bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Raman spectroscopy and quantum chemistry for featuring the structure of positively charged species in macrocyclic π‐conjugated diacetylene‐bridged oligothiophenes
Authors: Casado J. , Hernández V. , Ponce Ortiz R. , Ruiz Delgado M. C. , López Navarrete J. T. , Fuhrmann G. , Bäuerle P. 
Published: June 2004

AbstractDifferent types of stable positively charged defects compatible with the electronic and molecular structure of a series of macrocyclic molecular materials containing symmetrically butylated terthienyl or quinquethienyl segments connected through diacetylenic bridges were studied by means of Raman spectroscopy. In all cases iodine was used as the oxidant, whereas for the largest macrocycle in situ spectroelectrochemistry was also employed. Comparison of the Raman spectra obtained either electrochemically or on treatment with iodine indicates that iodine behaves as a moderate oxidant giving rise to fairly stable positive charged defects. The comparison of the Raman spectra obtained upon iodine doping for two series of homologous molecules, namely open‐chain diacetylene‐bridged and non‐bridged oligothiophenes, with those of the macrocyclic compounds suggests that each terthienyl or quinquethienyl building block is able to accommodate one positive charge in the form of a polaron. Density functional theory quantum chemical calculations were performed, at the DFT//B3LYP/3–21G* level, for two model systems to assess useful information about the evolution of the molecular structure and charge distribution upon oxidative doping of the compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Identification by Raman microscopy of pigments on early postage stamps: distinction between original 1847 and 1858–1862, forged and reproduction postage stamps of Mauritius
Authors: Chaplin Tracey D. , Jurado‐López Alicia , Clark Robin J. H. , Beech David R. 
Published: June 2004

AbstractAn extremely rare used 1847 1d orange–red Mauritian stamp, a rare 1847 2d deep blue unused stamp, a 1913 reproduction 2d stamp, early forgeries and 1858–1862 Britannia‐type Mauritian stamps were analysed using Raman microscopy in order to determine the identities of the pigments on the stamps. That in the printing ink of the 1d stamp was identified to be lead(II,IV) oxide (‘red lead’), with a cancel mark composed of carbon‐based black. Prussian blue was identified as having been used in the genuine and reproduction 2d issues, these being distinguished only by the presence of crystals of ultramarine blue dispersed between the paper fibres of the genuine issues. The 4d green Britannia‐type stamp is pigmented with ‘chrome green’, a mixture of Prussian blue and chrome yellow, and the 6d ‘vermilion’ Britannia‐type stamp is pigmented with vermilion. Raman microscopy was shown to be a rapid, highly specific and non‐destructive technique for the expertising of stamps whose authenticity is in question via the precise identification of the pigments used on the surface of each stamp and dispersed between the paper fibres. Copyright © 2004 John Wiley & Sons, Ltd.
Raman spectrum of fully reduced flavin
Authors: Zheng Yuangang , Carey Paul R. , Palfey Bruce A. 
Published: June 2004

AbstractProtein–flavin interactions modify the chemistry of the flavin, ‘tuning’ it to its biological function. In order to understand protein interactions with reduced flavins, the Raman spectrum of reduced FAD was recorded at pH values where the reduced isoalloxazine is neutral and anionic. Reduced isoalloxazine is a weaker Raman scatterer than oxidized isoalloxazine by at least an order of magnitude in both ionization states. Substitution of exchangeable protons for deuterium, the effect of ionization and DFT calculations allowed the assignment of the observed Raman bands to normal modes of vibration. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and Characterization of Polymeric Linseed Oil Grafted Methyl Methacrylate or Styrene
Authors: Cakmakli Birten , Hazer Baki , Tekin Ishak Ozel , Kizgut Sait , Koksal Murat , Menceloglu Yusuf 
Published: June 2004

AbstractSummary: Syntheses of wholly natural polymeric linseed oil (PLO) containing peroxide groups have been reported. Peroxidation, epoxidation and/or perepoxidation reactions of linseed oil, either under air or under oxygen flow at room temperature, resulted in polymeric peroxides, PLO‐air and PLO‐ofl, containing 1.3 and 3.5 wt.‐% of peroxide, with molecular weights of 2 100 and 3 780 Da, respectively. PLO‐air contained cross‐linked film up to 46.1 wt.‐% after a reaction time of 60 d, associated with a waxy, soluble part (PLO‐air‐s) that was isolated with chloroform extraction. PLO‐ofl was obtained as a waxy, viscous liquid without any cross‐linked part at the end of 24 d under visible irradiation and oxygen flow. Polymeric peroxides, PLO‐air‐s and PLO‐ofl initiated the free radical polymerization of both methyl methacrylate (MMA) and styrene (S) to give PMMA‐graft‐PLO and PS‐graft‐PLO graft copolymers in high yields with $\overline M _{\rm w}$ varying from 37 to 470 kDa. The polymers obtained were characterized by FT‐IR, 1H NMR, TGA, DSC and GPC techniques. Cross‐linked polymers were also studied by means of swelling measurements. PMMA‐graft‐PLO graft copolymer film samples were also used in cell‐culture studies. Fibroblast cells were well adhered and proliferated on the copolymer film surfaces, which is important in tissue engineering.Proliferation of the fibroplast cells on the PS‐graft‐PLO film.magnified imageProliferation of the fibroplast cells on the PS‐graft‐PLO film.
Novel Photopolymerizable Biodegradable Triblock Polymers for Tissue Engineering Scaffolds: Synthesis and Characterization
Authors: Chan‐Park Mary B. , Zhu Ai P. , Shen Jin Y. , Fan Ai L. 
Published: June 2004

AbstractSummary: For use in micro‐patterned scaffolds in tissue engineering, novel diacrylated triblock macromers (PLA‐b‐PCL‐b‐PLA, PGA‐b‐PCL‐b‐PGA and PCL‐b‐PEO‐b‐PCL) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). All diacrylated polymers were designed as triblock copolymers and involved biodegradable blocks of relatively non‐polar ε‐caprolactone (CL) and polar monomers such as glycolide (GA), lactide (LA) or ethylene oxide (EO). All triblock polymers were prepared in molecular weights of a few kilo daltons via the anionic ring‐opening polymerization (ROP) of the corresponding lactide, glycolide or caprolactone using stannous octoate [Sn(Oct)2] as catalyst. The polymers had low polydispersity indices, ranging from 1.23 to 1.56. Biodegradable polymeric networks were prepared with conversions of 72–84% via photopolymerization of the triblock diacrylated polymers with 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) as photoinitiator. PLA‐b‐PCL‐b‐PLA copolymers crumbled easily and were not suitable for micro‐patterning. PGA‐b‐PCL‐b‐PGA copolymers had higher water contact angles than PCL‐b‐PEO‐b‐PCL and were also cytocompatible with Fibroblasts 3T3.
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Concanavalin A Immobilized Affinity Adsorbents for Reversible Use in Yeast Invertase Adsorption
Authors: Yavuz Handan , Akgöl Sinan , Arica Yakup , Denizli Adil 
Published: June 2004

AbstractSummary: Concanavalin A (Con A) immobilized poly(2‐hydroxyethyl methacrylate) (PHEMA) beads were investigated for specific adsorption of yeast invertase from aqueous solutions. PHEMA beads were prepared by a suspension polymerization technique with an average size of 150–200 μm, and activated by epichlorohydrin. Con A was then immobilized by covalent binding onto these beads. The maximum Con A immobilization was found to be 10 mg/g. The invertase‐loading capability of the PHEMA/Con A beads was 107 mg/g. The maximum invertase adsorption capacity on the PHEMA/Con A adsorbents was observed at pH 5.0. The values of the Michaelis constant Km of invertase were significantly larger upon adsorption, indicating decreased affinity by the enzyme for its substrate, whereas Vmax was smaller for the adsorbed invertase. Adsorption improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with adsorption. The adsorbed enzyme activity was found to be quite stable in repeated experiments.Storage stability of adsorbed invertase.magnified imageStorage stability of adsorbed invertase.
Design of Temperature Sensitive Imprinted Polymer Hydrogels Based on Multiple‐Point Hydrogen Bonding
Authors: Liu Xue‐Yong , Guan Ying , Ding Xiao‐Bin , Peng Yu‐Xing , Long Xin‐Ping , Wang Xiao‐Chuan , Chang Kun 
Published: June 2004

AbstractSummary: Weakly cross‐linked temperature sensitive imprinted polymer hydrogels that recognize L‐pyroglutamic acid (Pga) molecules via multiple‐point hydrogen bonding were designed and synthesized. The amount of adsorption for Pga in imprinted hydrogels is 3–4 times higher than that in non‐imprinted hydrogels. The selectivity test of imprinted polymer gels was carried out by using a series of structurally related compounds Pga, pyrrolidine, 2‐pyrrolidone, L‐proline as substrates. The results show that imprinted polymer gels exhibit high selectivity for Pga as compared to all the other tested substrates. The imprinted polymer hydrogels show good temperature sensitivity, special selectivity and reusability, suggesting that the polymer hydrogels would have an enormous potential for application in controlled drug release and separation field.Schematic representation of the adsorption and release process of Pga by the imprinted polymeric gels.magnified imageSchematic representation of the adsorption and release process of Pga by the imprinted polymeric gels.
Modulation of Proteins Adsorption onto the Surface of Chitosan Complexed with Anionic Copolymers. Real Time Analysis by Surface Plasmon Resonance
Authors: Aguilar María R. , Gallardo Alberto , Lechuga Laura M. , Calle Ana , San Román Julio 
Published: June 2004

AbstractSummary: The interpolyelectrolyte complex formation between chitosan and anionic polyacrylic derivatives, bearing sulfonic moieties, as well as the protein adsorption onto the chitosan/polyacrylic complexes were studied by surface plasmon resonance (SPR) optical biosensor. This unique technique allows a real time monitoring of different surface molecular interactions with very high sensitivity. The acrylic macromolecules are two families of copolymers of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and, respectively, 2‐hydroxyethylmethacrylate (HEMA) and N,N′‐dimethylacrylamide (DMAA). The complexation process was evaluated through the SPR measurements resulting from the flowing of polyacrylic aqueous solution over the sensor previously coated with chitosan. The SPR was able to differentiate strong ionic bonds from other weak and reversible interactions. By means of the coated sensors (uncomplexed and the whole series of complexed chitosan), SPR cold be used for a simple “in vitro” protein adsorption analysis, by flowing aqueous solutions of albumin and fibrinogen. While both proteins were adsorbed on the uncomplexed chitosan, the complexed coatings exhibited different and very promising behaviors. In particular, they showed no adsorption or only selective adsorption of albumin.A SPR experimental set‐up in the Kretschmann configuration.magnified imageA SPR experimental set‐up in the Kretschmann configuration.
Korrosionsverhalten ausgewählter Werkstoffe in Lithiumbromid‐Lösung für den Anwendungsfall Absorptionskältemaschinen
Authors: Brandt B. 
Published: June 2004

AbstractAbsorptionskältemaschinen auf der Basis von Lithiumbromid‐Wasser stellen eine interessante Möglichkeit zur effizienten und energiesparenden Versorgung mit Kälte dar. Die zum Antrieb erforderliche Wärmeenergie kann idealerweise aus regenerativen Energien, wie z.B. Solarwärme, oder Abwärme aus der Industrie bereitgestellt werden. Um die Energieeffizienz zu steigern, können die Prozesse mehrstufig betrieben werden. Bei den dreistufigen, sogenannten Triple‐Effekt‐Anlagen, sind im Generator Temperaturen bis zu etwa 200–220°C erforderlich. Die Faktoren hohe Temperatur, hohe Halogenidkonzentration (Lithiumbromid) und die Anwesenheit von Wasserdampf führen zu einer besonders starken korrosiven Beanspruchung der Werkstoffe.Aufgabe des vorliegenden Beitrages war deshalb die Betrachtung handelsüblicher Werkstoffe und Inhibitoren auf ihre Eignung für Triple‐Effekt‐Absorptionskältemaschinen. Die Messungen wurden unter analogen Bedingungen in ruhender Lösung unter nahezu vollständigem Ausschluss von Luft durchgeführt.Die Untersuchungen haben ergeben, dass nichtrostender Stahl hinsichtlich seiner Materialstabilität besonders aussichtsreich ist. Weiterhin hat sich gezeigt, dass die Art des Inhibitors und das Zusammenwirken unterschiedlicher Phasen die Korrosion erheblich beeinflussen können.
Influence of drying temperature on the corrosion performance of chromate coatings on galvanized steel
Authors: Zhang X. , Böhm S. , Bosch A. J. , van Westing E. P. M. , de Wit J. H. W. 
Published: June 2004

AbstractThe influence of drying temperature on the corrosion performance of chromate coatings on electro‐galvanized (EG) steel has been investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements in 3.5% NaCl solutions. The chromate coatings were applied to the EG steel in a solution (pH 1.2) containing sodium dichromate and sulfuric acid at room temperature. The coatings were dried in an oven at three different temperatures: 60, 110 and 210°C. The surface of the chromate coatings was analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with energy‐dispersive spectrometry (EDS). The results show that the drying temperature significantly affects the morphology of the chromate coatings and consequently affects their corrosion behavior. The chromate coatings dried at 110°C had few cracks and the lowest corrosion current. The chromate coatings dried at 60°C showed passivity. The EIS results show that the chromate coatings dried at 60°C has the largest impedance in a neutral 3.5% NaCl solution. Drying at higher temperature (210°C) degrades the chromate coatings by widening the cracks and reducing soluble Cr(VI) in the chromate layer. The favorable drying temperature for the chromate coatings on the EG steel is between 60 and 110°C.
The effect of fluoride on the electrochemical behavior of Ti and some of its alloys for dental applications
Authors: Al‐Mayouf A. M. , Al‐Swayih A. A. , Al‐Mobarak N. A. , Al‐Jabab A. S. 
Published: June 2004

AbstractTitanium is the best metal for making dental implants and restorations. In the last decade, new titanium alloys have been developed in different areas of dentistry. Concurrently, treatments using fluoride supplementation, such as odontology fluoride containing gels, have also been widely used in odontology.The aim of this study is to investigate the electrochemical behaviour of a new titanium alloy containing Cu and Ag, in fluoride‐containing media, and compare it with the behavior of Ti and Ti6Al4V, which are used frequently as biomaterials. Open circuit potential, polarization resistance and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of titanium and its alloys is controlled by the fluoride ion concentration and the pH of the solution. The presence of F− ions in neutral solution does not hinder the formation of a protective layer of Ti and its alloys. Thus, the corrosion resistance of Ti is maintained in this medium. However, the corrosion of Ti and its alloys are enhanced in an acidic environment, because F− ions in the solution combines with H+ ion to form HF, even in low fluoride concentration.
Potential of biocorrosion in Danish district heatings sytems
Authors: Kjellerup B. V. , Olesen B. H. , Frølund B. , Nielsen P. H. 
Published: June 2004

AbstractDanish district heating (DH) systems utilise water with unique characteristics that include low conductivity, high pH, nutrient poor and anaerobic (oxygen free) conditions in order to reduce corrosion rates. This survey was carried out in order to investigate the potential for biofilm formation and biocorrosion in these systems. Determination of total bacterial numbers in water samples were performed in 29 DH systems and showed a range of 102–105 cells · ml−1. The potential for biofilm growth was further examined in corrosion monitoring units located at 6 DH locations. Total bacterial numbers in biofilm on mild steel were found in the range of 104–106 cells · cm−2. The mild steel coupons were examined for general corrosion rates based on weight loss together with an investigation of pitting corrosion. The general corrosion rates were up to 12 μm · year−1, while the pitting analysis showed pit depths up to 90 μm for half a year of exposure. Presence of sulphate reducing bacteria (SRB) was found in all systems tested with corrosion monitoring units, whereas sulphide was found to different extents in the biofilms on all mild steel coupons.It was shown that DH systems with the highest number of bacteria in the biofilm generally had the most pronounced corrosion. The results show that despite the nutrient poor environment in the DH systems the potential for biofilm formation and biocorrosion was present.
Metallic dental materials in patient's oral cavity acting as electrodes of electrochemical cells
Authors: Opydo W. , Opydo‐Szymaczek J. 
Published: June 2004

AbstractThe work was aimed at studying of standard potentials of commonly used metallic dental materials and determining of the effect of saliva conductivity and reaction on value of the potentials. The following materials have been examined: gold alloy (a material used for crowns and bridgeworks), chromium‐cobalt alloy (for frameworks in removable partial dentures), and silver amalgams (used for fillings) manufactured by three different companies.Taking into account that mucosa makes one of the electrodes existing in oral cavity the rest potentials of mucosa have been in vivo measured in several patients. Their values, converted with respect to NHE, oscillated within the range from + 0.31 V to + 0.47 V.Among metallic dental materials examined in the experiment maximal standard potential was found for the gold alloy, further materials having lower potentials, in decreasing order, were chromium‐cobalt alloy, and the amalgams Amalcap Plus, ANA 2000 and Septalloy.Significant differences between standard potentials of examined materials and mucosa indicate spontaneous formation of galvanic cells of electromotive force reaching even about 0.6 V.
Ronald Koningsveld
Authors: Hess Michael 
Published: June 2004

AbstractThis section contains news of the macromolecular community all over the world. Articles about, for example, people, projects, and market trends are welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de. The editorial office decides which articles will be published.
Investigation of the Peak Width of Polystyrene Prepared by Rotating‐Sector Polymerization in Microemulsion
Authors: Schnöll‐Bitai Irene , Pfeisinger Christian 
Published: June 2004

AbstractStyrene was polymerized by intermittent photoinitiation (at a constant sector speed and a light to dark ratio of 1:5) in microemulsion. The molecular weight distribution was measured by size‐exclusion chromatography and turned out to be extremely well structured. When the points of inflection were used for the calculation of the rate constant of propagation in analogy to pulsed‐laser polymerization/size‐exclusion chromatography (PLP‐SEC), values were obtained which were lower than those accepted for bulk polymerization but good agreement was achieved with a slightly modified equation. The absolute peak width (introduced as the difference between two successive points of inflection) turned out to be an invariant quantity no matter which type of distribution curve (number, molar mass, or hyper distribution) was analyzed, thus demonstrating the Poissonian character of the peaks. Furthermore, the relative peak widths (defined as the ratio of two successive points of inflection) for the first peak scattered between 1.35–1.45, those for the second peak between 1.26–1.30. After subtracting the respective value for the theoretical peak width, the same value for the first and second peaks was obtained for all experiments over a broad range of experimental parameters. As the appearing peaks are well resolved and narrow, the influence of axial dispersion on the results is, therefore, conclusively demonstrated. A simple procedure for the direct determination of axial dispersion is presented based on the relative peak widths and the additivity of the peak variances. The invariance of the peak widths is an easily verifiable theoretical and experimental prerequisite for this procedure.
Comparison of GPC traces of a microemulsion polymerization of styrene (t0 = 1.4 s, [M] = 4.326 mol · l−1; light‐to‐dark ratio 1:5; full line) and of a standard mixture (styrene, peak masses: 1 950, 89 400, 993 000; dashed line).imageComparison of GPC traces of a microemulsion polymerization of styrene (t0 = 1.4 s, [M] = 4.326 mol · l−1; light‐to‐dark ratio 1:5; full line) and of a standard mixture (styrene, peak masses: 1 950, 89 400, 993 000; dashed line).
Stereospecific Nature of Active Sites on TiCl4/MgCl2 Ziegler–Natta Catalyst in the Presence of an Internal Electron Donor
Authors: Liu Boping , Nitta Takashi , Nakatani Hisayuki , Terano Minoru 
Published: June 2004

AbstractBased on our previous study on the donor‐free TiCl4/MgCl2 catalyst, the stereospecific nature of active sites on this catalyst after the addition of an internal donor, ethylbenzoate (EB), was investigated by stopped‐flow propylene polymerization combined with temperature rising elution fractionation (TREF) and gel permeation chromatography (GPC) methods. The addition of donor EB was observed to significantly restrain the formation of aspecific sites (AS sites), to drastically promote formation of sites with the second highest isospecificity (IS2 sites) and to construct some new active sites with the highest isospecificity (IS3 sites). It was first observed that the formation of IS3 sites still strongly depends on the interaction between the catalyst and cocatalyst (up to 10 s of pretreatment) even in the presence of internal donor. Based on Busico and co‐workers' three sites model and our previous report, a plausible mechanism for the transformation of stereospecific active sites through some secondary bimetallic complexation reactions was proposed. The extraction of EB from the catalyst by the cocatalyst was found to initiate after 10 s of pretreatment resulting in partial transformation of IS3 sites into AS sites and IS1 sites.
Plausible mechanism for the transformation of active sites with lower isospecificity (AS sites) into the highest isospecific active site (IS3 sites) on the TiCl4/MgCl2 catalyst in the presence of internal donor EB during the pretreatment, X: Cl or Et; M: Mg or Ti. M and Mg are bound to the catalyst substrate through chlorine bridges; □: coordination vacancy.imagePlausible mechanism for the transformation of active sites with lower isospecificity (AS sites) into the highest isospecific active site (IS3 sites) on the TiCl4/MgCl2 catalyst in the presence of internal donor EB during the pretreatment, X: Cl or Et; M: Mg or Ti. M and Mg are bound to the catalyst substrate through chlorine bridges; □: coordination vacancy.