bluuebunny/crossref_metadata_2025 huggingface dataset:
Tax‐loss carryforward and futures hedging
Authors: Lien Donald , Metz Michael
Published: October 2002

Our research is motivated by the Corn Products vs Arkansas Best Supreme court decisions that brought on the controversy of the tax treatment of gains and losses from futures hedging. The usefulness of a futures contract as risk management tool depends on the tax code. In this paper we address implications of capital treatment of futures positions (disallowing offset for tax purposes) when tax‐loss carryover is allowed. Our analysis utilizes a two‐period model to capture the inter‐temporal effects. We investigate the optimal hedge ratios under these scenarios analytically where possible, and numerically where necessary. Copyright © 2002 John Wiley & Sons, Ltd.
Equity and arbitration in major league baseball
Authors: Fizel John , Krautmann Anthony C. , Hadley Lawrence
Published: October 2002

Equity theory argues that workers examine their job performance and salaries relative to workers in comparable situations. If compensation is inequitable, workers may adjust their behavior. We test the hypothesis that an arbitration‐eligible player in Major League Baseball is more likely to file for arbitration and/or proceed to an arbitration hearing if he feels he is underpaid relative to his comparison other. Bivariate probit is used to increase efficiency and correct for the sample bias in estimating decision models within the two‐step arbitration process. The results indicate that equity is a significant predictor of a player's unilateral decision to file but is an insignificant determinant of going to a hearing because of offsetting responses to equity by player and owner. Copyright © 2002 John Wiley & Sons, Ltd.
Design of fault‐tolerant networks for satellites (TWTA redundancy)
Authors: Bermond Jean‐Claude , Darrot Eric , Delmas Olivier
Published: October 2002

This article deals with the design of networks to be placed on satellites. These networks should connect inputs (corresponding to signals arriving at the satellite) to outputs (corresponding to amplifiers, also called Traveling Wave Tube Amplifiers (TWTA)), even in case of failures of amplifiers. The networks are made of links and expensive switches; hence, we want to minimize the number of switches subject to the following conditions: Each input and each output is connected to exactly one switch; each switch is adjacent to exactly four links; there are n inputs and n + k outputs; among the n + k outputs, k can fail permanently; and, finally, all the input signals should be sent to valid amplifiers, that is, outputs, via disjoint paths. So, the aim is to design networks having as few switches as possible and satisfying the following property: There exist n edge‐disjoint paths from the n inputs to any set of n outputs chosen from the n + k total number of outputs. We call such networks valid k‐fault tolerant networks. Let 𝒩(n, k) denote the minimum number of switches of a valid network with n inputs, n + k outputs, and k output failures. In this article, we give some details on the problem and some preliminary results such as the fact that 𝒩(n, k) ≥ n. We also propose a general construction which yields (under some conditions) 𝒩(n + n′, k) ≤ 𝒩(n, k) + 𝒩(n′, k). © 2002 Wiley Periodicals, Inc.
On the online shortest path problem with limited arc cost dependencies
Authors: Waller S. Travis , Ziliaskopoulos Athanasios K.
Published: October 2002

This paper is concerned with the stochastic shortest path problem with recourse when limited forms of spatial and temporal arc cost dependencies are accounted for. Recourse is defined as the opportunity for a decision maker to reevaluate his or her remaining path when en‐route information is available. Formulations with recourse typically provide opportunities for corrective actions when information becomes available; information here is modeled as arc cost dependencies, defined as spatial and temporal. System properties are stated and proved and solution algorithms are developed for limited cases of spatial and temporal arc cost dependencies. The numerical results verify some of the theoretical insights and demonstrate the applicability of the introduced algorithms. © 2002 Wiley Periodicals, Inc.
Multistars and directed flow formulations
Authors: Gouveia Luis , Hall Leslie
Published: October 2002

The Capacitated Minimum Spanning Tree Problem seeks a least‐cost spanning tree subject to a bound imposed on the number of nodes in each subtree pending from a given root node. Araque et al. (Technical Report SOR‐90‐12, Princeton University, 1990) introduced several classes of facet‐defining inequalities for the undirected version of the problem, most of which have straightforward analogs to the directed version and are also facet‐defining in that case (see Zhang, Master's thesis, 1993). The multistar constraints are one such class. Gouveia [Telecommun Syst 1 (1993), 51–56] showed that a directed flow formulation gives a polynomial representation of the class of directed multistar constraints. This equivalence shows how to obtain a polynomial‐time separation algorithm for this class of inequalities. In this paper, we show that the previous equivalence result implies that we can also separate in polynomial time the exponential‐sized class of undirected multistar constraints. We also show that “using a directed model” plays a key role in obtaining a polynomial‐time separation algorithm for this class of inequalities, that is, using a directed flow model seems to be crucial for obtaining a polynomial‐time separation algorithm for the class of undirected multistar constraints. © 2002 Wiley Periodicals, Inc.
Efficient algorithms for finding the (k, l)‐core of tree networks
Authors: Becker Ronald I. , Lari Isabella , Storchi Giovanni , Scozzari Andrea
Published: October 2002

Given a tree T = (V, E), with |V| = n, we consider the problem of selecting a subtree with at most k leaves and with a diameter of at most l which minimizes the sum of the distances of the vertices from the selected subtree. We call such a subtree the (k, l)‐core of T. We provide two algorithms; the first one for unweighted trees has time complexity of O(n2), whereas the second one for weighted trees has time complexity of O(n2log n). The idea for both the algorithms is that, by starting from the tree T, we construct new rooted trees where the maximum length of a path is at most l. Then, for each new tree, we can apply a greedy‐type procedure to find a subtree containing the root with at most k leaves and which minimizes the sum of the distances. © 2002 Wiley Periodicals, Inc.
The maximum principle violations of the mixed‐hybrid finite‐element method applied to diffusion equations
Authors: Hoteit H. , Mosé R. , Philippe B. , Ackerer Ph. , Erhel J.
Published: October 2002

The abundant literature of finite‐element methods applied to linear parabolic problems, generally, produces numerical procedures with satisfactory properties. However, some initial–boundary value problems may cause large gradients at some points and consequently jumps in the solution that usually needs a certain period of time to become more and more smooth. This intuitive fact of the diffusion process necessitates, when applying numerical methods, varying the mesh size (in time and space) according to the smoothness of the solution. In this work, the numerical behaviour of the time‐dependent solutions for such problems during small time duration obtained by using a non‐conforming mixed‐hybrid finite‐element method (MHFEM) is investigated. Numerical comparisons with the standard Galerkin finite element (FE) as well as the finite‐difference (FD) methods are checked. Owing to the fact that the mixed methods violate the discrete maximum principle, some numerical experiments showed that the MHFEM leads sometimes to non‐physical peaks in the solution. A diffusivity criterion relating the mesh steps for an artificial initial–boundary value problem will be presented. One of the propositions given to avoid any non‐physical oscillations is to use the mass‐lumping techniques. Copyright © 2002 John Wiley & Sons, Ltd.
A continuum sensitivity method for finite thermo‐inelastic deformations with applications to the design of hot forming processes
Authors: Ganapathysubramanian Shankar , Zabaras Nicholas
Published: October 2002

A computational framework is presented to evaluate the shape as well as non‐shape (parameter) sensitivity of finite thermo‐inelastic deformations using the continuum sensitivity method (CSM). Weak sensitivity equations are developed for the large thermo‐mechanical deformation of hyperelastic thermo‐viscoplastic materials that are consistent with the kinematic, constitutive, contact and thermal analyses used in the solution of the direct deformation problem. The sensitivities are defined in a rigorous sense and the sensitivity analysis is performed in an infinite‐dimensional continuum framework. The effects of perturbation in the preform, die surface, or other process parameters are carefully considered in the CSM development for the computation of the die temperature sensitivity fields. The direct deformation and sensitivity deformation problems are solved using the finite element method. The results of the continuum sensitivity analysis are validated extensively by a comparison with those obtained by finite difference approximations (i.e. using the solution of a deformation problem with perturbed design variables). The effectiveness of the method is demonstrated with a number of applications in the design optimization of metal forming processes. Copyright © 2002 John Wiley & Sons, Ltd.
All‐hexahedral element meshing: automatic elimination of self‐intersecting dual lines
Authors: Calvo Nestor A. , Idelsohn Sergio R.
Published: October 2002

There has been some degree of success in all‐hexahedral meshing. Standard methods start with the object geometry defined by means of an all‐quadrilateral mesh, followed by the use of the combinatorial dual to the mesh in order to define the internal connectivities among elements. For all of the known methods using the dual concept, it is necessary to first prevent or eliminate self‐intersecting (SI) dual lines of the given quadrilateral mesh. The relevant features of SI lines are studied, giving a method to remove them, which avoids deforming the original geometry. Some examples of resulting meshes are shown where the current meshing method has been successfully applied. Copyright © 2002 John Wiley & Sons, Ltd.
Life‐cycle cost optimization of steel structures
Authors: Sarma Kamal C. , Adeli Hojjat
Published: October 2002

This article addresses the life‐cycle cost optimization of steel structures. The main factors influencing the life‐cycle cost of a structure are delineated and their effects on various cost functions are discussed. A four‐criteria optimization model is presented for the life‐cycle cost optimization of steel structures. These criteria are (i) select discrete commercially available sections with the lowest cost, (ii) select commercially available sections with the lightest weight, (iii) select the minimum number of different types of commercially available sections, and (iv) select commercially available sections with the minimum total perimeter length. The last criterion models a representative type of cost incurred over the life of the structure, that is, preventative maintenance in the form of periodic painting of an exposed steel structure to avoid corrosion. The life‐cycle cost optimization model is based on fuzzy logic with the goal of formalizing the life‐cycle design process but with some input from the design engineer through introduction of weighting coefficients reflecting the relative importance of various criteria. The model is applied to a large steel structure with over 3300 members. Copyright © 2002 John Wiley & Sons, Ltd.
Direct modification for non‐conforming elements with drilling DOF
Authors: Choi Chang‐Koon , Lee Tae‐Yeol , Chung Keun‐Young
Published: October 2002

A unified approach to eliminate the undesirable lockings in distorted meshes for both non‐conforming quadrilateral membrane and hexahedral elements with drilling (or rotational) degrees of freedom is presented. The direct modification scheme is utilized in the formulation of non‐conforming modes to improve the general behaviour of isoparametric‐based elements. It is shown that the direct modification is very effective in eliminating the locking and this improvement of element behaviour may be doubled if the selective integration scheme is used simultaneously. To verify the validity of elements formulated by the proposed schemes and to evaluate their effectiveness, several numerical tests are carried out. The combined use of additional non‐conforming modes with the direct modification method and the selective integration technique plays an important role to improve the behaviour of elements, especially for distorted mesh cases. Test results also show that the results for both non‐conforming quadrilateral membrane and hexahedral elements obtained by the proposed schemes are equally satisfactory. Copyright © 2002 John Wiley & Sons, Ltd.
Mesh‐independent p‐orthotropic enrichment using the generalized finite element method
Authors: Duarte C. A. , Babuška I.
Published: October 2002

This paper is aimed at presenting a simple yet effective procedure to implement a mesh‐independent p‐orthotropic enrichment in the generalized finite element method. The procedure is based on the observation that shape functions used in the GFEM can be constructed from polynomials defined in any co‐ordinate system regardless of the underlying mesh or type of element used. Numerical examples where the solution possesses boundary or internal layers are solved on coarse tetrahedral meshes with isotropic and the proposed p‐orthotropic enrichment. Copyright © 2002 John Wiley & Sons, Ltd.
Enantiomerization of bridged 1,1′‐binaphthyls
Authors: Yi Ren , Hoz Shmaryahu
Published: October 2002

The activation energy for the isomerization of 1,1′‐binaphthyl in which positions 2 and 2′ are bridged at by an —O—CH2—O— unit was calculated at various computational levels. AM1 gave good agreement with the experimental results. The transition‐state structure was found to be entirely different from that calculated for the non‐bridged parent compound: whereas the latter has C2 symmetry, the former has C
s symmetry. The C
s symmetry transition state for the non‐bridged parent compound was also located and found to be ca 6 kcal mol−1 higher than the C2 one. However, in the bridged compound, the inclusion of the bridge counterbalanced this by raising the energy of the ground state, leaving the activation energy essentially unchanged. The isomerization of optically active bridged 1,1′‐binaphthyls bearing linear polyphenyl rods of varying length, at positions 6 and 6′, was recently employed as a probe to gain information on the effect of rubber and glassy polymers on reaction rates. The model showed that the rod segments of these molecules traverse long distances in order to reach the transition state, which was consistent with a strong rod length dependence on racemization of the bridged binaphthyls in the glassy state. However, the present results demonstrate an unexpected twisting motion in the racemization process, suggesting that the appended oligophenyl rods are displaced to about half the distance previously expected. This may contribute in part to the experimental observation in the rubbery state where the microviscosity affects the racemization as a function of the appended rods far less than expected. AM1 results also gave reasonable agreement with the experimental ponderal effect consistent with the prior conclusion of force constant independence of rod length for twisting about the 1,1′ bonds. Copyright © 2002 John Wiley & Sons, Ltd.
Structural studies on sulfonylbicyclo[n.2.0]alkan‐1‐ols
Authors: Healy Peter C. , Loughlin Wendy A. , McCleary Michelle A. , Pierens Gregory K. , Rowen Catherine C.
Published: October 2002

The structures of a series of sulfonylbicyclo[n.2.0]alkan‐1‐ols (n = 3–6) 1–6 were determined by single‐crystal x‐ray diffraction. A survey of the Cambridge Structural Database and Monte Carlo conformational searches using MacroModel were performed. Compounds 1, 3 and 4 show intramolecular hydrogen bonding. Compound 2 is stabilized by three‐centered ‘bifurcated’ intra‐ and intermolecular hydrogen bonds between the hydroxyl proton and the sulfone oxygens. Compounds 5 and 6 are stabilized by intermolecular hydrogen bonds formed between the trans 1‐hydroxy and sulfonyl moieties. In compounds 1–6, the degree of cyclotorsion of the four‐ five‐, six‐, seven‐ and eight‐membered rings adjacent to the bond between the bridgehead atoms C1 and C4 is reflected in the magnitude about the exterior angles about C1 (C2—C1—Cx) and C4 (C3—C4—C5). The six‐membered ring systems of 2, 5 and 6 showed noteworthy increases in the C5—C4—C1—Cx and C3—C4—C1—C2 torsion angles, and this was attributed to the conformational constraints of the pseudo‐chair conformation of the six‐membered ring. Similar conformational structure effects were observed in the modeled structures 1a–6a to those observed for the x‐ray structures 1–6. Copyright © 2002 John Wiley & Sons, Ltd.
Molecular polarizability of fullerenes and endohedral metallofullerenes
Authors: Torrens Francisco
Published: October 2002

The interacting induced dipoles polarization model implemented in our program POLAR is used for the calculation of the molecular dipole
µ and tensor quadrupole $\overline{\overline{{\mit \Theta}}}$ moments and also the dipole–dipole polarizability $\overline{\overline{\alpha}}$. The method is tested with Sc
n, C
n (fullerene and graphite) and endohedral Sc
n@C
m clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are of the same order of magnitude as from reference calculations performed with our version of the program PAPID. The bulk limit for the polarizability is estimated from the Clausius–Mossotti relationship. The polarizability trend for these clusters as a function of size is different from what one might have expected. The clusters are more polarizable than what one might have inferred from the bulk polarizability. Previous theoretical work yielded the same trend for Si
n, Ge
n and Ga
nAs
m small clusters. However, previous experimental work yielded the opposite trend for Si
n, Ga
nAs
m and Ge
nTe
m larger clusters. At present, the origin of this difference is problematic. One might argue that smaller clusters need not behave like those of intermediate size. The high polarizability of small clusters is attributed to dangling bonds at the surface of the cluster. In this respect, semiconductor clusters resemble metallic clusters. Copyright © 2002 John Wiley & Sons, Ltd.
Solvolyses of naphthoyl chlorides. Solvent effect and Grunwald–Winstein correlation analyses with YxBnCl scales
Authors: Liu Kwang‐Ting , Hwang Patty Y.‐H. , Chen Hun‐I
Published: October 2002

The solvolyses of 1‐naphthoyl (2), 2‐naphthoyl (3), 4‐methyl‐1‐naphthoyl (4) and 6‐methoxy‐2‐naphthoyl (5) chlorides in a variety of solvents were studied, and correlation analyses by using the single‐ and dual‐parameter Grunwald–Winstein equations were examined. An excellent linear relationship (R = 0.995) for 4, log (k/k0) = 0.733YxBnCl + 0.269NOTs, was observed. An SN1‐like mechanism with decreasing extent of nucleophilic solvent participation was found in the solvolysis of 2 and 4. 2‐Naphthoyl chloride is likely to have a mechanism at the borderline of SN1‐like dissociation and an addition–elimination process. 6‐Methoxy‐2‐naphthoyl chloride shows more SN1‐like character than 3 and is associated with nucleophilic solvent intervention more pronounced than that for 2 and 4. The applicability and the advantages of using the YxBnCl scale for different types of substrates are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Correlation of the rates of solvolyses of cinnamyl chloride
Authors: Koo In Sun , An Sun Kyoung , Yang Kiyull , Lee Ikchoon , Bentley T. William
Published: October 2002

Solvolytic rate constants (k) at 25 °C are reported for solvolyses of cinnamyl chloride (1) in binary mixtures of water with acetone, ethanol, methanol, methanol‐d and 2,2,2‐trifluoroethanol (TFE), and also in TFE–ethanol mixtures; product selectivities (S) are reported for aqueous ethanol and methanol: S = [ether product]/[alcohol product] × [water]/[alcohol solvent]. A good correlation observed between log k and the parameter YCl (solvent ionizing power) is improved only slightly by additional parameters (N for solvent nucleophilicity and/or I, an aromatic ring parameter). Rate ratios in solvents of the same YCl value but different nucleophilicities provide measures of the minimum extent of nucleophilic solvent assistance, and the value of 1.48 for [k40EW/k97TFE]
Y (EW = ethanol–water) is consistent with an essentially SN1 reaction mechanism. A linear relationship between 1/S and molar ratio of solvent was derived theoretically and validated experimentally for solvolyses of the above substrate from water up to 75% alcohol–water. The dependence of S on solvent composition and the absence of rate depression in the presence of added chloride anions are explained by product formation via a contact ion pair. Copyright © 2002 John Wiley & Sons, Ltd.
The intramolecular hydrogen bond and intrinsic proton affinity of neutral organic molecules: N,N ′,N ″‐tris (3‐aminopropyl)guanidine and some related systems
Authors: Kovačević Borislav , Glasovac Zoran , Maksić Zvonimir B.
Published: October 2002

Multiple aminopropyl substitutions of the initial N,N′,N″‐trimethylguanidine lead to high intrinsic absolute proton affinities (APA) and basicities culminating in APA = 268.4 kcal mol−1 (1 kcal = 4.184 kJ) in N,N′,N″‐tris(3‐aminopropyl)guanidine (9). The reason behind a high proton affinity is identified as a strong cationic resonance in the central guanidine moiety and the strength of the intramolecular hydrogen bonding (IMHB), which is enhanced upon protonation. A cooperative IMHB effect in 9 and 9H
+ realized by three N(sp3)H···N(sp3) H‐bridges is estimated to be as high as 14.7 and 33.0 kcal mol−1, respectively. It follows that the IMHB effect contributes 18.3 kcal mol−1 to the absolute proton affinity of 9, which is a respectable amount. The basicity of 9 in acetonitrile is estimated to be very high, as evidenced by the corresponding pKa = 28.8. A derivative of 9, N,N′,N″‐tris(3‐dimethylaminopropyl)guani‐dine (10), assumes an even higher superbasic proton affinity of 275 kcal mol−1 due to an additional relaxation effect caused by the methyl groups. The corresponding pKa(MeCN) = 29.4. Copyright © 2002 John Wiley & Sons, Ltd.
Keto–enol tautomerism of β‐ketoamides and characterization of a sterically crowded α‐amido‐β‐ketoamide
Authors: Sung Kuangsen , Wu Ru‐Rong , Sun Shu‐Yi
Published: October 2002

An α‐amido‐β‐ketoamide (1) and two α‐alkyl‐β‐ketoamides (2 and 3) were prepared and characterized, and their keto–enol tautomerism was studied by H/13C NMR spectroscopy. Both α‐alkyl‐β‐ketoamides 2 and 3 are in the keto form in CDCl3, and their enol forms cannot be detected by 1H/13C NMR spectroscopy, whereas the α‐amido‐β‐ketoamide 1 shows both keto and enol forms in CDCl3 with an experimental KE of 0.70 at 298 K. Copyright © 2002 John Wiley & Sons, Ltd.
Thermoresponsive properties of porous poly(N‐isopropylacrylamide) hydrogels prepared in the presence of nanosized silica particles and subsequent acid treatment
Authors: Serizawa Takeshi , Wakita Kazuaki , Kaneko Tatsuo , Akashi Mitsuru
Published: October 2002

Porous poly(N‐isopropylacrylamide) hydrogels were prepared by the free‐radical polymerization of its monomer and a suitable crosslinker in the presence of spherical silica particles of different sizes (74 and 1600 nm) and by the subsequent acid extraction of silica. The yields were 81–83%, and the yields were not affected by the silica content. Scanning electron microscopy observations revealed the porous structure of the hydrogels. Porous and nonporous hydrogels showed volume phase transitions from swelling states to deswelling states at approximately 30 °C, as analyzed by the ratio of the diameter of cylinder‐shaped hydrogels to that of the glass tube used for the hydrogel preparation at the corresponding temperature. Deswelling, which was analyzed by rapid changes in the temperature of the aqueous media from 20 to 40 °C, was facilitated by decreased silica particle size and increased silica content. The deswelling rate constant of the hydrogel prepared with 74‐nm silica at 10 v/v % (silica/solvent) was more than 1500 times greater than that of conventional hydrogels. Swelling was similarly analyzed through changes in the temperature from 40 to 20 °C and was independent of the pore structure. The deswelling–swelling cycle was repeatable with reasonable reproducibility. Moreover, the mechanical strength of the porous hydrogels was significantly maintained compared with that of conventional nonporous hydrogels. This method produced thermoresponsive hydrogels of suitable mechanical strength and remarkable deswelling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4228–4235, 2002
Synthesis and characterization of new organosoluble and gas‐permeable polyimides from bulky substituted pyromellitic dianhydrides
Authors: Kim Yun‐Hi , Ahn Seong‐Kuk , Kim Hyung Sun , Kwon Soon‐Ki
Published: October 2002

Two new pyromellitic dianhydrides, 1,4‐bis(4′‐t‐butylphenyl) pyromellitic dianhydride and 1,4‐bis(4′‐trimethylsilylphenyl) pyromellitic dianhydride, were synthesized via Suzuki coupling, oxidation, and dehydration. A series of new organosoluble polyimides were prepared from the obtained pyromellitic dianhydride and various aromatic diamines by the conventional polycondensation reaction followed by chemical imidization, as well as high‐temperature, one‐step polymerization. The structures of the dianhydrides and polymers were identified with various spectroscopies. The inherent viscosities of the resulting polymers were 0.62–1.89 dL/g. The synthesized polyimides showed good solubility in various organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, and p‐chlorophenol. These polymers had glass‐transition temperatures of 230–260 °C. Thermogravimetric analysis showed that all the polymers were stable, with 10% weight losses recorded above 490 °C in nitrogen. The polyimide films had good mechanical properties and high oxygen permselectivity to nitrogen. The oxygen permeability coefficient (P) and the permselectivity of oxygen to nitrogen (P/P) of the films were 13–56 barrer and 3.7–5.5, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4288–4296, 2002
Synthesis of new hydrolyzable polyurethanes from L‐gulonic acid‐derived diols and diisocyanates
Authors: Yamanaka Chiaki , Hashimoto Kazuhiko
Published: October 2002

New polyurethanes with lactone groups in the pendants and main chains were synthesized by the polyaddition of two kinds of L‐gulonolactone‐derived diols (2,3‐O‐isopropylidene‐L‐gulono‐1,4‐lactone and 5,6‐O‐isopropylidene‐L‐gulono‐1,4‐lactone) with hexamethylene diisocyanate and methyl (S)‐2,6‐diisocyanatohexanoate and by the subsequent deprotection of isopropylidene groups. They were hydrolyzed more quickly than the polyurethane derived from methyl β‐D‐glucofuranosidurono‐6,3‐lactone in a phosphate buffer solution, the pH value of which was 8.0, at 27 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4158–4166, 2002
Preparations of regioselectively methylated cellulose acetates and their 1H and 13C NMR spectroscopic analyses
Authors: Karakawa Makoto , Mikawa Yuji , Kamitakahara Hiroshi , Nakatsubo Fumiaki
Published: October 2002

Seven possible regioselectively methylated cellulose acetates (RS‐MCAs)—2,3,6‐tri‐O‐methyl cellulose acetate, 3,6‐di‐O‐methyl cellulose acetate, 2,6‐di‐O‐methyl cellulose acetate, 2,3‐di‐O‐methyl cellulose acetate, 6‐O‐methyl cellulose acetate, 3‐O‐methyl cellulose acetate, and 2‐O‐methyl cellulose acetate—were prepared for the first time from chemically synthesized cellulose derivatives obtained by cationic ring‐opening polymerization and then were analyzed by 1H and 13C NMR spectroscopy. The chemical shifts of ring protons and carbons were influenced by substituent groups (methyl or acetyl) and clearly reflected the pattern of substituent distribution in anhydroglucose units. These data may conveniently be used for the determination of the substituent distribution of methyl cellulose. The synthesized RS‐MCAs also may be used for the elucidation of the structure–property relationship. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4167–4179, 2002
Poly(ester urethane)s with polycaprolactone soft segments: A morphological study
Authors: Kloss Juliana , Munaro Marilda , De Souza Gabriel Pinto , Gulmine Joseane Valente , Wang Shu Hui , Zawadzki Sonia , Akcelrud Leni
Published: October 2002

Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft‐segment/hard‐segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide‐angle X‐ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL‐rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117–4130, 2002
Perfluoropolyether alkyl diesters: Structure effects of the alkyl group on the kinetics of the hydrolysis reactions
Authors: Tonelli Claudio , Di Meo Antonella , Barchiesi Emma
Published: October 2002

A series of perfluoropolyether bis‐carboxylic esters was synthesized and their hydrolytic stability investigated. Their formula is ROOCCF2O(CF2CF2O)p(CF2O)qCF2COOR, where p/q = 1.07 and p + q = 2.94. The alkyl group, R, varied both in terms of steric hindrance and electron‐withdrawing ability. Kinetic and thermodynamic data were obtained under homogeneous conditions and compared to a fully hydrogenated ester having a closely related structure CH3(CH2)3OOCCH2O(CH2CH2O)nCH2COO(CH2)3CH3, where n̄ = 10.6. Neutral ester hydrolysis (NEH) conditions were selected with methyl ethyl ketone as a solvent and a 3–4:1 water/ester ratio. The course of the reaction was monitored by 19F NMR or 1H NMR (when R = CH3CH2). Results indicated that the hydrolysis of fluorinated esters, with alkyl aliphatic substituents, is governed by steric hindrance of the substituents. Two distinctive kinetic regimes were observed. The first one, at low conversion, was characterized by lower kinetic constants and related to true NEH conditions. The second regime appeared at higher conversion when acidic autocatalysis dictated the reaction behavior. This is the only observed mechanism when esters more sensitive to the hydrolysis are considered. In these cases, polar factors prevail over steric considerations. Finally, all fluorinated esters of the class (I) showed a much higher reactivity than the hydrogenated ester whose hydrolysis took place only in the presence of a strong acidic catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4266–4280, 2002
Effect of introduction mode of hydroxyl functionality on morphology and film properties of cycloaliphatic diepoxide crosslinkable core‐shell latex
Authors: Teng Ganghua , Soucek Mark D.
Published: October 2002

Three series of core‐shell hydroxyl‐functionalized latexes were synthesized and then crosslinked with a cycloaliphatic diepoxide. The same amount of hydroxyl functional monomer was added during the core stage, shell stage, or partitioned equally between the core and the shell. The morphology of the latexes was examined with transmission electron microscopy and contact‐angle measurement. The stress‐strain behavior, viscoelastic properties, and water adsorption were evaluated for the latex films as a function of hydroxyl location. The location of hydroxyl groups within latex particles appeared to be dependent on the introduction mode of hydroxyl functional monomers. The introduction of hydroxyl groups during the shell polymerization resulted in a higher crosslinking density but a lower Tukon hardness and tensile properties. Not surprisingly, distribution of hydroxyl groups in both core and shell polymerization provided the lowest water adsorption and impact resistance as well as the highest tensile elongation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4256–4265, 2002
Synthesis and crosslinking of a series of dimeric liquid‐crystalline diglycidylester compounds containing imine groups
Authors: Ribera D. , Mantecón A. , Serra A.
Published: October 2002

We used readily available commercial reagents and well‐known procedures to synthesize a series of aromatic imine mesogenic diglycidylester compounds with dimeric architectures. The compounds obtained were characterized by spectroscopic techniques. Their liquid‐crystalline behavior was examined by differential scanning calorimetry, hot‐stage polarized optical microscopy (POM), and wide‐angle X‐ray scattering (WAXS) and related to the different structures that varied in the length of the central spacer. All the compounds exhibited nematic mesophases with the exception of the dimer with a three‐methylene central spacer that did not reveal liquid‐crystalline character. We investigated the crosslinking of the synthesized compounds and obtained liquid‐crystalline thermosets (LCTs) with several primary aromatic diamines in stoichiometric ratios or a tertiary amine as a catalyst. The curing processes were measured by calorimetry, and the thermal stability of the LCTs was evaluated by thermogravimetry. The ordered character of the LCTs was confirmed by POM and WAXS. Finally, the mechanical characterization of the LCTs obtained was examined by dynamic mechanical thermal analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4344–4356, 2002
Conducting graft copolymers of poly(3‐methylthienyl methacrylate) with pyrrole and thiophene
Authors: Çi̇rpan Ali , Alkan Selmi̇ye , Toppare Levent , Hepuzer Yeşi̇m , Yağci Yusuf
Published: October 2002

A thiophene‐functionalized methacrylate monomer (3‐methylthienyl methacrylate) was synthesized via the esterification of 3‐thiophene methanol with methacryloyl chloride. The methacrylate monomer was polymerized by free‐radical polymerization in the presence of azobisisobutyronitrile as the initiator. Graft copolymers of poly(3‐methylthienyl methacrylate) (PMTM2) and polypyrrole and of PMTM2 and polythiophene were synthesized by constant‐potential electrolyses. p‐Toluene sulfonic acid, sodium dodecyl sulfate, and tetrabutylammonium tetrafluoroborate were used as the supporting electrolytes. PMTM2‐coated platinum electrodes were used as anodes in the polymerization of pyrrole and thiophene. Moreover, the oxidative polymerization of poly(3‐methylthienyl methacrylate) (PMTM1) was studied with FeCl3 as the oxidant. The self‐polymerization of PMTM1 was also investigated by galvanostatic electrolysis both in dichloromethane and in propylene carbonate. The structures of PMTM1 and PMTM2 were investigated by several spectroscopic and thermal methods. The grafting process was elucidated with conductivity measurements, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy studies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4131–4140, 2002
Reversible addition–fragmentation chain‐transfer graft polymerization of styrene: Solid phases for organic and peptide synthesis
Authors: Barner Leonie , Zwaneveld Nik , Perera Senake , Pham Yen , Davis Thomas P.
Published: October 2002

The γ‐initiated reversible addition–fragmentation chain‐transfer (RAFT)‐agent‐mediated free‐radical graft polymerization of styrene onto a polypropylene solid phase has been performed with cumyl phenyldithioacetate (CPDA). The initial CPDA concentrations range between 1 × 10−2 and 2 × 10−3 mol L−1 with dose rates of 0.18, 0.08, 0.07, 0.05, and 0.03 kGy h−1. The RAFT graft polymerization is compared with the conventional free‐radical graft polymerization of styrene onto polypropylene. Both processes show two distinct regimes of grafting: (1) the grafting layer regime, in which the surface is not yet totally covered with polymer chains, and (2) a regime in which a second polymer layer is formed. Here, we hypothesize that the surface is totally covered with polymer chains and that new polymer chains are started by polystyrene radicals from already grafted chains. The grafting ratio of the RAFT‐agent‐mediated process is controlled via the initial CPDA concentration. The molecular weight of the polystyrene from the solution (PSfree) shows a linear behavior with conversion and has a low polydispersity index. Furthermore, the loading of the grafted solid phase shows a linear relationship with the molecular weight of PSfree for both regimes. Regime 2 has a higher loading capacity per molecular weight than regime 1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4180–4192, 2002
Structural characterization and gas‐transport properties of brominated matrimid polyimide
Authors: Guiver Michael D. , Robertson Gilles P. , Dai Ying , Bilodeau François , Kang Yong Soo , Lee Kwi Jong , Jho Jae Young , Won Jongok
Published: October 2002

The commercial polyimide Matrimid was modified by bromination for the purpose of improving its membrane‐transport properties as a gas‐separation material and providing functional group reactivity for further modifications. The unmodified and brominated polymers were characterized by elemental analysis and one‐dimensional and two‐dimensional NMR, which revealed that one bromine atom per repeat unit was incorporated regioselectively onto the indane aromatic ring. The thermal and physical properties of the polymers before and after bromination were also investigated. The gas‐transport properties of the unmodified and brominated polymers were compared. © 2002 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4193–4204, 2002
Synthesis and properties of amine‐containing poly(arylene ether sulfone) as an anion‐exchange matrix
Authors: Son Won‐Keun , Song Hea‐Young , Kim Sang‐Hern , Kim Hyung‐Joong , Kim Whan‐Gi
Published: October 2002

Poly(arylene ether sulfone) (PSF), showing good thermal stability and excellent mechanical properties, was synthesized as an anion‐exchange matrix. It was synthesized by the condensation polymerization between bisphenol A and 4,4′‐dichlorodiphenylsulfone. 1°‐Amine‐containing poly(arylene ether sulfone) (1°‐APSF) was synthesized by the reduction reaction of a nitrated PSF. Then, it was transferred to 3°‐amine‐containing poly(arylene ether sulfone) (3°‐APSF) by the alkylation of the amine of 1°‐APSF. The properties of PSF, 1°‐APSF, and 3°‐APSF were investigated by Fourier transform infrared, 1H NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The introduction of the 3°‐amine group into PSF increased the glass‐transition temperature but decreased thermooxidative stability. The ion‐exchange capacities of 1°‐APSF and 3°‐APSF were shown to be 2.24 and 2.86 mequiv/g, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4281–4287, 2002
New polymer syntheses. CXI. Aliphatic polyesters by the ring‐opening polycondensation of glutaric anhydride with ethylene or trimethylene carbonate
Authors: Kricheldorf Hans R. , Petermann Oliver
Published: October 2002

Several polycondensations of ethylene carbonate with succinic anhydride or glutaric anhydride (GA) were conducted in bulk. Low molar mass polyesters were obtained with pyridine‐type catalysts and GA. Analogous polycondensations of trimethylene carbonate (TMC) and GA were successful when quinoline, 4‐(N,N‐dimethylamino)pyridine, or BF3 · OEt2 was used as a catalyst. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed the formation of cyclic oligoesters and polyesters by backbiting degradation. Monomer mixtures containing an excess of TMC yielded copoly(ester carbonate)s with number‐average molecular weights up to 16,000 Da. Analogous copoly(ester carbonate)s were obtained from TMC and 3,3′‐tetramethylene glutaric anhydride. Furthermore, combined polycondensation/ring‐opening polymerization reactions of TMC and GA with L‐lactide or ϵ‐caprolactone were studied. All copolymers were characterized by viscosity measurements and by IR, 1H, and 13C NMR spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4357–4367, 2002
Hydrogen bonding and hydrophobic interactions between [60]fullerenated poly(2‐hydroxyethyl methacrylate) and poly(1‐vinylimidazole) or poly(4‐vinylpyridine)
Authors: Goh H. W. , Goh S. H. , Xu G. Q.
Published: October 2002

Miscible blends of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(1‐vinylimidazole) (PVI) have been formed in methanol/water (3/2 v/v) solutions. The incorporation of 0.6 wt % C60 into PHEMA leads to hydrophobic interactions and enhanced hydrogen bonding in miscible blends of [60]fullerenated poly(2‐hydroxyethyl methacrylate) (FPHEMA) with PVI. The incorporation of 2.6 wt % C60 into PHEMA increases its tendency to form interpolymer complexes with PVI. Interpolymer complexes are formed when FPHEMA samples containing 0.6, 1.4, and 2.6 wt % C60 are blended with poly(4‐vinylpyridine). The yields of the complexes increase with increasing C60 content in FPHEMA. Calorimetry and Fourier transform infrared spectroscopy studies suggest the importance of hydrophobic interactions in C60‐containing blends and complexes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4316–4327, 2002
Anionic polymerization of methyl methacrylate initiated with molybdenum and tungsten chloride/organolithium/triisobutylaluminum systems
Authors: Ihara Eiji , Tanaka Shinsuke , Inoue Kenzo
Published: October 2002

Molybdenum chloride (MoCl5 or 1a) and tungsten chloride (WCl6 or 1b)/phenyllithium (PhLi)/triisobutylaluminum (iBu3Al) systems were found to be quite effective for controlling the anionic polymerization of methyl methacrylate (MMA), affording high molecular weight poly(methyl methacrylate)s (PMMAs; number‐average molecular weight > 100,000) with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.25) quantitatively at 0 °C for 1 h in toluene. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses of PMMAs obtained with the 1a and 1b/organolithium (RM; n‐butyllithium, PhLi)/iBu3Al systems revealed that the initiation of MMA with the systems occurred by a nucleophilic attack of H− to the monomer. In addition, the MALDI‐TOF MS analyses indicated that the presence of iBu3Al was responsible for the controlled polymerization by improving the uniformity of the polymerization with respect to initiation and termination and by preventing a backbiting reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4302–4315, 2002
Effects of tanshinone I isolated from Salvia miltiorrhiza Bunge on arachidonic acid metabolism and in vivo inflammatory responses
Authors: Kim Sung Young , Moon Tae Cheol , Chang Hyeun Wook , Son Kun Ho , Kang Sam Sik , Kim Hyun Pyo
Published: October 2002

Arachidonic acid (AA) mainly released from the cell membrane by phospholipase A2 (PLA2) is converted to eicosanoids by the action of cyclooxygenase (COX) and lipoxygenase (LO). In order to find the specific inhibitors of AA metabolism especially PLA2 and COX‐2, 300 plant extracts were evaluated for their inhibitory activity on PGD2 production from cytokine‐induced mouse bone marrow‐derived mast cells in vitro. From this screening procedure, the methanol extract of Salvia miltiorrhiza was found to inhibit PGD2 production and the ethyl acetate subfraction gave the strongest inhibition of five subfractions tested. From this ethyl acetate subfraction, an activity‐guided isolation finally gave tanshinone I as an active principle. This investigation deals with the effects of tanshinone I on AA metabolism from lipopolysaccharide (LPS)‐induced RAW 264.7 cells and in vivo antiinflammatory activity. Tanshinone I inhibited PGE2 formation from LPS‐induced RAW macrophages (IC50 = 38 μM). However, this compound did not affect COX‐2 activity or COX‐2 expression. Tanshinone I was found to be an inhibitor of type IIA human recombinant sPLA2(IC50 = 11 μM) and rabbit recombinant cPLA2 (IC50 = 82 μM). In addition, tanshinone I showed in vivo antiinflammatory activity in rat carrageenan‐induced paw oedema and adjuvant‐induced arthritis. Copyright © 2002 John Wiley & Sons, Ltd.
Measurement of insulin sensitivity indices using 13C‐glucose and gas chromatography/combustion/isotope ratio mass spectrometry
Authors: Clapperton Allan T. , Coward W. Andrew , Bluck Leslie J. C.
Published: October 2002

Important aspects of glucose metabolism can be quantified by using the minimal model of glucose kinetics to interpret the results of intravenous glucose tolerance tests. The power of this methodology can be greatly increased by the addition of stable isotopically labelled tracer to the glucose bolus dose. This allows the separation of glucose disposal from endogenous glucose production and also increases the precision of the estimates of the physiological parameters measured. Until now the tracer of choice has been deuteriated glucose and the analytical technique has been gas chromatography/mass spectrometry (GC/MS). The consequence of this choice is that nearly 2 g of labelled material are needed and this makes the test expensive. We have investigated the use of 13C‐labelled glucose as the tracer in combination with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) as the analytical technique. This methodology offers superior analytical precision when compared with the conventional method and so the amount of tracer used, and hence the cost, can be reduced considerably. Healthy non‐obese male volunteers were recruited for a standard intravenous glucose tolerance test (IVGTT) protocol but 6,6‐2H‐glucose and 1‐13C‐glucose were administered simultaneously. Tracer/tracee ratios were derived from isotope ratio measurements of plasma glucose using both GC/MS and GC/C/IRMS. The results of these determinations indicated that the two tracers behaved identically under the test protocol. The combination of these results with plasma glucose and insulin concentration data allowed determination of the minimal model parameters S*
g and S*
i. The parameter relating to insulin‐assisted glucose disposal, S*
i, was found to be the same in the two techniques, but this was not the case for the non‐insulin‐dependent parameter S*
g. Copyright © 2002 John Wiley & Sons, Ltd.