50 research outputs found
Detection of diffuse interstellar bands in M31
We investigate the diffuse interstellar band (DIB) spectrum in the
interstellar medium of M31. The DEIMOS spectrograph of the W. M. Keck
observatory was used to make optical spectroscopic observations of two
supergiant stars, MAG 63885 and MAG 70817, in the vicinity of the OB78
association in M31 where the metallicity is approximately equal to solar. The
5780, 5797, 6203, 6283 and 6613 DIBs are detected in both sightlines at
velocities matching the M31 interstellar Na I absorption. The spectra are
classified and interstellar reddenings are derived for both stars. Diffuse
interstellar band (DIB) equivalent widths and radial velocities are presented.
The spectrum of DIBs observed in M31 towards MAG 63885 is found to be similar
to that observed in the Milky Way. Towards MAG 70817 the DIB equivalent widths
per unit reddening are about three times the Galactic average. Compared to
observations elsewhere in the Universe, relative to reddening the M31 ISM in
the vicinity of OB78 is apparently a highly favourable environment for the
formation of DIB carriers
Linear/circular spectropolarimetry of diffuse interstellar bands
Context. The identification of the carriers of diffuse interstellar bands
(DIBs) remains one of the long-standing mysteries in astronomy. The detection
of a polarisation signal in a DIB profile can be used to distinguish between a
dust or gas-phase carrier. The polarisation profile can give additional
information on the grain or molecular properties of the absorber. In order to
detect and measure the linear and circular polarisation of the DIBs we observed
reddened lines of sight showing continuum polarisation. For this study we
selected two stars HD 197770 and HD 194279. We used high-resolution (R~64.000)
spectropolarimetry in the wavelength range from 3700 to 10480 Angstrom with the
ESPaDOnS echelle spectrograph mounted at the CFHT.
Results. High S/N and high resolution Stokes V (circular), Q and U (linear)
spectra were obtained. We constrained upper limits by a factor of 10 for
previously observed DIBs. Furthermore, we analysed ~30 additional DIBs for
which no spectropolarimetry data has been obtained before. This included the
9577 A DIB and the 8621 A DIB.
Conclusions. The lack of polarisation in 45 DIB profiles suggests that none
of the absorption lines is induced by a grain-type carrier. The strict upper
limits, less than ~0.01%, derived for the observed lines-of-sight imply that if
DIBs are due to gas-phase molecules these carriers have polarisation
efficiencies which are at least 6 times, and up to 300 times, smaller than
those predicted for grain-related carriers.Comment: 6 pages + 13 pages online material, submitted to A&
Improved Production Process for Native Outer Membrane Vesicle Vaccine against Neisseria meningitidis
An improved detergent-free process has been developed to produce vaccine based on native outer membrane vesicles (NOMV) against Neisseria meningitidis serogroup B. Performance was evaluated with the NonaMen vaccine concept, which provides broad coverage based on nine distinct PorA antigens. Scalable aseptic equipment was implemented, replacing undesirable steps like ultracentrifugation, inactivation with phenol, and the use of preservatives. The resulting process is more consistent and gives a higher yield than published reference processes, enabling NOMV production at commercial scale. Product quality met preliminary specifications for 9 consecutive batches, and an ongoing study confirmed real-time stability up to 12 months after production. As the NOMV had low endotoxic activity and induced high bactericidal titres in mice, they are expected to be safe and effective in humans. The production process is not limited to NonaMen and may be applicable for other N. meningitidis serogroups and other gram-negative pathogens. The current results therefore facilitate the late-stage development and clinical evaluation of NOMV vaccines
A search for diffuse bands in the circumstellar envelopes of post-AGB stars
In this work we present the results of a systematic search for diffuse bands
(DBs, hereafter) in the circumstellar envelopes of a carefully selected sample
of post-AGB stars. We concentrated on the analysis of 9 of the DBs most
commonly found in the interstellar medium. The strength of these features is
determined using high resolution optical spectroscopy and the results obtained
are compared with literature data on field stars affected only by interstellar
reddening. Based on the weak features observed in the subsample of post-AGB
stars dominated by circumstellar reddening we conclude that the carrier(s) of
these DBs must not be present in the circumstellar environment of these
sources, or at least not under the excitation conditions in which DBs are
formed. The conclusion is applicable to all the post-AGB stars studied,
irrespective of the dominant chemistry or the spectral type of the star
considered. A detailed radial velocity analysis of the features observed in
individual sources confirms this result, as the Doppler shifts measured are
found to be consistent with an interstellar origin.Comment: Accepted for A&
A coincidence between a hydrocarbon plasma absorption spectrum and the lambda 5450 DIB
The aim of this work is to link the broad lambda 5450 diffuse interstellar
band (DIB) to a laboratory spectrum recorded through an expanding acetylene
plasma. Cavity ring-down direct absorption spectra and astronomical
observations of HD 183143 with the HERMES spectrograph on the Mercator
Telescope in La Palma and the McKellar spectrograph on the DAO 1.2 m Telescope
are compared. In the 543-547 nm region a broad band is measured with a band
maximum at 545 nm and FWHM of 1.03(0.1) nm coinciding with a well-known diffuse
interstellar band at lambda 5450 with FWHM of 0.953 nm. A coincidence is found
between the laboratory and the two independent observational studies obtained
at higher spectral resolution. This result is important, as a match between a
laboratory spectrum and a - potentially lifetime broadened - DIB is found. A
series of additional experiments has been performed in order to unambiguously
identify the laboratory carrier of this band. This has not been possible. The
laboratory results, however, restrict the carrier to a molecular transient,
consisting of carbon and hydrogen.Comment: 6 pages, 3 figures, accepted for publication in A&
Improved survival of patients with primary distant metastatic breast cancer in the period of 1995–2008. A nationwide population-based study in the Netherlands
Predicting survival of de novo metastatic breast cancer in Asian women: Systematic review and validation study
10.1371/journal.pone.0093755PLoS ONE94-POLN