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- MacDonald, Stuart W S, et al.
(author)
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Extrastriatal dopamine D2 receptor binding modulates intraindividual variability in episodic recognition and executive functioning.
- 2009
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In: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 47:11, s. 2299-2304
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Journal article (peer-reviewed)abstract
- Intraindividual variability (IIV) reflects lawful but transient within-person changes in performance. Increased IIV in cognition shares systematic associations with numerous conditions characterized by alterations in dopamine (DA) neuromodulation (e.g., old age, ADHD, schizophrenia, and Parkinson's disease). In a group of normal middle-aged adults, we examined links between PET-derived measures of D2 receptor binding in striatum, orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and hippocampus (HC) and IIV for tasks assessing recognition memory and executive functioning. An index of IIV, the intraindividual standard deviation (ISD), was computed across successful response latency trials for each cognitive outcome. Lower D2 binding in OC, ACC, and HC, but not striatum, was associated with increasing ISDs for the memory and executive measures. Consistent with neurocomputational models, the present findings suggest a role for extrastriatal DA neurotransmission in modulating variability in cognitive functioning.
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- Plos, M., et al.
(author)
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Non-Linear Analysis and Remaining Fatigue Life of Reinforced Concrete Bridges
- 2007
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Reports (peer-reviewed)abstract
- The work provides methods for non-linear structural analysis and fatigue safety evaluation in assessment of existing railway bridges. The use of non-linear analysis leads to higher load carrying capacities, but also to improved understanding of the structural response, forming a better basis for decisions in the assessment. The methods for fatigue assessment lead to increased remaining service life of reinforced concrete railway bridges.The achievements of the work are:• Models for assessment of concrete bridges by non-linear analysis are described, and examples and general recommendations for practical application of the methods aregiven.• An overview of the effect of corrosion on the bond properties has been developed through non-linear analyses and tests found in literature. Recommendations for practical assessment of anchorage capacity in corroded railway concrete bridges are presented.• The determination of reliable in-situ material properties in old concrete bridges is described,including properties for fully probabilistic analysis. A particular aim was to develop better methods to describe development of concrete properties with age and degree of hydration.• Recommendations are given regarding re-distribution of sectional forces and moments, obtained through linear structural analysis (with FEM). In a case study, a typical slab bridge was designed using different methods, and its response evaluated through nonlinearanalyses.• A good understanding of the load-carrying mechanisms in combined bending-shear-torsion gives a possibility to make more accurate assessments than with standard code methods. Methods and examples are presented.• A state-of-the-art review of fatigue behaviour of reinforced concrete railway bridges is presented and a methodology to assess the remaining fatigue life of existing reinforced concrete bridges subjected to railway traffic is developed.
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- Plos, Mario, et al.
(author)
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Structural assessment of railway concrete bridges : non-linear analysis and remaining fatigue life
- 2006
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In: Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost. - London : Taylor and Francis Group. - 0415403154 ; , s. 271-
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Conference paper (peer-reviewed)abstract
- For a sustainable development in Europe, there is a need to at least double the railway transports in the coming 20 years. In order to reach this, the residual service lives of existing concrete bridges need to be extended at the same time as they are subjected to higher axle loads, higher railway speeds and heavier traffic intensity. Today, many concrete bridges are replaced or strengthened because their reliability cannot be guaranteed based on the structural assessments made. The aim of the work presented here is to provide enhanced assessment methods that are able to prove higher load carrying capacities and longer fatigue lives for existing concrete railway bridges. One main objective is to facilitate the use of non-linear analysis for structural assessment. In addition to higher load carrying capacities, the methods give improved understanding of the structural response, forming a better basis for decisions in the assessment. Another main objective is to improve knowledge about the fatigue behaviour of concrete bridges and to develop realistic methods for the evaluation of remaining fatigue life of existing bridges. The emphasis here is on short-span bridges and secondary elements. The work presented is a part of the ongoing EU-project Sustainable Bridges. The results will be implemented in the Guideline for Load and Resistance Assessment of existing European Railway Bridges that is being developed
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