| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Ehlers, Todd A., et al.
(författare)
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Past, present, and future geo-biosphere interactions on the Tibetan Plateau and implications for permafrost
- 2022
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 234
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between the atmosphere, biosphere, cryosphere, hydrosphere, and geosphere are most active in the critical zone, a region extending from the tops of trees to the top of unweathered bedrock. Changes in one or more of these spheres can result in a cascade of changes throughout the system in ways that are often poorly understood. Here we investigate how past and present climate change have impacted permafrost, hydrology, and ecosystems on the Tibetan Plateau. We do this by compiling existing climate, hydrologic, cryosphere, biosphere, and geologic studies documenting change over decadal to glacial-interglacial timescales and longer. Our emphasis is on showing present-day trends in environmental change and how plateau ecosystems have largely flourished under warmer and wetter periods in the geologic past. We identify two future pathways that could lead to either a favorable greening or unfavorable degradation and desiccation of plateau ecosystems. Both paths are plausible given the available evidence. We contend that the key to which pathway future generations experience lies in what, if any, human intervention measures are implemented. We conclude with suggested management strategies that can be implemented to facilitate a future greening of the Tibetan Plateau.
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| 3. |
- Yang, Dong, et al.
(författare)
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Encapsulation of Halocarbons in a Tetrahedral Anion Cage
- 2015
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54:30, s. 8658-8661
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Tidskriftsartikel (refereegranskat)abstract
- Caged supramolecular systems are promising hosts for guest inclusion, separation, and stabilization. Well-studied examples are mainly metal-coordination-based or covalent architectures. An anion-coordination-based cage that is capable of encapsulating halocarbon guests is reported for the first time. This A(4)L(4)-type (A=anion) tetrahedral cage, [(PO4)(4)L-4](12-), assembled from a C-3-symmetric tris(bisurea) ligand (L) and phosphate ion (PO43-), readily accommodates a series of quasi-tetrahedral halocarbons, such as the Freon components CFCl3, CF2Cl2, CHFCl2, and C(CH3)F-3, and chlorocarbons CH2Cl2, CHCl3, CCl4, C(CH3)Cl-3, C(CH3)(2)Cl-2, and C(CH3)(3)Cl. The guest encapsulation in the solid state is confirmed by crystal structures, while the host-guest interactions in solution were demonstrated by NMR techniques.
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| 4. |
- Wu, Zhongbin, et al.
(författare)
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High-Performance Hybrid White Organic Light-Emitting Diodes with Superior Efficiency/Color Rendering Index/Color Stability and Low Efficiency Roll-Off Based on a Blue Thermally Activated Delayed Fluorescent Emitter
- 2016
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 26:19, s. 3306-3313
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Tidskriftsartikel (refereegranskat)abstract
- Thermally activated delayed fluorescence (TADF)-based white organic light-emitting diodes (WOLEDs) are highly attractive because the TADF emitters provide a promising alternative route to harvest triplet excitons. One of the major challenges is to achieve superior efficiency/color rendering index/color stability and low efficiency roll-off simultaneously. In this paper, high-performance hybrid WOLEDs are demonstrated by employing an efficient blue TADF emitter combined with red and green phosphorescent emitters. The resulting WOLED shows the maximum external quantum efficiency, current efficiency, and power efficiency of 23.0%, 51.0 cd A(-1), and 51.7 lm W-1, respectively. Moreover, the device exhibits extremely stable electroluminescence spectra with a high color rendering index of 89 and Commission Internationale de L'Eclairage coordinates of (0.438, 0.438) at the practical brightness of 1000 cd m(-2). The achievement of these excellent performances is systematically investigated by versatile experimental and theoretical evidences, from which it is concluded that the utilization of a blue-green-red cascade energy transfer structure and the precise manipulation of charges and excitons are the key points. It can be anticipated that this work might be a starting point for further research towards high-performance hybrid WOLEDs.
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| 5. |
- Zhao, Jie, et al.
(författare)
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Phosphate-induced fluorescence of a tetraphenylethene-substituted tripodal tris(urea) receptor
- 2016
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 45:17, s. 7360-7365
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Tidskriftsartikel (refereegranskat)abstract
- A tetraphenylethene (TPE)-decorated tripodal tris(urea) ligand L was synthesized, which shows large emission enhancement when binding to an orthophosphate anion (PO43-), but exhibits only weak or no fluorescence with other anions. The anion-binding and fluorescence properties were studied by X-ray crystal structure, NMR and fluorescence spectroscopy, and by DFT computations and the results demonstrate that the different fluorescence performance may be determined by the anion-binding modes (i.e., full-or half-encapsulation).
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| 6. |
- Zhang, Shengrui, et al.
(författare)
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Characteristic pollen source area and vertical pollen dispersal and deposition in a mixed coniferous and deciduous broad-leaved woodland in the Changbai mountains, northeast China.
- 2016
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 25:1, s. 29-43
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Tidskriftsartikel (refereegranskat)abstract
- Pollen influx (number of pollen grains cm−2 year−1) can objectively reflect the dispersal and deposition features of pollen within a certain time and space, and is often used as a basis for the quantitative reconstruction of palaeovegetation; however, little is known about the features and mechanisms of vertical dispersal of pollen. Here we present the results from a 5 year (2006–2010) monitoring program using pollen traps placed at different heights from ground level up to 60 m and surface soil samples in a mixed coniferous and deciduous broad-leaved woodland in the Changbai mountains, northeastern China. The pollen percentages and pollen influx from the traps have very similar characteristics to the highest values for Betula,Fraxinus, Quercus and Pinus, among the tree taxa and Artemisia, Chenopodiaceae and Asteraceae among the herb taxa. Pollen influx values vary significantly with height and show major differences between three distinct layers, above-canopy (≥32 m), within the trunk layer (8 ≤ 32 m) and on the ground (0 m). These differences in pollen influx are explained by differences in (i) the air flows in each of these layers and (ii) the fall speed of pollen of the various taxa. We found that the pollen recorded on the ground surface is a good representation of the major part of the pollen transported in the trunk space of the woodland. Comparison of the pollen influx values with the theoretical, calculated “characteristic pollen source area” (CPSA) of 12 selected taxa indicates that the pollen deposited on the ground surface of the woodland is a fair representation with 85–90 % of the total pollen deposited at a wind speed of 2.4 m s−1 coming from within ca. 1–5 km for Pinus and Quercus, ca. 5–10 km for Ulmus, Tilia, Oleaceae and Betula, ca. 20–40 km for Fraxinus, Poaceae, Chenopodiaceae, Populus andSalix, and ca. 30–60 km for Artemisia; it is also a good representation with 90–98 % of the total pollen deposited coming from within 60 km at a wind speed of 2.4 m s−1, or 100 km at a wind speed: 6 m s−1, for the 12 selected taxa used in the CPSA calculation. Furthermore, comparison with the vegetation map of the area around the sampling site shows that the pollen deposited on the ground represents all plant communities which grow in the study area within 70 km radius of the sampling site. In this study, the pollen percentages obtained from the soil surface samples are significantly biased towards pollen taxa with good preservation due to thick and robust pollen walls. Therefore, if mosses are available instead, soil samples should be avoided for pollen studies, in particular for the study of pollen-vegetation relationships, the estimation of pollen productivities and quantitative reconstruction of past vegetation. The results also indicate that the existing model of pollen dispersal and deposition, Prentice’s model, provides a fair description of the actual pollen dispersal and deposition in this kind of woodland, which suggests that the application of the landscape reconstruction algorithm would be relevant for reconstruction of this type of woodland in the past.
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| 7. |
- Wang, Tianhao, et al.
(författare)
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Regenerated Bamboo-Derived Cellulose Fibers/RGO-Based Composite for High-Performance Supercapacitor Electrodes
- 2020
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Ingår i: 7th annual international conference on material science and environmental engineering. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Bamboo-derived cellulose fibers/RGO carbon aerogel composite was prepared by using a facile aerogel-based method, in which bamboo pulp fibers were dissolved and incorporated in an ionic liquid system, and RGO was introduced by thermal reduction approach. The obtained bamboo-derived cellulose fibers/RGO carbon aerogel composite shows a large specific surface area, and excellent electrochemical performance. When the GO content was 2.5 wt%, the obtained composite showed a high specific surface area of 1957 m(2)/g, and high specific capacitance of 351 F/g in 6 M KOH electrolyte solution even with a more than 90% capacitance retention at a high scan rate of 200 mV/s. The bamboo-derived cellulose fibers/RGO composite electrodes show the low equivalent series resistance of 5.0 Omega and small charge transfer resistance of 0.30 Omega which further demonstrate the excellent electrochemical behaviors.
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| 8. |
- Yao, Lei, et al.
(författare)
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Atmospheric new particle formation from sulfuric acid and amines in a Chinese megacity
- 2018
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 361:6399, s. 278-281
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric new particle formation (NPF) is an important global phenomenon that is nevertheless sensitive to ambient conditions. According to both observation and theoretical arguments, NPF usually requires a relatively high sulfuric acid (H2SO4) concentration to promote the formation of new particles and a low preexisting aerosol loading to minimize the sink of new particles. We investigated NPF in Shanghai and were able to observe both precursor vapors (H2SO4) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H2SO4-dimethylamine (DMA)water (H2O) nucleation, including sulfuric acid dimers and H2SO4-DMA clusters. In a cluster kinetics simulation, the observed concentration of sulfuric acid was high enough to explain the particle growth to similar to 3 nanometers under the very high condensation sink, whereas the subsequent higher growth rate beyond this size is believed to result fromthe added contribution of condensing organic species. These findings will help in understanding urban NPF and its air quality and climate effects, as well as in formulating policies to mitigate secondary particle formation in China.
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| 9. |
- Jiao, Liping, et al.
(författare)
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Persistent toxic substances in remote lake and coastal sediments from Svalbard, Norwegian Arctic : Levels, sources and fluxes
- 2009
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 157:4, s. 1342-1351
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Tidskriftsartikel (refereegranskat)abstract
- Surface sediments from remote lakes and coastal areas from Ny-Ålesund, Svalbard, Norwegian Arctic were analyzed for polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). Relatively high levels of PAHs were encountered from several lakes from Ny-Ålesund, which were within the range of levels reported for European high mountain lakes and some urban/industrialized areas in the world, pointing to the role of remote Arctic lakes as potential reservoir of semi-volatile organic compounds. Specific patterns of PBDEs were observed, showing higher concentrations of lower brominated compounds such as BDE-7, 17 and 28. Estimated surface sediment fluxes of PAHs in Ny-Ålesund remote lakes were similar to those observed for some European high mountain lakes. The current PAH levels in sediments from three lakes exceeded Canadian sediment quality guidelines, suggesting the presence of possible risks for aquatic organisms and the need for further studies.
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| 10. |
- Li, Guoqiang, et al.
(författare)
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Orbital scale lake evolution in the Ejina Basin, central Gobi Desert, China revealed by K-feldspar luminescence dating of paleolake shoreline features
- 2018
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 482, s. 109-121
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Tidskriftsartikel (refereegranskat)abstract
- The Ejina Basin in the central Gobi Desert contains the terminal lakes of the Heihe River. Paleoenvironmental changes in the basin are important since its deposits are a significant source of Northern Hemisphere dust. In this study we employed a K-feldspar pIRIR dating technique to date shoreline features <= 940 m at multiple locations in the Ejina Basin similar to 45-50 m above the modern basin floor. Internal checks of luminescence characteristics were employed to test the reliability of the pIRIR dating. In combination with our previously reported stratigraphy and chronology of shorelines at <= 927 m in the Ejina Basin, these results imply that a paleolake was present in the basin prior to similar to 350 ka. Other high stands in the basin occurred at similar to 320-310 ka, 240-180 ka, 120-80 ka, and similar to 5 ka, corresponding to MIS 9, MIS 7, MIS 5 and the mid Holocene (MIS 1), respectively, indicating a strong link with glacial-interglacial cycles. Extensions of the East Asian Summer Monsoon (EASM) during interglacial periods, possibly interacting with the Westerlies, apparently caused higher precipitation and lake formation. The impact of orbital eccentricity on the EASM/Westerlies appears to be responsible for the formation of major lake/desert cycles on the northeastern margin of the Tibetan Plateau.
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