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| 3. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 4. |
- Kanoni, Stavroula, et al.
(författare)
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Implicating genes, pleiotropy, and sexual dimorphism at blood lipid loci through multi-ancestry meta-analysis.
- 2022
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Ingår i: Genome biology. - : Springer Science and Business Media LLC. - 1474-760X .- 1465-6906 .- 1474-7596. ; 23:1
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Tidskriftsartikel (refereegranskat)abstract
- Genetic variants within nearly 1000 loci are known to contribute to modulation of blood lipid levels. However, the biological pathways underlying these associations are frequently unknown, limiting understanding of these findings and hindering downstream translational efforts such as drug target discovery.To expand our understanding of the underlying biological pathways and mechanisms controlling blood lipid levels, we leverage a large multi-ancestry meta-analysis (N=1,654,960) of blood lipids to prioritize putative causal genes for 2286 lipid associations using six gene prediction approaches. Using phenome-wide association (PheWAS) scans, we identify relationships of genetically predicted lipid levels to other diseases and conditions. We confirm known pleiotropic associations with cardiovascular phenotypes and determine novel associations, notably with cholelithiasis risk. We perform sex-stratified GWAS meta-analysis of lipid levels and show that 3-5% of autosomal lipid-associated loci demonstrate sex-biased effects. Finally, we report 21 novel lipid loci identified on the X chromosome. Many of the sex-biased autosomal and X chromosome lipid loci show pleiotropic associations with sex hormones, emphasizing the role of hormone regulation in lipid metabolism.Taken together, our findings provide insights into the biological mechanisms through which associated variants lead to altered lipid levels and potentially cardiovascular disease risk.
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- Ramdas, S., et al.
(författare)
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A multi-layer functional genomic analysis to understand noncoding genetic variation in lipids
- 2022
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 109:8, s. 1366-1387
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge of genome-wide association studies (GWASs) is to translate phenotypic associations into biological insights. Here, we integrate a large GWAS on blood lipids involving 1.6 million individuals from five ancestries with a wide array of functional genomic datasets to discover regulatory mechanisms underlying lipid associations. We first prioritize lipid-associated genes with expression quantitative trait locus (eQTL) colocalizations and then add chromatin interaction data to narrow the search for functional genes. Polygenic enrichment analysis across 697 annotations from a host of tissues and cell types confirms the central role of the liver in lipid levels and highlights the selective enrichment of adipose-specific chromatin marks in high-density lipoprotein cholesterol and triglycerides. Overlapping transcription factor (TF) binding sites with lipid-associated loci identifies TFs relevant in lipid biology. In addition, we present an integrative framework to prioritize causal variants at GWAS loci, producing a comprehensive list of candidate causal genes and variants with multiple layers of functional evidence. We highlight two of the prioritized genes, CREBRF and RRBP1, which show convergent evidence across functional datasets supporting their roles in lipid biology.
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| 9. |
- Cho, Jang Ho, et al.
(författare)
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Design of an Intermediate Layer to Enhance Operator Awareness and Safety in Telesurgical Systems
- 2012
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Ingår i: Proc. 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS2012), October 7-12, 2012. Vilamoura, Algarve, Portugal. - 2153-0858 .- 2153-0866. ; , s. 1292-1297
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel control architecture for enhanced operator awareness and improved safety in telesurgical systems. We introduce an intermediate layer between the master and slave sides which allows us to modify the slave motion for safety and the force feedback for operator awareness. The intermediate layer is then designed with a performance objective for the specific task at hand. The control scheme is validated via experiments using a suture and an industrial manipulator. More specifically we show that operator awareness should be implemented as an integrated part of the safety level to maintain safety during surgery.
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| 10. |
- Cho, Jang Ho, et al.
(författare)
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Enhancement of Human Operator's Perceptual Sensitivity for Telesurgical Systems via Polytopic System Approach
- 2012
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Ingår i: 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012. - 9781457711992 ; , s. 75-80
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Konferensbidrag (refereegranskat)abstract
- A suturing including knot tying is one of the more difficult operations to learn in telesurgical systems. Apprentice surgeons commonly suffer from suture breakage or knot failure. The difficulty, generally, comes from the absence of feedback of interaction force cues in a medical device (e.g., a needle and a thread) . Even if there is haptic feedback to the operator, the operator may have a difficulty to detect a specific force such as suture breakage force. To deal with this problem, we propose a control method which can detect a suture breakage force more sensitively by considering human perception characteristics. A performance objective of the control method is designed according to the human perceptual factor, just noticeable difference. By convex optimization of the performance indices, a stabilizing H_inf controller is proposed for the telesurgical system. Finally, the proposed control scheme is validated via a simulation study.
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| 11. |
- Cho, Jang Ho, et al.
(författare)
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Gain-Scheduling Control of Teleoperation Systems Interacting With Soft Tissues
- 2013
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Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046. ; 60:3, s. 946-957
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Tidskriftsartikel (refereegranskat)abstract
- Surgical teleoperation systems are being increasingly deployed recently. There are, however, some unsolved issues such as nonlinear characteristics of the interaction between the slave robot and soft tissues and difficulty in employing force sensors in the surgical end-effectors of the slave. These issues make it difficult to generalize any approach to develop a control for the system. This paper addresses these issues by proposing a H-infinity suboptimal controller preserving robust stability and performance. The environment, i.e., soft tissues, is characterized with the nonlinear Hunt-Crossley model. This nonlinear characteristics of soft tissues are expressed with an affine combination of linear models within a predefined parameter polytope. For this linear parameter-varying system, a gain-scheduling control scheme is employed to design a suboptimal controller while guaranteeing its stability. To avoid using any force measurement in slave, we used position-position (PP) control architecture. The developed gain-scheduling control is validated with quantitative experimental results. The developed gain-scheduling PP control scheme shows good tracking capacity and high transparency for varied experimental conditions. Error of the transmitted impedance is significantly lower compared with other conventional control schemes for frequencies less than 2 Hz, which is frequently recommended for surgical teleoperation.
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| 12. |
- Cho, Jang Ho, et al.
(författare)
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On the H2 Decentralized Controller Synthesis for Delayed Bilateral Teleoperation Systems
- 2012
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Ingår i: 10th IFAC Symposium on Robot Control. - 1474-6670. - 9783902823113 ; , s. 393-398
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Konferensbidrag (refereegranskat)abstract
- Procedure for the synthesis of decentralized controllers for delayed bilateral teleoperation systems is proposed, based on the analytical solution of a global H2 optimization. Explicit state-space formulae for the optimal controller are presented. The controller possesses a neat structure, which preserves closed-loop stability regardless of the delay length. The behavior of the resulting teleoperation system is illustrated in simulations and verified by experiments.
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| 13. |
- From, Pål Johan, et al.
(författare)
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Hybrid Stiff/Compliant Workspace Control for Robotized Minimally Invasive Surgery
- 2014
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Ingår i: Proc. 2014 5th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob 2014), August 12-15, 2014. São Paulo, Brazil. - 2155-1774. - 9781479931262 ; , s. 345-351
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel control architecture for hybrid stiff and compliant control for minimally invasive surgery which satisfies the constraints of zero lateral velocity at the entry point for serial manipulators. For minimally invasive surgery it is required that there is no sideways motion at the point where the robots enter the abdomen. This is necessary to avoid any damage to the patient's body when the robot moves. We solve this at a kinematic level, i.e., we find a Jacobian matrix that maps the velocities in joint space to the end-effector velocities and at the same time guarantees that certain velocities at the entry point are zero. Because the new velocity variables are defined in the end-effector workspace we can use these for hybrid motion/force control. The approach is verified experimentally by implementing hybrid stiff and compliant control of the end effector and we show that the insertion point constraints are always satisfied.
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| 14. |
- Ghazaei, Mahdi, et al.
(författare)
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Trajectory Generation for Assembly Tasks Via Bilateral Teleoperation
- 2014
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Ingår i: Preprints of the 19th World Congress of the International Federation of Automatic Control (IFAC2014), Cape Town, South Africa. August 24-29, 2014. ; 47:3, s. 10230-10235
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Konferensbidrag (refereegranskat)abstract
- Abstract in UndeterminedFor assembly tasks, the knowledge of both trajectory and forces are usually required. Consequently, we may use kinesthetics or teleoperation for recording human demonstrations. In order to have a more natural interaction, the operator has to be provided with a sense of touch. We propose a bilateral teleoperation system which is customized for this purpose. We introduce different coordinate frames to make the design of a 6-DOF teleoperation straightforward. Moreover, we suggest using tele-admittance, which simplifies instructing the robot. The compliance due to the slave controller allows the robot to react quickly and reduces the risk of damaging the workpiece.
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| 15. |
- Kristalny, Maxim, et al.
(författare)
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On the Decentralized H2 Optimal Control of Bilateral Teleoperation Systems with Time Delays
- 2012
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Ingår i: [Host publication title missing]. - 0191-2216. ; , s. 6908-6914
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Konferensbidrag (refereegranskat)abstract
- Decentralized control of bilateral teleoperation systems with time delays is considered within the H2 optimization framework. We demonstrate that the problem is quadratically invariant and can be split into two independent model matching optimizations with partial multiplicative delay. The recent loop shifting techniques for delayed systems control are used then to find a complete analytical solution. Explicit state-space formulae for the optimal controller are derived in terms of standard Riccati equations associated with the centralized delay-free problem. It is shown that the resulting optimal controller admits an elegant and easy to implement structure.
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| 16. |
- Son, Hyoung Il, et al.
(författare)
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A psychophysical evaluation of haptic controllers: viscosity perception of soft environments
- 2014
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Ingår i: Robotica. - 0263-5747. ; 32:1, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, human viscosity perception in haptic teleoperation systems is thoroughly analyzed. An accurate perception of viscoelastic environmental properties such as viscosity is a critical ability in several contexts, such as telesurgery, telerehabilitation, telemedicine, and soft-tissue interaction. We study and compare the ability to perceive viscosity from the standpoint of detection and discrimination using several relevant control methods for the teleoperator. The perception-based method, which was proposed by the authors to enhance the operator's kinesthetic perception, is compared with the conventional transparency-based control method for the teleoperation system. The fidelity-based method, which is a primary method among perception-centered control schemes in teleoperation, is also studied. We also examine the necessity and impact of the remote-site force information for each of the methods. The comparison is based on a series of psychophysical experiments measuring absolute threshold and just noticeable difference for all conditions. The results clearly show that the perception-based method enhances both detection and discrimination abilities compare with other control methods. The results further show that the fidelity-based method confers a better discrimination ability than the transparency-based method, although this is not true with respect to detection ability. In addition, we show that force information improves viscosity detection for all control methods, as predicted from previous theoretical analysis, but improves the discrimination threshold only for the perception-based method.
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