bluuebunny/crossref_metadata_2025 huggingface dataset:
Extrusion die design for viscoplastic fluids
Authors: Liu Li‐Dah , Wen Shu‐Heng , Liu Ta‐Jo
Published: April 2003

We propose to apply two approaches to analyze the design and performance of extrusion dies that deliver wide and thin uniform sheets and films of fluids with yield stress. The first approach is based on the one‐dimensional lubrication approximation and the second approach is the three‐dimensional finite element simulation. The performance of a T‐die and a coat‐hanger die has been under investigation. The effects of two dimensionless groups, the Reynolds number Re and the Bingham number Bi, on lateral flow uniformity have been examined. Several design variations, such as opening the end of the manifold and inserting a choker bar into a die, have also been studied. © 1994 John Wiley & Sons, Inc.
Mechanical properties of polycarbonate–polysulfone and polycarbonate–polyetherimide blends
Authors: Kohlman William G. , Petrie Stephen P.
Published: April 2003

Five, ten, and twenty percent by weight blends of polysulfone in polycarbonate and polyetherimide in polycarbonate were produced by melt blending. The materials were injection molded into plaques. Mechanical analysis consisting of tensile, pendulum impact, and ballistic impact testing was conducted using the plaques or samples machined from the plaques. The average impact strength and percentage of ductile failures decreased with increasing composition of polysulfone and polyetherimide. The tensile test results indicate that a relationship exists between the percent composition and the yield strength for the blends with the blends showing an improvement in tensile strength. The ballistic testing results show that a possibly linear relationship exists between the percent composition and the critical velocity for complete penetration. Differential scanning calorimetry was conducted to measure the glass transition temperatures of the materials. The presence of two glass transition temperatures and lack of transparency have indicated that the blends are immiscible. © 1995 John Wiley & Sons, Inc.
Recent developments in in‐line spectroscopy/microscopy for monitoring extrusion processes
Authors: Xanthos M. , Patel S. H.
Published: April 2003

On‐line/in‐line measurement technologies are increasingly finding uses for controlling the quality of polymeric materials during all phases of production and for minimizing waste in the form of off‐spec materials. In addition to commercial/developmental sensors for rheological or spectroscopic monitoring of extrusion processes, prototype instruments have been recently developed for in‐line optical monitoring of multiphase polymer melts. In this article, examples of developments in in‐line/on‐line Fourier Transform Infrared (FTIR) and Near Infrared (NIR) spectroscopy and optical microscopy and their applications to extrusion processes will be presented. © 1995 John Wiley & Sons, Inc.
The dissolution/reprecipitation technique applied on high‐density polyethylene: I. Model recycling experiments
Authors: Poulakis J. G. , Papaspyrides C. D.
Published: April 2003

A model dissolution/reprecipitation process is studied for the recycling of high‐density polyethylene (HDPE). The process proposed basically comprises dissolution of the plastic in an appropriate solvent, reprecipitation by using a nonsolvent, thorough washing of the material obtained, and drying. The solvent mixtures involved are separated by distillation for further reuse. Toluene/acetone was tried as a potential solvent/nonsolvent pair and proved to be very satisfactory, similarly to the case of recycling low‐density polyethylene. Further investigation was focused on the effect of sample history through successive recycling cycles. The recycled grades were evaluated in terms of the following properties: melt flow index (MFI), molecular weight, crystallinity, mechanical performance in tensile mode, and grain size analysis. In all cases the recycled polymer exhibited excellent retention of its properties. © 1995 John Wiley & Sons, Inc.
Engineering analysis and design of twin‐screw extruders for reactive extrusion
Authors: Michaeli W. , Grefenstein A.
Published: April 2003

Process developments in reactive extrusion or reactive compounding are largely carried out in closely intermeshing corotating twin‐screw extruders. The aim of this article is to present an analytical process model for this reactor type in order to facilitate the design of screw geometry and the settings of process parameters. Taking simultaneously into account aspects of flow behavior, heat transfer, thermodynamics, physics, and chemistry, a powerful mathematical model has been developed which was compared with practical results (e.g., residence time, pressure buildup, drive energy, bulk temperature, and conversion) on lab and production scale machines. The experiments were mostly carried out for the anionic bulk polymerizations of nylon 6 and polystyrene. Furthermore the reactive blending of nylon 6 and polyethyleneterephthalate was examined. Based on these chemical systems the practical use of computer‐aided process design will be discussed. © 1995 John Wiley & Sons, Inc.
Further thoughts on the relationship between economic value added and stock market performance
Authors: Sparling David , Turvey Calum G.
Published: April 2003

As authors of a previous study questioning the strength of the relationship between EVA and shareholder value, and in light of the arguments posed by Keefe and Roush, we revisit the relationship between EVA and shareholder return and reexamine the evidence and issues surrounding the use of EVA as a tool for valuing investments. Using the Stern Stewart Fortune 1000 data, we examine two potential relationships for 33 food companies listed in the database. The first is between the absolute level of EVA in 2000 and 3‐, 5‐, and 10‐year shareholder returns. The second is between 3‐, 5‐, and 10‐year mean percentage changes EVA and 3‐, 5‐, and 10‐year shareholder returns. The correlations found were extremely weak in all instances tested. [EconLit citations: 9120, 9320, M410, Q130]. © 2003 Wiley Periodicals, Inc. Agribusiness 19: 255–267, 2003.
Hydrogen‐containing silicone resin as the crosslinking agent of heat‐curable silicone rubber
Authors: Zhao S. , Feng S.
Published: April 2003

The hydrosilation‐cured vulcanizates (HCV) of silicone rubber were prepared by using hydrogen‐containing silicone resin (HSR) as the crosslinking agent. The influences of both the amount and structure of HSR on hydrosilation‐curing silicone rubber (HCSR) were discussed. The results indicate that HSR is a good crosslinking agent for HCSR. The tensile strength, tearing strength, elongation at break, and hardness of the vulcanizates can reach 9.6 MPa, 37.8 kN/m, 870% and 56 SHA, respectively. The aging stability of the vulcanizates can be improved greatly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3066–3069, 2003
PP–PP‐g‐MAH–Org‐MMT nanocomposites. I. Intercalation behavior and microstructure
Authors: Xu Weibing , Liang Guodong , Wang Wei , Tang Shupei , He Pingsheng , Pan Wei‐Ping
Published: April 2003

The melt‐direct intercalation method was employed to prepare poly(propylene) (PP)–maleic anhydride grafted poly(propylene) (PP‐g‐MAH)–organic‐montmorillonite (Org‐MMT) nanocomposites. X‐ray diffractometry (XRD) was used to investigate the intercalation effect, crystallite size, and crystal cell parameter in these composites. Two kinds of maleated PP, with graft efficiencies of 0.6 and 0.9 wt %, and two sorts of manufacturing processes were used to prepare nanocomposites and then to investigate their effects on intercalation behavior. The results showed that the intercalation effect was enhanced by increasing the content of PP‐g‐MAH, using maleated PP with higher graft efficiency, and adopting the mold process. The crystallite size of nanocomposites perpendicular to the crystalline plane, such as (040), (130), (111), and (041), reached the minimum value when the content of PP‐g‐MAH was 20 wt %. This result indicated that the crystallite size of PP in nanocomposites decreased by proper addition of PP‐g‐MAH. Maximum values in tensile strength (40.2 MPa) and impact strength (24.3 J/m) were achieved when the content of PP‐g‐MAH was 10 and 20%, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3225–3231, 2003
Compatibilization and toughening of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 alloy with poly(ethylene 1‐octene): Mechanical properties, morphology, and rheology
Authors: Wang Xiaodong , Feng Wei , Li Hangquan , Jin Riguang
Published: April 2003

Blends of a poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO)/polyamide 6 (PA 6) alloy toughened with a novel polyolefin elastomer poly(ethylene‐1‐octene) (POE) were prepared via melt extrusion. In order to improve the compatibilization between POE and the PPO/PA 6 alloy, POE was grafted with maleic anhydride (MA), which could react with the amine group of PA 6. The Izod impact strength of the blends exhibited an optimum when the extent of MA grafting of POE was changed, which is an order of magnitude higher than that of the untoughened blends. The morphology revealed that the size of the POE particles decreased with an increasing MA grafting ratio of POE. Studies on the tensile properties and rheology of the blends were also carried out. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3110–3116, 2003
Effect of surface‐modifying macromolecules and membrane morphology on fouling of polyethersulfone ultrafiltration membranes
Authors: Zhang L. , Chowdhury G. , Feng C. , Matsuura T. , Narbaitz R.
Published: April 2003

Polyethersulfone (PES) ultrafiltration (UF) membranes with and without surface‐modifying macromolecules (SMMs) were prepared and characterized in terms of the mean pore size and pore‐size distribution, surface porosity, and pore density. The results demonstrated that both the mean pore size and the molecular weight cutoff (MWCO) of the SMM‐modified membranes are lower than those of the corresponding unmodified ones. Membrane fouling tests with humic acid as the foulant indicated that the permeate flux reduction of the SMM‐modified membranes was much less than that of the unmodified ones. Therefore, fouling was more severe for the unmodified membranes. Moreover, the dry weight of the humic acid deposited on the membrane surface was considerably higher for the unmodified membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3132–3138, 2003
Film extrusion and film weldability of poly(lactic acid) plasticized with triacetine and tributyl citrate
Authors: Ljungberg Nadia , Andersson Thorbjörn , Wesslén Bengt
Published: April 2003

Film extrusion and welding of biodegradable polymer films are important processes that must be considered in the development of compostable packaging materials. Film extrusion of poly(lactic acid) (PLA) has proved to be rather difficult because of its brittleness, but the flexibility of PLA can be improved by incorporation of a plasticizer in the material. PLA was plasticized with triacetine (TAc) and tributyl citrate (TbC). The blended materials and neat PLA were film extruded and the films were welded with constant heat (CH) welding. The films were analyzed by means of gas chromatography (GC), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), contact angle measurements, and tensile testing. Storage of the plasticized films resulted in an increased crystallinity and changes in the film properties, rendering CH welding difficult. The welding process had no influence on thermal properties, such as cold crystallization temperature, melting temperature, crystallization temperature, and degree of crystallinity, of neat PLA but caused significant changes in the crystallinity of the plasticized materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3239–3247, 2003
Effects of lignin as a filler on properties of soy protein plastics. I. Lignosulfonate
Authors: Huang Jin , Zhang Lina , Chen Fangeng
Published: April 2003

A series of biodegradable plastics from soy protein isolate (SPI) and lignosulfonate (LS) with a weight ratio of 0:10 to 6:4 were prepared with 40 wt % glycerol as a plasticizer by compression molding. Their properties were investigated by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), scanning electron microscopy (SEM), and tensile tests. The results indicated that the introduction of a moderate LS content from 30 to 40 parts in the blends could simultaneously enhance the tensile strength, elongation, and Young's modulus of soy protein plastics alone. Studies of the water sensitivity of the materials suggested that the strong interaction between LS and SPI could restrict the effect of water on the swelling and the damage of the materials, resulting in lower water absorption. The improvement of the properties was attributed mainly to the existence of the beneficial microphase separation and the formation of crosslinked structures because of the introduction of LS into soy protein plastics. Therefore, a model of a crosslinked network formed from SPI molecules with an LS center was established based on the existence of strong physical interactions between LS and SPI. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3284–3290, 2003
Assessment questionnaire on the personal style of the therapist PST‐Q
Authors: Fernández‐Álvarez Héctor , García Fernando , Lo Bianco Julio , Corbella Santomá Sergi
Published: April 2003

We posit the Personal Style of the Therapist (PST) construct. It is defined as ‘the set of characteristics that each therapist applies in every psychotherapeutic situation, thus shaping the main attributes of the therapeutic act’. Its background is examined and its main traits are described. It includes five bipolar dimensions: Instructional, Expressive, Engagement, Attentional and Operative. It may be assessed through a self‐descriptive inventory. We list the psychometric properties found when the instrument was applied to a sample of N = 189 therapists in Argentina. We calculated descriptive statistics of the sample (means and standard deviations) and reliability coefficients (test–retest and Cronbach's alpha). To examine the dimension of the data a factor analysis of the main components was carried out using Varimax rotation. Results and potential applications of the instrument are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Reversal of lipopolysaccharide‐induced thermal and behavioural hyperalgesia by quercetin
Authors: Anjaneyulu Muragundla , Chopra Kanwaljit
Published: April 2003

Lipopolysaccharide (LPS), a major constituent of the outer membrane of the cell wall of gram‐negative bacteria, is known to cause inflammatory pain. Quercetin, a dietary flavonoid, is claimed to have antiinflammatory activity in a few experimental studies. However, it is not known whether quercetin can reverse the hyperalgesia that is secondary to the inflammation. The aim of the present study was to evaluate the effect of quercetin on LPS‐induced alteration of pain perception in mice. Central perception of pain was assessed with the tail‐flick and hot plate methods and behavioural hyperalgesia was assessed by noting the animal's reactions such as redness, paw licking, and rearing after the intraplantar injection of LPS (10 μg/paw). Local administration of LPS induced significant hyperalgesia when measured by both central effects and behavioural reactions. Quercetin (50 and 100 mg/kg), like dexamethasone (0.5 mg/kg), attenuated central and behavioural hyperalgesia. This effect of quercetin was sensitive to reversal by naloxone (2 mg/kg). Our results thus indicate that quercetin protects against LPS‐induced hyperalgesia through modulation of the opioidergic system. Drug Dev. Res. 58:248–252, 2003. © 2003 Wiley‐Liss, Inc.
Discovery and investigation of lead compounds as binders to the Extra‐Domain B of the angiogenesis marker, fibronectin
Authors: Scheuermann Jörg , Volonterio Alessandro , Zerbe Oliver , Zanda Matteo , Neri Dario
Published: April 2003

Angiogenesis, the growth of new blood vessels from preexisting vessels, is a rare event in the adult (except in the case of the female reproductive cycle), but is a characteristic feature of diseases such as cancer, blinding ocular disorders (e.g., retinopathies), and rheumatoid arthritis. The ED‐B domain of fibronectin, a domain of 91 amino acids, inserted by a mechanism of alternative splicing of the primary transcript into the fibronectin molecule, is a high‐quality marker of angiogenesis and a target for molecular intervention, characterized by a high number of acidic residues on its surface, as well as some solvent‐exposed hydrophobic residues. A library of 113 low molecular‐weight organic compounds, containing both an aromatic moiety and at least one positive charge, was screened for binding to the ED‐B domain, using two‐dimensional heteronuclear NMR spectroscopy. One lead compound, 2,2‐diphenylethylamine, was found that binds specifically to the ED‐B domain, albeit with a dissociation constant in the millimolar range. Chemical modification of this scaffold revealed structural determinants required for binding, as well as amino acid residues in the ED‐B domain responsible for the interaction. The results presented represent the basis for the development of high‐affinity, low molecular‐weight binders by using a linked‐fragment approach or elongating the scaffold by means of combinatorial chemistry. Drug Dev. Res. 58:268–282, 2003. © 2003 Wiley‐Liss, Inc.
Predicted heats of combustion of some important organosilicon intermediates
Authors: Hshieh Fu‐Yu , Hirsch David B. , Beeson Harold D.
Published: April 2003

This short communication presents the predicted heats of combustion of 308 organosilicon intermediates. The net and gross heats of combustion were predicted using two previously developed empirical equations. These intermediates cover most of the important organosilicon compounds that are manufactured or used in the silicone industry. Copyright © 2003 John Wiley & Sons, Ltd.
A model to predict fire resistance of non‐load bearing wood‐stud walls
Authors: Takeda H.
Published: April 2003

The author has developed a series of computer models to predict the fire resistance of wood‐framed walls and floors. The models utilize two‐dimensional heat‐conduction equations and thermo‐physical property data to describe heat transfer through the assemblies. The model for wall assemblies WALL2D, the basic version of the wall model, has already been published in Fire and Materials. Recently, WALL2D has been extended to WALL2DN to analyse heat transfer through insulated walls and walls that experience openings at the joints between adjacent sheets of gypsum board. Since gypsum board shrinks at high temperatures, the joints between adjacent sheets of gypsum board open. Hot fire gases, thereby, enter the openings and heat the edge of the gypsum board and wood studs. The new model WALL2DN simulates the joint opening and describes the resultant effect of openings. The model also calculates heat transfer through insulation in the stud cavity and depicts the effect of insulation on the fire resistance of non‐load bearing wall assemblies. Insulation selected in WALL2DN is glass‐fibre insulation, rock‐fibre insulation, polystyrene foam and polyurethane foam. When walls are exposed to fire, the insulation in the cavity shrinks (and/or melts) and an empty space appears at the interface between insulation and gypsum board. The model simulates this shrinking behaviour of insulation in the cavity. Finally, the model was validated by comparing the predicted results to those from full‐scale standard fire‐endurance tests. Copyright © 2003 John Wiley & Sons, Ltd.
Annular liquid jets at high Reynolds numbers
Authors: Georgiou G.
Published: April 2003

The flow of annular liquid jets at high Reynolds numbers is analysed by means of the finite element method and the full‐Newton iteration scheme. Results have been obtained for various values of the inner to the outer diameter ratio and for non‐zero surface tension, using extremely long meshes. The annular film moves far from the symmetry axis at low values of the Reynolds number. At higher Reynolds numbers, the film moves towards the axis of symmetry and appears close to very far downstream, forming a round jet. Asymptotic results for the radius of the resulting round jet are provided. Copyright © 2003 John Wiley & Sons, Ltd.
Finite‐element simulation of incompressible fluid flow in an elastic vessel
Authors: Chen Harry Y. H. , Sheu Tony W. H.
Published: April 2003

Finite‐element simulation was performed to predict the incompressible Navier–Stokes flow in a domain, partly bounded by an elastic vessel, which is allowed to vary with time. Besides satisfying the physical conservation laws, both surface and the volume conservation laws are satisfied at the discrete level for ensuring the balance between physical and geometrical variables. Several problems which are amenable to analytical solutions were tested for validating the method. The simulated results are observed to agree favourably with analytical solutions. Having verified the applicability of the finite‐element code to problems involving moving grids, we consider an incompressible fluid flow bounded by rigid and elastic vessel walls. Our emphasis was placed on the validation of the formulation developed within the moving‐grid framework. Copyright © 2003 John Wiley & Sons, Ltd.
A new hybrid turbulence modelling strategy for industrial CFD
Authors: Basara B. , Jakirlic S.
Published: April 2003

This paper presents a new strategy for turbulence model employment with emphasis on the model's applicability for industrial computational fluid dynamics (CFD). In the hybrid modelling strategy proposed here, the Reynolds stress and mean rate of strain tensors are coupled via Boussinesq's formula as in the standard k–εmodel. However, the turbulent kinetic energy is calculated as the sum of the normal Reynolds‐stress components, representing the solutions of the appropriate transport equations. The equations governing the Reynolds‐stress tensor and dissipation rate have been solved in the framework of a ‘background’ second‐moment closure model. Furthermore, the structure parameter C‐µ has been re‐calculated from a newly proposed functional dependency $f(\overline{u_{i}u_{j}},\partial U_{i}/\partial x_{j})$ rather than kept constant. This new definition of C‐µ has been assessed by using direct numerical simulation (DNS) results of several generic flow configurations featuring different phenomena such as separation, reattachment and rotation. Comparisons show a large departure of C‐µ from the commonly used value of 0.09. The model proposed is computationally validated in a number of well‐proven fluid flow benchmarks, e.g. backward‐facing step, 180° turn‐around duct, rotating pipe, impinging jet and three‐dimensional (3D) Ahmed body. The obtained results confirm that the present hybrid model delivers a robust solution procedure while preserving most of the physical advantages of the Reynolds‐stress model over simple k–εmodels. A low Reynolds number version of the hybrid model is also proposed and discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Efficient discretization of pressure‐correction equations on non‐orthogonal grids
Authors: Lehnhäuser T. , Schäfer M.
Published: April 2003

An alternative discretization of pressure‐correction equations within pressure‐correction schemes for the solution of the incompressible Navier–Stokes equations is introduced, which improves the convergence and robustness properties of such schemes for non‐orthogonal grids. As against standard approaches, where the non‐orthogonal terms usually are just neglected, the approach allows for a simplification of the pressure‐correction equation to correspond to 5‐point or 7‐point computational molecules in two or three dimensions, respectively, but still incorporates the effects of non‐orthogonality. As a result a wide range (including rather high values) of underrelaxation factors can be used, resulting in an increased overall performance of the underlying pressure‐correction schemes. Within this context, a second issue of the paper is the investigation of the accuracy to which the pressure‐correction equation should be solved in each pressure‐correction iteration. The scheme is investigated for standard test cases and, in order to show its applicability to practical flow problems, for a more complex configuration of a micro heat exchanger. Copyright © 2003 John Wiley & Sons, Ltd.
The geochemical characteristics of the Paraná River suspended sediment load: an initial assessment
Authors: Depetris Pedro J. , Probst Jean‐Luc , Pasquini Andrea I. , Gaiero Diego M.
Published: April 2003

Most water in the Paraná River drainage basin is supplied by the tropical Upper Paraná (over 60% of the total annual water discharge, 550 km3). The total suspended solids (TSS) load (c. 80 × 106 t year−1), however, is essentially furnished (50–70%) by the mountainous, arid and mostly sediment‐mantled upper Bermejo River drainage basin. This characteristic suggests that the Paraná River solid load (TSS, 600 km upstream from the mouth) is largely recycled sedimentary material, whose discharge‐weighted mean chemical index of alteration is c. 71. The extended UCC‐normalized multi‐elemental diagrams are similar to those of other world rivers. Nevertheless, the detailed inspection of UCC‐normalized rare earth element (REE) ‘spidergrams’ reveals a lithological source for the Paraná River TSS that might be compatible with either tholeiitic flood basalts (widespread in the upper drainage) or with young Andean intermediate volcanic rocks. In view of the Bermejo River's dominant role as a sediment contributor, we feel that the signature preserved in the Paraná's TSS is the latter. Conversely, the Uruguay River TSS REE signature is certainly determined by the extensive weathering products of Jurassic–Cretaceous tholeiitic basalts. Copyright © 2003 John Wiley & Sons, Ltd.
Physicochemical variables and plankton from the Lower Delta of the Paraná River (Argentina) in relation to flow
Authors: de Cabo Laura , Puig Alba , Arreghini Silvana , Olguín Héctor F. , Seoane Rafael , Obertello Irene
Published: April 2003

This study evaluates temporal variations of physicochemical variables and densities of phytoplankton and zooplankton, under different flow conditions. Four samplings were carried out at four sites on the Lower Delta of the Paraná River (Argentina). This first approach was developed in 1995 and included a flood of high amplitude and average duration. Daily data analysis along the year qualified sampling water levels as very high, medium (two opportunities) and low level. Triplicate subsuperficial water samples were taken in the middle of the navigation channel. Dissolved oxygen, pH, conductivity and temperature were determined in situ; nutrients and concentration of major solutes in the laboratory. Quantitative samples of phytoplankton (concentrated by sedimentation) and zooplankton (80 l; 48 µm) were obtained. Temporal variation of most physical, chemical and biological variables exceeded the spatial variation. Physicochemical variables were mainly associated in time with the hydrological regime. In the main channel water exchange originated by the flood of marshy environments caused dissolved oxygen, nitrate and sulphate to decrease and phosphate, conductivity, bicarbonate, calcium and magnesium to increase. The dilution–concentration action of flow was evidenced in chloride variation (conservative ion). The plankton variables would be affected directly and indirectly by water level, and also by seasonal climatic condition. The densities of phytoplankton and zooplankton increased during low flow. For some organisms, the variation in density exceeded the simple concentration effect of flow decrease. The lowest plankton densities coincided with a temperature minimum. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling point and diffuse heavy metal emissions and loads in the Elbe basin
Authors: Vink Rona , Peters Steef
Published: April 2003

The reduction of pollutant loads in rivers requires a good comprehension of the contribution of all major (point and diffuse) sources in each sub‐basin. Due to the sudden change of a centrally planned economy to a free‐market economy in 1989, the River Elbe is one of the fastest changing transboundary river basins in Central Europe. The quantification of fluxes of heavy metals in the Elbe basin requires information on the spatial and temporal characteristics of emissions and on physical boundary conditions of the entire river basin. In this paper, a GIS‐based model METALPOL will be presented, that describes the load of five heavy metals (Cd, Cu, Hg, Pb, Zn) in the Elbe basin over the period 1985–1999 as a function of (1) emissions from point and diffuse sources, (2) runoff, (3) soil types, (4) land use and (5) hydrogeology. The results from the model were validated with the measured heavy metal loads and showed reasonable agreement. Between 64% (for Hg) and 84% (for Pb) of the total heavy metal emissions in the Elbe basin is supplied by inputs from diffuse sources. The diffuse hydrological pathways with the highest share are erosion and urban areas. In most cases the measured heavy metal load is lower than the sum of the heavy metal emissions. Retention processes (e.g. sedimentation) largely explain this behaviour and are found to be dependent on the specific runoff of a catchment. About 81–97% of variance for the different heavy metals can be explained by the dependency on specific runoff. The uncertainty analysis presented in this paper has also illustrated that the reliability of the model simulations is directly affected by the quality of the input data (especially point source and urban emissions) and the distribution of the input data like rainfall data, emission data, soil data and land cover data. Finally, scenario analysis indicated that the current proposed measures are not stringent enough to achieve large reductions in heavy metal loads in the Elbe basin. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling effects of forest canopies on slope stability
Authors: Keim Richard F. , Skaugset Arne E.
Published: April 2003

We investigated the potential effects of rainfall intensity smoothing by forest canopies on slope stability by modelling soil responses to measured rainfall and throughfall during high‐intensity rain. Field measurements showed that maximum intensities of precipitation were generally reduced under forest canopies at two sites in the Pacific Northwest, USA. Modelling soil water pore‐pressure responses of a hypothetical hillslope to the field data resulted in estimates of slope stability that were generally greater under forest canopy than for the same hillslope without forest canopy. Results indicate that smoothing of precipitation intensities may translate into overall greater stability of hillslopes under forest canopies. Copyright © 2003 John Wiley & Sons, Ltd.
Knowledge management: New York City taxi cab case study
Authors: Skok Walter
Published: April 2003

This paper discusses and analyses a case study of the New York City Medallion Taxi Cab Service (NYC MTCS), which has been operating successfully for many years and is a visible sign of the vibrancy of the ‘Big Apple’. The case study introduces the main stakeholders associated with the medallion cabs' licensing system, discusses current application and examination processes, and outlines how prospective cab drivers acquire knowledge of the possible routes. A comparison is then made with an earlier case study based on acquiring the ‘Knowledge’ to become a cab driver in London. This compares some theoretical perspectives with the practical situation in both cities in order to identify similarities and differences in the way knowledge is created and managed. Copyright © 2003 John Wiley & Sons, Ltd.
Recent advances in the chemistry of parainfluenza‐1 (Sendai) virus inhibitors
Authors: Saladino Raffaele , Ciambecchini Umberto , Nencioni Lucia , Palamara Anna Teresa
Published: April 2003

Purine and pyrimidine derivatives, antioxidants, fusion inhibitors, statins, prostaglandins, antibiotic nucleosides, inhibitors of Ca2+ homeostasis, carbohydrate derivatives, antisense polynucleotides and chimeras, are described as inhibitors of parainfluenza‐1 (Sendai) viral infections. © 2003 Wiley Periodicals, Inc. Med Res Rev, 23, No. 4, 427–455, 2003
Polymerization by transition metal derivatives XI. Stereospecific polymerization of butadiene in the presence of π‐allyl nickel halogenoacetates
Authors: Dawans F. , Teyssié Ph.
Published: April 2003

The catalytic properties of a series of π‐allyl nickel halogenoacetates are reported for the cis‐1,4 polymerization of butadiene. Correlations between the catalytic activity of the complexes and the electron‐with‐drawing properties of their counter‐anions were made.
Correlation between the enthalpy of fusion and the specific volume of crystallized polycarbonate of bisphenol A.
Authors: Mercier J. P. , Legras R.
Published: April 2003

Several measurements of the heat of fusion and of specific volume were carried out on bisphenol A‐polycarbonate of varying degrees of crystallinity. A linear correlation was established between these two physical variables and from this an enthalpy of fusion for the polycarbonate crystal of 26 Kcal. was deduced.
Linear polymerization of 2‐methylbut‐3YN‐2‐OL in the presence of CIS‐(PPh3)2 PtCl2
Authors: Furlani A. , Bicev P. , Carusi P. , Russo M. V.
Published: April 2003

2‐methylbut‐3‐yn‐2‐ol is polymerized to linear polymers of medium molecular weight (ca. 1700) in the presence of cis(PPh3)2PtCl2.

Trans(PPh3)2Pt(C≡C—C(CH3)2OH)2and trans (PPh3)2PtCl(C≡C—C(CH3)2OH) have been isolated in the course of the reaction. The property of (triphenylphosphine)‐Pt complexes of giving almost exclusively linear polymers of mono‐substituted acetylenes and the formation of σ‐Pt‐acetylides as active intermediates in the course of the polymerization reaction have been corroborated.
Polymerization of ethylene oxide with a calixarene‐based precursor: Synthesis of eight‐arm poly(ethylene oxide) stars by the core‐first methodology
Authors: Taton Daniel , Saule Myriam , Logan Jennifer , Duran Randolph , Hou Sijian , Chaikof Elliot L. , Gnanou Yves
Published: April 2003

Eight‐arm poly(ethylene oxide) (PEO) stars were prepared by the core‐first method with a newly designed octahydroxylated precursor. This compound was readily obtained in two steps from commercially available tert‐butylcalix[8]arene. The choice of the proper solvent of polymerization proved crucial to obtain PEO star materials with a narrow distribution of molar masses. For instance, the use of dimethyl sulfoxide (DMSO) resulted in PEO samples of rather large polydispersities (PDI: 1.3–1.5). In this solvent, the calixarene‐based precursor was only sparingly soluble, and an attempt to metalate its eight hydroxyl groups produced insoluble alkoxides. In addition, the presence of a side population of low‐molar‐mass species attributable to linear chains was detected because of the chain transfer of propagating alkoxides to DMSO. Polymerization experiments carried out in tetrahydrofuran (THF) as solvent afforded better control over the molar masses and PDIs. This was related to the better solubility of the octafunctional calixarene‐based precursor in THF and to the small tendency of the alkoxides formed to aggregate in that solvent. Under such conditions, all eight hydroxyl functions efficiently initiated the polymerization of ethylene oxide. In this way, well‐defined PEO stars (PDI < 1.2) of tunable molar masses incorporating a calixarene‐based core could be obtained, as it was supported by the characterization of the samples by size exclusion chromatography, NMR, and viscometry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1669–1676, 2003
Identification of free radicals trapped in solid methacrylated resins
Authors: Truffier‐Boutry Delphine , Gallez Xavier A. , Demoustier‐Champagne Sophie , Devaux Jacques , Mestdagh Michèle , Champagne Benoît , Leloup Gaëtane
Published: April 2003

Photopolymerization of methacrylated dental resins at room temperature leads to the appearance of long‐life free radicals because of system vitrification. These free radicals were observed by electronic paramagnetic resonance (EPR), and their characterization was undertaken by reference to the reactional mechanism, from the comparison with the model EPR signal and from theoretical simulation. Overlapping of two EPR signals assigned to two different kinds of radicals because of methacrylate end groups accounted for all the experimental and theoretical results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1691–1699, 2003
Modeling the reversible addition–fragmentation transfer polymerization process
Authors: Wang Aileen R. , Zhu Shiping
Published: April 2003

A kinetic model has been developed for reversible addition–fragmentation transfer (RAFT) polymerization with the method of moments. The model predicts the monomer conversion, number‐average molecular weight, and polydispersity of the molecular weight distribution. It also provides detailed information about the development of various types of chain species during polymerization, including propagating radical chains, adduct radical chains, dormant chains, and three types of dead chains. The effects of the RAFT agent concentration and the rate constants of the initiator decomposition, radical addition, fragmentation, disproportionation, and recombination termination of propagating radicals and cross‐termination between propagating and adduct radicals on the kinetics and polymer chain properties are examined with the model. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1553–1566, 2003
Syntheses of stereoregular and optically active polyamides from active 4‐chloro‐1‐benzotriazolyl diesters and diamines
Authors: Overberger C. G. , Lu C. X. , Chen C. C.
Published: April 2003

A new route to prepare optically active polyamides was established, based on the polycondensation of two new active diesters: the active diesters of 4‐chloro‐1 hydroxybenzotriazole, such as 1,1'‐(terephthaloyldioxy)bis(4‐chloro‐benzotriazole), and 1,1'‐(isophthaloyldioxy)bis(4‐chlorobenzotriazole), with optically active isomers of 2,4‐diaminopentane. Dipolar aprotic solvents such as N,N‐dimethylformamide and dimethyl sulfoxide were used as reaction solvents. The solution polycondensation carried out in solution at room temperature afforded optically active polyamides. The aminolysis of the two active diesters was carried out as a model reaction study.
Preparation of aromatic polyesters by direct polycondensation with thionyl chloride in pyridine
Authors: Higashi Fukuji , Mashimo Toshio , Takahashi Ikuo
Published: April 2003

Mechanistic features of the reaction with thionyl chloride in pyridine were studied in a model reaction of benzoic acid with p‐chlorophenol or aniline. The yields were significantly affected by the amounts of pyridine, favorably by four equivalents, and the nature of pyridine, suggesting that pyridines are not only HCl scavengers, but are also involved in the reaction itself. The reaction was assumed to proceed via a carboxylic sulfinic‐anhydride intermediate different from acyl chloride, and the intermediate was found to be not so reactive that it was completely alcoholyzed by the phenol at high temperatures of more than 60°C. The reaction was successfully applied to the preparation of aromatic polyesters of high molecular weights by the direct polycondensation of aromatic dicarboxylic acids and bisphenols in pyridine at 80°C.
Boron–nitrogen polymers. I. Mechanistic studies of borazine pyrolyses
Authors: Paciorek K. J. L. , Harris D. H. , Kratzer R. H.
Published: April 2003

Pyrolyses of B‐triamino‐N‐triphenyl‐, B‐triamino‐N‐trimethyl‐, and B‐trianilino‐borazines were performed between 150 and 300°C. Initial stages of degradation were accompanied by liberation of ammonia in addition to the expected aniline or methylamine; this was most pronounced for the methyl borazine. Aniline elimination proceeded more readily with the B‐anilino than the B‐amino isomer. Data obtained support a ring opening mechanism resulting in telomerizaton accompanied by aniline liberation and formation first of singly then doubly bridged dimers and finally doubly bridged tetramers. Thermal exposure up to 1000°C failed to give pure boron nitride; carbon was invariably retained.
Polymerization of para‐xylylene derivatives (parylene polymerization). III. Heat effects during deposition of parylene N at different temperatures
Authors: Gazicki M. , Surendran G. , James W. , Yasuda H.
Published: April 2003

Thermal effects accompanying the vacuum deposition of poly‐para‐xylene (Parylene N) at different temperatures have been studied by following the changes in the temperature of the substrate. Similarly to the case of polychloro‐para‐xylylene (Parylene C), two distinct exothermic effects were observed; one discrete, resulting in sharp exothermic spikes and the other continuous, resulting in the shift of the baseline. The spike effect, attributed to the solid‐state polymerization of para‐xylylene, is observed at the low‐temperature range, the upper limit of which moves higher for higher deposition rates. The shift of a baseline as a function of deposition temperature exhibits two maxima, one independent of deposition rate and the second moving toward higher temperatures (that is, toward the first maximum) for higher deposition rates. First maximum falls at about 72°C and is attributed to the melting point of para‐xylylene crystals. X‐ray diffraction studies of polymer samples have shown that the existence of the second maximum is always followed by the appearance of an additional crystalline phase in the respective range of deposition temperatures. When the deposition rate is high enough, the second maximum merges with the first one, or virtually disappears. Under such conditions the new crystalline phase is no more detectable. It is postulated that the evolution of the additional amount of heat resulting in the appearance of the second maximum is due to the cyclization reaction and the formation of cyclic oligomers. This reaction very likely requires a particular spatial arrangement of monomer molecules and, therefore, it is suggested to take place in certain domains of the crystalline lattice.
Synthesis of polyamide containing optically active thymine derivative as a grafted pendant
Authors: Lu C. X. , Ji Aixue , Overberger C. G.
Published: April 2003

A new route to polyamides containing optically active thymine groups as pendants has been established. The method is based on the grafting of (–) and (±)‐2‐(thymin‐1‐yl)propionic acid [(–) and (±) TPA] onto a polyamide containing hydroxyl groups. The hydroxy polyamide was prepared by selective N‐acylation of an active diester of N‐hydroxy‐5‐norborene‐2,3‐dicarboxamide (HONB), N,N'‐(isophthaloyl‐dioxy)‐bis(5‐norbornene‐2,3‐dicarboximide) (IPBONB), with 1,3‐diamino‐2‐hydroxypropane (AHP). Model compounds (−) and (±)‐(1,3‐dibenzoylamino‐2‐propyl)2‐(thymin‐1‐yl)propionate[(−) and (±) (BAPTP)] were prepared by direct, low‐temperature esterification before synthesizing the polymer.
Step‐growth cationic polymerization of α‐hydroxyisopropylferrocene
Authors: Zhan‐Ru Lin , Gonsalves Kenneth , Lenz Robert W. , Rausch Marvin D.
Published: April 2003

α‐Hydroxyisopropylferrocene, HPF, was synthesized in good yield and polymerized at 20°C with either SnCl4 or BF3OEt2. The polymerization proceeds by self‐alkylation of the stable intermediate ferrocenylcarbenium ion on the cyclopentadienyl ring to form oligomers that contain both homoannular and heteroannular links. The unusually high stability of the α‐isopropylferrocenylcarbenium ion was demonstrated by synthesizing and isolating α‐isopropylferrocenylcarbenium tetrafluoborate from HPF and using it to initiate the polymerization of styrene. Initiation was successful at 20° and at 0°C, but no polymerization occurred −78°C. The condensation of ferrocene and acetone in the presence of AlCl3 gave oligomers having structures very similar to those obtained from the cationic polymerization of isopropenylferrocene.
Investigation of miscibility by spectroscopic methods IV. How far is poly(vinyl chloride) miscible with s‐poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)? An answer from nonradiative energy transfer
Authors: Albert B. , Jerome R. , Teyssie Ph.
Published: April 2003

Miscibility of PVC with s.PMMA and SAN, respectively, has been investigated by nonradiative energy transfer. Blended by using a common solvent, the two polymer pairs are not homogeneous at a molecular level. They are likely to contain heterogeneities of a few nanometers depending on blend composition. At a comparable number average molecular weight, but a different polydispersity, SAN is seemingly less miscible with PVC than s.PMMA. That this behavior is of enthalpic or entropic origin, or mainly due to the method of mixing, cannot be settled so far.
Plasma polymerization of phenylsilane
Authors: Inagaki N. , Hirao H.
Published: April 2003

Comparative studies on plasma polymerizations of phenylsilane (PhSiH3) and toluene (PhCH3) have been carried out to prepare plasma polymers containing aromatic groups. The IR and ESCA spectra show that PhSiH3 and PhCH3 are subjected to ring‐opening reactions in a discharge state to form polymers involving alkyl chains as well as aromatic groups. The ring‐opening reactions are more feeble in the PhSiH3 system than in the PhCH3 system, which may be due to stabilization of phenyl–Si bonds in PhSiH3 by contribution of pπ−dπ bonding. Aromatic groups incorporated into the plasma polymers from PhSiH3 are mono‐substituted.
Polymers from renewable resources. II. Synthesis of polyamideimides by triphenyl‐phosphine–polyhalocompound activated polycondensation
Authors: Ray Sabyasachi Sinha , Kundu Achintya K. , Ghosh Malay , Maiti Sukumar
Published: April 2003

A comparative evaluation of triphenylphosphine–polyhalocompound‐activated polycondensation of amino carboxylic acid as well as amino carboxylic acid containing an imidogroup with thionyl chloride activated polycondensation of the above two types of acids has been discussed. The role of different polyhalocompounds, acid acceptors, sequence of addition of reactants, temperature of reaction, etc. has been studied. It was observed that the molecular weight of the polyamide and polyamideimide, as evident from their inherent viscosity data, is generally higher, but the yield is lower than those obtained by thionyl chloride method. The reaction by the former method appears to be faster than the latter. The influence of various reaction conditions and possible mechanism of the polycondensation have been discussed.
Synthesis of aliphatic polyesters containing tetracyanoquinodimethane units by low‐temperature polycondensation reactions
Authors: Day Roger W. , Karimi Houshang , Francis Cecil V. , Kinstle James F. , Chambers James Q.
Published: April 2003

The low‐temperature solution polycondensation reaction between 1,4‐bis‐(2′‐hydroxy‐ethoxy)benzene and adipyl chloride has been studied in N,N‐dimethylacetamide. The effect of temperature, concentration, and reaction time on the percent yield and product viscosity has been determined. Optimum conditions were established for the preparation of high molecular weight products and then applied to the synthesis of novel tetracyanoquinodimethane polyesters. Products were characterized by gel permeation chromatography.
The glass‐to‐gel transition in solvent‐swollen polystyrene networks
Authors: Gutierrez Mario H. , Ford Warren T.
Published: April 2003

Glass transition temperatures have been determined for polystyrenes crosslinked with 1–10% divinylbenzene and swollen with toluene, chloroform, N,N‐dimethylformamide, and tetrahydrofuran to as high as 0.7 weight fraction solvent. The Tg′s depend approximately on the weight fractions and the Tg′s of the components according to the empirical equation 1nTg = m1 1nTg1 + m2 1nTg2 of Pochan. The Tg′s of the networks swollen with toluene also fit approximately a quasithermodynamic equation of Karasz based on the Tg′s and the ΔCp′s at Tg of the components.