Here we report the observation of a linear carbon-atom chain, synthesized using an arc discharge from a graphite double anode. We use high-resolution TEM to evidence the formation of a carbon-atom chain along the axis of a needlelike structure consisting of concentric cylindrical graphitic shells. The atomic chain in the core of the innermost cylinder, by calculations on the basis of van der Waals interactions, demonstrates an extremely high thermal stability ͑up to 4200 K͒ and exhibits high mechanical strains.

The thermal conductivities of three types of single-wall carbon nanotubes are studied using the homogeneous non-equilibrium Green-Kubo method based on the Brenner potential. The thermal conductivity of a carbon nanotube is found to have dependence on its chirality. The thermal conductivities of three types of nanotube seem to have similar temperature dependence. The thermal conductivity of the chiral nanotube is lower than that of the other two types of nanotube.

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For dendritic cells (DCs) to initiate an immune response, their ability to migrate and to produce interleukin-12 (IL-12) is crucial. It has been previously shown that low-dose radiation (LDR) promoted IL-12 production by DCs, resulting in increased DC activity that contributed to LDR hormesis in the immune system. However, the molecular mechanism of LDR-induced IL-12 production, as well as the effect of LDR on DC migration capacity require further elucidation. Using the JAWSII immortalized mouse dendritic cell line, we showed that in vitro X-ray irradiation (0.2 Gy) of DCs significantly increased DC migration and IL-12 production, and upregulated CCR7. The neutralizing antibody against CCR7 has been shown to abolish LDR-enhanced DC migration, demonstrating that CCR7 mediates LDR-promoting DC migration. We identified nuclear factor kappaB (NF-κB) as the central signaling pathway that mediated LDR-enhanced expression of IL-12 and CCR7 based on findings that 0.2 Gy X-ray irradiation activated NF-κB, showing increased nuclear p65 translocation and NF-κB DNA-binding activity, while an NF-κB inhibitor blocked LDR-enhanced expression of IL-12 and CCR7, as well as DC migration. Finally, we demonstrated that 0.2 Gy X-ray irradiation promoted ATM phosphorylation and reactive oxygen species generation; however, only the ATM inhibitor abolished the LDR-induced NF-κB-mediated expression of IL-12 and CCR7. Altogether, our data show that exposure to LDR resulted in a hormetic effect on DCs regarding CCR7-mediated migration and IL-12 production by activating the ATM/NF-κB pathway.

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The thermal conductivity at 300 K of (10, 0) single-wall carbon nanotubes (SWNTs) that have been functionalized by chemical attachment of hydrogen atoms is studied by a nonequilibrium molecular dynamics (MD) method with Brenner II potential. The system exhibits a drop in thermal conductivity with functionalization. When 5% of nanotube carbon atoms are hydrogenated, the thermal conductivity is reduced by about a factor of 1.5. To clarify this effect the phonon spectra of the nanotubes are investigated.

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