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An increasing number of Bacillus strains have been identified, and the removal capacity of zearalenone (ZEN) was determined; however, they failed to reveal the detoxification mechanism and transformation product. Here, Bacillus subtilis Y816, which could transform 40 mg/L of ZEN within 7 h of fermentation, was identified and studied. First, the biotransformation products of ZEN and 17-β-estradiol (E2) were identified as ZEN-14-phosphate and E2-3-phosphate by HPLC-TOF-MS and NMR, respectively. An intracellular zearalenone phosphotransferase (ZPH) was found through transcriptome sequencing analysis of B. subtilis Y816. The phosphorylated reaction conditions of ZEN by ZPH were further revealed in this work. Furthermore, the phosphorylated conjugates showed reduced estrogenic toxicity compared with their original substances (ZEN and α/β-zearalenol) using an engineered yeast biosensor system. The first report on the phosphorylated conjugated mode of ZEN in B. subtilis Y816 will inspire new perspectives on the biotransformation of ZEN in Bacillus strains.

Fungal natural products are rich sources of clinical drugs. Particularly, the fungicolous fungi have a large number of biosynthetic gene clusters (BGCs) to produce numerous bioactive natural products, but most BGCs are silent in the laboratory. We have shown that a fungicolous fungus Calcarisporium arbuscula NRRL 3705 predominantly produces the highly reduced polyketide-type mycotoxins aurovertins. Here after evaluation of the aurovertin-null mutant ΔaurA as an efficient host, we further screened two strong promoters aurBp and A07068p based on RNA-Seq, and successfully activated an endogenous gene cluster from C. arbuscula as well as three additional exogenous BGCs from other fungi to produce polyketide-type natural products. Thus, we showed an efficient expression system from the fungicolous fungus C. arbuscula, which will be highly beneficial and complementary to the conventional Aspergillus and Penicillium fungal cell factories, and provides a useful toolkit for genome-wide mining of bioactive natural products from fungicolous fungi.

The current work presents zones of distinct catalytic selectivity during Cu-based CO2RR at high currents in gas diffusion electrodes.

Inspired by the catalytic mechanism of cytochrome P450 enzymes, we have evolved a fatty acid hydroxylase, P450BSβ, into a decarboxylase after four rounds of saturation mutagenesis that now predomin...

Soil microbes play essential roles in the biogeochemical processes of organic carbon and nutrient cycling. Many studies have reported various short-term effects of fertilization on soil microbes. However, less is known about the effects of longterm fertilization regimes on the rhizosphere. Therefore, the objective of this study was to explore how the soil microbial communities in the rhizosphere respond to different long-term fertilization strategies. Based on a 21-year field treatment experiment in Guizhou, China, we extracted phospholipid fatty acids (PLFAs) to determine the microbial community structure in both the non-rhizosphere (NR) and rhizosphere (R). Six treatments were included: no fertilizer (CK), mineral nitrogen fertilizer (N), N with potassium (NK), phosphorus with K (PK), NPK, and NPK combined with manure (MNPK). The results showed that total PLFAs under unbalanced mineral fertilization (N, NK and PK) were decreased by 45% on average in the NR compared with CK, whereas MNPK increased fungi and G– bacteria abundance significantly in both the NR (by 33 and 23%) and R (by 15 and 20%), respectively. In addition, all microbial groups in the R under these treatments (N, NK and PK) were significantly increased relative to those in the NR, except for the ratio of F/B and G+/G–, which might be due to the high nutrient availability in the R. Soil pH and SOC significantly regulated the soil microbial community and structure, explaining 51 and 20% of the variation in the NR, respectively. However, the rhizosphere microbial community structure was only significantly affected by soil pH (31%). We concluded that the soil microbial community in the NR was more strongly affected by long-term fertilization than that in the R due to the rhizosphere effect in the agricultural ecosystem. Rhizosphere nutrient conditions and buffering capacity could help microbial communities resist the change from the long-term fertilization.

In this article, we discuss the growth of entire functions represented by Laplace–Stieltjes transform converges on the whole complex plane and obtain some equivalence conditions about proximate growth of Laplace–Stieltjes transforms with finite order and infinite order. In addition, we also investigate the approximation of Laplace–Stieltjes transform with the proximate order and obtain some results containing the proximate growth order, the error, An∗, and λn, which are the extension and improvement of the previous theorems given by Luo and Kong and Singhal and Srivastava.

Catalyst free cyclocondensation of β-ethylthio-β-indolyl-α,β-unsaturated ketones with hydrazines has been developed, and 3-pyrazolyl indoles were efficiently synthesized in excellent yields. The catalyst free protocol avoids the use of a large excess of catalysts such as acids and bases, eliminating the discharge of harmful chemicals.

Herein, we report an engineered enzyme that can monooxygenate unprotected tryptophan into the corresponding 3a-hydroxyhexahydropyrrolo[2,3-b]indole-2-carboxylic acid (HPIC) in a single, scalable step with excellent turnover number and diastereoselectivity. Taking advantage of directed evolution, we analyzed the stepwise oxygen-insertion mechanism of tryptophan 2,3-dioxygenases, and transformed tryptophan 2,3-dioxygenase from Xanthomonas campestris into a monooxygenase for oxidative cyclization of tryptophans. It was revealed that residue F51 is vital in determining the product ratio of HPIC to N'-formylkynurenine. Our reactions and purification procedures use no organic solvents, resulting in an eco-friendly method to prepare HPICs for further applications.

A novel palladium-catalyzed Heck-type reaction of thiocarbamates has been designed to construct bridged seven-membered-ring systems that are otherwise challenging to prepare. Taking advantage of this newly developed method, enantioselective syntheses of lyconadins A-E (1-5), lycopecurine (6), and dehydrolycopecurine (7) have been realized in a divergent fashion. Our synthetic strategy also features an intramolecular cyclization of a N-chloroamine to forge the C6-N bond, a transannular Mannich-type reaction of a cyclic nitrone to stitch the C4 and C13 together, and a cyclocondensation to deliver the (dihydro-)pyridone motif.

Unlike energy efficiency and selectivity challenges, the kinetic effects of impure or intentionally mixed CO2 feeds on the catalytic reactivity of the direct electrochemical CO2 reduction reaction (CO2RR) have been poorly studied. Given that industrial CO2 feeds are often contaminated with CO, a closer investigation of the CO2RR under CO2/CO co-feed conditions is warranted. Here, we report mechanistic insights into the CO2RR reactivity of CO2/CO co-feeds on Cu-based nanocatalysts. Kinetic isotope-labelling experiments—performed in an operando differential electrochemical mass spectrometry capillary flow cell with millisecond time resolution—showed an unexpected enhanced production of C2H4, with a yield increase of almost 50%, from a cross-coupled 12CO2–13CO reactive pathway. The results suggest the absence of site competition between CO2 and CO molecules on the reactive surface at the reactant-specific sites. The practical significance of sustained local interfacial CO partial pressures under CO2 depletion is demonstrated by metallic/non-metallic Cu/Ni–N-doped carbon tandem catalysts. Our findings show the mechanistic origin of improved C2 product formation under co-feeding, but also highlight technological opportunities of impure CO2/CO process feeds for H2O/CO2 co-electrolysers. The mechanistic electrochemical mass spectrometry study of ethylene production on Cu-based nanocatalysts under CO2/CO co-feeds indicates the existence of separate, non-scrambling reactant-specific surface adsorption sites for CO2 and CO, which provides guidance for the design of CO2 reduction reaction electrocatalysts.

For CO2 reduction reactions, the Cu catalyst is unique, as compared with other metals, because of its ability to produce a wide range of hydrocarbon and oxygenated products. Previously, we have sho...

The electrochemical CO2 reduction reaction (CO2RR) is a promising technology for converting waste CO2 into chemicals which could be used as feedstock for the chemical industry or as synthetic fuels...

A nickel-catalyzed coupling of N-sulfonyl-1,2,3-triazole with various H-phosphine oxides for the construction of C(sp2)–P bonds is established. This unexpected reaction proceeds through a formal nickel-bound ketenimine pathway, representing a previously unknown 1,2-reactivity type of an azavinyl carbene. The method provides an efficient approach to the stereoselective and site-selective synthesis of α-aminovinylphosphoryl derivatives with moderate to good yield. A plausible mechanism is proposed based on experimental and theoretical studies.

We report a joint experimental–computational mechanistic study of electrochemical reduction of CO2 to CH4, catalyzed by solid-state Fe–N–C catalysts, which feature atomically dispersed, catalytical...

Celastrus orbiculatus is a medicinal plant belonging to the Celastraceae family. In this survey on the secondary metabolites of plants for obtaining antitumor substances, the chemical constituents of the stems of C. orbiculatus were investigated. Nortriptonoterpene (1), a new C19-norabietane diterpenoid, together with six other known abietane-type diterpenoids (2–7) and five known kaurane-type diterpenoids (8–12) were isolated and identified from the EtOAc extract of C. orbiculatus. Their structures were elucidated on the basis of extensive spectroscopic methods, including UV, IR, HR-ESI–MS, ECD, and NMR experiments, and by comparison with literature data. Compound 1 is a new C19-norabietane diterpenoid with 19 carbons. All compounds except for 10 and 11 were isolated from C. orbiculatus for the first time. The NMR data of 9 were reported for the first time. Compounds 1, 7 and 11 showed cytotoxicities against SGC-7901 with IC50 values of 63.2, 80.9 and 56.7 μM, respectively.

The number of catalytically active sites (site density, SD) and the catalytic turnover frequency (TOF) are critical for meaningful comparisons between catalytic materials and their rational improvement. SD and TOF numbers have remained elusive for PGM-free, metal/nitrogen-doped porous carbon electrocatalysts (MNC), in particular, FeNC materials that are now intensively investigated and widely utilized to catalyze the oxygen reduction reaction (ORR) in fuel cell cathodes. Here, we apply CO cryo sorption and desorption to evaluate SD and TOF numbers of a state-of-art FeNC ORR electrocatalyst with atomically dispersed coordinative FeNx (x ≤ 4) sites in acid and alkaline conditions. More specifically, we study the impact of thermal pretreatment conditions prior to assessing the number of sorption-active FeNx sites. We show that the pretreatment temperature sensitively affects the CO sorption uptake through a progressive thermal removal of airborne adsorbates, which, in turn, controls the resulting catalytic S...

Using solar energy to convert CO2 into valuable fuels or chemicals offers a powerful solution to urgent energy and environmental problems. However, the development of efficient and selective catalysts remains a considerable scientific challenge. To address this, catalytically active CoII centers can be anchored into the porous matrix of metal-organic frameworks (MOFs) by utilizing a robust Zr-based MOF (Zr-DMBD) functionalized with freestanding thiol groups to enable efficient post-synthetic metal insertion. The thus-prepared Zr-DMBD-Co MOF solids are modified by well-defined Co-thiolate units and have the capability of photocatalytically converting CO2 into CO with high efficiency and selectivity under visible-light irradiation in a water-containing system. The turnover number and CO selectivity reach as high as 97 941 and 98 %, respectively.

Five novel di- and tetra-nuclear rare earth complexes were synthesized by the variation of the solvent molecules: [Nd2(dbm)2(L)2(CH3OH)2]·0.75CH3OH (1), [Dy2(dbm)2(L)2(CH3OH)2]·4CH3OH (2), [Dy4(dbm)8(L)2(C3H7OH)2]·C3H7OH·2CH3CN (3), [Yb4(dbm)8(L)2(C3H7OH)2]·8CH3CN (4), [Y4(dbm)6(L)2(μ3-OH)2]·2CH3CN (5) (H2L = 2-[(2-hydroxyimino)propanehydrazide)methyl]-8-hydroxyquinoline, Hdbm = dibenzoylmethane). The structures of the complexes gradually transition from tetra-nuclear square grid-like clusters (5) to di-nuclear structure (1 and 2), and finally to tetra-nuclear chain clusters (3 and 4) with the increase of the alkyl chain of solvent molecules (μ3-OH → CH3OH → C3H7OH). 1 and 4 in the solid-state display the typical emissions of the NdIII ions and YbIII ions in the near-infrared region under visible-light excitation. For 2, more than one distinct relaxation process can be observed with an effective energy barrier ΔE/kB = 21.45 K, which is a typical behavior of single-molecule magnets (Hdc = 1000 Oe). This research shows that the magnetic properties can be modulated by tuning the solvent molecules to regulate the structures of complexes.

Distribution network is an important public infrastructure for national economic and social development, bearing the people’s growing expectation for better life. The new time urgently requires the construction of distribution network to be safer, better and more efficient. This paper relies on the team dream information system, Focusing on the safety, quality and schedule requirements of distribution network construction management, giving full play the supporting role of information system in engineering construction management, Creates closed-loop management of process nodes such as project preliminary design and feasibility study, materials, construction, completion, production, settlement and filing, so as to realize seamless connection of project preliminary design and feasibility study, efficient and transparent material management, deep integration of construction completion and close connection of production settlement, improve work efficiency and enhance the construction and management level of distribution network projects.

CO is the simplest product from CO2 electroreduction (CO2R), but the identity and nature of its rate-limiting step remain controversial. Here we investigate the activity of transition metals (TMs), metal–nitrogen-doped carbon catalysts (MNCs) and a supported phthalocyanine, and present a unified mechanistic picture of the CO2R to CO for these catalysts. Applying the Newns–Andersen model, we find that on MNCs, like TMs, electron transfer to CO2 is facile. We find CO2* adsorption to generally be limiting on TMs, whereas MNCs can be limited by either CO2* adsorption or by the proton–electron transfer reaction to form COOH*. We evaluate these computed mechanisms against pH-dependent experimental activity measurements on the CO2R to CO activity. We present a unified activity volcano that includes the decisive CO2* and COOH* binding strengths. We show that the increased activity of MNC catalysts is due to the stabilization of larger adsorbate dipoles, which results from their discrete and narrow d states. CO is a common product of the electrochemical reduction of CO2, but its formation mechanism remains elusive. Here, the authors present a unified mechanistic picture of CO2 reduction to CO on transition metal and single atom catalysts.

The electrochemical CO2 reduction reaction (CO2RR) to pure CO streams in electrolyzer devices is poised to be the most likely process for near-term commercialization and deployment in the polymer industry. The reduction of CO2 to CO is electrocatalyzed under alkaline conditions on precious group metal (PGM) catalysts, such as silver and gold, limiting widespread application due to high cost. Here, we report on an interesting alternative, a PGM-free nickel and nitrogen-doped porous carbon catalyst (Ni–N–C), the catalytic performance of which rivals or exceeds those of the state-of-the-art electrocatalysts under industrial electrolysis conditions. We started from small scale CO2-saturated liquid electrolyte H-cell screening tests and moved to larger-scale CO2 electrolyzer cells, where the catalysts were deployed as Gas Diffusion Electrodes (GDEs) to create a reactive three-phase interface. We compared the faradaic CO yields and CO partial current densities of Ni–N–C catalysts to those of a Ag-based benchmark, and its Fe-functionalized Fe–N–C analogue under ambient pressures, temperatures and neutral pH bicarbonate flows. Prolonged electrolyzer tests were conducted at industrial current densities of up to 700 mA cm−2. Ni–N–C electrodes are demonstrated to provide CO partial current densities above 200 mA cm−2 and stable faradaic CO efficiencies around 85% for up to 20 hours (at 200 mA cm−2), unlike their Ag benchmarks. Density functional theory-based calculations of catalytic reaction pathways help offer a molecular mechanistic basis of the observed selectivity trends on Ag and M–N–C catalysts. Computations lend much support to our experimental hypothesis as to the critical role of N-coordinated metal ion, Ni–Nx, motifs as the catalytic active sites for CO formation. Apart from being cost effective, the Ni–N–C powder catalysts allow flexible operation under acidic, neutral, and alkaline conditions. This study demonstrates the potential of Ni–N–C and possibly other members of the M–N–C materials family to replace PGM catalysts in CO2-to-CO electrolyzers.

One of the most appealing strategies to address the problems of global warming and energy shortage is to develop clean and sustainable energy source. To this end, considerable efforts have been devoted to designing well-defined catalysts for energy conversion. As an earth-abundant transition metal, nickel has been regarded to be an important catalytic center in molecular catalysts for redox reactions related to energy conversion. This Review focuses on the properties of nickel complexes as molecular catalysts in energy conversion driven by electricity or light, including water splitting and carbon dioxide (CO2) reduction.

A fluorescence microsphere suspension array technique has been developed as a promising tool for the molecular detection of Listeria monocytogene (LM), which is a dangerous food borne pathogen that can cause severe food intoxication in both humans and animals. In such a technique, fluorescent microspheres as the key matrix for detection are often decorated with neutral organic dyes, which usually suffer from instability, easy photobleaching and loss from the matrix. Herein, we design and synthesize a new organic–inorganic hybrid POM–pyrene compound [N(C4H9)4]2[V6O13{(OCH2)3CNH–CH2–C16H9}2] (1), which is employed as a negatively-charged fluorescent material to prepare a new class of fluorescent microspheres by a layer-by-layer electrostatic self-assembly method. As a result, such POM–pyrene-decorated fluorescent microspheres possess obvious luminescence properties, superior photo-stability and long-term stability. Therefore, the POM–pyrene-decorated fluorescent microspheres are conjugated by monoclonal anti-LM antibodies, and introduced into the fluorescence microsphere-based suspension immunoassay system for the detection of LM in food, which exhibits a high sensitivity. The lowest limit of detection (LOD) of LM in artificially contaminated meat is down to 6 CFU g−1 without cross-reactivity with other pathogens. Furthermore, the suspension immunoassay based on PS@POM–pyrene microspheres shows excellent specificity to LM, good repeatability and high efficiency in contrast to the conventional culture-based method.

The solar-driven CO2 reduction is a challenge in the field of "artificial photosynthesis", as most catalysts display low activity and selectivity for CO2 reduction in water-containing reaction systems as a result of competitive proton reduction. Herein, we report a dinuclear heterometallic complex, [CoZn(OH)L1 ](ClO4 )3 (CoZn), which shows extremely high photocatalytic activity and selectivity for CO2 reduction in water/acetonitrile solution. It achieves a selectivity of 98 % for CO2 -to-CO conversion, with TON and TOF values of 65000 and 1.8 s-1 , respectively, 4, 19, and 45-fold higher than the values of corresponding dinuclear homometallic [CoCo(OH)L1 ](ClO4 )3 (CoCo), [ZnZn(OH)L1 ](ClO4 )3 (ZnZn), and mononuclear [CoL2 (CH3 CN)](ClO4 )2 (Co), respectively, under the same conditions. The increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between ZnII and CoII , which dramatically lowers the activation barriers of both transition states of CO2 reduction.

An efficient catalytic asymmetric hydrophosphination of ortho-quinone methides with H-phosphine oxides is established. A chiral bifunctional squaramide is superior to catalyze this enantioselective carbon-phosphorus bond formation, delivering optically active α-arylmethyl phosphine oxides in high yields with high enantioselectivities (up to 94% yield, 99:1 er). Additionally, employing in situ-generated o-QMs for this hydrophosphination step economically provides the corresponding phosphine oxides with comparable yield and enantioselectivity.

Fusing the decarboxylase OleTJE and the reductase domain of P450BM3 creates a self-sufficient protein, OleT-BM3R, which is able to efficiently catalyze oxidative decarboxylation of carboxylic acids into linear α-olefins (LAOs) under mild aqueous conditions using O2 as the oxidant and NADPH as the electron donor. The compatible electron transfer system installed in the fusion protein not only eliminates the need for auxiliary redox partners, but also results in boosted decarboxylation reactivity and broad substrate scope. Coupled with the phosphite dehydrogenase-based NADPH regeneration system, this enzymatic reaction proceeds with improved product titers of up to 2.51 g L–1 and volumetric productivities of up to 209.2 mg L–1 h–1 at low catalyst loadings (∼0.02 mol %). With its stability and scalability, this self-sufficient biocatalyst offers a nature-friendly approach to deliver LAOs.

To accelerate the mulberry breeding program and examine the genome size and ploidy levels of 27 mulberry accessions of promising lines in Taiwan, nuclei suspensions were prepared from unfolded young leaves and analyzed by a flow cytometer. The genome size of each accession was estimated by referring to the standard genome size of chicken erythrocyte nuclei (CEN, 2.5 pg). Our results indicated that 25 among 27 investigated accessions in M. bombycis, M. alba, M. latifolia, M. australis, M. formosnensis, and M. atropurpurea are diploids with genome sizes ranging from 0.61 to 0.71 pg. ‘Elongated mulberry No. 1’ (M. laevigata) with a genome size of 1.06 pg is a triploid. Two populations were identified in the accession ‘67C001’ (M. australis Poir.) with a genome size of either 0.63 pg or 0.98 pg. Due to their similarity in appearance, we suspected that they are probably from the same origin, thus warranting further investigations. Several important vegetative characters of diploids and triploids have been estimated, including leaf length, leaf width, petiole length, petiole width, leaf thickness, and internode length, to document their correlation using the unpaired t-test. Subsequently, the statistical relationship between diploid and triploid species on some of these important characters, including leaf width, petiole width and internode length, was determined through binary regression analysis. We suggested that the internode length could provide a beneficial index to distinguish individuals with different ploidy levels in the field. Results of this study provide useful information to clarify the taxonomy of Morus and improve breeding programs aiming to advance horticulture and sericulture.

The intramolecular [2+2] cycloaddition of 1,3-dienes under visible light irradiation investigated by Yoon and his co-workers shows remarkably high yield and stereoselective differences under different photocatalysts. The reaction was speculated to be induced by energy transfer. However, the origin for these phenomena is still unclear. In this scene, the detailed mechanism for the [2+2] cycloaddition of 1,3-dienes under visible light has been investigated using density functional theory B3LYP and TPSSTPSS methods. The result shows that the reaction not only can be induced by energy transfer between photocatalysts and reactants, but also can be induced by electron transfer between them. The [2+2] cycloaddition induced by energy transfer is carried out along the potential energy surface (PES) of triplet excited states (T1) firstly, and then goes back to the singlet ground state (S0) via MECPs (minimum energy crossing points) between the PESs of the S0 and T1 states, forming the product in the S0 state. The [2+2] reaction induced by electron transfer proceeds along the doublet state PES of the cation radical reactant and the neutral four-membered ring product could be obtained by electron transfer from the corresponding reactant or reduced photocatalyst. The origin of stereoselectivity of the [2+2] reaction is attributed to the reaction mechanism difference under different photocatalysts.

The electrochemical CO2 reduction reaction (CO2RR) is a promising route for converting CO2 and excess renewable energy into valuable chemicals and synthetic fuels. Recently, carbon-based solid materials containing dopant-levels of transition metal and nitrogen (M–N–C) have emerged as a cost-effective, energy-efficient catalyst for the direct coreduction of CO2 and H2O to CO. Fe–N–C catalysts are particularly interesting as they can reduce CO further to hydrocarbons. Despite these promising reports, the influence of the reaction conditions on the catalytic performance of Fe–N–C catalysts has not been addressed. Here, we study the role of the electrolyte on the CO2RR selectivity. Unlike hydrogen or methane generation, catalytic CO production is independent of the electrolyte pH on the normal hydrogen electrode potential scale, suggesting a decoupled elementary proton–electron transfer mechanism for CO formation. The similarity between this heterogeneous charge-transfer reaction mechanism and that of molecul...

A catalyst developed from a CuII complex of (Et4 N)[Cu(pyN2Me2 )(HCO2 )]⋅0.5 CH3 OH⋅H2 O (1⋅0.5 CH3 OH⋅H2 O; pyN2Me2 =bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) shows a high activity to catalyze the reduction reaction of CO2 to CO driven by visible light in 4:1 acetonitrile/water (v:v) using [Ru(phen)3 ](PF6 )2 as photosensitizer and TEOA as sacrificial reductant, with a high TON of 9900 and a high CO selectivity of 98 %. The results of isotope labeling experiment, durability tests and energy dispersive spectroscopy reveal that 1 is robust during the photocatalytic process.

An elliptical ring is used to implement a novel type of high-static-low-dynamic vibration isolation. Under the compression deformation, the elliptical ring produces a nonlinear restoring force due to the coupling of the tension and the curvature caused by the stretching. For the elliptical ring under a uniaxial pressure, its force-displacement relation is derived from the Euler–Bernoulli beam theory. The force-displacement relation is experimentally validated via a digital force gauge. The dynamic equation is established for the elliptical ring isolator under a harmonic base excitation. It is revealed that the elliptical ring isolator is with high-static-low-dynamic stiffness. The harmonic balance method is applied to determine approximately steady-state responses of the vibration isolator, and thus the displacement transmissibility of the isolator can be analytically predicted. The analytical results show the effects of the eccentricity. The analytical outcomes are numerically confirmed by the direct integration of the dynamic equation. Under certain conditions, there is an optimal eccentricity for the fixed elliptical circumference, and the displacement transmissibility achieves a minimum value at the optimal eccentricity. The elliptical ring isolator is experimentally tested, and the experimental results validate the analytical outcomes.

A strategy toward tetrapetalones was explored including a site-selective ethylenation of the silyl enol ether A to afford a quaternary stereocenter that serves in a stereogenic capacity. Regio- and diastereoselective reactions were observed in conjunction with the oxidative formation of cation B, which included subsequent selective formation of either carbon-oxygen or carbon-carbon bonds at the δ or ζ position on the seven-membered ring. The fourth ring was formed using a Stetter reaction.

Metal–nitrogen–carbon (MNC) catalysts represent a potential means of reducing cathode catalyst costs in low temperature fuel cell cathodes. Knowledge-based improvements have been hampered by the difficulty to deconvolute active site density and intrinsic turnover frequency. In the present work, MNC catalysts with a variety of secondary nitrogen precursors are addressed. CO chemisorption in combination with Mossbauer spectroscopy are utilized in order to unravel previously inaccessible relations between active site density, turnover frequency, and active site utilization. This analysis provides a more fundamental description and understanding of the origin of the catalytic reactivity; it also provides guidelines for further improvements. Secondary nitrogen precursors impact quantity, quality, dispersion, and utilization of active sites in distinct ways. Secondary nitrogen precursors with high nitrogen content and micropore etching capabilities are most effective in improving catalysts performance.

This paper proposes an optimal 4H-silicon carbide trench MOS barrier Schottky (TMBS) Rectifier. The optimal structure of this rectifier is achieved by adding an N− wrapping region at the P+ shielding of the conventional TMBS structure, which significantly reduces the depletion region formed by the P+ shielding region. As a result, the proposed structure provides a lower ON-resistance comparing with the conventional P+ shielding structure. Moreover, we study the electric characteristics of the proposed structure via numerical simulation. Such a structure improves the specific ON-resistance and figure of merit of the conventional P+ shielding TMBS by 32.2% and 48.4%, respectively, and offers a high breakdown voltage, i.e., up to 1908 V.

Four novel μ-O bridged dinuclear Dy2 clusters have been synthesized successfully by utilizing an 8-hydroxyquinoline (8-HQ) Schiff base ligand and four different co-ligands: [Dy2(bfa)2(L)2(H2O)2]·4CH3OH (1), [Dy2(TTA)2(L)2(H2O)2]·4CH3OH (2), [Dy2(acac)2(L)2(H2O)2]·2H2O (3) and [Dy2(PhCOO)2(L)2(H2O)2] (4) (Hbfa = benzoyl trifluoroacetylacetone, HTTA = thiophene trifluoroacetylacetone, Hacac = acetylacetone, PhCOOH = benzoic acid, H2L = 2-[(4-pyridinebenzoylhydrazone)methyl]-8-hydroxyquinoline). Magnetic studies show that only complex 1 exhibits SMM behavior under a zero dc field with a magnetic relaxation barrier of 68.89 K. When a dc field of 1500 Oe is applied, the value of ΔE/kB increases to 72.63 K. The different dynamic magnetic behaviors of the four Dy2 complexes mainly originate from the tiny changes of the coordination environment and magnetic coupling interaction of the central ions caused by the different co-ligands. Meanwhile, it proves that the co-ligands play an important role in modulating the magnetic properties of Dy-SMMs based on 8-HQ derivatives.

The microstructure of aqueous CuCl2 has been studied through lots of technologies for many years; however, it remains a controversial subject. In this study, a new spectroscopic method has been proposed to analyze the UV-visible spectra of thin film of CuCl2/H2O solutions at different concentrations. This method is the combination of ratio spectra, difference spectra and second order difference spectra. By using this method, two new bands at ~230 and ~380 nm are obviously observed. The bands are assigned as the contacted ion pairs[CuCl3(H2O)n]- or[CuCl4(H2O)n]2-, which demonstrates that ion pairs exist in the CuCl2/H2O solution. Such finding agrees with the recent theoretical spectra obtained by time-dependent density functional theory. Furthermore, the populations of the contacted ion pairs are discussed. This study not only offers the direct spectroscopic evidence of[CuCl3(H2O)n]- or[CuCl4(H2O)n]2- in aqueous CuCl2, but also suggests that the spectroscopic analysis method is powerful to extract the weak bands in a strong overlapping spectrum.

A new tetranuclear pyrophosphate-bridged Cu(II) complex with 4,4′-bipyridine and 1,10-phenanthroline [Cu4(phen)4(bpy)2(P2O7)2]·10H2O (1) has been hydrothermal synthesized and characterized by single-crystal X-ray analysis, element analysis, IR spectroscopy, TG analysis, and UV–vis spectra. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic interactions between the neighbor Cu(II) centers in 1. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = − 13.16 cm− 1).

In this work we propose four non-coupled binding energies of intermediates as descriptors, or 'genes', for predicting the product distribution in CO2 electroreduction. Simple reactions can be understood by the Sabatier principle (catalytic activity vs. one descriptor), while more complex reactions tend to give multiple very different products and consequently the product selectivity is a more complex property to understand. We approach this, as a logistical classification problem, by grouping metals according to their major experimental product from CO2 electroreduction: H2, CO, formic acid and beyond CO* (hydrocarbons or alcohols). We compare the groups in terms of multiple binding energies of intermediates calculated by density functional theory. Here we find three descriptors to explain the grouping: the adsorption energies of H*, COOH* and CO*. To further classify products beyond CO*, we carry out formaldehyde experiments on Cu, Ag and Au and combine these results with the literature to group and differentiate alcohol or hydrocarbon products. We find that the oxygen binding (adsorption energy of CH3O*) is an additional descriptor to explain the alcohol formation in reduction processes. Finally, the adsorption energy of the four intermediates, H*, COOH*, CO* and CH3O*, can be used to differentiate, group and explain products in electrochemical reduction processes involving CO2, CO and carbon-oxygen compounds.

Direct electrochemical reduction of CO2 to fuels and chemicals using renewable electricity has attracted significant attention partly due to the fundamental challenges related to reactivity and selectivity, and partly due to its importance for industrial CO2-consuming gas diffusion cathodes. Here, we present advances in the understanding of trends in the CO2 to CO electrocatalysis of metal- and nitrogen-doped porous carbons containing catalytically active M–N x moieties (M = Mn, Fe, Co, Ni, Cu). We investigate their intrinsic catalytic reactivity, CO turnover frequencies, CO faradaic efficiencies and demonstrate that Fe–N–C and especially Ni–N–C catalysts rival Au- and Ag-based catalysts. We model the catalytically active M–N x moieties using density functional theory and correlate the theoretical binding energies with the experiments to give reactivity-selectivity descriptors. This gives an atomic-scale mechanistic understanding of potential-dependent CO and hydrocarbon selectivity from the M–N x moieties and it provides predictive guidelines for the rational design of selective carbon-based CO2 reduction catalysts.

In recent years, [2+2] cycloaddition under visible light has been a hot topic because of low energy consumption and high regio- and stereoselectivities when compared with reactions under UV irradiation. However, the mechanism of [2+2] cycloaddition under visible light irradiation is still unclear. In this research, the visible light catalytic intermolecular [2+2] cycloaddition of 3-ylideneoxindoles has been investigated using density functional theory B3LYP and M06-L methods. The calculated result shows that 3-ylideneoxindoles in triplet excited states can be formed by energy transfer from the triplet excited states of photocatalyst, and then the [2+2] cycloaddition is carried out along the potential energy surface of triplet states. The [2+2] cycloaddition of 3-ylideneoxindoles is more likely to generate head to head products due to the σ–π conjugation. Hydrogen bonds in pre-reaction complex play a key role in the reaction and the strong hydrogen bonding in pre-reaction complex goes against the [2+2] cycloaddition reaction. Furthermore, the electron-withdrawing group of the reactant is beneficial to the reaction because the C C double bond can be weakened by it.

The object of this study is to analyze the levels of seven toxic elements residues in raw bovine milk in China and assess the potential health risk of those residues. The 178 raw bovine milk samples were collected from eight main milk-producing provinces and from three types of milk stations in China, and were analyzed for arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), aluminum (Al), and nickel (Ni) using inductively coupled plasma-mass spectrometry (ICP-MS). Al, Pb, Hg, Ni, Cr, and As were detected in 47.8, 29.2, 28.1, 23.6, 12.4, and 9.0% of total milk samples, respectively, and Cd were not detected in all samples. The raw bovine milk samples with high levels of toxic elements were found in industrial areas, such as Heilongjiang and Shanxi. Nemerow pollution index analysis showed that the levels were lower in the samples from the processing plants than that from the large-scale farms and small farm cooperatives. The margin of exposure (MOE) values suggest that the levels of As, Pb, Hg, Cr, Al, and Ni in the raw milk samples are not causing a health risk for Chinese consumers, including adults and children. Nevertheless, the risk of Pb for infant and young children was more serious than adult.

Visible-light driven reduction of CO2 into chemical fuels has attracted enormous interest in the production of sustainable energy and reversal of the global warming trend. The main challenge in this field is the development of efficient, selective, and economic photocatalysts. Herein, we report a Co(II)-based homogeneous catalyst, [Co(NTB)CH3CN](ClO4)2 (1, NTB = tris(benzimidazolyl-2-methyl)amine), which shows high selectivity and stability for the catalytic reduction of CO2 to CO in a water-containing system driven by visible light, with turnover number (TON) and turnover frequency (TOF) values of 1179 and 0.032 s–1, respectively, and selectivity to CO of 97%. The high catalytic activity of 1 for photochemical CO2-to-CO conversion is supported by the results of electrochemical investigations and DFT calculations.

Einstein–Podolski–Rosen (EPR) entanglement states are achievable by combining two single-mode position and momentum squeezed states at a 50:50 beam splitter (BS). To generate the EPR mechanical entanglement, we consider the system consisted of two parametric optomechanical resonators, where two mechanical oscillators are linearly coupled. The linear coupling forms the symmetric and antisymmetric combinations of two mechanical modes, parallel to a 50:50 BS mixing. In the weak optomechanical coupling regime and via applying the opposite phases of parametric interactions, the symmetric and antisymmetric mechanical modes can be position and momentum squeezed, respectively. Therefore, two original mechanical modes are EPR entangled. Moreover, the mechanical thermal noise can decrease the entanglement. But with the parametric interaction enhanced optomechanical cooling, the influence of thermal noise on entanglement can be significantly suppressed, and the mechanical entanglement can be generated under ...

Currently, no catalysts are completely selective for the electrochemical CO2 Reduction Reaction (CO2RR). Based on trends in density functional theory calculations of reaction intermediates we find that the single metal site in a porphyrine-like structure has a simple advantage of limiting the competing Hydrogen Evolution Reaction (HER). The single metal site in a porphyrine-like structure requires an ontop site binding of hydrogen, compared to the hollow site binding of hydrogen on a metal catalyst surface. The difference in binding site structure gives a fundamental energy-shift in the scaling relation of ∼0.3 eV between the COOH* vs. H* intermediate (CO2RR vs. HER). As a result, porphyrine-like catalysts have the advantage over metal catalyst of suppressing HER and enhancing CO2RR selectivity.

This paper relates the study of random walks on graphs and directed graphs to random walks that arise in Monte Carlo methods applied to optimization problems. Previous results on simple graphs are surveyed and new results on the mixing times for Markov chains are derived.

The unusual (R) configuration previously assigned (with seemingly undoubted evidence) to purpuroin A and nakirodin A was disproved by synthesis. The optical rotation and NMR data for structure assigned for salt-free nakirodin A were made available for the first time. The difficulty and potential risk of error in configurational assignments of diastereomers for remote stereocenters were exemplified through MDN-0104. However, comparisons of the delicate 13C NMR deviations may still provide solutions to such problems.

The extract of the strain Aspergillus flavipes DL-11 exerted antibacterial activities against six Gram-positive bacteria. During the following bioassay-guided separation, ten diphenyl ethers (1-10), two benzophenones (11-12), together with two xanthones (13-14) were isolated. Among them, 4'-chloroasterric acid (1) was a new chlorinated diphenyl ether. Their structures were elucidated by extensive spectroscopic data analysis, including IR, HR-ESI-MS, NMR experiments, and by comparison with the literature data. All compounds showed moderate to strong antibacterial effects on different Gram-positive bacteria with MIC values that ranged from 3.13 to 50 μg/mL, but none of the compounds exhibited activity against Gram-negative bacteria Vibrio parahaemolyticus ATCC17802 (MIC>100 μg/mL). In particular, the MICs of some compounds are at the level of positive control.

The production of two-dimensional (2D) ultrathin metal-organic framework (MOF) nanosheets with functionalized surfaces is significant for extending their applications. To date, no protocol has been developed yet to solve this problem. Herein, we report a facile, mild, and efficient method to produce 2D monolayer MOF nanosheets with hydrophobic surfaces from layer-pillared 3D MOFs. This approach is based on the replacement of weaker coordinating pillar ligands with stronger coordinating capping ligands with the assistance of a high concentration gradient of the latter. Utilizing this method, the replacement of the 4,4'-bipyridine (bpy) pillars in two cadmium-based layer-pillared MOFs with alkylpyridine derivatives has been achieved, producing 2D MOF nanosheets with monolayer thickness and double-sided hydrophobic surfaces. The resulting hydrophobic 2D MOF nanosheets exhibit good performance for the separation of oil and water.