| 26. |
- Moradi, M. Mehdi, et al.
(författare)
-
Resample-smoothing of Voronoi intensity estimators
- 2019
-
Ingår i: Statistics and computing. - : Springer. - 0960-3174 .- 1573-1375. ; 29:5, s. 995-1010
-
Tidskriftsartikel (refereegranskat)abstract
- Voronoi estimators are non-parametric and adaptive estimators of the intensity of a point process. The intensity estimate at a given location is equal to the reciprocal of the size of the Voronoi/Dirichlet cell containing that location. Their major drawback is that they tend to paradoxically under-smooth the data in regions where the point density of the observed point pattern is high, and over-smooth where the point density is low. To remedy this behaviour, we propose to apply an additional smoothing operation to the Voronoi estimator, based on resampling the point pattern by independent random thinning. Through a simulation study we show that our resample-smoothing technique improves the estimation substantially. In addition, we study statistical properties such as unbiasedness and variance, and propose a rule-of-thumb and a data-driven cross-validation approach to choose the amount of smoothing to apply. Finally we apply our proposed intensity estimation scheme to two datasets: locations of pine saplings (planar point pattern) and motor vehicle traffic accidents (linear network point pattern).
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| 27. |
- Löfgren, Stefan, et al.
(författare)
-
Water chemistry in 179 randomly selected Swedish headwaterstreams related to forest production, clear-felling and climate
- 2014
-
Ingår i: Environmental Monitoring & Assessment. - : Springer Berlin/Heidelberg. - 0167-6369 .- 1573-2959. ; 186:12, s. 8907-8928
-
Tidskriftsartikel (refereegranskat)abstract
- From a policy perspective, it is important to understand forestry effects on surface waters from a landscape perspective. The EU Water Framework Directive demands remedial actions if not achieving good ecological status. In Sweden, 44 % of the surface water bodies have moderate ecological status or worse. Many of these drain catchments with a mosaic of managed forests. It is important for the forestry sector and water authorities to be able to identify where, in the forested landscape, special precautions are necessary. The aim of this study was to quantify the relations between forestry parameters and headwater stream concentrations of nutrients, organic matter and acid-base chemistry. The results are put into the context of regional climate, sulphur and nitrogen deposition, as well as marine influences. Water chemistry was measured in 179 randomly selected headwater streams from two regions in southwest and central Sweden, corresponding to 10 % of the Swedish land area. Forest status was determined from satellite images and Swedish National Forest Inventory data using the probabilistic classifier method, which was used to model stream water chemistry with Bayesian model averaging. The results indicate that concentrations of e.g. nitrogen, phosphorus and organic matter are related to factors associated with forest production but that it is not forestry per se that causes the excess losses. Instead, factors simultaneously affecting forest production and stream water chemistry, such as climate, extensive soil pools and nitrogen deposition, are the most likely candidates The relationships with clear-felled and wetland areas are likely to be direct effects.
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| 28. |
- Almquist, Joachim, 1980
(författare)
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Kinetic Models in Life Science — Contributions to Methods and Applications
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Kinetic models in life science combine mathematics and biology to answer questions from areas such as cell biology, physiology, biotechnology, and drug development. The idea of kinetic models is to represent a biological system by a number of biochemical reactions together with mathematical expressions for the reaction kinetics, i.e., how fast the reactions occur. This defines a set of mass balance differential equations for the modeled biochemical variables, whose solution determines the variables' temporal dynamics. Good kinetic models describe, predict, and enable understanding of biological systems, and provide answers to questions which are otherwise technically challenging, unethical, or expensive to obtain directly from experiments. This thesis investigates the workflow for building and using kinetic models. Briefly, the model question determines a suitable mathematical framework for the mass balance equations, prior knowledge informs selection of relevant reactions and kinetics, and unknown parameters are estimated from experimental data. A validated model is used for simulation and analysis, which is interpreted to gain biological insights. Three kinetic models were created to illustrate the workflow. First, a model of the antiplatelet drug ticagrelor and the investigational antidote MEDI2452 was developed for the mouse. The model unraveled the biological mechanisms of the pharmacokinetic interaction and predicted free ticagrelor plasma concentration, thereby contributing to the pharmaceutical development of MEDI2452. Second, a model of the Kv1.5 potassium ion channel was integrated within an existing electrophysiological model of a canine atrial cell. The effect of Kv1.5 block on the action potential was simulated, which improved understanding of blocking mechanisms and enabled assessing pharmacological treatment of atrial fibrillation. Third, a nonlinear mixed effects (NLME) model, with population-level distributions of kinetic parameters, was successfully used to describe cell-to-cell variability of the yeast transcription factor Mig1. This model demonstrated the innovative idea of applying NLME modeling to single cell data.Two studies of kinetic model-building methods are also presented. First, a novel parameter estimation algorithm for NLME models is explained. It computes exact gradients using sensitivity-equations, and represents a substantial advancement over its predecessor. Second, a modeling framework is proposed that combines stochastic differential equations with NLME modeling. This promising framework extends the current scope of NLME models by considering uncertainty in the model dynamics.
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| 29. |
- Miller, Frank, et al.
(författare)
-
A decision theoretical modeling for Phase III investments and drug licensing
- 2018
-
Ingår i: Journal of Biopharmaceutical Statistics. - : Informa UK Limited. - 1054-3406 .- 1520-5711. ; 28:4, s. 698-721
-
Tidskriftsartikel (refereegranskat)abstract
- For a new candidate drug to become an approved medicine, several decision points have to be passed. In this article, we focus on two of them: First, based on Phase II data, the commercial sponsor decides to invest (or not) in Phase III. Second, based on the outcome of Phase III, the regulator determines whether the drug should be granted market access. Assuming a population of candidate drugs with a distribution of true efficacy, we optimize the two stakeholders' decisions and study the interdependence between them. The regulator is assumed to seek to optimize the total public health benefit resulting from the efficacy of the drug and a safety penalty. In optimizing the regulatory rules, in terms of minimal required sample size and the Type I error in Phase III, we have to consider how these rules will modify the commercial optimization made by the sponsor. The results indicate that different Type I errors should be used depending on the rarity of the disease.
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| 30. |
- Lundengård, Karl, 1987-
(författare)
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Generalized Vandermonde matrices and determinants in electromagnetic compatibility
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Matrices whose rows (or columns) consists of monomials of sequential powers are called Vandermonde matrices and can be used to describe several useful concepts and have properties that can be helpful for solving many kinds of problems. In this thesis we will discuss this matrix and some of its properties as well as a generalization of it and how it can be applied to curve fitting discharge current for the purpose of ensuring electromagnetic compatibility.In the first chapter the basic theory for later chapters is introduced. This includes the Vandermonde matrix and some of its properties, history, applications and generalizations, interpolation and regression problems, optimal experiment design and modelling of electrostatic discharge currents with the purpose to ensure electromagnetic compatibility.The second chapter focuses on finding the extreme points for the determinant for the Vandermonde matrix on various surfaces including spheres, ellipsoids, cylinders and tori. The extreme points are analysed in three dimensions or more.The third chapter discusses fitting a particular model called the p-peaked Analytically Extended Function (AEF) to data taken either from a standard for electromagnetic compatibility or experimental measurements. More specifically the AEF will be fitted to discharge currents from the IEC 62305-1 and IEC 61000-4-2 standards for lightning protection and electrostatic discharge immunity as well as some experimentally measured data of similar phenomena.
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| 31. |
- Avelin, Benny, 1984-, et al.
(författare)
-
Boundary estimates for solutions to operators of p-Laplace type with lower order terms
- 2011
-
Ingår i: Journal of Differential Equations. - : Elsevier BV. - 0022-0396 .- 1090-2732. ; 250:1, s. 264-291
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we study the boundary behavior of solutions to equations of the form∇⋅A(x,∇u)+B(x,∇u)=0, in a domain Ω⊂Rn, assuming that Ω is a δ-Reifenberg flat domain for δ sufficiently small. The function A is assumed to be of p-Laplace character. Concerning B, we assume that |∇ηB(x,η)|⩽c|η|p−2, |B(x,η)|⩽c|η|p−1, for some constant c, and that B(x,η)=|η|p−1B(x,η/|η|), whenever x∈Rn, η∈Rn∖{0}. In particular, we generalize the results proved in J. Lewis et al. (2008) [12] concerning the equation ∇⋅A(x,∇u)=0, to equations including lower order terms.
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| 32. |
- Jonsson, Viktor, 1987, et al.
(författare)
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Modelling of zero-inflation improves inference of metagenomic gene count data
- 2019
-
Ingår i: Statistical Methods in Medical Research. - : SAGE Publications. - 0962-2802 .- 1477-0334. ; 28:12, s. 3712-3728
-
Tidskriftsartikel (refereegranskat)abstract
- Metagenomics enables the study of gene abundances in complex mixtures of microorganisms and has become a standard methodology for the analysis of the human microbiome. However, gene abundance data is inherently noisy and contains high levels of biological and technical variability as well as an excess of zeros due to non-detected genes. This makes the statistical analysis challenging. In this study, we present a new hierarchical Bayesian model for inference of metagenomic gene abundance data. The model uses a zero-inflated overdispersed Poisson distribution which is able to simultaneously capture the high gene-specific variability as well as zero observations in the data. By analysis of three comprehensive datasets, we show that zero-inflation is common in metagenomic data from the human gut and, if not correctly modelled, it can lead to substantial reductions in statistical power. We also show, by using resampled metagenomic data, that our model has, compared to other methods, a higher and more stable performance for detecting differentially abundant genes. We conclude that proper modelling of the gene-specific variability, including the excess of zeros, is necessary to accurately describe gene abundances in metagenomic data. The proposed model will thus pave the way for new biological insights into the structure of microbial communities.
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| 33. |
- Fridolfsson, Jonatan, 1992, et al.
(författare)
-
Physical activity spectrum discriminant analysis—A method to compare detailed patterns between groups
- 2021
-
Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 31:12, s. 2333-2342
-
Tidskriftsartikel (refereegranskat)abstract
- Investigating physical activity (PA) patterns as a detailed intensity spectrum instead of crude intensity categories have improved the ability to analyze the relationship between measured PA and health variables. The aim of this methodological study was to introduce and investigate the utility of using detailed PA intensity spectrum compared to crude PA intensity categories for comparison of PA between groups and between repeated measures. The study sample consisted of two groups of children, where one group was scheduled for extended physical education (PE) by daily classes while the other group followed usual PE schedule. Accelerometer data was processed into traditional crude PA intensity categories and into detailed PA intensity spectrum. Multivariate partial least squares regression for discriminant analysis (PLS-DA) was applied for PA intensity spectrum group comparison and compared to traditional univariate statistical analysis. Repeated measures were investigated using independent PLS-DA as well as multilevel PLS-DA for paired analysis. While traditional analysis of crude PA intensity categories was unable to find any group differences, multivariate analysis of the PA intensity spectrum identified statistically significant differences. By the extension of multilevel PLS-DA for paired comparison, a clear difference in the PA intensity spectrum was demonstrated between repeated measures. In conclusion, analysis of detailed PA intensity spectrum demonstrates utility for comparing detailed PA data between groups and between repeated measures in interventional and observational research.
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| 34. |
- Aas, Erik, et al.
(författare)
-
Limiting directions for random walks in classical affine Weyl groups
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Let be a finite Weyl group and the corresponding affine Weyl group. A random element of can be obtained as a reduced random walk on the alcoves of . By a theorem of Lam (Ann. Probab. 2015), such a walk almost surely approaches one of many directions. We compute these directions when is , and and the random walk is weighted by Kac and dual Kac labels. This settles Lam's questions for types and in the affirmative and for type in the negative. The main tool is a combinatorial two row model for a totally asymmetric simple exclusion process called the -TASEP, with four parameters. By specializing the parameters in different ways, we obtain TASEPs for each of the Weyl groups mentioned above. Computing certain correlations in these TASEPs gives the desired limiting directions.
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| 35. |
- Cronie, Ottmar, 1979, et al.
(författare)
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Some edge correction methods for marked spatio-temporal point process models
- 2011
-
Ingår i: Computational Statistics & Data Analysis. - : Elsevier BV. - 0167-9473 .- 1872-7352. ; 55:7, s. 2209-2220
-
Tidskriftsartikel (refereegranskat)abstract
- Three edge correction methods for (marked) spatio-temporal point processes are proposed. They are all based on the idea of placing an approximated expected behaviour of the process at hand (simulated realisations) outside the study region which interacts with the data during the estimation. These methods are applied to the so-called growth-interaction model. The specific choices of growth function and interaction function made are purely motivated by the forestry applications considered. The parameters of the growth and interaction functions, i.e. the parameters related to the development of the marks, are estimated using the least-squares approach together with the proposed edge corrections. Finally, the edge corrected estimation methods are applied to a data set of Swedish Scots pine.
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| 36. |
- Gerken, Jan, 1991, et al.
(författare)
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Geometric deep learning and equivariant neural networks
- 2023
-
Ingår i: Artificial Intelligence Review. - : Springer Nature. - 1573-7462 .- 0269-2821. ; 56:12, s. 14605-14662
-
Tidskriftsartikel (refereegranskat)abstract
- We survey the mathematical foundations of geometric deep learning, focusing on group equivariant and gauge equivariant neural networks. We develop gauge equivariant convolutional neural networks on arbitrary manifolds M using principal bundles with structure group K and equivariant maps between sections of associated vector bundles. We also discuss group equivariant neural networks for homogeneous spaces M= G/ K , which are instead equivariant with respect to the global symmetry G on M . Group equivariant layers can be interpreted as intertwiners between induced representations of G, and we show their relation to gauge equivariant convolutional layers. We analyze several applications of this formalism, including semantic segmentation and object detection networks. We also discuss the case of spherical networks in great detail, corresponding to the case M= S2= SO (3) / SO (2) . Here we emphasize the use of Fourier analysis involving Wigner matrices, spherical harmonics and Clebsch–Gordan coefficients for G= SO (3) , illustrating the power of representation theory for deep learning.
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| 37. |
- Bartoszek, Krzysztof
(författare)
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Quantifying the effects of anagenetic and cladogenetic evolution
- 2014
-
Ingår i: Mathematical Biosciences. - : Elsevier BV. - 0025-5564 .- 1879-3134. ; 254, s. 42-57
-
Tidskriftsartikel (refereegranskat)abstract
- An ongoing debate in evolutionary biology is whether phenotypic change occurs predominantly around the time of speciation or whether it instead accumulates gradually over time. In this work I propose a general framework incorporating both types of change, quantify the effects of speciational change via the correlation between species and attribute the proportion of change to each type. I discuss results of parameter estimation of Hominoid body size in this light. I derive mathematical formulae related to this problem, the probability generating functions of the number of speciation events along a randomly drawn lineage and from the most recent common ancestor of two randomly chosen tip species for a conditioned Yule tree. Additionally I obtain in closed form the variance of the distance from the root to the most recent common ancestor of two randomly chosen tip species.
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| 38. |
- Kurbasic, Azra
(författare)
-
Topics in Human Gene Mapping
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is interdisciplinary between Mathematical Statistics, Genetics, and Medicine. It mainly consists of topics in mathematical modelling of the correlation of inheritance of genes and disease in a family, a method called linkage analysis. It is organized as follows. First, a short introduction with the relevant background is given and then four papers are included. The first paper discusses hypothesis testing of linkage of a disease gene to a certain position on the chromosome. The focus is on the choice of lod scores and its relation to p-values. The second paper is a result of collaboration with the research groups in Lund and Denmark in the effort to localize the gene responsible for a malignant melanoma. Here, the theory presented in the first paper is used. The third paper concerns modelling of complex diseases, i.e. diseases governed by genetic contribution from at least two loci. We have studied the contribution of a particular locus to increased risk of relatives compared with population prevalence. Relative risk is modelled as the product of the relative risk at the main locus and the relative risk due to genetic contribution from other loci and shared environmental effects. Additionally, we show how this relative risk is related to probabilities of allele sharing identical by descent at the main locus and the power to detect linkage. The last paper contributes to the development of the algorithms used in the linkage and family based association analysis. One of the most demanding issues in these analyses is how to calculate the inheritance distribution at a certain position on the chromosome. The well established algorithms are based on the assumption that the markers used in the studies are in linkage equilibrium (LE). However, today's marker data have markers in linkage disequilibrium (LD). We develop a novel hidden Markov model algorithm for association and linkage analysis when markers are in LD.
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| 39. |
- Sundberg, Rolf, 1942-
(författare)
-
Statistical Modelling by Exponential Families
- 2019
-
Bok (refereegranskat)abstract
- This book is a readable, digestible introduction to exponential families, encompassing statistical models based on the most useful distributions in statistical theory, including the normal, gamma, binomial, Poisson, and negative binomial. Strongly motivated by applications, it presents the essential theory and then demonstrates the theory's practical potential by connecting it with developments in areas like item response analysis, social network models, conditional independence and latent variable structures, and point process models. Extensions to incomplete data models and generalized linear models are also included. In addition, the author gives a concise account of the philosophy of Per Martin-Löf in order to connect statistical modelling with ideas in statistical physics, including Boltzmann's law. Written for graduate students and researchers with a background in basic statistical inference, the book includes a vast set of examples demonstrating models for applications and exercises embedded within the text as well as at the ends of chapters.
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| 40. |
- Wiktorsson, Magnus
(författare)
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Approximation of Infinitely Divisible Random Variables with Application to the Simulation of Stochastic Processes
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of four papers A, B, C and D. Paper A and B treats the simulation of stochastic differential equations (SDEs). The research presented therein was triggered by the fact that there were not any efficient implementations of the higher order methods for simulating SDEs. So in practice the higher order methods required at least the same amount of work as the Euler method to obtain a given mean square error. The faster convergence rate of the higher order methods requires the simulation of the so called iterated Itô integrals. In (A) we use a shot-noise type series representation of one iterated Itô integral. We split the series representation into a sum of n terms and a remainder term and show that the remainder term is asymptotically Gaussian as n goes to infinity. We provide an explicit coupling of the remainder a Gaussian random variable and show that this improves the mean square error by a factor n^½. In (B) we provide a multi-dimensional extension of the results in (A) as well as the not previously known simultaneous characteristic function of all iterated Itô integrals obtained the n pairing m independent Wiener processes. In (C) we study the simulation of type G Lévy processes. Recall that random variable is said to be of type G if it is a Gaussian variance mixture. We note that type G Lévy processes are subordinated Wiener processes. We use a series representation of the subordinator, a tail-sum approximation and obtain an explicit coupling between type G Lévy processes and the sum of a compound Poisson process and a scaled Wiener process. We calculate the mean integrated square error for this approximation. We examine the convergence of the scaled tail-sum process to its mean value function and provide a sufficient condition for this convergence. In paper (D) we utilise the coupling results from paper (C) to obtain approximations of stochastic integrals with respect to type G Lévy processes. Depending on the properties of the integrator we obtain either point-wise mean square error results or mean integrated square error results for the approximation. We also show that a stochastic time change representation of stochastic integrals can be used to obtain useful approximations.
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| 41. |
- Jagers, Peter, 1941
(författare)
-
Branching Processes: A Personal Historical Perspective.
- 2020
-
Ingår i: Statistical Modeling for Biological Systems: In Memory of Andrei Yakovlev. - Cham : Springer International Publishing.
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The chapter, based on an Oberwolfach talk, gives a - personally biased - sketch of the development of branching processes, from the mid 19th Century to recently, emphasizing relations to bioscience and demography, and to society and culture in general.
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| 42. |
- Vanhatalo, Erik, et al.
(författare)
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Towards improved analysis methods for two-level factorial experiments with time series responses
- 2013
-
Ingår i: Quality and Reliability Engineering International. - : Wiley. - 0748-8017 .- 1099-1638. ; 29:5, s. 725-741
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic processes exhibit a time delay between the disturbances and the resulting process response. Therefore, one has to acknowledge process dynamics, such as transition times, when planning and analyzing experiments in dynamic processes. In this article, we explore, discuss, and compare different methods to estimate location effects for two-level factorial experiments where the responses are represented by time series. Particularly, we outline the use of intervention-noise modeling to estimate the effects and to compare this method by using the averages of the response observations in each run as the single response. The comparisons are made by simulated experiments using a dynamic continuous process model. The results show that the effect estimates for the different analysis methods are similar. Using the average of the response in each run, but removing the transition time, is found to be a competitive, robust, and straightforward method, whereas intervention-noise models are found to be more comprehensive, render slightly fewer spurious effects, find more of the active effects for unreplicated experiments and provide the possibility to model effect dynamics. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.
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| 43. |
- Fagerström, Cecilia, Docent, 1973-, et al.
(författare)
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Factorial validity and invariance of the Life Satisfaction Index in older people across groups and time: Addressing the heterogeneity of age, functional ability, and depression.
- 2012
-
Ingår i: Archives of gerontology and geriatrics (Print). - : Elsevier BV. - 0167-4943 .- 1872-6976. ; 55:2, s. 349-356
-
Tidskriftsartikel (refereegranskat)abstract
- In the last decades, extensive research efforts have been directed at exploring life satisfaction in old age, and the Life Satisfaction Index A scale (LSIA), developed by Neugarten et al. in the 1960s, is one of the most commonly used instruments. However, studies have focused on predicting and comparing changes in people’s life satisfaction without testing if the LSIA instrument is equally valid for different subgroups of people. The present study investigated the underlying dimensions of the LSIA in a Swedish population (n=1402) of people 60−96 years of age. The study also examined factorial invariance across age, gender, functional ability and depression during a six-year period. The results showed that while a five-factor solution of the LSIA did not exhibit an acceptable fit to the data, a three-factor solution did show a close fit. The two three-factor models that demonstrated the best fit showed invariance across gender and across time, but noninvariance across groups with different levels of reduced functional ability, depressive symptoms and age. These findings suggest that the psychometric properties of life satisfaction instruments like the LSIA need to be taken into consideration before drawing conclusions about life satisfaction when comparing older people of different ages and with different depression and function levels.
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| 44. |
- Andersson, Fredrik K., et al.
(författare)
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The mathematics of internet search engines
- 2008
-
Ingår i: Acta Applicandae Mathematicae - An International Survey Journal on Applying Mathematics and Mathematical Applications. - : Springer. - 0167-8019 .- 1572-9036. ; 104:2, s. 211-242
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a survey of techniques for ranking results in search engines, with emphasis on link-based ranking methods and the PageRank algorithm. The problem of selecting, in relation to a user search query, the most relevant documents from an unstructured source such as the WWW is discussed in detail. The need for extending classical information retrieval techniques such as boolean searching and vector space models with link-based ranking methods is demonstrated. The PageRank algorithm is introduced, and its numerical and spectral properties are discussed. The article concludes with an alternative means of computing PageRank, along with some example applications of this new method.
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| 45. |
- Destouni, Georgia
(författare)
-
Effects of water system uncertainties on effectiveness and efficiency of environmental policy and management
- 2007
-
Ingår i: International Workshop on Uncertainty in Environmental Modelling, Earth Sciences Centre, Uppsala University, 28-30 March, 2007.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Increasing water pollution and deterioration of aquatic ecosystems are serious environmental problems. Modelling of pollutant transport, mass transfer, attenuation and downstream loading, from various pollutant sources, along different hydrological pathways, to water recipients, is needed for relevant decisions on effective allocation of pollution abatement measures. However, it is for various reasons (measurement and monitoring gaps; scientifically unresolved modelling disagreements; large, irregular and deterministically unquantifiable or unpredictable natural variability) both difficult and uncertain to quantify the real effects of upstream pollutant emission changes on downstream pollutant loads and concentrations. Furthermore, it may also be highly uncertain which pollutant load and concentration level reductions that are necessary and sufficient for achieving good water quality and ecosystem status in different water environments. These uncertainties may have large effects on pollution abatement that need to be recognized and handled in environmental policy. We discuss here how the water system uncertainty effects may be set in a wider decision making context, by quantifying their implications for both the probability of success and the economic performance of different environmental policies and management strategies.
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| 46. |
- Willighagen, Egon, 1974-, et al.
(författare)
-
Linking the Resource Description Framework to cheminformatics and proteochemometrics
- 2011
-
Ingår i: Journal of Biomedical Semantics. - 2041-1480. ; 2:Suppl 1, s. 6-
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND :Semantic web technologies are finding their way into the life sciences. Ontologies and semantic markup have already been used for more than a decade in molecular sciences, but have not found widespread use yet. The semantic web technology Resource Description Framework (RDF) and related methods show to be sufficiently versatile to change that situation.RESULTS :The work presented here focuses on linking RDF approaches to existing molecular chemometrics fields, including cheminformatics, QSAR modeling and proteochemometrics. Applications are presented that link RDF technologies to methods from statistics and cheminformatics, including data aggregation, visualization, chemical identification, and property prediction. They demonstrate how this can be done using various existing RDF standards and cheminformatics libraries. For example, we show how IC50 and Ki values are modeled for a number of biological targets using data from the ChEMBL database.CONCLUSIONS :We have shown that existing RDF standards can suitably be integrated into existing molecular chemometrics methods. Platforms that unite these technologies, like Bioclipse, makes this even simpler and more transparent. Being able to create and share workflows that integrate data aggregation and analysis (visual and statistical) is beneficial to interoperability and reproducibility. The current work shows that RDF approaches are sufficiently powerful to support molecular chemometrics workflows.
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| 47. |
- Ivarsson, Andreas, et al.
(författare)
-
Are all predicted relationships linear by nature? : A note about quantile regression in sport and exercise psychology
- 2014
-
Ingår i: Advances in Contemporary Sport Psychology. - New York : Nova Science Publishers, Inc.. - 9781633216730 - 9781633216655 ; 6:2, s. 115-123
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Data in sport and exercise psychology research are often analyzed based on the assumption that the relationships between two or more variables are linear in nature. But are all relationships in sport and exercise settings linear? The aim of this paper is to: a) discuss the potential shortcomings with using linear regression analysis, b) introduce quantile regression analysis (Q-regression) as an alternative to linear regression, and c) give examples of how to use Q-regression analysis in order to overcome some of the shortcomings of linear regression analysis. A comparison between the results from a linear regression analysis and a Q-regression analysis shows differences between the two methods. More specifically, the independent variables in the results of the Q-regression analysis were shown to have non-linear relationships with the dependent variable in given examples. Researchers are encouraged to consider using Q-regression analysis in studies where non-linear relationships could be expected.
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| 48. |
- Otani, Hiroki, et al.
(författare)
-
Morphometric study on the characteristic external features of normal and abnormal human embryos
- 2008
-
Ingår i: Congenit Anom Kyoto. - : Wiley. ; 48:1, s. 18-28
-
Tidskriftsartikel (refereegranskat)abstract
- The embryonic period is characterized by organogenesis and accompanying dynamic changes in external features. The measurement of human embryos has been limited to whole body dimensions, such as crown-rump length. More detailed measurements would add quantitative information about these characteristic events and provide a better understanding of normal and abnormal embryonic development. In the present study, we defined axes, landmarks, and measurements for human embryos, and measured 250 externally normal human embryos at Carnegie stages 14-23 (6.5-29.3 mm in crown-rump length, approximately 5-8 weeks of estimated ovulation age) that were fixed in Bouin's solution and preserved in 10% formalin solution. The axes, landmarks, and measurements defined for human embryos are corresponding to those in human and primate fetuses. The whole body, head, face, and extremities were measured using a scale attached to a dissecting microscope. Axial length, head height plus ear-shoulder length plus trunk height, was designated as a new measurement of the whole body, which is comparable with crown-rump length. Approximate standards of these measurements were obtained. The ratios of some measurements to trunk height and between the different parts were also obtained, and several different developmental patterns were recognized. The reproducibility of each measurement was evaluated by measuring 50 specimens three times each at intervals of one or two months. As a pilot study for the application of the proposed measurements, 84 human embryos with external anomalies, including holoprosencephaly, anomalies of extremities, and pharyngeal arch anomalies, were measured using the same method, and a few tendencies characteristic to holoprosencephaly were noticed.
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| 49. |
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| 50. |
- Bayisa, Fekadu, et al.
(författare)
-
Regularised Semi-parametric Composite Likelihood Intensity Modelling of a Swedish Spatial Ambulance Call Point Pattern
- 2023
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Ingår i: Journal of Agricultural Biological and Environmental Statistics. - : Springer. - 1085-7117 .- 1537-2693. ; 28, s. 664-83
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the development of optimal dispatching strategies for prehospital resources, we model the spatial distribution of ambulance call events in the Swedish municipality Skelleftea during 2014-2018 in order to identify important spatial covariates and discern hotspot regions. Our large-scale multivariate data point pattern of call events consists of spatial locations and marks containing the associated priority levels and sex labels. The covariates used are related to road network coverage, population density, and socio-economic status. For each marginal point pattern, we model the associated intensity function by means of a log-linear function of the covariates and their interaction terms, in combination with lasso-like elastic-net regularized composite/Poisson process likelihood estimation. This enables variable selection and collinearity adjustment as well as reduction of variance inflation from overfitting and bias from underfitting. To incorporate mobility adjustment, reflecting people's movement patterns, we also include a nonparametric (kernel) intensity estimate as an additional covariate. The kernel intensity estimation performed here exploits a new heuristic bandwidth selection algorithm. We discover that hotspot regions occur along dense parts of the road network. A mean absolute error evaluation of the fitted model indicates that it is suitable for designing prehospital resource dispatching strategies. Supplementary materials accompanying this paper appear online.
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