Reduction of physiological stress by urban green space in a multisensory virtual experiment

Although stress is an increasing global health problem in cities, urban green spaces can provide health benefits. There is, however, a lack of understanding of the link between physiological mechanisms and qualities of urban green spaces. Here, we compare the effects of visual stimuli (360 degree virtual photos of an urban environment, forest, and park) to the effects of congruent olfactory stimuli (nature and city odours) and auditory stimuli (bird songs and noise) on physiological stress recovery. Participants (N = 154) were pseudo-randomised into participating in one of the three environments and subsequently exposed to stress (operationalised by skin conductance levels). The park and forest, but not the urban area, provided significant stress reduction. High pleasantness ratings of the environment were linked to low physiological stress responses for olfactory and to some extent for auditory, but not for visual stimuli. This result indicates that olfactory stimuli may be better at facilitating stress reduction than visual stimuli. Currently, urban planners prioritise visual stimuli when planning open green spaces, but urban planners should also consider multisensory qualities

On the influence of serotonin- and sex steroid-related genetic variation on mood, anxiety, personality, autism and transsexualism

Background: The neurotransmitter serotonin has been related to mood and anxiety, and variation in genes that encode important members of the serotonergic system may hence affect mood- and anxiety-related traits. Sex steroids influence brain development, and variation in genes encoding androgen and estrogen receptors, or enzymes needed for sex steroid synthesis, may be of importance for both personality traits and risk for psychiatric disorders. The specific aims of this thesis were: (i) to investigate the possible influence of serotonin-related genetic variation on the neural correlates of anxiety, and on mood- and anxiety-related phenotypes, including premenstrual dysphoric disorder (PMDD), depression and anxiety-related personality traits, (ii) to investigate the possible influence of sex steroid-related genetic variation on personality, autism spectrum disorder and transsexualism, and (iii) to try to ameliorate the chance of detecting effects of combinations of genetic variations by restricting the statistical analysis to particular patterns. Results: (i) The serotonin transporter (5-HTT) linked polymorphic region (5-HTTLPR) and a polymorphism in an important enzyme for serotonin synthesis (tryptophan hydroxylase 2; TPH2) were associated with amygdala response during presentation of angry faces in subjects with social phobia and controls. (ii) The same polymorphisms were associated with response to placebo and also with placebo-induced changes in amygdala activity during public speaking in subjects with social phobia. (iii) In men, genetic variation in the neurotrophic factor BDNF, which is closely related to the serotonergic system, was associated with the amount of serotonin transporter in the brain. (iv) Polymorphisms in genes that encode proteins important for the development of the serotonergic system (GATA2), for serotonin synthesis (TPH2) and for serotonergic transmission (5-HT3B) were associated with PMDD. (v) The 5-HTTLPR was shown to influence reports of controllable stressful life events in combination with the BDNF Val66Met polymorphism or anxiety-related personality traits in non-depressed men. (vi) Variants that may increase the function of the androgen receptor were associated with extraversion and spiritual acceptance in men. (vii) A variant that is associated with increased androgen receptor function was more common in women with autism spectrum disorder than in controls. (viii) The same androgen receptor polymorphism was associated with transsexualism in combination with polymorphisms in the genes encoding the estrogen receptor β or the testosterone-converting aromatase enzyme. (ix) A method that restricts the search for genetic combinations to monotone effect patterns was shown to increase the probability of finding gene-gene effects. Conclusions: The results support the notion that variation in genes that encode serotonin-related and sex steroid-related proteins are of importance for the psychiatric traits studied in this thesis

Sounds of Nature in the City: No Evidence of Bird Song Improving Stress Recovery

Noise from city traffic is one of the most significant environmental stressors. Natural soundscapes, such as bird songs, have been suggested to potentially mitigate or mask noise. All previous studies on masking noise use self-evaluation data rather than physiological data. In this study, while respondents (n = 117) watched a 360\ub0 virtual reality (VR) photograph of a park, they were exposed to different soundscapes and mild electrical shocks. The soundscapes-"bird song", "bird song and traffic noise", and "traffic noise"-were played during a 10 min recovery period while their skin conductance levels were assessed as a measure of arousal/stress. No significant difference in stress recovery was found between the soundscapes although a tendency for less stress in "bird song" and more stress in "traffic noise" was noted. All three soundscapes, however, significantly reduced stress. This result could be attributed to the stress-reducing effect of the visual VR environment, to the noise levels being higher than 47 dBA (a level known to make masking ineffective), or to the respondents finding bird songs stressful. Reduction of stress in cities using masking with natural sounds requires further studies with not only larger samples but also sufficient methods to detect potential sex differences

Choice of urea-spray models in CFD simulations of urea-SCR systems

The sensitivity of modeling choices to obtained results for Eulerian–Lagrangian CFD simulations of urea-SCR systems has been investigated for a system consisting of an AdBlue-spray located at the exhaust pipe wall, directed into the exhaust gas flow. The decomposition of urea is modeled as being heat transfer limited and taking place at a constant temperature (425 K). It is shown that modeling choices may affect the predicted extent of wall hit, which types of droplets that are predicted to hit the wall, and also where they will do so.The influence of the different forces due to drag, buoyancy, lift effects, thermophoresis and history effects was investigated, proving that only the forces due to drag and buoyancy are necessary to correctly describe droplet motion within this system. It is necessary to use a droplet drag coefficient that takes the current level of droplet distortion into account.A stochastic particle tracking model will describe the effects of turbulent dispersion, but also make the simulation results sensitive to the quality of the turbulence model\u27s prediction of the turbulent fluctuating velocities. Using such a model will also resolve some of the enhancement of heat and mass transfer caused by the continuous acceleration/deceleration of droplets by turbulent eddies