Near- and far-field study of polarization-dependent surface plasmon resonance in bowtie nano-aperture arrays.

Bowtie nano-apertures can confine light into deep subwavelength volumes with extreme field enhancement, making them a useful tool for various applications such as optical trapping, deep subwavelength imaging, nanolithography, and sensors. However, the correlation between the near- and far-field properties of bowtie nano-aperture arrays has yet to be fully explored. In this study, we experimentally investigated the polarization-dependent surface plasmon resonance in bowtie nano-aperture arrays using both optical transmission spectroscopy and photoemission electron microscopy. The experimental results reveal a nonlinear redshift in the transmission spectra as the gap size of the bowtie nanoaperture decreases for vertically polarized light, while the transmission spectra remain unchanged with different gap sizes for horizontally polarized light. To elucidate the underlying mechanisms, we present simulated charge and current distributions, revealing how the electrons respond to light and generate the plasmonic fields. These near-field distributions were verified by photoemission electron microscopy. This study provides a comprehensive understanding of the plasmonic properties of bowtie nano-aperture, enabling their further applications, one of which is the optical switching of the resonance wavelength in the widely used visible spectral region without changing the geometry of the nanostructure.

Encapsulating lithium at the microscale: selective deposition in carbon-doped graphitic carbon nitride spheres.

For stable lithium deposition without dendrites, three-dimensional (3D) porous structure has been intensively investigated. Here, we report the use of carbon-doped graphitic carbon nitride (C-doped g-C3N4) microspheres as a 3D host for lithium to suppress dendrite formation, which is crucial for stable lithium deposition. The C-doped g-C3N4microspheres have a high surface area and porosity, allowing for efficient lithium accommodation with high accessibility. The carbon-doping of the g-C3N4microspheres confers lithiophilic properties, which facilitate the regulation of Li+flux and dense filling of cavities with nucleated lithium, thereby preventing volume expansion and promoting dendrite-free Li deposition. The electrochemical performance was improved with cyclic stability and high Coulombic efficiency over 260 cycles at 1.0 mA cm-2for 1.0 mAh cm-2, and even over 70 cycles at 5.0 mA cm-2for 3.0 mAh cm-2. The use of C-doped g-C3N4microspheres as a 3D Li host shows promising results for stable lithium deposition without dendrite formation.

Geomimetic Hydrothermal Synthesis of Polyimide-Based Covalent Organic Frameworks.

Despite its abundance, water is not widely used as a medium for organic reactions. However, under geothermal conditions, water exhibits unique physicochemical properties, such as viscosity and a dielectric constant, and the ionic product become similar to those of common organic solvents. We have synthesized highly crystalline polyimide-based covalent organic frameworks (PICs) under geomimetic hydrothermal conditions. By exploiting triphenylene-2,3,6,7,10,11-hexacarboxylic acid in combination with various aromatic diamines, PICs with various pore dimensions and crystallinities were synthesized. XRD, FT-IR, and DFT calculations revealed that the solubility of the oligomeric intermediates under hydrothermal conditions affected the stacking structures of the crystalline PICs. Furthermore, the synthesized PICs demonstrate promising potential as an anode material in lithium-ion batteries owing to its unique redox-active properties and high surface area.

Understanding the Chemical Composition with Doping Aliovalent Ions, Followed by the Electrochemical Behavior for Surface-Modified Ni-Rich NMC Cathode Materials.

A comparative study of doping aliovalent ions, Zr- or Al-, into Ni-rich Li(Ni,Co,Mn)O2 cathode materials is conducted in terms of the electrochemical properties and chemical analysis, especially on the surface region. The solubility and chemical composition for the given sol-gel treatment matches well with the computational results with which the infinitesimal Zr-coating is identified as exhibiting increased charge capacity with prolonged cycle life. Specifically, the whole process can be understood by the suppressed lithium-ion charge transfer resistance (RCT) during the cycles, which can be facilitated by the decreased NiO formation during the cyclic reactions.

Compensation of a Second Harmonic Wave Included in an Incident Ultrasonic Wave for the Precise Measurement of the Acoustic Nonlinearity Parameter.

The incident second harmonic wave is a problematic issue for the precise measurement of the acoustic nonlinearity parameter. This paper proposes a compensation method to remove the effect of the incident second harmonic component in the measurement of the absolute acoustic nonlinearity parameter using the calibration method. For this, the second harmonic component detected by the receiving transducer is considered as the sum of the component due to material nonlinearity and the component included in the incident signal and a numerical calculation model is developed as a function of the propagation distance. In the model, the factors related to the material nonlinear parameter and the magnitude of the incident second harmonic component are unknown and these are determined by finding a value that best matches the experimental data according to the change in the propagation distance; compensation for the incident second harmonic component is then achieved. The case where the phase of the second harmonic wave due to material nonlinearity is opposite to that of the fundamental wave is also considered. To verify the validity of the proposed method, fused silica and aluminum alloy Al6061-T6 specimens with different thicknesses corresponding to the propagation distance are tested. The experimental results show that the nonlinear parameters changed significantly according to the propagation distance before compensation but were very stable after compensation. Additionally, the average values of the nonlinear parameter are 11.04 in the fused silica, which is within the literature value range (10.1 to 12.4), and that for the Al6061-T6 is 6.59, which is close to the literature value range (4.5 to 6.12).

Severe Fever with Thrombocytopenia Syndrome Virus in Ticks and SFTS Incidence in Humans, South Korea.

During 2016-2018, we collected 3,193 ticks from rural areas in South Korea to investigate the prevalence of severe fever with thrombocytopenia syndrome virus (SFTSV). We detected SFTSV in ticks at an infection rate (IR) of 11.1%. We noted increases in the human IR associated with the monthly SFTSV IR in ticks.

Comparison of outcomes after topography-modified refraction versus wavefront-optimized versus manifest topography-guided LASIK.

BACKGROUND: To compare the outcomes of myopia and myopic astigmatism corrected with topography-modified refraction laser in situ keratomileusis (TMR-LASIK), wavefront-optimized (WFO) LASIK, and topography-guided (TG) LASIK with a correction target based on the manifest refraction (manifest TG-LASIK). METHODS: This observational, retrospective cohort study included patients who underwent LASIK using the WaveLight® EX500 excimer laser to correct myopia and myopic astigmatism between August 2016 and July 2017. Patients who underwent TMR-LASIK (85 patients), WFO-LASIK (70 patients), or manifest TG-LASIK (40 patients) were enrolled, and only one eye from each patient was analyzed. All participants underwent measurement of the uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCVA), manifest refraction, vector analysis of astigmatic change, corneal topography, and corneal wavefront analysis at baseline and at every posttreatment visit. RESULTS: Three months postoperatively, a UDVA of 0.0 logMAR or better and manifest refraction spherical equivalent (MRSE) within ±0.5 diopters (D) did not differ across the TMR-, WFO-, and manifest TG-LASIK groups. However, the residual cylinder in the TMR group was significantly larger than that in the WFO and manifest TG groups. The magnitude of error in the TMR group measured using astigmatism vector analysis was significantly higher than that in the WFO and manifest TG groups. CONCLUSIONS: Although these three LASIK platforms achieved the predicted surgical outcomes, TMR-LASIK overcorrected astigmatism and showed a higher residual postoperative astigmatism compared with WFO- and manifest TG-LASIK.

Changes in timing of seasonal peak photosynthetic activity in northern ecosystems.

Seasonality in photosynthetic activity is a critical component of seasonal carbon, water, and energy cycles in the Earth system. This characteristic is a consequence of plant's adaptive evolutionary processes to a given set of environmental conditions. Changing climate in northern lands (>30°N) alters the state of climatic constraints on plant growth, and therefore, changes in the seasonality and carbon accumulation are anticipated. However, how photosynthetic seasonality evolved to its current state, and what role climatic constraints and their variability played in this process and ultimately in carbon cycle is still poorly understood due to its complexity. Here, we take the "laws of minimum" as a basis and introduce a new framework where the timing (day of year) of peak photosynthetic activity (DOYPmax ) acts as a proxy for plant's adaptive state to climatic constraints on its growth. Our analyses confirm that spatial variations in DOYPmax reflect spatial gradients in climatic constraints as well as seasonal maximum and total productivity. We find a widespread warming-induced advance in DOYPmax (-1.66 ± 0.30 days/decade, p < 0.001) across northern lands, indicating a spatiotemporal dynamism of climatic constraints to plant growth. We show that the observed changes in DOYPmax are associated with an increase in total gross primary productivity through enhanced carbon assimilation early in the growing season, which leads to an earlier phase shift in land-atmosphere carbon fluxes and an increase in their amplitude. Such changes are expected to continue in the future based on our analysis of earth system model projections. Our study provides a simplified, yet realistic framework based on first principles for the complex mechanisms by which various climatic factors constrain plant growth in northern ecosystems.

Characterization of Ti3+-doped TiO2 based composite electrode for lithium polymer secondary batteries.

Ti3+-doped TiO2 nanoparticles were synthesized and fabricated into a composite electrode as an anode material for lithium polymer batteries. The composite electrode contained polymer electrolyte (PE) to reduce interfacial resistance between the solid PE and electrode. The effect of PE content on the composite electrodes was analyzed by GITT, and it was found that PE significantly influenced lithium storage as well as internal resistance. A composite electrode was fabricated into a pouch type cell and exhibited a capacity of 160 mAh g-1 in the bent state, demonstrating the applicability of the Ti3+-doped TiO2 based composite electrode in lithium polymer secondary batteries.

Electromagnetic Acoustic Transducers for Robotic Nondestructive Inspection in Harsh Environments.

Elevated temperature, gamma radiation, and geometric constraints inside dry storage casks for spent nuclear fuel represent a harsh environment for nondestructive inspection of the cask and require that the inspection be conducted with a robotic system. Electromagnetic acoustic transducers (EMATs) using non-contact ultrasonic transduction based on the Lorentz force to excite/receive ultrasonic waves are suited for use in the robotic inspection. Periodic permanent magnet EMATs that actuate/receive shear horizontal guided waves are developed for application to robotic nondestructive inspection of stress corrosion cracks in the heat affected zone of welds in stainless steel dry storage canisters. The EMAT's components are carefully selected in consideration of the inspection environment, and tested under elevated temperature and gamma radiation doses up to 177 °C and 5920 krad, respectively, to evaluate the performance of the EMATs under realistic environmental conditions. The effect of gamma radiation is minimal, but the EMAT's performance is affected by temperatures above 121 °C due to the low Curie temperature of the magnets. Different magnets are needed to operate at 177 °C. The EMAT's capability to detect notches is also evaluated from B-scan measurements on 304 stainless steel welded plate containing surface-breaking notches.

Self-assembly of core-shell structures driven by low doping limit of Ti in LiCoO2: first-principles thermodynamic and experimental investigation.

Introducing additives is a general method of performance improvement in materials engineering, but details regarding whether the additive is doped in the host crystal or present as a secondary phase are usually examined from experimental experience, with a systematic theoretical prediction lacking, which sometimes causes controversy on the role of additives. In this study, the dopability of Ti in crystalline LiCoO2 (LCO) is investigated by a first-principles simulation method, and the doping limit is quantitatively calculated. The probability of Ti substitution for Co is examined and related to point-defect formation in LCO as a function of the general experimental variables of temperature and gas-phase partial pressures, enabling practical use of the theoretical model for real experiments. It was found that Ti substitution for Co, accompanied by the formation of a Li vacancy, is the most probable Ti doping form in LCO, but the doping limit is very low and most Ti would segregate into secondary phases. The theoretical prediction showed good agreement with the experimental results. Based on theoretical predictions, particles having LCO cores and Ti-rich shells are obtained from a simple sol-gel route followed by one-step firing without additional surface treatment. The high-voltage cyclability of LCO is greatly improved. The method demonstrated in this study may be a useful tool for screening suitable coating or doping elements for various material systems and provide a guide for designing simple spontaneous coating processes, as in this study.

Dual spectra band emissive Eu2+/Mn2+ co-activated alkaline earth phosphates for indoor plant growth novel phosphor converted-LEDs.

This paper reports designing a novel single composition blue/red color illuminating phosphor followed by fabricating "smart" agricultural/horticultural LED lighting. Color-tunable Eu2+/Mn2+ co-activated alkaline earth phosphates, Na(Sr,Ba)PO4 and Ca3Mg3(PO4)4, are considered, and the stable doping sites for the corresponding activators are identified by using first-principle DFT calculations. We can realize the designated color purity with stable thermal quenching preserved luminescence behavior is induced by the Eu2+ center positioned at different coordination states with intermixed Sr2+/Ba2+ sites in Na(Sr,Ba)PO4 hosts. Moreover, we demonstrate that the resultant LED lighting adopting the proposed novel phosphor composition stimulates the enhanced photosynthesis reaction for indoor hydroponics plants, such as oats and onions, which is superior to the narrow line emission band induced by the mixture of conventional red/green/blue LEDs. Thus, using the color-tunable single composition luminescent material may produce an innovative energy-efficient artificial lighting for indoor plant growth.

Estimation of leaf area index and its sunlit portion from DSCOVR EPIC data: Theoretical basis.

This paper presents the theoretical basis of the algorithm designed for the generation of leaf area index and diurnal course of its sunlit portion from NASA's Earth Polychromatic Imaging Camera (EPIC) onboard NOAA's Deep Space Climate Observatory (DSCOVR). The Look-up-Table (LUT) approach implemented in the MODIS operational LAI/FPAR algorithm is adopted. The LUT, which is the heart of the approach, has been significantly modified. First, its parameterization incorporates the canopy hot spot phenomenon and recent advances in the theory of canopy spectral invariants. This allows more accurate decoupling of the structural and radiometric components of the measured Bidirectional Reflectance Factor (BRF), improves scaling properties of the LUT and consequently simplifies adjustments of the algorithm for data spatial resolution and spectral band compositions. Second, the stochastic radiative transfer equations are used to generate the LUT for all biome types. The equations naturally account for radiative effects of the three-dimensional canopy structure on the BRF and allow for an accurate discrimination between sunlit and shaded leaf areas. Third, the LUT entries are measurable, i.e., they can be independently derived from both below canopy measurements of the transmitted and above canopy measurements of reflected radiation fields. This feature makes possible direct validation of the LUT, facilitates identification of its deficiencies and development of refinements. Analyses of field data on canopy structure and leaf optics collected at 18 sites in the Hyytiälä forest in southern boreal zone in Finland and hyperspectral images acquired by the EO-1 Hyperion sensor support the theoretical basis.

Eu(2+)-Activated Phase-Pure Oxonitridosilicate Phosphor in a Ba-Si-O-N System via Facile Silicate-Assisted Routes Designed by First-Principles Thermodynamic Simulation.

Eu(2+)-activated single phase Ba(2+)-oxonitridosilicate phosphors were prepared under a mild synthetic condition via silicate precursors, and their luminescent properties were investigated. Both the preferred oxonitridosilicate formation as for the available host compounds and thermodynamic stability within the Ba-Si-O-N system were elucidated in detail by the theoretical simulation based on the first-principles density functional theory. Those results can visualize the optimum synthetic conditions for Eu(2+)-activated highly luminescent Ba(2+)-oxonitridosilicates, especially Ba3Si6O12N2, as promising conversion phosphors for white LEDs, including Ba3Si6O9N4 and BaSi2O2N2 phases. To prove the simulated design rule, we synthesized the Ba3Si6O12N2:Eu(2+) phosphor using various silicate precursors, Ba2Si4O10, Ba2Si3O8, and BaSiO3, in a carbothermal reduction ambient and finally succeeded in obtaining a phase of pure highly luminescent oxonitridosilicate phosphor without using any solid-state nitride addition and/or high pressure synthetic procedures. Our study provides useful guidelines for robust synthetic procedures for developing thermally stable rare-earth-ion activated oxonitridosilicate phosphors and an established simulation method that can be effectively applied to other multigas systems.

Selection of Shear Horizontal Wave Transducers for Robotic Nondestructive Inspection in Harsh Environments.

Harsh environments and confined spaces require that nondestructive inspections be conducted with robotic systems. Ultrasonic guided waves are well suited for robotic systems because they can provide efficient volumetric coverage when inspecting for various types of damage, including cracks and corrosion. Shear horizontal guided waves are especially well suited for robotic inspection because they are sensitive to cracks oriented perpendicular or parallel to the wave propagation direction and can be generated with electromagnetic acoustic transducers (EMATs) and magnetostrictive transducers (MSTs). Both types of transducers are investigated for crack detection in a stainless steel plate. The MSTs require the robot to apply a compressive normal force that creates frictional force coupling. However, the coupling is observed to be very dependent upon surface roughness and surface debris. The EMATs are coupled through the Lorentz force and are thus noncontact, although they depend on the lift off between transducer and substrate. After comparing advantages and disadvantages of each transducer for robotic inspection the EMATs are selected for application to canisters that store used nuclear fuel.

In situ detection of laser-induced slip initiation on the silicon wafer surface.

We propose a real-time in situ method to detect slip initiation on the surface of silicon wafers during high-power laser beam irradiation. In this method, light is collected from the surface of a silicon wafer subjected to laser irradiation. When the slip is initiated, it strongly scatters the laser beam, allowing detection of the time of the slip initiation based on the resulting sudden increase in the scattering signal. To demonstrate the performance of this method, a silicon wafer specimen was illuminated by a near-infrared continuous-wave fiber laser beam (of wavelength 1070 nm) at four different laser powers, and the scattered light was detected. The scattering signal increased suddenly at the time of slip initiation. To confirm the occurrence of slip, the surface morphologies of the silicon specimens after laser irradiation were analyzed using an optical microscope; surface slips were observed only in the specimens for which the sudden increase in scattering had been detected. Thus, the proposed method is shown to be very effective for the real-time in situ detection of surface slip initiation induced by high-power laser beam irradiation on silicon wafers.

Color tuning and thermal quenching of different sensitizer ion, Mn2+ or Ce3+, doped Ba2Mg(BO3)2:Eu2+ phosphor.

Ba2Mg(BO3)2:Eu2+ phosphors incorporated with two different sensitizers, Mn2+ or Ce3+, were prepared and their emission properties, especially for color purity and thermal stability, were investigated thoroughly. The overall emission property induced by the Eu2+ ion and the resultant thermal behavior were strongly dependent on the type of codoped sensitizer ions, Mn2+ or Ce3+. Intense red emission peaking at 620 nm was obtained upon 370 nm excitation of the Mn2+-sensitized phosphor and the resultant light-emitting diode lamps using the given phosphor exhibited a more reddish emission with chromaticity coordinates of (0.602, 0.340). Thus, we can meet the purpose of illuminating elements by designing the proper chemical composition of the Eu2+-activated Ba2Mg(BO3)2 phosphor using different sensitizers: a more reddish emitting Mn2+-sensitized one for backlight units and a bright yellow-emitting Ce3+-sensitized one for solid-state lightings.

Mesoporous silica-assisted carbon free Li2MnSiO4 cathode nanoparticles for high capacity Li rechargeable batteries.

Porous and spherical Li2MnSiO4 nanoparticles have been synthesized through a facile sol-gel route via a mesoporous silica template. Galvanostatic charge-discharge of the resultant Li2MnSiO4 cathode exhibits enhanced charge-discharge capacity relative to that of particles prepared by the conventional sol-gel process, up to 25% in discharge capacity, even without any particulate process such as milling with conductive agents. The standout electrochemical performance could be attributed to the unique high surface-to-volume ratio, porous geometry and improved accommodation of transformation strains during the electrochemical lithiation-delithiation process.

Comparison of Outcomes after Wavefront-optimized and Topography-guided Transepithelial Photorefractive Keratectomy.

Purpose: To evaluate the outcomes of wavefront-optimized (WFO) and topography-guided (TG) transepithelial photorefractive keratectomy (transPRK) in the treatment of myopia and myopic astigmatism. Methods: Patients who underwent transPRK using the WaveLight® EX500 excimer laser for the correction of myopia and myopic astigmatism between January 2022 and March 2023 were divided into the WFO transPRK (77 eyes of 36 patients) or TG transPRK (63 eyes of 31 patients) groups in this retrospective, observational cohort study. The pre- and postoperative 3-month refractive and visual outcomes of the two groups were analyzed. Results: The uncorrected distance visual acuity was 0.0 logMAR or better in 95% of eyes 3 months postoperatively, and the mean manifest refraction spherical equivalent was within ± 1.0 diopter (D) in 90% of eyes. No significant differences were observed between the groups in terms of the UDVA or astigmatism. A significant induction of higher-order aberrations (HOAs) was observed in both groups. However, the induction of total corneal HOAs (P = .014) and spherical aberrations (P = .000) was significantly lower in the TG group than that in the WFO group. Conclusions: WFO and TG transPRK effectively improved the visual and refractive outcomes; however, the induction of total corneal HOAs and spherical aberration was lesser following the TG ablation.