| 1. |
- Tian, Ye, et al.
(författare)
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Holocene climate change in southern Oman deciphered by speleothem records and climate model simulations
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Qunf Cave oxygen isotope (& delta;O-18(c)) record from southern Oman is one of the most significant of few Holocene Indian summer monsoon cave records. However, the interpretation of the Qunf & delta;O-18(c) remains in dispute. Here we provide a multi-proxy record from Qunf Cave and climate model simulations to reconstruct the Holocene local and regional hydroclimate changes. The results indicate that besides the Indian summer monsoon, the North African summer monsoon also contributes water vapor to southern Oman during the early to middle Holocene. In principle, Qunf & delta;O-18(c) values reflect integrated oxygen-isotope fractionations over a broad moisture transport swath from moisture sources to the cave site, rather than local precipitation amount alone, and thus the Qunf & delta;O-18(c) record characterizes primary changes in the Afro-Asian monsoon regime across the Holocene. In contrast, local climate proxies appear to suggest an overall slightly increased or unchanged wetness over the Holocene at the cave site. Southern Oman speleothem oxygen isotope and multi-proxy data reveal diverse changes in the Afro-Indian summer monsoon circulations and local hydroclimate conditions during the Holocene, confirming climate model simulations.
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| 2. |
- Chen, Haiwei, et al.
(författare)
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Extending the environmental lifetime of unpackaged perovskite solar cells through interfacial design
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:30, s. 11604-11610
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processed oxo-functionalized graphene (oxo-G1) is employed to substitute hydrophilic PEDOT:PSS as an anode interfacial layer for perovskite solar cells. The resulting devices exhibit a reasonably high power conversion efficiency (PCE) of 15.2% in the planar inverted architecture with oxo-G1 as a hole transporting material (HTM), and most importantly, deploy the full open-circuit voltage (Voc) of up to 1.1 V. Moreover, oxo-G1 effectively slows down the ingress of water vapor into the device stack resulting in significantly enhanced environmental stability of unpackaged cells under illumination with 80% of the initial PCE being reached after 500 h. Without encapsulation, ∼60% of the initial PCE is retained after ∼1000 h of light soaking under 0.5 sun and ambient conditions maintaining the temperature beneath 30 °C. Moreover, the unsealed perovskite device retains 92% of its initial PCE after about 1900 h under ambient conditions and in the dark. Our results underpin that controlling water diffusion into perovskite cells through advanced interface engineering is a crucial step towards prolonged environmental stability.
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| 3. |
- Cheng, Hai, et al.
(författare)
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Milankovitch theory and monsoon
- 2022
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Ingår i: The Innovation. - : Elsevier BV. - 2666-6758. ; 3:6
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Forskningsöversikt (refereegranskat)abstract
- The widely accepted “Milankovitch theory” explains insolation-induced waxing and waning of the ice sheets and their effect on the global climate on orbital timescales. In the past half century, however, the theory has often come under scrutiny, especially regarding its “100-ka problem.” Another drawback, but the one that has received less attention, is the “monsoon problem,” which pertains to the exclusion of monsoon dynamics in classic Milankovitch theory even though the monsoon prevails over the vast low-latitude (∼30° N to ∼30° S) region that covers half of the Earth's surface and receives the bulk of solar radiation. In this review, we discuss the major issues with the current form of Milankovitch theory and the progress made at the research forefront. We suggest shifting the emphasis from the ultimate outcomes of the ice volume to the causal relationship between changes in northern high-latitude insolation and ice age termination events (or ice sheet melting rate) to help reconcile the classic “100-ka problem.” We discuss the discrepancies associated with the characterization of monsoon dynamics, particularly the so-called “sea-land precession-phase paradox” and the “Chinese 100-ka problem.” We suggest that many of these discrepancies are superficial and can be resolved by applying a holistic “monsoon system science” approach. Finally, we propose blending the conventional Kutzbach orbital monsoon hypothesis, which calls for summer insolation forcing of monsoons, with Milankovitch theory to formulate a combined “Milankovitch-Kutzbach hypothesis” that can potentially explain the dual nature of orbital hydrodynamics of the ice sheet and monsoon systems, as well as their interplays and respective relationships with the northern high-latitude insolation and inter-tropical insolation differential.
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| 4. |
- Comas-Bru, Laia, et al.
(författare)
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Evaluating model outputs using integrated global speleothem records of climate change since the last glacial
- 2019
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 15:4, s. 1557-1579
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Tidskriftsartikel (refereegranskat)abstract
- Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data-model comparisons. Here, we illustrate this using 456 globally distributed speleothem delta O-18 records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data-model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on delta O-18 values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.
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| 5. |
- Tan, Qiyang, et al.
(författare)
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Unravelling the roles of TiN-nanoparticle inoculant in additively manufactured 316 stainless steel
- 2024
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Ingår i: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 175, s. 153-169
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Tidskriftsartikel (refereegranskat)abstract
- As a potent grain refiner for steel casting, TiN is now widely used to refine γ-austenite in steel additive manufacturing (AM). However, the refining mechanism of TiN during AM remains unclear despite intensive research in recent years. This work aims to boost our understanding on the mechanism of TiN in refining the γ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour. Experimental results show that addition of 1 wt.% TiN nanoparticles led to complete columnar-to-equiaxed transition and significant refinement of the austenite grains to ∼2 µm in the 316 steel. Thermodynamic and kinetic simulations confirmed that, despite the rapid AM solidification, δ-ferrite is the primary solid phase during AM of the 316 steel and γ-austenite forms through subsequent peritectic reaction or direct transformation from the δ-ferrite. This implies that the TiN nanoparticles actually refined the δ-ferrite through promoting its heterogenous nucleation, which in turn refined the γ-austenite. This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Si δ-ferrite alloy, in which δ-ferrite forms directly from the melt and is retained at room temperature. The grain refinement is attributed to the good atomic matching between δ-ferrite and TiN. Grain refinement in the 316 steel through 1 wt.% TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strength-ductility synergy with yield strength of 561 MPa, tensile strength of 860 MPa and elongation of 48%.
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| 6. |
- Zhang, Hao, et al.
(författare)
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Repeated evolutionary transitions of flavobacteria from marine to non-marine habitats
- 2019
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Ingår i: Environmental Microbiology. - : Wiley-Blackwell. - 1462-2912 .- 1462-2920. ; 21:2, s. 648-666
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Tidskriftsartikel (refereegranskat)abstract
- The taxonomy of marine and non-marine organisms rarely overlap, but the mechanisms underlying this distinction are often unknown. Here, we predicted three major ocean-to-land transitions in the evolutionary history of Flavobacteriaceae, a family known for polysaccharide and peptide degradation. These unidirectional transitions were associated with repeated losses of marine signature genes and repeated gains of non-marine adaptive genes. This included various Na+-dependent transporters, osmolyte transporters and glycoside hydrolases (GH) for sulfated polysaccharide utilization in marine descendants, and in non-marine descendants genes for utilizing the land plant material pectin and genes facilitating terrestrial host interactions. The K+ scavenging ATPase was repeatedly gained whereas the corresponding low-affinity transporter repeatedly lost upon transitions, reflecting K+ ions are less available to non-marine bacteria. Strikingly, the central metabolism Na+-translocating NADH: quinone dehydrogenase gene was repeatedly gained in marine descendants, whereas the H+-translocating counterpart was repeatedly gained in non-marine lineages. Furthermore, GH genes were depleted in isolates colonizing animal hosts but abundant in bacteria inhabiting other non-marine niches; thus relative abundances of GH versus peptidase genes among Flavobacteriaceae lineages were inconsistent with the marine versus non-marine dichotomy. We suggest that phylogenomic analyses can cast novel light on mechanisms explaining the distribution and ecology of key microbiome components.
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