RESUMEN
Thousands of reports have demonstrated the exceptional performance of sensors based on carbon nanotube (CNT) transistors, with promises of transformative impact. Yet, the effect of long-term bias stress on individual CNTs, critical for most sensing applications, has remained uncertain. Here, we report bias ranges under which CNT transistors can operate continuously for months or more without degradation. Using a custom characterization system, the impacts of defect formation and charge traps on the stability of CNT-based sensors under extended bias are determined. In addition to breakdown, which is well-known, we identify three additional operational modes: full stability, slow decay, and fast decay. We identify a current drift behavior that reduces dynamic range by over four orders of magnitude but is avoidable with appropriate sensing modalities. Identification of these stable operation modes and limits for nanotube-based sensors addresses concerns surrounding their development for a myriad of sensing applications.
RESUMEN
PURPOSE: To study the extent to which patients with primary open-angle glaucoma (POAG) have subjective difficulties with dark (DA) adaptation and vision under low-luminance conditions and to correlate the reported difficulties with severity of disease, specifically visual field loss. DESIGN: Prospective, comparative case series. PARTICIPANTS: Two hundred twenty patients with and without POAG who sought treatment at an outpatient subspecialty glaucoma clinic between October 2016 and September 2018. METHODS: A questionnaire designed to assess difficulties with DA and vision under low luminance (the DA survey) was developed and given to patients during routine clinical evaluation in a hospital-based eye clinic. Retrospective data related to ocular health and glaucoma severity were abstracted from the medical record. A multiple regression analysis was performed to create a predictive model for POAG. MAIN OUTCOME MEASURES: Severity of glaucoma, specifically visual field loss, and classification of participants as glaucoma patients or control participants. RESULTS: Eighty-five patients with POAG and 127 control participants completed the questionnaire. Exploratory factor analysis of the DA survey using a principal components analysis showed that the items split into 2 dimensions: tasks that involved difficulty with vision under low luminance and those that required DA. Cronbach's α showed a high degree of internal consistency reliability (α = 0.88). Increasing DA survey score correlated with binocular visual field loss among patients with mild, moderate, and advanced POAG (P < 0.001). A model used to differentiate patients with POAG from control participants that included average and intereye difference in cup-to-disc ratio, family history of glaucoma, and DA survey score showed an accuracy, sensitivity, and specificity of 96.7%, 92.9%, and 99.2%, respectively. CONCLUSIONS: This pilot study revealed that problems with DA and vision under low luminance are commonly encountered by patients with POAG. These areas of visual disability are not assessed routinely in glaucoma care. A questionnaire assessing vision under low luminance and light-dark transitions may serve as a proxy for functional impairment in glaucoma. When paired with risk factors such as structural features of the optic nerve and family history, this survey instrument may be suitable to screen for patients with POAG.
