Leaf chlorophyll is central to the exchange of carbon, water and energy between the biosphere and the atmosphere, and to the functioning of terrestrial ecosystems. This paper presents the first ...spatially-continuous view of terrestrial leaf chlorophyll content (ChlLeaf) at the global scale. Weekly maps of ChlLeaf were produced from ENVISAT MERIS full resolution (300 m) satellite data using a two-stage physically-based radiative transfer modelling approach. Firstly, leaf-level reflectance was derived from top-of-canopy satellite reflectance observations using 4-Scale and SAIL canopy radiative transfer models for woody and non-woody vegetation, respectively. Secondly, the modelled leaf-level reflectance was input into the PROSPECT leaf-level radiative transfer model to derive ChlLeaf. The ChlLeaf retrieval algorithm was validated using measured ChlLeaf data from 248 sample measurements at 28 field locations, and covering six plant functional types (PFTs). Modelled results show strong relationships with field measurements, particularly for deciduous broadleaf forests (R2 = 0.67; RMSE = 9.25 μg cm-2; p < 0.001), croplands (R2 = 0.41; RMSE = 13.18 μg cm-2; p < 0.001) and evergreen needleleaf forests (R2 = 0.47; RMSE = 10.63 μg cm-2; p < 0.001). When the modelled results from all PFTs were considered together, the overall relationship with measured ChlLeaf remained good (R2 = 0.47, RMSE = 10.79 μg cm-2; p < 0.001). This result is an improvement on the relationship between measured ChlLeaf and a commonly used chlorophyll-sensitive spectral vegetation index; the MERIS Terrestrial Chlorophyll Index (MTCI; R2 = 0.27, p < 0.001). The global maps show large temporal and spatial variability in ChlLeaf, with evergreen broadleaf forests presenting the highest leaf chlorophyll values, with global annual median values of 54.4 μg cm-2. Distinct seasonal ChlLeaf phenologies are also visible, particularly in deciduous plant forms, associated with budburst and crop growth, and leaf senescence. It is anticipated that this global ChlLeaf product will make an important step towards the explicit consideration of leaf-level biochemistry in terrestrial water, energy and carbon cycle modelling.
•Global terrestrial leaf chlorophyll content maps are produced from satellite data.•A two-stage radiative transfer model inversion method is used.•The algorithm was extensively validated with 248 measurements covering six biomes.•Validation results are strong (R2 = 0.47, RMSE = 10.79 μg cm-2; p < 000.1).•Seasonal chlorophyll phenologies are visible from weekly data.
Objectives
To investigate the mental status of pregnant women and to determine their obstetric decisions during the COVID‐19 outbreak.
Design
Cross‐sectional study.
Setting
Two cities in China––Wuhan ...(epicentre) and Chongqing (a less affected city).
Population
A total of 1947 pregnant women.
Methods
We collected demographic, pregnancy and epidemic information from our pregnant subjects, along with their attitudes towards COVID‐19 (using a self‐constructed five‐point scale). The Self‐Rating Anxiety Scale (SAS) was used to assess anxiety status. Obstetric decision‐making was also evaluated. The differences between cities in all of the above factors were compared and the factors that influenced anxiety levels were identified by multivariable analysis.
Main outcome measures
Anxiety status and its influencing factors. Obstetric decision‐making.
Results
Differences were observed between cities in some background characteristics and women's attitudes towards COVID‐19 in Wuhan were more extreme. More women in Wuhan felt anxious (24.5 versus 10.4%). Factors that influenced anxiety also included household income, subjective symptom and attitudes. Overall, obstetric decisions also revealed city‐based differences; these decisions mainly concerned hospital preference, time of prenatal care or delivery, mode of delivery and infant feeding.
Conclusions
The outbreak aggravated prenatal anxiety and the associated factors could be targets for psychological care. In parallel, key obstetric decision‐making changed, emphasising the need for pertinent professional advice. Special support is essential for pregnant mothers during epidemics.
Tweetable
The COVID‐19 outbreak increased pregnant women's anxiety and affected their decision‐making.
Tweetable
The COVID‐19 outbreak increased pregnant women's anxiety and affected their decision‐making.
This article includes Author Insights, a video available at https://vimeo.com/rcog/authorinsights16381
The grain size of river sediments changes systematically downstream from source to sink, and is influenced by catchment lithology, geomorphology, hydrology, oceanography and, in modern settings, ...anthropogenic impacts. Compared with small, gravel-bedded river systems, less is known about large, sandy‐bed rivers, particularly from the river source to marine sink. In the present study, we examine longitudinal changes in sediment grain size along the middle and lower Yangtze River, downstream of the Three Gorges Dam (TGD), and along the major sediment dispersal pathway into the East China Sea, over a total length of 2100km. We also examine the spatial patterns of seabed sediment grain size in the East China Sea adjacent to the Yangtze Estuary (70,000km2 in area). In particular, we consider the impact of the TGD on the grain size of the riverbed and seabed sediments. Before the construction of the TGD, the relationship between median grain size and distance along the sandy bed of the middle and lower Yangtze showed a downstream fining trend that was exponential in form. After the TGD was built, erosion caused an abrupt gravel–sand transition to develop in the section immediately downstream of the TGD. In the Yangtze Estuary, flocculation and subsequent deposition of suspended riverine mud during the slack water period between flood and ebb tides led to the formation of an abrupt sand–mud transition. Muddy deposits along the major longshore sediment dispersal route also show an exponential fining trend. However, towards the open East China Sea, the modern riverine muds are replaced seawards by older sands. The mud margin there was found to have retreated landward significantly over the post-TGD period due to erosion driven by the significant decrease in sediment supply from the Yangtze River. We expect that the impact of the TGD on the grain size of bed sediments in the Yangtze River and the East China Sea will continue for some time, and the change in the grain size of bed sediments there will become more pronounced.
► Three Gorges Dam has impacted the pattern of grain-size in the Yangtze significantly. ► There exists an abrupt sand–mud transition in the channel of the Yangtze Estuary. ► The Yangtze mud shows an exponential fining along the sediment dispersal in the sea. ► The mud margin off the Yangtze mouth has retreated due to erosion in recent years.
We report a stable tensile recovery strain induced by a Ni4Ti3 nanoprecipitate in a Ni50.4Ti49.6 shape memory alloy (SMA) fabricated via selective laser melting (SLM), followed by a discussion on the ...underlying physical mechanism. In particular, the physical properties, such as morphology and size of the Ni4Ti3 nanoprecipitate were tailored by heat treatment, namely solid solution and aging treatment, of the SLM-fabricated (SLMed) SMA. The heat-treated SMA exhibited a three-stage phase transformation owing to the larger aspect ratio and smaller size of the Ni4Ti3 nanoprecipitate; furthermore, it exhibited a larger strain/stress field inside the grain interior region relative to the grain boundary region. The significantly larger endothermic and exothermic enthalpies in the heat-treated SMA relative to the SLMed counterpart were due to the substantial elimination of the dislocation and residual stress generated during SLM, and the lower Ni concentration in the B2 matrix induced by the formation of Ni-rich Ni4Ti3 nanoprecipitate. In particular, the stress-controlled loading and unloading tests led to a decrease in the endothermic and exothermic enthalpies of the heat-treated SMA. This is ascribed to the formation of stabilized B19′ martensite after the formation of high-density dislocations and enhanced strain/stress field around the coherent Ni4Ti3 nanoprecipitate during tensile cycles. Interestingly, a stable tensile recovery strain as high as 2.25–3.74% was obtained in the heat-treated SMA during the stress-controlled loading and unloading tests. Fundamentally, this was attributed to the saturation of the dislocations formed at critical tensile cycles, which can be achieved by the dislocation pile-up around the spherical Ni4Ti3 nanoprecipitate or the dislocation cut-through of the lenticular Ni4Ti3 nanoprecipitate. Finally, these results can provide significant insights into tailoring the microstructure and functional properties of NiTi SMAs by SLM.
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Tunable lattice resonances are demonstrated in a hybrid plasmonic crystal incorporating the phase-change material Ge2Sb2Te5 (GST) as a 20-nm-thick layer sandwiched between a gold nanodisk array and a ...quartz substrate. Non-volatile tuning of lattice resonances over a range Δλ of about 500 nm (1.89 µm to 2.27 µm) is achieved experimentally via intermediate phase states of the GST layer. This work demonstrates the efficacy and ease of resonance tuning via GST in the near infrared, suggesting the possibility to design broadband non-volatile tunable devices for optical modulation, switching, sensing and nonlinear optical devices.
El Niño/Southern Oscillation (ENSO) is the main climate mode that drives the interannual variability in climate and consequently vegetation greenness. While widespread green‐up has been reported and ...examined in tropical America during El Niño, it remains unclear how vegetation in tropical Asia changes during the period. Here, we used four remote sensing‐based leaf area index (LAI) products to investigate changes in vegetation greenness during the 2015/16 El Niño in tropical Asia. We found a strong green‐up during the 2015/16 El Niño in tropical Asia, with its regional average LAI stronger than that of tropical America. The drivers for the green‐up vary across the region, with radiation being the main driver for continental tropical Asia, and temperature and soil water anomalies in the west and east parts of maritime tropical Asia, respectively. These findings provide important insights into the response of tropical Asia's vegetation to extreme climate anomalies.
Plain Language Summary
El Niño is a climate pattern that is associated with warm and dry conditions in tropical forest regions. Significant climatic changes during El Niño thus affect vegetation greenness (i.e., growth, size of canopy, amount of leaves). While an increase in vegetation greenness has been reported in tropical America during El Niño, it remains unclear how vegetation in tropical Asia changes during the period. Here, we used satellite data to investigate changes in vegetation greenness during El Niño in 2015–2016 in tropical Asia. We found a strong increase in vegetation greenness in tropical Asia during this period. The cause of this increase in greenness varied across different parts of tropical Asia. In mainland tropical Asia, sunlight was the main driver, while in maritime Southeast Asia, temperature or soil moisture was the main driver. These findings help provide better understanding of how vegetation in tropical Asia responds to extreme climate events like El Niño.
Key Points
Tropical Asia experienced strong green‐up during the 2015/16 El Niño, stronger than that of tropical America
In continental tropical Asia, green‐up was mostly driven by anomalously high shortwave radiation
In maritime tropical Asia, green‐up was primarily driven either by anomalously warmer temperatures or drier soil moisture from the west to east
Midbrain dopamine neurons are an essential component of the basal ganglia circuitry, playing key roles in the control of fine movement and reward. Recently, it has been demonstrated that ...γ-aminobutyric acid (GABA), the chief inhibitory neurotransmitter, is co-released by dopamine neurons. Here, we show that GABA co-release in dopamine neurons does not use the conventional GABA-synthesizing enzymes, glutamate decarboxylases GAD65 and GAD67. Our experiments reveal an evolutionarily conserved GABA synthesis pathway mediated by aldehyde dehydrogenase 1a1 (ALDH1a1). Moreover, GABA co-release is modulated by ethanol (EtOH) at concentrations seen in blood alcohol after binge drinking, and diminished ALDH1a1 leads to enhanced alcohol consumption and preference. These findings provide insights into the functional role of GABA co-release in midbrain dopamine neurons, which may be essential for reward-based behavior and addiction.
Multi-pass submerged friction stir processing (M-SFSP) with an overlapping ratio of 50% was applied on as-cast AZ61 magnesium plate. The relationship between the microstructure and tensile behavior ...of the M-SFSP plate was investigated. With the cooling enhancement during processing, the grain size is significantly refined to be ~ 3.7 ± 1.7 μm in the stir zone. The initial network-like β-Mg
17
Al
12
second phase in the cast alloy is effectively fragmented and dissolved into magnesium matrix, as revealed by a consistent right shift of magnesium peaks in the XRD patterns due to the lattice shortening caused by the smaller aluminum atoms getting into magnesium matrix to form substitutional solid solution. Texture is modified with a lower intensity in the center of stir zone than at the top surface. Compared with the base material, the strength and ductility of the M-SFSP Mg plate are significantly improved, mainly due to grain refinement along with dislocation strengthening and solid solution strengthening. Despite texture weakening, the M-SFSP plate still exhibits mechanical anisotropy to a certain extent, depending on the initial texture and loading direction. Cracking is observed to initiate from the transitional zone and propagate along the microstructural band due to the presence of high local residual stresses.
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