Alternative Architectures

Approximately six years after Denkewalter s patent, two new architectures were published in 1985. Newkome et al. 41 relied on triester amidation with tris for the construction of polyols (8) possessing maximal 1 — 3 C-based branching. Repetition of the sequence was precluded by surface steric inhibition towards nucleophilic substitution. Tomalia et al. 42a reported the preparation of an entire series of dendrimers (9, up to the 7th tier) possessing trigonal, l— 2 N- based, branching centers. To date, availability has 

After Flory 46 and Stockmayer1471 published books describing the statistical mechanics of chain molecules and molecular fluids, respectively, which further laid the foundation of modern polymer analyses, theoretical examination of branched macromolecules continued to advance. 

Consideration was given to multibranching processes finite aggregation distribution (a sol), infinite aggregate (a gel) existence criteria, and relations for the determination of mole- and weight-average molecular masses of the finite aggregates. 

De Gennes (Nobel prize in Physics, 1991) and Hervet 51] published a statistical treatment of starburst dendrimers. They concluded from a mathematical growth model that steric hindrance limiting continued tier addition was dictated by the length of the spacer units that connect the branching centers. This reinforced the dense packing concept. 

These initial theoretical investigations, as well as the early alternative architectures that were synthesized, serve as an exordium for the expanding and synergistic discourse of dendritic material science. In-depth discussion pertaining to more recent synthetic and theoretical reports can be found beginning at Chapter 4. 

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Although linear polymers make up the bulk of commercial materials, alternate architectures such as crosslinked materials (thermosets), branched or graft copolymers, or dendrimers and hyperbranched polymers are used because of their unusual properties. 

Closing this section, a new metathesis-based method for the preparation of strictly alternating copolymers should be mentioned. Alternating diene metathesis polycondensation (ALTMET) was used to prepare a MCLCP consisting of an alternating architecture of a calamitic (linear rod-like core) and a banana-shaped (bend-shape core) mesogen (Fig. 24). 

Lipid bilayers and surface immobilized vesicles provide an alternative architecture for the micro- and nanofabrication of bioreactive and biocompatible platforms [63-67]. In recent years, the modification of solid surfaces with biological molecules has been widely studied as a means to obtain biomimetic interfaces for biomedical and environmental applications. Among the various formats of functionalized interfaces investigated, substrate-supported lipid bilayers have received considerable attention. Proteins have been successfully... 

An alternative architecture can be derived if projection along the /-axis is performed. In this case, 14 PEs are required, and non-local links should be employed in order to achieve the minimum execution time. Moreover, the methodology offers the flexibility to produce a variety of alternative arrays, depending on the specifications, by selecting DVs that lead to different partitions of the index space. 

Appropriate architectural design decisions are important for achieving quality attributes of software architectures. Reliability has not been sufficiently addressed and its quantitative impacts on software architectures have not been explicitly considered in existing software architectural design methodologies. As a result, current architectural strategies do not sufficiently consider the rationale behind the adoption of alternative architectures with respect to their reliabilities. 

Clause 7.4.4.3.2 specifies, br type A elements only, if it is determined that by following the HFT requirements specified in 7.4.4.3.1, for the situation where an HFT greater than 0 is required, additional failures would be introduced and lead to a decrease in the overall safety of the EUC, then a safer alternative architecture with reduced HFT may be implemented. In such a case this shall be justified and documented. The justification shall provide evidence that ... 

The more or less intelligent use of actuators, and therefore, of a digital network between them and the computers, is a strong alternative architecture. Boeing made a move in that direction starting with the Bill. The heart of the debate is the actuator control function. 

Figure 5.6 Alternative architecture for the shift register with synchronous initialization and aggregate array assignment.

The safety systems built on the loo2D modules have found a strong market in the general area of process plant applications. In some of the most demanding safety areas including offshore oil and gas and in the nuclear field these systems have to compete with the alternative architecture based on the principle of 2 out of 3 voting. These are known as triple modular redundant or TMR systems. The next diagram illustrates the principle. 

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