150 research outputs found
Zooming into local active galactic nuclei: The power of combining SDSS-IV MaNGA with higher resolution integral field unit observations
Ionised gas outflows driven by active galactic nuclei (AGN) are ubiquitous in
high luminosity AGN with outflow speeds apparently correlated with the total
bolometric luminosity of the AGN. This empirical relation and theoretical work
suggest that in the range L_bol ~ 10^43-45 erg/s there must exist a threshold
luminosity above which the AGN becomes powerful enough to launch winds that
will be able to escape the galaxy potential. In this paper, we present pilot
observations of two AGN in this transitional range that were taken with the
Gemini North Multi-Object Spectrograph Integral Field Unit (IFU). Both sources
have also previously been observed within the Sloan Digital Sky Survey-IV
(SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey.
While the MaNGA IFU maps probe the gas fields on galaxy-wide scales and show
that some regions are dominated by AGN ionization, the new Gemini IFU data zoom
into the centre with four times better spatial resolution. In the object with
the lower L_bol we find evidence of a young or stalled biconical AGN-driven
outflow where none was obvious at the MaNGA resolution. In the object with the
higher L_bol we trace the large-scale biconical outflow into the nuclear region
and connect the outflow from small to large scales. These observations suggest
that AGN luminosity and galaxy potential are crucial in shaping wind launching
and propagation in low-luminosity AGN. The transition from small and young
outflows to galaxy-wide feedback can only be understood by combining
large-scale IFU data that trace the galaxy velocity field with higher
resolution, small scale IFU maps.Comment: 14 pages, accepted for publication in MNRA
The Redshift Search Receiver 3 mm Wavelength Spectra of 10 Galaxies
The 3 mm wavelength spectra of 10 galaxies have been obtained at the Five
College Radio Astronomy Observatory using a new, very broadband receiver and
spectrometer, called the Redshift Search Receiver (RSR). The RSR has an
instantaneous bandwidth of 37 GHz covering frequencies from 74 to 111 GHz, and
has a spectral resolution of 31 MHz (~100 km/s). During tests of the RSR on the
FCRAO 14 m telescope the complete 3 mm spectra of the central regions of NGC
253, Maffei 2, NGC1068, IC 342, M82, NGC 3079, NGC 3690, NGC 4258, Arp 220 and
NGC 6240 were obtained. Within the wavelength band covered by the RSR, 20
spectral lines from 14 different atomic and molecular species were detected.
Based on simultaneous fits to the spectrum of each galaxy, a number of key
molecular line ratios are derived. A simple model which assumes the emission
arises from an ensemble of Milky Way-like Giant Nolecular Cloud cores can
adequately fit the observed line ratios using molecular abundances based on
Galactic molecular cloud cores. Variations seen in some line ratios, such as
13CO/HCN and HCO+/HCN, can be explained if the mean density of the molecular
gas varies from galaxy to galaxy. However, NGC 3690, NGC 4258 and NGC 6240 show
very large HCO+/HCN ratios and require significant abundance enhancement of
HCO+ over HCN, possible due to the proximity to active galactic nucleus
activity. Finally, the mass of dense molecular gas is estimated and we infer
that 25-85 % of the total molecular gas in the central regions of these
galaxies must have densities greater than 10^4 cm^-3.Comment: accepted for publication in A.
XANES investigation of the local structure of Co nanoclusters embedded in Ag
Ion-implanted cobalt atoms into a silver matrix with a layer thickness of about 20 nm were studied by x-ray absorption near-edge spectroscopy (XANES) at the Co edge. Full multiple scattering ab initio calculations of Co XANES at the edge provide a phase fingerprint to distinguish the Co structure of samples prepared at different doses and annealing temperatures. The bcc Co phase is formed for the as-prepared sample with 6 at. % and the fcc Co phase is formed at the expense of the bcc phase for the sample with 12 at. % after annealing at $400\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.
Manganese causes neurotoxic iron accumulation via translational repression of Amyloid Precursor Protein (APP) and H-Ferritin
For more than 150 years, it is known that occupational overexposure of manganese (Mn) causes movement disorders resembling Parkinson's disease (PD) and PD‐like syndromes. However, the mechanisms of Mn toxicity are still poorly understood. Here, we demonstrate that Mn dose‐ and time‐dependently blocks the protein translation of amyloid precursor protein (APP) and heavy‐chain Ferritin (H‐Ferritin), both iron homeostatic proteins with neuroprotective features. APP and H‐Ferritin are post‐transcriptionally regulated by iron responsive proteins, which bind to homologous iron responsive elements (IREs) located in the 5′‐untranslated regions (5′‐UTRs) within their mRNA transcripts. Using reporter assays, we demonstrate that Mn exposure repressed the 5′‐UTR‐activity of APP and H‐Ferritin, presumably via increased iron responsive proteins‐iron responsive elements binding, ultimately blocking their protein translation. Using two specific Fe2+‐specific probes (RhoNox‐1 and IP‐1) and ion chromatography inductively coupled plasma mass spectrometry (IC‐ICP‐MS), we show that loss of the protective axis of APP and H‐Ferritin resulted in unchecked accumulation of redox‐active ferrous iron (Fe2+) fueling neurotoxic oxidative stress. Enforced APP expression partially attenuated Mn‐induced generation of cellular and lipid reactive oxygen species and neurotoxicity. Lastly, we could validate the Mn‐mediated suppression of APP and H‐Ferritin in two rodent in vivo models (C57BL6/N mice and RjHan:SD rats) mimicking acute and chronic Mn exposure. Together, these results suggest that Mn‐induced neurotoxicity is partly attributable to the translational inhibition of APP and H‐Ferritin resulting in impaired iron metabolism and exacerbated neurotoxic oxidative stress
XANES investigation of the local structure of Co nanoclusters embedded in Ag. Phys
Ion-implanted cobalt atoms into a silver matrix with a layer thickness of about 20 nm were studied by x-ray absorption near-edge spectroscopy ͑XANES͒ at the Co K edge. Full multiple scattering ab initio calculations of Co XANES at the K edge provide a phase fingerprint to distinguish the Co structure of samples prepared at different doses and annealing temperatures. The bcc Co phase is formed for the as-prepared sample with 6 at. % and the fcc Co phase is formed at the expense of the bcc phase for the sample with 12 at. % after annealing at 400°C
Research on the relation of EEG signal chaos characteristics with high-level intelligence activity of human brain
Using phase space reconstruct technique from one-dimensional and multi-dimensional time series and the quantitative criterion rule of system chaos, and combining the neural network; analyses, computations and sort are conducted on electroencephalogram (EEG) signals of five kinds of human consciousness activities (relaxation, mental arithmetic of multiplication, mental composition of a letter, visualizing a 3-dimensional object being revolved about an axis, and visualizing numbers being written or erased on a blackboard). Through comparative studies on the determinacy, the phase graph, the power spectra, the approximate entropy, the correlation dimension and the Lyapunov exponent of EEG signals of 5 kinds of consciousness activities, the following conclusions are shown: (1) The statistic results of the deterministic computation indicate that chaos characteristic may lie in human consciousness activities, and central tendency measure (CTM) is consistent with phase graph, so it can be used as a division way of EEG attractor. (2) The analyses of power spectra show that ideology of single subject is almost identical but the frequency channels of different consciousness activities have slight difference. (3) The approximate entropy between different subjects exist discrepancy. Under the same conditions, the larger the approximate entropy of subject is, the better the subject's innovation is. (4) The results of the correlation dimension and the Lyapunov exponent indicate that activities of human brain exist in attractors with fractional dimensions. (5) Nonlinear quantitative criterion rule, which unites the neural network, can classify different kinds of consciousness activities well. In this paper, the results of classification indicate that the consciousness activity of arithmetic has better differentiation degree than that of abstract
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