Environmental stabilization

Polyacetylene is considered to be the prototypical low band-gap polymer, but its potential uses in device applications have been hampered by its sensitivity to both oxygen and moisture in its pristine and doped states. Poly(thienylene vinylene) 2 has been extensively studied because it shares many of the useful attributes of polyacetylene but shows considerably improved environmental stability. The low band gap of PTV and its derivatives lends itself to potential applications in both its pristine and highly conductive doped state. Furthermore, the vinylene spacers between thiophene units allow substitution on the thiophene ring without disrupting the conjugation along the polymer backbone. 

The selection of these compounds was made on the grounds of their toxicity, environmental stability, and tendency to undergo biomagnification the intention was to move toward their removal from the natural environment. In the REACH proposals of the European Commission (EC published in 2003), a similar list of 12 POPs was drawn up, the only differences being the inclusion of hexachlorobiphenyl and chlordecone, and the exclusion of the by-products, dioxins, and furans. The objective of the EC directive is to ban the manufacture or marketing of these substances. It is interesting that no fewer than eight of these compounds, which are featured on both lists, are insecticides. 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

The safest conclusion to draw at this point is that it is unsafe to generalize about the environmental stabilities of N -nitroso compounds. 

NoV are readily transferred from hands to fomites and vice versa (Bidawid et al., 2004 D Souza et al., 2006). The pronoimced environmental stability of NoV particles also contributes to the spread of outbreaks from point sources of surface contamination. All stability studies have made use of surrogate organisms to model NoV response to conditions, since the human virus is not easily grown in cell culture (Duizer et al., 2004b Straub et al., 2007). The murine norovirus (MNV) and the feline calicivirus (FCV) have both been used, with the mouse virus providing more... 

PCDDs are present as trace impurities in some commercial herbicides and chlorophenols. They can be formed as a result of photochemical and thermal reactions in fly ash and other incineration products. Their presence in manufactured chemicals and industrial wastes is neither intentional nor desired. The chemical and environmental stability of PCDDs, coupled with their potential to accumulate in fat, has resulted in their detection throughout the global ecosystem. The number of chlorine atoms in PCDDs can vary between one and eight to produce up to 75 positional isomers. Some of these isomers are extremely toxic, while others are believed to be relatively innocuous. 

Enhanced environmental stability was recently demonstrated for PLED with PFO 196/gold nanoparticle (5-10 nm) nanocomposite-emitting layer [337]. In addition, the gold nanoparticle-doped PLEDs (1.5 x 10-5 volume fraction of Au) demonstrated improved luminescent lifetime and 2-3 times higher QE, compared with pure PFO-based PLED. 

Douglas, G., Bence, A., Prince, R., McMillen, S., and Butler, E., 1996, Environmental Stability of Selected Petroleum Hydrocarbon Source and Weathering Ratios Environmental Science and Technology, Vol. 30, pp. 2332-2339. 

Despite the environmental stability of these compounds, a number of reports have indicated that under reducing conditions prevailing in sediments dioxins may undergo transformation reactions, including dechlorination. The potential importance of reductive dechlorination, and perhaps one of the reasons for the emphasis on this transformation process, is illustrated by recent evidence that... 

Xu et al. have reported a GO/DNA hydrogel with high mechanical strength, excellent environmental stability, high dye-adsorption capacity, and self-healing function... 

Interestingly, much work has been devoted to the development of substances in the class of cholinesterase inhibitors that have exceedingly high toxicity substances that also have properties (such as volatility and sufficient but not excessive environmental stability) that make them useful as agents of warfare. Most of those now stockpiled were first developed during World War II. Sarin and VX are perhaps the most well-known members of this class of compounds that have been especially designed to kill people. 

Within the framework of a cooperative research project founded by the EC, a procedure has been developed for the formulation of injectable bio-erodible nanoparticles with fairly uniform size distribution and high environmental stability that appear well suited for targeted administration of protein and peptide dmgs. 

R.A. Vaiin, S. Li, A. Calka, D. Wexler, Formation and environmental stability of nanocrystalline and amorphous hydrides in the 2Mg-Fe mixture processed by controlled reactive mechanical alloying (CRMA) , J. Alloys Compd. 313 (2004) 270-286. 

Kagan CR, Afzali A, Graham TO (2005) Operational and environmental stability of pentacene thin film transistors. Appl Phys Lett 86 193505... 

From the point of view of environmental stability, cadmium represents an... 

Ecology None None Environmental stability Environmental movement Accumulation Total effects on all non-target species... 

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