Mediating particle

The four fundamental forces, their governing equations, the mediating particles, their relative magnitudes, and their ranges are listed in Table 2.1. 

Force Law Equation Mediating Particle Relative Magnitude Range... 

For nucleon-nucleon strong interactions within nuclei, pions (= two-quark particles see below) may be the mediating particles Gluons are probably not involved directly, since the nucleons have no "color charge." The inter-nucleon potential goes to zero beyond 1.7fm = 1.7 x 10-15m. 

Type of interaction Mediating particle Relative force constant... 

A novel method that is now being probed for its utility in reverse microemulsion-mediated particle synthesis and provides interesting green chemistry involves use of supercritical fluids (e.g. CO2) or compressed liquids as the oil phase. Some description has been given in Chapters 1 and 2. In a later part of this Chapter, syntheses of a variety of substances like Ag [225-227], Cu [228] and CdS [229] are discussed. 

Unlike microemulsion-mediated particle synthesis, the macroemulsion method is relatively simple and mature. The main reasons behind this are that the properties of the final products are rather easily controlled by (a) the water phase properties like viscosity and (b) the engineering aspects mentioned in Section 6.2.1. The process, thus, is stabilized for bulk production of powders. However, some new developments on the process have been reported in recent times. One of them is the emulsion combustion method described in Chapter 5 [172, 173]. In this process, atomization and firing (800"-850 C) of the emulsion leads to the formation of dry and crystalline powders that can be directly collected in a bag filter. This is also a facile procedure for obtaining hollow particles, useful for thermal insulation and various other purposes [178]. 

The microemulsion process for material synthesis and other applications has sometimes been termed an emergent technology , and therefore, new developments are also taking place to increase the suitability of the process. One such important development that has taken place in microemulsion-mediated particle synthesis is the use of water-supercritical CO2 systems [225-227, 229, 425,445]. Though this system is also valid for macro- and miniemulsions, reports of particle synthesis (metals, sulfides, halides, as above) are so far essentially microemulsion-based. As the system is environment-friendly and follows some of the important requirements of green chemistry [452], this process is expected to be further matured into a technology for nanoparticle synthesis. The present scale of operation, however, is apparently very small. 

Folate Receptor-Mediated Particle Systems for Drug and Gene Delivery in Cancer Therapy... 

Oberdorster G, Ferrin J, Morrow PE. Volumetric loading of alveolar macrophages (AM) a possible basis for diminished AM-mediated particle clearance. Exp Lung Res 1992 18 87-104. 

Alveolar macrophage-mediated particle transport was inferred from observations of particle-containing macrophages on the luminal surfaces of airways... 

Another way of approaching the problem is to put the lung into overload, which for convenience, can be defined as a situation in which administration of sufficiently high loads of nontoxic insoluble dusts produces marked prolongation or even total failure of macrophage-mediated particle clearance (reviewed in 41,91). The mechanism of the overload effect is not entirely understood (see 91-94 for comments), but it is clear that, under overload conditions, the burden of free particles in the alveoli, the number of particles that are taken up by epithelial cells, and the number of particles translocated to the interstitium, all are greatly increased (41,91). 

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