Onion-type

Regev, D., Backov, R. and Faure, C. (2004) Gold nanopartides spontaneously generated in onion-type multilamellar vesides bilayers. Particle coupling imaged by cryo-TEM. Chemistry of Materials, 16, 5280-5285. 

Similar onion type micelles were obtained by the combination of PS-P2VP heteroarm-star copolymers with a P2VP-PEO diblock copolymer, as reported recently by Tsitsilianis et al. [269]. 

O Powerful penetrating sulfuraceous herbaceous of onion-type, but non-lachrymatory and not very tenacious. In extreme dilution sweet and more pleasant "natural" odor F Almost identical to its odor F Cooked onions... 

Figure 21.2 Assembly of mesosfructured hybrids, (a) Nanoparticles smaller than the darker gray block s R0 are miscible and assemble into a lamellar structure, (b) Nanoparticles larger than the darker gray block s R0 segregate, forming a nanoparticle-rich core around which lamellae assemble into an onion-type structure, (c) This can be used to generate compositionally heterogeneous nanostructures from tailored nanoparticle size distributions.10 (Reprinted with permission from S. C. Warren et al., Nature Mater. 2007, 6, 156-161. Copyright 2007 Macmillan Publishers Ltd.)...

Figure 21.4 Influence of nanoparticle size on silica-type mesostructuie. (a, b) TEM micrographs showing mesostructuies with a nanoparticle volume fraction

A. Onion-type Hybrid Multiscale Simulations and Algorithms 15... 

B. Application of Onion-type Hybrid Multiscale Simulation to Growth of Materials 17... 

Fig. 5. Schematic of onion-type hybrid multiscale simulation. At each scale a different model is used. Consecutive scale models are simultaneously solved in the overlap region where exchange of information occurs.

Hybrid multiscale simulation is the most developed branch of multiscale simulation and will be covered in this section. The onion-type hybrid simulation... 

Three algorithms, depicted in Fig. 4, have been proposed to solve onion-type hybrid multiscale models (Vlachos, 1997). The first applies to steady-state... 

There have been many hybrid multiscale simulations published recently in other diverse areas. It appears that the first onion-type hybrid multiscale simulation that dynamically coupled a spatially distributed 2D KMC for a surface reaction with a deterministic, continuum ODE CSTR model for the fluid phase was presented in Vlachos et al. (1990). Extension to 2D KMC coupled with ID PDE flow model was described in Vlachos (1997) and for complex reaction networks studied using 2D KMC coupled with a CSTR ODEs model in Raimondeau and Vlachos (2002a, b, 2003). Other examples from catalytic applications include Tammaro et al. (1995), Kissel-Osterrieder et al. (1998), Qin et al. (1998), and Monine et al. (2004). For reviews, see Raimondeau and Vlachos (2002a) on surface-fluid interactions and chemical reactions, and Li et al. (2004) for chemical reactors. 

The computational advantages of such multigrid methods arise from two key factors. First, microscopic simulations are carried out over microscopic length scales instead of the entire domain. For example, if the size of fine grid is 1% of the coarse grid in each dimension, the computational cost of the hybrid scheme is reduced by 10 2rf, compared with a microscopic simulation over the entire domain, where d is the dimensionality of the problem. Second, since relaxation of the microscopic model is very fast, QSS can be applied at the microscopic grid while the entire system evolves over macroscopic time scales. In other words, one needs to perform a microscopic simulation at each macroscopic node for a much shorter time than the macroscopic time increment, as was the case for the onion-type hybrid models as well. 

The discussion above focused on onion-type hybrid multiscale simulation. Finally, even though there are a limited number of examples published, I expect that the multigrid-type hybrid simulations share the same problems with onion-type hybrid multiscale models. In addition, appropriate boundary conditions for the microscopic grid model need to be developed to increase the accuracy and robustness of the hybrid scheme. Furthermore, the inverse problem of mapping coarse-grid information into a microscopic grid is ill posed. Thus, it is... 

Figure 2 Secondary electron micrographs of (a) presolar Sic, (b) presolar graphite (cauliflower type), and (c) presolar graphite (onion type). Photographs courtesy of Sachiko Amari and Scott Messenger.

The preformed Pt core may be regarded as a living-metal polymer on which the Pd atoms are deposited to give onion-type bimetallic nanoparticles (5 nm), the structure of which has been characterized by a combination of analytical methods. 

Fig. 1S.17. TEM picture of the onion-type multiplayer vesicles. (Reprinted with permission from Angeiv. Chem. Int. Ed. Engl., 2000, 39, 3310 [63].)...

FIGURE 11 Soot structure as (a) produced in the laboratory (Sergides et al, 1987), forming (b) basic structural units of 3-4 layers (Heidenreich et al, 1968), (c) randomly oriented basic structural units shown as a 2-dimensional schematic diagram, (d) onion-type particle with several condensation seeds (Heidenreich etal, 1968). 

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