Architecting complex systems for robustness

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2007.Vita.Includes bibliographical references (p. 121-128).Robust design methodologies are frequently utilized by organizations to develop robust and reliable complex systems. The intent of robust design is to create systems that are insensitive to variations from production, the environment, and time and use. While this process is effective, it can also be very time consuming and resource intensive for an engineering team. In addition, most robust design activity takes place at the detailed design phase, when the majority of the product life cycle cost has already been committed. Addressing robustness and the "ilities" at the architecture level may be more effective because it is the earliest and highest leverage point in the product development process. Furthermore, some system architectures are inherently more robust than others. In this thesis, a framework based on principles is proposed to architect complex systems for type I and II robustness. The principles are obtained by tracing the architectural evolution of the jet engine, which is an extremely complex system that has evolved to high reliability. This framework complements existing robust design methods, while simultaneously incorporating the robustness focus earlier in the product development process.by Jason C. Slagle.S.M

Use of a Portable Functional Near-Infrared Spectroscopy (fNIRS) System to Examine Team Experience During Crisis Event Management in Clinical Simulations

Objective: The aim of this study was to investigate the utilization of a portable functional near-infrared spectroscopy (fNIRS) system, the fNIRS PioneerTM, to examine team experience in high-fidelity simulation-based crisis event management (CEM) training for anesthesiologists in operating rooms.Background: Effective evaluation of team performance and experience in CEM simulations is essential for healthcare training and research. Neurophysiological measures with wearable devices can provide useful indicators of team experience to compliment traditional self-report, observer ratings, and behavioral performance measures. fNIRS measured brain blood oxygenation levels and neural synchrony can be used as indicators of workload and team engagement, which is vital for optimal team performance.Methods: Thirty-three anesthesiologists, who were attending CEM training in two-person teams, participated in this study. The participants varied in their expertise level and the simulation scenarios varied in difficulty level. The oxygenated and de-oxygenated hemoglobin (HbO and HbR) levels in the participants’ prefrontal cortex were derived from data recorded by a portable one-channel fNIRS system worn by all participants throughout CEM training. Team neural synchrony was measured by HbO/HbR wavelet transformation coherence (WTC). Observer-rated workload and self-reported workload and mood were also collected.Results: At the individual level, the pattern of HbR level corresponded to changes of workload for the individuals in different roles during different phases of a scenario; but this was not the case for HbO level. Thus, HbR level may be a better indicator for individual workload in the studied setting. However, HbR level was insensitive to differences in scenario difficulty and did not correlate with observer-rated or self-reported workload. At the team level, high levels of HbO and HbR WTC were observed during active teamwork. Furthermore, HbO WTC was sensitive to levels of scenario difficulty.Conclusion: This study showed that it was feasible to use a portable fNIRS system to study workload and team engagement in high-fidelity clinical simulations. However, more work is needed to establish the sensitivity, reliability, and validity of fNIRS measures as indicators of team experience

Learning Puppet security

If you are a security professional whose workload is increasing, or a Puppet professional looking to increase your knowledge of security, or even an experienced systems administrator, then this book is for you. This book will take you to the next level of security automation using Puppet. The book requires no prior knowledge of Puppet to get started

Human Factors Research in Anesthesia Patient Safety: Techniques to Elucidate Factors Affecting Clinical Task Performance and Decision Making

Patient safety has become a major public concern. Human factors research in other high-risk fields has demonstrated how rigorous study of factors that affect job performance can lead to improved outcome and reduced errors after evidence-based redesign of tasks or systems. These techniques have increasingly been applied to the anesthesia work environment. This paper describes data obtained recently using task analysis and workload assessment during actual patient care and the use of cognitive task analysis to study clinical decision making. A novel concept of “non-routine events” is introduced and pilot data are presented. The results support the assertion that human factors research can make important contributions to patient safety. Information technologies play a key role in these efforts

Effects of Intraoperative Reading on Vigilance and Workload during Anesthesia Care in an Academic Medical Center

Background: During routine cases, anesthesia providers may divert their attention away from direct patient care to read clinical (e.g., medical records) and/or nonclinical materials. The authors sought to ascertain the incidence of intraoperative reading and measure its effects on clinicians' workload and vigilance. Methods: In 172 selected general anesthetic cases in an academic medical center, a trained observer categorized the anesthesia provider's activities into 37 possible tasks. Vigilance was assessed by the response time to a randomly illuminated alarm light. Observer-and subject-reported workload were scored at random intervals. Data from Reading and Non-Reading Periods of the same cases were compared to each other and to matched cases that contained no observed reading. The cases were matched before data analysis on the basis of case complexity and anesthesia type. Results: Reading was observed in 35% of cases. In these 60 cases, providers read during 25 ؎ 3% of maintenance but not during induction or emergence. While Non-Reading Cases (n ‫؍‬ 112) and Non-Reading Periods of Reading Cases did not differ in workload, vigilance, or task distribution, they both had significantly higher workload than Reading Periods. Vigilance was not different among the three groups. When reading, clinicians spent less time performing manual tasks, conversing with others, and recordkeeping. Conclusions: Anesthesia providers, even when being observed, read during a significant percentage of the maintenance period in many cases. However, reading occurred when workload was low and did not appear to affect a measure of vigilance

Endothelial Cells Promote Human Immunodeficiency Virus Replication in Nondividing Memory T Cells via Nef-, Vpr-, and T-Cell Receptor-Dependent Activation of NFAT

Human endothelial cells (ECs) enhance human immunodeficiency virus (HIV) replication within CD4(+) memory T cells by 50,000-fold in a Nef-dependent manner. Here, we report that EC-mediated HIV type 1 replication is also dependent on an intact vpr gene. Moreover, we demonstrate that despite a requirement for engaging major histocompatibility complex (MHC) class II molecules and costimulators, EC-stimulated virus-producing cells (p24(high) T cells) do not proliferate, nor are they arrested in the cell cycle. Rather, they are minimally activated, sometimes expressing CD69 but not CD25, HLA-DR, VLA-1, or effector cytokines. Blocking antibodies to interleukin 2 (IL-2), IL-6, IL-7, or tumor necrosis factor do not inhibit viral replication. Cyclosporine effectively inhibits viral replication, as does disruption of the NFAT binding site in the viral long terminal repeat. Furthermore, in the presence of ECs, suboptimal T-cell receptor (TCR) stimulation with phytohemagglutinin L supports efficient viral replication, and suboptimal stimulation with toxic shock syndrome toxin 1 leads to viral replication selectively in the TCR-stimulated, Vβ2-expressing T cells. Collectively, these data indicate that ECs provide signals that promote Nef- and Vpr-dependent HIV replication in memory T cells that have been minimally activated through their TCRs. Our studies suggest a mechanism for HIV replication in vivo within the reservoir of circulating memory CD4(+) T cells that persist despite antiretroviral therapy and further suggest that maintenance of immunological memory by MHC class II-expressing ECs via TCR signaling may contribute to HIV rebound following cessation of antiretroviral therapy

Quantum spin liquids bootstrapped from Ising criticality in Rydberg arrays

Arrays of Rydberg atoms constitute a highly tunable, strongly interacting venue for the pursuit of exotic states of matter. We develop a new strategy for accessing a family of fractionalized phases known as quantum spin liquids in two-dimensional Rydberg arrays. We specifically use effective field theory methods to study arrays assembled from Rydberg chains tuned to an Ising phase transition that famously hosts emergent fermions propagating within each chain. This highly entangled starting point allows us to naturally access spin liquids familiar from Kitaev's honeycomb model, albeit from an entirely different framework. In particular, we argue that finite-range repulsive Rydberg interactions, which frustrate nearby symmetry-breaking orders, can enable coherent propagation of emergent fermions between the chains in which they were born. Delocalization of emergent fermions across the full two-dimensional Rydberg array yields a gapless Z2 spin liquid with a single massless Dirac cone. Here, the Rydberg occupation numbers exhibit universal power-law correlations that provide a straightforward experimental diagnostic of this phase. We further show that explicitly breaking symmetries perturbs the gapless spin liquid into gapped, topologically ordered descendants: Breaking lattice symmetries generates toric-code topological order, whereas introducing chirality generates non-Abelian Ising topological order. In the toric-code phase, we analytically construct microscopic incarnations of non-Abelian defects, which can be created and transported by dynamically controlling the atom positions in the array. Our work suggests that appropriately tuned Rydberg arrays provide a cold-atoms counterpart of solid-state 'Kitaev materials' and, more generally, spotlights a new angle for pursuing experimental platforms for Abelian and non-Abelian fractionalization.Comment: 17 pages, 7 figure