466 research outputs found
MARKETING OF COTTON FIBER IN THE PRESENCE OF YIELD AND PRICE RISK
An expected utility model and a chance constrained linear programming model were used to analyze four marketing strategies and seven crop insurance alternatives in cotton marketing in Georgia. The results obtained suggest that the existing marketing tools and insurance alternatives can be used successfully as a substitute for government support.Demand and Price Analysis, Marketing, Risk and Uncertainty,
Generalized exponential and logarithmic functions
AbstractGeneralizations of the exponential and logarithmic functions are defined and an investigation is made of two possible versions of these functions. Some applications are described, including computer arithmetic, properties of very large and very small numbers, and the determination of functional roots
Fiber depolymerization
Depolymerization is, by definition, a crucial process in the reversible assembly of various biopolymers. It may also be an important factor in the pathology of sickle cell disease. If sickle hemoglobin fibers fail to depolymerize fully during passage through the lungs then they will reintroduce aggregates into the systemic circulation and eliminate or shorten the protective delay (nucleation) time for the subsequent growth of fibers. We study how depolymerization depends on the rates of end- and side-depolymerization, kend and kside, which are, respectively, the rates at which fiber length is lost at each end and the rate at which new breaks appear per unit fiber length. We present both an analytic mean field theory and supporting simulations showing that the characteristic fiber depolymerization time View the MathML source depends on both rates, but not on the fiber length L, in a large intermediate regime 1 much less-than ksideL2/kend much less-than (L/d)2, with d the fiber diameter. We present new experimental data which confirms that both mechanisms are important and shows how the rate of side depolymerization depends strongly on the concentration of CO, acting as a proxy for oxygen. Our theory remains rather general and could be applied to the depolymerization of an entire class of linear aggregates, not just sickle hemoglobin fibers
Damping of Tensor Modes in Cosmology
An analytic formula is given for the traceless transverse part of the
anisotropic stress tensor due to free streaming neutrinos, and used to derive
an integro-differential equation for the propagation of cosmological
gravitational waves. The solution shows that anisotropic stress reduces the
squared amplitude by 35.6 % for wavelengths that enter the horizon during the
radiation-dominated phase, independent of any cosmological parameters. This
decreases the tensor temperature and polarization correlation functions for
these wavelengths by the same amount. The effect is less for wavelengths that
enter the horizon at later times. At the longest wavelengths the decrease in
the tensor correlation functions due to neutrino free streaming ranges from
10.7% for to 9.0% for . An Appendix gives a
general proof that tensor as well as scalar modes satisfy a conservation law
for perturbations outside the horizon, even when the anisotropic stress tensor
is not negligible.Comment: 14 pages. The original version of this paper has been expanded to
deal with perturbations of any wavelength. While for wavelengths short enough
to enter the horizon during radiation dominance, temperature and polarization
correlations are damped by 35.6%, at the longest wavelengths the damping is
from 9.0% to 11%. An added Appendix gives a general proof that tensor as well
as scalar modes satisfy a conservation law outside the horizon, even during
neutrino decoupling. Some references are also adde
Exponential-Potential Scalar Field Universes I: The Bianchi I Models
We obtain a general exact solution of the Einstein field equations for the
anisotropic Bianchi type I universes filled with an exponential-potential
scalar field and study their dynamics. It is shown, in agreement with previous
studies, that for a wide range of initial conditions the late-time behaviour of
the models is that of a power-law inflating FRW universe. This property, does
not hold, in contrast, when some degree of inhomogeneity is introduced, as
discussed in our following paper II.Comment: 16 pages, Plain LaTeX, 1 Figure to be sent on request, to appear in
Phys. Rev.
Shear and Mixing in Oscillatory Doubly Diffusive Convection
To investigate the mechanism of mixing in oscillatory doubly diffusive (ODD)
convection, we truncate the horizontal modal expansion of the Boussinesq
equations to obtain a simplified model of the process. In the astrophysically
interesting case with low Prandtl number, large-scale shears are generated as
in ordinary thermal convection. The interplay between the shear and the
oscillatory convection produces intermittent overturning of the fluid with
significant mixing. By contrast, in the parameter regime appropriate to sea
water, large-scale flows are not generated by the convection. However, if such
flows are imposed externally, intermittent overturning with enhanced mixing is
observed.Comment: 24 pages, 16 figures, Accepted for publication in Geophysical and
Astrophysical Fluid Dynamic
On the Circular Orbit Approximation for Binary Compact Objects In General Relativity
One often-used approximation in the study of binary compact objects (i.e.,
black holes and neutron stars) in general relativity is the instantaneously
circular orbit assumption. This approximation has been used extensively, from
the calculation of innermost circular orbits to the construction of initial
data for numerical relativity calculations. While this assumption is
inconsistent with generic general relativistic astrophysical inspiral phenomena
where the dissipative effects of gravitational radiation cause the separation
of the compact objects to decrease in time, it is usually argued that the
timescale of this dissipation is much longer than the orbital timescale so that
the approximation of circular orbits is valid. Here, we quantitatively analyze
this approximation using a post-Newtonian approach that includes terms up to
order ({Gm/(rc^2)})^{9/2} for non-spinning particles. By calculating the
evolution of equal mass black hole / black hole binary systems starting with
circular orbit configurations and comparing them to the more astrophysically
relevant quasicircular solutions, we show that a minimum initial separation
corresponding to at least 6 (3.5) orbits before plunge is required in order to
bound the detection event loss rate in gravitational wave detectors to < 5%
(20%). In addition, we show that the detection event loss rate is > 95% for a
range of initial separations that include all modern calculations of the
innermost circular orbit (ICO).Comment: 10 pages, 12 figures, revtex
Creating a community of praxis: integrating global citizenship and development education across campus at University College Cork
The Praxis Project, established at University College Cork (UCC), Ireland, in 2018, seeks to assess possible models of best practice with regard to the integration of global citizenship and development education (GCDE) into a cross-disciplinary, cross-campus, interwoven set of subject area pedagogies, policies and practices. This study â the first part of an eventual three-part framework â asserts that the themes, theories, values, skills, approaches and methodologies relevant to transformative pedagogical work are best underpinned by ongoing staff dialogue in order to build communities of support around such systemic pedagogical change. This article is based on a collaborative study with the first cohort of UCC staff (2020â1), which demonstrates many ways in which staff and students realised that smaller actions and carefully directed attention to specific issues opened doors to transformative thinking and action in surprising ways. From this viewpoint, the striking need emerged for taking a strategic approach to how GCDE is, and should be, integrated into learning across subject areas
Plane-symmetric inhomogeneous magnetized viscous fluid universe with a variable
The behavior of magnetic field in plane symmetric inhomogeneous cosmological
models for bulk viscous distribution is investigated. The coefficient of bulk
viscosity is assumed to be a power function of mass density . The values of cosmological constant for these models are
found to be small and positive which are supported by the results from recent
supernovae Ia observations. Some physical and geometric aspects of the models
are also discussed.Comment: 18 pages, LaTex, no figur
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