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An absorption line–splitting phenomenon, first reported by Cottrell and Lambert (1982a), has been shown to occur at about maximum light in the semi-regular pulsations of the R Coronae Borealis (RCB) star, RY Sgr (Lawson 1986). This has been interpreted as a shock wave propagating through the photospheric layers (Lawson and Cottrell 1986). We present spectroscopic observations of this star, taken to coincide with this line–splitting event. A sequence obtained during 1986 October revealed that this event extended over about 6 days (out of a period of about 40 days) and began at about the bluest B-V. This colour maximum, which corresponds to maximum photospheric temperatures and minimum radius, leads the V maximum by about 6 days.
Carbon, nitrogen and oxygen are of interest for stellar and galactic evolution for four main reasons. Firstly, they comprise most of the mass of elements heavier than helium, so their abundance reflects the bulk of chemical enrichment. Secondly, all of the oxygen, much of the carbon and perhaps some of the nitrogen is believed to be produced in shorter-lived stars more massive than those responsible for the Fe production (Tinsley 1979), so their abundance relative to Fe in very metal deficient objects should provide key information for modelling the chemical history of galaxies. Thirdly, because C and O comprise the bulk of the metals in stellar material (Fe:C:N:0 = 1:12:2.5:21 in the Sun) it is their abundance as well as that of iron, which is needed to compute evolutionary tracks for different metallicities. Finally, the O abundance will indicate whether CNO material has been mixed to the surface.
An estimated 800 million people live within 100 km of an active volcano in 86 countries and additional overseas territories worldwide [see Chapter 4 and Appendix B]1. Volcanoes are compelling evidence that the Earth is a dynamic planet characterised by endless change and renewal. Humans have always found volcanic activity fascinating and have often chosen to live close to volcanoes, which commonly provide favourable environments for life. Volcanoes bring many benefits to society: eruptions fertilise soils; elevated topography provides good sites for infrastructure (e.g. telecommunications on elevated ground); water resources are commonly plentiful; volcano tourism can be lucrative; and volcanoes can acquire spiritual, aesthetic or religious significance. Some volcanoes are also associated with geothermal resources, making them a target for exploration and a potential energy resource.
Much of the time volcanoes are not a threat because they erupt very infrequently or because communities have become resilient to frequently erupting volcanoes. However, there is an everpresent danger of a long-dormant volcano re-awakening or of volcanoes producing anomalously large or unexpected eruptions. Volcanic eruptions can cause loss of life and livelihoods in exposed communities, damage or disrupt critical infrastructure and add stress to already fragile environments. Their impacts can be both short-term, e.g. physical damage, and long-term, e.g. sustained or permanent displacement of populations. The risk from volcanic eruptions and their attendant hazards is often underestimated beyond areas within the immediate proximity of a volcano. For example, volcanic ash hazards can have effects hundreds of kilometres away from the vent and have an adverse impact on human and animal health, infrastructure, transport, agriculture and horticulture, the environment and economies. The products of volcanism and their impacts can extend beyond country borders, to be regional and even global in scale.
Although known historical loss of life from volcanic eruptions (since 1600 AD about 280,000 fatalities are recorded, Auker et al. (2013)) is modest compared to other major natural hazards, volcanic eruptions can be catastrophic for exposed communities. In 1985 the town of Armero in Colombia was buried by lahars (volcanic mudflows) with more than 21,000 fatalities due to relatively small explosive eruptions at the summit of Nevado del Ruiz volcano that partially melted a glacier (Voight, 1990).
General Practitioner consultation rates for influenza-like illness (ILI) are monitored through several geographically distinct schemes in the UK, providing early warning to government and health services of community circulation and intensity of activity each winter. Following on from the 2009 pandemic, there has been a harmonization initiative to allow comparison across the distinct existing surveillance schemes each season. The moving epidemic method (MEM), proposed by the European Centre for Disease Prevention and Control for standardizing reporting of ILI rates, was piloted in 2011/12 and 2012/13 along with the previously proposed UK method of empirical percentiles. The MEM resulted in thresholds that were lower than traditional thresholds but more appropriate as indicators of the start of influenza virus circulation. The intensity of the influenza season assessed with the MEM was similar to that reported through the percentile approach. The MEM pre-epidemic threshold has now been adopted for reporting by each country of the UK. Further work will continue to assess intensity of activity and apply standardized methods to other influenza-related data sources.
We carried out an extensive photometric and spectroscopic investigation of the SPB binary, HD 25558 (see Fig. 1 for the time and geographic distribution of the observations). The ~2000 spectra obtained at 13 observatories during 5 observing seasons, the ground-based multi-colour light curves and the photometric data from the MOST satellite revealed that this object is a double-lined spectroscopic binary with a very long orbital period of about 9 years. We determined the physical parameters of the components, and have found that both lie within the SPB instability strip. Accordingly, both components show line-profile variations consistent with stellar pulsations. Altogether, 11 independent frequencies and one harmonic frequency were identified in the data. The observational data do not allow the inference of a reliable orbital solution, thus, disentangling cannot be performed on the spectra. Since the lines of the two components are never completely separated, the analysis is very complicated. Nevertheless, pixel-by-pixel variability analysis of the cross-correlated line profiles was successful, and we were able to attribute all the frequencies to the primary or secondary component. Spectroscopic and photometric mode-identification was also performed for several of these frequencies of both binary components. The spectroscopic mode-identification results suggest that the inclination and rotation of the two components are rather different. While the primary is a slow rotator with ~6 d rotation period, seen at ~60° inclination, the secondary rotates fast with ~1.2 d rotation period, and is seen at ~20° inclination. Our spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field was detected in the primary.
The detailed analysis and results of this study will be published elsewhere.
An analysis was undertaken to measure age-specific vaccine effectiveness (VE) of 2010/11 trivalent seasonal influenza vaccine (TIV) and monovalent 2009 pandemic influenza vaccine (PIV) administered in 2009/2010. The test-negative case-control study design was employed based on patients consulting primary care. Overall TIV effectiveness, adjusted for age and month, against confirmed influenza A(H1N1)pdm 2009 infection was 56% (95% CI 42–66); age-specific adjusted VE was 87% (95% CI 45–97) in <5-year-olds and 84% (95% CI 27–97) in 5- to 14-year-olds. Adjusted VE for PIV was only 28% (95% CI −6 to 51) overall and 72% (95% CI 15–91) in <5-year-olds. For confirmed influenza B infection, TIV effectiveness was 57% (95% CI 42–68) and in 5- to 14-year-olds 75% (95% CI 32–91). TIV provided moderate protection against the main circulating strains in 2010/2011, with higher protection in children. PIV administered during the previous season provided residual protection after 1 year, particularly in the <5 years age group.
We report the major highlights of variable star research within the past three years. This overview is limited to intrinsically variable stars, because the achievements in variable star research stemming from binarity, or multiplicity in general, is covered by the summary report of Commissions 26 and 42.
We study a system of interacting renewal processes which is a model for neuronal activity. We show that the system possesses an exponentially large number (with respect to the number of neurons in the network) of limiting configurations of the ‘firing neurons’. These we call patterns. Furthermore, under certain conditions of symmetry we find an algorithm to control limiting patterns by means of the connection parameters.
An 8-month-old boy with global developmental delay, including visual and hearing inattention, was examined in the ophthalmic clinic. Monocular flash visual evoked potentials demonstrated a crossed asymmetry in scalp distribution, a feature considered to be pathognomic of albinism. Remarkably a foveal reflex was noted in each eye and this patient did not have nystagmus, iris transillumination, nor conspicuously pale fundi. The optic discs appeared normal. He was noted to have very fair skin and hair, with a small head and flat occiput. Cytogenetic studies demonstrated a microdeletion of the maternal chromosome 15q11–q13, and he was diagnosed with Angelman syndrome.
Three studies examined the sources of
learning by which children, very early in learning to read, formed correspondences between
letters and phonemes when these were not explicitly taught in the whole language instruction
they received. There were three classes of predicted knowledge sources: (a) induced sublexical
relations (i.e., induction of orthographic–phonological relations from the experience of
print words), (b) acrophones from letter names, and (c) transfer from spelling experience. The
results of Study 1 indicated that children used both sources (a) and (b). Study 2 results showed
that source (a) dominated when the letters were initial components of pseudowords rather than
isolated items. The transfer from phoneme-to-grapheme correspondences of the children's
spelling was examined in Study 3. The results were not consistent with the use of source (c). The
findings of these studies have implications for the question of how early in learning to read
children are able to use knowledge from their experience of print words as a source for
Liver samples from 10 Schistosoma mansoni-infected baboons all yielded eggs but neither their egg counts nor duration of infection (< 226 weeks) correlated with the slightly elevated liver collagen levels or minimal histological fibrosis observed. Approximately 10% of inert 9 and 15 μm diameter microspheres injected into the mesenterio veins of 2 baboons with acute, challenge S. mansoni infection reached their lungs (mainly 9 μm microspheres). Lung egg recoveries over 1000 were significantly less common among 175 baboons exposed once to S. monsoni infections than among 56 baboons exposed more than once. Among 221 S. mansoni-and S. haematobium-infected baboons, female worm, total tissue egg and lung egg recoveries were significantly correlated with each other but not with liver or (where available) spleen weights. Liver and spleen weights were strongly correlated with total body weight. Baboons did not develop significant liver fibrosis, even after prolonged schistosome infections. However, some liver ‘leakiness’ developed during acute primary and challenge infections, allowing small inert particles and eggs to pass to the lungs, but this ‘leakiness’ was not associated with resistance to challenge. In contrast to mice, such resistance in baboons cannot, therefore, be explained simply in terms of pathological changes due to previous infections.
White dwarfs fall in two main categories (1) the group with H-rich atmospheres (DA) the most numerous, and (2) the group with He-rich atmospheres (DB, DC, DF, DG, λ4670). Calculations of element separation (via gravitational settling) and convective mixing in white dwarf models have been made by Koester (1976) and Vauclair and Reisse (1977) in order to understand the existence and maintenance of these distinct groups and to predict at what stage during the cooling of the white dwarf some connection may occur between the two groups. Over the last few years, Wickramasinghe, Bessell and Cottrell (Wickramasinghe et al., 1977; Cottrell et al., 1977; Bessell and Wickramasinghe, 1979; Bessell, 1978 and Wickramasinghe and Bessell, 1979) have investigated the properties of cool (T < 6000K white dwarfs observationally and theoretically. We have attempted to establish at what temperature mixing does occur in DA white dwarfs, whether cool white dwarfs could be confused with G, K and M dwarfs, and if one can discriminate spectroscopically cool He and H-rich white dwarfs. In this paper we will discuss the spectra and colors of the coolest (Te < 5000K white dwarfs and compare them with model atmosphere calculations.