| 1. |
- Byström, Pär, et al.
(author)
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Substitution of top predators : effects of pike invasion in a subarctic lake
- 2007
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In: Freshwater Biology. - : John Wiley & Sons, Inc. - 0046-5070 .- 1365-2427. ; 52:7, s. 1271–1280-
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Journal article (peer-reviewed)abstract
- 1. Invasions of top predators may have strong cascading effects in ecosystems affecting both prey species abundance and lower trophic levels. A recently discussed factor that may enhance species invasion is climate change and in this context, we studied the effects of an invasion of northern pike into a subarctic lake ecosystem formerly inhabited by the native top predator Arctic char and its prey fish, ninespined stickleback. 2. Our study demonstrated a strong change in fish community composition from a system with Arctic char as top predator and high densities of sticklebacks to a system with northern pike as top predator and very low densities of sticklebacks. A combination of both predation and competition from pike is the likely cause of the extinction of char. 3. The change in top predator species also cascaded down to primary consumers as both zooplankton and predator-sensitive macroinvertebrates increased in abundance. 4. Although the pike invasion coincided with increasing summer temperatures in the study area we have no conclusive evidence that the temperature increase is the causal mechanism behind the pike invasion. But still, our study provides possible effects of future pike invasions in mountain lakes related to climate change. We suggest that future pike invasions will have strong effects in lake ecosystems, both by replacing native top consumers and through cascading effects on lower trophic levels.
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| 2. |
- Hailong, Liu, et al.
(author)
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A simulation study of particles generated from pellet wear contacts during a laboratory test
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Other publication (other academic/artistic)abstract
- In the blast furnace process, material losses occur due to mechanical wear between charged iron ore pellets and are exhausted in the form of dust in the off-gases. A redesigned tribometer combined with a ventilation chamber was developed to identify the dust emission from the mechanical wear contact of pellets. In order to obtain a better understanding of the measurement results, a coupled drift flux with a unified Eulerian deposition model was adopted to investigate particle dispersion and deposition during tests. Two influential factors, namely the air condition (5-20 l/min) and particle size (1-20 µm) were examined. The predicted results were presented by introducing two parameters, namely the measurable fraction and the deposition fraction. For each air condition, the measurable fraction declines while the deposition fraction rises as particle size grows. The critical size of the particles that becomes airborne and captured at the outlet was identified to be around 20 µm. In addition, a high airflow rate supplied at the inlet was observed to be favorable for improving the measurable fraction. Nevertheless, the results show that nearly 50 % of emitted particles (1-20 µm) that failed to be captured during tests. Thus it could be expected that these generated particles would be transported deeply in a blast furnace if they are not efficiently removed from the off-gas. As a consequence, they may influence the quality of the products. Furthermore, the validation of the simulation results against the experimental data was achieved by using the predicted measurable fraction.
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| 3. |
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| 4. |
- Letterstål, Anna, et al.
(author)
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Patients' experience of open repair of abdominal aortic aneurysm : preoperative information, hospital care and recovery
- 2010
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In: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 19:21-22, s. 3112-3122
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Journal article (peer-reviewed)abstract
- Aims and objectives. The aim was to elucidate patients' lived experience of the care pathway of going through open surgery for abdominal aortic aneurysm. Background. Open surgical treatment has a great impact on patients' health-related quality of life both before and after treatment. The transition from being independent and asymptomatic to dependent on nursing care can be difficult. To facilitate this process and provide high-quality care, patients' needs must be better understood. Design. An exploratory descriptive design was chosen to describe and understand patients' lived experience. Method. Audio-taped interviews were performed three months postoperatively, covering the care pathway before and after surgery. Interviews were analysed with qualitative content analysis. Results. The informants made a transition from becoming aware of the deadly risk associated with abdominal aortic aneurysm to gradually understanding the physical and emotional impact of the surgical procedure during the recovery process. The experience of not understanding fully the risks of undergoing surgery or its consequences on daily life made the informants unprepared for complications and limitations during the recovery period. Many concerns emerged, with a need for more dialogue and opportunities to understand their own care than those provided by the health care staff. Conclusions. To facilitate the transition process, health care staff should consider patients' unpreparedness for the physical and emotional impact that can follow diagnosis and treatment for abdominal aortic aneurysm and recognise the need for dialogue to enhance participation during recovery. Relevance to clinical practice. Throughout the care pathway, patients' need for information and for opportunities to reflect on bodily and emotional reactions to the diagnosis and treatment of abdominal aortic aneurysm should be recognised by nurses and physicians to support patients getting realistic expectations of the consequences of treatment and facilitate participation in decisions concerning care and medical treatment.
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| 5. |
- Letterstål, Anna, et al.
(author)
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Postoperative mobilization of patients with abdominal aortic aneurysm
- 2004
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In: Journal of Advanced Nursing. - : Wiley. - 0309-2402 .- 1365-2648. ; 48:6, s. 560-568
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Journal article (peer-reviewed)abstract
- Aim. This paper reports on a study which aimed to evaluate the effects of structured written preoperative information on patients’ postoperative psychological and physical wellbeing after surgery for abdominal aortic aneurysm (AAA).Background. The possible benefits of current booklets written by professionals on postoperative psychological and physical wellbeing in patients with AAA are unknown. Previous studies have shown that preoperative information has a favourable effect on both mood state and physical mobilization.Method. Fifty-two patients admitted for elective repair of AAA were selected consecutively and randomized to receive only verbal (control group), or verbal and written information in booklet form (experimental group). The booklet contained procedural and sensory information about the disease and its treatment. Two questionnaires were used to establish whether the booklet had any effect on perceived health, psychological and physical wellbeing postoperatively.Results. The two groups were similar regarding their perceived health but differed significantly regarding psychological wellbeing pre- and postoperatively. Patients in the experimental group were significantly sadder both pre- and postoperatively compared with those in the control group. Both groups were similar in postoperative physical wellbeing.Conclusion. This group of patients often has asymptomatic disease, with a short interval between diagnosis and major surgery. When patients receive an information booklet during this period, this seems to cause more worries than anticipated. Hence, a more supportive educational programme might benefit this patient group, both pre- and postoperatively.
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| 6. |
- Letterstål, Anna, et al.
(author)
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Risk attitude and preferences in person's hypothetically facing open repair of abdominal aortic aneurysm
- 2012
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In: Journal of Vascular Nursing. - : Elsevier BV. - 1062-0303 .- 1532-6578. ; 30:4, s. 112-117
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Journal article (peer-reviewed)abstract
- The aim of this study was to describe risk attitude and preference for treatment using a proxy measurement of a general population sample hypothetically facing treatment for open repair (OR) of abdominal aortic aneurysm (AAA). In a telephone interview, a standard gamble (SG) and a time trade-off (TTO) question were asked to elicit risk attitude and preference for treatment in a general population sample of 200 persons, stratified in four age groups. When facing the two questions of (1) either live a shorter life without an AAA compared to a longer life with an AAA (TTO) or (2) taking a risk of living with AAA compared to taking the risk with surgical treatment (SG), the oldest age group was neither willing to live a shorter life without AAA, nor willing to take a risk with surgical treatment to the same extent as the younger age groups: age 50-59 (TTO P = 0.03, SG P = < 0.001), age 60-69 (TTO P = 0.01, SG P = < 0.001), age 70-79 (TTO P = 0.02, SG P = 0.002). These results suggest that persons in the age groups over 80 years old in the general population sample are more inclined to go on living with an AAA without taking the immediate risk associated with OR as well as the postoperatively impaired health-related quality of life (HRQL). Preference for treatment in different age groups is important to consider during the decision-making process, especially for patients over 80 years old. Patient education about treatment options, specific risks as well as postoperative impairment of HRQL is necessary in this process.
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| 7. |
- Letterstål, Anna, et al.
(author)
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Risk attitudes to treatment among patients with severe intermittent claudication
- 2008
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In: Journal of Vascular Surgery. - : Elsevier. - 0741-5214 .- 1097-6809. ; 47:5, s. 988-994
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Journal article (peer-reviewed)abstract
- ObjectivesTo determine claudication patients' risk attitude to invasive treatment and whether this treatment is cost effective.MethodsQuality of life and health state utility status of 50 consecutive patients with severe intermittent claudication was assessed and compared with ankle-brachial pressure index values (ABPI) and results from treadmill tests before and after endovascular or open revascularization. Health utility scores were then calculated and used in a cost-utility analysis.ResultsBefore surgery, patients were assigned a utility score of 0.51 (EQ-5D index) for their disease, and the standard gamble (SG) and time trade-off (TTO) median scores were 0.88 and 0.70, respectively. Before treatment, a weak correlation (r = 0.43, P < .001) between having a high risk perception of treatment and patients' walking distance were observed, where patients able to walk short distances accepted a higher risk. After treatment, ABI (P = .003) and walking distance (P = .002) improved significantly as well the physical components of the quality of life instruments (P < .001). The surgical treatment generated an improvement in quality of life expressed in QALYs equivalent to 0.17. With an estimated survival of 5 years, it adds up to a value of 0.85, corresponding to a sum of 51,000 US$ gained.ConclusionsPatients with severe intermittent claudication are risk-seeking when it comes to surgical treatment and their risk attitude is correlated to their walking ability and quality of life. The incremental QALYs gained by treatment are achieved at a reasonable cost and revascularization appears to be cost effective.
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| 8. |
- Liu, Hailong, et al.
(author)
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A pin-on-disc study of airborne wear particles from dry sliding wheel-rail contacts
- 2016
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In: Civil-Comp Proceedings. - : Civil-comp press. - 1759-3433. ; 110
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Journal article (peer-reviewed)abstract
- Pin-on-disc laboratory tests were carried out to identify the generation of airborne wear particles in wheel-rail contacts under different sliding velocities. The results show that the sliding velocity significantly influences both the number and size distribution of airborne wear particles. A comparison of the contact temperature was obtained during tests. For tests with high sliding velocities (1.2 and 3.4 m/s), the particle number concentration level was related to the elevated contact temperature in selected time intervals. Moreover, morphological and elemental analyses of collected particles and pin worn surfaces were studied by using a scanning electron microscope and field emission-scanning electron microscope. The data suggests that the oxide layers were detected within the pin's worn surfaces and an abundant presence of iron-oxide containing particles was observed. Therefore, it can be concluded that abundant fine and ultrafine airborne particles are more likely to be produced from an oxidative wear process in a wheel-rail contact under high sliding velocities.
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| 9. |
- Liu, Hailong, et al.
(author)
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A simulation study of off-gas particles generated from contact between pellets in a laboratory test
- 2015
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In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 972-976
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Conference paper (peer-reviewed)abstract
- A pin-on-disc tribometer situated in a sealed cylindrical chamber was redesigned and used to find out the correlation between pellets properties and generated particles. To understand the results, it is important to understand the dust particle transport behavior inside the chamber. This could be achieved by using a simulation method. With the simulation, it is also possible to determine the operational parameters which in turn could be used to obtain good experimental results. Therefore, a model was built based on the same geometry as the particle measurement system. The flow field was firstly solved with the renormalized group (RNG) k-e turbulence model. Thereafter, a simplified drift-flux method was applied to simulate the particle transport inside the test chamber. Two important characteristics, gravitational separation and diffusion are considered in the modelling. Three groups of particles with different diameters (1nm, 1μm and 10μm) were released at the contact area between the pellets. The simulation results show that the influence of gravitational setting on particle transport is noticeable for 10μm particles, while the influence can be neglected for 1nm and 1μm. On the other hand, the diffusion has a lesser effect on particle dispersion for 1nm, 1μm and 10μm particles. Moreover, the particle loss rate was estimated by the ratio between the amount of released and escaped particles in elapsed time. The results show that the measurable portion of large micro-particles can be increased by increasing the inlet air velocity.
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| 10. |
- Liu, Hailong, et al.
(author)
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A Simulation Study of Particles Generated from Pellet Wear Contacts during a Laboratory Test
- 2016
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In: ISIJ INTERNATIONAL. - : Iron and Steel Institute of Japan. - 0915-1559. ; 56:11, s. 1910-1919
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Journal article (peer-reviewed)abstract
- In the blast furnace process, material losses occur due to mechanical wear between charged iron ore pellets and are exhausted in the form of dust in the off-gases. A redesigned tribometer combined with a ventilation chamber was developed to identify the dust emission from the mechanical wear contact of pellets. In order to obtain a better understanding of the measurement results, a coupled drift flux with a unified Eulerian deposition model was adopted to investigate particle dispersion and deposition during tests. Two influential factors, namely the air condition (5-20 L/min) and particle size (1-20 mu m) were examined. The predicted results were presented by introducing two parameters, namely the measurable fraction and the deposition fraction. For each air condition, the measurable fraction declines while the deposition fraction rises as particle size grows. The critical size of the particles that becomes airborne and captured at the outlet was identified to be around 20 mu m. In addition, a high airflow rate supplied at the inlet was observed to be favorable for improving the measurable fraction. Nevertheless, the results show that nearly 50% of emitted particles (1-20 mu m) that failed to be captured during tests. Thus it could be expected that these generated particles would be transported deeply in a blast furnace if they are not efficiently removed from the off-gas. As a consequence, they may influence the quality of the products. Furthermore, the validation of the simulation results against the experimental data was achieved by using the predicted measurable fraction.
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