Samuelson´s full duality and the use of directed acyclical graphs

To date, mixed demand systems have been all but ignored in empirical work. A possible reason for the scarcity of such applications is that one needs to know a priori which prices and quantities are endogenous in the mixed demand system. By using a directed acyclical graph (DAG), causal relationships among price and quantity variables are identified giving rise to a causally identified mixed demand system. A statistical comparison is made of the traditional Rotterdam model, a synthetic demand system, which subsumes the traditional Rotterdam model, and a Rotterdam mixed demand system identified through the use of a DAG. In this analysis, the respective demand systems consist of five products: steak, ground beef, beef roasts, pork, and chicken.directed acyclic graphs, mixed demand systems

SAMUELSON'S FULL DUALITY AND THE USE OF DIRECTED ACYCLICAL GRAPHS: THE BIRTH OF CAUSALLY IDENTIFIED DEMAND SYSTEMS

To date, mixed demand systems have been all but ignored in empirical work. A possible reason for the scarcity of such applications is that one needs to know a priori which prices and quantities are endogenous in the mixed demand system. By using a directed acyclical graph (DAG), causal relationships among price and quantity variables are identified giving rise to a causally identified demand system (CIDS). A statistical comparison is made of the traditional Rotterdam model with a Rotterdam mixed demand system identified through the use of a DAG. In this analysis, the respective Rotterdam demand systems consist of five products: steak, ground beef, roast beef, pork, and chicken.Demand and Price Analysis,

FABRICATED CUT BEEF PRICES AS LEADING INDICATORS OF FED CATTLE PRICE

Temporal relationships are investigated among fabricated cut prices, carcass value, and fed cattle prices. Also, linkages between fed cattle and wholesale beef prices are examined using vector autoregressive (VAR) techniques. Results, using daily prices over the 1980-85 period, suggested that fabricated cut prices and cattle prices are related to the imputed carcass value, carcass quote, and fed cattle prices. In addition, three fabricated cuts dominate as leading indicators of fed cattle prices of most fabricated cut prices. They are strip loin and bottom and top round prices. VAR models outperform the univariate and random-walk models of forecasting ability.Demand and Price Analysis, Livestock Production/Industries,

The Impacts of Foot and Mouth Disease Outbreaks on the Brazilian Meat Market

This study uses unrestricted vector autoregression method and historical decomposition with directed acyclic graphs to quantity the impacts of the foot and mouth disease outbreak on the Brazilian meat market for different levels of the industry (export, wholesale and farm). The imposition of an import ban by Russia on Brazilian meat exports is also analyzed. Results show that beef, pork, and chicken export prices all decreased after the FMD outbreak. More importantly, our findings indicate that all prices ended up recovering after the removal of the import ban by Russia in December 2007. As for the price margins in both beef and pork meat supply chains, the export-to-farm and export-to-wholesale margins were found to be very close to each other. On the other hand, the chicken price margin at the export level relative to the farm and wholesale levels had opposing directions trend movements. Finally, the historical decomposition of analysis of the export beef price revealed that the removal of the Russian ban on Brazilian meat imports had a very drastic positive influence on the beef industry supply chain in general.foot and mouth disease, Brazilian meat market, vector autoregression model, historical decomposition, directed acyclic graphs., Food Consumption/Nutrition/Food Safety, International Relations/Trade, Livestock Production/Industries,

Performance and degradation of Proton Exchange Membrane Fuel Cells: State of the art in modeling from atomistic to system scale

Jahnke, T. et al.Proton Exchange Membrane Fuel Cells (PEMFC) are energy efficient and environmentally friendly alternatives to conventional energy conversion systems in many yet emerging applications. In order to enable prediction of their performance and durability, it is crucial to gain a deeper understanding of the relevant operation phenomena, e.g., electrochemistry, transport phenomena, thermodynamics as well as the mechanisms leading to the degradation of cell components. Achieving the goal of providing predictive tools to model PEMFC performance, durability and degradation is a challenging task requiring the development of detailed and realistic models reaching from the atomic/molecular scale over the meso scale of structures and materials up to components, stack and system level. In addition an appropriate way of coupling the different scales is required. This review provides a comprehensive overview of the state of the art in modeling of PEMFC, covering all relevant scales from atomistic up to system level as well as the coupling between these scales. Furthermore, it focuses on the modeling of PEMFC degradation mechanisms and on the coupling between performance and degradation models.The research leading to this review has been partially supported by the European Union's Seventh Framework Program for the Fuel Cells and Hydrogen Joint Technology Initiative under the project PUMA MIND (grant agreement no 303419).Peer Reviewe

Bioprinting Neural Systems to Model Central Nervous System Diseases

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