3,274 research outputs found
Kinematics of the ring-like nebula SuWt 2
We present the first detailed spatio-kinematical analysis and modelling of
the Southern planetary nebula SuWt 2. This object presents a problem for
current theories of planetary nebula formation and evolution, as it is not
known to contain a central post-main sequence star.
Deep narrowband [NII]6584 images reveal the presence of faint bipolar lobes
emanating fromthe edges of the nebular ring. Longslit observations of the
H-alpha and [NII]6584 emission lines were obtained using EMMI on the 3.6-m
ESO-NTT. The spectra reveal the nebular morphology as a bright torus encircling
the waist of an extended bipolar structure. By deprojection, the inclination of
the ring is found to be 68\degr 2\degr (c.f. ~90\degr for the
double A-type binary believed to lie at the centre of the nebula), and the ring
expansion velocity is found to be 28 km/s.
Our findings are discussed with relation to possible formation scenarios for
SuWt 2. Through comparison of the nebular heliocentric systemic velocity, found
here to be -25 5 km/s, and the heliocentric systemic velocity of the
double A-type binary, we conclude that neither component of the binary could
have been the nebular progenitor. However, we are unable to rule out the
presence of a third component to the system, which would have been the nebula
progenitor.Comment: 7 pages, 4 figures. Accepted for publication in MNRA
Abell 41: shaping of a planetary nebula by a binary central star?
We present the first detailed spatio-kinematical analysis and modelling of
the planetary nebula Abell 41, which is known to contain the well-studied
close-binary system MT Ser. This object represents an important test case in
the study of the evolution of planetary nebulae with binary central stars as
current evolutionary theories predict that the binary plane should be aligned
perpendicular to the symmetry axis of the nebula.
Deep narrowband imaging in the light of [NII], [OIII] and [SII], obtained
using ACAM on the William Herschel Telescope, has been used to investigate the
ionisation structure of Abell 41. Longslit observations of the H-alpha and
[NII] emission were obtained using the Manchester Echelle Spectrometer on the
2.1-m San Pedro M\'artir Telescope. These spectra, combined with the narrowband
imagery, were used to develop a spatio-kinematical model of [NII] emission from
Abell 41. The best fitting model reveals Abell 41 to have a waisted, bipolar
structure with an expansion velocity of ~40km\s at the waist. The symmetry axis
of the model nebula is within 5\degr of perpendicular to the orbital plane of
the central binary system. This provides strong evidence that the close-binary
system, MT Ser, has directly affected the shaping of its nebula, Abell 41.
Although the theoretical link between bipolar planetary nebulae and binary
central stars is long established, this nebula is only the second to have this
link, between nebular symmetry axis and binary plane, proved observationally.Comment: 7 pages, 6 figures, Accepted for publication in MNRA
Exploiting Parallel R in the Cloud with SPRINT
BACKGROUND: Advances in DNA Microarray devices and next-generation massively parallel DNA sequencing platforms have led to an exponential growth in data availability but the arising opportunities require adequate computing resources. High Performance Computing (HPC) in the Cloud offers an affordable way of meeting this need. OBJECTIVES: Bioconductor, a popular tool for high-throughput genomic data analysis, is distributed as add-on modules for the R statistical programming language but R has no native capabilities for exploiting multi-processor architectures. SPRINT is an R package that enables easy access to HPC for genomics researchers. This paper investigates: setting up and running SPRINT-enabled genomic analyses on Amazon’s Elastic Compute Cloud (EC2), the advantages of submitting applications to EC2 from different parts of the world and, if resource underutilization can improve application performance. METHODS: The SPRINT parallel implementations of correlation, permutation testing, partitioning around medoids and the multi-purpose papply have been benchmarked on data sets of various size on Amazon EC2. Jobs have been submitted from both the UK and Thailand to investigate monetary differences. RESULTS: It is possible to obtain good, scalable performance but the level of improvement is dependent upon the nature of algorithm. Resource underutilization can further improve the time to result. End-user’s location impacts on costs due to factors such as local taxation. Conclusions: Although not designed to satisfy HPC requirements, Amazon EC2 and cloud computing in general provides an interesting alternative and provides new possibilities for smaller organisations with limited funds
Development of an Evidence-Based Best Practice Model for Teams Managing Crisis in Dementia: Protocol for a Qualitative Study
Background:
Teams working in the community to manage crisis in dementia are available, but with widely varying models of practice it is difficult to determine the effectiveness of such teams. The aim of this study is to develop a model of best practice for dementia services managing crisis, as well as a set of resources to help teams implement this model: these will be (respectively) the Best Practice Tool and Toolkit, to improve the effectiveness of crisis teams working with older people with dementia and their carers.
Objective:
To detail a protocol describing the development a ‘Best Practice Model,’ to include a Best Practice Tool and Toolkit intended to measure and improve practice delivery.
Methods:
This paper describes the protocol for a prospective study which will use qualitative methods to establish an understanding of current practice to develop a ‘Best Practice Model,’ to include a Best Practice Tool and Toolkit intended to measure and improve practice delivery. Participants (people with dementia, carers, staff members and stakeholders) from a variety of geographical areas, with a broad experience of crisis and non-crisis working, will be purposively selected to participate in qualitative methodology including interviews, focus groups, a consensus workshop, and development and field testing of both the Best Practice Tool and Toolkit.
Results:
Not applicable as protocol is describing a prospective study for development of a 'Best Practice Model' for Teams Managing Crisis in Dementia.
Conclusions:
This is the first study to systematically explore the requirements needed to fulfil effective and appropriate home management for people with dementia and their carers at a time of mental health crisis, as delivered by Teams Managing Crisis in Dementia (TMCDs). This systematic approach to development will support greater acceptability and validity of the Best Practice Tool and Toolkit and lay the foundation for a large scale trial with TMCDs across England to investigate effects on practice and impact on service provision, and associated experiences of people with dementia and their carers.
Clinical Trial: Not applicable
Are people who participate in cultural activities more satisfied with life?
The influence of various aspects of life on wellbeing has been extensively researched. However, despite little empirical evidence, participation in leisure activities has been assumed to increase subjective wellbeing. Leisure is important because it is more under personal control than other sources of life satisfaction. This study asked whether people who participate in cultural leisure activities have higher life satisfaction than people who do not, if different types of leisure have the same influence on life satisfaction and if satisfaction is dependent on the frequency of participation or the number of activities undertaken. It used data from UKHLS Survey to establish associations between type, number and frequency of participation in leisure activities and life satisfaction. Results showed an independent and positive association of participation in sport, heritage and active-creative leisure activities and life satisfaction but not for participation in popular entertainment, theatre hobbies and museum/galleries. The association of reading hobbies and sedentary-creative activities and life satisfaction was negative. High life satisfaction was associated with engaging in a number of different activities rather than the frequency of participation in each of them. The results have implications for policy makers and leisure services providers, in particular those associated with heritage recreation. Subjective wellbeing measures, such as life satisfaction, and not economic measures alone should be considered in the evaluation of services. The promotion of leisure activities which are active and promote social interaction should be considered in programmes aimed at improving the quality of life
Quantifying the impact of climate change on drought regimes using the Standardised Precipitation Index
The study presents a methodology to characterise short- or long-term drought events, designed to aid understanding of how climate change may affect future risk. An indicator of drought magnitude, combining parameters of duration, spatial extent and intensity, is presented based on the Standardised Precipitation Index (SPI). The SPI is applied to observed (1955–2003) and projected (2003–2050) precipitation data from the Community Integrated Assessment System (CIAS). Potential consequences of climate change on drought regimes in Australia, Brazil, China, Ethiopia, India, Spain, Portugal and the USA are quantified. Uncertainty is assessed by emulating a range of global circulation models to project climate change. Further uncertainty is addressed through the use of a high-emission scenario and a low stabilisation scenario representing a stringent mitigation policy. Climate change was shown to have a larger effect on the duration and magnitude of long-term droughts, and Australia, Brazil, Spain, Portugal and the USA were highlighted as being particularly vulnerable to multi-year drought events, with the potential for drought magnitude to exceed historical experience. The study highlights the characteristics of drought which may be more sensitive under climate change. For example, on average, short-term droughts in the USA do not become more intense but are projected to increase in duration. Importantly, the stringent mitigation scenario had limited effect on drought regimes in the first half of the twenty-first century, showing that adaptation to drought risk will be vital in these regions
Protocol for the development of an evidence-based ‘Best Practice Model’ for Teams Managing Crisis in Dementia
Background:
Teams working in the community to manage crisis in dementia are available, but with widely varying models of practice it is difficult to determine the effectiveness of such teams. The aim of this study is to develop a model of best practice for dementia services managing crisis, as well as a set of resources to help teams implement this model: these will be (respectively) the Best Practice Tool and Toolkit, to improve the effectiveness of crisis teams working with older people with dementia and their carers.
Objective:
To detail a protocol describing the development a ‘Best Practice Model,’ to include a Best Practice Tool and Toolkit intended to measure and improve practice delivery.
Methods:
This paper describes the protocol for a prospective study which will use qualitative methods to establish an understanding of current practice to develop a ‘Best Practice Model,’ to include a Best Practice Tool and Toolkit intended to measure and improve practice delivery. Participants (people with dementia, carers, staff members and stakeholders) from a variety of geographical areas, with a broad experience of crisis and non-crisis working, will be purposively selected to participate in qualitative methodology including interviews, focus groups, a consensus workshop, and development and field testing of both the Best Practice Tool and Toolkit.
Results:
Not applicable as protocol is describing a prospective study for development of a 'Best Practice Model' for Teams Managing Crisis in Dementia.
Conclusions:
This is the first study to systematically explore the requirements needed to fulfil effective and appropriate home management for people with dementia and their carers at a time of mental health crisis, as delivered by Teams Managing Crisis in Dementia (TMCDs). This systematic approach to development will support greater acceptability and validity of the Best Practice Tool and Toolkit and lay the foundation for a large scale trial with TMCDs across England to investigate effects on practice and impact on service provision, and associated experiences of people with dementia and their carers. Clinical Trial: Not applicabl
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Connectionist modal logic: Representing modalities in neural networks
AbstractModal logics are amongst the most successful applied logical systems. Neural networks were proved to be effective learning systems. In this paper, we propose to combine the strengths of modal logics and neural networks by introducing Connectionist Modal Logics (CML). CML belongs to the domain of neural-symbolic integration, which concerns the application of problem-specific symbolic knowledge within the neurocomputing paradigm. In CML, one may represent, reason or learn modal logics using a neural network. This is achieved by a Modalities Algorithm that translates modal logic programs into neural network ensembles. We show that the translation is sound, i.e. the network ensemble computes a fixed-point meaning of the original modal program, acting as a distributed computational model for modal logic. We also show that the fixed-point computation terminates whenever the modal program is well-behaved. Finally, we validate CML as a computational model for integrated knowledge representation and learning by applying it to a well-known testbed for distributed knowledge representation. This paves the way for a range of applications on integrated knowledge representation and learning, from practical reasoning to evolving multi-agent systems
Prompt letters to reduce non-attendance: applying evidence based practice
<p>Abstract</p> <p>Background</p> <p>Non-attendance rates in psychiatric outpatient clinics have been a topic of considerable interest. It is measured as an indicator of quality of service provision. Failed attendances add to the cost of care as well as having an adverse impact on patients leading to missing medications, delay in identifying relapses and increasing waiting list time. Recent trials have demonstrated that prompting letters sent to patients led to a decrease in non-attendance rates. We applied this evidence based practice in our community mental health setting to evaluate its impact.</p> <p>Methods</p> <p>Using a before and after study design, we sent prompting letters to all patients due to attend outpatient clinic appointments for a period of six months in 2007. Non-attendance rates were compared with the corresponding period in 2006. We also looked at trends of non-attendance prior to this intervention and compared results with other parts of our service where this intervention had not been applied.</p> <p>Results</p> <p>1433 prompting letters were sent out to all out-patient appointments made from June to November 2007. This resulted in an average non-attendance rate of 17% which was significantly less compared to 27% between June and November 2006 (RR 0.65, 95% CI 0.56 to 0.76, NNT 11). No downward trend in non-attendance rate was identified either prior to the intervention or when compared with similar teams across the city.</p> <p>Conclusion</p> <p>Prompt letters have been shown to reduce non-attendance rates in previous RCTs and systematic reviews. Our findings demonstrate a reduction in non-attendance rates with prompting letters even under non-trial conditions. Majority of the patients were constant during the two periods compared although there were some changes in medical personnel. This makes it difficult to attribute all the change, solely to the intervention alone. Perhaps our work shows that the results of pragmatic randomised trials are easily applicable and produce similar results in non-randomised settings. We found that prompting letters are a useful and easy to apply evidence based intervention to reduce non-attendance rates with a potential to achieve significant cost savings.</p
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