Plastic Life Cycle Research Articles

05/01210 Thermodynamic optimization of the life cycle of plastics by exergy analysis

05/01210 Thermodynamic optimization of the life cycle of plastics by exergy analysis

Thermodynamic optimization of the life cycle of plastics by exergy analysis

Decision-makers should strive for an efficient employment of resources for the whole industrial ecological system. The metabolization of resources should be optimized in thermodynamic terms. This contribution presents an effort to use exergy analysis as a quantitative tool in the thermodynamic optimization of the life cycle of plastics. Quantitative results on overall exergetic efficiencies of different industrial metabolic options are presented. Therefore, different waste treatment options of plastics will be considered, taking into account interacting industrial activities, such as virgin plastics production and heat and electricity production starting from natural resources. Copyright © 2004 John Wiley & Sons, Ltd.

The life cycle of Reticulitermes spp (Isoptera: Rhinotermitidae): what do we know?

The subterranean termites in the genus Reticulitermes have a complex and plastic life cycle, which has been the subject of a number of publications over the past century. Given the inherent difficulties in studying such cryptic, eusocial organisms it is not perhaps surprising that the literature on their biology has failed to reach a consensus. An overview of the literature is given, which is followed by a discussion of the various theories on the life cycle of Reticulitermes spp. A substantial proportion of the review focuses on the French literature, which constitutes the majority of the primary sources and can be difficult to access. There are many discrepancies in the literature in terms of the number of instars, the definition of workers and the question of whether they should be termed pseudergates or, potentially, an additional terminology used to differentiate between pseudergates and the true workers seen in the higher termites (Isoptera: Termitidae). It remains very difficult to compare publications as there is little conformity; a problem that is aggravated by a general absence of drawings of the relevant instars. Further work on the biology of Reticulitermes is clearly required. There is also a need for researchers to agree on a standard terminology for this genus. A glossary is provided for the various synonyms and definitions.

Impact of temperature on juvenile growth and age at first egg-laying of the Pacific reef squid Sepioteuthis lessoniana reared in captivity

Cephalopod mollusks exhibit highly plastic life cycle traits influenced primarily by the interactive effects of food availability, light cycle and temperature, with the latter perhaps the most influential. Hatchlings of the tropical reef squid Sepioteuthis lessoniana were hatched from field-collected eggs in the laboratory and cultured at different temperatures to evaluate the effect of temperature on growth rates. All groups showed rapid, sustained growth rates from hatching to a size of 10–25 g. Beyond this size range, growth was slower and not clearly exponential in form. Growth rate was closely linked to temperature. Squids grown at approximately 27 °C attained a size of 10 g in as little as 45 days at sustained growth rates of 12.2% body weight day−1 (%bw day−1), while squids cultured at 20 °C required almost 100 days to attain the same size at rates of 5.7%bw day−1. At an age of 55 days and approximately 1 g body weight, juvenile squids cultured at 20 °C were able to accelerate growth rates from 5.7%bw day−1 to over 12%bw day−1 when temperature was raised to 27 °C. They maintained this growth rate to a size of about 10 g and an age of at least 75 days post-hatching, indicating that body size and not age is the limiting factor for this rapid post-hatching growth. By comparison, conspecifics cultured near 27 °C from hatching had shifted out of the rapid post-hatching growth phase by day 50 at sizes between 10 and 50 g. The hatchlings from temperate to subtropical Japan had consistently higher growth rates at comparable temperatures than hatchlings from tropical Okinawa. When plotted as growth rate versus temperature, the Japanese group had a clearly higher slope to the relationship than the tropical populations, equivalent to a 2%bw day−1 difference in growth rate at 25 °C. Age at first egg-laying was decreased at higher culture temperatures; however, overall life span was not.