Minimum Wages and Welfare in a Hotelling Duopsony

Two firms choose locations (non-wage job characteristics) on the interval [0,1] prior to announcing wages at which they employ workers who are uniformly distributed; the (constant) marginal revenue products of workers may differ. Subgame perfect equilibria of the two-stage location-wage game are studied under laissez-faire and under a minimum wage regime. Up to a restriction for the existence of pure strategy equilibria, the imposition of a minimum wage is always welfare-improving because of its effect on non-wage job characteristics.duopsony, minimum wages, hotelling

Imperfectly Competitive Cycles with Keynesian and Walrasian Features

We consider a multi-sector overlapping generations model with imperfectly competitive firms in the output markets and wage setting trade unions in the labour markets. A coordination problem between firms creates multiple temporary equilibria which are either Walrasian or of the Keynesian unemployment type. There exist many deterministic and stochastic equilibrium cycles fluctuating between Keynesian recession and Walrasian boom periods with arbitrarily long phases in each regime. The cycles are in accordance with certain empirical regularities. Money is neutral and superneutral, but appropriate countercyclical fiscal policies stabilize the cycles in a textbook Keynesian way.Endogenous business cycles, Imperfect competition, Stabilization policy

Relationships Between Atomic Diffusion Mechanisms and Ensemble Transport Coefficients in Crystalline Polymorphs

Ionic transport in conventional ionic solids is generally considered to proceed via independent diffusion events or "hops''. This assumption leads to well-known Arrhenius expressions for transport coefficients, and is equivalent to assuming diffusion is a Poisson process. Using molecular dynamics simulations of the low-temperature B1, B3, and B4 AgI polymorphs, we have compared rates of ion-hopping with corresponding Poisson distributions to test the assumption of independent hopping in these common structure-types. In all cases diffusion is a non-Poisson process, and hopping is strongly correlated in time. In B1 the diffusion coefficient can be approximated by an Arrhenius expression, though the physical significance of the parameters differs from that commonly assumed. In low temperature B3 and B4 diffusion is characterised by concerted motion of multiple ions in short closed loops. Diffusion coefficients can not be expressed in a simple Arrhenius form dependent on single-ion free-energies, and intrinsic diffusion must be considered a many-body process

Molecular Dynamics Simulation of Coherent Interfaces in Fluorite Heterostructures

The standard model of enhanced ionic conductivities in solid electrolyte heterostructures follows from a continuum mean-field description of defect distributions that makes no reference to crystalline structure. To examine ionic transport and defect distributions while explicitly accounting for ion-ion correlations and lattice effects, we have performed molecular dynamics simulations of a model coherent fluorite heterostructure without any extrinsic defects, with a difference in standard chemical potentials of mobile fluoride ions between phases induced by an external potential. Increasing the offset in fluoride ion standard chemical potentials across the internal interfaces decreases the activation energies for ionic conductivity and diffusion and strongly enhances fluoride ion mobilities and defect concentrations near the heterostructure interfaces. Non-charge-neutral "space-charge" regions, however, extend only a few atomic spacings from the interface, suggesting a continuum model may be inappropriate. Defect distributions are qualitatively inconsistent with the predictions of the continuum mean-field model, and indicate strong lattice-mediated defect-defect interactions. We identify an atomic-scale "Frenkel polarisation" mechanism for the interfacial enhancement in ionic mobility, where preferentially oriented associated Frenkel pairs form at the interface and promote local ion mobility via concerted diffusion processes

Computer simulations of ionic liquids at electrochemical interfaces

Ionic liquids are widely used as electrolytes in electrochemical devices. In this context, many experimental and theoretical approaches have been recently developed for characterizing their interface with electrodes. In this perspective article, we review the most recent advances in the field of computer simulations (mainly molecular dynamics). A methodology for simulating electrodes at constant electrical potential is presented. Several types of electrode geometries have been investigated by many groups in order to model planar, corrugated and porous materials and we summarize the results obtained in terms of the structure of the liquids. This structure governs the quantity of charge which can be stored at the surface of the electrode for a given applied potential, which is the relevant quantity for the highly topical use of ionic liquids in supercapacitors (also known as electrochemical double-layer capacitors). A key feature, which was also shown by atomic force microscopy and surface force apparatus experiments, is the formation of a layered structure for all ionic liquids at the surface of planar electrodes. This organization cannot take place inside nanoporous electrodes, which results in a much better performance for the latter in supercapacitors. The agreement between simulations and electrochemical experiments remains qualitative only though, and we outline future directions which should enhance the predictive power of computer simulations. In the longer term, atomistic simulations will also be applied to the case of electron transfer reactions at the interface, enabling the application to a broader area of problems in electrochemistry, and the few recent works in this field are also commented upon.Comment: 12 pages, 10 figures, perspective articl

Physical and chemical investigations of alpha crystallin solutions

In this thesis static light scattering was used to systematically examine potential protocols to effectively isolate bovine eye lens alpha crystallin subunits, to enable confident reconstitution and study of homogeneous assemblies of subunits. The light scattering properties of alpha crystallin subunits that were separated from one another by anion-exchange chromatography in urea, and subsequently reconstituted in buffer that did not contain urea were also studied. Such reconstituted assemblies may prove useful for future work examining the dependence of interactions between gamma and alpha crystallin on alpha crystallin subunit composition, the properties of high concentration gamma-alpha mixtures and other mixtures, and possibly the preparation of crystals for xray crystallography. The light scattering data yielded a molecular weight of (5.900 +/- 0.005) x 105 g/mole for the starting, native bovine alpha crystallin protein. The dimensionless virial coefficient of the native alpha crystallin was 3.1, less than the hard-sphere value, 4, and possibly consistent with attractive interactions on top of hard-core repulsion. While light scattering showed that 6 M urea did not completely disassemble alpha, the molecular weight after incubation in 8 M urea was (2.0 +/- 0.5) x 104 g/mole, in excellent agreement with the known molecular weights calculated from the sequences of bovine alphaA and alphaB. Reconstituted subunits isolated by anion exchange chromatography, believed to be alphaA crystallin, pending further confirmation, assembled to form particles with a molecular weight of (5 +/- 3) x 104 g/mol. These results set the stage for further study of the lens protein interactions involving homogeneous alpha crystallin assemblies

Effect of dispersion interactions on the properties of LiF in condensed phases

Classical molecular dynamics simulations are performed on LiF in the framework of the polarizable ion model. The overlap-repulsion and polarization terms of the interaction potential are derived on a purely non empirical, first-principles basis. For the dispersion, three cases are considered: a first one in which the dispersion parameters are set to zero and two others in which they are included, with different parameterizations. Various thermodynamic, structural and dynamic properties are calculated for the solid and liquid phases. The melting temperature is also obtained by direct coexistence simulations of the liquid and solid phases. Dispersion interactions appear to have an important effect on the density of both phases and on the melting point, although the liquid properties are not affected when simulations are performed in the NVT ensemble at the experimental density.Comment: 8 pages, 5 figure