Search results for "VISCOSITY"
showing 10 items of 542 documents
Convergence of a high-order compact finite difference scheme for a nonlinear Black-Scholes equation
2004
A high-order compact finite difference scheme for a fully nonlinear parabolic differential equation is analyzed. The equation arises in the modeling of option prices in financial markets with transaction costs. It is shown that the finite difference solution converges locally uniformly to the unique viscosity solution of the continuous equation. The proof is based on a careful study of the discretization matrices and on an abstract convergence result due to Barles and Souganides.
Designing robust immediate release tablet formulations avoiding food effects for BCS class 3 drugs
2019
Abstract Food induced viscosity in the gastrointestinal tract is reported to reduce the bioavailability of tablets containing BCS class 3 drugs, mainly by retarding their disintegration and dissolution of the active pharmaceutical ingredient. The role of formulation factors in minimizing this negative food effect is largely unknown. Combinations of disintegrants were studied together with soluble and insoluble fillers and trospium chloride as model drug substance. Different batches of tablets were compressed at 10 kN and 30 kN, by incorporating different combinations of croscarmellose sodium (CSS), cross-linked (CPD) and sodium starch glycolate (SSG) at low level i.e, 2% + 2% and high level…
A first estimate of $\eta/s$ in Au+Au reactions at E$_{\rm lab}=1.23$ $A$GeV
2020
The HADES experiment at GSI has recently provided data on the flow coefficients $v_1,...,v_4$ for protons in Au+Au reactions at $E_{\rm lab} = 1.23$~$A$GeV (or $\sqrt{s_\mathrm{NN}}=2.4$ GeV). This data allows to estimate the shear viscosity over entropy ratio, $\eta/s$ at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of $\eta/s\approx0.65\pm0.15$ (or $(8\pm2)\,(4\pi)^{-1}$) at such low energies.
Pinning down QCD-matter shear viscosity in A + A collisions via EbyE fluctuations using pQCD + saturation + hydrodynamics
2015
We compute the initial energy densities produced in ultrarelativistic heavy-ion collisions from NLO perturbative QCD using a saturation conjecture to control soft particle production, and describe the subsequent space-time evolution of the system with hydrodynamics, event by event. The resulting centrality dependence of the low-$p_T$ observables from this pQCD + saturation + hydro ("EKRT") framework are then compared simultaneously to the LHC and RHIC measurements. With such an analysis we can test the initial state calculation, and constrain the temperature dependence of the shear viscosity-to-entropy ratio $\eta/s$ of QCD matter. Using these constraints from the current RHIC and LHC measu…
Zero-field nuclear magnetic resonance spectroscopy of viscous liquids
2014
Abstract We report zero-field NMR measurements of a viscous organic liquid, ethylene glycol. Zero-field spectra were taken showing resolved scalar spin–spin coupling (J-coupling) for ethylene glycol at different temperatures and water contents. Molecular dynamics strongly affects the resonance linewidth, which closely follows viscosity. Quantum chemical calculations have been used to obtain the relative stability and coupling constants of all ethylene glycol conformers. The results show the potential of zero-field NMR as a probe of molecular structure and dynamics in a wide range of environments, including viscous fluids.
Fractional characteristic times and dissipated energy in fractional linear viscoelasticity
2016
Abstract In fractional viscoelasticity the stress–strain relation is a differential equation with non-integer operators (derivative or integral). Such constitutive law is able to describe the mechanical behavior of several materials, but when fractional operators appear, the elastic and the viscous contribution are inseparable and the characteristic times (relaxation and retardation time) cannot be defined. This paper aims to provide an approach to separate the elastic and the viscous phase in the fractional stress–strain relation with the aid of an equivalent classical model (Kelvin–Voigt or Maxwell). For such equivalent model the parameters are selected by an optimization procedure. Once …
Molar masses and structure in solution of haemoglobin hyperpolymers--a common calibration of size exclusion chromatography of these artificial oxygen…
1997
We are developing artificial oxygen carriers for medical use, based on synthetic polymers--so-called hyperpolymers--obtained by cross-linking mammalian haemoglobins. One requirement with respect to the polymers is that they should not increase the oncotic pressure of blood remarkably--this can be realized by high molecular weights of the polymers with a narrow distribution. They may act as a oxygen transporting blood additive, and--in combination with a plasma expander--as a blood substitute. Another important and desired property of the artificial oxygen carrier is a low viscosity, which--first--is due to a high degree of uniformity of the polymer size (or molar mass) distribution and--sec…
Event-by-event fluctuations in a perturbative QCD plus saturation plus hydrodynamics model : Determining QCD matter shear viscosity in ultrarelativis…
2016
We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading-order perturbative QCD using a saturation conjecture to control soft-particle production and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries against the LHC and RHIC measurements. We compare also the computed event-by-event probability distribut…
Liquid viscosity and flow rate effects on interfacial area in packed columns
1989
Abstract The influences of liquid kinematic viscosity and liquid flow rate on effective interfacial area for chemical absorption in a Raschig ring packed column were studied by absorbing carbon dioxide into potassium carbonate-bicarbonate-arsenite solutions. The viscosities of the absorbing liquid were varied by the addition of sugar. Analysis of the data shows that an increase in liquid flow rate increases the effective interfacial area over the whole viscosity range considered. The influence of liquid viscosity is more complex as the interfacial area increases with viscosity for low values, while decreasing at higher viscosities. Two correlations have been developed to express this behavi…
Clinical disorders responsible for plasma hyperviscosity and skin complications
2017
In this brief review, we have examined some clinical disorders which are associated to an altered hemorheological profile and at times accompanied by skin ulcers. This skin condition may be, in fact, observed in patients with primary plasma hyperviscosity such as multiple myeloma, Waldenstrom macroglobulinemia, cryoglobulinemia, cryofibrinogenemia, dysfibrinogenemia and connective tissue diseases. It must be underlined that the altered hemorheological pattern is not the only responsible for this skin complication but, as it worsens the microcirculatory flow, it contributes to determine the occurrence of the skin ulcers.