| 1. |
- Abdo, A. A., et al.
(författare)
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Gamma-ray emission concurrent with the nova in the symbiotic binary V407 cygni
- 2010
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 329:5993, s. 817-821
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Tidskriftsartikel (refereegranskat)abstract
- Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable γ-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce π0 decay γ-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.
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| 2. |
- Abdo, A. A., et al.
(författare)
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Fermi large area telescope observations of PSR J1836+5925
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 712:2, s. 1209-1218
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments of the Fermi Large Area Telescope (LAT). Sitting 25 degrees off the Galactic plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8 million years, a spindown luminosity of 1.1 x 10(34) erg s(-1), and a large off-peak (OP) emission component, making it quite unusual among the known gamma-ray pulsar population. We present an analysis of one year of LAT data, including an updated timing solution, detailed spectral results, and a long-term light curve showing no indication of variability. No evidence for a surrounding pulsar wind nebula is seen and the spectral characteristics of the OP emission indicate it is likely magnetospheric. Analysis of recent XMM-Newton observations of the X-ray counterpart yields a detailed characterization of its spectrum, which, like Geminga, is consistent with that of a neutron star showing evidence for both magnetospheric and thermal emission.
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| 3. |
- Wolff, E. W., et al.
(författare)
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Changes in environment over the last 800,000 years from chemical analysis of the EPICA Dome C ice core
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:1-2, s. 285-295
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Tidskriftsartikel (refereegranskat)abstract
- The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and sequential ice. Numerous chemical species have been measured along the length of the cores. Here we concentrate on interpreting the main low-resolution patterns of major ions. We extend the published record for non-sea-salt calcium, sea-salt sodium and non-sea-salt sulfate flux to 800 ka. The non-sea-salt calcium record confirms that terrestrial dust originating from South America closely mirrored Antarctic climate, both at orbital and millennial timescales. A major cause of the main trends is most likely climate in southern South America, which could be sensitive to subtle changes in atmospheric circulation. Sea-salt sodium also follows temperature, but With a threshold at low temperature. We re-examine the use of sodium as a sea ice proxy, concluding that it is probably reflecting extent, with high salt concentrations reflecting larger ice extents. With this interpretation, the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials. Non-sea-salt sulfate flux is almost constant along the core, confirming the lack of change in marine productivity (for sulfur-producing organisms) in the areas of the Southern Ocean contributing to the flux at Dome C. For the first time we also present long records of reversible species such as nitrate and chloride, and show that the pattern of post-depositional losses described for shallower ice is maintained in older ice. It appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site, and the results suggest a possible correction to accumulation rates in one early interglacial. Taken together the chemistry records offer a number of constraints on the way the Earth system combined to give the major climate fluctuations of the late Quaternary period.
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| 4. |
- Anthoni, M, et al.
(författare)
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Smad3 regulates dermal cytokine and chemokine expression and specific antibody production in murine responses to a respiratory chemical sensitizer
- 2010
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Ingår i: International archives of allergy and immunology. - : S. Karger AG. - 1423-0097 .- 1018-2438. ; 151:2, s. 155-167
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Tidskriftsartikel (refereegranskat)abstract
- <i>Background:</i> The cytokine transforming growth factor-β(TGF-β) has important regulatory roles in the immune system. To investigate the role of intact TGF-β signaling during the contact hypersensitivity (CHS) response to a respiratory allergen, we exposed Smad3–/– mice to topical trimellitic anhydride (TMA). <i>Methods:</i> CHS was induced by topical application of TMA. The swelling of the TMA-exposed ears was analyzed, and lymph node, ear tissue and skin biopsies were collected for RNA isolation, histology and histochemical analyses. Lymph node cell proliferation was measured and blood samples were collected for analysis of TMA-specific immunoglobulin. <i>Results:</i> Topical TMA exposure resulted in increased mRNA expression of proinflammatory and suppressive cytokines (IL-1β, TNF-α, IL-6, IFN-γ, IL-4, IL-10, IL-17, IL-23, TGF-β), chemokines (CXCL9, CXCL10, CCL24) and chemokine receptors (CCR7, CCR8, CXCR2), increased numbers of CD3+ T cells in ear tissue, and lymphadenopathy in the Smad3–/– mice. The IL-10 result was confirmed at the protein level by immunohistochemistry. However, the ear-swelling response and infiltration of eosinophils, F4/80+ cells, CD11c+ cells and mast cells were similar in the Smad3–/– mice compared to their wild-type (WT) siblings. While TMA-specific IgE was induced equally in the WT and Smad3–/– mice, the concentration of TMA-specific IgG2a was significantly lower in the Smad3–/– mice. <i>Conclusions:</i> The Smad3 molecule contributes significantly to the regulation of the cytokine and chemokine network during the CHS response to TMA. The lack of Smad3 resulted in a potent Th2 shift, confirmed by strongly impaired IgG2a levels.
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| 5. |
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| 6. |
- Polyak, Leonid, et al.
(författare)
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History of sea ice in the Arctic
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:15-16, s. 1757-1778
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Tidskriftsartikel (refereegranskat)abstract
- Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO(2) after the Paleocene-Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13-14 million years. Ice was apparently most widespread during the last 2-3 million years, in accordance with Earth's overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorterterm (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.
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