| 51. |
- Chakwizira, Arthur, et al.
(författare)
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Diffusion MRI with pulsed and free gradient waveforms : effects of restricted diffusion and exchange
- 2023
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Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480 .- 1099-1492. ; 36:1
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring time-dependence with diffusion MRI yields observables sensitive to compartment sizes (restricted diffusion) and membrane permeability (water exchange). However, restricted diffusion and exchange have opposite effects on the diffusion-weighted signal, which can lead to errors in parameter estimates. In this work, we propose a signal representation that incorporates the effects of both restricted diffusion and exchange up to second order in b-value and is compatible with gradient waveforms of arbitrary shape. The representation features mappings from a gradient waveform to two scalars that separately control the sensitivity to restriction and exchange. We demonstrate that these scalars span a two-dimensional space that can be used to choose waveforms that selectively probe restricted diffusion or exchange, eliminating the correlation between the two phenomena. We found that waveforms with specific but unconventional shapes provide an advantage over conventional pulsed and oscillating gradient acquisitions. We also show that parametrisation of waveforms into a two-dimensional space can be used to understand protocols from other approaches that probe restricted diffusion and exchange. For example, we found that the variation of mixing time in filter-exchange imaging corresponds to variation of our exchange-weighting scalar at a fixed value of the restriction-weighting scalar. The proposed signal representation was evaluated using Monte Carlo simulations in identical parallel cylinders with hexagonal and random packing as well as parallel cylinders with gamma-distributed radii. Results showed that the approach is sensitive to sizes in the interval 4 - 12 μm and exchange rates in the simulated range of 0 to 20 s -1 , but also that there is a sensitivity to the extracellular geometry. The presented theory constitutes a simple and intuitive description of how restricted diffusion and exchange influence the signal as well as a guide to protocol design capable of separating the two effects.
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| 52. |
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| 53. |
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| 54. |
- Davoine, Celine, et al.
(författare)
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Functional metabolomics as a tool to analyze Mediator function and structure in plants
- 2017
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Ingår i: PLOS ONE. - : Public Library Science. - 1932-6203. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Mediator is a multiprotein transcriptional co-regulator complex composed of four modules; Head, Middle, Tail, and Kinase. It conveys signals from promoter-bound transcriptional regulators to RNA polymerase II and thus plays an essential role in eukaryotic gene regulation. We describe subunit localization and activities of Mediator in Arabidopsis through metabolome and transcriptome analyses from a set of Mediator mutants. Functional metabolomic analysis based on the metabolite profiles of Mediator mutants using multivariate statistical analysis and heat-map visualization shows that different subunit mutants display distinct metabolite profiles, which cluster according to the reported localization of the corresponding subunits in yeast. Based on these results, we suggest localization of previously unassigned plant Mediator subunits to specific modules. We also describe novel roles for individual subunits in development, and demonstrate changes in gene expression patterns and specific metabolite levels in med18 and med25, which can explain their phenotypes. We find that med18 displays levels of phytoalexins normally found in wild type plants only after exposure to pathogens. Our results indicate that different Mediator subunits are involved in specific signaling pathways that control developmental processes and tolerance to pathogen infections.
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| 55. |
- de Jong, Johnny
(författare)
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Extending the EU Renewable Energy Directive sustainability criteria to solid bioenergy from forests
- 2014
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Ingår i: Natural Resources Forum. - : Wiley. - 0165-0203. ; 38, s. 129-140
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Tidskriftsartikel (refereegranskat)abstract
- Solid bioenergy from forests plays and is expected to continue to play a key role to fulfil the renewable energy targets at the European Union level. When the Renewable Energy Directive was enacted, sustainability criteria were incorporated solely for biofuels and bioliquids. Sustainability criteria for solid bioenergy are also needed in order to prevent wood and primary forest residues from posing additional environmental risks to ecosystems. Acknowledging this, the European Commission has been working on extending the biofuels and bioliquids provisions to solid biomass. An internal draft was circulated in August 2013 which addressed the ways to both balance and mitigate the risks in three main topics: biodiversity; sustainable forest management; and greenhouse gases. This paper presents a set of criteria and indicators, developed during workshops with experts from Governments, scientific institutions, businesses and NGOs, that may be considered by the EU to assure that solid biomass from forests is obtained in an environmentally sustainable way.
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| 56. |
- de Jong, Johnny, et al.
(författare)
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Impact on species of conservation interest of forest harvesting for bioenergy purposes
- 2017
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 383, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- Wood harvested from logging residues, pre-commercial and conservation thinnings is increasingly being used as biofuel as a substitute for fossil fuels. Here, we review the additional impact that wood harvesting for energy purposes has on species of conservation interest (SCI) in Swedish forests compared with the effects of conventional management, a perspective that largely has not been taken into consideration. We compiled data from 122 studies of forest fuel extraction with short- and long-term perspectives at the stand and landscape level to examine whether the effects on SCI are due to an additional loss of bio-diversity as a result of cutting old forest or owing to competition from species that are favoured by the habitats formed by clearcutting. We also consider whether forest bioenergy extractions can be used to favour conservation values. The amount of logging residues has, in parallel to the amount of annually harvested trees, doubled during the past 50 years in Sweden and constitutes the major source of dead wood for biodiversity in managed forests. Common wood-inhabiting species, predominantly fungi, beetles and other insects, and to some extent lichens, are the main species affected by wood harvesting for energy purposes. The main cause for the decline of SCI is the impact already imposed by conventional forest management: clearcutting old forest stands with subsequent soil scarification. Few SCI survive clear-felling because these species typically require other types of conditions and substrates than the new dead-wood substrate created after clear-felling. We conclude that the logging residues of conifers could potentially be harvested with small to negligible impacts on SCI. However, owing to the limited number of landscape level analyses that have been performed and the inherent difficulties of assessing the effects of wood harvesting on rare SCI, we suggest that these findings need to be treated with caution and that further studies should be undertaken. Hardwood conservation thinnings and brushwood harvest may improve conservation values. Developing operational guidelines to help to mitigate ecological damage to biodiversity should be based on cautionary principles and requires further large-scale and long-term research. (C) 2016 Elsevier B.V. All rights reserved.
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| 57. |
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| 58. |
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| 59. |
- Dodig Crnkovic, Gordana, 1955
(författare)
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Natural Computational Architectures for Cognitive Info-Communication
- 2021
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Recent comprehensive overview of 40 years of research in cognitive architectures, (Kotseruba and Tsotsos 2020), evaluates modelling of the core cognitive abilities in humans, but only marginally addresses biologically plausible approaches based on natural computation. This mini review presents a set of perspectives and approaches which have shaped the development of biologically inspired computational models in the recent past that can lead to the development of biologically more realistic cognitive architectures. For describing continuum of natural cognitive architectures, from basal cellular to human-level cognition, we use evolutionary info-computational framework, where natural/ physical/ morphological computation leads to evolution of increasingly complex cognitive systems. Forty years ago, when the first cognitive architectures have been proposed, understanding of cognition, embodiment and evolution was different. So was the state of the art of information physics, bioinformatics, information chemistry, computational neuroscience, complexity theory, selforganization, theory of evolution, information and computation. Novel developments support a constructive interdisciplinary framework for cognitive architectures in the context of computing nature, where interactions between constituents at different levels of organization lead to complexification of agency and increased cognitive capacities. We identify several important research questions for further investigation that can increase understanding of cognition in nature and inspire new developments of cognitive technologies. Recently, basal cell cognition attracted a lot of interest for its possible applications in medicine, new computing technologies, as well as micro- and nanorobotics. Bio-cognition of cells connected into tissues/organs, and organisms with the group (social) levels of information processing provides insights into cognition mechanisms that can support the development of new AI platforms and cognitive robotics.
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| 60. |
- Dunér, David, et al.
(författare)
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Perseverance
- 2022. - 1
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Ingår i: Pandemic Ponderings. - Uppsala : Swedish Collegium for Advanced Study. - 9789198194838 ; , s. 73-85
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Bokkapitel (populärvet., debatt m.m.)
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