Zero In Equilibrium Research Articles

Application of the log-normal model for long term high affinity antibody/antigen interactions using Bio-Layer Interferometry

For more than 50 years, optical biosensors have been used to measure bio-molecular interactions. The most frequently applied binding model to fit biosensor data is the simple 1:1 binding model which requires the stabilization of the association phase to the equilibrium Req and the stabilization of the dissociation phase to the equilibrium zero. However, due to technical limitations many published biosensor measurements are finished before these requirements are fulfilled. In the present study, a long term binding interaction analysis with a monoclonal antibody, namely IgG 2F5 and UG37 a specific antigen with a promising biosensor platform, the Bio-Layer Interferometry, was performed. Data fitting with the simple 1:1 binding model to the association phase was inappropriate and the fitted parameters varied with the concentration and time, which contradicts the theory of the simple 1:1 binding model. Furthermore, extrapolation of the fits with individual times spans compared to 100 % of the obtained data systematically underestimated the actual observed binding curve. Interestingly, an alternative model based on the cumulative distribution function of the log-normal probability distribution remedied the aforementioned problems allowing $$\hbox {K}_\mathrm{L}$$ (which is the analog to the affinity constant $$\hbox {K}_\mathrm{D}$$ ) to be estimated. We further demonstrate that this model fits the biosensor data far better and is essentially less affected by the stabilization of the association phase to the equilibrium (Req) and the stabilization of the dissociation phase to the equilibrium zero. Finally, extrapolation with the log-normal model predicts the actually observed binding curve in a proper manner.

Spin accumulation at ferromagnet/nonmagnetic material interfaces

Many proposed and realized spintronic devices involve spin injection and accumulation at an interface between a ferromagnet and a nonmagnetic material. We examine the electric field, voltage profile, charge distribution, spin fluxes, and spin accumulation at such an interface. We include the effects of both screening and spin scattering. We also include both the spin-dependent chemical potentials ${\ensuremath{\mu}}_{\ensuremath{\uparrow},\ensuremath{\downarrow}}$ and the effective magnetic field ${\stackrel{P\vec}{H}}^{*}$ that is zero in equilibrium. For a Co/Cu interface, we find that the spin accumulation in the copper is an order of magnitude larger when both chemical potential and effective magnetic field are included. We also show that screening contributes to the spin accumulation in the ferromagnet; this contribution can be significant.

Stackelberg-Walras and Cournot-Walras Equilibria in Mixed Markets: A Comparison

In this note, we compare two strategic general equilibrium concepts: the Stackelberg-Walras equilibrium and the Cournot-Walras equilibrium. We thus consider a market exchange economy embodying atoms and a continuum of traders. It is shown that, when the preferences of the small traders are represented by Cobb-Douglas utility functions, the Stackel-berg-Walras and the Cournot-Walras equilibria can coincide only if 1) the endowments and preferences of atoms are identical and 2) the elasticity of the followers’ best response functions are equal to zero in equilibrium.

Lattice Boltzmann algorithm to simulate isotropic-nematic emulsions

We present lattice Boltzmann simulations of the dynamical equations of motion of a drop of isotropic fluid in a nematic liquid crystal solvent, both in the absence and in the presence of an electric field. The coupled equations we solve are the Beris-Edward equations for the dynamics of the tensor order parameter describing the nematic solvent, the Cahn-Hilliard equation for the concentration evolution, and the Navier-Stokes equations for the determination of the instantaneous velocity field. We implement the lattice Boltzmann algorithm to ensure that spurious velocities are close to zero in equilibrium. We first study the effects of the liquid crystal elastic constant, K, anchoring strength, W, and surface tension, sigma, on the shape of the droplet and on the director field texture in equilibrium. We then consider how the drop behaves as the director field is switched by an applied electric field. We also show that the algorithm allows us to follow the motion of a drop of isotropic fluid placed in a liquid crystal cell with a tilted director field at the boundaries.

Evolution criterion in nonequilibrium and a variational principle for equilibrium states of free-standing liquid crystalline films

Starting out with the thermodynamic balance equations of liquid crystalline films and the second law of thermodynamics, an analog to the global surface free energy is derived whose time derivative is negative definite out of equilibrium and zero in equilibrium. This evolution criterion allows one to formulate a variational principle for the equilibrium states by minimizing the modified global surface free energy derived above. Thus the quantity which is extremal in equilibrium in the case of free-standing crystalline films is not presupposed ad hoc, but derived from an evolution criterion based on the second law.

Light Scattering from Nonequilibrium Stationary States: The Implication of Broken Time-Reversal Symmetry

We report a theroetical prediction of a new feature in the spectrum of light scattered from a fluid in a nonequilibrium stationary state with a temperature gradient. The spectrum is not symmetric in the frequency shift and the Brillouin components have different intensities. The phenomenon is linked to the breaking of time-reversal symmetry and to the appearance of a static correlation function between momentum and number densities which is zero in equilibrium, but has a $\frac{1}{{k}^{2}}$ dependence in the stationary state. We suggest a light scattering experiment by means of which these predictions can be verified.