| 1. |
- Bergkvist, Sara, et al.
(författare)
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Transition from a two-dimensional superfluid to a one-dimensional mott insulator
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:11, s. 110401-1-110401-5
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional system of atoms in an anisotropic optical lattice is studied theoretically. If the system is finite in one direction, it is shown to exhibit a transition between a two-dimensional superfluid and a one-dimensional Mott insulating chain of superfluid tubes. Monte Carlo simulations are consistent with the expectation that the phase transition is of Kosterlitz-Thouless type. The effect of the transition on experimental time-of-flight images is discussed.
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| 2. |
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| 3. |
- Krarup, Peter-Martin, et al.
(författare)
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Rapid morphological changes and loss of collagen following experimental acute colonic obstruction
- 2013
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Ingår i: International Journal of Colorectal Disease. - : Springer Science and Business Media LLC. - 1432-1262 .- 0179-1958. ; 28:3, s. 341-347
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Tidskriftsartikel (refereegranskat)abstract
- Anastomosis of an acutely obstructed colon is associated with an increased risk of dehiscence. In experimental models, acute obstruction decreases collagen in the colonic wall, but the time course and propagation along the colon of the biochemical changes are unknown. Furthermore, there is a paucity of information on the correlation between these biochemical changes and histological features. Forty male Sprague Dawley rats were subjected to partial obstruction by placing a silicone ring around the left colon 30 mm above the reflection. Obstruction was maintained for 0, 1, 2, 3 or 4 days. Samples from five different locations along the colon were analysed on circumference, tissue water content, collagen concentration and histomorphology. Neutrophil and macrophage infiltration was characterized immunohistochemically. The colonic circumference and water content increased (p < 0.001), while the collagen concentration decreased by 48 % (p < 0.01) proximal to the obstruction already after 1 day. The degree of dilation and collagen reduction did not change significantly over the subsequent 3 days of obstruction, whereas the water content normalized by day 3. Mucosal and submucosal oedema and the relative neutrophil infiltration were highest after 1 day in the colonic segment proximal to the stenosis while the macrophage population continued to increase to day 4. Muscular necrosis in addition to ganglionitis and neuritis in the nervous plexus increased with duration of obstruction. The pronounced and rapid changes of the composition of cells and the extracellular matrix of the colonic wall following acute obstruction may be of guidance for present surgical treatments and future pharmacological interventions.
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| 4. |
- Rehn, Magnus, 1972-
(författare)
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Experimental and Numerical Investigations of Ultra-Cold Atoms
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I have been one of the main responsible for building a new laboratory for Bose-Einstein condensation with 87Rb. In particular, the experimental setup has been designed for performing experiments with Bose-Einstein condensates load into optical lattices of variable geometries. All parts essential for Bose-Einstein condensation are in place. Atoms are collected in a magneto-optical trap, transferred to another vacuum chamber, with better vacuum, and trapped in another magneto-optical trap. Atoms are successfully transferred to a dark magnetic trap, and system for diagnostics with absorption imaging has been realized. We have not yet been able to form a Bose-Einstein condensate, due to a range of technical difficulties. Equipment for alignment of optical lattices with flexible geometry has been designed, built, and tested. This tool has been proven to work as desired, and there is a great potential for a range of unique experiments with Bose-Einstein condensates in optical lattices of various geometries, including superlattices and quasi-periodic lattices. Numerical studies have been made on anisotropic optical lattices, and the existence of a transition between a 2D superfluid phase and a 1D Mott-insulating phase has been confirmed. We have shown that the transition is of Berezinskii-Kosterlitz-Thouless type. In another numerical study it has been shown that using stimulated Raman transitions is a practical method for transferring atoms between states in a double optical lattice. Thus, it will be possible to transfer populations between the lattices, with further applications in qubit read/write operations.
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| 5. |
- Rehn, Martin, et al.
(författare)
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GM6001 Increases Anastomotic Leakage following Colonic Obstruction Possibly by Impeding Epithelialization.
- 2015
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Ingår i: Surgical Infections. - : Mary Ann Liebert Inc. - 1557-8674 .- 1096-2964. ; 16:6, s. 702-708
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Tidskriftsartikel (refereegranskat)abstract
- Emergency operations performed on an obstructed colon are accompanied by an increased risk of anastomotic insufficiency. Tissue-destructive matrix metalloproteinase (MMP) activity is elevated in the obstructed colon and contributes to a loss of suture-holding submucosal collagen, which may be mediated by tumor necrosis factor (TNF)-α. Our aim was to study the effect of the non-selective MMP and TNF-α converting enzyme (TACE) inhibitor GM6001 (30 mg/kg) on anastomosis repair in obstructed left colon. GM6001 has been proved to be highly efficacious in elective anastomosis rodent models.
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| 6. |
- Rehn, Magnus, 1972-, et al.
(författare)
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One-dimensional phase transitions in a two-dimensional optical lattice
- 2008
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 49:2, s. 223-230
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Tidskriftsartikel (refereegranskat)abstract
- A phase transition for bosonic atoms in a two-dimensional anisotropic optical lattice is considered. If the tunnelling rates in two directions are different, the system can undergo a transition between a two-dimensional superfluid and a one-dimensional Mott insulating array of strongly coupled tubes. The connection to other lattice models is exploited in order to better understand the phase transition. Critical properties are obtained using quantum Monte Carlo calculations. These critical properties are related to correlation properties of the bosons and a criterion for commensurate filling is established.
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| 7. |
- Rehn, Martin, 1975-
(författare)
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Some computational aspects of attractor memory
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis I present novel mechanisms for certain computational capabilities of the cerebral cortex, building on the established notion of attractor memory. A sparse binary coding network for generating efficient representation of sensory input is presented. It is demonstrated that this network model well reproduces receptive field shapes seen in primary visual cortex and that its representations are efficient with respect to storage in associative memory. I show how an autoassociative memory, augmented with dynamical synapses, can function as a general sequence learning network. I demonstrate how an abstract attractor memory system may be realized on the microcircuit level -- and how it may be analyzed using similar tools as used experimentally. I demonstrate some predictions from the hypothesis that the macroscopic connectivity of the cortex is optimized for attractor memory function. I also discuss methodological aspects of modelling in computational neuroscience.
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| 8. |
- Saers, Robert, 1977-, et al.
(författare)
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A set-up for flexible geometry optical lattices
- 2008
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Ingår i: European Physical Journal. - : EDP Sciences. - 1286-0042 .- 1286-0050. ; 42:3, s. 269-273
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an alignment tool for optical lattices with arbitrary beam angles, allowing for optical potentials with a range of geometries and topographies. A calibration procedure has been introduced, giving a precision of 10 mrad in the chosen beam angle, and a high degree of flexibility. The tool has been tested in simplified experiments on the confinement and expansion of cold atoms in one-dimensional and two-dimensional optical lattices, and has proved to work well.
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| 9. |
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| 10. |
- Verbova, Marina, et al.
(författare)
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Normalårskorrigering av fossil CO2-emission från fastighetsuppvärmning och elproduktion 2013-2014 varav 2014 avser preliminära data : Resultatredovisning för perioden 1990-2014
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapportering av normalårskorrigerade fossila koldioxidutsläpp (CO2) utgör inget krav inom rapporteringen till UNFCCC, men de rapporterade länderna uppmuntras att genomföra en sådan rapportering. I Sverige finns starka önskemål från Miljödepartementet att genomföra denna rapportering. Genom en av SMED utvecklad metodik har Sverige årligen fr.o.m. submission 2001 redovisat normalårskorrigerade utsläpp från fastighetsuppvärmning och elproduktion för perioden 1990-”aktuellt år”.Metoden har successivt utvecklats sedan år 2004. Metoden omfattar en normalårskorrigering av utsläppen av fossil koldioxid som sammanhänger dels med svenska väderförhållanden som påverkar den totala fastighetsuppvärmningen, dels med variationer i tillgången på vattenkraft som påverkar elproduktionen.Väderförhållandena i Sverige varierar mycket mellan åren. Temperatur, instrålning och vind påverkar hur mycket energi som krävs för att värma upp fastigheter för att hålla normal inomhustemperatur. Nederbörden påverkar hur mycket vatten som rinner i vattendragen och därmed möjligheten att producera el med vattenkraft. Med SMHI:s ENLOSS-modell som grund görs beräkningar över hur behovet av fastighetsuppvärmning varierar för olika delar av Sverige och mellan olika år. Energibehovet ett visst år, jämfört med en 30-årig normalperiod (1965-1995), uttrycks i form av ett s.k. EnergiIndex. Dessa beräkningar kombineras därefter med bränslestatistik för fastighetsuppvärmning och elproduktion samt emissionsfaktorer för fossil CO2 för olika bränslen.För samtliga år under perioden 1990 – 2014, utom 1996 och 2010, har den summerade normalårskorrigerade fossila CO2-emissionen från fastighetsuppvärmning och elproduktion varit större än den verkliga. Detta sammanhänger med att milda vintrar och nederbördsrika år dominerat under perioden, som lett till ett mindre uppvärmningsbehov, mindre behov av fossileldad elproduktion och därmed mindre utsläpp av koldioxid än under ett normalt år.Trenden för den verkliga fossila CO2-emissionen är i stora drag fortsatt nedåtgående. Den normalårskorrigerade årliga fossila CO2-emissionen låg ungefär konstant under perioden 1990-1999. Värdena halverades i det närmaste under den efterföljande 10-årsperioden (alltså fram till 2009). Detta orsakades av bland annat en successivt ökad användning av icke-fossil energi, främst baserad på biobränsle. Trenden bryts av en ökning av den normalårskorrigerade årliga fossila CO2-emissionen 2010 och 2011, för att återgå i den nedangående trenden år 2012. År 2013 är utsläppen de lägsta under hela tidserien (sedan 1990).År 2014 var ett rekordvarmt år i Sverige och i praktiskt taget hela Sverige har varit soligare än normalt. Den höga årsmedeltemperaturen har skapats av långa perioder med varmt eller mycket varmt väder, och få perioder med ovanligt kallt väder. Användning av fossila bränslen för uppvärmning av fastigheter och produktion av el minskar en del jämfört med 2013, men den normalårskorrigerade CO2-emissionen skiljer sig inte nämnvärt åt mellan 2014 och 2013. Den stadiga nedgången i normalårskorrigerad CO2-emission mellan 1999 och 2009 förefaller därmed alltmer ha övergått i en utplaning under den senaste femårsperioden.
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