162 research outputs found
Comparison of two assays for human kallikrein 2
BACKGROUND: We compared two recently developed research assays for the
measurement of human kallikrein 2 (hK2) in serum: one fully automated
assay (Beckman Coulter Access immunoanalyzer) and one manual assay based
on the DELFIA technology. METHODS: We used two subsets of clinical
specimens consisting of 48 samples from prostate cancer patients and 210
samples from participants in an ongoing screening study (ERSPC). Both
subsets were measured in the Rotterdam laboratory, and the prostate cancer
samples were used for analytical comparison with the originating sites for
the assays: Beckman Coulter Research Department (San Diego, CA) and Turku
University (Turku, Finland). RESULTS: Both the Beckman Coulter and the
Turku assays performed very similarly between the Rotterdam laboratory and
the originating sites: the R(2) value for both comparisons was 0.99, and
the slope difference between sites was <20%. Deming regression analysis of
the DELFIA (y) and Access (x) assays yielded the following: for the
prostate cancer group, y = 1.17x - 0.01 (R(2) = 0.88; n = 48); and for the
ERSPC group, y = 0.62x - 0.01 (R(2) = 0.77). Breakdown of the latter group
into subgroups (nondiseased, benign prostatic hyperplasia, and prostate
cancer samples) gave only minor differences. The Access calibrators were
underrecovered by 13% in the DELFIA assay, whereas the DELFIA calibrators
were overrecovered by 45% in the Access assay. CONCLUSION: The DELFIA and
Access assays for hK2, which have similar analytical features, show
differences that cannot be explained by calibration
Optical Follow-up of New SMC Wing Be/X-ray Binaries
We investigate the optical counterparts of recently discovered Be/X-ray
binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700,
SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the
SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based
telescopes have been utilised in the optical follow-up, providing coverage in
both the red and blue bands. This has led to the classification of all of the
counterparts as Be stars and confirms that three lie within the Galactic
spectral distribution of known Be/X-ray binaries. SXP101 lies outside this
distribution becoming the latest spectral type known. Monitoring of the Halpha
emission line suggests that all the sources bar SXP700 have highly variable
circumstellar disks, possibly a result of their comparatively short orbital
periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8,
revealing that the emission is indeed harder during the passage of the X-ray
beam through the line of sight.Comment: 9 pages, 9 figures, 2 tables, accepted for publication in MNRA
Near and mid-infrared colours of star-forming galaxies in ELAIS fields
We present J and K-band near-infrared photometry of a sample of mid-infrared
sources detected by the Infrared Space Observatory (ISO) as part of the
European Large Area ISO-Survey (ELAIS) and study their classification and
star-forming properties. We have used the Preliminary ELAIS Catalogue for the
6.7 micron (LW2) and 15 micron (LW3) fluxes. All of the high-reliability LW2
sources and 80 per cent of the LW3 sources are identified in the near-IR survey
reaching K = 17.5 mag. The near- to mid-IR flux ratios can effectively be used
to separate stars from galaxies in mid-IR surveys. The stars detected in our
survey region are used to derive a new accurate calibration for the ELAIS
ISOCAM data in both the LW2 and LW3 filters. We show that near to mid-IR
colour-colour diagrams can be used to further classify galaxies, as well as
study star-formation. The ISOCAM ELAIS survey is found to mostly detect
strongly star-forming late-type galaxies, possibly starburst powered galaxies,
and it also picks out obscured AGN. The ELAIS galaxies yield an average mid-IR
flux ratio LW2/LW3 = 0.67 +/- 0.27. We discuss this [6.7/15] ratio as a star
formation tracer using ISO and IRAS data of a local comparison sample. We find
that the [K/15] ratio is also agood indicator of activity level in galaxies and
conclude that the drop in the [6.7/15] ratio seen in strongly star-forming
galaxies is a result of both an increase of 15 mic emission and an apparent
depletion of 6.7 mic emission. Near-IR data together with the mid-IR give the
possibility to estimate the relative amount of interstellar matter in the
galaxies.Comment: 18 pages, 15 figures; accepted for publication in MNRA
Properties of the solar neighbor WISE J072003.20-084651.2
The severe crowding towards the Galactic plane suggests that the census of
nearby stars in that direction may be incomplete. Recently, Scholz reported a
new M9 object at an estimated distance d~7 pc (WISE J072003.20-084651.2;
hereafter WISE0720) at Galactic latitude b=2.3 degr.
Our goals are to determine the physical characteristics of WISE0720, its
kinematic properties, and to address the question if it is a binary object, as
suggested in the discovery paper.
Optical and infrared spectroscopy from the Southern African Large Telescope
and Magellan, respectively, and spectral energy distribution fitting were used
to determine the spectral type of WISE0720. The measured radial velocity,
proper motion and parallax yielded its Galactic velocities. We also
investigated if WISE0720 may show X-ray activity based on archival data.
Our spectra are consistent with spectral type L0+/-1. We find no evidence for
binarity, apart for a minor 2-sigma level difference in the radial velocities
taken at two different epochs. The spatial velocity of WISE0720 does not
connect it to any known moving group, instead it places the object with high
probability in the old thin disk or in the thick disk. The spectral energy
distribution fit hints at excess in the 12 and 22 micron WISE bands which may
be due to a redder companion, but the same excess is visible in other late type
objects, and it more likely implies a shortcoming of the models (e.g., issues
with the effective wavelengths of the filters for these extremely cool objects,
etc.) rather than a disk or redder companion. The optical spectrum shows some
Halpha emission, indicative of stellar activity. Archival X-ray observations
yield no detection.Comment: A&A, accepted; 9 pages, 6 figure
The XMM large scale structure survey: optical vs. X-ray classifications of active galactic nuclei and the unified scheme
Our goal is to characterize AGN populations by comparing their X-ray and
optical classifications. We present a sample of 99 spectroscopically identified
X-ray point sources in the XMM-LSS survey which are significantly detected in
the [2-10] keV band, and with more than 80 counts. We performed an X-ray
spectral analysis for all of these 99 X-ray sources. Introducing the fourfold
point correlation coefficient, we find only a mild correlation between the
X-ray and the optical classifications, as up to 30% of the sources have
differing X-ray and optical classifications: on one hand, 10% of the type 1
sources present broad emission lines in their optical spectra and strong
absorption in the X-rays. These objects are highly luminous AGN lying at high
redshift and thus dilution effects are totally ruled out, their discrepant
nature being an intrinsic property. Their X-ray luminosities and redshifts
distributions are consistent with those of the unabsorbed X-ray sources with
broad emission lines. On the other hand, 25/32 are moderate luminosity AGN,
which are both unabsorbed in the X-rays and only present narrow emission lines
in their optical spectra. The majority of them have an optical spectrum which
is representative of the host galaxy. We finally infer that dilution of the AGN
by the host galaxy seems to account for their nature. 5/25 have been defined as
Seyfert 2. In conclusion, most of these 32 discrepant cases can be accounted
for by the standard AGN unified scheme, as its predictions are not met for only
12% of the 99 X-ray sources. ABRIDGEDComment: 25 pages, 19 figures, Accepted for publication in A&
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