Enantioselective cross-coupling of anhydrides with organozinc reagents: the controlled formation of carbon-carbon bonds through the nucleophilic interception of metalacycles

The construction of carbon-carbon bonds, particularly with concomitant control of newly formed asymmetric centers, is of paramount importance for the development of synthetic routes to complex organic molecules. While cross-coupling reactions for the generation of sp(2) carbon centers are well established, similar methodology for the formation and control of sp(3)-hydridized carbon stereocenters is extremely limited. We suggest that the nucleophilic interception of metalacycles provides the means to achieve such a transformation, wherein the metal complex serves to activate electrophiles, facilitate nucleophile addition, and ultimately control stereochemistry. One means of accessing these intermediates is through the use of simple meso-carboxylic anhydrides, which upon reaction with transition metals readily generate the desired metalacycles. Interception of the metalacycle with an appropriate carbon-based nucleophile generates an enantioenriched ketoacid, the product of the asymmetric desymmetrization of achiral starting materials. Early successes with achiral nickel catalysts and organozinc reagents provided the foundations for our approach. Alkylation of both succinic and glutaric anhydrides proceeds with a wide range of organozinc nucleophiles, forming 1,4- and 1,5-ketoacids in excellent yields. This reaction manifold has been extensively examined with a detailed kinetic study and mechanistic investigations utilizing mixed zinc reagents and alkene directing groups. This work has highlighted a number of unusual phenomena, including rate-limiting reductive elimination to form an sp(3)-sp(2) carbon-carbon bond. Despite excellent results with the achiral system, to date, all efforts to render the nickel-catalyzed reaction asymmetric have been limited to modest success. Palladium and rhodium complexes, with the use of chiral P-P and P-N ligands, respectively, have been identified as competent catalysts for the enantioselective addition of organozinc reagents to anhydrides. The arylation of a series of succinic anhydrides with Ph2Zn can be achieved in greater than 95% enantioselectivity using a Pd/Josiphos catalyst. Rhodium catalysts have proven amenable for the incorporation of in situ formed organozinc reagents, nucleophiles traditionally troublesome in transition metal catalysis due to the deleterious effects of residual halide ions. Highly functionalized organozinc nucleophiles, including those containing indole and furan, participate in this chemistry to provide the corresponding 1,4- and 1,5-ketoacids in excellent yield with greater than 85% enantioselectivity. This metalacycle interception methodology is currently being expanded to the use of other systems, most notably the asymmetric [2 + 2 + 2] cycloaddition of alkenes, alkynes, and isocyanates. Ongoing studies promise the extension of existing methodology toward the development of modular, fully intermolecular three-component couplings in which both metalacycle formation and nucleophilic interception can be controlled. Ultimately, we envision the use of heterocumulenes in such methodology, providing a route to complex products utilizing CO2 as an inexpensive C1 feedstock.     

Electromagnetic Fields and Induced Voltages on Underground Pipeline in the Vicinity of AC Traction System

Various regulations, aimed at the protection of human beings and electrical equipment against possible adverse effects resulting from exposure to electromagnetic fields, have been issued in many countries. Most of them are based on safety guidelines published by international expert groups. In this paper, electric and magnetic fields are calculated in the vicinity of 25 kV traction line supplying railway traction systems. Calculation results are compared to exposure limits specified by safety guidelines and regulations. Possible countermeasures for reduction of electromagnetic fields are proposed. Also, this paper presents a method for calculation of the induced voltages to an underground gas pipeline from a neighbouring 25 kV electric traction overhead line in case of short circuit. Calculations are performed with EMTP-ATP software. Possible countermeasures for reduction of induced voltages are proposed.     

Estimation of steel guitar strings corrosion by artificial neural network

The purpose of this work was to estimate the corrosion of steel guitar strings in the artificial sweat solution by applying artificial neural network (ANN). Measurements were conducted during 1, 2, 3 and 4 weeks. The results were used for training the most appropriate model of ANN. For evaluating the method efficiency, the comparison between measured data has been compared to values estimated by ANN. The high correlation coefficient and low mean absolute error between measured and estimated output values were observed. Therefore it can be concluded that ANN are promising tool for estimation of corrosion processes.     

Sustainability of energy,water, and environmental systems: a view of recent advances

Clean Technologies and Environmental Policy -     

Lipidomics Provides New Insight into Pathogenesis and Therapeutic Targets of the Ischemia—Reperfusion Injury

Lipids play an essential role in both tissue protection and damage. Tissue ischemia creates anaerobic conditions in which enzyme inactivation occurs, and reperfusion can initiate oxidative stress that leads to harmful changes in membrane lipids, the formation of aldehydes, and chain damage until cell death. The critical event in such a series of harmful events in the cell is the unwanted accumulation of fatty acids that leads to lipotoxicity. Lipid analysis provides additional insight into the pathogenesis of ischemia/reperfusion (I/R) disorders and reveals new targets for drug action. The profile of changes in the composition of fatty acids in the cell, as well as the time course of these changes, indicate both the mechanism of damage and new therapeutic possibilities. A therapeutic approach to reperfusion lipotoxicity involves attenuation of fatty acids overload, i.e., their transport to adipose tissue and/or inhibition of the adverse effects of fatty acids on cell damage and death. The latter option involves using PPAR agonists and drugs that modulate the transport of fatty acids via carnitine into the interior of the mitochondria or the redirection of long-chain fatty acids to peroxisomes.     

Quasi-robust control of biochemical reaction networks via stochastic morphing

One of the main objectives of synthetic biology is the development of molecular controllers that can manipulate the dynamics of a given biochemical network that is at most partially known. When integrated into smaller compartments, such as living or synthetic cells, controllers have to be calibrated to factor in the intrinsic noise. In this context, biochemical controllers put forward in the literature have focused on manipulating the mean (first moment) and reducing the variance (second moment) of the target molecular species. However, many critical biochemical processes are realized via higher-order moments, particularly the number and configuration of the probability distribution modes (maxima). To bridge the gap, we put forward the stochastic morpher controller that can, under suitable timescale separations, morph the probability distribution of the target molecular species into a predefined form. The morphing can be performed at a lower-resolution, allowing one to achieve desired multi-modality/multi-stability, and at a higher-resolution, allowing one to achieve arbitrary probability distributions. Properties of the controller, such as robustness and convergence, are rigorously established, and demonstrated on various examples. Also proposed is a blueprint for an experimental implementation of stochastic morpher.     

Evolutionary hyper-heuristic for solving the strip-packing problem

Strip-packing problem (marker making) is an optimization problem, where a set of cutting parts needs to be placed on a marker so that the items do not overlap, and do not exceed the boundaries of a marker. In this research a novel Grid algorithm is introduced, and improvement methods: Grid-BLP and Grid-Shaking. These algorithms were combined with genetic algorithm, and a novel placement order All equal first. An individual representation of a genetic algorithm has been developed that is consisted of placement sequence, rotation of a cutting part, the choice of a placement algorithm, and dynamic grid parameter. Experiments were conducted to determine the best placement algorithm for a dataset, and hyper-heuristic efficiency. The implementation has been developed and experiments were conducted in MATLAB using GEATbx toolbox on five datasets from textile industry: ALBANO, DAGLI, MAO, MARQUES and MAN SHIRT. The marker efficiency in percentage was recorded with best results: 85.17, 81.76, 78.67, 84.67 and 87.19% obtained for the datasets, respectively.     

Priority-based Energy Management Technique for Integration of Solar PV,Battery, and Fuel Cell Systems in an Autonomous DC Microgrid

Recent times have witnessed a significant positive trend in adoption of renewable energy sources and DC-based loads, which questions the efficiency and reliability of existing structure of electrical power system. DC microgrids are identified as potential solutions for addressing India's and other developing nations' rural electrification. This paper presents an energy management technique for isolated DC microgrids for academic readers, as well as provides an introduction to not-familiarized readers for understanding the common design challenges for implementing off-grid power systems. The principle of the proposed technique is based on law of energy conservation defined by the energy balance equation and is implemented by synthesizing the instantaneous current reference and hysteresis control with source priority, which was validated by rigors simulation studies in Matlab/Simulink. Furthermore, in order to demonstrate the modularity and scalability of the algorithm, it was tested on a prototype hardware test setup at the Solar Energy Research Centre, VIT University.     

Optimal non-active power compensation under non-sinusoidal conditions

This paper presents a new method of non-active power compensation in power systems under non-sinusoidal conditions. The basic idea of the compensation procedure stems from the condition for the minimum rms value of line currents. The application of optimization procedure, observing the above criterion, results in the required compensator. Three different compensators are derived: total non-active power compensator, compensator without energy storage, and reactive compensator. The paper introduces the factors which define the amount of active power in total power before and after the non-active power compensation. The compensation procedure is valid for single-phase and polyphase systems. Simulation results confirm the validity and applicability of the compensation procedure for a diversity of load currents.