| 1. |
- Davidsson, Kent, 1967, et al.
(författare)
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Potassium, chlorine, and sulfur in ash, particles, deposits, and corrosion during wood combustion in a circulating fluidized-bed boiler
- 2007
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 21:1, s. 71-81
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry.
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| 2. |
- Milberg, Per, et al.
(författare)
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A burning desire for smoke? Sampling insects favoured by forestfire in the absence of fire
- 2015
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Ingår i: Journal of Insect Conservation. - : Springer. - 1366-638X .- 1572-9753. ; 19:1, s. 55-65
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Tidskriftsartikel (refereegranskat)abstract
- Fire-favoured insects are difficult to sampleexcept opportunistically after forest fires. Here, we tested ifsmoke from a small fire could be an efficient way to samplesuch insects. Insects were sampled over ca. 10 h hours, byhand-picking and netting on screens put up around the fire.Two specimens of the rare and redlisted Hormopeza spp.(Diptera, Empididae) were caught. Large numbers([20,000) of Microsania spp. (Diptera, Platypezidae) werecaught, but none in the absence of smoke. The numbers ofMicrosania spp. clearly peaked in late afternoon, and ashort sampling period would be sufficient if targeting onlythis taxon. Of the almost 200 species of Coleoptera, 17 %were considered as fire-favoured, contributing 9 % of thespecimens, suggesting low efficiency of the method for thisgroup. Using 23 sites differing in fire history, catches ofMicrosania spp. were unaffected by numbers and area offorest fire (preceding 5 years and within 10 km radius overthe sampling sites). In contrast, there was a weak trend forthe proportion of fire-favoured Coleoptera to increase withincreasing number of fires. To conclude, smoke as producedin our study can clearly attract fire-favoured Diptera,but smoke had only a weak effect on fire-favoured Coleopterain the study area. It is still likely that selectivelypicking specimens of species attracted to smoke is a morecost-efficient method than using, e.g., Malaise traps thatcatch indiscriminately.
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| 3. |
- Persson, Anders, et al.
(författare)
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Effects of enrichment on simple aquatic food webs
- 2001
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Ingår i: The American Naturalist. ; 157:6, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on
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| 4. |
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| 5. |
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| 6. |
- Anniyev, Toyli, et al.
(författare)
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Complementarity between high-energy photoelectron and L-edge spectroscopy for probing the electronic structure of 5d transition metal catalysts
- 2010
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 12:21, s. 5694-5700
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the successful use of hard X-ray photoelectron spectroscopy (HAXPES) for selectively probing the platinum partial d-density of states (DOS) in a Pt-Cu nanoparticle catalyst which shows activity superior to pure Pt towards the oxygen-reduction reaction (ORR). The information about occupied Pt d-band states was complemented by Pt L-2-edge X-ray absorption near-edge spectroscopy (XANES), which probes unoccupied valence states. We found a significant electronic perturbation of the Pt projected d-DOS which was narrowed and shifted to higher binding energy compared to pure platinum. The effect of this electronic structure perturbation on the chemical properties of the nanoparticle surface is discussed in terms of the d-band model. We have thereby demonstrated that the combination of L-edge spectroscopy and HAXPES allows for an experimental derivation of the valence electronic structure in an element-specific way for 5d metal catalysts.
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| 7. |
- Bill-Axelson, Anna, et al.
(författare)
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Radical prostatectomy versus watchful waiting in localized prostate cancer : the Scandinavian prostate cancer group-4 randomized trial
- 2008
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press. - 0027-8874 .- 1460-2105. ; 100:16, s. 1144-1154
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The benefit of radical prostatectomy in patients with early prostate cancer has been assessed in only one randomized trial. In 2005, we reported that radical prostatectomy improved prostate cancer survival compared with watchful waiting after a median of 8.2 years of follow-up. We now report results after 3 more years of follow-up.METHODS: From October 1, 1989, through February 28, 1999, 695 men with clinically localized prostate cancer were randomly assigned to radical prostatectomy (n = 347) or watchful waiting (n = 348). Follow-up was complete through December 31, 2006, with histopathologic review and blinded evaluation of causes of death. Relative risks (RRs) were estimated using the Cox proportional hazards model. Statistical tests were two-sided.RESULTS: During a median of 10.8 years of follow-up (range = 3 weeks to 17.2 years), 137 men in the surgery group and 156 in the watchful waiting group died (P = .09). For 47 of the 347 men (13.5%) who were randomly assigned to surgery and 68 of the 348 men (19.5%) who were not, death was due to prostate cancer. The difference in cumulative incidence of death due to prostate cancer remained stable after about 10 years of follow-up. At 12 years, 12.5% of the surgery group and 17.9% of the watchful waiting group had died of prostate cancer (difference = 5.4%, 95% confidence interval [CI] = 0.2 to 11.1%), for a relative risk of 0.65 (95% CI = 0.45 to 0.94; P = .03). The difference in cumulative incidence of distant metastases did not increase beyond 10 years of follow-up. At 12 years, 19.3% of men in the surgery group and 26% of men in the watchful waiting group had been diagnosed with distant metastases (difference = 6.7%, 95% CI = 0.2 to 13.2%), for a relative risk of 0.65 (95% CI = 0.47 to 0.88; P = .006). Among men who underwent radical prostatectomy, those with extracapsular tumor growth had 14 times the risk of prostate cancer death as those without it (RR = 14.2, 95% CI = 3.3 to 61.8; P < .001).CONCLUSION: Radical prostatectomy reduces prostate cancer mortality and risk of metastases with little or no further increase in benefit 10 or more years after surgery.
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| 8. |
- Gustafsson, Lena, et al.
(författare)
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Rapid ecological response and intensified knowledge accumulation following a north European mega-fire
- 2019
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 34:4, s. 234-253
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Forskningsöversikt (refereegranskat)abstract
- Deepened knowledge on response of biota and ecological processes following fire is essential for a future with warmer climate and more disturbances. In 2014 the first mega-fire (13,100 ha) for at least a century in Scandinavia hit south-central Sweden, in a production forest landscape shaped by clearcutting forestry. Ecological dynamics is followed in >20 projects from universities, authorities and citizen science initiatives, rapidly accumulating substantial amounts of data. We outline projects and summarize their results during the first four years, demonstrating a rapid succession of fungi, lichens, vascular plants, birds, mammals, ticks, butterflies, beetles, and drastically altered carbon dynamics. We characterize forest operations including regeneration measures and point to patterns in pest and pathogen infestations. 8,000 ha is set aside for natural succession, with the rest harvested and managed for forest production, offering excellent opportunities for studies on salvage logging effects, already evident for birds. We demonstrate a strong regrowth of deciduous trees, and the protected part will in some decades likely develop into the largest deciduous-dominated area in boreal north Europe outside Russia. Continued studies of biodiversity and ecological processes are urgent for this unique area.
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| 9. |
- Lindström, B., et al.
(författare)
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Diesel fuel reformer for automotive fuel cell applications
- 2009
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 34:8, s. 3367-3381
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Tidskriftsartikel (refereegranskat)abstract
- Fuel economy and emission abatement are issues, which are highly prioritized areas in the automotive industry of today. The debate about climate change has in recent years even more emphasized the importance of these issues and has increased the search for finding sustainable technical solutions. This paper describes an effort to develop an innovative and environmentally-benign hydrogen generation system operating on commercial diesel fuel to avoid running the engine to supply electricity at stand-still. The use of a fuel cell-based auxiliary power unit (APU) has the potential of delivering electricity at high efficiencies independent of the heavy-duty truck engine. During the reformer development phase, spray formation and mixing of reactants proved to be crucial to obtain high reforming efficiencies and low diesel slip. The diesel is being injected through a nozzle creating a spray of fine droplets of a size which can establish rapid evaporation. Air and steam are being pre-heated and injected into the mixture chamber and subsequently mixed with the evaporated diesel fuel. Depending on the operating parameters, a part of the fuel is being oxidized and produces heat. Autothermal reforming was chosen to circumvent the heat transfer problem in catalytic steam reforming. By supplying heat directly to the catalyst surface by an oxidation reaction the heat demand of the strongly endothermic steam reforming reaction can be fulfilled. We employed CFD calculations, which revealed the importance of avoiding large recirculation zones leading to a prolonged residence time of the hydrocarbon molecules and causing auto-ignition and excessive temperatures in the catalyst. Five different reformer generations are being described and discussed in detail in this publication. The first one was based on a fixed bed reactor, while the other four all relied on catalytic monoliths enabling low pressure drops. The early reactor designs all suffered from auto-ignition and instability problems. The latter generations exhibited a considerably more stable temperature profile in the reformer. The conversion of diesel and the reformer efficiencies are significantly higher than the early generation diesel reformers.
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| 10. |
- Malmström, Johan
(författare)
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Efficient Methods to Calculate Mutual Coupling between Generic Antennas on Large Platforms
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents research on methods for calculating the mutual coupling between antennas. The mutual coupling between antennas is a measure of the amount of energy transmitted from one antenna that is received by another, and is a key parameter when installing antennas on platforms, such as aircraft. To avoid interference between systems connected to the antennas, the mutual coupling should be as low as possible. The risk for interference can be minimized in several ways; by designing the systems to be resistant to interference or to install the antennas in a way that makes the coupling between antennas low. This thesis focuses on the latter.Electromagnetic problems, such as finding the mutual coupling between antennas, can be calculated in simulations using commercial software. On large platforms, simulations become very computationally intensive. This thesis examines ways to efficiently calculate the mutual coupling between antennas on large platforms. The intention has been to develop methods that can be used in practical situations.One possible way to increase efficiency is to use appropriate approximations that simplify calculations. Two approximations have been evaluated; approximate wave propagation model and equivalent representations of antennas. Both of these approximations have the potential to reduced computation times, but suffer from the fact that the size of the errors introduced is not predictable. This contributes to an uncertainty in estimating the coupling between antennas that make them less interesting to use in applications. The reaction theorem, that describes the coupling as an interaction of electromagnetic fields, has been very useful in this work. Two novel formulations of the theorem have been derived that decompose fields into scattered components. It is shown that some of the components do not affect the reaction. The reaction theorem and the derived formulations have been used in two applications. The first application shows practical possibilities to calculate mutual impedance between two antennas installed on a common platform. It is also shown how the reaction theorem can be used to visualize coupling paths, which show how the coupling between the antennas is spatially distributed.The second application of the reaction theorem suggests an effective method for antenna placement on platforms that minimize the mutual impedance between antennas. The method enables field data to be reused, which significantly reduces the calculation time. Both suggested applications post-process electromagnetic field data. The field data can be determined with commercial software.The main results in this thesis are described in five articles and conference contributions that are or will be published in international scientific journals or at international conferences.
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| 11. |
- Pettersson, Håkan, et al.
(författare)
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Optically induced charge storage and current generation in InAs quantum dots
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 65:7, s. 0733041-0733044
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Tidskriftsartikel (refereegranskat)abstract
- We report on optically induced charge storage effects and current generation in self-assembled InAs quantum dots embedded in an InP matrix. Illumination with photons of energy higher than about 0.86 eV efficiently loads the dots with a maximum of about 1 hole/dot. The spectral response at lower photon energy is strongly enhanced at elevated temperatures. We present a detailed balance model for the dots and discuss the thermally assisted optical excitation processes pertinent to hole accumulation. We also show that these processes make the dots act as nanometer-scaled temperature-dependent current generators.
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| 12. |
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| 13. |
- Aguilera, Guillermo, et al.
(författare)
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Intensive management reduces butterfly diversity over time in urban green spaces
- 2019
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Ingår i: Urban Ecosystems. - : Springer Science and Business Media LLC. - 1083-8155 .- 1573-1642. ; 22:2, s. 335-344
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Tidskriftsartikel (refereegranskat)abstract
- Loss and fragmentation of semi-natural grasslands have had negative consequences for grassland biodiversity, such as butterflies. Urban parks and other urban green spaces have so far largely been overlooked as suitable butterfly habitats, although they could potentially sustain diverse butterfly populations over time. We analysed the temporal change in butterfly species assemblages in urban green spaces in the city of Malmö, Southern Sweden. We studied changes in species richness and abundance of butterflies between 2006 and 2015 in 20 public urban green spaces, characterized by different management regimes. We sampled butterflies in traditional parks with intense grass cutting regimes, in semi-natural grasslands mowed only a few times per year, and in un-managed or irregularly managed ruderal sites. We found a slight increase in the total number of butterfly species in the study area, but a general decline in local species numbers in urban green spaces. Traditional urban parks had the greatest loss of species over time, and altogether the lowest number of species. In contrast, semi-natural parks and ruderal sites had higher numbers of butterfly species and also lost fewer species over time. Our study shows that intensive management strategies in urban green spaces have a negative impact on butterfly assemblages over time. We suggest that less intensive management strategies can be used to create high-quality areas for flower-visiting insects in urban green spaces, possibly in combination with planting larval host plant species, depending on the park type and design.
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| 14. |
- Alexander, Naomi E., et al.
(författare)
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IMAGINE project : A low cost, high performance, monolithic passive mm-wave imager front-end
- 2012
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819492852
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Konferensbidrag (refereegranskat)abstract
- The FP7 Research for SME project IMAGINE - a low cost, high performance monolithic passive mm-wave imager front-end is described in this paper. The main innovation areas for the project are: i) the development of a 94 GHz radiometer chipset and matching circuits suitable for monolithic integration. The chipset consists of a W-band low noise amplifier, fabricated using the commercially available OMMIC D007IH GaAs mHEMT process, and a zero bias resonant interband tunneling diode, fabricated using a patented epi-layer structure that is lattice matched to the same D007IH process; ii) the development of a 94 GHz antenna adapted for low cost manufacturing methods with performance suitable for real-time imaging; iii) the development of a low cost liquid crystal polymer PCB build-up technology with performance suitable for the integration and assembly of a 94 GHz radiometer module; iv) the assembly of technology demonstrator modules. The results achieved in these areas are presented.
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| 15. |
- Andreasson, B., et al.
(författare)
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ASXL1 mutations, previous vascular complications and age at diagnosis predict survival in 85 WHO-defined polycythaemia vera patients
- 2020
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Ingår i: British Journal of Haematology. - : Wiley. - 0007-1048 .- 1365-2141. ; 189:5, s. 913-919
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Tidskriftsartikel (refereegranskat)abstract
- Polycythaemia vera (PV) patients have an overall comparatively favourable prognosis, but disease progression is very heterogeneous and life-threatening thrombosis and bleedings are frequent complications in untreated disease. Moreover, transformation to more severe secondary myelofibrosis and acute myeloid leukaemia can occur. The aim of this study was to identify gene mutations that could be used together with clinical data as prognostic markers to guide treatment decisions in PV patients. A well-characterized WHO-defined cohort of PV patients was used. Clinical data and blood values were evaluated and a myeloid sequencing panel was used to screen for additional mutations other than the diagnostic JAK2 V617F and JAK2 exon 12 mutations. In 78% of the PV patients, at least one mutation additional to JAK2 V617F was detected. Additional mutations in genes coding for epigenetic modifiers, like TET2, DNMT3A and ASXL1, were most frequent. When correlated to overall survival, mutations in ASXL1 were significantly associated with inferior survival. In an attempt to obtain prognostic guidance in a larger number of patients, the presence of ASXL1 mutations was combined with age and vascular complications prior to diagnosis. Based on these data we were able to define three risk groups that predicted survival.
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| 16. |
- Arnberg, Harriet, et al.
(författare)
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Pilotförsök för generell övervakning av pollinatörer – resultat för fältsäsongen 2021
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Lunds universitet har på uppdrag av Naturvårdsverket under 2021 utvärderat metodik för nationell pollinatörsövervakning. Metodiken bygger på rapporten ”Proposal for an EU pollinator monitoring scheme” som tagits fram av en expertgrupp inom EU (Potts m. fl. 2020) och ska kunna ge underlag för uppföljning av pollinatörer på nationell nivå med ett främsta fokus på landskapet utanför områden som omfattas av EU:s gemensamma jordbrukspolitik (CAP). Nationella anpassningar och möjliga förenklingar av det europeiska förslaget har utvärderats, och uppdraget har koordinerats med det förslag till övervakning av pollinatörer i jordbrukslandskapet som parallellt tagits fram av SLU. Under 2021 genomfördes inventering på 31 lokaler utplacerade i större delen av Sverige. Urvalet av lokaler gjordes så att det täckte in Sveriges tre biogeografiska regioner: den kontinentala (Götaland), den boreala (Götaland, Svealand, Norrland), samt den alpina regionen (Svealand, Norrland). För fältarbetet anlitades 18 inventerare på volontärbasis eller mot ersättning. Säsongen 2021 inleddes med framtagande av fällor och fältmateriel, etablerande av lokalnätverk, samt rekrytering av inventerare. Själva fältsäsongen påbörjades i början-mitten av juli och pågick med en provtagning per månad som mål. I södra Sverige pågick säsongen september ut medan den i norr avslutades när hösten infunnit sig i augusti-september.Flera olika metoder utvärderades, däribland färgskålefällor, transekter, blombesöksräkningar och nattfjärilsfällor. Såväl 2×2-km och 1×1-km rutor har inventerats och 6 respektive 24 timmars provtagning har testats. Totalt har 18 875 exemplar av 115 olika arter/grupper samlats in från färgskålefällorna. Vid transektinventeringen hittades 617 individer av 42 arter fjärilar, med 6,8 arter i snitt per 500 m transekt och 419 individer humlor, med 14,0 noterade exemplar i snitt per 500 m transekt. Totalt har 135 blombesöksräkningar gjorts och 391 exemplar av 136 arter nattfjärilar har insamlats och artbestämts med hjälp av nattfjärilsfällor. Det bör noteras att metodiken så här långt testats ca. en halv säsong och att det vore mycket värdefullt att utöka med en fältsäsong från april 2022 och framåt för att bland annat täcka in vårflygande solitärbin m. fl. grupper. Utifrån säsongens resultat rekommenderar vi 1×1-km rutor med 5 fällstationer per ruta snarare än 2×2-km rutor. Merarbetet för 2×2-km rutor och 10 fällstationer per ruta var betydande (mängd material att transportera, avstånd etc.), gav inte signifikant högre artantal, och de större rutorna var klart mindre populära bland inventerarna. Vi rekommenderar 6 timmars provtagning baserat på att det visade sig vara enklare att utföra samt resulterade i motsvarande artantal som 6 + 18 timmar respektive 24 timmar. För transektinventeringarna rekommenderar vi att a) fullständig artlista används för dagfjärilar, då inventerare i stor utsträckning har god artkännedom inom denna grupp, att b) den s.k. ”långlistan” (ett urval av typiska pollinatörer, Ahrné m. fl. 2021, Pettersson m. fl. 2022) provas i relation till enklare listor (exv. ”kortlistan”, Ahrné m. fl. 2021, Pettersson m. fl. 2022) för övriga tre grupper (humlor, solitärbin, blomflugor) och att c) utbildningsmaterial för ”långlistan” tas fram (online-resurser och föreläsningar). I sin enklaste form kan transektinventering fokusera på abundansmått (humlor, solitärbin, blomflugor) men vi rekommenderar en något högre taxonomisk upplösning motsvarande åtminstone kortlistan. För humlor kan metoder för mer detaljerad artidentifiering tas fram. Blombesöksräkningar (Carvell m. fl. 2016, Carvell m. fl. 2020) har visat sig vara en enkel och effektiv metod för att räkna pollinatörer och växt-pollinatörsinteraktioner. Metoden är populär bland volontärer och vi rekommenderar fortsatt användning och anpassning till svenska förhållanden.Nattfjärilsfällorna anlände sent på säsongen 2021 och behöver utvärderas under en längre period för att utrustningen och metodiken ska kunna testas väl, men initialt verkar de gett goda resultat. Vidare har vi gett i uppdrag till NRM att med hjälp av metabarcoding analysera en delmängd (95) av de sorterade och bestämda proverna från färgskålefällorna. Detta förväntas ge information om samstämmighet mellan metabarcoding och manuell analys.För att få en bild av hur pilotprojektets deltagare uppfattat uppdragets metodik och utmaningar har vi genomfört en detaljerad enkätundersökning motsvarande den i Carvell m. fl. (2016) bland inventerarna. Generellt har de varit positiva till sitt deltagande, pilotprojektets omfattning och samstämmiga i rekommendationen av 1×1-km rutor med 5 fällstationer per ruta. Många har i direkt kontakt med oss efterfrågat utbildningssatsningar för de svårare grupperna. Slutligen, för att erhålla data som speglar pollinatörssamhällets förändring över säsongen vore det önskvärt att fortsätta pilotförsöket i det etablerade lokalnätverket under 2022. Inventerare och utrustning finns på plats och kan påbörja säsongen så snart årstiden tillåter. En förlängning innebär även möjligheter till fördjupade analyser, i första hand ett mindre antal (4) 2×2-km rutor (Potts m. fl. 2020, ”superytor” i Pettersson m. fl. 2022) där kritiska mått som exv. effekten av fällantal, transektlängd, fångst¬period skulle kunna detaljstuderas med hjälp av anställd personal och därmed säkerställa analysstyrka. Det vore värdefullt för såväl det etablerade lokalnätverket som superytorna om utbildningsmaterial för långlistan kunde tas fram under 2022.
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| 17. |
- B. Araujo, Rafael, et al.
(författare)
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Adsorption energies on transition metal surfaces : towards an accurate and balanced description
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Density functional theory predictions of binding energies and reaction barriers provide invaluable data for analyzing chemical transformations in heterogeneous catalysis. For high accuracy, effects of band structure and coverage, as well as the local bond strength in both covalent and non-covalent interactions, must be reliably described and much focus has been put on improving functionals to this end. Here, we show that a correction from higher-level calculations on small metal clusters can be applied to improve periodic band structure adsorption energies and barriers. We benchmark against 38 reliable experimental covalent and non-covalent adsorption energies and five activation barriers with mean absolute errors of 2.2 kcal mol−1, 2.7 kcal mol−1, and 1.1 kcal mol−1, respectively, which are lower than for functionals widely used and tested for surface science evaluations, such as BEEF-vdW and RPBE.
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| 18. |
- B. Araujo, Rafael, et al.
(författare)
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Elucidating the role of Ni to enhance the methanol oxidation reaction on Pd electrocatalysts
- 2020
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 360
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Tidskriftsartikel (refereegranskat)abstract
- Amongst promising available technologies enabling the transition to renewable energy sources, electrochemical oxidation of alcohols, in a direct fuel cell or in an electrolysis reaction (H-2 production), can be an economically and sustainable alternative to currently used technologies. In this work, we highlight the advantages of a Pd-Ni bimetallic electrocatalyst for methanol electrooxidation - a convenient choice due to the low cost of Ni combined with the observed acceptable catalytic performance of Pd. We report a synergistic effort between experiments and theoretical calculations based on density functional theory to provide an in-depth understanding - at the atomistic level - of the origin of the enhanced electrochemical activity of methanol electrooxidation using the bimetallic catalysts Pd3Ni and PdNi over pure Pd. Cyclic voltammograms and High-Performance Liquid Chromatography (HPLC) demonstrate higher activity towards methanol electrooxidation with increased Ni concentration and, furthermore, higher selectivity for CO2. These effects are understood by: 1) changes in the methanol oxidation reaction mechanism. 2) Mitigation or suppression of CO poisoning on the Pd-Ni alloys as compared to the pure Pd catalyst. 3) A stronger tendency towards highly oxidized intermediates for the alloys. These findings elucidate the effects of a bimetallic electrocatalyst for alcohol electrooxidation as well as unambiguously suggest PdNi as a more cost-effective alternative electrocatalyst.
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| 19. |
- Bakx, Tristan R.M., et al.
(författare)
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Farmland birds occupying forest clear-cuts respond to both local and landscape features
- 2020
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127. ; 478
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural landscapes have changed fast in Europe, which has led to steep declines in farmland biodiversity. While this has differentially impacted “farmland species”, some of these seem to be able to use alternative man-made open habitats in forests, such as forest clear-cuts and powerline rights-of-way. We investigated the use of clear-cuts by two historically declining farmland birds, the Yellowhammer (Emberiza citrinella) and the Red-backed Shrike (Lanius collurio), to determine both local and landscape habitat characteristics of clear-cuts used for breeding. Among 101 clear-cuts visited in Scania, southern Sweden, 27% were occupied by Yellowhammers and 12% by Red-backed Shrikes. Yellowhammer occurrence in clear-cuts was positively related to local spruce cover (the planted tree species). There was also an interaction between clear-cut size and the proportion of farmland in the landscape, such that the positive effect of the proportion of farmland nearby was stronger for larger clear-cuts. Red-backed Shrike occurrence was positively related to clear-cut size and the local presence of piles of forest residues (tops and branches). The relation between occurrence and the proportion of clear-cuts in the landscape was positive for small clear-cuts and negative for larger ones. Yellowhammers and Red-backed shrikes are affected by both the local habitat structure in the clearcut and on the composition of the surrounding landscape, most likely because they use the clear-cut for nesting and the surroundings as complementary feeding habitat. To what extent clear-cuts as complementary breeding habitat to farmland may contribute to the conservation of Yellowhammers and Red-backed shrikes, as well as other farmland birds, is a promising path for future investigations.
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| 20. |
- Bauer, Silke, et al.
(författare)
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From Agricultural Benefits to Aviation Safety : Realizing the Potential of Continent-Wide Radar Networks
- 2017
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Ingår i: BioScience. - : Oxford University Press (OUP). - 0006-3568 .- 1525-3244. ; 67:10, s. 912-918
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Tidskriftsartikel (refereegranskat)abstract
- Migratory animals provide a multitude of services and disservices-with benefits or costs in the order of billions of dollars annually. Monitoring, quantifying, and forecasting migrations across continents could assist diverse stakeholders in utilizing migrant services, reducing disservices, or mitigating human-wildlife conflicts. Radars are powerful tools for such monitoring as they can assess directional intensities, such as migration traffic rates, and biomass transported. Currently, however, most radar applications are local or small scale and therefore substantially limited in their ability to address large-scale phenomena. As weather radars are organized into continent-wide networks and also detect "biological targets," they could routinely monitor aerial migrations over the relevant spatial scales and over the timescales required for detecting responses to environmental perturbations. To tap these unexploited resources, a concerted effort is needed among diverse fields of expertise and among stakeholders to recognize the value of the existing infrastructure and data beyond weather forecasting.
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| 21. |
- Becciu, Paolo, et al.
(författare)
-
Environmental effects on flying migrants revealed by radar
- 2019
-
Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587.
-
Forskningsöversikt (refereegranskat)abstract
- Migratory animals are affected by various factors during their journeys, and the study of animal movement by radars has been instrumental in revealing key influences of the environment on flying migrants. Radars enable the simultaneous tracking of many individuals of almost all sizes within the radar range during day and night, and under low visibility conditions. We review how atmospheric conditions, geographic features and human development affect the behavior of migrating insects and birds as recorded by radars. We focus on flight initiation and termination, as well as in-flight behavior that includes changes in animal flight direction, speed and altitude. We have identified several similarities and differences in the behavioral responses of aerial migrants including an overlooked similarity in the use of thermal updrafts by very small (e.g. aphids) and very large (e.g. vultures) migrants. We propose that many aerial migrants modulate their migratory flights in relation to the interaction between atmospheric conditions and geographic features. For example, aerial migrants that encounter crosswind may terminate their flight or continue their migration and may also drift or compensate for lateral displacement depending on their position (over land, near the coast or over sea). We propose several promising directions for future research, including the development and application of algorithms for tracking insects, bats and large aggregations of animals using weather radars. Additionally, an important contribution will be the spatial expansion of aeroecological radar studies to Africa, most of Asia and South America where no such studies have been undertaken. Quantifying the role of migrants in ecosystems and specifically estimating the number of departing birds from stopover sites using low-elevation radar scans is important for quantifying migrant–habitat relationships. This information, together with estimates of population demographics and migrant abundance, can help resolve the long-term dynamics of migrant populations facing large-scale environmental changes.
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| 22. |
- Benedict, Christian, et al.
(författare)
-
Acute sleep deprivation increases serum levels of neuron-specific enolase (NSE) and S100 calcium binding protein B (S-100B) in healthy young men.
- 2014
-
Ingår i: Sleep. - : Oxford University Press (OUP). - 1550-9109 .- 0161-8105. ; 37:1, s. 195-8
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate whether total sleep deprivation (TSD) affects circulating concentrations of neuron-specific enolase (NSE) and S100 calcium binding protein B (S-100B) in humans. These factors are usually found in the cytoplasm of neurons and glia cells. Increasing concentrations of these factors in blood may be therefore indicative for either neuronal damage, impaired blood brain barrier function, or both. In addition, amyloid β (Aβ) peptides 1-42 and 1-40 were measured in plasma to calculate their ratio. A reduced plasma ratio of Aβ peptides 1-42 to 1-40 is considered an indirect measure of increased deposition of Aβ 1-42 peptide in the brain.
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| 23. |
- Casalongue, Hernan G. Sanchez, et al.
(författare)
-
Operando Characterization of an Amorphous Molybdenum Sulfide Nanoparticle Catalyst during the Hydrogen Evolution Reaction
- 2014
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:50, s. 29252-29259
-
Tidskriftsartikel (refereegranskat)abstract
- Molybdenum sulfide structures, particularly amorphous MoS3 nanoparticles, are promising materials in the search for cost-effective and scalable water-splitting catalysts. Ex situ observations show that the nanoparticles exhibit a composition change from MoS3 to defective MoS2 when subjected to hydrogen evolution reaction (HER) conditions, raising questions regarding the active surface sites taking part in the reaction. We tracked the in situ transformation of amorphous MoS3 nanoparticles under HER conditions through ambient pressure X-ray photoelectron spectroscopy and performed density functional theory studies of model MoSx systems. We demonstrate that, under operating conditions, surface sites are converted from MoS3 to MoS2 in a gradual manner and that the electrolytic current densities are proportional to the extent of the transformation. We also posit that it is the MoS2 edge-like sites that are active during HER, with the high activity of the catalyst being attributed to the increase in surface MoS2 edge-like sites after the reduction of MoS3 sites.
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| 24. |
- Chapman, Jason W., et al.
(författare)
-
Seasonal migration to high latitudes results in major reproductive benefits in an insect
- 2012
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 109:37, s. 14924-14929
-
Tidskriftsartikel (refereegranskat)abstract
- Little is known of the population dynamics of long-range insect migrants, and it has been suggested that the annual journeys of billions of nonhardy insects to exploit temperate zones during summer represent a sink from which future generations seldom return (the “Pied Piper” effect). We combine data from entomological radars and ground-based light traps to show that annual migrations are highly adaptive in the noctuid moth Autographa gamma (silver Y), a major agricultural pest. We estimate that 10–240 million immigrants reach the United Kingdom each spring, but that summer breeding results in a fourfold increase in the abundance of the subsequent generation of adults, all of which emigrate southward in the fall. Trajectory simulations show that 80% of emigrants will reach regions suitable for winter breeding in the Mediterranean Basin, for which our population dynamics model predicts a winter carrying capacity only 20% of that of northern Europe during the summer. We conclude not only that poleward insect migrations in spring result in major population increases, but also that the persistence of such species is dependent on summer breeding in high-latitude regions, which requires a fundamental change in our understanding of insect migration.
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| 25. |
- Dahlin, Sandra, et al.
(författare)
-
Effect of biofuel- and lube oil-originated sulfur and phosphorus on the performance of Cu-SSZ-13 and V2O5-WO3/TiO2 SCR catalysts
- 2021
-
Ingår i: Catalysis Today. - : Elsevier B.V.. - 0920-5861 .- 1873-4308. ; 360, s. 326-339
-
Tidskriftsartikel (refereegranskat)abstract
- Two different SCR catalysts, V2O5-WO3/TiO2 and Cu-SSZ-13, were exposed to biodiesel exhausts generated by a diesel burner. The effect of phosphorus and sulfur on the SCR performance of these catalysts was investigated by doping the fuel with P-, S-, or P + S-containing compounds. Elemental analyses showed that both catalysts captured phosphorus while only Cu-SSZ-13 captured sulfur. High molar P/V ratios, up to almost 3, were observed for V2O5-WO3/TiO2, while the highest P/Cu ratios observed were slightly above 1 for the Cu-SSZ-13 catalyst. Although the V2O5-WO3/TiO2 catalyst captured more P than did the Cu-SSZ-13 catalyst, a higher degree of deactivation was observed for the latter, especially at low temperatures. For both catalysts, phosphorus exposure resulted in suppression of the SCR performance over the entire temperature range. Sulfur exposure, on the other hand, resulted in deactivation of the Cu-SSZ-13 catalyst mainly at temperatures below 300-350 °C. The use of an oxidation catalyst upstream of the SCR catalyst during the exhaust-exposure protects the SCR catalyst from phosphorus poisoning by capturing phosphorus. The results in this work will improve the understanding of chemical deactivation of SCR catalysts and aid in developing durable aftertreatment systems.
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| 26. |
- Dahlman-Höglund, Anna, 1964, et al.
(författare)
-
Antibodies given orally in the neonatal period can affect the immune response for two generations: evidence for active maternal influence on the newborn's immune system.
- 1999
-
Ingår i: Scandinavian journal of immunology. - 0300-9475. ; 50:6, s. 651-6
-
Tidskriftsartikel (refereegranskat)abstract
- Two day old Wistar rats were tube fed with 1 or 10 micrograms of a mouse IgG1 monoclonal anti-idiotypic (a-Id) antibody that was directed against an anti-Escherichia coli-K13 capsular polysaccharide antibody. A control group was given 10 micrograms of an unrelated control antibody. Six weeks after the administration of antibodies, the rats were intestinally colonised with an ovalbumin (OVA)-producing E. coli O6K13 strain. At 8 weeks of age, the male rats (first generation) and the offsprings of the female rats (second generation), were parenterally immunised with OVA and dead wild type E. coli O6K13, and the immune response was followed. In the rats of the first generation, there were no major differences between the groups in the immune response to the bacterium. However, the offspring of the neonatally a-Id administered rats had a profoundly affected immune response to the idiotypically connected antigen K13, but also to other antigens on the bacteria. Thus, a-Id treatment in the first generation gave, in the second generation, a greatly enhanced serum antibody response to the spatially related antigens OVA and O6 LPS, as well as to the idiotypically connected antigen K13. Concurrently, the in vitro spleen cell proliferative response to both OVA and the wild type bacterium was lowered. Overall, greater effects were seen with the higher dose of a-Id. In conclusion, our results demonstrate that by giving monoclonal antibodies idiotypically connected to a single bacterial component to neonatal rats, one profoundly influence the immune response also to other-spatially related-bacterial antigens in their offsprings.
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| 27. |
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| 28. |
- D'Hertefeldt, Tina, et al.
(författare)
-
Long-term persistence of GM oilseed rape in the seedbank
- 2008
-
Ingår i: Biology letters. - London : The Royal Society. - 1744-9561 .- 1744-957X. ; 4:3, s. 314-317
-
Tidskriftsartikel (refereegranskat)abstract
- Coexistence between genetically modified (GM) and non-GM plants is a field of rapid development and considerable controversy. In crops, it is increasingly important to understand and predict the GM volunteer emergence in subsequent non-GM crops. Theoretical models suggest recruitment from the seedbank over extended periods, but empirical evidence matching these predictions has been scarce. Here, we provide evidence of long-term GM seed persistence in conventional agriculture. Ten years after a trial of GM herbicide-tolerant oilseed rape, emergent seedlings were collected and tested for herbicide tolerance. Seedlings that survived the glufosinate herbicide (15 out of 38 volunteers) tested positive for at least one GM insert. The resulting density was equivalent to 0.01 plants m−2, despite complying with volunteer reduction recommendations. These results are important in relation to debating and regulating coexistence of GM and non-GM crops, particularly for planting non-GM crops after GM crops in the same field.
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| 29. |
- Engjom, Hilde, et al.
(författare)
-
COVID-19 in pregnancy—characteristics and outcomes of pregnant women admitted to hospital because of SARS-CoV-2 infection in the Nordic countries
- 2021
-
Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 0001-6349 .- 1600-0412. ; 100:9, s. 1611-1619
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Population-based studies about the consequences of SARS-CoV-2 infection (COVID-19) in pregnancy are few and have limited generalizability to the Nordic population and healthcare systems. Material and methods: This study examines pregnant women with COVID-19 in the five Nordic countries. Pregnant women were included if they were admitted to hospital between 1 March and 30 June 2020 and had a positive SARS-CoV-2 PCR test ≤14 days prior to admission. Cause of admission was classified as obstetric or COVID-19-related. Results: In the study areas, 214 pregnant women with a positive test were admitted to hospital, of which 56 women required hospital care due to COVID-19. The risk of admission due to COVID-19 was 0.4/1000 deliveries in Denmark, Finland and Norway, and 3.8/1000 deliveries in the Swedish regions. Women hospitalized because of COVID-19 were more frequently obese (p < 0.001) and had a migrant background (p < 0.001) compared with the total population of women who delivered in 2018. Twelve women (21.4%) needed intensive care. Among the 56 women admitted due to COVID-19, 48 women delivered 51 infants. Preterm delivery (n = 12, 25%, p < 0.001) and cesarean delivery (n = 21, 43.8%, p < 0.001) were more frequent in women with COVID-19 compared with women who delivered in 2018. No maternal deaths, stillbirths or neonatal deaths were reported. Conclusions: The risk of admission due to COVID-19 disease in pregnancy was low in the Nordic countries. A fifth of the women required intensive care and we observed higher rates of preterm and cesarean deliveries. National public health policies appear to have had an impact on the risk of admission due to severe COVID-19 disease in pregnancy. Nordic collaboration is important in collecting robust data and assessing rare outcomes.
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| 30. |
- Franzén, Markus, et al.
(författare)
-
Urban moth communities suggest that life in the city favours thermophilic multi-dimensional generalists
- 2020
-
Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 287:1928, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Biodiversity is challenged worldwide by exploitation, global warming, changes in land use and increasing urbanization. It is hypothesized that communities in urban areas should consist primarily of generalist species with broad niches that are able to cope with novel, variable, fragmented, warmer and unpredictable environments shaped by human pressures. We surveyed moth communities in three cities in northern Europe and compared them with neighbouring moth assemblages constituting species pools of potential colonizers. We found that urban moth communities consisted of multi-dimensional generalist species that had larger distribution ranges, more variable colour patterns, longer reproductive seasons, broader diets, were more likely to overwinter as an egg, more thermophilic, and occupied more habitat types compared with moth communities in surrounding areas. When body size was analysed separately, results indicated that city occupancy was associated with larger size, but this effect disappeared when body size was analysed together with the other traits. Our findings indicate that urbanization imposes a spatial filtering process in favour of thermophilic species characterized by high intraspecific diversity and multi-dimensional generalist lifestyles over specialized species with narrow niches.
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| 31. |
- Hagfeldt, A., et al.
(författare)
-
1.20 - Mesoporous Dye-Sensitized Solar Cells
- 2022
-
Ingår i: Comprehensive Renewable Energy, Second Edition: Volume 1-9. - : Elsevier BV. ; , s. 447-462
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Photovoltaics, or solar cells, are fast growing both with regards to industrialization and research. Globally, the total PV installation is around 40 GW and an annual growth rate of 45% has been experienced over recent years. In the comparison between different photovoltaic technologies a figure of merit is the production cost per peak watt of solar electricity produced. For so called second generation thin film solar cells production costs down to and even below 1 $ W−1 peak are reported. To be competitive with conventional energy sources for large-scale electricity production new PV technologies need to aim at production costs below 0.5 $ W−1 peak. The dye-sensitized solar cell (DSC) is a molecular solar cell technology which have the potential to achieve production costs below 0.5 $ W−1 peak. DSC is based on molecular and nanometer-scale components. Record cell efficiencies of 12%, promising stability data and means of energy efficient production methods have been accomplished. As selling points for the DSC technology the prospect of low-cost investments and fabrication are key features. DSCs offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. This chapter describes the basic principles of the operation of DSC, the state-of-the-art, the materials development that is currently taking place as well as the potentials for future development.
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| 32. |
- Hagfeldt, A., et al.
(författare)
-
Dye-Sensitized Photoelectrochemical Cells
- 2013. - 2
-
Ingår i: Solar cells. - Amsterdam, London : Elsevier. - 9780123869647 ; , s. 385-441
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Production cost per peak watt of solar electricity produced is critical to various PV technologies and second-generation thin-film solar cells. The dye-sensitized solar cell (DSC), a molecular solar cell technology, has the potential to significantly lower production costs below previous PV technologies. DSC research groups have been established around the world. Integration into different products opens up new commercial opportunities for niche applications with large flexibilities in product shape, colour, and transparency.
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| 33. |
- Hagfeldt, Anders, et al.
(författare)
-
Dye-sensitized Photoelectrochemical Cells
- 2012. - 2
-
Ingår i: Practical Handbook of Photovoltaics Findamentals and Applications, 2nd Edition. - Oxford : Academic Press. ; , s. 479-542
-
Bokkapitel (refereegranskat)abstract
- As part of the growing sustainable and renewable energy movement, the design, manufacture and use of photovoltaic devices is increasing in pace and frequency. The Handbook of Photovoltaics will be a 'benchmark' publication for those involved in the design, manufacture and use of these devices. The Handbook covers the principles of solar cell function, the raw materials, photovoltaic systems, standards, calibration, testing, economics and case studies. The editors have assembled a cast of internationally-respected contributors from industry and academia. The report is essential reading for: Physicists, electronic engineers, designers of systems, installers, architects, policy-makers relating to photovoltaics.
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| 34. |
- Hagfeldt, A., et al.
(författare)
-
Dye-sensitized photoelectrochemical cells
- 2018. - 3
-
Ingår i: McEvoy's Handbook of Photovoltaics: Fundamentals and Applications. - : Elsevier BV. ; , s. 503-565
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Production cost per peak watt of solar electricity produced is critical to various PV technologies and second-generation thin-film solar cells. The dye-sensitized solar cell (DSC), a molecular solar cell technology, has the potential to significantly lower production costs below previous PV technologies. DSC research groups have been established around the world. Integration into different products opens up new commercial opportunities for niche applications with large flexibilities in product shape, color, and transparency.
|
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| 35. |
- Hagfeldt, A., et al.
(författare)
-
Mesoporous dye-sensitized solar cells
- 2012
-
Ingår i: Reference Module in Earth Systems and Environmental Sciences. - : Elsevier. - 9780080878737 ; , s. 481-496
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Photovoltaics, or solar cells, are fast growing both with regards to industrialization and research. Globally, the total PV installation is around 40 GW and an annual growth rate of 45% has been experienced over recent years. In the comparison between different photovoltaic technologies a figure of merit is the production cost per peak watt of solar electricity produced. For so called second generation thin film solar cells production costs down to and even below 1 $/W-1 peak are reported. To be competitive with conventional energy sources for large-scale electricity production new PV technologies need to aim at production costs below 0.5 $/W-1 peak. The dye-sensitized solar cell (DSC) is a molecular solar cell technology which have the potential to achieve production costs below 0.5 $/W-1 peak. DSC is based on molecular and nanometer-scale components. Record cell efficiencies of 12%, promising stability data and means of energy efficient production methods have been accomplished. As selling points for the DSC technology the prospect of low-cost investments and fabrication are key features. DSCs offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. This chapter describes the basic principles of the operation of DSC, the state-of-the-art, the materials development that is currently taking place as well as the potentials for future development.
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| 36. |
- Holmer, Lars E., et al.
(författare)
-
The enigmatic early cambrian salanygolina : a stem group of rhynchonelliform chileate brachiopods?
- 2009
-
Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 52:1, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- New material of the enigmatic brachiopod Salanygolina obliqua Ushatinskaya from the Early Cambrian of Mongolia shows that it has a colleplax- a triangular plate - in the umbonal perforation, which is enlarged by resorption. This structure is otherwise only known from the equally enigmatic Palaeozoic orders Chileida and Dictyonellida (Rhynchonelliformea, Chileata). The colleplax in Salanygolina is here considered to be homologous with that of the chileates. Salanygolina is also provided with a ridge-like pseudodeltidium, which is another chileate feature. Other characters of Salanygolina, like the radial arrangement of adductor muscle scars and postero-medially placed internal oblique muscles are characteristic of chileates, but also found in the paterinates. In contrast, mixoperipheral dorsal valves with low rudimentary interareas are well known in paterinates, but not yet recorded from chileates. Thus, Salanygolina shows a mosaic combination of morphologic characters, known both from the paterinates and chileates, indicating that it may represent a stem group of the rhynchonelliform chileate brachiopods. The laminar phosphatic secondary shell of Salanygolina is composed of closely packed and nearly identical hexagonal prisms, oriented with their long axis normal to the laminae in a honeycomb pattern. The prism walls appear to have originally been composed of organic membranes and might represent precursors of the organic sheaths of calcite fibers that are typical of calcitic shells with a fibrous microstructure.
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| 37. |
- Juarez-Mosqueda, Rosalba, et al.
(författare)
-
Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes
- 2015
-
Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt-4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT), the (10,10) CNT and one of large diameter, respectively. Our results show that the H-2 molecule dissociates spontaneously on the Pt-4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt-4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt-4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role.
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| 38. |
|
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| 39. |
- Karlsson, Rasmus K. B., et al.
(författare)
-
Structural Changes in RuO2 during Electrochemical Hydrogen Evolution
- 2016
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:13, s. 7094-7102
-
Tidskriftsartikel (refereegranskat)abstract
- A comprehensive theoretical study of the X-ray photoelectron shifts for RuO2 during hydrogen evolution has been performed. The shifts have been calculated using first-principles density functional theory and are compared with previous theoretical and experimental results to reconsider the proposed structural changes occurring during hydrogen evolution on RuO2. We find that during hydrogen evolution hydrogen enters the rutile RuO2 lattice and converts oxygen groups into hydroxyl groups and that this process explains the experimentally observed increase in unit cell dimensions as well as observed chemical shifts. Furthermore, carbon contamination is the most likely explanation for a set of peaks previously identified as caused by a new RuO(OH)2 phase. We find that formation of metallic Ru is just one possible explanation for another peak in the X-ray photoelectron spectrum and that explanations including conversion of RuO2 into Ru(OH)3, or removal of oxygen from Ru active surface sites, also can explain the observed shifts. (Figure Presented)
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| 40. |
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| 41. |
- Karlsson, Rasmus K. B., et al.
(författare)
-
The electrocatalytic properties of doped TiO2
- 2015
-
Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 180, s. 514-527
-
Tidskriftsartikel (refereegranskat)abstract
- To rationally control the catalytic properties of heterogeneous catalysts is the goal in heterogeneous (electro)catalysis research. Recent developments of theoretical methods based on density functional theory have enabled computational screening of catalysts, to achieve fundamental understanding of which catalyst is optimal for a certain reaction. In the present work, such screening is employed to elucidate the electrocatalytic properties of doped rutile TiO2. Electrodes based on this material are widely used in industrial production of, e.g., chlorine and sodium chlorate. The screening covers 38 different dopants, including all fourth, fifth and sixth row transition metals. Several dopants are predicted to activate TiO2, resulting in a material optimal either for the oxygen evolution reaction, or for selective chlorine evolution. The results can serve as a map for the rational design of electrocatalysts based on TiO2.
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| 42. |
- Karlsson, Rasmus K. B., et al.
(författare)
-
Ti atoms in Ru0.3Ti0.7O2 mixed oxides form active and selective sites for electrochemical chlorine evolution
- 2014
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 146, s. 733-740
-
Tidskriftsartikel (refereegranskat)abstract
- The electrocatalytic properties of the (1 1 0) surface of Ru-doped TiO2, Ti-doped RuO2 and the industrially important Dimensionally Stable Anode (DSA) composition Ru0.3Ti0.7O2 have been examined using density functional theory. It is found that the oxygen adsorption energy on a Ti site is strongly affected by the presence of small amounts of Ru dopant, whereas oxygen adsorption is relatively unaffected by Ti dopants in RuO2. The calculations also indicate that coordinatively unsaturated Ti sites on Ru-doped TiO2 and on Ru0.3Ti0.7O2 could form active and selective sites for Cl-2 evolution. These results suggest a reason for why DSA shows a higher chlorine selectivity than RuO2 and propose an experimental test of the hypothesis.
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| 43. |
- Lang, Andreas, et al.
(författare)
-
Monitoring environmental effects on farmland Lepidoptera : Does necessary sampling effort vary between different bio-geographic regions in Europe?
- 2019
-
Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 102, s. 791-800
-
Tidskriftsartikel (refereegranskat)abstract
- In agro-ecosystems, environmental monitoring is fundamental to detect and survey changes related to land use change and management practices. Butterflies and moths have often been suggested as suitable indicators for monitoring environmental effects on biodiversity in farmlands. Here, we estimated the required sample size and monitoring effort necessary to run a Lepidoptera survey in European farmland, assessing in particular if monitoring investment would differ between representative bio-geographical regions. We operated linear 1-km long transect routes in farmland of Romania, Spain and Sweden from 2013 to 2015, and recorded butterflies and burnet moths (Papilionoidea, Zygaenidae). The transects were walked back and forth four times a season, and replicated yearly. The lepidopteran diversity was high in farmlands of Romania and Spain, but comparatively low in Sweden. The coefficient of variation (CV) of recorded species number differed between countries being lowest in Sweden and highest in Spain. In general, the CV dropped above a transect length of 400–800 m, thus indicating an increase in statistical power. Assuming a non-parametric test for matched samples, power calculations were conducted with the raw count data and with log-transformed count data for comparison. When using log-transformed data, the required sample size to detect an effect was less than 10 transects per country or region (in order to detect a 10% loss of species or a decrease of 30% in total abundance). Specific subgroups of species, e.g. protected species or specific indicator groups, showed a higher variance, thus requiring a higher sample size to detect effects ranging from 12 to 16 transects (equivalent to 21–29 working days per country and year). When using original, untransformed count data a considerably larger sample size would be needed. Actual time to be invested in field work differed between countries due to contrasting regional constraints and conditions. Nevertheless, the final monitoring effort in working days was similar between countries as the factors involved balanced out each other, in particular due to the differing year-to-year variations. Our study demonstrated the feasibility of an environmental monitoring programme in arable land using farmland butterflies across Europe. We present a suitable approach and guidelines as well as the necessary effort to be invested in future Europe-wide monitoring programmes of butterflies in agro-ecosystems, based on predictions of statistical power.
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| 44. |
- Lindström, B., et al.
(författare)
-
A brief history of catalysis
- 2003
-
Ingår i: CATTech. - 1384-6566 .- 1572-8811. ; 7:4, s. 130-138
-
Tidskriftsartikel (refereegranskat)abstract
- Historical studies are usually divided into segments of time that were marked by intellectual progress or specific achievements. Some periods are clearly identified by great events or an individual accomplishment that revolutionizes the entire concept. However, in most cases the advancement from one period to another is not marked by distinct accomplishments, but rather the result of a series of advances. This paper follows this conventional style and we have divided our subject of catalysis into five distinct periods.
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| 45. |
- Lindström, B., et al.
(författare)
-
Activity and characterization of Cu/Zn, Cu/Cr and Cu/Zr on gamma-alumina for methanol reforming for fuel cell vehicles
- 2002
-
Ingår i: Applied Catalysis A. - 0926-860X .- 1873-3875. ; 234:02-jan, s. 111-125
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Tidskriftsartikel (refereegranskat)abstract
- The influence of catalyst properties on the activity and selectivity of hydrogen generation by methanol reforming over copper-based catalysts impregnated on gamma-alumina pellets has been investigated. In the experiments, three sets of copper-based catalysts with various compositions were tested: Cu/Zn/Al2O3, Cu/Cr/Al2O3 and Cu/Zr/Al2O3. The catalysts were characterized using temperature programmed reduction (TPR), temperature programmed oxidation (TPO), SEM-EDS, Brunauer-Emmett-Teller (BET) surface area measurement and X-ray diffraction (XRD). The copper surface area was determined by pulse chemisorption using N2O. We found a correlation between the copper surface area and catalytic activity. The activity tests were performed in a fixed bed reactor with 15 g of spherical catalyst pellets using a gas hourly space velocity (GHSV) of 25,000. The results of the activity tests indicate that the choice of promoter and the catalyst composition greatly influence the activity as well as the selectivity for CO2 formation. The highest conversions were achieved for the zinc-containing catalysts (Cu/Zn/Al2O3) for both steam reforming and the combined reforming process. Complete conversion of methanol was only obtained for the zinc-containing catalysts when running the steam reforming process. The combined reforming process generally yielded A product stream containing lower carbon monoxide concentrations compared to steam reforming at the equivalent reactor temperature for all of the catalysts tested.
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| 46. |
- Lindström, B., et al.
(författare)
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Catalytic oxidation of liquid methanol as a heat source for an automotive reformer
- 2003
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Ingår i: Chemical Engineering & Technology. - : Wiley. - 0930-7516 .- 1521-4125. ; 26:4, s. 473-478
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Tidskriftsartikel (refereegranskat)abstract
- A reactor for catalytically oxidizing liquid methanol has been developed for supplying heat to an automotive reformer. In the tests presented in this paper we show that it is possible to catalytically combust liquid methanol by dispersing the methanol and air by a nebulizer over the catalysts. In the experiments we tested several base and noble metals and found that either platinum or palladium was required at the ignition zone. The tests also showed that it was possible to achieve complete combustion when only 25% of the catalyst bed contained a noble metal.
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| 47. |
- Lindström, B., et al.
(författare)
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Combined methanol reforming for hydrogen generation over monolithic catalysts
- 2003
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Ingår i: Chemical Engineering Journal. - 1385-8947 .- 1873-3212. ; 93:1, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation on hydrogen generation from methanol using monolithic catalysts is presented in this paper. The activity and carbon dioxide selectivity for the reforming of methanol over various binary copper-based materials, Cu/Cr, Cu/Zn and Cu/Zr, have been evaluated. The methanol reforming was performed using steam reforming and combined reforming (CMR, a combination of steam reforming and partial oxidation). The CMR process was carried out at two modes of operation: near auto-thermal and at slightly exothermal conditions. The catalysts have been characterized using BET surface area measurement, X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscopy (SEM-EDS). The results show that the choice of catalytic material has a great influence on the methanol conversion and carbon dioxide selectivity of the reforming reaction. The zinc-containing catalyst showed the highest activity for the steam reforming process, whereas the copper/chromium catalyst had the highest activity for the CMR process. The copper/zirconium catalyst had the highest CO2 selectivity for all the investigated process alternatives.
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| 48. |
- Lindström, B., et al.
(författare)
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Deactivation of copper-based catalysts for fuel cell applications
- 2001
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Ingår i: Catalysis Letters. - 1011-372X .- 1572-879X. ; 74:02-jan, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- The activity of copper catalysts for the steam reforming of methanol was investigated under deactivating conditions. The effects of adding poisonous substances which can occur in the fuel, such as sulphur and chlorine, were studied. Thermal ageing by sintering was observed while exposing the catalyst to high temperatures. The catalyst activity for steam reforming was greatly affected by the addition of low concentrations of sulphur and chlorine. Sulphur was more detrimental to the catalyst than chlorine.
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| 49. |
- Lindström, B., et al.
(författare)
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Development of a methanol fuelled reformer for fuel cell applications
- 2003
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Ingår i: Journal of Power Sources. - 0378-7753 .- 1873-2755. ; 118:02-jan, s. 71-78
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Tidskriftsartikel (refereegranskat)abstract
- A compact methanol reformer for fuel cell vehicles (FCVs) has, been developed and successfully tested. The reformer which has been constructed to serve a 5 Me fuel cell operates by combined reforming of methanol (CRM) (a combination of steam reforming and partial oxidation). The exploitable energy surplus in a fuel cell vehicle is low and therefore a combustion system for heating the reformer which utilizes a catalyst for both evaporation and oxidation of liquid methanol was developed. We were able to obtain start-up times in the region of 4-6 min depending on the oxygen-to-methanol ratio (OMR) used for the combined reforming reaction. The main drawback from decreasing the start-up time by increasing the oxygen-to-methanol ratio was that the CO concentrations in the product stream increased. The reforming reaction was performed over copper-based catalysts while the oxidation took place over a mixture of platinum and manganese-based catalysts. The catalysts were characterized using SEM-EDS, BET surface area measurement and X-ray diffraction (XRD).
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| 50. |
- Lindström, B., et al.
(författare)
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Hydrogen generation by steam reforming of methanol over copper-based catalysts for fuel cell applications
- 2001
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Ingår i: International journal of hydrogen energy. - 0360-3199 .- 1879-3487. ; 26:9, s. 923-933
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an investigation concerning the reforming of methanol over various base-metal oxide catalysts. Copper-based catalysts were effective for the steam reforming of methanol. The selectivity and conversion was studied in a flow reactor in the temperature interval 180-320 degreesC. The active materials were impregnated on gamma -alumina pellets using the wet impregnation method. The promoters used in the investigation were chromium (Cr), zinc (Zn) and zirconia (Zr). The copper content and promoter used played an important role in the catalyst's ability to selectively convert methanol at low temperatures. Catalysts with high copper contents generally gave higher conversions and selectivities for the steam reforming reaction. The use of ternary components generally increased the catalyst selectivity towards carbon dioxide. Zirconia had a positive influence on the catalytic performance at low temperatures. The possibilities for the use of reforming systems with copper-based catalysts in fuel cell applications are promising.
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