| 1. |
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| 2. |
- Carlsson, Patrick, 1975-, et al.
(författare)
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Intrinsic Defects in HPSI 6H-SiC : an EPR Study
- 2009
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Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publications. ; , s. 381-384
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Konferensbidrag (refereegranskat)abstract
- High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.
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| 3. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Approximate Databases : A support tool for approximate reasoning
- 2006
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Ingår i: Journal of applied non-classical logics. - : Éditions Hermès-Lavoisier. - 1166-3081 .- 1958-5780. ; 16:1-2, s. 87-118
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an experimental platform for approximate knowledge databases called the Approximate Knowledge Database (AKDB), based on a semantics inspired by rough sets. The implementation is based upon the use of a standard SQL database to store logical facts, augmented with several query interface layers implemented in JAVA through which extensional, intensional and local closed world nonmonotonic queries in the form of crisp or approximate logical formulas can be evaluated tractably. A graphical database design user interface is also provided which simplifies the design of databases, the entering of data and the construction of queries. The theory and semantics for AKDBs is presented in addition to application examples and details concerning the database implementation.
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| 4. |
- Gällström, Andreas, 1978-, et al.
(författare)
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Influence of Cooling Rate after High Temperature Annealing on Deep Levels in High-Purity Semi-Insulating 4H-SiC
- 2007
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Ingår i: Materials Science Forum, vol. 556-557. - : Trans Tech Publications. ; , s. 371-
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Konferensbidrag (refereegranskat)abstract
- The influence of different cooling rates on deep levels in 4H-SiC after high temperature annealing has been investigated. The samples were heated from room temperature to 2300°C, followed by a 20 minutes anneal at this temperature. Different subsequent cooling sequences down to 1100°C were used. The samples have been investigated using photoluminescence (PL) and IV characteristics. The PL intensities of the silicon vacancy (VSi) and UD-2, were found to increase with a faster cooling rate.
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| 5. |
- Hahn, S., et al.
(författare)
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Contact-Less Electrical Defect Characterization of Semi-Insulating 6H-SiC Bulk Material
- 2009
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Ingår i: Materials Science Forum Vols. 600-603. - : Trans Tech Publications. ; , s. 405-408
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Konferensbidrag (refereegranskat)abstract
- The novel technique microwave detected photo induced current transient spectroscopy (MD-PICTS) was applied to semi-insulating 6H-SiC in order to investigate the properties of inherent defect levels. Defect spectra can be obtained in the similar way to conventional PICTS and DLTS. However, there is no need for contacting the samples, which allows for non-destructive and spatially resolved electrical characterization. This work is focused on the investigation of semi-insulating 6H-SiC grown under different C/Si-ratios. In the corresponding MD-PICTS spectra several shallow defect levels appear in the low temperature range. However the peak assignment needs further investigation. Additionally different trap reemission dynamics are obtained for higher temperatures, which are supposed to be due to different compensation effects.
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| 6. |
- Janzén, Erik, 1954-, et al.
(författare)
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The Silicon vacancy in SiC
- 2009
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Konferensbidrag (refereegranskat)abstract
- A model is presented for the silicon vacancy in SiC. The previously reported photoluminescence spectra in 4H and 6H SiC attributed to the silicon vacancy are in this model due to internal transitions in the negative charge state of the silicon vacancy. The magnetic resonance signals observed are due to the initial and final states of these transitions.
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| 7. |
- Janzén, Erik, et al.
(författare)
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The silicon vacancy in SiC
- 2009
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Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 404:22, s. 4354-4358
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Tidskriftsartikel (refereegranskat)abstract
- The isolated silicon vacancy is one of the basic intrinsic defects in SiC. We present new experimental data as well as new calculations on the silicon vacancy defect levels and a new model that explains the optical transitions and the magnetic resonance signals observed as occurring in the singly negative charge state of the silicon vacancy in 4H and 6H SiC.
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| 8. |
- Magnusson, Martin, et al.
(författare)
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Abductive Reasoning with Filtered Circumscription
- 2009
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Ingår i: Proceedings of the <em>IJCAI-09 Workshop on Nonmonotonic Reasoning, Action and Change (NRAC)</em>. - Sydney : UTSePress. - 9780980284072
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Konferensbidrag (refereegranskat)abstract
- For logical artificial intelligence to be truly useful,its methods must scale to problems of realistic size.An interruptible algorithm enables a logical agentto act in a timely manner to the best of its knowledge,given its reasoning so far. This seems necessaryto avoid analysis paralysis, trying to thinkof every potentiality, however unlikely, beforehand.These considerations prompt us to look for alternativereasoning mechanisms for filtered circumscription,a nonmonotonic reasoning formalism usede.g. by Temporal Action Logic and Event Calculus.We generalize Ginsberg’s circumscriptive theoremprover and describe an interruptible theoremprover based on abduction that has been used tounify planning and reasoning in a logical agent architecture.
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| 9. |
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| 10. |
- Magnusson, Martin, 1978-
(författare)
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Deductive Planning and Composite Actions in Temporal Action Logic
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Temporal Action Logic is a well established logical formalism for reasoning about action and change that has long been used as a formal specification language. Its first-order characterization and explicit time representation makes it a suitable target for automated theorem proving and the application of temporal constraint solvers. We introduce a translation from a subset of Temporal Action Logic to constraint logic programs that takes advantage of these characteristics to make the logic applicable, not just as a formal specification language, but in solving practical reasoning problems. Extensions are introduced that enable the generation of action sequences, thus paving the road for interesting applications in deductive planning. The use of qualitative temporal constraints makes it possible to follow a least commitment strategy and construct partially ordered plans. Furthermore, the logical language and logic program translation is extended with the notion of composite actions that can be used to formulate and execute scripted plans with conditional actions, non-deterministic choices, and loops. The resulting planner and reasoner is integrated with a graphical user interface in our autonomous helicopter research system and applied to logistics problems. Solution plans are synthesized together with monitoring constraints that trigger the generation of recovery actions in cases of execution failures.
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| 11. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Deductive Planning with Inductive Loops
- 2008
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Ingår i: Proceedings of the 11th International Conference on Principles of Knowledge Representation and Reasoning (KR). - Menlo Park, CA, USA : AAAI Press. - 9781577353843 ; , s. 528-534
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Konferensbidrag (refereegranskat)abstract
- Agents plan to achieve and maintain goals. Maintenance that requires continuous action excludes the representation of plans as finite sequences of actions. If there is no upper bound on the number of actions, a simple list of actions would be infinitely long. Instead, a compact representation requires some form of looping construct. We look at a specific temporally extended maintenance goal, multiple target video surveillance, and formalize it in Temporal Action Logic. The logic's representation of time as the natural numbers suggests using mathematical induction to deductively plan to satisfy temporally extended goals. Such planning makes use of a sound and useful, but incomplete, induction rule that compactly represents the solution as a recursive fixpoint formula. Two heuristic rules overcome the problem of identifying a sufficiently strong induction hypothesis and enable an automated solution to the surveillance problem that satisfies the goal indefinitely.
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| 12. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Deductive Planning with Temporal Constraints
- 2007
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Ingår i: Commonsense 2007, the 8th International Symposium on Logical Formalizations of Commonsense Reasoning,2007. - Menlo Park, CA, USA : AAAI Press. - 9781577353140
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Konferensbidrag (refereegranskat)abstract
- Temporal Action Logic is a well established logical formalism for reasoning about action and change using an explicit time representation that makes it suitable for applications that involve complex temporal reasoning. We take advantage of constraint satisfaction technology to facilitate such reasoning through temporal constraint networks. Extensions are introduced that make generation of action sequences possible, thus paving the road for interesting applications in deductive planning. The extended formalism is encoded as a logic program that is able to realize a least commitment strategy that generates partial order plans in the context of both qualitative and quantitative temporal constraints.
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| 13. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Deductive Planning with Temporal Constraints using TAL
- 2006
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Ingår i: Proceedings of the International Symposium on Practical Cognitive Agents and Robots (PCAR). - Claremont, Australia : UWA Press. - 1740521307 ; , s. 141-
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Konferensbidrag (refereegranskat)abstract
- Temporal Action Logic is a well established logical formalism for reasoning about action and change using an explicit time representation that makes it suitable for applications that involve complex temporal reasoning. We take advantage of constraint satisfaction technology to facilitate such reasoning through temporal constraint networks. Extensions are introduced that make generation of action sequences possible, thus paving the road for interesting applications in deductive planning. The extended formalism is encoded as a logic program that is able to realize a least commitment strategy that generates partial order plans in the context of both qualitative and quantitative temporal constraints.
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| 14. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Logical Agents for Language and Action
- 2008
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Ingår i: 4th International Artificial Intelligence and Interactive Digital Entertainment Conference AIIDE 2008,2008. - Menlo Park, CA, USA : AAAI Press. - 9781577353911
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Konferensbidrag (refereegranskat)
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| 15. |
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| 16. |
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| 17. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Planning Speech Acts in a Logic of Action and Change
- 2009
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Ingår i: The Swedish AI Society Workshop 2009, SAIS 2009. - : Linköping University Electronic Press, Linköpings universitet. ; , s. 39-48
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cooperation is a complex task that necessarily involves communication and reasoning about others’ intentions and beliefs. Multi-agent communication languages aid designers of cooperating robots through standardized speech acts, sometimes including a formal semantics. But a more direct approach would be to have the robots plan both regular and communicative actions themselves. We show how two robots with heterogeneous capabilities can autonomously decide to cooperate when faced with a task that would otherwise be impossible. Request and inform speech acts are formulated in the same first-order logic of action and change as is used for regular actions. This is made possible by treating the contents of communicative actions as quoted formulas of the same language. The robot agents then use a natural deduction theorem prover to generate cooperative plans for an example scenario by reasoning directly with the axioms of the theory.
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| 18. |
- Magnusson, Martin, 1978-, et al.
(författare)
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Temporal Action Logic for Question Answering in an Adventure Game
- 2008
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Ingår i: Artificial General Intelligence, AGI 2008. - Amsterdam, Netherlands : IOS Press. - 9781586038335 ; , s. 236-247
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Konferensbidrag (refereegranskat)abstract
- Inhabiting the complex and dynamic environments of modern computer games with autonomous agents capable of intelligent timely behaviour is a significant research challenge. We illustrate this using Our own attempts to build a practical agent architecture on it logicist foundation. In the ANDI-Land adventure game concept players solve puzzles by eliciting information from computer characters through natural language question answering. While numerous challenges immediately presented themselves, they took on a form of concrete and accessible problems to solve, and we present some of our initial solutions. We conclude that games, due to their demand for human-like computer characters with robust and independent operation in large simulated worlds, might serve as excellent test beds for research towards artificial general intelligence.
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| 19. |
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| 20. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Deep levels and carrier compensation in V-doped semi-insulating 4H-SiC
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:20
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Tidskriftsartikel (refereegranskat)abstract
- Electron paramagnetic resonance was used to study semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range of 5.5× 1015 -1.1× 1017 cm-3. Our results show that the electrical activation of V is low and hence only in heavily V-doped 4H-SiC, vanadium is responsible for the SI behavior, whereas in moderately V-doped substrates, the SI properties are thermally unstable and determined by intrinsic defects. We show that the commonly observed thermal activation energy Ea ∼1.1 eV in V-doped 4H-SiC may be related to deep levels of the carbon vacancy. © 2007 American Institute of Physics.
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| 21. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Deep Levels Responsible for Semi-insulating Behaviour in Vanadium-doped 4H-SiC Substrates
- 2009
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Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publications. ; , s. 401-404
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Konferensbidrag (refereegranskat)abstract
- Semi-insulating (SI) 4H-SiC substrates doped with vanadium (V) in the range 5.5×1015 –1.1×1017 cm–3 were studied by electron paramagnetic resonance. We show that only in heavily V-doped 4H-SiC vanadium is responsible for the SI behavior, whereas in moderate V-doped substrates with the V concentration comparable or slightly higher than that of the shallow N donor or B acceptor, the SI properties are thermally unstable and determined by intrinsic defects. The results show that the commonly observed thermal activation energy Ea~1.1 eV in V-doped 4H-SiC, which was previously assigned to the single acceptor V4+/3+ level, may be related to deep levels of the carbon vacancy. Carrier compensation processes involving deep levels of V and intrinsic defects are discussed and possible thermal activation energies are suggested.
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| 22. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Defects and carrier compensation in semi-insulating 4H-SiC substrates
- 2007
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 75:15
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Tidskriftsartikel (refereegranskat)abstract
- Electron paramagnetic resonance (EPR) studies revealed that vacancies (VC and VSi), carbon vacancy-antisite pairs (VC CSi) and the divacancy (VC VSi) are common defects in high-purity semi-insulating (HPSI) 4H-SiC substrates. Their concentrations and some of their deep acceptor levels were estimated by EPR and photoexcitation EPR. The commonly observed thermal activation energies, Ea ∼0.8-0.9 eV, ∼1.1 eV, ∼1.25-1.3, and ∼1.5 eV, as determined from the temperature dependence of the resistivity, in different types of HPSI substrates were associated to different deep acceptor levels of VSi, VC, VC CSi, and VC VSi. The annealing behavior of these vacancy-related defects and their interaction at high temperatures (up to 1600°C) in HPSI materials were studied. Carrier compensation processes were proposed to explain the observed change of the thermal activation energy due to high temperature annealing. VC and VC VSi were suggested to be suitable defects for controlling the SI properties whereas the incorporation of VSi and VC CSi during the crystal growth or processing should be avoided for achieving stable HPSI materials. © 2007 The American Physical Society.
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| 23. |
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| 24. |
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| 25. |
- Thorgeirsson, Thorgeir E, et al.
(författare)
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A variant associated with nicotine dependence, lung cancer and peripheral arterial disease
- 2008
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 452:7187, s. 9-638
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Tidskriftsartikel (refereegranskat)abstract
- Smoking is a leading cause of preventable death, causing about 5 million premature deaths worldwide each year(1,2). Evidence for genetic influence on smoking behaviour and nicotine dependence (ND)(3-8) has prompted a search for susceptibility genes. Furthermore, assessing the impact of sequence variants on smoking-related diseases is important to public health(9,10). Smoking is the major risk factor for lung cancer (LC)(11-14) and is one of the main risk factors for peripheral arterial disease (PAD)(15-17). Here we identify a common variant in the nicotinic acetylcholine receptor gene cluster on chromosome 15q24 with an effect on smoking quantity, ND and the risk of two smoking- related diseases in populations of European descent. The variant has an effect on the number of cigarettes smoked per day in our sample of smokers. The same variant was associated with ND in a previous genomewide association study that used low- quantity smokers as controls(18,19), and with a similar approach we observe a highly significant association with ND. A comparison of cases of LC and PAD with population controls each showed that the variant confers risk of LC and PAD. The findings provide a case study of a gene - environment interaction(20), highlighting the role of nicotine addiction in the pathology of other serious diseases.
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| 26. |
- Thorleifsson, Gudmar, et al.
(författare)
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Common sequence variants in the LOXL1 gene confer susceptibility to exfoliation glaucoma
- 2007
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 317:5843, s. 1397-1400
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is a leading cause of irreversible blindness. A genome-wide search yielded multiple single-nucleotide polymorphisms (SNPs) in the 15q24.1 region associated with glaucoma. Further investigation revealed that the association is confined to exfoliation glaucoma (XFG). Two nonsynonymous SNPs in exon 1 of the gene LOXL1 explain the association, and the data suggest that they confer risk of XFG mainly through exfoliation syndrome (XFS). About 25% of the general population is homozygous for the highest-risk haplotype, and their risk of suffering from XFG is more than 100 times that of individuals carrying only low-risk haplotypes. The population-attributable risk is more than 99%. The product of LOXL1 catalyzes the formation of elastin fibers found to be a major component of the lesions in XFG.
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