| 1. |
- Bergström, Göran, 1964, et al.
(författare)
-
Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
- 2021
-
Ingår i: Circulation. - Philadelphia : American Heart Association. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
|
|
| 2. |
- Bergström, Göran, et al.
(författare)
-
Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
- 2021
-
Ingår i: Circulation. - : Wolters Kluwer. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
|
|
| 3. |
- Bäckström, Mattias, et al.
(författare)
-
Diurnal variations of abiotic parameters in a stream, recipient for drainage water in Ranstad, southwest Sweden
- 2002
-
Ingår i: Journal of Environmental Monitoring. - Cambridge : Royal Society of Chemistry. - 1464-0325 .- 1464-0333. ; 4:5, s. 772-777
-
Tidskriftsartikel (refereegranskat)abstract
- During 24 h, water samples were taken for determination of a number of key parameters in a water system containing high concentrations of FeII at circumneutral pH. None of the major constituents (Ca, Mg, Na, K and sulfate) showed diurnal variations, while dissolved oxygen and pH increased during the night. This increase could entirely be explained by the decrease in water temperature. However, the concentration of FeII slightly increased at constant concentration of total Fe during the night, opposite to earlier observations in other systems where the presence of FeII was shown to be controlled by photoreduction. Nocturnal peaks of FeII have also been observed in other systems with high iron concentrations, however, at acidic pH, but without obvious explanation. The mechanisms for this process therefore need further investigation.
|
|
| 4. |
- Börjesson Axén, Jenny, 1986-, et al.
(författare)
-
A dynamic gas pressure model for management of nickel metal hydride batteries
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The Nickel Metal Hydride (NiMH) battery has an active gas phase during operation. This is due in part to the aqueous electrolyte causing oxygen evolution on the positive nickel electrode, and in part due to the hydrogen stored in the negative metal hydride (MH) electrode being in equilibrium with gaseous hydrogen. The gas phase reactions are closely connected to the battery function and must therefore be accounted for when creating a successful battery management system (BMS).This study explores a pressure model for management of the NiMH battery. By using measured current, voltage, and temperature as input, the total pressure and gas composition can be modeled. Model parameters are fitted by comparing the modeled total pressure to the measured pressure. By using the system voltage signal, the difficulty of simultaneously modeling the voltage based on the current is circumvented. A model like this opens the way to new ways of battery system management through use of calculated partial pressures and deviations from the modeled total pressure. This can help increasing safety and longevity of battery systems.
|
|
| 5. |
- Börjesson Axén, Jenny, 1986-, et al.
(författare)
-
A Structural Investigation into the OCV Hysteresis of the Ni(OH)2 Electrode
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Powder X-ray diffraction (XRPD), X-ray absorption spectroscopy (EXAFS and XANES) and Raman spectroscopy were used to study chemical changes in the polycrystalline nickel hydroxide positive electrode material of a NiMH battery at four states of charge: 0%, 50% and 100% charged, and 50% discharged. The two 50% samples were at the same state of charge but in different hysteresis states, manifested by differences in the open circuit potential. The nickel hydroxide electrodes consist of particles in the µm size range, and all measurements were performed ex situ. The material studied was taken from commercial batteries and as such contained both metallic nickel particles, cobalt, and zinc dopants in the active Ni(OH)2 material as well as a cobalt oxide surface layer. Combining the results from all the characterization methods was necessary to better understand the chemistry behind the physio-chemical hysteresis behavior in this complex system. Our results show that there are structural differences between the two 50% samples. Comparison of the XRPD results and the EXAFS results on the nickel edge indicate a presence of the kinetically favored TP2-NiOOH phase in the transition between β-Ni(OH)2 and β-NiOOH and that the amount differs between the two hysteresis states. The measurements on the zinc edge using EXAFS and XANES suggest short range differences in the active material bulk that stems from disorder. Raman spectroscopy measurements show a difference in degree of lithium intercalation in the LiCoO2 surface layer between the hysteresis states. As electrochemistry takes place on the surface of the particles, it is likely that differences in the surface structure are responsible for the open circuit voltage hysteresis. However, due to the coherence of the structure differences detected, it is probable that they are all connected and have a part in the observed behavior.
|
|
| 6. |
- Börjesson Axén, Jenny, 1986-, et al.
(författare)
-
Creating a dynamic P2D model for the nickel metal hydride battery
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this study, a predictive voltage and pressure nickel metal hydride (NiMH) battery model is presented. The model was validated under conditions that would be seen in applications, with mixed charge and discharge usage patterns. The model is based on an extended P2D model using concentrated electrolyte and porous electrode theory. On top of the charging and discharging processes, the NiMH battery has additional side reactions that affects the battery behavior. These processes are important to include for a model to accurately reproduce the voltage and pressure behavior under usage like conditions. Two processes were identified as necessary for the model to be predictive: Open circuit voltage hysteresis and the gas phase reactions involving oxygen and hydrogen. To take these into account, results from two previous studies that modeled these phenomena separately was introduced into the model. Hysteresis was described using empirical mathematical expressions and the gas phase reactions were described using electrochemical rate equations.The results show that the resulting model is capable of qualitatively reproducing NiMH battery voltage and pressure behavior, both for a continuous charge/discharge cycle and a varied usage pattern with mixed charge and discharge pulses using different currents. The model was used to study the effect of changes in electrode thickness on the energy and power density during discharge. The mechanism behind the drop in cell voltage at the end of charge was also investigated and found to be connected to the temperature dependence of the oxygen evolution equilibrium potential. Although the model can be fine-tuned further to improve quantitative reproducibility, this study shows that taking the OCV hysteresis and gas phase reactions into account creates a basis for a NiMH battery model that can function for different usage patterns. Such a model has potential to improve the development and use of NiMH batteries, providing a tool to improve battery design and battery management algorithms.
|
|
| 7. |
- Börjesson Axén, Jenny, et al.
(författare)
-
Evaluation of hysteresis expressions in a lumped voltage prediction model of a NiMH battery system in stationary storage applications
- 2022
-
Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X .- 2352-1538. ; 48, s. 103985-
-
Tidskriftsartikel (refereegranskat)abstract
- As a part of battery system operation, battery models are often used to determine battery characteristics such as the state of charge (SOC) and the state of health (SOH). A phenomenon that has a large impact on battery model accuracy for NiMH batteries is open circuit voltage (OCV) hysteresis, which causes the OCV to differ not only with the SOC of the battery but also with the charge-discharge history. This characteristic is especially influential when running the system in applications with dynamic current patterns. A model including a way to emulate battery hysteresis behavior would improve the battery management system function. In this study a lumped battery model for cell voltage prediction was expanded to include an OCV hysteresis model. Different expressions to describe the hysteresis behavior were explored. The different models were then evaluated using both synthetic and real-life application experimental data. In all cases the error was reduced by adding a hysteresis component to the model. Using this type of model in the battery management system of stationary energy storage systems based on NiMH batteries could help make the state prediction more accurate. This, in turn, would allow for better optimization of the system operation, something that could help increase system efficiency and lifetime.
|
|
| 8. |
- Börjesson Axén, Jenny, et al.
(författare)
-
Short-Term Impact of AC Harmonics on Aging of NiMH Batteries for Grid Storage Applications
- 2021
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:5
-
Tidskriftsartikel (refereegranskat)abstract
- Batteries in energy storage systems are exposed to electrical noise, such as alternating current (AC) harmonics. While there have been many studies investigating whether Lithium-ion batteries are affected by AC harmonics, such studies on Nickel Metal Hydride (NiMH) batteries are scarce. In this study a 10 Ah, 12 V NiMH battery was tested with three different harmonic current frequency overlays during a single charge/discharge cycle: 50 Hz, 100 Hz, and 1000 Hz. No effect on battery internal temperature or gas pressure was found, indicating that NiMH battery aging is not affected by the tested harmonic AC frequencies. This can reduce the cost of energy storage systems, as no extra filters are needed to safeguard the batteries. Instead, the capacitive properties of the batteries give the possibility to use the battery bank itself as a high pass filter, further reducing system complexity and cost.
|
|
| 9. |
- Börjesson Axén, Jenny, 1986-
(författare)
-
The dynamic behavior of the NiMH battery – Creating a versatile NiMH battery model
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To facilitate the shift from fossil to renewable energy sources, energy storage is needed to cope with the intermittent nature of technologies such as solar, wind, and wave power. One storage alternative is battery-based stationary energy storage. There are many battery types to choose from, but Nickel Metal Hydride (NiMH) is a type that is especially well suited. These batteries have a high energy density, a large temperature operating window and are a safe alternative for large scale energy storage.In this thesis, the behavior of the NiMH battery is studied with the aim to develop a dynamic battery model, a model that is capable of reproducing the battery voltage and pressure, also for dynamic usage. Such a model can be used to facilitate development of NiMH batteries, improvement of the algorithms used in the Battery Management System (BMS), quality control, and dimensioning of energy storage systems. These improvements can lead to stationary energy storage with a higher efficiency and longer usable lifetime.To increase the understanding of the battery function, deeper study was carried out of two behaviors that are typical for the NiMH battery and are deemed to have a large impact on the battery: Open circuit voltage (OCV) hysteresis and the battery gas phase behavior. The OCV hysteresis complicates modelling because it causes the battery rest voltage at a certain degree of charge to depend on the charge/discharge path taken to get there. OCV hysteresis is not noticeable for all batteries, and it is especially prominent for the NiMH battery. The gas phase in the NiMH battery is active since the electrolyte is water based and the voltage window during operation causes oxygen evolution at the positive electrode. The oxygen is then recombined into water at the negative electrode. The amount of hydrogen in the gas phase varies over a cycle due to the the dependence on temperature and state of charge of the hydrogen equilibrium pressure over the negative metal hydride electrode.Two models were developed separately to study these behaviors. The models showed good qualitative reproduction capabilities. The hysteresis phenomenon was also studied using structural analysis methods. Differences were identified in the material structure between two samples of the positive electrode material at the same state of charge but different hysteresis states. These differences were found in both the bulk and the surface region of the particles. The differences in bulk were related to degree of disorder and the differences in the surface region to inhomogeneity in Li distribution in the cobalt oxyhydroxide layer. The gas composition was studied using mass spectrometry. The gas phase was mostly composed of nitrogen, but hydrogen was responsible for the majority of the pressure changes of the battery during a charge/discharge cycle. Oxygen could be detected at the end of charge, where it is produced due to high voltage on the positive electrode.Finally, the two models were added to a P2D-model. This model type is commonly used to simulate battery behavior, and is based on electrochemical theory with approximations used for the porous electrode behavior. The spacial distribution is modeled in one dimension with an additional dimension added locally to simulate intra particle diffusion. The combined model showed that the behavior seen from a NiMH during dynamic usage could be recreated qualitatively through adding OCV hysteresis and the gas phase behavior to this standard model type.
|
|
| 10. |
- Ekblom Bak, Elin, 1981-, et al.
(författare)
-
Accelerometer derived physical activity and subclinical coronary and carotid atherosclerosis : cross-sectional analyses in 22 703 middle-aged men and women in the SCAPIS study
- 2023
-
Ingår i: BMJ Open. - : BMJ Publishing Group Ltd. - 2044-6055. ; 13:11
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim included investigation of the associations between sedentary (SED), low-intensity physical activity (LIPA), moderate-to-vigorous intensity PA (MVPA) and the prevalence of subclinical atherosclerosis in both coronaries and carotids and the estimated difference in prevalence by theoretical reallocation of time in different PA behaviours.DESIGN: Cross-sectional.SETTING: Multisite study at university hospitals.PARTICIPANTS: A total of 22 670 participants without cardiovascular disease (51% women, 57.4 years, SD 4.3) from the population-based Swedish CArdioPulmonary bioImage study were included. SED, LIPA and MVPA were assessed by hip-worn accelerometer.PRIMARY AND SECONDARY OUTCOMES: Any and significant subclinical coronary atherosclerosis (CA), Coronary Artery Calcium Score (CACS) and carotid atherosclerosis (CarA) were derived from imaging data from coronary CT angiography and carotid ultrasound.RESULTS: High daily SED (>70% ≈10.5 hours/day) associated with a higher OR 1.44 (95% CI 1.09 to 1.91), for significant CA, and with lower OR 0.77 (95% CI 0.63 to 0.95), for significant CarA. High LIPA (>55% ≈8 hours/day) associated with lower OR for significant CA 0.70 (95% CI 0.51 to 0.96), and CACS, 0.71 (95% CI 0.51 to 0.97), but with higher OR for CarA 1.41 (95% CI 1.12 to 1.76). MVPA above reference level, >2% ≈20 min/day, associated with lower OR for significant CA (OR range 0.61-0.67), CACS (OR range 0.71-0.75) and CarA (OR range 0.72-0.79). Theoretical replacement of 30 min of SED into an equal amount of MVPA associated with lower OR for significant CA, especially in participants with high SED 0.84 (95% CI 0.76 to 0.96) or low MVPA 0.51 (0.36 to 0.73).CONCLUSIONS: MVPA was associated with a lower risk for significant atherosclerosis in both coronaries and carotids, while the association varied in strength and direction for SED and LIPA, respectively. If causal, clinical implications include avoiding high levels of daily SED and low levels of MVPA to reduce the risk of developing significant subclinical atherosclerosis.
|
|
