Abstract
Blazars are active galactic nuclei (AGN) whose relativistic jets point nearly to the line of sight. Their compact radio structure can be imaged with very long baseline interferometry (VLBI) ...on parsec scales. Blazars at extremely high redshifts provide a unique insight into the AGN phenomena in the early Universe. We observed four radio sources at redshift z > 4 with the European VLBI Network (EVN) at 1.7 and 5 GHz. These objects were previously classified as blazar candidates based on X-ray observations. One of them, J2134−0419 is firmly confirmed as a blazar with our VLBI observations, due to its relativistically beamed radio emission. Its radio jet extended to ∼10 milliarcsec scale makes this source a promising target for follow-up VLBI observations to reveal any apparent proper motion. Another target, J0839+5112 shows a compact radio structure typical of quasars. There is evidence for flux density variability and its radio ‘core’ has a flat spectrum. However, the EVN data suggest that its emission is not Doppler-boosted. The remaining two blazar candidates (J1420+1205 and J2220+0025) show radio properties totally unexpected from radio AGN with small-inclination jet. Their emission extends to arcsec scales and the Doppler factors of the central components are well below 1. Their structures resemble that of double-lobed radio AGN with large inclination to the line of sight. This is in contrast with the blazar-type modelling of their multiband spectral energy distributions. Our work underlines the importance of high-resolution VLBI imaging in confirming the blazar nature of high-redshift radio sources.
The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface ...(FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba₀.₆K₀.₄Fe₂As₂, the pairing strength is enhanced simultaneously (2Δ/Tcalmost equal to7) on the nearly nested FS pockets, i.e., the inner hole-like (α) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Δ/Tcalmost equal to3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe₁.₈₅Co₀.₁₅As₂, the FS nesting condition switches from the α to the β FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Δ/Tcalmost equal to6) is also found to switch to the nested β FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.
We show that the canonical seesaw mechanism implemented by the U(1)B−L gauge symmetry provides two-component dark matter naturally. The seesaw scale that breaks B − L defines a residual gauge ...symmetry to be Z6 = Z2 ⊗ Z3, where Z2 leads to the usual matter parity, while Z3 is newly recognized, transforming quark fields nontrivially. The dark matter components-that transform nontrivially under the matter parity and Z3, respectively-can gain arbitrary masses, despite the fact that the Z3 dark matter may be heavier than the light quarks u , d . This dark matter setup can address the XENON1T anomaly recently observed and other observables, given that the dark matter masses are nearly degenerate, heavier than the electron and the B − L gauge boson Z′, as well as the fast-moving Z3 dark matter has a large B − L charge, while the Z′ is viably below the beam dump experiment sensitive regime.
We demonstrate that limited participation can arise endogenously in the presence of model uncertainty and heterogeneous uncertainty-averse investors. When uncertainty dispersion among investors is ...small, full participation prevails in equilibrium. Equity premium is related to the average uncertainty among investors and a conglomerate trades at a price equal to the sum of its single-segment components. When uncertainty dispersion is large, investors with high uncertainty choose not to participate in the stock market, resulting in limited market participation. When limited participation occurs, participation rate and equity premium can decrease in uncertainty dispersion and a conglomerate trades at a discount.
Acute dacryocystitis is an atypical and rare manifestation of pediatric mononucleosis still widely underdiagnosed in clinical practice. We report this rare condition and describe challenges in its ...diagnosis and treatment on the basis of a presented case.
A 6-year-old Caucasian girl without any ophthalmic history was admitted for right preseptal cellulitis requiring intravenous antibiotic therapy. During hospitalization, she developed a fluctuating lump in the nasolacrimal region which resembled an abscess, both clinically and radiologically. There was no spontaneous purulent discharge. Serology was positive for acute mononucleosis and Epstein-Barr virus-related dacryocystitis was diagnosed. Following multidisciplinary discussion, she was treated conservatively with digital lacrimal sac massages and intravenous antibiotic therapy with an excellent outcome.
This rare form of Epstein-Barr virus is poorly documented in the literature, and thus barely known. As initial symptoms are nonspecific (rhinitis, fever, eyelid edema and erythema lack of purulent discharge, and moderate bilateral cervical lymphadenopathy), diagnosis is often difficult. Nevertheless, differentiating between dacryocystitis and abscess is crucial to select the appropriate treatment and avoid unnecessary, potentially harmful surgery. Conservative management of dacryocystitis appears to be the gold standard of treatment.
Acute dacryocystitis in children free of ophthalmic history should raise suspicion of primary Epstein-Barr virus infection. With conservative treatment, prognosis appears to be excellent; therefore, surgery should be avoided as much as possible.
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