Simultaneous X-ray/optical observations of GX 9+9 (4U 1728-16)

We report on the results of the first simultaneous X-ray (RXTE) and optical (SAAO) observations of the luminous low mass X-ray binary (LMXB) GX 9+9 in 1999 August. The high-speed optical photometry revealed an orbital period of 4.1958 hr and confirmed previous observations, but with greater precision. No X-ray modulation was found at the orbital period. On shorter timescales, a possible 1.4-hr variability was found in the optical light curves which might be related to the mHz quasi-periodic oscillations seen in other LMXBs. We do not find any significant X-ray/optical correlation in the light curves. In X-rays, the colour-colour diagram and hardness-intensity diagram indicate that the source shows characteristics of an atoll source in the upper banana state, with a correlation between intensity and spectral hardness. Time-resolved X-ray spectroscopy suggests that two-component spectral models give a reasonable fit to the X-ray emission. Such models consist of a blackbody component which can be interpreted as the emission from an optically thick accretion disc or an optically thick boundary layer, and a hard Comptonized component for an extended corona.Comment: 19 pages, 13 figures; accepted for publication in MNRA

Evidence for a 2 hr Optical Modulation in GS1826-24

We report the discovery of a 2.1hr optical modulation in the transient source GS1826-24, based on two independent high time-resolution photometric observing runs. There is additional irregular variability on shorter timescales. The source also exhibited an optical burst during each observation, with peak fluxes consistent with those of the three X-ray bursts so far detected by BeppoSAX. We compare the low-amplitude variation (0.06 mag) to that seen on the orbital periods of the short period X-ray bursters, X1636-536 and X1735-444, as well as the similarity in their non-periodic fluctuations. Other transient neutron star LMXBs possess short periods in the range 3.8-7.1 hrs. However, if confirmed as the orbital, a 2.1 hr modulation would make GS1826-24 unique and therefore of great interest within the context of their formation and evolution.Comment: 7 pages, 4 figures, to be published in MNRA

The optical counterpart to SAX J1808.4-3658: observations in quiescence

We report the first extensive set of optical photometric observations of the counterpart to SAX J1808.4-3658 (V4580 Sagittarius) in quiescence. The source was detected at V~21, 5 magnitudes fainter than at the peak of its 1998 outburst. However, a comparable ~6% semi-amplitude 2hr modulation of its flux is revealed. This has the same phasing and approximately sinusoidal modulation as seen during outburst and with photometric minimum when the pulsar is behind the companion. The lack of a double-humped morphology rules out an ellipsoidal origin, implying that the bulk of the optical flux does not arise from the companion. Moreover, applying crude modelling to the disc and X-ray irradiated face of the donor shows that the internal energy release of a remnant disc (with mass transfer driven by gravitational radiation) is sufficient to explain most of the optical emission, and with the modulation due to the varying contribution of the heated star's face. We note that this model is also consistent with the much lower X-ray to optical flux ratio in quiescence versus outburst, and with the phasing of the optical modulation.Comment: 7 pages, 5 figures, accepted version with very minor changes (after ref's report), to appear in MNRA

Boosting clinical performance: The impact of enhanced final year placements.

BACKGROUND: This study follows on from a study that investigated how to develop effective final year medical student assistantship placements, using multidisciplinary clinical teams in planning and delivery. AIMS: This study assessed the effects on objective structured clinical examination (OSCE) performance of the in-course enhanced "super-assistantship" placement introduced to a randomly selected sample of 2013-14 final year medical students at Leeds medical school. METHODS: Quantitative data analysis was used to compare the global grades of OSCE stations between students who undertook this placement against those who did not. RESULTS: There was a small overall improvement in the "super-assistantship" student scores across the whole assessment (effect size = 0.085). "Pre-op Capacity", "Admissions Prescribing" and "Hip Pain" stations had small-medium effect sizes (0.226, 0.215, and 0.214) in favor of the intervention group. Other stations had small effect sizes (0.107-0.191), mostly in favor of the intervention group. CONCLUSIONS: The "super-assistantship" experience characterized by increasing student responsibility on placement can help to improve competence and confidence in clinical decision-making "in a simulated environment". The clinical environment and multidisciplinary team must be ready and supported to provide these opportunities effectively. Further in-course opportunities for increasing final year student responsibility should be developed

Gravitational Radiation From Globular Clusters

Space-based gravitational wave detectors will have the ability to observe continuous low frequency gravitational radiation from binary star systems. They can determine the direction to continuous sources with an angular resolution approaching tens of arcminutes. This resolution should be sufficient to identify binary sources as members of some nearby globular clusters. Thus, gravitational radiation can be used to determine the population of hard binaries in globular clusters. For particularly hard binaries, the orbital period may change as a result of gravitational wave emission. If one of these binaries can be identified with a globular cluster, then the distance to that cluster can be determined. Thus, gravitational radiation may provide reddening-independent distance measurements to globular clusters.Comment: 26 pages, 1 figure, LaTeX, uses aasms4.sty, submitted to Ap.

Cross Cultural Workers for women and families from migrant and refugee backgrounds: a mixed-methods study of service providers perceptions

Background Women from migrant and refugee backgrounds who live in high-income countries are at increased risk of adverse perinatal outcomes, including mental health issues, preterm birth and maternal and infant mortality. There is a need to implement and evaluate models of care to meet their specific needs in order to improve health outcomes, their experiences of care, and overcome barriers to access. In Sydney, Australia, a unique model of care was implemented to support women and families from migrant and refugee backgrounds to access health and community-based services through the continuum of pregnancy to the early parenting period. This model of care is known as the Cross Cultural Workers (CCWs) in Maternity and Child and Family Health Service (the CCW Service). The aim of this study was to explore the perceptions of service providers regarding the CCW Service and identify recommendations for improvement. Methods A mixed-methods study was conducted consisting of surveys and face to face semi-structured interviews. Service providers were recruited from hospital-based maternity and community-based services. Survey data were analysed descriptively. Interviews were analysed using qualitative content analysis. Results Sixty-nine service providers completed surveys and 19 were interviewed. The CCW Service was highly regarded by service providers who perceived it to be critical in improving care for women from migrant and refugee backgrounds. The overarching theme from the interviews was the ability of the CCW Service to act as a ‘bridge to health’ through the provision of culturally responsive care. There were three main categories; supporting access to health and community-based services, improving the healthcare experience, and organisational factors, including part-time hours, capacity, heavy workloads and confusion/lack of clarity regarding the CCW role, which affected CCWs’ capacity to optimally support service providers in providing culturally responsive care. These limitations meant CCWs were not able to meet demand, and fully operationalise the model. Conclusion Service providers perceived the CCW model to be a culturally responsive model of care tailored to the needs of women and families from migrant and refugee backgrounds, that reduces barriers to access, and has the potential to improve perinatal outcomes, and women's experience and satisfaction with care

Calculation of nonzero-temperature Casimir forces in the time domain

We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a non-monotonic behavior previously demonstrated in a piston-like geometry.Comment: 5 pages, 2 figures, submitted to Physical Review A Rapid Communicatio

Regression of murine lung tumors by the let-7 microRNA.

MicroRNAs (miRNAs) have recently emerged as an important new class of cellular regulators that control various cellular processes and are implicated in human diseases, including cancer. Here, we show that loss of let-7 function enhances lung tumor formation in vivo, strongly supporting the hypothesis that let-7 is a tumor suppressor. Moreover, we report that exogenous delivery of let-7 to established tumors in mouse models of non-small-cell lung cancer (NSCLC) significantly reduces the tumor burden. These results demonstrate the therapeutic potential of let-7 in NSCLC and point to miRNA replacement therapy as a promising approach in cancer treatment

X-ray Sources and their Optical Counterparts in the Globular Cluster M4

We report on the Chandra X-ray Observatory ACIS-S3 imaging observation of the Galactic globular cluster M4 (NGC 6121). We detect 12 X-ray sources inside the core and 19 more within the cluster half-mass radius. The limiting luminosity of this observation is Lx~10e29 erg/sec for sources associated with the cluster, the deepest X-ray observation of a globular cluster to date. We identify 6 X-ray sources with known objects and use ROSAT observations to show that the brightest X-ray source is variable. Archival data from the Hubble Space Telescope allow us to identify optical counterparts to 16 X-ray sources. Based on the X-ray and optical properties of the identifications and the information from the literature, we classify two (possibly three) sources as cataclysmic variables, one X-ray source as a millisecond pulsar and 12 sources as chromospherically active binaries. Comparison of M4 with 47 Tuc and NGC 6397 suggests a scaling of the number of active binaries in these clusters with the cluster (core) mass.Comment: 11 pages, 6 figures, accepted for publication in ApJ. Figure 1 and 5 are of reduced qualit