A coupled weather‐aerosol model is used to study the effect of biomass burning aerosols on deep convection over the Borneo Island and surrounding oceans. Simulations are performed at the ...convection‐permitting scale (4 km) for 40 days during the boreal summer and include interactive fire emissions and the aerosol effect on radiative and microphysical processes. Intense burning occurs daily in the southern part of the island, and smoke propagates northward to regions of deep convection. The model captures well the observed diurnal cycle of precipitation and high cloud cover. Cloud microphysics and radiative aerosol impacts are considered separately. Modifications of the cloud microphysics by smoke aerosols reinforce deep convection near the central Borneo mountainous region. This reinforced convection is due to reduced shallow precipitation in the afternoon that leads to a warm planetary boundary layer anomaly at sunset enhancing deep convection at night. Aerosol absorptive properties strongly affect local and synoptic atmospheric responses. The radiative processes of moderately absorbing aerosols tend to reduce deep convection over most regions due to local surface cooling and atmosphere warming that increase the static stability. For more absorbing aerosols, however, the impact is reversed with increased nighttime convection over most regions. This is partly related to changes in the vertical water vapor divergence profiles that decrease the convergence toward Borneo for moderately absorbing aerosols and increase it for more absorbing ones. These changes in the synoptic circulation due to large‐scale aerosol perturbations are as important as local processes to explain the observed rainfall perturbation patterns.
Key Points
WRF‐Chem with aerosol‐aware microphysics is used to study effects of fire aerosols on the diurnal evolution of deep convection over Borneo
Microphysical and radiative aerosol effects are regionally variable and perturb mostly the nighttime convection
Aerosol absorption modulates the radiative effect by changing the atmospheric heating over the island and the low‐level moisture convergence
The exploitation of curcumin for oral disease treatment is limited by its low solubility, poor bioavailability, and low stability. Surface-functionalized poly-lactic-co-glycolic acid (PLGA) ...nanoparticles (NPs) have shown promising results to ameliorate selective delivery of drugs to the gastro-intestinal tract. In this study, curcumin-loaded PLGA NPs (C-PLGA NPs) of about 200 nm were surface-coated with chitosan (CS) for gastro-intestinal mucosa adhesion, wheat germ agglutinin (WGA) for colon targeting or GE11 peptide for tumor colon targeting. Spectrometric and zeta potential analyses confirmed the successful functionalization of the C-PLGA NPs. Real-time label-free assessment of the cell membrane-NP interactions and NP cell uptake were performed by quartz crystal microbalance coupled with supported lipid bilayers and by surface plasmon resonance coupled with living cells. The study showed that CS-coated C-PLGA NPs interact with cells by the electrostatic mechanism, while both WGA- and GE11-coated C-PLGA NPs interact and are taken up by cells by specific active mechanisms. In vitro cell uptake studies corroborated the real-time label-free assessment by yielding a curcumin cell uptake of 7.3 ± 0.3, 13.5 ± 1.0, 27.3 ± 4.9, and 26.0 ± 1.3 μg per 104 HT-29 cells for noncoated, CS-, WGA-, and GE11-coated C-PLGA NPs, respectively. Finally, preliminary in vivo studies showed that the WGA-coated C-PLGA NPs efficiently accumulate in the colon after oral administration to healthy Balb/c mice. In summary, the WGA- and GE11-coated C-PLGA NPs displayed high potential for application as active targeted carriers for anticancer drug delivery to the colon.
Inflammation is initiated and driven by a mixture of mediators, which modify effects of each other. This study analysed in vitro pro-inflammatory activity of inflammatory cytokines (TNFα and IL-1β) ...in a combination with a lipid DAMP molecule, oxidized palmitoyl-arachidonoyl-phosphatidylcholine (OxPAPC). The study was performed on endothelial and monocytic cell lines. The cells were treated with different concentrations of TNFα or IL-1β, OxPAPC and their combinations, either in the presence or absence of drugs regulating inflammation. Pro-inflammatory effects of TNFα/IL-1β and OxPAPC were estimated by analysis of chemokines CXCL8, CXCL2 and CXCL3 by ELISA and RT-PCR. Toxicity was determined by analysis of metabolic activity. Statistical significance was estimated by ANOVA and Dunnett's test. OxPAPC was a much weaker chemokine inducer as compared to TNFα or IL-1β. However, OxPAPC and TNFα/IL-1β together induced effects that were significantly stronger than the arithmetical sum of individual effects. This cooperative action of OxPAPC and TNFα was reversed by inhibitors of p38 MAPK. We hypothesise that the boosting of TNFα and IL-1β effects by OxPAPC may be more pathologically important than the action of the lipid alone. Inhibitors of p38 MAPK may become a tool for analysis of pathological role of oxidized phospholipids.
Machining experiments were conducted to evaluate the impact of cutting parameters on the hole quality and cutting forces in drilling Al2024-T3 aerospace alloy. Al2024-T3 specimen were drilled using ...Φ6-mm TiAlN-coated carbide twist drills under dry cutting conditions. The hole quality was inspected in terms of its surface roughness, burr and chip formations, hole size, circularity error and post-machining microhardness of the subsurface of the holes. An analysis of variance (ANOVA) was carried out to determine the percentage contribution of cutting parameters on cutting forces and the inspected hole quality parameters. A three-dimensional (3D) finite element (FE) model of drilling Al2024-T3 is developed using Abaqus/Explicit to predict thrust force and torque. The FE model was validated using experimental results and found to be in good agreement. The results of the study showed that the cutting parameters have a significant impact on cutting forces and inspected hole quality parameters. Drilling at feed rates of 100 and 300 mm/min and spindle speeds of 1000, 3000, and 6000 rpm are recommended for producing holes with smaller surface roughness, deviation from nominal hole size, circularity error and burrs.
The direct and semi-direct radiative effects of biomass burning aerosols (BBAs) are investigated over southern Africa and the southeastern Atlantic during the Aerosols, Radiation and Clouds in ...southern Africa (AEROCLO-sA) field campaign in September 2017. A reference convection-permitting simulation has been performed using the Meso-NH model with an online dust emission scheme, a strongly absorbing BBA tracer emitted using the daily Global Fire Emissions Database and online-computed backward Lagrangian trajectories. The simulation captures both the aerosol optical depth and the vertical distribution of aerosols as observed from airborne and spaceborne lidars. The occurrence of stratocumulus over the southeastern Atlantic, deep convective clouds over equatorial Africa and the large-scale circulation are all reproduced by the model. If the radiative effects of BBA are omitted in the model, we show that (i) the smoke plume is too low in altitude, (ii) the low-cloud cover is too weak, (iii) the deep convective activity is too frequent but not intense enough, (iv) the Benguela low-level jet is too strong, and (v) the southern African easterly jet is too weak. The Lagrangian analysis indicates that the radiative effect of BBA leads to the transport of BBA to higher altitudes, farther southwest and with a stronger diurnal oscillation. The higher smoke plume altitude can be explained by a combination of three factors: increased upward motion induced by the stronger southern African easterly jet, self-lofting of BBA and reduced subsidence associated with less frequent deep convective activity over western equatorial Africa.
Tropospheric trace gas and aerosol pollutants have adverse effects on health, environment and climate. In order to quantify and mitigate such effects, a wide range of processes leading to the ...formation and transport of pollutants must be considered, understood and represented in numerical models. Regional scale pollution episodes result from the combination of several factors: high emissions (from anthropogenic or natural sources), stagnant meteorological conditions, kinetics and efficiency of the chemistry and the deposition. All these processes are highly variable in time and space, and their relative contribution to the pollutants budgets can be quantified with chemistry-transport models. The CHIMERE chemistry-transport model is dedicated to regional atmospheric pollution event studies. Since it has now reached a certain level a maturity, the new stable version, CHIMERE 2013, is described to provide a reference model paper. The successive developments of the model are reviewed on the basis of published investigations that are referenced in order to discuss the scientific choices and to provide an overview of the main results.
Clouds play a key role in radiation and hence O3 photochemistry by
modulating photolysis rates and light-dependent emissions of biogenic
volatile organic compounds (BVOCs). It is not well known, ...however, how much
error in O3 predictions can be directly attributed to error in cloud
predictions. This study applies the Weather Research and Forecasting with
Chemistry (WRF-Chem) model at 12 km horizontal resolution with the Morrison
microphysics and Grell 3-D cumulus parameterization to quantify uncertainties
in summertime surface O3 predictions associated with cloudiness over
the contiguous United States (CONUS). All model simulations are driven by
reanalysis of atmospheric data and reinitialized every 2 days. In sensitivity
simulations, cloud fields used for photochemistry are corrected based on
satellite cloud retrievals. The results show that WRF-Chem predicts about
55 % of clouds in the right locations and generally underpredicts cloud
optical depths. These errors in cloud predictions can lead to up to 60 ppb
of
overestimation in hourly surface O3 concentrations on some days. The
average difference in summertime surface O3 concentrations derived from
the modeled clouds and satellite clouds ranges from 1 to 5 ppb for maximum
daily 8 h average O3 (MDA8 O3) over the CONUS. This represents up to
∼ 40 % of the total MDA8 O3 bias under cloudy conditions in
the tested model version. Surface O3 concentrations are sensitive to
cloud errors mainly through the calculation of photolysis rates (for
∼ 80 %), and to a lesser extent to light-dependent BVOC emissions.
The sensitivity of surface O3 concentrations to satellite-based cloud
corrections is about 2 times larger in VOC-limited than NOx-limited
regimes. Our results suggest that the benefits of accurate predictions of
cloudiness would be significant in VOC-limited regions, which are typical of
urban areas.
The Community Earth System Model version 2 (CESM2) includes three main atmospheric configurations: the Community Atmosphere Model version 6 (CAM6) with simplified chemistry and a simplified organic ...aerosol (OA) scheme, CAM6 with comprehensive tropospheric and stratospheric chemistry representation (CAM6‐chem), and the Whole Atmosphere Community Climate Model version 6 (WACCM6). Both, CAM6‐chem and WACCM6 include a more comprehensive secondary organic aerosols (SOA) approach using the Volatility Basis Set (VBS) scheme and prognostic stratospheric aerosols. This paper describes the different OA schemes available in the different atmospheric configurations of CESM2 and discusses differences in aerosol burden and resulting climate forcings. Derived OA burden and trends differ due to differences in OA formation using the different approaches. Regional differences in Aerosol Optical Depth with larger values using the comprehensive approach occur over SOA source regions. Stronger increasing SOA trends between 1960 and 2015 in WACCM6 compared to CAM6 are due to increasing biogenic emissions aligned with increasing surface temperatures. Using the comprehensive SOA approach further leads to improved comparisons to aircraft observations and SOA formation of ≈143 Tg/yr. We further use WACCM6 to identify source contributions of OA from biogenic, fossil fuel, and biomass burning emissions, to quantify SOA amounts and trends from these sources. Increasing SOA trends between 1960 and 2015 are the result of increasing biogenic emissions aligned with increasing surface temperatures. Biogenic emissions are at least two thirds of the total SOA burden. In addition, SOA source contributions from fossil fuel emissions become more important, with largest values over Southeast Asia. The estimated total anthropogenic forcing of OA in WACCM6 for 1995–2010 conditions is −0.43 W/m2, mostly from the aerosol direct effect.
Key Points
CESM2 (WACCM6) includes an updated secondary aerosol scheme using the volatility basis set approach
The new SOA parameterization results in regional changes in radiative forcings and aerosol optical depth
Positive SOA trends between 1960 and 2015 are caused by both increasing biogenic and anthropogenic sources
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