RESUMEN
A theoretical framework to increase the sensitivity of graphene-based surface plasmon resonance (SPR) biosensors by the application of electrical bias voltage across the sensor surface is presented. Graphene layers deposited on thin gold film (50 nm) form the sensor surface system where the surface plasmon is excited. The real and imaginary parts of the refractive index of this gold-graphene system can be controlled by tuning its chemical potential using electrical modulation. Numerical calculations show a promising method to enhance the sensitivity of graphene-based SPR biosensors.
Asunto(s)
Electricidad , Grafito , Resonancia por Plasmón de Superficie/métodos , Propiedades de SuperficieRESUMEN
OBJECTIVES: Record femoral accelerations using a smartphone accelerometer attached to the distal thigh during single-legged (SLS) and bilateral squats, and each squat condition occurred under two visual conditions: 1) normal vision and 2) visual perturbation with stroboscopic glasses. DESIGN: Repeated-measures cross-over with counter-balanced order for four total conditions. SETTING: Laboratory. PARTICIPANTS: 22 females and 16 males without lower extremity pathologies. MAIN OUTCOME MEASURES: 2D video assessment of frontal plane projection angle, composite amplitude index of smartphone accelerometer measurements, and bivariate correlations between these two outcomes. RESULTS: A significant interaction was found for stance x vision as the difference occurred within the SLS stance condition between the visual conditions (Normal: 9.85 ± 0.06; Stroboscopic: 9.86 ± 0.07; p = 0.008 with an adjusted alpha of 0.25). Femoral accelerations were not associated (r = -0.07) with 2D video assessment of frontal plane projection angle. CONCLUSIONS: Similar to other studies using smartphone accelerometry to assess movement quality, we found that the device could detect movement variation via femoral accelerations during SLS with visual perturbation in healthy individuals.
Asunto(s)
Aceleración , Acelerometría/instrumentación , Estimulación Luminosa , Muslo/fisiología , Adulto , Fenómenos Biomecánicos , Estudios Cruzados , Femenino , Humanos , Masculino , Teléfono Inteligente , Grabación en Video , Adulto JovenRESUMEN
We characterize the instability of an rf clock signal caused by free-space transmission of a frequency comb (FC) under typical laboratory conditions. The phase-noise spectra show the involvement of multiple random processes. For a 10 m transmission, the rms timing jitter integrated over 1-10(5) Hz is 95 fs, and the root Allan variance over 1 s is 4x10(-13). The measured Allan variance has a tau(-1) behavior and an excellent agreement with the phase noise measurement. These results indicate the feasibility of FC-based free-space rf clock distribution over short distances.