| 1. |
- Hashimoto, Takuya, et al.
(författare)
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The onset of star formation 250 million years after the Big Bang
- 2018
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 557:7705, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang(1-3). The abundance of star-forming galaxies is known to decline(4,5) from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. Here we report spectroscopic observations of MACS1149-JD1(6), a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age. We detect an emission line of doubly ionized oxygen at a redshift of 9.1096 +/- 0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. Our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes.
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| 2. |
- Rydberg, Claes-Erik, et al.
(författare)
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A multiply imaged z similar to 6.3 Lyman a emitter candidate behind Abell 2261
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 467:1, s. 768-777
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Tidskriftsartikel (refereegranskat)abstract
- While the Lyman alpha (Ly alpha) emission line serves as an important tool in the study of galaxies at z less than or similar to 6, finding Ly a emitters (LAE) at significantly higher redshifts has been more challenging, probably because of the increasing neutrality of the intergalactic medium above z similar to 6. Galaxies with extremely high rest-frame Ly alpha equivalent widths, EW(Ly alpha) greater than or similar to 150 A degrees, at z > 6, are good candidates for Ly alpha follow-up observations, and can stand out in multiband imaging surveys because of their unusual colours. We have conducted a photometric search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH), and report here the identification of three likely gravitationally lensed images of a single LAE candidate at z-6.3, behind the galaxy cluster Abell 2261 (z=0.225). In the process, we also measured with Keck/Multi-Object Spectrometer For Infra-Red Exploration the first spectroscopic redshift of a multiply imaged galaxy behind Abell 2261, at z=3.337. This allows us to calibrate the lensing model, which, in turn, is used to study the properties of the candidate LAE. Population III galaxy spectral energy distribution model fits to the CLASH broad-band photometry of the possible LAE provide a slightly better fit than Population I/II models. The best-fitting model suggests intrinsic EW(Ly alpha) approximate to 160 A degrees after absorption in the interstellar and intergalactic medium. Future spectroscopic observations will examine this prediction as well as shed more light on the morphology of this object, which indicates that it may be a merger of two smaller galaxies.
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| 3. |
- Rydberg, Claes-Erik, 1972-, et al.
(författare)
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A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift
- 2015
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 804:1
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Tidskriftsartikel (refereegranskat)abstract
- Population III galaxies are predicted to exist at high redshifts and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a foreground galaxy cluster. Population III galaxies that exhibit strong Lyα emission should furthermore be identifiable from broadband photometry because of their unusual colors. Here, we report on a search for such objects at z > 6 in the imaging data from the Cluster Lensing And Supernova survey with Hubble (CLASH), covering 25 galaxy clusters in 16 filters. Our selection algorithm returns five singly-imaged candidates with Lyα-like color signatures, for which ground-based spectroscopy with current 8-10 m class telescopes should be able to test the predicted strength of the Lyα line. None of these five objects have been included in previous CLASH compilations of high-redshift galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, we find that only two of these candidates are significantly better fitted by Population III models than by more mundane, low-metallicity stellar populations.
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| 4. |
- Rydberg, Claes-Erik, 1972-, et al.
(författare)
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A search for Population III galaxies in CLASH. II. A multiply-imaged candidate at z ~ 7.8 behind Abell 2261
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- While the Lyα emission line has served as an important tool in the study of galaxies at z < 6.5, Lyα emitters (LAE) have proved to be elusive at higher redshifts. If galaxies exhibiting high Lyα equivalent widths exist at z > 6.5, such rare objects may potentially stand out in multiband imaging surveys because of their unusual colors. We have conducted a search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH) survey, and here report on the discovery of three gravitationally lensed images of a single LAE candidate behind the Abell 2261 cluster. Model fits to the CLASH broadband photometry suggests very strong Lyα emission (rest-frame Lyα equivalent width EW(Lyα) > 200 Å, prior to any IGM correction) at a redshift of z ≈ 7.8.
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| 5. |
- Rydberg, Claes-Erik, 1972-, et al.
(författare)
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Detection of isolated Population III stars with the James Webb Space Telescope
- 2013
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 429:4, s. 3658-3664
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Tidskriftsartikel (refereegranskat)abstract
- The first Population III stars are predicted to form in minihaloes at z approximate to 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated Population III star or a small cluster of Population III stars down to z = 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed Population III stars are beyond the reach of JWST, and that even lensed Population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one 60 M-circle dot Population III star when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of Population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models.
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| 6. |
- Rydberg, Claes-Erik
(författare)
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Gravitational lensing as a probe of the first stars and galaxies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the potential for detection and identification of primordial stars, galaxies, and supernovae at high redshift.Simulations indicate that the first Population III stars should appear in minihalos of mass M = 105-106 Msol at z ≈ 10-30. To assess the detectability of these objects, theoretical models of these stars and their surrounding HII regions are used. We assess the plausibility of detection with the upcoming James Webb Space Telescope (JWST), using the gravitational lensing provided by the galaxy cluster MACSJ0717.5+3745. The conclusion is that the detection of these objects is highly improbable but not impossible.To investigate the prospects of detecting and identifying the first galaxies, the spectral synthesis code Yggdrasil is introduced. According to this code, JWST may be able to detect Population III galaxies with stellar masses as low as 105 Msol at z ≈ 10 in unlensed fields. We find that, over limited redshift intervals, it could be possible to use Hubble Space Telescope (HST) and/or JWST broadband color criteria to single out Population III galaxy candidates.The prospects of detecting gravitationally lensed Population III galaxies with JWST and HST is investigated. A lower limit to detect ≈1 Population III galaxy of ε ≈ 10-2 (HST/CLASH) and ε ≈ 10-3 (JWST using MACS J0717.5+3745 as lens) is derived, where ε is the baryon fraction converted to Population III stars in a host halo.By fitting HST/CLASH data to Yggdrasil and comparison grids, two Population III galaxy candidates are discovered. These two candidates are the first Population III galaxy candidates discovered at z > 6.5. A highly-magnified and doubly lensed extremely high-redshift (z ≈ 7.8) object is also identified.Finally the prospects of detecting core-collapse (CC) supernovae (SN) from the first galaxies at z ≈ 5-12 are investigated. The prediction is that no primordial SN is detectable, but 2-3 CC SN should be discovered by the HST/CLASH.
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| 7. |
- Schauer, Anna T. P., et al.
(författare)
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Lyman-Werner escape fractions from the first galaxies
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 467:2, s. 2288-2300
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Tidskriftsartikel (refereegranskat)abstract
- Direct collapse black holes forming in pristine, atomically cooling haloes at z approximate to 10-20 may act as the seeds of supermassive black holes (BHs) at high redshifts. In order to create a massive BH seed, the host halo needs to be prevented from forming stars. H-2 therefore needs to be irradiated by a large flux of Lyman-Werner (LW) UV photons in order to suppress H-2 cooling. A key uncertainty in this scenario is the escape fraction of LW radiation from first galaxies, which is the dominant source of UV photons at this epoch. To better constrain this escape fraction, we have performed radiation-hydrodynamical simulations of the growth of H II regions and their associated photodissociation regions in the first galaxies using the ZEUS-MP code. We find that the LWescape fraction crucially depends on the propagation of the ionization front (I-front). For an R-type I-front overrunning the halo, the LW escape fraction is always larger than 95 per cent. If the halo recombines later from the outside-in, due to a softened and weakened spectrum, the LW escape fraction in the rest frame of the halo (the near-field) drops to zero. A detailed and careful analysis is required to analyse slowly moving, D-type I-fronts, where the escape fraction depends on the microphysics and can be as small as 3 per cent in the near-field and 61 per cent in the far-field or as large as 100 per cent in both the near-field and the far-field.
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| 8. |
- Zackrisson, Erik, et al.
(författare)
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Bubble mapping with the Square Kilometre Array - I. Detecting galaxies with Euclid, JWST, WFIRST, and ELT within ionized bubbles in the intergalactic medium at z > 6
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 493:1, s. 855-870
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Tidskriftsartikel (refereegranskat)abstract
- The Square Kilometre Array (SKA) is expected to provide the first tomographic observations of the neutral intergalactic medium at redshifts z > 6 and pinpoint the locations of individual ionized bubbles during early stages of cosmic reionization. In scenarios where star-forming galaxies provide most of the ionizing photons required for cosmic reionization, one expects the first ionized bubbles to be centred on overdensities of such galaxies. Here, we model the properties of galaxy populations within isolated, ionized bubbles that SKA-1 should be able to resolve at z approximate to 7-10, and explore the prospects for galaxy counts within such structures with various upcoming near-infrared telescopes. We find that, for the bubbles that are within reach of SKA-1 tomography, the bubble volume is closely tied to the number of ionizing photons that have escaped from the galaxies within. In the case of galaxy-dominated reionization, galaxies are expected to turn up above the spectroscopic detection threshold of JWST and ELT in even the smallest resolvable bubbles at z <= 10. The prospects of detecting galaxies within these structures in purely photometric surveys with Euclid, WFIRST, JWST, or ELT are also discussed. While spectroscopy is preferable towards the end of reionization to provide a robust sample of bubble members, multiband imaging may be a competitive option for bubbles at z approximate to 10, due to the very small number of line-of-sight interlopers expected at these redshifts.
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| 9. |
- Zackrisson, Erik, et al.
(författare)
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Detecting gravitationally lensed Population III galaxies with the Hubble Space Telescope and the James Webb Space Telescope
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 427:3, s. 2212-2223
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Tidskriftsartikel (refereegranskat)abstract
- Small galaxies consisting entirely of Population III (pop III) stars may form at high redshifts, and could constitute one of the best probes of such stars. Here, we explore the prospects of detecting gravitationally lensed pop III galaxies behind the galaxy cluster J0717.5+3745 (J0717) with both the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). By projecting simulated catalogues of pop III galaxies at z similar to 715 through the J0717 magnification maps, we estimate the lensed number counts as a function of flux detection threshold. We find that the ongoing HST survey Cluster Lensing And Supernova survey with Hubble (CLASH), targeting a total of 25 galaxy clusters including J0717, potentially could detect a small number of pop III galaxies if similar to 1 per cent of the baryons in these systems have been converted into pop III stars. Using JWST exposures of J0717, this limit can be pushed to similar to 0.1 per cent of the baryons. Ultradeep JWST observations of unlensed fields are predicted to do somewhat worse, but will be able to probe pop III galaxies with luminosities intermediate between those detectable in HST/CLASH and in JWST observations of J0717. We also explain how current measurements of the galaxy luminosity function at z = 710 can be used to constrain pop III galaxy models with very high star formation efficiencies (similar to 10 per cent of the baryons converted into pop III stars).
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| 10. |
- Zackrisson, Erik, et al.
(författare)
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Finding high-redshift dark stars with the James Webb Space Telescope
- 2010
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Ingår i: Astrophysical Journal. - : The American Astronomical Society. - 0004-637X .- 1538-4357. ; 717:1, s. 257-267
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Tidskriftsartikel (refereegranskat)abstract
- The first stars in the history of the universe are likely to form in the dense central regions of similar to 10(5)-10(6) M-circle dot cold dark matter halos at z approximate to 10-50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive, and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 10(3) M-circle dot are intrinsically too faint to be detected by JWST at z > 6. However, by exploiting foreground galaxy clusters as gravitational telescopes do, certain varieties of cool (T-eff <= 30,000 K) dark stars should be within reach at redshifts up to z approximate to 10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least similar to 1% of the total stellar mass in such objects.
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| 11. |
- Zackrisson, Erik, et al.
(författare)
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Hunting for dark halo substructure using submilliarcsecond-scale observations of macrolensed radio jets
- 2013
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 431:3, s. 2172-2183
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Tidskriftsartikel (refereegranskat)abstract
- Dark halo substructure may reveal itself through secondary, small-scale gravitational lensing effects on light sources that are macrolensed by a foreground galaxy. Here, we explore the prospects of using Very Long Baseline Interferometry (VLBI) observations of multiply-imaged quasar jets to search for submilliarcsecond-scale image distortions produced by various forms of dark substructures in the 10(3)-10(8) M-circle dot mass range. We present lensing simulations relevant for the angular resolutions attainable with the existing European VLBI Network, the global VLBI array and an upcoming observing mode in which the Atacama Large Millimeter Array (ALMA) is connected to the global VLBI array. While observations of this type would not be sensitive to standard cold dark matter subhaloes, they can be used to detect the more compact forms of halo substructure predicted in alternative structure formation scenarios. By mapping approximately five strongly lensed systems, it should be possible to detect or robustly rule out primordial black holes in the 10(3)-10(6) M-circle dot mass range if they constitute greater than or similar to 1 per cent of the dark matter in these lenses. Ultracompact minihaloes are harder to detect using this technique, but 10(6)-10(8) M-circle dot ultracompact minihaloes could in principle be detected if they constitute greater than or similar to 10 per cent of the dark matter.
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| 12. |
- Zackrisson, Erik, et al.
(författare)
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Observational constraints on supermassive dark stars
- 2010
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1745-3925 .- 1365-2966. ; 407:1, s. L74-L78
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Tidskriftsartikel (refereegranskat)abstract
- Some of the first stars could be cooler and more massive than standard stellar models would suggest, due to the effects of dark matter annihilation in their cores. It has recently been argued that such objects may attain masses in the 104-107Msolar range and that such supermassive dark stars should be within reach of the upcoming James Webb Space Telescope. Notwithstanding theoretical difficulties with this proposal, we argue here that some of these objects should also be readily detectable with both the Hubble Space Telescope and ground-based 8-10 m class telescopes. Existing survey data already place strong constraints on 107Msolar dark stars at z ~ 10. We show that such objects must be exceedingly rare or short lived to have avoided detection.
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| 13. |
- Zackrisson, Erik, et al.
(författare)
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The Hubble Space Telescope colours of high-redshift Population III galaxies with strong Lya emission
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3925. ; 418:1, s. L104-L108
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Tidskriftsartikel (refereegranskat)abstract
- Population III (pop III) galaxies, made partly or exclusively of metal-free stars, are predicted to exist at high redshifts and may produce very strong Lya emission. A substantial fraction of these Lya photons are likely absorbed in the intergalactic medium at z > 6, but recent simulations suggest that significant Lya emission may be detectable up to z similar to 8.5, i.e. well into the reionization epoch. Here, we argue that high-redshift pop III galaxies with strong Lya emission can be identified in Hubble Space Telescope imaging data because of their unusual colours. We quantify this effect in some of the filters used in Y-band dropout searches for galaxies at z approximate to 8 and find that pop III galaxies with high Lya fluxes may exhibit much bluer J-H colours at z approximate to 8-10 than any normal type of galaxy at these redshifts. This colour signature can arise even if pop III stars account for as little as similar to 10(-3) to 10(-2) of the stellar mass in these galaxies. Some of the anomalously blue objects reported in current Y-band dropout samples do in fact meet the colour criteria for Lya-emitting pop III galaxies.
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| 14. |
- Zackrisson, Erik, et al.
(författare)
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THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 740:1, s. 13-
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Tidskriftsartikel (refereegranskat)abstract
- The James Webb Space Telescope (JWST) is expected to revolutionize our understanding of the high-redshift universe, and may be able to test the prediction that the first, chemically pristine (Population III) stars are formed with very high characteristic masses. Since isolated Population III stars are likely to be beyond the reach of JWST, small Population III galaxies may offer the best prospects of directly probing the properties of metal-free stars. Here, we present Yggdrasil, a new spectral synthesis code geared toward the first galaxies. Using this model, we explore the JWST imaging detection limits for Population III galaxies and investigate to what extent such objects may be identified based on their JWST colors. We predict that JWST should be able to detect Population III galaxies with stellar population masses as low as similar to 10(5) M(circle dot) at z approximate to 10 in ultra deep exposures. Over limited redshift intervals, it may also be possible to use color criteria to select Population III galaxy candidates for follow-up spectroscopy. The colors of young Population III galaxies dominated by direct starlight can be used to probe the stellar initial mass function (IMF), but this requires almost complete leakage of ionizing photons into the intergalactic medium. The colors of objects dominated by nebular emission show no corresponding IMF sensitivity. We also note that a clean selection of Population III galaxies at z approximate to 7-8 can be achieved by adding two JWST/MIRI filters to the JWST/NIRCam filter sets usually discussed in the context of JWST ultra deep fields.
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| 15. |
- Ambrosi, Aurelie, et al.
(författare)
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Development of heart block in children of SSA/SSB-autoantibody-positive women is associated with maternal age and displays a season-of-birth pattern
- 2012
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Ingår i: Annals of the Rheumatic Diseases. - London : BMJ Publishing Group. - 0003-4967 .- 1468-2060. ; 71:3, s. 334-340
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Tidskriftsartikel (refereegranskat)abstract
- Objective Congenital heart block may develop in the fetuses of Ro/SSA-positive and La/SSB-positive mothers. Recurrence rates of only 10-20% despite persisting maternal antibodies indicate that additional factors are critical for the establishment of heart block. The authors investigated the influence of other maternal and fetal factors on heart block development in a Swedish population-based cohort. less thanbrgreater than less thanbrgreater thanMethods The influence of fetal gender, maternal age, parity and time of birth on heart block development was analysed in 145 families, including Ro/La-positive (n=190) and Ro/La-negative (n=165) pregnancies. less thanbrgreater than less thanbrgreater thanResults There was a recurrence rate of 12.1% in Ro/La-positive women, and no recurrence in Ro/La-negative women. Fetal gender and parity did not influence the development of heart block in either group. Maternal age in Ro/La-positive pregnancies with a child affected by heart block was, however, significantly higher than in pregnancies resulting in babies without heart block (pandlt;0.05). Seasonal timing of pregnancy influenced the outcome. Gestational susceptibility weeks 18-24 occurring during January-March correlated with a higher proportion of children with heart block and lower vitamin D levels during the same period in a representative sample of Swedish women and a corresponding higher proportion of children with heart block born in the summer (pandlt;0.02). Maternal age or seasonal timing of pregnancy did not affect the outcome in Ro/La-negative pregnancies. less thanbrgreater than less thanbrgreater thanConclusion This study identifies maternal age and seasonal timing of pregnancy as novel risk factors for heart block development in children of Ro/La-positive women. These observations may be useful for counselling when pregnancy is considered.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Andersson, Lars, 1973-
(författare)
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Multi-robot Information Fusion : Considering spatial uncertainty models
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work presented in this thesis covers the topic of deployment for mobile robot teams. By connecting robots in teams they can perform a better job than each individual is capable of. It also gives redundancy, increases robustness, provides scalability, and increases efficiency. Multi-robot Information Fusion also results in a broader perspective for decision making. This thesis focuses on methods for estimating formation and trajectories and how these can be used for deployment of a robot team. The problems covered discuss what impact trajectories and formation have on the total uncertainty when exploring unknown areas. The deployment problem is approached using a centralized Kalman filter, for investigation of how team formation affects error propagation. Trajectory estimation is done using a smoother, where all information is used not only to estimate the trajectory of each robot, but also to align trajectories from different robots. Both simulation and experimental results are presented in the appended papers. It is shown that sensor placements can substantially affect uncertainty during deployment. When deploying a robot team the formation can be used as a tool for balancing error propagation among the robot states. A robust algorithm for associating rendezvous observations to align robot trajectories is also presented. Trajectory alignment is used as an efficient and cost-effective method for joining mapping information within robot teams. When working with robot teams, sensor placement and formation should be considered to obtain the maximum from the system. It is also of great value to mix robots with different characteristics since it is shown that using sensor fusion the robots can inherit each other’s characteristics if sensors are used correctly. Information sharing requires modularity and general models, which consumecomputational resources. Over time computer resources will become cheaper, allowing for distribution, and each robot will become more self-contained. Together with increased wireless bandwidth this will enable larger numbers of robots to cooperate.
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| 20. |
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| 21. |
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| 22. |
- Asplund, Annika, 1979, et al.
(författare)
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Hypoxic regulation of secreted proteoglycans in macrophages.
- 2010
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Ingår i: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 20:1, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- Macrophages are prominent in hypoxic areas of atherosclerotic lesions, and their secreted proteoglycans (PG), such as versican, can modulate the retention of lipoproteins and the activity of enzymes, cytokines, and growth factors involved in atherogenesis. In this study, we report the effects of hypoxia on PG secreted by human monocyte-derived macrophages (HMDM) and the potential regulation by the transcription factor hypoxia-inducible factor (HIF-1alpha and HIF-2alpha). We found that versican co-localized with HIF-1alpha in macrophage-rich areas in human advanced atherosclerotic lesions. Versican and perlecan mRNA expression increased after exposure to 0.5% O(2) (hypoxia) compared with 21% O(2) (control cells). Using precursors to GAG biosynthesis combined with immunoabsorption with a versican antibody an increased versican synthesis was detected at hypoxia. Furthermore, siRNA knockdown of HIF-1alpha and HIF-2alpha in THP-1 cells showed that the hypoxic induction of versican and perlecan mRNA expression involved HIF signaling. Versican expression was co-regulated by HIF-1alpha and HIF-2alpha but expression of perlecan was influenced only by HIF-1alpha and not by HIF-2alpha knockdown. The results show that oxygen concentration is an important modulator of PG expression in macrophages. This may be a novel component of the complex role of macrophages in atherosclerosis.
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| 23. |
- Aziz, Imran, et al.
(författare)
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60 GHz compact broadband antenna arrays with wide-angle beam steering
- 2019
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Ingår i: The Journal of Engineering. - : INST ENGINEERING TECHNOLOGY-IET. - 2051-3305. ; :8, s. 5407-5414
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Tidskriftsartikel (refereegranskat)abstract
- Highly integrated multilayered printed circuit board-based patch antenna arrays are proposed in this study for 60 GHz wireless communications. Electromagnetic coupling between two stacked patches is used to achieve the broadband performance. Different structures of single element antennas, two-element antenna arrays and four-element antenna arrays are presented. The two compact four-element antenna arrays show < -10 dB impedance bandwidth of 13 and 14.6% with 12 dBi peak gain. The arrays have the 3 dB gain bandwidth of 9 and 13%. A single column, four-element sub-array is used to design 4 x 16 antenna array. This array delivers 20.8 dBi peak gain with 13% impedance and gain bandwidth. Furthermore, a two-element series fed array is used to realise a 2 x 16 phased antenna array. This array is fed through a 16 x channel radio frequency IC to achieve the beam steering in +/- 50 degrees range.
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| 24. |
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| 25. |
- Bindler, Richard, 1963-, et al.
(författare)
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Reshaping the landscape: mining, metallurgy and a millennium of environmental changes in south-central Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Before the recognition of emerging environmental issues during the 20th century such as acid rain, mercury pollution, climate change and biodiversity loss, human activities had already significantly altered landscapes around the globe. As elsewhere in Europe, the introduction of agriculture into Sweden during the Bronze and Iron Ages led to changes in forest cover, especially in southern areas, but also more limited impacts in central and northern Sweden along river valleys and coastal areas. In central Sweden the rise and rapid spread of ore mining and metallurgy from the 12th and especially 13th century initiated a widespread reshaping of the landscape named after its mining heritage –Bergslagen (mining laws). This mineral rich 89,000 km2 region encompasses ~5000 metallurgical sites (furnaces, smelters, foundries, forges) and ~10000 mines registered in the Swedish National Antiquities Board’s database.Analyses of >30 lake-sediment records using a combination of geochemical, diatom and pollen analyses, in combination with archaeological and historical records and toponyms, add important details to the early, poorly documented history of mining/metallurgy as well as provide insights into some of the environmental impacts across this large landscape. These impacts included damming of lakes and regulation of watercourses for waterpower, increase in erosion, emission of metals to surface waters and the atmosphere (and leaching from slag piles), decrease in forest cover and changes in water quality. The discontinuous appearance of pollen from cultivated plants (cereals) indicates some limited settlement before the 12th century, but the regular occurrence thereafter of cereal pollen together with a sharp increase in charcoal particles and geochemical evidence of mining/metallurgical activities, indicates mining/metallurgy was a driving force for settlement. Decline in forest cover was gradual from the 13th century, but was more significant from the late 16th century when iron and copper production increased exponentially. The increased demand for charcoal and increased agriculture, including an expansion of summer forest farms, contributed to a reduction in inferred forest cover to 40–80% – as compared to pre-anthropogenic (≤2000 BP) values of 84–95%. From the 16th century charcoal became the limiting resource within Bergslagen and metallurgy expanded to regions adjoining Bergslagen, contributing to a more widespread decline in forest cover also beyond the Bergslagen landscape.In association with the increase in land-use activities and resulting changes in vegetation cover, there was a decline (20–50%) in spectrally inferred lake-water total organic carbon, which we hypothesize resulted from a decreased pool of labile soil carbon. In some lakes closely connected with blast furnaces, where the peasant-miners also lived and farmed, there was an increase in diatom-inferred lake-water pH – as observed previously in SW Sweden in association with Iron Age land use. Only in a suite of lakes in close proximity to the smelting of copper sulfide ores in the surroundings of Falun was there evidence for pre-20th century acidification.While current rates of environmental change may be unprecedented, they build on an already modified landscape. Because pre-industrial conditions, i.e., pre-19th century, are often used as a reference level the scale of current changes may underestimate the full extent of ecosystem and environmental impacts.
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| 26. |
- Birgander, Mats, et al.
(författare)
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Adrenergic and cardiac dysfunction in primary hyperparathyroidism.
- 2012
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Ingår i: Clinical Endocrinology. - : Wiley. - 1365-2265 .- 0300-0664. ; 76, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Primary hyperparathyroidism (PHPT) is associated with cardiovascular morbidity and premature death but the underlying mechanisms are incompletely understood. The aim of this study was to investigate if adrenergic dysfunction may be a contributing factor. Patients and methods: Forty-nine patients with mild PHPT (serum calcium 2.7 ± 0.1 mmol/L) and 48 control subjects, matched for age and sex, were examined; patients within 1 month before parathyroidectomy (PTX) and 6 months postoperatively; control subjects at inclusion. Heart rate variability (HRV) was analyzed in 24-hour electrocardiograms, and plasma concentrations of epinephrine and norepinephrine were measured at rest and immediately after standardized physical tests. Results: At baseline, the patients showed, compared to the controls, reduced stress-related increase of circulating epinephrine (P < 0.05) and norepinephrine (P < 0.05). No significant change was observed 6 months after PTX. At baseline, there were no significant differences between patients and controls in HRV or heart rate but 6 months after curative PTX, the patients showed significantly reduced HRV in both frequency and time domain, and their maximum and average heart rate had decreased (P = 0.011 and P = 0.018, respectively). The patients with the highest preoperative levels of circulating parathyroid hormone showed the greatest changes in heart rate and HRV postoperatively. Conclusions: This study demonstrates a previously unknown impairment of catecholamine response to physical stress in PHPT along with changes of HRV, also indicating adrenergic dysfunction. These factors should be considered in the ongoing controversy regarding the management of patients with mild "asymptomatic" PHPT.
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| 27. |
- Birgander, Mats, et al.
(författare)
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Cardiac Structure and Function Before and After Parathyroidectomy in Patients With Asymptomatic Primary Hyperparathyroidism
- 2009
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Ingår i: The Endocrinologist. - 1539-9192. ; 19:4, s. 154-158
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Tidskriftsartikel (refereegranskat)abstract
- Background: Primary hyperparathyroidism (PHPT) is associated with cardiac disease and increased risk of all-cause and cardiovascular mortality. We investigated cardiac structural and functional parameters before and after successful parathyroidectomy in asymptomatic PHPT patients. Methods and Results: Forty-nine PHPT patients (age: 62.9 +/- 11 years, 5 men) and 48 healthy control subjects, matched for age, sex and smoking status were enrolled in the study. PHPT patients were examined preoperatively and 6 and 12 months postoperatively. Structural and functional cardiac parameters were assessed by transthoracic echocardiography. One year after parathyroidectomy left ventricular (LV) mass, left atrial size, LV enddiastolic and endsystolic diameters, LV posterior wall and interventricular septum diameter, and right ventricular enddiastolic diameter were all increased in PHPT patients, although not significantly. As an indication of worsened LV diastolic function, the heart rate adjusted Doppler-derived deceleration time of the transmittal E-wave increased among PHPT patients (276 +/- 82-303 +/- 54 milliseconds, P = 0.004). There was also deterioration of LV ejection fraction (from 62.7 +/- 7 to 59.9 +/- 7.8%, P = 0.868) and mean atrioventricular plane displacement (from 13.2 +/- 2 to 12.6 +/- 2 mm, P = 0.029). Conclusion: There were no significant differences in heart function between hyperparathyroid and control subjects, and 6 months after parathyroidectomy, there was no change in heart function in hyperparathyroid subjects.
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| 28. |
- Birgander, Mats, et al.
(författare)
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Postexercise Cardiac Performance Among Patients With Mild Primary Hyperparathyroidism
- 2009
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Ingår i: The Endocrinologist. - 1539-9192. ; 19:6, s. 263-266
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Tidskriftsartikel (refereegranskat)abstract
- Primary hyperparathyroidism (pHPT) is associated with cardiac disease. This prospective study was designed to investigate changes in cardiac function before and after parathyroidectomy. Resting and post exercise cardiac function was compared with matched control subjects. Fifty patients (mean age 62.9 +/- 11 years, 45 women) and 50 healthy control subjects, matched for age and sex were studied. Resting and postmaximum exercise echocardiography/Doppler examination were performed at baseline and 6 months after parathyroidectomy. pHPT patients were tested at baseline and 6 months postoperatively. Control subjects were tested only at baseline. Patients were divided into 4 subgroups based on median preoperative levels of PTH and calcium (Ca): high (up arrow) PTI4/ up arrow Ca, up arrow PTH/low (down arrow) Ca, up arrow Ca/ down arrow PTH, and down arrow PTH/ down arrow Ca. No significant difference between pHPT patients and control subjects regarding post exercise systolic function were detected, There was a tendency of lowed E/A among pHPT patients which was significant in subgroup down arrow PTH/ down arrow Ca (1.07 +/- 0.3). Subgroup up arrow PTH/ up arrow Ca showed a lower S/D compared with control subjects at baseline (1.28 +/- 0.3 vs. 1.48 +/- 0.3, P = 0.029). No significant changes regarding post exercise echocardiographic parameters reflecting cardiac function were detected 6 months after parathyriodectomy. Patients with asymptomatic pHPT showed a tendency of elevated filling pressures and signs of impaired diastolic function during exercise.
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| 29. |
- Birgander, Mats, et al.
(författare)
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Relationship Between Mild Primary Hyperparathyroidism and Left Ventricular Structure and Diastolic Performance
- 2009
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Ingår i: The Endocrinologist. - 1539-9192. ; 19:4, s. 187-191
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Forskningsöversikt (refereegranskat)abstract
- Aim: This study aims to investigate cardiac structure and function in patients with asymptomatic primary hyperparathyroidism (pHPT) and if there is any relation to severity regarding serum levels of calcium (Ca) and parathyroid hormone. Methods and Results: We consecutively included 50 patients (mean age 62.9 +/- 11 years, 45 women) with clinically diagnosed pHPT. We prospectively recruited 50 healthy control subjects, matched for age and sex. Standard transthoracic echocardiographic examination was performed using the 4 standard views and structural parameters as well as left ventricular (LV) systolic and diastolic function was determined. Mean LV ejection fraction and atrioventricular plane displacement were on average normal and did not differ between patients and controls. However, pHPT patients had significantly greater LV mass (148 +/- 37 vs. 127 +/- 29 g, P = 0.002), LV end diastolic area (81 +/- 20 vs. 68 +/- 18 cm(2), p = 0.003), LV posterior wall diameter (8.9 +/- 1 vs. 8.1 +/- 1 min, P = 0.006), and LA size (21 +/- 3 vs. 19 +/- 2 mm, P < 0.001). A moderate to severe LV diastolic filling impairment was present in substantially more pHPT patients, compared with control subjects (36% vs. 4%, P < 0:001). Conclusion: Patients with asymptomatic pHPT showed LV structural changes and impaired LV diastolic function.
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| 30. |
- Brand, Björn, et al.
(författare)
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Prognostication and risk stratification by assessment of left atrioventricular plane displacement in patients with myocardial infarction.
- 2002
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Ingår i: International Journal of Cardiology. - 0167-5273. ; 83:1, s. 35-41
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Mean left atrioventricular plane displacement is strongly related to prognosis in patients with heart failure. We aimed to examine its value for prognostication and risk stratification in patients hospitalised for acute myocardial infarction. METHODS AND RESULTS: Left atrioventricular plane displacement was assessed by echocardiography in 271 consecutive patients with acute myocardial infarction. Mean prospective follow-up was 628 days. Atrioventricular plane displacement was readily assessed in all patients and was significantly lower in patients who died (n=41, 15.1%) compared to the survivors: 8.2(5.6) v. 10.0(5.5) mm, P<0.0001. Overall mortality was 31.3% in the lowest quartile with regard to atrioventricular plane displacement (<8.00 mm) and 10.1% in the combined upper three quartiles. Thus, the hazard ratio for an atrioventricular plane displacement <8.0 mm compared to 8 mm or more was 3.1, P=0.0001. The combined mortality/heart failure hospitalisation incidence was 43.8% in the lowest and 14.6% in the combined upper three quartiles: Risk ratio 3.0, P<0.0001. In multivariate analysis, including age and history of atrial fibrillation, left atrioventricular plane displacement was an independent prognostic marker. CONCLUSION: In post-myocardial infarction patients, echocardiographic assessment of atrioventricular plane displacement showed a strong, independent prognostic value. Determination of left atrioventricular plane displacement can be readily performed in virtually all patients, and may in clinical practice facilitate identification of high-risk patients.
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| 31. |
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| 32. |
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| 33. |
- Cerne, Olof, et al.
(författare)
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Rena Turen - Utvärdering av miljöanpassade bränslen i fritidsbåtar
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fritidsbåtars avgasutsläpp till vatten och luft har undersökts. Tre inombords dieselmotorer och en 2-takts utombordsmotor har testats med standardbränslen och miljöanpassade bränslen. För dieselmotorerna användes standarddiesel, syntetisk diesel (GTL), rapsmetylester (RME), jetbränsle samt olika blandningar av diesel och RME. 2-taktsmotorn testades med standardbensin, alkylatbensin samt etanol (E85). För testerna med etanol krävdes en konvertering av motorn. Ekotoxikologiska tester har gjorts på kylvatten från dieselmotorer och på vatten som bubblats med avgaser från utombordsmotor. GTL gav något lägre utsläpp till luft av partiklar, kolväten, kolmonoxid och kväveoxider än vad standarddiesel gav. RME gav betydligt lägre halt partiklar och kolväten men något mer kväveoxider. Kylvatten från en inombords dieselmotor var giftigt mot sebrafiskar och kräftdjur. kylvatten. GTL och RME gav ett kylvatten som var betydligt mindre giftigt mot sebrafiskar än vad standarddiesel gav. PAH-utsläppen till vatten från dieselmotorerna var 10-20 mg per liter diesel. Utsläppen från de traditionella 2-takts utombordarna dominerar tydligt utsläppsmängderna. Standardbensin gav höga halter av miljö- och hälsofarliga ämnen, bland annat bensen, PAHer och formaldehyd. En liter bensin gav cirka 2,3 g PAH. Alkylatbensin och etanolbränslet E85 gav betydligt mindre utsläpp. Sveriges fritidsbåtar släpper uppskattningsvis ut 75 ton PAH per år. Avgasvatten från utombordare var giftigt för bakterier, alger och kräftdjur. Standardbensin var giftigast för bakterier och kräftdjur. Alkylatbensin var mindre giftig mot bakterier och kräftdjur. För alger var skillnaden liten mellan standardbensin, alkylatbensin och E85. Merparten av fritidsbåtarnas förbrukning av bensin och diesel sker i kustvatten. Trots det kan det vara i sjöar och mindre vattendrag som effekterna av utsläppen är störst. Traditionella tvåtaktare används även i sjöar som utnyttjas till dricksvatten och fiske av matfisk och kräftor. Studien visar relativt stor miljöpåverkan från den traditionella 2-takts utombordare som undersökts. Resultaten indikerar att alkylatbensin ger betydligt mindre risker. E85 kan också vara ett alternativ till standardbensin. Det går utmärkt att köra en utombordare på E85, men det kräver en konvertering av motorn vilket gör att det inte är aktuellt för flertalet användare. De observerade emissionerna av aldehyder ger anledning till att studera detta närmare. Det verkar som om bensin ger mer formaldehyd än etanol, medan etanol ger mer acetaldehyd, men testerna är inte tillräckligt omfattande för att göra en fullständig bedömning. Projektet föreslår ytterligare undersökningar bland annat av kylvatten från inombordare och aldehyder i avgaser från utombordare
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| 34. |
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| 35. |
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| 36. |
- Cheng, Shi, et al.
(författare)
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Compact Reflective Microstrip Phase Shifter for Traveling Wave Antenna Applications
- 2006
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1531-1309 .- 1558-1764. ; 16:7, s. 431-433
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Tidskriftsartikel (refereegranskat)abstract
- A varactor diode based microstrip phase shifter for 5.8 GHz is presented. It is designed for use in microstrip traveling Wave antennas where there is a strict limitation on the available space for the phase shifters. To meet all requirements, a reflective type phase shifter is chosen. Such a phase shifter includes a hybrid coupler. A compact branch line coupler is designed to make the phase shifter fit between the radiating elements in the antenna, while maintaining sufficient electrical performance. Phase shifters are designed with different types of stubs connecting the diodes to ground. A phase tuning range of 621 is measured for a phase shifter with parallel open stubs, and 92 degrees with shorted stubs. Insertion loss is in both cases less than 0.6 dB. A complete five-element array antenna is built and characterized. Measurements show beam scanning angles within 32 degrees from broadside.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Cheng, Shi, et al.
(författare)
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Reduction of the coupling to external sources and modes of propagation by a nearly confocal resonator
- 2007
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Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 55:10, s. 2257-2261
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a numerical and experimental study of a nearly confocal resonator with spherical mirrors at 12 GHz. The geometry was chosen in order to have a large quality factor for the diffraction losses, and thereby a weak coupling to external parasitic TE and TM modes, that propagate in a pipe on which the resonator may be installed. In turn, this allows a significant improvement of its signal-to-noise ratio, e.g., when used as a beam monitor.
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| 41. |
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| 42. |
- Davies, Ronnie, et al.
(författare)
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A New General Pathway for Synthesis of Reference Compounds of N-Terminal Valine-Isocyanate Adducts
- 2010
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 23:3, s. 540-546
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Tidskriftsartikel (refereegranskat)abstract
- Adducts to Hb could be used as biomarkers to monitor exposure to isocyanates. Particularly useful is the measurement of carbamoylation of N-terminal valines in Hb, after detachment as hydantoins. The synthesis of references from the reactive isocyanates, especially diisocyanates, has been problematic due to side reactions and polymerization of the isocyanate starting material. A simpler, safer, and more general method for the synthesis of valine adducts of isocyanates has been developed using N-[(4-nitrophenyl)-carbamate]valine methylamide (NPCVMA) as the key precursor to adducts of various mono- and diisocyanates of interest. By reacting NPCVMA with a range of isocyanate-related amines, carbamoylated valines are formed without the use of the reactive isocyanates. The carbamoylated products synthesized here were cyclized with good yields of the formed hydantoins. The carbamoylated derivative from phenyl isocyanate also showed quantitative yield in a test with cyclization tinder the conditions used in blood. This new pathway for the preparation of N-carbamoylated model compounds overcomes the above-mentioned problems in the synthesis and is a general and simplified approach, which could make such reference compounds of adducts to N-terminal valine from isocyanates accessible for biomonitoring purposes. The synthesized hydantoins corresponding to adducts from isocyanic acid, methyl isocyanate, phenyl isocyanate, and 2,6-toluene diisocyanate were characterized by LC-MS analysis. The background level of the hydantoin from isocyanic acid in human blood was analyzed with the LC-MS conditions developed.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Grudén, Mathias, 1985-
(författare)
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Wireless Sensor Network and Radio Wave Propagation in Harsh Environments
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis cover two important subjects regarding the application of wireless sensor networks (WSNs). Both subjects are related to propagation mechanisms. The first subject is what the radio channel looks like and how it behaves. In this case three different, and extreme, environments are measured and characterized - a train, a half scale jet engine fan and a full scale military jet engine. The train environment is characterized by measure the path loss and fading over distance. For the case with the jet engines, difficulties were found to measure the path loss over distance, so in this case stationary antennas were used, but with the engine running. Each of these shows an extreme type of fading, also known as Rayleigh fading. For the case of jet engine at full speed (about 10 000 rpm), it was shown that the time between two consecutive fading dips where only 290 μs, which is about twice the length of a data package from the WSN involved in this project. The Rayleigh distributed amplitude fading occurs when there is a multipath environment, the radio waves propagate several different paths between the transmitter and receiver, which causes a superposition at the receiver. When having Rayleigh fading, the performance of the radio link is greatly reduced. When applying a WSN in this type of environment, the use of several antennas will improve the received power of the signal. This is done by adding extra antennas to a wireless system and in a clever way combine the signals, or select one of two signals from the antennas. In a book chapter and in a paper presented in the thesis, a new and low energy type of diversity is described. The performance of this new type of diversity is shown by having a two branch diversity and discretely shifting the phase of each branch before combining them. In this case, four relative phase shifts are performed during each symbol received. When performing a combining like this, the energy is saved by not having any decision circuitry. By using this type of diversity and using a 90 % signal reliability and an ideal environment, the diversity gain is 5.5 dB for an averaging detector and 10.3 dB for a peak detector. The drawback with this system is that it is only limited for systems using simple types of amplitude (ASK) or frequency (FSK) modulation.
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| 48. |
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| 49. |
- Hagberg, Linus, et al.
(författare)
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LCA calculations on Swedish wood pellet production chains - according to the Renewable Energy Directive
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The study includes calculations of typical life cycle emissions of greenhouse gases for representative Swedish pellet production chains in accordance with the calculation rules in RED (Directive 2009/28/EC). The study also intends to analyse how the directive is applicable on solid biofuels in general and on wood pellet production in particular, and to identify such aspects of the methodology in RED that are associated with obscurities, problems or lead to misleading results compared to other life cycle analysis principles. The report includes a large number of alternative calculations to show how different facts, assumptions and methodological choices affect the results. This includes the effect of what fuels are used for drying, different transport distances, assumed fuel mix for purchased electricity, the variance in efficiency between the investigated plants as well as the effect of different interpretations of the RED methodology for greenhouse gas calculations.
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| 50. |
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