Structure dependence

FIGURE 2.11 STM images of a Pd(lll) surface with an ordered oxygen p(2 x 2) structure (structure with a unit cell that is twice as large as the metal surface unit ceU in two directions). Oxygen atoms are imaged as bright bumps. Taken from Mendez et al. (2005) with permission from The American Physical Society. 

In a reactive environment, the reactants and products can induce other facets or completely new structures to become exposed. Undercoordinated sites at edges and comers are often particularly important for catalysis. The same kind of sites is found at steps on the surface. For the fee stmeture, a (211) step is often used to model undercoordinated sites. 

FIGURE 2.13 Schematic picture of a Pt particle consisting of 561 atoms. The particle is shaped so that it consists of (111) and (100) facets that are connected along edges that locally 

FIGURE2.14 Three examples showing the determination of Miller indices. (111) plane intercepting at 1 for x, y, andz. Center. (211) plane intercepting at A for x and y and 1 for z. Right (100) plane only intercepting atx=l. 

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Pastor G M, Dorantes-Davila J and Bennemann K H 1989 Size and structural dependence of the magnetic properties of small 3d-transition metal clusters Phys. Rev. B 40 7642... 

Each vibrational peak within an electronic transition can also display rotational structure (depending on the spacing of the rotational lines, the resolution of the spectrometer, and the presence or absence of substantial line broadening effects such as... 

Polymer-based, synthetic ion-exchangers known as resins are available commercially in gel type or truly porous forms. Gel-type resins are not porous in the usual sense of the word, since their structure depends upon swelhng in the solvent in which they are immersed. Removal of the solvent usually results in a collapse of the three-dimensional structure, and no significant surface area or pore diameter can be defined by the ordinaiy techniques available for truly porous materials. In their swollen state, gel-type resins approximate a true molecular-scale solution. Thus, we can identify an internal porosity p only in terms of the equilibrium uptake of water or other liquid. When crosslinked polymers are used as the support matrix, the internal porosity so defined varies in inverse proportion to the degree of crosslinkiug, with swelhng and therefore porosity typically being more... 

The decision to cathodically protect reinforced concrete structures depends on technical and economic considerations. Cathodic protection is not an economic process for small area displacements of the concrete due to corrosion of the reinforcing steel arising from insufficient concrete covering. On the other hand, the... 

Another principal difficulty is that the precise effect of local dynamics on the NOE intensity cannot be determined from the data. The dynamic correction factor [85] describes the ratio of the effects of distance and angular fluctuations. Theoretical studies based on NOE intensities extracted from molecular dynamics trajectories [86,87] are helpful to understand the detailed relationship between NMR parameters and local dynamics and may lead to structure-dependent corrections. In an implicit way, an estimate of the dynamic correction factor has been used in an ensemble relaxation matrix refinement by including order parameters for proton-proton vectors derived from molecular dynamics calculations [72]. One remaining challenge is to incorporate data describing the local dynamics of the molecule directly into the refinement, in such a way that an order parameter calculated from the calculated ensemble is similar to the measured order parameter. 

The change in the quaternary structure and the structural change in the 6-F helix as the molecule moves from one state to the other are intimately related. The dimer interactions in the T state are not compatible with the presence of the 6-F helix, which would, if present, clash with the neighbouring dimer. The quaternary structure of the T state requires that the 6-F helix be unwound. Conversely the R state quaternary structure depends on the presence of the 6-F helix. 

Operators select methods of repair for damaged bonded structure depending on the cause of the damage, size of the damage, type of bonded assembly and even the length of time until the next major overhaul of the aircraft. 

Implicit in the presumption of folding pathways is the existence of intermediate, partially folded conformational states. The notion of intermediate states on the pathway to a tertiary structure raises the possibility that segments of a protein might independently adopt local and well-defined secondary structures (a-helices and /3-sheets). The tendency of a peptide segment to prefer a particular secondary structure depends in turn on its amino acid composition and sequence. 

The composition of the mixture of products of different structures depends on the diacetylene diazomethane ratio (68LA124). With a 1 1 ratio of butadiyne and diazomethane, 3(5)-ethynylpyrazole dominates (55%). The yields of isomeric 3- and 5-ethynyl-l-methylpyrazoles are 8 and 11%, respectively. The double excess of diazomethane leads mainly to a mixture of N-methylated isomers (81%), 10% of 3(5)-ethynylpyrazole, and a small amount (3%) of bipyrazole (68LA124) (Scheme 3). 

By reaction of zinc-copper couple with diiodomethane 2 an organozinc species 4 is formed, similar to a Grignard reagent. Its structure cannot be fully described by a single structural formula. The actual structure depends on the reaction conditions—e.g. the solvent used this corresponds to the Schlenk equilibrium as it is observed with the Grignard reaction ... 

It has been shown by several authors that fee iron films exhibit a rich magnetic structure, depending very sensitively on the atomic volume. In particular in Fe... 

Isasi, J. A. and Metzger, M., Structure-dependent Corrosion of High-purity A1 in HNOj and H2SO4 , Corros. Sci., 11, 631 (1971)... 

The type of crystal structure depends on the ratio X Me, where X is the total number of anions (oxygen and fluorine) and Me is the total number of all cations that can fit into/occupy octahedral voids (tantalum, niobium, lithium and other metals with similar ionic radii). 

In this case, the elements of the crosslinked structure exhibit higher mobility, the permeability of the crosslinked structure depends on the degree of hydration. It should be noted that the pore size in hydrated crosslinked copolymers is determined by small-angle X-ray scattering or with the aid of electron microscopy using special methods of preparation for the CP samples [15],... 

The microphase structure was clearly observed in transmission electron micrographs of the film of amphiphilic copolymers cast from aqueous solutions [29, 31]. An important finding was that no microphase structure was observed for the film cast from organic solutions. This difference indicates that a microphase structure is formed in aqueous solution, but not in organic solution. Different hydrophobic groups showed considerably different morphological features i.e. whether microphase separation leads to a secondary or higher structure depends on the type of hydrophobic units in the copolymers [31],... 

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