| 1. |
- Rattigan, Eoghan, et al.
(författare)
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The cobalt oxidation state in preferential CO oxidation on CoOx/Pt(111) investigated by operando X-ray photoemission spectroscopy
- 2022
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:16, s. 9236-9246
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Tidskriftsartikel (refereegranskat)abstract
- The combination of a reducible transition metal oxide and a noble metal such as Pt often leads to active low-temperature catalysts for the preferential oxidation of CO in excess H2 gas (PROX reaction). While CO oxidation has been investigated for such systems in model studies, the added influence of hydrogen gas, representative of PROX, remains less explored. Herein, we use ambient pressure scanning tunneling microscopy and ambient pressure X-ray photoelectron spectroscopy on a CoOx/Pt(111) planar model catalyst to analyze the active phase and the adsorbed species at the CoOx/Pt(111) interface under atmospheres of CO and O2 with a varying partial pressure of H2 gas. By following the evolution of the Co oxidation state as the catalyst is brought to a reaction temperature of above 150 °C, we determine that the active state is characterized by the transformation from planar CoO with Co in the 2+ state to a mixed Co2+/Co3+ phase at the temperature where CO2 production is first observed. Furthermore, our spectroscopy observations of the surface species suggest a reaction pathway for CO oxidation, proceeding from CO exclusively adsorbed on Co2+ sites reacting with the lattice O from the oxide. Under steady state CO oxidation conditions (CO/O2), the mixed oxide phase is replenished from oxygen incorporating into cobalt oxide nanoislands. In CO/O2/H2, however, the onset of the active Co2+/Co3+ phase formation is surprisingly sensitive to the H2 pressure, which we explain by the formation of several possible hydroxylated intermediate phases that expose both Co2+ and Co3+. This variation, however, has no influence on the temperature where CO oxidation is observed. Our study points to the general importance of a dynamic reducibility window of cobalt oxide, which is influenced by hydroxylation, and the bonding strength of CO to the reduced oxide phase as important parameters for the activity of the system.
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| 2. |
- Allahverdiyeva, Yagut, et al.
(författare)
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NordAqua, a Nordic Center of Excellence to develop an algae-based photosynthetic production platform
- 2021
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Ingår i: Physiologia Plantarum. - : John Wiley & Sons. - 0031-9317 .- 1399-3054. ; 173:2, s. 507-513
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Tidskriftsartikel (refereegranskat)abstract
- NordAqua is a multidisciplinary Nordic Center of Excellence funded by NordForsk Bioeconomy program (2017–2022). The research center promotes Blue Bioeconomy and endeavours to reform the use of natural resources in a environmentally sustainable way. In this short communication, we summarize particular outcomes of the consortium. The key research progress of NordAqua includes (1) improving of photosynthetisis, (2) developing novel photosynthetic cell factories that function in a “solar-driven direct CO2 capture to target bioproducts” mode, (3) promoting the diversity of Nordic cyanobacteria and algae as an abundant and resilient alternative for less sustainable forest biomass and for innovative production of biochemicals, and (4) improving the bio-based wastewater purification and nutrient recycling technologies to provide new tools for integrative circular economy platforms.
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| 3. |
- Alvi, Sajid, 1987, et al.
(författare)
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Entropy Stabilized Medium High Entropy Alloy Anodes for Lithium-Ion Batteries
- 2024
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- One often proposed route to improved energy density for lithium-ion batteries is to use alloy anodes, such as silicon, able to store large amounts of lithium. Mechanical instability caused by the large expansion and contraction associated with (de)lithiation, and hence bad cyclability, has, however, so far hindered progress. As proof-of-concept of a remedy, we here present BiSbSe1.5Te1.5, a medium high-entropy alloy with improved cycling stability for conversion-alloying (de)lithiation reactions. We attain five to twenty times more stable cycles than previously reported for comparable metal-Se and -Te-based anodes, with a very good reversible capacity (464 mAh g−1) for up to 110 cycles- and this without using any carbonaceous materials to create a composite. Altogether, this highlights how alloy engineering and increased entropy materials can stabilize conversion-alloying electrodes.
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| 4. |
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| 5. |
- Bergman, Lina, et al.
(författare)
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Investigating Maternal Brain Alterations in Preeclampsia : the Need for a Multidisciplinary Effort
- 2019
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Ingår i: Current Hypertension Reports. - : Springer Science and Business Media LLC. - 1522-6417 .- 1534-3111. ; 21:9
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE OF REVIEW: To provide insight into the mechanisms underlying cerebral pathophysiology and to highlight possible methods for evaluation, screening, and surveillance of cerebral complications in preeclampsia.RECENT FINDINGS: The pathophysiology of eclampsia remains enigmatic. Animal studies show that the cerebral circulation in pregnancy and preeclampsia might be affected with increased permeability over the blood-brain barrier and altered cerebral blood flow due to impaired cerebral autoregulation. The increased blood pressure cannot be the only underlying cause of eclampsia and cerebral edema, since some cases of eclampsia arise without simultaneous hypertension. Findings from animal studies need to be confirmed in human tissues. Evaluation of brain alterations in preeclampsia and eclampsia is challenging and demands a multidisciplinary collaboration, since no single method can accurately and fully describe how preeclampsia affects the brain. Cerebral complications of preeclampsia are significant factors in maternal morbidity and mortality worldwide. No single method can accurately describe the full picture of how preeclampsia affects the brain vasculature and parenchyma. We recommend an international and multidisciplinary effort not only to overcome the issue of limited sample availability but also to optimize the quality of research.
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| 6. |
- Bergman, Lina, et al.
(författare)
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Preeclampsia and Increased Permeability Over the Blood–Brain Barrier : A Role of Vascular Endothelial Growth Receptor 2
- 2021
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Ingår i: American Journal of Hypertension. - : Oxford University Press. - 0895-7061 .- 1941-7225. ; 34:1, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cerebral complications in preeclampsia are leading causes of maternal mortality worldwide but the underlying pathophysiology is largely unknown and a challenge to study. Using an in vitro model of the human blood brain barrier (BBB), we explored the role of vascular endothelial growth factor receptor 2 (VEGFR2) in preeclampsia.METHODS: The human brain endothelial cell line (hCMEC/D3) cultured on Tranwells insert were exposed (12 h) to plasma from women with preeclampsia (n=28), normal pregnancy (n=28) and non-pregnant (n=16) controls. Transendothelial electrical resistance (TEER) and permeability to 70 kDa FITC-dextran were measured for assessment of BBB integrity. We explored possible underlying mechanisms, with focus on expression of tight junction proteins and phosphorylation of two tyrosine residues of VEGFR2, associated with vascular permeability and migration (pY951) and cell proliferation (pY1175). Plasma concentrations of soluble FMS like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) were measured in order to establish correlations with in vitro results.RESULTS: hCMEC/D3 exposed to plasma from women with preeclampsia exhibited reduced TEER and increased permeability to 70 kDa FITC-dextran. Further, these cells up-regulated the mRNA levels of VEGFR2, as well as pY951-VEGFR2; but reduced pY1175-VEGFR2 (p&0.05 in all cases). No difference in mRNA expression of tight junction protein was observed between gruops. There was no correlation between angiogenic biomarkers and BBB permeability.CONCLUSION: We present a promising in vitro model of the BBB in preeclampsia. Selective tyrosine phosphorylation of VEGFR2 may participate in the increased BBB permeability in preeclampsia irrespective of plasma concentrations of angiogenic biomarkers.
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| 7. |
- Calatayud, Joaquín, et al.
(författare)
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Positive associations among rare species and their persistence in ecological assemblages
- 2020
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Ingår i: Nature Ecology & Evolution. - : Nature Publishing Group. - 2397-334X. ; 4:1, s. 40-45
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Tidskriftsartikel (refereegranskat)abstract
- According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors; yet, they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. On the other hand, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most probable mechanisms underpinning this pattern and rare species persistence. The consistent results across taxa and geography suggest a general explanation for the maintenance of biodiversity in competitive environments. Analysing spatial association networks among >300 terrestrial and aquatic assemblages, the authors find that the majority of negative associations involve abundant species. In contrast, rare species form mostly positive associations, potentially explaining their persistence in natural communities.
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| 8. |
- Castaño Díaz, Carlos Mauricio, 1985, et al.
(författare)
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Mental Health of People Under Isolation During the covid-19 Outbreak: An Exploratory Study
- 2022
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Ingår i: Revista Colombiana de Psicologia. - : Universidad Nacional de Colombia. - 2344-8644 .- 0121-5469. ; 31:2, s. 27-43
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Tidskriftsartikel (refereegranskat)abstract
- We conducted an exploratory study using a survey inquiring on seven topics on how people were reacting to the covid-19 pandemic of 2020 aiming to trace a map of symptoms and feelings related to mental health and isolation. 1785 people participated in the survey. Additionally, we applied two psychological scales to analyze depression and stress (prevalent in previous studies). We found that people in isolation during the pandemic presented symptoms related to dissociative disorders, negative affect, and anxiety syndrome. Also, depression and stress had a high prevalence compared to the average rates indicated by the World Health Organisation and the Colombian Ministry of Health. The results indicated an association between depression and stress and being previously diagnosed with a mental health problem, and job and financial situation. Our results highlight the need to design prevention and intervention programmes to reduce the negative consequences of isolation. © 2022 Universidad Nacional de Colombia. All rights reserved.
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| 9. |
- Correales, Álvaro, et al.
(författare)
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Itô vs Stratonovich in the presence of absorbing states
- 2019
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Ingår i: Journal of Mathematical Physics. - : AIP Publishing. - 0022-2488 .- 1089-7658. ; 60:12
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Tidskriftsartikel (refereegranskat)abstract
- It is widely assumed that there exists a simple transformation from the Ito interpretation to the one by Stratonovich and back for any stochastic differential equation of applied interest. While this transformation exists under suitable conditions, and transforms one interpretation into the other at the price of modifying the drift of the equation, it cannot be considered universal. We show that a class of stochastic differential equations, characterized by the presence of absorbing states and of interest in applications, does not admit such a transformation. In particular, formally applying this transformation may lead to the disappearance of some absorbing states. In turn, this modifies the long-time, and even the intermediate-time, behavior of the solutions. The number of solutions can also be modified by the unjustified application of the mentioned transformation, as well as by a change in the interpretation of the noise. We discuss how these facts affect the classical debate on the Itô vs Stratonovich dilemma.
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| 10. |
- Ding, Pengji, et al.
(författare)
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Nonadiabaticity of cavity-free neutral nitrogen lasing
- 2017
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Ingår i: Physical Review A. - 2469-9926. ; 96:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on a theoretical study of cavity-free lasing of neutral nitrogen molecules in femtosecond laser filaments with a nonadiabatic Maxwell-Bloch model, compared with recent pump-seed experiments. The nonadiabaticity of the lasing process is revealed and it is found that electron-neutral collisions dominate the dipole dephasing rate. Moreover, we show that the asymmetry between forward and backward lasing not only depends on the different amplification lengths but also on the temporal dynamics of electron-neutral collisions. The comparison of the nonadiabatic model with simulations based on the adiabatic approximation (such as radiative transfer equations) explicitly sets a bound on the validity of the latter model for cavity-free nitrogen lasing phenomenon, which holds a unique potential in optical remote sensing applications.
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