Search

We have explored the effect of magnetic rare-earth dopants substitutionally incorporated on the Ba sites of BaSnO3 in terms of electronic transport, magnetism, and optical properties. We show that for Ba0.92R0.08SnO3 thin films (where R=La,Pr,Nd,Gd), there is a linear increase of mobility with carrier concentration across all doping schemes. La-doped films have the highest mobilities, followed by Pr- and Nd-doped films. Gd-doped samples have the largest ionic size mismatch with the Ba site and correspondingly the lowest carrier concentrations and electron mobilities. However, crystallinity does not appear to be a strong predictor of transport phenomena; our results suggest that point defects more than grain boundaries are key ingredients in tuning the conduction of BaSnO3 films grown by pulsed laser deposition. Pronounced, nonhysteretic x-ray magnetic dichroism signals are observed for Pr-, Nd-, and Gd-doped samples, indicating paramagnetism. Finally, we probe the optical constants for each of the BaSnO3 doping schemes and note that there is little change in the transmittance across all samples. Together these results shed light on conduction mechanisms in BaSnO3 doped with rare-earth cations.

This paper addresses the effect of interannual variability in jet stream orientation on weather systems over the North Atlantic basin (NAB). The observational analysis relies on 65 yr of NCEP-NCAR reanalysis (1948-2012). The total daily kinetic energy of the geostrophic wind (GTKE) is taken as a measure of storm activity over the North Atlantic. The NAB is partitioned into four rectangular regions, and the winter average of GTKE is calculated for each quadrant. The spatial GTKE average over all four quadrants shows striking year-to-year variability and is strongly correlated with the North Atlantic Oscillation (NAO). The GTKE strength in the northeast quadrant is closely related to the diffluence angle of the jet stream in the northwest quadrant. To gain insight into the relationship between the diffluence angle and its downstream impact, a quasigeostrophic baroclinic model is used. The results show that an initially zonal jet persists at its initial latitude over 30 days or longer, while a tilted jet propagates meridionally according to the Rossby wave group velocity, unless kept stationary by external forcing. A Gulf Stream-like narrow sea surface temperature (SST) front provides the requisite forcing for an analytical steady-state solution to this problem. This SST front influences the atmospheric jet in the northwest quadrant: It both strengthens the jet and tilts it northward at higher levels, while its effect is opposite at lower levels. Reanalysis data confirm these effects, which are consistent with thermal wind balance. The results suggest that the interannual variability found in the GTKE may be caused by intrinsic variability of the thermal Gulf Stream front.

This paper explores the three-way interactions between the Indian monsoon, the North Atlantic, and the tropical Pacific. Four climate records were analyzed: the monsoon rainfall in two Indian regions, the Southern Oscillation index for the tropical Pacific, and the NAO index for the North Atlantic. The individual records exhibit highly significant oscillatory modes with spectral peaks at 7-8 yr and in the quasi-biennial and quasi-quadrennial bands. The interactions between the three regions were investigated in the light of the synchronization theory of chaotic oscillators. The theory was applied here by combining multichannel singular-spectrum analysis (M-SSA) with a recently introduced varimax rotation of the M-SSA eigenvectors. A key result is that the 7-8-yr and 2.7-yr oscillatory modes in all three regions are synchronized, at least in part. The energy-ratio analysis, as well as time-lag results, suggests that the NAO plays a leading role in the 7-8-yr mode. It was found therewith that the South Asian monsoon is not slaved to forcing from the equatorial Pacific, although it does interact strongly with it. The time-lag analysis pinpointed this to be the case in particular for the quasi-biennial oscillatory modes. Overall, these results confirm that the approach of synchronized oscillators, combined with varimax-rotated M-SSA, is a powerful tool in studying teleconnections between regional climate modes and that it helps identify the mechanisms that operate in various frequency bands. This approach should be readily applicable to ocean modes of variability and to the problems of air-sea interaction as well. © 2013 American Meteorological Society.

This paper presents a predictability study of the Madden-Julian Oscillation (MJO) that relies on combining empirical model reduction (EMR) with the "past-noise forecasting" (PNF) method. EMR is a data-driven methodology for constructing stochastic low-dimensional models that account for nonlinearity, seasonality and serial correlation in the estimated noise, while PNF constructs an ensemble of forecasts that accounts for interactions between (i) high-frequency variability (noise), estimated here by EMR, and (ii) the low-frequency mode of MJO, as captured by singular spectrum analysis (SSA). A key result is that - compared to an EMR ensemble driven by generic white noise - PNF is able to considerably improve prediction of MJO phase. When forecasts are initiated from weak MJO conditions, the useful skill is of up to 30 days. PNF also significantly improves MJO prediction skill for forecasts that start over the Indian Ocean. Key Points Nonlinear stochastic MJO model with memory effects derived from RMM indices PNF method significantly improves MJO prediction PNF skill is comparable with skill reported for a dynamical multi-model ensemble ©2013. American Geophysical Union. All Rights Reserved.

Aqueous zinc-ion battery anodes face the twin challenges of dendrite growth and severe side reactions. Here a liquid-infiltrated Al 2 O 3 framework electrolyte (LIAFE) is developed to address these issues and enables stable long-life Zn anodes for over 4000 hours. The LIAFE shows a uniform morphology and exhibits enhanced performance.

The electrocatalytic reduction of CO 2 to CO is slowed by the energy cost of the hydrogenation step that yields adsorbed *COOH intermediate. Here, we report a hydrogen radical (H•)-transfer mechanism that aids this hydrogenation step, enabled by constructing Ni-partnered hetero-diatomic pairs, and thereby greatly enhancing CO 2 -to-CO conversion kinetics. The partner metal to the Ni (denoted as M) catalyzes the Volmer step of the water/proton reduction to generate adsorbed *H, turning to H•, which reduces CO 2 to carboxyl radicals (•COOH). The Ni partner then subsequently adsorbs the •COOH in an exothermic reaction, negating the usual high energy-penalty for the electrochemical hydrogenation of CO 2 . Tuning the H adsorption strength of the M site (with Cd, Pt, or Pd) allows for the optimization of H• formation, culminating in a markedly improved CO 2 reduction rate toward CO production, offering 97.1% faradaic efficiency (FE) in aqueous electrolyte and up to 100.0% FE in an ionic liquid solution., Competing Interests: Competing interests The authors declare no competing interest., (© 2024. The Author(s).)

Single-atom catalysts (SACs), featuring highly uniform active sites, tunable coordination environments, and synergistic effects with support, have emerged as one of the most efficient catalysts for various reactions, particularly for electrochemical CO 2 reduction (ECR). However, the scalability of SACs is restricted due to the limited choice of available support and problems that emerge when preparing SACs by thermal deposition. Here, an in situ reconstruction method for preparing SACs is developed with a variety of atomic sites, including nickel, cadmium, cobalt, and magnesium. Driven by electricity, different oxygen-containing metal precursors, such as MOF-74 and metal oxides, are directly atomized onto nitrogen-doped carbon (NC) supports, yielding SACs with variable metal active sites and coordination structures. The electrochemical force facilitates the in situ generation of bonds between the metal and the supports without the need for additional complex steps. A series of MN x O y (M denotes metal) SACs on NC have been synthesized and utilized for ECR. Among these, NiN x O y SACs using Ni-MOF-74 as a metal precursor exhibit excellent ECR performance. This universal and general SAC synthesis strategy at room temperature is simpler than most reported synthesis methods to date, providing practical guidance for the design of the next generation of high-performance SACs., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

All-soluble all-iron redox flow batteries (AIRFBs) are an innovative energy storage technology that offer significant financial benefits. Stable and affordable redox-active materials are essential for the commercialization of AIRFBs, yet the battery stability must be significantly improved to achieve practical value. Herein, ferrous complexes combined with the triisopropanolamine (TIPA) ligand are identified as promising anolytes to extend battery life by reducing cross-contamination due to a pronounced steric hindrance effect. The coordination structure and failure mechanism of our Fe-TIPA complexes were determined by molecular dynamics simulation and spectroscopic experiments. By coupling with [Fe(CN) 6 ] 4-/3- , Fe-TIPA/Fe-CN AIRFBs retained excellent stability exceeding 1831 cycles at 80 mA ⋅ cm -2 , yielding an energy efficiency of ~80 % and maintaining a steady discharge capacity. Moreover, the all-soluble electrolyte was tested in an industrial-scale Fe-TIPA/Fe-CN AIRFB prototype energy storage system, where an energy efficiency of 81.3 % was attained. Given the abundance of iron resources, we model the TIPA AIRFB electrolyte cost to be as low as 32.37 $/kWh, which is significantly cheaper than the current commercial level. This work demonstrates that steric hindrance is an effective measure to extended battery life, facilitating the commercial development of affordable flow batteries., (© 2024 Wiley-VCH GmbH.)

The value of aqueous zinc-ion rechargeable batteries is held back by the degradation of the Zn metal anode with repeated cycling. While raising the operating current density is shown to alleviate this anode degradation, such high cycling rates are not compatible with full cells, as they cause Zn-host cathodes to undergo capacity decay. A simple approach that improves anode performance while using more modest cathode-compatible current densities is required. This work reports reversible planar Zn deposition under cathode-compatible current densities can instead be achieved by applying external pressure to the cell. Employing multiscale characterization, this work illustrates how cycling under pressure results in denser and more uniform Zn deposition, analogous to that achieved under high cycling rates, even at low areal current densities of 1 to 10 mA cm -2 . Microstructural mechanical measurements reveal that Zn structures plated under lower current densities are particularly susceptible to pressure-induced compression. The ability to achieve planar Zn plating at cathode-compatible current densities holds significant promise for enabling high-capacity Zn-ion battery full cells., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Oxygen redox cathodes, such as Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , deliver higher energy densities than those based on transition metal redox alone. However, they commonly exhibit voltage fade, a gradually diminishing discharge voltage on extended cycling. Recent research has shown that, on the first charge, oxidation of O 2- ions forms O 2 molecules trapped in nano-sized voids within the structure, which can be fully reduced to O 2- on the subsequent discharge. Here we show that the loss of O-redox capacity on cycling and therefore voltage fade arises from a combination of a reduction in the reversibility of the O 2- /O 2 redox process and O 2 loss. The closed voids that trap O 2 grow on cycling, rendering more of the trapped O 2 electrochemically inactive. The size and density of voids leads to cracking of the particles and open voids at the surfaces, releasing O 2 . Our findings implicate the thermodynamic driving force to form O 2 as the root cause of transition metal migration, void formation and consequently voltage fade in Li-rich cathodes., (© 2024. The Author(s).)

Old man's beard (Clematis vitalba L.) is a liana species that has become invasive in many areas of its introduced range. Seeds are produced in abundance and are both physiologically and morphologically dormant upon maturity. To understand the importance of seeds to its invasiveness, changes in viability and dormancy of the aerial seed bank were tracked throughout the after-ripening period and during storage. Seeds collected every second month for 2 years were subjected to germination tests. Other seeds stored in outdoor ambient conditions or in a dry, chilled state were dissected before, during, and after imbibition, as well as during incubation, to measure embryo size. Less than 72% of seeds on the mother plant were viable. Viable seeds remained completely morpho-physiologically dormant throughout autumn, even when treated with nitrate. Physiological dormancy declined in response to seasonal changes, yet morphological dormancy did not change until seeds had been exposed to appropriate germination conditions for several days. Fully dormant autumn seeds decayed at higher rates during incubation than partially or fully after-ripened seeds, which were also more germinable and less dormant. Furthermore, seeds incubated in complete darkness were more likely to decay or remain dormant than those exposed to light. This study demonstrates that fewer than three-quarters of seeds produced are viable and further decay occurs after dispersal, yet total fertility is still very high, with enormous propagule pressure from seeds alone. Viable seeds are protected with two forms of dormancy; morphological dormancy requires additional germination cues in order to break after seasonal changes break physiological dormancy., (© 2024 The Authors. Plant Biology published by John Wiley & Sons Ltd on behalf of German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)

The human immunodeficiency virus (HIV)-encoded accessory protein Nef enhances pathogenicity by reducing major histocompatibility complex I (MHC-I) cell surface expression, protecting HIV-infected cells from immune recognition. Nef-dependent downmodulation of MHC-I can be reversed by subnanomolar concentrations of concanamycin A ( 1 ), a well-known inhibitor of vacuolar ATPase, at concentrations below those that interfere with lysosomal acidification or degradation. We conducted a structure-activity relationship study that assessed 76 compounds for Nef inhibition, 24 and 72 h viability, and lysosomal neutralization in Nef-expressing primary T cells. This analysis demonstrated that the most potent compounds were natural concanamycins and their derivatives. Comparison against a set of new, semisynthetic concanamycins revealed that substituents at C-8 and acylation of C-9 significantly affected Nef potency, target cell viability, and lysosomal neutralization. These findings provide important progress toward understanding the mechanism of action of these compounds and the identification of an advanced lead anti-HIV Nef inhibitory compound.

Aqueous zinc electrolytes offer the potential for cheaper rechargeable batteries due to their safe compatibility with the high capacity metal anode; yet, they are stymied by irregular zinc deposition and consequent dendrite growth. Suppressing dendrite formation by tailoring the electrolyte is a proven approach from lithium batteries; yet, the underlying mechanistic understanding that guides such tailoring does not necessarily directly translate from one system to the other. Here, it is shown that the electrostatic shielding mechanism, a fundamental concept in electrolyte engineering for stable metal anodes, has different consequences for the plating morphology in aqueous zinc batteries. Operando electrochemical transmission electron microscopy is used to directly observe the zinc nucleation and growth under different electrolyte compositions and reveal that electrostatic shielding additive suppresses dendrites by inhibiting secondary zinc nucleation along the (100) edges of existing primary deposits and encouraging preferential deposition on the (002) faces, leading to a dense and block-like zinc morphology. The strong influence of the crystallography of Zn on the electrostatic shielding mechanism is further confirmed with Zn||Ti cells and density functional theory modeling. This work demonstrates the importance of considering the unique aspects of the aqueous zinc battery system when using concepts from other battery chemistries., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

The narrow electrochemical stability window, deleterious side reactions, and zinc dendrites prevent the use of aqueous zinc-ion batteries. Here, aqueous "soggy-sand" electrolytes (synergistic electrolyte-insulator dispersions) are developed for achieving high-voltage Zn-ion batteries. How these electrolytes bring a unique combination of benefits, synergizing the advantages of solid and liquid electrolytes is revealed. The oxide additions adsorb water molecules and trap anions, causing a network of space charge layers with increased Zn 2+ transference number and reduced interfacial resistance. They beneficially modify the hydrogen bond network and solvation structures, thereby influencing the mechanical and electrochemical properties, and causing the Mn 2+ in the solution to be oxidized. As a result, the best performing Al 2 O 3 -based "soggy-sand" electrolyte exhibits a long life of 2500 h in Zn||Zn cells. Furthermore, it increases the charging cut-off voltage for Zn/MnO 2 cells to 2 V, achieving higher specific capacities. Even with amass loading of 10 mg MnO2 cm -2 , it yields a promising specific capacity of 189 mAh g -1 at 1 A g -1 after 500 cycles. The concept of "soggy-sand" chemistry provides a new approach to design powerful and universal electrolytes for aqueous batteries., (© 2023 Wiley-VCH GmbH.)

Electrochemical CO 2 reduction (ECR) is recognized as a sustainable and promising approach for the production of high-value chemicals. To facilitate widespread application of this technology, the design and construction of efficient cathodic electrocatalysts is critically important. Here we report the synthesis of atomically dispersed manganese on nitrogen-doped porous carbon (Mn SAs/NC) using a facile and scalable annealing method for catalyzing the ECR reaction. The as-obtained Mn SAs/NC delivers high activity and selectivity toward CO formation with a faradaic efficiency of 80.5±0.6%, over 5 times that of bare NC. The high activity is preserved even after 10 h of continuous polarization. The catalytic properties of our cost-effective Mn SAs/NC catalyst are readily tuned by regulating the nitrogen configurations and the percentage of Mn SAs via modulation of the nitrogen precursor and the thermal treatment conditions., (© 2022 Wiley-VCH GmbH.)

Many challenges in the electrochemical synthesis of ammonia have been recognized with most effort focused on delineating false positives resulting from unidentified sources of nitrogen. However, the influence of oxidizing anolytes on the crossover and oxidization of ammonium during the electrolysis reaction remains unexplored. Here it is reported that the use of analytes containing halide ions (Cl - and Br - ) can rapidly convert the ammonium into N 2 , which further intensifies the crossover of ammonium. Moreover, the extent of migration and oxidation of ammonium is found to be closely associated with external factors, such as applied potentials and the concentration of Cl - . These findings demonstrate the profound impact of oxidizing anolytes on the electrochemical synthesis of ammonia. Based on these results, many prior reported ammonia yield rates are calibrated. This work emphasizes the significance of avoiding selection of anolytes that can oxidize ammonium, which is believed to promote further progress in electrochemical nitrogen fixation., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

We report significantly enhanced electrochemical CO 2 reduction (ECR) to C 2 H 4 by tuning the interface of a metal oxide composite (CuO x /HfO 2 ), enabling a C 2 H 4 faradaic efficiency as high as 62.6 ± 1.3% at 300 mA cm -2 , in contrast to only 11.6 ± 1.6% over pure CuO. Collective knowledge from multiple control experiments, density functional theory calculations, and operando Raman study reveals that the CuO x -HfO 2 interface greatly strengthens CO 2 adsorption and the binding of *CO for further C-C coupling to yield C 2 H 4 .

Demand for ammonia continues to increase to sustain the growing global population. The direct electrochemical N 2 reduction reaction (NRR) powered by renewable electricity offers a promising carbon-neutral and sustainable strategy for manufacturing NH 3 , yet achieving this remains a grand challenge. Here, we report a synergistic strategy to promote ambient NRR for ammonia production by tuning the Te vacancies (V Te ) and surface hydrophobicity of two-dimensional TaTe 2 nanosheets. Remarkable NH 3 faradic efficiency of up to 32.2% is attained at a mild overpotential, which is largely maintained even after 100 h of consecutive electrolysis. Isotopic labeling validates that the N atoms of formed NH 4 + originate from N 2 . In situ X-ray diffraction indicates preservation of the crystalline structure of TaTe 2 during NRR. Further density functional theory calculations reveal that the potential-determining step (PDS) is ∗NH 2  + (H +  + e - ) → NH 3 on V Te -TaTe 2 compared with that of ∗ + N 2  + (H +  + e - ) → ∗N-NH on TaTe 2 . We identify that the edge plane of TaTe 2 and V Te serve as the main active sites for NRR. The free energy change at PDS on V Te -TaTe 2 is comparable with the values at the top of the NRR volcano plots on various transition metal surfaces., Competing Interests: The authors declare no competing interests., (© 2021 The Author(s).)

A reasonable prediction of infectious diseases' transmission process under different disease control strategies is an important reference point for policy makers. Here we established a dynamic transmission model via Python and realized comprehensive regulation of disease control measures. We classified government interventions into three categories and introduced three parameters as descriptions for the key points in disease control, these being intraregional growth rate, interregional communication rate, and detection rate of infectors. Our simulation predicts the infection by COVID-19 in the UK would be out of control in 73 days without any interventions; at the same time, herd immunity acquisition will begin from the epicentre. After we introduced government interventions, a single intervention is effective in disease control but at huge expense, while combined interventions would be more efficient, among which, enhancing detection number is crucial in the control strategy for COVID-19. In addition, we calculated requirements for the most effective vaccination strategy based on infection numbers in a real situation. Our model was programmed with iterative algorithms, and visualized via cellular automata; it can be applied to similar epidemics in other regions if the basic parameters are inputted, and is able to synthetically mimic the effect of multiple factors in infectious disease control.

MicroRNAs (miRNAs) are a family of small noncoding RNAs that regulate gene expression. Due to their important activity in the fine-tuning of protein translation, abnormal expression of miRNAs has been linked to many human diseases, making the targeting of miRNAs attractive as a novel therapeutic strategy. Accordingly, researchers have been heavily engaged in the discovery of small molecule modulators of miRNAs. With an interest in the identification of new chemical space for targeting miRNAs, we developed a high-throughput screening (HTS) technology, catalytic enzyme-linked click chemistry assay (cat-ELCCA), aimed at the discovery of small molecule ligands for pre-miR-21, a miRNA that is frequently overexpressed in human cancers. From our HTS campaign, we found that natural products, a source of many impactful human medicines, may be a promising source of potential pre-miR-21-selective maturation inhibitors. Herein we describe our first efforts in natural product inhibitor discovery leading to the identification of a depsipeptide class of natural products as RNA-binding inhibitors of Dicer-mediated miRNA processing., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.

Nef is an HIV-encoded accessory protein that enhances pathogenicity by down-regulating major histocompatibility class I (MHC-I) expression to evade killing by cytotoxic T lymphocytes (CTLs). A potent Nef inhibitor that restores MHC-I is needed to promote immune-mediated clearance of HIV-infected cells. We discovered that the plecomacrolide family of natural products restored MHC-I to the surface of Nef-expressing primary cells with variable potency. Concanamycin A (CMA) counteracted Nef at subnanomolar concentrations that did not interfere with lysosomal acidification or degradation and were nontoxic in primary cell cultures. CMA specifically reversed Nef-mediated down-regulation of MHC-I, but not CD4, and cells treated with CMA showed reduced formation of the Nef:MHC-I:AP-1 complex required for MHC-I down-regulation. CMA restored expression of diverse allotypes of MHC-I in Nef-expressing cells and inhibited Nef alleles from divergent clades of HIV and simian immunodeficiency virus, including from primary patient isolates. Lastly, we found that restoration of MHC-I in HIV-infected cells was accompanied by enhanced CTL-mediated clearance of infected cells comparable to genetic deletion of Nef. Thus, we propose CMA as a lead compound for therapeutic inhibition of Nef to enhance immune-mediated clearance of HIV-infected cells., Competing Interests: Competing interest statement: A provisional patent relating to this study has been filed., (Copyright © 2020 the Author(s). Published by PNAS.)

We report single yttrium sites anchored on carbon-coated TiO 2 for efficient and stable electrocatalytic N 2 fixation, delivering an NH 3 faradaic efficiency exceeding 11.0% and an NH 3 yield rate as high as 6.3 μg NH 3 h -1 mg cat. -1 at low overpotentials, thus surpassing many reported metal electrocatalysts.

The structural transformations of graphene defects have been extensively researched through aberration-corrected transmission electron microscopy (AC-TEM) and theoretical calculations. For a long time, a core concept in understanding the structural evolution of graphene defects has been the Stone-Thrower-Wales (STW)-type bond rotation. In this study, we show that undercoordinated atoms induce bond formation and breaking, with much lower energy barriers than the STW-type bond rotation. We refer to them as mediator atoms due to their mediating role in the breaking and forming of bonds. Here, we report the direct observation of mediator atoms in graphene defect structures using AC-TEM and annular dark-field scanning TEM (ADF-STEM) and explain their catalytic role by tight-binding molecular dynamics (TBMD) simulations and image simulations based on density functional theory (DFT) calculations. The study of mediator atoms will pave a new way for understanding not only defect transformation but also the growth mechanisms in two-dimensional materials., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

The commercialization of metal-air batteries requires efficient, low-cost, and stable bifunctional electrocatalysts for reversible electrocatalysis of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The modification of natural coal by heteroatoms such as N and S, or metal oxide species, has been demonstrated to form very promising electrocatalysts for the ORR and OER. However, it remains elusive and underexplored as to how the impurity elements in coal may impact the electrocatalytic properties of coal-derived catalysts. Herein, we explore the influence of the presence of various trace metals that are notable impurities in coal, including Al, Si, Ca, K, Fe, Mg, Co, Mn, Ni, and Cu, on the electrochemical performance of the prepared catalysts. The constructed Zn-air batteries are further shown to be able to power green LED lights for more than 80 h. The charge-discharge polarization curves exhibited excellent and durable rechargeability over 500 (ca. 84 h) continuous cycles. The promotional effect of the trace elements is believed to accrue from a combination of electronic structure modification of the active sites, enhancement of the active site density, and formation of a conductive 3-dimensional hierarchical network of carbon nanotubes.

Transmission electron microscopy (TEM) has long been an essential tool for understanding the structure of materials. Over the past couple of decades, this venerable technique has undergone a number of revolutions, such as the development of aberration correction for atomic level imaging, the realization of cryogenic TEM for imaging biological specimens, and new instrumentation permitting the observation of dynamic systems in situ . Research in the latter has rapidly accelerated in recent years, based on a silicon-chip architecture that permits a versatile array of experiments to be performed under the high vacuum of the TEM. Of particular interest is using these silicon chips to enclose fluids safely inside the TEM, allowing us to observe liquid dynamics at the nanoscale. In situ imaging of liquid phase reactions under TEM can greatly enhance our understanding of fundamental processes in fields from electrochemistry to cell biology. Here, we review how in situ TEM experiments of liquids can be performed, with a particular focus on microchip-encapsulated liquid cell TEM. We will cover the basics of the technique, and its strengths and weaknesses with respect to related in situ TEM methods for characterizing liquid systems. We will show how this technique has provided unique insights into nanomaterial synthesis and manipulation, battery science and biological cells. A discussion on the main challenges of the technique, and potential means to mitigate and overcome them, will also be presented., Competing Interests: We declare we have no competing interests., (© 2020 The Authors.)

Bacteria within the digestive tract of adult honey bees are likely to play a key role in the digestion of sugar-rich foods. However, the influence of diet on honey bee gut bacteria is not well understood. During periods of low floral abundance, beekeepers often supplement the natural sources of carbohydrate that honey bees collect, such as nectar, with various forms of carbohydrates such as sucrose (a disaccharide) and invert sugar (a mixture of the monosaccharides glucose and fructose). We compared the effect of these sugar supplements on the relative abundance of bacteria in the gut of bees by feeding bees from a single colony, two natural diets: mānuka honey, a monofloral honey with known antibacterial properties, and a hive diet; and artificial diets of invert sugar, sucrose solution, and sucrose solutions containing synthesised compounds associated with the antibacterial properties of mānuka honey. 16S ribosomal RNA (rRNA)-based sequencing showed that dietary regimes containing mānuka honey, sucrose and invert sugar did not alter the relative abundance of dominant core bacteria after 6 days of being fed these diets. However, sucrose-rich diets increased the relative abundances of three sub-dominant core bacteria, Rhizobiaceae, Acetobacteraceae, and Lactobacillus kunkeei, and decreased the relative abundance of Frischella perrara, all which significantly altered the bacterial composition. Acetogenic bacteria from the Rhizobiaceae and Acetobacteraceae families increased two- to five-fold when bees were fed sucrose. These results suggest that sucrose fuels the proliferation of specific low abundance primary sucrose-feeders, which metabolise sugars into monosaccharides, and then to acetate., Competing Interests: We have the following interests as this study received funding from New Zealand Apples & Pears Inc, Honey New Zealand (International) Limited, seven regional New Zealand Beekeeping clubs, Beeline Apiaries, Arataki Honey, Hawke’s Bay, Galatea Apiaries, and NZ Beeswax Ltd. The invert sugar used in the research was supplied free of charge by Natural Sugars NZ. There are no patents, products in development or marketed products to declare. This does not alter our adherence to the PLOS ONE policies on sharing data and materials.

Breeding systems of plants determine their reliance on pollinators and ability to produce seeds following self-pollination. Self-sterility, where ovules that are penetrated by self-pollen tubes that do not develop into seeds, is usually considered to represent either a system of late-acting self-incompatibility or strong early inbreeding depression. Importantly, it can lead to impaired female function through ovule or seed discounting when stigmas receive mixtures of self and cross pollen, unless cross pollen is able to reach the ovary ahead of self pollen ('prepotency'). Self-sterility associated with ovule penetration by self-pollen tubes appears to be widespread among the Amaryllidaceae. We tested for self-sterility in three Cyrtanthus species - C. contractus, C. ventricosus and C. mackenii - by means of controlled hand-pollination experiments. To determine the growth rates and frequency of ovule penetration by self- versus cross-pollen tubes, we used fluorescence microscopy to examine flowers of C. contractus harvested 24, 48 and 72 h after pollination, in conjunction with a novel method of processing these images digitally. To test the potential for ovule discounting (loss of cross-fertilisation opportunities when ovules are disabled by self-pollination), we pollinated flowers of C. contractus and C. mackenii with mixtures of self- and cross pollen. We recorded full self-sterility for C. contractus and C. ventricosus, and partial self-sterility for C. mackenii. In C. contractus, we found no differences in the growth rates of self- and cross-pollen tubes, nor in the proportions of ovules penetrated by self- and cross-pollen tubes. In this species, seed set was depressed (relative to cross-pollinated controls) when flowers received a mixture of self and cross pollen, but this was not the case for C. mackenii. These results reveal variation in breeding systems among Cyrtanthus species and highlight the potential for gender conflict in self-sterile species in which ovules are penetrated and disabled by pollen tubes from self pollen., (© 2019 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.)

Platinum atomic layers grown on graphene were investigated by atomic resolution transmission electron microscopy (TEM). These TEM images reveal the epitaxial relationship between the atomically thin platinum layers and graphene, with two optimal epitaxies observed. The energetics of these epitaxies influences the grain structure of the platinum film, facilitating grain growth via in-plane rotation and assimilation of neighbor grains, rather than grain coarsening from the movement of grain boundaries. This growth process was enabled due to the availability of several possible low-energy intermediate states for the rotating grains, the Pt-Gr epitaxies, which are minima in surface energy, and coincident site lattice grain boundaries, which are minima in grain boundary energy. Density functional theory calculations reveal a complex interplay of considerations for minimizing the platinum grain energy, with free platinum edges also having an effect on the relative energetics. We thus find that the platinum atomic layer grains undergo significant reorientation to minimize interface energy ( via epitaxy), grain boundary energy ( via low-energy orientations), and free edge energy. These results will be important for the design of two-dimensional graphene-supported platinum catalysts and obtaining large-area uniform platinum atomic layer films and also provide fundamental experimental insight into the growth of heteroepitaxial thin films.

In living cells, redox chains rely on nanoconfinement using tiny enclosures, such as the mitochondrial matrix or chloroplast stroma, to concentrate enzymes and limit distances that nicotinamide cofactors and other metabolites must diffuse. In a chemical analogue exploiting this principle, nicotinamide adenine dinucleotide phosphate (NADPH) and NADP + are cycled rapidly between ferredoxin-NADP + reductase and a second enzyme-the pairs being juxtaposed within the 5-100 nm scale pores of an indium tin oxide electrode. The resulting electrode material, denoted (FNR+E2)@ITO/support, can drive and exploit a potentially large number of enzyme-catalysed reactions., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Myeloperoxidase (MPO) is a highly abundant protein within the neutrophil that is associated with lipoprotein oxidation, and increased plasma MPO levels are correlated with poor prognosis after myocardial infarct. Thus, MPO inhibitors have been developed for the treatment of heart failure and acute coronary syndrome in humans. 2-(6-(5-Chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide PF-06282999 is a recently described selective small molecule mechanism-based inactivator of MPO. Here, utilizing PF-06282999, we investigated the role of MPO to regulate atherosclerotic lesion formation and composition in the Ldlr-/- mouse model of atherosclerosis. Though MPO inhibition did not affect lesion area in Ldlr-/- mice fed a Western diet, reduced necrotic core area was observed in aortic root sections after MPO inhibitor treatment. MPO inhibition did not alter macrophage content in and leukocyte homing to atherosclerotic plaques. To assess non-invasive monitoring of plaque inflammation, [18F]-Fluoro-deoxy-glucose (FDG) was administered to Ldlr-/- mice with established atherosclerosis that had been treated with clinically relevant doses of PF-06282999, and reduced FDG signal was observed in animals treated with a dose of PF-06282999 that corresponded with reduced necrotic core area. These data suggest that MPO inhibition does not alter atherosclerotic plaque area or leukocyte homing, but rather alters the inflammatory tone of atherosclerotic lesions; thus, MPO inhibition could have utility to promote atherosclerotic lesion stabilization and prevent atherosclerotic plaque rupture., Competing Interests: The authors are employees of Pfizer, Inc. and own Pfizer stock. The studies were funded by Pfizer, Inc. The compound described in this manuscript is patented under US patent 8,835,449. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials.

Replacement of Hg with non-toxic Au based catalysts for industrial hydrochlorination of acetylene to vinyl chloride is urgently required. However Au catalysts suffer from progressive deactivation caused by auto-reduction of Au(I) and Au(III) active sites and irreversible aggregation of Au(0) inactive sites. Here we show from synchrotron X-ray absorption, STEM imaging and DFT modelling that the availability of ceria(110) surface renders Au(0)/Au(I) as active pairs. Thus, Au(0) is directly involved in the catalysis. Owing to the strong mediating properties of Ce(IV)/Ce(III) with one electron complementary redox coupling reactions, the ceria promotion to Au catalysts gives enhanced activity and stability. Total pre-reduction of Au species to inactive Au nanoparticles of Au/CeO 2 &AC when placed in a C 2 H 2 /HCl stream can also rapidly rejuvenate. This is dramatically achieved by re-dispersing the Au particles to Au(0) atoms and oxidising to Au(I) entities, whereas Au/AC does not recover from the deactivation.

The presence of extended defects or nanopores in two-dimensional (2D) materials can change the electronic, magnetic and barrier membrane properties of the materials. However, the large number of possible lattice isomers of nanopores makes their quantitative study a seemingly intractable problem, confounding the interpretation of experimental and simulated data. Here we formulate a solution to this isomer cataloguing problem (ICP), combining electronic-structure calculations, kinetic Monte Carlo simulations, and chemical graph theory, to generate a catalogue of unique, most-probable isomers of 2D lattice nanopores. The results demonstrate remarkable agreement with precise nanopore shapes observed experimentally in graphene and show that the thermodynamic stability of a nanopore is distinct from its kinetic stability. Triangular nanopores prevalent in hexagonal boron nitride are also predicted, extending this approach to other 2D lattices. The proposed method should accelerate the application of nanoporous 2D materials by establishing specific links between experiment and theory/simulations, and by providing a much-needed connection between molecular design and fabrication.

Premise of the Study: Microsatellite markers were developed for New Zealand species of Corybas (Orchidaceae) to investigate population genetics and species delimitation., Methods and Results: From sequencing a total genomic DNA library (using Illumina MiSeq), we developed 22 microsatellite markers for C. obscurus . The di- and trinucleotide repeat loci were initially trialed on individuals representing seven Corybas taxa ( C . "rimutaka," C. confusus , C. hypogaeus , C. macranthus , C. obscurus , C. trilobus , and C. walliae ) and had one to eight alleles per locus. Twelve polymorphic markers were further tested on six Corybas populations from three of the seven taxa ( C. obscurus , C . "rimutaka," and C. trilobus ). Observed and expected heterozygosities ranged from 0-1 and 0-0.859, respectively. The utility of these 12 loci was further validated in five related Corybas species ( C. hypogaeus , C. obscurus , C. vitreus , C. walliae , and C . "rimutaka"; 38 individuals) representing populations from across the North and South Islands. The average value for genetic diversity among populations ( F ST ) of 0.439 shows differentiation among species., Conclusions: These markers will be useful for future studies aimed at delimiting species boundaries and examining the genetic diversity of the New Zealand Corybas species.

Herein, we report the characterization and antimicrobial activity of a previously unreported jadomycin (1) obtained from a culture of S. venezuelae ISP5230 with L-ornithine (Orn). 1 arises from the rearrangement of a putative five-membered ring containing jadomycin incorporating Orn, whereby intramolecular attack of the E-ring carbonyl from the δ-NH 2 group of the Orn side chain results in collapse of the oxazolone ring and formation of a stable six-membered lactam. This rearrangement produces a jadomycin with a 3a hemiaminal position that is susceptible to solvolysis. A structure-activity relationship is discussed based on the antimicrobial activity of 1 compared to previously reported jadomycins, providing evidence that the presence of a 3a hemiaminal enhances activity against Gram-positive bacteria. Additionally, assays to quantify reactive oxygen species (ROS) generation and cell viability were performed using a series of nine jadomycins. Compound 1 was found to produce the highest ROS activity and to possess the greatest cytotoxicity against MDA-MB-231 breast cancer cells.

Discovering highly efficient, environmentally friendly, and low-cost exfoliating media that can both disperse and protect black phosphorus (BP) remains a challenge. Herein, we demonstrate such a new molecule, N,N'-dimethylpropyleneurea (DMPU), for effective exfoliation and dispersion of two-dimensional BP nanosheets. A very high exfoliation efficiency of up to 16% was achieved in DMPU, significantly surpassing other good solvents. Exfoliated flakes are free from structural disorder or oxidation. Nanosheets retain high stability in DMPU even after addition of 25 vol% of common solvents. The solvation shell appears to protect the nanosheets from reacting with water and air, more remarkably than the best solvent N-cyclohexyl-2-pyrrolidone reported so far. Molecular dynamics simulations of the exfoliation process show that DMPU is among the effective solvents, although energetically it does not appear as favorable as some other amides. We also demonstrate that our exfoliated BP nanosheets exhibit excellent antimicrobial activities against both Escherichia coli and Staphylococcus aureus, outperforming other common two-dimensional materials of graphene and MoS2, suggesting promise in biomedical applications.

We demonstrate that silanization can control the adhesion of nanostructures to the SiN windows compatible with liquid-cell transmission electron microscopy (LC-TEM). Formation of an (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayer on a SiN window, producing a surface decorated with amino groups, permits strong adhesion of Au nanoparticles to the window. Many of these nanoparticles remain static, undergoing minimal translation or rotation during LC-TEM up to high electron beam current densities due to the strong interaction between the APTES amino group and Au. We then use this technique to perform a direct comparative LC-TEM study on the behavior of ligand and nonligand-coated Au nanoparticles in a Au growth solution. While the ligand coated nanoparticles remain consistent even under high electron beam current densities, the naked nanoparticles acted as sites for secondary Au nucleation. These nucleated particles decorated the parent nanoparticle surface, forming consecutive monolayer assemblies of ∼2 nm diameter nanoparticles, which sinter into the parent particle when the electron beam was shut off. This method for facile immobilization of nanostructures for LC-TEM study will permit more sophisticated and controlled in situ experiments into the properties of solid-liquid interfaces in the future.

The amphiphilic siderophore imaqobactin was isolated from the Arctic bacterium Variovorax sp. RKJM285, a strain isolated from marine sediment collected from an inlet near Clyde River, Nunavut, Canada. The 2D structure of imaqobactin was determined by a combination of LC-HRMS, MS/MS, and NMR spectroscopic methods. The absolute configuration of the depsipeptide core was determined by Marfey's analysis, and the relative configuration of the 4,7-diamino-3-hydroxy-2-methylheptanoic acid moiety was determined by NOESY and selective NOE experiments. The photoreductive properties of imaqobactin were tested and are discussed. Initial tests for antimicrobial and cytotoxic activity of imaqobactin were also performed, identifying moderate antimicrobial activity.

Polyketide synthase (PKS) derived natural products are biosynthesized by head-to-tail addition of acetate and malonate extender units resulting in linear extended-polyketide chains. Despite the well-documented structural diversity associated with PKS-derived natural products, C-C chain branching deviating from the usual linear pattern is relatively rare. Herein, type-II PKS angucyclic natural products containing a hemiaminal functionality were identified and proposed as the parent of a series of C-C-branched analogues. These C-C linked acetate or pyruvate branching units were located at the α-positions on the extended polyketide chains of jadomycins incorporating 3- and 4-aminomethylbenzoic acids. Labeling studies utilizing [1- 13 C]-d-glucose provided mechanistic evidence that the C-C bond formation occurred as a result of a previously unidentified post-PKS processing, additional to the enzymes encoded within the biosynthetic gene cluster. Selected compounds were evaluated in cytotoxic or antimicrobial assays.

Designing highly selective and energy-efficient electrocatalysts to minimize the competitive hydrogen evolution reaction in the electrochemical reduction of aqueous CO 2 remains a challenge. In this study, we report that doping Pd with a small amount of Te could selectively convert CO 2 to CO with a low overpotential. The PdTe/few-layer graphene (FLG) catalyst with a Pd/Te molar ratio of 1 : 0.05 displayed a maximum CO faradaic efficiency of about 90% at -0.8 V ( vs. a reversible hydrogen electrode, RHE), CO partial current density of 4.4 mA cm -2 , and CO formation turnover frequency of 0.14 s -1 at -1.0 V ( vs. a RHE), which were 3.7-, 4.3-, and 10-fold higher than those of a Pd/FLG catalyst, respectively. Density functional calculations showed that Te adatoms preferentially bind at the terrace sites of Pd, thereby suppressing undesired hydrogen evolution, whereas CO 2 adsorption and activation occurred on the high index sites of Pd to produce CO.

Jadomycins are natural products that kill drug-sensitive and multidrug-resistant (MDR) breast cancer cells. To date, the cytotoxic activity of jadomycins has never been tested in MDR breast cancer cells that are also triple negative. Additionally, there is only a rudimentary understanding of how jadomycins cause cancer cell death, which includes the induction of intracellular reactive oxygen species (ROS). We first created a paclitaxel-resistant, triple-negative breast cancer cell line [paclitaxel-resistant MDA-MB-231 breast cancer cells (231-TXL)] from drug-sensitive control MDA-MB-231 cells (231-CON). Using thiazolyl blue methyltetrazolium bromide cell viability-measuring assays, jadomycins B, S, and F were found to be equipotent in drug-sensitive 231-CON and MDR 231-TXL cells; and using ROS-detecting assays, these jadomycins were determined to increase ROS activity in both cell lines by up to 7.3-fold. Jadomycins caused DNA double-strand breaks in 231-CON and 231-TXL cells as measured by γ H2AX Western blotting. Coincubation with the antioxidant N -acetyl cysteine or pro-oxidant auranofin did not affect jadomycin-mediated DNA damage. Jadomycins induced apoptosis in 231-CON and 231-TXL cells as measured by annexin V affinity assays, a process that was retained when ROS were inhibited. This indicated that jadomycins are capable of inducing MDA-MB-231 apoptotic cell death independently of ROS activity. Using quantitative polymerase chain reaction, Western blotting, and direct topoisomerase inhibition assays, it was determined that jadomycins inhibit type II topoisomerases and that jadomycins B and F selectively poison topoisomerase II β We therefore propose novel mechanisms through which jadomycins induce breast cancer cell death independently of ROS activity, through inhibition or poisoning of type II topoisomerases and the induction of DNA damage and apoptosis., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)