521 research outputs found
Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations
Our Galaxy hosts the annihilation of a few low-energy
positrons every second. Radioactive isotopes capable of supplying such
positrons are synthesised in stars, stellar remnants, and supernovae. For
decades, however, there has been no positive identification of a main stellar
positron source leading to suggestions that many positrons originate from
exotic sources like the Galaxy's central super-massive black hole or dark
matter annihilation. %, but such sources would not explain the
recently-detected positron signal from the extended Galactic disk. Here we show
that a single type of transient source, deriving from stellar populations of
age 3-6 Gyr and yielding ~0.03 of the positron emitter Ti, can
simultaneously explain the strength and morphology of the Galactic positron
annihilation signal and the solar system abundance of the Ti decay
product Ca. This transient is likely the merger of two low-mass white
dwarfs, observed in external galaxies as the sub-luminous, thermonuclear
supernova known as SN1991bg-like.Comment: 28 pages main text with 4 figures in preprint style; 26 pages of
Supplementary Informatio
Pathways to Highly Oxidized Products in the Delta 3-Carene + OH System
Oxidation of the monoterpene Delta 3-carene (C10H16) is a potentially important and understudied source of atmospheric secondary organic aerosol (SOA). We present chamber-based measurements of speciated gas and particle phases during photochemical oxidation of Delta 3-carene. We find evidence of highly oxidized organic molecules (HOMs) in the gas phase and relatively low-volatility SOA dominated by C-7-C-10 species. We then use computational methods to develop the first stages of a Delta 3-carene photochemical oxidation mechanism and explain some of our measured compositions. We find that alkoxy bond scission of the cyclohexyl ring likely leads to efficient HOM formation, in line with previous studies. We also find a surprising role for the abstraction of primary hydrogens from methyl groups, which has been calculated to be rapid in the alpha-pinene system, and suggest more research is required to determine if this is more general to other systems and a feature of autoxidation. This work develops a more comprehensive view of Delta 3-carene photochemical oxidation products via measurements and lays out a suggested mechanism of oxidation via computationally derived rate coefficients.Peer reviewe
Toll-like Receptor 3 L412F Polymorphism Promotes a Persistent Clinical Phenotype in Pulmonary Sarcoidosis
Background: Sarcoidosis is a multisystemic disorder of unknown etiology, characterised by the
presence of non-caseating granulomas in target organs. In ninety percent of cases, there is
thoracic involvement. Fifty to seventy percent of pulmonary sarcoidosis patients will experience
acute, self-limiting disease. For the subgroup of patients who develop persistent disease, no
targeted therapy is currently available.
Aim: To investigate the potential of the single nucleotide polymorphism (SNP), Toll-like
receptor 3 Leu412Phe (TLR3 L412F; rs3775291), as a causative factor in the development of,
and in disease persistence in pulmonary sarcoidosis. To investigate the functionality of TLR3
L412F in vitro in primary human lung fibroblasts from pulmonary sarcoidosis patients.
Methods: Cohorts of Irish sarcoidosis patients (n=228), healthy Irish controls (n = 263) and a
secondary cohort of American sarcoidosis patients (n=123) were genotyped for TLR3 L412F.
Additionally, the effect of TLR3 L412F in primary lung fibroblasts from pulmonary sarcoidosis patients was quantitated following TLR3 activation in the context of cytokine and type I interferon production, TLR3 expression, and apoptotic- and fibroproliferative-responses.
Results: We report a significant association between TLR3 L412F and persistent clinical disease in two cohorts of Irish and American Caucasians with pulmonary sarcoidosis. Furthermore, activation of TLR3 in primary lung fibroblasts from 412F-homozygous pulmonary sarcoidosis patients resulted in reduced IFN-â and TLR3 expression, reduced apoptosis- and dysregulated fibroproliferative-responses compared with TLR3 wild-type patients.
Conclusions: This study identifies defective TLR3 function as a previously unidentified factor in persistent clinical disease in pulmonary sarcoidosis and reveals TLR3 L412F as a candidate biomarker
Indoor Air Quality
This is a report from the Air Quality Expert Group to the Department for Environment, Food and Rural Affairs; Scottish Government; Welsh Government; and Department of Agriculture, Environment and Rural Affairs in Northern Ireland, on indoor air quality in the UK. The information contained within this report represents a review of the understanding and evidence available at the time of writing
Comparison of serious inhaler technique errors made by device-naïve patients using three different dry powder inhalers: a randomised, crossover, open-label study
Background: Serious inhaler technique errors can impair drug delivery to the lungs. This randomised, crossover, open-label study evaluated the proportion of patients making predefined serious errors with Pulmojet compared with Diskus and Turbohaler dry powder inhalers. Methods: Patients ≥18 years old with asthma and/or COPD who were current users of an inhaler but naïve to the study devices were assigned to inhaler technique assessment on Pulmojet and either Diskus or Turbohaler in a randomised order. Patients inhaled through empty devices after reading the patient information leaflet. If serious errors potentially affecting dose delivery were recorded, they repeated the inhalations after watching a training video. Inhaler technique was assessed by a trained nurse observer and an electronic inhalation profile recorder. Results: Baseline patient characteristics were similar between randomisation arms for the Pulmojet-Diskus (n = 277) and Pulmojet-Turbohaler (n = 144) comparisons. Non-inferiority in the proportions of patients recording no nurse-observed serious errors was demonstrated for both Pulmojet versus Diskus, and Pulmojet versus Turbohaler; therefore, superiority was tested. Patients were significantly less likely to make ≥1 nurse-observed serious errors using Pulmojet compared with Diskus (odds ratio, 0.31; 95 % CI, 0.19–0.51) or Pulmojet compared with Turbohaler (0.23; 0.12–0.44) after reading the patient information leaflet with additional video instruction, if required. Conclusions These results suggest Pulmojet is easier to learn to use correctly than the Turbohaler or Diskus for current inhaler users switching to a new dry powder inhaler
The Highly Energetic Expansion of SN2010bh Associated with GRB 100316D
We present the spectroscopic and photometric evolution of the nearby (z =
0.059) spectroscopically confirmed type Ic supernova, SN 2010bh, associated
with the soft, long-duration gamma-ray burst (X-ray flash) GRB 100316D.
Intensive follow-up observations of SN 2010bh were performed at the ESO Very
Large Telescope (VLT) using the X-shooter and FORS2 instruments. Owing to the
detailed temporal coverage and the extended wavelength range (3000--24800 A),
we obtained an unprecedentedly rich spectral sequence among the hypernovae,
making SN 2010bh one of the best studied representatives of this SN class. We
find that SN 2010bh has a more rapid rise to maximum brightness (8.0 +/- 1.0
rest-frame days) and a fainter absolute peak luminosity (L_bol~3e42 erg/s) than
previously observed SN events associated with GRBs. Our estimate of the ejected
(56)Ni mass is 0.12 +/- 0.02 Msun. From the broad spectral features we measure
expansion velocities up to 47,000 km/s, higher than those of SNe 1998bw (GRB
980425) and 2006aj (GRB 060218). Helium absorption lines He I lambda5876 and He
I 1.083 microm, blueshifted by ~20,000--30,000 km/s and ~28,000--38,000 km/s,
respectively, may be present in the optical spectra. However, the lack of
coverage of the He I 2.058 microm line prevents us from confirming such
identifications. The nebular spectrum, taken at ~186 days after the explosion,
shows a broad but faint [O I] emission at 6340 A. The light-curve shape and
photospheric expansion velocities of SN 2010bh suggest that we witnessed a
highly energetic explosion with a small ejected mass (E_k ~ 1e52 erg and M_ej ~
3 Msun). The observed properties of SN 2010bh further extend the heterogeneity
of the class of GRB supernovae.Comment: 37 pages and 12 figures (one-column pre-print format), accepted for
publication in Ap
Hubble Space Telescope Observations of the Associated Absorption Systems in Q0122+0338
We have studied a spectrum of Q0122+0338 (z = 1.202) obtained by the FOS on
board HST. We present the analysis of three associated absorption systems at z
= 1.207, 1.199 and 1.166. The most complex of these at z = 1.207 shows strong
absorption from the highly ionized transitions of Lyman alpha, Lyman beta, N V,
O VI, Si III, Si IV, and possibly P V. We derive minimal ionic column densities
and compare them with those predicted from numerical photoionization models. We
find that conditions in the absorbing gas are consistent with an absorber with
metallicity twice solar and a total absorbing column density of N(H) = 2*10^19
cm^2. The kinematics of the absorption lines in the z = 1.207 system suggest
that a correlation exists between the relative velocity and the creation
ionization potential energy for each transition. This is evidence that a
complex, multi-component absorber exists. Althought the location of the
absorber is uncertain, we consider the origin of this absorption system using
the available data and discuss how the high-ionization, and high-metallicity
indicate that the absorber may be intrinsic to Q0122+0338.Comment: 16 pages, 5 figures, uses emulateapj.sty, accepted for publication in
Ap
GRB 020410: A Gamma-Ray Burst Afterglow Discovered by its Supernova Light
We present the discovery and monitoring of the optical transient (OT)
associated with GRB 020410. The fading OT was found by Hubble Space Telescope
(HST) observations taken 28 and 65 days after burst at a position consistent
with the X-ray afterglow. Subsequent re-examination of early ground based
observations revealed that a faint OT was present 6 hours after burst,
confirming the source association with GRB 020410. A deep non-detection after
one week requires that the OT re-brightened between day 7 and day 28, and
further late time HST data taken approximately 100 days after burst imply that
it is very red.We compare both the flux and color of the excess with supernova
models and show that the data are best explained by the presence of a Type Ib/c
supernova at a redshift z ~ 0.5, which occured roughly coincident with the day
of GRB.Comment: 23 Pages, 9 figures, submitted to Ap
Progress report no. 4
Statement of responsibility on title-page reads: editors: M.J. Driscoll, D.D. Lanning, I. Kaplan, A.T. Supple ; contributors: A. Alvim, G.J. Brown, J.K. Chan, T.P. Choong, M.J. Driscoll, G. A. Ducat, I.A. Forbes, M.V. Gregory, S.Y. Ho, C.M. Hove, O. K. Kadiroglu, R.J. Kennerley, D.D. Lanning, J.L. Lazewatsky, L. Lederman, A.S. Leveckis, V.A. Miethe, P. A. Scheinert, A.M. Thompson, N.E. Todreas, C.P. Tzanos, and P.J. WoodIncludes bibliographical referencesProgress report; June 30, 1973U.S. Atomic Energy Commission contract: AT(11-1)225
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