1,166 research outputs found
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
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