Large scale estimation of distribution algorithms for continuous optimisation

Modern real world optimisation problems are increasingly becoming large scale. However, searching in high dimensional search spaces is notoriously difficult. Many methods break down as dimensionality increases and Estimation of Distribution Algorithm (EDA) is especially prone to the curse of dimensionality. In this thesis, we device new EDA variants that are capable of searching in large dimensional continuous domains. We in particular (i) investigated heavy tails search distributions, (ii) we clarify a controversy in the literature about the capabilities of Gaussian versus Cauchy search distributions, (iii) we constructed a new way of projecting a large dimensional search space to low dimensional subspaces in a way that gives us control of the size of covariance of the search distribution and we develop adaptation techniques to exploit this and (iv) we proposed a random embedding technique in EDA that takes advantage of low intrinsic dimensional structure of problems. All these developments avail us with new techniques to tackle high dimensional optimization problems

An Assessment of the Level of Awareness of Eye Health Care Services Provided by Onesight in the Gambia

The objective of the Scorecard study was to assess the intervention of OneSight with respect to Awareness of their services in The Gambia and the perception of Gambians on eye care in The Gambia. More specifically in this paper, the scorecard assesses the level at which people are aware of the existence, the activities and the services offered by OneSight in The Gambia. The research employed both quantitative and qualitative methods. The study revealed that the majority of the sampled respondents are aware of refractive error i.e., about 90%. Their major source of information about eye care issues was through radio however, they gather important information from other sources such as healthcare workers and television. Most of the respondents who are aware of eyesight-related problems, typically obtained information through Government clinics, only 2.8% got their information from OneSight. It was also discovered that 94.6% of the respondents sought eye care treatment from health facilities as opposed to a home or local treatments. Based on the findings, practical implications and an agenda for future research are suggested. For instance, it is recommended that OneSight should strengthen community outreach programs, improve its communication strategies, create more visibility, and conduct more publicity events for more awareness about its programme and activities

How effective is Cauchy-EDA in high dimensions?

We consider the problem of high dimensional blackbox optimisation via Estimation of Distribution Algorithms (EDA) and the use of heavy-tailed search distributions in this setting. Some authors have suggested that employing a heavy tailed search distribution, such as a Cauchy, may make EDA better explore a high dimensional search space. However, other authors have found Cauchy search distributions are less effective than Gaussian search distributions in high dimensional problems. In this paper, we set out to resolve this controversy. To achieve this we run extensive experiments on a battery of high-dimensional test functions, and develop some theory which shows that small search steps are always more likely to move the search distribution towards the global optimum than large ones and, in particular, large search steps in high-dimensional spaces nearly always do badly in this respect. We hypothesise that, since exploration by large steps is mostly counterproductive in high dimensions, and since the fraction of good directions decays exponentially fast with increasing dimension, instead one should focus mainly on finding the right direction in which to move the search distribution. We propose a minor change to standard Gaussian EDA which implicitly achieves this aim, and our experiments on a sequence of test functions confirm the good performance of our new approach

Use of antibody tools to provide serologic evidence of elimination of Lymphatic filariasis in the Gambia

A current need in the global effort to eliminate lymphatic filariasis (LF) is the availability of reliable diagnostic tools that can be used to guide programmatic decisions, especially decisions made in the final stages of the program. This study conducted in The Gambia aimed to assess antifilarial antibody levels among populations living in historically highly LF-endemic areas and to evaluate the use of serologic tools to confirm the interruption of LF transmission. A total of 2,612 dried blood spots (DBSs) collected from individuals aged 1 year and above from 15 villages were tested for antibodies to Wb123 by enzyme-linked immunosorbent assay (ELISA). A subset of DBS (N = 599) was also tested for antibodies to Bm14 by ELISA. Overall, the prevalence of Wb123 was low (1.5%, 95% confidence interval [CI] 1.1-2.1%). In 7 of 15 villages (46.7%), there were no Wb123-positive individuals identified. Individuals with positive responses to Wb123 ranged in age from 3 to 100 years. Overall, Bm14 prevalence was also low (1.5%, 95% CI 0.7-2.8%). Bm14 positivity was significantly associated with older age (P < 0.001). The low levels of antibody responses to Wb123 observed in our study strongly suggest that sustainable LF transmission has likely ceased in The Gambia. In addition, our results support the conclusion that serologic tools can have a role in guiding programmatic decision making and supporting surveillance

Sex-differential non-vaccine specific immunological effects of diphtheria-tetanus-pertussis and measles vaccination

Vaccines can have nontargeted heterologous effects that manifest as increased protection against nonvaccine infections, as described for measles vaccine (MV), or increased susceptibility to infections and death, as described following diphtheria-tetanus-whole cell pertussis (DTP) vaccination. The mechanisms are unknown, and high-quality immunological studies are lacking. This study was designed to investigate the heterologous effects of MV and DTP in 302 Gambian infants. The results support a sex-differential immunosuppressive effect of DTP on innate proinflammatory responses and T-cell immunity. Males but not females receiving MV had enhanced proinflammatory innate responses. The results point to modified signaling via Toll-like receptor 4 (TLR4) as a possible mechanism for the effects on innate immunity. When both vaccines were administered together, purified protein derivative responses were enhanced in females but downregulated in males. Collectively, these data indicate immunological effects that could account for heterologous effects of MV and DTP, to take forward into prospective trials

Respiratory infections drive hepcidin-mediated blockade of iron absorption leading to iron deficiency anemia in African children.

Iron deficiency anemia (IDA) is the most prevalent nutritional condition worldwide. We studied the contribution of hepcidin-mediated iron blockade to IDA in African children. We measured hepcidin and hemoglobin weekly, and hematological, inflammatory, and iron biomarkers at baseline, 7 weeks, and 12 weeks in 407 anemic (hemoglobin < 11 g/dl), otherwise healthy Gambian children (6 to 27 months). Each child maintained remarkably constant hepcidin levels (P < 0.0001 for between-child variance), with half consistently maintaining levels that indicate physiological blockade of iron absorption. Hepcidin was strongly predicted by nurse-ascribed adverse events with dominant signals from respiratory infections and fevers (all P < 0.0001). Diarrhea and fecal calprotectin were not associated with hepcidin. In multivariate analysis, C-reactive protein was the dominant predictor of hepcidin and contributed to iron blockade even at very low levels. We conclude that even low-grade inflammation, especially associated with respiratory infections, contributes to IDA in African children