Flows and Decompositions of Games: Harmonic and Potential Games

In this paper we introduce a novel flow representation for finite games in strategic form. This representation allows us to develop a canonical direct sum decomposition of an arbitrary game into three components, which we refer to as the potential, harmonic and nonstrategic components. We analyze natural classes of games that are induced by this decomposition, and in particular, focus on games with no harmonic component and games with no potential component. We show that the first class corresponds to the well-known potential games. We refer to the second class of games as harmonic games, and study the structural and equilibrium properties of this new class of games. Intuitively, the potential component of a game captures interactions that can equivalently be represented as a common interest game, while the harmonic part represents the conflicts between the interests of the players. We make this intuition precise, by studying the properties of these two classes, and show that indeed they have quite distinct and remarkable characteristics. For instance, while finite potential games always have pure Nash equilibria, harmonic games generically never do. Moreover, we show that the nonstrategic component does not affect the equilibria of a game, but plays a fundamental role in their efficiency properties, thus decoupling the location of equilibria and their payoff-related properties. Exploiting the properties of the decomposition framework, we obtain explicit expressions for the projections of games onto the subspaces of potential and harmonic games. This enables an extension of the properties of potential and harmonic games to "nearby" games. We exemplify this point by showing that the set of approximate equilibria of an arbitrary game can be characterized through the equilibria of its projection onto the set of potential games

Competitive Equilibrium and Trading Networks: A Network Flow Approach

Under full substitutability of preferences, it has been shown that a competitive equilibrium exists in trading networks, and is equivalent (after a restriction to equilibrium trades) to (chain) stable outcomes. In this paper, we formulate the problem of finding an efficient outcome as a generalized submodular flow problem on a suitable network. Equivalence with seemingly weaker notions of stability follows directly from the optimality conditions, in particular the absence of improvement cycles in the flow problem. Our formulation yields strongly polynomial algorithms for finding competitive equilibria in trading networks, and testing (chain) stability

Active packaging of chicken meats with modified atmosphere including oxygen scavengers

The effects of modified atmosphere packaging (MAP-70\% CO2/30\%N-2) and iron-based oxygen scavengers (OS) with various absorption capacities (Ageless (R) 100, ss300, and ss500) as an active packaging system on microbiological and oxidative changes in chicken thigh meats were evaluated during refrigerated storage (4 degrees C) for 19 d at 3-day intervals. Total aerobic mesophilic bacteria counts exceeded the acceptability limit at d 7 in the control group without MAP (AIR), and at d 19 in MAP and OS containing samples. OS utilization resulted in around 1.5 and 1.0 log unit reductions in Pseudomonas spp. counts at d 7 and d 10 of storage, respectively, as compared with AIR and MAP groups (P < 0.05). MAP and OS groups had fewer (P < 0.05) conform counts than did the AIR group, with an approximately 1.0 log reduction observed at d 10. Although in some cases OS utilization resulted in lower TBARS values and carbonyl and sulphydryl contents, particularly during later stages of refrigerated storage as compared to AIR and MAP groups, in general, these effects were not always apparent. The results of this study suggested that MAP suppressed microbiological growth and retarded lipid and protein oxidation in chicken thigh meats, with a 9-day shelf-life extention with insignificant effects of OS

Nonthermal Processing Technologies for Stabilization and Enhancement of Bioactive Compounds in Foods

The processing of selected foods by nonthermal technologies is gaining relevance in the food industry because, in many cases, the final product keeps the nutritional value and other fresh-like characteristics of the original one. There are several nonthermal technologies including high pressure processing, pulsed electric fields, ultrasound, and cold plasma which are at different stages of development. The impact of a given technology on bioactive compounds is a good indicator to assess changes on the nutritional attributes of a given food product before and after processing. Quite frequently, it is mentioned that nonthermal technologies are very appropriate to process foods minimizing changes in quality attributes. This broad claim only applies for certain processing, packaging and storage conditions, and as expected, on the food product. There are extensive scientific publications on how these processes alter the food products, but the reported results have been attained by a disparity of treatments; therefore, comparisons of these results are difficult and sometimes useless. Nevertheless, the gathered information allows to identify, in many cases, valuable trends on how a process affects the different bioactive compounds of a given food product. At the same time, the available data allows to assert, that in general, nonthermal processing is a very sound alternative to conventional thermal treatments to minimize the impact of processing on bioactive compounds. This review summarizes and analyzes the effects of these processes on relevant bioactive compounds present in selected food products as reported in the scientific literature