Epitaxial growth of β-Ga2O3 (-201) thin film on fourfold symmetry CeO2 (001) substrate for heterogeneous integrations

β-Ga2O3 is a wide bandgap semiconductor material promising for many fields such as gas sensors, UV detectors, and high power electronics. Until now, most epitaxial β-Ga2O3 thin films could only...

Micropolar Modeling of Auxetic Chiral Lattices With Tunable Internal Rotation

Based on micropolar continuum theory, the closed-form stiffness tensor of auxetic chiral lattices with V-shaped wings and rotational joints were derived. Representative volume element (RVE) of the chiral lattice was decomposed into V-shape wings with fourfold symmetry. A unified V-beam finite element was developed to reduce the nodal degrees of freedoms of the RVE to enable closed-form analytical solutions. The elasticity constants were derived as functions of the angle of the V-shaped wings, nondimensional in-plane thickness of the ribs, and the stiffness of the rotational joints. The influences of these parameters on the coupled chiral and auxetic effects were systematically explored. The results show that the elastic moduli were significantly influenced by all three parameters, while Poisson's ratio was barely influenced by the in-plane thickness of the ribs but is sensitive to the angle of the V-shaped wings and the stiffness of the rotational springs. There is a transition region out of which the spring stiffness does not considerably affect the auxeticity and the overall lattice stiffness.

A carboxyfunctionalized (24)-1,6-pyrenophane-tetraene by glyoxylic Perkin condensation

Without employing high dilution conditions, the fourfold 2+2 Perkin reaction of 1,6-pyrenylene-diglyoxylic acid with its reduction product 1,6-pyrenylene-diacetic acid yields the corresponding tetrameric conjugated macrocycle in 25% overall yield after in-situ esterification. The macrocycle adopts a square fourfold symmetry in the crystal, with near-vertical pyrene walls that alternatingly tilt upwards and downwards.