scholarly journals A new sampling capability for uncertainty quantification in the Ice-sheet and Sea-level System Model v4.19 using Gaussian Markov random fields

2021 ◽  
Author(s):  
Kevin Bulthuis ◽  
Eric Y. Larour
Keyword(s):  
Random Fields ◽  
Ice Sheet ◽  
The Finite Element Method ◽  
Sources Of Uncertainty ◽  
Temporal Correlations ◽  
Matérn Covariance ◽  
Spatio Temporal ◽  
Matern Covariance ◽  
The Impact

Abstract. Assessing the impact of uncertainties in ice-sheet models is a major and challenging issue that needs to be faced by the ice-sheet community to provide more robust and reliable model-based projections of ice-sheet mass balance. In recent years, uncertainty quantification (UQ) has been increasingly used to characterize and explore uncertainty in ice-sheet models and improve the robustness of their projections. A typical UQ analysis involves first the (probabilistic) characterization of the sources of uncertainty followed by the propagation and sensitivity analysis of these sources of uncertainty. Previous studies concerned with UQ in ice-sheet models have generally focused on the last two steps but paid relatively little attention to the preliminary and critical step of the characterization of uncertainty. Sources of uncertainty in ice-sheet models, like uncertainties in ice-sheet geometry or surface mass balance, typically vary in space and potentially in time. For that reason, they are more adequately described as spatio(-temporal) random fields, which account naturally for spatial (and temporal) correlation. As a means of improving the characterization of the sources of uncertainties in ice-sheet models, we propose in this paper to represent them as Gaussian random fields with Matérn covariance function. The class of Matérn covariance functions provides a flexible model able to capture statistical dependence between locations with different degrees of spatial correlation or smoothness properties. Samples from a Gaussian random field with Matérn covariance function can be generated efficiently by solving a certain stochastic partial differential equation. Discretization of this stochastic partial differential equation by the finite element method results in a sparse approximation known as a Gaussian Markov random field. We solve this equation efficiently using the finite element method within the Ice-sheet and Sea-level System Model (ISSM). In addition, spatio-temporal samples can be generated by combining an autoregressive temporal model and the Matérn field. The implementation is tested on a set of synthetic experiments to verify that it captures well the desired spatial and temporal correlations. Finally, we demonstrate the interest of this sampling capability in an illustration concerned with assessing the impact of various sources of uncertainties on the Pine Island Glacier, West Antarctica. We find that both larger spatial and temporal correlations lengths will likely result in increased uncertainty in the projections.

scholarly journals Spatio-temporal control of phenylpropanoid biosynthesis by inducible complementation of a cinnamate 4-hydroxylase mutant

2020 ◽  
Author(s):  
Jeong Im Kim ◽  
Christopher Hidalgo-Shrestha ◽  
Nicholas D. Bonawitz ◽  
Rochus B. Franke ◽  
Clint Chapple
Keyword(s):  
Phenylpropanoid Pathway ◽  
Wild Type ◽  
Developmental Abnormalities ◽  
Casparian Strip ◽  
Phenylpropanoid Biosynthesis ◽  
Phenolic Esters ◽  
Spatio Temporal ◽  
The Impact ◽  
Developmental Window

ABSTRACTCinnamate 4-hydroxylase (C4H) is a cytochrome P450-dependent monooxygenase that catalyzes the second step of the general phenylpropanoid pathway. Arabidopsis reduced epidermal fluorescence 3 (ref3) mutants, which carry hypomorphic mutations in C4H, exhibit global alterations in phenylpropanoid biosynthesis and have developmental abnormalities including dwarfing. Here we report the characterization of a conditional Arabidopsis C4H line (ref3-2pOpC4H), in which wild-type C4H is expressed in the ref3-2 background. Expression of C4H in plants with well-developed primary inflorescence stems resulted in restoration of fertility and the production of substantial amounts of lignin, revealing that the developmental window for lignification is remarkably plastic. Following induction of C4H expression in ref3-2pOpC4H, we observed rapid and significant reductions in the levels of numerous metabolites, including several benzoyl and cinnamoyl esters and amino acid conjugates. These atypical conjugates were quickly replaced with their sinapoylated equivalents, suggesting that phenolic esters are subjected to substantial amounts of turnover in wild-type plants. Furthermore, using localized application of dexamethasone to ref3-2pOpC4H, we show that phenylpropanoids are not transported appreciably from their site of synthesis. Finally, we identified a defective Casparian strip diffusion barrier in the ref3-2 mutant root endodermis, which is restored by induction of C4H expression.HighlightThe work presented this paper provides evidence of metabolite turnover, plasticity of the developmental window for lignification, and the impact of reduced and restored cinnamate-4-hydroxylase (C4H) expression on the Casparian strip.

scholarly journals Multivariate statistical analysis and numerical modelling for the hydrogeological and hydrochemical characterization of a closed MSW landfill: the case study of Vizzolo-Predabissi

2020 ◽  
Author(s):  
Letizia Fumagalli ◽  
Gennaro Alberto Stefania ◽  
Chiara Zanotti ◽  
Davide Sartirana ◽  
Giuseppe Raffaello Di Martino ◽  
...  
Keyword(s):  
Flow Model ◽  
Groundwater Resources ◽  
Groundwater Flow Model ◽  
Multivariate Statistical ◽  
Hydrochemical Data ◽  
Spatio Temporal ◽  
The Impact ◽  
Hydrochemical Characterization

This work aims at assessing the impact on groundwater resources of a leachate overflow occurred in the landfill of Vizzolo-Predabissi (Milan, Italy) after its closure. Hydrogeological sections, piezometric maps, spatio-temporal and multivariate analysis of hydrochemical data enabled to define a conceptual model and to build a groundwater flow model, solved and calibrated by means of MODFLOW-NWT and PEST. The results of the study pointed out that the leachate overflow produced an impulsive contamination, currently in attenuation, which behaved differently in areas with different redox characteristics.

scholarly journals Classical metapopulation dynamics and eco-evolutionary feedbacks in dendritic networks

2015 ◽  
Author(s):  
Emanuel A. Fronhofer ◽  
Florian Altermatt
Keyword(s):  
Community Dynamics ◽  
Evolutionary Dynamics ◽  
Extinction Risk ◽  
Network Connectivity ◽  
Structured Populations ◽  
Metapopulation Dynamics ◽  
Temporal Correlations ◽  
Dendritic Networks ◽  
Spatio Temporal ◽  
The Impact

Eco-evolutionary dynamics are now recognized to be highly relevant for population and community dynamics. However, the impact of evolutionary dynamics on spatial patterns, such as the occurrence of classical metapopulation dynamics, is less well appreciated. Here, we analyse the evolutionary consequences of spatial network connectivity and topology for dispersal strategies and quantify the eco-evolutionary feedback in terms of altered classical metapopulation dynamics. We find that network properties, such as topology and connectivity, lead to predictable spatio-temporal correlations in fitness expectations. These spatio-temporally stable fitness patterns heavily impact evolutionarily stable dispersal strategies and lead to eco-evolutionary feedbacks on landscape level metrics, such as the number of occupied patches, the number of extinctions and recolonizations as well as metapopulation extinction risk and genetic structure. Our model predicts that classical metapopulation dynamics are more likely to occur in dendritic networks, and especially in riverine systems, compared to other types of landscape configurations. As it remains debated whether classical metapopulation dynamics are likely to occur in nature at all, our work provides an important conceptual advance for understanding the occurrence of classical metapopulation dynamics which has implications for conservation and management of spatially structured populations.

Uncertainty Quantification of Borehole Thermal Energy Storage Facilities

2020 ◽  
Author(s):  
Philipp Steinbach ◽  
Jens Lang ◽  
Daniel Otto Schulte ◽  
Ingo Sass
Keyword(s):  
Energy Storage ◽  
Uncertainty Quantification ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Simulation Tool ◽  
The Finite Element Method ◽  
Sources Of Uncertainty ◽  
Material Parameters ◽  
3D Simulation Model ◽  
The Impact

<p>Borehole thermal energy storages (BTES) have become a common implement for extracting and/or storing heat energy from and into the soil. Building these facilities is expensive, especially the drilling of boreholes, into which borehole heat exchangers are inserted. To cut costs, drilling methods, which can produce inaccuracies of varying degree, are utilized. This brings into question how much these inaccuracies could potentially affect the energy storage/extraction performance of a planned facility. To this end, we performed an uncertainty quantification for seasonally operated BTES facilities, where we studied the influence of geometries deviating from the planned layout and other sources of uncertainty, such as varying soil and material parameters.<br>In our research, we make use of a 3D simulation model for BTES facilities in a patch of soil with optional groundwater flow, designed as a system of partial differential equations (PDEs). The system is solved with a simulation toolkit, which was programmed as an extension for the finite element method solver KARDOS. The toolkit builds on previous work for the simulation tool BASIMO and was validated with benchmarks calculated with the commercial software FEFLOW, which specializes in heat transfer in porous media among other things. For the uncertainty quantification, we utilize an adaptive, anisotropic stochastic collocation method, which uses solutions of the PDE system as samples. We present the method and apply it to an illustrative as well as a practical example. Lastly, we discuss the results and assess the impact of deviating borehole paths on the performance of BTES facilities.</p>

The Analyses of Learning Strategies in English as a Second Language: Theoretical Classification and Measurement Test

2020 ◽  
Vol 4 (2) ◽  
pp. 118-129
Author(s):  
Asti Gumartifa ◽  
◽  
Indah Windra Dwie Agustiani
Keyword(s):  
Language Learning ◽  
Learning Outcomes ◽  
Learning Strategies ◽  
Learning Process ◽  
English Learners ◽  
English Language ◽  
Point Of View ◽  
Effective Learning ◽  
The Impact

Gaining English language learning effectively has been discussed all years long. Similarly, Learners have various troubles outcomes in the learning process. Creating a joyful and comfortable situation must be considered by learners. Thus, the implementation of effective learning strategies is certainly necessary for English learners. This descriptive study has two purposes: first, to introduce the classification and characterization of learning strategies such as; memory, cognitive, metacognitive, compensation, social, and affective strategies that are used by learners in the classroom and second, it provides some questionnaires item based on Strategy of Inventory for Language Learning (SILL) version 5.0 that can be used to examine the frequency of students’ learning strategies in the learning process. The summary of this study explains and discusses the researchers’ point of view on the impact of learning outcomes by learning strategies used. Finally, utilizing appropriate learning strategies are certainly beneficial for both teachers and learners to achieve the learning target effectively.

Sign in / Sign up

Export Citation Format

Share Document