Abstract
We analyze the parsec-scale jet kinematics from 2007 June to 2018 December of a sample of
γ
-ray bright blazars monitored roughly monthly with the Very Long Baseline Array (VLBA) at 43 GHz ...under the VLBA-BU-BLAZAR program. We implement a novel piecewise linear fitting method to derive the kinematics of 521 distinct emission knots from a total of 3705 total intensity images in 22 quasars, 13 BL Lacertae objects, and 3 radio galaxies. Apparent speeds of these components range from 0.01
c
to 78
c
, and 18.6% of knots (other than the “core”) are quasi-stationary. One-fifth of moving knots exhibit nonballistic motion, with acceleration along the jet within 5 pc of the core (projected) and deceleration farther out. These accelerations occur mainly at locations coincident with quasi-stationary features. We calculate the physical parameters of 273 knots with statistically significant motion, including their Doppler factors, Lorentz factors, and viewing angles. We determine the typical values of these parameters for each jet and the average for each subclass of active galactic nuclei. We investigate the variability of the position angle of each jet over the 10 yr of monitoring. The fluctuations in position of the quasi-stationary components in radio galaxies tend to be parallel to the jet, while no directional preference is seen in the components of quasars and BL Lacertae objects. We find a connection between
γ
-ray states of blazars and their parsec-scale jet properties, with blazars with brighter 43 GHz cores typically reaching higher
γ
-ray maxima during flares.
The quasar 3C 454.3 underwent a uniquely structured multifrequency outburst in 2016 June. The blazar was observed in the optical R-band by several ground-based telescopes in photometric and ...polarimetric modes, at γ-ray frequencies by the Fermi Large Area Telescope, and at 43 GHz with the Very Long Baseline Array. The maximum flux density was observed on 2016 June 24 at both optical and γ-ray frequencies, reaching mJy and ph cm−2 s−1, respectively. The 2016 June outburst possessed a precipitous decay at both γ-ray and optical frequencies, with the source decreasing in flux density by a factor of 4 over a 24 hr period in the R-band. Intraday variability was observed throughout the outburst, with flux density changes between 1 and 5 mJy over the course of a night. The precipitous decay featured statistically significant quasiperiodic microvariability oscillations with an amplitude of ∼2%-3% about the mean trend and a characteristic period of 36 minutes. The optical degree of polarization jumped from ∼3% to nearly 20% during the outburst, while the position angle varied by ∼120°. A knot was ejected from the 43 GHz core on 2016 February 25, moving at an apparent speed . From the observed minimum timescale of variability and derived Doppler factor δ = 22.6, we find the size of the emission region r 2.6 × 1015 cm. If the quasiperiodic microvariability oscillations are caused by periodic variations of the Doppler factor of emission from a turbulent vortex, we derive the rotational speed of the vortex to be ∼0.2c.
This article examines attempts at the Southwest Collection at Texas Tech University’s Southwest Collection/Special Collections Library (SWC/ SCL), in Lubbock, Texas, to integrate its oral history ...program into collection acquisition, arrangement, description, and discovery processes. Beginning with the creation of a staff position dedicated to acquisition, and continuing through an evolution of job duties resulting from COVID-19, the SWC’s oral historians now not only facilitate collection acquisition through extensive relationship building but also engage donors during arrangement and description. Such reconceptions have led to new processes and workflows, wherein oral history has become an endeavour of collaborative knowledge creation and an enabler of a more democratic archives.
Abstract
We present multi-epoch optical spectra of the
γ
-ray bright blazar 1156+295 (4C +29.45, Ton 599) obtained with the 4.3 m Lowell Discovery Telescope. During a multiwavelength outburst in late ...2017, when the
γ
-ray flux increased to 2.5 × 10
−6
phot cm
−2
s
−1
and the quasar was first detected at energies ≥100 GeV, the flux of the Mg
ii
λ
2798 emission line changed, as did that of the Fe emission complex at shorter wavelengths. These emission-line fluxes increased along with the highly polarized optical continuum flux, which is presumably synchrotron radiation from the relativistic jet, with a relative time delay of ≲2 weeks. This implies that the line-emitting clouds lie near the jet, which points almost directly toward the line of sight. The emission-line radiation from such clouds, which are located outside the canonical accretion-disk related broad-line region, may be a primary source of seed photons that are up-scattered to
γ
-ray energies by relativistic electrons in the jet.
ABSTRACT
Between 2009 and 2012, 118 soybean Glycine max (L.) Merr. accessions from the USDA Soybean Germplasm Collection were screened for resistance to soybean rust (Phakopsora pachyrhizi) at up to ...five locations in the southeastern United States. In 2009, plant introductions (PIs) from maturity groups III through IX were evaluated for relative disease severity and intensity of sporulation from uredinia compared with 12 susceptible cultivars from the same range of maturity groups. Resistance evaluations were based primarily on disease severity and intensity of sporulation from rust pustules. To assess resistance at several nurseries, a rust index score was calculated from the severity and sporulation ratings. Many of the PIs were moderately to highly resistant at the 2009 locations between Alabama and South Carolina, but the P. pachyrhizi population in Bossier City, LA, was virulent on most of those accessions. The 2011 rating data from Quincy, FL, indicated an increase in the virulence of the pathogen there since 2009, and this trend was observed again in 2012. In contrast, many of the same PIs developed substantially less soybean rust in Attapulgus, GA, in 2012. Despite the comparatively greater disease that many accessions had in Louisiana in 2009 and in Quincy in 2011 and 2012, at least 78 PIs were resistant in Georgia in 2012, and 20 of those were at least moderately resistant in both Florida and Georgia that year. No accessions were immune to rust at all of the nurseries, but PI 200492 (Rpp1), PI 547875 (a backcross line with Rpp1), and PI 567102B (Rpp6) were the most resistant of the accessions with named resistance genes and were among the most resistant accessions overall. Among the most resistant accessions with unknown resistance genes, PI 416826A, PI 417125, PI 567034, and PI 567104B consistently had effective levels of resistance in different locations and years. Information about the most resistant PIs and their reactions to soybean rust infection across years and locations will be useful for the development of rust‐resistant soybean cultivars in the United States.
We analyze the parsec-scale jet kinematics from 2007 June to 2018 December of a sample of \(\gamma\)-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43 GHz under the ...VLBA-BU-BLAZAR program. We implement a novel piece-wise linear fitting method to derive the kinematics of 521 distinct emission knots from a total of 3705 total intensity images in 22 quasars, 13 BL Lacertae objects, and 3 radio galaxies. Apparent speeds of these components range from \(0.01c\) to \(78c\), and 18.6\% of knots (other than the "core") are quasi-stationary. One-fifth of moving knots exhibit non-ballistic motion, with acceleration along the jet within 5 pc of the core (projected) and deceleration farther out. These accelerations occur mainly at locations coincident with quasi-stationary features. We calculate the physical parameters of 273 knots with statistically significant motion, including their Doppler factors, Lorentz factors, and viewing angles. We determine the typical values of these parameters for each jet and the average for each subclass of active galactic nuclei. We investigate the variability of the position angle of each jet over the ten years of monitoring. The fluctuations in position of the quasi-stationary components in radio galaxies tend to be parallel to the jet, while no directional preference is seen in the components of quasars and BL Lacertae objects. We find a connection between \(\gamma\)-ray states of blazars and their parsec-scale jet properties, with blazars with brighter 43 GHz cores typically reaching higher \(\gamma\)-ray maxima during flares.
We present multi-epoch optical spectra of the \(\gamma\)-ray bright blazar 1156+295 (4C +29.45, Ton 599) obtained with the 4.3~m Lowell Discovery Telescope. During a multi-wavelength outburst in late ...2017, when the \(\gamma\)-ray flux increased to \(2.5\times 10^{-6} \; \rm phot\; cm^{-2}\; s^{-1}\) and the quasar was first detected at energies \(\geq100\) GeV, the flux of the Mg II \(\lambda 2798\) emission line changed, as did that of the Fe emission complex at shorter wavelengths. These emission line fluxes increased along with the highly polarized optical continuum flux, which is presumably synchrotron radiation from the relativistic jet, with a relative time delay of \(\lesssim2\) weeks. This implies that the line-emitting clouds lie near the jet, which points almost directly toward the line of sight. The emission-line radiation from such clouds, which are located outside the canonical accretion-disk related broad-line region, may be a primary source of seed photons that are up-scattered to \(\gamma\)-ray energies by relativistic electrons in the jet.
The quasar 3C454.3 underwent a uniquely-structured multi-frequency outburst in June 2016. The blazar was observed in the optical \(R\) band by several ground-based telescopes in photometric and ...polarimetric modes, at \(\gamma\)-ray frequencies by the \emph{Fermi}\ Large Area Telescope, and at 43 GHz with the Very Long Baseline Array. The maximum flux density was observed on 2016 June 24 at both optical and \(\gamma\)-ray frequencies, reaching \(S^\mathrm{max}_\mathrm{opt}=18.91\pm0.08\) mJy and \(S_\gamma^\mathrm{max} =22.20\pm0.18\times10^{-6}\) ph cm\(^{-2}\) s\(^{-1}\), respectively. The June 2016 outburst possessed a precipitous decay at both \(\gamma\)-ray and optical frequencies, with the source decreasing in flux density by a factor of 4 over a 24-hour period in \(R\) band. Intraday variability was observed throughout the outburst, with flux density changes between 1 and 5 mJy over the course of a night. The precipitous decay featured statistically significant quasi-periodic micro-variability oscillations with an amplitude of \(\sim 2\)-\(3\%\) about the mean trend and a characteristic period of 36 minutes. The optical degree of polarization jumped from \(\sim3\%\) to nearly 20\% during the outburst, while the position angle varied by \(\sim120\degr\). A knot was ejected from the 43 GHz core on 2016 Feb 25, moving at an apparent speed \(v_\mathrm{app}=20.3c\pm0.8c\). From the observed minimum timescale of variability \(\tau_\mathrm{opt}^\mathrm{min}\approx2\) hr and derived Doppler factor \(\delta=22.6\), we find a size of the emission region \(r\lesssim2.6\times10^{15}\) cm. If the quasi-periodic micro-variability oscillations are caused by periodic variations of the Doppler factor of emission from a turbulent vortex, we derive a rotational speed of the vortex \(\sim0.2c\).
Oocytes are stockpiled with proteins and mRNA that are required to drive the initial mitotic divisions of embryogenesis. But are there proteins specific to meiosis whose levels must be decreased to ...begin embryogenesis properly? The Drosophila protein Cortex (Cort) is a female, meiosis-specific activator of the Anaphase Promoting Complex/Cyclosome (APC/C), an E3 ubiquitin ligase. We performed immunoprecipitation of Cortex followed by mass spectrometry, and identified the Polo kinase inhibitor Matrimony (Mtrm) as a potential interactor with Cort. In vitro binding assays showed Mtrm and Cort can bind directly. We found Mtrm protein levels to be reduced dramatically during the oocyte-to-embryo transition, and this downregulation did not take place in cort mutant eggs, consistent with Mtrm being a substrate of APC(Cort). We showed that Mtrm is subject to APC(Cort)-mediated proteasomal degradation and have identified a putative APC/C recognition motif in Mtrm that when mutated partially stabilized the protein in the embryo. Furthermore, overexpression of Mtrm in the early embryo caused aberrant nuclear divisions and developmental defects, and these were enhanced by decreasing levels of active Polo. These data indicate APC(Cort) ubiquitylates Mtrm at the oocyte-to-embryo transition, thus preventing excessive inhibition of Polo kinase activity due to Mtrm's presence.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
