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Precipitation Method (precipitation + method)
Selected AbstractsImprovement of Microwave Loss Tangent and Tunability of Ba0.55Sr0.45TiO3/MgO Composites Using the Heterogeneous Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Rui-Hong Liang Ba0.55Sr0.45TiO3/MgO composites were successfully prepared by the heterogeneous precipitation method and their structural, surface morphological, tunable properties, and dielectric properties at microwave frequency were systemically investigated. Compared with the sample prepared by the traditional solid-state method, the sample prepared by the heterogeneous precipitation method exhibits a smaller grain size, more uniform microstructure, higher tunability, and lower microwave loss, and these properties are very beneficial to the development of the microwave tunable devices application. Moreover, the effects of La2O3 doping on the dielectric and tunable properties of BST/MgO composites are investigated. The result shows that the La3+ -doped sample has higher tunability and lower microwave loss than the undoped one. [source] Growth and Phase Transformation of Nanometer-Sized Titanium Oxide Powders Produced by the Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2004Gwan Hyoung Lee We report an in situ TEM investigation of the growth and transformation in nanometer-sized titania powders. The powders were produced through precipitation of titanium tetrachloride under different pH conditions. The initial phase of the produced powders was amorphous or was a mixture of anatase and brookite according to the pH conditions. During calcination, the anatase particles grew and transformed into rutile. The transformation temperature increased with increasing pH value. In situ TEM observations showed that the anatase particles were absorbed into rutile, and then rutile particles grew by coalescence. Furthermore, small pores were observed to form in samples prepared with high pH from the effects of hydroxyl ions and zeta potential. Pore formation increased the surface area, which delayed the transformation and nucleation of rutile. This explains the difference of growth and transformation of titania powders produced under different pH conditions during calcination. [source] Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Ping-Hua Xiang NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO3)2·6H2O, and NH4HCO3 as the starting materials. The amorphous NiCO3·2Ni(OH)2·2H2O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ,8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ,30 nm. [source] Acetyl-CoA:1- O -alkyl- sn -glycero-3-phosphocholine acetyltransferase (lyso-PAF AT) activity in cortical and medullary human renal tissueFEBS JOURNAL, Issue 14 2003Tzortzis N Nomikos Platelet-activating factor (PAF) is one of the most potent inflammatory mediators. It is biosynthesized by either the de novo biosynthesis of glyceryl ether lipids or by remodeling of membrane phospholipids. PAF is synthesized and catabolized by various renal cells and tissues and exerts a wide range of biological activities on renal tissue suggesting a potential role during renal injury. The aim of this study was to identify whether cortex and medulla of human kidney contain the acetyl-CoA:1- O -alkyl- sn -glycero-3-phosphocholine acetyltransferase (lyso-PAF AT) activity which catalyses the last step of the remodeling biosynthetic route of PAF and is activated in inflammatory conditions. Cortex and medulla were obtained from nephrectomized patients with adenocarcinoma and the enzymatic activity was determined by a trichloroacetic acid precipitation method. Lyso-PAF AT activity was detected in both cortex and medulla and distributed among the membrane subcellular fractions. No statistical differences between the specific activity of cortical and medullary lyso-PAF AT was found. Both cortical and medullary microsomal lyso-PAF ATs share similar biochemical properties indicating common cellular sources. [source] Characterisation of soybean glycinin and ,-conglycinin fractionated by using MgCl2 instead of CaCl2INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2010Chong Liu Summary A simple two step precipitation method was used to investigate the effect of MgCl2 instead of CaCl2 on fractionation of soybean glycinin and ,-conglycinin. Compositional and physicochemical properties of the resulting protein fractions were characterised. The optimised procedure, in terms of protein yield, purity, phytate content and physicochemical properties, was obtained when the addition of 5 mm MgCl2 was used. After application of 5 mm MgCl2, the phytate content of the glycinin-rich and ,-conglycinin-rich fractions was about 0.4% and 1.3%, respectively, but the addition of 5 mm CaCl2 increased the phytate content of the glycinin-rich fraction to 1.25% and decreased that of ,-conglycinin-rich fraction to 0.67%. Low phytate protein product was suitable for use in infant formula and acidic food. The solubility of the glycinin-rich fractions with MgCl2 was significantly higher than that with CaCl2 at pH < 4.5. Application of MgCl2 improved thermal stability of the ,-conglycinin-rich fraction. [source] Effect of extrusion parameters on flavour retention, functional and physical properties of mixtures of starch and d -limonene encapsulated in milk proteinINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2006Sri Yuliani Summary The purpose of this research was to investigate the retention of flavour volatiles encapsulated in water-insoluble systems during high temperature,short time extrusion process. A protein precipitation method was used to produce water-insoluble capsules encapsulating limonene, and the capsules were added to the extruder feed material (cornstarch). A twin-screw extruder was used to evaluate the effect of capsule level of addition (0,5%), barrel temperature (125,145 °C) and screw speed (145,175 r.p.m.) on extruder parameters (torque, die pressure, specific mechanical energy, residence time distribution) and extrudate properties [flavour retention, texture, colour, density, expansion, water absorption index, water solubility index (WSI)]. Capsule level had a significant effect on extrusion conditions, flavour retention and extrudate physical properties. Flavour retention increased with the increase in capsule level from 0% to 2.5%, reached a maximum value at capsule level of 2.5% and decreased when the capsule level increased from 2.5% to 5%. The die pressure, torque, expansion ratio, hardness and WSI exhibited the opposite effect with the presence of capsules. [source] Synthesis and use of pHEMA microbeads with human EA.hy 926 endothelial cellsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Hervé Nyangoga Abstract Cancer has become a major problem in public health and the resulting bone metastases a worsening factor. Facing it, different strategies have been proposed and mechanisms involved in tumor angiogenesis are being studied. Enhanced permeability retention (EPR) effect is a key step in designing new anticancer drugs. We have prepared poly 2-hydroxyethyl methacrylate (pHEMA) microbeads to target human endothelial EA.hy 926 cells, a cell line derived from human umbilical vein endothelial cells. Microbeads were synthesized by emulsion precipitation method and carried positive or negative charges. EA.hy 926 cells were cultured in 24-well plates and microbeads were deposited on cells at various times. Scanning and transmission electron microscopy, flow cytometry, confocal microscopy, and three-dimensional (3D) reconstruction were used to characterize microbeads and their location outside and inside cells. Microbeads were uptaken by endothelial cells with a better internalization for negatively charged microbeads. 3D reconstruction of confocal optical sections clearly evidenced the uptake and internalization of microbeads by endothelial cells. pHEMA microbeads could represent potential drug carrier in tumor model of metastases. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] ISOLATION and CHARACTERIZATION of MANGO PEEL PECTINSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2000D.V. SUDHAKAR An efficient method for manufacture of pectin from Totapuri mango peels was standardized by studying various factors that govern the recovery and quality of pectin. Among the different organic and inorganic acids, 0.05 N HCl was found to be the best for recovery of pectin from mango peels. Optimum yield of pectin was obtained by taking two extractions each for one-hour duration employing a peel: extractant ratio of 1:2 and by alcohol precipitation method. Dried mango peels could be stored for six months at ambient conditions (14.5,33.9C) without any significant effect on the recovery of pectin. Pectin extract, an intermediate product in the manufacture of pectin, could be stored for one month either at low temperature (6C±2) or at ambient conditions (24.5,33.0C) by the addition of 700 ppm SO2 with minimum loss in the recovery of pectin. Using the optimum extracting conditions about 20.8% (DWB) of purified pectin was obtained from mango peels. the powdered pectin could be stored for over 6 months without any deterioration in quality when packed in airtight containers at ambient conditions. [source] Effect of Heat Treatment on Far Infrared Emission Properties of Tourmaline Powders Modified with a Rare EarthJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Dongbin Zhu Far infrared materials were prepared by precipitation method using natural tourmaline (XY3Z6Si6O18(BO3)3W4, where X is Na+, Ca2+, K+, or vacancy; Y is Mg2+, Fe2+, Mn2+, Al3+, Fe3+, Mn3+, Cr3+, Ti4+ or Li+; Z is Al3+, V3+, Cr3+, or Mg2+; and W is OH,, F,, or O2,) powders and cerium nitrate as raw materials. The results of Fourier transform infrared spectroscopy (FTIR) show that rare earth Ce can enhance the far infrared emission properties of tourmaline. Through characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), the mechanism by which rare earth Ce acts on the far infrared emission property of tourmaline was systematically studied. The XPS spectra show that the Fe3+ ratio inside tourmaline powders after heat treatment can be raised by doping Ce. Moreover, it is showed that Ce3+ is dominant inside the samples but its dominance is replaced by Ce4+ outside. In addition, XRD results indicate the formation of CeO2 crystallites during the heat treatment and further TEM observations show they exist as nanoparticles on the surface of tourmaline powders. Based on these results, we attribute the improved far infrared emission properties of Ce-doped tourmaline to the enhanced unit cell shrinkage of the tourmaline arisen from the oxidation of Fe2+ (0.074 nm in radius) to Fe3+ (0.064 nm in radius) inside the tourmaline caused by the redox shift between Ce4+ and Ce3+. [source] Precipitation of Carbonated Calcium Phosphate Powders from a Highly Supersaturated Simulated Body Fluid SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Ingo Hofmann Carbonated hydroxy apatite (CHA) powders were prepared by precipitation from a modified simulated body fluid (5 × M-SBF). The ionic concentrations were five times higher than in human blood plasma with the exception of Mg2+ and HCO3, concentrations that were reduced in order to accelerate crystal growth. Spheroaggregates of CHA platelets with molar (Ca+Mg)/P ratios ranging from 1.44 to 1.56 were obtained after precipitation at 50°C. The crystallite size in the c direction was approximately 31 nm and depending on the precipitation time, a CO32, content of 1.8,5.2 wt% was determined. Using this low-temperature precipitation method, CHA powders with a high specific surface area of 83 m2/g and a composition and crystallite size close to those of the mineral phase of human bone were obtained. [source] Improvement of Microwave Loss Tangent and Tunability of Ba0.55Sr0.45TiO3/MgO Composites Using the Heterogeneous Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Rui-Hong Liang Ba0.55Sr0.45TiO3/MgO composites were successfully prepared by the heterogeneous precipitation method and their structural, surface morphological, tunable properties, and dielectric properties at microwave frequency were systemically investigated. Compared with the sample prepared by the traditional solid-state method, the sample prepared by the heterogeneous precipitation method exhibits a smaller grain size, more uniform microstructure, higher tunability, and lower microwave loss, and these properties are very beneficial to the development of the microwave tunable devices application. Moreover, the effects of La2O3 doping on the dielectric and tunable properties of BST/MgO composites are investigated. The result shows that the La3+ -doped sample has higher tunability and lower microwave loss than the undoped one. [source] Characterization and Mechanical Performance of the Mg-Stabilized ,-Ca3(PO4)2 Prepared from Mg-Substituted Ca-Deficient ApatiteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Sanjeevi Kannan The preparation of Mg-stabilized ,-tricalcium phosphate (,-TCP) was carried out by an aqueous precipitation method and the characterization of the powders was performed by powder X-ray diffraction, FT-IR spectra, Raman spectroscopy, and elemental analysis. The transformation of calcium-deficient apatite into ,-TCP has occurred in the range of 700°,800°C. The calculated values for lattice parameters confirm the stabilization role played by Mg. The thermal stability of the Mg-stabilized ,-TCP powders was evident until 1400°C, thus broadening the sintering temperature range without transformation into the undesirable ,-TCP. Accordingly, the mechanical properties of the Mg-stabilized ,-TCP were improved in comparison with those of pure ,-TCP. [source] Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Ping-Hua Xiang NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO3)2·6H2O, and NH4HCO3 as the starting materials. The amorphous NiCO3·2Ni(OH)2·2H2O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ,8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ,30 nm. [source] Effect of medium molecular weight xanthan gum in rheology and stability of oil-in-water emulsion stabilized with legume proteinsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2005Evdoxia M Papalamprou Abstract Xanthan gum is a water-soluble extracellular polysaccharide that has gained widespread commercial use because of its strong pseudoplasticity and tolerance to high ionic strength, which bring unique rheological properties to solutions. This study compares and evaluates the emulsifying properties of oil-in-water (30:70 v/v) emulsions stabilized with lupin and soya protein isolates and medium molecular weight xanthan gum. The protein was obtained by an isoelectric precipitation method and the polysaccharide was produced by Xanthomonas campestris ATCC 1395 in batch culture in a laboratory fermenter (LBG medium) without pH control. The addition of xanthan gum in the emulsion formulation enhances emulsion stability through the phenomenon of thermodynamic incompatibility with the legume protein, resulting in an increase of the adsorbed protein at the interface. The emulsion stability is also enhanced by a network structure built by the polysaccharide in the bulk phase. Copyright © 2005 Society of Chemical Industry [source] Preparation of smallest microparticles of poly- D,L -lactide by modified precipitation method: Influence of the process parametersMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2008Ivana Jovanovi Abstract Biodegradable microspheres such as those made of poly- D,L -lactide (PDLLA) are widely investigated delivery systems for drugs or antigens. The aim of this study was to examine experimental conditions in order to produce PDLLA microspheres with the best properties for controlled and sustained drug delivery by the modified precipitation method. For this purpose, the following parameters were varied: co-solvent (methanol or ethanol), the concentration of stabilizer polyvinyl alcohol (PVA), chloroform-to-water ratio and the speed and time of homogenization. Scanning electron microscopy (SEM) and stereological analysis were used to characterize the particles. The average size and morphology of the microspheres varied substantially with preparation conditions from 8.44,1.25 ,m. Results showed that the smallest particles were obtained with methanol, 1% PVA and with 10 min of homogenization at 21,000 rpm. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source] Introducing proteomics in the undergraduate curriculum: A simple 2D gel electrophoresis exercise with serum proteinsBIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 1 2010Thomas D. Kim Abstract Two-dimensional gel electrophoresis (2DGE) remains an important tool in the study of biological systems by proteomics. While the use of 2DGE is commonplace in research publications, there are few instructional laboratories that address the use of 2DGE for analyzing complex protein samples. One reason for this lack is the fact that the preparation of samples for 2DGE is a complex and difficult process that can commonly yield gels of poor quality and resolution. In this experiment, we use a serum-based sample to mitigate many of the sample preparation issues that occur in cell-based sample preparations and incorporate a protein precipitation method that was developed to address the problem of high-abundance proteins and dynamic range in serum proteomics research. By focusing on 2DGE apart from many other facets of proteomic experimental design, students have the opportunity to gain fruitful experience in the use of this workhorse proteomics technique. This simplified focus also makes this exercise accessible to biochemistry instructors who are not active in proteomics; the requisite techniques may require some new equipment (i.e. an isoelectric focusing apparatus), but this exercise focuses on using familiar techniques (primarily electrophoresis) to cross the threshold of a new field, proteomics. [source] Effect of genipin-crosslinked chitin-chitosan scaffolds with hydroxyapatite modifications on the cultivation of bovine knee chondrocytesBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006Yung-Chih Kuo Abstract Chitin and chitosan were hybridized in various weight percentages by genipin crosslinkage under various prefreezing temperatures to form tissue-engineering scaffolds via lyophilization. In addition, deposition of hydroxyapatite (HA) on the surface of the porous scaffolds was performed by precipitation method to achieve modified chemical compositions for chondrocyte attachments and growths. The experimental results revealed that a lower prefreezing temperature or a higher weight percentage of chitin in the chitin-chitosan scaffolds would yield a smaller pore diameter, a greater porosity, a larger specific surface area, a higher Young's modulus, and a lower extensibility. Moreover, a higher chitin percentage could also result in a higher content of amine groups after crosslink and a lower onset temperature for the phase transition after thermal treatment. A decrease in the prefreezing temperature from ,4°C to ,80°C, an increase in the chitin percentage from 20% to 50%, and an increase in the cycle number of alternate immersion for HA deposition from 1 to 5 generated positive effects on the cell number, the content of glycosaminoglycans, and the collagen level over 28-day cultivation of bovine knee chondrocytes. © 2006 Wiley Periodicals, Inc. [source] A novel Method for the selective recovery and purification of ,-polyglutamic acid from Bacillus licheniformis fermentation brothBIOTECHNOLOGY PROGRESS, Issue 3 2010Bhavik Manocha Abstract Microbially produced gamma-polyglutamic acid (,-PGA) is a commercially important biopolymer with many applications in biopharmaceutical, food, cosmetic and waste-water treatment industries. Owing to its increasing demand in various industries, production of ,-PGA is well documented in the literature, however very few methods have been reported for its recovery. In this paper, we report a novel method for the selective recovery and purification of ,-PGA from cell-free fermentation broth of Bacillus licheniformis. The cell-free fermentation broth was treated with divalent copper ions, resulting in the precipitation of ,-PGA, which was collected as a pellet by centrifugation. The pellet was resolubilized and dialyzed against de-ionized water to obtain the purified ,-PGA biopolymer. The efficiency and selectivity of ,-PGA recovery was compared with ethanol precipitation method. We found that 85% of the original ,-PGA content in the broth was recovered by copper sulfate-induced precipitation, compared to 82% recovery by ethanol precipitation method. Since ethanol is a commonly used solvent for protein precipitation, the purity of ,-PGA precipitate was analyzed by measuring proteins that co-precipitated with ,-PGA. Of the total proteins present in the broth, 48% proteins were found to be co-precipitated with ,-PGA by ethanol precipitation, whereas in copper sulfate-induced precipitation, only 3% of proteins were detected in the final purified ,-PGA, suggesting that copper sulfate-induced precipitation offers better selectivity than ethanol precipitation method. Total metal content analysis of the purified ,-PGA revealed the undetectable amount of copper ions, whereas other metal ions detected were in low concentration range. The purified ,-PGA was characterized using infrared spectroscopy. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Determination of the Optimal Conditions for Synthesis of Silver Oxalate NanorodsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2008M. Pourmortazavi Abstract In this study, an orthogonal array design (OAD), OA9, was employed as a statistical experimental method for the controllable, simple and fast synthesis of silver oxalate nanorods. Ultrafine silver oxalate rods were synthesized by a precipitation method involving the addition of silver ion solution to the oxalate reagent. The effects of reaction conditions, i.e., silver and oxalate concentrations, flow rate of reagent addition and temperature, on the diameter of the synthesized silver oxalate rods were investigated. The effects of these factors on the width of the silver oxalate rods were quantitatively evaluated by the analysis of variance (ANOVA). The results showed that silver oxalate nanorods can be synthesized by controlling the silver concentration, flow rate and temperature. Finally, the optimum conditions for the synthesis of silver oxalate nanorods by this simple and fast method were proposed. The results of ANOVA showed that 0.001,mol/L silver ion concentration, 40,mL/min flow rate for the addition of the silver reagent to the oxalate solution and 0,°C temperature are the optimum conditions for producing silver oxalate nanorods with 107 ± 45,nm width. [source] Heterogeneous Gold Catalysts for Efficient Access to Functionalized LactonesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2008Florentina Nea Abstract A novel class of heterogeneous gold catalysts supported on zeolite beta-NH4+ was prepared by the deposition,precipitation method. This new class of catalyst showed interesting catalytic activities for the intramolecular cycloisomerization of ,-acetylenic carboxylic acids leading to functionalized ,-alkylidene ,-butyrolactones. Analysis of the supported gold species with in situ X-ray photoelectron spectroscopy (in situ XPS) suggests that cationic Au (possibly AuIII) can play an important role in such reactions. The high discrepancy in catalyst stability in favor of the Au supported on the zeolite system over bulk Au2O3 is explained by 1),the size of the particles and 2),the reversibility of the redox deactivating process (AuIII,AuI) in the presence of oxygen for the supported system. The efficiency of this system allowed reaction under mild heterogeneous conditions. The potential for catalyst recycling was also highlighted. [source] | ||||||||||||||||