Residual Particle Size Research Articles

Cloud Droplet Residual Particle Microphysics in Marine Stratocumulus Clouds Observed during the Monterey Area Ship Track Experiment

Abstract The effect of marine boundary layer pollution level (as determined by the aerosol particle number concentration) on the size distribution of aerosol particles that formed cloud droplets in marine stratiform clouds is examined. In situ measurements of cloud droplet residual particles with a counterflow virtual impactor during the Monterey Area Ship Track experiment are presented. The variation in residual particle size distribution and number concentration in clouds that formed in marine boundary layers with different pollution levels are discussed. The measurements show a constant shape of the residual particle size distributions for the variety of pollution levels encountered, even though the aerosol number concentration varied by up to a factor of 6. The measurements indicate that particles smaller than 0.1-μm radius controlled cloud droplet number concentrations in the clouds investigated. From literature values of the maximum supersaturations encountered in stratocumulus clouds, one can estim...

Incorporation of aerosol particles between 25 and 850 nm into cloud elements: measurements with a new complementary sampling system

The interpretation of the physico-chemical processes in clouds is facilitated by segregating in situ cloud elements from their carrier gas and small particles (interstitial aerosol). Thus, the present study focuses on the quantitative phase segregation of interstitial air from cloud phase by two complementary samplers with microphysical on-line analysis of the separated phases. An improved counterflow virtual impactor (CVI) was developed for the collection and subsequent evaporation of the condensed phase, releasing dissolved gaseous material and residual particles. This sampler operates in the size range of few micrometers up to 50 μm in cloud element diameter and is matched by an interstitial Round Jet Impactor sampling the gas phase with interstitial particles. Calibrations of both samplers verified the calculated cut sizes D 50 of 4, 5, and 6 μm and quantified the slope of the collection efficiency curves. Until this study no direct CVI measurements of the residual particle sizes far below the diameter of 0.1 μm were available. For the first time a CVI was connected to a Differential Mobility Particle Sizer (DMPS) scanning between 25 nm and 850 nm, thus, including the entire Aitken mode in the residual size analysis. Cloud studies on the Puy de Dôme, France, revealed residual particle sizes including Aitken mode (diameter D<100 nm) and accumulation mode ( D>100 nm). A major feature of the CVI data is expressed by the fact that despite incomplete incorporation of accumulation mode particles in cloud elements there are contributions of particles with diameters smaller than 0.1 μm to the number of residual particles. Cloud entrainment from height levels above the maximum supersaturation as wells as the size-dependent chemical composition of the aerosol population most likely produced the S-shaped size-dependent partitioning of residual particles. Compared to earlier studies the 50% partitioning diameters dropped significantly below 100 nm to roughly 70 nm.

A physically-based algorithm for estimating the relationship between aerosol mass and cloud droplet number

In this study, we present a relationship between total accumulation mode aerosol mass concentrations and cloud droplet number concentrations (Nd). The fundamental aim with the present method is to arrive at a physically-based conversion algorithm in which each step in the conversion is based on real physical processes that occur and can be observed in the atmosphere, and in which all of the fields involved can be observed or modeled. In the last conversion (the critical part in the algorithm), we use measurements of the size distributions of cloud droplet residual particles for different pollution conditions. This conversion assumes that the size of the residual particles can be described with a lognormal distribution function and uses the Hatch’Choate relationship to convert between residual volume and number. The relatively sparse data set with which we have developed the present algorithm results in a course classification of the aerosol mass field. Consequently, uncertainties need to be recognized when using the algorithm in its present form in model calculations. The algorithm has been used on data from 15 days and the agreement between calculated and observedNd values is, with one exception, within a factor of 2 and for many of these cases also much better than a factor of 2. In addition to the results of the algorithm itself, we also present a least-squares fit to the predicted Nd values. To improve the algorithm in the longer-term requires more data of scavenging fractions, particle chemical composition and density, and residual particle size distributions as a function of aerosol mass loading and cloud type.

Interaction of biochemical quality and particle size of crop residues and its effect on the microbial biomass and nitrogen dynamics following incorporation into soil

Mineralization of N from organic materials added to soil depends on the quality of the substrate as a carbon, energy and nutrient source for the saprophyt- ic microflora. Quality reflects a combination of bio- chemical and physical attributes. We investigated how biochemical composition interacts with particle size to affect the soil microflora and N dynamics following in- corporation of crop residues into soil. Four fresh shoot and root crop residues were cut into coarse and fine particle sizes, and incorporated into sandy-loam soil which was incubated under controlled environment conditions for 6 months. In the case of the highest bio- chemical quality material, potato shoot (C/N ratio of 10 : 1), particle size had no effect on microbial respira- tion or net N mineralization. For lower biochemical quality Brussels sprout shoot (C/N ratio of 15 : 1), re- ducing particle size caused microbial respiration to peak earlier and increased net mineralization of N dur- ing the early stages of decomposition, but reduced net N mineralization at later stages. However, for the low- est biochemical quality residues, rye grass roots (C/N ratio of 38 : 1) and straw (C/N ratio of 91 : 1) reducing particle size caused microbial respiration to peak later and increased net immobilization of N. For Brussels sprout shoot, reducing particle size decreased the C content and the C/N ratio of residue-derived light frac- tion organic matter (LFOM) 2 months following incor- poration. However C and N content of LFOM derived from the other materials was not affected by particle size. For materials of all qualities, particle size had little effect on biomass N. We conclude that the impact of particle size on soil microbial activities, and the protec- tion of senescent microbial tissues from microbial at- tack, is dependant on the biochemical quality of the substrate.

Small Ice Crystals in Cirrus Clouds: A Model Study and Comparison with In Situ Observations

Abstract An air parcel model including homogeneous freezing nucleation of ice crystals has been used to study the formation and development of cirrus clouds. In situ measurements taken during March 1994 over southern Germany were used for comparison with model predictions. Typical experimental data were chosen for a base-case model run. Using measured aerosol properties as input values, the model predicts the measured ice crystal size distribution. In particular, both measurements and model results show the presence of numerous small ice crystals (diameter between 1 and 20 μm). Both measurements and model results also show that small aerosol particles (below 0.1 μm diameter) are active in forming cirrus cloud particles. The modeled microphysical properties including ice crystal size distribution, number concentration, and the residual particle size distribution are in good agreement with the experimental data. Based on the measured parameter values, a model sensitivity study considering air parcel updraft...

Nitrogen dynamics under growth chamber conditions as influenced by method of alfalfa termination 2. Plant-available N release

Herbicide application has been proposed as an alternative to tillage for termination of established alfalfa (Medicago sativa L.) stands but it may alter the pattern and amount of N released from alfalfa residues. A controlled environment study was conducted to investigate the effect of termination technique on the availability of N to four barley (Hordeum vulgare L.) crops. Four treatments consisting of a factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (surface, incorporated) were established. Nitrogen uptake by the four consecutive crops of barley was measured during a 125-d period after termination. Termination method, particularly residue placement, strongly affected N release from alfalfa residues. Nitrogen accumulation by the initial barley crop accounted for &gt;60% of cumulative N uptake in incorporated treatments compared with 39% and 24% for herbicide and tillage treatments in which alfalfa residue was surface applied. Herbicide application also slightly increased N uptake by the initial barley crop. Nitrogen uptake by subsequent barley crops was not affected by termination method; however, cumulative N uptake remained substantially greater for incorporated treatments throughout the 125 d experiment. Effects of residue particle size on N release from alfalfa residues were small. These results suggest that herbicide termination in which residue is retained on the soil surface may reduce the short-term plant-available N supply. Provided that mineralization is sufficient to meet the N needs of subsequent crops, maintaining a smaller reservoir of soil inorganic N may be beneficial in reducing the potential for leaching or denitrification losses. Key words: Plant-available N, termination method, alfalfa, herbicide, tillage, growth chamber

Laser Light Scattering and Microscopic Properties of Milkfat Globules in Swiss Cheese Whey Low Density Lipid-containing Fraction

Improved utilization of cheese whey, a by-product of cheese manufacture, is a major concern of the cheese industry. Large amounts of whey and whey products are used as nutritional and functional ingredients by the food and dairy industry. However, the residual lipids that remain in the whey interfere with the manufacture of whey protein concentrates by ultrafiltration processing and also adversely affect the functional properties and flavor stability of whey protein concentrate and other dried whey products. Information on the size and microstructure of residual whey lipid particles should allow the food industry to develop new and improved processing technologies to remove them from whey and utilize them as a novel food ingredient. Residual whey lipid from Swiss cheese whey has been fractionated by high speed centrifugation into: (a) low-density lipid-containing fraction (LDLF); (b) medium-density lipid-containing fraction (MDLF); and (c) high-density lipid-containing fraction (HDLF). Our objective for this study was to investigate the size and microstructural properties of the smallest-sized LDLF particles recovered from Swiss cheese whey by high-speed centrifugation using laser light scattering spectrophotometry (LLSS), light microscopy and scanning electron microscopy. LLSS results revealed that the size of LDLF particles ranged from < 0.1–about 4 μm with a predominance in the larger sizes. Light microscopy size results for LDLF particles agreed with LLSS results and also confirmed their globular microstructure. Electron micrographs further confirmed the size and provided more detailed information on the microstructural properties of LDLF particles.

Drug Microencapsulation by PLA/PLGA Coacervation in the Light of Thermodynamics. 2. Parameters Determining Microsphere Formation

□ Phase separation (frequently called coacervation) of poly-(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) is a classical method for drug microencapsulation. Here, attempts have been made to describe this process in the light of thermodynamics. Different PLA/PLGAs were dissolved in either dichloromethane or ethyl acetate, phase separated by addition of the coacervating agent silicone oil (PDMS), and hardened in either octamethylcyclotetrasiloxane or hexane. Various stages of phase separation were defined microscopically, and the coacervate and continuous phases characterized with respect to volume, composition, polymer molecular weight, and rheological behavior. The optimal amount of PDMS was inversely proportional to the polymer molecular weight and hydrophilicity, and a coacervate viscosity of above 5–10Pas was required for stable coacervate droplets. The composition and, consequently, viscosity of the coacervate and continuous phases depended on the polymer–solvent–PDMS interactions, as analyzed by the parameters χ (Flory), δ (Hildebrand), and ΔintE (Hô). In general, the lattice model of Flory and Scott describing polymer–polymer incompatibility best explained the results. The interaction parameters and viscosity of the phases were also helpful to explain microsphere characteristics such as residual solvent and particle size. The data suggest that microsphere formation by polyester coacervation is primarily driven by molecular interactions between polymer, solvents, and coacervating agent.

Comparison of D-Dimer Activity and Residual Particle Size Produced Following Thrombus Disruption by Perfluorocarbon Containing Microbubbles Versus Urokinase in the Presence of Low Frequency Ultrasound

Comparison of D-Dimer Activity and Residual Particle Size Produced Following Thrombus Disruption by Perfluorocarbon Containing Microbubbles Versus Urokinase in the Presence of Low Frequency Ultrasound

Comparison of D-dimer activity and residual particle size produced following thrombus disruption by perfluorocarbon containing microbubbles versus urokinase in the presence of low frequency ultrasound

Comparison of D-dimer activity and residual particle size produced following thrombus disruption by perfluorocarbon containing microbubbles versus urokinase in the presence of low frequency ultrasound

Effect(s) of the demineralization process on the osteoinductivity of demineralized bone matrix.

The relationships between residual calcium levels and particle size of ground demineralized bone matrix and its osteoinductive potential were investigated using in vitro and in vivo assays. The effects of variable residual calcium levels, variable particle sizes, and donor age and gender were studied using a tissue culture-based bioassay (in vitro) as well as an athymic mouse (in vivo) bioassay. The osteoinductive potential of the bone-derived biomaterial was assessed by measuring the degree of new bone formation (change in percent calcium content after 4 weeks of implantation) in the in vivo assay and levels of alkaline phosphatase activity associated with cultures of human periosteal cells (HPO cells) in the in vitro assay, respectively. Slightly demineralized bone matrix and overly demineralized bone matrix possessed a degree of osteoinductive potential whereas bone demineralized to levels of approximately 2% residual calcium provided for maximum osteoinductive potential in both assay systems. The osteoinductive potential of ground demineralized bone varied relative to the particle size such that DBM particles ranging from 500 to 710 microns provided for the highest level of calcium deposition (increase of 8.1 weight percent calcium) after 4 weeks of implantation in muscle pouches of an athymic mouse, whereas explanted particles less than 250 microns showed the lowest level of calcium deposition (increase of only 2.8 weight percent calcium). In the donor age and gender study, DBM from different donors were divided into 5 age groups for both female and male donor derived bone: less than 20, 21 to 30, 31 to 40, 41 to 50, and 51 to 60 year old age groups. This study indicated that DBM from female donors in the 31 to 40 years old age group and male donors in the 41 to 50 year age group possess the highest osteoinductive potential, whereas DBM derived from donor bone from both female and male donors in the 51 to 60 year age group presented the lowest osteoinductive potential. DBM derived from male and female donors did not in general show significant differences in osteoinductive potential.

Experimental Investigation of Scaling Laws for Electrospraying: Dielectric Constant Effect

ABSTRACT Experiments were performed to investigate the effect of liquid dielectric constant on existing scaling laws for the electrospraying process. The variations of the droplet size and the emitted current were measured as a function of the dielectric constant for the electrospray operating in the cone-jet mode. Eight different solvents with dielectric constants, κ, ranging from 12.5 to 182 were tested. The residue particle size distributions were measured using a TSI scanning mobility particle sizer, (SMPS). The produced liquid droplet sizes were then calculated from the known solution concentrations. The results show that: (1) For the produced droplet size, Dd , experimental data are in agreement with the scaling law (G(κ) = 1.66κ −1/6) proposed by Ganan-Calvo et al. (1994) for solvents with high dielectric constants. The derivation in low dielectric constant cases may be that the assumption of Ganan-Calvo (1994) on the characteristic length may not hold for the present system; (2) for the emitted cu...

Removal of Copper in Aqueous Solution by Apple Wastes

Removal of copper from a solution was investigated to evaluate the cation-exchange capacities of apple residues from agricultural wastes. The effects of solution pH, ionic strength, co-ion, ligands, initial metal concentrations, and particle size of apple residues were studied. The optimal pH range for copper removal by apple residues was shown to be from pH 5.5 to 7.0, and the maximum percentage of copper removal was 91.2%. Increasing ionic strength, up to 0.1 N, has little effect on metal uptake. The presence of co-ions such as lead decreases the removal capacity of copper as expected. The presence of ligands, such as EDTA and ammonia, also reduces metal removal efficiency due to the formation of a metal-ligand complexation in solution. Equilibrium of copper sorption was established very rapidly initially and decreased markedly after 1 hour. Equilibrium isotherms of copper fit the Langmuir equation adequately. Column experiments showed that the dynamic capacity of chemically modified apple residues was four to five times higher than that of raw residues which contained acidic groups such as carboxylic and phenolic functional groups. The adsorbed copper ions were completely recovered with three bed volumes of 0.5 N HCl. Thus, modified apple residues could be applied successfully for metal removal from wastewater.

Decomposition of wheat straw and rye residues as affected by particle size

Effects of contact between the soil and crop residues on the processes of residue decomposition are still poorly understood. The objective of this study was to investigate the effects of residue particle size on the decomposition of wheat (Triticum aestivum L.) straw (C/N=270) and green rye (Secale cereale) residues (C/N=9). Residue particle size was used as a means to vary the contact between crop residues and the soil. Carbon mineralization was measured during 102 d for straw and 65 d for rye, on residues ranging in sizes from laboratory model (0.03 cm) to field-scale (10 cm). The soil was a silt (Typic Hapludalf) and the incubation was performed at 15 °C. The effects of particle size on C mineralization varied for the two residues. In the first two days of incubation, decomposition rate of rye increased with decreasing particle size but thereafter, the trend was reversed. In 65 days, 8% more C was decomposed in the 7-cm residues than in the 0.03-cm ones. For wheat straw, early decomposition (3–17 days) was faster for the small-sized particles (0.06 and 0.1 cm). Thereafter, the largest size classes (5 and 10 cm) decomposed faster. After 102 days, the very fine particles (≤ 0.1 cm) showed the greatest and the intermediate size classes (0.5 and 1 cm), the lowest amount of C mineralized. We hypothesized that greater availability and accessibility of N was responsible for the higher rates of decomposition observed for finely-ground wheat straw while a physical protection of finely ground residues was probably involved in the observed reverse effect for rye.

Nitrogen mineralization and denitrification as influenced by crop residue particle size

Managing the crop residue particle size has the potential to affect N conservation in agricultural systems. We investigated the influence of barley (Hordeum vulgare) and pea (Pisum sativum) crop residue particle size on N mineralization and denitrification in two laboratory experiments. Experiment 1: 15N-labelled ground (≤3 mm) and cut (25 mm) barley residue, and microcrystalline cellulose+glucose were mixed into a sandy loam soil with additional inorganic N. Experiment 2: inorganic15 N and C2H2 were added to soils with barley and pea material after 3, 26, and 109 days for measuring gross N mineralization and denitrification.

Physical basis for a droplet aerosol analysing method

A technique for the characterisation of droplet aerosols is presented and theoretically evaluated. The system, which finds applications for example in the experimental study of cloud formation and cloud water chemistry, relies on a four-step process. The droplet aerosol is electrically charged in a unipolar charging unit, followed by diffusion drying of the droplets, resulting in charged particles consisting of non-volatile matter (droplet residues). In the third step, the residual particles are classified by electrostatic spectrometry, and in the final step the residual particles are detected, collected or further characterised. The basic function in respect of the charging process and the particle interaction with water vapour is demonstrated by model calculations, which show that droplets which are activated in a thermodynamical sense can be separated from unactivated droplets. Different strategies for the application of the system are briefly outlined. By measuring two parameters, associated droplet size and residual particle size can be determined. Results from the first field measurement campaign of the resulting instrument are also briefly presented.

Electrospraying of conducting liquids for monodisperse aerosol generation in the 4 nm to 1.8 μm diameter range

An electrospraying system operated in the cone-jet mode is shown to produce monodisperse droplets in a wide size range and with good monodispersity. These highly charged droplets are rapidly discharged in a radioactive neutralizer. The produced droplet size can be further reduced by the evaporation process without experiencing the Rayleigh breakup. The experiment is performed using sucrose solutions and the liquid electrical conductivity is controlled by adding small amounts of nitric acid. The size distribution is quite monodisperse having a geometrical standard deviation of 1.1. The mean droplet size produced can be varied from 40 nm to 1.8 μm by changing the liquid feed rate and electrical conductivity. Using 0.1% sucrose concentration solution, the residue particle size is reduced by a factor of ten, in the range from 4 nm to 0.18 μm. The parameters affecting the particle size distribution, the measured spraying current, and the operating envelope have also been obtained and quantified.

Prediction of organic matter digestibility in vivo of grass silage by near infrared reflectance spectroscopy: effect of calibration method, residual moisture and particle size

The results of a study into the effects of calibration method, residual moisture content and sample particle size on the prediction of the organic matter digestibility in vivo of grass silages by near infrared reflectance spectroscopy are reported. A total of 182 grass silages with organic matter digestibility values measured with sheep were divided into calibration (103) and validation sets (79) on the basis of their spectral characteristics. Calibrations were developed using modified stepwise regression, modified partial least squares and principal components regression techniques with and without a scatter correction technique to reduce particle size effects. In addition, the use of a noise repeatability file during the calibration process was evaluated for its ability to reduce the effects of variation in sample residual moisture content. The highest predictive ability for organic matter digestibility was obtained using a second order derivative modified partial least squares regression with the use of both scatter correction and noise repeatability procedures. Validation statistics obtained were R 2 = 0.82, standard error of prediction 2.35 and slope 1.01. The best calibration was also shown to have acceptable analytical repeatability (2.44) and not to distinguish between silages made in clamps or as big bales wrapped in plastic.

Influence of coal rank and pretreatment on residual ash particle size

The influence of coal treatment (cleaning, sizing, and grind) on the generation of ash in the 0.5–8 μm size range was studied in a laboratory-scale flow reactor. The first objective of the work was to use deviations between the data and the basic breakup model of residual ash formation as a means of identifying non-ideal or second order effects that are active in this environmentally sensitive size range. The second objective was to identify how coal treatment affected the formation of this ash. The raw coals received only the treatment that would be appropriate for utility boiler firing, i.e., grinding in an industrial pulverizer to a broad size range centered at 30–50 μm. Initial experiments showed that many more fine particles were generated than would be predicted by the breakup model. In particular, a persistent mode at 1–2 μm appeared in most of the data. This mode was undiminished in coals cleaned of excluded mineral matter, which showed that the source of these particles was not small exclusions liberated during grinding. When the coals were subjected to aerodynamic sizing, the smaller cuts generated this 1–2 μm ash, while it was largely absent when the larger cuts were burned. This suggests that the formation is dominated by a mechanism based on the initial external surface area of the char, e.g., burnout of small inclusions at the inception of char combustion, or microfragmentation if it only occurs during the initial stages of char combustion. Larger coal particles tended to produce more aerosol due to the vaporization/condensation mechanism. These particles also tended to have very large breakup numbers, which suggests that fragmentation tends to produce similar sized fragments, independent of coal starting size. Comparison of the behavior of fine coals prepared by sizing vs. those prepared by grinding showed that aerosol yields ( D < 0.3 μm) were decreased for the fine sized coals. This was apparently due to the concentration of fine excluded minerals in this cut during the sizing process. Excluded minerals have previously been shown to suppress aerosol yields.

Effect of temperature on particle size change of coal in coal liquefaction with donor solvent.

In the previous paper, it was demonstrated that the reaction could be divided into three regions, and the modified double shrinking core model, the double shrinking core model and the shrinking core model were applied to regions I, II and III respectively. However, the influence of different conditions on coal particle size change is not fully understood.In the present paper, the influence of reaction temperature on changes in residue weight, particle size and density was examined, using Taiheiyo coal screened to 16/20 mesh as the starting materials. It was found that the effect of reaction temperature on coal particle change is very great in region I. Moreover, by assuming initial particle size using the double shrinking core model, the relation between reaction temperature and particle size change was clarified.