Search, Costly Price Adjustment and the Frequency of Price Changes - Theory and Evidence

We establish a new empirical finding that the intensity of search for the best price affects the frequency of nominal price changes. This relationship holds in very different economies and for various proxies for search intensity. We derive this relationship from a model of monopolistically competitive firms that face menu costs of changing nominal prices and heterogeneous consumers who search for the best price. We discuss alternative explanations and argue that they do not explain the observed correlations. Our results establish that pricing policies differ endogenously in the cross-section. This may be an important feature missing in many macroeconomic models based on nominal rigidities with exogenous frequency of price changes.Nominal rigidity; search; price adjustment

Fluid-fluid demixing transitions in colloid--polyelectrolyte star mixtures

We derive effective interaction potentials between hard, spherical colloidal particles and star-branched polyelectrolytes of various functionalities and smaller size than the colloids. The effective interactions are based on a Derjaguin-like approximation, which is based on previously derived potentials acting between polyelectrolyte stars and planar walls. On the basis of these interactions we subsequently calculate the demixing binodals of the binary colloid--polyelectrolyte star mixture, employing standard tools from liquid-state theory. We find that the mixture is indeed unstable at moderately high overall concentrations. The system becomes more unstable with respect to demixing as the star functionality and the size ratio grow.Comment: 24 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

Comment on "A centroid molecular dynamics study of liquid para hydrogen and ortho deuterium" [J. Chem. Phys. 121, 6412 (2004)]

We show that the two phase points considered in the recent simulations of liquid para hydrogen by Hone and Voth lie in the liquid-vapor coexistence region of a purely classical molecular dynamics simulation. By contrast, their phase point for ortho deuterium was in the one-phase liquid region for both classical and quantum simulations. These observations are used to account for their report that quantum mechanical effects enhance the diffusion in liquid para hydrogen and decrease it in ortho deuterium

Magnetic systems at criticality: different signatures of scaling

Different aspects of critical behaviour of magnetic materials are presented and discussed. The scaling ideas are shown to arise in the context of purely magnetic properties as well as in that of thermal properties as demonstrated by magnetocaloric effect or combined scaling of excess entropy and order parameter. Two non-standard approaches to scaling phenomena are described. The presented concepts are exemplified by experimental data gathered on four representatives of molecular magnets.Comment: 33 pages, 16 figure

On the 3D steady flow of a second grade fluid past an obstacle

We study steady flow of a second grade fluid past an obstacle in three space dimensions. We prove existence of solution in weighted Lebesgue spaces with anisotropic weights and thus existence of the wake region behind the obstacle. We use properties of the fundamental Oseen tensor together with results achieved in \cite{Koch} and properties of solutions to steady transport equation to get up to arbitrarily small \ep the same decay as the Oseen fundamental solution

Decrement Operators in Belief Change

While research on iterated revision is predominant in the field of iterated belief change, the class of iterated contraction operators received more attention in recent years. In this article, we examine a non-prioritized generalisation of iterated contraction. In particular, the class of weak decrement operators is introduced, which are operators that by multiple steps achieve the same as a contraction. Inspired by Darwiche and Pearl's work on iterated revision the subclass of decrement operators is defined. For both, decrement and weak decrement operators, postulates are presented and for each of them a representation theorem in the framework of total preorders is given. Furthermore, we present two sub-types of decrement operators

TEM investigations of laser texturized polycrystalline silicon solar cell

Purpose: The presented in this paper research results concern investigation of phase transformation of the surface structure of polycrystalline silicon solar cell. The surface of boron doped polycrystalline silicon wafers were texturised by means of diode-pumped pulsed neodymium-doped yttrium aluminium garnet laser crystal (Nd:YAG). Investigations were carried out on transmission electron microscope (TEM) to observe the changes that occurred after laser treatment of the surface layer. Changes in microstructure of the surface layer of solar cells under the influence of the laser beam are presented using the analysis phase and dislocations present in the microstructure. Observations were carried out on prepared thin foils. Moreover, diffraction patterns from selected regions of textured wafers were solved to qualify phase transformations under influence of laser beam. Design/methodology/approach: Investigations were carried out on the Transmission Electron Microscope JEM 3010 supplied by JEOL with 300 kV accelerating voltage equipped with an electronic camera configured with a computer. The microstructure was obtained in the bright field image as well dark field working in a magnification range of 10000x to ca. 100000x. Phases identification was performed by means of selected area diffraction (SAD) method, where for diffraction pattern calculations the computer software “Eldyf” was used, kindly supplied by the Institute of Materials Science, University of Silesia. Findings: The research included analyze of the influence of laser treatment conditions on geometry, roughness and size of laser made surface texture of silicon wafer applied for solar cells. Research limitations/implications: Paper contributes to research on silicon surface processing using laser beam. Practical implications: Conducted investigations may be applied in optimisation process of solar cell surface processing. Originality/value: The range of possible applications increases for example as materials for solar cells placed on building constructions, elements in electronics and construction parts in automobile industry

Green Synthesis of Glycopolymers Using an Enzymatic Approach

beta-Glucosidase and horseradish peroxidase (HRP) are used as biocatalysts in aqueous solution for the enzymatic synthesis of glycomonomers and the respective enzymatic polymerization toward glycopolymers. The biocatalytically synthesized monomers contain (meth)acrylate functionalities that are able to be polymerized by an enzyme-initiated polymerization using an HRP/hydrogen peroxide/acetylacetone ternary system. The structure of the glycomonomers and the respective glycopolymers as well as the monomer conversion after the reaction are determined by H-1 NMR spectroscopy. The synthesized glycopolymers have a dispersity and a number-average molecular weight up to 5.8 and 297 kg mol(-1), respectively. Thermal and degradation properties of the glycopolymers are studied by differential scanning calorimetry and thermogravimetric analysis. In addition, preparation of glycopolymers via conventional free radical polymerization is performed and the properties of the obtained polymers are compared with the enzymatically synthesized glycopolymers

Sexual Dimorphism of Staminate- and Pistillate-Phase Flowers of Saponaria officinalis (Bouncing Bet) Affects Pollinator Behavior and Seed Set

The sequential separation of male and female function in flowers of dichogamous species allows for the evolution of differing morphologies that maximize fitness through seed siring and seed set. We examined staminate- and pistillate-phase flowers of protandrous Saponaria officinalis for dimorphism in floral traits and their effects on pollinator attraction and seed set. Pistillate-phase flowers have larger petals, greater mass, and are pinker in color, but due to a shape change, pistillate-phase flowers have smaller corolla diameters than staminate-phase flowers. There was no difference in nectar volume or sugar content one day after anthesis, and minimal evidence for UV nectar guide patterns in staminate- and pistillate-phase flowers. When presented with choice arrays, pollinators discriminated against pistillate-phase flowers based on their pink color. Finally, in an experimental garden, in 2012 there was a negative correlation between seed set of an open-pollinated, emasculated flower and pinkness (as measured by reflectance spectrometry) of a pistillate-phase flower on the same plant in plots covered with shade cloth. In 2013, clones of genotypes chosen from the 2012 plants that produced pinker flowers had lower seed set than those from genotypes with paler flowers. Lower seed set of pink genotypes was found in open-pollinated and hand-pollinated flowers, indicating the lower seed set might be due to other differences between pink and pale genotypes in addition to pollinator discrimination against pink flowers. In conclusion, staminate- and pistillate-phase flowers of S. officinalis are dimorphic in shape and color. Pollinators discriminate among flowers based on these differences, and individuals whose pistillate-phase flowers are most different in color from their staminate-phase flowers make fewer seeds. We suggest morphological studies of the two sex phases in dichogamous, hermaphroditic species can contribute to understanding the evolution of sexual dimorphism in plants without the confounding effects of genetic differences between separate male and female individuals