DETERMINANTS OF PESTICIDE REGISTRATION FOR FOOD CROPS

An examination of intertemporal, crop-specific pesticide registration data to assess claims that EPA requirements discourage registration of safer pesticides, especially for minor crops. Results show that the likelihood of registration is increasing in crop market value and decreasing in pesticide safety, but these biases diminished between 1991 and 1995.Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety,

Energy loss of ions by electric-field fluctuations in a magnetized plasma

The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field the electric field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field this effect occurs only at low-velocities. In the opposite case of high-velocities the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e. the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term which depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.Comment: 12 pages, 3 figures, will be appear in Phys. Rev. E (July, 2011

Generalized time-invariant overtaking

We present a new version of the overtaking criterion, which we call generalized time invariant overtaking. The generalized time-invariant overtaking criterion (on the space of infinite utility streams) is defined by extending proliferating sequences of complete and transitive binary relations defined on finite dimensional spaces. The paper presents a general approach that can be specialized to at least two, extensively researched examples, the utilitarian and the leximin orderings on a finite dimensional Euclidean space.intergenerational justice, utilitarianism, leximin.

Construction of spherical cubature formulas using lattices

We construct cubature formulas on spheres supported by homothetic images of shells in some Euclidian lattices. Our analysis of these cubature formulas uses results from the theory of modular forms. Examples are worked out on the sphere of dimension n-1 for n=4, 8, 12, 14, 16, 20, 23, and 24, and the sizes of the cubature formulas we obtain are compared with the lower bounds given by Linear Programming

Generalized time-invariant overtaking

We present a new version of the overtaking criterion, which we call generalized time-invariant overtaking. The generalized time-invariant overtaking criterion (on the space of infinite utility streams) is defined by extending proliferating sequences of complete and transitive binary relations defined on finite dimensional spaces. The paper presents a general approach that can be specialized to at least two, extensively researched examples, the utilitarian and the leximin orderings on a finite dimensional Euclidean space.Intergenerational justice; Utilitarianism; Leximin

Optimal molecular alignment and orientation through rotational ladder climbing

We study the control by electromagnetic fields of molecular alignment and orientation, in a linear, rigid rotor model. With the help of a monotonically convergent algorithm, we find that the optimal field is in the microwave part of the spectrum and acts by resonantly exciting the rotation of the molecule progressively from the ground state, i.e., by rotational ladder climbing. This mechanism is present not only when maximizing orientation or alignment, but also when using prescribed target states that simultaneously optimize the efficiency of orientation/alignment and its duration. The extension of the optimization method to consider a finite rotational temperature is also presented.Comment: 14 pages, 12 figure

The Tactical and Strategic Value of Commodity Futures

Historically, commodity futures have had excess returns similar to those of equities. But what should we expect in the future? The usual risk factors are unable to explain the time-series variation in excess returns. In addition, our evidence suggests that commodity futures are an inconsistent, if not tenuous, hedge against unexpected inflation. Further, the historically high average returns to a commodity futures portfolio are largely driven by the choice of weighting schemes. Indeed, an equally weighted long-only portfolio of commodity futures returns has approximately a zero excess return over the past 25 years. Our portfolio analysis suggests that the a long-only strategic allocation to commodities as a general asset class is a bet on the future term structure of commodity prices, in general, and on specific portfolio weighting schemes, in particular. In contrast, we provide evidence that there are distinct benefits to an asset allocation overlay that tactically allocates using commodity futures exposures. We examine three trading strategies that use both momentum and the term structure of futures prices. We find that the tactical strategies provide higher average returns and lower risk than a long-only commodity futures exposure.