Etiology of Burst Suppression EEG Patterns

Burst-suppression electroencephalography (EEG) patterns of electrical activity, characterized by intermittent high-power broad-spectrum oscillations alternating with isoelectricity, have long been observed in the human brain during general anesthesia, hypothermia, coma and early infantile encephalopathy. Recently, commonalities between conditions associated with burst-suppression patterns have led to new insights into the origin of burst-suppression EEG patterns, their effects on the brain, and their use as a therapeutic tool for protection against deleterious neural states. These insights have been further supported by advances in mechanistic modeling of burst suppression. In this Perspective, we review the origins of burst-suppression patterns and use recent insights to weigh evidence in the controversy regarding the extent to which burst-suppression patterns observed during profound anesthetic-induced brain inactivation are associated with adverse clinical outcomes. Whether the clinical intent is to avoid or maintain the brain in a state producing burst-suppression patterns, monitoring and controlling neural activity presents a technical challenge. We discuss recent advances that enable monitoring and control of burst suppression

Perceived Stress, Resilience, and Wellbeing in Seasoned Isha Yoga Practitioners Compared to Matched Controls During the COVID-19 Pandemic

Background: Yoga practices, including breathing, meditation, and posture protocols (asanas), have been shown to facilitate physical and mental wellbeing. Methods: Seasoned yoga practitioners were recruited from the Isha Foundation. Recruitment of the comparison group was achieved using snowball sampling and were not yoga practitioners. Participants in the non-yoga group were randomized to a 3-min Isha practice or a comparator group asked to perform 15-min of daily reading. Participants completed a series of web-based surveys (REDCap) at baseline, 6, and 12 weeks. These surveys include validated scales and objective questions on COVID-19 infection and medical history. The validated questionnaires assess for: perceived stress (PSS), mood states [anxiety and depression (PHQ-4), joy (DPES-Joy subscale)], mindfulness attention and awareness (MAAS), resilience (BRS), mental wellbeing (WEMWBS) and recovery from traumatic event (PTGI). Weekly activity diaries were employed as a tool for collecting compliance information from study participants. Perceived stress scale scores were identified as primary outcome for this study. Findings: The median Perceived Stress Scale (PSS) score for the yoga practitioners compared to the active and placebo comparators was significantly lower at all time-points: baseline: 11 [IQR 7–15] vs. 16 [IQR 12–21] in both the active and placebo comparators (p \u3c 0.0001); 6 weeks: 9 [IQR 6–13] vs. 12 [IQR 8–17] in the active comparator and 14 [IQR 9–18] in the placebo comparator (p \u3c 0.0001); and 12 weeks: 9 [IQR 5–13] vs. 11.5 [IQR 8–16] in the active comparators and 13 [IQR 8–17] in the placebo comparator (p \u3c 0.0001). Among the randomized participants that were compliant for the full 12 weeks, the active comparators had significantly lower median PSS scores than the placebo comparators 12 weeks [10 (IQR 5–14) vs. 13 (IQR 8–17), p = 0.017]. Further, yoga practitioners had significantly lower anxiety at all three-time points (p \u3c 0.0001), lower depression at baseline and 6 weeks (p \u3c 0.0003), and significantly higher wellbeing (p \u3c 0.0001) and joy (p \u3c 0.0001) at all three-time points, compared to the active and placebo comparator groups. Interpretation: The lower levels of stress, anxiety, depression, and higher level of wellbeing and joy seen in the yoga practitioners compared to the active and placebo comparators illustrate the impact of regular yoga practices on mental health even during the pandemic

Papers in Modern Economic Growth Theory

This thesis seeks to develop our understanding of two emerging themes in economic growth theory: constrained optima in heterogeneous agent economies with non- trivial wealth distributions, and the relationship between energy use and long-run growth. The first paper proves the existence of constrained optima in a growth model with incomplete insurance markets and idiosyncratic risk, also known as the Aiyagari- Huggett model. A natural way to formulate an optimal policy problem in the Aiyagari-Huggett model is by using a constrained planner; the constrained plan- ner cannot complete markets, but must improve welfare subject to agents’ budget constraints. Because the planner must respect infinitely many agents’ idiosyncratic budget constraints, the state and control for the constrained planner are an infinite dimensional wealth distribution and policy function. The key mathematical chal- lenge the proof overcomes is non-compactness of feasibility correspondences in the constrained planner’s dynamic optimization problem, brought on by the infinite dimensional structure of the economy. The second paper computes constrained optima in an Aiyagari-Huggett model with labor-leisure choice. In an economy calibrated to U.S. wealth and income inequality, the paper finds the constrained planner increases aggregate capital and reduces aggregate hours worked. The resulting increase in wages and fall in interest rates shifts the distribution of consumption towards the consumption poor, since they rely more on labor income than capital income. However, in a constrained efficient allocation, only highly productive individuals increase saving, while less productive individuals reduce saving. Moreover, only the asset poor and less productive agents reduce work hours; the wealthy and highly productive increase work hours due to wealth effects. While total work hours fall, the increase in work hours by the most productive is sufficient to increase effective labor supply. The third paper turns to energy and growth. World and U.S. energy intensities have declined over the past century, falling, on average, approximately 1.2–1.5 percent a year. The decline has persisted through periods of non-increasing raw energy prices, suggesting the decline is in a large part driven by autonomous factors, inde- pendent of price changes. In this paper I use a model of Schumpetarian endogenous growth with directed technical change to understand the autonomous decline in energy intensity and consider if the decline will continue. In an economy with no state dependence, where existing knowledge does not make R&D more profitable, this paper shows that energy intensity continues to decline from profit driven energy augmenting innovation, albeit at a slower rate than output growth. In an economy with state dependence, however, energy intensity eventually stops declining because labor augmenting innovation crowds out energy augmenting innovation. In either case, energy use always increases as long as the raw price of energy stays constant

Designing electricity markets for high penetrations of zero or low marginal cost intermittent energy sources

Integrating intermittent renewable generation with near zero private marginal costs for generating electricity will change market outcomes, but this article emphasizes that this integration does not change the fundamental economic principles behind market design. Market designs still need to adequately price scarcity and all network constraints and services. Such pricing is required to deliver investment incentives for the right technologies to locate at the right locations to efficiently maintain a stable and reliable electrical network.Shanker acknowledges the support of the ANU Grand Challenge Project: Zero-Carbon Energy for the Asia-Pacific. We thank the presenters at the Future Electricity Markets Summit (Chandra Krishnamurthy, Paul Simshauser, and Simon Wilkie) for their thoughtful presentation

Etiology of Burst Suppression EEG Patterns

Burst-suppression electroencephalography (EEG) patterns of electrical activity, characterized by intermittent high-power broad-spectrum oscillations alternating with isoelectricity, have long been observed in the human brain during general anesthesia, hypothermia, coma and early infantile encephalopathy. Recently, commonalities between conditions associated with burst-suppression patterns have led to new insights into the origin of burst-suppression EEG patterns, their effects on the brain, and their use as a therapeutic tool for protection against deleterious neural states. These insights have been further supported by advances in mechanistic modeling of burst suppression. In this Perspective, we review the origins of burst-suppression patterns and use recent insights to weigh evidence in the controversy regarding the extent to which burst-suppression patterns observed during profound anesthetic-induced brain inactivation are associated with adverse clinical outcomes. Whether the clinical intent is to avoid or maintain the brain in a state producing burst-suppression patterns, monitoring and controlling neural activity presents a technical challenge. We discuss recent advances that enable monitoring and control of burst suppression.</jats:p

Investigating the effect of surface modification on the dispersion process of polymer nanocomposites

Achieving controlled nanoparticle dispersion through melt processing has been challenging as processing-structure rules for polymer nanocomposites are still not well-defined. This work focuses on developing a quantitative understanding of the filler–matrix compatibility and melt mixing parameters on the dispersion of nanoparticles. Filler-matrix compatibility was varied by surface modification of silica nanoparticles. A twin screw extruder was used to prepare the nanocomposites and TEM imaging and image analysis were used to quantitively characterize the microstructure. It was found that matrix–filler compatibility strongly affected the method of agglomerate breakdown and dispersion. Under similar conditions, compatible systems tended to disperse via rupture of agglomerates while incompatible systems were found to disperse via erosion. A map was created to predict the dispersion mechanism as a function of processing conditions and system compatibility and systems from this study and literature were found to be in good agreement with the map

Perioperative Multimodal General Anesthesia Focusing on Specific CNS Targets in Patients Undergoing Cardiac Surgeries: The Pathfinder Feasibility Trial

Multimodal general anesthesia (MMGA) is a strategy that utilizes the well-known neuroanatomy and neurophysiology of nociception and arousal control in designing a rational and clinical practical paradigm to regulate the levels of unconsciousness and antinociception during general anesthesia while mitigating side effects of any individual anesthetic. We sought to test the feasibility of implementing MMGA for seniors undergoing cardiac surgery, a high-risk cohort for hemodynamic instability, delirium, and post-operative cognitive dysfunction. Twenty patients aged 60 or older undergoing on-pump coronary artery bypass graft (CABG) surgery or combined CABG/valve surgeries were enrolled in this non-randomized prospective observational feasibility trial, wherein we developed MMGA specifically for cardiac surgeries. Antinociception was achieved by a combination of intravenous remifentanil, ketamine, dexmedetomidine, and magnesium together with bupivacaine administered as a pecto-intercostal fascial block. Unconsciousness was achieved by using electroencephalogram (EEG)-guided administration of propofol along with the sedative effects of the antinociceptive agents. EEG-guided MMGA anesthesia was safe and feasible for cardiac surgeries, and exploratory analyses found hemodynamic stability and vasopressor usage comparable to a previously collected cohort. Intraoperative EEG suppression events and postoperative delirium were found to be rare. We report successful use of a total intravenous anesthesia (TIVA)-based MMGA strategy for cardiac surgery and establish safety and feasibility for studying MMGA in a full clinical trial.Clinical Trial Number:www.clinicaltrials.gov; identifier NCT04016740 (https://clinicaltrials.gov/ct2/show/NCT04016740).</jats:p