bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell sheet engineering: intelligent polymer patterned surfaces for tissue engineered liver
Authors: Harimoto Masami , Yamato Masayuki , Kikuchi Akihiko , Okano Teruo 
Published: July 2003

AbstractWe describe a new culture system utilizing the temperature‐responsive polymer grafted surface for designing of cell position and layered tissue reconstruction. Organizing of the hepatic tissue structure by controlling the culture system, that is patterned co‐culture and layered cell sheet co‐culture achieved by moving the cultured cells from the culture surface, resulted in regulation of the hepatocyte function. The technique for cell sheet manipulation would promote the liver tissue engineering in quality.
Synthesis of functional polycarbonates by lipase‐catalyzed ring‐opening polymerization
Authors: Feng Jun , Zhuo Renxi , He Feng , Wang Xuli 
Published: July 2003

AbstractPoly(5‐benzyloxy‐trimethylene carbonate) (PBTMC), a new functional polycarbonate was synthesized by enzymatic ring‐opening polymerization in bulk at 150°C using Porcine pancreas lipase (PPL) or Candida rugosa lipase (CL) as catalyst. Influences of different polymerization conditions such as the source of enzyme, enzyme concentration and polymerization time on the molecular weight and yield were studied. The results showed that PPL exhibited higher activity than CL. Both higher molecular weight(Mn, 18953) and yield(98%) could be obtained by the use of PPL as catalyst. 1H NMR spectrum showed no decarboxylation occurrence during the ring‐opening polymerization.
Degradable polymers: design, synthesis and testing
Authors: Finne Anna , Ryner Maria , Albertsson Ann‐Christine 
Published: July 2003

AbstractThe object for our research is to mimic Nature's perfectly designed resorbable materials to obtain important materials, which are biocompatible and degradable. We have therefore synthesized different architectures and copolymers of aliphatic polyesters with ring‐opening polymerization. The first studies of these materials properties show that properties like hydrophilicity and tensile properties can be controlled.
Dextran‐spermine conjugate: an efficient vector for gene delivery
Authors: Azzam T. , Eliyahu H. , Makovitzki A. , Domb A.J. 
Published: July 2003

AbstractCationic Polysaccharides based on oligoamine‐dextran conjugates were synthesized and tested as vectors for gene transfection. Dextran with 40 kDa in average molecular weight was oxidized under mild conditions by potassium periodate to obtain the respective polyaldehydes in relatively high yields (∼90%). The oxidized dextran was reacted by reductive animation with various oligoamines of 2 to 4 amino groups to obtain the corresponding imine‐conjugates. These water‐soluble polymers were then reduced by excess of sodium borohydride to obtain the corresponding amine‐conjuagtes in 30‐40% overall yield. The electrostatic interactions of the representative polycations with plasmid DNA were evaluated as a function of charge ratio (+/−, polymer/DNA) and ionic strength of the medium applying the ethidium‐bromide quenching assay. Although most synthetic polycations formed stable complexes with Plasmid DNAs, only the dextran‐spermine conjugate of a defined amino content and molecular weight was able to transfect cells with high efficiency.
Controlling polymer structures by atom transfer radical polymerization and other controlled/living radical polymerizations
Authors: Matyjaszewski Krzysztof 
Published: July 2003

AbstractFundamentals of controlled/living radical polymerization (CRP) and Atom Transfer Radical Polymerization (ATRP), relevant to the synthesis of controlled polymer structures are described. Macromolecular brushes with star like structure are used as an example to illustrate synthetic power of ATRP.
An important biodegradable polymer – polylactone‐family polymer
Authors: Wang Shenguo , Cai Qing , Bei Jianzhong 
Published: July 2003

AbstractSystemic investigation on the synthesis and properties of aliphatic polylactones were carried out. And various materials were obtained with different degradation rates and mechanical properties. Two in vivo experiments were presented in this study to envision the biomedical applications of this kind of aliphatic polylactones.
Aggregation of ionic amphiphils in dilute solutions controlled by oppositely charged polyelectolyte templates
Authors: Kasaikin Victor A. , Zakharova Julia A. , Litmanovich Ekaterina A. , Ivleva Elena M. , Zezin Alexander B. , Kabanov Victor A. 
Published: July 2003

AbstractFormation and structure of water‐soluble complexes of poly(acrylic acid) (PA) and poly(diallyldimethylammonium chloride) (PDADMAC) with oppositely charged surfactants have been studied by elastic and quasi‐elastic laser light‐scattering and high‐speed sedimentation technique. It was experimentally shown that generation of intracomplex micellar phase is the necessary condition for formation of such complexes. Minimum aggregation number of the surfactant ions in the complex micelle was found to be determined by the chemical nature of the polymer.
Coordination structure of active site in synthetic hemoprotein (albumin‐heme) with dioxygen and carbon monoxide
Authors: Tsuchida Eishun , Nakagawa Akito , Komatsu Teruyuki 
Published: July 2003

AbstractRecombinant human serum albumin (rHSA) incorporating the tetraphenylporphinatoiron(II) derivative with a covalently linked proximal base (FeP) [albumin‐heme (rHSA‐FeP)] is a synthetic hemoprotein, which can bind and release dioxygen (O2) reversibly under physiological conditions. The coordination structure and spin‐state of the active site in rHSA‐FeP with O2 and carbon monoxide (CO) were revealed by magnetic circular dichroism (MCD), resonance Raman (RR), and infrared (IR) spectroscopy. Under an N2 atmosphere, the MCD spectrum of rHSA‐FeP showed the formation of the five‐coordinate ferrous high‐spin complex of FeP. Upon exposure of this solution to O2 or CO, the spectral pattern immediately changed to that of a six‐coordinate ferrous low‐spin species. The vibration stretching frequencies of the coordinated O2 (νO2) and CO (νCO) were observed at 1158 cm−1 and 1964 cm−1, respectively. The electronic structures of the O2‐ and CO‐adduct complexes of FeP in the hydrophobic pocket of albumin are both identical to those for FeP itself in toluene solution.
Synthesis and properties of carbon dioxide – epoxides copolymers from rare earth metal catalyst
Authors: Quan Zhilong , Min Jiadong , Zhou Qinhai , Xie Dong , Liu Jingjiang , Wang Xianhong , Zhao Xiaojiang , Wang Fosong 
Published: July 2003

AbstractTernary rare earth metal coordinate was used to the copolymerization of epoxides and carbon dioxide. Rare earth compound is crucial in raising the catalytic activity and improving the micro‐structure of the aliphatic polycarbonates. The Tg of the aliphatic polycarbonate is adjustable by controlling the relative molar ratio of the comonomers.
Novel characterization of branching and/or cross‐linking structures in condensation polymers by reactive pyrolysis‐gas chromatography in the presence of organic alkaline
Authors: Tsuge Shin , Ohtani Hajime , Oba Keishi 
Published: July 2003

AbstractThe reactive pyrolysis‐gas chromatography technique was applied to verify the branching and/or cross‐linking structures in an industrially available polycarbonate (PC) sample and its thermally treated one through identification of specific pyrolysis products directly reflecting the related abnormal structures. On the pyrogram of the thermally treated sample, the peaks reflecting the abnormal structures such as branching and/or cross‐linking were observed together with those reflecting main chain and end groups. Furthermore, the fact that some of those characteristic peaks were also observed on the pyrogram of the industrially available PC sample prepared by the melt method indicated that the branching and/or cross‐linking reactions would occur to some extent in the PC synthesized by the melt method.
Recent developments in oriented polymers for biomedical and engineering applications
Authors: Ward Ian Macmillan 
Published: July 2003

AbstractA review is presented of recent research at Leeds University which has been directed at devising novel methods for the production of oriented polymer structures. First, the new hot compaction process for oriented fibre and tapes is described, together with its applications to polyethylene and polypropylene where there are a number of practical developments. Secondly, there is the use of hydrostatic extrusion to make load bearing oriented products from hydroxyapatite filled polyethylenes. The production routes include the application of high pressure annealing prior to hydrostatic extrusion and the preparation of high modulus polyethylene fibre/hydroxyapatite billets as the starting point. Finally, recent progress on die‐drawing as a means to producing oriented monofilaments and biaxially oriented tubes is described, where the applications include polymer ropes, pipes for gas and water distribution and transparent cans for packaging.
Time‐resolved structural studies in fiber processing
Authors: Burger Christian , Ran Shaofeng , Fang Dufei , Cookson David , Yabuki Kazuyuki , Teramoto Yoshihiko , Cunniff Philip M. , Viccaro P. James , Hsiao Benjamin S. , Chu Benjamin 
Published: July 2003

AbstractTime‐resolved and off‐line synchrotron wide‐angle and small‐angle x‐ray scattering (WAXS and SAXS) was used to study the structure formation in poly‐p‐phenylenebenzobisoxazole (PBO) fibers during various stages of spinning, coagulation, and heating processes. WAXS data could be explained in terms of liquid‐crystalline structures of varying degrees of order. A structure model is proposed that is in accordance with the observed SAXS four‐point pattern.
Extruder processing for nanoblends and nanocomposites
Authors: Hu Guo‐Hua , Feng Lian‐Fang 
Published: July 2003

AbstractStructuring multiphase polymer materials to a micrometer scale (micro‐structuration) is a facile engineering practice. However, structuring them to a nanometer scale (nano‐structuration) is a formidable engineering challenge. In this paper, it is shown first why traditional extruder compounding processes only lead to micro‐structuration and then how one may use the extruder type of mixer to structure multiphase polymer materials at a nano‐meter scale to obtain nanostructured polymer blends (nanoblends) and nanostructured polymer composites (nanocomposites).
Bimodal polyethylene products from UNIPOLTM single gas phase reactor using engineered catalysts
Authors: Liu Han‐Tai , Davey Chris R. , Shirodkar Pradeep P. 
Published: July 2003

AbstractAdvanced catalyst engineering from Univation Technologies provides the capability to produce polyethylene with bimodal molecular weight distribution and bimodal composition distribution in a single gas phase reactor. This paper will discuss the structure‐property‐process relationship for these engineered polyethylene products. Examples of High Density Polyethylene (HOPE) polymers with bimodal molecular weight distribution will demonstrate the utility of the engineered catalysts in high molecular weight film production. Examples of Linear Low Density Polyethylene (LLDPE) polymers with broad comonomer composition distribution will demonstrate the utility of the engineered catalysts for high strength film applications. Examples of HOPE polymers with bidmoal molecular distribution and controlled comonomer distribution will demonstrate the capability of Univation's latest engineered catalysts for high performance pipe applications.
Multibranched star‐shaped polyethers
Authors: Lapienis Grzegorz , Penczek Stanislaw 
Published: July 2003

AbstractSynthesis of multibranched star‐shaped polyethers having poly(ethylene oxide)s (PEO) arms is described. The novel method of preparing these multibranched macromolecules consists in reaction of the ‐OH ended oligomers with dicyclic compounds; e.g. monoalkyl ethers of poly(ethylene oxide) with diepoxides in the presence of a basic catalyst, converting a part of the ∼OH groups into ∼OCσ end groups (alkoxide anions). Analysis of the structure of these macromolecules was mostly based on 1H NMR, MALDI‐TOF, and SEC with triple detection. The absolute values of Mw (LS), Mw/Mn, and [η] are given, indicating formation of macromolecules of high molar mass and highly branched. The number of branches was estimated by several methods, including comparison of the Mark‐Houwink (M‐H) dependencies of the obtained products with the M‐H dependence for PEO stars with exactly known number of arms. The final stars were phosphorylated at the −OH ended branches. Almost exclusively monoesters of phosphoric acid were found in 31P (1H) NMR.
Atom transfer radical polymerization of vinyl monomers in the presence of tetraethylthiuram disulfide
Authors: Qiu Kun‐Yuan , Li Peng , Chen Xiao‐Ping 
Published: July 2003

AbstractIn situ ATRPs of MMA, St in the presence of TD catalyzed by FeCl3/PPh3 and CuBr2/bpy have been studied, respectively. The results showed that the initiator Et2NCS2X (X = Cl or Br) and catalyst FeCl2 or CuBr were formed in situ from the initiating components and the polymerization exhibited living radical polymerization characteristics. In the case of St polymerization with TD/CuBr/bpy initiating system, an inverse ATRP was observed.
Ethene‐butadiene copolymers by single‐site catalysts
Authors: Kaminsky Walter , Hinrichs Benjamin 
Published: July 2003

AbstractConstrained geometry catalysts ([Me2Si(NtBu)(Me4Cp)]TiCl2) were used to copolymerize ethene and 1,3‐butadiene. It is possible to incorporate 17 mol% of butadiene, other catalyst systems such as CpTiCl3/MAO show much lower incorporation. More than 300 000 kg of copolymer can be obtained by one mol of the catalysts in one hour. The microstructure of the copolymers has been investigated by 1H‐ and 13C‐NMR spectroscopy. The butadiene is incorporated mainly in 1,4‐trans‐ and 1,2‐structure. The high amount of 9‐29% of vinyl groups offers the possibility of an easy vulcanisation. The molecular weights of these elastomers are high with values of 250 000. Important is the low glass transition temperature of −28 °C of a copolymer with 7 mol% of butadiene.
Synthesis of polyolefins with unique properties by using metallocene‐type catalysts
Authors: Imanishi Yukio , Naga Naofumi , Tsubooka Michiyo 
Published: July 2003

AbstractCopolymerization of ethylene and 1,5‐hexadiene (HD) by zirconocene catalysts proceeded via cyclization‐addition mechanism to form 1,3‐didsubstituted cyclopentane structure in the polyethylene chain. The 1,3‐cyclopentane structure was found to be taken in the crystalline structure of polyethylene (isomorphism) by partially chainging the trans zigzag chain into gauche conformation, thereby, inducing a transformation of orthorhombic crystal to pseudohexagonal crystal. Copolymerization of ethylene and cyclopentene (CPE) by zirconocene catalysts yielded copolymers having 1,2‐disubstituted cyclopentane structure in the polyethylene chain. The 1,2‐cyclopentane structure was not taken into the crystalline structure of polyethylene. The melting point (Tm) and the crystallinity (Xc) of polyethylene decreased by copolymerization of HD or CPE, and the Tm‐ and Xc‐decreasing effect of CPE was stronger than HD. For copolymers of propylene and HD or CPE obtained with isospecific zirconocene catalyst, the isomorphism was not ovserved.
Syntheses and characterizations of polypropene, polystyrene and their block copolymers with titanocene catalysts
Authors: Lin Shangan , Wu Qing , Chen Rui , Zhu Fangming 
Published: July 2003

AbstractPentamethylcyclopentadienyltitanium tribenzyloxide, Cp*Ti(OBz)3, was used as the catalyst precursor for polymerizations of propene and styrene. The titanocene catalyst affords atactic polypropene and syndiotactic polystyrene with high activities in the presence of methylalumimoxane (MAO). Block copolymerization of propene and styrene was carried out in the presence of Cp*Ti(OBz)3/MAO catalyst system by the means of external addition of triisobutylaluminum (TIBA) and sequential monomer feed. The copolymerization product is mainly a mixture of atactic polypropene(aPP) and syndiotactic polystyrene(sPS) homopolymers and aPP‐b‐sPS block copolymers, which can be separated into fractions with successive extraction with boiling methylethyl ketone(MEK), heptane, tetrahydrofuran(THF), and chloroform. Studies on thermal properties showed that rubbery phases and crystalline regions both appear in the block copolymer at the room temperature and that aPP‐b‐sPS block copolymer has better toughness than sPS.
Recent advances in the anionic synthesis of chain‐end functionalized polymers
Authors: Quirk Roderic P. , Cheong Tae‐Hee , Jiang Kevin , Gomochak Deanna L. , Yoo Taejun , Andes Keith T. , Mathers Robert T. 
Published: July 2003

AbstractRecent results for the preparation of chain‐end functionalized polymers using alkyllithium‐initiated anionic polymerization are described. Termination with 4‐chloro‐1,1,1‐trimethoxybutane has been used to prepare trimethoxy ortho ester (carboxyl)‐functionalized polymers. Functionalization with the oxiranes, glycidoxypropyltrimethoxysilane, 3,4‐epoxy‐1‐butene and 1,1,1‐trifluoro‐2,3‐epoxypropane, has been investigated to prepare trimethoxysilyl‐functionalized polymers, 1,3‐diene‐functionalized macro monomers and trifluoromethyl‐functionalized polymers, respectively. Secondary amine‐functionalized polymers have been prepared by termination with N‐(benzylidene)methylamine and also using an N‐benzyl tertiary amine‐functionalized alkyllithium initiator followed by hydrogenolysis of the benzyl group.
Stereocontrol using Lewis acids in radical polymerization
Authors: Okamoto Yoshio , Habaue Shigeki , Isobe Yutaka , Suito Yoshikatsu 
Published: July 2003

AbstractThe radical polymerization of various (meth)acrylamides in the presence of Lewis acids such as Yb(OTf)3 and Y(OTf)3 was carried out. The polymerization with Lewis acids led to highly isotactic polymers, while the polymers synthesized without Lewis acids were atactic or syndiotactic. The dependence of the polymer properties on the tacticity was also demonstrated.
Homo‐ and copolymerization of styrene using combined diphenylzinc‐additive initiator systems
Authors: Rabagliati Franco M. , Pérez Mónica A. , Cancino Rodrigo A. , Rodríguez Francisco J. , Caro Carlos J. 
Published: July 2003

AbstractCombined systems including diphenylzinc, Ph2Zn, a metallocene, and methylaluminoxane, MAO, have been employed to initiate styrene polymerization and the copolymerization of styrene with p‐alkylsubstituted styrenes and α‐olefins. Both polymerization and copolymerization processes depend on the nature of the metallocene included in the initiator system, the presence of Ph2Zn, the temperature, and the solvent used. S/1‐alkene copolymers were obtained when the initiator systems included a zirconocene, but not when a titanocene participated.
Ring‐opening polymerizations for the synthesis of sequence‐controlled copolymers
Authors: Cho Iwhan 
Published: July 2003

AbstractVarious prestructured cyclic monomers were synthesized and polymerized to construct the copolymers of controlled mer sequence. Substituted 8‐, 10‐ and 12‐membered cyclic olefins were polymerized by ROMP catalyst, i.e., W(OAr)2Cl4/Et4Pb. Those polymers obtained were the alternating terpolymers of butadiene and vinyl monomers. Cyclic monomers with mesogenic groups as substituents were prepared and polymerized successfully. The resulting polymers were highly liquid crystalline exhibiting rather lower transition temperatures than their monomeric analogs.
Structure‐property correlation of light‐emitting polymers containing alternating phenylene and thienylene/bithienylene repeating units
Authors: Xu Jingmei , Chan Hardy S.O. , Ng S.C. 
Published: July 2003

AbstractA number of series of fluorescent and conducting polymers containing alternating 3‐functionalized thienylene/ bithienylene and phenylene/ pyridyl/ biphenylene units were synthesized from a number of central symmetric high oligomers and characterized using UV‐Vis, photoluminescence, conductivity measurement, thermal analysis, electrochemistry, XRD and XPS. Structural variation of the polymers was realized by both side chain and polymer backbone modifications. Close structure‐property correlation of the polymers was observed. This paper mainly reports the results of two families of them, those substituted by alkyl pendant chains and electro‐withdrawing and donating groups.
Constructing robust crew schedules with bicriteria optimization
Authors: Ehrgott Matthias , Ryan David M. 
Published: July 2003

AbstractOptimization‐based computer systems are used by many airlines to solve crew planning problems by constructing minimal cost tours of duty. However, today airlines do not only require cost effective solutions, but are also very interested in robust solutions. A more robust solution is understood to be one where disruptions in the schedule (due to delays) are less likely to be propagated into the future, causing delays of subsequent flights. Current scheduling systems based solely on cost do not automatically provide robust solutions.These considerations lead to a multiobjective framework, as the maximization of robustness will be in conflict with the minimization of cost. For example crew changing aircraft within a duty period is discouraged if inadequate ground time is provided. We develop a bicriteria optimization framework to generate Pareto optimal schedules for the domestic airline. A Pareto optimal schedule is one which does not allow an improvement in cost and robustness at the same time.We developed a method to solve the bicriteria problem, implemented it and tested it with actual airline data. Our results show that considerable gain in robustness can be achieved with a small increase in cost. The additional cost is mainly due to an increase in overnights, which allows for a reduction of the number of aircraft changes. Copyright © 2003 John Wiley & Sons, Ltd.
An interactive fuzzy satisficing method for multiobjective stochastic linear programming problems using chance constrained conditions
Authors: Sakawa Masatoshi , Kato Kosuke 
Published: July 2003

AbstractTwo major approaches to deal with randomness or ambiguity involved in mathematical programming problems have been developed. They are stochastic programming approaches and fuzzy programming approaches. In this paper, we focus on multiobjective linear programming problems with random variable coefficients in objective functions and/or constraints. Using chance constrained programming techniques, the stochastic programming problems are transformed into deterministic ones. As a fusion of stochastic approaches and fuzzy ones, after determining the fuzzy goals of the decision maker, interactive fuzzy satisficing methods to derive a satisficing solution for the decision maker by updating the reference membership levels is presented. Copyright © 2003 John Wiley & Sons, Ltd.
Application of GIS and multicriteria evaluation in locating sustainable boundary between the tunari National Park and Cochabamba City (Bolivia)
Authors: Sharifi M.A. , van den Toorn W. , Rico A. , Emmanuel M. 
Published: July 2003

AbstractIncreased population growth and urbanization, has caused increase in demand for land around the city of Cochabamba, which has led to encroachment into the National Park and the construction of illegal settlements. This has created a number of problems, some of which are the direct consequences of the new settlements in the ‘Tunari’ foothills. These settlements constitute a threat to the environment and people because of their location in flood risk and aquifer recharge areas. In response to this problem the city authorities are considering relocating the boundary between the National Park and the city. This study has focused on the design and evaluation of alternative locations for a sustainable boundary between the north of ‘Cochabamba City’ and the southern boundary of the ‘Tunari National Park’. In this process, a rational and systematic approach of collaborative‐decision‐making, supported by geographical information systems (GIS) and multicriteria evaluation (MCE) has been employed and evaluated. Copyright © 2003 John Wiley & Sons, Ltd.