11,211 research outputs found
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Temporal Bayesian classifiers for modelling muscular dystrophy expression data
The analysis of microarray data from time-series experiments requires specialised algorithms, which take the temporal ordering of the data into account. In this paper we explore a new architecture of Bayesian classifier that can be used to understand how biological mechanisms differ with respect to time. We show that this classifier improves the classification of microarray data and at the same time ensures that the models can easily be analysed by biologists by incorporating time transparently. In this paper we focus on data that has been generated to explore different types of muscular dystrophy
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The robust selection of predictive genes via a simple classifier
Identifying genes that direct the mechanism of a disease from expression data is extremely useful in understanding how that mechanism works.
This in turn may lead to better diagnoses and potentially can lead to a cure for that disease. This task becomes extremely challenging when the
data are characterised by only a small number of samples and a high number of dimensions, as it is often the case with gene expression data.
Motivated by this challenge, we present a general framework that focuses on simplicity and data perturbation. These are the keys for the robust
identification of the most predictive features in such data. Within this framework, we propose a simple selective na¨ıve Bayes classifier discovered using a global search technique, and combine it with data perturbation to
increase its robustness to small sample sizes.
An extensive validation of the method was carried out using two applied datasets from the field of microarrays and a simulated dataset, all
confounded by small sample sizes and high dimensionality. The method has been shown capable of identifying genes previously confirmed or associated with prostate cancer and viral infections
From Golden Spirals to Constant Slope Surfaces
In this paper, we find all constant slope surfaces in the Euclidean 3-space,
namely those surfaces for which the position vector of a point of the surface
makes constant angle with the normal at the surface in that point. These
surfaces could be thought as the bi-dimensional analogue of the generalized
helices. Some pictures are drawn by using the parametric equations we found.Comment: 11 pages, 8 figure
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A Spatio-Temporal Bayesian Network Classifier for Understanding Visual Field Deterioration
Progressive loss of the field of vision is characteristic of a number of eye diseases
such as glaucoma which is a leading cause of irreversible blindness in the world. Recently,
there has been an explosion in the amount of data being stored on patients who suffer from visual deterioration including field test data, retinal image data and patient demographic data. However, there has been relatively little work in modelling
the spatial and temporal relationships common to such data. In this paper we introduce a novel method for classifying Visual Field (VF) data that explicitly models these spatial and temporal relationships. We carry out an analysis of this
method and compare it to a number of classifiers from the machine learning and statistical communities. Results are very encouraging showing that our classifiers are comparable to existing statistical models whilst also facilitating the understanding of underlying spatial and temporal relationships within VF data. The results
reveal the potential of using such models for knowledge discovery within ophthalmic databases, such as networks reflecting the ‘nasal step’, an early indicator of the onset of glaucoma. The results outlined in this paper pave the way for a substantial program of study involving many other spatial and temporal datasets, including retinal image and clinical data
Associations between EP-like lesions and pleuritis and post trimming carcass weights of finishing pigs in England
Herd health slaughter checks regularly identify enzootic pneumonia-like (EP-like) lesions and pleuritis. The aim of this paper is to determine the associations between these lesions and post-trimming carcass weight. Data were collected on the presence/absence and severity of EP-like lesions and presence/absence of pleuritis from pigs at the abattoir. Linear mixed models identified a significant association between an increase in EP-like lesion severity and a decrease in post-trimming carcass weight (P = 0.006) at the individual level. Each categorical increase in EP-like lesion severity (5 points step) was associated with a 0.37 kg reduction in post-trimming carcass weight. The presence of EP-like lesions in individual pigs, irrespective of severity (P = 0.034) and the presence of pleuritis (P = 0.038) were significantly associated with a reduction in post-trimming carcass weight of 1.26 kg and 1.25 kg respectively. The results confirm that the presence of these lesions at slaughter are associated with a significant decrease in production performance which can result in substantial economic implications for producers
The supercluster--void network III. The correlation function as a geometrical statistic
We investigate properties of the correlation function of clusters of galaxies
using geometrical models. On small scales the correlation function depends on
the shape and the size of superclusters. On large scales it describes the
geometry of the distribution of superclusters. If superclusters are distributed
randomly then the correlation function on large scales is featureless. If
superclusters and voids have a tendency to form a regular lattice then the
correlation function on large scales has quasi-regularly spaced maxima and
minima of decaying amplitude; i.e., it is oscillating. The period of
oscillations is equal to the step size of the grid of the lattice.
We calculate the power spectrum for our models and compare the geometrical
information of the correlation function with other statistics. We find that
geometric properties (the regularity of the distribution of clusters on large
scales) are better quantified by the correlation function. We also analyse
errors in the correlation function and the power spectrum by generating random
realizations of models and finding the scatter of these realizations.Comment: MNRAS LaTex style, 12 pages, 7 PostScript figures embedded, accepted
by MNRA
Nullity and Loop Complementation for Delta-Matroids
We show that the symmetric difference distance measure for set systems, and
more specifically for delta-matroids, corresponds to the notion of nullity for
symmetric and skew-symmetric matrices. In particular, as graphs (i.e.,
symmetric matrices over GF(2)) may be seen as a special class of
delta-matroids, this distance measure generalizes the notion of nullity in this
case. We characterize delta-matroids in terms of equicardinality of minimal
sets with respect to inclusion (in addition we obtain similar characterizations
for matroids). In this way, we find that, e.g., the delta-matroids obtained
after loop complementation and after pivot on a single element together with
the original delta-matroid fulfill the property that two of them have equal
"null space" while the third has a larger dimension.Comment: Changes w.r.t. v4: different style, Section 8 is extended, and in
addition a few small changes are made in the rest of the paper. 15 pages, no
figure
Consensus clustering and functional interpretation of gene-expression data
Microarray analysis using clustering algorithms can suffer from lack of inter-method consistency in assigning related gene-expression profiles to clusters. Obtaining a consensus set of clusters from a number of clustering methods should improve confidence in gene-expression analysis. Here we introduce consensus clustering, which provides such an advantage. When coupled with a statistically based gene functional analysis, our method allowed the identification of novel genes regulated by NFκB and the unfolded protein response in certain B-cell lymphomas
A Complete Finite Equational Axiomatisation of the Fracterm Calculus for Common Meadows
We analyse abstract data types that model numerical structures with a concept
of error. Specifically, we focus on arithmetic data types that contain an error
flag whose main purpose is to always return a value for division. To
rings and fields we add a division operator and study a class of algebras
called \textit{common meadows} wherein . The set of equations true
in all common meadows is named the \textit{fracterm calculus of common
meadows}. We give a finite equational axiomatisation of the fracterm calculus
of common meadows and prove that it is complete and that the fracterm calculus
is decidable
Does the galaxy correlation length increase with the sample depth?
We have analyzed the behavior of the correlation length, , as a function
of the sample depth by extracting from the CfA2 redshift survey volume--limited
samples out to increasing distances. For a fractal distribution, the value of
would increase with the volume occupied by the sample. We find no linear
increase for the CfA2 samples of the sort that would be expected if the
Universe preserved its small scale fractal character out to the distances
considered (60--100\hmpc). The results instead show a roughly constant value
for as a function of the size of the sample, with small fluctuations due
to local inhomogeneities and luminosity segregation. Thus the fractal picture
can safely be discarded.Comment: Accepted for publication in ApJ
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