686 results on '"Wiklund, Urban"'
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2. Our initial experience of monitoring the autoregulation of cerebral blood flow during cardiopulmonary bypass
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Andersen Leon, Appelblad Micael, Wiklund Urban, Sundström Nina, and Svenmarker Staffan
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cardiopulmonary bypass ,monitoring ,cerebral blood flow ,autoregulation ,near-infrared spectroscopy ,Medicine - Abstract
Background: Cerebral blood flow (CBF) is believed to be relatively constant within an upper and lower blood pressure limit. Different methods are available to monitor CBF autoregulation during surgery. This study aims to critically analyze the application of the cerebral oxygenation index (COx), one of the commonly used techniques, using a reference to data from a series of clinical registrations. Method: CBF was monitored using near-infrared spectroscopy, while cerebral blood pressure was estimated by recordings obtained from either the radial or femoral artery in 10 patients undergoing cardiopulmonary bypass. The association between CBF and blood pressure was calculated as a moving continuous correlation coefficient. A COx index > 0.4 was regarded as a sign of abnormal cerebral autoregulation (CA). Recordings were examined to discuss reliability measures and clinical feasibility of the measurements, followed by interpretation of individual results, identification of possible pitfalls, and suggestions of alternative methods. Results and Conclusion: Monitoring of CA during cardiopulmonary bypass is intriguing and complex. A series of challenges and limitations should be considered before introducing this method into clinical practice.
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- 2023
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3. Pulmonary function in a cohort of heart-healthy individuals from Northern Sweden—a comparison with discordant reference values
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Erelund, Sofia, Karp, Kjell, Arvidsson, Sandra, Johansson, Bengt, Sundström, Nina, and Wiklund, Urban
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- 2023
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4. Density Encoding Enables Resource-Efficient Randomly Connected Neural Networks
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Kleyko, Denis, Kheffache, Mansour, Frady, E. Paxon, Wiklund, Urban, and Osipov, Evgeny
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Computer Science - Machine Learning ,Statistics - Machine Learning - Abstract
The deployment of machine learning algorithms on resource-constrained edge devices is an important challenge from both theoretical and applied points of view. In this article, we focus on resource-efficient randomly connected neural networks known as Random Vector Functional Link (RVFL) networks since their simple design and extremely fast training time make them very attractive for solving many applied classification tasks. We propose to represent input features via the density-based encoding known in the area of stochastic computing and use the operations of binding and bundling from the area of hyperdimensional computing for obtaining the activations of the hidden neurons. Using a collection of 121 real-world datasets from the UCI Machine Learning Repository, we empirically show that the proposed approach demonstrates higher average accuracy than the conventional RVFL. We also demonstrate that it is possible to represent the readout matrix using only integers in a limited range with minimal loss in the accuracy. In this case, the proposed approach operates only on small n-bits integers, which results in a computationally efficient architecture. Finally, through hardware Field-Programmable Gate Array (FPGA) implementations, we show that such an approach consumes approximately eleven times less energy than that of the conventional RVFL., Comment: 7 pages, 7 figures
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- 2019
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5. Impaired Exercise Capacity and Mortality Risk in Adults With Congenital Heart Disease
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Wikner, Anna, Sandström, Anette, Rinnström, Daniel, Wiklund, Urban, Christersson, Christina, Dellborg, Mikael, Nielsen, Niels Erik, Sörensson, Peder, Thilén, Ulf, Johansson, Bengt, and Sandberg, Camilla
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- 2023
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6. Numerical modeling and synchrotron diffraction measurements of residual stresses in laser powder bed fusion manufactured alloy 625
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Malmelöv, Andreas, Hassila, Carl-Johan, Fisk, Martin, Wiklund, Urban, and Lundbäck, Andreas
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- 2022
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7. Diabetes and male sex are key risk factor correlates of the extent of coronary artery calcification: A Euro-CCAD study
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Nicoll, Rachel, Zhao, Ying, Wiklund, Urban, Diederichsen, Axel, Mickley, Hans, Ovrehus, Kristian, Zamorano, Jose, Gueret, Pascal, Schmermund, Axel, Maffei, Erica, Cademartiri, Filippo, Budoff, Matt, and Henein, Michael
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Biomedical and Clinical Sciences ,Clinical Sciences ,Heart Disease - Coronary Heart Disease ,Diabetes ,Cardiovascular ,Heart Disease ,Prevention ,Adult ,Age Factors ,Aged ,Cohort Studies ,Computed Tomography Angiography ,Coronary Artery Disease ,Cross-Sectional Studies ,Diabetic Angiopathies ,Europe ,Female ,Hospitals ,Special ,Humans ,Male ,Middle Aged ,Prevalence ,Registries ,Retrospective Studies ,Risk Factors ,Severity of Illness Index ,Sex Factors ,United States ,Vascular Calcification ,Coronary calcification extent ,Risk factors ,Gender ,Hypertension ,Endocrinology & Metabolism ,Clinical sciences - Abstract
Background and aimsAlthough much has been written about the conventional cardiovascular risk factor correlates of the extent of coronary artery calcification (CAC), few studies have been carried out on symptomatic patients. This paper assesses the potential ability of risk factors to associate with an increasing CAC score.MethodsFrom the European Calcific Coronary Artery Disease (Euro-CCAD) cohort, we retrospectively investigated 6309 symptomatic patients, 62% male, from Denmark, France, Germany, Italy, Spain and the USA. All had conventional cardiovascular risk factor assessment and CT scanning for CAC scoring.ResultsAmong all patients, male sex (OR = 4.85, p
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- 2017
8. Exploring the tribochemical wear and material transfer caused by Cu15Zn alloys on shearing tools
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Heinrichs, Jannica, Mikado, H., Donzel-Gargand, Olivier, Surreddi, K. B., Wiklund, Urban, Kawamura, S., Jacobson, Staffan, Heinrichs, Jannica, Mikado, H., Donzel-Gargand, Olivier, Surreddi, K. B., Wiklund, Urban, Kawamura, S., and Jacobson, Staffan
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Cemented carbide tools are extensively used in the zipper industry, including shearing of a pre-formed Cu15Zn wire into individual zipper elements. Although the work material is significantly softer than the tool, wear is the life limiting factor for the tools and is considered to be of tribochemical nature. So far it has not been explained, however, it is known that the wear rate of uncoated, as well as CrC and CrN coated, cemented carbide increases dramatically when Zn is omitted from the Cu alloy. In this paper, worn tool surfaces, including any transferred material, were studied to investigate the tribochemical wear mechanism in detail. Material transfer occurred onto all tool surfaces. Cu and Zn were separated on the sub-micron scale, and preferential transfer of one of the constituents was observed. This is reflected in the outermost surface of the sheared element, which shows a homogeneous composition elsewhere. Oxidation was observed of all tool surfaces, which indicates elements of oxidative wear. Further, any Zn transferred to the tool surfaces was oxidized. Thus, it is suggested that the presence of Zn reduces the oxygen available and consequently reduces the oxidation rate of the tool surfaces, leading to the protective effect previously observed.
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- 2024
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9. Altered hormonal and autonomic nerve responses to hypo- and hyperglycaemia are found in overweight and insulin-resistant individuals and may contribute to the development of type 2 diabetes
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Lundqvist, Martin H., Almby, Kristina, Wiklund, Urban, Abrahamsson, Niclas, Kamble, Prasad G., Pereira, Maria J., and Eriksson, Jan W.
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- 2021
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10. Holter study of heart rate variability in children and adolescents with long QT syndrome.
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Lundström, Anna, Eliasson, Håkan, Karlsson, Marcus, Wiklund, Urban, and Rydberg, Annika
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Objectives: This study aimed to retrospectively assess cardiac autonomic activity in children with LQTS, considering genotype, symptoms, sex, age, and beta‐blocker therapy (BB) and compare it to healthy controls. Methods: Heart rate variability (HRV), using power spectrum analysis, was analyzed in 575 Holter recordings from 116 children with LQTS and in 69 healthy children. The data were categorized into four age‐groups and four heart rate (HR) ranges. Results: In LQT1 and LQT2, increasing HR corresponded to significantly lower low (LF) and high frequency (HF) compared to controls. Total power (PTOT) was lower in all LQT1 age‐groups compared to controls at HR 120–140 bpm (1–15 years: p <.01; 15–18 years: p =.03). At HR 80–100, LQT1 patients aged 1–10 years had lower HF than LQT2 patients (1–5 years: p =.05; 5–10 years: p =.02), and LQT2 patients aged 15–18 years had lower HF than LQT1 patients (p <.01). Symptomatic patients aged 10–15 years had lower PTOT at HR 100–120 bpm than asymptomatic patients (p =.04). LQT1 girls aged 10–15 and 15–18 years had a lower PTOT (10–15 years: p =.04; 15–18 years: p =.02) than boys. Conclusion: This study shows a correlation between HR and changes in HRV parameters. At higher HRs, LQTS patients generally had lower HRV values than controls, suggesting an abnormal autonomic response. These results may strengthen the link between physical activity and arrhythmias in LQTS. [ABSTRACT FROM AUTHOR]
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- 2024
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11. The effect of laser scanning strategies on texture, mechanical properties, and site-specific grain orientation in selective laser melted 316L SS
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Marattukalam, Jithin James, Karlsson, Dennis, Pacheco, Victor, Beran, Přemysl, Wiklund, Urban, Jansson, Ulf, Hjörvarsson, Björgvin, and Sahlberg, Martin
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- 2020
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12. Machining of additively manufactured alloy 718 in as-built and heat-treated condition: surface integrity and cutting tool wear
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Holmberg, Jonas, primary, Berglund, Johan, additional, Brohede, Ulrika, additional, Åkerfeldt, Pia, additional, Sandell, Viktor, additional, Rashid, Amir, additional, Zhao, Xiaoyu, additional, Dadbakhsh, Sasan, additional, Fischer, Marie, additional, Hryha, Eduard, additional, Wiklund, Urban, additional, Hassila, Carl Johan Karlsson, additional, and Hosseini, Seyed, additional
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- 2023
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13. Cardiac response to water activities in children with Long QT syndrome type 1
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Lundström, Anna, primary, Wiklund, Urban, additional, Winbo, Annika, additional, Eliasson, Håkan, additional, Karlsson, Marcus, additional, and Rydberg, Annika, additional
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- 2023
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14. How stable is lung function in patients with stable chronic obstructive pulmonary disease when monitored using a telehealth system? A longitudinal and home-based study
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Holmner, Åsa, Öhberg, Fredrik, Wiklund, Urban, Bergmann, Eva, Blomberg, Anders, and Wadell, Karin
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- 2020
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15. Comparison of test methods estimating the stiffness of ultrathin coatings
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Tavares da Costa, Marcus Vinícius, Neagu, Cristian, Fayet, Pierre, Wiklund, Urban, Li, Hu, Leifer, Klaus, and Gamstedt, E. Kristofer
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- 2018
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16. Wear of cemented carbide tools in a copper alloy forging process : Verification of a new lab test
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Mikado, Hiroko, Heinrichs, Jannica, Wiklund, Urban, Jacobson, Staffan, Kawamura, Shingo, Mikado, Hiroko, Heinrichs, Jannica, Wiklund, Urban, Jacobson, Staffan, and Kawamura, Shingo
- Abstract
Cemented carbide tools are commonly used in both shearing and forging processes associated to zipper production. In the actual production, the tool life is often limited by wear after many millions of repeated contacts with copper alloys. A series of previous investigations has shown that the wear of the tools is tribochemical for both shearing and forging, however with different features. The mechanisms causing this wear are not well understood. To gain deeper insights into the active wear mechanisms during the copper alloy forging process, a new tribotester was proposed and developed. By this tester, a cemented carbide cylinder is repeatedly put in sliding contact with a rotating copper alloy cylinder in a crossed cylinders arrangement. The test was interrupted at selected intervals so that the cemented carbide cylinder could be repeatedly evaluated by SEM and EDS. It was revealed that the characteristic wear of actual tools, tribochemical smooth wear in common, and preferential removal of Co binder and partially Zn rich transfer for the forging tool, can be reproduced by this tribotester.
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- 2023
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17. Heart rate variability and cardiovascular risk factors in patients with rheumatoid arthritis : a longitudinal study
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Erelund, Sofia, Södergren, Anna, Wiklund, Urban, Sundström, Nina, Erelund, Sofia, Södergren, Anna, Wiklund, Urban, and Sundström, Nina
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Background: It is established that the risk of cardiovascular disease (CVD) is increased in patients with Rheumatoid Arthritis (RA). Heart rate variability (HRV) is a method for evaluating the activity in the cardiac autonomic nervous system. Our aim was to assess the longitudinal development of HRV in patients with RA and compare with healthy controls. Furthermore, we wanted to investigate associations between HRV, inflammatory disease activity and cardiovascular complications in patients with RA over time. Method: HRV was assessed with frequency-domain analysis at baseline and after five years in 50 patients with early RA, all being younger than 60 years. HRV indices were age-adjusted based on the estimated age-dependency in 100 age and sex matched healthy controls. Additionally, clinical data including serological markers, disease activity, and blood pressure were collected from the patients. Eleven years after inclusion CVD was assessed. Results: At baseline, patients with RA presented with lower HRV compared to controls during deep breathing (6 breaths/min), paced normal breathing (12 breaths/min) and after passive tilt to the upright position. No significant change in HRV was observed at the five-year follow-up. A significant negative correlation was found between HRV parameters and systolic blood pressure (SBP) at baseline. A significant positive correlation was found between heart rate and inflammatory markers at baseline but not after five years. Nine patients had developed CVD after 11 years, but no significant association was found with baseline HRV data. Conclusion: This study showed that patients with RA have autonomic imbalance both at an early stage of the disease and after five years, despite anti-rheumatic medication, but no correlation between HRV and inflammation markers were observed. Reduced HRV was also significantly negatively correlated with increased SBP. Hypertension is a common finding in patients with RA. Thus, significant decline of HRV
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- 2023
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18. Machining of additively manufactured alloy 718 in as-built and heat-treated condition : surface integrity and cutting tool wear
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Holmberg, Jonas, Berglund, Johan, Brohede, Ulrika, Åkerfeldt, Pia, Sandell, Viktor, Rashid, Amir, Zhao, Xiaoyu, Dadbakhsh, Sasan, Fischer, Marie, Hryha, Eduard, Wiklund, Urban, Hassila, Carl Johan Karlsson, Hosseini, Seyed, Holmberg, Jonas, Berglund, Johan, Brohede, Ulrika, Åkerfeldt, Pia, Sandell, Viktor, Rashid, Amir, Zhao, Xiaoyu, Dadbakhsh, Sasan, Fischer, Marie, Hryha, Eduard, Wiklund, Urban, Hassila, Carl Johan Karlsson, and Hosseini, Seyed
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Additive manufacturing (AM) using powder bed fusion is becoming a mature technology that offers great possibilities and design freedom for manufacturing of near net shape components. However, for many gas turbine and aerospace applications, machining is still required, which motivates further research on the machinability and work piece integrity of additive-manufactured superalloys. In this work, turning tests have been performed on components made with both Powder Bed Fusion for Laser Beam (PBF-LB) and Electron Beam (PBF-EB) in as-built and heat-treated conditions. The two AM processes and the respective heat-treatments have generated different microstructural features that have a great impact on both the tool wear and the work piece surface integrity. The results show that the PBF-EB components have relatively lower geometrical accuracy, a rough surface topography, a coarse microstructure with hard precipitates and low residual stresses after printing. Turning of the PBF-EB material results in high cutting tool wear, which induces moderate tensile surface stresses that are balanced by deep compressive stresses and a superficial deformed surface that is greater for the heat-treated material. In comparison, the PBF-LB components have a higher geometrical accuracy, a relatively smooth topography and a fine microstructure, but with high tensile stresses after printing. Machining of PBF-LB material resulted in higher tool wear for the heat-treated material, increase of 49%, and significantly higher tensile surface stresses followed by shallower compressive stresses below the surface compared to the PBF-EB materials, but with no superficially deformed surface. It is further observed an 87% higher tool wear for PBF-EB in as-built condition and 43% in the heat-treated condition compared to the PBF-LB material. These results show that the selection of cutting tools and cutting settings are critical, which requires the development of suitable machining parameters that are, QC 20240122
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- 2023
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19. Cardiac response to water activities in children with Long QT syndrome type 1
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Lundström, Anna, Wiklund, Urban, Winbo, Annika, Eliasson, Håkan, Karlsson, Marcus, Rydberg, Annika, Lundström, Anna, Wiklund, Urban, Winbo, Annika, Eliasson, Håkan, Karlsson, Marcus, and Rydberg, Annika
- Abstract
BACKGROUND: Swimming is a genotype-specific trigger in long QT syndrome type 1 (LQT1). OBJECTIVE: To examine the autonomic response to water activities in children and adolescents with LQT1. METHODS: In this cross-sectional study, LQT1 patients were age and sex matched to one healthy control subject. Electrocardiograms (ECGs) were recorded during face immersion (FI), swimming, diving, and whole-body submersion (WBS). Heart rate (HR) and heart rate variability (HRV) was measured. The high frequency (HF) component of HRV was interpreted to reflect parasympathetic activity, while the low frequency (LF) component was interpreted as reflecting the combined influence of sympathetic and parasympathetic activity on autonomic nervous modulation of the heart. RESULTS: Fifteen LQT1 patients (aged 7-19 years, all on beta-blocker therapy) and fifteen age and sex matched non-medicated controls were included. No significant ventricular arrhythmias were observed in the LQT1 population during the water activities. Out of these 15 matched pairs, 12 pairs managed to complete FI and WBS for more than 10 seconds and were subsequently included in HR and HRV analyses. In response to FI, the LQT1 group experienced a drop in HR of 48 bpm, compared to 67 bpm in the control group (p = 0.006). In response to WBS, HR decreased by 48 bpm in the LQT1 group and 70 bpm in the control group (p = 0.007). A significantly lower PTOT (p < 0.001) and HF (p = 0.011) component was observed before, during and after FI in LQT1 patients compared with the controls. Before, during and after WBS, a significantly lower total power (p < 0.001), LF (p = 0.002) and HF (p = 0.006) component was observed in the LQT1 patients. CONCLUSION: A significantly lower HR decrease in response to water activities was observed in LQT1 subjects on beta-blocker therapy, compared to matched non-medicated controls. The data suggests an impaired parasympathetic response in LQT1 children and adolescents. An aberrant autonomic ner
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- 2023
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20. Our initial experience of monitoring the autoregulation of cerebral blood flow during cardiopulmonary bypass
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Andersen, Leon, Appelblad, Micael, Wiklund, Urban, Sundström, Nina, Svenmarker, Staffan, Andersen, Leon, Appelblad, Micael, Wiklund, Urban, Sundström, Nina, and Svenmarker, Staffan
- Abstract
BACKGROUND: Cerebral blood flow (CBF) is believed to be relatively constant within an upper and lower blood pressure limit. Different methods are available to monitor CBF autoregulation during surgery. This study aims to critically analyze the application of the cerebral oxygenation index (COx), one of the commonly used techniques, using a reference to data from a series of clinical registrations. METHOD: CBF was monitored using near-infrared spectroscopy, while cerebral blood pressure was estimated by recordings obtained from either the radial or femoral artery in 10 patients undergoing cardiopulmonary bypass. The association between CBF and blood pressure was calculated as a moving continuous correlation coefficient. A COx index > 0.4 was regarded as a sign of abnormal cerebral autoregulation (CA). Recordings were examined to discuss reliability measures and clinical feasibility of the measurements, followed by interpretation of individual results, identification of possible pitfalls, and suggestions of alternative methods. RESULTS AND CONCLUSION: Monitoring of CA during cardiopulmonary bypass is intriguing and complex. A series of challenges and limitations should be considered before introducing this method into clinical practice.
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- 2023
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21. Crack initiation and early propagation in case hardened sintered PM steels under cyclic load
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Holmberg, Anders, Wiklund, Urban, Isaksson, Per, Kassman Rudolphi, Åsa, Holmberg, Anders, Wiklund, Urban, Isaksson, Per, and Kassman Rudolphi, Åsa
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In the present study, crack propagation through the case hardened region of two different PM steels manufactured with different powder size distributions and sintered at different temperatures has been investigated. EBSD was used to study the microstructure before and after case hardening, revealing the relationship between powder particle grains after sintering and prior austenite grains after case hardening. A novel approach was used to achieve short cracks (10–20 µm) with high repeatability. The cracks were then analysed using EBSD and SEM, revealing detailed and novel information about the crack propagation route in the materials. Both tested materials show the same crack propagation behaviour. If a prior grain/prior austenite boundary is present within an angle from the crack initiation site, the cracks will follow the boundary and thus propagate intergranular, suggesting that the preferred route of crack propagation in case hardened sintered steel is along these boundaries.
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- 2023
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22. Potential of nitrogen atomized alloy 625 in the powder bed fusion laser beam process
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Hassila, C.J., Paschalidou, Eirini-Maria, Harlin, P., Wiklund, Urban, Hassila, C.J., Paschalidou, Eirini-Maria, Harlin, P., and Wiklund, Urban
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Powder based metal additive manufacturing processes like Powder Bed Fusion – Laser Beam utilize gasatomized metal powders as feedstock material. Typically, for nickel-based alloys such as Alloy 625, argongas is used during the atomization process. Considering the larger environmental impact of argon gascompared to nitrogen gas, and the increasing use of gas atomized metal powders, the environmentalimpact of powder based additive manufacturing techniques could be mitigated if gas atomization ofalloys such as Alloy 625 using nitrogen was possible. This work investigates the feasibility of tailoringan alloy to allow atomization using nitrogen gas while remaining within the Alloy 625 specification.This is achieved by limiting the nitrogen pick-up during the atomization process, primarily by reducingthe titanium content. The metallurgical implications of this tailored alloy and the subsequent atomizationusing nitrogen, as well as the attained microstructure from the Powder Bed Fusion – Laser Beam processis investigated and compared to a more common 625 alloy composition which was atomized usingargon. Furthermore, the microstructural development of the alloys after heat treatments are evaluated.Lastly corrosive properties, as well as tensile and impact properties are evaluated both in the as-builtand hot isostatic pressed condition.
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- 2022
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23. Crack initiation and early propagation in case hardened sintered PM steels under cyclic load
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Holmberg, Anders, Wiklund, Urban, Isaksson, Per, Kassman Rudolphi, Åsa, Holmberg, Anders, Wiklund, Urban, Isaksson, Per, and Kassman Rudolphi, Åsa
- Abstract
In the present study, crack propagation through the case hardened region of two different PM steels manufactured with different powder size distributions and sintered at different temperatures has been investigated. EBSD was used to study the microstructure before and after case hardening, revealing the relationship between powder particle grains after sintering and prior austenite grains after case hardening. A novel approach was used to achieve short cracks (10–20 µm) with high repeatability. The cracks were then analysed using EBSD and SEM, revealing detailed and novel information about the crack propagation route in the materials. Both tested materials show the same crack propagation behaviour. If a prior grain/prior austenite boundary is present within an angle from the crack initiation site, the cracks will follow the boundary and thus propagate intergranular, suggesting that the preferred route of crack propagation in case hardened sintered steel is along these boundaries.
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- 2022
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24. ICD harm and benefit: risk scores applied to the Swedish ICD-treated LQTS population
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Sundström, Emilia, Jensen, Steen M., Diamant, Ulla-Britt, Wiklund, Urban, Rydberg, Annika, Sundström, Emilia, Jensen, Steen M., Diamant, Ulla-Britt, Wiklund, Urban, and Rydberg, Annika
- Abstract
The use of implantable cardioverter defibrillators (ICDs) in long QT syndrome (LQTS) patients is essential in high-risk patients. However, it is sometimes used in patients without high-risk profiles for whom the expected benefit may be lower than the risk of ICD harm. Here, we evaluated ICD benefit and harm by assessing risk according to risk scores and pre-ICD clinical characteristics. Design. We studied 109 Swedish LQTS patients drawn from the Swedish ICD and Pacemaker Registry with data collected from medical records. In addition to clinical characteristics, we used two risk scores to assess pre-ICD risk, and evaluated ICD benefit and harm. Results. Twenty percent of all patients received ≥1 appropriate shock with a first appropriate shock incidence rate of 4.3 per 100 person-years. A long QTc (≥550 ms) and double mutations were significantly associated with appropriate shock. Low risk scores among patients without pre-ICD aborted cardiac arrest were not significantly associated with low risk of first appropriate shock. The incidence rates of a first inappropriate shock and first complication were 3.0 and 7.6 per 100 person-years, respectively. Conclusion. Our findings on ICD harm emphasize the importance of careful individual pre-ICD consideration. When we applied two risk scores to patients without pre-ICD aborted cardiac arrest, we could not validate their ability to identify patients with low risk of appropriate shocks and patients who were assessed as having a low risk still received appropriate shocks. This further supports the complexity of risk stratification and the difficulty of using risk scores.
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- 2022
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25. Wear of cemented carbide forging dies used in zipper production
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Heinrichs, Jannica, Mikado, H., Wiklund, Urban, Kawamura, S., Jacobson, Staffan, Heinrichs, Jannica, Mikado, H., Wiklund, Urban, Kawamura, S., and Jacobson, Staffan
- Abstract
Cemented carbide tools are commonly used in both cutting and forging processes associated to zipper produc-tion. In production, the tools experience many millions of repeated contacts, hence they must be very durable to keep the wear at acceptable levels. Although the zipper elements in this investigation are made in a relatively soft CuZn alloy, the wear becomes significant and the tool life a production limiting factor. The wear process is to a large extent unknown. To increase the understanding, forging dies used for an increasing number of forgings in actual production, have been studied in detail. Initially the Co binder is preferentially worn off, and transferred CuZn partly fills the cavities. Interestingly, the repeating forging contacts lead to modification of the composition of the transferred material, which partly separates into Cu rich and Zn rich parts, where the Zn rich parts show a high presence of oxygen. During the life span of the tool, represented by the controlled use of forging tools to different percentages of their estimated life, the WC grains are gradually worn into faceted shapes. The most severely worn region of the forging dies develops an increasing surface roughness, which act to shape a corre-sponding pattern on the zipper elements.
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- 2022
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26. Vitamin D, liver-related biomarkers, and distribution of fat and lean mass in young patients with Fontan circulation
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Hansson, Lena, Sandberg, Camilla, Öhlund, Inger, Lind, Torbjörn, Sthen Bergdahl, Magne, Wiklund, Urban, Rylander Hedlund, Eva, Sjöberg, Gunnar, Rydberg, Annika, Hansson, Lena, Sandberg, Camilla, Öhlund, Inger, Lind, Torbjörn, Sthen Bergdahl, Magne, Wiklund, Urban, Rylander Hedlund, Eva, Sjöberg, Gunnar, and Rydberg, Annika
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Introduction/aim: Young patients with Fontan circulation may have low serum 25-hydroxyvitamin D levels, an affected liver, and unhealthy body compositions. This study aimed to explore the association between vitamin D intake/levels, liver biomarkers, and body composition in young Fontan patients. Method: We collected prospective data in 2017 to 2018, obtained with food-frequency questionnaires, biochemical analyses of liver biomarkers, and dual-energy X-ray absorptiometry scans in 44 children with Fontan circulation. Body compositions were compared to matched controls (n = 38). Linear regression analyses were used to investigate associations of biomarkers, leg pain, and lean mass on serum levels of 25-hydroxyvitamin D. Biomarkers were converted to z scores and differences were evaluated within the Fontan patients. Results: Our Fontan patients had a daily mean vitamin D intake of 9.9 µg and a mean serum 25-hydroxyvitamin D of 56 nmol/L. These factors were not associated with fat or lean mass, leg pain, or biomarkers of liver status. The Fontan patients had significantly less lean mass, but higher fat mass than controls. Male adolescents with Fontan circulation had a greater mean abdominal fat mass than male controls and higher cholesterol levels than females with Fontan circulation. Conclusion: Vitamin D intake and serum levels were not associated with body composition or liver biomarkers in the Fontan group, but the Fontan group had lower lean mass and higher fat mass than controls. The more pronounced abdominal fat mass in male adolescents with Fontan circulation might increase metabolic risks later in life., Originally included in thesis in manuscript form.
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- 2022
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27. Graphene as a lubricant on Ag for electrical contact applications
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Mao, Fang, Wiklund, Urban, Andersson, Anna M., and Jansson, Ulf
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- 2015
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28. ICD harm and benefit: risk scores applied to the Swedish ICD-treated LQTS population
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Sundström, Emilia, primary, Jensen, Steen M., additional, Diamant, Ulla-Britt, additional, Wiklund, Urban, additional, and Rydberg, Annika, additional
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- 2022
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29. Posture‐dependent collapse of the optic nerve subarachnoid space: a combined MRI and modeling study
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Holmlund, Petter, primary, Støverud, Karen, additional, Wåhlin, Anders, additional, Wiklund, Urban, additional, Malm, Jan, additional, Jóhannesson, Gauti, additional, and Eklund, Anders, additional
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- 2022
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30. Author Response: Posture-Dependent Collapse of the Optic Nerve Subarachnoid Space: A Combined MRI and Modeling Study
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Holmlund, Petter, primary, Støverud, Karen-Helene, additional, Wåhlin, Anders, additional, Wiklund, Urban, additional, Malm, Jan, additional, Jóhannesson, Gauti, additional, and Eklund, Anders, additional
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- 2021
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31. Density Encoding Enables Resource-Efficient Randomly Connected Neural Networks
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Kleyko, Denis, primary, Kheffache, Mansour, additional, Frady, E. Paxon, additional, Wiklund, Urban, additional, and Osipov, Evgeny, additional
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- 2021
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32. Solution-based synthesis of AgI coatings for low-friction applications
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Sundberg, Jill, Mao, Fang, Andersson, Anna M., Wiklund, Urban, and Jansson, Ulf
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- 2013
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33. Time Course of Metabolic, Neuroendocrine, and Adipose Effects During 2 Years of Follow-up After Gastric Bypass in Patients With Type 2 Diabetes
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Almby, Kristina E, primary, Katsogiannos, Petros, additional, Pereira, Maria J, additional, Karlsson, F Anders, additional, Sundbom, Magnus, additional, Wiklund, Urban, additional, Kamble, Prasad G, additional, and Eriksson, Jan W, additional
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- 2021
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34. Are ECG changes in heart-healthy individuals of various ages related to cardiac disease 20 years later?
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Erelund, Sofia, primary, Karp, Kjell, additional, Wiklund, Urban, additional, Arvidsson, Sandra, additional, and Hörnsten, Rolf, additional
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- 2021
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35. Wear of uncoated and PVD coated cemented carbide tools for processing of copper based materials part II : Exploring the sliding contact with pure copper
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Heinrichs, Jannica, Mikado, Hiroko, Wiklund, Urban, Jacobson, Staffan, Heinrichs, Jannica, Mikado, Hiroko, Wiklund, Urban, and Jacobson, Staffan
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Cemented carbide tools are successfully used to shear Cu alloy wire into zipper elements in the zipper industry. However, wear of the tools is the limiting factor for the production rate and the industry would benefit from more wear resistant tools. Previous investigations have indicated that the wear is tribochemical, and to investigate the role of Zn in commonly used Cu alloy testing is repeated against pure Cu in this work. The tool material used is a cemented carbide, in uncoated, CrC coated and CrN coated versions. The tests are performed in a simplified sliding test rig, combined with intermittent scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. The tools are gradually worn and Cu is adhered and transferred to all tool surfaces. This process results in a pattern consisting of ridges and valleys on uncoated cemented carbide and CrC. Both are worn significantly faster than CrN, where much of the original surface roughness still remains after the full test. These worn surfaces are similar to the corresponding surfaces worn against the previously tested Cu–Zn alloy. However, the wear rate is dramatically higher in the pure Cu tests.
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- 2021
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36. Vitamin D, liver-related biomarkers, and distribution of fat and lean mass in young patients with Fontan circulation
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Hansson, Lena, Sandberg, Camilla, Öhlund, Inger, Lind, Torbjörn, Sthen Bergdahl, Magne, Wiklund, Urban, Rylander Hedlund, Eva, Sjöberg, Gunnar, Rydberg, Annika, Hansson, Lena, Sandberg, Camilla, Öhlund, Inger, Lind, Torbjörn, Sthen Bergdahl, Magne, Wiklund, Urban, Rylander Hedlund, Eva, Sjöberg, Gunnar, and Rydberg, Annika
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Introduction/aim: Young patients with Fontan circulation may have low serum 25-hydroxyvitamin D levels, an affected liver, and unhealthy body compositions. This study aimed to explore the association between vitamin D intake/levels, liver biomarkers, and body composition in young Fontan patients. Method: We collected prospective data in 2017 to 2018, obtained with food-frequency questionnaires, biochemical analyses of liver biomarkers, and dual-energy X-ray absorptiometry scans in 44 children with Fontan circulation. Body compositions were compared to matched controls (n = 38). Linear regression analyses were used to investigate associations of biomarkers, leg pain, and lean mass on serum levels of 25-hydroxyvitamin D. Biomarkers were converted to z scores and differences were evaluated within the Fontan patients. Results: Our Fontan patients had a daily mean vitamin D intake of 9.9 µg and a mean serum 25-hydroxyvitamin D of 56 nmol/L. These factors were not associated with fat or lean mass, leg pain, or biomarkers of liver status. The Fontan patients had significantly less lean mass, but higher fat mass than controls. Male adolescents with Fontan circulation had a greater mean abdominal fat mass than male controls and higher cholesterol levels than females with Fontan circulation. Conclusion: Vitamin D intake and serum levels were not associated with body composition or liver biomarkers in the Fontan group, but the Fontan group had lower lean mass and higher fat mass than controls. The more pronounced abdominal fat mass in male adolescents with Fontan circulation might increase metabolic risks later in life., Originally included in thesis in manuscript form.
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- 2021
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37. Refeeding syndrome : multimodal monitoring and clinical manifestation of an internal severe neurotrauma
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Sundström, Nina, Brorsson, Camilla, Karlsson, Marcus, Wiklund, Urban, Koskinen, Lars-Owe D., Sundström, Nina, Brorsson, Camilla, Karlsson, Marcus, Wiklund, Urban, and Koskinen, Lars-Owe D.
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Refeeding syndrome (RFS) is a rare, potentially life-threatening, condition seen in malnourished patients starting refeeding. RFS may provoke seizures and acute encephalopathy and can be considered an internal severe neurotrauma in need of specific treatment. The objective was to describe course of disease, treatment and, for the first time, multimodal monitoring output in a comatose patient suffering RFS. After gastric-banding and severe weight loss, the patient initiated self-starving and was transferred to our intensive care unit (ICU) following rapid refeeding. At arrival, seizures, decrease in consciousness (GCS 7) and suspected acute encephalitis was presented. Serum albumin was 8 g/l. Intracranial pressure (ICP), invasive blood pressure and electrocardiography (ECG) were monitored. Pressure reactivity (PRx) and compliance (RAP) were calculated. The patient developed congestive heart failure, anuria and general oedema despite maximal neuro- and general ICU treatment. Global cerebral oedema and hypoperfusion areas with established ischemia were seen. ECG revealed massive cardiac arrhythmia and disturbed autonomic regulation. PRx indicated intact autoregulation (−0.06 ± 0.18, mean ± SD) and relatively normal compliance (RAP = 0.23 ± 0.13). After 15 days the clinical state was improved, and the patient returned to the primary hospital. RFS was associated with serious deviations in homeostasis, high ICP levels, ECG abnormalities, kidney and lung affections. It is of utmost importance to recognize this rare syndrome and to treat appropriately. Despite the severe clinical state, cerebral autoregulation and compensatory reserve were generally normal, questioning the applicability of indirect measurements such as PRx and RAP during neuro-intensive care treatment of RFS patients with cerebral engagement.
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- 2021
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38. Heart Rate Variability for Classification of Alert Versus Sleep Deprived Drivers in Real Road Driving Conditions
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Persson, Anna, Jonasson, Hanna, Fredriksson, Ingemar, Wiklund, Urban, Ahlstrom, Christer, Persson, Anna, Jonasson, Hanna, Fredriksson, Ingemar, Wiklund, Urban, and Ahlstrom, Christer
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Driver sleepiness is a contributing factor in many road fatalities. A long-standing goal in driver state research has therefore been to develop a robust sleepiness detection system. It has been suggested that various heart rate variability (HRV) metrics can be used for driver sleepiness classification. However, since heart rate is modulated not only by sleepiness but also by several other time-varying intra-individual factors such as posture, distress, boredom and relaxation, it is relevant to highlight not only the possibilities but also the difficulties involved in HRV-based driver sleepiness classification. This paper investigates the reliability of HRV as a standalone feature for driver sleepiness detection in a realistic setting. Data from three real-road driving studies were used, including 86 drivers in both alert and sleep-deprived conditions. Subjective ratings based on the Karolinska sleepiness scale (KSS) were used as ground truth when training four binary classifiers (k-nearest neighbours, support vector machine, AdaBoost, and random forest). The best performance was achieved with the random forest classifier with an accuracy of 85%. However, the accuracy dropped to 64% for three-class classification and to 44% for subject-independent, leave-one-participant-out classification. The worst results were obtained in the severely sleepy class. The results show that in realistic driving conditions, subject-independent sleepiness classification based on HRV is poor. The conclusion is that more work is needed to control for the many confounding factors that also influence HRV before it can be used as input to a driver sleepiness detection system., Funding Agencies|ADAS&ME Project - European Unions Horizon 2020 Research and Innovation Programme [688900]
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- 2021
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39. Author Response: Posture-Dependent Collapse of the Optic Nerve Subarachnoid Space : A Combined MRI and Modeling Study
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Holmlund, Petter, Stoverud, Karen-Helene, Wahlin, Anders, Wiklund, Urban, Malm, Jan, Jóhannesson, Gauti, Eklund, Anders, Holmlund, Petter, Stoverud, Karen-Helene, Wahlin, Anders, Wiklund, Urban, Malm, Jan, Jóhannesson, Gauti, and Eklund, Anders
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- 2021
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40. Semi in-situ measurement of microstructural changes in PM steel during indentation
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Holmberg, Anders, Andersson, Michael, Wiklund, Urban, Kassman Rudolphi, Åsa, Holmberg, Anders, Andersson, Michael, Wiklund, Urban, and Kassman Rudolphi, Åsa
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In the present study, microstructural changes of sintered steel under compressive load are studied by a novel method. The aim is to gain further understanding of how the pores and microstructure react to different loads, which is of interest for surface densification of PM steels. Images of polished cross-sections are acquired before and after Brinell-indentation. Distinct features of the before and after images are matched using image registration, revealing the microstructural changes underneath the surface of the PM steel due to plastic deformation by the indentation. The method is reliable and provides accurate measurement of microstructural changes providing data that will broaden the understanding of how the microstructure is altered at loads above the yield limit.
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- 2021
41. Time Course of Metabolic, Neuroendocrine, and Adipose Effects During 2 Years of Follow-up After Gastric Bypass in Patients With Type 2 Diabetes
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Almby, Kristina E., Katsogiannos, Petros, Pereira, Maria J., Karlsson, Anders, Sundbom, Magnus, Wiklund, Urban, Kamble, Prasad G., Eriksson, Jan, Almby, Kristina E., Katsogiannos, Petros, Pereira, Maria J., Karlsson, Anders, Sundbom, Magnus, Wiklund, Urban, Kamble, Prasad G., and Eriksson, Jan
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Context: Roux-en-Y gastric bypass surgery (RYGB) markedly improves glycemia in patients with type 2 diabetes (T2D), but underlying mechanisms and changes over time are incompletely understood. Objective: Integrated assessment of neuroendocrine and metabolic changes over time in T2D patients undergoing RYGB. Design and Setting: Follow-up of single-center randomized study. Patients: Thirteen patients with obesity and T2D compared to 22 healthy subjects. Interventions: Blood chemistry, adipose biopsies, and heart rate variability were obtained before and 4, 24, and 104 weeks post-RYGB. Results: After RYGB, glucose-lowering drugs were discontinued and hemoglobin A1c fell from mean 55 to 41 mmol/mol by 104 weeks (P<0.001). At 4 weeks, morning cortisol (P<0.05) and adrenocorticotropin (P=0.09) were reduced by 20%. Parasympathetic nerve activity (heart rate variability derived) increased at 4 weeks (P<0.05) and peaked at 24 weeks (P<0.01). C-reactive protein (CRP) and white blood cells were rapidly reduced (P<0.01). At 104 weeks, basal and insulin-stimulated adipocyte glucose uptake increased by 3-fold vs baseline and expression of genes involved in glucose transport, fatty acid oxidation, and adipogenesis was upregulated (P<0.01). Adipocyte volume was reduced by 4 weeks and more markedly at 104 weeks, by about 40% vs baseline (P<0.01). Conclusions: We propose this order of events: (1) rapid glucose lowering (days); (2) attenuated cortisol axis activity and inflammation and increased parasympathetic tone (weeks); and (3) body fat and weight loss, increased adipose glucose uptake, and whole-body insulin sensitivity (months-years; similar to healthy controls). Thus, neuroendocrine pathways can partly mediate early glycemic improvement after RYGB, and adipose factors may promote long-term insulin sensitivity and normoglycemia.
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- 2021
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42. Wear of cemented carbide forging dies used in zipper production
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Heinrichs, Jannica, Mikado, Hiroko, Wiklund, Urban, Kawamura, Shingo, Jacobson, Staffan, Heinrichs, Jannica, Mikado, Hiroko, Wiklund, Urban, Kawamura, Shingo, and Jacobson, Staffan
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- 2021
43. Aberrant autonomic pattern during the post-exercise recovery phase in long QT syndrome patients
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Lundström, Anna, Wiklund, Urban, Law, Lucy, Jensen, Steen M., Karlsson, Marcus, Rydberg, Annika, Lundström, Anna, Wiklund, Urban, Law, Lucy, Jensen, Steen M., Karlsson, Marcus, and Rydberg, Annika
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Objectives: It is well-established that the autonomic nervous system (ANS) plays a central role in arrhythmogenesis. During and after exercise the ANS is particularly active, and since long QT syndrome (LQTS) patients have an increased risk of lethal arrhythmias during physical activity, it is important to investigate the autonomic function in these patients. In this study we investigate the ANS response during and after exercise in LQTS patients and healthy age and sex matched controls. Methods: Forty-four genotype-verified adult LQTS patients and forty-four healthy age- and sex-matched controls performed a submaximal bicycle exercise stress test. Heart rate recovery (HRR) and heart rate variability (HRV) were analyzed from registered electrocardiogram (ECG) and vector electrocardiogram (VCG) recordings collected throughout rest, exercise and in the post-exercise phase. Results: LQTS patients had a slower HRR than controls at 1- and 4-min post-exercise (p < 0.001). During the post-exercise phase, LQTS patients had a lower total power (p < 0.001), low frequency power (p < 0.001) and high frequency power (p < 0.001) than controls. In the same phase, LQTS patients off betablocker (BB) treatment showed a lower high frequency power (p = 0.01) and different low frequency/high frequency ratio (p = 0.003) when comparing with LQTS patients on BB treatment. Conclusions: The parasympathetic effect on both HRR and HRV after exercise appears depressed in this LQTS patient cohort compared to healthy controls. This indicates an aberrant ANS response during the post-exercise phase which might be compensated by BB treatment. Our findings emphasize the importance of performing further investigations to identify the role of the ANS in LQTS arrhythmogenesis., Corrigendum: Anna Lundström, Urban Wiklund, Lucy Law, Steen Jensen, Marcus Karlsson, Annika Rydberg, Corrigendum to "Aberrant autonomic pattern during the post-exercise recovery phase in Long QT syndrome patients", Autonomic Neuroscience, 2022, 102931. DOI: 10.1016/j.autneu.2021.102931
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- 2021
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44. Effects of Gastric Bypass Surgery on the Brain : Simultaneous Assessment of Glucose Uptake, Blood Flow, Neural Activity, and Cognitive Function During Normo- and Hypoglycemia
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Almby, Kristina E., Lundqvist, Martin H., Abrahamsson, Niclas, Kvernby, Sofia, Fahlström, Markus, Pereira, Maria J., Gingnell, Malin, Karlsson, Anders, Fanni, Giovanni, Sundbom, Magnus, Wiklund, Urban, Haller, Sven, Lubberink, Mark, Wikström, Johan, Eriksson, Jan, Almby, Kristina E., Lundqvist, Martin H., Abrahamsson, Niclas, Kvernby, Sofia, Fahlström, Markus, Pereira, Maria J., Gingnell, Malin, Karlsson, Anders, Fanni, Giovanni, Sundbom, Magnus, Wiklund, Urban, Haller, Sven, Lubberink, Mark, Wikström, Johan, and Eriksson, Jan
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While Roux-en-Y gastric bypass (RYGB) surgery in obese individuals typically improves glycemic control and prevents diabetes, it also frequently causes asymptomatic hypoglycemia. Previous work showed attenuated counterregulatory responses following RYGB. The underlying mechanisms as well as the clinical consequences are unclear. In this study, 11 subjects without diabetes with severe obesity were investigated pre- and post-RYGB during hyperinsulinemic normo-hypoglycemic clamps. Assessments were made of hormones, cognitive function, cerebral blood flow by arterial spin labeling, brain glucose metabolism by F-18-fluorodeoxyglucose (FDG) positron emission tomography, and activation of brain networks by functional MRI. Post- versus presurgery, we found a general increase of cerebral blood flow but a decrease of total brain FDG uptake during normoglycemia. During hypoglycemia, there was a marked increase in total brain FDG uptake, and this was similar for post- and presurgery, whereas hypothalamic FDG uptake was reduced during hypoglycemia. During hypoglycemia, attenuated responses of counterregulatory hormones and improvements in cognitive function were seen postsurgery. In early hypoglycemia, there was increased activation post- versus presurgery of neural networks in brain regions implicated in glucose regulation, such as the thalamus and hypothalamus. The results suggest adaptive responses of the brain that contribute to lowering of glycemia following RYGB, and the underlying mechanisms should be further elucidated., K.E.A. and M.H.L. contributed equally.
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- 2021
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45. Posture-dependent collapse of the optic nerve subarachnoid space : A combined MRI and modeling study
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Holmlund, Petter, Stoverud, Karen-Helene, Wåhlin, Anders, Wiklund, Urban, Malm, Jan, Jóhannesson, Gauti, Eklund, Anders, Holmlund, Petter, Stoverud, Karen-Helene, Wåhlin, Anders, Wiklund, Urban, Malm, Jan, Jóhannesson, Gauti, and Eklund, Anders
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PURPOSE: We hypothesize that a collapse of the optic nerve subarachnoid space (ONSAS) in the upright posture may protect the eyes from large translamina cribrosa pressure differences (TLCPD) believed to play a role in various optic nerve diseases (e.g., glaucoma). In this study, we combined magnetic resonance imaging (MRI) and mathematical modeling to investigate this potential ONSAS collapse and its effects on the TLCPD. METHODS: First, we performed MRI on six healthy volunteers in 6° head-down tilt (HDT) and 13° head-up tilt (HUT) to assess changes in ONSAS volume (measured from the eye to the optic canal) with changes in posture. The volume change reflects optic nerve sheath (ONS) distensibility. Second, we used the MRI data and mathematical modeling to simulate ONSAS pressure and the potential ONSAS collapse in a 90° upright posture. RESULTS: The MRI showed a 33% decrease in ONSAS volume from the HDT to HUT (P < 0.001). In the upright posture, the simulations predicted an ONSAS collapse 25 mm behind lamina cribrosa, disrupting the pressure communication between the ONSAS and the intracranial subarachnoid space. The collapse reduced the simulated postural increase in TLCPD by roughly 1 mm Hg, although this reduction was highly sensitive to ONS distensibility, varying between 0 and 4.8 mm Hg when varying the distensibility by ± 1 SD. CONCLUSIONS: The ONSAS volume along the optic nerve is posture dependent. The simulations supported the hypothesized ONSAS collapse in the upright posture and showed that even small changes in ONS stiffness/distensibility may affect the TLCPD.
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- 2021
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46. Are ECG changes in heart-healthy individuals of various ages related to cardiac disease 20 years later?
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Erelund, Sofia, Karp, Kjell, Wiklund, Urban, Hörnsten, Rolf, Arvidsson, Sandra, Erelund, Sofia, Karp, Kjell, Wiklund, Urban, Hörnsten, Rolf, and Arvidsson, Sandra
- Abstract
Background: This research study aimed at assessing the electrocardiographic (ECG) changes caused by ageing in a cohort of healthy subjects with normal echocardiographic examinations. Methods: A total of 219 healthy individuals (119 males and 100 females) were evaluated for possible arrhythmias with a standard 12-lead resting ECG and 24-h Holter ECG. As the recordings were performed between 1998 and 2000, a 20-year follow-up study was carried out by assessing the local medical records to investigate whether the subjects had experienced any cardiovascular health complications or disease since the baseline assessment. Results: Eighty-three subjects (45 males and 38 females) presented with pathological ECG findings at baseline. The most common finding on analysis of Holter ECG recordings was premature atrial contractions, and the most severe pathological finding was episodes of ventricular tachycardia (eight subjects). Regarding the analysis of the standard 12-lead ECG, the most common finding was left ventricular hypertrophy, and the most severe pathological findings were ST-T changes and prolongation of the QT interval. Despite other cardiac examinations performed on these patients showing normal results, in combination with a strict inclusion criterion, this study showed that 28% of all subjects had pathological resting 12-lead ECGs at rest and 35% had pathological heart rhythms when assessed by 24-h Holter ECG. At follow-up, 21% of females and 43% of males had presented with ECG abnormalities, and 30% of females and 36% of males had cardiovascular disease. There was hypertension in 45% of females and in 58% of males. However, no association was found between the follow-up findings and ECG changes seen at baseline. Conclusion: Although most ECG changes found at baseline could be considered as a normal variation, they may progress to more severe heart complications as the subject ages. The results of this study also validate ECG findings of previous studies and underl
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- 2021
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47. Density Encoding Enables Resource-Efficient Randomly Connected Neural Networks
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Kleyko, Denis, Kheffache, Mansour, Frady, E. Paxon, Wiklund, Urban, Osipov, Evgeny, Kleyko, Denis, Kheffache, Mansour, Frady, E. Paxon, Wiklund, Urban, and Osipov, Evgeny
- Abstract
The deployment of machine learning algorithms on resource-constrained edge devices is an important challenge from both theoretical and applied points of view. In this brief, we focus on resource-efficient randomly connected neural networks known as random vector functional link (RVFL) networks since their simple design and extremely fast training time make them very attractive for solving many applied classification tasks. We propose to represent input features via the density-based encoding known in the area of stochastic computing and use the operations of binding and bundling from the area of hyperdimensional computing for obtaining the activations of the hidden neurons. Using a collection of 121 real-world data sets from the UCI machine learning repository, we empirically show that the proposed approach demonstrates higher average accuracy than the conventional RVFL. We also demonstrate that it is possible to represent the readout matrix using only integers in a limited range with minimal loss in the accuracy. In this case, the proposed approach operates only on small ${n}$ -bits integers, which results in a computationally efficient architecture. Finally, through hardware field-programmable gate array (FPGA) implementations, we show that such an approach consumes approximately 11 times less energy than that of the conventional RVFL.
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- 2021
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48. Changes in Heart Rate and Heart Rate Variability During Surgical Stages to Completed Fontan Circulation
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Alenius Dahlqvist, Jenny, Wiklund, Urban, Karlsson, Marcus, Hanséus, Katarina, Strömvall Larsson, Eva, Johansson Ramgren, Jens, Berggren, Håkan, Rydberg, Annika, Alenius Dahlqvist, Jenny, Wiklund, Urban, Karlsson, Marcus, Hanséus, Katarina, Strömvall Larsson, Eva, Johansson Ramgren, Jens, Berggren, Håkan, and Rydberg, Annika
- Abstract
Arrhythmia is related to heart rate variability (HRV), which reflects the autonomic nervous regulation of the heart. We hypothesized that autonomic nervous ganglia, located at the junction of the superior vena cava’s entrance to the heart, may be affected during the bidirectional Glenn procedure (BDG), resulting in reduced HRV. We aimed to investigate changes in heart rate and HRV in a cohort of children with univentricular heart defects, undergoing stepwise surgery towards total cavopulmonary connection (TCPC), and compare these results with healthy controls. Twenty four hours Holter-ECG recordings were obtained before BDG (n = 47), after BDG (n = 47), and after total cavopulmonary connection (TCPC) (n = 45) in patients and in 38 healthy controls. HRV was analyzed by spectral and Poincaré methods. Age-related z scores were calculated and compared using linear mixed effects modeling. Total HRV was significantly lower in patients before BDG when compared to healthy controls. The mean heart rate was significantly reduced in patients after BDG compared to before BDG. Compared to healthy controls, patients operated with BDG had significantly reduced heart rate and reduced total HRV. Patients with TCPC showed reduced heart rate and HRV compared with healthy controls. In patients after TCPC, total HRV was decreased compared to before TCPC. Heart rate was reduced after BDG procedure, and further reductions of HRV were seen post-TCPC. Our results indicate that autonomic regulation of cardiac rhythm is affected both after BDG and again after TCPC. This may be reflected as, and contribute to, postoperative arrhythmic events., Originally included in thesis in manuscript form with title: "Changes in heart rate variability during surgical stages to completed Fontan circulation"
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- 2021
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49. Successful noviceʼs training in obtaining accurate assessment of carotid IMT using an automated ultrasound system
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Vanoli, Davide, Wiklund, Urban, Lindqvist, Per, Henein, Michael, and Näslund, Ulf
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- 2014
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50. Posture-Dependent Collapse of the Optic Nerve Subarachnoid Space: A Combined MRI and Modeling Study
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Holmlund, Petter, primary, Støverud, Karen-Helene, additional, Wåhlin, Anders, additional, Wiklund, Urban, additional, Malm, Jan, additional, Jóhannesson, Gauti, additional, and Eklund, Anders, additional
- Published
- 2021
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