A scalable and efficient synthesis of the GPR40 agonist MK-8666 was developed from a simple pyridine building block. The key step to set the stereochemistry at two centers relied on an enzymatic dynamic kinetic reduction of an unactivated ketone. Directed evolution was leveraged to generate an optimized ketoreductase that provided the desired trans alcohol in >30:1 dr and >99% ee. Further, it was demonstrated that all four diastereomers of this hydroxy-ester could be prepared in high yield and selectivity. Subsequently, a challenging intramolecular displacement was carried out to form the cyclopropane ring system with perfect control of endo/exo selectivity. The endgame coupling strategy relied on a Pd-catalyzed C-O coupling to join the headpiece chloropyridine with the benzylic alcohol tailpiece.

Controlling zeta potential of PDMS surface coated with a layer of PEG is important for electroosmosis and electrophoresis in PDMS made microfluidic chips. Here, zeta potentials of PDMS surfaces modified by simple physisorption of PEG of different concentrations in phosphate buffer solutions, pure water, and PEG solution were reported. Coating PEG on PDMS surfaces was achieved by immersing a PDMS layer into the PEG solution for 10 min and then taking it out and placing it in an oven at 80 • C for 10 h. To avoid damaging the PEG layer on the PDMS surface, an induction current method was employed for zeta potential measurement. Zeta potentials of PEG modified PDMS in electrolyte solutions were measured. The results show that 2.5% PEG can effectively modify PDMS surface with positive zeta potential value in phosphate buffer solutions, pure water and 10% PEG solution. Further increase in PEG solution beyond 5% for surface modification has no obvious effect on zeta potential change.

Previous studies have reported a lateral migration in particle electrophoresis through a straight rectangular microchannel. This phenomenon arises from the inherent wall-induced electrical lift that can be exploited to focus and separate particles for microfluidic applications. Such a dielectrophoretic-like force has been recently found to vary with the buffer concentration. We demonstrate in this work that the particle zeta potential also has a significant effect on the wall-induced electrical lift. We perform an experimental study of the lateral migration of equal-sized polystyrene particles with varying surface charges under identical electrokinetic flow conditions. Surprisingly, an enhanced focusing is observed for particles with a faster electrokinetic motion, which indicates a substantially larger electrical lift for particles with a smaller zeta potential. We speculate this phenomenon may be correlated with the particle surface conduction that is a strong function of particle and fluid properties.

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Doubly fed induction generator (DFIG) may suffer from huge disturbance owing to the uncertainty of generator parameters and load fluctuation during operation process. Hence, in the context of virtual synchronous generator (VSG) technology and its power-frequency control characteristics, this paper presents a VSG-based nonlinear adaptive robust controller (NARC), aiming to enhance the comprehensive regulation performance of DFIG. Firstly, a nonlinear robust adaptive controller with disturbance rejection and uncertainty adaptive learning ability is designed by establishing an improved dynamic model of the rotor motion equation in VSG, so as to achieve the optimal regulation of DFIG with robustness and adaptability. Secondly, in order to realize the fast dynamic response and autonomous synchronization ability in DFIG, a modified control strategy of the grid side converter (GSC) in DFIG is constructed by voltage and current dual-loop control (DLC) and VSG, which not only retains the significant dynamic response ability of the current inner-loop in DLC, but also improves the inertia and damping of the system. Finally, simulation results indicate that the modified control strategy exhibits satisfied dynamic performance and reliability, and reveals the robustness and adaptability of the control strategy in response to external random interferences and internal uncertain parameters. INDEX TERMS Doubly fed induction generator, virtual synchronous generator, nonlinear adaptive robust control, voltage and current dual-loop control.

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