1,039 research outputs found
Adaption of the ex vivo mycobacterial growth inhibition assay for use with murine lung cells.
In the absence of a correlate(s) of protection against human tuberculosis and a validated animal model of the disease, tools to facilitate vaccine development must be identified. We present an optimised ex vivo mycobacterial growth inhibition assay (MGIA) to assess the ability of host cells within the lung to inhibit mycobacterial growth, including Bacille Calmette-Guérin (BCG) and Mycobacterium tuberculosis (MTB) Erdman. Growth of BCG was reduced by 0.39, 0.96 and 0.73 log10 CFU following subcutaneous (s.c.) BCG, intranasal (i.n.) BCG, or BCG s.c. + mucosal boost, respectively, versus naïve mice. Comparatively, a 0.49 (s.c.), 0.60 (i.n.) and 0.81 (s.c. + mucosal boost) log10 reduction in MTB CFU was found. A BCG growth inhibitor, 2-thiophenecarboxylic acid hydrazide (TCH), was used to prevent quantification of residual BCG from i.n. immunisation and allow accurate MTB quantification. Using TCH, a further 0.58 log10 reduction in MTB CFU was revealed in the i.n. group. In combination with existing methods, the ex vivo lung MGIA may represent an important tool for analysis of vaccine efficacy and the immune mechanisms associated with vaccination in the organ primarily affected by MTB disease
The bumpy light curve of supernova iPTF13z
A Type IIn supernova (SN) is dominated by the interaction of SN ejecta with
the circumstellar medium (CSM). Some SNe IIn (e.g., SN 2006jd) have episodes of
re-brightening ("bumps") in their light curves. We present iPTF13z, a SN IIn
discovered by the intermediate Palomar Transient Factory (iPTF) and
characterised by several bumps in its light curve. We analyse this peculiar
behaviour trying to infer the properties of the CSM and of the SN explosion, as
well as the nature of its progenitor star. We obtained multi-band optical
photometry for over 1000 days after discovery with the P48 and P60 telescopes
at Palomar Observatory. We obtained low-resolution optical spectra in the same
period. We did an archival search for progenitor outbursts. We analyse our
photometry and spectra, and compare iPTF13z to other SNe IIn. A simple
analytical model is used to estimate properties of the CSM. iPTF13z was a SN
IIn showing a light curve with five bumps during its decline phase. The bumps
had amplitudes between 0.4 and 0.9 mag and durations between 20 and 120 days.
The most prominent bumps appeared in all our different optical bands. The
spectra showed typical SN IIn characteristics, with emission lines of H
(with broad component FWHM ~ and narrow
component FWHM ~) and He I, but also with Fe II, Ca II,
Na I D and H P-Cygni profiles (with velocities of ~ ). A pre-explosion outburst was identified lasting days,
with mag around 210 days before discovery. Large, variable
progenitor mass-loss rates (~> 0.01 ) and CSM densities
(~> 10 g cm) are derived. We suggest that the light curve bumps
of iPTF13z arose from SN ejecta interacting with denser regions in the CSM,
possibly produced by the eruptions of a luminous blue variable star.Comment: Version 2: Update to match published paper. 21 pages, 14 figures,
abstract abridged to comply with arXiv length limit. In version 1 of the
paper on arXiv, Table 3 had some erroneous entries. Table 3 is now corrected
and available via VizieR. Version 1 comment: Accepted for publication in
Astronomy & Astrophysics (24 pages, 14 figures, abstract abridged by 20 % not
to exceed the arXiv length limit
Dust-to-metal ratios in damped Lyman-alpha absorbers: Fresh clues to the origins of dust and optical extinction towards gamma-ray bursts
Motivated by the anomalous dust-to-metal ratios derived in the literature for
gamma-ray burst (GRB) damped Lyman-alpha absorbers (DLAs), we measure these
ratios using the dust-depletion pattern observed in UV/optical afterglow
spectra associated with the ISM at the GRB host-galaxy redshifts. Our sample
consists of 20 GRB absorbers and a comparison sample of 72 QSO-DLAs with
redshift 1.2 < z < 4.0 and down to Z = 0.002 Z_Sol metallicities. The
dust-to-metal ratio in QSO- and GRB-DLAs increases both with metallicity and
metal column density, spanning ~10--110% of the Galactic value and pointing to
a non universal dust-to-metal ratio. The low values of dust-to-metal ratio
suggest that low-metallicity systems have lower dust fractions than typical
spiral galaxies and perhaps that the dust in these systems is produced
inefficiently, i.e. by grain growth in the low-metallicity regime with
negligible contribution from supernovae (SNe) and asymptotic giant branch (AGB)
stars. On the other hand, some GRB- and QSO-DLAs show high dust-to-metal ratio
values out to z ~ 4, requiring rapid dust production, such as in SN ejecta, but
also in AGB winds and via grain growth for the highest metallicity systems.
GRB-DLAs overall follow the dust-to-metal-ratio properties of QSO-DLAs, GRBs
probing up to larger column and volume densities. For comparison, the
dust-to-metal ratio that we derive for the SMC and LMC are ~82--100% and ~98%
of the Galactic value, respectively. The literature dust-to-metal ratio of the
low-metallicity galaxy I Zw 18 (< 37%) is consistent with the distribution that
we find. The dust extinction Av increases steeply with the column density of
iron in dust, N(Fe)dust, calculated from relative metal abundances, confirming
that dust extinction is mostly occurring in the host galaxy ISM. Most GRB-DLAs
display log N(Fe)dust > 14.7, above which several QSO-DLAs reveal H2
(abridged).Comment: 14 pages, 9 figures. A&A, in pres
Severidade da mancha de Ramulária em genótipos de algodoeiro em duas regiões produtoras do Brasil.
Cascaded four-wave mixing in tapered plasmonic nanoantenna
We study theoretically the cascaded four-wave mixing (FWM) in broadband
tapered plasmonic nanoantennas and demonstrate a 300-fold increase in nonlinear
frequency conversion detected in the main lobe of the nanoantenna far-field
pattern. This is achieved by tuning the elements of the nanoantenna to resonate
frequencies involved into the FWM interaction. Our findings have a potentially
broad application in ultrafast nonlinear spectroscopy, sensing, on-chip optical
frequency conversion, nonlinear optical metamaterials and photon sources
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