Response to Environment

In the previous sections on crazing primarily mechanical and molecular parameters have been discussed while the chemical environment was not considered as a variable. At this point an overview over the physico-chemical response of a crazable material to an active chemical environment will be given. (The chemical response to an active physical environment such as photodegradation or ozonolysis has been treated or referenced in 8 III). 

The physico-chemical actions of a (gaseous or liquid) chemical agent on a polymer involve adsorption and absorption of the agent, the swelling and/or plasticization of the matrix, the reduction of surface energies, and/or chemical reactions 

The solvent crazing in terms of polymer and liquid solubility parameters has been studied in detail by Andrews et al. [124, 126] and Kambour et al. [125, 128]. Kambour employed a wide range of swelling liquids with solubility parameters 5s between 5.34 and 19.2 cal He determined the equilibrium solubility Sv, expressed 

The crazing agent thus acts through its presence within the polymer matrix. In increasing the chain mobility (lowering Tg) it facilitates the primary and secondary steps of craze initiation nucleation and stabilization of a craze. This leads to the lowering of 0 and ej in brittle polymers such as PS. Easier nucleation and stabilization even cause the appearance of crazes in otherwise ductile materials such as PPO, PSU, PVC, or PC. 

The swelling, crazing, and cracking behavior of PMMA, PVC, and PSU in contact with some 70 different liquids was analyzed by Vincent and Raha [123]. They considered not only the solubility parameter 65 but also the value of the hydrogen bonding parameter Hqd based on the displacement of the OD infra-red absorption band in CH3OD in presence of the particular liquid and benzene. Better (but still no unique), correlation between the mode of failure and 63 and Hqd was obtained. 

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This clearly overstates the potential of demographic study to provide a mechanistic understanding of plant responses to environments and, if implemented, would lead to unnecessary delay in the development of generalising principles. The remainder of this chapter is founded on the assumption that the most direct route to a coherent predictive theory of plant responses to stress is likely to involve a synthesis of insights derived from plant population biology, ecophysiology, and many other fields of botanical endeavour. 

Multi-cell eukaryotes with nerves and brains As above plus Na+, K+, Cl- potentials New memory and responses to environment... 

Hall, A.E., and Schulze, E.-D. 1980. Stomatal response to environment and a possible interrelation between stomatal effects on transpiration and C02 assimilation. Plant Cell Environ 3 467-174. 

Long-term adaptations (mutations) may occur in response to environment changes that can alter completely the product distribution. 

In commenting on the unsatisfactory state of our knowledge of mycoparasitism obtained largely by means of dual-culture studies in vitro, Boosalis and Mankau (1965) state that this does not mean that studies in vitro should be discontinued. On the contrary, it points up the need for more basic work in vitro to elucidate the physiological and biochemical mechanisms of parasitism and to show how their mechanisms relate to susceptibility of the host fungus in response to environment. These studies would be followed up by studies in natural soils. This viewpoint seems most logical to the writer. 

Hall, A. E., Kaufmann,M.R. Stomatal response to environment with Sesamum indicum L. Plant Physiol. 55,455 59 (1975)... 

Hall, A. E., Schulze, E.D., Lange, O.L. Current perspectives of steady-state stomatal responses to environment. In Water and plant life. Problems and modern approaches. Ecol. Studies Vol. 19. Lange,O.L., Kappen,K., Schulze,E.D. (eds.), pp. 169-188. Berlin, Heidelberg, New York Springer 1976... 

Kjellen (2010) sheds fight on human and environment interaction from an operator s point of view. Under this model, people are viewed as an information processor who makes their own judgment in response to environment risks,... 

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