Agriculture and forest rodent problems and control in Italy

Rodent pest problems and their control in Italy are reviewed. Two rats, Rattus norvegicus and Rattus rattus, and the field mouse, Apodemus sylvaticus, are often important pests both in rural and forestry areas. Other species, such as voles, Microtus arvalis and Microtus (Pitymys) savii, in orchards and in horticulture, and Sciurus vulgaris and Myoxus (Glis) glis in forestry, sometimes represent serious problems. For each species the kind of damage and control is recorded, and additional considerations are supplied to the public and private organizations responsible for rodent control

A powerful hydrodynamic booster for relativistic jets

Velocities close to the speed of light are a robust observational property of the jets observed in microquasars and AGNs, and are expected to be behind much of the phenomenology of GRBs. Yet, the mechanism boosting relativistic jets to such large Lorentz factors is still essentially unknown. Building on recent general-relativistic, multidimensional simulations of progenitors of short GRBs, we discuss a new effect in relativistic hydrodynamics which can act as an efficient booster in jets. This effect is purely hydrodynamical and occurs when large velocities tangential to a discontinuity are present in the flow, yielding Lorentz factors $\Gamma \sim 10^2-10^3$ or larger in flows with moderate initial Lorentz factors. Although without a Newtonian counterpart, this effect can be explained easily through the most elementary hydrodynamical flow: i.e., a relativistic Riemann problem.Comment: 4 pages, 4 figures (1 in color). ApJ Letters accepte

Modeling High-Frequency Seafloor Backscattering of Gassy Sediments: The Eel River Margin Case

Models of acoustic backscatter typically take into account two different processes: interface scattering and volume scattering. What happens to these two contributions when the sediment is charged with gas bubbles? For the interface backscatter contribution we adopted the model developed by Jackson et al. (1986), but added modifications to accommodate gas bubbles, which when present, even in very small quantities, can dominate the acoustic characteristics of the sediment. The model parameters that are affected by gas content are the density ratio, the sound speed ratio and the loss parameter. To a first approximation, the model roughness parameters are not influenced by the presence of gas. For the volume backscatter contribution we developed a model based on the presence and distribution of gas in the sediment. We treat the bubbles as individual point scatters that sum to the bubble contribution. This bubble contribution is then added to the volume contribution of other scatters. A potential area to test the ideas outlined above is the highly sedimented, tectonically active, Eel River margin offshore Northern California. This continental margin reveals evidence of abundant subsurface gas and numerous seafloor expulsion features, where a large volume of marine data has been acquired as part of the STRATAFORM project. Two different sets of multibeam backscatter data acquired at 30kHz and 95kHz provide raw measurements for the backscatter as a function of grazing angle. These raw backscatter measurements are then radiometrically corrected in order to be compared with the results of the proposed model. Radiometric corrections include the removal of the time varying and angle varying gains applied during acquisition, calculation of the true grazing angle with respect to a bathymetric model, and correction for footprint size. Results of core data analysis at various sampling locations provide local measurements of gas content in the sediments that when compared to the model show general agreement

A Note on the Algebra of Operations for Hopf Cohomology at Odd Primes

Let $p$ be any prime, and let ${\mathcal B}(p)$ be the algebra of operations on the cohomology ring of any cocommutative $\mathbb{F}_p$-Hopf algebra. In this paper we show that when $p$ is odd (and unlike the $p=2$ case), ${\mathcal B}(p)$ cannot become an object in the Singer category of $\mathbb{F}_p$-algebras with coproducts, if we require that coproducts act on the generators of ${\mathcal B}(p)$ coherently with their nature of cohomology operation

Exact versus approximate beaming formulas in Gamma-Ray Burst afterglows

We present the exact analytic expressions to compute, assuming the emitted Gamma-Ray Burst (GRB) radiation is not spherically symmetric but is confined into a narrow jet, the value of the detector arrival time at which we start to "see" the sides of the jet, both in the fully radiative and adiabatic regimes. We obtain this result using our exact analytic expressions for the EQuiTemporal Surfaces (EQTSs) in GRB afterglows. We re-examine the validity of three different approximate formulas currently adopted for the adiabatic regime in the GRB literature. We also present an empirical fit of the numerical solutions of the exact equations, compared and contrasted with the three above approximate formulas. The extent of the differences is such as to require a reassessment on the existence and entity of beaming in the cases considered in the current literature, as well as on its consequences on the GRB energetics.Comment: 4 pages, 4 figures, to appear on ApJ Let

Human Capital Quality in the Brazilian States

Quality of human capital seems to be an extremely important feature to be disregarded in the evaluation of this factor impacts on income per worker (rate of growth and level). This is the reason for the emergence of many recent studies which includes some variable that takes into account the quality of human capital. The present study’s goal is to make an empirical analysis by using a human capital proxy that takes into account quantitative and qualitative aspects of this factor to measure with a higher level of accuracy the human capital direct impacts on Brazilian States output level in the years 1970, 1980, 1991, and 2000. The methods employed are Ordinary Least Squares (OLS), Iteratively Reweighted Least Squares (IRLS) and Panel Data regressions.Human Capital Quality, Income per Worker, Empirical Analysis of the Brazilian States, Iteratively Reweighted Least Squares, Panel Data