Janus icosahedral particles: amorphization driven by three-dimensional atomic misfit and edge dislocation compensation

Icosahedral nanoparticles composed of fivefold twinned tetrahedra have broad applications. The strain relief mechanism and angular deficiency in icosahedral multiply twinned particles are poorly understood in three dimensions. Here, we resolved the three-dimensional atomic structures of Janus icosahedral nanoparticles using atomic resolution electron tomography. A geometrically fivefold face consistently corresponds to a less ordered face like two hemispheres. We quantify rich structural variety of icosahedra including bond orientation order, bond length, strain tensor; and packing efficiency, atom number, solid angle of each tetrahedron. These structural characteristics exhibit two-sided distribution. Edge dislocations near the axial atoms and small disordered domains fill the angular deficiency. Our findings provide new insights how the fivefold symmetry can be compensated and the geometrically-necessary internal strains relived in multiply twinned particles.Comment: 30 pages, 5 figure

Spatial variability of δ18O and δ2H in North Pacific and Arctic Oceans surface seawater

This study presents new observations of stable isotopic composition (δ18O, δ2H and deuterium excess) in surface waters of the North Pacific and Arctic Oceans that were collected during the sixth Chinese National Arctic Research Expedition (CHINARE) from mid-summer to early autumn 2014. Seawater δ18O and δ2H decrease with increasing latitudes from 39°N to 75°N, likely a result of spatial variability in evaporation/precipitation processes. This explanation is further confirmed by comparing the δ18O–δ2H relationship of seawater with that of precipitation. However, effects of freshwater inputs on seawater stable isotopic composition are also identified at 30°N–39°N. Furthermore, we find a non-significant relationship between the isotopic parameters (δ2H and δ18О) and salinity from 73°N northwards in the Arctic Ocean, implying that sea ice melting/formation may have some effect. These results suggest that the isotopic parameters δ2H and δ18О are useful for tracing marine hydrological processes

Seasonal variation of atmospheric elemental carbon aerosols at Zhongshan Station, East Antarctica

Elemental carbon (or black carbon) (EC or BC) aerosols emitted by biomass burning and fossil fuel combustion could cause notable climate forcing. Southern Hemisphere biomass burning emissions have contributed substantially to EC deposition in Antarctica. Here, we present the seasonal variation of EC determined from aerosol samples acquired at Zhongshan Station (ZSS), East Antarctica. The concentration of EC in the atmosphere varied between 0.02 and 257.81 ng·m−3 with a mean value of 44.87±48.92 ng·m−3. The concentration of EC aerosols reached its peak in winter (59.04 ng·m−3) and was lowest (27.26 ng·m−3) in summer. Back trajectory analysis showed that biomass burning in southern South America was the major source of the EC found at ZSS, although some of it was derived from southern Australia, especially during winter. The 2019–2020 Australian bush fires had some influence on EC deposition at ZSS, especially during 2019, but the contribution diminished in 2020, leaving southern South America as the dominant source of EC

A new operando surface restructuring pathway via ion-pairing of catalyst and electrolyte for water oxidation

The highly efficient and stable electrolysis needs the rational control of the catalytically active interface during the reactions. Here we report a new operando surface restructuring pathway activated by pairing catalyst and electrolyte ions. Using SrCoO3-δ-based perovskites as model catalysts, we unveil the critical role of matching the catalyst properties with the electrolyte conditions in modulating catalyst ion leaching and steering surface restructuring processes toward efficient oxygen evolution reaction catalysis in both pH-neutral and alkaline electrolytes. Our results regarding multiple perovskites show that the catalyst ion leaching is controlled by catalyst ion solubility and anions of the electrolyte. Only when the electrolyte cations are smaller than catalyst's leaching cations, the formation of an outer amorphous shell can be triggered via backfilling electrolyte cations into the cationic vacancy at the catalyst surface under electrochemical polarization. Consequently, the current density of reconstructed SrCoO3-δ is increased by 21 folds compared to the pristine SrCoO3-δ at 1.75 V vs. reversible hydrogen electrode and outperforms the benchmark IrO2 by 2.1 folds and most state-of-the-art electrocatalysts in the pH-neutral electrolyte. Our work could be a starting point to rationally control the electrocatalyst surface restructuring via matching the compositional chemistry of the catalyst with the electrolyte properties

Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels

The Changes of Nutrition Labeling of Packaged Food in Hangzhou in China during 2008∼2010

OBJECTIVE: To understand the changes of the nutrition labeling of packaged food in China two years after the promulgation of the Regulation for Food Nutrition Labeling, which encourages food manufacturers to identify nutrition labeling. METHODS: Investigators copied out the nutrition information panel, nutrition claim and nutrient function claim of packaged food in a supermarket with prepared questionnaire and finished normative judgment in 2008 and 2010. RESULTS: 4693 and 5526 kinds of packaged food were investigated separately. Nutrition information panel, nutrition claim and nutrient function claim were found on the food label of 27.6%, 13.0% and 1.9% of packaged food respectively in 2008, while 35.1%, 7.7% and 2.3% in 2010. The nutrition information panel which labeled energy, protein, fat, carbohydrate and sodium was 597 (43.8%) and 1661 (85.9%) in 2008 and 2010, only 134 (9.8%) and 985 (51.0%) nutrition information panel were totally normalized. Nutrition claim and nutrient function claim focused on vitamin, mineral and dietary fiber. The total qualified proportions for nutrition claim were increased significantly for most of the nutrients, except for cholesterol. There were 6 (6.4%) and 5 (3.9%) nutrient function claims with hinting of therapeutic effects on diseases separately. CONCLUSION: Although the voluntary regulation remarkably improved the level of normalization for nutrition labeling, its role on the prevalence was minus. It's imperative to enforce nutrition labeling for not only China but also other countries, and furthermore, health education on nutrition labeling should be initiated to support the policy

Ancient marine sediment DNA reveals diatom transition in Antarctica

Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles

Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels

Fe and the other trace elements in a shallow ice core, East Antarctica

This dataset is presented the concentrations of dissolved Fe, Cr, and total dissoved Fe, La, S in a shallow ice core, which was drilled at Summit, East Antarctica