2,610 research outputs found
Integrating ontologies and argumentation for decision-making in breast cancer
This thesis describes some of the problems in providing care for patients with breast cancer. These are
then used to motivate the development of an extension to an existing theory of argumentation, which I
call the Ontology-based Argumentation Formalism (OAF). The work is assessed in both theoretical and
empirical ways.
From a clinical perspective, there is a problem with the provision of care. Numerous reports have
noted the failure to provide uniformly high quality care, as well as the number of deaths caused by
medical care. The medical profession has responded in various ways, but one of these has been the
development of Decision Support Systems (DSS). The evidence for the effectiveness of such systems is
mixed, and the technical basis of such systems remains open to debate. However, one basis that has been
used is argumentation.
An important aspect of clinical practice is the use of the evidence from clinical trials, but these trials
are based on the results in defined groups of patients. Thus when we use the results of clinical trials to
reason about treatments, there are two forms of information we are interested in - the evidence from
trials and the relationships between groups of patients and treatments. The relational information can be
captured in an ontology about the groups of patients and treatments, and the information from the trials
captured as a set of defeasible rules.
OAF is an extension of an existing argumentation system, and provides the basis for an
argumentation-based Knowledge Representation system which could serve as the basis for future DSS.
In OAF, the ontology provides a repository of facts, both asserted and inferred on the basis of formulae
in the ontology, as well as defining the language of the defeasible rules. The defeasible rules are used
in a process of defeasible reasoning, where monotonic consistent chains of reasoning are used to draw
plausible conclusions. This defeasible reasoning is used to generate arguments and counter-arguments.
Conflict between arguments is defined in terms of inconsistent formulae in the ontology, and by using
existing proposals for ontology languages we are able to make use of existing proposals and technologies
for ontological reasoning.
There are three substantial areas of novel work: I develop an extension to an existing argumentation
formalism, and prove some simple properties of the formalism. I also provide a novel formalism of the
practical syllogism and related hypothetical reasoning, and compare my approach to two other proposals
in the literature. I conclude with a substantial case study based on a breast cancer guideline, and in order
to do so I describe a methodology for comparing formal and informal arguments, and use the results of this to discuss the strengths and weaknesses of OAF. In order to develop the case study, I provide a
prototype implementation. The prototype uses a novel incremental algorithm to construct arguments and
I give soundness, completeness and time-complexity results. The final chapter of the thesis discusses
some general lessons from the development of OAF and gives ideas for future work
Exact steady state solution of the Boltzmann equation: A driven 1-D inelastic Maxwell gas
The exact nonequilibrium steady state solution of the nonlinear Boltzmann
equation for a driven inelastic Maxwell model was obtained by Ben-Naim and
Krapivsky [Phys. Rev. E 61, R5 (2000)] in the form of an infinite product for
the Fourier transform of the distribution function . In this paper we
have inverted the Fourier transform to express in the form of an
infinite series of exponentially decaying terms. The dominant high energy tail
is exponential, , where and the amplitude is given in terms of a converging
sum. This is explicitly shown in the totally inelastic limit ()
and in the quasi-elastic limit (). In the latter case, the
distribution is dominated by a Maxwellian for a very wide range of velocities,
but a crossover from a Maxwellian to an exponential high energy tail exists for
velocities around a crossover velocity , where .
In this crossover region the distribution function is extremely small, .Comment: 11 pages, 4 figures; a table and a few references added; to be
published in PR
‘My favourite things to do’ and ‘my favourite people’: Exploring salient aspects of children’s self-concept
This study explores the potential of the ‘draw-and-write’ method for inviting children to communicate salient aspects of their self-concept. Irish primary school children aged 10–13 years drew and wrote about their favourite people and things to do (social and active self). Children drew and described many salient activities (39 in total) and people – including pets. Results suggest that widely used, adult-constructed self-esteem scales for children, while multidimensional, are limited, and that ‘draw-and-write’ is an effective multimodal method with which children can express their social and active self-concepts
Aerodynamically Alleviated Marine Vehicles (AAMV) : development of a mathematical framework to design high speed marine vehicles with aerodynamic surfaces
In the last few decades, interest in high speed marine vehicles, both in civil and military marine transportation, has motivated the marine engineering community to develop new configurations [1]. Among these, the ‘aerodynamic alleviation concept’ [2] consists of using one or more aerodynamic surfaces to alleviate the weight of marine vehicles. The advantages are: lower hydrodynamic drag better damping of heave and pitch accelerations. At Cranfield University a research programme to study AAMV started five years ago. Firstly, an AAMV equilibrium attitude model has been developed and implemented in MATLAB [3]. Similar to the Savitsky model for planing craft [4], this model is able to estimate the attitude of a given AAMV. Secondly, the vehicle stability has been studied by developing a specific system of equations of motion, using a small disturbances assumption [5]. This article presents a possible AAMV configuration that illustrates the potential of such configurations and how mathematical models can be used as design tools
Spin dynamics of a trapped spin-1 Bose Gas above the Bose-Einstein transition temperature
We study collective spin oscillations in a spin-1 Bose gas above the
Bose-Einstein transition temperature. Starting from the Heisenberg equation of
motion, we derive a kinetic equation describing the dynamics of a thermal gas
with the spin-1 degree of freedom. Applying the moment method to the kinetic
equation, we study spin-wave collective modes with dipole symmetry. The dipole
modes in the spin-1 system are found to be classified into the three type of
modes. The frequency and damping rate are obtained as functions of the peak
density. The damping rate is characterized by three relaxation times associated
with collisions.Comment: 19 pages, 5 figur
Nanoindentation Response of 3D Printed PEGDA Hydrogels in a Hydrated Environment
Hydrogels are commonly used materials in tissue engineering and organ-on-chip devices. This study investigated the nanomechanical properties of monolithic and multilayered poly(ethylene glycol) diacrylate (PEGDA) hydrogels manufactured using bulk polymerization and layer-by-layer projection lithography processes, respectively. An increase in the number of layers (or reduction in layer thickness) from 1 to 8 and further to 60 results in a reduction in the elastic modulus from 5.53 to 1.69 and further to 0.67 MPa, respectively. It was found that a decrease in the number of layers induces a lower creep index (CIT) in three-dimensional (3D) printed PEGDA hydrogels. This reduction is attributed to mesoscale imperfections that appear as pockets of voids at the interfaces of the multilayered hydrogels attributed to localized regions of unreacted prepolymers, resulting in variations in defect density in the samples examined. An increase in the degree of cross-linking introduced by a higher dosage of ultraviolet (UV) exposure leads to a higher elastic modulus. This implies that the elastic modulus and creep behavior of hydrogels are governed and influenced by the degree of cross-linking and defect density of the layers and interfaces. These findings can guide an optimal manufacturing pathway to obtain the desirable nanomechanical properties in 3D printed PEGDA hydrogels, critical for the performance of living cells and tissues, which can be engineered through control of the fabrication parameters
Dissipative Dynamics of a Josephson Junction In the Bose-Gases
The dissipative dynamics of a Josephson junction in the Bose-gases is
considered within the framework of the model of a tunneling Hamiltonian. The
effective action which describes the dynamics of the phase difference across
the junction is derived using functional integration method. The dynamic
equation obtained for the phase difference across the junction is analyzed for
the finite temperatures in the low frequency limit involving the radiation
terms. The asymmetric case of the Bose-gases with the different order
parameters is calculated as well
Scattering of light and atoms in a Fermi-Dirac gas with BCS pairing
We theoretically study the optical properties of a Fermi-Dirac gas in the
presence of a superfluid state. We calculate the leading quantum-statistical
corrections to the standard column density result of the electric
susceptibility. We also consider the Bragg diffraction of atoms by means of
light-stimulated transitions of photons between two intersecting laser beams.
Bardeen-Cooper-Schrieffer pairing between atoms in different internal levels
magnifies incoherent scattering processes. The absorption linewidth of a
Fermi-Dirac gas is broadened and shifted. Bardeen-Cooper-Schrieffer pairing
introduces a collisional local-field shift that may dramatically dominate the
Lorentz-Lorenz shift. For the case of the Bragg spectroscopy the static
structure function may be significantly increased due to superfluidity in the
nearforward scattering.Comment: 13 pages, 6 figures; to appear in PR
Finite temperature excitations of a trapped Bose-Fermi mixture
We present a detailed study of the low-lying collective excitations of a
spherically trapped Bose-Fermi mixture at finite temperature in the
collisionless regime. The excitation frequencies of the condensate are
calculated self-consistently using the static Hartree-Fock-Bogoliubov theory
within the Popov approximation. The frequency shifts and damping rates due to
the coupled dynamics of the condensate, noncondensate, and degenerate Fermi gas
are also taken into account by means of the random phase approximation and
linear response theory. In our treatment, the dipole excitation remains close
to the bare trapping frequency for all temperatures considered, and thus is
consistent with the generalized Kohn theorem. We discuss in some detail the
behavior of monopole and quadrupole excitations as a function of the Bose-Fermi
coupling. At nonzero temperatures we find that, as the mixture moves towards
spatial separation with increasing Bose-Fermi coupling, the damping rate of the
monopole (quadrupole) excitation increases (decreases). This provides us a
useful signature to identify the phase transition of spatial separation.Comment: 10 pages, 8 figures embedded; to be published in Phys. Rev.
Impacts of Climate Change on indirect human exposure to pathogens and chemicals from agriculture
Objective: Climate change is likely to affect the nature of pathogens and chemicals in the environment and their fate and transport. Future risks of pathogens and chemicals could therefore be very different from those of today. In this review, we assess the implications of climate change for changes in human exposures to pathogens and chemicals in agricultural systems in the United Kingdom and discuss the subsequent effects on health impacts.
Data sources: In this review, we used expert input and considered literature on climate change ; health effects resulting from exposure to pathogens and chemicals arising from agriculture ; inputs of chemicals and pathogens to agricultural systems ; and human exposure pathways for pathogens and chemicals in agricultural systems.
Data synthesis: We established the current evidence base for health effects of chemicals and pathogens in the agricultural environment ; determined the potential implications of climate change on chemical and pathogen inputs in agricultural systems ; and explored the effects of climate change on environmental transport and fate of different contaminant types. We combined these data to assess the implications of climate change in terms of indirect human exposure to pathogens and chemicals in agricultural systems. We then developed recommendations on future research and policy changes to manage any adverse increases in risks.
Conclusions: Overall, climate change is likely to increase human exposures to agricultural contaminants. The magnitude of the increases will be highly dependent on the contaminant type. Risks from many pathogens and particulate and particle-associated contaminants could increase significantly. These increases in exposure can, however, be managed for the most part through targeted research and policy changes
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