Anestis Touloumis

Anestis Touloumis
University of Brighton · School of Computing, Engineering and Mathematics

PhD

About

35
Publications
3,409
Reads
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1,661
Citations
Additional affiliations
February 2017 - February 2019
University of Brighton
Position
  • Lecturer
September 2015 - January 2017
University of Brighton
Position
  • Lecturer
September 2011 - August 2015
University of Cambridge
Position
  • Research Associate
Education
August 2006 - August 2011
University of Florida
Field of study
  • Statistics
October 2003 - May 2006
University of Piraeus
Field of study
  • Applied Statistics
October 1998 - July 2003
Aristotle University of Thessaloniki
Field of study
  • Mathematics

Publications

Publications (35)
Article
Full-text available
The R package multgee implements the local odds ratios generalized estimating equations (GEE) approach proposed by Touloumis et al. (2013), a GEE approach for correlated multinomial responses that circumvents theoretical and practical limitations of the GEE method. A main strength of multgee is that it provides GEE routines for both ordinal (ordLOR...
Article
Estimating a covariance matrix is an important task in applications where the number of variables is larger than the number of observations. Shrinkage approaches for estimating a high-dimensional covariance matrix are often employed to circumvent the limitations of the sample covariance matrix. A new family of nonparametric Stein-type shrinkage cov...
Article
The structural information in high-dimensional transposable data allows us to write the data recorded for each subject in a matrix such that both the rows and the columns correspond to variables of interest. One important problem is to test the null hypothesis that the mean matrix has a particular structure without ignoring the potential dependence...
Article
In this article, we propose a generalized estimating equations (GEE) approach for correlated ordinal or nominal multinomial responses using a local odds ratios parameterization. Our motivation lies upon observing that: (i) modeling the dependence between correlated multinomial responses via the local odds ratios is meaningful both for ordinal and n...
Chapter
This paper is the first to establish the impact of colour on users’ ability to interpret the informational content of concept diagrams, a logic designed for ontology engineering. Motivation comes from results for Euler diagrams, which form a fragment of concept diagrams: manipulating curve colours affects user performance. In particular, using dist...
Article
Full-text available
Free rides and observational advantages occur in visualizations when they reveal facts that must be inferred from an alternative representation. Understanding whether these concepts correspond to cognitive advantages is important: do they facilitate information extraction, saving the ‘deductive cost’ of making inferences? This paper presents the fi...
Chapter
A key feature of diagrams is well-matchedness, referred to as iconicity in philosophy. A well-matched diagram has a structural resemblance to its semantics and is believed to be an effective representation. In this paper, we view well-matchedness as a feature of diagrams’ meaning carriers – syntactic relationships that convey meaning. Each meaning...
Article
Full-text available
This paper presents the first empirical investigation that compares Euler and linear diagrams when they are used to represent set cardinality. A common approach is to use area-proportional Euler diagrams but linear diagrams can exploit length-proportional straight-lines for the same purpose. Another common approach is to use numerical annotations....
Data
Supplementary material for: The efficacy of Euler diagrams and linear diagrams for visualizing set cardinality using proportions and numbers. (PDF)
Data
Dataset for study two: Linear diagrams. (CSV)
Data
Dataset for study three: Euler-P&N versus LD-P. (CSV)
Data
Dataset for study one: Euler diagrams. (CSV)
Conference Paper
OWL is recognized as the de facto standard notation for ontology engineering. The Manchester OWL Syntax (MOS) was developed as an alternative to symbolic description logic (DL) and it is believed to be more effective for users. This paper sets out to test that belief from two perspectives by evaluating how accurately and quickly people understand t...
Article
Full-text available
The development of diagrammatic logics is strongly motivated by the desire to make formal reasoning accessible to broad audiences. One major research problem, for which surprisingly little progress has been made, is to understand how to choose between semantically equivalent diagrams from the perspective of human cognition. The particular focus of...
Article
Full-text available
We developed the R package SimCorMultRes to facilitate simulation of correlated categorical (binary and multinomial) responses under a desired marginal model specification. The simulated correlated categorical responses are obtained by applying threshold approaches to correlated continuous responses of underlying regression models and the dependenc...
Conference Paper
In multiple-tissue experiments, gene expression is measured across multiple tissues for each subject. For each subject, the data measurements can be written as a matrix with the different multiple tissues indexing the columns and the genes indexing the rows. In this context, neither the genes nor the tissues are expected to be independent and strai...
Article
Full-text available
Motivation: By collecting multiple samples per subject, researchers can characterize intra-subject variation using physiologically relevant measurements such as gene expression profiling. This can yield important insights into fundamental biological questions ranging from cell type identity to tumour development. For each subject, the data measure...
Conference Paper
s: AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC Glioblastoma (GB) is advanced at the time of clinical presentation and response to treatment may be confounded by clonal heterogeneity and differential patterns of resistance in spatially distinct parts of the same tumor. However, we do not understand ho...
Article
Objective: We investigated the association between the functional, epigenetic, and expressional profile of human adventitial progenitor cells (APCs) and therapeutic activity in a model of limb ischemia. Approach and results: Antigenic and functional features were analyzed throughout passaging in 15 saphenous vein (SV)-derived APC lines, of which...
Article
Full-text available
Glioblastoma (GB), the most common and aggressive adult brain tumor, is characterized by extreme phenotypic diversity and treatment failure. Through fluorescence-guided resection, we identified fluorescent tissue in the sub-ependymal zone (SEZ) of GB patients. Histological analysis and genomic characterization revealed that the SEZ harbors malignan...
Conference Paper
Full-text available
INTRODUCTION: Glioblastoma (GB) is the most common and aggressive primary brain malignancy. Combining fluorescence-guided resection and neuroanatomy, we have identified three distinct compartments: the sub-ependymal zone (SEZ), the tumour mass (T) and the tumour margin (M). METHOD: RNA from T, SEZ and M of 15 GB patients was extracted for gene expr...
Conference Paper
Full-text available
BACKGROUND: Glioblastoma (GB) is the most common and aggressive primary brain malignancy. The disease is advanced at the time of clinical presentation and response to treatment may be confounded by clonal heterogeneity and differential patterns of resistance in spatially distinct parts of the same tumor. However, we do not understand how this compl...
Poster
Full-text available
In genetics, there are studies in which it is critical to write the data for each subject in a matrix such that both the rows and the columns correspond to features of interest. In this way, we avoid losing important interpretability aspects of the data. For example, suppose that for each subject gene expression levels are measured in different tis...
Conference Paper
Full-text available
Glioblastoma (GB) is the most common and aggressive primary brain malignancy. The disease is advanced at the time of clinical presentation and response to treatment may be confounded by clonal heterogeneity and differential patterns of resistance in spatially distinct parts of the same tumor. However, we do not understand how this complex environme...
Article
The structural information in high-dimensional transposable data allows us to write the data recorded for each subject in a matrix such that both the rows and the columns correspond to variables of interest. One important problem is to test the null hypothesis that the mean matrix has a particular structure without ignoring the potential dependence...
Conference Paper
Glioblastoma (GB), the most common and aggressive adult brain tumor, is characterized by phenotypic diversity and ultimately treatment failure. Using fluorescence-guided sampling we integrated copy number aberration, gene expression and molecular clock data to show that the sub-ependymal zone (SEZ) contains precursor cells of the corresponding mass...
Conference Paper
A generalized estimating equations (GEE) approach for correlated multinomial responses was proposed by Touloumis et al. (2013). This GEE approach utilizes marginalized local odds ratios structures to describe the "association" structure and thus, it enables GEE analysis for both ordinal and nominal response categories. To obtain efficient and parsi...
Article
Full-text available
Glioblastoma (GB) is the most common and aggressive primary brain malignancy, with poor prognosis and a lack of effective therapeutic options. Accumulating evidence suggests that intratumor heterogeneity likely is the key to understanding treatment failure. However, the extent of intratumor heterogeneity as a result of tumor evolution is still poor...
Conference Paper
Full-text available
In this paper, we propose the construction of confidence intervals for a binomial proportion and the difference of two independent binomial proportions via the bootstrap method. We also propose a test for the equality of paired proportions based on bootstrap. Applications of the bootstrap method for discrete data are limited. Astrand (2000) constru...

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