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The irreversible consumption of sodium in the initial several cycles greatly led to the attenuation of capacity, which caused the low initial coulombic efficiency (ICE) and obvious poor cycle stability. Pre-sodiation can effectively improve the electrochemical performance by compensating the capacity loss in the initial cycle. Here, carbon-coated sodium-pretreated iron disulfide (NaFeS2@C) has been synthesized through conventional chemical method and used in sodium metal battery as a cathode material. The calculated density of states (DOS) of NaFeS2@C is higher, which implies enhanced electron mobility and improved cycle reversibility. Because of the highly reversible conversion reaction and the compensation of irreversible capacity loss during the initial cycle, the Na/NaFeS2@C battery achieves ultra-high initial coulombic efficiency (96.7%) and remarkable capacity (751 mA·h·g−1 at 0.1 A·g−1). In addition, highly reversible electrochemical reactions and ultra-thin NaF-rich solid electrolyte interphase (SEI) also benefit for the electrochemical performance, even at high current density of 100 A·g−1, it still exhibits a reversible capacity of 136 mA·h·g−1, and 343 mA·h·g−1 after 2500 cycles at 5.0 A·g−1. This work aims to bring up new insights to improve the ICE and stability of sodium metal batteries.

Bacillus sp. DL-2 was isolated from the deep sea of the Western Pacific and further utilized as novel biocatalysts to efficiently asymmetrically hydrolyze (±)-1-phenylethyl acetate. After the optimization of hydrolytic reactions, chiral chemicals (R)-1-phenylethanol and (S)-1-phenylethyl acetate were obtained with high optical purities (96% and 99.8%, respectively). Our research is about the asymmeric hydrolysis of (±)-1-phenylethyl acetate using whole-cell biocatalysts. In addition, the optical purity of (S)-1-phenylethyl acetate generated through the kinetic resolution of (±)-1-phenylethyl acetate using the whole-cells of Bacillus sp. DL-2 was the highest report so far. Using the whole cells of deep sea bacterium Bacillus sp. DL-2 as the biocatalysts is an environmentally friendly method and will play critical roles in industrial asymmetric synthesis.

Chiral 1-phenylethanol and its ester derivative are important chiral chemicals in diverse industries and the preparation of those optically pure enantiomers is of great importance. One bacterium, Bacillus sp. DL-2, whose extracellular proteases could efficiently asymmetrically hydrolyse (±)-1-phenylethyl acetate, was isolated from the deep sea of the Western Pacific. After the immobilization of extracellular proteases and the optimization of enzymatic reactions, (R)-1-phenylethanol was prepared with the enantiomeric excess (e.e.) being 97% and the yield being 41%, respectively. The optimal resolution reaction condition for the preparation of (R)-1-phenylethanol using immobilized extracellular proteases was found to be 5-mM (±)-1-phenylethyl acetate, 360 mg/mL immobilized extracellular proteases, pH 6.5, and 20 °C for 2 h. (S)-1-phenylethyl acetate was generated through enzymatic kinetic resolution with the e.e. being as high as 99% and the yield being 71%, respectively. The optimal resolution reaction condition for the preparation of (S)-1-phenylethyl acetate was found to be 2.5-mM (±)-1-phenylethyl acetate, 440 mg/mL immobilized extracellular proteases, pH 7.5, and 35 °C for 10 h. Our report is the first report about the kinetic resolution of (±)-1-phenylethyl acetate using proteases and the enantio-preference of the proteases was found to be the same as those of most other esterases/lipases. Also notably, the optical purity of (S)-1-phenylethyl acetate generated through kinetic resolution using the proteases of Bacillus sp. DL-2 was the highest report so far. Proteases from deep-sea Bacillus sp. DL-2 are new contributions to the biocatalyst library for the preparation of valuable chiral alcohols and chiral esters through kinetic resolution.

We previously identified and characterized 1 novel deep-sea microbial esterase PHE21 and used PHE21 as a green biocatalyst to generate chiral ethyl (S)-3-hydroxybutyrate, 1 key chiral chemical, with high enantiomeric excess and yield through kinetic resolution. Herein, we further explored the potential of esterase PHE21 in the enantioselective preparation of secondary butanol, which was hard to be resolved by lipases/esterases. Despite the fact that chiral secondary butanols and their ester derivatives were hard to prepare, esterase PHE21 was used as a green biocatalyst in the generation of (S)-sec-butyl acetate through hydrolytic reactions and the enantiomeric excess, and the conversion of (S)-sec-butyl acetate reached 98% and 52%, respectively, after process optimization. Esterase PHE21 was also used to generate (R)-sec-butyl acetate through asymmetric transesterification reactions, and the enantiomeric excess and conversion of (R)-sec-butyl acetate reached 64% and 43%, respectively, after process optimization. Deep-sea microbial esterase PHE21 was characterized to be a useful biocatalyst in the kinetic resolution of secondary butanol and other valuable chiral secondary alcohols.

The two enantiomers of ethyl 3-hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)-3-hydroxybutyrate. Herein, we also functionally characterized one novel salt-tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)-3-hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio-selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates.

A novel esterase EstC10 from Bacillus sp. CX01 isolated from the deep sea of the Western Pacific Ocean and the functionalities of EstC10 was characterized. At present, the reports about the kinetic resolution of racemic methyl 2-chloropropionate were quite rare. So we developed deep-sea microbial esterase EstC10 as a novel biocatalyst in the kinetic resolution of racemic methyl 2-chloropropionate and generate (R)-methyl 2-chloropropionate with high enantiomeric excess (>99%) after the optimization of process parameters such as pH, temperature, organic co-solvents, surfactants, substrate concentration and reaction time. Notably, the optimal substrate concentration (80 mmol/L) of esterase EstC10 was higher than the kinetic resolution of another esterase, Est12-7 (50 mmol/L). The novel microbial esterase EstC10 identified from the deep sea was a promising green biocatalyst in the generation of (R)-methyl 2-chloropropionate as well of many other valuable chiral chemicals in industry.

Contour tracking is of great importance in many applications where contouring error is the minimization objective. In contrast to traditional, uncoordinated contour control where tracking error in each axis is controlled independently, coordinated contour control directly addresses the contouring error and therefore is more effective in rejecting disturbances or modeling errors. This paper proposes a feedforward strategy that increases contouring speed. A combined state-space system is first formed containing the model of each axis, and contouring error is expressed in terms of the states. Then the robust near-time-optimal command shaping technique is applied. A non-robust design and a 1 st -order robust design are compared. And a strategy is proposed to eliminate undesirable reversals that may occur in the robust design.

This paper introduces a robust time-optimal command shaping technique for the application of piezoelectric actuators on scanning tunneling microscopy (STM). Though feedback control has been widely used to improve the linearity, the maximum scan rate is substantially limited by the turn-around transients in the scan path. Therefore, feedforward approach is considered to improve the scan speed. In the authors' earlier work, a robust input design method based on the command shaping technique of constrained least-square optimization was proposed for a general class of systems without rigid-body mode. When this method is applied to velocity tracking, however, unique problems arise. This paper proposes a solution to these problems by modifying the sufficient condition in the frequency domain for robust inputs of velocity tracking, and the search procedure for the time-optimal solution is illustrated