ABSTRACT
Grain boundary (GB) precipitation-induced cracking is a significant issue for S31254 super austenitic stainless steel during hot working. Investigating the deformation behavior based on precipitate morphology and distribution is essential. In this study, continuous smaller and intermittent larger precipitates were obtained through heat treatments at 950 °C and 1050 °C. The microstructure evolution and mechanical properties influenced by precipitates were experimentally investigated using an in situ tensile stage inside a scanning electron microscope (SEM) combined with electron backscatter diffraction (EBSD). The results showed that continuous precipitates at 950 °C had a stronger pinning effect on the GB, making grain rotation difficult and promoting slip deformation in the plastic interval. Continuous precipitates caused severe stress concentration near GB and reduced coordinated deformation ability. Additionally, the crack propagation path changed from transcrystalline to intercrystalline. Furthermore, internal precipitates were a crucial factor affecting the initial crack nucleation position. Interconnected precipitates led to an intergranular fracture tendency and severe deterioration of the material's plasticity, as observed in fracture morphology.
ABSTRACT
Obstructive Sleep Apnea (OSA) is related to repeated upper airway collapse, intermittent hypoxia, and intestinal barrier dysfunction. The resulting damage to the intestinal barrier may affect or be affected by the intestinal microbiota. A prospective case-control was used, including 48 subjects from Sleep Medicine Center of Nanfang Hospital. Sleep apnea was diagnosed by overnight polysomnography. Fecal samples and blood samples were collected from subjects to detect fecal microbiome composition (by 16S rDNA gene amplification and sequencing) and intestinal barrier biomarkers-intestinal fatty acid-binding protein (I-FABP) and D-lactic acid (D-LA) (by ELISA and colorimetry, respectively). Plasma D-LA and I-FABP were significantly elevated in patients with OSA. The severity of OSA was related to differences in the structure and composition of the fecal microbiome. Enriched Fusobacterium, Megamonas, Lachnospiraceae_UCG_006, and reduced Anaerostipes was found in patients with severe OSA. Enriched Ruminococcus_2, Lachnoclostridium, Lachnospiraceae_UCG_006, and Alloprevotella was found in patients with high intestinal barrier biomarkers. Lachnoclostridium and Lachnospiraceae_UCG_006 were the common dominant bacteria of OSA and intestinal barrier damage. Fusobacterium and Peptoclostridium was independently associated with apnea-hypopnea index (AHI). The dominant genera of severe OSA were also related to glucose, lipid, neutrophils, monocytes and BMI. Network analysis identified links between the fecal microbiome, intestinal barrier biomarkers, and AHI. The study confirms that changes in the intestinal microbiota are associated with intestinal barrier biomarkers among patients in OSA. These changes may play a pathophysiological role in the systemic inflammation and metabolic comorbidities associated with OSA, leading to multi-organ morbidity of OSA.
Subject(s)
Microbiota , Sleep Apnea Syndromes , Sleep Apnea, Obstructive , Humans , Sleep Apnea, Obstructive/diagnosis , Polysomnography/methods , BiomarkersABSTRACT
PURPOSE: The aims were to use magnetic resonance imaging (MRI) to compare the efficacy of fat-suppressed proton-density turbo-spin-echo (FS-PD-TSE) images and T1-weighted (T1WIs) and T2-weighted images (T2WIs) in identifying cartilaginous endplate failure (CEF), and to propose a modified Rajasekaran classification based on the FS-PD-TSE sequence. METHODS: Thirty-one lumbar disc herniation (LDH) cases were enrolled. Totally, 155 discs and 310 endplates were evaluated by MRI with T1W, T2W, and FS-PD-TSE sequences. Disc degeneration (DD), LDH grades, and the total endplate score (TEPS) of CEF were evaluated. Chi-square, Spearman rank correlation analysis, and multiclass logistic regression were used to compared the sensitivity in diagnosing CEF. A modified Rajasekaran classification based on FS-PD-TSE sequence was established to diagnose CEF. The multiclass logistic regression model was used to analyse the relationship between modified Rajasekaran classification and DD and LDH. RESULTS: There were 117 (75.5%) segments with CEF in T1WIs, 115 (74.2%) in T2WIs, and 127 (81.9%) in FS-PD-TSE, respectively. Chi-square test showed FS-PD-TSE images were more sensitive than T1WIs and T2WIs (P < 0.05). Spearman rank correlation analysis revealed a significant correlation between TEPS and LDH and DD in T1WIs, T2WIs, and FS-PD-TSE images (P < 0.05). A multiclass logistic regression model showed that the incidence of DD and LDH significantly increased accordingly with increases in modified Rajasekaran classification (P < 0.05). CONCLUSION: The FS-PD-TSE sequence has high diagnostic value for lumbar CEF. CEF is a risk factor for LDH. The new classification for lumbar CEF based on the FS-PD-TSE sequence has good predictive ability for LDH and DD. These slides can be retrieved under Electronic Supplementary Material.
