Decompositions of large-scale biological systems based on dynamical properties.

MOTIVATION: Given a large-scale biological network represented as an influence graph, in this article we investigate possible decompositions of the network aimed at highlighting specific dynamical properties. RESULTS: The first decomposition we study consists in finding a maximal directed acyclic subgraph of the network, which dynamically corresponds to searching for a maximal open-loop subsystem of the given system. Another dynamical property investigated is strong monotonicity. We propose two methods to deal with this property, both aimed at decomposing the system into strongly monotone subsystems, but with different structural characteristics: one method tends to produce a single large strongly monotone component, while the other typically generates a set of smaller disjoint strongly monotone subsystems. AVAILABILITY: Original heuristics for the methods investigated are described in the article. CONTACT: altafini@sissa.it

Separate and combined effects of lactic acid, chitosan and modified atmosphere packaging on the shelf life of quail carcass under chilled conditions.

The shelf life of quail carcass was examined after imposing separate and combined treatments of spraying with lactic acid (LA, 1% v/v), dipping in chitosan (CH, 1% w/v) and placing the carcass in modified atmosphere package (MAP, 65% CO2 + 30% N2 + 5% O2) at 4 ±â€¯1 °C for 20 days. The control group was packed under similar atmospheric condition but without any antimicrobial agents. Microbiological populations, physicochemical properties and sensory attributes (color, odor and overall appearance) were monitored at 4-day intervals. All antibacterial treatments effectively lowered microbial numbers, compared to the control during chilled storage. The total viable count, as an indicator of meat spoilage, on day 8 of the storage in treated samples was 0.5-3.4 log CFU/g which was lower than the control. The weakest and strongest effects were caused by LA and LA + CH + MAP treatments, respectively. Similar impact intensity occurred in other microbial tests during refrigerated storage. Binary combination treatments of MAP and chitosan showed synergistic effects on controlling microbial growth, and had no significant difference with LA + CH + MAP. Evaluations on days 4 and 8 showed that all treatments significantly controlled microbial growth, pH value, peroxide value and reactive substances of thiobarbituric acid in comparison with the control (P < 0.05). Interestingly, total volatile basic nitrogen (TVB-N) values were sharply increased in all treatments, whereas the CH + MAP and LA + CH + MAP retained the TVB-N content below 30 mg/100 g, which is an indication of meat freshness. The LA + CH + MAP caused the lowest TVB-N value on days 4, 12, 16 and 20 (P < 0.05). On day 8 of storage, the scores of sensory attributes for the control group were less than the minimum score of acceptance (i.e. 5 points). The results of this study indicate that the LA + CH + MAP treatment rendered the samples favorable in terms of overall appearance (>7) during the entire chilled storage. It is noteworthy that organoleptic evaluations correlated well with physicochemical and microbiological data. Based on microbiological data and the overall appearance results of the carcasses, the shelf lives of the control, LA, CH, MAP, LA + MAP, LA + CH, CH + MAP and LA + CH + MAP samples were 6, 7, 11, 12, 12, 15, 20 and 20 days, respectively, under chilled conditions.