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- Karlsson, Kåre, et al.
(författare)
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Stress response in swedish ambulance personnel evaluated by Trier social stress test
- 2019
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Ingår i: Journal of Health and Environmental Research. - : Science Publishing Group. - 2472-3584 .- 2472-3592. ; 5:1, s. 14-23
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Tidskriftsartikel (refereegranskat)abstract
- According to previous research, ambulance personnel often consider themselves as healthy, but at the same time several studies show that they suffer from several stress-related illnesses, take early retirement and even suffer early death. The aim of this study was to explore mental stress during the Trier Social Stress Test. Questions were whether heart rate measurement could replace cortisol concentration in saliva as an indicator of stress and if there were differences between genders. During 20 Trier Social Stress Tests heart rate and salivary cortisol concentrations were measured. Heart rate was measured every 15 seconds and salivary cortisol was collected at seven occasions. Fourteen men and six women (sixteen ambulance nurses and four paramedics) participated. A questionnaire with background data was collected. Statistical analysis used was non-parametric tests to adjust for misalignment. During the Trier Social Stress Test women had their highest salivary cortisol concentration before start of test while the maximum values for men were 10 to 20 minutes after start. In contrast, there was no difference in heart rhythm before, during and after test between genders. No correlation between heart rate and salivary cortisol was found. There was no significant difference in stress response according to personnel’s age or level of education. Women and men exhibit different hormonal stress responses when it comes to performing unfamiliar actions, something that has not been seen before. Since no correlation could be seen between heart rate and salivary cortisol concentration they cannot replace each other as indicators of stress.
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| 2. |
- Zhu, Baiwei, 1990-, et al.
(författare)
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A study of formation and growth of the anodised surface layer on Al-Si casting alloys based on different analytical techniques
- 2015
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Konferensbidrag (refereegranskat)abstract
- One of the major limitations in the application of anodizing of aluminum casting alloys is the non-uniform thickness of the oxide layer. Previous researches have studied the formation of the oxide film during anodizing in detail. These investigations have mainly been limited to aluminum and wrought aluminum alloys, and only a few papers have given some insights about the formation of the oxide layer on cast aluminum alloys. The majority of cast aluminum alloys contains relatively higher amounts of Si and other elements (e.g. Cu and Fe) than wrought alloys. This paper aims to investigate the mechanisms of formation and growth of the anodized surface layer on Al-Si casting alloys by applying different analytical techniques such as optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray computer tomography (X-ray CT) scanning. Three different Al alloys with various Si content (2.4%, 3.5% and 5.5%) were investigated. Si morphological modification by Sr addition, as well as gradient solidification was used to vary the microstructural coarseness in a controlled manner to study the influence of these parameters on the growth of the oxide layer. The microstructure features of the anodized layer and the interface between matrix and the oxide layer were studied, employing optical microscopy (figure 1), and SEM/EDS (figure 2). X-Ray CT-scanning (figure 3) was used to examine the high density phases (Fe and Cu bearing phases) and also to give a 3-D view of the anodized oxide surface. Furthermore, TEM was used to examine the general filming behavior of anodized layer and the local effects associated with Si particles in the matrix.It was found that: (i) during anodizing, the oxide front grew around the Si particles and tends to engulf them; (ii) the oxide front grew inwards but did expand in other directions in the eutectic areas; (iii) a scalloped interface between substrate and oxide indicated different anodizing rates in dendrites and eutectic phases. The oxide front was moving faster in the primary dendrite Al-phase than in the eutectic, and the growth rate was particularly slow in larger eutectic areas; (iv) different anodizing rates in dendrite and eutectic phases resulted in thinner layers in specimens with lower SDAS (secondary dendrite arm spacing); and (v) a more uniform layer thickness in Sr-modified specimens illustrates that oxide growth speed was faster in modified eutectic phase. However, diffusion of Si or long distance between Si particles after modification could even results in the adverse situation with a bad anodized surface appearance.
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| 3. |
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| 4. |
- Zhu, Baiwei, 1990-, et al.
(författare)
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A study of formation and growth of the anodised surface layer on cast Al-Si alloys based on different analytical techniques
- 2016
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 101, s. 254-262
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to investigate the mechanisms of formation and growth of the anodised surface layer on Al-Si castings by applying different analytical techniques such as optical microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and X-ray computer tomography (X-ray CT) scanning. Three different Al alloys with various Si content (2.43%, 3.53% and 5.45%) were investigated. Si particle morphological modification by Sr addition, as well as directional solidification, was used to vary the microstructural coarseness in a controlled manner to study the influence of these parameters on the growth behaviour of the oxide layer. This study observed residual unanodised Al phases trapped beneath or between Si particles in the oxide layer. It was found, depending on the geometry and morphology of Si particles, that Al can be shielded by Si particles and prevented from oxidising.
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