Structural deficiency

Borides, in contrast to carbides and nitrides, are characterized by an unusual structural complexity for both metal-rich and B-rich compositions. This complexity has its origin in the tendency of B atoms to form one- two-, or three-dimensional covalent arrangements and to show uncommon coordination numbers because of their large size (rg = 0.88 10 pm) and their electronic structure (deficiency in valence electrons). The structures of the transition-element borides are well established " . 

Determine if structural deficiencies exist based on structural evaluations and blast resistance required. 

The standard prescription in this situation would be to apply the ab initio methods and to attempt to take into account missing correlations in their framework. This is, however, possible only for the systems of very modest size due to the M5 -=-M7 scalability of the correlated ab initio methods already mentioned. Using DFT methods in the situation when explicit correlations are necessary may be completely wrong, due to the structural deficiency of this class of methods, which precludes any treatment of nontrivial parts of correlations, requiring multiconfigurational wave function. 

Transition metal complexes (TMCs) represent another, somewhat better known, Holy Grail of the semiempirical theory. The HFR-based semiempirical methods and the DFT-based methods suffer from structure deficiency, which does not allow it to reproduce relative energies of electronic states of different spin multiplicity within their respective frameworks without serious ad hoc assumptions. 

Nodular regenerative hyperplasia (see chapter 36.4.3) is also deemed to be a benign hyperechoic structural deficiency. These multiple foci resemble grapes in their appearance and are found in the direct vicinity of vessels, possibly causing portal hypertension. Foci are 1-3 cm in size and may easily be confused with metastases. 

Throughout the book, dehydrons will be referred to in different ways depending on the context. Thus, the terms packing defect, wrapping defect, dehydron, structural deficiency, structural vulnerability will be used synonymously. Far from introducing a notational chaos, this name multiplicity bespeaks of the richness of the concept. 

A separate analysis reveals that such proteins contain an inordinately large number of disulfide bonds, with an average of 11 when normalized to 100 amino acids. These observations prompt us to investigate the relation between structural deficiency and disulfide bonds in search for a balance equation that reflects a statistical correlation between structural strengths and vulnerabilities of soluble proteins and polypeptides. The balance equation unraveled in this chapter is likely to impact the design of soluble proteins and enable a better control of their functional modulation in relation to environmental redox conditions. 

PDB entry Disulfide bonds Chain length Structural deficiencies Backbone HBs X Y Non-a/fS residues (%)... 

The dehydron/disulfide balance relation clearly identifies proteins with excess (Y > 5X + 20) or lack (Y < 5X + 20) of structural deficiencies, with the former likely to be more favorably denatured than the latter under equivalent redox and denatura-tion conditions. To test this prediction, thermodynamic data on thermal denaturation (Table 2.2) were obtained for an exhaustive set of proteins for which structural information was also available [7], Thus, the thermal denaturation free energy change, AG, under reducing conditions and comparable temperatures [11], was obtained for monomeric uncomplexed PDB-reported proteins with disulfide bonds and lacking prosthetic groups or ion coordination. A significant anticorrelation was found... 

The baseline structural deficiency Y = 20 represents the maximum of a tight distribution (standard deviation a = 2.25) of T-values for the structural deficiency of soluble proteins with no disulfide bridges. This baseline T-value implies that soluble proteins are not perfectly packed and maintain at least 20% of unburied backbone hydrogen bonds. Since such structural deficiencies locally promote backbone hydration, they belong to an intermediate region between order and disorder and hence represent markers of structural flexibility. Thus, because of its universality, the Y = 20 constant may be interpreted as the baseline flexibility needed for protein function. 

In this chapter, dehydrons were characterized as structural deficiencies. These deficiencies are of a special kind They are promoters of backbone hydration [4] and hence destabilizers of the native structure. On the other hand, disulfide bonds pre-formed in the denatured state reduce the structure-destabilizing conformational entropy cost associated with the folding process [12], hence stabilizing the native... 

As noted in Chap. 2, the worse wrapped proteins are potassium channel neurotoxins but their buttressing is actually adequate for an extracellular protein with such a level of structural deficiency. 

Fluorite-like structures deficient in cations seem to be rare an example is NaaUFg (earlier described as NaaUF9) in which there are discrete cubic UFg groups. The arrangement of the Na ions is the same as that of two-thirds of those ions in NagllFg, as shown in Fig. 6.10. On the other hand, there are a number of phases... 

Unlike most of the other FPP competitive inhibitors, manumycin is devoid of negatively charged groups such as carboxylates and phosphates. This structural deficiency, which is a distinct liability in most of the other FPP competitive inhibitors in terms of their cell penetration, actually helps to facilitate the entry of manumycin into cells. Consequently, several reports describing the activity of manumycin A in various ras-transformed cell cultures have appeared [107-109]. More significantly, manumycin A also reduces growth of Ki-ras-transformed tumors in a dose-dependent manner in BALB/c nude mice [110]. 

The annual direet cost of corrosion may be divided into (i) cost to replace structurally deficient bridges, and (ii) corrosion-associated life-cycle cost for remaining (nondeficient) bridges, including the cost of consuiiction, routine maintenance, patching, and rehabilitation. 

There are 543,019 concrete and steel bridges of which 78,448 are structurally deficient, leaving 464,571 bridges to be maintained for estimating purposes it is assumed that all these bridges have a conventionally reinforced concrete deck. The annualized life-cycle direct cost of original construction, routine maintenance, patching and rehabilitation for a black steel rebar deck costs between 18,000 and 22,000. These costs are both corrosion- and non-corrosion related. 

A principal structural deficiency of glass fabric (E-glass) RPs was their low modulus of elasticity. Development of new, higher modulus fibers. 

Event-based models are limited in their ability to represent accidents as complex processes, particularly at representing systemic accident factors such as structural deficiencies in the organization, management deficiencies, and flaws in the safety culture of the company or industry. We need to understand how the whole system, including the organizational and social components, operating together, led to the loss. While some extensions to event-chain models have been proposed, all are unsatisfactory in important ways. 

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