60 research outputs found
Role of Risk Stratification and Genetics in Sudden Cardiac Death
No full textSudden cardiac death (SCD) is a major public health issue due to its increasing incidence in the general population and the difficulty in identifying high-risk individuals. Nearly 300,000-350,000 patients in the United States and 4- to 5 million patients in the world die from SCD. Coronary artery disease and advanced heart failure are the main etiology for SCD. Ischemia of any cause precipitates lethal arrhythmias, and ventricular tachycardia and ventricular fibrillation are the most common lethal arrhythmias precipitating SCD. Pulse-less electrical activity, brady-arrhythmia and electromechanical dissociation also result in SCD. Most sudden cardiac deaths occur out-of-the-hospital setting, so it is difficult to estimate the public burden, which results in overestimating the incidence of SCD. The insufficiency and limited predictive value of various indicators and criteria for SCD result in the increasing incidences. As a result, there is a need to develop better risk stratification criteria and find modifiable variables to decrease the incidence. Primary and secondary prevention and treatment of SCD need further research. This critical review is focused on the etiology, risk factors, prognostic factors and importance of risk stratification of SCD.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
An Efficient and Convenient Method for the Synthesis of Dialkoxymethanes Using Kaolinite as a Catalyst.
No full textSynthesis and development of Chitosan anchored copper(II) Schiff base complexes as heterogeneous catalysts for N-arylation of amines
No full textResilient operations of smart electricity networks under security and reliability failures
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D. in Computational Science and Engineering, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 265-276).Blackouts (or cascading failures) in Electricity Networks (ENs) can result in severe consequences for economic activity, human safety and national security. Recent incidents suggest that risk of blackouts due to cyber-security attacks and extreme weather events is steadily increasing in many regions of the world.This thesis develops a systematic approach to evaluate and improve the resilience of ENs by addressing following questions: (a) How to model security and reliability failures and assess their impact on ENs? (b) What strategies EN operators can implement to plan for and quickly respond to such failures and minimize their overall impact? (c) How to leverage the operational flexibility of "smart" ENs to implement these strategies in a structured manner and provide guarantees against worst-case failure scenarios? We focus on three classes of cyber-physical failures: (i) Inefficient or unsafe economic dispatch decisions induced by an external hacker who exploits the vulnerabilities of control center software; (ii) Simultaneous disruption of a large number of customer-side components (loads and/or distributed generators) by a strategic remote adversary; (iii) Correlated failures of power system components caused by storm events (or hurricanes) with high-intensity wind fields.We develop new network models to capture the impact of these failures, while accounting for a broad range of operator response actions. These actions include: partial load control, pre-emptive disconnection of non-critical loads, active and reactive power supply by Distributed Energy Resources (DERs) capable of providing grid-forming services, and formation of microgrid islands. We develop practically relevant operational strategies to improve the ENs' resilience to failure classes (i) and (ii) (resp. (iii)) based on solutions of bilevel mixed integer programming (resp. two-stage stochastic optimization) formulations. Our bilevel mixed integer programming formulations capture the worst-case impacts of attacks on radial distribution networks operating under grid-connected or microgrid configurations.For the case when the operator response can be modeled as continuous decision variables, we provide a greedy heuristic that exploits the radial network structure and provides near-optimal solutions. For the more general case of mixed-binary decision variables, we develop a computationally tractable solution approach based on Benders Decomposition method. This approach can be used to evaluate the value of timely response actions in reducing various losses to the network operator during contingencies induced by attacker-induced failures. We provide some guidelines on improving the network resilience by proactive allocation of contingency resources, and securing network components in a strategic manner. Furthermore, under reasonable assumptions, we show that myopically reconnecting the disrupted components can be eective in restoring the network operation back to nominal condition.Our two-stage stochastic optimization formulation is motivated by the need of a decision-theoretic framework for allocating DERs and other contingency resources in ENs facing the risk of multiple failures due to high-intensity storm events. The stochastic model in this formulation captures the dependence of probabilistic failure rates on the spatio-temporal wind intensities. Importantly, the formulation allows for the formation of microgrid islands (powered by the allocated DERs), and considers joint DER dispatch and component repair decisions over a multi-period restoration time horizon. We present computational results based on the classical sample average approximation method, with Benders Decomposition applied to solve the mixed-binary programs associated with the restoration stage. Finally, we compare the optimal repair decisions with a simpler greedy scheduling strategy that satisfies soft-precedence constraints."Financial support provided by EPRI grant for "Modeling the Impact of ICT Failures on the Resilience of Electric Distribution Systems" (contract ID: 10000621), and NSF project "CPS Frontiers: Collaborative Research: Foundations Of Resilient CybErphysical Systems (FORCES)" (award number: CNS-1239054)"--Page 5by Devendra Shelar.Ph. D. in Computational Science and EngineeringPh.D.inComputationalScienceandEngineering Massachusetts Institute of Technology, Department of Civil and Environmental Engineerin
Unprecedented formation of a μ -oxobridged polymeric copper(II) complex: Evaluation of catalytic activity in synthesis of 5-substituted 1 H -tetrazoles
No full textThe reaction of CuCl2·2H2O with Schiff base ligand, 4-[(2-hydroxy-3-methoxybenzylidene)amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3-one] (hmdpH), in 1:1 molar ratio led to a novel and unprecedented oxo-bridged polymeric copper (II) complex, [Cu(μ-O) (hmdp)]n. The complex was isolated as crystalline solid and characterized by FTIR, UV–visible and EPR spectroscopic techniques. The molecular structure of the complex was also determined by single crystal X-ray diffraction studies. The formation of the complex is unique and unprecedented in the sense that one of the CH3 group of the 4-aminoantipyrene unit of the Schiff base ligand is oxidized in situ to CH2OH, during the complex formation. The catalytic potential of the complex has been demonstrated in the synthesis of a series of 5-substituted 1H-tetrazoles via [3 + 2]-cycloaddition reactions of substituted benzonitriles and sodium azide in ethylene glycol
Colloidal transport within nematic liquid crystals with arrays of obstacles
No full textWe have investigated the gravity-driven transport of spherical colloids suspended in the nematic liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) within microfluidic arrays of cylindrical obstacles arranged in a square lattice. Homeotropic anchoring at the surfaces of the obstacles created periodic director-field patterns that strongly influenced the motion of the colloids, whose surfaces had planar anchoring. When the gravitational force was oriented parallel to a principal axis of the lattice, the particles moved along channels between columns of obstacles and displayed pronounced modulations in their velocity. Quantitative analysis indicates that this modulation resulted from a combination of a spatially varying effective drag viscosity and elastic interactions engendered by the periodic director field. The interactions differed qualitatively from a sum of pair-wise interactions between the colloids and isolated obstacles, reflecting the distinct nematic environment created by confinement within the array. As the angle α between the gravitational force and principal axis of the lattice was varied, the velocity did not follow the force but instead locked into a discrete set of directions commensurate with the lattice. The transitions between these directions occurred at values of α that were different from those observed when the spheres were in an isotropic liquid, indicating the ability of the liquid crystal forces to tune the lateral displacement behavior in such devices.Peer reviewe
Palladium nanoparticles immobilized on a magnetic chitosan-anchored Schiff base: applications in Suzuki–Miyaura and Heck–Mizoroki coupling reactions
No full textA palladium nanocatalyst Fe3O4@CS-SB-Pd has been synthesized and characterized by FT-IR, XRD, XPS, FESEM, EDX, TEM, TGA, and ICP-AES analysis.</p
Synthesis and crystal structures of salen-type Cu(II) and Ni(II) Schiff base complexes : application in [3+2]-cycloaddition and A3-coupling reactions
No full textThe synthesis of two new salen-type Schiff base complexes of the type [Cu(L)]·0.5H2O, 1, and [Ni(L)], 2, from the reaction of a 6,6′-[(1E,1′E)-(cyclohexane-1,2-diylbis(azanylylidene))bis(methanylylidene)bis(3-(diethylamino)phenol)] salen-type Schiff base ligand (H2L) with Cu(OAc)2·H2O and Ni(OAc)2·4H2O in methanol at room temperature, respectively, is described. The complexes are isolated as coloured crystalline solids and characterized by elemental analysis, FT-IR spectroscopy, UV-visible spectroscopy and single crystal X-ray diffraction studies. The paramagnetic nature of complex 1, having giso = 2.076, was confirmed by EPR studies, which indicated a distorted square planar geometry of the complex. In contrast to this, the nickel complex was found to be diamagnetic in nature and it was additionally characterized by 1H NMR. The crystal structures of complexes 1 and 2 confirm the distorted square planar geometry of both the complexes. Complex 1 was found to be a better catalyst for the synthesis of a series of 5-substituted 1H-tetrazoles from nitriles and sodium azide via [3+2]-cycloaddition and for the A3-coupling reaction of aldehydes, secondary amines and terminal alkynes with a low catalyst loading (0.7 and 0.9 mol%, respectively) as compared to complex 2. Complex 1 is novel in the sense that, being a homogeneous catalyst, it can be recovered almost quantitatively in both reactions and recycled up to four times to afford good yields of the corresponding products
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