Improved interfacial property by small molecule ethanediamine for high performance inverted planar perovskite solar cells

We report a simple and effective method to realize desirable interfacial property for inverted planar perovskite solar cells(PSCs)by using small molecule ethanediamine for the construction of a novel polyelectrolyte hole transport material(P3CT-ED HTM).It is found that P3CT-ED can not only improve the hole transport property of P3CT-K but also improve the crystallinity of adjacent perovskite film.In addition,the introduction of ethanediamine into P3CT realigns the conduction and valence bands upwards,passivates surface defects and reduces nonradiative recombination.As a consequence,compared to P3CT-K hole transport layer(HTL)based devices,the average power conversion efficiency(PCE)is boosted from17.2% to 19.6% for the counterparts with P3CT-ED,with simultaneous enhancement in open circuit voltage and fill factor.The resultant device displays a champion PCE of 20.5% with negligible hysteresis.

青藏高原大气氧含量影响因素及其贡献率分析

已有工作认为,近地表空气中氧气相对含量在不同海拔上无明显变化.然而,对采集自青藏高原的数据利用主成分分析发现, 500 hPa的大气温度(500 hPa-T)、地表植被盖度及海拔对氧气相对和绝对含量都产生一定的影响.就氧气相对含量而言,植被盖度的方差解释率为33.1%, 500 hPa-T和海拔的方差解释率分别为28.5%和3.9%,总方差解释率为65.5%;通过理想气体状态方程计算得到氧气绝对含量,发现海拔对其方差解释率为45.9%,植被盖度和500h Pa-T分别为18.5%和14.5%,总方差解释率为78.9%.认识高海拔地区氧气相对和绝对含量与其对应的植被及气象要素间的关系,不仅对改善居住及生活在高海拔地区人类和家畜的健康具有重要指导作用,也对加深理解全球变化背景下高海拔地区的环境风险有重要的理论与实践意义.

Spatiotemporal Changes of Hazard Intensity-Adjusted Population Exposure to Multiple Hazards in Tibet During 1982–2015

The dynamic changes of population exposure to hazards in high-altitude areas are an important factor in the scientific evaluation of environmental risks. In this study,the hazards of hypoxia, earthquakes, and snowstorms in Tibet were respectively described by the percentage of oxygen at sea level, earthquake intensity, and mean annual maximum snow depth. The rates of population affected by hypoxia, earthquakes, and snowstorms were calculated by chronic mountain sickness and historical disaster data.Based on these, the study examined the change in population exposure to the three hazards and their combinations by hazard intensity level at the 1 km 9 1 km grid scale in1982–2015. The results show that population exposures to hypoxia, earthquakes, and snowstorms were about 745 thousand, 97 thousand, and 168 thousand in 2015,respectively, among a total population in Tibet of 3.24 million. These exposures were mainly concentrated in the3400–5000 m above sea level zone. The population exposed to hypoxia and earthquakes showed a rising trend from 1982 to 2015, while the population exposed tosnowstorms decreased after 2000 due to reduced snowstorm intensity. Hypoxia-earthquake and hypoxia-snowstorm are the main multiple hazard combinations that people in Tibet suffered from and their personátime exposures were estimated at around 842 thousand and 913 thousand in 2015, respectively, with an average annual increase of 1.7% and 1.3%. Hypoxia is the most important health risk in Tibet. The areas of high personátime exposure to multiple hazards of hypoxia-earthquake-snowstorm are the key areas for strengthening integrated risk governance.

From the water sources of the Tibetan Plateau to the ocean:State of nutrients in the Changjiang linked to land use changes and climate variability

Anthropogenic activity is an important driver of changes in the chemistry of nutrients(N,P,and Si)over watersheds at the sub-continental scale(e.g.,106km~2)and can markedly modify their seaward fluxes to the global ocean.In the present study,we reviewed the current status of nutrient chemistry in Changjiang(Yangtze River)based on data collected through 11 expeditions along a river course spanning 4,500 km and 15–20 major tributaries during 1997–2016 as well as monthly monitoring at the river mouth since 1980.The data were analyzed together with published results in the literature to synthesize the recent developments and current state of nutrients in the Changjiang.Previously published results from the Qinghai-Tibetan Plateau head waters were included to realize the systematics of nutrients for the whole drainage basin.Here,we showed that tributaries of the upper reaches of watersheds collectively determine the regime with high concentration and skewed species ratio of nutrients in the Changjiang mainstream,producing profound effects over a water course of 2,000–2,500 km further downstream and until the river mouth.Moreover,using data across the Three Gorges Reservoir(TGR)during 2003–2016,we evaluated the trapping and/or amplifying effects of the Three Gorges Dam(TGD)on nutrient chemistry.Tide-influenced river delta contributed an additional 20%dissolved inorganic phosphorus and 5–10%dissolved inorganic nitrogen and dissolved silicates to the seaward flux,dramatically affecting the stoichiometry of nutrients at the river mouth.Next,based on compiled data on supply and export,legacy nutrients were evaluated.Both nitrogen and phosphorus are in the accumulation phase over the watersheds,and the legacy nutrient fluxes are much higher than the annual riverine seaward fluxes.Finally,we demonstrated that the seaward fluxes of anthropogenic nutrients from the Changjiang exceed those from other top 10 largest rivers on this planet,which can be attributed to land use changes in the China over the last three to four decades.

Dynamic Assessment of Global Maize Exposure to Extremely High Temperatures

Exposure to extreme heat can severely harm crop growth and development,and it is essential to assess such exposure accurately to minimize risks to crop production.However,the actual distribution of crops and its changes have neither been examined in sufficient detail nor integrated into the assessments of exposure to ensure their accuracy.By examining the distribution of maize at a high resolution through species distribution modeling,we assessed the past and future exposure of maize to temperatures above 37℃worldwide.Such exposure is likely to be widespread and severe,mainly in the subtropics,and may even expand to the mid-latitudes to encompass some major maize-producing areas.Many areas at both high and low latitudes may become exposed for the first time in the next 20 years.By the 2050 s,the total area exposed could increase by up to 185%to 308.18 million ha,of which the area exposed for over 60 days may increase nearly sevenfold.The average length of exposure may increase by 69%to 27 days,and areas optimally suited to maize planting may see the fastest increase by up to 772%.Extreme heat can threaten global maize production severely,and measures to mitigate that threat and to adapt to it are urgently needed.

Development of tropoelastin-functionalized anisotropic PCL scaffolds for musculoskeletal tissue engineering

The highly organized extracellular matrix(ECM)of musculoskeletal tissues,encompassing tendons,ligaments and muscles,is structurally anisotropic,hierarchical and multi-compartmental.These features collectively contribute to their unique function.Previous studies have investigated the effect of tissue-engineered scaffold anisotropy on cell morphology and organization for musculoskeletal tissue repair and regeneration,but the hierarchical arrangement of ECM and compartmentalization are not typically replicated.Here,we present a method for multi-compartmental scaffold design that allows for physical mimicry of the spatial architecture of musculoskeletal tissue in regenerative medicine.This design is based on an ECM-inspired macromolecule scaffold.Polycaprolactone(PCL)scaffolds were fabricated with aligned fibers by electrospinning and mechanical stretching,and then surface-functionalized with the cell-supporting ECM protein molecule,tropoelastin(TE).TE was attached using two alternative methods that allowed for either physisorption or covalent attachment,where the latter was achieved by plasma ion immersion implantation(PIII).Aligned fibers stimulated cell elongation and improved cell alignment,in contrast to randomly oriented fibers.TE coatings bound by physisorption or covalently following 200 s PIII treatment promoted fibroblast proliferation.This represents the first cytocompatibility assessment of novel PIII-treated TE-coated PCL scaffolds.To demonstrate their versatility,these 2D anisotropic PCL scaffolds were assembled into 3D hierarchical constructs with an internally compartmentalized structure to mimic the structure of musculoskeletal tissue.

Modelling the development of biological structures displaying longitudinal geometries in vitro:culturing pluripotent stem cells on plasma-treated,growth factor-coupled polycaprolactone fibres

Many biological structures such as nerves,blood and lymphatic vessels,and muscle fibres exhibit longitudinal ge-ometries with distinct cell types extending along both the length and width of internal linear axes.Modelling these three-dimensional structures in vitro is challenging:the best-defined stem-cell differentiation systems are mono-layer cultures or organoids using pluripotent stem cells.Pluripotent stem cells can differentiate into functionally mature cells depending on the signals received,holding great promise for regenerative medicine.However,the integration of in vitro differentiated cell types into diseased tissue remains a challenge.Engineered scaffolds can bridge this gap if the appropriate signalling systems are incorporated into the scaffold.Here,we have taken a biomimicry approach to generate longitudinal structures in vitro.In this approach,mouse embryonic stem cells are directed to differentiate to specific cell types on the surface of polycaprolactone(PCL)fibres treated by plasma-immersion ion implantation and to which with lineage-specifying molecules have been covalently im-mobilised.We demonstrate the simplicity and utility of our method for efficiently generating high yields of the following cell types from these pluripotent stem cells:neurons,vascular endothelial cells,osteoclasts,adipocytes,and cells of the erythroid,myeloid,and lymphoid lineages.Strategically arranged plasma-treated scaffolds with differentiated cell types could ultimately serve as a means for the repair or treatment of diseased or damaged tissue.