Interactions between Membrane Inclusions on Fluctuating Membranes

We model membrane proteins as anisotropic objects characterized by symmetric-traceless tensors and determine the coupling between these order-parameters and membrane curvature. We consider the interactions between transmembrane proteins that respect up-down (reflection) symmetry of bilayer membranes and that have circular or non-circular cross-sectional areas in the tangent-plane of membranes. Using a field theoretic approach, we find non-entropic $1/R^{4}$ interactions between reflection-symmetry-breaking transmembrane proteins with circular cross-sectional area and entropic $1/R^{4}$ interactions between transmembrane proteins with circular cross-section that do not break up-down symmetry in agreement with previous calculations. We also find anisotropic $1/R^{4}$ interactions between reflection-symmetry-conserving transmembrane proteins with non-circular cross-section, anisotropic $1/R^{2}$ interactions between reflection-symmetry-breaking transmembrane proteins with non-circular cross-section, and non-entropic $1/R^{4}$ many-particle interactions among non-transmembrane proteins. For large $R$, these interactions might provide the dominant force inducing aggregation of the membrane proteins.Comment: REVTEX, 29 pages with 4 postscript figures compressed using uufiles. Introduction and Discussion sections revised. To appear in J. Phys. France I (September

Disclination Asymmetry in Deformable Hexatic Membranes and the Kosterlitz-Thouless Transitions

A disclination in a hexatic membrane favors the development of Gaussian curvature localized near its core. The resulting global structure of the membrane has mean curvature, which is disfavored by curvature energy. Thus a membrane with an isolated disclination undergoes a buckling transition from a flat to a buckled state as the ratio $\kappa/K_{A}$ of the bending rigidity $\kappa$ to the hexatic rigidity $K_{A}$ is decreased. In this paper we calculate the buckling transition and the energy of both a positive and a negative disclination. A negative disclination has a larger energy and a smaller critical value of $\kappa/K_{A}$ at buckling than does a positive disclination. We use our results to obtain a crude estimate of the Kosterlitz-Thouless transition temperature in a membrane. This estimate is higher than the transition temperature recently obtained by the authors in a renormalization calculation.Comment: REVTEX, 16 pages with 5 postscript figures compressed using uufiles. Accepted for publication in J. Phys. France

Time Varying Coefficient: An Application of Flexible Least Squares to Cattle Captive Supply

Although conventional linear regression techniques assume time constancy of parameters time varying coefficient or the problem of structural instability in econometric relationships has been recognized by econometricians. In this study, time varying impact of captive supply on fed cattle cash market price is investigated via flexible least squares approach. Time path of flexible least squares coefficient estimate indicates an approximately four fold increase in price impact of captive supply over the sample period, but even this multiplied price impact is small compared to the effect of boxed beef price which shows negligible time variation. The time path also aids in identification of structural breaks in the price impact of captive supply.time varying coefficient, flexible least squares, structural break, captive supply, Research Methods/ Statistical Methods,

Are the Kepler Near-Resonance Planet Pairs due to Tidal Dissipation?

The multiple-planet systems discovered by the Kepler mission show an excess of planet pairs with period ratios just wide of exact commensurability for first-order resonances like 2:1 and 3:2. In principle, these planet pairs could have both resonance angles associated with the resonance librating if the orbital eccentricities are sufficiently small, because the width of first-order resonances diverges in the limit of vanishingly small eccentricity. We consider a widely-held scenario in which pairs of planets were captured into first-order resonances by migration due to planet-disk interactions, and subsequently became detached from the resonances, due to tidal dissipation in the planets. In the context of this scenario, we find a constraint on the ratio of the planet's tidal dissipation function and Love number that implies that some of the Kepler planets are likely solid. However, tides are not strong enough to move many of the planet pairs to the observed separations, suggesting that additional dissipative processes are at play.Comment: 20 pages, including 7 figures; accepted for publication in Ap

THE USE OF BUDGETS IN FORECASTING THE ACTIVITY OF THE FIRM

The firm’s activity is recommended to develop in a permanent equilibrium between incomes and expenses. In the actual stage of transition of Romanian economy, the firms can not maintain this equilibrium because the expenses determined by the achievement of production overtake the level of the incomes obtained from the selling of production even when certain branches of activity are subsidized from the public budget. In these conditions, finding the methods that allow the sizing and control of the equilibrium relation between expenses and incomes represents a problem with which the firm’s management confronts. From this point of view the budget can become an instrument of correlation and especially of turning to good account the relation between incomes and expenses. Budgeting becomes a systematic economic practice that assumes the development of a process of formal assignment of financial resources that aim at the achievement of some established objectives for the future periods.budget, budgeting, forecasting, management by using budgets, expenditure budget, budget holders, manufacturing costs.