RESUMO
Macroscopic single-wall carbon nanotube (SWCNT) films of nanoscale thickness have significant potential for an array of applications that demand thin, transparent, conductive coatings. Using macroscopic micrometer thick polystyrene sheets as a reference, we characterize the elastic response of freestanding multifunctional SWCNT nanosheets possessing both exceptionally high Young's modulus and good durability. Thin SWCNT films (20-200 nm thick) asymmetrically "doped" with dilute concentrations of superparamagnetic colloids were suspended in ethanol as freestanding nanosheets. Through repeated and controlled deformation in an external magnetic field, we measure the temporal relaxation of nanosheet curvature back to equilibrium. From the relaxation time and its dependence on nanosheet thickness and length, we extract the SWCNT nanosheet modulus through a simple viscoelastic model. Our results are consistent with nearly ideal SWCNT rigidity percolation with moduli approaching 200 GPa and limited plasticity for sufficiently thick sheets, which we attribute to the screening of van der Waals interactions by the surrounding solvent and the macroscopic nature of the deformation.
RESUMO
Mutations inactivating the STS gene cause X-linked ichthyosis (XLI), whereas null mutations in the FLG gene cause ichthyosis vulgaris. Two brothers presented with XLI. One had a typical fine scaling, and the other was much more severely affected. Both patients carried STS missense mutation T165I. Furthermore, the more severely affected patient also carried heterozygous FLG mutation R501X, which was absent from his mildly affected brother. These data suggest that disrupting epidermal differentiation via different pathways can increase phenotypic severity. Owing to the high population frequency of FLG mutations, filaggrin is a possible genetic modifier in other genodermatoses.