Structural completeness

However, the use of this method on an industrial scale is cumbersome and the question arises whether it is reasonable to form the fibre and then melt it, in order to change its structure completely. Is it not better to form a structure with a great number of tie chains required for the attainment of high strength at once during crystallization of the melt ... 

For icosahedral packing, the transition from an inner core of one spheron to one of two spherons would be expected to take place between V = 90 and N = 92. The effect of the shell structure (completed mantle at 31 rather than 32 spherons) may explain why the transition occurs over the range 88 to 92 rather than more sharply at 90 to 92. 

The finding of preparatively available iminoboranes RB = NR some years ago opened exciting new possibilities not only in B—N chemistry, but also in coordination chemistry. The first examples of iminoborane-transition-metal complexes have now been published. The structurally completely characterized t-BuB = NBu-t adds, like its alkyne analog, to the 03(00)5 fragment as a bridging ligand. When Co2(CO)g and t-BuB = NBu-t are dissolved in pentane at 0°C, warming to RT and evaporation of unreacted iminoborane yields (t-BuBNBu-t)Co2(CO)5 (86%) as a black solid, which can be recrystallized from ether-nitromethane (1 3) ... 

In semiconductors such as silicon, each atom in the structural lattice has four outer electrons, each of which covalently pairs with an electron from one of the four neighboring atoms to form the interatomic bonds, i.e.- the "diamond" structure. Completely pure silicon thus has essentially no electrons available at room temperature for electron conduction, making it a very poor conductor. However, the key is getting the silicon pure enough. Originally, silicon was thought to be a natural semi-conductor until really pure silicon became available. 

The big wheel is structurally complete without any defect in the skeleton of the crown. The cavity measures about 20 A in diameter,... 

The authors work demonstrated that even samples as small as 2.5 mg could be studied yielding data with s/n > 5 1. They further demonstrated for samples with aromatic rings that 60 Hz optimization of the experiment was beneficial and that correlations to aliphatic carbons with smaller LJcc couplings did not experience a serious adverse impact due to the larger optimization but the reverse was not true. Correlations to aromatic carbons were not amenable to optimization biased toward aliphatic carbons (e.g. 40 Hz). Correlations observed in the 1,1-ADEQUATE spectrum of retrorsine (22) are shown on the structure. Complete 1,1-ADEQUATE correlations were not shown for delcosine (23) but the authors noted that the key correlations shown on the structure that were observed in the 1,1-ADEQUATE data were not observed in the H2BC spectrum acquired. The impact of the availability of the 1,1-ADEQUATE data on the Structure Elucidator CASE program is discussed in Section 7. 

Discussing the stereochemical outcome of the Claisen rearrangements, two aspects had to be considered. On the one hand, the relative configuration of the new stereogenic centers was found to be exclusively syn in 201 and 202, pointing out the passing of a chair-like transition state c-a and c-jS, respectively, including a Z-acylammonium enolate structure (complete simple diastereo-selectivity/internal asymmetric induction). 

Because the number of protein three-dimensional structures completed is relatively small, much of our understanding of the metal center structures comes from studies on inorganic model compounds. Although it is beyond the scope of this chapter to discuss these compounds separately, we have integrated some of the results in our discussion of the relevant protein structures. 

Nevertheless, as noted by Lewis and Randall, certain post-Gibbsian addenda appeared, which will be discussed in the present section. Some of these innovations, such as activity and fugacity (Section 5.8.1), were designed primarily to satisfy practical needs of representing experimental thermochemical data, with no deeper claims on the underlying structure of the theory. In contrast, the developments initiated by Nemst s heat theorem, culminating in what became widely known as the third law of thermodynamics, appear to call into question the structural completeness of the Gibbsian formalism. These developments will be critically discussed in Section 5.8.2. 

As indicated by XRD patterns, there exist just 2-3 broad peaks in the calcined acid-made materials (Fig. 3A). Moreover, the N2 adsorption/desorption isotherm shown in Fig. 3B, the calcined acid-made mesoporous silica indeed possesses a broad capillary condensation at the partial pressure p/p0 of ca. 0.2-0.4, indicating a broad pore size distribution with a FWHM ca. 1.0 nm calculated from the BJH method. This is attributed to the occurrence of partial collapse of the mesostructure during the high temperature calcination. The hexagonal structure completely collapsed when subjected to further hydrothermal treatment in water at 100 °C for 3 h. Mesoporous silica materials synthesized from the acid route are commonly believed to be less stable than those from the alkaline route [6,7]. 

Their results demonstrated the collapse of the pore structure of A1MCM-41, which occurred upon rehydration of the sample at room temperature. This phenomena was due to the hydrolysis of the bare Si-O-Si(Al) bonds in the presence of water vapor [18], When the A1MCM-41 sample was left in contact to air for 3 months, its structure completely collapsed [19]. NbMCM-41 materials exhibit relatively high hydrothermal stability, much higher than A1MCM-41 sieves. 

Both of those cases correspond to the local configuration arising in the Goldberg-Coxeter construction (see Chapter 2). Moreover, the choice of a local configuration determines the whole structure completely, i.e. there is only one choice globally. 

The torsion angle data on earlier structures completed prior to the use of automatic diffractometers are reported elsewhere U ). 

Stabilizers can be introduced into the pellets or the washcoats with the intention of slowing down the thermally induced decrease in the surface area of the porous structure itself, or of the active component. Both, the active materials and the stabilizers, are put sometimes only on the outer layers of the pellets or monoliths, while, in other cases they penetrate the porous structures completely. Such preferential distributions have very specific aims, the utilization of the active materials and their protection from poisoning being the most important ones. There exists a vast body of patent literature on such designs. 

Thus, the secondary structure is due to H bonds between backbone atoms and is independent of primary sequence the tertiary structure is due to bonds between R-group atoms and thus depends on the amino acid sequence. For monomeric proteins, which have only one amino acid chain, the tertiary structure completes the three-dimensional description. 

Due to recent advances in membrane development, nanofiltration membranes are nowadays increasingly used for applications in organic solvents [27, 58]. This narrows the gap between pervaporation and nanofiltration. It is even possible that the requirements for membrane structures completely overlap for the two processes whereas membrane stability becomes more important for nanofiltration membranes, the performance of pervaporation membranes could be improved by using an optimized (thinner) structure for the top layers. It might even be possible to use the same membranes in both applications. At this moment it is not possible to define which membrane structure is necessary for nanofiltration or for pervaporation, and which membrane is expected to have a good performance in nanofiltration, in pervaporation or in both. Whereas pervaporation membranes are dense, nanofiltration membranes... 

Kekule valence structure. The degree of freedom has been defined as the smallest number of choices to be made in the assignment of CC double bonds which determine a Kekule valence structure completely. For example, all three Kekule valence structures of naphthalene have df = 1, because if one assigns CC double bond character to any of the three vertical CC bonds in the naphthalene diagram (Fig. 4) the location of the remaining four CC bonds is completely determined. The same is true for anthracene, tetracene, and other linearly fused benzenoids. 

The encapsulated nanotubes produced in dichloroethane are shown in Fig. 9. Their morphology and the volume structure completely correspond to the mechanism of the fast formation of a nanotube and its simultaneous encapsulation proposed in paper [6],... 

Tryptophan fluorescence is very sensitive to the local environment. In an environment with a low polarity, tryptophan emits at a maximum of 320 nm. The peak position shifts to 355 nm in the presence of a polar environment. The loss of the protein tertiary structure (complete denaturation) induces a shift in tryptophan fluorescence to 355 nm. 

The structure of cleistopholine (154), was suggested by its high-resolution mass spectrum and its IR and NMR spectra (77). The H-NMR spectrum indicated the presence of a nearly symmetrically ortho-disubstituted benzene ring and a 2,3-disubstituted 4-methylpyridine ring that could best be accommodated by the 4-methyl-l-azaanthra-9,10-quinone structure. Complete assignment of its... 

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