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- Ohlsson, Sophie, et al.
(författare)
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Increased circulating levels of proteinase 3 in patients with anti-neutrophilic cytoplasmic autoantibodies-associated systemic vasculitis in remission.
- 2003
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Ingår i: Clinical and Experimental Immunology. - : Oxford University Press (OUP). - 0009-9104 .- 1365-2249. ; 131:3, s. 528-535
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Tidskriftsartikel (refereegranskat)abstract
- In systemic small vessel vasculitides, patients form autoantibodies against neutrophil granular proteins, anti-neutrophilic cytoplasmic autoantibodies (ANCA). Some correlation is seen between ANCA titre and disease activity, but whether this is cause or effect is still unknown. It has been reported that levels of proteinase 3 (PR3), one of the main ANCA antigens, are increased in patients with active disease. An increased level of circulating antigen could mean a predisposition to autoimmunity. In order to explore this we measured PR3 levels in patients with stable disease. In addition we measured neutrophil gelatinase-associated lipocalin (NGAL) as a specific marker of neutrophil degranulation, cystatin C as a marker of renal function as well as C-reactive protein (CRP), IL-6 and sTNFr1 as markers of inflammation. PR3, NGAL, IL-6 and sTNFr1 were measured in plasma by the ELISA technique. In the PR3 ELISA, we used anti-PR3 monoclonal antibodies as capture-antibodies and affinity-purified rabbit-anti-PR3 antibodies for detection. PR3-ANCA, myeloperoxidase (MPO)-ANCA, CRP and cystatin C were measured by routine methods. PR3 was significantly raised (P < 0·0001) in vasculitis patients (median 560 µg/l, range 110–3940, n = 59) compared with healthy blood donors (350 µg/l, 110–580, n = 30) as well as disease controls (360, 110–580, n = 46). No correlation was seen with disease activity, inflammation or renal function. The raised NGAL levels correlated strongly with decreased renal function (r = 0·8, P < 0·001). After correcting for this, slightly increased levels (110, 42–340, n = 59) were observed compared with healthy blood donors (81, 38–130, n = 25), but not compared with the disease controls (120, 57–260, n = 48). In the disease controls, there was a significant correlation between NGAL and proteinase 3 (r = 0·3, p < 0·05), but this was not the case in the vasculitis patients. Whether patients had PR3-ANCA or MPO-ANCA was of no significance. In our measurements, we found significantly raised levels of PR3 in plasma from patients with small vessel vasculitis, regardless of ANCA specificity. This was not due to decreased renal function, ongoing inflammation or neutrophil activation. Plausible mechanisms for this include defects in the reticuloendothelial system, genetic factors and selective neutrophil degranulation or leakage.
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- Grotz, Joel, 1974-
(författare)
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Interference Mitigation and Synchronization for Satellite Communications
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within this thesis, the satellite broadcast scenario of geostationary satellites is reviewed. The densely crowded geostationary arc in the common broadcast frequencies may create significant interference from adjacent satellites (ASI). The possible use of multiple-input receivers and of interference processing techniques is analyzed in this specific context. In addition the synchronization problem is studied under interference limited conditions for broadcast as well as broadband satellite systems.We address fixed satellite broadcast reception with the goal of decreasing the aperture of the receiving antenna. The front-end antenna size is commonly defined by the presence of interference from adjacent satellites. A small antenna aperture leads to interference from neighboring satellites utilizing the same frequency bands. We propose a multi-input reception system with subsequent joint detection which provides reliable communication in the presence of multiple interfering signals. An iterative least square technique is adopted combining spatial and temporal processing. This approach achieves robustness against pointing errors and against changing interference scenarios. Different temporal interference processing methods are evaluated, including Minimum Mean Square Error (MMSE) based iterative soft-decision interference cancellation as well as Iterative Least Square with Projection (ILSP) based approaches, which include spatial and temporal iterations. Furthermore the potential of an additional convolutional channel decoding step in the interference cancellation mechanism is verified.Also, we demonstrate how to accurately synchronize the signals as part of the detection procedure. The technique is evaluated in a realistic simulation study representing the conditions encountered in typical broadcast scenarios.In a second part of the thesis the problem of synchronization is reviewed in the context of interference limited scenarios for broadband satellite return channels. Spectral efficiency is of great concern in the return channel of satellite based broadband systems. In recent work the feasibility of increased efficiency by reducing channel spacing below the Symbol Rate was demonstrated using joint detection and decoding for a synchronized system. We extend this work by addressing the critical synchronization problem in the presence of adjacent channel interference (ACI) which limits performance as carrier spacing is reduced.A pilot sequence aided joint synchronization scheme for a multi-frequency time division multiple access (MF-TDMA) system is proposed. Based on a maximum likelihood (ML) criterion, the channel parameters, including frequency, time and phase are jointly estimated for the channel of interest and the adjacent channels. The impact of ACI on the synchronization and detection performance is investigated. It is shown that joint channel parameter estimation outperforms single carrier synchronization with reasonable additional computational complexity in the receiver. Based on the proposed synchronization scheme in conjunction with an appropriate joint detection mechanism the carrier spacing can be reduced significantly compared to current systems providing a substantial increase in spectral efficiency
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- Berne, Sofia, 1977, et al.
(författare)
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Cyberbullying assessment instruments: A systematic review
- 2013
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Ingår i: Aggression and Violent Behavior. - : Elsevier BV. - 1359-1789. ; 2013:18, s. 320-334
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Tidskriftsartikel (refereegranskat)abstract
- Although several instruments to assess cyberbullying have been developed, there is nevertheless a lack of knowledge about their psychometric properties. The aim of the present systematic review is to provide a representative overview of the current instruments designed to assess cyberbullying. Further, emphasis will be placed on the structural and psychometric properties of cyberbullying instruments, such as validity and reliability, as well as their conceptual and definitional basis. It will also provide criteria for readers to evaluate and choose instruments according to their own aims. A systematic literature review, limited to publications published prior to October 2010, generated 636 citations. A total of 61 publications fulfilled the delineated selection criteria and were included in the review, resulting in 44 instruments. Following a rater training, relevant information was coded using a structured coding manual. The raters were the nine authors of this review. Almost half of the instruments included in this review do not use the concept cyberbullying. The constructs measured by the instruments range from internet harassment behavior to electronic bullying behavior to cyberbullying. Even though many of the authors use other concepts than cyberbullying they claim that their instruments do measure it. For the purpose of this systematic review, we have chosen to categorize them as two different groups, cyberbullying instruments and related instruments. Additionally, most of the included instruments had limited reports of reliability and validity testing. The systematic review reveals a need for investigating the validity and reliability of most of the existing instruments, and resolving the conceptual and definitional fluctuations related to cyberbullying.
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- Hast, Anders, 1966-
(författare)
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Improved Algorithms for Fast Shading and Lighting
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shading is a technique that is used in computer graphics to make faceted objects appear smooth and more realistic. In the research presented in this thesis we have investigated how shading can be generated as efficiently as possible without sacrificing quality.In the classical approach to high quality shading proposed by Phong, the illumination equation is computed per pixel using an interpolated normal. The normals at the vertices are bi-linearly interpolated over the polygon to obtain a normal per pixel. Correct shading requires normalization of these normals, which is computationally demanding involving a square root. In our research we have shown how this normalization can be eliminated through the use of spherical interpolation and the Chebyshev recurrence formula, reducing the calculation to a few single arithmetic operations per pixel.Still a substantial setup operation is needed for each scanline. We have studied how also this can be made more efficient, with some limited progress so far. An alternative approach is to do the most of the setup on polygon level and incrementally compute the setup needed per scanline. In particular, we have studied quadratic shading approaches, i.e. fitting second degree surfaces to the polygons. The most successful approach has been through what we have called X-shading, where the setup is calculated by using an efficient approximation for the mid-edge normals. This setup is about four times faster than previously known methods.In the process of studying shading methods we have also made some contributions to improving bump-mapping and simulation of different kinds of light sources.The developed methods will be of interest in future generations of computer graphics software and hardware systems, ranging from high end systems to generate realistic movies and 3D games, to handheld devices such as mobile phones with graphics displays.
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- Hitczenko, Pawel, et al.
(författare)
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Weighted Random Staircase Tableaux
- 2014
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Ingår i: Combinatorics, probability & computing. - 0963-5483 .- 1469-2163. ; 23:6, s. 1114-1147
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns a relatively new combinatorial structure called staircase tableaux. They were introduced in the context of the asymmetric exclusion process and Askey-Wilson polynomials; however, their purely combinatorial properties have gained considerable interest in the past few years. In this paper we further study combinatorial properties of staircase tableaux. We consider a general model of random staircase tableaux in which symbols (Greek letters) that appear in staircase tableaux may have arbitrary positive weights. (We consider only the case with the parameters u = q = 1.) Under this general model we derive a number of results. Some of our results concern the limiting laws for the number of appearances of symbols in a random staircase tableaux. They generalize and subsume earlier results that were obtained for specific values of the weights. One advantage of our generality is that we may let the weights approach extreme values of zero or infinity, which covers further special cases appearing earlier in the literature. Furthermore, our generality allows us to analyse the structure of random staircase tableaux, and we obtain several results in this direction. One of the tools we use is the generating functions of the parameters of interest. This leads us to a two-parameter family of polynomials, generalizing the classical Eulerian polynomials. We also briefly discuss the relation of staircase tableaux to the asymmetric exclusion process, to other recently introduced types of tableaux, and to an urn model studied by a number of researchers, including Philippe Flajolet.
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