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- Andell, P., et al.
(författare)
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Intravascular Ultrasound Guidance Is Associated With Better Outcome in Patients Undergoing Unprotected Left Main Coronary Artery Stenting Compared With Angiography Guidance Alone
- 2017
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Ingår i: Circulation-Cardiovascular Interventions. - : Ovid Technologies (Wolters Kluwer Health). - 1941-7640 .- 1941-7632. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Background Small observational studies have indicated better outcome with intravascular ultrasound (IVUS) guidance when performing unprotected left main coronary artery (LMCA) percutaneous coronary intervention (PCI), but the overall picture remains inconclusive and warrants further investigation. We studied the impact of IVUS guidance on outcome in patients undergoing unprotected LMCA PCI in a Swedish nationwide observational study. Methods and Results Patients who underwent unprotected LMCA PCI between 2005 and 2014 because of stable coronary artery disease or acute coronary syndrome were included from the nationwide SCAAR (Swedish Coronary Angiography and Angioplasty Registry). Of 2468 patients, IVUS guidance was used in 621 (25.2%). The IVUS group was younger (median age, 70 versus 75 years) and had fewer comorbidities but more complex lesions. IVUS was associated with larger stent diameters (median, 4 mm versus 3.5 mm). After adjusting for potential confounders, IVUS was associated with significantly lower occurrence of the primary composite end point of all-cause mortality, restenosis, or definite stent thrombosis (hazard ratio, 0.65; 95% confidence interval, 0.50-0.84) and all-cause mortality alone (hazard ratio, 0.62; 95% confidence interval, 0.47-0.82). In 340 propensity score-matched pairs, IVUS was also associated with significantly lower occurrence of the primary end point (hazard ratio, 0.54; 95% confidence interval, 0.37-0.80). Conclusions IVUS was associated with an independent and significant outcome benefit when performing unprotected LMCA PCI. Potential mediators of this benefit include larger and more appropriately sized stents, perhaps translating into lower risk of subsequent stent thrombosis. Although residual confounding cannot be ruled out, our findings indicate a possible hazard when performing unprotected LMCA PCI without IVUS guidance.
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- Fabijan, Aleksander, et al.
(författare)
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Competitive Online Clique Clustering
- 2013
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Ingår i: Proceedings of the 8th International Conference on Algorithms and Complexity;8. - Berlin, Heidelberg : Springer. ; , s. 221-233
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Konferensbidrag (refereegranskat)abstract
- Clique clustering is the problem of partitioning a graph into cliques so that some objective function is optimized. In online clustering, the input graph is given one vertex at a time, and any vertices that have previously been clustered together are not allowed to be separated. The objective here is to maintain a clustering the never deviates too far in the objective function compared to the optimal solution. We give a constant competitive upper bound for online clique clustering, where the objective function is to maximize the number of edges inside the clusters. We also give almost matching upper and lower bounds on the competitive ratio for online clique clustering, where we want to minimize the number of edges between clusters. In addition, we prove that the greedy method only gives linear competitive ratio for these problems.
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- Hammar, Mikael, et al.
(författare)
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Competitive Exploration of Rectilinear Polygons
- 2006
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Ingår i: Theoretical Computer Science. - : Elsevier. - 0304-3975 .- 1879-2294. ; 354:3, s. 367-378
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Tidskriftsartikel (refereegranskat)abstract
- Exploring a polygon with robots, when the robots do not have knowledge of the surroundings can be viewed as an online problem. Typical for online problems is that decisions must be made based on past events without complete information about the future. In our case the robots do not have complete information about the environment. Competitive analysis can be used to measure the performance of methods solving online problems. The competitive ratio of such a method is the ratio between the method's performance and the performance of the best method having full knowledge of the future. We are interested in obtaining good bounds on the competitive ratio of exploring polygons and prove constant competitive strategies and lower bounds for exploring a simple rectilinear polygon in the $L_1$ metric.
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- Hammar, Mikael, et al.
(författare)
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The online freeze-tag problem
- 2006
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. ; 3887 LNCS, s. 569-579, s. 569-579
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Konferensbidrag (refereegranskat)abstract
- We consider the following problem from swarm robotics: given one or more "awake" robots in some metric space M, wake up a set of "asleep" robots. A robot awakens a sleeping robot by moving to the sleeping robot's position. When a robot awakens, it is available to assist in awakening other slumbering robots. We investigate offline and online versions of this problem and give a 2-competitive strategy and a lower bound of 2 in the case when M is discrete and the objective is to minimize the total movement cost. We also study the case when M is continuous and show a lower bound of 7/3 when the objective is to minimize the time when the last robot awakens.
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