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Results for “Particle Size”

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At least 973 records · Page 54Linked to original sources

PubMed1987

Studies on the promoting effect of lipid-surfactant mixed micelles (MM) on intestinal absorption of colloidal particles. Dependence on particle size and administration site.

The effect of oleic acid-HCO60 mixed micelles (MM) on the absorption of colloidal particles by the large intestine was investigated using the in situ closed loops of rats. Two species of colloidal particles with different sizes, colloidal inks (Platinum ink 2.4-10 nm, Rotring ink 100-800 nm) and colloidal gold particles (mean particle size 5, 20, 40 nm) were chosen. Macroscopic observation showed that in the case of Platinum ink the staining of the mucus of the whole large intestine was promoted by MM and the staining of the rectum remained even after removing the mucus layer. The regional lymph nodes and the thoracic lymph was also stained. On the other hand, in the case of Rotring ink, the stain in the large intestine after removing the mucus layer, in lymph nodes and in the thoracic duct lymph was not observed. The results of quantitative experiments using colloidal gold particles indicated: 1) the upper size limit of colloidal particles absorbed by the large intestine, under the influence of MM was approximately 40 nm, 2) colloidal gold particles were transported from the intestine selectively into the lymphatics and accumulated in the regional lymph nodes, 3) the absorption of colloidal gold particles was largely promoted by MM in the rectum area.

Animals↗

PubMed1984

Particle size of periodontal bone grafting materials.

Samples of autogenous bone obtained by high speed burs, low speed burs, hand chisels and bone blending; freeze-dried bone purchased from a tissue bank and alloplastic materials, such as Calcitite, Durapatite, Periograf and Synthograft used as donor material for periodontal bone grafting procedures, were evaluated histometrically. Particle sizes ranged from a mean of 210 X 105 mu for bone blend to 1559 X 783 mu for hand-chisel samples. Except for those two materials, all of the others were in the 300 to 500 microns (0.3-0.5 mm) range that seems to be preferred for use in periodontal defects.

Biocompatible Materials↗

PubMed2006

Effects of extended-release niacin on lipoprotein particle size, distribution, and inflammatory markers in patients with coronary artery disease.

In this study, niacin was added to existing therapy for 3 months in 54 subjects with stable coronary artery disease. Average total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglyceride levels were similar between groups. Three months of niacin treatment increased total HDL by 7.5% and decreased triglycerides by 15% compared with baseline values (p <0.005 for each), whereas total cholesterol and LDL levels remained unchanged. Addition of niacin resulted in a 32% increase in large-particle HDL (p <0.001), an 8% decrease in small-particle HDL (p = 0.0032), an 82% increase in large-particle LDL (p = 0.09), and a 12% decrease in small-particle LDL (p = 0.008). Niacin decreased lipoprotein-associated phospholipase A2 and C-reactive protein levels (20% and 15%, respectively, p <0.05 for the 2 comparisons). No significant changes from baseline were seen in any tested parameter in subjects who received placebo. In conclusion, addition of niacin to existing medical regimens for patients with coronary artery disease and already well-controlled LDL levels favorably improves the distribution of lipoprotein particle sizes and inflammatory markers in a manner that would be expected to confer atheroprotection. The effect of altering lipoprotein particle distribution and inflammatory markers on surrogate markers of atherosclerosis and clinical cardiovascular events in this population remains unclear.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2005

[Aging of spiked pyrene in two paddy soils and their particle-size fractions after soil incubation and changes in extractability and bio-availability to earthworm].

Effect of aging on bioavailability and extractability of persistent organic pollutants has recently been paid much attention in environmental studies. This study deals with aging of spiked pyrene, a four-ring polycyclic hydrocarbon, in two paddy soils and their particle-size fractions under laboratory incubation and change in its extractability and bioavailability. The bioavailability of aged pyrene was tested by an assay of exposure to earthworms (Eisenia foetida). The extractability of spiked pyrene was decreased by 15% to 23%, and the bioavailability to earthworm was decreased by 37% to 67% after incubation for 90 d compared to under no incubation. Meanwhile, there was no significant difference in the pyrene extractability between incubation with different size fractions of a single soil. Soil incubation resulted in lower extractability and, thus, lower environmental risk of the organic pollutants after incorporation in paddy soils and their aggregates. The different size fractions of paddy soils may exert different bioavailability when exposure to soil fauna. Thus, content and chemical extractability may not be appropriate index for assessing the potential environmental risk and bioavailability to soil fauna for persistent organic pollutants in paddy soils.

Animals↗

PubMed2002

Change in particle size distribution of fractal agglomerates during Brownian coagulation in the free-molecule regime.

Time evolution of particle size distribution of fractal agglomerates undergoing Brownian coagulation in the free-molecule regime was investigated. A simple analytical solution for the size distribution change was obtained by using the assumption that the size distribution during the coagulation process can be represented by a time-dependent log-normal function. The derived solution consists of three parameters of the log-normal distribution function. This study is believed to provide the first analytical solution for all the parameters of the log-normal distribution of fractal agglomerates undergoing coagulation in the free-molecule regime. To validate the derived solution, numerical computations were performed. The results were compared with the analytical solution and good agreement was obtained.

Journal Article↗

PubMed1993

Effect of particle size, packing density and agitation on penicillin production in solid state fermentation.

The use of a large particle size (14 mm) support (sugar cane bagasse) increased penicillin production by solid state fermentation by 37 %, however this effect was due to a higher sugar concentration in this bagasse fraction. Cultures with closer packing densities (0.35) produced 20 % more penicillin. Agitation did not have a negative effect on production if moisture loss during the operation is restituted.

Journal Article↗

PubMed2005

[Particle size determination using the method of dynamic light scattering].

Realising the lacks of the classic methods of particle size determination a new method was needed to be developed which became suitable for measurements in the nano range as well. The principle of this method was discovered more than 20 years ago but manufacturers are still able to insert novelties by developing and refining the technique of - dynamic light scattering. Importance of multiparticular systems increases in pharmaceutical technology. It is necessary to apply this new method to investigate them.

Light↗

PubMed1996

Amphotericin B intralipid formulation: stability and particle size.

Amphotericin B remains the drug of choice for treating systemic fungal infections, although toxicity limits its clinical use. Some studies reported the use of Intralipid deoxycholate amphotericin B as an alternative delivery system. An in-vitro study was performed to assess the compatibility of deoxycholate amphotericin B in Intralipid. With two types of dilution of deoxycholate amphotericin B (in 5% dextrose and Intralipid or in Intralipid alone) the solution stability was not constant with a clear yellow precipitate. We observed an increase in the size of the particles (1.5-4-fold). In light of these results Intralipid deoxycholate amphotericin B should not be routinely administered.

Amphotericin B↗

PubMed2002

Fractionation of elements by particle size of ashes ejected from Copahue Volcano, Argentina.

The volcano Copahue, Neuquén province, Argentina has shown infrequent explosive eruptions since the 18th century. Recently, eruptive activity and seismicity were registered in the period July-October, 2000. As a consequence, ash clouds were dispersed by winds and affected Caviahue village located at about 9 km east of the volcano. Samples of deposited particles from this area were collected during this episode for their chemical analysis to determine elements of concern with respect to the health of the local population and its environment. Different techniques were used to evaluate the distribution of elements in four particle size ranges from 36 to 300 microm. X-ray powder diffraction (XRD) was selected to detect major components namely, minerals, silicate glass, fragments of rocks and sulfurs. Major and minor elements (Al, Ca, Cl, Fe, K, Mg, Mn, Na, S, Si and Ti), were detected by energy dispersive X ray analysis (EDAX). Trace element (As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, U, V and Zn) content was quantified by inductively coupled plasma-mass spectrometry (ICP-MS). Nuclear activation analysis (NAA) was employed for the determination of Ce, Co, Cs, Eu, Hf, La, Lu, Rb, Sc, Sm, Ta and Yb. An enrichment was observed in the smallest size fraction of volcanic ashes for four elements (As, Cd, Cu and Sb) of particular interest from the environmental and human health point of view.

Argentina↗

PubMed1991

Plasma high density lipoprotein particle size alteration by simvastatin treatment in patients with hypercholesterolaemia.

Twenty-two patients with pronounced hypercholesterolaemia were treated with simvastatin in increasing doses, i.e. 10, 20 and 40 mg O.D. Each treatment regimen had a duration of 6 weeks. In addition to the expected low density lipoprotein (LDL)-lowering effect, simvastatin altered the plasma HDL particle size spectrum by selective elevation of the plasma HDL2b and HDL3a levels, as defined by polyacrylamide gradient gel electrophoresis (gge). While the reduction in LDL cholesterol by simvastatin was dose dependent, the effect on HDL was maximal already at 10 mg daily. On treatment with simvastatin 10 mg O.D., the plasma HDL2b and HDL3a concentrations increased by 30% (P less than 0.001) and 12% (P less than 0.01) respectively. On the corresponding treatment with simvastatin LDL cholesterol decreased by 31% (P less than 0.001). The very low density lipoprotein (VLDL) cholesterol to triglyceride ratio was significantly lowered by treatment with 10 mg simvastatin O.D. suggesting a compositional change in VLDL. Positive univariate correlations between treatment-induced decreases in plasma HDL3b/3c levels and VLDL triglyceride concentration were seen. It is suggested that inhibition of cholesterol synthesis in hypercholesterolaemic subjects by simvastatin treatment alters the composition of VLDL, which may affect the close relation between HDL and VLDL, in turn producing selective elevations of the plasma HDL2b and HDL3a levels.

Adult↗

PubMed1978

Effect on particle size of solubilization of wild-type and Re chemotype lipopolysaccharides solubilized with bovine serum albumin and triethylamine.

Disaggregation of wild-type and Re chemotype lipopolysaccharides (LPS) has been accomplished by solubilization with triethylamine followed by stabilization with bovine serum albumin in order to determine the degree of aggregation. Solubilization with 1.5% triethylamine was found to be more effective than with lower concentrations, as judged by permeation chromatography. Chromatographic analysis of triethylamine-bovine serum albumin-disaggregated LPS showed a range of particle sizes. Wild-type LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons, 250,000 daltons, and 20,000 daltons. Re LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons and 20,000 daltons. Untreated LPS was always greater than 4 X 10(6) daltons. Chemical characterization of the size classes revealed 3-keto-2-deoxyoctonate in all size classes and suggests that the O-antigenic side chain length may determine the aggregate size in solubilized LPS.

Carbohydrates↗

PubMed2024

Effects of initial corncob particle size on the short-term composting for preparation of cultivation substrates for Pleurotus ostreatus.

The short-term composting based on corncob for preparing Pleurotus ostreatus cultivation medium originated from agricultural production practices and so lacked systematic investigation. In this study, the influences of a Dafen (15 mm, DFT) and Xiaofen (5 mm, XFT) initial particle size (IPS) of corncob on the microbial succession and compost quality were examined. Results demonstrated that XFT compost was better suited for mushroom cultivation due to its high biological efficiency of 70 % and the absence of contamination. The composting microbes differed significantly between the DFT and XFT composts. During composting, the genera of Bacillus, Acinetobacter, Lactobacillus, Streptomyces, and Paenibacillus were majorly found in the DFT compost, while Acinetobacter, Lactobacillus, Puccinia, Bacteroides, and Bacillus genera dominated the XFT compost. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that throughout the thermophilic phase, XFT compost had much greater relative abundances of sequences relevant to energy, carbohydrate, and amino acid metabolism than DFT compost. Analysis of network correlations and Mantel tests indicated that IPS reduction could increase microbial interactions. Overall, adjusting the IPS of corncob to 5 mm increased microbial interactions, improved compost quality, and thereby boosted the P. ostreatus yield. These findings will be pertinent in optimizing the composting process of cultivation medium for P. ostreatus.

Composting↗

PubMed2000

Latex Particle Size Distribution by Dynamic Light Scattering: Computer Evaluation of Two Alternative Calculation Paths.

Two calculation paths for estimating the particle size distribution (PSD) of a polymer latex from single-angle dynamic light scattering (DLS) measurements are evaluated on the basis of a numerical example. In the more common "double-step method," two calculation steps are applied, with the intermediate estimation of the particle light intensity distribution (PLID). In the "single-step method," the calculation is performed in one operation. From the specification of several PSDs, a mathematical model is used to produce the synthetic measurements. An iterative procedure was applied for determining the diameter range and the number of PSD points. The inversion operations were carried out using a regularization technique. For narrow distributions with diameters in the range 100-1000 nm, the PSD and the PLID are similar in shape, and both calculation paths produce similar results. For broad PSDs in the range 100-1000 nm, and for arbitrary PSDs in the range 10-100 nm (i.e., in the Rayleigh region), the single-step method proved preferable. Copyright 2000 Academic Press.

Journal Article↗

PubMed2005

Physicochemical characterization and mercury speciation of particle-size soil fractions from an abandoned mining area in Mieres, Asturias (Spain).

Soils from old cinnabar mining areas usually exhibit high Hg contents, whose mobility depends on soil parameters and environmental conditions. This paper presents the study of the Hg speciation in soil samples from an abandoned Hg mine and metallurgical plant in Mieres (Asturias, Spain), in relation to their mineralogical and chemical composition and their particle-size distribution. A characterization of samples was made by X-Ray Diffraction Spectrometry, Scanning Electron Microscopy and Atomic Absorption and Emission Spectroscopy analyses. A sequential extraction method was applied to establish Hg mobility in the samples and their grain-size subsamples. The highest Hg mobility was found in well-developed soils, as a consequence of the adsorption processes by iron and manganese oxides, whereas in those more contaminated soils, a higher proportion of Hg was leached in the non-mobile fraction. A higher Hg mobility was found in the finest grain-size subsamples, probably due to the accumulation of clay minerals and oxides in these ranges.

Adsorption↗

PubMed2006

The influence of drug solubility and particle size on the pellet formulation in a rotoprocessor.

Pellets containing drugs of different properties were prepared in a Rotoprocessor in order to study changes in the formulation process and resulting pellet characteristics. Diltiazem hydrochloride, diclofenac sodium, and theophylline were chosen as model drugs. Pellet size distribution, sphericity, density, hardness, friability, and repose angle were determined using standard methods. The amount of water as a wetting agent necessary for successful pellet formulation was observed for each sample and changed depending on drug solubility, concentration, and particle size. The pelletization of freely soluble diltiazem hydrochloride required 24.8-23.1% of the wetting agent and its amount decreased as the drug concentration increased. The demand for water in the formulation of theophylline pellets was 31.0-34.4% and it increased with increasing drug concentration. The pellet samples containing both drugs were easy to prepare. However, the cohesion of micronized diclofenac sodium particles negatively influenced both the pellet size distribution and the formulation process itself. When the drug concentration exceeded 40%, it was not possible to produce pellets of an appropriate size and the process was not reproducible.

Algorithms↗

PubMed1979

Evaluation of changes in drug particle size during tableting by measurement of dissolution of disintegrated tablets.

Three poorly soluble drugs (chloramphenicol, phenacetin and prednisolone) were compressed into tablets of 10% drug content on a physical testing instrument at three different compression pressures. The dissolution profiles were determined by a modification of the U.S.P. method for drug suspensions, granules before compression, disintegrated and intact tablets. By comparison of the dissolution rates for disintegrated tablets with those for granules before compression, or suspensions, it is possible to separate the change in particle size during compression from the pressure-dependent dissolution behaviour of intact tablets. A comparative measurement of dissolution for disintegrated tablets with that for granules provides a useful method for elucidating the particle bonding or cleavage within the tablet during compression.

Drug Compounding↗

PubMed1997

Effect of particle sizes in India ink on its use in evaluation of apical seal.

We investigated the use of India ink as an indicator of root canal sealing ability. Sealing ability is one of the most important factors required of root canal cements. Various dyes have been used for this purpose. Methylene blue, radioisotopes and India ink have all been tried. However, there is no evidence that India ink is suitable as an indicator. We measured the particle size distribution of India ink to determine how this factor affects test results. In addition, we observed the surface texture of an experimentally developed calcium phosphate sealer and a commercially available root canal sealer using SEM. We found that a portion of the India ink particles were smaller than cracks on the two sealer surfaces, indicating, that India ink could pass through these cracks. We concluded that India ink is suitable as an indicator of root canal seal.

Calcium Phosphates↗

PubMed1994

Forage level and particle size effects on orchardgrass digestion by steers: II. Ruminal digestion kinetics of cell wall components.

Four steers (502 +/- 49 kg) with ruminal cannulas were used in a 4 x 4 Latin square experimental design with a 2 x 2 factorial arrangement of treatments to determine the effects of the dietary forage:concentrate ratio (96:4 and 60:40) and forage particle size (long hay and coarsely ground hay) on in situ ruminal digestion kinetics of orchardgrass hay DM and cell wall neutral monosaccharides, uronic acids, acetyl groups, and hydroxycinnamic acids. Dacron in situ bags containing orchardgrass hay were fermented for 0, 4, 8, 12, 18, 24, 48, and 96 h. Digestion profiles of DM and cell wall monomers in undigested residues recovered from the rumen were analyzed using a first-order, exponential equation to estimate the indigestible fraction (fi), the insoluble, potentially digestible fraction (fd), and the fractional rate constant (kd) of digestion of fd. Initial results indicated that fi was not consistently influenced by diet fed to the steers; thus, in situ digestion profiles were analyzed to estimate single fi and fd values common to all steers and diets and different estimates of kd for each steer x diet combination (16 total). Estimates of fi (percentage of original) for cell wall components were ranked in the following order: galactose (12.6), ferulic acid (13.9), arabinose (14.5), total uronic acids (15.4), glucose (19.8), xylose (28.4), p-coumaric acid (34.6), and acetyl groups (35.8).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗