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Timothy M. Walker

dblp:115/8979 · DBLP profile ↗
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5ranked-venue papers
1as first author
1since 2021 · last 2021
0000-0003-0421-9264ORCID · reported

Domains — the database's venue-derived domains; a paper can count in several

Applied, interdisciplinary, general and emerging computing · 4 · 1 since 2021Graphics, computer vision, multimedia, augmented reality and games · 1 · 1 first-author

Expertise — from the expertise taxonomy: the topics of the expert's papers under the CCF categories. A weight counts papers with recency: 1 for a paper about the topic, 0.3 when the topic is its context, halved every five years.

Interdisciplinary, comprehensive, and emerging computing
3 papers
Bioinformatics and computational biology · 100%

Topics — the 4 heaviest of 6, each with the papers that count most for it

TopicWeightPapersLastEvidence papers
Bioinformatics and computational biology › computational microbiology
antimicrobial resistance prediction
0.412019
DeepAMR for predicting co-occurrent resistance of Mycobacterium tuberculosis · Bioinform. 2019
Bioinformatics and computational biology › microbiology
antimicrobial resistance
0.312018
Machine learning for classifying tuberculosis drug-resistance from DNA sequencing data · Bioinform. 2018
Bioinformatics and computational biology › sequence analysis › sequencing data analysis
DNA sequencing analysis
0.312018
Machine learning for classifying tuberculosis drug-resistance from DNA sequencing data · Bioinform. 2018
Bioinformatics and computational biology
genomics
0.312018
Machine learning for classifying tuberculosis drug-resistance from DNA sequencing data · Bioinform. 2018

Methods — techniques the papers use, named apart from their topics

sparse principal component analysis · 0.4non-negative matrix factorization · 0.4multi-task learning · 0.4logistic regression · 0.4gradient tree boosting · 0.4deep denoising autoencoder · 0.4clustering · 0.4machine learning · 0.3classification · 0.3
YearPublicationVenuePosition
2021 An end-to-end heterogeneous graph attention network for Mycobacterium tuberculosis drug-resistance prediction
abstract
Antimicrobial resistance (AMR) poses a threat to global public health. To mitigate the impacts of AMR, it is important to identify the molecular mechanisms of AMR and thereby determine optimal therapy as early as possible. Conventional machine learning-based drug-resistance analyses assume genetic variations to be homogeneous, thus not distinguishing between coding and intergenic sequences. In this study, we represent genetic data from Mycobacterium tuberculosis as a graph, and then adopt a deep graph learning method-heterogeneous graph attention network ('HGAT-AMR')-to predict anti-tuberculosis (TB) drug resistance. The HGAT-AMR model is able to accommodate incomplete phenotypic profiles, as well as provide 'attention scores' of genes and single nucleotide polymorphisms (SNPs) both at a population level and for individual samples. These scores encode the inputs, which the model is 'paying attention to' in making its drug resistance predictions. The results show that the proposed model generated the best area under the receiver operating characteristic (AUROC) for isoniazid and rifampicin (98.53 and 99.10%), the best sensitivity for three first-line drugs (94.91% for isoniazid, 96.60% for ethambutol and 90.63% for pyrazinamide), and maintained performance when the data were associated with incomplete phenotypes (i.e. for those isolates for which phenotypic data for some drugs were missing). We also demonstrate that the model successfully identifies genes and SNPs associated with drug resistance, mitigating the impact of resistance profile while considering particular drug resistance, which is consistent with domain knowledge.
Yang Yang 0125, Timothy M. Walker, Samaneh Kouchaki, Tim E. A. Peto, Derrick W. Crook, David A. Clifton
Briefings Bioinform.2
2019 Application of machine learning techniques to tuberculosis drug resistance analysis
abstract
MOTIVATION: Timely identification of Mycobacterium tuberculosis (MTB) resistance to existing drugs is vital to decrease mortality and prevent the amplification of existing antibiotic resistance. Machine learning methods have been widely applied for timely predicting resistance of MTB given a specific drug and identifying resistance markers. However, they have been not validated on a large cohort of MTB samples from multi-centers across the world in terms of resistance prediction and resistance marker identification. Several machine learning classifiers and linear dimension reduction techniques were developed and compared for a cohort of 13 402 isolates collected from 16 countries across 6 continents and tested 11 drugs. RESULTS: Compared to conventional molecular diagnostic test, area under curve of the best machine learning classifier increased for all drugs especially by 23.11%, 15.22% and 10.14% for pyrazinamide, ciprofloxacin and ofloxacin, respectively (P < 0.01). Logistic regression and gradient tree boosting found to perform better than other techniques. Moreover, logistic regression/gradient tree boosting with a sparse principal component analysis/non-negative matrix factorization step compared with the classifier alone enhanced the best performance in terms of F1-score by 12.54%, 4.61%, 7.45% and 9.58% for amikacin, moxifloxacin, ofloxacin and capreomycin, respectively, as well increasing area under curve for amikacin and capreomycin. Results provided a comprehensive comparison of various techniques and confirmed the application of machine learning for better prediction of the large diverse tuberculosis data. Furthermore, mutation ranking showed the possibility of finding new resistance/susceptible markers. AVAILABILITY AND IMPLEMENTATION: The source code can be found at http://www.robots.ox.ac.uk/ davidc/code.php. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
Samaneh Kouchaki, Yang Yang 0125, Timothy M. Walker, A. Sarah Walker, Daniel J. Wilson 0001, Tim E. A. Peto, Derrick W. Crook, David A. Clifton
Bioinform.3
2019 DeepAMR for predicting co-occurrent resistance of Mycobacterium tuberculosis
abstract
MOTIVATION: Resistance co-occurrence within first-line anti-tuberculosis (TB) drugs is a common phenomenon. Existing methods based on genetic data analysis of Mycobacterium tuberculosis (MTB) have been able to predict resistance of MTB to individual drugs, but have not considered the resistance co-occurrence and cannot capture latent structure of genomic data that corresponds to lineages. RESULTS: We used a large cohort of TB patients from 16 countries across six continents where whole-genome sequences for each isolate and associated phenotype to anti-TB drugs were obtained using drug susceptibility testing recommended by the World Health Organization. We then proposed an end-to-end multi-task model with deep denoising auto-encoder (DeepAMR) for multiple drug classification and developed DeepAMR_cluster, a clustering variant based on DeepAMR, for learning clusters in latent space of the data. The results showed that DeepAMR outperformed baseline model and four machine learning models with mean AUROC from 94.4% to 98.7% for predicting resistance to four first-line drugs [i.e. isoniazid (INH), ethambutol (EMB), rifampicin (RIF), pyrazinamide (PZA)], multi-drug resistant TB (MDR-TB) and pan-susceptible TB (PANS-TB: MTB that is susceptible to all four first-line anti-TB drugs). In the case of INH, EMB, PZA and MDR-TB, DeepAMR achieved its best mean sensitivity of 94.3%, 91.5%, 87.3% and 96.3%, respectively. While in the case of RIF and PANS-TB, it generated 94.2% and 92.2% sensitivity, which were lower than baseline model by 0.7% and 1.9%, respectively. t-SNE visualization shows that DeepAMR_cluster captures lineage-related clusters in the latent space. AVAILABILITY AND IMPLEMENTATION: The details of source code are provided at http://www.robots.ox.ac.uk/∼davidc/code.php. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
Yang Yang 0125, Timothy M. Walker, A. Sarah Walker, Daniel J. Wilson 0001, Tim E. A. Peto, Derrick W. Crook, Farah Shamout, Tingting Zhu 0001, David A. Clifton
Bioinform.2
2018 Machine learning for classifying tuberculosis drug-resistance from DNA sequencing data
abstract
Motivation: Correct and rapid determination of Mycobacterium tuberculosis (MTB) resistance against available tuberculosis (TB) drugs is essential for the control and management of TB. Conventional molecular diagnostic test assumes that the presence of any well-studied single nucleotide polymorphisms is sufficient to cause resistance, which yields low sensitivity for resistance classification. Summary: Given the availability of DNA sequencing data from MTB, we developed machine learning models for a cohort of 1839 UK bacterial isolates to classify MTB resistance against eight anti-TB drugs (isoniazid, rifampicin, ethambutol, pyrazinamide, ciprofloxacin, moxifloxacin, ofloxacin, streptomycin) and to classify multi-drug resistance. Results: Compared to previous rules-based approach, the sensitivities from the best-performing models increased by 2-4% for isoniazid, rifampicin and ethambutol to 97% (P < 0.01), respectively; for ciprofloxacin and multi-drug resistant TB, they increased to 96%. For moxifloxacin and ofloxacin, sensitivities increased by 12 and 15% from 83 and 81% based on existing known resistance alleles to 95% and 96% (P < 0.01), respectively. Particularly, our models improved sensitivities compared to the previous rules-based approach by 15 and 24% to 84 and 87% for pyrazinamide and streptomycin (P < 0.01), respectively. The best-performing models increase the area-under-the-ROC curve by 10% for pyrazinamide and streptomycin (P < 0.01), and 4-8% for other drugs (P < 0.01). Availability and implementation: The details of source code are provided at http://www.robots.ox.ac.uk/~davidc/code.php. Contact: [email protected]. Supplementary information: Supplementary data are available at Bioinformatics online.
Yang Yang 0125, Katherine E. Niehaus, Timothy M. Walker, Zamin Iqbal, A. Sarah Walker, Daniel J. Wilson 0001, Tim E. A. Peto, Derrick W. Crook, E. Grace Smith, Tingting Zhu 0001, David A. Clifton
Bioinform.3
2013 Dynamic Recombination of Evolving Guitar Sounds (DREGS): A Genetic Algorithm Approach to Guitar Synthesizer Control
abstract
A system is described which integrates multiple hardware interfaces and software packages in order to control the parameters of a guitar synthesizer in real time. An interactive genetic algorithm is developed in order to create and explore parameter settings, and a mobile device wirelessly sets the fitness values. The synthesizer parameters are represented as genes within an individual, and individuals dynamically interact within a population as the user rates the resulting sounds by changing orientation.
Timothy M. Walker, Sean Whalen
ISM1