Stress-induced morphologies

Watanabe Y., Gould E., Daniels D.C., Cameron H., and McEwen B.S. (1992) Tianeptine attenuates stress-induced morphological changes in the hippocampus. Eur J Pharmacol 222 157-162. 

Romheld, V., and Marschner, H. (1981). Iron deficiency stress induced morphological and physiological changes in root tips on sunflower. Physiol. Plant. 53, 354-360. 

The aim for tree breeders and forest managers is to define and grow a plantation which will be elastic in its response to the large stresses induced by high wind speeds. Petty Swain (1985) have established models of the stress-strain responses of forest trees which may be used to define the sizes and morphologies of trees, for a defined range of wind speeds and elastic responses. A typical response of a plantation grown spruce tree to wind speed is shown on Fig. 2. This is a classic stress/strain curve, with an... 

Silvestre J, Fernandez AG, Palacios JN (1999) Effects of rolipram on the elevated plus-maze test in rats a preliminary study. J Psychopharmacol 13 274-277 Sousa N, Lukoyanov NV, Madeira MD, Almeida OF, Paula-Barbosa MM (2000) Reorganization of the morphology of hippocampal neurites and synapsed after stress-induced damage correlates with behavioral improvements. Neuroscience 97 253-266 Stanciu M, Radulovic J, Spiess J (2001) Phosphorylated cAMP response element binding protein in the mouse brain after fear conditioning relationship to Fos production. Mol Brain Res 94 15-24... 

Plate-like particles of interest in this context include mica, aluminum flake, hammered glass, magnesium hydroxide and talc. Physical properties of composites containing these additives depend strongly on the flow-induced morphology and on the distribution of residual stresses [31]. 

In practice, many fabrication processes take place under non-isothermal, non-quiescent and high-pressure conditions. Mechanical deformation and pressure can enhance the crystallisation as well as the crystal morphology, by aligning the polymer chains. This leads to pressure-induced crystallisation and to flow-induced or stress-induced crystallisation, which in fact is the basis for fibre melt-spinning (see Sect. 19.4.1)... 

Surface nano-morphology changes of photoreactive molecular crystals are an attractive area of research, because the phenomena could potentially be applied to photodriven nanometer-scale devices and provide important information on crystal-line-state reaction mechanisms and dynamics [2a, 21]. As described in Section 25.3.2, the single crystal of lEt, in which the CpEt rings have no reorientation freedom in the crystal, tends to collapse and degrade as the reaction proceeds. This observation for the crystal of lEt can be explained by the local stress induced by the photoreaction that is not suitably released by the crystal lattice. In such a crystal, does the surface morphology of the crystal change ... 

In this paper, we explore the morphological features of polyacetylene/polybutadiene (PA/PB) blends in detail via electron microscopic techniques. We have also extended our original study of stress induced property enhancement in blends with polyacetylene compositions in the 40-60% range (Blend paper 1, ref. 5). 

This category mainly comprises fiUed and reinforced polymer melts. There are numerous reviews on the topic [Chaffey, 1983 Goetder, 1984 Metzner, 1985 Utracki, 1987, 1988 Utracki and Vu-JQianh, 1992], There is particularly strong interest in flow of polymeric composites filled with anisometric, reinforcing, particles, with properties that strongly depend on the flow induced morphology and distribution of residual stresses. 

With the knowledge of the flow behavior of simpler systems, viz. suspensions, emulsions, block copolymers, as well as that of the mumal interactions between the rheology and thermodynamics near the phase separation, one may consider the flow of more complex systems where all these elements may play a role. Evidently, any constitutive equation that may attempt to describe flow of immiscible polymer blends should combine three elements the stress-induced effects on the concentration gradient an orientation function and the stress-strain description of the systems, including the flow-generated morphology. Such a comprehensive description stiU remains to be formulated. 

Tsebrenko et al. [1976] reported on fibrillation of POM in a copolyamide (CPA) matrix, as a result of flow through a capillary. Fine fibrils with diameters of about 20 j,m and length 3.2 mm were obtained during extrusion at T = T (POM) H- 6°C. The low extmsion temperature facilitated stress-induced crystallization of the POM fibers, preserving the morphology engendered at the entrance to the spinneret. 

---