1,381 research outputs found
Semantic keyword search for expert witness discovery
In the last few years, there has been an increase in the amount of information stored in semantically enriched knowledge bases, represented in RDF format. These improve the accuracy of search results when the queries are semantically formal. However framing such queries is inappropriate for inexperience users because they require specialist knowledge of ontology and syntax. In this paper, we explore an approach that automates the process of converting a conventional keyword search into a semantically formal query in order to find an expert on a semantically enriched knowledge base. A case study on expert witness discovery for the resolution of a legal dispute is chosen as the domain of interest and a system named SKengine is implemented to illustrate the approach. As well as providing an easy user interface, our experiment shows that SKengine can retrieve expert witness information with higher precision and higher recall, compared with the other system, with the same interface, implemented by a vector model approach
Semantic keyword search for expert witness discovery
In the last few years, there has been an increase in the amount of information stored in semantically enriched knowledge bases, represented in RDF format. These improve the accuracy of search results when the queries are semantically formal. However framing such queries is inappropriate for inexperience users because they require specialist knowledge of ontology and syntax. In this paper, we explore an approach that automates the process of converting a conventional keyword search into a semantically formal query in order to find an expert on a semantically enriched knowledge base. A case study on expert witness discovery for the resolution of a legal dispute is chosen as the domain of interest and a system named SKengine is implemented to illustrate the approach. As well as providing an easy user interface, our experiment shows that SKengine can retrieve expert witness information with higher precision and higher recall, compared with the other system, with the same interface, implemented by a vector model approach
Investigating neovascularization in rat decellularized intestine - an in vitro platform for studying angiogenesis
One of the main challenges currently faced by tissue engineers is the loss of tissues post
implantation due to delayed neovascularization. Several strategies are under
investigation to create vascularized tissue but none have yet overcome this problem. In
this study we produced a decellularized natural vascular scaffold from rat intestine to
use as an in vitro platform for neovascularization studies for tissue engineered
constructs. Decellularization resulted in almost complete (97%) removal of nuclei and
DNA, while collagen, glycosaminoglycans and laminin content was preserved.
Decellularization did, however, result in the loss of elastin and fibronectin. Some proangiogenic
factors were retained, as fragments of decellularized intestine were able to
stimulate angiogenesis in the chick chorioallantoic membrane assay. We demonstrated
that decellularization left perfusable vascular channels intact, and these could be repopulated
with human dermal microvascular endothelial cells. Optimization of reendothelialisation
of the vascular channels showed this was improved by continuous
perfusion of the vasculature and further improved by infusion of human dermal
fibroblasts into the intestinal lumen, from where they invaded into the decellularized
tissue. Finally we explored the ability of the perfused cells to form new vessels. In the
absence of exogenous angiogenic stimuli, Dll4, a marker of endothelial capillary-tip
cell activation during sprouting angiogenesis was absent, indicating the reformed
vasculature was largely quiescent. However, after addition of VEGFA, Dll4 positive
endothelial cells could be detected, demonstrating this engineered vascular construct
maintained its capacity for neovascularization. In summary we have demonstrated how
a natural xenobiotic vasculature can be used as an in vitro model platform to study
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neovascularization and provide information on factors that are critical for efficient reendothelialisation
of decellularized tissue
Fabrication of biodegradable synthetic vascular networks and their use as a model of angiogenesis
One of the greatest challenges currently faced in tissue engineering is the incorporation of vascular networks within tissue-engineered constructs. The aim of this study was to develop a technique for producing a perfusable, three-dimensional cell friendly model of vascular structures that could be used to study the factors affecting angiogenesis and vascular biology in engineered systems in more detail. Initially, biodegradable synthetic pseudo-vascular networks were produced via the combination of robocasting and electrospinning techniques. The internal surfaces of the vascular channels were then recellularized with human dermal microvascular endothelial cells (HDMECs) with and without the presence of human dermal fibroblasts (HDFs) on the outer surface of the scaffold. After 7 days in culture, channels that had been reseeded with HDMECs alone, demonstrated irregular cell coverage. However when using a co-culture of HDMECs inside and HDFs outside the vascular channels, coverage was found to be continuous throughout the internal channel. Using this cell combination, collagen gels loaded with vascular endothelial growth factor were deposited onto the outer surface of the scaffold and cultured for a further 7 days after which endothelial cell (EC) outgrowth from within the channels into the collagen gel was observed showing the engineered vasculature maintains its capacity for angiogenesis. Furthermore the HDMECs appeared to have formed perfusable tubules within the gel. These results show promising steps towards the development of an in vitro platform upon which to study angiogenesis and vascular biology in a tissue-engineering context
Current percolation and anisotropy in polycrystalline MgB
The influence of anisotropy on the transport current in MgB
polycrystalline bulk samples and wires is discussed. A model for the critical
current density is proposed, which is based on anisotropic London theory, grain
boundary pinning and percolation theory. The calculated currents agree
convincingly with experimental data and the fit parameters, especially the
anisotropy, obtained from percolation theory agree with experiment or
theoretical predictions.Comment: 5 pages, accepted for publication in Physical Review Letters
(http://prl.aps.org/
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Choice of steel for the ISABELLE magnet tubes
It is concluded that the low temperature ductility of cast duplex stainless steels can be reduced by high ferrite content, excessive amounts of nitrogen or strong carbide forming elements, and lack of heat treatment particularly at higher ferrite levels. While all samples investigated, with the exception of No. 14 (non-heat treated 12% delta), had mechanical properties more than adequate for the intended service, it was felt advisable to modify the specifications for the tube steels. The requirement is for CF8 as per ASTM specification number A743 with the following modifications: nitrogen content must not exceed 0.08%; niobium content must not exceed 0.1% and total of all carbide formers (Nb, Ti, V, W) must not exceed 0.2%; ferrite content of the casting, as determined from the heat chemistry using the DeLong diagram, must not exceed 10%. A743 already calls for suitable solution heat treatment
The status of rapid response learning in aging.
Strong evidence exists for an age-related impairment in associative processing under intentional encoding and retrieval conditions, but the status of incidental associative processing has been less clear. Two experiments examined the effects of age on rapid response learning – the incidentally learned stimulus-response association that results in a reduction in priming when a learned response becomes inappropriate for a new task. Specifically, we tested whether priming was equivalently sensitive in both age groups to reversing the task-specific decision cue. Experiment 1 showed that cue inversion reduced priming in both age groups using a speeded inside/outside classification task, and in Experiment 2 cue inversion eliminated priming on an associative version of this task. Thus, the ability to encode an association between a stimulus and its initial task-specific response appears to be preserved in aging. These findings provide an important example of a form of associative processing that is unimpaired in older adults
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