RESUMEN
The ability of thin materials to shape-shift is a common occurrence that leads to dynamic pattern formation and function in natural and man-made structures. However, harnessing this concept to rationally design inorganic structures at the nanoscale has remained far from reach due to a lack of fundamental understanding of the essential physical components. Here, we show that the interaction between organic ligands and the nanocrystal surface is responsible for the full range of chiral shapes seen in colloidal nanoplatelets. The adsorption of ligands results in incompatible curvatures on the top and bottom surfaces of the NPL, causing them to deform into helicoïds, helical ribbons, or tubes depending on the lateral dimensions and crystallographic orientation of the NPL. We demonstrate that nanoplatelets belong to the broad class of geometrically frustrated assemblies and exhibit one of their hallmark features: a transition between helicoïds and helical ribbons at a critical width. The effective curvature [Formula: see text] is the single aggregate parameter that encodes the details of the ligand/surface interaction, determining the nanoplatelets' geometry for a given width and crystallographic orientation. The conceptual framework described here will aid the rational design of dynamic, chiral nanostructures with high fundamental and practical relevance.
RESUMEN
Estudos histológicos, histoquímicos e de microscopia eletrônica revelaram uma calcificaçäo de células da musculatura esquelética no trem posterior de camundongos infectados com Trypanosoma cruzi cepa CL. Alguns destes animais mostraram uma paralisia. A evoluçäo da calcificaçäo, incluindo a possibilidade da colaboraçäo de um vírus e um possível papel desta patologia na forma nervosa da doença de Chagas, foi discutida com dados da literatura
Asunto(s)
Ratones , Animales , Femenino , Calcinosis/patología , Enfermedad de Chagas/patología , Enfermedades Musculares/patología , Parálisis/etiologíaRESUMEN
Os autores descrevem alguns pacientes portadores de SIDA que desenvolveram artropatia dos joelhos, tornozelos e pés, mencionando os achados histopatológicos encontrados na membrana sinoval desses enfermos. Comentam, ainda, as principais possíveis causas do acometimento articular e a literatura médica pertinente