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Sample records for adhesion model burgers

  1. Discrete Element Simulation of Asphalt Mastics Based on Burgers Model

    LIU Yu; FENG Shi-rong; HU Xia-guang

    2007-01-01

    In order to investigate the viscoelastic performance of asphalt mastics, a micro-mechanical model for asphalt mastics was built by applying Burgers model to discrete element simulation and constructing Burgers contact model. Then the numerical simulation of creep tests was conducted, and results from the simulation were compared with the analytical solution for Burgers model. The comparision snowed that the two results agreed well with each other, suggesting that discrete element model based on Burgers model could be employed in the numerical simulation for asphalt mastics.

  2. Burgers Turbulence

    Bec, Jeremie; Khanin, Konstantin

    2007-01-01

    The last decades witnessed a renewal of interest in the Burgers equation. Much activities focused on extensions of the original one-dimensional pressureless model introduced in the thirties by the Dutch scientist J.M. Burgers, and more precisely on the problem of Burgers turbulence, that is the study of the solutions to the one- or multi-dimensional Burgers equation with random initial conditions or random forcing. Such work was frequently motivated by new emerging applications of Burgers mod...

  3. Burgers turbulence

    The last decades witnessed a renewal of interest in the Burgers equation. Much activities focused on extensions of the original one-dimensional pressureless model introduced in the thirties by the Dutch scientist J.M. Burgers, and more precisely on the problem of Burgers turbulence, that is the study of the solutions to the one- or multi-dimensional Burgers equation with random initial conditions or random forcing. Such work was frequently motivated by new emerging applications of Burgers model to statistical physics, cosmology, and fluid dynamics. Also Burgers turbulence appeared as one of the simplest instances of a nonlinear system out of equilibrium. The study of random Lagrangian systems, of stochastic partial differential equations and their invariant measures, the theory of dynamical systems, the applications of field theory to the understanding of dissipative anomalies and of multiscaling in hydrodynamic turbulence have benefited significantly from progress in Burgers turbulence. The aim of this review is to give a unified view of selected work stemming from these rather diverse disciplines

  4. The decay of multiscale signals deterministic model of the Burgers turbulence

    Gurbatov, S N

    2000-01-01

    This work is devoted to the study of the decay of multiscale deterministicsolutions of the unforced Burgers' equation in the limit of vanishingviscosity. A deterministic model of turbulence-like evolution is considered. We con-struct the initial perturbation as a piecewise linear analog of the Weierstrassfunction. The wavenumbers of this function form a "Weierstrass spectrum", whichaccumulates at the origin in geometric progression."Reverse" sawtooth functionswith negative initial slope are used in this series as basic functions, whiletheir amplitudes are chosen by the condition that the distribution of energyover exponential intervals of wavenumbers is the same as for the continuousspectrum in Burgers turbulence. Combining these two ideas allows us to obtainan exact analytical solution for the velocity field. We also notice that suchmultiscale waves may be constructed for multidimensional Burgers' equation. This solution has scaling exponent h=-(1+n)/2 and its evolution in time isself-similar with logarithmi...

  5. Mathematical modeling and exact solutions to rotating flows of a Burgers' fluid

    The aim of this study is to provide the modeling and exact analytic solutions for hydromagnetic oscillatory rotating flows of an incompressible Burgers' fluid bounded by a plate. The governing time-dependent equation for the Burgers' fluid is different than those from the Navier-Stokes' equation. The entire system is assumed to rotate around an axis normal to the plate. The governing equations for this investigation are solved analytically for two physical problems. The solutions for the three cases, when the two times angular velocity is greater than the frequency of oscillation or it is smaller than the frequency or it is equal to the frequency (resonant case), are discussed in second problem. In Burgers' fluid, it is also found that hydromagnetic solution in the resonant case satisfies the boundary condition at infinity. Moreover, the obtained analytical results reduce to several previously published results as the special cases. (author)

  6. Burger Jihad

    Rytter, Mikkel

    2016-01-01

    Based on a number of ‘burger episodes’ during ten days of itikaf at a Sufi lodge in Pakistan, this article discusses the difficulties of religious self-cultivation among young Muslim pilgrims from Denmark. The focus on food and eating is not only used to discuss how religious brotherhoods and...

  7. Fractional modelling for BBM-Burger equation by using new homotopy analysis transform method

    Sunil Kumar

    2014-10-01

    Full Text Available The purpose of this study is to introduce a new analytical method namely, fractional homotopy analysis transform method (FHATM for series solution of the time fractional BBM-Burger equation. The homotopy analysis transform method is an innovative adjustment in Laplace transform algorithm (LTA for nonlinear fractional partial differential equation in fluid dynamics and makes the calculation much simpler. The proposed scheme finds the solutions of nonlinear problems without any discretization, restrictive assumptions and avoids the rounding off errors. The numerical solutions obtained by the proposed method indicate that the approach is easy to implement and computationally very attractive.

  8. Analytical solutions for wall slip effects on magnetohydrodynamic oscillatory rotating plate and channel flows in porous media using a fractional Burgers viscoelastic model

    Maqbool, Khadija; Anwar Bég, O.; Sohail, Ayesha; Idreesa, Shafaq

    2016-05-01

    The theoretical analysis of magnetohydrodynamic (MHD) incompressible flows of a Burgers fluid through a porous medium in a rotating frame of reference is presented. The constitutive model of a Burgers fluid is used based on a fractional calculus formulation. Hydrodynamic slip at the wall (plate) is incorporated and the fractional generalized Darcy model deployed to simulate porous medium drag force effects. Three different cases are considered: namely, the flow induced by a general periodic oscillation at a rigid plate, the periodic flow in a parallel plate channel and, finally, the Poiseuille flow. In all cases the plate(s) boundary(ies) are electrically non-conducting and a small magnetic Reynolds number is assumed, negating magnetic induction effects. The well-posed boundary value problems associated with each case are solved via Fourier transforms. Comparisons are made between the results derived with and without slip conditions. Four special cases are retrieved from the general fractional Burgers model, viz. Newtonian fluid, general Maxwell viscoelastic fluid, generalized Oldroyd-B fluid and the conventional Burgers viscoelastic model. Extensive interpretation of graphical plots is included. We study explicitly the influence of the wall slip on primary and secondary velocity evolution. The model is relevant to MHD rotating energy generators employing rheological working fluids.

  9. Exact Solutions of a Coupled Burgers System

    HUANG Ling

    2006-01-01

    The exact solutions of a new coupled Burgers system are studied in three different ways. The first type of solutions are found thanks to the coupled Burgers system possessing a simple single Burgers reduction. The second type of multiple soliton solutions are revealed via the decouple procedure. The third type of exact solutions are found by means of a prior ansatz and solutions of the heat conduction equation. Two different kinds of soliton fission phenomena of the model are discovered and a special type of completely elastic soliton collision without phase shift of the model is also displayed.

  10. The inviscid, compressible and rotational, 2D isotropic Burgers and pressureless Euler-Coriolis fluids: Solvable models with illustrations

    Choquard, Ph.; Vuffray, M.

    2014-10-01

    The coupling between dilatation and vorticity, two coexisting and fundamental processes in fluid dynamics (Wu et al., 2006, pp. 3, 6) is investigated here, in the simplest cases of inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids respectively modeled by single vortices confined in compressible, local, inertial and global, rotating, environments. The field equations are established, inductively, starting from the equations of the characteristics solved with an initial Helmholtz decomposition of the velocity fields namely a vorticity free and a divergence free part (Wu et al., 2006, Sects. 2.3.2, 2.3.3) and, deductively, by means of a canonical Hamiltonian Clebsch like formalism (Clebsch, 1857, 1859), implying two pairs of conjugate variables. Two vector valued fields are constants of the motion: the velocity field in the Burgers case and the momentum field per unit mass in the Euler-Coriolis one. Taking advantage of this property, a class of solutions for the mass densities of the fluids is given by the Jacobian of their sum with respect to the actual coordinates. Implementation of the isotropy hypothesis entails a radial dependence of the velocity potentials and of the stream functions associated to the compressible and to the rotational part of the fluids and results in the cancellation of the dilatation-rotational cross terms in the Jacobian. A simple expression is obtained for all the radially symmetric Jacobians occurring in the theory. Representative examples of regular and singular solutions are shown and the competition between dilatation and vorticity is illustrated. Inspired by thermodynamical, mean field theoretical analogies, a genuine variational formula is proposed which yields unique measure solutions for the radially symmetric fluid densities investigated. We stress that this variational formula, unlike the Hopf-Lax formula, enables us to treat systems which are both compressible and rotational. Moreover in the one

  11. Sample Structure of Forced Burgers Turbulence

    Nakazawa, H.

    1981-05-01

    Burgers equation in the inviscid limit with Gaussian white noise type force is analyzed as a model for a class of forced Burgers turbulence problems in the light of a classical work of stochastic differential equations for total energy and total variation (in the space variable) of the field are derived. Significance of the quantity total variation and the prospects on the existence of the invariant measure are also discussed.

  12. Spontaneous Stochasticity and Anomalous Dissipation for Burgers Equation

    Eyink, Gregory L.; Drivas, Theodore D.

    2015-01-01

    We develop a Lagrangian approach to conservation-law anomalies in weak solutions of inviscid Burgers equation, motivated by previous work on the Kraichnan model of turbulent scalar advection. We show that the entropy solutions of Burgers possess Markov stochastic processes of (generalized) Lagrangian trajectories backward in time for which the Burgers velocity is a backward martingale. This property is shown to guarantee dissipativity of conservation-law anomalies for general convex functions of the velocity. The backward stochastic Burgers flows with these properties are not unique, however. We construct infinitely many such stochastic flows, both by a geometric construction and by the zero-noise limit of the Constantin-Iyer stochastic representation of viscous Burgers solutions. The latter proof yields the spontaneous stochasticity of Lagrangian trajectories backward in time for Burgers, at unit Prandtl number. It is conjectured that existence of a backward stochastic flow with the velocity as martingale is an admissibility condition which selects the unique entropy solution for Burgers. We also study linear transport of passive densities and scalars by inviscid Burgers flows. We show that shock solutions of Burgers exhibit spontaneous stochasticity backward in time for all finite Prandtl numbers, implying conservation-law anomalies for linear transport. We discuss the relation of our results for Burgers with incompressible Navier-Stokes turbulence, especially Lagrangian admissibility conditions for Euler solutions and the relation between turbulent cascade directions and time-asymmetry of Lagrangian stochasticity.

  13. Spontaneous Stochasticity and Anomalous Dissipation for Burgers Equation

    Eyink, Gregory L

    2014-01-01

    We develop a Lagrangian approach to conservation-law anomalies in weak solutions of inviscid Burgers equation, motivated by previous work on the Kraichnan model of turbulent scalar advection. We show that the entropy solutions of Burgers possess Markov stochastic processes of (generalized) Lagrangian trajectories backward in time for which the Burgers velocity is a backward martingale. This property is shown to guarantee dissipativity of conservation-law anomalies for general convex functions of the velocity. The backward stochastic Burgers flows with these properties are not unique, however. We construct infinitely many such stochastic flows, both by a geometric construction and by the zero-noise limit of the Constantin-Iyer stochastic representation of viscous Burgers solutions. The latter proof yields the spontaneous stochasticity of Lagrangian trajectories backward in time for Burgers, at unit Prandtl number. It is conjectured that existence of a backward stochastic flow with the velocity as martingale is...

  14. Simulation of seismic waves at the Earth crust (brittle-ductile transition based on the Burgers model

    J. M. Carcione

    2014-06-01

    Full Text Available The Earth crust presents two dissimilar rheological behaviours depending on the in-situ stress-temperature conditions. The upper, cooler, part is brittle while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behaviour is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in-situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P- and S-wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P-S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.

  15. Rational Solutions in a Coupled Burgers System

    HUANG Ling

    2006-01-01

    Three types of the rational solutions for a new coupled Burgers system are studied in detail in terms of the reduction and decoupled procedures. The first two types of rational solutions are singular and valid for one type of model parameter c>0, and another type of rational solutions is nonsingular at any type and valid for another type of model parameter c<0.

  16. Adhesive joint and composites modeling in SIERRA.

    Ohashi, Yuki; Brown, Arthur A.; Hammerand, Daniel Carl; Adolf, Douglas Brian; Chambers, Robert S.; Foulk, James W., III (.,; )

    2005-11-01

    Polymers and fiber-reinforced polymer matrix composites play an important role in many Defense Program applications. Recently an advanced nonlinear viscoelastic model for polymers has been developed and incorporated into ADAGIO, Sandia's SIERRA-based quasi-static analysis code. Standard linear elastic shell and continuum models for fiber-reinforced polymer-matrix composites have also been added to ADAGIO. This report details the use of these models for advanced adhesive joint and composites simulations carried out as part of an Advanced Simulation and Computing Advanced Deployment (ASC AD) project. More specifically, the thermo-mechanical response of an adhesive joint when loaded during repeated thermal cycling is simulated, the response of some composite rings under internal pressurization is calculated, and the performance of a composite container subjected to internal pressurization, thermal loading, and distributed mechanical loading is determined. Finally, general comparisons between the continuum and shell element approaches for modeling composites using ADAGIO are given.

  17. Symmetry study of the coupled Burgers system

    Lian Zengju [Department of Physics, Ningbo University, Ningbo 315211 (China); Lou, S.Y. [Department of Physics, Ningbo University, Ningbo 315211 (China); Department of Physics, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2006-01-01

    The inverse of the recursion operator of a coupled Burgers equation is given explicitly. Three sets of infinitely many symmetries of the considered model are obtained by acting the recursion operator and it's inverse on the trivial symmetries, space translation, identity transformation and the scaling transformation respectively. These symmetries constitute an infinite dimensional Lie algebra.

  18. Symmetry study of the coupled Burgers system

    The inverse of the recursion operator of a coupled Burgers equation is given explicitly. Three sets of infinitely many symmetries of the considered model are obtained by acting the recursion operator and it's inverse on the trivial symmetries, space translation, identity transformation and the scaling transformation respectively. These symmetries constitute an infinite dimensional Lie algebra

  19. Interfacial adhesion of graphene by multiscale models

    Huang, Rui

    2014-01-01

    This article presents a multiscale study on adhesive interactions between graphene and its substrates. First, van der Waals (vdW) interactions between graphene and a SiO2 substrate are studied by first-principle density functional theory (DFT) calculations with dispersion corrections. It is found that the interaction strength is strongly influenced by changes of the SiO2 surface structures due to surface reactions with water. To scale up the model, molecular dynamics (MD) simulations are perf...

  20. Intermittency of Burgers' Turbulence

    Balkovsky, E; Kolokolov, I V; Lebedev, V

    1997-01-01

    We consider the tails of probability density function (PDF) for the velocity that satisfies Burgers equation driven by a Gaussian large-scale force. The saddle-point approximation is employed in the path integral so that the calculation of the PDF tails boils down to finding the special field-force configuration (instanton) that realizes the extremum of probability. For the PDFs of velocity and it's derivatives $u^{(k)} = \\partial_x^ku$, the general formula is found: $\\ln{\\cal P}(|u^{(k)}|) \\propto -(|u^{(k)}|/{\\rm Re}^k)^{3/(k+1)}$.

  1. Adhesive contact:from atomistic model to continuum model

    Fan Kang-Qi; Jia Jian-Yuan; Zhu Ying-Min; Zhang Xiu-Yan

    2011-01-01

    Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a selfconsistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.

  2. An explicit relaxation filtering framework based upon Perona-Malik anisotropic diffusion for shock capturing and subgrid scale modeling of Burgers turbulence

    Maulik, Romit

    2016-01-01

    In this paper, we introduce a relaxation filtering closure approach to account for subgrid scale effects in explicitly filtered large eddy simulations using the concept of anisotropic diffusion. We utilize the Perona-Malik diffusion model and demonstrate its shock capturing ability and spectral performance for solving the Burgers turbulence problem, which is a simplified prototype for more realistic turbulent flows showing the same quadratic nonlinearity. Our numerical assessments present the behavior of various diffusivity functions in conjunction with a detailed sensitivity analysis with respect to the free modeling parameters. In comparison to direct numerical simulation (DNS) and under-resolved DNS results, we find that the proposed closure model is efficient in the prevention of energy accumulation at grid cut-off and is also adept at preventing any possible spurious numerical oscillations due to shock formation under the optimal parameter choices. In contrast to other relaxation filtering approaches, it...

  3. Computational modeling of leukocyte adhesion cascade (LAC)

    Sarkar, Kausik

    2005-11-01

    In response to an inflammation in the body, leukocytes (white blood cell) interact with the endothelium (interior wall of blood vessel) through a series of steps--capture, rolling, adhesion and transmigration--critical for proper functioning of the immune system. We are numerically simulating this process using a Front-tracking finite-difference method. The viscoelastcity of the cell membrane, cytoplasm and nucleus are incorporated and allowed to change with time in response to the cell surface molecular chemistry. The molecular level forces due to specific ligand-receptor interactions are accounted for by stochastic spring-peeling model. Even though leukocyte rolling has been investigated through various models, the transitioning through subsequent steps, specifically firm adhesion and transmigration through endothelial layer, has not been modeled. The change of viscoelastic properties due to the leukocyte activation is observed to play a critical role in mediating the transition from rolling to transmigration. We will provide details of our approach and discuss preliminary results.

  4. Transient Growth in Stochastic Burgers Flows

    Poças, Diogo

    2015-01-01

    This study considers the problem of the extreme behavior exhibited by solutions to Burgers equation subject to stochastic forcing. More specifically, we are interested in the maximum growth achieved by the "enstrophy" (the Sobolev $H^1$ seminorm of the solution) as a function of the initial enstrophy $\\mathcal{E}_0$, in particular, whether in the stochastic setting this growth is different than in the deterministic case considered by Ayala & Protas (2011). This problem is motivated by questions about the effect of noise on the possible singularity formation in hydrodynamic models. The main quantities of interest in the stochastic problem are the expected value of the enstrophy and the enstrophy of the expected value of the solution. The stochastic Burgers equation is solved numerically with a Monte Carlo sampling approach. By studying solutions obtained for a range of optimal initial data and different noise magnitudes, we reveal different solution behaviors and it is demonstrated that the two quantities ...

  5. Multidimensional Potential Burgers Turbulence

    Boritchev, Alexandre

    2016-03-01

    We consider the multidimensional generalised stochastic Burgers equation in the space-periodic setting: partial {u}/partial t+(nabla f({u}) \\cdot nabla) {u}-ν Δ {u}= nabla η, quad t ≥ 0, {x} in{T}^d=({R}/ {Z})^d, under the assumption that u is a gradient. Here f is strongly convex and satisfies a growth condition, ν is small and positive, while η is a random forcing term, smooth in space and white in time. For solutions u of this equation, we study Sobolev norms of u averaged in time and in ensemble: each of these norms behaves as a given negative power of ν. These results yield sharp upper and lower bounds for natural analogues of quantities characterising the hydrodynamical turbulence, namely the averages of the increments and of the energy spectrum. These quantities behave as a power of the norm of the relevant parameter, which is respectively the separation ℓ in the physical space and the wavenumber k in the Fourier space. Our bounds do not depend on the initial condition and hold uniformly in {ν}. We generalise the results obtained for the one-dimensional case in [10], confirming the physical predictions in [4, 30]. Note that the form of the estimates does not depend on the dimension: the powers of {ν, |{{k}}|, ℓ} are the same in the one- and the multi-dimensional setting.

  6. Optimized Baxter model of protein solutions: electrostatics versus adhesion

    Prinsen, P.; Odijk, T.

    2004-01-01

    A theory is set up of spherical proteins interacting by screened electrostatics and constant adhesion, in which the effective adhesion parameter is optimized by a variational principle for the free energy. An analytical approach to the second virial coefficient is first outlined by balancing the repulsive electrostatics against part of the bare adhesion. A theory similar in spirit is developed at nonzero concentrations by assuming an appropriate Baxter model as the reference state. The first-...

  7. Exact Finite Difference Scheme and Nonstandard Finite Difference Scheme for Burgers and Burgers-Fisher Equations

    Lei Zhang; Lisha Wang; Xiaohua Ding

    2014-01-01

    We present finite difference schemes for Burgers equation and Burgers-Fisher equation. A new version of exact finite difference scheme for Burgers equation and Burgers-Fisher equation is proposed using the solitary wave solution. Then nonstandard finite difference schemes are constructed to solve two equations. Numerical experiments are presented to verify the accuracy and efficiency of such NSFD schemes.

  8. BOUNDARY CONTROL OF MKDV-BURGERS EQUATION

    TIAN Li-xin; ZHAO Zhi-feng; WANG Jing-feng

    2006-01-01

    The boundary control of MKdV-Burgers equation was considered by feedback control on the domain [0,1]. The existence of the solution of MKdV-Burgers equation with the feedback control law was proved. On the base, priori estimates for the solution was given. At last, the existence of the weak solution of MKdV-Burgers equation was proved and the global-exponential and asymptotic stability of the solution of MKdV-Burgers equation was given.

  9. Bønner og burgere

    Rytter, Mikkel

    2013-01-01

    Based on a number of burger incidents during ten days of itikaf at a Sufi astana (lodge) in Pakistan, this article discusses religious self-cultivation among Muslim pilgrims from Denmark. The focus on food and eating is not only used to discuss how religious brotherhoods and spiritual kinship are...

  10. Modeling and characterization of interfacial adhesion and fracture

    Yao, Qizhou

    2000-09-01

    The loss of interfacial adhesion is mostly seen in the failure of polymer adhesive joints. In addition to the intrinsic physical attraction across the interface, the interfacial adhesion strength is believed to highly depend on a number of factors, such as adhesive chemistry/structure, surface topology, fracture pattern, thermal and elastic mismatch across the interface. The fracture failure of an adhesive joint involves basically three aspects, namely, the intrinsic interfacial strength, the driving force for fracture and other energy dissipation. One may define the intrinsic interfacial strength as the maximum value of the intrinsic interfacial adhesion. The total work done by external forces to the component that contains the interface is partitioned into two parts. The first part is consumed by all other energy dissipation mechanisms (plasticity, heat generation, viscosity, etc.). The second part is used to debond the interface. This amount should equal to the intrinsic adhesion of the interface according to the laws of conservation of energy. It is clear that in order to understand the fundamental physics of adhesive joint failure, one must be able to characterize the intrinsic interfacial adhesion and be able to identify all the major energy dissipation mechanisms involved in the debonding process. In this study, both physical and chemical adhesion mechanisms were investigated for an aluminum-epoxy interface. The physical bonding energy was estimated by computing the Van de Waals forces across the interface. A hydration model was proposed and the associated chemical bonding energy was calculated through molecular simulations. Other energy dissipation mechanisms such as plasticity and thermal residual stresses were also identified and investigated for several four-point bend specimens. In particular, a micromechanics based model was developed to estimate the adhesion enhancement due to surface roughness. It is found that for this Al-epoxy system the major

  11. Standardised Models for Inducing Experimental Peritoneal Adhesions in Female Rats

    Bernhard Kraemer; Christian Wallwiener; Rajab, Taufiek K; Christoph Brochhausen; Markus Wallwiener; Ralf Rothmund

    2014-01-01

    Animal models for adhesion induction are heterogeneous and often poorly described. We compare and discuss different models to induce peritoneal adhesions in a randomized, experimental in vivo animal study with 72 female Wistar rats. Six different standardized techniques for peritoneal trauma were used: brushing of peritoneal sidewall and uterine horns (group 1), brushing of parietal peritoneum only (group 2), sharp excision of parietal peritoneum closed with interrupted sutures (group 3), isc...

  12. Viscous Instanton for Burgers' Turbulence

    Balkovsky, E.; Falkovich, G.; Kolokolov, I.; Lebedev, V.

    1996-01-01

    We consider the tails of probability density functions (PDF) for different characteristics of velocity that satisfies Burgers equation driven by a large-scale force. The saddle-point approximation is employed in the path integral so that the calculation of the PDF tails boils down to finding the special field-force configuration (instanton) that realizes the extremum of probability. We calculate high moments of the velocity gradient $\\partial_xu$ and find out that they correspond to the PDF w...

  13. Simulation of Cell Adhesion using a Particle Transport Model

    Chesnutt, Jennifer

    2005-11-01

    An efficient computational method for simulation of cell adhesion through protein binding forces is discussed. In this method, the cells are represented by deformable elastic particles, and the protein binding is represented by a rate equation. The method is first developed for collision and adhesion of two similar cells impacting on each other from opposite directions. The computational method is then applied in a particle-transport model for a cloud of interacting and colliding cells, each of which are represented by particles of finite size. One application might include red blood cells adhering together to form rouleaux, which are chains of red blood cells that are found in different parts of the circulatory system. Other potential applications include adhesion of platelets to a blood vessel wall or mechanical heart valve, which is a precursor of thrombosis formation, or adhesion of cancer cells to organ walls in the lymphatic, circulatory, digestive or pulmonary systems.

  14. On two models for charged particle systems: the cometary flow equation and the Burgers-Poisson system

    Two models for charged particle systems are considered. The first chapter treats a kinetic equation with a relaxation time model for wave-particle collisions in cometary flows. Similarly to the BGK-model of gas dynamics, it involves a projection onto the set of equilibrium distributions, nonlinearly dependent on moments of the distribution function. An earlier existence result is extended to bounded domains with reflecting boundaries and to initial conditions permitting vacuum regions. The long time behavior is investigated. Convergence on compact time intervals (shifted to infinity) to the set of equilibrium solutions is proven. All smooth equilibrium solutions are computed and classified according to their geometry. The subset of smooth equilibria satisfying boundary conditions is investigated. Finally, explicit solutions of the Euler equations for ideal gases are constructed as moments of equilibrium solutions. In the second chapter, a dispersive model equation is considered, which has been proposed by Whitham as a shallow water model, and which can also be seen as a caricature of two species Euler-Poisson problems. A number of formal properties as well as similarities to other dispersive equations is derived. A travelling wave analysis and some numerical tests are carried out. The equation features wave breaking in finite time. A local existence result for smooth solutions and a global existence result for weak entropy solutions is proved. Finally a small dispersion limit is carried out for situations where the solution of the limiting equation is smooth. (author)

  15. Convergence of Convectively Filtered Burgers Equation to the Entropy Solution of Inviscid Burgers Equation

    Norgard, Greg

    2008-01-01

    This document provides a proof that the solutions to Convectively Filtered Burgers equation, will converge to the entropy solution of Inviscid Burgers equation when certain restrictions are put on the initial conditions. It does so by first establishing convergence to a weak solution of Inviscid Burgers equation. That solution is then shown to be the entropy solution.

  16. Thermal inactivation of Salmonella spp. in pork burger patties.

    Gurman, P M; Ross, T; Holds, G L; Jarrett, R G; Kiermeier, A

    2016-02-16

    Predictive models, to estimate the reduction in Escherichia coli O157:H7 concentration in beef burgers, have been developed to inform risk management decisions; no analogous model exists for Salmonella spp. in pork burgers. In this study, "Extra Lean" and "Regular" fat pork minces were inoculated with Salmonella spp. (Salmonella 4,[5],12,i:-, Salmonella Senftenberg and Salmonella Typhimurium) and formed into pork burger patties. Patties were cooked on an electric skillet (to imitate home cooking) to one of seven internal temperatures (46, 49, 52, 55, 58, 61, 64 °C) and Salmonella enumerated. A generalised linear logistic regression model was used to develop a predictive model for the Salmonella concentration based on the internal endpoint temperature. It was estimated that in pork mince with a fat content of 6.1%, Salmonella survival will be decreased by -0.2407log10 CFU/g for a 1 °C increase in internal endpoint temperature, with a 5-log10 reduction in Salmonella concentration estimated to occur when the geometric centre temperature reaches 63 °C. The fat content influenced the rate of Salmonella inactivation (P=0.043), with Salmonella survival increasing as fat content increased, though this effect became negligible as the temperature approached 62 °C. Fat content increased the time required for patties to achieve a specified internal temperature (P=0.0106 and 0.0309 for linear and quadratic terms respectively), indicating that reduced fat pork mince may reduce the risk of salmonellosis from consumption of pork burgers. Salmonella serovar did not significantly affect the model intercepts (P=0.86) or slopes (P=0.10) of the fitted logistic curve. This predictive model can be applied to estimate the reduction in Salmonella in pork burgers after cooking to a specific endpoint temperature and hence to assess food safety risk. PMID:26686598

  17. Bacterial Adhesion to Hexadecane (Model NAPL)-Water Interfaces

    Ghoshal, S.; Zoueki, C. R.; Tufenkji, N.

    2009-05-01

    The rates of biodegradation of NAPLs have been shown to be influenced by the adhesion of hydrocarbon- degrading microorganisms as well as their proximity to the NAPL-water interface. Several studies provide evidence for bacterial adhesion or biofilm formation at alkane- or crude oil-water interfaces, but there is a significant knowledge gap in our understanding of the processes that influence initial adhesion of bacteria on to NAPL-water interfaces. In this study bacterial adhesion to hexadecane, and a series of NAPLs comprised of hexadecane amended with toluene, and/or with asphaltenes and resins, which are the surface active fractions of crude oils, were examined using a Microbial Adhesion to Hydrocarbons (MATH) assay. The microorganisms employed were Mycobacterium kubicae, Pseudomonas aeruginosa and Pseudomonas putida, which are hydrocarbon degraders or soil microorganisms. MATH assays as well as electrophoretic mobility measurements of the bacterial cells and the NAPL droplet surfaces in aqueous solutions were conducted at three solution pHs (4, 6 and 7). Asphaltenes and resins were shown to generally decrease microbial adhesion. Results of the MATH assay were not in qualitative agreement with theoretical predictions of bacteria- hydrocarbon interactions based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) model of free energy of interaction between the cell and NAPL droplets. In this model the free energy of interaction between two colloidal particles is predicted based on electrical double layer, van der Waals and hydrophobic forces. It is likely that the steric repulsion between bacteria and NAPL surfaces, caused by biopolymers on bacterial surfaces and aphaltenes and resins at the NAPL-water interface contributed to the decreased adhesion compared to that predicted by the XDLVO model.

  18. Effects of a Temperature-Sensitive, Anti-Adhesive Agent on the Reduction of Adhesion in a Rabbit Laminectomy Model

    Park, Jeong Woo; Bak, Koang Hum; Cho, Tae Koo; Chun, Hyoung-Joon; Ryu, Je Il

    2016-01-01

    Objective A common cause of failure in laminectomy surgery is when epidural, peridural, or perineural adhesion occurs postoperatively. The purpose of this study is to examine the efficacy of a temperature-sensitive, anti-adhesive agent (TSAA agent), Guardix-SG®, as a mechanical barrier for the prevention or reduction of peridural scar adhesion in a rabbit laminectomy model. Methods Twenty-six mature rabbits were used for this study. Each rabbit underwent two separate laminectomies at lumbar v...

  19. Standardised Models for Inducing Experimental Peritoneal Adhesions in Female Rats

    Bernhard Kraemer

    2014-01-01

    Full Text Available Animal models for adhesion induction are heterogeneous and often poorly described. We compare and discuss different models to induce peritoneal adhesions in a randomized, experimental in vivo animal study with 72 female Wistar rats. Six different standardized techniques for peritoneal trauma were used: brushing of peritoneal sidewall and uterine horns (group 1, brushing of parietal peritoneum only (group 2, sharp excision of parietal peritoneum closed with interrupted sutures (group 3, ischemic buttons by grasping the parietal peritoneum and ligating the base with Vicryl suture (group 4, bipolar electrocoagulation of the peritoneum (group 5, and traumatisation by electrocoagulation followed by closure of the resulting peritoneal defect using Vicryl sutures (group 6. Upon second look, there were significant differences in the adhesion incidence between the groups (P<0.01. Analysis of the fraction of adhesions showed that groups 2 (0% and 5 (4% were significantly less than the other groups (P<0.01. Furthermore, group 6 (69% was significantly higher than group 1 (48% (P<0.05 and group 4 (47% (P<0.05. There was no difference between group 3 (60% and group 6 (P=0.2. From a clinical viewpoint, comparison of different electrocoagulation modes and pharmaceutical adhesion barriers is possible with standardised models.

  20. Modified non-linear Burgers' equations and cosmic ray shocks

    Zank, G. P.; Webb, G. M.; Mckenzie, J. F.

    1988-01-01

    A reductive perturbation scheme is used to derive a generalized non-linear Burgers' equation, which includes the effects of dispersion, in the long wavelength regime for the two-fluid hydrodynamical model used to describe cosmic ray acceleration by the first-order Fermi process in astrophysical shocks. The generalized Burger's equation is derived for both relativistic and non-relativistic cosmic ray shocks, and describes the time evolution of weak shocks in the theory of diffusive shock acceleration. The inclusion of dispersive effects modifies the phase velocity of the shock obtained from the lower order non-linear Burger's equation through the introduction of higher order terms from the long wavelength dispersion equation. The travelling wave solution of the generalized Burgers' equation for a single shock shows that larger cosmic ray pressures result in broader shock transitions. The results for relativistic shocks show a steepening of the shock as the shock speed approaches the relativistic cosmic ray sound speed. The dependence of the shock speed on the cosmic ray pressure is also discussed.

  1. The adhesion model considering capillarity for gecko attachment system.

    Kim, Tae Wan; Bhushan, Bharat

    2008-03-01

    Geckos make use of approximately a million microscale hairs (setae) that branch off into hundreds of nanoscale spatulae to cling to different smooth and rough surfaces and detach at will. This hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. It is known that van der Waals force is the primary mechanism used to adhere to surfaces, and capillary force is a secondary effect that can further increase adhesive force. To investigate the effects of capillarity on gecko adhesion, we considered the capillary force as well as the solid-to-solid interaction. The capillary force expressed in terms of elliptical integral is calculated by numerical method to cope with surfaces with a wide range of contact angles. The adhesion forces exerted by a single gecko spatula in contact with planes with different contact angles for various relative humidities are calculated, and the contributions of capillary force to total adhesion force are evaluated. The simulation results are compared with experimental data. Finally, using the three-level hierarchical model recently developed to simulate a gecko seta contacting with random rough surface, the effect of the relative humidity and the hydrophobicity of surface on the gecko adhesion is investigated. PMID:17594962

  2. Direct adhesive measurements between wood biopolymer model surfaces.

    Gustafsson, Emil; Johansson, Erik; Wågberg, Lars; Pettersson, Torbjörn

    2012-10-01

    For the first time the dry adhesion was measured for an all-wood biopolymer system using Johnson-Kendall-Roberts (JKR) contact mechanics. The polydimethylsiloxane hemisphere was successfully surface-modified with a Cellulose I model surface using layer-by-layer assembly of nanofibrillated cellulose and polyethyleneimine. Flat surfaces of cellulose were equally prepared on silicon dioxide substrates, and model surfaces of glucomannan and lignin were prepared on silicon dioxide using spin-coating. The measured work of adhesion on loading and the adhesion hysteresis was found to be very similar between cellulose and all three wood polymers, suggesting that the interaction between these biopolymers do not differ greatly. Surface energy calculations from contact angle measurements indicated similar dispersive surface energy components for the model surfaces. The dispersive component was dominating the surface energy for all surfaces. The JKR work of adhesion was lower than that calculated from contact angle measurements, which partially can be ascribed to surface roughness of the model surfaces and overestimation of the surface energies from contact angle determinations. PMID:22924973

  3. Linear stability of shock waves for the Schrodinger-Burgers system

    Amorim, Paulo; Figueira, Mario; LeFloch, Philippe G

    2012-01-01

    We investigate a system coupling the nonlinear Schrodinger equation and the inviscid Burgers equation, which models interactions between short and long waves (for instance in fluids). Well-posedness for the associated Cauchy problem remains a difficult open problem and so we tackle it here via a linearization technique. We establish a linearized stability theorem for the Schrodinger-Burgers system when the reference solution is an entropy-satisfying shock wave to Burgers equation. Our proof is based on suitable energy estimates and on properties of hyperbolic equations with discontinuous coefficients. Numerical experiments support and expand our theoretical results.

  4. Oscillating flow of a Burgers' fluid in a pipe

    An analysis is made to see the influences of Hall current on the flow of a Burgers' fluid. The velocity field corresponding to flow in a pipe is determined. The closed form analytical solutions for several Newtonian and non-Newtonian fluid models can be obtained from the present analysis as the limiting cases. The purpose of this work is twofold. Firstly, to investigate the oscillating flow in a pipe using Burgers? fluid model. Secondly, to see the effects of Hall current on the velocity field. The flow in a pipe is induced due to imposition of an oscillating pressure gradient. An exact analytical solution to the governing problem is given using the Fourier transform technique. The obtained expression for the velocity field shows that there are pronounced effects of Hall and rheological parameters. The considered fluid model is a viscoelastic model and has been used to characterize food products such as cheese, soil, asphalt and asphalt mixes etc. (author)

  5. The relativistic Burgers equation on a FLRW background and its finite volume approximation

    Ceylan, Tuba; LeFloch, Philippe G.; Okutmustur, Baver

    2015-01-01

    A relativistic generalization of the inviscid Burgers equation was proposed by LeFloch, Makhlof, and Okutmustur and then investigated on a Schwarzschild background. Here, we extend their analysis to a Friedmann-Lemaitre-Robertson-Walker (FLRW) background. This problem is more challenging due to the existence of non-trivial spatially homogeneous solutions. First, we derive the relativistic Burgers model of interest and determine its spatially homogeneous solutions. Second, we design a numerica...

  6. The relativistic Burgers equation on a FLRW background and its finite volume approximation

    Ceylan, Tuba; LeFloch, Philippe G.; Okutmustur, Baver

    2015-01-01

    A relativistic generalization of the inviscid Burgers equation was proposed by LeFloch, Makhlof, and Okutmustur and then investigated on a Schwarzschild background. Here, we extend their analysis to a Friedmann–Lemaitre–Robertson–Walker (FLRW) background. This problem is more challenging due to the existence of non-trivial spatially homogeneous solutions. First, we derive the relativistic Burgers model of interest and determine its spatially homogeneous solutions. Second, we design a numerica...

  7. Convergence of a random walk method for the Burgers equation

    In this paper we consider a random walk algorithm for the solution of Burgers' equation. The algorithm uses the method of fractional steps. The non-linear advection term of the equation is solved by advecting ''fluid'' particles in a velocity field induced by the particles. The diffusion term of the equation is approximated by adding an appropriate random perturbation to the positions of the particles. Though the algorithm is inefficient as a method for solving Burgers' equation, it does model a similar method, the random vortex method, which has been used extensively to solve the incompressible Navier-Stokes equations. The purpose of this paper is to demonstrate the strong convergence of our random walk method and so provide a model for the proof of convergence for more complex random walk algorithms; for instance, the random vortex method without boundaries

  8. Slow Burgers Vortices in Hot Conformal Fluids

    Evslin, Jarah

    2011-01-01

    The quintessential vortex solution in (3+1)-dimensional nonrelativistic, incompressible fluid mechanics is the Burgers vortex. We show that, in a finite domain, conformal fluids also admit hot vortex solutions with everywhere nonrelativistic speeds. These are identical to Burgers' solution, except that their radius is reduced by a factor of 2/sqrt(3). A rough calculation indicates that at RHIC these vortices are indeed smaller than the fireball itself during thermalization. Similarly to the B...

  9. Organizational Communication and Workforce Diversity Case Company: Burger King, Finland

    Raqib, Maliha

    2015-01-01

    The purpose of this Bachelor’s thesis is to examine the internal work process related communication of Burger King, Finland. The main focus of this thesis is to assess the current communication flow and recognize communication weak points. Therefore, three investigative questions were formulated to understand the phenomena and provide development suggestions for further communication progress. The theoretical framework consists of theories related to basic human communication model, organ...

  10. Preliminary group classification for generalized inviscid Burger's equation

    Mahdipour-Shirayeh, A

    2010-01-01

    Preliminary group classification for a class of generalized inviscid Burger's equations in the general form $u_t+g(x, u)u_x = f(x, u)$ is given and additional equivalence transformations are found. Adduced results complete and essentially generalize recent works on the subject . A number of new interesting nonlinear invariant models which have non-trivial invariance algebras are obtained. The result of the work is a wide class of equations summarized in table form.

  11. Advances in modeling and design of adhesively bonded systems

    Kumar, S

    2013-01-01

    The book comprehensively charts a way for industry to employ adhesively bonded joints to make systems more efficient and cost-effective Adhesively bonded systems have found applications in a wide spectrum of industries (e.g., aerospace, electronics, construction, ship building, biomedical, etc.) for a variety of purposes. Emerging adhesive materials with improved mechanical properties have allowed adhesion strength approaching that of the bonded materials themselves. Due to advances in adhesive materials and the many potential merits that adhesive bonding offers, adhesive bonding has replac

  12. A mechanical model of biomimetic adhesive pads with tilted and hierarchical structures

    Schargott, M [Institute of Mechanics, Technische Universitaet Berlin, Strd 17 Juni 135, 10623 Berlin (Germany)], E-mail: martin.schargott@tu-berlin.de

    2009-06-01

    A 3D model for hierarchical biomimetic adhesive pads is constructed. It is based on the main principles of the adhesive pads of the Tokay gecko and consists of hierarchical layers of vertical or tilted beams, where each layer is constructed in such a way that no cohesion between adjacent beams can occur. The elastic and adhesive properties are calculated analytically and numerically. For the adhesive contact on stochastically rough surfaces, the maximum adhesion force increases with increasing number of hierarchical layers. Additional calculations show that the adhesion force also depends on the height spectrum of the rough surface.

  13. Viscous instanton for Burgers' turbulence

    Balkovsky, E; Kolokolov, I V; Lebedev, V

    1996-01-01

    We consider the tails of probability density functions (PDF) for different characteristics of velocity that satisfies Burgers equation driven by a large-scale force. The saddle-point approximation is employed in the path integral so that the calculation of the PDF tails boils down to finding the special field-force configuration (instanton) that realizes the extremum of probability. We calculate high moments of the velocity gradient \\partial_xu and find out that they correspond to the PDF with \\ln[{\\cal P}(\\partial_xu)]\\propto-(-\\partia l_xu/{\\rm Re})^{3/2} where {\\rm Re} is the Reynolds number. That stretched exponential form is valid for negative \\partial_xu with the modulus much larger than its root-mean-square (rms) value. The respective tail of PDF for negative velocity differences w is steeper than Gaussian, \\ln{\\cal P}(w)\\sim-(w/u_{\\rm rms})^3, as well as single-point velocity PDF \\ln{\\cal P}(u)\\sim-(|u|/u_{\\rm rms})^3. For high velocity derivatives u^{(k)}=\\partial_x^ku, the general formula is found: ...

  14. The adhesion model as a field theory for cosmological clustering

    The adhesion model has been proposed in the past as an improvement of the Zel'dovich approximation, providing a good description of the formation of the cosmic web. We recast the model as a field theory for cosmological large scale structure, adding a stochastic force to account for power generated from very short, highly non-linear scales that is uncorrelated with the initial power spectrum. The dynamics of this Stochastic Adhesion Model (SAM) is reminiscent of the well known Kardar-Parisi-Zhang equation with the difference that the viscosity and the noise spectrum are time dependent. Choosing the viscosity proportional to the growth factor D restricts the form of noise spectrum through a 1-loop renormalization argument. For this choice, the SAM field theory is renormalizable to one loop. We comment on the suitability of this model for describing the non-linear regime of the CDM power spectrum and its utility as a relatively simple approach to cosmological clustering

  15. Adhesion of Aeromonas sp. to cell lines used as models for intestinal adhesion.

    Kirov, S M; Hayward, L. J.; Nerrie, M. A.

    1995-01-01

    Adhesion to HEp-2 cells has been shown to correlate with enteropathogenicity for Aeromonas species. Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin. In this study strains of Aeromonas veronii biotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2). Quantitative assays showed identica...

  16. Generalized Cole–Hopf transformations for generalized Burgers equations

    B Mayil Vaganan; E Emily Priya

    2015-11-01

    A detailed review of the invention of Cole–Hopf transformations for the Burgers equation and all the subsequent works which include generalizations of the Burgers equation and the corresponding developments in Cole–Hopf transformations are documented.

  17. Forced Burgers Turbulence in 3-Dimensions

    Davoudi, J; Rahimi-Tabar, M R

    1999-01-01

    We investigate non-perturbative results of inviscid forced Burgers equation supplemented to continuity equation in three-dimensions. The exact two-point correlation function of density is calculated in three-dimensions. The two-point correlator $$ behaves as $ |{\\bf {x_1 - x_2}}|^{-\\alpha_3}$ and in the universal region $\\alpha_3 = 2 + universal region we show that the angular dependence of the velocity correlation function satisfies the same equation, which is found in the instanton approach by Gurarie and Migdal {[Phys. Rev. E {\\bf 54}, 4908 (1996)]}. The tail of the velocity increments is also found to behave as drive a Kramers-Moyal equation governing the evolution of the probability density function (PDF) of longitudinal velocity increments for three dimensional Burgers turbulence. In this region we prove Yakhot's conjecture {[Phys. Rev. E {\\bf 57}, 1737 (1998)]} for the equation of PDF for three dimensional Burgers turbulence. We also derive the intermittency exponents for the longitudinal structure fun...

  18. Algebraic dynamics solution and algebraic dynamics algorithm of Burgers equations

    2008-01-01

    Algebraic dynamics solution and algebraic dynamics algorithm of nonlinear partial differential evolution equations in the functional space are applied to Burgers equation. The results indicate that the approach is effective for analytical solutions to Burgers equation, and the algorithm for numerical solutions of Burgers equation is more stable, with higher precision than other existing finite difference algo-rithms.

  19. Axisymmetric Finite Element Modeling of Adhesive Joint Between a Laminated Composite and Metal Cylinder

    Talbot, Casey A.

    2011-01-01

    In order to incorporate fiber-reinforced composite materials in space structures, adhesive joining techniques are required. Because analytical models have a hard time capturing the complex stress state inherent to adhesively joining dissimilar materials, a different modeling technique was deemed necessary. A two-dimensional axisymmetric finite element model capable of capturing the three-dimensional stress state of cylindrical adhesive joints was developed. In order to rigorously validate the...

  20. Exact solution of generalized inviscid Burgers' equation

    Nadjafikhah, Mehdi

    2009-01-01

    Let $f,g:{\\Bbb R}\\to{\\Bbb R}$ be integrable functions, $f$ nowhere zero, and $\\phi (u)=\\int du/f(u)$ be invertible. An exact solution to the generalized nonhomogeneous inviscid Burgers' equation $u_t+g(u).u_x=f(u)$ is given, by quadratures.

  1. Transient flows of a Burgers' fluid

    An analysis is performed to develop the analytical solutions for some unsteady magnetohydrodynamic (MHD) flows of a Burgers' fluid between two plates. A uniform magnetic field is applied transversely to the fluid motion. The exact solutions are given for three problems. Results for the velocity fields are discussed and compared with the flows of Oldroyd-B, Maxwell, second grade and Newtonian fluids. (author)

  2. Structure of Shocks in Burgers Turbulencewith Stable Noise Initial Data

    Bertoin, Jean

    Burgers equation can be used as a simplified model for hydrodynamic turbulence. The purpose of this paper is to study the structure of the shocks for the inviscid equation in dimension 1 when the initial velocity is given by a stable Lévy noise with index α∈ (1/2,2]. We prove that Lagrangian regular points exist (i.e. there are fluid particles that have not participated in shocks at any time between 0 and t) if and only if α0$, there are fluid particles in any non-empty open interval.

  3. Optimized Baxter model of protein solutions: electrostatics versus adhesion

    Prinsen, P.; Odijk, T.

    2004-01-01

    A theory is set up of spherical proteins interacting by screened electrostatics and constant adhesion, in which the effective adhesion parameter is optimized by a variational principle for the free energy. An analytical approach to the second virial coefficient is first outlined by balancing the rep

  4. An innovative wheel–rail contact model for railway vehicles under degraded adhesion conditions

    Meli, E., E-mail: enrico.meli@unifi.it; Ridolfi, A., E-mail: a.ridolfi@unifi.it [University of Florence, Department of Industrial Engineering (Italy)

    2015-03-15

    The accurate modelling of the wheel–rail contact plays a fundamental role in the railway field since the contact forces heavily affect the vehicle dynamics, the wear of the contact surfaces and the vehicle safety. Concerning the wheel–rail contact, an important open problem is represented by the degraded adhesion. A realistic adhesion model is quite difficult to obtain because of the complex and highly non-linear behaviour of the adhesion coefficient and the presence of external unknown contaminants (the third body); this is especially true when degraded adhesion and large sliding between the wheel and rail contact surfaces occur.In this work the authors present an adhesion model particularly developed to describe degraded adhesion conditions. The new approach will have to be suitable to be employed within the wheel–rail contact models typical of the multibody applications. In other words, the contact model, comprising the new adhesion model, will have to guarantee a good accuracy and, at the same time, a high numerical efficiency to be implemented directly online inside the general multibody model of the vehicles (e.g. in Matlab-Simulink or Simpack environments) ( www.mathworks.com http://www.mathworks.com , 2012; www.simpack.com http://www.simpack.com , 2012).The model analysed in the paper is based on some of the main phenomena characterising the degraded adhesion, such as large sliding at the contact interface, high energy dissipation, the consequent cleaning effect on the contact surfaces and the final adhesion recovery due to the removal of external unknown contaminants.The adhesion model has been validated because of the experimental data provided by Trenitalia S.p.A. coming from on-track tests performed in Velim (Czech Republic). The tests have been carried out on a straight railway track under degraded adhesion conditions with the railway vehicle UIC-Z1 equipped with a fully-working Wheel Slide Protection (WSP) system.The validation highlighted the

  5. An innovative wheel–rail contact model for railway vehicles under degraded adhesion conditions

    The accurate modelling of the wheel–rail contact plays a fundamental role in the railway field since the contact forces heavily affect the vehicle dynamics, the wear of the contact surfaces and the vehicle safety. Concerning the wheel–rail contact, an important open problem is represented by the degraded adhesion. A realistic adhesion model is quite difficult to obtain because of the complex and highly non-linear behaviour of the adhesion coefficient and the presence of external unknown contaminants (the third body); this is especially true when degraded adhesion and large sliding between the wheel and rail contact surfaces occur.In this work the authors present an adhesion model particularly developed to describe degraded adhesion conditions. The new approach will have to be suitable to be employed within the wheel–rail contact models typical of the multibody applications. In other words, the contact model, comprising the new adhesion model, will have to guarantee a good accuracy and, at the same time, a high numerical efficiency to be implemented directly online inside the general multibody model of the vehicles (e.g. in Matlab-Simulink or Simpack environments) ( www.mathworks.com http://www.mathworks.com , 2012; www.simpack.com http://www.simpack.com , 2012).The model analysed in the paper is based on some of the main phenomena characterising the degraded adhesion, such as large sliding at the contact interface, high energy dissipation, the consequent cleaning effect on the contact surfaces and the final adhesion recovery due to the removal of external unknown contaminants.The adhesion model has been validated because of the experimental data provided by Trenitalia S.p.A. coming from on-track tests performed in Velim (Czech Republic). The tests have been carried out on a straight railway track under degraded adhesion conditions with the railway vehicle UIC-Z1 equipped with a fully-working Wheel Slide Protection (WSP) system.The validation highlighted the

  6. Mesoscopic Modeling of Blood Clotting: Coagulation Cascade and Platelets Adhesion

    Yazdani, Alireza; Li, Zhen; Karniadakis, George

    2015-11-01

    The process of clot formation and growth at a site on a blood vessel wall involve a number of multi-scale simultaneous processes including: multiple chemical reactions in the coagulation cascade, species transport and flow. To model these processes we have incorporated advection-diffusion-reaction (ADR) of multiple species into an extended version of Dissipative Particle Dynamics (DPD) method which is considered as a coarse-grained Molecular Dynamics method. At the continuum level this is equivalent to the Navier-Stokes equation plus one advection-diffusion equation for each specie. The chemistry of clot formation is now understood to be determined by mechanisms involving reactions among many species in dilute solution, where reaction rate constants and species diffusion coefficients in plasma are known. The role of blood particulates, i.e. red cells and platelets, in the clotting process is studied by including them separately and together in the simulations. An agonist-induced platelet activation mechanism is presented, while platelets adhesive dynamics based on a stochastic bond formation/dissociation process is included in the model.

  7. Dynamic Transitions of Generalized Burgers Equation

    Li, Limei; Ong, Kiah Wah

    2016-03-01

    In this article, we study the dynamic transition for the one dimensional generalized Burgers equation with periodic boundary condition. The types of transition are dictated by the sign of an explicitly given parameter b, which is derived using the dynamic transition theory developed by Ma and Wang (Phase transition dynamics. Springer, New York, 2014). The rigorous result demonstrates clearly the types of dynamics transition in terms of length scale l, dispersive parameter δ and viscosity ν.

  8. Decaying Turbulence in the Generalised Burgers Equation

    Boritchev, Alexandre

    2014-10-01

    We consider the generalised Burgers equation where f is strongly convex and ν is small and positive. We obtain sharp estimates for Sobolev norms of u (upper and lower bounds differ only by a multiplicative constant). Then, we obtain sharp estimates for the dissipation length scale and the small-scale quantities which characterise the decaying Burgers turbulence, i.e., the structure functions and the energy spectrum. The proof uses a quantitative version of an argument by Aurell et al. (J Fluid Mech 238:467-486, 1992). Note that we are dealing with decaying, as opposed to stationary turbulence. Thus, our estimates are not uniform in time. However, they hold on a time interval [ T 1, T 2], where T 1 and T 2 depend only on f and the initial condition, and do not depend on the viscosity. These results allow us to obtain a rigorous theory of the one-dimensional Burgers turbulence in the spirit of Kolmogorov's 1941 theory. In particular, we obtain two results which hold in the inertial range. On one hand, we explain the bifractal behaviour of the moments of increments, or structure functions. On the other hand, we obtain an energy spectrum of the form k -2. These results remain valid in the inviscid limit.

  9. Qualitative improvement of low meat beef burger using Aloe vera.

    Soltanizadeh, Nafiseh; Ghiasi-Esfahani, Hossein

    2015-01-01

    Low meat beef burgers have found their niche in the food markets in developing countries because of their lower price. However, these burgers still lack an acceptable quality. This study investigates the effects of different concentrations of Aloe vera on the quality of this food product. For this purpose, beef burgers were produced with 0%, 1%, 3%, and 5% Aloe vera and the changes in their cooking parameters, lipid oxidation, texture, and appeal to consumers over 7days of refrigerated storage were evaluated. Results indicate that Aloe vera contributed to some extent to decreased cooking loss and diameter reduction in the burgers. Increased concentrations of Aloe vera led to improvements in the water absorption and texture of the burgers as well as their lipid stability. However, a concentration level of 3% led to the most acceptability of the product to the panelists. Finally, it was found that Aloe vera acts as a hydrocolloid and improves the quality of burgers. PMID:25282702

  10. Moyal noncommutative integrability and the Burgers-KdV mapping

    The Moyal momentum algebra, is once again used to discuss some important aspects of NC integrable models and 2d conformal field theories. Among the results presented, we set up algebraic structures and makes useful convention notations leading to extract non trivial properties of the Moyal momentum algebra. We study also the Lax pair building mechanism for particular examples namely, the noncommutative KdV and Burgers systems. We show in a crucial step that these two systems are mapped to each other through the following crucial mapping ∂t2 → ∂t3 ≡ ∂t2∂x + α∂x3. This makes a strong constraint on the NC Burgers system which corresponds to linearizing its associated differential equation. From the CFT's point of view, this constraint equation is nothing but the analogue of the conservation law of the conformal current. We believe that the considered mapping might help to bring new insights towards understanding the integrability of noncommutative 2d-systems. (author)

  11. A Spectral Adaptive Mesh Refinement Method for the Burgers equation

    Nasr Azadani, Leila; Staples, Anne

    2013-03-01

    Adaptive mesh refinement (AMR) is a powerful technique in computational fluid dynamics (CFD). Many CFD problems have a wide range of scales which vary with time and space. In order to resolve all the scales numerically, high grid resolutions are required. The smaller the scales the higher the resolutions should be. However, small scales are usually formed in a small portion of the domain or in a special period of time. AMR is an efficient method to solve these types of problems, allowing high grid resolutions where and when they are needed and minimizing memory and CPU time. Here we formulate a spectral version of AMR in order to accelerate simulations of a 1D model for isotropic homogenous turbulence, the Burgers equation, as a first test of this method. Using pseudo spectral methods, we applied AMR in Fourier space. The spectral AMR (SAMR) method we present here is applied to the Burgers equation and the results are compared with the results obtained using standard solution methods performed using a fine mesh.

  12. Effects of a Temperature-Sensitive, Anti-Adhesive Agent on the Reduction of Adhesion in a Rabbit Laminectomy Model

    Park, Jeong Woo; Cho, Tae Koo; Chun, Hyoung-Joon; Ryu, Je Il

    2016-01-01

    Objective A common cause of failure in laminectomy surgery is when epidural, peridural, or perineural adhesion occurs postoperatively. The purpose of this study is to examine the efficacy of a temperature-sensitive, anti-adhesive agent (TSAA agent), Guardix-SG®, as a mechanical barrier for the prevention or reduction of peridural scar adhesion in a rabbit laminectomy model. Methods Twenty-six mature rabbits were used for this study. Each rabbit underwent two separate laminectomies at lumbar vertebrae L3 and L6, left empty (the control group) and applied 2 mL of the TSAA agent (the experimental group), respectively. Invasive scar formation or inflammation after laminectomy was quantitatively evaluated by measuring the thickness of the dura, the distance from the surface of dura to the scar tissues, the number of inflammatory cells in the scar tissues at the laminectomy site, and the concentration of collagen in histological sections. Results At 6 weeks postsurgery, the dura was significantly thinner and the distance from the surface of dura to the scar tissues was greater in the experimental group than in the control group (p=0.04 and p=0.01). The number of inflammatory cells was not significantly different in the two groups (p=0.08), although the mean number of inflammatory cells was relatively lower in the experimental group than in the control group. Conclusion The current study suggests that the TSAA agent, Guardix-SG®, could be useful as an interpositional physical barrier after laminectomy for the prevention or reduction of adhesion. PMID:27226857

  13. Model for probing membrane-cortex adhesion by micropipette aspiration and fluctuation spectroscopy

    Alert, Ricard; Casademunt, Jaume; Brugués, Jan; Sens, Pierre

    2016-01-01

    We propose a model for membrane-cortex adhesion that couples membrane deformations, hydrodynamics, and kinetics of membrane-cortex ligands. In its simplest form, the model gives explicit predictions for the critical pressure for membrane detachment and for the value of adhesion energy. We show that these quantities exhibit a significant dependence on the active acto-myosin stresses. The model provides a simple framework to access quantitative information on cortical activity by means of micro...

  14. Evaluation of explicit and implicit LES closures for Burgers turbulence

    Maulik, Romit

    2016-01-01

    In this work, we perform an aposteriori error analysis on implicit and explicit large eddy simulation closure models for solving the Burgers turbulence problem. Our closure modeling efforts include both functional and structural models equipped with various low-pass filters. We introduce discrete binomial smoothing filters and an enhanced version of the Van Cittert algorithm to accelerate the convergence of approximate deconvolution processes including regularization and relaxation filtering approaches. Our implicit modeling efforts consist of various high-order schemes including compact and non-compact fifth-order upwind schemes as well as weighted essential non-oscillatory (WENO) and compact reconstructed WENO (CRWENO) schemes, and the resulting schemes are shown to effectively converge to the direct numerical simulation (DNS) for increasing resolutions. Comparing with DNS and underresolved DNS computations, our numerical assessments illustrate the ability of these methods to capture the energy content near...

  15. A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

    Shi Wei-ping; Ren Lu-quan; Tian Li-mei

    2005-01-01

    Adhesive forces exist between soil and the surfaces of soil-engaging components; they increase working resistance and energy consumption. This paper tries to find an approach to reduce the adhesion and resistance of bulldozing plate. A simplified mechanical model of adhesion and resistance between soil and a non-smooth bulldozing plate is proposed. The interaction force between moist soil and a non-smooth bulldozing plate is analyzed. The pressure and friction distribution on the bulldozing plate are computed, and the anti-adhesive effect of a corrugated bulldozing plate is simulated numerically.Numerical results show that the wavy bulldozing plate achieves an effective drag reduction in moist soil. The optimal wavy shape of the corrugated bulldozing plate with the minimal resistance is designed. The basic principle of reducing soil adhesion of the non-smooth surface is discovered.

  16. Adhesive behaviour of gecko-inspired nanofibrillar arrays: combination of experiments and finite element modelling

    A polypropylene nanofibrillar array was successfully fabricated by template-assisted nanofabrication strategy. Adhesion properties of this gecko-inspired structure were studied through two parallel and independent approaches: experiments and finite element simulations. Experimental results show relatively good normal adhesion, but accompanied by high preloads. The interfacial adhesion was modelled by effective spring elements with piecewise-linear constitution. The effective elasticity of the fibre-array system was originally calculated from our measured elasticity of single nanowire. Comparisons of the experimental and simulative results reveal quantitative agreement except for some explainable deviations, which suggests the potential applicability of the present models and applied theories. (fast track communication)

  17. Contact Mechanics Modeling of Homogeneous and Layered Elastic-Plastic Media: Surface Roughness and Adhesion Effects

    Song, Zhichao

    2012-01-01

    The main objective of this dissertation was to analyze surface contact interaction at different length scales and to elucidate the effects of material properties (e.g., adhesion and mechanical properties), normal and shear (friction) surface tractions, and topography parameters (e.g., roughness) on contact deformation. To accomplish this objective, a surface adhesion model based on an interatomic potential was incorporated into finite element contact models of rough surfaces exhibiting multi-...

  18. Combined modeling of cell aggregation and adhesion mediated by receptor–ligand interactions under shear flow

    Yu Du

    2015-11-01

    Full Text Available Blood cell aggregation and adhesion to endothelial cells under shear flow are crucial to many biological processes such as thrombi formation, inflammatory cascade, and tumor metastasis, in which these cellular interactions are mainly mediated by the underlying receptor–ligand bindings. While theoretical modeling of aggregation dynamics and adhesion kinetics of interacting cells have been well studied separately, how to couple these two processes remains unclear. Here we develop a combined model that couples cellular aggregation dynamics and adhesion kinetics under shear flow. The impacts of shear rate (or shear stress and molecular binding affinity were elucidated. This study provides a unified model where the action of a fluid flow drives cell aggregation and adhesion under the modulations of the mechanical shear flow and receptor–ligand interaction kinetics. It offers an insight into understanding the relevant biological processes and functions.

  19. The adhesion model considering capillarity for gecko attachment system

    Kim, Tae Wan; Bhushan, Bharat

    2007-01-01

    Geckos make use of approximately a million microscale hairs (setae) that branch off into hundreds of nanoscale spatulae to cling to different smooth and rough surfaces and detach at will. This hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. It is known that van der Waals force is the primary mechanism used to adhere to surfaces, and capillary force is a secondary effect that can further increase adhesive force. To invest...

  20. Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

    Dongsheng Wang; Junyan Yi; Decheng Feng

    2014-01-01

    Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more ...

  1. Modeling of adhesion in tablet compression - I. atomic force microscopy and molecular simulation.

    Wang, J. J.; Li, T.; Bateman, S. D.; Erck, R.; Morris, K. R.; Energy Technology; Purdue Univ.; Novartis Pharmaceutical Corp.

    2003-04-01

    Adhesion problems during tablet manufacturing have been observed to be dependent on many formulation and process factors including the run time on the tablet press. Consequently, problems due to sticking may only become apparent towards the end of the development process when a prolonged run on the tablet press is attempted for the first time. It would be beneficial to predict in a relative sense if a formulation or new chemical entity has the potential for adhesion problems early in the development process. It was hypothesized that favorable intermolecular interaction between the drug molecules and the punch face is the first step or criterion in the adhesion process. Therefore, the rank order of adhesion during tablet compression should follow the rank order of these energies of interaction. The adhesion phenomenon was investigated using molecular simulations and contact mode atomic force microscopy (AFM). Three model compounds were chosen from a family of profen compounds. Silicon nitride AFM tips were modified by coating a 20-nm iron layer on the surfaces by sputter coating. Profen flat surfaces were made by melting and recrystallization. The modified AFM probe and each profen surface were immersed in the corresponding profen saturated water during force measurements using AFM. The work of adhesion between iron and ibuprofen, ketoprofen, and flurbiprofen in vacuum were determined to be -184.1, -2469.3, -17.3 mJ {center_dot} m-2, respectively. The rank order of the work of adhesion between iron and profen compounds decreased in the order: ketoprofen > ibuprofen > flurbiprofen. The rank order of interaction between the drug molecules and the iron superlattice as predicted by molecular simulation using Cerius2 is in agreement with the AFM measurements. It has been demonstrated that Atomic Force Microscopy is a powerful tool in studying the adhesion phenomena between organic drug compounds and metal surface. The study has provided insight into the adhesion problems

  2. Modeling keratinocyte wound healing dynamics: Cell-cell adhesion promotes sustained collective migration.

    Nardini, John T; Chapnick, Douglas A; Liu, Xuedong; Bortz, David M

    2016-07-01

    The in vitro migration of keratinocyte cell sheets displays behavioral and biochemical similarities to the in vivo wound healing response of keratinocytes in animal model systems. In both cases, ligand-dependent Epidermal Growth Factor Receptor (EGFR) activation is sufficient to elicit collective cell migration into the wound. Previous mathematical modeling studies of in vitro wound healing assays assume that physical connections between cells have a hindering effect on cell migration, but biological literature suggests a more complicated story. By combining mathematical modeling and experimental observations of collectively migrating sheets of keratinocytes, we investigate the role of cell-cell adhesion during in vitro keratinocyte wound healing assays. We develop and compare two nonlinear diffusion models of the wound healing process in which cell-cell adhesion either hinders or promotes migration. Both models can accurately fit the leading edge propagation of cell sheets during wound healing when using a time-dependent rate of cell-cell adhesion strength. The model that assumes a positive role of cell-cell adhesion on migration, however, is robust to changes in the leading edge definition and yields a qualitatively accurate density profile. Using RNAi for the critical adherens junction protein, α-catenin, we demonstrate that cell sheets with wild type cell-cell adhesion expression maintain migration into the wound longer than cell sheets with decreased cell-cell adhesion expression, which fails to exhibit collective migration. Our modeling and experimental data thus suggest that cell-cell adhesion promotes sustained migration as cells pull neighboring cells into the wound during wound healing. PMID:27105673

  3. A simple beam model to analyse the durability of adhesively bonded tile floorings in presence of shrinkage

    S. de Miranda

    2014-07-01

    Full Text Available A simple beam model for the evaluation of tile debonding due to substrate shrinkage is presented. The tile-adhesive-substrate package is modeled as an Euler-Bernoulli beam laying on a two-layer elastic foundation. An effective discrete model for inter-tile grouting is introduced with the aim of modelling workmanship defects due to partial filled groutings. The model is validated using the results of a 2D FE model. Different defect configurations and adhesive typologies are analysed, focusing the attention on the prediction of normal stresses in the adhesive layer under the assumption of Mode I failure of the adhesive.

  4. Modeling of the Peeling Process of Pressure-sensitive Adhesive Tapes with the Combination of Maxwell Elements

    Sato, Katsuhiko; Toda, Akihiko

    2004-01-01

    A simple model for the peeling process of pressure-sensitive adhesive tape is presented. The model consists of linear springs and dashpots and can be solved analytically. Based on the modeling, the curved profile of the peeling tape is spontaneously determined in terms of viscoelastic properties of adhesives. Using this model, two experimental results are discussed: critical peel rates in the peel force and the peel rate dependence of the detachment process of adhesive from the substrate.

  5. Adhesion of silver nanoparticles on the clay substrates; modeling and experiment

    Adhesion of silver nanoparticles on the montmorillonite and kaolinite substrates has been investigated using molecular modeling (force field calculations) that enabled the estimation and comparison of adhesion energies for Ag/montmorillonite and Ag/kaolinite nanocomposites and revealed the preferred orientation of Ag nanoparticles on the silicate substrates. Results of the modeling have been confronted with experiment (X-ray fluorescence, high-resolution transmission electron microscopy). This confrontation has shown that the results of the modeling are consistent with the experimental data and illustrated the capability of the molecular modeling for prediction of the nanoparticles orientation, structure and stability of the nanoparticle/substrate nanocomposite.

  6. Model for probing membrane-cortex adhesion by micropipette aspiration and fluctuation spectroscopy

    Alert, Ricard; Brugués, Jan; Sens, Pierre

    2016-01-01

    We propose a model for membrane-cortex adhesion which couples membrane deformations, hydrodynamics and kinetics of membrane-cortex ligands. In its simplest form, the model gives explicit predictions for the critical pressure for membrane detachment and for the value of adhesion energy. We show that these quantities exhibit a significant dependence on the active acto-myosin stresses. The model provides a simple framework to access quantitative information on cortical activity by means of micropipette experiments. We also extend the model to incorporate fluctuations and show that detailed information on the stability of membrane-cortex coupling can be obtained by a combination of micropipette aspiration and fluctuation spectroscopy measurements.

  7. Model for Probing Membrane-Cortex Adhesion by Micropipette Aspiration and Fluctuation Spectroscopy

    Alert, Ricard; Casademunt, Jaume; Brugués, Jan; Sens, Pierre

    2015-04-01

    We propose a model for membrane-cortex adhesion which couples membrane deformations, hydrodynamics and kinetics of membrane-cortex ligands. In its simplest form, the model gives explicit predictions for the critical pressure for membrane detachment and for the value of adhesion energy. We show that these quantities exhibit a significant dependence on the active acto-myosin stresses. The model provides a simple framework to access quantitative information on cortical activity by means of micropipette experiments. We also extend the model to incorporate fluctuations and show that detailed information on the stability of membrane-cortex coupling can be obtained by a combination of micropipette aspiration and fluctuation spectroscopy measurements.

  8. Application of Extended Tanh Method to Generalized Burgers-type Equations

    Hamid Panahipour

    2012-02-01

    Full Text Available In this paper, we show that the extended tanh method can be applied readily to generate exact soliton solutions of generalized forms of Burgers-KdV, Burgers-EW, two-dimensional Burgers-KdV and two-dimensional Burgers-EW equations.

  9. The deterministic and statistical Burgers equation

    Fournier, J.-D.; Frisch, U.

    Fourier-Lagrangian representations of the UV-region inviscid-limit solutions of the equations of Burgers (1939) are developed for deterministic and random initial conditions. The Fourier-mode amplitude behavior of the deterministic case is characterized by complex singularities with fast decrease, power-law preshocks with k indices of about -4/3, and shocks with k to the -1. In the random case, shocks are associated with a k to the -2 spectrum which overruns the smaller wavenumbers and appears immediately under Gaussian initial conditions. The use of the Hopf-Cole solution in the random case is illustrated in calculations of the law of energy decay by a modified Kida (1979) method. Graphs and diagrams of the results are provided.

  10. Dennexin peptides modeled after the homophilic binding sites of the neural cell adhesion molecule (NCAM) promote neuronal survival, modify cell adhesion and impair spatial learning

    Køhler, Lene B; Christensen, Claus; Rossetti, Clara; Fantin, Martina; Sandi, Carmen; Bock, Elisabeth; Berezin, Vladimir

    2010-01-01

    Neural cell adhesion molecule (NCAM)-mediated cell adhesion results in activation of intracellular signaling cascades that lead to cellular responses such as neurite outgrowth, neuronal survival, and modulation of synaptic activity associated with cognitive processes. The crystal structure of the...... between Ig1 and Ig3 and between Ig2 and Ig2, respectively, observed in the crystal structure. Although the two dennexin peptides differed in amino acid sequence, they both modulated cell adhesion, reflected by inhibition of NCAM-mediated neurite outgrowth. Both dennexins also promoted neuronal survival...... immunoglobulin (Ig) 1-2-3 fragment of the NCAM ectodomain has revealed novel mechanisms for NCAM homophilic adhesion. The present study addressed the biological significance of the so called dense zipper formation of NCAM. Two peptides, termed dennexinA and dennexinB, were modeled after the contact interfaces...

  11. The superposition method in seeking the solitary wave solutions to the KdV-Burgers equation

    Yuanxi Xie; Jilashi Tang

    2006-03-01

    In this paper, starting from the careful analysis on the characteristics of the Burgers equation and the KdV equation as well as the KdV-Burgers equation, the superposition method is put forward for constructing the solitary wave solutions of the KdV-Burgers equation from those of the Burgers equation and the KdV equation. The solitary wave solutions for the KdV-Burgers equation are presented successfully by means of this method.

  12. Improved model for the adhesion of μcantilevers: theory and experiments

    A nonlinear method is proposed to calculate the adhesion energy (strain energy release rate) of stiction-failed μcantilever beams with large deflections. The proposed method uses a nonlinear theory for the deflection of a beam and an energy method for calculating the beam’s strain energy. It is shown that current models used to predict μcantilevers’ profile breakdown when the beam deflection exceeds 27% of the thickness due to the onset of longitudinal stresses in the μcantilevers. Because the present model captures longitudinal stresses in the μcantilevers and consequently their contribution to the strain energy, mode I and mode II contributions to the adhesion energy can be discerned. A set of experiments are performed using the peel test scheme with poly-Si μcantilever stiction failed on a poly-Si substrate. Results processed using the present model indicate that the adhesion energy of the μcantilevers actually increases with increased height of the μcantilever’s base. This increase in the adhesion energy is attributed to the manner of loading that the μcantilevers experience which leads to increased contact area and the concomitant increase of adhesion. (paper)

  13. Numerical analysis of single particle impact in the context of Cold Spray: a new adhesion model

    Profizi, P.; Combescure, A.; Ogawa, K.

    2016-03-01

    A new adhesion model for numerical simulation of single particle impact in the context of Cold Spray is introduced. As in other studies, cohesive forces are put between the particle and substrate to account for adhesion. In this study however, the forces are put only when a local physical criterion is met. The physical phenomenon most often attributed to Cold Spray adhesion is a shear stress instability. The Johnson-Cook material law is used with a shear damage softening law to enable strong localization at the interface without the need for an extremely fine mesh. This localization is then detected as a drop in local yield stress value by the algorithm, which then implements a local cohesive force. The evolution of this cohesive force is defined by an energy dissipative cohesive model, using a surface adhesion energy as a material parameter. Each cohesive link is broken once all its associated surface energy is dissipated. A criterion on the damage value is also used to break a cohesive bond prematurely, to account for the effect of erosion at higher speeds. This model is found to reproduce the Cold Spray-like adhesion behavior with observed critical and maximum speeds.

  14. A New Material Model for 2D FE Analysis of Adhesively Bonded Composite Joints

    Libin ZHAO

    2014-12-01

    Full Text Available Effective and convenient stress analysis techniques play important roles in the analysis and design of adhesively bonded composite joints. A new material model is presented at the level of composite ply according to the orthotropic elastic mechanics theory and plane strain assumption. The model proposed has the potential to reserve nature properties of laminates with ply-to-ply modeling. The equivalent engineering constants in the model are obtained only by the material properties of unidirectional composites. Based on commercial FE software ABAQUS, a 2D FE model of a single-lap adhesively bonded joint was established conveniently by using the new model without complex modeling process and much professional knowledge. Stress distributions in adhesive were compared with the numerical results by Tsai and Morton and interlaminar stresses between adhesive and adherents were compared with the results from a detailed 3D FE analysis. Good agreements in both cases verify the validity of the proposed model. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.5960

  15. A Regularization of Burgers Equation using a Filtered Convective Velocity

    Norgard, Greg

    2008-01-01

    This paper examines the properties of a regularization of Burgers equation in one and multiple dimensions using a filtered convective velocity, which we have dubbed as convectively filtered Burgers (CFB) equation. A physical motivation behind the filtering technique is presented. An existence and uniqueness theorem for multiple dimensions and a general class of filters is proven. Multiple invariants of motion are found for the CFB equation and are compared with those found in viscous and inviscid Burgers equation. Traveling wave solutions are found for a general class of filters and are shown to converge to weak solutions of inviscid Burgers equation with the correct wave speed. Accurate numerical simulations are conducted in 1D and 2D cases where the shock behavior, shock thickness, and kinetic energy decay are examined. Energy spectrum are also examined and are shown to be related to the smoothness of the solutions.

  16. Burgers' turbulence problem with linear or quadratic external potential

    Barndorff-Nielsen, Ole Eiler; Leonenko, N.N.

    2005-01-01

    We consider solutions of Burgers' equation with linear or quadratic external potential and stationary random initial conditions of Ornstein-Uhlenbeck type. We study a class of limit laws that correspond to a scale renormalization of the solutions.......We consider solutions of Burgers' equation with linear or quadratic external potential and stationary random initial conditions of Ornstein-Uhlenbeck type. We study a class of limit laws that correspond to a scale renormalization of the solutions....

  17. Enhanced Lifespan of Smooth Solutions of a Burgers-Hilbert Equation

    Hunter, John

    2011-01-01

    We consider an initial value problem for a quadratically nonlinear inviscid Burgers-Hilbert equation that models the motion of vorticity discontinuities. We use a normal form transformation, which is implemented by means of a near-identity coordinate change of the independent spatial variable, to prove the existence of small, smooth solutions over cubically nonlinear time-scales. For vorticity discontinuities, this result means that there is a cubically nonlinear time-scale before the onset of filamentation.

  18. ANALISIS KEPUASAN KONSUMEN RESTORAN CEPAT SAJI MENGGUNAKAN METODE PARTIAL LEAST SQUARE (Studi Kasus: Burger King Bali)

    MADE SANJIWANI; KETUT JAYANEGARA; I PUTU EKA N. KENCANA

    2015-01-01

    The were two aims of this research. First is to get model of the relation between the latent variable quality of service and product quality to customer satisfaction. The second was to determine the influence of service quality on customer satisfaction and the influence of product quality on consumer satisfaction at Burger King Bali. This research implemented Partial Least Square method with 3 second order variables is the service quality, product quality, and customer satisfaction. In this r...

  19. On exact solutions for oscillatory flows in a generalized Burgers fluid with slip condition

    Hayat, Tasawar [Dept. of Mathematics, Quaid-i-Azam Univ., Islamabad (Pakistan); Dept. of Mathematics, Coll. of Sciences, KS Univ., Riyadh (Saudi Arabia); Najam, Saher [Theoretical Plasma Physics Div., PINSTECH, P.O. Nilore, Islamabad (Pakistan); Sajid, Muhammad; Mesloub, Said [Dept. of Mathematics, Coll. of Sciences, KS Univ., Riyadh (Saudi Arabia); Ayub, Muhammad [Dept. of Mathematics, Quaid-i-Azam Univ., Islamabad (Pakistan)

    2010-05-15

    An analysis is performed for the slip effects on the exact solutions of flows in a generalized Burgers fluid. The flow modelling is based upon the magnetohydrodynamic (MHD) nature of the fluid and modified Darcy law in a porous space. Two illustrative examples of oscillatory flows are considered. The results obtained are compared with several limiting cases. It has been shown here that the derived results hold for all values of frequencies including the resonant frequency. (orig.)

  20. Characterization and Development of General Material Models for use in Modeling Structures Bonded with Ductile Adhesives

    Cassino, Christopher

    2005-01-01

    Structural adhesives are materials that are capable of bearing significant loads in shear, and sometimes tension, over a range of strains and strain rates. Adhesively bonded structures can dissipate large amounts of mechanical energy and can be lighter and more efficient than many bolted or vibration welded parts. The largest barrier to using structural adhesives in more applications is the many challenges engineers are presented with when designing and analyzing adhesively bonded structures....

  1. Advanced adhesives in electronics

    Bailey, C

    2011-01-01

    Adhesives are widely used in the manufacture of electronic devices to act as passive and active components. Recently there has been considerable interest in the use of conductive adhesives. This book reviews key types of conductive adhesives, processing methods, properties and the way they can be modelled as well as potential applications.$bAdhesives for electronic applications serve important functional and structural purposes in electronic components and packaging, and have developed significantly over the last few decades. Advanced adhesives in electronics reviews recent developments in adhesive joining technology, processing and properties. The book opens with an introduction to adhesive joining technology for electronics. Part one goes on to cover different types of adhesive used in electronic systems, including thermally conductive adhesives, isotropic and anisotropic conductive adhesives and underfill adhesives for flip-chip applications. Part two focuses on the properties and processing of electronic ...

  2. A New Material Model for 2D FE Analysis of Adhesively Bonded Composite Joints

    Zhao, Libin; Wang, Yana; TianLiang QIN; Zhang, Jianyu

    2014-01-01

    Effective and convenient stress analysis techniques play important roles in the analysis and design of adhesively bonded composite joints. A new material model is presented at the level of composite ply according to the orthotropic elastic mechanics theory and plane strain assumption. The model proposed has the potential to reserve nature properties of laminates with ply-to-ply modeling. The equivalent engineering constants in the model are obtained only by the material properties of unidirec...

  3. Modeling of cell adhesion and deformation mediated by receptor-ligand interactions.

    Golestaneh, Amirreza F; Nadler, Ben

    2016-04-01

    The current work is devoted to studying adhesion and deformation of biological cells mediated by receptors and ligands in order to enhance the existing models. Due to the sufficient in-plane continuity and fluidity of the phospholipid molecules, an isotropic continuum fluid membrane is proposed for modeling the cell membrane. The developed constitutive model accounts for the influence of the presence of receptors on the deformation and adhesion of the cell membrane through the introduction of spontaneous area dilation. Motivated by physics, a nonlinear receptor-ligand binding force is introduced based on charge-induced dipole interaction. Diffusion of the receptors on the membrane is governed by the receptor-ligand interaction via Fick's Law and receptor-ligand interaction. The developed model is then applied to study the deformation and adhesion of a biological cell. The proposed model is used to study the role of the material, binding, spontaneous area dilation and environmental properties on the deformation and adhesion of the cell. PMID:26093646

  4. SPH modeling of adhesion in fast dynamics: Application to the Cold Spray process

    Profizi, Paul; Combescure, Alain; Ogawa, Kahuziro

    2016-04-01

    The objective of this paper is to show, in a specific case, the importance of modeling adhesive forces when simulating the bouncing of very small particles impacting a substrate at high speed. The implementation of this model into a fast-dynamics SPH code is described. Taking the example of an impacted elastic cylinder, we show that the adhesive forces, which are surface forces, play a significant role only if the particles are sufficiently small. The effect of the choice of the type of interaction law in the cohesive zone is studied and some conclusions on the relevance of the modeling of the adhesive forces for fast-dynamics impacts are drawn. Then, the adhesion model is used to simulate the Cold Spray process. An aluminum particle is projected against a substrate made of the same material at a velocity ranging from 200 to 1000 m ṡs-1. We study the effects of the various modeling assumptions on the final result: bouncing or sticking. Increasingly complex models are considered. At a 200 m ṡs-1 impact velocity, elastic behavior is assumed, the substrate being simply supported at its base and supplied with absorbing boundaries. The same absorbing boundaries are also used for all the other simulations. Then, plasticity is introduced and the impact velocity is increased up to 1000 m ṡs-1. At the highest velocities, the resulting strains are very significant. The calculations show that if the adhesion model is appropriately chosen, it is possible to reproduce the experimental observations: the particles stick to the substrate in a range of impact velocities surrounded by two velocity ranges in which the particles bounce.

  5. Localized Modeling of Biochemical and Flow Interactions during Cancer Cell Adhesion.

    Julie Behr

    Full Text Available This work focuses on one component of a larger research effort to develop a simulation tool to model populations of flowing cells. Specifically, in this study a local model of the biochemical interactions between circulating melanoma tumor cells (TC and substrate adherent polymorphonuclear neutrophils (PMN is developed. This model provides realistic three-dimensional distributions of bond formation and attendant attraction and repulsion forces that are consistent with the time dependent Computational Fluid Dynamics (CFD framework of the full system model which accounts local pressure, shear and repulsion forces. The resulting full dynamics model enables exploration of TC adhesion to adherent PMNs, which is a known participating mechanism in melanoma cell metastasis. The model defines the adhesion molecules present on the TC and PMN cell surfaces, and calculates their interactions as the melanoma cell flows past the PMN. Biochemical rates of reactions between individual molecules are determined based on their local properties. The melanoma cell in the model expresses ICAM-1 molecules on its surface, and the PMN expresses the β-2 integrins LFA-1 and Mac-1. In this work the PMN is fixed to the substrate and is assumed fully rigid and of a prescribed shear-rate dependent shape obtained from micro-PIV experiments. The melanoma cell is transported with full six-degrees-of-freedom dynamics. Adhesion models, which represent the ability of molecules to bond and adhere the cells to each other, and repulsion models, which represent the various physical mechanisms of cellular repulsion, are incorporated with the CFD solver. All models are general enough to allow for future extensions, including arbitrary adhesion molecule types, and the ability to redefine the values of parameters to represent various cell types. The model presented in this study will be part of a clinical tool for development of personalized medical treatment programs.

  6. Systemic EP4 Inhibition Increases Adhesion Formation in a Murine Model of Flexor Tendon Repair.

    Geary, Michael B; Orner, Caitlin A; Bawany, Fatima; Awad, Hani A; Hammert, Warren C; O'Keefe, Regis J; Loiselle, Alayna E

    2015-01-01

    Flexor tendon injuries are a common clinical problem, and repairs are frequently complicated by post-operative adhesions forming between the tendon and surrounding soft tissue. Prostaglandin E2 and the EP4 receptor have been implicated in this process following tendon injury; thus, we hypothesized that inhibiting EP4 after tendon injury would attenuate adhesion formation. A model of flexor tendon laceration and repair was utilized in C57BL/6J female mice to evaluate the effects of EP4 inhibition on adhesion formation and matrix deposition during flexor tendon repair. Systemic EP4 antagonist or vehicle control was given by intraperitoneal injection during the late proliferative phase of healing, and outcomes were analyzed for range of motion, biomechanics, histology, and genetic changes. Repairs treated with an EP4 antagonist demonstrated significant decreases in range of motion with increased resistance to gliding within the first three weeks after injury, suggesting greater adhesion formation. Histologic analysis of the repair site revealed a more robust granulation zone in the EP4 antagonist treated repairs, with early polarization for type III collagen by picrosirius red staining, findings consistent with functional outcomes. RT-PCR analysis demonstrated accelerated peaks in F4/80 and type III collagen (Col3a1) expression in the antagonist group, along with decreases in type I collagen (Col1a1). Mmp9 expression was significantly increased after discontinuing the antagonist, consistent with its role in mediating adhesion formation. Mmp2, which contributes to repair site remodeling, increases steadily between 10 and 28 days post-repair in the EP4 antagonist group, consistent with the increased matrix and granulation zones requiring remodeling in these repairs. These findings suggest that systemic EP4 antagonism leads to increased adhesion formation and matrix deposition during flexor tendon healing. Counter to our hypothesis that EP4 antagonism would improve the

  7. Antioxidant Small-spotted Catshark Burgers

    Joana Patriarca

    2014-06-01

    Full Text Available Tons of fish are rejected daily, not only on board, but also on shore during the industrial processing (INE, 2012. In order to reuse these wastes, restructured seafood products must be developed. On the other hand, in western countries a trend in the increase of the number of cancer cases is observed, especially among the youngsters (Steliarova-Foucher et al, 2004. A healthy and high quality nutrition plays an important role on cancer prevention (Davis et al, 2010; Kuno et al, 2012. Many authors found several phytochemical compounds naturally present in foods with powerful antioxidant properties. These have the ability to stop or delay the development of the tumors, by inducing apoptosis and prevent angiogenesis or metastasis (Kou et al, 2013. In the present work, it was developed a restructured functional food based on rejected small-spotted catshark. The functional capacity of this food is attained by the addition of ingredients with proven antioxidant ability. Studies have been made to optimize the antioxidant extraction process from the fish burger through different combinations of solvent extraction. Furthermore, the antioxidant activity of the restructured product was characterized in terms of total phenolic content (TPC, 2,2-diphenyl-1-picrylhydrazyl (DPPH radical scavenging activity and oxygen radical absorbance capacity (ORAC. Apparently, a higher level of antioxidants is detected when methanol is used for extraction during twelve hours at room temperature. The results also showed the functional fish product presents a higher capacity for DPPH reduction and increased values for ORAC by comparison with small-spotted catshark only.

  8. From flexibility to cooperativity: multiscale modeling of cadherin-mediated cell adhesion

    Wu, Yinghao

    2013-03-01

    Cadherins constitute a large family of Ca2 +-dependent adhesion molecules in the Inter-cellular junctions that play a pivotal role in the assembly of cells into specific three-dimensional tissues. Although the molecular mechanisms underlying cadherin-mediated cell adhesion are still not fully understood, it seems likely that both cis dimers that are formed by binding of extracellular domains of two cadherins on the same cell surface, and trans-dimers formed between cadherins on opposing cell surfaces, are critical to trigger the junction formation. Here we present a new multiscale computational strategy to model the process of junction formation based on the knowledge of cadherin molecular structures and its 3D binding affinities. The cell interfacial region is defined by a simplified system where each of two interacting membrane surfaces is represented as a two-dimensional lattice with each cadherin molecule treated as a randomly diffusing unit. The binding energy for a pair of interacting cadherins in this two-dimensional discrete system is obtained from 3D binding affinities through a renormalization process derived from statistical thermodynamics. The properties of individual cadherins used in the lattice model are based on molecular level simulations. Our results show that within the range of experimentally-measured binding affinities, cadherins condense into junctions driven by the coupling of cis and trans interactions. The key factor appears to be a loss of molecular flexibility during trans dimerization that increases the magnitude of lateral cis interactions. We have also developed stochastic dynamics to study the adhesion of multiple cells. Each cell in the system is described as a mechanical entity and adhesive properties between two cells are derived from the lattice model. The cellular simulations are used to study the specific problems of tissue morphogenesis and tumor metastasis. The consequent question and upcoming challenge is to understand the

  9. IgG Adhesion on Hydrophobic Surfaces: Theory, Modelling, and Application to ELISA

    de Thier, P

    2016-01-01

    Enzyme-Linked ImmunoSorbent Assays (ELISA) are a range of widely used analytical methods whose implementation requires to build antibodies (IgG) thin films onto surfaces predominantly made of polystyrene. The high hydrophobicity of polystyrene ensures a spontaneous and strong adhesion of proteins allowing to easily build IgG monolayers. Since the ELISA improvements definitely lie in the comprehension of physico-chemical mechanisms on which IgG immobilization on hydrophobic surfaces are relied, this work develops a theorization essay (thermodynamics of the so-called hydrophobic effect and of thin films building) emphasized by numerical modelling (random sequential additions model, i.e. RSA) and experimental estimations by atomic force microscopy (AFM) and ELISA. Keeping in mind the hydrophobic effect, thermodynamics (of irreversible processes) allows to explain why IgG adhesion on polystyrene occurs whereas numerical modelling approaches show a way of surface saturation leading to promote IgG orientations expe...

  10. On the Maximum Enstrophy Growth in Burgers Equation

    The regularity of solutions of the three-dimensional Navier-Stokes equation is controlled by the boundedness of the enstrophy ε. The best estimate available to-date for its rate of growth is dε/dt ≤ Cε3, where C > 0, which was recently found to be sharp by Lu and Doering (2008). Applying straightforward time-integration to this instantaneous estimate leads to the possibility of loss of regularity in finite time, the so-called blow-up, and therefore the central question is to establish sharpness of such finite-time bounds. We consider an analogous problem for Burgers equation which is used as a toy model. The problem of saturation of finite-time estimates for the enstrophy growth is stated as a PDE-constrained optimization problem, where the control variable φ represents the initial condition, which is solved numerically for a wide range of time windows T > 0 and initial enstrophies ε0. We find that the maximum enstrophy growth in finite time scales as ε0α with α ≈ 3/2. The exponent is smaller than α = 3 predicted by analytic means, therefore suggesting lack of sharpness of analytical estimates.

  11. Non-linear vorticity upsurge in Burgers flow

    Lam, F

    2016-01-01

    We demonstrate that numerical solutions of Burgers' equation can be obtained by a scale-totality algorithm for fluids of small viscosity (down to one billionth). Two sets of initial data, modelling simple shears and wall boundary layers, are chosen for our computations. Most of the solutions are carried out well into the fully turbulent regime over finely-resolved scales in space and in time. It is found that an abrupt spatio-temporal concentration in shear constitutes an essential part during the flow evolution. The vorticity surge has been instigated by the non-linearity complying with instantaneous enstrophy production while ad hoc disturbances play no role in the process. In particular, the present method predicts the precipitous vorticity re-distribution and accumulation, predominantly over localised regions of minute dimension. The growth rate depends on viscosity and is a strong function of initial data. Nevertheless, the long-time energy decay is history-independent and is inversely proportional to ti...

  12. Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

    Dongsheng Wang

    2014-01-01

    Full Text Available Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

  13. Modelling and laboratory studies on the adhesion fatigue performance for thin-film asphalt and aggregate system.

    Wang, Dongsheng; Yi, Junyan; Feng, Decheng

    2014-01-01

    Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system. PMID:25054187

  14. A Granule Model for Evaluating Adhesion of Pharmaceutical Binders

    Hossein Orafai

    2003-01-01

    Granule capability is defined in terms of the strength of individual granule and friability of granulation batch to withstand breaking, abrasion and compactibility. Binder(s) are added to perform the above properties .The common methods to asses their capability are to test crushing strength of the granules directly and to make statistical analysis and /or testing the friability of bulk granulation. In this work four substrate models including polymethylmetacrylate beads(PMMA),glass powder, a...

  15. Painlevé Analysis and Some Solutions of(2+1)-Dimensional Generalized Burgers Equations

    HONG Ke-Zhu; WU B-in; CHEN Xian-Feng

    2003-01-01

    Burgers equation ut = 2uux + uxx describes a lot of phenomena in physics fields, and it has attracted much attention.In this paper,the Burgers equation is generalized to (2+1) dimensions.By means of the Painlev(e') analysis,the most generalized Painlev(e') integrable(2+1)-dimensional integrable Burgers systems are obtained.Some exact solutions of the generalized Burgers system are obtained via variable separation approach.

  16. A Granule Model for Evaluating Adhesion of Pharmaceutical Binders

    Hossein Orafai

    2003-10-01

    Full Text Available Granule capability is defined in terms of the strength of individual granule and friability of granulation batch to withstand breaking, abrasion and compactibility. Binder(s are added to perform the above properties .The common methods to asses their capability are to test crushing strength of the granules directly and to make statistical analysis and /or testing the friability of bulk granulation. In this work four substrate models including polymethylmetacrylate beads(PMMA,glass powder, acetaminophen, and para-aminobebzoic acid were chosen. The binder models were corn starch, gelatin, methylcellulose (MC and hydroxypropylmethylcellulose (HPMC. After massing the substrates with the binder solutions, discs were produced by the mean of the mold technique. The discs were dried and conditioned and then tested for tensile strength while the failed areas were scanned by SEM. Various granulations were made and the results of friability and crush strength were compared with the discs strength .The bond areas in the SEM showed the trend with the binder concentration .A comparison of the standard deviation shows that discs have much lower level of the strength than granules. The resulting discs showed a higher performance which is related to the stems for the discs shape .In conclusion, this method is a simple and is applicable to differentiate efficacy of binder under studies.

  17. Optimal fixed-finite-dimensional compensator for Burgers' equation with unbounded input/output operators

    Burns, John A.; Marrekchi, Hamadi

    1993-01-01

    The problem of using reduced order dynamic compensators to control a class of nonlinear parabolic distributed parameter systems was considered. Concentration was on a system with unbounded input and output operators governed by Burgers' equation. A linearized model was used to compute low-order-finite-dimensional control laws by minimizing certain energy functionals. Then these laws were applied to the nonlinear model. Standard approaches to this problem employ model/controller reduction techniques in conjunction with linear quadratic Gaussian (LQG) theory. The approach used is based on the finite dimensional Bernstein/Hyland optimal projection theory which yields a fixed-finite-order controller.

  18. A CLASS OF ALTERNATING GROUP METHOD OF BURGERS' EQUATION

    王文洽

    2004-01-01

    Some new Saul' yev type asymmetric difference schemes for Burgers' equation is given, by the use of the schemes, a kind of alternating group four points method for solving nonlinear Burgers' equation is constructed here. The basic idea of the method is that the grid points on the same time level is divided into a number of groups, the difference equations of each group can be solved independently, hence the method with intrinsic parallelism can be used directly on parallel computer. The method is unconditionally stable by analysis of linearization procedure. The numerical experiments show that the method has good stability and accuracy.

  19. Nanobioprobe for the Determination of Pork Adulteration in Burger Formulations

    Ali, M. E.; MUSTAFA, S.; Hashim, U.; Che Man, Y. B.; K L Foo

    2012-01-01

    We report the development of a swine-specific hybrid nanobioprobe through a covalent integration of a fluorophore-labeled 27-nucleotide AluI-fragment of swine cytochrome b gene to a 3 nm gold nanoparticle for the determination of pork adulteration in processed meat products. We tested the probe to estimate adulterated pork in ready-to-eat pork-spiked beef burgers. The probe quantitatively detected 1–100% spiked pork in burger formulations with ≥90% accuracy. A plot of observed fluorescence ag...

  20. On the Stochastic Burgers Equation and the Axiom of Choice

    Noble, John M

    2010-01-01

    The equivalence of the Choice Axiom and Tychonov compactness was proved by Kelley in 1950. Tychonov compactness is required to prove existence of the minimiser of an action functional under standard hypotheses. Solutions to the inviscid Burgers equation may be constructed by considering the minimising trajectories of associated action functionals. This construction has been used in the literature to construct an invariant measure for the stochastic inviscid Burgers equation. This article compares results that may be obtained with and without using this representation and draws conclusions about the Choice Axiom.

  1. Analyzing the dynamics of the forced Burgers equation

    Nejib Smaoui

    2000-01-01

    Full Text Available We study numerically the long-time dynamics of a system of reaction-diffusion equations that arise from the viscous forced Burgers equation (ut+uux−vuxx=F. A nonlinear transformation introduced by Kwak is used to embed the scalar Burgers equation into a system of reaction diffusion equations. The Kwak transformation is used to determine the existence of an inertial manifold for the 2-D Navier-Stokes equation. We show analytically as well as numerically that the two systems have a similar, long-time dynamical, behavior for large viscosity v.

  2. CONVERGENCE OF ADOMIAN METHOD FOR SOLVING KDV– BURGER EQUATION

    M. S. El-Azab

    2012-05-01

    Full Text Available In this paper, convergence of Adomian decomposition method (ADM when applied to KdV–Burgers equation is proved. Two approaches for extracting the soliton solutions to the nonlinear dispersive and dissipative KdV– Burgers equation are implemented. The first one is the classical ADM while, the second is the modified ADM which is called the general iteration method. Test examples are given and a comparison between the two approaches is carried out to illustrate the pertinent feature of the general iteration method.

  3. B-spline collocation methods for numerical solutions of the Burgers' equation

    İdris Dağ; Dursun Irk; Ali Şahin

    2005-01-01

    Both time- and space-splitted Burgers' equations are solved numerically. Cubic B-spline collocation method is applied to the time-splitted Burgers' equation. Quadratic B-spline collocation method is used to get numerical solution of the space-splitted Burgers' equation. The results of both schemes are compared for some test problems.

  4. Mixed-Mode Cohesive Damage Model Applied to the Simulation of the Mechanical Behaviour of Laminated Composite Adhesive Joints

    de Moura, MFSF; Campilho, RDSG; Goncalves, JPM

    2009-01-01

    A study of the mechanical behaviour of laminated composite adhesive joints is presented in this paper. The study consists of both numerical simulations and experimental tests. It concentrates on single lap-shear joints made of carbon-epoxy laminated composites and an epoxy adhesive. The main objective is to verify the adequacy of cohesive damage models for the strength prediction of bonded joints. These models are attractive in modelling fracture problems since they do not require the definit...

  5. Transchromosomic cell model of Down syndrome shows aberrant migration, adhesion and proteome response to extracellular matrix

    Cotter Finbarr E

    2009-08-01

    Full Text Available Abstract Background Down syndrome (DS, caused by trisomy of human chromosome 21 (HSA21, is the most common genetic birth defect. Congenital heart defects (CHD are seen in 40% of DS children, and >50% of all atrioventricular canal defects in infancy are caused by trisomy 21, but the causative genes remain unknown. Results Here we show that aberrant adhesion and proliferation of DS cells can be reproduced using a transchromosomic model of DS (mouse fibroblasts bearing supernumerary HSA21. We also demonstrate a deacrease of cell migration in transchromosomic cells independently of their adhesion properties. We show that cell-autonomous proteome response to the presence of Collagen VI in extracellular matrix is strongly affected by trisomy 21. Conclusion This set of experiments establishes a new model system for genetic dissection of the specific HSA21 gene-overdose contributions to aberrant cell migration, adhesion, proliferation and specific proteome response to collagen VI, cellular phenotypes linked to the pathogenesis of CHD.

  6. Velocity and velocity-difference distributions in Burgers turbulence

    Boldyrev, S.; Linde, T.; Polyakov, A.

    2003-01-01

    We consider the one-dimensional Burgers equation randomly stirred at large scales by a Gaussian short-time correlated force. Using the method of dissipative anomalies, we obtain velocity and velocity-difference probability density functions and confirm the results with high-resolution numerical simulations.

  7. The Inviscid Burgers Equation with Brownian Initial Velocity

    Bertoin, Jean

    The law of the (Hopf-Cole) solution of the inviscid Burgers equation with Brownian initial velocity is made explicit. As examples of applications, we investigate the smoothness of the solution, the statistical distribution of the shocks, we determine the exact Hausdorff function of the Lagrangian regular points and investigate the existence of Lagrangian regular points in a fixed Borel set.

  8. Sensory profile of beef burger with reduced sodium content

    Camila Barbosa Carvalho

    2015-05-01

    Full Text Available This study determined the sensory profile of three beef burger samples, namely, CON (control, F25 (25% sodium reduction and F50 (50% sodium reduction, based on the Quantitative Descriptive Analysis (QDA. The samples´ microbial, physical and chemical composition was evaluated. Twelve panelists were selected and trained using as criteria the panelists´ discrimination power, reproducibility and consensus. Eleven terms were generated by the method of network descriptors. The intensity of each descriptor in each sample was evaluated by unstructured scale of 9 cm. Data were analyzed by ANOVA, Duncan´s mean test and principal component analysis. The sensory profile shows that low sodium beef burgers had lower fat and salty flavor when compared to untreated control and greater flavor and spice aroma. The above proves that reducing sodium intake causes increased perception burger tasters when compared to the presence of spices in the product. Treatment with 50% sodium reduction obtained the best results for texture softness and appearance. There was no significant difference (p < 0.05 in the chemical composition of ash, protein and fat in all burgers. In the case of general sensory attributes, treatments with sodium reduction obtained higher intensities of the attributes evaluated, except for meat and salt flavors.

  9. On a stochastic Burgers equation with Dirichlet boundary conditions

    Ekaterina T. Kolkovska

    2003-01-01

    Full Text Available We consider the one-dimensional Burgers equation perturbed by a white noise term with Dirichlet boundary conditions and a non-Lipschitz coefficient. We obtain existence of a weak solution proving tightness for a sequence of polygonal approximations for the equation and solving a martingale problem for the weak limit.

  10. On Nash equilibria for noncooperative games governed by Burgers equation

    Roubíček, Tomáš

    2007-01-01

    Roč. 132, č. 1 (2007), s. 41-50. ISSN 0022-3239 Grant ostatní: GA ČR(CZ) GA201/03/0934 Institutional research plan: CEZ:AV0Z10750506 Keywords : Nash equilibria * noncooperative games * Burgers equation Subject RIV: BA - General Mathematics Impact factor: 0.688, year: 2007

  11. Composites containing albumin protein or cyanoacrylate adhesives and biodegradable scaffolds: I. Acute wound closure study in a rat model

    Hoffman, Grant T.; Soller, Eric C.; Heintzelman, Douglas L.; Duffy, Mark T.; Bloom, Jeffrey N.; Gilmour, Travis M.; Gonnerman, Krista N.; McNally-Heintzelman, Karen M.

    2004-07-01

    Composite adhesives composed of biodegradable scaffolds impregnated with a biological or synthetic adhesive were investigated for use in wound closure as an alternative to using either one of the adhesives alone. Two different scaffold materials were investigated: (i) a synthetic biodegradable material fabricated from poly(L-lactic-co-glycolic acid); and (ii) a biological material, small intestinal sub mucosa, manufactured by Cook BioTech. The biological adhesive was composed of 50%(w/v) bovine serum albumin solder and 0.5mg/ml indocyanine green dye mixed in deionized water, and activated with an 808-nm diode laser. The synthetic adhesive was Ethicon's Dermabond, a 2-octyl-cyanoacrylate. The tensile strength of skin incisions repaired ex vivo in a rat model, by adhesive alone or in combination with a scaffold, as well as the time-to-failure, were measured and compared. The tensile strength of repairs formed using the scaffold-enhanced biological adhesives were on average, 80% stronger than their non-enhanced counterparts, with an accompanying increase in the time-to-failure of the repairs. These results support the theory that a scaffold material with an irregular surface that bridges the wound provides a stronger, more durable and consistent adhesion, due to the distribution of the tensile stress forces over the many micro-adhesions provided by the irregular surface, rather than the one large continuous adhesive contact. This theory is also supported by several previous ex vivo experiments demonstrating enhanced tensile strength of irregular versus smooth scaffold surfaces in identical tissue repairs performed on bovine thoracic aorta, liver, spleen, small intestine and lung tissue.

  12. Application of the Homotopy Analysis Method for Solving the Variable Coefficient KdV-Burgers Equation

    Dianchen Lu

    2014-01-01

    Full Text Available The homotopy analysis method is applied to solve the variable coefficient KdV-Burgers equation. With the aid of generalized elliptic method and Fourier’s transform method, the approximate solutions of double periodic form are obtained. These solutions may be degenerated into the approximate solutions of hyperbolic function form and the approximate solutions of trigonometric function form in the limit cases. The results indicate that this method is efficient for the nonlinear models with the dissipative terms and variable coefficients.

  13. Painlevé property, symmetries and symmetry reductions of the coupled Burgers system

    Lian, Zeng-Ju; Chen, Li-Li; Lou, Sen-Yue

    2005-08-01

    The Painlevé property, inverse recursion operator, infinite number of symmetries and Lie symmetry reductions of the coupled Burgers equation are given explicitly. Three sets of infinitely many symmetries of the considered model are obtained by acting the recursion operator and the inverse recursion operator on the trivial symmetries such as the identity transformation, the space translation and the scaling transformation respectively. These symmetries constitute an infinite dimensional Lie algebra while its finite dimensional Lie point symmetry subalgebra is used to find possible symmetry reductions and then the group invariant solutions.

  14. Peristaltic transport of a fractional Burgers' fluid with variable viscosity through an inclined tube

    Rachid, Hassan

    2015-12-01

    In the present study,we investigate the unsteady peristaltic transport of a viscoelastic fluid with fractional Burgers' model in an inclined tube. We suppose that the viscosity is variable in the radial direction. This analysis has been carried out under low Reynolds number and long-wavelength approximations. An analytical solution to the problem is obtained using a fractional calculus approach. Figures are plotted to show the effects of angle of inclination, Reynolds number, Froude number, material constants, fractional parameters, parameter of viscosity and amplitude ratio on the pressure gradient, pressure rise, friction force, axial velocity and on the mechanical efficiency.

  15. A class of blowup and global analytical solutions of the viscoelastic Burgers' equations

    An, Hongli, E-mail: hongli.an@connect.polyu.hk [College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Cheung, Ka-Luen, E-mail: kaluen@ied.edu.hk [Department of Mathematics and Information Technology, The Hong Kong Institute of Education, 10 Po Ling Road, Tai Po, New Territories (Hong Kong); Yuen, Manwai, E-mail: nevetsyuen@hotmail.com [Department of Mathematics and Information Technology, The Hong Kong Institute of Education, 10 Po Ling Road, Tai Po, New Territories (Hong Kong)

    2013-11-08

    In this Letter, by employing the perturbational method, we obtain a class of analytical self-similar solutions of the viscoelastic Burgers' equations. These solutions are of polynomial-type whose forms, remarkably, coincide with that given by Yuen for the other physical models, such as the compressible Euler or Navier–Stokes equations and two-component Camassa–Holm equations. Furthermore, we classify the initial conditions into several groups and then discuss the properties on blowup and global existence of the corresponding solutions, which may be readily seen from the phase diagram.

  16. A 3D ductile constitutive mixed-mode model of cohesive elements for the finite element analysis of adhesive joints

    Anyfantis, Konstantinos; Tsouvalis, Nicholas G.

    2013-01-01

    adhesive joint configurations. The specimens have been tested under uni-axial quasi-static load and the respective force and displacement loading history have been recorded. Corresponding numerical and experimental results have been compared for each joint case, respectively. Additionally, the developed...... criterion and damage propagation with the linear energetic fracture criterion. For verification and validation purposes of the proposed laws and mixed-mode model, steel adherends have been adhesively bonded with a structural ductile adhesive material in order to fabricate a series of single and double strap...

  17. Models for ultrasonic characterization of environmental degradation of interfaces in adhesive joints

    In this paper we discuss two models of environmental degradation of adhesive joints developed from experimental observation of the joint failure mode. It is found that after severe degradation, failure is dominated by the interfacial mode, i.e., by failure at the interface between adhesive and adherend. The fraction of failure in the interfacial mode was found to be related to the joint strength and to be proportional to the frequency shift of a minimum in the spectrum of the reflected ultrasonic signal. One model considers an interface as an interphase in the form of a nonhomogeneous layer composed of two phases: ''soft'' which is viscoelastic (degraded part of the interphase) and ''stiff'' corresponding to the nondamaged interphase. Increase of the ''soft'' phase fraction corresponds to the process of degradation in the interphase. The second model describes degradation in a form of disbonds filled by absorbed water at the interface. The disbonded interface is modeled by transverse spring boundary conditions, with the complex spring stiffness representing the quality of the bond. The influence of different disbond growth scenarios is considered. Advantages and drawbacks of these models are discussed

  18. Auto-cross-linked hyaluronic acid gel does not reduce intra-abdominal adhesions or abscess formation in a rat model of peritonitis.

    Sikkink, C.J.J.M.; Man, B.M. de; Bleichrodt, R.P.; Goor, H. van

    2006-01-01

    BACKGROUND: Prevention of adhesion and abscess formation would decrease mortality and morbidity after peritonitis. In this study the effect of a new anti-adhesive, auto-cross-linked hyaluronic acid polysaccharide (ACP) gel, on adhesion and abscess formation was studied in a rat peritonitis model. MA

  19. The Effect of Phospholipids (Surfactant on Adhesion and Biomechanical Properties of Tendon: A Rat Achilles Tendon Repair Model

    T. Kursat Dabak

    2015-01-01

    Full Text Available Adhesion of the tendon is a major challenge for the orthopedic surgeon during tendon repair. Manipulation of biological environment is one of the concepts to prevent adhesion. Lots of biochemicals have been studied for this purpose. We aimed to determine the effect of phospholipids on adhesion and biomechanical properties of tendon in an animal tendon repair model. Seventy-two Wistar rats were divided into 4 groups. Achilles tendons of rats were cut and repaired. Phospholipids were applied at two different dosages. Tendon adhesion was determined histopathologically and biomechanical test was performed. At macroscopic evaluation of adhesion, there are statistically significant differences between multiple-dose phospholipid injection group and Control group and also hyaluronic acid group and Control group (p0.008. Ultimate strength was highest at hyaluronic acid injection group and lowest at multiple-dose phospholipid injection group. Single-dose phospholipids (surfactant application may have a beneficial effect on the tendon adhesion. Although multiple applications of phospholipids seem the most effective regime to reduce the tendon adhesion among groups, it deteriorated the biomechanical properties of tendon.

  20. Wood adhesion cell segmentation scheme based on GVF-Snake model

    Zhao, Lei; Ma, Yan

    2010-08-01

    In order to extract the characteristic parameters of the wood cells accurately, this paper presents an efficient scheme for wood cell segmentation. This scheme is mainly based on GVF-Snake model and the method of image thinning. Firstly, computing the Category Roundness of every connectivity domain is done in order to get the degree of adhesion. Secondly, image thinning helps to get the skeleton of the cell. Finally, according to the location coordinates of skeleton and contour, it can determine the location of segmentation. Experimental results demonstrate the scheme for precise extraction with limited human intervention; it can also determine the correct edge of segmentation. Comparatively speaking, the inaccuracy is rather limited.

  1. Abdominal Adhesions

    ... adhesions? Abdominal adhesions can cause intestinal obstruction and female infertility—the inability to become pregnant after a year of trying. Abdominal adhesions can lead to female infertility by preventing fertilized eggs from reaching the uterus, ...

  2. Myxococcus xanthus gliding motors are elastically coupled to the substrate as predicted by the focal adhesion model of gliding motility

    Balagam, Rajesh; Czerwinski, Fabian; Sun, Mingzhai; Kaplan, Heidi B; Shaevitz, Joshua W; Igoshin, Oleg A

    2014-01-01

    Myxococcus xanthus is a model organism for studying bacterial social behaviors due to its ability to form complex multi-cellular structures. Knowledge of M. xanthus surface gliding motility and the mechanisms that coordinate it are critically important to our understanding of collective cell behaviors. Although the mechanism of gliding motility is still under investigation, recent experiments suggest that there are two possible mechanisms underlying force production for cell motility: the focal adhesion mechanism and the helical rotor mechanism which differ in the biophysics of the cell-substrate interactions. Whereas the focal adhesion model predicts an elastic coupling, the helical rotor model predicts a viscous coupling. Using a combination of computational modeling, imaging, and force microscopy, we find evidence for elastic coupling in support of the focal adhesion model. Using a biophysical model of the M. xanthus cell, we investigated how the mechanical interactions between cells are affected by intera...

  3. Large deformation analysis of adhesive by Eulerian method with new material model

    The material model to describe large deformation of a pressure sensitive adhesive (PSA) is presented. A relationship between stress and strain of PSA includes viscoelasticity and rubber-elasticity. Therefore, we propose the material model for describing viscoelasticity and rubber-elasticity, and extend the presented material model to the rate form for three dimensional finite element analysis. After proposing the material model for PSA, we formulate the Eulerian method to simulate large deformation behavior. In the Eulerian calculation, the Piecewise Linear Interface Calculation (PLIC) method for capturing material surface is employed. By using PLIC method, we can impose dynamic and kinematic boundary conditions on captured material surface. The representative two computational examples are calculated to check validity of the present methods.

  4. Theoretical model for adhesive friction between elastomers and rough solid surfaces

    Momozono, Satoshi; Nakamura, Kenya; Kyogoku, Keiji

    2010-03-01

    A theoretical model for the adhesive friction between elastomers and rough solid surfaces is proposed on the basis of opening crack propagation processes at the boundary of the contact interfaces and the rate processes of formation of molecular bonds on the solid surface. This model, which is expressed as a product of the terms related to the two abovementioned processes, requires some measurable and fitted parameters such as the frictional shear strength expressed as a function of viscoelastic dissipation, rate-dependent elasticity, density of bonded molecular chains at a contact junction, critical velocity related to viscoelastic relaxation, and critical velocity related to the rate process of formation of molecular bonds on the solid surface. The friction-velocity relationship exhibits a remarkable fit to previously obtained experimental results for polymers such as engineering rubber, gels, and plastics (glassy polymers), and all fitting parameters are physically reasonable. The viscoelastic index "n" is also related to the "glass-to-rubber transition" of a nanometer-thick polymer layer for frictional behavior. Thus, from a practical viewpoint, this model can be used effectively for fitting the adhesive friction behavior of polymers.

  5. Sailing the Deep Blue Sea of Decaying Burgers Turbulence

    Bauer, M; Bauer, Michel; Bernard, Denis

    1999-01-01

    We study Lagrangian trajectories and scalar transport statistics in decaying Burgers turbulence. We choose velocity fields, solutions of the inviscid Burgers equation, whose probability distributions are specified by Kida's statistics. They are time-correlated, not time-reversal invariant and not Gaussian. We discuss in some details the effect of shocks on trajectories and transport equations. We derive the inviscid limit of these equations using a formalism of operators localized on shocks. We compute the probability distribution functions of the trajectories although they do not define Markov processes. As physically expected, these trajectories are statistically well-defined but collapse with probability one at infinite time. We point out that the advected scalars enjoy inverse energy cascades. We also make a few comments on the connection between our computations and persistence problems.

  6. Sailing the deep blue sea of decaying Burgers turbulence

    Bauer, Michel; Bernard, Denis

    1999-07-01

    We study Lagrangian trajectories and scalar transport statistics in decaying Burgers turbulence. We choose velocity fields solutions of the inviscid Burgers equation whose probability distributions are specified by Kida's statistics. They are time-correlated, and neither time-reversal invariant nor Gaussian. We discuss in some detail the effect of shocks on trajectories and transport equations. We derive the inviscid limit of these equations using a formalism of operators localized on shocks. We compute the probability distribution functions of the trajectories although they do not define Markov processes. As physically expected, these trajectories are statistically well defined but collapse with probability one at infinite time. We point out that the advected scalars enjoy inverse energy cascades. We also make a few comments on the connection between our computations and persistence problems.

  7. Classical and Quantum Burgers Fluids: A Challenge for Group Analysis

    Philip Broadbridge

    2015-10-01

    Full Text Available The most general second order irrotational vector field evolution equation is constructed, that can be transformed to a single equation for the Cole–Hopf potential. The exact solution to the radial Burgers equation, with constant mass influx through a spherical supply surface, is constructed. The complex linear Schrödinger equation is equivalent to an integrable system of two coupled real vector equations of Burgers type. The first velocity field is the particle current divided by particle probability density. The second vector field gives a complex valued correction to the velocity that results in the correct quantum mechanical correction to the kinetic energy density of the Madelung fluid. It is proposed how to use symmetry analysis to systematically search for other constrained potential systems that generate a closed system of vector component evolution equations with constraints other than irrotationality.

  8. Intermittency in fractal Fourier hydrodynamics: Lessons from the Burgers equation.

    Buzzicotti, Michele; Biferale, Luca; Frisch, Uriel; Ray, Samriddhi Sankar

    2016-03-01

    We present theoretical and numerical results for the one-dimensional stochastically forced Burgers equation decimated on a fractal Fourier set of dimension D. We investigate the robustness of the energy transfer mechanism and of the small-scale statistical fluctuations by changing D. We find that a very small percentage of mode-reduction (D ≲ 1) is enough to destroy most of the characteristics of the original nondecimated equation. In particular, we observe a suppression of intermittent fluctuations for D < 1 and a quasisingular transition from the fully intermittent (D=1) to the nonintermittent case for D ≲ 1. Our results indicate that the existence of strong localized structures (shocks) in the one-dimensional Burgers equation is the result of highly entangled correlations amongst all Fourier modes. PMID:27078449

  9. Intermittency in Fractal Fourier Hydrodynamics: Lessons from the Burgers Equation

    Buzzicotti, Michele; Frisch, Uriel; Ray, Samriddhi Sankar

    2016-01-01

    We present theoretical and numerical results for the one-dimensional stochastically forced Burgers equation decimated on a fractal Fourier set of dimension $D$. We investigate the robustness of the energy transfer mechanism and of the small-scale statistical fluctuations by changing $D$. We find that a very small percentage of mode-reduction ($D \\lesssim 1$) is enough to destroy most of the characteristics of the original non-decimated equation. In particular, we observe a suppression of intermittent fluctuations for $D <1$ and a quasi-singular transition from the fully intermittent ($D=1$) to the non-intermittent case for $D \\lesssim 1$. Our results indicate that the existence of strong localized structures (shocks) in the one-dimensional Burgers equation is the result of highly entangled correlations amongst all Fourier modes.

  10. A weak Galerkin finite element method for Burgers' equation

    Chen, Yanli; Zhang, Tie

    2016-01-01

    We propose a weak Galerkin(WG) finite element method for solving the one-dimensional Burgers' equation. Based on a new weak variational form, both semi-discrete and fully-discrete WG finite element schemes are established and analyzed. We prove the existence of the discrete solution and derive the optimal order error estimates in the discrete $H^1$-norm and $L^2$-norm, respectively. Numerical experiments are presented to illustrate our theoretical analysis.

  11. Power Series Solution for Solving Nonlinear Burgers-Type Equations

    E. López-Sandoval

    2015-01-01

    Full Text Available Power series solution method has been traditionally used to solve ordinary and partial linear differential equations. However, despite their usefulness the application of this method has been limited to this particular kind of equations. In this work we use the method of power series to solve nonlinear partial differential equations. The method is applied to solve three versions of nonlinear time-dependent Burgers-type differential equations in order to demonstrate its scope and applicability.

  12. Conservation laws of inviscid Burgers equation with nonlinear damping

    Abdulwahhab, Muhammad Alim

    2014-06-01

    In this paper, the new conservation theorem presented in Ibragimov (2007) [14] is used to find conservation laws of the inviscid Burgers equation with nonlinear damping ut+g(u)ux+λh(u)=0. We show that this equation is both quasi self-adjoint and self-adjoint, and use these concepts to simplify conserved quantities for various choices of g(u) and h(u).

  13. Exact solutions of (3 + 1)-dimensional stochastic Burgers equation

    A generalized tan h function method is used for constructing exact travelling wave solutions of nonlinear stochastic partial differential equations. The main idea of this method is to take full advantage of the Riccati equation, which has more exact solutions. More Wick-type stochastic multiple soliton-like solutions and triangular periodic solutions are obtained for the (3 + 1)-dimensional Wick-type stochastic Burgers equation via Hermite transformation

  14. High Fat Diet Induces Adhesion of Platelets to Endothelium in Two Models of Dyslipidemia

    Gonzalez, Jaime; Donoso, Wendy; Díaz, Natalia; Albornoz, María Eliana; Huilcaman, Ricardo; Morales, Erik

    2014-01-01

    Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE−/− mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE−/− mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cells in vivo. These findings support studying the participation of platelets in the formation of atheromatous plate. PMID:25328689

  15. Asymptotics for the Korteweg-de Vries-Burgers Equation

    Nakao HAYASHI; Pavel I. NAUMKIN

    2006-01-01

    We study large time asymptotics of solutions to the Korteweg-de Vries-Burgers equation ut + uux - uxx + uxxx = 0, x ∈ R, t > 0.We are interested in the large time asymptotics for the case when the initial data have an arbitrary size. We prove that ifthe initial data u0 ∈ Hs (R) ∩L1 (R), where s > -1/2,then there exists a uniquesolution u (t,x) ∈ C∞ ((0, ∞);H∞ (R)) to the Cauchy problem for the Korteweg-de Vries-Burgers equation, which has asymptotics u (t) = t-1/2fM((·)t-1/2) + o(t-1/2) as t →∞, where fM is the self-similar solution for the Burgers equation. Moreover if xu0 (x) ∈ L1 (R),then the asymptotics are true u (t) = t-1/2fM((·)t-1/2) + O(t-1/2-γ),where γ∈ (0,1/2).

  16. Nanobioprobe for the Determination of Pork Adulteration in Burger Formulations

    We report the development of a swine-specific hybrid nanobioprobe through a covalent integration of a fluorophore-labeled 27-nucleotide AluI-fragment of swine cytochrome b gene to a 3 nm gold nanoparticle for the determination of pork adulteration in processed meat products. We tested the probe to estimate adulterated pork in ready-to-eat pork-spiked beef burgers. The probe quantitatively detected 1-100% spiked pork in burger formulations with ≥90% accuracy. A plot of observed fluorescence against the known concentration of AluI-digested pork DNA targets generated a concave curve, demonstrating a power relationship (y=2.956x0.509) with a regression coefficient (R2) of 0.986. No cross-species detection was found in a standard set of pork, beef, chicken, mutton, and chevon burgers. The method is suitable for the determination of very short-length nucleic acid targets which cannot be estimated by conventional and real-time PCR but are essential for the determination of micro RNA in bio diagnostics and degraded DNA in forensic testing and food analysis.

  17. The generalized Burgers equation with and without a time delay

    Nejib Smaoui

    2004-01-01

    Full Text Available We consider the generalized Burgers equation with and without a time delay when the boundary conditions are periodic with period 2π. For the generalized Burgers equation without a time delay, that is, ut=vuxx−uux+u+h(x, 00, u(0,t=u(2π,t, u(x,0=u0(x, a Lyapunov function method is used to show boundedness and uniqueness of a steady state solution and global stability of the equation. As for the generalized time-delayed Burgers equation, that is, ut(x,t=vuxx(x,t−u(x,t−τux(x,t+u(x,t, 00, u(0,t=u(2π,t, t>0, u(x,s=u0(x,s, 0

  18. The Inviscid, Compressible and Rotational, 2D Isotropic Burgers and Pressureless Euler-Coriolis Fluids; Theory and Illustrations

    Choquard, Philippe

    2013-01-01

    The coupling between dilatation and vorticity, two coexisting and fundamental processes in fluid dynamics is investigated here, in the simplest cases of inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids respectively modeled by single vortices confined in compressible, local, inertial and global, rotating, environments. The field equations are established, inductively, starting from the equations of the characteristics solved with an initial Helmholtz decomposition of the velocity fields namely a vorticity free and a divergence free part and, deductively, by means of a canonical Hamiltonian Clebsch like formalism, implying two pairs of conjugate variables. Two vector valued fields are constants of the motion: the velocity field in the Burgers case and the momentum field per unit mass in the Euler-Coriolis one. Taking advantage of this property, a class of solutions for the mass densities of the fluids is given by the Jacobian of their sum with respect to the actual coordinates. Implementatio...

  19. Human neutrophil Fc receptor-mediated adhesion under flow: a hollow fibre model of intravascular arrest.

    D'Arrigo, C; Candal-Couto, J J; Greer, M; Veale, D J; Woof, J M

    1995-04-01

    Human polymorphonuclear cells (PMN) were found to adhere to a novel model of blood vessel wall-associated IgG. The internal surfaces of cellulose acetate hollow fibres, of comparable internal diameter to small blood vessels, were coated with normal serum human IgG, heat-aggregated IgG (HAIgG), laminin or fibrinogen. Under conditions of flow mimicking those in a small vessel, PMN were found to adhere markedly only to immunoglobulin-coated fibres. Arrest on HAIgG was inhibited by excess soluble IgG but not by bovine serum albumin (BSA), demonstrating that the adhesion was IgG-specific and presumably mediated by Fc gamma R on the PMN surface. Pre-adsorption of serum components onto HAIgG-coated fibres enhanced PMN arrest, due most probably to fixation of complement components by immobilized HAIgG, resulting in additional potential to entrap PMN via complement receptors such as CR3. Treatment of PMN with the regulatory neuropeptide substance P also enhanced adhesion to HAIgG-coated fibres and caused increased surface expression of Fc gamma RI, Fc gamma RII and Fc gamma RIII. A mouse cell line derived from L cells, hR4C6, stably transfected with human Fc gamma RII, was found to adhere under flow to HAIgG-coated fibres, whilst untransfected parent L cells did not. This adhesion was similarly inhibited by excess soluble IgG, confirming the capability of Fc gamma R to mediate cell arrest. The study strongly suggests that Fc gamma R may play an important role in intravascular PMN arrest and we speculate that in inflammatory diseases PMN may adhere via Fc gamma R to immobilized immunoglobulin on the vascular endothelium, with subsequent degranulation and tissue damage. PMID:7535210

  20. Modelling liquid crystal elastomers and potential application as a reversibly switchable adhesive

    Adams, James

    2013-03-01

    Liquid crystal elastomers (LCEs) are rubbery materials that composed of liquid crystalline polymers (LCPs) crosslinked into a network. The rod-like mesogens incorporated into the LCPs are have random orientations in the high temperature isotropic phase, but can adopt the canonical liquid crystalline phases as the temperature is lowered. Smectic liquid crystal elastomers have highly anisotropic mechanical behaviour. This arises in side chain smectic-A systems because the smectic layers behave as if they are embedded in the rubber matrix. The macroscopic mechanical behaviour of these solids is sensitive to the buckling of the layers, so is a multiscale problem. A coarse grained free energy that includes the fine-scale buckling of the layers has been developed, which enables continuum modelling of these systems. In the first part of this talk I present a model of the mechanical behaviour of side chain smectic elastomers. The properties of nematic LCEs, such as their high loss tangent, and mechanical strain hardening, might enable them to be used as reversibly switchable pressure sensitive adhesive (PSA). PSAs are typically made from viscoelastic polymers. The quality of their adhesion can be measured by the tack energy, which is the work required to separate two bodies. To obtain a high tack energy a PSA should be capable of a large strain. It should strain soften at low strain to produce crack blunting, and then strain harden at high strain to stiffen the fibrils formed late in the debonding process. I will present a model of the tack energy of weakly crosslinked nematic polymers. To describe the constitutive properties of this system the nematic dumbbell model of Maffettone et al. was used. This constutitive model was then combined with the block model of Yamaguchi et al. describing PSAs. It was found that the parallel orientation of the nematic has a higher tack energy than both the isotropic and the perpendicular director orientation. This work is supported by

  1. Ex Vivo and In Vivo Mice Models to Study Blastocystis spp. Adhesion, Colonization and Pathology: Closer to Proving Koch's Postulates

    Ajjampur, Sitara S. R.; Png, Chin Wen; Chia, Wan Ni; Zhang, Yongliang; Tan, Kevin S. W.

    2016-01-01

    Blastocystis spp. are widely prevalent extra cellular, non-motile anerobic protists that inhabit the gastrointestinal tract. Although Blastocystis spp. have been associated with gastrointestinal symptoms, irritable bowel syndrome and urticaria, their clinical significance has remained controversial. We established an ex vivo mouse explant model to characterize adhesion in the context of tissue architecture and presence of the mucin layer. Using confocal microscopy with tissue whole mounts and two axenic isolates of Blastocystis spp., subtype 7 with notable differences in adhesion to intestinal epithelial cells (IEC), isolate B (ST7-B) and isolate H (more adhesive, ST7-H), we showed that adhesion is both isolate dependent and tissue trophic. The more adhesive isolate, ST7-H was found to bind preferentially to the colon tissue than caecum and terminal ileum. Both isolates were also found to have mucinolytic effects. We then adapted a DSS colitis mouse model as a susceptible model to study colonization and acute infection by intra-caecal inoculation of trophic Blastocystis spp.cells. We found that the more adhesive isolate ST7-H was also a better colonizer with more mice shedding parasites and for a longer duration than ST7-B. Adhesion and colonization was also associated with increased virulence as ST7-H infected mice showed greater tissue damage than ST7-B. Both the ex vivo and in vivo models used in this study showed that Blastocystis spp. remain luminal and predominantly associated with mucin. This was further confirmed using colonic loop experiments. We were also successfully able to re-infect a second batch of mice with ST7-H isolates obtained from fecal cultures and demonstrated similar histopathological findings and tissue damage thereby coming closer to proving Koch’s postulates for this parasite. PMID:27508942

  2. Numerical solutions of the generalized Burgers-Huxley equation by implicit exponential finite difference method

    İnan B.; Bahadir A. R.

    2015-01-01

    In this paper, numerical solutions of the generalized Burgers-Huxley equation are obtained using a new technique of forming improved exponential finite difference method. The technique is called implicit exponential finite difference method for the solution of the equation. Firstly, the implicit exponential finite difference method is applied to the generalized Burgers-Huxley equation. Since the generalized Burgers-Huxley equation is nonlinear the scheme leads to a system of nonlinear equatio...

  3. Cohesive zone modelling of interface fracture near flaws in adhesive joints

    Hansen, Peter Feraren; Jensen, Henrik Myhre

    2004-01-01

    of crack propagation on the location and shape of the crack front and on the initial joint strength. Subsequently, the cohesive zone model is used to model interface fracture through a planar adhesive layer containing a periodic array of elliptical flaws. The effects of flaw shape are investigated......, as well as the significance of fracture process parameters. The results from simulations of fracture in a bond containing circular flaws show that localization of crack propagation in the vicinity of a flaw has significant effect on the joint strength and crack front shape. The localization effects...... are highly dependent on the fracture process zone width relative to the flaw dimensions. It is also seen that with increasing fracture process zone width, the strength variation with the flaw shape decreases, however, the strength is effected over a wider range of propagation, (C) 2004 Elsevier Ltd...

  4. Analytical model of asymmetrical Mixed-Mode Bending test of adhesively bonded GFRP joint

    M. Ševčík

    2015-10-01

    Full Text Available This paper presents new analytical model of asymmetric mixed-mode bending (MMB specimen of adhesively bonded pultruded GFRP joints. An easily applicable relationship for the calculation of the strain energy release rate of the asymmetric MMB specimens is proposed based on the beam theory. The model is capable to analyze stacking sequence as well as various crack propagation paths. In the paper the effect of the various fiber bridging length and different crack propagation paths is analyzed analytically and supported by experimental results. The methodology and results presented in this paper could be utilized for the design of both joint geometry and lay-up of the laminates constituting the joint or for the prediction of the fracture behavior of such structures.

  5. Experimental simulation of model platelet adhesion to a semi-permeable wall exposed to flow disturbance

    DENG Xiaoyan; WANG Guixue; YANG Yang

    2003-01-01

    A sudden tubular expansion with a semi- permeable wall was constructed from a tubular dialysis membrane to investigate the effects of filtration flow and flow disturbance on particle deposition. The expansion was perfused with a dilute, neutrally buoyant suspension of 1.10 ?m diameter polystyrene latex spheres (as models of platelets) in Tris buffer solution containing 10% Dextran T70 and 2% bovine serum albumin. The results showed that adhesion of particles correlated positively with the filtration rate and inversely with the wall shear rate. In the vortex flow region distal to the expansion, particle adhesion was significantly elevated with a maximum at the reattachment point where the wall shear rate was the lowest and particles were constantly carried toward the vessel wall along the curved streamlines. In conclusion, filtration flow has a profound impact on the interaction of blood cells such as platelets with blood vessel walls, and the disturbed flow with a low wall shear rate can enhance the deposits of platelet thrombi to the vessel wall.

  6. Burgers equation with no-flux boundary conditions and its application for complete fluid separation

    Watanabe, Shinya; Matsumoto, Sohei; Higurashi, Tomohiro; Ono, Naoki

    2016-09-01

    Burgers equation in a one-dimensional bounded domain with no-flux boundary conditions at both ends is proven to be exactly solvable. Cole-Hopf transformation converts not only the governing equation to the heat equation with an extra damping but also the nonlinear mixed boundary conditions to Dirichlet boundary conditions. The average of the solution v bar is conserved. Consequently, from an arbitrary initial condition, solutions converge to the equilibrium solution which is unique for the given v bar. The problem arises naturally as a continuum limit of a network of certain micro-devices. Each micro-device imperfectly separates a target fluid component from a mixture of more than one component, and its input-output concentration relationships are modeled by a pair of quadratic maps. The solvability of the initial boundary value problem is used to demonstrate that such a network acts as an ideal macro-separator, separating out the target component almost completely. Another network is also proposed which leads to a modified Burgers equation with a nonlinear diffusion coefficient.

  7. Directional distribution of Burgers vectors of dislocation loops in ion-implanted silicon

    The possible directional distributions of Burgers vectors of perfect dislocation loops and dipoles formed in the silicon single crystals after ion implantation and annealing have been studied. (author)

  8. A systemic review of randomized controlled studies about prevention with pharmacologic agents of adhesion formation in the rat uterine horn model

    Oner, Gokalp; Ulug, Pasa

    2015-01-01

    Introduction Evaluation of treatment attempts in postoperative adhesion formation is pivotal for the prevention of several morbidities including infertility, pelvic pain, bowel obstruction, and subsequent intraoperative complications. The purpose of this systemic review was to assess the literature on the rat uterine horn model for adhesion formation and treatment modalities to prevent adhesion in the most frequently used experimental animal model. Material and methods We performed a systemic...

  9. Composites containing albumin protein or cyanoacrylate adhesives and biodegradable scaffolds: II. In vivo wound closure study in a rat model

    McNally-Heintzelman, Karen M.; Heintzelman, Douglas L.; Duffy, Mark T.; Bloom, Jeffrey N.; Soller, Eric C.; Gilmour, Travis M.; Hoffman, Grant T.; Edward, Deepak

    2004-07-01

    Our Scaffold-Enhanced Biological Adhesive (SEBA) system was investigated as an alternative to sutures or adhesives alone for repair of wounds. Two scaffold materials were investigated: (i) a synthetic biodegradable material fabricated from poly(L-lactic-co-glycolic acid); and (ii) a biologic material, small intestinal submucosa, manufactured by Cook BioTech. Two adhesive materials were also investigated: (i) a biologic adhesive composed of 50%(w/v) bovine serum albumin solder and 0.5mg/ml indocyanine green dye mixed in deionized water, and activated with an 808-nm diode laser; and (ii) Ethicon"s Dermabond, a 2-octyl-cyanoacrylate. The tensile strength and time-to-failure of skin incisions repaired in vivo in a rat model were measured at seven days postoperative. Incisions closed by protein solder alone, by Dermabond alone, or by suture, were also tested for comparison. The tensile strength of repairs formed using the SEBA system were 50% to 65% stronger than repairs formed by suture or either adhesive alone, with significantly less variations within each experimental group (average standard deviations of 15% for SEBA versus 38% for suture and 28% for adhesive alone). In addition, the time-to-failure curves showed a longevity not previously seen with the suture or adhesive alone techniques. The SEBA system acts to keep the dermis in tight apposition during the critical early phase of wound healing when tissue gaps are bridged by scar and granulation tissue. It has the property of being more flexible than either of the adhesives alone and may allow the apposed edges to move in conjunction with each other as a unit for a longer period of time and over a greater range of stresses than adhesives alone. This permits more rapid healing and establishment of integrity since the microgaps between the dermis edges are significantly reduced. By the time the scaffolds are sloughed from the wound site, there is greater strength and healing than that produced by adhesive alone or

  10. Effect of carbodiimide-derivatized hyaluronic acid gelatin on preventing postsurgical intra-abdominal adhesion formation and promoting healing in a rat model.

    Yuan, Fang; Lin, Long-Xiang; Zhang, Hui-Hui; Huang, Dan; Sun, Yu-Long

    2016-05-01

    Adhesions often occur after abdominal surgery. It could cause chronic pelvic pain, intestinal obstruction, and infertility. A hydrogel biomaterial, carbodiimide-derivatized hyaluronic acid gelatin (cd-HA gelatin), has been successfully used to reduce adhesion formation after flexor tendon grafting. This study investigated the efficacy of cd-HA gelatin in preventing postsurgical peritoneal adhesions in a rat model. The surgical traumas were created on the underlying muscle of the abdominal wall and the serosal layer of the cecum. The wounds were covered with or without cd-HA gelatin. Animals were euthanized at day 14 after surgery. Adhesion formation was assessed with adhesion degree and adhesion breaking strength. The healing of abdominal wall was evaluated with biomechanical testing and histological analysis. The adhesions occurred in all rats (n = 12) without cd-HA gelatin treatment. The application of cd-HA gelatin significantly reduced the adhesion rate from 100% to 58%. The decrease of adhesion breaking strength also manifested that cd-HA gelatin could reduce postsurgical intra-abdominal adhesion formation. Moreover, it was found that cd-HA gelatin was a safe material and could promote tissue healing. The cd-HA gelatin hydrogel could reduce the formation of intra-abdominal adhesions without adversely effects on wound healing. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1175-1181, 2016. PMID:26749008

  11. Thermosensitive hydrogel containing dexamethasone micelles for preventing postsurgical adhesion in a repeated-injury model

    Qinjie Wu; Ning Wang; Tao He; Jinfeng Shang; Ling Li; Linjiang Song; Xi Yang; Xia Li; Na Luo; Wenli Zhang; Changyang Gong

    2015-01-01

    Tissue adhesion is a common complication after surgery. In this work, a dexamethasone loaded polymeric micelles in thermosensitive hydrogel composite (Dex hydrogel) was prepared, which combined the anti-adhesion barrier with controlled release of anti-adhesion drug. Dexamethasone (Dex) was encapsulated in polymeric micelles (Dex micelles), and then the Dex micelles were loaded into biodegradable and thermosensitive hydrogel. The obtained Dex hydrogel showed a temperature-dependent sol-gel-sol...

  12. Computational modeling reveals that a combination of chemotaxis and differential adhesion leads to robust cell sorting during tissue patterning.

    Tan, Rui Zhen; Chiam, Keng-Hwee

    2014-01-01

    Robust tissue patterning is crucial to many processes during development. The "French Flag" model of patterning, whereby naïve cells in a gradient of diffusible morphogen signal adopt different fates due to exposure to different amounts of morphogen concentration, has been the most widely proposed model for tissue patterning. However, recently, using time-lapse experiments, cell sorting has been found to be an alternative model for tissue patterning in the zebrafish neural tube. But it remains unclear what the sorting mechanism is. In this article, we used computational modeling to show that two mechanisms, chemotaxis and differential adhesion, are needed for robust cell sorting. We assessed the performance of each of the two mechanisms by quantifying the fraction of correct sorting, the fraction of stable clusters formed after correct sorting, the time needed to achieve correct sorting, and the size variations of the cells having different fates. We found that chemotaxis and differential adhesion confer different advantages to the sorting process. Chemotaxis leads to high fraction of correct sorting as individual cells will either migrate towards or away from the source depending on its cell type. However after the cells have sorted correctly, there is no interaction among cells of the same type to stabilize the sorted boundaries, leading to cell clusters that are unstable. On the other hand, differential adhesion results in low fraction of correct clusters that are more stable. In the absence of morphogen gradient noise, a combination of both chemotaxis and differential adhesion yields cell sorting that is both accurate and robust. However, in the presence of gradient noise, the simple combination of chemotaxis and differential adhesion is insufficient for cell sorting; instead, chemotaxis coupled with delayed differential adhesion is required to yield optimal sorting. PMID:25302949

  13. Diffusive approximation of a time-fractional Burgers equation in nonlinear acoustics

    Lombard, Bruno

    2016-01-01

    A fractional time derivative is introduced into the Burgers equation to model losses of nonlinear waves. This term amounts to a time convolution product, which greatly penalizes the numerical modeling. A diffusive representation of the fractional derivative is adopted here, replacing this nonlocal operator by a continuum of memory variables that satisfy local-in-time ordinary differential equations. Then a quadrature formula yields a system of local partial differential equations, well-suited to numerical integration. The determination of the quadrature coefficients is crucial to ensure both the well-posedness of the system and the computational efficiency of the diffusive approximation. For this purpose, optimization with constraint is shown to be a very efficient strategy. Strang splitting is used to solve successively the hyperbolic part by a shock-capturing scheme, and the diffusive part exactly. Numerical experiments are proposed to assess the efficiency of the numerical modeling, and to illustrate the e...

  14. Inverting Glacial Isostatic Adjustment with Paleo Sea Level Records using Bayesian Framework and Burgers Rheology

    Caron, L.; Metivier, L.; Greff-Lefftz, M.; Fleitout, L.; Rouby, H.

    2015-12-01

    Glacial Isostatic Adjustment models most often assume a mantle with a viscoelastic Maxwell rheology and a given ice history model. Here we use a Bayesian Monte Carlo with Markov Chains formalism to invert the global GIA signal simultaneously for the mechanical properties of the mantle and for the volume of the various ice-sheets using as starting ice models two distinct previously published ice histories. Burgers as well as Maxwell rheologies are considered.The fitted data consist of 5720 paleo sea level records from the last 35kyrs, with a world-wide distribution. Our ambition is to present not only the best fitting model, but also the range of possible solutions (within the explored space of parameters) with their respective probability of explaining the data, and thus reveal the trade-off effects and range of uncertainty affecting the parameters. Our a posteriori probality maps exhibit in all cases two distinct peaks: both are characterized by an upper mantle viscosity around 5.1020Pa.s but one of the peaks features a lower mantle viscosity around 3.1021Pa.s while the other indicates lower mantle viscosity of more than 1.1022Pa.s. The global maximum depends upon the starting ice history and the chosen rheology: the first peak (P1) has the highest probability only in the case with a Maxwell rheology and ice history based on ICE-5G, while the second peak (P2) is favored when using ANU-based ice history or Burgers rheology, and is our preferred solution as it is also consistent with long-term geodynamics and gravity gradients anomalies over Laurentide. P2 is associated with larger volumes for the Laurentian and Fennoscandian ice-sheets and as a consequence of total ice volume balance, smaller volumes for the Antactic ice-sheet. This last point interfers with the estimate of present-day ice-melting in Antarctica from GRACE data. Finally, we find that P2 with Burgers rheology favors the existence of a tectosphere, i.e. a viscous sublithospheric layer.

  15. Burger King in Portugal : to lead or to follow?

    Patrone, Sara Saraiva

    2012-01-01

    In 2001, the Burger King (BK) brand, managed by Ibersol group entered the growing fast food Portuguese market. Marginally higher prices along with the fact of having entered the market 10 years after its most direct competitor (McDonald´s), led BK to a sub leader position. Although being recognized as offering superior quality products when compared to McDonald´s, BK´s growth margins in the Portuguese market have been decreasing since 2007. The company´s uncertainty situation, offers the p...

  16. Some More Solutions of Burgers' Equation

    In this work, similarity solutions of viscous one-dimensional Burgers' equation are attained by using Lie group theory. The symmetry generators are used for constructing Lie symmetries with commuting infinitesimal operators which lead the governing partial differential equation (PDE) to ordinary differential equation (ODE). Most of the constructed solutions are found in terms of Bessel functions which are new as far as authors are aware. Effect of various parameters in the evolutional profile of the solutions are shown graphically and discussed them physically

  17. Asymptotic Theory for the Probability Density Functions in Burgers Turbulence

    Weinan, E; Eijnden, Eric Vanden

    1999-01-01

    A rigorous study is carried out for the randomly forced Burgers equation in the inviscid limit. No closure approximations are made. Instead the probability density functions of velocity and velocity gradient are related to the statistics of quantities defined along the shocks. This method allows one to compute the anomalies, as well as asymptotics for the structure functions and the probability density functions. It is shown that the left tail for the probability density function of the velocity gradient has to decay faster than $|\\xi|^{-3}$. A further argument confirms the prediction of E et al., Phys. Rev. Lett. {\\bf 78}, 1904 (1997), that it should decay as $|\\xi|^{-7/2}$.

  18. Approximate solutions of general perturbed KdV-Burgers equations

    Baojian Hong

    2014-09-01

    Full Text Available In this article, we present some approximate analytical solutions to the general perturbed KdV-Burgers equation with nonlinear terms of any order by applying the homotopy analysis method (HAM. While compared with the Adomain decomposition method (ADM and the homotopy perturbation method (HPM, the HAM contains the auxiliary convergence-control parameter $\\hbar$ and the control function $H(x,t$, which provides a useful way to adjust and control the convergence region of solution series. The numerical results reveal that HAM is accurate and effective when it is applied to the perturbed PDEs.

  19. Three-dimensional multi-scale model of deformable platelets adhesion to vessel wall in blood flow.

    Wu, Ziheng; Xu, Zhiliang; Kim, Oleg; Alber, Mark

    2014-08-01

    When a blood vessel ruptures or gets inflamed, the human body responds by rapidly forming a clot to restrict the loss of blood. Platelets aggregation at the injury site of the blood vessel occurring via platelet-platelet adhesion, tethering and rolling on the injured endothelium is a critical initial step in blood clot formation. A novel three-dimensional multi-scale model is introduced and used in this paper to simulate receptor-mediated adhesion of deformable platelets at the site of vascular injury under different shear rates of blood flow. The novelty of the model is based on a new approach of coupling submodels at three biological scales crucial for the early clot formation: novel hybrid cell membrane submodel to represent physiological elastic properties of a platelet, stochastic receptor-ligand binding submodel to describe cell adhesion kinetics and lattice Boltzmann submodel for simulating blood flow. The model implementation on the GPU cluster significantly improved simulation performance. Predictive model simulations revealed that platelet deformation, interactions between platelets in the vicinity of the vessel wall as well as the number of functional GPIbα platelet receptors played significant roles in platelet adhesion to the injury site. Variation of the number of functional GPIbα platelet receptors as well as changes of platelet stiffness can represent effects of specific drugs reducing or enhancing platelet activity. Therefore, predictive simulations can improve the search for new drug targets and help to make treatment of thrombosis patient-specific. PMID:24982253

  20. Adhesion of DOPA-Functionalized Model Membranes to Hard and Soft Surfaces.

    Guvendiren, Murat; Brass, David A; Messersmith, Phillip B; Shull, Kenneth R

    2009-01-01

    The adhesive proteins secreted by marine mussels form a natural glue that cures rapidly to form strong and durable bonds in aqueous environments. These mussel adhesive proteins contain an unusual amino acid, 3,4-dihydroxy-L-phenylalanine (DOPA), which is largely responsible for their cohesive and adhesive strengths. In this study, we incorporated DOPA into diblock and triblock polymers and developed a membrane contact experiment to assess the adhesive interactions of these materials with TiO(2) and tissue surfaces. In a typical experiment a micrometer-thick DOPA-functionalized elastomeric membrane is attached to the end of a cylindrical glass tube. Application of a positive pressure to the tube brings the membrane into contact with the surface of interest. The negative pressure needed to separate the membrane from the substrate is a measure of the strength of the adhesive interaction. The test confirms previous results obtained with TiO(2) substrates. Because the membrane geometry is well suited for rough or chemically heterogeneous surfaces, it is ideal for studies of tissue adhesion. DOPA was found to give strong adhesion to tissue surfaces, with the strongest adhesion obtained when the DOPA groups were oxidized while in contact with the tissue surface. PMID:21461121

  1. Some remarks on Li-Sinai-type solutions of the Burgers equation

    Pauls, W.

    2011-07-01

    For a class of complex-valued initial conditions, we construct solutions for the inviscid Burgers equations of the same type as those recently introduced by Li and Sinai. Obtained by very simple considerations, these solutions correspond to stable distributions with 1 Gaussian type can be constructed for the viscous Burgers equation.

  2. Discrete Symmetries Analysis and Exact Solutions of the Inviscid Burgers Equation

    Hongwei Yang

    2012-01-01

    Full Text Available We discuss the Lie point symmetries and discrete symmetries of the inviscid Burgers equation. By employing the Lie group method of infinitesimal transformations, symmetry reductions and similarity solutions of the governing equation are given. Based on discrete symmetries analysis, two groups of discrete symmetries are obtained, which lead to new exact solutions of the inviscid Burgers equation.

  3. On the solution of two-dimensional coupled Burgers' equations by variational iteration method

    By means of variational iteration method the solutions of two-dimensional Burgers' and inhomogeneous coupled Burgers' equations are exactly obtained, comparison with the Adomian decomposition method is made, showing that the former is more effective than the later. In this paper, He's variational iteration method is given approximate solutions that can converge to its exact solutions faster than those of Adomain's method.

  4. Adhesive Categories

    Lack, Stephen; Sobocinski, Pawel

    2003-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well to...... rewriting on arbitrary adhesive categories....

  5. Adhesive Categories

    Lack, Stephen; Sobocinski, Pawel

    2004-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well to...... rewriting on arbitrary adhesive categories....

  6. Evaluation of the Effectiveness of Peritoneal Adhesion Prevention Devices in a Rat Model

    Poehnert, D; Grethe, L; Maegel, L; Jonigk, D; Lippmann, T; Kaltenborn, A; Schrem, H; Klempnauer, J; Winny, M

    2016-01-01

    Background: Abdominal operations are followed by adhesions, a prevalent cause of abdominal pain, and the most frequent cause for bowel obstruction and secondary female infertility. This rat study addresses adhesion prevention capability of Adept®, Interceed®, Seprafilm®, and a novel device, 4DryField® PH which is provided as powder and generates its effect as gel. Methods: Sixty-eight male Lewis rats had cecal abrasion and creation of an equally sized abdominal wall defect, and were grouped randomly: A control group without treatment (n=10); two groups treated with 4DryField® PH using premixed gel (n=15) or in-situ gel technique (n=16); one group each was treated with Seprafilm® (n=8), Interceed® (n=9), or Adept® (n=10). Sacrifice was on day 7 to evaluate incidence, quality, and quantity of adhesions, as expressed via adhesion reduction rate (AR). Histologic specimens were evaluated. Statistical analyses used ANOVA and unpaired t-tests. Results: 4DryField® PH significantly reduced incidence and severity of adhesions both as premixed gel (AR: 85.2%) and as in-situ made gel (AR: 100%), a comparison between these two application techniques showed no differences in efficacy. Seprafilm® did not reduce incidence but severity of adhesions significantly (AR: 53.5%). With Interceed® (AR: 3.7%) and Adept® (AR: 16.1%) no significant adhesion-reduction was achieved. Except for inflammatory response with Interceed®, histopathology showed good tissue compatibility of all other devices. Conclusion: 4DryField® PH and Seprafilm® showed significant adhesion prevention capabilities. 4DryField® PH achieved the highest adhesion prevention effectiveness without restrictions concerning mode of application and compatibility and, thus, is a promising strategy to prevent abdominal adhesions. PMID:27429589

  7. Modeling and design optimization of adhesion between surfaces at the microscale.

    Sylves, Kevin T. (University of Colorado, Boulder, CO)

    2008-08-01

    This research applies design optimization techniques to structures in adhesive contact where the dominant adhesive mechanism is the van der Waals force. Interface finite elements are developed for domains discretized by beam elements, quadrilateral elements or triangular shell elements. Example analysis problems comparing finite element results to analytical solutions are presented. These examples are then optimized, where the objective is matching a force-displacement relationship and the optimization variables are the interface element energy of adhesion or the width of beam elements in the structure. Several parameter studies are conducted and discussed.

  8. Burgers-like equation for spontaneous breakdown of the chiral symmetry in QCD

    Blaizot, Jean-Paul; Warchoł, Piotr

    2013-01-01

    We link the spontaneous breakdown of chiral symmetry in Euclidean QCD to the collision of spectral shock waves in the vicinity of zero eigenvalue of Dirac operator. The mechanism, originating from complex Burger's-like equation for viscid, pressureless, one-dimensional flow of eigenvalues, is similar to recently observed weak-strong coupling phase transition in large $N_c$ Yang-Mills theory. The spectral viscosity is proportional to the inverse of the size of the random matrix that replaces the Dirac operator in the universal (ergodic) regime. We obtain the exact scaling function and critical exponents of the chiral phase transition for the averaged characteristic polynomial for $N_c \\ge3$ QCD. We reinterpret our results in terms of known properties of chiral random matrix models and lattice data.

  9. Burgers-like equation for spontaneous breakdown of the chiral symmetry in QCD

    We link the spontaneous breakdown of chiral symmetry in Euclidean QCD to the collision of spectral shock waves in the vicinity of zero eigenvalue of the Dirac operator. The mechanism, originating from complex Burger's-like equation for viscid, pressureless, one-dimensional flows of eigenvalues, is similar to the recently observed weak-strong coupling phase transition in large Nc Yang–Mills theory. The spectral viscosity is proportional to the inverse size of the random matrix that replaces the Dirac operator in the universal (ergodic) regime. We obtain the exact scaling function and critical exponents of the chiral phase transition for the averaged characteristic polynomial for Nc⩾3 QCD. We reinterpret our results in terms of known properties of chiral random matrix models and lattice data

  10. Surface conductivity of insulators: one-dimensional initial value problems and the inviscid Burgers equation

    A generalized derivation of the equations governing surface carrier diffusion in the surface region of an insulator is presented, based on the Mott-Gurney model of ionic diffusion as first proposed in Liesegang et al (1995 J. Appl. Phys. 77 5782; 1996 J. Appl. Phys. 80 6336). The resulting non-linear equations are decoupled for the case of one-dimensional diffusion and we show that the decay of the electric field is described by the inviscid Burgers equation. Imposing initial and boundary conditions reflecting the experimental configuration for a Cartesian system as discussed in Liesegang et al, a general solution for the carrier density in the surface of an insulating sample is derived for the case of one-dimensional charge motion

  11. Effect of hyaluronic acid on postoperative intraperitoneal adhesion formation in the rat model

    Urman, B.; Gomel, V.; Jetha, N. (Department of Obstetrics and Gynecology, University of British Columbia, Vancouver (Canada))

    1991-09-01

    The aim of this study was to determine the effectiveness of hyaluronic acid solution in preventing intraperitoneal (IP) adhesions. The study design was prospective, randomized and blinded and involved 83 rats. Measured serosal injury was inflicted using a CO2 laser on the right uterine horn of the rat. Animals randomized to groups 1 and 2 received either 0.4% hyaluronic acid or its diluent phosphate-buffered saline (PBS) intraperitoneally before and after the injury. In groups 3 and 4, the same solutions were used only after the injury. Postoperative adhesions were assessed at second-look laparotomy. Histologic assessment of the fresh laser injury was carried out on uteri pretreated with hyaluronic acid, PBS, or nothing. Pretreatment with hyaluronic acid was associated with a significant reduction in postoperative adhesions and a significantly decreased crater depth. Hyaluronic acid appears to reduce postoperative IP adhesion formation by coating the serosal surfaces and decreasing the extent of initial tissue injury.

  12. Effect of hyaluronic acid on postoperative intraperitoneal adhesion formation and reformation in the rat model

    Urman, B.; Gomel, V. (Department of Obstetrics and Gynecology, University of British Columbia, Vancouver (Canada))

    1991-09-01

    The local application of 0.25% or 0.4% HA before the induction of a measured laser injury on the rat uterine horn was associated with a significant reduction (P less than 0.05) in postoperative IP adhesions when compared with the group of animals pretreated with the diluent vehicle PBS or received no pretreatment. However, 0.4% HA, when applied in a similar manner, was ineffective in reducing reformation of adhesions after microsurgical adhesiolysis.

  13. Experimental characterization and numerical simulation of composite adhesive joints using the cohesive zone model approach

    Sarrado Molina, Carlos

    2015-01-01

    The present thesis aims at developing robust numerical and experimental methods for the simulation of composite adhesive joints. Firstly, a new method for the experimental characterization of adhesive joints is presented. The proposed method widens the range of applicability of the existing methods at the same time that lowers the uncertainty of the results. By means of this method, a critical study on the validity of the existing experimental methods is presented, as well as the thorough cha...

  14. Staphylococcus aureus and Staphylococcus epidermidis adhesion to nanohydroxyapatite in the presence of model proteins

    Bacterial infections can have adverse effects on the efficacy, lifetime, and safety of an implanted device. The aim of this study was to investigate the initial adhesion of several strains, namely S. aureus and S. epidermidis, on two distinct types of nanohydroxyapatite (nanoHA), sintered at 725 °C and 1000 °C. A comparison was also made with nanohydroxyapatite having adsorbed fetal bovine serum (FBS), human fibronectin (FN) and human serum albumin (HSA). Adhered bacterial cells were examined by scanning electron microscopy and quantified as colony forming units after being released by sonication. The wettability of the sample surface with and without adsorbed protein was assessed by contact-angle measurements. NanoHA sintered at 1000 °C showed lower bacterial adhesion than this heat-treated at 725 °C. Adsorption of FBS onto the nanoHA surface caused a decrease in the adhesion of all strains on both materials. The bacterial adhesion patterns in the presence of FN were different for both nanoHA substrates; the adherence of the bacterial strains, except for the clinical strain of S. epidermidis, was significantly higher on nanoHA 1000 in comparison to nanoHA 1000 without protein and the bacterial adhesion on the FN-coated nanoHA 725 was lower in comparison to the bare nanoHA 725. The effect of HSA on bacterial adhesion was concentration and bacterial strain dependent. (paper)

  15. Real and Complex Turbulence for the Stochastic Burgers Equation

    Neate, A

    2004-01-01

    The inviscid limit of Burgers equation, with body forces white noise in time, is discussed in terms of the level surfaces of the minimising Hamilton-Jacobi function and the classical mechanical caustic. Presurfaces and precaustics are introduced by using the classical mechanical flow map. When the prelevel surface touches the precaustic, the geometry (number of cusps) on the level surface changes infinitely rapidly causing `real turbulence' (Davies, Truman and Zhao). Using an idea of Felix Klein, it is shown that the geometry (number of swallowtails) on the caustic also changes infinitely rapidly when the real part of the precaustic touches its complex counterpart, which we call `complex turbulence'. These two new kinds of turbulence are both inherently stochastic in nature. A complete analysis of this problem is given in terms of a reduced (one dimensional) action function. This characterises which parts of the original caustic are singular - an old problem in applied mathematics relevant for our `elementary...

  16. The Application of Hypoxanthine Activity as a Quality Indicator of Cold Stored Fish Burgers

    METİN, Suhendan; ERKAN, Nuray; VARLIK, Candan

    2002-01-01

    Seafoods are very perishable, and many different methods are used for the determination of their quality. Sensory and hypoxanthine values of cold stored trout burgers, which we prepared, were determined during a 28-day period. Burgers spoiled after the 21st day of storage. The TVB-N values were still very low when the burgers spoiled and the pH values decreased during their storage. Therefore total volatile bases nitrogen and pH analyses were not useful for the determination of the quality...

  17. QUALITY CHARACTERISTICS OF CHICKEN BURGERS ENRICHED WITH VEGETABLE OILS, INULIN AND WHEAT FIBER

    A. Cegielka

    2015-09-01

    Full Text Available The aim of the study was to modify the composition of chicken burgers in terms of nutritional value by substitution of 20% of pork jowl with a mixture of rapeseed oil and linseed oil, and addition of inulin (1% or wheat fiber (3%. Substitution of pork jowl with vegetable oils resulted in significant increase in polyunsaturated fatty acids, and rosemary extract retarded the oxidation process of lipids. Addition of wheat fiber was helpful in maintaining the thermal processing yield and texture of burgers. Microbiological quality of vacuum packed burgers subjected to 21-day storage at +4°C±1 and -20°C±1 was satisfactory.

  18. A numerical solution of the Burgers' equation using septic B-splines

    Ramadan, Mohamed A. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt)] e-mail: mramadan@mailer.eun.eg; El-Danaf, Talaat S. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt); Abd Alaal, Faisal E.I. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt)

    2005-11-01

    In this paper, numerical solutions of the nonlinear Burgers' equation are obtained by a method based on collocation of septic B-splines over finite elements. Applying the Von-Neumann stability analysis, the proposed method is shown to be unconditionally stable. Numerical solutions of the modified Burgers' equation are also obtained by making a simple change of the suggested numerical scheme for the Burgers' equation. The accuracy of the presented method is demonstrated by two test problems. The numerical results are found to be in good agreement with the exact solutions.

  19. A numerical solution of the Burgers' equation using septic B-sp lines

    Ramadan, Mohamed A. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt)] e-mail: mramadan@mailer.eun.eg; El-Danaf, Talaat S. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt); Abd Alaal, Faisal E.I. [Department of Mathematics, Faculty of Science, Menoufia University, Shiben El-Koom (Egypt)

    2005-11-01

    In this paper, numerical solutions of the nonlinear Burgers' equation are obtained by a method based on collocation of septic B-sp lines over finite elements. Applying the Von-Neumann stability analysis, the proposed method is shown to be unconditionally stable. Numerical solutions of the modified Burgers' equation are also obtained by making a simple change of the suggested numerical scheme for the Burgers' equation. The accuracy of the presented method is demonstrated by two test problems. The numerical results are found to be in good agreement with the exact solutions.

  20. Reductions and conserved quantities for discrete compound KdV-Burgers equations

    He Yu-Fang; Liu Yong-Song; Fu Jing-Li

    2011-01-01

    We present two methods to reduce the discrete compound KdV-Burgers equation, which are reductions of the independent and dependent variables: the translational invariant method has been applied in order to reduce the independent variables; and a discrete spectral matrix has been introduced to reduce the number of dependent variables.Based on the invariance of a discrete compound KdV-Burgers equation under infinitesimal transformation with respect to its dependent and independent variables, we present the determining equations of transformation Lie groups for the KdV-Burgers equation and use the characteristic equations to obtain new forms of invariants.

  1. Dynamical arrest, percolation, gelation, and glass formation in model nanoparticle dispersions with thermoreversible adhesive interactions.

    Eberle, Aaron P R; Castañeda-Priego, Ramón; Kim, Jung M; Wagner, Norman J

    2012-01-24

    We report an experimental study of the dynamical arrest transition for a model system consisting of octadecyl coated silica suspended in n-tetradecane from dilute to concentrated conditions spanning the state diagram. The dispersion's interparticle potential is tuned by temperature affecting the brush conformation leading to a thermoreversible model system. The critical temperature for dynamical arrest, T*, is determined as a function of dispersion volume fraction by small-amplitude dynamic oscillatory shear rheology. We corroborate this transition temperature by measuring a power-law decay of the autocorrelation function and a loss of ergodicity via fiber-optic quasi-elastic light scattering. The structure at T* is measured using small-angle neutron scattering. The scattering intensity is fit to extract the interparticle pair-potential using the Ornstein-Zernike equation with the Percus-Yevick closure approximation, assuming a square-well interaction potential with a short-range interaction (1% of particle diameter). (1) The strength of attraction is characterized using the Baxter temperature (2) and mapped onto the adhesive hard sphere state diagram. The experiments show a continuous dynamical arrest transition line that follows the predicted dynamical percolation line until ϕ ≈ 0.41 where it subtends the predictions toward the mode coupling theory attractive-driven glass line. An alternative analysis of the phase transition through the reduced second virial coefficient B(2)* shows a change in the functional dependence of B(2)* on particle concentration around ϕ ≈ 0.36. We propose this signifies the location of a gel-to-glass transition. The results presented herein differ from those observed for depletion flocculated dispersion of micrometer-sized particles in polymer solutions, where dynamical arrest is a consequence of multicomponent phase separation, suggesting dynamical arrest is sensitive to the physical mechanism of attraction. PMID:22148874

  2. The effect of temperature on adhesion forces between surfaces and model foods containing whey protein and sugar

    Goode, K. R.; Bowen, J.; Akhtar, N; Robbins, P. T.; Fryer, P. J.

    2013-01-01

    The formation of fouling deposit from foods and food components is a severe problem in food processing and leads to frequent cleaning. The design of surfaces that resist fouling may decrease the need for cleaning and thus increase efficiency. Atomic force microscopy has been used to measure adhesion forces between stainless steel (SS) and fluoro-coated glass (FCG) microparticles and the model food deposits (i) whey protein (WPC), (ii) sweetened condensed milk, and (iii) caramel. Measurements ...

  3. Surgical adhesives

    I. A. THOMAZINI-SANTOS

    2001-12-01

    Full Text Available The authors have performed a literature review of surgical adhesives, such as cyanoacrylate, collagen gelatin, and fibrin glue. They have included different types of commercial and non-commercial fibrin sealants and have reported on the different components in these adhesives, such as fibrinogen, cryoprecipitate, bovine thrombin, and thrombin-like fraction of snake venom.

  4. Lactobacillus Adhesion to Mucus

    Maxwell L. Van Tassell

    2011-05-01

    Full Text Available Mucus provides protective functions in the gastrointestinal tract and plays an important role in the adhesion of microorganisms to host surfaces. Mucin glycoproteins polymerize, forming a framework to which certain microbial populations can adhere, including probiotic Lactobacillus species. Numerous mechanisms for adhesion to mucus have been discovered in lactobacilli, including partially characterized mucus binding proteins. These mechanisms vary in importance with the in vitro models studied, which could significantly affect the perceived probiotic potential of the organisms. Understanding the nature of mucus-microbe interactions could be the key to elucidating the mechanisms of probiotic adhesion within the host.

  5. PHYSICOCHEMICAL, MICROBIOLOGICAL QUALITY AND OXIDATIVE STABILITY IN SPICED LAMB MEAT BURGERS

    Almudena Cózar

    2013-12-01

    Full Text Available The effect of adding two powdered spices (rosemary and thyme on the pH, colour coordinates, Cooking yield (CY Cooking loss (CL, Diameter Reduction (DR, Shear Force (SF, microbiological levels and lipid oxidation (LO in two types of lamb burgers (L= leg meat; LNB= leg+neck+breast meat was assessed over a six day period. Both spices increased stability during the storage period, LO values being six times lower than those of the non-spiced control group at 6 days. L samples showed higher CY, lower CL and DR than LNB burgers, with significant differences at 6 d (P < 0.001. The length of storage only affected (P < 0.01 these parameters in L burgers. In general, SF was higher in LNB than in L burgers but did not vary with time. The colour coordinates showed lower values in L than in LNB samples. The formulation type affected TVC and Pseudomonas spp.

  6. Statistical properties of large ensembles of exact solutions to Burgers' equation with random initial conditions

    The study of Burgers' equation is important to the understanding of the Navier-Stokes equation, as Burgers' equation is so often used in preliminary investigations of turbulence (i.e., statistical closures). In this work, the difficulties in implementing exact solutions to Burgers' equation have been overcome, allowing the study of the statistical properties of Burgers' equation using the exact solution for piecewise linear initial velocity fields. The statistical and spectral properties commonly used in studies of turbulence are presented for three different types of initial conditions. It is found that the energy spectrum quickly evolves to a self-similar functional form which can be simply characterized. A full-spectrum nonlinear similarity transformation based on this characterization is developed. It is found that the probability distribution of the velocity field approaches a bell-shaped distribution, but that the higher moments of this distribution do not rapidly approach those of a Gaussian distribution

  7. New multi-soliton solutions for generalized Burgers-Huxley equation

    Liu Jun

    2013-01-01

    Full Text Available The double exp-function method is used to obtain a two-soliton solution of the generalized Burgers-Huxley equation. The wave has two different velocities and two different frequencies.

  8. Finite symmetry transformation group and localized structures of the (2+1)-dimensional coupled Burgers equation

    Lei Ya; Yang Duo

    2013-01-01

    In this paper,the finite symmetry transformation group of the (2+ 1)-dimensional coupled Burgers equation is studied by the modified direct method,and with the help of the truncated Painlevé expansion approach,some special localized structures for the (2+ 1)-dimensional coupled Burgers equation are obtained,in particular,the dromion-like and solitoff-like structures.

  9. PAINLEV PROPERTY OF BURGERS-KDV EQUATION AND ITS EXACT SOLUTIONS

    2010-01-01

    In this paper, we introduce the Painlev property of the Burgers-KdV equation. Two types of exact solutions to the equation are obtained by the standard truncated expansion metIn this paper, we introduce the Painlev property of the Burgers-KdV equation. Two types of exact solutions to the equation are obtained by the standard truncated expansion method and the extended standard truncated expansion method, respectively.hod and the extended standard truncated expansion method, respectively.

  10. Modelling the Interfacial Adhesion in Polyethylene/Polypropylene Blends Compatibilized by Means of Reactive Extrusion

    Gerard, J. F.; Kotek, Jiří; Colbeaux, A.; Fenouillot, F.; Wautier, H.

    University of Florida: American Chemical Society, 2002, s. 419-420. (PMSE Preprints.. 86). [Spring Meeting of the American Chemical Society, Division of Polymeric Materials: Science and Engineering. Orlando (US), 07.04.2002-11.04.2002] R&D Projects: GA AV ČR KSK4050111 Keywords : PP/HDPE blend * compatibilization * interfacial adhesion Subject RIV: CD - Macromolecular Chemistry

  11. Chemical Composition and Storage Stability of Beef burger Steaks as Influenced by Cooking and Irradiation

    Meat industry in Egypt has a great economic potential, but till now it has not received adequate attention. Beef burgers were prepared (50 g, 1 cm thick steaks) and aerobically packaged into polyethylene pages then divided into control, cooking and gamma-irradiated (3 and 4 kGy) groups. Samples stored at (5±degree c) and periodically judged after 5, 10, 15, 20,25 and 30 days. The results showed that irradiation increased the shelf life of stored cooked beef burger, as compared to control samples. In addition, the dose of 3 kGy is considered the most adequate for irradiation of this meat product because it obtained the same results reflected by 4 kGy. The microbiological, chemical and sensorial testing for stored cooking and irradiated beef burger steaks were examined according an experimental design presented conditions that were adequate for human consumption of this product during the refrigeration storage periods. For the non-irradiated beef burger samples, bacterial contamination was the main limiting factor with respect to the shelf life, whereas for the irradiated beef burger samples this factor was lipid oxidation. Conclusion: The cooking before food irradiation may be of practical efficacy in enhancing the technical effectiveness and feasibility of irradiation of a variety of meat products. Recommendation: The necessity for a proper preservation method for marketing the processing beef burger steaks in each of its numerous retail markets should be established central irradiation units for processing and packing before distribution in these retail markets

  12. A numerical model of a HIL scaled roller rig for simulation of wheel-rail degraded adhesion condition

    Conti, Roberto; Meli, Enrico; Pugi, Luca; Malvezzi, Monica; Bartolini, Fabio; Allotta, Benedetto; Rindi, Andrea; Toni, Paolo

    2012-05-01

    Scaled roller rigs used for railway applications play a fundamental role in the development of new technologies and new devices, combining the hardware in the loop (HIL) benefits with the reduction of the economic investments. The main problem of the scaled roller rig with respect to the full scale ones is the improved complexity due to the scaling factors. For this reason, before building the test rig, the development of a software model of the HIL system can be useful to analyse the system behaviour in different operative conditions. One has to consider the multi-body behaviour of the scaled roller rig, the controller and the model of the virtual vehicle, whose dynamics has to be reproduced on the rig. The main purpose of this work is the development of a complete model that satisfies the previous requirements and in particular the performance analysis of the controller and of the dynamical behaviour of the scaled roller rig when some disturbances are simulated with low adhesion conditions. Since the scaled roller rig will be used to simulate degraded adhesion conditions, accurate and realistic wheel-roller contact model also has to be included in the model. The contact model consists of two parts: the contact point detection and the adhesion model. The first part is based on a numerical method described in some previous studies for the wheel-rail case and modified to simulate the three-dimensional contact between revolute surfaces (wheel-roller). The second part consists in the evaluation of the contact forces by means of the Hertz theory for the normal problem and the Kalker theory for the tangential problem. Some numerical tests were performed, in particular low adhesion conditions were simulated, and bogie hunting and dynamical imbalance of the wheelsets were introduced. The tests were devoted to verify the robustness of control system with respect to some of the more frequent disturbances that may influence the roller rig dynamics. In particular we verified

  13. A brand loyalty model for arts festivals / Susanna Elizabeth Burger

    Burger, Susanna Elizabeth

    2015-01-01

    The number of festivals and events worldwide as well as in South Africa has increased significantly over the past decade. With more than 600 festivals being staged annually in South Africa, it is clear that festivals are competing with each other to attract and retain visitors in order to remain sustainable. For this reason, creating and sustaining a loyal visitor base through marketing and branding activities has become increasingly important for festivals. This, however, is a complex task s...

  14. Nonempirical potentials in modelling of boron adhesion on a (110) tungsten surface

    Dorfman, S; Mundim, K C; Fuks, D; Gordon, A; Felsteiner, J

    2003-01-01

    We have performed the atomistic simulations of the adhesion process of a boron atom on a tungsten(110) surface on the basis of the generalized simulation annealing formalism. The interatomic potentials used in these simulations were obtained from ab initio total energy calculations on the basis of the recursion procedure. The nonempirical calculations have been carried out in the framework of density functional theory in the coherent potential approximation.

  15. Analytical modeling of mixed-Mode bending behavior of asymmetric adhesively bonded pultruded GFRP joints

    Ševčík, Martin; Shahverdi, M.; Hutař, Pavel; Vassilopoulos, Anastasios P.

    2015-01-01

    Roč. 147, OCT (2015), s. 228-242. ISSN 0013-7944 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA MŠk(CZ) EE2.3.30.0063 Institutional support: RVO:68081723 Keywords : Mixed-Mode delamination * Asymmetric joint * Adhesively bonded joint * Failure criterion * Analytical prediction * GFRP Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.767, year: 2014

  16. Damage modelling procedure and fastener positioning optimization of adhesively reinforced frictional interfaces

    Oinonen, Ahti

    2011-01-01

    This thesis is concerned with the development of the shear damage simulation procedure for combined mechanically clamped and adhesively reinforced frictional joint interfaces. The first step has been to experimentally measure the shear fracture behaviour of high strength steel interfaces using annular ring specimens subject to constant normal pre-stress. The experimental programme included variations of the pre-stress, surface roughness and epoxy curing temperature. Results showed that these ...

  17. Impairment of the Peritoneal Surface as a Decisive Factor for Intestinal Adhesions in Intraperitoneal Onlay Mesh Surgery - Introducing a New Rat Model

    Winny, M; Grethe, L; Maegel, L; Jonigk, D; Lippmann, T.; Klempnauer, J; Poehnert, D

    2016-01-01

    Background: Meshes implanted intraperitoneally are known to cause adhesions potentially resulting in complications such as chronic pain, enterocutaneous fistula, or mesh infection. This study introduces a model for investigation of intestine-to-mesh adhesions and evaluates as to whether missing of visceral peritoneum is causative. Methods: In 18 rats, rectangular 1.5 x 2 cm patches of an uncoated polypropylene mesh (Ultrapro®) were sewn to the inner abdominal wall next to the cecum. Additiona...

  18. Creep curve measurement to support wear and adhesion modelling, using a continuously variable creep twin disc machine

    Fletcher, D. I.; Lewis, S.

    2013-01-01

    Predictive modelling of wear and adhesion at rolling-sliding contacts such as a railway rail and wheel depends on understanding the relationship between slip and shear force at the contact surface, i.e. the creep verses force curve. This paper describes a new approach to creep curve measurement using a twin disc machine running with a continuous programmed variation of creep, enabling an entire creep curve to be defined in a single experiment. The work focuses on very low levels of creep, ran...

  19. Stokes' Second Problem for Magnetohydrodynamics Flow in a Burgers' Fluid: The Cases γ = λ2/4 and γ>λ2/4

    Khan, Ilyas; Ali, Farhad; Shafie, Sharidan

    2013-01-01

    The present work is concerned with exact solutions of Stokes second problem for magnetohydrodynamics (MHD) flow of a Burgers' fluid. The fluid over a flat plate is assumed to be electrically conducting in the presence of a uniform magnetic field applied in outward transverse direction to the flow. The equations governing the flow are modeled and then solved using the Laplace transform technique. The expressions of velocity field and tangential stress are developed when the relaxation time satisfies the condition γ = λ2/4 or γ>λ2/4. The obtained closed form solutions are presented in the form of simple or multiple integrals in terms of Bessel functions and terms with only Bessel functions. The numerical integration is performed and the graphical results are displayed for the involved flow parameters. It is found that the velocity decreases whereas the shear stress increases when the Hartmann number is increased. The solutions corresponding to the Stokes' first problem for hydrodynamic Burgers' fluids are obtained as limiting cases of the present solutions. Similar solutions for Stokes' second problem of hydrodynamic Burgers' fluids and those for Newtonian and Oldroyd-B fluids can also be obtained as limiting cases of these solutions. PMID:23667442

  20. Determination of Burgers vector of screw dislocations in 6H-SiC single crystals by synchrotron white beam x-ray topography

    Individual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-model images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. The sense of the Burgers vector can also be deduced from the above-mentioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations

  1. Stokes' second problem for magnetohydrodynamics flow in a Burgers' fluid: the cases γ = λ²/4 and γ>λ²/4.

    Ilyas Khan

    Full Text Available The present work is concerned with exact solutions of Stokes second problem for magnetohydrodynamics (MHD flow of a Burgers' fluid. The fluid over a flat plate is assumed to be electrically conducting in the presence of a uniform magnetic field applied in outward transverse direction to the flow. The equations governing the flow are modeled and then solved using the Laplace transform technique. The expressions of velocity field and tangential stress are developed when the relaxation time satisfies the condition γ =  λ²/4 or γ> λ²/4. The obtained closed form solutions are presented in the form of simple or multiple integrals in terms of Bessel functions and terms with only Bessel functions. The numerical integration is performed and the graphical results are displayed for the involved flow parameters. It is found that the velocity decreases whereas the shear stress increases when the Hartmann number is increased. The solutions corresponding to the Stokes' first problem for hydrodynamic Burgers' fluids are obtained as limiting cases of the present solutions. Similar solutions for Stokes' second problem of hydrodynamic Burgers' fluids and those for Newtonian and Oldroyd-B fluids can also be obtained as limiting cases of these solutions.

  2. Stokes' second problem for magnetohydrodynamics flow in a Burgers' fluid: the cases γ = λ²/4 and γ>λ²/4.

    Khan, Ilyas; Ali, Farhad; Shafie, Sharidan

    2013-01-01

    The present work is concerned with exact solutions of Stokes second problem for magnetohydrodynamics (MHD) flow of a Burgers' fluid. The fluid over a flat plate is assumed to be electrically conducting in the presence of a uniform magnetic field applied in outward transverse direction to the flow. The equations governing the flow are modeled and then solved using the Laplace transform technique. The expressions of velocity field and tangential stress are developed when the relaxation time satisfies the condition γ =  λ²/4 or γ> λ²/4. The obtained closed form solutions are presented in the form of simple or multiple integrals in terms of Bessel functions and terms with only Bessel functions. The numerical integration is performed and the graphical results are displayed for the involved flow parameters. It is found that the velocity decreases whereas the shear stress increases when the Hartmann number is increased. The solutions corresponding to the Stokes' first problem for hydrodynamic Burgers' fluids are obtained as limiting cases of the present solutions. Similar solutions for Stokes' second problem of hydrodynamic Burgers' fluids and those for Newtonian and Oldroyd-B fluids can also be obtained as limiting cases of these solutions. PMID:23667442

  3. Adhesive contact on power-law graded elastic solids: The JKR-DMT transition using a double-Hertz model

    Jin, Fan; Guo, Xu; Gao, Huajian

    2013-12-01

    A cohesive zone model of axisymmetric adhesive contact between a rigid sphere and a power-law graded elastic half-space is established by extending the double-Hertz model of Greenwood and Johnson (1998). Closed-form solutions are obtained analytically for the surface stress, deformation fields and equilibrium relations among applied load, indentation depth, inner and outer radii of the cohesive zone, which include the corresponding solutions for homogeneous isotropic materials and the Gibson solid as special cases. These solutions provide a continuous transition between JKR and DMT type contact models through a generalized Tabor parameter μ. Our analysis reveals that the magnitude of the pull-off force ranges from (3+k)πRΔγ/2 to 2πRΔγ, where k, R and Δγ denote the gradient exponent of the elastic modulus for the half-space, the radius of the sphere and the work of adhesion, respectively. Interestingly, the pull-off force for the Gibson solid is found to be identically equal to 2πRΔγ, independent of the corresponding Tabor parameter. The obtained analytical solutions are validated with finite element simulations.

  4. Technological aspects of manufacturing and numerical modelling of clinch-adhesive joints

    Sadowski, Tomasz; Golewski, Przemysław

    2015-01-01

    This short book describes the basic technological aspects involved in the creation of purely clinch and clinch-adhesive joints made of different types of adherent materials and employing different joining technologies. Basic parameters that need to be taken into account in the design process are also presented, while a comparison of experimental testing of the hybrid joint with simple clinching for a combination of different joining materials underlines the advantages of opting for hybrid joints. The book’s conclusions will facilitate the practical application of this new fastening technology.

  5. Effect of grilling and baking on physicochemical and textural properties of tilapia (Oreochromis niloticus) fish burger.

    Bainy, Eduarda Molardi; Bertan, Larissa Canhadas; Corazza, Marcos Lucio; Lenzi, Marcelo Kaminski

    2015-08-01

    The influence of two common cooking methods, grilling and baking, on chemical composition, water retention, fat retention, cooking yield, diameter reduction, expressible water, color and mechanical texture of tilapia (Oreochromis niloticus) fish burgers was investigated. Texture analyses were performed using a Warner-Bratzler test. The fish burger had a softer texture with a lower shear force than other meat products reported in the literature. There were no significant differences in proximate composition, diameter reduction, fat retention and expressible water between the grilled and oven-baked fish burgers. Cooking methods did not affect the cooking times and cooking rates. Warner-Bratzler parameters and color were significantly influenced by the cooking method. Grilling contributed to a shear force and work of shearing increase due to the lower cooking yield and water retention. Raw burgers had the highest L* (69.13 ± 0.96) and lowest b* (17.50 ± 0.75) values. Results indicated that baking yielded a product with better cooking characteristics, such as a desired softer texture with lower shear values (4.01 ± 0.54) and increased water retention (95.82 ± 0.77). Additionally, the baked fish burgers were lighter (higher L*) and less red (lower a*) than the grilled ones. PMID:26243932

  6. The inviscid Burgers equation with initial data of Brownian type

    She, Zhen-Su; Aurell, Erik; Frisch, Uriel

    1992-09-01

    The solutions to Burgers equation, in the limit of vanishing viscosity, are investigated when the initial velocity is a Brownian motion (or fractional Brownian motion) function, i.e. a Gaussian process with scaling exponent 0< h<1 (type A) or the derivative thereof, with scaling exponent -1< h<0 (type B). Largesize numerical experiments are performed, helped by the fact that the solution is essentially obtained by performing a Legendre transform. The main result is obtained for type A and concerns the Lagrangian function x(a) which gives the location at time t=1 of the fluid particle which started at the location a. It is found to be a complete Devil's staircase. The cumulative probability of Lagrangian shock intervals Δ a (also the distribution of shock amplitudes) follows a ( Δa)- h law for small Δ a. The remaining (regular) Lagrangian locations form a Cantor set of dimension h. In Eulerian coordinates, the shock locations are everywhere dense. The scaling properties of various statistical quantities are also found. Heuristic interpretations are provided for some of these results. Rigorous results for the case of Brownian motion are established in a companion paper by Ya. Sinai. For type B initial velocities (e.g. white noise), there are very few small shocks and shock locations appear to be isolated. Finally, it is shown that there are universality classes of random but smooth (non-scaling) initial velocities such that the long-time large-scale behavior is, after rescaling, the same as for type A or B.

  7. West Nile virus-induced cell adhesion molecules on human brain microvascular endothelial cells regulate leukocyte adhesion and modulate permeability of the in vitro blood-brain barrier model.

    Kelsey Roe

    Full Text Available Characterizing the mechanisms by which West Nile virus (WNV causes blood-brain barrier (BBB disruption, leukocyte infiltration into the brain and neuroinflammation is important to understand the pathogenesis of WNV encephalitis. Here, we examined the role of endothelial cell adhesion molecules (CAMs in mediating the adhesion and transendothelial migration of leukocytes across human brain microvascular endothelial cells (HBMVE. Infection with WNV (NY99 strain significantly induced ICAM-1, VCAM-1, and E-selectin in human endothelial cells and infected mice brain, although the levels of their ligands on leukocytes (VLA-4, LFA-1and MAC-1 did not alter. The permeability of the in vitro BBB model increased dramatically following the transmigration of monocytes and lymphocytes across the models infected with WNV, which was reversed in the presence of a cocktail of blocking antibodies against ICAM-1, VCAM-1, and E-selectin. Further, WNV infection of HBMVE significantly increased leukocyte adhesion to the HBMVE monolayer and transmigration across the infected BBB model. The blockade of these CAMs reduced the adhesion and transmigration of leukocytes across the infected BBB model. Further, comparison of infection with highly neuroinvasive NY99 and non-lethal (Eg101 strain of WNV demonstrated similar level of virus replication and fold-increase of CAMs in HBMVE cells suggesting that the non-neuropathogenic response of Eg101 is not because of its inability to infect HBMVE cells. Collectively, these results suggest that increased expression of specific CAMs is a pathological event associated with WNV infection and may contribute to leukocyte infiltration and BBB disruption in vivo. Our data further implicate that strategies to block CAMs to reduce BBB disruption may limit neuroinflammation and virus-CNS entry via 'Trojan horse' route, and improve WNV disease outcome.

  8. Efficacy of vitamin E and selenium for the prevention of intra-abdominal adhesions in rats: uterine horn models

    Ali Said Durmus

    2011-01-01

    Full Text Available OBJECTIVE: This study compares the efficacies of vitamin E and selenium, both individually and in combination, for the prevention of postoperative intra-abdominal adhesions in rats. METHODS: Forty-seven female rats were divided into five groups. The sham animals (S group, n = 7 were given only laparotomies and intraperitoneally received 0.9% NaCl (2 ml. In the 40 other rats, abrasions of the left uterine horn were performed, followed by intraperitoneal administration of either 2 ml 0.9% NaCl (C group, 10 mg vitamin E (vitamin E group, 0.2 mg/kg selenium (Se group or 10 mg vitamin E with 0.2 mg/kg selenium (vitamin E + Se group, with 10 animals in each treatment group. RESULTS: Adhesion formation was significantly reduced in animals in the Se and vitamin E + Se groups (p<0.05. Tissue catalase and glutathione peroxidase activities did not significantly differ between the groups. However, catalase and glutathione peroxidase activities and reduced glutathione levels were slightly increased in the vitamin E, Se and vitamin E + Se groups. In the vitamin E group, malondialdehyde concentrations were significantly lower than in the C group (p<0.05, but no significant differences were present among the S, C, Se and vitamin E + Se groups. Levels of nitric oxide were significantly higher in the C group than in the other groups (p<0.01. CONCLUSION: Intraperitoneal administration of selenium or combined vitamin E and selenium appears to be effective in preventing intra-abdominal adhesion formation in rat models through the reduction of lipid peroxidation products.

  9. Bacterial Adhesion & Blocking Bacterial Adhesion

    Vejborg, Rebecca Munk

    2008-01-01

    parameters, which influence the transition from a planktonic lifestyle to a sessile lifestyle, have been studied. Protein conditioning film formation was found to influence bacterial adhesion and subsequent biofilm formation considerable, and an aqueous extract of fish muscle tissue was shown to...... tract to the microbial flocs in waste water treatment facilities. Microbial biofilms may however also cause a wide range of industrial and medical problems, and have been implicated in a wide range of persistent infectious diseases, including implantassociated microbial infections. Bacterial adhesion is...... the first committing step in biofilm formation, and has therefore been intensely scrutinized. Much however, still remains elusive. Bacterial adhesion is a highly complex process, which is influenced by a variety of factors. In this thesis, a range of physico-chemical, molecular and environmental...

  10. Existence and uniqueness of entropy solution to initial boundary value problem for the inviscid Burgers equation

    Zhu, C

    2003-01-01

    This paper is concerned with the existence and uniqueness of the entropy solution to the initial boundary value problem for the inviscid Burgers equation. To apply the method of vanishing viscosity to study the existence of the entropy solution, we first introduce the initial boundary value problem for the viscous Burgers equation, and as in Evans (1998 Partial Differential Equations (Providence, RI: American Mathematical Society) and Hopf (1950 Commun. Pure Appl. Math. 3 201-30), give the formula of the corresponding viscosity solutions by Hopf-Cole transformation. Secondly, we prove the convergence of the viscosity solution sequences and verify that the limiting function is an entropy solution. Finally, we give an example to show how our main result can be applied to solve the initial boundary value problem for the Burgers equation.

  11. Existence and uniqueness of entropy solution to initial boundary value problem for the inviscid Burgers equation

    This paper is concerned with the existence and uniqueness of the entropy solution to the initial boundary value problem for the inviscid Burgers equation. To apply the method of vanishing viscosity to study the existence of the entropy solution, we first introduce the initial boundary value problem for the viscous Burgers equation, and as in Evans (1998 Partial Differential Equations (Providence, RI: American Mathematical Society) and Hopf (1950 Commun. Pure Appl. Math. 3 201-30), give the formula of the corresponding viscosity solutions by Hopf-Cole transformation. Secondly, we prove the convergence of the viscosity solution sequences and verify that the limiting function is an entropy solution. Finally, we give an example to show how our main result can be applied to solve the initial boundary value problem for the Burgers equation

  12. Existence and uniqueness of entropy solution to initial boundary value problem for the inviscid Burgers equation

    Zhu, Changjiang; Duan, Renjun [Laboratory of Nonlinear Analysis, Department of Mathematics, Central China Normal University, Wuhan 430079, People' s Republic of China (China)

    2003-02-28

    This paper is concerned with the existence and uniqueness of the entropy solution to the initial boundary value problem for the inviscid Burgers equation. To apply the method of vanishing viscosity to study the existence of the entropy solution, we first introduce the initial boundary value problem for the viscous Burgers equation, and as in Evans (1998 Partial Differential Equations (Providence, RI: American Mathematical Society) and Hopf (1950 Commun. Pure Appl. Math. 3 201-30), give the formula of the corresponding viscosity solutions by Hopf-Cole transformation. Secondly, we prove the convergence of the viscosity solution sequences and verify that the limiting function is an entropy solution. Finally, we give an example to show how our main result can be applied to solve the initial boundary value problem for the Burgers equation.

  13. Accurate Solutions of the Plasma Motion Equation May be Composed with the Accurate Solutions of the Burgers Equation

    Weng Jianping

    2005-01-01

    The travelling solutions of the Burgers equation may be used as the seed solutions.According to the fraction-type deforming relation between the Burgers equation and the plasma motion equation, some travelling solutions of the plasma motion equation are achieved with this seed solutions as discussed in this paper.

  14. The Legacy of the Burger Court and the Schools, 1969-1986. NOLPE Monograph/Book Series No. 41.

    Vacca, Richard S.; Hudgins, H. C., Jr.

    This book is limited to a study of the education opinions of the Supreme Court during the time that Warren Earl Burger served as Chief Justice. Over 100 opinions having direct bearing on education were issued during the Burger years, a total greater than in the entire Court's history. The first chapter presents the history of the establishment of…

  15. Effects of Rhodomyrtus tomentosa Leaf Extract on Staphylococcal Adhesion and Invasion in Bovine Udder Epidermal Tissue Model

    Mordmuang, Auemphon; Shankar, Shiv; Chethanond, Usa; Voravuthikunchai, Supayang Piyawan

    2015-01-01

    Bovine mastitis is one of the most important infectious diseases in dairy herds, and staphylococci are the most important etiologic agents of this disease. Antibiotics and chemical agents used in livestock for prevention and cure of the disease can accumulate in milk and give rise to food safety concerns. Rhodomyrtus tomentosa leaf extract was studied as an alternative approach to reduce the bacterial infections. The ethanolic extract of this plant demonstrated antibacterial activity with minimum inhibitory concentration (MIC) values as low as 16–64 μg/mL against staphylococcal isolates. In addition, the extract had an effect on the bacterial cell surface properties by increasing its hydrophobicity in a concentration dependent manner. To further extend the antibacterial efficacy, silver nanoparticles synthesized with the extract, a pure rhodomyrtone, and liposomal encapsulated rhodomyrtone were applied and their inhibitory effects on bacterial adhesion and invasion were determined by ex vivo study in a bovine udder epidermal tissue model. These agents exerted remarkable antibacterial activity against staphylococci and decreased the adhesion of the bacterial cells to the tissues. These results supported that R. tomentosa ethanolic extract could be applied as an alternative agent for bovine udder care in dairy farms. PMID:26501314

  16. On the MHD flow of fractional generalized Burgers' fluid with modified Darcy's law

    T. Hayat; M. Khan; S. Asghar

    2007-01-01

    This work is concerned with applying the fractional calculus approach to the magnetohydrodynamic(MHD) pipe flow of a fractional generalized Burgers' fluid in a porous space by using modified Darcy's relationship. The fluid is electrically conducting in the presence of a constant applied magnetic field in the transverse direction. Exact solution for the velocity distribution is developed with the help of Fourier transform for fractional calculus. The solutions for a Navier-Stokes, second grade, Maxwell, Oldroyd-B and Burgers' fluids appear as the limiting cases of the present analysis.

  17. The Statistics of Burgers Turbulence Initialized with Fractional Brownian Noise Data

    Ryan, Reade

    The statistics of the solution to the inviscid Burgers equation are investigated when the initial velocity potential is fractional Brownian motion. Using the theory of large deviations for Gaussian processes, we characterize the tails of the probability distribution functions (PDFs) of the velocity, the distance between shocks, and the shock strength. These PDFs are shown to decay like ``stretched'' exponentials of the form . Our method of proof can also be used to extend these results to a much larger class of Gaussian potentials. This work generalizes the results of Avellaneda and E [2, 3] on the inviscid Burgers equation with white-noise initial data.

  18. The Cauchy problem for the (generalized) Kadomtsev-Petviashvili-Burgers equation

    Molinet, Luc

    2000-01-01

    We investigate the Cauchy problem for the generalized Kadomtsev-Petviashvili-Burgers (KP-Burgers) equation in Sobolev spaces. This nonlinear wave equation has both dispersive and dissipative parts which makes it quite particular. After showing local existence by contraction principle for initial data $ \\varphi\\in H^s(\\mathbb R^2) $ such that $ {\\mathcal F}^{-1} (\\frac{k_2}{k_1} \\widehat{\\varphi})\\in H^r(\\mathbb R^2) $, $ 0{\\leqslant} r {\\leqslant} s- 1 $, we try to extend the s...

  19. A spectral domain decomposition approach for the generalized Burger's-Fisher equation

    In this study, we use the spectral collocation method using Chebyshev polynomials for spatial derivatives and fourth order Runge-Kutta method for time integration to solve the generalized Burger's-Fisher equation (B-F). Firstly, theory of application of Chebyshev spectral collocation method (CSCM) and domain decomposition on the generalized Burger's-Fisher equation is presented. This method yields a system of ordinary differential algebraic equations (DAEs). Secondly, we use fourth order Runge-Kutta formula for the numerical integration of the system of DAEs. The numerical results obtained by this way have been compared with the exact solution to show the efficiency of the method

  20. Note on the single-shock solutions of the Korteweg-de Vries-Burgers equation

    Kourakis, Ioannis; Verheest, Frank

    2011-01-01

    The well-known shock solutions of the Korteweg-de Vries-Burgers equation are revisited, together with their limitations in the context of plasma (astro)physical applications. Although available in the literature for a long time, it seems to have been forgotten in recent papers that such shocks are monotonic and unique, for a given plasma configuration, and cannot show oscillatory or bell-shaped features. This uniqueness is contrasted to solitary wave solutions of the two parent equations (Korteweg-de Vries and Burgers), which form a family of curves parameterized by the excess velocity over the linear phase speed.

  1. Exact Solutions for the (2+1)-Dimensional Nonlinear Modified Korteweg-de Vries-Burger Equation in Shallow Water

    In this work, we have investigated the solitary and shock waves solutions for the two-dimensional modified KdV-Burger (MKdV-B) equation that combines the effects of both dispersion and nonlinearity in shallow water model. The methods of energy integral approach and modified extended Tanh-function have been applied on the ordinary differential equation of the non dimensional MKdV-B equation to obtain the exact soliton solutions. We also found the dispersion relation of the linear non dimensional MKdV-B equation, which used to find the phase and group velocities; the relations between them are discussed. The results studied analytically and indicated in graphics

  2. Electrically Conductive Epoxy Adhesives

    Lan Bai

    2011-02-01

    Full Text Available Conductive adhesives are widely used in electronic packaging applications such as die attachment and solderless interconnections, component repair, display interconnections, and heat dissipation. The effects of film thickness as functions of filler volume fraction, conductive filler size, shape, as well as uncured adhesive matrix viscosity on the electrical conduction behavior of epoxy-based adhesives are presented in this work. For this purpose, epoxy-based adhesives were prepared using conductive fillers of different size, shape, and types, including Ni powder, flakes, and filaments, Ag powder, and Cu powder. The filaments were 20 μm in diameter, and 160 or 260 μm in length. HCl and H3PO4 acid solutions were used to etch and remove the surface oxide layers from the fillers. The plane resistance of filled adhesive films was measured using the four-point method. In all cases of conductive filler addition, the planar resistivity levels for the composite adhesive films increased when the film thickness was reduced. The shape of resistivity-thickness curves was negative exponential decaying type and was modeled using a mathematical relation. The relationships between the conductive film resistivities and the filler volume fractions were also derived mathematically based on the experimental data. Thus, the effects of surface treatment of filler particles, the type, size, shape of fillers, and the uncured epoxy viscosity could be included empirically by using these mathematical relations based on the experimental data. By utilizing the relations we proposed to model thickness-dependent and volume fraction-dependent conduction behaviors separately, we were able to describe the combined and coupled volume fraction-film thickness relationship mathematically based on our experimental data.

  3. Variable Separation Solutions for the (2+1)-Dimensional Burgers Equation

    唐晓艳; 楼森岳

    2003-01-01

    Considering that the multi-linear variable separation approach has been proved to be very useful to solve many (2+1)-dimensional integrable systems, we obtain the variable separation solutions of the Burgers equation with arbitrary number of variable separated functions. The Y-shaped soliton fusion phenomenon is revealed.

  4. Bifractality of the Devil's staircase appearing in the Burgers equation with Brownian initial velocity

    Aurell, E; Noullez, A; Blank, M

    1996-01-01

    It is shown that the inverse Lagrangian map for the solution of the Burgers equation (in the inviscid limit) with Brownian initial velocity presents a bifractality (phase transition) similar to that of the Devil's staircase for the standard triadic Cantor set. Both heuristic and rigorous derivations are given. It is explained why artifacts can easily mask this phenomenon in numerical simulations.

  5. Stochastic heat and Burgers equations and their singularities II - Analytical Properties and Limiting Distributions

    Davies, I M; Zhao, H

    2004-01-01

    We study the inviscid limit, $\\mu\\to 0$, of the stochastic viscous Burgers equation, for the velocity field $v^{\\mu}(x,t)$, $t>0$, $x\\in\\mathbb R^d$,\\frac{\\partial{v^{\\mu}}}{\\partial{t}} + (v^{\\mu}\\cdot\

  6. Exponential ergodicity for stochastic Burgers and 2D Navier-Stokes equations

    Goldys, B.; Maslowski, Bohdan

    2005-01-01

    Roč. 226, č. 1 (2005), s. 230-255. ISSN 0022-1236 R&D Projects: GA ČR(CZ) GA201/04/0750 Institutional research plan: CEZ:AV0Z10190503 Keywords : exponential ergodicity * v-uniform ergodicity * stochastic Burgers equation Subject RIV: BA - General Mathematics Impact factor: 0.806, year: 2005

  7. EXISTENCE OF WEAK SOLUTIONS FOR A DEGENERATE GENERALIZED BURGERS EQUATION WITH LARGE INITIAL DATA

    张辉

    2002-01-01

    It is obtained the existence of the weak solution for a degenerate generalized Burgers equation under the restriction u0 ∈ L∞. The main method is to add viscosity perturbation and obtain some estimates in L1 norm. Meanwhile it is obtained the solution is exponential decay when the initial data has compact support.

  8. A New Method to Construct Integrable Coupling System for Burgers Equation Hierarchy by Kronecker Product

    It is shown that the Kronecker product can be applied to construct a new integrable coupling system of soliton equation hierarchy in this paper. A direct application to the Burgers spectral problem leads to a novel soliton equation hierarchy of integrable coupling system. It indicates that the Kronecker product is an efficient and straightforward method to construct the integrable couplings.

  9. A unified approach to an augmented Burgers equation for the propagation of sonic booms.

    Yamamoto, Masafumi; Hashimoto, Atsushi; Aoyama, Takashi; Sakai, Takeharu

    2015-04-01

    Nonlinear propagation through a relaxing atmosphere of pressure disturbances extracted from a computational fluid dynamics (CFD) solution of the flow around a supersonic aircraft is simulated using an augmented Burgers equation. The effects of nonlinearity, geometrical spreading, atmospheric inhomogeneity, thermoviscous attenuation, and molecular vibration relaxation are taken into account. The augmented Burgers equation used for sonic boom propagation calculations is often solved by the operator splitting method, but numerical difficulties arise with this approach when dissipation is not effective. By re-examining the solution algorithms for the augmented Burgers equation, a stable method for handling the relaxation effect has been developed. This approach can handle the Burgers equation in a unified manner without operator splitting and, therefore, the resulting scheme is twice as fast as the original one. The approach is validated by comparing it with an analytical solution and a detailed CFD of dispersed plane wave propagation. In addition, a rise time prediction of low-boom supersonic aircraft is demonstrated. PMID:25920838

  10. Large Time Behaviour of Solutions of a System of Generalized Burgers Equation

    K T Joseph

    2005-11-01

    In this paper we study the asymptotic behaviour of solutions of a system of partial differential equations. When = 1 the equation reduces to the Burgers equation and was studied by Hopf. We consider both the inviscid and viscous case and show a new feature in the asymptotic behaviour.