Role of mechanical stress

The state of the amorphous phase, the structure of the crystalline phase, defects in the crystals and external impurities all influence the formation and behaviour of radicals in solid polymers. Mechano-radicals are formed in mechanically stressed samples. One of the characteristics of mechano-radicals is high reactivity at low temperatures compared with the corresponding radicals formed by photo-irradiation [136, 2012, 2013]. 

The radical concentration remains unchanged when the applied stress is 

Mechanical stress causes changes in the physical properties and chemical reactivity of polymers [397]. Macroscopic extension of a polymer film causes anisotropic orientation and extension of polymer chains. Stress can cause chain breaks and introduce radicals, which can initiate degradative processes such as oxidation or microcracking. 

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Ag incorporation into the textile. The percentage of the total silver emitted during one washing of the textiles varied considerably among products (from <1 to 45%). In the washing machine, the majority of the Ag (at least 50% but mostly >75%) was released in the size fraction >450 nm, indicating the dominant role of mechanical stress (Figure 8.3). These results have important implications for the risk assessment of Ag textiles and also for environmental fate studies of nano-Ag, because they show that... 

Stutzmann, M (1985). Role of mechanical stress in the light-induced degradation of hydrogenated amorphous silicon, AppZ. Phys. Lett., Vol. 47,21- 23, ISSN 0003-8979... 

The kinetics of tribochemical transformations. The role of mechanical stresses consists of not only the initiation of radical processes but in kinetic changes of the elemental stages of the chemical reactions with the participation of macromolecules as well. Plastic deformations increase reaction velocities that have been limited by travel of the reacting particles in the material bulk. Shear and tension accelerate the decay of the radicals with a free valence in the chain center. Chemical reactions are also affected by variations in the intra-molecular mobility and permolecular structure during pol3Tner deformation. 

For molecular liquids, Mishima et al. [24] found an amorphous-amorphous transition in water. The transition has recendy been studied in details [12]. Computer simulations also suggest the existence of LLT(s) in water [5,11,12,17,18]. Based on these findings, the connection of amorphous-amorphous transition and LLT in water was suggested and actively studied [11,12]. However, the LLT is hidden by crystallization in water, even if it exists. This makes an experimental study on the LLT extremely difficult especially for bulk water. It was also pointed out that the role of mechanical stress involved in amorphous-amorphous transition may complicate the connection [25]. 

As per our hypothesis, this study confirmed the significant influence of implant position angle (IPA) to the clinical response in varus and valgus positions (p=0.001 and p=0.008). Influence of patient weight was close to statistical significance in valgus (p=0.063), confirming well known role of mechanical stress and strain in BMD homeostasis of the femoral bone. Rapid bone loss at the medial bone/implant interface was statistically related to varus position, 77 /o of which became early clinical failures. 

The influence of mechanical strain and structural stress on the rate of weight loss and the decrease in DP in acid hydrolysis is in agreement with some considerations of Elema (17), who discussed the role of structural stresses in connection with weak links in the cellulose chain. It may be mentioned here, however, that our results on heterogeneous acid hydrolysis did not yield further evidence of these weak links. ... 

The role of the IF, and particularly the keratin filament system, in resisting the forces of mechanical stress has been well established. However, IFs also play a role in countering metabolic stress. Perhaps the best example is the cytoprotective role played by the simple epithelial keratins, K8/18. However, vimentin, desmin, peripherin, GFAP, the lens proteins phakinin, and filensin and other keratins have also been shown to associate with members of the small heat shock protein (HSP) family, including HSP27 and aB-crystallin (reviewed in Coulombe and Wong, 2004 Marceau et al., 2001 Nicholl and Quinlan, 1994). 

Reid AB, Kurten RC, McCullough SS, Brock RW, Hinson JA. Mechanisms of acetaminophen-induced hepatotoxicity Role of oxidative stress and mitochondrial permeability transition in freshly isolated mouse hepatocytes. J Pharmacol Exp Ther 2005 312 509-16. 

Reactive aldehydes generated from hpid peroxidation are involved in CVD (266). Another example lies with the role of oxidative stress in the pathophysiology of asthma (267). Lipid peroxidation, as determined by plasma iso-prostanes, is related to disease severity in mild asthma. Tumor cell lines are sensitive to PUFA and to associated oxidation products (268). This sensitivity depends on the antioxidant defense mechanism, as well as on culture conditions. Hydroperoxy docosahexaenoic acid is a major metabolite, responsible for the cytotoxicity of DHA. 

White beam synchrotron radiation was used in a topographical study [64] of the phase transition in [Ni(en)2 (NCS)2J single crystals. The short exposure times possible using this intense radiation enabled the strained centre of the crystal to be identified as the most imperfect zone, within which the nucleation and growth process was initiated. The phase transition commenced at defect sites. The role of generation and relaxation of mechanical stresses in influencing kinetics of solid state transformations was later reviewed [65]. 

CoNVERTi A., Del Borghi M., Ferraiolo G., Sommariva C., Mechanical mixing and biolo cal deactivation The role of shear stress application time, Chem. Engng.). 62 (1996), p. 155-167... 

Galaris D and Evangelou A (2002) The role of oxidative stress in mechanisms of metal-induced carcinogenesis. Crit Rev Oncol Hematol 42 93-103. 

Khodot V. 1980. Role of mechane in the stress state of a coal seam. Soviet Mining Science, 17(5) 460-466 (In Soviet). 

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