Optical pulsations in HZ Herculis. 5. Pulse-resolved spectrophotometry

Digital spectra of HZ Herculis were obtained with 10 A resolution in the 3,600 - 6,000 A region, synchronously dividing the 1.24-s optical pulsation period into eight 155-ms phase bins. The optical pulses are detected in the data, but their fractional amplitude is only 0.08 percent, a factor of 4 less than typically observed. The separate spectra of each one-eighth of the pulse are identical to within the statistics of the observation. If the X-ray to optical pulse reprocessing mechanism concentrates the optical pulsations into discrete spectral line features, data require the pulses to be distributed among more than four such lines

Simultaneous X-ray and optical observations of the flaring X-ray source, Aquila A-1

During the summer of 1978 the recurrent transient X-ray source, Aquila X-1, underwent its first major outburst in two years. The results of extensive observations at X-ray and optical wavelengths throughout this event, which lasted for approximately two months are presented. The peak X-ray luminosity was approximately 1.3 times that of the Crab and exhibited spectral dependent flickering on timescales approximately 5 minutes. The observations are interpreted in terms of a standard accretion disk model withparticular emphasis on the similarities to Sco X-1 and other dward X-ray systems, although the transient nature of the system remains unexplained. It was found that Aquila X-1 can be described adequately by the semi-detached Roche lobe model and yields a mass ratio of less than or approximate to 3.5

The rise of bubbles in a glass tube and the spectrum of bubbles produced by a splash

Bubbles produced by a volume of 500 cc of water falling through a distance of 1.07 m into a water-filled basin were allowed to rise into an adjacent water-filled tube whose top was sealed at a level of 1.7 m above the level of water in the basin. The rise of these bubbles was recorded on video at a height of 1.5 m above the level of the splash: larger bubbles were recorded first. A model has been devised to describe the rise of such bubbles. The rise speed of the bubbles at the level of the video camera decreased with time after a splash, becoming nearly constant after a few minutes. The model used this long term rise speed to estimate the nitrogen saturation in the water. Oxygen saturation is measured by an electrode. Given the saturation it was then possible to use the model to calculate the initial spectrum of bubbles rising up the tube from the splash (i.e. the spectrum of such bubbles a second or two after the splash, when bubble fractionation or coalescence has ceased). The smallest bubble that could be seen depends on the gas saturation, but was typically of initial radius 20 μm, corresponding to a radius of 50-70 μm at the level of the video. Such spectra were found at different saturations, distances from the splash and salinities. At gas saturations of 105%-120%, a peak appears in the spectrum at a radius of about 20 μm. The time of admission of bubbles into the tube after a splash could also be restricted. For unrestricted sampling times, dN/dr varied as r−1.5, when expressed as a power law. The spectrum above the peak value became steeper at later sampling times. At salinities below about 10 ppt, the number of bubbles of calculated initial radius \u3c 600 μm is reduced. While no attempt was made to produce a realistic breaking wave, these results are relevant to attempts to define a source function of bubbles at sea, and to comparisons between fresh and salt water experiments

The socio-economic status of women in central Sudan

Sexual inequality is rooted in many early histories and cultures and has often been compounded by a modernisation process imposed from the West which has progressively lowered the status of women since benefits have accrued mainly to the male sector of society. In the developing world where general living conditions are poor and the impact of development programmes most profound, the male/female differential of opportunity and expectation is consequently widening and the conditions of women's lives becoming increasingly restrictive. In Central Sudan the level of socio-economic development is low by global standards. The particular sociocultural and socioeconomic characteristics of the population must be taken into account when attempting to describe and explain the status of women in the region. In Central Sudan, Islam is of fundamental significance because of its influence on the male/female differential in general and because the religious orientation of the population influenced the effects of development planning in this region on the lives and status of women. Central Sudan is the home of Sudan's largest development project - the Gezira Irrigation Scheme. The influence of the Scheme is investigated here using a questionnaire-based research approach and seven sample villages. These villages are situated in areas which have been involved in the Scheme for differing lengths of time - sixty, thirty and ten years. This provided a crude representation of the temporal changes in socioeconomic conditions which are attributable to the influence of the Scheme. The Gezira Scheme has intervened in the process of change over an extensive geographical and social area involving the inhabitants of the area and migrant peoples from outside. Most indigenous households received tenancies but many Western Sudanese and non-nationals, particularly Nigerians, were attracted to the Scheme as wage-labourers

The school to work transition for young people who experience custody

We use individual-level population data to characterise the pathways followed by young people in England who experience custody. We identify a typology of pathways up to age 18 and a separate typology covering ages 19-22. Our results confirm the generally poor prospects among this group, showing 80 per cent to be firmly established as not in employment, education or training (NEET) by age 22. Despite the high level of deprivation in the population considered, prospects are still found to vary with specific markers of disadvantage. Managing to avoid NEET when 16-18 is an important part of the strategy for avoiding NEET when older. This suggests the importance of policy interventions aimed at re-engagement of those who experience custody as a young person

The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs

The performance and cost of the 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States were determined. The regional insolation data base is discussed. A range for the forecast cost of conventional electricity by region and nationally over the next several cades are presented

Radiation mechanisms and geometry of Cygnus X-1 in the soft state

We present X-ray/gamma-ray spectra of Cyg X-1 observed during the transition from the hard to the soft state and in the soft state by ASCA, RXTE and OSSE in 1996 May and June. The spectra consist of a dominant soft component below ~2 keV and a power-law-like continuum extending to at least ~800 keV. We interpret them as emission from an optically-thick, cold accretion disc and from an optically-thin, non-thermal corona above the disc. A fraction f ~ 0.6 of total available power is dissipated in the corona. We model the soft component by multi-colour blackbody disc emission taking into account the torque-free inner-boundary condition. If the disc extends down to the minimum stable orbit, the ASCA/RXTE data yield the most probable black hole mass of about 10 solar masses and an accretion rate about 0.5 L_E/c^2, locating Cyg X-1 in the soft state in the upper part of the stable, gas-pressure dominated, accretion-disc solution branch. The spectrum of the corona is well modelled by repeated Compton scattering of seed photons from the disc off electrons with a hybrid, thermal/non-thermal distribution. The electron distribution can be characterized by a Maxwellian with an equilibrium temperature of kT ~ 30--50 keV and a Thomson optical depth of ~0.3 and a quasi-power-law tail. The compactness of the corona is between 2 and 7, and a presence of a significant population of electron-positron pairs is ruled out. We find strong signatures of Compton reflection from a cold and ionized medium, presumably an accretion disc, with an apparent reflector solid angle ~0.5--0.7. The reflected continuum is accompanied by a broad iron K-alpha line.Comment: 18 pages, 12 figures, 2 landscape tables in a separate file. Accepted to MNRA

The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs

The performance and cost of four 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States was studied. Each region has different insolation characteristics which result in varying collector field areas, plant performance, capital costs and energy costs. The regional variation in solar plant performance was assessed in relation to the expected rise in the future cost of residential and commercial electricity supplied by conventional utility power systems in the same regions. A discussion of the regional insolation data base is presented along with a description of the solar systems performance and costs. A range for the forecast cost of conventional electricity by region and nationally over the next several decades is given

Discovery of powerful millisecond flares from Cygnus X-1

We have found a large number of very strong flares in the available XTE PCA data of Cyg X-1 (also seen in available HEXTE and BATSE data) with 13 flares satisfying our chosen threshold criterion, occuring both in the hard and the soft states. We analyze here in detail two of them. The strongest one took place in the soft state, with the 3-30 keV energy flux increasing 30 times with respect to the preceding 16-s average. The e-folding time is ~ 7 ms for the main flare and ~ 1 ms for its precursor. The spectrum strongly hardens during the flare. On the other hand, flares in the hard state have generally lower amplitudes and longer e-folding times, and their spectra soften during the flare, with the hardness of the spectrum at the flare peak similar for both types of the flares. The presence of the flares shows unusually dramatic events taking place in the accretion flow of Cyg X-1. On the other hand, the rate of occurence of hard-state flares shows they may represent a high-flux end of the distribution of shots present in usual lightcurves of Cyg X-1.Comment: Accepted for publication in MNRA

Using a hypothetical scenario to assess public preferences for colorectal surveillance following screening-detected, intermediate-risk adenomas: annual home-based stool test vs. triennial colonoscopy

Background To assess public preferences for colorectal cancer (CRC) surveillance tests for intermediate-risk adenomas, using a hypothetical scenario. Methods Adults aged 45–54 years without CRC were identified from three General Practices in England (two in Cumbria, one in London). A postal survey was carried out during a separate study on preferences for different first-line CRC screening modalities (non- or full-laxative computed tomographic colonography, flexible sigmoidoscopy, or colonoscopy). Individuals were allocated at random to receive a pack containing information on one first-line test, and a paragraph describing CRC surveillance recommendations for people who are diagnosed with intermediate-risk adenomas during screening. All participants received a description of two surveillance options: annual single-sample, home-based stool testing (consistent with Faecal Immunochemical Tests; FIT) or triennial colonoscopy. Invitees were asked to imagine they had been diagnosed with intermediate-risk adenomas, and then complete a questionnaire on their surveillance preferences. Results 22.1 % (686/3,100) questionnaires were returned. 491 (15.8 %) were eligible for analysis. The majority of participants stated a surveillance preference for the stool test over colonoscopy (60.8 % vs 31.0 %; no preference: 8.1 %; no surveillance: 0.2 %). Women were more likely to prefer the stool test than men (66.7 % vs. 53.6 %; p = .011). The primary reason for preferring the stool test was that it would be done more frequently. The main reason to prefer colonoscopy was its superiority at finding polyps. Conclusions A majority of participants stated a preference for a surveillance test resembling FIT over colonoscopy. Future research should test whether this translates to greater adherence in a real surveillance setting