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In electric vehicles (EVs), the low voltage dc‐dc converter (LDC) with synchronous rectifier switches (SRs) can be used to reduce conduction loss caused by the high load current and improve the efficiency. Therefore, it is important to design a proper turn‐on time of SRs. As a popular driving strategy for the SRs, the drain–source voltage across the SRs is sensed to generate the gate driving signal. However, when LLC dc–dc converter operates at O mode, there will be a voltage ringing across the SRs. If the ringing voltage reaches to the threshold voltage −Vth,on, it would make SRs turn‐on early and results in abnormally working of the converter. The novelty and contribution of this paper lie in: (1) elaborating on the voltage ringing across the SRs, (2) the accurate ringing model is established during O mode, and (3) a simple, lossless, and low‐cost filter circuit is used to solve the negative effect of the ringing voltage for LLC converter at high load current. A 1.26 kW experimental prototype with ≈250–430 V wide input voltage and ≈9–16 V wide output voltage is implemented, 96.7% peak efficiency and 96% full load efficiency are achieved with a 3.12 kW/L power density. The theoretical analysis has been validated by the simulated and experimental results, and the SR LLC dc–dc converter with the SR works efficiently and reliably with the proposed solution at a high load current. [ABSTRACT FROM AUTHOR]

In this paper, a reduced‐switch‐count two‐phase interleaved LLC converter with precise current balancing is proposed by using switching‐control‐capacitor (SCC) technology. Compared with the conventional SCC‐LLC converter, the proposed two‐phase SCC‐LLC converter reduces the switch count with the SCC circuits, and achieves excellent current sharing under all the tolerance conditions between the two‐phase resonant elements. In the proposed converter, the SCC circuit is only used in the first phase. The design of the SCC circuit parameters is analyzed to reduce the voltage stress of the SCC circuit and to ensure that two‐phase currents are balancing with large tolerance of resonant elements. A 2.16‐kW GaN‐based two‐phase interleaved SCC‐LLC converter prototype is established for data center application, and the experimental results show that the 98.1% peak efficiency, the 97.6% full load efficiency, and higher than 96% efficiency at the wide range from 3‐A to 40‐A load current are achieved. The precise current sharing lower than 1% is achieved by using a cheap ceramic capacitor with high tolerance, which validates the performance of the converter. [ABSTRACT FROM AUTHOR]

Naturally occurring echinocandin B and FR901379 are potent antifungal lipopeptides featuring a cyclic hexapeptide nucleus and a fatty acid side chain. They are the parent compounds of echinocandin drugs for the treatment of severe fungal infections caused by the Candida and Aspergilla species. To minimize hemolytic toxicity, the native fatty acid side chains in these drug molecules are replaced with designer acyl side chains. The deacylation of the N-acyl side chain is, therefore, a crucial step for the development and manufacturing of echinocandin-type antibiotics. Echinocandin E (ECE) is a novel echinocandin congener with enhanced stability generated via the engineering of the biosynthetic machinery of echinocandin B (ECB). In the present study, we report the discovery of the first echinocandin E acylase (ECEA) using the enzyme similarity tool (EST) for enzymatic function mining across protein families. ECEA is derived from Streptomyces sp. SY1965 isolated from a sediment collected from the Mariana Trench. It was cloned and heterologously expressed in S. lividans TK24. The resultant TKecea66 strain showed efficient cleavage activity of the acyl side chain of ECE, showing promising applications in the development of novel echinocandin-type therapeutics. Our results also provide a showcase for harnessing the essentially untapped biodiversity from the hadal ecosystems for the discovery of functional molecules. [ABSTRACT FROM AUTHOR]

Aiming at the air defense task requirements for an enemy's large-scale aircraft attack, this paper presents a plan generation algorithm which can quickly give an interception scheme. The main contribution of this paper is the modification of the standard A* algorithm and its combination of the optimization algorithm and air-defence mission. Firstly, the enemy's attack weapon and our defense platform are modeled, and kinetic equations and interception efficiency functions are constructed, and the intercepted criterions are established. Then, the interception-cost mixed optimal function is established to clarify the system optimization objective. Secondly, aiming at the characteristics of strong time sensitivity of air defense interception, a modified A* optimization algorithm with fast convergence characteristics is used to solve the optimization problems, the standard A* algorithm is modified and the optimal air defense interception plan under the condition of mixed performance index is given. Finally, the proposed method is verified by numerical simulations. [ABSTRACT FROM AUTHOR]

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Gastric cancer is one of the most common types of carcinoma with a threat to global health. MicroRNA-760 (miR-760) was significantly down-regulated in the primary tumour of patients with advanced gastric cancer. However, the role of miR-760 in gastric cancer is still unclear. Herein, miR-760 was down-regulated in gastric cancer tissues. Moreover, miR-760 overexpression and knockdown were conducted in gastric cancer cells (MGC-803 and SGC-7901) in vitro. The in vitro functional assays proved that miR-760 overexpression reduced cell viability, cell cycle, migration and invasion, promoted apoptosis and suppressed MMP activity in MGC-803 cells. Conversely, miR-760 knockdown led to the opposite in SGC-7901 cells. Notably, bone marrow stromal antigen 2 (BST2) was verified as a target gene of miR-760. MiR-760 mimics down-regulated BST2 level in gastric cancer tissues and in MGC-803 cells, whereas miR-760 inhibitor up-regulated its level in SGC-7901 cells. MiR-760-regulated cell properties through reduction of BST2. In addition, miR-760 inhibited tumourigenesis in a nude mouse xenograft model in vivo. In conclusion, our results demonstrated that miR-760 exhibited a suppressive role in gastric cancer via inhibiting BST2, indicating that miR-760/BST2 axis may provide promising therapeutic target for gastric cancer. [ABSTRACT FROM AUTHOR]

We present the discovery of a novel radical cation formed through one‐electron oxidation of an N‐heterocyclic carbene–carbodiimide (NHC–CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox‐flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox‐active NHC–CDI adducts and their persistent radical ions for various applications. [ABSTRACT FROM AUTHOR]

Replacing graphite with alloying Al negative electrodes would allow for the development of high energy density Li-ion batteries. However, large volume changes associated with the alloying/dealloying process often result in pulverization of the electrode and rapid capacity fade during cycling due to the continuous formation of solid electrolyte interphase (SEI) layers and loss of electronic contact. In this study, we report that increasing salt concentration in the electrolyte to > 5 mol dm-3 led to enhanced capacity retention during cycling of Li-Al half-cells, which was accompanied by nearly constant impedance for the Al electrode in lithium bis(fluorosulfonyl)imide (LiFSI)/dimethyl carbonate (DMC) 1:1.1 (mol/mol) superconcentrated electrolyte. X-ray photoelectron spectroscopy (XPS) revealed that a potential hold in the superconcentrated electrolyte formed an SEI layer with a greater LiF concentration than in standard 1 mol dm-3 solution. This was supported by Raman spectroscopy of LiFSI solutions in DMC, supplemented with density functional theory calculations, which showed an increased driving force for the reduction of FSI- anions to form LiF from Li+-coordinated DMC complexes with increasing salt concentration. Therefore, the enhanced capacity retention and stability can be attributed to the stability of LiF-rich SEI layers which limit carbonate reduction and charge transfer impedance growth. [ABSTRACT FROM AUTHOR]

The CdS(HS)/g-C3N4 photocatalysts with an intimate connection was successfully synthesized by a facile deposition method. The CdS hollow microspheres (CdS(HS)) were well anchored on the surface of g-C3N4 to form an intimate connection by the hydrogen bonding between g-C3N4 and CdS(HS). The structures, morphologies, optical and electrical properties and photocatalytic performance of samples were successfully characterized by multiple means. The CdS(HS)/g-C3N4 composites exhibited excellent photocatalytic activity and stability for the photodegradation of RhB, and the degradation rate constant of CdS(HS)/g-C3N4 with optimum CdS(HS) mass ratio of 0.25% was about 2.1 times higher than that of the pure g-C3N4 under the visible light irradiation for 20 min. After four cycles, the CdS(HS)(0.25%)/g-C3N4 composite still maintained the high photocatalytic activity with the RhB degradation efficiency of 95%. Surprisingly, the photocorrosion of CdS(HS) caused by the photogenerated holes was inhibited effectively. The improvement of these properties should be ascribed to the intimate connection between g-C3N4 and CdS(HS) and the hollow structure of CdS(HS). The photocatalytic mechanism was also analyzed systematically. Furthermore, it was of great interest that the CdS(HS)/g-C3N4 composites possessed an excellent sedimentation property and they can be easily separated from the solution, which will be propitious to practical application. [ABSTRACT FROM AUTHOR]

Metal-free graphitic carbon nitride (g-C3N4) and carbon quantum dots (CQDs) have a promising attention as to their superior photocatalytic activities and physicochemical properties. In the article, g-C3N4 and CQDs were connected effectively through porous modification of g-C3N4 by directly heating melamine hydrochlorid, which benefits to the enhancement of the composites’ photocatalytic activity. The structures and morphologies of the photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectrum and photoluminescence spectroscopy. Meanwhile, the porous g-C3N4 and CQDs composite (pg-C3N4/CQDs) exhibited the improved photocatalytic activity for the degradation of RhB under visible light irradiation, which may be contributed three reasons: (1) pg-C3N4 has much higher surface area (~ 20 times) and more stronger photocatalytic oxidation capacity than that of g-C3N4; (2) as the electron-sinks, CQDs can improve the photogenerated electron-hole pair’s separation; (3) CQDs can upconvert the light with wavelengths longer than 650 nm into the shorter wavelengths to increase light harvesting, while pg-C3N4 utilizes the light to degrade pollutants. In addition, the possible photocatalytic degraded mechanism was investigated in detail. This work will be useful for designing other CQDs-based photocatalysts and providing a promising approach to environmental purification. [ABSTRACT FROM AUTHOR]

Understanding and controlling non-covalent interactions associated with solvent molecules and redox-inactive ions provide new opportunities to enhance the reaction entropy changes and reaction kinetics of metal redox centers, which can increase the thermodynamic efficiency of energy conversion and storage devices. Here, we report systematic changes in the redox entropy of one-electron transfer reactions including [Fe(CN)6]3−/4−, [Fe(H2O)6]3+/2+ and [Ag(H2O)4]+/0 induced by the addition of redox inactive ions, where approximately twenty different known structure making/breaking ions were employed. The measured reaction entropy changes of these redox couples were found to increase linearly with higher concentration and greater structural entropy (having greater structure breaking tendency) for inactive ions with opposite charge to the redox centers. The trend could be attributed to the altered solvation shells of oxidized and reduced redox active species due to non-covalent interactions among redox centers, inactive ions and water molecules, which was supported by Raman spectroscopy. Not only were these non-covalent interactions shown to increase reaction entropy, but they were also found to systematically alter the redox kinetics, where increasing redox reaction energy changes associated with the presence of water structure breaking cations were correlated linearly with the greater exchange current density of [Fe(CN)6]3−/4−. [ABSTRACT FROM AUTHOR]

A novel rattle-type magnetic Fe3O4@Ag@H-BiOCl nanocomposite was prepared successfully by a facile solvothermal method. The structures, morphologies, magnetic and electronic properties and photocatalytic performance of as-prepared products were successfully characterized by multiple techniques. The results show that the composites exhibit an obvious cavity, excellent magnetic properties, largely increased electron-hole separation efficiency and visible-light absorption. Due to the existence of an inner cavity, this novel photocatalyst exhibits excellent adsorption and transfer performance to organic pollutants in aqueous systems. The photocatalytic activity of the materials was evaluated by the photocatalytic degradation of rhodamine B (RhB) and antibiotic agent ciprofloxacin (CIP). It was found that the Fe3O4@Ag@H-BiOCl exhibited much better photocatalytic performance than pure BiOCl, which displayed the degradation rates of RhB and CIP were 99.5 and 98.3% after 120 min under visible light irradiation, respectively. The enhanced photocatalytic activities may result from the synergetic promoting effect of surface plasmon resonance of Ag and facet-dependent oxygen vacancy of BiOCl, which significantly improves visible-light absorption capacity and separation rate of charge carriers. A possible mechanism of the enhancement of visible photocatalytic activity was proposed. This study provides a promising approach to improve visible-light-response and recycle photocatalysts to treat waste water. [ABSTRACT FROM AUTHOR]

When analyzing photovoltaic plant’s output characteristics, the time interval and the time length of data need to be considered. At present, there is no exact theoretical basis of the time length of data. In the case of a certain time interval, the selection of the time length of data is of great significance for the analysis of extracting photovoltaic characteristics. This paper takes a feature mining of fluctuation degree and generated energy according to cluster analysis. On the basis of this, a definition of “daily performance coefficient” is given to characterize data characteristics. The optimum sample size estimation of daily performance coefficient based on principles of probability and statistics is taken to obtain the time length of data under different permissible errors. As a criterion that best meets the objective situation for selecting the statistical properties of the random variable, maximum entropy principle from information entropy theory provides the time length of data-determining method with no other constraints. Based on information entropy theory, taking the issue of storage capacity configuration in Photovoltaic (PV)-storage system as an example, this paper studies the relation between storage capacity demand and the time length of data and the relation between information entropy and the time length of data. In this way, the time length of data for PV-storage system’s operating characteristic analysis is determined. [ABSTRACT FROM AUTHOR]

Understanding what controls Li–O2 battery discharge product chemistry and morphology is key to enabling its practical deployment as a low-cost, high-specific-energy energy conversion technology. Several studies have recently shown that the addition of substantial quantities (hundreds to thousands ppm) of water and weak acids to dimethoxyethane (DME)-based electrolytes can significantly increase Li–O2 battery discharge capacity, without substantially changing the discharge product chemistry, which remains Li2O2. The exact mechanisms behind these device-level improvements, however, are not yet understood. In this study, we show that the presence of water in a DME-based electrolyte decreases the rate of Li2O2 nucleation on the electrode surface during Li–O2 battery discharge, using potentiostatic electrochemical measurements, and direct, ex situ observations of Li2O2 particles. We also show that adding water to an acetonitrile (MeCN)-based electrolyte results in LiOH upon discharge, as opposed to only Li2O2. Using first principles calculations, we propose that this change in discharge product chemistry is attributable to increased proton availability, as shown by a lower pKa for water in MeCN than in DME. This study combines kinetic and morphological analyses with first principles calculations, and elucidates relationships among electrolyte composition, discharge product chemistry and growth mechanisms for the rational design of efficient metal–air batteries. [ABSTRACT FROM AUTHOR]

Charging kinetics and reversibility of Na–O2 batteries can be influenced greatly by the particle size of NaO2 formed upon discharge, and exposure time (reactivity) of NaO2 to the electrolyte. Micrometer-sized NaO2 cubes formed at high discharge rates were charged at smaller overpotentials compared to nanometer-sized counterparts formed at low rates. [ABSTRACT FROM AUTHOR]

Protontransfer reactions play a key role in the conversion ofbiomass derived sugars to chemicals. In this study, we employ highlevel ab initio theoretical methods, in tandem with solvation effectsto calculate the proton affinities (PA) and acidity constants (pKa) of various d-glucose and d-fructose tautomers (protonation–deprotonation processes).In addition, we compare the theoretically derived pH values of sugarsolutions against experimentally measured pH values in our lab. Ourresults demonstrate that the protonation of any of the O atoms ofthe sugars is thermodynamically preferred without any significantvariation in the PA values. Intramolecular hydrogen transfers, dehydrationreactions, and ring-opening processes were observed, resulting fromthe protonation of specific hydroxyl groups on the sugars. Regardingthe deprotonation processes (pKa), wefound that the sugars’ anomeric hydroxyls exhibit the highestacidity. The theoretically calculated pH values of sugar solutionsare in excellent agreement with experimental pH measurements at lowsugar concentrations. At higher sugar concentrations the calculationspredict less acidic solutions than the experiments. In this case,we expect the sugars to act as solvents increasing the proton solvationenergy and the acidity of the solutions. We demonstrated through linearrelationships that the pKavalues arecorrelated with the relative stability of the conjugate bases. Thelatter is related to hydrogen bonding and polarization of the C–O–bond. A plausible explanation for the good performanceof the direct method in calculating the pKavalues of sugars can be the presence of intramolecular hydrogenbonds on the conjugate base. Both theory and experiments manifestthat fructose is a stronger acid than glucose, which is of significantimportance in self-catalyzed biomass-relevant dehydration reactions. [ABSTRACT FROM AUTHOR]

Correction for ‘Revealing instability and irreversibility in nonaqueous sodium–O2 battery chemistry’ by Sayed Youssef Sayed et al., Chem. Commun., 2016, 52, 9691–9694. [ABSTRACT FROM AUTHOR]

Analysis of pulse waveform is a low cost, non-invasive method for obtaining vital information related to the conditions of the cardiovascular system. In recent years, different Pulse Decomposition Analysis (PDA) methods have been applied to disclose the pathological mechanisms of the pulse waveform. All these methods decompose single-period pulse waveform into a constant number (such as 3, 4 or 5) of individual waves. Furthermore, those methods do not pay much attention to the estimation error of the key points in the pulse waveform. The estimation of human vascular conditions depends on the key points' positions of pulse wave. In this paper, we propose a Multi-Gaussian (MG) model to fit real pulse waveforms using an adaptive number (4 or 5 in our study) of Gaussian waves. The unknown parameters in the MG model are estimated by the Weighted Least Squares (WLS) method and the optimized weight values corresponding to different sampling points are selected by using the Multi-Criteria Decision Making (MCDM) method. Performance of the MG model and the WLS method has been evaluated by fitting 150 real pulse waveforms of five different types. The resulting Normalized Root Mean Square Error (NRMSE) was less than 2.0% and the estimation accuracy for the key points was satisfactory, demonstrating that our proposed method is effective in compressing, synthesizing and analyzing pulse waveforms. [ABSTRACT FROM AUTHOR]

Fluorinases represent the only known biological catalysts capable of forming carbon-fluorine bonds, but their slow catalytic rate limits their broader application. In this study, two fluorinases, FlA Sbac and FlA Pbac , were identified from a pool of 12 718 nonredundant proteins using a genome-mining approach, with FlA Sbac showing high catalytic activity. Both newly identified fluorinases contain a Phe50 residue in place of the Trp50 typically found in fluorinases. Structural and mutagenesis studies revealed that the Trp50 or Phe50 residue at this position is crucial for fluorinase activity. This work highlights the utility of genomic enzymology in expanding the repertoire of biocatalysts for fluorination chemistry.

Li-O 2 batteries can provide significantly higher gravimetric energy density than Li-ion batteries, but their practical use is limited by a number of fundamental issues associated with oxidizing discharge products such as Li 2 O 2 and LiOH during charging. Soluble inorganic redox mediators (RMs) like LiI and LiBr have been shown to enhance round-trip efficiency where different solvents can greatly shift the redox potential of the RMs, significantly altering the overpotential during charging, as well as their oxidizing power against the discharge product. Unfortunately, other design requirements like (electro)chemical stability with the electrode as well as reactive discharge products greatly constrain the selection of solvent, making it impractical to additionally design the solvent to provide optimal RM performance. In this work, we demonstrate that interhalide RMs based on LiI/LiBr and LiI/LiCl mixtures can enable tuning of the oxidizing power of the RM in a given solvent. I-Br interhalides I 2 Br - to IBr 2 - showed increasing chemical oxidizing power toward Li 2 O 2 and LiOH with increasing Br, and DEMS measurements during charging of Li-O 2 cells demonstrated that these I-Br interhalide RMs led to increased O 2 evolution with respect to LiI and reduced charging potential and CO 2 evolution with respect to LiBr.

We present the discovery of a novel radical cation formed through one-electron oxidation of an N-heterocyclic carbene-carbodiimide (NHC-CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox-flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox-active NHC-CDI adducts and their persistent radical ions for various applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Correction for 'Revealing instability and irreversibility in nonaqueous sodium-O 2 battery chemistry' by Sayed Youssef Sayed et al., Chem. Commun., 2016, 52, 9691-9694.

Understanding what controls Li-O2 battery discharge product chemistry and morphology is key to enabling its practical deployment as a low-cost, high-specific-energy energy conversion technology. Several studies have recently shown that the addition of substantial quantities (hundreds to thousands ppm) of water and weak acids to dimethoxyethane (DME)-based electrolytes can significantly increase Li-O2 battery discharge capacity, without substantially changing the discharge product chemistry, which remains Li2O2. The exact mechanisms behind these device-level improvements, however, are not yet understood. In this study, we show that the presence of water in a DME-based electrolyte decreases the rate of Li2O2 nucleation on the electrode surface during Li-O2 battery discharge, using potentiostatic electrochemical measurements, and direct, ex situ observations of Li2O2 particles. We also show that adding water to an acetonitrile (MeCN)-based electrolyte results in LiOH upon discharge, as opposed to only Li2O2. Using first principles calculations, we propose that this change in discharge product chemistry is attributable to increased proton availability, as shown by a lower pKa for water in MeCN than in DME. This study combines kinetic and morphological analyses with first principles calculations, and elucidates relationships among electrolyte composition, discharge product chemistry and growth mechanisms for the rational design of efficient metal-air batteries.

Charging kinetics and reversibility of Na-O2 batteries can be influenced greatly by the particle size of NaO2 formed upon discharge, and exposure time (reactivity) of NaO2 to the electrolyte. Micrometer-sized NaO2 cubes formed at high discharge rates were charged at smaller overpotentials compared to nanometer-sized counterparts formed at low rates.

Although metastasis-associated protein 1 (MTA1) has been widely linked to tumor metastasis, the relevant mechanisms remain to be elucidated, especially in gastric cancer. The aim of this study was to examine whether the MTA1 gene is associated with the process of proliferation and invasion by regulating several molecular targets in gastric cancer. MTA1 expression in 61 gastric cancer tissue and adjacent noncancerous tissues was analyzed by immunohistochemistry. The prognostic value of MTA1 for overall survival and disease-free survival was determined by Kaplan-Meier estimates, and the significance of differences between curves was evaluated by the log-rank test. Furthermore, overexpression of MTA1 in SGC7901 and BGC823 cells promoted cell cycle progression, cell adhesion, and cell invasion. Our study found that MTA1 is overexpressed in gastric cancers, which contributes to malignant cell growth by facilitating cell cycle progression through upregulation of cyclin D1 and accelerates the migration and invasion of human gastric cancer cells by regulating expression of fibronectin and MMP2/MMP9. Taken together, MTA1 was involved in the pathogenesis of gastric cancer and might be a candidate therapeutic target in gastric cancer.