Subjective benefits from wearing self-fitting over-the-counter hearing aids in the real world.

Introduction: In 2022, the US Food and Drug Administration enacted final regulations to establish the category of over-the-counter (OTC) hearing aids aimed at reducing barriers to access hearing health care for individuals with self-perceived mild to moderate hearing loss. However, given the infancy of this device category, the effectiveness of OTC hearing aids in real-world environments is not yet well understood. Methods and results: To gain insights into the perceived benefit of self-fitting OTC hearing aids, a two-pronged investigation was conducted. In the primary investigation, 255 active users of a self-fitting OTC hearing aid were surveyed on their perceived benefit using an abridged form of the Satisfaction with Amplification in Daily Living (SADL) scale. The mean global (4.9) and subscale scores (Positive Effect (PE): 4.3; Negative Features (NF): 4.3; Personal Image (PI): 6.1) were within the range of those previously reported for users of prescription hearing aids. In the secondary investigation, 29 individuals with self-reported hearing impairment but no prior experience with the investigational self-fitting OTC hearing aids used the devices and reported their perceived benefit and satisfaction following short-term usage. For this prospective group, the global SADL (5.4) and subscale scores (PE: 4.8; NF: 4.9; PI: 6.5) following a minimum of 10 weeks of real-world use were also within the range of those previously reported for traditional hearing aid users. In addition, this prospective group was also asked quality of life questions which assessed psychological benefits of hearing aid use. Responses to these items suggest hearing aid related improvements in several areas spanning emotional health, relationships at home and at work, social life, participation in group activities, confidence and feelings about one's self, ability to communicate effectively, and romance. Discussion: Converging data from these investigations suggest that self-fitting OTC hearing aids can potentially provide their intended users with a level of subjective benefit comparable to what prescription hearing aid users might experience.

Reutilization of Silicon-Cutting Waste via Constructing Multilayer Si@SiO2@C Composites as Anode Materials for Li-Ion Batteries.

The rapid development of the photovoltaic industry has also brought some economic losses and environmental problems due to the waste generated during silicon ingot cutting. This study introduces an effective and facile method to reutilize silicon-cutting waste by constructing a multilayer Si@SiO2@C composite for Li-ion batteries via two-step annealing. The double-layer structure of the resultant composite alleviates the severe volume changes of silicon effectively, and the surrounding slightly graphitic carbon, known for its high conductivity and mechanical strength, tightly envelops the silicon nanoflakes, facilitates ion and electron transport and maintains electrode structural integrity throughout repeated charge/discharge cycles. With an optimization of the carbon content, the initial coulombic efficiency (ICE) was improved from 53% to 84%. The refined Si@SiO2@C anode exhibits outstanding cycling stability (711.4 mAh g-1 after 500 cycles) and rate performance (973.5 mAh g-1 at 2 C). This research presents a direct and cost-efficient strategy for transforming photovoltaic silicon-cutting waste into high-energy-density lithium-ion battery (LIB) anode materials.

IKBKE promotes the ZEB2-mediated EMT process by phosphorylating HMGA1a in glioblastoma.

IKBKE (Inhibitor of Nuclear Factor Kappa-B Kinase Subunit Epsilon) is an important oncogenic protein in a variety of tumors, which can promote tumor growth, proliferation, invasion and drug resistance, and plays a critical regulatory role in the occurrence and progression of malignant tumors. HMGA1a (High Mobility Group AT-hook 1a) functions as a cofactor for proper transcriptional regulation and is highly expressed in multiple types of tumors. ZEB2 (Zinc finger E-box Binding homeobox 2) exerts active functions in epithelial mesenchymal transformation (EMT). In our current study, we confirmed that IKBKE can increase the proliferation, invasion and migration of glioblastoma cells. We then found that IKBKE can phosphorylate HMGA1a at Ser 36 and/or Ser 44 sites and inhibit the degradation process of HMGA1a, and regulate the nuclear translocation of HMGA1a. Crucially, we observed that HMGA1a can regulate ZEB2 gene expression by interacting with ZEB2 promoter region. Hence, HMGA1a was found to promote the ZEB2-related metastasis. Consequently, we demonstrated that IKBKE can exert its oncogenic functions via the IKBKE/HMGA1a/ZEB2 signalling axis, and IKBKE may be a prominent biomarker for the treatment of glioblastoma in the future.

Insights into the influence of physicochemical parameters on the microbial community and volatile compounds during the ultra-long fermentation of compound-flavor Baijiu.

Introduction: While the variation in physicochemical parameters, microbial communities, metabolism, composition, and the proportion of volatile components in fermented grains (FG) affect final Baijiu quality, their complex interactions during the ultra-long fermentation of compound-flavor Baijiu (CFB) are still poorly understood. Methods: In this study, amplicon sequencing was used to analyze the microbial community, and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the volatile components in FG during ultra-long fermentation of CFB. The relationships between the dominant microbial communities, physicochemical parameters, and volatile components were analyzed using redundancy analysis and network analysis. Results: During ultra-long fermentation, bacterial diversity was initially higher than during the mid and late stages. Fungal diversity in the mid stages was higher than that initially and later in the process. A total of 88 volatile components, including six alcohols, 43 esters, eight aldehydes and ketones, 13 acids, and 18 other compounds were detected in FG. Starch and reducing sugars in FG strongly affected the composition and function of bacterial and fungal communities. However, acidity had little effect on the composition and function of the bacterial flora. Lactobacillus, Bacillus, Weissella, and Pichia were the core microbial genera involved in metabolizing the volatile components of FG. Discussion: We provide insights into the relationships and influences among the dominant microbial communities, physicochemical parameters, and volatile components during ultra-long fermentation of CFB. These insights help clarify the fermentation mechanisms of solid-state fermentation Baijiu (SFB) and control and improve the aroma quality of CFB.

Nickel-Catalyzed Radical Ring-Opening Phosphorylation of Cycloalkyl Hydroperoxides Leading to Distal Acylphosphine Oxides.

A facile and efficient nickel-catalyzed C-C bond cleavage/phosphorylation of various cycloalkyl hydroperoxides was developed. This radical ring-opening strategy provided practical access to structurally diverse distal ketophosphine oxides in one pot through concurrent C═O/C-P bond formation with high atom economy under mild room temperature and base-free conditions.

Systematic pan­cancer analysis identifies CDC45 as having an oncogenic role in human cancers.

Cell division cycle 45 (CDC45) is an essential protein required for the initiation of DNA replication. In the present study, the role of CDC45 across 33 cancers was systematically investigated. It was observed that the expression of CDC45 was significantly upregulated in most cancers, exhibiting a marked negative correlation with the overall survival. Next, there was no significant difference in prognosis between the genomically altered and unaltered groups with respect to clinical outcomes. A decreased level of CDC45 at the DNA promoter region was also identified in several cancers. Furthermore, CDC45 expression was associated with the levels of tumor­infiltrating immune cells in some specific cancer types. In addition, CDC45 was associated with m6A methylation, and CDC45 expression was primarily positively correlated with 'writers' and 'readers' in various cancers, particularly HNRNPC, RBM15 and YTHDC1. Gene enrichment analysis was also performed. In addition, the AUC of each cancer with respect to its 1­, 3­, and 5­year survival rates were explored. Finally, CCK­8 assays, EdU assays and cell cycle analysis were conducted. In conclusion, the present study demonstrated that CDC45 may be a potential biomarker and target for cancer treatment.

Contribution of the sensorimotor beta oscillations and the cortico-basal ganglia-thalamic circuitry during value-based decision making: A simultaneous EEG-fMRI investigation.

In decision neuroscience, the motor system has primarily been considered to be involved in executing choice actions. However, a competing perspective suggests its engagement in the evaluation of options, traditionally considered to be performed by the brain's valuation system. Here, we investigate the role of the motor system in value-based decision making by determining the neural circuitries associated with the sensorimotor beta oscillations previously identified to encode decision options. In a simultaneous EEG-fMRI study, participants evaluated reward and risk associated with a forthcoming action. A significant sensorimotor beta desynchronization was identified prior to and independent of response. The level of beta desynchronization showed evidence of encoding the reward levels. This beta desynchronization covaried, on a trial-by-trial level, with BOLD activity in the cortico-basal ganglia-thalamic circuitry. In contrast, there was only a weak covariation within the valuation network, despite significant modulation of its BOLD activity by reward levels. These results suggest that the way in which decision variables are processed differs in the valuation network and in the cortico-basal ganglia-thalamic circuitry. We propose that sensorimotor beta oscillations indicate incentive motivational drive towards a choice action computed from the decision variables even prior to making a response, and it arises from the cortico-basal ganglia-thalamic circuitry.

Reward and expectancy effects on neural signals of motor preparation and execution.

The magnitude and prospect of rewards can have strong modulatory effects on response preparation and execution. Importantly, reward-seeking behavior in real life happens under an environment characterized by uncertainty and dynamic changes. The current study investigated how the brain's motor and cognitive control system adapts to the dynamic changes in the environment in pursuit of rewards. To this end, we tested the effect of reward and expectancy on the hallmark neural signals that reflect activity in motor and prefrontal systems, the lateralized readiness potential (LRP) and the mediofrontal (mPFC) theta oscillations, while participants performed an expected and unexpected actions to retrieve rewards. To better capture the dynamic changes in neural processes represented in the LRP waveform, we decomposed the LRP into the preparation (LRPprep) and execution (LRPexec) components. In the comparison of LRP magnitude across task conditions, we found a greater LRPprep when large rewards were more likely, reflecting a greater motor preparation to obtain larger rewards. We also found a greater LRPexec when large rewards were presented unexpectedly, suggesting a greater motor effort placed for executing a correct movement when presented with large rewards. In the analysis of mPFC theta, we found a greater theta power prior to performing an unexpected than expected response, indicating its contribution in response conflict resolution. Collectively, these results demonstrate an optimized motor and cognitive control to maximize rewards under the dynamic changes of real-life environment.

Pan-cancer analysis indicates that MYBL2 is associated with the prognosis and immunotherapy of multiple cancers as an oncogene.

MYBL2 has been demonstrated to be an oncogene in some cancers, but there is no pan-cancer analysis at the macro level. We used multiple online or offline bioinformatic tools to examine the effects of MYBL2 in human cancers. We first identified that MYBL2 was highly expressed and related to the stage and grade of most cancers. The results of survival analysis from two databases showed that high MYBL2 expression was positively correlated with a poor prognosis for most cancer patients. We observed a significant difference in the promoter methylation level of MYBL2 in cancers such as colon adenocarcinoma and liver hepatocellular carcinoma versus normal controls. We found that MYBL2 can affect the tumor immune microenvironment by influencing the immune infiltration level and expression level of CD4+ T cells, CD8+ T cells, cancer-associated fibroblasts (CAFs) and immune checkpoint-associated cells. Functional enrichment analysis of MYBL2 identified that MYBL2 can play a crucial role in cancers by regulating spliceosomes, DNA replication and the cell cycle. Moreover, we verified the function of MYBL2 in three cancer cells of glioma, breast cancers and liver cancers, and the results showed that MYBL2 can regulate the cell cycle and proliferation ability of cancers.

miRNA-451 regulates the NF-κB signaling pathway by targeting IKKß to inhibit glioma cell growth.

Glioblastoma multiforme (GBM) is associated with a poor prognosis, and effective treatments are lacking. Our previous studies have shown that miRNA-451 is closely related to the development and progression of glioma. miRNA-451 is a tumor suppressor whose expression is negatively correlated with the WHO grades of gliomas, but its specific mechanism is still unclear. Research shows that NF-κB is highly expressed in early malignant glioma, and thus, the NF-κB signaling pathway has become an important target for the treatment of malignant glioma. Activation of IKK is a critical step in the activation of the classical NF-κB pathway. By performing a bioinformatics analysis, we found that IKKß is a potential direct target of miRNA-451 in glioma. In this study, we transfected lentivirus expressing miRNA-451 to test the effect of miRNA-451 overexpression on malignant glioma cell lines and confirmed that IKKß is a target gene of miRNA-451 by luciferase assay. By targeting IKKß, MTT, cell invasion and wound-healing assays showed that cell proliferation, cell invasion and migration were significantly suppressed in the LV-miRNA-451 group. Western blotting results showed that the expression levels of IKKß, p-p65, MMP-2, MMP-9, Cyclin D1, p16 and PCNA were significantly decreased in the LV-miRNA-451 group. In vivo, miRNA-451 significantly decreased glioma cell growth, and the survival of BALB/c-A nude mice was significantly prolonged. Immunohistochemistry showed that p-p65, Cyclin D1 and Ki67 expression was significantly reduced in the LV-miRNA-451 group. Taken together, these results suggest that miRNA-451 could regulate the NF-κB signaling pathway by targeting IKKß, which inhibits glioma cell growth in vitro and in vivo. Therefore, this study may provide novel insight into miRNA-451-targeted therapy for glioma.

LncRNA HAS2-AS1 Promotes Glioblastoma Proliferation by Sponging miR-137.

GBM (Glioblastoma multiform) is the most malignant tumor type of the central nervous system and has poor diagnostic and clinical outcomes. LncRNAs (Long non-coding RNAs) have been reported to participate in multiple biological and pathological processes, but their underlying mechanism remains poorly understood. Here, we aimed to explore the role of the lncRNA HAS2-AS1 (HAS2 antisense RNA 1) in GBM. GSE103227 was analyzed, and qRT-PCR was performed to measure the expression of HAS2-AS1 in GBM. FISH (Fluorescence in situ hybridization) was performed to verify the localization of HAS2-AS1. The interaction between HAS2-AS1 and miR-137 (microRNA-137) was predicted by LncBook and miRcode followed by dual-luciferase reporter assays, and the relationships among HAS2-AS1, miR-137 and LSD1 (lysine-specific demethylase 1) were assessed by WB (western blot) and qRT-PCR. Colony formation and CCK-8 (cell counting kit-8) assays were performed as functional tests. In vivo, nude mice were used to confirm the function of HAS2-AS1. HAS2-AS1 expression was upregulated in GBM cell lines, and HAS2-AS1 was localized mainly in the cytoplasm. In vitro, high HAS2-AS1 expression promoted proliferation, and knockdown of HAS2-AS1 significantly inhibited proliferation. Furthermore, HAS2-AS1 functioned as a ceRNA (competing endogenous RNA) of miR-137, leading to the disinhibition of its downstream target LSD1. The miR-137 level was downregulated by HAS2-AS1 overexpression and upregulated by HAS2-AS1 knockdown. In a subsequent study, LSD1 expression was negatively regulated by miR-137, while miR-137 reversed the LSD1 expression levels caused by HAS2-AS1. These results were further supported by the nude mouse tumorigenesis experiment; compared with xenografts with high HAS2-AS1 expression, the group with low levels of HAS2-AS1 exhibited suppressed proliferation and better survival. We conclude that lncRNA HAS2-AS1 promotes proliferation by functioning as a miR-137 decoy to increase LSD1 levels and thus might be a possible biomarker for GBM.

Research on track fastener positioning method based on local unidirectional template matching.

Commonly used fastener positioning methods include pixel statistics (PS) method and template matching (TM) method. For the PS method, it is difficult to judge the image segmentation threshold due to the complex background of the track. For the TM method, the search in both directions of the global is easily affected by complex background, as a result, the locating accuracy of fasteners is low. To solve the above problems, this paper combines the PS method with the TM method and proposes a new fastener positioning method called local unidirectional template matching (LUTM). First, the rail positioning is achieved by the PS method based on the gray-scale vertical projection. Then, based on the prior knowledge, the image of the rail and the surrounding area of the rail is obtained which is referred to as the 1-shaped rail image; then, the 1-shaped rail image and the produced offline symmetrical fastener template is pre-processed. Finally, the symmetrical fastener template image is searched from top to bottom along the rail and the correlation is calculated to realize the fastener positioning. Experiments have proved that the method in this paper can effectively realize the accurate locating of the fastener for ballastless track and ballasted track at the same time.

AMOTL2­knockdown promotes the proliferation, migration and invasion of glioma by regulating ß­catenin nuclear localization.

Glioblastoma multiforme (GBM) is the most prevalent type of malignant cancer in the adult central nervous system; however, its mechanism remains unclear. Angiomotin­like 2 (AMOTL2) is a member of the motin family of angiostatin­binding proteins. It has been reported as an oncogene in cervical and breast cancer, but its association with glioma remains unknown. The aim of the present study was to investigate AMOTL2­regulated processes in glioma cell lines using extensive in vitro assays and certain bioinformatics tools. These results revealed that AMOTL2 was downregulated in high­grade glioma cells and tissues, with patients with glioma exhibiting a high AMOTL2 expression having a higher survival rate. The results of the glioma cell phenotype experiment showed that AMOTL2 suppressed GBM proliferation, migration and invasion. In addition, immunoblotting, co­immunoprecipitation and immunofluorescence assays demonstrated that AMOTL2 could directly bind to ß­catenin protein, the key molecule of the Wnt signaling pathway, and regulate its downstream genes by regulating ß­catenin nuclear translocation. In conclusion, the present study demonstrated that AMOTL2 inhibited glioma proliferation, migration and invasion by regulating ß­catenin nuclear localization. Thus, AMOTL2 may serve as a therapeutic target to further improve the prognosis and prolong survival time of patients with glioma.

AFI-Net: Attention-Guided Feature Integration Network for RGBD Saliency Detection.

This article proposes an innovative RGBD saliency model, that is, attention-guided feature integration network, which can extract and fuse features and perform saliency inference. Specifically, the model first extracts multimodal and level deep features. Then, a series of attention modules are deployed to the multilevel RGB and depth features, yielding enhanced deep features. Next, the enhanced multimodal deep features are hierarchically fused. Lastly, the RGB and depth boundary features, that is, low-level spatial details, are added to the integrated feature to perform saliency inference. The key points of the AFI-Net are the attention-guided feature enhancement and the boundary-aware saliency inference, where the attention module indicates salient objects coarsely, and the boundary information is used to equip the deep feature with more spatial details. Therefore, salient objects are well characterized, that is, well highlighted. The comprehensive experiments on five challenging public RGBD datasets clearly exhibit the superiority and effectiveness of the proposed AFI-Net.

Mechanisms and functions of long non­coding RNAs in glioma (Review).

Glioma is one of the most common primary malignancies of the adult central nervous system with malignancy grades between I­IV. Among these four grades, glioblastoma is the most malignant and aggressive type of tumor and is characterized by a poor prognosis, high recurrence rate and short median survival time after initial diagnosis. Existing treatments, such as radiotherapy, chemotherapy and surgical resection, have poor therapeutic effects; therefore, it is necessary to discover novel targeted therapies to enhance the curative effect and improve prognosis. Recently, increasing evidence has shown that long non­coding RNAs (lncRNAs) participate in the vast majority of key physiological and pathological processes. Moreover, aberrant expression levels of lncRNAs are closely associated with the occurrence and development of glioma and other malignant phenotypes. The present review summarizes new insights into the functions and mechanisms of lncRNAs at the epigenetic, transcriptional and post­transcriptional levels, describes their ability to encode functional peptides in glioma and discusses their clinical potential as new biomarkers and prospective therapeutic targets.

Quercetin Antagonizes Glucose Fluctuation Induced Renal Injury by Inhibiting Aerobic Glycolysis via HIF-1α/miR-210/ISCU/FeS Pathway.

Background and Objective: Glucose fluctuation (GF) has been reported to induce renal injury and diabetic nephropathy (DN). However, the mechanism still remains ambiguous. Mitochondrial energy metabolism, especially aerobic glycolysis, has been a hotspot of DN research for decades. The activation of HIF-1α/miR210/ISCU/FeS axis has provided a new explanation for aerobic glycolysis. Our previous studies indicated quercetin as a potential therapeutic drug for DN. This study aims to evaluate levels of aerobic glycolysis and repressive effect of quercetin via HIF-1α/miR210/ISCU/FeS axis in a cell model of GF. Methods: The mouse glomerular mesangial cells (MCs) were exposed in high or oscillating glucose with or without quercetin treatment. Cell viability was measured by CCK8 assay. Aerobic glycolysis flux was evaluated by lactate acid, pH activity of PFK. Apoptosis level was confirmed by Annexin V-APC/7-AAD double staining and activity of caspase-3. TNF-α and IL-1ß were used to evaluate inflammation levels. Results: GF deteriorated inflammation damage and apoptosis injury in MCs, while quercetin could alleviate this GF-triggered cytotoxicity. GF intensified aerobic glycolysis in MCs and quercetin could inhibit this intensification in a dose-dependent manner. Quercetin prevented activities of two FeS-dependent metabolic enzymes, aconitase, and complex I, under GF injury in MCs. The mRNA expression and protein contents of HIF-1α were increased after GF exposure, and these could be alleviated by quercetin treatment. Knockdown of ISCU by siRNA and Up-regulating of miR-210 by mimic could weaken the effects of quercetin that maintained protein levels of ISCU1/2, improved cell viability, relieved inflammation injury, decreased apoptosis, and reduced aerobic glycolysis switch in MCs. Conclusion: Quercetin antagonizes GF-induced renal injury by suppressing aerobic glycolysis via HIF-1α/miR-210/ISCU/FeS pathway in MCs cell model. Our findings contribute to a new insight into understanding the mechanism of GF-induced renal injury and protective effects of quercetin.

Cultural modulation of early attentional responses to positive self-information: An ERP investigation of self-enhancement.

Westerners show a strong tendency to view themselves in a positive light (i.e., self-enhancement), but this tendency is substantially weaker among East Asians. At present, however, it remains inconclusive whether this cultural difference reflects genuine variation in spontaneous engagement in this motivational tendency or is driven by individuals' deliberate efforts to present oneself in culturally acceptable ways. In the present research, we sought to address this issue by examining whether culture modulates early attentional bias to self-name, presented in the context of positive (vs. negative) situations. Both European American and Asian American participants (N = 64) read a series of scenarios depicting either a positive or a negative life situation and were subsequently presented with their name or names of famous people or strangers. European Americans showed greater P2, an ERP component of early attentional arousal, when the self-name was primed with positive (vs. negative) situations. In contrast, Asian Americans' P2 in response to the self-name was not moderated by situation primes. Moreover, the degree to which P2 was enhanced in positive (vs. negative) situations was negatively correlated with Asian cultural values. These results demonstrate that cultural variation in self-enhancement may reflect genuine beliefs about the self, manifested automatically at an early stage of attentional processing.

Neurocognitive underpinnings of cross-cultural differences in risky decision making.

Culture permeates across human mind and behavior. Cultural influence is reported even in economic decision making, which involves basic cognitive process, once believed to be invariant across all humans. The current study investigated the neurocognitive processes underlying economic decision making in East Asians and European Americans, with an aim to understand the cross-cultural differences in the discrete mental processes of decision making. Participants performed a risky gambling task that captures the gain maximizing and loss minimizing strategies, while electroencephalography was simultaneously collected. Event-related potentials (ERPs) associated with spontaneous emotional arousal (P2) and effortful attentional allocation (P3) were examined to determine the cultural effects on mental processes during pre-decisional and post-decisional stages. Behaviorally, Americans showed greater loss minimization than Asians. ERPs demonstrated significant cultural differences during post-decisional evaluation of outcomes, but not during pre-decisional processes. In Asians', ERP associated with emotional arousal (P2) was strongly modulated by gains, while in Americans', ERP associated with attentional allocation (P3) was strongly modulated by losses. These results suggest that Americans make conscious efforts to be self-reliant when facing financial losses, whereas Asians are more emotionally aroused by financial gains, which invites a refinement to the current theoretical propositions about cultural influence on decision making.

Money for me and money for friend: An ERP study of social reward processing in adolescents and adults.

Peer relations during adolescence contribute significantly to the development of socio-cognitive skills and pro-sociality. The current study probed the characteristics of adolescent socio-cognitive processing through a card game where they earn money for self and friend. We investigated the choice preference and temporal dynamics of information processing by measuring ERP responses to wins or losses (valence) directed toward self and friend (recipient). Choice data showed that despite adults and adolescents earning equivalent amounts across recipients combined, adults won significantly more for self than a friend; no such difference was found in adolescents. The ERPs in response to choice outcomes showed that the valence information was processed earlier (at P2) in adults, while it was processed later (at P3) in adolescents. Furthermore, a strong effect of recipient was present in adults later in the time course (at P3), while such an effect was weak in adolescents; if any, adolescents showed sensitivity to recipient information earlier at P2. These ERP data suggest a relatively equal allocation of the P3-mediated attentional process to both self and friend's outcomes in adolescents, which parallels the choice behavior. Collectively our results characterize adolescent pro-sociality toward friends, reflecting the importance of peer relationship during this unique developmental period.

A SAFT Method for the Detection of Void Defect inside a Ballastless Track Structure Using Ultrasonic Array Sensors.

High-precision ultrasound imaging of void defects is critical for the performance and safety assessment of ballastless track structures. The sound propagation velocity of each layer in the ballastless track structure is quite different. However, the traditional concrete Synthetic Aperture Focusing Technique (SAFT) ultrasound imaging method is based on the assumption that the concrete has a single constant shear wave velocity. Thus, it is not a suitable method for the ultrasonic imaging of multilayer structures. In this paper, a Multilayer SAFT high-precision ultrasound imaging method is proposed. It is based on the ray-tracing technique and uses the Fermat principle to find the refraction point that minimizes the delay of the acoustic wave propagation path at the interface of the discrete layers. Then, the acoustic wave propagation path is segmented by the position of the refraction point, and the propagation delay of the ultrasonic wave is obtained segment by segment. Thus, the propagation delay of the ultrasonic wave is obtained one by one, so that the propagation delay of the ultrasonic wave in the multilayer structure can be accurately obtained. Finally, the focused image is obtained according to the SAFT imaging algorithm. The finite element simulation and experimental results show that the Multilayer SAFT imaging method can accurately track the propagation path of the ultrasonic wave in ballastless track structures, as well as accurately calculate the propagation delay of the ultrasonic wave and the lengths of void defects. The high accuracy of the Multilayer SAFT imaging represents a significant improvement compared to traditional SAFT imaging.