27,222 research outputs found
Clonal analysis of meningococci during a 26 year period prior to the introduction of meningococcal serogroup C vaccines
Meningococcal disease remains a public health burden in the UK and elsewhere. Invasive Neisseria meningitidis, isolated in Scotland between 1972 and 1998, were characterised retrospectively to examine the serogroup and clonal structure of the circulating population. 2607 isolates causing invasive disease were available for serogroup and MLST analysis whilst 2517 were available for multilocus sequence typing (MLST) analysis only. Serogroup distribution changed from year to year but serogroups B and C were dominant throughout. Serogroup B was dominant throughout the 1970s and early 1980s until serogroup C became dominant during the mid-1980s. The increase in serogroup C was not associated with one particular sequence type (ST) but was associated with a number of STs, including ST-8, ST-11, ST-206 and ST-334. This is in contrast to the increase in serogroup C disease seen in the 1990s that was due to expansion of the ST-11 clonal complex. While there was considerable diversity among the isolates (309 different STs among the 2607 isolates), a large proportion of isolates (59.9%) were associated with only 10 STs. These data highlight meningococcal diversity over time and the need for ongoing surveillance during the introduction of new meningococcal vaccines
The Phoenix Deep Survey: spectroscopic catalog
The Phoenix Deep Survey is a multi-wavelength survey based on deep 1.4 GHz
radio imaging, reaching well into the sub-100 microJy level. One of the aims of
this survey is to characterize the sub-mJy radio population, exploring its
nature and evolution. In this paper we present the catalog and results of the
spectroscopic observations aimed at characterizing the optically ``bright''
(R<~ 21.5 mag) counterparts of faint radio sources. Out of 371 sources with
redshift determination, 21% have absorption lines only, 11% show AGN
signatures, 32% are star-forming galaxies, 34% show narrow emission lines that
do not allow detailed spectral classification (due to poor signal-to-noise
ratio and/or lack of diagnostic emission lines) and the remaining 2% are
identified with stars. For the star-forming galaxies with a Balmer decrement
measurement we find a median extinction of A(Ha)=1.9 mag, higher than that of
optically selected samples. This is a result of the radio selection, which is
not biased against dusty systems. Using the available spectroscopic
information, we estimate the radio luminosity function of star-forming galaxies
in two independent redshift bins at z~0.1 and 0.3 respectively. We find direct
evidence for strong luminosity evolution of these systems consistent with L(1.4
GHz) ~ (1+z)^(2.7).Comment: 39 pages, 12 figures. References added, and minor changes to reflect
published versio
The Phoenix Deep Survey: X-ray properties of faint radio sources
In this paper we use a 50ks XMM-Newton pointing overlapping with the Phoenix
Deep Survey, a homogeneous radio survey reaching muJy sensitivities, to explore
the X-ray properties and the evolution of star-forming galaxies. UV, optical
and NIR photometry is available and is used to estimate photometric redshifts
and spectral types for radio sources brighter than R=21.5mag (total of 82).
Sources with R<21.5mag and spiral galaxy SEDs (34) are grouped into two
redshift bins with a median of z=0.240 and 0.455 respectively. Stacking
analysis for both the 0.5-2 and 2-8keV bands is performed on these subsamples.
A high confidence level signal (>3.5sigma) is detected in the 0.5-2keV band
corresponding to a mean flux of ~3e-16cgs for both subsamples. This flux
translates to mean luminosities of ~5e40 and 1.5e41cgs for the z=0.240 and
0.455 subsamples respectively. Only a marginally significant signal (2.6sigma)
is detected in the 2-8keV band for the z=0.455 subsample. We argue that the
stacked signal above is dominated by star-formation. The mean L_X/L_B ratio and
the mean L_X of the two subsamples are found to be higher than optically
selected spirals and similar to starbursts. We also find that the mean L_X and
L_1.4 of the faint radio sources studied here are consistent with the L_X-L_1.4
correlation of local star-forming galaxies. Moreover, the X-ray emissivity of
sub-mJy sources to z~0.3 is found to be elevated compared to local HII
galaxies. The observed increase is consistent with L_X evolution of the form
(1+z)^3. Assuming that our sample is indeed dominated by starbursts this is
direct evidence for evolution of such systems at X-ray wavelengths. Using an
empirical L_X to SFR conversion we estimate a global SFR density at z~0.3 of
\~0.029M_o/yr/Mpc in agreement with previous studies.Comment: 12 pages, 6 figures, accepted for publication in MNRA
Why HITnet kiosks didn\u27t hit the mark for sexual health education of Western Australian Aboriginal youth
Objective: To assess the use, appropriateness of, and staff feedback on specific sexual health modules, which were installed on Heuristic Interactive Technology (HITnet) kiosks at Aboriginal Community Controlled Health Services (ACCHS). The HITnet kiosks were aimed at Aboriginal youth visiting these sites.
Methods: Modules on the HITnet kiosks were assessed for (1) cultural appropriateness using Yunkaportaâs Aboriginal pedagogy framework and (2) compliance with the World Health Organizationâs (WHO) advice on key elements for comprehensive sexual health education for young people. Data measuring kiosk use were obtained through HITnet kiosk activity reports. An online survey of ACCHS staff was used to qualitatively assess use of, and staff perceptions of, HITnet kiosks.
Results: Kiosk modules were consistent with seven of the eight elements of Yunkaportaâs framework and all of the WHO recommendations. The most popular module generated 3,066 purposeful sessions and the least popular module generated 724 purposeful sessions across nine sites in 2012. While teenagers were the most frequent of the kiosk user groups (39.5% in 2012), the majority of users (56%) were not in the target group (i.e. elders 4%, adults 25%, children 27%). Key issues reported by ACCHS staff (n=11) included: lack of clarity regarding staff responsibility for overseeing kiosk functionality; kiosks attracting âinappropriate agesâ; and âlack of privacyâ based on kiosk location, screen visibility, and absence of headphones preventing discreet access.
Conclusions: The modules were tailored to a young Aboriginal audience through technology thought to be appealing to this group. However, barriers to use of the kiosk included kiosk design features, location, and lack of clarity around responsibility for kiosk operation.
Implications: Aboriginal youth need easy access to sexual health messages in a âsafeâ, non-judgmental space. Information and communication that is accessible via personal and mobile devices may be a better vehicle than public kiosks
The discovery of trapped energetic electrons in the outer cusp
We report on the POLAR/CEPPAD discovery of a trapped, 60°\u3cΞ\u3c120° pitch angle electron population in the outer cusp (7â9+ Re), whose energetic electron component extends from below 30 keV to âŒ2 MeV. Because the time variability in the outer cusp precludes mapping with POLAR, we have carried out test particle simulations using the Tsyganenko 1996 model (T96) to demonstrate the trapping of these energy electrons in the outer cusp region and the resonant frequencies of its trapped motion. We discuss the boundaries and regions of the cusp trap and show that it is analogous to the dipole trap. We show that the phase space densities observed there are equal or greater than the phase space densities observed in the radiation belts at constant magnetic moment, thus allowing the possibility of diffusive filling of the radiation belts from the cus
Bayesian estimation applied to multiple species
Observed data are often contaminated by undiscovered interlopers, leading to biased parameter estimation. Here we present BEAMS (Bayesian estimation applied to multiple species) which significantly improves on the standard maximum likelihood approach in the case where the probability for each data point being âpureâ is known. We discuss the application of BEAMS to future type-Ia supernovae (SNIa) surveys, such as LSST, which are projected to deliver over a million supernovae light curves without spectra. The multiband light curves for each candidate will provide a probability of being Ia (pure) but the full sample will be significantly contaminated with other types of supernovae and transients. Given a sample of N supernovae with mean probability, âšPâ©, of being Ia, BEAMS delivers parameter constraints equal to NâšPâ© spectroscopically confirmed SNIa. In addition BEAMS can be simultaneously used to tease apart different families of data and to recover properties of the underlying distributions of those families (e.g. the type-Ibc and II distributions). Hence BEAMS provides a unified classification and parameter estimation methodology which may be useful in a diverse range of problems such as photometric redshift estimation or, indeed, any parameter estimation problem where contamination is an issue
An Ultraviolet-Selected Galaxy Redshift Survey - II: The Physical Nature of Star Formation in an Enlarged Sample
We present further spectroscopic observations for a sample of galaxies
selected in the vacuum ultraviolet (UV) at 2000 \AA from the FOCA balloon-borne
imaging camera of Milliard et al. (1992). This work represents an extension of
the initial study of Treyer et al. (1998). Our enlarged catalogue contains 433
sources; 273 of these are galaxies, nearly all with redshifts z=0-0.4. Nebular
emission line measurements are available for 216 galaxies, allowing us to
address issues of reddening and metallicity. The UV and Halpha luminosity
functions strengthen our earlier assertions that the local volume-averaged star
formation rate is higher than indicated from earlier surveys. Moreover,
internally within our sample, we do not find a steep rise in the UV luminosity
density with redshift over 0<z<0.4. Our data is more consistent with a modest
evolutionary trend as suggested by recent redshift survey results. We find no
evidence for a significant number of AGN in our sample. We find the UV flux
indicates a consistently higher mean star formation rate than that implied by
the Halpha luminosity for typical constant or declining star formation
histories. Following Glazebrook et al. (1999), we interpret this discrepancy in
terms of a starburst model for our UV-luminous sources. Whilst we can explain
most of our observations in this way, there remains a small population with
extreme UV-optical colours which cannot be understood.Comment: 27 pages, 19 figures, accepted for publication in MNRA
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