Species defects

Both categories of transport discussed above involve the motion of defects relative to an otherwise ordered array of ions, so the transport is referred to as defect transport. The concentrations of such defects (as contrasted with the total atom concentrations within the oxide lattice) are the important quantities for mass transport, charge transport, and space—charge effects, so it is the species defect concentration which appears in the diffusion equation. Likewise, the diffusion coefficients... 

Fig. 48. Electrospray ionization mass spectrum of a Starburst PAMAM (generation = 3). Note the last significant peak M = 5154 daltons (degree of polymerization = 45), corresponding to the magic number for ideal structure. The remaining peaks at 5040, 4925 and 4812 correspond to M — x (114) species defects due to missing monomer units. The peaks at 5094, 4980 and 4865 correspond to M — x (60) species and have been assigned to defects arising from macrocycle formation...

A number of so-called species defects of metabolic conjugation have been documented, and a list Is presented In Table V. 

Table V. Some "Species Defects" in Metabolic Conjugation Reactions Reaction Affected species (reference)...

Though major taxonomic groups of bacteria differ considerably in the nature of their lipid A, the structure is highly conserved between closely related species. Defects in the synthesis of lipid A seem incompatible with survival, for mutants with abnormalities in the earliest stages of its synthesis have not been found. 

Highly reactive species/defects which upon reaction, recombination, or annihilation give off localized energy to produce ejected electrons. In polymers, for example, bond breaking is known to produce free radicals which frequently must diffuse and react via second-order reactions. Chemical reactions at surfaces are known to be accompanied by electron emission (called chemi-emission)(23,24) via nonradiative electronic transitions. 

As discussed in Section 7.2.3, radiation can induce segregation of alloy elements at defect sinks such as grain boundaries [101]. Typically, RIS is a result of inverse Kirkendall (IK) effects in which the evolution of defect concentration field drives the evolution of alloy composition field. ID rate theory modeling [44,101] is widely used to describe the coupled evolution between defect flux and composition flux. These rate theory models considered both vacancy-mediated and interstitial-mediated solute transport, as well as point defect recombination and defect loss to dislocations. At steady state, the solute segregation direction depends on the relative diffiisivity of different species-defect coupled diffusion. In austenitic Fe-Cr-Ni alloys, the vacancy-mediated solute diffusion alone is sufficient in describing the RIS trend and the interstitial-mediated solute diffusion is usually assumed to have a neutral contribution to RIS [44]. However, in Fe-Cr F/M alloys, both interstitial- and vacancy-mediated diffusion should be considered [102]. 

N-CNTs Oxidation of cyclohexane Nitrogen species Defects Reaction rate increased about five times with respect to AC and two times compared with undoped CNTs [132]... 

The chemistry of interest is often not merely the inhnite crystal, but rather how some other species will interact with that crystal. As such, it is necessary to model a system that is an inhnite crystal except for a particular site where something is diherent. The same techniques for doing this can be used, regardless of whether it refers to a defect within the crystal or something binding to the surface. The most common technique is a Mott-Littleton defect calculation. This technique embeds a defect in an inhnite crystal, which can be considered a local perturbation to the band structure. 

Structure Modification. Several types of stmctural defects or variants can occur which figure in adsorption and catalysis (/) surface defects due to termination of the crystal surface and hydrolysis of surface cations (2) stmctural defects due to imperfect stacking of the secondary units, which may result in blocked channels (J) ionic species, eg, OH , AIO 2, Na", SiO , may be left stranded in the stmcture during synthesis (4) the cation form, acting as the salt of a weak acid, hydrolyzes in aqueous suspension to produce free hydroxide and cations in solution and (5) hydroxyl groups in place of metal cations may be introduced by ammonium ion exchange, followed by thermal deammoniation. 

The intrinsic defects include paramagnetic and diamagnetic species (24,27,28). The paramagnetic defects have received the most study because they are readily detectable by electron spin resonance (esr) spectrometry. Paramagnetic defects that have been identified by esr include the center, 6i the... 

A number of diamagnetic defects are also beheved to exist in vitreous siUca. Because there is no direct way to study these species, their identification is either done indirecdy, such as by uv absorption, or by employing esr after the material has been made paramagnetic using ionizing or laser irradiation. 

With few exceptions, stains used in wood finishing are formulated to improve the appearance of the substrate. Unlike paints, sealers, and topcoats, stains are utilized either to accentuate the natural beauty of the wood or to hide inherent defects found in most species of wood. 

Fig. 7. Bombardment processes at the surface and in the near-surface region of a sputtering target, where represents the energetic particle used for bombarding the surface <), an adsorbed surface species 0> atoms and x, lattice defects.

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