Developing efficient and low‐cost electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance to many chemical and energy transformation technologies. The diversity and ...flexibility of metal oxides offer numerous degrees of freedom for enhancing catalytic activity by tailoring their physicochemical properties, but the active site of current metal oxides for OER is still limited to either metal ions or lattice oxygen. Here, a new complex oxide with unique hexagonal structure consisting of one honeycomb‐like network, Ba4Sr4(Co0.8Fe0.2)4O15 (hex‐BSCF), is reported, demonstrating ultrahigh OER activity because both the tetrahedral Co ions and the octahedral oxygen ions on the surface are active, as confirmed by combined X‐ray absorption spectroscopy analysis and theoretical calculations. The bulk hex‐BSCF material synthesized by the facile and scalable sol–gel method achieves 10 mA cm−2 at a low overpotential of only 340 mV (and small Tafel slope of 47 mV dec−1) in 0.1 m KOH, surpassing most metal oxides ever reported for OER, while maintaining excellent durability. This study opens up a new avenue to dramatically enhancing catalytic activity of metal oxides for other applications through rational design of structures with multiple active sites.
A new complex oxide with unique hexagonal structure consisting of one ordered (Co/Fe)O15 cluster, Ba4Sr4(Co0.8Fe0.2)4O15 (hex‐BSCF), is reported to show ultrahigh oxygen evolution reaction (OER) electrocatalytic activity because both the tetrahedral Co ions and the octahedral oxygen ions on the surface are active, as confirmed by combined X‐ray absorption spectroscopy analysis and theoretical calculations.
Four hexachlorosubphthalocyanines SubPcCl6‐X bearing different axial substituents (X) have been synthesized for use as novel electron acceptors in solution‐processed bulk‐heterojunction organic solar ...cells. Subphthalocyanines are aromatic chromophoric molecules with cone‐shaped structure, good solution processability, intense optical absorption in the visible spectral region, appropriate electron mobilities, and tunable energy levels. Solar cells with subphthalocyanines as the electron acceptor and PTB7‐Th as the electron donor exhibit a power conversion efficiency up to 4 % and an external quantum efficiency approaching 60 % due to significant contributions from both the electron donor and the electron acceptor to the photocurrent, indicating a promising prospect of non‐fullerene acceptors based on subphthalocyanines and structurally related systems.
A promising prospect: Subphthalocyanines SubPcCl6‐X bearing different axial substituents (X) are presented as novel electron acceptors in bulk‐heterojunction organic solar cells. Power conversion efficiencies up to 4 % were achieved due to photocurrent contribution from both electron donor and electron acceptor, which makes non‐fullerene acceptors based on SubPcs and structurally related systems a promising synthesis goal.
Social distancing to combat the COVID-19 pandemic has led to widespread reductions in air pollutant emissions. Quantifying these changes requires a business-as-usual counterfactual that accounts for ...the synoptic and seasonal variability of air pollutants. We use a machine learning algorithm driven by information from the NASA GEOS-CF model to assess changes in nitrogen dioxide (NO.sub.2) and ozone (O.sub.3) at 5756 observation sites in 46 countries from January through June 2020. Reductions in NO.sub.2 coincide with the timing and intensity of COVID-19 restrictions, ranging from 60 % in severely affected cities (e.g., Wuhan, Milan) to little change (e.g., Rio de Janeiro, Taipei). On average, NO.sub.2 concentrations were 18 (13-23) % lower than business as usual from February 2020 onward. China experienced the earliest and steepest decline, but concentrations since April have mostly recovered and remained within 5 % of the business-as-usual estimate. NO.sub.2 reductions in Europe and the US have been more gradual, with a halting recovery starting in late March. We estimate that the global NO.sub.x (NO + NO.sub.2) emission reduction during the first 6 months of 2020 amounted to 3.1 (2.6-3.6) TgN, equivalent to 5.5 (4.7-6.4) % of the annual anthropogenic total. The response of surface O.sub.3 is complicated by competing influences of nonlinear atmospheric chemistry. While surface O.sub.3 increased by up to 50 % in some locations, we find the overall net impact on daily average O.sub.3 between February-June 2020 to be small. However, our analysis indicates a flattening of the O.sub.3 diurnal cycle with an increase in nighttime ozone due to reduced titration and a decrease in daytime ozone, reflecting a reduction in photochemical production.
ABSTRACT
We study the global star formation rate (SFR) versus stellar mass (M*) correlation, and the spatially resolved SFR surface density (ΣSFR) versus stellar mass surface density (Σ*) ...correlation, in a sample of ∼2000 galaxies from the MaNGA MPL-5 survey. We classify galaxies and spatially resolved areas into star forming and retired according to their ionization processes. We confirm the existence of a star-forming main sequence (SFMS) for galaxies and spatially resolved areas, and show that they have the same nature, with the global as a consequence of the local one. The latter presents a bend below a limit Σ* value, ≈3 × 107 M$\odot$ kpc−2, which is not physical. Using only star-forming areas (SFAs) above this limit, a slope and a scatter of ≈1 and ≈0.27 dex are determined. The retired galaxies/areas strongly segregate from their respective SFMSs, by ∼−1.5 dex on average. We explore how the global/local SFMSs depend on galaxy morphology, finding that for star-forming galaxies and SFAs, there is a trend to lower values of star formation activity with earlier morphological types, which is more pronounced for the local SFMS. The morphology not only affects the global SFR due to the diminish of SFAs with earlier types, but also affects the local SF process. Our results suggest that the local SF at all radii is established by some universal mechanism partially modulated by morphology. Morphology seems to be connected to the slow aging and sharp decline of the SF process, and on its own it may depend on other properties as the environment.
The field of organic photovoltaics (OPV) represents one of the most promising technological areas. Porphyrins and phthalocyanines are perfectly suited for their integration in light energy conversion ...systems. These colored macrocycles exhibit very attractive physical properties, particularly very high extinction coefficients in the visible and near IR regions, where the maximum of the solar photon flux occurs, that is necessary for efficient photon harvesting, besides a rich redox chemistry, as well as photoinduced electron transfer and semiconducting capabilities.
Porphyrins and phthalocyanines are colored macrocycles exhibiting very high extinction coefficients in the visible and near IR regions, where the maximum of the solar photon flux occurs, that is basic for efficient photon harvesting.
•The remediation of two types of soils polluted with As, Cd, Cr, Pb and/or Zn was assessed using nZVI.•The nanoremediation of single- and multi-metal(loid) polluted soils was compared.•Metal(loid) ...characteristics and soil properties affect the effectiveness of nanoremediation.•The presence of several metal(loid)s could limit the effectiveness of nZVI.
The effectiveness of single- and multi-metal(loid) immobilization of As, Cd, Cr, Pb and Zn using different doses of nanoscale zero-valent iron (nZVI) was evaluated and compared in two different soils, a calcareous and an acidic one. The effectiveness of nZVI to immobilize metal(loid)s in soil strongly depended on the metal characteristics, soil properties, dose of nZVI and presence of other metal(loid)s. In the case of single contamination, this nanoremediation strategy was effective for all of the metal(loid)s studied except for Cd. When comparing the two soils, anionic metal(loid)s (As and Cr) were more easily retained in acidic soil, whereas cationic metal(loid)s (Cd, Pb and Zn), were immobilized more in calcareous soil. In multi-metal(loid) contaminated soils, the presence of several metal(loid)s affected their immobilization, which was probably due to the competitive phenomenon between metal(loid) ions, which can reduce their sorption or produce synergistic effects. At 10% of nZVI, As, Cr and Pb availability decreased more than 82%, for Zn it ranged between 31 and 75% and for Cd between 13 and 42%. Thus, the application of nZVI can be a useful strategy to immobilize As, Cr, Pb and Zn in calcareous or acidic soils in both single- or multi-metal(loid) contamination conditions.
Large π‐conjugated systems are key in the area of molecular materials. Herein, we prepare via AuI‐catalyzed cyclization a series of fully π‐conjugated anthracene‐fused oligo‐BODIPYs. Their structural ...and optoelectronic properties were studied by several techniques, ranging from X‐ray, UV/Vis, and cyclic voltammetry to transient absorption spectroscopy. As a complement, their electronic structures were explored by means of Density Functional Theory (DFT) calculations. Depending on the size and shape of the π‐conjugated skeleton, unique features—such as face‐to‐face supramolecular organization, NIR absorption and fluorescence as well as strong electron accepting character—were noted. All in all, the aforementioned features render them valuable for technological applications.
AuI‐catalyzed cyclization has been used to prepare a series of fully π‐conjugated anthracene‐fused oligo‐BODIPYs. The size and shape of the π‐conjugated skeleton determines the unique features of the compounds—such as their face‐to‐face supramolecular organization, NIR absorption and fluorescence as well as strong electron accepting character.
A battery of biomarkers was evaluated on Ruditapes philippinarum exposed during 14 days to caffeine, ibuprofen, carbamazepine and novobiocin (0.1, 1, 5, 10, 15, and 50µgL−1). The battery included ...general stress (lysosomal membrane stability – LMS) analysed in the hemolymph, and biochemical biomarkers analysed in digestive gland tissues including: biomarkers of phase I (etoxyresorufin O-deethylase – EROD, dibenzylfluorescein dealkylase – DBF), phase II (gluthathione-S-transferase – GST), oxidative stress (gluthathione reductase – GR, gluthathione peroxidase – GPX, lipid peroxidation – LPO), neurotoxicity (acetylcholinesterase activity – AChE), and genotoxicity (DNA damage). Pharmaceuticals tested induced the sublethal responses (even at the environmental range 0.1µgL−1). At this low concentration; caffeine, ibuprofen and carbamazepine decreased the LMS significantly compared with controls (p<0.05). The four compounds induced significantly the detoxification metabolism and oxidative stress (p<0.05). Neurotoxicity was noticed in clams exposed to caffeine and carbamazepine (p<0.05). Ibuprofen, carbamazepine and novobiocin produced genotoxic effects (p<0.05). Results from this research validate the use of biomarkers when assessing the effects of pharmaceuticals within a marine environmental risk assessment framework, using as a laboratory bioassay model the species R. philippinarum.
•Pharmaceuticals reduced the lysosomal membrane stability at the end of the assay.•Selected pharmaceutical induced detoxification pathways in clams.•Caffeine and carbamazepine produce neurotoxic effects.•Environmental concentrations of pharmaceuticals produce changes in biomarkers studied.•Battery of biomarkers was suitable for pharmaceutical toxicity assessment.
DNA barcoding has been used extensively to solve taxonomic questions and identify new species. Neotropical fishes are found in a wide variety of shapes and sizes, with a large number of species yet ...to be described, many of which are very difficult to identify. Characidae is the most species-rich family of the Characiformes, and many of its genera are affected by taxonomic uncertainties, including the widely-distributed, species-rich genus Astyanax. In this study, we present an extensive analysis of Astyanax covering almost its entire area of occurrence, based on DNA barcoding. The use of different approaches (ABGD, GMYC and BIN) to the clustering of the sequences revealed ample consistency in the results obtained by the initial cutoff value of 2% divergence for putative species in the Neighbor-Joining analysis using the Kimura-2-parameter model. The results indicate the existence of five Astyanax lineages. Some groups, such as that composed by the trans-Andean forms, are mostly composed of well-defined species, and in others a number of nominal species are clustered together, hampering the delimitation of species, which in many cases proved impossible. The results confirm the extreme complexity of the systematics of the genus Astyanax and show that DNA barcoding can be an useful tool to address these complexes questions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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