A finite subdivision rule for the n-dimensional torus

Cannon, Floyd, and Parry have studied subdivisions of the 2-sphere extensively, especially those corresponding to 3-manifolds, in an attempt to prove Cannon's conjecture. There has been a recent interest in generalizing some of their tools, such as extremal length, to higher dimensions. We define finite subdivision rules of dimension n, and find an n-1-dimensional finite subdivision rule for the n-dimensional torus, using a well-known simplicial decomposition of the hypercube. We hope to expand on this and find finite subdivision rules for many higher-dimensional manifolds, including hyperbolic n-manifolds.Comment: Accepted by Geometriae Dedicata; ublished version available onlin

A promising material for non-linear optics: Observation of second harmonic generation from 4-[N-(4-carboxypentyl)-N-methylamino]-4′-nitrostilbene- coated substrates

Glass coated with a nitro amino stilbene carboxylic acid using the Langmuir-Blodgett technique gave a non-centrosymmetric material exhibiting second harmonic generation, 1.06 to 0.53 μm

Cropping system effects on soil quality in the Great Plains: Synthesis from a regional project

Soils perform a number of essential functions affecting management goals. Soil functions were assessed by measuring physical, chemical, and biological properties in a regional assessment of conventional (CON) and alternative (ALT) management practices at eight sites within the Great Plains. The results, reported in accompanying papers, provide excellent data for assessing how management practices collectively affect agronomic and environmental soil functions that benefit both farmers and society. Our objective was to use the regional data as an input for two new assessment tools to evaluate their potential and sensitivity for detecting differences (aggradation or degradation) in management systems. The soil management assessment framework (SMAF) and the agro-ecosystem performance assessment tool (AEPAT) were used to score individual soil properties at each location relative to expected conditions based on inherent soil-forming factors and to compute index values that provide an overall assessment of the agronomic and environmental impact of the CON and ALT practices. SMAF index values were positively correlated with grain yield (an agronomic function) and total organic matter (an agronomic and environmental function). They were negatively correlated with soil nitrate concentration at harvest (an indicator of environmental function). There was general agreement between the two assessment tools when used to compare management practices. Users can measure a small number of soil properties and use one of these tools to easily assess the effectiveness of soil management practices. A higher score in either tool identifies more environmentally and agronomically sustainable management. Temporal variability in measured indicators makes dynamic assessments of management practices essential. Water-filled pore space, aggregate stability, particulate organic matter, and microbial biomass were sensitive to management and should be included in studies aimed at improving soil management. Reductions in both tillage and fallow combined with crop rotation has resulted in improved soil function (e.g., nutrient cycling, organic C content, and productivity) throughout the Great Plains

Characteristics of US-Based STEM Webcams \u3cem\u3eat a Glance\u3c/em\u3e

STEM organizations operate thousands of publicly available webcams, which have the potential to provide rich informal learning opportunities. To date, no research has analyzed the breadth of STEM webcams. In our study, we developed an inventory by performing internet searches for US-based STEM webcams and recorded operator name, organization type, webcam subject, etc. This inventory serves as the basis for a follow-up survey of webcam operators, which seeks to better understand the goals, outcomes, and investments of STEM webcam programs. We characterized nearly 1000 webcams that fit within our inclusion criteria. The majority of the cams fell within the life sciences or geosciences. Of the animal webcams, mammals (60%) and birds (23%) were strongly represented in contrast to reptiles (2%) and insects (4%). Within the mammal subjects, tigers, elephants, otters, and giraffes were most common (5-7% each). Within the 23 different bird webcam subjects, penguins (30%) and osprey (20%) were most common. Other studies have shown the over-representation of charismatic animals (e.g., elephants, giraffes, tigers, bears) in zoos, and our study suggests that webcams may amplify this phenomenon. Further, these preliminary results suggest that life sciences topics dominate STEM webcams, leaving potential for other visually engaging fields to participate

Estimated Worldwide Mortality Attributed to Secondhand Tobacco Smoke Exposure, 1990-2016

Importance: The World Health Organization estimates that the 1 billion individuals who smoke worldwide contribute to the 880 000 secondhand smoke (SHS)-related deaths among individuals who do not smoke each year. A better understanding of the scale of harm of SHS to those who do not smoke could increase awareness of the consequences of smoking and help to design measures to protect individuals who do not smoke, especially children. Objective: To calculate the number of individuals who smoke associated with the death of 1 individual who died of SHS exposure both on a global scale and in various World Bank regions. Design, Setting, and Participants: In this cross-sectional epidemiologic assessment, data from Our World in Data were used to tabulate the number of individuals who smoke in each country and number of premature deaths related to SHS in that country from 1990 to 2016. The mean number of cigarettes consumed in all countries was also included in analyses. Data were collected for the following World Bank regions: North America, Latin America and the Caribbean, Europe and Central Asia, the Middle East and North Africa, sub-Saharan Africa, South Asia, and East Asia and the Pacific from 1990 and 2016. Statistical analysis was conducted in July 2019. Exposure: Secondhand smoke. Main Outcomes and Measures: The pack-year index, calculated as the number of pack-years associated with the death of 1 individual who does not smoke but was exposed to SHS, and the SHS index, calculated as the number of individuals who smoked for 24 years (ie, the mean duration of smoking) associated with the death of 1 individual who does not smoke. Results: Globally, the SHS index changed favorably, from 31.3 (95% CI, 30.6-32.0) individuals who smoked associated with the death of 1 individual who did not smoke in 1990 to 52.3 (95% CI, 51.2-53.5) individuals who smoked in 2016. There was a wide regional variation in the 2016 secondhand smoke index, from 42.6 (95% CI, 41.6-43.5) individuals who smoked in the Middle East and North Africa to 85.7 (95% CI, 83.8-87.7) individuals who smoked in North America. Worldwide, the pack-year index also changed favorably from 751.9 (95% CI, 736.3-770.7) pack-years associated with 1 death in 1990 to 1255.9 (95% CI, 1227.2-1284.4) pack-years in 2016. Conclu

Evaluation of an Artificial Intelligence Coronary Artery Calcium Scoring Model from Computed Tomography

OBJECTIVES: Coronary artery calcium (CAC) scores derived from computed tomography (CT) scans are used for cardiovascular risk stratification. Artificial intelligence (AI) can assist in CAC quantification and potentially reduce the time required for human analysis. This study aimed to develop and evaluate a fully automated model that identifies and quantifies CAC. METHODS: Fully convolutional neural networks for automated CAC scoring were developed and trained on 2439 cardiac CT scans and validated using 771 scans. The model was tested on an independent set of 1849 cardiac CT scans. Agatston CAC scores were further categorised into five risk categories (0, 1–10, 11–100, 101–400, and > 400). Automated scores were compared to the manual reference standard (level 3 expert readers). RESULTS: Of 1849 scans used for model testing (mean age 55.7 ± 10.5 years, 49% males), the automated model detected the presence of CAC in 867 (47%) scans compared with 815 (44%) by human readers (p = 0.09). CAC scores from the model correlated very strongly with the manual score (Spearman’s r = 0.90, 95% confidence interval [CI] 0.89–0.91, p < 0.001 and intraclass correlation coefficient = 0.98, 95% CI 0.98–0.99, p < 0.001). The model classified 1646 (89%) into the same risk category as human observers. The Bland–Altman analysis demonstrated little difference (1.69, 95% limits of agreement: −41.22, 44.60) and there was almost excellent agreement (Cohen’s κ = 0.90, 95% CI 0.88–0.91, p < 0.001). Model analysis time was 13.1 ± 3.2 s/scan. CONCLUSIONS: This artificial intelligence–based fully automated CAC scoring model shows high accuracy and low analysis times. Its potential to optimise clinical workflow efficiency and patient outcomes requires evaluation. KEY POINTS: • Coronary artery calcium (CAC) scores are traditionally assessed using cardiac computed tomography and require manual input by human operators to identify calcified lesions. • A novel artificial intelligence (AI)–based model for fully automated CAC scoring was developed and tested on an independent dataset of computed tomography scans, showing very high levels of correlation and agreement with manual measurements as a reference standard. • AI has the potential to assist in the identification and quantification of CAC, thereby reducing the time required for human analysis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00330-022-09028-3

Research in Medical Education: Balancing Service and Science*

Since the latter part of the 1990’s, the English-speaking medical education community has been engaged in a debate concerning the types of research that should have priority. To shed light on this debate and to better understand its implications for the practice of research, 23 semi-structured interviews were conducted with “influential figures” from the community. The results were analyzed using the concept of “field” developed by the sociologist Pierre Bourdieu. The results reveal that a large majority of these influential figures believe that research in medical education continues to be of insufficient quality despite the progress that has taken place over the past 2 decades. According to this group, studies tend to be both redundant and opportunistic, and researchers tend to have limited understanding of both theory and methodological practice from the social sciences. Three factors were identified by the participants to explain the current problems in research: the working conditions of researchers, budgetary restraints in financing research in medical education, and the conception of research in the medical environment. Two principal means for improving research are presented: intensifying collaboration between PhD’s and clinicians, and encouraging the diversification of perspectives brought to bear on research in medical education

IGF-1 Mediated Neuroprotective Effects of Olfactory-Derived Mesenchymal Stem Cells on Auditory Hair Cells

IMPORTANCE: Mesenchymal stem cells (MSCs) have the capability of providing ongoing paracrine support to degenerating tissues. Since MSCs can be extracted from a broad range of tissues, their specific surface marker profiles and growth factor secretions can be different. We hypothesized that MSCs derived from different sources might also have different neuroprotective potential. OBJECTIVE: In this study, we extracted MSCs from rodent olfactory mucosa and compared their neuroprotective effects on auditory hair cell survival with MSCs extracted from rodent adipose tissue. METHODS: Organ of Corti explants were dissected from 41 cochlea and incubated with olfactory mesenchymal stem cells (OMSCs) and adipose mesenchymal stem cells (AMSCs). After 72 hours, Corti explants were fixed, stained, and hair cells counted. Growth factor concentrations were determined in the supernatant and cell lysate using Enzyme-Linked Immunosorbent Assay (ELISA). RESULTS: Co-culturing of organ of Corti explants with OMSCs resulted in a significant increase in inner and outer hair cell stereocilia survival, compared to control. Comparisons between both stem cell lines, showed that co-culturing with OMSCs resulted in superior inner and outer hair cell stereocilia survival rates over co-culturing with AMSCs. Assessment of growth factor secretions revealed that the OMSCs secrete significant amounts of insulin-like growth factor 1 (IGF-1). Co-culturing OMSCs with organ of Corti explants resulted in a 10-fold increase in IGF-1 level compared to control, and their secretion was 2 to 3 times higher compared to the AMSCs. CONCLUSIONS: This study has shown that OMSCs may mitigate auditory hair cell stereocilia degeneration. Their neuroprotective effects may, at least partially, be ascribed to their enhanced IGF-1 secretory abilities compared to AMSCs