| 1. |
- Kim, Jae-Young, et al.
(författare)
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Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
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Tidskriftsartikel (refereegranskat)abstract
- 3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array, at an angular resolution of ∼20 μas (at a redshift of z = 0:536 this corresponds to ∼0:13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation.We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across diffierent imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet.We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1:3 and ∼1:7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≤1010 K, a magnitude or more lower than typical values seen at ≥7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
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| 2. |
- Freund, David, et al.
(författare)
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International high-tech SMEs innovative foreign knowledge inflows : effects of host country weak network ties and absorptive capacity
- 2020
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Ingår i: Multinational Business Review. - : EMERALD GROUP PUBLISHING LTD. - 1525-383X. ; 28:3, s. 333-354
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The main purpose of this study is to explain the combined effects of host country weak network ties and absorptive capacity on the innovative foreign knowledge inflows of international high-tech small- and medium-sized enterprises (SMEs). Design/methodology/approach Data are drawn from the two largest and most authoritative German Federal Government census-databases of biotech and nanotech SMEs. A structured survey questionnaire was administered and regression analysis adopted. Findings This study demonstrates weak network ties in the host country and developing absorptive capacity produce a combined effect that positively influences international high-tech SMEs innovative foreign knowledge inflows. Also, host country weak network ties and absorptive capacity when considered separately, each respectively, positively influence innovative foreign knowledge inflows. Practical implications The results help inform key personnel in international high-tech SMEs about the relevance of host country weak network ties and absorptive capacity for foreign knowledge inflows. In addition, the results help policymakers and think-tanks to promote tailored advice and guidance e.g. those policymakers implementing the EU Entrepreneurship 2020 Action Plan. Originality/value There is a recent call in the literature to combine network theory and absorptive capacity theory to better explain knowledge creation in the context of international high-tech SMEs knowledge sourcing. By addressing this call, the study provides a more refined and comprehensive account of international high-tech SMEs innovative foreign knowledge inflows.
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