The relationship between food particle size and larval size in Simulium noelleri Friederichs

SUMMARY. 1. In a laboratory experiment, larvae of Simulium noelleri were fed on polystyrene latex microspheres of a range of diameters from 5 to 100 μm.
2. Examination of the particle size distribution in the water used in the experiment showed those <13μm to be the most numerous (87% of all particles present). Particles of this size made up 57±2% (mean ±SE)of the total of those in the gut of larvae.
3. Comparison of particle composition in the gut contents and the water of the experiment, using Jacob's index of electivity, showed that larvae of all sizes filtered proportionally fewer of the particles <13 μm and more of those >13μm.
4. As larvae increased in size they became better able to filter the largest particles present (>52μm in diameter) and less well able to filter the smallest particles (<13μm in diameter).
5. Gut retention time was longer in larger larvae.
6. The biology of S. noelleri , which inhabits lake outlets in high population densities, is considered in the light of these findings.     

Comparison of aerosol and bioaerosol collection on air filters

Air filters efficiency is usually determined by non-biological test aerosols, such as potassium chloride particles, Arizona dust or di-ethyl-hexyl-sebacate (DEHS) oily liquid. This research was undertaken to asses, if application of non-biological aerosols reflects air filters capacity to collect particles of biological origin. The collection efficiency for non-biological aerosol was tested with the PALAS set and ISO Fine Test Dust. Flow rate during the filtration process was 720 l/h, and particles size ranged 0.246–17.165 μm. The upstream and downstream concentration of the aerosol was measured with a laser particle counter PCS-2010. Tested bioaerosol contained 4 bacterial strains of different shape and size: Micrococcus luteus, Micrococcus varians, Pseudomonas putida and Bacillus subtilis. Number of the biological particles was estimated with a culture-based method. Results obtained with bioaerosol did not confirmed 100% filters efficiency noted for the mineral test dust of the same aerodynamic diameter. Maximum efficiency tested with bacterial cells was 99.8%. Additionally, cells reemission from filters into air was also studied. Bioaerosol contained 3 bacterial strains: Micrococcus varians, Pseudomonas putida and Bacillus subtilis. It was proved that the highest intensity of the reemission process was during the first 5 min. and reached maximum 0.63% of total number of bacteria retained in filters. Spherical cells adhered stronger to the filter fibres than cylindrical ones. It was concluded that non-biological aerosol containing particles of the same shape and surface characteristics (like DEHS spherical particles) can not give representative results for all particles present in the filtered air.     

Are ball-rolling (Scarabaeini,Gymnopleurini, Sisyphini) and tunnelling scarabaeine dung beetles equally choosy about the size of ingested dung particles?

Abstract.  1. The maximum size of ingested particles was determined in 11 species of ball-rolling, adult dung beetle (Scarabaeidae: Scarabaeinae) by mixing small latex or glass balls of known diameter into their food. The tribes Scarabaeini, Gymnopleurini, and Sisyphini (four, four, and three species respectively) were represented, with mean body sizes ranging from 0.33 to 4.0 g fresh weight.
2. Only particles with maximum diameters of 4–85 µm were ingested. Hence rollers, like other known beetles feeding on fresh dung, filter out larger, indigestible plant fragments and confine ingestion to small particles of higher nutritional value.
3. The maximum diameter of ingested particles increased significantly with body weight, whereas taxon (tribe) had no additional effect. Because big rollers accept larger particles than do tunnellers (which make dung stores for feeding and breeding in the soil immediately below the pat) of similar weight, the slope of the diameter-against-weight regression for rollers was significantly higher than that found earlier for tunnellers.
4. An explanation could be that a typical food ball made by a roller is considerably smaller than the amount of dung available to a feeding tunneller of the same size. If the roller were as choosy about particle size as the tunneller, it might not get enough food. This applies to large rollers in particular because their food balls contain a higher proportion of coarse fibres than those made by small species.     

Rapid detection of lactobacillus and yeast concentrations using a particle size distribution analyser

Aims:  To see the possibility of particle size distribution analyser (PSDA) in detecting concentration of lactobacillus contaminants in yeast fermentation.
Methods and Results:  A PSDA was used to rapidly determine the size and concentration of lactobacillus and Saccharomyces cerevisiae . Data showed that the aerodynamic diameters of Lactobacillus casei and S. cerevisiae cells were around 0·63 and 2·9 μm, respectively, with both cultures showing a linear relationship between cell density and particle count on a size distribution curve of PSDA. In addition, Lactobacillus fermentum showed high similarity in bacterial size distribution and particle count numbers with L. casei . The PSDA also rapidly detected (within 1 min) the cell concentrations of S. cerevisiae and L. casei in a mixed sample with different concentration ratios with 10⁷–10⁹ cells ml⁻¹ of detection range.
Conclusions:  PSDA was demonstrated to be useful for the rapid detection of lactobacillus and S. cerevisiae concentrations.
Significance and Impact of the Study:  This is the first report concerning PSDA to detect the concentration of bacteria and yeast. This method can be useful in the actual field during ethanol fermentation because of relatively easy handling and rapid detection.     

What do dung beetles eat?

Abstract.  1. Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2–5 to 130 μm, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a 'typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 μm.
2. Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76–89% water. Costs of a 20 μm MDIP were often low, since 69–87% of the total nitrogen in bulk dung other than that of elephant and rhino (40–58%) was available to selective feeders.
3. Nitrogen concentrations were high – and C/N ratios low – in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios.
4. Estimated C/N ratios of 13–39 in bulk dung (sheep–elephant) were decreased by selective feeding to 7.3–12.6 in the ingested material. In assimilated food, ratios are probably only 5–7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon.
5. The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20–106 μm are modest, especially in dung with a low C/N ratio.     

Dung feeding in adult scarabaeines (tunnellers and endocoprids): even large dung beetles eat small particles

Abstract 1. The maximum size of ingested particles was determined in 15 species of adult dung beetle (Scarabaeidae: Scarabaeinae) by mixing small latex or glass balls of known diameter into the dung used as food. Twelve species (tribes Coprini, Onitini, Oniticellini, and Onthophagini) were tunnellers (making dung stores for feeding and breeding in the soil below the pat) and three species (tribe Oniticellini) were endocoprids (feeding and breeding in the dung pat itself).
2. The test species, covering a wide range of body size (fresh weights 0.05–7.4 g), ingested minute particles only (maximum diameter 8–50 µm), and there was a statistically significant but numerically small increase in particle size with body weight.
3. When the effect of body size was taken into account, taxon (tribe), ecological group (tunneller/endocoprid), and dung preference (coarse/fine) had no significant effect on the size of ingested particles.
4. Tests using two tunnelling species did not indicate that beetles use their mandibles to grind dung particles prior to ingestion.
5. The results suggest essentially the same feeding mechanism in all adult tunnelling or endocoprid scarabaeines that eat fresh dung. Larger, indigestible plant fragments are avoided by filtration, and ingestion is confined to very small particles of higher nutritional value.     

Microprojectile particle effect on stable transformation of black spruce via bombardment

Three types of microprojectile particles, 1.0-μm gold, 1.3-μm tungsten, and 1.6-μm gold, were studied for their effectiveness on genetic transformation of black spruce via bombardment with somatic embryos as the target tissue. Different particles resulted in different levels of transient expression of theGUS reporter gene; 1.0-μm gold particles produced the highest level of expression, and 1.6-μm gold particles produced the lowest level. Particle type also affected stable transformation; 1.0-μm gold particles had a 10-fold higher stable transformation efficiency than did 1.6-μm gold particles and a 2-fold higher efficiency than did 1.3-μm tungsten particles. This study indicates that microprojectile particle type and size are important in bombardment-mediated plant transformation.     

Evaluation of ultrafiltration cartridges for a water sampling apparatus

Aims:  To determine the efficiency of various ultrafiltration cartridges (UFC) in concentrating test micro-organisms from drinking water.
Methods and Results:  Replicate drinking water samples from three potable water supplies were dosed with Bacillus anthracis Sterne, Francisella tularensis LVS, Yersinia pestis CO92, bacteriophages MS2 and phi-X174, and Cryptosporidium parvum. The test micro-organisms were dosed together in 100 l of water, which was then recirculated through one of five different UFC until the retentate volume was reduced to c. 500 ml. The micro-organisms were assayed before and after ultrafiltration concentration and per cent recoveries were calculated. There were nine statistically significant differences among pairs of filters out of a possible 180 different combinations of UFC, test micro-organisms, and water types.
Conclusions:  No filter consistently performed better or worse than the others for each test micro-organism in all water samples tested.
Significance and Impact of the Study:  This study provides performance data on the ability of several different UFC to concentrate a panel of test micro-organisms from three sources of potable water. Water utilities and first responders may use these data when selecting UFC for use in emergency response protocols. This study also provides additional data as to the efficacy of ultrafiltration for recovering bacteria, virus-like particles, and protozoan oocysts from water samples.     

Supercritical assisted atomization: A novel technology for microparticles preparation of an asthma-controlling drug

The objective of this study was to produce microparticles of a new asthma-controlling drug by supercritical assisted atomization (SAA), proposed as an alternative to conventional jet-milling process. SAA is based on the solubilization of supercritical carbon dioxide in a liquid solution containing the drug; the ternary mixture is then sprayed through a nozzle, and microparticles are formed as a consequence of the enhanced atomization. SAA process parameters studied were precipitator temperature, nozzle diameter, and drug concentration in the liquid solution. Their influence was evaluated on morphology and size of precipitated particles. Spherical particles with mean particle size ranging from 1 to 3 μm of the new anti-asthma drug were produced by SAA. The mass median aerodynamic diameter (MMAD) of the SAA micronized particles and of the conventional jet-milled drug was used to compare, the results obtainable using the 2 techniques. Particularly, MMADs from 1.6 to 4.0 μm were obtained by SAA at the optimum operating conditions and by varying the concentration of the solution injected. MMAD of 6.0 μm was calculated for the jet-milled drug. SAA samples also exhibited narrower particle size distribution (PSD). A good control of particle size and distribution together with no drug degradation was obtained by SAA process. Published: October 22, 2005     

Formulation of a dry powder influenza vaccine for nasal delivery

The purpose of this research was to prepare a dry powder vaccine formulation containing whole inactivated influenza virus (VIIV) and a mucoadhesive compound suitable for nasal delivery. Powders containing WIIV and either lactose or trehalose were produced by lyophilization. A micro-ball mill was used to reduce the lyophilized cake to sizes suitable for nasal delivery. Chitosan flakes were reduced in size using a cryo-milling technique. Milled powders were sieved between 45 and 125 μm aggregate sizes and characterized for particle size and distribution, morphology, and flow properties. Powders were blended in the micro-ball mill without the ball. Lyophilization followed by milling produced irregularly shaped, polydisperse particles with a median primary particle diameter of ≈21 μm and a yield of ≈37% of particles in the 45 to 125 μm particle size range. Flow properties of lactose and trehalose powders after lyophilization followed by milling and sieving were similar. Cryo-milling produced a small yield of particles in the desired size range (<10%). Lyophilization followed by milling and sieving produced particles suitable for nasal delivery with different physicochemical properties as a function of processing conditions and components of the formulation. Further optimization of particle size and morphology is required for these powders to be suitable for clinical evaluation. Published: March 10, 2006     

Resource utilization by the freshwater deposit feeder Ptychoptera townesi (Diptera: Ptychopteridae)

SUMMARY 1. False crane fly larvae, Ptychoptera townesi (Diptera), occurred in high densities in a flow-controlled section of stream where fine particulate organic matter (FPOM; 0.45 μm to 1 mm in diameter) had accumulated, but were quite rare both upstream and downstream from the section.
2. In laboratory studies, P. townesi grew only on FPOM less than 250 μm. Larvae consistently grew fastest when fed small particles (0.45–53 μm in diameter).
3. Ptychoptera townesi consumed relatively small amounts (0.002 mg per mg animal dry mass day⁻¹) of FPOM (0.45–53 μm). They had long gut content passage times (greater than 19 h) and relatively high efficiencies of conversion of ingested food to body substance (20.7%). Gut content passage times were variable, and depended partially on the nature of the substrate.
4. False crane fly larvae compacted FPOM into faecal pellets considerably larger in size than particles ingested. They lost mass when allowed to feed on their own faecal material, as well as on faeces greater than 250 μm in diameter produced by shredders. However, they survived and grew on shredder faeces (53–500 μm in diameter) that contained a mixture of smaller particles and particles too large for ingestion.
5. The overall pattern of resource utilization by P. townes involved slow handling of relatively small volumes of food, which probably passed once only through a complex alimentary tract.     

Size Effects on the Uptake of Particles by Populations of Tetrahymena pyriformis Cells

Flow cytometry has been used to make direct measurements of rates of uptake of latex microspheres from dilute, monodisperse suspensions by Tetrahymena pyriformis. Measurements were made for five different sizes of microspheres, ranging from 1.09 to 6.17 μm diameter. Fractions of cells in the population that did not ingest the microspheres offered were also determined. In addition, the size distributions, as indicated by the forward angle light scattering intensity which is measured by the instrument, were determined for the whole population and for the subpopulations of cells that did and did not ingest the particles, for each particle size used. It was found that the fraction of cells that did not ingest the particles was small and independent of particle size when this was less than about 2.7 μm, but increased with particle size when particle size was increased above this value. The so-called maximum clearance rate, which can be calculated from the data, was found to increase monotonically with particle size if it were based only on those cells which actually ingested the particles offered. However, a plot of maximum clearance rate vs. particle size exhibited a maximum if the clearance rate were based on all cells present in the population.     

Preparation of phosphorus and carbohydrate microcapsules for manipulating dietary C : P ratio for aquatic suspension-feeders

SUMMARY 1. Dietary phosphorus can be limiting for aquatic animals such as suspension-feeders. However, our understanding has been limited by the difficulty of manipulating dietary P without altering other aspects of food quality. We microencapsulated various forms of bioavailable P with carbohydrate to manipulate dietary C : P ratio for suspension-feeders.
2. Calcium phosphate, sodium hexametaphosphate, sodium tripolyphosphate and tetrasodium pyrophosphate were each mixed with a concentrated solution of a carbohydrate base (either maltodextrin or potato starch) and microencapsulated using an interfacial polymerisation technique. Each of the 10 types of capsules produced had a particle size ideal for suspension-feeders (3–10 μm).
3. Leakage rates were low (<12% of capsule weight per day). Relative enzymatic breakdown in vitro by carbohydrases (amylase or cellulase) was similar among the 10 capsule types and was always at least 15 times the comparable leakage rate.
4. Release of dissolved P from enzyme-treated capsules varied depending on capsule P content. Liberation of P from capsules prepared from 20% w/w sodium hexametaphosphate in maltodextrin (molar C : P = 1.8) was three times greater than all other types, and this combination appears most suitable as a dietary supplement for zooplankton.
5. Although P content and capsule integrity were greatly influenced by choice of carbohydrate, choice of P compound, and the mixing ratio of the two, P-rich artificial microparticles can be produced that have low leakiness, high digestibility, and a physical size suitable for aquatic suspension-feeders. Therefore, microcapsules represent promising tools for manipulating dietary C : P for suspension feeders.     

The interaction of surface and dust particle size on the pick-up and grooming behaviour of the German cockroachBlattella germanica

The relationship between the particle size of an inert silica dust, its up-take from different surfaces and the grooming behaviour of males, gravid females, and fifth and sixth instar nymphs of the German cockroachBlattella germanica (Dictyoptera: Blattellidae) (L.) was investigated. The normal grooming behaviour of gravid females, nymphs and males differed according to sex and age. The gravid females and nymphs exhibited greater grooming activity than the males, especially of the antennae and the legs. Gravid females, nymphs, and adult males exhibited increased grooming activity after exposure to dust in the size range 0.5–63 μm, but there was no significant difference in grooming behaviour from the control when cockroaches were exposed to dust sizes greater than 70 μm. Antennal grooming by males was greater than leg grooming when exposed to all dust sizes, except size particles ranging 4.5–7.5 μm. A dust pick-up experiment indicated that the average amount of dust transferred toB. germanica is affected by particle size, the porosity of the treated surface, and the sex and age of the cockroaches. Gravid females picked up greater amounts of dust than fifth and sixth instar nymphs, which in turn picked up more dust than males. Silica dust particles (0.5–7.5 μm) were picked up more effectively than larger particle sizes, by all three categories, males, females and fifth and sixth instar nymphs of cockroach on all three test surfaces plastic, ceramic and unpainted plywood. Plywood was the least effective surface for transfer of dust, of all sizes, to males, females and nymphs.     

Dispersion of the bio-aerosol produced by the oak processionary moth

The oak processionary moth (Thaumetopoea processionea L.) is found in oak forests in most European countries. The caterpillars bear urticating hairs (setae) as a chemical defence. These hairs break off and are small enough to become airborne and be transported by the wind. Upon contact with humans the toxin can cause an allergic reaction that ranges from a skin rash to respiratory distress. In order to measure the terminal settling velocity of this bioaerosol, we used a small elutriator and tested its functionality with particles of known aerodynamic diameter. We determined that the mean settling velocity of the setae is about 1 cm/s, corresponding to an aerodynamic diameter of 19 μm for setae with a diameter of 6 μm and a length of 190 μm. The dispersion of the hairs in the atmosphere for a typical summer day was calculated by means of an Eulerian model. The results of this calculation revealed that the maximum concentrations in the atmosphere on a typical summer day reach 20–30% of the concentration found directly at the source. Those maximum concentrations are reached at a distance from the source that varies between 174 and 562 m, depending on the atmospheric stability and the settling velocity.

Collection characteristics of a batch-type wetted wall bioaerosol sampling cyclone

The collection efficiency and sample retention of a batch-type wetted wall bioaerosol sampling cyclone (BWWC) were experimentally characterized. The BWWC is designed to sample air at 400 l/min and concentrate the particles into 12 ml of water. Aerosol is transported into a cylindrically-shaped axial flow cyclone through a tangential slot and the particles are impacted on the inner wall, which is wetted by air shear acting on a liquid pool at the base of the cyclone. The retention of collected particles and the aerosol collection efficiency of the BWWC were evaluated with polystyrene latex beads (PSL), sodium fluorescein/oleic acid droplets, and Bacillus atrophaeus (aka BG) spores. The retention of particles was determined by adding hydrosol directly into the device, running the BWWC for a pre-set period of time, and then determining the amount of particulate matter recovered relative to the initial amount. For 1-μm diameter PSL, 90% of the particles were recoverable from the cyclone body immediately after their introduction; however, only 10% were retained in the collection liquid after 8 h of operation. The aerosol sampling efficiency was determined by comparing the amount of particulate matter collected in the liquid with that collected by a reference filter. The collection efficiency was 50–60% for 1- and 3-μm polystyrene (PSL) particles, and 1.5% for 10-μm oleic acid particles. The efficiency for 3-μm oleic acid droplets was 35%. Explanations are provided for the difference between liquid and solid particle behavior, and for the low efficiency for the large liquid particles. The collection efficiency for single spore BG was slightly lower than that for 1-μm PSL.     

Filtering mechanism of the honey bee proventriculus

ABSTRACT. The fine structure and function of a honey bee's ( Apis mellifera Linn.) proventriculus were studied by scanning electron microscopy and video-recording. Our observations revealed that the proventriculus is used to engulf pollen and other particles which contaminate the nectar carried into the crop. The four lips are closed and opened, pulled backwards and straightened by the external circular muscles and internal longitudinal muscles. Combs of filiform-hairs (70 μm in length) located on the margins of the lips 'catch' and filter particles from the fluid. By repeated filtering, opening and closing actions of the hairs and lips, particles are filtered and collected in pouches between the ventricular folds to form boluses and are eventually passed into the midgut. In the present experiment, particle sizes ranging from 0.5 to 100 μm in diameter, including dandelion pollen ( Taraxacum officinale Web.), Torula yeast ( Candida utilis Lodder et Kreger-Van Rij), bee disease spores of Nosema apis Zander and Bacillus larvae White, and man-made particles can be filtered by the hairs. Small particles (0.23 μm in diameter) filter through the hair and return back to the fluid. Large particles (100–200 μm in diameter) are caught between the stylets of the mouthparts and are not ingested. These observations suggest that the particle size plays an important role in determining what can be taken by the mouthparts and the proventriculus and what can later be utilized as a food source by the bee. The role of the proventriculus in disease transmission is also discussed.     

Regular arrays of intramembranous particles in the plasmalemma of guard cell and mesophyll cell protoplasts of Vicia faba

Freeze fractures of the plasmalemma membranes of guard-cell and mesophyll protoplasts of Vicia faba demonstrate that the inner monolayer of the plasmalemma is compartmentalized into areas with distinct, highly organized structures. Between areas of intramembranous particles dispersed randomly on a relatively smooth fracture face, membrane domains showing an extremely regular planar, hexagonal array of particles are interspersed. The dimensions of these hexagonal lattices are about 0.5 m in diameter, the center-to-center spacing is about 22 nm, and the particle size is about 9 nm. The particle in the hexagonal arrays are accompanied by complementary pits in the opposite monolayer fracture of the plasmalemma membrane.The freeze-fracture preparation was performed by using an improved Leybold Bioetch device which provides a sufficiently high cooling rate and allows the omission of cryoprotectants, like glycerol.Presented by H. Schnabl on the Workshop on Plant Membrane Transport, Toronto, Canada, July 1979     

Investigation of the anti-fungal activity of coptisine on Candida albicans growth by microcalorimetry combined with principal component analysis

Aims:  This study investigated the anti-fungal activity of coptisine on Candida albicans growth.
Methods and Results:  The metabolic power-time curves of Candida albicans growth at 37°C affected by coptisine were measured by microcalorimetry using an LKB-2277 Bioactivity Monitor with stop-flow mode. Then, the diameter of inhibitory zones in the agar layer was observed using agar cup method, and the minimal inhibitory concentration (MIC) of coptisine on Candida albicans growth was determined by serial dilution method. From the principal component analysis on nine quantitative parameters obtained from the power-time curves, we could easily evaluate the anti-fungal activity of coptisine by analysing the change of values of the main two parameters, growth rate constant k and maximum power output in the log phase P _{m, log}. The results showed that coptisine had strong anti-fungal activity: at a low concentration (45  μ g ml⁻¹) began to inhibit the growth of Candida albicans and at a high concentration (500  μ g ml⁻¹) completely inhibited Candida albicans growth. Coptisine gave big inhibitory zones with diameters between 11 and 43 mm within test range, and the MIC of it was 1000  μ g ml⁻¹.
Conclusions:  Coptisine had strong anti-fungal activity on Candida albicans growth. The method of microcalorimetry applied for the assay of anti-fungal activity of coptisine was quantitative, sensitive and simple.
Significance and Impact of the Study:  This work will provide useful information for the development of chemical biology policy in the use of anti-microbials in food and drug production.     

Aerodynamic particle size analysis of aerosols from pressurized metered-dose inhalers: Comparison of andersen 8-stage cascade impactor,next generation pharmaceutical impactor,and model 3321 aerodynamic particle sizer aerosol spectrometer

The purpose of this research was to compare three different methods for the aerodynamic assessment of (1) chloroflurocarbon (CFC)-fluticasone propionate (Flovent), (2) CFC-sodium cromoglycate (Intal), and (3) hydrofluoroalkane (HFA)-beclomethasone dipropionate (Qvar) delivered by pressurized metered dose inhaler. Particle size distributions were compared determining mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction <4.7 μm aerodynamic diameter (FPF_{<4.7 μm}). Next Generation Pharmaceutical Impactor (NGI)-size distributions for Flovent comprised finer particles than determined by Andersen 8-stage impactor (ACI) (MMAD=2.0±0.05 μm [NGI]; 2.8±0.07 μm [ACI]); however FPF_{<4.7 μm} by both impactors was in the narrow range 88% to 93%. Size distribution agreement for Intal was better (MMAD=4.3±0.19 μm (NGI), 4.2±0.13 μm (ACI), with FPF_{<4.7 μm} ranging from 52% to 60%. The Aerodynamic Particle Sizer (APS) undersized aerosols produced with either formulation (MMAD=1.8±0.07 μm and 3.2±0.02 μm for Flovent and Intal, respectively), but values of FPF_{<4.7 μm} from the single-stage impactor (SSI) located at the inlet to the APS (82.9%±2.1% [Flovent], 46.4%±2.4% [Intal]) were fairly close to corresponding data from the multi-stage impactors. APS-measured size distributions for Qvar (MMAD=1.0±0.03 μm; FPF_{<4.7 μm}=96.4% ±2.5%), were in fair agreement with both NGI (MMAD=0.9±0.03 μm; FPF_{<4.7 μm}=96.7%±0.7%), and ACI (MMAD=1.2±0.02 μm, FPF_{<4.7 μm}=98%±0.5%), but FPF_{<4.7 μm} from the SSI (67.1%±4.1%) was lower than expected, based on equivalent data obtained by the other techniques. Particle bounce, incomplete evaporation of volatile constituents and the presence of surfactant particles are factors that may be responsible for discrepancies between the techniques.