Conjecturing-Based Computational Discovery of Patterns in Data

Modern machine learning methods are designed to exploit complex patterns in data regardless of their form, while not necessarily revealing them to the investigator. Here we demonstrate situations where modern machine learning methods are ill-equipped to reveal feature interaction effects and other nonlinear relationships. We propose the use of a conjecturing machine that generates feature relationships in the form of bounds for numerical features and boolean expressions for nominal features that are ignored by machine learning algorithms. The proposed framework is demonstrated for a classification problem with an interaction effect and a nonlinear regression problem. In both settings, true underlying relationships are revealed and generalization performance improves. The framework is then applied to patient-level data regarding COVID-19 outcomes to suggest possible risk factors.Comment: 25 pages, 6 figure

Nitrogen Management in a Maize-Groundnut Crop Rotation of Humid Tropics: Effect on N2O Emission

Development of appropriate land management techniques to attain sustainability and increase the N use efficiency of crops in the tropics has been gaining momentum. The nitrous oxides (N2Os) affect global climate change and its contribution from N and C management systems is of great significance. Thus, N transformations and N2O emission during maize-groundnut crop rotation managed with various N sources were studied. Accumulation of nitrate (NO3 –) and its disappearance happened immediately after addition of various N sources, showing liming effect. The mineral N retained for 2–4 weeks depending on the type and amount of N application. The chicken manure showed rapid nitrification in the first week after application during the fallow period, leading to a maximum N2O flux of 9889 μg N2O-N m–2 day– 1. The same plots showed a residual effect by emitting the highest N2O (4053 μg N2O-N m–2 day– 1) during maize cultivation supplied with a halfrate of N fertilizer. Application of N fertilizer only or in combination with crop residues exhibited either lowered fluxes or caused a sink during the groundnut and fallow periods due to small availability of substrates and/or low water-filled pore space (<40%). The annual N2O emission ranged from 1.41 to 3.94 kg N2O-N ha–1; the highest was estimated from the chicken manure plus crop residues and half-rate of inorganic N-amended plots. Results indicates a greater influence of chicken manure on the N transformations and thereby N2O emission

Community shifts and carbon translocation within metabolically-active rhizosphere microorganisms in grasslands under elevated CO₂

International audienceThe aim of this study was to identify the microbial communities that are actively involved in the assimilation of rhizosphere-C and are most sensitive in their activity to elevated atmospheric CO2 in a temperate semi-natural low-input grassland ecosystem. For this, we analyzed 13C signatures in microbial biomarker phospholipid fatty acids (PLFA) from an in-situ 13CO2 pulse-labeling experiment in the Giessen Free Air Carbon dioxide Enrichment grasslands (GiFACE, Germany) exposed to ambient and elevated (i.e. 50% above ambient) CO2 concentrations. Short-term 13C PLFA measurements at 3 h and 10 h after the pulse-labeling revealed very little to no 13C enrichment after 3 h in biomarker PLFAs and a much greater incorporation of new plant-C into fungal compared to bacterial PLFAs after 10 h. After a period of 11 months following the pulse-labeling experiment, the 13C enrichment of fungal PLFAs was still largely present but had decreased, while bacterial PLFAs were much more enriched in 13C compared to a few hours after the pulse-labeling. These results imply that new rhizodeposit-C is rapidly processed by fungal communities and only much later by the bacterial communities, which we attributed to either a fungal-mediated translocation of rhizosphere-C from the fungal to bacterial biomass or a preferential bacterial use of dead root or fungal necromass materials as C source over the direct utilization of fresh root-exudate C in these N-limited grassland ecosystems. Elevated CO2 caused an increase in the proportional 13C enrichment (relative to the universal biomarker 16:0) of the arbuscular mycorrhizal fungal biomarker PLFA 16:1?5 and one gram-positive bacterial biomarker PLFA i16:0, but a decrease in the proportional 13C enrichment of 18:1?9c, a commonly used though questionable fungal biomarker PLFA. This suggests enhanced fungal rhizodeposit-C assimilation only by arbuscular mycorrhizal fungal species under elevated CO2

Automated conjecturing II : chomp and reasoned game play

We demonstrate the use of a program that generates conjectures about positions of the combinatorial game Chomp—explanations of why certain moves are bad. These could be used in the design of a Chomp-playing program that gives reasons for its moves. We prove one of these Chomp conjectures—demonstrating that our conjecturing program can produce genuine Chomp knowledge. The conjectures are generated by a general purpose conjecturing program that was previously and successfully used to generate mathematical conjectures. Our program is initialized with Chomp invariants and example game boards—the conjectures take the form of invariant-relation statements interpreted to be true for all board positions of a certain kind. The conjectures describe a theory of Chomp positions. The program uses limited, natural input and suggests how theories generated on-the-fly might be used in a variety of situations where decisions—based on reasons—are required

Breath analysis by gas chromatography-mass spectrometry and electronic nose to screen for pleural mesothelioma : a cross-sectional case-control study

Rationale: Malignant pleural mesothelioma (MPM) is mainly caused by previous exposure to asbestos fibers and has a poor prognosis. Due to a long latency period between exposure and diagnosis, MPM incidence is expected to peak between 2020-2025. Screening of asbestos-exposed individuals is believed to improve early detection and hence, MPM management. Recent developments focus on breath analysis for screening since breath contains volatile organic compounds (VOCs) which reflect the cell’s metabolism. Objectives: The goal of this cross-sectional, case-control study is to identify VOCs in exhaled breath of MPM patients with gas chromatography-mass spectrometry (GC-MS) and to assess breath analysis to screen for MPM using an electronic nose (eNose). Methods: Breath and background samples were taken from 64 subjects: 16 healthy controls (HC), 19 asymptomatic former asbestos-exposed (AEx) individuals, 15 patients with benign asbestos-related diseases (ARD) and 14 MPM patients. Samples were analyzed with both GC-MS and eNose. Results: Using GC-MS, AEx individuals were discriminated from MPM patients with 97% accuracy, with diethyl ether, limonene, nonanal, methylcyclopentane and cyclohexane as important VOCs. This was validated by eNose analysis. MPM patients were discriminated from AEx+ARD participants by GC-MS and eNose with 94% and 74% accuracy, respectively. The sensitivity, specificity, positive and negative predictive values were 100%, 91%, 82%, 100% for GC-MS and 82%, 55%, 82%, 55% for eNose, respectively. Conclusion: This study shows accurate discrimination of patients with MPM from asymptomatic asbestos-exposed persons at risk by GC-MS and eNose analysis of exhaled VOCs and provides proof-of-principle of breath analysis for MPM screening

Impact of critical illness and withholding of early parenteral nutrition in the pediatric intensive care unit on long-term physical performance of children:a 4-year follow-up of the PEPaNIC randomized controlled trial

Background: Many critically ill children face long-term developmental impairments. The PEPaNIC trial attributed part of the problems at the level of neurocognitive and emotional/behavioral development to early use of parenteral nutrition (early-PN) in the PICU, as compared with withholding it for 1 week (late-PN). Insight in long-term daily life physical functional capacity after critical illness is limited. Also, whether timing of initiating PN affects long-term physical function of these children remained unknown. Methods: This preplanned follow-up study of the multicenter PEPaNIC randomized controlled trial subjected 521 former critically ill children (253 early-PN, 268 late-PN) to quantitative physical function tests 4 years after PICU admission in Leuven or Rotterdam, in comparison with 346 age- and sex-matched healthy children. Tests included handgrip strength measurement, timed up-and-go test, 6-min walk test, and evaluation of everyday overall physical activity with an accelerometer. We compared these functional measures for the former critically ill and healthy children and for former critically ill children randomized to late-PN versus early-PN, with multivariable linear or logistic regression analyses adjusting for risk factors. Results: As compared with healthy children, former critically ill children showed less handgrip strength (p &lt; 0.0001), completed the timed up-and-go test more slowly (p &lt; 0.0001), walked a shorter distance in 6 min (p &lt; 0.0001) during which they experienced a larger drop in peripheral oxygen saturation (p ≤ 0.026), showed a lower energy expenditure (p ≤ 0.024), performed more light and less moderate physical activity (p ≤ 0.047), and walked fewer steps per day (p = 0.0074). Late-PN as compared with early-PN did not significantly affect these outcomes. Conclusions: Four years after PICU admission, former critically ill children showed worse physical performance as compared with healthy children, without impact of timing of supplemental PN in the PICU. This study provides further support for de-implementing the early use of PN in the PICU. Trial registration ClinicalTrials.gov, NCT01536275; registered on February 22, 2012.</p

Divergent community trajectories with climate change across a fine‐scale gradient in snow depth

Abstract: Fine‐scale microclimate variation due to complex topography can shape both current vegetation distributional patterns and how vegetation responds to changing climate. Topographic heterogeneity in mountains is hypothesized to mediate responses to regional climate change at the scale of metres. For alpine vegetation especially, the interplay between changing temperatures and topographically mediated variation in snow accumulation will determine the overall impact of climate change on vegetation dynamics. We combined 30 years of co‐located measurements of temperature, snow and alpine plant community composition in Colorado, USA, to investigate vegetation community trajectories across a snow depth gradient. Our analysis of long‐term trends in plant community composition revealed notable directional change in the alpine vegetation with warming temperatures. Furthermore, community trajectories are divergent across the snow depth gradient, with exposed parts of the landscape that experience little snow accumulation shifting towards stress‐tolerant, cold‐ and drought‐adapted communities, while snowier areas shifted towards more warm‐adapted communities. Synthesis: Our findings demonstrate that fine‐scale topography can mediate both the magnitude and direction of vegetation responses to climate change. We documented notable shifts in plant community composition over a 30‐year period even though alpine vegetation is known for slow dynamics that often lag behind environmental change. These results suggest that the processes driving alpine plant population and community dynamics at this site are strong and highly heterogeneous across the complex topography that is characteristic of high‐elevation mountain systems

Can community-based peer support promote health literacy and reduce inequalities? A realist review.

Background Community-based peer support (CBPS) has been proposed as a potentially promising approach to improve health literacy (HL) and reduce health inequalities. Peer support, however, is described as a public health intervention in search of a theory, and as yet there are no systematic reviews exploring why or how peer support works to improve HL. Objective To undertake a participatory realist synthesis to develop a better understanding of the potential for CBPS to promote better HL and reduce health inequalities. Data sources Qualitative evidence syntheses, conceptual reviews and primary studies evaluating peer-support programmes; related studies that informed theoretical or contextual elements of the studies of interest were included. We conducted searches covering 1975 to October 2011 across Scopus, Global Health (including MEDLINE), ProQuest Dissertations & Theses database (PQDT) [including the Education Resources Information Center (ERIC) and Social Work Abstracts], The King’s Fund Database and Web of Knowledge, and the Institute of Development Studies supplementary strategies were used for the identification of grey literature. We developed a new approach to searching called ‘cluster searching’, which uses a variety of search techniques to identify papers or other research outputs that relate to a single study. Study eligibility criteria Studies written in English describing CBPS research/evaluation, and related papers describing theory, were included. Study appraisal and synthesis methods Studies were selected on the basis of relevance in the first instance. We first analysed within-programme articulation of theory and appraised for coherence. Cross-programme analysis was used to configure relationships among context, mechanisms and outcomes. Patterns were then identified and compared with theories relevant to HL and health inequalities to produce a middle-range theory. Results The synthesis indicated that organisations, researchers and health professionals that adopt an authoritarian design for peer-support programmes risk limiting the ability of peer supporters (PSs) to exercise autonomy and use their experiential knowledge to deliver culturally tailored support. Conversely, when organisations take a negotiated approach to codesigning programmes, PSs are enabled to establish meaningful relationships with people in socially vulnerable groups. CBPS is facilitated when organisations prioritise the importance of assessing community needs; investigate root causes of poor health and well-being; allow adequate time for development of relationships and connections; value experiential cultural knowledge; and share power and control during all stages of design and implementation. The theory now needs to be empirically tested via further primary research. Limitations Analysis and synthesis were challenged by a lack of explicit links between peer support for marginalised groups and health inequalities; explicitly stated programme theory; inconsistent reporting of context and mechanism; poor reporting of intermediate process outcomes; and the use of theories aimed at individual-level behaviour change for community-based interventions. Conclusions Peer-support programmes have the potential to improve HL and reduce health inequalities but potential is dependent upon the surrounding equity context. More explicit empirical research is needed, which establishes clearer links between peer-supported HL and health inequalities

Atypical vessels as an early sign of intracardiac myxoma?

We report on a woman with previously unknown left atrial myxoma, who underwent percutaneous coronary intervention. 45 months after the initial coronary angiography, echocardiography demonstrated a large atrial myxoma, which was not seen echocardiographically before. The retrospective analysis of the pre-intervention coronary angiography revealed atypical vessels in the atrial septum, which are interpreted as early signs of myxoma