Thermodynamically Guided Improvement of Fe-Mn-Al-Ni Shape-Memory Alloys.

A microstructural informed thermodynamic model is utilized to tailor the pseudoelastic performance of a series of Fe-Mn-Al-Ni shape-memory alloys. Following this approach, the influence of the stability and the amount of the B2-ordered precipitates on the stability of the austenitic state and the pseudoelastic response is revealed. This is assessed by a combination of complementary nanoindentation measurements and incremental-strain tests under compressive loading. Based on these investigations, the applicability of the proposed models for the prediction of shape-memory capabilities of Fe-Mn-Al-Ni alloys is confirmed. Eventually, these thermodynamic considerations enable the guided enhancement of functional properties in this alloy system through the direct design of alloy compositions. The procedure proposed renders a significant advancement in the field of shape-memory alloys.

Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete.

Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are unfavourable in terms of sustainability. In this work, a prestressing method using novel Fe-Mn-Al-Ni shape memory alloy rebars as a tensioning system in UHPC is investigated. A generated stress of about 130 MPa was measured for the shape memory alloy rebars. For the application in UHPC, the rebars are prestrained prior to the manufacturing process of the concrete samples. After sufficient hardening of the concrete, the specimens are heated inside an oven to activate the shape memory effect and, thus, to introduce the prestress into the surrounding UHPC. It is clearly shown that an improvement in maximum flexural strength and rigidity is achieved due to the thermal activation of the shape memory alloy rebars compared to non-activated rebars. Future research will have to focus on the design of the shape memory alloy rebars in relation to construction applications and the investigation of the long-term performance of the prestressing system.

Impact of prophylactic intra-aortic balloon pump on early outcomes in patients with severe left ventricular dysfunction undergoing elective coronary artery bypass grafting with cardiopulmonary bypass.

OBJECTIVE: Our aim was to analyse whether prophylactic preoperative intraaortic balloon pump (IABP) improves outcomes in hemodynamically stable patients with low left ventricular ejection fraction (LVEF ≤30%) undergoing elective myocardial revascularization (CABG) using cardiopulmonary bypass (CPB). Secondary aim was to identify the predictors for low cardiac output syndrome (LCOS). METHODS: Prospectively collected data of 207 consecutive patients with LVEF ≤30% undergoing elective isolated CABG with CPB from 01/2009 to 12/2019, 136 with and 71 patients without IABP, were retrieved retrospectively. Patients with prophylactic IABP were matched 1:1 with patients without IABP by a propensity score matching. Stepwise logistic regression was conducted to identify predictors of postoperative LCOS in the propensity-matched cohort. P value ≤0.05 was considered significant. RESULTS: Reduced postoperative LCOS (9.9% vs. 26.8%, P = 0.017) was observed in patients receiving prophylactic IABP. Stepwise logistic regression identified preoperative IABP as preventive factor for postoperative LCOS [Odds Ratio (OR) 0.19,95% Confidence Interval (CI), 0.06-0.55, P = 0.004]. The need of vasoactive and inotropic support was lower in patients with prophylactic IABP at 24, 48 and 72 h after surgery (12.3 [8.2-18.6] vs. 22.2 [14.4-28.8], P < 0.001, 7.7 [3.3-12.3] vs.16.3 [8.9-27.8], P < 0.001 and 2.4 [0-7] vs. 11.5 [3.1-26], P < 0.001, respectively). The patients in both groups did not differ in terms of in-hospital mortality (7.0% vs. 9.9%, P = 0.763). There were no major IABP-related complications. CONCLUSIONS: Elective patients with left ventricular ejection fraction ≤30% undergoing CABG with CPB and prophylactic IABP insertion had less low cardiac output syndrome and similar in-hospital mortality.

Artificial intelligence-based early detection of acute kidney injury after cardiac surgery.

OBJECTIVES: This study aims to improve the early detection of cardiac surgery-associated acute kidney injury using artificial intelligence-based algorithms. METHODS: Data from consecutive patients undergoing cardiac surgery between 2008 and 2018 in our institution served as the source for artificial intelligence-based modelling. Cardiac surgery-associated acute kidney injury was defined according to the Kidney Disease Improving Global Outcomes criteria. Different machine learning algorithms were trained and validated to detect cardiac surgery-associated acute kidney injury within 12 h after surgery. Demographic characteristics, comorbidities, preoperative cardiac status and intra- and postoperative variables including creatinine and haemoglobin values were retrieved for analysis. RESULTS: From 7507 patients analysed, 1699 patients (22.6%) developed cardiac surgery-associated acute kidney injury. The ultimate detection model, 'Detect-A(K)I', recognizes cardiac surgery-associated acute kidney injury within 12 h with an area under the curve of 88.0%, sensitivity of 78.0%, specificity of 78.9% and accuracy of 82.1%. The optimal parameter set includes serial changes of creatinine and haemoglobin, operative emergency, bleeding-associated variables, cardiac ischaemic time and cardiac function-associated variables, age, diuretics and active infection, chronic obstructive lung and peripheral vascular disease. CONCLUSIONS: The 'Detect-A(K)I' model successfully detects cardiac surgery-associated acute kidney injury within 12 h after surgery with the best discriminatory characteristics reported so far.

Abnormal body perception and neural activity in the insula in depression: an fMRI study of the depressed "material me".

OBJECTIVES: In addition to affective-cognitive symptoms, patients with major depressive disorder (MDD) suffer from somato-vegetative symptoms, suggesting abnormal interoceptive awareness of their "material me". While recent imaging studies have extensively investigated affective-cognitive symptoms in MDD, the neural correlates of somato-vegetative symptoms and abnormal interoception remain unclear. Since the "material me" has been especially associated with the anterior insula in healthy subjects, we hypothesized abnormalities in this region during interoceptive awareness in MDD. METHODS: We therefore investigated behavioural and neural correlates of interoception in healthy and depressed subjects using the Body Perception Questionnaire (BPQ) and a well established heartbeat perception task in fMRI. RESULTS: MDD patients showed significantly higher scores in the BPQ and reduced neural activity during rest periods, particularly in the bilateral anterior insula. In contrast to healthy subjects, BPQ scores no longer correlated with activity during rest periods in the anterior insula. Both BPQ scores and left anterior insula signal changes correlated with depression severity. CONCLUSIONS: We demonstrate for the first time abnormal body perception and altered activity in the insula during rest in MDD. Our results suggest that these behavioural and neural abnormalities are closely related to these patients' somato-vegetative abnormalities and their abnormal "material me".