The effect of inbreeding on racing performance in Norwegian cold-blooded trotters

International audienc

Training machine learning force fields for simulations of a hybrid organic-inorganic perovskite system

Machine learning force fields (MLFF) have become gradually more popular within the field of material science as of late. Especially within molecular dynamics (MD) simulations have MLFFs seen prominent results, with both accuracy and efficiency comparable to traditional methods. In this study, a MLFF software called NeuralIL has been used to calculate the interatomic forces of a hybrid organic-inorganic perovskite material (DMMgF). Various NeuralIL architectures were explored, and several models showing promising results were selected for flexible cell MD simulations in the functional code Jax-MD. Finally, the accuracy of the NeuralIL-based MD was assessed by investigating whether the simulations could reproduce the phase transition of DMMgF in accordance with experimental data. The interatomic force calculations provided by NeuralIL showcased the model's high capability to reproduce ab initio levels of accuracy. A mean absolute error of 0.020 eV/Å was the lowest seen in test sets that had configurations with ground truth forces calculated from density functional theory. From a variety of NeuralIL architectures explored, a selection was chosen for Jax-MD simulations. Stability in the volume fluctuations was achieved for a single model, with the rest crashing or showing un-physical results. The results shed light on challenges related to training data and overfitting when using MLFF in MD simulations. The phase transition of DMMgF was not shown in accordance with experimental data, although indications of structural changes concurrent with expectations were evident in some simulations. Possible weaknesses in the methodology are discussed as reasons, with special emphasis on the diversity of the training data

The use of fixed effect models and mixed models to estimate single gene associated effects on polygenic traits

International audienc

Cultivar development of kelps for commercial cultivation - Past lessons and future prospects

Cultivated kelps and other macroalgae have great potential in future provision of food, feed, bioenergy, fertilizer, and raw material for a range of chemical products including pharmaceuticals, food and feed additives, and cosmetics. Only a few species are currently cultivated, almost exclusively in Asia. There is a range of species that could be utilized in different parts of the world, providing that protocols for reproduction, propagation, and cultivation are developed. Domestication of species involves selection of traits that are desirable in cultivation and in the utilization of the harvested biomass. Genetic improvement of cultivated species through recombination of alleles and selection (breeding) has ensured high productivity and product quality in both agri- and aquaculture and will likely do so for macroalgae cultivation and use as well. According to the published literature, genetic improvement of kelps in Asia has so far largely relied on utilization of heterosis expressed in certain combinations of parental material, sometimes species hybrids. Here, we explore and evaluate the various methods that could be used in kelp breeding and propose an initial simple and low-cost breeding strategy based on recurrent mixed hybridization and phenotypic selection within local populations. We also discuss the genetic diversity in wild populations, and how this diversity can be protected against genetic pollution, either by breeding and cultivating local populations, or by developing cultivars that are not able to establish in, or hybridize with, wild populations.publishedVersio

A periodic analysis of longitudinal binary responses: a case study of clinical mastitis in Norwegian Red cows

A Bayesian procedure for analyzing longitudinal binary responses using a periodic cosine function was developed. It was assumed that, after adjustment for "seasonal" effects, the oscillation of the underlying latent variables for longitudinal binary responses was a stationary series. Based on this assumption, a single dimension sinusoidal analysis of longitudinal binary responses using the Gibbs sampling and Metropolis algorithms was implemented in a study of clinical mastitis records of Norwegian Red cows taken over five lactations

The relationship between Norwegian Red heifer growth and their first-lactation test-day milk yield: A field study

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The Virtual Element Method as a Common Framework for Finite Element and Finite Difference Methods - Numerical and Theoretical Analysis

Consistent discretizations of differential equations on polygonal and polyhedral grids is an active area of research. This is of particular interest in applications where the grid is constructed to capture the physical properties of the domain on which the differential equation is defined, for example in subsurface modelling. Recent developments in this area includes the mimetic finite difference method, which mimics the physical and mathematical properties of the problem. Construction of such methods involves choosing a term to ensure stability. Mimetic finite differences has later evolved into a finite element-like approach called the virtual element method, which is the topic of this thesis. The work presented here consists of three parts: (i) A literature study of the virtual element method for Poisson problems, (ii) an analysis of the construction of the stability term of the virtual element method, and (iii) a MATLAB implementation of the virtual element method in two and three dimensions, for first and second order, accompanied by numerical examples. A detailed proof of the well-posedness of the operator involved in constructing the virtual element function space is presented. We also present a detailed proof of that this projection can be calculated exactly for any function in the virtual element function space. Moreover, we show how the stability term can be chosen such that the bilinear form of the virtual element method equals the bilinear form it approximates. This is used to show that the stability term can be chosen such that local stiffness matrix of the first order virtual element is equal to the local stiffness matrix of the first order finite element method for certain cell geometries. It is also used to show that we can choose the stability term to obtain the same system of linear equations as for finite difference stencils. The MATLAB implementation is used to solve simple problems in two and three dimensions. We also use the implementation to investigate how the stability term can be used to minimize the error of the approximation in different norms. Finally, the implementation is compared to some of the most common methods used in reservoir simulations: Two-point and multipoint flux approximation, and mimetic finite differences. The implementation is robust to irregular cell geometries and high aspect ratios, and converges as predicted by the theory. Moreover, for pressure problems, it produces solutions which are close to or better than the solutions produced by the mentioned reservoir simulation methods

Isotope fractionation in juvenile and large rainbow trout (Oncorhynchus mykiss): Repeatability of stable isotope measures and their relationship to growth rate

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