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We investigate the anisotropic frequency-dependent dielectric, THz and IR response of liquid water confined between two planar graphene sheets with force-field- and density-functional-theory-based molecular dynamics simulations. Using spatially resolved anisotropic spectra, we demonstrate the critical role of the volume over which the spectral response is integrated when reporting spatially averaged electric susceptibilities. To analyze the spectra, we introduce a unique decomposition into bulk, interfacial, and confinement contributions, which reveals that confinement effects on the spectra occur only for systems with graphene separation below 1.4 nm, for all frequencies. Based on this decomposition, we discuss the molecular origin of the main absorption features of nanoconfined water from the GHz to the IR regime. We show that, at low frequencies, the 15 GHz Debye peak of interfacial water is redshifted due to a slowdown of collective water reorientations. At high frequencies, the OH stretch at 100 THz blue shifts and a signature of free OH groups emerges, while the HOH bend mode at 50 THz is redshifted. Strikingly, in nanoconfinement, the 20 THz libration band shifts to below 15 THz and broadens drastically, spanning two orders of magnitude in frequency. These results are rationalized by the collective water motion and the structure of the hydrogen-bond network at the water–graphene interface and in two-dimensional water layers, which reveals the intricate behavior of nanoconfined water and its spectral properties. [ABSTRACT FROM AUTHOR]

Low-dimensional nanostructures, especially one-dimensional materials, exhibit remarkable anisotropic characteristics due to their low symmetry, making them promising candidates for polarization-sensitive photodetection. Here, we present a chemical vapor deposition synthesis method for tellurium suboxide (TeOx), confirming the practicality of photodetectors constructed from TeOx nanowires (NWs) in high-responsivity, broadband, and polarization-sensitive detection. By precisely controlling the thermodynamics and kinetics of TeOx NWs growth, we achieve large-scale growth of TeOx NWs with highly controllable dimensions and propose a method to induce intrinsic built-in strain in TeOx NWs. Photodetectors based on quasi-one-dimensional TeOx NWs with ohmic contact demonstrate broadband spectral response (638–1550 nm), high responsivity (13 700 mA·W−1), and superior air stability. Particularly, owing to the inherent structural anisotropy of the photodetectors, they exhibit polarization-sensitive photodetection, with anisotropy ratios of 1.70 and 1.71 at 638 and 808 nm, respectively. [ABSTRACT FROM AUTHOR]

The temperature dependence of spectra can reveal important insights into the structural and dynamical behavior of the system being probed. In the case of linear spectra, this has been exploited to investigate the thermodynamic driving forces governing the spectral response. Indeed, the temperature derivative of a spectrum can be used to obtain effective energetic and entropic profiles as a function of the measured frequency. The former can further be used to predict the temperature-dependent spectrum via a van't Hoff relation. However, these approaches are not directly applicable to nonlinear, complex-valued spectra, such as vibrational sum-frequency generation (SFG) or two-dimensional infrared (2D-IR) photon echo spectra. Here, we show how the energetic and entropic driving forces governing such nonlinear spectra can be determined and used within a generalized van't Hoff relation to predict their temperature dependence. The central idea is to allow the underlying energetic profiles to themselves be complex-valued. We illustrate this approach for 2D-IR spectra of water and SFG spectra of the air–water interface and demonstrate the accuracy of the generalized van't Hoff relationship and its implications for the origin of temperature-dependent spectral changes. [ABSTRACT FROM AUTHOR]

Solution-processed organic photodetectors (OPDs) with spectral response in the near-infrared (NIR) region have broad applications such as in industries, spectroscopic/medical instruments, communications, image sensing, and environmental monitoring. OPDs capable of selective spectral response are particularly appealing for applications including secure optical data link and color image sensing systems. Here, we report an organic photodetector with a highly selective spectral response to near-infrared radiation without the use of a color filter. The operation of the OPDs takes advantage of a charge collection narrowing effect, resulting in a narrowband response at 760 nm with a full width at half maximum of 47 nm and an external quantum efficiency of 46%. Owing to the features of the narrowband response in NIR, our organic photodetectors are used as optical signal receivers for an optical communication system, which achieves a data transmission rate of 12.6 kB/s with a low bit error rate on the order of 10−4. We further investigated the response bandwidth in devices with different active layer thicknesses and area size and their response bandwidth under different reverse bias conditions as well. The optimized device shows a −3 dB response bandwidth of 3.02 MHz and a data transmission rate of 1.41 Mbit/s. The results highlight the promising potential of the nonfiltered OPDs for a variety of applications, including light communication, short-range data transmission, and image sensing. [ABSTRACT FROM AUTHOR]

We present new results on the underlying guest–host interactions and spectral characterization of a CO2 molecule confined in the cages of the sI clathrate hydrate. Such types of porous solids raise computational challenges, as they are of practical interest as gas storage/capture materials. Accordingly, we have directed our efforts toward addressing their modeling in a proper manner, ensuring the quality of the input data and the efficiency of the computational approaches. The computational procedure for spectral simulations, within the multi-configurational time-dependent Hartree framework, involves the development of a fully coupled Hamiltonian, including an exact kinetic energy operator and a many-body representation of the potential, along with dipole moment surfaces, both obtained through neural network machine learning techniques. The resulting models were automatically trained and tested on extensive datasets generated by PW86PBE-XDM calculations, following the outcome of previous benchmark studies. Our simulations enable us to explore various aspects of the quantized dynamics upon confinement of CO2@D/T, such as constrained rotational–translational quantum motions and the averaged position/orientation of the CO2 guest in comparison to the experimental data available. Particularly notable are the distinct energy patterns observed in the computed spectra for the confined CO2 in the D and T cages, with a considerably high rotational–translational coupling in the CO2@T case. Leveraging reliable computations has proved instrumental, highlighting the sensitivity of the spectral features to the shape and strength of the potential interactions, with the explicit description of many-body contributions being significant. [ABSTRACT FROM AUTHOR]

The influence of light spectral properties on circadian rhythms is of substantial interest to laboratory-based investigation of the circadian system and to field-based understanding of the effects of artificial light at night. The trade-offs between intensity and spectrum regarding masking behaviors are largely unknown, even for well-studied organisms. We used a custom LED illumination system to document the response of wild-type house mice (Mus musculus) to 1-h nocturnal exposure of all combinations of four intensity levels (0.01, 0.5, 5 and 50 lx) and three correlated color temperatures (CCT; 1750, 1950 and 3000 K). Higher intensities of light (50 lx) suppressed cage activity substantially, and consistently more for the higher CCT light (91% for 3000 K, 53% for 1750 K). At the lowest intensity (0.01 lx), mean activity was increased, with the greatest increases for the lowest CCT (12.3% increase at 1750 K, 3% increase at 3000 K). Multiple linear regression confirmed the influence of both CCT and intensity on changes in activity, with the scaled effect size of intensity 3.6 times greater than that of CCT. Activity suppression was significantly lower for male than for female mice. Assessment of light-evoked cFos expression in the suprachiasmatic nucleus at 50 lx showed no significant difference between high and low CCT exposure. The significant differences by spectral composition illustrate a need to account for light spectrum in circadian studies of behavior, and confirm that spectral controls can mitigate some, but certainly not all, of the effects of light pollution on species in the wild.

Photomultiplication-type organic photodetectors (PM-OPDs) have been stimulating more and more researchers' interest owing to their extremely high external quantum efficiency (EQE). To prepare high-performance PM-OPDs with a broadband spectral response range from visible to near-infrared and investigate the role of energy levels of the donor and acceptor on its responsiveness, the non-fullerene acceptor Y6 was added into the P3HT:PC71BM system in this work. The photomultiplication phenomenon with the highest EQE has been achieved under both forward and reverse bias when the ratio of Y6 in two acceptors approaches 80 wt. %. The introduction of Y6 not only promotes the formation of moderate hole traps in the active layer but also results in an appropriate amount of low injection barriers to allow more electron injection from the external circuit. Therefore, the spectral response of the device with 80 wt. % Y6 has been broadened from 750 to 950 nm, and the champion EQE of 15 691% at 10 V and 7639% at −20 V at 850 nm was achieved. This work reveals the importance of hole-trapping ability determined by the energy level difference between the donor and the acceptor for the selection of the multiplication system and provides a scheme for the design of high-performance broadband PM-OPDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cs 3 Bi 2 I 9 /Au heterostructure nanocomposites were prepared via a simple electrostatic self-assembly process. • The incorporation of Au NPs in Cs 3 Bi 2 I 9 nanoplates induced an inversion for positive to negative photoconductivity. • The nanocomposite-based photodetectors demonstrated a broadband negative photoresponse (405–1550 nm). • The negative photoconductivity effect related photogenerated carrier dynamics were investigated in detail. The negative photoconductivity (NPC) effect is becoming an increasingly significant factor in the development of next-generation optoelectronics. However, research in the field of NPC-dominated optoelectronics remains in its infancy and frequently encounters challenges related to fabrication complexity, slow photoresponse speed, instability, and a limited spectral response range. Herein, a Cs 3 Bi 2 I 9 /Au heterostructure nanocomposite was prepared via a simple self-assembly process utilizing electrostatic interactions with Au nanoparticles (NPs) and lead-free Cs 3 Bi 2 I 9 nanoplates. The Cs 3 Bi 2 I 9 /Au nanocomposite-based photodetectors (PDs) demonstrate a broadband photoresponse (405–1550 nm), enhanced rise/fall times (27.2/40.0 µs), and reduced noise density (4.7 × 10−13 A/Hz1/2 at 1 Hz). In contrast to the positive photoconductivity (PPC) effect observed in colloidally synthesized Cs 3 Bi 2 I 9 nanoplate-based PDs, the NPC can be attributed to the decrease in photocurrent under light illumination during the processes of recombination and trapping of photogenerated carriers induced by the incorporation of Au NPs. These findings are expected to provide valuable insights into achieving high-performance NPC-dominated PDs by regulating the dynamics of photogenerated carriers in perovskite heterostructures. [ABSTRACT FROM AUTHOR]

Physiological or genetic assays and computational modeling are valuable tools for understanding animals' visual discrimination capabilities. Yet sometimes, the results generated by these methods appear not to jive with other aspects of an animal's appearance or natural history, and behavioral confirmatory tests are warranted. Here we examine the peculiar case of a male jumping spider that displays red, black, white, and UV color patches during courtship despite the fact that, according to microspectrophotometry and color vision modeling, they are unlikely able to discriminate red from black. To test whether some optical or neurological component could have been missed using these methods, we conduct mate choice experiments. Some females are presented with a choice between males with their red leg coloration painted over with either red or black paint, while other females are presented with a choice between males with the same coloration painted over by either red or white paint. This latter pairing of red and white males should have been easily distinguishable to the spiders and served as a control to ensure our experimental setup was conducive to natural mating behavior. Red males were more likely to mate than white males (P = 0.035), whereas red and black males had identical mating success (P = 1.0). This suggests that previous physiological and computational work on these spiders was correct in concluding that they are unable to discriminate between red and black. Any functional significance of displaying both colors, rather than only black, remains unresolved. [ABSTRACT FROM AUTHOR]

This paper proposes a novel intensity measure (IM) based on the geometric mean of acceleration response spectral ordinates to assess the probabilistic performance of structures subjected to seismic loading. Instead of relying solely on the fundamental period, the proposed IM is evaluated across a fixed period range for all structural systems, which allows consideration of higher mode effects and period changes due to nonlinearity. The proposed seismic IM is evaluated using two established indices sufficiency and efficiency. Sufficiency quantifies the independence of an engineering demand parameter at a specific intensity level with ground motion characteristics such as seismic magnitude (M) and distance from site to fault plane (R). It is calculated by linear regression analysis, or using gradient-based relative sufficiency measures. On the other hand, efficiency is measured as dispersion across ground motions at a given intensity level for any physical response quantity. It helps to reduce computational demand for failure probability assessment by considering a smaller number of records compared to an inefficient IM for similar confidence levels. The effectiveness of the proposed IM along with 10 other IMs is demonstrated on single degree of freedom systems with various fundamental periods by performing nonlinear time history analysis using a far-field ground motion record set. The study is also extended to five degree of freedom lumped mass stick models, 2D models (4-, 8-, and 12-story archetype steel frames), and 3D reinforced concrete shear wall building model. The results indicate that the proposed IM limits dispersion to within 10% for long-time period structures, and demonstrates improved sufficiency across different structural systems. For example, gradient of the proposed IM with respect to magnitude M and site-to-source distance R for a 12-story steel frame is reduced by 42.9% and 94%, respectively, compared to spectral acceleration at fundamental time period. Potential application of this research lies in efficiently conducting seismic reliability assessment and design for structural systems. [ABSTRACT FROM AUTHOR]

The detection of ultraviolet (UV) radiation is of paramount importance, and has expanding applications in industrial, scientific, environmental, and biomedical fields. Using heterojunctions to fabricate UV photodetectors (PDs) is an effective approach for achieving multi-band detection. This study reports on high-responsivity β-Ga2O3/GaN heterojunction UV PDs, featuring tunable multi-band detection capabilities. The as-fabricated PDs demonstrate an exceptional photoresponsivity of 91.2 mA W−1 under 250 nm illumination at zero bias. Furthermore, the spectral response of the Ga2O3/GaN heterojunction PDs can be precisely modulated by varying the applied bias voltage, facilitating distinct UVC-dominated and broadband UVA/UVC detection modes with enhanced detectivity. The underlying mechanism responsible for the tunable spectral responses is elucidated. This research not only introduces a straightforward and practical approach for developing multi-band UV PDs regulated by bias voltage, but also provides a comprehensive understanding of the physical mechanisms driving the photoelectric response. These advancements address the increasing demand for UV PDs, and provide guidance for the optimization of device performance and the discussion of intrinsic physical mechanisms in this field. [ABSTRACT FROM AUTHOR]

We explore a new approach for the parsimonious, generalizable, efficient, and potentially automatable characterization of spectral diversity of sparse targets in spectroscopic imagery. The approach focuses on pixels which are not well modeled by linear subpixel mixing of the Substrate, Vegetation and Dark (S, V, and D) endmember spectra which dominate spectral variance for most of Earth's land surface. We illustrate the approach using AVIRIS-3 imagery of anthropogenic surfaces (primarily hydrocarbon extraction infrastructure) embedded in a background of Arctic tundra near Prudhoe Bay, Alaska. Computational experiments further explore sensitivity to spatial and spectral resolution. Analysis involves two stages: first, computing the mixture residual of a generalized linear spectral mixture model; and second, nonlinear dimensionality reduction via manifold learning. Anthropogenic targets and lakeshore sediments are successfully isolated from the Arctic tundra background. Dependence on spatial resolution is observed, with substantial degradation of manifold topology as images are blurred from 5 m native ground sampling distance to simulated 30 m ground projected instantaneous field of view of a hypothetical spaceborne sensor. Degrading spectral resolution to mimicking the Sentinel-2A MultiSpectral Imager (MSI) also results in loss of information but is less severe than spatial blurring. These results inform spectroscopic characterization of sparse targets using spectroscopic images of varying spatial and spectral resolution. [ABSTRACT FROM AUTHOR]

The design of optical sensors aims at providing, among other things, the highest precision in the determination of the target measurand. Many sensor systems rely on a spectral transducer to map changes in the measurand into spectral shifts of a resonance peak in the reflection or transmission spectrum, which is measured by a readout device (e.g., a spectrometer). For these spectral transducers, figures of merit have been defined which are based on specific assumptions on the readout and the data analysis. In reality, however, different transducers achieve optimal performance with different types of readout. Additionally, some transducers present a more complex spectral response for which existing figures of merit do not apply. In this paper, we investigate an approach to quantifying the potential performance of a given transducer for a more general class of readout methods. Starting from the Cramér–Rao lower bound, we define a new figure of merit, the integrated spectral sensitivity, which is directly related to the physical limit of precision and applicable to a wide variety of sensing systems. We apply this analysis to two different examples of transducers. The results bring useful insights into the design of optical sensors. [ABSTRACT FROM AUTHOR]

Thermochromic sensors employing cholesteric liquid crystal droplets offer customizable temperature and spectral responses through molecular adjustments of nematic mesogens. Embedded in a polymer matrix, these portable sensors enable direct, reversible temperature visualization on the skin, demonstrating potential for advanced sensing applications. [Display omitted] Rapid and accurate detection and visualization of temperature variations near the human body hold significant importance. This study presents thermochromic colloids capable of adjusting the detectable temperature range and reflection wavelength over a wide spectrum. The systematic investigation focuses on understanding the influence of the molecular structure of nematic mesogens on the morphological dynamics of cholesteric liquid crystal droplets and their associated thermochromic behaviors. A tunable colorimetric temperature range (i.e., from 10 to 40 °C) and high sensitivity (i.e., Δ λ Δ T −1 > 100nm °C−1) are realized through precise modulation of the alkyl chain lengths in cyanobiphenyls molecules, combined with a cholesteryl oleyl carbonate as a chiral dopant. We demonstrate the efficiency of a binary mixture of different mesogens, enabling customized structural colors with desired temperature responses. Finally, inspired by the ability of the octopus to camouflage through the elongation or contraction of its pigment cells, thermochromic droplets are embedded within a polymer matrix, resulting in a portable skin patch that offers quick, reversible, and direct temperature visualization of the human body. [ABSTRACT FROM AUTHOR]

This work presents a high-sensitivity temperature sensing system utilizing an enhanced Vernier effect implemented in cascaded fiber loop interferometers. High-sensitivity temperature sensors based on the Vernier effect have broad application prospects, but the sensitivity of traditional measurement schemes is difficult to improve further due to the limited variation in the difference between two free spectrum ranges (FSRs). Our sensing system incorporates two fiber loop interferometers and a single-mode fiber to form a Vernier spectral response, characterized by two complementary optical filter responses. As the temperature of the sensing fiber changes, one FSR decreases, and the other increases, respectively, enhancing the difference value between the two FSRs to form an enhanced Vernier effect. Experimental results demonstrate that the temperature sensitivity of a traditional Vernier effect measurement is only −298.29 kHz/°C, while our proposed enhanced Vernier effect sensing system achieves a sensitivity of 618.14 kHz/°C, which is 92 times higher than that of a two-arm optical carrier-based microwave interferometry (OCMI) sensing system and 2.07 times higher than that of a traditional Vernier effect sensing system. This approach with an enhanced Vernier effect scheme based on cascaded fiber loop interferometers can be used to design high-sensitivity sensing systems for biometrics, smart cities, and the Internet of Things. [ABSTRACT FROM AUTHOR]

Adhesive joining has the severe limitation that damages/defects developed in the bondline are difficult to assess. Conventional non-destructive examination (NDE) techniques are adequate to reveal disbonding defects in fabrication and delamination near the end of service life but are not helpful in detecting and monitoring in-service degradation of the joint. Several techniques suitable for long-term joint integrity monitoring are proposed. Fiber Bragg grating (FBG) sensors embedded in the joint are one of the promising candidates. It has the advantages of being close to the damage and immune to environmental attack and electromagnetic interference. Damage and disbonding inside an adhesive joint will give rise to a non-uniform strain field that may bring about peak splitting and chirping of the FBG spectrum. It is shown that the evolution of the full spectral responses can closely reveal the development of damages inside the adhesive joints during tensile and fatigue failures. However, recording and comparing the successive full spectra in the course of damage is tedious and can be subjective. An energy modulation interrogation technique is proposed using a pair of tunable optical filters. Changes in the full FBG spectral responses are modulated by the filters and converted into a conveniently measurable voltage output by photodiodes. Monitoring damage development can then be easily automated, and the technique is well-suited for practical applications. Filter spectrum width of 5 nm and initial overlap with the FBG spectrum to give 40% of the maximum output voltage is found to be optimal for measurement. The technique is tested on embedded FBGs from different adhesive lap-joint specimens and successfully reflected the severity of changes in the full spectral shapes during the course of tensile failure. Moreover, the trends in these PD outputs corroborate with the V value previously proposed to describe the qualitative change in FBG spectral shape. [ABSTRACT FROM AUTHOR]

Research suggested that color vision evolved for the purpose of seeing skin color modulations signaling emotion or mood. Hence people want to find the connection of the cone sensitivities with the skin spectral reflectance. In this article the W and V shapes based on skin spectral reflectance measured at different positions and from different ethnic groups (Kurdish, Caucasian, Thai, Chinese) were investigated. First, it was found that the measured skin spectral reflectance from all body positions and ethnic groups have a V shape between 400 and 450 nm and a W shape between 520 and 610 nm. The W and V shapes from the measured skin spectral reflectance are clearly different from those from the spectral reflectance generated from the physical model. The V shape and W shape do not exist with spectral reflectances measured from artificial skin color. Second, it was found that the wavelengths where the left trough assumes for the W shape are different from the wavelength where the M cone peaks, and the wavelengths where the central peak of the W shape assumes are different from the wavelength where the L cone peaks, which are different from the results from literature. Third, it was found that the skin spectral reflectance varies with body positions and ethnic groups. The W shapes turn to be a "U" shape for the spectral reflectance measured at back of the hand and inner forearm positions. The spectral reflectance measured from Kurdish starts decreasing for each body positions for wavelength greater than 700 nm, which is clearly different from the spectral reflectance measured from the Chinese and Caucasian ethnic groups. The findings of this paper are valuable for improving the physical model for generating skin spectral reflectance, reconstructing skin spectral reflectance based on image, identifying human skin color from spectral imaging and rendering of human skin color in computer graphics. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive and integrated databank of the Iranian strong ground motions that occurred from 1973 to 2018. The databank consists of 7196 three-component acceleration records from 3180 earthquakes and 1157 stations in Iran. In this paper, the characteristics of this databank are presented in terms of event, station, and recording distributions. The events are characterized by magnitude in the range 2.4–7.7. Shear wave velocity has been measured and reported at 603 strong motion stations of the databank. In this study, three different empirical techniques are applied to classify the stations. A new method is proposed for site classification based on the correlation coefficient between the horizontal-to-vertical (H/V) response spectral ratios of the ground motion records recorded by each station. All the acceleration time histories in the databank have been uniformly processed using filtering and wavelet de-noising methods to remove high- and low-frequency noise. Moreover, by comparison between the Fourier Amplitude Spectrum (FAS) of the noises detected in all acceleration time series by the filtering and the wavelet de-noising methods, it was determined that the mean FAS of the noises detected by the wavelet de-noising method in most of the frequencies is higher than mean and mode of FAS of the noises detected by the filtering method. [ABSTRACT FROM AUTHOR]

Water pollution has become a severe problem to threaten the environmental safety and human health. To address the issue, the preparation of novel and broad-spectrum photocatalysts is the key strategy to efficiently remove pollutants from water. In this work, a novel 1D/2D LaOCl:Yb3+,Er3+/BiOBr nanofibers S-scheme heterojunction photocatalyst is devised and facilely constructed for the first time by combining a mono-axis electrospinning with a solvothermal method. BiOBr nanosheets are uniformly grown on the surface of LaOCl:Yb3+,Er3+ nanofibers, forming one dimensional/two dimensional (1D/2D) nanostructures to increase specific surface area and promote separation and migration of photo-generated carriers. Yb3+ and Er3+ co-doping can broaden the spectral response range to achieve full spectral response, and further Yb3+ and Er3+ co-doping can convert non-available infrared light into available visible light to boost photocatalytic capability. Meanwhile, the S-scheme heterojunction provides effective transmission channels for the transfer of photo-generated carriers. Synergistic effect among the above favorable advantages achieves preeminent photocatalytic activity. The degradation efficiencies of 1D/2D LaOCl:Yb3+,Er3+/BiOBr nanofibers to methylene blue (MB), tetracycline hydrochloride (TCH) and ceftriaxone sodium (CRO) reach 97.44 % (60 min), 96.00 % (60 min) and 78.70 % (30 min) under simulated sunlight irradiation, respectively. The degradation cycle measurements of dye and antibiotics indicate that 1D/2D LaOCl:Yb3+,Er3+/BiOBr nanofibers photocatalyst has superior recyclable stability. The intermediate products formed by the photocatalytic degradation of MB, TCH and CRO are detected by liquid chromatography-mass spectrometry (LC-MS), and possible photocatalytic degradation pathways are speculated. The reasonable reaction mechanism of upconversion (UC) luminescence-enhanced photocatalytic performance is elucidated based on sound experimental results. This work provides a new research strategy for constructing environmentally friendly new broad-spectrum and high-efficiency photocatalysts. [Display omitted] • Full-spectrum-active LaOCl:Yb3+,Er3+/BiOBr heterojunction photocatalyst is designed. • 1D/2D nanostructure provides more active sites and avails fast transfer of carries. • S-scheme heterojunction and Yb3+/Er3+ co-doping broaden the spectral response range. • Yb3+/Yb2+ redox centers raise carriers separation efficiency and boost ·O 2 − content. • Synergy of UC emission and S-scheme 1D/2D heterojunction boosts catalytic ability. [ABSTRACT FROM AUTHOR]

Soil spectroscopy offers a method for quantitatively analysing soil chromophores and employing a screening approach. However, utilizing general models with this data at once doesn't consistently yield accurate results in determining soil parameters. Ambiguities in response within certain domains of the reflectance spectrum are observed. To address this issue, a method is proposed where quantities associated with spectral response are outputted within well-defined domains corresponding to specific parameters. This article introduces a novel approach centred on identifying features from reflectance spectra to assess soil properties and mitigate issues arising from a heterogeneous soil dataset. The focus is on swiftly automating the classification of soil spectral data by extracting features directly related to the varied composition of chromophores in the samples. These features are categorized for each chromophore parameter and analysed using linear discriminant analysis (LDA). The study employs the '309 soil samples' from the GEO-CRADLE open spectral soil library in Greece. Specifically, relevant data from six spectral responses are extracted to separate and quantify certain soil parameters such as clay content, NO3− levels, and SOM (Soil Organic Matter), despite their interrelations. We developed a method to visually represent the determination outcomes quantitatively by establishing three threshold parameter values: 1.6% for SOM, 19% for clay, and 13.6 ppm for NO3−. These determinations will span the explored ranges of '0.3 to 4.18%' for SOM, "3 to 48%" for clay, and '0 to 661.2 ppm' for NO3−. Utilizing supervised LDA proves notable classification rates of 93.3% for the SOM task, 90% for the Clay task, and 86.6% for NO3− with the specific cut-off value parameter. The final result is presented as a map showing the positions of various prediction samples, highlighting the percentages of clay and organic matter relative to 19% and 1.6%, respectively, as well as the nitrate concentration in these samples relative to 13.6 ppm. [ABSTRACT FROM AUTHOR]

We describe a testbed to characterize the optical response of compact superconducting on-chip spectrometers in development for the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) mission. EXCLAIM is a balloon-borne far-infrared experiment to probe the CO and CII emission lines in galaxies from redshift 3.5 to the present. The spectrometer, called µ-Spec, comprises a diffraction grating on a silicon chip coupled to kinetic inductance detectors (KIDs) read out via a single microwave feedline. We use a prototype spectrometer for EXCLAIM to demonstrate our ability to characterize the spectrometer's spectral response using a photomixer source. We utilize an on-chip reference detector to remove the spectral structure introduced by the off-chip optics and a silicon etalon to calibrate the absolute frequency. [ABSTRACT FROM AUTHOR]

Purpose: There is a strong inducement to develop new inorganic materials to substitute the current industrial pigments, which are known for their poor ultraviolet absorbent and low photoluminescence (PL) properties. The purpose of this paper is to invent a better rare-earth-based pigment material as a spectral modifier with good luminescence properties to enhance the spectral response for photovoltaic panel application. Design/methodology/approach: Different phosphor samples made of nano-calcium carbonate (CaCO3) with varied wt.% of the dopant Dysprosium doped calcium borophosphate (CBP/Dy) as (W0 – 0%, W1 – 3,85%, W2 – 7.41%, W3 –10.71% and W4 –13.79%) were prepared via the solid-state diffusion method at 600 °C for 6 h using a muffle furnace. The structural, morphological and luminescence properties of the CaCO3:CBP/Dy powder samples were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and PL test. Findings: The XRD, SEM and FTIR results verified the crystalline formation, morphological behaviour and vibration bonds of synthesized CBP/Dy-doped CaCO3 powder samples. XRD pattern revealed that the synthesized powder samples exhibit crystalline structured materials, and SEM results showed irregular shape and porous-like structured morphologies. FTIR spectrum shows prominent bands at 712, 874 and 1,404 cm−1, corresponding to asymmetric stretching vibrations of CO32− groups and out-of-plane bending. PL characterization of CBP/Dy-doped CaCO3 (sample W) shows emission at 427 nm (λmax) under the excitation of 358 nm. The intensity of PL emission spectra drops due to the concentration quenching effect, while the maximum PL intensity is observed in the W3 phosphor powder system. Research limitations/implications: This phosphor powder is expected to find out the potential application such as a spectral modifier which is applied to match the energy of photons with solar cell bandgap to improve spectral absorption and lead to better efficiency. Originality/value: The introduction of a nano-CaCO3:CBP/Dy hybrid powder system with good luminescence properties to be used as spectral modifiers for solar cell application has been synthesized in the lab, which is a novel attempt. [ABSTRACT FROM AUTHOR]

The inhomogeneity of spectral pixel response is an unavoidable phenomenon in hyperspectral imaging, which is mainly manifested by the existence of inhomogeneity banding noise in the acquired hyperspectral data. It must be carried out to get rid of this type of striped noise since it is frequently uneven and densely distributed, which negatively impacts data processing and application. By analyzing the source of the instrument noise, this work first created a novel non-uniform noise removal method for a spatial dimensional push sweep hyperspectral imaging system. Clean and clear medical hyperspectral brain tumor tissue images were generated by combining scene-based and reference-based non-uniformity correction denoising algorithms, providing a strong basis for further diagnosis and classification. The precise procedure entails gathering the reference dark background image for rectification and the actual medical hyperspectral brain tumor image. The original hyperspectral brain tumor image is then smoothed using a weighted least squares algorithm model embedded with bilateral filtering (BLF-WLS), followed by a calculation and separation of the instrument fixed-mode fringe noise component from the acquired reference dark background image. The purpose of eliminating non-uniform fringe noise is achieved. In comparison to other common image denoising methods, the evaluation is based on the subjective effect and unreferenced image denoising evaluation indices. The approach discussed in this paper, according to the experiments, produces the best results in terms of the subjective effect and unreferenced image denoising evaluation indices (MICV and MNR). The image processed by this method has almost no residual non-uniform noise, the image is clear, and the best visual effect is achieved. It can be concluded that different denoising methods designed for different noises have better denoising effects on hyperspectral images. The non-uniformity denoising method designed in this paper based on a spatial dimension push-sweep hyperspectral imaging system can be widely used. [ABSTRACT FROM AUTHOR]

Successful foraging of piscivores is often dependent upon light availability in their visual habitat and is often influenced by a number of abiotic and biotic factors. In north-temperate lakes, dissolved organic carbon concentrations vary greatly, thus likely influencing foraging success. To understand the impact this has on the walleye (Sander vitreus), we sought to study foraging success at various light intensities under physiologically relevant downwelling light conditions in a laboratory foraging arena. Using electroretinography to determine physiologically relevant light conditions in adult walleye, we found that fish exhibit broad spectral sensitivity that was greatest from 500 to 550 nm. Under optimal light conditions (525 nm), we next determined the reaction distance and foraging success of age-0 walleye at various light intensities. The average reaction distance of age-0 walleye increased rapidly from 12 cm in complete darkness to 27 cm at civil twilight (1 lx or 3.16 × 1013 photons m−2 s−1) and then plateaued, ranging from 28 to 30 cm at higher light intensities. Prey capture success of age-0 walleye was greatest under low light conditions, averaging 20.5% from nautical twilight to civil twilight at − 3° solar altitude (0.05–1 lx or 1.58 × 1011–3.16 × 1013 photons m−2 s−1) and declined to 10–12% as light intensity increased and in full darkness. Walleye may be best suited for environments with predominantly green downwelling light and age-0 foraging was most successful at nautical and civil twilight. In north-temperate lakes, dissolved organic carbon concentrations can fluctuate interannually due to climate change. Defining preferred juvenile walleye foraging conditions allows for predictions of climate change influences on walleye habitat and age-0 recruitment. [ABSTRACT FROM AUTHOR]

The photoluminescent response of organic materials upon applied stimuli is a key property that can be easily utilized for their implementation in simple and inexpensive sensing devices. A wide spectral response together with an accessible detection constitutes two crucial features required for promising sensing materials. Here, a new energy donor‐acceptor intermolecular system in thin films is developed, realizing a gradual and irreversible change on the photoluminescent emission determined by the thermal history of the sample. These changes are principally induced in the excited state intramolecular proton transfer (ESIPT) type donor molecule that governs the overall interaction of the system as a consequence of the thermal events. Three main fluctuating channels of emission are observed, which are distinguished by the shifting of the acceptor emission and the relative intensity of all the spectral features. These effects are translated into a temperature responsive configuration that creates a widely tunable chromatic emission strictly consistent with its thermal history. The application of the thin films as wide range thermal indicators is demonstrated for simple visual inspection and for ratiometric sensing, showing noticeable color changes and remarkable sensitivities of over 14% °C−1. [ABSTRACT FROM AUTHOR]

Selenium (Se), as a typical elemental semiconductor, has garnered significant attention due to its excellent carrier mobility, outstanding photoconductivity, and broad spectral response. However, Se micro‐ and nanostructures exhibit inherently low nonlinear optical coefficients, necessitating substantial enhancement of their nonlinear optical properties. In this study, trigonal Se (t‐Se) microwires (MWs) and t‐Se/MoS2 mixed‐dimensional vertical heterostructures are synthesized using the atmospheric pressure vapor phase deposition method. the influence of precursor concentration on the growth of t‐Se MWs is systematically investigated, and computational fluid dynamics simulations are employed to elucidate the growth mechanism. Open‐aperture Z‐scan measurements reveal that the nonlinear optical properties of t‐Se/MoS2 mixed‐dimensional vertical heterostructures are significantly enhanced compared to those of t‐Se MWs and monolayer MoS2 nanosheets. First‐principles calculations based on density functional theory, along with surface potential measurements indicate that effective charge transfer across the interfaces of the vertical heterostructures is critical for enhancing their nonlinear optical properties. This study provides valuable insights into the development of next‐generation nonlinear optical materials and advanced devices. [ABSTRACT FROM AUTHOR]

Meta‐lenses can offer potential improvements over traditional optical components in imaging, display, and detection. Initial meta‐lenses strive for uniform spectral responses over broadband for full‐color imaging. Nevertheless, enhancing wavelength selectivity remains crucial for specific applications, such as fluorescence imaging and augmented reality, requiring specific wavelengths. Current methods struggle to balance nonlocal resonance with local phase control or introduce an additional filter layer. Here, an all‐dielectric resonant meta‐lens for wavelength‐selective focusing based on the Fresnel zone plate design is experimentally demonstrated. The coupling between nonlocal lattice resonance and local Mie‐type resonance is effectively manipulated to control the reflection and bandwidth. Without considering the balance between nonlocal resonance excitation and local phase control, the resonant meta‐lens can reflectively focus at a resonant wavelength of 460 nm while allowing normal transmission at non‐resonant wavelengths, which is generally restricted in conventional metallic counterparts. Simulation (experimental) results indicate a high color purity of 90% (66%), surpassing those of meta‐lenses with filtering functions. A multi‐resonant meta‐lens is further designed for red, green, and blue colors. This work offers enhanced options for wavelength‐selective meta‐lenses, expanding their potential in optical imaging and display applications. [ABSTRACT FROM AUTHOR]

A high‐capacity lithium‐niobate‐on‐insulator (LNOI) optical transmitter for next‐generation passive optical‐networks (PONs) is proposed and demonstrated with ultra‐low temperature‐dependence for the first time by simultaneously introducing Z‐ and Y‐propagation LNOI photonic waveguides. There are five wavelength‐division‐multiplexed channels involved with the center wavelengths of 1270/1300/1342/1537/1577 nm, and the photonic filters are realized by integrating amplitude‐apodized multimode waveguide gratings (MWGs) and mode (de)multiplexers designed with Z‐propagation LNOI photonic waveguides, which are found to be with a low thermo‐optic coefficient and thus enable the athermalization. Meanwhile, high‐speed optical modulators connected at the add ports of the photonic filters for the 1342/1577 nm channels are developed with Y‐propagation LNOI photonic waveguides with the maximal electro‐optic effect. For the fabricated on‐chip optical transmitter, box‐like spectral responses are achieved with ultra‐low excess losses of <0.5 dB and low inter‐channel crosstalk of < −26 dB for all the channels whose bandwidths are respectively ∼16/20/4/15/5 nm as expected. The present LNOI photonic chip is nearly athermal, exhibiting very low temperature‐dependence less than 8.7 pm/°C in the full wavelength range of >300 nm. Finally, high‐capacity data transmissions of 50/100 Gbps on‐off‐keying signals and 100/200 Gbps four‐level‐pulse‐amplitude‐modulated signals are demonstrated, providing a promising solution for next‐generation PONs. [ABSTRACT FROM AUTHOR]

Photocatalysis via sunlight conversion holds an enormous potential for tackling universal energy demand and environmental pollution. However, the inadequate conversion of irradiated sunlight severely limits the efficiency of semiconductor photocatalysts, where usually responsible factors, including light absorption, separation of photo-generated electron-hole pairs, and interfacial charge kinetics do not contribute efficiently. Herein, the recent advances in the most versatile and emerging design strategies as viable routes to overcome inadequate sunlight conversion efficiency in photocatalytic applications are discussed. This review first introduces various design strategies to expand the spectral response of photocatalysts, which extend light harvesting toward a large fraction of the solar spectrum, and dictate how photons' high potential is utilized to generate electron-hole pairs. We then discuss efficient strategies to obtain high separation of electron-hole pairs, and—when compared to high recombination loss of charge carriers—increased lifetime plays a pivotal role in promoting sunlight conversion. Furthermore, to elucidate the relationship between charge kinetics and sunlight conversion, the next section includes an in-depth discussion of various strategies, which clarify that charge migration and subsequent utilization can be enhanced by manipulating charge kinetics. Novel insights into the future views, which illustrate how high-performance photocatalysts require enhanced sunlight conversion, are also discussed. This review offers guidance toward emerging photocatalytic strategies for improved sunlight conversion. • Advances in sunlight conversion strategies over photocatalysts are discussed. • Key role of light absorption, charge separation, and charge kinetics in sunlight conversion is explained. • The current bottlenecks are discussed and future insights are provided. [ABSTRACT FROM AUTHOR]

As a modality of optical imaging, fluorescence imaging of biochemical analytes holds significant potential in the field of disease diagnosis and therapy. However, the non‐responsive fluorophores are not able to selectively and sensitively detect lesions, resulting in a poor signal‐to‐background ratio and compromised accuracy. The utilization of activatable sensors, in contrast, is capable of effectively overcoming these limitations by displaying variations in fluorescence intensity and spectral wavelength in response to physiological parameters. Aggregation‐induced emission luminogens (AIEgens), particularly those emitting fluorescence in the near‐infrared (NIR, 700–1700 nm) window, have practical application prospects in disease theranostics due to their excellent photostability, deeper penetration depth, and enhanced fluorescence intensity in physiological environments. In this review, an overview of the advancements in research on NIR AIEgens for internal stimuli‐activated diagnosis and treatment of diseases is provided. The design principles of responsive NIR AIEgens and their biomedical applications are exemplified with representative examples, categorized based on the type of stimuli. Finally, the review concludes with a brief discussion of the challenges, opportunities, and future prospects of activatable NIR AIEgens in the field of disease photo theranostics. [ABSTRACT FROM AUTHOR]

Background: This research proposes an easy to apply quality assurance pipeline for hyperspectral imaging (HSI) systems used for plant phenotyping. Furthermore, a concept for the analysis of quality assured hyperspectral images to investigate plant disease progress is proposed. The quality assurance was applied to a handheld line scanning HSI-system consisting of evaluating spatial and spectral quality parameters as well as the integrated illumination. To test the spatial accuracy at different working distances, the sine-wave-based spatial frequency response (s-SFR) was analysed. The spectral accuracy was assessed by calculating the correlation of calibration-material measurements between the HSI-system and a non-imaging spectrometer. Additionally, different illumination systems were evaluated by analysing the spectral response of sugar beet canopies. As a use case, time series HSI measurements of sugar beet plants infested with Cercospora leaf spot (CLS) were performed to estimate the disease severity using convolutional neural network (CNN) supported data analysis. Results: The measurements of the calibration material were highly correlated with those of the non-imaging spectrometer (r>0.99). The resolution limit was narrowly missed at each of the tested working distances. Slight sharpness differences within individual images could be detected. The use of the integrated LED illumination for HSI can cause a distortion of the spectral response at 677nm and 752nm. The performance for CLS diseased pixel detection of the established CNN was sufficient to estimate a reliable disease severity progression from quality assured hyperspectral measurements with external illumination. Conclusion: The quality assurance pipeline was successfully applied to evaluate a handheld HSI-system. The s-SFR analysis is a valuable method for assessing the spatial accuracy of HSI-systems. Comparing measurements between HSI-systems and a non-imaging spectrometer can provide reliable results on the spectral accuracy of the tested system. This research emphasizes the importance of evenly distributed diffuse illumination for HSI. Although the tested system showed shortcomings in image resolution, sharpness, and illumination, the high spectral accuracy of the tested HSI-system, supported by external illumination, enabled the establishment of a neural network-based concept to determine the severity and progression of CLS. The data driven quality assurance pipeline can be easily applied to any other HSI-system to ensure high quality HSI. [ABSTRACT FROM AUTHOR]

The Planet SuperDove sensors produce eight-band, three-meter resolution images covering the blue, green, red, red-edge, and NIR spectral bands. Variations in spectral response in the data used to perform atmospheric correction combined with low signal-to-noise over ocean waters can lead to visible striping artifacts in the downstream ocean-color products. It was determined that the striping artifacts could be removed from these products by filtering the top of the atmosphere radiance in the red and NIR bands prior to selecting the aerosol models, without sacrificing high-resolution features in the imagery. This paper examines an approach that applies this filtering to the respective bands as a preprocessing step. The outcome and performance of this filtering technique are examined to assess the success of removing the striping effect in atmospherically corrected Planet SuperDove data. [ABSTRACT FROM AUTHOR]

Photodetection technology has garnered extensive research attention due to its wide‐ranging applications in fields such as infrared (IR) imaging, environmental monitoring, and optical communication. Dirac semimetals, characterized by high carrier mobility, zero bandgap, and broad spectral response, show great promise in the development of high‐performance photodetectors. The combination of Dirac semimetals and semiconductors in heterostructures enables broadband photodetection from ultraviolet (UV) to long‐wave infrared (LWIR), offering a new approach to extending the wavelength range of photodetection. This review explores 2D Dirac semimetal/semiconductor heterojunction photodetectors (DSSHP), beginning with an overview of the unique properties of Dirac semimetals. It then discusses various photoresponse mechanisms across different wavelength ranges. Additionally, strategies for enhancing photodetector performance are reviewed and analyzed based on their underlying principles. Finally, the key challenges for Dirac semimetal photodetectors are summarized, and potential future developments are outlined. [ABSTRACT FROM AUTHOR]

Shortwave infrared (SWIR) image sensors have unique functions in many optical applications, leading to widespread attention in developing next‐generation materials and photodetector technologies. Organic photodetectors (OPDs) are highly promising due to their flexibility in molecular design and processability. However, integrating OPDs with silicon readout integrated circuits (ROICs) poses numerous challenges, often resulting in underestimated device performance and limiting technological progress. To address the requirements of integrating top‐illuminated OPD with ROICs and to enhance the external quantum efficiency (EQE), optical microcavities are introduced into the OPDs. The EQE in the SWIR region can be effectively enhanced by properly adjusting the thicknesses of the photoactive layer (PAL) and interlayers. Simulations of the optical field distribution further support the active functions of the microcavity structure. The spatial variation of the microcavities allows the spectral response to shift from 1000 to 1400 nm, and the optimized device achieves an EQE of 25.8% at 1260 nm. Finally, the OPDs are integrated with a silicon‐based test kit, and the results reveal comparable sensing performance, demonstrating the high potential of microcavity resonance for device integration. This design effectively improves the integration of OPDs with traditional ROICs and advances SWIR‐based organic image sensor technology further toward commercialization. [ABSTRACT FROM AUTHOR]

As a novel V‐VI ternary topological insulator, Sb2Te2Se, has recently garnered great attention that has motivated both theoretical and experimental investigations. Numerous simulations have proved that 2D ternary Sb2Te2Se is a promising candidate for various optoelectronic devices. However, there are only a few experimental reports focusing on 2D Sb2Te2Se‐based devices due to the lack of a facile synthetic approach. Herein, few‐layered 2D Sb2Te2Se nanosheets are prepared by efficient liquid phase exfoliation and their photoresponse performance is systematically investigated using a photoelectrochemical type photodetector. As revealed, the 2D Sb2Te2Se‐based photodetector exhibits a significant photoresponse in alkaline electrolytes with excellent long‐term cycling stability (decrement of 3.3% during 15000 cycles). In addition, a wide spectral response ranging from 365 to 700 nm could be achieved, indicating great potential for broad‐band photodetection. With this initial exploration work, it is anticipated that 2D ternary Sb2Te2Se materials can be developed for future optoelectronic devices with high performance. [ABSTRACT FROM AUTHOR]

As unique building blocks for advancing optoelectronics, 2D semiconducting transition metal dichalcogenides have garnered significant attention. However, most previously reported MoS2 photodetectors respond only to visible light with limited absorption, resulting in a narrow spectral response and low sensitivity. Here, a surrounding homojunction MoS2 photodetector featuring localized p‐type nitrogen plasma doping on the surface of n‐type MoS2 while preserving a high‐mobility underlying channel for rapid carrier transport is engineered. The establishment of p‐n homojunction facilitates the efficient separation of photogenerated carriers, thereby boosting the device's intrinsic detection performance. The resulting photoresponsivity is 6.94 × 104 A W−1 and specific detectivity is 1.21 × 1014 Jones @ 638 nm, with an optimal light on/off ratio of ≈107 at VGS = −27 V. Notably, the introduction of additional bands within MoS2 bandgap through nitrogen doping leads to an extrinsic broadband response to short‐wave infrared. The device exhibits a photoresponsivity of 34 A W−1 and a specific detectivity of up to 5.92 × 1010 Jones @ 1550 nm. Furthermore, the high‐performance broadband response is further demonstrated through imaging and integration with waveguides, paving the way for next generation of multifunctional imaging systems and high‐performance photonic chips. [ABSTRACT FROM AUTHOR]

Tuned mass damper (TMD) is a single‐terminal damper, while inerter is a two‐terminal one, which are effective control devices. So, a hybrid damper with a series‐parallel inerter system and a TMD (SPIS‐TMD) in series is proposed. The main work of the manuscript is as follows. Firstly, based on the mechanical diagram of SPIS‐TMD and its equipment on the roof of a high‐rise structure, the general form of seismic motion equation was derived using dynamic finite element technology. Secondly, based on the method of quadratic decomposition for power spectrum density function (QD‐PSDF), the concise analytic solutions for zero‐, first‐, and second‐order response spectral moments (ZFSO‐RSMs) of the general response of structure with SPIS‐TMD were deduced. Thirdly, in response to the numerous parameters that affect the safety of high‐rise structures and the varying difficulty for obtaining SPIS‐TMD's parameters, an optimization analysis technique was proposed, which is constrained by dynamic reliability and SPIS‐TMD's parameter weights. Finally, three examples were given and results show the following. (1) The proposed analytical solutions for ZFSO‐RSMs are correct and high efficiency and can be extended to analysis of stationary seismic responses of general linear structures. (2) Calculating results of ZFSO‐RSMs of general responses with the number of vibration modes corresponding to a participation weight of 100% is exactly the same as those with all vibration modes, and the calculating time of the case of the participation weight of 100% is less than 1/12 that of the case of all vibration modes. (3) The failure probabilities of the structure with SPIS‐TMD with optimal parameters using the proposed method (with a limit failure probability of 0.1587), the structure only equipped with TMD with the same TMD's parameters as SPIS‐TMD, and the structure without dampers are 0.1570, 0.7060, and 0.9778, respectively. It indicates that under the same conditions, the hybrid damper SPIS‐TMD has a better damping effect than a single TMD. [ABSTRACT FROM AUTHOR]

The article in the Journal of Neurogenetics discusses the pioneering work of Bill Pak in using the PDA phenotype to screen a network of phototransduction genes and signaling pathways. Pak's research on the TRP channel and its impact on neurobiology and sensory research is highlighted. The PDA screen, based on the phenomenon of prolonged depolarizing afterpotential, was developed by Pak and proved to be a powerful method for isolating visual mutants in Drosophila. The article details the complex phototransduction cycle and the significance of the PDA mutants identified by Pak's lab in advancing our understanding of the Drosophila visual system. [Extracted from the article]

An analytical study of wave theory-based multilayered SPR-based fiber optic biosensor by shinning Bessel-Gauss (BG) beam is proposed here for early diagnosis of dengue infection. At first, this wave theory-based analytical model shined by Gaussian (G) beam is validated with the already reported experimental data, where the obtained results are in good accord with the experimental findings presented by Y. M. Kamil et al. in 2018. So, it affords the experimental confirmation of the validity of the proposed theory. The enhancement in sensitivity is 1.99 times ascertained by employing G beam for our proposed structure at a spectral sensitivity of 10.008 nm/nM. This theoretical investigation has then been extended utilizing the BG beam, where the observed sensitivity is increased to 59,602.00 dB/RIU and 20.016 nm/nM with a resolution of 1.68 × 10–7, which is 3.98 times higher than the referred published work. Here, the limit of detection is 0.06 pM with a minimum change in transmitted output power of 0.8658 milliwatt/RIU. When the DENV-II E protein concentration ranges from 0.08 pM to 0.6 nM, higher spectral shifts are observed. Consequently, enhancements in sensitivity and resolution can be achieved at reduced concentrations, paving the idea of diagnosis of dengue infection at an early stage. [ABSTRACT FROM AUTHOR]

Yield forecasting and within-field yield variation is essential information that helps farmers develop sustainable agriculture. However, such information still needs to be included for most of them, and remote sensing is an alternative to provide it. Our objective was to assess Random Forest regression models composed of unique GLCM texture measures as an alternative to usual empirical models that use spectral response and auxiliary data, which is complex and reaches varied results. Eleven GLCM texture models based on eight texture measures of a single spectral layer were assessed to represent soybean field yield variation in two sites and seasons. Several models achieved satisfactory results, reaching R2 from 0.90 to 0.95 and RMSE from 0.06 to 0.26 t/ha. Models above 15-window size are recommended for the soybean yield prediction as window size is an essential attribute to GLCM performance. Models derived from the bands individually (red, red-edge, near-infrared, and short wavelength infrared) were more sensitive to the window size than those derived from vegetation indices (EVI, GNDVI, GRNDVI, NDMI, NDRE, NDVI, SFDVI). The data aggregated by texture measures improve the individual spectral responses, providing alternatives to predict soybean within-field yield variation using random forest models. [ABSTRACT FROM AUTHOR]

Semiconductor oxides are widely used in the field of optical materials due to their broad spectral response, tunable structure, low cost, high chemical and thermal stability, among other advantages. The design and fabrication of photochromic materials in semiconductor oxides have shown tremendous potential in various fields such as optoelectronic displays, optical storage, and light-stimulated responses. In this work, we have designed and fabricated a novel inorganic photochromic material by doping Sm3+ ions into the semiconductor oxide CaBiNb2O9 (CBN). The introduction of Sm3+ ions induces the formation of oxygen vacancies and cationic vacancies in CBN, greatly enhancing the photochromic effect of the matrix. CaBiNb2O9: Sm3+ (CBN: Sm) can achieve reversible photochromic response through 254 nm light irradiation and 350 ℃ thermal stimulation, and exhibit excellent stability and fatigue resistance. The photochromic process and performance of the CBN: Sm materials were characterized, and the potential mechanisms were analyzed and discussed. The conducted research and insights will provide support for other researchers in the design and fabrication of photochromic materials based on semiconductor oxides. [ABSTRACT FROM AUTHOR]

A charged colloidal (dust) particle immersed in a plasma with an ion flow creates a disturbed region behind it, known as a wake. The paper considers a system of two charged and strongly coupled microparticles aligned along the ion flow in a weakly ionized plasma (e.g., in the plasma sheath of a ground-based RF discharge) and confined vertically by an external electric field. Using the OpenDust code, a fully self-consistent numerical simulation of the dynamics of dust particles and the ionic component is carried out. It is demonstrated that the inhomogeneity of the wake field from the upstream particle can significantly change the spectrum of vertical (longitudinal) vibrations of both particles in the system and has a negligible effect on their horizontal (transverse) vibrations. In particular, a relationship exists between horizontal and vertical particle oscillations, manifested as an additional mode of vertical vibrations of particles corresponding to the doubled frequency of their relative horizontal vibrations. In accordance with the model of nonreciprocally coupled stochastically driven oscillators, analytical expressions are derived for the vibrational spectra of particles taking into account the spatial variations in particle charges caused by inhomogeneities in the surrounding plasma. The proposed theory improves the experimental method of spectral response to stochastic processes, enabling the measurement of effective forces, particle friction coefficients, and temperatures of their heat sources, as well as the horizontal charge gradient of the lower particle oscillating in the wake field of the upper one. [ABSTRACT FROM AUTHOR]

The 1934 M w 8.2 Bihar–Nepal earthquake was one of the devastating earthquakes, which made seismologists realize the importance of proper seismic hazard analysis and design aspects in India. The event occurred way before proper seismic networks were implemented and hence there are no recorded ground motions available for this event. This study, thus aims to generate possible ground motions for the 1934 M w 8.2 Bihar–Nepal event. The complex geographical features, ambiguous source information and lack of ground motion data make the simulation and validation of ground motions very difficult. In this regard, the broad-band (BB) ground motions are simulated and validated for the most recent well-documented Himalayan event, that is, the 2015 M w 7.9 Nepal earthquake in order to calibrate the model and simulation methodology. For this purpose, the computational model is presented for a region of 1000 km × 670 km (longitude 80–89 °E and latitude 23–30 °N) in the Indo-Gangetic Basin to simulate the low-frequency (LF) ground motions using spectral element method. These deterministically simulated LF ground motions are combined with stochastically simulated high-frequency (HF) ground motions based on an improved seismological model. The seismic moment and dimensions of the rupture plane are used to generate ten samples for the finite fault source model having different slip distribution along the rupture plane as a random field. The BB ground motions (0.01–25 Hz) are obtained by merging LF and HF ground motions in the time domain by matching them at a frequency of ∼0.3 Hz. Such BB results are simulated at a grid of stations and at locations where modified Mercalli intensity (MMI) values are available. The estimated MMI values and the observed MMI values are compared to emphasize the efficacy of the model. The maximum PGA estimated from the simulated ground motions in horizontal and vertical directions are observed to be 0.48 g and 0.4 g. Further, 5 per cent damped response spectra and spectral amplification are analysed concerning the sediment depth of the Indo-Gangetic Basin. The results from the study can serve as inputs for dynamic analysis and the design of earthquake-resistant structures across different locations in the Indo-Gangetic Basin. [ABSTRACT FROM AUTHOR]

Arctic sea-ice surface temperature (IST) is an important environmental and climatic parameter. Currently, wide-swath sea-ice surface temperature products have a spatial resolution of approximately 1000 m. The Medium Resolution Spectral Imager (MERSI-I) offers a thermal infrared channel with a wide-swath width of 2900 km and a high spatial resolution of 250 m. In this study, we developed an applicable single-channel algorithm to retrieve ISTs from MERSI-I data. The algorithm accounts for the following challenges: (1) the wide range of incidence angle; (2) the unstable snow-covered ice surface; (3) the variation in atmospheric water vapor content; and (4) the unique spectral response function of MERSI-I. We reduced the impact of using a constant emissivity on the IST retrieval accuracy by simulating the directional emissivity. Different ice surface types were used in the simulation, and we recommend the sun crust type as the most suitable for IST retrieval. We estimated the real-time water vapor content using a band ratio method from the MERSI-I near-infrared data. The results show that the retrieved IST was lower than the buoy measurements, with a mean bias and root-mean-square error (RMSE) of −1.928 K and 2.616 K. The retrieved IST is higher than the IceBridge measurements, with a mean bias and RMSE of 1.056 K and 1.760 K. Compared with the original algorithm, the developed algorithm has higher accuracy and reliability. The sensitivity analysis shows that the atmospheric water vapor content with an error of 20% may lead to an IST retrieval error of less than 1.01 K. [ABSTRACT FROM AUTHOR]

In the past decades, satellite hyperspectral remote sensing instruments have been providing key measurements for environmental monitoring, such as the analysis of water and air quality, soil usage, weather forecasting, or climate change. The success of this technology, however, relies on an accurate knowledge of the instrument's spectral response functions (SRFs). Usually, the SRFs are assessed on-ground and then monitored on-flight using tedious analysis of the acquired radiances coupled with instrumental models; nonetheless, the complete retrieval of the SRFs is generally out of reach. In this context, EUMETSAT has developed a novel SRF retrieval methodology, with the intention of applying it routinely to the current Metop IASI instruments and soon to Metop-SG IASI-NG, and MTG-S IRS. By making use of spatiotemporal colocations of different detectors within a single instrument or between different platforms, relative SRFs may be retrieved on-flight without any a priori knowledge. The presented methodology is suited for instruments acquiring radiances with contiguous sampling over large spectral bands as the SRFs are retrieved by analyzing the neighboring channels' correlations. This article focuses on Fourier transform spectrometers (FTS) in the far infrared as they possess these characteristics per design, but it is believed that the method could be extended to other technology and spectral bands. The SRFs are further processed to evaluate the relative self-apodization functions (SAFs), as they represent the discrepancies between the detectors at the interferograms level, the primary measurements of FTS. The following article presents both simulations and applications of the SRF retrieval for the three IASI instruments aboard the Metop platforms of the EPS program. We analyze both IASI sensors aboard Metop-B and C as well as the evolution of Metop-A IASI over 13 years of operation. [ABSTRACT FROM AUTHOR]

Evaluation of ground motion induced by underground blasting is a growing concern due to increased mining of large underground deposits. A numerical analysis is first conducted on the wave propagation characteristics, taking into account geological conditions and ground topography, and it is compared to that resulting from open-pit blasts. Then systemic experiments are conducted at two ore blocks in an underground mine. Predictions are made for peak particle velocity (PPV), frequency, and their combination for ground motions, which are then compared to inside rock vibrations induced by the same ore block blasts. Due to traditional inadequate prediction, the response spectral analysis and the normalized pseudo velocity response spectra (NPVRS) are employed to create a novel approach for illustrating ground motions. The results of numerical calculation and experimental analysis allow for the following conclusions: the wave propagation induced by underground blasting along the ground surface is more complex than that from open-pit blasts; the effect of charge weight on ground vibration decreases with a power factor (n) in the scaling attenuation equation lower than 1/3, as opposed to the typically acceptance of n being 1/2 for open-pit blasts and 1/3 for inside rock vibration induced by underground blasting; the frequency significantly drops from inside rock to ground surface; the NPVRS is a reasonable indicator for quantifying ground motions at specific positions with connecting structural responses, the relative displacement in the concerning frequency range of 5–20 Hz is linearly proportional to ground peak amplitudes. Highlights: A systematic experimental work on surface ground motion induced by underground blasting Comparison of inside rock and ground vibration from underground blasting Decreasing effect of charge weight on ground vibration induced by underground blasting Normalized pseudo velocity response spectra (NPVRS) can be simplified as the same at a specific position for effectively predicting ground vibrations [ABSTRACT FROM AUTHOR]

Mathura city, located in Uttar Pradesh, India, faces a high earthquake risk due to its proximity to earthquake-prone regions, population growth, and nearby seismic sources. This study aims to assess seismic hazard by estimating Peak Ground Acceleration (PGA) values for a 2% probability of exceedance in 50 years, with a return period of 2475 years. Using Deterministic Seismic Hazard Analysis (DSHA), we created seismic hazard maps and spectral acceleration response curves. Since we lacked region-specific Ground Motion Prediction Equations (GMPEs), a logic tree approach consisting of four different models to estimate PGA values was used, each assigned a weight based on likelihood. Our analysis predicts future PGAs from 0.14 to 0.35 g. The study identifies the northern parts of Mathura, including Bajna, Nauhjhil, Surir, Shahpur, and Kosi, as more vulnerable to seismic hazards. The seismic hazard maps were divided into three regions, and the site-specific spectral acceleration responses were produced with IS-1893, Part 1 (2016) for 5% damping, assuming bedrock conditions. [ABSTRACT FROM AUTHOR]

The 1H and 13C NMR spectra of the N‐(3,5‐dichloro‐4‐hydroxyphenyl)‐ 2,4,6‐triphenylpyridinium perchlorate and of its deprotonated betaine 4‐(2,4,6‐triphenylpyridinio)‐2,6‐dichlorophenolate (Wolfbeis's ET(33) dye) were recorded in various solvents and analyzed in search of solvent‐dependent shifts that characterize their solvatomagnetism, which was compared with the well‐known UV–vis spectral behavior of this important solvatochromic dye. Although the NMR spectra of ET(33) and its phenolic precursor in different solvents correlated only poorly with their UV–vis spectral responses, they provided valuable information on specific structural features and solute–solvent interactions that are not available from their UV–vis spectra. [ABSTRACT FROM AUTHOR]

The effect of optical stimulation at a frequency of 10 Hz (OS10Hz) on temporal parameters of sensorimotor activity in healthy subjects (n=32) was studied. The expression of the activation response was determined by the ratio of spectral power values (SPα2, μV2) of the high frequency (10-13 Hz) subrange of the α-rhythm of the initial EEG with closed and opened eyes and the frequency of the maximum α-peak (IAPF). A test for simple motor reaction time was performed under normal and OS10Hz conditions. According to the change in the variability of simple motor reaction time (SDSMRT) under OS10Hz compared to the normal conditions, the subjects were classified into two groups: those who showed a decrease (group 1) and those who showed an increase (group 2) in SDSMRT. The subjects of group 1 had significantly higher IAPF (in the O1 lead with eyes closed) and activation reaction intensity (in the O2, O1, P4, P3, and F3 leads) compared to the subjects of group 2. The obtained data suggest that OS10Hz changes the parameters of psychomotor reactions of an individual, and the direction of changes is mediated by individual features of the initial EEG. [ABSTRACT FROM AUTHOR]

On‐chip spectral imaging based on engineered spectral modulation and computational spectral reconstruction provides a promising scheme for portable spectral cameras. However, the angle dependence of modulation units results in the angle sensitivity of spectral imaging, which limits its practical applications. Here, metal is utilized instead of dielectric materials to realize on‐chip angle‐robust computational spectral imaging based on a group of topology‐optimized plasmonic metasurface units under a 30° field‐of‐view, and demonstrate angle‐insensitive spectral imaging in the wavelength range of 450–750 nm for average polarization. Furthermore, it is experimentally verified that the angle‐insensitive spectral filtering effects of the fabricated metasurface units, and demonstrated angle‐robust spectral reconstruction with a fidelity of over 98% as well as spectral imaging for a standard color checker. This approach expands the application scale of spectral imaging, which has great potential on metal‐based on‐chip multimodal imaging with dimension of depth, polarization, spectrum and so on. [ABSTRACT FROM AUTHOR]