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- Gren, Per
(author)
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A pulsed TV holography system for the study of transients in experimental mechanics
- 2000
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Doctoral thesis (other academic/artistic)abstract
- An all-electronic system for pulsed holographic interferometry called pulsed TV holography is developed. This is a whole-field non-contacting optical measurement method suitable for studies of transient events like wave propagation in solids and fluids. Chemical wet processing of holographic film and optical reconstruction of holograms are no longer needed. The technique was first developed using a double pulsed ruby laser as light source. The holograms are recorded directly on a CCD-detector. Quantitative data of changes in optical path length, caused either by a deformation of a solid object or a change in refractive index in a fluid, are calculated directly in a computer. The system for pulsed TV holography has recently been further developed by the purchase of a new pulsed laser (twin cavity, injection seeded pulsed Nd:YAG) and a CCD camera (PCO Sensicam) with higher spatial resolution and dynamic range. In the survey of this thesis the increased versatility compared to a ruby laser based system is discussed. During the development of the pulsed TV holography system a number of experiments in mechanics and acoustics have been accomplished. Bending waves in impacted plates propagating at a speed of about 2000 m/s are easily “frozen” due to the short duration laser pulses (<30 ns). These waves act as supersonic travelling acoustic sources and generate sound waves in the surrounding air. For the first time, transient sound fields from impacted plates have been visualised and measured using pulsed holographic interferometry. In another experiment, we have demonstrated that the pulsed TV holography system is feasible in combination with tomography. By recording a three-dimensional acoustic pressure field from a number of viewing directions followed by a tomographic reconstruction, the pressure in any point can be calculated. Finally, a method to restore fringes lost by large bulk motions is proposed. This technique may become very attractive in the study of vibrations (preferable transient) on moving or rotating objects. In conclusion, pulsed TV holography is proved to be a fast and reliable method to quantitatively study transients in mechanics and acoustics. The technique has a great potential in experimental mechanics in the future.
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| 2. |
- Heinze, Stanley
(author)
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Neuroethology: Unweaving the Senses of Direction.
- 2015
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In: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 25:21, s. 1034-1037
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Journal article (peer-reviewed)abstract
- Three recent studies have significantly advanced our understanding of the highly conserved central complex of the insect brain, showing how it provides an internal representation of body orientation, encodes behaviorally relevant sensory cues, and at the same time controls motor actions.
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| 3. |
- Hellblom-Thibblin, Tina, et al.
(author)
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Teachers´ perceptions of children´s diversity in different educational settings : Some issues to discuss from a research study
- 2015
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In: Children and Young People in School and in Society. - : Nova Science Publisher. - 9781634834957 ; , s. 87-199
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Book chapter (peer-reviewed)abstract
- In this chapter issues from a study about teachers’ perceptions of children’s diversity in different educational settings are discussed. The chapter also focuses on how these issues can be understood from an ecological point of view. The theoretical framework, used in the referred study, was influenced by an ecological approach to understand children's capabilities in relation to transitions and the learning process. The empirical data originates from focused thema interviews with 36 teacher from preschool, preschool class and first grade in primary school. The result shows that teachers’ perceptions of children´s different capabilites and experiences were influenced by factors from micro to macro level and emphasised the complexity of a dynamic process. Obstacles regarding children's learning and development changed from preschool to first grade in primary school. Teachers' perceptions of diversity involve both ideas of including and also excluding processes, besides dimensions linked to identity and social relations but also changes related to different educational settings. What teachers perceive as "problems", challenges and implications for measures in different educational settings can be of valuable knowledge for all professionals who are interested in children's learning journeys from preschool to school.
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| 4. |
- Lindahl, B. Ingemar B., et al.
(author)
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Consciousness and Neural Force Fields
- 2016
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In: Journal of consciousness studies. - 1355-8250 .- 2051-2201. ; 23:7-8, s. 228-253
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Journal article (peer-reviewed)abstract
- This article compares Wolfgang Kohler's pioneering field theory of the consciousness brain relation with Benjamin Libet's conscious mental field theory and Karl Popper's mental force field hypothesis. In the discussion of Kohler's theory we devote special attention to his analysis of problems of sense perception and to his explanation of figural after-effects. Both Libet and Popper take consciousness to causally interact with the brain, and we argue that even Kohler presupposes an interactionist interpretation of the consciousness brain relation. We argue that nothing necessarily rules out that consciousness as something subjective may causally interact with the brain as something objective. We discuss an evolutionary argument for the theory that consciousness causally interacts with the brain, and we consider some arguments for consciousness having had a survival value.
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| 5. |
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| 6. |
- Lindahl, Patric, et al.
(author)
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Performance and optimisation of triple quadrupole ICP-MS for accurate measurement of uranium isotopic ratios
- 2021
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In: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 36:10, s. 2164-2172
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Journal article (peer-reviewed)abstract
- The performance characteristics of the Agilent 8900 triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) system were evaluated and optimised concerning stability in measurements of uranium isotopic ratios. Multiple measurement parameters were evaluated for the determination of U isotopic ratios in certified standard solutions containing U-233, U-235 and U-238. Large irregular biases during repeated measurements of U isotopic ratios were observed using two identical ICP-MS/MS instruments. Depending on the mass filter resolution settings, the accuracy of U isotopic ratios can deviate up to 100% from the certified reference value. These variations in U isotopic ratios are primarily recognised as irregular drifts in the mass calibration of the two mass filters. This mass calibration drift is dependent on the isotope mass with a more pronounced drift for heavier isotopes. In order to solve the problem the resolution settings were optimised for both mass filters, which resulted in considerable improvement in precision and accuracy. A precision of 0.07% (relative standard deviation) for long-term measurement of U-233/U-235 ratios was achieved. Mass bias corrected U isotopic ratios agree very well with certified reference values with overall relative deviations from reference values of 0.005% and 0.17% for the SQ mode and MS/MS mode, respectively. The impact of the first mass filter in the MS/MS mode has a significant effect on the mass bias discrimination process and hence the accuracy of U isotopic ratios.
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| 7. |
- Perrotta, S., et al.
(author)
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Left thoracotomy for recurrent left ventricular pseudoaneurysm
- 2010
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In: Journal of cardiovascular medicine (Hagerstown, Md.). - 1558-2035.
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Journal article (peer-reviewed)abstract
- A 63-year-old man developed a left ventricular pseudoaneurysm 6 months after surgery for coronary artery disease, mitral valve insufficiency and left ventricular aneurysm. The grafts were patent and the mitral valve competent, so it was decided to resect the pseudoaneurysm. The heart was approached through a left posterolateral thoracotomy using a femoral arteriovenous cardiopulmonary bypass with moderate hypothermia (25 degrees C) and fibrillatory arrest. The postoperative course was uneventful. At follow-up, 55 months after surgery, the patient is doing well and magnetic resonance reveals absence of pseudoaneurysm and increased left ventricular ejection fraction. In patients with left ventricular pseudoaneurysm undergoing redo surgery, especially in the presence of patent coronary grafts, left thoracotomy seems to be a suitable alternative to full sternotomy.
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| 9. |
- Tyler, Torbjörn
(author)
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Geographical distribution of allozyme variation in relation to post-glacial history in Carex digitata, a widespread European woodland sedge
- 2002
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In: Journal of Biogeography. - : Wiley. - 1365-2699 .- 0305-0270. ; 29:7, s. 919-930
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Journal article (peer-reviewed)abstract
- Aim To investigate the distribution, and broad-scale geographical patterns, of variation, in the widespread boreo-nemoral woodland herb Carex digitata throughout its native European range. To interpret the revealed geographical pattern of variation in terms of glacial survival, post-glacial migration and inter-regional gene-flow. Location The whole of Europe divided into twenty-five geographical regions. Methods Genetic variation at nine polymorphic allozyme loci was analysed in 10-25 individuals from 66 populations from throughout the European range of C. digitata . Allele frequencies were calculated both at the level of populations and at the level of geographical regions, and these frequencies were used to calculate the Cavalli-Sforza chord distance (CSCD). CSCD between neighbouring regions were presented on geographical maps. CSCD at both the population and the regional level were subjected to UPGMA cluster analysis. Standard measures of genetic diversity were calculated and divided into within population, region and species components. Results Most alleles had a scattered distribution throughout, but several alleles were mainly found in Fennoscandia and regional allelic richness was the highest here. Cluster analysis on the level of populations did not recover any geographical structure. However, genetic distances between regions, each consisting of 1-4 populations, revealed a clear geographical pattern. Genetic distances were low between (1) Scandinavian and British regions and (2) between Mediterranean regions, moderate between Central European regions and high between far-east European and Caucasian regions. Main conclusions A post-glacial scenario involving independent glacial survivals in south-eastern European Russia, the Caucasian Mountains, the Mediterranean area and central Europe is proposed. Northern Europe (i.e. Fennoscandia) appears to have been colonized through many independent long-distance dispersals from different extra-Fennoscandian populations. High regional population densities in Fennoscandia are assumed to have facilitated accumulation of genetic variation and inter-regional gene-flow as compared with more southern populations which are generally of restricted size and appear to have been mutually isolated and subjected to strong genetic drift.
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