Automated design of genetic programming of classification algorithms.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Over the past decades, there has been an increase in the use of evolutionary algorithms (EAs) for data mining and knowledge discovery in a wide range of application domains. Data classification, a real-world application problem is one of the areas EAs have been widely applied. Data classification has been extensively researched resulting in the development of a number of EA based classification algorithms. Genetic programming (GP) in particular has been shown to be one of the most effective EAs at inducing classifiers. It is widely accepted that the effectiveness of a parameterised algorithm like GP depends on its configuration. Currently, the design of GP classification algorithms is predominantly performed manually. Manual design follows an iterative trial and error approach which has been shown to be a menial, non-trivial time-consuming task that has a number of vulnerabilities. The research presented in this thesis is part of a large-scale initiative by the machine learning community to automate the design of machine learning techniques. The study investigates the hypothesis that automating the design of GP classification algorithms for data classification can still lead to the induction of effective classifiers. This research proposes using two evolutionary algorithms,namely,ageneticalgorithm(GA)andgrammaticalevolution(GE)toautomatethe design of GP classification algorithms. The proof-by-demonstration research methodology is used in the study to achieve the set out objectives. To that end two systems namely, a genetic algorithm system and a grammatical evolution system were implemented for automating the design of GP classification algorithms. The classification performance of the automated designed GP classifiers, i.e., GA designed GP classifiers and GE designed GP classifiers were compared to manually designed GP classifiers on real-world binary class and multiclass classification problems. The evaluation was performed on multiple domain problems obtained from the UCI machine learning repository and on two specific domains, cybersecurity and financial forecasting. The automated designed classifiers were found to outperform the manually designed GP classifiers on all the problems considered in this study. GP classifiers evolved by GE were found to be suitable for classifying binary classification problems while those evolved by a GA were found to be suitable for multiclass classification problems. Furthermore, the automated design time was found to be less than manual design time. Fitness landscape analysis of the design spaces searched by a GA and GE were carried out on all the class of problems considered in this study. Grammatical evolution found the search to be smoother on binary classification problems while the GA found multiclass problems to be less rugged than binary class problems

Pacing-Induced Alterations in Left Ventricular Mechanical Properties: Effect of Pacing Sites

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Stents in pediatric and adult congenital cardiac catheterization in France in 2013

Stents have contributed to the development of the interventional catheterization for congenital heart diseases (CHD). The aim of this study was to describe indications, results and adverse events in current practice.MethodsThe participation to this study was proposed to all catheterization laboratories specialized in CHD in France (M3C network). All cases with stents implantation in 2013 in pediatric and adult CHD were retrospectively included. Adverse events were assessed using the Bergersen classification.Results174 stents were implanted during 132 procedures in 127 patients by 6 main operators in 9 centers. Patients were aged 15.7±15.1years old (min 5day-old - max 70years old). Sixteen types of procedures were identified. Main indications were transcatheter pulmonary valve replacement (29 patients, 23.0%), pulmonary artery branches angioplasty (34 patients, 27.0%), aortic (re)coarctation stenting (37 patients, 29.4%) and ductus arteriosus stenting (11 patients, 8.7%). 18 patients (14.3%) were under one y.o and 35 (27.8%) were over 18y.o. Main pathologies were tetralogy of Fallot and variants (ACC-CHD 8.3, n=45, 35.7%), and aortic coarctation (ACC-CHD 9.2, n=36, 28.6%). More than 1 stent was implanted in 32 procedures (24.4%, max. 5 stents). Main stents implanted were the CP stent (33.0%), EV3 LD max (22.0%), Valeo (16.2%) and valved stents (15.0%). 98.5% procedures were considered as successful. Serious adverse events were observed in 12.9%. After multivariate adjustment, only procedure type was related to the risk of total adverse events (OR: 3.0, 95%CI 1.1–7.9) but not to stent related adverse events. Age, weight, center, operator, type of stents, stent diameter, genetic disorder and type of CHD were not significantly related to the risk of adverse events.ConclusionStents are used in various CHD catheterization procedures, from infancy to adult age. Adverse events rate is significant and seems related to the type of procedure

A National Survey of Teachers on Antiretroviral Therapy in Malawi: Access, Retention in Therapy and Survival

BACKGROUND: HIV/AIDS is having a devastating effect on the education sector in sub-Saharan Africa. A national survey was conducted in all public sector and private sector facilities in Malawi providing antiretroviral therapy (ART) to determine the uptake of ART by teachers and their outcomes while on treatment. METHODOLOGY/PRINCIPAL FINDINGS: A retrospective cohort study was carried out based on patient follow-up records from ART Registers and treatment master cards in all 138 ART clinics in Malawi; observations were censored on September 30(th) 2006. By this date, Malawi's 102 public sector and 36 private sector ART clinics had registered a total of 72,328 patients for treatment. Of these, 2,643 (3.7%) were teachers. Adjusting for double-registration caused by clinic transfers, it is estimated that 2,380 individual teachers had ever accessed ART. There were 15% of teachers starting ART in WHO clinical stage 1 or 2 with a CD4-lymphocyte count of <or=250/mm(3) and 85% starting in stage 3 or 4. By 30(th) September 2006, 1,850 teachers were alive on ART (3.5% of all teachers in Malawi). The probability of being alive on ART at 6-months, 12-months, 18-months and 24-months after treatment initiation was 84%, 79%, 75% and 73% respectively. Retention in treatment was better for women (adjusted HR = 1.8) and in those starting ART in WHO Clinical Stage 1 and 2 (adjusted HR = 1.8). CONCLUSION/SIGNIFICANCE: Rapid scale up of ART has allowed 2,380 HIV-positive teachers to access life-prolonging treatment. There is evidence that this intervention can help to mitigate some of the shortages of teaching personnel in resource-poor countries affected by a generalised HIV epidemic

Proarrhythmic remodelling of the right ventricle in a porcine model of repaired tetralogy of Fallot

OBJECTIVE: The growing adult population with surgically corrected tetralogy of Fallot (TOF) is at risk of arrhythmias and sudden cardiac death. We sought to investigate the contribution of right ventricular (RV) structural and electrophysiological remodelling to arrhythmia generation in a preclinical animal model of repaired TOF (rTOF). METHODS AND RESULTS: Pigs mimicking rTOF underwent cardiac MRI functional characterisation and presented with pulmonary regurgitation, RV hypertrophy, dilatation and dysfunction compared with Sham-operated animals (Sham). Optical mapping of rTOF RV-perfused wedges revealed a significant prolongation of RV activation time with slower conduction velocities and regions of conduction slowing well beyond the surgical scar. A reduced protein expression and lateralisation of Connexin-43 were identified in rTOF RVs. A remodelling of extracellular matrix-related gene expression and an increase in collagen content that correlated with prolonged RV activation time were also found in these animals. RV action potential duration (APD) was prolonged in the epicardial anterior region at early and late repolarisation level, thus contributing to a greater APD heterogeneity and to altered transmural and anteroposterior APD gradients in rTOF RVs. APD remodelling involved changes in Kv4.3 and MiRP1 expression. Spontaneous arrhythmias were more frequent in rTOF wedges and more complex in the anterior than in the posterior RV. CONCLUSION: Significant remodelling of RV conduction and repolarisation properties was found in pigs with rTOF. This remodelling generates a proarrhythmic substrate likely to facilitate re-entries and to contribute to sudden cardiac death in patients with rTOF

Cardiac Resynchronization Therapy for Left Ventricular Dysfunction Induced by Chronic Right Ventricular Pacing in a Child

Cardiac resynchronization therapy (CRT) has been proven its value in adult patients with congestive heart failure of low ejection fraction and wide QRS duration. Contrast to adult patients, CRT has been rarely applied for young patients. We report on a 9-yr-old boy with progressive left ventricular (LV) dilatation and dysfunction following chronic VVI pacemaker therapy for congenital complete atrioventricular block associated with maternal anti-SSA/Ro and SSB/La antibody. His LV dysfunction was improved after epicardially established CRT