| 1. |
- Abdollahi, S., et al.
(författare)
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Fermi Large Area Telescope Fourth Source Catalog
- 2020
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 247:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
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| 2. |
- Abdollahi, S., et al.
(författare)
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Incremental Fermi Large Area Telescope Fourth Source Catalog
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 260:2
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Tidskriftsartikel (refereegranskat)abstract
- We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi Large Area Telescope (LAT) catalog of γ-ray sources. Based on the first 12 years of science data in the energy range from 50 MeV to 1 TeV, it contains 6658 sources. The analysis improves on that used for the 4FGL catalog over eight years of data: more sources are fit with curved spectra, we introduce a more robust spectral parameterization for pulsars, and we extend the spectral points to 1 TeV. The spectral parameters, spectral energy distributions, and associations are updated for all sources. Light curves are rebuilt for all sources with 1 yr intervals (not 2 month intervals). Among the 5064 original 4FGL sources, 16 were deleted, 112 are formally below the detection threshold over 12 yr (but are kept in the list), while 74 are newly associated, 10 have an improved association, and seven associations were withdrawn. Pulsars are split explicitly between young and millisecond pulsars. Pulsars and binaries newly detected in LAT sources, as well as more than 100 newly classified blazars, are reported. We add three extended sources and 1607 new point sources, mostly just above the detection threshold, among which eight are considered identified, and 699 have a plausible counterpart at other wavelengths. We discuss the degree-scale residuals to the global sky model and clusters of soft unassociated point sources close to the Galactic plane, which are possibly related to limitations of the interstellar emission model and missing extended sources.
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| 3. |
- Abdollahi, S., et al.
(författare)
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Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 933:2
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Tidskriftsartikel (refereegranskat)abstract
- Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum, with a low-energy break around 200 MeV, was detected in the gamma-ray spectra of four supernova remnants (SNRs), IC 443, W44, W49B, and W51C, with the Fermi Large Area Telescope. This detection provided direct evidence that cosmic-ray protons are (re-)accelerated in SNRs. Here, we present a comprehensive search for low-energy spectral breaks among 311 4FGL catalog sources located within 5° from the Galactic plane. Using 8 yr of data from the Fermi Large Area Telescope between 50 MeV and 1 GeV, we find and present the spectral characteristics of 56 sources with a spectral break confirmed by a thorough study of systematic uncertainty. Our population of sources includes 13 SNRs for which the proton–proton interaction is enhanced by the dense target material; the high-mass gamma-ray binary LS I+61 303; the colliding wind binary η Carinae; and the Cygnus star-forming region. This analysis better constrains the origin of the gamma-ray emission and enlarges our view to potential new cosmic-ray acceleration sites.
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| 4. |
- Agahi, Neda, et al.
(författare)
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Social integration and alcohol consumption among older people : A four-year follow-up of a Swedish national sample
- 2019
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Ingår i: Drug And Alcohol Dependence. - : Elsevier BV. - 0376-8716 .- 1879-0046. ; 196, s. 40-45
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Tidskriftsartikel (refereegranskat)abstract
- Background: Today’s older people drink more alcohol than earlier cohorts of older people. Social integration has been identified as an important factor for older people’s drinking, but the association is complex. This study investigates both high and low levels of social integration and their associations with longitudinal patterns of alcohol consumption among older women and men.Methods: Longitudinal nationally representative data of older Swedish women and men aged over 65 – the Swedish Level of Living Survey (LNU) and Swedish Panel Study of Living Conditions of the Oldest Old (SWEOLD) – from 2010/2011 and 2014 (n = 1048). Associations between social contacts and social activities at baseline and longitudinal patterns of drinking frequency were examined with multinomial logistic regression analyses. Results: Men reported drinking alcohol more often than women, but the most common drinking frequency among both women and men was to drink monthly or less. Drinking habits were generally stable over time. People with high levels of social activity at baseline were more likely to have a stable daily or weekly drinking frequency or increased drinking frequency over the four-year follow-up period, particularly women. People with low levels of social contacts and/or social activities were less likely to have a stable daily or weekly drinking frequency, compared to people in the low and stable drinking frequency group.Conclusions: Alcohol consumption is embedded in a social context, older people drink in social situations and social integration predicts continued drinking patterns.
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| 5. |
- Ahlgren, Katrin, et al.
(författare)
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Continuity and change : migrants’ experiences of adult language education in Sweden
- 2020
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Ingår i: European Journal for Research on the Education and Learning of Adults. - : Linkoping University Electronic Press. - 2000-7426 .- 2000-7426. ; 11:3, s. 399-414
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Tidskriftsartikel (refereegranskat)abstract
- This article aims to explore continuity and change in adult migrants’ experiences of Swedish for immigrants (SFI), a state-subsidised language programme for basic Swedish. The study has a longitudinal and comparative design, drawing on discourse analysis of qualitative interviews conducted with language learners in 2001/2002 and 2015/2016. This period was characterized by important societal shifts, defined by increased migration, growing tension between discourses on rights and obligations of adult migrants living in Sweden, and an intensified marketisation of the Swedish education system derived from neoliberal principles. The study describes how these changes affected SFI as well as the conceivable impact that restructuring the language programme had on the learners. Ultimately, the study highlights tensions between various state initiatives that impacted the language programme and the SFI participants’ experiences of being adult language learners.
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| 6. |
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| 7. |
- Ahlström Söderling, Ragnar
(författare)
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Regionala företags förutsättningar för internationell konkurrenskraft : utvärdering av en undersökningsmetod
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Kan man bedöma om företag med tillväxtpotential även har kompetens att ta tillvara den? Denna fundering ligger till grund för den studie som redovisas i den här avhandlingen. Syftet med studien är i första hand att utvärdera hur en ”Best Business Practice”- modell kan bidra till ökad förståelse, hos myndigheter och andra samhällsaktörer, för vilka befintliga företag i en region som kan ha förutsättningar att vara internationellt konkurrenskraftiga med avseende på de processutövanden och processresultat som föreligger i deras operativa verksamhet. Utvärderingen baseras på en kartläggning av tillverkande arbetsställen i Dalarnas län med minst 10 anställda som genomfördes 2002.Studien i Dalarna bekräftar undersökningsmodellens antagande om en relation mellan gott processutövande och bra processresultat. Analyser visar att företag med höga värden på såväl processutövande som processresultat (de Ledande företagen) har högre sannolikhet för att redovisa en hög och ökande marknadsandel, förbättrad produktivitet, ökande nettokassaflöde, god och förbättrad lönsamhet samt en högre avkastningsgrad än företag med låga värden på dessa parametrar (de Sladdande företagen). Studien indikerar även ett samband mellan tillväxt och processresultat då de flesta företagen med hög tillväxt redovisar höga värden på undersökningsmetodens indexet för processresultat samtidigt som de flesta företagen med negativ tillväxt har låga värden på detta index. De marknadsledande företagen i studien skiljer sig från övriga företag genom att oftare använda sig av benchmarking. I sina benchmarkingprocesser fokuserar de på ett bredare spann av jämförelsemått, jämför sig oftare med företag inom andra branscher såväl som andra länder samt lägger en större fokus på innovations- och verksamhetsmått.. De marknadsledande företagen är även mer innovativa, både vad gäller introduktion av nya produkter som av nya processer. Utvärderingen redovisar att undersökningsmetoden har en del tveksamheter men trots det ger möjlighet att skaffa en mängd information och kunskap om näringslivets status i en region. Den visar på vilka företag som har processer på plats för att kunna expandera och vilka som behöver ”se om sitt hus” för att ha möjlighet att fortsätta sin verksamhet.Det räcker dock inte med kunskap. Kunskapen behöver omsättas i handling. En fråga som avhandlingen leder fram till är vilka som kan och vill agera på denna typ av information?
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| 8. |
- Ahmadi, Fereshteh, 1958-, et al.
(författare)
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Mode, senmodernitet, identitet
- 2012
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Ingår i: Sociologisk forskning. - Uppsala : Sveriges sociologförbund. - 0038-0342 .- 2002-066X. ; 49:2, s. 129-144
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Tidskriftsartikel (refereegranskat)abstract
- A common discussion in the late modern era is the role that tradition plays concerning individualidentity. This forms a background to our article that focuses on consumer culture andone of its characteristics – fashion. To what extent does consumer culture and fashion contributeto the undermining of traditions, and how does this affect individual identity? Wediscuss two interpretations of consumption in shaping individual identity: the first interpretationmaintains that by consumption individuals obtain an increasing freedom of choicemakingthem free from the power of tradition, and thereby responsible for their lifestylechoices. According to the second interpretation, the free choice is illusory. This choiceisstrongly influenced by factors such as social class and producers’ manipulative skills. Contrastingclassical social theorists with contemporary fashion theory we argue that late modernfashion is characterized by quick changes and pluralism that often stand in contrast totradition. We further discuss the increased importance of taste and new diffusion patternsas signs of a more individualized fashion, and discuss neo-tribalism as a post-traditional kindof community.
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| 9. |
- Ahrne, Göran
(författare)
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Upptäckten av det globala
- 2007
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Ingår i: Sociologisk forskning. - : Sveriges sociologförbund. - 0038-0342 .- 2002-066X. ; 44:1, s. 69-76
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Ajello, M., et al.
(författare)
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A gamma-ray pulsar timing array constrains the nanohertz gravitational wave background
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 376:6592, s. 521-523
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Tidskriftsartikel (refereegranskat)abstract
- After large galaxies merge, their central supermassive black holes are expected to form binary systems. Their orbital motion should generate a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background use pulsar timing arrays, which perform long-term monitoring of millisecond pulsars at radio wavelengths. We used 12.5 years of Fermi Large Area Telescope data to form a gamma-ray pulsar timing array. Results from 35 bright gamma-ray pulsars place a 95% credible limit on the GWB characteristic strain of 1.0 x 10(-14) at a frequency of 1 year(-1). The sensitivity is expected to scale with t(obs), the observing time span, as t(obs)(-13/6). This direct measurement provides an independent probe of the GWB while offering a check on radio noise models.
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