Defects memory effect

In the shape-memory transformation described, only the shape of the parent phase is remembered . It is called the one-way shape-memory effect. It is also possible to produce alloys that display two-way shape-memory effects. In these materials, both the shape of the parent phase and the martensitic phase is remembered . This reversible effect is caused by the fact that the nucleation of the martensite is very sensitive to the stress field. Introduction of lattice defects such as precipitates can restrict the number of variants that form and the positions where they nucleate. Such materials generate the martensitic shape on cooling below the temperature Mf. Cycling between higher and lower temperatures causes the alloy to switch alternately between the two shapes. There is considerable research interest in developing and exploiting two-way shape-memory effect alloys at present. 

The idea of introducing fractional derivatives in diffusion equations to account for long-range memory effects has given rise to a large number of publications. In this context, the work by Metzler, Glockle, and Nonnenmacher is noteworthy [297]. They realized that (6.10) suffers from a pathological defect For d/ = 1 and dy, = 2 one should recover the standard diffusion equation however, this is not the case. To overcome this difficulty they propose... 

Viscoelastic phenomena may be described through three aspects, namely stress relaxation, creep and recovery. Stress relaxation is the decline in stress with time in response to a constant applied strain, at a constant temperature. Creep is the increase in strain with time in response to a constant applied stress, at a constant temperature. Recovery is the tendency of the material to return partially to its previous state upon removal of an applied load. The material is said to have memory as if it remembers where it came from. Because of the memory effect, in transient flows the behavior of viscoelastic fluids wUl be dramatically different from that of Newtonian fluids. Viseoelastie fluids are fiiU of instabilities. Some examples inelude instabilities in Taylor-Couette flow, in eone-and-plate and plate-and-plate flows (Larson 1992). The extrudate distortion, commonly called melt fraeture, is a notorious example of viscoelastic instability in polymer processing. The viseoelastie instability in injection molding can result in specific surface defects such as tiger stripes (Bogaerds et al. 2004). 

Design Philosophy 2 create order in a disordered system, such as alignment of random defects in martensite to produce reverse shape memory effect, and/or create disorder in an ordered system, such as non-polar direction poling of PZN-PT and PMN-PT single crystals to increase responsiveness of the system to an external field. 

When the nanotube is withdrawn from the monolayer, the defects remain in the monolayer for some time after the load on the nanotube has returned to zero. Similar memory effects have been observed in surface force apparatus experiments (42). 

In those days, there are some technical difficulties in realizing FLC displays. One was that it was difficult to keep LC layer thickness being very thin of around 2 pm in order to utilize its memory effect. The other was that because of stiffness of ferroelectric smectic layer structure, defects in the alignment of the LC orientation could easily be produced by mechanical shocks. 

It has been known for many years that antimuscarinic drugs like hyoscine, which enter the brain, cause amnesia when used clinically, e.g. pre-operatively, to reduce bronchial secretions. In experimental studies in both humans and animals they disrupt both the acquisition and the performance of learned behaviour. Anti-cholinestrase drugs have the opposite effect. It is by no means certain, however, that the memory defects induced by antimuscarinics are identical to those seen in AzD. 

However, there could also be an alternate rationale. Belyaeva et al (Ref 49) suggest that the decompn of crystalline RDX begins at crystal defects already present or temp induced (possibly also induced by pre-irradiation). De-compn leads to deformation of the crystal lattice and more defects. If decompn products cannot diffuse, they crack the crystal which leads to a suddenly increased evolution of gas. This model can explain the memory and preirradiation effects, but is incapable of explaining... 

The primary approach currently used to detect and characterize potential neurotoxicants involves the use of animal models, particularly rodents. Behavioral and neurophysiological tests, often similar to the ones used in humans, are typically administered. The sensitivity of these measures to neurotoxicant exposure is widely accepted. Although it is often not possible to test toxicant effects on some higher behavioral functions in animals (e.g., verbal ability, cognitive flexibility), there are other neurobehavioral outcomes such as memory loss, motivational defects, somatosensory deficits, and motor dysfunction that can be successfully modeled in rodents. These behaviors are based on the ability of the nervous system to integrate multiple inputs and outputs, thus they cannot be modeled adequately in vitro. Although the bulk of neurotoxicity data has been collected in rodents, birds and primates are also used to model human behavioral outcomes. 

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