98 research outputs found
Sporadic appearance of paralytic spongiform neurodegeneration in a colony of inbred mice is associated with CNS retrovirus expression
Abstract
Exogenous and endogenous retroviruses (RV) have been known to induce vacuolar central nervous system neuropathology. Two mice which were juvenile inbred Rocky Mountain White (IRW), showed signs of spontaneous degenerate motor neuron disease. Signs included wasting, unkempt fur, adduction reflex upon tail elevation, kyphosis, and stilted gait by postnatal day 18 (P18). Brains and spinal cords were examined with H&E staining and stained with a broadly reactive retrovirus antibody. When compared to brains of mice with normal vacuolar pathology as well as mice infected with prototypic non-neurovirulent RV, Fr57E and prototypic neurovirulent RV FrCasE, the subject showed less severity but were clearly distinguishable from the non-virulent RV. Spongiosis was seen in the motor areas in both mice. Immunohistochemical staining showed reactive retroviral antibodies, which is evidence of viral protein expression in glia and endothelia. The type of RV present will take further investigation. The ability for spontaneous appearance of competent RV replication arising from endogenous RV in mice that also can induce neurological disease are highlighted. Similar spontaneous retroviral gene expression in humans have been attributed to diseases such as multiple sclerosis and amyotrophic lateral sclerosis. Understanding the viral re-emergence will shed light on the cause of human and animal retroviral disease
Synthetic Mudscapes: Human Interventions in Deltaic Land Building
In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to
mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta
landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of
measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are
denied by traditional inhabitation.
Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the
foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further
inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined
by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The
social, economic, and ecological evolution of the region are defended by an expanded web of growing land
A deep survey of short GRB host galaxies over : implications for offsets, redshifts, and environments
A significant fraction (30\%) of well-localized short gamma-ray bursts
(sGRBs) lack a coincident host galaxy. This leads to two main scenarios:
\textit{i}) that the progenitor system merged outside of the visible light of
its host, or \textit{ii}) that the sGRB resided within a faint and distant
galaxy that was not detected by follow-up observations. Discriminating between
these scenarios has important implications for constraining the formation
channels of neutron star mergers, the rate and environments of gravitational
wave sources, and the production of heavy elements in the Universe. In this
work, we present the results of our observing campaign targeted at 31 sGRBs
that lack a putative host galaxy. Our study effectively doubles the sample of
well-studied sGRB host galaxies, now totaling 72 events of which lack a
coincident host galaxy to deep limits (\,\, or
\,\, AB mag), and represents the largest homogeneously
selected catalog of sGRB offsets to date. We find that 70\% of sub-arcsecond
localized sGRBs occur within 10 kpc of their host's nucleus, with a median
projected physical offset of kpc. Using this larger population, we
discover a redshift evolution in the locations of sGRBs: bursts at low-
occur at larger offsets compared to those at \,\,.
Furthermore, we find evidence for a sample of hostless sGRBs at
\,\, that are indicative of a larger high- population,
further constraining the sGRB redshift distribution and disfavoring log-normal
delay time models.Comment: Submitted to MNRAS. 39 pages, 18 Figures, 4 Table
The CGM-GRB Study. II. Outflow-Galaxy Connection at z similar to 2-6
We use a sample of 27 gamma-ray bursts (GRBs) at redshift z = 2-6 to probe the outflows in their respective host galaxies (log(M ∗/M ⊙) ∼9-11) and search for possible relations between the outflow properties and those of the host galaxies, such as M ∗, the star formation rate (SFR), and the specific SFR (sSFR). First, we consider three outflow properties: outflow column density (N out), maximum outflow velocity (V max), and normalized maximum velocity (V norm = V max/V circ,halo, where V circ,halo is the halo circular velocity). We observe clear trends of N out and V max with increasing SFR in high-ion-traced outflows, with a stronger (>3σ) V max-SFR correlation. We find that the estimated mass outflow rate and momentum flux of the high-ion outflows scale with SFR and can be supported by the momentum imparted by star formation (supernovae and stellar winds). The kinematic correlations of high-ion-traced outflows with SFR are similar to those observed for star-forming galaxies at low redshifts. The correlations with SFR are weaker in low-ion outflows. This, along with the lower detection fraction in low-ion outflows, indicates that the outflow is primarily high-ion dominated. We also observe a strong (>3σ) trend of normalized velocity (V norm) decreasing with halo mass and increasing with sSFR, suggesting that outflows from low-mass halos and high-sSFR galaxies are most likely to escape and enrich the outer circumgalactic medium (CGM) and intergalactic medium with metals. By comparing the CGM-GRB stacks with those of starbursts at z ∼2 and z ∼0.1, we find that over a broad redshift range, the outflow strength strongly depends on the main-sequence offset at the respective redshifts, rather than simply the SFR
A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A
We report observations of the optical counterpart of the long gamma-ray burst
(LGRB) GRB 221009A. Due to the extreme rarity of being both nearby () and highly energetic ( erg), GRB
221009A offers a unique opportunity to probe the connection between massive
star core collapse and relativistic jet formation across a very broad range of
-ray properties. Adopting a phenomenological power-law model for the
afterglow and host galaxy estimates from high-resolution Hubble Space Telescope
imaging, we use Bayesian model comparison techniques to determine the
likelihood of an associated SN contributing excess flux to the optical light
curve. Though not conclusive, we find moderate evidence
() for the presence of an additional component arising
from an associated supernova, SN 2022xiw, and find that it must be
substantially fainter ( 67% as bright at the 99% confidence interval) than
SN 1998bw. Given the large and uncertain line-of-sight extinction, we attempt
to constrain the supernova parameters (, ,
and ) under several different assumptions with respect to the
host galaxy's extinction. We find properties that are broadly consistent with
previous GRB-associated SNe: - ,
- , and - . We note that these properties are weakly
constrained due to the faintness of the supernova with respect to the afterglow
and host emission, but we do find a robust upper limit on the of
. Given the tremendous range in isotropic
gamma-ray energy release exhibited by GRBs (7 orders of magnitude), the SN
emission appears to be decoupled from the central engine in these systems.Comment: 18 pages, accepted to ApJL, 4 tables, 5 figures. Updated abstract in
Previe
A lanthanide-rich kilonova in the aftermath of a long gamma-ray burst
Kilonovae are a rare class of astrophysical transients powered by the
radioactive decay of nuclei heavier than iron, synthesized in the merger of two
compact objects. Over the first few days, the kilonova evolution is dominated
by a large number of radioactive isotopes contributing to the heating rate. On
timescales of weeks to months, its behavior is predicted to differ depending on
the ejecta composition and merger remnant. However, late-time observations of
known kilonovae are either missing or limited. Here we report observations of a
luminous red transient with a quasi-thermal spectrum, following an unusual
gamma-ray burst of long duration. We classify this thermal emission as a
kilonova and track its evolution up to two months after the burst. At these
late times, the recession of the photospheric radius and the rapidly-decaying
bolometric luminosity () support the
recombination of lanthanide-rich ejecta as they cool.Comment: 47 pages, 14 figures, 9 tables; submitted; a minor typo fixe
A structured jet explains the extreme GRB 221009A
Long duration gamma-ray bursts (GRBs) are powerful cosmic explosions,
signaling the death of massive stars. Among them, GRB 221009A is by far the
brightest burst ever observed. Due to its enormous energy
(10 erg) and proximity (0.15), GRB
221009A is an exceptionally rare event that pushes the limits of our theories.
We present multi-wavelength observations covering the first three months of its
afterglow evolution. The X-ray brightness decays as a power-law with slope
, which is not consistent with standard predictions for
jetted emission. We attribute this behavior to a shallow energy profile of the
relativistic jet. A similar trend is observed in other energetic GRBs,
suggesting that the most extreme explosions may be powered by structured jets
launched by a common central engine.Comment: Submitted version. 53 pages, 9 figures, 6 table
A search for optical and near-infrared counterparts of the compact binary merger GW190814
We report on our observing campaign of the compact binary merger GW190814,
detected by the Advanced LIGO and Advanced Virgo detectors on August 14th,
2019. This signal has the best localisation of any observed gravitational wave
(GW) source, with a 90% probability area of 18.5 deg, and an estimated
distance of ~ 240 Mpc. We obtained wide-field observations with the Deca-Degree
Optical Transient Imager (DDOTI) covering 88% of the probability area down to a
limiting magnitude of = 19.9 AB. Nearby galaxies within the high
probability region were targeted with the Lowell Discovery Telescope (LDT),
whereas promising candidate counterparts were characterized through
multi-colour photometry with the Reionization and Transients InfraRed (RATIR)
and spectroscopy with the Gran Telescopio de Canarias (GTC). We use our optical
and near-infrared limits in conjunction with the upper limits obtained by the
community to constrain the possible electromagnetic counterparts associated
with the merger. A gamma-ray burst seen along its jet's axis is disfavoured by
the multi-wavelength dataset, whereas the presence of a burst seen at larger
viewing angles is not well constrained. Although our observations are not
sensitive to a kilonova similar to AT2017gfo, we can rule out high-mass (> 0.1
M) fast-moving (mean velocity >= 0.3c) wind ejecta for a possible
kilonova associated with this merger.Comment: 17 pages, 11 figures, 5 tables; updated acknowledgement section.
Accepted for publication in MNRAS (10 September 2020
Updated sesame genome assembly and fine mapping of plant height and seed coat color QTLs using a new high-density genetic map
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