In vivo super-resolution photoacoustic computed tomography by localization of single dyed droplets

The spatial resolution of photoacoustic (PA) computed tomography (PACT) is limited by acoustic diffraction. Here, we report in vivo superresolution PACT, which breaks the acoustic diffraction limit by localizing the centers of single dyed droplets. The dyed droplets generate much stronger PA signals than blood and can flow smoothly in blood vessels; thus, they are excellent tracers for localization-based superresolution imaging. The flowing droplets were first localized, and then their center positions were used to construct a superresolution image that exhibits sharper features and more finely resolved vascular details. A 6-fold improvement in spatial resolution has been realized in vivo

Entropy and a convergence theorem for Gauss curvature flow in high dimension

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Tuning the electronic properties of monolayer and bilayer PtSe\u3csub\u3e2\u3c/sub\u3e \u3ci\u3evia\u3c/i\u3e strain engineering

The recently synthesized monolayer PtSe2 belongs to the class of two-dimensional transition metal dichalcogenide (TMDC) materials (Nano Lett., 2015, 15, 4013). Based on first-principles calculations, we show that the band gaps of monolayer and bilayer PtSe2 can be tuned over a wide range via strain engineering. Both isotropic and uniaxial strains are investigated. For bilayer PtSe2, the vertical out-of-plane strain is also considered. In most cases, the strain can reduce the band gap except for the bilayer PtSe2 under the isotropic strain (Ɛ≤ 4%) for which the band gap can be slightly enlarged. Importantly, the monolayer can be transformed from the indirectgap to the direct-gap semiconductor at the compressive strain of Ɛy = -8%. Moreover, the bilayer can undergo the semiconductorto- metal (S–M) transition at a critical vertical strain due to the chemical interaction (p orbital coupling) between the Se atoms of the two opposite layers. Overall, the ability to modulate the band gap of monolayer and bilayer PtSe2 over an appreciable range of strains opens up new opportunities for their applications in nanoelectronic devices