| 1. |
- Cao, Lina, et al.
(författare)
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Atomically dispersed iron hydroxide anchored on Pt for preferential oxidation of CO in H-2
- 2019
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 565:7741, s. 631-635
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Tidskriftsartikel (refereegranskat)abstract
- Proton-exchange-membrane fuel cells (PEMFCs) are attractive next-generation power sources for use in vehicles and other applications(1), with development efforts focusing on improving the catalyst system of the fuel cell. One problem is catalyst poisoning by impurity gases such as carbon monoxide (CO), which typically comprises about one per cent of hydrogen fuel(2-4). A possible solution is on-board hydrogen purification, which involves preferential oxidation of CO in hydrogen (PROX)(3-7). However, this approach is challenging(8-15) because the catalyst needs to be active and selective towards CO oxidation over a broad range of low temperatures so that CO is efficiently removed (to below 50 parts per million) during continuous PEMFC operation (at about 353 kelvin) and, in the case of automotive fuel cells, during frequent cold-start periods. Here we show that atomically dispersed iron hydroxide, selectively deposited on silica-supported platinum (Pt) nanoparticles, enables complete and 100 per cent selective CO removal through the PROX reaction over the broad temperature range of 198 to 380 kelvin. We find that the mass-specific activity of this system is about 30 times higher than that of more conventional catalysts consisting of Pt on iron oxide supports. In situ X-ray absorption fine-structure measurements reveal that most of the iron hydroxide exists as Fe-1(OH)(x) clusters anchored on the Pt nanoparticles, with density functional theory calculations indicating that Fe-1(OH)(x)-Pt single interfacial sites can readily react with CO and facilitate oxygen activation. These findings suggest that in addition to strategies that target oxide-supported precious-metal nanoparticles or isolated metal atoms, the deposition of isolated transition-metal complexes offers new ways of designing highly active metal catalysts.
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| 2. |
- Cao, Shun, et al.
(författare)
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High-temperature ultra-broad UV–MIR high-efficiency absorber based on double ring-shaped titanium nitride resonators
- 2021
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Ingår i: Optics Communications. - : Elsevier B.V.. - 0030-4018 .- 1873-0310. ; 485
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Tidskriftsartikel (refereegranskat)abstract
- An ultrabroad absorber based on double-ring-shaped titanium nitride (TiN) nanoresonators, which can work in high temperatures, is proposed and numerically studied. The absorber with some optimal parameters exhibits an averaged absorption of 94.6% in the range of 200–4000 nm (from ultraviolet to mid-infrared) and a band from 200–3518 nm having an absorption > 90%. We have demonstrated in detail the physical mechanisms of the ultra-broad absorption, including the dielectric lossy property of TiN material itself in shorter wavelengths and plasmonic resonances caused by the metallic property of TiN nano-resonators in longer wavelengths. In addition, the absorber shows polarization independent and wide-angle acceptance. Another absorber with double TiN nano-rings of different heights has flatter and higher absorption efficiency (more than 95% absorption) at 200–2860 nm waveband. These properties make the proposed absorbers based on TiN has great potentials in many applications, such as light trapping, photovoltaics, thermal emitters.
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| 3. |
- Gao, Jinlong, et al.
(författare)
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Planar laser-induced imaging of CH3 for high resolution single-shot reaction-zone visualization in premixed methane/air flames over broad stoichiometric ratios
- 2022
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel approach for single-shot planar imaging of CH3 radicals in premixed methane and air flames. A 213 nm beam from the 5th harmonic of an Nd:YAG laser was resonantly absorbed by the CH3 radicals, which were excited to the highly pre-dissociative upper level and dissociated to H2 and CH (X), as the main dissociation channel. The CH radicals were consequently excited by a 388 nm beam from an alexandrite laser, and the fluorescence from the excited CH radicals was collected off-resonant at 431 nm. Using this Photo-Fragmentation Planar Laser-Induced Fluorescence (PF-PLIF) technique, instantaneous flame front structures, represented by CH3 radicals, can be visualized with high spatial resolution over a broad range of stoichiometric ratios. Signal-to-noise ratios up to 50 were observed for premixed methane/air flame with stoichiometric ratio as low as 0.26. The CH radicals naturally presented in flame front are more than 400 times lower in concentration than the CH3 radicals in premixed methane/air flames even at the conditions close to stoichiometric or slightly fuel rich cases where the highest CH concentrations exist, and the CH3/CH concentration ratios increase dramatically moving towards fuel lean conditions. By adopting a structured illumination of the 213 nm pump beam, the naturally presented CH radicals were visualized simultaneously with CH3 at slightly fuel rich laminar flames, where the CH signal intensity was 5 times lower than that from CH3. The results indicate that the CH3 PF-PLIF technique can provide much stronger signal than the CH PLIF and presented a much promising potential for applications in fuel-lean flames. Finally, the CH3 PF-PLIF was performed in premixed turbulent flames to demonstrate the feasibility of this technique for flame front visualization in turbulent premixed flames.
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| 4. |
- Luo, Lei, et al.
(författare)
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Thermal performance in latticework ducts with various endwall shapes for aero-craft turbine cooling
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 126
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Tidskriftsartikel (refereegranskat)abstract
- The latticework duct plays an important role in turbine blade cooling for aircraft engines. The present numerical research provided information about the thermal performance in latticework ducts with different endwall shapes. Each latticework duct analyzed in this study had a crossing angle of 90° and 11 sub channels on both the two sides of the endwall. A numerical investigation was conducted at five Reynolds numbers (11,000 to 55,000) and six endwall shapes. The local Nu number and flow structures were analyzed in detail. For a rectangular latticework duct, a jet region generated considerable Nusselt numbers, and the helical flow leaded to a uniform Nu number. Moreover, the turning and jet effects caused a high friction factor. The results also showed that an appropriate endwall shape could increase the thermal performance in a latticework duct. The different endwall shapes mainly altered the flow structure nearby the sidewall of the latticework, especially for the spiral flow. Moreover, the endwall shape also influenced the heat transfer and flow behavior. This phenomenon occurred because the different endwall shapes increased the turbulence of the cooling air to different extents.
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| 5. |
- Swift, Imogen J, et al.
(författare)
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A systematic review of progranulin concentrations in biofluids in over 7,000 people-assessing the pathogenicity of GRN mutations and other influencing factors.
- 2024
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Ingår i: Alzheimer's Research & Therapy. - 1758-9193. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic heterozygous mutations in the progranulin gene (GRN) are a key cause of frontotemporal dementia (FTD), leading to significantly reduced biofluid concentrations of the progranulin protein (PGRN). This has led to a number of ongoing therapeutic trials aiming to treat this form of FTD by increasing PGRN levels in mutation carriers. However, we currently lack a complete understanding of factors that affect PGRN levels and potential variation in measurement methods. Here, we aimed to address this gap in knowledge by systematically reviewing published literature on biofluid PGRN concentrations.Published data including biofluid PGRN concentration, age, sex, diagnosis and GRN mutation were collected for 7071 individuals from 75 publications. The majority of analyses (72%) had focused on plasma PGRN concentrations, with many of these (56%) measured with a single assay type (Adipogen) and so the influence of mutation type, age at onset, sex, and diagnosis were investigated in this subset of the data.We established a plasma PGRN concentration cut-off between pathogenic mutation carriers and non-carriers of 74.8ng/mL using the Adipogen assay based on 3301 individuals, with a CSF concentration cut-off of 3.43ng/mL. Plasma PGRN concentration varied by GRN mutation type as well as by clinical diagnosis in those without a GRN mutation. Plasma PGRN concentration was significantly higher in women than men in GRN mutation carriers (p=0.007) with a trend in non-carriers (p=0.062), and there was a significant but weak positive correlation with age in both GRN mutation carriers and non-carriers. No significant association was seen with weight or with TMEM106B rs1990622 genotype. However, higher plasma PGRN levels were seen in those with the GRN rs5848 CC genotype in both GRN mutation carriers and non-carriers.These results further support the usefulness of PGRN concentration for the identification of the large majority of pathogenic mutations in the GRN gene. Furthermore, these results highlight the importance of considering additional factors, such as mutation type, sex and age when interpreting PGRN concentrations. This will be particularly important as we enter the era of trials for progranulin-associated FTD.
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| 6. |
- Visseren-Hamakers, Ingrid, et al.
(författare)
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Transformative governance of biodiversity: insights for sustainable development : Transformative governance of biodiversity: insights for sustainable development
- 2021
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Ingår i: Current Opinion in Environmental Sustainability. - : Elsevier BV. - 1877-3443 .- 1877-3435. ; 53:21, s. 20-28
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Tidskriftsartikel (refereegranskat)abstract
- While there is much debate on transformative change among academics and policymakers, the discussion on how to govern such change is still in its infancy. This article argues that transformative governance is needed to enable the transformative change necessary for achieving global sustainability goals. Based on a literature review, the article unpacks this concept of transformative governance. It is: integrative, to ensure local solutions also have sustainable impacts elsewhere (across scales, places, issues and sectors); inclusive, to empower those whose interests are currently not being met and represent values embodying transformative change for sustainability; adaptive, enabling learning, experimentation, and reflexivity, to cope with the complexity of transformative change; and pluralist, recognizing different knowledge systems. We argue that only when these four governance approaches are: implemented in conjunction; operationalized in a specific manner; and focused on addressing the indirect drivers underlying sustainability issues, governance becomes transformative.
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