RESUMEN
The gate-tunable absorption properties of graphene make it suitable for terahertz (THz) absorbers. However, the realization of a graphene-based THz absorber faces challenges between the difficulty of patterning graphene for processing and the intrinsically low absorbance of graphene with the high electric field needed to change the conductivity of graphene. This report presents an electrically tunable graphene THz absorber where a single-layer graphene film and a gold reflective layer are separated by a polyimide (PI) dielectric layer to form an easily fabricated three-layer Salisbury screen structure. The carrier density of the graphene layer can be efficiently tuned by a small external electrical gating (-5V-5â V) with the assistance of an ion gel layer. The voltage modulation of the Fermi energy level (EF) of graphene was confirmed by Raman spectra, and the variation of the device absorbance was confirmed using a THz time-domain spectroscopy system (THz-TDS). The measurements show that the EF is adjusted in the range of 0-0.5â eV, and THz absorbance is adjusted in the range of 60%-99%. The absorber performs well under different curvatures, and the peak absorbance is all over 95%. We conducted further analysis of the absorber absorbance by varying the thickness of the PI dielectric layer, aiming to examine the correlation between the resonant frequency of the absorber and the dielectric layer thickness. Our research findings indicate that the proposed absorber holds significant potential for application in diverse fields such as communication, medicine, and sensing.
RESUMEN
The substrate impurities scattering will lead to unstable temperature-sensitive behavior and poor linearity in graphene temperature sensors. And this can be weakened by suspending the graphene structure. Herein, we report a graphene temperature sensing structure, with suspended graphene membranes fabricated on the cavity and non-cavity SiO2/Si substrate, using monolayer, few-layer, and multilayer graphene. The results show that the sensor provides direct electrical readout from temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which results in better sensitivity and wide-range temperature sensing. In addition, monolayer graphene is almost no temperature sensitivity. And the few-layer graphene temperature sensitivity, lower than that of the multilayer graphene cavity structure (3.50%/°C), is 1.07%/°C. This work demonstrates that piezoresistive in suspended graphene membranes can effectively enhance the sensitivity and widen the temperature sensor range in NEMS temperature sensors.
RESUMEN
OBJECTIVE: To explore the molecular mechanism of cleft palate induced by chemicals. METHODS: Retinoic acid was used as a known teratogen to induce cleft palate in ICR mice and a suppression subtractive hybridization (SSH) technique was applied to identify differentially expressed genes that related to cleft palate of ICR mice. RESULTS: 14 reverse differently and 9 forward differentially expressed clones were obtained. Some clones were selected to be sequenced and aligned to GenBank. CONCLUSION: In this study, suppressed Gpc3 and Insulin-Induced protein 1 could affect growth of palate shelves and resulted in cleft palate by reducing the size of the palate shelves. Down-regulation of Ptprs interfered with a cell signal pathway and down-regulation of Tn C inhibited the cell de-adhesion and expression of Egfr, then suppressed Egfr prevented the normal expression of MMPs that influenced the medial edge epithelium disruption and caused cleft palate. Tn C could bind to Ptprs and Gpcs, and HSPGs were ligands for Ptrps. Up-regulate of Rps25 might play a role in cleft palate by excessively apoptosis.
