bluuebunny/crossref_metadata_2025 huggingface dataset:
Tetrahedral mesh generation and optimization based on centroidal Voronoi tessellations
Authors: Du Qiang , Wang Desheng
Published: January 2003

The centroidal Voronoi tessellation based Delaunay triangulation (CVDT) provides an optimal distribution of generating points with respect to a given density function and accordingly generates a high‐quality mesh. In this paper, we discuss algorithms for the construction of the constrained CVDT from an initial Delaunay tetrahedral mesh of a three‐dimensional domain. By establishing an appropriate relationship between the density function and the specified sizing field and applying the Lloyd's iteration, the constrained CVDT mesh is obtained as a natural global optimization of the initial mesh. Simple local operations such as edges/faces flippings are also used to further improve the CVDT mesh. Several complex meshing examples and their element quality statistics are presented to demonstrate the effectiveness and efficiency of the proposed mesh generation and optimization method. Copyright © 2003 John Wiley & Sons, Ltd.
Digital redesign of analog controllers based on minimizing integral of squared errors
Authors: Hwang Chyi , Chang Fang‐Pi , Hwang Jyh‐Haur
Published: January 2003

Digital redesign is to replace an existing well‐designed analog feedback controller by a digital one along with a sampler and a hold. In this paper, we present a digital redesign technique which takes into account both closed‐loop and intersample behaviour. More precisely, we give a numerical procedure to optimally discretize an analog controller such that the integral of the squared error between the closed‐loop step responses of the analog and digital controlled systems is minimized. A parametric expression is derived for evaluating the integral performance index. With this expression, the optimal digital redesign problem becomes an optimal parameter selection problem which can be solved using existing optimal parameter search algorithms. Moreover, it allows one to obtain optimal reduced‐order digital controllers for sampled‐data control systems over a range of sampling periods. Copyright © 2003 John Wiley & Sons, Ltd.
Optimality of greedy and sustainable policies in the management of renewable resources
Authors: Rapaport A. , Sraidi S. , Terreaux J.P.
Published: January 2003

We consider a discrete‐time modelling of renewable resources, which regenerate after a delay once harvested. We study the qualitative behaviour of harvesting policies, which are optimal with respect to a discounted utility function over infinite horizon. Using Bellman's equation, we derive analytically conditions under which two types of policies (greedy and sustainable) are optimal, depending on the discount rate and the marginal utility. For this particular class of problems, we show also that the greedy policy is attractive in a certain sense. The techniques of proof lie on concavity, comparison of value functions and Lyapunov‐like functions. Copyright © 2003 John Wiley & Sons, Ltd.
Optimal control for non‐linear integrodifferential functional equations
Authors: Jeong Jin‐Mun , Park Jong‐Yeoul
Published: January 2003

An optimal control problem for a non‐linear control system with a hemicontinuous and coercive operator is studied. The existence, uniqueness, and a variation of solutions of the system are also given. An example is presented to illustrate the theory. Copyright © 2003 John Wiley & Sons, Ltd.
Miscibility of poly(vinyl alcohol)/polyacrylamide blends before and after gamma irradiation
Authors: El‐din Horia M Nizam , El‐Naggar Abdel Wahab M , Ali Faten I
Published: January 2003

Films of polymer blends having various contents of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) were prepared by the solution casting technique using water as a common solvent. The thermal, mechanical and morphological properties of these blends before and after exposure to various doses of gamma radiation, up to 100 kGy, have been investigated. The visual observation and reflectance measurements show that PVA/PAM blends are miscible over a wide range of composition. Moreover, the differential scanning calorimetry (DSC) thermograms show only a single glass transition temperature (Tg), but not those of PVA or PAM homopolymers, giving further support to the complete compatibility of such blends. The Tg of PVA/PAM blends decreases with increasing content of PAM but increases after exposure to gamma irradiation, indicating the occurrence of crosslinking. These findings were demonstrated by the scanning electron micrographs of the fracture surfaces and the tensile mechanical properties. The TGA thermograms and percentage mass loss at different decomposition temperatures show that unirradiated PVA homopolymer possesses higher thermal stability than PAM homopolymer and their blends within the heating temperature range investigated, up to 250 °C. An opposite trend is observed within the temperature range 300–500 °C. In general, the thermal stability of homopolymers or their blends improves slighly after exposure to an irradiation dose of 100 kGy. These findings are clearly confirmed by the calculated activation energies of the thermal decomposition reaction of the homopolymers and the blends.

© 2003 Society of Chemical Industry
Synthesis of amphiphilic magnetic microspheres by dispersion copolymerization of styrene and poly(ethylene oxide) macromonomer
Authors: Liu Xue‐Yong , Ding Xiao‐Bin , Zheng Zhao‐Hui , Peng Yu‐Xing , Chan Albert S C , Yip C W , Long Xin‐Ping
Published: January 2003

Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g−1.

© 2003 Society of Chemical Industry
Impact modification of waste PET by polyolefinic elastomer
Authors: Chaudhari K P , Kale D D
Published: January 2003

Waste poly(ethylene terephthalate) [PET] and a polyolefinic elastomer (POE), Engage™ 8150, were melt blended in a co‐rotating twin screw extruder having initial distributive mixing followed by high shearing/stretching. Compositions having POE up to 10% with and without poly(ethylene‐co‐acrylic acid), as a compatibilizer were studied. The blends were characterized for mechanical, thermal and rheological properties as well as for morphological characteristics. Incorporation of POE improved the impact properties of PET very significantly.

© 2003 Society of Chemical Industry
New nanocomposite materials based on polymerization of [oligo(oxyethylene) methacrylates] in the presence of montmorillonite clay
Authors: Salahuddin Nehal , Rehab Ahmed
Published: January 2003

Intercalation of poly[oligo(oxyethylene) methacrylates] onto sodium montmorillonite (MMT) clay has been investigated. A polymer–clay hybrid has been synthesized through intercalation of the monomer followed by its solution free‐radical polymerization. Eight polymer–clay hybrids were prepared using different weight ratios of clay, different oligo(oxyethylene) lengths and different proportions of crosslinker. Evidence of the development of nanostructures is obtained from scanning electron microscopy, and wide‐angle X‐ray diffraction studies support these results which show disappearance of the peak characteristic to d001 spacing. In this hybrid MMT is dispersed homogeneously in the polymer matrix.

© 2003 Society of Chemical Industry
Plasma‐induced grafting of hydroxyethyl methacrylate (HEMA) onto chitosan membranes by a swelling method
Authors: Li Yeping , Liu Li , Fang Yue‐e
Published: January 2003

Hydroxyethyl methacrylate (HEMA) was grafted onto chitosan membranes by plasma‐graft polymerization. Effects of monomer concentration, plasma power and plasma time on the amount of grafting were investigated. The results showed that there were two processes: grafting polymerization and etching of the membrane. The surface of the grafted membrane was evaluated by FTIR. Scanning electron microscopy indicated that the surface morphology of the grafted membrane could be adjusted through plasma power. Water contact angles of the chitosan surface decreased from 78.2° to 45.4° while the amount of grafting increased from 0 to 12.2%, indicating improved hydrophilicity of the membrane surface. Permeation coefficients through the original membrane, the membrane treated at 55 W for 15 min, and the membrane treated at 55 W for 30 min for creatinine were 9.12 × 10−7, 10.6 × 10−7 and 8.57 × 10−7 cm2 s−1, respectively. Thermogravimetry and mechanical testing showed that there were no significant changes on the bulk property of chitosan membrane after modification.

© 2003 Society of Chemical Industry
Decreasing miscibility with greater heterogeneity in ternary polymer blend: poly(cyclohexyl methacrylate), poly(α‐methyl styrene) and poly(4‐methyl styrene)
Authors: Chang Li Ling , Woo E M
Published: January 2003

A ternary blend system comprising poly(cyclohexyl methacrylate) (PCHMA), poly(α‐methyl styrene) (PαMS) and poly(4‐methyl styrene) (P4MS) was investigated by thermal analysis, optical and scanning electron microscopy. Ternary phase behaviour was compared with the behaviour for the three constituent binary pairs. This study showed that the ternary blends of PCHMA/PαMS/P4MS in most compositions were miscible, with an apparent glass transition temperature (Tg) and distinct cloud‐point transitions, which were located at lower temperatures than their binary counterparts. However, in a closed‐loop range of compositions roughly near the centre of the triangular phase diagram, some ternary blends displayed phase separation with heterogeneity domains of about 1 µm. Therefore, it is properly concluded that ternary PCHMA/PαMS/P4M is partially miscible with a small closed‐loop immisciblity range, even though all the constituent binary pairs are fully miscible. Thermodynamic backgrounds leading to decreased miscibility and greater heterogeneity in a ternary polymer system in comparison with the binary counterparts are discussed.

© 2003 Society of Chemical Industry
Hyperbranched polyacrylates prepared by self‐condensing vinyl copolymerization in the presence of a tetrafunctional initiator
Authors: Hong Chun‐Yan , Zou Ying‐Fang , Pan Cai‐Yuan
Published: January 2003

Hyperbranched copolymers were synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐[(2‐bromopropionyl)oxy]ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of a tetrafunctional initiator, 6,6‐bis[5‐(α‐bromoisobutyryloxy)‐2‐oxapentyl]‐4,8‐dioxaundecane‐yl‐1,11 dibromoisobutyrate (THABI). The structures of the polymers obtained were characterized by NMR and size exclusion chromatography/right‐angle laser‐light scattering/differential viscometry/differential refractometry. Molecular weight, molecular weight distribution and degree of branching were influenced by conversion and initial feed molar ratio of BPEA, MA and THABI. The addition of THABI can narrow the polydispersity of the hyperbranched copolymers obtained. The results are consistent with our previous simulation work.

© 2003 Society of Chemical Industry
Alignment behaviour of liquid crystals on ethyl cellulose films with banded‐texture structure
Authors: Yan Lifeng , Zhu Qingshi , Ikeda Tomiki
Published: January 2003

Films were formed by casting and shearing ethyl cellulose in chloroform at high coating speed and thin coating thickness. The films were used as alignment layers for liquid crystals. Atomic force microscopy and polarizing optical microscopy (POM) were used to identify the banded‐texture structure of the films. The alignments of nematic liquid crystal 4‐cyano‐4′‐n‐pentylbiphenyl (5CB) droplets on the films were observed by POM. Furthermore, the time‐dependent alignment behaviour of 5CB on the films was recorded and studied.

© 2003 Society of Chemical Industry
Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology, structure, crystallization, and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)
Authors: Tsuji Hideto , Yamada Tamami , Suzuki Masakazu , Itsuno Shinichi
Published: January 2003

Blended films of poly(L‐lactide) [ie poly(L‐lactic acid)] (PLLA) and poly(ϵ‐caprolactone) (PCL) without or mixed with 10 wt% poly(L‐lactide‐co‐ϵ‐caprolactone) (PLLA‐CL) were prepared by solution‐casting. The effects of PLLA‐CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA‐CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross‐section of the PLLA/PCL blend film. The melting temperatures (Tm) of PLLA and PCL in the films remained unchanged upon addition of PLLA‐CL, while the crystallinities of PLLA and PCL increased at PLLA contents [XPLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4–0.7 and at most of the XPLLA values, respectively. The addition of PLLA‐CL improved the tensile strength and the Young modulus of the films at XPLLA of 0.5–0.8 and of 0–0.1 and 0.5–0.8, respectively, and the elongation at break of the films at all the XPLLA values. These findings strongly suggest that PLLA‐CL was miscible with PLLA and PCL, and that the dissolved PLLA‐CL in PLLA‐rich and PCL‐rich phases increased the compatibility between these two phases.

© 2003 Society of Chemical Industry
Flow behaviour and microstructure evolution in novel SiO2/PP/LCP ternary composites: effects of filler properties and mixing sequence
Authors: Lee Mun Wai , Hu Xiao , Li Lin , Yue Chee Yoon , Tam Kam Chiu
Published: January 2003

When silica (SiO2) fillers were introduced into the polypropylene (PP) and liquid‐crystalline polymer (LCP) blend, it was found that the mixing sequence, the filler size, and the filler surface nature affected the rheology of the composites and the morphology of the LCP phase in the ternary composite. In particular, the compatibility between the filler and the PP matrix was found to exert a strong influence on the droplet‐fibril transition. The incorporation of the hydrophobic silica to the LCP/PP blend facilitated the fibrillation of LCP because the hydrophobic filler demonstrated affinity towards the hydrophobic PP matrix. The preferential residence of the hydrophobic silica in the PP phase would minimise the LCP domain disruption leading to the formation of LCP fibrils with high aspect ratios. The use of fine filler and in situ blending, which promoted the filler–LCP interaction, could prevent coalescence, inhibit deformation and hinder fibril development as well.

© 2003 Society of Chemical Industry
Influence of chitosan characteristics on polymer properties. I: Crystallographic properties
Authors: Jaworska Malgorzata , Sakurai Kensuke , Gaudon Pierre , Guibal Eric
Published: January 2003

The properties of chitosan depend on several parameters including its origin (shrimp, squid, fungi etc), characteristics (mol fraction of N‐acetylation; molecular weight) and treatments used to condition it (dissolving, precipitation, drying). These parameters can influence the material's sorption properties for metal ions. It has been suggested that the changes in sorption properties are related to the crystallinity of the material. The present work focuses on the study of the crystallographic properties of samples prepared from shrimp, squid and fungi sources, with different characteristics and conditioned by several physical treatments (dissolving, reprecipitation and drying, including oven‐drying, freeze‐drying), prior to subsequent studies of their sorption properties for platinum (discussed in Part II of this manuscript).

© 2003 Society of Chemical Industry
Influence of chitosan characteristics on polymer properties: II. Platinum sorption properties
Authors: Jaworska Malgorzata , Kula Karolina , Chassary Philippe , Guibal Eric
Published: January 2003

The sorption of platinum on glutaraldehyde cross‐linked chitosan was investigated at pH 2, using several chitosan samples prepared from different origins and characterized by different mol fractions of N‐acetylation (FA). The influence of material conditioning was also tested: chitosan was dissolved and then re‐precipitated and/or dried (using either oven‐drying or freeze‐drying). The influence of the different characteristics and treatments on both sorption isotherms and uptake kinetics was checked. Part I has studied the effect of preparation and source on sample crystallinity. Shrimp chitosan has a greater sorption affinity for platinum than fungal chitosan and squid chitosan respectively. Sorption kinetics were found comparable for fungal chitosan and shrimp chitosan, while diffusion was more restricted in squid chitosan due to the higher crystallinity. Decreasing the FA increased sorption capacity for shrimp chitosan but decreased sorption levels for squid material. While FA did not influence sorption kinetics for shrimp material it strongly decreased kinetics for squid chitosan. The type of drying procedure hardly affected sorption kinetics and isotherms but when a re‐precipitation step was included in the preparation procedure, the material had to be freeze‐dried to maintain high sorption properties. The freeze‐drying did not control sorption performance, except in the case of re‐precipitated material.

© 2003 Society of Chemical Industry
Segmented polymer networks containing amino‐dendrimers
Authors: Tanghe Leen M , Goethals Eric J , Du Prez Filip
Published: January 2003

Polymer networks in which poly(propylene imine) dendrimers (Astramol™) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films.

© 2003 Society of Chemical Industry
Polyimides containing s‐triazine rings
Authors: Patel Hashmukh S , Patel Vimal C
Published: January 2003

A series of new polyimides containing s‐triazine rings have been synthesized via Diels–Alder intermolecular polymerization of 2,6‐bis(2‐furanylmethylimino)‐4‐isopropoxy‐1,3,5‐triazine with various bis(maleimide)s. All the poly(imino‐s‐triazine imide)s were characterized by elemental analyses, FTIR spectral studies, number average molecular weight (
M
n) by non‐aqueous conductometric titration and thermogravimetry. Glass‐fibre reinforced composites were prepared via an in situ Diels–Alder intermolecular reaction between 2,6‐bis(2‐furanylmethylimino)‐4‐isopropoxy‐1,3,5‐triazine and various bis(maleimide)s. The composites were characterized for chemical resistivity and mechanical properties.

© 2003 Society of Chemical Industry
Random orientation of in situ composites based on liquid‐crystalline polymers by compression moulding
Authors: Xie X L , Yang T Q , Tang C Y
Published: January 2003

In this study, randomly oriented in situ composites based on liquid‐crystalline polymers (LCPs) were prepared by thermal compression moulding. The LCP employed was a semi‐flexible liquid‐crystalline copolyesteramide with 30 mol% of p‐aminobenzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). The matrices were poly(butylene terephthalate) (PBT) and polyamide 66 (PA66). The rheological properties, compatibility and morphological structures of these in situ composites were investigated. The results showed that PA66‐LCP and PBT–LCP component pairs of the composites are miscible in the molten state, but partially compatible in the solid state. The ratios of viscosity, λ1 = ηLCP/ηPA66 and λ2 = ηLCP/ηPBT, are all greater than 1.0. However, the melt viscosity of the LCP/PBT and LCP/PA66 blend is much lower than that of PBT and PA66, and it decreases markedly with increasing LCP content. When the LCP/PA66 or LCP/PBT blends are compression moulded, the LCP/PA66 or LCP/PBT melts and flows easily due to their low viscosity, and the LCP phases in the melts deform easily along the flow directions, which are random. It leads to uniformly dispersed LCP micro‐fibres randomly orientation in the thermoplastic matrix due to the compatibility between the blending components.

© 2003 Society of Chemical Industry
Monte Carlo simulation of gas phase polymerization of 1,3‐butadiene. Part II: Kinetics optimization and confirmation
Authors: Ling Jun , Ni Xufeng , Zhang Yifeng , Shen Zhiquan
Published: January 2003

Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage.

© 2003 Society of Chemical Industry
Melt polycondensation of L‐lactic acid to poly(L‐lactic acid) with Sn(II) catalysts combined with various metal alkoxides
Authors: Moon Sung Il , Kimura Yoshiharu
Published: January 2003

Melt polycondensation of L‐lactic acid (LA) was examined in the presence of binary catalyst systems consisting of SnCl2·2H2O and metal alkoxides as co‐catalysts. Among the co‐catalysts examined, viz (Al(O
iPr)3,Ti(O
iPr)4,Y(O
iPr)3,Si(OEt)4 and Ge(OEt)4), Ge(OEt)4 was found to be the most effective in enhancing the catalytic activity of Sn(II). With an optimized composition of SnCl2·2H2O–Ge(OEt)4, the molecular weight (Mn) of PLLA reached 40 000 Da in a short reaction time (<15 h) at the optimum reaction conditions of 180 °C and 10 Torr. This catalyst system was also superior to the conventional single metal ion catalysts such as Sn(II) in terms of racemization and discolouration of the resultant polymer. The metal alkoxides, added as co‐catalysts, should work as oxo acids that can effectively control the catalytic activity of Sn(II) ion in the direct polycondensation of LA, in a manner similar to that of proton acids.

© 2003 Society of Chemical Industry
Electrosynthesis and characterization of a new electro‐active polymer from 2‐phenylazo‐1‐naphthol
Authors: Rehan Hyman H
Published: January 2003

Cyclic voltammetry was used to electropolymerize 2‐phenylazo‐1‐naphthol in 0.2 M NaOH in 30% ethanol/water and in acetonitrile (MeCN). Very thin electro‐inactive polymer films were obtained in alcoholic NaOH while the films formed in MeCN were much thicker and electro‐active in acid solutions. Based on IR and electrochemical behaviour, poly (2‐phenylazo‐1‐naphthol) (PPAN) is assumed to consist of two polymeric segments, in ratios that depend on the nature of the polymerization solvent. Head‐to‐tail coupling led to formation of ether linkages and the electro‐inactive segments, while tail‐to‐tail coupling led to formation of aromatic CC and quinone moieties in the polymer skeleton and the electro‐active segments. The redox processes of the quinone/quinol transformations were studied by cyclic voltammetry and chronocoulometry. NaOH‐formed films were superior in corrosion protection of steel in 0.5 M sulfuric acid than MeCN‐formed films. PPAN films formed in MeCN were found to mediate the oxidation of ascorbic acid at lower oxidation potential.

© 2003 Society of Chemical Industry
From science teacher to teacher leader: Leadership development as meaning making in a community of practice
Authors: Howe Ann C. , Stubbs Harriett S.
Published: January 2003

The process through which three science teachers became active, effective teacher leaders in their schools, their profession, and their communities was investigated. A model of leadership development, proposed by Palus and Drath (Evolving leaders: A model for promoting leadership development in programs, Center for Creative Leadership, Greensboro, NC, 1995), was used as a framework for analyzing and understanding the experiences and forces that led these teachers to become leaders. Development of the teacher leaders was prompted by their involvement in SCI‐LINK, a program that began as a way to link environmental scientists and science teachers, and grew over a period of 6 years to become a constellation of activities and a learning community of teachers, scientists, and science educators. Four elements of SCI‐LINK that promoted and supported leadership development are identified. Implications for leadership development in science education and other subject areas are discussed. © 2003 Wiley Periodicals, Inc. Sci Ed 87:281–297, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10022
An instructional model for a radical conceptual change towards quantum mechanics concepts
Authors: Kalkanis George , Hadzidaki Pandora , Stavrou Dimitrios
Published: January 2003

We believe that physics education has to meet today's requirement for a qualitative approach to Quantum Mechanics (QM) worldview. An effective answer to the corresponding instructional problem might allow the basic ideas of QM to be accessed at an early stage of physics education. This paper presents part of a project that aims at introducing a sufficient, simple, and relevant teaching approach towards QM into in‐/preservice teacher education, i.e., at providing teachers with the indispensable scientific knowledge and epistemological base needed for a reform of science education along the aforementioned line. The investigation of teacher–learners' (t‐ls') initial knowledge indicated that their main misconceptions appear to be the result of their pre‐/inuniversity traditional instruction, which causes the overlapping/mix‐up of the conceptual frameworks of Classical Physics (CP) and QM. Assuming that these misconceptions form by nature epistemological obstacles to the acquisition of QM knowledge, the educational strategy proposed here aims at leading t‐ls to form a conceptual structure that includes CP and QM as two totally independent conceptual systems. Accepting, furthermore, that the complete distinction of these systems demands a radical reconstruction of t‐ls' initial knowledge, we present here an instructional model that bases the required reconstruction on the juxtaposition of two models that constitute the signal point of twentieth century's “paradigm shift”: (a) Bohr's semiclassical atom model, and (b) the model of the atom accepted by modern physics theory. © 2003 Wiley Periodicals, Inc. Sci Ed 87:257–280, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10033
Science and technology education for citizenship: The potential role of the press
Authors: Dimopoulos Kostas , Koulaidis Vasilis
Published: January 2003

This paper aims to explore the potential suitability of the press as a teaching resource for raising scientific literacy for citizenship within science education. Our methodology is based on a content analysis of a sample of 1867 articles about science and technology from four Greek newspapers. The analysis showed that the press is potentially a useful tool for teaching certain aspects of science and technology for citizenship since it (a) provides a constant flow of relevant articles on a regular basis, (b) gives prominence to techno‐scientific issues that prevail in the public arena (digital technologies, advances in biotechnology and genetic engineering, environmental degradation), (c) identifies the various social actors and forces (mainly coming from the world of politics and the business world) that impinge on the collective decision‐making procedures about these issues, (d) portrays the kind of the social impacts of science and technology in an optimistic way, albeit tempered by considerable levels of concern, and (e) presents all the relevant news in context, thereby adding relevance and meaningfulness to the techno‐scientific concepts under discussion. In addition to strong points, the press has also weak points as a teaching resource in science classes. These weaknesses are mostly related to the underpresentation of techno‐scientific subject matter and the internal mechanisms that lead to the production of the corresponding knowledge. Consequently, press material can be used in the science classes in a complementary way to the conventional material already used so as to illuminate crucial aspects of science and technology in the public that seem to be missing from the official pedagogic discourse of science education. © 2003 Wiley Periodicals, Inc. Sci Ed 87:241–256, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10054
Study of classroom practice and classroom contexts amongst senior high school biology teachers in Harare, Zimbabwe
Authors: Gwimbi Eric M. , Monk Martin
Published: January 2003

Thirty‐three senior high‐school biology teachers in Harare, Zimbabwe, participated in the study. Self‐report data on school contexts was used to cluster the teachers according to their own perceptions of the contextual circumstances in their schools. The clustering differentiated self‐perceived better and poorer resourced schools. In theory lessons, teachers from the self‐perceived better resourced schools were observed to use less individual organization, less written exercises, more whole class organization, and more listening to the teacher than to the teachers in the poorer schools. In practical lessons teachers in the better self‐perceived better resourced schools were observed to use less whole class organization, less small group organization, more individual organization, less listening to teacher, less teacher explanation, less teacher questioning, and to conduct more practical. An interpretation of these findings is made in terms of the fit between a teacher's classroom practice and their self‐perceived classroom context. © 2003 Wiley Periodicals, Inc. Sci Ed 87:207–223, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10056
Genetics inquiry: Strategies and knowledge geneticists use in solving transmission genetics problems
Authors: Thomson Norman , Stewart James
Published: January 2003

Scientists are increasingly challenged to solve problems that require conceptualizing and understanding dynamic complex natural systems. Computer simulations have become an integral tool in helping solve complex problems because they can be effectively used to model dynamic systems. Today's reform standards advocate that science teachers and students be involved in scientific inquiry that is consistent with the practice of science. The goal of this research is to determine methods of inquiry geneticists' use in solving dynamic complex computer‐generated transmission genetics problems, specifically, their strategies and conceptual knowledge. Six geneticists representing three areas of genetics (transmission, molecular, and population) solved four problem types. Using their solution protocols, and through interviews, a hierarchical framework and pathway for solving the problems were developed. For science education researchers, teachers, and students, it is hoped the geneticists' insights and the framework developed can provide a guide for inquiry‐based problem solving that extends beyond genetics. © 2003 Wiley Periodicals, Inc. Sci Ed 87:161–180, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10065
How literacy in its fundamental sense is central to scientific literacy
Authors: Norris Stephen P. , Phillips Linda M.
Published: January 2003

This paper draws upon a distinction between fundamental and derived senses of literacy to show that conceptions of scientific literacy attend to the derived sense but tend to neglect the fundamental sense. In doing so, they fail to address a central component of scientific literacy. A notion of literacy in its fundamental sense is elaborated and contrasted to a simple view of reading and writing that still has much influence on literacy instruction in schools and, we believe, is widely assumed in science education. We make suggestions about how scientific literacy would be viewed differently if the fundamental sense of literacy were taken seriously and explore some educational implications of attending to literacy in its fundamental sense when teaching science. © 2003 Wiley Periodicals, Inc. Sci Ed 87:224–240, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10066
Perceived consequences of evolution: College students perceive negative personal and social impact in evolutionary theory
Authors: Brem Sarah K. , Ranney Michael , Schindel Jennifer
Published: January 2003

Evolutionary science has consequences for individuals and society, ranging from the way we interpret human behavior to our notions of spirituality and the purpose of our existence. Popular portrayals of evolution depict a paradoxical theory, a source of knowledge and human connections, but also a threat to our humanity and freedom. Using quantitative and qualitative methodology, we examined how college‐educated adults (n= 135) from diverse ethnic and religious backgrounds perceive the impact of evolutionary theory on individuals and society. We identified a continuum of perspectives, ranging from strong creationist to strong evolutionist. Using the model of “knowledge as an ecology” (Demastes, Good, & Peebles, Science Education, 79, 637–666, 1995; Nardi & O'Day, Information ecologies: Using technology with heart, MIT Press, Cambridge, MA, 1999), we examined the relationships among participants' beliefs, their perceptions regarding the social and personal impact of evolutionary theory, their prior exposure to and knowledge of evolutionary theory, and their opinions regarding the teaching of evolution. Evolutionists and creationists differed in their prior exposure to evolutionary theory, and their opinions about some aspects of teaching, but showed striking similarities regarding perceived impact. All groups viewed the consequences of accepting evolutionary principles in a way that might be considered undesirable: increased selfishness and racism, decreased spirituality, and a decreased sense of purpose and self‐determination. From a science education perspective, this one‐sided interpretation is troublesome because it runs counter to the available evidence and theories in evolutionary science, and we consider ways of fostering more balanced presentation and appraisal of evolutionary theory. © 2003 Wiley Periodicals, Inc.Sci Ed87:181–206, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10045
Ambulatory epidural anesthesia and the duration of labor
Authors: Karraz M.A.
Published: February 2003

Objectives: Ambulatory epidural analgesia has become a common option for women in labor in France. We tested the hypothesis that a method of epidural analgesia that allowed women to walk had specific advantages regarding mode of delivery, consumption of local anesthetic, oxytocin requirement, and labor duration. Methods: Two hundred and twenty‐one women with uncomplicated pregnancies who presented in spontaneous labor between 36 and 42 weeks of gestation or who were scheduled for induced labor were randomly divided into two groups, ambulatory and non‐ambulatory. All were given intermittent epidural injections of 0.1% ropivacaine with 0.6 μg/ml sufentanil for analgesia during labor (P<0.05 was considered significant). None of the women had previous cesarean delivery. Results: There were no significant differences between the two groups in mode of delivery, consumption of local anesthetic, or oxytocin requirement. However, a significant difference was noted in labor duration (173.4±109.9 min vs. 236.4±130.6 min; P=0.001). Conclusions: Walking with ambulatory labor analgesia shortens labor duration but has no other effect on the progress and outcome of labor.
The prevalence and timing of cervical cerclage placement in multiple gestations
Authors: Parilla B.V. , Haney E.I. , MacGregor S.N.
Published: February 2003

Objectives: To investigate the prevalence and timing of cervical cerclage placement in multiple gestations. Methods: Our perinatal database was queried for all multiple gestations delivered at Evanston Hospital from 12/95 through 12/00. This list was then cross‐matched with billing and medical records for ‘incompetent cervix’ and ‘cerclage.’ The medical records of all deliveries ≤26 weeks were reviewed in order to ascertain if cervical incompetence was responsible for the preterm delivery. Results: There were 802 deliveries of multiple gestations ≥14 weeks over a 5‐year period. The number of patients that underwent cerclage placement was 29 or 3.6%. The mean gestational age at cerclage placement was 18.6±4.5 weeks (range 11–24.6). Twelve were elective or prophylactic while 17 were ‘urgent’ or ‘emergent.’ The mean gestational age for the 17 emergent cerclages was 21.4±2.2 weeks (range 16.6–24.6). When compared with those patients who did not undergo cerclage placement, there was no difference in maternal demographics including age, parity, or previous full‐term delivery. There was a significant difference in the gestational age at delivery for the cerclage vs. no cerclage group; 29.3±5.6 vs. 34.4±4.6 weeks, respectively, and in the frequency of losses at ≤26 weeks; 8/23 (38%) vs. 48/707 (6.8%), P<0.001. Ten of the losses in the no cerclage group appeared consistent with incompetent cervix for a total of 39/802 or 4.9% rate of cervical incompetence in our multiple gestation population. Conclusions: The relatively low prevalence of cervical incompetence in our multiple gestations does not justify prophylactic cervical cerclage placement. Expectant management with serial cervical examinations starting at 16–18 weeks appears more prudent.
The FIGO Save the Mothers Initiative: The Uganda–Canada collaboration
Authors: Lalonde A.B. , Okong P. , Mugasa A. , Perron L.
Published: February 2003

In 1998, the ob/gyn associations of Uganda and Canada launched, under the umbrella of the FIGO Save the Mothers Initiative, a district‐wide intervention which aimed to increase the availability and utilization of emergency obstetric care (EmOC) services in a rural district of Uganda. The article describes the experience of two professional ob/gyn associations in the development, implementation, monitoring and evaluation of the project. Preliminary results after 24 months of intervention indicate important gains in the capacity of health professionals to deliver EmOC, the availability of emergency transportation services and met need for EmOC.
A continuous lineage of rat adenohypophysis stromal cells: characterisation and effects on GH3B6 prolactin‐secreting cell behaviour1
Authors: Alves Leandro M , Werneck Cláudio C , Martins Rita de Cássia L , Silva Luiz‐Cláudio F , Taffarel Marília , Borojevic Radovan , Nasciutti Luiz E
Published: February 2003

Summry— Although some studies have shown a possible modulation of the stroma on the hormonal secretion, it is not clear as to what are the requirements for these cellular interactions. In the present work, a homogeneous and continuous lineage of rat adenohypophysis stromal cells (APS9 cells) obtained from rat adenohypophysis primary culture was established. Using immunocytochemical methods and electron microscopy, we have characterised APS9 cells as elongated fibroblastoid‐like cells with intercellular contacts, expressing α‐smooth muscle actin, type IV collagen and laminin. By biochemical procedures, higher amounts of chondroitin sulphate and heparan sulphate were found in the pericellular and extracellular compartments of APS9 cell culture. In order to evaluate the possible effects of APS9 cell on GH3B6 prolactin‐secreting cell survival and/or proliferation, we established co‐culture and proliferation assays. When GH3B6 cells were cultivated on APS9 cell substrate, they displayed an organisation of many cellular cords strongly attached and covering all the stromal cell area, establishing punctual interactions or extensive surface associations between adjacent cells. Prolactin immunoreactivity appeared to be more scattered throughout the cytoplasm and accumulated in its periphery. When plated on glass coverslips, on newborn rat skin fibroblasts, on murine haematopoietic bone marrow stroma cell line or on murine foetal liver stroma cell line, GH3B6 cells changed their organisation and presented a decrease in cell number and adherence to the substrate. Our results showed that the APS9 cell/GH3B6 cell interactions favour cell growth and probably PRL secretion, and raises questions about the specificity of different organs and/or animal species stromas on the hormone secretion.
Clustering layers and boundary layers in spatially inhomogeneous phase transition problems
Authors: Nakashima Kimie , Tanaka Kazunaga
Published: February 2003

Résumé.
Nous étudions dans cet article l’existance de solutions « multi-couches » du problème de transition de phase suivant :

\begin{align*}
-\varepsilon^2u_{xx}+W_u(x,u)&=0 \quad \text{in } (0,1),\\
u_x(0)=u_x(1)&=0
\end{align*}

où

ε>0

est un petit paramètre et

W(x,u)

est un potentiel à double parts « équlibre ». En particulier, nous montrons l’existence de solutions avec couches limites et couches.
Linear instability implies nonlinear instability for various types of viscous boundary layers
Authors: Desjardins B. , Grenier E.
Published: February 2003

The aim of this paper is to give a simple proof to the fact that linear instability implies nonlinear instability for two classes of boundary layers: Ekman layers, mixed Ekman Hartmann layers. In the case of rotating fluids, we prove that linear instability of Ekman boundary layers (as studied in Lilly’s work [14]) implies nonlinear instability in

L^∞

norm. This result describes the onset of turbulence at high enough Reynolds numbers. Application of these techniques to MHD models is also given.

L’objectif de cet article est de donner une preuve simple du fait que l’instabilité linéaire entraine l’instabilité non linéaire pour deux classes de couches limites : couches limites d’Ekman, couches limites mixtes Ekman Hartmann. Dans le cas de fluides tournants, on montre que l’instabilité linéaire des couches d’Ekman (étudiée par Lilly dans [14]) implique l’instabilité non linéaire en norme

L^∞

. Ce résultat décrit l’apparition de la turbulence pour des Reynolds suffisament grands. Des applications de ces techniques à des modèles de MHD sont aussi données.
Mitogens are increased in the systemic circulation during bone callus healing
Authors: Kaspar Daniela , Neidlinger‐Wilke Cornelia , Holbein Oliver , Claes Lutz , Ignatius Anita
Published: February 2003

The influence of mechanical tissue strain caused by flexible fracture fixation on the systemic occurrence of systemic mitogens during callus healing was investigated. For this purpose the mitogenic capacity and growth factor concentration of sera from patients undergoing fracture treatment were determined. Sera from 9 patients whose fractures had been stabilized by external fixation were collected before and during fracture treatment. The sera were added to cell culture media of the osteoblastic cell line SaOS‐2. After 5‐6 days cell proliferation was measured. Transforming growth factor‐β1 (TGF‐β1) and insulin‐like growth factor‐I (IGF‐I) concentrations were analyzed in serum samples from different healing stages. Statistics: paired Wilcoxon‐test. Sera from fracture patients decreased SaOS‐2 proliferation in the first week after surgery (p<0.05) compared to sera obtained prior to surgery. In the fourth or fifth week proliferation increased significantly (p<0.03). The increased proliferation of the SaOS‐2 cells was associated with elevated levels of TGF‐β and IGF‐I (p<0.05). The higher mitogenic activity of sera suggests an increased level of circulating mitogens. In a previous study this increase had also been observed in patients during distraction osteogenesis treatment but not in patients with primary bone healing by a stable fixated plate. It is therefore assumed that their release from the fracture site is a consequence of mechanical stimulation by interfragmentary movement of fracture ends.

© 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
The effect of selected growth factors on human anterior cruciate ligament cell interactions with a three‐dimensional collagen‐GAG scaffold
Authors: Murray M. Meaney , Rice K. , Wright R. J. , Spector M.
Published: February 2003

Our work focuses on development of a collagen‐glycosamimoglycan (CG) scaffold to facilitate ligament healing in the gap between the ruptured ends of the human anterior cruciate ligament (ACL). In the present investigation, we evaluated the effects of selected growth factors on human ACL cell responses important in tissue regeneration, namely cell migration, proliferation, collagen production, and expression of α‐smooth muscle actin (SMA).

Methods: Explants from six human ACLs were cultured on top of a CG scaffold. Culture conditions were with either 2% FBS (control), or 2% FBS supplemented with TGF‐β1, PDGF‐AB, EGF, or FGF‐2. Histologic cell distribution, total DNA content, proliferation rate, rate of collagen synthesis, scaffold diameter and percentage of SMA positive cells were determined at two, three and four weeks.

Results: The addition of TGF‐β1 to the culture medium resulted in increased cell number, increased collagen production and increased expression of SMA within the scaffold. Supplementation with PDGF‐AB resulted in increased cell proliferation rates within the scaffold and increased collagen production. The addition of FGF‐2 resulted in increased cell proliferation rates and slowed rates of scaffold shrinkage when compared with the control group.

Discussion: This work suggests that certain growth factors can alter the biologic functions of human ACL cells in a CG scaffold implanted as a bridge at the site of an ACL rupture. Based on these findings, the addition of selected growth factors to an implantable CG scaffold may facilitate ligament healing in the gap between the ruptured ends of the human ACL.

© 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.