297 research outputs found
Population synthesis of classical low-mass X-ray binaries in the Galactic Bulge
Aims. We model the present-day population of 'classical' low-mass X-ray
binaries (LMXBs) with neutron star accretors, which have hydrogen-rich donor
stars. Their population is compared with that of hydrogen-deficient LMXBs,
known as ultracompact X-ray binaries (UCXBs). We model the observable LMXB
population and compare it to observations. Methods. We combine the binary
population synthesis code SeBa with detailed LMXB evolutionary tracks to model
the size and properties of the present-day LMXB population in the Galactic
Bulge. Whether sources are persistent or transient, and what their
instantaneous X-ray luminosities are, is predicted using the thermal-viscous
disk instability model. Results. We find a population of ~2.1 x 10^3 LMXBs with
neutron star accretors. Of these about 15 - 40 are expected to be persistent
(depending on model assumptions), with luminosities higher than 10^35 erg s^-1.
About 7 - 20 transient sources are expected to be in outburst at any given
time. Within a factor of two these numbers are consistent with the observed
population of bright LMXBs in the Bulge. This gives credence to our prediction
of the existence of a population of ~1.6 x 10^3 LMXBs with low donor masses
that have gone through the period minimum, and have present-day mass transfer
rates below 10^-11 Msun yr^-1. Conclusions. Even though the observed population
of hydrogen-rich LMXBs in the Bulge is larger than the observed population of
(hydrogen-deficient) UCXBs, the latter have a higher formation rate. While
UCXBs may dominate the total LMXB population at the present, the majority would
be very faint, or may have become detached and produced millisecond radio
pulsars. In that case UCXBs would contribute significantly more to the
formation of millisecond radio pulsars than hydrogen-rich LMXBs. [abridged]Comment: 8 pages, 10 figures. Accepted for publication in Astronomy and
Astrophysics. v2: minor language correction
Formation of the planet around the millisecond pulsar J1719-1438
Context. Recently the discovery of PSR J1719-1438, a 5.8 ms pulsar with a
companion in a 2.2 hr orbit, was reported. The combination of this orbital
period and the very low mass function is unique. The discoverers, Bailes et
al., proposed an ultracompact X-ray binary (UCXB) as the progenitor system.
However, the standard UCXB scenario would not produce this system as the time
required to reach this orbital period exceeds the current estimate of the age
of the Universe. The detached state of the system aggravates the problem. Aims.
We want to understand the evolutionary history of PSR J1719-1438, and determine
under which circumstances it could have evolved from an UCXB. Methods. We model
UCXB evolution varying the donor size and investigate the effect of a wind mass
loss from the donor, and compare the results with the observed characteristics
of PSR J1719-1438. Results. An UCXB can reach a 2.2 hr orbit within the age of
the Universe, provided that 1) the millisecond pulsar can significantly heat
and expand the donor by pulsar irradiation, or 2) the system loses extra
orbital angular momentum, e.g. via a fast wind from the donor. Conclusions. The
most likely scenario for the formation of PSR J1719-1438 is UCXB evolution
driven by angular momentum loss via the usual gravitational wave emission,
which is enhanced by angular momentum loss via a donor wind of ~3x10^-13
Msun/yr. Depending on the size of the donor during the evolution, the companion
presently probably has a mass of ~1-3 Jupiter masses, making it a very low mass
white dwarf as proposed by Bailes et al. Its composition can be either helium
or carbon-oxygen. A helium white dwarf companion makes the long (for an UCXB)
orbital period easier to explain, but the required inclination makes it a
priori less likely than a carbon-oxygen white dwarf.Comment: 5 pages, 4 figures. Accepted for publication in Astronomy and
Astrophysics. v2: Updated a referenc
Time-resolved X-Shooter spectra and RXTE light curves of the ultra-compact X-ray binary candidate 4U 0614+091
In this paper we present X-Shooter time resolved spectroscopy and RXTE PCA
light curves of the ultra-compact X-ray binary candidate 4U 0614+091. The
X-Shooter data are compared to the GMOS data analyzed previously by Nelemans et
al. (2004). We confirm the presence of C III and O II emission features at ~
4650 {\AA} and ~ 5000 {\AA}. The emission lines do not show evident Doppler
shifts that could be attributed to the motion of the donor star/hot spot around
the center of mass of the binary. We note a weak periodic signal in the
red-wing/blue-wing flux ratio of the emission feature at ~ 4650 {\AA}. The
signal occurs at P = 30.23 +/- 0.03 min in the X-Shooter and at P = 30.468 +/-
0.006 min in the GMOS spectra when the source was in the low/hard state. Due to
aliasing effects the period in the GMOS and X-Shooter data could well be the
same. We deem it likely that the orbital period is thus close to 30 min,
however, as several photometric periods have been reported for this source in
the literature already, further confirmation of the 30 min period is warranted.
We compare the surface area of the donor star and the disc of 4U 0614+091 with
the surface area of the donor star and the disc in typical hydrogen-rich
low-mass X-ray binaries and the class of AM Canum Venaticorum stars and argue
that the optical emission in 4U 0614+091 is likely dominated by the disc
emission. Additionally, we search for periodic signals in all the publicly
available RXTE PCA light curves of 4U 0614+091 which could be associated with
the orbital period of this source. A modulation at the orbital period with an
amplitude of ~ 10% such as those that have been found in other ultra-compact
X-ray binaries (4U 0513-40, 4U 1820-30) is not present in 4U 0614+091.Comment: Accepted for publication in MNRAS, 11 pages, 7 figure
LKB1/KRAS mutant lung cancers constitute a genetic subset of NSCLC with increased sensitivity to MAPK and mTOR signalling inhibition
LKB1/STK11 is a multitasking tumour suppressor kinase. Germline inactivating mutations of the gene are responsible for the Peutz-Jeghers hereditary cancer syndrome. It is also somatically inactivated in approximately 30% of non-small-cell lung cancer (NSCLC). Here, we report that LKB1/KRAS mutant NSCLC cell lines are sensitive to the MEK inhibitor CI-1040 shown by a dose-dependent reduction in proliferation rate, whereas LKB1 and KRAS mutations alone do not confer similar sensitivity. We show that this subset of NSCLC is also sensitised to the mTOR inhibitor rapamycin. Importantly, the data suggest that LKB1/KRAS mutant NSCLCs are a genetically and functionally distinct subset and further suggest that this subset of lung cancers might afford an opportunity for exploitation of anti-MAPK/mTOR-targeted therapies
Evaluation of effectiveness of the PlasmaJet surgical device in the treatment of advanced stage ovarian cancer (PlaComOv-study): study protocol of a randomized controlled trial in the Netherlands
Background: The most important goal for survival benefit of advanced stage ovarian cancer is to surgically remove
all visible tumour, because complete cytoreductive surgery (CCS) has been shown to be associated with prolonged
survival.
In a remarkable number of women, CCS is very challenging. Especially in women with many small metastases on
the peritoneum and intestinal surface, conventional CCS with electrosurgery is not able to be “complete” in
removing safely all visible tumour.
In this randomized controlled trail (RCT) we investigate whether the use of the PlasmaJet Surgical Device increases
the rate of CCS, and whether this indeed leads to a longer progression free and overall survival.
The main research question is: does the use of the PlasmaJet Surgical Device in surgery for advanced stage ovarian
cancer result in an increased number of complete cytoreductive surgeries when compared with conventional
surgical techniques. Secondary study objectives are: 30-day morbidity, duration of surgery, blood loss, length of
hospitalisation, Quality of Life, disease-free survival, overall survival, percentage colostomy, cost-effectiveness.
Methods: The study design is a multicentre single-blinded superiority RCT in two university and nine non-university
hospitals in The Netherlands. Three hundred and thirty women undergoing cytoreductive surgery for advanced
stage ovarian carcinoma (FIGO Stage IIIB-IV) will be randomized into two arms: use of the PlasmaJet (intervention
group) versus the use of standard surgical instruments combined with electrocoagulation (control group). The
primary outcome is the rate of complete cytoreductive surgery in both groups.
Secondary study objectives are: 30-day morbidity, duration of surgery, blood loss, length of hospitalisation, Quality of
Life, disease-free survival, overall survival, percentage colostomy, cost-effectiveness. Quality of life will be evaluated
using validated questionnaires at baseline, at 1 and 6 months after surgery and at 1, 2, 3 and 4 years after surgery
Discussion: We hypothesize the additional value of the use of the PlasmaJet in CCS for advanced stage epithelial
ovarian cancer. More knowledge about efficacy, side effects, recurrence rates, cost effectiveness and pathology findings
after using the PlasmaJet Device is advocated. This RCT may aid in this void
IGAPS: the merged IPHAS and UVEX optical surveys of the Northern Galactic Plane
The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i, r, narrow-band Hα, g, and U_(RGO). The IGAPS footprint fills the Galactic coordinate range, |b| 5σ confidence)
Integrated Epigenome Profiling of Repressive Histone Modifications, DNA Methylation and Gene Expression in Normal and Malignant Urothelial Cells
Epigenetic regulation of gene expression is commonly altered in human cancer. We have observed alterations of DNA
methylation and microRNA expression that reflect the biology of bladder cancer. This common disease arises by distinct
pathways with low and high-grade differentiation. We hypothesized that epigenetic gene regulation reflects an interaction
between histone and DNA modifications, and differences between normal and malignant urothelial cells represent
carcinogenic events within bladder cancer. To test this we profiled two repressive histone modifications (H3K9m3 and
H3K27m3) using ChIP-Seq, cytosine methylation using MeDIP and mRNA expression in normal and malignant urothelial cell
lines. In genes with low expression we identified H3K27m3 and DNA methylation each in 20–30% of genes and both marks
in 5% of genes. H3K9m3 was detected in 5–10% of genes but was not associated with overall expression. DNA methylation
was more closely related to gene expression in malignant than normal cells. H3K27m3 was the epigenetic mark most
specifically correlated to gene silencing. Our data suggest that urothelial carcinogenesis is accompanied by a loss of control
of both DNA methylation and H3k27 methylation. From our observations we identified a panel of genes with cancer
specific-epigenetic mediated aberrant expression including those with reported carcinogenic functions and members
potentially mediating a positive epigenetic feedback loop. Pathway enrichment analysis revealed genes marked by H3K9m3
were involved with cell homeostasis, those marked by H3K27m3 mediated pro-carcinogenic processes and those marked
with cytosine methylation were mixed in function. In 150 normal and malignant urothelial samples, our gene panel correctly
estimated expression in 65% of its members. Hierarchical clustering revealed that this gene panel stratified samples
according to the presence and phenotype of bladder cancer
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