Spectroscopy Modeling Research Articles

Spectroscopic Modeling of Luminous Transients Powered by H-rich and He-rich Circumstellar Interaction

Abstract In this study, we perform detailed spectroscopic modeling to analyze the interaction of circumstellar material (CSM) with ejecta in both hydrogen-rich and hydrogen-poor superluminous supernovae (SLSNe), by systematically varying properties such as the CSM density, composition, and geometry to explore their effects on spectral lines and light-curve evolution. Using advanced radiative transfer simulations with the new, open-source SuperLite code to generate synthetic spectra, we identify key spectroscopic indicators of CSM characteristics. Our findings demonstrate that spectral lines of hydrogen and helium exhibit significant variations due to differences in CSM mass and composition. In hydrogen-rich Type II SLSNe, we observe pronounced hydrogen emission lines that correlate strongly with a dense, extended CSM, suggesting massive, eruptive mass-loss histories. Conversely, in hydrogen-poor SLSNe, we recover mostly featureless spectra at early times, with weak hydrogen lines appearing only in the very early phases of the explosion, highlighting the quick ionization of traces of hydrogen present in the CSM. We analyze the properties of the resulting emission lines, particularly H α and H β , for our models using sophisticated statistical methods. This analysis reveals how variations in the SN progenitor and CSM properties can lead to distinct spectroscopic evolutions over time. These temporal changes provide crucial insights into the underlying physics driving the explosion and the subsequent interaction with the CSM. By linking these spectroscopic observations to the initial properties of the progenitor and its surrounding material, our study offers a useful tool for probing the pre-explosion histories of these explosive events.

The NuSTAR Local AGN N H Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe

Abstract Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of N H > 1024 cm−2. To tackle this issue, we present the NuSTAR Local AGN N H Distribution Survey (NuLANDS)—a legacy sample of 122 nearby (z < 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 μm. We show that optically classified Type 1 and 2 AGN in NuLANDS are indistinguishable in terms of optical [O iii] line flux and mid-to-far-infrared AGN continuum bolometric indicators, as expected from an isotropically selected AGN sample, while Type 2 AGN are deficient in terms of their observed hard X-ray flux. By testing many X-ray spectroscopic models, we show the measured line-of-sight column density varies on average by ∼1.4 orders of magnitude depending on the obscurer geometry. To circumvent such issues, we propagate the uncertainties per source into the parent column density distribution, finding a directly measured Compton-thick fraction of 35% ± 9%. By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration. This bias implies an even higher intrinsic obscured AGN fraction may be possible, although tests for additional biases arising from our infrared selection find no strong effects on the measured column density distribution. NuLANDS thus holds potential as an optimized sample for future follow-up with current and next-generation instruments aiming to study the local AGN population in an isotropic manner.

ExoMol line lists – LXI. A trihybrid line list for rovibronic transitions of the hydroxyl radical (OH)

Abstract The hydroxyl radical (OH) is a species of high importance in exoplanetary studies, the interstellar medium, and in stellar spectra. Terrestrially it is a significant component of combustion chemistry, an oxidizer in the upper atmosphere, and a source of telluric bands. Internally contracted multi-reference configuration interaction potential energy curves (PECs), spin-orbit couplings, electronic angular momentum couplings, and (transition) dipole moments for eight electronic states of OH are computed and refined against empirical energy levels to produce an OH spectroscopic model. A line list consisting of rovibronic term values, allowed electronic dipole transitions, Einstein-A coefficients, and partition functions for varying temperature and a continuum absorption data set are then produced by variational solution of the coupled-channel Schrödinger equations using the nuclear motion code Duo. Marvel energy levels substitute equivalent levels in the OH line list, with estimated uncertainties in experimentally dark regions, following an established hybridization procedure. Predissociation lifetimes of the A 2Σ+ state are calculated using a stabilization method and convoluted with natural lifetimes to include predissociative effects. Continuum absorption cross sections for T ∈ [100, 200, ..., 8000] K and zero pressure are provided in the range of 0 → 80 000 cm−1 with a step size of 0.01 cm−1. Comparison with available literature cross sections exhibits strong agreement. The line list is suitable for high-resolution studies up to 8000 K. The OH MYTHOS dataset is available for download via www.exomol.com.

Quality Differences in Frozen Mackerel According to Thawing Method: Potential Classification via Hyperspectral Imaging

Seafood quality preservation remains a critical focus in the food industry, particularly as the freeze–thaw process significantly impacts the freshness and safety of aquatic products. This study investigated quality changes in frozen mackerel subjected to two thawing methods, room temperature (RT) and running water (WT), and assessed the potential of hyperspectral imaging (HSI) for classifying these methods. After thawing, mackerel samples were stored at 5 °C for 21 days, with physicochemical, textural, and spectroscopic analyses tracking quality changes and supporting the development of a spectroscopic classification model. Compared with the WT method, the RT method delayed changes in key quality indicators, including pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC), by 1–2 days, suggesting it may better preserve initial quality. Texture profile analysis showed similar trends, supporting the benefit of RT in maintaining quality. A major focus was on using HSI to assess quality and classify thawing methods. HSI achieved high classification accuracy (Rc2 = 0.9547) in distinguishing thawing methods up to three days post-thaw, with 1100, 1200, and 1400 nm wavelengths identified as key spectral markers. The HIS’s ability to detect differences between thawing methods, even when conventional analyses showed minimal variation, highlights its potential as a powerful tool for quality assessment and process control in the seafood industry, enabling detection of subtle quality changes that traditional methods may miss.

ExoMol line lists – LXV. Mid-Infrared rovibronic spectroscopy of isotopologues of NiH

Abstract New line lists for four isotopologues of nickel monohydride, 58NiH, 60NiH, 62NiH, and 58NiD are presented covering the wavenumber range <10000 cm−1 (λ > 1 μm), J up to 37.5 for transitions within and between the three lowest-lying electronic states, X 2Δ, W 2Π, and V 2Σ+. The line lists are applicable for temperatures up to 5000 K. The line lists calculations are based on a recent empirical NiH spectroscopic model [Havalyova et al. J. Quant. Spectrosc. Radiat. Transf., 272, 107800, (2021)] which is adapted for the variational nuclear-motion code Duo. The model consists of potential energy curves, spin-orbit coupling curves, electronic angular momentum curves, spin-rotation coupling curves, Λ-doubling correction curve for 2Π states and Born-Oppenheimer breakdown (BOB) rotational correction curves. New ab initio dipole moment curves, scaled to match the experimental dipole moment of the ground state, are used to compute Einstein A coefficients. The BYOT line lists are included in the ExoMol database at www.exomol.com.

Electrochemical Activity of Oxygen in Li-Ion Battery Cathodes from X-Ray Spectroscopic Modeling

As demand for better performance in energy storage increases, a clear understanding of the charge compensating mechanism in Li-ion battery cathodes is essential for developing next generation battery chemistries and materials. X-ray core level spectroscopies, e.g. x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS), allow for experimental measurement of the electronic structure of battery materials before and after charge, providing the clearest physical picture of electrochemical device operation.Here, we present numerical modeling of the XAS/RIXS of various battery chemistries compared to experimental measurements in situ. Modeling spectroscopic changes before and after discharge using not only density functional theory (DFT) based techniques but also exact diagonalization atomic multiplet formalisms prove crucial in these materials to accurately model correlation effects seen in their spectra, where reversible changes in the transition metal L3-edge spectroscopy may erroneously point to cationic redox. We address the common concept of transition metal redox, highlight the essential role of oxygen in both reversible and irreversible processes, and the break down in the standard paradigm of cationic/anionic redox.

Development and demonstration of a two-color nitric oxide vibrational temperature diagnostic using spectrally-resolved ultraviolet laser absorption

Development of a new ultraviolet (UV) laser absorption diagnostic has enabled the probing of nitric oxide (NO) in the second excited vibrational state (v” = 2) for inferences of quantum-state-specific number density and vibrational temperature time-histories. Spectroscopic modeling informed the selection of the new 246.3222 nm wavelength, as this wavelength exhibits high sensitivity for thermometry in the 2000 – 8000 K temperature range. This 246.3222 nm absorption feature consists of contributions from the R12(24.5), R11(15.5), Q22(24.5), and Q21(15.5) transitions all originating in the v” = 2 state. Absorption cross-sections at this selected wavelength were measured in reflected shock experiments for sweeps of both wavelength and temperature. The wavelength sweep investigated cross-sections over a 246.3202 – 246.3246 nm range at 4590 K, and the temperature sweep measured cross-sections over a 2500 – 7500 K range at the peak of the absorption feature (246.3222 nm). Cross-section results agree with the Stanford NO gamma-band model to within ±5%, confirming the use of the model for subsequent thermometry studies. Thermometry was demonstrated in reflected shock experiments probing the vibrational relaxation and chemical reactions in 2% NO diluted in either argon (Ar) or nitrogen (N2). These experiments leverage previous UV laser absorption diagnostics that probe NO in the ground vibrational state (v” = 0) using the R11(26.5), R12(34.5), Q21(26.5) , and Q22(34.5) transitions near 224.8155 nm and the Q11(12.5) , R12(19.5) , P21(12.5) , and Q22(19.5) transitions near 226.1026 nm, which were studied in Ref. [1]. The combination of the new diagnostic wavelength with previously validated diagnostics yields low-uncertainty vibrational temperature time-histories that are in excellent agreement with previously inferred vibrational relaxation time results from Refs. [2] and [3]. Future work will apply this two-color nitric oxide vibrational temperature diagnostic to probe the vibrational temperature of NO formed in high-temperature, shock-heated air at conditions relevant to hypersonic and reentry vehicles.

Measurements and kinetic modeling of O2 vibrational Kknetics in O2-Ar mixtures partially dissociated by a Ns pulse discharge

Abstract Vibrational kinetics of O2 is studied during the O atom recombination in an O2-Ar mixture, partially dissociated by a burst of ns discharge pulses in a heated plasma flow reactor. The time-resolved temperature in the discharge afterglow is determined by Rayleigh scattering. Time-resolved O atom number density is measured by ps Two-Photon absorption Laser Induced Fluorescence (TALIF), calibrated in xenon. Time-resolved vibrational level populations of molecular oxygen, O2(v=8-20), are measured by ps Laser Induced Fluorescence (LIF), with the absolute calibration by NO LIF. Time-resolved ozone number density is monitored by broadband UV absorption. The results are compared with the predictions of a state-specific kinetic model. The experimental data indicate a rapid initial decay of O2(v) populations generated by electron impact in the discharge, due to the vibration-translation (V-T) relaxation by O atoms. This is followed by a slower population reduction, on the time scale much longer compared to that for V-T relaxation or vibration-vibration (V-V) exchange. Both O atoms and the O2(v) populations decay on the same time scale, indicating that chemical reactions initiated by the O atom recombination result in the generation of vibrationally excited O2 molecules. These trends are reproduced by the kinetic model, which shows that the reaction of O atoms with ozone is the dominant pathway of O2(v) generation at the present conditions. The predicted relative O2(v) populations are close to the experimental results, but absolute number densities differ from the experimental data. This is likely due to uncertainties in the absolute calibration of LIF measurements and in the spectroscopic model used in the data reduction. The present work demonstrates the capability for the absolute, time-resolved measurements of vibrationally excited O2 in recombining gas flows, to quantify the energy partition in the recombination reactions.

Spectroscopic Measurements and Models of Energy Deposition in the Substrate of Quantum Circuits by Natural Ionizing Radiation

Naturally occurring background radiation is a potential source of correlated decoherence events in superconducting qubits that will challenge error-correction schemes. In order to characterize the radiation environment in an unshielded laboratory representative of superconducting qubits’ environments, we performed broadband, spectroscopic measurements of background radiation events inside a millikelvin refrigerator. The spectrometer was designed to mimic the size and composition of a quantum circuit. Specifically, we measured the background radiation spectra in silicon substrates of two thicknesses, 500 and 1500 µm, and one area, 25 mm2. The observed spectra span energies from a few kilo-electron-volts up to nearly 10 MeV, are nearly featureless, and decrease in intensity by a factor of 40 000 between 100 keV and 3 MeV for the 500-µm substrate. We integrate the spectra to obtain the average event rates and deposited power levels. These quantities correspond to a rate of 0.023 events per second and a power of 4.9 keV s−1, when counting events that deposit at least 40 keV for the 500-µm-thick substrate. We find that the cryogenic measurements are in good agreement with predictions based on simple measurements of the terrestrial gamma-ray flux outside the refrigerator, published models of cosmic-ray fluxes, a crude model of the cryostat, and radiation-transport simulations. This model requires no free parameters to predict the background radiation spectra in the silicon substrates. The agreement between measurements and predictions demonstrates that the model we present can be used to assess the relative contributions of terrestrial and cosmic-ray sources to background radiation interactions in silicon substrates of varying thickness. These spectroscopic measurements are performed with a novel combination of superconducting microresonators located on micromachined silicon islands that define the interaction volume with background radiation. The resonators transduce deposited energy to a readily detectable electrical signal. Microresonator readout closely resembles dispersive superconducting qubit readout, so similar devices—with or without micromachined islands—are suitable for integration with superconducting quantum circuits as detectors for background radiation events. For our specific laboratory conditions, we find that gamma-ray emissions from radioisotopes are responsible for the majority of events that deposit E<1MeV. We present results demonstrating that the background radiation spectrum contains relevant contributions from cosmic-ray particles other than muons, particularly a tail of multi-mega-electron-volt events due to protons and neutrons. These observations suggest several paths to reducing the impact of background radiation on quantum circuits, supported by an empirically validated model for generating reliable predictions of radiation interactions with silicon substrates. Published by the American Physical Society 2024

A simple model for spectroscopic analyses of active stars

Abstract Spectroscopic analyses of young late-type stars suffer from systematic inaccuracies, typically under-estimating metallicities but over-estimating abundances of certain elements including oxygen and barium. Effects are stronger in younger and cooler stars, and recent evidence specifically indicates a connection to the level of chromospheric activity. We present here a two-component spectroscopic model representing a non-magnetic baseline plus a magnetic spot, and analyse the resulting synthetic spectra of young solar analogues using a standard spectroscopic technique. For a moderately active star with solar parameters and chromospheric activity index $\log R_\text{HK}^{\prime }= -4.3$ (∼100 Myr), we predict that [Fe/H] is underestimated by 0.06 dex while vmic is overestimated by 0.2 km s−1; for higher activity levels we predict effects as large as 0.2 dex and 0.7 km s−1. Predictions are in agreement with literature data on solar twins, and indicate that the model is a plausible explanation to the observed effects. The model is simple enough that it can be included in spectroscopic packages with only changes to the underlying spectrum synthesis modules, if a $\log R_\text{HK}^{\prime }$ value is provided.

Modelling absorption and emission profiles from accretion disc winds with WINE

Context. Fast and massive winds are ubiquitously observed in the UV and X-ray spectra of active galactic nuclei (AGNs) and other accretion-powered sources. Several theoretical and observational pieces of evidence suggest they are launched at accretion disc scales, carrying significant mass and angular momentum. Thanks to such high-energy output, they may play an important role in transferring the energy released by accretion to the surrounding environment. In the case of AGNs, this process can help to set the so-called co-evolution between an AGN and its host galaxy, which mutually regulates their growth across cosmic time. To precisely assess the effective role of UV and X-ray winds at accretion disc scales, it is necessary to accurately measure their properties, including mass and energy rates. However, this is a challenging task, due to both the limited signal-to-noise ratio of available observations and the limitations of the models currently used in the spectral analysis. Aims. We aim to maximise the scientific return of current and future observations by improving the theoretical modelling of these winds through our Winds in the Ionised Nuclear Environment (WINE) model. WINE is a spectroscopic model specifically designed for disc winds in AGNs and compact accreting sources, which couples photoionisation and radiative transfer with special relativistic effects and a three-dimensional model of the emission profiles. Methods. We explore with WINE the main spectral features associated with the disc winds in AGNs, with a particular emphasis on the detectability of the wind emission in the total transmitted spectrum. We explore the impact of the wind ionisation, column density, velocity field, and geometry in shaping the emission profiles. We simulated observations with the X-ray microcalorimeter Resolve on board the recently launched XRISM satellite and the X-IFU on board the future Athena mission. This allows us to assess the capabilities of these telescopes in the study of disc winds in X-ray spectra of AGNs for the typical physical properties and exposure times of the sources included in the XRISM performance verification phase. Results. The wind kinematic and geometry (together with the ionisation and column density) deeply affect both shape and strength of the wind spectral features. Thanks to this, both Resolve and, on a longer timescale, X-IFU will be able to accurately constrain the main properties of disc winds over a broad range of ionisation, column densities, and covering factors. We also investigate the impact of the spectral energy distribution (SED) on the resulting appearance of the wind. Our findings reveal a dramatic difference in the gas opacity when using a soft, Narrow Line Seyfert 1-like SED compared to a canonical powerlaw SED with a spectral index of Γ ≈ 2.

A comprehensive study of five candidate δ Scuti-type pulsators in detached eclipsing binaries

Context. Pulsating stars in eclipsing binaries (EBs) provide an excellent opportunity to obtain precise, model-independent stellar parameters for studying these oscillations in detail. One of the most common classes of pulsators found in such EBs exhibits δ Scuti-type oscillations. Characterising these pulsators using the precise stellar parameters obtained using EB modelling can help us better understand such stars, and provide strong anchors for asteroseismic studies. Aims. We performed a comprehensive photometric and spectroscopic analysis of candidate pulsators in detached EBs, to add to the sample of such systems with accurately determined absolute parameters. Methods. We performed radial velocity and light curve modelling to estimate the absolute stellar parameters, and detailed spectroscopic modelling to obtain the global metallicity and temperatures. Frequency power spectra were obtained using residuals from binary modelling. Finally, we used isochrones to determine the age of the stars, and compared the estimated physical parameters to the theoretically obtained values. Results. We present a detailed analysis of four candidate δ Scuti-type pulsators in EBs, and update the light curve analysis of the previously studied system TIC 308953703. The masses and radii of components are constrained to a high accuracy, which helps us constrain the age of the systems. We perform a Fourier analysis of the observed oscillations, and try to explain their origin. For TIC 81702112, we report tidal effects causing amplitude variation in the oscillation frequencies over the orbital phase.

Mechanistic insights into the interaction of anxiolytic drugs with human serum albumin in a ternary system utilizing spectroscopic and molecular modeling approaches

In recent years, buspirone has been co-administered with sertraline to resolve sexual disorders caused by sertraline. Therefore, the present study was conducted to investigate the interaction effect of two antidepressants and anxiolytic drugs, sertraline and buspirone, on human serum albumin (HSA) using spectroscopic and molecular docking techniques. Fluorescence emission spectroscopy and molecular docking were used to calculate the binding affinity and determine the best binding sites for these two drugs. Additionally, UV-visible and circular dichroism spectroscopy were performed to investigate the effect of these drugs on the conformational changes of HSA. The results showed that both drugs have a strong ability to quench the fluorescence of HSA through a static mechanism, and cause structural changes in HSA. It was also found that binding of sertraline and buspirone to HSA is spontaneous (ΔG° <) and hydrophobic interactions, van der Waals forces and hydrogen bonds play a significant role in these interactions in the ternary system. In addition, molecular docking data showed that both drugs bind with high affinity to the Trp residue in subdomain IIA. The binding constants (Kb) for (HSA-SRH)-BSH and (HSA-BSH)-SRH were equal to 6.30 and 3.99, respectively, at 298 K. This study demonstrates that the presence of the second drug (buspirone/sertraline) affects the interaction and binding affinity of the first drug (sertraline/buspirone) to human serum albumin.

Determination of the particle size distribution of cube-shaped colloidal perovskite quantum dots from photoluminescence spectra: A combined theoretical-experimental approach.

A theoretical-experimental approach is proposed to convert the photoluminescence spectra of colloidal perovskite quantum dot ensembles into accurate estimates for their intrinsic particle size distribution functions. Two main problems were addressed and properly correlated: the size dependence of the first excitonic transition in a single cube-shaped quantum dot and the inhomogeneous broadening of the fluorescence line shape due to the size nonuniformity of the chemically prepared quantum dot suspension in addition to the single-dot homogeneous broadening. By applying the reported methodology to CsPbBr3 quantum dot samples belonging to the strong and intermediate confinement regimes, the calculated size distributions exhibited close agreement with those obtained from transmission electron microscopy, with precise estimates for the average particle size and standard deviation. Specifically for strongly confined ultrasmall CsPbBr3 quantum dots, the presented spectroscopic model for size distribution computation is based on a new analytical expression for the size-dependent bandgap, which was developed within the framework of the finite-depth square-well effective mass approximation accounting for band nonparabolicity effects. Such a quantum mechanical approach correctly predicts the expected transition to the intermediate confinement regime in sufficiently large quantum dots, which are traditionally described by the well-known bandgap equation in the infinite potential barrier limit with a spatially correlated electron-hole wavefunction and nonparabolic carrier effective masses. The proposed calculation scheme originates from general theoretical considerations so that it can be readily adapted to semiconductor quantum dots of many other systems, from all inorganic metal halides to hybrid perovskite materials, regardless of the adopted chemical synthesis route.

Geographical Traceability of Millet by Mid-Infrared Spectroscopy and Feature Extraction

To identify the geographical origin of millet accurately, 36 samples of Guangling millet, Qinzhouhuang millet, Liuseng millet, Qiananhuang millet, and 33 samples of Yuzhou millet were collected. Mid-infrared (mid-IR) spectra of all the samples were obtained. Denoising, standard normal variate (SNV), multiplicative scatter correction (MSC), and normalization were carried out to preprocess the data. Principal component analysis (PCA) was used to reduce the dimension of the data, combined with support vector machine (SVM), and the geographical origin of the five kinds of millet was identified. The recognition accuracy of the training set (99.2%) and the prediction set (98.3%) were highest when using the first 12 principal components, indicating that the established mid-IR spectroscopic identification model was feasible and effective. PCA, window analysis, hierarchical clustering analysis, and SVM were combined to extract the feature information of mid-IR spectra of millet from five producing areas. Five wavenumbers, 1026, 1053, 1685, 1715, and 1744 cm-1, were found to be with small correlation, and the recognition accuracy of the training set and the prediction set based on these five features were 95.8% and 100.0%, respectively. The feature extraction method established here could be used to improve the prediction efficiency of the identification model and provide data support for the analysis of differential components.

The Standardized Spectroscopic Mixture Model

The standardized spectral mixture model combines the specificity of a physically based representation of a spectrally mixed pixel with the generality and portability of a spectral index. Earlier studies have used spectrally and geographically diverse collections of broadband and spectroscopic imagery to show that the reflectance of the majority of ice-free landscapes on Earth can be represented as linear mixtures of rock and soil substrates (S), photosynthetic vegetation (V) and dark targets (D) composed of shadow and spectrally absorptive/transmissive materials. However, both broadband and spectroscopic studies of the topology of spectral mixing spaces raise questions about the completeness and generality of the Substrate, Vegetation, Dark (SVD) model for imaging spectrometer data. This study uses a spectrally diverse collection of 40 granules from the EMIT imaging spectrometer to verify the generality and stability of the spectroscopic SVD model and characterize the SVD topology and plane of substrates to assess linearity of spectral mixing. New endmembers for soil and non-photosynthetic vegetation (NPV; N) allow the planar SVD model to be extended to a tetrahedral SVDN model to better accommodate the 3D topology of the mixing space. The SVDN model achieves smaller misfit than the SVD, but does so at the expense of implausible fractions beyond [0, 1]. However, a refined spectroscopic SVD model still achieves small (&lt;0.03) RMS misfit, negligible sensitivity to endmember variability and strongly linear scaling over more than an order of magnitude range of spatial resolution.

Exploration of the role of Hibiscus esculentus (okra) mucilage for the removal of phenothiazinium dyes from water body: Spectroscopic, thermodynamic and molecular modeling study

Environmental pollution poses a major problem now a day. Several dyes, in the form of industrial waste, pollute water body and may cause adverse effects to human health. In this paper ADME and toxicity of fives Phenothiazinium group of dyes Methylene blue (MB), Azure A (AA), Azure B (AB), Azure C (AC) and Toluidine Blue O (TBO) were predicted using Swiss ADME and Protox II tools. Results showed these dyes may herm for living organism due to their carcinogenic, mutagenic and hepatotoxic properties. Removal efficiency of these dyes using okra plant product were determined using spectroscopic, thermodynamic and molecular modeling study. It was revealed that these dyes adsorb on the surface of okra leaf mostly at pH 7.0 and the adsorption isotherms were found to fit in Langmuir and Freundlich isotherm model, while Temkin model fails to do this. Mucilage present in different parts of okra plant plays a significant role on removal of these dyes and is able to remove near about 71–92 % of dyes from water body by itself. As this process did not fit in any of above said adsorption isotherm model, it may be suggested that some other mechanism may happen. Further studies explore that these dyes bound to the hydrophobic pocket of mucilage with binding affinity in the order of 105 M−1 and the bindings were exothermic in nature with enthalpy change in the range of − 2.94 to − 4.28 kcal/mole. Molecular docking study validate all the experimental results obtained from spectroscopic and thermodynamic study and enlighten the role of structure of dyes on their binding affinity to mucilage. This paper will help to systematically understand the role of okra plant products on removal efficiency of Phenothiazinium group of dyes with their structural variations.

Effects of Changes in Pectin Constitution on Optical Properties and Firmness of Peach Flesh during Storage.

Understanding the fundamental light-sample interaction process is a crucial step toward the development of vibrational spectroscopy to determine fruit texture (i.e., firmness). This study aimed to investigate the effect of pectin constitution, including total pectin, water-soluble pectin, protopectin contents, and protopectin index (PI), on the optical properties and firmness of 'Baifeng' and 'Xiahui 8' peach flesh at the different softening degrees during postharvest storage of 6 days at 20 °C. The firmness of 'Baifeng' and 'Xiahui 8' peaches significantly (p < 0.05) changed with a decreasing rate from 90.3% to 92.2%. Peach firmness of these two cultivars correlated well with PI contents (r > 0.912) and showed good internal correlations with optical scattering properties. The light absorption coefficient (μa) and reduced scattering coefficient (μ's) at 600-1600 nm were measured using a single integrating sphere system combined with an inversion algorithm. This relationship of μa and μ's with peach firmness and pectin constitution was first analyzed. Notably, the specific μ's at 660 nm, 950 nm, 1203 nm, and 1453 nm showed a satisfactory prediction of peach firmness and PI of 'Xiahui 8' (R2 ≥ 0.926) and 'Baifeng' peaches (R2 ≥ 0.764), respectively. Furthermore, the prediction models were established based on partial least squares regression coupled with optical properties, and considerable prediction performances were obtained for tissue firmness (Rp2 ≥ 0.863) and PI based on μ's (Rp2 ≥ 0.802). Consequently, these results further verified that the spectroscopic prediction model for peach firmness could be related to the high correlations between PI in tissues and their optical scattering properties. Future research interests could include the development of optical absorption and scattering sensors for rapid and efficient determination of peach firmness.

Can Soil Spectroscopy be a Strong Alternative to the Conventional Methods of Analysis?

Soil is considered as the source of life on the globe. Although, numerous research studies, the soil is not completely understood whereas it is dynamic complex matrix include many simultaneous processes. The conventional methods of soil testing are the most reliable for assessing the land productivity and management. Unfortunately, these methods are time consuming and laborious as well as costly and hazardous to the environment. Therefore, the soil spectroscopy technique provides the functions of detecting, characterizing, quantifying and mapping several soil properties based on the uses of different kinds of the sensors (ground-based, airborne-based, and satellite-based). An integration of soil spectroscopic data, data processing, and modelling is considered as an effective tool for estimating soil parameters. Although these advanced techniques able to predict the majority of soil properties, there are some of these properties require more experiments for building accurate calibration models for estimation. Moreover, creating accurate soil spectral libraries (SSLs) for specific areas or soil types is very crucial for saving time, effort, expenses of soil surveying, sampling, and analysis. The application of these SSLs has a big limitation of the continuous variability of the soil properties over time. Thus, establishing extensive spectral libraries is important and mandatory for covering the small scaled areas’ variabilities as well as available soil types. Till now, the soil spectroscopy is not entirely replacing the conventional testing methods of soils because these techniques need future applications to be trusted and guaranteed of their effectiveness.

Green Syngas Production from Natural Lignin, Sunlight, and Water over Pt-Decorated InGaN Nanowires.

Transformation of lignin to syngas can turn waste into treasure yet remains a tremendous challenge because of its naturally evolved stubborn structure. In this work, light-driven reforming of natural lignin in water for green syngas production is explored using Pt-decorated InGaN nanowires. The spectroscopic characterizations, isotope, and model compound experiments, as well as density function theory calculation, disclose that among a variety of groups including aromatic ring, -OH, -OCH3, -C3H7 with complex chemical bonds of O-H, C-H, C-C, C-O, etc., InGaN nanowires are cooperative with Pt for preferably breaking the C-O bond of the rich O-CH3 group in lignin to liberating ⋅CH3 by photogenerated holes with a minimum dissociation energy of 2.33 eV. Syngas are subsequently yielded from the continuous evolution of ⋅CH3 and ⋅OH from photocatalytic reforming of lignin in water. Together with the superior optoelectronic attributes of Pt-decorated InGaN nanowires, the evolution rate of syngas approaches 43.4 mol ⋅ g-1 ⋅ h-1 with tunable H2/CO ratios and a remarkable turnover number (TON) of 150, 543 mol syngas per mol Pt. Notably, the architecture demonstrates a high light efficiency of 12.1 % for syngas generation under focused light without any extra thermal input. Outdoor test ascertains the viability of producing syngas with the only inputs of natural lignin, water, and sunlight, thus presenting a low-carbon route for synthesizing transportation fuels and value-added chemicals.