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PubMed2005

Effect of feed particle size and feed processing on morphological characteristics in the small and large intestine of pigs and on adhesion of Salmonella enterica serovar Typhimurium DT12 in the ileum in vitro.

A 2 x 2 factorial experiment with pigs was undertaken to investigate the effect of particle size (fine and coarse) and feed processing (pelleted and nonpelleted) on morphological characteristics in the small intestine, cecum, and colon of pigs and on the adhesion of Salmonella enterica serovar Typhimurium DT12 to the ileum in vitro. Ninety-six pigs (average BW = 33 +/- 7 kg) were fed the experimental diets. After 4 wk, 24 pigs were selected (six pigs per diet) and euthanized, and tissue samples were taken from the mid and distal small intestine, cecum, and distal colon. The effects of particle size and feed processing on villus height and crypt depth in the small intestine were minor. Feeding coarse diets increased (P = 0.05) the crypt depth in the colon. The crypt depth was 420 +/- 12 and 449 +/- 12 microm in pigs fed finely and coarsely ground feed, respectively. Pigs fed pelleted diets had a larger (P = 0.01) staining area for neutral mucins, as well as for acidic and sulfomucins on the villi of the distal small intestine than pigs fed nonpelleted diets. The area was 41, 46, and 33% larger for neutral, acidic, and sulfomucins, respectively. The mucin-staining areas of the crypts in the cecum and the colon were not affected by the experimental diets. Examination of lectin binding characteristics of the distal small intestine and the cecum did not reveal any differences between the experimental diets. Using a pig intestine organ culture model, Salmonella adhered less (P < 0.05) to the ileal tissue of pigs fed the nonpelleted diets than to those fed pelleted diets; the adherence was 60% less in these pigs. Results of this study suggest that pigs fed pelleted diets secrete mucins that are capable of binding Salmonella enterica serovar Typhimurium DT12 and thereby allowing for colonization. Therefore, pigs fed a nonpelleted diet are better protected against Salmonella infections than pigs fed a pelleted diet.

Animal Feed↗
PubMed1989

Effect of drug (core) particle size on the dissolution of theophylline from microspheres made from low molecular weight cellulose acetate propionate.

Three particle sizes (450, 120, and 5 microns) of theophylline were encapsulated in low molecular weight cellulose acetate propionate (intrinsic viscosity, 1.08 dl/g) by the solvent evaporation method. The theoretical drug content for all the batches of microspheres was 50% (w/w). Particle size analysis revealed that about 50% of the microspheres containing the large theophylline crystals (average length of 450 microns) were greater than 500 microns in diameter, whereas only about 35% of the microspheres containing the medium drug crystals (average length of 120 microns) were greater than 500 microns in diameter. The drug content of the larger microspheres prepared from the large drug crystals and the medium drug crystals was much greater than the theoretical drug content (50%, w/w); however, the drug content of all the batches of microspheres containing micronized drug was close to 50% (w/w). Release of the drug in simulated intestinal fluid was very rapid from microspheres containing large and medium drug crystals, while release was slower and more predictable from microspheres made from micronized drug.

Cellulose↗
PubMed1994

Effect of tidal volume on the output and particle size distribution of hypertonic saline from an ultrasonic nebulizer.

The purpose of the present study was to measure the output and particle size distribution of hypertonic saline from an ultrasonic nebulizer over the range of tidal volumes (VT) used in an epidemiological survey of asthma in children. A Starling pump was used to generate different VTs from 250 to 500 ml, at different respiratory rates of 12 and 20 breaths.min-1, to cover the normal range of respiratory pattern of children aged 7-14 yrs. The Starling pump was connected to a Timeter Compuneb Ultrasonic Nebulizer Model MP 500 with 24 cm of corrugated aerosol tubing, ID 2.2 cm, and a two-way non-rebreathing valve. Nebulizer output was measured by weighing the nebulizer chamber plus tubing and valve before and after each nebulization. To measure particle size distribution, a Malvern Particle Sizer M 3.0 (laser diffraction) was used, with a special adapter attached between valve and Starling pump. Nebulizer output increased linearly from 1.6 to 2.5 ml.min-1 for VT 250 to 500 ml, with little influence by the respiratory frequency. Furthermore, we found that in the range of VT = 300-500 ml the mass median aerodynamic diameter (MMAD) was 2.61 microns, with 100% of the particles less than 5 microns, whereas at VT = 150-250 ml the MMAD was 8.89 microns, with 90% larger than 5 microns. As output from this ultrasonic nebulizer correlates linearly with tidal volumes, size correction may not be necessary in hypertonic saline challenge tests in children. Above a VT of 300 ml, the MMAD is in the respirable range, with 100% of particles less than 5 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1996

Multilocus genetic determinants of LDL particle size in coronary artery disease families.

Recent interest in atherosclerosis has focused on the genetic determinants of low-density lipoprotein (LDL) particle size, because of (i) the association of small dense LDL particles with a three-fold increased risk for coronary artery disease (CAD) and (ii) the recent report of linkage of the trait to the LDL receptor (chromosome 19). By utilizing nonparametric quantitative sib-pair and relative-pair analysis methods in CAD families, we tested for linkage of a gene or genes controlling LDL particle sizes with the genetic loci for the major apolipoproteins and enzymes participating in lipoprotein metabolism. We confirmed evidence for linkage to the LDL receptor locus (P=.008). For six candidate gene loci, including apolipoprotein(apo)B, apoAII, apo(a), apoE-CI-CII, lipoprotein lipase, and high-density lipoprotein-binding protein, no evidence for linkage was observed by sib-pair linkage analyses (P values ranged from .24 to .81). However, in addition, we did find tentative evidence for linkage with the apoAI-CIII-AIV locus (chromosome 11) (P=.06) and significant evidence for linkage of the cholesteryl ester transfer protein locus (chromosome 16) (P=.01) and the manganese superoxide dismutase locus (chromosome 6) (P=.001), thus indicating multilocus determination of this atherogenic trait.

Adolescent↗
PubMedDate not supplied

A detailed numerical study of the evolution of soot particle size distributions in laminar premixed flames.

In this work, two numerical techniques, viz. the method of moments and a discrete h-p-Galerkin method, have been applied for numerical simulation of soot formation in a laminar premixed acetylene/oxygen/argon flame. From the evolution of the PAH and the soot particle size distributions, new insight into the different processes of soot formation is provided. For this, the single submodels have been examined with respect to their influence on the PAH and the soot particle size distributions. The particle inception step was studied in detail by comparing the simulated PAH size distributions with experimental results. Additionally, an estimation of the interaction energy of layered PAH dimers was performed by quantum chemical calculations. From these results, some evidence for the particle inception model employing coalescence of PAH molecules has been found. The numerical results for the gas phase chemical species, the particle number densities and volume fractions of soot as well as for the soot particle size distributions are compared with experimental data. Thereby, the consistency of the entire model is demonstrated.

Journal Article↗
PubMed1990

[Influences of composition on brush wear of composite resins. Influences of particle size and content of filler].

The influences of the composition on abrasion resistance of composite resins were examined using various experimental composite resins which had various matrix resin, filler size and content. The abrasion test was conducted by the experimental toothbrush abrasion testing machine developed in our laboratory. Three series of heat-curing composite resins were tested. One series was made from a Bis-MPEPP or UDMA monomer, and a silica filler with an average particle size of 0.04, 1.9, 3.8, 4.3, 7.5, 13.8 and 14.1 microns. The filler content of this series was constant at 45 wt%. The second series contained a silica filler of 4.3 microns in a content ranging from 35 to 75 wt%. The third series contained a microfiller (0.04 microns) and macrofiller (4.3 microns) in total content of 45 wt%. In this series, the microfiller was gradually replaced by 5, 15, 25 and 45 wt% of the macrofiller. The results obtained for these three series indicated that the abrasion resistance of composite resins was controlled by the inorganic filler, mainly filler size and content. The abrasion loss did not vary with the difference of matrix resin. When the particle size of the filler was below about 5 microns, the abrasion resistance decreased markedly with the decrease in filler size. The composite resin which contained a 0.04 or 1.9 micron filler was less resistant to toothbrush wear than the unfilled matrix resin. However, the microfiller also contributed to abrasion resistance when used in combination with the macrofiller, although abrasion resistance decreased with the increase in the microfiller concentration. The increase of filler content clearly improved the abrasion resistance when used the macrofiller. The analysis of these results and SEM observations of the brushed surfaces of samples suggested that the toothbrush abrasion was three-body abrasion caused by the abrasive in the toothpaste, and affected by the difference in the particle size between abrasive and filler, and between the abrasive size and the interparticle distance of the filler.

Absorption↗
PubMedDate not supplied

Effect of lecithins on BCG-alginate-PLL microcapsule particle size and stability upon storage.

Alginate-PLL microcapsules containing BCG were prepared by emulsification/internal gelation of an alginate solution dispersed within a vegetable oil containing lecithins as emulsifiers. The lecithins studied were soy bean lecithin at 0.1, 0.5, 1 and 2% concentration; and dried egg yolk lecithin at 0.1, 0.25, 0.5 and 1%. The microcapsule particle size showed a dependence upon the amount and type of lecithin added to the oil. Increasing the emulsifying agent concentration was found to reduce particle size, from 50.9 microm obtained when lecithins were not used in the emulsification step, to 13.9 microm obtained when 1% dried egg yolk lecithin was employed. The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Once prepared, microcapsules were freeze-dried using 5% trehalose as cryoprotectant in order to preserve their stability upon storage. The stability of the microcapsules was assayed over 12 months at room temperature, finding that alginate-PLL microcapsules were stable up to 6 months. Moreover, in the case of microcapsules prepared with lecithins, a significant increase in particle size was observed, from 16.9 microm at the beginning of the study to 25.2 microm at 12 months storage.

Alginates↗
PubMedDate not supplied

Dependency of tissue necrosis on gelatin sponge particle size after canine hepatic artery embolization.

PURPOSE: To determine the optimal size of gelatin sponge particles (GSPs) to produce maximum tumor necrosis with minimum side effects after canine hepatic artery embolization (HAE). METHODS: GSPs were separated into four size ranges: A, up to 200 microns (mean 152) as Gelfoam powder; B, 200-500 microns (mean 336) as Gelfoam powder; C, 500-1000 microns (mean 649) as Spongel; and D, 1000-2000 microns (mean 1382) as Spongel. Three mongrel dogs were assigned randomly to HAE with each particle size. On day 7 after HAE, the livers were removed and subjected to pathological examination. RESULTS: The mean volume of liver necrosis was 11% after embolization, with particle size A, 36.3% with B, 0% with C, and 1% with D. Coagulation necrosis was found in all livers with particles of sizes A and B, and in 1 of 6 with sizes C and D. Bile duct injury was found in five of six dogs with sizes A and B and in none with sizes C and D. Gallbladder necrosis was found in one dog with size B and pancreas necrosis in one with size A. CONCLUSION: GSPs of 500 microns are considered optimally effective for tissue necrosis according to this model.

Animals↗
PubMed1994

Influence of particle size and chemical composition on efficiency of clearance mechanisms: electron microscopy studies on humans.

This article compares the presence of solid particles in lung parenchyma samples collected from accident victims and in bronchoalveolar lavage fluid taken from patients diagnosed with pulmonary carcinoma. Analysis by electron microscopy showed differences in particle size between the two groups, which could be attributable both to differences in original particle size and to their solubility in the biological environment.

Bronchoalveolar Lavage Fluid↗
PubMed2005

Analysis of ochres from Clearwell Caves: the role of particle size in determining colour.

Three ochre samples (A (orange-red in colour), B (red) and C (purple)) from Clearwell Caves, (Gloucestershire, UK) have been examined using an integrated analytical methodology based on the techniques of IR and diffuse reflectance UV-visible-NIR spectroscopy, X-ray diffraction, elemental analysis by ICP-AES and particle size analysis. It is shown that the chromophore in each case is haematite. The differences in colour may be accounted for by (i) different mineralogical and chemical composition in the case of the orange ochre, where higher levels of dolomite and copper are seen and (ii) an unusual particle size distribution in the case of the purple ochre. When the purple ochre was ground to give the same particle size distribution as the red ochre then the colours of the two samples became indistinguishable. An analysis has now been completed of a range of ochre samples with colours from yellow to purple from the important site of Clearwell Caves.

Calcium Carbonate↗
PubMed1999

The effect of wheat bran particle size on laxation and colonic fermentation.

OBJECTIVE: Due to perceived inferior fecal bulking ability, finely ground wheat bran is not recommended for treatment of colonic disorders, despite possible short chain fatty acid generation with potential benefits for colonic mucosal health. We therefore tested the effects of very fine particle size wheat bran on colonic function. METHODS: Two studies, each with three phases, were undertaken in healthy subjects in a randomized crossover design. In one study (metabolic, n=23) subjects took three diets containing either an additional 19 g/d dietary fiber with mean particle size (MPS) 50 microm or 758 microm in bread or a control low fiber bread. In the other study where the supplement was provided as a breakfast cereal (ad libitum, n=24) the respective wheat bran MPS were 692 microm and 1158 microm and the control was low fiber. Fecal collections were obtained during the last week of each diet. In the metabolic study, fecal short chain fatty acids were measured and 12-hour breath gas collections obtained. RESULTS: In both studies, wheat bran supplements significantly increased fecal bulk compared to the control (p<0.004), with no significant differences between brans of different particle size and no differences in fecal water content. However, higher fecal butyrate concentrations (p<0.007), butyrate output and breath CH4 levels (p=0.025) were seen on the low MPS wheat bran compared to the other two treatments, suggesting increased bacterial fermentation. CONCLUSIONS: Fine MPS wheat bran is an effective fecal bulking agent and may have added advantages if increased butyrate concentrations promote colonic mucosal integrity.

Adult↗
PubMed2006

Discrimination between sediment and soil samples for forensic purposes using elemental data: an investigation of particle size effects.

This paper reports the results of an investigation to quantify variations in elemental concentrations amongst different particle size fractions obtained from a suite of sediment samples collected from the River Avon, UK. Concentrations of 49 elements determined by inductively coupled plasma spectrometry (ICP-AES and ICP-MS) were compared using conventional and multivariate statistical methods in order to assess compositional differences between different size fractions and between different samples. The results showed significant differences between different size fractions and the bulk sediments, but indicated that all of the size fractions considered (<150, 63-150, 20-63 and <20microm) provided an adequate basis on which to identify associations and differences between samples. It was concluded that, while in certain specific circumstances it may be most appropriate to make forensic comparisons based on a very narrowly defined particle size range, for the majority of purposes the <150microm fraction provides the best compromise between sample size requirements and data resolution.

Cluster Analysis↗
PubMed2000

Electrostatic respirator filter media: filter efficiency and most penetrating particle size effects.

New electrostatic filter media has been developed for use in 42 CFR 84 negative pressure particulate respirator filters. This respirator filter media was not available for evaluation prior to the change from 30 CFR 11 to 42 CFR 84. Thus, characterization of this filter media is warranted. In this study, the new 42 CFR 84 electrostatic respirator filters were investigated with respect to filter penetration and most penetrating particle size. Three different models of N95 filters, along with one model each of the N99, R95, and P100 class filters were used in this study. First, three of each filter were loaded with a sodium chloride (NaCl) aerosol, and three of each filter were loaded with a dioctyl phthalate (DOP) aerosol to obtain normal background penetration results for each filter. Then, two new filters of each type were dipped in isopropanol for 15 seconds and allowed to dry. This isopropanol dip should reduce or eliminate any electrostatic charge on the fibers of each filter, as reported in the technical literature. These dipped filters, along with controls of each filter type, were tested on a TSI 8160 filter tester to determine the most penetrating particle size. These same filters were then tested against a NaCl aerosol to get final penetration values. Electret filters rely heavily on their electrostatic charge to provide adequate filter efficiencies, and correlations between penetration and a filter's electrostatic characteristics are found in the technical literature. In all six of the filter models tested, filter penetration values increased considerably and the most penetrating particle size noticeably shifted toward larger particles. These results are important in better understanding how these new filter materials perform under various conditions, and they indicate the need for additional research to define environmental conditions that may affect electrostatic filter efficiency.

Equipment Design↗
PubMed2000

A study on dust emission, particle size distribution and formaldehyde concentration during machining of medium density fibreboard.

A study to characterise the quantity, particle size distribution and morphology of dust created during the machining of MDF was carried out. Four different types of MDF boards were included in this study, including a 'zero-formaldehyde' board that contains isocyanate-based resin, rather than urea-formaldehyde resin. In addition, natural softwood (pine) and natural hardwood (oak) were included in the study, for comparison with MDF. The results show that in general, the dust generated by machining MDF is comparable in terms of particle size distribution and morphology with the dust generated by similarly machining hardwood or softwood. The quantity of dust generated during sanding is higher for sanding MDF compared with sanding either hardwood or softwood. However, for sawing there is no significant difference between MDF and natural woods, in terms of the quantity of dust generated. Free formaldehyde in the air was less than 0.17mg m(-3) during machining of the Class B (higher formaldehyde potential) MDF board. There was no measurable isocyanate in the dust generated from the boards.

Air Pollutants, Occupational↗
PubMed1985

Changes in very low density lipoprotein particle size and production in response to sucrose feeding and hyperinsulinemia.

The effects of chronic (2 weeks) hyperinsulinemia on the production of very low density lipoprotein (VLDL) triglyceride and on VLDL particle size were examined. Hyperinsulinemia was induced by a constant sc infusion of 6 U porcine insulin/day from an osmotic minipump. To avoid profound hypoglycemia, these rats received chow plus 10% sucrose in their drinking water. Therefore, two control groups were examined; one receiving chow plus the same amount of sucrose (high carbohydrate control) and the other receiving chow only (chow control). The constant infusion model was compared to a previously reported model of hyperinsulinemia. In that model, NPH insulin was injected for 2 weeks twice daily in incrementally increasing doses (final dose, 6 U/day) into rats that were also fed chow and given 10% sucrose drinking water. Results with the injection model were similar to those previously reported: an increase in triglyceride production in face of a decrease in FFA, a minimal decrease in serum triglyceride, and some decrease in serum glucose. The infusion model produced the same increase in triglyceride production and decrease in fatty acid concentration. However, it differed in producing an increase in serum triglyceride and no change in serum glucose. The former suggested that in the infusion model triglyceride removal was not stimulated as much as in the injection model. Since there was no hypoglycemia in the infusion model, it was unlikely that VLDL changes were caused by an increase in counter regulatory hormones. VLDL particle size was increased in the high carbohydrate controls. This indicated that changes in sucrose supplementation led to the production of more triglyceride-filled VLDL particles. Hyperinsulinemia was not accompanied by any further increase in particle size. Thus, the hyperinsulinemia-induced increase in VLDL-triglyceride production was accompanied by an equivalent increase in VLDL particle production.

Animals↗
PubMed1999

Quantitative analysis of polyvinyl alcohol on the surface of poly(D, L-lactide-co-glycolide) microparticles prepared by solvent evaporation method: effect of particle size and PVA concentration.

Polyvinyl alcohol (PVA) is an emulsion stabilizer that is used in the solvent evaporation method for poly(D,L-lactide-co-glycolide) (PLG) microparticles preparation. In this study, the surface binding of PVA on PLG microparticles was quantitatively examined by employing gel permeation chromatography. The PVA binding can affect hydrophobicity and digestibility of the microparticle surface. GPC analysis detected the presence of PVA bound on the microparticle surfaces in an irreversible manner. The PVA content per weight of microparticle increased with the specific surface area as the particle size decreased. The surface PVA density, which is the PVA content per unit surface area of microparticle, changed with particle size in a biphasic manner. In the size range larger than 1 microm, the surface PVA density increased from 0.8 mg/m2 to 2.2 mg/m2 as the particle size decreased. But below 1 microm, the surface PVA density remained unchanged at about 1.8 mg/m2. The surface PVA density of PLG microparticles prepared in different PVA concentrations (0.1, 1, 5, 10% w/v) showed similar values and size dependency, indicating that the PVA concentration of the continuous phase did not affect the surface PVA density of PLG microparticles. These data suggest that the influence of the surface PVA layer would be larger in the smaller particles, but be independent of the PVA concentration of the continuous phase in the manufacturing process.

Adsorption↗
PubMed2002

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

The objective was to determine the influence of alfalfa silage particle length on milk yield, milk composition, and chewing activity. Sixteen multiparous lactating Holsteins were used in each of two separate feeding trials over a 2-yr period providing two repetitions. Each trial was based on 4 x 4 Latin squares with 21-d periods. All four diets (2-yr average, dry basis) contained a basal level of 10.7% neutral detergent fiber from corn silage and 2.3% neutral detergent fiber from chopped alfalfagrass hay. One of the diets served as a low forage, low fiber control and contained only the basal forages. The other three diets contained an additional 8.6% neutral detergent fiber from coarser alfalfa silage, finely rechopped alfalfa silage or an equal mixture ofthe two. An increase in the forage content above the basal amount using alfalfa silage increased 4% fat-corrected milk yield, milk fat yield and concentration, eating time, and total chewing time. Dry matter intake was not influenced by diet. Linear increases in rumination and total chewing times were observed as the mean particle size of the alfalfa silage increased from finer to coarser. There was no linear effect of alfalfa silage particle size on milk yield, 4% fat-corrected milk yield, dry matter intake, or milk composition.

Animals↗