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- Andersson, Christer, 1982, et al.
(författare)
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Epitaxial and Layout Optimization of SiC Microwave Power Varactors
- 2011
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Ingår i: Asia-Pacific Microwave Conference Proceedings, APMC (APMC 2011 ;Melbourne, VIC; 5 - 8 December 2011). - 9780858259744 ; , s. 1642-1645
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Konferensbidrag (refereegranskat)abstract
- SiC Schottky diode varactors have been designed for use in tunable microwave power circuits. Epitaxial growth results show excellent material uniformity with low access layer sheet resistances. Two types of device layouts have been evaluated. Island type layouts reduce the parasitic series resistance by 50-60% compared to typical finger layouts. The Q-factors of downscaled island devices are approaching the intrinsic material performance, but are limited by an increasing parasitic parallel capacitance.
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- Carlsson, Anders, 1980-
(författare)
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Role of mast cells and probiotics in the regulation of intestinal barrier function
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The intestinal mucosa is the largest contact area and one of the most important barriers to the outside environment. It is highly specialized in aiding us digest and absorb nutrients. It is daily exposed to several potentially dangerous substances and microorganisms, which if they were allowed to pass into the body, could give rise to diseases. Throughout the small intestine certain sites specialized in antigen sampling are found. These sites are named Peyer’s patches and are lymphoid follicles. The epithelium covering the Peyer’s patches is called follicle-associated epithelium and is specialized in antigen sampling and uptake. The special epithelium enables presentation of luminal antigen to immune cells in the underlying follicle.Persistent life stress and stressful life events affect the course of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) through largely unknown mechanisms. Regulation of epithelial permeability to antigens is crucial for the balance between inflammation and immune-surveillance, and increased intestinal permeability has been shown in patients with ulcerative colitis and Crohns disease. Vasoactive intestinal polypeptide (VIP) and corticotropin-releasing factor have been implicated as important mediators of stress-induced abnormalities in intestinal mucosal functions in animal models. Both of these mediators have been reported to regulate bowel ion secretion in humans during stress and uptake of horseradish peroxidase in rodents. Probiotics have been shown to ameliorate the deleterious effects of stress on intestinal function, but mechanisms remain to be elucidated.The aim of this thesis was to elucidate whether mast cells play an important role in intestinal barrier function during stress and inflammation. Moreover, we wanted to determine whether probiotics can ameliorate the mucosal barrier integrity during stress and inflammation.To study the function of mast cells we conducted in vitro experiments on cell lines and ex vivo experiments in Ussing chambers on mouse, rat and human intestinal tissue. The Ussing chamber technique measures electrophysiological properties of the tissue and also gives the possibility to study transcellular and paracellular passage of markers and bacteria. Immunohistology and confocal microscopy have been used to identify mast cells and receptors of interest.Our results show that stress affects the follicle-associated epithelium barrier by mechanisms involving VIP and mast cells. These findings were corroborated by the localization of VIP receptors on mucosal mast cells. Furthermore, pretreatment with probiotics was effective in protecting the gut against stress-induced intestinal barrier dysfunction and mucosal inflammation. This protection appeared to involve a mast cell and peroxisome proliferatoractivated receptor-γ dependent mechanism.
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- Carlsson, Patrick, 1975-, et al.
(författare)
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The EI4 EPR centre in 6H SiC
- 2010
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Ingår i: Physica Scripta, Vol. T141. - : IOP Publishing. ; , s. 014013-
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Konferensbidrag (refereegranskat)abstract
- We present the results of our recent electron paramagnetic resonance (EPR) studies of the EI4 EPR centre in electron-irradiated high-purity semi-insulating 6H SiC. Higher signal intensities and better resolution compared with previous studies have enabled a more detailed study of the hyperfine (hf) structure. Based on the observed hf structure due to the interaction with Si and C neighbours, the effective spin S = 1, the C-1h-symmetry and the annealing behaviour, we suggest a carbon vacancy-carbon antisite complex in the neutral charge state, VCVCCSi0, with the vacancies and the antisite in the basal plane, as a new defect model for the centre.
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- Cöster, Maria C., et al.
(författare)
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Validation of Two Foot and Ankle Scores – SEFAS (Self-reported Foot And Ankle Score) and AOFAS
- 2014
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: The American Orthopedic Foot and Ankle Score (AOFAS) is for many foot and ankle surgeons the gold standard for evaluation of foot and ankle disorders. The score comprises of four different questionnaires depending on which region is evaluated, and covers three different constructs; pain, function and range of motion and alignment. AOFAS however, requires clinical examination, and can therefore not be used as a patient-reported outcome measure (PROM). In contrast, the Self-Reported Foot and Ankle Score (SEFAS) is a PROM that recently has been validated with good results in patients with foot and ankle disorders. The SEFAS contains 12 questions and covers different constructs such as pain, function and limitation of function. The aim of this study was to compare the SEFAS and AOFAS in patients with disorders in the great toe, the hindfoot and ankle, taking psychometric properties for scores into account.PATIENTS AND METHODS: The SEFAS and AOFAS scores were completed by 73 patients with disorders in the great toe and by 89 patients with disorders in the hindfoot or ankle. The time it took to complete the questionnaire was measured in 17 patients. In all patients, construct validity for SEFAS versus AOFAS was estimated by Spearman´s correlation coefficient and we also evaluated if there were any floor and ceiling effects. Test-retest reliability (intra-observer reliability) was measured for SEFAS in 68 patients and for AOFAS in 33 patients with intra-class correlation coefficient (ICC). Inter-observer reliability was calculated in nine patients for AOFAS using ICC. Responsiveness, i.e. the ability of a score to detect changes after a surgical intervention, was estimated by effect size (ES) and standardized response mean (SRM) in 120 patients for SEFAS and in 112 patients for AOFAS.RESULTS: The SEFAS was completed more than three times faster than AOFAS (165 seconds versus 515 seconds). SEFAS had good convergent validity (strong correlation) with AOFAS with a Spearman´s correlation coefficient of 0.64 in patients with great toe disorders and 0.65 in patients with hind foot/ankle disorders. There were no floor or ceiling effects in either of the scores. ICC was in patients with great toe disorders 0.94 (95% CI: 0.87-0.97) for SEFAS and 0.77 (95% CI: 0.39-0.93) for AOFAS, and in patients with hindfoot/ankle disorders 0.92 (95%CI: 0.85-0.95) for SEFAS and 0.52 (95%CI: 0.13-0.77) for AOFAS. ES was 1.4 for SEFAS and 1.8 for AOFAS and SRM 1.4 for SEFAS and 1.6 for AOFAS in patients with great toe disorders. ES was 1.2 for SEFAS and 1.1 for AOFAS and SRM 1.1 for SEFAS and 0.9 for AOFAS in patients with hindfoot/ ankle disorders. Inter-observer reliability was 0.43 (95% CI: 0.0-0.84) for AOFAS.DISCUSSION AND CONCLUSION: In this study there was a strong correlation between SEFAS and AOFAS indicating good construct validity for SEFAS. Both scores had good responsiveness and no floor or ceiling effects. The test-retest reliability was better for SEFAS than AOFAS while the inter-observer reliability was low for AOFAS. Finally, SEFAS was completed three times faster than AOFAS. In conclusion we consider SEFAS at least equal to AOFAS for evaluation of patients with foot and ankle disorders, and as no clinical examination is demanded in SEFAS, it is an ideal instrument for evaluation of clinical patient outcome in national registers.
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- Cöster, Maria, et al.
(författare)
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Validity, reliability, and responsiveness of the Self-reported Foot and Ankle Score (SEFAS) in forefoot, hindfoot, and ankle disorders
- 2014
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Ingår i: Acta Orthopaedica. - London : Informa Healthcare. - 1745-3674 .- 1745-3682. ; 85:2, s. 187-194
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: The self-reported foot and ankle score (SEFAS) is a questionnaire designed to evaluate disorders of the foot and ankle, but it is only validated for arthritis in the ankle. We validated SEFAS in patients with forefoot, midfoot, hindfoot, and ankle disorders.PATIENTS AND METHODS: 118 patients with forefoot disorders and 106 patients with hindfoot or ankle disorders completed the SEFAS, the foot and ankle outcome score (FAOS), SF-36, and EQ-5D before surgery. We evaluated construct validity for SEFAS versus FAOS, SF-36, and EQ-5D; floor and ceiling effects; test-retest reliability (ICC); internal consistency; and agreement. Responsiveness was evaluated by effect size (ES) and standardized response mean (SRM) 6 months after surgery. The analyses were done separately in patients with forefoot disorders and hindfoot/ankle disorders.RESULTS: Comparing SEFAS to the other scores, convergent validity (when correlating foot-specific questions) and divergent validity (when correlating foot-specific and general questions) were confirmed. SEFAS had no floor and ceiling effects. In patients with forefoot disorders, ICC was 0.92 (CI: 0.85-0.96), Cronbach's α was 0.84, ES was 1.29, and SRM was 1.27. In patients with hindfoot or ankle disorders, ICC was 0.93 (CI: 0.88-0.96), Cronbach's α was 0.86, ES was 1.05, and SRM was 0.99.INTERPRETATION: SEFAS has acceptable validity, reliability, and responsiveness in patients with various forefoot, hindfoot, and ankle disorders. SEFAS is therefore an appropriate patient- reported outcome measure (PROM) for these patients, even in national registries.
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- Dimopoulou, Angeliki, et al.
(författare)
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MDCT angiography with 3D image reconstructions in the evaluation of failing arteriovenous fistulas and grafts in hemodialysis patients
- 2011
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 52:9, s. 935-942
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Tidskriftsartikel (refereegranskat)abstract
- Background: Arteriovenous fistulas and grafts are the methods of choice for vascular access in renal failure patients in need of hemodialysis. Their major complication, however, is stenosis, which might lead to thrombosis. Purpose: To demonstrate the usefulness of 16-MDCTA with 3D image reconstructions, in long-term hemodialysis patients with dysfunctional arteriovenous fistulas and grafts (AVF and AVG). Material and Methods: During a 17-month period, 31 patients with dysfunctional AVF and AVG (24 AVF and seven AVG) were examined with MDCTA with 3D image postprocessing. Parameters such as comprehension of the anatomy, quality of contrast enhancement, and pathological vascular changes were measured. DSA was then performed in 24 patients. Results: MDCTA illustrated the anatomy of the AVF/AVG and the entire vascular tree to the heart, in a detailed and comprehensive manner in 93.5% of the evaluated segments, and depicted pathology of AVF/AVG or pathology of the associated vasculature. MDCTA demonstrated a total of 38 significant stenoses in 25 patients. DSA verified 37 stenoses in 24 patients and demonstrated two additional stenoses. MDCTA had thus a sensitivity of 95%. All 24 patients were treated with percutaneous transluminal angioplasty (PTA) with good technical results. Conclusion: MDCTA with 3D reconstructions of dysfunctioning AVFs and AVGs in hemodialysis patients is an accurate and reliable diagnostic method helping customize future intervention.
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