ABSTRACT Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may ...represent an important stage in the evolution of galaxies. Most known hot DOGs are located at , due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at , where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 ( ). We find evidence of a broadened component in Mg ii, which would imply a black hole mass of and an Eddington ratio of . WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of . The source has an intrinsic 2-10 keV luminosity of , a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.
Enantioselective Organocatalysis Using SOMO Activation Beeson, Teresa D; Mastracchio, Anthony; Hong, Jun-Bae ...
Science (American Association for the Advancement of Science),
04/2007, Letnik:
316, Številka:
5824
Journal Article
Recenzirano
The asymmetric α-addition of relatively nonpolar hydrocarbon substrates, such as allyl and aryl groups, to aldehydes and ketones remains a largely unsolved problem in organic synthesis, despite the ...wide potential utility of direct routes to such products. We reasoned that well-established chiral amine catalysis, which activates aldehydes toward electrophile addition by enamine formation, could be expanded to this important reaction class by applying a single-electron oxidant to create a transient radical species from the enamine. We demonstrated the concept of singly occupied molecular orbital (SOMO) activation with a highly selective α-allylation of aldehydes, and we here present preliminary results for enantioselective heteroarylations and cyclization/halogenation cascades.
Galaxy mergers and gas accretion from the cosmic web drove the growth of galaxies and their central black holes at early epochs. We report spectroscopic imaging of a multiple merger event in the most ...luminous known galaxy, WISE J224607.56-052634.9 (W2246-0526), a dust-obscured quasar at redshift 4.6, 1.3 billion years after the Big Bang. Far-infrared dust continuum observations show three galaxy companions around W2246-0526 with disturbed morphologies, connected by streams of dust likely produced by the dynamical interaction. The detection of tidal dusty bridges shows that W2246-0526 is accreting its neighbors, suggesting that merger activity may be a dominant mechanism through which the most luminous galaxies simultaneously obscure and feed their central supermassive black holes.
To understand the generation and propagation processes of electromagnetic ion cyclotron (EMIC) waves under different geomagnetic conditions in the inner magnetosphere, we performed a statistical ...study of EMIC wave properties observed by the Van Allen Probes from February 2013 to December 2016. We divided EMIC waves into two groups: those associated with and those occurring without injections observed by the Geostationary Operational Environmental Satellites (GOES‐13 and GOES‐15). We found that the EMIC wave polarization sense ε increased and the normalized frequency X decreased with increasing |MLAT|. Inside the plasmasphere, He+ EMIC waves were predominantly observed with left‐hand polarization (ε< −0.3) and higher wave normal angles (θk = 30–40° ). Those associated with injections showed the most intense wave power at 14–16 MLT, compared to periods without injections when these waves exhibit a similar wave power but on the dayside. H+ EMIC waves were predominantly observed outside the plasmasphere on the dayside and showed a mixture of left‐hand and linear polarizations (ε = −0.3–0.0) with lower wave normal angles (θk = 20–30° ) regardless of injections. Moreover, H+ EMIC waves were accompanied by a solar wind dynamic pressure enhancement (ΔPsw = 0.5 nPa). From these observations, we suggest that hot injected plasma contributes to the generation of intense He+ EMIC waves in the afternoon sector. A mixture of expanding cold plasmaspheric ions and coexisting hot ring current ions acts as the free energy source for He+ EMIC waves on the dayside during quiet times. Solar wind dynamic pressure enhancements are likely the major driver of H+ EMIC waves outside the plasmasphere.
Key Points
The spatial distributions of EMIC wave properties and |MLAT| dependence of polarization sense ε and normalized frequency X are examined
Possible generation processes of EMIC waves under different environments in the inner magnetosphere are suggested
He+ EMIC waves inside the plasmasphere have left‐hand polarization while linear H+ EMIC waves outside the plasmasphere are dominant
Using the Arase and Van Allen Probes satellite observations, we investigate the nonlinear electromagnetic ion cyclotron (EMIC) rising‐tone (RT) emissions with an increase of the solar wind dynamic ...pressure in the dayside magnetosphere. We find that EMIC RT emissions are accompanied by the extended dayside uniform zone (DUZ) over |MLAT| < 25° due to the dayside magnetospheric compression by an increase in Pdyn. Using the observed plasma and magnetic field data, we modeled the threshold amplitude for the nonlinear EMIC waves and compared it with the observation. The small gradient of the ambient magnetic field strongly contributes to the reduction in the threshold amplitude of nonlinear wave growth compared to other parameters. When the threshold amplitude falls to comparable level of pre‐existing EMIC waves, EMIC RT emissions are immediately triggered, suggesting direct evidence that the DUZ is the preferred condition to cause the nonlinear EMIC RT emission in the dayside magnetosphere.
Plain Language Summary
Electromagnetic ion cyclotron (EMIC) waves play an important role in controlling the dynamics of charged particles in the inner magnetosphere. Especially, nonlinear EMIC rising‐tone (RT) emissions can cause the rapid loss of relativistic electrons and ring current ions. Here, we present direct evidence demonstrating that the distortion of the dayside magnetic field causes nonlinear EMIC RT emission in response to the intensification of the solar wind dynamic pressure. Remarkably, these nonlinear EMIC waves are generated through a reduction in the threshold wave amplitudes by the distortion of the magnetic fields, even in the absence of any significant change in the pre‐existing EMIC wave amplitude. The present result provides new insights into a triggering process of nonlinear plasma waves in the magnetosphere.
Key Points
Electromagnetic ion cyclotron (EMIC) waves with rising‐tone (RT) elements were observed in the dayside magnetosphere during an increase in the solar wind dynamic pressure
Increasing solar wind dynamic pressure extends the dayside uniform zone of the magnetic field to higher magnetic latitudes
The uniform zone leads to the reduction of the nonlinear threshold wave amplitude, which triggers nonlinear EMIC RT emissions
To understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and ...without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES‐13 and GOES‐15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES‐13 and GOES‐15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He+ EMIC waves have higher occurrence rate inside the plasmasphere, while H+ EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He+ EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H+ flux within energies of 1–50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H+ flux increase. From these observations, we suggest that injected hot ions are the major driver of He+ EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He+ EMIC waves on the dayside. However, H+ EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes.
Key Points
A statistical study of EMIC waves associated with and without injections based the Van Allen Probes and GOES satellites is performed
The spatial occurrence distributions of the EMIC waves and relationship between EMIC wave activity and energetic H+ flux are examined
He+ EMIC waves are dominantly observed inside the plasmasphere, while H+ EMIC waves are predominantly detected outside the plasmasphere
Abstract Objectives The pathogenesis of late preterm birth remains elusive for the mechanisms of disease responsible. Placental examination can often provide important clues for the pathogenesis of ...pregnancy complications. This study was conducted to determine placental pathologic findings according to the gestational age and the clinical circumstances of preterm birth. Study design Placental pathologic findings and obstetrical and neonatal outcomes were reviewed in a consecutive preterm birth cohort from a single tertiary center ( N = 1206). Placentas of term births ( N = 300) were used as normal controls. Results Acute chorioamnionitis (22.7% vs. 16.7%), maternal vascular underperfusion (6.4% vs. 0.5%), and chronic chorioamnionitis (20.8% vs. 10.5%) were significantly more frequent in preterm births than in term births ( P < 0.05, for each). Among preterm births, chronic chorioamnionitis was the most common pathology of late preterm birth (gestational age <37 and ≥34 weeks), while acute chorioamnionitis was the most common lesion of extremely preterm birth (gestational age <28 weeks). While the frequency of acute chorioamnionitis decreased with advancing gestation, that of chronic chorioamnionitis increased ( P < 0.001, for each). The upward trend of the frequency of chronic chorioamnionitis was related to advancing gestation in both spontaneous and indicated preterm births ( P < 0.001, for each). Conclusions Chronic chorioamnionitis is a common pathology of late preterm birth. It is suggested that chronic chorioamnionitis, a feature of maternal anti-fetal rejection, is an important etiology of preterm birth, especially of late preterm birth.
Plasmaspheric hiss can cause energetic electron precipitation from the magnetosphere to the Earth's upper atmosphere and affect the ionospheric electron density profiles. In this study, we use Arase ...satellite measurements in the dayside plasmasphere to model the electron precipitation and the resultant ionospheric response, and compare the results to the electron density measured by the Poker Flat Incoherent Scatter Radar (PFISR). We analyzed two close conjunction events between Arase and PFISR at L ∼ 6 in the afternoon sector, when Arase was in the outer plasmasphere and traveled into the plasmaspheric plumes. Modest or strong hiss waves were observed with amplitudes higher than 50 pT during both events. Quasilinear modeling suggests that the hiss waves could cause intense electron precipitation ranging from several keV to several hundred keV energies. The electron density profiles at 60–90 km modeled by the Boulder Electron Radiation to Ionization (BERI) model suggest significant electron density enhancements due to the precipitating electrons. PFISR simultaneously observed electron density enhancements during both events, and provided evidence for the electron precipitation at altitudes down to <70 km. The temporal modulation of hiss caused the modulated density profiles in BERI modeling, but was not evident in PFISR observations. The modeled altitude profiles of the perturbed electron density overall agree with PFISR observation. At altitudes below 75 km, the modeled electron densities are lower than the observation, suggesting additional high energy electron precipitation possibly due to low frequency (<50 Hz) waves or hiss wave powers ducted to high latitudes.
Key Points
Two Poker Flat Incoherent Scatter Radar (PFISR)‐Arase conjunction events are identified at the dayside plasmasphere when hiss wave amplitudes reach 50–100 pT at L ∼ 6
Hiss‐driven electron precipitation obtained from quasilinear simulation is used to model ionospheric density profiles at 60–90 km altitude
Modeled electron densities overall agree with PFISR observations with differences in the temporal modulation and at altitudes below 75 km
Induction of antigen-specific immune activation by the maturation of dendritic cells (DCs) is a strategy used for cancer immunotherapy. In this study, we find that FimH, which is an Escherichia coli ...adhesion portion, induces toll-like receptor 4-dependent and myeloid differentiation protein 2-independent DC maturation in mice in vivo. A combined treatment regimen with FimH and antigen promotes antigen-specific immune activation, including proliferation of T cells, production of IFN-γ and TNF-α, and infiltration of effector T cells into tumors, which consequently inhibits tumor growth in mice in vivo against melanoma and carcinoma. In addition, combined therapeutic treatment of anti-PD-L1 antibodies and FimH treatment efficiently inhibits CT26 tumor growth in BALB/c mice. Finally, FimH promotes human peripheral blood DC activation and syngeneic T-cell proliferation and activation. Taken together, these findings demonstrate that FimH can be a useful adjuvant for cancer immunotherapy.
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