Temperature-induced structural transition in-situ in porcine lens — Changes observed in void size distribution

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

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Effect of fly ash on the air void size distribution entrained by selected anionic, cationic and nonionic surfactants in hardened cement mortars

Cement and Concrete Composites ◽

10.1016/j.cemconcomp.2021.104253 ◽

2021 ◽

Vol 124 ◽

pp. 104253

Author(s):

Qi Liu ◽

Zhitao Chen ◽

Yingzi Yang

Keyword(s):

Fly Ash ◽

Size Distribution ◽

Nonionic Surfactants ◽

Hardened Cement ◽

Void Size ◽

Cement Mortars ◽

Air Void

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Methodology for determining rom size distribution

Rem Revista Escola de Minas ◽

10.1590/0370-44672014670184 ◽

2014 ◽

Vol 67 (4) ◽

pp. 405-412

Author(s):

Christiane Ribeiro da Silva ◽

Vládia C. G. de Souza ◽

Jair C. Koppe

Keyword(s):

Size Distribution ◽

Distribution Curve ◽

Size Distributions ◽

Sampling Protocol ◽

Product Size ◽

Operational Conditions ◽

Specific Protocol ◽

Open Side ◽

Ore Dressing

A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented according to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

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The aerosol-climate model ECHAM5-HAM

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-1125-2005 ◽

2005 ◽

Vol 5 (4) ◽

pp. 1125-1156 ◽

Cited By ~ 787

Author(s):

P. Stier ◽

J. Feichter ◽

S. Kinne ◽

S. Kloster ◽

E. Vignati ◽

...

Keyword(s):

Size Distribution ◽

Climate Model ◽

Normal Modes ◽

Anthropogenic Activity ◽

Climate Modelling ◽

Extensive Evaluation ◽

Wide Range ◽

Log Normal ◽

Year 2000

Abstract. The aerosol-climate modelling system ECHAM5-HAM is introduced. It is based on a flexible microphysical approach and, as the number of externally imposed parameters is minimised, allows the application in a wide range of climate regimes. ECHAM5-HAM predicts the evolution of an ensemble of microphysically interacting internally- and externally-mixed aerosol populations as well as their size-distribution and composition. The size-distribution is represented by a superposition of log-normal modes. In the current setup, the major global aerosol compounds sulfate (SU), black carbon (BC), particulate organic matter (POM), sea salt (SS), and mineral dust (DU) are included. The simulated global annual mean aerosol burdens (lifetimes) for the year 2000 are for SU: 0.80 Tg(S) (3.9 days), for BC: 0.11 Tg (5.4 days), for POM: 0.99 Tg (5.4 days), for SS: 10.5 Tg (0.8 days), and for DU: 8.28 Tg (4.6 days). An extensive evaluation with in-situ and remote sensing measurements underscores that the model results are generally in good agreement with observations of the global aerosol system. The simulated global annual mean aerosol optical depth (AOD) is with 0.14 in excellent agreement with an estimate derived from AERONET measurements (0.14) and a composite derived from MODIS-MISR satellite retrievals (0.16). Regionally, the deviations are not negligible. However, the main patterns of AOD attributable to anthropogenic activity are reproduced.

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Combining airborne in situ and ground-based lidar measurements for attribution of aerosol layers

10.5194/acp-2017-1085 ◽

2018 ◽

Author(s):

Anna Nikandrova ◽

Ksenia Tabakova ◽

Antti Manninen ◽

Riikka Väänänen ◽

Tuukka Petäjä ◽

...

Keyword(s):

Boundary Layer ◽

Size Distribution ◽

Aerosol Size Distribution ◽

Long Range Transport ◽

Back Trajectories ◽

Clear Sky ◽

Temporal And Spatial Variability ◽

Range Transport ◽

Temporal And Spatial

Abstract. Understanding the distribution of aerosol layers is important for determining long range transport and aerosol radiative forcing. In this study we combine airborne in situ measurements of aerosol with data obtained by a ground-based High Spectral Resolution Lidar (HSRL) and radiosonde profiles to investigate the temporal and vertical variability of aerosol properties in the lower troposphere. The HSRL was deployed in Hyytiälä, Southern Finland, from January to September 2014 as a part of the US DoE ARM (Atmospheric Radiation Measurement) mobile facility during the BAECC (Biogenic Aerosols – Effects on Cloud and Climate) Campaign. Two flight campaigns took place in April and August 2014 with instruments measuring the aerosol size distribution from 10 nm to 10 µm at altitudes up to 3800 m. Two case studies from the flight campaigns, when several aerosol layers were identified, were selected for further investigation: one clear sky case, and one partly cloudy case. During the clear sky case, turbulent mixing ensured low temporal and spatial variability in the measured aerosol size distribution in the boundary layer whereas mixing was not as homogeneous in the boundary layer during the partly cloudy case. The elevated layers exhibited greater temporal and spatial variability in aerosol size distribution, indicating a lack of mixing. New particle formation was observed in the boundary layer during the clear sky case, and nucleation mode particles were also seen in the elevated layers that were not mixing with the boundary layer. Interpreting local measurements of elevated layers in terms of long-range transport can be achieved using back trajectories from Lagrangian models, but care should be taken in selecting appropriate arrival heights, since the modelled and observed layer heights did not always coincide. We conclude that higher confidence in attributing elevated aerosol layers with their air mass origin is attained when back trajectories are combined with lidar and radiosonde profiles.

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Developing and Evaluating Ice Cloud Parameterizations for Forward Modeling of Radar Moments Using in situ Aircraft Observations

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-14-00112.1 ◽

2015 ◽

Vol 32 (5) ◽

pp. 880-903 ◽

Cited By ~ 27

Author(s):

Maximilian Maahn ◽

Ulrich Löhnert ◽

Pavlos Kollias ◽

Robert C. Jackson ◽

Greg M. McFarquhar

Keyword(s):

Size Distribution ◽

Power Law ◽

Particle Mass ◽

Maximum Diameter ◽

Doppler Spectrum ◽

Doppler Velocity ◽

Radar Observations ◽

Size Relation ◽

Particle Area

AbstractObserving ice clouds using zenith pointing millimeter cloud radars is challenging because the transfer functions relating the observables to meteorological quantities are not uniquely defined. Here, the authors use a spectral radar simulator to develop a consistent dataset containing particle mass, area, and size distribution as functions of size. This is an essential prerequisite for radar sensitivity studies and retrieval development. The data are obtained from aircraft in situ and ground-based radar observations during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) campaign in Alaska. The two main results of this study are as follows: 1) An improved method to estimate the particle mass–size relation as a function of temperature is developed and successfully evaluated by combining aircraft in situ and radar observations. The method relies on a functional relation between reflectivity and Doppler velocity. 2) The impact on the Doppler spectrum by replacing measurements of particle area and size distribution by recent analytical expressions is investigated. For this, higher-order moments such as skewness and kurtosis as well as the slopes of the Doppler spectrum are also used as a proxy for the Doppler spectrum. For the area–size relation, it is found that a power law is not sufficient to describe particle area and small deviations from a power law are essential for obtaining consistent higher moments. For particle size distributions, the normalization approach for the gamma distribution of Testud et al., adapted to maximum diameter as size descriptor, is preferred.

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Technical Note: Evaporation of polar stratospheric cloud particles, in situ, in a heated inlet

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-97-2005 ◽

2005 ◽

Vol 5 (1) ◽

pp. 97-106 ◽

Cited By ~ 2

Author(s):

T. Eidhammer ◽

T. Deshler

Keyword(s):

Particle Size ◽

Nitric Acid ◽

Size Distribution ◽

Technical Note ◽

Ternary Solution ◽

Slow Evaporation ◽

Partial Pressures ◽

Polar Stratospheric Cloud ◽

Stratospheric Clouds

Abstract. In December 2001 and 2002 in situ aerosol measurements were made from balloon-borne platforms within polar stratospheric clouds (PSC) which contained particles of supercooled ternary solution (STS), nitric acid trihydrate (NAT) and ice. Particle size and number concentrations were measured with two optical particle counters. One of these included an ~80cm inlet heated to K to evaporate the PSC particles and thus to obtain measurements, within PSCs, of the size distribution of the particles upon which the PSCs condensed. These measurements are compared to models, described here, that calculate the evaporation of PSC particles at and for an inlet transition time of about 0.1s. The modeled evaporation for STS agrees well with the measurements. For NAT the modeled evaporation is less than the evaporation measured. The primary uncertainty concerns the phase and morphology of NAT particles as they are brought to temperatures >50K above equilibrium temperatures for NAT at stratospheric partial pressures. The slow evaporation of NAT in heated inlets could be used to identify a small NAT component within a mixed phase PSC dominated by STS.

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Particle Size Distribution and Morphology of in Situ Suspension Polymerized Toner

Industrial & Engineering Chemistry Research ◽

10.1021/ie0301029 ◽

2003 ◽

Vol 42 (22) ◽

pp. 5568-5575 ◽

Cited By ~ 27

Author(s):

Jun Yang ◽

Ting-Jie Wang ◽

Hong He ◽

Fei Wei ◽

Yong Jin

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution

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Effect of Grain Size Distribution on Recrystallisation Kinetics in an Fe-30Ni Model Alloy

Metals ◽

10.3390/met9030369 ◽

2019 ◽

Vol 9 (3) ◽

pp. 369 ◽

Cited By ~ 1

Author(s):

Mo Ji ◽

Claire Davis ◽

Martin Strangwood

Keyword(s):

Grain Size ◽

Size Distribution ◽

Grain Size Distribution ◽

Cold Deformation ◽

Avrami Exponent ◽

Model Alloy ◽

Avrami Parameter ◽

In Situ Heating

This paper discusses the role of grain size distribution on the recrystallisation rates and Avrami values for a Fe-30 wt. % Ni steel, which was used as a model alloy retaining an austenitic structure to room temperature. Cold deformation was used to provide uniform macroscopic strain distributions (strains of 0.2 and 0.3), followed by recrystallisation during annealing at 850–950 °C. It was shown that the Avrami parameter was directly related to the grain size distribution, with a lower Avrami exponent being seen for a larger average and wider grain size distribution. A method to predict the Avrami exponent from the grain size distribution was proposed. In situ heating in an SEM with EBSD showed the recrystallisation kinetics to be affected by differences in stored energy and nucleation in the different grain sizes supporting the proposed relationship.

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