| 1. |
- Forssén, Jens, et al.
(författare)
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A model of sound scattering by atmospheric turbulence for use in noise mapping calculations
- 2014
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Ingår i: Acta Acoustica united with Acustica. - : S. Hirzel Verlag. - 1610-1928 .- 1861-9959. ; 100:5, s. 810-815
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Tidskriftsartikel (refereegranskat)abstract
- Sound scattering due to atmospheric turbulence limits the noise reduction in shielded areas. An engineering model is presented, aimed to predict the scattered level for general noise mapping purposes including sound propagation between urban canyons. Energy based single scattering for homogeneous and isotropic turbulence following the Kolmogorov model is assumed as a starting point and a saturation based on the von Kármán model is used as a first-order multiple scattering approximation. For a single shielding obstacle the scattering model is used to calculate a large dataset as function of the effective height of the shielding obstacle and its distances to source and receiver. A parameterisation of the dataset is used when calculating the influence of single or double canyons, including standardised air attenuation rates as well as façade absorption and Fresnel weighting of the multiple façade reflections. Assuming a single point source, an aver aging over three receiver positions and that each ground reflection causes energy doubling, the final engineering model is formulated as a scattered level for a shielding building without canyon plus a correction term for the effect of a single or a double canyon, assuming a flat rooftop of the shielding building. Input parameters are, in addition to geometry and sound frequency, the strengths of velocity and temperature turbulence.
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| 2. |
- Forssén, Jens, 1968, et al.
(författare)
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A Model of Sound Scattering by Atmospheric Turbulence for Use in Noise Mapping Calculations
- 2014
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Ingår i: Acta Acustica united with Acustica. - : Wissenschaftliche Verlagsgesellschaft mbH. - 1610-1928 .- 1861-9959. ; 100:5, s. 810-815
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Tidskriftsartikel (refereegranskat)abstract
- Sound scattering due to atmospheric turbulence limits the noise reduction in shielded areas. An engineering model is presented, aimed to predict the scattered level for general noise mapping purposes including sound propagation between urban canyons. Energy based single scattering for homogeneous and isotropic turbulence following the Kolmogorov model is assumed as a starting point and a saturation based on the von Karman model is used as a first-order multiple scattering approximation. For a single shielding obstacle the scattering model is used to calculate a large dataset as function of the effective height of the shielding obstacle and its distances to source and receiver. A parameterisation of the dataset is used when calculating the influence of single or double canyons, including standardised air attenuation rates as well as facade absorption and Fresnel weighting of the multiple facade reflections. Assuming a single point source, an aver aging over three receiver positions and that each ground reflection causes energy doubling, the final engineering model is formulated as a scattered level for a shielding building without canyon plus a correction term for the effect of a single or a double canyon, assuming a flat rooftop of the shielding building. Input parameters are, in addition to geometry and sound frequency, the strengths of velocity and temperature turbulence.
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| 3. |
- Gu, Weigang, et al.
(författare)
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Neurotransmitter synthesis in poststroke cortical neurogenesis in adult rats.
- 2010
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Ingår i: Stem cell research. - : Elsevier. - 1876-7753 .- 1873-5061. ; 4:2, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- Neurogenesis occurs in the cerebral cortex of adult rats after focal cerebral ischemia. Whether or not the newborn neurons could synthesize neurotransmitters is unknown. To elucidate such a possibility, a photothrombotic ring stroke model with spontaneous reperfusion was induced in adult male Wistar rats. The DNA duplication marker BrdU was repeatedly injected, and the rats were sacrificed at various times after stroke. To detect BrdU nuclear incorporation and various neurotransmitters, brain sections were processed for single/double immunocytochemistry and single/double/triple immunofluorescence. Stereological cell counting was performed to assess the final cell populations. At 48 h, 5 days, 7 days, 30 days, 60 days and 90 days after stroke, numerous cells were BrdU-immunolabeled in the penumbral cortex. Some of these were doubly immunopositive to the cholinergic neuron-specific marker ChAT or GABAergic neuron-specific marker GAD. As analyzed by 3-D confocal microscopy, the neurotransmitters acetylcholine and GABA were colocalized with BrdU in the same cortical cells. In addition, GABA was colocalized with the neuron-specific marker Neu N in the BrdU triple-immunolabeled cortical cells. This study suggests that the newborn neurons are capable of synthesizing the neurotransmitters acetylcholine and GABA in the penumbral cortex, which is one of the fundamental requisites for these neurons to function in the poststroke recovery.
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| 4. |
- Hornikx, Maarten, 1980, et al.
(författare)
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Urban background noise mapping : The multiple-reflection correction term
- 2014
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Ingår i: Acta Acoustica united with Acustica. - 1610-1928 .- 1861-9959. ; 100:2, s. 293-305
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Tidskriftsartikel (refereegranskat)abstract
- Mapping of road traffic noise in urban areas according to standardized engineering calculation methods systematically results in an underestimation of noise levels at areas shielded from direct exposure to noise, such as inner yards. In most engineering methods, road traffic lanes are represented by point sources and noise levels are computed utilizing point-to-point propagation paths. For a better prediction of noise levels in shielded urban areas, an extension of engineering methods by an attenuation term Acan has been proposed, including multiple reflections of the urban environment both in the source and in the receiver area.The present work has two main contributions for the ease of computing Acan. Firstly, it is shown by numerical calculations that Acan may be divided into independent source and receiver environment terms, As and Ar. Based on an equivalent free field analogy, the distance dependence of these terms may moreover be expressed analytically. Secondly, an analytical expression is proposed to compute As and Ar for 3D configurations from using 2D configurations only. The expression includes dependence of the street width-to-height ratio, the difference in building heights and the percentage of facade openings in the horizontal plane. For the expression to be valid, the source should be separated from the receiver environment by at least four times the street width.
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| 5. |
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| 7. |
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| 8. |
- Jiang, Wei, et al.
(författare)
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Establishing a photothrombotic 'ring' stroke model in adult mice with late spontaneous reperfusion : quantitative measurements of cerebral blood flow and cerebral protein synthesis.
- 2006
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Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 26:7, s. 927-936
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Tidskriftsartikel (refereegranskat)abstract
- This study sought to establish the photothrombotic ‘ring’ stroke model with late spontaneous reperfusion in adult mice. By applying a 3.0-mm diameter laser ring-beam (514 nm, 0.21 mm thick, 0.65 W/cm2) onto the exposed skull for 60 secs with concurrent erythrosin B (4.25 mg/kg) intravenous infusion for 15 secs, the centrally located cortical region within the ring locus was progressively encroached by an annular ring-shaped perfusion deficit. In this region, local cerebral blood flow (ICBF) measured by 1aser-Doppler flowmetry declined promptly after irradiation to 43% of the baseline value at 30 mins poststroke. Using double tracer autoradiography, quantitative ICBF measured with [14C]iodoantipyrine was 46 to 17 to 58 ml/100 g/mins at 4 h to 48 h to 7 days postischemia in this area. Cerebral protein synthesis (CPS), as detected by [3H]leucine incorporation into protein, transiently decreased to 57% to 38% to 112% at 4 h to 48 h to 7 days postischemia in the center region. Morphologically, some neurons in the center region appeared swollen at 4 h. At 48 h, the majority of neurons were severely swollen with eosinophilia and pyknosis, whereas at 7 days poststroke’ the tissue morphology became partly restored. The center within the mouse photothrombotic ring lesion thus exhibits reversible alterations of local CBF, CPS and tissue morphology that are reminiscent of the cortical penumbra in other models of focal cerebral ischemia.
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| 9. |
- Van Renterghem, Timothy, et al.
(författare)
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Improving the accuracy of engineering models at shielded building facades: experimental analysis of turbulence scattering
- 2013
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Ingår i: 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013. - 9781632662675 ; , s. 5-
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Konferensbidrag (refereegranskat)abstract
- Noise mapping models are able to accurately predict directly exposed facade levels near busy roads on condition that sufficiently detailed traffic data is available. At the non-directly exposed side of the building, however, common practice application of standard methods strongly underpredicts sound pressure levels, potentially leading to an incorrect assessment of noise annoyance and sleep disturbance. The concept of background noise mapping was proposed before, which has the important advantage that it can increase the accuracy of existing noise maps at a limited computational cost. In this study, long-term meteorological and noise data showed that turbulence scattering contributes significantly to the noise level at shielded facades, already at sound frequencies below 1 kHz. Periods with strong atmospheric turbulence are dominant for long-term equivalent noise levels as typically used in strategic noise maps. A comparison between predictions and measurements show that rather high turbulence strengths should be used when producing noise maps.
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| 10. |
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