Stealth radome with an ultra-broad transparent window and a high selectivity transition band.

Stealth radome (SR), especially with an ultra-broad and nearly transparent window between two absorption bands, plays a crucial role in stealth techniques, antenna radomes, and so on. However, current devices have the defects of narrow transmission bands, high insertion loss, and wide transition bands between the transmission and absorption bands, which are unfavorable for the stealth of broadband radar and communication systems. In this paper, a novel SR with an ultra-broad and high-efficiency inter-absorption band transparent window is proposed by combining broadband resonance lumped circuits with a multi-layer cascaded frequency-selective surface (FSS). The equivalent circuit model (ECM) and transmission line method (TLM) are provided and analyzed as a guideline for the SR design. The SR consists of a resistive lossy layer loaded with wide passband lumped circuits and two stacked lossless FSS layers to collectively achieve the high selectivity and ultra-broad transmission band. Simulated results indicate that the proposed SR exhibits an ultra-broad passband from 8.2 to 11.2 GHz (31%) with transmission amplitude more than 0.85 and two 90% absorption bands over 6.8-7.8 GHz and 12-13 GHz, and the transition bands at both sides are only 0.4 GHz and 0.8 GHz, respectively. Our findings can stimulate the promising applications of SR in broadband stealth devices with integrated ultra-broad communication capability or in other electromagnetic (EM) compatibility facilities.

Mid-infrared biomimetic moth-eye-shaped polarization-maintaining and angle-insensitive metalens.

Metalenses can potentially reduce the size and complexity of existing cameras, displays, and other optical devices, owing to their capability of flexible manipulation of the polarization, amplitude, and phase of light. However, metalenses capable of maintaining polarization and broadband wavefront shaping under arbitrarily polarized excitation have not been studied. In this study, we present the first demonstration of a biomimetic moth-eye-shaped metalens for polarization-maintaining, broadband and angle-insensitive focusing under an arbitrarily polarized excitation in the mid-infrared waveband (3.1-8.0 µm). Modulation and focusing efficiencies of 92% and 90%, respectively, were achieved. Moreover, a bifocal moth-eye-shaped metalens operating at normal and oblique incidences was realized. Compared to previously reported metalenses, the one proposed in this study exhibited a better focusing under oblique incidence, ensuring light transmission as effectively as a traditional lens. This study paves the way for the development of polarization-maintaining, broadband, and angle-insensitive microscale optical devices and imaging systems.

Multifunctional all-dielectric metasurface quarter-wave plates for polarization conversion and wavefront shaping.

Different from conventional optical waveplates, which suffer from limited functionalities and bulky configurations, metasurfaces provide full-range birefringence control along with unprecedented capabilities of wavefront shaping at any wavelength range of interest with properly designed anisotropic meta-atoms, thereby resulting in miniaturized planar meta-waveplates with excellent and fancy functionalities beyond the conventional counterparts. In this Letter, we design a set of dielectric metasurface quarter-wave plates (QWPs) that enable efficient circular-to-linear polarization conversion along with complete phase control over the converted linearly polarized beam under circularly polarized (CP) excitation. Capitalizing on this meta-QWP platform, we numerically demonstrate two advanced multifunctional meta-QWPs (i.e., a beam-steerer and a focusing metalens) to generate different wavefronts with homogeneous and inhomogeneous linear polarization distributions under CP excitation, mimicking the functionalities of cascaded multi-stage optical components. Owing to the compactness, flexibility, and versatility, such meta-QWPs are capable of integrating more advanced applications in polarization optics.

Helicity-dependent continuous varifocal metalens based on bilayer dielectric metasurfaces.

Metasurfaces offer a unique platform to realize flat lenses, reducing the size and complexity of imaging systems and thus enabling new imaging modalities. In this paper, we designed a bilayer helicity-dependent continuous varifocal dielectric metalens in the near-infrared range. The first layer consists of silicon nanopillars and functions as a half-wave plate, providing the helicity-dependent metasurface by combining propagation phase and geometric phase. The second layer consists of phase-change material Sb2S3 nanopillars and provides tunable propagation phases. Upon excitation with the circularly polarized waves possessing different helicities, the metalens can generate helicity-dependent longitudinal focal spots. Under the excitation of linear polarized light, the helicity-dependent dual foci are generated. The focal lengths in this metalens can be continuously tuned by the crystallization fraction of Sb2S3. The zoom range is achieved from 32.5 µm to 37.2 µm for right circularly polarized waves and from 50.5 µm to 60.9 µm for left circularly polarized waves. The simulated focusing efficiencies are above 75% and 87% for the circularly and linearly polarized waves, respectively. The proposed metalens has potential applications in miniaturized devices, including compact optical communication systems, imaging, and medical devices.

High-efficiency broadband vortex beam generator based on transmissive metasurface.

Vortex beam has attracted growing attention in recent years due to its remarkable abilities in the communication system since it is believed to be an effective way to improve the channel capacity efficiency. However, available vortex beam generators suffer from the issues of complex configurations, low efficiency as well as narrow bandwidths, especially for the transmissive case. Here, we proposed a broadband transmissive metasurface to generate vortex beam with l=1 in a broad band ranging from 8GHz to 13 GHz. We enhance the working bandwidth by carefully designing the meta-atoms which provide high transmittances along with similar slopes of the phase responses within a large frequency interval. More importantly, the designed vortex beam generator exhibits very high working efficiencies (more than 83% within the whole working band). Our finding opens a door for the design of high-efficiency broadband transmissive vortex beam generators and operating at other frequency domains.

High-efficiency transparent vortex beam generator based on ultrathin Pancharatnam-Berry metasurfaces.

Vortex beam generators are promising to improve the transmission data rate and enlarge the communication capacity due to the fact that they inherently carry the orbital angular momentum (OAM). However, current available devices are limited because of high profiles and low efficiencies, especially for the transmissive case. Here, we propose a new strategy to design an ultrathin (0.07λ0) transmissive Pancharatnam-Berry (PB) metasurface with nearly unit transmittance. The carefully optimized metasurface integrates an anisotropic crossbar structure with positive permittivity and a holey metallic ring resonator with negative permittivity based on certain criterions placed on both sides of a dielectric substrate, which realize an exact π phase difference due to the control of permittivities at both polarizations. As a proof of concept, a microwave vortex beam generator is designed, fabricated and experimentally characterized. Both measured far-field and near-field characterizations are in excellent agreement with numerical simulations, indicating that our transmissive PB meta-device (operating at 10.6 GHz) exhibits a maximum experimental efficiency of 87%. Our findings can motivate the realizations of high-performance transmissive PB meta-devices with a very low profile or operation at other frequency domains.

Physiologically Based Pharmacokinetic Modeling of Oxycodone in Children to Support Pediatric Dosing Optimization.

PURPOSE: Physiologically-based pharmacokinetic (PBPK) modeling offers a unique modality to predict age-specific pharmacokinetics. The objective of this study was to assess the ability of PBPK model to predict plasma exposure of oxycodone, a widely used opioid for pain management, in adults and children. METHODS: A full PBPK model of oxycodone following intravenous and oral administration was developed using a 'bottom-up' and 'top-down' combined strategy. The model was then extrapolated to pediatrics through a reasonable scaling method. The adult and pediatric model was evaluated using data from 17 clinical PK studies by testing predicted/observed goodness of fit. The mean fold error for PK parameters was calculated. Finally, we used the validated PBPK model to visualize adult-children dose conversion for oxycodone. RESULTS: The developed PBPK model successfully predicted the oxycodone disposition in adults, wherein the predicted versus observed AUC, Cmax, and tmax were within 0.90 to 1.20-fold difference. After scaling anatomy/physiology, protein binding, and clearance, the model showed satisfactory prediction performance for pediatric populations as predicted AUC were within the 1.50-fold range of the observed values. According to the application of PBPK model, we found that different intravenous doses should be given in children of different ages compared to a standard 0.1 mg/kg in adults, while a progressive increasing dose with age growth following oral administration is recommended for children. CONCLUSIONS: The current example provides the opportunity for using the PBPK model to guide dose adjustment of oxycodone in the design of future pediatric clinical studies.

Upregulated OCT3 has the potential to improve the survival of colorectal cancer patients treated with (m)FOLFOX6 adjuvant chemotherapy.

PURPOSE: To investigate the influence of organic cation transporter 3 (OCT3) expression on the effect of the combination regimen of 5-fluorouracil, folinic acid and oxaliplatin ((m)FOLFOX6) in colorectal cancer (CRC) patients. METHODS: This is a retrospective study conducted at a single centre (Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, China). Patients with stage IIb-IV resectable CRC who were being postoperatively treated with (m)FOLFOX6 as a first-line adjuvant chemotherapy regimen for at least 5 cycles and had resected primary tumour samples available were eligible for the study. Patients who preoperatively received chemotherapy and/or radiotherapy or were treated with targeted drugs or other anticancer drugs were excluded from the study. Immunohistochemical staining and digital image analysis were used to assess OCT3 expression in tumour samples. According to OCT3 expression level, the receiver operating characteristic curve (ROC curve) was used to divide the patients into two groups. Cox proportional risk regression was performed with the forward LR (forward stepwise regression based on maximum likelihood estimation) method using SPSS17.0 software. The primary endpoint was the 2-year progression-free survival. RESULTS: In total, 57 patients were included between 2014 and 2016 according to the inclusion and exclusion criteria (22 had low OCT3 expression, and 35 had high OCT3 expression). The mean age was 55.7 (30-74) years, and 37 of the total patients were male. According to TNM stage, 5 patients had stage IV disease, 44 patients had stage III disease, and 8 patients had stage II disease. Through Cox regression analysis, we found that among patients receiving the (m)FOLFOX6 regimen, those with higher OCT3 expression had a higher two-year progression-free survival rate than those with lower OCT3 expression (P = 0.038). The hazard ratio of patients with high OCT3 expression compared with patients with low OCT3 expression was 0.247. Besides, it was found that the age of patients was negatively correlated with expression level of OCT3, which can explain why patients over 70 years do not benefit from oxaliplatin-containing chemotherapy. CONCLUSIONS: High OCT3 expression in CRC tissues may be a protective factor for CRC patients treated with (m)FOLFOX6.

Selected and Enhanced Single Whispering-Gallery Mode Emission from a Mesostructured Nanomembrane Microcavity.

Quantum sciences are revolutionizing computing and communication technologies, in which single-photon emitters are the key components for creating strong quantum entanglement. Color centers in diamonds in coupled-cavity systems are considered great candidates for the efficient generation of quantum carriers over other solid-state emitters. Owing to the multi-mode nature of high quality factor ( Q) diamond cavities, however, it is a grand challenge to the achievement of single photon emission with high rate and indistinguishability. To this end, a single-mode high- Q diamond cavity is highly desired. Here, we report a diamond mesostructured nanomembrane microcavity of a discrete rotational symmetry that selectively produces the desired single-mode emission in a broad spectrum. The strategic rolling up of a flexible diamond nanomembrane with aligned holes effectively defines the designed symmetry while maintaining the high- Q resonance through the whispering-gallery mode supported in the central hollow microcavity. The demonstrated diamond mesostructured microcavity features a distinct and enhanced single-mode emission, a step toward efficient quantum sources with designed positions or bands for quantum information technology.

Construction of Long Narrow Gaps in Ag Nanoplates.

Hexagonal Ag nanoplates with long and ultranarrow gaps (about 90 nm in length, 2 nm in width) are synthesized via seed-mediated growth method. By growing around the polymer shell on the seed, the Ag domain cannot merge at the meet-up point, leaving a long narrow gap in the resulting plate. These gapped nanoplates exhibit high sensitivity in SERS detection, with limitation of 10-9 M for 2-naphthalenethiol.

Polarization-selective dual-wavelength gap-surface plasmon metasurfaces.

In this paper, we present a general method to realize polarization-selective dual-wavelength gap-surface plasmon metasurfaces (GSPMs), which are composed of strongly anisotropic meta-atoms periodically arranged in a rectangular lattice with two degrees of freedom to independently control the reflection phase and amplitude of orthogonal linear polarizations at two discrete wavelengths. We design and demonstrate dual-wavelength GSPMs as polarization beam splitters and focusing metamirrors operating at 850 and 1550 nm simultaneously. Our work provides a general approach to design multiwavelength, multifunctional metasurfaces with various potential applications.

Trifunctional metasurfaces: concept and characterizations.

Achieving multiple diversified functionalities in a single flat device is crucial for electromagnetic (EM) integration. While many recent efforts were devoted to designing multifunctional metasurfaces, most meta-devices realized so far typically exhibit only two functionalities. In this paper, we propose a generic strategy to design trifunctional metasurfaces, based on carefully designed single structure meta-atoms possessing polarization-controlled transmission/reflection properties. As a proof of our concept, we design and fabricate a trifunctional metasurface possessing simultaneously three distinct functionalities including beam splitting, deflecting, and focusing, and perform both far-field and near-field microwave experiments to demonstrate the predicted functionalities of the fabricated device. Experimental results are in good agreement with numerical simulations. These findings can motivate the realizations of high-performance multifunctional meta-devices in different frequency domains and with diversified functionalities.

Polypyrrole Composite Nanoparticles with Morphology-Dependent Photothermal Effect and Immunological Responses.

Polypyrrole composite nanoparticles with controlled shape are synthesized, which exhibit a morphology-dependent photothermal effect: the raspberry-like composite nanoparticles have a much better photothermal effect than the spherical ones, and the immune responses to the nanocomposites are also dependent on their morphology. The outstanding performance of the nanocomposites promises their potential application in photothermal therapy and immunotherapy of cancer.

Polarization-independent broadband meta-surface for bifunctional antenna.

Functional integration is crucial and has become a research interest in recent years; however, available efforts suffer from low efficiency and narrow operating bandwidth. Here, we propose a novel strategy to design bifunctional meta-surface with high efficiency and largely enhanced bandwidth in reflection geometry. For demonstration, we designed and fabricated a bifunctional meta-surface which enables both focusing and anomalous reflection under different polarizations. The working bandwidth is significantly extended by using the dual-resonant three-turn meander-line resonator (TMLR) element which provides an almost consistent phase response within a large frequency interval. For potential applications, we engineered a bifunctional antenna by launching the designed meta-surface with proper feed sources. Numerical and experimental results coincide well, indicating bifunctionalities of high gain pencil-beam radiation (reflectarray) and beam steering radiation with comparable performances. Our results can stimulate the realizations of high-performance meta-surfaces and antenna systems.

Low-threshold optical bistabilities in ultrathin nonlinear metamaterials.

Optical bistability typically occurs only when the optical thickness in the device or the input light power is unfavorably large. Here we show that, for a class of plasmonic metamaterials consisting of ultrathin holey metallic plates filled with nonlinear materials, the optical bistability can occur with an ultralow excitation power. We present a realistic design working at 0.2 THz and perform full-wave simulations to quantitatively study its optical bistability properties. An analytical model is developed to explain the inherent physics and provides a general design guideline for future development.

Achieving Photonic Spin Hall Effect, Spin-Selective Absorption, and Beam Deflection with a Vanadium Dioxide Metasurface.

Metasurface-based research with phase-change materials has been a prominent and rapidly developing research field that has drawn considerable attention in recent years. In this paper, we proposed a kind of tunable metasurface based on the simplest metal-insulator-metal structure, which can be realized by the mutual transformation of insulating and metallic states of vanadium dioxide (VO2) and can realize the functional switching of photonic spin Hall effect (PSHE), absorption and beam deflection at the same terahertz frequency. When VO2 is insulating, combined with the geometric phase, the metasurface can realize PSHE. A normal incident linear polarized wave will be split into two spin-polarized reflection beams traveling in two off-normal directions. When VO2 is in the metal state, the designed metasurface can be used as a wave absorber and a deflector, which will completely absorb LCP waves, while the reflected amplitude of RCP waves is 0.828 and deflects. Our design only consists of one layer of artificial structure with two materials and is easy to realize in the experiment compared with the metasurface of a multi-layer structure, which can provide new ideas for the research of tunable multifunctional metasurface.

Machine learning in predicting antimicrobial resistance: a systematic review and meta-analysis.

INTRODUCTION: Antimicrobial resistance (AMR) is a global health threat; rapid and timely identification of AMR improves patient prognosis and reduces inappropriate antibiotic use. METHODS: Relevant literature in PubMed, Web of Science, Embase and Institute of Electrical and Electronics Engineers prior to 28 September 2021 was searched. Any study that deployed machine learning (ML) or a risk score as a tool to predict AMR was included in the final review; there were 25 studies that employed the ML algorithm to predict AMR. RESULTS: Extended spectrum ß-lactamases, methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem resistance were the most common outcomes in studies with a specific resistance pattern. The most common algorithms in ML prediction were logistic regression (n = 14 studies), decision tree (n = 14) and random forest (n = 7). The area under the curve (AUC) range for ML prediction was 0.48-0.93. The pooled AUC for ML prediction was 0.82 (0.78-0.85). Compared with risk score, higher specificity [87% (82-91) vs. 37% (25-51)] was indicated for ML prediction, but not sensitivity [67% (62-72) vs. 73% (67-79)]. CONCLUSIONS: Machine learning might be a potential technology for AMR prediction; however, retrospective methodology for model development, nonstandard data processing and scarcity of validation in a randomised controlled trial or real-world study limit the application of these models in clinical practice.

Experimental Realization of a Superdispersion-Enabled Ultrabroadband Terahertz Cloak.

Invisibility has been a topic of long-standing interest owing to the advent of metamaterials and transformation optics, but still faces open challenges after its tremendous development in recent decades. One of the big challenges is the narrow bandwidth, as the realization of an invisibility cloak is usually based on a metamaterial-an artificial composite material composed of subwavelength resonator structures that are always associated with dispersion. Different from previous works that have tried to eliminate the material dispersion to enhance the bandwidth of an invisibility cloak, here, it is found that by judiciously harnessing the material dispersion, the bandwidth of the cloak can still be significantly increased. Interestingly, the material dispersion does not violate the law of causality. As a proof of concept, an ultrabroadband terahertz (THz) carpet cloak is experimentally demonstrated through an array of superdispersive microparticles, rendering the target object invisible to detection by both time- and frequency-domain wideband systems. The work presents a feasible invisibility strategy that is closer to practical applications and may pave a brand-new way for the development of dispersion-dominated ultrabroadband metadevices.

Nonlinear responses in optical metamaterials: theory and experiment.

We employed both theoretical calculations and experiments to study the nonlinear responses in optical metamaterials. The spectra of second-harmonic generations measured on a fishnet metamaterial are in quantitative agreements with calculations based on full-wave numerical simulations combined with field integrations, both exhibiting ~80 times enhancements at the magnetic resonance frequency. Our calculations explained several interesting features observed experimentally, and suggested an optimal metamaterial structure to yield the strongest nonlinear signals.

Fundamentals and applications of spin-decoupled Pancharatnam-Berry metasurfaces.

Manipulating circularly polarized (CP) electromagnetic (EM) waves at will is significantly important for a wide range of applications ranging from chiral-molecule manipulations to optical communication. However, conventional EM devices based on natural materials suffer from limited functionalities, bulky configurations, and low efficiencies. Recently, Pancharatnam-Berry (PB) phase metasurfaces have shown excellent capabilities in controlling CP waves in different frequency domains, thereby allowing for multi-functional PB meta-devices that integrate distinct functionalities into single and flat devices. Nevertheless, the PB phase has intrinsically opposite signs for two spins, resulting in locked and mirrored functionalities for right CP and left CP beams. Here we review the fundamentals and applications of spin-decoupled metasurfaces that release the spin-locked limitation of PB metasurfaces by combining the orientation-dependent PB phase and the dimension-dependent propagation phase. This provides a general and practical guideline toward realizing spin-decoupled functionalities with a single metasurface for orthogonal circular polarizations. Finally, we conclude this review with a short conclusion and personal outlook on the future directions of this rapidly growing research area, hoping to stimulate new research outputs that can be useful in future applications.