Bottom-up methods

The bottom-up method uses the same substitution and expansion techniques, except that now, the operation begins at the bottom of the tree and proceeds up. Equations containing only basic failures are successively substituted for higher faults. The bottom-up approach can be more laborious and time-consuming however, the minimal cutsets are now, 1 obtained for every intermediate fault as well as the top event. 

The bottom up methods of wet chemical nanoparticle preparation rely basically on the following methods ... 

There are several bottom-up methods for the preparation of nanoparticles and also colloidal nanometals. Amongst these, the salt-reduction method is one of the most powerful in obtaining monodisperse colloidal particles. Electrochemical methods, which gained prominence recently after the days of Faraday, are not used to prepare colloidal nanoparticles on a large scale [26, 46], The decomposition of lower valent transitional metal complexes is gaining momentum in recent years for the production of uniform particle size nanoparticles in multigram amounts [47,48],... 

The vendor claims that the IWDV process is uniquely applicable to virtually all types of buried wastes, including organic compounds, hazardous metals, and radionuclides. The bottom-up method of vitrification reduces the risk of an explosion during treatment. The electrode system requires no cooling water and operates at near 100% efficiency. 

In contrast, a new type of redox polymer-coated electrode has recently been fabricated using the bottom-up method, in which redox-active molecules are connected with molecular wires, and the wires act as the current collector.11-13 In this case, electrons can be transported through the wires, and control of the electron transfer pathway is possible by changing the structure of the molecular wires. If the wire has a linear structure, redox active molecules with the wire connections exhibit a structure similar to that of a beaded curtain (Fig. lb), in which the electron transfers in a straightforward manner along each line. Furthermore, when the wire is composed of redox active molecules, we observe the promising phenomenon that the electron transfers via the redox process in the wire, whose mechanism would... 

FIGURE 1. Two types of films with redox complexes on the electrode, (a) Conventional redox polymer film (redox sites (circles) are randomly located), (b) Highly ordered film prepared by the bottom-up method. 

In this section, we describe the fabrication of metal complex oligomer and polymer wires composed of bis(terpyridine)metal complexes using the bottom-up method.11 13 This method has an advantage in fabricating organized structures of rigid redox polymer wires with the desired numbers of redox metal complexes. We also present a new electron-transport mechanism applicable to the organized redox polymer wires-coated electrode. 

In this chapter, we presented three different systems of molecular assemblies using molecular wires. The first involved the fabrication of the molecular wire system with metal complex oligomer or polymer wires composed of bis(terpyridine)metal complexes using the bottom-up method. This system showed characteristic electron transfer distinct from conventional redox polymers. The second involved the fabrication of a photoelectric conversion system using ITO electrodes modified with porphyrin-terminated bis(terpyr-idine)metal complex wires by the stepwise coordination method, which demonstrated that the electronic nature of the molecular wire is critical to the photoelectron transfer from the porphyrin to ITO. This system proposed a new, facile fabrication method of molecular assemblies effective for photoelectron transfer. The third involved the fabrication of a bioconjugated photonic system composed of molecular wires and photosystem I. The feasibility of the biophotosensor and the biophotoelectrode has been demonstrated. This system proposed that the bioconjugation and the surface bottom-up fabrication of molecular wires are useful approaches in the development of biomo-lecular devices. These three systems of molecular assemblies will provide unprecedented functional molecular devices with desired structures and electron transfer control. 

Antisolvent precipitation is a bottom-up method wherein two phases are involved the initial creation of crystal nuclei of drugs and the subsequent growth. Formation... 

The goal of materials research is really the reverse process, the bottom-up method. In this approach, it is hoped that perfect well-controlled nanoparticles, nanostrucmres, and nanocrystals can be synthesized, which may be compacted into macroscopic nanocrystalline samples, or assembled into superlattice arrays, which may, in mrn, be used in a variety of applications such as nanoelectronic or magnetic devices. Some scientists have even envisioned a time when so-called molecular assemblers will be able to mechanically position individual atoms or molecules, one at a time, in some predefined way (Drexler, 1986). The feasibility of such machines has been hotly debated but, regardless, such systems engineering goals are not really within the scope of this chapter. At present, methods for synthesizing metal and ceramic clusters and nanoparticles fall in one of two broad categories liquid phase techniques or vapor/aerosol methods. 

Microfabrication has emerged from microelectronics manufacturing and is using its proven processes and process sequences. Additionally, specific methods have been developed to fabricate mechanical, electrical, optical, or sensor structures, which are characteristics of microfabrication. In order to stay within the scope of this book, only top-down methods, that is, the manufacture of smaller structures with higher functionality from larger structures by the use of subtractive methods, will be discussed. Bottom-up methods, which create larger structures by ordered arrangement of small units (molecules, nanoparticles), are still in their infancy and mainly employed for biosensors. 

One-way bottom-up methods. These involve a single transfer of information from a QM calculation to a classical simulation, e.g. by using QM calculations to parameterize the classical potentials used in MM force fields. 

Nanostructured metal colloids have been obtained by both top-down and bottom-up methods. The so-called top-down method is generally accomplished by... 

An experimental determination of reproducibility should also coincide with a theoretical calculation based on the known, or estimated, precision of the individual steps of the method. The so-called bottom up method as part of an uncertainty audit, is included in the principles of valid analytical measurement (YAM) [7-9],... 

This is true of the component-by-com-ponent ( bottom-up ) method for evaluating uncertainty that is directly in line with GUM. Also this is true for the top-down approach [20] that provides a valuable alternative when poorly understood steps are involved in the CMP and a full mathematical model is lacking. An important point is that the top-down methodology implies a reconciliation of information available with the required one that is based on a detailed analysis of the factors which affect the result. For both approaches to work advantageously a clear specification of the analytical procedure is evidently a necessary condition. 

There is a wide range of so-called bottom-up methods for achieving complex structural hierarchies within polyfluorene nanostructures. Synthesis of block... 

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