Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating

Our study employed large-eddy simulation (LES) based on a one-equation subgrid-scale model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. Unstable thermal stratification was produced by heating the ground of the street canyon. Using the Boussinesq approximation, thermal buoyancy forces were taken into account in both the Navier–Stokes equations and the transport equation for subgrid-scale turbulent kinetic energy (TKE). The LESs were validated against experimental data obtained in wind-tunnel studies before the model was applied to study the detailed turbulence, temperature, and pollutant dispersion characteristics in the street canyon of aspect ratio 1. The effects of different Richardson numbers (Ri) were investigated. The ground heating significantly enhanced mean flow, turbulence, and pollutant flux inside the street canyon, but weakened the shear at the roof level. The mean flow was observed to be no longer isolated from the free stream and fresh air could be entrained into the street canyon at the roof-level leeward corner. Weighed against higher temperature, the ground heating facilitated pollutant removal from the street canyon.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Monitorin

Investigation on the Dispersal Characteristics of Liquid Breakup in Vacuum

This work presents an experimental study on the dispersal characteristics of a liquid jet ejecting into vacuum. The liquid breaking experiments of several kinds of liquid under different pressure and temperature conditions are carried out in a flash chamber. The stability of the jet and the sizes of the droplets or the icing particles formed during liquid flashing dispersing are analyzed. The influences of the superheat degree, spray velocity, and the mass of the volatile liquid mixing in the nonvolatile liquid on these characteristics are discussed. Moreover, the applicability of the two definitions of superheat degree is discussed. The results show that the superheat degree is an important parameter influencing the pattern of the breaking liquid, and the jet velocity has a large influence on the distribution of particle sizes. In addition, mixing some volatile liquid with nonvolatile liquid can enhance the dispersion of the latter

Perceived cost potential field cellular automata model with an aggregated force field for pedestrian dynamics

postprin

Large-eddy simulatoin of flow field and pollutant dispession in urban street canyons under unstable atmospheric

Thermal stratification plays an important role in the air flow and pollutant dispersion processes. This study employed a large-eddy simulation (LES) code based on a one-equation subgrid-scale (SGS) model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. The unstable thermal stratification was simulated by heating the ground level of the street canyons. The thermal buoyancy forces were, using the Boussinesq assumption, taken into account in both the Navier-Stokes equations and the transport equation for SGS turbulent kinetic energy (TKE). The LES had been validated against experimental data obtained in wind tunnel studies before it was applied to study the detailed turbulence and pollutant dispersion characteristics in urban street canyons. The effects of different bulk Richardson number (Rb) were investigated. Several typical temperature differences between the street bottom and ambient air were configured to simulate the scenarios occurring at different times during the day.postprintThe 7th International Conference of Urban Climate (ICUC-7), Yokohama, Japan, 29 June-3 July 2009

Reply to Comment by Velasco on “High-Resolution, Multilayer Modeling of Singapore’s Urban Climate Incorporating Local Climate Zones”

In response to the comment on our paper “High‐resolution, multilayer modeling of Singapore's urban climate incorporating local climate zones,” we provide detailed response to each of the incorrect accusations with scientifically based evidence. We have evaluated our model using all the available observational data, and the results showed good agreement. Our modeling study includes assumptions, as all modeling work does, and we have discussed their rationales and possible implications

Kinase inhibit region of SOCS3 attenuates IL6-induced proliferation and astrocytic differentiation of neural stem cells via cross talk between signaling pathways

Aims: Efficiency of neural stem cells (NSCs) therapy for brain injury is restricted by astrogliosis around the damaged region, in which JAK2/STAT3 signaling plays a key role. The SOCS3 that can directly inhibit JAK/STAT3 pathway. Here, we investigated the effects of a fusion peptide that combined kinase inhibitory region (KIR) of SOCS3 and virus trans-activator of transcription (TAT) on biological behavior of cultured NSCs under inflammatory conditions. Methods: NSCs were isolated from embryonic brain of SD rats, TAT-KIR was synthesized, and penetration rate was evaluated by flow cytometry (FACS). CCK8, immunostaining, and FACS were used to detected of TAT-KIR on the proliferation of NSCs. The expressions of GFAP and β tubulin III positive cells induced by IL6 with/without TAT-KIR were examined by immunostaining and Western blotting to observe the NSCs differentiation, and the effect of TAT-KIR on signaling cross talk was observed by Western blotting. Results: Penetration rate of TAT-KIR into primary cultured NSCs was up to 94%. TAT-KIR did not affect the growth and viability of NSCs. It significantly reduced the NSCs proliferation that enhanced by IL-6 stimulation via blocking the cell cycle progression from the G0/G1 to S phase. In addition, TAT-KIR attenuated astrocytic differentiation and kept high level of neuronal differentiation derived from IL-6-induced NSCs. The fate of NSCs differentiation under inflammatory conditions was affected by TAT-KIR, which was associated with synchronous inhibition of STAT3 and AKT, while promoting JNK expression. Conclusion: TAT-KIR mimetic of SOCS3 could be a promising approach for brain repair via regulating the biological behaviors of exogenous NSCs

Contributions of residential coal combustion to the air qualityin Beijing–Tianjin–Hebei (BTH), China: a case study

In the present study, the WRF-Chem model is used to assess contributions of residential coal combustion (RCC) emissions to the air quality in Beijing-Tianjin-Hebei (BTH) during a persistent air pollution episode from 9 to 25 January 2014. In general, the predicted temporal variations and spatial distributions of the mass concentrations of air pollutants are in good agreement with observations at monitoring sites in BTH. The WRF-Chem model also reasonably reproduces the temporal variations in aerosol species when compared with the aerosol mass spectrometer measurements in Beijing. The RCC emissions play an important role in the haze formation in BTH, contributing about 23.1% of PM2.5 (fine particulate matter) and 42.6% of SO2 during the simulation period on average. Organic aerosols dominate the PM2.5 from the RCC emissions in BTH, with a contribution of 42.8 %, followed by sulfate (17.1 %). The air quality in Beijing is remarkably improved when the RCC emissions in BTH and the surrounding areas are excluded in model simulations, with a 30% decrease in PM2.5 mass concentrations. However, if only the RCC emissions in Beijing are excluded, the local PM2.5 mass concentration is decreased by 18.0% on average. Our results suggest that the implementation of the residential coal replacement by clean energy sources in Beijing is beneficial to the local air quality. Should residential coal replacement be carried out in BTH and its surrounding areas, the air quality in Beijing would be improved remarkably. Further studies would need to consider uncertainties in the emission inventory and meteorological fields

Effects of tachyplesin on the regulation of cell cycle in human hepatocarcinoma SMMC-7721 cells

AIM: To investigate the effects of tachyplesin on the cell cycle regulation in human hepatcarcinoma cells. METHODS: Effects of tachyplesin on the cell cycle in human hepatocarcinoma SMMC-7721 cells were assayed with flow cytometry. The protein levels of p53, p16, cyclin D1 and CDK4 were assayed by immunocytochemistry. The mRNA levels of p21(WAF1/CIP1) and c-myc genes were examined with in situ hybridization assay. RESULTS: After tachyplesin treatment, the cell cycle arrested at G(0)/G(1) phase, the protein levels of mutant p53, cyclin D1 and CDK4 and the mRNA level of c-myc gene a were decreased, whereas the levels of p16 protein and p21(WAF1/CIP1) mRNA increased. CONCLUSION: Tachyplesin might arrest the cell at G(0)/G(1) phase by upregulating the levels of p16 protein and p21(WAF1/CIP1) mRNA and downregulating the levels of mutant p53, cyclin D1 and CDK4 proteins and c-myc mRNA, and induce the differentiation of human hepatocacinoma cells

Effects of tachyplesin on proliferation and differentiation of human hepatocellular carcinoma SMMC-7721 cells

AIM: To investigate the antitumor activities of tachyplesin on human hepatocellular carcinoma (HCC) cells. METHODS: Tachyplesin, isolated from acid extracts of Chinese horseshoe crab ( Tachypleus tridentatus) hemocytes, was used to treat the human HCC cell line SMMC-7721. Effects of tachyplesin on the proliferation of SMMC-7721 cells were measured with trypan blue dye exclusion test and HE staining. The morphology and ultrastructure of the cells were examined by light microscopy and transmission electron microscopy, respectively. The activities of gamma-glutamyltransferase (gamma-GT) and tyrosine aminotransferase (TAT) were assayed with biochemical methods. The levels of alpha fetoprotein (alpha-FP), proliferating cell nuclear antigen (PCNA), p21(WAF1/CIP1) and c-myc were examined by immunocytochemistry. RESULTS: After treatment with tachyplesin 3.0 mg/L, the proliferation of SMMC-7721 cells was inhibited significantly, with the cell growth inhibitory rate amounted to 55.57% and the maximum cell mitotic index declined by 43.68%. The morphology and ultrastructure underwent restorational alteration. The activity of gamma-GT declined while TAT activity increased obviously, and the levels of alpha-FP and PCNA decreased. Moreover, the expression of p21(WAF1/CIP1) protein was up-regulated and that of c-myc protein was down-regulated. CONCLUSION: Tachyplesin could effectively inhibit the proliferation of hepatocarcinoma cells, reverse the malignant morphological and ultrastructural characteristics, alter the levels of enzymes and antigens, regulate the expression of differentiation-associated oncogene and tumor suppressor gene, and induce hepatocarcinama cell differentiation