Direct-stacking models

A. Type I—Direct-Stacking Models Transthyretin and Superoxide Dismutase... 

This direct-stacking model (Olofsson et al., 2004 Serag et al., 2002) therefore proposes that TTR maintains much of its native structure, including the native dimer interface, in the fibrillar state. A new interaction interface is gained with the shifting of /(-strands at the ends of two sheets, driving fibril formation. 

D) Cartoon representation of the direct-stacking model of h/]2m fibrils, from Benya-mini et al. (2003). Rectangles represent the intact strands, where /(-strands B, E, and D mosdy obscure the view of strands F and C. /(-Strands A and G of the monomer have separated from the core (dotted lines), allowing stacking of the remaining strands to form a continuous /(-sheet. The gained interactions are indicated by the closed circles. 

In summary, two different Gain-of-Interaction models have been proposed for the fibrillar structure of /12m. The cross-(3 spine model (Ivanova et al., 2004) proposes a core composed of C-terminal /1-hairpins, and the direct-stacking model (Benyamini et al., 2003) proposes a core of native-like /12m molecules with their N- and C-terminal strands displaced. 

The initial design is analysed using CA at a component level for their combined ability to achieve the important customer requirement, this being the tolerance of 0.2 mm for the plunger displacement. Only those characteristics involved in the tolerance stack are analysed. The worst case tolerance stack model is used as directed by the customer. This model assumes that each component tolerance is at its maximum or minimum limit and that the sum of these equals the assembly tolerance, given by equation 2.16 (see Chapter 3 for a detailed discussion on tolerance stack models) ... 

Two models have been proposed for how this dimeric structure may relate to the structure of cystatin C in the fibril. The first (Janowski et at, 2001) proposes that run-away domain swapping (like that shown in Fig. 11C) can account for the assembly and stability of the fibril. In this model, one monomer would swap /(I-a 1-/12 into a second monomer, the second would swap its /(I-a 1-/12 into a third, and so on. The second model (Staniforth et al., 2001) proposes a direct stacking of domain-swapped dimers, where /i5 of each subunit of the dimer would interact with /(I of a subunit of the adjacent dimer. In this way, the dimers would stack to form continuous /1-sheets. Both models arrange the /(-sheets parallel to the fibril axis with component /(-strands perpendicular to the axis, as in a cross-/ structure, although no diffraction pattern has been reported for cystatin fibrils. 

Other types and aspects of polymer-electrolyte fuel cells have also been modeled. In this section, those models are quickly reviewed. This section is written more to inform than to analyze the various models. The outline of this section in terms of models is stack models, impedance models, direct-methanol fuel-cell models, and miscellaneous models. 

Fig. 6 Stacking model for the muconate derivatives in the crystalline state and the definition of stacking parameters used for the prediction of the topochemical polymerization reactivity, d c the intermolecular distance between the 2 and 5 carbons, is the stacking distance between the adjacent monomers in a column. 6 and 02 are the angles between the stacking direction and the molecular plane in orthogonally different directions [59]...

The Q2D approach was utilized to construct the models of PEFC [261-263] and DMFC [264, 265] stacks. Assembling the cells into a stack leads to another overhead one needs to transport the current through the bipolar plates (BPs) separating individual cells. The respective voltage loss can be calculated on the basis of the model [262]. Generally, in-plane current in BPs can flow in any direction the plates are thus true 2D objects [265], A promising approach to stack modeling would be a combination of Q2D models for the description of individual cells with fully 2D models of current and heat transport in the BPs. 

As shown in Fig. 3, the XANES spectra are similar as a whole, but clearly different from each other at individual temperatures and shift as shown by the directed arrows with increasing temperature. Two different stacking models, T and M, of the complex molecules depending on the temperature, are shown in Fig. 4(c). The bond distances and angles of the model at room temperature are shown in Table I. 

In Section 9.2 below, a summary of the nomenclature used in the chapter is given. In Section 9.3, a summary of fuel cell stack geometry, and a discussion of the dimensional reductions used in the model is given. In Section 9.4, the model of 1-D MEA transport is presented, followed by Section 9.5 on the model of channel flow for a unit cell and Section 9.6 on the electrical and thermal coupling in a stack environment. In Section 9.7, a summary of the stack model is given followed by its discretization. In Section 9.8, the iterative solution strategy for the discrete system is presented, followed by sample computational results in Section 9.9. The current state of stack modeling in this framework and future directions are summarized in the final section. 

The last term in Eq. (28.36), gext> considers aU heat fluxes in the stack direction, for example, heat exchange with a neighboring fuel cell. According to the general assumptions (see Section 28.2.1), this term is zero. However, this assumption may be lifted if this cell model is extended to a stack model (e.g., [18]). 

Assumption 2 In a unit cell of the two-scale HA model we assume a quasi-ID flow if we have a stacked model with parallel clay minerals, and the stacks are assumed to be randomly distributed. Therefore the permeability obtained by the MD/HA procedure is isotropic, and water can flow in any direction. 

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