دکتر احمد گلی

Despite the significant economic and environmental advantages of friction stir spot welding (FSSW) and its amazing results in welding similar and dissimilar metals and alloys, some of which were known as unweldable, it has some structural and characteristic defects such as keyhole formation, hook defects, and bond line oxidation. This has prompted researchers to focus on these defects and propose and investigate techniques to treat or compensate for their deteriorating effects on microstructural and mechanical properties under different loading conditions. In this experimental study, sheets of AA6061-T6 aluminum alloy with a thickness of 1.8 mm were employed to investigate the influence of reinforcement by graphene nanoplatelets (GNPs) with lateral sizes of 1–10 µm and thicknesses of 3–9 nm on the static and fatigue behavior of FSSW lap joints. The welding process was carried out with constant, predetermined welding parameters and a constant amount of nanofiller throughout the experiment. Cross-sections of as-welded specimens were tested by optical microscope (OM) and energy-dispersive spectroscopy (EDS) to ensure the incorporation of the nanographene into the matrix of the base alloy by measuring the weight percentage (wt.%) of carbon. Microhardness and tensile tests revealed a significant improvement in both tensile shear strength and micro-Vickers hardness due to the reinforcement process. The fatigue behavior of the GNP-reinforced FSSW specimens was evaluated under low and high cycle fatigue conditions. The reinforcement process had a detrimental effect on the fatigue life of the joints under cyclic loading conditions. The microstructural analysis and examinations conducted during this study revealed that this reduction in fatigue strength is attributed to the agglomeration of GNPs at the grain boundaries of the aluminum matrix, leading to porosity in the stir zone (SZ), the formation of continuous brittle phases, and a transition in the fracture mechanism from ductile to brittle. The experimental results, including fracture modes, are presented and thoroughly discussed. © 2025 by the authors.

The Combined Effect of High-Intensity Interval Training and Time-Restricted Feeding on the AKT-IGF-1-mTOR Signaling Pathway in the Muscle Tissue of Type 2 Diabetic Rats

( Article . )

Mohebinejad M., Kazeminasab F., Ghanbari rad M., Bagheri, R., Razi M., Willoughby, D.S., Dutheil, F., Sepanta, M., Sadeghi, P., Goli, A., Fini, E.

Nutrients (20726643)(9)pp. 6475-6489

Background/Objectives: High-intensity interval training (HIIT) and time-restricted feeding (TRF) have shown potential in enhancing glucose metabolism, increasing insulin sensitivity, and promoting muscle health. This study investigates the combined effects of HIIT and TRF on the AKT-IGF-1-mTOR signaling pathway in the muscle tissue of type 2 diabetic (T2D) rats. Methods: 42 male Wistar rats (4–5 weeks of age) were included in the study. The animals were randomly divided into two groups: 1. Standard diet (SD) non-diabetic (n = 7) and 2. High-fat diet (HFD n = 35) for 4 weeks. T2D was induced by intraperitoneal injection (IP) of streptozotocin (STZ) at 35 mg/kg. Animals with blood glucose levels ≥ 250 mg/dL were considered diabetic. Diabetic rats were randomly divided into five groups (n = 7): 1. Diabetes-HIIT (D-HIIT), 2. Diabetes-TRF (D-T), 3. Diabetes-combined TRF and HIIT (D-T+HIIT), 4. Diabetes-Untreated Control (D), and 5. Diabetes with metformin (D-MET). The HIIT protocol and TRF regimen were followed for 10 weeks. Muscle tissue was collected for histological analysis, and the expression of proteins related to the AKT-IGF-1-mTOR pathway was measured. Results: Blood glucose levels, insulin resistance (IR), and markers of muscle degradation were significantly improved in the D-T+HIIT and D-MET groups compared to the non-diabetes group. Furthermore, the activation of the AKT and mTOR signaling proteins, as well as increased IGF-1 expression, was significantly elevated in the D-T+HIIT group compared to the diabetic control group and other treatment groups, and approached levels observed in the non-diabetes group. Additionally, muscle fiber size and overall tissue structure were improved in the treatment groups, particularly in the D-T+HIIT group. Conclusions: The combination of HIIT and TRF appears to offer superior benefits in improving muscle protein synthesis, and glucose regulation in T2D rats, as compared to either HIIT or TRF alone. These findings highlight the potential of this combined approach for addressing muscle-related complications in T2D. © 2025 by the authors.