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- Wikander, Kjell, et al.
(author)
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Alternative catalysts and carbon support material for PEMFC
- 2006
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In: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 6:1, s. 21-25
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Journal article (peer-reviewed)abstract
- In order to investigate the possibility of increasing the reactivity for oxygen reduction reaction (ORR) of the cathode in a PEMFC a series of Pt/C catalysts was prepared using water-in-oil microemulsions for synthesizing Pt nanoparticles. The Pt nanoparticles were deposited on porous carbon support (Vulcan XC-72 or a mesoporous carbon) and the catalysts were processed into MEAs. The MEA samples were evaluated and compared with a commercial sample and with Pt/C catalyst samples prepared using a conventional direct impregnation method. The mesoporous carbon support investigated as a potential alternative to Vulcan XC72 has a very high specific surface area and a narrow pore size distribution. The materials were characterized with XRD, TEM, SEM-EDX, N-2 sorption and steady state polarization. It was found that it is possible to increase the ORR reactivity using the microemulsion route for formation of Pt nanoparticles. It was concluded that the MEA processing conditions for the mesoporous carbon support have to be modified to reach improved ORR reactivity, likely due to the large differences in specific surface area, porosity and conductivity compared to the Vulcan carbon.
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1897 : Mediehistorier kring Stockholmsutställningen
- 2006
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Editorial collection (other academic/artistic)abstract
- När börjar mediehistorien? Mediehistoria var länge liktydigt med historien om 1900-talets massmedier press, radio, teve och film. I den här boken skildras istället ett äldre medielandskap. Med utgångspunkt i Stockholmsutställningen 1897 beskriver författarna det utbud av gamla och nya medier som samlades på utställningen, från äldre attraktioner som camera obscura, dioramor och vaxfigurer till spektakulära nyheter som fonograf, kinematograf och röntgenbilder. Boken ger inblickar i några av det sena 1800-talets ledande medieindustrier, och diskuterar bland annat frågor om mediekonsumtion, publikpositioner och historiska medieringsvillkor. De medietekniker som presenterades på Stockholmsutställningen 1897 lagrade på samma gång utställningen för framtiden. Ett centralt tema är därför hur dessa medieringar blivit identiska med minnet av utställningen, och hur detta arkiv organiserats utifrån mediernas specifika egenskaper. På den DVD-skiva som medföljer boken har ett nytt mediearkiv skapats över Stockholmsutställningen 1897 och dess många länkar till en bredare mediekultur.
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| 6. |
- Ahlford, Marianne, et al.
(author)
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Uppsala Underdogs - A Robot Soccer Project
- 2006
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Reports (pop. science, debate, etc.)abstract
- In this paper, we describe the four-legged soccer team Uppsala Underdogs developed by a group of 4th year computer science students at Uppsala University during the fall of 2004. The project is based on the experience from two similar previous projects. This year the emphasis of the project has been on distribution of data and on support for evaluation and reconfiguration of strategies. To support data distribution, a middleware has been developed, which implements a replication algorithm and provides a clean interface for the other software modules (or behaviors). To enable easy reconfiguration of strategies, an automata-based graphical description language has been developed, which can be compiled into code that uses the database and the lower level modules, such as tactics and positioning, to make decisions and control the robot. In addition, a graphical simulator has been developed in which the strategies can be evaluated.
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| 7. |
- Alén, Claes, 1949, et al.
(author)
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Test Embankments on Lime/Cement Stabilized Clay
- 2005
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In: Deep Mixing 05.
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Journal article (peer-reviewed)abstract
- In a large expansion of the infrastructure in Western Sweden a divided highway and a double railroad track for high speed trains are being planned in the Eastern part of the Göta river valley. Lime/cement columns were considered an attractive method for foundation in many of the cases. In order to improve the accuracy of the settlement calculations, which was considered crucial in the project, four test embankments were constructed. The results from these test embankments are reported in this paper. The embankments, which were constructed in two lifts, about a year and a half apart, were monitored in terms of settlement at the surface as well as at different depths. Measurements were taken in the columns as well as in the clay in between the columns and also below the stabilized soil. A number of piezometers were installed and also a couple of inclinometers. In the paper the overall behaviour of the stabilized soil is analysed and comparison with generally accepted assumptions is made. The results comprise an important base for another paper where a new approach to settlement calculations for lime/cement stabilized soil.
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| 8. |
- Allgardsson, Anders, et al.
(author)
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An unusual dimeric inhibitor of acetylcholinesterase : cooperative binding of crystal violet
- 2017
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In: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 22:9
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Journal article (peer-reviewed)abstract
- Acetylcholinesterase (AChE) is an essential enzyme that terminates cholinergic transmission by a rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for treatment of various cholinergic deficiencies, including Alzheimer's disease and myasthenia gravis. In a previous high throughput screening campaign, we identified the dye crystal violet (CV) as an inhibitor of AChE. Herein, we show that CV displays a significant cooperativity for binding to AChE, and the molecular basis for this observation has been investigated by X-ray crystallography. Two monomers of CV bind to residues at the entrance of the active site gorge of the enzyme. Notably, the two CV molecules have extensive intermolecular contacts with each other and with AChE. Computational analyses show that the observed CV dimer is not stable in solution, suggesting the sequential binding of two monomers. Guided by the structural analysis, we designed a set of single site substitutions, and investigated their effect on the binding of CV. Only moderate effects on the binding and the cooperativity were observed, suggesting a robustness in the interaction between CV and AChE. Taken together, we propose that the dimeric cooperative binding is due to a rare combination of chemical and structural properties of both CV and the AChE molecule itself.
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| 9. |
- Allgardsson, Anders, et al.
(author)
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Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-6
- 2016
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In: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 113:20, s. 5514-5519
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Journal article (peer-reviewed)abstract
- Organophosphorus nerve agents interfere with cholinergic signaling by covalently binding to the active site of the enzyme acetylcholinesterase (AChE). This inhibition causes an accumulation of the neurotransmitter acetylcholine, potentially leading to overstimulation of the nervous system and death. Current treatments include the use of antidotes that promote the release of functional AChE by an unknown reactivation mechanism. We have used diffusion trap cryocrystallography and density functional theory (DFT) calculations to determine and analyze prereaction conformers of the nerve agent antidote HI-6 in complex with Mus musculus AChE covalently inhibited by the nerve agent sarin. These analyses reveal previously unknown conformations of the system and suggest that the cleavage of the covalent enzyme-sarin bond is preceded by a conformational change in the sarin adduct itself. Together with data from the reactivation kinetics, this alternate conformation suggests a key interaction between Glu202 and the O-isopropyl moiety of sarin. Moreover, solvent kinetic isotope effect experiments using deuterium oxide reveal that the reactivation mechanism features an isotope-sensitive step. These findings provide insights into the reactivation mechanism and provide a starting point for the development of improved antidotes. The work also illustrates how DFT calculations can guide the interpretation, analysis, and validation of crystallographic data for challenging reactive systems with complex conformational dynamics.
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| 10. |
- Andersson, C. David, et al.
(author)
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Divergent Structure-Activity Relationships of Structurally Similar Acetylcholinesterase Inhibitors
- 2013
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In: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 56:19, s. 7615-7624
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Journal article (peer-reviewed)abstract
- The molecular interactions between the enzyme acetylcholinesterase (AChE) and two compound classes consisting of N-[2-(diethylamino)ethyl]benzenesulfonamides and N-[2-(diethylamino)ethyl]benzenemethanesulfonamides have been investigated using organic synthesis, enzymatic assays, X-ray crystallography, and thermodynamic profiling. The inhibitors' aromatic properties were varied to establish structure activity relationships (SAR) between the inhibitors and the peripheral anionic site (PAS) of AChE. The two structurally similar compound classes proved to have distinctly divergent SARs in terms of their inhibition capacity of AChE. Eight X-ray structures revealed that the two sets have different conformations in PAS. Furthermore, thermodynamic profiles of the binding between compounds and AChE revealed class-dependent differences of the entropy/enthalpy contributions to the free energy of binding. Further development of the entropy-favored compound class resulted in the synthesis of the most potent inhibitor and an extension beyond the established SARs. The divergent SARs will be utilized to develop reversible inhibitors of AChE into reactivators of nerve agent-inhibited AChE.
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