Microcosms references

Coming." At this time eschatological discourse was co-opted into the service of the esoteric sciences, most especially into alchemical theory in the twelfth century Latin translation of the Turba philosophorum (Arabic original ca. 900 AD). Christian interpolations were added to this text referring to the death and resurrection of the chemicals in apocalyptic terms." The process of distillation in Christian alchemy symbolised death and resurrection, as well as the union of Macrocosm and Microcosm. To the alchemists the death and resurrection of the stone in the manner of a human being was the clearest indication that alchemy was a divine, not a human science. 

FIGURE 20.8 Relative tradeoffs between physical (microcosm) and mathematical models as affected by effluent complexity. (From U.S. EPA, Assessing the Geochemical Fate of Deep-Well-Injected Hazardous Waste A Reference Guide, EPA/625/6-89/025a, U.S. EPA, Cincinnati, OH, June 1990.)... 

Microcosm type Organism Survival (days) Conditions Comments Reference... 

One remark can be made refering to the significance of the specific heat dissipation rate (dQ/dt per cell). The nutrient enrichment induced the appearence of an energetically expensive metabolic phase followed by a secondary decrease which indicated a metabolic recovery. This phenomenon was independent of oxygen availability, i.e. in "summer" microcosms where the oxygen tension was severely limited (after enrichment), a similar energetic recovery was observed as in "winter" microcosms (figure 5). 

Methionine as a Precursor of DMS. Methionine was recognized as a precursor of methylated sulfur compounds about 50 years ago (see 12 for references). Subsequent studies have shown the production of volatile methylated sulfides from methionine in many environments. The emphasis has been on anaerobic transformation in studies with natural samples or microcosms. Francis et al. (181 observed the production of methanethiol, DMS and DMDS from methionine in soil incubations. The production of the volatile sulfur... 

Microcosm and mesocosm studies can be directly designed for the purpose of EQS derivation (e.g., the exposure scenario, communities to be monitored, etc.). Guidance for design and conduction of microcosm and mesocosm studies can be found in the references given for pesticide risk assessment, but OECD has recently published a guideline for a lentic field test that is not focused on pesticides alone (OECD 2006b). 

Practical aspects. Some endpoints need more elaborate experimental setups than others, for example, microcosm or mesocosm studies on community responses compared to simple beaker tests for determining effects on the survival of a single species. As a consequence, possibilities for the replication or repeating of tests may be limited. This may affect the possibility of meeting requirements for a proper analysis of the resulting toxicity data against the 2 reference models of CA and IA. 

Over the last 20 years a variety of multispecies toxicity tests have been developed. These tests, usually referred to as microcosms or mesocosms, range in size from 1 1 (the mixed flask culture) to thousands of liters in the case of the pond mesocosms. A review by Gearing (1989) listed 11 freshwater artificial stream methods, 22 laboratory freshwater microcosms ranging from 0.1 to 8,4001, and 18 outdoor freshwater microcosms ranging from 8 to 18,000,000 1. In order to evaluate and design multispecies toxicity tests, it is crucial to understand the fundamental differences compared to singlespecies tests. A more extensive discussion has been published (Landis, Matthews, and Matthews 1996) and the major points are summarized below. 

Often, impacts are quantified using a reference site as a negative control for comparison to other sites under question. Similarly, multispecies toxicity tests, microcosms, and mesocosms attempt to detect differences between the control treatment and the dosed treatment groups. 

The interfacial mechanism refers to the microcosmic mechanism of the interface function. Generally, the resin phase is in solution or melt flow state to contact with the filler to form composite materials after a curing reaction or cooling curing. In this process, how the resin interacts with the filler becomes of more and more concern. 

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