Mineral dust is an important component of the climate
system, interacting with radiation, clouds, and biogeochemical systems and
impacting atmospheric circulation, air quality, aviation, and solar ...energy
generation. These impacts are sensitive to dust particle size distribution
(PSD), yet models struggle or even fail to represent coarse (diameter (d)
>2.5 µm) and giant (d>20 µm) dust
particles and the evolution of the PSD with transport. Here we examine three
state-of-the-art airborne observational datasets, all of which measured the
full size range of dust (d=0.1 to >100 µm) at different
stages during transport with consistent instrumentation. We quantify the
presence and evolution of coarse and giant particles and their contribution
to optical properties using airborne observations over the Sahara (from the
Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical
eastern Atlantic (from the AER-D field campaign). Observations show significantly more abundant coarse and giant dust
particles over the Sahara compared to the SAL: effective diameters of up to
20 µm were observed over the Sahara compared to 4 µm in the
SAL. Excluding giant particles over the Sahara results in significant
underestimation of mass concentration (40 %), as well as underestimates of
both shortwave and longwave extinction (18 % and 26 %, respectively, from
scattering calculations), while the effects in the SAL are smaller but
non-negligible. The larger impact on longwave extinction compared to
shortwave implies a bias towards a radiative cooling effect in dust models,
which typically exclude giant particles and underestimate coarse-mode
concentrations. A compilation of the new and published effective diameters against dust age since uplift
time suggests that two regimes of dust transport exist. During the initial
1.5 d, both coarse and giant particles are rapidly deposited. During the
subsequent 1.5 to 10 d, PSD barely changes with transport, and the coarse
mode is retained to a much greater degree than expected from estimates of
gravitational sedimentation alone. The reasons for this are unclear and
warrant further investigation in order to improve dust transport schemes
and the associated radiative effects of coarse and giant particles in
models.
This study aims to prepare infant formula concentrates (IFs) simulating human milk fat globule (HMFG) composition, size and distribution. Mixed plant oil (21.3% palm oil, 2.8% flaxseed oil, 2.6% ...soybean oil, 29.9% rapeseed oil and 43.4% corn oil) and concentrated whey protein were applied to mimic triacylglycerols and phospholipids in HMFG respectively. IF1-IF6 were produced by different homogenization pressures or physically mixed with different proportions. IF4, prepared with 95% IF1 (4.29 μm), 1% IF2 (0.497 μm) and 4% IF3 (9.43 μm), showed a mean particle size of 3.96 μm and 49.77% milk fat globule membrane protein, and had the closest size distribution and interface with HMFG. The prepared IFs showed good stability with the Turbiscan stability index (IF6 (1.75)<IF5 (2.41)<IF4 (2.8)) at the 12th hour, which could be predicted by their initial proportion. This study provides new insight into simulating HMFG composition and structure for further development of novel infant formulas that are better for infant digestion and absorption.
•Infant formula concentrate (IF) simulat human milk fat globule (HMFG) composition, size and distribution was produced.•The mixed plant oil used in IF was prepared simulated to triacylglycerol structure of HMFGs.•IF1 (4.29 μm), IF2 (0.497 μm) and IF3 (9.43 μm) were prepared to mimic the different particle size range of HMFGs.•A mixture of different IFs shows the closest particle size distribution to HMFGs.•The interfacial proteins and stability of IFs could be predicted by their physically mixing proportion initially.
This paper examines the effects of size range, distribution and content of reactive aggregate on concrete expansion and deterioration due to Alkali–Silica Reaction (ASR). The ASR model was formulated ...within the Multiphysics framework of the Lattice Discrete Particle Model to account for the heterogeneous character of ASR expansion, cracking and damage. The adopted model was extended in this study to include a general piecewise linear sieve curve that allows selecting the coarse aggregate pieces to be reactive or non-reactive according to content and size range of actual reactive aggregate. The overall framework was calibrated and validated by comparing simulation results with three sets of experimental data from the literature. The results demonstrate that the model can capture all the main features of the experimental evidence. In particular, the so-called “pessimum size” of ASR expansion is captured and explained as the competition results between porosity and diffusion effects in the ASR model. Based on simulation results, it is shown that ASR-induced cracks are mainly generated by the presence of reactive aggregates of different sizes producing heterogeneous expansion at the mesoscale. The loss in mechanical properties is found to be strongly related to these cracks and the heterogeneous expansion as opposed to the measured macroscopic strain.
The FeCoNiCuAl high-entropy alloy powders are prepared in equimolar ratio by mechanical alloying in different milling time and then annealing at 773 K. The microstructure, morphology, particle size, ...magnetic and electromagnetic performance of powders were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), laser scattering particle size distribution analyzer, vibrating sample magnetometer (VSM) and vector network analyzer. The results indicate that flaky particles, which formed in the process of ball milling, show a soft magnetic character, as well as, the ranges of coercivity (Hc) are 67.6–105.1 Oe and the values of saturation magnetization (Ms) range from 69.1 emu/g to 94.2 emu/g. As the increasing of the milling time, the real parts of complex permittivity (ε′) increase firstly and then decrease, however, the imaginary parts of complex permittivity (ε″) close to zero for all the samples. Meanwhile, the real parts of complex permeability (μ′) are 1.26–1.56 and the imaginary parts of complex permeability (μ″) are 0.28–0.36 with change of milling time. The reflection loss (RL) of powders can reach −10 dB or less and 30 h-milling sample shows the maximum RL is −19.17 dB at 7.84 GHz with the thickness of 2 mm. After annealing, there appear two new phases, CoFe2O4 and AlFe3, that improve the values of Ms. The increased particles sizes and the enhanced values of Ms of powders all can promote complex permittivity and complex permeability. In addition, the RL also can get increased. These encouraging findings provide the potential advantages of high-entropy alloys for microwave absorption application.
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•The mechanical milling method was designed to prepare flaky FeCoNiCuAl HEA powders.•The Cu elements increase the ductility and conductivity of the FeCoNiCuAl HEA powders.•Variety of aspect radio and phases lead to the change of electromagnetic properties for milling and annealing HEA powders.•The maximum reflection loss (RL) can reach −19.17 dB at 7.84 GHz with the thickness of 2 mm.
Daily global burned area mapping of Earth from remotely sensed data is of considerable interest and indicates a clear user need, despite well-known accuracy limitations. Many studies report global ...and regional indicators of spatial and temporal accuracy to evaluate the quality of burned area products, but tend to rely on relatively sparse validation data. In this paper, an extensive validation data set covering 223 million ha over the Brazilian Cerrado for the 2015 fire season is used to thoroughly evaluate how the accuracy of burned area products relying on distinct spectral channels (SWIR+NIR versus NIR) and spatial resolution (250 m, 500 m, and both) depends on fire size.
Toward this end, we consider publicly available burned area products MCD64A1 (v006) at 500 m and FireCCI51 at 250 m and use a recently proposed graph-based patch algorithm, which is flexible enough to combine 250–500 m bands.
The trade-off between spatial resolution and spectral channels for the problem at hand reveals that better spatial resolution (NIR at 250 m) is preferable to a broader range of spectral channels (NIR + SWIR at 500 m) for small burns (<250 ha), but that this relation is not preserved for large burns (>1000 ha). Also, this study shows that combining both spectral indices into a single classifier leads to the most accurate burned area map. The analysis by land cover type indicates that overall accuracy is highest for grasslands and savannas, with grasslands benefiting the most from the use of SWIR bands. Results also indicate that burned areas can be classified with accuracy measured by the Dice Coefficient close to 80% for fire sizes larger than 500 ha, which corresponds to 60% of the total burned area, but accuracy lower than 36% for fire sizes smaller than 250 ha. In particular, our analysis suggests that the validation of burned area products always should be linked to the description of fire size distribution since it is a fundamental driver of accuracy.
Results show that MODIS daily burned area mapping at 250–500 m spatial resolution can exhibit high temporal accuracy, with almost unbiased estimates and standard deviation close to 1.5 days, indicating an accurate characterization of the spread of large fires.
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•Burned area (BA) dates exhibit bias under 1 day and standard deviation under 2 days.•Fire size is the main driver of accuracy, ahead of land cover and BA algorithms.•Adding 500 m NIR + SWIR improves accuracy of 250 m NIR based BA products.•Using NIR, accuracy for fires smaller than 250 ha increases by 14% over MCD64A1.•Validation of BA products should take fire size distribution into account.
Compared to conventional preparation methods for supported heterogeneous catalysts, the use of colloidal nanoparticles (NPs) allows for a precise control over size, size distribution, and ...distribution/location of the NPs on the support. However, common colloidal syntheses have restrictions that limit their applicability for industrial catalyst preparation. We present a simple, surfactant‐free, and scalable preparation method for colloidal NPs to overcome these restrictions. We demonstrate how precious‐metal NPs are prepared in alkaline methanol, how the particle size can be tuned, and how supported catalysts are obtained. The potential of these colloids in the preparation of improved catalysts is demonstrated by two examples from heterogeneous catalysis and electrocatalysis.
The Co4Cat process is a simple method to obtain stable colloidal dispersions of precious‐metal nanoparticles in alkaline mono‐alcohols. The surfactant‐free method bears economic advantages for the preparation of supported catalysts with improved performance.
Desalination performance of capacitive deionization (CDI), a promising deionization technology, depends significantly upon the compositions and internal structures of electrode materials. Herein, ...hollow ZIFs-derived nanoporous carbons (HZCs) were prepared via chemical etching method and subsequent pyrolysis. Particularly, the tannic acid as an etching agent was employed to tailor hollow structure. The resultant HZCs possess high surface area, wide pore size distribution, obvious hollow cavity and high nitrogen content. Moreover, HZCs electrodes exhibited a significantly improved CDI performance over the solid ZIFs-derived nanoporous carbons (SZCs) electrodes. The improved electrosorption rate and capacity (15.31 mg g-1 at 1.2 V) of HZCs electrode imply that hollow structure facilitates the transportation for both ions and mass on CDI process. Besides, the further cycle experiment exhibits a great regeneration stability of HZCs electrode over 20 adsorption-desorption cycles. All these results indicate that HZCs should be a promising candidate for CDI application.
Hollow ZIFs-derived porous carbons (HZCs) was prepared via chemistry etching method and subsequent pyrolysis, then utilized as CDI electrodes. The as-prepared electrode exhibits excellent capacitive deionization performance and great stability. Display omitted
•The hollow ZIFs-derived porous carbons (HZCs) as CDI electrodes was simply prepared.•HZCs possessed the large surface area and rich mesopores.•CDI performance on the as-prepared electrodes shows a high level among the reported carbon electrodes.•The improved electrosorption rate and capacity of HZCs electrode proved the superiority of hollow structure on CDI process.
•Properties of eight cement grouts with various composition and grains are presented.•Effects of W/C ratios (1.0–3.0), fineness, SP and composition are studied.•Rheological parameters, fresh states ...and mechanical properties are determined.•Property optimization and grouting effectiveness for MC based grouts are discussed.
To ensure excellent rheological behavior, penetrability and mechanical property of microfine cement (MC) grout in the field work, it is essential to obtain and control its property by laboratory tests. In this study, rheological and mechanical properties of six different MC grouts (three portland-based and three slag-blended) and two ordinary Portland cements (ASTM I and III) are measured. MC suspension was prepared at five W/C ratios (1.0, 1.2, 1.5, 2.0 and 3.0) without or with superplasticizer (SP). The properties investigated in this study were: particle size distribution, rheological properties (apparent viscosity, yield stress and plastic viscosity), fresh states (mini-slump, bleed capacity and final setting time) and mechanical properties (early strength development, compressive strength, flexural strength, elasticity modulus, shrinkage/expansion and sand-consolidation strength). The results showed that rheological behaviors and mechanical properties of MC grouts were affected obviously by the W/C ratio, cement fineness, cement type and the addition of SP, etc. All MC suspensions behaved as the Bingham fluids and were stable for W/C=1.0, 1.2 and 1.5. The detrimental effect of finer grain size on viscosity can be negated by using SP. To ensure less leaching, sufficient fluidity and enough penetrability in sand voids or micro cracks, the W/C ratio was recommended as 1.0–2.0. The SP dosages should not be excessive to avoid instability, oversaturation or long-setting.
Black carbon (BC) is one of the main components of ambient particulate matter. Previous studies have suggested that BC is more toxic than PM2.5 (mass concentration of all sub-2.5 μm particles). One ...possible reason for the greater toxicity is that BC is typically in a size range which penetrates easily into lung alveoli and BC particles have a large surface area due to their fractal structure. Due to these properties, toxic gaseous compounds can condensate on the surface of BC particles and then be transported effectively into human lungs, causing a large lung-depositing surface area (LDSA) of particles. In this study, we investigated the relationship between BC and LDSA concentrations in street canyon, highway, and harbour environments in the Helsinki Metropolitan area. In all the studied environments, BC and LDSA concentrations were strongly correlated. In the harbour, cases where marine traffic was considered as the main emission source, the average LDSA per BC mass was 2.4–2.7 times higher than in the road traffic environments. This result was linked to a larger lung depositing size of BC, suggesting that condensation and coagulation of other co-emitted compounds can have a major role in the lung deposition of BC. Thus, BC emissions from marine traffic can cause higher exposure of other co-emitted toxic compounds in the human lungs than the road traffic. The fraction of LDSA linked to BC emissions in the street canyon, the highway, and the harbour were 33%, 30%, and 47%, respectively, whereas the fractions of BC mass in PM1 concentration were 14%, 14%, and 7%, respectively. The results show that BC emissions contribute much more to LDSA than to mass concentration, which indicates that the possible strong negative health effects linked to ambient BC mass concentration could be related to the high LDSA concentration.
•Characteristics of LDSA investigated in a harbour and near traffic in Helsinki area.•BC emitted from marine traffic is linked to higher LDSA per mass than road traffic.•BC emissions contribute more to LDSA (30–47% of total LDSA) than to PM1 (7–14%).•In the harbour, higher absorption Ångström exponent was connected to higher LDSA.•Health hazard of BC might be related to high LDSA and other co-emitted species.
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