219 research outputs found
Immunohistochemical characteristics of porcine intrahepatic nerves under physiological conditions and after bisphenol A administration
Background: The neurochemistry of hepatic nerve fibres was investigated in large animal models after dietary exposure to the endocrine disrupting compound known as bisphenol A (BPA).
Materials and methods: Antibodies against neuronal peptides were used to study changes in hepatic nerve fibres after exposure to BPA at varying concentrations using standard immunofluorescence techniques. The neuropeptides investigated were substance P (SP), galanin (GAL), pituitary adenylate cyclase activating polypeptide (PACAP), calcitonin gene regulated peptide (CGRP) and cocaine and amphetamine regulated transcript (CART). Immunoreactive nerve fibres were counted in multiple sections of the liver and among multiple animals at varying exposure levels. The data was pooled and presented as mean ± standard error of the mean.
Results: It was found that all of the nerve fibres investigated showed upregulation of these neural markers after BPA exposure, even at exposure levels currently considered to be safe. These results show very dramatic increases in nerve fibres containing the above-mentioned neuropeptides and the altered neurochemical levels may be causing a range of pathophysiological states if the trend of over-expression is extrapolated to developing humans.
Conclusions: This may have serious implications for children and young adults who are exposed to this very common plastic polymer, if the same trends are occurring in humans
A New Constraint on the Escape Fraction in Distant Galaxies Using Gamma-ray Burst Afterglow Spectroscopy
We describe a new method to measure the escape fraction fesc of ionizing
radiation from distant star-forming galaxies using the afterglow spectra of
long-duration gamma-ray bursts (GRBs). Optical spectra of GRB afterglows allow
us to evaluate the optical depth of the host ISM, according to the neutral
hydrogen column density N(HI) observed along the sightlines toward the
star-forming regions where the GRBs are found. Different from previous effort
in searching for faint, transmitted Lyman continuum photons, our method is not
subject to background subtraction uncertainties and does not require prior
knowledge of either the spectral shape of the host galaxy population or the IGM
Lya forest absorption along these GRB sightlines. Because most GRBs occur in
sub-L_* galaxies, our study also offers the first constraint on fesc for
distant low-mass galaxies that dominate the cosmic luminosity density. We have
compiled a sample of 27 GRBs at redshift z>2 for which the underlying N(HI) in
the host ISM are known. These GRBs together offer a statistical sampling of the
integrated optical depth to ionizing photons along random sightlines from
star-forming regions in the host galaxies, and allow us to estimate the mean
escape fraction averaged over different viewing angles. We find
=0.02\pm 0.02 and place a 95% c.l. upper limit <= 0.075 for these
hosts. We discuss possible biases of our approach and implications of the
result. Finally, we propose to extend this technique for measuring at
z~0.2 using spectra of core-collapse supernovae.Comment: Five journal pages, including one figure; ApJL in pres
The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20
Gamma-ray bursts are the most luminous explosions that we can witness in the
Universe. Studying the most extreme cases of these phenomena allows us to
constrain the limits for the progenitor models. In this Letter, we study the
prompt emission, afterglow, and host galaxy of GRB 120624B, one of the
brightest GRBs detected by Fermi, to derive the energetics of the event and
characterise the host galaxy in which it was produced. Following the
high-energy detection we conducted a multi-wavelength follow-up campaign,
including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray
observations from the Chandra X-ray Observatory and at
sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was
performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the
burst and determine a redshift of z = 2.1974 +/- 0.0002 through the
identification of emission lines of [OII], [OIII] and H-alpha from the host
galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54
erg, amongst the most luminous ever detected. The observations of the afterglow
indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2
< 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/-
6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B
is hosted by a luminous galaxy, which we also proof to be compact, with a very
intense star formation. It is one of the most luminous host galaxies associated
with a GRB, showing that the host galaxies of long GRBs are not always blue
dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
Superluminous supernovae (SLSNe) are very bright explosions that were only
discovered recently and that show a preference for occurring in faint dwarf
galaxies. Understanding why stellar evolution yields different types of stellar
explosions in these environments is fundamental in order to both uncover the
elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In
this paper, we present the first results of our project to study SUperluminous
Supernova Host galaxIES, focusing on the sample for which we have obtained
spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in
our sample) occur in a class of galaxies that is known as Extreme Emission Line
Galaxies (EELGs). The probability of this happening by chance is negligible and
we therefore conclude that the extreme environmental conditions and the SLSN
phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more
massive, more metal-rich galaxies with softer radiation fields. Therefore, if
SLSNe-II constitute a uniform class, their progenitor systems are likely
different from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average,
not found in as extreme environments as H-poor SLSNe. We propose that H-poor
SLSNe result from the very first stars exploding in a starburst, even earlier
than GRBs. This might indicate a bottom-light initial mass function in these
systems. SLSNe present a novel method of selecting candidate EELGs independent
of their luminosity.Comment: Published version, matches proofs. Accepted 2015 February 13. 23
pages, 8 figures, 4 tables. Minor changes with respect to previous versio
Discovery of the broad-lined Type Ic SN 2013cq associated with the very energetic GRB 130427A
Long-duration gamma-ray bursts (GRBs) at z < 1 are in most cases found to be
accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The
highest-energy GRBs are mostly located at higher redshifts, where the
associated SNe are hard to detect observationally. Here we present early and
late observations of the optical counterpart of the very energetic GRB 130427A.
Despite its moderate redshift z = 0.3399+/-0.0002, GRB 130427A is at the high
end of the GRB energy distribution, with an isotropic-equivalent energy release
of Eiso ~ 9.6x10^53 erg, more than an order of magnitude more energetic than
other GRBs with spectroscopically confirmed SNe. In our dense photometric
monitoring, we detect excess flux in the host-subtracted r-band light curve,
consistent with what expected from an emerging SN, ~0.2 mag fainter than the
prototypical SN 1998bw. A spectrum obtained around the time of the SN peak
(16.7 days after the GRB) reveals broad undulations typical of SNe Ic-BL,
confirming the presence of a SN, designated SN 2013cq. The spectral shape and
early peak time are similar to those of the high expansion velocity SN 2010bh
associated with GRB 100316D. Our findings demonstrate that high-energy
long-duration GRBs, commonly detected at high redshift, can also be associated
with SNe Ic-BL, pointing to a common progenitor mechanism.Comment: 12 pages, 4 figures, 1 table, accepted for publication in Ap
Recommended from our members
Telerehabilitation Training to Facilitate Improved Reading Ability with New Magnification Devices for Low Vision
SignificanceThis pilot study provides some insight about the potential benefits of telerehabilitation training to improve the reading ability of adults with low vision using magnifiers, to spur future work with larger groups. Telerehabilitation services can be implemented clinically to facilitate access to follow-up care for low vision.PurposeA recent Cochrane systematic review revealed that there are no published visual function outcomes for telerehabilitation with handheld magnification devices for low vision; thus, this study aimed to provide evidence for its preliminary efficacy.MethodsOne to 4 months after receiving a new magnification device (i.e., handheld or stand optical magnifier or portable electronic magnifier), 14 adult low vision patients (with any visual acuity level or ocular diagnosis) received two training sessions at home via telerehabilitation with their vision rehabilitation provider located remotely in-office. Telerehabilitation included a loaner smartphone for Zoom videoconferencing with remote control access software. The Minnesota Low-Vision Reading Test was administered during each of the telerehabilitation sessions to assess near reading (acuity and speed) with the new magnifier.ResultsMean reading acuity with the magnifier was 0.17 logMAR across subjects before training at telerehabilitation session 1, which significantly improved to 0.09 on average a few weeks later at telerehabilitation session 2 (95%confidence interval, -0.001 to -0.16; P = .047). Logarithm reading speed with the magnifier for the reading acuity level at session 1 improved significantly by 0.18 log words per minute on average for the same text size at session 2 (95% confidence interval, 0.06 to 0.29; P = .002). With the magnifier at session 2, 71% of participants gained at least 0.1 log unit in reading acuity, and half improved by >0.01 in log reading speed; all participants with increased reading speed also improved in reading acuity ( P = .02).ConclusionsThese preliminary data support that telerehabilitation can enhance reading ability and efficiency with newly prescribed magnifiers as an alternative option to in-office vision rehabilitation
Low-Luminosity Gamma-Ray Bursts as a Distinct GRB Population:A Firmer Case from Multiple Criteria Constraints
The intriguing observations of Swift/BAT X-ray flash XRF 060218 and the
BATSE-BeppoSAX gamma-ray burst GRB 980425, both with much lower luminosity and
redshift compared to other observed bursts, naturally lead to the question of
how these low-luminosity (LL) bursts are related to high-luminosity (HL)
bursts. Incorporating the constraints from both the flux-limited samples
observed with CGRO/BATSE and Swift/BAT and the redshift-known GRB sample, we
investigate the luminosity function for both LL- and HL-GRBs through
simulations. Our multiple criteria, including the log N - log P distributions
from the flux-limited GRB sample, the redshift and luminosity distributions of
the redshift-known sample, and the detection ratio of HL- and LL- GRBs with
Swift/BAT, provide a set of stringent constraints to the luminosity function.
Assuming that the GRB rate follows the star formation rate, our simulations
show that a simple power law or a broken power law model of luminosity function
fail to reproduce the observations, and a new component is required. This
component can be modeled with a broken power, which is characterized by a sharp
increase of the burst number at around L < 10^47 erg s^-1}. The lack of
detection of moderate-luminosity GRBs at redshift ~0.3 indicates that this
feature is not due to observational biases. The inferred local rate, rho_0, of
LL-GRBs from our model is ~ 200 Gpc^-3 yr^-1 at ~ 10^47 erg s^-1, much larger
than that of HL-GRBs. These results imply that LL-GRBs could be a separate GRB
population from HL-GRBs. The recent discovery of a local X-ray transient
080109/SN 2008D would strengthen our conclusion, if the observed non-thermal
emission has a similar origin as the prompt emission of most GRBs and XRFs.Comment: 22 pages, 9 figures, 3 tables; MNRAS, in press; Updated analysis and
figure
Looking Into the Fireball: ROTSE-III and Swift Observations of Early GRB Afterglows
We report on a complete set of early optical afterglows of gamma-ray bursts
(GRBs) obtained with the ROTSE-III telescope network from March 2005 through
June 2007. This set is comprised of 12 afterglows with early optical and
Swift/XRT observations, with a median ROTSE-III response time of 45 s after the
start of gamma-ray emission (8 s after the GCN notice time). These afterglows
span four orders of magnitude in optical luminosity, and the contemporaneous
X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray
flares, the broadband synchrotron spectra show that the optical and X-ray
emission originate in a common region, consistent with predictions of the
external forward shock in the fireball model. However, the fireball model is
inadequate to predict the temporal decay indices of the early afterglows, even
after accounting for possible long-duration continuous energy injection. We
find that the optical afterglow is a clean tracer of the forward shock, and we
use the peak time of the forward shock to estimate the initial bulk Lorentz
factor of the GRB outflow, and find 100<Gamma_0<1000, consistent with
expectations.Comment: 31 pages, 5 figures, submitted to Ap
Stress hormones or general well-being are not altered in immune-deficient mice lacking either T- and B- lymphocytes or Interferon gamma signaling if kept under specific pathogen free housing conditions
It is controversially discussed whether immune-deficient mice experience severity in the absence of infection. Because a comprehensive analysis of the well-being of immune-deficient mice under specific pathogen free conditions is missing, we used a multi-parametric test analyzing, corticosterone, weight, nest building and facial expression over a period of 9 month to determine the well-being of two immune-deficient mouse lines (recombination activating gene 2- and interferon gamma receptor-deficient mice). We do not find evidence for severity when comparing immune-deficient mice to their heterozygous immune-competent littermates. Our data challenge the assumption that immune-deficiency per se regardless of housing conditions causes severity. Based on our study we propose to use objective non-invasive parameters determined by laboratory animal science for decisions concerning severity of immune-deficient mice
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