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| 2. |
- Eriksson, Rolf, 1979-
(författare)
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The Utility of Manganese for Magnetic Resonance Imaging of Transient Myocardial Ischemia
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to improve the diagnosis of coronary artery disease, better methods for detection of myocardial perfusion defects would be useful. One of the methods used for myocardial perfusion evaluation today is magnetic resonance imaging. This method could be improved if a contrast agent that induced long-lasting contrast enhancement in the myocardium could be developed. The paramagnetic manganese(II) ion has promising properties for meeting this need, since it enters cardiomyocytes through voltage-gated calcium channels and remains inside the cells for a long time after an intravenous injection. If these properties can be utilized, manganese-enhanced MRI has potential for detecting transient periods of ischemia in a manner similar to the conventional SPECT stress test.To investigate the contrast-enhancing properties of the manganese(II) ion, a series of experiments was performed in pigs, using a manganese salt (MnCl2) and two manganese-based chelates (MnDPDP and MnHPTA) and measuring the longitudinal relaxation rates before and after contrast agent administration. This was done in normal pig myocardium at rest and during dobutamine-induced stress with several different doses of contrast agent, and in a model for coronary artery stenosis using MnCl2 administered during dobutamine stress to determine whether transient ischemia could be detected with this contrast agent.The results of these experiments showed that of the three contrast agents, MnCl2 induces the greatest increase in ΔR1, followed by MnHPTA. Using MnCl2 it was possible to produce images on which transient myocardial ischemia was visible, but only during the first 30 minutes after contrast agent injection.The stenosis model is still far from the clinical situation and several complications, including the potential toxicity of the manganese(II) ion, remain to be overcome. However, the results from this model are promising for the future development of manganese- enhanced magnetic resonance imaging of transient myocardial ischemia.
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| 3. |
- Hedström, Erik, et al.
(författare)
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Importance of perfusion in myocardial viability studies using delayed contrast-enhanced magnetic resonance imaging
- 2006
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 24:1, s. 77-83
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate whether an extracellular gadolinium-(Gd)-based contrast agent (CA) enters nonperfused myocardium during acute coronary occlusion, and whether nonperfused myocardium presents as hyperintense in delayed contrast-enhanced (DE) MR images in the absence of CA in that region. MATERIALS AND METHODS: The left anterior descending coronary artery (LAD) was occluded for 200 minutes in six pigs. The longitudinal relaxation rate (R(1)) in blood, perfused myocardium, and nonperfused myocardium was repeatedly measured using a Look-Locker sequence before and during the first hour after administration of Gd-DTPA-BMA. RESULTS: While blood and perfused myocardium showed a major increase in R(1) after CA administration, nonperfused myocardium did not. R(1) in nonperfused myocardium was significantly lower than in blood and perfused myocardium during the first hour after CA administration. When the signal from perfused myocardium was nulled, demarcation of the hyperintense nonperfused myocardium was achieved in all of the study animals. CONCLUSION: Gd-DTPA-BMA does not enter ischemic myocardium within one hour after administration during acute coronary occlusion. The ischemic region with complete absence of CA still appears bright when the signal from perfused myocardium is nulled using inversion-recovery DE-MRI. This finding is important for understanding the basic pathophysiology of inversion-recovery viability imaging, as well as for imaging of acute coronary syndromes.
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| 4. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Synthesis and structural characterization of perovskite type proton conducting BaZr1-xInxO3-delta (0.0 <= x <= 0.75)
- 2006
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 177:17-18, s. 1395-1403
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Tidskriftsartikel (refereegranskat)abstract
- Solid state sintering has been used to prepare the cubic perovskite structured compounds BaZr1-xInxO3-delta (0.0 <= x <= 0.75). Analysis of X-ray powder diffraction (XRPD) data reveals that the unit cell parameter, a, increases linearly with an increased Indium concentration. XRPD data was also used to demonstrate the completion of sample hydration, which was reached when the materials showed a set of single-phase Bragg-peaks. Dynamic thermogravimetric analysis (TGA) data showed that approx. 89% of the total number of available oxygen vacancies can be filled in BaZr1-xInxO3-delta for x=0.50, and that the maximum water uptake occurs below 300 degrees C. Rietveld analysis of the room temperature neutron powder diffraction (NPD) data confirmed the average cubic symmetry (space group Pm-3m), and an expansion of the unit cell parameter after the hydration reaction. The strong O-H stretch band, 2500-3500 cm(-1), in the infrared absorbance spectrum clearly manifests the presence of protons in the hydrated material. Proton conductivity of hydrated BaZr1-xInxO3-delta, x=0.75 was investigated during heating and cooling cycles under dry argon atmosphere. The total conductivity during the heating cycle was nearly two orders of magnitude greater than that of cooling cycle at 300 degrees C, whilst these values were similar at higher temperatures i.e. T > 600 degrees C.
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| 5. |
- Andersson, Andreas, 1980-
(författare)
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Utmattningsanalys av järnvägsbroar : En fallstudie av stålbroarna mellan Stockholm Central och Söder Mälarstrand, baserat på teoretiska analyser och töjningsmätningar
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Föreliggande avhandling omfattar en fallstudie av utmattningsrisken för järnvägsbroarna mellan Stockholm Central och Söder Mälarstrand. Ett stort antal utmattningssprickor i broarna över Söderström och Söder Mälarstrand har sedan länge varit kända. I samband med en bärighetsutredning av sträckan har ett stort antal anslutningspunkter i samtliga broar identifierats som kritiska avseende utmattningsrisk. Sträckan är den mest trafikerade i Sverige och de förenklade beräkningsmetoder som anges i Banverkets föreskrift för bärighetsberäkningar är i vissa fall inte tillämpliga. De formella bärighetsberäkningarna har visat på flerfaldiga överskridanden i utnyttjandegrad gällande utmattning. I de punkter som beräkningarna visar störst risk för utmattning har inga sprickor påträffats, trots omfattande förbandsbesiktningar. Beräkningarna baseras på typiserade spänningskollektiv och givet antal spänningsväxlingar, oberoende av den aktuella trafikmängden. Enligt bärighetsnormen ges möjlighet att beakta den verkliga trafikmängden baserat på historiskt bruttotonnage och typiserade trafiklaster. Dessa beräkningar har utförts och visar på ännu större risk för utmattning, jämfört med den förenklade metoden. I syfte att på ett ännu mer nyanserat sätt uppskatta utmattningsrisken har en metod använts, baserat på uppskattning av den faktiska trafikmängden och dess fördelningar. Beräkningarna baseras på trafikdata tillgänglig från Banverket. Metoden är tillämplig på andra järnvägsbroar på andra sträckor. Utöver teoretiska beräkningar har töjningsmätningar utförts. Under 2006 utförde dåvarande Carl Bro AB töjningsmätningar på bro över Söder Mälarstrand och viadukt söder om Söder Mälarstrand, avseende några enskilda tågöverfarter. Under 2008 utförde KTH Brobyggnad omfattande töjningsmätningar på bro över Söderström, avseende all trafik under en månads tid.
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| 6. |
- Andersson, Linda, et al.
(författare)
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De-aluminated zeolite Y as a Tool to Study Endocytosis, A Delivery System Revealing Differences between Human Peripheral Dendritic Cells
- 2007
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Ingår i: Scandinavian Journal of Immunology. - : Blackwell Publishing. - 0300-9475 .- 1365-3083. ; 66:1, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- We report the use of nano-meter sized zeolite particles as a novel approach to follow the endosomal acidification and proteolysis inside a viable cell. The method was verified by using human peripheral monocytes, a well known endocytosing cell population. Zeolite particles were subsequently used to investigate the endocytosing mechanisms of human peripheral dendritic cells (DCs). Probes detecting pH neutral and acidic endosomes were adsorbed to de-aluminated zeolite Y, and used to detect endocytosis in immature human peripheral blood DCs. Both the myeloid (mDCs) and the plasmacytoid (pDCs) dendritic cell subsets had an endocytosing capacity comparable to peripheral blood monocytes. However, the majority of both subsets of DCs retained their endosomes at a neutral pH during the first hours after endocytosis and only a small number of the mDCs showed any formation of acidic endosomes.Proteolytic degradation of endocytosed proteins was detected using self-quenched DQ-ovalbumin adsorbed to zeolite particles. Interestingly, a clear difference in proteolytic degradation of endocytosed ovalbumin was observed between the two subsets of DCs. The mDC showed an efficient degradation of ovalbumin, while the pDC population displayed no or only minor proteolytic degradation. In conclusion, zeolite particles provide a useful tool to study the endocytosing mechanisms, and an efficient carrier of bio-molecules into the endosomal pathways of viable cells.
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| 7. |
- Andersson, Linda, et al.
(författare)
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Detection of endocytosis using de-aluminated zeolite
- 2006
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nano-meter sized particles of de-aluminated zeolite Y has a high adsorption capacity of both low molecular weight bio-molecules and macromolecules. In this study we used de-aluminated zeolite Y as a novel approach to study the mechanisms of endocytosis in immature human peripheral blood dendritic cells (DCs). Probes detecting pH neutral and acidic endosomes were adsorbed to the zeolite and used as a tracer of the endosomal pathway of a cell in the form of acidification and lysosomal function. Both the myeloid (M-DCs) and the plasmacytoid (P-DCs) dendritic cell subsets showed an endocytosing capacity comparable to peripheral blood monocytes but only the M-DCs were able to form acidic endosomes after internalization of zeolite particles. Furthermore, during lipopolysaccharide (LPS) stimulation of the DCs population, an enhanced induction of acidic endosomes was only seen in the M-DC population. Proteolytic degradation of endocytosed proteins was detected using self-quenched DQ-ovalbumin adsorbed to zeolite particles and our results showed a clear difference between the two DC populations. The M-DC population, that showed formation of acidic endosomes, also showed proteolytic degradation of ovalbumin. The P-DC population on the other hand, showed no formation of acidic and no proteolytic degradation of ovalbumin. Various bio-molecules can be adsorbed by de-aluminated zeolites and in conclusion we propose the use of zeolite particles as a useful tool in the study of the endocytosing mechanisms of a cell.
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| 8. |
- Andersson, Linda, et al.
(författare)
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Receptor-mediated endocytosis of particles by peripheral dendritic cells
- 2008
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Ingår i: Human Immunology. - : Elsevier BV. - 0198-8859 .- 1879-1166. ; :69, 625-633, 2008
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Tidskriftsartikel (refereegranskat)abstract
- Human peripheral dendritic cells (DCs) are antigen-presenting cells with the ability to internalize antigen and present antigen-derived peptides to T cells. Human DCs express several receptors on the surface for endocytosis and other recognition receptors that bind to microbes or microbial products, which are internalized and processed. Here, we report the use of nanometer-size zeolite particles as a tool to study receptor-mediated endocytosis by the two subsets of immature DCs, myeloid (mDC) and plasmacytoid (pDC) dendritic cells. A major difference in receptor-mediated endocytosis was observed between the two populations of peripheral DCs. The pDC population demonstrated an almost complete lack of receptor-mediated endocytosis of zeolite particles, whereas the mDC population demonstrated a clear receptor-mediated endocytosis. Fc receptors are expressed by both peripheral DC populations and lipoteichoic acid (LTA) and lipopolysaccharide (LPS) are known ligands of the Toll-like receptor (TLR)-2 and TLR4, respectively, both TLRs expressed by human mDCs. An efficient receptormediated endocytosis of immunoglobulin G-, LTA-, and LPS-coated zeolite particles was observed by the mDC population and their endocytosing capacity depended strongly on the density of the ligand adsorbed onto the zeolite particles. In conclusion, an efficient receptor-mediated endocytosis was observed from the mDC population, whereas the pDCs demonstrated an almost complete lack of receptor-mediated endocytosis and nanometer-size dealuminated zeolite particles were a useful tool for studying receptor-mediated endocytosis in human peripheral DCs.
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| 9. |
- Andersson, Roy, et al.
(författare)
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Similarities and differences between TQM, six sigma and lean
- 2006
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Ingår i: TQM Magazine. - : Emerald. - 0954-478X .- 1758-6887. ; 18:3, s. 282-296
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Purpose – During the last decades, different quality management concepts, including total quality management (TQM), six sigma and lean, have been applied by many different organisations. Although much important work has been documented regarding TQM, six sigma and lean, a number of questions remain concerning the applicability of these concepts in various organisations and contexts. Hence, the purpose of this paper is to describe the similarities and differences between the concepts, including an evaluation and criticism of each concept.Design/methodology/approach – Within a case study, a literature review and face‐to‐face interviews in typical TQM, six sigma and lean organisations have been carried out.Findings – While TQM, six sigma and lean have many similarities, especially concerning origin, methodologies, tools and effects, they differ in some areas, in particular concerning the main theory, approach and the main criticism. The lean concept is slightly different from TQM and six sigma. However, there is a lot to gain if organisations are able to combine these three concepts, as they are complementary. Six sigma and lean are excellent road‐maps, which could be used one by one or combined, together with the values in TQM.Originality/value – The paper provides guidance to organisations regarding the applicability and properties of quality concepts. Organisations need to work continuously with customer‐orientated activities in order to survive; irrespective of how these activities are labelled. The paper will also serve as a basis for further research in this area, focusing on practical experience of these concepts.
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| 10. |
- Bergenfelz, Anders, et al.
(författare)
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Impact of modern techniques on short-term outcome after surgery for primary hyperparathyroidism: a multicenter study comprising 2,708 patients.
- 2009
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Ingår i: Langenbeck's archives of surgery / Deutsche Gesellschaft für Chirurgie. - : Springer Science and Business Media LLC. - 1435-2451 .- 1435-2443. ; 394:5, s. 851-60
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Tidskriftsartikel (refereegranskat)abstract
- Preoperative localization procedures and the use of intraoperative parathyroidism (iOPTH) have led to a shift of paradigm from bilateral neck exploration to focused parathyroidectomy in primary hyperparathyroidism (pHPT). However, only a small number of randomized trials from specialized centers have been published. The main purpose of the study was to analyze the impact of localization procedures and iOPTH on short-term outcome after pHPT surgery in a multi-institutional setting.
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