Plasmon-Free Surface-Enhanced Raman Spectroscopy Using α-Type MoO3 Semiconductor Nanorods with Strong Light Scattering in the Visible Regime.

Recent developments in semiconductor-based surface-enhanced Raman scattering (SERS) have achieved numerous advancements, primarily centered on the chemical mechanism. However, the role of the electromagnetic (electromagnetic mechanism) contribution in advancing semiconductor SERS substrates is still underexplored. In this study, we developed a SERS substrate based on densely aligned α-type MoO3 (α-MoO3) semiconductor nanorods (NRs) with rectangular parallelepiped ribbon shapes with width measuring several hundred nanometers. These structural attributes strongly affect light transport in the visible range by multiple light scattering generated in narrow gaps between NRs, contributing to the improvement of SERS performance. Engineering the nanostructure and chemical composition of NRs realized high SERS sensitivity with an enhancement factor of 2 × 108 and a low detection limit of 5 × 10-9 M for rhodamine 6G (R6G) molecules, which was achieved by the stoichiometric NR sample with strong light scattering. Furthermore, it was observed that the scattering length becomes significantly shorter compared with the excitation wavelength in the visible regime, which indicates that light transport is strongly modified by mesoscopic interference related to Anderson localization. Additionally, high electric fields were found to be localized on the NR surfaces, depending on the excitation wavelength, similar to the SERS response. These optical phenomena indicate that electromagnetic excitation processes play an important role in plasmon-free SERS platforms based on α-MoO3 NRs. We postulate that our study provides important guidance for designing effective EM-based SERS-active semiconductor substrates.

Robust QRS detection based on simulated degenerate optical parametric oscillator-assisted neural network.

Accurately detecting the depolarization QRS complex in the ventricles is a fundamental requirement for cardiovascular disease detection using electrocardiography (ECG). In contrast to traditional signal enhancement algorithms, emerging neural network approaches have shown promise for QRS detection because of their generalizability on complex data. However, the inevitable noise present during ECG recording leads to a decrease in the performance of neural networks. To enhance the robustness and performance of neural network-based QRS detectors, we propose a simulated degeneration unit (SDU)-assisted convolutional neural network (CNN). An SDU simulates the physical degeneration process of interfering optical pulses, which can effectively suppress in-band noise. Through comprehensive performance evaluations on three open-source databases, the SDU-enhanced CNN-based approach demonstrated better performance in detecting QRS complexes than other recently reported QRS detectors. Furthermore, real-world noise injection tests indicate that the optimal noise robustness boundary for the CNN equipped with SDU is 167-300% higher than that for the CNN without SDU.

Revolutionary Potential of ChatGPT in Constructing Intelligent Clinical Decision Support Systems.

Recently, Chatbot Generative Pre-trained Transformer (ChatGPT) is recognized as a promising clinical decision support system (CDSS) in the medical field owing to its advanced text analysis capabilities and interactive design. However, ChatGPT primarily focuses on learning text semantics rather than learning complex data structures and conducting real-time data analysis, which typically necessitate the development of intelligent CDSS employing specialized machine learning algorithms. Although ChatGPT cannot directly execute specific algorithms, it aids in algorithm design for intelligent CDSS at the textual level. In this study, besides discussing the types of CDSS and their relationship with ChatGPT, we mainly investigate the benefits and drawbacks of employing ChatGPT as an auxiliary design tool for intelligent CDSS. Our findings indicate that by collaborating with human expertise, ChatGPT has the potential to revolutionize the development of robust and effective intelligent CDSS.

Real-time detection of acetone gas molecules at ppt levels in an air atmosphere using a partially suspended graphene surface acoustic wave skin gas sensor.

To improve the quality of modern life in the current society, low-power, highly sensitive, and reliable healthcare technology is necessary to monitor human health in real-time. In this study, we fabricated partially suspended monolayer graphene surface acoustic wave gas sensors (G-SAWs) with a love-mode wave to effectively detect ppt-level acetone gas molecules at room temperature. The sputtered SiO2 thin film on the surface of a black 36°YX-LiTaO3 (B-LT) substrate acted as a guiding layer, effectively reducing the noise and insertion loss. The G-SAWs exhibited enhanced gas response towards acetone gas molecules (800 ppt) in a real-time atmosphere. The high sensitivity of the G-SAW sensor can be attributed to the elasticity and surface roughness of the SiO2 film. In addition, the G-SAW sensor exhibited rapid response and recovery at room temperature. This study provides a potential strategy for diagnosing different stages of diabetes in the human body.

Enhancing Performance of Convolutional Neural Network-Based Epileptic Electroencephalogram Diagnosis by Asymmetric Stochastic Resonance.

Epilepsy is a chronic disorder that leads to transient neurological dysfunction and is clinically diagnosed primarily by electroencephalography. Several intelligent systems have been proposed to automatically detect seizures, among which deep convolutional neural networks (CNNs) have shown better performance than traditional machine-learning algorithms. Owing to artifacts and noise, the raw electroencephalogram (EEG) must be preprocessed to improve the signal-to-noise ratio prior to being fed into the CNN classifier. However, because of the spectrum overlapping of uncontrollable noise with EEG, traditional filters cause information loss in EEG; thus, the potential of classifiers cannot be fully exploited. In this study, we propose a stochastic resonance-effect-based EEG preprocessing module composed of three asymmetrical overdamped bistable systems in parallel. By setting different asymmetries for the three parallel units, the inherent noise can be transferred to the different spectral components of the EEG through the asymmetric stochastic resonance effect. In this process, the proposed preprocessing module not only avoids the loss of information of EEG but also provides a CNN with high-quality EEG of diversified frequency information to enhance its performance. By combining the proposed preprocessing module with a residual neural network, we developed an intelligent diagnostic system for predicting seizure onset. The developed system achieved an average sensitivity of 98.96% on the CHB-MIT dataset and 95.45% on the Siena dataset, with a false prediction rate of 0.048/h and 0.033/h, respectively. In addition, a comparative analysis demonstrated the superiority of the developed diagnostic system with the proposed preprocessing module over other existing methods.

Giant Spin-Valve Effect in Planar Spin Devices Using an Artificially Implemented Nanolength Mott-Insulator Region.

Developing technology to realize oxide-based nanoscale planar integrated circuits is in high demand for next-generation multifunctional electronics. Oxide circuits can have a variety of unique functions, including ferromagnetism, ferroelectricity, multiferroicity, superconductivity, and mechanical flexibility. In particular, for spin-transistor applications, the wide tunability of the physical properties due to the presence of multiple oxide phases is valuable for precise conductivity matching between the channel and ferromagnetic electrodes. This feature is essential for realistic spin-transistor operations. Here, a substantially large magnetoresistance (MR) ratio of up to ≈140% is demonstrated for planar-type (La,Sr)MnO3 (LSMO)-based spin-valve devices. This MR ratio is 10-100 times larger than the best values obtained for semiconductor-based planar devices, which have been studied over the past three decades. This structure is prepared by implementing an artificial nanolength Mott-insulator barrier region using the phase transition of metallic LSMO. The barrier height of the Mott-insulator region is only 55 meV, which enables the large MR ratio. Furthermore, a successful current modulation, which is a fundamental functionality for spin transistors, is shown. These results open up a new avenue for realizing oxide planar circuits with unique functionalities that conventional semiconductors cannot achieve.

Reconfigurable magnon interference by on-chip dynamic wavelength conversion.

Spin waves (SWs), an ultra-low power magnetic excitation in ferro or antiferromagnetic media, have tremendous potential as transport less data carriers for post-CMOS technology using their wave interference properties. The concept of magnon interference originates from optical interference, resulting in a historical taboo of maintaining an identical wavevector for magnon interference-based devices. This makes the attainment of on-chip design reconfigurability challenging owing to the difficulty in phase tuning via external fields. Breaking the taboo, this study explores a novel technique to systematically control magnon interference using asymmetric wavevectors from two different SW modes (magnetostatic surface SWs and backward volume magnetostatic SWs) in a microstructured yttrium iron garnet crossbar. Using this system, we demonstrate phase reconfigurability in the interference pattern by modulating the thermal landscape, modifying the dispersion of the interfering SW modes. Thus, we manifest that such a tunable interference can be used to implement reconfigurable logic gates operating between the XNOR and XOR modes by using symmetric and asymmetric interference, respectively.

Short-term memory capacity analysis of Lu3Fe4Co0.5Si0.5O12-based spin cluster glass towards reservoir computing.

Reservoir computing is a brain heuristic computing paradigm that can complete training at a high speed. The learning performance of a reservoir computing system relies on its nonlinearity and short-term memory ability. As physical implementation, spintronic reservoir computing has attracted considerable attention because of its low power consumption and small size. However, few studies have focused on developing the short-term memory ability of the material itself in spintronics reservoir computing. Among various magnetic materials, spin glass is known to exhibit slow magnetic relaxation that has the potential to offer the short-term memory capability. In this research, we have quantitatively investigated the short-term memory capability of spin cluster glass based on the prevalent benchmark. The results reveal that the magnetization relaxation of Co, Si-substituted Lu3Fe5O12 with spin glass behavior can provide higher short-term memory capacity than ferrimagnetic material without substitution. Therefore, materials with spin glass behavior can be considered as potential candidates for constructing next-generation spintronic reservoir computing with better performance.

Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer.

The two-dimensional electron gas (2DEG) formed at interfaces between SrTiO3 (STO) and other oxide insulating layers is promising for use in efficient spin-charge conversion due to the large Rashba spin-orbit interaction (RSOI). However, these insulating layers on STO prevent the propagation of a spin current injected from an adjacent ferromagnetic layer. Moreover, the mechanism of the spin-current flow in these insulating layers is still unexplored. Here, using a strongly correlated polar-metal LaTiO3+δ (LTO) interlayer and the 2DEG formed at the LTO/STO interface in an all-epitaxial heterostructure, we demonstrate giant spin-to-charge current conversion efficiencies, up to ~190 nm, using spin-pumping ferromagnetic-resonance voltage measurements. This value is the highest among those reported for all materials, including spin Hall systems. Our results suggest that the strong on-site Coulomb repulsion in LTO and the giant RSOI of LTO/STO may be the key to efficient spin-charge conversion with suppressed spin-flip scattering. Our findings highlight the hidden inherent possibilities of oxide interfaces for spin-orbitronics applications.

Sensitivity enhancement in magnetic sensor using CoFeB/Y3Fe5O12 resonator.

Magnonics, an emerging research field that uses the quanta of spin waves as data carriers, has a potential to dominate the post-CMOS era owing to its intrinsic property of ultra-low power operation. Spin waves can be manipulated by a wide range of parameters; thus, they are suitable for sensing applications in a wide range of physical fields. In this study, we designed a highly sensitive, simple structure, and ultra-low power magnetic sensor using a simple CoFeB/Y3Fe5O12 bilayer structure. We demonstrated that the CoFeB/Y3Fe5O12 bilayer structure can create a sharp rejection band in its spin-wave transmission spectra. The lowest point of this strong rejection band allows the detection of a small frequency shift owing to the external magnetic field variation. Experimental observations revealed that such a bilayer magnetic sensor exhibits 20 MHz frequency shifts upon the application of an external magnetic field of 0.5 mT. Considering the lowest full width half maximum, which is about 2 MHz, a sensitivity of 10-2 mT order can be experimentally achieved. Furthermore, the higher sensitivity in the order of 10-6 T (µT) has been demonstrated using the sharp edge of the rejection band of the CoFeB/Y3Fe5O12 bilayer device. A Y-shaped spin waves interference device with two input arms consisting of CoFeB/Y3Fe5O12 and Y3Fe5O12 has been theoretically investigated. We proposed that such a structure can demonstrate a magnetic sensitivity in the range of [Formula: see text] T (nT) at room temperature. The sensitivity of the sensor can be further enhanced by tuning the width of the CoFeB metal stripe.

Near-Zero-Index Slabs on Bloch Surface Wave Platform for Long-Range Directional Couplers and Optical Logic Gates.

Near-zero-index materials and structures, with their extraordinary optical behaviors of phase-free propagation resulting in directional radiation, provide a possible approach for directional coupling and optical logic gates in photonic integrated circuits. However, the radiation from the near-zero-index structures is limited to a short range of a few hundreds of nanometers. A Bloch surface wave (BSW), an electromagnetic surface wave that can be excited at the interface between an all-dielectric multilayer and a dielectric medium with a low-loss optical mode, provides a solution to increase the propagation length. In this work, we present a nanostructured near-zero-index slab integrated on the all-dielectric metal-free BSW platform for long-range surface wave radiation. By employing the long-range directional surface-wave radiation, a directional coupler and optical logic gates based on the BSW near-zero-index slabs are realized. The proposed directional couplers achieve long coupling distances (the electric-field magnitude ratio between the input slab and output slab is 0.22 with a 50 µm coupling distance), which is 2 orders of magnitude longer than that of conventional directional couplers based on evanescent wave coupling. By controlling the interference pattern of the BSW between the slabs, the XOR logic gate is experimentally demonstrated with a significant extinction ratio of 27.9 dB at telecommunications wavelengths. The BSW near-zero-index logic gates and the directional coupler with long-range light propagation provide an approach to the development of photonic integrated circuits and metal-free surface wave-based applications.

Broadband Dielectric Spectroscopic Analysis toward Characterization of the Hydration State and Bioprotective Superiority of Trehalose.

Alteration of the hydrogen-bond (H-bond) network by trehalose is acknowledged as a bioprotective agent. However, most studies exploring the hydration superiority of the trehalose structure are limited structure are limited by the computational cost or a narrow-range spectrum. In the present study, the structural and dynamical behaviors of the H-bond network of trehalose and maltose solutions were observed and compared with a broadband dielectric spectrum (100 MHz-18 THz) to investigate the influence of the trehalose structure on the bioprotective function. From the relaxation time, the reorientation cooperativity, resonant frequency, and damping constant of water-water vibration, the symmetric structure of trehalose allowed a more significant H-bond strengthening effect and homogeneous aqueous environment. In contrast, the difference in the hydration number between trehalose and maltose was negligible. Thus, the enhanced H-bond strengthening effect and homogeneous aqueous environment owing to the symmetric structure are the essential factors that contribute to the remarkable bioprotective effect of trehalose.

Gas Sensor Array Using a Hybrid Structure Based on Zeolite and Oxide Semiconductors for Multiple Bio-Gas Detection.

Semiconductor-type gas sensors, composed of metal-oxide semiconductors and porous zeolite materials, are attractive devices for bio-gas detection, particularly when used as bio-gas sensors such as electronic nose application. Previous studies have shown such detection can be obtained with a separate gas concentrator and a sensor device using zeolites and oxide semiconductors of WO3 nanoparticles. By applying the gas concentrator, porous molecular structures alter both the gas sensitivity and the selectivity, and even can be used to define the sensor characteristics. Based on such a gas sensor design, we investigated the properties of an array of three sensors made of a layer of WO3 nanoparticles coated with zeolites with different interactions between gas molecule adsorption and desorption. The array was tested with four volatile organic compounds, each measured at different concentrations. The results confirm that the features of individual zeolites combined with the hybrid gas sensor behavior, along with the differences among the sensors, are sufficient for enabling the discrimination of volatile compounds when disregarding their concentration.

Nonlabeled detection of specific intermolecular bondings by terahertz surface plasmon resonance of topological insulator.

The terahertz (THz) band, which corresponds to intermolecular binding energy, is the key to achieving a nonlabeled biosensor. To realize high-sensitivity binding detection, we focused on surface plasmon resonance (SPR) in the THz range. Using THz-SPR enhanced a in topological insulator, we expect to observe the synergistic effects of two resonance phenomena, namely intermolecular vibrational resonance and SPR. In this Letter, we report the nonlabeled detection of biomolecular binding by the topological insulator THz-SPR. Bi2Se3 was processed in a microribbon array to enhance the SPR in the THz range. The avidin-biotin specific binding, which is similar to the antigen-antibody reaction mechanism and has powerful interactions, was observed owing to enhancement by Bi2Se3 THz-SPR. This work paves the way for a system to directly measure specific molecular bonds using topological insulators.

High-Mobility 2D Hole Gas at a SrTiO3 Interface.

Strontium titanate (SrTiO3 or STO) is important for oxide-based electronics as it serves as a standard substrate for a wide range of high-temperature superconducting cuprates, colossal magnetoresistive manganites, and multiferroics. Moreover, in its heterostructures with different materials, STO exhibits a broad spectrum of important physics such as superconductivity, magnetism, the quantum Hall effect, giant thermoelectric effect, and colossal ionic conductivity, most of which emerge in a two-dimensional (2D) electron gas (2DEG) formed at an STO interface. However, little is known about its counterpart system, a 2D hole gas (2DHG) at the STO interface. Here, a simple way of realizing a 2DHG with an ultrahigh mobility of 24 000 cm2 V-1 s-1 is demonstrated using an interface between STO and a thin amorphous FeOy layer, made by depositing a sub-nanometer-thick Fe layer on an STO substrate at room temperature. This mobility is the highest among those reported for holes in oxides. The carrier type can be switched from p-type (2DHG) to n-type (2DEG) by controlling the Fe thickness. This unprecedented method of forming a 2DHG at an STO interface provides a pathway to unexplored hole-related physics in this system and enables extremely low-cost and high-speed oxide electronics.

Enhancing Detection Sensitivity of ZnO-Based Infrared Plasmonic Sensors Using Capped Dielectric Ga2O3 Layers for Real-Time Monitoring of Biological Interactions.

Surface plasmon resonances on Ga-doped ZnO (ZnO/Ga) layer surfaces (ZnO-SPRs) have attracted substantial attention as alternative plasmonic materials in the infrared range. We present further enhancement of the detection limits of ZnO-SPRs to monitor biological interactions by introducing thin dielectric layers into ZnO-SPRs, which remarkably modify the electric fields and the corresponding decay lengths on the sensing surfaces. The presence of a high-permittivity dielectric layer of Ga2O3 provides high wavelength sensitivities of the ZnO-SPRs due to the strongly confined electric fields. The superior sensing capabilities of the proposed samples were verified by real-time monitoring of the biological interactions between biotin and streptavidin molecules. Introduction of the high-permittivity dielectric layer into ZnO-SPRs effectively enhances the detection sensitivity and therefore allowed for the observation of biological interactions. This paper provides useful information for the development of optical detection techniques for use in biological fields based on ZnO from the viewpoints of plasmonic applications.

Hidden peculiar magnetic anisotropy at the interface in a ferromagnetic perovskite-oxide heterostructure.

Understanding and controlling the interfacial magnetic properties of ferromagnetic thin films are crucial for spintronic device applications. However, using conventional magnetometry, it is difficult to detect them separately from the bulk properties. Here, by utilizing tunneling anisotropic magnetoresistance in a single-barrier heterostructure composed of La0.6Sr0.4MnO3 (LSMO)/LaAlO3 (LAO)/Nb-doped SrTiO3 (001), we reveal the presence of a peculiar strong two-fold magnetic anisotropy (MA) along the [110]c direction at the LSMO/LAO interface, which is not observed in bulk LSMO. This MA shows unknown behavior that the easy magnetization axis rotates by 90° at an energy of 0.2 eV below the Fermi level in LSMO. We attribute this phenomenon to the transition between the e g and t 2g bands at the LSMO interface. Our finding and approach to understanding the energy dependence of the MA demonstrate a new possibility of efficient control of the interfacial magnetic properties by controlling the band structures of oxide heterostructures.

Highly sensitive SERS analysis of the cyclic Arg-Gly-Asp peptide ligands of cells using nanogap antennas.

The cyclic RGD (cRGD) peptide ligands of cells have become widely used for treating several cancers. We report a highly sensitive analysis of c(RGDfC) using surface enhanced Raman spectroscopy (SERS) using single dimer nanogap antennas in aqueous environment. Good agreement between characteristic peaks of the SERS and the Raman spectra of bulk c(RGDfC) with its peptide's constituents were observed. The exhibited blinking of the SERS spectra and synchronization of intensity fluctuations, suggest that the SERS spectra acquired from single dimer nanogap antennas was dominated by the spectrum of single to a few molecules. SERS spectra of c(RGDfC) could be used to detect at the nanoscale, the cells' transmembrane proteins binding to its ligand. SERS of cyclic RGD on nanogap antenna.

Plasmonic-Field Interactions at Nanoparticle Interfaces for Infrared Thermal-Shielding Applications Based on Transparent Oxide Semiconductors.

This paper describes infrared plasmonic responses in three-dimensional (3D) assembled films of In2O3:Sn nanoparticles (NPs). The introduction of surface modifications to NPs can facilitate the production of electric-field interactions between NPs due to the creation of narrow crevices in the NP interfaces. In particular, the electric-field interactions along the in-plane and out-of-plane directions in the 3D assembled NP films allow for resonant splitting of plasmon excitations to the quadrupole and dipole modes, thereby realizing selective high reflections in the near- and mid-infrared range, respectively. The origins of these plasmonic properties were revealed from electric-field distributions calculated by electrodynamic simulations that agreed well with experimental results. The interparticle gaps and their derived plasmon couplings play an important role in producing high reflective performances in assembled NP films. These 3D assemblies of NPs can be further extended to produce large-size flexible films with high infrared reflectance, which simultaneously exhibit microwave transmittance essential for telecommunications. This study provides important insights for harnessing infrared optical responses using plasmonic technology for the fabrication of infrared thermal-shielding applications.

Analysis of Small Ischemic Lesions in the Examinees of a Brain Dock and Neurological Examination of Animals Subjected to Cortical or Basal Ganglia Photothrombotic Infarction.

We analyzed cases of small brain ischemic lesions found in examinees of a brain dock (neurological health screening center). Small cerebral infarction was found in 17 % of the examinees (733 cases). White matter lesions were found in 24 %. Infarctions were located in the cortex or subcortical white matter in 31 % and in the basal ganglia in 44 % of cases. Infratentorial infarction was found in 1.6 %. We have developed an animal model of small infarction in the cortex or basal ganglia induced by photothrombosis in rodents. Sprague-Dawley rats or Mongolian gerbils were anesthetized and photothrombotic infarction was induced in the left caudate nucleus or parietal cortex by light exposure via an optic fiber and intravenous Rose Bengal dye injection. Histological examination revealed development of a small spherical infarction surrounding the tip of the optic fiber. The lesion turned to a cyst by 6 weeks after lesioning. Neurological deficits were found in animals both with cortical and caudate infarction. Behavioral changes in an open field test differed with the lesion site. Neurological deficits were sustained longer in animals with larger infarctions. Thus, photothrombotic infarction is useful for analyzing location-dependent and size-dependent neurological and neuropathological changes after cerebral infarction.