Precision and Recall Reject Curves for Classification

For some classification scenarios, it is desirable to use only those classification instances that a trained model associates with a high certainty. To obtain such high-certainty instances, previous work has proposed accuracy-reject curves. Reject curves allow to evaluate and compare the performance of different certainty measures over a range of thresholds for accepting or rejecting classifications. However, the accuracy may not be the most suited evaluation metric for all applications, and instead precision or recall may be preferable. This is the case, for example, for data with imbalanced class distributions. We therefore propose reject curves that evaluate precision and recall, the recall-reject curve and the precision-reject curve. Using prototype-based classifiers from learning vector quantization, we first validate the proposed curves on artificial benchmark data against the accuracy reject curve as a baseline. We then show on imbalanced benchmarks and medical, real-world data that for these scenarios, the proposed precision- and recall-curves yield more accurate insights into classifier performance than accuracy reject curves.Comment: 11 pages, 3 figures. Updated figure label

Rejection and online learning with prototype-based classifiers in adaptive metrical spaces

Fischer L. Rejection and online learning with prototype-based classifiers in adaptive metrical spaces. Bielefeld: Universität Bielefeld; 2016.The rising amount of digital data, which is available in almost every domain, causes the need for intelligent, automated data processing. Classification models constitute particularly popular techniques from the machine learning domain with applications ranging from fraud detection up to advanced image classification tasks. Within this thesis, we will focus on so-called prototype-based classifiers as one prominent family of classifiers, since they offer a simple classification scheme, interpretability of the model in terms of prototypes, and good generalisation performance. We will face a few crucial questions which arise whenever such classifiers are used in real-life scenarios which require robustness and reliability of classification and the ability to deal with complex and possibly streaming data sets. Particularly, we will address the following problems: - Deterministic prototype-based classifiers deliver a class label, but no confidence of the classification. The latter is particularly relevant whenever the costs of an error are higher than the costs to reject an example, e.g. in a safety critical system. We investigate ways to enhance prototype-based classifiers by a certainty measure which can efficiently be computed based on the given classifier only and which can be used to reject an unclear classification. - For an efficient rejection, the choice of a suitable threshold is crucial. We investigate in which situations the performance of local rejection can surpass the choice of only a global one, and we propose efficient schemes how to optimally compute local thresholds on a given training set. - For complex data and lifelong learning, the required classifier complexity can be unknown a priori. We propose an efficient, incremental scheme which adjusts the model complexity of a prototype-based classifier based on the certainty of the classification. Thereby, we put particular emphasis on the question how to adjust prototype locations and metric parameters, and how to insert and/or delete prototypes in an efficient way. - As an alternative to the previous solution, we investigate a hybrid architecture which combines an offline classifier with an online classifier based on their certainty values, thus directly addressing the stability/plasticity dilemma. While this is straightforward for classical prototype-based schemes, it poses some challenges as soon as metric learning is integrated into the scheme due to the different inherent data representations. - Finally, we investigate the performance of the proposed hybrid prototype-based classifier within a realistic visual road-terrain-detection scenario

Prevalence, distribution and evolutionary significance of the IS629 insertion element in the stepwise emergence of Escherichia coli O157:H7

<p>Abstract</p> <p>Background</p> <p>Insertion elements (IS) are known to play an important role in the evolution and genomic diversification of <it>Escherichia coli </it>O157:H7 lineages. In particular, IS<it>629 </it>has been found in multiple copies in the <it>E. coli </it>O157:H7 genome and is one of the most prevalent IS in this serotype. It was recently shown that the lack of O157 antigen expression in two O rough <it>E. coli </it>O157:H7 strains was due to IS<it>629 </it>insertions at 2 different locations in the <it>gne </it>gene that is essential for the O antigen biosynthesis.</p> <p>Results</p> <p>The comparison of 4 <it>E. coli </it>O157:H7 genome and plasmid sequences showed numerous IS<it>629 </it>insertion sites, although not uniformly distributed among strains. Comparison of IS<it>629</it>s found in O157:H7 and O55:H7 showed the presence of at least three different IS<it>629 </it>sub-types. O157:H7 strains carry IS<it>629 </it>elements sub-type I and III whereby the ancestral O55:H7 carries sub-type II. Analysis of strains selected from various clonal groups defined on the <it>E. coli </it>O157:H7 stepwise evolution model showed that IS<it>629 </it>was not observed in sorbitol fermenting O157 (SFO157) clones that are on a divergent pathway in the emergence of O157:H7. This suggests that the absence of IS<it>629 </it>in SFO157 strains probably occurred during the divergence of this lineage, albeit it remains uncertain if it contributed, in part, to their divergence from other closely related strains.</p> <p>Conclusions</p> <p>The highly variable genomic locations of IS<it>629 </it>in O157:H7 strains of the A6 clonal complex indicates that this insertion element probably played an important role in genome plasticity and in the divergence of O157:H7 lineages.</p

Exploring pluralism – Different stakeholder views of the expected and realised value of strategic environmental assessment (SEA)

This paper explores the concept of pluralism by evaluating different stakeholder views on the expected and realised value of strategic environmental assessment (SEA). The research followed a single embedded case study approach (of a national-level SEA for renewable energy planning in South Africa) and engaged with four different stakeholder groups, namely government, industry, conservation groups, and interested and affected parties (IAPs). A total of 21 different value expectations (VEs) across all four stakeholder groups were identified. However, stakeholder groups contrast significantly in terms of VEs, with government concerned more with process and mandate; industry with cost, efficiency and certainty; conservation groups with data and technical aspects; and the IAPs with local scale issues. In terms of realisation of VEs the results suggest that SEA does provide opportunities for learning; focussing project level EIA and providing spatial guidance on the location of projects. However, SEA was less successful in realising integration of decision making and alignment of policy within government. Recognition and better understanding of the pluralistic nature of expected and realised VEs could potentially improve the legitimacy of SEA processes and methodologies if they are designed and implemented to accommodate pluralism

Diabetes in sub-Saharan Africa – from policy to practice to progress: targeting the existing gaps for future care for diabetes

The global prevalence and impact of diabetes has increased dramatically, particularly in sub-Saharan Africa. This region faces unique challenges in combating the disease including lack of funding for noncommunicable diseases, lack of availability of studies and guidelines specific to the population, lack of availability of medications, differences in urban and rural patients, and inequity between public and private sector health care. Because of these challenges, diabetes has a greater impact on morbidity and mortality related to the disease in sub-Saharan Africa than any other region in the world. In order to address these unacceptably poor trends, contextualized strategies for the prevention, identification, management, and financing of diabetes care within this population must be developed. This narrative review provides insights into the policy landscape, epidemiology, pathophysiology, care protocols, medication availability, and health care systems to give readers a comprehensive summary of many factors in these domains as they pertain to diabetes in sub-Saharan Africa. In addition to providing a review of the current evidence available in these domains, potential solutions to address the major gaps in care will be proposed to reverse the negative trends seen with diabetes in sub-Saharan Africa

Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

We report serendipitous detections of line emission with ALMA in band 3, 6, and 7 in the central parsec of the Galactic center at an up to now highest resolution (<0.7''). Among the highlights are the very first and highly resolved images of sub-mm molecular emission of CS, H13CO+, HC3N, SiO, SO, C2H, and CH3OH in the immediate vicinity (~1'' in projection) of Sgr A* and in the circumnuclear disk (CND). The central association (CA) of molecular clouds shows three times higher CS/X (X: any other observed molecule) luminosity ratios than the CND suggesting a combination of higher excitation - by a temperature gradient and/or IR-pumping - and abundance enhancement due to UV- and/or X-ray emission. We conclude that the CA is closer to the center than the CND is and could be an infalling clump consisting of denser cloud cores embedded in diffuse gas. Moreover, we identified further regions in and outside the CND that are ideally suited for future studies in the scope of hot/cold core and extreme PDR/XDR chemistry and consequent star formation in the central few parsecs

Mitigating The Burden Of Diabetes In Sub-Saharan Africa Through An Integrated Diagonal Health Systems Approach

Diabetes is a chronic non-communicable disease (NCD) presenting growing health and economic burdens in sub-Saharan Africa (SSA). Diabetes is unique due to its cross-cutting nature, impacting multiple organ systems and increasing the risk for other communicable and non-communicable diseases. Unfortunately, the quality of care for diabetes in SSA is poor, largely due to a weak disease management framework and fragmented health systems in most sub-Saharan African countries. We argue that by synergizing disease-specific vertical programs with system-specific horizontal programs through an integrated disease-system diagonal approach, we can improve access, quality, and safety of diabetes care programs while also supporting other chronic diseases. We recommend utilizing the six World Health Organization (WHO) health system building blocks – 1) leadership and governance, 2) financing, 3) health workforce, 4) health information systems, 5) supply chains, and 6) service delivery – as a framework to design a diagonal approach with a focus on health system strengthening and integration to implement and scale quality diabetes care. We discuss the successes and challenges of this approach, outline opportunities for future care programming and research, and highlight how this approach can lead to the improvement in the quality of care for diabetes and other chronic diseases across SSA

HIV Stigma: Perspectives from Kenyan Child Caregivers and Adolescents Living with HIV

Stigma shapes all aspects of HIV prevention and treatment, yet there are limited data on how HIV-infected youth and their families are affected by stigma in sub-Saharan Africa. The authors conducted a qualitative study using focus group discussions among 39 HIV-infected adolescents receiving care at HIV clinics in western Kenya and 53 caregivers of HIV-infected children. Participants felt that while knowledge and access to treatment were increasing, many community members still held negative and inaccurate views about HIV, including associating it with immorality and believing in transmission by casual interactions. Stigma was closely related to a loss of social and economic support but also included internalized negative feelings about oneself. Participants identified treatment-related impacts of stigma, including nonadherence, nondisclosure of status to child or others, and increased mental health problems. Qualitative inquiry also provided insights into how to measure and reduce stigma among affected individuals and families