Practical expressions for the internal energy and pressure of Yukawa fluids

Simple practical expressions are put forward, which allow to estimate thermodynamic properties of Yukawa fluids in a wide range of coupling, up to the fluid-solid phase transition. These expressions demonstrate excellent agreement with the available results from numerical simulations. The approach provides simple and accurate tool to estimate thermodynamic properties of Yukawa fluids and related systems in a broad range of parameters.Comment: To be published in Phys. Rev.

Fluid approach to evaluate sound velocity in Yukawa systems (complex plasmas)

The conventional fluid description of multi-component plasma, supplemented by an appropriate equation of state for the macroparticle component, is used to evaluate the longitudinal sound velocity of Yukawa fluids. The obtained results are in very good agreement with those obtained earlier employing the quasi-localized charge approximation and molecular dynamics simulations in a rather broad parameter regime. Thus, a simple yet accurate tool to estimate the sound velocity across coupling regimes is proposed, which can be particularly helpful in estimating the dust-acoustic velocity in strongly coupled dusty (complex) plasmas. It is shown that, within the present approach, the sound velocity is completely determined by particle-particle correlations and the neutralizing medium (plasma), apart from providing screening of the Coulomb interaction, has no other effect on the sound propagation. The ratio of the actual sound velocity to its "ideal gas" (weak coupling) scale only weakly depends on the coupling strength in the fluid regime, but exhibits a pronounced decrease with the increase of the screening strength. The limitations of the present approach in applications to real complex plasmas are briefly discussed.Comment: Physical Review E (in press

Simulating atmospheric d13CO2 during the last 740,000 years: Model-based estimates in the context of ice core measurements

The ratio of the stable carbon isotopes of atmospheric CO2 (δ 13 CO2 ) contains valuable information on the processes which are operating on the global carbon cycle. However current δ 13 CO2 ice core records are still limited in both resolution, temporal coverage as well as precision. To make optimal use of the existing and future δ 13 CO2 ice core records an estimate of the expected temporal variability would help to constrain for the acceptable measurement uncertainty and resolution to successfully retrieve the characteristic variability in δ 13 CO2 . In this study we performed simulations with the carbon cycle box model BICYCLE with special emphasis on atmospheric δ 13 CO2, proposing how changes in δ 13 CO2 might have evolved over the last 740,000 years. The overall model dynamic is validated with reconstructions of δ 13 C in benthic foraminifera in thedeep Pacific and with atmospheric CO2 ice core data. On glacial/interglacial timescales lower surface ocean temperature is most important for lower glacial δ 13 CO2 , followed by the release of isotopically lighter terrestrial carbon. In addition, changes in the terrestrial biosphere also dominate deep ocean δ 13 CO2 but have only a limited effect on atmospheric pCO2 . All other oceanic processes lead to higher than present glacial δ 13 CO2 . Taken all processes together the effects nearly cancel each other and there are nearly no glacial/interglacial amplitudes in δ 13 CO2 in line with ice core data. However faster variations of up to 0.3 occur throughout the whole simulation period. Due to our model configuration, terrestrial carbon storage is very sensitive to temperature changes over northern hemispheric lands, which accompany the reorganization of the Atlantic meridional ocean circulation during fast climate fluctuations (Dansgaard/Oeschger events). These fast events intensify the frequency and amplitude in δ 13 CO2 . However, due to ocean uptake of additional carbon as well as the signal attenuation in ice cores, the amplitudes of such events are strongly time scale dependent

A COMPARATIVE ANALYSIS OF FOOD QUALITY ASSURANCE SCHEMES: THE CASE OF NEULAND AND EUREPGAP

Food Quality Assurance Schemes (QAS) are widely applied in the European Union. Neuland and EurepGAP represent two different approaches. Neuland differentiates meat clearly by a strict emphasis on rules regarding animal welfare to provide consumers with meat produced at a high animal welfare standard. EurepGAP certifies the compliance to international accepted standards with regard to Good Agricultural Practise to ease the exchange of products throughout the supply chain. In terms of overall benefits and costs, the study showed that for both QAS the benefits clearly outweigh the costs. This paper compares the schemes and their implications for the agro-food chain.Quality Assurance Schemes, Food policy, Food chain, Agribusiness, Food Consumption/Nutrition/Food Safety,

COALITION DEVELOPMENT IN THE AGRICULTURAL MARKETING SYSTEM

The theory of agricultural coalition formation is enhanced by incorporating non-monetary benefits, risk, and fairness. Producer's expected utility and investment decisions in the agricultural cooperative are affected by their perception about non-monetary benefits, risk and fairness associate with the cooperative investment. (Revised edition added in August 2002)Marketing,

INVESTMENT DECISIONS IN NEW GENERATION COOPERATIVES: A CASE STUDY OF VALUE ADDED PRODUCTS (VAP) COOPERATIVE IN ALVA, OKLAHOMA

Explaining the phenomena of new generation cooperatives development is important to understand why some producers invest in new generation cooperative investment and some do not. Results from Tobit analysis suggests that non-monetary benefits from investment are significant factors that influence producer investment decisions in new generation cooperative.Agribusiness,