| 1. |
- Johansson, Linda, et al.
(författare)
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Surface acoustic wave induced particle manipulation in a PDMS channel : principle concepts for continuous flow applications
- 2012
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Ingår i: Biomedical microdevices (Print). - : Springer Science and Business Media LLC. - 1387-2176 .- 1572-8781. ; 14:2, s. 279-289
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Tidskriftsartikel (refereegranskat)abstract
- A device for acoustic particle manipulation in the40 MHz range for continuous-flow operation in a 50 μm wide PDMS channel has been evaluated. Unidirectionalinterdigital transducers on a Y-cut Z-propagation lithiumniobate wafer were used to excite a surface acoustic wavethat generated an acoustic standing wave inside the microfluidicchannel. It was shown that particle alignment nodeswith different inter-node spacing could be obtained,depending on device design and driving frequency. Theobserved inter-node spacing differed from the standard halfwavelengthinter-node spacing generally employed in bulkacoustic transducer excited resonant systems. This effectand the related issue of acoustic node positions relative thechannel walls, which is fundamental for most continuousflow particle manipulation operations in channels, wasevaluated in measurements and simulations. Specificapplications of particle separation and alignment wherethese systems can offer benefits relative state-of the artdesigns were identified.
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| 2. |
- Johansson, Linda, et al.
(författare)
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Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel
- 2012
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 22:2, s. 025018-
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Tidskriftsartikel (refereegranskat)abstract
- Surface acoustic wave (SAW) excitation of an acoustic field in a trapezoidal glass microfluidic channel for particle manipulation in continuous flow has been demonstrated. A unidirectional interdigital transducer (IDT) on a Y-cut Z-propagation lithium niobate (LiNbO3) substrate was used to excite a surface acoustic wave at approximately 35 MHz. An SU8 layer was used for adhesive bonding of the superstrate glass layer and the substrate piezoelectric layer. This work extends the use of SAWs for acoustic manipulation to also include glass channels in addition to prior work with mainly poly-di-methyl-siloxane channels. Efficient alignment of 1.9 mu m polystyrene particles to narrow nodal regions was successfully demonstrated. In addition, particle alignment with only one IDT active was realized. A finite element method simulation was used to visualize the acoustic field generated in the channel and the possibility of 2D alignment into small nodal regions was demonstrated.
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| 3. |
- Kronqvist, Nina, et al.
(författare)
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Sequential pH-driven dimerization and stabilization of the N-terminal domain enables rapid spider silk formation
- 2014
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 5:1, s. 3254-
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms controlling the conversion of spider silk proteins into insoluble fibres, which happens in a fraction of a second and in a defined region of the silk glands, are still unresolved. The N-terminal domain changes conformation and forms a homodimer when pH is lowered from 7 to 6; however, the molecular details still remain to be determined. Here we investigate site-directed mutants of the N-terminal domain from Euprosthenops australis major ampullate spidroin 1 and find that the charged residues D40, R60 and K65 mediate intersubunit electrostatic interactions. Protonation of E79 and E119 is required for structural conversions of the subunits into a dimer conformation, and subsequent protonation of E84 around pH 5.7 leads to the formation of a fully stable dimer. These residues are highly conserved, indicating that the now proposed three-step mechanism prevents premature aggregation of spidroins and enables fast formation of spider silk fibres in general.
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| 4. |
- Landreh, M., et al.
(författare)
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A pH-dependent dimer lock in spider silk protein
- 2010
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Ingår i: Journal of Molecular Biology. - : Academic Press. - 0022-2836 .- 1089-8638. ; 404:2, s. 328-336
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Tidskriftsartikel (refereegranskat)abstract
- Spider dragline silk, one of the strongest polymers in nature, is composed of proteins termed major ampullate spidroin (MaSp) 1 and MaSp2. The N-terminal (NT) domain of MaSp1 produced by the nursery web spider Euprosthenops australis acts as a pH-sensitive relay, mediating spidroin assembly at around pH 6.3. Using amide hydrogen/deuterium exchange combined with mass spectrometry (MS), we detected pH-dependent changes in deuterium incorporation into the core of the NT domain, indicating global structural stabilization at low pH. The stabilizing effects were diminished or abolished at high ionic strength, or when the surface-exposed residues Asp40 and Glu84 had been exchanged with the corresponding amides. Nondenaturing electrospray ionization MS revealed the presence of dimers in the gas phase at pH values below--but not above--6.4, indicating a tight electrostatic association that is dependent on Asp40 and Glu84 at low pH. Results from analytical ultracentrifugation support these findings. Together, the data suggest a mechanism whereby lowering the pH to <6.4 results in structural changes and alteration of charge-mediated interactions between subunits, thereby locking the spidroin NT dimer into a tight entity important for aggregation and silk formation.
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| 5. |
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| 6. |
- Askarieh, Glareh, et al.
(författare)
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Self-assembly of spider silk proteins is controlled by a pH-sensitive relay
- 2010
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 465:7295, s. 236-8
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Tidskriftsartikel (refereegranskat)abstract
- Nature's high-performance polymer, spider silk, consists of specific proteins, spidroins, with repetitive segments flanked by conserved non-repetitive domains. Spidroins are stored as a highly concentrated fluid dope. On silk formation, intermolecular interactions between repeat regions are established that provide strength and elasticity. How spiders manage to avoid premature spidroin aggregation before self-assembly is not yet established. A pH drop to 6.3 along the spider's spinning apparatus, altered salt composition and shear forces are believed to trigger the conversion to solid silk, but no molecular details are known. Miniature spidroins consisting of a few repetitive spidroin segments capped by the carboxy-terminal domain form metre-long silk-like fibres irrespective of pH. We discovered that incorporation of the amino-terminal domain of major ampullate spidroin 1 from the dragline of the nursery web spider Euprosthenops australis (NT) into mini-spidroins enables immediate, charge-dependent self-assembly at pH values around 6.3, but delays aggregation above pH 7. The X-ray structure of NT, determined to 1.7 A resolution, shows a homodimer of dipolar, antiparallel five-helix bundle subunits that lack homologues. The overall dimeric structure and observed charge distribution of NT is expected to be conserved through spider evolution and in all types of spidroins. Our results indicate a relay-like mechanism through which the N-terminal domain regulates spidroin assembly by inhibiting precocious aggregation during storage, and accelerating and directing self-assembly as the pH is lowered along the spider's silk extrusion duct.
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| 7. |
- Borell, Lena, et al.
(författare)
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Kognitiva köket - framtidens kök
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Äldre personer som har en demenssjukdom eller andra medicinska diagnoser som kan leda till kognitiva problem och som bor i egna hem är en växande grupp. Samtidigt så förväntas alla oavsett funktionsnedsättning kunna hantera matlagning och andra köksrelaterade aktiviteter på egen hand. Personer med kognitiva problem, och personer som arbetar med denna grupp definierar problem relaterade till matlagning och att hålla ordning i köket som några av de viktigaste att lösa (Wherton and Monk 2008). Att kunna utföra köksrelaterade aktiviteter betraktas som något som höjer livskvaliteten. Trots det växande behovet av att kunna skapa köksmiljöer och köksprodukter, både generellt och med individuella anpassningar, finns det i dag ingen samlad kunskap om hur sådana miljöer och produkter bäst kan utformas. I det här projektet ses köket som en plats där flera dimensioner av livet pågår. Förutom matlagning och förvaring av mat så är köket även en plats för socialt umgänge, och utgör vardagens nav. Kökets roll i hemmet är alltså central. Projektet utgår från att det är möjligt att skapa inkluderande köksmiljöer som tar hänsyn till personer med nedsatt kognition, men som samtidigt förenklar för alla. Modern design av kök handlar idag mycket om eleganta ytor och dolda, och därmed svårdefinierade, funktioner vilket skapar problem för personer med kognitiva funktionsnedsättningar. Dessa problem måste lyftas fram och diskuteras för att kunna utforma framtida inkluderande köksmiljöer. Syftet med projektet är att, i dialog med intressenter och experter inom området, sammanställa och generera kunskap om hur kök och köksprodukter kan designas för att underlätta för äldre människor med kognitiva nedsättningar att kunna använda sina kök utan problem.
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| 8. |
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| 9. |
- Cakici, Baki, 1984-
(författare)
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Disease surveillance systems
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent advances in information and communication technologies have made the development and operation of complex disease surveillance systems technically feasible, and many systems have been proposed to interpret diverse data sources for health-related signals. Implementing these systems for daily use and efficiently interpreting their output, however, remains a technical challenge. This thesis presents a method for understanding disease surveillance systems structurally, examines four existing systems, and discusses the implications of developing such systems. The discussion is followed by two papers. The first paper describes the design of a national outbreak detection system for daily disease surveillance. It is currently in use at the Swedish Institute for Communicable Disease Control. The source code has been licenced under GNU v3 and is freely available. The second paper discusses methodological issues in computational epidemiology, and presents the lessons learned from a software development project in which a spatially explicit micro-meso-macro model for the entire Swedish population was built based on registry data.
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| 10. |
- Cappel, Ute B., et al.
(författare)
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Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:10, s. 4345-4358
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Tidskriftsartikel (refereegranskat)abstract
- We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO2/dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO2 but that there are states in the band gap of TiO2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO2, when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2-,7,7-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.
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