Species interactions differ in their genetic robustness

Conflict and cooperation between bacterial species drive the composition and function of microbial communities. Stability of these emergent properties will be influenced by the degree to which species' interactions are robust to genetic perturbations. We use genome-scale metabolic modeling to computationally analyze the impact of genetic changes when Escherichia coli and Salmonella enterica compete, or cooperate. We systematically knocked out in silico each reaction in the metabolic network of E. coli to construct all 2583 mutant stoichiometric models. Then, using a recently developed multi-scale computational framework, we simulated the growth of each mutant E. coli in the presence of S. enterica. The type of interaction between species was set by modulating the initial metabolites present in the environment. We found that the community was most robust to genetic perturbations when the organisms were cooperating. Species ratios were more stable in the cooperative community, and community biomass had equal variance in the two contexts. Additionally, the number of mutations that have a substantial effect is lower when the species cooperate than when they are competing. In contrast, when mutations were added to the S. enterica network the system was more robust when the bacteria were competing. These results highlight the utility of connecting metabolic mechanisms and studies of ecological stability. Cooperation and conflict alter the connection between genetic changes and properties that emerge at higher levels of biological organization.The authors thank reviewers for comments that substantially improved this manuscript. BG and DS were partially supported by grants from the US Department of Energy (DE-SC0004962) and NIH (R01GM089978 and R01GM103502). (DE-SC0004962 - US Department of Energy; R01GM089978 - NIH; R01GM103502 - NIH)Published versio

Visualization of metabolic interaction networks in microbial communities using VisANT 5.0

The complexity of metabolic networks in microbial communities poses an unresolved visualization and interpretation challenge. We address this challenge in the newly expanded version of a software tool for the analysis of biological networks, VisANT 5.0. We focus in particular on facilitating the visual exploration of metabolic interaction between microbes in a community, e.g. as predicted by COMETS (Computation of Microbial Ecosystems in Time and Space), a dynamic stoichiometric modeling framework. Using VisANT's unique metagraph implementation, we show how one can use VisANT 5.0 to explore different time-dependent ecosystem-level metabolic networks. In particular, we analyze the metabolic interaction network between two bacteria previously shown to display an obligate cross-feeding interdependency. In addition, we illustrate how a putative minimal gut microbiome community could be represented in our framework, making it possible to highlight interactions across multiple coexisting species. We envisage that the "symbiotic layout" of VisANT can be employed as a general tool for the analysis of metabolism in complex microbial communities as well as heterogeneous human tissues.This work was supported by the National Institutes of Health, R01GM103502-05 to CD, ZH and DS. Partial support was also provided by grants from the Office of Science (BER), U.S. Department of Energy (DE-SC0004962), the Joslin Diabetes Center (Pilot & Feasibility grant P30 DK036836), the Army Research Office under MURI award W911NF-12-1-0390, National Institutes of Health (1RC2GM092602-01, R01GM089978 and 5R01DE024468), NSF (1457695), and Defense Advanced Research Projects Agency Biological Technologies Office (BTO), Program: Biological Robustness In Complex Settings (BRICS), Purchase Request No. HR0011515303, Program Code: TRS-0 Issued by DARPA/CMO under Contract No. HR0011-15-C-0091. Funding for open access charge: National Institutes of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. (R01GM103502-05 - National Institutes of Health; 1RC2GM092602-01 - National Institutes of Health; R01GM089978 - National Institutes of Health; 5R01DE024468 - National Institutes of Health; DE-SC0004962 - Office of Science (BER), U.S. Department of Energy; P30 DK036836 - Joslin Diabetes Center; W911NF-12-1-0390 - Army Research Office under MURI; 1457695 - NSF; HR0011515303 - Defense Advanced Research Projects Agency Biological Technologies Office (BTO), Program: Biological Robustness In Complex Settings (BRICS); HR0011-15-C-0091 - DARPA/CMO; National Institutes of Health)Published versio

Amortissement d'une poutre par traitement viscoélastique contraint et analyse du régime transitoire suite à un impact

Les poutres -- Modèle viscoélastique -- Les poutres sandwich -- Les traitements partiels contraints -- Régime transitoire -- Model -- MOdel validation -- Paramètres du système et force d'impact -- Erreur de causalité -- Influence de la longueur du tampon amortissant -- Influence des épaisseurs des couches de viscoélastique et de contrainte du tampon amortissant

La miséricorde selon Saint Jean Eudes

Si la miséricorde fut à une certaine époque inspiration profonde de l'agir chrétien, il est malheureux que sa saveur se soit estompée au cours des siècles pour être reléguée aux oubliettes. Cette recherche a pour fin première de faire redécouvrir la valeur de cette vertu qui, au XVIIème siècle, a été à la source de di verses initiatives pastorales, de plusieurs fondations religieuses et même avec les nuances qu'il faudrait apporter, de l'envoi des premiers missionnaires, hommes et femmes, en Amérique. Touché par la décadence du peuple de Dieu rencontrée dans toutes ces couches sociales, y compris le clergé, saint Jean Eudes fut tour à tour fondateur des Congrégations de Notre-Dame de Charité du Refuge (1641) et de Jésus et Marie (1643). Il voulait ainsi proposer des applications concrètes et permanentes de cette miséricorde qui l'habitait au plus profond de son être. La richesse des écrits légués en héritage à ses fils et à ses filles, et rassemblés sous le titre d'Oeuvres Complètes, constitueront l'assise de ce travail qui permettra de reconnaître comment cette vertu de miséricorde demeure encore aujourd'hui source fondamentale d'un agir chrétien authentique

Effectiveness of stratospheric solar-radiation management as a function of climate sensitivity

If implementation of proposals to engineer the climate through solar-radiation management (SRM) ever occurs, it is likely to be contingent on climate sensitivity. However, modelling studies examining the effectiveness of SRM as a strategy to offset anthropogenic climate change have used only the standard parameterizations of atmosphere–ocean general circulation models that yield climate sensitivities close to the Coupled Model Intercomparison Project mean. Here, we use a perturbed-physics ensemble modelling experiment to examine how the response of the climate to SRM implemented in the stratosphere (SRM-S) varies under different greenhouse-gas climate sensitivities. When SRM-S is used to compensate for rising atmospheric concentrations of greenhouse gases, its effectiveness in stabilizing regional climates diminishes with increasing climate sensitivity. However, the potential of SRM-S to slow down unmitigated climate change, even regionally, increases with climate sensitivity. On average, in variants of the model with higher sensitivity, SRM-S reduces regional rates of temperature change by more than 90% and rates of precipitation change by more than 50%.Engineering and Applied Science

Quantifying paradigm change in demography

<b>Background</b>: Demography is a uniquely empirical research area amongst the social sciences. We posit that the same principle of empiricism should be applied to studies of the population sciences as a discipline, contributing to greater self-awareness amongst its practitioners. <b>Objective</b>: The paper aims to include measurable data in the study of changes in selected demographic paradigms and perspectives. <b>Methods</b>: The presented analysis is descriptive and is based on a series of simple measures obtained from the free online tool Google Books Ngram Viewer, which includes frequencies of word groupings (n-grams) in different collections of books digitised by Google. <b>Results</b>: The tentative findings corroborate the shifts in the demographic paradigms identified in the literature -- from cross-sectional, through longitudinal, to event-history and multilevel approaches. <b>Conclusions</b>: These findings identify a promising area of enquiry into the development of demography as a social science discipline. We postulate that more detailed enquiries in this area in the future could lead to establishing History of Population Thought as a new sub-discipline within population sciences

Los semilleros: escenarios de investigación formativa que fortalecen la Formación Profesional Integral

This article has the purpose of contributing to the understanding of the research incubator strategy as a scenario that enables the application of formative research and research training for the strengthening of Comprehensive Vocational Training in SENA. From the conceptual interpretation, the analysis of the institutional pedagogical and normative framework and thediscussion of the practices developed in the SEMSALUD research incubator, reflections are presented around the following questions: ¿What is formative research and how is it related to the work of the seedlings? ¿What is the pedagogical purpose of formative research at SENA? ¿What practices enable the articulation of formative research, research training and researchincubators for the strengthening of Comprehensive Vocational Training?Este artículo tiene el propósito de aportar a la comprensión de la estrategia de semilleros como un escenario que posibilita la aplicación de la investigación formativa y la formación en investigación para el fortalecimiento de la Formación Profesional Integral en el SENA. Desde la interpretación conceptual, el análisis del marco pedagógico y normativo institucional y la discusión de las prácticas desarrolladas en el semillero de investigación SEMSALUD, se presentan reflexiones alrededor de los siguientes interrogantes: ¿Qué es la investigación formativa y cómo se relaciona con el quehacer de los semilleros? ¿Cuál es el propósito pedagógico de la investigación formativa en el SENA? ¿Qué prácticas posibilitan la articulación de la investigación formativa, la formación en investigación y los semilleros para el fortalecimiento de la Formación Profesional Integral

Differentiable Simulation of a Liquid Argon Time Projection Chamber

Liquid argon time projection chambers (LArTPCs) are widely used in particle detection for their tracking and calorimetric capabilities. The particle physics community actively builds and improves high-quality simulators for such detectors in order to develop physics analyses in a realistic setting. The fidelity of these simulators relative to real, measured data is limited by the modeling of the physical detectors used for data collection. This modeling can be improved by performing dedicated calibration measurements. Conventional approaches calibrate individual detector parameters or processes one at a time. However, the impact of detector processes is entangled, making this a poor description of the underlying physics. We introduce a differentiable simulator that enables a gradient-based optimization, allowing for the first time a simultaneous calibration of all detector parameters. We describe the procedure of making a differentiable simulator, highlighting the challenges of retaining the physics quality of the standard, non-differentiable version while providing meaningful gradient information. We further discuss the advantages and drawbacks of using our differentiable simulator for calibration. Finally, we provide a starting point for extensions to our approach, including applications of the differentiable simulator to physics analysis pipelines

Photoprotection for people with skin of colour: needs and strategies

Skin of colour or pigmented skin has unique characteristics: it has a higher eumelanin-to-pheomelanin ratio, more mature melanosomes, an increased amount of melanin distributed in the upper layers of the epidermis, and more efficient DNA repair compared with lighter skin. However, individuals with skin of colour are at a significant risk of skin damage caused by ultraviolet radiation, including the development of photodermatoses and photoageing changes such as uneven skin tone, and are predisposed to pigmentary disorders. In fact, one of the most common conditions leading to dermatology consultations by patients with skin of colour is photoexacerbated pigmentary disorders. Unfortunately, individuals with skin of colour may be less prone to engage in photoprotective measures, including the use of sunscreens. Physicians are also less likely to prescribe sunscreens for them. There is thus a clear need for better education on photodamage and for more efficient and suitable photoprotection in populations with skin of colour. However, this need has thus far only partially been met, and the development of sunscreen products designed to provide optimal photoprotection for people with skin of colour remains a challenge. Targeted sunscreens for individuals with skin of colour require optimal cosmetic appeal (leaving no white residue and not disrupting skin tone). They should include broad-spectrum [ultraviolet (UV)B/UVA] protection with high sun protection factor, as well as protection against long-wave UVA (UVA1) and visible light, as these wavelengths are capable of inducing or augmenting pigmentary disorders. They may also contain depigmenting agents for patients with pigmentary disorders