Warped accretion discs and the long periods in X-ray binaries

Precessing accretion discs have long been suggested as explanations for the long periods observed in a variety of X-ray binaries, most notably Her X-1/HZ Her. We show that an instability of the disc's response to the radiation reaction force from the illumination by the central source can cause the disc to tilt out of the orbital plane and precess in something like the required manner. The rate of precession and disc tilt obtained for realistic values of system parameters compare favourably with the known body of data on X-ray binaries with long periods. We explore other possible types of behaviour than steadily precessing discs that might be observable in systems with somewhat different parameters. At high luminosities, the inner disc tilts through more than 90 degrees, i.e. it rotates counter to the usual direction, which may explain the torque reversals in systems such as 4U 1626-67.Comment: submitted to MNRAS, 17-Dec-97, revised submit 2-Nov-98. 15 pages LaTeX, 11 postscript figures in-tex

Variations in the dip properties of the low-mass X-ray binary XB 1254-69 observed with XMM-Newton and INTEGRAL

We have analysed data from five XMM-Newton observations of XB 1254-69, one of them simultaneous with INTEGRAL, to investigate the mechanism responsible for the highly variable dips durations and depths seen from this low-mass X-ray binary. Deep dips were present during two observations, shallow dips during one and no dips were detected during the remaining two observations. At high (1-4 s) time resolution ``shallow dips'' are seen to include a few, very rapid, deep dips whilst the ``deep'' dips consist of many similar very rapid, deep, fluctuations. The folded V-band Optical Monitor light curves obtained when the source was undergoing deep, shallow and no detectable dipping exhibit sinusoid-like variations with different amplitudes and phases. We fit EPIC spectra obtained from "persistent" or dip-free intervals with a model consisting of disc-blackbody and thermal comptonisation components together with Gaussian emission features at 1 and 6.6 keV modified by absorption due to cold and photo-ionised material. None of the spectral parameters appears to be strongly correlated with the dip depth except for the temperature of the disc blackbody which is coolest (kT ~ 1.8 keV) when deep dips are present and warmest (kT ~ 2.1 keV) when no dips are detectable. We propose that the changes in both disc temperature and optical modulation could be explained by the presence of a tilted accretion disc in the system. We provide a revised estimate of the orbital period of 0.16388875 +/- 0.00000017 day.Comment: 16 pages, 10 figures, 4 tables. Accepted for publication in A&

Observational Implications of Precessing Protostellar Discs and Jets

We consider the dynamics of a protostellar disc in a binary system where the disc is misaligned with the orbital plane of the binary, with the aim of determining the observational consequences for such systems. The disc wobbles with a period approximately equal to half the binary's orbital period and precesses on a longer timescale. We determine the characteristic timescale for realignment of the disc with the orbital plane due to dissipation. If the dissipation is determined by a simple isotropic viscosity then we find, in line with previous studies, that the alignment timescale is of order the viscous evolution timescale. However, for typical protostellar disc parameters, if the disc tilt exceeds the opening angle of the disc, then tidally induced shearing within the disc is transonic. In general, hydrodynamic instabilities associated with the internally driven shear result in extra dissipation which is expected to drastically reduce the alignment timescale. For large disc tilts the alignment timescale is then comparable to the precession timescale, while for smaller tilt angles $\delta$, the alignment timescale varies as $(\sin \delta)^{-1}$. We discuss the consequences of the wobbling, precession and rapid realignment for observations of protostellar jets and the implications for binary star formation mechanisms.Comment: MNRAS, in press. 10 pages. Also available at http://www.ast.cam.ac.uk/~mbat

A BeppoSAX observation of Her X-1 during the first main-on after an anomalous low-state: evidence for rapid spin-down

Results of a BeppoSAX observation of Her X-1 in 2000 October during the first main-on state after the longest recorded anomalous low-state are presented. The 0.1-30 keV spectrum, light curve and pulse profile are all consistent with those measured during previous main on-states, indicating that Her X-1 has resumed its regular 35 day cycle with similar on-state properties as before. However, from a comparison of the measured pulse period with that obtained close to the start of the anomalous low-state, it is evident that Her X-1 continued to spin-down strongly during the anomalous low-state such that the pulse period has returned to a similar value as ~15 years ago. Additionally, the occurrence time of the main-on states after the end of the anomalous low-state indicate that a change in the length, or phasing, of the 35-day cycle occurred during the anomalous low-state.Comment: 5 pages, 5 figures, accepted for publication in A&

Swedish snuff and incidence of cardiovascular disease. A population-based cohort study

<p>Abstract</p> <p>Background</p> <p>The relationship between smoking and an increased incidence of cardiovascular diseases is well known. Whether smokeless tobacco (snuff) is related to myocardial infarction (MI) or stroke is still controversial. Aim of this study was to explore whether snuff users have an increased incidence of MI or stroke.</p> <p>Methods</p> <p>A total of 16 754 women and 10 473 men (aged 45–73 years), without history of cardiovascular disease (CVD), belonging to the population-based "Malmö Diet and Cancer" study were examined. Incidence of MI and stroke were monitored over 10.3 years.</p> <p>Results</p> <p>Snuff was used by 737 (7.0%) men and 75 (0.4%) women, respectively. Among men, snuff was significantly associated with low occupation level, single civil status, high BMI and with current and former smoking. In women, snuff was associated with lower systolic blood pressure. A total of 964 individuals (3.5%), i.e.544 men (5.3%) and 420 (2.5%) women suffered a MI during the follow-up period. The corresponding numbers of incident stroke cases were 1048, i.e. 553 men (5.3%) and 495 (3.0%) women, respectively. Snuff was not associated with any statistically significant increased risk of MI or stroke in men or women. The relative risks (RR) in male snuff users compared to non-users were 1.05 (95% confidence interval (CI): 0.8–1.4, p = 0.740) for incident MI and 0.97 (0.7–1.4, p = 0.878) for stroke, after taking age and potential confounders into account. In women none of the 420 (2.5%) women who were snuff users had a MI and only one suffered a stroke during the follow-up.</p> <p>Conclusion</p> <p>Several life-style risk factors were more prevalent in snuff-users than in non-users. However, the present study does not support any relationship between snuff and incidence of cardiovascular disease in men.</p

Broad band variability of SS433: Accretion disk at work?

We present broad band power spectra of variations of SS433 in radio, optical and X-ray spectral bands. We show that at frequencies lower than 1e-5 Hz the source demonstrates the same variability pattern in all these bands. The broad band power spectrum can be fitted by one power law down to frequencies ~1e-7 Hz with flattening afterwards. Such a flattening means that on time scales longer than ~1e7 sec the source variability becomes uncorrelated. This naturally leads to the appearance of quasi-poissonian flares in the source light curve, which have been regularly observed in radio and optical spectral bands. The radio flux power spectrum appears to have a second break at Fourier frequencies ~1e-5 Hz which can be caused by the smearing of the intrinsic radio variability on timescale of the light-crossing time of the radio emitting region. We find a correlation of the radio and optical fluxes of SS433 and the radio flux is delayed by about ~2 days with respect to the optical one. Power spectra of optical and X-ray variabilities continue with the same power law from 1e-7 Hz up to ~0.01-0.05 Hz. The broad band power spectrum of SS433 can be interpreted in terms of self-similar accretion rate modulations in the accretion disk proposed by Lyubarskii (1997) and elaborated by Churazov et al. (2001). We discuss a viscous time-scale in the accretion disk of SS433 in implication to the observed broad band power spectrum.Comment: 8 pages, 2 figures. Submitted to A&

Drivers and barriers to acceptance of human-papillomavirus vaccination among young women: a qualitative and quantitative study

<p>Abstract</p> <p>Background</p> <p>Human papillomavirus (HPV) is a necessary cause of cervical dysplasia and cancer, and of genital warts. Few studies have examined attitudes to HPV vaccination since the introduction of HPV vaccines. We aimed to investigate the reasons for young women's acceptance or rejection of the quadrivalent HPV vaccine after its general availability in Denmark.</p> <p>Method</p> <p>A literature review assessed attitudes towards HPV vaccination and the information was used to identify relevant questions for telephone and focus group interviews with women aged 16-26 who had decided to receive or reject HPV vaccination. 435 women across Denmark were interviewed by telephone. Qualitative interviews were undertaken in focus groups with 33 women living in Odense who had completed the telephone survey. Four focus groups were set up according to age (16-20 and 21-26 years of age) and acceptance/rejection of the vaccine.</p> <p>Results</p> <p>Of 839 women initially contacted by telephone, 794 were included, 411 (49%) said they accepted vaccination but only 201 (24%) had actually received the vaccine and these latter were interviewed. 242 women said they refused vaccination of which 234 were interviewed. Women who were undecided were excluded from the study. Prevention of cervical cancer was the main driver for acceptance of the vaccine, followed by parental encouragement and financial support, personal experience of someone with cancer and recommendation by health-care professionals. The greatest barrier to vaccination was its cost. A lack of information about the benefits of vaccination for sexually active women was also an important barrier and the older participants in particular considered that they were too old to be vaccinated. Knowledge about HPV and its role in the development of cervical cancer and genital warts was poor.</p> <p>Conclusions</p> <p>The difference between intention to be vaccinated and starting vaccination was considerable, and a large proportion of women aged 16-26 did not wish to be vaccinated. If the most important barriers to vaccination were addressed (cost and a lack of information about vaccination benefits), it is likely that the uptake of vaccination in Denmark would increase substantially.</p

Knowledge of human papillomavirus infection and its prevention among adolescents and parents in the greater Milan area, Northern Italy

<p>Abstract</p> <p>Background</p> <p>In order to be widely accepted by users, the implementation of a new health intervention requires them to be adequately informed about its clinical importance, benefits and risks. The aim of this study was to provide data on the knowledge of Italian adolescents and parents concerning human papillomavirus (HPV) infection and its prevention in order to allow the development of adequate training programmes.</p> <p>Methods</p> <p>Between 2 May and 15 June 2008, we made a cross-sectional survey of 863 high school students and 2,331 parents of middle and high school students using two anonymously completed questionnaires covering the knowledge of HPV infection and related diseases, and attitudes to vaccinations. The approached schools were a convenience sample of the schools of the greater Milan area, Northern Italy.</p> <p>Results</p> <p>More mothers than fathers were aware that HPV infection could concern their children (58% <it>vs </it>53%; p = 0.004) and were favourable towards vaccinating their children against HPV (68% <it>vs </it>65%; p = 0.03); among the students, more females than males were aware that HPV infection could concern themselves (45% <it>vs </it>26%; p < 0.001) and would undergo vaccination against HPV (68% <it>vs </it>40%; p < 0.001). The parents' propensity to vaccinate their children against HPV was significantly associated with professing the Catholic religion (odds ratio - OR = 0.61, 95% confidence interval - CI 0.46-0.82, being atheist), the gender of the offspring (OR = 1.88, 95% CI 1.53-2.30, having at least one daughter), a propensity to vaccinations in general (OR = 23.1, 95% CI 13.7-38.8), a knowledge that HPV vaccine is aimed at preventing cervical cancer (OR = 2.31, 95% CI 1.69-3.16), and an awareness that HPV could affect their own children (OR = 3.52, 95% CI 2.89-4.29). The students who were aware that HPV infection could affect themselves were more in favour of to HPV vaccination, regardless of whether they were male (OR = 5.73, 95% CI 2.85-11.5) or female (OR = 2.39, 95% CI 1.66-3.46).</p> <p>Conclusions</p> <p>Both students and parents seem to underestimate the likelihood of HPV infection, and this is associated with a lower propensity for vaccination. This is an important indication for future training programmes concerning HPV prevention designed to increase the acceptance of HPV vaccine in families.</p

Developing cancer warning statements for alcoholic beverages

Background: There is growing evidence of the increased cancer risk associated with alcohol consumption, but this is not well understood by the general public. This study investigated the acceptability among drinkers of cancer warning statements for alcoholic beverages. Methods: Six focus groups were conducted with Australian drinkers to develop a series of cancer-related warning statements for alcohol products. Eleven cancer warning statements and one general health warning statement were subsequently tested on 2,168 drinkers via an online survey. The statements varied by message frame (positive vs negative), cancer reference (general vs specific), and the way causality was communicated (‘increases risk of cancer’ vs ‘can cause cancer’). Results: Overall, responses to the cancer statements were neutral to favorable, indicating that they are unlikely to encounter high levels of negative reaction from the community if introduced on alcoholic beverages. Females, younger respondents, and those with higher levels of education generally found the statements to be more believable, convincing, and personally relevant. Positively framed messages, those referring to specific forms of cancer, and those using ‘increases risk of cancer’ performed better than negatively framed messages, those referring to cancer in general, and those using the term ‘can cause cancer’. Conclusion: Cancer warning statements on alcoholic beverages constitute a potential means of increasing awareness about the relationship between alcohol consumption and cancer risk