We investigated the role of zoledronic acid on the regenerate and native bone after consolidation and removal of the external fixator in a rabbit model of distraction osteogenesis using 28 New Zealand white rabbits.The rabbits were randomly distributed into two groups. The first group received three doses of zoledronic acid (ZA) 0.1 mg/kg subcutaneously at weekly intervals while the second group received injections of sterile saline. Distraction started on day 7 at a rate of 0.8 mm/day for 12 days.At week 3 the average lengthening, regenerate density, and regenerate continuity were comparable between the two groups.At week 11 the regenerate in the treated group had a significant increase in Bone Mineral Density (BMD) and Bone Mineral Content (BMC) compared to the placebo group. On axial compression, the regenerate showed an increase in the peak load and a higher modulus of elasticity in the treated group. At 6 months, radiographs demonstrated signs of osteopenia of the proximal metaphysis in the control group, and failure of new bone formation around the pin sites in the treated group. BMC and BMD value differences between the two groups were not statistically significant. Histologically, there was persistence of more bone trabeculae in the medullary canal of the regenerate with the persistence of the pin-holes in the treated group. Mechanically, the regenerates in the treated group remain stronger in resisting the axial compression. The proximal fragment in the treated group exhibited a statistically significant decrease in the peak load, toughness and efail %. In conclusion, bisphosphonate-treated rabbits have a stronger regenerate during distraction, and directly after removal of the fixator. They do not develop disuse osteopenia in their lengthened tibia. This treatment may shorten the time in the external fixator and prevent fragility fractures in the treated extremity. However, its long-term safety has not yet been established.

Carbon blacks or fullerenes mixed with a cobalt matrix have been shock compressed using a mouse-trap system. X-ray analysis has revealed the formation of cubic diamond and a turbostratic phase, while transmission electron microscopy and electron diffraction have demonstrated moreover the presence of a significant monocrystalline phase corresponding to the carbyne form. (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

We have examined by C-13 solid-state NMR crystalline quality of cubic diamond produced either via firing of explosive compositions, or through compression of mixtures containing carbonaceous precursors with metallic matrix. In particular MAS technique was used to estimate sp(3)/sp(2) phases ratios for the obtained condensed carbon, whereas functionality of surface carbon atoms was studied rather via CP-MAS method. (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

Nanodiamonds obtained from detonation of explosives with negative oxygen balance were annealed under vacuum up to 1500 degrees C and turbostratic graphitic carbon (the largest X-ray peak corresponding to d(002) = 0.344 nm) was observed. High-resolution electron microscopic observation shows the complete transformation of crystalline nanodiamonds into up to 9 concentric shells (onion-like structure). Pentagonal carbon cycles have been identified in these onion-like structures by STM. This observation is consistent with former results showing the formation of quasi-spherical particles formed by closed carbon shells either in detonation or by irradiation of soot and tubular carbon by an electron beam. These results support the idea that the usual planar graphitic structure is not the only equilibrium structure of carbon under normal conditions; the shell structure could represent a solid carbon equilibrium structure. (C) Academie des sciences/Elsevier, Paris.

A comprehensive bibliography describes the current knowledge about the synthesis of diamond. The synthesis by explosives has been realized by a simple device allowing us to follow the thermal and light effects. Carbon yields (detonation soot) are from 32 to 36% by using TNT and hexolite. The presence of diamond, about 60%, in the soot, has been confirmed by X-ray diffraction. The synthesis by shock compression has been carried out by an original device. The X-ray results of the carbon products obtained from different carbon precursors (graphite, coal, carbon black) show the presence of nanodiamonds because of the high pressure applied by our device. The diamond yield is influenced by the particle size and the dispersion of black carbon. The obtained nanodiamonds have a structure of a diamond core with a graphitic shell. It seems that the graphitic shell observed systematically around the diamond particles are formed during the regraphitisation of diamonds when the pressure drops sharply and the temperature of the sample stays high. The copper powder, acting as a thermal buffer, makes it possible to stop the process before the total graphitisation. Finally our experience shows that we can obtain diamond with all the carbon materials on condition that adequate pressures and temperatures are applied. The synthesis process of diamond by shock seems reconstructive, which could correspond to the very first steps of the synthesis by high pressure and high temperature.