bluuebunny/crossref_metadata_2025_split huggingface dataset:
Manifestation of electrolyte ion size effect on electrochemical behavior of poly(ferrocenylsilane) films
Authors: Wang Xue‐Jie , Wang Li , Wang Jian‐Jun , Chen Tao 
Published: April 2006

AbstractThe influences of supporting electrolyte ion size on the cyclic voltammetric (CV) behavior of high‐molecular‐weight poly(ferrocenylsilane) films in organic solvents were investigated. Three supporting electrolytes with various ion sizes were tested. Electrolyte anions, as counter ions, take part in charge neutrality in the films, so that the size of anion affects the CV behavior of the films remarkably. The large anions are difficult to penetrate into the films, the resistances of the large ions migrating in films are more, the rates of the electroactive species diffusing in the films are slow, and the CV behavior of the polymer films exhibit irreversible features. The electrolyte cations do not take part in charge neutrality in the films, so that the size of cation does not actually affect the CV behavior of the films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 515–523, 2006
Preparation and performances of poly(phthalazinone ether sulfone ketone) hollow fiber membranes with excellent thermotolerance
Authors: Zhu Li‐Ping , Zhu Bao‐Ku , Xu You‐Yi 
Published: April 2006

AbstractThe cloud points of PPESK/NMP/H2O ternary system at different temperatures were measured by titrimetric method. The binodal lines in the ternary phase diagram of the poly(phthalazinone ether sulfone ketone (PPESK) dope system was determined, on the basis of the cloud point experimental data being linearly fitted with the semiempirical linear cloud point correlation. Furthermore, phase separation behavior during the phase inversion of PPESK membrane‐forming system was discussed in terms of the phase diagram. Then, dry–wet spinning technique was employed in manufacturing PPESK hollow fiber membranes by immersion precipitation method. The cross‐section morphologies of hollow fibers were observed by scanning electronic microscopy. Also, the effects of dope solution composition and spinning parameters, including the coagulant composition and the spinning temperature on the separation performances of fibers, were evaluated by permeability measurements. The thermotolerance of the PPESK hollow fiber membranes prepared in the work was examined for the permeation operation at different temperatures and pressure differences. The experimental results showed that pure water flux increases several fold along with the temperature increases from 20 to 80°C at different operation pressures, while the solute rejection only decreases slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 878–884, 2006
Experiments and simulation of pH‐responsive N‐isopropylacrylamide–acrylic acid copolymer hydrogels
Authors: Tao Yong , Zhao Jiong‐Xin , Wu Cheng‐Xun 
Published: April 2006

AbstractIn this study, N‐isopropylacrylamide–acrylic acid (NIPAAm–AAc) copolymer hydrogels were synthesized by radical polymerization. The equilibrium and dynamic water uptake of these copolymer hydrogels were investigated as a function of acrylic acid content of copolymer, pH, and temperature. The pH‐dependent swelling ratio of the hydrogels was distinguishable between two pH‐modulating methods. In addition, a modified thermodynamic simulation that is able to predict pH‐dependent swelling of polyanionic gels was developed. In the simulation, the influence of ionic strength on dissociation of carboxyl groups was taken into consideration. Also a new relation between Debye length and volume change of gels was derived from the approximation used in derivation of ionic osmotic pressure. The predictions from this modified equation were reasonably good compared with experiments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 323–330, 2006
Enzymatic degradation of poly(D,L‐lactide) and its blends with poly(vinyl acetate)
Authors: Mahalik J. P. , Madras Giridhar 
Published: April 2006

AbstractThe enzymatic degradation of poly(D,L‐lactide) (PLA) was investigated using two different lipases, Novozym 435 and Lipolase. The optimum temperature was 50°C for the enzymatic degradation of PLA. The effect of various solvents on the degradation of PLA was investigated at 50°C using Novozym 435, and toluene was found to be the best solvent among the solvents investigated. The enzymatic degradation of the blends of PLA and PVAc was investigated at 50°C in toluene. The enzymatic degradation of the blends of PLA and PVAc showed that there is an interaction between the polymers during degradation, which results in the reduction of degradation rate of both polymers in the blend. A continuous distribution model was used to determine the rate coefficients for polymer degradation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 657–680 2006
A kinetic investigation of polyurethane polymerization for reactive extrusion purposes
Authors: Verhoeven V. W. A. , Padsalgikar A. D. , Ganzeveld K. J. , Janssen L. P. B. M. 
Published: April 2006

AbstractThe effects of the reaction conditions on the kinetics of two different polyurethane systems were investigated. To do so, three different kinetic methods were compared: adiabatic temperature rise (ATR), measurement kneader, and high‐temperature measurements. For the first polyurethane system, consisting of 4,4‐diphenylmethane diisocyanate (4,4‐MDI), butane diol, and a polyester polyol, the reaction conditions did not seem to matter; a kinetically controlled reaction was implicated for all reaction conditions. The reaction was second order in isocyanate concentration and 0.5th order in catalyst concentration and had an activation energy of 52 kJ/mol. The second polyurethane system consisted of a mixture of 2,4‐diphenylmethane diisocyanate and 4,4‐MDI, methyl propane diol, and a polyester polyol. For this system, each of the three measurement methods showed different behavior. Only at a low catalyst concentration did the ATR experiments show catalyst dependence; at higher catalyst levels and for the other two measurement methods, no catalyst dependence was present. Furthermore, the ATR experiments proceeded much faster. Presumably, for this system, the rapid diffusion interfacial of the species present was hindered by the presence of bulky oligomer molecules. The result was a diffusion limitation reaction at low conversions and an inhomogeneous distribution of species at higher conversions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 370–382, 2006
Synthesis of polyethylene using ultrasonic energy with a metallocene catalyst
Authors: Bahattab Mohammed A. 
Published: April 2006

AbstractEthylene polymer was synthesized by the treatment of a metallocene catalyst Zr(CP)2Cl2 solution with ultrasonic energy. Ultrasonic energy irradiation was used to change the polymer structure of the formed polymer. Different ultrasonic energy irradiation times were applied to the metallocene catalyst solution. The ultrasonic energy had an effect on the average molecular weight, molecular weight distribution, and polymer productivity. A lower average molecular weight and a narrower molecular weight distribution were produced with a longer ultrasonic irradiation time. The polymer productivity was almost constant when the metallocene catalyst was treated with ultrasonic energy. Finer polyethylene particles were produced with longer ultrasonic irradiation times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 756–759, 2006
Analysis of the structural parameters of polyacrylonitrile fibers containing nanohydroxyapatite
Authors: Mikołajczyk Teresa , Rabiej Stanisław , Boguń Maciej 
Published: April 2006

AbstractThe structural parameters and strength properties of a new generation of polyacrylonitrile fibers have been analyzed. These fibers, after being carbonized, can be used in biomaterial engineering. They are characterized by a high tensile strength of 31–43 cN/tex. An advantageous influence of nanoparticles added to the fiber matter on the degree of crystallinity has been found. When nanoparticles of hydroxyapatite are incorporated into these fibers, their degree of crystallinity increases by about 5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 760–765, 2006
The Bingel Monoadducts of La@C82: Synthesis, Characterization, and Electrochemistry
Authors: Feng Lai , Wakahara Takatsugu , Nakahodo Tsukasa , Tsuchiya Takahiro , Piao Qiuyue , Maeda Yutaka , Lian Yongfu , Akasaka Takeshi , Horn Ernst , Yoza Kenji , Kato Tatsuhisa , Mizorogi Naomi , Nagase Shigeru 
Published: April 2006

AbstractThe reaction of La@C82 with diethyl bromomalonate in the presence of base (the Bingel reaction) generated five monoadducts which have been fully characterized. It was found that four of them (mono‐A, ‐B, ‐C, and ‐D) are ESR‐inactive, suggesting singly bonded regioisomers. In contrast, the fifth product (mono‐E) is ESR‐active, indicating that it possesses a cyclic moiety between the appended malonate group and the fullerene cage, analogous to conventional Bingel adducts. The differences in the molecular structures of mono‐A, ‐B, ‐C, and ‐E result in varying thermal stabilities and electrochemical behavior. In particular, the singly bonded monoadducts undergo the retro‐Bingel reaction either under thermal treatment or during electron transfer on the cyclic voltammetric timescale. However, mono‐E shows remarkable thermal stability and perfect reversibility under the same experimental conditions.
Development of a class of multiple time‐stepping schemes for convection–diffusion equations in two dimensions
Authors: Lin R. K. , Sheu Tony W. H. 
Published: April 2006

AbstractIn this paper we present a class of semi‐discretization finite difference schemes for solving the transient convection–diffusion equation in two dimensions. The distinct feature of these scheme developments is to transform the unsteady convection–diffusion (CD) equation to the inhomogeneous steady convection–diffusion‐reaction (CDR) equation after using different time‐stepping schemes for the time derivative term. For the sake of saving memory, the alternating direction implicit scheme of Peaceman and Rachford is employed so that all calculations can be carried out within the one‐dimensional framework. For the sake of increasing accuracy, the exact solution for the one‐dimensional CDR equation is employed in the development of each scheme. Therefore, the numerical error is attributed primarily to the temporal approximation for the one‐dimensional problem. Development of the proposed time‐stepping schemes is rooted in the Taylor series expansion. All higher‐order time derivatives are replaced with spatial derivatives through use of the model differential equation under investigation. Spatial derivatives with orders higher than two are not taken into account for retaining the linear production term in the convection–diffusion‐reaction differential system. The proposed schemes with second, third and fourth temporal accuracy orders have been theoretically explored by conducting Fourier and dispersion analyses and numerically validated by solving three test problems with analytic solutions. Copyright © 2006 John Wiley & Sons, Ltd.
A Simple and Efficient Route to Prepare Inorganic Compound/Polymer Composites in Supercritical Fluids
Authors: Wang Jiaqiu , Zhang Chengliang , Liu Zhimin , Ding Kunlun , Yang Zhenzhong 
Published: April 2006

AbstractSummary: A simple and efficient route to prepare inorganic compound/polymer composites in CO2‐based supercritical solution is presented. By this method, using polymeric hollow spheres as a substrate and Eu(NO3)3 as precursor, Eu2O3/polymer composites are successfully fabricated via the decomposition of the precursor in a supercritical CO2/ethanol mixture at 120 °C. The resulting composites are characterized by means of transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. It is indicated that besides being decorated on the outer surface of the polymer spheres, Eu2O3 nanoparticles are imbedded in the shell and further into the hollow cavity of the polymer spheres. The loading content and particle size of Eu2O3 on the polymer spheres can be controlled by changing the concentration of precursor in the solutions. The photoluminescence spectrum of the composites exhibit two peaks at 592 and 615 nm, which indicates that the composites can be used as optical material to emit red light. This method is also extended to the preparation of other inorganic compound/polymer composites with different functions.Eu2O3 nanoparticles are decorated on the outer surface of the polymer spheres.magnified imageEu2O3 nanoparticles are decorated on the outer surface of the polymer spheres.
Fabrication of Micropatterned Gold Nanoparticle Arrays as a Template for Surface‐Initiated Polymerization of Stimuli‐Responsive Polymers
Authors: Jung Jaeyoen , Kim Ki Woo , Na Kyunga , Kaholek Marian , Zauscher Stefan , Hyun Jinho 
Published: April 2006

AbstractSummary: This paper demonstrates a new, reliable, and simple method for fabricating micropatterned nanoparticle arrays that can serve as templates for the surface‐initiated polymerization of polymer brushes. As a proof of concept, we micropatterned gold nanoparticles (Au‐NPs, ≈10 nm) onto glass, silicon, polystyrene, and gold surfaces by a simple three‐step process: (1) microcontact printing of soluble polymer, (2) incubation with a solution of Au‐NPs, and (3) lift‐off of the template in a mixture of ethanol and deionized water. 40 µm wide features were successfully fabricated without any significant defects or nonspecific adsorption on the background. To demonstrate the utility of these Au‐NP templates, we subsequently polymerized N‐isopropylacrylamide by surface‐initiated polymerization, using a surface‐bound initiator.Synthesis of PNIPAAm brushes from micropatterned Au‐NP.magnified imageSynthesis of PNIPAAm brushes from micropatterned Au‐NP.
Die Parkinson‐Krankheit: Molekulare Mechanismen und Genetik
Authors: Büeler Hansruedi 
Published: April 2006

AbstractAus den vorangegangenen Abschnitten geht hervor, dass die molekularen Mechanismen, welche dem dopaminergen Nervenzelltod zugrunde liegen, bei sporadischer und genetischen Formen der PK ähnlich und überlappend sind. Oxidativer Stress, Dysfunktion und Degeneration der Mitochondrien sowie ungenügender Abbau von neurotoxischen Proteinen spielen bei der PK eine zentrale pathologische Rolle. Darüber hinaus kann Dopamin den Nervenzelltod beschleunigen, indem es durch kovalente Bindung toxische α‐Synuklein‐Fibrillen stabilisiert und die Löslichkeit und E3‐Ligase‐Aktivität von Parkin reduziert. Dadurch wird zumindest teilweise die Selektivität der Neurodegeneration bei der PK erklärt. Rezessive “Parkinson‐Gene” schützen Mitochondrien und Neuronen gegen oxidativen und proteotoxischen Stress und verhindern Apoptose. Dominante “Parkinson‐Gene” haben eine gegenteilige Wirkung. Mutationen im Gen für α‐Synuklein beschleunigen die Bildung von toxischen α‐Synuklein‐Fibrillen, welche Dopaminvesikel permeabilisieren, Proteasomenaktivität hemmen und mitochondriale Apoptose induzieren können. Parkin scheint eine besonders wichtige Funktion für das Überleben dopaminerger Neuronen einzunehmen, einerseits als Schutzfaktor gegen oxidativen Stress und mitochondriale Degeneration, andererseits (als E3‐Ligase) beim kontrollierten Abbau neurotoxischer Substratproteine (z.B. α‐Sp22, CDCrel‐1 und Pael‐R). In Zukunft werden die bereits geschaffenen und neue Tiermodelle der PK ohne Zweifel weiter dazu beitragen, die molekularen und zellulären Mechanismen des dopaminergen Nervenzelltods besser zu verstehen und damit gezieltere und effektivere Therapien für die PK zu entwickeln.
Hydrogen bonding, steric effects and thermodynamics of partitioning
Authors: Abraham Michael H. , Dearden John C. , Bresnen Gaynor M. 
Published: April 2006

AbstractThe descriptors in the Abraham solvation equation, especially the solute hydrogen bond acidity descriptor, A, have been compared to values of ΔHo and ΔSo for partitioning in the water–cyclohexane and water–octanol systems obtained by Dearden and Bresnen. It is shown that effects on ΔHo and ΔSo due to internal hydrogen bonding parallel very closely effects on A values for substituted phenols and substituted benzoic acids, thus suggesting a common structural origin. Steric effects of ortho‐substituted methyl groups in phenols, benzoic acids and acetanilides on ΔHo and ΔSo also parallel effects on the Abraham solvation parameters. Some of these steric effects, such as those in 2,6‐dimethylacetanilide, can be very large. Both the thermodynamics of partitioning and the Abraham descriptors suggest that in 2,6‐dihydroxybenzoic acid there is only one internal hydrogen bond, and that 2‐nitroresorcinol behaves as though it had two internal hydrogen bonds. Copyright © 2006 John Wiley & Sons, Ltd.
Assessing the acid–base and conformational properties of histidine residues in human prion protein (125–228) by means of pKa calculations and molecular dynamics simulations
Authors: Langella Emma , Improta Roberto , Crescenzi Orlando , Barone Vincenzo 
Published: April 2006

AbstractA thorough study of the acid–base behavior of the four histidines and the other titratable residues of the structured domain of human prion protein (125–228) is presented. By using multi‐tautomer electrostatic calculations, average titration curves have been built for all titratable residues, using the whole bundles of NMR structures determined at pH 4.5 and 7.0. According to our results, (1) only histidine residues are likely to be involved in the first steps of the pH‐driven conformational transition of prion protein; (2) the pKa's of His140 and His177 are ≈7.0, whereas those of His155 and His187 are < 5.5. 10‐ns long molecular dynamics simulations have been performed on five different models, corresponding to the most significant combinations of histidine protonation states. A critical comparison between the available NMR structures and our computational results (1) confirms that His155 and His187 are the residues whose protonation is involved in the conformational rearrangement of huPrP in mildly acidic condition, and (2) shows how their protonation leads to the destructuration of the C‐terminal part of HB and to the loss of the last turn of HA that represent the crucial microscopic steps of the rearrangement. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Standardization of sample preparation, staining and sampling methods for automated sperm head morphometry analysis of boar spermatozoa
Authors: García‐Herreros M. , Aparicio I. M. , Barón F. J. , García‐Marín L. J. , Gil M. C. 
Published: April 2006

SummaryThe accuracy of computer‐assisted sperm morphometry analysis (CASMA) depends on the careful preparation, fixation and staining of spermatozoa. The efficiency of CASMA may be enhanced by developing optimized protocols. The aim of the present study was to evaluate the influence of sperm washing and the use of three staining techniques [rapid Panoptic, Hemacolor and Harris's Haematoxylin (HH)] on image‐processing accuracy and boar sperm head morphometry. Sperm washing had a significant effect on samples stained with rapid Panoptic, increasing the percentage of correctly binarized sperm heads and the contrast between cells and background. However, rapid Panoptic yielded the lowest percentage of properly digitized sperm heads. HH provided the highest cell/background contrast, and also greater sperm head staining intensity, but discrimination of sperm midpieces was considered insufficient. Hemacolor occupied an intermediate position, providing acceptable colour intensity and satisfactory cell/background contrast. Use of different staining procedures prompted dimensional differences in sperm head morphometry. Significant differences between animals were observed for all morphometric parameters. Low within‐animal variation coefficients reflected a homogeneous sperm head population. Between‐animal variation coefficients were relatively high for Hemacolor and HH, and significantly high for the rapid Panoptic stain. Using Panoptic and HH, stable morphometric measurements required at least 100 properly digitized sperm heads rather than 200, while Hemacolor required only 50 spermatozoa. These results indicate that both washing of semen and staining procedures significantly affect the accuracy of image processing and sperm head dimensions. Hemacolor and HH proved to be the best staining techniques for evaluating sperm head dimensions in boar.
Helminthes could influence the outcome of vaccines against TB in the tropics
Authors: ELIAS D. , AKUFFO H. , BRITTON S. 
Published: April 2006

SUMMARY Helminthes, infections widespread in the tropics, are known to elicit a wide range of immunomodulation characterized by dominant Th2 type immune responses, chronic immune activation as well as up‐regulated regulatory T cell activity. Such a wide range of immunomodulation caused by helminthes may have an impact on the host's ability to cope with subsequent infections and/or may affect the efficacy of vaccination. Indeed studies conducted in humans living in helminth‐endemic areas and in animal models showed that helminth infection makes the host more permissive to mycobacterial infections and less able to benefit from vaccination. These observations have fundamental practical consequences if confirmed by large and appropriately controlled clinical studies. Eradication of worms could offer an affordable, simple and novel means to reduce the burden of the tuberculosis problem that at the moment seems to be getting out of control in sub‐Saharan Africa. This information would also be of great relevance in the design of vaccines against diseases of major public health importance, including malaria and HIV/AIDS.
Comparison of cytokine plasma levels in human African trypanosomiasis
Authors: Courtin David , Jamonneau Vincent , Mathieu Jean‐François , Koffi Mathurin , Milet Jacqueline , Yeminanga Claude Sese , Kumeso Victor Kande Betu , Cuny Gérard , Bilengue Constantin Miaka Mia , Garcia André 
Published: April 2006

SummaryBackground  Immunological studies suggest that human African trypanosomiasis (HAT) is associated with inflammatory responses. A better understanding of the complex cytokine interactions regulating HAT infections is essential to elucidate the mechanisms of generalized immunosuppression.Method  We determined levels of interleukin (IL)‐2, IL‐4, IL‐6, IL‐10, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ protein levels in plasma samples from three groups of individuals from the Democratic Republic of Congo: (i) HAT cases; (ii) seropositive individuals for whom parasite detection was negative and (ii) controls.Results  Plasma levels of six cytokines were significantly higher in HAT cases than in both controls (P < 0.003) and seropositive individuals (P < 0.016). IL‐2 and IL‐10 concentrations were significantly lower (P < 0.02) in the seropositive group than in the control one.Conclusion  Human African trypanosomiasis leads to the development of strong cytokine responses, indicating the potential involvement of IL‐2 and IL‐10 in the phenomenon of seropositivity without parasitological confirmation. This strongly suggests the involvement of immunity in this particular aspect of HAT epidemiology.