MXenes have emerged as promising materials for various mechanical applications due to their outstanding physicochemical merits, multilayered structures, excellent strength, flexibility, and electrical conductivity. Despite the substantial progress achieved in the rational design of MXenes nanostructures, the tutorial reviews on the mechanical properties of self-standing MXenes were not yet reported to our knowledge. Thus, it is essential to provide timely updates of the mechanical properties of MXenes, due to the explosion of publications in this filed. In pursuit of this aim, this review is dedicated to highlighting the recent advances in the rational design of self-standing MXene with unique mechanical properties for various applications. This includes elastic properties, ideal strengths, bending rigidity, adhesion, and sliding resistance theoretically as well as experimentally supported with various representative paradigms. Meanwhile, the mechanical properties of self-standing MXenes were compared with hybrid MXenes and various 2D materials. Then, the utilization of MXenes as supercapacitors for energy storage is also discussed. This review can provide a roadmap for the scientists to tailor the mechanical properties of MXene-based materials for the new generations of energy and sensor devices.

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Early detection of tooth cracks is crucial for effective condition-based monitoring and decision making. The scope of this work was to bring more insight into the vibration behavior of spur gears in the presence of single and multiple simultaneous tooth cracks. The investigation was conducted in both time and frequency domains. A finite element analysis was performed to determine the variation in stiffness with respect to the angular position for different combinations of crack lengths. A simplified nonlinear lumped parameter model of a one-stage gearbox with six degrees of freedom was then developed to simulate the vibration response of faulty external spur gears. Four different multiple-crack scenarios were proposed and studied. The performances of various statistical fault detection indicators were considered and investigated. The simulation results obtained via MATLAB indicated that, as the severity of a single crack increases, the values of the time domain statistical indicators increase also, but at different rates. Moreover, the number of cracks was found to have a negative effect on the values of all the performance indicators, except for the RMS. The number and amplitude of the sidebands in the frequency spectrum were also considered, while assessing the severity of the faults in each scenario. It was observed that, in the case of consecutive tooth cracks, the number of spectrum peaks and the number of cracks were consistent in the frequency range of 4-5 kHz. The main finding of this study was that the peak spectral amplitude was the most sensitive indicator of the number and severity of cracks.

Background Brachial plexus block has substituted general anesthesia in the majority of patients planned for upper limb surgeries as it avoids the undesired effects of the medications used in general anesthesia as well as the stress response associated with airway manipulation. Opioid agonist–antagonists such as nalbuphine are used as adjuvant to improve the anesthetic properties of bupivacaine. Verapamil has an additive effect in brachial plexus blockade in the form of decreasing the consumption of analgesics in the postoperative period with reducing onset time and extending the duration of motor and sensory blockade. The aim of this study is to investigate the adjuvant effect of verapamil versus nalbuphine to 0.5% bupivacaine in brachial plexus block as regards onset, duration of sensory and motor blockade and postoperative analgesic augmentation. The study is randomized, prospective, double-blinded, comparative study where 90 patients subjected to arm, forearm and hand surgeries were randomized into three groups, group A received 30 ml of plain bupivacaine 0.5% plus 2 ml of normal saline, group B received 30 ml of bupivacaine 0.5% plus 2 ml verapamil equivalent to 5 mg, group C received 30 ml of bupivacaine 0.5% plus 10 mg of nalbuphine diluted in 2 ml of normal saline. Results Results of this study showed that group C and group B sensory block time onset was 7.25 ± 1.5 vs. 10.92 ± 3.84 min, P < 0.001 and was shorter than that in group A (13.2 ± 2.66 min). In addition, the motor block onset was (11.10 ± 1.24 vs. 13.50 ± 3.77 min, P < 0.001) shorter than group A (17.16 ± 1.30 min). In group C and group B, sensory block duration was 396 ± 32.17 vs. 355.83 ± 18.48 min, P < 0.001, respectively and was longer than that in group A (321.13 ± 25.08 min). Also, there was prolonged motor block duration in group C and group B recording (338.92 ± 25.2 vs. 302.93 ± 15.24 min, P < 0.001) and was longer than that in group A (280.70 ± 32.35 min). Time of demand of rescue analgesia dose was significantly long in group C and group B (449.53 ± 52.45 vs. 418.13 ± 41.12 min, P < 0.001) and was longer than group A (361.31 ± 21.42 min). Both verapamil and nalbuphine have additive effect to bupivacaine improving the all anesthetic parameters of the block. Conclusion Both drugs produce favorable enhancement of time onset and effective prolongation of duration of sensory and motor blockade and extend the period of postoperative analgesia with superiority to nalbuphine over verapamil.

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