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Stability Study (stability + study)

Distribution by Scientific Domains

Polymers and Materials Science	54%
Chemistry	18%

Selected Abstracts

Isotactic Poly(propylene)/Monoalkylimidazolium-Modified Montmorillonite Nanocomposites: Preparation by Intercalative Polymerization and Thermal Stability Study

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 24 2004
Aihua He
Abstract Summary: Poly(propylene)/monoalkylimidazolium-modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl4/MgCl2/MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability. X-ray diffraction patterns of PP/IMMT (MMT,=,2.2 wt.-%) nanocomposite before and after processing. [source]

Stability study of inverse suspension copolymerization of 1,1,3,3-tetramethylguandium acrylate and N,N, -methylenebisacrylamide

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010
Jie Dong
Abstract In a previous study, we synthesized crosslinked P(TMGA- co -MBA) via an inverse suspension copolymerization of 1,1,3,3-tetramethylguandium acrylate (TMGA) and N,N,-methylenebisacrylamide (MBA) and found that the product is a good SO2 sorbent. However, the polymerization stability appeared to be poor under some reaction conditions and is far from being elucidated. In this study, the inverse suspension copolymerization was carried out using cyclohexane as solvent, Span60 as dispersant, and ammonium persulfate (APS) as initiator. The effects of the reaction conditions such as stirring speed, dispersant concentration, and temperature on the polymerization stability and particle size were systematically examined. It is found that the polymerization stability is a strong function of these parameters. Stable crosslinked poly(TMGA- co -MBA) particles from micrometer to millimeter diameters were synthesized under optimized conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Storage stability study of margarines produced from enzymatically interesterified fats compared to margarines produced by conventional methods.

EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7-8 2005
Physical properties
Abstract In this study, margarine hardstocks were produced from two enzymatically interesterified fats at conversion degrees of 80 and 100%, a chemically randomized fat and a physically mixed fat, respectively. These four hardstocks blended with 50% of sunflower oil were mainly used for the production of table margarines in a pilot plant. Storage stability studies were carried out at storage temperatures of 5 and 25,°C during 12,wk. Margarines from the enzymatically interesterified fats were compared to the margarines produced by conventional methods and to selected commercial products. The changes in the physical properties of margarines, including hardness, dropping point, crystal form, and sensory evaluation, were examined during storage. It was observed that margarine storage stability increased with increasing conversion degree. The color of margarines made from the enzymatically interesterified fats was more similar to that of the physically mixed fat than that of the margarine from the chemically randomized fat, which had less color. Crystal transformation was accelerated at high storage temperature. Crystal size was not only related to the types of crystals, but also to the driving force of temperature difference. A larger crystal size was observed at 5,°C than at 25,°C for the margarine made from the blend. Margarines produced from interesterified fats had better physical properties than the blend. Overall, the margarine produced from the enzymatically fully converted fat had physical properties similar to the margarine produced from the chemically interesterified fat. [source]

Aging stability of complete blood count and white blood cell differential parameters analyzed by Abbott CELL-DYN Sapphire hematology analyzer

INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 1 2009
P. HEDBERG
Summary This study presents the results of an aging stability study of complete blood count (CBC) and leukocyte differential parameters using the Abbott CELL-DYN Sapphire hematology analyzer. Stability studies showed no substantial change in CBC parameters up to 24,48 h at +23 ± 2 °C (room temperature), except for optical platelet count (PLTo). For specimens aged over 24, the value of impedance platelet count yielded more reliable results than the routine PLTo. White blood cell (WBC) differential parameters, except eosinophils, were stable for up to 48 h at +23 ± 2 °C. CBC parameters were stable for 72 h, except mean platelet volume, which slightly increased between 48 and 72 h, at +4 °C. WBC differentials were stable 48,72 h, with a slight decrease observed in absolute neutrophils and lymphocytes at +4 °C. [source]

N -[3-[4-(2-methoxyphenyl) piperaziny-1-yl]propyl]cyclam: synthesized as a potential 5-HT1A receptor ligand and labelled with 99mTc-nitrido core

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2008
Fenglong Wang
Abstract This paper reports the synthesis of new potential 5-HT1A receptor ligand N -[3-[4-(2-methoxyphenyl)piperaziny-1-yl]propyl]cyclam (MPPC) and radiolabelling of it with 99mTc-nitrido core. The novel neutral complex 99mTcN-MPPC combines 1,4,8,11-tetraazacyclotetradecane (cyclam) ligand as chelate moiety for 99mTc-nitrido with a 1-(2-methoxyphenyl)piperazine moiety derived from WAY 100635 via a 3-carbon alkyl chain. This provided a reliable and reproducible method for attaching the technetium to the pharmacophore moiety of WAY 100635. 99mTcN-MPPC was prepared by a two-step procedure and the radiochemical purity was found to be greater than 95%. It was hydrophilic and stable for at least 4,h at room temperature. In vivo stability study in normal rats showed that no degradation of 99mTcN-MPPC was found in deproteinated blood samples at 2,h post-injection. This effective 99mTc-labelling strategy for obtaining neutral 99mTc nitrido complexes would be a useful tool to prepare new SPECT agents to image 5-HT1A receptor with cyclam conjugated ligands. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Core-shell particles with glycopolymer shell and polynucleoside core via RAFT: From micelles to rods

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2009
Samuel Pearson
Abstract Amphiphilic block copolymers were synthesized via the reversible addition fragmentation chain transfer (RAFT) copolymerisation of 2-methacrylamido glucopyranose (MAG) and 5,- O -methacryloyl uridine (MAU). Homopolymerisations of both monomers using (4-cyanopentanoic acid)-4-dithiobenzoate (CPADB) proceeded with pseudo first order kinetics in a living fashion, displaying linear evolution of molecular weight with conversion and low PDIs. A bimodal molecular weight distribution was observed for PMAU at low conversions courtesy of hybrid behavior between living and conventional free radical polymerization. This effect was more pronounced when a PMAG macroRAFT agent was chain extended with MAU, however, in both cases, good control was attained once the main RAFT equilibrium was established. A stability study on PMAU found that its hydrolysis is diffusion controlled, and is accelerated at physiological pH compared with neutral conditions. Self-assembly of four block copolymers with increasing hydrophobic (PMAU) block lengths produced micelles, which demonstrated an increased tendency to form rods as the PMAU block length increased. Interestingly, none of the block copolymers were surface-active. An initial assessment of PMAU's ability to bind the nucleoside adenosine through base pairing was highly promising, with DSC measurements indicating that adenosine is fully miscible in the PMAU matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1706,1723, 2009 [source]

Synthesis and stability study of dental monomers containing methacrylamidoethyl phosphonic acids

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2007
Xiaoming Xu
Abstract Three new dental monomers containing methacrylamidoethyl phosphonic acids were synthesized. The structures of the synthesized monomers were determined with electrospray mass spectrometry (ESMS), Fourier transform infrared, and NMR. The hydrolytic stabilities of the synthesized monomers and a commercial monomer, 2-methacryloyloxyethyl phosphoric acid (MEP; used as a control), were studied with flow injection (FI)/ESMS, 1H NMR, and 31P NMR analysis of a CD3OD/D2O (4:1 v/v) solution of each monomer before and after storage at 60 °C for 2 months. The 1H NMR and 31P NMR chemical shifts of the monomers 2-methacrylamidoethylphosphonic acid (I) and N,N,-[4,4,-(propane-2,2-diyl)-bis(phenoxy-2-hydroxypropyl)]-bis(2-methacrylamidoethylphosphonic acid) (II) showed little change after storage at 60 °C for 2 months, but those of MEP changed significantly. FI/ESMS also showed that MEP was nearly completely decomposed, whereas monomers I and II remained largely intact. MEP could react with H2ZrF6 to form ternary zirconium fluoride complexes that were partially soluble in methanol, but all the monomers containing phosphonic acids formed precipitates. This study demonstrates that ESMS is a more sensitive and effective method than NMR for studying the hydrolytic stability or degradation of dental monomers. The new monomers containing methacrylamidoethyl phosphonic acids have higher hydrolytic stability than methacrylate phosphate monomers and may be used in dental bonding agents and other dental materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 99,110, 2007 [source]

Isotactic Poly(propylene)/Monoalkylimidazolium-Modified Montmorillonite Nanocomposites: Preparation by Intercalative Polymerization and Thermal Stability Study

Linear instability of ideal flows on a sphere

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2009
Yuri N. Skiba
Abstract A unified approach to the normal mode instability study of steady solutions to the vorticity equation governing the motion of an ideal incompressible fluid on a rotating sphere is considered. The four types of well-known solutions are considered, namely, the Legendre-polynomial (LP) flows, Rossby,Haurwitz (RH) waves, Wu,Verkley (WV) waves and modons. A conservation law for disturbances to each solution is derived and used to obtain a necessary condition for its exponential instability. By these conditions, Fjörtoft's (Tellus 1953; 5:225,230) average spectral number of the amplitude of an unstable mode must be equal to a special value. In the case of LP flows or RH waves, this value is related only with the basic flow degree. For the WV waves and modons, it depends both on the basic flow degree and on the spectral distribution of the mode energy in the inner and outer regions of the flow. Peculiarities of the instability conditions for different types of modons are discussed. The new instability conditions specify the spectral structure of growing disturbances localizing them in the phase space. For the LP flows, this condition complements the well-known Rayleigh,Kuo and Fjörtoft conditions related to the zonal flow profile. Some analytical and numerical examples are considered. The maximum growth rate of unstable modes is also estimated, and the orthogonality of any unstable, decaying and non-stationary mode to the basic flow is shown in the energy inner product. The analytical instability results obtained here can also be applied for testing the accuracy of computational programs and algorithms used for the numerical stability study. It should be stressed that Fjörtoft's spectral number appearing both in the instability conditions and in the maximum growth rate estimates is the parameter of paramount importance in the linear instability problem of ideal flows on a sphere. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Thermal stability study of conductive polyaniline/polyimide blend films on their conductivity and ESR measurement,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2002
Moon Gyu Han
Abstract Conductivity stability at thermal environment of conductive polyaniline-complexes/polyimide (PANI-complexes/PI) blends, which were doped by camphorsulfonic acid (CSA) and dodecylbenzenesulfonic acid (DBSA), respectively, were investigated by conductivity measurements, electron spin resonance (ESR) spectra, differential and scanning thermometer (DSC). In the conversion process of PANI/Polyamic acid (PAA) to PANI/PI, the blend endeavored some kinds of alteration such as decomplexation of moisture and solvent, dissociation of dopant, crosslinking of PANI chain, and the imidization of PAA chain. PANI-DBSA/PI showed higher thermal stability of conductivity than PANI-CSA/PI, and both samples showed nearly linear decay of conductivity with increasing temperature showing greatly enhancement of conductivity stability. When they were exposed at near or over glass transition temperature, the conductivity decay became faster. The conductivity stability at base environment was also higher for PANI-DBSA/PI due to difficulty in accessing of hydroxyl ion to PANI, which were resulted from dopant. DBSA-doped blends showed increased polaron mobility and concentration at relatively high temperature, which led to extremely higher conductivity and its stability at high temperature. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Quantitative determination of capsaicin, a transient receptor potential channel vanilloid 1 agonist, by liquid chromatography quadrupole ion trap mass spectrometry: evaluation of in vitro metabolic stability

BIOMEDICAL CHROMATOGRAPHY, Issue 2 2009
Francis Beaudry
Abstract Capsaicin is the most abundant pungent molecule present in red peppers and it is widely used for food flavoring, in pepper spray in self-defense devices and more recently in ointments for the relief of neuropathic pain. Capsaicin is a selective agonist of transient receptor potential channel, vanilloid subfamily member 1. A selective and sensitive quantitative method for the determination of capsaicin by LC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 × 2 mm C18 Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 µL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10,5000 ng/mL was used in the calibration curve constructed in rat plasma. The interbatch precision and accuracy observed were 6.5, 6.7, 5.3 and 101.2, 102.7, 103.5% at 50, 500 and 5000 ng/mL, respectively. An in vitro metabolic stability study was performed in rat, dog and mouse liver microsomes and the novel analytical method was adapted and used to determine intrinsic clearance of capsaicin. Results suggest very rapid degradation with T1/2 ranging from 2.3 to 4.1 min and high clearance values suggesting that drug bioavailability will be considerably reduced, consequently affecting drug response and efficacy. Copyright © 2008 John Wiley & Sons, Ltd. [source]