Structural reconfiguration

We have examined one view of structural design, and we will focus our attention later on in Section 7.4 how to reconfigure a composite structure as opposed to a metal structure. That reconfiguration process will be our principal interest. In this section, we simply address the basic structural design process irrespective of the materials used. 

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While the conditional gene knockout experiments are supportive of a role for the NMDA receptors in memory, they are less than fully conclusive in linking the synaptic coincidence-detection feature of the NMDA receptor to memory formation. Like all loss-of-function studies, CA1-specific gene-knockout experiments could, in theory, produce memory impairment via a mechanism independent of the coincidence-detection function of the NMDA receptor. For example, one may argue that the physical absence of the NMDA receptor channels may cause subtle structural reconfiguration at the synapse, thereby altering normal synaptic transmission. Therefore, the memory impairment in CA1-specific NR1 knockout mice does not allow a firm conclusion that the coincidence-detection function of NMDA receptors controls learning and memory processes at the cellular level. 

Figure 4.1 depicts the structural reconfiguration patterns. The graphical notation is used to show supply chain units added or removed as the result of reconfiguration, as well as supply chain links added or removed. This graphical representation is useful to show a to-be supply chain network after the reconfiguration assuming that the supply chain network shown in Fig. 2.3 illustrated the as-is supply chain network. 

FIGURE 3 Variable stiffness laminate materials concept for producing large structural reconfigurations. 

Figure 7-36 Configuration Trade-offs 7.4.5 Reconfiguration of Composite Structures...

Recall from discussion of the structural design process in Section 7.2 that reconfiguration of the structure is an essential step. Reconfiguration occurs either to increase the capability or to decrease the weight because the structure has more than adequate capability. The term ca-pabi/ity s meant to include margin of safety relative to fracture, adequate resistance to buckling, sufficient difference of excitation frequency from resonant frequencies, etc. 

FIGURE 6.1 Chemical structure of a-tocopherol (1) and its model compound PMC (la). Here and in the following the R-substituent denotes the Reconfigured isoprenoid C16H33 side chain of the tocopherol. 

Luminescent changes with shifts in pH usually are due to reconfiguration of a fluorophore s tt-electron cloud if an atom on the ring system becomes protonated or unprotonated. Since the BODIPY structure lacks an ionizable group, alterations in pH have no effect on its spectral attributes. 

Fig. 2.—Chemical structure of lipid A of the Escherichia coli Re mutant strain F515. The hydroxyl group at position 6 constitutes the attachment site of Kdo. The numbers in circles indicate the number of carbon atoms present in the fatty acyl chains. The 14 0(3-OH) residues possess the (Reconfiguration. The glycosylic phosphate group may be substituted by a phosphate group (see Table I) (46,65,69).

The first pH indicators studied possessed the acid-base site (phenol, aniline, or carboxylic acid) as an integral part of the fluorophore. Structurally, in the most general sense, pH sensitivity is due to a reconfiguration of the fluorophorets re-electron system that occurs on protonation. Consequently, the acid and the base forms often show absorption shifts and also, when the two forms fluoresce, emission shifts or at least, when only one form emits, a pH-dependent fluorescence intensity. This class of compounds has been reviewed 112 and the best structures have to be designed according to the medium probed and the technique used. After a short consideration of physiological pH indicators we will describe the main photophysical processes sensible to protonation. 

Maleic can be made by oxidation of butane or benzene. The process would otherwise be virtually impossible without the use of vanadium pen-toxide as the Catalyst. It enables extensive reconfiguration of either feedstoclcs molecular structure into the anhydride structure. 

Fig. 4.37 (a) On the Ir (001) surface, for an island of fewer than 6 Ir atoms, a two-dimensional structure is mctastable, whereas the linear chain structure is stable. (/) An island of 6 Ir atoms equilibrated at 460 K ( 7) one atom is field evaporated from the 6-atom island (Hi) upon heating to 450 K, the two-dimensional five-atom island reconfigures to a linear chain, (b) For an island of 6 or more Ir atoms, the linear chair is mctastable whereas the two-dimensional island is stable. (/) 6 Ir atoms in a linear chain, equilibrated at 315 K (if) upon heating to 450 K, the island transforms into a two-dimensional structure. From Schwoebcl ... 

As in the MD method, PES for KMC can be derived from first-principles methods or using empirical energy functionals described above. However, the KMC method requires the accurate evaluation of the PES not only near the local minima, but also for transition regions between them. The corresponding empirical potentials are called reactive, since they can be used to calculate parameters of chemical reactions. The development of reactive potentials is quite a difficult problem, since chemical reactions usually include the breaking or formation of new bonds and a reconfiguration of the electronic structure. At present, a few types of reactive empirical potentials can semi-quantitatively reproduce the results of first-principles calculations these are EAM and MEAM potentials for metals and bond-order potentials (Tersoff and Brenner) for covalent semiconductors and organics. 

This concept may also be extended to polynuclear helicates [38]. When 2-amino-quinoline and 4-chloroaniline were mixed with the phenanthroline dialdehyde shown in Scheme 1.10, a dynamic library of potential ligands was observed to form. The addition of copper(I) causes this library to collapse, generating only dicopper and tricopper helicates. As in the mononuclear case of Scheme 1.9, the driving force behind this selectivity appeared to be the formation of structures in which all ligand and metal valences are satisfied. The use of supramolecular (coordination) chemistry to drive the covalent reconfiguration of intraligand bonds thus... 

Two-terminal devices might seem more natural for the molecular-scale systems than three-terminal ones because of the technological difficulties in manipulating small structures. Furthermore, chemical assembly of molecular devices usually results in a periodic structure. This observation resulted in the idea to have a two-terminal switch, electronically reconfigurable, where a relatively high voltage (e.g. —2V or +2V in [62], which uses a 2-catenane-based molecule) (Fig. (7a)) is applied to close or open the switch, but a relatively low voltage to read (M). 1 V) [60]. These molecular switches [62], a mono-layer of rotaxane molecules, are not field-activated but can be described as small electro-chemical cells, which are characterized by... 

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