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Rana pretiosa
Number of Pages: 4Integrative BiologyGeological Science
Effect of Density on the Population Dynamics of Perognathus Formosus and its Relationships within a Desert Ecosystem
Human B cell lineages associated with germinal centers following influenza vaccination are measurably evolving
The poor efficacy of seasonal influenza virus vaccines is often attributed to pre-existing immunity interfering with the persistence and maturation of vaccine-induced B cell responses. We previously showed that a subset of vaccine-induced B cell lineages are recruited into germinal centers (GCs) following vaccination, suggesting that affinity maturation of these lineages against vaccine antigens can occur. However, it remains to be determined whether seasonal influenza vaccination stimulates additional evolution of vaccine-specific lineages, and previous work has found no significant increase in somatic hypermutation among influenza-binding lineages sampled from the blood following seasonal vaccination in humans. Here, we investigate this issue using a phylogenetic test of measurable immunoglobulin sequence evolution. We first validate this test through simulations and survey measurable evolution across multiple conditions. We find significant heterogeneity in measurable B cell evolution across conditions, with enrichment in primary response conditions such as HIV infection and early childhood development. We then show that measurable evolution following influenza vaccination is highly compartmentalized: while lineages in the blood are rarely measurably evolving following influenza vaccination, lineages containing GC B cells are frequently measurably evolving. Many of these lineages appear to derive from memory B cells. We conclude from these findings that seasonal influenza virus vaccination can stimulate additional evolution of responding B cell lineages, and imply that the poor efficacy of seasonal influenza vaccination is not due to a complete inhibition of vaccine-specific B cell evolution
The Ionized Gas and Nuclear Environment in NGC 3783 V. Variability and Modeling of the Intrinsic Ultraviolet Absorption
We present results on the location, physical conditions, and geometry of the
outflow in the Seyfert 1 galaxy NGC 3783 from a study of the variable intrinsic
UV absorption. Based on 18 observations with HST/STIS and 6 observations with
FUSE, we find: 1) The absorption from the lowest-ionization species in each of
the three strong kinematic components varied inversely with the continuum flux,
indicating the ionization structure responded to changes in the photoionizing
flux over the weekly timescales sampled by our observations. 2) A multi-
component model with an unocculted NLR and separate BLR and continuum
line-of-sight covering factors predicts saturation in several lines, consistent
with the lack of observed variability. 3) Column densities for the individual
metastable levels are measured from the resolved C III *1175 absorption complex
observed in one component. Based on our computed metastable level populations,
the electron density of this absorber is ~3x10^4 cm^-3. Photoionization
modeling results place it at ~25 pc from the central source. 4) Using
time-dependent calculations, we are able to reproduce the detailed variability
observed in this absorber, and derive upper limits on the distances for the
other components of 25-50 pc. 5) The ionization parameters derived for the
higher ionization UV absorbers are consistent with the modeling results for the
lowest-ionization X-ray component, but with smaller total column density. They
have similar pressures as the three X-ray ionization components. These results
are consistent with an inhomogeneous wind model for the outflow in NGC 3783. 6)
Based on the predicted emission-line luminosities, global covering factor
constraints, and distances derived for the UV absorbers, they may be identified
with emission- line gas observed in the inner NLR of AGNs. (abridged)Comment: 30 pages, 18 figures (7 color), emulateapj, accepted for publication
in The Astrophysical Journa
The Ionized Gas and Nuclear Environment in NGC 3783. I. Time-Averaged 900 ks Chandra Grating Spectroscopy
We present results from a 900 ks exposure of NGC 3783 with the High-Energy
Transmission Grating Spectrometer on board the Chandra X-ray Observatory. The
resulting X-ray spectrum has the best combination of signal-to-noise and
resolution ever obtained for an AGN. This spectrum reveals absorption lines
from H-like and He-like ions of N, O, Ne, Mg, Al, Si, and S. There are also
possible absorption lines from H-like and He-like Ar and Ca. We also identify
inner-shell absorption from lower-ionization ions such as Si_VII-Si_XII and
S_XII-S_XIV. The iron absorption spectrum is very rich; L-shell lines of
Fe_XVII-Fe_XXIV are detected, strong complex of M-shell lines, and probable
resonance lines from Fe_XXV. The absorption lines are blueshifted relative to
the systemic velocity by a mean velocity of -590+-150 km/s. We resolve many of
the absorption lines, and their mean FWHM is 820+-280 km/s. We do not find
correlations between the velocity shifts or the FWHMs with the ionization
potentials of the ions. Most absorption lines show asymmetry, having more
extended blue wings than red wings. In O_VII we have resolved this asymmetry to
be from an additional absorption system at ~ -1300 km/s. The two X-ray
absorption systems are consistent in velocity shift and FWHM with the ones
identified in the UV lines of C IV, N V, and H I. Equivalent width measurements
for all lines are given and column densities are calculated for several ions.
We resolve the narrow Fe_K\alpha line at 6398.2+-3.3 eV to have a FWHM of
1720+-360 km/s, which suggests that this narrow line may be emitted from the
outer part of the broad line region or the inner part of the torus. We also
detect a `Compton shoulder' redward of the narrow Fe_K\alpha line which
indicates that it arises in cold, Compton-thick gas.Comment: 19 pages, 12 figures (2 in color), emulateapj5, accepted for
publication in The Astrophysical Journal Supplement
An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
Quasars are the most luminous non-transient objects known and as a result
they enable studies of the Universe at the earliest cosmic epochs. Despite
extensive efforts, however, the quasar ULAS J1120+0641 at z=7.09 has remained
the only one known at z>7 for more than half a decade. Here we report
observations of the quasar ULAS J134208.10+092838.61 (hereafter J1342+0928) at
redshift z=7.54. This quasar has a bolometric luminosity of 4e13 times the
luminosity of the Sun and a black hole mass of 8e8 solar masses. The existence
of this supermassive black hole when the Universe was only 690 million years
old---just five percent of its current age---reinforces models of early
black-hole growth that allow black holes with initial masses of more than about
1e4 solar masses or episodic hyper-Eddington accretion. We see strong evidence
of absorption of the spectrum of the quasar redwards of the Lyman alpha
emission line (the Gunn-Peterson damping wing), as would be expected if a
significant amount (more than 10 per cent) of the hydrogen in the intergalactic
medium surrounding J1342+0928 is neutral. We derive a significant fraction of
neutral hydrogen, although the exact fraction depends on the modelling.
However, even in our most conservative analysis we find a fraction of more than
0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are
probing well within the reionization epoch of the Universe.Comment: Updated to match the final journal versio
The Ionized Gas and Nuclear Environment in NGC 3783. IV. Variability and Modeling of the 900 ks CHANDRA Spectrum
We present a detailed spectral analysis of the data obtained from NGC 3783
during the period 2000-2001 using Chandra. This analysis leads us to the
following results. 1) NGC 3783 fluctuated in luminosity by a factor ~1.5 during
individual observations (~170 ks duration). These fluctuations were not
associated with significant spectral variations. 2) On a longer time scale
(20-120 days), we found the source to exhibit two very different spectral
shapes. The main difference between these can be well-described by the
appearance and disappearance of a spectral component that dominates the
underlying continuum at the longest wavelengths. The spectral variations are
not related to the brightening or the fading of the continuum at short
wavelengths in any simple way. 3) The appearance of the soft continuum
component is consistent with being the only spectral variation, and there is no
need to invoke changes in the opacity of the absorbers. 4) Photoionization
modeling indicates that a combination of three ionized absorbers, each split
into two kinematic components, can explain the strengths of almost all the
absorption lines and bound-free edges. All three components are thermally
stable and seem to have the same gas pressure. 5) The only real discrepancy
between our model and the observations concerns the range of wavelengths
absorbed by the iron M-shell UTA feature. This most likely arises as the result
of our underestimation of the poorly-known dielectronic recombination rates
appropriate for these ions. 6) The lower limit on the distance of the absorbing
gas in NGC 3783 is between 0.2 and 3.2 pc. The assumption of pressure
equilibrium imposes an upper limit of about 25 pc on the distance of the
least-ionized component from the central source. (abridged)Comment: 16 pages, 12 figures (9 in color), emulateapj5, accepted for
publication in The Astrophysical Journa
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