Observation of Nonlinear Exceptional Points with a Complete Basis in Dynamics.

The exotic physics associated with exceptional points (EPs) is always under the scrutiny of theoretical and experimental science. Recently, considerable effort has been invested in the combination of nonlinearity and non-Hermiticity. The concept of nonlinear EPs (NEPs) has been introduced, which can avoid the loss of completeness of the eigenbasis in dynamics while retaining the key features of linear EPs. Here, we present the first direct experimental demonstration of a NEP based on two non-Hermition coupled circuit resonators combined with a nonlinear saturable gain. At the NEP, the response of the eigenfrequency to perturbations demonstrates a third-order root law and the eigenbasis of the Hamiltonian governing the system dynamics is still complete. Our results bring this counterintuitive aspect of the NEP to light and possibly open new avenues for applications.

T-cell lymphopenia is associated with an increased infecting risk in children after cardiopulmonary bypass.

BACKGROUND: children who undergo CPB operations are at an elevated risk of infection due to immunosuppression. This study aims to investigate the association between lymphopenia following CPB and early postoperative infection in children. METHODS: A retrospective analysis including 41 children under 2 years old underwent CPB. Among them, 9 subjects had an early postoperative infection, and 32 subjects were period-matched without infection. Inflammatory cytokines, serum CRP and PCT values were measured in plasma, additionally, circulating total leucocyte and lymphocyte subpopulations were counted. RESULTS: Infected subjects exhibited significantly higher levels of inflammatory cytokines, including IL-6, IL-8, IL-10, IL-1ß and TNF-α, than non-infected subjects after CPB. Additionally, lower absolute number of lymphocyte and their subpopulations CD3+ T cells, CD4+ T-helper cells and CD8+cytotoxic T-cells, were observed in infected subjects. The impairment of T-cells Immune was found to be associated with higher levels of inflammatory cytokines IL-10. The ROC demonstrated that the absolute number of CD3+ T-cells <1934/ul, CD4+ T helper cells <1203/ul and CD8+cytotoxic T-cells <327/ul were associated with early postoperative infection. CONCLUSION: Higher levels of inflammatory cytokines resulted in T-cells lymphopenia after CPB, which significantly increasing the risk of postoperative infection in infants and young children. IMPACT: Infection complications after cardiopulmonary bypass (CPB) in pediatric CHD patients are serious issues, identifing the infection from after CPB remains a challenging. CPB can release numerous inflammatory cytokines associated with T cells lymphopenia, which increases the risk of postoperative infection after surgery. Monitoring T cells lymphopenia maybe more beneficial to predict early postoperative infection than C-reactive protein and procalcitonin.

Routing light with different wavevectors using synthetic dimensions.

Synthetic dimensions have drawn intense recent attention in investigating higher-dimensional topological physics and offering additional degrees of freedom for manipulating light. It has been demonstrated that synthetic dimensions can help to concentrate light with different frequencies at different locations. Here, we show that synthetic dimensions can also route light from different incident directions. Our system consists of an interface formed by two different photonic crystals. A synthetic dimension ξ is introduced by shifting the termination position of the photonic crystal on the right-hand side of the interface. We identify a correspondence between ξ and the interface state such that light incident from a specific direction can be collected. Thus, routing incident light from different directions is achieved by designing an interface with a proper distribution of ξ. Traditionally, this goal is achieved with a standard 4f optical system using a convex lens, and our approach offers the possibility for such a capability within a few lattice sites of photonic crystals. Such an approach reduces the size of the system, making it easier for integration. Our work provides, to our knowledge, a new direction for routing light with different momentums and possibly contributes to applications such as lidar.

Association between physical activity and cardiovascular parameters in 7-year-old children: a Chinese cross-sectional study.

INTRODUCTION: Physical activity (PA) is believed to play an important part in many aspects during childhood and adolescence, especially cardiorespiratory fitness and cardiometabolic health. However, whether different levels of PA in daily life influence the structure or function of heart in school-aged children remains unknown. We aimed to investigate the association between PA and cardiovascular parameters in 7-year-old children. METHODS: Follow-up data from the Shanghai Prenatal Cohort Study and the Shanghai Birth Cohort was analyzed. Perinatal information including both maternal and offspring datum was recorded. A refined questionnaire was used to evaluate the frequency and duration of children's PA levels. Blood pressure, echocardiography, and anthropometry assessment were conducted during the follow-up of 7-year-old children. RESULTS: Overall, high PA level was associated with higher left ventricle posterior wall thickness in diastole (LVPWd, ß coefficient: 0.36, 95% CI: 0.12, 0.61), higher left ventricle mass index (LVMI, ß = 0.28, 95% CI: 0.07, 0.48), mitral E/a ratio (ß = 0.47, 95% CI: 0.22, 0.71) and slower heart rate (ß = -0.32, 95% CI: -0.57, -0.07), compared to low PA level. Medium PA level was associated with lower diastolic blood pressure (DBP, ß = -0.18, 95% CI: -0.35, -0.01). In subgroup analysis, increased relative wall thickness (RWT) was found in high PA level boys (ß = 0.36, 95% CI: 0.05, 0.67), and systolic blood pressure (SBP) showed a significant decrease in high PA level girls (ß = -0.42, 95% CI: -0.78, -0.06). CONCLUSIONS: This study suggested non-athlete children having higher PA level were associated with thicker left ventricle (LV) walls and better LV diastolic function, as well as slower heart rate and DBP at the age of 7. Furthermore, disparity in the association between PA level with morphological heart patterns and blood pressure existed in different sex category.

Acute suppurative terminal cholangitis: Clinical characteristics of a new subtype of acute cholangitis.

BACKGROUND: Acute suppurative terminal cholangitis (ASTC) is rarer than acute obstructive cholangitis and is not well studied. To explore this subtype of acute cholangitis, we described our clinical experience with ASTC. METHODS: We performed a retrospective review of patients with ASTC admitted to our center from September 2014 to August 2020. We analyzed their clinical characteristics, including etiology, clinical manifestations, imaging features, treatment and prognosis. RESULTS: A total of 32 ASTC patients were included in the analysis. The majority of the patients had a history of biliary operations, and clinical manifestations were occult and atypical. The positive rate of bacterial culture was 46.9%. All the patients had typical imaging features on computed tomography and magnetic resonance imaging. Treatment with effective antibiotics was provided as soon as diagnosis was established. After treatment, most patients had a good outcome. Elevated levels of total bilirubin, aspartate aminotransferase, procalcitonin and gamma-glutamyltransferase were the characteristics of critically ill patients and were associated with relatively poor prognosis. CONCLUSIONS: Our results demonstrated that ASTC should be recognized as a new subtype of acute cholangitis, and that earlier diagnosis and more personalized treatments are needed.

Offshore Oil Spill Detection Based on CNN, DBSCAN, and Hyperspectral Imaging.

Offshore oil spills have the potential to inflict substantial ecological damage, underscoring the critical importance of timely offshore oil spill detection and remediation. At present, offshore oil spill detection typically combines hyperspectral imaging with deep learning techniques. While these methodologies have made significant advancements, they prove inadequate in scenarios requiring real-time detection due to limited model detection speeds. To address this challenge, a method for detecting oil spill areas is introduced, combining convolutional neural networks (CNNs) with the DBSCAN clustering algorithm. This method aims to enhance the efficiency of oil spill area detection in real-time scenarios, providing a potential solution to the limitations posed by the intricate structures of existing models. The proposed method includes a pre-feature selection process applied to the spectral data, followed by pixel classification using a convolutional neural network (CNN) model. Subsequently, the DBSCAN algorithm is employed to segment oil spill areas from the classification results. To validate our proposed method, we simulate an offshore oil spill environment in the laboratory, utilizing a hyperspectral sensing device to collect data and create a dataset. We then compare our method with three other models-DRSNet, CNN-Visual Transformer, and GCN-conducting a comprehensive analysis to evaluate the advantages and limitations of each model.

Nonlinear Exceptional Points with a Complete Basis in Dynamics.

Exceptional points (EPs) are special spectral singularities at which two or more eigenvalues, and their corresponding eigenvectors, coalesce and become identical. In conventional wisdom, the coalescence of eigenvectors inevitably leads to the loss of completeness of the eigenbasis. Here, we show that this scenario breaks down in general at nonlinear EPs (NEPs). As an example, we realize a fifth-order NEP (NEP_{5}) within only three coupled resonators with both a theoretical model and simulations in circuits. One stable and another four auxiliary steady eigenstates of the nonlinear Hamiltonian coalesce at the NEP_{5}, and the response of eigenfrequency to perturbations demonstrates a fifth-order root law. Intriguingly, the biorthogonal eigenbasis of the Hamiltonian governing the system dynamics is still complete, and this fact is corroborated by a finite Petermann factor instead of a divergent one at conventional EPs. Consequently, the amplification of noise, which diverges at other EPs, converges at our NEP_{5}. Our finding transforms the understanding of EPs and shows potential for miniaturizing various key applications operating near EPs.

Serum 25-hydroxyvitamin D status of a large Chinese population from 30 provinces by LC-MS/MS measurement for consecutive 3 years: differences by age, sex, season and province.

PURPOSE: We aimed to describe the vitamin D status and its distribution in different age groups, sexes, seasons, and provinces of a large Chinese population. METHODS: This study retrospectively analyzed 1,528,685 results of serum 25-hydroxyvitamin D (25(OH)D) in the central laboratory of KingMed Diagnostics. The samples were from the individuals aged 0-119 years old in 30 provinces of China. Serum 25(OH)D was measured by an accurate commercial liquid chromatography-tandem mass spectrometry (LC-MS/MS) method from January 2017 to December 2019. The subjects were stratified by age, sex, the season of blood collection, and the province of residence. RESULTS: The median 25(OH)D concentration was 25.5 ng/mL (interquartile range (IQR) 18.7-32.7 ng/mL) in males and 20.8 ng/mL (IQR 14.4-28.2 ng/mL) in females. Overall, the median 25(OH)D concentration decreased with age in both males and females. Males had a 0.2-2.4 ng/mL higher median 25(OH)D concentration than females in different age groups. Vitamin D deficiency (25(OH)D < 15 ng/mL for the individuals under 14 years old; < 20 ng/mL for the individuals over 14 years old) was found in 21.3% of males and 43.6% of females. Significant seasonal variation of serum 25(OH)D concentrations was repeatedly observed in 3 years, with median concentration higher in summer (25.3 ng/mL (IQR 19.3-31.9 ng/mL)) and lower in winter (18.5 ng/mL (IQR 12.3-26.6 ng/mL)). Vitamin D status varied by province. The median 25(OH)D concentration was the highest in Hainan (31.0 ng/mL (IQR 24.9-39.2 ng/mL)) and the lowest in Qinghai (14.4 ng/mL (IQR 9.6-20.0 ng/mL)). 25(OH)D2 was detected in 12.2% of the results, and no significant seasonal variation was observed. CONCLUSION: In China, vitamin D deficiency is prevalent in the population participating in clinical vitamin D measurement. Age and sex differences in vitamin D levels were observed in our study. Seasonal variation and provincial differences are important aspects of serum vitamin D status. 25(OH)D2 cannot be ignored entirely in clinical measurement practice in China.

Longitudinal change of circulating tumor cell level and its relationship with immune checkpoint inhibitor-based treatment benefits in unresectable, metastatic colorectal cancer patients.

OBJECTIVE: Circulating tumor cell (CTC) exerts diagnostic and prognostic value in colorectal cancer (CRC) patients. This study intended to further investigate the longitudinal change of CTC count, and its correlation with the prognosis of immune checkpoint inhibitor (ICI)-based treatments in unresectable, metastatic CRC patients. METHODS: Fifty-six unresectable, metastatic CRC patients receiving ICI-based treatments were enrolled. CTC count was assessed by the CellSearch system at baseline and month (M)2 in their peripheral blood samples. RESULTS: Forty-one (73.2%) and sixteen (28.5%) patients had CTC count ≥1 and ≥5 at baseline, respectively. Meanwhile, CTC count at M2 was decreased versus that at baseline (median (interquartile range): 1.0 (0.0-3.0) versus 3.0 (0.0-5.0)) (p < 0.001). Besides, increased CTC count at baseline (p = 0.009) and M2 (p = 0.006) associated with a reduced overall response rate. Baseline CTC count ≥5 related to worse progression-free survival (PFS) (p = 0.007), but baseline CTC count ≥1 did not; additionally, baseline CTC count ≥1 (p = 0.043) and ≥5 (p = 0.016) linked to shorter overall survival (OS). Furthermore, M2 CTC count ≥1 (p = 0.002) and ≥5 (p < 0.001) both correlated with poor PFS; meanwhile, M2 CTC count ≥1 (p = 0.006) and ≥5 (p < 0.001) also related to worse OS. After adjustment, only CTC count at M2 ≥ 5 independently associated with unsatisfactory PFS (hazard ratio (HR)=3.218, p = 0.011) and OS (HR = 3.229, p = 0.038). CONCLUSIONS: CTC count is decreased during ICI-based treatments, its reduction represents satisfactory treatment outcomes in unresectable, metastatic CRC patients. Notably, the CTC count at 5 as a cutting threshold after a two-month treatment has an impressive prognostic value.

Predictive value of fetal echocardiographic parameters in surgical strategy for Tetralogy of Fallot.

OBJECTIVES: This study aimed to evaluate whether fetal echocardiographic parameters were predictive of the postnatal surgical treatment required for fetuses with Tetralogy of Fallot (TOF). METHODS: The fetal echocardiographic and postnatal clinical data of all cases of prenatal TOF at Xinhua Hospital from 2016 to 2020 were reviewed. Patients were categorized based on the operation type, and cardiac parameters were compared between groups. RESULTS: Of the 37 fetuses assessed, the development of the pulmonary valve annulus (PVA) was significantly poorer in the transannular patch group. Patients with a prenatal PVA z-score (Schneider's method) ≥ -2.645, a PVA z-score (Lee's method) ≥ -2.805, a PVA/aortic valve annulus diameter ratio ≥ .697, and a pulmonary annulus index ≥ .823 were more likely to undergo pulmonary valve-sparing surgery. There was a strong correlation between prenatal and postnatal PVA z-scores. The PVA growth potential was greater in the pulmonary valve-sparing surgery group. CONCLUSIONS: PVA-related parameters evaluated by fetal echocardiography can predict the type of surgical intervention required and are valuable in improving prenatal counseling in fetal cases of TOF.

Development of human serum matrix-based unconjugated estriol-certified reference material by recommended ID-LC-MS/MS reference method.

To solve long-term lack of traceability of commercial calibrator kits and standardize clinical routine assays, we developed a human serum matrix-based unconjugated estriol (uE3) reference material (RM) with five concentration gradients. The RMs of uE3 were certified by the National Institute of Metrology (NIM) with the codes of GBW (E) 091048, GBW (E) 091049, GBW (E) 091050, GBW (E) 091051, and GBW (E) 091052. The RMs were determined by isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) reference method which was developed in our group and recommended by the Joint Committee on Traceability on Laboratory Medicine (JCTLM). GBW09224 is intended for use as a primary reference material to enable the SI-traceable measurement of uE3. This study describes the development process of these certified RMs. The candidate material was prepared by collecting from the remaining serum samples after routine clinical testing. Satisfactory homogeneity and stability were shown in these RMs. They are also commutable between the reference method and the three routine clinical immunoassay systems. To improve the accuracy of value assignment, a collaborative study in nine reference laboratories was conducted which was performed according to ISO/WD 15725-1 and all of the reference laboratories have been confirmed by China National Accreditation Service for Conformity Assessment (CNAS). The raw results were statistically analyzed and processed, coupled with uncertainty evaluation, to obtain the certified value: GBW (E) 091048 is 22.1 ± 1.3 nmol/L, GBW (E) 091049 is 33.6 ± 1.6 nmol/L, GBW (E) 091050 is 10.4 ± 0.8 nmol/L, GBW (E) 091051 is 15.5 ± 1.0 nmol/L, GBW (E) 091052 is 47.0 ± 2.0 nmol/L. The preparation process of human serum matrix-based reference material and the lack of these type of secondary (commutable) reference material of unconjugated estriol lead to the interruption of its traceability chain, which is a problem to be solved in its standardization as mentioned in the metrological traceability in ISO 17511, 2020.

Erratum: Retrieving Ideal Precision in Noisy Quantum Optical Metrology [Phys. Rev. Lett. 123, 040402 (2019)].

This corrects the article DOI: 10.1103/PhysRevLett.123.040402.

Retrieving Ideal Precision in Noisy Quantum Optical Metrology.

Quantum metrology employs quantum effects to attain a measurement precision surpassing the limit achievable in classical physics. However, it was previously found that the precision returns the shot-noise limit (SNL) from the ideal Zeno limit (ZL) due to the photon loss in quantum metrology based on Mech-Zehnder interferometry. Here, we find that not only can the SNL be beaten, but also the ZL can be asymptotically recovered in a long-encoding-time condition when the photon dissipation is exactly studied in its inherent non-Markovian manner. Our analysis reveals that it is due to the formation of a bound state of the photonic system and its dissipative noise. Highlighting the microscopic mechanism of the dissipative noise on the quantum optical metrology, our result supplies a guideline to realize the ultrasensitive measurement in practice by forming the bound state in the setting of reservoir engineering.

Comparing the simultaneous determination of cis- and trans-palmitoleic acid in fish oil using HPLC and GC.

BACKGROUND: Cis- and trans-palmitoleic acids (Cis-POA and trans-POA) are isomers of palmitoleic acid, a monounsaturated fatty acid which affects glucose and lipid metabolism, and reduces insulin resistance. Trans-POA is used as a biomarker for indicating the risk of type II diabetes and coronary heart disease, but no methods of analysis or distinguishing between cis-POA and trans-POA have yet been reported. METHOD: An accurate and precise HPLC method was developed to determine cis- and trans-POA simultaneously, and compared with results from a GC method. Cis- and trans-POA were analyzed by HPLC on a reverse-phase BDS-C18 column, equilibrated and eluted with acetonitrile (A) and water (B). In the established and validated GC method used for comparison, potassium hydroxide ester exchange was chosen to derivatize the cis- and trans-POA, before being determined. RESULTS: The calibration curves for cis- and trans-POA were linear over the range 0.05 to 500 µg/mL. The HPLC method exhibited good sensitivity, precision and accuracy. The limits of detection (LOD) for cis- and trans-POA were 0.2 and 0.05 µg/mL, respectively. The method successfully determined cis- and trans-POA in fish oil. For the GC method, the contents of cis-POA quantified were similar to those from the HPLC method, but the contents of trans-POA revealed significant variation between the two methods. CONCLUSIONS: After a comprehensive consideration of the characteristics of the saponification and methyl esterification methods which have been tested and verified, the HPLC method was found to be suitable for determining cis- and trans-POA contents in fish oil. It was also suggested that in natural fish oil, cis-POA may be in the glyceride state, and trans-POA almost completely in the free acid form. In comparison with the GC method, the HPLC method provided a simpler process and faster analyses for identifying and determining cis- and trans-POA. The study has also provided technical support for studying the pharmacological differences and relationship between structure and activity of cis- and trans-POA. This could help physicians to analyze patients' samples more quickly in 10 min and therefore provide a more rapid diagnosis of problems relating to the risk of type II diabetes and coronary heart disease.

Prognostic Value of Ki67 Expression for Patients with Surgically Resected Hepatocellular Carcinoma: Perspectives from a High Incidence Area.

BACKGROUND: Antigen Ki-67 (Ki67) is a documented tumor biomarker known to be aberrantly expressed in many human cancers. However, to our knowledge, its prognostic value for surgically resected hepatocellular carcinoma (HCC) for high incidence areas of China has not been described. METHODS: We retrospectively investigated 339 patients with HCC who underwent surgery to remove the primary cancer at one center in Fujian, China, an area with a high incidence of HCC from 2004 to 2012. Immunohistochemistry (IHC) was used to quantify Ki67 expression in surgically resected HCC (RHCC) tissues. The survival curves were estimated by Kaplan-Meier analysis and the prognostic significance of Ki67 was analyzed using the log-rank test. The identification of relevant prognostic factors was performed by multivariate Cox regression analysis. RESULTS: Differential Ki67 expression was measured in 339 tissues from HCC. Among them 155 showed high Ki67 expression (≥ 3+), whereas the other 184 had low expression of Ki67 (-, +, or ++). High Ki67 was significantly related to preoperative serum α-fetoprotein > 400 µg/L (p = 0.001) and decreased aminotransferase (ALT) (p < 0.001). Moreover, multivariate Cox regression analysis confirmed that high Ki67 expression was strongly associated with increased death risk (HR = 2.287, 95% CI: (1.652 - 3.166)) and recurrence risk (HR = 1.625, 95% CI: (1.162 - 2.274)). CONCLUSIONS: High Ki76 expression has prognostic value for poor survival for RHCC patients, and detection of Ki67 with IHC may be promising for estimating survival for RHCC patients in areas with high-incidence for this disease in China.

Protective effects of leucine on redox status and mitochondrial-related gene abundance in the jejunum of intrauterine growth-retarded piglets during early weaning period.

The aim of this study was to investigate the effects of dietary supplementation with 0.35% l-leucine on redox status and gene abundance relating to mitochondrial biogenesis and function in the jejunum of intrauterine growth-retarded (IUGR) piglets during early weaning period. According to a 2 × 2 factorial arrangement, 16 IUGR and 16 normal body weight (NBW) piglets were fed a basal diet without l-leucine supplementation or a basal diet plus 0.35% l-leucine supplementation from the age of 14 to 35 d. The results showed that compared with NBW piglets, IUGR piglets had a lower (p < 0.05) jejunal DNA concentration, a reduced (p < 0.05) manganese superoxide dismutase (MnSOD) and total antioxidant capability (T-AOC) activities and mitochondrial DNA content in the jejunum. Leucine supplementation increased (p < 0.05) MnSOD and T-AOC activities and decreased (p < 0.05) the malondialdehyde content in the jejunum of IUGR piglets. The mRNA gene abundance of nuclear respiratory factor-1 (NRF1), mitochondrial transcription factor A (TFAM), ATP synthase (ATPs), cytochrome c oxidase V (CcOX V), cytochrome c and glucokinase in the jejunum of IUGR piglets was reduced (p < 0.05) compared with NBW piglets. However, NRF1, peroxisome proliferation-activated receptor gamma coactivator-1 alpha, TFAM, ATPs and CcOX I mRNA gene abundance in the jejunum of IUGR piglets were increased (p < 0.05) by diets supplemented with leucine. These data indicate that leucine supplementation has therapeutic potential for attenuating intestinal oxidative stress and mitochondrial dysfunction in IUGR piglets during the early period of life via increasing enzyme activities and up-regulating mRNA gene abundance.

Prognostic Value of Pre-Operative Platelet to Lymphocyte Ratio in Patients with Resected Primary Hepatocellular Carcinoma.

BACKGROUND: The platelet to lymphocyte ratio (PLR) is a readily available cancer biomarker but its prognostic value for patients with resected primary hepatocellular carcinoma (HCC) is uncertain. Thus, we investigated the relationship between PLR and survival of patients with resected primary HCC in the Fujian area, a high occurrence area of HCC in China. METHODS: This retrospective study included 337 patients with primary HCC who underwent surgical removal of primary liver cancer between 2004 and 2012 in Fuzhou General Hospital in Fujian, China. Pre-operative peripheral blood PLR was measured by platelet counts divided by lymphocyte counts. PLR and clinical factors were associated with a X2 test and data were analyzed with a Kaplan-Meier plus log rank analysis. Independent prognostic factors related to survival were assessed with multivariable analysis. RESULTS: Subjects were classified by a median PLR value of 91 (low: ≤ 91, n = 169 and high: > 91, n = 168). HighPLR patients died more often (57.7% vs. 35.5%, p = 4.3 x 10-5 and 39 months vs. 88 months, p < 0.001, respectively) and high PLR was associated with a nearly 2-fold elevated death risk (hazard ratio [HR]:1.815, 95% confidence interval (CI): 1.298 - 2.537, p = 4.85 x 10-4). Serum AFP, TNM stage and tumor size were also independent prognostic factors for patients with resected primary HCC according to multivariable analysis. CONCLUSIONS: PLR may be useful as a biomarker for assessing survival of resected primary HCC patients.

[Rapid Measurement of Carbon Dioxide with Laser-Induced Breakdown Spectroscopy Based on Atomic and Molecular Spectrum].

With the rapid development of economy and industrialization, global warming is becoming the most serious sensitive global climate issues, which causes the rising of sea level and many other negative effects. The cause of global warming is the emission of greenhouse gases and carbon dioxide is the main component of greenhouse gases. The control of CO2 emssion is beneficial to addressing gobal climate change and environmental degradation. Therefore, it's important to develop a rapid detection of CO2 for accurate control. There are amounts of methods to detect CO2 at present, including titration, electrochemical method, gas chromatography, infrared absorption spectroscopy and so on, however, t they still have the deficiency for online monitoring in industrial field. laser induced breakdown spectroscopy (LIBS), which is developing rapidly in recent few decades, is a detecting technology with characteristics of time-saving and synchronous measuring of multicomponent. What's more, there is no need for sample pretreating. To develop the online monitoring technique of CO2 emission in the industrial field, LIBS was employed to measure CO2 in this study. The mass flow controller was used to adjust the flow of high purity CO2 and N2 to obtain mixed gas with different CO2 concentrations. The mixed gas was firstly mixed in an air mixing chamber for thorough mixing and then sent to the sample cell for LIBS measurement. The evolution of C atomic spectral line and CN molecular band with different delay times were being studied, which demonstrated parts of CO2 react with air ambient to form CN molecular during the plasma generation, the CN molecular band should be taken into consideration for quantitative analysis, and the parameters were optimized for synchronous measurement of C line and CN band: 800 ns was the optimal delay time. During the plasma generation, many factors in the plasma may interact with others, the analysis index had close relationship wih serval measuring parameters. With the consideration of the effect of C, CN and the self-absorption in high concentration, multivariate calibration method was employed to establish calibration models of CO2. The results showed that the correlation coefficients R2 and the slope were 0.978 and 0.981, respectively. Compared with calibrated with single factor, the multivariate method improved the reliability of the model. What's more, the feasibility of the application of LIBS to measure CO2 rapidly was proved.

[Influence of laser energy on measurement of unburned carbon in fly Ash particle flow].

The fly ash particle flow was produced by a screw feeder and then ablated by a pulse laser to create plasma. The emission spectra of fly ash were detected by laser-induced breakdown spectroscopy. The present paper focused on the influence of laser energy on the measurement of unburned carbon. Seven groups of pulse laser in the range of 40 to 130 mJ were used to ablate the fly ash particle flow. The results show that the carbon line intensity is increased linearly with the increases in laser energy, but the SNR of carbon line increases in the range of 40 to 90 mJ and then trends to saturation, while the elimination rate of false data decreases. In this experiment, laser energy ranging from 90 to 100 mJ can enhance the plasma emission signal and improve the true spectral data of fly ash particle flow. So laser energy has close correlations with the ablation of the particle flow and the carbon line intensity. Reasonable laser energy is good for the effective ablation of the fly ash particle flow to get plasma spectra signals with good SNR.