| 1. |
- Gustafsson, Fredrik, et al.
(författare)
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On Threshold Optimization in Fault Tolerant Systems
- 2008
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Ingår i: Proceedings of the 17th IFAC World Congress. ; , s. 7883-7888
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Konferensbidrag (refereegranskat)abstract
- Fault tolerant systems are considered, where a nominal system is monitored by a fault detection algorithm, and the nominal system is switched to a backup system in case of a detected fault. Conventional fault detection is in the classical setting a trade-off between detection probability and false alarm probability. For the considered fault tolerant system, a system failure occurs either when the nominal system gets a fault that is not detected, or when the fault detector signals an alarm and the backup system breaks down. This means that the trade-off for threshold setting is different and depends on the overall conditions, and the characterization and understanding of this trade-off is important. It is shown that the probability of system failure can be expressed in a general form based on the probability of false alarm and detection power, and based on this form the influence ratio is introduced. This ratio includes all information about the supervised system and the backup system that is needed for the threshold optimization problem. It is shown that the influence ratio has a geometrical interpretation as the gradient of the receiver operating characteristics (ROC) curve at the optimal point, and furthermore, it is the threshold for the optimal test quantity in important cases.
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| 2. |
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| 3. |
- Jonsson, Mats, et al.
(författare)
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Radiation induced spent nuclear fuel dissolution under deep repository conditions
- 2007
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:20, s. 7087-7093
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of spent nuclear fuel dissolution in groundwater is an important part of the safety assessment of a deep geological repository for high level nuclear waste. In this paper we discuss the most important elementary processes and parameters involved in radiation induced oxidative dissolution of spent nuclear fuel. Based on these processes, we also present a new approach for simulation of spent nuclear fuel dissolution under deep repository conditions. This approach accounts for the effects of fuel age, burn up, noble metal nanoparticle contents, aqueous H-2 and HCO3- concentration, water chemistry, and combinations thereof. The results clearly indicate that solutes consuming H2O2 and combined effects of noble metal nanoparticles and H-2 have significant impact on the rate of spent nuclear fuel dissolution. Using data from the two possible repository sites in Sweden, we have employed the new approach to estimate the maximum rate of spent nuclear fuel dissolution. This estimate indicates that H-2 produced from radiolysis of groundwater alone will be sufficient to inhibit the dissolution, completely for spent nuclear fuel older than 100 years.
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| 4. |
- Lerner, Mikael, et al.
(författare)
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The RBCC gene RFP2 (leu5) encodes a novel transmembrane E3 ubiquitin ligase involved in ERAD
- 2007
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Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 18:5, s. 1670-1682
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Tidskriftsartikel (refereegranskat)abstract
- RFP2, a gene frequently lost in various malignancies, encodes a protein with RING finger, B-box, and coiled-coil domains that belongs to the RBCC/TRIM family of proteins. Here we demonstrate that Rfp2 is an unstable protein with auto-polyubiquitination activity in vivo and in vitro, implying that Rfp2 acts as a RING E3 ubiquitin ligase. Consequently, Rfp2 ubiquitin ligase activity is dependent on an intact RING domain, as RING deficient mutants fail to drive polyubiquitination in vitro and are stabilized in vivo. Immunopurification and tandem mass spectrometry enabled the identification of several putative Rfp2 interacting proteins localized to the endoplasmic reticulum (ER), including valosin-containing protein (VCP), a protein indispensable for ER-associated degradation (ERAD). Importantly, we also show that Rfp2 regulates the degradation of the known ER proteolytic substrate CD3-delta, but not the N-end rule substrate Ub-R-YFP (yellow fluorescent protein), establishing Rfp2 as a novel E3 ligase involved in ERAD. Finally, we show that Rfp2 contains a C-terminal transmembrane domain indispensable for its localization to the ER and that Rfp2 colocalizes with several ER-resident proteins as analyzed by high-resolution immunostaining. In summary, these data are all consistent with a function for Rfp2 as an ERAD E3 ubiquitin ligase.
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| 5. |
- Nielsen, Fredrik, et al.
(författare)
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Geometrical alpha- and beta-dose distributions and production rates of radiolysis products in water in contact with spent nuclear fuel
- 2006
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 359:02-jan, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical model for the dose distribution and production rates of radiolysis products in water surrounding spent nuclear fuel has been developed, based on the geometrical and energetic properties of radiation. The nuclear fuel particle is divided into layers, from which the radiation emits. The water is likewise divided into layers, where the doses are distributed. The doses are stored in vectors which are added to determine the total dose rate. A complete inventory with over 200 radionuclides has been used as input data for the model. The purpose of the model is to describe the geometrical dose distribution as a function of fuel age and burn-up, to be used as input data for kinetic modeling of the fuel dissolution. The results show that the P-dose contribution close to the spent fuel surface is negligible. Also, the variation in the relative OC/P dose contribution between different ages and burn-ups is insignificant. The alpha- and beta-dose rates vary between different burn-ups of the same age; the younger the fuel is, the larger is the difference. Exponential functions have been fitted to the relations between fuel age and average dose rate, giving useful expressions for determining average dose rates for fuel ages other than those covered in this work.
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| 6. |
- Nielsen, Fredrik, et al.
(författare)
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Simulation of radiation induced dissolution of spent nuclear fuel using the steady-state approach. A comparison to experimental data
- 2008
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 374:1-2, s. 286-289
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Tidskriftsartikel (refereegranskat)abstract
- Using the recently developed steady-state model for simulation of radiation induced dissolution of spent nuclear fuel in water we have estimated the rate of dissolution for relatively fresh fuel to 1.64 x 10(-9) Mol m(-2) s(-1). A series of experiments have been performed on fuel fragments in deoxygenated water containing 10 mM HCO3-. The dissolution rates obtained from these experiments range from 2.6 x 10(-10) to 1.6 x 10-9 Mol m(-2) s(-1). The leaching time in the experiments is 40 days or less and during this time the amount of released uranium increases linearly with time which indicates that the system has reached steady-state. The excellent agreement between the estimated dissolution rate and the dissolution rates obtained from the spent nuclear fuel leaching experiments indicates that the steady-state approach can indeed be used to predict the rate of spent nuclear fuel dissolution.
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| 7. |
- Nielsen, Fredrik, et al.
(författare)
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Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel
- 2008
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 372:1, s. 32-35
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Tidskriftsartikel (refereegranskat)abstract
- A simple mathematical model describing the hydrogen peroxide concentration profile in water surrounding a spent nuclear fuel pellet as a function of time has been developed. The water volume is divided into smaller elements, and the processes that affect hydrogen peroxide concentration are applied to each volume element. The model includes production of H2O2 from alpha-radiolysis, surface reaction between H2O2 and UO2 and diffusion. Simulations show that the surface concentration of H2O2 increases fairly rapidly and approaches the steady-state concentration. The time to reach steady-state is sufficiently short to be neglected compared to the times of interest when simulating spent fuel dissolution under deep repository conditions. Consequently, the steady-state approach can be used to estimate the rate for radiation-induced spent nuclear fuel dissolution.
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| 8. |
- Nielsen, Fredrik, et al.
(författare)
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Simulations of H2O2 concentration profiles in the water surrounding spent nuclear fuel taking mixed radiation fields and bulk reactions into account
- 2008
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 374:1-2, s. 281-285
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Tidskriftsartikel (refereegranskat)abstract
- To simulate the dynamics of the concentration gradient of hydrogen peroxide in groundwater surrounding spent nuclear fuel under various conditions, a model has been developed. The model treats the water volume as a sequence of volume elements, and applies the processes that affect hydrogen peroxide concentration to each volume element. The surface steady-state concentrations of H2O2, and the time. to reach steady-state, have been determined under different conditions. The processes accounted for in the model are radiolytic production of H2O2 from alpha- and beta-radiation, surface reactions consuming H2O2, homogeneous reactions consuming H2O2, and diffusion. The system has been modeled mainly for different surface reaction rate constants and homogeneous (bulk) reaction rate constants. The simulations show that the surface concentration of H2O2 approaches the steady-state concentration very rapidly and that the impact of homogeneous (bulk) reactions consuming H2O2 On the steady-state concentration is significant.
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| 9. |
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| 10. |
- Nielsen, Niklas, et al.
(författare)
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Successful resuscitation with mechanical CPR, therapeutic hypothermia and coronary intervention during manual CPR after out-of-hospital cardiac arrest
- 2005
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Ingår i: Resuscitation. - : Elsevier BV. - 1873-1570 .- 0300-9572. ; 65:1, s. 111-113
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Tidskriftsartikel (refereegranskat)abstract
- A 62-year-old man suffered out-of-hospital cardiac arrest and was treated with mechanical compression-decompress ion during transport to the hospital. In the emergency department, 28 min after cardiac arrest, spontaneous circulation returned briefly but the patient rapidly became asystolic and mechanical compression-decompression was again applied. After further resuscitation a spontaneous circulation returned and the patient was transferred, deeply comatose, to the coronary intervention laboratory while therapeutic hypothermia was induced. In the laboratory the heart arrested again and coronary angiography was performed during manual CPR revealing a left main stem occlusion. After successful reperfusion of the heart the patient was transferred to the intensive care unit with an intra-aortic balloon pump. The patient was treated with hypothermia for 24 h and awoke without neurological sequelae after a sustained intensive care period of 13 days. The present case is an example of how modern resuscitation principles implementing new clinical and experimental findings may strengthen the chain of survival during resuscitation.
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