8,110 research outputs found
A boundary element regularised Stokeslet method applied to cilia and flagella-driven flow
A boundary element implementation of the regularised Stokeslet method of
Cortez is applied to cilia and flagella-driven flows in biology.
Previously-published approaches implicitly combine the force discretisation and
the numerical quadrature used to evaluate boundary integrals. By contrast, a
boundary element method can be implemented by discretising the force using
basis functions, and calculating integrals using accurate numerical or analytic
integration. This substantially weakens the coupling of the mesh size for the
force and the regularisation parameter, and greatly reduces the number of
degrees of freedom required. When modelling a cilium or flagellum as a
one-dimensional filament, the regularisation parameter can be considered a
proxy for the body radius, as opposed to being a parameter used to minimise
numerical errors. Modelling a patch of cilia, it is found that: (1) For a fixed
number of cilia, reducing cilia spacing reduces transport. (2) For fixed patch
dimension, increasing cilia number increases the transport, up to a plateau at
cilia. Modelling a choanoflagellate cell it is found that the
presence of a lorica structure significantly affects transport and flow outside
the lorica, but does not significantly alter the force experienced by the
flagellum.Comment: 20 pages, 7 figures, postprin
Automatic organisation of retrieved images into a hierarchy
Image retrieval is of growing interest to both search engines and academic researchers with increased focus on both content-based and
caption-based approaches. Image search, however, is different from document retrieval: users often search a broader set of retrieved
images than they would examine returned web pages in a search engine. In this paper, we focus on a concept hierarchy generation
approach developed by Sanderson and Croft in 1999, which was used to organise retrieved images in a hierarchy automatically
generated from image captions. Thirty participants were recruited for the study. Each of them conducted two different kinds of
searching tasks within the system. Results indicated that the user retrieval performance in both interfaces of system is similar.
However, the majority of users preferred to use the concept hierarchy to complete their searching tasks and they were satisfied with
using the hierarchical menu to organize retrieved results, because the menu appeared to provide a useful summary to help users look
through the image results
Designing multilingual information access to Tate Online
The Tate is Britain's premier national art gallery and includes content from internationally-renowned artists such as Constable and Turner. Like most cultural heritage institutions, the Tate provides online access to a large amount of digitized material. Given the international importance of content provided by the Tate Gallery, multilingual access would seem an ideal way in which to increase accessibility to the collections, and thereby increase traffic to the website. In this short paper we propose using the Tate as a case study for cross-language research and evaluation, determining the gallery’s requirements and the multilingual needs of their end-users
Building a diversity featured search system by fusing existing tools
This paper describes our diversity featured retrieval system which are built for the task
of ImageCLEFPhoto 2008. Two existing tools are used: Solr and Carrot. We have
experimented with different settings of the system to see how the performance changes.
The results suggest that the system can indeed increase diversity of the retrieved results
and keep the precision about the same
Creating a test collection to evaluate diversity in image retrieval
This paper describes the adaptation of an existing test collection
for image retrieval to enable diversity in the results set to be
measured. Previous research has shown that a more diverse set of
results often satisfies the needs of more users better than standard
document rankings. To enable diversity to be quantified, it is
necessary to classify images relevant to a given theme to one or
more sub-topics or clusters. We describe the challenges in
building (as far as we are aware) the first test collection for
evaluating diversity in image retrieval. This includes selecting
appropriate topics, creating sub-topics, and quantifying the overall
effectiveness of a retrieval system. A total of 39 topics were
augmented for cluster-based relevance and we also provide an
initial analysis of assessor agreement for grouping relevant
images into sub-topics or clusters
Following basal stem rot in young oil palm plantings
The PCR primer GanET has previously been shown to be suitable for the specific amplification of DNA from Ganoderma boninense. A DNA extraction and PCR method has been developed that allows for the amplification of the G. boninense DNA from environmental samples of oil palm tissue. The GanET primer reaction was used in conjunction with a palm-sampling programme to investigate the possible infection of young palms through cut frond base surfaces. Ganoderma DNA was detected in frond base material at a greater frequency than would be expected by comparison with current infection levels. Comparisons are made between the height of the frond base infected, the number of frond bases infected, and subsequent development of basal stem rot. The preliminary results suggest that the development of basal stem rot may be more likely to occur when young lower frond bases are infected
The impact of private sector provision on equitable provision of coronary revascularisation
Objective: To investigate the impact of including private sector data on assessments of equity of coronary revascularisation provision using NHS data only.
Design: Analyses of Hospital Episodes Statistics and private sector data by age, sex, and PCT of residence. For each PCT, the share of London's total population and revascularisations (all admissions, NHS-funded, and privately-funded admissions) were calculated. GINI coefficients were derived to provide an index of inequality across sub-populations, with parametric bootstrapping to estimate confidence intervals.
Setting: London Participants London residents undergoing coronary revascularisation April 2001 - December 2003. Intervention Coronary artery bypass graft or angioplasty
Main outcome measures: Directly-standardised revascularisation rates, GINI coefficients.
Results: NHS-funded age-standardised revascularisation rates varied from 95.2 to 193.9 per 100,000 and privately funded procedures from 7.6 to 57.6. Although the age distribution did not vary by funding, the proportion of revascularisations among women that were privately funded (11.0%) was lower than among men (17.0%). Privately funded rates were highest in PCTs with the lowest death rates (p=0.053). NHS-funded admission rates were not related to deprivation nor age-standardised deaths rates from coronary heart disease. Privately-funded admission rates were lower in more deprived PCTs. NHS provision was significantly more egalitarian (Gini coefficient 0.12) than the private sector (0.35). Including all procedures was significantly less equal (0.13) than NHS funded care alone.
Conclusion: Private provision exacerbates geographical inequalities. Those responsible for commissioning care for defined populations must have access to consistent data on provision of treatment wherever it takes place
Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model
The impact of convection on tropospheric O<sub>3</sub> and its precursors has been examined in a coupled chemistry-climate model. There are two ways that convection affects O<sub>3</sub>. First, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> itself. Convection lifts lower tropospheric air to regions where the O<sub>3</sub> lifetime is longer, whilst mass-balance subsidence mixes O<sub>3</sub>-rich upper tropospheric (UT) air downwards to regions where the O<sub>3</sub> lifetime is shorter. This tends to decrease UT O<sub>3</sub> and the overall tropospheric column of O<sub>3</sub>. Secondly, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> precursors. This affects O<sub>3</sub> chemical production and destruction. Convection transports isoprene and its degradation products to the UT where they interact with lightning NO<sub>x</sub> to produce PAN, at the expense of NO<sub>x</sub>. In our model, we find that convection reduces UT NO<sub>x</sub> through this mechanism; convective down-mixing also flattens our imposed profile of lightning emissions, further reducing UT NO<sub>x</sub>. Over tropical land, which has large lightning NO<sub>x</sub> emissions in the UT, we find convective lofting of NO<sub>x</sub> from surface sources appears relatively unimportant. Despite UT NO<sub>x</sub> decreases, UT O<sub>3</sub> production increases as a result of UT HO<sub>x</sub> increases driven by isoprene oxidation chemistry. However, UT O<sub>3</sub> tends to decrease, as the effect of convective overturning of O<sub>3</sub> itself dominates over changes in O<sub>3</sub> chemistry. Convective transport also reduces UT O<sub>3</sub> in the mid-latitudes resulting in a 13% decrease in the global tropospheric O<sub>3</sub> burden. These results contrast with an earlier study that uses a model of similar chemical complexity. Differences in convection schemes as well as chemistry schemes – in particular isoprene-driven changes are the most likely causes of such discrepancies. Further modelling studies are needed to constrain this uncertainty range
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