Full-range Gate-controlled Terahertz Phase Modulations with Graphene Metasurfaces

Local phase control of electromagnetic wave, the basis of a diverse set of applications such as hologram imaging, polarization and wave-front manipulation, is of fundamental importance in photonic research. However, the bulky, passive phase modulators currently available remain a hurdle for photonic integration. Here we demonstrate full-range active phase modulations in the Tera-Hertz (THz) regime, realized by gate-tuned ultra-thin reflective metasurfaces based on graphene. A one-port resonator model, backed by our full-wave simulations, reveals the underlying mechanism of our extreme phase modulations, and points to general strategies for the design of tunable photonic devices. As a particular example, we demonstrate a gate-tunable THz polarization modulator based on our graphene metasurface. Our findings pave the road towards exciting photonic applications based on active phase manipulations

Effects of sitagliptin on blood glucose, lipids, pancreatic β cell secretory function and insulin resistance in patients with type 2 diabetes mellitus

Purpose: To study the influence of sitagliptin on blood glucose, lipid and pancreatic β cell function in type II diabetes mellitus (T2DM) patients.Methods: Two groups of T2DM patients (100/group) received either metformin only (control group), or metformin plus sitaglipin (study group) for 3 months. Blood lipid profiles, fasting blood glucose (FBG), indices of pancreatic function and insulin resistance were assayed using standard biochemical methods.Results: The metformin-sitaglipin combination resulted in significant decreases in FBG, 2-h PBG, HbAlc total cholesterol (TC), triacylglycerol, and low-density lipoprotein cholesterol (LDL-C), when compared with the metformin-only treatment (p < 0.05). Although there were significant decreases in pancreatic secretion of insulin, fasting insulin, and 2 h postprandial insulin in the two groups, these parameters were significantly lower in the metformin-only treated patients than in those with combination treatment (p < 0.05).Conclusion: Sitagliptin normalizes fasting blood glucose, lipid profiles and insulin secretion in type II diabetes mellitus (T2DM) patients.Keywords: Type 2 diabetes mellitus, Sitagliptin, Blood glucose, Pancreatic islet function, Insuli