Structured Model Conserving Biomass for the Size-spectrum Evolution in Aquatic Ecosystems

Mathematical modelling of the evolution of the size-spectrum dynamics in aquatic ecosystems was discovered to be a powerful tool to have a deeper insight into impacts of human- and environmental driven changes on the marine ecosystem. In this article we propose to investigate such dynamics by formulating and investigating a suitable model. The underlying process for these dynamics is given by predation events, causing both growth and death of individuals, while keeping the total biomass within the ecosystem constant. The main governing equation investigated is deterministic and non-local of quadratic type, coming from binary interactions. Predation is assumed to strongly depend on the ratio between a predator and its prey, which is distributed around a preferred feeding preference value. Existence of solutions is shown in dependence of the choice of the feeding preference function as well as the choice of the search exponent, a constant influencing the average volume in water an individual has to search until it finds prey. The equation admits a trivial steady state representing a died out ecosystem, as well as - depending on the parameterregime - steady states with gaps in the size spectrum, giving evidence to the well known cascade effect. The question of stability of these equilibria is considered, showing convergence to the trivial steady state in a certain range of parameters. These analytical observations are underlined by numerical simulations, with additionally exhibiting convergence to the non-trivial equilibrium for specific ranges of parameters

Etude sur les tendances nocturnes de la ville de Sion: Qu’annonce le crépuscule du soir au coeur du Valais ?

La vie nocturne de la ville de Sion prend vie dès que le soleil s’est couché et se termine dès que ce dernier se lève. Mais que se passe-t-il durant ce lapse de temps et quelle importance faut-il y accorder ? Cette étude cherche à démontrer d’une part l’étendue de la vie nocturne d’un point de vue touristique en milieu urbain et d’autre part elle tente d’explorer la situation actuelle de la ville de Sion afin de pouvoir évaluer son impact auprès des différents protagonistes de la nuit. Pour se faire, une analyse quantitative et qualitative est alors nécessaire afin d’évaluer l’offre et la demande du marché mais aussi une décomposition scientifique et précise de chacune des caractéristiques de la vie nocturne sédunoise en plus des facteurs qui peuvent l’influencer

Stabilization of an α-helix by short adjacent accessory foldamers

AbstractTemplate-based stabilization of α-peptide helices with short accessory non-peptide helical foldamers fused either at the N- or C-terminus or at both ends of the peptide segment has been investigated by NMR spectroscopy in polar solvents and by X-ray diffraction. In this work, we focused on aliphatic N,N′-linked oligoureas that form predictable and well-defined helical structures akin to α-helices. Our results indicate that urea oligomers have the ability to enforce a peptide segment to adopt a well-defined α-helical structure and may suggest a general approach to stabilize short helical peptide epitopes for the development of modulators of protein–protein interactions

Predicting the ages of galaxies with an artificial neural network

We present a new method of predicting the ages of galaxies using a machine learning (ML) algorithm with the goal of providing an alternative to traditional methods. We aim to match the ability of traditional models to predict the ages of galaxies by training an artificial neural network (ANN) to recognize the relationships between the equivalent widths of spectral indices and the mass-weighted ages of galaxies estimated by the MAGPHYS model in data release 3 (DR3) of the Galaxy and Mass Assembly (GAMA) survey. We discuss the optimization of our hyperparameters extensively and investigate the application of a custom loss function to reduce the influence of errors in our input data. To quantify the quality of our predictions we calculate the mean squared error (MSE), mean absolute error (MAE) and R2 score for which we find MSE = 0.020, MAE = 0.108 and R2 = 0.530. We find our predicted ages have a similar distribution with standard deviation σp = 0.182 compared with the GAMA true ages σt = 0.207. This is achieved in approximately 23 s to train our ANN on an 11th Gen Intel Core i9-11900H running at 2.50 GHz using 32 GB of RAM. We report our results for when light-weighted ages are used to train the ANN, which improves the accuracy of the predictions. Finally, we detail an evaluation of our method relating to physical properties and compare with other ML techniques to encourage future applications of ML techniques in astronomy

Multi-stage reactive formation of troctolites in slow-spreading oceanic lithosphere (Erro-Tobbio, Italy): a combined field and petrochemical study

partially_open5Many recent studies have investigated the replacive formation of troctolites from mantle protoliths and the compositional evolution of the percolating melt during melt-rock interaction processes. However, strong structural and geochemical constraints for a replacive origin have not yet been established. The Erro-Tobbio impregnated mantle peridotites are primarily associated with a hectometre-size troctolitic body and crosscutting gabbroic dikes, providing a good field control on melt-rock interaction processes and subsequent magmatic intrusions. The troctolitic body exhibits high inner complexity, with a host troctolite (Troctolite A) crosscut by a second generation of troctolitic metre-size pseudo-tabular bodies (Troctolite B). The host Troctolite A is characterized by two different textural types of olivine, corroded deformed millimetre- to centimetre-size olivine and fine-grained rounded undeformed olivine, both embedded in interstitial to poikilitic plagioclase and clinopyroxene. Troctolite A shows melt-rock reaction microstructures indicative of replacive formation after percolation and impregnation of mantle dunites by a reactive melt. The evolution of the texture and Crystallographic Preferred Orientation (CPO) of olivine are correlated and depend on the melt/rock ratio involved in the impregnation process. A low melt/rock ratio allows the preservation of the protolith structure, whereas a high melt/rock ratio leads to the disaggregation of the pre-existing matrix. The mineral compositions in Troctolite A define reactive trends, indicative of the buffering of the melt composition by assimilation of olivine during impregnation. The magmatic Troctolite B bodies are intruded within the pre-existing Troctolite A and are characterized by extreme textural variations of olivine, from decimetre-size dendritic to fine-grained euhedral crystals embedded in poikilitic plagioclase. This textural variability is the result of olivine assimilation during melt-rock reaction and the correlated increase in the degree of undercooling of the percolating melt. In the late gabbroic intrusions, mineral compositions are consistent with the fractional crystallization of melts modified after the reactive crystallization of Troctolites A and B. The Erro-Tobbio troctolitic body has a multi-stage origin, marked by the transition from reactive to fractional crystallization and diffuse to focused melt percolation and intrusion, related to progressive exhumation. During the formation of the troctolitic body, the melt composition was modified and controlled by assimilation and concomitant crystallization reactions occurring at low melt supply. Similar processes have been described in ultra-slow spreading oceanic settings characterized by scarce magmatic activity.openBasch, Valentin; Rampone, Elisabetta; Crispini, Laura; Ferrando, Carlotta; Ildefonse, Benoit; Godard, MargueriteBasch, Valentin; Rampone, Elisabetta; Crispini, Laura; Ferrando, Carlotta; Ildefonse, Benoit; Godard, Marguerit

Noise reduction in single-shot images using an auto-encoder

We present an application of auto-encoders to the problem of noise reduction in single-shot astronomical images and explore its suitability for upcoming large-scale surveys. Auto-encoders are a machine learning model that summarizes an input to identify its key features, and then from this knowledge predicts a representation of a different input. The broad aim of our auto-encoder model is to retain morphological information (e.g. non-parametric morphological information) from the survey data while simultaneously reducing the noise contained in the image. We implement an auto-encoder with convolutional and max pooling layers. We test our implementation on images from the Panoramic Survey Telescope and Rapid Response System that contain varying levels of noise and report how successful our auto-encoder is by considering mean squared error, structural similarity index, the second-order moment of the brightest 20 per cent of the galaxy’s flux M20, and the Gini coefficient, while noting how the results vary between original images, stacked images, and noise-reduced images. We show that we are able to reduce noise, over many different targets of observations, while retaining the galaxy’s morphology, with metric evaluation on a target-by-target analysis. We establish that this process manages to achieve a positive result in a matter of minutes, and by only using one single-shot image compared to multiple survey images found in other noise reduction techniques

Education Aspirations and Barriers to Achievement for Street‐Involved Youth in Victoria, Canada

Much of the literature on street‐involved youth focuses on their deficits, including their high risk of withdrawing before completing high school, which is often interpreted as a rejection of formal education. Missing from the literature is an understanding of street‐involved youth’s educational aspirations. We employed thematic analysis of qualitative data from in‐person interviews with a purposive sample of street‐involved youth (N = 69) residing in one city in Canada, who were partly or fully disengaged from school at the time of the interview. We asked the youth to talk about their opinions of formal education, its importance for young people, whether learning was important for them, and whether they imagined returning to school/continuing with school. We discovered that the majority of youth had a positive view of school/formal education and stated they liked learning new things and recognized the benefits of continuing/completing their education. At the same time, the youth identified material hardship and other barriers to achieving their educational goals. We discuss these findings in light of the relevant literature and make policy recommendations to improve educational success for youth struggling with poverty and homelessness in Canada

Epidemiology, causes, evolution and outcome in a single-center cohort of 1116 critically ill patients with hypoxic hepatitis

Background: Hypoxic hepatitis (HH) is a type of acute hepatic injury that is histologically characterized by centrilobular liver cell necrosis and that is caused by insufficient oxygen delivery to the hepatocytes. Typical for HH is the sudden and significant increase of aspartate aminotransferase (AST) in response to cardiac, circulatory or respiratory failure. The aim of this study is to investigate its epidemiology, causes, evolution and outcome. Methods: The screened population consisted of all adults admitted to the intensive care unit (ICU) at the Ghent University Hospital between January 1, 2007 and September 21, 2015. HH was defined as peak AST > 5 times the upper limit of normal (ULN) after exclusion of other causes of liver injury. Thirty-five variables were retrospectively collected and used in descriptive analysis, time series plots and Kaplan-Meier survival curves with multi-group log-rank tests. Results: HH was observed in 4.0% of the ICU admissions at our center. The study cohort comprised 1116 patients. Causes of HH were cardiac failure (49.1%), septic shock (29.8%), hypovolemic shock (9.4%), acute respiratory failure (6.4%), acute on chronic respiratory failure (3.3%), pulmonary embolism (1.4%) and hyperthermia (0.5%). The 28-day mortality associated with HH was 45.0%. Mortality rates differed significantly (P = 0.007) among the causes, ranging from 33.3% in the hyperthermia subgroup to 52.9 and 56.2% in the septic shock and pulmonary embolism subgroups, respectively. The magnitude of AST increase was also significantly correlated (P 20x ULN, respectively. Conclusion: This study surpasses by far the largest cohort of critically ill patients with HH. HH is more common than previously thought with an ICU incidence of 4.0%, and it is associated with a high all-cause mortality of 45.0% at 28 days. The main causes of HH are cardiac failure and septic shock, which include more than 3/4 of all episodes. Clinicians should search actively for any underlying hemodynamic or respiratory instability even in patients with moderately increased AST levels

Implications of the 2740 Ma Cote Gold Au(-Cu) deposit for Archean gold metallogeny and porphyry Au deposit formation in the Archean Swayze greenstone belt, northern Ontario

International audienceOre-deposit models, which are fundamental to mineral exploration, result from integrating robust field observations with high-quality mineral-chemical-isotopic data. New discoveries departing from current models demand explanation, and in some cases new deposit models result (e.g., IOCG). The recent (2009/2010) discovery of the Cote Gold Au(-Cu) deposit in the Archean Swayze greenstone belt, northern Ontario, challenges the age-restricted view of porphyry Cu-Au models. The +8 Moz Au deposit is hosted by a subvolcanic tonalite-diorite intrusive complex where magmatic-hydrothermal breccia bodies occur. Gold mineralization, of disseminated-, fracture-and vein-types, is spatially associated with hydrothermal biotite and muscovite alteration that is similar to potassic and phyllic alteration, respectively, in porphyry-type settings. A robust program involving core logging and field mapping with structural analysis integrated with detailed petrographic studies, geochronology, lithogeochemistry, isotopes, and fluid inclusion studies (microthermometry and evaporate mound SEM-EDS analysis) was used to assess the deposit's origin. That the age of host rocks (U-Pb zircon, titanite) and timing of alteration (U-Pb titanite) and mineralization (Re-Os molybdenite) centre on 2740 Ma and pre-dates the age of regional deformation (ca. 2680 Ma), in addition to the co-spatial nature of mineralization and alteration, suggests a magmatic-hydrothermal connection. Structural analysis of auriferous quartz veins also indicates a relationship to the intrusive centre versus regional deformation, which is further supported by a 2740 Ma molybdenite age for one such gold-mineralized vein. Fluid-chemical data indicates fluid mixing with ?34S (py, cpy, moly = 0 ± 1‰) and fluid inclusions (mixed H2O-CO2 fluid (XCO2=0.10); Na-K-CaFe -Mn-Cl-F-S chemistry) suggesting a magmatic fluid reservoir whereas ?18O (qtz = 7-12‰) also indicates a possible seawater contribution. These observations are best reconciled with a deposit model involving Au(-Cu) mineralization originating from exsolution of magmatic fluids from a high-level, hydrous intermediate magma in the same manner as models for younger porphyry analogues