Variations in strain affect friction and microstructure evolution in copper under a reciprocating tribological load

The microstructure of the materials constituting a metallic frictional contact strongly influences tribological performance. Being able to tailor friction and wear is challenging due to the complex microstructure evolution associated with tribological loading. Here, we investigate the effect of the strain distribution on these processes. High-purity copper plates were morphologically surface textured with two parallel rectangles—referred to as membranes—over the entire sample length by micro-milling. By keeping the width of these membranes constant and only varying their height, reciprocating tribological loading against sapphire discs resulted in different elastic and plastic strains. Finite element simulations were carried out to evaluate the strain distribution in the membranes. It was found that the maximum elastic strain increases with decreasing membrane stiffness. The coefficient of friction decreases with increasing membrane aspect ratio. By analyzing the microstructure and local crystallographic orientation, we found that both show less change with decreasing membrane stiffness

International Multi-Institutional Experience with Presentation and Management of Aortic Arch Laterality in Aberrant Subclavian Artery and Kommerell's Diverticulum

BACKGROUND: Aberrant subclavian artery (ASA) with or without Kommerell's diverticulum (KD) is a rare anatomic aortic arch anomaly that can cause dysphagia and/or life-threatening rupture. The objective of this study is to compare outcomes of ASA/KD repair in patients with a left versus right aortic arch. METHODS: Using the Vascular Low Frequency Disease Consortium methodology, a retrospective review was performed of patients ≥18 years old with surgical treatment of ASA/KD from 2000 to 2020 at 20 institutions. RESULTS: 288 patients with ASA with or without KD were identified; 222 left-sided aortic arch (LAA), and 66 right-sided aortic arch (RAA). Mean age at repair was younger in LAA 54 vs. 58 years (P = 0.06). Patients in RAA were more likely to undergo repair due to symptoms (72.7% vs. 55.9%, P = 0.01), and more likely to present with dysphagia (57.6% vs. 39.1%, P < 0.01). The hybrid open/endovascular approach was the most common repair type in both groups. Rates of intraoperative complications, death within 30 days, return to the operating room, symptom relief and endoleaks were not significantly different. For patients with symptom status follow-up data, in LAA, 61.7% had complete relief, 34.0% had partial relief and 4.3% had no change. In RAA, 60.7% had complete relief, 34.4% had partial relief and 4.9% had no change. CONCLUSIONS: In patients with ASA/KD, RAA patients were less common than LAA, presented more frequently with dysphagia, had symptoms as an indication for intervention, and underwent treatment at a younger age. Open, endovascular and hybrid repair approaches appear equally effective, regardless of arch laterality

Contemporary Outcomes after Treatment of Aberrant Subclavian Artery and Kommerell\u27s Diverticulum

OBJECTIVE: Aberrant Subclavian Artery (ASA) and Kommerell\u27s Diverticulum (KD) are rare vascular anomalies that may be associated with lifestyle-limiting and life-threatening complications. The aim of this study is to report contemporary outcomes after invasive treatment of ASA/KD using a large international dataset. METHODS: Patients who underwent treatment for ASA/KD (2000-2020) were identified through the Vascular Low Frequency Disease Consortium (VLFDC), a multi-institutional collaboration to investigate uncommon vascular disorders. We report early and mid-term clinical outcomes including stroke and mortality, technical success, and other operative outcomes including reintervention rates, patency and endoleak. RESULTS: Overall, 285 patients were identified during the study period. The mean patient age was 57; 47% were female and 68% presented with symptoms. A right-sided arch was present in 23%. Mean KD diameter was 47.4 mm (range 13-108). The most common indication for treatment was symptoms (59%), followed by aneurysm size (38%). The most common symptom reported was dysphagia (44%). A ruptured KD was treated in 4.2% of cases, with a mean diameter of 43.9 mm (range 18-100). An open procedure (Open) was performed in 101 cases (36%); the most common approach was ASA ligation with subclavian transposition. An endovascular or hybrid approach (Endo/Hybrid) was performed in 184 (64%); the most common approach was thoracic endograft and carotid-subclavian bypass. A staged operative strategy was employed more often than single setting repair (55% vs. 45%). Compared to Endo/Hybrid, those in the Open group were more likely to be younger (49 vs. 61 years; p \u3c .0001), female (64% vs. 36%; p \u3c .0001) and symptomatic (85% vs. 59%; p \u3c .0001). Complete/partial symptomatic relief at 1 year after intervention was 82.6%. There was no association between modality of treatment and symptom relief (open 87.2% vs. endo/hybrid 78.9%; p=0.13). Post-intervention, 11 (4.5%) subclavian occlusions occurred; 3 were successfully thrombectomized resulting in a primary and secondary patency of 95% and 96% respectively, at a median follow-up of 39 months. Among the 33 (12%) reinterventions, the majority were performed for endoleak (36%), and more reinterventions occurred in the Endo/Hybrid than Open group (15% vs. 6%; p = .02). Overall survival was 87.3% at a median follow-up of 41 months. The 30-day stroke and death rates were 4.2% and 4.9%, respectively. Urgent/emergent presentation was independently associated with increased risk of 30-day mortality (OR 19.8, 95% CI 3.3-116.6), overall mortality (OR 3.6, 95% CI 1.2-11.2) and intraoperative complications (OR 8.3, 95% CI 2.8-25.1). Females had higher risk of reintervention (OR 2.6, 95% CI 1-6.5). At an aneurysm size of 44.4 mm, Receiver Operator Characteristic (ROC) curve analysis suggested that 60% of patients would have symptoms. CONCLUSIONS: Treatment of ASA/KD can be performed safely with low rates of mortality, stroke and reintervention, and high rates of symptomatic relief regardless of repair strategy. Symptomatic and urgent operations were associated with worse outcomes in general, and female gender was associated with a higher likelihood of reintervention. Given the worse overall outcomes when symptomatic and the inherent risk of rupture, consideration of repair at 40 mm is reasonable in most patients. ASA/KD can be repaired in asymptomatic patients with excellent outcomes and young healthy patients may be considered better candidates for open approaches versus endovascular/hybrid modalities, given the lower likelihood of reintervention and lower early mortality rate