Carbon particles in rubber are at first distributed as individual particles by the shearing action of milling, but the individual particles are in a state of Brownian movement due to the kinetic energy of the system. This causes the particles to drift about at a rate determined by the size of the particles, or particle aggregates, and the effective viscosity of the segments of the rubber molecules which is less than one hundredth of that of bulk rubber. The particles thus soon come into contact with each other, and since they are of a disordered crystalline structure and possess relatively high free surface forces, they cohere. The mobility of the aggregates of the particles is much less than that of the individual particles, due to their large size and size relative to that of the rubber molecules, so finally they are relatively immobilized into a scaffoldlike structure of carbon particles. This structure can be broken by external forces, and the broken structural units reform in vulcanized rubber to a structural state at a rate, and to an extent determined by the kinetic energy of the system. The idea of increasing structure formation with rise in temperature is apparently contrary to the kinetic theory, but the persistance of a stable conductivity value in passage from a high to a lower temperature rules out particle motion as the prime cause of conductivity. Furthermore the attainment of a discrete value for the conductivity (Figure 19) at any temperature rather than an alteration of the rate of change towards some maximum value, suggests that temperature activated energy barriers exist—possibly between the carbon and the rubber—which have to be broken before the carbon particles are free to move. Such a system explains the conductive properties of carbon-rubber mixes containing carbon particles of 250 to 300 A.U. diameter, but the properties of systems containing carbons of greatly different particle size may be considerably different. There is some evidence that the cohesion of carbon particles into structural units is sufficiently high to withstand the shearing forces involved during milling and processing treatments of unvulcanized rubber, and so carbon, structure formation from individual particles is of an irreversible nature. As the structural units grow in size under the influence of the kinetic energy of the system they become increasingly less mobile. This gives rise to permanent reduction in conductivity if the structure built up is violently disturbed; for example, if unvulcanized rubber is remilled after appreciable structural formation has taken place.

JNK signaling is an essential component of ATC cell proliferation and survival after radiation therapy. Hence, pharmacological interference with JNK pathway in combination with radiotherapy may be a promising treatment of ATC.

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Aneurysmal bone cyst is a benign, locally destructive lesion of bone. Based on progressive cortical thinning pathological fractures are common, and are often the presenting feature. Despite the long experience of orthopaedists, radiologists and pathologists with aneurysmal bone cyst there is limited knowledge regarding the cause of the lesion and optimal treatment. Common methods of treatment vary considerably in the literature, particularly in children. A large variety of bone substitutes have been used to fill the cystic lesions. To date there has been no graft material which can be regarded as completely satisfactory. Our experience with freshly isolated autologous bone marrow derived mononuclear cells combined with β-tricalcium phosphate and absorbable atelocollagen for bone formation is presented. The concept of this treatment is based on stimulation of natural events continuously present in living bone appear to be a reasonable and beneficial alternative to promote healing of bone cysts and offering both osteoinduction and osteoconductive features.

The processes of craniofacial tissues development and regeneration are largely dependent on sequential and reciprocal interactions between mesenchymal and epithelial components. These processes involve a series of inductive and permissive interactions that result in the determination, differentiation, and organization of craniofacial tissues. Stem cells and growth factors represent a very interesting research field for craniofacial tissues regeneration. They represent a potential key component in autologous graft for craniofacial tissues regeneration. An ideal goal of oral-craniofacial dental reconstructive therapy is to establish treatment modalities that predictably restore functional tissues. One major area of focus has been that of dental materials with marked improvements in the design of materials used to restore teeth/periodontium/bone lost as a consequence of disease or disorders. Interest in these technologies continues to increase in dental application as a substitute for traditional treatments and artificial components. Recent progress in the studies of molecular basis of tooth development, adult stem cell biology, and regeneration will provide fundamental knowledge for the realization of human craniofacial tissues regeneration in the near future.

Replacing missing bone or adding mass to existing bone is often essential to the success of a dental implant. A large variety of graft materials have been used for maxillary and mandibular atrophy. To date there has been no graft material, which can be regarded as completely satisfactory. Our experience with freshly isolated autologous bone marrow-derived mononuclear cells combined with β-tricalcium phosphate for augmentation of the extremely atrophied maxilla is presented. These techniques are based on stimulation of natural events continuously present in living bone (ie, the process of bone remodeling). The property of the mixture material for bone augmentation to place dental implant was discussed.

The processes of new vessels formation in tissues are supported by two definite mechanisms: de novo development of blood vessels (vasculogenesis) through the accumulation of progenitor cells during early prenatal stage, and extension of a pre-existing microcirculatory network by endothelial cell germination (angiogenesis), the essential mechanism of blood vessel formation in postnatal period. Angiogenesis is associated with a series of inductive, permissive and restrictive communications that result in the appearance, differentiation, and formation of new vessels. The goal of therapeutic angiogenesis is to improve blood circulation, relay survival factors and regenerative stem cell populations to sites of tissue repair, and ultimately recover function and form of the tissue. Growth factors and bone marrow mononuclear cells represent a very interesting research field for the realization of therapeutic angiogenesis in ischemic tissues. They provide a potential key component in the healing processes of ischemic injured tissues.

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