Particle Size Distribution Measurements Research Articles

Fluorescence Lifetime and Intensity of Thioflavin T as Reporters of Different Fibrillation Stages: Insights Obtained from Fluorescence Up-Conversion and Particle Size Distribution Measurements.

Thioflavin T (ThT) assay is extensively used for studying fibrillation kinetics in vitro. However, the differences in the time course of ThT fluorescence intensity and lifetime and other physical parameters of the system, such as particle size distribution, raise questions about the correct interpretation of the aggregation kinetics. In this work, we focused on the investigation of the mechanisms, which underlay the difference in sensitivity of ThT fluorescence intensity and lifetime to the formation of protein aggregates during fibrillation by the example of insulin and during binding to globular proteins. The assessment of aggregate sizes and heterogeneity was performed using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Using the sub-nanosecond resolution measurements, it was shown that the ThT lifetime is sensitive to the appearance of as much as a few percent of ThT bound to the high-affinity sites that occur simultaneously with an abrupt increase of the average particle size, particles concentration, and size heterogeneity. The discrepancy between ThT fluorescence intensity and a lifetime can be explained as the consequence of a ThT molecule fraction with ultrafast decay and weak fluorescence. These ThT molecules can only be detected using time-resolved fluorescence measurements in the sub-picosecond time domain. The presence of a bound ThT subpopulation with similar photophysical properties was also demonstrated for globular proteins that were attributed to non-specifically bound ThT molecules with a non-rigid microenvironment.

Particle Size Distribution Measurements of Neat and Water-Emulsified Oxymethylene Ethers in a Heavy-Duty Diesel Engine

Diesel-fueled compression ignition engines display a distinct trade-off in particulate matter (PM) and nitrogen oxide (NOX) emissions due to the nature of diffusive combustion. The modification of fuel properties has drawn much attention since these methods offer additional potential to reduce emissions. Oxygenated fuels are reported to greatly diminish particle emissions while water emulsification of regular diesel causes a significant decrease in NOX. However, recent studies indicate that these fuel-based approaches may lead to an increase in nanoparticle emissions, which are known to be more dangerous to human health than large particles. This has raised the question about whether current engine technology is prone to nanoparticle formation.In this work, the authors present a detailed study on combustion and emission performance of the oxygenate fuel Oxymethylene Ether (OMEn, the mixture contains neat OME with chain length n = 2 − 6). In a novel approach, a single-cylinder heavy-duty diesel engine was fueled with both neat and water-emulsified OME to combine the two fuel-based methods in order to simultaneously reduce both NOX and particle emissions to a great extent. Particular emphasis was put on the particle size distribution (PSD) of emitted PM to elaborate a potentially severe drawback of these fuel-based approaches. In the process, hydrogenated vegetable oil (HVO) was used as the diesel reference fuel. The findings are summarized as such: PSD measurements of OME2-6 reveal similar particle diameters in mid-load operation and a shift to smaller particles at unfavorable engine operations compared to HVO. Water-emulsified OME2-6 reduces NOX by roughly 2-3% with a one percent increase in water concentration while maintaining a nearly constant combustion efficiency. Adverse effects on nanoparticle formation by water emulsification were not observed.

Non-destructive quantification of fragmentation within tablets after compression from scattering analysis of terahertz transmission measurements.

Material deformation behaviour has a critical impact on tablet formation. Fragmentation is one of the key mechanisms affecting the strength of a final compact, however, quantitative methods for estimating fragmentation are often complex, destructive and time-consuming. The purpose of this study was to investigate the applicability of terahertz time-domain spectroscopy (THz-TDS) to quantify fragmentation upon tableting. Up to five size fractions of microcrystalline cellulose (MCC), dibasic calcium phosphate (DCP), and lactose monohydrate (lactose) in the range of <125µm up to the range of 355-500µm were compressed into tablets and analysed with THz-TDS. The effective refractive index and absorbance spectra of whole tablets were measured in transmission, and the optical properties were clearly affected by fragmentation upon compression. The scattering observed from the absorbance spectra was fitted into a power law equation (y=AνB). It was observed that up to pressures of 50MPa the values of parameter A that were extracted from the power law fit decreased exponentially with increasing compression pressure. For higher compression pressures the value of A remained constant. This observation was more pronounced for DCP, followed by lactose and then MCC and the effect was more pronounced for larger compared to smaller initial particles. The non-destructive measurements correlated with previously obtained results based on particle size distribution measurements of the particles before compression and those obtained from destructive analysis of tablets. The terahertz method can resolve similar differences in fragmentation behaviour upon compression compared to the particle size analysis but requires no sample preparation.

Developing a novel colloidal model for predicting asphaltene precipitation from crude oil by alkane dilution

This research aims to propose a thermodynamic model for predicting asphaltene precipitation upon diluting a crude oil with a paraffinic solvent. To this end, a thorough mathematical formulation was carried out to derive a novel micellization model based on the associative properties of asphaltenic compounds. It was assumed that asphaltenes exist in the oil both as monomeric molecules and aggregated cores; with stabilization latter by attachment of resin on its periphery. The aggregation equilibrium was established by taking into account asphaltene's lyophobic tendency, heat of resin adsorption, and interfacial tension between micelle and oil media which is the main driving factor contributing to Gibbs free energy of micellization. In this study, the mean diameter of asphaltene aggregates at different dilution ratios was incorporated into the framework of modeling approach, by measuring particle size distribution of asphaltenes at varying n-heptane fractions. The data density of pure asphaltene for an Iranian crude-oil sample was used in calculations. The proposed model favorably predicted the precipitation trend of the crude oil diluted at varying fractions of n-heptane. This model shows that taking into account the size of asphaltene aggregates can significantly improve the prediction accuracy of the micellization model, compared to the simple model, with normalized root-mean-square error of 9.4 and 28.7, respectively. A detailed sensitivity analysis was performed to gain insight into physical implication of the model parameters.

Nonvolatile ultrafine particles observed to form trimodal size distributions in non-road diesel engine exhaust

Some recent findings regarding the negative health effects of particulate matter increase the relevance of the detailed characteristics of particulate emissions from different sources and especially the nonvolatile fraction of particles. In this study, the nonvolatile fraction of ultrafine particulate emissions from a non-road diesel engine was studied. The measurements were carried out in an engine laboratory and the exhaust sample was taken from the engine-out location with various steady state driving modes. Four different fuels, including fossil fuel, soybean methyl ester (SME), rapeseed methyl ester (RME), and renewable paraffinic diesel (RPD), were used. In the sampling system, the sample was diluted and led through a thermodenuder removing the volatile fraction of particles. The measured particle size distributions of nonvolatile particles were found to be trimodal. Based on the size distribution data as well as the morphology and elemental composition of particles in transmission electron microscopy (TEM) samples, we were able to draw conclusions from the most probable origin of the different particle modes, and the modes were named accordingly. From larger to smaller in particle size, the modes were a soot mode, lubricating oil originated core (LC) mode, and a fuel originated core (FC) mode. All of these three modes were detected with every driving mode, but differences were seen, for example, between different fuels. In addition, a trade-off was observed in the concentrations of the LC mode and the soot mode as a function of the engine torque.

Sampling and conditioning of engine blow-by aerosols for representative measurements by optical particle counters

Particle size distributions (PSDs) of engine blow-by aerosol are commonly obtained with an optical particle counter (OPC), but representative measurements are challenging due to high number concentrations, elevated temperatures, presence of saturated vapor, as well as unsteady flow conditions. A comprehensive study of blow-by aerosol sampling/conditioning and OPC performance in such an environment was therefore conducted, based on a commercial OPC (Palas Promo 2000).Single (1:9) and double-stage (1:80) sampling/dilution/conditioning systems were devised and their transfer functions characterized in the OPC sensor range of 0.3–17 μm. With (mostly inertial) particle losses >90% at 10 μm, correcting for them was crucial for reliable PSD measurements. The effect of saturated oil vapor on droplet growth during cool-down and dilution of the sample flow was investigated between 80 and 120 °C, based on actual vapor concentration data. Without dilution, droplet growth became significant above 100 °C while diluting 1:20 with 20 °C air suppressed growth.Tests of over-all sampling and dilution strategy with engine blow-by aerosol gave excellent reproducibility and good agreement (after loss corrections) with reference data regarding PSD in the 0.3–10 μm range as well as total mass. The actual engine blow-by PSD was significantly broader though, exceeding the OPC range on both ends. Number-to-mass conversion of OPC data under-reported total mass by 10%–20% (depending on sensor range) compared to weighed filter samples, provided OPC contamination with oil deposits was avoided. A re-calibration procedure is proposed to deal adequately also with pressure pulsations resulting from engine operation.

Bovine colostrum whey: Postpartum changes of particle size distribution and immunoglobulin G concentration at different filtration pore sizes

Bovine colostrum, as vital as it is for calves, is also a valuable source of functional components with rich health benefits for humans. Bovine colostrum whey consists of a large number of bioactive proteins and peptides. The most abundant of these is IgG. Particle size distribution (PSD) is an important feature of many of the processes in the dairy food industries. Despite this, scientific literature on PSD of colostrum whey is scarce. The goal of this research was to describe bovine colostrum whey PSD with an emphasis on postpartum milking time, filtration (pore size 450, 100, and 20 nm), IgG concentration, and lactation number. For this purpose, 4 postpartum milking colostrum samples were sequentially milked from 46 Holstein cows at 12 ± 1 h intervals. Colostrum whey was prepared by renneting and diluted (1:200) for PSD analyses by a Malvern Zetasizer Nano ZS (Malvern Instruments Ltd., Malvern, UK). Immunoglobulin G concentration of these diluted colostrum whey samples were analyzed by an Octet K2 (Molecular Devices LLC, San Jose, CA) system. Linear mixed model analysis revealed significant effects of filter pore size, postpartum milking, and lactation on colostrum whey IgG concentrations. The percentage of particles in the size interval 5 to 15 nm (the hydrodynamic diameter of IgG is around 10 nm) had an intermediate positive correlation (r = 0.50) with IgG concentration. Furthermore, we showed that PSD was associated with IgG concentration, postpartum milking time, and lactation number. The PSD measurement results showed the mean hydrodynamic diameter of 100 nm pore size filtered colostrum whey to be around 10 nm. This, with the IgG concentration results, suggests that even though the size of IgG is around 10 nm, a 100 nm pore size is adequate for membrane-involved IgG separations. In terms of energy efficiency of the filtration process, the use of a larger filter pore size can make a remarkable difference, for example, in pressurizing and cooling costs. Our work contributes to the development of sustainable and widely available colostrum-derived food and feed supplements.

Formulation and evaluation of β-cyclodextrin polymer microspheres for improved HTHP filtration control in water-based drilling fluids

β-cyclodextrin polymer (β-CDP) microspheres were investigated as high temperature resistant filtration reducers for water-based drilling fluid in this study. The microspheres were synthesized by crosslinking reaction between β-CD and epichlorohydrin with inverse emulsion polymerization. The structural and morphological characteristics of the prepared microspheres were examined by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), particle size distribution measurement, and thermogravimetry analysis (TGA). The filtration control properties of the microsphere were evaluated via American Petroleum Institute (API) filtration test and high temperature and high pressure (HTHP) filtration test. The results indicated that β-CDP microspheres could effectively reduce the filtration of bentonite suspension both before and after thermal aging at 200 °C without significant influence on drilling fluid's rheology. A substantially enhanced filtration control behavior was observed after thermal aging, which was contrary with conventional filtration reducers. The β-CDP microspheres could absorb a large number of water and became swellable and deformable, which enhanced the compressibility of filter cake. What is more, hydrothermal reaction occurred for part of β-CDP microspheres under high temperature environment, resulting in the formation of numerous carbon spheres ranging from hundreds of nanometers to several micrometers. The β-CDP microspheres, bentonite particles and small carbon spheres in combination contributed to form a dense and compact filter cake with low permeability. β-CDP microspheres were potential candidates as environmental friendly and high temperature filtration reducers in deep well drilling.

Isolation, purification, structure characterization of a novel glucan from Huangshui, a byproduct of Chinese Baijiu, and its immunomodulatory activity in LPS-stimulated THP-1 cells

Huangshui (HS) has attracted considerable attention for the utilization of aroma compounds and microorganisms containing presently. However, little work has been done on biological polysaccharides in HS. In this study, a novel water-eluted HS polysaccharide, HSP-W, was identified as an α-D-glucan with a Mw of 166.00 kDa. It was consisted of a 1,4 linked α-D-Glcp backbone with the substitution at O-6 with 1,6-linked α-D-Glcp residue and non-reducing terminal of β-Glc-1→ through monosaccharide composition, IR, methylation, and NMR analyses. SEM, AFM, and particle size distribution measurements showed that HSP-W had relatively clustered spherical shape with different sizes from nanoscale to micrometer. Additionally, HSP-W significantly induced NO and ROS production as well as the release of IL-1β, IFN-γ, TNF-α, and IL-6, and upregulated pinocytic and phagocytic capacities of THP-1 cells. Meanwhile, HSP-W treatment markedly enhanced mRNA and protein expressions of these cytokines. HS probably has potential application as an immunostimulatory agent.

Control foaming performance of phosphate rocks used for wet-process of phosphoric acid production by phosphoric acid

Wet-process of phosphoric acid production generates significant amounts of foam which limit plant production efficiency. The control of foaming performance of phosphate rocks and defoaming mechanism has been studied by foaming performance test, X-ray powder diffraction analysis, X-ray fluorescence analysis, contact angle measurement and particle size distribution measurement respectively. The results show that carbonate minerals were digested easily than apatite in phosphoric acid solution. The maximum foam volume (MFV) and equilibrium foam volume (EFV) of phosphate rock could effectively be reduced by Phosphoric acid pretreatment. Pretreatment time and solid content of slurry play a vital role in defoaming process as well. The defoaming efficiency of phosphoric acid was as good as commercial defoamer DF. The foaming performance of phosphate rocks is in directly proportional to the content of carbonate minerals. The defoaming mechanism of phosphoric acid should be attributed to the selective digestion of carbonate minerals in phosphate rocks, not due to the slight change of particle size distribution and surface wettability of phosphate rock.

Comparison of Various Particle-Size Distribution-Measurement Methods

Summary Sieve analysis, sedimentation, and laser diffraction (LD) have been the methods of choice in determining particle-size distribution (PSD) for sand control design. However, these methods do not provide any information regarding the particle shape. In this study, we introduce the application of dynamic image analysis (DIA) to characterize particle sizes and shape descriptors of sand-bearing formations. DIA, which is an advanced method of particle size and shape characterization, along with other PSD measurement methods, including sieving, sedimentation, and LD, were used to study size and shape variations of 372 unconsolidated formation sand samples from North America, Latin America, and the Middle East. Different methods were compared in the estimation of PSD and fines content, which are the primary factors important in sand-control design. Through minimizing the sampling and measurement errors, the deviation between different PSD measurement techniques was attributed solely to the shape of the particles and the amount of fine fraction. For fines-content measurement, the values obtained through Feret min parameter values (the minimum size of a particle along all directions) calculated by DIA and sieving measurement are comparable within a 5% confidence band. The deviation between the results of different methods becomes more significant by increasing fines content. Moreover, this deviation increases for less isodiametric grains. The fines and clay content show higher values when measured by any wet analysis. LD also tends to overestimate the fines fraction and underestimate silt/sand fraction compared with other dry techniques. By comparing the deviation of the DIA and sieving at standard mesh sizes, an algorithm has been developed that chooses the equivalent sphere sizes of DIA with minimum deviation from sieving. This study performs several measurements on formation sands to illustrate the real advantage of the new methods over traditional measurement techniques. Furthermore, particle-shape descriptors were used to explain the deviation between the results of different PSD measurement methods.

Evaluation of Particle Size Distribution Metrics to Estimate the Relative Contributions of Different Size Fractions Based on Measurements in Arctic Waters.

The size distribution of suspended particles influences several processes in aquatic ecosystems, including light propagation, trophic interactions, and biogeochemical cycling. The shape of the particle size distribution (PSD) is commonly modeled as a single‐slope power law in oceanographic studies, which can be used to further estimate the relative contributions of different particle size classes to particle number, area, and volume concentration. We use a data set of 168 high size‐resolution PSD measurements in Arctic oceanic waters to examine variability in the shape of the PSD over the particle diameter range 0.8 to 120 μm. An average value of −3.6 ± 0.33 was obtained for the slope of a power law fitted over this size range, consistent with other studies. Our analysis indicates, however, that this model has significant limitations in adequately parameterizing the complexity of the PSD, and thus performs poorly in predicting the relative contributions of different size intervals such as those based on picoplankton, nanoplankton, and microplankton size classes. Similarly, median particle size was also generally a poor indicator of these size class contributions. Our results suggest that alternative percentile diameters derived from the cumulative distribution functions of particle number, cross‐sectional area, and volume concentration may provide better metrics to capture the overall shape of the PSD and to quantify the contributions of different particle size classes.

Layered Double Hydroxides with Intercalated Permanganate and Peroxydisulphate Anions for Oxidative Removal of Chlorinated Organic Solvents Contaminated Water

The contamination by chlorinated organic solvents is a worldwide problem as they can deeply penetrate aquifers, accumulating in the sub-surface as lenses of highly hazardous pollutants. In recent years, so called in situ oxidation processes have been developed to remediate chlorinated organic solvents from groundwater and soil by injecting solutions of oxidising agents such as permanganate or peroxydisulphate. We here present modified layered double hydroxides (LDHs) with intercalated oxidising agents that might serve as new reactants for these remediation strategies. LDHs might serve as support and stabiliser materials for selected oxidising agents during injection, as the uncontrolled reaction and consumption might be inhibited, and guarantee that the selected oxidants persist in the subsurface after injection. In this study, LDHs with hydrotalcite- and hydrocalumite-like structures intercalated with permanganate and peroxydisulphate anions were synthesised and their efficiency was tested in batch experiments using trichloroethene or 1,1,2-trichloroethane as the target contaminants. All samples were characterised using powder X-ray diffraction, thermal analysis coupled with mass spectrometry to directly analyse evolving gases, and Fourier-transform infrared spectroscopy. Additionally, particle size distribution measurements were carried out on the synthesised materials. Results of the batch experiments confirmed the hypothesis that oxidising agents keep their properties after intercalation. Permanganate intercalated LDHs proved to be most efficient at degrading trichloroethene while peroxydisulphate intercalated Ca,Al-LDHs were the most promising studied reactants degrading 1,1,2-trichloroethane. The detection of dichloroethene as well as the transformation of the studied reactants into new LDH phases confirmed the successful degradation of the target contaminant by oxidation processes generated from the intercalated oxidising agent.

Method for the determination of preferential orientation of marine particles from laser diffraction measurements.

In situ laser diffractometry (LD) is increasingly used in oceanographic studies to estimate sediment transport, particle fluxes and to assess the concentration of marine phytoplankton. It enables an accurate characterization of the size distribution of suspended particles from the scattering signal produced by their interaction with a collimated laser beam. LD reliably reflects the sizes of suspensions dominated by nearly spherical particles; however, when complex particle morphologies dominate the suspension (e.g. phytoplankton) the resulting particle size distribution (PSD) may present significant variations attributed to different factors. In particular, the orientation of non-spherical particles - which abound in the sea - modifies LD measurements of PSDs. While this may be interpreted as a drawback for some studies (i.e. when precise measurement of the volume concentration is required), we propose that detailed analysis of this signal provides information on particle orientation. We use PDMS micropillars with prescribed elliptical cross-sections to experimentally determine the dependence between the spatial orientation of elongated particles and changes in the PSD measured with a LISST laser diffractometer. We show that LD can be used to adequately characterize the different dimensions of the non-spherical particles at specific orientations. Using this property, we describe and validate a method to infer the preferential orientation of particles in the sea. Our study opens new perspectives in the use of in-situ LD in ocean research.

In Situ Microphysical Observations of a Multicell Storm Using a Balloon‐Borne Video Disdrometer During Deep Convective Clouds and Chemistry

AbstractThe microphysical characteristics of severe storms and deep convection are challenging but critical in situ observations. Adjustments to modeled microphysical parameters, radar‐based hydrometeor classifications, and lightning initiation research all depend on an accurate depiction of real‐world particle size distributions. To obtain these observations, a balloon‐borne particle imaging device known as the Particle Size, Image, and Velocity probe has been developed at the National Severe Storms Laboratory that is capable of measuring particle size distributions of different particle habits on vertical scales as small as 50 m. The Particle Size, Image, and Velocity observations show that there are rapid shifts in particle counts between successive analysis layers, documenting the small‐scale heterogeneity present inside deep convection. Furthermore, when examining functional fits using both a two and three moment scheme on the total distribution as well as individual particle habits, it is clear that a single prescribed parameter space is not adequate to describe the observations collected. When comparing radar reflectivity calculated from the distribution to independent observations from ground based mobile radars, the two sources agree to within 5 dBZ. This provides confidence to the particle density assumptions made here.

Statistical/Numerical Model of the Powder-Gas Jet for Extreme High-Speed Laser Material Deposition

Extreme high-speed laser material deposition, known by its German acronym EHLA, is a new variant of laser material deposition (LMD) with powdered additives. This variant’s process control is unlike that of LMD, where the powder melts as it contacts the melt pool. In the EHLA process, the laser beam melts the powder above the surface of the substrate to deliver a liquid to the melt pool. At a given intensity distribution in a laser beam, the heating of powder particles in the beam path depends largely on the three-dimensional powder particle density distribution (PDD) and the relative position within the laser beam caustic. As a key element of a comprehensive numerical process model for EHLA, this paper presents a statistical/numerical model of the powder-gas jet, as previously published in Experimentelle und modelltheoretische Untersuchungen zum Extremen Hochgeschwindigkeits-Laserauftragschweißen. The powder-gas jet is characterized experimentally and described with a mathematical model. This serves to map the PDD of the powder-gas flow—and particularly the particle trajectories for different grain fractions—as well as the powder mass flows and carrier and inert gas settings, to a theoretical model. The result is a numerical description of the particle trajectories that takes into account the measured particle size distribution with calculations made on the assumption of a constant particle velocity and linear trajectories of the particles.

Physicochemical Properties and Resistant Starch Content of Corn Tortilla Flours Refrigerated at Different Storage Times.

The tortilla is a foodstuff that has a short shelf-life, causing great losses to the industry. The objective of this work was to evaluate, for the first time, the physicochemical properties and resistant starch (RS) content of flours. These were obtained from nixtamalized corn tortillas made with traditional and industrial (commercial) methods, stored at 4 °C for 7, 15, and 30 days. The flours were characterized by measuring particle size distribution, color, water absorption index (WAI), water solubility index (WSI), viscosity, calcium, and RS content. Additionally, chemical proximate analysis, scanning electron microscopy (SEM), and thermal analysis were conducted. Storage at 4 °C increased the friability of tortillas and shifted the particle size distribution toward a greater content of coarse particles in corn tortilla flours. The commercial corn tortilla flours showed higher WAI and WSI values than the traditional corn tortilla flours. On the other hand, the traditional corn tortilla flours exhibited higher RS content values than commercial corn tortilla flours as well as peak viscosity. X-ray diffractograms revealed the presence of amylose-lipid complexes (RS5) in experimental samples. The thermograms evidenced three endotherms corresponding to corn starch gelatinization and melting of type I and type II amylose–lipid complexes.

Development of a new nanoparticle sizer equipped with a 12-channel multi-port differential mobility analyzer and multi-condensation particle counters

Abstract. Measuring particle size distributions precisely is an important concern in addressing environmental and human health-related issues. To measure particle size distributions, a scanning mobility particle sizer (SMPS) is often used. However, it is difficult to analyze particle size distributions under fast-changing concentration conditions because the SMPS cannot respond fast enough to reflect current conditions due to the time necessary for voltage scanning. In this research, we developed a new nanoparticle sizer (NPS), which consists of a multi-port differential mobility analyzer (MP-DMA) with 12 sampling ports and multi-condensation particle counters (M-CPCs) that simultaneously measure concentrations of particles classified by the sampling ports. The M-CPC can completely condense particles larger than 10 nm, and the total particle concentrations measured by each CPC in the M-CPCs and an electrometer were in agreement up to 20 000 no.cm-3. We conducted size distribution measurements under steady-state conditions using an aerosol generator and under unsteady conditions by switching the aerosol supply on or off. The data obtained by the NPS corresponded closely to the SMPS measurement data for the steady-state particle concentration case. In addition, the NPS could successfully capture the changes in particle size distribution under fast-changing particle concentration conditions. Finally, we present NPS measurement results of size distributions in a common situation (cooking) as an exemplary real-world application.

Comparison of standardized sampling and measurement reference systems for aircraft engine non-volatile particulate matter emissions

The International Civil Aviation Organization has established new regulatory standards for emissions certification of non-volatile particulate matter (nvPM) from aircraft turbine engines. The adoption of the nvPM emissions regulatory standards required development of a standardized sampling and measurement methodology, and rigorous testing. Three reference systems for aircraft engine nvPM emissions measurement, compliant with the specifications for the standardized methodology, were independently developed. This paper reports the results of the first inter-comparison of these three reference systems using a CFM56-7B26/3 aircraft engine to establish repeatability and intermediate precision of the sampling and measurement systems as part of the multi-agency international collaborative projects: Aviation-Particle Regulatory Instrumentation Demonstration Experiment (A-PRIDE) 5/Studying, sAmpling and Measuring of aircraft ParticuLate Emissions (SAMPLE) III - SC03. The instruments used in the three reference systems recorded nvPM mass and number concentration, which were converted to their respective emission indices for comparison. The reference systems generally agreed to within 15% of the average nvPM number emission index and 30% of the average nvPM mass emission index. The only exception was for the nvPM mass instruments, which exhibited a higher variation as the concentration levels approached the limit of detection. The additional measured particle size distributions could be approximated to lognormal distributions with the geometric mean diameter ranging from 15 nm to 38 nm, and the geometric standard deviation varying between 1.53 and 1.92. The results from this study are a benchmark for the variability in standardized sampling and measurement systems for measuring aircraft engine nvPM emissions.

Preparation and characterization of stable fluorescent As4S4/ZnS/Fe3O4 nanosuspension capped by Poloxamer 407 and folic acid

Novel drug delivery systems containing advanced materials are currently the focus of many scientists, particularly in the field of medicine. Nowadays, these materials can play an important role when the authors talk about human health and especially the need to develop personalized treatment. In this work, multiparticulate As4S4/ZnS/Fe3O4 nanocomposite based on components possessing promising therapeutic, photoluminescent, and magnetic functionality was prepared by the milling. Subsequently, it was covered with the bio-compatible polymer Poloxamer 407 and/or folic acid for the functionalization of inorganic material. The samples were studied from the structural (X-ray powder diffraction analysis), magnetic, and optical (UV–Vis and photoluminescence spectroscopies) point of view. Particle size distribution and zeta potential measurements were performed to determine long-term stability of these nanosuspensions. Fourier transform infrared spectroscopy was used to identify bonding between organic and inorganic entities. Prominent optical fluorescence properties were found in a sample containing folic acid.