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The paper is devoted to investigation of spectral parameters of constricted arc plasma, as a foundation for further development of basic approaches to controlling of plasma-arc technologies of material treatment and welding. The relevance of application of spectrometric analysis of the welding arc consists in obtaining the possibility of sufficiently accurate control of its temperature and energy input into the product being welded, recording initiation of weld defects (internal pores), determination of atmospheric oxygen ingress into the weld pool, etc. The spectral composition, temperature and concentration of the constricted welding arc plasma were determined in the paper to more precisely define its physical characteristics at 80 and 100 A currents, in order to establish the further applicability of dynamic spectral analysis of a constricted plasma arc in control of welding processes. As modern spectrometers with CCD-detectors of the spectral range of 200 ÷ 1100 nm have the resolution of the order of 0.35 nm, which 2-3 times exceeds the quantization step by the measured wavelength, and may lead to considerable errors, an approach is proposed to increase the accuracy of spectrometric measurements to acceptable values. Radiation spectra of the constricted welding arc measured in the wavelength range of 650 ÷ 1000 nm allowed within the model of local thermodynamic equilibrium calculating the excitation temperature of the main spectral range components: Ar I and O I. It was established that the excitation temperature of electron levels of Ar atoms in the welding arc plasma only weakly depends on the discharge current, and it is equal to 13500 ± 500 K. Excitation temperature of O I electron levels was equal to 10000 ± 500 K at arc current of 100 A and to 7200 ± 500 K at 80 A current. Electron density of high-current welding arc plasma was measured by Stark broadening of Ar I lines (696.543; 772.4; 912.3 nm). It was found that with the rise of current of the constricted welding arc by 20%, an increase of charge concentration in the arc plasma by 1.5 times and of its temperature by 1.2 times are observed. [ABSTRACT FROM AUTHOR]

The paper is devoted to investigation of spectral parameters of constricted arc plasma, as a foundation for further development of basic approaches to intellectual controlling of plasma-arc technologies of material treatment and welding. The relevance of application of spectrometric analysis of the welding arc consists in obtaining the possibility of sufficiently accurate control of its temperature and energy input into the product being welded, recording initiation of weld defects (including internal pores), determination of atmospheric oxygen ingress into the weld pool, etc. The spectral composition, temperature and concentration of the constricted welding arc plasma were determined in the paper to more precisely define its physical characteristics at 80 and 100 A currents, in order to establish the further applicability of dynamic spectral analysis of a constricted plasma arc in control of welding processes. As modern spectrometers with CCD-detectors of the spectral range of 200÷1100 nm have the resolution of the order of 0.35 nm, which 2-3 times exceeds the quantization step by the measured wavelength, and may lead to considerable errors, an approach is proposed to increase the accuracy of spectrometric measurements to acceptable values. Radiation spectra of the constricted welding arc measured in the wavelength range of 650÷1000 nm allowed within the model of local thermodynamic equilibrium calculating the excitation temperature of the main spectral range components: Ar I and O I. It was established that the excitation temperature of electron levels of Ar atoms in the welding arc plasma only weakly depends on the discharge current, and it is equal to 13500 ± 500 K. Excitation temperature of O I electron levels was equal to 10000 ± 500 К at arc current of 100 A and to 7200 ± 500 К at 80 A current. Electron density of high-current welding arc plasma was measured by Stark broadening of Ar I lines (696.543; 772.4; 912.3 nm). It was found that with the rise of current of the constricted welding arc by 20%, an increase of charge concentration in the arc plasma by 1.5 times and of its temperature by 1.2 times are observed.

We have experimentally studied the influence of the local ionosphere, namely the ionospheric Alfvén resonator (IAR) and the lower ionospheric resonator at altitudes 80–300 km (sub-IAR) on the amplitude and polarization of the first Schumann resonance. The study is based on spectral analysis of data from simultaneous monitoring of ULF magnetic noise components at a meridional chain of stations: high-latitude stations Barentsburg and Lovozero, mid-latitude observatory NNGU NIRFI (NL, Nizhny Novgorod Region), a low-latitude station in Israel. We have also used monitoring data from the Borok and Crete observatories. At the stations in dark conditions, significant variations were found in the spectrum of the polarization parameter ε at the frequency of the first Schumann resonance (SR). Moreover, these variations had different character at different observatories. Analysis of the daily dynamics of the parameter ε has shown that these variations are associated with the influence of local sub-IAR having different optical thickness and quality factor at these observatories. The influence of sub-IAR on polarization in the SR band was found to depend on the ratio of the boundary frequency fb (the frequency that separates the negative and positive polarization of ULF magnetic noise) to the frequency of the first SR. The IAR influence on the polarization and amplitude of magnetic fields in the frequency band of the first Schumann resonance was discovered only at the NL and Lovozero stations: a high-quality Alfvén resonator in the ionosphere above the NL station could cause the SR frequency band to change and its central frequency to shift. Analysis of low-frequency data from the observatories separated by distances of 400 km has revealed that the influence of local ionospheric resonators can lead to a difference in the amplitude characteristics of the first SR even at such distances. It has also been shown that the influence of the IAR and sub-IAR resonators on the azimuthal angle of the magnetic field vector in the frequency band of the first SR is less noticeable and can generate variations in this parameter by 10°–20°. Numerical calculations performed for the spherical waveguide model made it possible to adequately interpret the features of the daily dynamics of the parameter ε in the frequency range of the first SR.

Objective To investigate the value of dual-layer detector spectral CT in the differential diagnosis of arterial phase hyperenhancement (APHE) liver metastases and hepatocellular carcinoma (HCC). Methods Fifty-three patients with clinical or pathologically confirmed APHE liver metastasis (23) and HCC (30) from December 2021 to June 2023 were included in this retrospective study . The spectral CT parameters on the standardized virtual monoenergetic image (VMI) including tumor / liver standardized iodine no water (NINW-Ltumor to liver), tumor/liver standardized iodine density (NID-L), tumor/liver standardized Z-effective (NZeff-L), and tumor/abdominal aorta NZeff (NZeff-Atumor to aorta) were calculated. The receiver operating characteristic (ROC) curve and Cohen d were used to analyze the diagnostic effectiveness of these parameters. Results In the arterial phase, the CT values of liver on 40 keV (NCT-L40keV), 50 keV (NCT-L50keV), and 60 keV (NCT-L60keV) VMI, NINW-L, NID-L, NZeff-L and NZeff-A of APHE liver metastases were significantly less than that of HCC (P<0.05). The area under the ROC curve of NINW-L in the arterial phase was the highest at 0.752. The 0.298 threshold value of NINW -L in the arterial phase had the best differentiation between liver metastases and HCC with 63.3% sensitivity and 87.0% specificity. Conclusion NCT-L40keV, NINW-L and NID-L in the arterial phase are valuable for differentiating APHE liver metastasis from HCC. [ABSTRACT FROM AUTHOR]

The rapid and accurate diagnosis of nitrogen content in apple orchard soil is of great significance for the rational application of nitrogen fertilizer in orchards to improve apple yield and quality. An apple orchard in Shuangquan Town, Changqing District, Jinan City, Shandong Province, was taken as the experimental area. The optimal method for extracting spectral characteristic bands and screening spectral characteristic indices (SCIs) of soil total nitrogen (TN) for independent and comprehensive fertilization periods was explored. Independent and comprehensive soil TN content estimation models were constructed and optimized for each and the entire fertilization period, respectively. The results show that compared with the correlation coefficient method, stepwise multiple linear regression (SMLR) performs better in extracting hyperspectral characteristic bands of soil TN content. It helps to achieve a higher modeling accuracy, smaller root mean square error (RMSE), and is more conducive to avoiding the influence of multicollinearity of model variables. The sensitive areas of soil TN content in the SCI do not undergo significant changes due to different fertilization periods. Among them, the ratio spectral indices (RSIs) are in the range of 800–900 nm, 1900–1950 nm, and 2200–2300 nm, while the sensitive areas of the difference spectral index (DI) and Normalized difference spectral index (NDSI) are in the range of 1900–1950 nm and 2200–2300 nm. The combination of SCI and characteristic bands significantly improves the prediction accuracy of soil TN estimation models. The independent and comprehensive estimation models for each fertilization period based on the BP (back propagation) neural network optimized by the Mind Evolution Algorithm (MEA-BPNN) can achieve a more stable and accurate estimation of soil TN. Finally, using soil spectral characteristic bands selected through continuum removal (CR) transformation and SMLR, combined with SCI, the model based on the MEA-BPNN (CR-SCI-MEA-BPNN) has the best prediction performance. The modeling determination coefficients R2 for each fertilization period reached 0.94, 0.95, 0.92, and 0.94, respectively, with RMSE of 0.0032, 0.0024, 0.0035, and 0.0027. The R2 and RMSE of the modeling and validation set of the entire fertilization period comprehensive model are 0.899, 0.0038, and 0.89, 0.0041, respectively. The results of this article provide technical support for promoting the timely monitoring of soil TN content and guiding rational fertilization in apple orchards. [ABSTRACT FROM AUTHOR]

Acutality: Heart rate variability, allows you to assess the state of the autonomic nervous system, which is useful for studying the condition of athletes, including endurance athletes, for example, ski racers. The stress index indicator is often used to assess the impact of stress on a person. It is shown that the stress index is closely correlated with the intensity of metabolism and with the indicators of energy consumption of the body.Objective. To provide information on the values of the stress index for athletes depending on a number of factors, including their sports specialization, and for ski racers on the volume and intensity of the training load during the preparatory, competitive, transitional periods of the ski season.Materials and methods. The literature analysis in the Pubmed database for the last 10 years in English and Russian languages has been carried out.Conclusion. A review of the literature on the magnitude of the stress index showed that athletes who train for endurance, this indicator is low, especially among ski racers, if it is compared with the magnitude of the index in representatives of other sports, as well as with healthy people who do not play sports. There is no information about the value of the stress index in athletes in foreign literature, but there is such information in the domestic literature, which allowed us to present this review, which also includes the results of our research.

Induced polarization (IP) effect is widely used in the search of disseminated minerals all over the world. Spectral parameters computed from time‐domain IP data play a significant role in characterizing the sources, but mineral identification still remains a challenge. In this paper, the Levenberg–Marquardt method of inversion is adopted in estimating the spectral parameters from time‐domain IP data to identify the polarizable sources. The algorithm is tested on synthetic time‐domain IP data for its robustness to variable noise levels. Model sensitivity analyses on synthetic data were also studied with respect to acquisition time and each individual model parameter. Error analyses on extracted parameters indicated that these are well resolved and correlated if the relaxation time is within the range of acquisition time. The parameters remain poorly resolved/unresolved for smaller values of chargeability and frequency dependence. The algorithm has also been tested over known case histories of time‐domain IP data and compared the estimated spectral parameters with those of published results. The inferences drawn from computed spectral parameters on field‐observed IP transients are in good correlation with other data sets and borehole information. The methodology has successfully shown its usefulness in identifying large polarizable sources occurring at shallow levels from time‐domain IP data. [ABSTRACT FROM AUTHOR]

Nitrogen is a fundamental component for building amino acids and proteins, playing a crucial role in the growth and development of plants. Leaf nitrogen concentration (LNC) serves as a key indicator for assessing plant growth and development. Monitoring LNC provides insights into the absorption and utilization of nitrogen from the soil, offering valuable information for rational nutrient management. This, in turn, contributes to optimizing nutrient supply, enhancing crop yields, and minimizing adverse environmental impacts. Efficient and non-destructive estimation of crop LNC is of paramount importance for on-field crop management. Spectral technology, with its advantages of repeatability and high-throughput observations, provides a feasible method for obtaining LNC data. This study explores the responsiveness of spectral parameters to soybean LNC at different vertical scales, aiming to refine nitrogen management in soybeans. This research collected hyperspectral reflectance data and LNC data from different leaf layers of soybeans. Three types of spectral parameters, nitrogen-sensitive empirical spectral indices, randomly combined dual-band spectral indices, and "three-edge" parameters, were calculated. Four optimal spectral index selection strategies were constructed based on the correlation coefficients between the spectral parameters and LNC for each leaf layer. These strategies included empirical spectral index combinations (Combination 1), randomly combined dual-band spectral index combinations (Combination 2), "three-edge" parameter combinations (Combination 3), and a mixed combination (Combination 4). Subsequently, these four combinations were used as input variables to build LNC estimation models for soybeans at different vertical scales using partial least squares regression (PLSR), random forest (RF), and a backpropagation neural network (BPNN). The results demonstrated that the correlation coefficients between the LNC and spectral parameters reached the highest values in the upper soybean leaves, with most parameters showing significant correlations with the LNC (p < 0.05). Notably, the reciprocal difference index (VI6) exhibited the highest correlation with the upper-layer LNC at 0.732, with a wavelength combination of 841 nm and 842 nm. In constructing the LNC estimation models for soybeans at different leaf layers, the accuracy of the models gradually improved with the increasing height of the soybean plants. The upper layer exhibited the best estimation performance, with a validation set coefficient of determination (R2) that was higher by 9.9% to 16.0% compared to other layers. RF demonstrated the highest accuracy in estimating the upper-layer LNC, with a validation set R2 higher by 6.2% to 8.8% compared to other models. The RMSE was lower by 2.1% to 7.0%, and the MRE was lower by 4.7% to 5.6% compared to other models. Among different input combinations, Combination 4 achieved the highest accuracy, with a validation set R2 higher by 2.3% to 13.7%. In conclusion, by employing Combination 4 as the input, the RF model achieved the optimal estimation results for the upper-layer LNC, with a validation set R2 of 0.856, RMSE of 0.551, and MRE of 10.405%. The findings of this study provide technical support for remote sensing monitoring of soybean LNCs at different spatial scales. [ABSTRACT FROM AUTHOR]

In order to rapidly and accurately monitor cadmium contamination in lettuce and understand the growth conditions of lettuce under cadmium pollution, lettuce is used as the test material. Under different concentrations of cadmium stress and at different growth stages, relative chlorophyll content of lettuce leaves, the cadmium content in the leaves, and the visible-near infrared reflectance spectra are detected and analyzed. An inversion model of the cadmium content and relative chlorophyll content in the lettuce leaves is established. The results indicate that cadmium concentrations of 1 mg/kg and 5 mg/kg promote relative chlorophyll content, while concentrations of 10 mg/kg and 20 mg/kg inhibit relative chlorophyll content. The cadmium content in the leaves increases with increasing cadmium concentrations. Cadmium stress caused a "blue shift" in the red edge position only during the mature period, while the red valley position underwent a "blue shift" during the seedling and growth periods and a "red shift" during the mature period. The green peak position exhibited a "blue shift". After model validation, it was found that the model constructed using the ratio of red edge area to yellow edge area and the normalized values of red edge area and yellow edge area effectively estimated the cadmium content in lettuce leaves. The model established using the normalized vegetation index of the red edge and the ratio of the peak green value to red shoulder amplitude can effectively estimate the relative chlorophyll content in lettuce leaves. This study demonstrates that the visible-near infrared spectroscopy technique holds great potential for monitoring cadmium contamination and estimating chlorophyll content in lettuce. [ABSTRACT FROM AUTHOR]

ObjectiveLeaf chlorophyll content (LCC) of flue-cured Tobacco is an important indicator for characterizing the photosynthesis, nutritional status, and growth of the crop. Tobacco is an important economic crop with leaves as the main harvest object, it is crucial to monitor its LCC. Hyperspectral data can be used for the rapid estimation of LCC in flue-cured tobacco leaves, making it of great significance and application value. The purpose of this study was to efficiently and accurately estimate the LCC of flue-cured tobacco during different growth stages.MethodsZhongyan 100 was chose as the research object, five nitrogen fertilization levels were set. In each plot, three plants were randomly and destructively sampled, resulting in a total of 45 ground samples for each data collection. After transplanting, the reflectance data of the flue-cured tobacco canopy at six growth stages (32, 48, 61, 75, 89, and 109 d ) were collected using a UAV equipped with a Resonon Pika L hyperspectral. Spectral indices for the LCC estimation model of flue-cured tobacco were screened in two ways: (1) based on 18 published vegetation indices sensitive to LCC of crop leaves; (2) based on random combinations of any two bands in the wavelength range of 400‒1000 nm. The Difference Spectral Index (DSI), Ratio Spectral Index (RSI), and Normalized Spectral Index (NDSI) were calculated and plotted against LCC. The correlations between the three spectral indices and leaf LCC were calculated and plotted using contour maps. Five regression models, unary linear regression (ULR), multivariable linear regression (MLR), partial least squares regression (PLSR), support vector regression (SVR), and random forest regression (RFR), were used to estimate the chlorophyll content. A regression estimate model of LCC based on various combinations of spectral indices was eventually constructed by comparing the prediction accuracies of single spectral index models multiple spectral index models at different growth stages.Results and Discussions]The results showed that the LCC range for six growth stages was 0.52‒2.95 mg/g. The standard deviation and coefficient of variation values demonstrated a high degree of dispersion in LCC, indicating differences in fertility between different treatments at the test site and ensuring the applicability of the estimation model within a certain range. Except for 109 d after transplanting, most vegetation indices were significantly correlated with LCC (p

Objective: To assess the diagnostic value of spectral parameters in differentiating adrenal adenomas from metastases based on dual-layer detector spectral CT (DLSCT). Materials and methods: Patients with adenomas or metastases who underwent enhanced DLSCT of the adrenals were enrolled. The CT values of virtual non-contrast images (CTVNC), iodine density (ID) values, and Z-effective (Z-eff) values, the normalized iodine density (NID) values, slopes of spectral HU curves (s-SHC), and iodine-to-CTVNC ratios of the tumors were measured in each phase. Receiver operating characteristic (ROC) curves were used to compare the diagnostic values. Results: Ninety-nine patients with 106 adrenal lesions (63 adenomas, 43 metastases) were included. In the venous phase, all spectral parameters were significantly different between adenomas and metastases (all p < 0.05). The combined spectral parameters showed a better diagnostic performance in the venous phase than in other phase (p < 0.05). The iodine-to-CTVNC value had a larger area under the ROC curve (AUC) than the other spectral parameters in the differential diagnosis of adenomas and metastases, with a diagnostic sensitivity and specificity of 74.4% and 91.9%, respectively. In the differential diagnosis of lipid-rich adenomas, lipid-poor adenomas and metastases, the CTVNC value and s-SHC value also had a larger AUC than the other spectral parameters, with a diagnostic sensitivity of 97.7%, 79.1% and specificity of 91.2%, 93.1%, respectively. Conclusion: On DLSCT, the combined spectral parameters in the venous phase could help better distinguish adrenal adenomas from metastases. The iodine-to-CTVNC, CTVNC and s-SHC values had the highest AUC values in differentiating adenomas, lipid-rich adenomas and lipid-poor adenomas from metastases, respectively. [ABSTRACT FROM AUTHOR]

An algebraic system is introduced which is very useful for performing scattering calculations in quantum field theory. It is the set of all real numbers greater than or equal to −m2 with parity designation and a special rule for addition and subtraction, where m is the rest mass of the scattered particle.

The rapid and accurate diagnosis of nitrogen content in apple orchard soil is of great significance for the rational application of nitrogen fertilizer in orchards to improve apple yield and quality. An apple orchard in Shuangquan Town, Changqing District, Jinan City, Shandong Province, was taken as the experimental area. The optimal method for extracting spectral characteristic bands and screening spectral characteristic indices (SCIs) of soil total nitrogen (TN) for independent and comprehensive fertilization periods was explored. Independent and comprehensive soil TN content estimation models were constructed and optimized for each and the entire fertilization period, respectively. The results show that compared with the correlation coefficient method, stepwise multiple linear regression (SMLR) performs better in extracting hyperspectral characteristic bands of soil TN content. It helps to achieve a higher modeling accuracy, smaller root mean square error (RMSE), and is more conducive to avoiding the influence of multicollinearity of model variables. The sensitive areas of soil TN content in the SCI do not undergo significant changes due to different fertilization periods. Among them, the ratio spectral indices (RSIs) are in the range of 800–900 nm, 1900–1950 nm, and 2200–2300 nm, while the sensitive areas of the difference spectral index (DI) and Normalized difference spectral index (NDSI) are in the range of 1900–1950 nm and 2200–2300 nm. The combination of SCI and characteristic bands significantly improves the prediction accuracy of soil TN estimation models. The independent and comprehensive estimation models for each fertilization period based on the BP (back propagation) neural network optimized by the Mind Evolution Algorithm (MEA-BPNN) can achieve a more stable and accurate estimation of soil TN. Finally, using soil spectral characteristic bands selected through continuum removal (CR) transformation and SMLR, combined with SCI, the model based on the MEA-BPNN (CR-SCI-MEA-BPNN) has the best prediction performance. The modeling determination coefficients R2 for each fertilization period reached 0.94, 0.95, 0.92, and 0.94, respectively, with RMSE of 0.0032, 0.0024, 0.0035, and 0.0027. The R2 and RMSE of the modeling and validation set of the entire fertilization period comprehensive model are 0.899, 0.0038, and 0.89, 0.0041, respectively. The results of this article provide technical support for promoting the timely monitoring of soil TN content and guiding rational fertilization in apple orchards.

New values of neutron fluxes and spectral parameters f and α were determined experimentally in all irradiation devices of the TRIGA Mark I IPR-R1 nuclear research reactor at Nuclear Technology Development Centre (CDTN), Belo Horizonte, Brazil. Sets of monitors Au, Fe, Zn and Zr were irradiated bare and Cd-covered, according to "Cd-ratio for multi-monitor" method. Values were validated by analysing the certified reference material BCR-320R irradiated in chosen channels. The calculations were made based on irradiation channel values and the average values of the Carousel. The results of En-score point out that the k0-method is producing reliable results. From now on, the values of mass fractions in several matrices, the production and studies with radioisotopes will be more accurate and the activities calculated more precisely. [ABSTRACT FROM AUTHOR]

An algebraic system is introduced which is very useful for performing scattering calculations in quantum field theory. It is the set of all real numbers greater than or equal to −m2 with parity designation and a special rule for addition and subtraction, where m is the rest mass of the scattered particle. [ABSTRACT FROM AUTHOR]

While heavy rainfall frequently takes place in southern China during summer monsoon seasons, quantitative precipitation forecast skills are relatively poor. Therefore, detailed knowledge about the raindrop size distribution (DSD) is useful in improving the quantitative precipitation estimation and forecast. Based on the data during 2018-2022 from 86 stations in a ground-based optical disdrometer measurement network, the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution (N(D)), mass-weighted mean diameter (Dm) and other integral DSD parameters such as radar reflectivity (Z), rainfall rate (R) and liquid water content (LWC). In addition, the effects of geographical locations, weather systems (tropical cyclones, frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered. The results are shown as follows. 1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation, and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution. The relationships between the Z and R for stratiform and convective precipitation are also derived for the province, i.e., Z = 332.34 R1.32 and Z = 366.26 R1.42 which is distinctly different from that of the Next-generation Weather Radar (NEXRAD) Z-R relationship in United States. 2) In the rainy season (April-September), the Dm, R and LWC are larger than those in the dry season (October- March). Moreover the above parameters are larger, especially in mid-May, which is the onset of the South China Sea summer monsoon. 3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dm and a larger normalized intercept parameter (log10Nw), suggestive of maritime-like rainfall. Dm is larger and log10Nw is smaller in the inland area, suggestive of continental-like rainfall. 4) Affected by such weather systems as the tropical cyclone, frontal system and summer monsoon, the DSD shows characteristics with distinct differences. Furthermore, frontal system rainfall tends to present a continental-like rainfall, tropical cyclone rainfall tends to have a maritime-like rainfall, and summer monsoon rainfall characteristic are between maritime- and continental-like cluster (raindrop concentration and diameter are higher than continental cluster and maritime cluster, respectively. [ABSTRACT FROM AUTHOR]

The objective of the study was to document the vocal parameters in Madhya sthayi and Taara sthayi in Indian Carnatic singers. The study deployed a prospective, observational, repeated-measures group design. The study comprised 15 trained Carnatic singers with a senior degree in Carnatic singing. Participants were asked to sing an ascending glide and descending glide from Madhya sthayi to Taara sthayi and back to the Madhya sthayi. The acoustic and the cepstral parameters were extracted at Madhya sthayi and Taara sthayi. As a part of spectral measures, harmonic amplitude differences were calculated at both registers of singing. The results showed that the average fundamental frequency at Madhya sthayi was equal to G# (C3 on the musical scale). At Taara sthayi, the average fundamental frequency was corresponding to F# (C4 on the musical scale). Among the acoustic measures, namely range of fundamental frequency, jitter, shimmer, and all the spectral measures, showed significantly higher mean values at Taara sthayi. The mean values of harmonic-to-noise ratio and the cepstral peak prominence were significantly higher at Madhya sthayi. The present study results captivate the attention of voice pathologists to develop pitch-specific normative data for the evaluation of voice in Carnatic singers. [ABSTRACT FROM AUTHOR]

Nitrogen is a fundamental component for building amino acids and proteins, playing a crucial role in the growth and development of plants. Leaf nitrogen concentration (LNC) serves as a key indicator for assessing plant growth and development. Monitoring LNC provides insights into the absorption and utilization of nitrogen from the soil, offering valuable information for rational nutrient management. This, in turn, contributes to optimizing nutrient supply, enhancing crop yields, and minimizing adverse environmental impacts. Efficient and non-destructive estimation of crop LNC is of paramount importance for on-field crop management. Spectral technology, with its advantages of repeatability and high-throughput observations, provides a feasible method for obtaining LNC data. This study explores the responsiveness of spectral parameters to soybean LNC at different vertical scales, aiming to refine nitrogen management in soybeans. This research collected hyperspectral reflectance data and LNC data from different leaf layers of soybeans. Three types of spectral parameters, nitrogen-sensitive empirical spectral indices, randomly combined dual-band spectral indices, and “three-edge” parameters, were calculated. Four optimal spectral index selection strategies were constructed based on the correlation coefficients between the spectral parameters and LNC for each leaf layer. These strategies included empirical spectral index combinations (Combination 1), randomly combined dual-band spectral index combinations (Combination 2), “three-edge” parameter combinations (Combination 3), and a mixed combination (Combination 4). Subsequently, these four combinations were used as input variables to build LNC estimation models for soybeans at different vertical scales using partial least squares regression (PLSR), random forest (RF), and a backpropagation neural network (BPNN). The results demonstrated that the correlation coefficients between the LNC and spectral parameters reached the highest values in the upper soybean leaves, with most parameters showing significant correlations with the LNC (p < 0.05). Notably, the reciprocal difference index (VI6) exhibited the highest correlation with the upper-layer LNC at 0.732, with a wavelength combination of 841 nm and 842 nm. In constructing the LNC estimation models for soybeans at different leaf layers, the accuracy of the models gradually improved with the increasing height of the soybean plants. The upper layer exhibited the best estimation performance, with a validation set coefficient of determination (R2) that was higher by 9.9% to 16.0% compared to other layers. RF demonstrated the highest accuracy in estimating the upper-layer LNC, with a validation set R2 higher by 6.2% to 8.8% compared to other models. The RMSE was lower by 2.1% to 7.0%, and the MRE was lower by 4.7% to 5.6% compared to other models. Among different input combinations, Combination 4 achieved the highest accuracy, with a validation set R2 higher by 2.3% to 13.7%. In conclusion, by employing Combination 4 as the input, the RF model achieved the optimal estimation results for the upper-layer LNC, with a validation set R2 of 0.856, RMSE of 0.551, and MRE of 10.405%. The findings of this study provide technical support for remote sensing monitoring of soybean LNCs at different spatial scales.

In order to rapidly and accurately monitor cadmium contamination in lettuce and understand the growth conditions of lettuce under cadmium pollution, lettuce is used as the test material. Under different concentrations of cadmium stress and at different growth stages, relative chlorophyll content of lettuce leaves, the cadmium content in the leaves, and the visible-near infrared reflectance spectra are detected and analyzed. An inversion model of the cadmium content and relative chlorophyll content in the lettuce leaves is established. The results indicate that cadmium concentrations of 1 mg/kg and 5 mg/kg promote relative chlorophyll content, while concentrations of 10 mg/kg and 20 mg/kg inhibit relative chlorophyll content. The cadmium content in the leaves increases with increasing cadmium concentrations. Cadmium stress caused a “blue shift” in the red edge position only during the mature period, while the red valley position underwent a “blue shift” during the seedling and growth periods and a “red shift” during the mature period. The green peak position exhibited a “blue shift”. After model validation, it was found that the model constructed using the ratio of red edge area to yellow edge area and the normalized values of red edge area and yellow edge area effectively estimated the cadmium content in lettuce leaves. The model established using the normalized vegetation index of the red edge and the ratio of the peak green value to red shoulder amplitude can effectively estimate the relative chlorophyll content in lettuce leaves. This study demonstrates that the visible-near infrared spectroscopy technique holds great potential for monitoring cadmium contamination and estimating chlorophyll content in lettuce.

Mt. Vesuvius is a high-hazard active volcano surrounded by a densely populated area. Since human activities generate high levels of seismic noise, recognizing low-amplitude seismic events in the signals recorded by the local seismic monitoring network operating at Vesuvius is very difficult. Here, we describe an automatic procedure applied to continuous data with the aim of finding low-amplitude–low-frequency events hidden in the recorded signals. The methodology is based on the computation of two spectral parameters, central frequency Ω and shape factor ẟ, at selected sites, and the coherence of the seismic signal among different sites. The proposed procedure is applied to 28 months of recordings from 2019 to 2021, tuning the search parameters in order to find low-frequency signals similar to those occasionally observed in the past at the same volcano. The results allowed us to identify 80 seismic events that have the spectral features of low-frequency earthquakes or tremor. Among these, 12 events characterized by sufficiently high signal-to-noise ratio have been classified as deep low-frequency earthquakes, most of which are not reported in the catalog. The remaining events (more than 60) are characterized by similar spectral features but with an extremely low amplitude that prevents any reliable location of the source and definitive classification. The results of this work demonstrate that the low-frequency endogenous activity at Mt. Vesuvius volcano is more frequent that previously thought. [ABSTRACT FROM AUTHOR]

Introduction: Spectral and cepstral analyses of voice have potential clinical implications and can be used as a quantitative acoustic index to assess vocal function in various phases of the menstrual cycle. However, only a handful of studies have attempted to investigate these measures to document the vocal changes across various phases of the menstrual cycle and the results are not conclusive. Therefore, the study aimed to document the acoustic, spectral, and cepstral parameters of voice across the four phases of the menstrual cycle. Methods: Phonation samples were recorded during four phases of the menstrual cycle --menstrual phase, follicular phase, ovulation phase, and luteal phase -- from 30 female participants. None of the participants reported any hormone-related problems, presence, or history of any voice problems and had a regular menstrual cycle at least from the past 5 years. All the phonation samples were analyzed, and the acoustic, spectral, and cepstral parameters were extracted. Results: Fundamental frequency, H1-H2, and cepstral peak prominence (CPP) values were significantly different across the phases of the menstrual cycle. Across the phases of the menstrual cycle, the fundamental frequency, H1-H2, and the CPP values were optimal during the follicular phase and the deviant values were noted during the luteal phase of the menstrual cycle. Conclusion: Future investigations could include the analysis of cepstral and spectral parameters extracted from both the phonation and speech samples that can provide more penetrating and ample in-depth insights into the voice changes across the various phases of the menstrual cycle. [ABSTRACT FROM AUTHOR]

Mt. Vesuvius is a high-hazard active volcano surrounded by a densely populated area. Since human activities generate high levels of seismic noise, recognizing low-amplitude seismic events in the signals recorded by the local seismic monitoring network operating at Vesuvius is very difficult. Here, we describe an automatic procedure applied to continuous data with the aim of finding low-amplitude–low-frequency events hidden in the recorded signals. The methodology is based on the computation of two spectral parameters, central frequency Ω and shape factor ẟ, at selected sites, and the coherence of the seismic signal among different sites. The proposed procedure is applied to 28 months of recordings from 2019 to 2021, tuning the search parameters in order to find low-frequency signals similar to those occasionally observed in the past at the same volcano. The results allowed us to identify 80 seismic events that have the spectral features of low-frequency earthquakes or tremor. Among these, 12 events characterized by sufficiently high signal-to-noise ratio have been classified as deep low-frequency earthquakes, most of which are not reported in the catalog. The remaining events (more than 60) are characterized by similar spectral features but with an extremely low amplitude that prevents any reliable location of the source and definitive classification. The results of this work demonstrate that the low-frequency endogenous activity at Mt. Vesuvius volcano is more frequent that previously thought.

Tropical peat water dissolved organic matter (DOM) fractions spectral parameters correlate with the formation of carcinogenic disinfection by-products (DBPs), haloacetic acids (HAAs). Peat water DOM has been fractionated using Superlite DAX-8, Amberlite XAD-4, and Amberlite IRA-958 resins to separate hydrophobic acid (HPOA), transphilic (TPH), hydrophilic-charged (HPIC), and hydrophilic-neutral (HPIN). The formation potential of HAA was determined using the total concentration of 5 HAAs (HAA5). The DOM characteristic was determined using dissolved organic carbon (DOC) and ultraviolet–visible (UV–Vis) absorbance was evaluated at 200–700 nm. The HPOA fraction dominates the DOM of tropical peat water with a 40% DOC concentration when the HPIC fraction was the slighter. The spectral absorbance ratios (E4/E6 and A253/A203) and spectral slopes (S206–213, S251–280, S281–295, and S>295) have a strong positive correlation with HAA5 formation potential (HAA5FP). Similarly, the absorbance ratio A210/A254 and spectral slopes S200–205 are strongly correlated to HAA5FP, but in a negative direction. In contrast, the E2/E3 and A280/A350 spectral ratio, and spectral slopes (S214-227, and S228–250), has a weaker correlation with HAA5FP. The E2/E3 and A280/A350 ratios and S251–280 S200–205 spectral slope show a strong relationship with the brominated HAA5FP (B-HAA5FP). The spectral parameters of DOM fractions can be used as surrogate parameters of HAA5FP of peat water. [ABSTRACT FROM AUTHOR]

The operating life of power transformers is determined by the insulation state of the transformer insulating materials, which has been widely recognized. Herein, it is a new attempt to diagnose the state of the transformer mineral insulating oil by the terahertz time-domain spectroscopy (THz-TDS), taking advantage of its high signal-to-noise ratio and fast, accurate, and stable data acquisition characteristics. First, the THz time-domain waveforms of mineral insulating oils with different insulation states prepared by the accelerated thermal aging method were measured. Second, the Fabry-Perot (F-P) effect of instruments and container is eliminated using the improved electromagnetic wave transfer function. Then, the THz spectral parameters of insulating oils, such as absorption coefficient and refractive index, can be calculated. Meanwhile, the dielectric properties of insulating oils in the terahertz region are obtained. Finally, compared with traditional physicochemical diagnostic indicators, the results preliminarily prove that THz-TDS technology can effectively evaluate the state of the mineral insulating oil.

The purpose of this study was to assess validity, stability and sensitivity, of 4 spectral parameters–median frequency (Fmed), mean frequency (Fmean), Dimitrov index (DI), and mean instant frequency (Fmi)–in measuring localized muscle fatigue in swimming and to investigate their correlation with the variations of kinematic data and mechanical fatigue. Electrophysiological measures of muscle fatigue were obtained in real-time during a 100 m front crawl test at maximum speed in 15 experienced swimmers, using surface electromyography in six muscles employed in front crawl, while kinematic data of swimming was measured from video analysis. Mechanical fatigue was measured as the difference between muscle strength prior to and immediately after the 100 m front crawl in a dry-land multi-stage isometric contraction test. Statistically significant fatigue (p < 0.0001) was found for all spectral parameters in all muscles. Fmed and Fmean varied between 10 and 25%, DI between 50 and 150%, and Fmi between 5 and 10%. Strong correlation (Pearson r ≥ 0.5) with mechanical fatigue was found for all spectral parameters except for Fmi and it was strongest for Fmed and Fmean. From our study, it turns out that Fmed and Fmean are more valid and stable parameters to measure fatigue in swimming, while DI is more sensitive.

In the three-dimensional domain a Boussinesq type nonlinear partial integro-differential equation of the fourth order with a degenerate kernel, integral form conditions, spectral parameters and reflecting argument is considered. The solution of this partial integro-differential equation is studied in the class of generality functions. The method of separation of variables and the method of a degenerate kernels are used. Using these methods, the nonlocal boundary value problem is integrated as a countable system of ordinary differential equations. When we define the arbitrary integration constants there are possible five cases with respect to the first spectral parameter. Calculated values of the spectral parameter for each case. Further, the problem is reduced to solving countable system of linear algebraic equations. Irregular values of the second spectral parameter are determined. At irregular values of the second spectral parameter the Fredholm determinant is degenerate. Other values of the second spectral parameter, for which the Fredholm determinant does not degenerate, are called regular values. Taking the values of the first spectral parameter into account for regular values of the second spectral parameter the corresponding solutions were constructed and we obtained the countable system of nonlinear integral equations for each of five cases. To establish the unique solvability of this countable system of nonlinear integral equations we use the method of successive approximations and the method of compressing mappings. Using the Cauchy–Schwarz inequality and the Bessel inequality, we proved the absolute and uniform convergence of the obtained Fourier series. The stability of the solution of the boundary value problem with respect to given functions in integral conditions is proved. The conditions under which the solution of the boundary value problem will be small are studied. For the irregular values of the second spectral parameter each of the five cases is checked separately. The orthogonality conditions are used. Cases are determined in which the problem has an infinite number of solutions and these solutions are constructed as Fourier series. For other cases, the absence of nontrivial solutions of the problem is proved. The corresponding theorems are formulated. [ABSTRACT FROM AUTHOR]

The problems of solvability and construction of solutions of a nonlocal boundary value problem for the second-order Fredholm integro-differential equation with degenerate kernel, integral conditions, spectral parameters and reflecting deviation are considered. Using the method of the degenerate kernel, the boundary value problem is integrated as an ordinary differential equation. When we define the arbitrary integration constants there are possible five cases with respect to the first spectral parameter. Calculated values of the spectral parameter for each case. Further, the problem is reduced to solving systems of linear algebraic equations. Irregular values of the second spectral parameter are determined. At irregular values of the second spectral parameter the Fredholm determinant is degenerate. Other values of the second spectral parameter, for which the Fredholm determinant does not degenerate, are called regular values. Taking the values of the first spectral parameter into account for regular values of the second spectral parameter the corresponding solutions were constructed for each of five cases. The stability of the solution of the boundary value problem for given values in integral conditions is proved. The conditions under which the solution of the boundary value problem will be small are studied. For the irregular values of the second spectral parameter each of the five cases is checked separately. The orthogonality conditions are used. Cases are determined in which the problem has an infinite number of solutions and these solutions are constructed. For other cases, the absence of nontrivial solutions of the problem is proved. [ABSTRACT FROM AUTHOR]

This study aims at investigating the interface between emotion and intonation patterns (more specifically, duration and pitch amplitude of speech). To this end, the acoustic properties of spectral parameters related to speech prosody are investigated. The results of acoustic and Statistical analysis show that mean level and range of FO in the contours vary strongly as a function of the degree of activation of the portrayed emotions. The results also indicate that FO/pitch and other vocal aspects affected by emotion and/or emotional arousal in collected samples of speech in Persian.

Nowadays, the obtainment of an accurate numerical solution of fixed source discrete ordinates problems is relevant in many areas of engineering and science. In this work, we extend the hybrid Finite Element Spectral Green's Function method (FEM-SGF), originally developed to solve eigenvalue diffusion problems, for fixed source problems using as a mathematical model, the discrete ordinates formulation in one energy group with isotropic scattering in slab geometry. This new method, Extended Linear Discontinuous Discrete Ordinates (ELD-SN), is based on the use of neutron balance equations and the construction of a hybrid auxiliary equation. This auxiliary equation combines a linear discontinuous approximation and spectral parameters to approximate the neutron angular flux inside the cell. Numerical results for benchmark problems are presented to illustrate the accuracy and computational performance of our methodology. ELD-SN method is free from spatial truncation errors in S2 quadrature, and generate good results in the other quadrature sets. This method is more accurate than the conventional Diamond Difference (DD) and Linear Discontinuous (LD) methods, but surpassed by the Spectral Green's Function (SGF) method, for quadrature order greater than two.

Buoy-based observations of wave spectra during the passage of three typhoons in the northern South China Sea are examined. Though most spectra of mature typhoon-generated waves are unimodal, double-peaked spectra account for a significant proportion during the growing and decaying stages. This is due either to the superposition of swells on local wind waves or to the mechanism of nonlinear interaction between different wave components. The growth rate of energy density is an effective way to predict spectrum variation. The dominant wave direction depends on the location of the typhoon center to the site, but the direction spread shows no regularity in distant regions. In this study, a new six-parameter spectral formula is proposed to represent double-peaked spectra and is shown to provide a better fit than previous models. The theoretical relationship between shape parameter and spectral width is still applicable to each peak. The characteristics of the variations of spectral parameters are analyzed. It is demonstrated that the spectral parameters are not only related to the typhoon intensity and typhoon track, but also have strong intercorrelations. Moreover, the growth relation between significant wave height and significant wave period is obtained to fit the typhoon-generated waves. [ABSTRACT FROM AUTHOR]

Source characterisation in time-domain induced polarisation (IP) data is more cumbersome than in frequency-domain IP data. The time-domain IP phenomenon is a linear superposition of individual relaxations caused by various polarisable sources. We have adopted the relaxation time distribution (RTD) method, a technique used in dielectric and chemical physics for analysing the relaxation phenomenon to characterise these sources. In this paper, the RTD method is first tested on synthetic data to evaluate its ability to estimate Cole–Cole spectral parameters, and then the effect of using a number of repetition rates is tested. Results indicate that chargeability and relaxation time are underestimated if the measurement duration is less than or equal to the relaxation time. Spectral parameters estimated using the RTD method on the published time-domain IP data are in good agreement with those estimated from empirical methods. The RTD method has also been tested on time-domain IP data measured on borehole core samples in the laboratory. These results inferred the possible polarisable sources and agree with petrological microscope observations. The RTD method was employed successfully to characterise the IP sources from ground time-domain IP data over four known mineralised bodies. [ABSTRACT FROM AUTHOR]

The problems of the existence and construction of solutions of a nonlocal boundary value problem for the homogeneous second-order Fredholm integrodifferential equation with a degenerate kernel and with two spectral parameters are considered. The singularities arising from the definition of arbitrary (unknown) constants are studied. The values of the spectral parameters are calculated and the solvability of the boundary value problem is established. The corresponding theorems are proven. Meaningful examples are provided. [ABSTRACT FROM AUTHOR]

• A high-resolution absorption spectrometer has been developed by combining the direct absorption spectroscopy (DAS) technique with a distributed feedback (DFB) diode laser operating at a center wavelength of 760 nm. • Experimental measurements of spectral parameters for the O 2 line at 13146.58047 cm−1 have been conducted to enhance the signal processing algorithm model for field application. • A sensing technology based on tunable diode laser absorption spectroscopy (TDLAS) has been proposed, enabling real-time analysis of oxygen (O 2) content in the human breathing gas. In this paper, a high-resolution laser absorption spectrometer is developed using a distributed feedback (DFB) diode laser in the spectral region near 760 nm, which is designed for the highly sensitive detection of oxygen (O 2) in breathing gas. To investigate the spectrometer performance, O 2 absorption line at 13146.580 cm−1 was selected, and detailed experiments on air-broadening coefficient, self-broadening coefficient and spectral line intensity were conducted. Compared to the corresponding data listed in the HITRAN2020 database, the results show that the errors for air-broadening coefficient, self-broadening coefficient and line intensity, were −6.832%, 4.082% and 4.667%, respectively. Finally, the developed laser absorption spectrometer was primarily evaluated for real-time analysis of O 2 content in human breath analysis. The results indicate that the measured O 2 concentrations in several volunteers range from 16% to 16.5%, which is in agreement with the levels reported in the literature for healthy humans. [ABSTRACT FROM AUTHOR]

The questions of the one-value solvability of an inverse boundary value problem for a mixed type integro-differential equation with Caputo operators of different fractional orders and spectral parameters are considered. The mixed type integro-differential equation with respect to the main unknown function is an inhomogeneous partial integro-differential equation of fractional order in both positive and negative parts of the multidimensional rectangular domain under consideration. This mixed type of equation, with respect to redefinition functions, is a nonlinear Fredholm type integral equation. The fractional Caputo operators’ orders are smaller in the positive part of the domain than the orders of Caputo operators in the negative part of the domain under consideration. Using the method of Fourier series, two systems of countable systems of ordinary fractional integro-differential equations with degenerate kernels and different orders of integro-differentation are obtained. Furthermore, a method of degenerate kernels is used. In order to determine arbitrary integration constants, a linear system of functional algebraic equations is obtained. From the solvability condition of this system are calculated the regular and irregular values of the spectral parameters. The solution of the inverse problem under consideration is obtained in the form of Fourier series. The unique solvability of the problem for regular values of spectral parameters is proved. During the proof of the convergence of the Fourier series, certain properties of the Mittag–Leffler function of two variables, the Cauchy–Schwarz inequality and Bessel inequality, are used. We also studied the continuous dependence of the solution of the problem on small parameters for regular values of spectral parameters. The existence and uniqueness of redefined functions have been justified by solving the systems of two countable systems of nonlinear integral equations. The results are formulated as a theorem.

The questions of solvability of a nonlocal inverse boundary value problem for a mixed pseudohyperbolic-pseudoelliptic integro-differential equation with spectral parameters are considered. Using the method of the Fourier series, a system of countable systems of ordinary integro-differential equations is obtained. To determine arbitrary integration constants, a system of algebraic equations is obtained. From this system regular and irregular values of the spectral parameters were calculated. The unique solvability of the inverse boundary value problem for regular values of spectral parameters is proved. For irregular values of spectral parameters is established a criterion of existence of an infinite set of solutions of the inverse boundary value problem. The results are formulated as a theorem.

Apparent quantum yields (Φ) of photochemically produced reactive intermediates (PPRIs) formed by dissolved organic matter (DOM) are vital to element cycles and contaminant fates in surface water. Simultaneous determination of Φ PPRI values from numerous water samples through existing experimental methods is time consuming and ineffective. Herein, machine learning models were developed with a systematic data set including 1329 data points to predict the values of three Φ PPRIs (Φ 3DOM* , Φ 1O2 , and Φ ·OH ) based on DOM spectral parameters, experimental conditions, and calculation parameters. The best predictive performances for Φ 3DOM* , Φ 1O2 , and Φ ·OH were achieved using the CatBoost model, which outperformed the traditional linear regression models. The significances of the wavelength range and spectral parameters on the three Φ PPRI predictions were revealed, suggesting that DOM with lower molecular weight, lower aromatic content, and a more autochthonous portion possessed higher Φ PPRIs . Chain models were constructed by adding the predicted Φ 3DOM* as a new feature into the Φ 1O2 and Φ ·OH models, which consequently improved the predictive performance of Φ 1O2 but worsened the Φ ·OH prediction likely due to the complex formation pathways of ·OH. Overall, this study offered robust Φ PPRI prediction across interlaboratory differences and provided new insights into the relationship between PPRIs formation and DOM properties.

Background: Kidney microvasculopathy is the baseline pathophysiological feature of diabetic kidney disease (DKD). We aimed to evaluate the spectral computed tomography (CT) parameters for detecting renal perfusion changes among diabetic patients., Methods: From August 2020 to June 2022, 34 patients (age, 57.7±10.7 years; male, 20) clinically diagnosed with type 2 diabetes mellitus (DM) and 19 DM-free individuals (age, 48.1±16.9 years; male, 12) were selected for analysis. The series participants formed the DM group and control group, respectively. Spectral parameters, including effective atomic number (Z eff ), iodine density (ID), normalized iodine density (NID) and the slope of the energy spectrum curves (λ), between the 2 groups were analyzed using independent samples t -test. Receiver operator characteristic (ROC) curves were used to evaluate the diagnostic performance of spectral parameters for detecting renal perfusion changes., Results: The results indicate that in both cortical and medullary phases, the values of Z eff , ID, NID, and λ 40-70 for the renal cortex of the DM group were significantly higher than those in the control group (P<0.05). In the cortex phase, the diagnostic efficacy of cortical spectral CT parameters discriminating DM patients from controls was as follows: the area under ROC curve (AUC) of ID value was 0.816 [95% confidence interval (CI): 0.679-0.921] at the optimal cutoff value 4.14, the AUC of Z eff value was 0.800 (95% CI: 0.668-0.901) at the optimal cutoff value 9.26, the AUC of λ 40-70 value was 0.822 (95% CI: 0.675-0.918) at the optimal cutoff value 8.26, and the AUC of NID value was 0.851 (95% CI: 0.684-0.926) at the optimal cutoff value 0.37. In medullary phase: the AUC of ID value was 0.769 (95% CI: 0.617-0.846) at the optimal cutoff value 5.08, the AUC of Z eff value was 0.763 (95% CI: 0.614-0.837) at the optimal cutoff value 9.58, the AUC of λ 40-70 value was 0.766 (95% CI: 0.617-0.839) at the optimal cutoff value 10.07, and the AUC of NID value was 0.79 (95% CI: 0.623-0.855) at the optimal cutoff value 1.37., Conclusions: Spectral CT could serve as an alternative protocol for the early identification of kidney injury in diabetic patients., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-22-1400/coif). The authors have no conflicts of interest to declare., (2023 Quantitative Imaging in Medicine and Surgery. All rights reserved.)

We report on the spectroscopic investigation of Er 3+ doped BaF 2 single crystals. High-quality crystals have been gown by the Bridgman-Stockbarger pulling technique. The room temperature absorption, excitation, emission and fluorescence decay spectra of the luminescent Er 3+ ions inserted in BaF 2 fluoride single crystals have been investigated. Using the Judd-Ofelt (JO) theory, the intensity parameters of Er 3+ ions have been calculated to be Ω 2  = 0.949 × 10 −20  cm 2 , Ω 4  = 0.975 × 10 −20  cm 2 and Ω 6  = 1.258 × 10 −20  cm 2 . These parameters were then used to calculate the radiative transition probabilities (A JJ′ ), branching ratios (β JJ′ ) and radiative lifetimes (τ rad ) of the main laser emitting levels of Er 3+ ions. The obtained spectroscopic properties are compared to those of Er 3+ transitions in other fluoride and oxide hosts. The excitation spectrum in the UV–Visible spectral range is very close to the absorption spectrum indicating that all observed absorption levels can excite the Erbium green emission. The emission spectrum is mainly dominated by the green emission alongside a weak red emission. For the main transitions, there is a good agreement between the emission spectrum and the spontaneous emission probabilities given by the JO analysis. Using the Fuchtbauer–Ladenburg method, the emission cross-section of the three main visible emission were determined in addition to other important laser parameters such radiative quantum efficiency and optical gain. [ABSTRACT FROM AUTHOR]

The 10–11 July 2015 partial collapses of the lava dome in the crater of Volcán de Colima, México, were accompanied by a sequence of two-stage multiple PDCs, separated by a 15-h interval, with a total bulk volume of 14.2 × 10 6 m 3 of fragmentary material and runout distances reaching 9.1 and 10.3 km, respectively (Reyes-Dávila et al., 2016). Broad-band seismic signals, associated with the PDCs and recorded at seismic station EZ5 installed at a distance of 4 km from the crater, were used for analysis of the 20-h eruption process. This process included two stages of the multiple PDCs emplacements, two one-hour periods of preliminary events to each of the stages, and the inter-stage period. Analysis of seismic signals allowed us to identify the types of volcanic events composing this eruption episode and estimate their quantitative characteristics and spectral parameters of generated seismic signals. It was shown that the seismic signals produced by PDCs emplacements, recorded during the two stages, were characterized by different characteristics. The second stage PDCs had radiated greater seismic energy than the PDCs emplaced during the first stage. Spectral analysis of the seismic signals, produced by PDCs, indicates a clearly separation in frequency content at 1.95 Hz between the higher-frequency events of the first stage and the lower-frequency events of the second stage of the PDCs emplacements. The obtained difference in the spectral contents of the seismic signals, produced by the movement of two multiple PDCs, may be supposed as a consequence of the proposed relative difference in the volumes of the PDCs of two multiple sequences due to a difference in the level of radiated seismic energy and a change in bottom conditions of the ravines during their passing along the ravines. Results of seismic study were used in discussion of the nature of the two-stage eruptive process. [ABSTRACT FROM AUTHOR]

The Niudong Buried Hill Field, which lies in the Baxian Depression of the Bohai Bay Basin, is the deepest oil/gas accumulation in eastern China. Its Precambrian dolomite reservoir occurs at burial depths of 5860 m–6027 m. This paper attempts to document the hydrocarbon charging and accumulation history in this field, which could greatly enhance the understanding of the mechanisms for the formation of deep hydrocarbon accumulations. Our previous study of oil trapped in fluid inclusions has demonstrated that the ratio parameters of the fluorescence spectral intensities at 425 nm and 433 nm (Q 425/433 ratio), and at 419 nm and 429 nm (Q 419/429 ratio) can be more effective for revealing hydrocarbon charging history than the previously-used fluorescence parameters such as Lambda max and red/green quotient as well as fluorescence colors. The hydrocarbon charging and accumulation history in the Niudong Buried Hill Field was studied with an integrated approach involving the application of these two spectral parameters of petroleum inclusion fluorescence as well as utilization of other data including homogenization temperatures of aqueous inclusions coeval with petroleum inclusions, and cross-cutting relationships of cements and “oil veins” in pores and fractures. The results indicate that the dolomite reservoir in the Niudong Buried Hill Field experienced three episodes of hydrocarbon charging. In the first two episodes (between 38.5Ma and 25Ma), the low mature and mature oils, which were derived from source rocks in the Sha-4 Member of the Eocene Shahejie Formation, migrated into the reservoir, but part of them leaked out due to normal faulting at the updip margin of the buried hill. These early-charged oils were preserved mainly in small pores in micritic dolomites by oil-wettability and capillary pressure. In the Neogene, the basin subsided as a whole and local faults at the updip margin became inactive and played a sealing role. By approximately 13Ma, the source rocks became highly mature and the generated hydrocarbons then migrated into the reservoir and accumulated. Therefore, the last charging is the most important for hydrocarbon accumulation in the Niudong Buried Hill Field. [ABSTRACT FROM AUTHOR]