bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of the binding of retinoic acid to β‐lactoglobulin B by affinity capillary electrophoresis
Authors: Lynen Frédéric , Van Thuyne Wim , Borremans Frans , Vanhoenacker Gerd , Sandra Pat 
Published: February 2003

AbstractThe quantification of the binding strength between retinoic acid and the primary binding site of β‐lactoglobulin B by dynamic equilibrium affinity capillary electrophoresis (DE‐ACE) is described. Although the peaks for retinoic acid were broad, a distinctive shift in migration time could be observed upon complexation allowing the construction of a binding curve and three linearised plots. By performing the corresponding linear and non‐linear regression analyses, an apparent dissociation constant varying between 1.4 and 2.2 μM was measured in a 100 mM Tris‐acetate buffer at pH 8.2 with 30 mM Na2SO4 and 1% EtOH as additives. The sample was prepared by adding a concentrated solution of retinoic acid in ethanol to the background electrolyte, such as to obtain a final 1% solution of ethanol and 5 μM retinoic acid in the buffer. It was shown that an MEKC‐based approach, attempted to improve the solubility of retinoic acid in the aqueous buffer, could not be used to perform a binding study.
Determination of metabolites of benzene, toluene, ethylbenzene, and xylene by β‐cyclodextrin modified capillary electrophoresis
Authors: Wang Chin‐Yu , Huang Ching‐Te , Hsieh You‐Zung 
Published: February 2003

AbstractA β‐cyclodextrin modified capillary electrophoresis method for determining the metabolites of benzene, toluene, ethyl benzene, and xylene (BTEX) is described. Creatinine and uric acid were also examined as reference compounds. By employing a 20 mM, pH 10.0 borax‐NaOH buffer containing 7‐mM of β‐CD, ten analytes could be successfully separated within 10 min on a 50 μm capillary at an electric potential of 25 kV. The effects of pH and the concentration of β‐CD on the separation of the ten analytes are discussed. Under optimized separation conditions, the relative standard deviations for the migration times of the analytes were less than 0.93% and the correlation coefficients of the analyte linear calibration graphs exceeded 0.998 in the range from 1 to 300 μg/mL. Analyses of BTEX metabolites in urine samples from both occupationally exposed and non‐exposed subjects are shown herein. BTEX metabolites were determined in the urine sample of a gas station attendant.
Determination of low concentrations of organochlorine pesticides and PCBs in fish feed and fish tissues from aquaculture activities by gas chromatography with tandem mass spectrometry
Authors: Serrano Roque , Barreda Mercedes , Pitarch Elena , Hernández Félix 
Published: February 2003

AbstractA sensitive and rapid multiresidual method has been developed for the determination of organochlorine compounds in fish feed and fish tissues. The method is based on automated off‐line normal‐phase liquid chromatography (NPLC) clean‐up prior to GC‐MS/MS. Analytes are extracted by refluxing in n‐hexane and fats present in the hexanic extracts are removed by automated NPLC, using n‐hexane and ethyl acetate as mobile phase. Both NPLC and acid digestion with sulphuric acid have been evaluated as clean‐up techniques for the analysis of these kinds of fatty samples. Thus, acid digestion is recommended before NPLC when large amounts of fat are present in the extracts. Purified extracts are then analysed by GC‐MS/MS (electron impact, EI) using the extracted ion mode. The high efficiency of elimination of fats from the extracts together with optimised MS/MS detection leads to high sensitivity in the multiresidue determination of analytes, reaching limits of detection at the sub‐ppb level in this type of fatty samples (up to 19% lipids fresh weight). The developed procedure represents an improvement over current methodologies for the analysis of organochlorine compounds (OCs) in fatty samples as regards to solvent consumption and automation, allowing the application of automated off‐line NPLC (26 min per sample) prior to GC determination. Besides, changes of solvent are not necessary during analysis. The application of the developed procedure to real world samples of fish feed and cultured fish revealed the presence of HCB, DDTs, and PCBs at ng g–1 levels.
Recovery evaluation of lipophilic markers from Echinacea purpurea roots applying microwave‐assisted solvent extraction versus conventional methods
Authors: Hudaib Mohammad , Gotti Roberto , Pomponio Romeo , Cavrini Vanni 
Published: February 2003

AbstractIn the present study the recovery from roots of lipophilic markers (mainly alkamides) of Echinacea purpurea (L.) Moench for analysis by GC/MS was evaluated by applying microwave‐assisted solvent extraction (MASE), as a new extraction approach, versus two other conventional methods (Soxhlet and ultrasonic extraction). A preliminary screening of the three methods, using the best‐reported parameters (solvent and extraction time) for Soxhlet (as a reference method) and ultrasonic extraction, showed MASE and ultrasonic extraction (using 70% methanol as the solvent system in both) to be superior methods to Soxhlet extraction in two solvent systems. Both methods, MASE and ultrasound, were further evaluated applying different ratios of methanol‐water (60 to 100% methanol) as the solvent system. In these investigations, MASE showed significantly higher recoveries than the ultrasonic technique over the 70–100% methanol range while comparable values were obtained at 60% methanol. The best recovery of the individual alkamides and the whole lipophilic fraction was obtained at 70% methanol. The MASE method could serve as good alternative procedure for the preparation of more chemically potent samples and/or crude extracts from Echinacea species.
Delamination of polymeric coatings on silidized iron
Authors: Rebhan M. , Rohwerder M. , Stratmann M. 
Published: February 2003

AbstractThe delamination of polymeric coatings (pc) on iron and steel is a phenomena everybody knows e.g. from his rusting car. The damage caused by it costs the Western countries hundreds of millions Euro every year. Hence it is a very important task for the steel industry and also for scientists to improve the stability of the pc on iron and steel.The authors developed a new corrosion protection of iron by covering it with a thin layer of a‐SiO2:Fe. An adhesion promoter sticks on top of it so that the pc adhers well. The delamination of the pc as function of the surface preparation (roughness, adhesion promoter) is described in this paper. The Scanning Kelvin Prove (SKP) is utilized to detect the delamination.
Photoinduced Refractive Index Change of Polymer Films Containing Mesoionic Sulfur‐Substituted Phenyloxatriazolones
Authors: Kato Yuichi , Horie Kazuyuki 
Published: February 2003

AbstractWe measured photoinduced refractive index changes (see Figure) of polymer films containing various sulfur‐containing mesoionic compounds. PMMA films containing 30 wt.‐% of 3‐phenyl‐1,2,3,4‐thiatriazole‐5‐thione (3PTTT) showed refractive index changes of −0.036 during photoirradiation, at a wavelength far from the resonant region. An increase in the number of sulfur atoms in the mesoionic compounds doped in PMMA films resulted in the increase in refractive index changes during photoirradiation. The estimation and comparison of the changes in specific refraction and densities of the systems suggest that the change in electronic structure mainly contributes to the refractive index changes of the film in the case of 3PTTT, while the changes in both electronic structure and density equally contribute to the refractive index change in the film with 3‐phenyl‐1,2,3,4‐oxatriazole‐5‐thione (3POTT).
Refractive indices, n, of PMMA films containing various weight fractions of 3POTT (square) and 3PTTT (circle). Open symbols are for n before photoirradiation, filled ones are for n after photoirradiation.magnified imageRefractive indices, n, of PMMA films containing various weight fractions of 3POTT (square) and 3PTTT (circle). Open symbols are for n before photoirradiation, filled ones are for n after photoirradiation.
Studies on the Synthesis and Conductivity of a Novel Reactive Ladder‐Like Poly(β‐cyanoethylsilsesquioxane) and Poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)]
Authors: Zhang Yong , Guo Guangqing , Sun Jin , Zhou Xiaoshu , Xie Ping , Zhang Rongben , Fu Pengfei 
Published: February 2003

AbstractTwo novel reactive poly(β‐cyanoethylsilsesquioxane) (CN‐T) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] (CN‐Me‐T) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, 1H NMR, 29Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10−6 S · cm−1 at room temperature and obviously increased with the raise of temperature.
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Anionic Polymerizations of 1‐Adamantyl Methacrylate and 3‐Methacryloyloxy‐1,1′‐biadamantane
Authors: Ishizone Takashi , Tajima Hiroyuki , Torimae Hiroshi , Nakahama Seiichi 
Published: February 2003

AbstractAnionic polymerizations of 1‐adamantyl methacrylate (1) and 3‐methacryloyloxy‐1,1′‐biadamantane (2) were carried out in THF at −50 to −78 °C for 24 h. The initiator employed was either [1,1‐bis(4′‐trimethylsilylphenyl)‐3‐methylpentyl]lithium (3)/lithium chloride, or diphenylmethylpotassium. The polymerizations of 1 and 2 proceeded quantitatively to afford the polymers having the predicted molecular weights based on the molar ratios of monomers and initiators and the narrow molecular weight distributions (Mw/Mn = 1.05–1.18), indicating the living character of the polymerization systems of 1 and 2. Novel well‐defined block copolymers, poly[2‐block‐(tert‐butyl methacrylate)], poly(2‐block‐isoprene‐block‐2), and poly[[(2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)methyl methacrylate]‐block‐2], were anionically synthesized by the sequential copolymerization of 2 and comonomers. The poly(2) had the significantly higher glass transition temperature (Tg) of 236 °C and decomposed over 370 °C, while poly(1) started to decompose at around 320 °C before its Tg was reached. This thermal stability can be explained by the substituent effects of the bulky adamantyl and 1,1′‐biadamantyl moieties.
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Synthesis and Characterization of Hyperbranched Polyethylenes Made with Nickel‐α‐Diimine Catalysts
Authors: Kunrath Fábio A. , Mota Fábio F. , Casagrande Osvaldo L. , Mauler Raquel S. , de Souza Roberto F. 
Published: February 2003

AbstractThe polymerization of ethylene in the presence of 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediiminenickel(II) dichloride (1) and methylaluminoxane (MAO) gives hyperbranched polyethylene (HBPE) in appropriate reaction conditions. The system 1/MAO is active in solvents like toluene or hexane at temperatures as high as 80 °C and ethylene pressures ranging from 1 to 15 atm. The polyethylenes obtained show high molecular weights (up to 467 kg · mol−1) and more than 218 branches per 1 000 backbone carbon atoms, qualifying these materials as hyperbranched. Dynamic‐mechanical thermal analysis (DMTA) of these materials shows high β‐transitions, directly related to the branch content of these polyethylenes.
DMTA analysis of polyethylenes obtained with 1/MAO at 0, 30, and 50 °C (corresponding to entries 1, 2 and 3).magnified imageDMTA analysis of polyethylenes obtained with 1/MAO at 0, 30, and 50 °C (corresponding to entries 1, 2 and 3).
Control of In‐Plane and Out‐Of‐Plane Reorientation in Photo‐Cross‐Linkable Copolymer Liquid‐Crystal Films by Irradiation with Linearly Polarized Ultraviolet Light and Annealing
Authors: Kawatsuki Nobuhiro , Furuso Nobuyoshi , Uchida Emi , Yamamoto Tohei 
Published: February 2003

AbstractThis paper describes thermally enhanced in‐plane and out‐of‐plane reorientation of mesogenic groups in copolymer liquid‐crystal (CPLC) films that have a photo‐cross‐linkable 4‐(4′‐methoxycinnamoyl)biphenyl (MCB) side group and a 4‐methoxybiphenyl (4MB) side group. The side groups are cross‐linked by irradiation with linearly polarized ultraviolet (LPUV) light and subsequent annealing. Due to axis‐selective photo‐cross‐linking, a small negative optical anisotropy is observed for all CPLCs after exposure to LPUV light. When the composition of the 4MB comonomer is less than 45 mol‐%, thermal treatment in the liquid‐crystalline temperature range causes in‐plane reorientation of the film and results in an in‐plane order parameter of 0.71. In contrast, when the composition of the 4MB is increased, out‐of‐plane reorientation is generated. Three‐dimensional molecular reorientation and inclined out‐of‐plane reorientation are achieved by adjusting the exposure angle.
Angular dependence of UV absorption spectrum of film 3. The inset shows a conoscope observation of the film. The film was annealed at 130 °C for 10 min.magnified imageAngular dependence of UV absorption spectrum of film 3. The inset shows a conoscope observation of the film. The film was annealed at 130 °C for 10 min.
Specific Roles of Al‐Alkyl Cocatalyst in the Origin of Isospecificity of Active Sites on Donor‐Free TiCl4/MgCl2 Ziegler‐Natta Catalyst
Authors: Liu Boping , Nitta Takashi , Nakatani Hisayuki , Terano Minoru 
Published: February 2003

AbstractThe formation, deactivation and transformation of stereospecific active sites on the donor‐free TiCl4/MgCl2 catalyst induced by short time reaction with triethylaluminium (TEA) cocatalyst (pretreatment time: 0 ∼ 60 s) were investigated by stopped‐flow propylene polymerization combined with temperature rising elution fractionation (TREF) and gel permeation chromatography (GPC) methods. We got the first report that the origin of isospecificity of active sites derived from the catalyst substrate and cocatalyst were individually observed without and with TEA pretreatment, respectively. Based on the three‐sites model of Corradini and Busico et al., a plausible mechanism of the formation and transformation of stereospecific active sites was proposed using active sites models in terms of specified roles of Al‐alkyl cocatalyst. It was demonstrated that the introduction of bulky alkyl groups instead of chlorine atoms into the neighborhood of active sites seems to be crucial for the generation of active sites with the highest isospecificity.
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Chromatic Transitions in Polydiacetylene Langmuir‐Blodgett Films due to Molecular Recognition at the Film Surface Studied by Spectroscopic Methods and Surface Analysis
Authors: Geiger Elisabeth , Hug Paul , Keller Beat A. 
Published: February 2003

AbstractLangmuir‐Blodgett films of polydiacetylene are used to create a biosensor on the basis of a surface host‐guest recognition process. Functionalizing a 10 wt.‐% fraction of the diacetylene monomer with biotin leads to a visually observable color change in the resulting polymerized film when streptavidin in the molar ratio streptavidin:biotin = 1:2 is added. The chromatic transition, caused by a shortening of the conjugation length of the π‐electron system in the polydiacetylene backbone, is investigated by monitoring the change of visible optical absorption and Raman spectroscopy. Chemical species and to some extent also the presence of surface‐immobilized peptide are identified via time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS) signal assignment and XPS studies.Optical spectra of the blue LB film consisting of two layers PDA 1 and one layer of a mixture containing 10 wt.‐% 7 in 1, the film after 10 min immersion in tris(hydroxymethyl)aminomethane hydrochloride buffer (pH 7.3 at 21 °C) and after 2 h immersion in streptavidin solution (protein:biotin molar ratio = 1:2).magnified imageOptical spectra of the blue LB film consisting of two layers PDA 1 and one layer of a mixture containing 10 wt.‐% 7 in 1, the film after 10 min immersion in tris(hydroxymethyl)aminomethane hydrochloride buffer (pH 7.3 at 21 °C) and after 2 h immersion in streptavidin solution (protein:biotin molar ratio = 1:2).
Amorphous‐Smectic Glassy Main‐Chain LCPs, 1. Poly(ether esters) Derived from Hydroxybibenzoic Acid and (R,S)‐ and (R)‐2‐Methylpropane‐1,3‐diol
Authors: del Campo Aránzazu , Bello Antonio , Pérez Ernesto , García‐Bernabé Abel , Díaz Calleja Ricardo 
Published: February 2003

AbstractThe synthesis and the characterization of main‐chain liquid‐crystalline poly(ether esters), derived from hydroxybibenzoic acid and (R,S)‐ and (R)‐2‐methylpropane‐1,3‐diol, are reported. These polymers show an interesting thermal behavior. They develop mesophases with a slow rate of formation, allowing the easy quenching of the melt into: a) the glassy amorphous state, b) the glassy liquid‐crystalline state, or c) a mixture of both, depending on the thermal treatment. The extent of the transformation and the symmetry of the different phases have been determined by means of calorimetric and X‐ray diffraction methods. Dielectric spectroscopy results provide additional evidence for the detection of distinct glass transitions. The results show that the racemic polymer forms a low‐ordered SmCalt mesophase, while a more ordered phase is obtained in the case of the enantiomerically pure polymer. The comparison of the properties of the different states evidences the special behavior and properties of the glass transition (Tg) in these polymers. Emphasis is paid to the location of the Tg of the liquid‐crystalline state in comparison to the Tg of the amorphous state. It is found that the glass transition of the SmCalt glass in R,S‐PBO3 (the poly(ether ester) derived from hydroxybibenzoic acid and (R,S)‐2‐methylpropane‐1,3‐diol) appears at lower temperatures than the glass transition of the amorphous state. However, in R‐PBO3 (the poly(ether ester) derived from hydroxybibenzoic acid and (R)‐2‐methylpropane‐1,3‐diol), where the more ordered phase is present, the glass transition follows the classical tendency of semicrystalline polymers.magnified image
Bulk and Solution Copolymerization of Butyl Acrylate/Methyl Methacrylate at Elevated Temperatures
Authors: Dubé Marc A. , Hakim Malik , McManus Neil T. , Penlidis Alexander 
Published: February 2003

AbstractA series of bulk and solution (in toluene) copolymerizations of butyl acrylate/methyl methacrylate were performed independently at two laboratories. The runs were at elevated temperatures ranging from 90 to 140 °C conducted to high conversion levels, and samples were characterized for conversion, cumulative copolymer composition and number‐ and weight‐average molecular weights and distribution. Variation of the comonomer feed composition, temperature, and the solvent, initiator and chain transfer agent concentrations was studied. Using a mechanistic model, conversion data were predicted to high conversions using terminal model kinetics at 90 and 115 °C. The copolymer composition data conformed to the terminal kinetic model over the entire temperature range. Solvent effects were reflected by changes in the butyl acrylate rate constants.Composition vs. conversion. Effect of feed composition for runs at 140 °C.magnified imageComposition vs. conversion. Effect of feed composition for runs at 140 °C.
Glass‐Transition Temperature (Tg) of Free‐Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 1. A Study on Tg of Atactic Monodisperse Polystyrenes
Authors: Minagawa Masatomo , Kanoh Hiroyasu , Tanno Satoshi , Nishimoto Yuhko 
Published: February 2003

AbstractThe glass‐transition temperature (Tg) of several atactic monodisperse polystyrenes (PSt)s was studied by an inverse gas chromatographic (IGC) analysis, as a preliminary study for the detection of the Tg of polyacrylonitrile. The Tg of PSt with different molecular weights was clearly obtained by this method. The agreement in the Tg values obtained by IGC and by differential scanning calorimetry (DSC) was quite good within the molecular‐weight range Mp = 7 600–2 430 000 (where, Mp = (Mn × Mw)1/2). This method has a wide universality for the detection of the Tg of polymers. Several essential factors were extracted for the establishment of the optimum conditions for IGC measurements, such as the concentration of polymer toward a clay matrix (10 wt.‐%), and the type of lower probe, decane. The best probe was determined empirically from the most effective detection in the IGC measurements of PSt.Molecular‐weight dependence of the Tg of PSt. Experimental data obtained here are indicated by an arrow. Other data was taken from ref.21magnified imageMolecular‐weight dependence of the Tg of PSt. Experimental data obtained here are indicated by an arrow. Other data was taken from ref.21
Synthesis of Silica‐Supported Metallocene Catalysts for Olefin Polymerization
Authors: Bortolussi Frédéric , Broyer Jean‐Pierre , Spitz Roger , Boisson Christophe 
Published: February 2003

AbstractFour supported metallocene catalysts were synthesized directly on silica [Si(CpZrCp), Si(CpZrInd), Si(IndZrCp), and Si(IndZrInd)]. The first ligand was chemically tethered to silica (internal ligand) while the second was free from silica (external ligand). The polymerization of ethylene and the copolymerization of ethylene with hexene were investigated. The activity of the catalysts and the molecular weights of the polymers were found to depend on the position of the ligands. In all cases, high‐molecular‐weight polyethylene with moderate polydispersity was obtained. Moreover, the copolymerization of ethylene with hexene provided a homogeneous polymer.Reaction of ZrCl4(OC4H8)2 with modified silica (SiCp).magnified imageReaction of ZrCl4(OC4H8)2 with modified silica (SiCp).
Cu(S2CNEt2)Cl‐Catalyzed Reverse Atom‐Transfer Radical Polymerization of Vinyl Monomers
Authors: Li Peng , Qiu Kun‐Yuan 
Published: February 2003

AbstractA new copper catalyst containing chlorine and a photo‐labile diethylthiocarbamoylthiyl group was successfully employed in the reverse ATRP of methyl methacrylate (MMA). The polymeric chains were end‐capped with S2CNEt2, due to pseudo‐halogen atom‐transfer reaction between active and dormant species. Photopolymerization of this PMMA in the presence of fresh MMA and styrene monomers at ambient temperature yielded chain‐extended PMMA and MMA/styrene block copolymers, respectively.
GPC traces of (A) PMMA end‐capped with a photo‐labile group (pre‐PMMA), (B) chain‐extended PMMA (post‐PMMA), and (C) PMMA/styrene block copolymer (PMMA‐b‐PSt).magnified imageGPC traces of (A) PMMA end‐capped with a photo‐labile group (pre‐PMMA), (B) chain‐extended PMMA (post‐PMMA), and (C) PMMA/styrene block copolymer (PMMA‐b‐PSt).
Quantifying Polymer Swelling Employing a Linear Variable Differential Transformer: CO2 Effects on SBS Triblock Copolymer
Authors: Shenoy Suresh , Woerdeman Dara , Sebra Robert , Garach‐Domech Alberto , Wynne Kenneth J. 
Published: February 2003

AbstractA linear variable differential transformer (LVDT) was employed to evaluate CO2‐polymer plasticization. Preliminary results on polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) elastomer are presented. At 22 °C under CO2 pressure, SBS undergoes compression due to hydrostatic pressure. However, sample expansion occurs upon depressurization. At 45 °C, SBS undergoes swelling of 0.7% due to CO2 plasticization, while no post‐pressurization expansion is observed. The contrasting result is explained by change in PS domain mobility and discontinuity in the density‐pressure relationship.
Linear displacement of SBS as a function of time at 56 and 134 bar CO2.magnified imageLinear displacement of SBS as a function of time at 56 and 134 bar CO2.