We report a method for in situ atomic-scale observation of electrochemical delithiation in a working all-solid-state battery using a state-of-the-art chip based in situ transmission electron ...microscopy (TEM) holder and focused ion beam milling to prepare an all-solid-state lithium-ion battery sample. A battery consisting of LiCoO2 cathode, LLZO solid state electrolyte and gold anode was constructed, delithiated and observed in an aberration corrected scanning transmission electron microscope at atomic scale. We found that the pristine single crystal LiCoO2 became nanosized polycrystal connected by coherent twin boundaries and antiphase domain boundaries after high voltage delithiation. This is different from liquid electrolyte batteries, where a series of phase transitions take place at LiCoO2 cathode during delithiation. Both grain boundaries become more energy favorable along with extraction of lithium ions through theoretical calculation. We also proposed a lithium migration pathway before and after polycrystallization. This new methodology could stimulate atomic scale in situ scanning/TEM studies of battery materials and provide important mechanistic insight for designing better all-solid-state battery.
Graphene of thickness a few atomic layers has been grown in Ni/a-C bilayers at temperatures as low as 300 °C by Ni-induced crystallization of the amorphous carbon (a-C) in high vacuum. The mechanism ...of such very low-temperature growth of graphene has been investigated by a combinatorial experimental approach including x-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy and transmission electron microscopy. The growth of this few atomic layer thickness graphene has been found to be mediated by a coupled grain-boundary (GB) diffusion/surface diffusion mechanism. GBs in the top Ni sublayer provide fast diffusion paths for C atoms through the Ni layer, as a result of which graphene layers form above the Ni. The revealed low-temperature growth mechanism of graphene induced by contact with a metal can be applicable in advancing research fields as metal-matrix graphene composites and advanced energy storage devices.
Display omitted
Past vegetation responses to climate change in semi-arid and arid regions are not yet well understood, especially in northeastern China. This study provides new evidence for long-term vegetation ...changes and their possible driving forces in northeastern China's Songnen sandy lands by employing a multiproxy approach applied to well-dated aeolian sand-paleosol sediments. Pollen analyses and data on total organic carbon (TOC) are used to reconstruct paleovegetation dynamics whereas grain size data are used for interpreting independent paleoclimate changes. Results show that Chenopodiaceae and Ephedra plants dominated in a brief early period that was followed by an abrupt transition to Artemisia and Asteraceae plants with the encroachment of dry steppes between 9000 and 7000 cal yr BP. From 7000 to 3200 cal yr BP, Chenopodiaceae plant dominated the region. During the 3200 to 400 cal yr BP interval Ulmus, Salix, and Tribulus abundance increased while Chenopodiaceae abundance decreased. After 400 cal yr BP, Poaceae plants generally expanded and the regional landscape alternated between dry steppe and steppe. In addition, changes in the regional vegetation exhibit 1000 yr periodic oscillations especially during 9000 to 4500 cal yr BP. By comparing these features with regional climate change, we suggest that regional paleovegetation dynamics were linked to East Asia Summer Monsson (EASM) circulation. These findings reveal a pronounced long-term relationship between vegetation and climate change in semi-arid regions worldwide.
•Holocene vegetation and climate were reconstructed for a portion of the Songnen sandy lands.•Dry steppes dominated the Q64C area of Songnen sandy lands.•Vegetation of the region had clear 1000 yr periodic oscillations.•Vegetation appears to vary with geomorphological setting within the Songnen sandy lands.
Perkinsosis, a disease caused by the protist Perkinsus, is responsible for mass mortalities of many molluscan species worldwide. The rapid, early and accurate detection of Perkinsus infection is ...necessary to react to outbreaks, and manage disease transmission. Current methods for diagnosis of Perkinsus spp. are time-consuming or require professional equipment and experienced personnel, rendering them unsuitable for field application. Recombinase polymerase amplification (RPA) assay is a highly sensitive and selective isothermal amplification technique that operates at temperatures of 37-42 °C, requires minimal sample preparation, and is capable of amplifying as low as 1-10 target DNA copies in less than 20 minutes.
We report a novel RPA assay that amplifies the internal transcriber spacer (ITS) region of P. beihaiensis, which, followed by rapid detection of amplicons using a lateral flow (LF) strip, enables easy visualization of results by the naked eye.
The LF-RPA assay successfully amplified P. beihaiensis DNA using a set of primers of 20-25 bp in length. After incubation at 37 °C for 25 min, results were read within 5 min by the naked eye on a lateral flow strip. Our LF-RPA assay was comparably sensitive to qPCR assay, and capable of detecting as few as 26 copies of P. beihaiensis DNA. Cross-amplification occurred with other two Perkinsus species, P. olseni and P. chesapeaki, but not with other potential pathogen taxa in culture environments. We compared the performance of LF-RPA, conventional PCR and qPCR assays on 60 oyster samples. While LF-RPA assay results were 86.2% as sensitive, 77.4% as specific, and generally in agreement with those of conventional PCR results, they were more (93.3%) sensitive, (86.7%) specific, and agreed better with qPCR assay results. Future research should focus on developing simple DNA extraction methods that do not require professional laboratories and complicated extraction procedures, to facilitate application of this LF-RPA assay in the field.
Our LF-RPA assay provides a rapid and efficient method for detecting species of Perkinsus. This novel assay has potential to be used in field applications.
Most technologically important electrode materials for lithium-ion batteries are essentially lithium ions plus a transition-metal oxide framework. However, their atomic and electronic structure ...evolution during electrochemical cycling remains poorly understood. Here we report the in situ observation of the three-dimensional structural evolution of the transition-metal oxide framework in an all-solid-state battery. The in situ studies LiNi
Mn
O
from various zone axes reveal the evolution of both atomic and electronic structures during delithiation, which is found due to the migration of oxygen and transition-metal ions. Ordered to disordered structural transition proceeds along the , , directions and inhomogeneous structural evolution along the direction. Uneven extraction of lithium ions leads to localized migration of transition-metal ions and formation of antiphase boundaries. Dislocations facilitate transition-metal ions migration as well. Theoretical calculations suggest that doping of lower valence-state cations effectively stabilize the structure during delithiation and inhibit the formation of boundaries.
•Soil phytoliths can estimate tree cover and separate the forest from grassland.•The ecotone has experienced many expansions and expansions in the Holocene.•East Asian monsoon modulated precipitation ...was the dominant driver.
Robust forecasts of ecological transformations resulting from ongoing and future climate change are urgently needed. Paleoecological records of vegetation dynamics, combined with records of past climate, can contribute to these forecasts, but the relationship between vegetation and climate is often poorly understood. We synthesized a phytolith dataset using >500 topsoil samples and 6 sedimentary profiles from temperate Northeast China. The modern topsoil dataset was calibrated to quantitatively estimate tree cover and grass cover. Based on the threshold of tree cover, we explored the spatial and temporal variations of the forest-grassland ecotone in NE China as well as possible driving mechanisms. Phytoliths provided reliable quantitative estimates of tree/grass cover, accurately distinguishing sites that are currently forest from grassland in this temperate region. The forest-grassland ecotone expanded westward from 7 to 5 ka, retreated eastward from 4 to 2 ka, and then expanded westward again, migrating <100 km throughout this period. The interval of maximum tree cover varied spatiotemporally from east to west during the Holocene. Precipitation from the East Asian summer monsoon was likely the dominant driver of spatial and temporal variations in the forest-grassland ecotone in NE China, with lesser contributions from the Westerly Jet.
For future vegetation projections and conservation planning in grassland ecosystems, accurate estimates of past plant cover changes in grassland composition and their responses to the various driving ...factors are essential. This study quantitatively reconstructs the past regional plant cover in the Songnen grasslands (northeastern China) and explores the relative importance of climate, fire, and human activity on vegetation dynamics.
For this purpose, the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model is applied to three pollen records from two areas, two in the center of the Songnen grasslands and one located in an area marginal to the grasslands.
Results from the most reliable REVEALS scenarios show that from the mid-Holocene, steppe (mean cover 40.6%) and dry steppe (mean cover 54.2%) alternately dominated the central part of the Songnen grasslands while the marginal grasslands were mainly characterized by alternating broadleaved forests (mean cover 26.3%), coniferous forests (mean cover 41.9%) and dry steppes (mean cover 30.1%).
By comparing the plant cover results with previous published regional climate, fire and human activity records, the results show that long term vegetation dynamics were mainly driven by East Asia Summer Monsoon (EASM) and the related precipitation variations, but was also affected by fire frequency and human activity. Moreover, vegetation evolution was sensitive to abrupt cooling events including the 4.2 ka BP and stacked ice-rafted debris (IRD) events; the change from steppe to dry steppe, for example, was driven by these abrupt climate changes. Fire events can alter the original vegetation stability allowing the vegetation to respond rapidly to climate changes while human activity merely has limited influence on vegetation changes.
Phytolith records have provided a new perspective on the reconstruction and interpretation of palaeovegetation in forested regions. However, the reliability of phytolith records for vegetation ...reconstruction in northern temperate forest regions has not been fully determined, and it needs to be assessed before they can be used in palaeoecological contexts. To address this issue, we analyzed surface soil phytolith assemblages at 108 sites and established a modern soil phytolith reference database for five dominant vegetation communities in Northeast China. The phytolith reference dataset was then used to analyze a stratigraphic sequence of fossil phytolith assemblages from the same region to confirm the reliability of the phytolith-based paleovegetation reconstruction. The results demonstrate that both the phytolith assemblages of surface soils and the phytolith indices (Iw, Ic, Iph and W/G) vary substantially in different temperate forest habitats, and the indices are also well correlated with the vegetation inventory data. Thus, we conclude that modern soil phytoliths are reliable analogues for reconstructing paleovegetation. The modern phytolith reference-based paleovegetation reconstruction indicates that the study area has experienced substantial vegetation change since the late-glacial. The vegetation types ranged from open Larix mixed forest to open woodland, to closed broadleaf forest, and finally to closed Pinus koraiensis mixed forest. The phytolith-based vegetation types since the late-glacial are consistent with those reconstructed by a pollen record from the same stratigraphic profile, and thus our study confirms the reliability of phytolith analysis for interpreting both the entire vegetation landscape and vegetation changes in the northern temperate forest region. Moreover, fossil phytoliths also provide additional information - including the composition of grasses in the understory, changes in the proportions of C3/C4 plants, Larix abundance and tree cover density - which complements that provided by pollen analysis. Our study provides new perspectives on the reliability of phytoliths for reconstructing vegetation dynamics in the northern temperate forest region, and it provides a robust foundation for the application of phytolith analysis in the region.
•Surface soil phytolith reference was established for NE China to identify different temperate forest types.•Based on the modern phytolith dataset we reconstructed the paleovegetation of a peat profile since the late-glacial.•Our work confirmed the reliability of phytolith-based paleovegetation reconstruction in the northern temperate forest region.
Exploring the Mid-Late Holocene interactions between ecological and climate variations in semi-arid areas such as Songnen grasslands (northeastern China) provide insights into how future vegetation ...changes and hydrological variations may have an impact on semi-arid ecosystems, in general. In this study, we present a high-resolution palaeoecological dataset covering the past 7300 years. For this purpose, a peat section has been sampled from the shore of Dabusu lake situated in the southwestern part of the Songnen grasslands. We use pollen analyses to reconstruct the regional and local vegetation dynamics, and measure TOC (total organic carbon) and the degree of peat humification to study changes in regional and local biomass. Diatom analysis, grain size analysis, and CaCO3 contents are used to assess the water-table fluctuations of the Dabusu peatlands. The results show that from 7300 to 6000 cal BP, Dabusu peatlands were characterized by grasslands, dominated by Poaceae plants and high-water level. From 6000 to 910 cal BP, forest-steppes and dry-steppes dominated in the region alternatively. The water level of Dabusu peatlands experienced relatively low levels following an earlier rapid decline around 6000–5100 cal BP. Then after a slight increase between 5100 and 4000 cal BP, it remained at a relatively low level until 910 cal BP. After 910 cal BP, steppe vegetation dominated in the region and the water level of Dabusu peatlands slightly rose. By comparing these features with regional climate change, we show that EASM circulations might be the main driving forces controlling the regional paleovegetation dynamics and hydrological variations. This outcome is critical for the understanding of the long-term interactions between vegetation, hydrology, and climate of mid-latitude semi-arid grasslands.
•Steppes, dry-steppes, forest-steppes, dry steppes, and steppes have dominated the Songnen grasslands since the mid-Holocene.•After the highest water level, Dabusu peatlands had a low water level interspersed by two relatively high water level periods.•EASM circulations might be the main driving forces controlling the regional paleovegetation and hydrological variations.
Ecosystems in arid regions with sandy substrates are vulnerable to various environmental challenges. Understanding the vegetation evolution of such regions over a long timescale and the possible ...drivers of change is important for optimizing ecological restoration. In this paper, we present multi-proxy data to understand Holocene vegetation dynamics and their drivers in the Horqin Sandy Land in northern China. Phytoliths are used to reconstruct vegetation; grain size and magnetic susceptibility are used to reconstruct the climate; and sedimentary charcoal contents and the numbers of regional archaeological sites are used to reconstruct the fire activity and human activity intensity, respectively. Results indicate that the Horqin Sandy Land was covered mainly by grassland vegetation during the Holocene, and that the trajectory of vegetation evolution was as follows: sparse and species-poor Leymus chinensis grassland from 9300 to 6150 cal yr BP, relatively sparse and species-rich mesophytic herb grassland from 6150 to 2300 cal yr BP, and dense and species-rich L. chinensis grassland from 2300 to 250 cal yr BP. Climate change was the main driver of vegetation evolution, but fire and human activities also influenced the vegetation to varying degrees. Fire made the greatest contribution to the vegetation change during the 6150–2300 cal yr BP interval, and human activities contributed throughout the 8200–2300 cal yr BP interval. The evolution of plant species richness and the number of C3 plants show a significant ∼1000-yr periodicity during 9300–4500 cal yr BP, which we speculate was caused by the effect of solar activity on East Asian monsoon intensity, which likely controlled the vegetation change on a millennial timescale.
•The Holocene vegetation in Horqin Sandy Land is qualitatively reconstructed.•Climate dominated the vegetation evolution, while fire and human activity were additional influences.•The vegetation change shows a ∼ 1000-yr periodicity during 9300–4500 cal yr BP.•The vegetation change on a millennium cycle was likely driven by the solar activity.
PDF
