Structural defects/anomalies

A birth defect, a synonym for the clinical term congenital anomaly , is defined as an anatomical and/or functional defect resulting from disturbance of normal developmental processes. This definition includes a wide range of defects, from a visualized structural defect such as spina bifida to microscopic and metabolic defects such as phenylketonuria. Terms such as malformation, disruption, deformation, and sequence have been utilized to describe various manifestations (Jones, 1988). 

Similar to PbSe, the controlled growth of lead telluride, PbTe, on (111) InP was demonstrated from aqueous, acidic solutions of Pb(II) and Cd(II) nitrate salts and tellurite, at room temperature [13]. The poor epitaxy observed, due to the presence of polycrystalline material, was attributed to the existence of a large lattice mismatch between PbTe and InP (9%) compared to the PbSe/InP system (4.4%). The characterization techniques revealed the absence of planar defects in the PbTe structure, like stacking faults or microtwins, in contrast to II-VI chalcogenides like CdSe. This was related to electronic and structural anomalies. 

Thermal transmission testing is an excellent way of detecting various types of anomalies such as surface corrosion under paint before the corrosion becomes visually evident. Thin, single-layer structures, such as aircraft skin panels, can be inspected for surface and subsurface discontinuities. This test is simple and inexpensive, although materials with poor heat-transfer properties are difficult to test, and the joint must be accessible from both sides. For nonmetallic materials, the defect diameter must be on the order of 4 times its depth below the surface to obtain a reliable thermal indication. For metals, the defect diameter must be approximately 8 times its depth. Some bright surfaces such as bare copper and aluminum do not emit sufficient infrared radiation and may require a darkening coating on their surface. 

Other interesting examples of the behaviour of the considered samples are given in Fig. 32. Samples with high Tg which are chemically less defective have lower E25 values. These anomalies in the mechanical properties of epoxy polymers prepared at low Tcure are very difficult to understand in terms of conventional concepts of the relationship between the structure of polymer glasses with their mechanical properties. 

Levanytrk AP, Osipov W, Sigov AS, Sobyanin AA (1979) Change of defect structure and the resultant anomalies in the properties of substances near phase-transition points. Soviet Physics JEPT 49 176-188... 

In solids, as in liquids, macroscopic behavior is a consequence of microscopic structure. Even more, in solids the structure defines the thermodynamic phase, and deviations from the nominal structure are true anomalies—defects. In contrast, defects are so prevalent in fluids that the term loses currency fluids are described instead by fluctuations, reflecting the diminished (albeit consequential) role of structure in fluid-phase behavior. Structure in solids is a much more cooperative and large-scale phenomenon than in liquids. This means that changes in the structure of solids do not happen incrementally or in isolation. Changes in structure are... 

Randomly stacked defects of the building modules have been observed these defects, which are common in a modular structure and alter the stoichiometry, are suggested [19] to be a possible source of anomalies noted in the superconducting behaviour of single crystals belonging to compounds of the series here described. 

USil ss crystallizes in a defect ThSi2 structure and its x(T) curve slowly increases with decreasing T down to 78 K (Misiuk and Trzebiatowski 1979). No anomaly appears in the p versus T curve down to 1 K (Kadowaki et al. 1987a) and hence a non-magnetic ground state can be tentatively assumed for USij 88. The value of y lies between 70 and 80 mJ/mol K2, which was estimated by Kadowaki et al. (1987a) on the basis of the relation between y and the low-temperature AT2 term of the resistivity found for number of U and Ce compounds (fig. 2.3 Kadowaki and Woods 1986). 

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