Gray, McMahan

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends betweenmore » each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.« less

Very high-density planets: a possible remnant of gas giants.

PubMed

Mocquet, A; Grasset, O; Sotin, C

2014-04-28

Data extracted from the Extrasolar Planets Encyclopaedia (see http://exoplanet.eu) show the existence of planets that are more massive than iron cores that would have the same size. After meticulous verification of the data, we conclude that the mass of the smallest of these planets is actually not known. However, the three largest planets, Kepler-52b, Kepler-52c and Kepler-57b, which are between 30 and 100 times the mass of the Earth, have indeed density larger than an iron planet of the same size. This observation triggers this study that investigates under which conditions these planets could represent the naked cores of gas giants that would have lost their atmospheres during their migration towards the star. This study shows that for moderate viscosity values (10(25) Pa s or lower), large values of escape rate and associated unloading stress rate during the atmospheric loss process lead to the explosion of extremely massive planets. However, for moderate escape rate, the bulk viscosity and finite-strain incompressibility of the cores of giant planets can be large enough to retain a very high density during geological time scales. This would make those a new kind of planet, which would help in understanding the interior structure of the gas giants. However, this new family of exoplanets adds some degeneracy for characterizing terrestrial exoplanets.

Dual Mode Thin Film Bulk Acoustic Resonators (FBARs) Based on AlN, ZnO and GaN Films with Tilted c-Axis Orientation

DTIC Science & Technology

2010-01-01

TERMS MEMS , acoustic wave devices, acoustic wave sensors Qing-Ming Wang University of Pittsburgh 123 University Place University Club Pittsburgh, PA...resonators,” Proc. SPIE Vol. 6223, 62230I, Micro ( MEMS ) and Nanotechnologies for Space Applications; Thomas George, Zhong-Yang Cheng; Eds. (May...microelectromechanical resonators has been recognized as a technological challenge in the current microelectronics and MEMS development. The

Polymerization stress evolution of a bulk-fill flowable composite under different compliances.

PubMed

Guo, Yongwen; Landis, Forrest A; Wang, Zhengzhi; Bai, Ding; Jiang, Li; Chiang, Martin Y M

2016-04-01

To use a compliance-variable instrument to simultaneously measure and compare the polymerization stress (PS) evolution, degree of conversion (DC), and exotherm of a bulk-fill flowable composite to a packable composite. A bulk-fill flowable composite (Filtek Bulk-fill, FBF) and a conventional packable composite (Filtek Z250, Z250) purchased from 3M ESPE were investigated. The composites were studied using a cantilever-beam based instrument equipped with an in situ near infrared (NIR) spectrometer and a microprobe thermocouple. The measurements were carried out under various instrumental compliances (ranging from 0.3327μm/N to 12.3215μm/N) that are comparable to the compliances of clinically prepared tooth cavities. Correlations between the PS and temperature change as well as the DC were interpreted. The maximum PS of both composites at 10min after irradiation decreased with the increase in the compliance of the cantilever beam. The FBF composite generated a lower final stress than the Z250 sample under instrumental compliances less than ca. 4μm/N; however, both materials generated statistically similar PS values at higher compliances. The reaction exotherm and the DC of both materials were found to be independent of compliance. The DC of the FBF sample was slightly higher than that of the packable Z250 composite while the peak exotherm of FBF was almost double that of the Z250 composite. For FBF, a characteristic drop in the PS was observed during the early stage of polymerization for all compliances studied which was not observed in the Z250 sample. This drop was shown to relate to the greater exotherm of the less-filled FBF sample relative to the Z250 composite. While the composites with lower filler content (low viscosity) are generally considered to have lower PS than the conventional packable composites, a bulk-fill flowable composite was shown to produce lower PS under a lower compliance of constraint as would be experienced if the composite was used as the base material in clinical procedures. Published by Elsevier Ltd.

Velocity distribution in a turbulent flow near a rough wall

NASA Astrophysics Data System (ADS)

Korsun, A. S.; Pisarevsky, M. I.; Fedoseev, V. N.; Kreps, M. V.

2017-11-01

Velocity distribution in the zone of developed wall turbulence, regardless of the conditions on the wall, is described by the well-known Prandtl logarithmic profile. In this distribution, the constant, that determines the value of the velocity, is determined by the nature of the interaction of the flow with the wall and depends on the viscosity of the fluid, the dynamic velocity, and the parameters of the wall roughness.In extreme cases depending on the ratio between the thickness of the viscous sublayer and the size of the roughness the constant takes on a value that does not depend on viscosity, or leads to a ratio for a smooth wall.It is essential that this logarithmic profile is the result not only of the Prandtl theory, but can be derived from general considerations of the theory of dimensions, and also follows from the condition of local equilibrium of generation and dissipation of turbulent energy in the wall area. This allows us to consider the profile as a universal law of velocity distribution in the wall area of a turbulent flow.The profile approximation up to the maximum speed line with subsequent integration makes possible to obtain the resistance law for channels of simple shape. For channels of complex shape with rough walls, the universal profile can be used to formulate the boundary condition when applied to the calculation of turbulence models.This paper presents an empirical model for determining the constant of the universal logarithmic profile. The zone of roughness is described by a set of parameters and is considered as a porous structure with variable porosity.

Effect of chain extension on rheology and tensile properties of PHB and PHB-PLA blends

NASA Astrophysics Data System (ADS)

Bousfield, Glenn

Poly(3-hydroxybutyrate), referred to as PHB, is a bacterially-synthesized and biodegradable polymer which is being considered as a substitute for non-biodegradable bulk polymers like polypropylene. PHB is naturally extremely isotactic and naturally has a very high degree of crystallinity, resulting in a stiff but brittle material. The stability of PHB crystals also means that the melting point of the polymer is approximately 170°C, high with respect to similar polymers. For instance, the melting point of poly(4-hydroxybutyrate) is only 53°C (Saito, Nakamura, Hiramitsu, & Doi, 1996). Above 170°C, PHB is subject to a thermomechanical degradation mechanism, meaning that the polymer cannot be melted without degrading. One possible solution to the problem of degradation is to add a chain extender to the molten polymer to increase average molecular weight to counteract the molecular weight lost to degradation. In this work, a variety of chain extenders (JoncrylRTM ADR 4368-C, pyromellitic dianhydride, hexamethylene diisocyanate, polycarbodiimide) were compounded with a random copolymer of 98 mol% 3-hydroxybutyrate and 2 mol% 3-hydroxyvalerate (referred to as PHB) in concentrations ranging from 0.25% to 4%, to determine which chain extender functionality worked best with PHB. Molecular weight change was inferred from torque monitored during compounding, and from complex viscosity determined from parallel-plate rheology. None of the chain extenders changed the rate of degradation of PHB, although Joncryl increased the complex viscosity of the polymer. PHB was also blended with Poly(L-lactic acid), referred to as PLLA in PHB/PLLA ratios of 100/0, 75/25, 50/50, 25/75 and 0/100, to determine the effect of blending on the thermal stability of PHB. Again, thermal stability was determined by monitoring torque during compounding and by measuring complex viscosity through parallel-plate rheology. Blends in which PHB was the more abundant phase, as well as the 50% PHB/50% PLA blend continued to degrade, and the PLLA did not in these cases significantly increase complex viscosity. By contrast, the 25/75 PHB/PLLA blend had a complex viscosity equal to the neat PLLA blend, and both of the blends remained stable. All five blends were also produced with 1% Joncryl to observe the effect of Joncryl on the blends. In the 50/50 blend and the blends in which PLLA was the major component, complex viscosity increased by at least an order of magnitude, while in the 75/25 PHB/PLLA blend and the neat PHB blend, the effect of Joncryl was to increase complex viscosity only by a factor of 2. The effect of blending and of Joncryl on PHB-PLA blends was further investigated through uniaxial tensile stress testing of compression moulded samples of the blends, neat and with 1% Joncryl. The results showed an increase in tensile stress at yield and tensile strain at break for blends with the addition of Joncryl, although Young's modulus was somewhat diminished for these blends. In conclusion, chain extenders were not effective in reversing the effect of thermomechanical degradation, possibly because they do not change the resistance to bond rotation in PHB chains, or because they are not reactive with acrylates, although the exact cause has not been determined.

Comparing near-infrared conventional diffuse reflectance spectroscopy and hyperspectral imaging for determination of the bulk properties of solid samples by multivariate regression: determination of Mooney viscosity and plasticity indices of natural rubber.

PubMed

Juliano da Silva, Carlos; Pasquini, Celio

2015-01-21

Conventional reflectance spectroscopy (NIRS) and hyperspectral imaging (HI) in the near-infrared region (1000-2500 nm) are evaluated and compared, using, as the case study, the determination of relevant properties related to the quality of natural rubber. Mooney viscosity (MV) and plasticity indices (PI) (PI0 - original plasticity, PI30 - plasticity after accelerated aging, and PRI - the plasticity retention index after accelerated aging) of rubber were determined using multivariate regression models. Two hundred and eighty six samples of rubber were measured using conventional and hyperspectral near-infrared imaging reflectance instruments in the range of 1000-2500 nm. The sample set was split into regression (n = 191) and external validation (n = 95) sub-sets. Three instruments were employed for data acquisition: a line scanning hyperspectral camera and two conventional FT-NIR spectrometers. Sample heterogeneity was evaluated using hyperspectral images obtained with a resolution of 150 × 150 μm and principal component analysis. The probed sample area (5 cm(2); 24,000 pixels) to achieve representativeness was found to be equivalent to the average of 6 spectra for a 1 cm diameter probing circular window of one FT-NIR instrument. The other spectrophotometer can probe the whole sample in only one measurement. The results show that the rubber properties can be determined with very similar accuracy and precision by Partial Least Square (PLS) regression models regardless of whether HI-NIR or conventional FT-NIR produce the spectral datasets. The best Root Mean Square Errors of Prediction (RMSEPs) of external validation for MV, PI0, PI30, and PRI were 4.3, 1.8, 3.4, and 5.3%, respectively. Though the quantitative results provided by the three instruments can be considered equivalent, the hyperspectral imaging instrument presents a number of advantages, being about 6 times faster than conventional bulk spectrometers, producing robust spectral data by ensuring sample representativeness, and minimizing the effect of the presence of contaminants.

Dynamical studies of confined fluids and polymers

NASA Astrophysics Data System (ADS)

Grabowski, Christopher A.

Soft matter, a class of materials including polymers, colloids, and surfactant molecules, are ubiquitous in our everyday lives. Plastics, soaps, foods and living organisms are mostly comprised of soft materials. Research conducted to understand soft matter behavior at the molecular level is essential to create new materials with unique properties. Self-healing plastics, targeted drug delivery, and nanowire assemblies have all been further advanced by soft matter research. The author of this dissertation investigates fundamental soft matter systems, including polymer solutions and melts, colloid dispersions in polymer melts, and interfacial fluids. The dynamics of polymers and confined fluids were studied using the single-molecule sensitive technique of fluorescence correlation spectroscopy (FCS). Here, fluorescent dyes are attached to polymer coils or by introducing free dyes directly into the solution/film. Complementary experiments were also performed, utilizing atomic force microscopy (AFM) and ellipsometry. FCS and AFM experiments demonstrated the significant difference in properties of thin fluid films of the nearly spherical, nonpolar molecule TEHOS (tetrakis(2-ethylhexoxy)silane) when compared to its bulk counterpart. AFM experiments confirmed TEHOS orders in layers near a solid substrate. FCS experiments show that free dyes introduced in these thin films do not have a single diffusion coefficient, indicating that these films have heterogeneity at the molecular level. FCS experiments have been applied to study the diffusion of gold colloids. The diffusion of gold colloids in polymer melts was found to dramatically depart from the Stokes-Einstein prediction when colloid size was smaller than the surrounding polymer mesh size. This effect is explained by noting the viscosity experienced by the colloid is not equivalent to the overall bulk viscosity of the polymer melt. The conformational change of polymers immersed in a binary solvent was measured via FCS. This experiment was conducted to test a theory proposed by Brochard and de Gennes, who postulated a polymer chain undergoes a collapse and a dramatic re-swelling as the critical point of the binary mixture is approached. Measuring polymer chain diffusion as a function of temperature, this theory was confirmed. To my knowledge, this was the first experimental evidence of contraction/re-swelling for polymers in critical binary solvents.

Physical Accuracy of Q Models of Seismic Attenuation

NASA Astrophysics Data System (ADS)

Morozov, I. B.

2016-12-01

Accuracy of theoretical models is a required prerequisite for any type of seismic imaging and interpretation. Among all geophysical disciplines, the theory of seismic and tidal attenuation is the least developed, and most practical studies use viscoelastic models based on empirical Q factors. To simplify imaging and inversions, the Qs are often approximated as frequency-independent or following a power law with frequency. However, simplicity of inversion should not outweigh the problematic physical accuracy of such models. Typical images of spatially-variable crustal and mantle Qs are "apparent," analogously to pseudo-depth, apparent-resistivity images in electrical imaging. Problems with Q models can be seen from controversial general observations present in many studies; for example: 1) In global Q models, bulk attenuation is much lower than the shear one throughout the whole Earth. This is considered a fundamental relation for the Earth; nevertheless, it is also very peculiar physically and suggests a negative Q for the Lamé modulus. This relation is also not supported by most first-principle models of materials and laboratory studies. 2) The Q parameterization requires that the entire outer core of the Earth is assigned zero attenuation, despite its large volume, presence of viscosity and shear deformation in free oscillations. 3) In laboratory and surface-wave studies, the bulk and shear Qs can be different for different wave modes, different sample sizes boundary conditions on the surface. Similarly, the Qs measured from body-S, Love, Lg, or ScS waves may not equal each other. 4) In seismic coda studies, the Q is often found to be linearly (or even faster) increasing with frequency. Such character of energy dissipation is controversial physically, but can be readily explained as an artifact of inaccurately-known geometrical spreading. To overcome the physical inaccuracies and apparent character of seismic attenuation models, mechanical theories of materials need to be considered more often instead of the viscoelastic Q. Such theories can be based on methods of theoretical continuum mechanics and include solid/fluid viscosity, Coulomb friction, pore-fluid flows, grain and dislocation movement, and/or thermoelasticity.

Quantifying mantle structure and dynamics using plume tracing in seismic tomography

NASA Astrophysics Data System (ADS)

O'Farrell, K. A.; Eakin, C. M.; Jackson, M. G.; Jones, T. D.; Lekic, V.; Lithgow-Bertelloni, C. R.

2017-12-01

Directly linking deep mantle processes with surface features and dynamics is a complex problem. Hotspot volcanism gives us surface observables of mantle signatures, but the depth and source of the mantle plumes feeding these hotspots are highly debated. To address these issues, it is necessary to consider the entire journey of a plume through the mantle. By analyzing the behavior of mantle plumes we can constrain the vigor of mantle convection, the net rotation of the mantle and the role of thermal versus chemical anomalies as well as the bulk physical properties such as the viscosity profile. To do this, we developed a new algorithm to trace plume-like features in shear-wave (Vs) seismic tomography models based on picking local minima in the velocity and searching for continuous features with depth. We applied this method to recent tomographic models and find 60+ continuous plume conduits that are > 750 km long. Approximately a third of these can be associated with known hotspots at the surface. We analyze the morphology of these continuous conduits and infer large scale mantle flow patterns and properties. We find the largest lateral deflections in the conduits occur near the base of the lower mantle and in the upper mantle (near the thermal boundary layers). The preferred orientation of the plume deflections show large variability at all depths and indicate no net mantle rotation. Plate by plate analysis shows little agreement in deflection below particular plates, indicating these deflected features might be long lived and not caused by plate shearing. Changes in the gradient of plume deflection are inferred to correspond with viscosity contrasts in the mantle and found below the transition zone as well as at 1000 km depth. From this inferred viscosity structure, we explore the dynamics of a plume through these viscosity jumps. We also retrieve the Vs profiles for the conduits and compare with the velocity profiles predicted for different mantle adiabat temperatures. We are able to constrain the average temperature anomaly of the conduits to be around 150 K. We use these thermal anomalies in conjunction with our measured plume tilts/deflections to further explore the dynamics of plume conduits in the lower mantle and transition zone.

Thermodynamic Derivation of the Activation Energy for Ice Nucleation

NASA Technical Reports Server (NTRS)

Barahona, D.

2015-01-01

Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to ice nucleation. A key parameter in the theoretical description of ice nucleation is the activation energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of ice formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the ice-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the ice-liquid interface. Within this framework the activation energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the ice-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the activation energy has a strong dependency on temperature and a weak dependency on water activity. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of ice in haze aerosol particles. The new model provides an independent estimation of the activation energy and the homogeneous ice nucleation rate, and it may help to improve the interpretation of experimental results and the development of parameterizations for cloud formation.

Investigating Microphysics of Intracluster Medium with Advanced Hydrodynamic Simulations and X-Ray Observations

NASA Astrophysics Data System (ADS)

Markevitch, Maxim

Clusters of galaxies are the largest virialized mass concentrations in the Universe, and have long been recognized as sensitive cosmological probes. It is becoming increasingly clear that to realize their full potential for cosmology, we need to drastically reduce uncertainties in the cluster mass estimates and their relation to various cluster observables that arise from our lack of knowledge of the microphysics of the intracluster medium (ICM). Such ICM properties as thermal conductivity, viscosity, strength and structure of the magnetic fields, the energy in the cosmic ray components and electron-ion equilibration rates are very uncertain. Each of these can have a significant impact on the cluster thermal balance and the quantities that we observe in the X-ray, SZ, and radio bands. Theoretical estimates of thermal conductivity and viscosity are particularly uncertain -- by orders of magnitude. The heat can be conducted only along the magnetic field lines, but by some estimates, even along the lines it can be effectively suppressed by small- scale field fluctuations. Even less understood is the physical nature and the magnitude of viscosity, which bears directly on the ICM heating and mixing processes and the damping of turbulence. We have identified a method to constrain these quantities by contrasting high-quality X-ray observations of merging clusters with our high-resolution magnetohydrodynamic simulations that would follow the evolution of the magnetic field and include various levels of anisotropic conduction and viscosity. Thermal conduction can best be constrained by comparing X-ray temperature maps for several well-observed merging clusters with the maps for their simulated analogs. The conduction at interesting levels is expected to erase any small-scale temperature nonuniformities on timescales comparable to that of the merger. Currently, the most readily observable effect of viscosity is the suppression of instabilities in the cluster `cold fronts' -- sharp, arc-like contact discontinuities often observed in the cluster high- resolution X-ray images. Most of the observed cold fronts are very smooth, but some are visibly affected by instabilities. We will constrain the viscosity (largely independently of its exact physical nature) by including various levels of viscosity in the simulation of a strategically selected sample of cold front clusters. The forthcoming Astro-H mission opens another avenue to study the ICM viscosity and related phenomena -- by directly observing turbulence in merging and relaxed clusters. The turbulence in our merger simulations with varying viscosity could be directly compared to the levels eventually observed by Astro-H. Over the past several years, we have developed most of the machinery necessary for the above simulations by adding the appropriate code for diffusive physics into FLASH -- the high-resolution, grid-based magnetohydrodynamic code. As part of the proposed project, we will (a) add a few missing physical ingredients to the code and (b) simulate a sample of merging clusters, carefully selected from the XMM and Chandra archives to provide the strongest constraints on thermal conduction and viscosity in the ICM. The comparison with observations will result in strict limits on these microphysical quantities, adding an important element into the astrophysical foundation for the use of clusters as cosmological tools. The proposed research is directly relevant to the ROSES ATP solicitation, because it is a theoretical/numerical study of the physical processes in galaxy clusters, which will lead to predictions that can be tested with observations by the NASA space astrophysics missions XMM, Chandra and Astro-H.

University of California Conference on Statistical Mechanics (4th) Held March 26-28, 1990

DTIC Science & Technology

1990-03-28

and S. Lago, Chem. Phys., Z, 5750 (1983) Shear Viscosity Calculation via Equilibrium Molecular Dynamics: Einstenian vs. Green - Kubo Formalism by Adel A...through the application of the Green - Kubo approach. Although the theoretical equivalence between both formalisms was demonstrated by Helfand [3], their...like equations and of different expressions based on the Green - Kubo formalism. In contrast to Hoheisel and Vogelsang’s conclusions [2], we find that

Ambient Effects on Basalt and Rhyolite Lavas under Venusian, Subaerial, and Subaqueous Conditions

NASA Technical Reports Server (NTRS)

Bridges, Nathan T.

1997-01-01

Both subaerial and subaqueous environments have been used as analog settings for Venus volcanism. To assess the merits of this, the effects of ambient conditions on the physical properties of lava on Venus, the seafloor, and land on Earth are evaluated. Rhyolites on Venus and on the surface of Earth solidify before basalts do because of their lower eruption temperatures. Rhyolite crust is thinner than basalt crust at times less than about an hour, especially on Venus. At later times, rhyolite crust is thicker because of its lower latent heat relative to basalt. The high pressure on the seafloor and Venus inhibits the exsolution of volatiles in lavas. Vesicularity and bulk density are proportional, so that lavas of the same composition should be more dense on the seafloor and less dense on land. Because viscosity depends partly upon the fraction of unvesiculated water in a melt, basalts with the same initial volatile abundance will be least viscous on the seafloor and most viscous on land. Assuming the same preeruptive H2O contents, molten rhyolites on Venus will have viscosities approx. 10% that of rhyolites on land. Despite lower expected viscosities, under-water flows are more buoyant and should have heights like subaerial and Venusian lavas of the same composition and extrusive history. In cases where the influence of crust is insignificant, a volume of rhyolite will have a higher aspect ratio than the same volume of basalt, no matter what the environment. If flow rheology is dominated by the presence of strong crust, aspect ratios differ little among environments or between compositions. These analyses support a rhyolitic interpretation for the composition of Venusian festooned flows and a basaltic interpretation for the composition of Venusian steep-sided domes. Although ambient effects are significant, extrusion rate and eruption history must also be considered to explain analogous volcanic landforms on Earth and Venus.

Point-to-plane and plane-to-plane electrostatic charge injection atomization for insulating liquids

NASA Astrophysics Data System (ADS)

Malkawi, Ghazi

An electrostatic charge injection atomizer was fabricated and used to introduce and study the electrostatic charge injection atomization methods for highly viscous vegetable oils and high conductivity low viscosity aviation fuel, JP8. The total, spray and leakage currents and spray breakup characteristics for these liquids were investigated and compared with Diesel fuel data. Jet breakup and spray atomization mechanism showed differences for vegetable oils and lower viscosity hydrocarbon fuels. For vegetable oils, a bending/spinning instability phenomenon was observed similar to the phenomenon found in liquid jets of high viscosity polymer solutions. The spray tip lengths and cone angles were presented qualitatively and quantitatively and correlated with the appropriate empirical formulas. The different stages of the breakup mechanisms for such oils, as a function of specific charges and flow rates, were discussed. In order to make this method of atomization more suitable for practical use in high flow rate applications, a blunt face electrode (plane-to-plane) was used as the charge emitter in place of a single pointed electrode (point-to-plane). This allowed the use of a multi-orifice emitter that maintained a specific charge with the flow rate increase which could not be achieved with the needle electrode. The effect of the nozzle geometry, liquid physical properties and applied bulk flow on the spray charge, total charge, maximum critical spray specific charge and electrical efficiency compared with the needle point-to-plane atomizer results was presented. Our investigation revealed that the electrical efficiency of the atomizer is dominated by the charge forced convection rate rather than charge transport by ion motilities and liquid motion by the electric field. As a result of the electric coulomb forces between the electrified jets, the multi-orifice atomizer provided a unique means of dispersing the fuel in a hollow cone with wide angles making the new method suitable for variety of combustion applications.

Simulation of shear thickening in attractive colloidal suspensions.

PubMed

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F

2017-03-01

The influence of attractive forces between particles under conditions of large particle volume fraction, ϕ, is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris and M. M. Denn PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one a contact frictional interaction and the second a repulsive force often found in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress, kT/a 3 , and a characteristic stress based on the combination of interparticle force, i.e. σ ∼ F 0 /a 2 with kT the thermal energy, F 0 the repulsive force scale and a the particle radius. At sufficiently large ϕ, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan and C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.

Morphogenetic Implications of Peristalsis-Driven Fluid Flow in the Embryonic Lung

PubMed Central

Bokka, Kishore K.; Jesudason, Edwin C.; Lozoya, Oswaldo A.; Guilak, Farshid; Warburton, David; Lubkin, Sharon R.

2015-01-01

Epithelial organs are almost universally secretory. The lung secretes mucus of extremely variable consistency. In the early prenatal period, the secretions are of largely unknown composition, consistency, and flow rates. In addition to net outflow from secretion, the embryonic lung exhibits transient reversing flows from peristalsis. Airway peristalsis (AP) begins as soon as the smooth muscle forms, and persists until birth. Since the prenatal lung is liquid-filled, smooth muscle action can transport fluid far from the immediately adjacent tissues. The sensation of internal fluid flows has been shown to have potent morphogenetic effects, as has the transport of morphogens. We hypothesize that these effects play an important role in lung morphogenesis. To test these hypotheses in a quantitative framework, we analyzed the fluid-structure interactions between embryonic tissues and lumen fluid resulting from peristaltic waves that partially occlude the airway. We found that if the airway is closed, fluid transport is minimal; by contrast, if the trachea is open, shear rates can be very high, particularly at the stenosis. We performed a parametric analysis of flow characteristics' dependence on tissue stiffnesses, smooth muscle force, geometry, and fluid viscosity, and found that most of these relationships are governed by simple ratios. We measured the viscosity of prenatal lung fluid with passive bead microrheology. This paper reports the first measurements of the viscosity of embryonic lung lumen fluid. In the range tested, lumen fluid can be considered Newtonian, with a viscosity of 0.016 ± 0.008 Pa-s. We analyzed the interaction between the internal flows and diffusion and conclude that AP has a strong effect on flow sensing away from the tip and on transport of morphogens. These effects may be the intermediate mechanisms for the enhancement of branching seen in occluded embryonic lungs. PMID:26147967

Predominance of sperm motion in corners.

PubMed

Nosrati, Reza; Graham, Percival J; Liu, Qiaozhi; Sinton, David

2016-05-23

Sperm migration through the female tract is crucial to fertilization, but the role of the complex and confined structure of the fallopian tube in sperm guidance remains unknown. Here, by confocal imaging microchannels head-on, we distinguish corner- vs. wall- vs. bulk-swimming bull sperm in confined geometries. Corner-swimming dominates with local areal concentrations as high as 200-fold that of the bulk. The relative degree of corner-swimming is strongest in small channels, decreases with increasing channel size, and plateaus for channels above 200 μm. Corner-swimming remains predominant across the physiologically-relevant range of viscosity and pH. Together, boundary-following sperm account for over 95% of the sperm distribution in small rectangular channels, which is similar to the percentage of wall swimmers in circular channels of similar size. We also demonstrate that wall-swimming sperm travel closer to walls in smaller channels (~100 μm), where the opposite wall is within the hydrodynamic interaction length-scale. The corner accumulation effect is more than the superposition of the influence of two walls, and over 5-fold stronger than that of a single wall. These findings suggest that folds and corners are dominant in sperm migration in the narrow (sub-mm) lumen of the fallopian tube and microchannel-based sperm selection devices.

Predominance of sperm motion in corners

PubMed Central

Nosrati, Reza; Graham, Percival J.; Liu, Qiaozhi; Sinton, David

2016-01-01

Sperm migration through the female tract is crucial to fertilization, but the role of the complex and confined structure of the fallopian tube in sperm guidance remains unknown. Here, by confocal imaging microchannels head-on, we distinguish corner- vs. wall- vs. bulk-swimming bull sperm in confined geometries. Corner-swimming dominates with local areal concentrations as high as 200-fold that of the bulk. The relative degree of corner-swimming is strongest in small channels, decreases with increasing channel size, and plateaus for channels above 200 μm. Corner-swimming remains predominant across the physiologically-relevant range of viscosity and pH. Together, boundary-following sperm account for over 95% of the sperm distribution in small rectangular channels, which is similar to the percentage of wall swimmers in circular channels of similar size. We also demonstrate that wall-swimming sperm travel closer to walls in smaller channels (~100 μm), where the opposite wall is within the hydrodynamic interaction length-scale. The corner accumulation effect is more than the superposition of the influence of two walls, and over 5-fold stronger than that of a single wall. These findings suggest that folds and corners are dominant in sperm migration in the narrow (sub-mm) lumen of the fallopian tube and microchannel-based sperm selection devices. PMID:27211846

Er:YAG and CTH:YAG laser radiation: contact versus non-contact enamel ablation and sonic-activated bulk composite placement

NASA Astrophysics Data System (ADS)

Buckova, M.; Kasparova, M.; Dostalova, T.; Jelinkova, H.; Sulc, J.; Nemec, M.; Fibrich, M.; Bradna, P.; Miyagi, M.

2013-05-01

Laser radiation can be used for effective caries removal and cavity preparation without significant thermal effects, collateral damage of tooth structure, or patient discomfort. The aim of this study was to compare the quality of tissue after contact or non-contact Er:YAG and CTH:YAG laser radiation ablation. The second goal was to increase the sealing ability of hard dental tissues using sonic-activated bulk filling material with change in viscosity during processing. The artificial caries was prepared in intact teeth to simulate a demineralized surface and then the Er:YAG or CTH:YAG laser radiation was applied. The enamel artificial caries was gently removed by the laser radiation and sonic-activated composite fillings were inserted. A stereomicroscope and then a scanning electron microscope were used to evaluate the enamel surface. Er:YAG contact mode ablation in enamel was quick and precise; the cavity was smooth with a keyhole shaped prism and rod relief arrangement without a smear layer. The sonic-activated filling material was consistently regularly distributed; no cracks or microleakage in the enamel were observed. CTH:YAG irradiation was able to clean but not ablate the enamel surface; in contact and also in non-contact mode there was evidence of melting and fusing of the enamel.

Local geology controlled the feasibility of vitrifying Iron Age buildings

USGS Publications Warehouse

Fabian B Wadsworth,; Michael J Heap,; Damby, David; Kai-Uwe Hess,; Jens Najorka,; Jérémie Vasseur,; Dominik Fahrner,; Donald B Dingwell,

2017-01-01

During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called ‘vitrified forts’. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

AC Calorimetry and Thermophysical Properties of Bulk Glass-Forming Metallic Liquids

NASA Technical Reports Server (NTRS)

Johnson, William L.

2000-01-01

Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

NASA Astrophysics Data System (ADS)

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2016-09-01

A stable nanoscale thermal hot spot, with temperature approaching 100 °C , is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z , collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore.

PubMed

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2016-09-23

A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

Experimental investigation on the failure of T-joints at elevated temperature under unaxial loading

NASA Astrophysics Data System (ADS)

Bahri, N. F.; Afendi, M.; Razlan, Z. M.; Nor, A.; Baharuddin, S. A.

2017-09-01

In this study, the mechanical properties and maximum failure load of a bulk and T-joints subjected to tensile loading were investigated experimentally. A bulk and the T-joint specimens were fabricated and tested in order to investigate the effects of temperature conditions on the failure of the joints. The adherent and adhesive used for T-joint are 304 L stainless steel and Hysol E 214 HP with the adhesive thickness of 1.0 mm. The tensile test of the bulk specimen and adhesively T-joint were conducted by using a universal testing machine (UTM) at room temperature (RT), 55 °C, 75 °C, 100 °C and 120 °C, respectively. It was found that as the temperature increases, the failure force strength decreases for bulk and T-joint specimen. Data obtained from the tests at 120 °C showed the failure force of the bulk adhesive decreased by approximately 44 % compared to the specimen tested at RT. Next, the bulk of Hysol failure force result was compared with Araldite at RT and 100 °C. Araldite data was taken from the previous study [1]. It has also been found that the bulk for Hysol has higher failure force compared to Araldite at RT and 100 °C.

Methane and CO2 Adsorption and Transport in Carbon-based Systems from Experiments and Molecular Simulation

NASA Astrophysics Data System (ADS)

Wilcox, Jennifer; Firouzi, Mahnaz; Rupp, Erik; Haghapanah, Reza; Wang, Beibei

2013-04-01

Carbon capture and sequestration is one strategy that could potentially mitigate gigatons of CO2 emissions per year; however, technical obstacles have thus far hindered wide-scale deployment of this strategy. To design efficient and reliable strategies for either carbon capture or sequestration at the full-scale, one needs to understand the chemical and physical properties of CO2 and its interaction with its local surroundings at the molecular-scale. To investigate the chemical and physical properties of CO2 and its local surroundings at the molecular-scale, surface characterization studies are carried out alongside theoretical model efforts. Experimental investigation of CO2 interactions with organic-based porous materials ranging in complexity from functionalized graphene and activated carbon to various-rank coal and gas shale samples to create a set of realistic models that take into account both surface and pore heterogeneity. Integration of theory and experiments takes place to allow for the relevant physics at the molecular-level to be revealed. Determining adsorption and transport phenomena of CO2 (and mixtures, including H2O, and CH4) within the model pore systems can be used to understand the complex pore matrices of carbon-based sorbents, coal, and the organic components of gas shale that are crucial to determining their carbon capture or sequestration potential. Non-equilibrium molecular dynamics (NEMD) simulations of pure carbon dioxide, methane, helium and their mixtures have been carried out in carbon slit pores to investigate gas slippage and Klinkenberg effects in the organic matrices of coal and gas shale rocks. NEMD techniques are ideally suited for the experimental situation in which an external driving force, such as a chemical potential or pressure gradient, are applied on the system. Simulations have been conducted to determine the effect of pore size and exposure to an external potential on the velocity profile and slip-stick boundary conditions. The simulations indicate that molecule-wall collisions influence the velocity profile, which deviates significantly from the Navier-Stokes hydrodynamic prediction for micro and mesopores. Also, the shape of the velocity profile is found to be independent of the applied pressure gradient in micropores. The results indicate that the velocity profile is uniform for pore sizes less than 2 nm (micropores). As pore sizes increase to 10 nm, parabolic profiles are observed due to the reduced interaction of gas molecules with the pore walls. Interestingly, in small pores unlike in large pores, the gas velocity at the walls is non-zero and predicted gas transport is somewhat enhanced as the gas flow transitions from a parabolic velocity profile to plug-flow. In addition, a 3-D pore network, representative of porous carbon-based materials, has been generated atomistically using the Voronoi tessellation method. Simulations have been carried out to determine the effect of the pore structure and modeled viscosity on permeability and Klinkenberg parameters. The use of the bulk-phase viscosity for estimating the permeability of CO2 in units of Darcy in a 3-D micropore network is not an appropriate assumption as it significantly underestimates the CO2 permeability given that CO2 is an adsorbing gas with strong pore wall interactions. On the other hand, since the transport properties of CH4 are less influenced by the pore walls compared with CO2, the use of the bulk-phase CH4 viscosity estimates are a reasonable assumption. The application of this work is to advance our understanding of gas transport and to provide insight into mechanisms of gas-surface interactions in the complex natural systems such as gas shale so that we can make accurate capacity estimates in addition to assisting in enhancing natural gas recovery from these systems. These results will potentially have important implications on CO2 adsorption and transport in carbon-based materials and geologic formations and may provide an understanding of the limitations of the use of bulk-phase fluid viscosities to model transport properties for nanoconfined fluids.

Numerical estimation of deformation energy of selected bulk oilseeds in compression loading

NASA Astrophysics Data System (ADS)

Demirel, C.; Kabutey, A.; Herak, D.; Gurdil, G. A. K.

2017-09-01

This paper aimed at the determination of the deformation energy of some bulk oilseeds or kernels namely oil palm, sunflower, rape and flax in linear pressing applying the trapezoidal rule which is characterized by the area under the force and deformation curve.The bulk samples were measured at the initial pressing height of 60 mm with the vessel diameter of 60 mm where they were compressed under the universal compression machine at a maximum force of 200 kN and speed of 5 mm/min.Based on the compression test, the optimal deformation energy for recovering the oil was observed at a force of 163 kN where there was no seed/kernel cake ejection in comparison to the initial maximum force used particularly for rape and flax bulk oilseeds.This information is needed for analyzing the energy efficiency of the non-linear compression process involving a mechanical screw press or expeller.

Origin of matter and space-time in the big bang

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathews, G. J.; Kajino, T.; Yamazaki, D.

We review the case for and against a bulk cosmic motion resulting from the quantum entanglement of our universe with the multiverse beyond our horizon. Within the current theory for the selection of the initial state of the universe from the landscape multiverse there is a generic prediction that pre-inflation quantum entanglement with other universes should give rise to a cosmic bulk flow with a correlation length of order horizon size and a velocity field relative to the expansion frame of the universe. Indeed, the parameters of this motion are are tightly constrained. A robust prediction can be deduced indicatingmore » that there should be an overall motion of of about 800 km/s relative to the background space time as defined by the cosmic microwave background (CMB). This talk will summarize the underlying theoretical motivation for this hypothesis. Of course our motion relative to the background space time (CMB dipole) has been known for decades and is generally attributed to the gravitational pull of the local super cluster. However, this cosmic peculiar velocity field has been recently deduced out to very large distances well beyond that of the local super cluster by using X-ray galaxy clusters as tracers of matter motion. This is achieved via the kinematic component of the Sunyaev-Zeldovich (KSZ) effect produced by Compton scattering of cosmic microwave background photons from the local hot intracluster gas. As such, this method measures peculiar velocity directly in the frame of the cluster. Similar attempts by our group and others have attempted to independently assess this bulk flow via Type la supernova redshifts. In this talk we will review the observation case for and against the existence of this bulk flow based upon the observations and predictions of the theory. If this interpretation is correct it has profound implications in that we may be observing for the first time both the physics that occurred before the big bang and the existence of the multiverse beyond our horizon.« less

Theoretical study on the sound absorption of electrolytic solutions. I. Theoretical formulation.

PubMed

Yamaguchi, T; Matsuoka, T; Koda, S

2007-04-14

A theory is formulated that describes the sound absorption of electrolytic solutions due to the relative motion of ions, including the formation of ion pairs. The theory is based on the Kubo-Green formula for the bulk viscosity. The time correlation function of the pressure is projected onto the bilinear product of the density modes of ions. The time development of the product of density modes is described by the diffusive limit of the generalized Langevin equation, and approximate expressions for the three- and four-body correlation functions required are given with the hypernetted-chain integral equation theory. Calculations on the aqueous solutions of model electrolytes are performed. It is demonstrated that the theory describes both the activated barrier crossing between contact and solvent-separated ion pairs and the Coulombic correlation between ions.

Theoretical study on the sound absorption of electrolytic solutions. I. Theoretical formulation

NASA Astrophysics Data System (ADS)

Yamaguchi, T.; Matsuoka, T.; Koda, S.

2007-04-01

A theory is formulated that describes the sound absorption of electrolytic solutions due to the relative motion of ions, including the formation of ion pairs. The theory is based on the Kubo-Green formula for the bulk viscosity. The time correlation function of the pressure is projected onto the bilinear product of the density modes of ions. The time development of the product of density modes is described by the diffusive limit of the generalized Langevin equation, and approximate expressions for the three- and four-body correlation functions required are given with the hypernetted-chain integral equation theory. Calculations on the aqueous solutions of model electrolytes are performed. It is demonstrated that the theory describes both the activated barrier crossing between contact and solvent-separated ion pairs and the Coulombic correlation between ions.

Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC

NASA Astrophysics Data System (ADS)

Mäntysaari, Heikki; Schenke, Björn; Shen, Chun; Tribedy, Prithwish

2017-09-01

Results for particle production in √{ s} = 5.02TeV p + Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients vn, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean transverse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.

Microfluidic System Simulation Including the Electro-Viscous Effect

NASA Technical Reports Server (NTRS)

Rojas, Eileen; Chen, C. P.; Majumdar, Alok

2007-01-01

This paper describes a practical approach using a general purpose lumped-parameter computer program, GFSSP (Generalized Fluid System Simulation Program) for calculating flow distribution in a network of micro-channels including electro-viscous effects due to the existence of electrical double layer (EDL). In this study, an empirical formulation for calculating an effective viscosity of ionic solutions based on dimensional analysis is described to account for surface charge and bulk fluid conductivity, which give rise to electro-viscous effect in microfluidics network. Two dimensional slit micro flow data was used to determine the model coefficients. Geometry effect is then included through a Poiseuille number correlation in GFSSP. The bi-power model was used to calculate flow distribution of isotropically etched straight channel and T-junction microflows involving ionic solutions. Performance of the proposed model is assessed against experimental test data.

Black branes in a box: hydrodynamics, stability, and criticality

NASA Astrophysics Data System (ADS)

Emparan, Roberto; Martınez, Marina

2012-07-01

We study the effective hydrodynamics of neutral black branes enclosed in a finite cylindrical cavity with Dirichlet boundary conditions. We focus on how the Gregory-Laflamme instability changes as we vary the cavity radius R. Fixing the metric at the cavity wall increases the rigidity of the black brane by hindering gradients of the redshift on the wall. In the effective fluid, this is reflected in the growth of the squared speed of sound. As a consequence, when the cavity is smaller than a critical radius the black brane becomes dynamically stable. The correlation with the change in thermodynamic stability is transparent in our approach. We compute the bulk and shear viscosities of the black brane and find that they do not run with R. We find mean-field theory critical exponents near the critical point.

Degassing-induced crystallization of basaltic magma and effects on lava rheology

USGS Publications Warehouse

Lipman, P.W.; Banks, N.G.; Rhodes, J.M.

1985-01-01

During the north-east rift eruption of Mauna Loa volcano, Hawaii, on 25 March-14 April 1984 (Fig. 1), microphenocryst contents of erupted lava increased from 0.5 to 30% without concurrent change in either bulk magma composition or eruption temperature (1,140 ?? 3 ??C). The crystallization of the microphenocrysts is interpreted here as being due to undercooling of the magma 20-30 ??C below its liquidas; the undercooling probably resulted from separation and release of volatiles as the magma migrated 12 km from the primary summit reservoir to the eruption site on the north-east rift zone. Such crystallization of magma during an eruption has not been documented previously. The undercooling and crystallization increased the effective viscosity of the magma, leading to decreased eruption rates and stagnation of the lava flow. ?? 1985 Nature Publishing Group.

Effect of implanted Cu/low-density polyethylene nanocomposite on the morphology of endometrium in the mouse.

PubMed

Xia, Xianping; Xie, Changsheng; Zhu, Changhong; Cai, Shuizhou; Yang, Xiangliang

2007-08-01

To investigate the damage of endometrium caused by the implanted Cu/low-density polyethylene (LDPE) nanocomposite and the contraceptive effect of this novel copper-containing intrauterine device material. Experimental animal study. TongJi Medical College of Huazhong University of Science and Technology. Sixty healthy female mice. Twenty mice received no implants, 20 mice received the Cu/LDPE nanocomposite, and 20 mice received bulk copper. Morphologic features of the endometrium, contraceptive effect, and surface condition of the implanted implants. The contraceptive effect of both the Cu/LDPE nanocomposite and bulk copper is 100%, the damage of the endometrium caused by the Cu/LDPE nanocomposite is much less than that caused by bulk copper, and the surface of the implanted Cu/LDPE nanocomposite is much smoother and much softer than that of the implanted bulk copper. The contraceptive effect of the Cu/LDPE nanocomposite is comparable with that of bulk copper, and the damage of the endometrium caused by the Cu/LDPE nanocomposite is much less than that caused by bulk copper. The endometrium injury is related to the surface condition of the implanted intrauterine device material.

Constraining Lithospheric Stress on Mars From Mars Global Surveyor (MGS) Topography, Gravity, and Crustal Thickness

NASA Astrophysics Data System (ADS)

Dimitrova, L. L.; Holt, W. E.; Haines, A. J.

2004-12-01

The quantification of lithospheric dynamics on Mars is of fundamental importance to the understanding of Martian geologic history and surface morphology. The global stress field associated with gravitational potential energy differences (GPE) constitutes a significant fraction of the total stress field. We have obtained 0.25 × 0.25 degree data sets of MOLA topography and crustal thickness from Zuber et al 2000. We calculate the GPE associated with the topography by vertically integrating density to a given lithospheric depth using either Airy isostasy assumptions or the crustal thickness model of Zuber et al 2000. Using a finite-element thin sheet method we solve the full 3-D force-balance equations for stress magnitudes and orientations within the lithosphere associated with the horizontal gradients in GPE. We assume ρ crust = 2900~ kg m-3, ~ρ mantle = 3500~ kg m-3, ~g = 3.7~ ms-2 and various lithospheric thicknesses. We explore both viscous and elastic rheologies. It is interesting to note that our solutions depend on the rheology only through the ratio of shear and bulk moduli for the elastic case or the shear and bulk viscosities for the viscous case. Finally, we also calculate the expected style and orientation of the associated elastic strain. To first order, all stress field solutions are consistent with a tectonically inactive region relaxing due to excess or deficit of mass. Thus topographic highs e.g., Tharsis Mons, Olympus Mons, and Alba Patera, are in deviatoric extension, while topographic lows e.g., Valles Marineras and impact basins, are in deviatoric compression. At short wavelengths, however, features are regionally supported and differences in the stress field solutions occur between the Airy isostasy and the crustal thickness models. For example, several lowlands e.g., Isidis and Argyre Planitae, are in deviatoric extension in the crustal thickness model. Increasing the lithospheric depth increases the magnitudes of stresses but does not change the deformation style. Comparisons of viscous and elastic solutions with the same ratio of the shear and bulk viscosities for the viscous case and shear and bulk moduli for the elastic case show small variations in stress magnitudes and orientations among the solutions. We compare our results with inferred fault styles and orientations e.g., Mege 2001, Montessi and Zuber 2003. The GPE variations appear to match the radial graben features on Tharsis, as well as the wrinkle ridges at lower elevations. However, they do not predict the wrinkle ridges on the flanks of Tharsis and some grabens around Alba Patera extend into the lower topography regions beyond the area where the GPE associated stresses predict extension. Calculations of Banerdt and Glombek 2000 show the importance of flexural loading on the stress field. Their flexural loading solution provides compression at higher elevations on Tharsis that may explain some of the wrinkle ridges not predicted by GPE variations. Therefore, it appears that a combined solution of GPE inferred vertically integrated deviatoric stresses and the flexurally produced stresses will provide a better fit to the fault styles and orientations observed on Mars.

Effective method to control the levitation force and levitation height in a superconducting maglev system

NASA Astrophysics Data System (ADS)

Yang, Peng-Tao; Yang, Wan-Min; Wang, Miao; Li, Jia-Wei; Guo, Yu-Xia

2015-11-01

The influence of the width of the middle magnet in the permanent magnet guideways (PMGs) on the levitation force and the levitation height of single-domain yttrium barium copper oxide (YBCO) bulks has been investigated at 77 K under the zero field cooled (ZFC) state. It is found that the largest levitation force can be obtained in the system with the width of the middle magnet of the PMG equal to the size of the YBCO bulk when the gap between the YBCO bulk and PMG is small. Both larger levitation force and higher levitation height can be obtained in the system with the width of the middle magnet of the PMG larger than the size of the YBCO bulk. The stiffness of the levitation force between the PMG and the YBCO bulk is higher in the system with a smaller width of the middle magnet in the PMG. These results provide an effective way to control the levitation force and the levitation height for the superconducting maglev design and applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 51342001 and 50872079), the Key-grant Project of Chinese Ministry of Education (Grant No. 311033), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120202110003), the Innovation Team in Shaanxi Province, China (Grant No. 2014KTC-18), and the Fundamental Research Funds for the Central Universities, China (Grant Nos. GK201101001 and GK201305014), and the Outstanding Doctoral Thesis Foundation Project of Shaanxi Normal University, China (Grant Nos. X2011YB08 and X2012YB05).

Chemical analyses of geothermal waters from a South Louisiana well

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hankins, B.E.; Chavanne, R.E.; Ham, R.A.

1977-11-16

The abandoned Edna Delcambre No. 1 gas well, about 8 miles south of Delcambre, Louisiana was reopened and bottom-hole and flowing samples were collected. McNeese State University was responsible for the analyses of the products of the well. Typical values from the analyses are shown for such quantities as: pH, turbidity, conductance, density, total dissolved solids, hardness, viscosity, dissolved silicates, chlorides, bicarbonates, etc. Some observations on these values are made. (MHR)

Quantifying properties of hot and dense QCD matter through systematic model-to-data comparison

DOE PAGES

Bernhard, Jonah E.; Marcy, Peter W.; Coleman-Smith, Christopher E.; ...

2015-05-22

We systematically compare an event-by-event heavy-ion collision model to data from the CERN Large Hadron Collider. Using a general Bayesian method, we probe multiple model parameters including fundamental quark-gluon plasma properties such as the specific shear viscosity η/s, calibrate the model to optimally reproduce experimental data, and extract quantitative constraints for all parameters simultaneously. Furthermore, the method is universal and easily extensible to other data and collision models.

Low-momentum dynamic structure factor of a strongly interacting Fermi gas at finite temperature: A two-fluid hydrodynamic description

NASA Astrophysics Data System (ADS)

Hu, Hui; Zou, Peng; Liu, Xia-Ji

2018-02-01

We provide a description of the dynamic structure factor of a homogeneous unitary Fermi gas at low momentum and low frequency, based on the dissipative two-fluid hydrodynamic theory. The viscous relaxation time is estimated and is used to determine the regime where the hydrodynamic theory is applicable and to understand the nature of sound waves in the density response near the superfluid phase transition. By collecting the best knowledge on the shear viscosity and thermal conductivity known so far, we calculate the various diffusion coefficients and obtain the damping width of the (first and second) sounds. We find that the damping width of the first sound is greatly enhanced across the superfluid transition and very close to the transition the second sound might be resolved in the density response for the transferred momentum up to half of Fermi momentum. Our work is motivated by the recent measurement of the local dynamic structure factor at low momentum at Swinburne University of Technology and the ongoing experiment on sound attenuation of a homogeneous unitary Fermi gas at Massachusetts Institute of Technology. We discuss how the measurement of the velocity and damping width of the sound modes in low-momentum dynamic structure factor may lead to an improved determination of the universal superfluid density, shear viscosity, and thermal conductivity of a unitary Fermi gas.

A Generic Theory of the Integer Quantum Hall Effect

NASA Astrophysics Data System (ADS)

Shen, Yu

The integer quantum Hall effect (IQHE) is usually modeled by a Galilean or rotationally invariant Hamiltonian. These are not generic symmetries for electrons moving in a crystal background and can potentially confuse non-topological quantities with topological ones and identify otherwise distinct geometrical properties. In this thesis we present a generic theory for the IQHE. First we show that a generic guiding-center coherent state, defined by a natural metric in each Landau level, has the form of an antiholomorphic function times a Gaussian factor. Then by numerically solving the eigenproblem for a quartic Hamiltonian and finding the roots of the antiholomorphic part we are able to define a topological spin sn = n + 1/2 where n is the number of central roots that are enclosed by the semiclassical orbit. We derive a generic formula for the Hall viscosity in the absence of rotational symmetry and show that the previous interpretation of the scalar Hall viscosity as the "intrinsic orbital angular momentum" breaks down since the concept of angular momentum requires the presence of rotational symmetry. We also calculate generic electromagnetic responses and differentiate between universal terms that are diagonal with respect to Landau level index and non-universal terms that depend on inter-Landau-level mixing. We conclude that the generic theory offers a fundamental definition for the topological spin and reveals finer structure in the geometrical properties of the IQHE.

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.

2012-06-01

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293-333 K) and frequency range (50-5×106 Hz). The frequency dependence of ac conductivity, σac, has been investigated by the universal power law, σac(ω)=Aωs. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.

[Development of a system for static measurement of skin-muscle hardness and a fundamental study on its applications].

PubMed

Honda, T

1990-10-01

There have been many attempts to quantitatively measure the hardness of skin-muscle, but no objective method for doing so has been established, because there is no universal standard for the hardness of organisms. The author considered elasticity and viscosity as the most important mechanical properties of the hardness of skin-muscle and applied the Maxwell model, in which a spring and a dash-pot are arranged in a series, to the static mechanical behavior of skin-muscle. A relatively large globular pressing body with a radius of 5 mm was set as a transducer in the measuring system, so that the conformity of the practically measured values to those calculated theoretically by the model was increased. Strain of skin-muscle is expressed as a function of the load, which includes indices of elasticity (1/M) (M(N/mm2) = E/(1-lambda 2) (E: Young's modulus, lambda:Poisson's ratio)) and viscosity (1/eta) (eta:modulus of viscosity) in a particular region. Because hardness is defined as the degree of resistance against transformation by loading, decreases in the indices of both elasticity and viscosity mean increases of hardness. With 150 male and female office workers chosen as the subjects, the model was examined and the indices were calculated. The results were as follows. 1) Very good conformity of practically measured values to those calculated theoretically by the Maxwell model was recognized within the range of load velocity from 0.3 G to 3.0 G (N/sec). 2) In both males and females the regions with values nearest to those of a Newtonian fluid were, in descending order, the distal phalanxes of digiti 2-4, the palm, the distal phalanx of the first digitus and the arm. In reverse order these regions approached complete elasticity. 3) In males it was suggested that the element of viscosity in the region of the biceps brachii muscle and the hardness in the regions of the brachioradialis, the flexor carpi radialis and palmalis longus muscles and the distal phalanxes of the 4th and the 5th digiti were increased with age. In females, a decrease in hardness in the region of the biceps brachii muscle with age was observed. 4) The indices of not only elasticity, but also of viscosity in females were higher than those in males. The results showed that for both elasticity and viscosity, the hardness of skin-muscles in males were higher than that in females. Furthermore, the index of plasticity was determined by examining the mark remaining after unloading, and good correlation of the index to age was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Simulation Of The Synovial Fluid In A Deformable Cavity

NASA Astrophysics Data System (ADS)

Martinez-Gutierrez, Nancy; Ibarra-Bracamontes, Laura A.

2016-11-01

The main components of a synovial joint are a cartilage and a biofluid known as the synovial fluid. The results were obtained using the FLUENT software to simulate the behavior of the synovial fluid within a deformable cavity with a simple geometry. The cartilage is represented as a porous region. By reducing the available region for the fluid, a fluid displacement into the cartilage is induced. The total pressure reached in the interface of the deformable cavity and the porous region is presented. The geometry and properties of the system are scaled to values found in a knee joint. The effect of deformation rate, fluid viscosity and properties of the porous medium on the total pressure reached are analyzed. The higher pressures are reached either for high deformation rate or when the fluid viscosity increases. This study was supported by the Mexican Council of Science and Technology (CONACyT) and by the Scientific Research Coordination of the University of Michoacan in Mexico.

A universal route for the simultaneous extraction and functionalization of cellulose nanocrystals from industrial and agricultural celluloses

NASA Astrophysics Data System (ADS)

Chen, Guo-Yin; Yu, Hou-Yong; Zhang, Cai-Hong; Zhou, Ying; Yao, Ju-Ming

2016-02-01

A simple route was designed to extract the cellulose nanocrystals (CNCs) with formate groups from industrial and agricultural celluloses like microcrystalline cellulose (MCC), viscose fiber, ginger fiber, and bamboo fiber. The effect of reaction time on the microstructure and properties of the CNCs was investigated in detail, while microstructure and properties of different CNCs were compared. The rod-like CNCs (MCC) with hundreds of nanometers in length and about 10 nm in width, nanofibrillated CNCs (ginger fiber bamboo fiber) with average width of 30 nm and the length of 1 μm, and spherical CNCs (viscose fiber) with the width of 56 nm were obtained by one-step HCOOH/HCl hydrolysis. The CNCs with improved thermal stability showed the maximum degradation temperature ( T max) of 368.9-388.2 °C due to the introduction of formate groups (reducibility) and the increased crystallinity. Such CNCs may be used as an effective template for the synthesis of nanohybrids or reinforcing material for high-performance nanocomposites.

Spin-up flow of ferrofluids: Asymptotic theory and experimental measurements

NASA Astrophysics Data System (ADS)

Chaves, Arlex; Zahn, Markus; Rinaldi, Carlos

2008-05-01

We treat the flow of ferrofluid in a cylindrical container subjected to a uniform rotating magnetic field, commonly referred to as spin-up flow. A review of theoretical and experimental results published since the phenomenon was first observed in 1967 shows that the experimental data from surface observations of tracer particles are inadequate for the assessment of bulk flow theories. We present direct measurements of the bulk flow by using the ultrasound velocity profile method, and torque measurements for water and kerosene based ferrofluids, showing the fluid corotating with the field in a rigid-body-like fashion throughout most of the bulk region of the container, except near the air-fluid interface, where it was observed to counter-rotate. We obtain an extension of the spin diffusion theory of Zaitsev and Shliomis, using the regular perturbation method. The solution is rigorously valid for αK≪√3/2 , where αK is the Langevin parameter evaluated by using the applied field magnitude, and provides a means for obtaining successively higher contributions of the nonlinearity of the equilibrium magnetization response and the spin-magnetization coupling in the magnetization relaxation equation. Because of limitations in the sensitivity of our apparatus, experiments were carried out under conditions for which α ˜1. Still, under such conditions the predictions of the analysis are in good qualitative agreement with the experimental observations. An estimate of the spin viscosity is obtained from comparison of flow measurements and theoretical results of the extrapolated wall velocity from the regular perturbation method. The estimated value lies in the range of 10-8-10-12kgms-1 and is several orders of magnitude higher than that obtained from dimensional analysis of a suspension of noninteracting particles in a Newtonian fluid.

A coupled melt-freeze temperature index approach in a one-layer model to predict bulk volumetric liquid water content dynamics in snow

NASA Astrophysics Data System (ADS)

Avanzi, Francesco; Yamaguchi, Satoru; Hirashima, Hiroyuki; De Michele, Carlo

2016-04-01

Liquid water in snow rules runoff dynamics and wet snow avalanches release. Moreover, it affects snow viscosity and snow albedo. As a result, measuring and modeling liquid water dynamics in snow have important implications for many scientific applications. However, measurements are usually challenging, while modeling is difficult due to an overlap of mechanical, thermal and hydraulic processes. Here, we evaluate the use of a simple one-layer one-dimensional model to predict hourly time-series of bulk volumetric liquid water content in seasonal snow. The model considers both a simple temperature-index approach (melt only) and a coupled melt-freeze temperature-index approach that is able to reconstruct melt-freeze dynamics. Performance of this approach is evaluated at three sites in Japan. These sites (Nagaoka, Shinjo and Sapporo) present multi-year time-series of snow and meteorological data, vertical profiles of snow physical properties and snow melt lysimeters data. These data-sets are an interesting opportunity to test this application in different climatic conditions, as sites span a wide latitudinal range and are subjected to different snow conditions during the season. When melt-freeze dynamics are included in the model, results show that median absolute differences between observations and predictions of bulk volumetric liquid water content are consistently lower than 1 vol%. Moreover, the model is able to predict an observed dry condition of the snowpack in 80% of observed cases at a non-calibration site, where parameters from calibration sites are transferred. Overall, the analysis show that a coupled melt-freeze temperature-index approach may be a valid solution to predict average wetness conditions of a snow cover at local scale.

Dynamics of aqueous binary glass-formers confined in MCM-41.

PubMed

Elamin, Khalid; Jansson, Helén; Swenson, Jan

2015-05-21

Dielectric permittivity measurements were performed on water solutions of propylene glycol (PG) and propylene glycol monomethyl ether (PGME) confined in 21 Å pores of the silica matrix MCM-41 C10 in wide frequency (10(-2)-10(6) Hz) and temperature (130-250 K) ranges. The aim was to elucidate how the formation of large hydrogen bonded structural entities, found in bulk solutions of PGME, was affected by the confined geometry, and to make comparisons with the dynamic behavior of the PG-water system. For all solutions the measurements revealed four almost concentration independent relaxation processes. The intensity of the fastest process is low compared to the other relaxation processes and might be caused by both hydroxyl groups of the pore surfaces and by local motions of water and solute molecules. The second fastest process contains contributions from both the main water relaxation as well as the intrinsic β-relaxation of the solute molecules. The third fastest process is the viscosity related α-relaxation. Its concentration independency is very different compared to the findings for the corresponding bulk systems, particularly for the PGME-water system. The experimental data suggests that the surface interactions induce a micro-phase separation of the two liquids, resulting in a full molecular layer of water molecules coordinating to the hydrophilic hydroxyl groups on the surfaces of the silica pores. This, in turn, increases the geometrical confinement effect for the remaining solution even more and prevents the building up of the same type of larger structural entities in the PGME-water system as in the corresponding bulk solutions. The slowest process is mainly hidden in the high conductivity contribution at low frequencies, but its temperature dependence can be extracted for the PGME-water system. However, its origin is not fully clear, as will be discussed.

Bond strength and microleakage of current dentin adhesives.

PubMed

Fortin, D; Swift, E J; Denehy, G E; Reinhardt, J W

1994-07-01

The purpose of this in vitro study was to evaluate shear bond strengths and microleakage of seven current-generation dentin adhesive systems. Standard box-type Class V cavity preparations were made at the cemento-enamel junction on the buccal surfaces of eighty extracted human molars. These preparations were restored using a microfill composite following application of either All-Bond 2 (Bisco), Clearfil Liner Bond (Kuraray), Gluma 2000 (Miles), Imperva Bond (Shofu), OptiBond (Kerr), Prisma Universal Bond 3 (Caulk), Scotchbond Multi-Purpose (3M), or Scotchbond Dual-Cure (3M) (control). Lingual dentin of these same teeth was exposed and polished to 600-grit. Adhesives were applied and composite was bonded to the dentin using a gelatin capsule technique. Specimens were thermocycled 500 times. Shear bond strengths were determined using a universal testing machine, and microleakage was evaluated using a standard silver nitrate staining technique. Clearfill Liner Bond and OptiBond, adhesive systems that include low-viscosity, low-modulus intermediate resins, had the highest shear bond strengths (13.3 +/- 2.3 MPa and 12.9 +/- 1.5 MPa, respectively). Along with Prisma Universal Bond 3, they also had the least microleakage at dentin margins of Class V restorations. No statistically significant correlation between shear bond strength and microleakage was observed in this study. Adhesive systems that include a low-viscosity intermediate resin produced the high bond strengths and low microleakage. Similarly, two materials with bond strengths in the intermediate range had significantly increased microleakage, and one material with a bond strength in the low end of the spectrum exhibited microleakage that was statistically greater. Thus, despite the lack of statistical correlation, there were observable trends.

Conditions of viscosity measurement for detecting irradiated peppers

NASA Astrophysics Data System (ADS)

Hayashi, Toru; Todoriki, Setsuko; Okadome, Hiroshi; Kohyama, Kaoru

1995-04-01

Viscosity of gelatinized suspensions of black and white peppers decreased depending upon dose. The viscosity was influenced by gelatinization and viscosity measurement conditions. The difference between unirradiated pepper and an irradiated one was larger at a higher pH and temperature for gelatinization. A viscosity parameter normalized with the starch content of pepper sample and the viscosity of a 5% suspension of corn starch could get rid of the influence of the conditions for viscosity measurement such as a type of viscometer, shear rate and temperature.

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2013 CFR

2013-10-01

... viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is unloaded. High viscosity Category C NLS means any Category C NLS having a...

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2014 CFR

2014-10-01

... viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is unloaded. High viscosity Category C NLS means any Category C NLS having a...

Lignin model compounds as bio-based reactive diluents for liquid molding resins.

PubMed

Stanzione, Joseph F; Sadler, Joshua M; La Scala, John J; Wool, Richard P

2012-07-01

Lignin is a copious paper and pulping waste product that has the potential to yield valuable, low molecular weight, single aromatic chemicals when strategically depolymerized. The single aromatic lignin model compounds, vanillin, guaiacol, and eugenol, were methacrylated by esterification with methacrylic anhydride and a catalytic amount of 4-dimethylaminopyridine. Methacrylated guaiacol (MG) and methacrylated eugenol (ME) exhibited low viscosities at room temperature (MG: 17 cP and ME: 28 cP). When used as reactive diluents in vinyl ester resins, they produced resin viscosities higher than that of vinyl ester-styrene blends. The relative volatilities of MG (1.05 wt% loss in 18 h) and ME (0.96 wt% loss in 18 h) measured by means of thermogravimetric analysis (TGA) were considerably lower than that of styrene (93.7 wt% loss in 3 h) indicating the potential of these chemicals to be environmentally friendly reactive diluents. Bulk polymerization of MG and ME generated homopolymers with glass transition temperatures (T(g)s) of 92 and 103 °C, respectively. Blends of a standard vinyl ester resin with MG and ME (50 wt % reactive diluent) produced thermosets with T(g)s of 127 and 153 °C, respectively, which are comparable to vinyl ester-styrene resins, thus demonstrating the ability of MG and ME to completely replace styrene as reactive diluents in liquid molding resins without sacrificing cured-resin thermal performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Approaching a realistic force balance in geodynamo simulations

PubMed Central

Yadav, Rakesh K.; Gastine, Thomas; Christensen, Ulrich R.; Wolk, Scott J.; Poppenhaeger, Katja

2016-01-01

Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints. In typical geodynamo models, viscous and inertial forces are not much smaller than the Coriolis force, and the Lorentz force plays a subdominant role; this has led to conclusions that these simulations are viscously controlled and do not represent the physics of the geodynamo. Here we show, by a direct analysis of the relevant forces, that a MAC balance can be achieved when the viscosity is reduced to values close to the current practical limit. Lorentz force, buoyancy, and the uncompensated (by pressure) part of the Coriolis force are of very similar strength, whereas viscous and inertial forces are smaller by a factor of at least 20 in the bulk of the fluid volume. Compared with nonmagnetic convection at otherwise identical parameters, the dynamo flow is of larger scale and is less invariant parallel to the rotation axis (less geostrophic), and convection transports twice as much heat, all of which is expected when the Lorentz force strongly influences the convection properties. PMID:27790991

Pre-equilibrium dynamics and heavy-ion observables

NASA Astrophysics Data System (ADS)

Heinz, Ulrich; Liu, Jia

2016-12-01

To bracket the importance of the pre-equilibrium stage on relativistic heavy-ion collision observables, we compare simulations where it is modeled by either free-streaming partons or fluid dynamics. These cases implement the assumptions of extremely weak vs. extremely strong coupling in the initial collision stage. Accounting for flow generated in the pre-equilibrium stage, we study the sensitivity of radial, elliptic and triangular flow on the switching time when the hydrodynamic description becomes valid. Using the hybrid code iEBE-VISHNU [C. Shen, Z. Qiu, H. Song, J. Bernhard, S. Bass and U. Heinz, Comput. Phys. Commun. 199 (2016) 61] we perform a multi-parameter search, constrained by particle ratios, integrated elliptic and triangular charged hadron flow, the mean transverse momenta of pions, kaons and protons, and the second moment < pT2 > of the proton transverse momentum spectrum, to identify optimized values for the switching time τs from pre-equilibrium to hydrodynamics, the specific shear viscosity η / s, the normalization factor of the temperature-dependent specific bulk viscosity (ζ / s) (T), and the switching temperature Tsw from viscous hydrodynamics to the hadron cascade UrQMD. With the optimized parameters, we predict and compare with experiment the pT-distributions of π, K, p, Λ, Ξ and Ω yields and their elliptic flow coefficients, focusing specifically on the mass-ordering of the elliptic flow for protons and Lambda hyperons which is incorrectly described by VISHNU without pre-equilibrium flow.

Roles of bulk viscosity on Rayleigh-Taylor instability: Non-equilibrium thermodynamics due to spatio-temporal pressure fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, Tapan K., E-mail: tksen@iitk.ac.in; Bhole, Ashish; Shruti, K. S.

Direct numerical simulations of Rayleigh-Taylor instability (RTI) between two air masses with a temperature difference of 70 K is presented using compressible Navier-Stokes formulation in a non-equilibrium thermodynamic framework. The two-dimensional flow is studied in an isolated box with non-periodic walls in both vertical and horizontal directions. The non-conducting interface separating the two air masses is impulsively removed at t = 0 (depicting a heaviside function). No external perturbation has been used at the interface to instigate the instability at the onset. Computations have been carried out for rectangular and square cross sections. The formulation is free of Boussinesq approximationmore » commonly used in many Navier-Stokes formulations for RTI. Effect of Stokes’ hypothesis is quantified, by using models from acoustic attenuation measurement for the second coefficient of viscosity from two experiments. Effects of Stokes’ hypothesis on growth of mixing layer and evolution of total entropy for the Rayleigh-Taylor system are reported. The initial rate of growth is observed to be independent of Stokes’ hypothesis and the geometry of the box. Following this stage, growth rate is dependent on the geometry of the box and is sensitive to the model used. As a consequence of compressible formulation, we capture pressure wave-packets with associated reflection and rarefaction from the non-periodic walls. The pattern and frequency of reflections of pressure waves noted specifically at the initial stages are reflected in entropy variation of the system.« less

Microscale Characterization of the Viscoelastic Properties of Hydrogel Biomaterials using Dual-Mode Ultrasound Elastography

PubMed Central

Hong, Xiaowei; Stegemann, Jan P.; Deng, Cheri X.

2016-01-01

Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger’s viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. PMID:26928595

SLIME: scattering labeled imaging of microvasculature in excised tissues using OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liu, Yehe; Gu, Shi; Watanabe, Michiko; Rollins, Andrew M.; Jenkins, Michael W.

2017-02-01

Abnormal coronary development causes various health problems. However, coronary development remains one of the highly neglected areas in developmental cardiology due to limited technology. Currently, there is not a robust method available to map the microvasculature throughout the entire embryonic heart in 3D. This is a challenging task because it requires both micron level resolution over a large field of view and sufficient imaging depth. Speckle-variance optical coherence tomography (OCT) has reasonable resolution for coronary vessel mapping, but limited penetration depth and sensitivity to bulk motion made it impossible to apply this method to late-stage beating hearts. Some success has been achieved with coronary dye perfusion, but smaller vessels are not efficiently stained and penetration depth is still an issue. To address this problem, we present an OCT imaging procedure using optical clearing and a contrast agent (titanium dioxide) that enables 3D mapping of the coronary microvasculature in developing embryonic hearts. In brief, the hearts of stage 36 quail embryos were perfused with a low viscosity mixture of polyvinyl acetate (PVA) and titanium dioxide through the aorta using micropipette injection. After perfusion, the viscosity of the solution was increased by crosslinking the PVA polymer chains with borate ions. The tissue was then optically cleared. The titanium dioxide particles remaining in the coronaries provided a strong OCT signal, while the rest of the cardiac structures became relatively transparent. Using this technique, we are able to investigate coronary morphologies in different disease models.

Compaction and Crystallisation in Magma Chambers: Towards a Model of the Skaergaard Intrusion

NASA Astrophysics Data System (ADS)

McKenzie, D. P.

2010-12-01

The equations governing the conservation of mass, momentum and energy are first simplified by using the extended Boussinesq approximation, and then solved numerically to study the time dependent behaviour of a compacting solidifying layer at the base of a magma chamber when variations in the horizontal plane can be neglected. The most important result is that the concept of a trapped liquid fraction, which has been widely used to model the bulk composition of layered intrusions, is a useful concept to describe the steady state behaviour of compacting layers. The result is at first sight surprising, because there is relative movement between the melt and crystals during compaction, and the system is therefore open. The reason why it is correct is because both the melt and the crystals are moving downwards in a frame fixed to the upper surface of the compacting layer. Since the mass of all elements must be conserved, what goes into the top of the layer as melt and solid must come out of its bottom as a solid when the behaviour is not time dependent. However, when time dependent behaviour occurs the concept of a trapped liquid fraction ceases to be useful. The governing equations are then used to model the concentration of phosphorous in the lower part of the Skaergaard intrusion, where it behaves incompatibly. The observed behaviour requires the viscosity of the solid part of the compacting layer to have a viscosity of about 10^18 Pa s.

Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography.

PubMed

Hong, Xiaowei; Stegemann, Jan P; Deng, Cheri X

2016-05-01

Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger's viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Anomalously large bend elastic constant and faster electro-optic response in anisotropic gels formed by a dipeptide

NASA Astrophysics Data System (ADS)

Bhargavi, R.; Nair, Geetha G.; Prasad, S. Krishna; Prabhu, Rashmi; Yelamaggad, C. V.

2011-04-01

We report rheological, static, and dynamic Freedericksz transformation measurements on an anisotropic thermoreversible gel formed by gelation of a nematic liquid crystal (NLC) with a monodisperse dipeptide. The storage and loss modulii obtained from a low strain oscillatory shear experiment display that the material forms a weak anisotropic gel, and undergoes a sharp thermal transition to an anisotropic sol state. Freedericksz transformation studies employing an electric field for the reorientation of the molecules present a surprising result: the gel possesses a very large Frank bend elastic constant value, which is orders of magnitude higher than that for the high temperature sol state as well as that for the neat NLC used. On the other hand, the splay elastic constant shows relatively a small increase. Further, these elastic constants show systematic but nonlinear variation with the concentration of the gelator. Attractive features of the electro-optic switching when the sol transforms to the gel state are the vanishing of the undesirable backflow effect, and nearly an order of magnitude decrease in the switching speed. In both the gel and sol states the extracted rotational viscosities are comparable to the values of the neat NLC at corresponding temperatures. In contrast, the bulk dynamic viscosity is more than three orders of magnitude higher in the gel. The studies also demonstrate that the anisotropic gel to anisotropic sol transition seen in this weak gel can be tracked by simply monitoring the static or the dynamic Freedericksz transformation.

Constraints on the rheology of the partially molten mantle from numerical models of laboratory experiments

NASA Astrophysics Data System (ADS)

Rudge, J. F.; Alisic Jewell, L.; Rhebergen, S.; Katz, R. F.; Wells, G. N.

2015-12-01

One of the fundamental components in any dynamical model of melt transport is the rheology of partially molten rock. This rheology is poorly understood, and one way in which a better understanding can be obtained is by comparing the results of laboratory deformation experiments to numerical models. Here we present a comparison between numerical models and the laboratory setup of Qi et al. 2013 (EPSL), where a cylinder of partially molten rock containing rigid spherical inclusions was placed under torsion. We have replicated this setup in a finite element model which solves the partial differential equations describing the mechanical process of compaction. These computationally-demanding 3D simulations are only possible due to the recent development of a new preconditioning method for the equations of magma dynamics. The experiments show a distinct pattern of melt-rich and melt-depleted regions around the inclusions. In our numerical models, the pattern of melt varies with key rheological parameters, such as the ratio of bulk to shear viscosity, and the porosity- and strain-rate-dependence of the shear viscosity. These observed melt patterns therefore have the potential to constrain rheological properties. While there are many similarities between the experiments and the numerical models, there are also important differences, which highlight the need for better models of the physics of two-phase mantle/magma dynamics. In particular, the laboratory experiments display more pervasive melt-rich bands than is seen in our numerics.

Temperature effects on the universal equation of state of solids

NASA Technical Reports Server (NTRS)

Vinet, P.; Ferrante, J.; Smith, J. R.; Rose, J. H.

1986-01-01

Recently it has been argued based on theoretical calculations and experimental data that there is a universal form for the equation of state of solids. This observation was restricted to the range of temperatures and pressures such that there are no phase transitions. The use of this universal relation to estimate pressure-volume relations (i.e., isotherms) required three input parameters at each fixed temperature. It is shown that for many solids the input data needed to predict high temperature thermodynamical properties can be dramatically reduced. In particular, only four numbers are needed: (1) the zero pressure (P=0) isothermal bulk modulus; (2)it P=0 pressure derivative; (3) the P=0 volume; and (4) the P=0 thermal expansion; all evaluated at a single (reference) temperature. Explicit predictions are made for the high temperature isotherms, the thermal expansion as a function of temperature, and the temperature variation of the isothermal bulk modulus and its pressure derivative. These predictions are tested using experimental data for three representative solids: gold, sodium chloride, and xenon. Good agreement between theory and experiment is found.

Temperature effects on the universal equation of state of solids

NASA Technical Reports Server (NTRS)

Vinet, Pascal; Ferrante, John; Smith, John R.; Rose, James H.

1987-01-01

Recently it has been argued based on theoretical calculations and experimental data that there is a universal form for the equation of state of solids. This observation was restricted to the range of temperatures and pressures such that there are no phase transitions. The use of this universal relation to estimate pressure-volume relations (i.e., isotherms) required three input parameters at each fixed temperature. It is shown that for many solids the input data needed to predict high temperature thermodynamical properties can be dramatically reduced. In particular, only four numbers are needed: (1) the zero pressure (P = 0) isothermal bulk modulus; (2) its P = 0 pressure derivative; (3) the P = 0 volume; and (4) the P = 0 thermal expansion; all evaluated at a single (reference) temperature. Explicit predictions are made for the high temperature isotherms, the thermal expansion as a function of temperature, and the temperature variation of the isothermal bulk modulus and its pressure derivative. These predictions are tested using experimental data for three representative solids: gold, sodium chloride, and xenon. Good agreement between theory and experiment is found.

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

PubMed Central

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2017-01-01

A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte. PMID:27715110

An accurate estimation method of kinematic viscosity for standard viscosity liquids

NASA Astrophysics Data System (ADS)

Kurano, Y.; Kobayashi, H.; Yoshida, K.; Imai, H.

1992-07-01

Deming's method of least squares is introduced to make an accurate kinematic viscosity estimation for a series of 13 standard-viscosity liquids at any desired temperature. The empirical ASTM kinematic viscosity-temperature equation is represented in the form loglog( v+c)=a-b log T, where v (in mm2. s-1) is the kinematic viscosity at temperature T (in K), a and b are the constants for a given liquid, and c has a variable value. In the present application, however, c is assumed to have a constant value for each standard-viscosity liquid, as do a and b in the ASTM equation. This assumption has since been verified experimentally for all standard-viscosity liquids. The kinematic viscosities for the 13 standard-viscosity liquids have been measured with a high accuracy in the temperature range of 20 40°C using a series of the NRLM capillary master viscometers with an automatic flow time detection system. The deviations between measured and estimated kinematic viscosities were less than ±0.04% for the 10 standard-viscosity liquids JS2.5 to JS2000 and ±0.11% for the 3 standard-viscosity liquids JS15H to JS200H, respectively. From the above investigation, it was revealed that the uncertainty in the present estimation method is less than one-third that in the usual ASTM method.

Blood viscosity monitoring during cardiopulmonary bypass based on pressure-flow characteristics of a Newtonian fluid.

PubMed

Okahara, Shigeyuki; Zu Soh; Takahashi, Shinya; Sueda, Taijiro; Tsuji, Toshio

2016-08-01

We proposed a blood viscosity estimation method based on pressure-flow characteristics of oxygenators used during cardiopulmonary bypass (CPB) in a previous study that showed the estimated viscosity to correlate well with the measured viscosity. However, the determination of the parameters included in the method required the use of blood, thereby leading to high cost of calibration. Therefore, in this study we propose a new method to monitor blood viscosity, which approximates the pressure-flow characteristics of blood considered as a non-Newtonian fluid with characteristics of a Newtonian fluid by using the parameters derived from glycerin solution to enable ease of acquisition. Because parameters used in the estimation method are based on fluid types, bovine blood parameters were used to calculate estimated viscosity (ηe), and glycerin parameters were used to estimate deemed viscosity (ηdeem). Three samples of whole bovine blood with different hematocrit levels (21.8%, 31.0%, and 39.8%) were prepared and perfused into the oxygenator. As the temperature changed from 37 °C to 27 °C, the oxygenator mean inlet pressure and outlet pressure were recorded for flows of 2 L/min and 4 L/min, and the viscosity was estimated. The value of deemed viscosity calculated with the glycerin parameters was lower than estimated viscosity calculated with bovine blood parameters by 20-33% at 21.8% hematocrit, 12-27% at 31.0% hematocrit, and 10-15% at 39.8% hematocrit. Furthermore, deemed viscosity was lower than estimated viscosity by 10-30% at 2 L/min and 30-40% at 4 L/min. Nevertheless, estimated and deemed viscosities varied with a similar slope. Therefore, this shows that deemed viscosity achieved using glycerin parameters may be capable of successfully monitoring relative viscosity changes of blood in a perfusing oxygenator.

Dynamics of flexible fibers and vesicles in Poiseuille flow at low Reynolds number.

PubMed

Farutin, Alexander; Piasecki, Tomasz; Słowicka, Agnieszka M; Misbah, Chaouqi; Wajnryb, Eligiusz; Ekiel-Jeżewska, Maria L

2016-09-21

The dynamics of flexible fibers and vesicles in unbounded planar Poiseuille flow at low Reynolds number is shown to exhibit similar basic features, when their equilibrium (moderate) aspect ratio is the same and vesicle viscosity contrast is relatively high. Tumbling, lateral migration, accumulation and shape evolution of these two types of flexible objects are analyzed numerically. The linear dependence of the accumulation position on relative bending rigidity, and other universal scalings are derived from the local shear flow approximation.

Quantitatively Mapping Cellular Viscosity with Detailed Organelle Information via a Designed PET Fluorescent Probe

PubMed Central

Liu, Tianyu; Liu, Xiaogang; Spring, David R.; Qian, Xuhong; Cui, Jingnan; Xu, Zhaochao

2014-01-01

Viscosity is a fundamental physical parameter that influences diffusion in biological processes. The distribution of intracellular viscosity is highly heterogeneous, and it is challenging to obtain a full map of cellular viscosity with detailed organelle information. In this work, we report 1 as the first fluorescent viscosity probe which is able to quantitatively map cellular viscosity with detailed organelle information based on the PET mechanism. This probe exhibited a significant ratiometric fluorescence intensity enhancement as solvent viscosity increases. The emission intensity increase was attributed to combined effects of the inhibition of PET due to restricted conformational access (favorable for FRET, but not for PET), and the decreased PET efficiency caused by viscosity-dependent twisted intramolecular charge transfer (TICT). A full map of subcellular viscosity was successfully constructed via fluorescent ratiometric detection and fluorescence lifetime imaging; it was found that lysosomal regions in a cell possess the highest viscosity, followed by mitochondrial regions. PMID:24957323

Inference of mantle viscosity for depth resolutions of GIA observations

NASA Astrophysics Data System (ADS)

Nakada, Masao; Okuno, Jun'ichi

2016-11-01

Inference of the mantle viscosity from observations for glacial isostatic adjustment (GIA) process has usually been conducted through the analyses based on the simple three-layer viscosity model characterized by lithospheric thickness, upper- and lower-mantle viscosities. Here, we examine the viscosity structures for the simple three-layer viscosity model and also for the two-layer lower-mantle viscosity model defined by viscosities of η670,D (670-D km depth) and ηD,2891 (D-2891 km depth) with D-values of 1191, 1691 and 2191 km. The upper-mantle rheological parameters for the two-layer lower-mantle viscosity model are the same as those for the simple three-layer one. For the simple three-layer viscosity model, rate of change of degree-two zonal harmonics of geopotential due to GIA process (GIA-induced J˙2) of -(6.0-6.5) × 10-11 yr-1 provides two permissible viscosity solutions for the lower mantle, (7-20) × 1021 and (5-9) × 1022 Pa s, and the analyses with observational constraints of the J˙2 and Last Glacial Maximum (LGM) sea levels at Barbados and Bonaparte Gulf indicate (5-9) × 1022 Pa s for the lower mantle. However, the analyses for the J˙2 based on the two-layer lower-mantle viscosity model only require a viscosity layer higher than (5-10) × 1021 Pa s for a depth above the core-mantle boundary (CMB), in which the value of (5-10) × 1021 Pa s corresponds to the solution of (7-20) × 1021 Pa s for the simple three-layer one. Moreover, the analyses with the J˙2 and LGM sea level constraints for the two-layer lower-mantle viscosity model indicate two viscosity solutions: η670,1191 > 3 × 1021 and η1191,2891 ˜ (5-10) × 1022 Pa s, and η670,1691 > 1022 and η1691,2891 ˜ (5-10) × 1022 Pa s. The inferred upper-mantle viscosity for such solutions is (1-4) × 1020 Pa s similar to the estimate for the simple three-layer viscosity model. That is, these analyses require a high viscosity layer of (5-10) × 1022 Pa s at least in the deep mantle, and suggest that the GIA-based lower-mantle viscosity structure should be treated carefully in discussing the mantle dynamics related to the viscosity jump at ˜670 km depth. We also preliminarily put additional constraints on these viscosity solutions by examining typical relative sea level (RSL) changes used to infer the lower-mantle viscosity. The viscosity solution inferred from the far-field RSL changes in the Australian region is consistent with those for the J˙2 and LGM sea levels, and the analyses for RSL changes at Southport and Bermuda in the intermediate region for the North American ice sheets suggest the solution of η670,D > 1022, ηD,2891 ˜ (5-10) × 1022 Pa s (D = 1191 or 1691 km) and upper-mantle viscosity higher than 6 × 1020 Pa s.

Resolving ultrafast exciton migration in organic solids at the nanoscale

NASA Astrophysics Data System (ADS)

Ginsberg, Naomi

The migration of Frenkel excitons, tightly-bound electron-hole pairs, in photosynthesis and in organic semiconducting films is critical to the efficiency of natural and artificial light harvesting. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton migration lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore. By combining the ultrafast super-resolved measurements with exciton hopping simulations we furthermore specify the nature (in addition to the extent) of exciton migration as a function of the intrinsic and ensemble chromophore energy scales that determine a spatio-energetic landscape for migration. In collaboration with: Samuel Penwell, Lucas Ginsberg, University of California, Berkeley and Rodrigo Noriega University of Utah.

Effect of bulk Lorentz violation on anisotropic brane cosmologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heydari-Fard, Malihe, E-mail: heydarifard@qom.ac.ir

2012-04-01

The effect of Lorentz invariance violation in cosmology has attracted a considerable amount of attention. By using a dynamical vector field assumed to point in the bulk direction, with Lorentz invariance holding on the brane, we extend the notation of Lorentz violation in four dimensions Jacobson to a five-dimensional brane-world. We obtain the general solution of the field equations in an exact parametric form for Bianchi type I space-time, with perfect fluid as a matter source. We show that the brane universe evolves from an isotropic/anisotropic state to an isotropic de Sitter inflationary phase at late time. The early timemore » behavior of anisotropic brane universe is largely dependent on the Lorentz violating parameters β{sub i},i = 1,2,3 and the equation of state of the matter, while its late time behavior is independent of these parameters.« less

40 CFR 60.562-1 - Standards: Process emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... viscosity product is being produced using single or multiple end finishers or a high viscosity product is...-jet ejectors are used as vacuum producers and a high viscosity product is being produced using... low viscosity product is being produced using single or multiple end finishers or a high viscosity...

40 CFR 60.562-1 - Standards: Process emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... viscosity product is being produced using single or multiple end finishers or a high viscosity product is...-jet ejectors are used as vacuum producers and a high viscosity product is being produced using... low viscosity product is being produced using single or multiple end finishers or a high viscosity...

A Simple BODIPY-Based Viscosity Probe for Imaging of Cellular Viscosity in Live Cells

PubMed Central

Su, Dongdong; Teoh, Chai Lean; Gao, Nengyue; Xu, Qing-Hua; Chang, Young-Tae

2016-01-01

Intracellular viscosity is a fundamental physical parameter that indicates the functioning of cells. In this work, we developed a simple boron-dipyrromethene (BODIPY)-based probe, BTV, for cellular mitochondria viscosity imaging by coupling a simple BODIPY rotor with a mitochondria-targeting unit. The BTV exhibited a significant fluorescence intensity enhancement of more than 100-fold as the solvent viscosity increased. Also, the probe showed a direct linear relationship between the fluorescence lifetime and the media viscosity, which makes it possible to trace the change of the medium viscosity. Furthermore, it was demonstrated that BTV could achieve practical applicability in the monitoring of mitochondrial viscosity changes in live cells through fluorescence lifetime imaging microscopy (FLIM). PMID:27589762

A Simple BODIPY-Based Viscosity Probe for Imaging of Cellular Viscosity in Live Cells.

PubMed

Su, Dongdong; Teoh, Chai Lean; Gao, Nengyue; Xu, Qing-Hua; Chang, Young-Tae

2016-08-31

Intracellular viscosity is a fundamental physical parameter that indicates the functioning of cells. In this work, we developed a simple boron-dipyrromethene (BODIPY)-based probe, BTV, for cellular mitochondria viscosity imaging by coupling a simple BODIPY rotor with a mitochondria-targeting unit. The BTV exhibited a significant fluorescence intensity enhancement of more than 100-fold as the solvent viscosity increased. Also, the probe showed a direct linear relationship between the fluorescence lifetime and the media viscosity, which makes it possible to trace the change of the medium viscosity. Furthermore, it was demonstrated that BTV could achieve practical applicability in the monitoring of mitochondrial viscosity changes in live cells through fluorescence lifetime imaging microscopy (FLIM).

Superparamagnetic nanoparticle-based viscosity test

NASA Astrophysics Data System (ADS)

Wu, Kai; Liu, Jinming; Wang, Yi; Ye, Clark; Feng, Yinglong; Wang, Jian-Ping

2015-08-01

Hyperviscosity syndrome is triggered by high blood viscosity in the human body. This syndrome can result in retinopathy, vertigo, coma, and other unanticipated complications. Serum viscosity is one of the important factors affecting whole blood viscosity, which is regarded as an indicator of general health. In this letter, we propose and demonstrate a Brownian relaxation-based mixing frequency method to test human serum viscosity. This method uses excitatory and detection coils and Brownian relaxation-dominated superparamagnetic nanoparticles, which are sensitive to variables of the liquid environment such as viscosity and temperature. We collect the harmonic signals produced by magnetic nanoparticles and estimate the viscosity of unknown solutions by comparison to the calibration curves. An in vitro human serum viscosity test is performed in less than 1.5 min.

Scientific Objectives of the Critical Viscosity Experiment

NASA Technical Reports Server (NTRS)

Berg, R. F.; Moldover, M. R.

1993-01-01

In microgravity, the Critical Viscosity Experiment will measure the viscosity of xenon 15 times closer to the critical point than is possible on earth. The results are expected to include the first direct observation of the predicted power-law divergence of viscosity in a pure fluid and they will test calculations of the value of the exponent associated with the divergence. The results, when combined with Zeno's decay-rate data, will strengthen the test of mode coupling theory. Without microgravity viscosity data, the Zeno test will require an extrapolation of existing 1-g viscosity data by as much as factor of 100 in reduced temperature. By necessity, the extrapolation would use an incompletely verified theory of viscosity crossover. With the microgravity viscosity data, the reliance on crossover models will be negligible allowing a more reliable extrapolation. During the past year, new theoretical calculations for the viscosity exponent finally achieved consistency with the best experimental data for pure fluids. This report gives the justification for the proposed microgravity Critical Viscosity Experiment in this new context. This report also combines for the first time the best available light scattering data with our recent viscosity data to demonstrate the current status of tests of mode coupling theory.

Effect of Qingnao tablet on blood viscosity of rat model of blood stasis induced by epinephrine

NASA Astrophysics Data System (ADS)

Xie, Guoqi; Hao, Shaojun; Ma, Zhenzhen; Liu, Xiaobin; Li, Jun; Li, Wenjun; Zhang, Zhengchen

2018-04-01

To establish a rat model of blood stasis with adrenaline (Adr) subcutaneous injection and ice bath stimulation. The effects of different doses on the blood viscosity of blood stasis model rats were observed. The rats were randomly divided into 6 groups: blank control group (no model), model group, positive control group, high, middle and low dose group. The whole blood viscosity and plasma viscosity were detected by blood viscosity instrument. Compared with the blank group, model group, high shear, low shear whole blood viscosity and plasma viscosity were significantly increased, TT PT significantly shortened, APTT was significantly prolonged, FIB increased significantly, indicating that the model was successful. Compared with the model group, can significantly reduce the Naoluotong group (cut, low cut). Qingnaopian high dose group (low cut), middle dose group (cut, low shear blood viscosity) (P<0.01), Can significantly reduce Naoluotong qingnaopian group, high dose group (P<0.01), plasma viscosity decreased qingnaopian plasma viscosity in low dose group (P<0.05). Conclusion: qingnaopian could improve the blood rheology of blood stasis mice abnormal index, decrease the blood viscosity, blood stasis has certain hemostatic effect.