bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zirconium and Hafnium Complexes with (Allylsilyl)(η‐amidosilyl)‐η5‐cyclopentadienyl Ligands: Synthesis, Structure and Reactivity
Authors: Ramos Cristina , Royo Pascual , Lanfranchi Maurizio , Pellinghelli Maria Angela , Tiripicchio Antonio 
Published: August 2005

AbstractThe disubstituted cyclopentadiene C5H4(SiMe2Cl)[SiMe2(CH2CH=CH2)] was isolated by reaction of the lithium salt [Li{C5H4SiMe2(CH2CH=CH2)}] with SiMe2Cl2. It was then treated with NH2tBu and LiNH(2,6‐Me2C6H3) to give the (aminosilyl)cyclopentadienes C5H4[SiMe2(CH2CH=CH2)][SiMe2(NHR)], which were further deprotonated to their dilithium salts [Li2{1‐SiMe2NR‐3‐SiMe2(CH2CH=CH2)C5H3}] (R = tBu, 2,6‐Me2C6H3). Reactions of the metal halides ZrCl4(THF)2 and HfCl4 with these dilithium salts, followed by alkylation of the resulting dichloro complexes, afforded the (η1‐amidosilyl)‐η5‐cyclopentadienyl complexes [M{η5‐C5H3(SiMe2‐η1‐NR)[SiMe2(CH2CH=CH2)]}X2] (R = tBu, 2,6‐Me2C6H3; X = Cl, Me, CH2Ph; M = Zr, Hf). Only the bis(iminoacyl) complexes [M{η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}{η2‐CR=N(2,6‐Me2C6H3)}2] (M = Zr, Hf; R = Me, CH2Ph) could be isolated when the dialkylzirconium and ‐hafnium complexes were treated with CN(2,6‐Me2C6H3); these were slowly transformed into the C–C‐coupled diazametallacyclopentene compounds [M{η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}{η1‐N(2,6‐Me2C6H3)‐CR=CR‐η1‐N(2,6‐Me2C6H3)}] (R = Me, CH2Ph, M = Zr; R = Me, M = Hf) when their toluene solutions were heated to 70 °C–80 °C for long periods (2–4 d). The structural characterisation of all of the new compounds is described and the molecular structure of the dimeric dichlorozirconocene [ZrCl(μ‐Cl){η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}]2, was determined by X‐ray diffraction methods. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis, Structure, and Spectral Properties of Bis(pyrrol‐2‐yl)pyridines
Authors: Trofimov Boris A. , Vasil'tsov Alexander M. , Schmidt Elena Yu. , Zorina Nadezhda V. , Afonin Andrey V. , Mikhaleva Al'bina I. , Petrushenko Konstantin B. , Ushakov Igor A. , Krivdin Leonid B. , Belsky Vitaly K. , Bryukvina Lyubov I. 
Published: September 2005

Abstract2,6‐Bis(pyrrol‐2‐yl)pyridine (4), 2‐(pyrrol‐2‐yl)‐6‐[2‐(1‐vinylpyrrol‐2‐yl)]pyridine (5), 2,6‐bis[2‐(1‐vinylpyrrol‐2‐yl)]pyridine (6), 2,6‐dimethyl‐3,5‐bis[2‐(1‐vinylpyrrol‐2‐yl)] pyridine (9), 3‐acetyl‐2,6‐dimethyl‐5‐[2‐(1‐vinylpyrrol‐2‐yl)]pyridine (10), and 2,6‐dimethyl‐3‐(pyrrol‐2‐yl)‐5‐[2‐(1‐vinylpyrrol‐2‐yl)]pyridine (11) have been synthesized from the oximes of the corresponding diacetylpyridines in a one‐pot procedure by treatment with acetylene in MOH/DMSO systems (M = Li, K) at 80–140 °C under pressures of 25–30 atm, thus illustrating the applicability and general character of the reaction for synthesis of diverse dipyrrole‐pyridine assemblies and their N‐vinyl and acetyl derivatives. A stable 4·DMSO complex with bifurcated NH···O···HN bonding has been isolated and its X‐ray structure determined. Quantum chemical analysis at the B3LYP/6‐311G* level shows that the cis‐cis conformation of 4 is most stable, with the cis‐trans and trans‐trans forms accordingly less favorable by 3.2 and 7.8 kcal mol–1. Activation barriers of cis‐cis‐to‐cis‐trans and cis‐trans‐to‐trans‐trans dynamics are 8.3 and 9.5 kcal mol–1, respectively, which means that internal rotation of the pyrrole rings in 4 is essentially hindered. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
An “Attachment Through Coordination” Approach to Side Chain Dendritic Polymers
Authors: Andreopoulou Aikaterini K. , Kallitsis Joannis K. 
Published: September 2005

AbstractThis paper reports the synthesis of side chain dendritic polymers by a newly developed “attachment through coordination” methodology. Initially, aromatic/aliphatic polyethers bearing two uncomplexed terpyridine (tpy) groups per repeating unit are prepared, and dendritic fragments core‐functionalized with tpy‐RuIIICl3 moieties are afterwards attached onto these free tpy side groups. The two second‐generation alkoxy‐decorated side dendrons employed here provided solubility in the final polymeric system and potential for the development of ordered structures. Selective complexation between terpyridines and ruthenium ions proved to be an efficient tool for the complete coverage of all initial polymeric‐tpy groups. Perfectly substituted dendronized polymers carrying two (dendritic)tpy‐RuII‐tpy side moieties per repeating unit were thus synthesized, as demonstrated by their 1H NMR characterization. A polymerizable macromonomer diol already carrying the side (dendritic)tpy‐RuII‐tpy moieties was synthesized at the same time, enabling subsequent polymerization through the “macromonomer” growth approach. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis of Glycidol‐ and Sugar‐Derived Bicyclic β‐ and γ/δ‐Amino Acids for Peptidomimetic Design
Authors: Danieli Elisa , Trabocchi Andrea , Menchi Gloria , Guarna Antonio 
Published: September 2005

AbstractConstrained bicyclic β‐ and γ/δ‐amino acids using glycidol and sugar derivatives were developed. The synthetic strategies involved epoxide ring opening of a glycidol derivative, and subsequent coupling with sugar‐derived amines, leading to di‐ or trisubstitued bicyclic scaffolds after cyclisation with trifluoroacetic acid. Achievement of β‐ or γ/δ‐amino acids was accomplished by changing the protecting group strategy of the starting materials. Compatibility of the scaffold with solid‐phase peptide synthesis was assessed by preparing model peptidomimetics using acid‐ and base‐labile resins, thus giving a new tool for peptidomimetic design. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Efficient and Copper‐Free Sonogashira Cross‐Coupling Reaction Catalyzed by Pd(OAc)2/Pyrimidines Catalytic System
Authors: Li Jin‐Heng , Zhang Xu‐Dong , Xie Ye‐Xiang 
Published: September 2005

AbstractAn efficient and copper‐free catalyst system for Sonogashira cross‐coupling reaction is presented. In the presence of 3 mol‐% of Pd(OAc)2 and 6 mol‐% of 2‐aminopyrimidine‐4,6‐diol, various aryl iodides and bromides can be coupled smoothly with terminal alkynes to afford the corresponding coupled alkynes in moderate to excellent yields under mild conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Determination of Cadmium by Differential Pulse Adsorptive Stripping Voltammetry in the Present of Captopril
Authors: Gholivand Mohammad Bagher , Nassab Hamid Rashidi , Mosavat Ali reza 
Published: August 2005

AbstractA new method is presented for determination of cadmium based on cathodic adsorptive stripping of the complex of cadmium with captopril,1‐[(2S)‐3‐mercapto‐2‐methylpropionyl]‐L‐praline (CPL) at a hanging mercury drop electrode(HMDE). The most suitable operating conditions and parameters, such as pH, deposition potential, deposition time, ligand concentration, and others were selected and the determination of cadmium from aqueous solutions using the standard additions method was possible. Under the optimum conditions and for an accumulation time of 60 s, the measured peak current is proportional to the concentration of cadmium over the range of 1–300 nM. The limit of detection at S/N ratio of 3 was 0.3 nM and a relative standard deviation of 2.5% at 0.1 μM was achieved. The interference of other cations and anions was studied. The method was designed in order to determination of Cd in four analytical grade salts, with satisfactory results.
The Use of Thin‐Layer Electroanalysis in the Study of the Chemisorption and Anodic Oxidation of Aromatic Molecules at Smooth Polycrystalline Palladium
Authors: Chen Xiaole , Sanabria‐Chinchilla Jean , Soriaga Manuel P. 
Published: August 2005

AbstractThin‐layer electroanalytical chemistry has been used in the study of the chemisorption and anodic oxidation of hydroquinone and benzoquinone at smooth polycrystalline palladium electrode surfaces in aqueous sulfuric acid solutions. The results were reminiscent of those obtained previously on smooth polycrystalline platinum: i) At low aqueous‐solution concentrations, the diphenol is oxidatively chemisorbed to form surface‐coordinated benzoquinone oriented parallel to the surface. ii) At higher concentrations, the oxidative chemisorption occurs via CH activation to yield an edge‐oriented diphenolic species. iii) Chemisorption from benzoquinone solutions leads to species identical to those from hydroquinone solutions. iv) The extent of anodic oxidation of the chemisorbed organic depends upon the initial adsorbed‐molecule orientation: the flat‐adsorbed species are oxidized completely to carbon dioxide, whereas oxidation of the edge‐chemisorbed species yields other (unidentified) products that are chemisorbed upon regeneration of the oxide‐free surface.
Electrochemical Quartz Crystal Microbalance Studies on Cytochrome c/Polyelectrolyte Multilayer Assemblies on Gold Electrodes
Authors: Beissenhirtz M. K. , Kafka J. , Schäfer D. , Wolny M. , Lisdat F. 
Published: August 2005

AbstractPolyelectrolyte multilayer assemblies containing proteins are of interest for applications such as sensors, bioreactors, and bioelectronics. A multilayer electrode was built up by the layer‐by‐layer strategy consisting of alternating layers of cytochrome c and poly(aniline sulfonic acid). The electrode showed a linear increase of redox active protein with the number of deposited layers. The principle of electrode preparation was transferred from needle electrodes to planar surfaces in order to further the understanding of electron transfer through the layer assembly by means of electrochemical quartz crystal microbalance studies. The deposition process was followed on‐line by detection of the frequency shift of the crystals and was found to be rather fast (minutes). The total mass deposited was found to correlate well with the electrochemical response of the immobilized cyt.c. Furthermore, the influence of the polyelectrolyte was investigated by addition of PSS to the PASA solution. The strong interaction of the former polyelectrolyte seemed to hinder the electron transfer although a multilayer formation was proved. Dilution of the protein solution with redox inactive apo‐cyt.c led to a strong decrease of the voltammetric signal, well beyond the percentage of apo‐cyt.c inside the assembly. Thus, arguments for an electron transfer via protein–protein interaction were found.
Voltammetric Sensing of Trace Metals at a Poly(pyrrole‐malonic acid) Film Modified Carbon Electrode
Authors: Heitzmann Marie , Basaez Luis , Brovelli Francisco , Bucher Christophe , Limosin Danielle , Pereira Eduardo , Rivas Bernabé L. , Royal Guy , Saint‐Aman Eric , Moutet Jean‐Claude 
Published: August 2005

AbstractThe oxidative electropolymerization of the (3‐pyrrol‐1‐ylpropyl)malonic acid monomer 1 is a simple and reproducible one‐step procedure for the synthesis of complexing polymer film modified electrodes, which have been applied to the electroanalysis of Cu(II), Pb(II), Cd(II) and Hg(II) ions by preconcentration upon complexation, followed by anodic stripping analysis. The detection limits were determined from square‐wave voltammetry at 0.5 nM, 5 nM, 50 nM and 0.2 μM for Pb(II), Cu(II), Hg(II) and Cd(II), respectively, after 10 min preconcentration. The modified electrodes showed a better selectivity toward copper(II) ions. Analysis of copper in a tap water sample agreed well with ICPMS analysis results.
A Reference Electrode for Electrochemical and Cryoelectrochemical Use in Tetrahydrofuran Solvent
Authors: Paddon Christopher A. , Compton Richard G. 
Published: August 2005

AbstractWe report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc+) are prepared to give a 4 mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4 mM to 40 μM and 20 °C to −45 °C respectively. In addition, it is shown by steady–state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc+) otherwise seen in THF is suppressed by ion‐pairing with PF$\rm{ {_{6}^{-}}}$ using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte.
Electrochemical Properties and Application of Mixed Silver‐Bismuth Electrodes
Authors: Skogvold Silje M. , Mikkelsen Øyvind , Schrøder Knut H. 
Published: August 2005

AbstractElectrochemical properties of silver electrodes with 2, 4, 6, 10 and 15% bismuth have systematically been investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Increased overpotential towards hydrogen evolution reaction (HER) was found as a result of increasing amount of added bismuth. This was also demonstrated in acid solution where zinc was successfully detected on mixed electrodes, but failed on pure silver electrodes. Formation and decomposition of oxide products formed on the different electrode surfaces were studied by cyclic voltammetry, and in addition to known species found on sliver, also peaks attributed to bismuth were achieved and examined. Zinc, cadmium, and lead were measured in the low μg/L range on the mixed electrodes, and good linearity (r2=0.998) was found for 2 to 10 μg/L. Lead was measured down to 0.1 μg/L. Further it was found in DPASV that the zinc peak significantly shifted towards a more negative value with increasing amount of bismuth in the silver electrodes. The same was also observed for cadmium and lead, but in a less extent. Finally a silver electrode containing 15% bismuth was used for continuous analyses in a polluted river for 6 weeks.
Electrochemical Characterization of Screen‐Printed Carbon Electrodes by Modification with Chitosan Oligomers
Authors: Lee Shyh‐Hwang , Fang Hung‐Yuan , Chen Wen‐Chang 
Published: August 2005

AbstractThe kinetics on the current amplification of the disposable screen‐printed carbon electrodes (SPCEs) by modification with chitosan oligomers (COs), coupled with the Fe(CN)$\rm{ {_{6}^{3-/4-}}}$ redox system, were characterized with the variation of electron‐transfer rate constant (k°) and the electroactive area (Aea) at electrode surface. The nonlinear response characteristics of peak currents with increase in Fe(CN)$\rm{ {_{6}^{3-}}}$ bulk concentrations complicated the estimation of Aea in cyclic voltammetric analysis. Upon the modification with COs, the rate constant of SPCEs was not much influenced and the current amplification was characterized with the increase of a better estimated Aea, obtained from electrochemical impedance measurements and verified with the reciprocal of electron‐transfer resistances linearly proportional to the Fe(CN)$\rm{ {_{6}^{3-/4-}}}$ bulk concentrations. It is hereby provided for an evaluation of the carbon based electrodes with modification.
Laccase Biosensor Based on N‐Succinimidyl‐3‐Thiopropionate‐Functionalized Gold Electrodes
Authors: Mena M. L. , Carralero V. , González‐Cortés A. , Yáñez‐Sedeño P. , Pingarrón J. M. 
Published: August 2005

AbstractA laccase biosensor, in which the enzyme was immobilized on N‐succinimidyl‐3‐thiopropionate (NSTP)‐modified gold electrodes, is reported. Two different approaches for the preparation of N‐succinimidyl‐terminated monolayers were evaluated: a) activation of a preformed 3‐mercaptopropionic acid (MPA) SAM by reaction with 1‐(3‐dimethylaminopropyl)‐ 3‐ethylcarbodiimide (EDC) and N‐hydroxysulfosuccinimide (NHS); b) assembling of dithiobisuccinimidyl propionate (DTSP). NSTP‐modified electrodes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Biosensors prepared by covalent binding of the enzyme and by cross‐linking with glutaraldehyde atop NSTP‐modified electrodes were compared in terms of sensitivity and operational range for caffeic acid. A much better analytical performance was found using the latter approach. Variables affecting the amperometric detection (enzyme loading, pH and applied potential) were optimized. The operational stability and characteristics of functioning of the laccase biosensor in terms of repeatability of the amperometric measurements, reproducibility with different biosensors and useful lifetime, were evaluated. The kinetic parameters of the enzyme reactions and the analytical characteristics of the corresponding calibration plots were calculated for eight phenolic compounds. Limits of detection of 0.07 μM, 0.05 μM and 0.09 μM were obtained for caffeic acid, catechol and 3,4‐dihydroxyphenylacetic acid (DOPAC), respectively. The practical usefulness of the developed biosensor was evaluated by estimating the “pool” of phenolic compounds in olive oil mill wastewaters (OMW).
Particle clusters in gravel‐bed rivers: an experimental morphological approach to bed material transport and stability concepts
Authors: Wittenberg Lea , Newson Malcolm D. 
Published: September 2005

AbstractStructured gravel river beds clearly exert a major influence on bed stability. Indexing structural stability by field measurements of bed strength neglects the processes operating to entrain and transport bed material in different parts of each structure. This study takes a morphological approach to interpreting the critical processes, using particle tracing to determine the movement of individual cluster particles over a range of flood event magnitudes and durations. The experiment was carried out on the River South Tyne, UK; it uses flow hydrographs measured nearby and also benefits from previous studies of historical development, channel morphology and sediment transport at the same site. More than 30 clusters were monitored over a seven‐month period during which clusters occupied 7–16 per cent of the bed. Threshold flows delimiting three apparently contrasting bed sediment process regimes for cluster particles are tentatively set at 100 m3 s−1 and 183 m3 s−1; durations of flow at these levels are critical for cluster development, rather than flow peak values. Wake particles are transported most easily. Flow straightening in the wandering channel planform reduces the stability of clusters, since mechanical strength is markedly reduced by this change of direction. The overall area covered by clusters between significant transport events varies little, implying a dynamic equilibrium condition. Copyright © 2005 John Wiley & Sons, Ltd.
On coupling the Reynolds‐averaged Navier–Stokes equations with two‐equation turbulence model equations
Authors: Lee Seungsoo , Whan Choi Dong 
Published: September 2005

AbstractTwo methods for coupling the Reynolds‐averaged Navier–Stokes equations with the q–ω turbulence model equations on structured grid systems have been studied; namely a loosely coupled method and a strongly coupled method. The loosely coupled method first solves the Navier–Stokes equations with the turbulent viscosity fixed. In a subsequent step, the turbulence model equations are solved with all flow quantities fixed. On the other hand, the strongly coupled method solves the Reynolds‐averaged Navier–Stokes equations and the turbulence model equations simultaneously. In this paper, numerical stabilities of both methods in conjunction with the approximated factorization‐alternative direction implicit method are analysed. The effect of the turbulent kinetic energy terms in the governing equations on the convergence characteristics is also studied. The performance of the two methods is compared for several two‐ and three‐dimensional problems. Copyright © 2005 John Wiley & Sons, Ltd.
Tensile deformation of NiTi wires
Authors: Gall Ken , Tyber Jeff , Brice Valerie , Frick Carl P. , Maier Hans J. , Morgan Neil 
Published: September 2005

AbstractWe examine the structure and properties of cold drawn Ti‐50.1 at % Ni and Ti‐50.9 at % Ni shape memory alloy wires. Wires with both compositions possess a strong <111> fiber texture in the wire drawing direction, a grain size on the order of micrometers, and a high dislocation density. The more Ni rich wires contain fine second phase precipitates, while the wires with lower Ni content are relatively free of precipitates. The wire stress–strain response depends strongly on composition through operant deformation mechanisms, and cannot be explained based solely on measured differences in the transformation temperatures. We provide fundamental connections between the material structure, deformation mechanisms, and resulting stress–strain responses. The results help clarify some inconsistencies and common misconceptions in the literature. Ramifications on materials selection and design for emerging biomedical applications of NiTi shape memory alloys are discussed. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Hydrogel optimization for cultured elastic chondrocytes seeded onto a polyglycolic acid scaffold*
Authors: Terada Shinichi , Yoshimoto Hiroshi , Fuchs Julie R. , Sato Michio , Pomerantseva Irina , Selig Martin K. , Hannouche Didier , Vacanti Joseph P. 
Published: September 2005

AbstractThe purpose of this study was to compare the effect of different hydrogels on the production of tissue‐engineered cartilage based on polyglycolic acid (PGA). Chondrocytes were isolated from adult sheep auricles. Alginate, Type I collagen, methylcellulose, and pluronic F127 hydrogels were evaluated, as were controls prepared without hydrogels. Proliferated chondrocytes were mixed with each hydrogel at 20 × 106 cells/mL and seeded onto PGA (1 × 1 × 0.2 cm, n = 60). The constructs were cultured with serum‐free medium containing 5 ng/mL TGF‐β2 and 5 ng/mL des(1‐3)IGF‐I in rotational bioreactors for up to 6 weeks. The cellular morphology, histology, and biochemistry were analyzed. Type I collagen, methylcellulose, and pluronic F127 displayed improved cartilage matrix deposition in terms of histology and biochemistry compared to alginate. It was not concluded that the combined seeding of chondrocytes and hydrogels on a PGA scaffold had significantly better effects than cell seeding without hydrogels. However, the histology and other useful findings in this ECM analyses suggested that Type I collagen and MC hydrogels were the best candidates for cartilage regeneration, because of their stimulation for chondrocyte proliferation in a three‐dimensional culture as well as cartilage regeneration. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Synthesis and characterization of novel polyanhydrides with tailored erosion mechanisms
Authors: Torres María P. , Vogel Brandon M. , Narasimhan Balaji , Mallapragada Surya K. 
Published: September 2005

AbstractWe have designed a new synthesis route to create polyanhydrides based on monomers that contain hydrophilic entities within highly hydrophobic backbones. The method results in polyanhydrides that can be easily processed into drug‐containing tablets. The synthesis, characterization, and erosion studies of polyanhydride copolymers based on 1,6‐bis(p‐carboxyphenoxy)hexane (CPH), which is highly hydrophobic, and 1,8‐bis(p‐carboxyphenoxy)‐3,6‐dioxaoctane (CPTEG), which has hydrophilic oligomeric ethylene glycol segments in the monomer unit, was performed using a combination of molecular spectroscopy, thermal analysis, gravimetry, and scanning electron microscopy. The studies demonstrate that by increasing the CPH content in the CPTEG:CPH copolymers, the erosion of the system can be tailored from bulk‐eroding to surface‐eroding mechanism. These systems have promise as protein carriers. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006