13,783 research outputs found
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 interactions between reflection-symmetry-breaking
transmembrane proteins with circular cross-sectional area and entropic
interactions between transmembrane proteins with circular
cross-section that do not break up-down symmetry in agreement with previous
calculations. We also find anisotropic interactions between
reflection-symmetry-conserving transmembrane proteins with non-circular
cross-section, anisotropic interactions between
reflection-symmetry-breaking transmembrane proteins with non-circular
cross-section, and non-entropic many-particle interactions among
non-transmembrane proteins. For large , 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 of the bending rigidity
to the hexatic rigidity 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 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.
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