| 1. |
- Tesi, Bianca, et al.
(författare)
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Gain-of-function SAMD9L mutations cause a syndrome of cytopenia, immunodeficiency, MDS, and neurological symptoms
- 2017
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Ingår i: Blood. - : AMER SOC HEMATOLOGY. - 0006-4971 .- 1528-0020. ; 129:16, s. 2266-2279
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Tidskriftsartikel (refereegranskat)abstract
- Several monogenic causes of familial myelodysplastic syndrome (MDS) have recently been identified. We studied 2 families with cytopenia, predisposition to MDS with chromosome 7 aberrations, immunodeficiency, and progressive cerebellar dysfunction. Genetic studies uncovered heterozygous missense mutations in SAMD9L, a tumor suppressor gene located on chromosome arm 7q. Consistent with a gain-of-function effect, ectopic expression of the 2 identified SAMD9L mutants decreased cell proliferation relative to wild-type protein. Of the 10 individuals identified who were heterozygous for either SAMD9L mutation, 3 developed MDS upon loss of the mutated SAMD9L allele following intracellular infections associated with myeloid, B-, and natural killer (NK)-cell deficiency. Five other individuals, 3 with spontaneously resolved cytopenic episodes in infancy, harbored hematopoietic revertant mosaicism by uniparental disomy of 7q, with loss of the mutated allele or additional in cis SAMD9L truncating mutations. Examination of 1 individual indicated that somatic reversions were postnatally selected. Somatic mutations were tracked to CD34 1 hematopoietic progenitor cell populations, being further enriched in B and NK cells. Stimulation of these cell types with interferon (IFN)-alpha or IFN-gamma induced SAMD9L expression. Clinically, revertant mosaicism was associated with milder disease, yet neurological manifestations persisted in 3 individuals. Two carriers also harbored a rare, in trans germ line SAMD9L missense loss-of-function variant, potentially counteracting the SAMD9L mutation. Our results demonstrate that gain-of-function mutations in the tumor suppressor SAMD9L cause cytopenia, immunodeficiency, variable neurological presentation, and predisposition to MDS with 27/del(7q), whereas hematopoietic revertant mosaicism commonly ameliorated clinical manifestations. The findings suggest a role for SAMD9L in regulating IFN-driven, demand-adapted hematopoiesis.
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| 2. |
- Davidsson, Kent, 1967, et al.
(författare)
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Potassium, chlorine, and sulfur in ash, particles, deposits, and corrosion during wood combustion in a circulating fluidized-bed boiler
- 2007
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 21:1, s. 71-81
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry.
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| 3. |
- Johansson, Linda C, 1983, et al.
(författare)
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Structure of a photosynthetic reaction centre determined by serial femtosecond crystallography.
- 2013
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Serial femtosecond crystallography is an X-ray free-electron-laser-based method with considerable potential to have an impact on challenging problems in structural biology. Here we present X-ray diffraction data recorded from microcrystals of the Blastochloris viridis photosynthetic reaction centre to 2.8Å resolution and determine its serial femtosecond crystallography structure to 3.5Å resolution. Although every microcrystal is exposed to a dose of 33MGy, no signs of X-ray-induced radiation damage are visible in this integral membrane protein structure.
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| 4. |
- Jones, Geraint H., et al.
(författare)
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The Comet Interceptor Mission
- 2024
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Ingår i: Space Science Reviews. - : Springer Nature. - 0038-6308 .- 1572-9672. ; 220:1
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.
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| 5. |
- Andersson, Magnus, et al.
(författare)
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A proposed time-resolved X-ray scattering approach to track local and global conformational changes in membrane transport proteins
- 2008
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Ingår i: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 16:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved X-ray scattering has emerged as a powerful technique for studying the rapid structural dynamics of small molecules in solution. Membrane-protein-catalyzed transport processes frequently couple large-scale conformational changes of the transporter with local structural changes perturbing the uptake and release of the transported substrate. Using light-driven halide ion transport catalyzed by halorhodopsin as a model system, we combine molecular dynamics simulations with X-ray scattering calculations to demonstrate how small-molecule time-resolved X-ray scattering can be extended to the study of membrane transport processes. In particular, by introducing strongly scattering atoms to label specific positions within the protein and substrate, the technique of time-resolved wide-angle X-ray scattering can reveal both local and global conformational changes. This approach simultaneously enables the direct visualization of global rearrangements and substrate movement, crucial concepts that underpin the alternating access paradigm for membrane transport proteins.
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| 6. |
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| 7. |
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| 8. |
- Andersson, Magnus, et al.
(författare)
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Structural Dynamics of Light-Driven Proton Pumps
- 2009
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Ingår i: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 17:9, s. 1265-1275
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Tidskriftsartikel (refereegranskat)abstract
- Bacteriorhodopsin and proteorhodopsin are simple heptahelical proton pumps containing a retinal chromophore covalently bound to helix G via a protonated Schiff base. Following the absorption of a photon, all-trans retinal is isomerized to a 13-cis conformation, initiating a sequence of conformational changes driving vectorial proton transport. In this study we apply time-resolved wide-angle X-ray scattering to visualize in real time the helical motions associated with proton pumping by bacteriorhodopsin and proteorhodopsin. Our results establish that three conformational states are required to describe their photocycles. Significant motions of the cytoplasmic half of helix F and the extracellular half of helix C are observed prior to the primary proton transfer event, which increase in amplitude following proton transfer. These results both simplify the structural description to emerge from intermediate trapping studies of bacteriorhodopsin and reveal shared dynamical principles for proton pumping.
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| 9. |
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| 10. |
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| 11. |
- Andersson, S., et al.
(författare)
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Sulfur recirculation for increased electricity production in Waste-to-Energy plants
- 2014
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 34:1, s. 67-78
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur recirculation is a new technology for reducing boiler corrosion and dioxin formation. It was demonstrated in full-scale tests at a Waste to Energy plant in Goteborg (Sweden) during nearly two months of operation. Sulfur was recirculated as sulfuric acid from the flue gas cleaning back to the boiler, thus creating a sulfur loop. The new technology was evaluated by extensive measurement campaigns during operation under normal conditions (reference case) and operation with sulfur recirculation. The chlorine content of both fly ash and boiler ash decreased and the sulfur content increased during the sulfur recirculation tests. The deposit growth and the particle concentration decreased with sulfur recirculation and the dioxin concentration (I-TEQ) of the flue gas was reduced by approximately 25%. Sulfuric acid dew point measurements showed that the sulfuric acid dosage did not lead to elevated SO3 concentrations, which may otherwise induce low temperature corrosion. In the sulfur recirculation corrosion probe exposures, the corrosion rate decreased for all tested materials (16Mo3, Sanicro 28 and Inconel 625) and material temperatures (450 degrees C and 525 degrees C) compared to the reference exposure. The corrosion rates were reduced by 60-90%. Sulfur recirculation prevented the formation of transition metal chlorides at the metal/oxide interface, formation of chromate and reduced the presence of zinc in the corrosion products. Furthermore, measured corrosion rates at 525 degrees C with sulfur recirculation in operation were similar or lower compared to those measured at 450 degrees C material temperature in reference conditions, which corresponds to normal operation at normal steam temperatures. This implies that sulfur recirculation allows for higher steam data and electricity production without increasing corrosion.
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| 12. |
- Aquila, Andrew, et al.
(författare)
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Time-resolved protein nanocrystallography using an X-ray free-electron laser
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:3, s. 2706-2716
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 µs after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems.
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| 13. |
- Arnlund, David, et al.
(författare)
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Visualizing a protein quake with time-resolved X-ray scattering at a free-electron laser
- 2014
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Ingår i: Nature Methods. - : Springer Science and Business Media LLC. - 1548-7091 .- 1548-7105. ; 11:9, s. 923-926
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Tidskriftsartikel (refereegranskat)abstract
- We describe a method to measure ultrafast protein structural changes using time-resolved wide-angle X-ray scattering at an X-ray free-electron laser. We demonstrated this approach using multiphoton excitation of the Blastochloris viridis photosynthetic reaction center, observing an ultrafast global conformational change that arises within picoseconds and precedes the propagation of heat through the protein. This provides direct structural evidence for a 'protein quake': the hypothesis that proteins rapidly dissipate energy through quake-like structural motions.
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| 14. |
- Barty, A., et al.
(författare)
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Self-terminating diffraction gates femtosecond X-ray nanocrystallography measurements
- 2012
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Ingår i: Nature Photonics. - 1749-4885 .- 1749-4893. ; 6:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis1. For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information1, 2, 3, 4. Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology5 should enable structural determination from submicrometre protein crystals with atomic resolution.
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| 15. |
- Bergkvist, Markus, et al.
(författare)
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A Hybrid Micro-Simulator for Determining the Effects of Governmental Control Policies on Transport Chains
- 2005
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Ingår i: Multi-Agent and Multi-Agent Based Simulation. - New York City : Springer.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- A simulation-based tool is described which will be used to investigate how the actors in a transport chain are expected to act when different types of governmental control policies are applied, such as, fuel taxes, road tolls, vehicle taxes and requirements on vehicles. The simulator is composed of two layers, one layer simulating the physical activities taking place in the transport chain, e.g., production, storage, and transports of goods, and another layer simulating the different actors’ decision making processes. The decision layer is implemented by a multi-agent system where each agent corresponds to a particular actor and models the way it acts in different situations. The simulator will be used for analyzing the costs and environmental effects, and will in this way provide guidance in decision making regarding control policies. In addition, it will be possible for companies to use the simulator in order to determine cost-effective strategies given different (future) scenarios.
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| 16. |
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| 17. |
- Birch Tyrberg, Rasmus, et al.
(författare)
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Students’ and teachers’ attitudes towards PBL-curriculum components in a medical programme : a follow-up study
- 2021
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Ingår i: MedEdPublish. - : Association for Medical Education in Europe. - 2312-7996. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim was to explore students' and teachers' attitudes towards horizontal and vertical integration and other components of the curriculum, and to compare these results with data from a study at our medical school published in 2002.Methods: A questionnaire with 17 questions regarding different components of our curriculum was sent to students and staff at our medical school. They were asked to rate the importance of different components on a Likert scale from 1-6. We compared the answers between the two groups, and also compared them with the results from 2002.Results: Horizontal and vertical integration were rated as very important components (Teachers (n=283) median 5 and 5, Students (n=596) 6 and 5 respectively). Students valued lectures and clinical rotations more highly than teachers. Teachers considered laboratory training, training in searching scientific literature, scientific projects, basic education in ethics, reading and discussion of fictional literature, interprofessional components and examinations as significantly more important than the students did.Conclusions: Attitudes have remained positive towards horizontal and vertical integration despite major changes in the curriculum. The majority of the components of our curriculum were well appreciated, indicating that our curriculum is robust, but some components warrant inspection and possible revision.
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| 18. |
- Blennow, Kaj, 1958, et al.
(författare)
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No association between the alpha2-macroglobulin (A2M) deletion and Alzheimer's disease, and no change in A2M mRNA, protein, or protein expression.
- 2000
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Ingår i: Journal of neural transmission (Vienna, Austria : 1996). - : Springer Science and Business Media LLC. - 0300-9564 .- 1435-1463. ; 107:8-9, s. 1065-79
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Tidskriftsartikel (refereegranskat)abstract
- A polymorphism consisting of a deletion near the 5' splice site of exon 18 on the alpha2-macroglobulin (A2M) gene (A2M-2) has been suggested to be associated with Alzheimer's disease (AD) in family-based studies. We studied the A2M-2 allele together with the ApoE alleles in a large series on patients with AD (n = 449) and age-matched controls (n = 349). Neuropathologically confirmed diagnoses were available in 199 cases (94 AD and 107 control cases). We found no increase in A2M-2 genotype or allele frequencies in AD (27.5% and 14.6%) versus controls (26.4% and 14.9%). In contrast, a marked increase (p < 0.0001) in ApoE epsilon4 genotype or allele frequencies was found in AD (66.6% and 41.2%) as compared with controls (29.8% and 16.5%), suggesting sufficient statistical power in our sample. No relation was found between the A2M-2 and the ApoE epsilon4 allele. No change in A2M exon 17-18 mRNA size or sequence or A2M protein size was found in cases carrying the A2M-2 deletion, suggesting that there is no biological consequences of the A2M intronic deletion. No change in A2M protein level in cerebrospinal fluid was found in AD, suggesting that the A2M-2 allele does not effect the A2M protein expression in the brain. The lack of an association between the A2M-2 allele and AD in the present study, and the lack of abnormalities in the A2M mRNA or protein suggest that the A2M-2 allele is not associated with AD.
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| 19. |
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| 20. |
- Borg, O Anders, et al.
(författare)
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Photochemistry of bromofluorobenzenes.
- 2006
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Ingår i: J Phys Chem A Mol Spectrosc Kinet Environ Gen Theory. - 1089-5639. ; 110, s. 7045-
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Tidskriftsartikel (refereegranskat)
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| 21. |
- Borg, O. Anders, et al.
(författare)
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Predissociation of Chlorobenzene, beyond the pseudo-diatomic model
- 2008
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 456:4-6, s. 123-126
-
Tidskriftsartikel (refereegranskat)abstract
- Dissociation of chlorobenzene via the lowest singlet excited state has been investigated by means of pump-probe femtosecond spectroscopy and spin-orbit corrected ab initio quantum chemistry. We have found that the so far accepted model with a (1)pi pi* -> (3)pi/n sigma* reaction mechanism has to be amended. We suggest that the mechanism goes via a transition from (1)pi pi* to a pi sigma* state that is to 90% a singlet. Further, three nuclear degrees of freedom required to describe the dissociation have been defined.
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| 22. |
- Borgström, Magnus, 1973-
(författare)
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Controlling Charge and Energy Transfer Processes in Artificial Photosynthesis : From Picosecond to Millisecond Dynamics
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes an interdisciplinary project, where the aim is to mimic the initial reactions in photosynthesis. In photosynthesis, the absorption of light is followed by the formation of charge-separated states. The energy stored in these charge-separated states is further used for the oxidation of water and reduction of carbon dioxide. In this thesis the photo-induced processes in a range of supramolecular complexes have been investigated with time resolved spectroscopic techniques. The complexes studied consist of three types of units; photosensitizers (P) capable of absorbing light, electron acceptors (A) that are easily reduced and electron donors (D) that are easily oxidised. Our results are important for the future design of artificial photosystems, where the goal is to produce hydrogen from light and water. Two molecular triads with a D-P-A architecture are presented. In the first one, a photo-induced charge-separated state was formed in an unusually high yield (φ>90%). In the second triad, photo-irradiation led to the formation of an extremely long-lived charge-separated state (τ = 500 ms at 140K). This is also the first synthetically made triad containing a dinuclear manganese unit as electron donor.Further, two sets of P-A dyads are presented. In both, the expected photo-induced reduction of the electron acceptor is diminished due to competing energy transfer to the triplet state of the acceptor.Finally, a P-P-A complex containing two separate photosensitizers is described. The idea is to produce high-energy charge-separated states by using the energy from two photons.
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| 23. |
- Brackmann, Christian, et al.
(författare)
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Optical and mass spectrometric study of the pyrolysis gas of wood particles
- 2003
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 57:2, s. 216-222
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Tidskriftsartikel (refereegranskat)abstract
- A detailed experimental investigation has been made of the pyrolysis-the first step in biomass combustion-of single birchwood particles. In addition to mass spectrometric and gravimetric analysis, the pyrolysis volatiles were characterized by different optical techniques. Absorption measurements showed a nearly featureless absorption in the ultraviolet spectral region with a continuously stronger absorption for shorter wavelengths. Using different excitation wavelengths, laser-induced fluorescence measurements revealed generally broad spectra in the spectral region from 300-500 nm, which are characteristic spectral signatures for larger hydrocarbons. The optical data were monitored at different times in the pyrolysis process of the particles and compared with the results from the mass spectrometric and gravimetric analysis. The sensitivity of the optical techniques for differentiation between specific molecules was rather low, although formaldehyde could be observed both in absorption and fluorescence spectra. Laser-induced fluorescence measurements were also made for two-dimensional visualization of the pyrolysis volatiles; emitted from heated birchwood particles, indicating much higher flows along the fiber direction than across.
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| 24. |
- Carlsson, Bengt, et al.
(författare)
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Security Aspects on Inter-Organizational Cooperation Using Wrapper Agents
- 2005
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Konferensbidrag (refereegranskat)abstract
- The significance of electronic information exchange in interorganizational cooperation is well-known. We will here focus on the particular requirements of SMEs. We describe a general “wrapper agent” solution based on open source freeware that makes it possible (in principle) for any business system to exchange information with any other business system. It has been successfully applied in a pilot study involving two companies in a transport chain using different business systems. We also suggest further improvements by addressing security and privacy issues as well as an extended, possibly dynamic, set of involved companies and higher levels of cooperation.
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| 25. |
- Carlsson, Bengt, et al.
(författare)
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Security aspects on inter-organizational cooperation using wrapper agents
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The significance of electronic information exchange in inter-organizational cooperation is well-known. We will here focus on the particular requirements of SMEs. We describe a general wrapper agent solution based on open source freeware that makes it possible (in principle) for any business system to exchange information with any other business system. It has been successfully applied in a pilot study involving two companies in a transport chain using different business systems. We also suggest further improvements by addressing security issues as well as an extended, possibly dynamic, set of involved companies and higher levels of cooperation.
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| 26. |
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| 27. |
- Davidsson, Anette, et al.
(författare)
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Influence of reconstruction algorithms on image quality in SPECT myocardial perfusion imaging
- 2017
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Ingår i: Clinical Physiology and Functional Imaging. - : John Wiley & Sons. - 1475-0961 .- 1475-097X. ; 37:6, s. 655-662
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: We investigated if image- and diagnostic quality in SPECT MPI could be maintained despite a reduced acquisition time adding Depth Dependent Resolution Recovery (DDRR) for image reconstruction. Images were compared with filtered back projection (FBP) and iterative reconstruction using Ordered Subsets Expectation Maximization with (IRAC) and without (IRNC) attenuation correction (AC).MATERIALS AND METHODS: Stress- and rest imaging for 15 min was performed on 21 subjects with a dual head gamma camera (Infinia Hawkeye; GE Healthcare), ECG-gating with 8 frames/cardiac cycle and a low-dose CT-scan. A 9 min acquisition was generated using five instead of eight gated frames and was reconstructed with DDRR, with (IRACRR) and without AC (IRNCRR) as well as with FBP. Three experienced nuclear medicine specialists visually assessed anonymized images according to eight criteria on a four point scale, three related to image quality and five to diagnostic confidence. Statistical analysis was performed using Visual Grading Regression (VGR).RESULTS: Observer confidence in statements on image quality was highest for the images that were reconstructed using DDRR (P<0·01 compared to FBP). Iterative reconstruction without DDRR was not superior to FBP. Interobserver variability was significant for statements on image quality (P<0·05) but lower in the diagnostic statements on ischemia and scar. The confidence in assessing ischemia and scar was not different between the reconstruction techniques (P = n.s.).CONCLUSION: SPECT MPI collected in 9 min, reconstructed with DDRR and AC, produced better image quality than the standard procedure. The observers expressed the highest diagnostic confidence in the DDRR reconstruction.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Davidsson, Jan, et al.
(författare)
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Structural determination of a transient isomer of CH2I2 by picosecond x-ray diffraction
- 2005
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 94:24
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrafast time-resolved spectroscopic studies of complex chemical reactions in solution are frequently hindered by difficulties in recovering accurate structural models for transient photochemical species. Time-resolved x-ray and electron diffraction have recently emerged as techniques for probing the structural dynamics of short lived photointermediates. Here we determine the structure of a transient isomer of photoexcited CH2I2 in solution and observe the downstream reactions of the initial photoproducts. Our results illustrate how geminate recombination proceeds via the formation of a transient covalent bond onto the iodine atom remaining with the parent molecule. Further intramolecular rearrangements are thus required for the CH2I-I isomer to return to CH2I2. The generation of I-3(-) from those iodine radicals escaping the solvent cage is also followed with time.
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| 32. |
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| 33. |
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| 34. |
- Davidsson, Paul, et al.
(författare)
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A Criteria-Based Approach to Evaluating Road User Charging Systems
- 2018
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Ingår i: Procedia Computer Science. - : Elsevier. - 1877-0509. ; 130, s. 142-149
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Tidskriftsartikel (refereegranskat)abstract
- A set of important criteria to consider when evaluating potential road user charging system (RUCS) are identified. These criteria are grouped into five categories: charging precision, system costs & societal benefits, flexibility & modifiability, operational aspects, and security & privacy. The criteria are then used in a comparative analysis of five RUCS candidates for heavy goods vehicles. Two solutions are position-based systems and one is based on tachographs. The two remaining solutions are based on fuel taxes. For each of the solutions we estimate how well it fulfils each of the criteria. One way of making general comparisons of the approaches is to give each of the criteria a specific weight corresponding to how important it is. We show that these weights heavily influence the outcome of the comparison. We conclude by pointing out a number of important issues needing attention in the process of developing RUCS.
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| 35. |
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| 36. |
- Davidsson, Paul, et al.
(författare)
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Agreement Technologies for Supporting the Planning and Execution of Transports
- 2013
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Ingår i: Agreement Technologies, Law, Governance and Technology Series. - Dordrecht : Springer Netherlands. - 9789400755833 ; , s. 533-547
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Bokkapitel (refereegranskat)abstract
- The use of agreement technologies in the planning and execution of goods transports is analyzed. We have previously suggested an approach called Plug and Play Transport Chain Management (PnP TCM) that provides agent-based support for key tasks, such as, finding the best sequence of transport services for a particular goods transport, monitoring the execution of the transport, and managing the interaction between the involved actors. In this paper we analyze five agreement technologies in the context of PnP TCM, i.e., semantics, norms, organizations, argumentation and negotiation, and trust. We conclude that all five technologies play a critical role in the realization of PnP TCM.
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| 37. |
- Davidsson, Paul, et al.
(författare)
-
Agreement technologies for supporting the planning and execution of transports
- 2013
-
Ingår i: Agreement Technologies. - Dordrecht : Springer. - 9789400755826 - 9789400755833 ; , s. 533-547
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The use of agreement technologies in the planning and execution of goods transports is analyzed. We have previously suggested an approach called Plug and Play Transport Chain Management (PnP TCM) that provides agent-based support for key tasks, such as, finding the best sequence of transport services for a particular goods transport, monitoring the execution of the transport, and managing the interaction between the involved actors. In this paper we analyze five agreement technologies in the context of PnP TCM, i.e., semantics, norms, organizations, argumentation and negotiation, and trust. We conclude that all five technologies play a critical role in the realization of PnP TCM.
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| 38. |
- Davidsson, Paul, et al.
(författare)
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An agent-based approach to transport chain management
- 2009
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Ingår i: ICE-B 2009. - Milan : INSTICC-INST SYST TECHNOLOGIES INFORMATION CONTROL & COMMUNICATION. ; , s. 175-182
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Konferensbidrag (refereegranskat)abstract
- A novel application of agent-mediated electronic commerce is presented. It concerns developing and maintaining efficient and effective transport solutions. The suggested approach is inspired by the concepts of virtual enterprises and breeding environments, as well as peer-to-peer technology. We discuss the requirements of such an approach and outline a software architecture meeting these requirements.
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| 39. |
- Davidsson, Per, 1958-, et al.
(författare)
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COVID-19 as External Enabler of entrepreneurship practice and research
- 2021
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Ingår i: BRQ Business Research Quarterly. - : Sage Publications. - 2340-9436 .- 2340-9444. ; 24:3, s. 214-223
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Tidskriftsartikel (refereegranskat)abstract
- For decades, entrepreneurship and strategy research has been dominated by agent-centric and inward-looking theoretical perspectives. The ongoing COVID-19 pandemic demonstrates the limits of this stance, as its influence on business has been both enormous and palpable. For the most part, the effects of the pandemic are no doubt negative. Business research—and presumably business practice—typically address such influence in terms of failure, resilience, and crisis management among existing businesses. Contrasting this prevalent discourse, we focus instead on positive influence of the pandemic for some emerging and new ventures. We analyze the many possible positive effects on entrepreneurship practice and highlight also positive effects on entrepreneurship research. We illustrate both positives by applying the External Enabler framework.
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| 40. |
- Davidsson, Per, 1958-, et al.
(författare)
-
Environmental change, strategic entrepreneurial action, and success : Introduction to a special issue on an important, neglected topic
- 2023
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Ingår i: Strategic Entrepreneurship Journal. - : John Wiley & Sons. - 1932-4391 .- 1932-443X. ; 17:2, s. 322-334
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Research Summary: The two premises that underpin this SEJ Special Issue on Environmental Change, Strategic Entrepreneurial Action, and Success are that all environmental changes provide positive potentials for some ventures, and that this has been under-emphasized in past theory and research. After stating these premises and illustrating how present research treats the environment, we proceed to explain how the five articles selected for the special issue advance our thinking in this domain. We then broaden our discussion to how future entrepreneurship research can make further progress by studying interaction among environmental changes as well as their links to entrepreneurial agents, contexts (sectoral, spatial, organizational, etc.) and the entrepreneurial artifact (emerging venture). Throughout, the focus is on the enabling rather than constraining role of environmental changes.Managerial Summary: The COVID-19 pandemic, the digital revolution, and the sustainability transition forced by climate change demonstrate significant business impact of environmental changes, including potentials for new business initiatives. This editorial and the five vanguard articles included in this SEJ Special Issue on Environmental Change, Strategic Entrepreneurial Action, and Success outline how future research can develop better theory and evidence on this important topic. The articles address matters ranging from how COVID-19 facilitated some technology firms' recruiting and reignited media firms' dormant initiatives to how environmental degradations sparked entrepreneurial ecosystem development in Kenya, how the level of environmental dynamism at a venture's birth impact its current ability to benefit from change, and the consequences of passing on potentials provided by environmental change.
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| 41. |
- Davidsson, Per, 1958-, et al.
(författare)
-
External enablement of new venture creation : A framework
- 2020
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Ingår i: Academy of Management Perspectives. - : Academy of Management. - 1558-9080 .- 1943-4529. ; 34:3, s. 311-332
-
Tidskriftsartikel (refereegranskat)abstract
- In searching for conceptualizations that offer an alternative perspective to “entrepreneurial opportunities”, the notion of external enablers has recently been suggested for capturing the influence on entrepreneurial action and outcomes exerted by external conditions like new technologies, regulatory or demographic shifts, and changes to the socio-cultural, economic, political, or natural environments. We take the external enabler perspective several steps further. We develop a new framework that conceptualizes external enablers in terms of their characteristics, roles, and mechanisms and detail their implications for entrepreneurial action and outcomes. We argue that this framework provides a more productive perspective for theorizing about the influence of external, actor-independent factors on venture creation processes than Discovery Theory’s notion of objective, pre-existing opportunities. At the same time, it is compatible with the dynamic-agentic view of new venture creation proposed by varieties of Creation Theory. For researchers who are interested in instances of societal change from a sociological or historical vantage point, the framework facilitates theorizing across such instances and about the microfoundations of aggregate-level changes. Additional domains that can benefit from our new framework include design- and strategy-oriented research and practice.
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| 42. |
- Davidsson, Per, 1958-, et al.
(författare)
-
Fulfilling the Process Promise : A Review and Agenda for New Venture Creation Process Research
- 2021
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Ingår i: Entrepreneurship. - : Sage Publications. - 1042-2587 .- 1540-6520. ; 45:5, s. 1083-1118
-
Tidskriftsartikel (refereegranskat)abstract
- We review new venture creation process research in leading journals over the past 30 years, applying a broad view of “process.” While we find a rich and varied literature with significant quantitative and qualitative growth, the review reveals considerable room for future contributions in this important area of entrepreneurship research. In an agenda building on review results, exemplary articles, and theory development advice from other sources, we discuss several types of such future contributions. We hope that our efforts can inspire emerging scholars, colleagues, research leaders, and institutional actors to contribute to a bright future for this core domain of entrepreneurship research.
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| 43. |
- Davidsson, Paul, et al.
(författare)
-
Multi Agent Based Simulation of Transport Chains
- 2008
-
Konferensbidrag (refereegranskat)abstract
- An agent-based tool for micro-level simulation of transport chains (TAPAS) is described. It is more powerful than traditional approaches as it is able to capture the interactions between individual actors of a transport chain, as well as their heterogeneity and decision making processes. Whereas traditional approaches rely on assumed statistical correlation between different parameters, TAPAS relies on causality, i.e., the decisions and negotiations that lead to the transports being performed. An additional advantage is that TAPAS is able to capture time aspects, such as, the influence of timetables, arrival times, and time-differentiated taxes and fees. TAPAS is composed of two layers, one layer simulating the physical activities taking place in the transport chain, e.g., production, storage, and transports of goods, and another layer simulating the different actors’ decision making processes and interaction. The decision layer is implemented as a multi-agent system using the JADE platform, where each agent corresponds to a particular actor. We demonstrate the use of TAPAS by investigating how the actors in a transport chain are expected to act when different types of governmental control policies are applied, such as, fuel taxes, road tolls, and vehicle taxes. By analyzing the costs and environmental effects, TAPAS provides guidance in decision making regarding such control policies. We argue that TAPAS may also complement existing approaches in different ways, for instance by generating input data such as transport demand. Since TAPAS models a larger part of the supply chain, the transport demand is a natural part of the output. Studies may concern operational decisions like choice of consignment size and frequency of deliveries, as well as strategic decisions like where to locate storages, terminals, etc., choice of producer, and adaptation of vehicle fleets.
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| 44. |
- Davidsson, Paul, et al.
(författare)
-
On the Integration of Agent-Based and Mathematical Optimization Techniques
- 2007
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Ingår i: 1st KES International Symposium on Agent and Multi-Agent Systems. - : SPRINGER-VERLAG BERLIN. - 9783540728290 ; , s. 1-10
-
Bokkapitel (refereegranskat)abstract
- The strengths and weaknesses of agent-based approaches and classical optimization techniques are compared. Their appropriateness for resource allocation problems were resources are distributed and demand is changing is evaluated. We conclude that their properties are complementary and that it seems beneficial to combine the approaches. Some suggestions of such hybrid systems are sketched and two of these are implemented and evaluated in a case study and compared to pure agent and optimization-based solutions. The case study concerns allocation of production and transportation resources in a supply chain. In one of the hybrid systems, optimization techniques were embedded in the agents to improve their decision making capability. In the other system, optimization was used for creating a long-term coarse plan which served as input the agents that adapted it dynamically. The results from the case study indicate that it is possible to capitalize both on the ability of agents to dynamically adapt to changes and on the ability of optimization techniques for finding high quality solutions.
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| 45. |
- Davidsson, Paul, et al.
(författare)
-
Plug and Play Transport Chain Management : Agent-Based Support to the Planning and Execution of Transports
- 2011
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Ingår i: e-Business and Telecommunications. - Berlin, Heidelberg : Springer. ; , s. 139-155, s. 139-155
-
Konferensbidrag (refereegranskat)abstract
- A novel approach to efficiently plan and execute effective transport solutions is presented. It provides agent-based support for key tasks, such as, finding the best sequence of transport services for a particular goods transport, monitoring the execution of the transport, as well as the interaction between the involved actors. The approach is based on the FREIGHTWISE framework in which a minimal set of information packages is defined. The purpose is to capture all the information that needs to be communicated between the actors involved in a transport, such as, transport users, transport providers, and infrastructure managers, during the complete process from planning to termination. The approach is inspired by the concepts of virtual enterprises and breeding environments. We analyse the requirements of such an approach and describe a multi-agent system architecture meeting these requirements.
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| 46. |
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| 47. |
- Davidsson, Paul, et al.
(författare)
-
The Fourth Wave of Digitalization and Public Transport : Opportunities and Challenges
- 2016
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 8:12
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the opportunities and challenges of the forth wave of digitalization, also referred to as the Internet of Things (IoT), with respect to public transport and how it can support sustainable development of society. Environmental, economical, and social perspectives are considered through analysis of the existing literature and explorative studies. We conclude that there are great opportunities for both transport operators and planners, as well as for the travelers. We describe and analyze a number of concrete opportunities for each of these actors. However, in order to realize these opportunities, there are also a number of challenges that needs to be addressed. There are both technical challenges, such as data collection issues, interoperability, scalability and information security, and non-technical challenges such as business models, usability, privacy issues, and deployment.
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| 48. |
- Davidsson, Paul, et al.
(författare)
-
Towards a prediction model for people movements in urban areas
- 2013
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Ingår i: First International Workshop on Multiagent-based Societal Systems. - Saint Paul, Minnesota, USA : Association for Computing Machinery (ACM).
-
Konferensbidrag (refereegranskat)abstract
- The aim of this work is to develop a new type of service for predicting and communicating urban activity. This service provides short-term predictions (hours to days), which can be used as a basis for different types of resource allocation and planning, e.g. concerning public transport, personnel, or marketing. The core of the service consists of a forecasting engine that based on a prediction model processes data on different levels of detail and from various providers. This paper explores the requirements and features of the forecast engine. We conclude that agent-based modeling seems as the most promising approach to meet these requirements. Finally, some examples of potential applications are described along with analyses of scientific and engineering issues that need to be addressed.
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| 49. |
- Davidsson, Sabina, 1972-
(författare)
-
Infection induced chronic inflammation and it's association with prostate cancer initiation and progression
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An association between cancer development and inflammation has long been suggested. Approximately 20% of all human cancers in adults are assumed to result from chronic inflammation. The aim of this thesis was to investigate if infection-induced chronic inflammation plays a role in prostate carcinogenesis.Our results revealed a greater infiltration of the bacterium Propionibacterium acnes in the prostate tissue obtained from men with prostate cancer compared to men without any histological evidence of the disease. These findings indicate that prostate cancer could potentially be included in the list of cancers with an infectious etiology.Further, we investigated whether chronic inflammation has a role in disease progression. Our results demonstrated that men with lethal prostate cancer had pronounced infiltration of immune cells with suppressive function of the anti-tumor immune response compared to men with a more indolent prostate cancer.Confirmation of our results may open up avenues for targeted prostate cancer treatment by offering men with chronic inflammation alternative therapies such as anti-inflammatory drugs. If the involvement of P. acnes in prostate cancer development is replicated in other studies, vaccination therapies may be feasible. To further individualize prostate cancer therapy, bolstering the anti-tumor immune response in order to reduce tumor progression may be determined to be advantageous for some patients.
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| 50. |
- Davidsson, Sabina, 1972-, et al.
(författare)
-
Multilocus sequence typing and repetitive-sequence-based PCR (DiversiLab) for molecular epidemiological characterization of Propionibacterium acnes isolates of heterogeneous origin
- 2012
-
Ingår i: Anaerobe. - : Elsevier. - 1075-9964 .- 1095-8274. ; 18:4, s. 392-399
-
Tidskriftsartikel (refereegranskat)abstract
- Propionibacterium acnes is a gram-positive bacillus predominantly found on the skin. Although it is considered an opportunistic pathogen it is also been associated with severe infections. Some specific P. acnes subtypes are hypothesized to be more prone to cause infection than others. Thus, the aim of the present study was to investigate the ability to discriminate between P. acnes isolates of a refined multilocus sequence typing (MLST) method and a genotyping method, DiversiLab, based on repetitive-sequence-PCR technology.The MLST and DiversiLab analysis were performed on 29 P. acnes isolates of diverse origins; orthopedic implant infections, deep infections following cardiothoracic surgery, skin, and isolates from perioperative tissue samples from prostate cancer. Subtyping was based on recA, tly, and Tc12S sequences.The MLST analysis identified 23 sequence types and displayed a superior ability to discriminate P. acnes isolates compared to DiversiLab and the subtyping. The highest discriminatory index was found when using seven genes. DiversiLab was better able to differentiate the isolates compared to the MLST clonal complexes of sequence types.Our results suggest that DiversiLab can be useful as a rapid typing tool for initial discrimination of P. acnes isolates. When better discrimination is required, such as for investigations of the heterogeneity of P. acnes isolates and its involvement in different pathogenic processes, the present MLST protocol is valuable.
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