Home alone: autonomous extension and correction of spatial representations

In this paper we present an account of the problems faced by a mobile robot given an incomplete tour of an unknown environment, and introduce a collection of techniques which can generate successful behaviour even in the presence of such problems. Underlying our approach is the principle that an autonomous system must be motivated to act to gather new knowledge, and to validate and correct existing knowledge. This principle is embodied in Dora, a mobile robot which features the aforementioned techniques: shared representations, non-monotonic reasoning, and goal generation and management. To demonstrate how well this collection of techniques work in real-world situations we present a comprehensive analysis of the Dora system’s performance over multiple tours in an indoor environment. In this analysis Dora successfully completed 18 of 21 attempted runs, with all but 3 of these successes requiring one or more of the integrated techniques to recover from problems

Managing time budgets shared between planning and execution

Agents operating in domains with time budgets shared between planning and execution must carefully balance the need to plan versus the need to act. This is because planning and execution consume the same time resource. Excessive planning can delay the time it takes to achieve a goal, and so reduce the reward attained by an agent. Whereas, insufficient planning will mean the agent creates and executes low reward plans. This thesis looks at three ways to increase the reward achieved by an agent in domains with shared time budgets. The first way is by optimising time allocated to planning, using two different methods -- an optimal plan duration predictor and an online loss limiter. A second is by finding ways to act in a goal-directed manner during planning. We look at using previous plans or new plans generated quickly as heuristics for acting whilst planning. In addition, we present a way of describing actions that are mid-execution to speed the transition between planning and execution. Lastly, this thesis presents a way in which to manage time budgets in multi-agent domains. We use market-based task allocation with deadlines to produce faster task allocation and planning

Wavelet spectral testing : application to nonstationary circadian rhythms

Rhythmic data are ubiquitous in the life sciences. Biologists need reliable statistical tests to identify whether a particular experimental treatment has caused a significant change in a rhythmic signal. When these signals display nonstationary behaviour, as is common in many biological systems, the established methodologies may be misleading. Therefore, there is a real need for new methodology that enables the formal comparison of nonstationary processes. As circadian behaviour is best understood in the spectral domain, here we develop novel hypothesis testing procedures in the (wavelet) spectral domain, embedding replicate information when available. The data are modelled as realisations of locally stationary wavelet processes, allowing us to define and rigorously estimate their evolutionary wavelet spectra. Motivated by three complementary applications in circadian biology, our new methodology allows the identification of three specific types of spectral difference. We demonstrate the advantages of our methodology over alternative approaches, by means of a comprehensive simulation study and real data applications, using both published and newly generated circadian datasets. In contrast to the current standard methodologies, our method successfully identifies differences within the motivating circadian datasets, and facilitates wider ranging analyses of rhythmic biological data in general

Preparation of Large Monodisperse Vesicles

Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (∼100 nm in diameter) results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-µm-diameter pores eliminates vesicles larger than 5 µm in diameter. Dialysis of extruded vesicles against 3-µm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 µm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of ∼4 µm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery

Comparison of empirically derived and model-based estimates of key population HIV incidence and the distribution of new infections by population group in sub-Saharan Africa

Background: The distribution of new HIV infections among key populations, including female sex workers (FSWs), gay men and other men who have sex with men (MSM), and people who inject drugs (PWID) are essential information to guide an HIV response, but data are limited in sub-Saharan Africa (SSA). We analyzed empirically derived and mathematical model-based estimates of HIV incidence among key populations and compared with the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates.Methods: We estimated HIV incidence among FSW and MSM in SSA by combining meta-analyses of empirical key population HIV incidence relative to the total population incidence with key population size estimates (KPSE) and HIV prevalence. Dynamic HIV transmission model estimates of HIV incidence and percentage of new infections among key populations were extracted from 94 country applications of 9 mathematical models. We compared these with UNAIDS-reported distribution of new infections, implied key population HIV incidence and incidence-to-prevalence ratios.Results: Across SSA, empirical FSW HIV incidence was 8.6-fold (95% confidence interval: 5.7 to 12.9) higher than total population female 15–39 year incidence, and MSM HIV incidence was 41.8-fold (95% confidence interval: 21.9 to 79.6) male 15–29 year incidence. Combined with KPSE, these implied 12% of new HIV infections in 2021 were among FSW and MSM (5% and 7% respectively). In sensitivity analysis varying KPSE proportions within 95% uncertainty range, the proportion of new infections among FSW and MSM was between 9% and 19%. Insufficient data were available to estimate PWID incidence rate ratios. Across 94 models, median proportion of new infections among FSW, MSM, and PWID was 6.4% (interquartile range 3.2%–11.7%), both much lower than the 25% reported by UNAIDS.Conclusion: Empirically derived and model-based estimates of HIV incidence confirm dramatically higher HIV risk among key populations in SSA. Estimated proportions of new infections among key populations in 2021 were sensitive to population size assumptions and were substantially lower than estimates reported by UNAIDS.</div

The immune status of migrant populations in Europe and implications for vaccine-preventable disease control: a systematic review and meta-analysis.

BACKGROUND: Ensuring vaccination coverage reaches established herd immunity thresholds (HIT) is the cornerstone of any vaccination programme. Diverse migrant populations in European countries have been associated with cases of vaccine-preventable diseases (VPD) and outbreaks, yet it is not clear to what extent they are an under-immunised group. METHODS: We did a systematic review and meta-analysis to synthesise peer-reviewed published primary research reporting data on the immune status of migrants in EU/EEA countries, the UK and Switzerland, calculating their pooled immunity coverage for measles, mumps, rubella, and diphtheria using random-effects models. We searched on Web of Science, Embase, Global Health and MEDLINE (January 1st 2000 to June 10th 2022), with no language restrictions. The protocol is registered with PROSPERO (CRD42018103666). FINDINGS: Of 1103 abstracts screened, 62 met eligibility criteria, of which 39 were included in the meta-analysis. The meta-analysis included 75 089 migrants, predominantly from outside Europe. Pooled immunity coverage among migrant populations was well below the recommended HIT for diphtheria (n = 7, 57.4% [95% CI: 43.1-71.7%] I2 = 99% vs HIT 83-86%), measles (n = 21, 83.7% [95% CI: 79.2-88.2] I2 = 99% vs HIT 93-95%), and mumps (n = 8, 67.1% [95% CI: 50.6-83.6] I2 = 99% vs HIT 88-93%), and midway for rubella (n = 29, 85.6% [95% CI: 83.1-88.1%] I2 = 99% vs HIT 83-94%), with high heterogeneity across studies. INTERPRETATION: Migrants in Europe are an under-immunised group for a range of important VPDs, with this study reinforcing the importance of engaging children, adolescents, and adults in 'catch-up' vaccination initiatives on arrival for vaccines, doses, and boosters they may have missed in their home countries. Co-designing strategies to strengthen catch-up vaccination across the life-course in under-immunised groups is an important next step if we are to meet European and global targets for VPD elimination and control and ensure vaccine equity

Understanding the views of adult migrants around catch-up vaccination for missed routine immunisations to define strategies to improve coverage: A UK in-depth interview study.

BACKGROUND: The World Health Organization's (WHO) Immunization Agenda 2030 emphasises ensuring equitable access to vaccination across the life course. This includes placing an emphasis on migrant populations who may have missed key childhood vaccines, doses, and boosters due to disrupted healthcare systems and the migration process, or differing vaccination schedules in home countries. Guidelines exist in the UK for offering catch-up vaccinations to adolscent and adult migrants with incomplete or uncertain vaccination status (including MMR, Td-IPV, MenACWY, HPV), but emerging evidence suggests awareness and implementation in primary care is poor. It is unclear whether patient-level barriers to uptake of catch-up vaccinations also exist. We explored experiences and views around catch-up vaccination among adult migrants from a range of backgrounds, to define strategies for improving catch-up vaccination policy and practice. METHODS: In-depth semi-structured interviews were carried out in two phases with adult migrant populations (refugees, asylum seekers, undocumented migrants, those with no recourse to public funds) on views and experiences around vaccination, involving a team of peer researchers from specific migrant communities trained through the study. In Phase 1, we conducted remote interviews with migrants resident in the UK for < 10 years, from diverse backgrounds. In Phase 2, we engaged specifically Congolese and Angolan migrants as part of a community-based participatory study. Topic guides were developed iteratively and piloted. Participants were recruited using purposive, opportunistic and snowball sampling methods. Interviews were conducted in English (interpreters offered), Lingala or French and were audio-recorded, transcribed and analysed using a thematic framework approach in NVivo 12. RESULTS: 71 participants (39 in Phase 1, 32 in Phase 2) were interviewed (Mean age 43.6 [SD:12.4] years, 69% female, mean 9.5 [SD:7] years in the UK). Aside from COVID-19 vaccines, most participants reported never having been offered vaccinations or asked about their vaccination history since arriving in the UK as adults. Few participants mentioned being offered specific catch-up vaccines (e.g. MMR/Td-IPV) when attending a healthcare facility on arrival in the UK. Vaccines such as flu vaccines, pregnancy-related or pre-travel vaccination were more commonly mentioned. In general, participants were not aware of adult catch-up vaccination but regarded it positively when it was explained. A few participants expressed concerns about side-effects, risks/inconveniences associated with access (e.g. links to immigration authorities, travel costs), preference for natural remedies, and hesitancy to engage in further vaccination campaigns due to the intensity of COVID-19 vaccination campaigns. Trust was a major factor in vaccination decisions, with distinctions noted within and between groups; some held a healthcare professional's recommendation in high regard, while others were less trusting towards the healthcare system because of negative experiences of the NHS and past experiences of discrimination, injustice and marginalisation by wider authorities. CONCLUSIONS: The major barrier to adult catch-up vaccination for missed routine immunisations and doses in migrant communities in the UK is the limited opportunities, recommendations or tailored vaccination information presented to migrants by health services. This could be improved with financial incentives for provision of catch-up vaccination in UK primary care, alongside training of healthcare professionals to support catch-up immunisation and raise awareness of existing guidelines. It will also be essential to address root causes of mistrust around vaccination, where it exists among migrants, by working closely with communities to understand their needs and meaningfully involving migrant populations in co-producing tailored information campaigns and culturally relevant interventions to improve coverage