Applying model-based systems engineering to architecture optimization and selection during system acquisition

2018 Fall.Includes bibliographical references.The architecture selection process early in a major system acquisition is a critical step in determining the overall affordability and technical performance success of a program. There are recognized deficiencies that frequently occur in this step such as poor transparency into the final selection decision and excessive focus on lowest cost, which is not necessarily the best value for all of the stakeholders. This research investigates improvements to the architecture selection process by integrating Model-Based Systems Engineering (MBSE) techniques, enforcing rigorous, quantitative evaluation metrics with a corresponding understanding of uncertainties, and stakeholder feedback in order to generate an architecture that is more optimized and trusted to provide better value for the stakeholders. Three case studies were analyzed to demonstrate this proposed process. The first focused on a satellite communications System of Systems (SoS) acquisition to demonstrate the overall feasibility and applicability of the process. The second investigated an electro-optical remote sensing satellite system to compare this proposed process to a current architecture selection process typified by the United States Department of Defense (U.S. DoD) Analysis of Alternatives (AoA). The third case study analyzed the evaluation of a service-oriented architecture (SOA) providing satellite command and control with cyber security protections in order to demonstrate rigorous accounting of uncertainty through the architecture evaluation and selection. These case studies serve to define and demonstrate a new, more transparent and trusted architecture selection process that consistently provides better value for the stakeholders of a major system acquisition. While the examples in this research focused on U.S. DoD and other major acquisitions, the methodology developed is broadly applicable to other domains where this is a need for optimization of enterprise architectures as the basis for effective system acquisition. The results from the three case studies showed the new process outperformed the current methodology for conducting architecture evaluations in nearly all criteria considered and in particular selects architectures of better value, provides greater visibility into the actual decision making, and improves trust in the decision through a robust understanding of uncertainty. The primary contribution of this research then is improved information support to an architecture selection in the early phases of a system acquisition program. The proposed methodology presents a decision authority with an integrated assessment of each alternative, traceable to the concerns of the system's stakeholders, and thus enables a more informed and objective selection of the preferred alternative. It is recommended that the methodology proposed in this work is considered for future architecture evaluations

Heritability and risk factors for perceived physical fatigability in the long life family study

The new construct of fatigability—fatigue in relation to a defined activity of a specific intensity and duration—constitutes an objective metric by which to assess the degree to which someone is physically limited due to fatigue. Measuring fatigability accounts for self-pacing bias and thus provides greater capacity to assess fatigue’s role in the disablement pathway. Fatigability may also be more sensitive to interventions, particularly those targeting increased physical activity. Fatigability is an important early predictor in the disablement pathway, having been associated with poorer physical function, yet little is known about its genetic basis or association with age and sex. We examined heritability and risk factors of perceived physical fatigability using the Pittsburgh Fatigability Scale (PFS, 0-50, higher score=higher fatigability) in the Long Life Family Study, a cohort of two generations of older adults enriched for familial exceptional survival. PFS scores (mean±SD) and proportion with higher fatigability (% PFS ≥15) increased across age strata: 60-69 (N=1009, 11.0+-7.6, 28%), 70-79 (N=847, 12.5+-8.1, 37%), 80-89 (N=253, 19.3+-9.9, 65.2%), and ≥90 (N=266, 28.6+-9.8, 89.5%), p<0.0001, adjusted for sex, field center, and family structure. Females reported higher perceived physical fatigability than males, with the largest difference in the 80-89 age strata, 74.8% vs. 53.5%, respectively, p<0.0001. Fatigue was significantly associated with several markers of physical function, with physical activity, and with depression. After adjustment for age, sex, and field center, the residual heritability of fatigability was 0.263 (p=6.6*10^-9). These findings are significant for public health because they identify individuals most at risk of fatigability, who should be targeted in the development of interventions

Exclusion of Giant Coronary Artery Aneurysm with Covered Stent Combined with Coil Embolization of Vessel Outflow

Background: Coronary artery aneurysms (CAA) are rare abnormal dilatation of the coronary arteries. They are termed giant if their diameter exceeds the reference vessel diameter by more than 4 times or if they are more than 8 mm in diameter. If not treated, they have a tendency to rupture, thrombose or embolize. There is however no definite therapy for CAA. Various therapies suggested in the management of aneurysms include surgical resection, covered stent implantation or coil embolization. Methods: We describe a case of coiling of a potential collateral vessel feeding the giant coronary aneurysm retrogradely and covered stenting of main branch to exclude the aneurysm. Results: Transcatheter embolization was successfully done. No late complications were seen during 1 year CT angiography. Conclusion: Dual stent and coil embolization is safe and effective for vessel outflow during the treatment of giant coronary artery aneurysm. Further long term outcomes will have to be determined through serial CT angiographies

Transient Mid-Ventricular Ballooning Due to Bad Dream in a Postmenopausal Woman

Mid ventricular ballooning syndrome (MBS) was diagnosed in a 55-year-old woman who was admitted to emergency room due to acute chest pain. The trigger for the chest pain was reported as “bad dream” about her husband. MBS, a variant of Tako-tsubo Cardiomyopathy is more common in postmenopausal women and the triggers have been linked to stress involving the husband. Sudden catecholamine surge during nightmare augmented by estrogen deficiency in postmenopausal women may be the underlying mechanism. There are many unanswered questions related to the etiology of MBS. With supportive treatment, prognosis is excellent

Acute Stent Thrombosis Following Concomitant Balloon Aortic Valvuloplasty and Percutaneous Coronary Intervention

Balloon aortic valvuloplasty is often used as a palliative measure or as a bridge to transcatheter aortic valve replacement in the management of aortic stenosis in high risk or inoperable patients. Severe aortic stenosis coexisting with coronary artery disease is not uncommon. In these circumstances, adjuvant percutaneous coronary intervention may be warranted. The safety and efficacy of combined valve and coronary intervention strategies has been recently studied. An increased incidence of complications when both procedures are performed in the same setting may throw new challenges. We report a case of fatal acute stent thrombosis following balloon aortic valvuloplasty and percutaneous coronary intervention

Mechanical Thrombectomy in Post-Transplant Heart

Coronary allograft vasculopathy (CAV) is an accelerated form of coronary artery disease that is responsible for significant mortality after cardiac transplantation. We report a case of CAV with significant thrombus burden which was managed with mechanical thrombectomy. Both aspiration and mechanical thrombectomy can be safely done in cardiac transplant recipients and may be considered in order to minimize exposure to coronary artery bypass procedure. This is especially valuable in emergency circumstances

Better Virological Outcomes Among People Living With Human Immunodeficiency Virus (HIV) Initiating Early Antiretroviral Treatment (CD4 Counts ≥500 Cells/µL) in the HIV Prevention Trials Network 071 (PopART) Trial in South Africa.

BACKGROUND: There have been concerns about reduced adherence and human immunodeficiency virus (HIV) virological suppression (VS) among clinically well people initiating antiretroviral therapy (ART) with high pre-ART CD4 cell counts. We compared virological outcomes by pre-ART CD4 count, where universal ART initiation was provided in the HIV Prevention Trials Network 071 (PopART) trial in South Africa prior to routine national and international implementation. METHODS: This prospective cohort study included adults initiating ART at facilities providing universal ART since January 2014. VS (1000 copies/mL), and viral rebound were compared between participants in strata of baseline CD4 cell count. RESULTS: The sample included 1901 participants. VS was ≥94% among participants with baseline CD4 count ≥500 cells/µL at all 6-month intervals to 30 months. The risk of an elevated viral load (≥400 copies/mL) was independently lower among participants with baseline CD4 count ≥500 cells/µL (3.3%) compared to those with CD4 count 200-499 cells/µL (9.2%) between months 18 and 30 (adjusted relative risk, 0.30 [95% confidence interval, .12-.74]; P = .010). The incidence rate of VF was 7.0, 2.0, and 0.5 per 100 person-years among participants with baseline CD4 count <200, 200-499, and ≥500 cells/µL, respectively (P < .0001). VF was independently lower among participants with baseline CD4 count ≥500 cells/µL (adjusted hazard ratio [aHR], 0.23; P = .045) and 3-fold higher among those with baseline CD4 count <200 cells/µL (aHR, 3.49; P < .0001). CONCLUSIONS: Despite previous concerns, participants initiating ART with CD4 counts ≥500 cells/µL had very good virological outcomes, being better than those with CD4 counts 200-499 cells/µL. CLINICAL TRIALS REGISTRATION: NCT01900977