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Sökning: WFRF:(Hansson Anders)

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1.
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2.
  • Ahlsson, Anders, et al. (författare)
  • Is There a Weekend Effect in Surgery for Type A Dissection? : Results From the Nordic Consortium for Acute Type A Aortic Dissection Database
  • 2019
  • Ingår i: Annals of Thoracic Surgery. - : Elsevier. - 0003-4975 .- 1552-6259. ; 108:3, s. 770-776
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Aortic dissection type A requires immediate surgery. In general surgery populations, patients operated on during weekends have higher mortality rates compared with patients whose operations occur on weekdays. The weekend effect in aortic dissection type A has not been studied in detail.Methods: The Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) registry includes data for 1,159 patients who underwent type A dissection surgery at 8 Nordic centers during 2005 to 2014. This study is based on data relating to surgery conducted during weekdays versus weekends and starting between 8:00 AM and 8:00 Pm ("daytime") versus from 8:00 Pm to 8:00 AM ("nighttime"), as well as time from symptoms, admittance, and diagnosis to surgery. The influence of timing of surgery on the 30-day mortality rate was assessed using logistic regression analysis.Results: The 30-day mortality was 18% (204 of 1,159), with no difference in mortality between surgery performed on weekdays (17% [150 of 889]) and on weekends (20% [54 of 270], p = 0.45), or during nighttime (19% [87 of 467]) versus daytime (17% [117 of 680], p = 0.54). Time from symptoms to surgery (median 7.0 hours vs 6.5 hours, p = 0.31) did not differ between patients who survived and those who died at 30 days. Multivariable regression analysis of risk factors for 30-day mortality showed no weekend effect (odds ratio, 1.04; 95% confidence interval, 60.67 to 1.60; p = 0.875), but nighttime surgery was a risk factor (odds ratio, 2.43; 95% confidence interval, 1.29 to 4.56; p = 0.006).Conclusions: The 30-day mortality in surgical repair of aortic dissection type A was not significantly affected by timing of surgery during weekends versus weekdays. Nighttime surgery seems to predict increased 30-day mortality, after correction for other risk factors.
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3.
  • Ahlsson, Anders, et al. (författare)
  • Is there a weekend effect in surgery for type A dissection? - Results from the NORCAAD database
  • 2019
  • Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 1552-6259 .- 0003-4975. ; 108:3, s. 770-776
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Aortic dissection type A requires immediate surgery. In general surgery populations, patients operated during weekends have higher mortality rates compared to patients operated on weekdays. The weekend effect in aortic dissection type A has not been studied in detail.METHODS: The Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) registry includes patients (N=1,159) who underwent type A dissection surgery at eight Nordic centers during 2005-2014. This study is based on data relating to surgery conducted during weekdays vs. weekends, and starting between 8 am and 8 pm ("daytime") vs. from 8 pm to 8 am ("nighttime"), as well as time from symptoms/admittance/diagnosis to surgery. The influence of timing of surgery on 30-day mortality was assessed using logistic regression analysis.RESULTS: The 30-day mortality was 18% (204/1,159), with no difference in mortality between surgery performed on weekdays (17%, 150/889) and on weekends (20%, 54/270, p=0.45), or during nighttime (19%, 87/467) vs. daytime (17%, 117/680, p=0.54). Time from symptoms to surgery (median 7.0 hours vs. 6.5 hours, p=0.31) did not differ between patients who survived and those dead at 30 days. Multivariable regression analysis of risk factors for 30-day mortality showed no weekend effect (OR 1.04 [0.67-1.60], p=0.875), but nighttime surgery was a risk factor (OR 2.43 [1.29-4.56], p=0.006).CONCLUSIONS: Thirty-day mortality in surgical repair of aortic dissection type A was not significantly affected by timing of surgery during weekends vs. weekdays. Nighttime surgery seems to predict increased 30-day mortality, after correction for other risk factors.
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4.
  • Geirsson, Arnar, et al. (författare)
  • Hospital volumes and later year of operation correlates with better outcomes in acute Type A aortic dissection
  • 2018
  • Ingår i: European Journal of Cardio-Thoracic Surgery. - : Oxford University Press. - 1010-7940 .- 1873-734X. ; 53:1, s. 276-281
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: Acute Type A aortic dissection remains a life-threatening disease, but there are indications that its surgical mortality is decreasing. The aim of this report was to study how surgical mortality has changed and what influences those changes.METHODS: Nordic Consortium for Acute Type A Aortic Dissection is a retrospective database comprising 1159 patients (mean age 61.6 ± 12.2 years, 68% male) treated for acute Type A aortic dissection at 8 centres in Denmark, Finland, Iceland and Sweden from 2005 to 2014. Data gathered included demographics, symptoms, type of procedure, complications and 30-day mortality.RESULTS: The annual number of operations increased significantly from 85 in 2005 to 150 in 2014 (P < 0.001). Chest pain was present in 85% of patients, 24% were hypotensive on presentation and 28% had malperfusion syndrome. Open distal anastomosis technique under hypothermic circulatory arrest was used in 85% of cases and its use increased significantly throughout the study. The 30-day mortality decreased from 24% in 2005 to 13% in 2014 (P = 0.003). Independent predictors for 30-day mortality were preoperative cardiac arrest, malperfusion syndrome, Penn Class C, Penn Class B and C and cardiopulmonary bypass time, whereas later calendar year and higher hospital operative volumes predicted improved survival.CONCLUSIONS: Surgical mortality for acute Type A aortic dissection remains high but has decreased significantly over the last decade. This correlated with later year of operation and increased the number of operations performed per year, indicating that cumulative surgical experience contributes significantly to improved surgical outcomes.
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5.
  • Geirsson, Arnar, et al. (författare)
  • The Nordic Consortium for Acute type A Aortic Dissection (NORCAAD) : objectives and design
  • 2016
  • Ingår i: Scandinavian Cardiovascular Journal. - : Taylor & Francis. - 1401-7431 .- 1651-2006. ; 50:5-6, s. 334-340
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: The Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) is a collaborative effort of Nordic cardiac surgery centers to study acute type A aortic dissection (ATAAD). Here, we outline the overall objectives and the design of NORCAAD.Design: NORCAAD currently consists of eight centers in Denmark, Finland, Iceland and Sweden. Data was collected for patients undergoing surgery for ATAAD from 2005 to 2014. A total of 194 variables were retrospectively collected including demographics, past medical history, preoperative medications, symptoms at presentation, operative variables, complications, bleeding and blood transfusions, need for late reoperations, 30-day mortality and long-term survival.Results: Information was gathered in the database for 1159 patients, of which 67.6% were male. The mean age was 61.5 +/- 12.1 years. The mean follow-up was 3.1 +/- 2.9 years with a total of 3535 patient years.Conclusions: NORCAAD provides a foundation for close collaboration between cardiac surgery centers in the Nordic countries. Substudies in progress include: short-term outcomes, long-term survival, time interval from diagnosis until operation, effects of surgical techniques, malperfusion syndrome, renal failure, bleeding and neurological complications on outcomes and the rate of late reoperations.
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6.
  • Hansson, L-A, et al. (författare)
  • A synthesis of animal movement across scales
  • 2014
  • Ingår i: Animal Movement Across Scales. - : Oxford University Press. - 9780199677184 ; , s. 259-267
  • Bokkapitel (refereegranskat)abstract
    • This chapter aims at synthesizing the knowledge presented in the chapters of the book’s three sections by addressing evolutionary compromises, dispersal, gene flow, and assisted movements. How climate change and other environmental changes at different scales may affect animal movement, migration, and dispersal in the future are also summarized here. Moreover, how the different senses are utilized for navigation and orientation and how these may lead to different movement and migration patterns are also discussed. Finally, how the recent technical revolution has affected animal movement research is addressed and the view on future perspectives of animal movement research is also provided.
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7.
  • Malmgren, Linnea, et al. (författare)
  • The complexity of kidney disease and diagnosing it - Cystatin C, selective glomerular hypofiltration syndromes and proteome regulation.
  • 2023
  • Ingår i: Journal of Internal Medicine. - : John Wiley & Sons. - 0954-6820 .- 1365-2796. ; 293:3, s. 293-308
  • Tidskriftsartikel (refereegranskat)abstract
    • Estimation of kidney function is often part of daily clinical practice, mostly done by using the endogenous GFR-markers creatinine or cystatin C. A recommendation to use both markers in parallel in 2010 has resulted in new knowledge concerning the pathophysiology of kidney disorders by identification of a new set of kidney disorders, selective glomerular hypofiltration syndromes. These syndromes, connected to strong increases in mortality and morbidity, are characterised by a selective reduction in the glomerular filtration of 5-30 kDa molecules, such as cystatin C, compared to the filtration of small molecules < 1kDa dominating the glomerular filtrate e.g., water, urea, creatinine. At least two types of such disorders, shrunken or elongated pore syndrome, are possible according to the pore model for glomerular filtration. Selective glomerular hypofiltration syndromes are prevalent in investigated populations, and patients with these syndromes often display normal measured GFR or creatinine-based GFR-estimates. The syndromes are characterised by proteomic changes promoting the development of atherosclerosis, indicating antibodies and specific receptor-blocking substances as possible new treatment modalities. Presently, the KDIGO guidelines for diagnosing kidney disorders do not recommend cystatin C as a general marker of kidney function and will therefore not allow the identification of a considerable number of patients with selective glomerular hypofiltration syndromes. Furthermore, as cystatin C is uninfluenced by muscle mass, diet or variations in tubular secretion and cystatin C-based GFR-estimation equations do not require controversial race or sex terms, it is obvious that cystatin C should be a part of future KDIGO guidelines.
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8.
  • Ankelhed, Daniel, 1980- (författare)
  • On low order controller synthesis using rational constraints
  • 2009
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In order to design robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the plant, the problem is no longer convex and it is then relatively hard to solve. These problems become very complex, even when the order of the system to be controlled is low.The approach used in the thesis is based on formulating the constraint on the maximum order of the plant as a polynomial equation. By using the fact that the polynomial is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex polynomial function is to be minimized over a convex set defined by linear matrix inequalities.To solve this optimization problem, two methods have been proposed. The first method is a barrier method and the second one is a method based on a primal-dual framework. These methods have been evaluated on several problems and compared with a well-known method found in the literature. To motivate this choice of method, we have made a brief survey of available methods available for solving the same or related problems.The proposed methods emerged as the best methods among the three for finding lower order controllers with the same or similar performance as the full order controller. When the aim is to find the lowest order controller with no worse than +50% increase in the closed loop H-infinity norm, then the three compared methods perform equally well.
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9.
  • Bjurbom, Markus, et al. (författare)
  • Type A Aortic Dissection Repair in Patients With Prior Cardiac Surgery
  • 2023
  • Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 115:3, s. 591-598
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Emergency surgery for acute type A aortic dissection in patients with previous cardiac surgery is controversial. This study aimed to evaluate the association between previous cardiac surgery and outcomes after surgery for acute type A aortic dissection, to appreciate whether emergency surgery can be offered with acceptable risks. Methods: All patients operated on for acute type A aortic dissection between 2005 and 2014 from the Nordic Consortium for Acute Type A Aortic Dissection database were eligible. Patients with previous cardiac surgery were compared with patients without previous cardiac surgery. Univariable and multivariable statistical analyses were performed to identify predictors of 30-day mortality and early major adverse events (a secondary composite endpoint comprising 30-day mortality, perioperative stroke, postoperative cardiac arrest, or de novo dialysis). Results: In all, 1159 patients were included, 40 (3.5%) with previous cardiac surgery. Patients with previous cardiac surgery had higher 30-day mortality (30% vs 17.8%, P = .049), worse medium-term survival (51.7% vs 71.2% at 5 years, log rank P = .020), and higher unadjusted prevalence of major adverse events (52.5% vs 35.7%, P = .030). In multivariable analysis, previous cardiac surgery was not associated with 30-day mortality (odds ratio 0.78; 95% CI, 0.30-2.07; P = .624) or major adverse events (odds ratio 1.07; 95% CI, 0.45-2.55, P = .879). Conclusions: Major adverse events after surgery for acute type A aortic dissection were more frequent in patients with previous cardiac surgery. Previous cardiac surgery itself was not an independent predictor for adverse events, although the small sample size precludes definite conclusions. Previous cardiac surgery should not deter from emergency surgery.
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10.
  • Bjursten, Henrik, et al. (författare)
  • Once after a full moon : acute type A aortic dissection and lunar phases
  • 2022
  • Ingår i: Interactive Cardiovascular and Thoracic Surgery. - : Oxford University Press. - 1569-9293 .- 1569-9285. ; 34:1, s. 105-110
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: Acute type A aortic dissection (ATAAD) is a rare but severe condition, routinely treated with emergent cardiac surgery. Many surgeons have the notion that patients with ATAAD tend to come in clusters, but no studies have examined these observations. This investigation was undertaken to study the potential association between the lunar cycle and the incidence of ATAAD.METHODS: We collected information on 2995 patients who underwent ATAAD surgery at centres from the Nordic Consortium for Acute Type A Aortic Dissection collaboration. We cross-referenced the time of surgery with lunar phase using a case-crossover design with 2 different definitions of full moon (>99% illumination and the 7-day full moon period).RESULTS: The period when the moon was illuminated the most (99% definition) did not show any significant increase in incidence for ATAAD surgery. However, when the full moon period was compared with all other moon phases, it yielded a relative risk of 1.08 [95% confidence interval (CI) 1.00-1.17, P = 0.057] and, compared to waxing moon, only the relative risk was 1.11 (95% CI 1.01-1.23, P = 0.027). The peak incidence came 4-6 days after the moon was fully illuminated.CONCLUSIONS: This study found an overrepresentation of surgery for ATAAD during the full moon phase. The explanation for this is not known, but we speculate that sleep deprivation during full moon leads to a temporary increase in blood pressure, which in turn could trigger rupture of the aortic wall. While this finding is interesting, it needs to be corroborated and the clinical implications are debateable.
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11.
  • Björnfot, Cecilia, et al. (författare)
  • Cerebral arterial stiffness is linked to white matter hyperintensities and perivascular spaces in older adults : a 4D flow MRI study
  • 2024
  • Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : Sage Publications. - 0271-678X .- 1559-7016.
  • Tidskriftsartikel (refereegranskat)abstract
    • White matter hyperintensities (WMH), perivascular spaces (PVS) and lacunes are common MRI features of small vessel disease (SVD). However, no shared underlying pathological mechanism has been identified. We investigated whether SVD burden, in terms of WMH, PVS and lacune status, was related to changes in the cerebral arterial wall by applying global cerebral pulse wave velocity (gcPWV) measurements, a newly described marker of cerebral vascular stiffness. In a population-based cohort of 190 individuals, 66–85 years old, SVD features were estimated from T1-weighted and FLAIR images while gcPWV was estimated from 4D flow MRI data. Additionally, the gcPWV’s stability to variations in field-of-view was analyzed. The gcPWV was 10.82 (3.94) m/s and displayed a significant correlation to WMH and white matter PVS volume (r = 0.29, p < 0.001; r = 0.21, p = 0.004 respectively from nonparametric tests) that persisted after adjusting for age, blood pressure variables, body mass index, ApoB/A1 ratio, smoking as well as cerebral pulsatility index, a previously suggested early marker of SVD. The gcPWV displayed satisfactory stability to field-of-view variations. Our results suggest that SVD is accompanied by changes in the cerebral arterial wall that can be captured by considering the velocity of the pulse wave transmission through the cerebral arterial network.
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12.
  • Chapman, Ben, et al. (författare)
  • A foraging cost of migration for a partially migratory cyprinid fish
  • 2013
  • Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration in many systems posits that migration is driven by seasonal changes to a predation/growth potential (p/g) trade-off that a wide range of animals face. In this study we assess a key assumption of this model for a common cyprinid partial migrant, the roach Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems.
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13.
  • Chapman, Ben B, et al. (författare)
  • Patterns of Animal Migration
  • 2014
  • Ingår i: Animal movement across scales. - : Oxford University Press. - 9780199677184 ; , s. 11-35
  • Bokkapitel (refereegranskat)
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14.
  • Chemtob, Raphaelle A., et al. (författare)
  • Stroke in acute type A aortic dissection : the Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD)
  • 2020
  • Ingår i: European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 58:5, s. 1027-1034
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: Stroke is a serious complication in patients with acute type A aortic dissection (ATAAD). Previous studies investigating stroke in ATAAD patients have been limited by small cohorts and have shown diverging results. We sought to identify risk factors for stroke and to evaluate the effect of stroke on outcomes in surgical ATAAD patients. METHODS: The Nordic Consortium for Acute Type A Aortic Dissection database included patients operated for ATAAD at 8 Scandinavian Hospitals between 2005 and 2014. RESULTS: Stroke occurred in 177 (15.7%) out of 1128 patients. Patients with stroke presented more frequently with cerebral malperfusion (20.6% vs 6.3%, P < 0.001), syncope (30.6% vs 17.6%, P < 0.001), cardiogenic shock (33.1% vs 20.7%, P < 0.001) and pericardial tamponade (25.9% vs 14.7%, P < 0.001) and more often underwent total aortic arch replacement (10.7% vs 4.7%, P = 0.016), compared to patients without stroke. In the 86 patients presenting with cerebral malperfusion, 38.4% developed stroke. Thirty-day and 5-year mortality in patients with and without stroke were 27.1% vs 13.6% and 42.9% vs 25.6%, respectively. Stroke was an independent predictor of early- [odds ratio 2.02, 95% confidence interval (CI) 1.34-3.05; P < 0.001] and midterm mortality (hazard ratio 1.68, 95% CI 1.27-2.23; P < 0.001). CONCLUSIONS: Stroke in ATAAD patients is associated with increased early- and midterm mortality. Preoperative cerebral malperfusion and impaired haemodynamics, as well as total aortic arch replacement, were more frequent among patients who developed stroke. Importantly, a large proportion of patients presenting with cerebral malperfusion did not develop a permanent stroke, indicating that signs of cerebral malperfusion should not be considered a contraindication for surgery.
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15.
  • Chemtob, Raphaelle A, et al. (författare)
  • Stroke in acute type A aortic dissection: the Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD).
  • 2020
  • Ingår i: European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery. - 1873-734X. ; 58:5, s. 1027-1034
  • Tidskriftsartikel (refereegranskat)abstract
    • Stroke is a serious complication in patients with acute type A aortic dissection (ATAAD). Previous studies investigating stroke in ATAAD patients have been limited by small cohorts and have shown diverging results. We sought to identify risk factors for stroke and to evaluate the effect of stroke on outcomes in surgical ATAAD patients.The Nordic Consortium for Acute Type A Aortic Dissection database included patients operated for ATAAD at 8 Scandinavian Hospitals between 2005 and 2014.Stroke occurred in 177 (15.7%) out of 1128 patients. Patients with stroke presented more frequently with cerebral malperfusion (20.6% vs 6.3%, P<0.001), syncope (30.6% vs 17.6%, P<0.001), cardiogenic shock (33.1% vs 20.7%, P<0.001) and pericardial tamponade (25.9% vs 14.7%, P<0.001) and more often underwent total aortic arch replacement (10.7% vs 4.7%, P=0.016), compared to patients without stroke. In the 86 patients presenting with cerebral malperfusion, 38.4% developed stroke. Thirty-day and 5-year mortality in patients with and without stroke were 27.1% vs 13.6% and 42.9% vs 25.6%, respectively. Stroke was an independent predictor of early- [odds ratio 2.02, 95% confidence interval (CI) 1.34-3.05; P<0.001] and midterm mortality (hazard ratio 1.68, 95% CI 1.27-2.23; P<0.001).Stroke in ATAAD patients is associated with increased early- and midterm mortality. Preoperative cerebral malperfusion and impaired haemodynamics, as well as total aortic arch replacement, were more frequent among patients who developed stroke. Importantly, a large proportion of patients presenting with cerebral malperfusion did not develop a permanent stroke, indicating that signs of cerebral malperfusion should not be considered a contraindication for surgery.
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16.
  • Engström, Gunnar, et al. (författare)
  • The Swedish CArdioPulmonary BioImage Study : objectives and design
  • 2015
  • Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 278:6, s. 645-659
  • Tidskriftsartikel (refereegranskat)abstract
    • Cardiopulmonary diseases are major causes of death worldwide, but currently recommended strategies for diagnosis and prevention may be outdated because of recent changes in risk factor patterns. The Swedish CArdioPulmonarybioImage Study (SCAPIS) combines the use of new imaging technologies, advances in large-scale 'omics' and epidemiological analyses to extensively characterize a Swedish cohort of 30 000 men and women aged between 50 and 64 years. The information obtained will be used to improve risk prediction of cardiopulmonary diseases and optimize the ability to study disease mechanisms. A comprehensive pilot study in 1111 individuals, which was completed in 2012, demonstrated the feasibility and financial and ethical consequences of SCAPIS. Recruitment to the national, multicentre study has recently started.
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17.
  • Folkersen, Lasse, et al. (författare)
  • Association of genetic risk variants with expression of proximal genes identifies novel susceptibility genes for cardiovascular disease
  • 2010
  • Ingår i: Circulation. - 1942-325X .- 1942-3268. ; 3:4, s. 365-373
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Population-based genome-wide association studies have identified several single nucleotide polymorphisms (SNPs) associated with cardiovascular disease or its risk factors. Genes in close proximity to these risk-SNPs are often thought to be pathogenetically important based on their location alone. However, the actual connections between SNPs and disease mechanisms remain largely unknown. METHODS AND RESULTS: To identify novel susceptibility genes, we investigated how 166 SNPs previously found to be associated with increased cardiovascular risk and/or predisposing metabolic traits relate to the expression of nearby genes. Gene expression in 577 samples of aorta, liver, mammary artery, and carotid atherosclerotic plaque was measured using expression arrays. For 47 SNPs, the expression levels of proximal genes (located within 200 kb) were affected (P<0.005). More than 20 of these genes had not previously been identified as candidate genes for cardiovascular or related metabolic traits. SNP-associated gene effects were tissue-specific and the tissue specificity was phenotype-dependent. CONCLUSIONS: This study demonstrates several instances of association between risk-SNPs and genes immediately adjacent to them. It also demonstrates instances in which the associated gene is not the immediately proximal and obvious candidate gene for disease. This shows the necessity of careful studies of genetic marker data as a first step toward application of genome-wide association studies findings in a clinical setting.
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18.
  • Geirsson, Arnar, et al. (författare)
  • Differential outcomes of open and clamp-on distal anastomosis techniques in acute type A aortic dissection
  • 2019
  • Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier. - 0022-5223 .- 1097-685X. ; 157:5, s. 1750-1758
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: Open-distal anastomosis is the preferred technique over clamp-on technique for surgical repair of acute type A aortic dissection (ATAAD). The aim of this study was to define how outcomes of ATAAD were affected by the use of either technique.Methods: Nordic Consortium for Acute Type A Aortic Dissection includes 8 academic cardiothoracic hospitals in 4 Nordic countries. The cohort consisted of 1134 patients, 153 clamp-on and 981 open-distal, from 2005 to 2014.Results: Patients who underwent operation with the clamp-on were younger, more frequently had coronary artery disease, bicuspid aortic valve, hypotension/shock or syncope, and a greater PennClass than open-distal patients. Postoperative cerebral vascular accident occurred less frequently in clamp-on (14/153, 10%) compared with the open-distal group (190/981, 20%). Clamp-on had greater 30-day mortality (39/153, 25%) than the open-distal group (158/981, 16%), and 5-year survival was also worse in clamp-on (61.8% +/- 4.4%) compared with the open-distal group (73.0% +/- 1.6%). The open-distal technique was used more frequently in greater-volume hospitals but was not independently associated with 30-day mortality. Preoperative condition was an independent risk factor whereas hospital volume and later year of operation were beneficial in regard to short-term outcome. Open-distal was independently associated with improved mid-term survival.Conclusions: Patients who underwent operation with the clamp-on were sicker on presentation and had worse short-and mid-term survival compared with the open-distal group. Patients in the open-distal group had greater rates of cerebrovascular complications. The results support the routine use of open-distal anastomosis as the primary operative strategy for ATAAD, although clamp-on can be performed successfully in select cases.
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19.
  • Gertow, Karl, et al. (författare)
  • Identification of the BCAR1-CFDP1-TMEM170A Locus as a Determinant of Carotid Intima-Media Thickness and Coronary Artery Disease Risk
  • 2012
  • Ingår i: Circulation: Cardiovascular Genetics. - 1942-325X .- 1942-3268. ; 5:6, s. 656-665
  • Tidskriftsartikel (refereegranskat)abstract
    • Background-Carotid intima-media thickness (cIMT) is a widely accepted marker of subclinical atherosclerosis. To date, large-scale investigations of genetic determinants of cIMT are sparse. Methods and Results-To identify cIMT-associated genes and genetic variants, a discovery analysis using the Illumina 200K CardioMetabochip was conducted in 3430 subjects with detailed ultrasonographic determinations of cIMT from the IMPROVE (Carotid Intima Media Thickness [IMT] and IMT-Progression as Predictors of Vascular Events in a High Risk European Population) study. Segment-specific IMT measurements of common carotid, bifurcation, and internal carotid arteries, and composite IMT variables considering the whole carotid tree (IMTmean, IMTmax, and IMTmean-max), were analyzed. A replication stage investigating 42 single-nucleotide polymorphisms for association with common carotid IMT was undertaken in 5 independent European cohorts (total n=11 590). A locus on chromosome 16 (lead single-nucleotide polymorphism rs4888378, intronic in CFDP1) was associated with cIMT at significance levels passing multiple testing correction at both stages (array-wide significant discovery P=6.75x10(-7) for IMTmax; replication P=7.24x10(-6) for common cIMT; adjustments for sex, age, and population substructure where applicable; minor allele frequency 0.43 and 0.41, respectively). The protective minor allele was associated with lower carotid plaque score in a replication cohort (P=0.04, n=2120) and lower coronary artery disease risk in 2 case-control studies of subjects with European ancestry (odds ratio [95% confidence interval] 0.83 [0.77-0.90], P=6.53x10(-6), n=13 591; and 0.95 [0.92-0.98], P=1.83x10(-4), n= 82 297, respectively). Queries of human biobank data sets revealed associations of rs4888378 with nearby gene expression in vascular tissues (n=126-138). Conclusions-This study identified rs4888378 in the BCAR1-CFDP1-TMEM170A locus as a novel genetic determinant of cIMT and coronary artery disease risk in individuals of European descent. (Circ Cardiovasc Genet. 2012;5:656-665.)
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20.
  • Grubb, Anders, et al. (författare)
  • Generation of a new cystatin C-based estimating equation for glomerular filtration rate by use of 7 assays standardized to the international calibrator
  • 2014
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 60:7, s. 974-986
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND:Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays.METHODS:Use of the recently introduced certified reference material, ERM-DA471/IFCC, and further work to achieve high agreement and equivalence of 7 commercially available cystatin C assays allowed a substantial decrease of the CV of the assays, as defined by their performance in an external quality assessment for clinical laboratory investigations. By use of 2 of these assays and a population of 4690 subjects, with large subpopulations of children and Asian and Caucasian adults, with their GFR determined by either renal or plasma inulin clearance or plasma iohexol clearance, we attempted to produce a virtually assay-independent simple cystatin C-based equation for estimation of GFR.RESULTS:We developed a simple cystatin C-based equation for estimation of GFR comprising only 2 variables, cystatin C concentration and age. No terms for race and sex are required for optimal diagnostic performance. The equation, [Formula: see text] is also biologically oriented, with 1 term for the theoretical renal clearance of small molecules and 1 constant for extrarenal clearance of cystatin C.CONCLUSIONS:A virtually assay-independent simple cystatin C-based and biologically oriented equation for estimation of GFR, without terms for sex and race, was produced.
  •  
21.
  • Hansson, Jörgen, et al. (författare)
  • Clearance of Flight Control Laws for Time-Varying Parameters
  • 2003
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • In this article exponential stability of the closed loop for the Saab AB VEGAS model controlled by a gain-scheduled linear fractional transformation controller is investigated for time-varying Mach-number. The analysis is based on parameter-dependent Lyapunov-functions which are obtained by investigating feasibility of linear matrix inequalities.
  •  
22.
  • Hansson, Lars-Anders, et al. (författare)
  • A lake as a microcosm : Reflections on developments in aquatic ecology
  • 2013
  • Ingår i: Aquatic Ecology. - : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 47, s. 125-135
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present study, we aim at relating Forbes' remarkable paper on "The lake as a microcosm", published 125 years ago, to the present status of knowledge in our own research group. Hence, we relate the observations Forbes made to our own microcosm, Lake Krankesjon in southern Sweden, that has been intensively studied by several research groups for more than three decades. Specifically, we focus on the question: Have we made any significant progress or did Forbes and colleagues blaze the trail through the unknown wilderness and we are mainly paving that intellectual road? We conclude that lakes are more isolated than many other biomes, but have, indeed, many extensions, for example, input from the catchment, fishing and fish migration. We also conclude that irrespective of whether lakes should be viewed as microcosms or not, the paper by Forbes has been exceptionally influential and still is, especially since it touches upon almost all aspects of the lake ecosystem, from individual behaviour to food web interactions and environmental issues. Therefore, there is no doubt that even if 125 years have passed, Forbes' paper still is a source of inspiration and deserves to be read. Hence, although aquatic ecology has made considerable progress over the latest century, Forbes might be viewed as one of the major pioneers and visionary scientists of limnology.
  •  
23.
  •  
24.
  • Hansson, Lars-Anders, et al. (författare)
  • Consumption patterns, complexity and enrichment in aquatic food chains
  • 1998
  • Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
  • Tidskriftsartikel (refereegranskat)abstract
    • The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
  •  
25.
  • Hansson, Lars-Anders, et al. (författare)
  • Food-chain length alters community responses to global change in aquatic systems
  • 2013
  • Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 3, s. 228-233
  • Tidskriftsartikel (refereegranskat)abstract
    • Synergies between large-scale environmental changes, such as climate change1 and increased humic content (brownification)2, will have a considerable impact on future aquatic ecosystems. On the basis of modelling, monitoring and experimental data, we demonstrate that community responses to global change are determined by food-chain length and that the top trophic level, and every second level below, will benefit from climate change, whereas the levels in between will suffer. Hence, phytoplankton, and thereby algal blooms, will benefit from climate change in three-, but not in two-trophic-level systems. Moreover, we show that both phytoplankton (resource) and zooplankton (consumer) advance their spring peak abundances similarly in response to a 3 °C temperature increase; that is, there is no support for a consumer/resource mismatch in a future climate scenario. However, in contrast to other taxa, cyanobacteria—known as toxin-producing nuisance phytoplankton3—benefit from a higher temperature and humic content irrespective of the food-chain composition. Our results are mirrored in natural ecosystems. By mechanistically merging present food-chain theory with large-scale environmental and climate changes, we provide a powerful framework for predicting and understanding future aquatic ecosystems and their provision of ecosystem services and water resources.
  •  
26.
  • Hansson, Lars-Anders, et al. (författare)
  • Food-chain length alters community responses to global change in aquatic systems
  • 2013
  • Ingår i: Nature Climate Change. - 1758-6798. ; 3:3, s. 228-233
  • Tidskriftsartikel (refereegranskat)abstract
    • Synergies between large-scale environmental changes, such as climate change(1) and increased humic content (brownification)(2), will have a considerable impact on future aquatic ecosystems. On the basis of modelling, monitoring and experimental data, we demonstrate that community responses to global change are determined by food-chain length and that the top trophic level, and every second level below, will benefit from climate change, whereas the levels in between will suffer. Hence, phytoplankton, and thereby algal blooms, will benefit from climate change in three-, but not in two-trophic-level systems. Moreover, we show that both phytoplankton (resource) and zooplankton (consumer) advance their spring peak abundances similarly in response to a 3 degrees C temperature increase; that is, there is no support for a consumer/resource mismatch in a future climate scenario. However, in contrast to other taxa, cyanobacteria-known as toxin-producing nuisance phytoplankton(3)-benefit from a higher temperature and humic content irrespective of the food-chain composition. Our results are mirrored in natural ecosystems. By mechanistically merging present food-chain theory with large-scale environmental and climate changes, we provide a powerful framework for predicting and understanding future aquatic ecosystems and their provision of ecosystem services and water resources.
  •  
27.
  • Henryson, Kajsa, et al. (författare)
  • Environmental performance of crop cultivation at different sites and nitrogen rates in Sweden
  • 2019
  • Ingår i: Nutrient Cycling in Agroecosystems. - : SPRINGER. - 1385-1314 .- 1573-0867. ; 114:2, s. 139-155
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitrogen (N) fertilisation has positive and negative effects on the environmental impact of crop cultivation. The mechanisms governing these effects are highly site-dependent, a factor often ignored in assessments of the environmental impact of crop cultivation. By assessing outputs of crop rotations using a life cycle approach, this study explored how greenhouse gas emissions and marine eutrophication caused by crop cultivation (including upstream processes such as production of farm inputs) depend on fertiliser rate and the site at which the cultivation occurs. Cereal unit (CU) was used as the functional unit. The calculations were based on data from multi-site long-term field experiments in Sweden and site-dependent data and models for non-measured processes. Cultivation at three N levels was evaluated, where the highest N rate was close to current average practices and the lowest level corresponded to one-third of that. Site characteristics had a stronger influence on both greenhouse gas emissions and marine eutrophication (variations of up to 330% and 490%, respectively, within N levels) than N level (variations of up to 74% and 59%, respectively, within sites). Main sources of variation in greenhouse gas emissions were soil nitrous oxide emissions (58-810g CO2eqCU-1) and soil organic carbon changes (14-720g CO2eqCU-1), while variations in marine eutrophication were mainly explained by field-level waterborne N losses (0.9-8.2g NeqCU-1). The large variation between sites highlights the importance of considering site characteristics when assessing the environmental impact of crop cultivation and evaluating the environmental consequences of crop management practices.
  •  
28.
  • Isaksson, Anders, et al. (författare)
  • High-Throughput LC-MS/MS Method for Determination of the Alcohol Use Biomarker Phosphatidylethanol in Clinical Samples by Use of a Simple Automated Extraction Procedure-Preanalytical and Analytical Conditions
  • 2018
  • Ingår i: The Journal of Applied Laboratory Medicine. - : Oxford University Press (OUP). - 2576-9456 .- 2475-7241. ; 2:6, s. 880-892
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Phosphatidylethanol (PEth) is an alcohol use biomarker with higher clinical sensitivity and specificity than commonly used alcohol markers. Since its introduction as a clinical alcohol-marker in 2006, the number of samples sent to our laboratory for the determination of PEth has shown a strong annual increase. This has prompted the need to develop a cost-effective and reliable analytical procedure with high capacity. METHODS: An LC-MS/MS method for the determination of PEth 16:0/18:1 with a short turnaround time (3 min) has been evaluated with respect to accuracy, sensitivity, and precision. We compared this method with a previously used HPLC method, as well as a manual and a simplified automated method for sample workup, and investigated potential causes of analytic and preanalytic errors. RESULTS: The method shows limits of detection and quantification of 0.0075 μmol/L (5.2 ng/mL) and <0.05 μmol/L (<35 ng/mL), respectively. During a 2.1-year period, the method has shown a total CV < 8% for control samples (n = 2808) in the range of 0.10 (70) to 3.5 μmol/L (2461 ng/mL). The simplified automated method for sample preparation works equally well as the manual one. No specific and clinically significant causes of preanalytic errors were found. CONCLUSIONS: This LC-MS/MS method with automated sample workup is well suited for a clinical laboratory with LC-MS/MS experience and has the capability, proven from several years of use, to produce reliable PEth results in a high-volume laboratory (>50000 clinical samples/year).
  •  
29.
  • Olsson, Christian, et al. (författare)
  • Medium-term survival after surgery for acute Type A aortic dissection is improving
  • 2017
  • Ingår i: European Journal of Cardio-Thoracic Surgery. - : Oxford University Press. - 1010-7940 .- 1873-734X. ; 52:5, s. 852-857
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: To report long-term survival and predictors of mortality in patients included in a large, contemporary, multicentre, multinational database: Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD), which consists of 8 centres in 4 Nordic countries.METHODS: Currently, NORCAAD includes 1159 patients operated between 2005 and 2014. In 30-day survivors (n = 955, 82%), the Kaplan-Meier and Cox proportional hazard methods were used to analyse medium-term (up to 8 years) survival and relative survival versus a matched normal population. Pre- and intraoperative predictors were expressed as hazard ratio (HR) with 95% confidence interval (95% CI).RESULTS: Cumulative follow-up was 3514 patient-years with a median of 3.2 years (range 0-10.2 years). Survival was 95% (95% CI 93-96) at 1 year, 86% (95% CI 83-88) at 5 years and 76% (95% CI 72-81) at 8 years. Relative survival versus a matched normal population was 95% (95% CI 94-97) at 1 year, 90% (95% CI 87-93) at 5 years and 85% (95% CI 80-90) at 8 years. In multivariable analysis, increased age (HR 1.05 per year, 95% CI 1.04-1.07), previous abdominal or thoracic aortic repair (HR 3.2, 95% CI 1.6-6.4) and chronic renal disease (HR 2.7, 95% CI 1.2-6.2) were associated with increased medium-term mortality. Open distal anastomosis (HR 0.55, 95% CI 0.35-0.87) and operation in the 2010-2014 period (HR 0.90, 95% CI 0.83-0.97) were associated with decreased medium-term mortality.CONCLUSIONS: Medium-term survival after acute Type A aortic dissection in the NORCAAD registry is satisfactory, close to a matched normal population and improved in the later part of the study period. The use of open distal anastomosis was associated with decreased medium-term mortality.
  •  
30.
  • Oudin, Anna, et al. (författare)
  • Impact of national holidays and weekends on incidence of acute type A aortic dissection repair
  • 2022
  • Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies have demonstrated that environmental and temporal factors may affect the incidence of acute type A aortic dissection (ATAAD). Here, we aimed to investigate the hypothesis that national holidays and weekends influence the incidence of surgery for ATAAD. For the period 1st of January 2005 until 31st of December 2019, we investigated a hypothesised effect of (country-specific) national holidays and weekends on the frequency of 2995 surgical repairs for ATAAD at 10 Nordic cities included in the Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) collaboration. Compared to other days, the number of ATAAD repairs were 29% (RR 0.71; 95% CI 0.54–0.94) lower on national holidays and 26% (RR 0.74; 95% CI 0.68–0.82) lower on weekends. As day of week patterns of symptom duration were assessed and the primary analyses were adjusted for period of year, our findings suggest that the reduced surgical incidence on national holidays and weekends does not seem to correspond to seasonal effects or surgery being delayed and performed on regular working days.
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31.
  • Pan, Emily, et al. (författare)
  • Outcome after type A aortic dissection repair in patients with preoperative cardiac arrest
  • 2019
  • Ingår i: Resuscitation. - : Elsevier. - 0300-9572 .- 1873-1570. ; 144, s. 1-5
  • Tidskriftsartikel (refereegranskat)abstract
    • AIM OF THE STUDY: Patients presenting with acute type A aortic dissection (ATAAD) and cardiac arrest before surgery are considered to have very poor prognosis, but limited data is available. We used a large database to evaluate the outcome of ATAAD patients with a cardiac arrest before surgery.METHODS: We evaluated 1154 surgically treated ATAAD patients from the Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) database between 2005 and 2014. Patients with (n = 44, 3.8%) and without preoperative cardiac arrest were compared and variables univariably associated with mortality in the cardiac arrest group were identified. Median follow-up time was 2.7 years (interquartile range 0.5-5.5).RESULTS: Thirty-day mortality in the arrest and non-arrest group was 43.2% and 16.6%, respectively (odds ratio [OR] 3.83, CI 2.06-7.09; P < 0.001). In the nine patients with ongoing cardiopulmonary resuscitation when cardiopulmonary bypass was initiated, five died intraoperatively and one died after 65 days. In patients surviving the operation, stroke was significantly more common in the arrest group (48.4% vs 18.2%; OR 4.21, CI 2.05-8.67; P < 0.001). In total, 50.0% (22/44) of the arrest patients survived to the end of follow-up. Non-survivors in the arrest group more often had DeBakey type I dissection, cardiac tamponade, cardiac malperfusion and higher preoperative serum lactate (all P < 0.05).CONCLUSIONS: Early mortality and complications after ATAAD surgery in patients with a preoperative cardiac arrest are high, but mid-term outcome after surviving the initial period is acceptable. Preoperative cardiac arrest should not be considered an absolute contraindication for a surgical ATAAD repair.
  •  
32.
  • Persson, Anders, et al. (författare)
  • Effects of enrichment on simple aquatic food webs
  • 2001
  • Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 157:6, s. 654-669
  • Tidskriftsartikel (refereegranskat)abstract
    • Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on populations and that equilibrium population densities will change at the top trophic level and every second level below. We experimentally tested these predictions in three aquatic food web configurations subjected to either high or low nutrient additions. The results were structured by viewing the systems as either food chains or webs and showed that trophic level biomass increased with enrichment, which contradicts food chain theory. However, within each trophic level, food web configuration affected the extent to which different functional groups responded to enrichment. By dividing trophic levels into functional groups, based on vulnerability to consumption, we were able to identify significant effects that were obscured when systems were viewed as food chains. The results support the prediction that invulnerable prey may stabilize trophic-level dynamics by replacing other, more vulnerable prey. Furthermore, the vulnerable prey, such as Daphnia and edible algae, responded as predicted by the paradox of enrichment hypothesis; that is, variability in population density increased with enrichment. Hence, by describing ecosystems as a matrix of food web interactions, and by recognizing the interplay between interspecific competition and predation, a more complete description of the ecosystem function was obtained compared to when species were placed into distinct trophic levels.
  •  
33.
  • Persson, Anders, et al. (författare)
  • Effects of enrichment on simple aquatic food webs
  • 2001
  • Ingår i: The American Naturalist. ; 157:6, s. 654-669
  • Tidskriftsartikel (refereegranskat)abstract
    • Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on
  •  
34.
  • Uimonen, Mikko, et al. (författare)
  • Outcome After Surgery for Acute Type A Aortic Dissection With or Without Primary Tear Resection
  • 2022
  • Ingår i: Annals of Thoracic Surgery. - : Elsevier. - 0003-4975 .- 1552-6259. ; 114:2, s. 492-501
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The outcome in patients after surgery for acute type A aortic dissection without replacement of the part of the aorta containing the primary tear is undefined.METHODS: Data of 1122 patients who underwent surgery for acute type A aortic dissection in 8 Nordic centers from January 2005 to December 2014 were retrospectively analyzed. The patients with primary tear location unfound, un-known, not confirmed, or not recorded (n = 243, 21.7%) were excluded from the analysis. The patients were divided into 2 groups according to whether the aortic reconstruction encompassed the portion of the primary tear (tear resected [TR] group, n = 730) or not (tear not resected [TNR] group, n = 149). The restricted mean survival time ratios adjusted for patient characteristics and surgical details between the groups were calculated for all-cause mortality and aortic reoperation-free survival. The median follow-up time was 2.57 (interquartile range, 0.53-5.30) years.RESULTS: For the majority of the patients in the TR group, the primary tear was located in the ascending aorta (83.6%). The reconstruction encompassed both the aortic root and the aortic arch in 7.4% in the TR group as compared with 0.7% in the TNR patients (P < .001). There were no significant differences in all-cause mortality (adjusted restricted mean survival time ratio, 1.01; 95% confidence interval, 0.92-1.12; P = .799) or reoperation-free survival (adjusted restricted mean survival time ratio, 0.98; 95% confidence interval, 0.95-1.02; P = .436) between the TR and TNR groups.CONCLUSIONS: Primary tear resection alone does not determine the midterm outcome after surgery for acute type A aortic dissection. (Ann Thorac Surg 2022;114:492-501) (c) 2022 by The Society of Thoracic Surgeons.
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35.
  • Zindovic, Igor, et al. (författare)
  • Malperfusion in acute type A aortic dissection : An update from the Nordic Consortium for Acute Type A Aortic Dissection
  • 2019
  • Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier. - 0022-5223 .- 1097-685X. ; 157:4, s. 1324-1333
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: To evaluate the effect of preoperative malperfusion on 30-day and late mortality and postoperative complications using data from the Nordic Consortium for Acute Type A Aortic Dissection (ATAAD) registry.Methods: We studied 1159 patients who underwent ATAAD surgery between January 2005 and December 2014 at 8 Nordic centers. Multivariable logistic and Cox regression analyses were performed to identify independent predictors of 30-day and late mortality.Results: Preoperative malperfusion was identified in 381 of 1159 patients (33%) who underwent ATAAD surgery. Thirty-day mortality was 28.9% in patients with preoperative malperfusion and 12.1% in those without. Independent predictors of 30-day mortality included any malperfusion (odds ratio, 2.76; 95% confidence interval [CI], 1.94-3.93), cardiac malperfusion (odds ratio, 2.37; 95% CI, 1.34-4.17), renal malperfusion (odds ratio, 2.38; 95% CI, 1.23-4.61) and peripheral malperfusion (odds ratio, 1.95; 95% CI, 1.26-3.01). Any malperfusion (hazard ratio, 1.72; 95% CI, 1.21-2.43), cardiac malperfusion (hazard ratio, 1.89; 95% CI, 1.24-2.87) and gastrointestinal malperfusion (hazard ratio, 2.25; 95% CI, 1.18-4.26) were predictors of late mortality. Malperfusion was associated with significantly poorer survival at 1, 3, and 5 years (95.0% +/-0.9% vs 88.7% +/-1.9%, 90.1% +/-1.3% vs 84.0% +/-2.4%, and 85.4% +/-1.7% vs 80.8% +/-2.7%; log rank P = .009).Conclusions: Malperfusion has a significant influence on early and late outcomes in ATAAD surgery. Management of preoperative malperfusion remains a major challenge in reducing mortality associated with surgical treatment of ATAAD.
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36.
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37.
  • Andersen, Martin, et al. (författare)
  • Distributed Robust Stability Analysis of Interconnected Uncertain Systems
  • 2012
  • Ingår i: Proceedings of the 51st IEEE Conference on Decision and Control. - 0743-1546. - 9781467320641 - 9781467320658 ; , s. 1548-1553
  • Konferensbidrag (refereegranskat)abstract
    • This paper considers robust stability analysis of a large network of interconnected uncertain systems. To avoid analyzing the entire network as a single large, lumped system, we model the network interconnections with integral quadratic constraints. This approach yields a sparse linear matrix inequality which can be decomposed into a set of smaller, coupled linear matrix inequalities. This allows us to solve the analysis problem efficiently and in a distributed manner. We also show that the decomposed problem is equivalent to the original robustness analysis problem, and hence our method does not introduce additional conservativeness.
  •  
38.
  • Andersen, Martin S., et al. (författare)
  • Robust Stability Analysis of Sparsely Interconnected Uncertain Systems
  • 2014
  • Ingår i: IEEE Transactions on Automatic Control. - : IEEE. - 0018-9286 .- 1558-2523. ; 59:8, s. 2151-2156
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we consider robust stability analysis of large-scale sparsely interconnected uncertain systems. By modeling the interconnections among the subsystems with integral quadratic constraints, we show that robust stability analysis of such systems can be performed by solving a set of sparse linear matrix inequalities. We also show that a sparse formulation of the analysis problem is equivalent to the classical formulation of the robustness analysis problem and hence does not introduce any additional conservativeness. The sparse formulation of the analysis problem allows us to apply methods that rely on efficient sparse factorization techniques, and our numerical results illustrate the effectiveness of this approach compared to methods that are based on the standard formulation of the analysis problem.
  •  
39.
  • Ankelhed, Daniel, et al. (författare)
  • A Partially Augmented Lagrangian Method for Low Order H-Infinity Controller Synthesis Using Rational Constraints
  • 2011
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • When designing robust controllers, H-infinity synthesis is a common tool touse. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex, even when the order of the system is low.The approach used in this work is based on formulating the constraint onthe maximum order of the controller as a polynomial (or rational) equation.This equality constraint is added to the optimization problem of minimizingan upper bound on the H-innity norm of the closed loop system subjectto linear matrix inequality (LMI) constraints. The problem is then solvedby reformulating it as a partially augmented Lagrangian problem where theequality constraint is put into the objective function, but where the LMIsare kept as constraints.The proposed method is evaluated together with two well-known methodsfrom the literature. The results indicate that the proposed method hascomparable performance in most cases, especially if the synthesized con-troller has many parameters, which is the case if the system to be controlledhas many input and output signals.
  •  
40.
  • Ankelhed, Daniel, et al. (författare)
  • A Partially Augmented Lagrangian Method for Low Order H-Infinity Controller Synthesis Using Rational Constraints
  • 2012
  • Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 57:11, s. 2901-2905
  • Tidskriftsartikel (refereegranskat)abstract
    • This technical note proposes a method for low order H-infinity synthesis where the constraint on the order of the controller is formulated as a rational equation. The resulting nonconvex optimization problem is then solved by applying a partially augmented Lagrangian method. The proposed method is evaluated together with two well-known methods from the literature. The results indicate that the proposed method has comparable performance and speed.
  •  
41.
  • Ankelhed, Daniel, et al. (författare)
  • A Primal-Dual Method for Low Order H-Infinity Controller Synthesis
  • 2010
  • Ingår i: Proceedings of Reglermöte 2010. - Lund : Linköping University Electronic Press.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • When designing robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex, even when the order of the system is low.The approach used in this work is based on formulating the constraint on the maximum order of the controller as a polynomial (or rational) equation. By using the fact that the polynomial (or rational) is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex function is to be minimized over a convex set defined by linear matrix inequalities.The proposed method is evaluated together with a well-known method from the literature. The results indicate that the proposed method performs slightly better.
  •  
42.
  • Ankelhed, Daniel, et al. (författare)
  • A Primal-Dual Method for Low Order H-Infinity Controller Synthesis
  • 2009
  • Ingår i: Proceedings of the 48th IEEE Conference on Decision and Control held jointly with the 28th Chinese Control Conference. - : IEEE. - 9781424438716 - 9781424438723 ; , s. 6674-6679
  • Konferensbidrag (refereegranskat)abstract
    • When designing robust controllers, H-infinity synthesisis a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex,even when the order of the system is low.The approach used in this work is based on formulating the constraint on the maximum order of the controller as a polynomial (or rational) equation. By using the fact that the polynomial (or rational) is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex function is to be minimized over a convex set defined by linear matrix inequalities.The proposed method is evaluated together with a wellknown method from the literature. The results indicate that the proposed method performs slightly better.
  •  
43.
  • Ankelhed, Daniel, et al. (författare)
  • A Quasi-Newton Interior Point Method for Low Order H-Infinity Controller Synthesis
  • 2011
  • Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 56:6, s. 1462-1467
  • Tidskriftsartikel (refereegranskat)abstract
    • This technical note proposes a method for low order H-infinity synthesis where the constraint on the order of the controller is formulated as a rational equation. The resulting nonconvex optimization problem is then solved by applying a quasi-Newton primal-dual interior point method. The proposed method is evaluated together with a well-known method from the literature. The results indicate that the proposed method has comparable performance and speed.
  •  
44.
  •  
45.
  • Ankelhed, Daniel, 1980- (författare)
  • On design of low order H-infinity controllers
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • When designing controllers with robust performance and stabilization requirements, H-infinity synthesis is a common tool to use. These controllers are often obtained by solving mathematical optimization problems. The controllers that result from these algorithms are typically of very high order, which complicates implementation. Low order controllers are usually desired, since they are considered more reliable than high order controllers. However, if a constraint on the maximum order of the controller is set that is lower than the order of the so-called augmented system, the optimization problem becomes nonconvex and it is relatively difficult to solve. This is true even when the order of the augmented system is low.In this thesis, optimization methods for solving these problems are considered. In contrast to other methods in the literature, the approach used in this thesis is based on formulating the constraint on the maximum order of the controller as a rational function in an equality constraint. Three methods are then suggested for solving this smooth nonconvex optimization problem.The first two methods use the fact that the rational function is nonnegative. The problem is then reformulated as an optimization problem where the rational function is to be minimized over a convex set defined by linear matrix inequalities (LMIs). This problem is then solved using two different interior point methods.In the third method the problem is solved by using a partially augmented Lagrangian formulation where the equality constraint is relaxed and incorporated into the objective function, but where the LMIs are kept as constraints. Again, the feasible set is convex and the objective function is nonconvex.The proposed methods are evaluated and compared with two well-known methods from the literature. The results indicate that the first two suggested methods perform well especially when the number of states in the augmented system is less than 10 and 20, respectively. The third method has comparable performance with two methods from literature when the number of states in the augmented system is less than 25.
  •  
46.
  • Ankelhed, Daniel, et al. (författare)
  • Suboptimal Model Reduction using LMIs with Convex Constraints
  • 2006
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • An approach to model reduction of LTI systems using Linear Matrix Inequalities (LMIs) in an H-infinity framework is presented, where non-convex constraints are replaced with stricter convex constraints thus making it suboptimal. The presented algorithms are compared with the Optimal Hankel reduction algorithm, and are shown to achieve better results (i.elower H-infinity errors) in cases where some of the Hankel singular values are close, but not equal to each other.
  •  
47.
  • Aronsson, Per, et al. (författare)
  • An operational decision support tool for stump harvest
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • A multi-criteria decision support tool was developed to optimise stump harvesting for energy in Sweden. The decision tool takes account of multiple, sometimes conflicting, criteria relating to stump harvest; energy and climate, economics, biodiversity, and soil and water. Data on harvested stems are used as primary input data in the tool. Such data are routinely collected in harvester computers. The tool effectively deals with mixed sets of data; quantitative harvest data are re-calculated to metric (e.g. stump biomass), and qualitative data (e.g. biodiversity implications) are incorporated. A digital terrain map derived from air-borne laser scanning provides basic data for estimating soil wetness, while digital maps of water courses, key habitats and protected areas, or other sensitive habitats, are used to identify potentially and practically harvestable stumps.In four sub-models, an index from 0 to 10 is calculated for each stump, with 0 representing ‘Not at all suitable’ and 10 ‘Highly suitable for extraction’. Through this, a stump of high value for wood-living species is assigned a low index in the biodiversity sub-model and a large, easily accessible stump is assigned a high index in the economic sub-model. When calculating the net index, the sub-indices can be weighted according to the preferences of the end-user.An energy and climate sub-model incorporates greenhouse gas (GHG) emissions from forest operations and the effect of advancing GHG emissions when stump biomass is incinerated instead of being left to decompose. In the economic sub-model the potential monetary return from each stump is calculated based on estimated revenue from harvested stump biomass and the costs of stump harvesting and forwarding operations (based on cost functions and GIS calculations of transport distances).The biodiversity sub-model considers four types of wood-dependent organisms (lichens, mosses, insects and fungi) in terms of their habitat requirements, vulnerability, sun exposure preferences, locality, etc. A panel of external experts has drawn up a grading scale of stump values for the different taxonomic groups. The proximity to key habitats and exposure to sunlight are derived from a spatial model.Soil and water issues are handled within a sub-model estimating the consequences for long-term soil fertility (nutrient cycling and soil compaction) and water (leaching of plant nutrients and mercury, and particle transport due to soil damage by heavy machinery).The tool offers the end-user possibilities to prioritise and plan for cost-effective stump harvesting, while minimising negative environmental impacts.
  •  
48.
  • Axehill, Daniel, 1978- (författare)
  • Applications of Integer Quadratic Programming in Control and Communication
  • 2005
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The main topic of this thesis is integer quadratic programming with applications to problems arising in the areas of automatic control and communication. One of the most widespread modern control principles is the discrete-time method Model Predictive Control (MPC). The main advantage with MPC, compared to most other control principles, is that constraints on control signals and states can easily be handled. In each time step, MPC requires the solution of a Quadratic Programming (QP) problem. To be able to use MPC for large systems, and at high sampling rates, optimization routines tailored for MPC are used. In recent years, the range of application of MPC has been extended from constrained linear systems to so-called hybrid systems. Hybrid systems are systems where continuous dynamics interact with logic. When this extension is made, binary variables are introduced in the problem. As a consequence, the QP problem has to be replaced by a far more challenging Mixed Integer Quadratic Programming (MIQP) problem. Generally, for this type of optimization problems, the computational complexity is exponential in the number of binary optimization variables. In modern communication systems, multiple users share a so-called multi-access channel, where the information sent by different users is separated by using almost orthogonal codes. Since the codes are not completely orthogonal, the decoded information at the receiver is slightly correlated between different users. Further, noise is added during the transmission. To estimate the information originally sent, a maximum likelihood problem involving binary variables is solved. The process of simultaneously estimating the information sent by multiple users is called multiuser detection. In this thesis, the problem to efficiently solve MIQP problems originating from MPC is addressed. Two different algorithms are presented. First, a polynomial complexity preprocessing algorithm for binary quadratic programming problems is presented. By using the algorithm, some, or all, binary variables can be computed efficiently already in the preprocessing phase. In simulations, the algorithm is applied to unconstrained MPC problems with a mixture of real and binary control signals. It has also been applied to the multiuser detection problem, where simulations have shown that the bit error rate can be significantly reduced by using the proposed algorithm as compared to using common suboptimal algorithms. Second, an MIQP algorithm tailored for MPC is presented. The algorithm uses a branch and bound method where the relaxed node problems are solved by a dual active set QP algorithm. In this QP algorithm, the KKT-systems are solved using Riccati recursions in order to decrease the computational complexity. Simulation results show that both the QP solver and the MIQP solver proposed have lower computational complexity than corresponding generic solvers.
  •  
49.
  • Barbu, Mikael, et al. (författare)
  • Dextran- versus crystalloid-based prime in cardiac surgery: A prospective randomized pilot study.
  • 2020
  • Ingår i: The Annals of thoracic surgery. - : Elsevier BV. - 1552-6259 .- 0003-4975. ; 110:5, s. 1541-7
  • Tidskriftsartikel (refereegranskat)abstract
    • The optimum priming fluid for the cardiopulmonary bypass (CPB) circuit is still debated. We compared a new hyperoncotic priming solution containing dextran 40, which has an electrolyte composition that mimics extracellular fluid, with a standard crystalloid-based prime.Eighty cardiac surgery patients were included in this double-blind randomized single-centre study. The patients were randomized to either a dextran-based prime or a crystalloid prime containing Ringer acetate and mannitol. The primary endpoint was colloid oncotic pressure (COP) in serum during CPB. Secondary endpoints included fluid balance, bleeding and transfusion requirements, pulmonary function, hemolysis, systemic inflammation, and markers of renal, hepatic, myocardial, and brain injury. Blood samples were collected before, during, and after CPB.COP was higher in the dextran group than in the crystalloid prime group on CPB (18.8±2.9 vs. 16.4±2.9 mmHg, p<0.001) and 10 min after CPB (19.2±2.7 vs. 16.8±2.9 mmHg, p<0.001). Patients in the dextran group required less intravenous fluid during CPB (1090±499 vs. 1437±543 ml; p=0.003) and net fluid balance was less positive 12h after surgery (+1,431±741 vs. +1,901±922 ml; p=0.014). Plasma free hemoglobin was significantly lower in the dextran group 2h after CPB (0.18±0.11 vs 0.41±0.33, p=0.001). There were no significant differences in bleeding, transfusion requirements, organ function, systemic inflammation, or brain and myocardial injury markers between the groups at any time point.Our results suggest that a hyperoncotic dextran-based priming solution preserves intraoperative COP compared to crystalloid prime. Larger studies with clinically valid endpoints are necessary to evaluate hyperoncotic prime solutions further.
  •  
50.
  • Bergman, Eva, et al. (författare)
  • Synthesis of theoretical and empirical experineces from nutrient and cyprinid reductions in Lake Ringsjön
  • 1999
  • Ingår i: Hydrobiologia. - 0018-8158. ; 404, s. 145-156
  • Tidskriftsartikel (refereegranskat)abstract
    • The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
  •  
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