MODELING FARM AND OFF-FARM ECONOMIC LINKAGES TO ANALYZE THE IMPACTS OF AN AREA-WIDE INSECT MANAGEMENT PROGRAM ON A REGIONAL ECONOMY

This study evaluated the impacts of the boll weevil eradication program at the farm level and on the west Tennessee region. Budgets, an acreage response model, and an input-output model were used to evaluate direct and indirect program impacts. The program generates small but positive economic benefits for the region.Crop Production/Industries,

Scaling of the magnetic reconnection rate with symmetric shear flow

The scaling of the reconnection rate during (fast) Hall magnetic reconnection in the presence of an oppositely directed bulk shear flow parallel to the reconnecting magnetic field is studied using two-dimensional numerical simulations of Hall reconnection with two different codes. Previous studies noted that the reconnection rate falls with increasing flow speed and shuts off entirely for super-Alfvenic flow, but no quantitative expression for the reconnection rate in sub-Alfvenic shear flows is known. An expression for the scaling of the reconnection rate is presented

CSF lactate dehydrogenase activity in patients with Creutzfeldt-Jakob disease exceeds that in other dementias

The diagnosis of Creutzfeldt- Jakob disease (CJD) is still made by exclusion of other dementias. We now evaluated lactate dehydrogenase (LDH) in the cerebrospinal fluid (CSF) as a possible additional diagnostic tool. CSF LDH levels of patients with CJD ( n = 26) were compared with those in other dementias ( n = 28). LDH isoenzymes were determined in a subset ( n = 9). Total LDH and isoenzyme LDH-1 were significantly higher, whereas the fractions of LDH-2 and LDH-3 were significantly lower in CJD patients. We conclude that in addition to established CSF parameters, LDH and its isoenzymes might serve as a further help to discriminate between CJD and other dementias. Copyright (C) 2004 S. Karger AG, Basel

Comments on the classification of the finite subgroups of SU(3)

Many finite subgroups of SU(3) are commonly used in particle physics. The classification of the finite subgroups of SU(3) began with the work of H.F. Blichfeldt at the beginning of the 20th century. In Blichfeldt's work the two series (C) and (D) of finite subgroups of SU(3) are defined. While the group series Delta(3n^2) and Delta(6n^2) (which are subseries of (C) and (D), respectively) have been intensively studied, there is not much knowledge about the group series (C) and (D). In this work we will show that (C) and (D) have the structures (C) \cong (Z_m x Z_m') \rtimes Z_3 and (D) \cong (Z_n x Z_n') \rtimes S_3, respectively. Furthermore we will show that, while the (C)-groups can be interpreted as irreducible representations of Delta(3n^2), the (D)-groups can in general not be interpreted as irreducible representations of Delta(6n^2).Comment: 15 pages, no figures, typos corrected, clarifications and references added, proofs revise

Recombination dramatically speeds up evolution of finite populations

We study the role of recombination, as practiced by genetically-competent bacteria, in speeding up Darwinian evolution. This is done by adding a new process to a previously-studied Markov model of evolution on a smooth fitness landscape; this new process allows alleles to be exchanged with those in the surrounding medium. Our results, both numerical and analytic, indicate that for a wide range of intermediate population sizes, recombination dramatically speeds up the evolutionary advance

Do we (need to) care about canopy radiation schemes in DGVMs? Caveats and potential impacts

Dynamic global vegetation models (DGVMs) are an essential part of current state-of-the-art Earth system models. In recent years, the complexity of DGVMs has increased by incorporating new important processes like, e.g., nutrient cycling and land cover dynamics, while biogeophysical processes like surface radiation have not been developed much further. Canopy radiation models are however very important for the estimation of absorption and reflected fluxes and are essential for a proper estimation of surface carbon, energy and water fluxes. The present study provides an overview of current implementations of canopy radiation schemes in a couple of state-of-the-art DGVMs and assesses their accuracy in simulating canopy absorption and reflection for a variety of different surface conditions. Systematic deviations in surface albedo and fractions of absorbed photosynthetic active radiation (faPAR) are identified and potential impacts are assessed. The results show clear deviations for both, absorbed and reflected, surface solar radiation fluxes. FaPAR is typically underestimated, which results in an underestimation of gross primary productivity (GPP) for the investigated cases. The deviation can be as large as 25% in extreme cases. Deviations in surface albedo range between −0.15 ≤ Δα ≤ 0.36, with a slight positive bias on the order of Δα ≈ 0.04. Potential radiative forcing caused by albedo deviations is estimated at −1.25 ≤ RF ≤ −0.8 (W m−2), caused by neglect of the diurnal cycle of surface albedo. The present study is the first one that provides an assessment of canopy RT schemes in different currently used DGVMs together with an assessment of the potential impact of the identified deviations. The paper illustrates that there is a general need to improve the canopy radiation schemes in DGVMs and provides different perspectives for their improvement

Local Equation of State and Velocity Distributions of a Driven Granular Gas

We present event-driven simulations of a granular gas of inelastic hard disks with incomplete normal restitution in two dimensions between vibrating walls (without gravity). We measure hydrodynamic quantities such as the stress tensor, density and temperature profiles, as well as velocity distributions. Relating the local pressure to the local temperature and local density, we construct a local constitutive equation. For strong inelasticities the local constitutive relation depends on global system parameters, like the volume fraction and the aspect ratio. For moderate inelasticities the constitutive relation is approximately independent of the system parameters and can hence be regarded as a local equation of state, even though the system is highly inhomogeneous with heterogeneous temperature and density profiles arising as a consequence of the energy injection. Concerning the local velocity distributions we find that they do not scale with the square root of the local granular temperature. Moreover the high-velocity tails are different for the distribution of the x- and the y-component of the velocity, and even depend on the position in the sample, the global volume fraction, and the coefficient of restitution.Comment: 14 pages, 14 figures of which Figs. 13a-f and Fig. 14 are archived as separate .gif files due to upload-size limitations. A version of the paper including all figures in better quality can be downloaded at http://www.theorie.physik.uni-goettingen.de/~herbst/download/LocEqSt.ps.gz (3.8 MB, ps.gz) or at http://www.theorie.physik.uni-goettingen.de/~herbst/download/LocEqSt.pdf (4.9 MB, pdf