Geometric Mean Diameter Research Articles

Impact of engineering properties of grass seeds in developing post-harvest operations and machineries

Engineering properties of grass seeds are most important for the development of post-harvest mechanization and operations. Therefore engineering properties of fluffy as well as true seeds were determined in view of its important in development of post-harvest mechanization. The mean values of length, width, thickness, arithmetic mean diameter, geometric mean diameter, sphericity, surface area, volume, thousands seed mass and bulk density of fluffy Deenanath grass seed were observed in the range of 5.23-7.17 mm, 2.10-3.44 mm, 1.17-2.49 mm, 3.07- 4.13 mm, 2.53- 3.69 mm, 41.01-60.13 %, 19.12-43.70 mm2, 3.70-18.24 mm3, 0.789-0.849 g and 7.41-7.89 kg/m3 respectively. However, for true seeds of Deenanath grass, the range of these values varied from 2.23-2.65 mm, 0.69-0.95 mm, 0.47-0.69 mm, 1.16-1.40 mm, 0.93-1.17 mm, 38.69-47.33 %, 2.67-4.31 mm2, 3.60-9.64 mm3, 0.468-0.488 g and 602.97-624.29 kg/m3 respectively moisture level of 9 % db. Determined properties of fluffy as well as true seeds of Deenanath would be utilized to develop threshing, cleaning, grading, seed storage and packaging operations and machineries.

Molecular size of surfactants affects their degree of enrichment in the sea spray aerosol formation

Sea spray aerosol (SSA), the largest source of natural primary aerosol, plays an important role in atmospheric chemical processes and the earth radiation balance. Its formation process is controlled by many factors. In this study, ethylene glycol (EG) and polyethylene glycol (PEG) with three different molecular weights (200, 400, 600) were used to investigate the influence of molecular size on the properties of submicron SSA produced by plunging jet from an adjustable home-built SSA generator. Different parameters were tested to obtain the optimum experimental conditions. The addition of EG and PEG inhibited the production of SSA and increased the geometric mean diameter (GMD) between 10 and 35 nm. However, PEG with a molecular weight of 600 could promote the production of SSA at higher concentrations, which means that the molecular weight and concentration of the polymer would affect the production efficiency of SSA. Combining with the measurement of surface tension, we found no clear relationship between surface tension and the yield of SSA, due to the properties of the substances themselves. Transmission electron microscopy images show that the addition of EG and PEG could significantly change the structure of salt nuclei in SSA. PEG was significantly enriched in SSA (with enrichment factors within the range 92.9–133.4), and the enrichment was independent of the sampling time, while increasing with the increase of molecular weight. Our results highlight the influence of polymer molecular weight on the properties of SSA, and their importance to improve the accuracy of aerosol emission model parameters.

Experimental study of castor oil–diesel–n-butanol blends used in a CRDI diesel engine with double injection strategy

ABSTRACT In the present study, experimental investigations were carried out on a diesel engine fuelled with castor oil–diesel–n-butanol blends to determine the combustion characteristics and emissions. In comparison with diesel fuel, the blends represented the retarded start of combustion (SOC), the higher peak in-cylinder pressure and heat release rate, and the shortened combustion duration. The brake-specific fuel consumption of the blends was higher by 7% for CD80B20, and 11% for CD60B40, respectively, whereas the difference of the brake thermal efficiency was less than 3%. The blends exhibited bi-modal particle size distribution (PSD), and diesel showed uni-modal behaviour under all operating conditions. The total number concentration of blends was larger, but the geometric mean diameters were 83, 47 and 40 nm for diesel fuel, CD80B20 and CD60B40, respectively. Nitrogen oxide emissions of the blends were higher by 14% and slightly increased with the growth of n-butanol content in the blends. Carbon monoxide (CO) and hydrocarbon (HC) emissions were decreased at 1000 r/min and increased at 1400 r/min.

Determination of Natural Flow Rates of Some Chickpea Varieties on Different Surfaces and Surface Angles

In this study, some physical properties of Gökçe chickpea (registered variety) and Spanish chickpea (local population) variety cultivated in Konya Province were determined. Flow rates of chickpea varieties were detected at four different conveyor channel angles (24°, 28°, 32° and 36°) and on three different surfaces (galvanized sheet, painted sheet and steel sheet surfaces). Length, width, thickness, geometric mean diameter, sphericity, repose angle, thousand grain weight, bulk density values of Gökçe chickpeas at 8.90% moisture level are 10.09 mm, 7.34 mm, 7.74 mm and 8.30 mm, 0.82, 18.04°, 364.6 g and 746.82 kg m -3 and for Spanish variety at 10.40% moisture level are 12.16 mm, 8.22 mm, 9.01 mm, 9.65 mm, 0.79, 16.01°, 481.96 g, 690.21 kg m -3 were determined respectively. These varieties, the static friction coefficient values on galvanized sheet, painted sheet and steel sheet surfaces were found to be 0.335 and 0.351, 0.401 and 0.445, 0.388 and 0.435, respectively. Flow rates increased as the channel conveyor angle increased on galvanized sheet, painted sheet and steel sheet surfaces. The increase rates for Gökçe and Spanish chickpeas on these surfaces were 207% and 189%, 630% and 522%, 291% and 202%, respectively. When the surface averages are taken into account, average flow rates of 1.69 kg s -1 on the galvanized sheet surface, 1.24 kg s -1 on the painted sheet surface and 1.54 kg s -1 on the steel sheet surface were obtained and found to be statistically significant. The difference between the surfaces is due to the roughness values of the surfaces. The lowest average roughness value was found on the galvanized sheet surface (1.13 µm), and the highest on the painted surface (2.06 µm). According to the triple interaction results, the highest flow rate value was obtained on the galvanized sheet surface and the conveyor angle of 36° in both chickpea varieties, and the lowest flow values were obtained at the conveyor angle of 24° on the painted sheet surface.

Growth Analysis of Untreated Meningiomas under Observation.

When meningiomas are small or asymptomatic, the decision to observe rather than treat requires balancing the growth potential of the lesion with the outcome and side effects of treatment. The aim of this study is to characterize the growth patterns of untreated meningiomas to better inform the clinical decision-making process. Patients with meningiomas were identified from 2005 to 2015. Those without treatment who had been followed for 1.5 years, with three magnetic resonance imaging (MRI) scans, were identified. Scans were measured with orthogonal diameters, geometric mean diameters, and volumes using the ABC/2 method. Regression modeling determined what growth pattern these parameters best approximated. Two hundred and fifteen MRI scans for 34 female (82.9%) and 7 male (17%) patients with 43 tumors were evaluated. Initial tumor volumes ranged from 0.13 to 9.98 mL. The mean and median initial volumes were 2.44 and 1.52 mL, respectively. Follow-up times ranged from 21 to 144 months, with a median of 70 months. There were 12 tumors (28%) whose growth rates were significantly greater than zero. For all tumors, use of a linear regression model allowed accurate prediction of the future size using prior data. Three-quarters of presumptive meningiomas managed conservatively do not grow significantly. The remainder have significant growth over time, and the behavior could be approximated with linear regression models.

Comparative study on combustion and particulate emissions for diesel-biodiesel and diesel-diglyme blends

Experiments were conducted on a 4-cylinder direct-injection diesel engine using ultralow sulfur diesel blended with biodiesel or diglyme to investigate the influence on combustion and particulate emission characteristics. Five biodiesel blends and five diglyme blends with oxygen concentrations of 2%, 4%, 6%, 8% and 10% were prepared respectively and tested separately at five engine loads of maximum torque speed of 2400 rpm with same boundary condition. With the increase of oxygen content, in-cylinder pressure and heat release curve advanced for both blends but the peak values were lower than of diesel, the trend was more obvious for diglyme blends. Besides combustion centre was slightly varied for biodiesel fuels but postponed significantly for diglyme blends. Meanwhile, smoke opacity, brake specific particulate emissions and the geometric mean diameter of particle decreased accompanying with the increase in soluble organic fraction proportion, and biodiesel blends had more obvious variations. In addition, the total particle number concentration and the particle smaller than 100 nm in diameter increased gradually and unidirectionally for biodiesel blended fuels, but for diglyme blends, the peak value of the total particle was found from the blend containing 2% oxygen and the particles from all diglyme blends were higher than that from diesel. Compared with biodiesel, diglyme fuels had more particulate and particles emissions on the same oxygen base.

Changes in soil aggregate stability and aggregate-associated organic carbon during old-field succession in karst valley.

Soil is the largest carbon pool whose change will have an impact on the terrestrial carbon cycle in the terrestrial ecosystem. Old-field succession on abandoned farmland, which usually has a noticeable effect on soil status, is a common phenomenon in karst valley where human activity alters frequently. In order to understand the changes in the accumulation of organic carbon (OC) in aggregates and bulk soil in different stages of old-field succession on abandoned farmland in the karst valley area, soil samples were collected at 0-10-cm and 10-20-cm depth representing three typical stages of old-field succession, i.e., abandoned farmland, secondary grass, and secondary shrub in Qingmuguan karst valley area, Chongqing City, Southwest China. Results displayed that during old-field succession (1) the mean weight diameter and geometric mean diameter of the aggregates increased and the fractal dimension decreased; (2) OC content within aggregates and bulk soil had no significant change in topsoil (0-10cm); OC content within microaggregates and bulk soil had a significant reduction in subsoil (10-20cm); the OC content within silt and clay fractions was significantly higher than that within the other two kinds of aggregates; (3) bulk-soil OC storage had no significant change but its accumulation relied more on the increase in the number of larger aggregates. It is concluded that the old-field succession in karst valley was beneficial to protect against soil erosion by improving soil aggregate stability, but had a limited effect on soil organic carbon sequestration.

Utilizing an electrical low-pressure impactor to indirectly probe water uptake via particle bounce measurements

Abstract. Secondary organic aerosol (SOA), formed through oxidation of volatile organic compounds (VOCs), displays complex viscosity and phase behaviors influenced by temperature, relative humidity (RH), and chemical composition. Here, the efficacy of a multi-stage electrical low-pressure impactor (ELPI) for indirect water uptake measurements was studied for ammonium sulfate (AS) aerosol, sucrose aerosol, and α-pinene-derived SOA. All three aerosol systems were subjected to greater than 90 % chamber relative humidity, with subsequent analysis indicating persistence of particle bounce for sucrose aerosol of 70 nm (initial dry diameter) and α-pinene-derived SOA of number geometric mean diameters between 39 and 136 nm (initial dry diameter). On the other hand, sucrose aerosol of 190 nm (initial dry diameter) and AS aerosol down to 70 nm (initial dry diameter) exhibited no particle bounce at elevated RH. Partial drying of aerosol within the lower diameter ELPI impaction stages, where inherent and significant RH reductions occur, is proposed as one explanation for particle bounce persistence.

Biochemical composition and shape-dimensional traits of rosehip genotypes

Abstract In the present study, the biochemical composition and shape and dimensional traits of 25 rosehip (Rosa canina) genotypes were investigated. The shape and dimensional traits were determined by image processing technique. Seed-propagated rosehip genotypes belonging to R. canina were collected from the natural flora of Mesudiye (Ordu) and Talas (Kayseri) districts. Antioxidant activity (39.510–72.673 mmol · kg−1), total flavonoids (287.80–1,686.20 mg quercetin equivalent (QE) · kg−1) and total phenolics (38,519.40–79,080.60 mg gallic acid equivalent · kg−1) of the genotypes exhibited large variations. Width (12.2 mm) and thickness (12.5 mm) of fruits averages were found to be close to each other. The genotypes exhibited fruit lengths between 12.0 mm and 29.5 mm. Average projected area at horizontal orientation (179.7 mm2) was greater than the projected area at vertical orientation (120.4 mm2). Sphericity average was calculated as 71.4%. According to principal component (PC) analysis, the most important dimensional traits discriminating genotypes from each other were identified as surface area, geometric mean diameter and volume. In terms of shape attributes, distinctive differences were observed in sphericity, circularity, elongation and surface closure rates (SCR) of the genotypes. According to elliptic Fourier analysis (EFA), genotypes look like a sphere. In terms of shape, there were long, spherical, flat bottomed, pointed bottomed and asymmetric-looking genotypes indicating how environment and genotype affect the fruit shape. The greatest shape variation was transverse contraction and expansion. According to the clustering analysis for shape attributes, rosehip genotypes were classified into six groups. Dendrogram, scatter plots of linear discriminant analysis and paired comparison test results put forth the shape differences of the genotype successfully.

Number concentration and size distribution of soot aerosols of heptane fire at low pressures

SummaryThe number concentration and size distribution of soot aerosols are imperative parameters in fire detection which is closely related to safety management, risk assessment, and fire analysis. The experiment of n‐heptane pool fire is conducted in a pressure chamber which simulates the 101, 90.9, 80.8, 70.7, 60.6, and 50.5 kPa environments. The influence of air pressure on the number concentration and size distribution of soot aerosols is investigated. The DMS500 fast particulate analyzer is used to analyze the number concentration and size distribution of gas samples. Both the geometric mean diameter and count median diameter of smoke particles increases with pressure. A second‐order polynomial equation with correlation coefficient of 0.99 is fitted to the geometric mean diameter of particles against pressure. The particle number concentration is significantly decreased when pressure is reduced according to a linear relationship with correlation coefficient of 0.92. The environmental pressure puts influence on the soot optical properties that affect fire smoke detection technologies used in the regions of different altitudes or air pressures.

A cross sectional study on airborne inhalable microorganisms, endotoxin, and particles in pigeon coops – Risk assessment of exposure

Pigeon breeding is associated with symptoms of the airways. The aim of this study is to illuminate the bacteriological and toxicological characteristics of airborne dust in pigeon coops. Airborne dust was sampled in 31 urban pigeon coops with homing and fancy pigeons, and following the dust was characterized. In total 141 different bacterial species were identified using MALDI-TOF MS, and of these 11 species are classified in risk group 2. Of the cultivable bacteria, Staphylococcus equorum was present in the highest concentration. Microorganisms in the dust were able to form biofilm, and the amount correlated positively with the number of bacteria. Next generation sequencing showed 180 genera with Acinetobacter in highest reads. On average 999 ± 225 ZOTUs were observed per sample with a Shannon-Wiener biodiversity index of 6.17 ± 0.24. Of the identified species the following have previously been suggested as causative agents of extrinsic allergic alveolitis: Alcaligenes faecalis, Bacillus subtilis, Pantoea agglomerans, Sphingobacterium spiritivorum, Thermoactinomyces sp., and Streptomyces albus. Staphylococcus was present on particles with sizes between 1.1 and > 7.0 μm with a geometric mean diameter of particles on 4.7 ± 1.1 μm. Concentrations of airborne endotoxin and dust were elevated compared to references, and the geometric mean concentrations were 102 EU/m3 and 1.07 mg dust/m3, respectively. Upon exposure to the airborne dust human granulocytes produced Reactive Oxidative Species during the first 5 min, and then no further reaction was observed. The concentrations of bacteria in general, Staphylococcus spp., and endotoxin and biodiversity were associated significantly with season, temperature and/or relative humidity, but not with type or density of pigeons. The bacterial composition and biodiversity indices were not affected by type of pigeon. In conclusion, the exposure to bacteria and endotoxin in pigeon houses should not be neglected in the evaluation of causative agents of airways symptoms among pigeon breeders.

Response of soil aggregate stability and erodibility to different treatments on typical steppe in the Loess Plateau, China

Vegetation restoration is an effective means to increase the stability of aggregates and the ability of soil to resist erosion. At present, there are few studies on soil aggregate stability in contour trench and fish‐scale pit grasslands (FPGs). Therefore, to determine the effects of different treatments on the stability of aggregates in the Loess Plateau, grazing grassland (GG), fencing grassland (FG), contour trench grassland (CG), and FPG were selected to compare distributions of soil aggregates, the soil aggregate stability, and soil erodibility K value. The results showed that <0.25‐mm and >5‐mm aggregates were the main components. The mass percentage of 5–0.25‐mm aggregates in FG was significantly higher than that in GG, CG, or FPG. The proportion of large water‐stable aggregates, mean weight diameter, and geometric mean diameter values were significantly higher in GG than in FG, CG, or FPG for topsoil, while FG had the highest WR0.25 (70.21%) for subsoil. The opposite trends were found for fractal dimension and percentage of aggregate destruction values. The K values for CG and FPG were found to be significantly higher than those for GG and FG. A correlation analysis indicated that soil organic carbon can promote the stability of soil aggregates. A negative correlation was found between the comprehensive score and K values. In summary, FG had positive effects on soil aggregate stability and erodibility. This finding can guide the local government to adopt enclosure measures when implementing ecological restoration of degraded grasslands.

Assessment of physical, microstructural, thermal, techno-functional and rheological characteristics of apple (Malus domestica) seeds of Northern Himalayas

In this research, two common apple seed cultivars Viz: ‘Golden Delicious’ (GD) and ‘Red Delicious’ (RD) of Northern Himalayan region were characterized for physical, techno-functional, microstructure, thermal, and rheological properties. Seeds showed a significant difference in width, arithmetic, and geometric mean diameters, volume, and surface area. Proximate analysis results revealed that seed flours have high oil content (> 20%) and are potentially rich sources of protein (> 40%). Color analysis of flours indicated their satisfactory whiter color with higher brightness values (L* ˃ 75), resulting from the reduced particle size which allows greater light penetration and relatively lower a* (< 1.5) and b* (< 11) values. Techno-functional attributes including water/oil absorption capacity, emulsifying capacity, and emulsion stability were significantly higher in RD than GD flour. There was also a significant difference in the average particle size of seed flours. Flour micrographs indicated the presence of oval/spherical-shaped starch granules embedded in dense protein matrix while, Differential Scanning calorimeter (DSC) revealed exothermic transition enthalpies for seed flours. Additionally, seed flours depicted high elastic modulus (G′), suggesting their suitability for modifying food texture. It was concluded that apple seeds exhibit significant potential for use in formulating protein-enriched foods while contributing to reducing industrial wastage.

Effects of different fertilizer application practices on newly reclaimed soil structure and its nutrient content

Effects of organic fertilizer practice (OF), organic fertilizer combined with chemical fertilizer practice (OC), and conventional fertilization practice (CF) on soil structure were evaluated by combining micro and macro analyses in newly reclaimed cultivated land. Soil organic matter (SOM), cation exchange capacity (CEC), soil bulk density (BD), soil moisture content (SMC), and aggregate stability were also analyzed. The CF soil structure was mainly composed of moderately separated block and angular structures with the minimum SOM (7.08 g/kg) and the highest BD (1.40 g/cm3), and the pore type was mainly simple surface cracks. Compared with CF, OF and OC significantly increased SOM content by 59.3 and 29.6% (p &lt; 0.05) and CEC by 13.5 and 5.2%, respectively. The newly reclaimed soil structure was improved to a moderately separated clump structure and a well-developed aggregated structure, and the number of composite accumulation pores gradually increased. Moreover, OF and OC were associated with higher mean weight diameter (MWD), geometric mean diameter (GMD) values, and lower BD and fractal dimension (D) values. The water-stable macroaggregates (R0.25) and the aggregate stability of newly reclaimed soil were significantly increased, with a stronger improvement observed under OF. These results confirm the benefits of OC and OF practices on the structural stability, water and fertilizer retention characteristics of newly reclaimed cultivated land, and will be conductive to improving the soil quality and achieving sustainable soil development. Bangladesh J. Bot. 50(3): 781-794, 2021 (September) Special

Kinetic time courses of inhaled silver nanoparticles in rats.

Silver nanoparticles (Ag NPs) are priority substances closely monitored by health and safety agencies. Despite their extensive use, some aspects of their toxicokinetics remain to be documented, in particular following inhalation, the predominant route of exposure in the workplace. A same experimental protocol and exposure conditions were reproduced two times (experiments E1 and E2) to document the kinetic time courses of inhaled Ag NPs. Rats were exposed nose-only to 20nm Ag NPs during 6h at a target concentration of 15mg/m3 (E1: 218,341 ± 85,512 particles/cm3; E2, 154,099 ± 5728 particles/cm3). The generated aerosol showed a uniform size distribution of nanoparticle agglomerates with a geometric mean diameter ± SD of 79.1 ± 1.88nm in E1 and 92.47 ± 2.19nm in E2. The time courses of elemental silver in the lungs, blood, tissues and excreta were determined over 14days following the onset of inhalation. Excretion profiles revealed that feces were the dominant excretion route and represented on average (± SD) 5.1 ± 3.4% (E1) and 3.3 ± 2.5% (E2) of the total inhaled exposure dose. The pulmonary kinetic profile was similar in E1 and E2; the highest percentages of the inhaled dose were observed between the end of the 6-h inhalation up to 6-h following the end of exposure, and reached 1.9 ± 1.2% in E1 and 2.5 ± 1.6% in E2. Ag elements found in the GIT followed the trend observed in lungs, with a peak observed at the end of the 6-h inhalation exposure and representing 6.4 ± 4.9% of inhaled dose, confirming a certain ingestion of Ag NPs from the upper respiratory tract. Analysis of the temporal profile of Ag elements in the liver showed two distinct patterns: (i) progressive increase in values with peak at the end of the 6-h inhalation period followed by a progressive decrease; (ii) second increase in values starting at 72h post-exposure with maximum levels at 168-h followed by a progressive decrease. The temporal profiles of Ag elements in lymphatic nodes, olfactory bulbs, kidneys and spleen also followed a pattern similar to that of the liver. However, concentrations in blood and extrapulmonary organs were much lower than lung concentrations. Overall, results show that only a small percentage of the inhaled dose reached the lungs-most of the dose likely remained in the upper respiratory tract. The kinetic time courses in the gastrointestinal tract and liver showed that part of the inhaled Ag NPs was ingested; lung, blood and extrapulmonary organ profiles also suggest that a small fraction of inhaled Ag NPs progressively reached the systemic circulation by a direct translocation from the respiratory tract.

Effects of different nitrogen application rates on soil water stable aggregates and N2O emission in winter wheat field.

Excessive nitrogen application would deteriorate soil structure and increase greenhouse gas emission. We set up six treatments, i.e., N0, N120, N180, N240, N300and N360(nitrogen application rates of 0, 120, 180, 240, 300 and 360 kg·hm-2, all straws returned into the field in situ) in the nitrogen fertilizer experimental site to investigate the effects of different nitrogen application rates on soil N2O emission, soil water-filled porosity (WFPS), soil temperature, nitrate and ammonium contents, composition and stability of water stable aggregates in winter wheat filed in 2018-2020. The results showed that there was a significant positive correlation between soil N2O emission and nitrogen application rate. There was no correlation between WFPS and nitrogen application rate. Soil temperature in the 0-10 cm layer decreased significantly with the increases of nitrogen application rates. There was a significant positive correlation between nitrate and ammonium contents and nitrogen application rate. With the increases of nitrogen application rates, the content of water stable aggregates with diameter &gt;2 mm decreased, while that of water-stable aggregates with diameter &lt;0.5 mm increased. The particle size of soil water-stable aggregates also decreased gradually. There was a significant negative correlation between nitrogen application rate with mean weight diameter (MWD) and geometric mean diameter, while no correlation with fractal dimension. The fitting equation between MWD and N2O emission flux was y=3928.3e-2.171x (R2=0.55, P&lt;0.001), indicating that N2O emission increased markedly as MWD decreasing. The increases in nitrogen application rate reduced soil temperature in the 0-10 cm layer, increased nitrate and ammonium contents, decreased the average particle size of soil water stable aggregates, and the stability of soil aggregates, and increased soil N2O emission.

Effects of different tillage systems on soil properties, and yield and yield components of barley

ABSTRACT This study was carried out to assess the influence of tillage systems on soil characteristics as well as barely yield. The two-year experiment with the tillage systems (NT, no-tillage; MT, minimum-tillage; and CT, conventional-tillage) and barley cultivars was done. Vetch was pre-planting in the rotation with barley. About 30% of vetch residue remained in the NT and MT systems, but in CT, these residues were buried by moldboard. Results showed that NT was superior to MT and CT in terms of the soil properties, earthworm number and earthworm body mass. Remains of vetch, as a pre-planted crop, were effective in increasing these indicators. Also, the improvement of these indicators made the no-tillage superior to the MT and CT in terms of geometric mean diameter, mean weight diameter and soil moisture content. In contrast, soil porosity was higher in CT system. In conclusion, soil structure improved during the two years of the experiment when MT or NT was used, while CT was not effective in improving the soil structure. Grain yield (5973 kg ha−1) and NFS (5163) were higher in NT than MT and CT, suggesting that the change in soil structure has provided a better environment for the yield.

Calibration and evaluation of a broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and cloud condensation nuclei (CCN) activity

Abstract. For understanding and assessing aerosol–cloud interactions and their impact on climate, reliable measurement data on aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to an existing differential mobility analyzer (DMA) with CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (Fact−Saerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under three different thermal gradient (dT) conditions (dT=6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: first, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on the particle size and κ to be investigated. To minimize the effect of multiply charged particles, a small geometric mean diameter (Dg) and geometric standard deviation (σg) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02 per 100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, intercomparison experiments between typical DMA-CCN and BS2-CCN measurements were performed with a laboratory-generated aerosol mixture and ambient aerosols. Good agreement of κ values between DMA-CCN and BS2-CCN measurements for both experiments shows that the BS2-CCN system can measure CCN activity well compared to the existing measurement method and can measure a broad range of hygroscopicity distributions with a high time resolution (∼1 s vs. a few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection and estimation of aerosol chemical composition.

Experimental study of hydraulic properties in grain packs: Effects of particle shape and size distribution

Uniform and multi-dispersed grain packs have been frequently used to conceptually study flow in porous media. Numerical simulations were previously used to address the effect of particle shape on characteristics, such as pore space fractal dimension, moisture characteristic curve (MCC) and saturated hydraulic conductivity (SHC) of grain packs. However, experimental observations are still required since fractal-based approaches have been extensively proposed to model various properties in porous media. In this study, 16 angular sand and 16 spherical glass bead samples with different particle size distributions (PSDs) from well- to poorly-sorted were packed. The MCC was measured using the combination of sandbox and pressure plates methods. The pore space fractal dimension (DMCC), calculated from the measured MCC, ranged from 0.80 to 2.86 in sand and from ‐0.18 to 2.81 in glass bead packs, which indicated that DMCC may be negative in homogeneous media (e.g., glass bead packs) consistent with several studies in the literature. Results showed greater DMCC for the sand packs than the glass bead packs with the same geometric mean diameter values and PSDs. This clearly demonstrated the effect of particle shape on DMCC in the studied packs. The critical path analysis (CPA) approach was used to estimate the SHC measured using the constant-head method. We found that the CPA estimated the SHC accurately, within a factor of four of the measurements on average. Although the CPA is theoretically known to be accurate in media with broad pore size distributions, we experimentally found that it estimated the SHC in various types of grain packs reasonably well.

Size distribution monitoring for chemical mechanical polishing slurries: An intercomparison of electron microscopy, dynamic light scattering, and differential mobility analysis

In chemical mechanical planarization (CMP), a particle slurry is used in polishing semiconductor wafers. Key to CMP performance is the size distribution of the particles. We evaluate the potential of an aerosol technique, namely differential mobility analysis (in a liquid nanoparticle sizer, LNS, system) to characterize size distributions of CMP slurries. LNS measurements are compared to size distributions inferred from electron microscopy (SEM), and dynamic light scattering (DLS). LNS measurements are more repeatable than DLS measurements, and for 4 silica slurries, LNS distributions are in better agreement with SEM measurements than DLS. We find also that the LNS can quantify multimodal size distributions. For non-silica slurries, LNS, DLS, and SEM measurements have geometric mean diameters which can vary from another by 10 nm or more. However, because each measurement type is internally consistent, the combination of LNS and DLS, which are automated, yields augmented information on slurry properties.