Stability Constrained Reinforcement Learning for Real-Time Voltage Control in Distribution Systems

Deep Reinforcement Learning (RL) has been recognized as a promising tool to address the challenges in real-time control of power systems. However, its deployment in real-world power systems has been hindered by a lack of explicit stability and safety guarantees. In this paper, we propose a stability constrained reinforcement learning method for real-time voltage control in both single-phase and three-phase distribution grids and we prove that the proposed approach provides a voltage stability guarantee. The key idea underlying our approach is an explicitly constructed Lyapunov function that certifies stability. We demonstrate the effectiveness of our approach with both single-phase and three-phase IEEE test feeders, where the proposed method can reduce the transient control cost by more than 25\% and shorten the response time by 21.5\% on average compared to the widely used linear policy, while always achieving voltage stability. In contrast, standard RL methods often fail to achieve voltage stability.Comment: arXiv admin note: text overlap with arXiv:2109.1485

The role of Sirt7 and Sirt1 in adipocyte differentiation and maintenance of metabolic homeostasis

Sirtuins are NAD+-dependent protein deacetylases or ADP-ribosyltransferases, which play decisive roles in chromatin silencing, cell cycle regulation, cellular differentiation, metabolism, stress resistance and tumorigenesis. In mammals, sirtuins emerged as key metabolic sensors in various tissues and play a prominent role in metabolic adaptation to energy/nutrient stress. Sirt1 and Sirt6 are believed to act synergistically to prevent liver steatosis, especially under high-fat diet. Sirt1 and Sirt2 inhibit adipogenesis, and Sirt1 promotes the brown remodeling of white adipose tissue to control the metabolic balance in adipose tissue. Sirt7 was postulated to regulate rDNA transcription by associating with RNA polymerase I (Pol I) and maintain oncogenic transformation through deacetylation of histone H3K18, but the role of Sirt7 in metabolic regulation has remained enigmatic. Here, using the Sirt7 knockout mice and Sirt7 knock down approaches, my results describe the role of Sirt7 in maintenance of metabolic homeostasis in liver and the adipocytes differentiation in white adipose tissue. In liver, Sirt7 is required for the stimulation of hepatic rDNA transcription in response to insulin and is necessary for the fasting/refeeding adaptation. The second part of the study demonstrates the essential role of Sirt7 in adipocytes differentiation and white adipose tissue homeostasis. Absence of Sirt7 resulted in increased protein accumulation and activity of Sirt1 and restricted formation of white adipose tissue. In addition, my thesis shows that Sirt7 interacts with Sirt1 and restricts Sirt1 activity by inhibition of Sirt1 auto-deacetylation. These data uncover a new level of complexity in regulation of sirtuin activity and identify autocatalytic posttranscriptional modification as a new principle for regulation of Sirt1 activity. The antagonistic interactions between the two nuclear sirtuins are crucial to establish a well-balanced signalling network required for the maintenance of metabolic homeostasis. In the last part of this thesis, two Sirt1 targeting mouse strains were generated, which allow conditional, tissue specific inactivation of the Sirt1 gene and double knock out Sirt1 and Sirt7 in mice. These mouse models will help to further evaluate the sirtuin functions and the cross-regulatory network between Sirt1 and Sirt7 in the whole body or in the individual tissues.Sirtuine sind NAD+-abhängige Protein Deacetylasen und/oder ADP-Ribosyltransferasen, die entscheidende Rollen in einer Vielzahl von Prozessen spielen. Dazu gehören: Zellzyklusregulation, Differenzierung, metabolische Regulation, Stressresistenz sowie Tumorentstehung und Chromatin-Remodellierung. In Säugetieren nehmen Sirtuine eine Schlüsselrolle als metabolische Sensoren ein und regulieren die Adaptation auf Energie- und Nährstoffveränderungen. Synergistische Funktionen wurden für Sirt1 und Sirt6 in der Leber beschrieben. Beide Sirtuine wirken der Entwicklung von Lebersteatose, insbesondere bei fettreicher Ernährung, entgegen. Bei der Differenzierung von weißem Fettgewebe (Adipogenese) wurde eine hemmende Wirkung von Sirt1 und Sirt2 beobachtet. Des Weiteren, fördert Sirt1 die Entstehung von braunem Fettgewebe aus weißem Fett und kontrolliert somit die metabolische Balance im Fettgewebe. Für Sirt7 wurde bislang eine Funktion in der Regulation der rDNA Transkription durch die Interaktion mit der RNA-Polymerase I postuliert, eine Rolle in der Regulation metabolischer Prozesse konnte bis jetzt aber noch nicht nachgewiesen werden. In meiner Arbeit konnte ich mittels der Sirt7 Knock Out Maus bzw. verschiedener Sirt7 Knock Down Versuche belegen, dass Sirt7 eine Rolle in der Aufrechterhaltung der metabolischen Homöostase in der Leber und in der Differenzierung von Adipozyten in weißem Fettgewebe spielt. In der Leber ist Sirt7 für die Anregung der rDNA Transkription als Antwort auf eine Stimulation durch Insulin notwendig. Zudem konnte belegt werden, dass Sirt7 für eine Anpassung an Hungerphasen und anschließender Nahrungsaufnahme erforderlich ist. Im zweiten Teil meiner Arbeit konnte ich zeigen, dass die Funktion von Sirt7 in der Differenzierung von Adipozyten und in der Homöostase des weißen Fettgewebes essentiell ist. Hier resultiert der Verlust von Sirt7 in einer vermehrten Proteinakkumulation und einer erhöhten Aktivität von Sirt1, die der Fettgewebsentstehung entgegen wirkt. Hier konnte durch meine Arbeit eine Interaktion zwischen Sirt7 und Sirt1 belegt werden, welche mit einem Aktivitätsverlust von Sirt1 durch Inhibierung dessen Auto-Deacetylasefunktion einhergeht. Diese Ergebnisse decken eine neue Stufe der Komplexität der Aktivitätsanpassung der Sirtuine auf und identifizieren eine posttranskriptionelle Modifizierung als einen neuen Weg der Sirt1 Regulation durch dessen autokatalytische Aktivität. Die antagonistische Interaktion zwischen diesen zwei nukleären Sirtuinen ist entscheidend um eine ausgewogene Verknüpfung einzelner Signalwege herzustellen, die für die Aufrechterhaltung der metabolischen Homöostase notwendig sind. Im letzten Teil meiner Arbeit wurden zwei konditionelle Sirt1 Knock Out Mausstämme generiert, welche einerseits eine gewebsspezifische Inaktivierung von Sirt1 und zum anderen die gleichzeitige Ausschaltung von Sirt1 und Sirt7 in Mäusen erlauben. Die entstandenen Mausmodelle können helfen, die Funktionen von Sirt1 und Sirt7 und deren gegenseitige Beeinflussung im gesamten Organismus oder speziell in einzelnen Organen genauer zu untersuchen

Dry Needling for Spine Related Disorders: a Scoping Review

Introduction/Background: The depth and breadth of research on dry needling (DN) has not been evaluated specifically for symptomatic spine related disorders (SRD) from myofascial trigger points (TrP), disc, nerve and articular structures not due to serious pathologies. Current literature appears to support DN for treatment of TrP. Goals of this review include identifying research published on DN treatment for SRD, sites of treatment and outcomes studied. Methods: A scoping review was conducted following Levac et al.’s five part methodological framework to determine the current state of the literature regarding DN for patients with SRD. Results: Initial and secondary search strategies yielded 55 studies in the cervical (C) region (71.43%) and 22 in the thoracolumbar-pelvic (TLP) region (28.57%). Most were randomized controlled trials (60% in C, 45.45% in TLP) and clinical trials (18.18% in C, 22.78% in TLP). The most commonly treated condition was TrP for both the C and TLP regions. In the C region, DN was provided to 23 different muscles, with the trapezius as treatment site in 41.88% of studies. DN was applied to 31 different structures in the TLP region. In the C region, there was one treatment session in 23 studies (41.82%) and 2–6 treatments in 25 (45.45%%). For the TLP region, one DN treatment was provided in 8 of the 22 total studies (36.36%) and 2–6 in 9 (40.9%). The majority of experimental designs had DN as the sole intervention. For both C and TLP regions, visual analogue scale, pressure pain threshold and range of motion were the most common outcomes. Conclusion: For SRD, DN was primarily applied to myofascial structures for pain or TrP diagnoses. Many outcomes were improved regardless of diagnosis or treatment parameters. Most studies applied just one treatment which may not reflect common clinical practice. Further research is warranted to determine optimal treatment duration and frequency. Most studies looked at DN as the sole intervention. It is unclear whether DN alone or in addition to other treatment procedures would provide superior outcomes. Functional outcome tools best suited to tracking the outcomes of DN for SRD should be explored.https://doi.org/10.1186/s12998-020-00310-

Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.

BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6 months was conducted. Follow-up lasted 30 days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, p = 0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, p = 0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, p < 0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, p < 0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Mortality of emergency abdominal surgery in high-, middle- and low-income countries

Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low- or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI). Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression. Results: Data were obtained for 10 745 patients from 357 centres in 58 countries; 6538 were from high-, 2889 from middle- and 1318 from low-HDI settings. The overall mortality rate was 1⋅6 per cent at 24 h (high 1⋅1 per cent, middle 1⋅9 per cent, low 3⋅4 per cent; P < 0⋅001), increasing to 5⋅4 per cent by 30 days (high 4⋅5 per cent, middle 6⋅0 per cent, low 8⋅6 per cent; P < 0⋅001). Of the 578 patients who died, 404 (69⋅9 per cent) did so between 24 h and 30 days following surgery (high 74⋅2 per cent, middle 68⋅8 per cent, low 60⋅5 per cent). After adjustment, 30-day mortality remained higher in middle-income (odds ratio (OR) 2⋅78, 95 per cent c.i. 1⋅84 to 4⋅20) and low-income (OR 2⋅97, 1⋅84 to 4⋅81) countries. Surgical safety checklist use was less frequent in low- and middle-income countries, but when used was associated with reduced mortality at 30 days. Conclusion: Mortality is three times higher in low- compared with high-HDI countries even when adjusted for prognostic factors. Patient safety factors may have an important role. Registration number: NCT02179112 (http://www.clinicaltrials.gov)

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Multi-step stochastic ADMM in high dimensions: Applications to sparse optimization and matrix decomposition

In this paper, we consider a multi-step version of the stochastic ADMM method with efficient guarantees for high-dimensional problems. We first analyze the simple setting, where the optimization problem consists of a loss function and a single regularizer (e.g. sparse optimization), and then extend to the multi-block setting with multiple regularizers and multiple variables (e.g. matrix decomposition into sparse and low rank components). For the sparse optimization problem, our method achieves the minimax rate of O(s log d/T) for s-sparse problems in d dimensions in T steps, and is thus, unimprovable by any method up to constant factors. For the matrix decomposition problem with a general loss function, we analyze the multi-step ADMM with multiple blocks. We establish O(1/T) rate and efficient scaling as the size of matrix grows. For natural noise models (e.g. independent noise), our convergence rate is minimax-optimal. Thus, we establish tight convergence guarantees for multi-block ADMM in high dimensions. Experiments show that for both sparse optimization and matrix decomposition problems, our algorithm outperforms the state-of-the-art methods