In Situ Defect Engineering of Controllable Carrier Types in WSe2 for Homomaterial Inverters and Self-Powered Photodetectors.

WSe2 has a high mobility of electrons and holes, which is an ideal choice as active channels of electronics in extensive fields. However, carrier-type tunability of WSe2 still has enormous challenges, which are essential to overcome for practical applications. In this work, the direct growth of n-doped few-layer WSe2 is realized via in situ defect engineering. The n-doping of WSe2 is attributed to Se vacancies induced by the H2 flow purged in the cooling process. The electrical measurements based on field effect transistors demonstrate that the carrier type of WSe2 synthesized is successfully transferred from the conventional p-type to the rarely reported n-type. The electron carrier concentration is efficiently modulated by the concentration of H2 during the cooling process. Furthermore, homomaterial inverters and self-powered photodetectors are fabricated based on the doping-type-tunable WSe2. This work reveals a significant way to realize the controllable carrier type of two-dimensional (2D) materials, exhibiting great potential in future 2D electronics engineering.

Particle size distribution measurement based on the angular scattering efficiency factor spectra inversion-simulation and experiment.

The quantification of the particle size distribution (PSD) within a particle system is significant to various domains, including atmospheric and environmental sciences, material science, civil engineering, and human health. The scattering spectrum reflects the PSD information of the particle system. Researchers have developed high-precision and high-resolution PSD measurements for monodisperse particle systems through scattering spectroscopy. However, for polydisperse particle systems, current methods based on light scattering spectrum and Fourier transform analysis can only obtain the information of the particle component, but cannot provide the relative content information of each component. In this paper, a PSD inversion method based on the angular scattering efficiency factors (ASEF) spectrum is proposed. By establishing a light energy coefficient distribution matrix, and then measuring the scattering spectrum of the particle system, PSD can be measured in conjunction with inversion algorithms. The simulations and experiments conducted in this paper substantiate the validity of the proposed method. Unlike the forward diffraction approach that measures the spatial distribution of scattered light I(θ) for inversion, our method uses the multi-wavelength distribution information of scattered light ß(λ). Moreover, the influences of noise, scattering angle, wavelength, particle size range, and size discretization interval on PSD inversion are studied. The method of condition number analysis is proposed to identify the appropriate scattering angle, particle size measurement range, and size discretization interval, and it can reduce the root mean square error(RMSE) of PSD inversion. Furthermore, the method of wavelength sensitivity analysis is proposed to select the spectral band with higher sensitivity to particle size changes, thereby improving the computational speed and avoiding the problem of diminished accuracy caused by the reduction of the number of wavelengths used.

Intrinsic Nonlinear Hall Effect and Gate-Switchable Berry Curvature Sliding in Twisted Bilayer Graphene.

Though the observation of the quantum anomalous Hall effect and nonlocal transport response reveals nontrivial band topology governed by the Berry curvature in twisted bilayer graphene, some recent works reported nonlinear Hall signals in graphene superlattices that are caused by the extrinsic disorder scattering rather than the intrinsic Berry curvature dipole moment. In this Letter, we report a Berry curvature dipole induced intrinsic nonlinear Hall effect in high-quality twisted bilayer graphene devices. We also find that the application of the displacement field substantially changes the direction and amplitude of the nonlinear Hall voltages, as a result of a field-induced sliding of the Berry curvature hotspots. Our Letter not only proves that the Berry curvature dipole could play a dominant role in generating the intrinsic nonlinear Hall signal in graphene superlattices with low disorder densities, but also demonstrates twisted bilayer graphene to be a sensitive and fine-tunable platform for second harmonic generation and rectification.

Footstrike angle cut-off values to classify footstrike pattern in runners.

Footstrike angle (FSA) has been widely used to classify footstrike pattern (FSP). However, inconsistent FSA cut-off values were adopted in previous studies. This study aimed to validate the FSA cut-off values in runners. Stride index, the gold standard to determine FSP, and FSA were obtained when 15 experienced runners, 14 novice runners and 14 untrained individuals performed 3-min run on an instrumented treadmill at their preferred running speeds in habitual, rearfoot, midfoot and forefoot strike patterns. According to the receiver operating characteristic curve associated with the Youden index, the optimal FSA cut-off values were -0.8° (i.e., cut-off angle for forefoot strike) -7.4° (i.e., cut-off angle for rearfoot strike) for runners. We observed minor differences in the FSA cut-off values across runners with various running experience and a wider cut-off range for midfoot strikers when a modified strike index was utilized. This validation study established cut-off footstrike angles for runners' FSP classification.

Ultra-high resolution particle size measurement based on scattering spectrum analysis-simulation and experiment.

This paper focuses on the properties of light scattering spectra from a spherical particle and their application for particle size measurement. The influence of particle size and scattering angle on the scattering spectra are investigated and simulated. An ultra-resolution particle dimension measurement method was proposed based on detecting the peak of scattering spectra. An accurate spectral peak location strategy based on the spectral shape features is adopted to reduce the spectra peak positioning error caused by dispersion. The size of smaller particle is measured by locating a wide scattering spectral peak at a larger scattering angle to achieve higher measurement sensitivity, while the size of larger particle is measured by locating a narrow scattering spectral peak at a smaller angle to achieve a larger measurement range. If the spectral resolution of the spectrometer is 0.8 nm, the particle size resolution of 1.1 nm and 8.3 nm are achieved for measured particles with sizes ranging from 0.25µm to 1µm and measured particles with sizes ranging from 1µm to 10µm, respectively. And if the spectrometer with picometer resolution is used, the particle size resolution is expected to be on the order of picometers.

Improving the accuracy of high-repetition-rate LIBS based on laser ablation and scanning parameters optimization.

Laser-induced breakdown spectroscopy system based on high-repetition-rate microchip laser (HR-LIBS) has been widely used in elemental analysis due to its high energy stability, good portability and fast spectral acquisition speed. However, repeated ablation on powder pellets like soil and coal using HR-LIBS system encounters the problem of serious decline in measurement accuracy. In this work, the relationship between laser ablation and scanning parameters, their correlation with spectral intensity, as well as the optimization approach were fundamentally studied. The correlations among the crater overlapping rate, crater depth and spectral intensity were obtained. An HR-LIBS system with microchip laser (4 kHz repetition rate, 100 µJ laser pulse energy) to perform repeated scanning ablation was established. A theoretical model of the ablation crater morphology for repeated scanning ablation was developed. By taking soil pellets as the experimental samples, the linear fitting curves of crater depth and the spectral intensity ratio were established with the R2 of 0.90∼0.99. The experimental results showed that as the crater depth developed during repeated ablation, the Si-normalized spectral intensity decreased, and thus the spectral repeatability decreased. It was found that by optimizing the overlapping rate to form a flat crater bottom, the confinement effect of the crater on the plasma could be avoided. As a result, the spectral repeatability was significantly improved. The relative standard deviation (RSD) of Si-normalized spectral intensity was improved from 5% to 0.6%. Finally, repeated ablation was performed with the optimized overlapping rate on soil pellets. The R2 of calibration curves of Fe, Mg, Ca, and Al were all above 0.993, and the average RSDs were between 0.5% and 1%. This study provides a fast, accurate, and stable method for the analysis of the samples consisting of various materials with high heterogeneity.

Spatial intensity distribution model of fluorescence emission considering the spatial attenuation effect of excitation light.

The fluorescence quantitative analysis method of a solution is widely applied in chemical analysis, clinical medicine testing, environmental monitoring, food safety detection, and so on. It is based on the linear relationship between the intensity of fluorescence emission and the concentration of the substance in solution. Without consideration of the spatial attenuation effect of excitation light, it is applied only to a dilute solution. In this research, a fluorescence emission model is established based on the interaction and propagation law between the excitation light and the fluorescent substances. The spatial attenuation effect of excitation light is analyzed by an element analysis method, and the spatial intensity distribution of fluorescence is revealed. Further, a high accuracy model between the received fluorescence intensity and concentration is obtained. Applications of this model and further design will allow for high throughput fluorescence analysis and the analysis of fluorescent substances with ultra-wide range concentration, such as on-line testing fluorescent dyes in the textile industry, monitoring protein plasma in biomedical field, and high-throughput DNA fluorescence analysis etc. As an example, based on this model, an ultra-wide concentration range (0.02 - 250 mg/L) detection of tryptophan with high accuracy (R2 = 0.9994, RRMSE = 0.0356) is realized.

High accuracy determination of copper in copper concentrate with double genetic algorithm and partial least square in laser-induced breakdown spectroscopy.

There are many challenges in the determination of elements in complex matrix such as soil, coal and minerals by laser induced breakdown spectroscopy (LIBS) method. Due to the influence of matrix effect, instability of laser plasma and fluctuation of laser parameters, the repeatability and accuracy of quantitative results are always not satisfactory. In order to improve the accuracy, high-energy laser (30mJ-100mJ) with precise control was utilized in many laboratories. In this paper, quantitative analysis of copper in copper concentrate by low-energy (10µJ) LIBS is studied. In order to reduce the influence of matrix effect and other factors, a partial least square regression method based on double genetic algorithm (DGA-PLS) is proposed. The detail operations are as follow: the reference spectral lines are automatically selected by GA as the optimal internal standard for spectral normalization. Then the GA is used to select variables from the normalized spectra for PLS. The results showed that, for univariate model, the coefficient of determination (R2) was improved from 0.6 to 0.97 by the optimal internal standard normalization. Compared with tradition PLS, the root mean square error of cross validation (RMSECV) and root mean square error of prediction (RMSEP) of PLS trained by the normalized spectral data decreased from 1.4% and 0.42% to 0.9% and 0.29% respectively. Compared with the normalized PLS, the RMSECV and RMSEP of the DGA-PLS trained by the normalized and feature selected spectral data decreased from 0.9% and 0.29% to 0.26% and 0.21% respectively. The results show that DGA-PLS can significantly reduce matrix effect, improve prediction accuracy and reduce the risk of overfitting in determination of copper in copper concentrate.

Muscle activity and vibration transmissibility during whole-body vibration in chronic stroke.

PURPOSE: This study aimed to investigate the influence of whole-body vibration (WBV) frequency, amplitude, and body posture on lower limb muscle activation among people with chronic stroke, and whether the EMG response to vibration stimulus differed between paretic and non-paretic side. The relationship between muscle activation and WBV transmission was also examined. METHOD: Thirty-two participants with chronic stroke performed three different exercises on the WBV platform with different vibration conditions (frequency: 20 Hz, 30 Hz, 40 Hz; amplitude: 0.8 mm, 1.5 mm), or without vibration. Muscle activity in bilateral vastus medialis (VM), medial hamstrings (MH), tibialis anterior (TA), and medial gastrocnemius (MG) was measured by surface electromyography. Acceleration at the platform and bilateral hips and knees was measured by tri-axial accelerometers. RESULTS: Significantly greater muscle activity was observed in the bilateral MG (P < 0.001), TA (P < 0.001), and MH (P < 0.001), but not VM, compared with the same exercises without WBV. WBV with higher amplitude or higher frequency led to greater augmentation of muscle activation (P < 0.05). Body posture significantly affected leg muscle activation (P < 0.001). WBV-induced muscle activation was largely similar between paretic and non-paretic sides, except the TA. Greater WBV-induced leg muscle activation was associated with lower WBV transmissibility measured at the more proximal joints (P < 0.05). CONCLUSION: Adding WBV to exercise significantly increased muscle activation in the MG, TA, and MH on both the paretic and non-paretic sides of chronic stroke survivors, and the increase was dependent on the WBV amplitude, frequency, and body posture.

Dual-Task Exercise Reduces Cognitive-Motor Interference in Walking and Falls After Stroke.

Background and Purpose- Functional community ambulation requires the ability to perform mobility and cognitive task simultaneously (dual-tasking). This single-blinded randomized controlled study aimed to examine the effects of dual-task exercise in chronic stroke patients. Methods- Eighty-four chronic stroke patients (24 women; age, 61.2±6.4 years; time since stroke onset, 75.3±64.9 months) with mild to moderate motor impairment (Chedoke-McMaster leg motor score: median, 5; interquartile range, 4-6) were randomly allocated to the dual-task balance/mobility training group, single-task balance/mobility group, or upper-limb exercise (control) group. Each group exercised for three 60-minute sessions per week for 8 weeks. The dual-task interference effect was measured for the time to completion of 3 mobility tests (forward walking, timed-up-and-go, and obstacle crossing) and for the correct response rate during serial-3-subtractions and verbal fluency task. Secondary outcomes included the Activities-specific Balance Confidence Scale, Frenchay Activities Index, and Stroke-specific Quality of Life Scale. The above outcomes were measured at baseline, immediately after, and 8 weeks after training. Fall incidence was recorded for a 6-month period posttraining. Results- Only the dual-task group exhibited reduced dual-task interference in walking time posttraining (forward walking combined with verbal fluency [9.5%, P=0.014], forward walking with serial-3-subtractions [9.6%, P=0.035], and the timed-up-and-go with verbal fluency [16.8%, P=0.001]). The improvements in dual-task walking were largely maintained at the 8-week follow-up. The dual-task cognitive performance showed no significant changes. The dual-task program reduced the risk of falls and injurious falls by 25.0% (95% CI, 3.1%-46.9%; P=0.037) and 22.2% (95% CI, 4.0%-38.4%; P=0.023), respectively, during the 6-month follow-up period compared with controls. There was no significant effect on other secondary outcomes ( P>0.05). Conclusions- The dual-task program was effective in improving dual-task mobility, reducing falls and fall-related injuries in ambulatory chronic stroke patients with intact cognition. It had no significant effect on activity participation or quality of life. Clinical trial registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT02270398.

Effects of whole body vibration on muscle spasticity for people with central nervous system disorders: a systematic review.

OBJECTIVES: To examine the effects of whole-body vibration on spasticity among people with central nervous system disorders. METHODS: Electronic searches were conducted using CINAHL, Cochrane Library, MEDLINE, Physiotherapy Evidence Database, PubMed, PsycINFO, SPORTDiscus and Scopus to identify randomized controlled trials that investigated the effect of whole-body vibration on spasticity among people with central nervous system disorders (last search in August 2015). The methodological quality and level of evidence were rated using the PEDro scale and guidelines set by the Oxford Centre for Evidence-Based Medicine. RESULTS: Nine trials with totally 266 subjects (three in cerebral palsy, one in multiple sclerosis, one in spinocerebellar ataxia, and four in stroke) fulfilled all selection criteria. One study was level 1b (PEDro⩾6 and sample size>50) and eight were level 2b (PEDro<6 or sample size ⩽50). All three cerebral palsy trials (level 2b) reported some beneficial effects of whole-body vibration on reducing leg muscle spasticity. Otherwise, the results revealed no consistent benefits on spasticity in other neurological conditions studied. There is little evidence that change in spasticity was related to change in functional performance. The optimal protocol could not be identified. Many reviewed studies were limited by weak methodological and reporting quality. Adverse events were minor and rare. CONCLUSION: Whole-body vibration may be useful in reducing leg muscle spasticity in cerebral palsy but this needs to be verified by future high quality trials. There is insufficient evidence to support or refute the notion that whole-body vibration can reduce spasticity in stroke, spinocerebellar ataxia or multiple sclerosis.

Magnetically modulated laser-induced resistance effect observed in Metal-Oxide-Semiconductor structure of Cr/SiO(2)/Si.

In this study, we report our finding of laser-induced resistance effect in metal-oxide-semiconductor (MOS) structure of Cr/SiO(2)/Si. Under the irradiation of a laser beam, the effect shows a large linear resistance change ratio of 92% with a spatial sensitivity of 0.79 MΩ/mm. In particular, by the application of an external magnetic field perpendicular to the Cr film, the resistance change ratio is increased to 110%. This effect is attributed to the Lorentz force acting on the photo-generated carriers in the inversion layer of MOS structures. The work suggests an approach for the development of new type magnetically modulated photoelectric devices.

Tanshinone IIA inhibits the proliferation, migration and invasion of ectopic endometrial stromal cells of adenomyosis via 14-3-3ζ downregulation.

BACKGROUND: Adenomyosis is a specific subtype of endometriosis and recent evidences have indicated that Tanshinone IIA (TSIIA) might be a potential therapeutic option for endometriosis. Meanwhile, endometrial stromal cells (ESCs) of adenomyosis might play crucial roles in the progression of this disease, emphasizing the importance of targeting ESCs in the treatment of adenomyosis. Furthermore, previous evidences also implicated that deregulated 14-3-3ζ expression might be associated with therapeutic effects of certain drugs. AIM OF THE STUDY: The aim of this study is to evaluate the potential involvement of 14-3-3ζ in the process of TSIIA-treated adenomyosis. MATERIALS AND METHODS: Ectopic endometrial stromal cells (EESCs) were isolated from a total of 3 patients with adenomyosis. Cells were treated with TSIIA and infected with 14-3-3ζ-overexpressing adenovirus, the expression level of 14-3-3ζ was determined by western blotting (WB), cell viability was detected by Cell Counting Kit-8 (CCK8), cell invasion and migration was evaluated by transwell assay, and cell apoptosis was detected by flow cytometry. RESULTS: TSIIA could decrease cell viability, induce cell apoptosis, and inhibit cell migration and invasion in EESCs. Mechanistically, TSIIA markedly reduced the expression of 14-3-3ζ in EESCs, and overexpression of 14-3-3ζ could restore the ability of cell viability, migration and invasion, but has no effect on cell apoptosis. CONCLUSIONS: TSIIA could be a promising novel therapeutic agent for adenomyosis, via inducing cell apoptosis, inhibiting cell viability, migration and invasion in EESCs. Furthermore, the effects of cell viability, migration and invasion were mediated in 14-3-3ζ-dependent manner while that of cell apoptosis was mediated in 14-3-3ζ-independent manner.

Frequent POLE1 p.S297F mutation in Chinese patients with ovarian endometrioid carcinoma.

The catalytic subunit of DNA polymerase epsilon (POLE1) functions primarily in nuclear DNA replication and repair. Recently, POLE1 mutations were detected frequently in colorectal and endometrial carcinomas while with lower frequency in several other types of cancer, and the p.P286R and p.V411L mutations were the potential mutation hotspots in human cancers. Nevertheless, the mutation frequency of POLE1 in ovarian cancer still remains largely unknown. Here, we screened a total of 251 Chinese samples with distinct subtypes of ovarian carcinoma for the presence of POLE1 hotspot mutations by direct sequencing. A heterozygous somatic POLE1 mutation, p.S297F (c.890C>T), but not p.P286R and p.V411L hotspot mutations observed in other cancer types, was identified in 3 out of 37 (8.1%) patients with ovarian endometrioid carcinoma; this mutation was evolutionarily highly conserved from Homo sapiens to Schizosaccharomyces. Of note, the POLE1 mutation coexisted with mutation in the ovarian cancer-associated PPP2R1A (protein phosphatase 2, regulatory subunit A, α) gene in a 46-year-old patient, who was also diagnosed with ectopic endometriosis in the benign ovary. In addition, a 45-year-old POLE1-mutated ovarian endometrioid carcinoma patient was also diagnosed with uterine leiomyoma while the remaining 52-year-old POLE1-mutated patient showed no additional distinctive clinical manifestation. In contrast to high frequency of POLE1 mutations in ovarian endometrioid carcinoma, no POLE1 mutations were identified in patients with other subtypes of ovarian carcinoma. Our results showed for the first time that the POLE1 p.S297F mutation, but not p.P286R and p.V411L hotspot mutations observed in other cancer types, was frequent in Chinese ovarian endometrioid carcinoma, but absent in other subtypes of ovarian carcinoma. These results implicated that POLE1 p.S297F mutation might be actively involved in the pathogenesis of ovarian endometrioid carcinoma, but might not be actively involved in other subtypes of ovarian carcinoma.

Quantitative assessment and monitoring of microplastics and nanoplastics distributions and lipid metabolism in live zebrafish using hyperspectral stimulated Raman scattering microscopy.

Microplastics (MP) and nanoplastics (NP) pollutions pose a rising environmental threat to humans and other living species, given their escalating presence in essential resources that living subjects ingest and/or inhale. Herein, to elucidate the potential health implications of MP/NP, we report for the first time by using label-free hyperspectral stimulated Raman scattering (SRS) imaging technique developed to quantitatively monitor the bioaccumulation and metabolic toxicity of MP/NP within live zebrafish larvae during their early developmental stages. Zebrafish embryos are exposed to environmentally related concentrations (3-60 µg/ml) of polystyrene (PS) beads with two typical sizes (2 µm and 50 nm). Zebrafish are administered isotope-tagged fatty acids through microinjection and dietary intake for in vivo tracking of lipid metabolism dynamics. In vivo 3D quantitative vibrational imaging of PS beads and intrinsic biomolecules across key zebrafish organs reveals that gut and liver are the primary target organs of MP/NP, while only 50 nm PS beads readily aggregate and adhere to the brain and blood vessels. The 50 nm PS beads are also found to induce more pronounced hepatic inflammatory response compared to 2 µm counterparts, characterized by increased biogenesis of lipid droplets and upregulation of arachidonic acid detected in zebrafish liver. Furthermore, Raman-tagged SRS imaging of fatty acids uncovers that MP/NP exposure significantly reduces yolk lipid utilization and promotes dietary lipid storage in zebrafish, possibly associated with developmental delays and more pronounced food dilution effects in zebrafish larvae exposed to 2 µm PS beads. The hyperspectral SRS imaging in this work shows that MP/NP exposure perturbs the development and lipid metabolism in zebrafish larvae, furthering the understanding of MP/NP ingestions and consequent toxicity in different organs in living species.

High-throughput fluorescence quantification method based on inner filter effect and fluorescence imaging analysis.

The application of the inner filter effect (IFE) in fluorescent substance determination is gaining popularity. In this paper, a theory of the fluorescence distribution along with the excitation light path is derived from our previous research about the spatial micro-element method. According to the relationship between the summation of fluorescence intensities along the vertical direction at a certain position on the excitation light path and the position, a high-concentration and wide-range fluorescent substance quantification method based on the IFE and fluorescence imaging analysis is proposed. Correspondingly, a high-throughput fluorescent substance quantification detection system is constructed. In order to validate the method, solutions of rhodamine B in different concentrations are used for principle validation, concentration prediction, and experimental investigation on the influence of integration time and lens distortion. The high-throughput system enables the simultaneous measurement of six samples, realizing the high-concentration and wide-range quantification of rhodamine B (100-600 mg/L) with high precision (R2 = 0.9992, MRE = 2.34 %). By setting the filter wheel, the system can measure the concentration of fluorescent substances with different emission wavelengths. The improvement of experimental device is expected to reduce the single sample capacity to tens of microliters and increase the overall sample quantity to tens or even hundreds. The proposed method and system are beneficial to fluorescence measurement in fields such as biomedicine and dye research and to the improvement of high-throughput fluorescence quantitative PCR instruments.

Prevalence, Genotype Diversity, and Distinct Pathogenicity of 205 Gammacoronavirus Infectious Bronchitis Virus Isolates in China during 2019-2023.

Gammacoronavirus infectious bronchitis virus (IBV) causes a highly contagious disease in chickens and seriously endangers the poultry industry. The emergence and co-circulation of diverse IBV serotypes and genotypes with distinct pathogenicity worldwide pose a serious challenge to the development of effective intervention measures. In this study, we report the epidemic trends of IBV in China from 2019 to 2023 and a comparative analysis on the antigenic characteristics and pathogenicity of isolates among major prevalent lineages. Phylogenetic and recombination analyses based on the nucleotide sequences of the spike (S) 1 gene clustered a total of 205 isolates into twelve distinct lineages, with GI-19 as a predominant lineage (61.77 ± 4.56%) exhibiting an overall increasing trend over the past five years, and demonstrated that a majority of the variants were derived from gene recombination events. Further characterization of the growth and pathogenic properties of six representative isolates from different lineages classified four out of the six isolates as nephropathogenic types with mortality rates in one-day-old SPF chickens varying from 20-60%, one as a respiratory type with weak virulence, and one as a naturally occurring avirulent strain. Taken together, our findings illuminate the epidemic trends, prevalence, recombination, and pathogenicity of current IBV strains in China, providing key information for further strengthening the surveillance and pathogenicity studies of IBV.

Determination of trace chromium (VI) using a hollow-core metal-cladding optical waveguide sensor.

A biosensor capable of highly sensitive detection of trace chromium (VI) with a simple hollow-core metal-cladding waveguide (HCMW) structure is theoretically modeled and experimentally demonstrated. Owing to the high sensitivity of the excited ultrahigh-order modes in the waveguide, a tiny variation of the extinction coefficients in the waveguide guiding layer where the chromate ions reacts with the diphenylcarbazide (DPC) can lead to a significant change of light intensity in the reflection spectrum. The experimental results indicate that using the proposed method, the chromium (VI) sensitivity detection limit can be as low as 1.2 nM, which represents a 16-fold improvement compared to the surface plasmon field-enhanced resonance light scattering (SP-RLS) method, and a 4-fold improvement compared to the flame atomic absorption spectrometry and fluorimetry spectroscopy, respectively.

Accurate correction method and algorithm of fluorescence secondary inner filter effect (sIEF) in fluorescence quantitative analysis.

Fluorescence spectroscopy is a reliable and widely used analytical method. The fluorescence inner filter effect (IFE) is one of the main obstacles in the application of fluorescence spectroscopy and an error source in fluorescence analysis, resulting in the fluorescence spectrum distortion, the spectral shape distortion, and the nonlinearity between fluorescence intensity and fluorophore concentration. An optimized parameter reflecting the self-absorption effect - the fluorescence attenuation absorption index of secondary inner filter effect (sIFE) nopt - is proposed in this paper. Considering the received fluorescence in a direction perpendicular to the incident light, it is related to the solute-solvent system of the fluorescent substance, neither the geometric parameters of the cuvette and the light beam nor the concentration of the fluorescent substance. nopt can accurately reflect the degree to which the fluorescence is affected by the sIFE and correct for any non-ideality of the shapes of excitation/emission beams. The principle and determination method of nopt are explained in detail. Accordingly, an algorithm for the fluorescence spectroscopic correction by nopt is designed. To verify the method, the fluorescence spectra and absorbance spectra of the solutions of fluorescein sodium, rhodamine B, rhodamine 6G, and chlorophyll-a with a series of concentration gradients were measured, respectively. The influence of solvent effect on sIFE correction was also studied. The experiments show that different solute-solvent systems of the fluorescent substances have their own nopt. The novel algorithm can determine the nopt, correct the intensity attenuation and the peak red-shift of the fluorescence spectrum caused by the sIFE, expand the linear range of the concentration predicted by the fluorescence intensity, reduce the error of the prediction model, and improve the measurement accuracy.

CFSA-AGD: An accurate crosstalk fluorescence spectroscopic decomposition method for identifying and quantifying FDOMs in aquatic environments.

Fluorescent substances exist in various aquatic environments and other environmental media. It is a critical task to identify the components accurately and quantify their contents precisely. Based on the Crosstalk Fluorescence Spectroscopy Analysis (CFSA) model, a fluorescence spectroscopic decomposition using the Alternating Gradient Descent (AGD) algorithm is developed. By reducing the residual error of the model through alternating iterations, the CFSA-AGD method achieves unsupervised model training and automatic spectroscopic decomposition without extra experimental operations such as dilution or absorbance measurement, exempting from tedious modeling process. The objectives of this work are to validate that the CFSA-AGD method can comprehensively address the decomposition of fluorescence spectral crosstalk. Furthermore, the novel method is applied to the spectroscopic decomposition of natural FDOMs in aquatic environments as a standard tool. The spectral data analyzing the performance of this method is verified and compared with the conventional methods through the experiment on standard samples. The results indicate that CFSA-AGD has higher spectroscopic decomposition accuracy and gives more abundant information on the characteristic spectra with less residual error than parallel factor analysis. This means that the fluorescence spectra of natural FDOMs can be decomposed into the characteristic fluorescence emission spectra of single components with higher accuracy and the characteristic fluorescence absorption spectra that cannot be obtained by the conventional methods. Meanwhile, it improves the analytical precision of the contents (from R2 ≥ 0.9778 to R2 ≥ 0.9920) and reduces the ultimate residual error by two orders of magnitude (from 1.42 × 10-1 to 4.68 × 10-3) when the method is used to estimate the measured fluorescence spectra.