Class of Einstein--Maxwell Dilatons

Three different classes of static solutions of the Einstein--Maxwell equations non--minimally coupled to a dilaton field are presented. The solutions are given in general in terms of two arbitrary harmonic functions and involve among others an arbitrary parameter which determines their applicability as charged black holes, dilaton black holes or strings. Most of the known solutions are contained as special cases and can be non--trivially generalized in different ways.Comment: Published in Physical Review D, R310 (1995

The paracrinology of tubal ectopic pregnancy

As part of successful human reproduction, the Fallopian tube must provide a suitable environment for pre-implantation development of the embryo and for efficient transport of the embryo to the uterus for implantation. These functions are coordinated by paracrine interactions between tubal epithelial, smooth muscle and immune cells and the cells of the developing embryo. Alterations in these signals can lead to a tubal microenvironment encouraging of embryo implantation and to dysregulated tubal motility, ultimately resulting in inappropriate and early implantation of the embryo in the Fallopian tube. Here, we highlight novel and emerging concepts in tubal physiology and pathobiology, such as the induction of a receptive phenotype within the Fallopian tube, leading to ectopic implantation. Chlamydia trachomatis infection is a risk factor for tubal ectopic pregnancy. Activation of toll-like receptor 2 (TLR-2) in the Fallopian tube epithelium, by C. trachomatis has recently been demonstrated, leading to the dysregulation of factors involved in implantation and smooth muscle contractility, such as prokineticins (PROK), activin A and interleukin 1 (IL-1). The Fallopian tube has also recently been shown to harbour a unique population of immune cells, compared to the endometrium. In addition, the complement of immune cells in the Fallopian tube has been reported to be altered in Fallopian tube from women with ectopic pregnancy. There are increasing data suggesting that vascularisation of the Fallopian tube, by the embryo during ectopic pregnancy, differs from that initiated in the uterus during normal pregnancy. This too, is likely the result of paracrine signals between the embryo and the tubal microenvironment

The Patchy Accretion Disc in HT Cassiopeiae

We have reconstructed the temperatures and surface densities in the quiescent accretion disc in HT Cas by performing a "Physical Parameter Eclipse Mapping" analysis of archival UBVR observations. Using a simple hydrogen slab model and demanding a smooth, maximally artefact-free reconstruction, we derive a formal distance to HT Cas of 207 +- 10 pc, significantly larger than the 133 +- 14 pc we derive from a re-analysis of the data in the literature. We argue that the larger derived distance is probably incorrect but is not produced by inaccuracies in our spectral model or optimization method. The discrepancy can be resolved if the emission regions on the disc are patchy with a filling factor of about 40% of the disc's surface. This solves the problem with the high effective temperatures in the disc -- reducing them to around 6 500 K within a radius of 0.2 R_L1 -- and reduces the derived temperature of the white dwarf and/or boundary layer from 22600 to 15500 K. We discuss several possible sources of the chromospheric emission and its patchiness, including irradiation of the disc, thermal instabilities, spiral-wave-like global structures, and magnetically active regions associated with dynamo action and/or Balbus-Hawley instabilities.Comment: 19 pages, Latex, 25 figures, accepted by MNRA

X-ray and optical periodicities in X-ray binaries. I.A0535+26

A homogeneous set of UBV photometry (354 data points obtained between 1983 and 1998) for the Be/X-ray binary A0535+26 = V725Tau is analysed, aiming to look for possible periodic component(s). After subtraction of the long-term variation it was found that only a 103-day periodic component remains in the power spectra in both the V and B colour bands. The probability of chance occurrence of such a peak is less than 0.1%. There are no signs of optical variability at the X-ray period (111 d). We discuss possible reasons for a 103-day modulation and suggest that it corresponds to a beat frequency of the orbital period of the neutron star and the precession period (~1400 d) either of an accretion disc around the neutron star or a warped decretion disc around the Be star.Comment: LaTeX, 6 pages, 5 figures, uses psfig.st

Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths

We present numerical models of the circumstellar disks of Be stars, and we describe the resulting synthetic H-alpha emission lines and maps of the wavelength-integrated emission flux projected onto the sky. We demonstrate that there are monotonic relationships between the emission line equivalent width and the ratio of the angular half-width at half maximum of the projected disk major axis to the radius of the star. These relationships depend mainly upon the temperatures of the disk and star, the inclination of the disk normal to the line of sight, and the adopted outer boundary for the disk radius. We show that the predicted H-alpha disk radii are consistent with those observed directly through long baseline interferometry of nearby Be stars (especially once allowance is made for disk truncation in binaries and for dilution of the observed H-alpha equivalent width by continuum disk flux in the V-band).Comment: 12 pages, 2 figures, ApJL in pres

A Radial Velocity Study of CTCV J1300-3052

We present time-resolved spectroscopy of the eclipsing, short period cataclysmic variable CTCV J1300-3052. Using absorption features from the secondary star, we determine the radial velocity semi-amplitude of the secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These parameters are found to be in excellent agreement with previous mass determinations found via photometric fitting techniques, supporting the accuracy and validity of photometric mass determinations in short period CVs.Comment: Accepted for publication in MNRAS (24th January 2012). 10 pages, 9 figures (black and white

Kilohertz QPO Peak Separation Is Not Constant in Scorpius X-1

We report on a series of twenty ~10^5 c/s, 0.125 msec time-resolution RXTE observations of the Z source and low-mass X-ray binary Scorpius X-1. Twin kilohertz quasi-periodic oscillation (QPO) peaks are obvious in nearly all observations. We find that the peak separation is not constant, as expected in some beat-frequency models, but instead varies from ~310 to ~230 Hz when the centroid frequency of the higher-frequency peak varies from ~875 to ~1085 Hz. We detect none of the additional QPO peaks at higher frequencies predicted in the photon bubble model (PBM), with best-case upper limits on the peaks' power ratio of 0.025. We do detect, simultaneously with the kHz QPO, additional QPO peaks near 45 and 90 Hz whose frequency increases with mass accretion rate. We interpret these as first and second harmonics of the so-called horizontal-branch oscillations well known from other Z sources and usually interpreted in terms of the magnetospheric beat-frequency model (BFM). We conclude that the magnetospheric BFM and the PBM are now unlikely to explain the kHz QPO in Sco X-1. In order to succeed in doing so, any BFM involving the neutron star spin (unseen in Sco X-1) will have to postulate at least one additional unseen frequency, beating with the spin to produce one of the kHz peaks.Comment: 6 pages including 3 figure

Determinants of non-adherence to treatment for tuberculosis in high-income and middle-income settings: a systematic review protocol

INTRODUCTION: Treatment for tuberculosis (TB) is highly effective if taken according to prescribed schedules. However, many people have difficulty adhering to treatment which can lead to poorer clinical outcomes, the development of drug resistance, increased duration of infectivity and consequent onward transmission of infection. A range of approaches are available to support adherence but in order to target these effectively a better understanding of the predictors of poor adherence is needed. This review aims to highlight the personal, sociocultural and structural factors that may lead to poor adherence in high-income and middle-income settings. METHODS AND ANALYSIS: Seven electronic databases, Medline, EMBASE, CINAHL, PsycInfo, The Cochrane Library, Scopus and Web of Science, will be searched for relevant articles using a prespecified search strategy. Observational studies will be targeted to explore factors that influence adherence to treatment in individuals diagnosed with TB. Screening title and abstract followed by full-text screening and critical appraisal will be conducted by two researchers. Data will be extracted using the Population, Exposure, Comparator, Outcomes, Study characteristics framework. For cross-study assessment of strength of evidence for particular risk factors affecting adherence we will use the Grading of Recommendations, Assessment, Development and Evaluation tool modified for prognostic studies. A narrative synthesis of the studies will be compiled. A meta-analysis will be considered if there are sufficient numbers of studies that are homogenous in study design, population and outcomes. DISSEMINATION: A draft conceptual framework will be identified that (A) identifies key barriers to adherence at each contextual level (eg, personal, sociocultural, health systems) and (B) maps the relationships, pathways and mechanisms of effect between these factors and adherence outcomes for people with TB. The draft conceptual framework will guide targeting of adherence interventions and further research. PROSPERO REGISTRATION NUMBER: CRD42017061049