115 research outputs found
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&
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
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 , the alignment timescale varies as . 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&
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
Bone fractures and feeling at risk for osteoporosis among women in Japan: patient characteristics and outcomes in the National Health and Wellness Survey
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 (âincreases risk of cancerâ vs âcan cause cancerâ). 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 âincreases risk of cancerâ performed better than negatively framed messages, those referring to cancer in general, and those using the term âcan cause cancerâ. Conclusion: Cancer warning statements on alcoholic beverages constitute a potential means of increasing awareness about the relationship between alcohol consumption and cancer risk
Racial disparities in adult all-cause and cause-specific mortality among us adults: mediating and moderating factors
The Effect of Energy Labelling on Menus and a Social Marketing Campaign on Food-Purchasing Behaviours of University Students
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