Hydrodynamic modelling of accretion flows

In the proceedings of this, and of several recent close binary conferences, there have been several contributions describing smoothed particle hydrodynamics simulations of accretion disks. It is apposite therefore to review the numerical scheme itself with emphasis on its advantages for disk modelling, and the methods used for modelling viscous processes.Comment: 3 pages, to appear in proceedings of IAU Colloquium 194: Compact binaries in the galaxy and beyon

Surprisingly different star-spot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB

We aim to understand how stellar parameters such as mass and rotation impact the distribution of star-spots on the stellar surface. To this purpose, we have used Doppler imaging to reconstruct the surface brightness distributions of three fully convective M dwarfs with similar rotation rates. We secured high cadence spectral time series observations of the 5.5 au separation binary GJ 65, comprising GJ 65A (M5.5V, Prot = 0.24 d) and GJ 65B (M6V, Prot = 0.23 d). We also present new observations of GJ 791.2A (M4.5V, Prot = 0.31 d). Observations of each star were made on two nights with UVES, covering a wavelength range from 0.64 - 1.03μm. The time series spectra reveal multiple line distortions that we interpret as cool star-spots and which are persistent on both nights suggesting stability on the time-scale of 3 d. Spots are recovered with resolutions down to 8.3° at the equator. The global spot distributions for GJ 791.2A are similar to observations made a year earlier. Similar high latitude and circumpolar spot structure is seen on GJ 791.2A and GJ 65A. However, they are surprisingly absent on GJ 65B, which instead reveals more extensive, larger, spots concentrated at intermediate latitudes. All three stars show small amplitude latitude-dependent rotation that is consistent with solid body rotation. We compare our measurements of differential rotation with previous Doppler imaging studies and discuss the results in the wider context of other observational estimates and recent theoretical predictions

Microfluidic chromatography for early stage evaluation of biopharmaceutical binding and separation conditions

Optimization of separation conditions for biopharmaceuticals requires evaluation of a large number of process variables. To miniaturize this evaluation a microfluidic column (1.5 mu L volume and 1cm height) was fabricated and packed with a typical process scale resin. The device was assessed by comparison to a protein separation at conventional laboratory scale. This was based upon measurement of the quality of packing and generation of breakthrough and elution curves. Dynamic binding capacities from the microfluidic column compared well with the laboratory scale. Microfluidic scale gradient elution separations also equated to the laboratory column three orders of magnitude larger in scale

Phosphomolybdenum Blue Detection – A Review of Characteristics, Achievements, Challenges and Future Prospects

Phosphate detection in the environment (especially, water bodies) is very essential in view of its consequent pollution effects on eutrophication. Continuous monitoring of phosphate concentration (and phosphorus compounds in general) in water samples has been based on phosphomolybdenum blue formation coupled with spectrophotometric detection. Continu­ous flow injection analyses (FIA) are well known to present numerous advantages over batch methods. Furthermore, the development of on-chip micro-channel analytical (μFIA) systems begun and have gained much attention within the last two decades in view of the striking advantages over conventional FIA techniques. This paper reviews published information on detection of phosphomolybdenum blue in conventional systems as well as on micro-chip. It reports on the challenges encountered (interference from other complex anions), the achieve­ments made so far (intereference removal by electrokinetic separation) and what the future holds (simultaneous determination)

Examining stress and response to stress in medical students and new medical graduates

MOST MEMBERS OF THE MEDICAL PROFESSION feel stressed at some time. If stress is ongoing, impairment may occur (defined as being unable to safely or reliably perform one’s role). A continuum appears to exist between functioning well, being distressed and becoming impaired, with external (environment-related) and internal (personalrelated) stressors determining where an individual will lie on the continuum. We are conducting a study which aims to determine whether distress in new medical graduates can be predicted before the graduates become impaired and unable to safely or reliably perform their role. Study commencement Our study, which commenced in 1997, initially looked at predictors for “troubled” and “troublesome” interns. Hospital- based focus groups comprising interns (postgraduate Year 1), resident medical officers (postgraduate Year 2 and above), ward-based nursing staff and medical administrators reported on internal and external stressors for junior medical staff. Residents and nurses reported similar external stressors, whereas the internal stressors reported by the two groups were quite different (Box 1). Residents tended to report issues relating to “troubled” interns (eg, poor support, few outside interests), whereas nurses identified factors relating more to “troublesome” interns (eg, poor attitude, unprofessionalism). In other words, resident staff seemed to be able to identify their stressed and at-risk peers before effects on performance were observed (Box 1)

Discovery and modelling of disc precession in the M31 X-ray binary Bo 158?

The low mass X-ray binary (LMXB) associated with the M31 globular cluster Bo 158 is known to exhibit intensity dips on a ~2.78 hr period. This is due to obscuration of the X-ray source on the orbital period by material on the outer edge of the accretion disc. However, the depth of dipping varied from <10% to \~83% in three archival XMM-Newton observations of Bo 158. Previous work suggested that the dip depth was anticorrelated with the X-ray luminosity. However, we present results from three new XMM-Newton observations that suggest that the evolution of dipping is instead due to precession of the accretion disc. Such precession is expected in neutron star LMXBs with mass ratios <0.3 (i.e. with orbital periods <4 hr), such as the Galactic dipping LMXB 4U 1916-053. We simulated the accretion disc of Bo 158 using cutting-edge 3D smoothed particle hydrodynamics (SPH), and using the observed parameters. Our results show disc variability on two time-scales. The disc precesses in a prograde direction on a period of 81+/-3 hr. Also, a radiatively-driven disc warp is present in the inner disc, which undergoes retrograde precesson on a \~31 hr period. From the system geometry, we conclude that the dipping evolution is driven by the disc precession. Hence we predict that the dipping behaviour repeats on a ~81 hr cycle.Comment: 6 pages, 4 figures, to appear in proceedings "The X-ray Universe 2005", San Lorenzo de El Escoriale (Madrid, Spain), 26-30 September 200

Regulation of Chromatin Remodeling by Inositol Polyphosphates

Chromatin remodeling is required for efficient transcription of eukaryotic genes. In a genetic selection for budding yeast mutants that were defective in induction of the phosphate-responsive PHO5 gene, we identified mutations inARG82/IPK2, which encodes a nuclear inositol polyphosphate kinase. In arg82 mutant strains, remodeling ofPHO5 promoter chromatin is impaired, and the adenosine triphosphate–dependent chromatin-remodeling complexes SWI/SNF and INO80 are not efficiently recruited to phosphate-responsive promoters. These results suggest a role for the small molecule inositol polyphosphate in the regulation of chromatin remodeling and transcription

Photometric observations of the radio bright B[e]/X-ray binary CI Cam

We present multiwavelength (optical, IR, radio) observations of CI Cam, the optical counterpart to the transient X-ray source XTE J0421+560. Pre-outburst quiescent observations reveal the presence of a dusty envelope around the system. Pronounced short term variability is observed at all wavebands from U-K, but no indication of prior flaring of a similar magnitude to the 1998 April outburst is found in these data. Data obtained during the 1998 April X-ray flare reveal pronounced optical-radio flaring. The optical flux was observed to quickly return to quiescent levels, while the radio flare was of much longer duration. The optical component is likely to result from a combination of free-free/free-bound emission, emission line and thermal dust emission, caused by re-radiation of the X-ray flux, while the behaviour of the multiwavelength radio data is consistent with emission from expanding ejecta emitting via the synchrotron mechanism. Post-outburst (1998 August-1999 March) U-M broadband photometric observations reveal that while the optical (UBV) flux remains at pre-outburst quiescent levels, near IR (JHKLM) fluxes exceed the pre-outburst fluxes by ~0.5 magnitudes. Modelling the pre- and post-outburst spectral energy distribution of CI Cam reveals that the structure and/or composition of the dusty component of the circumstellar envelope appears to have changed. Due to a lack of information on the precise chemical composition of the dust within the system several explanations for this behaviour are possible, such as the production of new dust at the inner edge of the envelope, or modification of the composition of the dust due to X-ray irradiation

Suppressed Far-UV stellar activity and low planetary mass-loss in the WASP-18 system

WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (R′HK activity parameter lies slightly below the basal level; there is no significant time-variability in the log R′HK value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of HST aimed at explaining this anomaly. From the star’s spectral energy distribution, we infer the extinction (E(B − V) ≈ 0.01mag) and then the ISM column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C II, C III, C IV, Si IV). Comparing the C II/C IV flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star-planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si IV line, yields an XUV integrated flux at the planet orbit of 10.2 erg s−1 cm−2. We employ the rescaled XUV solar fluxes to model of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10−20MJ Gyr−1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape