bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short melamine fiber filled nitrile rubber composites
Authors: R. S. Rajeev , Bhowmick Anil K. , De S. K. , Bandyopadhyay S. 
Published: August 2003

AbstractThis article reports the development of a new composite based on acrylonitrile butadiene rubber (NBR) and melamine fiber. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to study the effect of a dry bonding system in improving the adhesion between the fiber and the matrix. Mechanical properties of the composites are improved in the presence of the dry bonding system comprising of resorcinol, hexamethylene tetramine (hexamine), and hydrated silica. SEM and atomic force microscopic (AFM) images show that there are distinct changes in the fiber‐matrix interphase with the incorporation of the dry bonding system. A strong attachment of the fiber to the matrix is found in the SEM photomicrographs of the tensile fracture surfaces of the composites containing the dry bonding system. AFM section analysis and surface plot show that the improvement in tensile strength and modulus in the presence of the dry bonding system is due to the formation of a well‐defined interphase between the fiber and the matrix. The width of the interphase between the fiber and the matrix is increased in the presence of the dry bonding system, which is reflected in the mechanical properties and aging characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 544–558, 2003
Behavior of acrylic acid–itaconic acid hydrogels in swelling, shrinking, and uptakes of some metal ions from aqueous solution
Authors: Rodríguez Elena , Katime Issa 
Published: August 2003

AbstractAn experimental research of the absorption properties of metal ions onto synthetic hydrogel obtained by solution polymerization of acrylic acid and itaconic acid in presence of N,N′‐methylenebisacrylamide as crosslinking agent was carried out. The swelling behavior in aqueous salt solutions was studied as a function of divalent cation concentration (Cu2+, Zn2+, Ni2+, Co2+, Cd2+, Pb2+, Hg2+) in the external solution ranging from 10−5 to 1M, at 25°C. The ability of these hydrogels to bind cations was measured at different pH values and metal ion concentrations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 530–536, 2003
Quality control in scholarly publishing: A new proposal
Authors: Mizzaro Stefano 
Published: August 2003

AbstractThe Internet has fostered a faster, more interactive and effective model of scholarly publishing. However, as the quantity of information available is constantly increasing, its quality is threatened, since the traditional quality control mechanism of peer review is often not used (e.g., in online repositories of preprints, and by people publishing whatever they want on their Web pages).This paper describes a new kind of electronic scholarly journal, in which the standard submission‐review‐publication process is replaced by a more sophisticated approach, based on judgments expressed by the readers: in this way, each reader is, potentially, a peer reviewer. New ingredients, not found in similar approaches, are that each reader's judgment is weighted on the basis of the reader's skills as a reviewer, and that readers are encouraged to express correct judgments by a feedback mechanism that estimates their own quality. The new electronic scholarly journal is described in both intuitive and formal ways. Its effectiveness is tested by several laboratory experiments that simulate what might happen if the system were deployed and used.
Efficient Synthesis of 2‐Alkylidene‐3‐iminoindoles, Indolo[1,2‐b]isoquinolin‐5‐ones, δ‐Carbolines, and Indirubines by Domino and Sequential Reactions of Functionalized Nitriles
Authors: Langer Peter , Anders Joachim T. , Weisz Klaus , Jähnchen Judith 
Published: August 2003

AbstractThe sodium hydride mediated cyclization of arylacetonitriles with oxalic acid bis(imidoyl) dichlorides, aza‐analogues of oxalyl chloride, afforded functionalized 2‐alkylidene‐3‐iminoindoles with very good regio‐ and E/Z selectivity. Excellent chemoselectivities were observed for functionalized substrates. Based on these results a domino “cyclization–lactamization” reaction of bis(imidoyl) chlorides with methyl 2‐(cyanomethyl)benzoate was developed. This process allowed a convenient one‐pot synthesis of indolo[1,2‐b]isoquinolin‐5‐ones related to tryptanthrin. A new and convenient synthesis of δ‐carbolines by intramolecular electrocyclization–elimination reactions of 2‐alkylidene‐3‐iminoindoles was developed. It was shown that δ‐carbolines selectively bind to triplex or duplex DNA (intercalation). Indirubine analogues were prepared by deprotection and lactonization of functionalized 2‐alkylidene‐3‐iminoindoles.
Pluronic L61 Accelerates Flip–Flop and Transbilayer Doxorubicin Permeation
Authors: Krylova Oxana O. , Melik‐Nubarov Nikolay S. , Badun Gennadii A. , Ksenofontov Alexander L. , Menger Fred M. , Yaroslavov Alexander A. 
Published: August 2003

AbstractIt has recently been found that Pluronics (block copolymers of ethylene oxide, EO, and propylene oxide, PO) favor the permeability and accumulation of anthracycline antibiotics, for example doxorubicin (Dox), in tumor cells. In an effort to understand these results, the interaction of EO2/PO32/EO2 (Pluronic L61) with unilamellar egg yolk vesicles (80–100 nm in diameter) was examined. A partition coefficient Kp=[Pl]membrane/[Pl]water=45 was determined. This corresponds to adsorption of about 20 polymer molecules to the surface of each vesicle in a 20 μM polymer solution. Despite this rather weak adsorption, Pluronic has a substantial effect upon the transmembrane permeation rate of Dox and upon the phospholipid flip–flop rate within the bilayers. Thus, the Dox permeation rate increases threefold and the flip–flop rate increases sixfold in 20 μM Pluronic. The two rates increase linearly with the amount of adsorbed polymer. The obvious ability of Pluronics to increase the mobility of membrane components may have important biomedical consequences.
Tracking Chemical Kinetics in High‐Throughput Systems
Authors: Boelens Hans F. M. , Iron David , Westerhuis Johan A. , Rothenberg Gadi 
Published: August 2003

AbstractCombinatorial chemistry and high‐throughput experimentation (HTE) have revolutionized the pharmaceutical industry—but can chemists truly repeat this success in the fields of catalysis and materials science? We propose to bridge the traditional “discovery” and “optimization” stages in HTE by enabling parallel kinetic analysis of an array of chemical reactions. We present here the theoretical basis to extract concentration profiles from reaction arrays and derive the optimal criteria to follow (pseudo)first‐order reactions in time in parallel systems. We use the information vectorfand introduce in this context theinformation gain ratio,χr, to quantify the amount of useful information that can be obtained by measuring the extent of a specified reactionrin the array at any given time. Our method is general and independent of the analysis technique, but it is more effective if the analysis is performed on‐line. The feasibility of this new approach is demonstrated in the fast kinetic analysis of the carbon–sulfur coupling between 3‐chlorophenylhydrazonopropane dinitrile andβ‐mercaptoethanol. The theory agrees well with the results obtained from 31 repeated CS coupling experiments.
Preparative and Electrochemical Investigations on the Electron Sponge Behavior of Cobalt Telluride Clusters: CO Substitution in [Co11Te7(CO)10]n− Ions (n=1, 2) by PMe2Ph and Crystal Structure of [Co11Te7(CO)5(PMe2Ph)5]
Authors: Brunner Henri , Cattey Hélène , Meier Walter , Mugnier Yves , Stückl A. Claudia , Wachter Joachim , Wanninger Robert , Zabel Manfred 
Published: August 2003

AbstractThe reaction of the cluster salts [Cp${^{{\ast}}_{2}}$Nb(CO)2]n[Co11Te7(CO)10] (Cp*=C5Me5; n=1, 2) with excess PMe2Ph gave the neutral, dark brown clusters [Co11Te7(CO)6(PMe2Ph)4] (5) and [Co11Te7(CO)5(PMe2Ph)5] (6) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6 was determined by X‐ray crystallography. Like its precursor anion, it consists of a pentagonal‐prismatic [Co11Te7] core, but with a ligand sphere composed of five CO and five PMe2Ph ligands. Detailed electrochemical studies of both reactions reveal that a stepwise substitution of CO ligands in the initial cluster anions takes place leading to intermediate [Co11Te7(CO)10−m(PMe2Ph)m]n− ions (m=1–5; n=1, 2). Each of these intermediates is distinguished by at least one oxidation and two reduction waves, giving rise to a total of 21 redox couples and 27 electroactive species. The electron sponge character of the new compounds is particularly pronounced in 5, which exhibits charges n between +1 and −4 corresponding to metal valence electron counts of between 146 and 151.
Galactose Oxidase Models: Tuning the Properties of CuII–Phenoxyl Radicals
Authors: Philibert Aurélie , Thomas Fabrice , Philouze Christian , Hamman Sylvain , Saint‐Aman Eric , Pierre Jean‐Louis 
Published: August 2003

AbstractFour tripodal ligands with an N3O coordination sphere were synthesized: (2‐hydroxy‐3‐tert‐butyl‐5‐nitrobenzyl)bis(2‐pyridylmethyl)amine (LNO2H), (2‐hydroxy‐3‐tert‐butyl‐5‐ fluorobenzyl)bis(2‐pyridylmethyl)amine (LFH), (2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)bis(2‐pyridylmethyl)amine (LtBuH) and (2‐hydroxy‐3‐tert‐butyl‐5‐methoxybenzyl)bis(2‐pyridylmethyl)amine (LOMeH). Their square‐pyramidal copper(II) complexes, in which the phenol subunit occupies an axial position, were prepared and characterized by X‐ray crystallography and UV/Vis and EPR spectroscopy. The phenolate moieties of the copper(II) complexes of LtBuH and LOMeH were electrochemically oxidized to phenoxyl radicals. These complexes are EPR‐active (S=1), highly stable (kdecay=0.008 min−1 for [CuII(LOMe.)(CH3CN)]2+) and stoichiometrically oxidise benzyl alcohol. Two additional tripodal ligands providing an N2O2 coordination sphere were also studied: (2‐pyridylmethyl)(2‐hydroxy‐3‐tert‐butyl‐5‐methoxybenzyl)(2‐hydroxy‐3‐tert‐butyl‐5‐nitrobenzyl)amine (L′OMeNO2H2) and (2‐pyridylmethyl)bis(2‐hydroxy‐3‐tert‐butyl‐5‐ methoxy)benzylamine (L′OMe2H2). Their copper(II) complexes were isolated as dimers ([Cu${^{{\rm II}}_{2}}$(L′OMe2)2], [Cu${^{{\rm II}}_{2}}$(L′OMeNO2)2]) that are converted to monomers on addition of pyridine. The complexes were investigated by X‐ray crystallography and UV/Vis and EPR spectroscopy. Their one‐electron electrochemical oxidation leads to copper(II)–phenoxyl systems that are less stable than those of the N3O complexes. The N2O2 complexes are more reactive than the N3O analogues: they aerobically oxidize benzyl alcohol to benzaldehyde at a higher rate, as well as ethanol to acetaldehyde (40–80 turnovers).
Supramolecular [6]Chochin and “Big Mac” Made from Chiral Piedfort Assemblies
Authors: Czugler Mátyás , Weber Edwin , Párkányi László , Korkas Petros P. , Bombicz Petra 
Published: August 2003

AbstractFacile chemical synthesis of the natural chiral‐pool‐derived host 1 and its subsequent crystallization (“supramolecular synthesis”) from different solvents yielded crystalline assemblies. Crystal structure determinations of five of the so formed solvent‐inclusion compounds (1 a–1 e) reveal hexagonal symmetries in four cases. The structural characteristics of these chiral host–guest ensembles with varying stoichiometries can be best described as assemblies formed through intra‐pair hydrogen bridges of host molecules into Piedfort pairs of differing complexity. Hitherto undescribed, these Piedfort pairs also form even larger regular assemblies that we designate “Big Mac”‐like shapes. In the only nonhexagonal case, six independent host molecules form a huge supramolecular analogue of [6]benzocyclophane, also known as [6]chochin, extending this giant supermolecule through intermolecular hydrogen bonds into macroscopic (mm‐size) dimensions. As all these crystals are inherently chiral, and new model systems for solid‐state applications can be envisaged.
Chemistry of Bridging Phosphanes: PdI Dimers Bearing 2,5‐Dipyridylphosphole Ligands
Authors: Leca François , Sauthier Mathieu , Deborde Valérie , Toupet Loïc , Réau Régis 
Published: August 2003

AbstractTwo synthetic routes to PdI dimers that feature a bridging 1‐phenyl‐ and 1‐cyclohexyl‐2,5‐di(2‐pyridyl)phosphole ligand, 3 a and 3 b, respectively, are described. The first involves a conproportionation process between PdII and Pd0 complexes, while the second involves ligand displacement from a preformed PdI dimer. Both routes are operable for 1‐phenylphosphole 1 a, whereas the former failed with 1‐cyclohexylphosphole 1 b. A mechanistic study revealed that the conproportionation pathway implies a reversible oxidative addition of the PC(phenyl) bond of PdII‐coordinated 1 a to Pd0 leading to a bimetallic PdII complex 5. The structures of complexes 3 a and 3 b were studied by means of X‐ray diffraction. The similarity of these solid‐state structures suggests that the bridging mode of the P atom is due to μ‐1κN:1,2κP:2κN coordination of ligands 1 a, b. The electrochemical behaviour and UV/Vis absorption properties of complexes 3 a, b are reported. Complex 3 a is inert towards CO, PPh3 and 1,3‐dipoles. It reacted with dimethylacetylene dicarboxylate to give complex 6 as a result of insertion of the alkyne into the PdPd bond. X‐ray diffraction studies of complexes 5 and 6 are also presented.
Ab Initio Study on the Mechanism of the Atmospheric Reaction OH+O3→HO2+O2
Authors: Peiró‐García Julio , Nebot‐Gil Ignacio 
Published: August 2003

AbstractThe atmospheric reaction (1) OH + O3→HO2 + O2 was investigated theoretically by using MP2, QCISD, QCISD(T), and CCSD(T) methods with various basis sets. At the highest level of theory, namely, QCISD, the reaction is direct, with only one transition state between reactants and products. However, at the MP2 level, the reaction proceeds through a two‐step mechanism and shows two transition states, TS1 and TS2, separated by an intermediate, Int. The different methodologies employed in this paper consistently predict the barrier height of reaction (1) to be within the range 2.16–5.11 kcal mol−1, somewhat higher than the experimental value of 2.0 kcal mol−1.
Evaluation of one‐ and two‐equation low‐Re turbulence models. Part I—Axisymmetric separating and swirling flows
Authors: Yaras M. I. , Grosvenor A. D. 
Published: August 2003

AbstractThis first segment of the two‐part paper systematically examines several turbulence models in the context of three flows, namely a simple flat‐plate turbulent boundary layer, an axisymmetric separating flow, and a swirling flow. The test cases are chosen on the basis of availability of high‐quality and detailed experimental data. The tested turbulence models are integrated to solid surfaces and consist of: Rodi's two‐layer k–ε model, Chien's low‐Reynolds number k–ε model, Wilcox's k–ω model, Menter's two‐equation shear‐stress‐transport model, and the one‐equation model of Spalart and Allmaras. The objective of the study is to establish the prediction accuracy of these turbulence models with respect to axisymmetric separating flows, and flows of high streamline curvature. At the same time, the study establishes the minimum spatial resolution requirements for each of these turbulence closures, and identifies the proper low‐Mach‐number preconditioning and artificial diffusion settings of a Reynolds‐averaged Navier–Stokes algorithm for optimum rate of convergence and minimum adverse impact on prediction accuracy. Copyright © 2003 John Wiley & Sons, Ltd.
Phosphorylation of starch and dextrin by dry‐heating in the presence of phosphate, and their calcium phosphate‐solubilizing ability
Authors: Nakano Tomoki , Salvador Arvin S. , Tamochi Jiro , Sugimoto Yasushi , Ibrahim Hisham R. , Toba Yasuhiro , Aoe Seiichiro , Kawakami Hiroshi , Aoki Takayoshi 
Published: August 2003

AbstractStarch and dextrin were phosphorylated by dry‐heating in the presence of phosphate, and their properties were examined. The phosphorylation of starch was accelerated with decreasing moisture, rising incubation temperature and prolongation of the incubation period. However, a rise in incubation temperature, and lengthened incubation period caused increased browning and degradation. A decrease in the pH from 5.5 to 3.0 resulted in a modest increase of phosphorylation, but also marked browning and degradation. When potato starch was phosphorylated at 140°C and pH 5.5 for 24 h, its phosphorus content was increased up to 3.47%, with fewer side reactions. Phosphorlylated starch and dextrin had calcium phosphate‐solubilizing abitity. Phosphorylated dextrin with 2.42% phosphorus had about half the calcium phosphate‐solubilizing ability of casein phosphopeptide (CPP). The possibility of substituting of phosphorylated starch and dextrin for CPP as a calcium phosphate‐absorption enhancing material is discussed herein.
Bayesian analysis of multilocus association in quantitative and qualitative traits
Authors: Kilpikari Riika , Sillanpää Mikko J. 
Published: August 2003

AbstractA Bayesian model‐based method for multilocus association analysis of quantitative and qualitative (binary) traits is presented. The method selects a trait‐associated subset of markers among candidates, and is equally applicable for analyzing wide chromosomal segments (genome scans) and small candidate regions. The method can be applied in situations involving missing genotype data. The number of trait loci, their marker positions, and the magnitudes of their gene effects (strengths of association) are all estimated simultaneously. The inference of parameters is based on their posterior distributions, which are obtained through Markov chain Monte Carlo simulations. The strengths of the approach are: 1) flexible use of oligogenic models with unknown number of loci, 2) performing the estimation of association jointly with model selection, and 3) avoidance of the multiple testing problem, which typically complicates the approaches based on association testing. The performance of the method was tested and compared to the multilocus conditional search procedure by analyzing two simulated data sets. We also applied the method to cystic fibrosis haplotype data (two‐locus haplotypes), where gene position has already been identified. The method is implemented as a software package, which is freely available for research purposes under the name BAMA.Genet Epidemiol25:122–135, 2003. © 2003 Wiley‐Liss, Inc.
Optimal two‐stage genotyping in population‐based association studies
Authors: Satagopan Jaya M. , Elston Robert C. 
Published: August 2003

AbstractWe propose a cost‐effective two‐stage approach to investigate gene‐disease associations when testing a large number of candidate markers using a case‐control design. Under this approach, all the markers are genotyped and tested at stage 1 using a subset of affected cases and unaffected controls, and the most promising markers are genotyped on the remaining individuals and tested using all the individuals at stage 2. The sample size at stage 1 is chosen such that the power to detect the true markers of association is 1−β1 at significance level α1. The most promising markers are tested at significance level α2 at stage 2. In contrast, a one‐stage approach would evaluate and test all the markers on all the cases and controls to identify the markers significantly associated with the disease. The goal is to determine the two‐stage parameters (α1, β1, α2) that minimize the cost of the study such that the desired overall significance is α and the desired power is close to 1−β, the power of the one‐stage approach. We provide analytic formulae to estimate the two‐stage parameters. The properties of the two‐stage approach are evaluated under various parametric configurations and compared with those of the corresponding one‐stage approach. The optimal two‐stage procedure does not depend on the signal of the markers associated with the study. Further, when there is a large number of markers, the optimal procedure is not substantially influenced by the total number of markers associated with the disease. The results show that, compared to a one‐stage approach, a two‐stage procedure typically halves the cost of the study. Genet Epidemiol 25:149–157, 2003. © 2003 Wiley‐Liss, Inc.
Lysine 445 is a molecular indicator of subunit‐specific AMPA receptor binding domains
Authors: Sessoms Sikes J. Suzanne , Verdoorn Todd 
Published: August 2003

AbstractDespite strong homology between subunits of AMPA‐type glutamate receptors, heteromeric assemblies in different brain regions vary in subunit composition and functional properties. We have previously shown that charge substitution at K445 decreases the apparent potency of AMPA for GluR‐A receptors, although an analogous mutation is a low conductance B subunit of AB heteromers did not diminish AMPA potency. To examine the subunit selectivity of K445, we now measure the apparent potency of AMPA and glutamate at recombinant homomeric receptors containing the high‐conductance, unedited (586Q) GluR‐B subunit (GluR‐B(Q)) using two‐electrode voltage‐clamp. We find the decrease in apparent potency of AMPA is recapitulated for homomeric GluR‐B(Q)K449E receptors, and is rescued by coexpression with wild‐type GluR‐A. These data are consistent with the hypothesis that AMPAR subunit composition is critical to agonist‐dependent receptor activation, and suggest that GluR‐A plays a dominant role in mediating
receptor activation by AMPA.
Thermally stable porous supramolecular frameworks based on the metal and π–π stacking directed self‐assembly of 2,6‐pyridyldicarboxylic acid bis‐4‐pyridylamide
Authors: Noveron Juan C. , Chatterjee Biswaroop , Arif Atta M. , Stang Peter J. 
Published: August 2003

AbstractWe report the formation of two thermally stable supramolecular structures based on 2,6‐pyridyldicarboxylic acid bis‐4‐pyridylamide (PyI) and bis(hexafluoroacetylacetonato)manganese(II) that exhibits a microporous structure with cavities bearing hydrogen bonding motifs that can enclathrate acetone and methanol molecules via well‐positioned hydrogen bonding interactions. Single‐crystal x‐ray diffraction in combination with thermogravimetric analysis and X‐ray powder diffraction (XRPD) studies were utilized to study the structure and thermal behavior of trans‐[Mn(hfacac)2(PyI)2]·2(CH3)2CO (1) and trans‐[Mn(hfacac)2(PyI)2]·2CH3OH (2). Our studies indicated that 1 and 2 are isostructural with respect to their supramolecular assembly and trap solvent molecules along the crystallographic b direction via the inwardly directed hydrogen bonding motifs of the PyI component. These solvent molecules can be thermally removed to generate a crystalline material with micropores bearing hydrogen bonding rich sites within an overall supramolecular matrix similar to 1 and 2. The removal of the guest solvent molecules is reversible and can be followed with XRPD. Copyright © 2003 John Wiley & Sons, Ltd.
Variation of the π‐electron delocalization in exocyclically substituted heptafulvene derivatives
Authors: Stępień Beata T. , Krygowski Tadeusz M. , Cyrański Michał K. 
Published: August 2003

AbstractEleven mono‐ and eight di‐exocyclically substituted heptafulvene derivatives were optimized at the B3LYP/6–311+G** level of theory. The aromaticity indices REC (ring energy content), Schleyer's NICS,3He NMR chemical shift and anisotropy of magnetic susceptibility and the geometry based descriptor HOMA were used to estimate the extent of cyclic π‐electron delocalization due to the substituent effect. A dramatic variation of these indices was found for electron‐accepting substituents indicating great sensitivity of the π‐electron structure of the ring. In the case of monosubstituted derivatives all indices exhibit a perfect or at least very good equivalence, whereas for disubstituted species the mutual correlations are markedly worse. Copyright © 2003 John Wiley & Sons, Ltd.