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At least 289 records · Page 16Linked to original sources

PubMed2003

Characterization of particle sizes in bulk pharmaceutical solids using digital image information.

The purpose of this study was to demonstrate a novel method of extracting relevant information from undispersed bulk powder surfaces to be used in particle size analysis. A new surface imaging approach for undispersed powders combined with multivariate modeling was used. Digital surface images of various granule batches were captured using an inventive optical setup in controlled illumination conditions. A descriptor, the gray scale difference matrix (GSDM), which describes the particle size of granular material was generated and extracted from the powder surface image information. Partial least squares (PLS) modeling was used to create a model between the GSDM and the particle size distribution of granules measured with sieving. The use of lateral illumination and the combining of information from 2 surface images strengthened the shading effects on the powder surfaces. The shading effects exposed the topography or the visual texture of the powder surfaces. This textural information was efficiently extracted using the GSDM descriptor. The goodness-of-fit (R2) for the created PLS model was 0.91 and the predicted variation (Q2) was 0.87, indicating a good model. The model covered granule sizes in the size range of approximately 20 to 2500 microm. The extracted descriptor was effectively used in particle size measurement. This study confirms that digital images taken from undispersed bulk powder surfaces contain substantial information needed for particle size distribution analysis. The use of the GSDM enabled the utilization of bulk powder surface information and provided a fast method for particle size measurement.

Chemistry, Pharmaceutical↗

PubMed1999

Influence of particle size on the effectiveness of the fiber in corn silage.

This experiment evaluated the influence of particle size on the effectiveness of fiber in corn silage relative to that in hay crop, which consisted of mostly alfalfa silage. Fifteen multiparous Holstein cows were assigned to five treatments in each of 2 yr. The design was replicated but truncated 5 x 5 Latin squares with three 21-d periods in 1994 and four 21-d periods in 1995. The five diets (2-yr average, dry basis) were a basal, low fiber control with 12% neutral detergent fiber (NDF) from hay crop forage (60% of total diet NDF); a high fiber control with 22% NDF from hay crop forage (82% of total diet NDF); and three diets each containing 12% NDF from hay crop forage and 9% NDF from coarse corn silage, fine corn silage, or an equal mixture of the two. An increase in the forage content above the basal amount with either hay crop or corn silage increased rumination and total chewing time. No detectable differences in rumination, total chewing time, or milk fat concentration were detected among the corn silage diets. In yr 1, yield of milk components and dry matter intake were greater for cows fed the four low alfalfa diets, but there was no effect due to particle size of the corn silage. In yr 2, linear increases in milk, fat, and protein yields were observed as the mean particle size of the corn silage decreased. Reduction of corn silage particle size did not affect chewing behavior.

Animals↗

PubMed1996

Relationship between drug percolation threshold and particle size in matrix tablets.

PURPOSE: Since a previous qualitative study carried out by us showed the existence of an important influence of the particle size on the percolation thresholds and taking into account that the existing theoretical models can only provide qualitative explanation to this influence, the purpose of this work is to carry out the first quantitative study of the influence of the particle size over the drug percolation thresholds. METHODS: Matrix tablets have been elaborated using potassium chloride as drug model and Eudragit RS-PM as matrix forming material. Five different KCl particle size fractions have been employed whereas the Eudragit RS-PM particle size was kept constant. In-vitro release assays were carried out for all the elaborated lots. The drug percolation thresholds were estimated following the method proposed by Bonny and Leuenberger. RESULTS: A linear relationship has been found between the drug particle size and the corresponding drug percolation threshold. CONCLUSIONS: This finding confirms the results previously obtained in our qualitative study and has important repercussions in the design of pharmaceutical solid dosage forms. If this linear behaviour is general, the percolation threshold can soon become a useful preformulation parameter.

Chemical Phenomena↗

PubMed1995

Relationship between particle size of barium glass filler and water sorption of light-cured composite resin.

The reaction of barium glass filler with water was determined by investigation of the effects of the particle size of barium glass filler on the water sorption rate and the mechanical properties of composite resin. Barium glass and quartz were milled to obtain powders with different average particle sizes. These powders were silanized and used as inorganic filler in composite resin. Photoactivated base monomer was loaded at 65% (w/w) with these fillers to prepare the composite resin paste. The water sorption of barium glass filled resin was always more than that of quartz filled resin. The amount of sorbed water obtained by barium glass filled resin increased as the particle size decreased. The particle size of the quartz filler did not affect the water sorption. The flexural strength of barium filled resin decreased after water immersion more than that of the quartz filled resin as the particle size decreased. These results suggest that the water durability of barium glass is low and the surface of barium glass filler is damaged by water. Water would be retained in the interface between the barium glass filler and the matrix resin.

Absorption↗

PubMed1994

Effect of grain particle size on performance. 2. Grain texture interactions.

Diets were prepared with corn, wheat, or sorghum ground in a hammer mill and sieved to obtain coarse, medium, and fine particle size fractions. Their effect on broiler performance from hatch to 7 d and from 7 to 21 d of age was studied. The effect of particle size on the size and pH of the gastrointestinal organs was also determined. The three textures obtained for each grain were uniform in geometric mean diameter (GMD) and geometric standard deviation (GSD). Grain by texture interactions were not significant. Independent of grain source, the best performance was obtained with diets prepared from the medium texture. In these diets, the GMD of the grains varied from 1.13 to 1.23 mm and the GSD from 1.19 to 1.35. The fine fraction (GMD .57 to .67 mm) resulted in the lowest performance and that resulting from the coarse fraction (GMD 2.01 to 2.10 mm) was intermediate. At 7 and 21 d of age, gizzard weight and content were positively related to particle size. At the age of 21 d, duodenum weight and content was highest in chicks fed the fine diets. The pH of the gizzard content decreased with increasing grain particle size, whereas that of the small intestinal content increased. Some grain effects were also observed on the gastrointestinal tract. Gizzard weight was greatest in the cornfed birds. Wheat-fed chicks had the heavier intestines and contents. After overnight feed deprivation, feed consumption by 7-d-old chicks was related to the particle size during the first 2 h of refeeding, with greater intake of medium and coarse grains.

Animal Feed↗

PubMedDate not supplied

Arabinogalactan-coated superparamagnetic iron oxide: effect of particle size in liver MRI.

OBJECTIVE: We evaluated the effect of particle size on MR contrast-enhancing properties of arabinogalactan-coated superparamagnetic iron oxide (AG-SPIO) in tumor-bearing rats. MATERIALS AND METHODS: T2*-weighted gradient-recalled echo MR studies were performed on rats with surgically implanted liver tumors before and after AG-SPIO administration. Contrast-to-noise ratio (CNR) and percent contrast enhancement (PCE) were calculated for animals given small (15.7 +/- 9.5 nm: n = 6), medium (49.1 +/- 19.7 nm; n = 4), and large (86.9 +/- 27.5 nm; n = 4) particles intravenously (10 mumol Fe/kg). RESULTS: Postcontrast CNRs were 15.8 +/- 6.9, 8.9 +/- 4.1, and 10.0 +/- 1.8 for small, medium, and large particle groups, respectively. The PCE was -60.0 +/- 3.3, -75.5 +/- 7.9, and -80.5 +/- 1.2%. There was a significant difference in preversus postcontrast CNR for all particle sizes (p < 0.001) and in PCE for small particles as compared with the two larger sizes (p < 0.001). There was no between-group statistical difference in postcontrast CNR for any particle size. CONCLUSION: Larger AG-SPIO particles slightly improve liver contrast enhancement, but have no significant effect on hepatic lesion detection as assessed by CNR.

Animals↗

PubMed1999

High-resolution, submicron particle size distribution analysis using gravitational-sweep sedimentation.

Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, pigments, lacquers, and emulsions must be characterized. There is a rich history of methods developed for the polymer industry finding use in the biochemical sciences. Two such methods are presented. These use analytical ultracentrifugation to determine the density and size distributions for submicron-sized particles. Both methods rely on Stokes' equations to estimate particle size and density, whereas turbidity, corrected using Mie's theory, provides the concentration measurement. The first method uses the sedimentation time in dispersion media of different densities to evaluate the particle density and size distribution. This method works provided the sample is chemically homogeneous. The second method splices together data gathered at different sample concentrations, thus permitting the high-resolution determination of the size distribution of particle diameters ranging from 10 to 3000 nm. By increasing the rotor speed exponentially from 0 to 40,000 rpm over a 1-h period, size distributions may be measured for extremely broadly distributed dispersions. Presented here is a short history of particle size distribution analysis using the ultracentrifuge, along with a description of the newest experimental methods. Several applications of the methods are provided that demonstrate the breadth of its utility, including extensions to samples containing nonspherical and chromophoric particles.

Deuterium Oxide↗

PubMed1993

Effect of a high-fat meal on the bioavailability of phenytoin in a commercial powder with a large particle size.

The effect of a high-fat meal on the bioavailability of free acid phenytoin (DPH) from Hydantol powder with a large particle size (mean particle size, 190 microns) was investigated in four healthy male subjects. The drug was administered as a single oral 5 mg/kg dose of free acid DPH in the fasting state, with a low-fat meal, or with a high-fat meal using a crossover study design. Seven blood samples were collected over a 34-h period following drug administration, and the drug plasma concentrations were determined by GLC. In comparison with the fasting state results, the mean area under the plasma concentration-time curve up to infinity after administration (AUC0-infinity) and the peak plasma concentration (Cmax) of DPH from Hydantol powder significantly increased about 2-fold with the intake of the high-fat meal and about 1.5-fold with the intake of the low-fat meal. The elimination rate constant was not significantly different among the three treatments. The increased bioavailability with the high-fat meal probably resulted from accelerated dissolution of the poorly soluble Hydantol powder due to the stimulation of bile flow or delay of the gastric emptying time caused by the fat intake.

Adult↗

PubMed2003

Effects of insulin resistance and type 2 diabetes on lipoprotein subclass particle size and concentration determined by nuclear magnetic resonance.

The insulin resistance syndrome (IRS) is associated with dyslipidemia and increased cardiovascular disease risk. A novel method for detailed analyses of lipoprotein subclass sizes and particle concentrations that uses nuclear magnetic resonance (NMR) of whole sera has become available. To define the effects of insulin resistance, we measured dyslipidemia using both NMR lipoprotein subclass analysis and conventional lipid panel, and insulin sensitivity as the maximal glucose disposal rate (GDR) during hyperinsulinemic clamps in 56 insulin sensitive (IS; mean +/- SD: GDR 15.8 +/- 2.0 mg. kg(-1). min(-1), fasting blood glucose [FBG] 4.7 +/- 0.3 mmol/l, BMI 26 +/- 5), 46 insulin resistant (IR; GDR 10.2 +/- 1.9, FBG 4.9 +/- 0.5, BMI 29 +/- 5), and 46 untreated subjects with type 2 diabetes (GDR 7.4 +/- 2.8, FBG 10.8 +/- 3.7, BMI 30 +/- 5). In the group as a whole, regression analyses with GDR showed that progressive insulin resistance was associated with an increase in VLDL size (r = -0.40) and an increase in large VLDL particle concentrations (r = -0.42), a decrease in LDL size (r = 0.42) as a result of a marked increase in small LDL particles (r = -0.34) and reduced large LDL (r = 0.34), an overall increase in the number of LDL particles (r = -0.44), and a decrease in HDL size (r = 0.41) as a result of depletion of large HDL particles (r = 0.38) and a modest increase in small HDL (r = -0.21; all P < 0.01). These correlations were also evident when only normoglycemic individuals were included in the analyses (i.e., IS + IR but no diabetes), and persisted in multiple regression analyses adjusting for age, BMI, sex, and race. Discontinuous analyses were also performed. When compared with IS, the IR and diabetes subgroups exhibited a two- to threefold increase in large VLDL particle concentrations (no change in medium or small VLDL), which produced an increase in serum triglycerides; a decrease in LDL size as a result of an increase in small and a reduction in large LDL subclasses, plus an increase in overall LDL particle concentration, which together led to no difference (IS versus IR) or a minimal difference (IS versus diabetes) in LDL cholesterol; and a decrease in large cardioprotective HDL combined with an increase in the small HDL subclass such that there was no net significant difference in HDL cholesterol. We conclude that 1) insulin resistance had profound effects on lipoprotein size and subclass particle concentrations for VLDL, LDL, and HDL when measured by NMR; 2) in type 2 diabetes, the lipoprotein subclass alterations are moderately exacerbated but can be attributed primarily to the underlying insulin resistance; and 3) these insulin resistance-induced changes in the NMR lipoprotein subclass profile predictably increase risk of cardiovascular disease but were not fully apparent in the conventional lipid panel. It will be important to study whether NMR lipoprotein subclass parameters can be used to manage risk more effectively and prevent cardiovascular disease in patients with the IRS.

Adult↗

PubMed2006

Regularized inversion method for retrieval of aerosol particle size distribution function in W(1,2) space.

A determination of the aerosol particle size distribution function by using the particle spectrum extinction equation is an ill-posed integral equation of the first kind. To overcome this, we must incorporate regularization techniques. Most of the literature focuses on the Phillips-Twomey regularization or its variations. However, there are drawbacks for some applications in which the real aerosol distributions have large oscillations in a Junge-type distribution. The reason for this is that the scale matrix based on the norm of the second differences in the Phillips-Twomey regularization is too ill- conditioned to filter the large perturbations induced by the small algebraic spectrum of the kernel matrix and the additive noise. Therefore we reexamine the aerosol particle size distribution function retrieval problem and solve it in W1,2 space. This setting is based on Sobolev's embedding theorem in which the approximate solution best simulates the true particle size distribution functions. For choosing the regularization parameters, we also develop an a posteriori parameter choice method, which is based on the discrepancy principle. Our numerical results are based on the remote sensing data measured by the CE318 sunphotometer in Jia Xiang County, Shan Dong Province, China, and are performed to show the feasibility of the proposed algorithms.

Journal Article↗

PubMed1999

Dielectric Dispersion of Colloidal Suspensions in the Presence of Stern Layer Conductance: Particle Size Effects.

In this work, we discuss the role that particle size plays in the manifestations of surface conduction on the dielectric response of colloidal dispersions. To that aim, experimental data on the dielectric constant of polystyrene suspensions of two different particle diameters (23 and 530 nm) are first compared to the predictions of a classical or standard model (E. H. B. DeLacey and L. R. White, J. Chem. Soc. Faraday Trans. 2 77, 2007 (1983)), and it is found that, while the latter explains reasonably the dielectric behavior of the smallest particles, it considerably underestimates the phenomenon in the case of large particles. To explain these results in terms of contributions of ion motions in the inner region of the double layer of the particles, the approach followed by C. S. Mangelsdorf and L. R. White (J. Chem. Soc. Faraday Trans. 86, 2859 (1990)) is used to incorporate surface conductance in the theory of dielectric response of suspensions. In ac fields it is found that the model considerably improves the comparison between theory and experiment, whereas its use seems unnecessary for the smallest particles, where, whatever the combination used for the parameters of the theory, its predictions do not differ from the standard theory. Only in the case of the larger particles studied does the introduction of surface conductance play any role. A comparison between both types of theoretical results in a wide range of particle sizes demonstrates that Stern layer conductance always increases the magnitude of the low-frequency dielectric constant of suspensions, but its effect is less important the smaller the particle size and the larger the zeta potential for fixed ionic conditions in the dispersion medium. Copyright 1999 Academic Press.

Journal Article↗

PubMed1997

Fractional esterification rate of cholesterol in high density lipoprotein is correlated with low density lipoprotein particle size in children.

Small low density lipoprotein (LDL) particles are thought to be more atherogenic than larger LDL particles, although this association may depend on plasma triglyceride (TG) and high density lipoprotein (HDL) levels. To help prevent coronary artery disease (CAD), it may be useful to understand risk factors during childhood and adolescence. In the present study, we evaluated low density lipoprotein particle size (LDL-size) by 2-16% gradient gel electrophoresis in 70 healthy children (30 boys and 40 girls) along with conventional lipid and lipoprotein parameters which are thought to affect LDL-size. The fractional and molar esterification rates (FER and MER) of cholesterol in plasma and HDL were also determined. As expected, plasma levels of TG, HDL-cholesterol (HDL-C) and apoA-I were closely associated with LDL-sizes in both sexes (boys: r = -0.694, 0.708 and 0.701, girls: r = -0.579, 0.551 and 0.539, P < 0.001). However, a closer association was found between FER in HDL (FER(HDL)) and LDL-size (boys: r= -0.874, girls: r= -0.642, P < 0.001). In a stepwise multiple regression analysis, FER(HDL) alone accounted for 76% and 41% of the variability in LDL-size in boys and girls, respectively. MER in HDL accounted for additional 4% and 19% in boys and girls, respectively. Other parameters, including plasma TG, HDL-C and apoA-I had no significant additional effects. Thus, the determination of FER(HDL) is useful to predict the particle size of LDL in children.

Adolescent↗

PubMed1979

Effect of particle size distribution on hexamethylmelamine toxicity in rats.

Single oral dose toxicities of six hexamethylmelamine samples with different particle size distributions were evaluated in Osborne-Mendel rats. The calculated LD50 values for the 6 samples were 1706 to 2150 mg/kg )10,236 to 12,900 mg/m2). The two samples with median particle size less than 40 micron were more toxic than the other 4 samples. Among the latter samples, severity of toxic effects was not correlated with particle size. Leukocytes, lymphocytes, platelets and body weight showed dose-related decreases for all samples. Particle size appeared to have a minimal effect on these variables. The drug produced toxic effects on rapidly proliferating tissues: lymphoid, hematopoietic and germinal epithelium. At lethal doses, microscopic lesions were lymphoid tissue hypoplasia, bone marrow hypoplasia with elevated myeloid:erythroid ratios and spermatogenic arrest. The major target organs at nonlethal doses were bone marrow and germ cells, with germinal epithelium showing the most severe lesions.

Altretamine↗

PubMed1995

Effects of mill type and particle size uniformity on growth performance, nutrient digestibility, and stomach morphology in finishing pigs.

The effects of particle size uniformity and mill type used to grind corn were determined in three experiments. In Exp. 1, 120 pigs (47.8 kg initial BW) were used. Treatments were 1) a 40:60 blend of coarsely rolled (in a roller mill) and finely ground (in a hammermill) corn with a large standard deviation (sgw) of particle size (sgw of 2.7), 2) hammermilled corn with an sgw of 2.3, and 3) roller-milled corn with an sgw of 2.0. Mean particle size of the corn was approximately 850 microns for all treatments. Growth performance was not affected (P > .11); but, stomach keratinization tended to be less severe (P < .08) and apparent nutrient digestibilities were greater (P < .008) when the sgw was smaller. In Exp. 2, 128 pigs (55.3 kg initial BW) were used. Treatments were corn ground in a hammermill and a roller mill to 800 and 400 microns. Pigs fed corn ground to 400 microns were more efficient (P < .004) and had greater apparent digestibilities of DM, N, and GE (P < .001) than pigs fed corn ground to 800 microns. Mill type did not affect growth performance (P > .40), but pigs fed corn ground in the roller mill had greater apparent nutrient digestibilities (P < .008). In Exp. 3, 128 pigs (67.3 kg initial BW) were used. Treatments were corn ground to 400 microns in a hammermill and a roller mill fed in meal and pelleted forms. Pigs fed pelleted diets had greater ADG (P < .003) and gain/feed (P < .03) but also had greater incidence of ulcers (P < .04). Pigs fed roller-milled corn were more efficient (P < .05) and had a lower incidence of ulcers (P < .04), but diets with hammermilled corn had lower sgw and greater apparent digestibilities of nutrients (P < .02). Our results suggest that mill type had inconsistent effects on growth performance, but more uniform particle sizes consistently gave greater nutrient digestibilities.

Animal Feed↗

PubMed2006

Influence of different purification techniques on triamcinolone yield and particle size spectrum.

BACKGROUND: To systematically investigate the common purification techniques for commercially available triamcinolone acetonide preparations and the influence of different filter parameters on final yield, reproducibility and particle size spectrum. METHODS: Two non-filter techniques using either sedimentation or centrifugation, and two different filter techniques were tested. Filters with different characteristics were investigated with the pore size ranging from 0.1 to 5.0 microm, and the filter diameter ranging from 4 to 30 mm. Only sterile standard syringe filters with low adsorptive characteristics (hydrophilic cellulose filter membranes) for pharmaceutical use were employed. For quantification, triamcinolone acetonide was dissolved in 60% methanol and measured spectrophotometrically at 239 nm. The crystal size spectrum was determined using a particle size analyzer that combines electronic pulse area analysis and resistance measurement. RESULTS: Depending on the purification technique used the resulting triamcinolone doses differed significantly. While the centrifugation method achieved purification without relevant loss, the sedimentation method yielded only 28.7% compared to the original commercial suspension, and in addition, the predictability was low (range 8.1-17.2 mg). With filter techniques high and consistent doses with a good reproducibility were achieved, but results were highly dependent on the filter characteristics. The final triamcinolone amount inversely correlated with the filter diameter due to a uniform loss of crystalline particles. In contrast, enlarging the pore size caused a substantial shift in the particle size spectrum due to a selective loss of small crystalline particles. CONCLUSIONS: The most common purification techniques vary notably in regard to final triamcinolone doses, reproducibility and particle size spectrum. The appropriate choice of the filter parameters seems to be more important than assumed, as pore size and filter diameter substantially influence both the final TA doses and the particle size of the TA crystals.

Centrifugation↗

PubMed2006

Polydisperse particle size characterization by ultrasonic attenuation spectroscopy in the micrometer range.

The theoretical advantages of ultrasonic attenuation spectroscopy for particle size are currently not fully utilized. Especially in the region of larger particles, there is a lack of experimental confirmation of applicable models which may be used to infer particle sizes from measured attenuation spectra. With the present work, an attempt is made to supply experimental data, obtained with a commercially available ultrasonic attenuation spectrometer, and model calculations, which are based on the resonant scattering theory. It is shown that measured attenuation results for various combinations of disperse and continuous phase for both polydisperse emulsions and suspensions are reproducible by calculation. The approach is further examined for suspensions of porous particles. Here, the resonant scattering approach is combined with the Biot model for poroelasticity to obtain attenuation results with several fractions of titania aggregates, differing in particle size and pore diameter. The results indicate that the theory of resonant scattering is a valid approach if applied to particle size characterization in the large particle limit.

Journal Article↗

PubMed1975

Effect of particle size on the bioavailability of digoxin.

The bioavailability of digoxin in three tablets prepared from materials with different particle sizes was measured in healthy volunteers in a cross-over study using an alcoholic solution of digoxin as a reference standard. Its bioavailability in tablets with particle sizes of 7 mu or 13 mu was 78-97% of that of digoxin in solution. The tablet with largest particle size (102 mu) showed markedly lower bioavailability than the reference solution, namely 39%. It is obvious that particle size is an important determinant of the dissolution rate and bioavailability of digoxin.

Administration, Oral↗

PubMed2004

The effect of particle size of commercial soybean meal on performance and nutrient utilization of broiler chicks.

An experiment was conducted to determine the effects of soybean meal (SBM) particle size on broiler performance, particularly P utilization. This experiment utilized a 2 x 2 x 2 factorial design with the following variables: SBM particle size, P level, and diet type, either corn-SBM or semipurified. SBM was obtained from a processing plant before (geometric mean diameter 1,239 microm) and after (891 microm) hammer milling. The P levels were 0.5% total P for deficient diets and 0.7% total P for adequate P diets. The coarse SBM improved bone ash (P < 0.05), gain:feed ratios (P < 0.1), and plasma P levels (P < 0.1). The diets with 0.5% P resulted in overall poorer performance as 16-d BW was reduced, gain:feed ratio decreased, bone ash decreased, and rickets incidence increased. Chicks fed the semipurified diets also had lower 16-d BW, lower gain-to-feed ratio, and lower bone ash. There was a significant interaction between the diet type and the soy particle size when the corn-SBM meal diets were fed because the coarse SBM increased plasma P levels, whereas there was little effect when the semipurified diets were fed. There were also significant interactions observed between these variables on growth and gain:feed ratio in that the coarse SBM elicited a much more dramatic response when incorporated into the semipurified diets as opposed to the corn-SBM diets. The results suggest that large particle size soybean meal may be more efficiently utilized than fine particle size soybean meal.

Animal Nutritional Physiological Phenomena↗