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Particle Size Measurements (particle + size_measurement)
Selected AbstractsOnline Particle Size Measurement in Microgel Particle Suspensions: Principles and Data AnalysisCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 10 2010Prof. Dr.-Ing. Abstract If a gelled system is subjected to shearing or the concentration of reactive components is low, microgel particles are formed. Since labile microgel particles with high water capacities can often be found in food systems, and as they are important for the textural properties, particle size measurement is relevant for fundamental research and control of industrial processes. A chord length measurement system was tested for online particle sizing. [source] Characterization of the interactions between polymethacrylate-based aqueous polymeric dispersions and aluminum lakesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2001Nasser Nyamweya Abstract Instability in film coating formulations can arise from interactions between aluminum lake pigments and aqueous polymeric dispersions. The purpose of this study was to characterize the interactions between three polymethacrylate-based aqueous polymeric dispersions (Eudragit® RS 30 D, Eudragit® L 30 D-55, and Eudragit® NE 30 D) and aluminum lakes. Particle size measurements, pH stability profiles, zeta potential measurements, and microscopy were used to study mixed dispersions of the polymeric latices and the lakes. Interactions leading to dispersion instability were related to the surface charge of the components in the formulation. Interactions between the ionic polymers and the lakes arose from instability of the lakes outside a certain pH range resulting in the release of electrolytes, which led to aggregation of the polymeric particles. Interactions between the nonionic polymer and the lakes were related to the polymer modifying the surface charge of the lakes, resulting in aggregation of the pigment particles. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1937,1947, 2001 [source] Improvement of the Dispersion of Al2O3 Slurries Using EDTA-4NaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2006Jingxian Zhang Polyacrylic acid (PAA) is known to be an effective dispersant for Al2O3 powder in aqueous media. However, at high solid loading (>55 vol%), the dispersion of the Al2O3 suspensions became difficult with only PAA as a dispersant. In this paper, ethylenediaminetetraacetic acid, tetrasodium salt, dihydrate (EDTA-4Na) was introduced to improve the dispersion of the Al2O3 suspensions. With the aid of EDTA-4Na, the adsorption amount of sodium polyacrylic acid (PAA-Na) increased, while the apparent viscosity of 60 vol% Al2O3 slurries decreased significantly. Particle size measurements showed that EDTA-4Na could help to reduce larger agglomerates, possibly by modifying the adsorbed layer thickness. The interactions between EDTA-4Na and PAA-Na were studied using Fourier-transform infrared spectroscopy analysis. Results showed that it was possible to introduce EDTA-4Na as the second dispersant to improve the dispersion of high solid content Al2O3 slurries. [source] Online Particle Size Measurement in Microgel Particle Suspensions: Principles and Data AnalysisCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 10 2010Prof. Dr.-Ing. Abstract If a gelled system is subjected to shearing or the concentration of reactive components is low, microgel particles are formed. Since labile microgel particles with high water capacities can often be found in food systems, and as they are important for the textural properties, particle size measurement is relevant for fundamental research and control of industrial processes. A chord length measurement system was tested for online particle sizing. [source] A Polygenetic Landform At Stígá, Örćfajökull, Southern IcelandGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2004Tim Harris Abstract Recent research has identified problems inherent in the identification and description of landforms. Morphologically similar small-scale glacial and periglacial landforms can be misinterpreted, thus hindering environmental reconstruction. This study reveals that a landform resembling a moraine at Stígárjökull, southern Iceland, is the product of both glacial deposition and mass movement. The landform has two distinct morphological and sedimentological components: a basal, lithologically diverse component, and an upper, lithologically homogenous component. Clast lithological analysis, particle shape and particle size measurements demonstrate that the basal component of the landform consists of sediment whose characteristics match nearby moraines. In contrast, the source of the upper component is a narrow outcrop of rock above the valley floor. Evidence suggests that frost-shattered material was transported across a perennial snow patch to a small moraine, leading to growth of the ,moraine'. This combination of processes is unlikely to be unique, but the geological peculiarities of the field site permitted their identification. It is possible that many similar ,moraines' could be enlarged by subaerial feeding, leading to false reconstruction of glacier form and/or associated rates of erosion and sedimentation. Such polygenetic landform genesis therefore has implications for environmental reconstruction. [source] Interaction between the fluorinated amphiphilic copolymer poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)- graft -poly(SPEG) and DNAJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010Ling Li Abstract A synthesized copolymer, synthesized from HFMA (hexaflurobutyl methacrylate) and SPEG (PHFMA- g -PSPEG), was synthesized. PHFMA- g -PSPEG intercalated to the DNA base pair via a strong hydrophobic force, and this was conformed by ultraviolet spectroscopy, transmittance measurements, micropolarity measurements, resonance light scattering (RLS) spectroscopy, and particle size measurements. The copolymer was used as a new probe to detect DNA according to the RLS technique. The hydrophobic interaction between PHFMA- g -PSPEG and DNA significantly enhanced the RLS signal, and the enhanced RLS intensity at 422 nm was proportional to the nucleic acid concentration within the range of 0.09,0.90 mg/L with a detection limit (3,) of 4.0 ,g/L. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Using a modified shepards method for optimization of a nanoparticulate cyclosporine a formulation prepared by a static mixer techniqueJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2008Dionysios Douroumis Abstract An innovative methodology has been used for the formulation development of Cyclosporine A (CyA) nanoparticles. In the present study the static mixer technique, which is a novel method for producing nanoparticles, was employed. The formulation optimum was calculated by the modified Shepard's method (MSM), an advanced data analysis technique not adopted so far in pharmaceutical applications. Controlled precipitation was achieved injecting the organic CyA solution rapidly into an aqueous protective solution by means of a static mixer. Furthermore the computer based MSM was implemented for data analysis, visualization, and application development. For the optimization studies, the gelatin/lipoid S75 amounts and the organic/aqueous phase were selected as independent variables while the obtained particle size as a dependent variable. The optimum predicted formulation was characterized by cryo-TEM microscopy, particle size measurements, stability, and in vitro release. The produced nanoparticles contain drug in amorphous state and decreased amounts of stabilizing agents. The dissolution rate of the lyophilized powder was significantly enhanced in the first 2 h. MSM was proved capable to interpret in detail and to predict with high accuracy the optimum formulation. The mixer technique was proved capable to develop CyA nanoparticulate formulations. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:919,930, 2008 [source] Determination of fluidized bed granulation end point using near-infrared spectroscopy and phenomenological analysisJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2005W. Paul Findlay Abstract Simultaneous real-time monitoring of particle size and moisture content by near-infrared spectroscopy through a window into the bed of a fluidized bed granulator is used to determine the granulation end point. The moisture content and particle size determined by the near-infrared monitor correlates well with off-line moisture content and particle size measurements. The measured particle size is modeled using a population balance approach, and the moisture content is shown to follow accepted models during drying. Given a known formulation, with predefined parameters for peak moisture content, final moisture content, and final granule size, the near-infrared monitoring system can be used to control a fluidized bed granulation by determining when binder addition should be stopped and when drying of the granules is complete. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:604,612, 2005 [source] Transition from microemulsion to emulsion polymerization: Mechanism and final propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2004Kevin D. Hermanson Abstract Microemulsion and emulsion polymerization can have some similarities in starting conditions and polymerization mechanisms, but the resulting latices are unalike in particle size and molecular weight. Here we show that polymerizations can be formulated that display the characteristics often separately associated with microemulsion or emulsion polymerization. Kinetic modeling and particle size measurements show that emulsion polymerizations with initial concentrations close to the microemulsion,emulsion phase boundary demonstrate relatively fast consumption of monomer droplets and produce smaller particles. Because of their high surfactant concentrations, none of the emulsion polymerizations examined demonstrate the classical Smith,Ewart kinetics usually associated with emulsion polymerization. Instead these emulsion polymerizations have a long period of particle nucleation that subsides only after the disappearance of monomer droplets. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5253,5261, 2004 [source] Selection of Descriptors for Particle Shape CharacterizationPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2003Abstract Conventional shape descriptors, formed from a ratio of two particle size measurements, are among the simplest of the many methods used for quantitative particle shape characterization. However, a significant limitation of using one of these shape descriptors is that its value is often not unique to a specific shape. Use of several different shape descriptors may circumvent this problem but, as particle size can be defined in a large number of ways, a similarly large number of shape descriptors can be defined. While some differ substantially, others are only subtly different, conveying similar information. Thus, it is not obvious which of the many possible descriptors should be utilized. In this paper, two-dimensional particle shape descriptors obtained by image analysis of six different commercially sourced powders were considered. Techniques of cluster and correlation analysis were applied to assist in identifying redundant descriptors for shape characterization of these powder particles, allowing for efficient description of shape using a reduced set. It was found that at least two descriptors are required: aspect ratio and the square root of form factor. Significantly, each descriptor is most sensitive to a different attribute of shape: elongation and ruggedness, respectively. [source] | |||||||||||||