Model turbulent floods with the Smagorinski large eddy closure

Floods, tides and tsunamis are turbulent, yet conventional models are based upon depth averaging inviscid irrotational flow equations. We propose to change the base of such modelling to the Smagorinksi large eddy closure for turbulence in order to appropriately match the underlying fluid dynamics. Our approach allows for large changes in fluid depth to cater for extreme inundations. The key to the analysis underlying the approach is to choose surface and bed boundary conditions that accommodate a constant turbulent shear as a nearly neutral mode. Analysis supported by slow manifold theory then constructs a model for the coupled dynamics of the fluid depth and the mean turbulent lateral velocity. The model resolves the internal turbulent shear in the flow and thus may be used in further work to rationally predict erosion and transport in turbulent floods

Distribution Functions of the Nucleon and Pion in the Valence Region

We provide an experimental and theoretical perspective on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain; namely, Bjorken-x \gtrsim 0.4. This domain is key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. We focus on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the Standard Model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, we explain that an upgraded Jefferson Lab facility is well-suited to provide new data on the nucleon, while a future electron ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, J-PARC and GSI, to push into the large-x domain for both mesons and nucleons. We argue furthermore that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum field theory; and a fuller exploitation of those methods.Comment: Review article: 133 double-spaced pages, 44 figures, 6 table

Evaluation of Two Systems Used to Extract Alfalfa Weevil Larvae (Coleoptera: Curculionidae) from Alfalfa Samples

A modified Berlese funnel system was developed to extract alfalfa weevil larvae (Hypera postica) from quadrats 30.5 cm on a side. Data from this system were comp.wed with simultaneous data from a hand sorting extraction system. In most instances, the modified Berlese system was as efficient as the hand sorting method and the number of man hours required to process samples by hand was far greater than that required by the Berlese system

RISK AND STRUCTURAL CHANGE IN AGRICULTURE: HOW INCOME SHOCKS INFLUENCE FARM SIZE

Farm-level Census data and county-level income shock data reveal that past unexpected income shocks affect the rate of change in average farm size. Average farm size increases more quickly in counties experiencing negative income shocks as compared to counties experiencing positive income shocks. This result cannot be explained by perfect-market models, which predict farm size should adjust according to changes in the relative prices of labor and capital. We posit a model wherein cash flows affect liquidity, which in turn affects farm borrowing and capital costs. In the model, farms that do not face liquidity constraints benefit from negative income shocks because they reduce land values, so these farms expand while liquidity-constrained farms contract. Observed farm consolidation patterns and farm exit rates are consistent with a model wherein liquidity constraints affect small farms more than large farms.farm size, farm structure, income shocks, liquidity constraint, risk, Agricultural Finance, Industrial Organization,

Do Government Payments Influence Farm Business Survival?

Using a unique farm-level panel data set derived from three U.S. Agricultural Censuses, we estimate a Cox proportional hazard model to examine the effect of direct government payments on the survival of farm businesses, paying particular attention to the differential effect of payments across farm size categories. For identification the study exploits variation in payments resulting from historical differences in 'base acreage' in otherwise similar farms. We find an increase in government payments has a small but statistically significant positive effect on the rate of farm survival, and the magnitude of this effect increases with farm size.Agricultural and Food Policy,

Government Payments and Farmland Concentration

Over the last twenty five years commodity crop farms have steadily declined in number and grown in average size, and production has shifted to larger operations. During the same period, the share of agricultural payments going to large farms has increased, in large part because payments are tied to actual or historical crop production. This study evaluates whether payments from federal farm programs may have contributed to the concentration of farmland. Using zip code-level data constructed from the micro files of the 1987-2002 Agriculture Censuses the study estimates the association between government payments per acre and subsequent growth in weighted median farmland area. A semi-parametric generalized additive model controls for location and initial concentration levels, and narrows comparisons to nearby zip codes with similar average farm sizes. Findings indicate, both with and without spatial controls, that government payments are strongly associated with subsequent concentration growth.Agricultural and Food Policy,

Commodity Payments, Farm Business Survival, and Farm Size Growth

In the last 25 years, U.S. crop farms have steadily declined in number and grown in average size, as production has shifted to larger operations. Larger farms tend to receive more commodity program payments because most payments are tied to a farm’s current or historical production, but whether payments have contributed to farm growth is uncertain. This study uses farm-level data from the census of agriculture to determine whether there is a statistical relationship between farm commodity program payments and greater concentration in production. The analysis indicates that, at the regional level, higher commodity program payments per acre are associated with subsequent farm growth. Also, higher payments per acre are associated with higher rates of farm survival and growth.agricultural payments, farm size, farm survival, concentration, consolidation, government payments, commodity programs., Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Crop Production/Industries, Farm Management,