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Dynamic selection of visible wavelengths using resonant TiO2 nanostructures
No full text<jats:title>Abstract</jats:title>
<jats:p>All-dielectric nanoarrays have strong electromagnetic resonances with various interesting applications and are tuned by adjusting their geometrical parameters. However, their optical properties are permanently encoded during fabrication. This study presents robust dynamically tunable all-dielectric nanoresonators for controllable, reversible, and reproducible color filtering. Our design uses an array of TiO<jats:sub>2</jats:sub> nanodiscs embedded in a transparent, stretchable polydimethylsiloxane (PDMS) membrane and exhibits a narrow spectral response due to Mie magnetic and electric dipole resonances hybridized with the TiO<jats:sub>2</jats:sub> nanodiscs lattice modes. By mechanically stretching the PDMS membrane, the pitch of the TiO<jats:sub>2</jats:sub> nanodiscs was increased and the spectral location of the resonances was altered. Additionally, an optically asymmetric structure was fabricated by partially embedding TiO<jats:sub>2</jats:sub> nanodiscs in PDMS. Thus, the magnitude of the Rayleigh anomaly diffraction, which could interrupt the dipole resonances, was reduced. Our design has sharp, frequency-tunable resonances in the visible spectrum, and we demonstrated dynamic tunability by stretching the metasurfaces.</jats:p>
Development of Multiphysics Framework to Analyze Dynamic Gap Heat Transfer and Cross-Flow Effect on Partial Rod Ejection Accident
No full textA coupling framework named Multi-Physics CORE (MPCORE) is developed to analyze the multiphysics phenomenon in a nuclear reactor. MPCORE performs two-way coupling between two physics modules. A rod ejection accident (REA) is an important design-basis accident that results in an instantaneous power surge in the case of prompt criticality. Hence, this technical note studies the passive response of a nuclear reactor core in the case of a similar rapid reactivity insertion. Stand-alone calculations by neutronics, thermal-hydraulic (TH), or fuel performance (FP) modules use conservative options for other physics modules. Thus, multiphysics analysis provides a more realistic assessment of actual prospective damage. MPCORE employs an adaptive time-step feature to reduce execution time. Moreover, it performs in-memory transfer of data between different modules. This technical note evaluates the performance of the TH module with cross flow (subchannel) and without cross flow (one-dimensional). For the FP module, the effect of dynamic and static gap heat transfer coefficient models is also quantified. Hence, four combinations with these two TH and FP options are simulated. The following are the safety parameters compared for different models: departure from nucleate boiling ratio, linear power, fuel enthalpy, fuel centerline temperature, cladding outer surface temperature, and coolant temperature
Extension of matRad with a modified microdosimetric kinetic model for carbon ion treatment planning: Comparison with Monte Carlo calculation
No full textBackgroundTreatment planning is essential for in silico particle therapy studies. matRad is an open-source research treatment planning system (TPS) based on the local effect model, which is a type of relative biological effectiveness (RBE) model. PurposeThis study aims to implement a microdosimetric kinetic model (MKM) in matRad and develop an automation algorithm for Monte Carlo (MC) dose recalculation using the TOPAS code. In addition, we provide the developed MKM extension as open-source tool for users. MethodsCarbon beam data were generated using TOPAS MC pencil beam irradiation. We parameterized the TOPAS MC beam data with a double-Gaussian fit and modeled the integral depth doses and lateral spot profiles in the range of 100-430 MeV/u. To implement the MKM, the specific energy data table for Z = 1-6 and integrated depth-specific energy data were acquired based on the Kiefer-Chatterjee track structure and TOPAS MC simulation, respectively. Generic data were integrated into matRad, and treatment planning was performed based on these data. The optimized plan parameters were automatically converted into MC simulation input. Finally, the matRad TPS and TOPAS MC simulations were compared using the RBE-weighted dose calculation results. A comparison was made for three geometries: homogeneous water phantom, inhomogeneous phantom, and patient. ResultsThe RBE-weighted dose (D-RBE) distribution agreed with TOPAS MC within 1.8% for all target sizes for the homogeneous phantom. For the inhomogeneous phantom, the relative difference in the range of 80% of the prescription dose in the distal fall-off region (R80) between the matRad TPS and TOPAS MC was 0.6% (1.1 mm). D-RBE between the TPS and the MC was within 4.0%. In the patient case, the difference in the dose-volume histogram parameters for the target volume between the TPS and the MC was less than 2.7%. The relative difference in R80 was 0.7% (1.2 mm). ConclusionsThe MKM was successfully implemented in matRad TPS, and the RBE-weighted dose was comparable to that of TOPAS MC. The MKM-implemented matRad was released as an open-source tool. Further investigations with MC simulations can be conducted using this tool, providing a good option for carbon ion research
Multimodal Wrinkle Micro-Nanoarchitectonics by Patterned Surface Material Properties for Transformative Structural Coloration
No full textWhen an external stimulus is used to generate nanoscale wrinkles on the ductile top surface of a multilayered substrate, the geometrical and optical features are known to be controlled by the material and structural properties of the laminated film. Herein, a thin tri-layer film is fabricated that can generate various wrinkles on transparent and flexible films in the presence of external mechanical bending. In particular, the wavelength of the wrinkles is shown to be controllable on the tens of nanometers scale by modulating the material properties of each layer. This active modulation plays a critical role in determining the resulting structural color spectra. In other words, the wrinkles function as a diffraction grating so that the film displays bright structural colors under bending conditions. After the bending stress is released, the wrinkles disappear, and the film returns to its transparent state. Finally, the remarkable potential of the material and structural patterning technique is demonstrated for structural coloration applications such as multimodal displays and novel barcode-based anti-counterfeiting
Synthesis of gallium phosphide quantum dots with high photoluminescence quantum yield and their application as color converters for LEDs
No full textGroup III-V quantum dots (QDs) are preferred over Group II-VI materials because of their relatively mild toxicity. In this study, a facile synthetic method to obtain gallium phosphide (GaP) QDs with color con-version performance is reported. Colloidal GaP QDs were produced via a hot-injection method using an optimized combination of precursors. The products showed controllable emissions from 400 to 520 nm, depending on the band gap. High photoluminescence (PL) quantum yields of 35-40% with a full width at half maximum (FWHM) of 75 nm were achieved in the green emission region. In addition, the green-emission GaP QDs were applied as a color-conversion material for optical devices with UV and blue LED chips. An average color conversion efficiency of 15% was achieved. This study demonstrates the pos-sibility of using GaP QDs as a competitive color-conversion material.(c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved
MicroRNA-29 Ameliorates Fibro-Inflammation and Insulin Resistance in HIF1??-Deficient Obese Adipose Tissue by Inhibiting Endotrophin Generation
No full textThe metabolic roles of type VI collagen and its cleavage peptide endotrophin in obese adipose tissue (AT) are well established. However, the mechanisms regulating endotrophin generation remain elusive. Herein, we identified that several endotrophin containing peptides were generated from the COL6A3 chain through the action of hypoxia-induced matrix metalloproteinases. Hypoxia is an upstream regulator of COL6A3 expression and the proteolytic processing that regulates endotrophin generation. Hypoxia-inducible factor 1?? and the hypoxia-associated suppression of microRNA-29 cooperatively control the levels of COL6A3 and MMPs, responsible for endotrophin generation in hypoxic ATs. Adipocyte-specific Hif1?? knock-out (APN-HIF1??KO) mice fed a chronic high-fat diet exhibited the significant amelioration of both local fibro-inflammation in AT and systemic insulin resistance compared with their control littermates, partly through the inhibition of endotrophin generation. Strikingly, adenovirus-mediated miR-29 overexpression in the ATs of APN-HIF1??KO mice in obesity significantly decreased endotrophin levels
