bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic Ladder Polymers by Polycondensation of Silylated Tetrahydroxy‐tetramethylspirobisindane with 1,4‐Dicyanotetrafluorobenzene
Authors: Kricheldorf Hans R. , Fritsch Detlev , Vakhtangishvili Lali , Schwarz Gert 
Published: November 2005

AbstractSummary: 5,5′,6,6′‐Tetra(trimethylsiloxy)‐4,4,4,4′‐tetramethyl‐1,1‐spirobisindane was polycondensed with 1,4‐dicyanotetrafluorobenzene under variation of solvent temperature, time, and feed ratio. Under optimized reaction conditions, all products detectable by MALDI‐TOF mass spectrometry (up to masses around 8 000 Da) proved to be cyclic ladder oligomers and polymers. In N‐methylpyrrolidone and dimethylsulfoxide odd‐numbered cycles were formed in addition to the prevailing even‐numbered ones. However, in sulfolane exclusively even‐numbered cycles were obtained (detectable up to masses around 10 000 Da), together with even‐numbered linear chains. Temperatures above 100 °C enhanced the molecular weights by side reactions. With the less reactive cyano‐2,3,5,6‐tetrafluorobenzene (CTB) again cycles were formed, but their content and the conversions were lower. Polycondensation of CTB up to 160 °C and all polycondensations of cyanopentafluorobenzene gave crosslinked products.Synthesis of cyclic ladder polymers.magnified imageSynthesis of cyclic ladder polymers.
Kinetic Peculiarities of Ethylene Polymerization over Homogeneous Bis(imino)pyridine Fe(II) Catalysts with Different Activators
Authors: Barabanov Artem A. , Bukatov Gennady D. , Zakharov Vladimir A. , Semikolenova Nina V. , Echevskaja Ljudmila G. , Matsko Michail A. 
Published: November 2005

AbstractSummary: Method of polymerization inhibition by radioactive carbon monoxide (14CO) has been used to determine the number of active centers (CP) and propagation rate constant (kP) for ethylene polymerization with homogeneous complex 2,6‐(2,6‐(Me)2C6H3NCMe)2C5H3NFeCl2 (LFeCl2), activated with methylalumoxane (MAO) or Al(i‐Bu)3. With both activators the rate profile of polymerization was unstable: high activity [0.8 × 103–1.5 × 103 kg PE per (molFe · h · atm) at 35 °C] of the initial period sharply decreases (sevenfold in 10 min). In the beginning of polymerization with the catalysts LFeCl2/MAO and LFeCl2/Al(i‐Bu)3, the CP values were found to be 8 and 41% of total Fe‐complex content in catalysts, respectively, and decreased 1.5–2‐fold in 9 min. As polymerization proceeds, the kP value for LFeCl2/MAO system decreases from 5 × 104 to 1.5 × 104 L · (mol · s)−1 LFeCl2/MAO, and for LFeCl2/Al(i‐Bu)3 system from 2.6 × 104 to 0.82 × 104 L · (mol · s)−1. Data on the effect of polymerization time on polyethylene molar mass distribution are presented. Basing on the obtained results it was suggested that highly reactive, but unstable centers, dominating at short polymerization times, produce low‐molar‐mass polyethylene, while polyethylene with higher molar mass is produced by less active (low kP) and more stable centers.Data showing change in molar mass distribution of polyethylene with polymerization time.magnified imageData showing change in molar mass distribution of polyethylene with polymerization time.
A Low Temperature Polycondensation for the Preparation of Highly Fluorinated Poly(arylene ether sulfone)s Containing Crosslinkable Pentafluorostyrene Moieties
Authors: Ding Jianfu , Qi Yinghua , Day Michael , Jiang Jia , Callender Claire L. 
Published: November 2005

AbstractSummary: The polycondensation of pentafluorophenyl sulfone (PPSO) with hexafluorobisphenol A (6F‐BPA), or a model compound, 4‐phenoxylphenol (POPOH), has been studied in order to find optimized reaction conditions for the preparation of fluorinated poly(arylene ether sulfone)s (FPAESs). It was found that PPSO had a very high reactivity in N,N‐dimethylacetamide (DMAc), allowing the reaction to occur at temperatures as low as 22 °C, even in the absence of any catalyst. This reaction was promoted by the addition of a trace amount of potassium fluoride (KF). Increasing the amount of KF to 1.05 equiv enhanced the conversion and allowed the reaction to be completed in a short time. Under this reaction condition, KF acted as a catalyst to activate the phenol group and also acted as a base to absorb the HF, which was a by‐product of the polycondensation, to produce high molecular weight polymer. The use of calcium hydride (CaH2) instead of KF as a base in this reaction produced a similar effect with a slightly lower reaction rate. Both base systems were also applicable to the reaction of pentafluorostyrene (FSt) with 6F‐BPA. However, a much higher reaction temperature (125 °C) was required due to the low reactivity of FSt. Reacting FSt with an excess of 6F‐BPA produced a mixture of mono‐ and di‐substituted products of FSt with a controllable ratio, which could further react with PPSO to produce a polymer containing crosslinkable FSt moieties both as end‐capping groups and inserting units. This structure allowed the molecular weight of the polymer and the content of FSt to be adjusted independently. Crosslinked films of this polymer demonstrated an excellent processability and performance in waveguide applications, having refractive indices of 1.5061 (TE) and 1.5038 (TM), and a straight waveguide loss of 0.7 dB · cm−1.Reaction scheme for the preparation of fluorinated poly(arylene ether sulfone)s.magnified imageReaction scheme for the preparation of fluorinated poly(arylene ether sulfone)s.
Molecular Structure of 113C‐C2H4/C3H6 Copolymers Prepared in the Presence of Half Sandwich Titanium Methyl – B(C6F5)3 Catalysts
Authors: Sessa Irene , Csok Zsolt , Zambelli Adolfo 
Published: November 2005

AbstractSummary: Copolymers of propylene with 113C‐ethylene (99% isotopic purity) have been prepared in the presence of Cp*Ti(CH3)3 – B(C6F5)3 (I) or CpTi(CH3)3 – B(C6F5)3 (II) (Cp = cyclopentadienyl, Cp* = pentamethylcyclopentadienyl). 13C NMR analysis confirms previous findings that propylene polymerization in the presence of I is highly regioselective and somewhat isoselective, while catalyst II produces regioblock polypropylene. In the presence of II, polymerization is slightly syndioselective and the average size of the primary regioblocks seems larger than that of the secondary ones. Moreover, secondary insertion seems more syndioselective than the primary.13C NMR spectra of samples I.2 and II.2.magnified image13C NMR spectra of samples I.2 and II.2.
Functional calculus under Kreiss type conditions
Authors: Vitse Pascale 
Published: November 2005

AbstractIt is shown that for an algebraic Banach space operator T , the Kreiss condition, ‖(zI – T )–1‖ ≤ $ {C \over {| z | - 1} } $, |z | > 1, implies the following functional calculus estimate

where deg(T ) is the degree of the minimal polynomial annihilating T . This result extends the known estimates of the powers of T for Kreiss operators on finite dimensional spaces. In the case of a general Kreiss operator, an estimate of the rational calculus is proved:

Similar estimates hold for the polynomial calculus under generalized Kreiss conditions. A link is also established between the sharp constant in the first estimate and the norm of the best solution for a Nevanlinna–Pick type interpolation problem in analytic Besov classes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Certain classes of potentials for p ‐Laplacian to be non‐degenerate
Authors: Zhang Meirong 
Published: November 2005

AbstractGiven a positive integer n and an exponent 1 ≤ α ≤ ∞. We will find explicitly the optimal bound rn such that if the Lα norm of a potential q (t ) satisfies ‖q ‖ < rn then the n th Dirichlet eigenvalue of the onedimensional p ‐Laplacian with the potential q (t ): (|u ′|p –2 u ′)′ + (λ + q (t )) |u |p –2u = 0 (1 < p < ∞) will be positive. Using these bounds, we will construct, for the Dirichlet, the Neumann, the periodic or the antiperiodic boundary conditions, certain classes of potentials q (t ) so that the p ‐Laplacian with the potential q (t ) is non‐degenerate, which means that the above equation with λ = 0 has only the trivial solution verifying the corresponding boundary condition. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and Self‐Assembly of Amphiphilic Diblock Copolymers using a Fluorescently Labeled N‐Alkoxyamine Initiator
Authors: Tsimelzon Anna , Deamer David , Braslau Rebecca 
Published: November 2005

AbstractSummary: An initiator for nitroxide mediated ‘living’ free radical polymerization was prepared with a fluorescent tag attached to the initiating alkyl radical terminus. This was used to synthesize amphiphilic poly(acrylic acid)‐block‐polystyrene diblock copolymers, which self assembled in a tetrahydrofuran/buffer solution to form structures that are visible by fluorescence.
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Mass spectrometry in bioinorganic analytical chemistry
Authors: Łobiński Ryszard , Schaumlöffel Dirk , Szpunar Joanna 
Published: November 2005

AbstractA considerable momentum has recently been gained by in vitro and in vivo studies of interactions of trace elements in biomolecules due to advances in inductively coupled plasma mass spectrometry (ICP MS) used as a detector in chromatography and capillary and planar electrophoresis. The multi‐isotopic (including non‐metals such as S, P, or Se) detection capability, high sensitivity, tolerance to matrix, and large linearity range regardless of the chemical environment of an analyte make ICP MS a valuable complementary technique to electrospray MS and MALDI MS. This review covers different facets of the recent progress in metal speciation in biochemistry, including probing in vitro interactions between metals and biomolecules, detection, determination, and structural characterization of heteroatom‐containing molecules in biological tissues, and protein monitoring and quantification via a heteroelement (S, Se, or P) signal. The application areas include environmental chemistry, plant and animal biochemistry, nutrition, and medicine. © 2005 Wiley Periodicals, Inc. Mass Spec Rev 25:255–289, 2006
Solution Properties of Partially Hydrolysed Polyacrylamide and Chitosan Mixed Solutions
Authors: Lima Vidal Rosangela Regia , Pereira Fagundes Fábio , Cabral de Menezes Sonia Maria , Machado da Silva Ruiz Naira , Balaban Garcia Rosangela 
Published: November 2005

AbstractSummary: In this paper, the properties of a partially hydrolysed polyacrylamide with a low charge density and chitosan mixtures were evaluated in an aqueous acid solution. The formation of a soluble complex was followed by conductometry and potentiometry, and the stoichiometry at the titration endpoint was investigated as a function of the polyanion added. The influence of salts on the titration endpoint and on the rheological behavior of the mixed solutions was also studied. The mixture of equal concentration of both polymers, in the absence of salt, presented synergy, with a significant viscosity increase. Nevertheless, in the presence of salts, this mixture presented minimum viscosity. These results were discussed as a function of the polymers structural features and the environment used in the study.
Polymer Blend for Electrolyte and Electrode Coatings
Authors: Lavall Rodrigo L. , Trigueiro João Paulo C. , Borges Raquel S. , Ferlauto André S. , Furtado Clascídia A. , Silva Glaura G. 
Published: November 2005

AbstractSummary: The thermal and morphological properties of PEO/copolyether electrolyte and carbon black composite have been studied. A copolyether poly(propylene glycol)‐block‐poly(ethylene glycol)‐block‐poly(propylene glycol) bis(2‐aminopropyl ether) was used at 20 wt.‐% in relation to PEO in order the improve the carbon black dispersion through interaction with the amino end capped function. The polymer matrix presented semicrystalline structure and the addition of LiClO4 and carbon black decreases significantly the crystallinity of the system. Sub‐micrometric dispersion of carbon black was observed. The conductivity results as a function of temperature exhibited a typical VTF behaviour for the electrolyte. Almost constant conductivities of 2 × 10−4 S · cm−1 were observed for the composite with 5 wt.‐% of carbon black, in the range of temperature between 35 and 95 °C, which indicates a significantly contribution of electronic conduction.
Nanostructured Proton‐Conducting Membranes for Fuel Cell Applications
Authors: Tan Ai Ren , Magno de Carvalho Luisa , de Souza Gomes Ailton 
Published: November 2005

AbstractSummary: Composite polymer membranes based on sulfonated poly(arylene ether sulfone) (SPSU) containing benzimidazole derivatives (BIzD) and heteropolyacid for use in fuel cells were prepared. The effects of both the increment in BBIzD component and the procedure of mixing on the morphology and proton conductivity were investigated. The heteropolyacid (HPA) extracted in water decreased with the addition of BBIzD in the composite. The interactions developed among the sulfonate groups, the benzimidazole derivatives and the HPA were verified by Fourier transform infrared (FTIR). The network of interactions established in the composite membrane based on SPSU containing benzimidazole derivatives and phosphotungstic acid (HPW) in the ratio of SPSU/BBIzC4(8:1) in equivalents and SPSU/HPW(7:3) in mass resulted in a very high proton conductivity at 110 °C.
Study of [Thienylene‐dialkoxy phenylene] Conjugated Materials
Authors: Silva R. A. , Cury L. A. , Mazzoni M. S. , Soares E. , Guimarães P. S. S. , Serein‐Spirau F. , Löis S. , Moreau J. , Lère‐Porte J.‐P. 
Published: November 2005

AbstractSummary: In this work we report on the electrochromic and optical studies of thin films of thienylene‐dialkoxyphenylene. The films for the optical measurements were prepared by spin casting on glass and silicon substrates. Photoluminescence and absorption spectra were recorded in the temperature range from 300 K. The differences between the spectra of the polymer and the oligomer can be attributed to a higher mean conjugation length in the polymer than in the oligomer. We present also a first principles theoretical calculation which shows that the conjugated oligomer has an HOMO‐LUMO energy around 2.0 eV, which is consistent with the experimental data.
Synthesis and Characterization of Modified Chitosan Through Immobilization of Complexing Agents
Authors: Justi Karin Cristiane , Fávere Valfredo T. , Laranjeira Mauro C. M. , Neves Ademir , Casellato Annelise 
Published: November 2005

AbstractSummary: The complexation agents 2[‐bis‐(pyridylmethyl)aminomethyl]‐4‐methyl‐6‐formyl‐phenol (BPMAMFF) and 2‐[2‐(hydroxybenzyl)‐2‐(pyridylmethyl)aminomethyl]‐4‐methyl‐6‐formyl‐phenol (HBPAMFF) were immobilized on chitosan biopolymer in order to obtain new adsorbent materials for metal ions. The chitosan derivatives were characterized by IR spectroscopy, DSC, TGA, and CHN analysis. The characterization study proved that the chitosan surface was chemically modified with both complexing agents and however, it is expected that these modifications improve the selectivity for metal ions specific in relation to the chitosan.
Thermal Stability of Biodegradable Films Based on Soy Protein and Corn Starch
Authors: Soares Rosane M. D. , Scremin Fernanda F. , Soldi Valdir 
Published: November 2005

AbstractSummary: In this paper, films were prepared from soy protein and corn starch in different proportions and thermal stability and kinetic parameters were determined through degradation reactions in an inert atmosphere. Solid residues and decomposition products were identified by infrared spectroscopy. Films from corn starch were less thermally stable than soy protein films. The films containing both components had lower thermal stabilities when compared to those of the pure biopolymers. The mechanism of starch thermal degradation seems to occur in a single step, which can be confirmed by the constant E‐values during the thermal degradation reaction. For the pure protein and its mixtures an increase in the activation energy was observed during the reaction. Solid residues for protein at different temperatures showed mainly bands related to CO stretching, angular deformation of NH and CH groups. For starch, absorptions related to free and bound OH, CO stretching of CO2, CO and carbonyl compounds were observed. For the 50/50 mixture bands related to soy protein and corn starch were observed. The gaseous products for soy protein showed absorptions related to CO2, CO, CO, NH3 and CH stretching. For pure starch absorptions related to OH stretching from alcohol, CO from CO2, CO and carbonyl compounds. The 50/50 mixture had the same characteristics as pure soy protein and corn starch.
Isometric and Isotensional Force‐Length Profiles in Polymethylene Chains
Authors: Zemanová Martina , Bleha Tomáš 
Published: November 2005

AbstractSummary: The force‐length curves and related thermodynamic quantities of single polymethylene (PM) chains in the high‐force region were calculated by the statistical mechanics. Two statistical mechanics ensembles (isometric and isotensional) were used to represent the chain stretching under the conditions, respectively, of the fixed length L or of the fixed force F in single‐chain experiments by AFM and related techniques. The input deformation potentials of highly extended conformations of PM chains were obtained from the molecular‐mechanics calculations. Variations of the energy, entropy, and Helmholtz energy with the end‐to‐end length L of chains were computed under the condition of fixed length. The ensuing isometric profile of the mean force 〈F〉(L) is non‐monotonic, featuring a sawtooth‐like pattern of ascending peaks. In contrast, the mechanical equation under isotensional conditions, given by the variation of the mean length 〈L〉(F), shows a conventional monotonous shape with a distinct plateau region at low temperatures. The considerable difference in the shapes of 〈F〉(L) and 〈L〉(F) curves arises from the large fluctuations of mean values due to the small number of conformers present in molecules at high strains. The computed data should be relevant to the AFM stretching experiments on short polyethylenes or on other soft matter materials involving linear paraffinic chains. It is argued that the dual character of elastic response described by the conjugated force profiles is a universal feature of mechanochemistry of chain molecules whenever the chain length discontinuously increases at a transition.Force‐length curves of short polymethylene chains at 300 K.magnified imageForce‐length curves of short polymethylene chains at 300 K.
Cleaning versus replacement in power plant air preheaters: a comparison between deterministic and stochastic goal programming models
Authors: Ballestero Enrique , Gonzalez Ignacio 
Published: November 2005

AbstractPower plants lose efficiency when the air preheater elements are not replaced or cleaned as they deteriorate. Replacing is more expensive than cleaning but more secure to preserve power and lifetime. How many baskets should be then replaced and how many cleaned to achieve ‘satisficing’ goals of cost, power and lifetime? We design deterministic/stochastic goal programming approaches to this problem and develop a decision case for usual preheaters. Some discrepancies in results between both approaches appear, the deterministic model advising to replace less baskets than the stochastic, which is plausible due to the risk variable. Copyright © 2005 John Wiley & Sons, Ltd.
Comparing graphic and symbolic classification in interactive multiobjective optimization
Authors: Miettinen Kaisa , Kaario Katja 
Published: November 2005

AbstractIn interactive multiobjective optimization systems, the classification of objective functions is a convenient way to direct the solution process in order to search for new, more satisfactory, solutions in the set of Pareto optimal solutions. Classification means that the decision maker assigns the objective functions into classes depending on what kind of changes in their values (in relation to the current values) are desirable.Here we study the role of user interfaces in implementing classification in multiobjective optimization software and how classification should be realized. In this way, we want to pay attention to the usability of multiobjective optimization software. Typically, this topic has not been of interest in the multiobjective optimization literature. However, usability aspect is important because in interactive classification‐based multiobjective optimization methods, the classification is the core of the solution process. We can say that the more convenient the classification is, the more efficient the system or the method is and the better it supports the work of the decision maker.We report experiments with two classification options, graphic and symbolic ones, which are used in connection with an interactive multiobjective optimization system WWW‐NIMBUS. The ideas and conclusions given are applicable for other interactive classification‐based method, as well. Copyright © 2005 John Wiley & Sons, Ltd.
Some remarks on the asymptotic behaviour of the solutions of a class of parabolic problems
Authors: Philippin G. A. , Proytcheva V. 
Published: November 2005

AbstractThis paper deals with a class of semilinear parabolic problems. We establish sufficient conditions on the data forcing the solution to blow up at finite time τ and derive an upper bound for τ. Moreover, we show that if the problem is modified in some way, the solution decays exponentially in time and depends continuously on the data. Copyright © 2005 John Wiley & Sons, Ltd.
Extinction and permanence of the predator–prey system with stocking of prey and harvesting of predator impulsively
Authors: Dong Lingzhen , Chen Lansun , Sun Lihua 
Published: November 2005

AbstractIn this paper, a predator–prey system with stocking of prey and harvesting of predator impulsively is studied. Here, the prey population is stocked with a constant quantity and the predator population is harvested at a rate proportional to the species itself at fixed moments. Under some conditions, the existence and global asymptotic stability of the boundary periodic solution are proved, which implies that the system will be extinct; and given some different restrictions, ultimate positive upper and lower bounds of all solutions are obtained, showing the system being permanent. At last, two examples are given to illustrate our results. Copyright © 2005 John Wiley & Sons, Ltd.
Accelerating cine phase‐contrast flow measurements using k‐t BLAST and k‐t SENSE
Authors: Baltes Christof , Kozerke Sebastian , Hansen Michael S. , Pruessmann Klaas P. , Tsao Jeffrey , Boesiger Peter 
Published: November 2005

AbstractConventional phase‐contrast velocity mapping in the ascending aorta was combined with k‐t BLAST and k‐t SENSE. Up to 5.3‐fold net acceleration was achieved, enabling single breath‐hold acquisitions. A standard phase‐contrast (PC) sequence with interleaved acquisition of the velocity‐encoded segments was modified to collect data in 2 stages, a high‐resolution undersampled and a low‐resolution fully sampled training stage. In addition, a modification of the k‐t reconstruction strategy was tested. This strategy, denoted as “plug‐in,” incorporates data acquired in the training stage into the final reconstruction for improved data consistency, similar to conventional keyhole. “k‐t SENSE plug‐in” was found to provide best image quality and most accurate flow quantification. For this strategy, at least 10 training profiles are required to yield accurate stroke volumes (relative deviation <5%) and good image quality. In vivo 2D cine velocity mapping was performed in 6 healthy volunteers with 30–32 cardiac phases (spatial resolution 1.3 × 1.3 × 8–10 mm3, temporal resolution of 18–38 ms), yielding relative stroke volumes of 106 ± 18% (mean ± 2*SD) and 112 ± 15% for 3.8× and 5.3× net accelerations, respectively. In summary, k‐t BLAST and k‐t SENSE are promising approaches that permit significant scan‐time reduction in PC velocity mapping, thus making high‐resolution breath‐held flow quantification possible. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.