At microscale level, the mechanical response of the most anterior stroma is complex and nonlinear. The microstructure (fibers' packing, number of cross-links, water content) and the combination of elastic (collagen fibers) and viscous (matrix) components of the tissue influence the type of viscoelastic response. Efforts in modeling the biomechanics of human corneal tissue at micrometric level are needed.
It is commonly assumed that the advent of democracy tends to bring about social welfare improvements. Few studies, however, have examined empirically the impact of third-wave democratisation processes on social policies in developing countries, particularly in sub-Saharan Africa. Through a diachronic comparison, this paper examines the effects of Ghana's democratisation process on the evolution of its health policy. It shows that the emergence of democratic competition played an important role in the recent adoption of a crucial health reform. A policy feedback effect on politics and a process of international policy diffusion were additional but secondary factors.
Using an atomic force microscopy, we have measured the separation dependence of the force between an atomically flat mica sheet and a micrometer-sized glass sphere immersed in the nematic liquid crystal. As the mica surface induces a strong parallel alignment and the treated glass sphere induces a strong perpendicular alignment on the liquid crystal, a repulsive force is observed due to the elastically deformed nematic liquid crystal. We observe that below a critical separation d(th) approximately 10 nm, the system undergoes a structural transition, thus relaxing the distortion. The results are interpreted within the eigenvalue exchange mechanism using the Landau-de Gennes tensorial approach.
Articles you may be interested inFast electro-optic device controlled by dielectric response of planarly aligned cholesteric liquid crystalsThe helical flexoelectro-optic effect produces a submillisecond, temperature-independent in-plane rotation of the optical axis and is potentially interesting for the display industry. The main drawback is that it relies on a texture, the uniform lying helix ͑ULH͒, which is intrinsically unstable. We present a method based on the use of periodic polymeric microchannels to create highly ordered and stable ULH structures. Electro-optic measurements performed on a test device show a large contrast ratio between bright and dark states ͑better then 100:1͒, fast switching ͑200 s͒, and large optical rotation ͑Ͼ30°͒.
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