| 1. |
- Holmén, Anders, 1967, et al.
(författare)
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Assignment of electronic transition moment directions of adenine from linear dichroism measurements
- 1997
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 119:50, s. 12240-12250
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Tidskriftsartikel (refereegranskat)abstract
- The electronic spectra of a series of adenine derivatives have been investigated with respect to the number of electronic transitions, their intensities, and transition moments. The experimental work includes linear dichroism (LD) measurements on samples partially oriented in stretched polymer poly(vinyl alcohol) films, fluorescence anisotropy (FA), and: magnetic circular dichroism (MCD). The UV spectra of both 7-methyladenine (7MA) and 9-methyladenine (9MA) are resolved into contributions from five pi --> pi* transitions (I-V). Their polarizations relative to the C-4-C-5 axis are for 7MA +45 degrees (I, 36 600 cm(-1)), -16 degrees (II, 39 500 cm(-1)), -28 degrees (III, 42 600 cm(-1)), +76 degrees (IV 45 800 cm(-1)) and similar to-29 degrees (V, similar to 47 700 cm(-1)); and for 9MA +66 degrees (I, 36 700 cm(-1)), +19 degrees (II, 38 820 cm(-1)), -15 degrees (III, 43 400 cm(-1)), -21 degrees (IV, 46 800 cm(-1)), and similar to-64 degrees (V, similar to 48 320 cm(-1)). The experimental results are correlated with results from semiempirical INDO/S and ab initio CIS/6-31G(d) and CASPT2 molecular orbital calculations. The transition moments are found to be conserved when the adenine amino group has been substituted with either one or two methyl groups. In addition, LD and MCD spectra for 6-(dimethylamino)-9-ethylpurine, which is soluble in nonpolar solvents, have been measured in stretched polyethylene film and cyclohexane, respectively. The results indicate that the electronic transition moments of the 9-substituted adenine chromophore are essentially the same in a polar and a nonpolar solvent. On the basis of the. results,for 7MA and 9MA, the reduced LD and absorption spectra of adenine are analyzed in terms of contributions from the 7-H and 9-H tautomers of adenine. By comparison with theoretical and experimental results for purine and 2-aminopurine regarding the position of the lowest n --> pi* transition, we are able to confidently position the lowest n --> pi* transition in 9MA very close to the lowest pi --> pi* transition. The proximity of the first (1)n pi* and (1) pi pi* states in adenine might be related to the efficient nonradiative deactivation of the lowest excited (1) pi pi* state.
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| 2. |
- Holmén, Anders, 1967, et al.
(författare)
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Ir Transition Moments of 1,3-Dimethyluracil - Linear Dichroism Measurements and Ab-Initio Calculations
- 1994
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Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 98:19, s. 4998-5009
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Tidskriftsartikel (refereegranskat)abstract
- The vibrational transition moment directions of 1,3-dimethyluracil (DMU), 1,3-dimethyluracil-5-d (DMU-5-d), and 1,3-dimethyluracil-6-d (DMU-6-d) have been determined from measurements of polarized IR spectra on samples partially aligned in stretched poly(vinyl alcohol) and by ab initio calculations at the HF/6-31G* level of approximation. The agreement between experiments and theory is good. IR spectra of DMU, DMU-5-d, and DMU-6-d in KBr and in D2O form, together with the calculated spectra and the IR polarizations, the basis for some reassignments. Special attention is paid to the double-bond region, where the high-frequency carbonyl stretching mode is assigned to an in-phase vibration of the C4O and the C2O. This vibration is polarized in a direction almost bisecting the angle between the two carbonyl bonds, in agreement with an in-phase assignment. The low-frequency mode is the out-of-phase vibration of the two carbonyl groups, and it is consequently polarized perpendicular to the high-frequency mode. In order to determine the orientation axis of DMU in the polymer matrix, the UV linear dichroism (LD) spectrum was measured and the polarizations of the electronic transitions were estimated from a semiempirical self-consistent reaction field (SCRF) calculation including solvent effects. The combined information from IR LD and UV LD shows that the molecular orientation axis in the stretched film experiment is parallel to the first pi --> pi* transition in DMU.
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| 3. |
- Albinsson, Anders
(författare)
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”De va svinhögt typ 250 kilo” : Förskolebarns mätande av längd, volym och tid i legoleken
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of the dissertation is to study, describe and analyses which comparative measurement activities preschool children construct and use, and how they solve problems and communicate when they use the comparative measurement activities whilst playing with Lego (“the Lego play”). The measurement activities chosen are length/height, quantity and time.The empirical material is based on data from two preschool classes with children aged 2 – 5 year, It was collected through participant observation (video captures) of the children’s Lego play. The theoretical starting points in this study are grounded in childhood sociology and the sociocultural perspective. The study assumes the childhood sociology perspective by viewing the children as competent and active in creating meaning as well as controlling and influencing their own and others’ social environment. The sociocultural perspective gives prominence to development and learning, and its related tools and concepts are used to analyses the results of the study. That is, the Lego play is studied in a social context from the child’s perspective, and the sociocultural perspective describes and analyses the child’s use of mathematics and the acquisition of knowledge in the Lego play in a sociocultural context.The results show that children measuring length/height and quantity explored a store of measurement tools in order to make comparisons, and adapted these to the context in question. These were own body, other body, artefacts, numbers and counting. The measurements were used individually and with others, and the solving of the own or shared problems constituted a large share of the time spent constructing models during Lego play. By contrast, the time concept was used mainly as a tool when the children played with their finished Lego models. Thus, a time perspective was added to the child’s finished model, which inspired thoughts and reflections about time used in the Lego play. The children used the time concepts of the present, the past and the future, and also considered the concept of velocity in the context of the timescale. The children’s communication had a large impact on the Lego play, and they expressed their ideas verbally, physically and through action. The children’s use of mathematics was prominent and meaningful during the Lego play.
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| 4. |
- Albinsson, Anders, 1958-, et al.
(författare)
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Förskolebarn använder mätning i legoleken
- 2016
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Ingår i: Venue. - Linköping : Linköpings universitet. - 2001-788X.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- I legoleken använder förskolebarn mätning på många olika sätt. De växlar mellan olika mätredskap och måttenheter, beroende på kontext och önskat mätresultat. Genom mätningar löser barnen problem i legoleken. Mätresultatet kommuniceras genom att visa, förklara och argumentera med matematiska begrepp.
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| 5. |
- Albinsson, David, 1990, et al.
(författare)
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Copper catalysis at operando conditions - bridging the gap between single nanoparticle probing and catalyst-bed-averaging
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- In catalysis, nanoparticles enable chemical transformations and their structural and chemical fingerprints control activity. To develop understanding of such fingerprints, methods studying catalysts at realistic conditions have proven instrumental. Normally, these methods either probe the catalyst bed with low spatial resolution, thereby averaging out single particle characteristics, or probe an extremely small fraction only, thereby effectively ignoring most of the catalyst. Here, we bridge the gap between these two extremes by introducing highly multiplexed single particle plasmonic nanoimaging of model catalyst beds comprising 1000 nanoparticles, which are integrated in a nanoreactor platform that enables online mass spectroscopy activity measurements. Using the example of CO oxidation over Cu, we reveal how highly local spatial variations in catalyst state dynamics are responsible for contradicting information about catalyst active phase found in the literature, and identify that both surface and bulk oxidation state of a Cu nanoparticle catalyst dynamically mediate its activity.
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| 6. |
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| 8. |
- Albinsson, Pär-Anders, et al.
(författare)
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High Precision Touch Screen Interaction
- 2003
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Ingår i: Proceedings of the ACM Conference on Human Factors Computing Systems, April 5–10, Fort Lauderdale, USA. ; , s. 105–112-
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Konferensbidrag (refereegranskat)
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| 9. |
- Albinsson, Pär-Anders, 1975-
(författare)
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Interacting with command and control systems : Tools for operators and designers
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Command and control is central in all distributed tactical operations such as rescue operations and military operations. It takes place in a complex system of humans and artefacts, striving to reach common goals. The command and control complexity springs from several sources, including dynamism, uncertainty, risk, time pressure, feedback delays and interdependencies. Stemming from this complexity, the thesis approaches two important and related problem areas in command and control research. On a general level, the thesis seeks to approach the problems facing the command and control operators and the problems facing the designers in the associated systems development process.We investigate the specific problem of operators losing sight of the overall perspective when working with large maps in geographical information systems with limited screen area. To approach this problem, we propose high-precision input techniques that reduce the need for zooming and panning in touch-screen systems, and informative unit representations that make better use of the screen area available. The results from an experimental study show that the proposed input techniques are as fast and accurate as state-of-the-art techniques without the need to resort to zooming. Furthermore, results from a prototype design show that the proposed unit representation reduces on-screen clutter and makes use of off-screen units to better exploit the valuable screen area.Developing command and control systems is a complex task with several pitfalls, including getting stuck in exhaustive analyses and overrated reliance on rational methods. In this thesis, we employ a design-oriented research framework that acknowledges creative and pragmatic ingredients to handle the pitfalls. Our approach adopts the method of reconstruction and exploration of mission histories from distributed tactical operations as a means for command and control analysis. To support explorative analysis of mission histories within our framework, we propose tools for communication analysis and tools for managing metadata such as reflections, questions, hypotheses and expert comments. By using these tools together with real data from live tactical operations, we show that they can manage large amounts of data, preserve contextual data, support navigation within data, make original data easily accessible, and strengthen the link between metadata and supporting raw data. Furthermore, we show that by using these tools, multiple analysts, experts, and researchers can exchange comments on both data and metadata in a collaborative and explorative investigation of a complex scenario.
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