bluuebunny/crossref_metadata_2025 huggingface dataset:
On the ethylene‐norbornene copolymerization mechanism
Authors: Tritto Incoronata , Boggioni Laura , Sacchi Maria Carmela , Locatelli Paolo , Ferro Dino R.
Published: June 2004

Results of our studies on polymerization kinetics and tests of copolymerization statistical models of ethylene‐norbornene (E‐N) copolymers obtained on the basis of microstructures determined by 13C NMR analysis are reported. Ethylene‐norbornene (E‐N) copolymers were synthesized by catalytic systems composed of racemic isospecific metallocenes, i‐Pr[(3Pri‐Cp)(Flu)]ZrCl2 or a constrained geometry catalyst (CGC) and methylaluminoxane.

Polymerization kinetics revealed that E‐N copolymerization is quasi living under standard polymerization conditions. Calculations of the number of active sites and of chain propagation and chain transfer turnover frequencies indicate that the metal is mainly in the Mt‐N* state, while the Mt‐E* state contributes more to transfer and propagation rates.

The first‐order and the second‐order Markov statistics have been tested by using the complete tetrad distribution obtained from 13C NMR analysis of copolymer microstructures. The root‐mean‐square deviations between experimental and calculated tetrads demonstrate that penultimate (second‐order Markov) effects play a decisive role in E‐N copolymerizations. Results show clues for more complex effects depending on the catalyst geometry in copolymers obtained at high N/E feed ratios.

Comonomer concentration was shown to have a strong influence on copolymer microstructure and copolymer properties.

The copolymer microstructure of alternating isotactic copolymers obtained with i‐Pr[(3Pri‐Cp)(Flu)]ZrCl2 have been described at pentad level. Second‐order Markov statistics better describes also the microstrucure of these copolymers.
Living random copolymerization of ethene and norbornene using ansa‐fluorenylamidodimethyltitanium complex
Authors: Hasan Tariqul , Shiono Takeshi , Ikeda Tomiki
Published: June 2004

Ethene‐norbornene copolymerizations were conducted by (t‐BuNMe2SiFlu)TiMe2 (1) activated with dried methylaluminoxane (MAO) (free from Me3Al) at 0°C and 20°C under atmospheric pressure of ethene at various norbornene concentrations. At 0°C and high norbornene concentration, the molecular weight of the copolymer increased linearly against polymerization time while keeping narrow molecular‐weight distribution. The 13C NMR spectrum revealed that random copolymer with 53 mol‐% of norbornene was obtained. The glass transition temperature was above 150°C.
New organic supports for metallocene catalysts applied in olefin polymerizations
Authors: Klapper Markus , Jang Yong‐Jun , Bieber Kirsten , Nemnich Tanja , Nenov Nikolay , Müllen Klaus
Published: June 2004

Nano‐sized latex particles as organic supports for metallocenes applied in olefin polymerizations are introduced. The particles are functionalized with nucleophilic surfaces such as polyethylenoxide (PEO), polypropyleneoxide (PPO) or pyridine units allowing an immobilization of the metallocene catalysts via a non‐covalent immobilization process. The latices are obtained by emulsion or miniemulsion polymerization with styrene, divinylbenzene as the crosslinker, and either PEO or PPO functionalized styrene or 4‐vinylpyridine for surface functionalization. The supported catalysts, e.g. [Me2Si(2MeBenzInd)2ZrCl2/MAO] on PPO containing latices or Cp2ZrMe2/([Ph3C][B(C6F5)4]) on pyridine functionalized materials were tested in ethylene polymerizations. Remarkably, high activities and excellent product morphologies were obtained. The influence of the degree of surface functionalization on activity and productivity was investigated. Furthermore, the fragmentation of the catalyst was studied by electron microscopy using bismuth‐labeled latex particles or by fluorescence and confocal fluorescence microscopy using dye‐labeled supports.

Finally, a self‐immobilizing catalyst/monomer system is presented. It is demonstrated that by using PEO‐functionalized olefins, the metallocenes were immobilized on the monomers. Subjecting these mixtures to an ethylene copolymerization, again high activities and productivities as well as polyolefin beads with high bulk densities are observed, indicating that an extra supporting process for controlling the product size and shape of the polyolefins is not necessary for these monomers.
Heterogenization of metalorganic catalysts of olefin polymerization and evaluation of active site non‐uniformity
Authors: Novokshonova Lyudmila , Kovaleva Natalia , Meshkova Irina , Ushakova Tatiana , Krasheninnikov Vadim , Ladygina Tatiana , Leipunskii Ilia , Zhigach Alexey , Kuskov Michail
Published: June 2004

Heterogenized activators ‐ “support‐H2O/AlR3” (where R=Me, iBu, support=montmorillonite, zeolite), synthesized directly on the support, form with metallocenes metal alkyl complexes highly active in olefin polymerization without the use of commercial methylaluminoxane (MAO). It was shown by the method of temperature programmed desorption with the application of mass‐spectrometry (TPD‐MS) that the aluminumorganic compound in support‐H2O/AlR3 is in general similar to the structure of commercial MAO. The heterogenization of Zr‐cenes on support‐H2O/AlR3 is accompanied by the appearance of the energy non‐uniformity of active sites. The activation energy of thermal destruction of active Zr‐C bonds in the active sites of prepared catalysts changes in the range from 25 to 32 kcal/mol.
Fluorenyl based syndiotactic specific metallocene catalysts structural features, origin of syndiospecificity
Authors: Razavi Abbas , Bellia Vincenzo , De Brauwer Yves , Hortmann Kai , Peters Liliane , Sirole Sabine , Van Belle Stephan , Thewalt Ulf
Published: June 2004

The stereochemistry of propylene insertion/propagation reactions with a variety of Cs symmetric fluorenyl‐ containing single site catalysts is discussed. Our recent results indicate that independent of the chemical composition of the ancillary ligand fragments, or nature of the transition metal, active sites with local Cs symmetry and enantiotopic coordination positions behave syndioselectively in the general context of chain migratory insertion mechanism. Perfect bilateral symmetry neither exists nor is required in these processes. In this context the mechanism of syndiospecific polymerization is revisited by taking into account the structural characteristics and catalytic behavior of the original metallocene based (η5‐C5H4‐CMe2‐η5‐C13H8) MCl2/ MAO; M = Zr (1), Hf (2) catalyst systems and new syndiotactic specific systems including (η5‐C5H4‐CPh2‐η5‐3,6‐di‐tBut‐C13H6)ZrCl2 (3), η1,η5‐(μMe2Si)(3,6‐di‐tBut‐Flu)(t‐ButN)MCl2/ MAO; M =Ti (4), Zr (5) and η1,η5‐(μMe2Si)(2,7‐di‐tBut‐Flu)(t‐ButN)MCl2/ MAO; M = Ti (6), Zr (7).
Observation and identification of the catalytically active species of bis(phenoxy‐imine) group 4 transition metal complexes for olefin polymerization using 1H NMR spectroscopy
Authors: Makio Haruyuki , Fujita Terunori
Published: June 2004

Solution structures of bis(phenoxy‐imine) group 4 transition metal complexes (FI Catalysts) were investigated using 1H NMR spectroscopy. At least two isomers exist in equilibrium for FI Catalysts precursors, bis[N‐(3‐tert‐butylsalicylidene)anilinato]zirconium(IV) dichloride (1), and bis[N‐(3,5‐dicumylsalicylidene)anilinato]zirconium(IV) dichloride (2), while bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium(IV) dichloride (3) exhibits only one isomer under the conditions examined. Upon activation with MAO, all FI Catalysts (1‐3) generate two species at ambient temperature judging from some key signals in the 1H NMR. When temperature is raised (up to 75°C), one species (1a‐3a) converts irreversibly to the other species (1b‐3b). The resulting species, 1b‐3b, are stereochemically rigid, in contrast to precursors 1 and 2. Species 3b, derived from a living FI Catalyst, exhibited virtually no reactivity toward olefin insertion. The imine protons of species 1b‐3b are temperature and solvent polarity sensitive. Two possibilities are proposed for the assignment of species 1b‐3b, i) heterobinuclear complexes of group 4 metal and alkylaluminum with methyl and/or chlorine as bridging groups and ii) phenoxy‐imine ligated aluminum complexes whose ligands are transferred from the group 4 metal. The latter is more probable from the separate synthesis of LAlMe2 (L: phenoxy‐imine ligand). When 3 was activated with MAO in the presence of olefins, a new imine signal was observed. This species (3c for ethylene and 3d for propylene) is thermally more robust than 3a toward transformation to 3b and assignable to the living propagating species.
Polymerization of norbornene with Co(II) complexes
Authors: Pelascini Frédéric , Peruch Frédéric , Lutz Pierre Joseph , Wesolek Marcel , Kress Jacky
Published: June 2004

The norbornene polymerization was studied in the presence of 6 pyridine bis(imine) cobalt(II) complexes activated with methylaluminoxane (MAO). Norbornene was also polymerized with CoCl2 associated to MAO. All these catalytic systems generate an addition polymerization of norbornene, yielding fully saturated polymers. It was shown that the polymerization yield and the molar masses are highly dependant on several reaction parameters (monomer concentration, [Al]/[Co] ratio, polymerization temperature and time) and the frame of the ligand.
Experimental and calculated vibrational spectra and structure of Ziegler‐Natta catalyst precursor: 50/1 comilled MgCl2‐TiCl4
Authors: Brambilla Luigi , Zerbi Giuseppe , Nascetti Stefano , Piemontesi Fabrizio , Morini Giampiero
Published: June 2004

The vibrational Infrared and Raman Spectra of a MgCl2‐TiCl4 Ziegler‐Natta catalyst precursor with a 50/1 MgCl2/TiCl4 ratio have been recorded. The Raman spectrum of this catalyst precursor, in the range 50‐500 cm−1, shows clear scattering lines which can be assigned to the complex MgCl2‐TiCl4, well separated from those of the initial species. Analogous, but less clear signals can be found in the infrared spectrum. Vibrational symmetry analysis and quantum chemical calculations of suitable models of MgCl2‐TiCl4 complex have been made for the interpretation of the experimentally recorded spectra. The observed spectroscopic signals can be explained in terms of the existence of only one type of MgCl2‐TiCl4 complex where the TiCl4 molecules are complexed on the MgCl2 along the (110) lateral cuts in a local C2v symmetry with the Ti atoms in an octahedral coordination.
Defects distribution of metallocene and MgCl2‐supported Ziegler‐Natta isotactic poly(propylenes) as revealed by fractionation and crystallization behaviors
Authors: Alamo Rufina G.
Published: June 2004

The inter and intramolecular distribution of defects of poly(propylenes) of the Ziegler‐Natta (ZN) and metallocene (M) types, with matched molar masses and overall defect concentrations, are inferred from the crystallization and polymorphic behavior of their narrow molecular mass fractions. The fractions obtained from the M‐iPP display a range in molecular masses but the same concentration of defects and provide direct evidence of the uniform intermolecular defect distribution and the “single site” nature of the catalyst. The stereodefects of the ZN‐iPP fractions are more concentrated in the low molecular mass fractions, corroborating a broad interchain distribution of the nonisotactic content. In addition, the invariance of the linear growth rates among the ZN fractions and very low contents of the gamma polymorph, developed even by the most defected ZN fraction, are consistent with a stereo blocky intramolecular distribution of defects in the ZN‐iPP molecules. In contrast to the linear growth rates, which are sensitive to the defect microstructure, the overall crystallization rates correlate with nucleation density and not necessarily with the iPP chain microstructure.
Structural characterization and mechanical behavior of metallocenic copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene
Authors: Cerrada María L. , Benavente Rosario , Pereña José M. , Pérez Ernesto , Moniz‐Santos Jorge , Ribeiro M. Rosário
Published: June 2004

The relationships between structure and mechanical properties have been established in several copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene synthesized by a metallocene catalyst. A dependence with composition and polymerization temperature has been found for different structural and mechanical parameters. The branches cannot be incorporated into the orthorhombic crystal lattice and, consequently, structural parameters such as crystallinity and crystal size are considerably affected as 5,7‐dimethylocta‐1,6‐diene content increases in the copolymer. These structural changes influence significantly the rigidity of the copolymers and a decrease of this parameter, determined from either storage modulus or microhardness, with increasing 5,7‐dimethylocta‐1,6‐diene molar fraction is found. The location of the different viscoelastic relaxations is also strongly dependent on composition.
Polymacromonomers with polyolefin branches synthesized by free‐radical homopolymerization of polyolefin macromonomer with a methacryloyl end group
Authors: Kaneko Hideyuki , Kojoh Shin‐ichi , Kawahara Nobuo , Matsuo Shingo , Matsugi Tomoaki , Kashiwa Norio
Published: June 2004

Polymacromonomers with polyolefin branches were successfully synthesized by free‐radical homopolymerization of polyolefin macromonomer with a methacryloyl end group. Propylene‐ethylene random copolymer (PER) with a vinylidene end group was prepared by polymerization using a metallocene catalyst. Then, the unsaturated end group was converted to a hydroxy end group via hydroalumination and oxidation. The PER with the hydroxy end group was easily reacted with methacryloyl chloride to produce methacryloyl‐terminated PER (PER macromonomer; PERM). The free‐radical polymerization of thus‐obtained PERM was done using 2,2′‐azobis(isobutyronitorile) (AIBN) as a free‐radical initiator. From NMR analyses, the obtained polymers were identified as poly(PERM). Based on gel permeation chromatography (GPC), the estimated degree of polymerization (Dp) of these polymers were about 30. Thus, new class of polymacromonomers with polyolefin branches was synthesized.
Polymerization with Fischer‐Tropsch olefins – a new challenge in polymer science
Authors: Tincul Ioan , Lufuno Siphuma , Rawatlal Randhir
Published: June 2004

Co‐ and ter‐polymerization of ethylene with Fischer‐Tropsch derived olefins having odd carbon number and branched olefins are investigated. A method of preparation of a robust, high productivity Ziegler‐Natta catalyst suitable for ethylene co‐polymerization with Fischer Tropsch olefin is reviewed. In supporting titanium tetrachloride, an attempt was made to control the titanium oxidation state. The resulting experimental data were fitted to a sub‐sites model that associates titanium oxidation state with catalyst activity.
Comparative analysis of the clathrate forms of syndiotactic polystyrene, poly (p‐methylstyrene) and poly (m‐methylstyrene)
Authors: Petraccone Vittorio , Tarallo Oreste
Published: June 2004

The crystal structures of the clathrate forms of syndiotactic polystyrene (s‐PS), poly (p‐methylstyrene) (s‐PPMS) and poly (m‐methylstyrene) (s‐PMMS) containing guest molecules having widely different steric hindrance are compared in detail. Common features and differences concerning the packing of the chains, the shape and the dimensions of the cavities and the stability of the forms deprived of the guest molecules are pointed out. A new clathrate form of s‐PPMS containing CS2 is also described.
A Semi‐Microscopic Modeling for Polymer Flow Reactors
Authors: Hua Chi C. , Hsu Fu Y. , Chang Mu G. , Kan Chun J.
Published: June 2004

Summary: A nonisothermal plug‐flow reactor for ethylene polymerization is reexamined so as to illustrate the principle and effect of a refined, semi‐microscopic modeling. The novel feature of the current simulation is the application of a Monte Carlo scheme to exactly solve the free‐radical polymerization involved, whereas a reptation‐based molecular theory is introduced in a self‐consistent manner to simulate more accurately the reactant fluid viscosity during polymerization. The simulation is shown to capture some in‐depth consequences of reaction‐transport coupling that cannot be revealed by a traditional, macroscopic type of modeling. The principle of a future extension for dealing with more complex flow reactors is briefly discussed.

Comparison of the predicted temperature profile between Monte Carlo‐based simulation and the ones using moment equations together with two different weight distributions is shown with experimental data for LDPE.

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Comparison of the predicted temperature profile between Monte Carlo‐based simulation and the ones using moment equations together with two different weight distributions is shown with experimental data for LDPE.
Alterations of the Dutt1/Robo1 gene in lung adenocarcinomas induced by N‐nitrosobis(2‐hydroxypropyl)amine in rats
Authors: Tsujiuchi Toshifumi , Sasaki Yasutaka , Oka Yasuo , Kuniyasu Hiroki , Tsutsumi Masahiro
Published: June 2004

Abnormalities of tumor suppressor genes (TSGs) on chromosome 3p are known to be important for the development of human lung cancers. In the present study, we investigated alterations of the Dutt1/Robo1 gene, as a possible tumor suppressor in this region, in rat lung adenocarcinomas induced by N‐nitrosobis(2‐hydroxypropyl)amine (BHP). Male Wistar rats, 6‐wk‐old, were given 2000 ppm BHP in their drinking water for 12 wk and maintained without further treatment until killed at wk 25. A total of 12 lung adenocarcinomas were obtained and total RNAs were extracted from each for assessment of aberrant transcripts of the Dutt1/Robo1 gene by reverse transcription (RT)‐polymerase chain reaction (PCR) analysis. Aberrant transcripts bearing deletions of nucleotides (nt) 55–4318, 89–4346, 605–4221, and 929–4318 were detected in four of 12 adenocarcinomas (33.3%). Loss or reduced expression of the Dutt1/Robo1 gene was not found in any of the adenocarcinomas. Genomic DNAs extracted from six adenocarcinomas for Southern blot analysis did not show any evidence of deletion or gross rearrangement of the Dutt1/Robo1 gene. These results suggest that alterations of the Dutt1/Robo1 gene may be involved in the development of some lung adenocarcinomas induced by BHP in rats. © 2004 Wiley‐Liss, Inc.
Towards an understanding of organic anion transporters: Structure–function relationships
Authors: You Guofeng
Published: June 2004

Organic anion transporters (OAT) play essential roles in the body disposition of clinically important anionic drugs, including anti‐viral drugs, anti‐tumor drugs, antibiotics, anti‐hypertensives, and anti‐inflammatories. The activities of OATs are directly linked to drug toxicity and drug–drug interactions. So far, four members of the OAT family have been identified: OAT1, OAT2, OAT3, and OAT4. These transporters share several common structural features including 12 transmembrane domains, multiple glycosylation sites localized in the first extracellular loop between transmembrane domains 1 and 2, and multiple phosphorylation sites present in the intracellular loop between transmembrane domains 6 and 7, and in the carboxyl terminus. The impact of these structural features on the function of these transporters has just begun to be explored. In the present review, the author will summarize recent progress made from her laboratory as well as from others, on the molecular characterization of the structure–function relationships of OATs, including particular amino acid residues/regions of the transporter protein (“molecular domains”) that potentially determine transport characteristics. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 6, 762–774, 2004
Construction of albumin multilayer coating onto plasma treated poly(vinyl chloride) via electrostatic self‐assembly
Authors: Ji Jian , Tan Qinggang , Shen Jiacong
Published: June 2004

Multilayer films consisting of polyethylenimine (PEI) and albumin were successffully prepared on plasma treated poly(vinyl chloride) (PVC) via electrostatic self‐assembly of the PEI and albumin. The layer‐by‐layer assembly of the PEI/albumin on plasma treated PVC was monitored by contact angle and 125I radiolabeled method. The stability of the mutilayer coating was determined by 125I radiolabeled method. The results revealed that less than 10% albumin was eluted by a phosphate buffered saline (PBS) solution in 45 days. The static platelet adhesion indicated that the PEI/albumin deposited PVC could resist the platelet adhesion effectively. Such an easy processing and shape‐independent method may have good potential for surface modification of cardiovascular device. Copyright © 2004 John Wiley & Sons, Ltd.
Studies on grafting of tris(2‐methoxyethoxy)vinylsilane onto ethylene‐propylene‐diene terpolymer
Authors: Ramar P. , Alagar M.
Published: June 2004

New graft copolymer was prepared by incorporating tris(2‐methoxyethoxy)vinylsilane (TMEVS) on ethylene‐propylene‐diene terpolymer (EPDM) by using dicumyl peroxide (DCP) as initiator, in Haake Rheocord 90 torque rheometer. The effect of EPDM concentration, TMEVS concentration, reaction time, reaction temperature and initiator concentration on the graft co polymerization was studied. The grafting efficiency of TMEVS on EPDM was confirmed by Fourier Transform infrared (FT‐IR) spectroscopy. The grafting efficiency increased with increase in the silane concentration upto 6% by weight. The grafting efficiency decreased beyond 6% by weight due to homopolymerization of TMEVS and non‐availability of carbon–carbon double bond in the EPDM terpolymer. The thermal properties of peroxide cured EPDM and hot water cured EPDM‐g‐TMEVS were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. The results show thermal properties like degradation tempertature and glass transition temperature of the EPDM‐g‐TMEVS were increased due to introduction of TMEVS on to EPDM terpolymer as well as the formation of thermally stable three‐dimensional network. Copyright © 2004 John Wiley & Sons, Ltd.
The mechanical and thermal behaviors of glass bead filled polypropylene
Authors: Yuan Qiang , Jiang Wei , An Lijia , Li R. K. Y.
Published: June 2004

Notch Izod impact strength of poly(propylene) (PP)/glass bead blends was studied as a function of temperature. The results indicated that the toughness for various blends could undergo a brittle‐ductile transition (BDT) with increasing temperature. The BDT temperature (TBD) decreased with increasing glass bead content. Introducing the interparticle distance (ID) concept into the study, it was found that the critical interparticle distance (IDc) reduced with increasing test temperature correspondingly. The static tensile tests showed that the Young's modulus of the blends decreased slightly first and thereafter increased with increasing glass bead content. However, the yield stress decreased considerably with the increase in glass bead content. Dynamic mechanical analysis (DMA) measurements revealed that the heat‐deflection temperature of the PP could be much improved by the incorporation of glass beads. Moreover, the glass transition temperature (Tg) increased obviously with increasing glass beads content. Differential scanning calorimetry (DSC) results implied that the addition of glass beads could change the crystallinity as well as the melting temperature of the PP slightly. Thermogravimetric analysis (TGA) measurements implied that the decomposition temperature of the blend could be much improved by the incorporation of glass beads. Copyright © 2004 John Wiley & Sons, Ltd.
Effect of Pluronic F127 on the pore structure of macrocellular biodegradable polylactide foams
Authors: Zhang Rong , Weng Wenjian , Du Piyi , Zhao Gaoling , Shen Ge , Han Gaorong
Published: June 2004

Thermally induced phase separation technique was utilized to fabricate biodegradable poly(l‐lactic acid) (PLLA) macrocellular foams which were capable of being applied in tissue engineering. The block copolymer Pluronic F127 composed of (polyethyleneoxide)‐(polypropyleneoxide)‐(polyethyleneoxide) [(PEO)‐(PPO)‐(PEO)] was used as a porogen. Water/dioxane mixtures with different volume ratios were used as solvents. The addition of Pluronic F127 could induce an appearance of large pores (50–200 μm) besides small pores (10–20 μm) or a change from a solid–liquid phase separation to a liquid–liquid phase separation. The role of Pluronic F127 depends on the water/dioxane ratios in the PLLA/dioxane/water system. The X‐ray diffraction patterns and porosity measurement results showed that Pluronic F127 was crystallized and existed on the pore wall. The effect of Pluronic F127 on changing pore structure is attributed to the occurrence of the interaction of the lipophilic PPO blocks in Pluronic F127 with PLLA clews, consequently, this results in PLLA aggregation and early phase separation on cooling. Copyright © 2004 John Wiley & Sons, Ltd.
Radiation‐grafted solid polymer electrolyte membrane: studies of fluorinated ethylene propylene (FEP) copolymer‐g‐acrylic acid grafted membranes and their sulfonated derivatives
Authors: Patri M. , Hande V. R. , Phadnis Swati , Deb P. C.
Published: June 2004

Acrylic acid was grafted onto FEP by simultaneous radiation technique and the resulting membranes were sulfonated. Results of dynamic mechanical properties of the membranes showed that storage modulus and temperature at tan δ(max) increases on grafting. X‐ray diffraction (XRD) analysis of the grafted and sulfonated membranes showed decreasing trend in crystallinity with increase in degree of grafting. From scanning electron microscopy (SEM) studies it was confirmed that grafting takes place by the front mechanism. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and characteristics of novel chelate fiber containing amine and amidine groups
Authors: Shin Dong Hun , Ko Young Gun , Choi Ung Su , Kim Woo Nyon
Published: June 2004

A polyacrylonitrile (PAN) fiber was adopted for the backbone of a chelate polymer and poly(acrylo‐amidino ethylene amine) (PAEA) was prepared through a one‐step reaction between the PAN fiber and ethylenediamine (EDA). The maximum removal capacity and degree of substitution were 7.8 meq per gram of dried PAEA and 98%, respectively. The PAEA was tested as an adsorbent in single and two‐component metal aqueous solutions under changing pH. The Cu2+ ion accomplished maximum adsorption amount at pH 3 and the order of maximum adsorbed amounts on PAEA is Cu2+ > Ag+ > Zn2+ > Ni2+ > Pb2+ in molar basis. FT‐IR spectroscopy was employed to characterize the chemical bonding in metal aqueous solutions and surface morphology was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Copyright © 2004 John Wiley & Sons, Ltd.
Preparation and characterization of PVC/PANI conductive composite with extremely low percolation threshold
Authors: Wang Yangyong , Jing Xinli
Published: June 2004

Aniline was polymerized in the presence of poly(vinyl chloride) (PVC) powders in hydrochloric acid to in situ prepare poly(vinyl chloride)/polyaniline (PVC/PANI) composite particles. UV‐vis spectra and FT‐IR spectra indicate PANI in PVC/PANI composite particles possessed a higher oxidation state with decreased aniline content in reactants. Both conductivity and impact strength of the dodecylbenzenesulfonic acid (DBSA) doped PANI composites (PVC/PANI‐DBSA), which were compression molded from the in situ prepared PVC/PANI particles, increase with the pressing temperature and decrease with the increase of DBSA doped PANI (PANI‐DBSA) loading. An excellent electric conductivity of 5.06 × 10−2 S/cm and impact strength of 0.518 KJ/m2 could be achieved for the in situ synthesized and subsequently compression molded composite. Copyright © 2004 John Wiley & Sons, Ltd.
Cancer incidence among adolescents in France
Authors: Desandes Emmanuel , Lacour Brigitte , Sommelet Danièle , Buemi Antoine , Danzon Arlette , Delafosse Patricia , Grosclaude Pascale , Mace‐Lesech Josette , Raverdy‐Bourdon Nicole , Tretarre Brigitte , Velten Michel , Brugieres Laurence
Published: June 2004

Background

In France, cancer ranks third as the most significant cause of mortality in young people. However, the incidence, the survival, and the management of adolescent cancers have never been studied. The aim of this study is to investigate incidence rate (IR) of adolescents with cancer from data recorded in French Cancer Registries covering eight administrative areas, representing 10% of the French population, over a 10‐year period (from 1988 to 1997).

Procedure

Data from the FRANCIM network of French population‐based Cancer Registries were used to analyze cancer incidence among adolescents aged from 15 to 19 years, excluding basal cell carcinomas of skin.

Results

In total, 699 cases were recorded. Of these, 22.9% were lymphomas, 12.7% germ‐cell tumors, 11.9% leukemias, 10.6% central‐nervous‐system tumors, 10.0% bone neoplasms, 7.6% soft‐tissue sarcomas, and 19.5% tumors of adulthood (thyroid carcinomas 4.9%, melanomas 9.0%, and other carcinomas 5.6%). The overall IR was 172.9 per million adolescents (M/F: 1.2) with an annual increase of 3% (P = 0.58). Over the two 5‐year periods (1988–1992 and 1993–1997) the IR increases significantly for malignant melanomas (respectively 10.4 and 21.2; P = 0.04).

Conclusions

Our findings are similar to that reported by previous studies performed in European and North‐American countries. Future studies need to focus on the etiology explaining the increase in incidence, the management and the impact of the type of care on outcomes. © 2004 Wiley‐Liss, Inc.
Outcome in children with pulmonary Langerhans cell histiocytosis
Authors: Braier Jorge , Latella Antonio , Balancini Blanca , Castaños Claudio , Rosso Diego , Chantada Guillermo , Ripoli Mario , Goldberg Julio
Published: June 2004

Background

The aim of this study was to evaluate features and outcome of children with Langerhans cell Histiocytosis (LCH) and pulmonary involvement.

Procedure

Retrospective evaluation of LCH patients was performed from 1987 to 2001. Multisystem patients were classified according to the pattern of organ system involvement into Groups: A (no pulmonary, hematologic, or hepatic involvement), B (pulmonary involvement), C (pulmonary and hematologic or hepatic involvement), and D (hematologic or hepatic involvement). All had skin, bone, or lymph node involvement. Chest X‐ray was performed in all patients and computed tomography (CT) in 21. Diagnostic lung biopsy was performed in five patients.

Results

Pulmonary involvement was found in 36/220 patients studied. Two patients had isolated pulmonary involvement. Multisystem involvement was present in 83 patients, 34 of whom had pulmonary involvement. In 20/36 patients, tachypnea, cough, and thoracic pain occurred. Diffuse interstitial involvement was found in all cases. Pulmonary function tests were performed in nine patients, six of whom revealed mild to moderate restrictive respiratory involvement. The two patients having isolated pulmonary involvement survived 2 and 2.7 years after diagnosis. Median follow‐up of all multisystem patients was 2.1 years, with a 5‐year survival probability of 0.59. The 5‐year survival probability of Groups A–D was 0.94, 0.83, 0.23, and 0.40, respectively. The survival difference between Groups B and C was statistically different (P < 0.0071).

Conclusions

According to our data, pulmonary compromise without other risk organ involvement does not appear to be a negative prognostic factor in our study. © 2004 Wiley‐Liss, Inc.
Hepatoblastoma in a girl with biliary atresia: Coincidence or co‐incidence
Authors: Taat F. , Bosman D.K. , Aronson D.C.
Published: June 2004

Hepatoblastoma (HB) and biliary atresia (BA) are both rare conditions that occurred in the patient described. This is the second such case in the literature. An explanation for this apparent coincidence could possibly be found in the existance of pluripotent liver stem cells. In humans, small epithelial cells (SEC) behave as pluripotent stem cells. These are cells that can develop as biliary epithelial cells or as liver parenchymal cells, and are thought to be the precursor cell of HB. They are present in a much higher concentration in the livers of patients with BA, which may make them prone to develop HB. © 2004 Wiley‐Liss, Inc.
Outcome of children with B cell lymphoma in Venezuela with the LMB‐89 protocol
Authors: Acquatella G. , Insausti C.L. , García R. , Gómez R. , Hernández M. , Carneiro M. , Santos S. , Nouel A.
Published: June 2004

Background

We analyzed the results of the LMB‐89 protocol performed in seven centers in Venezuela in 96 children having B‐cell non‐Hodgkin lymphoma treated from 1995 to 2002.

Procedure

Mean age was 7.1 years with 71 (74%) been male. Eighty‐two patients (85%) had diffuse small cell lymphoma Burkitt and Burkitt‐like, and 14 (15%) had diffuse large B‐cell lymphoma. Initial disease sites included the abdomen in 67%, peripheral nodes in 8%, and mediastinal in 4%. Treatment was directed to risk groups as described for LMB‐89 protocol. Group A: seven patients (7%), group B: 80 patients (83%), and group C: nine patients (9%).

Results

Mean follow‐up was 35 ± 31 months. Complete remission (CR) occurred in 70 patients (73%); four patients (6%) had relapse during the first year and ten patients (10%) had progressive disease. Overall survival (OS) and event free survival (EFS) were 85 and 80% at 1 year, and 82 and 75% at 2 years, respectively. The EFS by therapeutic groups at 3 years was A: 100%; B: 76%, and C: 56%. Toxicity: neutropenia in 75%, thrombocytopenia in 63%, febrile neutropenia in 39%. Viral infections: hepatitis B in 20%, hepatitis C in 2%, and Herpes zoster in 3%. Tumor lysis syndrome (TLS) occurred in 9% during induction phase with a high mortality of 44% (urate‐oxidase was available only at the end of the study).

Conclusions

The high mortality rate during induction phase prohibited a better EFS. Prophylactic use of xantine‐oxidase may improve future results. The high incidence of hepatitis B requires a vaccination program. © 2004 Wiley‐Liss, Inc.
The value of postoperative radiotherapy in childhood nonrhabdomyosarcoma soft tissue sarcoma
Authors: Paulino Arnold C. , Ritchie Justine , Wen B‐Chen
Published: June 2004

Objective

To determine the value of postoperative radiotherapy (RT) in the management of nonrhabdomyosarcoma soft tissue sarcoma (NRSTS) of childhood.

Procedure

From 1964 to 2000, 62 children with a median age of 14 years were seen at the University of Iowa and underwent a wide local excision for non‐metastatic NRSTS. Tumors were high grade in 36 (58%) and >5 cm in 24 (39%). Margins of resection were negative (Group I) in 37 (60%) and positive (Group II) in 25 (40%). Postoperative RT was delivered to 20 patients (32%); eight of 37 (22%) Group I and 12 of 25 (48%) Group II children received postoperative RT. Chemotherapy was employed in 19 patients (31%). Median follow‐up was 9.6 years.

Results

The 5‐ and 10‐year overall survival rates for Group I were 69 and 63% and for Group II were 66 and 60%. The 5‐ and 10‐year local control rate was 66%. On multivariate analysis, size of tumor (P < 0.001) and postoperative RT (P = 0.017) were prognostic factors for local control. All 13 Group I children with low grade, ≤5 cm tumors were locally controlled without RT. For Group II patients, 2‐ and 5‐year local control rates were 92 and 82% with postoperative RT and 51 and 43% for no RT (P = 0.0426).

Conclusions

Local control was improved by the addition of postoperative RT in tumors with positive margins of resection. © 2004 Wiley‐Liss, Inc.
Wnt/Frizzled signaling in Ewing sarcoma
Authors: Üren Aykut , Wolf Vladimir , Sun Yu‐Feng , Azari Amir , Rubin Jeffrey S. , Toretsky Jeffrey A.
Published: June 2004

Background

The Ewing sarcoma family of tumors (ESFT) is a set of neuroectodermal malignancies that typically presents in the second decade and has a poor prognosis due to metastatic disease. Wnt signaling has a critical role in the normal development of multiple neuroectodermal tissues and also contributes to the neoplastic properties of tumor cells of neuroectodermal origin.

Procedure

We surveyed the expression of Wnts and their receptors in nine ESFT cell lines by RT‐PCR analysis. We also tested biological response of ESFT cell lines to exogenous Wnts in β‐catenin stabilization, actin stress fiber formation, and chemotaxis assays.

Results

We detected Wnt‐10b in all the lines, and most also expressed Wnt‐5a, Wnt‐11, and Wnt‐13. Several Frizzleds (Fz) and the Wnt co‐receptors, low density lipoprotein‐receptor‐like proteins 5 and 6 were also expressed. We observed a marked stimulation of the β‐catenin/canonical Wnt pathway in ESFT cells treated with Wnt‐3a. Wnt‐3a induced morphologic changes characterized by the formation of long cytoplasmic extensions in ESFT cells. We also observed chemotaxis of ESFT cells in response to Wnt‐3a.

Conclusions

These results provide evidence that components of Wnt/Fz pathway are expressed and an intact Wnt/Frizzled signaling pathway exists in ESFT cell lines. Activation of the Wnt pathway in ESFT suggests that Wnt modulates cell motility rather than cell proliferation. Hence, activation of this pathway may influence metastatic potential of ESFT. © 2004 Wiley‐Liss, Inc.
Is routine chest radiography necessary for the initial evaluation of fever in neutropenic children with cancer?
Authors: Renoult Edith , Buteau Chantal , Turgeon Nathalie , Moghrabi Albert , Duval Michel , Tapiero Bruce
Published: June 2004

Background

The yield of routine chest radiography (CXR) as part of the initial management of febrile neutropenic pediatric oncology patients is questionable.

Procedure

We retrospectively analyzed the clinical records of neutropenic (absolute neutrophil count ≤0.5 × 109/L) children with cancer, admitted with oral temperature ≥38°C to our institution, between January 2001 and October 2002. Following admission, patients received tobramycin plus (piperacillin or ticarcillin–clavulanic acid). Admission routine CXRs were reviewed. Clinical and radiological features were compared with the discharge diagnosis. Age, underlying disease, and the presence of pulmonary symptoms or signs were studied as possible predictors of CXR findings related to pneumonia.

Results

In total, 88 patients experienced 170 episodes of fever. A routine admission CXR was obtained for 157 of the episodes. Radiologists found 20 (12.7%) abnormal CXR (6 with a segmental or lobar consolidation considered as a pneumonia). In addition, two patients with abnormal admission CXR developed lobar consolidation on a repeat film, later in their hospital course. There were no differences in age and type of underlying disease between children with or without pneumonia. Respiratory symptoms were initially present in 58 cases. Seven (12%) had pneumonia. Among the 99 asymptomatic cases only one (1%) patient had a pneumonia (P = 0.0041). This child had a positive blood culture for P. aeruginosa at the time of admission. None of the children had initial therapy modified on the basis of radiologic findings.

Conclusion

In this study, pneumonia is an unusual cause of fever (5%), especially in the absence of respiratory signs or symptoms (1%). Admission CXR should be reserved for the neutropenic pediatric oncology patient presenting with fever and abnormal respiratory findings. © 2004 Wiley‐Liss, Inc.
The discovery of two kinds of ion pairs
Authors: Smid Johannes
Published: June 2004

The discovery and implications of the existence of two kinds of ion pairs in solutions of carbanion salts is described. Also discussed are the factors controlling tight–loose ion pair equilibrium: the nature of the carbanion and its counterion, temperature, pressure, solvent, and cation‐complexing additives. A few examples are presented of the effect of these ionic species on the mechanisms of anionic polymerization and proton transfer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3655–3667, 2004
PREDICT modeling and in‐silico screening for G‐protein coupled receptors
Authors: Shacham Sharon , Marantz Yael , Bar‐Haim Shay , Kalid Ori , Warshaviak Dora , Avisar Noa , Inbal Boaz , Heifetz Alexander , Fichman Merav , Topf Maya , Naor Zvi , Noiman Silvia , Becker Oren M.
Published: June 2004

G‐protein coupled receptors (GPCRs) are a major group of drug targets for which only one x‐ray structure is known (the nondrugable rhodopsin), limiting the application of structure‐based drug discovery to GPCRs. In this paper we present the details of PREDICT, a new algorithmic approach for modeling the 3D structure of GPCRs without relying on homology to rhodopsin. PREDICT, which focuses on the transmembrane domain of GPCRs, starts from the primary sequence of the receptor, simultaneously optimizing multiple ‘decoy’ conformations of the protein in order to find its most stable structure, culminating in a virtual receptor‐ligand complex. In this paper we present a comprehensive analysis of three PREDICT models for the dopamine D2, neurokinin NK1, and neuropeptide Y Y1 receptors. A shorter discussion of the CCR3 receptor model is also included. All models were found to be in good agreement with a large body of experimental data. The quality of the PREDICT models, at least for drug discovery purposes, was evaluated by their successful utilization in in‐silico screening. Virtual screening using all three PREDICT models yielded enrichment factors 9‐fold to 44‐fold better than random screening. Namely, the PREDICT models can be used to identify active small‐molecule ligands embedded in large compound libraries with an efficiency comparable to that obtained using crystal structures for non‐GPCR targets. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Fault tree analysis for risk assessment in the Borexino experiment
Authors: Caputo Antonio C. , Palumbo Mario , Tartaglia Roberto
Published: June 2004

This paper outlines a methodological approach utilizing quantitative risk analyses and cost–benefits evaluation in order to select the most cost‐effective options for risk reduction in industrial plants including structural changes and preventive maintenance. The methodology is based on quantification of top events resorting to fault trees, a sensitivity analysis of the probability of occurrence of top events, and a comparison of corrective measures based on cost and effectiveness criteria. The method is applied to a case study represented by the pseudocumene purification plant of the Borexino experiment in order to show its capability. The experiment is located in the Gran Sasso National Laboratory operated by the Italian National Institute for Nuclear Physics. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 121–131, 2004
Estimation of risk indices of chemicals during transportation
Authors: Rao K. Rajeshwar , Rao S. Venkateswar , Chary V.
Published: June 2004

The National Fire Protection Association (NFPA) rankings for health, flammability, reactivity, and special hazards have been considered the basis for calculating the risk indices of materials in transportation as they have adopted the United Nations criteria for toxicity and corrosivity, which also addresses hazards in transportation to some extent. Using these NFPA rankings a method has been developed to calculate the risk indices of chemicals during transportation. Other factors such as quantity of material moving, distance between the point of release and population, rate of dispersion and probability of an accident were also considered in this paper for calculating the transportation risk index of a chemical. This index can be used as a guide for assessing the potential hazards of a chemical during its transportation. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 149–154, 2004
Emergency venting requirements for tempered systems considering partial vapor–liquid separation with disengagement parameters greater than unity: Part II: Application
Authors: D'Alessandro Robert
Published: June 2004

Part 1 of this two‐paper series presented closed‐form analytical expressions for the two‐phase emergency relief requirements of top‐vented vertical cylindrical containers when the fluids involved exhibit partial disengagement. Both churn‐turbulent flow and bubbly flow fluid behaviors, with disengagement parameters greater than unity, were considered. Energy input from either runaway reactions or uncontrolled external heat was included. The methods are limited to systems that are tempered and do not contain noncondensable components. In Part 2, the models developed in Part 1 are applied to specific points along the venting transient, yielding expressions for the required flow rate under emergency conditions. Part 2 elaborates on the limitations of the models, illustrates the use of the models with numerical examples, and compares the results against previous work. The effect of disengagement parameters greater than unity is illustrated in terms of both the required relieving rate and the mass remaining inside the container when disengagement occurs. © 2004 American Institute of Chemical Engineers Process Sag Prog 23: 86–98, 2004
Process safety in the future—A view from the chemistry
Authors: Leggett David J.
Published: June 2004

This paper advances the thesis that a complete assessment of the chemical process safety must be founded on specific chemical hazards data. Usually, these data can only be obtained from appropriately designed experiments using the correct testing techniques. The basis of safety and the window of safe operations arise from the relevant process safety data.

BakerRisk's experience with the chemical processing industry (CPI) has shown that the PSM elements Safety Information, Process Hazards Analysis, and Operating Procedures are often documented without adequate hazards test data for the covered process. The information is often qualitative; it may be taken from inappropriate laboratory data and may not address the specific process deviation or worst‐case situation(s). This lack of hazards test data represents an information void that tabletop or literature process hazard analyses alone cannot fill. Five observations and recommendations are offered:

Chemical process safety supported by hazards testing is the right thing to do, whether the process is covered or not and whether the process is at the manufacturing stage or not;

Hazards testing to identify and evaluate potential upset conditions should be an integral part of a company's process safety program. It is a major information source for process hazard analyses;

The information obtained is specific to the thermodynamics and kinetics of the process chemistry;

The information enables clear identification of operational, thermal, and reactivity hazards of processes involving highly hazardous chemicals;

The scope of the chemical hazards testing should be matched with the quantities of chemicals involved and the development stage of the product. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 163–169, 2004
A fast thermal activity interpreter for controlling chemical reaction hazards
Authors: Fauske Hans K.
Published: June 2004

A quick and inexpensive method to facilitate product control in assuring safe chemicals management in transportation and storage is introduced. Product safety measures related to large quantities of reactive chemicals require frequent measurements of thermal activity (TA) at low temperature in order to control the potential for contamination, etc., that can accelerate the reaction rate.

The fast thermal activity interpreter (FTAI) instrument is designed to monitor chemical systems undergoing gaseous decomposition reactions with the capability of interpreting TAs of the order of 1 μW/g or a self heat rate of the order of 10−5°C min−1. Recognizing the need for frequent sampling, the FTAI takes about 1 h to run an analysis.

The FTAI concept provides an easy means for determining activation energies and rate laws of gaseous decomposition reactions at ambient temperature conditions and is also well suited to measure material oxidation or corrosion reaction rates involving oxygen consumption. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 108–113, 2004