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Sökning: WFRF:(Nilsson Hampus)

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3.
  • Alfredsson, Hampus, et al. (författare)
  • Infrastructure modeling for large-scale introduction of electric aviation
  • 2022
  • Ingår i: 35th International Electric Vehicle Symposium and Exhibition (EVS35).
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents the results of the MODELflyg research project funded by the Swedish Transport Administration to gain more knowledge about ground charging infrastructure demand for the electrification of air traffic. An integrated simulation model was developed including flight traffic data processing, modelling of battery electric aircraft performance, and charging simulations. Several different options are available to select specific air traffic flows of interest, including scheduling algorithms for electric aviation adapted timetables. Furthermore, a smart-charging algorithm was developed to lower peak power demand at each airport from simultaneous charging of multiple electric aircraft.
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5.
  • Altermark, Niklas, et al. (författare)
  • Crafting the "Well-rounded citizen" : Empowerment and the government of counterradicalization
  • 2018
  • Ingår i: International Political Sociology. - : Oxford University Press (OUP). - 1749-5679 .- 1749-5687. ; 12:1, s. 53-69
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years, counterradicalization work has come to focus on empowering vulnerable communities and individuals through programs implemented by local governments and welfare services. This article examines this new regime of counterradicalization, focusing on how such programs seek to immunize people allegedly susceptible to radicalization by making them "active citizens." In contrast to the stated ambitions of these programs and much scholarly work on prevention, we do not see counterradicalization by citizenship empowerment as a way of giving back power to the communities where terrorism emerges. Rather, these programs are set up to manage the self-image and behaviors of individuals perceived as "risky," which means that they operate by shaping subjects. Undertaking an in-depth analysis of two programs of prevention through empowerment, we outline the rationalities underpinning this new way of countering radicalization, showing how they make use of "citizenship" as a political technology.
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6.
  • Altermark, Niklas, et al. (författare)
  • State measurements of benefit fraud : Why expert elicitations cannot be used to measure incorrect personal assistance payments
  • 2020
  • Ingår i: Scandinavian Journal of Disability Research. - 1501-7419. ; 22:1, s. 158-167
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last decade, personal assistance programs have suffered from cutbacks, resulting in a public debate about the future of the service. This debate has largely been framed by public commission estimations of the level of incorrect personal assistance payments, where the idea that circa 10% of all assistance payments are incorrect repeatedly has been used to justify measures designed to decrease costs. These estimates have been generated with the Expert Elicitation Method (EEM), originally developed to assess uncertainty and risks based on hard scientific data. In this study, we aim to answer two questions: (1) whether the method is suited to estimate incorrect payments and (2) whether the application of the method follows scientifically agreed upon methodological recommendations. By a systematic literature review about the method and when it can be used, we conclude that the EEM is not applicable to estimate incorrect payments. In a second step, we examine whether the applications of the Swedish public commission follow common methodological recommendations in the research literature, concluding that assessments of incorrect personal assistance payments do not meet basic requirements of how the method is supposed to be used. Hence, our overall conclusion is that the application of the EEM to estimate incorrect payments in personal assistance should not be relied upon to guide policy decisions.
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7.
  • Andersson, Martin, et al. (författare)
  • The anomalous hyperfine structure of Al II
  • 2012
  • Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 45:13
  • Tidskriftsartikel (refereegranskat)abstract
    • The hyperfine structure of a large number of transitions in Al II cannot be described using A and B hyperfine constants and the hyperfine structure is therefore said to be anomalous. In this paper, we have studied the hyperfine structure of a few transitions in Al II, 3s5s(3)S-3s5p(3)P, 3s4d(3)D-3s5p(3)P and 3s5p(3)P-3s5d(3)D, by combining theory and experiment. It is shown that the anomalous hyperfine structure is due to strong off-diagonal hyperfine interaction resulting not only in a deplacement of the energies of the hyperfine levels, but also resulting in large intensity redistribution among the individual hyperfine lines. It is shown that the hyperfine mixing in 3s4d(3)D and 3s5d(3)D is very large, whereas small but not negligible in 3s5p(3)P. By combining experimental spectra and theory we could obtain accurate wavefunctions for the 3s4d(3)D and 3s5d(3)D hyperfine levels which were used to calculate the gf-values of all individual hyperfine transitions not only for 3s5p(3)P, but also for 3s3p(3)P and 3s4p(3)P, where the off-diagonal hyperfine interaction leads to negligible intensity redistribution.
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8.
  • André, Hampus, et al. (författare)
  • Are second-hand shell jackets better than users think? A comparison of perceived, assessed and measured functionality throughout lifespans
  • 2024
  • Ingår i: Resources, Conservation and Recycling. - : Elsevier B.V.. - 0921-3449 .- 1879-0658. ; 204, s. 107470-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the case of outdoor shell jackets, this research studies obsolescence and potential lifespan extension by re-examining how product functionality, objectively and subjectively, develops over the course of product lifespans. In particular, the study focuses on second-hand stores for outdoor products. Functionality is indicated by user perceptions, visual assessments, laboratory measurements and price data, collected at first use, second-hand resale and end-of-life. Perceived functionality and price decline more rapidly (5–6 % per year) than assessed and measured functionality (around 3 % per year). This could be explained by properties related to appearance, which are not assessed nor measured but influence user perceptions and price. Discontentment regarding such properties appears more relevant for obsolescence than inadequate performance, suggesting the potential for design for attachment and timeless design. The relative stability of measured functionality over time suggests that a barrier for second-hand sales, concern about performance, could be ameliorated by a potential functionality-label.
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9.
  • Bean, Jacob L., et al. (författare)
  • The CRIRES search for planets around the lowest-mass stars. I. High-precision near-infrared radial velocities with an ammonia gas cell
  • 2010
  • Ingår i: Astrophysical Journal. - 0004-637X. ; 713:1, s. 410-422
  • Tidskriftsartikel (refereegranskat)abstract
    • Radial velocities measured from near-infrared (NIR) spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields NIR radial velocity precision comparable to that routinely obtained in the visible. We are carrying out an NIR radial velocity planet search program targeting a sample of the lowest-mass M dwarfs using the CRIRES instrument on the Very Large Telescope. In this first paper in a planned series about the project, we describe a method for measuring high-precision relative radial velocities of these stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the "iodine cell" technique that has been used very successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile (IP) model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneously as well using spectrum synthesis with a time-resolved model of the atmosphere over the observatory. The free parameters in the complete model are the wavelength scale of the spectrum, the IP, adjustments to the water and methane abundances in the atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift. Tests of the method based on the analysis of hundreds of spectra obtained for late-M dwarfs over 6 months demonstrate that precisions of similar to 5 m s(-1) are obtainable over long timescales, and precisions of better than 3 m s(-1) can be obtained over timescales up to a week. The obtained precision is comparable to the predicted photon-limited errors, but primarily limited over long timescales by the imperfect modeling of the telluric lines.
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10.
  • Bean, Jacob L., et al. (författare)
  • The crires search for planets around the lowest-mass stars. I. High-precision near-infrared radial velocities with an ammonia gas cell
  • 2010
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 713:1, s. 410-422
  • Tidskriftsartikel (refereegranskat)abstract
    • Radial velocities measured from near-infrared (NIR) spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields NIR radial velocity precision comparable to that routinely obtained in the visible. We are carrying out an NIR radial velocity planet search program targeting a sample of the lowest-mass M dwarfs using the CRIRES instrument on the Very Large Telescope. In this first paper in a planned series about the project, we describe a method for measuring high-precision relative radial velocities of these stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the "iodine cell" technique that has been used very successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile (IP) model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneously as well using spectrum synthesis with a time-resolved model of the atmosphere over the observatory. The free parameters in the complete model are the wavelength scale of the spectrum, the IP, adjustments to the water and methane abundances in the atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift. Tests of the method based on the analysis of hundreds of spectra obtained for late-M dwarfs over 6 months demonstrate that precisions of ∼ 5 m s−1 are obtainable over long timescales, and precisions of better than 3 m s−1 can be obtained over timescales up to a week. The obtained precision is comparable to the predicted photon-limited errors, but primarily limited over long timescales by the imperfect modeling of the telluric lines.
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11.
  • Bean, Jacob L., et al. (författare)
  • The proposed giant planet orbiting VB 10 does not exist
  • 2010
  • Ingår i: Astrophysical Journal Letters. - 2041-8213. ; 711:1, s. 19-23
  • Tidskriftsartikel (refereegranskat)abstract
    • We present high-precision relative radial velocities of the very low mass star VB 10 that were obtained over a time span of 0.61 years as part of an ongoing search for planets around stars at the end of the main sequence. The radial velocities were measured from high-resolution near-infrared spectra obtained using the CRIRES instrument on the Very Large Telescope with an ammonia gas cell. The typical internal precision of the measurements is 10 m s(-1). These data do not exhibit significant variability and are essentially constant at a level consistent with the measurement uncertainties. Therefore, we do not detect the radial velocity variations of VB 10 expected due to the presence of an orbiting giant planet similar to that recently proposed by Pravdo & Shaklan based on apparent astrometric perturbations. In addition, we do not confirm the similar to 1 km s(-1) radial velocity variability of the star tentatively detected by Zapatero Osorio and colleagues with lower precision measurements. Our measurements rule out planets with M-p > 3 M-Jup and the orbital period and inclination suggested by Pravdo & Shaklan at better than 5 sigma confidence. We conclude that the planet detection claimed by Pravdo & Shaklan is spurious on the basis of this result. Although the outcome of this work is a non-detection, it illustrates the potential of using ammonia cell radial velocities to detect planets around very low mass stars.
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12.
  • Bean, Jacob L., et al. (författare)
  • The proposed giant planet orbiting VB 10 does not exist
  • 2010
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 711:1, s. L19-L23
  • Tidskriftsartikel (refereegranskat)abstract
    • We present high-precision relative radial velocities of the very low mass star VB 10 that were obtained over a time span of 0.61 years as part of an ongoing search for planets around stars at the end of the main sequence. The radial velocities were measured from high-resolution near-infrared spectra obtained using the CRIRES instrument on the Very Large Telescope with an ammonia gas cell. The typical internal precision of the measurements is 10 m s−1. These data do not exhibit significant variability and are essentially constant at a level consistent with the measurement uncertainties. Therefore, we do not detect the radial velocity variations of VB 10 expected due to the presence of an orbiting giant planet similar to that recently proposed by Pravdo & Shaklan based on apparent astrometric perturbations. In addition, we do not confirm the ∼1 km s−1 radial velocity variability of the star tentatively detected by Zapatero Osorio and colleagues with lower precision measurements. Our measurements rule out planets with Mp > 3 MJup and the orbital period and inclination suggested by Pravdo & Shaklan at better than 5σ confidence. We conclude that the planet detection claimed by Pravdo & Shaklan is spurious on the basis of this result. Although the outcome of this work is a non-detection, it illustrates the potential of using ammonia cell radial velocities to detect planets around very low mass stars.
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14.
  • Biemont, E., et al. (författare)
  • Lifetime measurements and calculations in Y+ and Y2+ ions
  • 2011
  • Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 414:4, s. 3350-3359
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a new set oftheoretical transition probabilities in Y II, obtained using a multiconfiguration relativistic Hartree-Fock method including core polarization. The overall quality of the calculations is assessed by comparisons with new and previous lifetime measurements. In this paper, we report new measurements of five lifetimes in the 4d5p and 5s5p configurations, in the energy range of 32 048-44 569 cm(-1), obtained by the time-resolved laser-induced fluorescence method. A similar theoretical model, applied to Y III, leads to results in good agreement with new laser measurements of two 5p levels obtained in this work and with previous beam-foil results for 5d and 6s levels. An extensive set of oscillator strengths is also proposed for Y III.
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16.
  • Blackwell-Whitehead, Richard, et al. (författare)
  • Infrared Mn I laboratory oscillator strengths for the study of late type stars and ultracool dwarfs
  • 2011
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 525
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. The aim of our new laboratory measurements is to measure accurate absolute oscillator strengths for neutral manganese transitions in the infrared needed for the study of late-type stars and ultracool dwarfs. Methods. Branching fractions have been measured by high resolution Fourier transform spectroscopy and combined with radiative level lifetimes in the literature to yield oscillator strengths. Results. We present experimental oscillator strengths for 20 Mn I transitions in the wavelength range 3216 to 13 997 angstrom, 15 of which are in the infrared. The transitions at 12 899 angstrom and 12 975 angstrom are observed as strong features in the spectra of late-type stars and ultracool dwarfs. We have fitted our calculated spectra to the observed Mn I lines in spectra of late-type stars. Using the new experimentally measured Mn I log(gf) values together with existing data for Mn I hyperfine structure splitting factors we determined the manganese abundance to be log N(Mn) = -6.65 +/- 0.05 in the atmosphere of the Sun, log N(Mn) = 6.95 +/- 0.20 in the atmosphere of Arcturus, and log N(Mn) = -6.70 +/- 0.20 in the atmosphere of M 9.5 dwarf 2MASSW 0140026+270150.
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18.
  • Burheim, Madeleine, et al. (författare)
  • Experimental oscillator strengths of Al I lines for near-infrared astrophysical spectroscopy
  • 2023
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Elemental abundances can be determined from stellar spectra, making it possible to study galactic formation and evolution. Accurate atomic data is essential for the reliable interpretation and modeling of astrophysical spectra. In this work, we perform laboratory studies on neutral aluminium. This element is found, for example, in young, massive stars and it is a key element for tracing ongoing nucleosynthesis throughout the Galaxy. The near-infrared (NIR) wavelength region is of particular importance, since extinction in this region is lower than for optical wavelengths. This makes the NIR wavelength region a better probe for highly obscured regions, such as those located close to the Galactic center.Aims. We investigate the spectrum of neutral aluminium with the aim to provide oscillator strengths (f-values) of improved accuracy for lines in the NIR and optical regions (670–4200 nm).Methods. Measurements of high-resolution spectra were performed using a Fourier transform spectrometer and a hollow cathode discharge lamp. The f-values were derived from experimental line intensities combined with published radiative lifetimes.Results. We report oscillator strengths for 12 lines in the NIR and optical spectral regions, with an accuracy between 2 and 11%, as well as branching fractions for an additional 16 lines. 
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19.
  • Bäckström, Erik, et al. (författare)
  • Experimentally determined oscillator strengths in Rh II
  • 2013
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:20, s. 205001-
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents new experimentally determined branching fractions and oscillator strengths (log gf) for lines originating from 17 levels belonging to 5 terms of the first excited odd configuration 4d(7)(D-4) 5p in Rh II. The intensity calibrated spectra of Rh II have been recorded with a Fourier transform spectrometer between 25000 and 45000 cm(-1) (2200-4000 angstrom). In this region, 49 lines have been identified and measured. By combining the branching fractions obtained from the spectra with previously measured lifetimes, log gf values are reported. The new results are compared with previous theoretical work.
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20.
  • Bäckström, Erik, et al. (författare)
  • The FERRUM project : metastable lifetimes in Cr II
  • 2012
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 420:2, s. 1636-1639
  • Tidskriftsartikel (refereegranskat)abstract
    • Parity forbidden radiative transitions from metastable levels are observed in spectra of low-density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron-group elements, and part of this project concerns forbidden lines. The radiative lifetimes of the metastable energy levels 3 d4(a 3 D)4 s c4 D 5/2 and 3 d4(a 3 D)4 s c4 D 7/2 of singly ionized chromium have been measured. The experiment has been performed at the ion storage ring CRYRING. We employed a laser-probing technique developed for measuring long lifetimes. In this article, we present the lifetimes of these levels to be t5/2= 1.28(16) s and t7/2= 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.
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22.
  • Ekblad, Hampus, et al. (författare)
  • Cykelgator i Göteborg - att vara eller inte vara
  • 2024
  • Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 493-493
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • I och med den relativt nya regleringen Cykelgata önskade Göteborgs Stad utvärdera behovet av regleringen samt hur gatorna skulle kunna utformas med tankesättet som ingår i konceptet Cykelgata. Det finns flera oklarheter kring hur cykelgator ska implementeras och regleringen medför lite vägledning för hur gatorna ska planeras och utformas, därför vill man testa hur det kan funka och var. Inom studien har en omvärldsbevakning genomförts för att samla in erfarenheter om hur olika städer i Sverige och internationellt planerar och utformar cykelanpassade gator eller cykelgator. Utöver detta har ett koncept tagits fram för hur cykelgator skulle kunna se ut samt hur faktiska gator skulle kunna utfromas. Inom uppdraget har även en översikt gjorts av behovet av regleringen (och således skylten) "cykelgata" gjorts. Danmark, Finland och Tyskland har reglering för cykelgator medan Nederländerna och Norge inte har det. Gemensamt för länderna med reglering för cykelgata är att det finns vägmärke för cykelgator med officiell status där maxhastighet på 30 km/h ingår. I Danmark regleras även parkeringen längs gatan samt att det är tillåtet att cykla i bredd. I Finland innefattar regleringen flera krav som färgad asfalt, anordnad bilparkering samt förslag på två sektioner. I Tyskland regleras fordon utöver cyklar och elektrisk mikromobilitet med tilläggstavla. Oavsett reglering eller inte så finns det i samtliga städer och länder rekommendationer på planeringsprinciper och utformningselement. Exempel på planeringsprinciper är begränsning av antal fordon per dygn, en nedre gräns för antal cyklister, begränsningar för genomfartstrafik, kollektivtrafik och tung trafik. Exempel på utformningselement är körbana i mitten som uppmanar cyklister att färdas i mitten och sidoytor i avvikande färg eller material, förslag på bredder, anordnade parkeringsplatser, hastighetssäkring, väjningsplikt från anslutande gator samt målad cykelsymbol. Omvärldsbevakningen pekar därmed på att regleringen inte är tillräcklig och att det oftast krävs kompletterande utformningselement för att säkerställa att cykelmiljön på gatan blir trygg och säker, därmed cykelanpassad. Utifrån omvärldsbevakningen har förslag på planeringsprinciper och utformningselement tagits fram för Göteborgs Stad. En analys har genomförts för att utreda hur regleringen kan användas som ett verktyg för att förbättra cykelinfrastrukturen jämfört med andra verktyg som finns.  
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23.
  • En båge genom tiden - ritualer kring en göteborgshistoria. Om Flickläroverket i Artisten
  • 2024
  • Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
    • 1929 bildades Göteborgs första Högre allmänna läroverk för Flickor – Flickläroverket som fick en byggnad 1935 i det kulturella centrumet, Götaplatsen. Efter några år som Kjellbergska gymnasiet, sedan Komvux, blev byggnaden del av Artisten, Högskolan för scen och musik, HSM 1992. Byggnaden har burit kvinnors utbildning, konst och kultur över många generationer, en minneskedja som nu är bruten. Boken - En båge genom tiden – ritualer kring en göteborgshistoria – en konst- och forskningsantologi – är resultatet av de offentliga minnesdagar där de deltagande drygt 200 kvinnorna (70– 97 år) som varit elever på Flickläroverket, studenter vid Artisten, konstnärer och forskare – bidrog till och deltog i gestaltande ritualer, minnesrum, dans, utställningar och samtal som gav liv åt en utbildningskultur och konst som berört samhället i generationer. I boken bidrar ett 20-tal Göteborgsbaserade konstnärer och forskare med olika perspektiv på byggnadens poetiska, sociala och konstnärliga dimensioner. Bland annat beskrivs återskapandet av Bågdansen, som dansades varje år vid Lucia mellan 1934-1972. Här beskrivs även den medie-debatt som ledde till räddningen av målningen Dansen av Nils Nilsson från 1935 och hur nedtagningen gick till. Tillsammans med ett rikt foto- och bildmaterial, filmdokumentationer och ett ljudarkiv utgör boken ett tidsdokument där konst fungerar som minnesbärare över tid och rum.
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24.
  • Engström, Lars, et al. (författare)
  • The FERRUM project : Experimental transition probabilities from highly excited even 5s levels in Cr ii
  • 2014
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 570
  • Tidskriftsartikel (refereegranskat)abstract
    • We report lifetime measurements of the five levels in the 3d4(a5D)5s e6D term in Cr ii at an energy around 83 000 cm-1, and log(g f ) values for 38 transitions from the investigated levels. The lifetimes are obtained using time-resolved, laser-induced fluorescence on ions from a laser-produced plasma. Since the levels have the same parity as the low-lying states directly populated in the plasma, we used a two-photon excitation scheme. This process is greatly facilitated by the presence of the 3d4(a5D)4p z6F levels at roughly half the energy di erence. The f -values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode lamp recorded with a Fourier transform spectrometer.
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25.
  • Engström, Lars, et al. (författare)
  • The FERRUM project : Experimental transition probabilities from highly excited even 5s levels in Cr II
  • 2014
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 570, s. A34-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report lifetime measurements of the five levels in the 3d(4)(a(5)D)5s e(6)D term in Cr II at an energy around 83 000 cm(-1), and log(gf) values for 38 transitions from the investigated levels. The lifetimes are obtained using time-resolved, laser-induced fluorescence on ions from a laser-produced plasma. Since the levels have the same parity as the low-lying states directly populated in the plasma, we used a two-photon excitation scheme. This process is greatly facilitated by the presence of the 3d(4)(a(5)D)4p z(6)F levels at roughly half the energy difference. The f-values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode lamp recorded with a Fourier transform spectrometer.
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26.
  • Eriksson, Mattias, et al. (författare)
  • Fluorescence Fe II lines as traces of fast outflows of white dwarf winds
  • 2007
  • Ingår i: Baltic Astronomy. - 1392-0049. ; 16:01, s. 95-97
  • Tidskriftsartikel (refereegranskat)abstract
    • A set of equations are put into a code forming a procedure to derive intensities of fluorescence lilies based on both physical properties of the fluorescent plasma and its location relative to the origin of the pumping emission. In a first test, the code is applied to symbiotic stars, and effort is made to explain the circumstances under which the two known Fell channels pumped by C IV are activated. For the channel at 1548.204 angstrom, which is most frequently observed to be active, there is a good agreement between the results of the calculations and the observed Fell line strengths. Fluorescence lines resulting from pumping through the other channel at 1548.411 angstrom can occur, according to the results of the calculations, only in the systems where a fast outflow from the white dwarf wind is present. The evidences of the white dwarf winds are found in the literature for all the symbiotic systems in which observation of the Fell fluorescence lines from the w(2)D(3/2) level is reported. 
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27.
  • Eriksson, M, et al. (författare)
  • Modeling of C IV pumped fluorescence of Fe II in symbiotic stars
  • 2008
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 477:1, s. 255-265
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims. We describe how the C IV lambda 1548.18 line pumps the 1548.20 and 1548.41 angstrom channels of Fe II in symbiotic stars through the process known as photo-ionization by accidental resonance (PAR). We describe where and why Fe II fluorescence arises in symbiotic stars and whether the Fe II lambda 1548.41 channel can only be activated when there is a white-dwarf wind present in the system. Further, we aim to show how an analysis of the PAR-pumped lines helps to understand the phyisical conditions that they manifest. Methods. We calculate intensities of the C IV-pumped Fe II fluorescence lines in symbiotic stars, corresponding to the y(4)H(11/)2 and w(2)D(3/2) levels, based on a simple geometrical model of the emitting regions. We apply the model to seven symbiotic stars, known to have Fe II fluorescence lines pumped by C IV in their spectra. We compare the predicted intensities to the observed intensities of the selected symbiotic stars. Results. We find that we can reproduce the observed fluorescence intensities of the seven symbiotic stars in our sample, using parameters that are consistent with their known properties. We show that PAR-produced lines can be used as a diagnostic tool to derive important physical parameters of a stellar system. We suggest that the detection of Fe II lines corresponding to the w2D3/2 level in certain symbiotic stars provide evidence of hot shells expanding with velocities of at least hundreds km s(-1) in those systems.
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28.
  • Erlandsson, Martin, et al. (författare)
  • Underlagsdata för hållbarhetsbedömning i BioMapp
  • 2024
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Denna rapport utgör en samlad dokumentation av underlags data, med avseende på de olika industriprocesser som ingår i visualiseringsverktyget BioMapp. De skogsindustriella processerna som beskrivs i rapportens bilagor baseras på en allmänt accepterad inventeringsmetodik för att beskriva skogsbaserade produkters miljöpåverkan och andra hållbarhetsindikatorer i ett livscykelperspektiv. Det systemanalytiska verktyg som används i projektet är livscykelanalys (LCA) på så sätt som det tillämpas i miljövarudeklarationer för produkter (EPD).De inventeringsdata som redovisas har en ambition att vara representativa för den typ av processer och miljöbelastning som är relevanta för svenska förhållande. Det har dock inte varit möjligt inom ramen för projektet att göra kompletta branschsammanställningar.
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29.
  • Fadavi Roudsari, Anita, 1978, et al. (författare)
  • Three-wave mixing traveling-wave parametric amplifier with periodic variation of the circuit parameters
  • 2023
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 122:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the implementation of a near-quantum-limited, traveling-wave parametric amplifier that uses three-wave mixing (3WM). To favor amplification by 3WM, we use superconducting nonlinear asymmetric inductive element (SNAIL) loops, biased with a dc magnetic flux. In addition, we equip the device with dispersion engineering features to create a stopband at the second harmonic of the pump and suppress the propagation of the higher harmonics that otherwise degrade the amplification. With a chain of 440 SNAILs, the amplifier provides up to 20 dB gain and a 3-dB bandwidth of 1 GHz. The added noise by the amplifier is found to be less than one photon.
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30.
  • Fahlvik, Nils, et al. (författare)
  • Simulation of the long-term effects of different strategies for precommercial thinning in Pinus sylvestris
  • 2018
  • Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 33, s. 347-356
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of the intensity and timing of precommercial thinning (PCT) on stand development and financial return was studied in Scots pine stands. Functions describing the early development of the stand structure after PCT were developed. The functions were based on 195 plots within 41 PCT experiments in Sweden. The dimension distribution of the established stand was estimated and used as input to the decision support system Heureka, to simulate the stand development until final felling. The studied treatments included PCT to 1000, 2000 and 3000 stems ha(-1) at mean heights of 2, 4 and 6 m. Separate simulations were carried out for different site fertilities. Mean annual volume increment increased with increasing number of stems after PCT whereas the timing of PCT had only a small effect. The land expectation value (LEV) generally decreased with increasing mean height at PCT, primarily because of the increased cost of PCT. LEV decreased with increasing number of stems after PCT at low fertility sites whereas only minor differences were found for PCT to 1000 and 2000 stems ha(-1) at medium and high fertility sites. The general pattern persisted when different scenarios of future timber quality were simulated.
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31.
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32.
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33.
  • Fölster, Jens, et al. (författare)
  • Förslag till bedömningsgrunder för näringsämnen i sjöar och vattendrag
  • 2021
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Bedömningsgrunder för klassning av ekologisk status har en central betydelse för vattenförvaltningen. Målet är att alla vatten ska uppnå minst god status som definieras som en maximal tillåten avvikelse från ett referensvärde. Klassningen ska i första hand göras med de biologiska kvalitetsfaktorerna, medan de fysikalisk/kemiska ska ha en stödjande funktion till de biologiska. I praktiken har dock de fysikalisk/kemiska större betydelse än så. Dels för att det för många vattenförekomster bara finns vattenkemiska data och dels för att de fysikalisk kemiska kvalitetsfaktorerna är mer direkt kopplade till påverkan för flera påverkanstyper och därför lättare kan ge underlag för åtgärdsbehov.Tillämpningen av den nuvarande klassningen av ekologisk status för näringsämnen har påvisat brister i hur de är konstruerade. I de nuvarande bedömningsgrunderna för sjöar användes skogssjöar (< 10 % jordbruk i avrinningsområdet) för att definiera referenstillståndet för näringsämnen vilket troligen ger för lågt referensvärde och därmed för stor påverkan eftersom skogsmark generellt är naturligt näringsfattigare än jordbruksmark. För jordbrukslandskapets vattendrag (> 10% jordbruksmark i avrinningsområdet) används det halva modellerade rotzonsläckaget från obrukad jord (ogödslad och oskördad vall) som referenstillstånd. Halveringsfaktorn är godtyckligt vald för att ta hänsyn till retentionen mellan rotzonen och vattendraget. Det har heller inte gjorts någon harmonisering mellan bedömningen av näringspåverkan från biologiska respektive kemiska kvalitetsfaktorer.Syftet med detta projekt har varit att förbättra beräkningen av referensvärden för totalfosfor så att de särskilda förhållandena i jordbrukslandskapets sjöar och vattendrag bättre beaktas, samt att harmonisera klassgränserna för ekologisk status med de biologiska kvalitetsfaktorerna. Förutom att utveckla bedömningsgrunderna för TotP, kommer även motsvarande bedömningsgrunder för totalkväve (TotN) tas fram som stöd för vattenförvaltningen och för att kunna jämföra med motsvarande klassning i andra EU-länder. Förslag på nya klassgränser för ekologisk status gjordes med utgångspunkt från de biologiska kvalitetsfaktorerna med stöd av koncept som tagits fram inom ECOSTAT.Dataunderlaget för studien utgjordes av provplatser i 210 vattendrag och 146 sjöar. Provplatserna valdes ut för att de hade tillräckligt med data och att de låg i utloppet av vattenförekomstområden för att möjliggöra en jämförelse med PLC-beräkningar. För utvärdering av modellerna för sjöar användes även data från 5080 sjöar i Omdrevsprogrammet.Det förslag vi tagit fram bygger på regressionsmodeller baserad på vattenkemi och landskapsparametrar. I regressionsmodellen för totalfosfor i vattendrag ingick följande förklarande variabler: Färg (absorbans), sulfat, summan av kalcium och magnesium, genomsnittlig lerhalt i avrinningsområdet, altitud, andel sankmark i avrinningsområdet och andel vatten i avrinningsområdet, i ordning efter hur mycket de bidrar till modellen. Eftersom kartunderlag för lerhalten bara finns för södra och mellersta Sverige, är underlaget till modellen begränsad till den delen av landet. För att kunna tillämpa modellen i norra Sverige behöver man uppskatta lerhalten. För sjöar togs en motsvarande regressionsmodell fram med följande variabler: Medeldjup, färg (absorbans), sulfat, magnesium och andel sankmark i avrinningsområdet ordning efter hur mycket de bidrar till modellen. Eftersom lerhalten inte blev signifikant för sjöar kunde data från hela landet användas. Alternativa modeller togs fram för de fall då en del av de ingående mätvariablerna saknas. Dessa har dock större fel en de föreslagna.Motsvarande modeller togs fram för referensvärden för totalkväve. För vattendrag omfattade modellen följande variabler: Färg (absorbans), kalcium, nordsydkoordinat, andel vatten samt andel skog i avrinningsområdet, altitud, östvästkoordinat och avrinningsområdets area i ordning efter hur mycket de bidrar till modellen. Motsvarande modell för sjöar innehöll följande variabler: Färg (absorbans) kalcium, medeldjup, altitud och östvästkoordinat i ordning efter hur mycket de bidrar till modellen.Eftersom färgen (absorbans) ingår i modellerna för både fosfor och kväve och det påvisats långsiktiga trender i både färg och näringsämnen i vatten opåverkade av övergödning, behöver modellerna löpande uppdateras med senaste mätdata. Detta gör det samtidigt möjligt att basera underlaget på den senaste versionen av PLCberäkningarna inför varje vattencykel.Klassgränser för totalfosfor togs fram med det loglinjära sambandet mellan totalfosfor och klorofyll. I bedömningsgrunder för växtplankton är det olika klassgränser för olika typer av sjöar. Skillnaden mellan typerna kan delvis bero på slumpvisa skillnader i dataunderlaget eller för södra Sverige att andelen jordbruksmark i referensdataunderlaget är större än övriga regioner. Eftersom klassningen för totalfosfor är objektsspecifik valde vi därför att använda samma klassgränser för alla vattentyper. Medelvärdet för gränsen mellan god och måttlig status låg nära den nuvarande gränsen, 0,5. Vi valde därför att behålla de nuvarande klassgränserna för påverkansklassning för totalfosfor.Ett försök att tillämpa motsvarande metodik på vattendrag genom att relatera TotP till diatoméindexet IPS visade på svaga samband och gav inget underlag för att sätta klassgränser. Det beror troligen på att IPS inte är ett rent näringsindex utan ett bredare renvattensindex. Vi föreslår därför samma klassgränser för påverkan av TotP i vattendrag som för sjöar och på sikt utveckla ett rent näringsindex för diatoméer.För totalkväve föreslås samma klassgränser som för totalfosfor efter som det saknas underlag för samband mellan totalkväve och biologiska kvalitetsfaktorer i de fosforbegränsade sjöarna och vattendragen i Sverige.För vattendragen ger det nya förslaget något striktare bedömning jämfört med nuvarande föreskrift med större andel med måttlig status eller sämre. För sjöar däremot fick en mindre andel av sjöarna måttlig status eller sämre när andelen jordbruksmark var större än 10 %. För sjöar med mindre jordbrukspåverkan var det ingen skillnad mellan förslagen. För vattendragen gav en klassning med totalkväve en mindre andel med måttlig status eller sämre jämfört med TotP, medan för sjöarna var skillnaden liten.I det presenterade förslaget till bedömningsgrunder för näringsämnen görs beräkningarna helt med uppmätt vattenkemi och geografiska data och är därmed inte direkt beroende av modelldata för en statusklassning. Detta är bättre i enlighet med vattendirektivets krav på hur en statusklassning ska göras jämfört med det nuvarande, där det modellerade läckaget från ogödslad vall ingår i bedömningen av jordbruksdominerade vattendrag. Samtidigt är regressionsmodellerna kalibrerade mot den processbaserade modelleringen av bakgrundshalter som görs inom PLC. Detta gör att klassningen av ekologisk status för näringsämnen harmoniserar med Sveriges rapportering till HELCOM och OSPAR. För sjöar är det framför allt de med stor jordbrukspåverkan som får en mer relevant bedömning jämfört med tidigare. För vattendragen är hela dataunderlaget förbättrat. Det nya förslaget tar bättre hänsyn till att den mark man bedriver jordbruk på är naturligt mer näringsrik och erosionsbenägen jämfört med annan mark. Samtidigt efterfrågar vi en bredare diskussion om det är rimligt att låta en helt obrukad jord utgöra referenstillståndet för näringsläckage när marken har brukats århundraden och ibland längre.
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34.
  • Gran, Ulf, 1973, et al. (författare)
  • Off-shell structure of twisted (2,0) theory
  • 2014
  • Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; 2014:11
  • Tidskriftsartikel (refereegranskat)abstract
    • A $Q$-exact off-shell action is constructed for twisted abelian (2,0) theory on a Lorentzian six-manifold of the form $M_{1,5} = C\times M_4$, where $C$ is a flat two-manifold and $M_4$ is a general Euclidean four-manifold. The properties of this formulation, which is obtained by introducing two auxiliary fields, can be summarised by a commutative diagram where the Lagrangian and its stress-tensor arise from the $Q$-variation of two fermionic quantities $V$ and $\lambda^{\mu\nu}$. This completes and extends the analysis in [arXiv:1311.3300].
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35.
  • Gurell, Jonas, 1981-, et al. (författare)
  • The FERRUM project : Laboratory-measured transition probabilities for Cr II
  • 2010
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511:A68
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: We measure transition probabilities for Cr II transitions from the z ^4H_J, z ^2D_J, y ^4F_J, and y ^4G_J levels in the energy range 63000 to 68000 cm^{-1}. Methods:Radiative lifetimes were measured using time-resolved laser-induced fluorescence from a laser-produced plasma. In addition, branching fractions were   determined from intensity-calibrated spectra recorded with a UV Fourier transform spectrometer. The branching fractions and radiative lifetimes were combined   to yield accurate transition probabilities and oscillator strengths. Results: We present laboratory measured transition probabilities for 145 Cr II lines and radiative lifetimes for 14 Cr II levels. The laboratory-measured   transition probabilities are compared to the values from semi-empirical calculations and laboratory measurements in the literature.
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36.
  • Gurell, Jonas, 1981-, et al. (författare)
  • The FERRUM project : Transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes
  • 2009
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 508:1, s. 525-529
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [Fe II] transitions that are observed as strong features in astrophysical spectra. Aims. We measure lifetimes for the 3d(6)((3)G)4s a (4)G(11/2) and 3d(6)((3)D)4s b (4)D(1/2) metastable levels in Fe II and experimental transition probabilities for the forbidden transitions 3d(7) a (4)F(7/2,9/2)-3d(6)((3)G)4s a (4)G(11/2). Methods. The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. Results. The lifetimes of the a (4)G(11/2) and the b (4)D(1/2) levels have been measured and have the following values, tau = 0.75 +/- 0.10 s and tau = 0.54 +/- 0.03 s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a (4)F(7/2,9/2)-a (4)G(11/2) at 4243.97 and 4346.85 angstrom. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.
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37.
  • Gustafsson, Victor, et al. (författare)
  • Mimir - Streaming operators classification with artificial neural networks
  • 2019
  • Ingår i: DEBS 2019 - Proceedings of the 13th ACM International Conference on Distributed and Event-Based Systems. - New York, NY, USA : ACM. ; , s. 258-259
  • Konferensbidrag (refereegranskat)abstract
    • Streaming applications are used for analysing large volumes of continuous data. Achieving efficiency and effectiveness in data streaming imply challenges that gen all the more important when different parties (i) define applications' semantics, (ii) choose the stream Processing Engine (SPE) to use, and (iii) provide the processing infrastructure (e.g., cloud or fog), and when one party's decisions (e.g., how to deploy applications or when to trigger adaptive reconfigurations) depend on information held by a distinct one (and possibly hard to retrieve). In this context, machine learning can bridge the involved parties (e.g., SPEs and cloud providers) by offering tools that learn from the behavior of streaming applications and help take decisions. Such a tool, the focus of our ongoing work, can be used to learn which operators are run by a streaming application running in a certain SPE, without relying on the SPE itself to provide such information. More concretely, to classify the type of operator based on a desired level of granularity (from a coarse-grained characterization into stateless/stateful, to a fine-grained operator classification) based on general application-related metrics. As an example application, this tool could help a Cloud provider decide which infrastructure to assign to a certain streaming application (run by a certain SPE), based on the type (and thus cost) of its operators.
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38.
  • Hansen, C. J., et al. (författare)
  • Silver and palladium help unveil the nature of a second r-process
  • 2012
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 545
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The rapid neutron-capture process, which created about half of the heaviest elements in the solar system, is believed to have been unique. Many recent studies have shown that this uniqueness is not true for the formation of lighter elements, in particular those in the atomic number range 38 < Z < 48. Among these, palladium (Pd) and especially silver (Ag) are expected to be key indicators of a possible second r-process, but until recently they have been studied only in a few stars. We therefore target Pd and Ag in a large sample of stars and compare these abundances to those of Sr, Y, Zr, Ba, and Eu produced by the slow (s-) and rapid (r-) neutron-capture processes. Hereby we investigate the nature of the formation process of Ag and Pd. Aims. We study the abundances of seven elements (Sr, Y, Zr, Pd, Ag, Ba, and Eu) to gain insight into the formation process of the elements and explore in depth the nature of the second r-process. Methods. By adopting a homogeneous one-dimensional local thermodynamic equilibrium (1D LTE) analysis of 71 stars, we derive stellar abundances using the spectral synthesis code MOOG, and the MARCS model atmospheres. We calculate abundance ratio trends and compare the derived abundances to site-dependent yield predictions (low-mass O-Ne-Mg core-collapse supernovae and parametrised high-entropy winds), to extract characteristics of the second r-process. Results. The seven elements are tracers of different (neutron-capture) processes, which in turn allows us to constrain the formation process(es) of Pd and Ag. The abundance ratios of the heavy elements are found to be correlated and anti-correlated. These trends lead to clear indications that a second/weak r-process, is responsible for the formation of Pd and Ag. On the basis of the comparison to the model predictions, we find that the conditions under which this process takes place differ from those for the main r-process in needing lower neutron number densities, lower neutron-to-seed ratios, and lower entropies, and/or higher electron abundances. Conclusions. Our analysis confirms that Pd and Ag form via a rapid neutron-capture process that differs from the main r-process, the main and weak s- processes, and charged particle freeze-outs. We find that this process is efficiently working down to the lowest metallicity sampled by our analysis ([Fe/H] = -3.3). Our results may indicate that a combination of these explosive sites is needed to explain the variety in the observationally derived abundance patterns.
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39.
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40.
  • Hartman, Henrik, et al. (författare)
  • Experimental and theoretical lifetimes and transition probabilities in Sb i
  • 2010
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physiological Society. - 1050-2947 .- 1094-1622. ; 82:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We present experimental atomic lifetimes for 12 levels in Sb i. The levels belong to the 5p2(3P)6s 2P, 4P, and 5p2(3P)5d 4P, 4F, and 2F terms. The lifetimes were measured using time-resolved laser-induced fluorescence. In addition, we report calculations of transition probabilities in Sb i using a multiconfigurational Dirac-Hartree-Fock method. The physical model was tested through comparisons between theoretical and experimental lifetimes for 5d and 6s levels. The lifetimes of the 5d 4F3/2,5/2,7/2 levels (19.5, 7.8, and 54 ns, respectively) depend strongly on the J value. This is explained by different degrees of level mixing for the different levels in the 4F term.
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41.
  • Hartman, Henrik, et al. (författare)
  • Laboratory Atomic Astrophysics for near-infrared Stellar Spectroscopy
  • 2021
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Astronomical infrared observations are of increasing importance for stellar spectroscopy. The analysis of element abundance relies on high-quality observations, stellar models, and ultimately on accurate atomic data. With the growing number of near-IR astronomical observations and surveys, the absence of highaccuracy data is becoming apparent and a severe limiting factor.We run a program to take up the task to provide evaluated, high-accuracy atomic data for important transitions in the near-infrared spectral region, mainly 1-5 microns. A combinations of both experimental and theoretical techniques is used, to provide complete sets of data with a low uncertainty. FTS measurements of a discharge are combined with laser induced fluorescence techniques, and GRASP2k and ATSP2k atomic structure calculations for the theoretical values.
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42.
  • Hartman, Henrik, et al. (författare)
  • Radiative data for highly excited 3d84d levels in Ni II from laboratory measurements and atomic calculations
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 600
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d84d levels of astrophysical interest in singly ionized nickel. Methods: Radiative lifetimes of seven high-lying levels of even parity in Ni II (98 400-100 600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects. Results: A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194-520 nm depopulating even parity 3d84d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.
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43.
  • Hartman, Henrik, et al. (författare)
  • The FERRUM project : Experimental lifetimes and transition probabilities from highly excited even 4d levels in Fe ii
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584:A24
  • Tidskriftsartikel (refereegranskat)abstract
    • We report lifetime measurements of the 6 levels in the 3d6(5D)4d e6G term in Fe ii at an energy of 10.4 eV, and f -values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laserproduced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d6(5D)4p z6F levels at roughly half the energy di erence. The f -values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode discharge lamp recorded with a Fourier transform spectrometer. The data is important for benchmarking atomic calculations of astrophysically important quantities and useful for spectroscopy of hot stars.
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44.
  • Hartman, Henrik, et al. (författare)
  • The FERRUM project: Experimental lifetimes and transition probabilities from highly excited even 4d levels in Fe II
  • 2015
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584
  • Tidskriftsartikel (refereegranskat)abstract
    • We report lifetime measurements of the 6 levels in the 3d(6)(5D)4d e(6)G term in Fe II at an energy of 10.4 eV, and f-values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laser-produced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d(6)(D-5)4p z(6)F levels at roughly half the energy difference. The f-values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode discharge lamp recorded with a Fourier transform spectrometer. The data is important for benchmarking atomic calculations of astrophysically important quantities and useful for spectroscopy of hot stars.
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45.
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46.
  • Holmes, Charlotte, et al. (författare)
  • Experimentally Measured Radiative Lifetimes and Oscillator Strengths in Neutral Vanadium
  • 2016
  • Ingår i: Astrophysical Journal Supplement Series. - : Bibliopolis, Edizioni di Filosofia e Scienze. - 0067-0049 .- 1538-4365. ; 224:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a new study of the V i atom using a combination of time-resolved laser-induced fluorescence and Fourier transform spectroscopy that contains newly measured radiative lifetimes for 25 levels between 24,648 cm-1 and 37,518 cm-1 and oscillator strengths for 208 lines between 3040 and 20000 Å from 39 upper energy levels. Thirteen of these oscillator strengths have not been reported previously. This work was conducted independently of the recent studies of neutral vanadium lifetimes and oscillator strengths carried out by Den Hartog et al. and Lawler et al., and thus serves as a means to verify those measurements. Where our data overlap with their data, we generally find extremely good agreement in both level lifetimes and oscillator strengths. However, we also find evidence that Lawler et al. have systematically underestimated oscillator strengths for lines in the region of 9000 ± 100 Å. We suggest a correction of 0.18 ± 0.03 dex for these values to bring them into agreement with our results and those of Whaling et al. We also report new measurements of hyperfine structure splitting factors for three odd levels of V i lying between 24,700 and 28,400 cm-1.
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47.
  • Ivarsson, Stefan, et al. (författare)
  • Improved oscillator strengths and wavelengths for Os I and Ir I, and new results on early r-process nucleosynthesis
  • 2003
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 409:3, s. 1141-1149
  • Tidskriftsartikel (refereegranskat)abstract
    • The radioactive decay of 238U and 232Th has recently been used to determine ages for some of the oldest stars in the Universe. This has highlighted the need for accurate observational constraints on production models for the heaviest r-process elements which might serve as stable references, notably osmium and iridium. In order to provide a firmer basis for the observed abundances, we have performed laser-induced fluorescence measurements and Fourier Transform Spectroscopy to determine new radiative lifetimes and branching fractions for selected levels in Os I and Ir I. From these data, we determine new absolute oscillator strengths and improved wavelengths for18 Os I and 4 Ir I lines. A reanalysis of VLT spectra of CS 31082-001and new results for other stars with Os and Ir detections show that (i):the lines in the UV and lambda 4260 yield reliable Os abundances, while those at lambda lambda 4135, 4420 are heavily affected by blending; (ii): the Os and Ir abundances are identical in all the stars; (iii): the heavy-element abundances in very metal-poor stars conform closely to the scaled solar r-process pattern throughout the range 56 <= Z <= 77; and (iv): neither Os or Ir nor any lighter species are suitable as reference elements for the radioactive decay of Th and U.Based in part on observations obtained with the Very Large Telescope of the European Southern Observatory at Paranal, Chile.
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48.
  • Johansson, Sveneric, et al. (författare)
  • The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
  • 2002
  • Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
  • Konferensbidrag (refereegranskat)abstract
    • We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Šin detail.
  •  
49.
  • Johnsson, Holger, et al. (författare)
  • Model applications
  • 2012
  • Ingår i: Productive agriculture adapted to reduced nutrient losses in future climate : model and stakeholder based scenarios of Baltic Sea catchments. ; , s. 57-149
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
50.
  • Karlsson, Martin, et al. (författare)
  • Health, happiness, inequality
  • 2010
  • Ingår i: Expert Review of Pharmacoeconomics & Outcomes Research. - : Informa UK Limited. - 1473-7167 .- 1744-8379. ; 10:1, s. 497-500
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • At the beginning of June 2010, the conference 'Health. Happiness. Inequality. Modelling the Pathways between Income Inequality and Health' was held in Darmstadt, Germany. Invited speakers and presenters traveled from all over the world; and researchers from several different subdisciplines were represented at the conference. The common denominator of participants was an interest in how societal income inequality affects individual health and life satisfaction. New and fascinating research results were presented and participants engaged in many interesting discussions.
  •  
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