Experimental Demonstration of >230{\deg} Phase Modulation in Gate-Tunable Graphene-Gold Reconfigurable Mid-Infrared Metasurfaces

Metasurfaces offer significant potential to control far-field light propagation through the engineering of amplitude, polarization, and phase at an interface. We report here phase modulation of an electronically reconfigurable metasurface and demonstrate its utility for mid-infrared beam steering. Using a gate-tunable graphene-gold resonator geometry, we demonstrate highly tunable reflected phase at multiple wavelengths and show up to 237{\deg} phase modulation range at an operating wavelength of 8.50 {\mu}m. We observe a smooth monotonic modulation of phase with applied voltage from 0{\deg} to 206{\deg} at a wavelength of 8.70 {\mu}m. Based on these experimental data, we demonstrate with antenna array calculations an average beam steering efficiency of 50% for reflected light for angles up to 30{\deg}, relative to an ideal metasurface, confirming the suitability of this geometry for reconfigurable mid-infrared beam steering devices

3D-Patterned Inverse-Designed Mid-Infrared Metaoptics

Modern imaging systems can be enhanced in efficiency, compactness, and application through introduction of multilayer nanopatterned structures for manipulation of light based on its fundamental properties. High transmission efficiency multispectral imaging is surprisingly elusive due to the commonplace use of filter arrays which discard most of the incident light. Further, most cameras do not leverage the wealth of information in polarization and spatial degrees of freedom. Optical metamaterials can respond to these electromagnetic properties but have been explored primarily in single-layer geometries, limiting their performance and multifunctional capacity. Here we use advanced two-photon lithography to realize multilayer scattering structures that achieve highly nontrivial optical transformations intended to process light just before it reaches a focal plane array. Computationally optimized multispectral and polarimetric sorting devices are fabricated with submicron feature sizes and experimentally validated in the mid-infrared. A final structure shown in simulation redirects light based on its angular momentum. These devices demonstrate that with precise 3-dimensional nanopatterning, one can directly modify the scattering properties of a sensor array to create advanced imaging systems.Comment: 32 pages, 4 main figures, 12 supplementary figure

Active terahertz quantum-cascade composite right/left-handed metamaterial

We report the demonstration of a composite right/left-handed (CRLH) metamaterial waveguide for terahertz quantum-cascade (QC) lasers. By incorporating gap capacitors (∼ 250 nm) in the top metallization of a metal-metal waveguide operating in a higher order lateral mode, we have realized a CRLH transmission line that supports traveling modes with negative effective phase indices (i.e., left-handed or backward-wave propagation). The CRLH metamaterial waveguide is employed as an active leaky-wave antenna for a terahertz QC-laser. Directional single-lobed beams launched in the backwards direction at angles of - 4 ° and - 63 ° were experimentally observed at excitation frequencies 2.59 and 2.48 THz, respectively. © 2013 American Institute of Physics

Terahertz composite right-left handed transmission-line metamaterial waveguides

We report terahertz metamaterial waveguides based on the concept of composite right/left-handed transmission-lines. The waveguides are implemented in a metal-insulator-metal geometry fabricated with spin-coated Benzocyclobutene and contact photolithography. Angle-resolved reflection spectroscopy shows strong resonant absorption features corresponding to both right-handed and left-handed (backward wave) propagating modes within the leaky-wave bandwidth. Tuning of the waveguide dispersion is achieved by varying the effective lumped element series capacitance. The experimental results are in good agreement with full-wave finite element method simulations as well as an intuitive transmission-line circuit model. © 2012 American Institute of Physics

Effect of real-time computer-aided polyp detection system (ENDO-AID) on adenoma detection in endoscopists-in-training: a randomized trial

Background The effect of computer-aided polyp detection (CADe) on adenoma detection rate (ADR) among endoscopists-in-training remains unknown. Methods We performed a single-blind, parallel-group, randomized controlled trial in Hong Kong between April 2021 and July 2022 (NCT04838951). Eligible subjects undergoing screening/surveillance/diagnostic colonoscopies were randomized 1:1 to receive colonoscopies with CADe (ENDO-AID(OIP-1), Olympus Co., Japan) or not (control) during withdrawal. Procedures were performed by endoscopists-in-training with <500 procedures and <3 years’ experience. Randomization was stratified by patient age, sex, and endoscopist experience (beginner vs intermediate-level, <200 vs 200-500 procedures). Image enhancement and distal attachment devices were disallowed. Subjects with incomplete colonoscopies or inadequate bowel preparation were excluded. Treatment allocation was blinded to outcome assessors. The primary outcome was ADR. Secondary outcomes were ADR for different adenoma sizes and locations, mean number of adenomas, and non-neoplastic resection rate. Results 386 and 380 subjects were randomized to CADe and control groups, respectively. The overall ADR was significantly higher in CADe than control group (57.5% vs 44.5%, adjusted relative risk 1.41, 95%CI 1.17-1.72, p<0.001). The ADRs for <5mm (40.4% vs 25.0%) and 5-10mm adenomas (36.8% vs 29.2%) were higher in CADe group. The ADRs were higher in CADe group in both right (42.0% vs 30.8%) and left colon (34.5% vs 27.6%), but there was no significant difference in advanced ADR. The ADRs were higher in CADe group among beginners (60.0% vs 41.9%) and intermediate-level endoscopists (56.5% vs 45.5%). Mean number of adenomas (1.48 vs 0.86) and non-neoplastic resection rate were higher in CADe group (52.1% vs 35.0%). Conclusions Among endoscopists-in-training, the use of CADe during colonoscopies was associated with increased overall ADR. (ClinicalTrials.gov: NCT04838951

Metformin intervention prevents cardiac dysfunction in a murine model of adult congenital heart disease.

OBJECTIVE: Congenital heart disease (CHD) is the most frequent birth defect worldwide. The number of adult patients with CHD, now referred to as ACHD, is increasing with improved surgical and treatment interventions. However the mechanisms whereby ACHD predisposes patients to heart dysfunction are still unclear. ACHD is strongly associated with metabolic syndrome, but how ACHD interacts with poor modern lifestyle choices and other comorbidities, such as hypertension, obesity, and diabetes, is mostly unknown. METHODS: We used a newly characterized mouse genetic model of ACHD to investigate the consequences and the mechanisms associated with combined obesity and ACHD predisposition. Metformin intervention was used to further evaluate potential therapeutic amelioration of cardiac dysfunction in this model. RESULTS: ACHD mice placed under metabolic stress (high fat diet) displayed decreased left ventricular ejection fraction. Comprehensive physiological, biochemical, and molecular analysis showed that ACHD hearts exhibited early changes in energy metabolism with increased glucose dependence as main cardiac energy source. These changes preceded cardiac dysfunction mediated by exposure to high fat diet and were associated with increased disease severity. Restoration of metabolic balance by metformin administration prevented the development of heart dysfunction in ACHD predisposed mice. CONCLUSIONS: This study reveals that early metabolic impairment reinforces heart dysfunction in ACHD predisposed individuals and diet or pharmacological interventions can be used to modulate heart function and attenuate heart failure. Our study suggests that interactions between genetic and metabolic disturbances ultimately lead to the clinical presentation of heart failure in patients with ACHD. Early manipulation of energy metabolism may be an important avenue for intervention in ACHD patients to prevent or delay onset of heart failure and secondary comorbidities. These interactions raise the prospect for a translational reassessment of ACHD presentation in the clinic

Mitochondrial Uncoupling Protein-2 (UCP2) Mediates Leptin Protection Against MPP+ Toxicity in Neuronal Cells

Mitochondrial dysfunction is involved in the pathogenesis of neurodegenerative diseases, including Parkinson’s disease (PD). Uncoupling proteins (UCPs) delink ATP production from biofuel oxidation in mitochondria to reduce oxidative stress. UCP2 is expressed in brain, and has neuroprotective effects under various toxic insults. We observed induction of UCP2 expression by leptin in neuronal cultures, and hypothesize that leptin may preserve neuronal survival via UCP2. We showed that leptin preserved cell survival in neuronal SH-SY5Y cells against MPP+ toxicity (widely used in experimental Parkinsonian models) by maintaining ATP levels and mitochondrial membrane potential (MMP); these effects were accompanied by increased UCP2 expression. Leptin had no effect in modulating reactive oxygen species levels. Stable knockdown of UCP2 expression reduced ATP levels, and abolished leptin protection against MPP+-induced mitochondrial depolarization, ATP deficiency, and cell death, indicating that UCP2 is critical in mediating these neuroprotective effects of leptin against MPP+ toxicity. Interestingly, UCP2 knockdown increased UCP4 expression, but not of UCP5. Our findings show that leptin preserves cell survival by maintaining MMP and ATP levels mediated through UCP2 in MPP+-induced toxicity