Spontaneous oscillation of an active filament under viscosity gradients.

We investigate the effects of uniform viscosity gradients on the spontaneous oscillations of an elastic, active filament in viscous fluids. Combining numerical simulations and linear stability analysis, we demonstrate that a viscosity gradient increasing from the filament's base to tip destabilises the system, facilitating its self-oscillation. This effect is elucidated through a reduced-order model, highlighting the delicate balance between destabilising active forces and stabilising viscous forces. Additionally, we reveal that while a perpendicular viscosity gradient to the filament's orientation minimally affects instability, it induces asymmetric ciliary beating, thus generating a net flow along the gradient. Our findings offer new insights into the complex behaviours of biological and artificial filaments in complex fluid environments, contributing to the broader understanding of filament dynamics in heterogeneous viscous media.

Tumor microenvironment-responsive versatile "Trojan horse" theranostic nanoplatform for magnetic resonance imaging-guided multimodal synergistic antitumor treatment.

A natural killer (NK)-92 cell membrane-camouflaged mesoporous MnO2-enveloped Au@Pd (Au@Pd@MnO2) nanoparticles (denoted as APMN NPs)-based versatile biomimetic theranostic nanoplatform was developed for magnetic resonance (MR) imaging-guided multimodal synergistic antitumor treatments. In this core-shell nanostructure, an Au@Pd core induced near-infrared (NIR)-activatable hyperthermal effects and nanozyme catalytic activity, while a mesoporous MnO2 shell not only afforded a high drug-loading capability, tumor microenvironment (TME)-triggered MR imaging and drug release, but also endowed catalase-, glutathione peroxidase-, and Fenton-like activities. Furthermore, the NK-92 cell membrane camouflaging endowed the NPs with enhanced tumor-targeting capability, immune escape function, and membrane protein-mediated tumoral uptake property. The doxorubicin-loaded APMN (D-APMN) NPs exhibited TME-responsive drug release properties. Furthermore, the cellular uptake, in vivo MR imaging, and NIR thermal imaging confirmed the active tumor-targeting capability and TME-responsive MR imaging property of these biomimetic NPs. An antitumor efficacy test, histological analyses, and blood biochemical profiles suggested that the developed D-APMN NPs possessed a high antitumor activity and biosafety in tumor-bearing nude mice. Therefore, the developed APMN NPs held great potential as an intelligent and comprehensive theranostic nanoplatform for tumor-specific bioimaging and TME-responsive multimodality treatment based on photothermal therapy, chemodynamic therapy, and chemotherapy. STATEMENT OF SIGNIFICANCE: Exploring intelligent and comprehensive theranostic nanoplatforms to integrate tumor-specific bioimaging and TME-responsive multimodal therapy effectively is a challenge. Herein, we successfully developed a new kind of NK-92 cell membrane-camouflaged mesoporous MnO2-enveloped Au@Pd nanoparticles (APMN NPs)-based versatile biomimetic theranostic nanoplatform for the potential MR imaging-guided multimodal synergistic antitumor treatments. These NPs could integrate unique structural, optical, multiple-catalytic, paramagnetic, and biological merits of NK-92 cell membrane, Au@Pd cores and mesoporous MnO2 shell in a single nanoplatform. The NK-92 cell membrane camouflaging endowed the NPs with enhanced tumor-targeting capability, immune escape function, and membrane protein-mediated tumoral uptake property. The new information obtained from this study may be beneficial to promote the development of novel TME-responsive versatile "Trojan horse" theranostic nanoplatforms for efficient MR imaging-guided multimodal synergistic treatment.

Biomimetic ZIF8 Nanosystem With Tumor Hypoxia Relief Ability to Enhance Chemo-Photothermal Synergistic Therapy.

Tumor hypoxic microenvironment can reduce the therapeutic effects of chemotherapy, radiotherapy, photodynamic therapy, immunotherapy, etc. It is also a potential source of tumor recurrence and metastasis. A biomimetic nanosystem based on zeolitic imidazolate framework 8 (ZIF8), which had multifunctions of hypoxia relief, chemotherapy, and photothermal therapy, was established to improve tumor hypoxic microenvironment and overcome the corresponding therapeutic resistance. ZIF8 enveloped with DOX and CuS nanoparticles (DC@ZIF8) was synthesized by a sedimentation method. Red blood cell membrane and catalase (CAT) were coated onto DC@ZIF8 and biomimetic nanosystem (DC@ZIF8-MEMC) was formed. The designed DC@ZIF8-MEMC had a shape of polyhedron with an average particle size around 254 nm. The loading content of DOX, CAT, and CuS was 4.9%, 6.2%, and 2.5%, separately. The release of DOX from DC@ZIF8-MEMC was pH dependent and significantly faster at pH 5 due to the degradation of ZIF8. DC@ZIF8-MEMC exhibited outstanding photothermal conversion properties and excellent antitumor effect in vitro and in vivo. Moreover, the hypoxia relief by CAT was proved to have good sensitization effect on chemo-photothermal combined therapy. DC@ZIF8-MEMC is a prospective nanosystem, which can realize great chemo-photothermal synergistic antitumor effect under the sensitization of CAT. The biomimetic multifunctional nanoplatform provides a potential strategy of chemo-photothermal synergistic antitumor effect under the sensitization of CAT.

Upcoming flow promotes the bundle formation of bacterial flagella.

Flagellated bacteria swim by rotating a bundle of helical flagella and commonly explore the surrounding environment in a "run-and-tumble" motility mode. Here, we show that the upcoming flow could impact the bacterial run-and-tumble behavior by affecting the formation and dispersal of the flagellar bundle. Using a dual optical tweezers setup to trap individual bacteria, we characterized the effects of the imposed fluid flow and cell body rotation on the run-and-tumble behavior. We found that the two factors affect the behavior differently, with the imposed fluid flow increasing the running time and decreasing the tumbling time and the cell body rotation decreasing the tumbling time only. Using numerical simulations, we computed the flagellar bundling time as a function of flow velocity, which agrees well with our experimental observations. The mechanical effects we characterized here provide novel, to our knowledge, ingredients for further studies of bacterial chemotaxis in complex environments such as dynamic fluid environments.

Personal black carbon exposure and its determinants among elderly adults in urban China.

Personal exposure to air pollution is affected by its concentration in the microenvironment and individual time-activity patterns. To investigate personal black carbon (BC) exposure levels and identify their potential determinants, we conducted a panel study among 67 elderly residents aged 60-69 years in Jinan, China. Personal BC exposure was measured using portable real-time monitors, while corresponding ambient BC concentrations and meteorological conditions were also collected from the local central site. Time-activity and household characteristics were recorded. A linear mixed-effects model was used to identify potential determinants of personal BC exposure. The daily average personal BC exposure concentration was 4.1 ± 2.0 µg/m3 (±standard deviation, SD), which was significantly lower than the ambient concentration (4.6 ± 2.5 µg/m3) (p < 0.001). Strong correlation (Spearman's r = 0.63, p < 0.001) was found between personal and ambient BC concentrations. The fixed-site monitoring ambient concentration cannot fully reflect the actual personal exposure concentration. Ambient BC concentration, ambient temperature, relative humidity, education level and air purifier use were significant determinants of personal BC exposure. Our findings highlight the need for detailed assessment of personal exposure on health risk assessment of BC and also help develop strategies for targeted risk reduction.

Novel ß-1,3-d-glucan porous microcapsule enveloped folate-functionalized liposomes as a Trojan horse for facilitated oral tumor-targeted co-delivery of chemotherapeutic drugs and quantum dots.

In this study, a new type of ß-1,3-d-glucan porous microcapsule (GPM)-enveloped and folate conjugated chitosan-functional liposome (FCL), FCL@GPM, was developed for the potential oral co-delivery of chemotherapeutic drugs and quantum dots (QDs) with facilitated drug absorption and antitumor efficacy. In this dual-particulate system, multiple FCLs serve as the cores for effective loading, folate-mediated tumor-targeting, facilitated intracellular accumulation, and pH-responsive controlled release of chemotherapeutic agents, while a GPM acts as the shell for affording macrophage-mediated tumor selectivity. Gefitinib (GEF) was selected as a chemotherapeutic agent, while acid degradable ZnO QDs were selected due to their dual role as an anticancer agent for synergistic chemotherapy and as a fluorescent probe for potential cancer cellular imaging. The GEF and ZnO QD co-loaded FCL@GPMs (GEF/ZnO-FCL@GPMs) exhibited a prolonged release manner with limited release before uptake by intestinal cells. Furthermore, Peyer's patch uptake, macrophage uptake, cytotoxicity, and biodistribution of FCL@GPMs were tested. In addition, GEF and ZnO QD co-loaded FCLs (GEF/ZnO-FCLs) not only have a tumor acidity responsive release property, but also induce a superior cytotoxicity on cancer cells as compared to GEF. Moreover, a 1.75-fold increase in the bioavailability of GEF delivered from GEF/ZnO-FCL@GPMs as compared to its trademarked drug (Iressa®). As a result, GEF/ZnO-FCL@GPMs exerted a superior antitumor efficacy (1.47-fold) as compared to the trademarked drug in mice. Considered together, the developed FCL@GPMs, combining the unique physicochemical and biological benefits of FCLs and GPMs, possess great potential as an efficient delivery system for the co-delivery of chemotherapeutic agents and quantum dots.

High catalytic activity of CuY catalysts prepared by high temperature anhydrous interaction for the oxidative carbonylation of methanol.

CuY catalysts were prepared by high temperature anhydrous interaction between NH4Y zeolite and copper(ii) acetylacetonate Cu(acac)2 and the activities were measured for the oxidative carbonylation of methanol to dimethyl carbonate under atmospheric pressure. The bulk and surface properties of the as-prepared catalyst were characterized by XRD, H2-TPR and XPS techniques. The activation atmosphere of the CuY catalyst and the testing temperature of the catalytic activity was systematically studied. During activation, nitrogen promotes the auto-reduction of Cu2+ to form the Cu+ active center, but deposited carbon on the surface of the CuY catalyst covers the active center, even plugging the channel, resulting in lower catalytic activity. Oxygen eliminates deposited carbon, but is not so good for the auto-reduction of Cu2+. Nitrogen doped with a small amount of oxygen not only eliminates the deposited carbon, but also promotes the auto-reduction of Cu2+ to form more Cu+ active centers. With the testing temperature increasing, the catalytic activity increases first and then decreases. When the testing temperature is 170 °C, the CuY catalyst with satisfactory activity and stability showed an excellent catalytic activity with 525.1 mg g-1 h-1 space time yield of DMC (STYDMC) and 18.9% methanol conversion. Then the longevity was investigated at 170 °C for 150 h. During the initial reaction period of 40 h, the STYDMC value was constant. In the next 20 h, the catalytic activity slightly decreased. But in the last 90 h, the catalytic performance is very stable and the STYDMC value remains 480 mg g-1 h-1. The main cause of deactivation is the growth of the particles.

Estimating the daily PM2.5 concentration in the Beijing-Tianjin-Hebei region using a random forest model with a 0.01°â€¯× 0.01° spatial resolution.

High spatiotemporal resolution fine particulate matter (PM2.5) simulations can provide important exposure data for the assessment of long-term and short-term health effects. Satellite-based aerosol optical depth (AOD) data, meteorological data, and topographic data have become key variables for PM2.5 estimation. In this study, a random forest model was developed and used to estimate the highest resolution (0.01°â€¯× 0.01°) daily PM2.5 concentrations in the Beijing-Tianjin-Hebei region. Our model had a suitable performance (cv-R2 = 0.83 and test-R2 = 0.86). The regional test-R2 value in southern Beijing-Tianjin-Hebei was higher than that in northern Beijing-Tianjin-Hebei. The model performance was excellent at medium to high PM2.5 concentrations. Our study considered meteorological lag effects and found that the boundary layer height of the one-day lag had the most important contribution to the model. AOD and elevation factors were also important factors in the modeling process. High spatiotemporal resolution PM2.5 concentrations in 2010-2016 were estimated using a random forest model, which was based on PM2.5 measurements from 2013 to 2016.

Development and Evaluation of Multifunctional Poly(Lactic-co-glycolic acid) Nanoparticles Embedded in Carboxymethyl ß-Glucan Porous Microcapsules as a Novel Drug Delivery System for Gefitinib.

In this study, a new kind of folic acid (FA)-conjugated and chitosan (CS)-coated poloxamer 407 (P407)/poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), FCPP NPs, were prepared, and further micro-encapsulated by carboxymethyl ß-glucan microcapsules (MCs) to produce a multifunctional system of NPs embedded in MCs (NEMs) for potential lung tumor-targeted delivery of gefitinib. The prepared gefitinib-loaded FCPP (GFB/FCPP) NPs showed a hydrodynamic diameter of 255.4 ± 14.5 nm and existed in an amorphous state. After encapsulation in carboxymethyl ß-glucan MCs, the GFB/FCPP-based NEMs (GFB/FCPP-NEMs) also exhibited a spherical morphology with a median diameter (d50) of around 2.2 µm. After hydration, GFB/FCPP- NEMs can quickly dissociate into its primary particles, GFB/FCPP NPs. Our in vitro drug release study revealed that these GFB/FCPP-NEMs exhibited a pH-responsive prolonged release property. In addition, the cellular uptake study demonstrated that FCPP-NEMs serve as an efficient carrier to enhance the delivery of the entrapped drug into the target lung tumor cells. Moreover, the GFB/FCPP-NEMs induced a superior cytotoxic effect compared with free gefitinib. The inhibitory concentration to achieve 50% cell death (IC50) of GFB/FCPP-NEMs in A549 cells was 3.82-fold lower than that of free gefitinib. According to these results, FCPP-NEMs hold a great potential as a multifunctional and high-performance biomaterial for lung tumor targeting delivery, pH-responsive sustained release, facilitated cellular uptake, and enhanced antitumor effect of antitumor drugs, like gefitinib.

Fraction n-Butanol of Radix Notoginseng Protects PC12 Cells from Aß25-35-Induced Cytotoxicity and Alleviates Cognitive Deficits in SAMP8 Mice by Attenuating Oxidative Stress and Aß Accumulation.

Chinese medicine has been used for Alzheimer's disease (AD) treatment for thousands of years with more effective and fewer side effects. Therefore, developing effective potential candidates from Chinese medicine against AD would be considered as critical and efficient therapy for AD treatment. This study was designed to evaluate the neuronal protective effect of fraction n-butanol (NB) of Radix Notoginseng on Aß25-35-induced PC12 cells, explore the effect of the tested fraction on spatial learning and memory, and characterize the impacts of fraction NB on antioxidant enzymes, Aß production, and APP and BACE1 expressions. The results revealed that fraction NB could promote proliferation of PC12 cells and protect and rescue PC12 cells from Aß25-35-induced cell death. Moreover, fraction NB could improve spatial learning and memory impairments of senescence-accelerated prone8 (SAMP8) mice and attenuate oxidative stress and reduce the production of Aß by inhibiting the expressions of APP and BACE1 in the brains of SAMP8 mice. The result of single dose acute toxicity assay showed that fraction NB had a mild toxicity in vivo. The pronounced actions against AD and in vivo low toxicity of fraction NB suggest that fraction NB may be a useful alternative to the current AD treatment.

Protective effect of Co-enzyme Q10 On doxorubicin-induced cardiomyopathy of rat hearts.

Q10 is a powerful antioxidant often used in medical nutritional supplements for cancer treatment. This study determined whether Q10 could effectively prevent cardio-toxicity caused by doxorubicin treatment. Four week old SD rats were segregated into groups namely control, doxorubicin group (challenged with doxorubicin), Dox + Q10 group (with doxorubicin challenge and oral Q10 treatment), and Q10 group (with oral Q10 treatment). Doxorubicin groups received IP doxorubicin (2.5 mg/kg) every 3 days and Q10 groups received Q10 (10 mg/kg) every day. Three weeks of doxorubicin challenge caused significant reduction in heart weight, disarray in cardiomyocyte arrangement, elevation of collagen accumulation, enhancement of fibrosis and cell death associated proteins, and inhibition of survival proteins. However, Q10 effectively protected cardiomyocytes and ameliorated fibrosis and cell death induced by doxorubicin. Q10 is, therefore, evidently a potential drug to prevent heart damage caused by doxorubicin. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 679-689, 2017.

Short-term effects of multiple ozone metrics on daily mortality in a megacity of China.

Epidemiological studies have widely demonstrated association between ambient ozone and mortality, though controversy remains, and most of them only use a certain metric to assess ozone levels. However, in China, few studies have investigated the acute effects of ambient ozone, and rare studies have compared health effects of multiple daily metrics of ozone. The present analysis aimed to explore variability of estimated health effects by using multiple temporal ozone metrics. Six metrics of ozone, 1-h maximum, maximum 8-h average, 24-h average, daytime average, nighttime average, and commute average, were used in a time-series study to investigate acute mortality associated with ambient ozone pollution in Guangzhou, China, using 3 years of daily data (2006-2008). We used generalized linear models with Poisson regression incorporating natural spline functions to analyze the mortality, ozone, and covariate data. We also examined the association by season. Daily 1- and 8-h maximum, 24-h average, and daytime average concentrations yielded statistically significant associations with mortality. An interquartile range (IQR) of O3 metric increase of each ozone metric (lag 2) corresponds to 2.92 % (95 % confidence interval (CI) 0.24 to 5.66), 3.60 % (95 % CI, 0.92 to 8.49), 3.03 % (95 % CI, 0.57 to 15.8), and 3.31 % (95 % CI, 0.69 to 10.4) increase in daily non-accidental mortality, respectively. Nighttime and commute metrics were weakly associated with increased mortality rate. The associations between ozone and mortality appeared to be more evident during cool season than in the warm season. Results were robust to adjustment for co-pollutants, weather, and time trend. In conclusion, these results indicated that ozone, as a widespread pollutant, adversely affects mortality in Guangzhou.

[Concentrations and health risks of toxic metals in surface dust in kindergartens of Beijing].

Dust intake is an important source of children's metal exposure. To explore the contamination level and health risk of toxic metals in kindergartens, surface dust samples were collected with self-made sampler in representative kindergartens in urban Beijing and concentrations of Pb, Hg, Cd, As were analyzed. It was found that Cd, Hg, Pb accumulated in indoor dust in different degrees with a significant seasonal variation. The geometric means of Pb, Cd, Hg, As concentrations were 63.12 microg x g(-1), 1.67 microg x g(-1), 0.06 microg x g(-1), 0.22 microg x g(-1) in summer and 117.40 microg x g(-1), 4.52 microg x g(-1), 0.95 microg x g(-1), 0.88 microg x g(-1) in winter, respectively. Geo-accumulation indexes calculated for each metal showed a severe contamination of Pb and Cd in indoor surface dusts. The results of exposure and health risk assessment of target substances displayed that the oral intake of dust metals was much higher than that of dermal pathways for children. However, no obvious carcinogenic and non-carcinogenic risks were found for all metals. The Pb, against other species, had the highest non-carcinogenic risk to children, Hazard Index of which was 0.12. Therefore, the health risk of Ph in indoor dust should raise the concern.

Meta-analysis of the Chinese studies of the association between ambient ozone and mortality.

To investigate short-term effects of ambient ozone exposure on mortality in Chinese cities, we conducted a meta-analysis of 10 effect estimates of 5 short-term studies, which reported associations between ambient ozone and mortality in Chinese mainland cities. And we estimated pooled effects by non-accidental mortality, cardiovascular mortality, and respiratory mortality. Combined estimates and their 95%CI were tested by RevMan 5, and Funnel plots were used for the bias analysis. For a 10 µg m(-3) increase of maximum 8-h average concentration of ozone, the percent change for non-accidental mortality, cardiovascular mortality, and respiratory mortality were 0.42 (95%CI, 0.32-0.52%), 0.44% (95%CI, 0.17-0.70%) and 0.50% (95%CI, 0.22-0.77%), respectively. Compared with pooled estimates from other meta-analyses on ambient ozone-associated mortality, our pooled estimate for non-accidental mortality was slightly higher than previous ones and pooled estimate for cardiovascular mortality was consistent with others. However, we observed significantly positive association between ambient ozone and respiratory mortality, which were generally nonsignificant in earlier studies. By combining estimates from published evidence, a small but substantial association between ambient ozone level and mortality was observed in Mainland China.

Acidic and basic properties and buffer capacity of airborne particulate matter in an urban area of Beijing.

Particles with aerodynamic diameters <10 microm (PM(10)) and particles with aerodynamic diameters <2.5 microm (PM(2.5)) were sampled during summer 2006 in Beijing and mass concentrations, water-soluble ionic compounds concentrations, and acidic buffer capacity were analyzed. Results show that the mass concentration ranges of PM(10) and PM(2.5) were from 56.4 to 226.6 microg/m(3) and from 31.3 to 200.7 microg/m(3) during sampling days, respectively. Concentrations of F(-), Cl( -), NO3(-), NO2(-), SO4(2-), Ac(-), Ca(2+), Na(+), K(+), Mg(2+), and NH4(+) in particles were analyzed by ion chromatography. Microtitration was adapted to determine the acidic-basic property and the change of the buffering systems in different pH of the aqueous solution in which the PM is suspended. The major alkalinity and buffer capacity of particles were analyzed and calculated. The average carbonate buffer capacity was 0.3 mmol/g in PM(2.5) and 0.7 mmol/g in PM(10). The average acetic acid buffer capacity was 0.1 mmol/g in PM(2.5) and 0.3 mmol/g in PM(10). Carbonate and acetic acid are the main species for the buffer capacity in the particle phase. The average mass of carbonate was 71.0 mg/g in PM(10) and 46.7 mg/g in PM(2.5). The average mass of acetic acid was 11.2 mg/g in PM(2.5) and 20.0 mg/g in PM(10).

[Relationship between atmospheric particles and rain water chemistry character].

Rain and atmospheric particle samples were collected in the rural area of Taian and Shenzhen in 2007, respectively. Rain sampling was carried out during the precipitation process and several samples were got from the beginning of one precipitation to the end. The chemical character changes during precipitation and the changes of concentration of particles before and after rain were studied in this research to understand the contribution of particles on the rain chemical character and the rain-out effect for particles. The volume-weighted mean pH of rainwater in Taian was 5.97 and the total concentration of ions was 1 187.96 microeq x L(-1). The mass concentration of PM10 in Taian was 131.76 microg/m3 and that of PM2.5 was 103.84 microg/m3. The volume-weighted mean pH of rainwater in Shenzhen was 4.72 and the total concentration of ions was 175.89 microeq x L(-1). The mass concentration of PM10 in Shenzhen was 56.66 microg/m3 and that of PM2.5 was 41.52 microg/m3. During precipitation process pH and ion concentration of rain decrease and it is shown the neutralizing effect happens. The difference between rainwater of Taian and Shenzhen is due to cloud water acidity, atmospheric particles character and atmospheric acid-basic gases concentration. The clean-up effect of Na+ and Ca2+ by rain is high and which of NH4+ and NO3- is low. The clean-up effect for mass concentration, ions concentration and element concentration of particles by rain are significant.

[Numerical simulation study of SOA in Pearl River Delta region].

Secondary organic aerosols (SOA) is an important component of the atmospheric particle pollution, thus, determining the status and sources of SOA pollution is the premise of deeply understanding the occurrence, development law and the influence factors of the atmospheric particle pollution. Based on the pollution sources and meteorological data of Pearl River Delta region, the study used the two-dimensional model coupled with SOA module to stimulate the status and source of SOA pollution in regional scale. The results show: the generation of SOA presents obvious characteristics of photochemical reaction, and the high concentration appears at about 14:00; SOA concentration is high in some areas of Guangshou and Dongguan with large pollution source-emission, and it is also high in some areas of Zhongshan, Zhuhai and Jiangmen which are at downwind position of Guangzhou and Dongguan. Contribution ratios of several main pollution sources to SOA are: biogenic sources 72.6%, mobile sources 30.7%, point sources 12%, solvent and oil paint sources 12%, surface sources less than 5% respectively.

Tracheal compliance and limit flow rate changes in a murine model of asthma.

Trachea is the unique passage for air to flow in and out. Its tone is of importance for the respiration system. However, investigation on how tracheal tone changes due to asthma is limited. Aiming at studying how the mechanical property changes due to asthma as well as the compliance and flow limitation, the following methods are adopted. Static and passive pressure-volume tests of rats' trachea of the asthmatic and control groups are carried out and a new type of tube law is formulated to fit the experimental data, based on which changes of compliance and limit flow rate are investigated. In order to give explanation to such changes, histological examinations with tracheal soft tissues are made. The results show that compliance, limit flow rate and material constants included in the tube law largely depend on the longitudinal stretching ratio. Compared with the control group, the tracheal compliance of asthmatic animals decreases significantly, which results in an increased limit flow rate. Histological studies indicate that asthma can lead to hyperplasia/hypertrophy of smooth muscle cells, and increase elastin and collagen fibres in the muscular membrane. Though decreasing compliance increases stability, during the onset of asthma, limit flow rate is much smaller due to the lower transmural pressure. Asthma leads to a stiffer trachea and the obtained results reveal some aspects relevant to asthma-induced tracheal remodelling.

Modeling of air quality with a modified two-dimensional Eulerian model: a case study in the Pearl River Delta (PRD) region of China.

A modified two-dimensional Eulerian air quality model was used to simulate both the gaseous and particulate pollutant concentrations during October 21-24, 2004 in the Pearl River Delta (PRD) region, China. The most significant improvement to the model is the added capability to predict the secondary organic aerosols (SOA) concentrations because of the inclusion of the SOA formation chemistry. The meteorological input data were prepared using the CALMET meteorological model. The concentrations of aerosol-bound species such as NO3-, NH4+, SO4(2-), and SOA were calculated in the fine particle size range (< 2.5 microm). The results of the two-dimensional model were compared to the measurements at the ground level during the PRD Intensive Monitoring Campaign. Overall, there were good agreements between the measured and modeled concentrations of inorganic aerosol components and O3. Both the measured and the modeled results indicated that the maximum hourly 03 concentrations exceeded the China National Air Quality Standard. The predicted 24-h average SOA concentrations were in reasonable agreement with those predicted by the method of minimum OC/EC ratio.

Using bromine gas to enhance mercury removal from flue gas of coal-fired power plants.

Bromine gas was evaluated for converting elemental mercury (Hg0) to oxidized mercury, a form that can readily be captured by the existing air pollution control device. The gas-phase oxidation rates of Hg0 by Br2 decreased with increasing temperatures. SO2, CO, HCl, and H2O had insignificant effect, while NO exhibited a reverse course of effect on the Hg0 oxidation: promotion at low NO concentrations and inhibition at high NO concentrations. A reaction mechanism involving the formation of van der Waals clusters is proposed to accountfor NO's reverse effect. The apparent gas-phase oxidation rate constant, obtained under conditions simulating a flue gas without flyash, was 3.61 x 10(-17) cm3 x molecule(-1) x s(-1) at 410 K corresponding to a 50% Hg0 oxidation using 52 ppm Br2 in a reaction time of 15 s. Flyash in flue gas significantly promoted the oxidation of Hg0 by Br2, and the unburned carbon component played a major role in the promotion primarily through the rapid adsorption of Br2 which effectively removed Hg0 from the gas phase. At a typical flue gas temperature, SO2 slightly inhibited the flyash-induced Hg0 removal. Conversely, NO slightly promoted the flyash induced Hg0 removal by Br2. Norit Darco-Hg-LH and Darco-Hg powder activated carbons, which have been demonstrated in field tests, were inferred for estimating the flyash induced Hg0 oxidation by Br2. Approximately 60% of Hg0 is estimated to be oxidized with the addition of 0.4 ppm of gaseous Br2 into full scale power plant flue gas.