Biological attack

Fig. 8. The resistance of cellulose fibers to biological attack via sod-burial testing.

During this early period, a very ingenious free-radical route to polyesters was used to introduce weak linkages into the backbones of hydrocarbon polymers and render them susceptible to bio degradabihty (128—131). Copolymerization of ketene acetals with vinyl monomers incorporates an ester linkage into the polymer backbone by rearrangement of the ketene acetal radical as illustrated in equation 13. The ester is a potential site for biological attack. The chemistry has been demonstrated with ethylene (128—131), acryhc acid (132), and styrene (133). 

Not only may the cooling-tower plume be a source of fog, which in some weather conditions can ice roadways, but the plume also carries salts from the cooling water itself. These salts may come from salinity in the water, or may be added by the cooling-tower operator to prevent corrosion and biological attack in the column. 

Eor practical purposes, the sapwood of all species may be considered to be susceptible to biodeterioration. The heartwood of some species, however, contains toxic extractives that protect it against biological attack. Among the native species that have decay-resistant or highly decay-resistant heartwood are bald cypress, redwood, cedars, white oak, black locust, and black walnut (60). Douglas-fir, several of the pines, the larches, and honey locust... 

Specifics on the type of biological attack. This must be done by some other method such as chemical analysis of the solution (plus consideration given to limitations to the use of these several electrochemical techniques for MIC studies, noted previously under Corrosion Testing Laboratoiy Tests and subsequent subsections). 

Corrosion morphology must be consistent with biological attack. 

Most wood species are subject to some form of biological attack, a hazard not encountered by most other constructional materials. Fungal decay and attack by termites and other insect borers and marine borers are the main problems. The heartwood of many timber species and the sapwood of most species can be impregnated with wood preservatives to prevent these problems. 

The main hazard to timber is biological attack. In milder climates this is mainly rot due to fungal infections together with insect borers. In hot... 

The heartwood of various timber species shows a wide range of resistance to biological attack. The natural durability of heartwood) is assessed by ground contact tests and according to survival, classified into five ctegories - very durable (>25 years), durable (15-25 years) moderately durable (10-15 years) non-durable (5-10 years) and perishable, (<5 years). 

Cellulose acetate (CA), which is of poor chemical stability, tends to hydrolyze over time, is subject to biological attack, and can operate at only a limited pH range of 3.0 to 6.5 at 0 to 30 °C. It is widely available at low cost and is tolerant of continuous low-level chlorine exposure, such as is found in many city waters. 

Aromatic polyamide (aramid) is of excellent chemical stability and can operate over a pH range of 4.0 to 11.0 at 0 to 35 °C. It is not susceptible to biological attack, but cannot tolerate chlorine. 

Recommendation 1 The Transportation Security Administration, with its responsibility for the federal oversight of security operations at U.S. airports, should integrate strategies for defense against chemical/biological attacks into its broader security plan for protecting the U.S. air transportation system. The line of authority and... 

Finding 2 No specific strategies, approaches, or procedures have been developed to defend the U.S. air transportation system against chemical/biological attacks. 

Finding 4 Although the rapid detection of a chemical/ biological attack and identification of the agent used are worthwhile objectives, a defensive strategy that depends exclusively on a detection-system alarm before action is taken (i.e., employment of a detect and react strategy) has several serious limitations. 

By mutual agreement between the committee and the sponsor, the broad focus on transportation security in the statement of task was narrowed to the threat of chemical and biological attacks on the U.S. air transportation system. 

FIGURE 1-1 Generic airport diagram showing various airport spaces and some likely sites for chemical/biological attacks. 

A defensive strategy against chemical/biological attacks that does not rely on a detection event to initiate a response... 

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