| 1. |
- Yang, Jin, et al.
(författare)
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Climatic Forcing of Plio-Pleistocene Formation of the Modern Limpopo River, South Africa
- 2021
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:14
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the evolution of river systems in southern Africa is fundamental to constrain the evolution of landscape and sediment dispersal patterns. It is widely considered that the upper Zambezi River was connected with the Limpopo River during the Cretaceous, forming what was then the largest river in Africa. Crustal flexure during the Paleogene severed the upper Zambezi drainage from the Limpopo, setting the framework of the modern Zambezi and Limpopo River systems. We present first evidence-based on heavy-mineral assemblages from cores drilled offshore of the Limpopo River mouth and samples collected in different reaches of the modern Limpopo River, integrated with magnetic susceptibility, detrital-zircon geochronology, and geomorphological analysis-suggesting that the current Limpopo River formed recently in the Plio-Quaternary. Plio-Quaternary climate change is envisaged to have controlled the recent dynamics of river drainage and consequent distribution of sediment loads, as observed in many other transcontinental rivers worldwide.
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| 2. |
- An, Rui, et al.
(författare)
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Photostability and Photodegradation Processes in Colloidal CsPbI3 Perovskite Quantum Dots
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:45, s. 39222-39227
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Tidskriftsartikel (refereegranskat)abstract
- All-inorganic CsPbI3 perovskite quantum dots (QDs) have attracted intense attention for their successful application in photovoltaics (PVs) and optoelectronics that are enabled by their superior absorption capability and great photoluminescence (PL) properties. However, their photostability remains a practical bottleneck and further optimization is highly desirable. Here, we studied the photostability of as-obtained colloidal CsPbI3 QDs suspended in hexane. We found that light illumination does induce photodegradation of CsPbI3 QDs. Steady-state spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and transient absorption spectroscopy verified that light illumination leads to detachment of the capping agent, collapse of the CsPbI3 QD surface, and finally aggregation of surface Pb0. Both dangling bonds containing surface and Pb0 serve as trap states causing PL quenching with a dramatic decrease of PL quantum yield. Our work provides a detailed insight about the correlation between the structural and photophysical consequences of the photodegradation process in CsPbI3 QDs and may lead to the optimization of such QDs toward device applications.
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| 3. |
- Chen, Junsheng, et al.
(författare)
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Photostability of the Oleic Acid-Encapsulated Water-Soluble CdxSeyZn1-xS1-y Gradient Core-Shell Quantum Dots
- 2017
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 2:5, s. 1922-1929
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Tidskriftsartikel (refereegranskat)abstract
- Composite systems where quantum dots (QDs) are combined with other nanomaterials (e.g., gold nanorods) in aqueous solutions have attracted broad attention - both for their potential in applications and for studies of fundamental processes. However, high-quality QDs are typically prepared in organic solvents, and the transfer of QDs to an aqueous phase is needed to create the desired QD composites. Photostability of the transferred QDs - both the steady-state and photo-induced dynamic properties - is essential for studying the processes in the composites and for their applications. We present a detailed study of the photostability of aqueous CdxSeyZn1-xS1-y gradient core-shell QDs obtained by various approaches using linker exchange and surfactant encapsulation. Beside the steady-state photoluminescence (PL) emission stability, we also study changes in the PL decay. From the variety of the studied samples, the water-soluble QDs encapsulated by a double layer of oleic acid show superior properties, that is, stable PL emission and PL decay under continuous light or pulsed-laser light irradiation. We demonstrate that the double-layer encapsulation of QDs can be used to create QDs-metal nanoparticle composites.
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| 4. |
- Jiang, Simin, et al.
(författare)
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Sensing Mechanism and Excited-State Dynamics of a Widely Used Intracellular Fluorescent pH Probe : pHrodo
- 2023
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Ingår i: The Journal of Physical Chemistry Letters. - 1948-7185. ; 14:46, s. 10482-10488
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Tidskriftsartikel (refereegranskat)abstract
- The pHrodo with an “off–on” response to the changes of pH has been widely used as a fluorescent pH probe for bioimaging. The fluorescence off–on mechanism is fundamentally important for its application and further development. Herein, the sensing mechanism, especially the relevant excited-state dynamics, of pHrodo is investigated by steady-state and time-resolved spectroscopy as well as quantum chemical calculations, showing that pHrodo is best understood using the bichromophore model. Its first excited state (S1) is a charge transfer state between two chromophores. From S1, pHrodo relaxes to its ground state (S0) via an ultrafast nonradiative process (∼0.5 ps), which causes its fluorescence to be “off”. After protonation, S1 becomes a localized excited state, which accounts for the fluorescence being turned “on”. Our work provides photophysical insight into the sensing mechanism of pHrodo and indicates the bichromophore model might be relevant to a wide range of fluorescent probes.
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| 5. |
- Liu, Zhengtao, et al.
(författare)
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Multi-omics network analysis on samples from sequential biopsies reveals vital role of proliferation arrest for Macrosteatosis related graft failure in rats after liver transplantation
- 2023
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Ingår i: Genomics. - : Elsevier BV. - 0888-7543 .- 1089-8646. ; 115:6
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the molecular impact of graft MaS on post-transplant prognosis, based on multi-omics integrative analysis. Rats were fed by methionine-choline deficient diet (MCD) for MaS grafts. Samples were collected from grafts by sequential biopsies. Transcriptomic and metabolomic profilings were assayed. Post-transplant MaS status showed a close association with graft failure. Differentially expressed genes (DEGs) for in-vivo MaS were mainly enriched on pathways of cell cycle and DNA replication. Post-transplant MaS caused arrests of graft regeneration via inhibiting the E2F1 centered network, which was confirmed by an in vitro experiment. Data from metabolomics assays found insufficient serine/creatine which is located on one‑carbon metabolism was responsible for MaS-related GF. Pre-transplant MaS caused severe fibrosis in long-term survivors. DEGs for grafts from long-term survivors with pre-transplant MaS were mainly enriched in pathways of ECM-receptor interaction and focal adhesion. Transcriptional regulatory network analysis confirmed SOX9 as a key transcription factor (TF) for MaS-related fibrosis. Metabolomic assays found elevation of aromatic amino acid (AAA) was a major feature of fibrosis in long-term survivors. Graft MaS in vivo increased post-transplant GF via negative regulations on graft regeneration. Pre-transplant MaS induced severe fibrosis in long-term survivors via activations on ECM-receptor interaction and AAA metabolism.
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| 6. |
- Piao, Shilong, et al.
(författare)
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Evaluation of terrestrial carbon cycle models for their response to climate variability and to CO2 trends
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 19:7, s. 2117-2132
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to evaluate 10 process-based terrestrial biosphere models that were used for the IPCC fifth Assessment Report. The simulated gross primary productivity (GPP) is compared with flux-tower-based estimates by Jung etal. [Journal of Geophysical Research 116 (2011) G00J07] (JU11). The net primary productivity (NPP) apparent sensitivity to climate variability and atmospheric CO2 trends is diagnosed from each model output, using statistical functions. The temperature sensitivity is compared against ecosystem field warming experiments results. The CO2 sensitivity of NPP is compared to the results from four Free-Air CO2 Enrichment (FACE) experiments. The simulated global net biome productivity (NBP) is compared with the residual land sink (RLS) of the global carbon budget from Friedlingstein etal. [Nature Geoscience 3 (2010) 811] (FR10). We found that models produce a higher GPP (133 +/- 15Pg Cyr-1) than JU11 (118 +/- 6Pg Cyr-1). In response to rising atmospheric CO2 concentration, modeled NPP increases on average by 16% (5-20%) per 100ppm, a slightly larger apparent sensitivity of NPP to CO2 than that measured at the FACE experiment locations (13% per 100ppm). Global NBP differs markedly among individual models, although the mean value of 2.0 +/- 0.8Pg Cyr-1 is remarkably close to the mean value of RLS (2.1 +/- 1.2 Pg Cyr-1). The interannual variability in modeled NBP is significantly correlated with that of RLS for the period 1980-2009. Both model-to-model and interannual variation in model GPP is larger than that in model NBP due to the strong coupling causing a positive correlation between ecosystem respiration and GPP in the model. The average linear regression slope of global NBP vs. temperature across the 10 models is -3.0 +/- 1.5Pg Cyr-1 degrees C-1, within the uncertainty of what derived from RLS (-3.9 +/- 1.1Pg Cyr-1 degrees C-1). However, 9 of 10 models overestimate the regression slope of NBP vs. precipitation, compared with the slope of the observed RLS vs. precipitation. With most models lacking processes that control GPP and NBP in addition to CO2 and climate, the agreement between modeled and observation-based GPP and NBP can be fortuitous. Carbon-nitrogen interactions (only separable in one model) significantly influence the simulated response of carbon cycle to temperature and atmospheric CO2 concentration, suggesting that nutrients limitations should be included in the next generation of terrestrial biosphere models.
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| 7. |
- Yang, B, et al.
(författare)
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Lead-Free, Air-Stable All-Inorganic Cesium Bismuth Halide Perovskite Nanocrystals
- 2017
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 56:41, s. 12471-12475
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Tidskriftsartikel (refereegranskat)abstract
- Lead-based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead-based and the other is the poor stability. Lead-free all-inorganic perovskite Cs3Bi2X9 (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560nm synthesized by a facile room temperature reaction. The ligand-free Cs3Bi2Br9 NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2%. The PLQE can be increased to 4.5% when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2-20ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30days.
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| 8. |
- Zhang, Hanzhi, et al.
(författare)
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Large-number detrital zircon U-Pb ages reveal global cooling caused the formation of the Chinese Loess Plateau during Late Miocene
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:41
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Tidskriftsartikel (refereegranskat)abstract
- The formation and evolution of the landscape of the Chinese Loess Plateau (CLP) is debated because of uncertainties regarding dust provenance. We present a quantitative estimation of dust source contributions to the CLP, based on more than 37,100 detrital zircon U-Pb ages, combined with mineral assemblages and isotope analyses. Our results reveal that the CLP was stepwise formed by similar to 8 million years (Ma) and is mainly composed of material from the Northeastern Qinghai-Tibetan Plateau, with stepwise shifts in relative contributions of different eolian silt sources occurring at similar to 2.6 Ma and 1.5 to 1.2 Ma. We infer that these changes were driven by stepwise global cooling, which induced aridification and enhanced silt production in glaciated-cold climate dust source regions, as well as dust ablation in the expanded and regions. We propose that global cooling, rather than regional tectonic deformation, was the main driver of the formation and evolution of the CLP during late Cenozoic.
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| 9. |
- Zhang, Wei, et al.
(författare)
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Revealing the sensing mechanism of a fluorescent pH probe based on a bichromophore approach
- 2022
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:43, s. 26731-26737
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence sensing plays an increasingly important role in biology and biomedicine. For many practical applications of fluorescent probes, an “off-on” response is preferred. The question of how fluorescence quenching/enhancement occurs is fundamental and of high importance for application and design of new fluorescent probes. The sensing mechanism of an aminorhodamine (TMARh) pH probe is investigated using femtosecond transient absorption spectroscopy and quantum chemical calculations, showing that this probe is best understood using the bichromophore model rather than the more common models such as photoinduced electron transfer or intramolecular charge transfer. Under excitation in the main absorption band at 530 nm, a fast internal conversion to the first excited state (S1) is observed for TMARh; meanwhile, no new transient components are obtained when TMARh is excited directly to S1 in the weakly absorbing red tail at 630 nm. It is confirmed that the S1 of TMARh is a dark “off” state. Theoretical calculations show that the S1 “off” state is an intramolecular charge transfer state from an aminophenyl group to a rhodamine chromophore. After protonation of the aminophenyl group, to yield HTMARh, the transient S2/S1 internal conversion process that occurs in TMARh under 530 nm excitation is absent, suggesting that the charge transfer state becomes highly unfavorable. All calculations and spectral data confirm that HTMARh has localized transition in the rhodamine chromophore, in agreement with this being the bright “on” state of the pH probe. The current work not only provides a photophysical insight into the sensing mechanism of this specific probe, but also shows that the bichromophore model is useful and may be relevant for analyzing other probes or in the designing of new ones.
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| 10. |
- Zhao, Li, et al.
(författare)
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Excited-state dynamics of 4-hydroxyisoindoline-1,3-dione and its derivative as fluorescent probes
- 2024
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Ingår i: Physical chemistry chemical physics : PCCP. - 1463-9084. ; 26:17, s. 13506-13514
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescent probes have become promising tools for monitoring the concentration of peroxynitrite, which is linked to many diseases. However, despite focusing on developing numerous peroxynitrite based fluorescent probes, limited emphasis is placed on their sensing mechanism. Here, we investigated the sensing mechanism of a peroxynitrite fluorescent probe, named BHID-Bpin, with a focus on the relevant excited state dynamics. The photoexcited BHID-Bpin relaxes to its ground state via an efficient nonradiative process (∼300 ps) due to the presence of a minimum energy conical intersection between its first excited state and ground state. However, upon reacting with peroxynitrite, the Bpin moiety is cleaved from BHID-Bpin and BHID is formed. The formed BHID exhibits strong dual band fluorescence which is caused by an ultrafast excited-state intramolecular proton transfer process (∼1 ps).
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