Large-Eddy-simulation analysis of airflows and strong wind hazards in urban areas

Understanding the characteristics of urban airflows with complex geometrical features is very important from viewpoints of assessing strong wind hazards in the region. This study investigated turbulent airflows and strong wind hazards in an urban area by conducting large-eddy simulations (LESs) with explicit representations of buildings and structures. A business district, including historical architectures, of Kyoto City was chosen. The sensitivity experiments with realistic and idealized building arrangements indicated that the actual, complicated arrangement of buildings as well as the building height variability would enhance an unsteady nature of airflows in urban canopy. An analysis of strong wind hazards under a typhoon condition shows that sustained winds are stronger along streamwise-oriented major streets and over open spaces while instantaneous winds become stronger especially within areas with a mixture of high-rise buildings embedded in low-rise building areas/open spaces. It was indicated that wind gustiness increases with the decrease in building plane-area index. The analysis suggested that both the building height variability and the complex arrangement of buildings are considered to enhance the gustiness of surface winds. This study demonstrated that an LES model is practically useful for assessing the strong wind hazards in urban areas

Alpha7 nicotinic ACh receptor mediated neuroprotective action by nicotine and GTS-21: An approach by the hippocampal organotypic slice cultures.

Nicotine, main constituent of tabaco, is known as a nicotinic acetylcholine receptor (nAChR) agonist and increases cognitive performance. 3-(2,4-dimethoxybenzylidene)-anabaseine (GTS-21) is derived from the marine worm toxin, anabaseine, and is alpha7-selective nAChR (D7-nAChR) agonist. Both nicotine and GTS-21 were expected as therapeutic agents of Alzheimer’s disease. Several studies showed that nicotine and GTS-21 protected neuron by activating nAChR, especially D7-nAChR. It has been reported that D7-nAChR has been shown to be an essential regulator of inflammation. The purpose of this study is to examine the neuroprotective and anti-inflammatory effects of nicotine and GTS-21 using organotypic hippocampal slice cultures. Kainic acid (KA, 5-50µM) induced concentration- and time-dependent neuronal cell death in the hippocampal organotypic slice cultures. The pretreatment with nicotine and GTS-21 tended to decrease in KA toxicity. In a CA3 area-specific analysis, pretreatment with nicotine resulted in significant inhibition of KA-induced neurotoxicity. The results suggest that nicotine may protect KA-induced neuronal cell death via D7-nAChR. We also examined anti-inflammatory effects of nicotine and GTS-21. Hippocampal slices were pretreated with nicotine or GTS-21, and then treated with lipopolysaccharide (LPS). LPS treatment induced concentration-dependent increases in TNFD and IL-1E gene expressions. LPS-induced TNFD gene expression, but not IL-1E was suppressed by GTS-21 pretreatment. These results suggest that D7-nAChR might be involved in the microglia activation towards a neuroprotective role by suppressing inflammatory cytokine

Research Activities in the Department of Nursing

Research activity at the Department of Nursing is overviewed from the point of research topics, the theme of the projects admitted for grant from the Ministry of Education and Science of Japan, and expected research topics, trying to clarify the needs and challenges of the Department from multilateral aspects in future research activities. The Department of Nursing, Aino University is currently divided into the five areas and further into 12 fields. On the other hand, according to the Scientific Research Grant Program (2015 fiscal year), the research topics in nursing science is subdivided into the five areas; a) basic nursing, b) clinical nursing, c) lifelong developmental nursing, d) elderly nursing, and e) community health nursing

Properties of mixing length and dispersive stress in airflows over urban-like roughness obstacles with variable height

Effects of obstacle-height variability on mixing length and dispersive stress are investigated by conducting large-eddy simulations of airflows over arrays of roughness obstacles with variable height. We evaluate differences among three simulations of flows over obstacles with no, moderate, and high obstacle-height variability. Within the canopies, effective mixing length shows one local maximum and minimum in the simulation with no obstacle-height variability but two maxima and minima in the simulations with obstacle-height variability. The number of the local maxima and minima corresponds to that of the shear layers seen at the heights of obstacle tops. Enhanced dispersive stress appears within the canopy between the heights of the lower- and higher-obstacle tops in the simulations with obstacle-height variability. Particularly in the simulations with high obstacle-height variability, the magnitude of dispersive stress becomes comparable to that of the Reynolds stress at the height of the lower-obstacle top. These results suggest that actual urban areas with high building-height variability should signicantly affect properties of mixing length and dispersive stres

Large-Eddy-Simulation Study of the Effects of Building-Height Variability on Turbulent Flows over an Actual Urban Area

Large-eddy simulation (LES) is used to investigate the effects of building-height variability on turbulent flows over an actual urban area, the city of Kyoto, which is reproduced using a 2-m resolution digital surface dataset. Comparison of the morphological characteristics of Kyoto with those of European, North American, and other Japanese cities indicates a similarity to European cities but with more variable building heights. The performance of the LES model is validated and found to be consistent with turbulence observations obtained from a meteorological tower and from Doppler lidar. We conducted the following two numerical experiments: a control experiment using Kyoto buildings, and a sensitivity experiment in which all the building heights are set to the average height over the computational region hall . The difference of Reynolds stress at height z=2.5h[all] between the control and sensitivity experiments is found to increase with the increase in the plan-area index ( λp ) for λp>0.32 . Thus, values of λp≈0.3 can be regarded as a threshold for distinguishing the effects of building-height variability. The quadrant analysis reveals that sweeps contribute to the increase in the Reynolds stress in the control experiment at a height z=2.5h[all] . The exuberance in the control experiment at height z=0.5h[all] is found to decrease with increase in the building-height variability. Although the extreme momentum flux at height z=2.5h[all] in the control experiment appears around buildings, it contributes little to the total Reynolds stress and is not associated with coherent motions

Large-Eddy Simulation of Plume Dispersion in the Central District of Oklahoma City by Coupling with a Mesoscale Meteorological Simulation Model and Observation

Contaminant gas dispersion within an urban area resulting from accidental or intentional release is of great concern to public health and social security. When estimating plume dispersion in a built-up urban area under real meteorological conditions by computational fluid dynamics (CFD), a crucial issue is how to prescribe the input conditions. There are typically two approaches: using the outputs of a mesoscale meteorological simulation (MMS) model and meteorological observations (OBS). However, the influences of the different approaches on the simulation results have not been fully demonstrated. In this study, we conducted large-eddy simulations (LESs) of plume dispersion in the urban central district of Oklahoma City under real meteorological conditions by coupling with a MMS model and OBS obtained at a single stationary point, and evaluated the two different coupling simulations in comparison with the field experiments. The LES–MMS coupling showed better performance than the LES–OBS one. The latter one also showed a reasonable performance comparable to the acceptance criteria on the model prediction within a factor of two of the experimental data. These facts indicate that the approach using observations at a single stationary point still has enough potential to drive CFD models for plume dispersion under real meteorological conditions