bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological cure characterization of phosphazene–triazine polymers
Authors: Reghunadhan Nair C.P. , Ninan K.N.
Published: February 2003

Cyclomatrix phosphazene–triazine network polymers were synthesized by co‐curing a blend of tris(2‐allylphenoxy), triphenoxy cyclotriphosphazene (TAP), and tris(2‐allylphenoxy) s‐triazine (TAT) with bis(4‐maleimido phenyl) methane (BMM). The co‐curing of the three‐component resin was investigated by dynamic mechanical analysis using rheometry. The cure kinetics of the Diels–Alder step was studied by examining the evolution of the rheological parameters, such as storage modulus (G′), loss modulus (G″), and complex viscosity (η*), for resins of varying compositions at different temperatures. The curing conformed to an overall second‐order phenomenological equation, taking into account a self‐acceleration effect. The kinetic parameters were evaluated by multiple‐regression analysis. The absence of a definite trend in the cure process with blend composition ratio was attributed to the occurrence of a multitude of competitive reactions whose relative rates depend on the reactant ratio and the concentration of the products formed from the initial phase of reaction. The cure was accelerated by temperature for a given composition, whereas the self‐acceleration became less prominent at higher temperature. Gelation was accelerated by temperature. The gel conversion decreased with increase in maleimide concentration and, for a given composition, it was independent of the cure temperature. The activation energy for the initial reaction and the crosslinking process were estimated for a composition with a maleimide‐to‐allyl ratio of 2 : 1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 908–914, 2003
Cyclization reaction in poly(acrylonitrile/itaconic acid) copolymer: An isothermal differential scanning calorimetry kinetic study
Authors: Devasia Renjith , Nair C. P. Reghunadhan , Sivadasan P. , Katherine B. K. , Ninan K. N.
Published: February 2003

The kinetics of the cyclization reaction in the poly(acrylonitrile/itaconic acid) (PAN) copolymer in the temperature range 175–200°C was studied by isothermal differential scanning calorimetry (DSC). The reaction conforms to an nth‐order autocatalytic model, with an overall order of 2. The kinetic parameters were derived by multiple regression analysis. The activation energy is 110.3 kJ/mol for the acid‐catalyzed reaction and 153.2 kJ/mol for the autocatalytic part. The autocatalysis indicates the catalysis of the nitrile group cyclization by the initially formed pyrimidine groups. The kinetic parameters were used to predict the reaction profile at a given temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 915–920, 2003
Compatibilization efficacy of poly(isoprene–butyl acrylate) block copolymers in natural/acrylic rubber blends
Authors: Wootthikanokkhan J. , Tongrubbai B.
Published: February 2003

Poly(isoprene–butyl acrylate) block copolymers with a variety of molecular weights and compositions were prepared via a controlled free‐radical polymerization with an iniferter. Subsequently, the block copolymers were used as compatibilizers in natural/acrylic rubber blends. Scanning electron micrographs revealed a cocontinuous morphology in the case of the normal blends with a low natural rubber content (20 wt %), whereas the blends that contained more natural rubber showed a dispersed‐particle morphology. When the rubbers were blended with 5 wt % block copolymer, the particle size decreased, and the tensile strength of the resulted blends increased, regardless of the block copolymer characteristics. For the blend that exhibited a cocontinuous morphology, the most effective compatibilizer was the block copolymer with an average molecular weight of 22,000 g/mol, containing mainly (87%) polyisoprene block. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 921–927, 2003
Modification of polyethylene–octene elastomer by silica through a sol–gel process
Authors: Wu Chin‐San , Liao Hsin‐Tzu
Published: February 2003

In this study, tetraethoxysilane (TEOS) and a metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for the preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, a maleic anhydride‐grafted polyethylene–octene elastomer (POE‐g‐MAH), used as the continuous phase, was also investigated. Characterizations of POE‐g‐MAH/SiO2 and POE/SiO2 hybrids were performed by Fourier transform infrared (FTIR) and 29Si solid‐state nuclear magnetic resonance (NMR) spectrometers, a differential scanning calorimeter (DSC), a thermogravimetry analyzer, and an Instron mechanical tester. The results showed that the POE‐g‐MAH/SiO2 hybrid could improve the properties of the POE/SiO2 hybrid because the interfacial force between the polymer matrix and the silica network was changed from hydrogen bonds into covalent SiOC bonds through dehydration of hydroxy groups in POE‐g‐MAH with residual silanol groups in the silica network. The existence of covalent SiOC bonds was proved by FTIR spectra. For the POE/SiO2 and POE‐g‐MAH/SiO2 hybrids, maximum values of the tensile strength and the glass transition temperature were found at 9 wt % SiO2 since a limited content of silica might be linked with the polymer chains through the covalent bond. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 966–972, 2003
Theoretical energy consideration of the gas‐phase polymerization of sodium acrylate
Authors: Sanderson Ronald D. , Sadiku E. Rotimi
Published: February 2003

The kinetics of the spray polymerization of sodium acrylate were investigated. The technique in which the heat of polymerization was used for solvent removal showed better energy efficiency than the solution or emulsion polymerization methods for preparing sodium polyacrylate. The monomer solution was injected into the nozzle of the spray machine via a venturi effect to siphon up the solution. Two siphon tubes feeding through two control valves into a mixing chamber before the spray operation resulted in separate feeds of a sodium hydroxide solution and a mixture of acrylic acid, water, and a catalyst. These two feeds generated the heat of neutralization of sodium acrylate. This heat raised the temperature of the monomer solution to the reaction temperature, thereby initiating the exothermic polymerization reaction. Theoretical calculations of these energy sources were compared with the energy required to give a dry product. The results revealed that the energy cost for spray polymerization was 4783.5 kJ kg−1, whereas the energy cost was 7830.4 kJ kg−1 for the conventional system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 928–935, 2003
Initiation of surface graft polymerization by ceric ions on polymer microspheres
Authors: Wang Ping‐Hua
Published: February 2003

The surface graft polymerization of acrylamide on poly(styrene‐co‐acrylonitrile) copolymer microspheres by the initiation of ceric ions was studied. The grafting was verified by IR spectra and X‐ray photoelectron spectroscopy measurements. The resultant microspheres with surface‐grafted polymer chains were employed in the preparation of polymer‐microsphere‐supported palladium composite particles. The composite particles were then studied by transmission electron microscopy and X‐ray diffraction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 936–940, 2003
Miscibility and phase structure of binary blends of polylactide and poly(vinylpyrrolidone)
Authors: Zhang Guobao , Zhang Jianming , Zhou Xiaoshu , Shen Deyan
Published: February 2003

The miscibility, crystallization behavior, and component interactions of two binary blends, poly(L‐lactide) (L‐PLA)/poly(vinylpyrrolidone) (PVP) and poly(D,L‐lactide) (DL‐PLA)/PVP, were studied with differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy. The composition‐dependent changes of the glass‐transition temperature (Tg) and degree of crystallinity (Xc) of the L‐PLA phase indicated that L‐PLA and PVP were immiscible over the composition range investigated. However, the sharp decrease of Xc with increasing PVP content in the second heating run demonstrated that the cold crystallization process of L‐PLA was remarkably restricted by PVP. In DL‐PLA/PVP blends, the existence of two series of isolated Tg's indicated that DL‐PLA and PVP were phase‐separated, but evidence showed that there was some degree of interaction at the interface of the two phase, especially for the blends with low DL‐PLA contents. FTIR measurements showed that there was no appreciable change in the spectra of L‐PLA/PVP with respect to the coaddition of each component spectrum, implying the immiscibility of the two polymers. In contrast to L‐PLA, the intermolecular interaction between DL‐PLA and PVP was detected by FTIR; this was evidenced by the observation of a high‐frequency shift of the CO stretching vibration band of PVP with increasing DL‐PLA content, which suggested some degree of miscibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 973–979, 2003
Molecular mobility in starchy materials studied by electron spin resonance
Authors: Riquet Anne‐Marie , Feigenbaum Alexandra , Colonna Paul , Lourdin Denis
Published: February 2003

Phase transitions in hydrated starch–sorbitol system were investigated both by molecular (electron spin resonance, ESR) and macroscopic (differential scanning calorimetry, DSC) methods. In rapid‐tumbling region, one did not observe the same phenomena by DSC and by ESR. The transitions observed by ESR, which seemed to reflect more the interactions probe–matrix than plasticization, probably corresponded to the interactions probe–sorbitol. For system concentrated in plasticizer, it was conceivable to admit that a demixion of sorbitol occurred. In slow‐tumbling region, a correspondence in temperature mobility changes measured by mechanical spectroscopy and ESR was observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 990–997, 2003
Influence of fillers on the mechanical response of an amorphous liquid‐crystalline polymer
Authors: Guerrica‐Echevarría G. , Eguiazábal J. I. , Nazábal J.
Published: February 2003

A semirigid and amorphous commercial liquid‐crystalline copolyester (Rodrun) was filled with mica and calcium carbonate (up to 25 wt %) by direct injection molding. The fillers led to decreases in the processability, as observed by torque increases, but maintained the thermal resistance of Rodrun. The effects of the two fillers on the modulus of elasticity, ductility, and tensile strength were the same or very similar. The decrease in the tensile strength (20% for a 10% filler content) was compensated by a generally slight increase in the modulus of elasticity, whatever the filler content was. This balance of properties found in these new liquid‐crystalline‐polymer‐based materials and the important savings that the fillers bring may spread the applications of these materials' matrices. © 2003 Wley Periodicals, Inc. J Appl Polym Sci 88: 998–1003, 2003
High‐resolution carbon nuclear magnetic resonance study of styrene/α‐methylstyrene/acrylonitrile terpolymers
Authors: Nogueira Regina F. , Tavares Maria Inês B.
Published: February 2003

Terpolymers formed from styrene, α‐methylstyrene (AMS), and acrylonitrile (AN) were prepared in different proportions. According to the reaction conditions, the terpolymers presented random sequence distributions. AMS, because of steric hindrance, presented a high degree of instability, which promoted depolymerization. AN promoted a long insertion of AMS monomers, which caused an acceleration of the propagation reaction. This also caused a depolymerization process. With 13C‐NMR solution analysis, it was possible to detect the depolymerization process. With solid‐state NMR results, it was demonstrated that AMS constituted the highest mobility domain. Finally, the values determined for the proton spin–lattice relaxation time in the rotating frame confirmed that the prepared terpolymers were random, but a homogeneous monomer distribution sequence was also observed from this parameter. © 2003 Wley Periodicals, Inc. J Appl Polym Sci 88: 1004–1009, 2003
Modeling and analysis of a gas sweeping process for polycarbonate polymerization
Authors: Kim Dae‐Hyung , Ha Kyoung‐Su , Rhee Hyun‐Ku , Ho Song Kwang
Published: February 2003

This article deals with (1) the development of a mathematical model for the finishing polycarbonate polymerization process with a horizontal, rotating disk‐type reactor with countercurrent gas sweeping and (2) the performance analysis of the reactor system with the model. We propose a model describing a reactor system consisting of two phases in which the byproduct (phenol) is removed from the polymer melt phase to the countercurrently flowing vapor phase to facilitate the forward reaction and, therefore, produce a high molecular weight polymer compatible with the products of commercial grades. The vapor phase is represented by the tanks‐in‐series model, whereas the polymer melt phase is regarded as a plug flow reactor. The major concerns here are the influences of the reactor operating conditions, including the catalyst concentration, reaction temperature, mass‐transfer rate, melt‐phase residence time, and vapor‐phase velocity, on the polymer molecular weight, the melt‐phase concentrations of various components, and the molar fraction of phenol in the vapor phase. To corroborate the validity of the proposed model and investigate the complex phenomena of the process, we have conducted a series of simulation studies with various operating policies, and we compare the performance of the process with the performances of the cocurrent process and the vacuum process. According to the results of this study, this new type of reactor system shows satisfactory performance and is sometimes even better than the conventional high‐ vacuum process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1010–1021, 2003
Novel refreshableN‐halamine polymeric biocides: Grafting hydantoin‐containing monomers onto high performance fibers by a continuous process
Authors: Sun Yuyu , Sun Gang
Published: February 2003

In this study, a continuous “pad‐dry‐cure” process was developed for the first time to graft a cycloamine monomer, 3‐allyl‐5,5‐dimethylhydantoin (ADMH), onto several high performance fibers, including Nomex, Kermel, and a PBI/Kevlar blend. The influence of reaction conditions on the grafting copolymerizaiton was studied. It was found that in the presence of a difunctional monomer, poly(ethylene glycol)–diacrylate (PEG–DIA), ADMH could be readily grafted onto these fibers. After exposure to chlorine, the hydantoin structures in the grafted samples could be transformed intoN‐halamines, which provided powerful, durable, and regenerable antibacterial activities against both gram‐negative and gram‐positive bacteria. The influence of hydrophobic/rigid properties of the fabrics on grafting reactions as well as on their antibacterial activities was discussed, and the importance of full contact was emphasized. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1032–1039, 2003
Mechanical properties of epoxy‐based hybrid composites containing glass beads and α,ω‐oligo(butylmethacrylate)diol
Authors: Schröder N. , Könczöl L. , Döll W. , Mülhaupt R.
Published: February 2003

A novel phase‐separating liquid rubber based on oligo(alkylmethacrylate) in combination with microglass beads was used to toughen an anhydride‐cured epoxy resin. The resulting hybrid composites, containing 5 or 10 wt % of oligomeric liquid rubber and between 10 and 60 wt % glass beads as well as composites containing corresponding amounts of glass beads but no liquid rubber, were characterized mechanically. The experimental data show that modification with glass beads results in increased stiffness and toughness compared to the neat resin but reduces tensile strength. Compared to the glass bead–filled composites, additional modification with methacrylic rubber leads to a further increase in toughness and also to an increase in strength but does not alter stiffness and glass‐transition temperature. This synergistic behavior is explained by the fact that the rubber separates preferably on the surface of the glass bead, forming a core–shell morphology during curing. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1040–1048, 2003
Synthesis and kinetic behavior of stereotriblock polybutadiene using dilithium as initiator
Authors: Wang Yurong , Li Guanghui , Leng Ying , Yang Xiao , Gu Mingchu
Published: February 2003

Anionic polymerization of butadiene was conducted in cyclohexane using 1,1,4,4‐tetraphenyl‐1,4‐dilithium butane (TPB–DiLi) as initiator and dipiperidinoethane (DPE) as modifier. The polymer design effects of DPE/TPB–DiLi (simplified as DPE/Li) and polymerization temperature on the 1,2 content of polybutadiene (PB) were examined and 1,2‐polybutadiene (1,2‐PB) with a nearly 100% 1,2 content was obtained. 1,2–1,4–1,2‐Stereotriblock polybutadiene (STPB) can be synthesized easily by means of one feed reaction. DSC and DMA analyses showed that STPB with the designed molecular structure (molecular weight, block ratio, and 1,2 content in 1,2 blocks) has two Tg's and two loss moduli and exhibits microphase separation. Studies on reaction kinetics established the polymerization kinetics equation of 1,4‐PB as −d[M]/dt = 0.356[C]0.5[M], indicating the first‐order relationship between polymerization rate and monomer concentration. At 50°C, the addition of the strong polar modifier DPE into the system increased the reaction rate. The apparent propagating activating energies before and after DPE addition were also determined in this study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1049–1054, 2003
Structure and thermal degradation of poly(N‐phenyl acrylamide) and poly(N‐phenyl methacrylamide)
Authors: Li Xin‐Gui , Huang Mei‐Rong , Zhu Zhi‐Liang , Jin Yi , Wang Xue‐Song
Published: February 2003

Poly(N‐phenyl acrylamide) (PPA) and poly(N‐phenyl methacrylamide) (PPMA) were prepared by using N‐phenyl acrylamide and N‐phenyl methacrylamide as monomer, respectively, in tetrahydrofuran using azobisisobutyronitrile as initiator. FT‐IR, 1H‐NMR, and GPC were used to characterize their molecular structure. The PPA obtained exhibited higher molecular weight and wider molecular weight distribution than that of PPMA. Their thermal degradation and kinetics were systematically investigated in two atmospheres of nitrogen and air from room temperature to 800°C by thermogravimetric analysis at 10°C/min. Based on the thermal decomposition reactions in nitrogen and air, it is shown that a three‐step degradation process in nitrogen and a four‐step degradation process for two polymers were observed in this investigation. The initial thermal degradation temperature was lower than 190°C. Under two atmospheres, PPA exhibits higher degradation temperature, higher temperature at the maximum weight‐loss rate, faster maximum weight‐loss rates, and larger weight loss for the first‐stage decomposition, as well as higher char yield at 500°C than those of PPMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1065–1071, 2003
Structure and properties of poly(o‐methoxyaniline)–clay nanocomposite materials
Authors: Yeh Jui‐Ming , Chin Chih‐Ping
Published: February 2003

In this study, we prepared a series of polymer–clay nanocomposite (PCN) materials that consisted of an emeraldine base of poly(o‐methoxyaniline) and layered montmorillonite. Organic o‐methoxyaniline monomers were first intercalated into the interlayer regions of organophilic clay hosts followed by a one‐step in situ oxidative polymerization. The as‐synthesized PCN materials were subsequently characterized by FTIR spectroscopy, wide‐angle powder X‐ray diffraction, and transmission electron microscopy. The molecular weights of PMA extracted from PCN materials and bulk PMA were determined by GPC with THF as eluant. Effects of the material composition on the thermal stability, flame resistance, electrical conductivity, and corrosion inhibition performance of PMA, along with a series of PCN materials in the form of fine powder and coating, were also studied by TGA, limiting oxygen index measurements, four‐point probe technique, and electrochemical corrosion measurements, respectively. Morphological images of as‐synthesized materials were also investigated by SEM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1072–1080, 2003
Toughening of polypropylene with styrene/ethylene‐butylene/styrene triblock copolymer: Effects of reactive and nonreactive compatibilization
Authors: Bassani A. , Pessan L. A.
Published: February 2003

The effects of the compatibilization on the toughening of polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene triblock copolymer (SEBS) in a twin‐screw extruder were investigated. The compatibilizers used were an SEBS functionalized with maleic anhydride, a PP functionalized with acrylic acid, and a bifunctional compound, p‐phenylenediamine (PPD). The effects of the compatibilization were evaluated through the mechanical properties and by the determination of the phase morphology of the blends by scanning electron microscopy. Reactive compatibilized blends show up to a 30‐fold increase in impact strength compared to neat PP, which was likely to have been due to the reaction of the bifunctional compound (PPD) with the acid acrylic and maleic anhydride groups, which rendered both morphological and mechanical stability to these blends. The addition of the PPD to the blends significantly changed their phase morphologies, leading to larger dispersed particles' average diameters, probably due to the morphological stabilization at the initial processing steps during extrusion, with the occurrence of the chemical reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1081–1094, 2003
Water uptake and mechanical characteristics of natural filler–polypropylene composites
Authors: Tajvidi Mehdi , Ebrahimi Ghanbar
Published: February 2003

Water uptake characteristics and some mechanical properties of polypropylene composites containing three types of natural fillers, purified α‐cellulose, wastepaper fibers, and wood flour were studied. The fiber contents were 15, 25, and 35% by weight. Two percent maleic anhydride polypropylene (MAPP) was also added to the mix, as the compatibilizer agent. Mixing process was performed in a Brabender Plasticorder until a constant torque was reached. Composites made out of these combinations were then pressed in a laboratory press and ASTM standard test specimens were cut out of the sheets. Water absorption and tensile tests were performed on these specimens. The results showed a significant difference between the various filler types regarding water uptake. Water uptake also increased by the increase in filler content. Tensile strength and elongation at break in composites declined when compared with pure polypropylene, but their modulus of elasticity increased. Among the three types of fillers, no significant discrepancies were observed in terms of improving mechanical properties in composites. Filler content increase had no drastic effect regarding strength improvement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 941–946, 2003
Influence of the CaCO3 nanoparticles on the molecular orientation of the polypropylene matrix
Authors: García‐López D. , Merino J. C. , Pastor J. M.
Published: February 2003

The presence of aggregates of CaCO3 nanoparticles in an isotactic polypropylene matrix processed by extrusion promotes the apparition of residual stresses. These stresses are removed with a thermal treatment of the composite, but a higher molecular orientation is then produced. The chain orientation inside the sample is nonhomogeneous due to the presence of the aggregates of nanoparticles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 947–952, 2003
Polyamide 6/clay nanocomposites using a cointercalation organophilic clay via melt compounding
Authors: Liu Xiaohui , Wu Qiuju , Berglund Lars A. , Lindberg H. , Fan Jiaqi , Qi Zongneng
Published: February 2003

Polyamide 6/clay nanocomposites (PA6CN) were prepared via the melt compounding method by using a new kind of organophilic clay, which was obtained through cointercalation of epoxy resin and quaternary ammonium into Na‐montmorillonite. The dispersion effect of this kind of organophilic clay in the matrix was studied by means of X‐ray diffraction (XRD) and transmission electron microscopy (TEM); the silicate layers were dispersed homogeneously and nearly exfoliated in the matrix. This was probably the result of the strong interaction between epoxy groups and amide end groups of PA6. The mechanical properties and heat distortion temperature (HDT) of PA6CN increased dramatically. The notched Izod impact strength of PA6CN was 80% higher than that of PA6 when the clay loading was 5 wt %. Even at 10 wt % clay content, the impact strength was still higher than that of PA6. The finely dispersed silicate layers and the strong interaction between silicate layers and matrix decreased the water absorption. At 10 wt % clay content, PA6CN only absorbs half the amount of water compared with PA6. The dynamic mechanical properties of PA6CN were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 953–958, 2003
Mathematical, logical, and formal methods in information retrieval: An introduction to the special issue
Authors: Crestani Fabio , Dominich Sandor , Lalmas Mounia , van Rijsbergen Cornelis Joost (Keith)
Published: February 2003

Research on the use of mathematical, logical, and formal methods, has been central to Information Retrieval research for long time. Research in this area is important not only because it helps enhancing retrieval effectiveness, but also because it helps clarifying the underlying concepts of Information Retrieval. In this article we outline some of the major aspects of the subject, and summarize the papers of this special issue with respect to how they relate to these aspects. We conclude by highlighting some directions of future research, which are needed to better understand the formal characteristics of Information Retrieval.
Embedding term similarity and inverse document frequency into a logical model of information retrieval
Authors: Losada David E. , Barreiro Alvaro
Published: February 2003

We propose a novel approach to incorporate term similarity and inverse document frequency into a logical model of information retrieval. The ability of the logic to handle expressive representations along with the use of such classical notions are promising characteristics for IR systems. The approach proposed here has been efficiently implemented and experiments against test collections are presented.
Unitary operators on the document space
Authors: Hoenkamp Eduard
Published: February 2003

When people search for documents, they eventually want content, not words. Hence, search engines should relate documents more by their underlying concepts than by the words they contain. One promising technique to do so is Latent Semantic Indexing (LSI). LSI dramatically reduces the dimension of the document space by mapping it into a space spanned by conceptual indices. Empirically, the number of concepts that can represent the documents are far fewer than the great variety of words in the textual representation. Although this almost obviates the problem of lexical matching, the mapping incurs a high computational cost compared to document parsing, indexing, query matching, and updating. This article accomplishes several things. First, it shows how the technique underlying LSI is just one example of a unitary operator, for which there are computationally more attractive alternatives. Second, it proposes the Haar transform as such an alternative, as it is memory efficient, and can be computed in linear to sublinear time. Third, it generalizes LSI by a multiresolution representation of the document space. The approach not only preserves the advantages of LSI at drastically reduced computational costs, it also opens a spectrum of possibilities for new research.
Towards context sensitive information inference
Authors: Song D. , Bruza P.D.
Published: February 2003

Humans can make hasty, but generally robust judgements about what a text fragment is, or is not, about. Such judgements are termed information inference. This article furnishes an account of information inference from a psychologistic stance. By drawing on theories from nonclassical logic and applied cognition, an information inference mechanism is proposed that makes inferences via computations of information flow through an approximation of a conceptual space. Within a conceptual space information is represented geometrically. In this article, geometric representations of words are realized as vectors in a high dimensional semantic space, which is automatically constructed from a text corpus. Two approaches were presented for priming vector representations according to context. The first approach uses a concept combination heuristic to adjust the vector representation of a concept in the light of the representation of another concept. The second approach computes a prototypical concept on the basis of exemplar trace texts and moves it in the dimensional space according to the context. Information inference is evaluated by measuring the effectiveness of query models derived by information flow computations. Results show that information flow contributes significantly to query model effectiveness, particularly with respect to precision. Moreover, retrieval effectiveness compares favorably with two probabilistic query models, and another based on semantic association. More generally, this article can be seen as a contribution towards realizing operational systems that mimic text‐based human reasoning.
Query expansion and query translation as logical inference
Authors: Nie Jian‐Yun
Published: February 2003

A number of studies have examined the problems of query expansion in monolingual Information Retrieval (IR), and query translation for crosslanguage IR. However, no link has been made between them. This article first shows that query translation is a special case of query expansion. There is also another set of studies on inferential IR. Again, there is no relationship established with query translation or query expansion. The second claim of this article is that logical inference is a general form that covers query expansion and query translation. This analysis provides a unified view of different subareas of IR. We further develop the inferential IR approach in two particular contexts: using fuzzy logic and probability theory. The evaluation formulas obtained are shown to strongly correspond to those used in other IR models. This indicates that inference is indeed the core of advanced IR.
Enhancing retrieval with hyperlinks: A general model based on propositional argumentation systems
Authors: Picard Justin , Savoy Jacques
Published: February 2003

Fast, effective, and adaptable techniques are needed to automatically organize and retrieve information on the ever‐increasing World Wide Web. In that respect, different strategies have been suggested to take hypertext links into account. For example, hyperlinks have been used to (1) enhance document representation, (2) improve document ranking by propagating document score, (3) provide an indicator of popularity, and (4) find hubs and authorities for a given topic. Although the TREC experiments have not demonstrated the usefulness of hyperlinks for retrieval, the hypertext structure is nevertheless an essential aspect of the Web, and as such, should not be ignored. The development of abstract models of the IR task was a key factor to the improvement of search engines. However, at this time conceptual tools for modeling the hypertext retrieval task are lacking, making it difficult to compare, improve, and reason on the existing techniques. This article proposes a general model for using hyperlinks based on Probabilistic Argumentation Systems, in which each of the above‐mentioned techniques can be stated. This model will allow to discover some inconsistencies in the mentioned techniques, and to take a higher level and systematic approach for using hyperlinks for retrieval.
Incidence of metopism in the Lebanese population
Authors: Baaten P.J.J. , Haddad M. , Abi‐Nader K. , Abi‐Ghosn A. , Al‐Kutoubi A. , Jurjus A.R.
Published: February 2003

This study was carried out on 968 skull X‐rays to determine the incidence of the metopic suture in the Lebanese population. Complete and incomplete metopism was present in 0.82% and 0.93% of cases, respectively, leading to an overall incidence of 1.75%. In both categories, the incidence was relatively higher in males (1.84%) than in females (1.62%). Persons living in rural areas had a higher incidence of complete and incomplete metopism compared to persons living in urban areas, with ratios of 4:1 and 4:2, respectively. Other findings included an absence of frontal sinuses in all but one skull with complete metopism, accessory ossicles in the majority of cases of complete metopism (7/8), and hydrocephalus in one case. Medical records did not reveal any other associated diseases or abnormalities. Despite the low incidence of metopic suture in the Lebanese population, in X‐ray diagnosis of fractures of the frontal bone, metopic suture must not be ruled out. Clin. Anat. 16:148–151, 2003. © 2003 Wiley‐Liss, Inc.
Simultaneous occurrence of a thyromediastinal muscle, a truncus bicaroticobrachialis, and a left superior vena cava
Authors: Barbaix E. , Kerckaert I. , D'Herde K. , Depreter M. , Espeel M.
Published: February 2003

A case is presented of a combination of anatomical anomalies found in a 67‐year‐old female cadaver during routine dissection by medical students. They include a thyromediastinal muscle, a truncus bicaroticobrachialis, and a left superior vena cava, with complete absence of the right superior vena cava, but with a normal azygos vein opening into the right atrium at the expected site of entry of the superior vena cava. No associated congenital cardiac malformations were found. Clinical implications include the difficulty of heart catheterization through the subclavian veins and misleading images on CT or MRI scans, where the azygos vein could be mistaken for a right superior vena cava. Clin. Anat. 16:176–181, 2003. © 2003 Wiley‐Liss, Inc.
What arteries are detectable in the precarinal space on contrast‐enhanced CT?
Authors: Kuiper Stefan , Zhang Ming , Almquist Sam , Doyle Terrence C.A.
Published: February 2003

Although the precarinal space is critical in the interpretation of computed tomography (CT) of the thorax, vascular structures within the space have not been well documented. The aim of this study was to investigate vascular structures in the precarinal space that are detectable with contrast‐enhanced CT scans. Contrast‐enhanced CT chest scans from 90 patients aged 17–78 years (41 male, 49 female) were analyzed retrospectively. Twenty‐two cadavers aged 54–93 years (13 male, 9 female) were used for gross anatomic study. We found that 9 of 90 cases of the contrast‐enhanced CT scans had vessel‐like structures detectable in the precarinal space, located primarily anterior to the right main bronchus. Single or double arteries were identified in the precarinal space of 19 cadavers. Thirteen of the 23 arteries observed were the right bronchial artery and 10 were the left bronchial artery. In two cadavers, a single right bronchial artery (2.5 and 4.0 mm in diameter), which could have been detected with contrast‐enhanced CT, originated from the aortic arch and the root of the left subclavian artery and coursed in the precarinal space. Based on the variation in the location and size of the bronchial arteries observed in this study, we suggest that vascular structures are detectable in the precarinal space with contrast‐enhanced CT, particularly anterior to the right main bronchus. Clin. Anat. 16:114–118, 2003. © 2003 Wiley‐Liss, Inc.
Anatomy of the arcus tendineus fasciae pelvis in females
Authors: Pit Maarten J. , De Ruiter Marco C. , Lycklama À Nijeholt August A.B. , Marani Enrico , Zwartendijk Jaap
Published: February 2003

Because of its proximity to the urethra, the anterior part of the arcus tendineus fasciae pelvis (ATFP) may be used in urethrosuspension procedures for urinary stress incontinence. In this study, 10 embalmed female cadaver hemipelves were dissected and their gross anatomy described. In females, the ATFP is a condensation of the endopelvic fascia. The anterior attachment of the ATFP is to the caudal inner surface of the body of the pubic bone at a site averaging 4 mm lateral to the pubic symphysis and covering an average area of 53 mm2. Posteriorly, it attaches to the medial surface of the ischial spine. In nine of the 10 hemipelves the first anterior centimeters of the ATFP have a clear lateral fixation either to the lateral part of the levator ani muscle (n = 1), to the fascia covering the obturator internus muscle (n = 7), or to the obturator membrane (n = 1). Medially from the ATFP derives a 2–3‐cm long flat fibrous attachment to the posterolateral aspect of the urethra. In eight unembalmed cadavers, the ATFP gave way at a pulling force of 8.2 kg (range = 3.5–11.5 kg). The ATFP resists caudal movement of the proximal anterior vaginal wall and the urethra in the upright posture and, therefore, may be suitable for urethrosuspension procedures. Clin. Anat. 16:131–137, 2003. © 2003 Wiley‐Liss, Inc.
Investigation of connective tissue attachments to the cervical spinal dura mater
Authors: Humphreys B.K. , Kenin Shahar , Hubbard Bradley B. , Cramer Gregory D.
Published: February 2003

The connective tissue attachments to the cervical spinal dura mater originating from the ligamentum nuchae (LN) and rectus capitis posterior minor (RCPM) muscle were evaluated in 30 cadaveric spines. Magnetic resonance images (MRIs) were correlated with the attachments in four cadaveric specimens. Attachments from the LN to the RCPM were also identified. The LN and the RCPM to dura attachments were found in all 30 specimens. Our results indicate that: 1) the attachments between the LN and RCPM and the dura occur between vertebrae C1‐C2 and the occipital bone and C1, respectively, and that they are substantial normal anatomic attachments, 2) attachments between the LN and RCPM are usually present, and 3) the attachments between the LN and dura mater can be identified on MRI. These latter attachments may play a role in neck pain, making their MRI appearance clinically important. Clin. Anat. 16:152–159, 2003. © 2003 Wiley‐Liss, Inc.
Attitudes of medical and dental students to dissection
Authors: Snelling J. , Sahai A. , Ellis H.
Published: February 2003

Guy's, King's, and St. Thomas's School of Medicine encourages students to learn anatomy from human dissection. Today, there is a worldwide move of anatomy‐based teaching away from dissection to prosection. This study investigates how attitudes toward dissection vary with gender and ethnicity. We assessed students' reactions and concerns regarding the dissecting room, any coping strategies they use to combat them, and analyzed effective methods of teaching anatomy to medical and dental students. Three questionnaires were distributed amongst 474 first‐year medical and dental students before dissection and 1 week and 12 weeks after exposure to the dissecting room. Over the 3 months we found significant changes in the concerns of students about dissection. There were also significant differences (P < 0.05) between medical and dental students, males and females, and students of differing ethnic backgrounds, which persisted over 12 weeks. Both medical and dental students found tutorials and textbooks of most value in learning anatomy. Dental students found prosection more useful than medical students (P < 0.001) though neither group demonstrated a significant preference for prosection over dissection. Of concern, 7% reported recurring images of cadavers and 2% insomnia after commencing dissection. Interest in the subject matter and discussion were the commonest methods used to combat stress. This study contributes to the ongoing debate about the value of the dissecting room in the medical school curriculum. Clin. Anat. 16:165–172, 2003. © 2003 Wiley‐Liss, Inc.
Growth cones contain a dynamic population of neurofilament subunits
Authors: Chan Walter K.‐H. , Yabe Jason T. , Pimenta Aurea F. , Ortiz Daniela , Shea Thomas B.
Published: February 2003

Neurofilaments (NFs) are classically considered to transport in a primarily anterograde direction along axons, and to undergo bulk degradation within the synapse or growth cone (GC). We compared overall NF protein distribution with that of newly expressed NF subunits within NB2a/d1 cells by transfection with a construct encoding green fluorescent protein (GFP) conjugated NF‐M subunits. GCs lacked phosphorylated NF epitopes, and steady‐state levels of non‐phosphosphorylated NF subunits within GC were markedly reduced compared to those of neurite shaft as indicated by conventional immunofluorescence. However, GCs contained significant levels of GFP‐tagged subunits in the form of punctate or short filamentous structures that in some cases exceeded that visualized along the shaft itself, suggesting that GCs contained a relatively higher concentration of newly synthesized subunits. GFP‐tagged NF subunits within GCs co‐localized with non‐phosphorylated NF immunoreactivity. GFP‐tagged subunits were observed within GC filopodia in which steady‐state levels of NF subunits were too low to be detected by conventional immunofluorescence. Selective localization of fluorescein versus rhodamine fluorescene was observed within GCs following expression of NF‐M conjugated to DsRed1‐E5, which shifts from fluorescein to rhodamine fluorescence within hours after expression; axonal shafts contained a more even distribution of fluorescein and rhodamine fluorescence, further indicating that GCs contained relatively higher levels of the most‐recently expressed subunits. GFP‐tagged structures were rapidly extracted from GCs under conditions that preserved axonal structures. These short filamentous and punctate structures underwent rapid bi‐directional movement within GCs. Movement of GFP‐tagged structures within GCs ceased following application of nocodazole, cytochalasin B, and the kinase inhibitor olomoucine, indicating that their motility was dependent upon microtubules and actin and, moreover, was due to active transport rather than simple diffusion. Treatment with the protease inhibitor calpeptin increased overall NF subunits, but increased those within the GC to a greater extent than those along the shaft, indicating that subunits in the GC undergo more rapid turnover than do those within the shaft. Some GCs contained coiled aggregates of GFP‐tagged NFs that appeared to be contiguous with axonal NFs. NFs extended from these aggregates into the advancing GC as axonal neurites elongated. These data are consistent with the presence of a population of dynamic NF subunits within GCs that is apparently capable of participating in regional filament formation during axonal elongation, and support the notion that NF polymerization and transport need not necessarily occur in a uniform proximal‐distal manner. Cell Motil. Cytoskeleton 54:195–207, 2003. © 2003 Wiley‐Liss, Inc.
Role of the two type II myosins, Myo2 and Myp2, in cytokinetic actomyosin ring formation and function in fission yeast
Authors: Mulvihill Daniel P. , Hyams Jeremy S.
Published: February 2003

The formation and contraction of a cytokinetic actomyosin ring (CAR) is essential for the execution of cytokinesis in fission yeast. Unlike most organisms in which its composition has been investigated, the fission yeast CAR contains two type II myosins encoded by the genes myo2+ and myp2+. myo2+ is an essential gene whilst myp2+ is dispensable under normal growth conditions. Myo2 is hence the major contractile protein of the CAR whilst Myp2 plays a more subtle and, as yet, incompletely documented role. Using a fission yeast strain in which the chromosomal copy of the myo2+ gene is fused to the gene encoding green fluorescent protein (GFP), we analysed CAR formation and function in the presence and absence of Myp2. No change in the rate of CAR contraction was observed when Myp2 was absent although the CAR persisted longer in the contracted state and was occasionally observed to split into two discrete rings. This was also observed in myp2Δ cells following actin depolymerisation with latrunculin. CAR contraction in the absence of Myp2 was completely abolished in the presence of elevated levels of chloride ions. Thus, Myp2 appears to contribute to the stability of the CAR, in particular at a late stage of CAR contraction, and to be a component of the signalling pathway that regulates cytokinesis in response to elevated levels of chloride. To determine whether the presence of two type II myosins was a feature of cytokinesis in other fungi that divide by septation, we searched the genomes of two filamentous fungi, Aspergillus fumigatus and Neurospora crassa, for myosin genes. As in fission yeast, both A. fumigatus and N. crassa contained myosins of classes I, II, and V. Unlike fission yeast, both contained a single type II myosin gene that, on the basis of its tail structure, was more reminiscent of Myp2 than Myo2. The significance of these observations to our understanding of septum to formation and cleavage is discussed. Cell Motil. Cytoskeleton 54:208–216, 2003. © 2003 Wiley‐Liss, Inc.
Dynamics of the endoplasmic reticulum during early development of Drosophila melanogaster
Authors: Bobinnec Yves , Marcaillou Christiane , Morin Xavier , Debec Alain
Published: February 2003

In this study, we analyze for the first time endoplasmic reticulum (ER) dynamics and organization during oogenesis and embryonic divisions of Drosophila melanogaster using a Protein Disulfide Isomerase (PDI) GFP chimera protein. An accumulation of ER material into the oocyte takes place during the early steps of oogenesis. The compact organization of ER structures undergoes a transition to an expanded reticular network at fertilization. At the syncytial stage, this network connects to the nuclear envelope as each nucleus divides. Time‐lapse confocal microscopy on PDI transgenic embryos allowed us to characterize a rapid redistribution of the ER during the mitotic phases. The ER network is massively recruited to the spindle poles in prophase. During metaphase most of the ER remains concentrated at the spindle poles and shortly thereafter forms several layers of membranes along the ruptured nuclear envelope. Later, during telophase an accumulation of ER material occurs at the spindle equator. We also analyzed the subcellular organization of the ER network at the ultrastructural level, allowing us to corroborate the results from confocal microscopy studies. This dynamic redistribution of ER suggests an unexpected regulatory function for this organelle during mitosis. Cell Motil. Cytoskeleton 54:217–225, 2003. © 2003 Wiley‐Liss, Inc.