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At least 19 recordsLinked to original sources
PubMed2006

Spray pattern analysis for metered dose inhalers I: Orifice size, particle size, and droplet motion correlations.

Factors that influence spray pattern measurements of pressurized, metered-dose inhalers have been evaluated. Spray patterns were correlated with changes in actuator orifice diameter, particle size profiles, and calculated estimates of particle-size dynamics of plumes during a spray. Spray patterns, regardless of actuator orifice size, were ellipsoid in the vertical direction. Measures of elliptical ratio, major axis, and minor axis were significantly influenced by orifice size in a non-linear fashion over the range of orifice sizes investigated. Spray patterns also correlated with particle size profile and spray geometry measurements. Spray distribution asymmetry may be related to droplet evaporation and sedimentation processes. However, the spray patterns did not appear sensitive to changes in gravitational force acting on the plume. Instead, it is postulated that elliptical spray patterns may have dependence on fluid dynamic processes within the inhaler actuator. Developing an understanding of these processes may provide a basis for developing spray pattern tests with relevance to product performance.

Aerosol Propellants↗
PubMed1999

Simultaneous In-Situ Measurement of Local Particle Size, Particle Concentration, and Velocity of Aerosols.

Photon correlation spectroscopy has been applied to the characterization of (quasi-)monodisperse aerosols. The experiments were carried out with an experimental standard pin hole setup on laminar flowing aerosols of the submicrometer particle size range. It is shown that beside local mean particle size and local aerosol velocity simultaneously the local particle number concentration may be obtained from a single measured autocorrelation function. The proposed procedure does not require calibration. It is pointed out that measurement conditions can be adapted to the properties of the aerosol to be characterized, thus allowing characterization of aerosols over a wide parameter range, e.g., it is not restricted to the case of low particle concentration. The experimental results are compared to data from literature, data from reference measurements and data from a theoretical model, respectively. The method can also be usefull for characterization of other fluid-particle systems as hydrosols. Copyright 1999 Academic Press.

Journal Article↗
PubMed1982

Particle size reduction by a hammer mill I: Effect of output screen size, feed particle size, and mill speed.

A hammer mill is an impact mill commonly used in pharmaceutical manufacturing for reducing particle size for a variety of drugs. Commercial grade ammonium sulfate was milled as a model powder. This salt was sieved to obtain particle size fractions with average diameters of 1.3, 0.9, and 0.72 mm which were used as feed particles. The milled material was analyzed for particle size distribution (PSD) using standard sieves. At a moderate speed (approximately 2500 rpm), the feed size did not result in a significantly changed arithmetic mean diameter, dx of milled particles. A new particle size reduction constant, k, is proposed as a result of a linear relationship between dx and output screen size, dss. As dss decreases, the PSD range of milled particles narrows; as mill speed increases (approximately 5000 rpm), dx decreases. The decrease is of a greater magnitude for larger dss (2 mm) than for a smaller dss (1 mm). At low speeds (approximately 1000 rpm), the PSD is wider compared to medium and high speeds.

Ammonium Sulfate↗
PubMed1984

Particle size distributions and particle size alterations in microemulsions.

Several component diagrams for different alcohols as cosurfactants and potassium oleate as the surfactant were investigated. Between the regions of the water-in-oil microemulsion and the micellar solution (reverse micelles), and diagrams showed a zone of instability which was determined by particle size analysis by means of photon correlation spectroscopy (PCS). The polydispersity of the internal phase was determined at the instant of microemulsion formation and after fixed intervals of storage. At the edge of the microemulsion region, a rapid increase in particle size due to coalescence followed by breaking was observed. If a slow transition toward the region of solubilization could be seen by a slow decrease of the droplet size, coalescence was observed after storage. In the middle of the microemulsion region, the particle radius, however, was almost constant for a long interval. The velocity of the microemulsion formation depended on the alcohol used. In some cases a very fast formation (milliseconds) was observed; in others, macroemulsions were formed which became transparent within a few hours or days. PCS was used to follow the dynamic process of formation and breaking of such systems with droplet diameters of 5-200 nm by obtaining the mean hydrodynamic diameters. Distribution curves were calculated by the Laplace transform of the correlation function. The practicability of the method was demonstrated with mono- and polydispersed latex suspensions and microemulsions.

Emulsions↗
PubMed2006

Effects of surface charge, micro-bubble size and particle size on removal efficiency of electro-flotation.

Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar.

Aluminum Chloride↗
PubMed2006

Pulmonary bioassay studies with nanoscale and fine-quartz particles in rats: toxicity is not dependent upon particle size but on surface characteristics.

Pulmonary toxicology studies in rats demonstrate that nanoparticles are more toxic than fine-sized particles of similar chemistry. This study, however, provides evidence to contradict this theory. The aims of the study were (1) to compare the toxicity of synthetic 50 nm nanoquartz I particles versus (mined) Min-U-Sil quartz ( approximately 500 nm); the toxicity of synthetic 12 nm nanoquartz II particles versus (mined) Min-U-Sil ( approximately 500 nm) versus (synthetic) fine-quartz particles (300 nm); and (2) to evaluate the surface activities among the samples as they relate to toxicity. Well-characterized samples were tested for surface activity and hemolytic potential. In addition, groups of rats were instilled with either doses of 1 or 5 mg/kg of carbonyl iron (CI) or various alpha-quartz particle types in phosphate-buffered saline solution and subsequently assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation, and histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postexposure. Exposures to the various alpha-quartz particles produced differential degrees of pulmonary inflammation and cytotoxicity, which were not always consistent with particle size but correlated with surface activity, particularly hemolytic potential. Lung tissue evaluations of three of the quartz samples demonstrated "typical" quartz-related effects--dose-dependent lung inflammatory macrophage accumulation responses concomitant with early development of pulmonary fibrosis. The various alpha-quartz-related effects were similar qualitatively but with different potencies. The range of particle-related toxicities and histopathological effects in descending order were nanoscale quartz II = Min-U-Sil quartz > fine quartz > nanoscale quartz I > CI particles. The results demonstrate that the pulmonary toxicities of alpha-quartz particles appear to correlate better with surface activity than particle size and surface area.

Animals↗
PubMed2006

Pulmonary instillation studies with nanoscale TiO2 rods and dots in rats: toxicity is not dependent upon particle size and surface area.

Pulmonary toxicology studies in rats demonstrate that nanoparticles administered to the lung are more toxic than larger, fine-sized particles of similar chemistry at identical mass concentrations. The aim of this study was to evaluate the acute lung toxicity in rats of intratracheally instilled pigment-grade TiO2 particles (rutile-type particle size = approximately 300 nm) versus nanoscale TiO2 rods (anatase = 200 nm x 35 nm) or nanoscale TiO2 dots (anatase = approximately 10 nm) compared with a positive control particle type, quartz. Groups of rats were instilled with doses of 1 or 5 mg/kg of the various particle types in phosphate-buffered saline (PBS). Subsequently, the lungs of PBS- and particle-exposed rats were assessed using bronchoalveolar lavage fluid biomarkers, cell proliferation methods, and by the histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postinstillation exposure. Exposures to nanoscale TiO2 rods or nanoscale TiO2 dots produced transient inflammatory and cell injury effects at 24 h postexposure (pe) and were not different from the pulmonary effects of larger sized TiO2 particle exposures. In contrast, pulmonary exposures to quartz particles in rats produced a dose-dependent lung inflammatory response characterized by neutrophils and foamy lipid-containing alveolar macrophage accumulation as well as evidence of early lung tissue thickening consistent with the development of pulmonary fibrosis. The results described herein provide the first example of nanoscale particle types which are not more cytotoxic or inflammogenic to the lung compared to larger sized particles of similar composition. Furthermore, these findings run counter to the postulation that surface area is a major factor associated with the pulmonary toxicity of nanoscale particle types.

Animals↗
PubMed2004

Use of dimensionless residence time to study variations in breakthrough behaviour in expanded beds formed from varied particle size distributions.

This work demonstrates an experimental method for studying breakthrough behaviour in expanded beds. The behaviour of beds made with differently sized particles were studied at varying flowrates. The use of a dimensionless residence time measurement allowed a more valid comparison of breakthrough characteristics in expanded bed operation by compensating for the changes in bed volume that occur during expansion. We demonstrate that bed breakthrough behaviour can be compared directly even when the beds contain different-sized particles and hence have different expanded volumes. By utilising this concept we demonstrate that, in the case of the Alcohol Dehydrogenase (ADH) / STREAMLINE Phenyl system used here, there was little or no variation in ADH breakthrough behaviour between beds of differently sized particles operating at flowrates above 100 cm/h. This suggests that the higher specific surface area and hence binding capacity of smaller particles is negated in this case due to mass transfer limitations and the increase in system void volume even at normal operating flowrates of 200-300 cm/h.

Algorithms↗
PubMed1979

Effect of drug content and drug particle size on the change in particle size during tablet compression.

Three size fractions for each of three poorly soluble drugs were compressed into 10 mm diameter tablets of four different dilution ratios. The compression was carried out on a physical testing instrument at four compression levels of 49.0, 98.1, 196.2 and 294.3 MN m-2. The effect of drug content and drug particle size on the change in particle size during tableting was examined by the determination of the dissolution rate for disintegrated tablets. A linear relation was obtained when plotting 1n(T80%) versus drug content. There was a critical particle size where the phenomena of cleavage and bonding during tableting balanced each other, but this varied with drug content.

Chemistry, Pharmaceutical↗
PubMed1995

Dispersion coefficients of a protein and DNA fragment in polyacrylamide gel electrophoresis as a function of parameters defining the effective gel pore size and particle size.

The dispersion coefficient, D', of the representative homogeneous protein, conalbumin, decreases linearly as the polyacrylamide concentration increases from 4 to 14%T (2%C), and varies in a biphasic fashion as %C (Bis) is increased from 2 to 20%, with a broad peak between 5 and 15%C. D' increases linearly with the concentration of the initiator, potassium persulfate, in the range of 0.01-0.15%. D' remains constant when the field strength is varied from 5 to 15 V/cm. A DNA fragment (1857 bp) exhibits a constant D' in 4-6% polyacrylamide (2%C) at a field strength of 1 V/cm, and a linearly increasing D' at 5 V/cm, in analogy to its previously observed behavior in agarose gels. In solutions of uncrosslinked polyacrylamide, the decrease of the D' of conalbumin with polymer concentration is not significantly different from that in 2% N, N'-methylenebisacrylamide-crosslinked gels in the range of 4-14%T, while the decrease of mobility with polyacrylamide concentration is much steeper in 2% crosslinked compared to uncrosslinked polymer. Finally, delta (log D')/ delta T was found to be proportional to the retardation coefficient, KR (= -delta (log mu)/ delta T), in polyacrylamide gels. The ratio of -delta (log D')/ delta T over KR increases with field strength in the range of 5-15 V/cm.

Conalbumin↗
PubMed1998

In vitro toxicity of respirable-size particles of diatomaceous earth and crystalline silica compared with asbestos and titanium dioxide.

The relationship between particle characteristics and in vitro toxicity was investigated using Chinese hamster ovary cells. Test dusts included respirable natural (Nat) and flux-calcined (FC) diatomaceous earth (DE), quartz, cristobalite, TiO2, and chrysotile and crocidolite asbestos. All dusts elicited a qualitatively similar, concentration-dependent response: particle uptake, induction of micro- and polynuclei, and reduction in cell proliferation. However, similar mass concentrations of the dusts yielded a 35-fold range of toxicity: chrysotile > crocidolite > Nat DE > FC DE > quartz > Cristobalite > TiO2. In vitro toxicity did not correlate with crystalline silica content, surface area, composition, volume, particles/cm2, or fibrous geometry. Toxicity was closely associated with the number of particles/cm2 culture surface that had at least one dimension > 7.5 mu. Thus particle size but not shape could be a determinant of in vitro toxicity. Particle size might also impact in vivo pathogenesis.

Animals↗
PubMed2002

The effect of droplet size and powder particle size on the mechanisms of nucleation and growth in fluid bed melt agglomeration.

This study was performed in order to evaluate the effects of binder droplet size and powder particle size on agglomerate formation and growth in fluid bed spray agglomeration using a meltable binder. Three different lactose grades, 100, 125 or 350 mesh, were agglomerated using polyethylene glycol (PEG) 3000 at two different concentrations, 11.5 or 22% (volume/mass), and three spray droplet sizes, 30, 60 or 90 microm were applied. The ratio of droplet size/particle size was found to determine whether the mechanism of nucleation was distribution or immersion. Distribution was promoted by a low ratio, whereas immersion was promoted by a high ratio. Distribution as nucleation mechanism led to a more open agglomerate structure and immersion to a denser structure. When the nucleation phase was terminated, coalescence between rewetted nuclei or agglomerates was the growth mechanism with both preceding mechanisms of nucleation. A larger particle size of the lactose led to larger agglomerates. The difference in the effect on growth between the 30 and 60 microm droplets was generally low. The 90 microm droplets at 22% binder concentration offered a potential for uncontrollable growth giving rise to markedly larger agglomerates and a lower reproducibility than 30 and 60 microm droplets.

Particle Size↗
PubMed2002

Particle size and morphology of UHMWPE wear debris in failed total knee arthroplasties--a comparison between mobile bearing and fixed bearing knees.

Osteolysis induced by ultrahigh molecular weight polyethylene wear debris has been recognized as the major cause of long-term failure in total joint arthroplasties. In a previous study, the prevalence of intraoperatively identified osteolysis during primary revision surgery was much higher in mobile bearing knee replacements (47%) than in fixed bearing knee replacements (13%). We postulated that mobile bearing knee implants tend to produce smaller sized particles. In our current study, we compared the particle size and morphology of polyethylene wear debris between failed mobile bearing and fixed bearing knees. Tissue specimens from interfacial and lytic regions were extracted during revision surgery of 10 mobile bearing knees (all of the low contact stress (LCS) design) and 17 fixed bearing knees (10 of the porous-coated anatomic (PCA) and 7 of the Miller/Galante design). Polyethylene particles were isolated from the tissue specimens and examined using both scanning electron microscopy and light-scattering analyses. The LCS mobile bearing knees produced smaller particulate debris (mean equivalent spherical diameter: 0.58 microm in LCS, 1.17 microm in PCA and 5.23 microm in M/G) and more granular debris (mean value: 93% in LCS, 77% in PCA and 15% in M/G).

Aged↗
PubMed2006

Preparation of hemoglobin-loaded nano-sized particles with porous structure as oxygen carriers.

Hb (hemoglobin)-loaded particles (HbP) encapsulated by a biodegradable polymer used as oxygen carrier were prepared. A modified double emulsion and solvent diffusion/evaporation method was adopted. All experiments were performed based on two types of biodegradable polymers, poly(epsilon-caprolactone) (PCL) and poly(epsilon-caprolactone-ethylene glycol) (PCL-PEG). The biodistribution and the survival time in blood of the particles were investigated in a mouse model. Encapsulation efficiency and pore-connecting efficiency were evaluated by a novel sulfocyanate potassium method. The influence of process parameters on the particle size and pore-connecting efficiency (PCE%) of nanoparticles have been discussed. The prepared conditions: solvent, external aqueous phase, pressure were discussed. The system utilizing dichloromethane (DCM)/ethyl acetate (EA) as a solvent with an unsaturated external aqueous phase yielded the highest encapsulation efficiency (87.35%) with a small mean particle size (153 nm). The formation of porous channels was attributed to the diffusion of solvent. The PCE% was more sensitive to the rate of solvent diffusion that was obviously affected by the preparation temperature. The PCE% reached 87.47% when PCL-PEG was employed at 25 degrees C. P(50) of HbP was 27 mmHg, which does not seem to be greatly affected by the encapsulation procedure. In vivo, following intravenous injection of 6-coumarin labeled HbP, the major organ accumulating Hb-loaded particles was the liver. The half-life of nano-sized PCL HbP was 3.1 times as long as the micro-sized PCL HbP. Also, Nano-sized as well as a PEGylated surface on HbP is beneficial for prolonged blood residence (7.2 fold increase).

Animals↗