NO2-Sensitive SnO2 Nanoparticles Prepared Using a Freeze-Drying Method.

The n-type semiconductor SnO2 with a wide band gap (3.6 eV) is massively used in gas-sensitive materials, but pure SnO2 still suffers from a high operating temperature, low response, and tardy responding speed. To solve these problems, we prepared small-sized pure SnO2 using hydrothermal and freeze-drying methods (SnO2-FD) and compared it with SnO2 prepared using a normal drying method (SnO2-AD). The sensor of SnO2-FD had an ultra-high sensitivity to NO2 at 100 °C with excellent selectivity and humidity stability. The outstanding gas sensing properties are attributed to the modulation of energy band structure and the increased carrier concentration, making it more accessible for electron exchange with NO2. The excellent gas sensing properties of SnO2-FD indicate its tremendous potential as a NO2 sensor.

Using XGBoost for Predicting In-Stent Restenosis Post-DES Implantation: Role of Lymphocyte-to-Monocyte Ratio and Residual Cholesterol.

Objective: This study aims to investigate their correlation and predictive utility for in-stent restenosis (ISR) in patients with acute coronary syndrome (ACS) following percutaneous coronary intervention (PCI). Methods: We collected medical records of 668 patients who underwent PCI treatment from January 2022 to December 2022. Based on follow-up results (ISR defined as luminal narrowing ≥ 50% on angiography), all participants were divided into ISR and non-ISR groups. The XGBoost machine learning (ML) model was employed to identify the optimal predictive variables from a set of 31 variables. Discriminatory ability was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC), while calibration and performance of the prediction models were assessed using the Hosmer-Lemeshow (HL) test and calibration plots. Clinical utility of each model was evaluated using decision curve analysis (DCA). Results: In the XGBoost importance ranking of predictive factors, LMR and RC ranked first and fourth, respectively. The AUC of the entire XGBoost ML model was 0.8098, whereas the model using traditional stepwise backward regression, comprising five predictive factors, had an AUC of 0.706. The XGBoost model showed superior predictive performance with a higher AUC, indicating better discrimination and predictive accuracy for ISR compared to traditional methods. Conclusion: LMR and RC are identified as cost-effective and reliable biomarkers for predicting ISR risk in ACS patients following drug-eluting stent (DES) implantation. LMR and RC represent cost-effective and reliable biomarkers for predicting ISR risk in ACS patients following drug-eluting stent implantation. Enhances the accuracy and clinical utility of ISR prediction models, offering clinicians a robust tool for risk stratification and personalized patient management.

Alkalinity control in sludge propels the conversion of concrete slurry waste into micro- and nano-sized biogenic CaCO3.

The utilization of Bacillus sp. for the production of bio-CaCO3 in concrete crack repair and strength enhancement has attracted considerable attention. However, microbial-induced calcium carbonate precipitation (MICP) has yet to be explored as a precedent with activated sludge. Here calcium sourced from concrete slurry waste (CSW) and carbon from sludge microbial ß-oxidation under alkaline were used to generate micro/nano CaCO3. The results indicate that the main crystalline form of the generated precipitated particles is calcite, with a particle size ranging from 0.7 to 10 µm. Minimal heavy metals were found in the supernatant following settling. And at the optimum pH of 8.5-9, carbon capture reached 743 mg L-1, and CaCO3 production reached 1,191 mg L-1, and dominant phylum were Proteobacteria and Bacteroidota, with Thauera being a prevalent genus adept in ß-oxidation. Mass balance analysis showed that alkali promotes microbial ß-oxidation of organisms to produce CO2 and facilitate storage. Thus, the alkaline regulation of metabolism between microbe and CSW provides a novel way of sludge to initiate MICP.

Suppressed Defects by Functional Thermally Cross-Linked Fullerene for High-Efficiency Tin-Lead Perovskite Solar Cells.

Mixed tin-lead (Sn-Pb) perovskites have attracted the attention of the community due to their narrow bandgap, ideal for photovoltaic applications, especially tandem solar cells. However, the oxidation and rapid crystallization of Sn2+ and the interfacial traps hinder their development. Here, cross-linkable [6,6]-phenyl-C61-butyric styryl dendron ester (C-PCBSD) is introduced during the quenching step of perovskite thin film processing to suppress the generation of surface defects at the electron transport layer interface and improve the bulk crystallinity. The C-PCBSD has strong coordination ability with Sn2+ and Pb2+ perovskite precursors, which retards the crystallization process, suppresses the oxidation of Sn2+, and improves the perovskite bulk and surface crystallinity, yielding films with reduced nonradiative recombination and enhanced interface charge extraction. Besides, the C-PCBSD network deposited on the perovskite surface displays superior hydrophobicity and oxygen resistance. Consequently, the devices with C-PCBSD obtain PCEs of up to 23.4% and retained 97% of initial efficiency after 2000 h of storage in a N2 atmosphere.

Machine Learning-Based Prediction of In-Stent Restenosis Risk Using Systemic Inflammation Aggregation Index Following Coronary Stent Placement.

Introduction: Coronary artery disease (CAD) remains a significant global health challenge, with percutaneous coronary intervention (PCI) being a primary revascularization method. In-stent restenosis (ISR) post-PCI, although reduced, continues to impact patient outcomes. Inflammation and platelet activation play key roles in ISR development, emphasizing the need for accurate risk assessment tools. The systemic inflammation aggregation index (AISI) has shown promise in predicting adverse outcomes in various conditions but has not been studied in relation to ISR. Methods: A retrospective observational study included 1712 patients post-drug-eluting stent (DES) implantation. Data collected encompassed demographics, medical history, medication use, laboratory parameters, and angiographic details. AISI, calculated from specific blood cell counts, was evaluated alongside other variables using machine learning models, including random forest, Xgboost, elastic networks, logistic regression, and multilayer perceptron. The optimal model was selected based on performance metrics and further interpreted using variable importance analysis and the SHAP method. Results: Our study revealed that ISR occurred in 25.8% of patients, with a range of demographic and clinical factors influencing the risk of its development. The random forest model emerged as the most adept in predicting ISR, and AISI featured prominently among the top variables affecting ISR prediction. Notably, higher AISI values were positively correlated with an elevated probability of ISR occurrence. Comparative evaluation and visual analysis of model performance, the random forest model demonstrates high reliability in predicting ISR, with specific metrics including an AUC of 0.9569, accuracy of 0.911, sensitivity of 0.855, PPV of 0.81, and NPV of 0.948. Conclusion: AISI demonstrated itself as a significant independent risk factor for ISR following DES implantation, with an escalation in AISI levels indicating a heightened risk of ISR occurrence.

Analysis of the correlation between the systemic inflammatory response index and the severity of coronary vasculopathy.

This study aims to analyze the correlation between Systemic Inflammatory Response Index (SIRI) and the severity of coronary artery stenosis in patients with coronary heart disease (CHD). It also aims to assess the predictive value of SIRI for the severity of coronary artery stenosis. A total of 2990 patients who underwent coronary angiography were included in this study. The Gensini score was used to estimate the severity of coronary vascular lesions. The predictive ability of SIRI for CHD was evaluated using receiver operating characteristic (ROC) curves. Binary multivariate logistic regression analysis was used to predict the likelihood of CHD based on the SIRI index. The results showed that people with higher SIRI index were more likely to have CHD (P < 0.001). After controlling for other risk factors, the highest quartile had a significantly higher incidence of coronary artery disease compared to the lowest quartile (odds ratio [OR] 2.25, 95% confidence interval [CI] 1.73-3.92, P < 0.001). Furthermore, the Gensini score was significantly higher in the fourth quartile group (T4) compared to the first (T1) and second (T2) quartile groups (P < 0.001). Additionally, the SIRI index was significantly higher in the group with severe coronary artery lesions compared to the mild and moderate groups (P < 0.001). The SIRI index also showed a higher predictive ability for the extent of coronary lesions under the ROC curve compared to other commonly used markers, including platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and neutrophil-to-lymphocyte ratio (NLR) (P < 0.001). Therefore, SIRI index positively correlates with coronary artery stenosis in CHD patients, serving as an effective early screening marker for assessing stenosis severity.

How group structure impacts the numbers at risk for coronary artery disease: polygenic risk scores and nongenetic risk factors in the UK Biobank cohort.

The UK Biobank (UKB) is a large cohort study that recruited over 500,000 British participants aged 40-69 in 2006-2010 at 22 assessment centers from across the United Kingdom. Self-reported health outcomes and hospital admission data are 2 types of records that include participants' disease status. Coronary artery disease (CAD) is the most common cause of death in the UKB cohort. After distinguishing between prevalence and incidence CAD events for all UKB participants, we identified geographical variations in age-standardized rates of CAD between assessment centers. Significant distributional differences were found between the pooled cohort equation scores of UKB participants from England and Scotland using the Mann-Whitney test. Polygenic risk scores of UKB participants from England and Scotland and from different assessment centers differed significantly using permutation tests. Our aim was to discriminate between assessment centers with different disease rates by collecting data on disease-related risk factors. However, relying solely on individual-level predictions and averaging them to obtain group-level predictions proved ineffective, particularly due to the presence of correlated covariates resulting from participation bias. By using the Mundlak model, which estimates a random effects regression by including the group means of the independent variables in the model, we effectively addressed these issues. In addition, we designed a simulation experiment to demonstrate the functionality of the Mundlak model. Our findings have applications in public health funding and strategy, as our approach can be used to predict case rates in the future, as both population structure and lifestyle changes are uncertain.

Single-cell profiling of response to neoadjuvant chemo-immunotherapy in surgically resectable esophageal squamous cell carcinoma.

BACKGROUND: The efficacy of neoadjuvant chemo-immunotherapy (NAT) in esophageal squamous cell carcinoma (ESCC) is challenged by the intricate interplay within the tumor microenvironment (TME). Unveiling the immune landscape of ESCC in the context of NAT could shed light on heterogeneity and optimize therapeutic strategies for patients. METHODS: We analyzed single cells from 22 baseline and 24 post-NAT treatment samples of stage II/III ESCC patients to explore the association between the immune landscape and pathological response to neoadjuvant anti-PD-1 combination therapy, including pathological complete response (pCR), major pathological response (MPR), and incomplete pathological response (IPR). RESULTS: Single-cell profiling identified 14 major cell subsets of cancer, immune, and stromal cells. Trajectory analysis unveiled an interesting link between cancer cell differentiation and pathological response to NAT. ESCC tumors enriched with less differentiated cancer cells exhibited a potentially favorable pathological response to NAT, while tumors enriched with clusters of more differentiated cancer cells may resist treatment. Deconvolution of transcriptomes in pre-treatment tumors identified gene signatures in response to NAT contributed by specific immune cell populations. Upregulated genes associated with better pathological responses in CD8 + effector T cells primarily involved interferon-gamma (IFNγ) signaling, neutrophil degranulation, and negative regulation of the T cell apoptotic process, whereas downregulated genes were dominated by those in the immune response-activating cell surface receptor signaling pathway. Natural killer cells in pre-treatment tumors from pCR patients showed a similar upregulation of gene expression in response to IFNγ but a downregulation of genes in the neutrophil-mediated immunity pathways. A decreased cellular contexture of regulatory T cells in ESCC TME indicated a potentially favorable pathological response to NAT. Cell-cell communication analysis revealed extensive interactions between CCL5 and its receptor CCR5 in various immune cells of baseline pCR tumors. Immune checkpoint interaction pairs, including CTLA4-CD86, TIGIT-PVR, LGALS9-HAVCR2, and TNFSF4-TNFRSF4, might serve as additional therapeutic targets for ICI therapy in ESCC. CONCLUSIONS: This pioneering study unveiled an intriguing association between cancer cell differentiation and pathological response in esophageal cancer patients, revealing distinct subgroups of tumors for which neoadjuvant chemo-immunotherapy might be effective. We also delineated the immune landscape of ESCC tumors in the context of clinical response to NAT, which provides clinical insights for better understanding how patients respond to the treatment and further identifying novel therapeutic targets for ESCC patients in the future.

Regiodivergent Hydrosilylation of Polar Enynes to Synthesize Site-Specific Silyl-Substituted Dienes.

Herein, we present catalyst-regulated switchable site-selective hydrosilylation of enynes, which are suitable for a wide range of alkyl and aryl substituted polar enynes and exhibit excellent functional group compatibility. Under the optimized conditions, silyl groups can be precisely installed at various positions of 1,3-dienes. While α- and γ-silylation products were obtained under platinum-catalytic systems, ß-silylation products were delivered with [Cp*RuCl]4 as catalyst. This process lead to the formation of 1,3-dienoates with diverse substitutions, which would pose challenges with other methodologies.

Outcomes following the excision of sarcoma and chest wall reconstruction using 3D printed implant.

The survival outcomes of patients with chest wall sarcomas (CWS) were evaluated after receiving wide excision and chest wall reconstruction by using three-dimensional printed (3DP) implants. The survival outcomes evaluating the effect of 3DP implants for chest wall reconstruction is lacking. Here, forty-nine patients with CWS underwent radical wide excision and chest wall reconstruction using 3DP implants. The surgical data and long-term survival outcomes were collected and analyzed. With a median follow-up of 36 months, the disease-free survival (DFS) and overall survival (OS) were 31.7% and 58.5%, respectively. In addition, the 3-year DFS and OS can be significantly differentiated using the classification criteria of tumor grade, tumor size tumor area. Hence, wide excision and chest wall reconstruction using three-dimensional printed implants are a safe and effective treatment for chest wall sarcoma. The novel classification criteria of tumor size and area have the potential to predict the prognosis of CWS.

Early postoperative endoscopy for predicting anastomotic leakage after minimally invasive esophagectomy: A large-volume retrospective study.

BACKGROUND: Anastomotic leakage is one of the most severe adverse events of minimally invasive esophagectomy for esophageal cancer. Early postoperative endoscopy is considered to be the most objective means to diagnose anastomotic leakage, but its safety is questioned by clinicians. This study aimed to evaluate the safety and effectiveness of early postoperative endoscopy in predicting anastomotic leakage. METHODS: Patients who underwent minimally invasive esophagectomy (from January 2017 to June 2021) in our center were identified and divided into early postoperative endoscopy and control groups according to whether they underwent early postoperative endoscopy within 72 hours after surgery. Propensity score matching was used to balance baseline characteristics. The incidence of postoperative adverse events was compared between the 2 groups, risk variables for anastomotic leakage were identified using logistic regression, and abnormal endoscopic findings related to anastomotic leakage occurrence were explored. RESULTS: A total of 436 patients were enrolled, of whom 134 underwent early postoperative endoscopy. One hundred and thirty-two pairs were matched by propensity score matching, and baseline characteristics were well-balanced. Both before and after propensity score matching, early postoperative endoscopy did not increase the incidence of postoperative adverse events (chyle leak, hypoproteinemia, pneumonia, etc) and in-hospital mortality. Notably, the incidence of anastomotic leakage (9.8% vs 22.7%) and the length of mean postoperative hospital stay (17.6 vs 20.9 days) was significantly decreased in the early postoperative endoscopy group. Finally, based on the findings under early postoperative endoscopy, we found that gastric graft ischemia is related to a higher incidence of anastomotic leakage (P = .023). CONCLUSION: Early postoperative endoscopy does not increase postoperative adverse events after minimally invasive esophagectomy and may guide early prediction and intervention strategies for anastomotic leakage in patients undergoing minimally invasive esophagectomy.

Anchoring Charge Selective Self-Assembled Monolayers for Tin-Lead Perovskite Solar Cells.

Self-assembled monolayers (SAMs) have displayed great potential for improving efficiency and stability in p-i-n perovskite solar cells (PSCs). The anchoring of SAMs at the conductiv metal oxide substrates and their interaction with perovskite materials must be rationally tailored to ensure efficient charge carrier extraction and improved quality of the perovskite films. Herein, SAMs molecules with different anchoring groups and spacers to control the interaction with perovskite in the p-i-n mixed Sn-Pb PSCs are selected. It is found that the monolayer with the carboxylate group exhibits appropriate interaction and has a more favorable orientation and arrangement than that of the phosphate group. This results in reduced nonradiative recombination and enhanced crystallinity. In addition, the short chain length leads to an improved energy level alignment of SAMs with perovskite, improving hole extraction. As a result, the narrow bandgap (≈1.25 eV) Sn-Pb PSCs show efficiencies of up to 23.1% with an open-circuit voltage of up to 0.89 V. Unencapsulated devices retain 93% of their initial efficiency after storage in N2 atmosphere for over 2500 h. Overall, this work highlights the underexplored potential of SAMs for perovskite photovoltaics and provides essential findings on the influence of their structural modification.

A gene-based score for the risk stratification of stage IA lung adenocarcinoma.

OBJECTIVE: We aim to molecularly stratify stage IA lung adenocarcinoma (LUAD) for precision medicine. METHODS: Twelve multi-institution datasets (837 cases of IA) were used to classify the high- and low-risk types (based on survival status within 5 years), and the biological differences were compared. Then, a gene-based classifying score (IA score) was trained, tested and validated by several machine learning methods. Furthermore, we estimated the significance of the IA score in the prognostic assessment, chemotherapy prediction and risk stratification of stage IA LUAD. We also developed an R package for the clinical application. The SEER database (15708 IA samples) and TCGA Pan-Cancer (1881 stage I samples) database were used to verify clinical significance. RESULTS: Compared with the low-risk group, the high-risk group of stage IA LUAD has obvious enrichment of the malignant pathway and more driver mutations and copy number variations. The effect of the IA score on the classification of high- and low-risk stage IA LUAD was much better than that of classical clinicopathological factors (training set: AUC = 0.9, validation set: AUC = 0.7). The IA score can significantly predict the prognosis of stage IA LUAD and has a prognostic effect for stage I pancancer. The IA score can effectively predict chemotherapy sensitivity and occult metastasis or invasion in stage IA LUAD. The R package IAExpSuv has a good risk probability prediction effect for both groups and single stages of IA LUAD. CONCLUSIONS: The IA score can effectively stratify the risk of stage IA LUAD, offering good assistance in precision medicine.

Biotoxicity of Halide Perovskites in Mice.

Halide perovskites are crystalline semiconductors with exceptional optoelectronic properties, rapidly developing toward large-scale applications. Lead (II) (Pb2+ ) is the core element used to prepare halide perovskites. Pb2+ can displace key 2+ elements, including calcium, zinc and iron, that regulate vital physiological functions. Sn2+ can replace Pb2+ within the perovskite structure and, if accidentally dispersed in the environment, it readily oxidizes to Sn4+ , which is compatible with physiological functions and thus potentially safe. The 3+ salt bismuth (III) (Bi3+ ) is also potentially safe for the same reason and useful to prepare double perovskites. Here, this work studies the biotoxicity of Pb, Sn, and Bi perovskites in mice for the first time. This work analyses histopathology and growth of mice directly exposed to perovskites and investigate the development of their offspring generation. This study provides the screening of organs and key physiological functions targeted by perovskite exposure to design specific studies in mammalians.

Apoptotic bodies inhibit inflammation by PDL1-PD1-mediated macrophage metabolic reprogramming.

Apoptosis triggers immunoregulation to prevent and suppress inflammation and autoimmunity. However, the mechanism by which apoptotic cells modulate immune responses remains largely elusive. In the context of allogeneic mesenchymal stem cells (MSCs) transplantation, long-term immunoregulation is observed in the host despite the short survive of the injected MSCs. In this study, utilizing a mouse model of acute lung injury (ALI), we demonstrate that apoptotic bodies (ABs) released by transplanted human umbilical cord MSCs (UC-MSCs) convert the macrophages from a pro-inflammatory to an anti-inflammatory state, thereby ameliorating the disease. Mechanistically, we identify the expression of programmed cell death 1 ligand 1 (PDL1) on the membrane of UC-MSCs-derived ABs, which interacts with programmed cell death protein 1 (PD1) on host macrophages. This interaction leads to the reprogramming of macrophage metabolism, shifting from glycolysis to mitochondrial oxidative phosphorylation via the Erk-dependent pathway in ALI. Importantly, we have reproduced the PDL1-PD1 effects of ABs on metabolic switch using alveolar macrophages from patients with ALI, suggesting the potential clinical implications of developing therapeutic strategies for the patients.

Electrochemical Phenyl-Carbonyl Coupling Reaction of Aromatic Aldehydes or Ketones.

An electrochemical phenyl-carbonyl coupling reaction of aromatic aldehydes or ketones to synthesize 4-(hydroxy(phenyl)methyl)benzaldehyde derivatives has been developed. The method shows high chemoselectivity, broad functional group compatibility, atom economy, and environmental benignity and has good potential applicability.

Synthesis and Transformation of Bis(silyl)-Substituted Conjugated Vinylallene Compounds.

We develop a copper-catalyzed disilylation of polysubstituted pent-1-en-4-yn-3-yl acetate derivatives, which in one pot furnishes the bis(silyl)-substituted vinylallenes in moderate yields under mild reaction conditions. The reaction shows broad substrate scope and single stereoselectivity. Besides, we develop a method to decrease the electrocyclization temperature of vinylallenes for the synthesis of methylenecyclobutenes by installing bis(silyl) substituents. And the effect of a silyl substituent on electrocyclization of vinylallenes was studied via DFT computation. The synthetic method features broad substrate scope and excellent stereoselectivity.

Effects of zero-valent iron (ZVI) on nitrogen conversion, transformation of sulfamethoxazole (SMX) and abundance of antibiotic resistance genes (ARGs) in aerobic granular sludge process.

Even after pre-treatment, livestock and poultry wastewater still contain high concentrations of ammonia and residual antibiotics. These could be removed economically using the aerobic granular sludge (AGS) process with zero-valent iron (ZVI). The interaction of antibiotics and nitrogen in this process needs to be clarified and controlled, however, to achieve good removal performance. Otherwise, antibiotics might generate transformation products (TPs) with higher toxicity and lead to the emergence of antibiotic-resistant bacteria carrying antibiotic resistance genes (ARGs), which could cause persistent toxicity and the risk of disease transmission to the ecological environment. This study investigated the impact of ZVI on AGS for nitrogen and sulfamethoxazole (SMX) removal. The results show that AGS could maintain good ammonia removal performance and that the existence of SMX had a negative impact on ammonia oxidation activities. ZVI contributed to an increase in the abundance of nitrite oxidation bacteria, denitrifying bacteria and the functional genes of nitrogen removal. This led to better total nitrogen removal and a decrease in N2O emission. Accompanied by biological nitrogen transformation, SMX could be transformed into 14 TPs through five pathways. ZVI has the potential to enhance transformation pathways with TPs of lower ecotoxicity, thereby reducing the acute and chronic toxicity of the effluent. Unfortunately, ZVI might enhance the abundance of sul1, sul2, and sul3 in AGS, which increases the risk of sulfonamide antibiotic resistance. In AGS, Opitutaceae, Xanthomonas, Spartobacteria and Mesorhizobium were potential hosts for ARGs. This study provides theoretical references for the interaction of typical antibiotics and nitrogen in the biological treatment process of wastewater and bioremediation of natural water bodies.

Predictive Value of COPD History on In-Stent Restenosis in Coronary Arteries Following Percutaneous Coronary Intervention.

Objective: Chronic obstructive pulmonary disease (COPD) is a prevalent chronic respiratory disease that poses a significant health risk to individuals. Patients with COPD are predisposed to a higher incidence of coronary artery disease (CAD) than the general population. This study aims to investigate the correlation between COPD and the incidence of in-stent restenosis (ISR) after percutaneous coronary intervention (PCI). Methods: This study retrospectively analyzed the clinical data and laboratory test results of patients who underwent PCI at our hospital between January 2018 and December 2021 to investigate the relationship between COPD and drug-Eluting Stents (DES) postoperative ISR. We employed the best subset method to select the most suitable combination of predictive factors, utilizing the data, and verified the precision of the model by means of internal validation. We ultimately assessed the performance of the prediction model using an ROC curve. Results: The research indicates that COPD is an independent risk factor for ISR after PCI (OR=2.437, 95% CI [1.336, 4.495], P=0.004). The analysis revealed an area under the receiver operating characteristic (ROC) curve of 0.783 for the training group and 0.705 for the testing group, indicating a model fitting for both groups (both > 0.5). Conclusion: COPD history is a dependable predictor of stent restenosis post percutaneous coronary intervention.

Simulation study of an x-ray sub-picosecond resolution detection system based on time-domain amplification.

This study proposes what we believe to be a novel x-ray detection system that achieves a temporal resolution of 930 fs with photorefractive and four-wave mixing effects. The system comprises two parts: a signal-conversion system and signal-acquisition system. The signal-conversion system is based on the photorefractive effect, which converts x-ray evolution into the variation of infrared interference intensity. The signal-conversion sensor consists of ultra-fast response LT-GaAs and a high-resolution interference cavity, achieving a resolution of  767 fs. The signal-acquisition system consists of a time-domain amplification system based on four-wave mixing and a high-resolution signal-recording system with a resolution of 21 ps, providing a temporal resolution of 525 fs.