Convex Relaxations and Approximations of Chance-Constrained AC-OPF Problems

This paper deals with the impact of linear approximations for the unknown nonconvex confidence region of chance-constrained AC optimal power flow problems. Such approximations are required for the formulation of tractable chance constraints. In this context, we introduce the first formulation of a chance-constrained second-order cone (SOC) OPF. The proposed formulation provides convergence guarantees due to its convexity, while it demonstrates high computational efficiency. Combined with an AC feasibility recovery, it is able to identify better solutions than chance-constrained nonconvex AC-OPF formulations. To the best of our knowledge, this paper is the first to perform a rigorous analysis of the AC feasibility recovery procedures for robust SOC-OPF problems. We identify the issues that arise from the linear approximations, and by using a reformulation of the quadratic chance constraints, we introduce new parameters able to reshape the approximation of the confidence region. We demonstrate our method on the IEEE 118-bus system

Chance-Constrained AC Optimal Power Flow Integrating HVDC Lines and Controllability

The integration of large-scale renewable generation has major implications on the operation of power systems, two of which we address in this work. First, system operators have to deal with higher degrees of uncertainty due to forecast errors and variability in renewable energy production. Second, with abundant potential of renewable generation in remote locations, there is an increasing interest in the use of High Voltage Direct Current lines (HVDC) to increase transmission capacity. These HVDC transmission lines and the flexibility and controllability they offer must be incorporated effectively and safely into the system. In this work, we introduce an optimization tool that addresses both challenges by incorporating the full AC power flow equations, chance constraints to address the uncertainty of renewable infeed, modelling of point-to-point HVDC lines, and optimized corrective control policies to model the generator and HVDC response to uncertainty. The main contributions are twofold. First, we introduce a HVDC line model and the corresponding HVDC participation factors in a chance-constrained AC-OPF framework. Second, we modify an existing algorithm for solving the chance-constrained AC-OPF to allow for optimization of the generation and HVDC participation factors. Using realistic wind forecast data, for 10 and IEEE 39 bus systems with HVDC lines and wind farms, we show that our proposed OPF formulation achieves good in- and out-of-sample performance whereas not considering uncertainty leads to high constraint violation probabilities. In addition, we find that optimizing the participation factors reduces the cost of uncertainty significantly

Importance of clinical examination in diagnostics of Osgood-Schlatter Disease in boys playing soccer or basketball

Introduction: Osgood–Schlatter disease is an irritation of the patellar tendon at the tibial tubercle. Sports with jumps, running, and repeated contractions of knee extension apparatus are considered to be importantexternal risk-factors which could cause Osgood–Schlatter disease.Objectives of the study are to draw attention to the importance of clinical examination in diagnostics of Osgood–Schlatter disease in boys playing soccer or basketball.Methods: The research included data obtained from 120 boys, average age of 14 years. Examinees were split into two groups, one with young athletes which regularly have soccer or basketball trainings and thesecond one with boys who do not participating in sports. We performed anthropological measurements and clinical examinations of both knees and hips for both groups. For the statistical analysis we used pointbiserialcorrelation coefficient.Results: Based on clinical examination, Osgood–Schlatter disease was diagnosed in 51 examinees (42.5%). In “athletic group” Osgood–Schlatter disease had 31 boys or 52%, comparing with “non-athletic group” wherewe found 20 adolescents with disease (33%). Number of boys with Osgood–Schlatter disease was higher for 19% in “athletic group” comparing with “non-athletic group”. Comparing incidence rate for boys in both groups with diagnosed II and III level of Osgood–Schlatter disease we found that rate is higher in “athletic group” 2.25 times comparing with “non-athletic group”.Conclusions: Clinical examination is critical method in the process of diagnosing Osgood–Schlatter disease especially for identifying II and III level of this disease

Umzingelte Bühnen

Diese Diplomarbeit stellt eine Grundlagenforschung in der Sarajevoer Theaterszene während der Belagerung der bosnisch-herzegowinischen Hauptstadt (April 1992 – Februar 1996) dar. Zweierlei Forschungskerne standen dabei im Mittelpunkt: Einerseits wurde das im Mai 1992 neu gegründete „Sarajevoer Kriegstheaters/Sarajevski Ratni Teatar/ SARTR“ in seiner Entstehung und historischen Entwicklung von 1992 bis heute betrachtet, andererseits wurde anhand dieser Institution auch versucht, Rückschlüsse auf die damalige Produktions- und Rezeptionssituation in Sarajevo zu ziehen. Im historischen Teil dieser Diplomarbeit liegt der Fokus auf der Belagerungsperiode. Nachdem andere Theaterhäuser der Stadt vorgestellt und ein grober Einblick in deren Tätigkeiten im Laufe des Krieges gegeben wurde, wurde anhand von Zeitungsausschnitten der damaligen Zeit sowie noch unveröffentlichten Materialien des SARTRs die historische Entwicklung dieses Hauses nachgezeichnet. Auch wurde die Phase nach 1996 betrachtet, wobei den Schlussteil dieser Diplomarbeit ein Blick in die theaterpolitische Neuorientierung unter dem seit Anfang 2012 amtierenden Direktor Nihad Kresevljakovic bildet. Dabei wurde die Frage nach der Möglichkeit einer Fortführung von „Kriegstheater“ in Zeiten des Friedens gestellt. Ebenso wurde das erste Stück des SARTRs, Skloniste, im Rahmen dieser Diplomarbeit vom Verfasser unter dem Titel Der Unterschlupf ins Deutsche übersetzt und im Anhang, zusammen mit anderen Materialien, beigelegt. Anhand einer text- und inszenierungsanalytischen Herangehensweise an das Stück, welches insbesondere der Frage nach der Sinnhaftigkeit von Theater während des Krieges nachgeht, sowie mit Hilfe zahlreicher Aussagen von ZeitzeugInnen wurde versucht, Rückschlüsse über die Besonderheiten dieses Belagerungstheaters zu ziehen. Hierfür wurden zahlreiche TheatermacherInnen (SchauspielerInnen, Regisseure, andere Kulturschaffende) dieser Zeit, aber auch VertreterInnen des damaligen Publikums befragt. Anhand des Primärtextes und der Interviews wurden Rückschlüsse zur veränderten Ko-Präsenz von SchauspielerIn und ZuschauerIn geschlossen, das Theater als (Schutz)ort neu definiert, dem illusorischen Element von Theater während des Krieges nachgegangen sowie die politische Funktion des damaligen Theaters hinterfragt

Fine-tuning of SIRT1 expression is essential to protect the liver from cholestatic liver disease

Cholestasis comprises aetiologically heterogeneous conditions characterized by accumulation of bile acids in the liver that actively contribute to liver damage. Sirtuin 1 (SIRT1) regulates liver regeneration and bile acid metabolism by modulating farnesoid X receptor (FXR); we here investigate its role in cholestatic liver disease. We determined SIRT1 expression in livers from patients with cholestatic disease, in two experimental models of cholestasis, as well as in human and murine liver cells in response to bile acid loading. SIRT1-overexpressing (SIRT oe ) and hepatocyte-specific SIRT1-KO (knockout) mice (SIRT hep–/– ) were subjected to bile duct ligation (BDL) and were fed with a 0.1% DDC (3,5-diethoxycarbonyl-1,4-dihydrocollidine) diet to determine the biological relevance of SIRT1 during cholestasis. The effect of NorUDCA (24-norursodeoxycholic acid) was tested in BDL/SIRT oe mice. We found that SIRT1 was highly expressed in livers from cholestatic patients, mice after BDL, and Mdr2 knockout mice (Mdr2 –/– ) animals. The detrimental effects of SIRT1 during cholestasis were validated in vivo and in vitro. SIRT oe mice showed exacerbated parenchymal injury whereas SIRT hep–/– mice evidenced a moderate improvement after BDL and 0.1% DDC feeding. Likewise, hepatocytes isolated from SIRT oe mice showed increased apoptosis in response to bile acids, whereas a significant reduction was observed in SIRT hep–/– hepatocytes. Importantly, the decrease, but not complete inhibition, of SIRT1 exerted by norUDCA treatment correlated with pronounced improvement in liver parenchyma in BDL/SIRT oe mice. Interestingly, both SIRT1 overexpression and hepatocyte-specific SIRT1 depletion correlated with inhibition of FXR, whereas modulation of SIRT1 by NorUDCA associated with restored FXR signaling. Conclusion: SIRT1 expression is increased during human and murine cholestasis. Fine-tuning expression of SIRT1 is essential to protect the liver from cholestatic liver damage

Bioreactor technologies to support liver function in vitro

Liver is a central nexus integrating metabolic and immunologic homeostasis in the human body, and the direct or indirect target of most molecular therapeutics. A wide spectrum of therapeutic and technological needs drives efforts to capture liver physiology and pathophysiology in vitro, ranging from prediction of metabolism and toxicity of small molecule drugs, to understanding off-target effects of proteins, nucleic acid therapies, and targeted therapeutics, to serving as disease models for drug development. Here we provide perspective on the evolving landscape of bioreactor-based models to meet old and new challenges in drug discovery and development, emphasizing design challenges in maintaining long-term liver-specific function and how emerging technologies in biomaterials and microdevices are providing new experimental models.National Institutes of Health (U.S.) (R01 EB010246)National Institutes of Health (U.S.) (P50-GM068762-08)National Institutes of Health (U.S.) (R01-ES015241)National Institutes of Health (U.S.) (P30-ES002109)5UH2TR000496-02National Science Foundation (U.S.). Emergent Behaviors of Integrated Cellular Systems (CBET-0939511)United States. Defense Advanced Research Projects Agency. Microphysiological Systems Program (W911NF-12-2-0039