| 1. |
- Aarnio, Karoliina, et al.
(författare)
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Etiologic subtypes of first and recurrent ischemic stroke in young patients using A-S-C-O and TOAST classification criteria: A retrospective follow-up study
- 2024
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Ingår i: EUROPEAN STROKE JOURNAL. - 2396-9873 .- 2396-9881.
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Scarce data exist on the etiology of recurrent ischemic strokes (ISs) among young adults. We analyzed the etiology of first-ever and recurrent events and the differences between them.Patients and methods: Patients aged 15-49 years with a first-ever IS in 1994-2007 were included in the Helsinki Young Stroke Registry. In this retrospective cohort study, data on recurrent ISs were identified from Care Register for Health Care until the end of 2017 and Causes of Death Register and from patient records until the end of 2020. All first-ever and recurrent ISs were classified using Atherosclerosis-Small vessel disease-Cardioembolism-Other Cause (A-S-C-O) and Trial of Org 10172 in Acute Stroke Treatment (TOAST) classifications.Results: A total of 970 patients were included (median age at index IS 46 years, interquartile range 43-48, 33% women), of which 155 (16.0%) patients had recurrent IS, with 8 (5.2%) fatal cases and 5 (3.2%) unverifiable cases. The median follow-up was 17.4 (IQR 13.9-21.7) years. Median time from the index event to the first recurrent event was 4.5 (interquartile range [IQR] 1.6-10.2) years. Recurrence was more often due to definite cardioembolism (10.7% vs 18.0%, p = 0.013), while the proportion of other definite A-S-C-O subgroups remained the same. With TOAST classification, the proportion of true cryptogenic ISs decreased (16.7% vs 6.7%, p = 0.003), while those with incomplete evaluation increased (9.3% vs 19.3%, p = 0.015). Other TOAST phenotypes remained the same.Conclusion: The proportion of definite cardioembolism increased at recurrence using the A-S-C-O classification and the number of cryptogenic ISs decreased using the TOAST classification, while cases with incomplete evaluation increased. Most etiologies remained the same.
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| 2. |
- Kivisaari, Pyry, et al.
(författare)
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Bipolar Monte Carlo simulation of hot carriers in III-N LEDs
- 2015
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Ingår i: 2015 International Conference on Simulation of Semiconductor Processes and Devices, SISPAD 2015. - 9781467378581 ; , s. 393-396
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Konferensbidrag (refereegranskat)abstract
- We carry out bipolar Monte Carlo (MC) simulations of electron and hole transport in a multi-quantum well light-emitting diode with an electron-blocking layer. The MC simulation accounts for the most important interband recombination and intraband scattering processes and solves self-consistently for the non-quasiequilibrium transport. The fully bipolar MC simulator results in better convergence than our previous Monte Carlo-drift-diffusion (MCDD) model and also shows clear signatures of hot holes. Accounting for both hot electron and hot hole effects increases the total current and decreases the efficiency especially at high bias voltages. We also present our in-house full band structure calculations for GaN to be coupled later with the MC simulation in order to enable even more detailed predictions of device operation.
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| 3. |
- Kivisaari, Pyry, et al.
(författare)
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Bipolar Monte Carlo simulation of hot carriers in III-N LEDs
- 2015
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Ingår i: 15th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2015. - 9781479983797 ; 2015-May, s. 11-12
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Konferensbidrag (refereegranskat)abstract
- We perform fully bipolar Monte Carlo simulations of electrons and holes in III-Nitride multi-quantum well light-emitting diodes (LEDs) to investigate the effects of hot carriers. Our results show how accounting for hot carriers affects the current-voltage characteristics and device efficiency. We also discuss the effects of bandstructure details on the simulation results. Further simulations with versatile QW and EBL configurations are needed to confirm the relationship between hot carrier effects and current-voltage characteristics.
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| 4. |
- Kivisaari, Pyry, et al.
(författare)
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Monte Carlo study of non-quasiequilibrium carrier dynamics in III–N LEDs
- 2016
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Ingår i: Optical and Quantum Electronics. - : Springer Science and Business Media LLC. - 0306-8919 .- 1572-817X. ; 48:2
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Tidskriftsartikel (refereegranskat)abstract
- Hot carrier effects have been observed in recent measurements of III–Nitride (III–N) light-emitting diodes. In this paper we carry out bipolar Monte Carlo simulations for electrons and holes in a typical III–N multi-quantum well (MQW) LED. According to our simulations, significant non-quasiequilibrium carrier distributions exist in the barrier layers of the structure. This is observed as average carrier energies much larger than the 1.5kBT corresponding to quasi-equilibrium. Due to the small potential drop over the MQW being modest, the non-quasiequilibrium carriers can be predominantly ascribed to nnp and npp Auger processes taking place in the QWs. Further investigations are needed to determine the effects of hot carriers on the macroscopic device characteristics of real devices.
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| 5. |
- Löytynoja, Tuomas, 1987-
(författare)
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Quantum and quantum-classical calculations of core-ionized molecules in varied environments
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computational quantum chemistry methods have been applied in two particular cases: to provide insight to photoionization induced fragmentation of HgBr2 and HgCl2 molecules, and to study core-electron binding energies and chemical shifts of molecules in liquid, surface adsorbed and polymeric environments in the framework of quantum mechanics/molecular mechanics (QM/MM). In the photodissociation studies the computational work is based on the relativistic Dirac equation as the systems present strong spin-orbit interaction affecting the fragmentation processes. In the QM/MM studies of ethanol-water mixtures and molecules physisorbed on silver surfaces the structures are provided by classical molecular dynamics simulations to analyze the distribution of the binding energies of core-orbitals and effects of their surroundings. In the case of polymethyl methacrylate polymer the impact of a QM-MM boundary and a polymeric environment are studied. The theoretical backgrounds of the computational methods applied and the obtained results are discussed.
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