Halogen Engineering for Operationally Stable Perovskite Solar Cells via Sequential Deposition

The performance of perovskite solar cells (PSCs) relies on the synthesis method and chemical composition of the perovskite materials. So far, PSCs that have adopted two‐step sequential deposited perovskite with the state‐of‐art composition (FAPbI₃)_1?x(MAPbBr₃)_x (x < 0.05) have achieved record power conversion efficiency (PCE), while their one‐step antisolvent dripping counterparts with typical composition Cs_0.05FA_0.81MA_0.14Pb(I_0.85Br_0.15)₃ with more bromine have exhibited much better long‐term operational stability. Thus, halogen engineering that aims to elevate bromine content in sequential deposited perovskite film would push operational stability of PSCs toward that of antisolvent dripping deposited perovskite materials. Here, a Br‐rich seeding growth method is devised and perovskite seed solution with high bromine content is introduced into a PbI₂ precursor, leading to bromine incorporation in the resulting perovskite film. Photovoltaic devices fabricated by Br‐rich seeding growth method exhibit a PCE of 21.5%, similar to 21.6% for PSCs having lower bromine content. Whereas, the operational stability of PSCs with higher bromine content is significantly enhanced, with over 80% of initial PCE retained after 500 h tracking at maximum power point under 1‐sun illumination. This work highlights the vital importance of halogen composition for the operational stability of PSCs, and introduces an effective way to incorporate bromine into mixed‐cation‐halide perovskite film via sequential deposition method.     

以达托霉素产生菌菌株改造为主线的微生物工程综合实验的探索和实践

为使本科学生更好地掌握微生物工程的基本实验操作技能和前沿研究技术,探索将教师的科研成果转化为教学实验,构建了以达托霉素产生菌菌株改造为主线的微生物工程综合实验。在教学模式、实验内容设计、教学安排和考核方式等方面进行实践,取得了较好的教学效果,培养了本科学生的科研技能、科研思维和研究素质。     

FT overexpression induces precocious flowering and normal reproductive development in Eucalyptus

Eucalyptus trees are among the most important species for industrial forestry worldwide. However, as with most forest trees, flowering does not begin for one to several years after planting which can limit the rate of conventional and molecular breeding. To speed flowering, we transformed a Eucalyptus grandis × urophylla hybrid (SP7) with a variety of constructs that enable overexpression of FLOWERING LOCUS T (FT). We found that FT expression led to very early flowering, with events showing floral buds within 1–5 months of transplanting to the glasshouse. The most rapid flowering was observed when the cauliflower mosaic virus 35S promoter was used to drive the Arabidopsis thaliana FT gene (AtFT). Early flowering was also observed with AtFT overexpression from a 409S ubiquitin promoter and under heat induction conditions with Populus trichocarpa FT1 (PtFT1) under control of a heat‐shock promoter. Early flowering trees grew robustly, but exhibited a highly branched phenotype compared to the strong apical dominance of nonflowering transgenic and control trees. AtFT‐induced flowers were morphologically normal and produced viable pollen grains and viable self‐ and cross‐pollinated seeds. Many self‐seedlings inherited AtFT and flowered early. FT overexpression‐induced flowering in Eucalyptus may be a valuable means for accelerating breeding and genetic studies as the transgene can be easily segregated away in progeny, restoring normal growth and form.     

Relationship between Riparian Vegetation and Stream Benthic Communities at Three Spatial Scales

We examined the influence of riparian vegetation on macroinvertebrate community structure in streams of the Upper Thames River watershed in southwestern Ontario. Thirty-three μ-basins (129–1458 ha) were used to identify land cover variables that influenced stream macroinvertebrates. Micro-basins represented the entire drainage area of study streams and were similar in stream order (first, second) and land cover (agricultural or forest; no urban). We described the structure and composition of riparian vegetation and benthic macroinvertebrate communities at the outflow reach. The nature of the land cover was quantified for the stream network buffer (30 m) and the whole μ-basin. The objective of this study was to measure the magnitude and nature of the relationship between the riparian vegetation and benthic macroinvertebrate community at the outflow reach, stream network buffer, and whole μ-basin scales. Taxon richness (including total number of Ephemeroptera, Plecoptera, and Trichoptera taxa) and Simpson’s diversity of the macroinvertebrate community all increased with increased tree cover in the riparian zone at the outflow reach scale. Simpson’s equitability was lower with greater agricultural land cover in the stream network buffer. No relationship between the macroinvertebrate community and land cover was found at the whole μ-basin scale. Analysis of the influence of land cover on stream communities within a spatial hierarchy is important for understanding the interactions of stream ecosystems with their adjacent landscapes.     

Three-dimensional adipose tissue model using low shear bioreactors

Summary Presented here are techniques developed to culture and analyze three-dimensional (3-D) adipose-like tissues as a means to bridge the gap between current liminations in culturing preadipocytes (PAs) and that of providing clinically relevant volumes of adipose tissue useful for soft tissue engineering stratgies in reconstructive surgery. Pilot studies were performed to determine techniques to visualize and analyze 3-D PA-like tissues as well as to develop successful strategies to culture 3T3-L1 cells in a high aspect ratio vessel rotating-wall bioreactor both with and without microcarriers. Next, a series of cultures were accessed to verify these techniques as well as to compare the culture of the cells with and without microcarriers. Finally, a perfused rotating-wall bioreactor was used to further investigate the nature of the aggregates or tissues being generated. The aggregates that formed in the perfused system were analyzed via histology and in vivo animal studies. PA-like tissues as large as 4–5 mm in diameter without microcarriers that were capable of lipid-loading and composed of viable cells were achieved. We have successfully demonstrated that large tissue aggregates can be grown in bioreactor culture systems.     

内蒙古温带草原区植被盖度变化及其与气象因子的关系

利用1982-1999年内蒙古地区NOAA/AVHRR的NDVI数字遥感影像,对内蒙古温带草原区植被盖度进行了反演,探讨了近20a来温带草原植被盖度的变化情况,并对植被盖度与不同组合方式的降水及气温数据进行了相关分析,探讨了植被盖度与气象因子的关系。结果表明:①近20a来温带草原植被盖度呈上升趋势,占总面积72%的草原植被盖度发生了增长,3种不同草原类型中典型草原盖度上升趋势最为明显;②温带草原生长季平均盖度、逐月盖度与降水成正相关关系,与气温呈负相关关系,其中降水对盖度的影响存在着时滞及累积效应;③3种草原类型植被盖度对气象因子的敏感性不同,荒漠草原植被盖度与气温和降水相关性最强,其次为典型草原与草甸草原。     

The weed seed bank of soils in a landscape segment in southern Bavaria – II. Relation to environmental variables and to the surface vegetation

In the first part of their investigations of the weed seed bank in a 110 ha landscape segment in southern Bavaria, Albrecht & Forster (1996) showed that there was a tremendous spatial variability in seed density as well as in species composition. The intention of the present paper was to elucidate the reasons for this variability. For this purpose, the influence of soil conditions, land use practices, and soil fauna, all of which are environmental factors potentially affecting the weed seed bank, were investigated.Highly significant correlations were observed between the soil seed bank, preceding management variables, and the available field capacity. In contrast, multiple regression analyses between seed banks and the chemical characteristics of the soil, soil fauna, and actual management showed either minor correlation or none at all. Thus, prior management and water supply must be supposed to have had the most decisive influence on the soil seed bank.Several environmental variables affect arable weed populations, not so much through the soil seed bank but through the germination, establishment, and reproduction phases in the field. For this reason the relations between the apparent weed flora and the potential vegetation in the soil also were investigated. The correlation of the soil seed content and the density of individuals on the soil surface was highly significant. The analysis for a single species revealed that the seed bank/field density-ratios of different taxa vary from below 10:1 up to 100:1 and more. This wide range may be related to the life-forms and ecological requirements characteristic for each species.Finally, comparisons of the environmental variables with the soil seed bank and surface vegetation allowed ranking of the variables as to their importance for these two stadia of plant population development. These investigations indicated that the preceding management by different farmers exerted a more decisive influence on the number of seeds in the soil. In contrast, the actual grain yield and N-content in a soil showed a closer relationship to the soil surface vegetation. With regard to the species composition, no distinct differences in the environmental relationships between the soil seed bank and the soil surface vegetation could be observed.