64 research outputs found
Observations of the X-ray Nova GRO~J0422+32: II: Optical Spectra Approaching Quiescence
We present results obtained from a series of 5~\AA\ resolution spectra of the
X-ray Nova GRO~J0422+32 obtained in 1993~October, when the system was
approximately 2 magnitudes above quiescence, with . The data
were obtained in an effort to measure the orbital radial velocity curve of the
secondary, but detection of the narrow photospheric absorption lines needed to
do this proved elusive. Instead we found wide absorption bands reminiscent of
M~star photospheric features. The parameters determined by fitting accretion
disk line profiles (Smak profiles) to the H line are similar to those
found in several strong black-hole candidates. Measurements of the velocity of
the H line are consistent with an orbital period of 5.1~hours and a
velocity semi-amplitude of the primary of ~\kms. These measurements,
when combined with measurements of the velocity semi-amplitude of the secondary
made by others, indicate that the mass ratio . If the secondary
follows the empirical mass-radius relation found for CVs, the low implies a
primary mass of \mo, and a rather low (face-on) inclination. The
H EW is found to be modulated on the orbital period with a phasing that
implies a partial eclipse of the disk by the secondary, but simultaneous R~band
photometry shows no evidence for such an eclipse.Comment: Accepted for ApJ, plain latex, 5 figures available as self-extracting
uuendoced, compressed, tarfiles (from uufiles
Aql X-1 in Outburst and Quiescence
We present photometry and spectroscopy of the soft x-ray transient Aql X-1.
Optical photometry during an active state shows a strong (0.6 mag peak-to-peak)
modulation at a period of 19 hours. Infrared (K'-band) photometry during a
quiescent state limits any ellipsoidal variations to <0.07 mag (peak-to-peak),
which implies an inclination i<31 (90% limit). Spectroscopy in a quiescent
state shows at most very small radial velocity variations, which implies a very
low inclination of i<12 (90% limit). The low inclination is rather unexpected
given the large photometric modulation seen in the active state. The upper
limit to the equivalent width of the anomalous Li 6707A line is <0.3A, which is
similar to the measured strength of this line in several other x-ray
transients.Comment: Accepted for publication in ApJ, 12 pages, 5 figure
A Catalog of Transient X-ray Sources in M31
From October 1999 to August 2002, 45 transient X-ray sources were detected in
M31 by Chandra and XMM-Newton. We have performed spectral analysis of all
XMM-Newton and Chandra ACIS detections of these sources, as well as flux
measurements of Chandra HRC detections. The result is absorption-corrected
X-ray lightcurves for these sources covering this 2.8 year period, along with
spectral parameters for several epochs of the outbursts of most of the
transient sources. We supply a catalog of the locations, outburst dates, peak
observed luminosities, decay time estimates, and spectral properties of the
transient sources, and we discuss similarities with Galactic X-ray novae. Duty
cycle estimates are possible for 8 of the transients and range from 40% to 2%;
upper limits to the duty cycles are estimated for an additional 15 transients
and cover a similar range. We find 5 transients which have rapid decay times
and may be ultra-compact X-ray binaries. Spectra of three of the transients
suggest they may be faint Galactic foreground sources. If even one is a
foreground source, this suggests a surface density of faint transient X-ray
sources of >~1 deg.Comment: 63 pages, 22 figures, 3 tables, accepted for publication in Ap
Endometrial epithelial cells are potent producers of tracheal antimicrobial peptide and serum amyloid A3 gene expression in response to E. coli stimulation
Endometrial epithelial cells play a critical role in mediating inflammatory mechanisms key to
bacterial clearance and tissue re-modelling postpartum. This study characterised innate immune
gene expression by bovine endometrial epithelial cells from three animals in response to
Escherichia coli, a common cause of bovine uterine disease. Expression of key innate immune
genes, encoding Toll-like receptor 4 (TLR4), the transcription factor NFkB1, the chemokine
interleukin 8 (IL8), inflammatory cytokines (interleukins IL1β, IL6; tumour necrosis factor,
TNF), β-defensins (lingual antimicrobial peptides LAP, tracheal antimicrobial peptide TAP) and
acute phase proteins (haptoglobin, HP; serum amyloid A, SAA3) was examined in endometrial
epithelial cells stimulated with E. coli for 6 and 24 h using qRT-PCR. Expression of all genes
was increased significantly (P < 0.05) 6 h post-stimulation. Expression of IL1b, TNF and SAA3
genes was increased by 121-, 357- and 721-fold, respectively (P < 0.05). Twenty four hours
post-stimulation, IL1b, IL6, IL8, TNF and LAP gene expression was decreased compared to 6 h,
whereas TAP and SAA3 expression was further increased to 209- and 3452-fold (P < 0.05). E.
coli driven expression of immune effector genes demonstrates potent immune, antimicrobial and
regulatory capacity of endometrial epithelial cells to respond to this pathogen.http://www.elsevier.com/locate/vetimmhb2013ab201
New Evidence for Black Hole Event Horizons from Chandra
Previously we claimed that Black Hole X-ray Novae (BHXN) in quiescence are
much less luminous than equivalent Neutron Star X-ray Novae (NSXN). This claim
was based on the quiescent detection of a single short period BHXN (A0620-00,
P(orb)=7.8 hrs) and two longer period BHXN (GRO J1655-40, P(orb)=62.9 hrs; V404
Cyg, P(orb)=155.3 hrs), along with sensitive upper limits. We announce the
detection of two more short period BHXN (GRO J0422+32, P(orb)=5.1 hrs; GS
2000+25, P(orb)=8.3 hrs), an upper limit for a third which is improved by two
orders of magnitude (4U 1543-47, P(orb)=27.0 hrs) and a new, much lower
quiescent measurement of GRO J1655-40. Taken together, these new Chandra
measurements confirm that the quiescent X-ray luminosities of BHXN are
significantly lower than those of NSXN. We argue that this provides strong
evidence for the existence of event horizons in BHXN.Comment: Submitted to ApJ Letters, 4 pages, 2 figure
Whey proteins: targets of oxidation, or mediators of redox protection.
peer-reviewedBovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with α-Lactalbumin more susceptible than β-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins
The Frequency of Binary Stars in the Core of 47 Tucanae
Differential time series photometry has been derived for 46422 main-sequence
stars in the core of 47 Tucanae. The observations consisted of near-continuous
160-s exposures alternating between the F555W and F814W filters for 8.3 days in
1999 July with WFPC2 on the Hubble Space Telescope. Using Fourier and other
search methods, eleven detached eclipsing binaries and fifteen W UMa stars have
been discovered, plus an additional ten contact or near-contact non-eclipsing
systems. After correction for non-uniform area coverage of the survey, the
observed frequencies of detached eclipsing binaries and W UMa's within 90
arcseconds of the cluster center are 0.022% and 0.031% respectively. The
observed detached eclipsing binary frequency, the assumptions of a flat binary
distribution with log period and that the eclipsing binaries with periods
longer than about 4 days have essentially their primordial periods, imply an
overall binary frequency of 13 +/- 6 %. The observed W UMa frequency and the
additional assumptions that W UMa's have been brought to contact according to
tidal circularization and angular momentum loss theory and that the contact
binary lifetime is 10^{9} years, imply an overall binary frequency of 14 +/- 4
%. An additional 71 variables with periods from 0.4 - 10 days have been found
which are likely to be BY Draconis stars in binary systems. The radial
distribution of these stars is the same as that of the eclipsing binaries and W
UMa stars and is more centrally concentrated than average stars, but less so
than the blue straggler stars. A distinct subset of six of these stars fall in
an unexpected domain of the CMD, comprising what we propose to call red
stragglers.Comment: Accepted for publication in the Astrophysical Journal, 65 pages
including 26 figure
A study of the impacts of variable factors on built environment graduates’ prospects
This paper investigates the impacts of variable factors, such as practical experience and factors related to study style, on employment outcomes and patterns of built environment graduates in Australia. This paper also compares the employment prospects of different built environment sub-disciplines, including Architecture, Construction, Real Estate and Urban Planning and Regional Studies. Practical experience and the possibility of work with final year employers after graduation were found to have a statistically significant impact on the employment outcomes for graduates of built environment and all of its sub-disciplines. However, degree level and type of university attended were not found to have a statistically significant impact. Attendance type and employment mode in the final year of study had a statistically significant impact on the employment patterns for graduates of built environment and all of its sub-disciplines. The graduates who studied part-time and worked full-time in their final year of study were more likely to secure full-time jobs after graduation. The findings of this paper can be used by built environment graduates to identify the variable factors which they can change in order to enhance their employment prospects
Long term follow up of high risk children: who, why and how?
Background: Most babies are born healthy and grow and develop normally through childhood. There are, however, clearly identifiable high-risk groups of survivors, such as those born preterm or with ill-health, who are destined to have higher than expected rates of health or developmental problems, and for whom more structured and specialised follow-up programs are warranted. Discussion This paper presents the results of a two-day workshop held in Melbourne, Australia, to discuss neonatal populations in need of more structured follow-up and why, in addition to how, such a follow-up programme might be structured. Issues discussed included the ages of follow-up, and the personnel and assessment tools that might be required. Challenges for translating results into both clinical practice and research were identified. Further issues covered included information sharing, best practice for families and research gaps. Summary A substantial minority of high-risk children has long-term medical, developmental and psychological adverse outcomes and will consume extensive health and education services as they grow older. Early intervention to prevent adverse outcomes and the effective integration of services once problems are identified may reduce the prevalence and severity of certain outcomes, and will contribute to an efficient and effective use of health resources. The shared long-term goal for families and professionals is to work toward ensuring that high risk children maximise their potential and become productive and valued members of society. Electronic supplementary material The online version of this article (doi:10.1186/1471-2431-14-279) contains supplementary material, which is available to authorized users
A Black Hole in the Superluminal source SAX J1819.3-2525 (V4641 Sgr)
(shortened) Spectroscopic observations of the fast X-ray transient and
superluminal jet source SAX J1819.3-2525 (V4641 Sgr) reveal a best fitting
period of P_spect=2.81678 +/- 0.00056 days and a semiamplitude of K_2=211.0 +/-
3.1 km/sec. The optical mass function is f(M)=2.74 +/- 0.12 solar masses. We
find a photometric period of P_photo=2.81730 +/- 0.00001 days using a light
curve measured from photographic plates. The folded light curve resembles an
ellipsoidal light curve with two maxima of roughly equal height and two minima
of unequal depth per orbital cycle. The secondary star is a late B-type star
which has evolved off the main sequence. Using a moderate resolution spectrum
(R=7000) we measure T_eff=10500 +/- 200K, log(g)=3.5 +/- 0.1, and
V_rot*sin(i)=123 +/- 4 km/sec (1 sigma errors). Assuming synchronous rotation,
our measured value of the projected rotational velocity implies a mass ratio of
Q=M_1/M_2=1.50 +/- 0.08 (1sigma). The lack of X-ray eclipses implies an upper
limit to the inclination of i<70.7 deg. On the other hand, the large amplitude
of the folded light curve (about 0.5 mag) implies a large inclination (i>60
deg). Using the above mass function, mass ratio, and inclination range, the
mass of the compact object is in the range 8.73 < M_1 < 11.70 solar masses and
the mass of the secondary star is in the range 5.49 < M_2 < 8.14 solar masses
(90% confidence). The mass of the compact object is well above the maximum mass
of a stable neutron star and we conclude that V4641 Sgr contains a black hole.Comment: 17 pages, 12 figures, emulateapj5.sty, submitted to Ap
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