| 1. |
- Björkenstam, C., et al.
(författare)
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Suicide in first episode psychosis : A nationwide cohort study
- 2014
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Ingår i: Schizophrenia Research. - : Elsevier BV. - 0920-9964 .- 1573-2509. ; 157:1-3, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Relatively little is known about suicide in diagnostic subtypes of first episode psychosis (FEP). Our aim was to assess suicide rates and potential risk factors for suicide in FEP. Methods: This is a national register-based cohort study of patients born in 1973-1978 in Sweden and who were hospitalized with a FEP between ages 15 and 30 years (n = 2819). The patients were followed from date of discharge until death, emigration, or 31st of December 2008. The suicide rates for six diagnostic subtypes of FEP were calculated. Suicide incidence rate ratios (IRRs) were calculated to evaluate the association between suicide and psychiatric, familial, social, and demographic factors. Results: In total 121 patients died by suicide. The overall suicide rate was 4.3 (95% confidence interval [CI] 3.5-5.0) per 1000 person-years. The highest suicide rates were found in depressive disorder with psychotic symptoms and in delusional disorder. In an adjustedmodel, the strongest risk factors for suicide were self-harm (IRR 2.7, CI 1.7-4.4) or a conviction for violent crime (IRR 2.0, CI 1.3-3.2). Also having a first-degree relative with a schizophrenia/bipolar diagnosis (IRR 2.1, CI 1.2-3.6) or substance use disorder (IRR 2.0, CI 1.2-3.2) were significant risk factors for suicide. Conclusions: Impulsive behavior such as self-harm as well as having a family history of severe mental disorder or substance use are important risk factors for suicide in FEP.
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| 2. |
- Björkenstam, E., et al.
(författare)
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A five year diagnostic follow-up of 1840 patients after a first episode non-schizophrenia and non-affective psychosis
- 2013
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Ingår i: Schizophrenia Research. - : Elsevier BV. - 0920-9964 .- 1573-2509. ; 150:1, s. 205-210
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveIt is not clear which patients with a first psychotic episode will develop schizophrenia. We performed a diagnostic follow-up of patients treated for a first time non-affective, non-schizophrenia psychosis and explored potential predictors of a subsequent schizophrenia or schizoaffective diagnosis.MethodsThis register-based cohort study comprises individuals born between 1973 and 1978 in Sweden, with a first hospital-treated psychosis excluding schizophrenia, schizoaffective disorder, bipolar disorder and depressive disorder with psychotic symptoms (n = 1840). The patients were followed for five years regarding subsequent diagnoses. Psychiatric, social, family history of psychiatric illness, premorbid intellectual level, head injuries and obstetrical complications were investigated by logistic regression as predictors of schizophrenia or schizoaffective diagnosis.ResultsDuring the follow-up, 18% were diagnosed with schizophrenia or schizoaffective disorder, 5% were diagnosed with bipolar disorder, whereas 29% were not re-admitted to a psychiatric clinic. Patients with a first-degree relative hospitalized for schizophrenia and/or bipolar disorder had an increased risk of subsequent diagnosis for schizophrenia or schizoaffective disorder (odds ratio 1.9 and 95% confidence interval 1.1 to 3.0)), whereas previous severe criminality was associated with a decreased risk (odds ratio 0.5, 95% confidence interval 0.3–0.8).ConclusionDiagnostic outcome was diverse after a first non-schizophrenia and non-affective psychosis. Family history of severe mental illness and no previous conviction for severe criminality were the strongest risk factors for a future schizophrenia or schizoaffective diagnosis.
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| 3. |
- Björkenstam, C., et al.
(författare)
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School grades, parental education and suicide : a national register-based cohort study
- 2010
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Ingår i: Journal of Epidemiology and Community Health. - : BMJ. - 0143-005X .- 1470-2738.
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Tidskriftsartikel (refereegranskat)abstract
- Background To investigate whether school performance is a risk factor for suicide death later in life and, if so, to what extent this is explained by intergenerational effects of parental education. Methods This population-based cohort study comprises national birth cohorts between 1972 and 1981 in Sweden. We followed 898 342 students, graduating between 1988 and 1997 from the 9 years of compulsory school, equivalent to junior high school, until 31 December 2006, generating 11 148 758 person-years and 1490 suicides. Final school grades, in six categories, and risk of suicide were analysed with Poisson regression. Results The incidence rate ratio (RR) for suicide death for students with the lowest grades was 4.57 (95% CI 2.82 to 7.40) for men and 2.67 (1.42 to 5.01) for women compared to those with highest grades after adjustment for a number of sociodemographic and parental morbidity variables, such as year of graduation, parental education, lone parenthood, household receiving social welfare or disability pension, place of schooling, adoption, maternal age and parent's mental illness. Students with grades in the middle categories had RRs in between. These relationships were not modified by parental education. Conclusions The strong association between low school grades and suicide in youth and young adulthood emphasises the importance of both primary and secondary prevention in schools.
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| 4. |
- Björkenstam, C., et al.
(författare)
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Suicidal behavior among delinquent former child welfare clients
- 2013
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Ingår i: European Child and Adolescent Psychiatry. - : Springer Science and Business Media LLC. - 1018-8827 .- 1435-165X. ; 22:6, s. 349-355
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Tidskriftsartikel (refereegranskat)abstract
- Child welfare clients represent a high-risk group for delinquency and adult criminality, but also for future suicidal behavior. We examine associations between delinquency and suicidal behavior in a national child welfare population. This register-based cohort study is based on data for all Swedish former child welfare clients born between 1972 and 1981 that experienced interventions before their adolescent years. We followed 27,228 individuals from age 20 years until 31 December 2006. Juvenile delinquency was defined as being convicted of at least one crime between age 15 and 19. The risk of suicidal behavior was calculated as incidence rate ratios (IRRs). Fifteen percent of the women and 40 % of the men had at least one conviction between the age 15 and 19. The adjusted risk of suicidal behavior among women with five or more convictions was 3.5 (95 % CI 2.0-6.2); corresponding IRR for men was 3.9 (95 % CI 3.1-4.9). Child welfare experience-specifically of out-of-home care-in combination with delinquency is a potent risk factor for suicidal behavior among young adults. However, we cannot exclude that some of this association is an epiphenomenon of uncontrolled confounders, such as impulsivity or severity of psychiatric disease. Despite this caveat, results should be disseminated to practitioners in the health and correction services.
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| 5. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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A framework for motion planning of digital humans using discrete mechanics and optimal control
- 2017
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Ingår i: Proceedings of the 5th International Digital Human Modeling Symposium. - : Federal Institute for Occupational Safety and Health. ; , s. 64-71
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a framework for digital human modelling using discrete mechanics and optimal control. Discrete mechanics is particularly well suited for modelling the dynamics of constrained mechanical systems, which is almost always the case when considering complex human models interacting with the environment. We demonstrate that, by using recently developed recursive dynamics algorithms, we are able to efficiently use discrete mechanics in direct optimal control methods to plan for complex motions. Besides a proper mechanical model, an appropriate objective function is paramount to achieve realistic motions as a solution to an optimal control problem. Hence, several different objective functions, such as for example minimum time or minimum applied torque over the joints, are compared, and the resulting motions are analyzed and evaluated. To further improve the model, we include basic muscular models for the muscles of the shoulder, arm and wrist, and examine how this affects the motions.
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| 6. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Assembly path planning by distance field based shrinking
- 2012
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Ingår i: Proceedings of the 4th CIRP Conference on Assembly Technologies and Systems: Technologies and Systems for Assembly Quality, Productivity and Customization, Editor: Professor S. Jack Hu, May 20- 22, 2012, Ann Arbor, Michigan, USA. - 9780615640228 ; 4, s. 179-182
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method to support dynamic packing in cases when no collision-free path can be found. The method, which is primarily based on path planning and shrinking of geometries, suggests a minimal geometry design change that results in a collision-free assembly path. A new method to shrink geometry based on adaptively sampled distance fields is suggested. Compared to previous work, the new method is less sensitive to input mesh quality. The method works directly on the triangle mesh and requires neither tetrahedralization nor calculation of a medial axis. The algorithm paired with a state of the art path planner has been applied to several industrial cases demonstrating that the proposed method can be used effectively for assembly verification during geometry design.
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| 7. |
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| 8. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Digital Human Motion Planning of Operation Sequences Using Optimal Control of Hybrid Systems
- 2020
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Ingår i: Advances in Transdisciplinary Engineering. ; 11, s. 115-120
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Konferensbidrag (refereegranskat)abstract
- In IPS-IMMA the operation sequence planning tool offers an easy and powerful way to construct, analyze, and simulate sequences of human operations. So far, the simulations created using this tool have been quasi-static solutions to the operation sequence. In this paper we present new functionality for motion planning of digital human operation sequences which also takes the dynamics of the human into consideration. The new functionality is based discrete mechanics and optimal control and will be seamlessly integrated into to the IPS-IMMA software through the operation sequence planning tool. First, the user constructs an operation sequence using the operation sequence planning tool in IPS-IMMA. The operation sequence is then converted into a discrete optimal control problem which is solved using a nonlinear programming solver. Finally, the solution can be played back and analyzed in the graphical interface of IPS-IMMA. In order to obtain physically correct solutions to complex sequences consisting of several consecutive and dependent operations, we view the digital human as a hybrid system, i.e. a system containing both continuous and discrete dynamic behavior. In particular, the optimal control problem is divided into multiple continuous phases, connected by discrete events. The variational integrators used in discrete mechanics are particularly well suited for modelling the dynamics of constrained mechanical systems, which is almost always the case when considering complex human models interacting with the environment. To demonstrate the workflow, we model and solve an industrial case where the dynamics of the system plays an important part in the solution.
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| 9. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Efficient sequencing of industrial robots through optimal control
- 2014
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Ingår i: 5th CIRP Conference on Assembly Technologies and Systems, November 13-14, 2014, Dresden, Germany. - : Elsevier BV. - 2212-8271. ; 23:C, s. 194-199
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Konferensbidrag (refereegranskat)abstract
- In a production plant for complex assembled products there could be up to several hundred robots used for handling and joining operations. Thus, improvements in robot motion can have a huge impact on equipment utilization and energy consumption. By combining recent algorithms for collision free numerical optimal control and for optimal sequencing, we are able to cut down on energy consumption without sacrificing cycle time. The algorithm has been successfully applied to several industrial cases demonstrating that the proposed method can be used effectively in practical applications to find fast and energy efficient solutions.
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| 10. |
- Björkenstam, Staffan C, 1981, et al.
(författare)
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Energy Efficient and Collision Free Motion of Industrial Robots using Optimal Control
- 2013
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089.
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Konferensbidrag (refereegranskat)abstract
- In a production plant for complex assembled products there could be up to several hundred of robots used for handling and joining operations. Thus, improvement in robot motions can have a huge impact on equipment utilization and energy consumption. These are two of the most important aspects of sustainability in a production system. Therefore, this paper presents an algorithm for generating efficient and collision free motion of industrial robots using path planning and direct transcription methods for numerical optimal control. As a measure of efficiency for moving between configurations we use a combination of the energy norm of the applied actuator torques and the cycle time. Velocity and torque limits are handled and modeled as hard constraints. However, more general problems can be solved by the same approach. Our novel algorithm solves the problem in three steps; (i) first a path planning algorithm calculates an initial collision free path, (ii) a convex optimal control problem is then formulated to follow this path, and finally (iii) a nonlinear optimal control problem is solved to iteratively improve the trajectory. The resulting trajectory is guaranteed to be collision free by restrictions in the configuration space based on a local sensitivity analysis. The algorithm has been successfully applied to several industrial cases demonstrating that the proposed method can be used effectively in practical applications.
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