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The ability to additively manufacture structures on-orbit has the potential to fundamentally alter the traditional paradigm for how large spacecraft are constructed and launched into space. The space environment presents several unique challenges for additive manufacturing, including the need to operate in a vacuum. This paper presents the design, analysis, and test results for a passively cooled fused filament fabrication (FFF) 3D printer capable of manufacturing parts out of engineering-grade thermoplastics in the vacuum of space. Four high-temperature materials were successfully printed in high vacuum, including polyetherketoneketone, carbon-nanotube-polyetherketoneketone, polyetherimide, and carbon-nanotube-polyetherimide. Over 100 test coupons were printed in a vacuum and tested to confirm the feasibility of applying the FFF process in this environment. Lessons learned were documented throughout the vacuum printing test campaigns and are discussed here. This paper is part of a two-part series. Part I presented results for using a low-temperature hotend capable of printing hobby-grade materials in high vacuum and documented initial findings and lessons learned. Part II presents the results for a high-temperature hotend capable of printing engineering-grade plastics that are suitable for on-orbit manufacturing. The combined results of the two papers in this series can be used to inform future on-orbit additive manufacturing. [ABSTRACT FROM AUTHOR]

On-orbit manufacturing and assembly have become major research and development topics for government and commercial entities seeking the capability to build very large structures in space. Additive manufacturing is well suited to this paradigm since the process is highly automated, produces little material waste, and allows for a large degree of geometric freedom. This paper presents a design for a 3D printer that operates in high vacuum. The vacuum 3D printer has completed multiple thermal vacuum test campaigns, with dozens of parts printed to date using low-temperature thermoplastics. Testing of material coupons shows that samples printed in vacuum have strength properties generally within a standard deviation of samples printed at ambient pressure. The overall results from multiple successful tests of the vacuum 3D printer promote the feasibility of on-orbit additive manufacturing while exposed to the space environment. This paper is part one of a two-part series. Part I presents the results using a low-temperature hotend capable of printing hobby-grade materials and documents some initial findings and lessons learned for applying FFF in vacuum. Part II presents the results for a high-temperature hotend capable of printing engineering grade plastics that are suitable for on-orbit manufacturing. The combined results of the two papers in this series can be used to inform future on-orbit additive manufacturing applications as well as potential uses on future moon missions. [ABSTRACT FROM AUTHOR]

Background: Exercise-based cardiac rehabilitation (EBCR) plays a pivotal role in the management of acute myocardial infarction (AMI). Studies have shown that older individuals have a worse prognosis after an AMI, attesting to the importance of risk reduction strategies. We aimed at assessing the impact of age (patients dichotomized as ≥65 years old or <65 years old) on the functional benefits of an EBCR program among AMI survivors. Design: Observational, retrospective cohort study. Participants: All patients admitted due to an AMI who completed a phase II EBCR program after discharge, between November 2012 and April 2017. Intervention: EBCR program. Measurements: Functional parameters were assessed by a symptom-limited cardiopulmonary exercise test. Results: A total of 379 patients were included (30% aged ≥65 years). After the EBCR program, peak oxygen uptake (pVO2) and exercise duration increased significantly. Patients aged ≥65 years presented with more comorbidities and a lower functional capacity. Those aged ≥65 years presented significantly smaller improvements in pVO2 (0.79 ± 2.61 vs. 1.60 ± 3.11 mL/kg/min, p = 0.016) and exercise duration [75 (59–120) vs. 120 s (60–180), p = 0.002]. This was maintained after adjusting for several potential confounders. Conclusion: Older patients have a worse functional capacity than their younger counterparts. Still, a contemporary EBCR program was associated with significant functional improvements among those aged ≥65 years. The smaller improvements even after adjustments for potential confounders suggest that physiological differences may contribute to this finding. These results highlight the relevance of EBCR among this higher-risk subgroup. [ABSTRACT FROM AUTHOR]

Introduction: Exercise-based cardiac rehabilitation (EBCR) programs are of paramount importance in the management of acute myocardial infarction (AMI) survivors. Albeit this, female patients tend to be less referred for these programs, while also having a poorer prognosis. We aimed at assessing the impact of a contemporary EBCR program on functional parameters after an AMI, and specifically the impact of gender on its potential benefits., Methods: Observational, retrospective cohort study including all patients admitted to a tertiary center due to an AMI who completed a phase II EBCR program after discharge, between November 2012 and April 2017. Functional parameters were assessed by a symptom-limited cardiopulmonary exercise test (CPET). Patients were dichotomized according to gender., Results: A total of 379 patients were included, 19% of whom were women. After the program, peak oxygen uptake (pVO2) and exercise duration increased significantly (P<0.001). Though female patients presented a lower pVO2 and completed a shorter CPET at both the beginning and end of the study, there were no differences in the magnitude of improvement in these parameters between both groups [pVO2 delta 1.37 ± 3.08 vs 1.31 ± 2.62 mL/kg/min, P=0.876; CPET duratio n delta 120 (60-167) vs 85 (60-146), P=0.176]., Conclusions: A contemporary EBCR program was associated with significant improvements in functional parameters, as assessed by CPET. Though female patients had lower levels of pVO2, the benefits of this program were similar among groups. These results highlight the importance of EBCR among this higher risk subset of patients., Competing Interests: None., (AJCD Copyright © 2020.)