| 1. |
- Degerman, David, 1989-, et al.
(författare)
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Demonstrating Pressure Jumping as a Tool to Address the Pressure Gap in High Pressure Photoelectron Spectroscopy of CO and CO2 Hydrogenation on Rh(211)
- 2024
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Ingår i: ChemPhysChem. - 1439-4235 .- 1439-7641. ; 25:1
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Tidskriftsartikel (refereegranskat)abstract
- Operando probing by x-ray photoelectron spectroscopy (XPS) of certain hydrogenation reactions are often limited by the scattering of photoelectrons in the gas phase. This work describes a method designed to partially circumvent this so called pressure gap. By performing a rapid switch from a high pressure (where acquisition is impossible) to a lower pressure we can for a short while probe a remnant of the high pressure surface as well as the time dynamics during the re-equilibration to the new pressure. This methodology is demonstrated using the CO2 and the CO hydrogenation reaction over Rh(211). In the CO2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CHx adsorbates over chemisorbed CO. This contrasts against previous static operando spectra acquired at lower pressures. Furthermore, the pressure jumping method yields a faster acquisition and more detailed spectra than static operando measurements above 1 bar. In the CO hydrogenation reaction, we observe that CHx accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation.
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| 2. |
- Degerman, David, 1989-, et al.
(författare)
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Effect of CO2-Rich Syngas on the Chemical State of Fe(110) during Fischer-Tropsch Synthesis
- 2024
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Ingår i: The Journal of Physical Chemistry C. - 1932-7447 .- 1932-7455. ; 128:13, s. 5542-5552
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Tidskriftsartikel (refereegranskat)abstract
- We have used in situ X-ray photoelectron spectroscopy to obtain information about the chemical state of a Fe single-crystal catalyst upon addition of CO2 in the syngas feed during Fischer–Tropsch synthesis (FTS) between 85 and 550 mbar. We found that at certain temperatures, the ternary mixture of CO, CO2, and H2 yields a chemical state which is resemblant of neither the CO hydrogenation nor the CO2 hydrogenation reaction mixtures in isolation. The addition of CO2 to a CO + H2 reaction mixture mostly affects the chemical state at low-temperature FTS conditions (i.e., below 254 °C). In this temperature span, the ternary reaction mixture resulted in a carburized surface, whereas the CO + H2 reaction led to surface oxidation. We propose a hypothesis, where a carbonate intermediate produced by CO2 interaction with Fe oxide aids the reduction of the Fe oxide, paving the way for the carburization of the Fe by dissociated CO. Very small differences in the spectra of the CO + H2 and the CO + CO2 + H2 reaction mixtures were observed above 254 °C, suggesting that the CO2 is a spectator in these conditions. Changing the total pressure of both the CO hydrogenation and ternary reaction mixture causes quantitative changes in the spectra at both low- and high-temperature FTS conditions, the degree of oxidation/carburization was affected in the low-temperature-FTS regime, and the degree of hydrocarbon build-up was affected in the high-temperature-FTS.
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| 3. |
- Goodwin, Christopher M., 1989-, et al.
(författare)
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Operando Probing of the Surface Chemistry During the Haber-Bosch Process
- 2024
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 625:7994, s. 282-286
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Tidskriftsartikel (refereegranskat)abstract
- The Haber-Bosch process produces NH3 from N2 and H21,2, typically with Fe and Ru3. HB has been proposed as the most important scientific invention in the 20th century4. The chemical state during reaction has been proposed as oxides5, nitrides2, metallic, or surface nitride6. The proposed rate-limiting step has been the dissociation of N27–9, reaction of adsorbed nitrogen10, or desorption of NH311. Due to the vacuum requirement for surface-sensitive techniques, studies at reaction conditions are limited to theory computations12–14. We determined the surface composition, during NH3 production, at pressures up to 1 bar and temperatures as high as 723 K on flat, stepped Fe, and stepped Ru single crystal surfaces using operando X-ray Photoelectron Spectroscopy15. We found that all surfaces remain metallic. On Fe only a small amount of adsorbed N remains, yet Ru’s surface is almost adsorbate free. At 523 K, high amines (NHx) coverages appear on the stepped Fe surface. The results show that the rate-limiting step on Ru is always N2 dissociation. Still, on Fe the hydrogenation step involving adsorbed N atoms is essential for the total rate, as predicted by theory13. If the temperature is lowered on Fe, the rate-limiting steps switch and become surface species’ hydrogenation.
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| 4. |
- Klevebro, Susanna, et al.
(författare)
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Arachidonic acid and docosahexaenoic acid levels correlate with the inflammation proteome in extremely preterm infants
- 2024
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Ingår i: Clinical Nutrition. - : Elsevier BV. - 0261-5614 .- 1532-1983. ; 43:5, s. 1162-1170
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Tidskriftsartikel (refereegranskat)abstract
- Background & aim: Clinical trials supplementing the long-chain polyunsaturated fatty acids (LCPUFAs) docosahexaenoic acid (DHA) and arachidonic acid (AA) to preterm infants have shown positive effects on inflammation-related morbidities, but the molecular mechanisms underlying these effects are not fully elucidated. This study aimed to determine associations between DHA, AA, and inflammation-related proteins during the neonatal period in extremely preterm infants. Methods: A retrospective exploratory study of infants (n = 183) born below 28 weeks gestation from the Mega Donna Mega trial, a randomized multicenter trial designed to study the effect of DHA and AA on retinopathy of prematurity. Serial serum samples were collected after birth until postnatal day 100 (median 7 samples per infant) and analyzed for phospholipid fatty acids and proteins using targeted proteomics covering 538 proteins. Associations over time between LCPUFAs and proteins were explored using mixed effect modeling with splines, including an interaction term for time, and adjusted for gestational age, sex, and center. Results: On postnatal day one, 55 proteins correlated with DHA levels and 10 proteins with AA levels. Five proteins were related to both fatty acids, all with a positive correlation. Over the first 100 days after birth, we identified 57 proteins to be associated with DHA and/or AA. Of these proteins, 41 (72%) related to inflammation. Thirty-eight proteins were associated with both fatty acids and the overall direction of association did not differ between DHA and AA, indicating that both LCPUFAs similarly contribute to up- and down-regulation of the preterm neonate inflammatory proteome. Primary examples of this were the inflammation-modulating cytokines IL-6 and CCL7, both being negatively related to levels of DHA and AA in the postnatal period. Conclusions: This study supports postnatal non-antagonistic and potentially synergistic effects of DHA and AA on the inflammation proteome in preterm infants, indicating that supplementation with both fatty acids may contribute to limiting the disease burden in this vulnerable population. Clinical registration number: ClinicalTrials.gov (NCT03201588).
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| 5. |
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| 6. |
- Lähteenaro, Meri, et al.
(författare)
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Phylogenomic species delimitation of the twisted-winged parasite genus Stylops (Strepsiptera)
- 2024
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Ingår i: Systematic Entomology. - : John Wiley & Sons. - 0307-6970 .- 1365-3113. ; 49:2, s. 294-313
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Tidskriftsartikel (refereegranskat)abstract
- The twisted-winged parasite genus Stylops has a history of different species concepts with varying host specificity resulting in diverse species diversity estimates in different regions of the Holarctic. The adoption of a supergeneralist species concept in Europe, proposing synonymization of all Western Palaearctic Stylops species, did not facilitate taxonomic clarity and obscured the available life-history data in the region for decades. Lack of molecular data has allowed divergent opinions on species hypotheses and little opportunity for evaluating them in this morphologically challenging genus. To solve these discrepancies and gain novel information about host associations, we applied whole-genome sequencing to 163 specimens, representing a significant portion of putative European species. We evaluate the existing and conflicting species hypotheses with molecular species delimitation using Species bOundry Delimitation using Astral (SODA) and use a maximum likelihood phylogeny to investigate host associations of the species. Furthermore, we evaluate the effect of a number of loci used in SODA for the number of inferred species. We find justification for synonymization of multiple species and indications of undescribed species, as well as new host-parasite relationships. We show that the number of inferred species in SODA is exceedingly and positively correlated with the number of loci used, urging for cautious application. The results of our study bring clarity to the Western Palaearctic species diversity of Stylops. Furthermore, the comprehensive molecular dataset generated in this study will be a valuable resource for future studies on Stylops and the evolution of parasites in general.
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| 7. |
- Lähteenaro, Meri, et al.
(författare)
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Phylogenomic species delimitation of the twisted-winged parasite genus Stylops (Strepsiptera)
- 2024
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Ingår i: Systematic Entomology. - 0307-6970 .- 1365-3113. ; 49:2, s. 294-313
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Tidskriftsartikel (refereegranskat)abstract
- The twisted-winged parasite genus Stylops has a history of different species concepts with varying host specificity resulting in diverse species diversity estimates in different regions of the Holarctic. The adoption of a supergeneralist species concept in Europe, proposing synonymization of all Western Palaearctic Stylops species, did not facilitate taxonomic clarity and obscured the available life-history data in the region for decades. Lack of molecular data has allowed divergent opinions on species hypotheses and little opportunity for evaluating them in this morphologically challenging genus. To solve these discrepancies and gain novel information about host associations, we applied whole-genome sequencing to 163 specimens, representing a significant portion of putative European species. We evaluate the existing and conflicting species hypotheses with molecular species delimitation using Species bOundry Delimitation using Astral (SODA) and use a maximum likelihood phylogeny to investigate host associations of the species. Furthermore, we evaluate the effect of a number of loci used in SODA for the number of inferred species. We find justification for synonymization of multiple species and indications of undescribed species, as well as new host–parasite relationships. We show that the number of inferred species in SODA is exceedingly and positively correlated with the number of loci used, urging for cautious application. The results of our study bring clarity to the Western Palaearctic species diversity of Stylops. Furthermore, the comprehensive molecular dataset generated in this study will be a valuable resource for future studies on Stylops and the evolution of parasites in general.
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| 8. |
- Nilsson, Anders, et al.
(författare)
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Empowered or enchained? : Exploring consumer perspectives on Direct Load Control
- 2024
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Ingår i: Energy Policy. - : Elsevier. - 0301-4215 .- 1873-6777. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- Demand Response has become a central focus in policy discussions, attracting heightened attention for its potential key role in fostering enhanced demand flexibility. Direct Load Control (DLC) holds particular promise, requiring reduced consumer involvement compared to strategies relying on manual responses to time -varying pricing. However, the participation rate of residential consumers in DLC programs remains low, emphasizing the need for a more profound understanding of consumers' perspectives on DLC. Drawing from 15 in-depth interviews with Swedish households participating in a program involving direct load control of heat pumps, this study aims to explore the experiences and perceptions of consumers, providing in-depth understanding on factors that may serve as motivators, barriers and enablers for participation. Key findings include: financial benefits and interest in technology were the main motivations for participation; pre-existing knowledge and awareness of energy -related matters shaped consumers' attitudes to DLC; trust in the service provider was a key enabling factor for participation. The study further suggests that DLC does not inevitably lead to a perceived loss of control among participants, but, if implemented in alignment with their specific conditions, needs and preferences, may also foster a sense of empowerment.
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| 9. |
- Shry, Samuel, 1991-, et al.
(författare)
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Challenges in downstream dam passage and the effect of dam removal on Atlantic salmon (Salmo salar) smolt migrations
- 2024
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Ingår i: Journal of Fish Biology. - : John Wiley & Sons. - 0022-1112 .- 1095-8649.
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Tidskriftsartikel (refereegranskat)abstract
- Migration is critical for life-cycle completion in diadromous fish species. River connectivity is vital in facilitating these large-scale movement events, but the extent of present-day river fragmentation can interfere with these migrations. Fish passage solutions (FPSs) are commonly implemented with the aim of improving river connectivity. In our study, we investigated the performance of two types of FPSs, spill regimes and complete dam removal, on Atlantic salmon (Salmo salar) smolt migrations. We used acoustic telemetry to monitor migration behavior and passage success of 120 wild smolts released in three different groups/sites: one group with two dams to pass to reach the river mouth, a second group with one dam to pass, and a control group without any barriers to pass (upstream of a recently removed hydroelectric dam). Smolt passage probabilities were similar for the two studied dams (87% and 86%) but showed variation in path choice, delay times, and loss rates. Passage success was influenced by several factors, such as body size, diel period, and water temperature, but not flow. Cumulative passage success to the river mouth was 61%, with most individuals being lost within lentic river stretches, either in the forebays of hydroelectric power stations or in naturally wide river stretches. Within the recently rehabilitated river sections (post dam removal), passage speeds were significantly faster than all other sections of the river (post-rehabilitation x = 56.1 km/day) with significantly faster speeds compared to pre-rehabilitation (pre-x = 28.0 km/day). Our findings provide valuable information on the benefits of dam removal and highlight the need for further rehabilitation measures in upriver reaches where barriers still affect downstream passage.
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| 10. |
- Stikvoort, Britt, et al.
(författare)
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Serving two masters : How dual price signals can undermine demand flexibility
- 2024
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Ingår i: Energy Policy. - : Elsevier. - 0301-4215 .- 1873-6777. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- Demand-side flexibility is often encouraged via demand response programs, where users are incentivized to adjust their electricity consumption based on price signals in tariffs. The design and implementation of these signals are vital, as they link conditions of the energy system with user behaviour. As a result of energy system separation into stages of generation, many users are required to simultaneously respond to two price signals. While existing research has mainly examined responses to a single signal, this study highlights the complexities when users must react to two signals simultaneously. It presents a case study using two distinct price signals: real-time pricing (RTP) and a demand charge, analysing the implications such dual price signals could have on users. The study reveals the empirical incompatibility of these signals, leading to conflicting user goals. Such interference complicates decision-making for demand flexibility, potentially eroding user trust in retailers and system operators. The study ends with proposing an alternative tariff, resolving the dual price situation, which facilitates user comprehension and decision-making, and thus enhances the potential for demand flexibility.
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