Recent laboratory studies suggest that secondary organic aerosol (SOA) formation rates are higher than assumed in current models. There is also evidence that SOA removal by dry and wet deposition ...occurs more efficiently than some current models suggest and that photolysis and heterogeneous oxidation may be important (but currently ignored) SOA sinks. Here, we have updated the global GEOS-Chem model to include this new information on formation (i.e., wall-corrected yields and emissions of semi-volatile and intermediate volatility organic compounds) and on removal processes (photolysis and heterogeneous oxidation). We compare simulated SOA from various model configurations against ground, aircraft and satellite measurements to assess the extent to which these improved representations of SOA formation and removal processes are consistent with observed characteristics of the SOA distribution. The updated model presents a more dynamic picture of the life cycle of atmospheric SOA, with production rates 3.9 times higher and sinks a factor of 3.6 more efficient than in the base model. In particular, the updated model predicts larger SOA concentrations in the boundary layer and lower concentrations in the upper troposphere, leading to better agreement with surface and aircraft measurements of organic aerosol compared to the base model. Our analysis thus suggests that the long-standing discrepancy in model predictions of the vertical SOA distribution can now be resolved, at least in part, by a stronger source and stronger sinks leading to a shorter lifetime. The predicted global SOA burden in the updated model is 0.88 Tg and the corresponding direct radiative effect at top of the atmosphere is −0.33 W m−2, which is comparable to recent model estimates constrained by observations. The updated model predicts a population-weighed global mean surface SOA concentration that is a factor of 2 higher than in the base model, suggesting the need for a reanalysis of the contribution of SOA to PM pollution-related human health effects. The potential importance of our estimates highlights the need for more extensive field and laboratory studies focused on characterizing organic aerosol removal mechanisms and rates.
Purpose
Carbon-fibre-reinforced polymers (CFRP) have been developed by the aviation industry to reduce aircraft fuel burn and emissions of greenhouse gases. This study presents a life cycle ...assessment (LCA) of an all-composite airplane, based on a Boeing 787 Dreamliner. The global transition of aircraft to those of composite architecture is estimated to contribute 20–25 % of industry CO
2
reduction targets. A secondary stage of the cradle-to-grave analysis expands the study from an individual aircraft to the global fleet.
Methods
An LCA was undertaken utilising SimaPro 7.2 in combination with Ecoinvent. Eco-indicator 99 (E) V2.05 Europe EI 99 E/E was the chosen method to calculate the environmental impact of the inventory data. The previously developed aviation integrated model was utilised to construct a scenario analysis of the introduction of composite aircraft against a baseline projection, through to 2050, to model CO
2
emissions due to their particular relevance in the aviation sector.
Results and discussion
The analysis demonstrated CFRP structure results in a reduced single score environmental impact, despite the higher environmental impact in the manufacturing phase, due to the increased fossil fuel use. Of particular importance is that CFRP scenario quickly achieved a reduction in CO
2
and NO
x
atmospheric emissions over its lifetime, due to the reduced fuel consumption. The modelled fleet-wide CO
2
reduction of 14–15 % is less than the quoted emission savings of an individual aircraft (20 %) because of the limited fleet penetration by 2050 and the increased demand for air travel due to lower operating costs.
Conclusions
The introduction of aircraft based on composite material architecture has significant environmental benefits over their lifetime compared to conventional aluminium-based architecture, particularly with regards to CO
2
and NO
x
a result of reduced fuel burn. The constructed scenario analyses the interactions of technology and the markets they are applied in, expanding on the LCA, in this case, an observed fleet-wide reduction of CO
2
emission of 14–15 % compared to an individual aircraft of 20 %.
The spatial distribution and properties of submicron organic aerosol (OA)
are among the key sources of uncertainty in our understanding of aerosol
effects on climate. Uncertainties are particularly ...large over remote regions
of the free troposphere and Southern Ocean, where very few data have been
available and where OA predictions from AeroCom Phase II global models span 2 to 3 orders of magnitude, greatly exceeding the model spread over
source regions. The (nearly) pole-to-pole vertical distribution of
non-refractory aerosols was measured with an aerosol mass spectrometer
onboard the NASA DC-8 aircraft as part of the Atmospheric Tomography (ATom)
mission during the Northern Hemisphere summer (August 2016) and winter
(February 2017). This study presents the first extensive characterization of
OA mass concentrations and their level of oxidation in the remote
atmosphere. OA and sulfate are the major contributors by mass to submicron
aerosols in the remote troposphere, together with sea salt in the marine
boundary layer. Sulfate was dominant in the lower stratosphere. OA
concentrations have a strong seasonal and zonal variability, with the
highest levels measured in the lower troposphere in the summer and over the
regions influenced by biomass burning from Africa (up to 10 µg sm−3). Lower concentrations (∼0.1–0.3 µg sm−3)
are observed in the northern middle and high latitudes and very low
concentrations (<0.1 µg sm−3) in the southern middle and
high latitudes. The ATom dataset is used to evaluate predictions of eight
current global chemistry models that implement a variety of commonly used
representations of OA sources and chemistry, as well as of the AeroCom-II
ensemble. The current model ensemble captures the average vertical and
spatial distribution of measured OA concentrations, and the spread of the
individual models remains within a factor of 5. These results are
significantly improved over the AeroCom-II model ensemble, which shows large
overestimations over these regions. However, some of the improved agreement
with observations occurs for the wrong reasons, as models have the tendency
to greatly overestimate the primary OA fraction and underestimate the
secondary fraction. Measured OA in the remote free troposphere is highly
oxygenated, with organic aerosol to organic carbon (OA ∕ OC) ratios of
∼2.2–2.8, and is 30 %–60 % more oxygenated than in current
models, which can lead to significant errors in OA concentrations. The
model–measurement comparisons presented here support the concept of a more
dynamic OA system as proposed by Hodzic et al. (2016), with enhanced removal
of primary OA and a stronger production of secondary OA in global models
needed to provide better agreement with observations.
The adsorption of human hepatocellular carcinoma cells (HepG2) on cellulose nanofibril (CNF) films is studied in this work in real time by surface plasmon resonance. The effect of poly-l-lysine, ...laminin 521, and cell medium components on HepG2-CNF interaction is evaluated in order to develop future CNF-based systems with tuned cell adhesion properties for different tissue engineering applications. Keyword: Real time Cell Adhesion.
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The development of in vitro cell models that mimic cell behavior in organs and tissues is an approach that may have remarkable impact on drug testing and tissue engineering applications in the future. Plant-based, chemically unmodified cellulose nanofibrils (CNF) hydrogel is a natural, abundant, and biocompatible material that has attracted great attention for biomedical applications, in particular for three-dimensional cell cultures. However, the mechanisms of cell-CNF interactions and factors that affect these interactions are not yet fully understood. In this work, multi-parametric surface plasmon resonance (SPR) was used to study how the adsorption of human hepatocellular carcinoma (HepG2) cells on CNF films is affected by the different proteins and components of the cell medium. Both human recombinant laminin-521 (LN-521, a natural protein of the extracellular matrix) and poly-l-lysine (PLL) adsorbed on CNF films and enhanced the attachment of HepG2 cells. Cell medium components (glucose and amino acids) and serum proteins (fetal bovine serum, FBS) also adsorbed on both bare CNF and on protein-coated CNF substrates. However, the adsorption of FBS hindered the attachment of HepG2 cells to LN-521- and PLL-coated CNF substrates, suggesting that serum proteins blocked the formation of laminin-integrin bonds and decreased favorable PLL-cell electrostatic interactions. This work sheds light on the effect of different factors on cell attachment to CNF, paving the way for the utilization and optimization of CNF-based materials for different tissue engineering applications.
Organic aerosols (OA) represent a significant fraction of total submicron particulate matter (PM1) concentrations globally, including densely populated megacities such as Seoul. However, scientific ...understanding of the atmospheric formation and removal processes of OA, especially for secondary organic aerosols (SOA), is still highly uncertain. In this study, we examine the characteristics of SOA formation in Seoul during spring‐summer 2016 and fall‐winter 2017/2018, using airborne and ground observations along with a 3‐D global chemical transport model, GEOS‐Chem. We use four different SOA schemes in the model, including simplified and complex volatility‐based frameworks, and evaluate them by comparing the simulations with the observations to examine how our scientific understanding embedded in each SOA scheme affects the observed biases. Our analysis of the model performance of each scheme also provides the most suitable approach in simulating SOA in a typical urban environment. Comparisons of the simulated versus observed OA concentrations show that model biases range from −72% to +118%, with considerable variability among different schemes and seasons. We find that the inclusion of semi/intermediate volatile precursors, in addition to the traditional precursors, and chemical aging (functionalization) are important factors to simulate surface SOA concentrations in Seoul. However, a comparison of observed and simulated SOA/∆CO enhancement ratios suggests that most schemes underpredict SOA aging in upper levels in the boundary layer. We also find that the simplified SOA scheme can reproduce observed OA but often shows overestimation in surface air, indicating that uncertainties exist in bottom‐up emissions and precursor parameterization in Seoul.
Plain Language Summary
We compare four different modeling approaches for simulating secondary organic aerosol (SOA) formation, accounting for a significant fraction of total fine particulate matter concentrations in Seoul, Korea. Using GEOS‐Chem, a chemical transport model, we find that current SOA schemes show large variabilities. Including an additional precursor species and further oxidation (i.e., chemical aging) of simulated SOA improves model performance. We also find that a simplified scheme with less computational cost can reproduce observed values but generally shows an overestimation in Seoul, indicating uncertainties in parameterization.
Key Points
Model evaluation of simulated organic aerosols (OA) using different secondary organic aerosols (SOA) schemes in Seoul shows large variability
The inclusion of semi/intermediate volatile precursors and chemical aging are important factors in reducing model biases
The simplified SOA scheme can reproduce observed OA, but uncertainties exist in precursor parameterization in Seoul
Purpose
The lack of effective screening methods and systemic understanding of interaction mechanisms complicates the stabilizer selection process for nanocrystallization. This study focuses on the ...efficiency of stabilizers with various molecular compositions and structures to stabilize drug nanocrystals.
Methods
Five structurally different polymers were chosen as stabilizers for indomethacin nanocrystals. The affinity of polymers onto drug surfaces was measured using surface plasmon resonance (SPR) and contact angle techniques. Nanosuspensions were prepared using the wet-ball milling technique and their physico-chemical properties were thoroughly characterized.
Results
SPR and contact angle measurements correlated very well with each other and showed that the binding efficiency decreased in the order L64 > 17R4 > F68 ≈ T908 ≈ T1107, which is attributed to the reduced PPO/PEO ratio and different polymer structures. The electrostatic interactions between the protonated amine of poloxamines and ionized indomethacin enhanced neither the affinity nor the properties of nanosuspensions, such as particle size and physical stability.
Conclusions
A good stabilizer should have high binding efficiency, full coverage, and optimal hydrophobic/hydrophilic balance. A high affinity combined with short PEO chains (L64, 17R4) caused poor physical stability of nanosuspensions, whereas moderate binding efficiencies (F68, T908, T1107) with longer PEO chains produced physically stable nanosuspensions.
The aim of this paper is to analyse the contribution of micro-mechanical parameters, on the macroscopic behaviour of a short fibre reinforced thermoplastic composites (SFRTC). By developing an ...algorithm to provide a representative random micro-structure, a comparative analysis of different micro-mechanical parameters, such as aspect ratio (AR) and fibre orientation (FO), was conducted and compared with the existing analytical models. A study of different aspect ratios and different fibre orientations has been carried out in order to examine their effect on the linear elastic properties of SFRTC. Aspect ratios from one to ten have been analysed for the cases of fully oriented 0° fibres, miss-oriented fibres and randomly oriented fibres. A representative volume element (RVE) was used to investigate the effect of the representative size. Results were analysed statistically through
X
2
test, and the subsequent representative realisations were compared with the theoretical predictions.
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