Design and analysis of electrothermal metasurfaces

Electrothermal metasurfaces have attracted extensive attention due to their ability to dynamically control thermal infrared radiation. Although previous studies were mainly focused on the metasurfaces with infinite unit cells, the finite-size effect can be a critical design factor for developing thermal metasurfaces with fast response and broad temperature uniformity in practice. Here, we study the thermal metasurfaces consisting of gold nanorods with a finite array size, which, with only several periods, can achieve a resonance close to that of the infinite case. More importantly, such a small footprint due to the finite array size results in the response time down to a nanosecond level. Furthermore, the number of the unit cells in the direction perpendicular to the axis of the nanorods is found to be insensitive to the resonance and response time, thus providing a tunability in aspect ratio that can boost the temperature uniformity in the sub-Kelvin level.Comment: 14 pages, 5 figure

Physics-Informed Convolutional Transformer for Predicting Volatility Surface

Predicting volatility is important for asset predicting, option pricing and hedging strategies because it cannot be directly observed in the financial market. The Black-Scholes option pricing model is one of the most widely used models by market participants. Notwithstanding, the Black-Scholes model is based on heavily criticized theoretical premises, one of which is the constant volatility assumption. The dynamics of the volatility surface is difficult to estimate. In this paper, we establish a novel architecture based on physics-informed neural networks and convolutional transformers. The performance of the new architecture is directly compared to other well-known deep-learning architectures, such as standard physics-informed neural networks, convolutional long-short term memory (ConvLSTM), and self-attention ConvLSTM. Numerical evidence indicates that the proposed physics-informed convolutional transformer network achieves a superior performance than other methods.Comment: Submitted to Quantitative Financ

Effective-zero-thickness terahertz slot antennas using stepped structures

Metallic nanostructures play an essential role in electromagnetic manipulations due to the localization and enhancement of electromagnetic waves in nanogaps. Scaling down the dimensions of the gap, such as the gap width and the thickness, is an effective way to enhance light-matter interaction with colossal field enhancement. However, reducing the thickness below 10 nanometers still suffers from fabrication difficulty and unintended direct transmission through metals. Here, we fabricate effective-zero-thickness slot antennas by stepping metals in the vicinity of the gaps to confine electromagnetic waves in tiny volumes. We analyze and simulate terahertz transmission, and demonstrate the absorption enhancement of molecules in the slot antennas. Our fabrication technique provides a simple but versatile tool for maximum field enhancement and molecular sensing. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Accurate Direct Measurements of Far-Field Thermal Infrared Emission and its Dynamics

Accurate direct measurements of far-field thermal infrared emission become increasingly important because conventional methods, relying on indirect assessments, such as reflectance/transmittance, are inaccurate or even unfeasible to characterize state-of-art devices with novel spectra, directionalities, and polarizations. The direct collection of the far-field emission from these tiny devices is also challenging because of their shrinking footprints and uncontrollable radiation noises from their surroundings. Here, we demonstrate a microscopic lock-in FTIR system that realizes significant improvement in signal-to-noise ratio (SNR) by combining a microscope and a lock-in amplifier with an FTIR. The lock-in FTIR is ultrasensitive, with a specific detectivity 10^6 times higher than commercial ones, to overcome the optical loss and background noise during the emission light collection. Based on an analytical model of the signal detection process, we also explore the combination of modulated Joule heating and global heating to fulfill the potential of our system for noise reduction. Our findings show that, compared to previous studies, more than 3 times lower temperatures are sufficient to generate a measurable signal. Under a heating temperature of around 125 {\deg}C, we can achieve an SNR of about 23.7, which is far above the true-signal-threshold (SNR of about 3.0). Furthermore, the system can respond fast enough (up to 175kHz) to record spectral-resolved dynamics of microdevices in the frequency domain. The measurable frequency range can be extended up to MHz or even GHz level by a high-speed circuit model. We believe the system together with the analytical signal processing can be beneficial for next-generation thermal infrared material and device exploration, boosting the applications in lighting, sensing, imaging, and energy harvesting on a small scale.Comment: 19 pages, 4 figure

Angstrom-Scale Active Width Control of Nano Slits for Variable Plasmonic Cavity

Nanogap slits can operate as a plasmonic Fabry-Perot cavity in the visible and infrared ranges due to the gap plasmon with an increased wavenumber. Although the properties of gap plasmon are highly dependent on the gap width, active width tuning of the plasmonic cavity over the wafer length scale was barely realized. Recently, the fabrication of nanogap slits on a flexible substrate was demonstrated to show that the width can be adjusted by bending the flexible substrate. In this work, by conducting finite element method (FEM) simulation, we investigated the structural deformation of nanogap slit arrays on an outer bent polydimethylsiloxane (PDMS) substrate and the change of the optical properties. We found that the tensile deformation is concentrated in the vicinity of the gap bottom to widen the gap width proportionally to the substrate curvature. The width widening leads to resonance blueshift and field enhancement decrease. Displacement ratio ((width change)/(supporting stage translation)), which was identified to be proportional to the substrate thickness and slit period, is on the order of 10(-5) enabling angstrom-scale width control. This low displacement ratio comparable to a mechanically controllable break junction highlights the great potential of nanogap slit structures on a flexible substrate, particularly in quantum plasmonics

A case of hepatoblastoma misdiagnosed as combined hepatocellular carcinoma and cholangiocarcinoma in an adult

Hepatoblastoma usually occurs in children under the age of 2 years, with very few cases reported in adults. We experienced a case of adult hepatoblastoma in a 36-year-old female with chronic hepatitis B. She had experienced sudden onset abdominal pain. Her serum alpha-fetoprotein level was markedly elevated, and abdominal CT showed a 9-cm mass with internal hemorrhage in the right hepatic lobe with hemoperitoneum, so an emergency hepatic central bisectionectomy was performed. The initial histologic examination revealed that the mass mimicked combined hepatocellular carcinoma and cholangiocarcinoma with spindle-cell metaplasia of the cholangiocarcinoma element. Follow-up abdominal CT performed 3 months later showed a 5.5-cm metastatic mass in the left subphrenic area. Laparoscopic splenectomy with mass excision was performed, and hepatoblastoma was confirmed histologically. A histologic re-examination of previously obtained surgical specimens also confirmed the presence of hepatoblastoma. Metastatic hepatoblastoma was found at multiple sites of the abdomen during follow-up, and so chemotherapy with cisplatin, 5-fluorouracil (5-FU), and vincristine was applied, followed by carboplatin and doxorubicin. Despite surgery and postoperative chemotherapy, she died 12 months after symptom onset

Topology-Changing Broadband Metamaterials Enabled by Closable Nanotrenches

One of the most straightforward methods to actively control optical functionalities of metamaterials is to apply mechanical strain deforming the geometries. These deformations, however, leave symmetries and topologies largely intact, limiting the multifunctional horizon. Here, we present topology manipulation of metamaterials fabricated on flexible substrates by mechanically closing/opening embedded nanotrenches of various geometries. When an inner bending is applied on the substrate, the nanotrench closes and the accompanying topological change results in abrupt switching of metamaterial functionalities such as resonance, chirality, and polarization selectivity. Closable nanotrenches can be embedded in metamaterials of broadband spectrum, ranging from visible to microwave. The 99.9% extinction performance is robust, enduring more than a thousand bending cycles. Our work provides a wafer-scale platform for active quantum plasmonics and photonic application of subnanometer phenomena

Phase II randomized trial of neoadjuvant metformin plus letrozole versus placebo plus letrozole for estrogen receptor positive postmenopausal breast cancer (METEOR)

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Abstract Background Neoadjuvant endocrine therapy with an aromatase inhibitor has shown efficacy comparable to that of neoadjuvant chemotherapy in patients with postmenopausal breast cancer. Preclinical and clinical studies have shown that the antidiabetic drug metformin has anti-tumor activity. This prospective, multicenter, phase II randomized, placebo controlled trial was designed to evaluate the direct anti-tumor effect of metformin in non-diabetic postmenopausal women with estrogen-receptor (ER) positive breast cancer. Methods/Design Patients meeting the inclusion criteria and providing written informed consent will be randomized to 24 weeks of neoadjuvant treatment with letrozole (2.5 mg/day) and either metformin (2000 mg/day) or placebo. Target accrual number is 104 patients per arm. The primary endpoint will be clinical response rate, as measured by calipers. Secondary endpoints include pathologic complete response rate, breast conserving rate, change in Ki67 expression, breast density change, and toxicity profile. Molecular assays will be performed using samples obtained before treatment, at week 4, and postoperatively. Discussion This study will provide direct evidence of the anti-tumor effect of metformin in non-diabetic, postmenopausal patients with ER-positive breast cancer. Trial registration ClinicalTrials.gov Identifier NCT0158936