Centrifugal Sedimentation Method Research Articles

Acoustic wave in a suspension of magnetic nanoparticle with sodium oleate coating

The ultrasonic propagation in the water-based magnetic fluid with doubled layered surfactant shell was studied. The measurements were carried out both in the presence as well as in the absence of the external magnetic field. The thickness of the surfactant shell was evaluated by comparing the mean size of magnetic grain extracted from magnetization curve with the mean hydrodynamic diameter obtained from differential centrifugal sedimentation method. The thickness of surfactant shell was used to estimate volume fraction of the particle aggregates consisted of magnetite grain and surfactant layer. From the ultrasonic velocity measurements in the absence of the applied magnetic field, the adiabatic compressibility of the particle aggregates was determined. In the external magnetic field, the magnetic fluid studied in this article becomes acoustically anisotropic, i.e., velocity and attenuation of the ultrasonic wave depend on the angle between the wave vector and the direction of the magnetic field. The results of the ultrasonic measurements in the external magnetic field were compared with the hydrodynamic theory of Ovchinnikov and Sokolov (velocity) and with the internal chain dynamics model of Shliomis, Mond and Morozov (attenuation).

Evaluating Stability of Aqueous Multiwalled Carbon Nanotube Nanofluids by Using Different Stabilizers

The 0.5 wt.% multiwalled carbon nanotubes/water nanofluids (MWNFs) were produced by using a two‐step synthetic method with different types and concentrations of stabilizers. The static position method, centrifugal sedimentation method, zeta potential measurements, and rheological experiments were used to assess the stability of the MWNFs and to determine the optimal type and fixed MWCNTs‐stabilizer concentration of stabilizer. Finally, MWNFs with different concentrations of MWCNTs were produced using the optimal type and fixed concentration ratio of stabilizer, and their stability, thermal conductivity, and pH were measured to assess the feasibility of using them in heat transfer applications. MWNFs containing SDS and SDBS with MWCNTs‐stabilizer concentration ratio were 5 : 2 and 5 : 4, respectively, showed excellent stability when they were evaluated by static position, centrifugal sedimentation, zeta potential, and rheological experiments at the same time. The thermal conductivity of the MWNFs indicated that the most suitable dispersing MWNF contained SDBS. MWNFs with MWCNTs concentrations of 0.25, 0.5, and 1.0 wt.% were fabricated using an aqueous SDBS solution. In addition, the thermal conductivity of the MWNFs was found to have increased, and the thermal conductivity values were greater than that of water at 25°C by 3.20%, 8.46%, and 12.49%.

遠心沈降分析法を用いた分散・凝集評価法

遠心沈降分析法を用いた分散・凝集評価法

Validation of dynamic light scattering and centrifugal liquid sedimentation methods for nanoparticle characterisation

A variety of techniques exists to analyse the size and size distribution of nanoparticles in a suspension. However, these nanoparticle characterisation methods have been rarely fully validated and appropriate reference materials with properly assigned SI traceable values are not easily found. This paper presents results of in-house validation studies of Dynamic Light Scattering (DLS) and Centrifugal Liquid Sedimentation (CLS) methods. During these studies, a silica nanoparticle reference material was tested under repeatability and intermediate precision conditions. The trueness of the DLS and CLS methods was investigated by measuring gold and polystyrene nanoparticle reference materials. Furthermore, for each method, an uncertainty budget has been established. Both method validation and estimation of reliable measurement uncertainties are prerequisites for the certification of new nanoparticle reference materials.

多波長偏光を用いたサブミクロン粒径計測(熱工学,内燃機関,動力など)

Feasibility of a newly developed size determination method for sub-micron particles using multi-wavelength polarized lights is investigated, experimentally. According to the Mie's theory the polarization ratios of scattered lights are calculated numerically, which is a function of the particle diameter, the refraction index, and the wavelength of the incident light. Polystyrene particles are used as the test particles, which are suspended in purified water. The arithmetic mean diameters of them are varied from 0.356 to 0.77μm, which is measured with a centrifugal sedimentation method. In order to extend the measurement range of convestional polarization ratio methods, three kinds of He-Ne lasers, whose wavelengths are 543.5, 594.1, and 632.8nm, are used. The laser beams passes through the particles, and the scattered images are acquired with a digital CCD camera set in parallel and perpendicular directions to the polarization plane of the incident light. The polarization ratios of the scattered lights are estimated from these scattered light images, and the acquired data are compared with the analytical values. It is shown that, by use of the multi-wavelength polarization ratio method, the measurement range of the particle size can be extended up to the order of 1μm, and that the accuracy of the results lies from 0.1% to 7.6%, when compared with the results of a centrifugal sedimentation method.

Intestinal Parasite Infections in Pigs and Beef Cattle in Rural Areas of Chungcheongnam-do, Korea

The present study was performed to investigate the infection status of intestinal parasites in pigs and beef cattle in rural areas of Chungcheongnam-do, Korea. From November 2009 to April 2010, a total of 241 fecal samples of pigs and beef cattle (136 and 105, respectively) were examined by direct smear and centrifugal sedimentation methods. The overall positive rates of intestinal parasites among pigs and beef cattle were 73.5% and 4.8%, respectively, and the double-infection rate was 10.3% in pigs. Of 136 specimens from pigs, Balantidium coli, Ascaris suum, and Entamoeba spp. infections were found in 88 (64.7%), 24 (17.6%), and 5 cases (3.7%), respectively. Of 105 beef cattle, Entamoeba spp. infections were detected in 5 cases (4.8%). From these results, it is shown that pigs raised on rural farms in Chungcheongnam-do had a high B. coli infection rate and a moderate A. suum infection rate. These results demonstrate that environmentally resistant cysts or eggs could be widespread on the farms examined, and thus an effective hygienic management system is needed to prevent them from serving as the source of infection for human beings.

Factors associated with gastrointestinal parasite infection in dogs in Rio de Janeiro, Brazil

Factors associated with parasitism by helminths and protozoans in 500 dogs presented to three veterinary clinics in the municipality of Rio de Janeiro from November 2003 to September 2004 were evaluated. Dogs were submitted to physical examination and owners were interviewed about the animal's management. One fecal sample from each dog was examined by centrifugal flotation and sedimentation methods followed by the safranin–methylene blue staining technique. Positive results for gastrointestinal parasites were detected in 46.4% of the examined samples. Infection with protozoans (29.6%) was more frequent than with helminths (23.2%). Cryptosporidium sp. (26.2%) and Ancylostoma sp. (15.2%) were the most frequent parasites. Logistic regression analysis showed that age (p<0.001), access to soil (p<0.001), hygiene of the environment (p=0.001), illness (p=0.007), owner's level of education (p<0.006) and veterinary clinic (p=0.043) were associated with gastrointestinal parasite infections in dogs. Treatment and control are especially important for puppies. Adult dogs should be submitted to fecal examination before treatment, placing special emphasis on those that present one or more factors associated with infection.

Monitoring the stability of nanosized silica dispersions in presence of polycations by a novel centrifugal sedimentation method

AbstractThe stability of Aerosil‐silica dispersions is analyzed in dependence on the addition of polycations with different charge density and hydrophobic modification using the analytical centrifuge LUMiSizer. This novel centrifugal sedimentation method allows the direct calculation of the stability parameters like sedimentation velocity and prediction of the shelf life. The highly charged polycation poly (diallyl‐dimethylammonium chloride) (PDADMAC) is compared with tailored cationic polyelectrolytes of equal degree of polymerization but lower and different charge density as well as various hydrophobic substitutions. The used technique allows to accelerate demixing and to quantify the stability of dispersions in a direct way. All polymers under study are able to stabilize aerosil dispersions, but the shelf life strongly depends on the polymer concentration. Typically for polycations, the stability increases with the polymer concentration whereas at low‐polymer content flocculation can be detected. In this context, the behavior of PDADMAC and three cationic PVB derivatives is similar, but, whereas the stability of PDADMAC containing dispersions decreases at higher polymer concentrations, PVB derivatives are effective stabilizers at higher concentrations too. The highest increase of the stability with increasing polymer concentration is obtained with the ampholytic terpolymer TP that has the lowest cationic charge. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A comparative study of particle size analysis in fine powder: The effect of a polycomponent particulate system

We report the particle size distribution of poly component particulate systems studied in three kinds of experimental methods. Six analyzers, such as Mastersizer Microplus (Malvern Instruments Ltd., UK), LS230 (Coulter Electronics Ltd., USA) LMS30 (Seishin, Japan), Analysette22 (Fritsch, Germany), HELOS (Sympatec, Germany) based on a laser diffraction and scattering method, and the SKC-2000S (Seishin Co., Ltd., Japan) based on the centrifugal sedimentation method, were used to study the particle size distribution. The results do not show reasonably good agreement between the different analyzers and different sample systems. There is a discrepancy regarding the absolute values, which can be explained by the fact the techniques used are based on different measuring principles. The results of the present study reflect that the investigator must carefully select the particle size analyzer for a particular application. Therefore, we suggest that it is necessary to measure the particle size distribution by using at least two types of analyzers or more of different makers.

ANALYSIS METHOD OF GRAIN SIZE DISTRIBUTION OF FINE SUSPENDED SEDIMENT IN DAM RESERVOIRS

Long term persistence of high turbidity water is one of the major water quality issues in rivers with a dam reservoir. This phenomenon is influenced by the grain size of fine sediment carried by floodwater into the reservoir. In his paper, analysis methodology of grain size distributions of fine sediment is discussed to propose the most proper method. Three analysis methods -sedimentation experiment in a tall tube, laser diffraction-dispersion method and centrifugal sedimentation method- are applied to several kinds of fine sediment sampled from river water and reservoir bed and the results are compared. From the results, laser diffraction-dispersion method with preprocess of sonication is proposed as most suitable for practical analysis of fine sediment in river water.

Primary and Aggregate Size Distributions of PM in Tail Pipe Emissions form Diesel Engines

Particulate matter (PM) emission exhausted from diesel engine should be reduced to keep the clean air environment. PM emission was considered that it consisted of coarse and aggregate particles, and nuclei-mode particles of which diameter was less than 50 nm. However the detail characteristics about these particles of the PM were still unknown and they were needed for more physically accurate measurement and more effective reduction of exhaust PM emission. In this study, the size distributions of solid particles in PM emission were reported. PMs in the tail-pipe emission were sampled from three type diesel engines. Sampled PM was chemically treated to separate the solid carbon fraction from other fractions such as soluble organic fraction (SOF). The electron microscopic and optical-manual size measurement procedures were used to determine the size distribution of primary particles those were formed through coagulation process from nuclei-mode particles and consisted in aggregate particles. The centrifugal sedimentation method was applied to measure the Stokes diameter of dry-soot. Aerodynamic diameters of nano and aggregate particles were measured with scanning mobility particle sizer (SMPS). The peak aggregate diameters detected by SMPS were fallen in the same size regime as the Stokes diameter of dry-soot. Both of primary and Stokes diameters of dry-soot decreased with increases of engine speed and excess air ratio. Also, the effects of fuel properties and engine types on primary and aggregate particle diameters were discussed.

Influence of additive content of anionic polymer dispersant on dense alumina suspension viscosity

This paper reports on a new method to analyze the adsorbed structure of an anionic polymer dispersant on an alumina powder surface in dense suspension with different additive content by using an atomic force microscope (AFM). Anionic polymer dispersants were adsorbed on both the polished surface of a thin piece of sintered alumina and the surface of alumina powders in dense alumina suspension. After separation of the thin alumina piece and a clear layer from the dense suspension achieved by centrifugal sedimentation method, the adsorbed structure and electrosteric interactions of polymer dispersion on the polished surface of the sintered alumina were examined by using AFM. At an optimum additive content, which was obtained at the minimum viscosity of suspension, the maximum repulsive force was observed. At this point the adhesive force between the alumina surface and the tip of the AFM cantilever almost disappeared. With an excess addition of polymer dispersant, a decrease of electrosteric repulsion force was observed because the free polymers in solution compressed the adsorbed polymers. Both the decrease of electrosteric repulsion and the re-bridging of the dispersant between particles caused an increase of the suspension viscosity.

A high‐luminance and high‐resolution CRT for projection HDTV display

Abstract— We have developed a 3‐in. YAG (yttrium aluminum garnet) projection CRT for an HDTV display. The densely packed phosphor screen with a multi‐layer interference filter is prepared by depositing phosphor on a YAG faceplate using a centrifugal sedimentation method. The tube's envelope is made from a glass whose expansion coefficient is well‐matched with that of YAG. The focusing characteristics of an optimally designed pre‐focusing electron gun and focusing magnet are improved for a HDTV display application. As a result, the green, red, and blue tubes reached luminances of 1.4 × 105, 6.2 × 104, and 8 × 103 cd/m2 at a cathode current of 1.0 mA and an anode voltage of 29 kV, respectively, with a half‐intensity linewidth of 85 μm. An experimental 48‐in. rear‐projection TV set using the YAG projection tubes achieves more than 1000‐TV‐lines horizontal resolution and 300‐cd/m2 mean white luminance.

A new sizing technique for fine powders dispersed in air

We have recently developed a sizing technique for fine powders by combining a boiling method with a DMA (differential mobility analyzer)-CNC (condensation nucleus counter) system. In the boiling method, particle aggregates are broken up into their primary particles, and then the particle size distribution is accurately measured by the DMA-CNC system. In the present work, we have applied this method to the particle size measurement of several kinds of fine powders including tightly coagulated particles and nonspherical particles (needlelike and flakelike particles). The results are in good agreement with those obtained by electron microscope and centrifugal sedimentation methods.

ASSESSMENT OF RED BLOOD CELL DEFORMABILITY BY CENTRIFUGAL SEDIMENTATION

A centrifugal sedimentation method (CSM) is proposed for the assessment of deformability of red blood cells. The method is based on the premise that a red blood cell (RBC) should deform in a centrifugal field due to the variation of the centrifugal acceleration with the distance from the center of rotation. This change in shape of the RBC leads to a change in the rate of sedimentation in the centrifugal field. The rate of sedimentation, which serves as a measure of deformability, is characterized by an apparent sedimentation coefficient (ASC) and its normalized value (NASC), which is calculated by comparison with a control group of normal RBCs. It has been shown that the NASC is sensitive to the speed of rotation, to treatments with glutaraldehyde, diamide, or chlorpromazine, to heat treatment and to osmotic pressure variations.

Size Measurement of Fine Powders Using the Differential Mobility Analyzer—Application of Boiling Method for Aerosol Generation

ABSTRACT A method for aerosol generation, termed the “boiling method,” was previously developed to effectively disperse in air a powder consisting of coagulated submicron particles into their primary particles. Here, in order to apply the boiling method to the particle size measurement of a fine powder, the method is combined with a particle size measurement system comprising a differential mobility analyzer (DMA) and a condensation nucleus counter (CNC). To avoid the presence of residue particles after evaporation, Fluorinert (perfluorocarbon) has been chosen as the boiling liquid medium. The particle size distributions measured for several kinds of powders are in good agreement with the results obtained by electron microscope and centrifugal sedimentation method. The method is found to be useful for the particle sizing of fine powders in air. Moreover, the method can also be successfully used as a continuous generator of monodisperse aerosol particles having a high concentration.

金属粉の製造および評価試験 鉄，ニッケル，銅およびニオブ線の放電爆発による微粉体の作製

The fine powders were prepared by the explosion of iron, nickel, copper and niobium wires in air or under an argon gas atmosphere, which resulted from electric discharge. Concerning the collected powders, the properties and metal contents were examined.The average particle. sizes which were measured by the centrifugal sedimentation method were less than 1.0μm in all powders, and decreased to 0.3-0.5μm with an increase in the energy ratio. They also did not depend on the kind of wire and atmosphere. The crystallite sizes of the oxide powders made from iron and nickel wires in air decreased with an increase in the energy ratio, and became to constant value, 40-50nm at higher energy ratio. The products obtained in air were mainly oxides, and ones obtained under an argon gas atmosphere were metal and oxides. Reducing the energy ratio led to increasing in the metal contents in the powders, which prepared by the explosion of nickel, copper and niobium wires under an argon gas atmosphere, to 40, 100 and 30%, respectively.

Fluorescent microspheres to measure organ perfusion: validation of a simplified sample processing technique.

A disadvantage of nonradioactive microsphere techniques is that the processing of samples is time-consuming and complex. We developed and validated a simplified processing method for the fluorescent microsphere (FM) technique. In seven anesthetized dogs with coronary artery stenosis up to six different FM and five different radioactivity labeled microspheres (RM) were injected. Two FM and two RM labels were injected simultaneously to enable inter- and intramethod comparison. After gamma-counting samples of blood, myocardium (n = 168), and other organs (n = 59) were digested in test tubes with 2 N ethanolic KOH (60 degrees C, 48 h), microspheres were sedimented by centrifugation, dye was extracted in the same tube, and fluorescence was measured. With this processing method, recovery of FM was approximately 100%. Good correlations for inter- and intramethod comparisons were found [r = 0.985 +/- 0.01 (mean +/- SD)]. The lower intermethod correlation for blue microspheres (r = 0.958) indicates that the use of this label is less desirable. RM and FM endocardial-to-epicardial blood flow ratios correlated well (r = 0.974). With this one-vessel centrifugal sedimentation method and at least five fluorescently labeled microspheres, blood flow can be reliably measured in various organs, including ischemic myocardium.

遠心沈降法における粒子濃度変化の補正

遠心沈降法における粒子濃度変化の補正

Particle size analysis of plasticized PVC dispersion resins using the photometric centrifugal sedimentation method

There are many known methods for determining the particle size distribution of PVC dispersion resins. Most of these methods require that the resin be in an aqueous medium. PVC dispersion resins are used primarily in a plasticizer medium. The shearing action that takes place when the resin is mixed in plasticizer and the subsequent solvating action of the plasticizer affect the particle size distribution of the dispersion resin. It is advantageous to be able to determine the particle size distribution of the plasticized resin since it can affect various properties such as rheology, gloss and foam quality. It is the purpose of this paper to show that a fast zonal sedimentation technique can be used to analyze the less than 20 μ particle size fraction of a dispersion resin after it has been mixed in a plasticizer system. This can be accomplished in less than 90 minutes. This technique can be used to relate particular dispersion resin properties to the particle size distribution of the resin. The method can also be used as a quality control test.