High-Energy Density Redox Flow Lithium Battery with Unprecedented Voltage Efficiency

A redox flow lithium battery (RFLB) has decoupled energy storage and power generation units like a conventional redox flow battery, while it stores energy in solid materials by virtue of the unique redox targeting concept. Hence, it presents superior energy density and represents a promising approach for large-scale energy storage. In a RFLB, the potential difference between the redox shuttle molecules used in the same electrolyte normally brings about an intrinsic voltage hysteresis, resulting in a compromised voltage efficiency of the battery. Here we report a novel redox shuttle molecule pair to minimize the voltage hysteresis: anatase TiO₂ is reduced by bis­(pentamethylcyclopentadienyl)­chromium (CrCp*₂), while Li_<i>x</i>TiO₂ is oxidized by cobaltocene (CoCp₂). The potential difference between CoCp₂ and CrCp*₂ is only 0.15 V. A redox flow lithium battery is successfully demonstrated with an unprecedented voltage efficiency of 84%. The RFLB shows good cycling stability, and >90% Coulombic efficiency was demonstrated in the first 50 cycles

Main parameters of optimization algorithms.

With the participation in automatic generation control (AGC), a large-scale wind farm should distribute the real-time AGC signal to numerous wind turbines (WTs). This easily leads to an expensive computation for a high-quality dispatch scheme, especially considering the wake effect among WTs. To address this problem, a hierarchical power control (HPC) is constructed based on the geographical layout and electrical connection of all the WTs. Firstly, the real-time AGC signal of the whole wind farm is distributed to multiple decoupled groups in proportion of their regulation capacities. Secondly, the AGC signal of each group is distributed to multiple WTs via the data-driven surrogate-assisted optimization, which can dramatically reduce the computation time with a small number of time-consuming objective evaluations. Besides, a high-quality dispatch scheme can be acquired by the efficient local search based on the dynamic surrogate. The effectiveness of the proposed technique is thoroughly verified with different AGC signals under different wind speeds and directions.</div

Illustration of group division of WTs in a large-scale wind farm.

Illustration of group division of WTs in a large-scale wind farm.</p

The flowchart of DDSO based HPC for a large-scale wind farm.

The flowchart of DDSO based HPC for a large-scale wind farm.</p

Optimization process of each WT group by DDSO for a step AGC signal with a constant wind speed.

(a) Group #1, (b) Group #2, (c) Group #3, (d) Group #4, and (e) Group #5.</p

Structure and Dynamics of DNA and RNA Double Helices Obtained from the CCG and GGC Trinucleotide Repeats

Expansions of both GGC and CCG sequences lead to a number of expandable, trinucleotide repeat (TR) neurodegenerative diseases. Understanding of these diseases involves, among other things, the structural characterization of the atypical DNA and RNA secondary structures. We have performed molecular dynamics simulations of (GCC)_<i>n</i> and (GGC)_<i>n</i> homoduplexes in order to characterize their conformations, stability, and dynamics. Each TR has two reading frames, which results in eight nonequivalent RNA/DNA homoduplexes, characterized by CpG or GpC steps between the Watson–Crick base pairs. Free energy maps for the eight homoduplexes indicate that the C-mismatches prefer anti–anti conformations, while G-mismatches prefer anti–syn conformations. Comparison between three modifications of the DNA AMBER force field shows good agreement for the mismatch free energy maps. The mismatches in DNA-GCC (but not CCG) are extrahelical, forming an extended e-motif. The mismatched duplexes exhibit characteristic sequence-dependent step twist, with strong variations in the G-rich sequences and the e-motif. The distribution of Na⁺ is highly localized around the mismatches, especially G-mismatches. In the e-motif, there is strong Na⁺ binding by two G­(N7) atoms belonging to the pseudo GpC step created when cytosines are extruded and by extrahelical cytosines. Finally, we used a novel technique based on fast melting by means of an infrared laser pulse to classify the relative stability of the different DNA-CCG and -GGC homoduplexes

Response process of wind farm for a step AGC signal with a constant wind speed.

(a) AGC signal of each group, (b) Power regulation of each group obtained by DDSO, (c) Power regulation of each WT in Group #3 obtained by DDSO, and (d) Power regulation of the whole WF.</p

Structure and Dynamics of DNA and RNA Double Helices Obtained from the CCG and GGC Trinucleotide Repeats

Expansions of both GGC and CCG sequences lead to a number of expandable, trinucleotide repeat (TR) neurodegenerative diseases. Understanding of these diseases involves, among other things, the structural characterization of the atypical DNA and RNA secondary structures. We have performed molecular dynamics simulations of (GCC)_<i>n</i> and (GGC)_<i>n</i> homoduplexes in order to characterize their conformations, stability, and dynamics. Each TR has two reading frames, which results in eight nonequivalent RNA/DNA homoduplexes, characterized by CpG or GpC steps between the Watson–Crick base pairs. Free energy maps for the eight homoduplexes indicate that the C-mismatches prefer anti–anti conformations, while G-mismatches prefer anti–syn conformations. Comparison between three modifications of the DNA AMBER force field shows good agreement for the mismatch free energy maps. The mismatches in DNA-GCC (but not CCG) are extrahelical, forming an extended e-motif. The mismatched duplexes exhibit characteristic sequence-dependent step twist, with strong variations in the G-rich sequences and the e-motif. The distribution of Na⁺ is highly localized around the mismatches, especially G-mismatches. In the e-motif, there is strong Na⁺ binding by two G­(N7) atoms belonging to the pseudo GpC step created when cytosines are extruded and by extrahelical cytosines. Finally, we used a novel technique based on fast melting by means of an infrared laser pulse to classify the relative stability of the different DNA-CCG and -GGC homoduplexes

Detailed parameters of WT.

With the participation in automatic generation control (AGC), a large-scale wind farm should distribute the real-time AGC signal to numerous wind turbines (WTs). This easily leads to an expensive computation for a high-quality dispatch scheme, especially considering the wake effect among WTs. To address this problem, a hierarchical power control (HPC) is constructed based on the geographical layout and electrical connection of all the WTs. Firstly, the real-time AGC signal of the whole wind farm is distributed to multiple decoupled groups in proportion of their regulation capacities. Secondly, the AGC signal of each group is distributed to multiple WTs via the data-driven surrogate-assisted optimization, which can dramatically reduce the computation time with a small number of time-consuming objective evaluations. Besides, a high-quality dispatch scheme can be acquired by the efficient local search based on the dynamic surrogate. The effectiveness of the proposed technique is thoroughly verified with different AGC signals under different wind speeds and directions.</div

Lewis Base Promoted Intramolecular Acylcyanation of α-Substituted Activated Alkenes: Construction of Ketones Bearing β-Quaternary Carbon Centers

A novel phosphine-promoted intramolecular acylcyanation of α-substituted activated alkenes has been developed, which provides a unique access to densely functionalized acyclic ketones bearing β- quaternary carbon centers with a remarkable feature that both α- and β-positions of activated alkene are functionalized