Towards a mathematical understanding of learning from few examples with nonlinear feature maps

We consider the problem of data classification where the training set consists of just a few data points. We explore this phenomenon mathematically and reveal key relationships between the geometry of an AI model's feature space, the structure of the underlying data distributions, and the model's generalisation capabilities. The main thrust of our analysis is to reveal the influence on the model's generalisation capabilities of nonlinear feature transformations mapping the original data into high, and possibly infinite, dimensional spaces.Comment: 18 pages, 8 figure

Graphical augmentations to the funnel plot assess the impact of additional evidence on a meta-analysis

AbstractObjectiveWe aim to illustrate the potential impact of a new study on a meta-analysis, which gives an indication of the robustness of the meta-analysis.Study Design and SettingA number of augmentations are proposed to one of the most widely used of graphical displays, the funnel plot. Namely, 1) statistical significance contours, which define regions of the funnel plot in which a new study would have to be located to change the statistical significance of the meta-analysis; and 2) heterogeneity contours, which show how a new study would affect the extent of heterogeneity in a given meta-analysis. Several other features are also described, and the use of multiple features simultaneously is considered.ResultsThe statistical significance contours suggest that one additional study, no matter how large, may have a very limited impact on the statistical significance of a meta-analysis. The heterogeneity contours illustrate that one outlying study can increase the level of heterogeneity dramatically.ConclusionThe additional features of the funnel plot have applications including 1) informing sample size calculations for the design of future studies eligible for inclusion in the meta-analysis; and 2) informing the updating prioritization of a portfolio of meta-analyses such as those prepared by the Cochrane Collaboration

The Boundaries of Verifiable Accuracy, Robustness, and Generalisation in Deep Learning

In this work, we assess the theoretical limitations of determining guaranteed stability and accuracy of neural networks in classification tasks. We consider classical distribution-agnostic framework and algorithms minimising empirical risks and potentially subjected to some weights regularisation. We show that there is a large family of tasks for which computing and verifying ideal stable and accurate neural networks in the above settings is extremely challenging, if at all possible, even when such ideal solutions exist within the given class of neural architectures

Test-retest reliability of the isometric soleus strength test in elite male academy footballers.

BACKGROUND Currently there is no reliability data is available for the isometric soleus strength test (ISST), commonly used as a monitoring tool in elite football settings. ISST for other muscle groups, most notably the hamstrings, is utilised to identify injury risk and readiness to train/play. PURPOSE To profile athletes efficiently, performance practitioners require optimal measures that are reliable. The aim of this study was to investigate the test-retest reliability of the ISST of the soleus and validate a standardised protocol for its use within an elite male football population. STUDY DESIGN The present study represents a test-retest reliability single cohort study. METHODS Thirty elite male footballers (age = 22.8±5.0 years, height = 180.0±0.08 cm, weight = 70.57±4.0 kg) performed the ISST, through 3 maximum 3-second hold efforts with 1-minute rest between repetitions and 48 hours between tests, in each test. The test was performed mid-competitive season. All data bilaterally was checked for normality through a Shapiro-Wilk Test before a Pearson’s Correlation and Bland-Altman’s analysis was performed. RESULTS Test-retest reliability demonstrated high reliability for ISST bilaterally (Right: ICC 0.89; Left: ICC 0.79, p<0.05). Standard errors of measurement (SEM) (%) was 8.75% and minimal detectable change (MDC) was 35.55 (N) for Peak Force (PF) measures of the ISST. Levels of agreement were found bilaterally for ISST (Right: p=0.09, CI: -153.21-10.95; Left: p=0.52, CI: -139.81-72.33). CONCLUSION This study demonstrated high reliability for the ISST. The ISST is a valid and reliable method for assessing PF characteristics of the soleus in elite male academy footballers. This test may be beneficial for performance practitioners for profiling soleus function of athletes. Findings indicate that the ISST displays high test-retest reliability in elite male academy football populations and should be considered in performance profiling of the athlete

Collaborative Autoethnographic Writing as Communal Curative

This collaborative autoethnography reflects on how each author experienced COVID-19 and associated precarity. We explore the ways in which this experience relates to our identities (both particular and plural), and our positionalities in terms of privilege and marginality. As a collective of diverse collaborators, we confront dialectical questions of self and society. Our contributions reveal our advantage/disadvantage, mobility/immobility, and the borders and boundedness before/during/after COVID-19. We show the power of curative writing in collaborative autoethnography and how the sharing of our experiences of vulnerability represents an invitation to human connection

Dynamics and Excitation of Radio Galaxy Emission-Line Regions - I. PKS 2356-61

Results are presented from a programme of detailed longslit spectroscopic observations of the extended emission-line region (EELR) associated with the powerful radio galaxy PKS 2356-61. The observations have been used to construct spectroscopic datacubes, which yield detailed information on the spatial variations of emission-line ratios across the EELR, together with its kinematic structure. We present an extensive comparison between the data and results obtained from the MAPPINGS II shock ionization code, and show that the physical properties of the line-emitting gas, including its ionization, excitation, dynamics and overall energy budget, are entirely consistent with a scenario involving auto-ionizing shocks as the dominant ionization mechanism. This has the advantage of accounting for the observed EELR properties by means of a single physical process, thereby requiring less free parameters than the alternative scheme involving photoionization by radiation from the active nucleus. Finally, possible mechanisms of shock formation are considered in the context of the dynamics and origin of the gas, specifically scenarios involving infall or accretion of gas during an interaction between the host radio galaxy and a companion galaxy.Comment: 35 pages, LaTeX, uses aas2pp4.sty file, includes 9 PostScript figures. Two additional colour plates are available from the authors upon request. Accepted for publication in the Astrophysical Journa

Identification of factors associated with stillbirth in Zimbabwe – a cross sectional study

From Springer Nature via Jisc Publications RouterHistory: received 2021-04-15, accepted 2021-08-29, registration 2021-09-06, pub-electronic 2021-09-29, online 2021-09-29, collection 2021-12Publication status: PublishedAbstract: Introduction: 98% of the 2.6 million stillbirths per annum occur in low and middle income countries. However, understanding of risk factors for stillbirth in these settings is incomplete, hampering efforts to develop effective strategies to prevent deaths. Methods: A cross-sectional study of eligible women on the postnatal ward at Mpilo Hospital, Zimbabwe was undertaken between 01/08/2018 and 31/03/2019 (n = 1779). Data were collected from birth records for maternal characteristics, obstetric and past medical history, antenatal care and pregnancy outcome. A directed acyclic graph was constructed with multivariable logistic regression performed to fit the corresponding model specification to data comprising singleton pregnancies, excluding neonatal deaths (n = 1734), using multiple imputation for missing data. Where possible, findings were validated against all women with births recorded in the hospital birth register (n = 1847). Results: Risk factors for stillbirth included: previous stillbirth (29/1691 (2%) of livebirths and 39/43 (91%) of stillbirths, adjusted Odds Ratio (aOR) 2628.9, 95% CI 342.8 to 20,163.0), antenatal care (aOR 44.49 no antenatal care vs. > 4 antenatal care visits, 95% CI 6.80 to 291.19), maternal medical complications (aOR 7.33, 95% CI 1.99 to 26.92) and season of birth (Cold season vs. Mild aOR 14.29, 95% CI 3.09 to 66.08; Hot season vs. Mild aOR 3.39, 95% CI 0.86 to 13.27). Women who had recurrent stillbirth had a lower educational and health status (18.2% had no education vs. 10.0%) and were less likely to receive antenatal care (20.5% had no antenatal care vs. 6.6%) than women without recurrent stillbirth. Conclusion: The increased risk in women who have a history of stillbirth is a novel finding in Low and Middle Income Countries (LMICs) and is in agreement with findings from High Income Countries (HICs), although the estimated effect size is much greater (OR in HICs ~ 5). Developing antenatal care for this group of women offers an important opportunity for stillbirth prevention

Evidence synthesis as the key to more coherent and efficient research

<p>Abstract</p> <p>Background</p> <p>Systematic review and meta-analysis currently underpin much of evidence-based medicine. Such methodologies bring order to <it>previous </it>research, but <it>future </it>research planning remains relatively incoherent and inefficient.</p> <p>Methods</p> <p>To outline a framework for evaluation of health interventions, aimed at increasing coherence and efficiency through i) making better use of information contained within the existing evidence-base when designing future studies; and ii) maximising the information available and thus potentially reducing the need for future studies.</p> <p>Results</p> <p>The framework presented insists that an up-to-date meta-analysis of existing randomised controlled trials (RCTs) should always be considered before future trials are conducted. Such a meta-analysis should inform critical design issues such as sample size determination. The contexts in which the use of individual patient data meta-analysis and mixed treatment comparisons modelling may be beneficial before further RCTs are conducted are considered. Consideration should also be given to how any newly planned RCTs would contribute to the totality of evidence through its incorporation into an updated meta-analysis. We illustrate how new RCTs can have very low power to change inferences of an existing meta-analysis, particularly when between study heterogeneity is taken into consideration.</p> <p>Conclusion</p> <p>While the collation of existing evidence as the basis for clinical practice is now routine, a more coherent and efficient approach to planning future RCTs to strengthen the evidence base needs to be developed. The framework presented is a proposal for how this situation can be improved.</p

Management and site effects on carbon balances of European mountain meadows and rangelands

We studied carbon balances and carbon stocks of mountain rangelands and meadows in a network of 8 eddy covariance sites and 14 sites with biomass data in Europe. Net ecosystem exchange of pastures and extensively managed semi-natural rangelands were usually close to zero, while meadows fixed carbon, with the exception of one meadow that was established on a drained peatland. When we accounted for off-site losses and inputs also the carbon budget of meadows approached zero. Soil carbon stocks in these ecosystems were high, comparable to those of forest ecosystems, while carbon stocks in plant biomass were smaller. Since soil carbon stocks of abandoned mountain grasslands are as high as in managed ecosystems, it is likely that the widespread abandonment of mountain rangelands used currently as pastures will not lead to an immediate carbon sink in those ecosystems

Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

No abstract available