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At least 217 records · Page 12Linked to original sources

PubMed1997

Effects of dietary fat restriction on particle size of plasma lipoproteins in postmenopausal women.

Hypertriglyceridemia is an independent risk factor for coronary artery disease (CAD) and is also commonly associated with other coronary risk factors, ie, small, dense low-density lipoprotein (LDL) particles and low plasma levels of high-density lipoprotein cholesterol (HDL-C). Dietary fat restriction is recommended for the prevention of nutrition-related cancers. Low-fat, high-carbohydrate intake can increase plasma triglyceride (TG) and decrease HDL-C. In general, plasma TG levels are inversely related to the particle size of LDL. We investigated the effects of dietary fat restriction on the concentration and particle size of plasma lipoproteins in 14 healthy postmenopausal women (aged 61 +/- 11 years). During a 4-month period of eucaloric controlled feeding, dietary fat was reduced stepwise from a habitual intake of 33% +/- 8% to 23% and then to 14% of daily energy. Changes in the plasma lipid level and particle size of very-low-density lipoprotein (VLDL), LDL, and HDL were determined at the end of each dietary phase. Increasing carbohydrate intake without weight loss was associated with an increase in plasma TG (1.86 +/- 0.30 v 2.47 +/- 0.37 mmol/L) and decreases in total cholesterol (5.82 +/- 0.25 v 5.40 +/- 0.21 mmol/L), LDL-C (3.07 +/- 0.18 v 2.61 +/- 0.21 mmol/L), HDL-C (1.42 +/- 0.1 v 1.24 +/- 0.1 mmol/L), and apolipoprotein (apo) A1 (5.14 +/- 0.25 v 4.61 +/- 0.36 mmol/L), whereas plasma apo B did not change. The particle size of VLDL increased (42.7 +/- 1.4 v 47.0 +/- 0.9 nm). However, there was no change in either LDL (25.1 +/- 0.2 v 25.3 +/- 0.2 nm) or HDL particle size. Although at each level of dietary fat intake LDL particle size correlated inversely with plasma TG and apo B, there was no relationship between the increase in plasma TG and LDL particle size. These results show that hypertriglyceridemia caused by a eucaloric high-carbohydrate intake is not associated with a decrease in LDL particle size. Therefore, carbohydrate-induced hypertriglyceridemia may not have the same atherogenic potential as genetic hypertriglyceridemias.

Aged↗

PubMed2004

Physical properties of organic particulate UV absorbers used in sunscreens II. UV-attenuating efficiency as function of particle size.

In this study the UV-attenuating properties of microparticles consisting of a benzotriazole derivative were investigated, which are used as absorbers for UV radiation in cosmetic sunscreens. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. In order to study even smaller particles, the sample with particle size 0.16 microm was fractionated further by centrifugation. Particle sizes were measured using fiberoptic quasi-elastic light scattering (FOQELS) and laser diffractometry. The UV-attenuating properties of the dispersions with different particle sizes were assessed using UV spectroscopy. With decreasing particle size the efficiency of the UV extinction of the dispersion increases up to a particle size of 80 nm. For particles smaller than 80 nm the UV extinction decreases again indicating an optimum at 80 nm. From reflection spectroscopic measurements it was found that scattering makes about 10%, and absorption 90%, of the UV-attenuating effect of the particles, which are obtained at the end of the milling process.

Centrifugation↗

PubMed2003

Multimodal particle size distributions emitted from HFA-134a solution pressurized metered-dose inhalers.

The purpose of this research was to investigate the measurement and in vitro delivery implications of multimodal distributions, occurring near or in the respirable range, emitted from pressurized metered-dose inhalers (pMDIs). Particle size distributions of solution pMDIs containing hydrofluoroalkane-134a (HFA-134a) and ethanol were evaluated using 2 complementary particle-sizing methods: laser diffraction (LD) and cascade impaction (CI). Solution pMDIs were formulated from mixtures of HFA-134a (50%-97.5% wt/wt) and ethanol. A range of propellant concentrations was selected for a range of vapor pressures. The fluorescent probe, Rhodamine B, was included for chemical analysis. The complementary nature of LD and CI allowed identification of 2 dominant particle size modes at 1 and 10 micro m or greater. Increasing propellant concentrations resulted in increases in the proportion of the size distributions at the 1- micro m mode and also reduced the particle size of the larger droplet population. Despite significant spatial differences and time scales of measurement between the particle-sizing techniques, the fine particle fractions obtained from LD and CI were practically identical. This was consistent with LD experiments, which showed that particle sizes did not decrease with increasing measurement distance, and may be explained by the absence of significant evaporation/disintegration of larger droplets. The fine particle fractions (FPFs) emitted from HFA-134a/ethanol solution pMDI can be predicted on the basis of formulation parameters and is independent of measurement technique. These results highlight the importance of presenting particle size distribution data from complementary particle size techniques.

Aerosols↗

PubMed1991

Effects of various non-esterified fatty acids on the particle size redistribution of high density lipoproteins induced by the human cholesteryl ester transfer protein.

The effects of various non-esterified fatty acids on the CETP-mediated particle size redistribution of HDL were studied by incubating HDL3 and CETP for 24 h at 37 degrees C in the absence or in the presence of either saturated, monounsaturated or polyunsaturated non-esterified fatty acids. In the absence of non-esterified fatty acids, CETP induced a redistribution of the initial population of HDL3 (Stokes' radius 4.3 nm) by promoting the appearance of one larger (Stokes' radius 4.8 nm) and two smaller (Stokes' radii 3.9 and 3.7 nm) HDL subpopulations. Whereas the non-esterified fatty acids alone did not modify the HDL3 distribution profile, they were able to alter markedly the capacity of CETP to induce the particle size redistribution of HDL. All the saturated fatty acids with at least 10 carbons were able to increase the formation of the very small sized particles (Stokes' radius 3.7 nm) in a concentration dependent manner, the medium chain fatty acids (12 and 14 carbons) being the best activators. The potential effect of non-esterified fatty acids was also influenced by the presence of double bonds in their monomeric carbon chain. While at low concentrations of non-esterified fatty acids (0.1 mmol/l) the enhancement of the formation of very small HDL particles appeared to be greater with oleic and linoleic acids than with stearic acid, at higher concentrations (0.4 mmol/l), oleic, linoleic and arachidonic acids decreased the formation of the 3.7 nm radius particles. The inhibition of the process at high concentrations of unsaturated fatty acids was linked to the degree of unsaturation of their carbon chain, arachidonic acid being the strongest inhibitor. The present study has demonstrated that non-esterified fatty acids can modulate the particle size redistribution of HDL3 mediated by the cholesteryl ester transfer protein even in the absence of any other lipoprotein classes. The effect of non-esterified fatty acid is dependent on both the length and the degree of unsaturation of their monomeric carbon chain.

Carrier Proteins↗

PubMed1995

LDL particle size in mildly hypertriglyceridemic subjects: no relation to insulin resistance or diabetes.

We examined 18 Type 2 diabetic and 19 non-diabetic subjects in order to determine the association between insulin resistance and LDL particle size distribution in mildly hypertriglyceridemic and hyperinsulinemic subjects with and without Type 2 diabetes. Insulin sensitivity of the patients was characterized by their insulin-stimulated glucose uptake rate determined by euglycemic clamp technique. LDL particle size distribution was determined by nondenaturing polyacrylamide gradient gel electrophoresis. Type 2 diabetic and non-diabetic subjects had closely similar serum lipid and lipoprotein concentrations as well as the mean particle diameters of the major LDL peak (246 +/- 6 A and 244 +/- 6 A, respectively). To evaluate the effect of insulin resistance on LDL particle size the participants were categorized into two subgroups using the median of their insulin-stimulated glucose uptake rate (14.67 mumol/kg/min) as a cut-off point. Neither lipid and lipoprotein concentrations nor the LDL particle size distributions differed between the more insulin resistant group (nine diabetic and nine non-diabetic subjects) and less insulin resistant group (nine diabetic and ten non-diabetic subjects). LDL particle size was not associated with the insulin-stimulated glucose uptake rate or with the mean 24-h concentration of serum insulin. Mean 24-h concentration of serum triglycerides was the strongest discriminator for LDL particle size (r = -0.44, P < 0.01). In conclusion, neither Type 2 diabetes nor insulin resistance seem to have any direct effect on LDL particle size in mildly hypertriglyceridemic subjects. The fact that LDL particle size was associated with serum triglycerides indicates that the effect of diabetes and insulin resistance on LDL particle size could be explained by the effects of insulin resistance and/or hyperinsulinism on VLDL metabolism.

Blood Glucose↗

PubMed2006

Influence of granulation and compaction on the particle size of ibuprofen--development of a size analysis method.

The aim of this work was to study the impact of the process on drug particle size. We chose ibuprofen, practically insoluble in water, as granulometry greatly influences its dissolution rate. We developed an original method using a laser granulometer to assess the size of ibuprofen within a blend before and after granulation and then compression. Wet granulation was performed with a Lodige and a Diosna granulator. The granules were then compressed. The evolution of ibuprofen particle size after these operations was checked. Two grades of ibuprofen differing in size were studied: ibuprofen 25 and ibuprofen 50. After the wet granulation of ibuprofen 50 with a Lodige or a Diosna granulator, a decrease in size was observed. This could be caused by shocks occurring in the granulator. On the other hand, after compression of the granules, ibuprofen particle size increased and was greater than that measured before granulation. Compression could induce some fragmentation of ibuprofen associated with the plastic deformation and then, under pressure, a closeness of the fragments or deformed particles which could bind or associate with one another because the melting point of ibuprofen is not very high. In the case of ibuprofen 25, the same phenomena were observed after compression. But, after granulation, particle size was not modified. There was little breaking of ibuprofen particles in the granulator because they are much smaller than those of ibuprofen 50. This work shows the impact of the process on drug particle size when producing tablets. The method developed made it possible to differentiate and measure the size of ibuprofen particles in a blend.

Ibuprofen↗

PubMed1978

The influence of digoxin particle size on absorption of digoxin and the effect of propantheline and metoclopramide.

1 The influence of particle size on absorption of digoxin was studied in ten healthy volunteers who received 0.5 mg digoxin as two standard Lanoxin tablets, or tablets containing micronized digoxin or large particle size digoxin. Tablets were given 30 min after 15 mg propantheline, 10 mg metoclopramine or a placebo tablet, and following an overnight fast. 2 The overall mean cumulative 4 day urinary excretion of digoxin was significantly lower (P less than 0.01) after large particle size digoxin than after standard or micronized digoxin. Mean cumulative urinary excretion following large particle size digoxin was reduced when administered after metoclopramide and increased after propantheline, the difference between these two treatments being significant (P less than 0.05). There was a significantly lower (P less than 0.05) overall mean cumulative excretion following standard by comparison with micronized digoxin. However, by comparison with placebo, neither metoclopramide nor propantheline significantly altered mean cumulative excretion after standard or micronized digoxin. Propantheline and metoclopramide affect absorption of digoxin from formulations of large particle size and slow dissolution rate only.

Adult↗

PubMed1997

Effect of hydroxyapatite particle size on myoblasts and fibroblasts.

After surgery, the bone and soft tissues around integrated biomaterials can be adversely affected by implant-related factors acting over a period of years. However, few studies have directly addressed the effects upon the adjacent soft tissue. The present study was designed to test the biological effects of various sized hydroxyapatite (HA) particles on myoblasts and fibroblasts. Both the myoblasts and fibroblasts were mixed in in vitro culture with 0.1% (1 mg ml(-1)) of various sized HA particles (0.5-3.0, 37-63, 177-250, 420-841 microm) for 1 h, 3 h, 1 day, 3 days and 7 days to test their effects on the cell culture. The results show that adding HA particles into a cell culture can decrease the cell count significantly. The transforming growth factor-beta1 (TGF-beta1) concentrations in the culture medium decreased significantly on addition of HA particles. When calculated as a ratio to the cell number, the TGF-beta1 titre increased most significantly in the groups of medium-sized particles. The prostaglandin E2 (PGE2) concentrations in the medium increased significantly. The changes in TGF-beta1 and PGE2 concentrations with the smallest particles were most significant and persisted longer. The inhibitory effects of the HA particles on the cell culture were mediated by the increased synthesis of PGE2. Caution should be exercised before considering the use of an HA product which could easily break down into a fine powder.

Animals↗

PubMed1987

Particle-size distribution of bitolterol mesylate solution delivered by four compressed-air nebulizer devices.

The particle-size distribution of bitolterol mesylate solution delivered by four types of compressed-air nebulizers was determined. Before nebulization, bitolterol mesylate solution 0.2% w/v was diluted to 0.0833% w/v with 0.9% sodium chloride solution. The following commercially available nebulizers were tested: DeVilbiss Nebulizer Model 645, Hudson 1720 (Updraft) Hand Held Nebulizer, Bard Inspiron 002220 Mini-Neb Nebulizer, and Bunn Mini Mist Set model 0140-041. The particle-size distribution of nebulized solutions was determined with a cascade impactor contained in an in vitro apparatus designed to simulate use by a patient. Assays of bitolterol mesylate in the cascade impactor apparatus were done by high-performance liquid chromatography. Only slight differences were found in the particle-size distributions among the four types of nebulizers; the calculated average particle size ranged from 3.0 to 3.6 micron. All nebulizers tested showed satisfactory, comparable particle-size distributions and performance with bitolterol mesylate solution.

Aerosols↗

PubMed2004

Characterization of microparticles in raw, treated, and distributed waters by means of elemental and particle size analyses.

The elemental composition and particle size distribution of suspended particles in raw water, treated water, and distributed water were determined to understand the behavior of particles during the water treatment-distribution process. The weight of suspended particles collected on a 0.6-microm filter was 1.1 times (raw water), 1.4 times (treated water), and 1.5 times (distributed water) that collected on a 2.7-microm filter, suggesting that smaller particles may remain after conventional water treatment. Organic suspended particles were removed less efficiently than inorganic suspended particles. After sand filtration, the Al content in the fixed suspended solids (FSS) markedly increased, indicating that either a small percentage of aluminium floc passed through during sand filtration or dissolved aluminum precipitated after sand filtration. The Mn and Fe concentrations increased after chlorination. The percentages of carbon and nitrogen in the volatile suspended solids (VSS) were roughly the same in the raw, treated, and distributed waters. The carbon/nitrogen/phosphate/VSS ratios indicated that the VSS of the suspended particles consisted of organic matter originating from microorganisms. The major constituents of the FSS in the treated and distributed waters were compounds of Fe, Al, Ca, Mg, and Mn, but these compounds accounted for only 16% or less of the FSS in raw water, indicating the existence of Si compounds. In distribution pipes, the total suspended solids concentration, especially the FSS concentration, was higher than that of water just after treatment. The Fe concentration in distributed water increased, probably due to oxidation and rusting of iron pipes.

Aluminum↗

PubMed2004

Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry.

Particle size is a fundamental property of any sediment, soil or dust deposit which can provide important clues to nature and provenance. For forensic work, the particle size distribution of sometimes very small samples requires precise determination using a rapid and reliable method with a high resolution. The Coulter trade mark LS230 laser granulometer offers rapid and accurate sizing of particles in the range 0.04-2000 microm for a variety of sample types, including soils, unconsolidated sediments, dusts, powders and other particulate materials. Reliable results are possible for sample weights of just 50 mg. Discrimination between samples is performed on the basis of the shape of the particle size curves and statistical measures of the size distributions. In routine forensic work laser granulometry data can rarely be used in isolation and should be considered in combination with results from other techniques to reach an overall conclusion.

Forensic Medicine↗

PubMed2003

Effects of forage particle size, forage source, and grain fermentability on performance and ruminal pH in midlactation cows.

Our study investigated the effects of, and interactions between, forage particle size, level of dietary ruminally fermentable carbohydrate (RFC), and level of dietary starch on performance, chewing activity, and ruminal pH for dairy cows fed one level of dietary NDF. Twelve cows (48 DIM) were assigned to six treatments in a replicated 6 x 6 Latin square. Treatments were arranged in an incomplete 2 x 2 x 2 factorial design. Factors were: dry cracked shelled corn (DC, low RFC) or ground high-moisture corn (HMC; high RFC), finely chopped or coarse silage, and alfalfa silage as the only forage or a 50:50 ratio (DM basis) of alfalfa and corn silage. Diets combining HMC with only alfalfa silage were not included in the experiment. Diets were fed for ad libitum intake as a TMR with a concentrate:forage ratio of 61:39. Diets based on only alfalfa silage and diets based on a mix of alfalfa and corn silage averaged 18.6 and 15.8% CP, 25.8 and 24.7% NDF, 17.7 and 14.8% ADF, and 29.1 and 37.3% starch, respectively. Mean particle sizes were 5.3, 2.7, 5.6, and 2.8 mm for coarse alfalfa, fine alfalfa, coarse corn silage, and fine corn silage, respectively. Decreasing forage particle size decreased DMI (23.3 vs. 21.6 kg) and organic matter intake (22.0 vs. 20.2 kg). Increasing RFC decreased DMI (22.8 vs. 21.0 kg) and organic matter intake (21.5 vs. 20.0 kg). Decreasing forage particle size increased energy-corrected milk for alfalfa based diets (34.9 vs. 37.4 kg). Percentage of milk fat decreased with decreasing forage particle size (3.07 vs. 2.90%) and increased level of RFC (3.04 vs. 2.57%). Percentage of protein increased when corn silage partially replaced alfalfa silage (2.84 vs. 2.90%) but decreased when HMC replaced DC (2.90 vs. 2.84%). Apparent total tract digestibility of DM (66.7 vs. 68.5%), OM (65.9 vs. 70.7%), and starch (88.9 vs. 93.4%) increased when level of RFC was increased. Increasing level of RFC decreased mean ruminal pH from 5.82 to 5.67 and decreased minimum pH. Hours per day at which pH was <5.8, and area <5.8, increased when corn silage partially replaced alfalfa silage (2.6 vs. 4.4 h and 8.9 h x pH vs. 11.4 h x pH) and decreased further when level of RFC was increased (4.4 vs. 6.4 h and 11.4 h x pH vs. 14.3 h x pH). Decreasing forage particle size in HMC diets increased hours and area <5.8, but for DC diets, the effect of forage particle size depended on forage source. Interactions were found between level of physically effective fiber, forage source, and level of RFC on production and pH, complicating the inclusion of these effects in dairy ration formulation and evaluation.

Allantoin↗

PubMed2006

Analysis of the effect of particle size on polymorphic quantitation by Raman spectroscopy.

Raman spectroscopy has been widely used to monitor various aspects of the crystallization process. Although it has long been known that particle size can influence Raman signal, relatively little research has been conducted in this area, in particular for mixtures of organic materials. The aim of this study was to investigate the effect of particle size on quantification of polymorphic mixtures. Several sets of calibration samples containing different particle size fractions were prepared and Raman spectra were collected with different probes. Calibration models were built using both univariate and multivariate analysis. It was found that, for a single component system, Raman intensity decreased with increasing particle size. For mixtures, calibration models generated from the same particle size distribution as the sample yielded relatively good predictions of the actual sample composition. However, if the particle sizes of the calibration and unknown samples were different, prediction errors resulted. For extreme differences in particle sizes, prediction errors of up to 20% were observed. Prediction errors could be minimized by changing the sampling optics employed.

Journal Article↗

PubMed2003

The effect of resin particle size on the rate of ion release: interactions in mixed bed systems.

The aim of the present study is to evaluate the influence of resin particle sizes on the rate of ions release from a mixture of ion-exchange resins (named NMTD) which supplies calcium, fluoride, and phosphate ions as the main mineral content, and to elucidate the different phenomena taking place through the related ion-exchange process. The final goal of the study, related to dental application (enamel restoration), is to limit the particle size range, since the rate of ion release is a key parameter in the successful achievement of such objective. Weak-type ion-exchange resins, loaded with the appropriate ions, were ground and sieved into granulometric fractions of bead diameters of 0.1-0.075, 0.075-0.063, and 0.063-0.05 mm. Particle size was controlled by a laser diffraction particle distribution analyzer. The experiments on the kinetics of ions release were carried out under batch conditions in artificial saliva desorption solution thermostatized at 37 degrees C. The release of Ca(2+) and F(-) was determined by corresponding ion-selective electrodes automatically controlled, whereas H(2)PO(4)(-) was measured spectrophotometrically by the inductively coupled plasma-optical emission technique (ICP-OES). The results of this study show that the process of ion-exchange for the different particle size fractions of resins is critical for the study of the kinetics release of the ions immobilized in the corresponding mixed bed polymeric matrices. In fact, despite the apparent narrow range of particle sizes of the mixed bed systems studied, appreciable differences in the rate of ions release are obtained. Since the ion release rate is depending on the contact surface, an increase of factor of 2 in particle size represents an increase of an order of magnitude of the resin contact surface due to the resin porosity. In this concern, it has been observed that the rate of ions release increases when particle size decreases. The interactions occurring during the ion release from the mixed bed resins (containing calcium-, fluoride-, and phosphate-loaded resins) can be interpreted by the following phenomena: H(2)PO(4)(-), which hardly modifies its rate of release in the presence of Ca(2+) and F(-) in the mixture, promotes a considerable increase in the rate of Ca(2+) release due to the formation of a calcium dihydrogen phosphate soluble complex. F(-) also produces an acceleration in the rate of Ca(2+) release due to the formation of solid CaF(2 )on the surface of cationic resin particles, which in contrast leads to a decrease in the rate of F(-) release.

Journal Article↗

PubMed1999

Low-density lipoprotein particle size and coronary artery disease in a childhood-onset type 1 diabetes population.

Low-density lipoprotein (LDL) cholesterol has been widely recognized as a strong predictor of coronary artery disease (CAD). Recently, studies have examined the influence of LDL particle size (an integral part of the insulin resistance syndrome) on the development of CAD in the general population. This report examines the correlates of LDL particle size and its association with CAD in a type 1 diabetes population. We evaluated the interrelationships between LDL particle size and the presence of CAD in a cohort of childhood-onset type 1 diabetic subjects using the Pittsburgh Epidemiology of Diabetes Complications (EDC) study. LDL particle size was measured in 337 subjects (mean age, 35.6 years; mean diabetes duration, 27.2 years) who underwent the 8-year follow-up examination. LDL particle size was determined by vertical polyacrylamide gel (2% to 16%) electrophoresis. Subjects with the small dense LDL particle phenotype (<235.5 angstroms) [corrected] had a longer diabetes duration, higher cholesterol, triglyceride, LDL, fibrinogen, waist to hip ratio (WHR), and hemoglobin A1 (HbA1), and lower high-density lipoprotein (HDL) cholesterol compared with subjects with the large LDL particle phenotype (>257 angstroms) [corrected]. Males were also more likely to have an increased body mass index (BMI) and CAD, while females were more likely to have hypertension and a family history of type 2 diabetes (a potential marker of insulin resistance and CAD risk). The odds ratio ([OR] 95% confidence, interval [CI]) using logistic regression analysis for LDL particle size in association with CAD was 0.79 (0.60 to 1.04). Multivariate modeling indicated that the duration of type 1 diabetes, depressive symptomatology, and triglycerides were independently associated with the presence of CAD. We conclude that although small dense LDL particle size is associated with CAD in our type 1 diabetes population, its borderline association can largely be explained by the triglyceride concentration. However, as in the general population, LDL particle size is associated with many elements of the insulin resistance syndrome, including a family history of type 2 diabetes, and is likely an important element in the contribution of insulin resistance to the development of CAD in type 1 diabetes.

Adult↗

PubMed1994

A comparative study of particle size dependency of IR and XRD methods for quartz analysis.

Quartz (SiO2) is considered a probable carcinogen. In order to enforce health and safety standards, techniques that can accurately determine the quartz content of materials are necessary. Currently, two techniques dominate quartz analysis--the infrared (IR) spectrophotometry method and the X-ray diffraction (XRD) method. Unfortunately, there are problems associated with these techniques, such as sample preparation and particle size effect. This study focuses on particle size effect on quartz determination by both IR and XRD. Seven size groups of pure quartz samples, with mean diameters from 1.5 to 20 microns, were used. A set of samples with different quartz masses was prepared for each size group and subjected to both IR and XRD analysis. Two sets of calibration curves, one each from IR and XRD, were obtained. It was found that both IR and XRD methods are size-dependent but in an opposite way. As particle size increases, IR peak height decreases and XRD peak height increases for the same quartz content (mass). Since both methods are particle size-dependent, it is important that the standard quartz sample and samples of interest have similar particle size distributions. Specifically, when coal dust samples are ashed before analysis, the after-ashing particle size distribution should be used. Particle size distribution will change after ashing and it is the after-ashed particles that directly affect the IR and XRD analysis.

Calibration↗

PubMed1984

Particle size stability of intralipid and mixed total parenteral nutrition mixtures.

The determination of the particle size of Intralipid fat emulsions by the non-perturbing method of photon correlation spectroscopy has been extended to include particle size determination using the Coulter counter and optical microscopy. Although little increase in particle size in 3-litre bags containing total parenteral nutrition mixtures was observed with the methods involving large dilutions, creaming was observed and optical microscopy showed aggregation and some coalescence to have taken place. The problem of re-dispersion upon dilution of aggregated (but not coalesced) fat emulsions makes direct optical observation essential in assessing the stability and safety of such fat emulsion mixtures. The effect of electrolytes (NaCl and CaCl2) on creaming, particle size and electrophoretic mobility showed both minimum stability and minimum zeta potential at 3 X 10(-3) mol dm-3 CaCl2 and at 2.5 X 10(-1) mol dm-3 NaCl. Thus, these maximum levels for electrolytes in total parenteral mixtures are indicated.

Adult↗

PubMed1995

The effect of variation in powder particle size on the doughing and manipulation times and some mechanical properties of acrylic resin.

In this study, the hypothesis examined is that differences in polymer particle size affect the doughing and manipulation times and the mechanical properties of the cured product. Six batches of polymers were used varying in particle size from <38 micrometers diameter to > 75 micrometers diameter. A penetration test was undertaken to investigate the influence of polymer particle size on the doughing and manipulation times of acrylic resin. It was demonstrated that the particle size in the range examined influenced the doughing and manipulation times, the smaller particle sizes having shorter times. No significant difference was demonstrated in the impact resistance of surface hardness of acrylic resin specimens constructed from polymers of varying particle size and although there were some significant differences in the transverse (flexural) strength these were small in real terms. Further, the molecular weight of the polymerised product was found to be consistently higher than that of the original powder component.

Acrylic Resins↗