| 1. |
- Moskalenko, Sveatoslav A., et al.
(författare)
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Two-dimensional magnetoexciton-polariton
- 2012
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Ingår i: JOURNAL OF NANOPHOTONICS. - 1934-2608. ; 6, s. 061806-
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Tidskriftsartikel (refereegranskat)abstract
- The Hamiltonian describing the interaction of the two-dimensional (2-D) magnetoexcitons with photons propagating with arbitrary-oriented wave vectors in the three-dimensional (3-D) space is deduced. The magnetoexcitons are characterized by the numbers n(e) and n(h) of the electron and hole Landau quantizations, by circular polarization (sigma) over right arrow (M) of the holes in the p-type valence bands and by in-plane wave vectors (k) over right arrow (parallel to). The photons are characterized by the wave vectors (k) over right arrow with in-plane component (k) over right arrow (parallel to) and perpendicular component k(z), which is quantized in the case of microresonator. The interaction is governed by the conservation law of the in-plane components (k) over right arrow (parallel to)of the magnetoexcitons and photons and by the rotational symmetry around the axis perpendicular to the layer, which leads to the alignment of the magnetoexcitons under the influence of the photons with circular polarization (sigma) over right arrow (+/-)((k) over right arrow) and with probability proportional to vertical bar (sigma) over right arrow (+/-)((k) over right arrow) . (sigma) over right arrow (M)*vertical bar(2.)
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| 2. |
- Iashchishyn, Igor A., et al.
(författare)
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Intranasally Administered S100A9 Amyloids Induced Cellular Stress, Amyloid Seeding, and Behavioral Impairment in Aged Mice
- 2018
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Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 9:6, s. 1338-1348
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid formation and neuroinflammation are major features of Alzheimer's disease pathology. Proinflammatory mediator S100A9 was shown to act as a link between the amyloid and neuroinflammatory cascades in Alzheimer's disease, leading together with Aβ to plaque formation, neuronal loss and memory impairment. In order to examine if S100A9 alone in its native and amyloid states can induce neuronal stress and memory impairment, we have administered S100A9 species intranasally to aged mice. Single and sequential immunohistochemistry and passive avoidance behavioral test were conducted to evaluate the consequences. Administered S100A9 species induced widespread cellular stress responses in cerebral structures, including frontal lobe, hippocampus and cerebellum. These were manifested by increased levels of S100A9, Box, and to a lesser extent activated caspase-3 immunopositive cells. Upon administration of S100A9 fibrils, the amyloid oligomerization was observed in the brain tissues, which can further exacerbate cellular stress. The cellular stress responses correlated with significantly increased training and decreased retention latencies measured in the passive avoidance test for the SI00A9 treated animal groups. Remarkably, the effect size in the behavioral tests was moderate already in the group treated with native S100A9, while the effect sizes were large in the groups administered S100A9 amyloid oligomers or fibrils. The findings demonstrate the brain susceptibility to neurotoxic damage of S100A9 species leading to behavioral and memory impairments. Intranasal administration of S100A9 species proved to be an effective method to study amyloid induced brain dysfunctions, and 5100A9 itself may be postulated as a target to allay early stage neurodegenerative and neuroinflammatory processes.
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| 3. |
- Johannesson, Gudlaugur, et al.
(författare)
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Cosmic-Ray Propagation in Light of the Recent Observation of Geminga
- 2019
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 879:2
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Tidskriftsartikel (refereegranskat)abstract
- The High Altitude Water Cherenkov (HAWC) telescope recently observed extended emission around the Geminga and PSR. B0656+14 pulsar wind nebulae (PWNe). These observations have been used to estimate cosmic-ray (CR) diffusion coefficients near the PWNe that appear to be more than two orders of magnitude smaller than the diffusion coefficients typically derived for the interstellar medium from measured abundances of secondary species in CRs. Two-zone diffusion models have been proposed as a solution to this discrepancy, where the slower diffusion zone (SDZ) is confined to a small region around the PWN. Such models are shown to successfully reproduce the HAWC observations of the Geminga PWN while retaining consistency with other CR data. It is found that the size of the SDZ influences the predicted positron flux and the spectral shape of the extended gamma-ray emission at lower energies that can be observed with the Fermi Large Area Telescope. If the two observed PWNe are not unique, then it is likely that there are similar pockets of slow diffusion around many CR sources elsewhere in the Milky Way. The consequences of such a picture for Galactic CR propagation is explored.
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| 4. |
- Johannesson, Gudlaugur, et al.
(författare)
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The Three-dimensional Spatial Distribution of Interstellar Gas in the Milky Way : Implications for Cosmic Rays and High-energy Gamma-ray Emissions
- 2018
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 856:1
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Tidskriftsartikel (refereegranskat)abstract
- Direct measurements of cosmic ray (CR) species combined with observations of their associated gamma-ray emissions can be used to constrain models of CR propagation, trace the structure of the Galaxy, and search for signatures of new physics. The spatial density distribution of interstellar gas is a vital element for all these studies. So far, models have employed the 2D cylindrically symmetric geometry, but their accuracy is well behind that of the available data. In this paper, 3D spatial density models for neutral and molecular hydrogen are constructed based on empirical model fitting to gas line-survey data. The developed density models incorporate spiral arms and account for the warping of the disk, and the increasing gas scale height with radial distance from the Galactic center. They are employed together with the GALPROP CR propagation code to investigate how the new 3D gas models affect calculations of CR propagation and high-energy gamma-ray intensity maps. The calculations reveal non-trivial features that are directly related to the new gas models. The best-fit values for propagation model parameters employing 3D gas models are presented and they differ significantly from those derived with the 2D gas density models that have been widely used. The combination of 3D CR and gas density models provide a more realistic basis for the interpretation of non-thermal emissions from the Galaxy.
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| 5. |
- Moskalenko, Igor V., et al.
(författare)
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GalProp code for galactic cosmic ray propagation and associated photon emissions
- 2019
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Ingår i: Proceedings of Science. - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- The last decade brought spectacular advances in the astrophysics of cosmic rays (CRs) and γ-ray astronomy. These observations pose a considerable challenge to conventional astrophysics thus leaving an ample discovery space for new phenomena. Understanding the conventional astrophysical backgrounds is vital in moving to the new territory. The state-of-the-art CR propagation code called GALPROP is designed to address exactly this challenge. Having 23 years of development behind it, the GALPROP code has become a de-facto standard in astrophysics of CR, diffuse γ-rays, and searches of new physics. The GALPROP code uses information from astronomy, particle, and nuclear physics to predict CRs, grays, synchrotron emission and its polarization in a self-consistent manner - it provides the modeling code unifying the many results of individual measurements in physics and astronomy spanning in energy coverage, types of instrumentation, and the nature of detected species. The range of physical validity of the GALPROP code covers sub-keV - PeV energies for particles and from micro-eV - PeV for photons. The GALPROP framework includes the code and independently developed datasets, such as interstellar gas (H2, H I, H II), radiation and magnetic fields distributions as well as the nuclear and particle production cross sections. The code and the datasets are public and are extensively used by many experimental collaborations, and by thousands of individual researchers worldwide for interpretation of their data and for making predictions. We will present latest updates to the GALPROP framework that improve its accuracy and capabilities and will discuss its applications. As always, the latest release of the code and datasets is available through the WebRun, a service to the scientific community enabling easy use of the GALPROP via web browsers.
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| 6. |
- Moskalenko, Igor V., et al.
(författare)
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GALPROP Code for Galactic Cosmic Ray Propagation and Associated Photon Emissions
- 2022
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Ingår i: Proceedings of Science. - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- Signatures of new phenomena are abundant – thanks to the new instrumentation launched into space and built on the ground. Modern technologies employed by those instruments provide measurements with unmatched precision, enabling searches for subtle signatures of dark matter (DM) and new physics in cosmic rays (CRs) and photon emissions. Understanding the conventional astrophysical backgrounds is vital in moving to the new territory. The state-of-the-art CR propagation code called GalProp is designed to address exactly this challenge. Having 25 years of development behind it, the GalProp framework has become a de-facto standard in astrophysics of CRs, diffuse photon emissions (radio- to γ-rays), and searches of new physics. GalProp uses information from astronomy, particle, and nuclear physics to predict CRs and their associated emissions and their polarization in a self-consistent manner – it provides the modeling framework unifying the many results of individual measurements in physics and astronomy spanning in energy coverage, types of instrumentation, and the nature of detected species. The range of physical validity of the GalProp framework covers sub-keV–PeV energies for particles and from μeV–PeV for photons. Combining GalProp with HelMod, a heliospheric transport code, into a unified framework considerably extends its capabilities providing a consolidated description of CR transport from their sources to the near-Earth orbit. The framework and the datasets are public and are extensively used by many experimental collaborations, and by thousands of individual researchers worldwide for interpretation of their data and for making predictions. This paper details the latest updates to the GalProp framework, further developments of its initially auxiliary datasets that grew into independent studies of the Galactic structure – distributions of gas, dust, radiation and magnetic fields as well as further extension of its capabilities.
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| 7. |
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